The effect of final heat treatment temperature on radiation response of V-4Cr-4Ti

Neutron irradiation in JMTR at 673 K to ∼0.11 dpa and post-irradiation examinations were carried out on V-4Cr-4Ti (NIFS-HEAT-2) heat-treated at 1073-1373 K for 1 h, for the purpose of optimizing the heat treatment conditions considering the effect of neutron irradiation. After irradiation, hardness and Charpy impact properties were similar with each other at 1073-1273 K, which is in strong contrast with the unirradiated V-4Cr-4Ti, which showed clearly minimum hardness and optimum impact property at 1173 K. Significant hardening and an increase in DBTT occurred after irradiation, however, at 1373 K. TEM observations showed similar microstructure with high density of precipitates and very low dislocation density at 1173-1273 K following irradiation. The mechanism of the weak dependence of properties after irradiation for the heat treatment temperatures between 1073 and 1273 and implication of the present study to determining annealing temperature was discussed.