Stability and structure of the δ phase of the U-Zr alloys

Homogeneity range and crystal structure of the intermediate δ phase in the U-Zr alloy were examined by electron probe microanalysis, X-ray diffraction and differential thermal analysis, using the alloys prepared by arc-melting. The homogeneity range of the δ phase was found to be 64.2-78.2 at%Zr at 600deg C and 66.5-80.2 at% Zr at 550deg C. The powder diffraction patterns of the δ phase agreed with an unusual structure of modified C32, in which the (0,0,0) sites are preferentially occupied by Zr atoms, and the (2/3, 1/3, 1/2) and (1/3, 2/3, 1/2) sites randomly shared by U and Zr atoms. (orig.)