EFFECT OF HE ON VOID FORMATION AND RADIATION-INDUCED SEGREGATION IN DUAL-BEAM IRRADIATED FE-CR-NI

To investigate the effect of helium on void formation and radiation-induced segregation, dual-beam irradiation with electrons and helium ions has been carried out for an Fe-Cr-Ni alloy by using a 1000 keV HVEM and a 300 keV ion-accelerator. From the measurement of dislocation loop growth, the vacancy migration energy was estimated at different injection rates of helium. The value increased with increasing injection rate of helium, which means strong trapping between vacancies and helium atoms. As a result the mutual recombination of point defects is retarded and the formation of secondary defects can be enhanced. Namely, on increase the densities of voids and dislocations was observed, as compared with the result without helium. With respect to the radiation-induced segregation, depletion of Ni and enrichment of Cr in the irradiated area were detected. The segregation of Ni and Cr was suppressed with increasing helium. From these results the role of helium on radiation-induced segregation is discussed on the basis of vacancy trapping and internal sinks.