The recovery of gas-vacancy-complexes in Fe irradiated with high energy H or He ions

Abstract

Isochronal annealing experiments for Fe irradiated with H or He ions were carried out to study interactions between gas atoms and vacancy clusters. The accelerating energy of H and He ions was 1.0 MeV and 3.3 MeV, respectively. The total dose was 1.0 × 1021 H ions/m2 (0.2 dpa) and 9.6 × 1019 He ions/m2 (0.3 dpa), and the irradiation temperature was 300°C. Positron annihilation lifetime and coincidence Doppler broadening (CDB) measurements were carried out after irradiation and annealing for 1 hour up to the complete recovery temperature. Microvoids were detected after H or He ion irradiation. The characteristic difference was mainly shown in the recovery of vacancy type defects. The recovery of vacancy type defects introduced by H ion irradiation finished completely at 450°C, while that by He ion irradiation finished at 1000°C. It suggests that H-vacancy complexes were less stable than He-vacancy complexes. In addition, vacancy clusters formed by He ion irradiation grew after annealing at 600°C. This was caused by the emission of He atoms from small He-vacancy clusters and the coalescence between free vacancies and vacancy clusters, and by the migration and coalescence of He bubbles.