Interdiffusion experiments were performed using single-phase diffusion couples of Ni3Al at 1223 to 1473K. The interdiffusion coefficient was obtained from the concentration profiles measured by electron-probe microanalysis. The interdiffusion coefficient, D̃, was 4 to 8 times larger than the tracer-diffusion coefficient of Ni, ZNi*, and increased with increasing Al concentration. For the stoichiometric composition, it could be expressed as,

D̃(m2/s) = 2.5 x 10-3exp[-305(kJ/mol)/RT]

By applying the Darken-Manning equation, the diffusion coefficient of Al, DAl*, was evaluated from D̃, DNi* reported in the literature and the thermodynamic factor evaluated from experimental data on the thermodynamic activity. The magnitude of DAl* thus estimated was smaller by a factor of 3 to 4 at 1400K than that of DNi* over the temperature range examined. Thus, DAl* ≈ (0.25 - 0.38)DNi* at 1400K.

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

Figure 2

Diffusion of Al and Ti in a Ni75.5Al24.5/Ni76.5Al11.0Ti12.5 couple

White circles, i = Ti; black circles, i = Al