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Materials Science & Engineering A

journal homepage: www.elsevier.com/locate/msea

Influence of texture and grain refinement on the mechanical behavior ofAA2219 fabricated by high shear solid state material deposition

O.G. Riveraa, P.G. Allisona,⁎, L.N. Brewerb, O.L. Rodriguezc, J.B. Jordona, T. Liub,W.R. Whittingtond, R.L. Martense, Z. McClellandf, C.J.T. Masona, L. Garciaf, J.Q. Sug,N. Hardwickg

a Department of Mechanical Engineering, The University of Alabama, Tuscaloosa, AL, United StatesbDepartment of Metallurgical and Materials Engineering, The University of Alabama, Tuscaloosa, AL, United StatescMaterials and Processes Laboratory, Marshall Space Flight Center, NASA, Huntsville, AL, United Statesd Center of Advanced Vehicular Systems, Mississippi State University, Starkville, MS, United Statese Central Analytical Facility, The University of Alabama, Tuscaloosa, AL, United StatesfUS Army Engineer Research and Development Center, Vicksburg, MS, United Statesg Aeroprobe Corporation, Christiansburg, VA, United States

A R T I C L E I N F O

Keywords:Additive manufacturingAluminum alloysCharacterizationElectron microscopyHardnessStress/strain measurements

A B S T R A C T

Issues with rapid grain growth, hot cracking and poor ductility have hindered the additive manufacturing andrepair of aluminum alloys. Therefore, this is the first investigation to spatially correlate the processing-structure-property relations of a precipitation hardened aluminum alloy 2219 (AA2219) material with respect to de-position orientations and build layers. The AA2219 material was processed by a high deposition rate (1000 cm3/h) solid-state additive deposition process known as Additive Friction Stir Deposition or MELD. An equiaxed grainmorphology was observed in the three orientations, where Electron Backscatter Diffraction (EBSD) identified alayer-dependent texture with a strong torsional fiber A texture in the top of the build transitioning to weakertextures in the middle and bottom layers. Interestingly, the tensile behavior reflected the texture layer-depen-dence with tensile strength increasing from the bottom to the top of the deposition. However, there were nostatistically significant differences in hardness measured from the top to the bottom of the deposition.Furthermore, no orientation dependence on mechanical properties was observed for compression and tensionspecimens tested at quasi-static (0.001/s) and high (1500/s) strain rate. Transmission Electron Microscopy(TEM) determined a lack of θ′ precipitates in the as-deposited cross-section, therefore resulting in no pre-cipitation strengthening.

1. Introduction

The solid state material deposition process known as MELD orAdditive Friction Stir Deposition (AFS-Deposition) is a transformativeprocess for solid-state additive manufacturing (AM), repair, joining, oradding secondary features, which is being reported for the first time ondeposited aluminum alloys, specifically Aluminum Alloy (AA) 2219.This solid state deposition process shares some similarities to other highshear and elevated temperature solid-state processes such as shear ex-trusion or friction stir welding and processing (FSW/P), but is sig-nificantly different in the aspect that feedstock material flows through arotating hollow tool with the feedstock material being deposited onto asubstrate while remaining completely in the solid state. As described inprevious research by Rivera et al. [1] on MELD processed IN625, the

solid state material deposition can either feed from solid or metalpowder material, pushing it through a non-consumable rotating cy-lindrical tool. This will generate heat and plastically deform the feed-stock material under controlled pressure from the tool while layers arebuilt upon a substrate. Once a layer is added, the tool height increasesto begin the deposition for the next layer, creating a strong me-tallurgical bond between layers. Some advantages of this process aregrain refinement, homogenization, and reduction of porosity. Duringthe process, temperatures are similar to those in the stir zone (SZ) ofFSW, which are estimated to be between 0.6 and 0.9 Tm, where Tm isthe melting point of the material [2]. Being a highly scalable process,with deposition rates for aluminum alloys over 1000 cm3/h, this pro-cess allows for repairing, coating, and/or building fully-dense mate-rials.

https://doi.org/10.1016/j.msea.2018.03.088Received 29 September 2017; Received in revised form 20 March 2018; Accepted 21 March 2018

⁎ Corresponding author.E-mail address: [email protected] (P.G. Allison).

Materials Science & Engineering A 724 (2018) 547–558

Available online 23 March 20180921-5093/ © 2018 Elsevier B.V. All rights reserved.

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Unique features of the AA2219 is that the material is a precipitationstrengthened alloy with a variety of beneficial properties such as highstrength-to-weight ratio, suitable weldability, resistance to stress cor-rosion cracking, and superior properties at cryogenic temperatures[3,4]. The mechanical properties of AA2219 spread through a widetemperature range from −250 to +250 °C [5], that in addition to theaforementioned benefits makes this alloy attractive for aerospace ap-plications. AA2219 has been successfully joined by different conven-tional joining processes, such as gas metal arc welding [6], gas tungstenarc welding [6], plasma arc welding [7], and FSW [3,4,6,8,9].

Little AM research on AA2219 has been reported to date. However,

AA2219 electron beam freeform (EBF) AM has been reported in theopen literature [10–12], in which they observed that, by varying theprocess parameters, the microstructure varied from fine equiaxed grainsto dendritic. In addition, the researchers reported tensile mechanicalproperties of the as-deposited AA2219 using EBF had a yield strength(YS), ultimate tensile strength (UTS), and elongation of 100MPa,275MPa, and 18%, respectively [10–12].

FSW of AA2219, which is based on a similar solid-state concept,provides a starting point for understanding the microstructure evolu-tion that occurs during solid-state processing. FSW has been a usefuloption for welding similar and dissimilar metals that were originallypresented in 1991 by TWI [13], and with prior FSW research onAA2219 examining the effectiveness, optimal parameters, and me-chanical properties [3,8,14,15]. FSW is popular in multiple industries,such as aerospace and automotive, due to higher effective weld prop-erties when compared to other welding techniques due to better re-tention of base material mechanical properties, less distortion and lessweld defects [16,17]. Additive FSW has even been investigated by anumber of researchers where plates of stacked material are joined to-gether by a pin-tool penetrating into the successively stacked plates[18–20]. However, MELD depositions significantly differ from additiveFSW where now material is extruded through a hollow rotating tool.The microstructure of FSW components has also been a point of interestamong researchers with specific emphasis on the stir zone (SZ), alsoknown as the nugget [3,21]. This is the area where the grains re-crystallize, and grain refinement is observed [3,8,21]. The mechanicalproperties in this region are desirable, and for that reason a processingtechnique called FSP was also developed [22–25]. The FSP techniquehas also been a topic of interest experiencing significant research[22,24–26]. In both FSW and FSP as well as MELD, the microstructuremay experience dynamic recrystallization (DRX) [23–25]. There aretwo types of DRX in the literature, continuous DRX and discontinuousDRX. The difference between them is that, in continuous DRX, newgrains are formed by a gradual increase in the misorientation betweenthe subgrains [24,25]. Under discontinuous DRX, grains with high-angle grain boundaries form through dynamic nucleation and growthfrom a previously deformed microstructure. Previous research has de-monstrated that it is common for aluminum alloys to undergo dynamicrecovery (DRV) during hot deformation [24,25]. Additionally, researchby Su et al. [21–26] on AA7075 has shown that the FSW and FSP willexperience different mechanisms such as discontinuous DRX, DRV, andcontinuous DRX at different stages of the microstructural evolution[21,24,25].

