Abstract Plasticity in body centered cubic (BCC) crystals is shown to be controlled by slow screw dislocation motion, owing to the thermally-activated process of kink pair nucleation and migration. Through three dimensional discrete dislocation dynamics simulations, this work unravels the mystery of how such slow screw dislocation behavior contributes to extremely rapid strain bursts in submicron BCC tungsten (W) pillars, which is typical of BCC metals. It is found that strain bursts are dominated by the motion of non-screw dislocations at low strain rate, but are more influenced by screw dislocations at high strain rate. The total, and partial strain burst magnitude due to screw dislocations alone, are found to exhibit rate dependence following a power law statistics with exponent of 0.65. Similar power law statistics are also obeyed for the standard deviation of the corresponding plastic strain rate. The role of screw dislocations is attributed to the changing nature of dislocation source operation at different strain rates. The corresponding spatial distribution of plastic deformation is also discussed based on the uniqueness of the simulation method in reproducing the distribution of slipped area and plastic strain with very high spatial resolution.

中文翻译：

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慢螺旋位错在控制体心立方金属快速应变雪崩动力学中的作用

摘要 由于扭结对成核和迁移的热激活过程，体心立方 (BCC) 晶体的塑性受慢螺旋位错运动控制。通过三维离散位错动力学模拟，这项工作揭示了这种缓慢的螺旋位错行为如何导致亚微米 BCC 钨 (W) 柱中极快的应变爆发的奥秘，这是 BCC 金属的典型特征。发现应变爆发在低应变率下主要由非螺旋位错的运动控制，但在高应变率下受螺旋位错的影响更大。根据指数为 0.65 的幂律统计，发现单独由螺旋位错引起的总的和部分的应变爆发幅度表现出速率依赖性。相应塑性应变率的标准偏差也遵循类似的幂律统计。螺位错的作用归因于不同应变率下位错源操作的变化性质。基于模拟方法在以非常高的空间分辨率再现滑移面积和塑性应变分布的独特性，还讨论了塑性变形的相应空间分布。