From Solidification Processing to Microstructure to Mechanical Properties: A Multi-scale X-ray Study of an Al-Cu Alloy Sample

Metallurgical and Materials Transactions A, Sep 2017

We follow an Al-12 at. pct Cu alloy sample from the liquid state to mechanical failure, using in situ X-ray radiography during directional solidification and tensile testing, as well as three-dimensional computed tomography of the microstructure before and after mechanical testing. The solidification processing stage is simulated with a multi-scale dendritic needle network model, and the micromechanical behavior of the solidified microstructure is simulated using voxelized tomography data and an elasto-viscoplastic fast Fourier transform model. This study demonstrates the feasibility of direct in situ monitoring of a metal alloy microstructure from the liquid processing stage up to its mechanical failure, supported by quantitative simulations of microstructure formation and its mechanical behavior.

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From Solidification Processing to Microstructure to Mechanical Properties: A Multi-scale X-ray Study of an Al-Cu Alloy Sample

From Solidification Processing to Microstructure to Mechanical Properties: A Multi-scale X-ray Study of an Al-Cu Alloy Sample D. TOURRET 0 J.C.E. MERTENS 0 E. LIEBERMAN 0 S.D. IMHOFF 0 J.W. GIBBS 0 K. HENDERSON 0 K. FEZZAA 0 A.L. DERIY 0 T. SUN 0 R.A. LEBENSOHN 0 B.M. PATTERSON 0 A.J. CLARKE 0 0 D. TOURRET is with the Sigma Division, Los Alamos National Laboratory , P.O. Box 1663, Los Alamos, NM 87545 , and also with the IMDEA Materials Institute , Calle Eric Kandel 2, 28906 Getafe, Madrid , Spain. J.C.E. MERTENS, E. LIEBERMAN, K. HENDERSON, R.A. LEBENSOHN, and B.M. PATTERSON are with the Materials Science and Technology Division, Los Alamos National Laboratory , P.O. Box 1663 , Los Alamos, NM 87545. S.D. IMHOFF and J.W. GIBBS are with the Sigma Division, Los Alamos National Laboratory. K. FEZZAA, A.L. DERIY, and T. SUN are with the Argonne National Laboratory, Advanced Photon Source, Lemont, IL 60439. A.J. CLARKE is with the Sigma Division, Los Alamos National Laboratory, and also with the Department of Metallurgical and Materials Engineering, Colorado School of Mines , 1500 Illinois Street, Golden, CO 80401. Contact We follow an Al-12 at. pct Cu alloy sample from the liquid state to mechanical failure, using in situ X-ray radiography during directional solidification and tensile testing, as well as three-dimensional computed tomography of the microstructure before and after mechanical testing. The solidification processing stage is simulated with a multi-scale dendritic needle network model, and the micromechanical behavior of the solidified microstructure is simulated using voxelized tomography data and an elasto-viscoplastic fast Fourier transform model. This study demonstrates the feasibility of direct in situ monitoring of a metal alloy microstructure from the liquid processing stage up to its mechanical failure, supported by quantitative simulations of microstructure formation and its mechanical behavior. I. INTRODUCTION PROGRESS in understanding the links between processing routes, microstructures, properties, and performance of structural technological materials depends on our ability to observe materials in situ throughout their life cycle, and to quantitatively simulate these individual links. In terms of in situ imaging, the use of X-ray radiography and computed tomography has spread rapidly within most branches of materials science within the past two decades.[ 1 ] These techniques are particularly relevant to metallic alloys, and have been extensively employed in solidification processing,[ 2–5 ] three-dimensional (3D) rendering of microstructures and their evolution,[2] and in experimental mechanics.[ 6 ] X-ray imaging, in particular 3D tomography, has reached a sufficient level of maturity to be capable of providing quantitative measurements.[ 7 ] Solidification processing of metallic alloys (and in particular aluminum-based alloys) has been thoroughly investigated using two-dimensional (2D) radiography of thin sample experiments, often in controlled directional solidification conditions.[ 8–22 ] Resulting studies shed light onto mechanisms such as morphological transitions,[ 8–11 ] dendritic and eutectic growth,[ 11–15 ] dendritic fragmentation,[ 16–20 ] gravity-induced buoyancy and solute transport,[ 15–17,20,21 ] and the formation of major solidification defects such as freckles.[ 21,22 ] Metallic alloy solidification and microstructure evolution have also been extensively studied using 3D computed tomography.[ 23–31 ] Studies have mostly focused on mechanisms of solidification at low growth rates,[ 23,24 ] dendritic coarsening,[25] morphological transitions of equiaxed grains,[ 31 ] or the formation of intermetallics.[ 26,27 ] Recently, advanced techniques to increase temporal resolution have allowed resolving the evolution of complex dendritic morphologies at higher cooling rates[ 28,29 ] and exploring cellular-to-dendritic morphological transitions.[ 30 ] Computed X-ray tomography has also become widespread in the field of experimental mechanics. It has primarily been used to observe mechanical testing of polymers (e.g., Reference 32), metallic alloys (e.g., References 33 through 35), and metallic foams (e.g., References 36 and 37). Recent advances in fast tomography now allow observing the progression of a crack during fracture of materials of increasingly lower ductility (e.g., up to 20 Hz[ 38 ]). At the crossroads of processing and properties, X-ray in situ imaging has also been extensively used to investigate the mechanical behavior of semi-solid materials.[ 39–48 ] Such studies, usually realized for isothermal conditions with a partially melted sample, have helped to determine key mechanisms of failure or defect formation in a state of tension, e.g., linking the mushy zone permeability and the lack of liquid feeding to hot tearing defects,[ 40,43,44 ] as well as in compression,[ 45–48 ] highlighting the opening of internal pores[ (...truncated)


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D. Tourret, J. C. E. Mertens, E. Lieberman, S. D. Imhoff, J. W. Gibbs, K. Henderson, K. Fezzaa, A. L. Deriy, T. Sun, R. A. Lebensohn, B. M. Patterson, A. J. Clarke. From Solidification Processing to Microstructure to Mechanical Properties: A Multi-scale X-ray Study of an Al-Cu Alloy Sample, Metallurgical and Materials Transactions A, 2017, pp. 1-18, DOI: 10.1007/s11661-017-4302-8