Due to a variety of end uses for AA2219, the mechanical propertiesof multiple tempers were investigated in previous FSW research [3,4,8].Tensile and microhardness testing on FSW butt welds of thick AA2219-

Build Direction(BD)

Deposit (AA2219)

Tool traverse direction(longitudinal direction)

(LD)

Transversedirection (TD)Substrate (AA2219-T851)

A B

Hollow RotatingTool

Solid or PowderAdditive Feedstock

Layer 3Layer 2Layer 1

Substrate

Fig. 1. (A) Schematic of the solid state material deposition (MELD) process with solid feedstock material extruded through a hollow tool. (B) Representative figure ofthe as-deposited AA2219 identifying the longitudinal, transverse, and build directions.

Table 1Chemical composition of AA2219 [29].

Elements Al Cu Mn Ti V Zr

Percentage 93.06 6.3 0.30 0.06 0.10 0.18

Fig. 2. Locations of the Vickers microhardness testing along the as-depositedAA2219.

Fig. 3. Schematic of the microindentation grid used to analyze the transversecross-section of the as-deposited AA2219 in the three different longitudinallocations.

O.G. Rivera et al. Materials Science & Engineering A 724 (2018) 547–558

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O and –T87 plates have been investigated previously [3,6] with mi-crohardness testing showing a maximum value of 95 HV [3]. Additionalresearch on FSW butt welds of AA2219-T6 thick plates with standardtensile specimens reporting tensile YS, UTS and elongation values of345MPa, 410MPa, and 15%, respectively [8]. For comparison pur-poses, and due to range of tempers studied in literature, AA2219-O willbe used as a baseline.

Additionally, since MELD is a solid state deposition process withsimilarities to FSW and FSP, the prior FSW research discussed subse-quently aides in elucidating mechanisms occurring during this solidstate deposition of AA2219. Specifically at the microstructural level,prior FSW AA2219 research has shown a refined equiaxed micro-structure in the weld zone is attainable, which improves strength andhardness [3,8,9,27]. Additionally, the aforementioned investigationsobserved coarsening of the Al2Cu, or θ, particles, where the θ particlesare present in the base material but smaller in size than in the weldzone. Li and Shen [27] attributed growth of the θ particles from acombined action of three different formation mechanisms, i.e., Ag-gregation Mechanism and Diffusion Mechanism I and II. Furthermore,research by Cao and Kou [14] concluded that there was no evidence ofliquation in FSW AA2219, since the welds only contain θ particles andno eutectic particles. Subsequently, there is a wide range of reportedsizes of the θ particles dependent on the FSW processing parameters,with sizes reaching up to 150 µm [4,8,14,27]. Previous research by

Kang et al.[28] performed Transmission Electron Microscopy (TEM) inFSW of AA2219-T8, where they found θ′ precipitates in the base ma-terial and only θ phase precipitates in the SZ.

This is the first manuscript to report the microstructure and re-sultant mechanical properties of AA2219 produced by the MELD solidstate deposition process. Electron Backscatter Diffraction (EBSD) andTEM are used to quantitatively characterize the microstructure of as-deposited AA2219. Mechanical properties in tension and compressionin quasi-static and high rates are reported.

2. Materials and methods

Aeroprobe Corporation, who created and patented this technology,provided MELD fabricated samples by pushing a solid AA2219-T851bar through a hollow rotating tool to deposit the material onto anAA2219-T851 plate substrate. During the MELD process, the solidfeedstock material was added, and heat generated by friction betweenthe feedstock material and the tool shoulder under hydrostatic pressureand the substrate plastically deformed both feedstock and substrate asthey were stirred together to metallurgically bond the material to thesubstrate and the successive layers of AA219 as depicted in Fig. 1. Theaverage chemical composition of the rod-stock material is shown inTable 1. In this study, 100mm long MELD AA2219 depositions con-sisted of 6 layers that were approximately 1mm in thickness per layer.

Fig. 4. Inverse pole figure (IPF) orientation maps comparing the microstructure between (A) feedstock AA2219-T851 material and (B) as-deposited AFS AA2219.Note the difference in scales between the two maps.

Fig. 5. 3D IPF orientation map microstructure representation of the (A) feedstock AA2219-T851 material (100 µm scale bars) compared to the (B) as-depositedAA2219 material (15 µm scale bars). Arrows point to the direction that the material is feed through the tool of the solid state deposition process.


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From this point on, the build direction will be referred to as BD, thetransverse direction as TD, and the longitudinal direction as LD.

A wire EDM milled flat dogbone sub-compact tensile specimensfrom the AA2219 depositions that has previously been used for bothhigh strain rate (HR) and quasi-static (QS) tensile experiments on cast,wrought, and AM alloys [30–32]. The flat dogbones had a gauge lengthof 4.5 mm, width of 2.0 mm and thickness of 1.5mm [1]. The tensilespecimens were machined from the bottom, middle, and top of thebuild in the longitudinal direction (LD) and transverse direction (TD).An EDM also machined the compression specimens with a diameter of6mm and a height of 6mm. The compression specimens were ma-chined from the build direction (BD), TD and LD orientations to ex-amine directional dependence of mechanical properties in the speci-mens (see Fig. 9). As a first investigation, cross-sections were takenfrom the beginning, middle, and end of the as-deposited material (seeFig. 10) to quantify spatial dependence of the initial microstructure andVickers microhardness (see Fig. 2) in the deposition. For micro-structural characterization, the three cross-sections were stepwise po-lished using an aqueous lubricant down to a 1200 grit SiC paper, then

polished using 1- and 0.3-µm diamond suspension and a final polish of0.05 µm with a colloidal silica suspension.

Vickers microindentation (Fig. 3) analyzed the hardness through thecross-section of the as-deposited material in the 3 different locations. Aload of 0.1 kg f held for 10 s was used for the hardness tests, as de-scribed in ASTM E384-16 [33]. An indentation grid (Fig. 11) consistingof 10 rows with spacing between the rows of 1mm and 9 columnsspaced at 2.5mm, which complied with ASTM E384-16 [33] probed theas-deposited cross-section. Minimum and maximums values representthe error bars, and are taken into consideration when determiningstatistical differences in the data [34,35].

A Tescan Lyra FIB-FESEM equipped with an EDAX Hikari SuperEBSD camera and an Octane Elite Silicon Drift Detector was used forEBSD, electron dispersive X-ray spectroscopy (EDX), and fractography.EBSD scans were run at the same magnification along the build direc-tion over an area of approximately 50 × 50 µm, with a step size of0.1 µm. The scans were performed at 20 kV and a beam current of5.5 nA. Line scans were performed from top to bottom of the as-de-posited cross-section to spatially quantify grain size. In addition, images

Fig. 6. Grain boundary maps and grain reference orientation deviation (GROD) maps generated from the EBSD data from the “top”, “middle” and “bottom” sectionsof the deposition. For the grain boundary maps, black lines represent high angle grain boundaries with a misorientation angle of greater than 10°, while low angleboundaries are colored red and have misorientation angles between 2° and 10°. The color scale for the GROD maps is from 0 (blue) to 20° (red).


