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Program & abstract booklet of

2nd Symposium on Innovative Measurement and Analysis for Structural Materials

第２回革新的構造材料のための先端計測拠点国際会議

SIP-IMASMInnovative measurement and analysis for structural materials

2016

Sept. 27 – 29, 2016 AIST Tsukuba Center

The SIP-IMASM is supported by the Structural Materials for Innovation (SM4I), Cross-ministerial Strategic Innovation Promotion Program (SIP).

AIST16-C00015

The 2nd Symposium on SIP Innovative measurement and analysis for structural materials (SIP-IMASM 2016)

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9/27(Tue.) 09:00 Registration

Session chair: Paul Fons (AIST) 09:50 Guest speech Eizo Matsumoto (CAO)

Introduction Masataka Ohkubo (AIST) "Welcome to SIP-IMASM 2016"

Session chair: Masataka Ohkubo (AIST) 10:20 Keynote 1 Yutaka Kagawa (U. Tokyo) "Materials Integration : Request for Advanced Measurement

and Analysis"

11:00 Break

11:10 Keynote 2 Jenn-Ming Yang (UCLA) "Recent Innovations in Advanced Composite Materials" 12:00 Symposium Photo, Lunch

Session chair: Masao Kimura, Yasuo Takeichi (KEK) 13:30 Keynote 3 Daisuke Koyama (Rolls-Royce) "Technology Strategy for Future Civil Large Aeroengines"

14:20 Invited Shin-etsu Fujimoto (NSSC) "Optimization of Polymer Designs"

14:50 IMASM-1 Akira Uedono (U. Tsukuba) "Positron annihilation studies of free-volumes in epoxy resins for CFRP"

15:10 Coffee Break

15:30 Invited Koichi Hasegawa (MHI) "Development of composite materials for aircraft structures" Kiyoka Takagi (MHI)

16:00 IMASM-2 Nao Terasaki (AIST) "Mechanoluminescent visualization of strain distribution in structural material"

16:20 IMASM-3 Yasuo Takeichi (KEK) "Microscopic Observation of Tensile Damages and Chemical Properties of Carbon Fibre Reinforced Plastic Composites"

16:40 Poster session (see page 4-5)

18:00 Banquet

2nd Symposium on Innovative Measurement and Analysis for Structural Materials (SIP-IMASM2016)


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Session chair: Akira Uedono, Kimikazu Sasa (U. Tsukuba)

08:50 Keynote 4 Andreas Wagner (HZDR Germany) "Positron Annihilation Spectroscopy for Materials Science"

09:40 IMASM-4 Paul Fons (AIST) " The Role of Trace Light Elements in Heat-Resistant Steel"

10:00 IMASM-5 Brian O’Rourke (AIST) "Positron Annihilation Spectroscopy for Structural Materials"

10:20 Break

10:30 Keynote 5 Timo Sajavaara (U. Jyväskylä) "Advanced Ion Beam Analysis for Materials and Thin Film Research"

11:20 IMASM-6 Akiyoshi Yamazaki (U.Tsukuba) "Present Status of Development of the Ion Microbeam System for Additive Light Elements in Structural Materials at the University of Tsukuba"

11:40 IMASM-7 Takashi Nagoshi (AIST) "Deformation Behaviour of Fully Nano-Twinned BCT Material in a Micro-Compression Test"

12:00 Lunch

Session chair: Tadakatsu Ohkubo, Hiroaki Mamiya (NIMS) 13:30 Invited Reki Takaku (Toshiba) "Development of Turbine Materials for Power Generation"

14:00 Invited Tadashi Furuhara (Tohoku U.) "Application of 3D atom probe for designing nano-scale inhomogeneities in alloy steels"

14:30 IMASM-8 Taisuke Sasaki(NIMS) "Microstructure characterization of structural materials by laser assisted 3D atom probe"

14:50 Invited Makoto Uchida (Osaka City U.) "Computational Modeling of Inelastic Deformation Behavior of Thermosetting Polymers"

15:20 Coffee Break

15:30 Invited Kaneaki Tsuzaki (Kyusyu U.) "Unsolved issues in Ti alloys: microstructure and fatigue"

16:00 IMASM-9 Masataka Ohkubo (AIST) "Evaluation of Crack Occurrence from Microscale Strain Distributions of Titanium Alloy in Tensile Tests by Advanced Moiré and DIC Techniques"

16:20 Invited Hideaki Matsubara (Tohoku U.) "Material and performance design of ceramics coating - the case study of thermal barrier coating"

16:50 IMASM-10 Masao Kimura (KEK) "Advance techniques for analysis of microstructure and chemical states their developments and combination with materials informatics in order to reveal a crack formation and its propagation "

17:10 IMASM-11 Hong Xin Wang (NIMS) "Advanced in situ multi-scale characterization of hardness of carbon-fiber-reinforced plastic"

17:30 IMASM-12 Hideki Hatano (NIMS) "Development of ~3.2micron band efficient mid-IR laser for the application to Laser Ultrasonic Testing of CFRP"

17:50 Closing


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CFRP & Polymer 1-1 Akira Uedono (U. Tsukuba) "Positron annihilation studies of free-volumes in epoxy resins for CFRP"

1-2 Takeaki Kakizaki (U. Tsukuba) "Effect of free volumes on mechanical properties of epoxy resins for carbon-fiber-reinforced polymers"

1-3 Hong Jun Zhang (U. Tsukuba) "Temperature dependences of free volumes and mechanical properties of epoxy resins for CFRP"

1-4 Nao Terasaki (AIST) "Mechanoluminescent visualization of strain distribution in structural material"

1-5 Hong Xin Wang (NIMS) "Advanced in situ multi-scale characterization of hardness of carbon-fiber-reinforced plastic"

1-6 Hideki Hatano (NIMS) "Development of ~3.2micron band efficient mid-IR laser for the application to Laser Ultrasonic Testing of CFRP"

1-7 Masahiro Kusano (NIMS) "Non-destructive evaluation of defects in CFRP samples by OPO mid-IR laser ultrasonic testing"

1-8 Kanae Oguchi (U. Tokyo) "Numerical analysis of ultrasound propagation excited by mid-IR laser at delamination in CFRP laminate"

1-9 Rumi Kitazawa (KEK) "In situ Damage Observation in Carbon Fiber Reinforced Plastic Composite using 3D Computed Tomography"

1-10 Yoshihisa Tanaka (NIMS) "In-situ measurement of interfacial thermal deformation and residual stress for hybrid composite materials"

Metals

2-1 Fons Paul (AIST) "The Role of Trace Light Elements in Heat-Resistant Steel"

2-2 Qinghua Wang (AIST) "Evaluation of Crack Occurrence from Microscale Strain Distributions of Titanium Alloy in Tensile Tests by Advanced Moiré and DIC Techniques"

2-3 Masataka Ohkubo (AIST) "Integrated Analysis of Trace Light Elements in Heat Resistant Alloys

− Multiscale Elemental Imaging and XAFS Spatially-Averaged Analysis−"

2-4 Shoji Ishibashi (AIST) "Theoretical Calculation of Positron Annihilation Parameters for Vacancy-Related Defects in Mg"

2-5 Yoshihisa Harada (AIST) "Fatigue Damage Evaluation of Austenitic Steel SUS316L"

2-6 Hiroaki Mamiya (NIMS) "Small-angle X-ray scattering study on nanoheterostructure in structural materials"

2-7 Agata Kowalska (NIMS) "Influence of Ti on Ni-free ODS austenitic alloy"

2-8 Norimichi Watanabe (NIMS) "Characterization of micrometer-sized precipitates in heat-resistant steels using TOF-SIMS"

2-9 Toru Hara (NIMS) "Multiscale and multidimensional microstructure analysis using orthogonally-arranged FIB-SEM"

2-10 Byeongchan Suh (NIMS) "Analyses of partitioning behaviour of boron and nitrogen in metal carbide and Nb/V-enriched carbonitrides by using atom probe tomography”

Ceramics & Coating


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3-1 Yasuo Takeichi (KEK) "XRF-XRD Surface Mapping and X-Ray Computed Tomography Observations of Thermal Barrier Coatings"

3-2 Masao Kimura (KEK) "Chemical states mapping using XAFS/XAFS-CT and its analysis using a mathematical approach of homology"

3-3 Masao Kimura (KEK) "Dynamic analysis of laser shock-induced fragmentation of copper foil"

3-4 Kenichi Kimijima (KEK) "In situ observation of chemical species near solid/liquid interface in a pitting process"

3-5 Kenichi Kimijima (KEK) "Development of XAFS/XRD simultaneous measurement technique at high temperatures"

3-6 Yumiko Takahashi (KEK) "Non-destructive Characterization of internal structure of structure materials using synchrotron X-ray CT"

3-7 Keiichi Hirano (KEK) "X-ray analyzer-based phase-contrast computed laminography"

Instruments 4-1 Brian O’Rourke (AIST) "Positron Annihilation Spectroscopy for Structural Materials"

4-2 Takashi Nagoshi (AIST) "Deformation Behaviour of Fully Nano-Twinned BCT Material in a Micro-Compression Test"

4-3 Akiyoshi Yamazaki (U. Tsukuba) "Present Status of Development of the Ion Microbeam System for Additive Light Elements in Structural Materials at the University of Tsukuba"

4-4 Kimikazu Sasa (U. Tsukuba) "Construction of an Ion Beam Analysis Facility for Structural Materials at the University of Tsukuba"

4-5 Go Fujii (AIST) "Development of energy dispersive X-ray spectrometry system for nanometer-scale mapping of light elements"

4-6 Toshio Hyodo (KEK) "Performance Test of a Pulse Stretching System for Materials Science at KEK Slow Positron Facility II"

4-7 Tokushi Kizuka (U.Tsukuba) "Development of 2000 K Class High Temperature In Situ Transmission Electron Microscopy for Study of Heat-Resistant Materials"

4-8 Shogo Kikuchi (U.Tsukuba) "High Temperature In Situ Transmission Electron Microscopyof Heat-Resistant Ceramics"

4-9 Manabu Tezura (U.Tsukuba) "Development of Picometer Scale Specimen Manipulation for High Temperature In Situ Transmission Electron Microscopy of Heat-Resistant Materials"

4-10 Hisashi Yamawaki (NIMS) "Computer Simulation for nonlinear ultrasonic generation at unbonded interface in solid”

9:00-12:10 Lab Tour AIST, NIMS） Details to be announced. 14:00-17:30 SIP Colloquium special 1st. (in Japanese)


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Welcome to SIP-IMASM 2016 September 27th – 29th, Tsukuba, Japan

On behalf of the organizing committee, I give you a welcome to the 2nd Symposium of Cross-Ministerial Strategic

Innovation Promotion Program − Innovative Measurement and Analysis for Structural Materials (SIP-IMASM), which takes place at the AIST Tsukuba center in Japan on September 27 - 29, 2016. It consists of a two day workshop and a one day lab tour. The lab tour is followed by a colloquium in Japanese on "Multiscale X-rays analysis of innovative structural materials from atoms to components." All of the sessions are open to the public.

The keynote talks are given by the authorities: professor Yutaka Kagawa (University of Tokyo), professor Jenn-Ming Yang (UCLA), professor Timo Sajavaara (University of Jyväskylä), Dr. Andreas Wagner (HZDR), and Dr. Daisuke Koyama (Rolls-Royce Japan). The invited talks of the leaders of the SIP units for material development and modelling are accompanied by the annual reports of the SIP-IMASM team. The symposium consists of such target-material-oriented sessions as polymer and CFRP, calculations, metals, ceramics, and innovative instrumentation. We believe that you can get in touch with the importance of innovative measurement and analysis, and hope that this symposium enhances the collaboration between the scientists in both of the material research and analytical instrumentation.

The SIP-IMASM team are formed by National Institute of Advanced Industrial Science and Technology (AIST), National Institute for Materials Science (NIMS), University of Tsukuba, High Energy Accelerator Research Organization (KEK), and University of Tokyo. We are a member of the domain of “Materials Integration” under the program of Structural Materials for Innovation (SM4I) whose program director is professor Teruo Kishi. The SM4I project aims at solving current problems in developing structural materials for aircraft and power plants, and shortening the time necessary for R&D. In addition to Materials Integration, there are three domains: Fiber Reinforced Plastics, Heat-Resistant Alloys, and Ceramic Environmental Barrier Coating, which are our target materials.

We try to acquire information that is inherent in structural materials and essential for the improvement of mechanical properties and the prediction of lifetimes. There are two strategic challenges for “manifest but unrevealed information” that has never been measured before, and “integrated analysis” that is to find out latent information. The manifest but unrevealed information falls into four categories: “Theme-1, stress and cracks,” “Theme-2, trace light elements,” “Theme-3, heterogeneous boundaries,” “Theme-4, vacancies and defects,” and “Theme-5, delamination.” The SIP-IMASM team is utilizing the R&D resources in Tsukuba and Tokyo: three large-scale facilities such as the accelerator-and-radioisotope based positron beams, high energy ion accelerators, and synchrotron radiation photon sources. Furthermore, those facilities are enhanced by the use of leading-edge multiscale analytical instrumentation with superconducting X-ray spectroscopy, three-dimensional atom probe, Moire interferometry, TEM at high temperatures, etc as well as mechanical tests. The integrated analysis carried out as “Theme-0” is the most challenging task to find out what parameters govern mechanical properties of innovative materials with nanoscale texture. Your comment and suggestion to us are always welcome.

September 27, 2016 Masataka Ohkubo, Chair of SIP-IMASM2016


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Keynote 1

Yutaka Kagawa


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Materials Integration: Request for advanced measurement and analysis

Yutaka Kagawa Department of Materials Engineering, Graduate School of Engineering, The University of Tokyo

RCAST 6-6-1 Komaba, Meguro-ku, Tokyo153-8904, JAPAN

[email protected]

The major purpose of Materials Integration for structural materials is to create a new tool for reducing the time required for the research and development of materials and components. Through the MI tools, the relationship between materials, processing, structure and performance becomes easy to understand. The relationship is also applicable to all length and time scales. The understanding of this relationship at various levels is very effective for research and development.

The MI system also enables inverse problems related to materials engineering. For example, the best microstructure of a material to achieve maximum performance is obtainable within a short time through the developed MI system. Thus, the system is very effective at understanding performance changes during long term applications. The system also provides information on the effect of service environment on the time dependent performance of materials and components. These computer-based estimations help to save research and development time. The goal of the MI system is to understand the performance of materials and components. Important performances include fatigue, creep, corrosion, etc. These factors are all time dependent and the applications are based on long-term use conditions. A full understanding of the change of performance with service time under service conditions is important. Without know-how and/or experience, the MI system enables reduction of research and development time, because the system can predict changes within a very short time. We do not need to do extensive experimental research and development.

The MI system can make good use of new research at the forefront of science and technology .We can use both the new researches and the extensive research results of past research and development. In addition to the currently used approaches in the field of materials science and engineering, new engineering approaches have used big-data analysis, databases, and their applications have been incorporated into the Materials Integration system. Problems related to the research and development of materials is solved using knowledge from various fields. In the future, the MI system has the potential to combine an IoT (Internet of Things) and AI (Artificial Intelligence), and is expected to become more effective tool for research and development of materials engineering-related fields.

To use the MI system, measurement of undetermined properties is very helpful to increase accuracy of the results. Recently, various new experimental techniques have been developed and the techniques allow revealing very important behaviors, both from micro- and macro-scales. In summary, the proposed Materials Integration system provides new integrated knowledge and the method to use that knowledge. The present talk shows some examples of important new measurement technologies for research and development of advanced structural materials. Major attention of the talk is focused for the best combination of measurement-analysis-simulation for virtual design and test of structural materials. Achievement of this relationship is expected to open new doors for new types of materials engineering tools.


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Keynote 2

Jenn-Ming Yang


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Recent Developments in Advanced Composite Materials

Jenn-Ming Yang Department of Materials Science and Engineering

University of California Los Angeles, CA 90095-1595

E-mail: [email protected]

Composite materials are being used extensively in lightweight, highly-loaded structures in aerospace, automotive and energy-generating applications. However, composites account for only about 1 percent of the total structural materials market by volume in 2016. This provides ample opportunity to grow in various industries by replacing traditional structural materials, such as steel and aluminum [1]. To expand the applications of composites across various industrial sectors, many innovations aiming toward increasing performance, reducing material and manufacturing cost, and shortening process cycle time will be needed.

In this presentation, recent developments in fibers, matrices and manufacturing technology as well as the repair and recycling of composite materials will be discussed.

References .

[1] S. Mazumdar, Comp. Manuf, Jan-Feb, 2016.


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Keynote 3

Daisuke Koyama


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Technology Strategy for Future Civil Large Aeroengines

Daisuke Koyama1)

1)Engineering & Technology, Rolls-Royce Japan Co., Ltd. (3-2-5 Kasumigaseki, Chiyoda, Tokyo, Japan 100-6031)


Since jet propulsion system started to be used for aircraft in first half of the 20th century, the gas turbine aeroengine has been evolving in civil applications to ensure better safety and reliability. Today’s civil large aeroengine has dramatically improved both and is, therefore, recognised as one of the most advanced mechanical systems created

to date. Such a successful deployment has been primarily driven by customers’ commercial requirement for low fuel burn as well as stakeholders’ commitment to lower environmental emissions. It is also understood that the civil aeroengine will evolve further in this direction during the forthcoming decades.

Firstly, low specific fuel consumption, SFC, is of major interest to aircraft operators in these years because it directly realises less fuel cost per unit. Recent operators, including low cost carriers, pay higher attention to this performance than ever for securing business competitiveness. Low SFC also results in less emission of CO2 per unit and is consequently friendlier to the environment. To achieve lower SFC, it is important to improve both propulsive efficiency and thermal efficiency. Higher temperature capability and high bypass ratio architecture can respectively be successful strategies to get such improvements, if trade-off and/or optimisation can be properly managed amongst various parameters, designs and considerations. In addition, lower airplane weight always improves fuel burn. Secondly, for less emission of NOx and noise from airplanes, lean burn combustion and aerodynamic solutions on fan and exhaust designs have been actively pursued to address. Mechanical engineering has generally been taking the leading role to meet the requirements. In those developments, materials engineering can play another important role under tight inter-linkage to mechanical engineering and design efforts. Our aeroengines have accepted, and will continue to incorporate, more variety of advanced materials than before. For example, new materials have been pursued as possible solutions to meet performance requirements to date, including non-metallic materials as well as carbon fibre reinforced plastics, metal matrix composite, ceramic matrix composite, hybrid bearings, titanium aluminide, higher temperature Ni-base alloys and so on. Japan’s capability in material science and engineering helps our aeroengines be further advanced and more competitive.

Beyond 2030, propulsive systems for airplanes will be further evolved to meet long term requirements, especially on lower emissions to the environment. Disruptive innovation may be essential to provide a solution to the requirements and could open a new era of airplanes for civil transport. Hybrid systems of gas turbine and electric propulsion would also be a possibility in the future. Many discussions are in progress for solutions but are still at an early stage. There are, therefore, still many of missing elements and unresolved questions on future systems. Various opportunities have been, and will be, actively identified, discussed and considered in relevant communities and collaboration. World class technologies may provide human beings with the way forward.

Current family of Trent Vision 5 & 10 Architectures Aeroengines in further future


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Optimization of Polymer Design

Shin-etsu Fujimoto1), Tetsuya Kobayashi1), Noriaki Ochi1), Shinichiro Sakurai1), Kyoko Adachi1), Genki Takeuchi1), Yuichi Taniguchi2) and Keiichi Hayashi2)

1) Basic Technology Integration Center, Nippon Steel and Sumikin Chemical Co., Ltd. (1-Tsukiji, Kisarazu, Chiba, 292-0835, Japan) 2) Epoxy Resin Materials Center, Nippon Steel and Sumikin Chemical Co., Ltd. (11-5, Kitasode, Sodegaura, Chiba, 299-0266, Japan)


We examine the relationship between molecular structures and the mechanical performance of structural thermosetting polymers to develop practical optimal design and comprehensive evaluation support tool for advanced structural polymer materials. The molecular structures of epoxy polymers are calculated using molecular dynamics (MD) simulations, and a database of the simulation results is constructed using an advanced mathematical method. The database can provide the relationships between the molecular structures and material heterogeneities that affect the mechanical performance of the materials.

Initially, we focused on structural epoxy polymers and prepared some model epoxy resin samples. Mechanical tests, positron annihilation-based free volume measurements, nano-palpation atomic force microscopy (AFM) analysis, and full atom and coarse-grained MD simulations were conducted to clarify the relationship between molecular structures and mechanical properties. Additionally, the material heterogeneities were quantified via persistent homology analysis. Then, databases were created based on these results and applied to solve inverse problems.

The effects of conversion on mechanical properties were confirmed by subjecting the polymer samples to mechanical tests. The free volumes of the polymer samples increased as their conversion by positron annihilation increased. This finding is in good agreement with the MD simulation results.

The heterogeneities of the polymer materials are reflected in dynamic systems of the structural materials, including their fracture and damage mechanics. Therefore, we aim to develop a polymer materials integration (MI) system consisting of practical modules that can be used to correlate the spatial and temporal scales.

In addition to the conventional approaches used to study polymers, the development of approaches based on fresh perspectives has been enabled through the combined efforts of many researchers with expertise in various scientific and technological fields. Thus, our research and development have evolved, and we now pursue high-level, novel polymer MI studies. For example, the use of mathematical approaches enables combining different technical elements to define the components of polymer materials.

The figure presents a simulation result obtained using an MD method. This simulation enables the determination of the effects of the molecular structures on the curing reaction. The relationships of the molecular structures and constitutive laws can be determined using the series of MD simulations with appropriate force field potentials as parameters. This information will be useful in assembling screening modules for the molecular structures and in designing advanced structural polymer materials.

Fig. 1. MD simulation results.


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Positron annihilation studies of free volumes in epoxy resins for CFRP

A. Uedono1), H. J. Zhang1), S. Sellaiyan1), T. Kakizaki1), Y. Taniguchi2), K. Hayashi2) 1) Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan

2) Epoxy Resin Materials Center, Nippon Steel & Sumikin Chemical Co. Ltd., Kitasode 11 5, Sodegaura, Chiba 299-0266, Japan


Positron annihilation is a non-destructive tool for investigating vacancy-type defects and open spaces (free volumes)

in materials. Detectable defects are monovacancies to open spaces with the size of sub-nm in crystalline and amorphous materials. It has no restriction of sample temperature or conductivity. This technique can be applied to a variety of materials, such as metals, semiconductors, insulators, and polymers.

