Synergistic Effects of Grain Boundary and Chemical Short-Range Order on Radiation Resistance in NiCoCr Alloys

Short-range order (SRO) in medium-entropy alloys (MEA) affects radiation resistance by reducing the diffusivity of irradiation-induced defects as lattice distortion increases. To gain insights into how SRO influences defect dynamics under irradiation, we conducted molecular dynamics-based cascade simulations on a NiCoCr alloy known for its high radiation resistance and hardness. Specifically, we explored the synergistic effects of SRO and grain boundaries (GBs) on irradiation resistance. The number of surviving defects in alloys with chemical SRO (CSRO) were similar to those in a random solution alloy (RSA) in both single crystal (SC) and low-energy GB configurations. Conversely, in high-energy GB structures, which act as defect sinks, CSRO exhibited more surviving interstitials with a fewer number of vacancies than those in RSA. These conflicting effects occur because SRO affects the efficiency of defect sinks, which preferentially absorb interstitials. These results demonstrate that the influence of SRO on radiation resistance depends on the presence of defect sinks.