Diffusion of Al and Al-Substituting Elements in Ni₃Al at Elevated Temperatures

Abstract

Diffusion of Ti, V, Nb, Mo and Ta in Ni₃Al phase was investigated at different temperatures using Ni–Al–X (X = Ti, V, Nb, Mo, Ta) pseudo-binary diffusion couples. The magnitude of the interdiffusion coefficients was in the descending order of V, Mo, Ti, Nb and Ta at all experimental temperatures ranging from 1423 to 1573 K. Diffusion data obtained in this study was compared with those of Re and Ru available in the literature as Re and Ru are recently being added in modern Ni-based superalloys. Diffusion retardation occurred for Ti, V, Nb, Mo and Ta as compared to Ru, and this can be explained by the anti-site diffusion mechanism. The high activation energy for anti-site formation is required for β-site (Al-site) elements, such as Ti, V, Nb, Mo and Ta. However, as Ru can diffuse either by α- (Ni-site) or β-site preferences without creating local disorder, Ru diffusion is not retarded by the anti-site diffusion mechanism.