When a positron is implanted into condensed matter, it annihilates with an electron and emits two 511-keV γ quanta [1]. The energy distribution of annihilation γ-rays is broadened by the momentum component of the annihilating electron-positron pair pL, which is parallel to the emitting direction of the γ-rays. The energy of the γ-rays is given by Eγ = 511 ± ΔEγ keV. Here, the Doppler shift ΔEγ is given by ΔEγ = pLc/2, where c is the speed of light. A freely diffusing positron may be localized in an open space, such as a vacancy or free volume, because of Coulomb repulsion from positively charged ion cores.

For amorphous polymers, positronium (Ps: a hydrogen-like bound state between a positron and an electron) may form in open volumes (Fig. 1). Ps exhibits two spin states: para-Ps (p-Ps), a singlet state, and ortho-Ps (o-Ps), a triplet state. The intrinsic lifetimes of p-Ps and o-Ps are 125 ps and 142 ns, respectively [1-3]. P-Ps annihilates via the 2-γ process, and the energy of the emitted γ-rays is 511 keV (pL ≅ 0). O-Ps primarily exhibits three-photon (3γ) annihilation that produces a continuous energy distribution from 0 to 511 keV. When o-Ps is trapped by free volumes, the positron involved in o-Ps may annihilate with an electron of free volume interiors to emit two γ-rays before 3γ-annihilation (pick-off annihilation). A large free volume reduces the probability of this process and increases the o-Ps lifetime. Thus, one can estimate the size of free volumes from the measurements of the o-Ps lifetime. The relationship between the pore diameter and the lifetime of o-Ps is shown in Fig. 2. In this study, we have used positron annihilation spectroscopy to study behaviors of free volumes in epoxy resins for CFRP.

Epoxy resins with different chemical structures were prepared. The lifetimes of positrons in the samples were measured were measured as a function of sample temperature to evaluate the size of free volumes and the free volume rate. It was found that a clear correlation between the free volume size/rate and mechanical properties of those polymers, such as tensile/flexural modulus and break strain. It was demonstrated that positron annihilation can be used as a sophisticated non-destructive observation technique to characterize epoxy resins for CFRP.

References [1] Principle and Application of Positron and Positronium Chemistry, Ed. Y. C. Jean and D. M. Schrader (World Scientific,

Singapore, 2003) p. 167. [2] A. Uedono, S. Murakami, K. Inagaki, K. Iseki, N. Oshima, and R. Suzuki, Thin solid films 552, 82 (2013). [3] A. Uedono, S. Armini, Y. Zhang, T. Kakizaki, R. Krause-Rehberg, W. Anwand, A. Wagner, Appl. Surf. Sci. 368, 272 (2016).

Fig. 1. Schematics of free volumes in branched and

network polymers.

Fig. 2. Relationship between the pore diameter and the

lifetime of o-Ps. The inset shows the annihilation of o-Ps from the pick-off process.


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Development of Composite Materials for Aircraft Structures

Kiyoka Takagi1), Koichi Hasegawa2) 1) Aircraft & Missile Systems Division, Integrated Defense & Space Systems, Mitsubishi Heavy Industries, Ltd.

(10, Oye-cho, Minato-ku, Nagoya, Aichi) 2) Manufacturing Technology Research Department, Research & Innovation Center, Mitsubishi Heavy Industries, Ltd.

(10, Oye-cho, Minato-ku, Nagoya, Aichi)

E-mail: 1) [email protected]

Carbon fiber reinforced polymer composites have been extensively used in commercial aircraft structures over the last decade. For example, the structural weight for those in the Boeing 787 and the Airbus A350XWB reaches 50 % and 52 %, respectively. This is mainly ascribed to the excellent fatigue properties and corrosion resistance of the composites throughout aircraft service life (~30 years) compared to conventional aluminium alloys, along with the higher specific strength and modulus of the composites allowing for weight reduction.

This type of composites are made of continuous carbon fibers which typically have more than 10 times the strength of steels, and a cured epoxy resin system which aligns and stabilizes the individual fiber. For their manufacturing, a prescribed number of thin sheets of aligned fibers impregnated with the uncured resin called ‘prepreg’ are stacked and then consolidated with heat and pressure in an autoclave equipment to form laminates. Thus, the composites show significant anisotropy where strength in the stacking direction is prominently low, while strength in fiber directions is highly competitive to aluminium alloys. Therefore, when designing structures using composites, it is considered that the load in the stacking direction will be minimized. However, local mismatch in the rigidity inevitably arising from varying structural details such as internal frames that stiffen external skins and inspection holes, considerable loads in such undesirable direction tend to result in those areas. Those loads can be detrimental enough to initiate fracture in the resin or the fiber/resin interface whichever will be the weak link, growing to delaminations and leading to catastrophic failure of the structure.

In addition, it is a common practice in the structural design of composites to assure damage tolerance assuming the existence of a certain size of internal damage. This is due to the detectable size limits of non-destructive inspection techniques for internal defects occurring as-manufactured or internal damage like delaminations which may arise from impact loads but, unlike metals, are hardly visible from the surface. Thus, mechanical properties taking into account the pre-existing internal damage such as CAI (Compression After Impact) or TAI (Tension After Impact) are considered as important design values.

Based on the above features, it is of primary importance in developing aerospace grade composites to achieve greater resistance to propagation of internal damage under service loads along with having high impact energy absorption capability to restrain damage size. This is one of the two main objectives of the SIP A11 unit project “Development of high-productive high toughness composites”. The other is to enhance competitiveness in composite manufacturing cost compared to that for aluminium by providing improved processing characteristics which lead to higher processing cycle.

It has been widely agreed that these properties are greatly dependant on toughness of the resin and interfacial bond strength of fiber and resin. However, detailed mechanisms of the damage initiation and its progress are rather complicated and have not been fully understood due to the heterogeneous nature of the microstructure of composites combining fibers, resin and toughening thermoplastic agents and resultant multiple failure paths. This has tended to cause material development to be based on classical try and error approach and limited the extent of performance enhancement. Thus, there has been an increasing need for methodology to characterize composites in micro or nano scale for better understanding the failure mechanisms and specifying dominant factors associated with the critical properties. The characterization methods required will involve not only those for more sophisticated and accurate observation throughout the entire failure process but also for quantifying physical and chemical interaction between the material constituents.


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Mechanoluminescent visualization of strain distribution in structural material

Nao Terasaki1), Yuki Fujio1) 1) National Institute of Advanced Industrial Science and Technology (AIST),

Advanced Manufacturing Research Institute, 807-1 Shuku-machi, Tosu, Saga 841-0052, Japan


Elasticoluminescent material is a novel mechanoluminescent (ML) functional ceramic powder (controllable size: 10 nm―100 μm, representative and the most efficient ML material: SrAl2O4:Eu2+) and it can emit intensive light repeatedly accompanied by mechanical stress such as deformation, friction, impact, even in elastic deformation region. The ML intensity is proportional to Mises strain energy of the material.1,2 Thus, when dispersedly coated onto a structure, each particle acts as a sensitive mechanical sensor, while the two-dimensional (2D) emission pattern of the whole assembly reflects the dynamical strain/stress distribution inside the structure (Fig. 1) and the mechanical information around the defect and crack or the in-visible tip.1

Fig. 1. Feature of ML sensor

Meanwhile, in the field of a next-generation automotive and aerospace, multi-material concept has been rapidly accelerated, in which various kinds of material such as high-tensile strengthen steel, aluminum (Al), titanium (Ti) and carbon fiber reinforced plastic (CFRP) are used at the same time at appropriate position for each purpose. Actually, CFRP and other composite material are intentionally used in airplanes in high ratio (50 % for Boring 787, and 53 % for airbus A350 XWB) and automotive car not only in a concept car and a racing car but also in a popular car such as BMW i-3/8 from the viewpoint of light weight vehicle and energy saving. In the presentation, we would like to introduce (1) the ML technique and the high potential for diagnosis of mechanical information in structure material and the adhesive parts, such as (2) a stress distribution in adhesive, (3) a strain contribution on CFRP (carbon fiber reinforced plastic) as shown in Fig. 2, and (4) visualization of destructive origin on CFRP.

Fig. 2. Visualization of strain contribution on CFRP during tensional and torsional load.

References [1] C. N. Xu, N. Ueno, N. Terasaki, H. Yamada, Mechanoluminescence and novel structural health diagnosis (book style), Tokyo:

NTS (2012).

[2] N. Terasaki and C. N. Xu, Sensors Journal IEEE, 13, 3999 (2013).

[3] Y. Fujio, N. Terasaki et. al. , Int. J. Hydrogen Energy, 41, 1333 (2015).


17

Microscopic Observation of Tensile Damages and Chemical Properties of Carbon Fibre Reinforced Plastic Composites

Y. Takeichi1), Y. Niwa1), T. Ishii1), R. Kitazawa1), and M. Kimura1) 1) Institute of Materials Structure Science, High Energy Accelerator Research Organization

(1-1 Oho, Tsukuba, Ibaraki, 305-0801 Japan)


Carbon fibre reinforced plastic (CFRP) composites are of growing use in aircrafts because of their high specific strength and stiffness. Micromechanism of damages and microscopic chemical properties of CFRPs is a key to understand the mechanical properties and durability of these materials. Recent reports pioneered the micromechanical analysis of fractures under quasi-static stress [1] and fatigue failures [2] in CFRPs from three-dimensional dataset obtained using synchrotron X-ray computed tomography (CT).

We have developed a laboratory source X-ray CT combined with magnifying optics and in situ tensile, flexural, and compression test systems. 0/90/0 degree laminate plates of Mitsubishi Rayon HYEJ25-36 fibres were shaped into a notched specimen. Tensile stress was applied with obtaining the strain-stress (S-S) curve, while X-ray CT observations were performed at several extension points. Up to 40 % of fracture strength (~1500 MPa) was found to be the elastic region and no internal cracks or fractures were discernible. Initiation and increase of 0 degree ply splits, transverse ply cracks and delamination between plies were observed with successive X-ray CT imaging with increasing the tensile stress up to fracture strength. Figure 1 shows the longitudinal views exploited from three-dimensional dataset, which was obtained by high-resolution CT observation after the tensile test. The tensile stress was applied in the vertical direction. 0 degree ply splits shown in Fig. 1(a) are found to be bridged with fibre breaks. This was associated with misaligned fibres in the literature [1]. Delamination between 0 and 90 degree plies shown in Fig. 1(b) resembles the echelon cracks reported for a split in resin-rich region [1]. Detailed fracture micromechanism could be obtained associating the X-ray CT images with macroscopic S-S curves.

Microscopic chemical imaging of CFRPs is important to explain the intrinsic properties of these materials. Near-edge X-ray absorption fine structure (NEXAFS) is useful to discern different chemical properties of fibres, resins and adhesive agents for laminating. Soft X-ray scanning transmission X-ray microscopy (STXM) [3] has the spatial resolution of ~40 nm, and is therefore capable of investigating the intra-fibre structures and fibre-resin boundaries with chemical contrast using NEXAFS. CFRP specimen were prepared using focused ion beam and were observed using STXM at the Photon Factory, BL-13A. Figure 2 shows an X-ray transmission image of CFRP at the photon energy of 315 eV, representing the carbon density distribution. Intra-fibre distribution of chemical properties could be explored by analysing photon-energy dependent chemical imaging. (a)

(b)

Fig. 1. Logitudinal views obtained from reconstructed volume data of fractured CFRP, showing (a) 0 degree ply splits and (b) delamination.

Fig. 2. STXM image of a sectioned CFRP obtained at the photon energy of 315 eV.

[1] A. E. Scott, M. Mavrogordato, P. Wright, I. Sinclair, and S. M. Spearing, Compos. Sci. Technol., 71, 1471 (2011). [2] S. C. Garcea, I. Sinclair, and S. M. Spearing, Compos. Sci. Technol., 109, 32 (2015). [3] Y. Takeichi, N. Inami, H. Suga, C. Miyamoto, T. Ueno, K. Mase, Y. Takahashi, and K. Ono, Rev. Sci. Instrum., 87, 013704

(2016).


18

Keynote 4

Andreas Wagner


19

Positron Annihilation Spectroscopy for Materials Science

A. Wagner1), W. Anwand1), R. Krause-Rehberg2), M. O. Liedke1), K. Potzger1) 1) Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstr. 400, 01328 Dresden, Germany

2) Martin-Luther-Universität Halle, Institut für Physik, 06099 Halle, Germany


Early experiments on the interaction of positrons (the anti-particles of electrons) with materials revealed a significant sensitivity on the electronic structure. Especially, open-volume defects, such as vacancies, vacancy agglomerates, and dislocations cause attractive electric potentials due to the lack of the repulsive positive potential of the nuclei. With diffusion lengths in the order of 100 nm positrons probe large volumes before getting trapped at positively charged defects which in turn results in a sensitivity of defect concentrations of about 1 in 107 atoms (in metals) . While annihilation lifetimes increase with increasing defect sizes due to reduced local electron densities, one can also infer the momentum-distributions of the annihilation electrons which in turn tell about the chemical compositions in the vicinity of defects. Doppler-broadening spectroscopy and annihilation lifetime spectroscopy have therefore found widespread applications in defect studies in pure metals, alloys, and semiconductors. With increasing defect sizes the formation of the electron-positron bound state – called Positronium (Ps) – becomes possible. While the spin-parallel triplet state has a vacuum annihilation lifetime of 142 ns, this annihilation lifetime gets reduced when the Ps bounces off the walls of porous materials and flipping to the spin-singlet state with 125 ps. In contrast to standard intrusion techniques, porosimetry studies with positrons can be applied for closed porosity as well.

The Helmholtz-Center at Dresden-Rossendorf operates several user beamlines for materials research employing positron annihilation. SPONSOR (Slow POsitroN System Of Rossendorf) uses moderated positrons from 22Na decay which are post-accelerated to energies from 27 eV to 37 keV which are guided magnetically towards the samples under study [1]. The energy dependent range allows performing depth-dependent (coincidence) Doppler-broadening spectroscopy of thin films with thicknesses up to about 1 µm. SPONSOR has been extended by a new installation called AIDA (Apparatus for In-Situ Defect Analysis) which additionally allows temperature-dependent positron annihilation spectroscopy (PAS) from 50 to 1200 K, in-situ ion irradiation and sputtering with noble and reactive gases (up to 5keV ion energy), thin film deposition (Molecular Beam Epitaxy), and four-point probe resistometry. First experiments with this facility on open volume defects in Fe60Al40 alloys have been performed and the results will be presented [2]. Two other user facilities dedicated to positron annihilation lifetime and Doppler-broadening studies in materials research are being operated at a superconducting electron linear accelerator. Hard X-rays from electron-bremsstrahlung generate positrons from pair production. Both installations employ bunched continuous-wave (CW) electron beams with energies between 15 MeV and 30 MeV. The CW-operation results in significantly reduced pile-up effects in the detectors in comparison to normal conducting accelerators. Electron bunch lengths below 10 ps FWHM allows positron annihilation lifetime spectroscopy measurements with high timing resolutions. The bunch repetition rate is adjustable to 26 MHz / 2n, n=0, 1, 2 ... 16 matching wide spans in positron or positronium lifetimes. The GiPS (Gamma-induced Positron Source) generates energetic electron-positron pairs inside the sample under investigation from hard x-rays impinging onto the sample [3]. Therefore, the source is especially suited for materials which are not qualified for vacuum conditions or because they are imposing hazardous conditions or intrinsic radioactivity. Exemplary defect studies on the skyrmoin-lattice compound MnSi [4] will be presented. MePS (the Monoenergetic Positron Source) utilizes positrons with fixed energies ranging from 500 eV to 16 keV[3]. A magnetic beam transport system guides positrons to the samples under investigation. A dedicated chopper/buncher system is used to maintain a high timing resolution for depth-dependent annihilation lifetime studies in thin films. The signal-to-noise ratio is beyond 104 while lifetime resolutions of around 280 ps FWHM have been obtained. Applications of porosimetric studies in low-k dielectrics will be presented. [6]. The MePS facility has partly been funded by the Federal Ministry of Education and Research (BMBF) with the grant PosiAnalyse (05K2013). The initial AIDA system was funded by the Impulse- und Networking fund of the Helmholtz-Association (FKZ VH-VI-442 Memriox). The AIDA facility was funded through the Helmholtz Energy Materials Characterization Platform.

[1] W. Anwand, et al., Defect and Diffusion Forum Vl. 331 25 (2012). [2] M. O. Liedke, et al., Journal of Applied Physics 117 163908 (2015). [3] M. Butterling, et al., Nuclear Instruments and Methods in Physics Research B 269, 2623 (2011). [4] M. Reiner, et al., Scientific Reports 6, 29109 (2016). [5] M. Jungmann, et al., Journal of Physics: Conference Series 443, 012088 (2013) [6] A. Uedono, et al., Applied Surface Science 368, 272 (2016).


20

The Role of Trace Light Elements in Heat-Resistant Steel

P. Fons, S. Shiki, M. Ohkubo National Institute of Advanced Industrial Science & Technology (AIST), 1-1-1 Higashi, Tsukuba, 305-8573, Japan

E-mail:[email protected]

High Cr-Content ferritic steels have long been used for steam pipe applications in conventional power plants

due to their relatively low cost and excellent durability. Recently, the urgent need to reduce CO2 emissions from power plants has driven a strong need to increase operating temperatures and pressures in a bid to increase thermodynamic efficiency. Advanced ultra-critical power plants have been proposed to operate with steam temperatures in the range 970-1000K while lower temperature parts will operate at temperatures below 920K. While the highest temperature components will likely be fabricated from Ni-based alloys, lower temperature parts will be fabricated from advanced high-Cr martensitic steel alloys to reduce costs. Strain-induced coarsening shown to occur during short-duration creep testing has been demonstrated to lead to segregation of the alloy microstructure, however, B has been found to greatly increase the stability of both M23C6 precipitates as well as the corresponding interfaces in 9Cr (0.08C, 9Cr, 3W, 3Co, 0-0.2V, 0.05Nb (wt.%) with small amounts of N) heat resistant steels developed by the National Institute for Materials Science.[1] In this report, we present preliminary data on B and N locations in samples with varying concentrations of B and N using a combination of K-edge x-ray absorption near-edge spectroscopy (XANES), and V K-edge extended x-ray absorption spectroscopy (EXAFS). Samples and Experiment

Four 9Cr samples with varying (300, 70, 20, and 30 wt% ppm) concentrations of N were prepared. All samples were normalized at 1100°C and subsequently air-quenched, followed by a tempering at 750°C for two hours to reduce the concentration of defects induced by the martensitic transformation. The first three samples with varying N concentrations (300, 70, and 20 wt% ppm) and a fourth 30 N ppm creeped sample (650 , 160 MPa, 2246h ) were cut into cylinders approximately 1 cm in diameter and 0.5 in height and chemo-mechanically polished to a mirror finish. Preliminary XAFS measurements were then carried out at the B- and N K-edges at beamlines bl16a and bl13 at the Photon Factory in Tsukuba, Japan. EXAFS at the Vanadium K-edge were also carried at the Aichi synchrotron to ascertain the local structure about V atoms in each sample. All measurements were carried out in fluorescence mode. A superconducting tunnel junction detector with an energy resolution of better than 11 eV was used for the B (188 eV) and N ( 410 eV) K-edges [2], while a 9-channel silicon drift detector was used for detection of the V (5472 eV) K-edge. Discussion and Conclusion

Cross-sectional SEM analysis of the 300 ppm N sample exhibited the presence of BN precipitates that lead to poor creep performance, however no BN precipitates could be observed in the remaining samples. Preliminary XAFS measurements at the B K- edge confirmed the presence of BN precipitates in the 300 nm N sample due to the characteristic sharp π* peak at 192 eV of the BN phase. No clear peak could be seen in the other samples, but the combination of low absorption cross section of B and low B concentration is likely to limit the detection of B in chemical configurations without sharp resonance peaks. N K-edge measurements suggest that most of the 0.2 wt% V is in solid solution in the ferrite matrix as can be seen by the characteristic shape of the EXAFS region of the spectra > 100 eV above the edge, but the presence of VN precipitates could be discerned in the XANES region in the close vicinity of the absorption edge as can be seen in figure 1. N K-edge measurements indicated the presence of BN in both the 300 ppm N sample and the 70 ppm N sample as well. As XANES is sensitive to structures less than 1 nm in size, this suggests the presence of sub-critical BN grains even in the 70 ppm sample. Further details of the contribution of light trace elements to the microstructure of heat resistant steels will be discussed.

Fig. 1. Vanadium K-edge EXAFS spectra for steel samples with differing N concentrations References

[1] H. Kushima, K. Kumura, F. Abe,Tetsu-to-Hagane, 85, 841 (1999) (in Japanese). [2] M. Ohkubo, S. Shiki, M. Ukibe, N. Matsubayashi, Y. Kitajima, and S. Nagamachi, Sci. Rep. 2, 831 (2012). [3] N. Oshima, R. Suzuki, T. Ohdaira, A. Kinomura, T. Narumi, A. Uedono and M. Fujinami, Rad. Phys. Chem., 78, 1096 (2008)


21

Positron Annihilation Spectroscopy for Structural Materials

Brian E. O’Rourke1), Nagayasu Oshima1) 1) National Institute of Advanced Industrial Science and Technology, 1-1-1, Umezono, Tsukuba, Ibaraki, 305-8564, Japan


Positron annihilation spectroscopy (PAS) is a powerful method to evaluate atomic-scale structure and defects and is applicable to various materials [1-3]. In general the macroscopic properties of structural materials such as mechanical strength, heat-resistance etc. are affected by the atomic-scale and/or nano-meter-scale structure. Such structures are sensitive to the environmental conditions during manufacture or processing and/or the external loading. For the development of high-performance structural materials it is important to evaluate these atomic-scale and/or nano-meter-scale structures. Using PAS we are studying atomic-scale defects such as atomic defects and nano-void in metals/ ceramics and intermolecular spaces (free volume) in polymers.

