Aluminum alloying enhances helium irradiation resistance in CoCrFeNi high entropy alloys

This study investigates the swelling behavior and defect evolution of FCC Al x CoCrFeNi high entropy alloys (HEAs) under high temperature helium (He) ion irradiation. Helium irradiation resistance improves systematically as the aluminum content increases. The aluminum containing alloys exhibit smaller He bubbles, higher bubble number densities, lower swelling, and more effectively suppressed dislocation growth, especially at high fluence. This improvement is mainly attributed to the enhanced local lattice distortion introduced by aluminum. The increased atomic size mismatch reduces the mobility of vacancies and He related defects, promotes defect recombination, and favors more dispersed bubble nucleation sites. Fine dislocation loops formed in the aluminum containing alloys also act as effective defect sinks, thereby further suppressing defect coarsening. These findings provide new insights into the role of aluminum in regulating He irradiation damage and offer guidance for the design of He irradiation resistant alloys.