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were taken in the longitudinal, build direction, and long transversedirections to elucidate the 3D microstructure of the deposition. EBSDdata were post-processed using the Neighbor Pattern Averaging andReindexing (NPAR) option in the EDAX TEAM software, followed bythe grain dilation algorithm with setting of a minimum grain size of 2pixels, and a grain must contain multiple rows of pixels. For grain re-ference orientation deviation (GROD) maps, any pixel with an patternindexing confidence index of< 0.2 was removed from the map. Atransmission electron microscope (TEM) FEI TECNAI F-20 was used inscanning mode (STEM) at 200 kV to study the size, geometry, and typeof the precipitates. In particular, STEM experiments used a high-angle-annular dark field (HAADF) detector, imaging in STEM mode, a spotsize of 6, camera length of 100mm, C2 aperture 2, and a dwell time of16 μs. The specimens for the TEM were prepared using the lift-outmethod with a Focused Ion Beam (FIB) FEI Quanta 200 3D Dual Beammicroscope. TEM specimens were lifted out of the feedstock materialfor comparison purposes and from three locations (top, middle andbottom) in the as-deposited cross-section.

An electromechanical Instron 5185 load-frame with a 50 kN loadcell performed the ambient temperature QS tensile and compressionexperiments at a strain rate of 0.001/s. The HR tensile and compressionexperiments were conducted on a Kolsky tension/compression bar. The12.7 mm diameter 350 Maraging steel striker, incident and transmittedKolsky bar system performed both the HR tension and compressionexperiments. The dynamic tensile and compression experiments wereperformed at a strain rate of 1500/s. Strain was measured using a videocamera, where the video strain data was processed using a Matlabroutine that employs a normalized cross-correlation technique(normxcorr2) [36,37]. The same tensile specimen was used for testingof both QS and HR for comparison purposes of material behaviorespecially elongation to failure.

3. Results and discussion

EBSD analysis of the feedstock material and the as-deposited

microstructures provides a comparison of texture and grain size thatresult from the solid state material deposition process. The EDAXsoftware calculated the grain diameter by measuring the area of theequiaxed grains, and reported an average grain size of approximately30 µm for the feedstock material (Fig. 4A). In the deposited material,the measured average grain size of approximately 2.5 µm shows sig-nificant grain refinement (Fig. 4B) as compared with the feedstockmaterial.

To further elucidate the microstructural changes occurring duringthe solid state deposition process, Fig. 5 shows a 3D EBSD representa-tion of the feedstock material and the as-deposited material. In Fig. 5A,EBSD orientation maps show that the feedstock material started as arolled plate before being machined into a rod for the solid state materialdeposition process. In addition, EBSD scans in Fig. 5B were performedacross the as-build cross-section of specimen from the middle of thebuild to show a 3D reconstruction of the microstructure. Additionally,EBSD was performed from the top to bottom of the as-built cross-sec-tion, and the grain size was uniform with no variations between layers.

The EBSD data suggests that DRX is taking place in the stirred re-gion of the material during the MELD process. The significant reductionin grain size observed in the EBSD data (Figs. 4 and 5) is the first pointindicating recrystallization. In addition, many of these grains have lowlevels of intragranular misorientation, as evidenced by the GROD maps(Fig. 6B, D and F). Recrystallized grains should display lower levels ofintergranular misorientation due to their lower dislocation densities.While the temperature during MELD was not directly measured, it isgenerally thought that friction stir processes increase the temperatureof the material in the stir zone to temperatures between 60% and 90%of the melting point [2], high enough to produce recrystallizationduring the intense shear deformation of the solid state deposition pro-cess. The grain boundary maps in (Fig. 6A, C, and E) provide furtherinformation about the possible nature of the recrystallization process.The presence of a significant fraction of low angle boundaries (red linesin Fig. 6A, C, and E) in an otherwise recrystallized microstructuresuggests that new grain boundaries are being formed during the

Fig. 7. Hardness bar chart of the as-deposited AA2219 onthe transverse cross-section of the deposited material, witherror bars representing minimum and maximum valuesrecorded in that layer. EBSD IPF maps of the top, middle,and bottom of the deposition with the corresponding grainsize are shown. In the y-axis, 0 is the top and 6 is thebottom of the deposition. There is a total of 6 layers withan average thickness of 1mm.


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dynamic deformation process and that the migration of these bound-aries will produce DRX. It should also be noted that these low anglegrain boundaries are directly associated with the regions of high in-tragranular misorientation in the GROD maps (Fig. 6B, D, and F).Doherty et al. [38], describes DRX as a process in which new grain

structures are produced in a deformed material via the creation andmigration of grain boundaries driven by the stored energy of de-formation. Dynamic recrystallization happens during the deformationprocess, and as such, one would expect to see some low angle grainboundaries in some grains during the DRX process. This descriptiondescribes the data presented here in this paper. Humphreys distin-guishes between a discontinuous recrystallization process in which thegrain nucleation and growth occur heterogeneously throughout thematerial and a continuous process in which recrystallized grain nu-cleation and growth happen uniformly and gradually; and as such,there is no identifiable nucleation and growth stages [39]. Baker et al.,uses the term “continuous dynamic recrystallization” as defined byHumphreys, to describe the stir zone microstructures produced by FSWin ODS steels [40]. Similar, DRX microstructures have been observedfor FSW of AA7075 aluminum alloys as well [21].

The hardness results from the microindentation experiments aredepicted in Fig. 7 as a bar plot from top to bottom of the as-depositedcross section. Error bars showing the minimum and maximum hardnessvalues for each respective probed layer have also been included in theplot. The average hardness values plotted in Fig. 7 reflect a trend of

Fig. 8. EBSD texture plots of the as-deposited AA2219 build direction representing the texture in (A) the top of the build, (B) the middle, and (C) the bottom.

A {111} {111}

TT (BD)

111

C {001}

Fig. 9. Redrawn schematic representing a combination of two of the four idealtorsional orientations for FCC aluminum as reported by Montheillet et al. [41].


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slightly higher hardness values in the top of the material with a gradualdecrease towards the bottom of the deposition. However, when alsoexamining the standard deviation in the data, there is no clear statis-tical difference in hardness from the top to the bottom of the as-de-posited cross-section. Additionally, in Fig. 7, EBSD IPF maps of thegrain morphology and size are shown next to the hardness bars to in-dicate that the top portion of the deposit (from 0 to 2mm) has a grainsize of 2.6 µm, the middle region (2–4mm) has a grain size of 2.5 µm,and the bottom region (4–6mm) has a grain size of 2.5 µm. Since nodifference in the grain size is observed from the top to the bottom of theas-deposited cross-section, one may then deduce that there is no mea-surable Hall-Petch effect in the material from the top to the bottom. Itshould also be noted that the hardness of the feedstock material issignificantly higher than any of the as-deposited material measuredsince the feedstock is heat-treated.

