Annealing effects on mechanical properties and microstructure of F82H irradiated at ⩽60 °C with 800 MeV protons

Martensitic steel F82H was irradiated with 800 MeV protons up to 7.8 dpa at low temperatures ⩽60 °C. Tensile tests have been performed at 22, 160, 250, 350 and 400 °C. The microstructure of specimens with doses of 6–7.8 dpa after annealing 20 min and 2 h at 160, 250, 350 and 400 °C has been studied. The tensile results show that the yield of irradiated specimens decreases gradually with increasing test temperature. The ductility starts to recover at about 300 °C and is substantially recovered at 400 °C. The recovery depends on irradiation dose. The TEM results indicate that the number density of dislocation loops induced by irradiation decreases with annealing temperature, while the mean size of loops increases only slightly at 400 °C. A part of dislocation loops transferred into network dislocations and resulted in increase of network dislocation density. However, the total dislocation density (including loops) decreases gradually with annealing temperature.