Effect of hydrogen, helium and dose rate on the evolution of dislocation loop in pure iron during in-situ ion irradiation

Abstract

Simulating neutron irradiation with ion irradiation requires considering the comprehensive effects of hydrogen, helium and dose rate to fully understand the microstructure evolution of material in an irradiation environment. Here, the characterization and evolution of dislocation loops in pure iron were investigated under heavy ion irradiation with four different injected gas ion types (Fe+, Fe++H2+, Fe++He+and Fe++H2++He+) and under dual-beam (Fe++He+) irradiation with four different dose rates using in-situ transmission electron microscopy at 723 K. Comparing to the single-beam (Fe+) irradiation, the additional injection of H or He, or co-injected H and He, mainly promoted the nucleation of dislocation loops at the early stage of irradiation and enhanced loop growth after that. Among them, the simultaneous irradiation of triple beams (Fe++H2++He+) was most pronounced. Moreover, triple-beam (Fe++H2++He+) irradiation resulted in the highest ratio of the rotation of loop habit-plane. Under dual-beam (Fe++He+) irradiation, the results demonstrated that as the dose rate increased, the loop density increased and the loop size decreased. Moreover, the fraction of 〈100〉 loops at low dose rate was noticeably greater than that at high dose rate. The results of the current work provide important references for a better understanding of the effectiveness of ion irradiation in simulating neutron irradiation.