Plasticity of bcc micropillars controlled by competition between dislocation multiplication and depletion
Plasticity of bcc micropillars controlled by competition between dislocation multiplication and depletion
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DOI：
10.1016/j.actamat.2013.02.011
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发表时间：
2013-05
期刊：
影响因子：
9.4
通讯作者：
I. Ryu;W. Nix;W. Cai
中科院分区：
文献类型：
--
作者：
I. Ryu;W. Nix;W. Cai
最近的微柱实验表明，在小的柱直径强的尺寸效应。这种“越小越强”的现象被广泛认为涉及位错运动，可以使用位错动力学（DD）模拟来研究。本文利用三维DD模型研究了体心立方微柱体在压缩条件下的集体位错行为。在Weinberger和Cai的分子动力学（MD）模拟之后，我们考虑了一个表面控制的交叉滑移过程，涉及图像力和非平面核心结构，导致在不存在人工位错源或钉扎点的情况下倍增。模拟显示尺寸效应和初始位错密度和应变速率对强度的影响，这似乎与最近的实验结果和这里描述的一个简单的位错动力学模型是很好的协议。此外，在高应变率下，塑性主要由位错运动的动力学决定，而不是它们的弹性相互作用。
Recent micropillar experiments have shown strong size effects at small pillar diameters. This “smaller is stronger” phenomenon is widely believed to involve dislocation motion, which can be studied using dislocation dynamics (DD) simulations. In the present paper, we use a three-dimensional DD model to study the collective dislocation behavior in body-centered cubic micropillars under compression. Following the molecular dynamics (MD) simulations of Weinberger and Cai, we consider a surface-controlled cross-slip process, involving image forces and non-planar core structures, that leads to multiplication without the presence of artificial dislocation sources or pinning points. The simulations exhibit size effects and effects of initial dislocation density and strain rate on strength, which appear to be in good agreement with recent experimental results and with a simple dislocation kinetics model described here. In addition, at the high strain rates considered, plasticity is governed mainly by the kinetics of dislocation motion, not their elastic interactions.