EBSD was also used to assess the microtextures generated in the as-deposited microstructures. The pole figures (PF) in Fig. 8 show thevariation in texture across the as-deposited cross section. As seen inFig. 8A, the material has a strong texture (MRD = 8.3) in the top of thebuild that weakens toward the middle (Fig. 8B) and the bottom

(Fig. 8C) of the deposition (MRD = 3.9). Previous research byMontheillet et al. [41] showed the four typical torsional textures thatmay be found in FCC aluminum, and Fig. 9 shows the texture fiber type-A and type-C in the {111} PF from which the fiber texture A can becorrelated to the {111} PFs in Fig. 8A. In Fig. 8A, the < >{111} 110 fibercomponent and a split of the {111} 110 fiber component are evident.In the middle of the deposition (Fig. 8B) and in the bottom of the de-position (8-C), there is a combination of fiber A and C texture. Forcomparison, a weak Goss type rolling texture in the feedstock materialwas seen. Fig. 10 shows the {111} PFs from the top, middle, and bottomat a different angle to elucidate the torsional texture (torsional axis isout of the plane of the page). Research by Fonda et al. [42], reportedsimilar torsional textures for FSW of AA2195.

Crystallographic texture in a polycrystalline material refers to thepreferential orientation of the grains in the material. Strong texture in amaterial may cause anisotropic behavior during plastic deformation,and, when the mechanical behavior of a material changes due to tex-ture, it is known as texture strengthening [43–45]. As seen in Figs. 8and 10, the stronger texture in the top of the as-deposited material mayresult in variations in mechanical behavior when compared to themiddle and the bottom layers.

TEM analysis further identifies how the feedstock material changesfrom the bottom, middle, and top regions of the deposition, whichcorrelates to the EBSD IPF maps shown in Fig. 7. STEM-HAADF imagesfrom the feedstock material (Fig. 11A) show many, small (< 100 nm) θ′precipitates, as expected from AA2219-T8 and T851. These precipitatesare responsible for the high yield strength levels measured in thefeedstock material. For the AFS-deposited material, Fig. 11B–D showSTEM-HAADF micrographs for the bottom, middle, and top regions,respectively, that contain larger θ (Al2Cu) precipitates. All the STEMmicrographs from the bottom, middle, and top depict similar size andtype (θ phase) precipitates. No θ′ precipitates were observed indicatingthat there should not be any precipitation strengthening after the solidstate deposition. It should be noted that it is the spacing between pre-cipitates that is responsible for increased yield strength for large pre-cipitates. The average distance between precipitates in the solid statedeposition material is much larger than in the feedstock material, andas such, there is very little precipitation strengthening. As mentionedbefore, previous research by Kang et al. [28] in FSW of AA2219 foundthe same θ′ precipitates in the base material and θ precipitates in the SZ.

These TEM results suggest that the temperatures during MELDprocessing are high enough to first dissolve the θ′ precipitates and thenthe cooling rate is slow enough that larger, θ phase particles form.According to the work of Lorimer [46], the solvus temperature of θ′precipitates in the Al-Cu system is around 753 K (480 °C). Friction stirwelding and friction stir processing can generate temperatures in thestir zone ranging from 60% to 90% of the melting point [2]. Thesetemperatures could exceed the solvus, thus dissolving the θ′ phase. Infact, the data presented here suggests that the stir zone temperaturesreach at least 80% of the melting point of the material, the approximatesolvus temperature for the Al-Cu system. As the material does not coolquickly during further solid-state material deposition processing, the θphase will nucleate and grow. Future work will monitor the tempera-tures during the solid state material deposition process to provide fur-ther insight about this precipitate evolution.

Next, the average QS and HR tensile behaviors for LD orientedspecimens from the top, middle, and bottom layers with the associateduncertainty bands corresponding to the maximum and minimum ex-perimental values are plotted in Fig. 12A and B. For both QS and HR(Fig. 12A and B), the top layer exhibits higher YS and tensile strength(TS) than the middle and bottom layers (see Table 2 for results).

Additionally, in Fig. 12A a clear delineation is observed with max-imum YS and TS observed in the top layer specimens that decreases for

Fig. 10. Reoriented EBSD texture plots of the as-deposited AA2219 (observingfrom the top) representing the texture in (A) the top, (B) the middle, and (C) thebottom of the build.


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Fig. 11. TEM micrographs (A) feedstock material showing θ′ precipitates, (B) bottom, (C) middle, and (D) top, TEM micrographs showing θ precipitates and grainstructure from the build cross-section Zone 2 for the as-deposited AA2219 (see Fig. 7 for reference of locations). (Note: magnification in (A) is much higher than B–D).

0.00 0.05 0.10 0.15 0.20 0.25 0.300

50

100

150

200

250

300

350

400

TrueStress(MPa)

True Strain (mm/mm)

Top LayerMiddle LayerBottom Layer

0.00 0.05 0.10 0.15 0.20 0.25 0.300

50

100

150

200

250

300

350

400

TrueStress(MPa)

True Strain (mm/mm)

Top LayerMiddle LayerBottom Layer

Fig. 12. As-deposited tensile results comparing deposition layer dependency in (A) quasi-static and (B) high rate. For both strain rates, the plots identify that the toplayer is strongest followed by the middle and bottom layer.


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the middle layer specimens and then the bottom layer specimens havingthe lowest YS and TS. However, for the specimens tested at HR, Fig. 12Bshows that the top layer specimens have the highest YS and TS, but no

observable difference is seen between the HR YS and TS behavior forthe middle and bottom layer specimens.

Furthermore, compression QS and HR experiments examined thestress-state and strain rate dependence of the as-deposited material.Fig. 13 plots the average (3 specimens) QS and HR compressive beha-vior up to a strain of 0.25 for the TD, DB, and LD directions with un-certainty bands corresponding to minimum and maximum experi-mental values. The QS compressive data shows a near isotropicresponse of the as-deposited AA2219, with an average YS of approxi-mately 145MPa for the TD, 140MPa for the BD, and 150MPa for theLD directions. For the HR compressive material behavior, the TD has ahigher yield than the BD and LD directions, with an average YS ofapproximately 295MPa for the TD, 238MPa for the BD, and 225MPafor the LD directions. In QS, the material experiences more strainhardening and higher TS than at HR. However, as expected the HRachieves higher YS than QS, but the HR does not experience as muchstrain hardening and eventually plateaus. The QS and HR compressionexperiments were stopped at a maximum strain of 0.25mm/mm sincethe material did not fracture.

To compare stress-state asymmetry, the average QS and HR tensilebehavior for the TD and LD directions with the associated uncertaintybands corresponding to the maximum and minimum experimental va-lues are plotted in Fig. 14. The QS tensile TD specimens achieved anaverage YS of 148MPa, an TS of 363MPa, and εf of 0.24mm/mm. TheQS tensile LD specimens achieved an average YS of 143MPa, an TS of355MPa, and εf of 0.26mm/mm. The QS tensile specimens in bothdirections exhibited a ductile failure (Fig. 15) with strain hardening andsoftening after yielding. Similar to the compressive behavior, the ma-terial shows more strain hardening in the QS case, when compared tothe HR, which after yielding exhibits a stress-strain curve plateau. TheHR tensile TD and LD specimens achieved average YS of 235 and240MPa, TS of 240 and 240MPa, and εf of 0.37 and 0.37, respectively.The HR fractography (Fig. 16) revealed a ductile behavior with a cup-cone fracture surface. For both QS and HR cases, isotropic behavior inthe two orientations are observed for the tensile mechanical behavior.

