The High Temperature Tensile Properties of Ferritic-martensitic and Austenitic Steels after Irradiation in an 800 Mev Proton Beam

This study examines the effect of tensile test temperatures ranging from 50°C to 600°C on the tensile properties of a modified 9Cr-1Mo ferritic steel (T91) and a 316L stainless steel (SS) after high energy proton irradiation at about 35°C-67°C. After 1-3 dpa, the proton-irradiated T91 steel was tensile tested at temperatures from 50°C to 600°C. It was observed that the yield strength and ultimate strength decreased monotonically as a function of tensile test temperature, whereas the uniform elongation remained at approximately 1% for tensile test temperatures up to 250°C and then increased for tensile test temperatures up to and including 500°C. At 600°C, the uniform elongation was observed to be less than the values at 400°C and 500°C. Uniform elongation of the irradiated material tensile tested at 400°C to 600°C was observed to be greater than the values for the unirradiated material at the same temperatures. No changes in microstructure were observed in T91 transmission electron microscopy specimens heated up to 500°C prior to observation. Tensile tests on the 9 dpa specimens of T91 followed similar trends. The 316L SS was irradiated to doses up to 10 dpa and tested at 300°C. Tensile tests done in conjunction with shear punch tests suggest that the tensile properties change substantially within the first 2 dpa, but further changes occur when irradiated to 10 dpa. Most notably, the uniform elongation after 10 dpa is estimated from shear punch data to drop to near zero at a mechanical test temperature of 300°C.