Effect of material configuration and welding parameter on weld formability and mechanical properties of bobbin tool friction stir welded Al-Cu and Al-Mg aluminum alloys

The microstructure and mechanical properties of joints between Al-Cu and Al-Mg aluminum alloys using bobbin tool friction stir welding (BT-FSW) were studied. The joints were fabricated for different material configurations at various welding speeds. Results show that there are no detectable defects when the soft Al-Mg alloy is placed on the advancing side (AS). It was found that some hard-oriented grains in the stir zone on the Al-Cu side remain unchanged. In addition, the development of different deformation and recrystallization textures weakens the texture intensity. Both 5–2 (with Al-Mg on the AS, referred as a 5–2 joint) and 2–5 (with Al-Cu on the AS, referred as a 2–5 joint) joints exhibit a half N shape hardness distribution on the 5A06 side and the profile of hardness on the 2A70 side exhibits a half W shape distribution. There is no discernible effect on tensile strength from changes in the welding parameters for the 5–2 joints. The 2–5 joints fracture at the defects, while the 5–2 joints without defects fracture at the heat-affected zone, with the micro-defects which are difficult to identify in the Band Pattern zone, and joint line remnant causing fracture. All joints deformation occurs on the 5A06 side, and the Portevin-Le Chatelier band that appears in the joint extends from the base material to the heat affected zone.