Overcoming strength-ductility trade-off in high-entropy alloys by tuning chemical short-range order and grain size

The chemical short-range order (CSRO) and grain size affect the strength and ductility of high-entropy alloys (HEAs). However, their superposition effect has not yet been studied, limiting further improvement in performance. In this work, we examined the synergistic effect of the CSRO and grain size on the tensile properties of CoCrFeMnNi at room temperature by conducting atomic simulations, because performing an experimental investigation on the formation and movement of dislocations is difficult. The results showed that the preferable locations of the various elements were different. Cr and Mn were preferentially distributed on the grain boundary, Co and Fe were enriched inside the grain, and Ni accumulated in the transition zone from the grain boundary to the intragranular region. In addition, increasing the CSRO appropriately can optimize the density and distribution of dislocations, simultaneously enhancing the strength and ductility of HEAs. Furthermore, an inverse Hall-Petch relation was observed in the system without the CSRO. The simulation computation revealed that the critical grain size that induces the inverse Hall-Petch relation is approximately 13.1 nm. However, the presence of the CSRO eliminates the inverse Hall-Petch relation.