Binary, ternary and quaternary interdiffusion experiments have been investigated in cobalt solid solutions including Al, Cr, and Ni elements at 1423 K. The direct interdiffusion coefficients of Al, Cr and Ni are positive. Among them, the coefficients of Al are the largest, and those of Ni are the smallest. The indirect interdiffusion coefficients between Al and Cr are positive, but those between Al (or Cr) and Ni are negative. The addition of Al element to Co solid solution largely enhances diffusion but the addition of Cr and Ni elements slightly enhances diffusion. The effect of the addition of elements on interdiffusion are evaluated quantitatively from the 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 evaluated values of interdiffusion coefficients are in good agreement with the experimental ones.
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