Creep rupture properties of helium implanted V–4Cr–4Ti alloy NIFS-HEAT-2

The influence of transmutational helium on creep response of a V–4Cr–4Ti reference alloy called NIFS-HEAT-2 was examined. This is a candidate structural material for future fusion applications. Helium ions were injected into creep specimens at 700 °C to a concentration of about 100 appm utilizing homogenous α-particle irradiation at an accelerator. Post-implantation creep rupture tests were carried out at the same temperature in a vacuum environment. Creep lifetime had a tendency to be increased by helium implantation, reflecting a slight decrease in minimum creep rate. Creep data showed a power-law creep behavior, and there was good agreement in obtained stress exponents between helium implanted and unimplanted cases. Some morphological changes were detected on creep-ruptured surfaces, such as reduction of necking and initiation of intercrystalline separation.