Chemical short-range order modulation of crack self-healing in NiCoCrFeMn during irradiation: A molecular dynamics study

High-entropy alloys (HEAs) are promising candidates for advanced nuclear structural materials, owing to their superior mechanical properties and irradiation resistance under extreme service conditions. However, microcracks generated during fabrication and service significantly limit their operational lifespan. The evolution of chemical short-range order (SRO) under irradiation exerts a pivotal regulatory effect on the crack self-healing behavior of HEAs. In this study, molecular dynamics simulations were systematically performed to elucidate the regulatory mechanism of SRO on crack healing behavior in NiCoCrFeMn HEAs under ion-induced cascade collisions. The results reveal that an optimal SRO degree induced by 600 K annealing achieves a balanced trade-off between point defect density and atomic mobility. This leads to complete crack closure with 100% healing efficiency, significantly outperforming the random solid solution (RSS) and other degree of SRO models. Specifically, SRO guides the selective segregation, enrichment, and filling of Co, Fe, and other elements in the crack region, while promoting the formation of a dense, entangled three-dimensional dislocation network dominated by 1/6<112> Shockley partial dislocations and 1/6<110> stair-rod dislocations. Additionally, irradiation-induced amorphous regions undergo recrystallization into stable FCC/HCP phases, further facilitating crack self-healing and ensuring long-term structural integrity under irradiation. Collectively, SRO governs the crack self-healing process in NiCoCrFeMn HEAs by synergistically modulating defect evolution, atomic migration, dislocation dynamics, and phase transformation. This work overcomes the inherent limitations of conventional RSS-based HEA designs and offers critical theoretical insights and guidance for the precise SRO engineering of next-generation irradiation-tolerant and self-healing nuclear structural materials.