Void Swelling in Electron-Irradiated Fe-Cr-Ni Model Alloys

Abstract

A study of the void swelling produced by 1-MeV electron irradiation in high-purity Fe-Cr-Ni alloys has been performed in order to obtain a better understanding of the composition dependence of swelling in this system. Alloys with 16 wt% chromium and 20 to 75 wt% nickel, with or without helium preinjection, were irradiated in a high-voltage electron microscope, at a displacement rate of 22 dpa/h in the temperature range 370 to 600°C, to maximum damage levels up to 105 dpa. An increase in nickel concentration was found to reduce void density, to increase incubation dose, and to shift the swelling-rate maximum to lower temperatures. A helium preinjection of 70 appm reduces strongly the effect of material composition. The application of a simple void-growth model to the experimental results shows that the changes of point-defect parameters with nickel concentration produce variations of the calculated swelling rate that exhibit the observed trends. However these variations are of only marginal amplitude, as compared with the swelling-rate variations resulting from the observed microstructural changes. The bias factor was found to decrease with decreasing temperature in the 20 wt% Ni alloy; it also decreased at 500°C, with increasing nickel concentration.