Influence of post-weld heat-treatment on global and local mechanical properties of friction stir welded AA6082 and AA7050 to Ti6Al4V

This study investigates the macroscopic as well as local mechanical properties of dissimilar aluminium-titanium joints obtained via friction stir welding, followed by heat treatments. For this purpose, the two widely used alloys AA6082 (AlMgSi) and AA7050 (AlCuZn) are friction-stir lap welded to Ti6Al4V. Post-weld heat-treatment between 6 and 48 h with a temperature range up to 420 °C is applied to investigate the diffusion behaviour. Besides the well-established lap-shear test, micro tensile tests were performed to investigate the local mechanical properties of the interface in the weld. Heat-treatment temperatures above 120 °C resulted in an increase of up to 40 % in strength compared to as-welded. UTS values reached up to 157 N/mm² and 225 N/mm². The diffusion kinetics of AlMgSi alloys is found to be significantly higher than that of AlCuZn alloys with Mg having the most significant influence on diffusion.