Analysis of constituent redistribution in the γ (bcc) U–Pu–Zr alloys under gradients of temperature and concentrations

Abstract Rods of a ternary alloy (71U–19Pu–10Zr by weight percent) were annealed under a temperature gradient of 220°C/cm for 41 days and examined for micro-structural development and compositional redistribution. An enrichment of Zr with concurrent depletion of U was observed within the γ (bcc) phase region on the hot-end side (T≅740°C). The experimental redistribution of the elements in the γ (bcc) phase was analyzed in the framework of multicomponent mass transport with due consideration of thermotransport and ternary diffusional interactions. Based on a new analysis involving an integration of interdiffusion fluxes in the diffusion zone, kinetic parameters related to the thermotransport and ternary interdiffusion were calculated for each component i over selected ranges of composition. The thermotransport coefficients of U, Pu, and Zr were in the approximate ratio of 1:2:−4.5 in the hot-end region. In addition, the interdiffusion flux contributions arising from the gradients of temperature and concentrations of U and Zr were estimated.