Yimer Mohammed Meaza, Wubeshet Debela Abeyot, Qin Xiangge
School of Materials Science and Engineering, Jiamusi University, 258th Xuefu Street, Xiangyang District, Heilongjiang, 154007 PR China.
Heliyon. 2023 May 5;9(5):e16039. doi: 10.1016/j.heliyon.2023.e16039. eCollection 2023 May.
Twin thickness-dependent deformation and the transition from strengthening to softening in twinned silicon nanowires are investigated using molecular dynamics simulations with cylindrical and hexagonal cross sections. The results show that the transition from strengthening to softening occurs at critical twin thicknesses of 8.1 nm (11.0 TB s) with cylindrical cross section and 11.0 nm (8 TBs) with hexagonal cross section with decreasing twin thickness, and that the strongest twin thickness originates from a transition in the initial plasticity mechanism from full dislocation nucleation and interaction with the TBs to partial dislocation nucleation and gliding parallel to the TBs. Moreover, it is found that the relationship between peak stress and twin thickness can be divided into two regions. Several full and partial dislocations are formed in the regions with strengthening twin thickness range. The accumulation and pile-up of these dislocations and their interaction with the TBs at high density cause the Hall-Petch strengthening behavior. In contrast, few full and partial dislocations are formed with softening twin thickness range. These dislocations are nucleated and propagate parallel to the TBs, resulting in TB migration that causes inverse Hall-Petch softening behavior. Our simulation results provide sufficient insight into the mechanical behavior of twinned silicon nanowires with cylindrical and hexagonal cross sections. The study will be helpful to the further understanding of CTB-related mechanical behaviors of non-metallic materials and non-metallic system.
利用分子动力学模拟研究了具有圆柱形和六边形横截面的孪晶硅纳米线中与孪晶厚度相关的变形以及从强化到软化的转变。结果表明，随着孪晶厚度减小，从强化到软化的转变分别发生在圆柱形横截面的临界孪晶厚度8.1纳米（11.0个孪晶层间距）和六边形横截面的11.0纳米（8个孪晶层间距）处，并且最强孪晶厚度源于初始塑性机制从全位错形核并与孪晶界相互作用到部分位错形核并平行于孪晶界滑移的转变。此外，发现峰值应力与孪晶厚度之间的关系可分为两个区域。在强化孪晶厚度范围内的区域会形成若干全位错和部分位错。这些位错的积累和堆积以及它们在高密度下与孪晶界的相互作用导致了霍尔 - 佩奇强化行为。相反，在软化孪晶厚度范围内形成的全位错和部分位错很少。这些位错形核并平行于孪晶界传播，导致孪晶界迁移，从而引起反霍尔 - 佩奇软化行为。我们的模拟结果为具有圆柱形和六边形横截面的孪晶硅纳米线的力学行为提供了充分的见解。该研究将有助于进一步理解非金属材料和非金属体系中与共格孪晶界相关的力学行为。
