Microchemistry of Proton-Irradiated Austenitic Alloys Under Conditions Relevant to Lwr Core Components

Abstract

AbstractOver 1200 measurements of grain boundary composition and microstructure have been made on 14 different austenitic Fe-Cr-Ni alloys following proton irradiation in the temperature range 200-600°C and in the dose range 0.1-3.0 dpa. Grain boundary composition measurements revealed that Cr depletes at grain boundaries, Ni enriches and Fe can either enrich or deplete depending on alloy composition. Analysis of temperature and composition dependence of RIS revealed that the magnitude and direction of grain boundary segregation depends on alloy composition because the value of migration enthalpy differs among the alloy constituents, and diffusivities of the alloy constituents are composition-dependent. The dose dependence of segregation revealed ordering in Ni-base alloys and temperature dependence was used to show that RIS occurs by vacancy exchange rather than an interstitial binding mechanism. The dependence of segregation on composition is consistent with all known, relevant neutron data.