In PAS, positrons obtained from radio-isotopes or accelerators are injected into the material under study. Positrons quickly (~1 ps) lose their energy and start thermal diffusion before annihilation. Thermalized positrons can effectively trap into the open-volume defects because there is no electrically repulsive force at the open-volume defects due to absence of positively charged nucleus. Positon annihilation parameters such as positron annihilation lifetime and energy-shift (Doppler-shift) of the annihilation gamma-ray from 511 keV is strongly dependent on the environmental structure at the positron annihilation site. For example positron annihilation time (i.e. positron lifetime) becomes longer if the size of the open volume defects become larger. Therefore, by measuring the positron lifetime spectrum and/or energy spectrum of annihilation gamma-ray we can evaluate atomic-scale defects, nano-voids, inter molecular spaces (free volume) etc. There are two main analytical methods in PAS, namely positron annihilation lifetime spectroscopy (PALS) and Doppler broadening of annihilation radiation (DBAR). We use three measurement techniques for PAS studies, i) fast positron method (bulk measurement methods), ii) slow positron beam method (near surface measurement method) and (iii) positron microbeam method (defect mapping measurement methods [4]).

In the SIP project we are studying various structural materials such as steels, titanium alloys and high strength polymers. For example, we have investigated the distribution of defects induced in stainless steel after electrical discharge machining [5], and defects in steel induced via cyclical stress. Using the unique properties of the AIST positron microprobe we plan to measure the evolution of hydrogen embrittlement in steel in-situ. A summary of our recent results and some future plans will be presented at the conference. [1] R. Krause-Rehberg, H. S. Leipner, Positron Annihilation in Semi-conductors (Springer-Verlag, Berlin, 1999) [2] P. Coleman (Ed.), Positron Beams and their applications, (World Scientific, 2000) [3] P. J. Schultz and K. G. Lynn, Rev. Mod. Phys. 60 701 (1988) [4] N. Oshima, R. Suzuki, T. Ohdaira, A. Kinomura, S. Kubota, H. Watanabe, K. Tenjinbayashi, A. Uedono and M. Fujinami, J.

Phys. Conf. Series, 262, 012044 (2011) [5] L. Jiang, B. E. O’Rourke and N. Oshima, 1st Symposium on SIP Innovative Measurement and Analysis for Structural Materials

(SIP-IMASM 2015), Book of Abstracts.


22

Keynote 5

Timo Sajavaara


23

Advanced Ion Beam Analysis for Materials and Thin Film Research

Timo Sajavaara1), Jaakko Julin1), Marko Käyhkö1), Mikko Laitinen1), Kai Arstila1) 1) Department of Physics, University of Jyväskylä, P.O.Box 35, 40014 University of Jyväskylä, Finland


Ion beam analysis (IBA) techniques such as Rutherford Backscattering Spectrometry (RBS), Elastic Recoil Detection Analysis (ERDA) and Particle Induced X-ray Emission (PIXE) have, despite the harder and harder competition, retained their special position among other techniques providing information about the elemental composition. The greatest asset of IBA techniques has earlier been and still is the ability to provide quantitative information from measured samples over large range of elements. The materials analysis needs are all the time developing and, for instance, better depth resolution, higher mass resolution, lower ion induced damage and high spatial resolution are today common requirements. Therefore the IBA techniques and the instrumentations need to be actively developed to answer these needs. This paper focuses to the latest developments in the IBA techniques covering the work done in Jyväskylä and elsewhere.

Today energy dispersive superconductive transition-edge sensors (TES) have matured to the state that they are used in number of applications, thanks to their superior energy resolution and sensitivity. Here we present the Jyväskylä TES-PIXE measurement setup [1], in which TES detector arrays are used to detect X-rays in proton and heavy ion PIXE. The energy resolution of a TES detector, when used in PIXE, is over an order of magnitude better compared to silicon drift detectors (SDD) and comparable to that of WD detectors (see Fig.1). This makes it possible to recognize spectral lines in materials analysis that have previously been impossible to resolve over large energy range (1.0–15 keV), and even obtain chemical information from the analyzed sample. Our 160 sensors with total active area of 15.6 mm2 are cooled to the operation temperature of about 65 mK.

Today the most versatile ion beam analysis tool in thin film characterization is the time-of- flight elastic recoil detection analysis (TOF-ERDA), which can be used for quantitative depth profiling of all elements in thin films, including hydrogen. TOF-ERDA can reach depth resolution of 2 nm or better without the need for reference samples or any prior information of the sample under study. The recent development towards low energy (<6 MeV incident beam) measurements will be shown together with examples. Furthermore, the ion beam analysis potential of helium ion microscopes utilizing 40 keV He beams focused down to sub-nm beam spot sizes will be discussed.

Fig. 1. (above) PIXE energy spectrum of fly ash (bio:peat fuel with 50:50 ratio) measured using silicon drift detector and TES. (below) A zoom to the 5 keV region of the spectrum above.

References [1] M. R. J. Palosaari, M. Käyhkö, K. M. Kinnunen, M. Laitinen, J. Julin, J. Malm, T. Sajavaara, W. B. Doriese, J. Fowler, C.

Reintsema, D. Swetz, D. Schmidt, J. N. Ullom, I. J. Maasilta, Phys. Rev. Applied 6 (2016) 024002


24

Present Status of Development of the Ion Microbeam System for Additive Light Elements in Structural Materials at the University of Tsukuba

A. Yamazaki1), K. Sasa1,2), S. Ishii2), M. Kurosawa3), S. Tomita1), S. Shiki4), G. Fujii4), M. Ukibe4), M. Ohkubo4), A. Uedono1,2), E. Kita1,5)

1) Faculty of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571, Japan

2) Research Facility Center for Science and Technology, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8577, Japan

3) Faculty of Life and Environmental Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8572, Japan

4) National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan

5) National Institute of Technology, Ibaraki College, 866 Nakane, Hitachinaka, Ibaraki 312-8508, Japan


A new submicron scanning nuclear microprobe line has been constructed in the early 2016 at the accelerator facility in the University of Tsukuba. Figure 1 shows the schematic view of the ion microbeam line at the 6 MV tandem accelerator facility. A microbeam scanning endstage OM-2000 (Oxford Microbeams Ltd., UK), which consists of a collimator slit (shown as the second slit in the Fig. 1), two-dimensional scanning coils, magnetic quadrupole triplet for beam focusing, and a target chamber, has been installed at the end of this system. The distance from the object slit (shown as the first slit in the Fig. 1) to the target position is 8730 mm, and the working distance is 180 mm. This ion microbeam system will be mainly used for X-ray imaging of two dimensional distributions for light elements in structural materials using particle induced X-ray emission (PIXE) technique. A silicon drift detector (SDD) with a thin window of Si3N4 has been installed for utilizing characteristic X-rays emitted from light elements such as boron, carbon, and nitrogen, which are common for additive elements in structural materials. In addition, A superconducting tunnel junction (STJ) array detector [1, 2] is going to be installed to perform PIXE for light elements measurements more efficiently. Combining a microbeam scanning technology with the X-ray detectors, we plan to obtain two-dimensional maps of additive light elements in structural materials. And also a new target chamber for installing the STJ detector is being fabricated and will replace the present target chamber in this fall. This new chamber utilizes a BGO detector used for nuclear reaction analysis (NRA) to observe hydrogen in structural material.

The experiments for obtaining a proton microbeam and for transporting a 15N beam used for NRA measurements are proceeding. Present results will be shown in our contribution.

Fig. 1. Schematic view of the ion microbeam line at the 6 MV tandem accelerator facility.

References [1] M. Ukibe, S. Shiki, Y. Kitajima, M. Ohkubo, X-ray Spectrom., 40, 297 (2011). [2] S. Shiki, M. Ukibe, Y. Kitajima, M. Ohkubo, J. Low Temp. Phys., 167, 748 (2012).


25

Deformation Behaviour of Fully Nano-Twinned BCT Material in a Micro-Compression Test

Takashi Nagoshi 1), Yuuki Karasawa 2), Akinobu Shibata 3), Masato Sone2) 1) Advanced Industrial Science and Technology (1-2-1 Namiki, Tsukuba-shi, 305-8564, Ibaraki, Japan)

2) Tokyo Institute of Technology (2-12-1 Ookayama, Meguro-ku, 152-8550,Tokyo, Japan) 3) Kyoto University (36-1 Yoshida-Hommachi, Sakyo-ku, 606-8501, Kyoto, Japan)


Nano-twinned materials have a great interest in recent years as one of the approach to obtain the incredibly high strength without losing uniform elongation. Many researchers have reported mechanical properties of nano-twinned materials with fcc structure [1,2]. The deformation behavior of nano-twinned materials other than fcc structure, however, has yet to be studied, due to difficulties in formation of nanoscale twins. One of the ferrous α’ martensites (bct structure), thin plate martensite, contains nano-spaced transformation twins extended from one martensite/austenite interface to the other[3]. In the present study, we fabricate square shaped pillar from a selected martensite variant and following compression test was conducted to evaluate mechanical properties and clarify deformation mechanisms of the fully nano-twinned materials with bct structure.

An Fe-31Ni-10Co-3Ti (mass%) was used in this study. Thin plate martensites were thermally transformed by sub-zero cooling to 77K and 4K and followed by rolling at 77K to increase the volume fraction of thin plate martensite. Orientations of austenite and martensite were determined by scanning electron microscopy (SEM) equipped with electron backscattered diffraction pattern detector. Tensile test of the sample with varied martensite volume fraction conducted to investigate the effect of the martensite on strengthening. A micro-sized square pillar (20 x 20 x 40 μm) was fabricated from thin plate martensite by using focused ion beam without any tapering. Channeling contrast image in scanning ion microscope showed that the fabricated pillar was composed of fully nano-twinned structure incorporated with few different martensite variants.

Volume fraction of the martensite phase increased with decreasing temperature of sub-zero cooling and further increase with cryorolling. Martensite volume fraction of 50% was achieved by cryorolled at 77K with 20% reduction. Tensile test reveals the increasing strength with increasing volume fraction of martensite phase. Yield strength increased from 300 MPa for fully austenite sample to 800 MPa for half martensite sample. Tensile tests indicates strong martensite phase strengthen the material. Micro-testing of the single variant of martensite conducted to investigate the mechanical properties of martensite itself.

The result of micro-compression test shown in Fig. 1a. In micro-compression test of the fabricated pillar, yield drop from 1200 MPa to 750 MPa was observed which suggested that the catastrophic twin deformation and following deformation occurred inside the deformation twin. SEM images shown in Fig. 1b indicates the slip operated in the post deformed area by twin deformation. Such deformation behavior implies the possibility to improve elongation without sacrificing the strength.

Fig. 1. (a) Stress strain curve in micro-compression test and (b) SEM images after deformation

References [1] L. Lu et al. Science, 304, 422 (2004)

[2] A.Shibata, T. Murakami, S. Morito, T. Furuhara, T. Maki, J. Japan Inst. Metals, 73, 290 (2009).

[3] M. Maki, I. Tamura, J. Japan Inst. Metals, 23, 229 (1982)


26

Development of Turbine Materials for Power Generation

Reki Takaku1) 1) Power and Industrial Systems R&D Center, Toshiba Corporation,

2-4, Suehiro-cho, Tsurumi-ku, Yokohama 230-0045, Japan


Development of high temperature gas turbines and steam turbines has been conducted to achieve higher thermal efficiency. In recent years, combined cycle power plants of 1600°C-class gas turbine and coal-fired power plants of 620°C-class are operated. Development of high temperature materials as well as cooling and coating technologies has played an important role in developing the turbines.

In 1100°C-class gas turbines conventional casted Ni-based superalloys were used for blades, and directional solidified and single crystal superalloys were developed and used for higher temperature ones. In the steam turbines of ultra super critical (USC) plant, 9~12 Cr steels were developed and used for hot parts such as rotors, blades, casings and valves. 700°C-class advanced-ultra super critical (A-USC) steam turbine is currently being developed with support from the Japanese government, and Ni-based superalloys for large-scale components are being developed and evaluated.

Materials for low pressure steam turbine components used in lower temperature also play an important role to increase thermal efficiency or unit capacity. For example, the last stage blade became longer by applying precipitation hardening stainless steels or Ti alloys, and rotor material of the last stage became stronger to hold the longer blade. We are now trying to develop large scale turbine disk with high strength and toughness through evolution of ultrafine grained structures (Fig. 1) in Structural Materials for Innovation (SM4I) of Cross-ministerial Strategic Innovation Promotion Program (SIP).

Fig. 1. Development of large scale and high strength wrought steam turbine disk in SIP-SM4I.


27

Application of 3D Atom Probe for Designing Nano-Scale Inhomogeneities in Alloy Steels

T. Furuhara1), Y. –J. Zhang2), G. Miyamoto1) 1) Institute for Materials Research, Tohoku University (2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan)

2) Graduate Student, Department of Metallurgy, Tohoku University (2-1-1 Katahira, Aoba-ku, Sendai 980-8577, Japan)


In low carbon steels containing strong carbide-forming elements, nano-sized alloy carbides can be formed and dispersed into the matrix during heat treatments. Recently, high strength sheet steels were produced by utilizing interphase precipitation of alloy carbides accompanying ferrite transformation during hot rolling processes and achieved superior strength-ductility balance, especially high yield strength and large local elongation [1]. Alloy carbides can effectively strengthen ferrite matrix by an Orowan-type dispersion hardening mechanism [2]. However, it becomes more difficult to analyze strengthening mechanism when the carbide size becomes finer than a few nanometers. Thus, we have been systematically investigating microstructure of interphase precipitation of nano-sized carbides by three dimensional atom probe (3DAP) microscopy. So, in this presentation, the examples of such analyses for better understanding in designing microstructure are briefly described.

Combined addition of carbide-forming elements is effective in strengthening [1,4]. Fig. 1 shows variations in α hardness with the total atomic fraction of V, Nb and Ti addition. Although increase of the alloying elements leads to larger hardening, the Ti or Nb addition is more effective than the V addition at the same amount. With Nb or Ti substitution into the 0.1V alloy, the hardness of α grains becomes significantly increased. Fig. 2 shows the three-dimensional V and Ti atom maps of α grains in the 0.2V, 0.2Ti and 0.1V-0.1Ti-added alloys, i.e. with almost the same amount of addition isothermally transformed at 923K, respectively. The clusters in these maps are alloy carbides, whose number density and average radius are shown correspondingly. It is clear that the dispersion of TiC in (b) is much finer than the case of VC in (a). Through the substitution of 0.1V by 0.1Ti, i.e. from 0.2V into 0.1V-0.1Ti, the dispersion of precipitates becomes much finer as shown (c) and (d), while the difference between 0.1V-0.1Ti and 0.2Ti is relatively small. V and Ti atoms are enriched into the same regions, indicating that co-precipitation of V and Ti. Since, combined addition of alloying elements resulted in slow coarsening during further annealing [5], it is an alloy designing method worthwhile for exploring further in industrial applications.

Also, crystallographic character of ferrite (α) /austenite (γ) interface is also an important factor in refinement of carbide dispersion. Figs. 4(a) and (b) show the variations in number density and size of VC precipitates with the deviation angles of orientation relationship (OR) from the exact K-S one (Δθ), respectively [6]. According to these figures, as α/γ OR deviates from the exact K-S OR, number density of VC increases significantly at first and remains almost constant at Δθ larger than 5 degree. In contrast, the effect of Δθ on the VC size appears to be relatively trivial. Nano-indentation experiments at the same region of the 3DAP analyses clearly demonstrated that finer VC dispersion corresponds to higher nano-hardness [3]. Thus controlling α/γ boundary character in processing can be an interesting idea for further strengthening in low-carbon steels.

This work was funded through the CREST Basic Research Program entitled “Creation of Innovative Functions of Intelligent Materials on the Basis of Element Strategy”.

References [1] Y. Funakawa et al., ISIJ Int. 44, 1945 (2004). [2] N. Kamikawa et al., ISIJ Int. 54, 212 (2014). [3] Y. -J. Zhang et al., Acta Mater. 84, 375 (2015). [4] Y. -J. Zhang et al., CAMP-ISIJ, The 171st ISIJ meeting, Tokyo (2016). [5] Y. Funakawa, K. Seto, Tetsu-to-Hagané 44, 1945 (2004). [6] Y. -J. Zhang et al., Scripta Mater., 69, 17 (2013).

Fig. 1 Variations in α hardness with V, Nb and Ti fraction added. Open and solid symbols indicate single and multiple additions, respectively.

Fig. 2: Element maps of α in (a) 0.2V, (b) 0.2Ti, and (c), (d) 0.1V-0.1Ti alloys transformed at 923K. (a), (c) : V maps, (b), (d): Ti maps.

Fig. 3 Variations in (a) number density and (b) size of VC with misorientation angle from the K-S orientation relationship at the interface, Δθ.


28

Microstructure characterization of structural materials by laser assisted 3D atom probe

Taisuke Sasaki, Byeong-Chan Suh, Tadakatsu Ohkubo, Kazuhiro Hono Research Center for Magnetic and Spintronic Materials,

National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, Japan Email: [email protected]

Recent successful implementations of pulse lasers to assist field evaporation substantially improved the yield of

success in 3D atom probe (3DAP) analyses of "easily ruptured" specimens such as martensitic steel. The specimen preparation using a dual beam FIB machine also made it possible to perform site-specific 3D atom probe analysis from grain boundaries and interfaces etc.. These advances have broadened the application areas of the atom probe technique. In this talk, we will overview our recent work on the analysis of some structural materials by 3D atom probe. 1. Boron partitioning behavior in 9Cr martensitic steel

Creep strength of a martensitic 9Cr steel is substantially improved by the trace addition of boron [1]. However, the mechanism for the improved creep property is still under debate due to the technical difficulties to detect light elements in high resolution (e.g. segregation of born along the grain boundaries and nanoscale secondary phase). This study aims at clarifying the boron partitioning behaviour in 9Cr steel by 3DAP.

To investigate the boron partitioning behaviour by 3DAP, a needle like specimen including a prior austenite grain boundary and a secondary phase was prepared using dual-beam FIB/SEM as shown in Fig. 1 (a). Figure 1 (b) and (c) show the 3D atom map including B and C, and Nb and V, respectively. Note that the line in Fig. 1 (c) shows the prior austenite grain boundary. As shown in Fig. 1 (b), boron is enriched in the carbon enriched particle. Beside the carbide, there are two particles enriched in Nb and V, which is expected to be Nb/V nitride particle. However, there is no boron segregation along the prior austenite grain boundaries.

2. Chemistry of oxide particles in oxide dispersion strengthened Co-based superalloy Co-based alloys are used as stationary turbine blades and combustion containers of the industrial gas turbine. Since

the discovery of the Co–Al–W based alloy strengthened by γ’ phase of Co(Al,W)3, which is stable even above 1000 OC, the service temperature of the Co-based alloy has substantially increased [2]. Oxide dispersion strengthening (ODS) can be another promising way to increase the service temperature since the oxide particles such as Al2O3, and Y2O3 have melting temperatures of above 2000 oC, which is higher compared to that of γ’ phase.

Figure 2 shows 3D atom map obtained from a Co-3Al-1.5Y2O3-1.2Hf ODS alloy. Majority of fine oxide particles are Al2O3 phase. At the oxide matrix interface, Y and Hf are segregated. The fine oxide dispersion was kept during annealing at 1000oC. This is because their growth is inhibited by the solute drag-like effect by Y and Hf segregated at the Al2O3/matrix interface.

References [1] M. Tabuchi, H. Hongo, F. Abe, Metall. Mater. Trans. A, 45, 5068 (2013). [2] J. Sato, T. Omori, K. Oikawa, I. Ohnuma, R. Kainuma, K. Ishida, Science 312 90-91 (2006).

Figure 2: (a) 3Datom map of Al, Y and Hf, and O obtained from a hard region in the as sintered sample, (b) is proximity diagram analyzed from an Al-enriched oxides displayed using the isoconcentration surface of Al.

Figure 1 (a) BSE image of sharp and needle-like specimen, and 3DAP maps of (b) C/B, and (c) V/Nb elements


29

Computational Modeling on Inelastic Deformation of Thermosetting Polymers Based on Molecular Chain Behavior

Makoto UCHIDA1), Yoshiteru AOYAGI2), Kazuyuki SHIZAWA3) 1) Graduate School of Engineering, Osaka City University (3-3-138 Sugimoto, Sumiyoshi-ku, Osaka, Japan)

2) Graduate School of Engineering, Tohoku University (6-6-01 Aoba, Aramaki, Aoba-ku, Sendai, Japan) 3) Department of Mechanical Engineering, Keio University (3-14-1 Hiyoshi, Kohoku-ku, Yokohama, Japan)


The fiber-reinforced polymers are widely used in the engineering structures as an alternative material of metals. The thermosetting polymer is usually employed for matrix of the composite. For the sake of improvement of performance of composite materials, a theoretical model, which can predict the complicated characteristics in the mechanical behavior of polymer matrix (e.g., nonlinearity and rate-dependency of the stress-strain relationship, effects of the cure condition, aging, ultraviolet on the mechanical property), is very important. Usually, linear or simple nonlinear constitutive models, which are developed to reproduce the mechanical behavior of metals, are employed for thermosetting polymer matrix. However, to reflect the microscopic information obtained from experiments in microscopic scale and molecular dynamics simulation, a specific constitutive model for the thermosetting polymer should be established based on the kinetics of molecular chain.

Our research group developed the molecular chain plastic model [1, 2] and the molecular chain network model [3, 4] to reproduce the mechanical behaviors of thermoplastic polymers. These models can represent the time-dependent nonlinear stress-strain relationship from small to very large strain range of the materials. In this study, the concept of the molecular chain network model is primarily presented. In the molecular chain network model, the 8-chain model [5] is employed for the constitutive equation of thermosetting polymer. This model can represent the hardening of material due to orientation of the molecular chain. In this equation, two material parameters, CR, the rubber elasticity modulus, and N, the number of the segment for a chain, are used. Effects of these parameters on the stress-strain response are shown in Fig.1. The slope of the stress-strain curve increases with CR while the elongation and slope increase with N. Based on this model, nonlinearity and rate-dependency are introduced into the model.

(a) Effect of CR (b) Effect of N Fig. 1. Effects of material parameters on the stress-strain response of thermosetting polymer.

