A MATHEMATICAL-MODEL FOR THE DISSOLUTION KINETICS OF MG2SI-PHASES IN AL-MG-SI ALLOYS DURING HOMOGENIZATION UNDER INDUSTRIAL CONDITIONS

A numerical analysis of the homogenisation treatment of aluminium allo ys under industrial circumstances is presented. The basis of this stud y is a mathematical model which is applicable to the dissolution of st oichiometric multicomponent phases in both finite and infinite ternary media. It handles both complete and incomplete particle dissolution a s 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 p arameters, such as particle size distribution, initial matrix concentr ation profile and particle geometry on the dissolution- and matrix hom ogeneity kinetics is analysed. Then, the impact of the heating-rate an d local temperature on the homogenisation kinetics is investigated. Co nclusions 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-pr ecipitates. (C) 1998 Elsevier Science S.A. All rights reserved.