Simulation and control of microstructure evolution during hot extrusion of hard aluminium alloys

Controlling the microstructure distribution in the final product is challenging and demanding work for the aluminium extrusion industry. This can only be achieved when the microstructure evolution during deformation is fundamentally understood. In this paper, some physical models which are based on dislocation density, subgrain size, and misorientation have been integrated into a commercial finite element modelling program simulating extrusion. The volume fraction recrystallised after press quench and the recrystallised grain size after solution treatment are studied. The influences of die configuration, container temperature and die temperature on the recrystallisation behaviour are detailed. Following this successful prediction, a uniform distribution of microstructure along the length of the extrudate has been obtained by adjusting the ram speed according to the calculated subgrain size at die exit. The calculated histories of temperature and subgrain size during deformation are presented. The problems of this new process are illustrated. Further work on simulation and control of microstructure is finally discussed.