Resolidification of the mushy zone of multiphase and multicomponent alloys in a temperature gradient – Experiments and modeling

Resolidification of the mushy zone of multiphase and multicomponent alloys in a temperature gradient is investigated. Experiments of gradient annealing are conducted for a multiphase Cu-40 wt.%Al alloy and an Al-1 wt.%Mg-5 wt.%Si alloy with varying holding times, and the resulting microstructures are evaluated with respect to the evolution of phase fractions and concentration distributions. A numerical model that describes the macroscopic mass transport along the temperature gradient out of the mushy zone and that predicts the evolution of phase fractions and concentration distributions for multicomponent and multiphase alloys is put forward, and the calculation results are compared with the experimental observations. Full qualitative agreement is achieved between experiment and simulation. Effects in a resolidifying mushy zone of a multiphase alloy such as local solutal melting prior to resolidification that have so far not been documented in the literature are captured by the model.