Evolution of defects with isochronal annealing in helium-irradiated 316L studied by slow positron beam

Abstract

The evolution of defects with isochronal annealing between 373 and 1273 K in 316L stainless steels, irradiated by helium ions at room temperature (RT), has been studied by the slow positron Doppler broadening spectroscopy (DBS). The results showed that with annealing temperature between RT and 673 K, the S parameters of sample were maintained. It indicates that below 673 K, on the one hand, some vacancies introduced by irradiation were gathered to form vacancy clusters and on the other hand, some vacancies migrated and recovered. From 773 K to 1073 K, there was continuous growth of HenVm cluster, resulting in rapid increasing of S parameter. After 1073 K, unstable HenVm clusters dissociated into vacancies and He atoms. The vacancies were vanished rapidly, which decreases the concentration of vacancy defects, leading to decline of S parameter.