Low-temperature tensile behavior of irradiated austenitic stainless steels

Low-temperature properties of type 316 austenitic stainless steels, such as mechanical properties and corrosion susceptibility during and after neutron irradiation, are currently a concern in relation to future fusion devices. Type 316 austenitic stainless steel was chosen primarily as the first wall and blanket structural material for the next machines such as the International Thermonuclear Experimental Reactor (ITER). However, there have been few data obtained up to now because of both difficulties of irradiation and lack of interest in such properties at ITER operating conditions, especially at temperatures below 500C. Here, the low-temperature tensile properties of type 316 stainless steel (J316) and Japanese Primary Candidate Alloy (JPCA) irradiated in spectrally tailored Oak Ridge Research Reactor (ORR) and in High Flux Isotope Reactor (HFIR) capsules are summarized. The yield and tensile strengths in the ORR-irradiated specimens were found to increase with increasing irradiation temperatures up to 330C followed by a decrease with increasing temperature. This strength maximum was accompanied by an elongation minimum. Similar trend curves were observed in the HFIR-irradiated specimens, although the temperature of peak strength was shifted higher. The behavior can be understood roughly in terms of microstructural development of dislocation loops and recovery of network dislocations during irradiation. The temperature of peak strength seems to depend on irradiation conditions such as He:dpa ratio and irradiation dose rate