Wang Jiangwei, Wang Yanming, Cai Wei, Li Jixue, Zhang Ze, Mao Scott X
Center of Electron Microscopy and State Key Laboratory of Silicon Materials, School of Materials Science and Engineering, Zhejiang University, Hangzhou, 310027, China.
Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, USA.
Sci Rep. 2018 Mar 15;8(1):4574. doi: 10.1038/s41598-018-23015-z.
Shear band in metallic crystals is localized deformation with high dislocation density, which is often observed in nanopillar deformation experiments. The shear band dynamics coupled with dislocation activities, however, remains unclear. Here, we investigate the dynamic processes of dislocation and shear band in body-centered cubic (BCC) tungsten nanowires via an integrated approach of in situ nanomechanical testing and atomistic simulation. We find a strong effect of surface orientation on dislocation nucleation in tungsten nanowires, in which {111} surfaces act as favorite sites under high strain. While dislocation activities in a localized region give rise to an initially thin shear band, self-catalyzed stress concentration and dislocation nucleation at shear band interfaces cause a discrete thickening of shear band. Our findings not only advance the current understanding of defect activities and deformation morphology of BCC nanowires, but also shed light on the deformation dynamics in other microscopic crystals where jerky motion of deformation band is observed.
金属晶体中的剪切带是具有高位错密度的局部变形，这在纳米柱变形实验中经常被观察到。然而，剪切带动力学与位错活动的耦合仍不清楚。在这里，我们通过原位纳米力学测试和原子模拟的综合方法，研究体心立方（BCC）钨纳米线中位错和剪切带的动态过程。我们发现表面取向对钨纳米线中位错形核有强烈影响，其中{111}面在高应变下是优先形核位点。虽然局部区域的位错活动会产生最初较薄的剪切带，但剪切带界面处的自催化应力集中和位错形核会导致剪切带离散增厚。我们的发现不仅推进了目前对BCC纳米线缺陷活动和变形形态的理解，也为其他观察到变形带急动运动的微观晶体中的变形动力学提供了线索。
