A novel experimental method of estimating tracer and intrinsic diffusion coefficients from multicomponent diffusion profiles

TL;DR

This paper introduces a new experimental method to estimate tracer and intrinsic diffusion coefficients in multicomponent systems, validated on NiCoFeCr, enabling analysis where traditional radiotracer methods are challenging.

Contribution

The authors developed equations and a method for estimating diffusion coefficients in pseudo-ternary diffusion couples, validated with experimental data, advancing diffusion analysis in multicomponent systems.

Findings

Excellent agreement with radiotracer data for NiCoFeCr

First experimental estimation of intrinsic diffusion coefficients in multicomponent systems

Method applicable to systems where radiotracer techniques are difficult

Abstract

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.