References [1] H. Hara and K. Shizawa, Advanced Structured Materials, 64, 97 (2015). [2] H. Nada, H. Hara, Y. Tadano and K. Shizawa, Int. J. Mech. Sci., 93, 120 (2015). [3] Y. Tomita, T. Adachi and S. Tanaka, Eur. J. Mech. A/Solids, 16, 745 (1997). [4] M. Uchida and N. Tada, Int. J. Plast., 49, 164 (2013). [5] E. M. Arruda and M. C. Boyce, J. Mech. Phys. Solids, 41, 389 (1993).

CR=25MPa, N=1.10CR=50MPa, N=1.10CR=75MPa, N=1.10CR=100MPa, N=1.10

Stre

ss [M

Pa]

Strain0 0.1 0.2 0.3 0.4 0.5 0.6

250

500

750

1000

1250

CR=50MPa, N=1.05CR=50MPa, N=1.10CR=50MPa, N=1.15CR=50MPa, N=1.20

Stre

ss [M

Pa]

Strain0 0.1 0.2 0.3 0.4 0.5 0.6

250

500

750

1000

1250


30

Unsolved Issues in Ti Alloys: Microstructure and Fatigue

Kaneaki TSUZAKI1), Nobuhiro TSUJI2)

1) Kyushu University, Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan 2) Kyoto University, Yohida-honmachi, Sakyo-ku, Kyoto 606-850, Japan


Materials science and engineering in Japan has so high competitiveness in the world that we are in the position to lead both academia and industry in this field. In order to establish the innovation of structural materials which greatly advance and meet the demands of society for new occurrence such as environmental issues, there are continuous stringent requirements for the improvement of various properties in the structural materials. However, research field on structural materials are diverse across the several research fields. We will contribute to the success of the SIP for innovative structural materials, taking the responsibility of being the parts of Materials Integration Region with a number of advanced researches on "interface" as the keyword.

In this research project, we take the following five research issues, individual theme, as specific indispensable themes

to success of the SIP for innovative structural materials. (1) Casting and solidification (Super alloy): process (2) Formation of interface microstructure (Ti alloy): process (3) Fatigue and fracture (Ti alloy): property (4) High temperature phenomena (Ceramics): property (5) Hydrogen embrittlement (High strength steel): property These research topics are fundamental but critical. They are relating to the formation of microstructure in structural

materials through solidification, phase transformation, deformation, recrystallization, and grain growth. They are also relating to the controlling factors of performance of structural materials such as fatigue, creep and hydrogen embrittlement. This project is not only aiming to solve the individual theme as an example but also to provide base fundamental tools and general-purpose data that enable to predict the performance and to accelerate the development of various structural materials. We also play the role of "interface" to bridge SIP and other projects carried out in such as MEXT and METI projects on a variety of structure materials. The results of this challenge will serve to strengthen the sustainable innovation and academic field on structural materials.

In the SIP-IMASM symposium, we will present our current results of the research on aerospace titanium alloys:

microstructure and fatigue. Inter-unit researches with IMASM are also introduced.

Fig.1 Research target and problems. Fig.2 Complicated thermo-mechanical process.

+

Compressor Discs of Jet Engines

-What is the strong and weakest microstructures for creep and fatigue?- How can we obtain the strong microstructure without weak structures?

Problems

Shorter R&D lead time


31

Evaluation of Crack Occurrence from Microscale Strain Distributions of Titanium Alloy in Tensile Tests by Advanced Moiré and DIC Techniques

Q. Wang1), S. Ri1), Y. Tanaka2), K. Naito2), M. Koyama3), K. Tsuzaki3), M. Ohkubo1) 1) Research Institute for Measurement and Analytical Instrumentation, National Institute of Advanced

Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568, Japan 2) National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan

3) Department of Mechanical Engineering, Kyushu University, 744 Motooka Nishi-ku, Fukuoka 819-0395, Japan E-mail: [email protected]

Full-field deformation analysis of titanium (Ti) alloys were performed in a small region around a notch root and in a large area by using digital image correlation (DIC) and Moiré methods complementarily. Prediction of crack occurrence positions were successful through microscale strain distribution measurement. Slip line formations in oblique angles were found to arise during tensile tests.

Background Heat-resistant Ti alloys hold great promise for applications in aircrafts, spacecrafts, automobiles, etc. To understand

instability behaviour and find out failure mechanisms, it is imperative to investigate its microscale deformation distribution before crack occurrence under tensile loads non-destructively.

Experiments and methods Two specimens of Ti-6Al-4V were analysed by DIC and Moiré methods. The thicknesses and the minimum widths

of the specimens were 1 mm and 1.8 mm, respectively. For the specimen #1, a notch with a width of 5 μm and a length of 100 μm was formed by focused ion beam milling, and a cross grating pattern with a pitch of 500 nm was fabricated by electron beam lithography in an area of 500×500 μm2 around one end of the notch (Fig. 1(a)). For the specimen #2, a cross grating pattern with a pitch of 3 μm was produced by UV nanoimprint lithography in an area of 1.8×15 mm2. For the specimen #1, the tensile test was carried out in a QUANTA scanning electron microscope, and the deformation distribution in a small region near the notch were analysed by DIC [1]. For the specimen #2, the tensile test was performed under a LASERTEC laser scanning microscope. Full-field deformation distributions in a large area were measured by a developed single-shot spatial phase-shifting Moiré method [2] to visualize stress concentration spots.

Strain distributions before micro crack occurrence Figure 1 shows the distributions of x-direction strain, y-direction strain, and shear strain in 23×18 μm2 for #1 under

511 MPa, and ones under 537 MPa in 219×204 μm2 for #2. For #1 with the notch, the x-direction strain is maximum and the y-direction strain is minimum along the oblique line from the middle of one end of the notch as shown in Figs. 1(c)-1(e). For #2 without a notch in Figs. 1(h)-1(j), the high strain yellow spots shows a cross pattern, which may be peculiar to a lamella microstructure of the Ti alloy with indication of crack formation positions. Our experiments have verified that a crack occurs along the oblique line on #1, and slips emerges along the cross pattern on #2. Under a greater tensile load, the cracks appear at the regions marked by the blue circles shown in Figs. 1(b) and 1(g). It has been demonstrated that the microscale strain distribution measurement enables accurate prediction of crack occurrence.

Fig. 1. (a)-(e) grating pattern for DIC and strain distributions in 23×18 μm2 on a Ti alloy with a notch, and (f)-

(j) grating pattern for Moiré method and strain distributions in 219×204 μm2 on a Ti alloy without a notch.

References [1] Y. Tanaka, K. Naito, S. Kishimoto and Y. Kagawa, Nanotechnology, 22, 115704 (2011).

[2] Q. Wang, S. Ri, H. Tsuda, S. Kishimoto, Y. Tanaka, Y. Kagawa, Proc. SPIE, 9524, 95240I (2015).


32

Material and performance design of ceramics coating – the case study of thermal barrier coating

Hideaki Matsubara Tohoku University

Graduate School of Environmental Studies Aoba 6-6-2-20 Aramaki Aoba-ku Sendai 980-8579, Japan


The Monte Carlo (MC) method and the finite element method (FEM) have been used for the simulations of the

microstructures. The MC simulation was applied to the microstructural development of sintering and grain growth at the solid state and under the presence of a liquid phase. The compound effects of the second particle, liquid phase and anisotropy were successfully analyzed by the MC simulations in order to design complex and important microstructures in sintered materials. The MC simulation has currently remarkable development for the capability to design complex three-dimensional microstructure involving continuous or network structure of particles or pores in sintered materials. Furthermore, the combination method between MC and FEM has been developed to predict precise shrinkage behaviors during sintering process.

In the Japanese national project, "Structural Material for Inovation, Cross-ministerial Strategic Innovation Promotion Program(SIP), computer simulation studies are promoted for the design of ceramics coating materials. We study the computer simulation for microstructure of ceramics coating with pore, gap and particle with nano scale and the microstructure change during coating process and long time working at high temperature. Microstructure change, mechanical properties degradation and peeling (delamination) are also predicted by the simulation.

Fig.1 Images of simulation for ceramics coating.

Fig. 2 Simulation for microstructure development at the initial stage of deposition. (a)horizontal substrate, (b)tilted substrate, (c)porous structure by substrate rotation.

Fig. 3 Simulation for sintering of porous coating layer.


33

Advance techniques for analysis of microstructure and chemical states their developments and combination with materials informatics

in order to reveal a crack formation and its propagation

M. Kimura1,2), Y. Takeichi1,2), Y. Niwa1), R. Kitazawa1), K. Kimijima1), H. Nitani1,2), T. Ishii1), M. Ito1), K. Takahashi1) , H. Abe1,2), A. Hori1)

1)High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki, Japan 2) Dept. Mater. Structure Sci., School of High Energy Accelerator Sci., SOKENDAI (The Graduate University for Advanced Studies)

Tsukuba, Ibaraki 305-0801, Japan E-mail: [email protected]

In order to reveal crack formation and its propagation in structural materials such as carbon fiber reinforced plastic (CFRP) composites, heat-resistant alloys, and thermal and environmental barrier coatings (TBC and EBC), we need to obtain the three-dimensional (3D) information not only on their microstructures but also on the chemical states of composing elements. This is because crack formation and its propagation are affected by the inhomogeneity or heterogeneity in microstructures and bonding between and/or within composites that progress during heat cycles in air in service. These microscopic heterogeneities are often the main factors causing macroscopic stress, and thus are very important to design the composite materials in terms of micromechanics.

Macroscopic heterogeneity We have developed in situ observation techniques of microstructure with a mechanical load, and applied to CFRP, TBC, and EBC in collaboration with materials developing teams such as A02, A11, and C41. A typical example is shown in Fig. 1: microstructures of TBC, as deposited and after 300 heat cycles. EBC specimens, ZrO2-4mol.%Y2O3 / Co-32wt.%Ni-21wt.%Cr-8wt.%Al-0.5wt.%Y / IN738LC, were heat-treated for various number of cycles: heating at 1393 K for 40 min. and cooling at 393 K for 5 min. Quantitative analysis of the change of microstructure is now on progress, and the effects of sintering during heat cycles are being investigated in collaboration with materials informatics (MI) teams such as D68 and D69.

We have also established the observation approach of 2D chemical-state mapping using x-ray absorption fine structures (XAFS) [1-3]. This approach was applied to investigate the reduction reaction of iron-ore sinters. The heterogeneity of iron states: FeIII, FeII, and Fe0, could be mapped with a special resolution as small as 20 μm. It was shown that the reduction reaction initiates and progresses heterogeneously within a specimen, depending on the chemical compositions. The heterogeneous reduction results in crack formation, and the relationship between the heterogeneity of iron chemical states and crack formation is now being scrutinized using a mathematical approach of homology in collaboration with a MI team of D72.

Microscopic heterogeneity We have finished designing a new observation system of XAFS-CT where microstructures and chemical states can be observed simultaneously with a spatial resolution as small as 50 nm using synchrotron radiation. The collimated x-ray beam shines a specimen, and the transmitted beam was focused using Fresnel zone plate (FZ) (Fig.2). We demonstrated the validity of this approach by the experiments at SSRL facility in USA. We successfully measured the heterogeneity of microstructures and chemical states in specimens such as iro-ore sinters, Ni-supper alloy, and a sinter plate of Yb2Si2O7. The new system is now under construction and will be installed at the beamline of NW2A at Advanded Ring (AR), KEK in 2016FY.

Scale-bridging and collaboration with MI We plan to combine the microscopic and macroscopic approaches to achieve a multi-scale analysis or scale-bridging in collaboration with MI teams, and apply these approaches to CFRP composites, heat-resistant alloys, and TBC/EBC with materials developing teams.

References [1] M. Kimura, Y. Takeichi et al., Procd. of Asia Steel int. conf. 2015(Yokohama, Oct. 5 – 8, 2015). [2] M. Kimura, Y. Takeichi et al., Invited talk at Denver X-ray conference 2016, and the proceeding paper in preparation. [3] M. Kimura , Y. Takeichi et al., Presented at Int. conf. X-ray Microscopy conference 2016, and the proceeding paper in

preparation.

Fig.1 Microstructures of TBC: as deposited and after 300 heat cycles.

Synchrotron radiation (undulator)Capillary (X-ray condensor)

SpecimenDetector Fresnel zone plate

Fig.2 Schematic of the new system of XAFS-CT that will be installed at AR NW2A, KEK in 2016FY.


34

Advanced in situ multi-scale characterization of hardness of carbon-fiber-reinforced plastic

Hongxin Wang1), Hideki Masuda1), Hideaki Kitazawa1), Keiko Onishi1), Masamichi Kawai2), and Daisuke Fujita1) 1) National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan

2) University of Tsukuba, Tsukuba, Ibaraki 305-8577, Japan


Hardness is a functional indicator of characterization of soft or hard materials. Generally, it is the local area mechanical properties of materials response to the overall performances under certain conditions. Hardness is a measurable parameter, mainly used to test the mechanical quality of materials and to determine a reasonable processing technology.

Carbon-fiber-reinforced plastic (CFRP) [1] is one of the most-advanced composite materials with a high-strength structure. This kind of composite material contains two parts: a carbon-fiber-reinforcement part (which provides strength) and a plastic-matrix part (which binds the reinforcement together). Since CFRP is lighter than aluminum, stronger than iron, and has higher elasticity than titanium, it is widely used for industrial applications such as aerospace [2], automobile [3], civil engineering [4], and sports goods [5]. The achievements of modern industry have benefited greatly from testing and evaluation of the mechanical properties of materials. In practice, testing and evaluation of the hardness of materials are a direct bridge connecting material design and industrial applications. Consequently, for developing CFRP in various industrial fields, it is very important to understand the hardness of CFRP.

In situ multi-scale characterization of hardness of CFRP is demonstrated by a traditional hardness tester [6], instrumented indentation tester [7] and atomic-force-microscope (AFM)-based nanoindentation [8]. In particular, due to the large residual indentation and nonuniform distribution of the microscale carbon fibers, the Vickers hardness could not be calculated by the traditional hardness tester. In addition, the clear residual microindentation could not be formed on the CFRP by instrumented indentation tester because of the large tip half angle of the Berkovich indenter. Therefore, as shown in an AFM image (Fig. 1), an efficient technique for characterizing the true nanoscale hardness of CFRP was proposed and evaluated. The local hardness of the carbon fibers or plastic matrix on the nanoscale did not vary with nanoindentation location. The Vickers hardnesses of the carbon fiber and plastic matrix determined by AFM-based nanoindentation were 340 ± 30 kgf/mm2 and 40 ± 2 kgf/mm2, respectively.

Fig. 1. (a) (b) and (c) AFM images of cross sections of CFRP. AFM nanoindentation test on (b) plastic matrix (PM), and (c) a carbon fiber (CF). Loading force: (b) 1.1, 1, 0.7, 0.8, and 0.9 μN; (c) 5, 5.5, 6, 6.5, and 6.9 μN (from top to bottom).

References [1] C. Bakis, L. Bank, V. Brown, E. Cosenza, J. Davalos, J. Lesko, A. Machida, S. Rizkalla, and T. Triantafillou, J. Compos.

Constr. 6, 73 (2002).

[2] C. Soutis, Mater. Sci. Eng. A, 412, 171 (2005).

[3] R. Shida, K. Tsumuraya, S. Nakatsuka, and J. Takahashi, 9th Japan Int. SAMPE Symp. 2005.

[4] V. Karbhari, J. Chin, D. Hunston, B. Benmokrane, T. Juska, R. Morgan, J. Lesko, U. Sorathia, and D. Reynaud, J. Compos. Constr. 7, 238 (2003).

[5] NetComposites, ICC and Kookaburra Agree to Withdrawal of Carbon Bat, 2006.

[6] S.A. Shahdad, J.F. McCabe, S. Bull, S. Rusby, and R.W. Wassell, Dent. Mater. 23, 1079 (2007).

[7] M.R. VanLandingham, J. Res. Natl. Inst. Stand. Technol. 108, 249 (2003).

[8] H. Nili, K. Kalantar-zadeh, M. Bhaskaran, and S. Sriram, Prog. Mater. Scie. 58, 1 (2013).

CF

PM(a) (c CF PM

5.0 μ

5.5 μ

6.0 μ

6.5 μ

6.9 μ

(b)

PM

1.1 μ

1.0 μ

0.7 μ

0.8 μ

0.9 μ

CF

CF


35

Development of ~3.2micron band efficient mid-IR laser for the application to Laser Ultrasonic Testing of CFRP

Hideki Hatano1), Masahiro Kusano2), Makoto Watanabe2), Shunji Takekawa1), Hisashi Yamawaki2), Kanae Oguchi3), Manabu Enoki3) 1) Electroceramics Gr., National Institute for Materials Science, 1-1, Namiki, Tsukuba-shi, Ibaraki 305-0044 Japan

2) Integrated Smart Materials Gr., National Institute for Materials Science, 1-2-1, Sengen, Tsukuba-shi, Ibaraki 305-0047 Japan 3) University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033 Japan


Carbon composite material such as carbon fiber reinforced plastic (CFRP) is a unique structural material that is both strong and lightweight. Its potential use in many technologies is widely recognized and it is beginning to appear in some transportation products (Boeing Dreamliner, Airbus 380, and BMW i3 car). One key aspect of composite technology is the need for a non-destructive diagnostic to detect flaws during both composite manufacturing and during its service life. Laser ultrasonic testing (LUT) is a promising method to detect flaws. However current LUT technology for CFRP uses a pulsed CO2 TEA laser for ultrasonic generation, but a smaller lightweight solid state light source is more desirable. Recent work [1] has shown that light with a wavelength in the vicinity of 3.2 μm (the strong carbon-hydrogen stretching absorption band in epoxy resin) is suitable for ultrasonic generation in CFRP materials. At present, there is no commercial mid-IR light source suitable for applying LUT for CFRP.

We have reported the development of an efficient, high pulse energy mid-IR light source using quasi-phase-matched (QPM) optical parametric oscillation (OPO) in periodically poled Mg-doped stoichiometric LiTaO3 (Mg:SLT) crystal as the nonlinear optic material. We demonstrated effective ultrasonic generation capability of mid-IR laser (~3.2μm) with the least laser damage compared with Nd:YAG 1.06μm wavelengths[2]. Fig.1 shows the OPO wavelength converter we developed, which emits >10mJ mid-IR output from 50mJ pump laser of 1.06micron wavelength.

On top of this, recently [3], we demonstrated a further increase in idler conversion efficiency using difference mixing. The OPO downconverts a pump light of frequency ωp into two frequencies: a signal frequency ωs and idler frequency ωi such that ωp=ωs+ωi. Energy conservation indicates that one signal and one idler photon are generated for each pump photon that is converted, which limits the idler photon conversion efficiency. If a difference frequency mixing (DFM) process is added to the cavity, the unwanted signal wave can be further downconverted into the desired idler wave and a difference frequency ωd =ωs-ωi. This additional mechanism of idler generation increases the overall conversion efficiency for the idler output and can be realized as intracavity OPO+DFM as is shown schematically in Fig.2. The QPM PPSLT technology is used to compensate the phase mismatch in both the OPO and the DFM processes.

In this talk, we demonstrate our mid-IR laser source and defect detection in CFRP samples using the developed mid-IR laser as ultrasonic generation source.

.

References [1] M. Dubois, P. W. Lorraine, R. J. Filkins, T. E. Drake, K.R. Yawn K R and S-Y Chuang, Ultrasonics, 40, 809 (2002).

[2] H. Hatano, M. Watanabe, K. Kitamura, M. Naito, H. Yamawaki and R. Slater, J. Opt. 17, 094011 (2015).

[3] H. Hatano, M. Watanabe, S. Takekawa, H Yamawaki, K. Oguchi, M. Enoki and R Slater, CLEO 2016(San Jose, USA), JTh-2A (2016).

Fig.1. A photograph of developed OPO wavelength conversion module and the optical resonator inside it.

isp

111+=

i

i

s

s

p

p

OPO

TnTnTn )()()(1 111=

isd

111=

d

d

i

i

s

s

DFM

TnTnTn )()()(1 222=

Fig. 2. Concept of photon recycling using OPO+DFM

configuration. The symbols ω, λ, Λ, n, T represent radian frequency, wavelength, QPM grating pitch, optical index, temperature, respectively, and subscripts p, s, i, d denote pump, signal, idler, differential, respectively.


36

Poster papers

IMASM CFRP & Polymer


37

Effect of free volumes on mechanical properties of epoxy resins for carbon-fiber-reinforced polymers

T. Kakizaki1), H. J. Zhang1), S. Sellaiyan1), A. Uedono1), Y. Taniguchi2), K. Hayashi2) 1) Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan2) Epoxy Resin

Materials Center, Nippon Steel & Sumikin Chemical Co. Ltd., Kitasode 11 5, Sodegaura, Chiba 299-0266, Japan

E-mail: [email protected]; [email protected]

Positron annihilation is a non-destructive tool for investigating vacancy-type defects and open spaces (free volumes) in materials. Detectable defects are monovacancies to open spaces with the size of sub-nm in crystalline and amorphous materials. It has no restriction of sample temperature or conductivity. This technique can be applied to a variety of materials, such as metals, semiconductors, insulators, and polymers.

When a positron is implanted into amorphous polymers, positronium (Ps: a hydrogen-like bound state between a positron and an electron) may form in open volumes. Ps exhibits two spin states: para-Ps (p-Ps), a singlet state, and ortho-Ps (o-Ps), a triplet state. The intrinsic lifetimes of p-Ps and o-Ps are 125 ps and 142 ns, respectively [1-3]. p-Ps annihilates via the 2-γ process, and the energy of the emitted γ-rays is 511 keV (pL ≅ 0). o-Ps primarily exhibits three-photon (3γ) annihilation that produces a continuous energy distribution from 0 to 511 keV. When o-Ps is trapped by free volumes, the positron involved in o-Ps may annihilate with an electron of free volume interiors to emit two γ-rays before 3γ-annihilation (pick-off annihilation). A large free volume reduces the probability of this process and increases the o-Ps lifetime. Thus, one can estimate the size of free volumes from the measurements of the o-Ps lifetime. In this study, we have used positron annihilation spectroscopy to study correlations between the size of free volumes and the mechanical properties of epoxy resins for CFRP.

