A double-serpentine diffusion path which twice crossed the straight line that joined the terminal alloy compositions on a ternary isotherm was found for a diffusion couple which consisted of two annealed (1000C, 48h) β (B2) Fe-Ni-Al alloys. The couple developed a Ni concentration profile which exhibited 2 regions of mass loss, separated by a region of mass gain on one side of the Matano plane. Using an additional couple whose path intersected the double serpentine path, ternary interdiffusion coefficients were determined at the intersection composition. Average values of the ternary interdiffusion coefficients were determined over selected composition ranges of the couple, and were used to model the concentration profiles. The cross-coefficient, DNiAlFe, was negative and was comparable in magnitude to the main coefficient, DNiNi. The double-serpentine diffusion path was characterized by large diffusional interactions among the components, and by appreciable variations in the interdiffusion coefficients over various composition-ranges.

A Double-Serpentine Diffusion Path for a Ternary Diffusion Couple. Y.H.Sohn, M.A.Dayananda: Acta Materialia, 2000, 48[7], 1427-33