Sho, Kano, Yang, Huilong, McGrady, John, Motoki, Nakajima, Masami, Ando, Takashi, Nozawa, and Hiroaki, Abe
The purpose of the present study is to clarify the phase stability of the corroded layer in reduced activation ferritic/martensitic steels under irradiation. The oxide film of F82H steel was subjected to ion irradiation using 2.8 MeV-Fe2+ at 573 K. For post-irradiation experiments, grazing incident X-ray diffraction (GIXRD) and Raman analysis was conducted to clarify the features of the oxide layer with variation of the irradiation dose. The dominant phase of the oxide film was identified as FeCr2O4, which co-existed with up to ~30% of the residual matrix phase. The fraction of the residual matrix decreased as the irradiation dose increased, the phase transformation from FeCr2O4 to Fe3O4 was confirmed. The hypothesis for the phase transformation of FeCr2O4 to Fe3O4 under irradiation was proposed based on the experimental results. Specifically, FeCr2O4 phase is unstable under irradiation, and tends to become stable after absorbing Fe atoms from the residual matrix in the corrosion layer. As a result, the Fe concentration in the oxide layer increased under irradiation, the phase transformation of FeCr2O4 to Fe3O4 is presumed under irradiation. However, concerns of the mechanism about the instability of FeCr2O4 under irradiation, and better stability of Fe3O4 phase relative to FeCr2O4 phase have to be further considered to achieve a better understanding.