Numerical modeling of diffusion induced phase transformations in mechanically stressed lead-free alloys

The present work investigates diffusion-induced phase evolution in solid mixtures under the presence of thermo-elastic strains. Based on five statements for an entropy principle we explain how to construct the constitutive equations for the entropy flux, the stress tensor, and the diffusion flux in multi-component solid mixtures. We show, first, that the obtained results agree with the classical results of thermodynamics of fluid mixtures and, second, that they allow for a theoretical description of phase formation and evolution. Finally we specialize to binary alloys and present various numerical studies for the brazing alloy Ag–Cu, for which the required material data is reliably documented.