Thermodynamic Assessment of the U-Ti-Zr System and Atomic Mobility of Its bcc Phase

In the present work, the thermodynamic assessment of the U-Ti-Zr ternary system was performed by using the CALPHAD (Calculation of Phase Diagrams) method based on phase diagram data as well as the reliable thermodynamic descriptions of the U-Ti, U-Zr, and Ti-Zr binary systems. The calculated isothermal sections and vertical section of the U-Ti-Zr system are in good agreement with the experimental results. Subsequently, based on the available experimental diffusion data, the atomic mobility parameters of the U-Ti binary system were assessed by means of DICTRA software. The calculated interdiffusion coefficients and composition profiles of the bcc U-Ti alloys are consistent with the experimental data. On this basis, the kinetic database of the bcc U-Ti-Zr alloys was constructed by extrapolation in combination with reliable atomic mobility parameters of the U-Zr and Ti-Zr binary sub-systems from the literature.