Abstract: Multi-principal element alloys (MPEAs) have attracted much attention as future nuclear materials due to their extraordinary radiation resistances. In this work, we have elucidated the development of local chemical orderings (LCOs) and their influences on radiation damage behavior in the typical CrFeNi MPEA by hybrid-molecular dynamics and Monte Carlo simulations. It was found that considerable LCOs consisting of the Cr-Cr and Ni-Fe short-range orders existed in the ordered configuration with optimized system energy. Through modeling the accumulation cascades up to 1000 recoils, we revealed that the size of defect clusters and dislocation loops is smaller in the ordered configuration than those in the random one, although the former formed more Frenkel pairs (i.e., self-interstitials and vacancies). In addition, the distribution of dislocation loops is relatively more dispersed in the ordered configuration, and the stair-rod dislocations related to irradiation swelling are also smaller, implying that the existence of LCOs is conducive to enhancing radiation damage tolerance. To understand the underlying mechanism, the effects of LCOs on the formation and evolution of defects and radiation resistance were discussed from the aspects of atomic bonding, migration path, and energy of defect diffusion, which provides theoretical guidance for the design of MPEAs with enhanced radiation resistance.

Key words: Multi-principal element alloys, Local chemical ordering, Radiation damage, Dislocation evolution, Molecular dynamics simulation