Epoxy resins for CFRP with different properties were prepared. For those samples, we have varied curing agents, thermoplastics, curing conditions, etc. The tensile and flexural properties were measured at room temperature. Clear correlations between o-Ps lifetime (the size of free volumes) and the mechanical properties, such as tensile modulus, tensile strain at break, flexural modulus, flexural strength, and flexural strain at break, were revealed (Fig. 1). However, no clear correlation between fracture toughness and the free volume size was found. Those results suggests that the free volumes size affects the mechanical properties in the epoxy resins.

It was demonstrated that positron annihilation can be used as a sophisticated non-destructive observation technique to characterize epoxy resins for CFRP.

References [1] Principle and Application of Positron and

Positronium Chemistry, Ed. Y. C. Jean and D. M. Schrader (World Scientific, Singapore, 2003) p. 167.

[2] A. Uedono, S. Murakami, K. Inagaki, K. Iseki, N. Oshima, and R. Suzuki, Thin solid films 552, 82 (2013).

[3] A. Uedono, S. Armini, Y. Zhang, T. Kakizaki, R. Krause-Rehberg, W. Anwand, A. Wagner, Appl. Surf. Sci. 368, 272 (2016).


38

Temperature dependences of free volumes and mechanical properties of epoxy resins for CFRP

H. J. Zhang1), S. Sellaiyan1), T. Kakizaki1), A. Uedono1), Y. Taniguchi2), K. Hayashi2) 1) Division of Applied Physics, Faculty of Pure and Applied Science, University of Tsukuba, Tsukuba, Ibaraki 305-8573, Japan

2) Epoxy Resin Materials Center, Nippon Steel & Sumikin Chemical Co. Ltd., Kitasode 11 5, Sodegaura, Chiba 299-0266, Japan

E-mail: [email protected]; [email protected]

Six types of epoxy resins with different chemical structures were designed as the matrices of CFRP. Positron annihilation spectroscopy was utilized to evaluate the temperature dependence of free-volume holes in the samples in the temperature range from 30 to 210 [1]. The variation of free-volume hole size as a function of temperature could be fitted by two fitting lines. The intersection point of the fitting lines, which is denoted as Tg(PAL), corresponds to the glass transition temperature (the threshold temperature of segmental motion of the polymers). The dynamic mechanical analysis was carried out to study the temperature dependence of mechanical properties including the storage modulus, loss modulus, and the corresponding damping factor. It was found that, from the temperature of Tg(PAL), the storage modulus begins to decrease drastically with increasing temperature, while the loss modulus begins to increase with increasing temperature. The experimental results indicate that, positron annihilation spectroscopy could be utilized to characterize the change of microstructure of the epoxy resins.

References [1] Y. C. Jean, J. D. Van Horn, W. -S. Hung, and K. -R. Lee, Macromolecules 46, 7133 (2013).


39

Non-destructive evaluation of defects in CFRP samples by OPO mid-IR laser ultrasonic testing

Masahiro Kusano1), Hideki Hatano2), Makoto Watanabe1), Shunji Takekawa2), Masanobu Naito3), and Hisashi Yamawaki1) 1) Integrated Smart Materials Gr., National Institute for Materials Science, 1-2-1, Sengen, Tsukuba-shi, Ibaraki 305-0047 Japan

2) Electroceramics Gr., National Institute for Materials Science, 1-1, Namiki, Tsukuba-shi, Ibaraki 305-0044 Japan 3) Adhesive Materials Gr., National Institute for Materials Science, 1-2-1, Sengen, Tsukuba-shi, Ibaraki 305-0047 Japan


Introduction

Carbon fiber reinforced plastics (CFRPs) are used as constructive materials of airplanes, space crafts and automobiles because their specific properties are higher than those of metal materials. While CFRPs are applied to main parts in products, the demand of their reliability and safety are also on the rise. CFRP products can have defects such as voids, delamination, and cracks during manufacturing processes and in-service periods. In order to detect such defects in advance, non-destructive testing (NDT) methods are needed.

We developed laser ultrasonic testing (LUT) equipment provided with the mid-IR OPO laser for effective generation of ultrasonic wave in CFRPs. In my poster presentation, some results of defected CFRP samples measured by the equipment will be shown. Materials and methods

As an artificially defected samples, a 2 mm thick CFRP with a hole 1 mm diameter was prepared. The scanning area and the cross section are shown in Fig.1 (a) and (b), respectively. In our LUT equipment, mid-IR laser ( ) is irradiated on a sample for the generation of ultrasonic wave. The wave is detected by a laser interferometer ( ) so that the equipment can achieve not only non-destructive but also contactless measurement. The equipment can be used both in transmission mode and reflection mode. Further details are described in reference [1]. Results

As shown in Fig 1 (c), the blue area of C-scan image in transmission mode corresponds to the hole part because the ultrasonic wave is difficult to propagate through an air gap such a hole. On the other hand, the yellow and green areas in reflection mode in Fig. 1 (d) also show the hole part because ultrasonic wave reflects at the hole. In the same way, our equipment can detect voids, delamination, and adhesion failure areas between CFRP/CFRP or CFRP/metal.

Conclusion These results indicate that our LUT equipment can be a promising NDT method for CFRP products. For more

extended application, we improve the equipment more for challenging problems such as thicker samples, fine defects, and intricately shaped products.

References [1] H. Hatano, M. Watanabe, K. Kitamura, M. Naito, H. Yamawaki, and R. Slater, J. Opt., 17 (9,) 094011(2015).

Fig. 1. (a) Scanning area and (b) cross section of the sample. C-scan images of CFRP samples with defects in (c) transmission mode (d) reflection mode.


40

Numerical analysis of ultrasound propagation excited by mid-IR laser at delamination in CFRP laminate

Kanae Oguchi1), Manabu Enoki1), Hisashi Yamawaki2) , Hideki Hatano3) , Masahiro Kusano2) , Makoto Watanabe2) 1) Department of Materials Engineering, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656 Japan

2) Integrated Smart Materials Gr., National Institute for Materials Science, 1-2-1, Sengen, Tsukuba-shi, Ibaraki 305-0047 Japan 3) Electroceramics Gr., National Institute for Materials Science, 1-1, Namiki, Tsukuba-shi, Ibaraki 305-0044 Japan


CFRP are used as structure materials of aircraft for their light weight, high strength and rigidity. During the operation, under the dynamic load in a harsh environmental condition, periodical NDT is necessity for aircraft parts to avoid the fatal defect which lead to severe accidents. Thus effective on-line quality inspection method is demanded. Dubois presented that the irradiation of the light with the wavelength in the vicinity of 3.2μm can excite the ultrasound wave effectively in CFRP for the appropriate value of optical depth [1]. We are developing an optical parametric oscillator to generate mid-IR light, and trying to build an accurate and efficiency LUT system for CFRP using a mid-IR light [2]. To develop the practical system, effects of the various factors such as laser parameters, optical depth and propagation tendency in CFRP should be taken into account. In the present study, laser ultrasound propagation simulations were carried out in 7 ply CFRP laminate and CFRP matrix resin, by considering the optical depth of the material and laser irradiation conditions. The comparison between the simulation and experimental results shows the good agreement and verify the applicability of the model. Furthermore, ultrasound propagation simulation in CFRP with delamination be is carried out.

The numerical model of ultrasound propagation is established with FEM. The 7 ply CFRP is modelled using the physical properties of Unidirectional CFRP (UD-CFRP). As shown in Fig. 1, the model incorporates all 7 ply layers individually at the appropriate location in a laminate using the corresponding rotated stiffness matrices of the UD-CFRP. Then the square shape delamination is located at interlaminar region of the laminate. When the surface of the specimen is irradiated laser, the heated region with curtain thickness in depth direction is generated. In a heated region, the temperature distribution in a depth direction was set based on the relation of the optical depth and the laser intensity. The pulse density of 10 mJ and the laser beam radius on the specimen surface of 1 mm are used in calculations. Fig. 2 shows the laser ultrasound propagation in a 7 ply CFRP laminate with and without delamination. The complicated ultrasound propagation behaviour is demonstrated in a figure. In the case with delamination, we can see that the ultrasound reflection wave at the surface of the specimen for the delamination area, and at the edge of the delamination, ultrasound scattering is observed. The simulation was performed with different laser irradiation parameters, then the obtained ultrasound propagation properties are analysed in relation with the size and location of the defect.

References [1] M. Dubois, P. W. Lorraine, R. J. Filkins, T. E. Drake, K.R. Yawn K R and S-Y Chuang, Ultrasonics, 40, 809 (2002). [2] H. Hatano, M. Watanabe, K. Kitamura, M. Naito, H. Yamawaki and R. Slater, J. Opt. 17, 094011 (2015).

Fig. 1 Modeling of CFRP laminate. Fig. 2 Laser ultrasound propagation in 7 ply CFRP laminate with and without delamination.


41

In situ Damage Observation in Carbon Fiber Reinforced Plastic Composite using 3D Computed Tomography

R. Kitazawa1), T. Ishii1), M. Ito1), Y. Takeichi1,2), Y. Niwa1), M. Kimura1,2) 1) High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki, Japan

2) Dept. Mater. Structure Sci., School of High Energy Accelerator Sci., SOKENDAI (The Graduate University for Advanced Studies) Tsukuba, Ibaraki 305-0801, Japan


Carbon fiber and carbon fiber reinforced plastic (CFRP) composite are promising material for application for aircraft and spacecraft by their light weight and high strength and toughness. Determination of a crack initiation and its propagation mechanism develops innovative application. Conventional method for damage characterization is indirect; observation from the surface of a tested specimen is widely used, and the results are considered based on empirical principles and/or according to micro mechanics theories. Recently, in situ X-ray computed tomography (X-CT) using synchrotron radiation has been applied for damage visualization during tensile testing of CFRP composite [1, 2], where damage initiation and propagation mechanism can be observed with a spatial resolution.

In this study, crack initiation and its propagation was investigated using in situ X-CT for multi-layered uni-directional carbon fiber reinforced plastic composites. Then the results were compared with the stress/strain distribution calculated with the finite element method (FEM). 0,90,0 degree multi layered uni-directional carbon fiber reinforced plastic HYEJ25-36, Mitsubishi Rayon Co., Ltd., was machined into tensile specimens of which the shape and dimension are shown in Fig. 1. Tensile strain was applied to the specimen with cylindrical pins inserted into four holes of the specimen and strain was hold during X-CT measurements. Figure 2 shows (a) in situ X-CT image around major damages and (b) schematic of their positions in layers in the specimen observed before macroscopic failure. In Fig.2, position A shows delamination in the parallel direction observed in the 0 degree ply, and position B shows delamination and separation in the 90 degrees ply.

Stress distribution causing damages was simulated with FEM. Equivalent stress was highest in the center of the notch for each layer. Maximum axial stresses were parallel to the fiber alinement. Carbon fiber, Young's modulus of which is higher than that of epoxy resin, accumulates more stress than epoxy resin. Fracture strength perpendicular to the fiber alinement is estimated to be 3% of that parallel to the fiber direction. Initiation of delamination assumed to be mainly influenced by the tensile stress perpendicular to the fiber direction and the shear stress. The places of crack and delamination initiation seem to be closely related with the distribution of intermediate principal stress.

It was shown that in situ X-CT provided us the information on crack initiation and its propagation. Further observation, including uni-directional CFRP, and its analysis proceeds in order to predict damages in CFRP components.

Fig. 1 Shape and dimension of the specimen.

References

[1] A. J. Moffat, P. Wright, J.-Y. Buffie`re, I. Sinclair and S. M. Spearing, Scripta Mater., 59, 1043 (2008).

[2] S. C. Garcea, I. Sinclair and S. M. Spearing, Compos. Sci. Technol., 109 32 (2015).

Fig. 2 (a) X-CT image around major damages and (b) schematic of their positions in layers.


42

In-situ measurement of interfacial thermal deformation and residual stress

for hybrid composite materials

Yoshihisa Tanaka1), Kimiyoshi Naito1), Hideki Kakisawa1) 1) National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, Japan,

Phone and fax numbers: +81-29-859-2240 and +81-29-859-2401

Corresponding author’s email: [email protected]

The hybrid composite materials consisting of alternating lightweight metal and carbon fiber-reinforced polymer composite is widely used as fuselage skin materials for aircraft. The composite materials generally have better fatigue and creep resistance, specific strength, and stiffness compared to conventional materials. The mechanical properties of the composite are strongly affected by the interfacial bonding strength and residual stresses. When the composite is cooled down to room temperature from the fabrication temperature, the thermal residual stresses arise from the differential coefficient of thermal expansion (CTE) of the metal and carbon fiber (including longitudinal and transverse direction) [1]. The interface mechanical properties and residual stresses play an important rule in determining the composite strength and the fracture resistance. In the present study, major attention has been focused on the measurement method of local deformation and strain distribution around the interfaces including residual stress.

Conventional titanium alloy Ti–6AL–4V sheet and two types of CFRP reinforced with ultrahigh strength PAN-based (IM600) carbon fiber and ultrahigh modulus pitch-based (K13D) carbon fiber were used in this study. Two types of CFRP/Ti hybrid composites materials (FMLs) were fabricated using an autoclave method.

In order to measure the thermal deformation and strain distribution and residual stress, in-situ heating/cooling stage was installed into the FE-SEM chamber which is having the electron beam lithography system to fabricate a fine patterning (Fig.1(a)). The small sample was cut from the FML using diamond cutting machine. The grid pattern with 1 μm spacing was drawn onto the sample surface using electron beam lithography method. The deformation and strain distribution at the interface during thermal loading was measured by electron moiré method (Fig.1(b)) [2]and digital image correlation methods using In-situ FE-SEM observations at different length scales [3]. The residual stress in CFRP and Ti alloy for both FML to the longitudinal direction can be calculated using CTE and elastic modulus. The tensile residual stress was observed in Ti alloy whereas the CFRP was in compression. The localized compressive strain clearly appears in the epoxy matrix between carbon fibers due to the positive transverse CTE of carbon fiber (Fig.1(c)).

Fig. 1. (a) Experimental setup for in-situ FE-SEM observation with electron beam lithography system installed heating/cooling stage into the chamber, (b) a typical example of macroscopic thermal deformation observed by electron moiré method in the transverse direction, (c) strain distribution around carbon fiber/matrix interface at

the magnification of the boxed region in (b).

Acknowledgement

A part of this research was supported by "Cross-ministerial Strategic Innovation Promotion Program (SIP), Structural Materials for Innovation" from Japan Science and Technology Agency, JST.

References [1] Kulkarni R. and Ochoa O., “Transverse and longitudinal CTE measurements of carbon fibers and their impact on interfacial

residual stress in composites. Journal of Composite Materials”, 40(8), 733-754 (2006). [2] S. Kishomoto, “Electron moiré method”, J. Soc. Exp. Mech., (3)1, 9-14, (2003). [3] Y. Tanaka, K. Naito, S. Kishimoto and K. Kagawa, “Development of a pattern to measure multiscale deformation and strain

distribution via in situ FE-SEM observations”, Nanotechnology, 22, 115704-115709 (2011).


43

Poster papers

IMASM Metals


44

Integrated Analysis of Trace Light Elements in Heat Resistant Alloys − Multiscale Elemental Imaging and XAFS Spatially-Averaged Analysis−

Masataka Ohkubo 1), Paul Fons 1), Shigetomo Shiki 1), Go Fujii 1), Masahiro Ukibe 1), Norimichi Watanabe 2), Hideaki Kitazawa 2), Taisuke Sasaki 2), Tadakatsu Ohkubo 2), Kazuhiro Hono 2), Masao Kimura 3), Yoshinori Kitajima 3), Kazuhiko Mase 3), Fujio Abe 2)

1) National Institute of Advanced Industrial Science and Technology, 1-1-1, Umezono, Tsukuba, Ibaraki, 305-8564, Japan 2) National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, Ibaraki, 305-0047, Japan

3) High Energy Accelerator Research Organization, 1-1, Oho Tsukuba, Ibaraki, 305-0801 Japan


Advanced heat resistant alloys have been developed with, for example, solute strengthening and precipitation strengthening, which result in microstructures in multiscale from grain sizes (~100 µm) to nano-precipitates (~10 nm) for a long term stability at high temperatures. The addition or contamination of trace light elements significantly influence mechanical properties. For example, a 9%Cr martensitic steel with about 100 ppm of boron and nitrogen impurities, which was developed by National Institute for Materials Science (NIMS), has a creep lifetime improved by a factor of more than 100 at 650 °C. The heat resistant alloy is promising for advanced ultra-supercritical (A-USC) boilers. Titanium alloys for aeroengines contain the light elements of carbon, nitrogen, and oxygen unintentionally or intentionally. Mechanical properties almost always depend on the light elements to a great extent. However, for example, the mechanism of creep strengthening by boron and nitrogen is controversial. Frequently, the location and the physical and chemical state of the dilute light elements have not been even understood, mainly because measurement and analysis of the trace and dilute light elements in the alloy matrices are difficult. This is one of the reasons for the fact the strengthening mechanism by light elements is controversy. Therefore, we have to develop new method of innovative measurement and analysis for structural materials (IMASM), which is a combination of multiscale imaging and X-ray absorption fine structure (XAFS) analysis that provides spatially-averaged physical-chemical properties of the trace and dilute light elements.

There are possibilities that the light elements exist in different phases such as solid solution matrices, precipitates, and grain boundaries. Especially, nano-scale precipitation to block the movement of dislocations is essential for strengthening the steels. Therefore, the first choice to analyze the light elements is elemental imaging. However, widely spread SEM with energy dispersive X-ray spectroscopy (SEM-EDS) normally cannot cover the fluorescent X-rays from trace light elements in a soft-X-ray region below ~1 keV, from the point of view of insufficient K-line separation. In this study, therefore, we employed EPMA with wave-length dispersive X-ray spectroscopy (WDS), TOF-SIMS, and 3D atom probe. In addition to these elemental imaging methods, physical-chemical properties are required to understand the mechanism of strengthening. Fluorescence-yield XAFS is a direct method to investigate physical and chemical properties of specific elements. A home-made XAFS instrument with a superconducting EDS detector (SC-XAFS) [1] that has the same elemental separation ability as WDS was installed at the beam lines of KEK PF, and provided XAFS analysis for boron.

We report on boron in a series of model samples of the 9%Cr martensitic heat resistant steels. The boron atoms were found to be enriched at prior austenite grain boundaries (PAGBs) and in the sub-µm M23C6 precipitates. Furthermore, non-negligible amount of boron existed inside the prior austenite grains, probably formed a solid solution. However, the ion intensity does not correspond to boron concentration directly. Therefore, new X-ray analytical instrument with a sensitivity of the same as TOF-SIMS for light elements is required to perform quantitative analysis. In an average of 1 mm region, XAFS shows only the sharp peak due to the 1s to π* electronic state transition, which apparently shows the presence of hexagonal BN phase for Fig. 1 (b). Integrated analysis of boron, nitrogen, and other metal elements that have chemical bonding with boron may give us a concrete answer for the strengthening mechanism.

[1] M. Ohkubo, S. Shiki, M. Ukibe, N. Matsubayashi, Y. Kitajima, S. Nagamachi, Sci. Rep. 2, 831 (2012).

(a) (b)

Fig. 1. 100-µm-square elemental mapping with TOF-SIMS for boron (BO2-) in the vicinity of PAGBs of 9%Cr

steels with nitrogen at 15 ppm (a) and 71 ppm (b) and boron at 130-150 ppm. The ion intensity is scaled from black to white. The small white spots indicate the M23C6 precipitates with a high B concentration of 2%, which was confirmed with EPMA and 3D atom probe. The boron atoms are also found in the matrix.


45

Theoretical Calculation of Positron Annihilation Parameters for Vacancy-Related Defects in Mg

Shoji Ishibashi1) 1) Research Center for Computational Design of Advanced Functional Materials (CD-FMat), National Institute of Advanced

Industrial Science and Technology (AIST), Tsukuba, Ibaraki 305-8568, Japan


The positron is known as a powerful probe for detecting vacancy-type defects in metals and semiconductors [1]. The momentum distribution of positron-annihilation radiation and the positron lifetime vary according to the local environment of the annihilation site. This makes it possible to detect defects and to distinguish them. For precipitation hardening in Mg alloys, it is thought that the interaction between vacancies and solute atoms plays an important role. In the present study, positron annihilation parameters such as S, W and τ as well as ratio curves of one-dimensionally-projected momentum distributions of positron-annihilation radiation for vacancy-related defects in Mg have been theoretically calculated.

All the calculations have been performed with our computational code QMAS (Quantum MAterials Simulator) [2,3]. Electronic wave functions were described with the plane-wave basis in the framework of the projector augmented-wave (PAW) method [4]. The two-component density-functional-theory formalism proposed by Boroński and Nieminen [5] was used to obtain positron states. For trapped states of positrons, the positron effect on the electronic structure and the atomic arrangement were explicitly taken into account [6,7].

As an example of the obtained results, ratio curves of the one-dimensionally-projected momentum distributions of positron-annihilation radiation for vacancy (V), V-Ca and V-Zn in Mg against it perfect crystal are shown in Fig. 1. It indicates the possibility that V-Zn can be distinguished from a usual vacancy (V). Systematic variations of positron annihilation parameters (S, W and τ) will be presented also.

Acknowledgements The author is grateful to Professor Akira Uedono, Professor Kazuhiro Hono, Dr. Taisuke Sasaki and Dr. Masanori Kohyama for useful information and stimulating discussions. This work was partly supported by the Cross-Ministerial Strategic Innovation Promotion Program - Unit D66 - Innovative Measurement and Analysis for Structural Materials (SIP-IMASM), operated by the Cabinet Office, Japan, and also by the Strategic Programs for Innovative Research (SPIRE), MEXT, and the Computational Materials Science Initiative (CMSI), Japan, under grant number hp160234.

0 1 2 3 4 5 60.00.20.40.60.81.01.2

R

p (a.u.)

V V-Ca V-Zn

Mg

Fig. 1. Ratio curve for vacancy (V)., V-Ca and V-Zn in Mg against its perfect crystal

References [1] M.J. Puska and R.M. Nieminen, Rev. Mod. Phys. 66, 841 (1994). [2] S. Ishibashi, T. Tamura, S. Tanaka, M. Kohyama and K. Terakura, Phys. Rev. B 76, 153310 (2007). [3] S. Ishibashi and A. Uedono, J. Phys.: Conf. Ser. 505, 012010 (2014). [4] P. Blöchl, Phys. Rev. B 50, 17953 (1994). [5] E. Boroński and R. M. Nieminen, Phys. Rev. B 34, 3820 (1986). [6] S. Ishibashi, J. Phys. Soc. Jpn. 84, 083703 (2015). [7] S. Ishibashi and A. Uedono, J. Phys.: Conf. Ser. 674, 012020 (2016).


