Helium effects on the microstructural evolution of reactor irradiated ferritic and austenitic steels

Abstract

Abstract Microstructural evolution in neutron irradiated austenitic stainless steels and Cr-Mo ferritic steels is reviewed. Important highlights are: (1) there is a strong correlation between precipitation and void evolution in austenitic steels; (2) helium affects precipitate evolution in austenitic steels, but observations indicate no effect on precipitation in ferritic steels; (3) helium has a pronounced effect on the cavity evolution of the two steel types. Helium effects are explained in terms of the interrelationship between microstructural evolution and point-defect annihilation processes. In stainless steel, three relative regimes of microstructural behavior for different helium generation rate-displacement rate ratios are recognized: (1) “low” He/dpa ratio, where helium effects on the radiation-induced microstructural evolution are negligible or develop slowly, (2) “medium” He/dpa ratio, where helium effects strongly enhance the microstructural changes, and (3) “high” He/dpa ratio, where helium e...