文献类型：期刊文献

英文题名：Amorphization induced by 60° shuffle dislocation pileup against different grain boundaries in silicon bicrystal under shear

作者：Chen, Hao[1,2];Levitas, Valery I.[3,4];Xiong, Liming[2]

机构：[1]East China Univ Sci & Technol, Minist Educ, Key Lab Pressure Syst & Safety, Shanghai 200237, Peoples R China;[2]Iowa State Univ, Dept Aerosp Engn, Ames, IA 50010 USA;[3]Iowa State Univ, Dept Aerosp Engn & Mech Engn, Ames, IA 50011 USA;[4]Ames Lab, Div Mat Sci & Engn, Ames, IA USA

年份：2019

卷号：179

起止页码：287

外文期刊名：ACTA MATERIALIA

收录：;EI(收录号：20193607397061);WOS:【SCI-EXPANDED(收录号:WOS:000488417400026)】；

基金：We acknowledge the support of NSF (CMMI-1536925) and the Extreme Science and Engineering Discovery Environment (XSEDE allocations TG MSS170003 and MSS170015). LX also acknowledges the support from NSF (DMR-1807545). VIL also acknowledges supports of ARO (W911NF-17-1-0225), NSF (DMR-1904830), ONR (N00014-19-1-2082), and Iowa State University (Vance Coffman Faculty Chair Professorship).

语种：英文

外文关键词：Silicon under shear; 60 degrees dislocation pileup; Grain boundaries; Amorphous shear band; Molecular dynamics

摘要：Molecular dynamics (MD) simulations of the amorphous band nucleation and growth ahead of the tip of a shuffle 60 dislocation pileup at different grain boundaries (GBs) in diamond-cubic (dc) silicon (Si) bicrystal under shear are performed. Amorphization initiates when the local resolved shear stress reaches approximately the same value required for amorphization in a perfect single crystal (8.6-9.3 GPa) for the same amorphization plane. Since the local stresses at the tip of a dislocation pileup increase when the number of the dislocations in a pileup is increased, the critical applied shear stress T-ap for the formation of an amorphous shear band significantly decreases with the dislocation accumulation at the GBs. In particular, when the number of the dislocations in a pileup increases from 3 to 8, the critical shear stress drops from 4.7 GPa to 1.6 GPa for both the Sigma 9 and Sigma 19 GBs and from 4.6 GPa to 2.1 GPa for the 2 Sigma GB, respectively. After the formation of steps and disordered embryos at the GBs, the atomistic mechanisms responsible for the subsequent amorphous shear band formations near different GBs are found to distinct from each other. For a high-angle GB, such as Sigma 3, an amorphous band propagates through the crystalline phase along the (112) plane. For the Sigma 9 GB, dislocations disassociate and the stacking faults form, which then precede the formation of an amorphous band along the (110) plane. For the Sigma 19 GB, the one-layer stacking fault along the (111) plane transforms into an interesting intermediate phase: a two-layer band with the atomic bonds being aligned along the (111) plane (i.e., rotated by 30 degrees with respect to the atomic bonds outside the band). This intermediate phase transforms to the amorphous band along the (111) plane under a further shearing. The obtained results represent an atomic-level confirmation of the effectiveness of dislocation pileup at the nucleation site for various strain-induced phase transformations (PTs), and exhibit some limitations. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.