Abstract As the numbers of medium- to high-entropy alloys being studied and impressive structural properties they exhibit increase rapidly, questions regarding the role played by their complex chemical fluctuations rise concomitantly. Here, using a combination of large-scale molecular dynamics (MD), a hybrid MD and Monte-Carlo simulation method, and crystal defect analysis, we investigate the role lattice distortion (LD) and chemical short-range order (CSRO) play in the nucleation and evolution of dislocations and nanotwins with straining in single crystal and nanocrystalline CoCrNi, a medium entropy alloy (MEA). LD and CSRO effects are elucidated by comparisons with responses from a hypothetical pure A-atom alloy, which bears the same bulk properties of the nominal MEA but no LD and no CSRO. The analysis reveals that yield strengths are determined by the strain to nucleate Shockley partial dislocations, and LD lowers this strain, while higher degrees of CSRO increase it. We show that while these partials prefer to nucleate in the CoCr clusters, regardless of their size, they find it increasingly difficult to propagate away from these sites as the level of CSRO increases. After yield, nanotwin nucleation occurs via reactions of mobile Shockley partials and is promoted in MEAs, due to the enhanced glide resistance resulting from LD and CSRO.

中文翻译：

---

晶格畸变和化学短程有序对中熵合金CoCrNi变形机制的影响

摘要 随着正在研究的中高熵合金的数量及其令人印象深刻的结构性能迅速增加，有关其复杂化学波动所起作用的问题也随之增加。在这里，结合大规模分子动力学 (MD)、混合 MD 和蒙特卡罗模拟方法以及晶体缺陷分析，我们研究了晶格畸变 (LD) 和化学短程有序 (CSRO) 在位错和纳米孪晶在单晶和纳米晶 CoCrNi（一种中等熵合金 (MEA)）中的成核和演化。通过与假设的纯 A 原子合金的响应进行比较，阐明了 LD 和 CSRO 效应，该合金具有与标称 MEA 相同的整体特性，但没有 LD 和 CSRO。分析表明，屈服强度由使肖克利部分位错成核的应变决定，LD 降低了该应变，而更高程度的 CSRO 增加了它。我们表明，虽然这些部分更喜欢在 CoCr 簇中成核，无论它们的大小如何，但随着 CSRO 水平的增加，它们发现越来越难以从这些位点传播。在屈服之后，由于 LD 和 CSRO 导致的滑动阻力增强，纳米孪晶成核通过可移动的肖克利部分的反应发生，并在 MEA 中得到促进。他们发现随着 CSRO 水平的提高，越来越难以从这些网站传播出去。在屈服之后，由于 LD 和 CSRO 导致的滑动阻力增强，纳米孪晶成核通过可移动的肖克利部分的反应发生，并在 MEA 中得到促进。他们发现随着 CSRO 水平的提高，越来越难以从这些网站传播出去。在屈服之后，由于 LD 和 CSRO 导致的滑动阻力增强，纳米孪晶成核通过可移动的肖克利部分的反应发生，并在 MEA 中得到促进。