The diffusion of Re and Ru in the γ'-Ni3Al phase was investigated at 1423 to 1523K by using pseudo-binary diffusion couples. It was found that the concentration gradient of Re appeared to promote the up-hill diffusion of Al, whereas that of Ru did not promote Al up-hill diffusion. The cross interdiffusion coefficients, DAlReNi and DAlRuNi, were independent of the matrix ordering since they were qualitatively comparable 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. The diffusivities in the γ’ phase could be described by:Re:     D(m2/s) = 1.5 x 101exp[-467.5(kJ/mol)/RT]

Ru:     D(m2/s) = 1.3 x 10-3exp[-318.7(kJ/mol)/RT]

Furthermore, the present results suggested that the diffusion of Ru in Ni3Al was governed mainly by the diffusion in Ni sub-lattice and the diffusion of Re was mainly controlled by the formation of antisite defects in the Ni sub-lattice with a negligible contribution from the antisite bridge mechanism.

Diffusion of Re and Ru in the γ' Phase of Ni Based Alloys. E.Mabruri, S.Sakurai, Y.Murata, T.Koyama, M.Morinaga: Materials Transactions, 2008, 49[6], 1441-5

Table 2

DIrIr Interdiffusion Coefficients in Ni-Al-Ir Alloys at 1473K