46

Fatigue Damage Evaluation of Austenitic Steel SUS316L

Yoshihisa Harada1), Yosuke Inoue1),2), Tomoya Senda1),2), Takashi Nagoshi1), Brian E. O’Rourke3), Nagayasu Oshima3) 1) Advanced Manufacturing Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-2-

1Namiki, Tsukuba, Ibaraki, 305-8564, Japan. 2) Graduate School of Systems and Information, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8571, Japan. 3) Research Institute for Measurement and Analytical Instrumentation, National Institute of Advanced Industrial Science and

Technology (AIST), 1-1-1Umezono, Tsukuba, Ibaraki, 305-8568, Japan.


Structural components for electric power plants and/or transportation demand to materials integrity and operational life prediction. Especially, material behavior in operating environments such as a nuclear reactor, high temperature turbines, and combustion processes requires understanding in order to continue safe operation. Fatigue, defined as permanent structural change due to fluctuating stresses and strains, is a major problem. Therefore, inspection method of plastic and fatigue deformation has been required as the standard damage and/or early fatigue damage estimation procedure for above structural components. Macroscopic fatigue properties are attributed to microstructures such as dislocation structures, grain boundaries, crystal orientations and precipitates [1,2].

In this study, electron backscatter diffraction (EBSD) and positron annihilation methods were applied to analysis of low-cycle fatigue damage in an austenitic stainless steel (SUS316L) which is mostly used in the primary water line of power reactors. Samples of various degrees of fatigue with strain control from room temperature, 26°C to high temperature, 550°C were prepared for the above measurement methods. Low-cycle fatigue tests were conducted at Δε=0.4% and 1.5% strains at the strain rate of 0.1%/sec. As shown in Fig.1, the average misorientation, Mave obtained by KAM (Kernel Average Misorientation) showed a proportional increase with the fatigue damage to cycle to fatigue, Nf. As compared with the room temperature fatigue damaged sample, the high temperature fatigue damaged sample had a slightly decreased average misorientation at each cycle. This decrease was considered to be due to the recovery of dislocations at higher temperature. Positron annihilation lifetime measurements showed an increase in the positron lifetime for fatigued SUS316L samples compared to the as-received sample.

References [1] A.J. Schwartz, M. Kumar, B.L. Adams, D.P. Field, (Eds.) [Electron Backscatter Diffraction in Materials Science], Springer,

New York, (2009). [2] J.H. Hartley, R.H. Howell, P. Asoka-Kumar, P.A. Sterne, D. Akers and A. Denison, “Positron annihilation studies of fatigue in

304 stainless steel”, Appl. Surf. Sci., 149, 204-206 (1999).

0

0.2

0.4

0.6

0.8

1

0 0.5 1

Mis

orie

ntat

ion

aver

age,

Mav

e [deg

.]

Fatigue life ratio, N/N f

10-4

10-3

10-2

10-1

100

0 0.5 1 1.5 2 2.5 3

As-receivedN/N

f=0.5, R.T.

N/Nf=1, R.T.

N/Nf=0.5, H.T.

N/Nf=1, H.T.

Nor

mal

ized

Inte

nsity

[a.u

.]

Positron Lifetime [ns]

Fig. 1. Local misorientation average (Mave) as a function of fatigue life ratio.

Fig. 2. Positron lifetime spectrum measurement.


47

Small-angle X-ray scattering study on nanoheterostructure in structural materials

H. Mamiya1), A. Kowalska1,2), N. Watanabe1), H. Kitazawa1)

1) Quantum Beam Unit, National Institute for Materials Science (NIMS) 2) Faculty of Materials Science and Engineering, Warsaw University of Technology (WUT)


Small angle X-ray scattering (SAXS) technique is an experimental method to determine heterostructure on nanoscale. It has been considered a key technique along with transmission electron microscopy (TEM) in studying structural materials, because nucleation and growth of nano-precipitates play an important role in age-hardenable alloys and formation and coalescence of nano-voids are highly correlated with fracture toughness in various structural materials. One advantage of using SAXS complementarily is accuracy from a statistical point of view, since the cross-sectional area of SAXS is some mm2. Another advantage is high penetrability enabling measurements for a deep part of bulky samples in various environments. In other words, we can detect small variations of the mean size, number density and spatial correlation in different positions during manufacturing process and deterioration in use. In this study, we prepared facilities for in-situ measurement of SAXS at high temperatures or under stress, and apply them to investigation on steels, superalloys, and fiber reinforced materials.

We replaced X-ray source of Nanostar (Bruker Corp.) with an advanced rotating molybdenum anode generator with Goebel mirror, in order to improve penetrability by using intensive hard X-ray beam at 17.5 keV. Then we prepared infrared furnace (1700 K) and tensile tester (200 N) on XZ scanning stage in vacuum chamber of Nanostar. Consequently, we succeed observation of variation in nanoheterostructure of various structural materials such as the aging treatment induced nucleation and growth for Ni3(Al, Ti)-based γ′-precipitates in the nickel–chromium-based superalloy [1] and as the stress induced change of nanostructure in Inconel 718 (see Fig. 1). The details will be given in the presentation. This work is supported by SIP-IMASM (D66).

Fig. 1. Stress induced change of small angle X-ray scattering in Inconel 718 (a), and stress-strain curve obtained in this in-situ experiment (b). Experimental setup is shown in (c).

References [1] H. Mamiya, J. Rabajczyk, N. Watanabe, A. Kowalska, H. Kitazawa, J. Alloys Comp., 681, 367 (2016).


48

Influence of Ti on Ni-free ODS austenitic alloy

A. Kowalska1,2), M. Ciemiorek1), N. Watanabe1), H. Mamiya1), M. Ohnuma3), H. Kitazawa1), M. Lewndowska2) 1) Quantum Beam Unit, National Institute for Materials Science (NIMS)

2) Faculty of Materials Science and Engineering, Warsaw University of Technology (WUT) 3) Faculty of Engineering, Hokkaido University


The concepts of new fusion and fission rectors influence developing of novel materials. Important issue are structural materials, which have to withstand long-time operation in high temperature in irritation environment. There are several candidates for such application and one of them are ODS steels.

The ferritic ODS steels were wildly investigated. However several difficulties were found, because of the characteristic of BCC structure. The disadvantages can be eliminated by applying austenitic structure. Nonetheless, typical austenitic steels contain high activation elements, like nickel or molybdenum, what is undesirable in such application. Instead of them can be used nitrogen and manganese, which same as Ni and Mo stabilize the austenitic structure and ensure high mechanical properties [1].

During milling austenitic powder, cold welding is dominant to fracturing. It causes growth of the powder particles, influence creation of nanoparticles with size above 40nm and as an effect lover mechanical properties. To avoid such effect, titanium powder was applied. It is also widely known, the Ti powder created small nanoclusters with Y2O3, what ensure higher strength. However, obtaining FCC structure with Ti addition is a challenge. Titanium is a strong ferrite stabilizer, an even small amount of it cause phase transformation to ferrite.

The purpose of the research was manufacturing Fe-Cr-Mn-N-Y2O3 and Fe-Cr-Mn-N-Y2O3-Ti alloy with austenitic structure and comparing their properties.

In the study we have manufactured ODS nickel-free nitrogen-containing austenitic alloy, by mechanical alloying (MA) followed by spark plasma sintering (SPS). The material was made from elemental powders of iron, manganese, chromium, yttrium oxides and additionally with titanium. There were prepared four alloys, with 0, 0.1, 0.2 and 0.5% of Ti.

The MA process was curried under N2 atmosphere, which was source of the nitrogen in the material. The powder was milled for 40h. During milling, occurred ferrite to austenite phase transformation, what was investigated by XRD. The SEM images, analyzed by MicroMeter software package [2], shows that addition of Ti caused significant decrease of powder particles size. The as-milled powder was sintered for 5 min in 950 C. The XRD was performed to study the phase’s changes. Mechanical properties was studied by Vickers micro hardness test. It proves the positive influence of Ti on the HV0.1. To study nanoparticles, was held SAXS test, which is very popular method to obtain quantitative information about nanostructures [4, 5]. .

References [1] J. Rawersa, M. Grujicicb, Mater Sci Eng A, 207, (1996) [2] J. Michalski, et al., Materials Science-Poland, 23, (2005) [3] M. Ratti, D, Leuvrey, M. H. Mathon, Y. de Carlan, Journal of Nuclear Materials, (2009) [4] H. Mamiya, J. Rabajczyk, N. Watanabe, A. Kowalska, H. Kitazawa, Journal of Alloys and Compounds, p. 367–373, 681,

(2016) [5] Z. Oksiuta, P. Kozikowski, M. Lewandowska, M. Ohnuma, K. Suresh, K.J. Kurzydlowski, Journal of Materials Science,

p. 4620-4625, 48, (2013)


49

Characterization of micrometer-sized precipitates in heat-resistant steels using TOF-SIMS

Norimichi Watanabe1), Hiroaki Mamiya1), Fujio Abe1), Masataka Ohkubo2), Hideaki Kitazawa1) 1) National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047 Japan

2) National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba 305-8560 Japan


1. Introduction It is necessary to develop heat-resistant steel that can be used for a long time under high pressure and temperatures

to enhance the power-generation efficiency of thermal power plants. The major problem in the development of heat-resistant steels is the phenomenon of creep. It is known that a creep lifetime in heat-resistant steels is once prolonged when concentration of added nitrogen increases, but the creep lifetime decreases as nitrogen is further added [1]. Although some models have been proposed for explaining this phenomenon, the mechanism of this improvement of creep strength by addition of microelements has not been settled. Therefore, it is important to investigate the relation between the structure and light elements distribution and mechanical characteristics to understand the mechanism of this phenomenon. We used TOF-SIMS (Time-of-Flight Secondary Ion Mass Spectrometry) which can measure light elements to investigate the microelements distribution because it is difficult to detect light elements such as boron and nitrogen using the usual EDS (Energy dispersive X-ray Spectrometry). In this study, we focused on precipitates of μm size in heat-resistant steels and investigated these precipitates in detail using TOF-SIMS. 2. Experiment

The measurement sample was 9Cr-3W-3Co-0.2V-0.05Nb steel with 130 ppm boron and 15, 71, or 300 ppm nitrogen. The samples were solution heat treated at about 1150 for 1h in steel with 15 ppm and 300 ppm nitrogen and 3h in steel with 71 ppm nitrogen. They were tempered at about 770 for 4h. The samples were measured with PHI TRIFT V nanoTOF (Ulvac-Phi Inc.). 3. Results and Discussion

We measured the distribution of microelements in heat-resistant steels with different nitrogen concentrations using TOF-SIMS. Precipitation of boron was remarkable in the samples with higher nitrogen concentration. Many boron precipitates of μm size were observed in the sample with 300 ppm nitrogen, and we investigated these precipitates in detail. In the sample with 71 ppm nitrogen, we observed manganese, silicon, aluminum, and oxygen precipitated in the same area as boron. Carbide was also observed in these precipitates, as shown in Fig. 1. Silicate and carbide were compositely precipitated in the boron precipitates of μm size. Silicate was similarly observed in the boron precipitates in the sample with 300 ppm nitrogen, although carbide was not seen. We found that the μm-sized precipitates containing boron are different from the conventionally known M23C6 precipitates in prior austenite grain boundary. The structure of the precipitates which we measured this time consists of a plurality of phases, and all precipitates contain boron. Soluble boron which suppresses the coarsening of M23C6 precipitates is expelled from the parent phase by adding nitrogen, and form composite precipitates. As a result, soluble boron decreases and solid-solution strengthening is weakened. Although it is considered that creep strength is weakened because of precipitation of boron nitride (BN), it is natural to think that since the composite precipitates containing boron in addition to BN precipitates decreases soluble boron, the creep lifetime is shorter. 4. Conclusions We measured two-dimensional images of microelements in heat-resistant steels using TOF-SIMS. As the nitrogen concentration in heat-resistant steel increases, the presence of boron precipitates of μm size also increases. In addition, the boron precipitates of μm size were compositely precipitated with silicate and carbide. It is possible that the increase in boron precipitates weakens the strengthening mechanism of soluble boron.

References [1] Fujio Abe, Sci. Technol. Adv. Mater., 9, 013002 (2008).

10 μm

B+ Si+Mn+ CrC+

Fig.1 Two-dimensional image of B+, Mn+, Si+ and CrC+ in the μm-sized precipitate using TOF-SIMS.


50

Multiscale and multidimensional microstructure analysis using orthogonally-arranged FIB-SEM

Toru HARA1), Akira FUKUSHIMA2), Kazuhiro KUMETA3), Hideaki KITAZAWA1) 1) National Institute for Materials Science, Sengen, Tsukuba, Ibaraki 305-0047, Japan

2) Mitsubishi Heavy Industries Aero Engines, Ltd., Higashi-Tanaka, Komaki, Aichi, 485-0826, Japan 3) Nitivy Co.Ltd, Akashi-cho, Chuo-ku, Tokyo 104-0044, Japan


Introduction

We are developing a methodology of microstructure analysis of materials to understand the relationship between properties and microstructure. For proper and accurate understanding of the materials, in most cases, multiscale observation is essentially important; we would like to observe the same target region from wide area, low magnification toward high resolution images. In addition to the multiscale observation, ‘multidimensional’ information such as time, composition, orientation of crystals, etc., are also expected to measure simultaneously.

In order to realize multiscale and multidimensional observation, we have been developing an analytical method with utilizing orthogonally-arranged focused-ion-beam (FIB) – scanning electron microscope (SEM) instrument (Hitachi High-Tech Science, Co.) [1,2]. This equipment was originally developed to observe the microstructure in 3 dimensionally with a serial-sectioning method; orthogonal configuration as shown figure 1 realizes high-contrast and high-resolution SEM image-set for 3D reconstruction image. Compositional information and crystal orientation can also be obtained simultaneously, and scanning-transmission image can also be observed with a thin foil electron transparent specimen. The purpose of this study is to develop microstructure characterization technique through wide range of magnification from the same area of one specimen to reveal hierarchical structure of advanced materials.

Samples and methods

Samples used in this study are ceramic fibers that intend to use in ceramic matrix composites (CMC) layer in ceramics coating. These fibers have been developed by SIP C45 ‘Oxide ceramics matrix composite coating’ group [3]. Sample diameter is around 10 microns. We investigate several fibers to reveal the relationship between microstructure and properties with an apparatus mentioned above. A method applied in this study is described in Fig. 2. As the first step, morphology of a fiber was observed by SEM(1), then target region was picked up and sliced for 3D observation(2),(3). After serial sectioning, a final fragment was observed by a transmission mode in the FIB-SEM(4). All these observations can be performed in one apparatus. This means that the TEM sample prepared by this method has complete 3D information of adjacent volume. In combination with following TEM observation, we have succeeded to obtain many kinds of information such as surface condition, void structure from 3D observation, compositional and crystal orientation information, etc. from the same peace of fiber simultaneously.

References [1] T.Hara, K.Tsuchiya, K.Tsuzaki, X.Man, T.Asahata, A.Uemoto, J. Alloys and Compounds, 577, 717(2013). [2] T.Hara, KENBIKYO, 49, 53(2014). in Japanese. [3] SIP, Structural Materials for Innovation, C45 Oxide Ceramics Matrix Composite Coating, (MHI Aero Engine, NIMS,

Artkagaku, Nitivy), in Development of Ceramic Environmental Barrier Coating region.

Figure 1. (a) Configuration of orthogonally-arranged FIB-SEM. (b) Schematic of serial-sectioning configuration.

Figure 2. Observation sequence in orthogonally-arranged FIB-SEM. All (1)-(4) observation are carried out continuously in one equipment.


51

Analyses of partitioning behaviour of boron and nitrogen in metal carbide and Nb/V-enriched carbonitrides by using atom probe tomography

Byeong-Chan Suh1), Taisuke Sasaki1), Fujio Abe2), Kazuhiro Hono1) 1)Research Center for Magnetic and Spintronic Materials,

National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, Japan 2) Materials Reliability Unit, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki, Japan

Email: [email protected] Trace additions of boron and nitrogen improve the creep strength in 9Cr martensitic steel [1, 2]. The improvement of

the creep strength has been attributed to the inhibition to the recrystallization along the prior austenite grain boundaries (PAGBs) due to the boron segregation along the PAGBs. However, the role of boron and nitrogen still remains unclear since it has been difficult to fully characterize their partitioning behavior in nano and atomic scale by transmission electron microscope (TEM). This study aims at clarifying the partitioning behavior of boron and nitrogen in the tempered 9Cr martensitic steel (MARBN12 steel) by laser-assisted 3D atom probe (3DAP). The 3DAP analyses were carried out using a locally built laser-assisted atom probe with a femtosecond laser pulse at a wavelength of 343 nm [3].

As shown in the secondary electron SEM image (Fig. 1a), PAGBs are observed as indicated by broken lines. 3DAP analyses were performed from a PAGB and packet/block boundary, which is away from 70 μm ~ from PAGBs. These boundaries are marked by red and blue rectangles in Fig. 1a, respectively. Figure 1b is 3D atom maps obtained from a region including PAGB. Unlike a previous work [2], no boron segregation was observed along the PAGB. Rather, boron is enriched in M23C6 metal carbide phase, and the boron concentration in the metal carbide is 2.5 at.%. In addition, Nb/V-enriched carbonitrides are also observed; however, boron was not enriched within these Nb/V-enriched carbonitrides. Boron was also partitioned into metal carbides along the packet/block boundaries, which is ~70 μm away from PAGB (Fig. 1 c). The boron concentration near the particle surface is 2.5 at.%, which is similar to that in the metal carbide along PAGB. However, the boron concentration is only 1.0 at.% within the metal carbide. Therefore, the high boron concentration of boron (2.5 at.%) at the carbide/matrix interface is considered to prevent coarsening of metal carbides during creep deformation. Thermally stable and fine Nb/V-enriched carbonitrides were also observed at packet/block boundaries.

Unlike previous belief, boron is not segregated along PAGBs in 9Cr martensitic steel. Rather, boron is enriched in metal carbides. The boron enrichment in the metal carbide is expected to improve the thermal stability of the metal carbides. Along with the metal carbides, thermally stable fine Nb/V-enriched carbontrides are also formed. These thermally stable particles decreases the grain boundary energy, which causes the inhibition to the recrystallization along the PAGBs. This leads to an improvement of creep property.

Fig. 1. (a) SEM image of MARBN 12 steel, and 3D atom maps obtained from the region including (b) PAGB and (c) packet/block boundaries marked as blue and red rectangles, respectively.

References [1] F. Abe, T. Horiuchi, M. Taneike, K. Sawada, Mater. Sci. Eng. A, 378, 299, (2004). [2] M. Tabuchi, H. Hongo, F. Abe, Metall. Mater. Trans. A, 45, 5068 (2013). [3] K. Hono, T. Ohkubo, Y.M. Chen, M. Kodzuka, K. Oh-ishi, H. Sepehri-Amin, F. Li, T. Kinno, S. Tomiya, Y. Kanitani,

Ultramicroscopy, 111, 576, (2011).


52

Poster papers

IMASM Ceramics & Coating


53

XRF-XRD Surface Mapping and X-Ray Computed Tomography Observations of Thermal Barrier Coatings

Y. Takeichi1), H. Nitani1), Y. Niwa1), T. Ishii1), R. Kitazawa1), and M. Kimura1) 1) Institute of Materials Structure Science, High Energy Accelerator Research Organization

(1-1 Oho, Tsukuba, Ibaraki, 305-0801 Japan)


Thermal barrier coatings (TBC) are known to play an important role in enhancing the operating temperatures of gas-turbine engines [1]. Microstructures of chemical and crystallographic properties of TBCs provide suggestive infor-mation about spallation and failure mechanism, and then the durability of these materials. Synchrotron-based XRD analysis was reported to be a powerful tool to analyse the crystallographic properties of TBCs [2].

We have developed a experimental station for XRF-XAFS-XRD mapping using a ~20 μm sychrotron X-rays [3]. Figure 1 shows a result of XRD surface mapping experiment on a TBC specimen after 100 cycles of 1393 K heat treatments, comprises ZrO2-4 mol.% Y2O3 / CoNiCrAlY / IN738LC. X-ray energy was set to 11.64 keV and the incident angle was 15 degree. The top coat YSZ was delaminated in the left side of the field of view. Total-area diffraction pattern were fitted using calculated patterns of three phases; YSZ (Y=0.22), YSZ (Y=0.65) phases and fcc-Ni3Al alloy phase representing CoNiCrAlY. Diffraction peak at position 1 in Fig. 1(a) mainly consists of the (200) reflection of YSZ (Y=0.22) and (110) of YSZ (Y=0.065) phases. Dominant contributions at positions 2–4 are (111) reflection of CoNiCrAlY, (211) of YSZ (Y=0.065), and (220) of YSZ (Y=0.065), respectively. The XRD intensity mapping at the peak positions 1–4 are displayed in Figs. 1(b–e), respectively. One can clealy recognize the bare bond coat phases (fig. 1(c)) from the remaining top coat. Moreover, heterogeneity of crystal orientation in the columnar top coat was visualized. This would be of importance in the degradation of top coats, such as sintering.

We have also developed a laboratory source X-ray CT combined with magnifying optics. The effect of the heat treatment in the microstructure of the top and bond coats in the TBC specimen were observed. Figure 2 shows the sectional views of the the same series of specimen as fig. 1, before and after 300 cycles of heat treatments. Columnar structure in the YSZ top coat was found to be ocasionally grouped into "carrot-shaped" grains, even in the as-depo specimen. These grains were associated with cracks at the boundary between top and bond coats. Porus bond coat, that was low-pressure sprayed CoNiCrAlY, was found to increase its porosity after the heat treatments, and to have a ratcheted surface possibly due to oxdiation. These observations are suggestive of relationship between the microstructures and spallation of the top coats.

Fig. 1. (a) Total-area XRD pattern and (b-e) XRD intensity mapping of a TBC specimen after 100 cycles of heat treatments. In (a), fitted XRD pattern using two different YSZ phases and fcc-Ni3Al alloy phase representing CoNiCrAlY are plotted together with the experimental XRD pattern. Lines below the pattern curve indicate the predicted peak position from the three phases. XRD intensity map at peak positions of 1–4 in (a) are displayed in (b–e), respectively.

