  A few decades earlier, Kirkaldy and Lane proposed an indirect method of
estimating the tracer and intrinsic diffusion coefficients in a ternary system
(without showing experimental verification), which is otherwise impossible
following the Kirkendall marker experiments. Subsequently, Manning proposed the
relations between the tracer and intrinsic diffusion coefficients in the
multicomponent system by extending the Onsager formalism (although could not be
estimated by intersecting the diffusion couples). By solving these issues in
this article, we have now proposed the equations and method for estimating
these parameters in pseudo-ternary diffusion couples in which diffusion paths
can be intersected in multicomponent space. We have chosen NiCoFeCr system for
verification of this method because of the availability of good quality
diffusion couple experiments and estimated tracer diffusion coefficients of all
the components measured by the radiotracer method. An excellent match is found
when the tracer diffusion coefficients estimated following the newly proposed
method are compared with the data estimated following the radiotracer method.
Following, the intrinsic diffusion coefficients are estimated experimentally in
a multicomponent system for the first time highlighting diffusional
interactions between the components. We have further shown that the intrinsic
diffusion coefficients are the same (if the vacancy wind effect is
negligible/neglected) when estimated from other types of diffusion couples
(pseudo-binary and body diagonal) in the same multi-component system. This
method can be now extended to the Al, Ga, Si containing systems in which the
estimation of tracer diffusion coefficients following the radiotracer method is
difficult/impossible because of various reasons.

Materials Science