Change in the properties of Fe-Cr-Ni and Fe-Cr-Mn austenitic steels under mixed and fast neutron irradiation

Detailed investigations are performed on mechanical properties, swelling and structure of different types of Fe-Cr-Ni and Fe-Cr-Mn austenitic stainless steels irradiated in the SM-2 high-flux research reactor and BOR-60 fast reactor. Steel irradiation temperatures are ranging from 100 up to 800 degrees C and the maximum achieved level of damage doses is 60 dpa for Fe-Cr-Mn steel (with 4-5% of Ni) and 30 dpa for steels of the C-12Cr-20Mn-W-T type. Presented are dose dependencies of swelling and mechanical properties of Fe-Cr-Ni and Fe-Cr-Mn steels. It is shown that at temperatures below 530 degrees C the investigated Fe-Cr-Mn steel systems are less susceptible to swelling as compared to Fe-Cr-Ni ones. Fe-Cr-Mn steels showed a lower value of irradiation embrittlement after irradiation in the mixed spectrum at temperatures from 100 up to 400 degrees C and much higher embrittlement after irradiation from 350 up to 400 degrees C in the fast spectrum in comparison with Fe-Cr-Ni steels. Higher hardening rate of Fe-Cr-Mn steels after their irradiation in BOR-60 is attributed to the presence of dislocation loops and defects of high density in the structure. The structural change features in Fe-Cr-Mn steels under irradiation are considered taking into account austenite stabilization in the initial state.