Fig. 2. Sectional views of (a) as-depo and (b) after 300 cycles heat treatment of TBC specimen.

[1] D. R. Clarke and C. G. Levi, Annu. Rev. Mater. Res., 33, 383 (2003).

[2] J. Almer, U. Lienert, R. L. Peng, C. Schlauer, and M. Odén, J. Appl. Phys., 94, 697 (2003).

[3] N. Igarashi, N. Shimizu, A. Koyama, T. Mori, H. Ohta, Y. Niwa, H. Nitani, H. Abe, M. Nomura, T. Shioya, K. Tsuchiya, and K. Ito, J. Phys.: Conf. Ser., 425, 072016 (2013).


54

Chemical states mapping using XAFS/XAFS-CT and its analysis using a mathematical approach of homology

M. Kimura1,2), Y. Takeichi1,2), I. Obayashi3), Y. Niwa1), R. Kitazawa1), H. Hiraoka3)

1)High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki, Japan 2) Dept. Mater. Structure Sci., School of High Energy Accelerator Sci., SOKENDAI (The Graduate University for Advanced Studies) 3) The Advanced Institute for Materials Research (AIMR), Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi, Japan

Tsukuba, Ibaraki 305-0801, Japan E-mail: [email protected]

In order to reveal crack formation and its propagation in structural materials such as carbon fiber reinforced plastic (CFRP) composites, heat-resistant alloys, and thermal and environmental barrier coatings (TBC and EBC), we need to obtain the three-dimensional (3D) information not only on their microstructures but also on the chemical states of composing elements. This is because crack formation and its propagation are affected by the inhomogeneity or heterogeneity in microstructures and bonding between and/or within composites that progress during heat cycles in air in service. These microscopic heterogeneities are often the main factors causing macroscopic stress, and thus are very important to design the composite materials in terms of micromechanics.

Macroscopic chemical mapping We have also established the observation approach of 2D chemical-state mapping using x-ray absorption fine

structures (XAFS) [1-3]. This approach was applied to investigate the reduction reaction of iron-ore sinters. The heterogeneity of iron states: FeIII, FeII, and Fe0, could be mapped with a special resolution as small as 20 μm. It was shown that the reduction reaction initiates and progresses heterogeneously within a specimen, depending on the chemical compositions.

The heterogeneous reduction results in crack formation, and the relationship between the heterogeneity of iron chemical states and crack formation is now being scrutinized using a mathematical approach of homology in collaboration with a MI team of D72.

Microscopic chemical mapping

We have finished designing a new observation system of XAFS-CT where microstructures and chemical states can be observed simultaneously with a spatial resolution as small as 50 nm using synchrotron radiation. The collimated x-ray beam shines a specimen, and the transmitted beam was focused using Fresnel zone plate (FZ) (Fig.2). We demonstrated the validity of this approach by the experiments at SSRL facility in USA. We successfully measured the heterogeneity of microstructures and chemical states in specimens such as iro-ore sinters, Ni-supper alloy, and a sinter plate of Yb2Si2O7. The new system is now under construction and will be installed at the beamline of NW2A at Advanded Ring (AR), KEK in 2016FY.

We investigated the reduction reaction of iro-ore sinters using XAFS-CT at SSRL. The microscopic heterogeneity of iron chemical states could be observed with a special resolution as small as 70-80nm. These results are combined the macroscopic observation obtained by 2D chemical-state mapping using XAFS, and the initiation and propagation of reaction are discussed with a special attention to their relation to crack formation.

References [1] M. Kimura, Y. Takeichi et al., Procd. of Asia Steel int. conf. 2015(Yokohama, Oct. 5 – 8, 2015). [2] M. Kimura, Y. Takeichi et al., Invited talk at Denver X-ray conference 2016, and the proceeding paper in preparation. [3] M. Kimura , Y. Takeichi et al., Presented at Int. conf. X-ray Microscopy conference 2016, and the proceeding paper in

preparation.

Fig.1 Result of iron chemical mapping of a reduced iron-ore sinter.

Synchrotron radiation (undulator)Capillary (X-ray condensor)

SpecimenDetector Fresnel zone plate

Fig.2 Schematic of the new system of XAFS-CT that will be installed at AR NW2A, KEK in 2016FY.


55

Dynamic analysis of laser shock-induced fragmentation of copper foil

Masao Kimura1,2), Yasuhiro Niwa1), Tokushi Sato3), Kei Takahashi1), Kohei Ichiyanagi1) 1)Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki, Japan

2) SOKENDAI, 1-1 Oho, Tsukuba, Ibaraki, Japan 3) CFEL, DESY, Notkestrasse 85, 22607, Hamburg, Germany


X-ray absorption fine structure (XAFS) is a very powerful tool to obtain the radial structural information for sample

without long-range order. Dispersive XAFS (DXAFS) is one of special technique of XAFS specialized for dynamical observation; a XAFS spectrum of whole energy range of interest can be obtained using bent crystal at once without any mechanical movements [1]. We have developed the new system of DXAFS at NW2A beam line at PF-AR in KEK. A single-shot XAFS spectrum can be captured with just one pulse of X-ray by synchronizing an X-ray pulse with a laser one, and the time resolution of measurement equals to the pulse duration of X-ray (ca.100 ps). The transient state after laser irradiation can be obtained with sub-nanosecond.

It is known that materials show unique structures under extreme conditions such as high pressure and high temperature. Using high-power laser as a trigger leads us to investigate the dynamics of irreversible structure changes in the extreme conditions, which is indispensable to understand many phenomena such as phase transition, fragmentation, and spin. Irreversible phenomena such as shock-induced lattice response and photo-induced protein reaction are studied mainly by using time-resolved X-ray diffraction technique [2,3], and no studies were reported using XAFS. One reason of this situation is difficulty to measure the XAFS spectrum with single-shot X-ray pulse. Since a double crystal monochromator repeats stop and move to select the required energy in the conventional step-by-step XAS spectrometer, it takes very long time to obtained a spectrum with single-shot X-ray pulse. On the other hand, a XAFS spectrum can be acquired rapidly with single-shot X-ray pulse by DXAFS measurement using appropriate X-ray detector. DXAFS is a powerful tool for structural investigations in fast reactions. The irreversible dynamics of local structures and spin dynamics under the laser-induced extreme conditions can be investigated as short as nanoseconds. The system was applied to the mechanistic study of the fragmentation of copper foil induced by laser irradiation.

A copper foil was laser-shocked with Nd:YAG laser (wavelength:1064 nm, laser power: 0.2 TW cm-2, pulse width:10 ns and beam size:300 µm and time evolution of XAFS spectra and EXAFS oscillations around Cu K-edge was clearly obtained by changing delay times from 0 to 300 ns (Fig. 1(a) and (b)), where a spectrum obtained with step-scan measurement was also shown as a reference. The distinct energy shift of copper K-edge was not observed. This indicates that the valence of the copper does not change and the copper keeps metallic state during destruction in several hundred nanoseconds. As shown in Fig. 1, the spectral structure and the EXAFS oscillation characteristic of metallic copper were observed within 10 ns after laser irradiation. On the other hand, EXAFS oscillations were gradually decreased after 30 ns and they almost disappeared at 100 ns. The mechanism of destruction induced by the laser-shock will be discussed based on these results.

References [1] T. Matsushita, et al, Jpn, J. Appl. Phys., 20, 2223 (1981). [2] K. Ichiyanagi, et al, Appl. Phys. Lett., 91, 231918 (2007). [3] K. Ichiyanagi, et al, Appl. Phys. Lett., 101, 181901 (2012).

Fig. 1 XAFS spectra of cupper foil in various delay times


56

In situ observation of chemical species near solid/liquid interface in a pitting process

K. Kimijima1), Y. Niwa1), M. Kimura1), 2) 1) Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK)

1-1 Oho, Tsukuba-shi, 305-0801 JAPAN TEL +81-29-864-5200 (ex. 2547), E-mail: [email protected]

2) School of High Energy Accelerator Science, SOKENDAI, 1-1 Oho, Tsukuba-shi, 305-0801 JAPAN

The corrosion of metal and alloy under a wet environment includes a series of process: ionization of constituent elements by electron transfer reaction (oxidation) at the solid/liquid interface and dissolve of metal into the solution, diffusion of the dissolved ions, and formation of hydroxides. These reactions depend on the environments near the interface, which change with the progress of the corrosion reaction itself. One of the most important environments is the concentration of chemical species near the solid/liquid interface that is different from that of uniform corrosion. This is the case of pitting corrosion, and it is difficult to understand its mechanism only by ex situ observation. Therefore, an in situ measurement technique with a time and a spatial resolution is required. In this study, the observation of diffusion behavior of dissolved ions and reaction among them near the solid/liquid interface were attempted in order to understand corrosion reactions at the early stage.

The X-ray absorption spectrum (XAS) measurement was performed using an in situ electrochemical cell (Fig. 1) [1], which can detect states of dissolved metal ions in a minute space simulating pitting corrosion. The change in concentrations and structures of dissolved ions were observed at different distances from the solid/liquid interface as a function of reaction time: t. A sheet of SUS304 (Cr 18 %, Ni 8 %) with a thickness of 200 μm was used as a sample, and worked as an electrode. LiBr aqueous solution (1.0 M) was used for an electrolyte. A typical measurement of corrosion was carried out by applying potential of 0.8 V vs. Ag/AgCl on the specimen. The size of an X-ray beam was set to 500 μm (horizontal) × 90 μm (vertical) (FWHM). As the corrosion progress, the interface shifted to –Z direction (Fig. 1), but the interface shape along the horizontal direction remained sufficiently smooth compared with the beam size. XAS for Fe, Cr, and Br K-edges were measured by the transmission geometry using QXAFS technique at BL-9A of Photon Factory (PF), High Energy Accelerator Research Organization (KEK).

Fig. 1(a) Schematic diagram of the electrochemical-in situ XAFS cell, (b) Fe absorption vs. the reaction time.

The X-ray absorption spectrum changed according to the progress of the corrosion reaction. Figure 1b shows typical results of change of absorption (Δμt) at the energy of white line at different distances from the solid/liquid interface as a function of the reaction time: t. These results showed that the absorption of Fe rapidly increases at the early stage of reaction and as the reaction advanced, the change in the absorption becomes small and reaches an equilibrium state. It was also shown that the absorption change also heavily depends on the distance from the interface. The same measurements were also performed for Cr and Br. These results will be discussed by paying a special attention to the relationship of the concentration change of Fe, Cr, and Br and their coordination structures.

References

[1] M. Kimura, et al., J. Synchrotron Rad., 8, (2001) 487.


57

Development of XAFS/XRD simultaneous measurement technique at high temperatures

K. Kimijima1), Y. Takeichi1), 2), Y. Niwa1), K. Takahashi1), M. Kimura1), 2) 1) Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK)

1-1 Oho, Tsukuba-shi, 305-0801 JAPAN TEL +81-29-864-5200 (ex. 2547), E-mail: [email protected]

2) School of High Energy Accelerator Science, SOKENDAI, 1-1 Oho, Tsukuba-shi, 305-0801 JAPAN

We have tried to develop an advanced observation technique for simultaneous measurements of X-ray absorption spectroscopy (XAS) and XRD at the conditions where structural materials for aerospace are used: heat cycles up to 1773 K under gas. As the first step, we have developed a system only for XAS, and showed results for a ceramic coating material: a sintered plate of Yb2Si2O7.

In order to conduct XAS measurement while the sample is maintained at high temperature, it is necessary to control the atmosphere, to reach target temperature (up to 1773 K) and to make the optical system that allows for spectrum measurement. A prototype furnace was manufactured which can only obtain X-ray absorption spectrum, where a specimen is heated using an infrared gold image furnace. The furnace has a window for X-ray incident and one for observation of fluorescence. The uniform heat area is sufficiently larger compared with the beam size of the X-ray irradiation. XAFS spectrum was measured using the furnace. A plate of Yb2Si2O7 sinter with a size of 8 × 8 × 0.5 mm3 was used as a sample. XAFS measurement around Yb LIII-edge (8.9 keV) was performed by the fluorescence yield method. All experiments were carried out at BL-9C, Photon Factory (PF), High Energy Accelerator Research Organization (KEK). The structural change was investigated during heating cycles in air: heating at 1573 K and cooling at room temperature.

Fig. 1(a) XANES spectra, (b) radial structure function at R.T. and 1300 °C.

Figure 1a shows the XANES spectra of Yb2Si2O7 around Yb LIII edge. No energy shift of spectrum was observed before and after heating, showing that the valence of Yb does not change. The radial structure functions which are obtained by Fourier transform of EXAFS oscillation with a range of k = 10-120 nm-1, are shown in Figure 1b. Because EXAFS oscillations changed reversibly during heating cycles, it means that no irreversible structural change is caused during heating cycles.

It has been shown that the prototype system has an enough potential for our purpose, though further technical improvements, such as maintaining a sample at the precise position during heat cycles, are necessary. Designing adding additional windows for the diffracted beam for XRD is also challenging.

We continue to develop a new system where XRD as well as XAFS measurements can be performed simultaneously based on these results. We would expect to obtain important information for materials designing and materials informatics through measuring the structure information in a short range order by XAFS and that in a long range order by XRD.


58

Non-destructive Characterization of internal structure of structure materials using synchrotron X-ray CT

Yumiko Takahashi, Keiichi Hirano, Kazuyuki Hyodo and Masao Kimura

Institute of Materials Structure Science, High Energy Accelerator Research Organization, 1-1 Oho, Tsukuba, Ibaraki 305-0801, Japan. E-mail: [email protected]

Thermal barrier coating (TBC) is a key technology for high-temperature application of structural engineering materials such as Ni-base super alloy and silicon carbide fiber-reinforced silicon carbide matrix (SiC/SiC) composite which are the promising materials as aerospace propulsion systems [1]. Expanded application to more demanding environment requires that TBC’s basic thermo-mechanical characteristics be understood. For this purpose, synchrotron radiation x-ray computed tomography (CT) of TBC system was performed. This method is a powerful tool for visualizing the inner structures of various specimens non-destructively, because of high brilliance and wide range selectivity of x-ray energy of synchrotron radiation.

The experiments were performed at the vertical wiggler beamline BL-14B and BL-14C of the Photon Factory, High Energy Accelerator Research Organization (KEK). The x-ray energy was adjusted to 24 keV using a Si(220) double-crystal monochromator. The image obtained by x-rays transmitted through a sample was expanded in the horizontal plane by a Si(220) asymmetric crystal (an incident angle is 1.1 deg, the magnification factor is about 8) to increase the spatial resolution, then recorded on an x-ray charge-coupled device (CCD) camera (Photonic Science, VHR). The x-ray CCD camera consisted of a GdO2S:Tb scintillator, a glass fiber plate (taper =1:1) and a CCD sensor. The effective pixel size was 7.4 μm (H) × 7.4 μm (V), and the number of pixels were 4872 (H) × 3248 (V). A series of radiographic images taken with rotating the sample around the vertical axis are reconstructed via filtered back-projection (FBP) method [2]. The mullite coated SiC substrates which were heat treated at various temperatures were provided as a sample. Samples were 1/4 section of a disk (12.7 mm diameter, 2 mm thickness). The thickness of mullite layer was 240 μm.

Figure 1 shows the crack distribution that was extracted from the volume rendering of an absorption contrast CT image of the sample heat treated at 1415°C for 2h. Measured images expanded horizontally were reduced to the original ratio by image processing. Most of cracks formed within the coating reach the interface between the coating layer and the substrate and stop there. There are few cracks extending into the substrate. In addition, some cracks which have extended along the interface after reaching there were also observed. The details of the results will be discussed in the poster presentation.

The absorption contrast CT using synchrotron radiation provides 3-D images of the internal structure of TBC system in high quality. The results showed the validity of this technique for evaluation of TBC.

Fig. 1. Crack distribution of heat treated TBC system.

References [1] Nitin P. Padture et al., Science 296, 280 (2002). [2] K. Uesugi and Y. Suzuki, Materia Jpn, 45, 451 (2006) (Japanese).

2 mm

Mullite layer

SiC substrate


59

X-ray analyzer-based phase-contrast computed laminography

Keiichi Hirano, Yumiko Takahashi, Kazuyuki Hyodo and Masao Kimura Institute of Materials Structure Science, High Energy Accelerator Research Organization,

Tsukuba, Ibaraki 305-0801, Japan


We have developed x-ray analyzer-based phase-contrast computed laminography for imaging regions of interest(ROIs) in laterally extended flat specimens of weak absorption contrast [1].

The optical setup is schematically shown in Fig. 1(a). The optics consist of an asymmetrically cut first crystal (collimator) and a symmetrically cut second crystal (analyzer) arranged in a nondispersive (+, −) diffraction geometry. The incident monochromatic x-ray beam is collimated and expanded in the horizontal plane by the first crystal and propagates through a sample. The refraction caused by the sample is analyzed by the second crystal. The beam diffracted by the second crystal is observed by an x-ray area detector.

To verify the feasibility of our method, we performed experiments at the vertical-wiggler beamline BL-14B of the Photon Factory. At first, the white beam from the light source was monochromated at 0.0733 nm by a Si(111) double-crystal monochromator. Then, the monochromatic beam linearly polarized in the vertical direction was incident to the optics. For the collimator, we used an asymmetric Si(220) crystal. The angle between the crystal surface and the diffracting lattice planes was 10°, and the Bragg angle was 11°. As a result, the incident beam was expanded by 10.9 times in the horizontal plane. Then the central part of the expanded beam was selected by a slit. For the analyzer, we used a symmetric Si(220) crystal. Both the collimator and the analyzer were made of non-doped float-zone silicon crystal, and their surfaces were mechanochemically polished in order to remove defects and strain fields. The beam diffracted by the analyzer was recorded by a fiber-coupled x-ray CCD camera. The pixel size was 6.45 μm (H) × 6.45 μm (V) and the number of pixels was 1392 (H) × 1040 (V).

As the sample, we used a nylon mesh. The period of the mesh was about 1 mm. From the set of obtained refraction maps, we calculated the phase-contrast sectional image of the sample as shown in Fig. 1(b). This result shows that both of our optics and algorithm work well. In this image, a strong circular artifact is also observed. This artifact originates from the joint of the sample holder. Due to this artifact, the FOV was limited to about 6 mm in diameter. Clear phase-contrast sectional images can be obtained as long as the ROI is located inside this FOV. We will be able to expand the FOV by replacing the polypropylene tube of the sample holder with a larger one. (a) (b)

Collimator crystal

Analyzer crystal

X-ray area detector

X-ray eam u

v

w

z1

z2

y1

y2

x1

x2Sample

Fig. 1 (a) X-ray optics for analyzer-based phase-contrast computed laminography. (b) Reconstructed phase-contrast sectional image of the nylon mesh. The size of the image is 8.9 mm (H) × 8.9 mm (V).

References [1] K. Hirano, Y. Takahashi, K. Hyodo and M. Kimura, submitted to J. Synchrotron Rad.


60

Poster papers

IMASM Instruments


61

Construction of an Ion Beam Analysis Facility for Structural Materials at the University of Tsukuba

Kimikazu Sasa 1), 2), Akiyoshi Yamazaki 2), Shigeo Tomita 2), Masanori Kurosawa 3), Satoshi Ishii 1), Hiroshi Naramoto 1), Masao Sataka 1), Hiroshi Kudo 1), Eiji Kita 2), Akira Uedono 1), 2)

1) Tandem Accelerator Complex, University of Tsukuba (1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577, Japan) 2) Graduate School of Pure and Applied Sciences, University of Tsukua (1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8571, Japan)

3) Graduate School of Life and Environmental Sciences, University of Tsukuba (1-1-1 Tennodai, Tsukuba, Ibaraki, 305-0006, Japan)


The University of Tsukuba, Tandem Accelerator Complex (UTTAC) is a major center of ion beam research in Japan. We have operated and maintained the 1 MV Tandetron accelerator, the 1 MV high-resolution Rutherford back scattering (RBS) system and the radio-isotope utilization equipment. We planned to construct a new horizontal-type 6 MV tandem accelerator for ion beam analysis (IBA) of structural materials at UTTAC [1]. A five-year plan for the new accelerator’s construction was started in 2011. The 6 MV tandem accelerator was designed and developed by the National Electrostatics Corp., USA in collaboration with the University of Tsukuba [2]. The main accelerator (model 18SDH-2 Pelletron) is a dual acceleration electrostatic accelerator. The accelerator tank is 2.74 m in diameter and 10.5 m long. The generator operates reliably to terminal voltages as high as 6.5 MV. Stability is estimated to be better than 1 kV at a 6.0 MV terminal voltage. Maximum beam currents are predicted to be up to 3 μA for proton and 50 μA for heavy ions. It was installed at the University of Tsukuba in March 2014. We started routine experiments on ion beam applications by means of the new system since March 2016. The 6 MV tandem accelerator is used for various ion-beam research projects, such as accelerator mass spectrometry (AMS) [3], microbeam applications, particle-induced X-ray emission (PIXE) analysis, heavy ion RBS and elastic recoil detection (ERD) analyses, nuclear reaction analysis for hydrogen in materials and high-energy ion irradiation for semiconductor. There are new four beam courses from L1 to L4 for ion beam analysis on the structural materials in the accelerator room. The IBA system equipped with a high-precision four-axis goniometer is located on the L1 beam course. It is used for heavy ion RBS and ERD analyses on structural materials. A large environmental testing chamber (1 m in diameter) on the L2 beam course is mainly used for the radiation-resistant testing for materials. In addition, a microbeam equipment has been constructed with the Oxford microbeams quadrupole lens system [4] that is used to obtain a beam diameter of 1 μm on the L3 beam course. We will also install a superconducting detector [5] for high-sensitivity PIXE analysis of light element in materials in collaboration with the National Institute of Advanced Industrial Science and Technology (AIST). The L4 beam course is the rare-particle detection system for AMS. It will be applied for rare-particle tracer experiments in structural materials by using AMS techniques. It will start routine IBA measurements of structural materials in 2016.

Fig. 1. Photograph of the 6 MV tandem accelerator for various ion beam applications on structural materials at the University of Tsukuba.

