Effect of micro-segregation on irradiation hardening in ion-irradiated RAFM steel

Ando, Masami; Sakasegawa, Hideo   ; Tanigawa, Hiroyasu; Kasada, Ryuta*

RAFM is the candidate for the blanket structural materials of DEMO reactor. JAEA is developing a F82H steel as the RAFM under BA activity. F82H steels are tendency to cause a micro-segregation of tungsten around the center of plate thickness during a fabrication process of a large scale heat. In the case of a rich-tungsten in the matrix, Laves phase was formed easily and then its precipitations cause an embrittlement in F82H without neutron irradiation. Moreover, it is also a problem that this micro-segregation affects the irradiation hardening, fracture toughness and impact property after neutron irradiation. The purpose of this study is to investigate the effect of this micro-segregation on irradiation hardening of ion-irradiated F82H. For micro-hardness profiles across W-segregation bands in BA07 irradiated specimens, extra-hardening is hardly detected around those bands. In this results, the W-micro segregation in F82H did not affect irradiation hardening up to 10 dpa.