Predicting microsegregation in multicomponent aluminum alloys – progress in thermodynamic consistency

Abstract

Abstract Recent developments in modeling the interaction of thermodynamics and kinetics during microsegregation formation in multicomponent alloys are reported. A model accounting for solid state back diffusion, dendrite arm coarsening, dendrite tip undercooling, eutectic undercooling and thermodynamic correction of the interface concentrations is presented. By coupling the solution of the diffusion equation in the liquid and solid phases with the thermochemistry library ChemApp, the phase equilibria at the solid–liquid interface are calculated at each time step. Using an activity based method for identifying multiphase equilibria and metastable extensions of the stability range of phases, a thermodynamically consistent implementation of eutectic undercooling in multicomponent systems is achieved. The model is equipped with a userfriendly interface that allows setting the model parameters interactively and that presents the results (solute distribution, phase fractions, secondary arm spacing) in a pertinent way.