STRESS-STRAIN RELATIONS OF IRRADIATED STAINLESS-STEELS BELOW 673-K

Most specimens, irrespective of thermo-mechanical treatment, exhibited proof stress levels of above 800 MPa and uniform elongations below 1% after irradiation in the High Flux Isotope Reactor (HFIR). Only the solution annealed specimens irradiated at a low temperature of 328 K showed uniform elongations larger than 5% and proof stresses smaller than 800 MPa. Irradiation in the High Flux Reactor (HFR) caused more hardening than did irradiation in the HFIR. Ductility loss and change in work hardening characteristics by HFR irradiation were evaluated from reduction of area values. Residual ductility was revealed to be larger than 0.5 in natural strain, and the irradiation was estimated to have a small effect on work hardening characteristics and on fracture stress. The ductility of the irradiated alloys was found to be about 58% of that for the unirradiated alloys, as has been previously reported for irradiation in the HFIR. It was also demonstrated that true stress-strain relations, except for the fracture conditions, could be represented by Swift's type constitutive equation.