Relationships between welding parameters, aging conditions, and weld properties in AA7075-T6 friction stir welds

The influence of processing parameters and several combinations of natural as well as artificial aging on the mechanical properties of friction stir welded AA7075-T6 is analyzed in the present investigation. Different sets of welding parameters were employed to obtain joints characterized by different peak temperatures and thermal cycles. The joint obtained with the highest welding speed has guaranteed the best mechanical properties. The latter were shown to be strongly correlated to heat input, which influences both densities of dislocations in nugget zone grains and growth and dissolution of strengthening precipitates in the heat-affected zone that establish the mechanical characteristics of friction stir welds. On the other hand, artificial aging has drastically reduced the strain at break due to strain localization in the heat affected zones while it has proved its effectiveness in stabilizing the mechanical properties when exposed to further natural aging at room temperature.