Aluminium has great capabilities since it is lightweight, durable, corrosion-resistant, highly conductive and recyclables. But with traditional fusion welding it is very difficult to join them together especially when dissimilar metals like AA2024 T3 and AA7475 T761 cannot be even welded using fusion technique. This work “Project intDemo” SAAB Technologies were trying to attempt the same. During this study we checked the possibility of joining these aluminium alloys. The feasibility of obtaining a T joint with full penetration is also scrutinised. The weld is later examined to check properties such as hardness and microstructure so as to understand its relationship. 

The mode of experiment is trial by error thus it consumes a lot of time and energy. Due to the shortage of research relating to the metals AA2024 T3 and AA7475 T761, a literature study has been conducted to understand the weld characteristics associated with these metals. Previous studies illustrated lap joints and Butt joints but not a T joint with Lap and Butt configuration.

During the project we had access to friction stir cell and material lab in PTC Trollhättan. With 90% of base plate thickness as tool reach, it is possible to obtain full penetration in the weld with an rpm of 1500,6500N axial force ,3 mm/s weld speed at 1° tilt angle. A full profile hardness is performed, and a histogram is plotted using Matlab TM. The results show that Kissing bond defects at the retreating side of the T-joints and hook at the advancing side. However, these deflects do not greatly influence the hardness of the weld. Heat affected zone significantly influences the hardness due to the grain coursing effect. Hardness profile also gives the idea that cooling after the welding can help regain hardness of the naturally aged metal. Also, the T761 condition in 7475 impacts the loss of hardness in HAZ and TMAZ regions of the weld.