Evolution of vacancy-type defects and hardening behaviors of T91 induced by 1.625Â MeV Fe-ions at different temperatures

Irradiation temperature is one of the most important parameters which determine the evolution of structural materials' properties. In this study, the evolution of vacancy-type defects and hardening behaviors of T91 steel induced by Fe-ion irradiation at different temperatures were investigated. The 1.625 MeV Fe ions were implanted in T91 to the fluence of 2.5 × 1015 ions/cm2 at temperatures from room temperature (RT) to 550 °C. After irradiation, the samples were analyzed by positron annihilation spectroscopy (PAS) and nano-indention technology (NIT). It was found that the sample irradiated at RT possessed the largest concentration of vacancy-type defects. At higher temperatures, the variation of vacancy-type defects concentrations were in a trend of Cv550 °C < Cv300 °C < Cv450 °C. All the samples were hardened to different extents after irradiation. The hardness values increased initially and decreased afterward with the increasing temperatures, and the peak hardening is present at 300 °C.