SEM fractographic analysis of both QS and HR (Figs. 15 and 16,respectively), show ductile failure behavior for the as-depositedAA2219 material. SEM QS fractography images with increasing mag-nifications are shown in Fig. 15A–D. Similarly, the HR SEM fracto-graphy images are shown in increasing magnifications in Fig. 16A–D.Both QS and HR fracture surfaces exhibited microvoids and dimples.

Based on the data in this paper, the YS of as-deposited AA2219appears dominated by the grain size, i.e. Hall-Petch type strengthening.Multiple factors can contribute to the YS of a material as shown in Eq.(1).

= + + + + +σ σ σ σ σ σ σY O SSS WH HP P TXTR (1)

where, σY is the material YS, σO is the Peierls-Nabarro stress [47], σSSS isthe solid solution strengthening [2,8,9,48], σWH is the work hardeningbased upon dislocation density [38,49], σHP is the Hall-Petchstrengthening [2–4,50], σP is the precipitation strengthening[2,8,51,52], and σTXTR is the texture strengthening [43–45].

Since these samples were fabricated by a solid-state process, a

Table 2Comparison of as-deposited AA2219 YS, TS, and εf based on location and strain rate. Values in parenthesis are the standard deviations.

Location Top Middle Bottom

Strain Rate 0.001/s 2500/s 0.001/s 2500/s 0.001/s 2500/s

YS (MPa) 159 (0.7) 275 (0.6) 140 (1.0) 242 (4.2) 125 (3.5) 225 (4.2)TS (MPa) 390 (2.1) 283 (1.4) 364 (5.2) 245 (1.4) 335 (7.1) 236 (8.5)εf (%) 25 (0.7) 37 (0.7) 27 (2.1) 41 (0.7) 28 (1.4) 42 (2.1)

Fig. 13. As-deposited compression experiment results comparing the longtransverse, short transverse, and longitudinal directions in quasi-static (0.001/s) and high rate (2500/s). The quasi-static long transverse, short transverse, andlongitudinal achieved a YS of 145, 140, and 150MPa, respectively. The highrate long transverse, short transverse, and longitudinal achieved a YS of 295,238, and 225MPa, respectively. All compression tests were stopped at a strainof 0.25.

Fig. 14. As-deposited tensile results comparing the long transverse and long-itudinal directions in quasi-static (0.001/s) and high rate (2500/s). The quasi-static long transverse and longitudinal achieved a YS of 148 and 143MPa, TS of363 and 355MPa and εf of 0.24 and 0.26, respectively. The high rate longtransverse and longitudinal achieved a YS of 235 and 240MPa, TS of 240 and240MPa and εf of 0.37 and 0.37, respectively.


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change in chemical composition from the feedstock material is notexpected, and thus, the σO and σSSS contributions are unlikely to bedifferent between the feedstock and the as-deposited material. Anywork hardening present in the feedstock material is removed by theMELD process, thus negating the contribution of σWH . From Fig. 5, it isclear that the grain size in the as-deposited material is significantlyrefined from the feedstock and as such, the σHP contribution should belarge in the as-deposited material. The fine precipitates present in thefeedstock material are all removed by the solid-state deposition process,and so, σP will be quite small in the as-deposited material. Lastly, thereis a difference in the texture between the feedstock and the as-depositedmaterial, so there could be a texture strengthening component, σTXTR,but its magnitude is unclear.

Using similar reasoning, our current explanation for the small de-crease in YS from the top layer of the deposition to the bottom is thatthe YS is controlled by texture strengthening. The grain size, shown inFig. 7, is the same for all of the layers (top, middle, and bottom). Noneof these three layers possess the fine precipitates necessary for pre-cipitation strengthening. The composition and dislocation density arenot expected to be different between the three layers. In contrast, thetop layer was the most textured of the three layers. This texture reducedsignificantly in the middle and bottom layers; and, in addition, thenature of the texture changed from an A-fiber only to a mixture of A-and C-fibers. Further work would be necessary to estimate the directimpact of these textures on YS.

The averaged as-deposited AA2219 tensile properties are compared

to AA2219 tensile properties from various manufacturing or joiningtechniques in Table 3. The MELD process (highlighted in gray inTable 3) resulted in higher YS, UTS (converted from TS to engineeringUTS for comparison purposes) and strain to failure than AA2219-O andas-deposited EBF AA2219. Additionally, MELD AA2219 resulted in in-creases in the same three properties compared to FSW 2219-O. TheMELD AA2219 mechanical properties are below those of AA2219-T851,but as shown previously in the TEM data (Fig. 11), the nano-pre-cipitates that provide the precipitation strengthening of AA2219 wereeliminated during the MELD. Previous research on EBF by Tamingerand Hafley [10] showed that after depositing the AA2219 and per-forming the T62 heat treatment; the material properties of wroughtAA2219-T62 were achieved, suggesting that MELD AA2219 would beheat treatable as with the EBF AA2219. The strain to failure was notdirectly compared to published literature data since this study used asubscale specimen for both QS and HR experiments instead of a largerASTM E8 tensile coupon, but a column of strain to failure is providedfor a qualitative reference in Table 3.

4. Summary and conclusions

This is the first manuscript to detail the microstructure and me-chanical properties of solid state material deposition AA2219 fabricatedfrom AA2219-T851 feedstock material.

• EBSD results revealed a strong grain refinement from the high shear

Fig. 15. Fractography of QS (strain rate of 0.001/s) as-deposited tensile specimens tested to fracture. 15-A, 15-B, 15-C and 15-D (scale bars are 200, 100, 10, and5 µm, respectively) are SEM images.


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and elevated temperature process. A uniform grain size was foundfrom the top to the bottom of the as-deposited cross-section.

• The top layer had the highest YS and TS, followed by the middle andbottom, respectively. This small difference can be attributed totexture strengthening.

• EBSD PFs showed that the material has a strong torsional fiber Atexture in the top of the build, and a mixture of A and C texture inthe middle and bottom sections.

• TEM showed that there are no θ′ precipitates in the as-depositedcross-section, therefore no precipitation strengthening should beexpected. The mechanical properties of the as-deposited AA2219material are higher than AA2219-O, but the values are below those

of AA2219-T851 since there are no θ′ precipitates providing strengthto the material.

• As mentioned above, previous research by Taminger and Hafley[10] showed that after applying the T62 temper to the as-built EBFmaterial, the materials mechanical properties matched those of aAA2219-T62. This is extremely important, since being able to regainthose microstructural and mechanical properties that the T62 andT851 tempers provide is crucial for the applications of this alloy.

• The strain rate dependence was examined, and at HR, the materialexperienced higher yield strength and lower tensile strength. At HR,the material strain hardening was less than when tested at QS wherethe HR material stress-strain curve plateaus after yielding [53].

• Texture strengthening appears to be the mechanism responsible forthe changes in behavior between the top, middle, and bottom layersof the deposition.

• The tensile specimens in HR specimens also exhibited more strain tofailure than in the tensile specimens in QS.

References

[1] O.G. Rivera, P.G. Allison, J.B. Jordon, O.L. Rodriguez, L.N. Brewer, Z. McClelland,et al., Microstructures and mechanical behavior of Inconel 625 fabricated by solid-state additive manufacturing, Mater. Sci. Eng. A 694 (2017) 1–9, http://dx.doi.org/10.1016/j.msea.2017.03.105.

