MMRC 2004Metals and Materials Research Metals and Materials Research

Colloquium Colloquium

April 7, 2004April 7, 2004

Department of Metals and Materials EngineeringUniversity of British ColumbiaVancouver BC CANADA

Metals and Materials Research Colloquium Schedule

April 7, 2004

Presenter Title

Session I: (10:00 am – 11:00 am)

A. Thirumalai High Temperature

Microsegregation and back diffusion study of RR-2100 series Ni-base single crystal superalloys

C. Estey Metals Processing Residual Stress Formation during the Quenching of an Aluminum Wheel

K. Mukherjee Microstructure Grain-Refinement in Dual-Phase Steel

Session II: (11:10 – 11:50)

M. Mazinani Microstructure Deformation Behaviour of an Intercritically Annealed

Dual-Phase Steel F. Cao Ceramics Measurements of The Effective Thermal Conductivity of Oxides

System

LUNCH (11:50 – 13:00)

Session III: (13:00 – 14:00)

E. Asselin Electrochemical De-alloying of a Ni-Cr-Mo alloy in ammoniated sulphate solution

S. Zhou Ceramics Hydration Studies on Magnesia-Containing Bricks

Q. Guoming Hydrometallurgy Minor Element Behavior in the INCO CRED Process

Metals and Materials Research ColloquiumMMRC

Abstracts 2004

MMRC2004 April, 2004

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Microsegregation and back diffusion study of RR-2100 series Ni-base single crystal superalloys

Anand Thirumalai

High Temperature Materials; Dr. Roger Reed & Dr. A. Akhtar Ampel Room # 412

Department of Metals and Materials Engineering, University of British Columbia

Research Summary: Solute redistribution during solidification of alloys has important effects both on the freezing characteristics and on the structure of the solidified material. The rate at which the concentration gradients within the solid and liquid phases get eliminated determines the solute redistribution. If the system is always in thermodynamic equilibrium then the solidification behaviour can be described by the lever rule, which assumes complete mixing of the solute in both the solid and liquid phases. A complementary case to the lever rule is the Scheil treatment wherein there is no solute diffusion in the solid. In practice however, solidifying alloy systems lie between these two limits. In such systems microsegregation can be modeled by assuming complete mixing of solute in the liquid phase with partial mixing in the solid phase. This partial mixing controlled by solute diffusion is termed “back diffusion.” Microsegregation at the length scale of the secondary dendrite is well characterized by either semi-analytical or numerical models that address back diffusion. The present study aims at characterizing microsegregation at the length scale of the primary dendrite and developing a mathematical model for the solute redistribution.

(a) (b)

Figure (a) Dendrites in the quenched region. Figure (b) WDX image showing rhenium content variation along the height of the dendrite in the quenched region.

MMRC2004 April, 2004

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Residual Stress Formation during the Quenching of an Aluminum Wheel

Christina Estey

Materials Processing; Steve Cockcroft & Daan Maijer AMPEL Building, Room 412

Department of Metals and Materials Engineering, University of British Columbia

Research Summary: Al-Si-Mg casting alloys are being used for die cast wheel production due to their excellent castability, corrosion resistance and good mechanical properties in the heat-treated condition. The mechanical properties of this aluminum alloy (A356) can be greatly improved by a heat treatment process, which consists of a solution heat treatment, a quenching operation and an age hardening heat treatment. The quench is a critical operation in determining the mechanical properties as well as the amount of wheel deformation. The large thermal gradients that arise during quenching induce large thermal stresses, which in turn, can cause in-elastic yielding leading to distortion of the wheel. To develop a better understanding of the process, mathematical modeling is being applied to simulate the thermal stress formation during quenching and thereby understand the factors that influence wheel deformation. This presentation will focus on the development of uncoupled thermal and stress models for the quenching operation of an aluminum wheel. The thermal model requires an accurate description of the temperature-dependent thermal physical properties for A356 in the solution treated condition, as well as the heat transfer coefficient, which was acquired experimentally. For the stress model, accurate constitutive behavior data for the A356 alloy is required in determining the residual stress formation in the wheel. The magnitude of the residual stress, leading to wheel distortion will then be analyzed.

Thermal Model Representation of the A356 Die Cast Aluminum Wheel during the Quench

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De-alloying of a Ni-Cr-Mo alloy in ammoniated sulphate solution

Edouard Asselin Hydrometallurgy Group; A. Alfantazi, S. Rogak

Frank Forward Building, Room 301B Department of Metals and Materials Engineering, University of British Columbia

