Diffusion in L12-Ni3Al with ternary alloying additions of Ir, Ta and Re was investigated at 1200C using solid-to-solid diffusion couples, and examined with respect to site preference in ordered intermetallic compound. In addition to determination of average ternary interdiffusion coefficients, average effective interdiffusion coefficients were determined directly from the experimental concentration profiles. Ni had the highest average effective interdiffusion coefficient, followed by Al, Ir, Re and Ta. The average effective interdiffusion coefficients for Ir, Re and Ta were much smaller than those for Ni and Al. Tracer diffusion coefficients determined by extrapolation technique, and available literature also followed the same trend. The relative tendency of Ni, Al, Ir, Re and Ta to occupy the α-Ni and β-Al sites were correlated to these diffusion coefficients, with due consideration for diffusion mechanisms and coordination of atoms.

Site Preference and Diffusion in Ni3Al Alloyed with Ir, Ta or Re at 1200C. Garimella, N., Choi, H.J., Sohn, Y.H.: Defect and Diffusion Forum, 2010, 297-301, 1322-27

Table 3

DNiNi and DAlAl interdiffusion coefficients in Ni-Al-Ir alloys at 1473K