Mechanical Properties and Fracture Behavior of 20% Cold-Worked 316 Stainless Steel Irradiated to Very High Neutron Exposures
SourceStainless steels irradiated in EBR-II at temperatures in the range 380 to 500°C tend to exhibit saturation of mechanical properties at relatively low fluence levels. At fluences on the order of 13 to 15 × 1022 n/cm2 (E > 0.1 MeV), however, there is a rapid increase in hardness just after the onset of void swelling. The hardness increase is not attributed just to the voids themselves but rather to an indirect effect of voids on nickel depletion in the alloy matrix. The strong dependence of stacking fault energy on nickel and chromium content and particularly on deformation temperature combine to promote extensive stress-induced formation of ε-martensite at room temperature. This leads to a very brittle failure mode characterized as quasi-cleavage. At higher deformation temperatures it leads to a failure mode designated as channel fracture.