[2] R.S. Mishra, Z.Y. Ma, Friction stir welding and processing, Mater. Sci. Eng. R Rep.50 (2005) 1–78, http://dx.doi.org/10.1016/j.mser.2005.07.001.

[3] W. Xu, J. Liu, G. Luan, C. Dong, Temperature evolution, microstructure and

Fig. 16. Fractography of HR (strain rate of 2500/s) as-deposited tensile specimens tested to fracture. 16-A, 16-B, 16-C and 16-D (scale bars are 500, 100, 10, and5 µm, respectively) are SEM images.

Table 3Comparison of AA2219 YS, UTS, and εf of different manufacturing processes.

Condition YS (MPa) UTS (MPa) εf (%)

AA 2219-O [29] 75 170 18AA 2219-T62 [29] 290 415 10AA 2219-T851 [29] 350 455 10MELD AA 2219 (As Deposited) [This

research]143–148 355–363 24–26

FSW AA 2219-T8 (SZ) [52] 208–210 363–366 18.6–21.3FSW AA 2219-T6 [8] – 255–336 –FSW AA 2219-O [3] 86.6–111.4 150.6–187.8 4.9–10.2EBF AA 2219 (As Deposited) [10] 112 283 19.4EBF AA 2219 (Deposit + T62) [10] 290 416 11.1


557

http://dx.doi.org/10.1016/j.msea.2017.03.105http://dx.doi.org/10.1016/j.msea.2017.03.105http://dx.doi.org/10.1016/j.mser.2005.07.001

mechanical properties of friction stir welded thick 2219-O aluminum alloy joints,Mater. Des. 30 (2009) 1886–1893, http://dx.doi.org/10.1016/j.matdes.2008.09.021.

[4] Q. Li, A. Wu, Y. Li, G. Wang, D. Yan, J. Liu, Influence of temperature cycles on themicrostructures and mechanical properties of the partially melted zone in the fusionwelded joints of 2219 aluminum alloy, Mater. Sci. Eng. A 623 (2015) 38–48, http://dx.doi.org/10.1016/j.msea.2014.11.047.

[5] G.V. Narayana, V.M.J. Sharma, V. Diwakar, K.S. Kumar, R.C. Prasad, Fracture be-haviour of aluminium alloy 2219–T87 welded plates, Sci. Technol. Weld. Join. 9(2004) 121–130, http://dx.doi.org/10.1179/136217104225017035.

[6] K. Elangovan, V. Balasubramanian, S. Babu, Developing an empirical relationship topredict tensile strength of friction stir welded AA2219 aluminum alloy, J. Mater.Eng. Perform. 17 (2008) 820–830, http://dx.doi.org/10.1007/s11665-008-9240-6.

[7] J.A. Hartman, R.J. Beil, G.T. Hahn, Effect of copper-rich regions on tensile prop-erties of VPPA weldments of 2219-T87 aluminum, Am. Weld. Soc. (1987).

[8] B. Li, Y. Shen, W. Hu, The study on defects in aluminum 2219-T6 thick butt frictionstir welds with the application of multiple non-destructive testing methods, Mater.Des. 32 (2011) 2073–2084, http://dx.doi.org/10.1016/j.matdes.2010.11.054.

[9] H. Doude, J. Schneider, B. Patton, S. Stafford, T. Waters, C. Varner, Optimizing weldquality of a friction stir welded aluminum alloy, J. Mater. Process. Technol. 222(2015) 188–196, http://dx.doi.org/10.1016/j.jmatprotec.2015.01.019.

[10] K.M. Taminger, R.A. Hafley, Electron beam freeform fabrication: a rapid metaldeposition process, in: Proceedings of the 3rd Annual Automotive CompositesConference, 2003, pp. 9–10. 〈http://www.ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040042496_2004036110.pdf〉.

[11] K.M. Taminger, R.A. Hafley, Electron beam freeform fabrication for cost effectivenear-net shape manufacturing, Nato Avt. 139 (2006).

[12] K.M.B. Taminger, R.A. Hafley, Characterization of 2219 aluminum poduced byelectron beam freeform fabrication, in: Proceedings of the 13th Solid FreeformFabrication Symposium, 2002.

[13] W.M.W. Thomas, I. Norris, E.D. Nicholas, J.C. Needham, M.G. Murch, P. Temple-Smith, et al., Friction Stir Welding—Process Developments and Variant Techniques,1991. 〈http://www.google.com/patents/US5460317%5Cnhttp://scholar.google.com/scholar?hl=en&btnG=Search&q=intitle:5,460,317#3%5Cnhttp://scholar.google.com/scholar?hl=en&btnG=Search&q=intitle:5460317#3%5Cnhttp://hegesztesportal.hu/hegesztes/tudastar/wt_fsw.pdf〉.

[14] G. Cao, S. Kou, Friction stir welding of 2219 aluminum: behavior of θ (Al2Cu)particles, Weld. J. 84 (2005) 1–8.

[15] M. Eskandari, A. Najafizadeh, A. Kermanpur, M. Karimi, Potential application ofnanocrystalline 301 austenitic stainless steel in lightweight vehicle structures,Mater. Des. 30 (2009) 3869–3872, http://dx.doi.org/10.1016/j.matdes.2009.03.043.

[16] R.I. Rodriguez, J.B. Jordon, H.M. Rao, H. Badarinarayan, W. Yuan, H. El Kadiri,et al., Microstructure, texture, and mechanical Properties of friction stir spot weldedrare-earth containing magnesium ZEK100 alloy sheets, Mater. Sci. Eng. A (2014),http://dx.doi.org/10.1016/j.msea.2014.09.010.

[17] R.I. Rodriguez, J.B. Jordon, P.G. Allison, T. Rushing, L. Garcia, Microstructure andmechanical properties of dissimilar friction stir welding of 6061-to-7050 aluminumalloys, Mater. Des. 83 (2015) 60–65, http://dx.doi.org/10.1016/j.matdes.2015.05.074.

[18] S. Palanivel, H. Sidhar, R.S. Mishra, Friction stir additive manufacturing: route tohigh structural performance, JOM 67 (2015) 616–621, http://dx.doi.org/10.1007/s11837-014-1271-x.

[19] S.M. Puleo, Additive Friction Stir Manufacturing of 7055 Aluminum Alloy,University of New Orleans, 2016.

[20] S. Palanivel, P. Nelaturu, B. Glass, R.S. Mishra, Friction stir additive manufacturingfor high structural performance through microstructural control in an Mg basedWE43 alloy, Mater. Des. 65 (2014) 934–952, http://dx.doi.org/10.1016/j.matdes.2014.09.082.

[21] J.Q. Su, T.W. Nelson, R. Mishra, M. Mahoney, Microstructural investigation offriction stir welded 7050-T651 aluminium, Acta Mater. 51 (2003) 713–729, http://dx.doi.org/10.1016/S1359-6454(02)00449-4.

[22] J.Q. Su, T.W. Nelson, C.J. Sterling, Friction stir processing of large-area bulk UFGaluminum alloys, Scr. Mater. 52 (2005) 135–140, http://dx.doi.org/10.1016/j.scriptamat.2004.09.014.

