Phase transformation of metastable cubic g-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: Alloys; Enrichment; Fuels; Microstructure; Molybdenum; Phase transformations; Reactors; Uranium
• ISSN: 0925-8388
• 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 super(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 super(235)) fuel and also for the upcoming new reactors. U-Mo alloy with minimum 8 wt% molybdenum shows excellent metastability with cubic g-phase in cast condition. However, it is important to characterize the decomposition behaviour of metastable cubic g-uranium in its equilibrium products for in reactor fuel performance point of view. The present paper describes the phase transformation behaviour of cubic g-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 g-phase to break the cast structure and then they were aged at 500 C for 68 h and 240 h, so that metastable cubic g-uranium will undergo eutectoid decomposition to form equilibrium phases of orthorhombic a-uranium and body centered tetragonal U sub(2)Mo intermetallic compound. U-Mo alloy samples with different ageing history were then characterized by XRD for phase and development of microstructure.