Density and thermal expansion of liquid U-Nb alloys

The density and volumetric thermal expansion of U-Nb alloys were measured in the liquid phase by gamma densitometry. Compositions varied from 0 to 25 wt% Nb, and data were obtained over a temperature range of 200-300 K above the liquidus temperature for each of the six alloys. The density of each molten alloy was found to vary linearly with temperature. For pure uranium the density in the liquid phase is given by p/g cm-3 = 16.95-12.9 x 10-4[T/K)-1407]. The liquid density at the liquidus temperature was found to vary smoothly with alloy composition. From the liquid density and thermal expansion data, the molar volume was calculated for each alloy. For intermediate compositions, the data indicate a volume expansion, typified by an excess molar volume of approximately 4% at 2000 K for alloys near 40 at% Nb. Experimental measurements at high temperature were also made of the solid phase linear thermal expansion for pure uranium and for the 10 and 15 wt% Nb materials. (author)