The Kirkendall effect in single-phase multicomponent systems: dependence on drift and entropy distribution

Abstract

This paper concerns interdiffusion in a diffusion couple and determination of the Kirkendall plane. The “entropy density” model is proposed in which the entropy is used to predict the position of the Kirkendall plane in a multicomponent system. It is shown that the marker position depends on the drift velocity and pressure field only. Application of the model is presented for ternary CoFeNi diffusion couples of three various initial compositions. The concentration profiles and entropy densities are calculated for each diffusion couple. The positions of the Kirkenadl planes are determined and compared with those obtained by velocity-curve and trajectory methods.

Keywords:

• Kirkendall plane
• marker
• Darken velocity
• interdiffusion
• bi-velocity method
• entropy

Acknowledgments

This work has been supported by the National Science Centre (NCN) in Poland, decision number DEC-2011/03/B/ST8/05970. The software CADiff available from author.

Notes

1. When thermodynamic activities equal to the concentration of the component a_i = c_i, then the chemical potential can be defined as: