In this work, the effects of strain rate on mechanical deformation and microstructural evolution of CoCrFeMnNi high-entropy alloy (HEA) under quasi-static and dynamic compression were investigated. The HEA exhibited high strain-rate sensitivity values (m = 0.028) of yield strength under quasi-static conditions. In particular, due to the viscous drag effect, the variation of yield strength with strain rate under dynamic compression was much larger than that under quasi-static compression. Microstructural analysis using electron backscatter diffraction shows profuse twinning under both conditions. The dynamically deformed specimens exhibited strongly localized deformation regions (i.e., adiabatic shear bands). The process of dynamic compressive behavior in this HEA is competitive between hardening by dislocation and twinning, and thermal softening. To analyze numerically the flow behavior of the HEA under dynamic conditions, the modified Johnson-Cook model considering adiabatic temperature rise was employed. The modified Johnson-Cook model offered good agreement with experimental results regarding dynamic flow curves of this HEA.

在这项工作中，研究了在准静态和动态压缩下，应变速率对CoCrFeMnNi高熵合金（HEA）的机械变形和组织演变的影响。在准静态条件下，HEA表现出高的屈服强度应变率敏感性值（m = 0.028）。特别地，由于粘性阻力效应，在动态压缩下屈服强度随应变率的变化远大于在准静态压缩下的屈服强度随应变率的变化。使用电子反向散射衍射的微结构分析显示在两种条件下均存在大量孪晶。动态变形的样品表现出强烈的局部变形区域（即绝热剪切带）。该HEA中的动态压缩行为过程在位错和孪晶硬化与热软化之间具有竞争性。为了对HEA在动态条件下的流动行为进行数值分析，采用了考虑绝热温升的改进Johnson-Cook模型。修改后的Johnson-Cook模型与该HEA的动态流动曲线的实验结果非常吻合。