Simulation of atomic mobilities, diffusion coefficients and diffusion paths in bcc_A2 and bcc_B2 phases of the Al-Ni-Fe system

The influence of composition and temperature on the atomic mobilities of Al, Ni and Fe in the bcc_A2 and bcc_B2 Al-Ni-Fe phases was investigated based on a recently developed phenomenological model, together with the newly published thermodynamic description. The experimental interdiffusivities and tracer diffusivities of Ni and Fe in various Al-Ni-Fe alloys available in the literature were critically evaluated. The calculated diffusivities can reasonably reproduce the experimental ones. The calculated iso-diffusivity lines in the B2 phase show a minimum around the quasi-binary section at 50 at.% Al for the main diffusivities of both Al and Ni, while for the cross diffusivities of Al and Ni, they show significantly different characteristics when changing from negative to positive values. The obtained atomic mobilities were further used to predict the concentration profiles and diffusion paths in a variety of B2 Al-Ni-Fe diffusion couples. The comparison reveals the importance of full diffusion-distance measurement for the accurate determination of diffusion coefficients.