Irradiation responses of an oxide-dispersion strengthened 15-15Ti austenitic stainless steel after He and D ion irradiations

Microstructure of 15-15Ti steel and oxide-dispersion strengthened (ODS) 15-15Ti steel samples after D/He ion irradiations was characterized by transmission electron microscopy (TEM). High densities of dislocation loops were observed in both samples after He ion irradiation. Frank dislocation loops (FDL) in the edge-on geometry are clearly observed through the rel-rod dark-field technique. In addition, high densities of He bubbles were also observed in both samples. Radiation defects such as the "black-dot" defects were generated under D ion irradiation in both samples. The nanoindentation results indicate that irradiation hardening occurred in both samples, and it is shown that bubbles are weak strength obstacles, while dislocation loops are medium to strong strength obstacles. Radiation induced segregation (RIS) is observed at the grain boundaries of both samples after irradiation by the energy-dispersive spectrum analysis. Irradiation defects and irradiation effects observed for ODS samples are all lower than for 15-15Ti samples. The oxide particles stay stable in the irradiated ODS sample after different irradiation processes. The pinning of dislocation loops by oxide particles and the adsorption of He bubbles at the oxide particle/matrix interface can be observed, indicating the beneficial effects of the oxide particles in improving the irradiation resistance of the 15-15Ti steel.