RELATION BETWEEN FABRICATION PARAMETERS AND GRAIN-BOUNDARY INTERNAL-FRICTION PEAKS IN COMMERCIAL AL-MG-SI ALLOYS

The polycrystalline Al-Mg-Si alloys (Al alloy 6063) have an internal friction peak at 480 K (1 Hz) attributed to grain boundary relaxation in the presence of particles. The aim of this work is to check the influence of certain fabrication parameters (the alloy chemical composition, the extrusion temperature and the homogenization conditions) on the grain boundary internal friction peaks of a special set of alloys. The relaxation strength increases with increasing Si content. This effect is due to an enhancement of Si grain boundary precipitation. We do not observe the dependence on the excess Si (with respect to the stoichiometric chemical composition) predicted by others authors. The extrusion temperature indicates a separation of the alloys into different groups obeying different beta and Si grain boundary precipitation. The homogenization parameters do not seem to be important in this case.