Evidence for a mechanism of swelling variation with composition in irradiated Fe-Cr-Ni alloys

Abstract

Abstract Irradiations with 4 MeV Ni ions and 200–400 keV He ions were carried out on two alloys, Fe-15Cr-15Ni and Fe-15Cr-35Ni, at 675°C and doses up to 84dpa. Both dual-ion irradiation experiments and sequenced He injection-anneal-Ni irradiations were used. The dual-ion experiment showed that the two alloys exhibited large differences in microstructural development, with the low nickel alloy having significantly greater swelling. The injection-anneal-irradiation experiment was designed to test the hypothesis, suggested by our earlier work, that the lower swelling of the high nickel alloy may result from a larger critical radius/critical number of gas atoms required to achieve bias driven swelling. This experiment provided a direct measurement of these critical quantities by the induction of a bimodal cavity size distribution. The measurement gave minimum critical radii of about 5nm for the high nickel alloy and < 0·5nm for the low nickel alloy, values consistent with the hypothesized mechanism. The basis...