Influence of solute-source composition on composition-dependent interdiffusion coefficient

Abstract

The validity of a long-held implicit assumption that the composition-dependent interdiffusion coefficient is a material parameter that is isothermally constant, irrespective of solute-source composition, is studied theoretically and experimentally. Solute concentration distributions under the influence of diffusion-induced stress generation and relaxation are numerically simulated, and the results are used to compute and compare composition-dependent interdiffusion coefficients under different solute-source compositions. The results of both the theoretical and experimental analyses show that solute-source concentration can significantly change the composition dependency of interdiffusion coefficient, in contrast to what is often implicitly assumed. Accordingly, the use of concentration-dependent interdiffusion functions, obtained from pure-metal/pure-metal diffusion couples, to predict or analyze diffusion effects when the solute-source is an alloy instead of a pure-metal can be grossly inaccurate.

Keywords

• Interdiffusion coefficient
• Concentration
• Solute source
• Theoretical
• Experimental
• Diffusion Couple