Material responses of ferritic steels by 14 MeV neutron bombardments at 20 and 300 K

Mechanical properties of 14 MeV neutron irradiated ferritic steels were studied. Irradiations at RTNS-II were carried out at 20 and 300 K and post irradiation tensile test was performed at 4.2, 77 and 300 K. The fluence dependence of the irradiation hardening could be understood as dispersion hardening from irradiation induced complex defects. The temperature dependence of yield stress for 20 K irradiated specimens suggests that the thermal component of yield stress was understood also by dispersion hardening mechanism from defect clusters. Thermal component of irradiation hardening was dominant in 20 K irradiated specimens and the most parts of which was annealed out at room temperature. On the other hand, 300 K irradiation mainly produces athermal component of irradiation hardening, which is about half of that for 20 K irradiated specimens. (orig.)