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Phase relations in the U-Mo-Al ternary system

Funded under: FP7-EURATOM


The phase relations in the U-Mo-Al system of quenched samples annealed at 800 °C for 2 weeks and at 400 °C for 2 months have been established using X-ray powder diffraction, scanning electron microscopy and energy dispersive spectroscopic analysis performed at room temperature. Two ternary Al-rich phases, UMo(2-x)Al(20+x) and U(6)Mo(4+x)Al(43-x) are found stable at 800 °C and 400 °C. They show significant homogeneity ranges resulting from Mo/Al substitution mechanism on various mixed crystallographic sites, as evidenced by single-crystal structure refinements. Substitution of up to 25 at.% of Al by Mo atoms is also observed for UAl(2) (cubic MgCu(2)-type) giving a quite large extension (UAl(2-x)Mo(x), 0 < x < 0.5) into the ternary system. Larger substitution (0.6 < x < 0.7 at T = 800 °C) stabilizes another ternary Laves phase, UAl(2-x)Mo(x) with the hexagonal MgZn(2)-type. There is no detectable solubility of Mo in UAl(4), and it is of the order of 1 at.% in UAl(3). The interaction layers between the gamma U-Mo alloys and the Al matrix in nuclear fuel plates can be successively estimated as composed of the two- and three-phase fields equilibrium indicated on the assessment of the phase relations drawn for samples heat-treated at 400 °C.

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Authors: NOËL H, Laboratoire de Chimie du Solide et Matériaux, Université de Rennes1, Rennes (FR);TOUGAIT O, Laboratoire de Chimie du Solide et Matériaux, Université de Rennes1, Rennes (FR);DUBOIS S, Département de Recherches sur la Fusion Contrôlée, Association Euratom-CEA sur la Fusion, CEA Cadarache, Saint-Paul-lez-Durance (FR)
Bibliographic Reference: An oral paper given at:Twelfth Symposium on Thermochemistry and Thermophysics of Nuclear Materials Organised by: Universität Wien (AT) Held in: Pörtschach (AT)
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