Laser micro-joining of Al and Cu foils with high strength and ductility

•The laser spiral spot welding of Al foil and Cu foil is successfully achieved with a maximum strength of 138.2 MPa.•The research explores the effects of keyhole and molten pool flow on joint morphology and microstructure evolution.•The controlled formation of IMC, alternated with ductile phases, effectively restricts crack propagation, enhancing shear strength and ductility. The micro-joining of Al foil and Cu foil is crucial for various industrial applications, such as manufacturing power lithium-ion batteries packs for electric and hybrid vehicles. An ongoing challenge in this process is the unsatisfactory joint strength, attributed to crack susceptibility and poor joint ductility. This issue is primarily caused by the continuous formation of an intermetallic compounds (IMC) layer between Al foil and Cu foil. This study investigates the microstructure and mechanical properties of Al/Cu lapped joints using laser spiral spot welding technique with a continuous-wave (CW) fiber laser. The research explores the effects of keyhole and molten pool flow on joint morphology and microstructure evolution, linking these aspects to joint fracture behaviors. The results demonstrate that CW laser spiral spot welding achieves defect-free joints with excellent mechanical properties. The controlled formation of IMC, alternated with ductile phases, effectively restricts crack propagation, enhancing shear strength and ductility. Optimal welding parameters, such as a laser power of 450 W and welding speed of 350 mm/s, yield joints with a maximum shear strength of 138.2 MPa, which represents a significant improvement over previous spiral spot welded joints and highlights the potential of CW laser welding for efficient and high-strength Al/Cu metal foil joints.