The effect of simultaneous deformation and annealing on the precipitation behaviour and mechanical properties of an Al–Mg–Si alloy

The influence of simultaneous deformation and annealing on the precipitation behaviour and the mechanical properties of an AA6060 Al–Mg–Si alloy were investigated by Transmission Electron Microscopy (TEM) and tensile testing. The results were compared to similar heat-treatments of the un-deformed material and of a material which was pre-deformed 10% before a subsequent annealing. The deformations applied in the present work were simultaneous by 0.6% within 10 min of heat treatment at 190 °C, and by 10% within 100 min and 300 min at 190 °C. The results show that the precipitation kinetics, microstructure and the tensile strength are greatly dependent on the specific deformation mode applied. When deformation and annealing of the material are simultaneous, precipitation takes place at dislocations which are moving through the material. These precipitates are of post-β′′-type. Compared to the pre-deformed material, the strength addition by the precipitates is larger in the simultaneous deformation mode due to a finer precipitate distribution, while the strength addition by dislocations appears to be lower. The total yield strength of all peak hardness conditions is similar, due to a compensation of different strength contributions with the highest contribution by precipitates in the un-deformed material.