Irradiation-induced void swelling and solute segregation in a V-ion-irradiated V-15 wt % Cr bcc alloy

Abstract

Specimens of a V-15 wt % Cr alloy were irradiated at 650°C with 3.5 MeV 51V + ions to peak dose levels of 5 to 60 dpa. At 650°C, the swelling increased sharply and monotonically with an increase in dose. At 55 dpa, the voids were ≈ 900 Å in diameter and the swelling (≈ 20%) was more than two orders of magnitude higher than for unalloyed V. Precipitates that are observed after irradiation of unalloyed V were not found in the V-15 wt % Cr alloy. A cellular dislocation structure was found to develop with peak doses to ≈ 30 dpa. Voids were generally observed to lie on the peripheries of the dense dislocation cell walls or in areas of relatively low dislocation density. Auger analysis showed that Cr segregates to the irradiated surface (and presumably to other defect sinks). Redistribution of Cr occurred to depths of ≈ 1000 Å, suggesting non-Gibbsian segregation. Cr segregation to defect sinks is consistent with the idea that undersize solute atoms preferentially migrate via interstitial fluxes.