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.
Grassel et al. (Tue,) studied this question.