Diffusivities and atomic mobilities in fcc_A1 Ni-X (X=Ge, Ti and V) alloys

Based on three groups of Ni/Ni-9 at% Ge diffusion couples, interdiffusion coefficients were determined in the face-centered (fcc_A1) Ni-Ge alloys at 1173, 1273 and 1373 K by means of the Boltzmann-Matano method coupled with electronic probe microanalysis (EPMA) technique. On the basis of various critically-reviewed experimental diffusivities as well as the available thermodynamic descriptions, atomic mobilities in fcc_A1 Ni-X (X=Ge, Ti and V) alloys were assessed by means of DIffusion Controlled TRAnsformation (DICTRA) software package. For the self-diffusivities in dynamically unstable fcc_A1 Ge, Ti and V, a semi-empirical correlation was employed. Moreover, the first-principles calculations were also used to calculate the activation energy for self-diffusion in fcc_A1 Ge. Comprehensive comparison between the calculated and the measured diffusivities shows that most of the experimental data can be reproduced by the atomic mobilities obtained in the present work. In addition, the reliability of the currently obtained atomic mobilities in fcc_A1 Ni-X (X=Ge, Ti and V) alloys were further validated by comparing the model-predicted concentration-distance profiles and the experimental ones.