Experimental molecular dynamics for individual atomic-scale plastic events in nanoscale crystals
Experimental molecular dynamics for individual atomic-scale plastic events in nanoscale crystals
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DOI：
10.1016/j.jmps.2021.104687
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发表时间：
2021-10-28
影响因子：
5.3
通讯作者：
Mao, Scott X.
中科院分区：
文献类型：
--
作者：
Zheng, Sixue;Shinzato, Shuhei;Mao, Scott X.
实验确定屈服和塑性流动的临界应力对于理解纳米尺度金属的原子尺度力学行为是最重要的，由于其固有的高应变率和经验原子间势，这在计算分子动力学中是有限的。在这里，我们提出了一种原位原子尺度的实验力学，即所谓的实验分子动力学，它能够研究具有不同晶体结构的纳米金属中各个原子尺度塑性事件的应力-应变关系，包括全位错滑移、形变孪生和剪切带。通过分析晶格应变计、面间间距和应变片长度的变化，得到了局部应力、应变及其关系。利用这种方法，研究了个别塑性事件的剧烈应力降和应变猝发的特征。得到了激活原子级缺陷形核和长大的临界应力。新发展的基于原位力学方法的实验分子动力学方法具有准静态应变率的优点，与计算方法相比不需要原子间势，这可能为建立基于应力的原子尺度屈服和塑性流动准则提供新的线索。
The experimental determination of critical stresses for yielding and plastic flow is of upmost importance for the understanding of the atomic-scale mechanical behaviors of nanoscale metals, which is limited in computational molecular dynamics due to their inherent high strain rates and empirical interatomic potentials. Here, we propose an in situ atomic-scale experimental mechanics, the so-called experimental molecular dynamics, which is capable of studying the stressstrain relations with respect to the individual atomic-scale plastic events, including full dislocation slip, deformation twinning and shear band in nanoscale metals with different crystal structures. The local stress, strain and their relationships were obtained based on the analyses of the change in lattice strain gauge, interplanar spacing and gauge length. Using this method, drastic stress drops and strain bursts, the characteristics of individual plastic events, are investigated. The critical stresses for activating the nucleation and growth of atomic-scale defects are obtained. The newly developed experimental molecular dynamics with in situ mechanics approach has the advantage of quasi-static strain rate and no requirement of interatomic potentials over the computational one, which may provide new clues to establish the stress-based criteria for atomicscale yielding and plastic flow.