The interdiffusion coefficients of Al-replacing elements in Ni-Al-X (X = Ti, V or Nb) were estimated by using diffusion couples of Al rich pseudo-binary systems at 1423, 1473 and 1523K. In order to obtain the interdiffusion coefficients of the pseudo-binary systems, the experimental data were analyzed by the Sauer and Freise method, and the impurity diffusion coefficients of Ti, V and Nb in Ni3Al were estimated by applying the Darken-Manning equation. The magnitude of the interdiffusion coefficient decreased in the order - V, Ti, Nb - at all three temperatures. The impurity diffusion coefficients could be described by the expressions:

DTi = 4.4 x 10-1exp[-422(kJ/mol)/RT]

DV = 5.3 x 10-2exp[-387(kJ/mol)/RT]

DNb = 2.1 x 10-1exp[-479(kJ/mol)/RT]

The activation enthalpies obtained from the experimental data confirmed the retardation of Ti, V and Nb diffusion in Ni3Al by the anti-site diffusion mechanism. These results were consistent with previous work on diffusion of Re and Ru in Ni3Al.

Diffusion of Ti, V and Nb in Ni3Al at Elevated Temperatures. Fukaya, H., Moniruzzaman, M., Murata, Y., Morinaga, M., Koyama, T., Hashimoto, W., Tanaka, K., Inui, H.: Defect and Diffusion Forum, 2010, 297-301, 384-9