Binary, ternary and quaternary interdiffusion were investigated in Co solid solutions with Al, Cr and Ni at 1423K. The direct interdiffusion coefficients of Al, Cr and Ni were positive. Among them, the Al coefficients were the largest, and those for Ni were the smallest. The indirect interdiffusion coefficients between Al and Cr were positive, but those between Al or Cr, and Ni, were negative. The addition of Al to Co solid solutions largely enhanced diffusion, but the addition of Cr and Ni only slightly enhanced diffusion (figure 10). The effect of added elements on interdiffusion was evaluated quantitatively from factors related to the solidus temperature of Co solid solutions, the diffusivity of elements in pure Co and the interaction parameters between solute elements. The predicted values of the interdiffusion coefficients were in good agreement with the experimental ones.

Y.Minamino, Y.Koizumi, N.Tsuji, T.Yamada, T.Takahashi: Materials Transactions, 2003, 44[1], 63-71

Figure 10

Concentration Dependence of Binary Interdiffusion Coefficients in Co Alloys