MODELING OF DENDRITIC STRUCTURE AND MICROSEGREGATION IN SOLIDIFICATION OF Al-RICH QUATERNARY ALLOYS

摘要

A two-dimensional cellular automaton (CA) model is coupled with a CALPHAD tool for the simulation of dendritic growth and microsegregation in solidification of quaternary alloys. The dynamics of dendritic growth is calculated according to the difference between the local equilibrium liquidus temperature and the actual temperature, incorporating with the Gibbs-Thomson effect and preferential dendritic growth orientations. Based on the local liquid compositions determined by solving the solutal transport equation in the domain, the local equilibrium liquidus temperature and the solid concentrations at the solid/liquid (SL) interface are calculated by the CALPHAD tool. The model was validated through the comparisons of the simulated results with the Scheil predictions for the solid composition profiles as a function of solid fraction in an Al-6wt%Cu-0.6wt%Mg-lwt%Si alloy. It is demonstrated that the model is capable of not only reproducing realistic dendrite morphologies, but also reasonably predicting microsegregation patterns in solidification of Al-rich quaternary alloys.