Laves phases in the U – Mo – Zr system

Abstract

Molybdenum and zirconium are known as alloying elements for uranium, used in the production of metallic nuclear fuels. Based on the binary systems it is expected that compound Mo2Zr, a Laves phase with the C15 structure, should be present in ternary alloys. We report here the existence of a C14 variant, in parallel to the C15 phase, both dissolving uranium. This confirms the heuristic hypothesis of Stein (2011) [24] about the stabilization of Laves variants depending on the crystallographic arguments. The relation of the presence (attested by X-ray diffraction) of both variants with the composition and with processing is discussed with regard of the microstructure developments in mechanical processing and heat treatments of two alloys with compositions U – 3 Mo – 9 Zr and U – 9Mo – 3 Zr (in wt%).