Microstructure control and extrudability of aluminium-Mg-Si alloys microalloyed with manganese

Abstract
The hot deformation behaviour of AA 6063 and AA 6005 aluminium alloys has been related to chemical composition and the microstructural evolution occurring during the various heat treatment procedures prior to extrusion. It was shown that a small addition of manganese significantly accelerates the homogenising process (transformation of the plate-like beta-AlFeSi phase to the more rounded alpha-AlFeSi phase) which gives better hot formability and ductility. The mechanical behaviour of Al-Mg-Si alloys during hot working at low and intermediate strains was described by a new model for the accumulation and annihilation by climb of geometrically necessary dislocations at non-deformable precipitates. Strain hardening behaviour at high strains correlated with the reduction in spacing between grain boundary precipitates.