Robotic friction stir welding in lightweight battery assembly of extrusion-cast aluminium alloys

The present study focuses on developing lightweight assembly of two different aluminium alloys extruded and high pressure die cast (HPDC) for battery frame assembly in BEV. The goal is to produce defect-free welds in lap configuration with smooth surface finish. Stationary shoulder friction stir welding (SSFSW) was employed with welding speeds of 3–15 mm/s. EBSD analysis revealed two groups of grains in the stir zone (SZ) due to dynamic recrystallization. Moreover, the grain size of the SZ significantly decreased compared to both alloys. The cast alloy contains large iron particles, and that were broken by the rotating probe, and the stirred material consisted of fine dispersed precipitates. Tensile-shear test found the fracture location at the hook area near to cast, and a model representing fracture behavior is also discussed. With increasing welding speed from 3 to 5 mm/s, the tensile strength found ∼95 and ∼100 MPa, respectively without any significance difference in the fracture behavior and location. Overall, this study provides valuable insights such as materials mixing, grain refinement, and joint strength in dissimilar joining using SSFSW. The findings could be useful in developing optimized welding parameters and improving the overall quality and productivity of the SSFSW process for battery pack assembly in BEV.