A mathematical model for the dissolution kinetics of Mg2Si-phases in Al–Mg–Si alloys during homogenisation under industrial conditions

A numerical analysis of the homogenisation treatment of aluminium alloys under industrial circumstances is presented. The basis of this study is a mathematical model which is applicable to the dissolution of stoichiometric multicomponent phases in both finite and infinite ternary media. It handles both complete and incomplete particle dissolution as well as the subsequent homogenisation of the matrix. The precipitate volume fraction and matrix homogeneity are followed during the entire homogenisation treatment. First, the influence of the metallurgical parameters, such as particle size distribution, initial matrix concentration profile and particle geometry on the dissolution- and matrix homogeneity kinetics is analysed. Then, the impact of the heating-rate and local temperature on the homogenisation kinetics is investigated. Conclusions for an optimal homogenisation treatment of aluminium alloys may be drawn. The model presented is general but the calculations were performed for the system Al–Mg–Si with an Al-rich matrix and Mg2Si-precipitates.