Simulation and control of dispersoids and dispersoid-free zones during homogenizing an AlMgSi alloy

Dispersoids and dispersoid-free zones (DFZs) near grain boundaries are produced when homogenizing as-cast alloys. The distribution and size of dispersoid precipitates and the width of DFZs affect subsequent alloy extrudability performance. A multicomponent Scheil model, coupled to a thermodynamic databank package (MTDATA) was used to calculate the concentration profiles of solutes and predict the width of the DFZs. In an attempt to eliminate the DFZs and refine the microstructure, equal channel angular extrusion was performed prior to homogenization. This had the effect of both reducing the size and improving the distribution of dispersoids, minimizing the extent of the DFZs and refining the grain size owing to recrystallization of the deformed structure during homogenization.