Combined measurements of composition-dependent tracer-, impurity- and intrinsic diffusion coefficients and atomic correlation factors from a binary diffusion couple

Abstract

A fundamental understanding of atomic diffusion is crucial for technological advances in the application of multi-component alloys. The augmented tracer-interdiffusion couple approach provides the composition-dependent tracer diffusion coefficients (mobilities) along the whole diffusion path. This study introduces a novel methodology for accessing the vacancy flux calculations in a diffusion couple, substantiating a rich variety of the diffusion parameters accessible by a single diffusion couple experiment aside of the interdiffusion coefficients. We demonstrate that the composition-dependent thermodynamic factors and Manning’s factors can be estimated using this approach. Furthermore, the composition-dependent correlation factors of the diffusing elements in a diffusion couple are estimated for the first time. A modified tracer-interdiffusion couple approach is applied to estimate the composition-dependent impurity diffusion coefficients by placing suitable radiotracers at the Matano plane. The Onsager coefficients are estimated for the whole concentration range under investigation. Under the vacancy flux in the Ni–Fe diffusion couple, Cr, Co, and Mn atoms are biased towards the Ni-rich side, though the vacancy flux-driven drift of the Mn atoms is most pronounced.