上海科技大学知识管理系统

The nickel-based Hastelloy N alloy samples were implanted with helium ions at room temperature and then annealed at 600 degrees C (sample S-2), 800 degrees C (sample S-3) and 900 degrees C (sample S-4) for 1 hour, respectively. The effects of post-irradiation isochronous annealing on defects evolution and hardening in the alloy were investigated by transmission electron microscopy (TEM) and nanoindenter. TEM characterization shows that the mean diameter and number density of helium bubbles in sample S-2 keep unchanged. It is found that the increments of helium bubbles size in samples S-3 and S-4 are mainly caused by migration and coalescence (MC) and Ostwald ripening (OR) mechanisms, respectively. Additionally, the MC mechanism can promote the formation of dislocation loops due to matrix atoms diffusion. In sample S-4, the recovery effects of defects are striking, resulting in a significant reduction in the number density of dislocation loops. The values of Vac. / He. at different regions have been calculated to explain the size variation of helium bubbles in all the samples. Moreover, nanohardness increments calculated by dispersed barrier hardening (DBH) model agree with those measured by nanoindentation. (C) 2021 Elsevier B.V. All rights reserved.