Experiments were performed by using single-phase diffusion couples at temperatures ranging from 1223 to 1473K. The interdiffusion coefficient was deduced from concentration profiles which were measured by means of electron-probe micro-analysis. It was found that the interdiffusion coefficient was 4 to 8 times larger than the tracer diffusion coefficient of Ni, and increased with increasing Al concentration. In the case of the stoichiometric composition, it could be described by:

D (m2/s) = 10-2.6 exp[-305(kJ/mol)/RT]

By applying the Darken-Manning equation, the diffusivity of Al was estimated. The resultant value was smaller, by a factor of 3 to 4, at 1400K than that for Ni diffusivity.

Single-Phase Interdiffusion in Ni3Al T.Ikeda, A.Almazouzi, H.Numakura, M.Koiwa, W.Sprengel, H.Nakajima: Acta Materialia, 1998, 46[15], 5369-76