Compensation of Linear Misalignments in EN AW-6082-T6 Aluminium Sheets by Multi-Pin Wire-Based Friction Stir Welding

Linear misalignment (LM) can arise from dimensional tolerances, positioning inaccuracies, limited component stiffness, and clamping constraints, particularly in large-scale welded structures. While filler-assisted fusion welding provides some flexibility for accommodating such geometrical deviations, conventional friction stir welding (FSW) relies on direct tool–workpiece contact and a fixed pin geometry, making pronounced out-of-plane deviations particularly challenging. This study investigates the compensation of severe LM by multi-pin wire-based friction stir welding (W-FSW) of 2 mm thick EN AW-6082-T6 aluminium sheets using continuously supplied EN AW-6082 filler wire. LM values of 1.0 and 1.5 mm, corresponding to 50% and 75% of the base material thickness, were introduced with the elevated sheet positioned on either the advancing or retreating side. Welding without filler material resulted in pronounced bonding defects and lack of penetration. In contrast, continuous filler-material supply enabled all investigated LM configurations to be compensated and resulted in substantially improved joint consolidation. Tensile strengths between 198.8 and 210.0 MPa were achieved, compared with 208.71 MPa for a reference W-FSW joint without LM. All tensile specimens fractured outside the joining zone within the softened heat-affected zone, showing that the compensated LM region did not control the final fracture location under the investigated tensile-test conditions. Multi-pin W-FSW therefore demonstrates a substantially increased tolerance towards severe out-of-plane joint deviations.