References [1] K. Sasa, AIP 1533, 184 (2013). [2] K. Sasa, S. Ishii, K. Kita, T. Moriguchi, H. Oshima, D. Sekiba, Y. Tajima, T. Takahashi, Y. Yamato, JACoW, Proceedings of

HIAT2016, 285 (2015). [3] K. Sasa, T. Takahashi, M. Matsumura, T. Matsunaka, Y. Satou, D. Izumi, K. Sueki, Nucl. Instrum. Methods B 361, 124 (2015). [4] G.W. Grime, F. Watt, Nucl. Instrum. Methods B 30, 227 (1988). [5] M. Ohkubo, S. Shiki, M. Ukibe, N. Matsubayashi, Y. Kitajima, S. Nagamachi, Scientific Reports 2, article number:831 (2012).


62

Development of energy dispersive X-ray spectrometry system for nanometer-scale mapping of light elements

Go Fujii1), Masahiro Ukibe1), Shigetomo Shiki1), Masataka Ohkubo1) 1) Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology (AIST),

1-1-1, Umezono, Tsukuba, Ibaraki, 305-8568, Japan


The creep strength and life of heat-resistant steels can be improved by adding a small amount of light elements, such as boron(B), carbon(C) and nitrogen(N). For example, in 9 % Cr heat-resistant steels, specific compounds with nano-size(~ 100 nm), which are called to be MX (M: Nb, V, Cr and X: C, N) carbonitrides, are closely related to the creep strengthening of the steels[1]. The lamellar microstructure in Ti alloys has layer thicknesses in a nanoscale range. Addition or contamination of C, N, O significantly influences mechanical properties, but element distribution has not been known well. Thus, in order to understand the influence of the light elements on the heat-resistant alloys, a microscopic distribution analysis of the light elements is very important. Energy-dispersive X-ray spectroscopy (EDS) combined with scanning electron microscopes (SEMs) is suitable to obtain the spatial information of an elemental composition in a sample non-destructively. In particular, by using low acceleration voltage SEMs (LVSEMs), it is theoretically possible to identify and quantify elemental composition of sample surfaces with a lateral resolution of nanoscale[2]. However, the conventional EDS system, in which semiconductor detectors like silicon drift detectors (SDDs) used for the measurement of fluorescence X-ray, is unsuitable for the above purpose because an energy-resolving power of the semiconductor detector is insufficient to achieve clear separation of the K-lines of light elements as well as the L-lines of matrix elements.

In this work, we have developed a prototype EDS-SEM system with high energy-resolving power and high throughput by using superconducting-tunnel-junction (STJ) array X-ray detectors. The EDS-SEM system is consisted of an SEM with a tungsten filament, a polycapillary X-ray optics, and an energy-dispersive X-ray detector based on the 100-pixel STJ array. The STJ array detector exhibits an energy resolution of 7 eV in full width at half-maximum (FWHM) for 400 eV, a total sensitive area of larger than 1 mm2, and a counting rate of more than 100 kcps in a soft X-ray range less than ~1 keV[3]. Especially, the energy resolution of the STJ array is much higher than that of SDDs (about 50 eV in FWHM) [4]. A fluorescence X-ray spectrum measured with the developed EDS-SEM system for a pure BN sample was displayed in Fig. 1. The B-Kα (188 eV), C-Kα (277 eV), N-Kα (393 eV), and O-Kα (525 eV) lines were clearly distinguished. The C-Kα and O-Kα lines were emitted from carbon and oxide compound materials on the surface of the BN, respectively. The energy resolution for N-Kα line of the STJ array detector was 10 eV in FWHM, which was almost equal to that of wavelength-dispersive X-ray spectroscopy (WDS) for electron probe microanalyzers (EPMAs). The measurement results of heat resistant steels and Ti alloys are reported.

Fig. 1. EDS-SEM system with a STJ array detector and fluorescence X-ray spectrum for the light elements.

References [1] M. Taneike, F. Abe, and K. Sawada, Nature, 424, 294 (2003). [3] R Wuhrer and K Moran, IOP Conf. Ser.: Mater. Sci. Eng., 109, 012019 (2016). [4] M. Ukibe, G. Fujii, S. Shiki, Y. Kitajima, and M. Ohkubo, J. Low Temp. Phys., 184, 200 (2016). [5] D.M. Schlosser, P. Lechner, G. Lutz, A. Niculae, H. Soltaua, L. Struder, R. Eckhardt, K. Hermenaua, G. Schaller, F. Schopper,

O. Jaritschin, A. Liebel, A. Simsek, C. Fiorini, and A. Longoni, Nucl. Inst. Methods in Phys., 624, 270 (2010).


63

Performance Test of a Pulse Stretching System for Materials Science at KEK Slow Positron Facility II

K. Wada*, M. Masaki, I. Mochizuki, M. Kimura, and T. Hyodo Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK),

1-1 Oho, Tsukuba, Ibaraki 305-0003, Japan


The Slow Positron Facility at High Energy Accelerator Research Organization (KEK-SPF) provides a high-intensity pulsed slow-positron beam created by using a dedicated 50-MeV linac. The pulsed beam is successfully used for experiments of positronium negative ions, positronium time-of-flight (Ps-TOF), and total-reflection high-energy positron diffraction (TRHEPD). The pulse width of 1.2 μs or 1-10 ns (variable) of this beam is, however, too long for the positron lifetime spectroscopy (PALS) and too short (or too many positrons are stuffed in a pulse) for the energy spectroscopy and angular correlation measurements of the annihilation γ-rays (ACAR). In order to make such ordinary positron annihilation measurements available, a pulse stretching system is necessary.

At National Institute of Advanced Industrial Science and Technology (AIST), such system is already used for PALS experiments; after stretching the pulse, the beam is re-pulsed at a re-pulsing section to be 100-ps pulse width at around 1 MHz repetition rate, which is suitable for PALS. However, the beam loses much intensity during the re-pulsing process. The initial beam has an energy spread of 20 eV, but a part of it is trimmed to be an energy spread of 10 eV at the pulse stretching system, where the positrons are trapped in a Penning-Malmberg trap and the exit electrode voltage is reduced to let the trapped positrons go out downstream. Furthermore re-pulsing section with a chopper and bunchers accepts only positrons with energy spread of 5 eV.

In order to obtain, in the SIP collaboration, a know-how to prevent the losses of the AIST positron beam, we have developed at KEK-SPF a low-loss pulse stretching section providing DC-like beam with a much smaller energy spread. This system is also essentially a Penning-Malmberg trap. A cylindrical entrance electrode, a 6-m long trapping electrode, and an exit electrode were implemented. The entrance electrode voltage, normally kept at 5.5 kV, is temporarily lowered to 4.5 kV to let a 1.2-μs-width positron pulse with an energy of 4.8±0.05 keV into the trapping electrode. Positrons then travel along a solenoid magnetic field down to and are reflected back from the exit electrode kept at 5.0 kV. The entrance electrode voltage is raised back to 5.5 kV before the positrons come back so that the positrons are trapped. The trapping electrode voltage is then increased gradually, instead of reducing the exit electrode voltage, letting the positrons spill over the exit electrode which is kept at a constant voltage. By adjusting the sweeping speed of the trapping electrode voltage, we obtain a pulse stretched beam of a width up to 20-ms with a fixed energy of 5.0 keV. It is operated at 50Hz synchronized with the linac operation.

In order to check the performance of the pulse-stretching section a gate valve at its downstream was closed to let the positrons annihilate on it. The annihilation γ-rays were detected with a plastic scintillator mounted on a photomultiplier tube, whose anode signals were observed by a digital oscilloscope. It was confirmed that the 50Hz positron pulse was certainly stretched up to 20 ms at the same frequency. The temporal distribution of the positrons in the stretched pulse is adjustable by changing the temporal variation of the trapping electrode voltage.

This pulse stretching technique can be transferred to AIST PALS system. The concept of the present system is also applicable for the energy elevation of a pulsed slow-positron beam.

This work was partly supported by Toray Science and Technology Grant, Cross-ministerial Strategic Innovation Promotion Program (SIP, unit D66) operated by the cabinet office, and Grant-in-Aid for Scientific Research (S) No. 24221007 from JSPS.

*Present address: Quantum Beam Science Center, National Institutes for Quantum and Radiological Science and Technology, 1233 Watanuki, Takasaki, Gunma 370-1292, Japan


64

Development of 2000 K Class High Temperature In Situ Transmission Electron Microscopy for Study of Heat-Resistant Materials

Tokushi Kizuka1) †, Shogo Kikuchi1), Manabu Tezura1), and Tomo-o Terasawa1, 2) 1) Division of Materials Science, Faculty of Pure and Applied Sciences, Univ. of Tsukuba

(1-1-1, Tennoudai, Tsukuba, Ibaraki 305-8573, Japan) 2) Present address: Institute of Materials and Systems for Sustainability, Nagoya Univ.

(Furocho, Chikusa, Nagoya, Aichi 464-8603, Japan)

†E-mail: [email protected]

Transmission electron microscopy (TEM) provides all the kinds of the information of microstructures, i.e., crystal structures, textures, compositions, surfaces, interfaces, grain boundaries, and point defects. Thus, this method has contributed to the progress of materials science. In particular, in situ TEM enables the analysis of the microstructural dynamics in various environments in which materials are actually used. Since high-temperature environments are subjects to advanced structural materials, heating stages for in situ TEM have been developed. Various structural dynamics relating to texture control, e.g., recrystallization, phase transition, precipitation, and dislocation movement, have been investigated, resulting in the feedback of material design. However, the typical maximum temperature of commercial heating stages has still been limited under 1200 K, which is at least 500 K lower than the temperatures required for the studies of recent advanced heat-resistant structural materials, such as engine and aircraft materials. The authors developed a new type of a 1300 K class high temperature stage for TEM of various shaped materials, i.e., bulk materials in addition to nanometer-sized isolated nanostructures, such as particles, fibers, and thin films, as reported in the 1st Symposium on SIP Innovative Measurement and Analysis for Structural Materials (SIP-IMASM 2015). The authors have taken over the challenge and have made various improvements of the previous heating system, e.g., the materials and shape of heater, the mounting manner of the heater, the purpose-built power cable assemble, and the dedicated power supply system. As a result, we have achieved the possible heating temperature up to 2000 K [1], which is the maximum temperature of the heating stage of TEM that have been already constructed. In this paper, we report the results.

We designed a new type of heaters for in situ TEM on the basis of a Joule-heating method. The heater was mounted on a current controlled specimen holder of the transmission electron microscope for dynamic atomistic observation at the University of Tsukuba (JEOL JEM-2011KZ-Custom). Figure 1 shows a photograph of the specimen holder.

Fig. 1. The 2000 K-heating specimen holder for TEM.

The heating state of the heater and specimen inside the microscope was monitored using an optical microscope attached to the column of the electron microscope. The stability of the heating stage was confirmed by in situ high-resolution observation of the lattice fringes, as reported in this symposium [2]. In addition to the improvement of the maximum temperature, we found that the developed heating stage can be applied to most of transmission electron microscopes without any additional modification since the structure of the stage is simple. Therefore, we expect that our heating stage will open new fields of study of microstructural dynamics of heat-resistant materials at high temperatures up to 2000 K.

This study was supported by Cross-ministerial Strategic Innovation Promotion Program – Unit D66 – Innovative measurement and analysis for structural materials.

References [1] Tomo-o Terasawa, Shogo Kikuchi, Manabu Tezura, and Tokushi Kizuka, J. Nanosci. Nanotechnol., in print. [2] Shogo Kikuchi, Manabu Tezura, Tomo-o Terasawa, and Tokushi Kizuka, in this symposium.


65

High Temperature In Situ Transmission Electron Microscopy of Heat-Resistant Ceramics

Shogo Kikuchi1), Manabu Tezura1), Tomo-o Terasawa1, 2), and Tokushi Kizuka1) † 1) Division of Materials Science, Faculty of Pure and Applied Sciences, Univ. of Tsukuba

(1-1-1, Tennoudai, Tsukuba, Ibaraki 305-8573, Japan) 2) Present address: Institute of Materials and Systems for Sustainability, Nagoya Univ.

(Furocho, Chikusa, Nagoya, Aichi 464-8603, Japan)


In our research group in SIP-IMASM project, we have developed high temperature in situ transmission electron microscopy (TEM) that provides all the kinds of the information of high temperature dynamics of microstructures of heat-resistant materials. This is because this method has contributed to the progress of materials science of heat-resistant materials. We have already developed a new type of a 1300 K class high temperature stage for TEM of various shaped materials, as reported in the 1st Symposium on SIP Innovative Measurement and Analysis for Structural Materials (SIP-IMASM 2015). We have made further various improvements of the previous heating system and could succeed the increase in the heating temperature up to 2000 K, as reported in this symposium and the original paper [1, 2]. The maximum temperature of our heating stage is the highest in the published scientific information. In this study, we report the application of this high temperature in situ TEM to heat-resistant ceramics.

Various heart-resistant ceramics were prepared using ion-beam sputtering and were deposited on originally designed mesh heaters. The deposited heaters were mounted on the specimen holder for high temperature in situ TEM. The holder was then inserted into the transmission electron microscope for dynamic atomistic observation at the University of Tsukuba (JEOL JEM-2011KZ-Custom) [3, 4]. Figure 1 shows a photograph of the microscope. The specimen chamber of the microscope was evacuated, first by a turbomolecular pump and then by an ion pump, resulting in a vacuum of 1 × 10−5 Pa. Inside the microscope, bias voltage was applied to the heater to increase the specimen temperature. The heating state of the heater and specimen inside the microscope was monitored using an originally designed optical microscope attached to the column of the microscope. During the heating process, structural dynamics was observed in situ by lattice imaging via high-resolution TEM using a video capture system. The time resolution of image observation was 40 ms. The high-resolution imaging and the signal detection of temperature were simultaneously recorded and analysed for each image using our own software. Thus, we confirmed that the method enabled the investigation of high temperature dynamics of the interior, surfaces, grain boundaries, interfaces, and point defects of heat-resistant ceramics at the atomic scale.

Fig. 1. The 2000 K-heating TEM.


References [1] Tokushi Kizuka, Shogo Kikuchi, Manabu Tezura, and Tomo-o Terasawa in this symposium. [2] Tomo-o Terasawa, Shogo Kikuchi, Manabu Tezura, and Tokushi Kizuka, J. Nanosci. Nanotechnol., in print. [3] Tokushi Kizuka and Shin Ashida, Sci. Rep. 5, 13529 (2015). [4] Manabu Tezura and Tokushi Kizuka, Sci. Rep. 6, 29708 (2016).


66

Development of Picometer Scale Specimen Manipulation for High Temperature In Situ Transmission Electron Microscopy of Heat-Resistant Materials

Manabu Tezura1) and Tokushi Kizuka1) † 1) Division of Materials Science, Faculty of Pure and Applied Sciences, Univ. of Tsukuba

(1-1-1, Tennoudai, Tsukuba, Ibaraki 305-8573, Japan)


Advanced structural materials have been used in various kinds of ultimate environments. In particular, heat-resistant materials used in engine and aircraft elements are subjected to high temperatures at 1700 K. In addition, high strain and stress caused by thermal expansion in such high temperatures leads to fatal damages of the materials. Hence, an effective method to develop advanced heat-resistant structural materials is to observe directly the microstructural dynamics in replicated conditions of environments of actual usage. In situ transmission electron microscopy (TEM) of mechanical deformation of materials at high temperatures achieves full potential of realization of such investigation and serves indubitably one of the objectives of the project relating to this symposium. However, some problems in apparatuses using in previously-developed in situ TEM have stunted the application; the maximum heating temperature was at highest 1000 K and the deformation manner was restricted to uniaxial tensile ones with rough displacement steps of micrometer scales. For the improvement of heating temperature, we already developed a new type of a 1300 K class high temperature stage for TEM, as reported in the 1st Symposium (SIP-IMASM 2015). We have also made further various improvements of the previous heating system and could succeed the increase in the heating temperature up to 2000 K, as reported in this symposium and the original paper [1, 2]. On the other hand, the development of the specimen manipulation for high temperature in situ TEM of deformation is not engaged, In this study, we report the development of picometer scale specimen manipulation for high temperature in situ TEM.

The method used was based on in situ high-resolution TEM for experimental mechanics of materials. We introduced a new type of piezomanipulation system for various deformation tests, e.g., tensile, compression, and shear. A schematic of this method is shown in Fig. 1. The transmission electron microscope for nanometer manipulation at the University of Tsukuba (JEOL JEM-2011KZ-Custom) was used. Using this in situ TEM, we examined the deformation of molybdenum, silver, zinc, and the manipulation of isolated nanocarbon [3–5].

Fig. 1. Picometer specimen manipulation in in situ TEM for deformation.


References [1] Tomo-o Terasawa, Shogo Kikuchi, Manabu Tezura, and Tokushi Kizuka, J. Nanosci. Nanotechnol., in print. [2] Tokushi Kizuka and Shin Ashida, Sci. Rep. 5, 13529 (2015). [3] Manabu Tezura and Tokushi Kizuka, Sci. Rep. 6, 29708 (2016). [4] Kohei Yamada and Tokushi Kizuka, Nanosci. Nanotecnol. Lett., in print (2016). [5] Kohei Yamada, Tokushi Kizuka, J. Phys. Soc. Jpn., accepted.


67

Computer Simulation for nonlinear ultrasonic generation at unbonded interface in solid.

Hisashi Yamawaki1), Kanae Oguchi3), Hideki Hatano2), Makoto Watanabe1), Manabu Enoki3) 1) National Institute for Materials Science, 1-2-1, Sengen, Tsukuba, Ibaraki 305-0047 Japan

2) National Institute for Materials Science, 1-1, Namiki, Tsukuba, Ibaraki 305-0044 Japan 3) University of Tokyo, 7-3-1, Hongo, Bunkyo-ku, Tokyo 113-0033 Japan


For detection of closed cracks in solid materals, nonlinear ultrasonic generation at closed interface in solid is utilized in advanced nondestructive testing (NDT). Incidence of ultrasonic waves with high amplitude at unbonded interface in solid causes transient opening of the interface, and repetitive opening-closing behaviour generates deformed ultrasonic waves at the interface. However, detailed mechanism of the generation and quantitative evaluation of nonlinear ultrasonic is still under investigation. In our previous research[1], mechanisms of the generation were investigated by 1-dimenstional computer simulation using finite difference method (FDM), and it was shown that opening-closing motion of the interface generated saw-tooth like displacement waveform of transmitted waves. Based on the results obtained by the 1-D. calculation, 2-D. computer simulation of ultrasonic waves at the closed interface in solid was performed using the Improved-FDM[2]. Principle of the 2-D. and 3-D. calculation model of closed interface was basically same as one of the 1-D. model. The interface was represented by small region constructed with calculation units of FDM, and longitudinal stress of the interface region was used to determine state of the interface. When the longitudinal stress perpendicular to the interface was plus value (tensile stress), the interface was assumed to be open and the interface region was treated as gap. As a result of 2-D. simulation, when longitudinal wave entered the interface perpendicularly, the behaviour of the interface causing generation of saw-tooth like ultrasonic displacement was observed as well as shown in 1-D. calculation. In the case of the angled incident on the interface, not only saw-tooth displacement but also slipping of interface boundary were observed, simultaneously. By the simulation, basic mechanisms of the nonlinear ultrasonic generation at closed interface was clarified, and it will make possible to utilize quantitatively the nonlinear ultrasonic for materials evaluation. Calculated results of ultrasonic behaviour at unbonded interface in solid.

Fig. 1 shows ultrasonic displacements of front and back nodes of closed interface in FDM. In 1-D solid, compression stress(T0=-1Pa) was distributed uniformly. The stress acts as force to close the interface. When ultrasonic stress amplitude was enough strong for opening the interface, opening-closing motion occurred. Noticeable point was that saw-tooth waveform of the back node had period of constant particle velocity (=T0VL/C0) during the opening.

Fig. 2 shows 2-D calculation for angled incidence of longitudinal wave at closed interface. Displacement waveforms for direction perpendicular to the interface are same with the 1-D calculation. Waveforms for parallel direction to the interface indicate slipping motion of the interface. In the case of calculation with limited length of the interface, amount of slipping is limited by the edges of the interface.

References [1] H. Yamawaki, Journal of Physics: Conference Series 520, 012020 (2014) [2] H. Yamawaki, J. of the Japanese Society for Non-Destructive Inspection 59 624 (2010 in Japanese)

Fig. 1. Displacement waveforms of nodes at closed interface obtained by 1-D. calculation with FDM. It shows evidently basic mechanism of the nonlinear ultrasonic generation[1].

Fig. 2. Visualization and waveforms of displacement at closed interface. Angled incidence of longitudinal wave causes saw-tooth motion in x-direction and slip motion in y-direction.


68

City bus stops (Namiki ni-chome and highway bus)


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Timetable (Namiki ni-chome and highway bus)


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Free shuttle bus from Tsukuba station to AIST


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Timetable of free shuttle bus


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Tsukuba Express (TX) and JR lines


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Timetable of the Tsukuba Express (TX)


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Timetable of JR lines


75

Lunch guide Please ask the Japanese staff for details.


76

Program & Abstract Booklet 2nd Symposium on Innovative Measurement and Analysis for Structural Materials

Published on September 27, 2016 Editor

National Institute of Advanced Industrial Science and Technology (AIST) 1-1-1, Umezono, Tsukuba, Ibaraki, 305-8568, Japan Committee for the 2st Symposium on Innovative Measurement and Analysis for Structural Materials TEL: 029-861-5685, URL: https://staff.aist.go.jp/m.ohkubo/SIP-IMASM e-mail: [email protected] M. Ohkubo, Y. Harada, P. Fons, B. O’Rourke, Y. Mizoguchi, A. Miyoshi, and N. Koizumi

No part of this report should be reproduced or copied without permission from the editor and the authors.

2016

2

2016 9 27

305-8568 1-1-1

2

TEL: 029-861-5685, URL: https://staff.aist.go.jp/m.ohkubo/SIP-IMASM e-mail: [email protected]

The 2nd Symposium on SIP Innovative Measurement and Analysis for Structural Materials (SIP-IMASM 2016)

The 2nd Symposium on SIP Innovative Measurement and Analysis for Structural Materials (SIP-IMASM 2016)

AIST16-C00015

program & abstract booklet of symposium on … › m.ohkubo › sip-imasm › sympo › 2016 ›...

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