Cross-kinks control screw dislocation strength in equiatomic bcc refractory alloys
Cross-kinks control screw dislocation strength in equiatomic bcc refractory alloys
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DOI：
10.1016/j.actamat.2021.116875
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发表时间：
2021-04
期刊：
影响因子：
9.4
通讯作者：
Xinran Zhou;Sicong He;J. Marian
中科院分区：
文献类型：
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作者：
Xinran Zhou;Sicong He;J. Marian
具有体心立方（bcc）结构的难熔多元素合金（RMEA）由于其作为高温应用的候选材料的高潜力而在过去十年中成为许多研究的对象。这些合金中的大多数在高温下显示出显著的强度，这不能用基于热激活螺位错运动的体心立方塑性的标准模型来解释。一些工作已经指出，化学能波动是RMEA强度的一个重要方面，标准模型没有捕捉到。在这项工作中，我们量化的贡献螺旋位错的强度等原子Nb-Ta-V合金使用的动力学Monte Carlo模型拟合从原子计算得到的溶液能量。在协议与分子动力学模拟，我们发现，化学能量波动沿着的位错线导致可测量的浓度扭结在很宽的温度范围内的平衡。一小部分这些形式的交叉扭结配置，最终发现控制螺旋位错运动和材料强度。我们的模拟（i）证实，交叉扭结和自钉扎的演变是强有力的贡献者，在这种合金中的所谓的“鸡尾酒”效应在低温下，和（ii）证实的概念，螺位错塑性单独不能解释bcc RMEA的高温强度。
Refractory multi-element alloys (RMEA) with body-centered cubic (bcc) structure have been the object of much research over the last decade due to their high potential as candidate materials for high-temperature applications. Most of these alloys display a remarkable strength at high temperatures, which cannot be explained by the standard model of bcc plasticity based on thermally-activated screw dislocation motion. Several works have pointed to chemical energy fluctuations as an essential aspect of RMEA strength that is not captured by standard models. In this work, we quantify the contribution of screw dislocations to the strength of equiatomic Nb-Ta-V alloys using a kinetic Monte Carlo model fitted to solution energetics obtained from atomistic calculations. In agreement with molecular dynamics simulations, we find that chemical energy fluctuations along the dislocation line lead to measurable concentrations of kinks in equilibrium in a wide temperature range. A fraction of these form cross-kink configurations, which are ultimately found to control screw dislocation motion and material strength. Our simulations (i) confirm that the evolution of cross kinks and self-pinning are strong contributors to the so-called ‘cocktail’ effect in this alloy at low temperature, and (ii) substantiate the notion that screw dislocation plasticity alone cannot explain the high temperature strength of bcc RMEA.