Microstructural study of gamma phase stability in U-9 wt.% Mo alloy

The stability of the gamma phase in cast U-9 wt.% Mo alloy with respect to different thermo-mechanical treatments was investigated. The bcc allotrope of U, desirable due to its irradiation withstanding characteristics, could be retained in a metastable state in this alloy even without rapid cooling from the high temperature gamma phase. The presence of 9 wt.% of Mo in the gamma-U phase together with a homogenization annealing heat treatment at 1000 C for 24 h increased the stability of the gamma phase against eutectoid decomposition into alpha-U and gamma (U2Mo) phases. The mechanism of eutectoid decomposition, engendering different types of microstructure, and the crystallographic orientation relationships, amongst constituent phases, were established through transmission electron microscopy. (C) 2011 Elsevier B.V. All rights reserved.