Research Summary: During the process of Supercritical Water Oxidation (SCWO) organic chemical streams are oxidized at high temperature and pressure, typically in excess of 374ºC and 22.1 MPa. These conditions can create highly corrosive environments and eventually SCWO reactor tube failures. Corrosion in SCWO systems is one of the major stumbling blocks to the successful implementation of this technology. Ni-Cr-Mo alloys have seen widespread use in severe-service applications such as SCWO. Understanding the corrosion mechanisms of Ni-Cr-Mo alloys is a key issue in forecasting and preventing corrosion related failures. Recently it has been suggested that these alloys are susceptible to selective leaching of Ni at high temperatures and pressures when in the presence of complexing agents. To our knowledge, there is no previous study on the subject of de-alloying of Ni-Cr-Mo alloys at any temperature. This work has focused on the corrosion characteristics of alloy 625 (UNS N06625 - 58%Ni, 22%Cr, 9%Mo, 4%Nb) in ammoniated sulphate solutions in an effort to correlate room temperature results with those obtained under the conditions of SCWO. It is demonstrated that de-alloying is highly potential dependant and occurs most rapidly at transpassive potentials. Furthermore, the corrosion morphology observed on alloy 625 at room temperature is analogous to the morphology observed in its de-alloyed layers at high temperatures and pressures. This suggests that room temperature electrochemical experiments have a useful predictive capacity extending to conditions beyond those at which they are performed.

(A) (B)

Transpassive corrosion product on surface of alloy 625 after 36 hours immersion in ammoniated sulphate solution - (a)surface micrograph (b) cross section EDS map

MMRC2004 April, 2004

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Deformation Behaviour of an Intercritically Annealed Dual-Phase Steel

Mohammad Mazinani

Microstructure Engineering Group; Supervisor: W.J. Poole Office: AMPEL Building, Room 260

Department of Metals and Materials Engineering, University of British Columbia

Research Summary: Ferrite-martensite dual-phase (DP) steels with a good combination of high strength and high ductility are of great importance to industry, particularly the automotive sector. The aim of this research was to study the deformation behaviour of martensite phase and its effect on the stress-strain behaviour of low carbon (0.06%C) cold-rolled C-Mn-Mo DP steel samples with different martensite contents and morphologies. Heat treatment cycles to produce DP steel samples were conducted in the Gleeble machine. Depending on the heating rate by which steel samples were heated up to the intercritical temperatures, martensite phase with two distinct morphologies was formed, a) almost equiaxed with heating rate of 1 ºC/sec, b) mostly banded martensite islands with 100 ºC/sec heating rate. The measurement of martensite deformation was conducted on the fractured tensile specimens using the image analysis software available through a series of thickness measurement of martensite islands in different regions of the steel microstructure. Despite the elastic behaviour of martensite phase in DP steels with relatively higher carbon contents reported in the literature, martensite phase in this low carbon DP steel was found to undergo plastic deformation during tensile loading. Moreover, sample orientation was found a parameter affecting the martensite strain. In the DP steel sample with 41% martensite (with a banded martensite structure), the martensite phase experienced the true strain of about 8% during tensile loading in the longitudinal direction, but this strain decreased to about 4% in the same steel sample when loaded in the transverse direction.

0

4

8

12

16

0 2 4 6 8 10 12 14 16 18 20 22 24 26

Average Thickness of Segments (µm)

Freq

uenc

y (%

)

Undeformed Region Uniform Deformation Region

Tensile Strain in Martensite = 8%

Relative thickness of martensite islands in two different regions, undeformed and uniform deformation region, in a DP steel with 41% martensite loaded in the longitudinal direction.

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Hydration Studies on Magnesia-Containing Bricks

Shuxin Zhou Ceramics Group; Dr.T. Troczynski & Dr. G. Oprea

AMPEL, Room 124C Department of Metals and Materials Engineering, University of British Columbia

Research Summary: Magnesia, which has a high refractoriness and high corrosion resistance to basic slags or molten metals, is a very valuable raw material for the refractory industry. Magnesia-based refractories are very extensively used in metallurgical furnaces and cement kilns as fired or unfired products. The major concern for the users of magnesia-based materials is the degradation of the refractories by the hydration of magnesia. The hydration of pure MgO or refractory grades of granular magnesia was extensively studied, however, there was scarce research on the hydration of magnesia bricks. The current work is to investigate the hydration at various conditions, such as different temperatures of steam and relative humidity levels. The changes in properties of magnesia bricks, such as modulus of elasticity, air permeability, pore size, and pore size distribution, were correlated with the hydration data. The mechanisms and processes of hydration of MgO in magnesia-containing bricks will be proposed. Based on this results, the effective solutions to improve the hydration resistance of MgO-containing bricks will be developed.

0

0.3

0.6

0.9

1.2

1.5

1.8

0 20 40 60 80Hydration Time, hrs

Wei

ght I

ncre

ase,

% No.1No.2No.3No.4

The changes in the weight with the time in boiling water for different MgO bricks. MgO CaO/SiO2 No.1 87.3% 7.0 No.2 92.2% 1.7 No.3 93.0% 0.4 No.4 96.5% 2.5

MMRC2004 April, 2004

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Measurements of The Effective Thermal Conductivity of Oxides System

Feng Cao

Metals Processing Group; Ray Meadowcroft, Peter Barr Frank Forward Building, Room 208B

Department of Metals and Materials Engineering, University of British Columbia

Research Summary: Firstly, a new experimental apparatus was introduced for measuring the effective thermal conductivity of oxides systems under high temperature and in shear flow. By using the same apparatus, we can also measure the effective thermal conductivity of systems under high temperature and/or in shear flow. Secondly, the experimental plan would lead to the identification of the important system variables and the understanding of their impact on the effective thermal conductivity values as well as the values for each individual heat transfer mechanism. Thirdly, the mathematical modeling of the corresponding heat transfer situation would be established. The reliability of the mathematical model would be verified by comparing the values produced by the model and by the experiment.

Apparatus designed for measuring the thermal conductivity of oxides system

MMRC2004 April, 2004

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Minor Element Behavior in the INCO CRED Process

Qin, Guoming Hydrometallurgy Group; David B. Dreisinger

Frank Forward Building, Room 406 Department of Metals and Materials Engineering, University of British Columbia

Research Summary: In INCO's Copper Refinery Electrowinning Department the copper sulfide residue containing precious metals is subjected to an oxidative pressure leach. The leach produces a copper sulfate solution and basic copper sulfate and precious metals solids. The basic copper sulfate is releached with sulfuric acid and produce copper sulfate solution and a precious metals residue. Our goal is to investigate the behavior of minor elements during the leach process. The minor elements include iron, arsenic, bismuth, antimony, selenium, tellurium, lead, nickel and cobalt. The distribution and concentrations of these elements were studied, as well as oxygen consumption in pressure leaching. Especially the selenium speciation in the filtrate solution was measured. We have mainly investigated the behavior of elements in the following conditons: the copper/acid ratios (in electolyte), copper/sulfur ratios (in feed) and impurities addition (in electrolyte). From these laboratory experiments the mionr element behavior can be explored. In order to analyze the selenium species in the solutions, we developed a feasible methed with Atomic Fluorescence Spectrometry with Hydride Generation. The solution was pretreated with ion-exchange column to remove references without loss of selenium. Future work will be focused on the effect of oxygen consumption on the behavior of minor elements during oxidative pressure leaching process.

Fig.1 SEM micrograph of final residue Fig.2 Effect of Cu/S ratio on distrbution of selenium

MMRC2004 April, 2004

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Grain-Refinement in Dual-Phase Steel

Krishnendu Mukherjee Microstructure Engineering Group; Dr. Matthias Militzer

Office: AMPEL 349 Department of Metals and Materials Engineering, University of British Columbia

Research Summary: Currently, grain refinement is being studied to increase strength in steel. For automotive applications this strengthening mechanism can only be applied when there is no considerable decrease in ductility. In this regard dual phase steel is a potential candidate. The aim of the present study is to refine ferrite grain size in a commercial grade dual phase steel with a tensile strength of 600 MPa (DP 600). Deformation Induced Ferrite Transformation (DIFT) was selected as the grain refining technology. In this method steel is rapidly cooled from the austenitisation temperature to 15-50°C above the Ar3 temperature to produce metastable austenite. The steel is then deformed and quenched to produce fine grained ferrite. The effect of austenitisation temperature, deformation temperature, and amount of deformation on the final microstructure has been determined with tests performed on a Gleeble 3500 thermomechanical simulator. Figure 1 shows the maximum ferrite grain refinement which was observed for a true strain of 0.6 at a deformation temperature of 685°C where the final microstructure consists of an inhomogeneous ferrite grain size with predominantly submicron sized grains but also a few larger grains (~4 mm). Future work will involve investigating the effect of DIFT on a base steel (having the same chemistry as of the dual phase steel studied, but with no Mo).

Figure 1: Optical microstructure of dual phase steel (DP 600) after applying a true strain of 0.6 at a deformation temperature of 685°C.

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Biographies

Anand Thirumalai

B. Tech., Indian Institute of Technology at Roorkee

Thesis Title: Back diffusion study of RR-2100 series Ni-base Single crystal superalloys Supervisor: Dr. Roger Reed

Edouard Asselin

B. A. Sc., University of Ottawa Thesis Title: De-alloying of Ni-based alloys in high temperature/high pressure environments Supervisor: Dr. Akram Alfantasi Dr. Steve Rogak

Christina Estey

B.A.Sc., Univ. British Columbia Thesis Title: Mathematical Modeling of Deformation in Die Cast A356 Wheels during Heat Treating

Supervisor: Dr. Steve Cockcroft Dr. Dan Maajer

Mohamed Mazinani B. Sc., Sharif University of

Technology, M. Sc. University of Tehran

Thesis Title: Deformation behaviour of dual-phase steel Supervisosr: Dr. Warren Poole

Shuxin Zhou

B. Eng., Tianjin University M. Eng. Shanghai Institute of Ceramics

Thesis Title: Hydration Mechanisms of Magnesia-Containing Refractory Bricks Supervisosr: Dr. Tom Troczynski Dr. George Opera

Guoming Qin

B.Eng. Kunming University of Science & Technology Thesis Title: Minor element behaviour in INCO CRED process Supervisosr: Dr. D. Dreisinger

Krishendu Mukherjee B. Eng., Bengal Engineering

College, M. Eng. Indian Institute of Technology

Thesis Title: Grain Refinement in Dual-Phase Steel Supervisosr: Dr. Mathias Militzer

Feng Cao

B. Eng., Northeastern University, China

Thesis Title: Measurements of The Effective Thermal Conductivity of Oxides System Supervisosr: Dr. R. Meadowcroft Dr. P. Barr