Effects of nanosized precipitates on irradiation behavior of CoCrFeNi high entropy alloys

Highlights: • Effects of precipitates in HEAs on irradiation damage resistance were explored. • HEAs have shown high irradiation-induced hardening resistance. • The HEA containing massive precipitates showed improved irradiation resistance. • The superior irradiation resistance of the aged HEAs is due to disordering and dissolution of precipitates. -- Abstract: Evolution of nanosized precipitates in typical (CoCrFeNi)₉₄Ti₂Al₄ high entropy alloys under irradiation and its effect on the irradiation resistance were investigated in detail. The as-solutionized samples and the aged samples with massive nanosized precipitates were irradiated at ambient temperatures with a dose ranging from 10 to 49 dpa of 4 MeV Au ions. It was found that the ordered precipitates became disordered quickly at the early stage under 10 dpa irradiation, accompanying with the dissolution process which became more and more severer at higher doses. After irradiation, the hardness slightly changed in the aged specimens containing massive precipitates, but increased by> 30% in the as-solutionized ones with no precipitates. The obvious hardness increment in the as-solutionized samples is due to the creation of defects while the small variations of the hardness in the aged specimens can be ascribed to the disordering and dissolution of precipitates. In addition, the size of dislocation loops induced by the irradiation in the aged specimens is much smaller than that in the as-solutionized samples. We confirmed that presence of the nanosized precipitates delayed defect evolution and reduced the sizes of dislocation loops.