Microstructural study of slow cooled hyper-eutectic U-15 wt.% Cr alloy

The microstructure of slow cooled U-15wt.%Cr alloy has been characterized using X-ray diffraction, microhardness measurements, scanning and transmission electron microscopy techniques. The results indicate that even under slow cooling (1 K min^-1), it is not possible to avoid the retention of high temperature tetragonal β-U phase; accordingly, the room temperature microstructure is found to be a mixture of (α-U+Cr)_eq+(β-U)_noneq phases. While, the (α-U+Cr)_eq occurs with a typical eutectoid colony morphology, the (β-U) phase exhibits a faceted one. Further, as observed in a transmission electron microscope, the faceted (β-U) phase is found to be constituted of fine grained β-U and Cr-particles, which arise out of sluggish β → α-U+Cr diffusional decomposition during slow cooling. (author)