Phase transformation of metastable cubic γ-phase in U–Mo alloys

• Published in: Journal of alloys and compounds 2010-09, Vol.506 (1), p.253-262
• Main Authors: Sinha, V.P., Hegde, P.V., Prasad, G.J., Dey, G.K., Kamath, H.S.
• Format: Article
• Language: English
• Subjects: Alloy and microstructure; Condensed matter: structure, mechanical and thermal properties; Constant-composition solid-solid phase transformations: polymorphic, massive, and order-disorder; Cross-disciplinary physics: materials science; rheology; Crystalline state (including molecular motions in solids); Crystallographic aspects of phase transformations; pressure effects; Density; Exact sciences and technology; Materials science; Metastable; Phase; Phase diagrams and microstructures developed by solidification and solid-solid phase transformations; Physics; Structure of solids and liquids; crystallography; X-ray diffraction
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2010.06.187

Over the past decade considerable efforts have been put by many fuel designers to develop low enriched uranium (LEU < 20%U 235) base U–Mo alloy as a potential fuel for core conversion of existing research and test reactors which are running on high enriched uranium (HEU > 85%U 235) fuel and also for the upcoming new reactors. U–Mo alloy with minimum 8 wt% molybdenum shows excellent metastability with cubic γ-phase in cast condition. However, it is important to characterize the decomposition behaviour of metastable cubic γ-uranium in its equilibrium products for in reactor fuel performance point of view. The present paper describes the phase transformation behaviour of cubic γ-uranium phase in U–Mo alloys with three different molybdenum compositions (i.e. 8 wt%, 9 wt% and 10 wt%). U–Mo alloys were prepared in an induction melting furnace and characterized by X-ray diffraction (XRD) method for phase determination. Microstructures were developed for samples in as cast condition. The alloys were hot rolled in cubic γ-phase to break the cast structure and then they were aged at 500 °C for 68 h and 240 h, so that metastable cubic γ-uranium will undergo eutectoid decomposition to form equilibrium phases of orthorhombic α-uranium and body centered tetragonal U 2Mo intermetallic compound. U–Mo alloy samples with different ageing history were then characterized by XRD for phase and development of microstructure.