Observation of Micro-scale Surface Morphology with Microtexture Development During Plane Strain Tensile Deformation in A
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t is well known that magnesium (Mg) has a shortage of independent slip systems to accommodate plastic deformation at room temperature. This limit of operating slip systems in Mg stems from its low-symmetry hexagonal close-packed crystal structure and much higher critical resolved shear stress (CRSS) of non-basal slip modes than that of ð0001Þh11 20i basal slip.[1–7] In order to accommodate deformation on account of external forces, the deformation twinning, which has a relatively low CRSS, easily forms during plastic deformation at low temperature. Deformation twinning is a significant deformation mechanism in Mg alloys; hence much research has focused on the fundamental understanding and advanced application of several deformation twins.[8–12] Among them, 1012 h1011i tensile twin is primarily observed during tensile loading along c-axis and accompanies the rotation of the c-axis by 86 deg.[8] KEUNHO LEE and KYUNG IL KIM, Ph.D. Students, KYU HWAN OH and HEUNG NAM HAN, Professors, are with the Department of Materials Science and Engineering and RIAM, Seoul National University, Seoul 151-744, Republic of Korea. Contact e-mail: [email protected] SE-JONG KIM, Senior Researcher, is with the Material Deformation Department, Korea Institute of Materials Science Changwon, Gyeongnam 642-831, Republic of Korea. DONGWOO SUH, Associate Professor, is with the Graduate Institute of Ferrous Technology, Pohang University of Science and Technology, Pohang 790-784, Republic of Korea. Manuscript submitted August 6, 2014. Article published online November 25, 2014 12—VOLUME 46A, JANUARY 2015
This crystallographic rotation induces a local material flow and a complex strain state in the regions of the tensile twin, influencing a deformation texture in Mg alloys. For an accurate analysis of the strain state caused by the tensile twinning, it is necessary to investigate tensile twin regions through three dimensional (3D) observation during in situ deformation. Meanwhile, many studies have utilized in situ electron backscattered diffraction (in situ EBSD) technique during deformation to elucidate deformation mechanism of various metals and alloys from their microstructural evolution at the micro-scale level.[13–15] In addition, microstructure-based computational simulations such as crystal plasticity finite element methods (CP-FEM)[16–19] and crystal plasticity fast Fourier transform-based model[13,20] have supported experimental proofs, and predicted how materials are deformed under external deformation conditions. Especially, recent investigations have used the 3D reconstructed microstructure obtained from by EBSD combined with focused ion beam, or synchrotron X-ray microtomography as an initial microstructure for the simulation.[21– 23] As for the Mg alloys, a 3D CP-FEM simulation that considered both crystallographic slip and deformation twinning was done to explain the heterogeneity of the stress concentration as well as the slip and twin activities.[18,19] However, there are few experimental reports regarding 3D observation of microstruct
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