Effect of cold-work on the radiation-induced deformation of austenitic stainless steels

Austenitic stainless steels will be used in ITER as a major structural material. Although, initially supplied in annealed condition, cold-working is inevitable during construction or operation. Martensite would be introduced by cold-work in the case of unstabilized stainless steels. In this study, the effect of cold-work on the irradiation creep was examined under 17 MeV proton irradiation (2 × 10−7 dpa/s) at 288 °C for stabilized (SUS 316L) and unstabilized (SUS 304) stainless steels. Radiation-induced stress relaxation was also evaluated using the creep data. The stress dependence of irradiation creep was different for the two steels; linear for SUS 316L and quadratic for SUS 304. This difference would influence the stress relaxation, which is faster in SUS 316L. The behavior of SUS 316L is consistent with computer simulation for evenly distributed network dislocations, while that of SUS 304 appears to originate from the dislocations localized in the vicinity of martensite boundaries.