A double-serpentine diffusion path for a ternary diffusion couple

摘要

A double-serpentine diffusion path that crosses thestraight line joining the terminal alloy corn-positions twice on aternary isotherm is reported for a diffusion couple assembled withtwo fi (B_2) Fe-Ni-Al alloys and annealed at 1000 deg C for 2days. The couple developed a Ni concentration profile that exhib-ited two regions of mass loss separated by a region of mass gain onone side of the Matano plane. With an additional couple whosepath intersected the double serpentine path, ternary interdiffusioncoefficients were determined at the composition of intersection.Also, average values of the ternary interdiffusion coefficients,D_(ij)~(approx= Fe)(i,j=Al, Ni), were determined over selectedcomposition ranges of the couple and employed to model theconcentration profiles. The cross D_(NiAl)~(approx= Fe)coefficient was negative and comparable in magnitude to the mainD_(NiNi)~(approx= Fe) coefficient. The double-serpentinediffusion path was characterized by large diffusional inter-actionsamong the components and appreciable variations in theinterdiffusion coefficients over different compositional ranges.