[23] J. Su, T.W. Nelson, C.J. Sterling, A new route to bulk nanocrystalline materials, J.Mater. Res. 18 (2003) 1757–1760.

[24] J. Su, T.W. Nelson, C.J. Sterling, Grain refinement of aluminum alloys by frictionstir processing, Philos. Mag. 86 (2006) 1–24, http://dx.doi.org/10.1023/A:1012882413401.

[25] J.-Q. Su, T.W. Nelson, C.J. Sterling, Microstructure evolution during FSW/FSP ofhigh strength aluminum alloys, Mater. Sci. Eng. A 405 (2005) 277–286, http://dx.doi.org/10.1016/j.msea.2005.06.009.

[26] J.Q. Su, T.W. Nelson, T.R. McNelley, R.S. Mishra, Development of nanocrystallinestructure in Cu during friction stir processing (FSP), Mater. Sci. Eng. A 528 (2011)5458–5464, http://dx.doi.org/10.1016/j.msea.2011.03.043.

[27] B. Li, Y. Shen, The investigation of abnormal particle-coarsening phenomena infriction stir repair weld of 2219-T6 aluminum alloy, Mater. Des. 32 (2011)3796–3802, http://dx.doi.org/10.1016/j.matdes.2011.03.029.

[28] J. Kang, Z.C. Feng, J.C. Li, G.S. Frankel, G.Q. Wang, A.P. Wu, Friction stir weldingof Al alloy 2219-T8: part I – evolution of precipitates and formation of abnormalAl2Cu, Metall. Mater. Trans. A Phys. Metall. Mater. Sci. 47A (2016) 4553–4565,http://dx.doi.org/10.1007/s11661-016-3648-7.

[29] J.G. Kaufman, Introduction to Aluminum Alloys and Tempers, ASM International,Metals Park, OH, 2000.

[30] W.R. Whittington, A.L. Oppedal, S. Turnage, Y. Hammi, H. Rhee, P.G. Allison, et al.,Capturing the effect of temperature, strain rate, and stress state on the plasticity andfracture of rolled homogeneous armor (RHA) steel, Mater. Sci. Eng. A 594 (2014)82–88, http://dx.doi.org/10.1016/j.msea.2013.11.018.

[31] P.G. Allison, H. Grewal, Y. Hammi, H.R. Brown, W.R. Whittington,M.F. Horstemeyer, Plasticity and fracture modeling/experimental study of a porousmetal under various strain rates, temperatures, and stress states, J. Eng. Mater.Technol. 135 (2013) 41008, http://dx.doi.org/10.1115/1.4025292.

[32] P.G. Allison, M.F. Horstemeyer, Y. Hammi, H.R. Brown, M.T. Tucker, Y.K. Hwang,Microstructure-property relations of a steel powder metal under varying tempera-tures, strain rates, and stress states, Mater. Sci. Eng. A 529 (2011) 335–344, http://dx.doi.org/10.1016/j.msea.2011.09.037.

[33] ASTM E384, Standard test method for microindentation hardness of materials,ASTM Int. (2015) 1–24, http://dx.doi.org/10.1520/E0384-16.

[34] H. Al-Khalid, A. Alaskari, S. Oraby, Statistical and graphical assessment of cir-cumferential and radial hardness variation of AISI 4140, AISI 1020 and AA 6082aluminum alloy, Materials (Basel) 5 (2012) 12–26, http://dx.doi.org/10.3390/ma5010012.

[35] H.W. Coleman, W.G. Steele, Experimentation and Uncertainty Analysis forEngineers, second Ed., John Wiley & Sons, Inc, New York, NY, 1999.

[36] J.P. Lewis, Fast template matching template matching by cross correlation 2 nor-malized cross correlation normalized cross correlation in the transform domain,Pattern Recognit. 10 (1995) 120–123 〈http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.157.3888&rep=rep1&type=pdf〉.

[37] R.M. Haralick, L.G. Shapiro, Computer Robot Vision, vol. 2, Addison-WesleyPublishing Company, Boston, MA, 1992.

[38] R.D. Doherty, D.A. Hughes, F.J. Humphreys, J.J. Jonas, D.J. Jensen, M.E. Kassner,et al., Current issues in recrystallization: a review, Mater. Sci. Eng. A 238 (1997)219–274, http://dx.doi.org/10.1016/S0921-5093(97)00424-3.

[39] F.J. Humphreys, A unified theory of recovery, recrystallization and grain growth,based on the stability and growth of cellular microstructures—I. The basic model,Acta Mater. 45 (1997) 4231–4240, http://dx.doi.org/10.1016/S1359-6454(97)00070-0.

[40] B.W. Baker, E.S.K. Menon, T.R. Mcnelley, L.N. Brewer, B. El-Dasher, J.C. Farmer,et al., Processing-microstructure relationships in friction stir welding of MA956oxide dispersion strengthened steel, Metall. Mater. Trans. E 1 (2014) 318–330,http://dx.doi.org/10.1007/s40553-014-0033-6.

[41] F. Montheillet, M. Cohen, J.J. Jonas, Axial stresses and texture development duringthe torsion testing of Al, Cu and α-Fe, Acta Metall. 32 (1984) 2077–2089, http://dx.doi.org/10.1016/0001-6160(84)90187-1.

[42] R.W. Fonda, J.F. Bingert, Texture variations in an aluminum friction stir weld, Scr.Mater. 57 (2007) 1052–1055, http://dx.doi.org/10.1016/j.scriptamat.2007.06.068.

[43] W.F. Hosford, Mechanical Behavior of Materials, second ed., Cambridge UniversityPress, New York, 2010.

[44] U.F. Kocks, C.N. Tome, H.-R. Wenk, Texture and Anisoropy: Preferred Orientationsin Polycrystals and their Effect on Materials Properties, Cambridge University Press,Cambridge, UK, 1998.

[45] M.A. Meyers, K.K. Chawla, Mechanical Behavior of Materials, second ed.,Cambridge University Press, New York, NY, 2010.

[46] G.W. Lorimer, Precipitation in aluminum alloys, Precip. Process. Solids (1978)87–117.

[47] F.R.N. Nabarro, Fifty-year study of the Peierls-Nabarro stress, Mater. Sci. Eng. A234–236 (1997) 67–76, http://dx.doi.org/10.1016/S0921-5093(97)00184-6.

[48] Ø. Ryen, B. Holmedal, O. Nijs, E. Nes, E. Sjölander, H.-E. Ekström, Strengtheningmechanisms in solid solution aluminum alloys, Metall. Mater. Trans. A 37 (2006)1999–2006, http://dx.doi.org/10.1007/s11661-006-0142-7.

[49] M. Horstemeyer, D. McDowell, J. Fan, From atom to autos, a new design paradigmusing microstructure-property modelling, Monotonic Load. Cond. Sandia. Part 1:Mo, 2001. 〈http://scholar.google.com/scholar?hl=en&btnG=Search&q=intitle:from+atoms+to+autos:+A+New+Design+Paradigm+Using+microstructure-property+modeling#3〉.

[50] N. Hansen, Hall-petch relation and boundary strengthening, Scr. Mater. 51 (2004)801–806, http://dx.doi.org/10.1016/j.scriptamat.2004.06.002.

