This work characterizes the crystallographic evolution of unirradiated U-X wt.% Zr (X = 6, 10, 20, 30) while cooling from equilibration, single phase ?-U-Zr, at 900 °C to ambient temperature using time-of-flight neutron diffraction. The ß-U phase was unobserved during cooling at 1 °C/min in all alloys. All alloys followed the phase transformation pathway of ?-U-Zr??-U-Zr+a-U?a-U +d-UZr2 with an observed miscibility gap in ?-U-Zr. The a-U and d-UZr2 transformation took place simultaneously in the U-30 wt.% Zr sample. These findings strengthen the need to re-approach the U-Zr phase diagram in entirety. Bulk volumetric CTEs agree well with published data, strengthening the quantification of lattice-specific CTEs reported in this study. A compositionally dependent discontinuity in thermal expansion, increasing in magnitude with decreasing U content, occurs during the ?-U-Zr?a-U+d-UZr2 transformation. The ?-U-Zr lattice parameter was measured to have a compositional dependency.
