Extrudable Al-Si-Mg Alloys: Simulation of Microsegregation and Homogenization

Abstract

Extrudable Al-alloys of the 6xxx series are subjected to a homogenization treatment prior to extrusion in order to remove inhomogeneities generated during casting. Microsegregation of elements and phases is developed as a result of the solidification process. During homogenization, several phenomena take place such as the dissolution of various phases, the transformation of iron intermetallics, spheroidization of the remaining intermetallics, and reprecipitation during cooling. All these phenomena affect the extrudability of the material. An integrated simulation of microsegregation and homogenization is described. Microsegregation is simulated with the application of the Scheil-Gulliver model, employing computational thermodynamics. A Dual Grain Model has been developed for the simulation of homogenization, taking into account the variability of the grain size in the as-cast material. In this way, it is possible to simulate the dissolution of Mg2Si and the transformation of iron intermetallics concurrently. The results of the simulations provide a deeper understanding of the effects of processing on alloy microstructure and can be used toward the design of the homogenization process of extrudable Al-alloys.