STABILITY AND STRUCTURE OF THE DELTA-PHASE OF THE U-ZR ALLOYS

Homogeneity range and crystal structure of the intermediate delta-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 delta-phase was found to be 64.2-78.2 at% Zr at 600-degrees-C and 66.5-80.2 at% Zr at 550-degrees-C. The powder diffraction patterns of the delta-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.