Data on chemical diffusion in γ′ (Ni3Al) containing on average 22.67at%Al were obtained from an analysis of the rate constants for coarsening of the γ phase (Ni-Al solid solution) precipitates in a γ′ matrix. The data on coarsening were obtained at 923 to 1073K and values of the chemical diffusion coefficient (table 1) were extracted from the rate constants using the thermodynamic model of Ikeda et al. (1998) 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 were in excellent agreement with data on chemical diffusion from more conventional high-temperature diffusion experiments conducted at 1400 to 1600K. The results indicated that the high-temperature data could be extrapolated to lower temperatures with great confidence.

Chemical Diffusion in Hypostoichiometric Ni3Al from Data on Coarsening of Ni-Al Solid Solution Precipitates. Ma, Y., Ardell, A.J.: Materials Science and Engineering A, 2009, 516[1-2], 259-62