Microstructure evolution of modified 310S austenitic stainless steels under argon ion irradiation at different temperatures

The effects of oversized additive atoms on microstructure evolution in 310S stainless steel under irradiation was investigated. Ar ion irradiations were conducted on modified 310S stainless steels at 290 °C and 550 °C. SC-1 was modified with Zr and SC-2 was modified with Nb, Ta and W. Compared with SC-2, lower density, smaller vacancy clusters formed in SC-1 at 290 °C. When irradiation temperature was increased from 290 °C to 550 °C, the average size of vacancy clusters increased while the number density dropped to a lower value in SC-1; however, in SC-2, the average size and number density of vacancy clusters shifted to larger values. At 550 °C, lower density and larger size of vacancy clusters were observed in SC-1 compared with that in SC-2. In addition, precipitates enriched with Ni were observed in SC-1, while Nb- and Ta-enriched precipitates were found in SC-2. A possible mechanism is discussed.