孪晶结构Cu纳米线塑性变形机制的分子动力学模拟研究

孪晶结构Cu纳米线塑性变形机制的分子动力学模拟研究

郝龙虎¹，黄  铭¹，卢  艳¹，张  泽^1，2，王立华^1*，韩晓东^1*

（1.北京工业大学固体微结构与性能研究所，北京市先进材料微观结构与性能重点实验室，北京100124；2.浙江大学材料科学与工程学院，浙江 杭州 310008）

摘 要  孪晶结构的金属纳米线因具有优异的力学性能而受到广泛关注，然而之前的研究对象都为孪晶界垂直于纵轴的孪晶结构纳米线。本文采用分子动力学模拟的方法，研究了孪晶界平行于纵轴方向的Cu纳米线的力学行为。结果发现纳米线的屈服应力随孪晶厚度的减小而不断增大，表明孪晶厚度减小对孪晶结构的Cu纳米线的强度具有显著强化效应。此外，孪晶结构Cu纳米线的塑性变形机制受孪晶厚度的影响。当孪晶厚度＞3个原子层时，它们的塑性变形由Shockley偏位错与孪晶界相交主导；当孪晶厚度减小到3个原子层时，Cu纳米线的塑性变形通过晶格畸变和原子重排导致新的晶粒形成来实现。

关键词  分子动力学模拟；纳米线；塑性变形；位错；共格孪晶界

中图分类号：O77⁺2；O763；TB383  文献标识码：A   doi:10.3969/j.issn.1000-6281.2019.04.001

Molecular dynamics simulation of the plastic deformation mechanisms of twin-structured Cu nanowires

HAO Long-hu¹, HUANG Ming¹, LU Yan¹, ZHANG Ze^1，2, WANG Li-hua^1*, HAN Xiao-dong^1*

(1. Beijing Key Lab of Microstructure and Property of Advanced Material, Institute of Microstructure and Properties of Advanced Materials, Beijing University of Technology, Beijing 100124; 2.Department of Materials Science, Zhejiang University, Hangzhou Zhejiang310027, China)

Abstract  The twin-structured metals nanowires(NWs) have attracted strong interest because of their excellent mechanical properties. However, most of previous studies were focused on those NWs with twin boundary (TB) that were perpendicular to the NWs’ longitudinal axis. In this paper, the mechanical behavior of Cu NWs with a coherent twin boundary parallel to their longitudinal axiswas investigated using molecular dynamics simulation. Our results show that the twin-structure nanowires exhibited a strong twin thickness strengthening effect, which leads to their yielding stress continuing to increase as the twin thickness decreases. Yet, the plastic deformation mechanisms of these nanowires were significantly affected by the twin thickness. For the nanowires with relatively thicker twin, their plastic deformation was controlled by partial dislocations intersecting the coherent twin boundary. As the twin thickness decreases into three atomic layers, the plasticity was accommodated by lattice distortion and rearrangement that led to the twin-structure lattice being transferred into a single-crystal.

Keywords  molecular dynamic simulation; plastic deformation; dislocation; coherent twin boundary; nanowire

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