Influence of damage rate on irradiation hardening behavior in proton-irradiated Fe-Cu alloy

To investigate the effects of damage rate on irradiation-induced hardening and microstructural evolution, proton irradiation experiments were conducted on Fe-0.05 wt.%Cu binary alloy samples over a wide range of ion fluxes spanning three orders of magnitude. The samples were then subjected to nano-indentation tests and microstructural observations. Nano-indentation hardness tests revealed greater hardening at lower damage rates, even under the same damage level. TEM observation showed that larger but fewer dislocation loops formed under low damage rate conditions, while high damage rates produced smaller but denser dislocation loops. STEM/EDS analysis showed that as the damage rate decreased, the number density and diameter of Cu-rich precipitates increased, and the Cu concentration therein increased. Irradiation hardening contribution was estimated by invoking the dispersed-barrier hardening model and the Russell-Brown model indicating that the effect of damage rate on irradiation hardening controlled by CRPs is dominant. Since kinetic modeling simulation showed enhanced vacancy mobility at lower damage rates and enhanced Cu-rich precipitate formation, it supported the experimental results. Our findings suggest that damage rate has a significant effect on irradiation hardening behavior, and that low damage rate significantly contributes to the nucleation and growth process of Cu-rich precipitates by thermal diffusion during prolonged irradiation.