Atomic mobilities, diffusivities and their kinetic implications for U–XX (X=Ti, Nb and Mo) bcc alloys

Based on various kinds of diffusivities as well as the thermodynamic descriptions within the CALPHAD framework, the atomic mobilities of U, Ti, Nb and Mo are explored in this work with the DICTRA software. The mobility end-members are evaluated from the impurity diffusivities as well as the extrapolated interdiffusivities, while the interaction parameters for atomic mobilities are determined from the tracer diffusivities, the intrinsic diffusivities and the interdiffusivities. The reliability of such purely kinetic quantities is carefully verified by the comparison between the calculated and experimentally measured quantities, including the concentration profiles in Ti/U diffusion couples. This work is established to provide fundamental information for U-based alloy design when the kinetics of microstructure evolution is of prime concern.

► The atomic mobilities of U, Ti, Nb and Mo have been established. ► Various kinds of diffusivities for U–Ti, U–Nb and U–Mo alloys have been explored. ► Diffusion simulations have been made for two Ti/U diffusion couples.