Effect of two-steps heat treatments on irradiation hardening in F82H irradiated at 573 K

Irradiation hardening and embrittlement due to neutron irradiation around 573 K are the important issues on RAF/M steels. It is expected that the improvement of irradiation hardening might be one of effective ways to control the mechanical properties of RAF/M after irradiation. In this study, the purposes are to investigate the effect of heat treatments on irradiation hardening of irradiated F82H variants and to compare the irradiation hardening based on ΔHardness with the irradiation hardening obtained by ΔYield Stress about F82H. Neutron irradiation was performed in HFIR at 573 K. The ion-beam irradiation experiment at ∼573 K was carried out at the TIARA facility of JAEA. For the results of tensile test and hardness test of F82H and F82H heat treatment variants neutron-irradiated at 573 K, all specimens caused irradiation hardening. The irradiation hardening (ΔHardness) obtained by hardness test is almost same level for neutron- and ion-irradiated F82H specimens, however irradiation hardening (ΔYield Stress) of F82H Mod-1 A (two-steps heat treated F82H: high temperature tempering and then low temperature tempering) is smaller than that of F82H.