[51] M.E. Fine, Precipitation hardening of aluminum alloys, Metall. Trans. A 6 (1975)625–630, http://dx.doi.org/10.1007/BF02672283.

[52] J. Kang, Z.C. Feng, J.C. Li, G.S. Frankel, G.Q. Wang, A.P. Wu, Friction stir weldingof Al alloy 2219-T8: part II-mechanical and corrosion, Metall. Mater. Trans. A Phys.Metall. Mater. Sci. 47A (2016) 4566–4577, http://dx.doi.org/10.1007/s11661-016-3646-9.

[53] R. Bobbili, V. Madhu, A.K. Gogia, Tensile behaviour of aluminium 7017 alloy atvarious temperatures and strain rates, J. Mater. Res. Technol. 5 (2016) 190–197,http://dx.doi.org/10.1016/j.jmrt.2015.12.002.


558

http://dx.doi.org/10.1016/j.matdes.2008.09.021http://dx.doi.org/10.1016/j.matdes.2008.09.021http://dx.doi.org/10.1016/j.msea.2014.11.047http://dx.doi.org/10.1016/j.msea.2014.11.047http://dx.doi.org/10.1179/136217104225017035http://dx.doi.org/10.1007/s11665-008-9240-6http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref7http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref7http://dx.doi.org/10.1016/j.matdes.2010.11.054http://dx.doi.org/10.1016/j.jmatprotec.2015.01.019http://www.ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040042496_2004036110.pdfhttp://www.ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20040042496_2004036110.pdfhttp://refhub.elsevier.com/S0921-5093(18)30445-3/sbref10http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref10http://www.google.com/patents/US5460317%5Cnhttp://scholar.google.com/scholar?hl=en�&�btnG=Search�&�q=intitle:5,460,317#3%5Cnhttp://scholar.google.com/scholar?hl=en�&�btnG=Search�&�q=intitle:5460317#3%5Cnhttp://hegesztesportal.hu/hegesztes/tudastar/wt_fsw.pdfhttp://www.google.com/patents/US5460317%5Cnhttp://scholar.google.com/scholar?hl=en�&�btnG=Search�&�q=intitle:5,460,317#3%5Cnhttp://scholar.google.com/scholar?hl=en�&�btnG=Search�&�q=intitle:5460317#3%5Cnhttp://hegesztesportal.hu/hegesztes/tudastar/wt_fsw.pdfhttp://www.google.com/patents/US5460317%5Cnhttp://scholar.google.com/scholar?hl=en�&�btnG=Search�&�q=intitle:5,460,317#3%5Cnhttp://scholar.google.com/scholar?hl=en�&�btnG=Search�&�q=intitle:5460317#3%5Cnhttp://hegesztesportal.hu/hegesztes/tudastar/wt_fsw.pdfhttp://www.google.com/patents/US5460317%5Cnhttp://scholar.google.com/scholar?hl=en�&�btnG=Search�&�q=intitle:5,460,317#3%5Cnhttp://scholar.google.com/scholar?hl=en�&�btnG=Search�&�q=intitle:5460317#3%5Cnhttp://hegesztesportal.hu/hegesztes/tudastar/wt_fsw.pdfhttp://refhub.elsevier.com/S0921-5093(18)30445-3/sbref11http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref11http://dx.doi.org/10.1016/j.matdes.2009.03.043http://dx.doi.org/10.1016/j.matdes.2009.03.043http://dx.doi.org/10.1016/j.msea.2014.09.010http://dx.doi.org/10.1016/j.matdes.2015.05.074http://dx.doi.org/10.1016/j.matdes.2015.05.074http://dx.doi.org/10.1007/s11837-014-1271-xhttp://dx.doi.org/10.1007/s11837-014-1271-xhttp://dx.doi.org/10.1016/j.matdes.2014.09.082http://dx.doi.org/10.1016/j.matdes.2014.09.082http://dx.doi.org/10.1016/S1359-6454(02)00449-4http://dx.doi.org/10.1016/S1359-6454(02)00449-4http://dx.doi.org/10.1016/j.scriptamat.2004.09.014http://dx.doi.org/10.1016/j.scriptamat.2004.09.014http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref19http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref19http://dx.doi.org/10.1023/A:1012882413401http://dx.doi.org/10.1023/A:1012882413401http://dx.doi.org/10.1016/j.msea.2005.06.009http://dx.doi.org/10.1016/j.msea.2005.06.009http://dx.doi.org/10.1016/j.msea.2011.03.043http://dx.doi.org/10.1016/j.matdes.2011.03.029http://dx.doi.org/10.1007/s11661-016-3648-7http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref25http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref25http://dx.doi.org/10.1016/j.msea.2013.11.018http://dx.doi.org/10.1115/1.4025292http://dx.doi.org/10.1016/j.msea.2011.09.037http://dx.doi.org/10.1016/j.msea.2011.09.037http://dx.doi.org/10.1520/E0384-16http://dx.doi.org/10.3390/ma5010012http://dx.doi.org/10.3390/ma5010012http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref31http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref31http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.157.3888�&�rep=rep1�&�type=pdfhttp://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.157.3888�&�rep=rep1�&�type=pdfhttp://refhub.elsevier.com/S0921-5093(18)30445-3/sbref33http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref33http://dx.doi.org/10.1016/S0921-5093(97)00424-3http://dx.doi.org/10.1016/S1359-6454(97)00070-0http://dx.doi.org/10.1016/S1359-6454(97)00070-0http://dx.doi.org/10.1007/s40553-014-0033-6http://dx.doi.org/10.1016/0001-6160(84)90187-1http://dx.doi.org/10.1016/0001-6160(84)90187-1http://dx.doi.org/10.1016/j.scriptamat.2007.06.068http://dx.doi.org/10.1016/j.scriptamat.2007.06.068http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref39http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref39http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref40http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref40http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref40http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref41http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref41http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref42http://refhub.elsevier.com/S0921-5093(18)30445-3/sbref42http://dx.doi.org/10.1016/S0921-5093(97)00184-6http://dx.doi.org/10.1007/s11661-006-0142-7http://scholar.google.com/scholar?hl=en�&�btnG=Search�&�q=intitle:fromtoms+outos:++ew+esign+aradigm+singicrostructure-propertyodeling#3http://scholar.google.com/scholar?hl=en�&�btnG=Search�&�q=intitle:fromtoms+outos:++ew+esign+aradigm+singicrostructure-propertyodeling#3http://scholar.google.com/scholar?hl=en�&�btnG=Search�&�q=intitle:fromtoms+outos:++ew+esign+aradigm+singicrostructure-propertyodeling#3http://dx.doi.org/10.1016/j.scriptamat.2004.06.002http://dx.doi.org/10.1007/BF02672283http://dx.doi.org/10.1007/s11661-016-3646-9http://dx.doi.org/10.1007/s11661-016-3646-9http://dx.doi.org/10.1016/j.jmrt.2015.12.002

Influence of texture and grain refinement on the mechanical behavior of AA2219 fabricated by high shear solid state material depositionIntroductionMaterials and methodsResults and discussionSummary and conclusionsReferences

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