Impact properties of NIFS-HEAT-2 (V–4Cr–4Ti) after YAG laser welding and neutron irradiation at 563 K

Weld specimens of the reference low activation vanadium alloy, NIFS-HEAT-2, were irradiated up to the neutron fluence of 4.5 × 1023 nm−2 (0.08 dpa) at 563 K in JMTR. The weld metal showed larger irradiation hardening than that of the base metal, and the weld metal showed an embrittlement at 77 K. However, irradiation hardening at the weld metal was effectively reduced by post weld heat treatment at 873 and 1223 K. Mechanisms of irradiation hardening, and behavior of C, N and O impurities in the weld metal was discussed, based on the characterization of radiation defects.