Stick-slip dynamics of coherent twin boundaries in copper
Stick-slip dynamics of coherent twin boundaries in copper
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DOI：
10.1016/j.actamat.2009.06.051
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发表时间：
2009-09-01
期刊：
影响因子：
9.4
通讯作者：
Ghoniem, N. M.
中科院分区：
文献类型：
--
作者：
Hu, Qiyang;Li, Lan;Ghoniem, N. M.
通过分子动力学(MD)计算机模拟，确定了共格孪晶界(CTB)的迁移动力学和潜在的原子机制。研究了纳米孪晶铜晶体在外加剪切载荷下的运动动力学和相关的有效迁移的细节。研究表明，由此产生的CTB迁移速度的大小和方向取决于剪切加载方向。研究发现，孪晶界上的(112)型剪切使其横向迁移速度达到最大。在平行于Tb面但倾向于(112)方向的方向上剪切，耦合程度较小，当剪切方向沿(110)方向时，最终导致孪晶界单独滑移。研究发现，CTB的运动动力学可描述为两步“粘滑”过程。原子组态分析表明，动力学的“棒状”相与晶体中的累积应变有关，这种应变是通过1/6[112]型孪生部分位错的形核而突然释放的。在与孪晶界相邻的原子层中，原子的配位洗牌发生在位错成核之前。动力学的“滑移”相由形核孪晶部分位错的快速传播及其沿孪晶界的扩展所控制。(C)2009年Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
The migration kinetics of coherent twin boundaries (CTBs) and the underlying atomistic mechanisms are determined through molecular dynamics (MD) computer simulations. Details of motion dynamics and associated effective migration of CTBs are examined for nanotwinned copper crystals under externally applied shear loading. The present study reveals that the magnitude and direction of the resulting CTB migration velocity is dependent on the shear-loading orientation. It is found that (112)-type shearing on {111} twin boundaries maximizes their transverse migration velocity. Shearing at directions which remain parallel the TB plane but are inclined to the 112)-direction results in a smaller degree of coupling, and finally to twin boundary sliding alone when the shear direction is along (110). It is found that the dynamics of CTB motion can be described as a two-step "stick-slip" process. Analysis of atomic configurations indicates that the "stick" phase of the dynamics is associated with accumulated strain in the crystal, and that such strain is suddenly released by the nucleation of 1/6 [112]-type twinning partial dislocations. In atomic layers adjacent to the twin boundary, coordinated shuffling of atoms is found to take place immediately before dislocation nucleation. The "slip" phase of the dynamics is shown to be controlled by fast propagation of nucleated twinning partial dislocations and their spreading along the twin boundary. (C) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.