LAUSR

A uranium-22.5 at.%zirconium (U-10 wt.%Zr) ingot was manufactured by traditional arc casting. The sample was characterized by high-pressure preferred-orientation time-of-flight neutron diffractometry with in situ heating reaching 900°C. The phase transitions, lattice parameter ratios, and linear coefficients of thermal expansion were investigated experimentally. Contradictory to commonly referenced phase diagrams, the results of this work showed that the β -U+ γ ″-UZr dual-phase region is not present in U-22.5 at.%Zr. Rather, only two phase transformations were observed upon cooling. These transformations occurred at 655°C and 600°C and corresponded to γ -UZr →  α -U+ γ ″-UZr →  α -U+ δ -UZr 2 , respectively. The linear coefficients of thermal expansion were measured for α -U, δ -UZr 2 , and γ -UZr. The thermal expansion of α -U was shown to be anisotropic in nature with significant lattice contraction in the 010 b direction. Similar anisotropy albeit to a lesser extent was observed in δ -UZr 2 with contraction in the 001 c direction.