Study on the Chemical Short-Range Order and Its Effect on Displacement Cascade in Non-equiatomic NiCoCr Medium-Entropy Alloys

Abstract

Chemical short-range order (CSRO) structures are important features in medium-/high-entropy alloys (M/HEAs) and significantly influence their mechanical properties under irradiation. In this work, molecular dynamics (MD) simulations were employed to investigate the influence of CSRO structures on displacement cascade in non-equiatomic NiCoCr MEAs. Two groups of non-equiatomic MEAs with different compositions were designed. The results show that the CSRO structures separate into Ni-rich regions and the Co-Cr regions, which play different roles during point defect evolution. Formation energy and migration energy barriers of point defects were calculated to explain these differences. The Ni-rich regions suppress point defect formation due to their higher formation energy, whereas the Co-Cr regions promote point defect recombination due to their lower migration energy barrier. By adjusting elemental content, the degree of Ni-rich and Co-Cr regions can be varied, thereby altering their effects on point defect evolution. This work aims to provide theoretical support for optimizing mechanical properties through the regulation of CSRO structures and compositional adjustments in M/HEAs under irradiation.