Walter Williams

A uranium-22.5at.% zirconium (U-10 wt.% Zr) ingot was manufactured by traditional arc-casting. The sample was characterized with the High-Pressure-Preferred Orientation (HIPPO) time-of-flight neutron diffractometer with in-situ heating reaching 900°C. The experiment investigated phase transitions, lattice parameter ratios, and linear coefficients of thermal expansion. Contradictory to commonly referenced phase diagrams, this work has shown that the β-U+γ’’-UZr dual phase region is not present in U-22.5at.% 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-UZr2, respectively. The linear coefficients of thermal expansion were measured for α-U, δ-UZr2, and γ-UZr. The thermal expansion of α-U was shown to be anisotropic in nature with a significant lattice contraction in the 010b direction. To a lesser extent, a similar anisotropy was observed in δ-UZr2¬ with a contraction in the 001c direction.