Chemical diffusion in hypostoichiometric Ni3Al from data on coarsening of Ni–Al solid solution precipitates

Data on chemical diffusion in γ′ (Ni3Al) containing on average 22.67 at.% Al were obtained from the analysis of the rate constants for coarsening of γ phase (Ni–Al solid solution) precipitates in a γ′ matrix. The data on coarsening were obtained over the temperature range 923–1073 K and values of the chemical diffusion coefficient were extracted from the rate constants using the thermodynamic model of Ikeda et al. [T. Ikeda, H. Numakura, M. Koiwa, Acta Mater. 46 (1998) 6605–6613] to obtain the curvature of the free-energy of mixing of Ni3Al, in conjunction with reliable estimates of the other necessary thermo-physical parameters. The data so obtained are in excellent agreement with data on chemical diffusion from more conventional high-temperature diffusion experiments conducted over the temperature range 1400–1600 K. The results indicate that the high-temperature data can be extrapolated to lower temperatures with great confidence.