Interdiffusion coefficients within the β-phase region of the nickel–cobalt–chromium–aluminum (Ni–Co–Cr–Al) quaternary system were estimated by square root diffusivity analysis. The obtained results indicated that the cross interdiffusion coefficients Dij (i ≠ j, i, j = Al, Cr, Co) other than DAlCo were less than the main interdiffusion coefficients Dij (i = j), and that the values of DAli were greater than those of DCri and DCoi. This finding suggests that the addition of chromium decreases the interdiffusion coefficients of aluminum and cobalt, but the addition of cobalt did not cause an obvious change in the interdiffusion coefficients of aluminum and chromium in the β-phase region. The different effects associated with the additions of chromium and cobalt were qualitatively discussed in light of the relationship between the thermodynamic properties of the system and Wagner's interaction parameter. The results revealed that the different effects could be ascribed to the stronger thermodynamic interactions between aluminum and cobalt compared to that between aluminum and chromium.

Interdiffusion Within the Β-Phase Region of the Ni–Co–Cr–Al Quaternary System. H.Wei, H.Y.Zhang, X.F.Sun, M.S.Dargusch, X.Yao: Journal of Alloys and Compounds, 2010, 493[1-2], 507-16