Oxidation of β-Nb and Zr(Fe, V) 2 precipitates in oxide films formed on advanced Zr-based alloys

Abstract

The incorporation of precipitates β-Nb and Zr(Fe, V) 2 into the oxide films formed on advanced Zr-based alloys (Zr–1%Nb and Zr–0.5%Sn–0.6%Fe–0.3%V) is studied by transmission electron microscopy, on cross-sectional thin foils. The main results are: (1) the oxidation of both precipitates is delayed compared to the zirconium matrix, (2) the precipitates remain unoxidized in the inner part of the oxide layer, up to about 300 nm from the metal–oxide interface. In another terms, they undergo no modification (neither structural nor chemical) in the innermost part of the oxide film, (3) the chemical composition of precipitates evolves during their oxidation. These results are compared to previous results dealing with the incorporation of Zr(Fe, Cr) 2 precipitates into the oxide layer of Zircaloy-4 and discussed in relation to the oxidation process.