Improvement in weld quality of Al and Cu joints using dual-beam laser welding

The high weld quality of dissimilar aluminum (Al)/copper (Cu) joint is essential to improve the reliability of connecting components in secondary batteries. This study was aimed at enhancing the weld quality of dissimilar AlCu joints to connect tab-to-busbar in secondary batteries. AA1050 and Ni-coated Cu (C1100) sheets were lap-welded using dual-beam laser welding with a continuous-wave (CW) laser for welding and a pulsed laser for preheating. Consequently, the weld quality was investigated by characterizing the morphology, microstructure, and mechanical and electrical properties of the joints. For comparison of the weld quality, single-beam welding was also performed. Soundly welded joints were achieved using a dual-beam at a CW laser power range of 1000–1400 W for fixed pulsed laser power and welding speed of 100 W and 80 mm/s, respectively. Microstructural analysis of the weld indicated that the upper weld metal (WM) comprised α-Al and AlCu eutectic phases, whereas the lower WM exhibited mixed morphology of different phases including Al2Cu, AlCu, Al3Cu4, and Al4Cu9. Further, the electrical resistance was linearly correlated with weld penetration depth, exhibiting a minimum of 352.3 μΩ against a penetration depth of 341.7 μm. In addition, The Vickers microhardness and lap shear tensile testing of soundly welded sample (A4) exhibited an average hardness value of 921.7 HV in the lower WM, and the average tensile load for the welded sample was 247.4 N. This study provides valuable insights for improving the weld quality of reliable AlCu dissimilar joints for connecting tab-to-busbar in secondary batteries.