Diffusion of Re and Ru in the γ′ Phase of Ni Based Alloys

Abstract

The diffusion of Re and Ru in the γ′-Ni₃Al phase has been investigated at a range of temperatures 1423–1523 K by using the pseudo-binary diffusion couples. It was found that the concentration gradient of Re appeared to promote the uphill diffusion of Al, whereas that of Ru did not promote the Al uphill diffusion. The cross interdiffusion coefficients of \\ ildeD_AlRe^Ni and \\ ildeD_AlRu^Ni were independent of the matrix ordering since they were comparable qualitatively between those in the γ′-Ni₃Al and in the γ-Ni phases. The tracer diffusion coefficients for Re and Ru in Ni₃Al were estimated by extrapolation and the obtained activation energies were consistent with the site preferences of the elements reported in the literature. Further, the results of this work suggest that the diffusion of Ru in Ni₃Al is mostly governed by the diffusion in Ni sublattice and the diffusion of Re is mainly controlled by the formation of anti-site defects in the Ni sublattice with negligible contribution of the anti-site bridge mechanism.