Simultaneous measurement of tracer and interdiffusion coefficients: an isotopic phenomenological diffusion formalism for the binary alloy

Abstract

In this paper, a new development of the classic Onsager phenomenological formalism is derived using relations based on linear response theory. The development concerns the correct description of the fluxes of the atomic isotopes. The resulting expressions in the laboratory frame are surprisingly simple and consist of terms coming from the standard interdiffusion expressions and from Fick’s first law, where the tracer diffusion coefficient is involved thus providing a better understanding of the relationship between the two approaches – Fick’s first law and the Onsager phenomenological formalism. From an experimental application perspective, the new development is applied to the binary alloy case. The formalism provides the means to obtain the interdiffusion coefficient and tracer diffusion coefficients simultaneously from analysis of the interdiffusion composition profiles in a single experiment.

Keywords:

• diffusion
• SIMS
• theoretical

Acknowledgements

The authors (IVB and GEM) gratefully acknowledge encouraging discussions with emeritus professor Alan Allnatt (University of Western Ontario).This research was primarily supported under the Australian Research Council Discovery Projects funding scheme (project number DP130101464). Two of the authors (Kulkarni and Sohn) are also grateful for the financial support from the US Department of Energy, Assistant Secretary for Energy Efficiency and Renewable Energy, Office of Vehicle Technologies, Automotive Lightweight Materials Program under contract DE-AC05-00OR22725 with UT-Battelle, LLC.