Ternary diffusion in Cu-rich fcc Cu–Al–Si alloys at 1073 K

• Interdiffusivities in Cu-rich fcc Cu–Al–Si alloys at 1073 K were determined.
• The present results were compared with experimental data in boundary binary systems.
• The present results were validated by thermodynamic constraints and Fick’s law.
• The sign of ternary cross diffusivities was predicted in terms of thermodynamics.

Utilizing six groups of bulk diffusion couples and with electron probe microanalysis technique, the composition dependence of ternary interdiffusion coefficients in Cu-rich fcc Cu–Al–Si alloys at 1073 K were determined by the Matano-Kirkaldy method. Using a three-dimensional representation, the obtained main ternary diffusion coefficients were found to be consistent with the experimental data in boundary binaries available in the literature. The reliability of the obtained interdiffusivities was further validated by thermodynamic constraints as well as by Fick’s second law applied to numerical simulation. The sign of the ternary cross diffusivities in fcc Cu–Al–Si alloys, which shows a noticeable effect on microstructure, was also successfully predicted in terms of thermodynamics.