PNNL

This work describes the microstructural evolution in an alloy of uranium with 10 wt% molybdenum (U10Mo), with minor addition of a third alloying element, namely, Cr, Ni, or Co, at 0.2 wt%. The microstructures of arc-melted buttons in as-cast condition show significant Mo segregation. The segregation behavior of Cr, Ni, and Co was investigated through detailed scanning electron microscope imaging. A homogenization heat treatment at 900 C for 48 h results in uniform Mo distribution and associated grain growth in all of the four alloys that were fabricated. Further, formation of multiple phases was noted in U-9.8 wt% Mo-0.2 wt% Ni and U-9.8 wt% Mo-0.2 wt% Co alloys after the homogenization annealing step. The greatest grain-boundary-initiated eutectoid transformation was observed when the homogenized U-9.8 wt% Mo-0.2 wt% Ni alloy was aged at 500 C for 20 h. The least eutectoid transformation occurred in U10Mo.