Grain size dependent mechanical properties of CoCrFeMnNi high-entropy alloy investigated by shear punch testing

The effect of grain size on the mechanical properties of an equiatomic CoCrFeNiMn high-entropy alloy (HEA) was investigated by shear punch testing (SPT) and Vickers hardness measurements. A Hall–Petch relationship was developed for the dependency of shear yield stress (SYS) on the average grain size (D). The correlation of the SYS and ultimate shear strength (USS) to the tensile yield stress (TYS) and ultimate tensile strength (UTS) values were also studied. A wide range of grain sizes was obtained by the thermomechanical processing of cold rolling and elevated-temperature annealing, where the primary recrystallization and grain growth phenomena were used for grain refinement and grain coarsening, respectively. Based on the obtained results and literature data, the Hall–Petch relationships of SYS = 88.9 + 301.1/√D and TYS = 167 + 520/√D were proposed, respectively. Moreover, the relationships of TYS = 1.76 × SYS and UTS = 1.33 × USS were obtained, where the former is in excellent agreement with the von Mises yield criterion based on the plasticity theory, and the latter is influenced by the work-hardening behavior of the material and dynamic phenomena during plastic deformation.