A Study on Weldability and Mechanical Properties of Prismatic Battery Aluminum Alloy Materials According to Laser Welding Patterns

This study investigates the laser welding characteristics and mechanical properties of the Can-Cap butt joint in 600 mm ultra-large prismatic batteries, which are emerging as next-generation electric vehicle (EV) and energy storage system (ESS) platforms. To overcome the high reflectivity and thermal conductivity of aluminum alloys, a green laser with a wavelength of 515 nm was utilized to weld 0.7 mm thick Al3003-H14 sheets. The effects of welding patterns (straight and wobble) and scanning speeds on the weldability, cross-sectional defects, microstructural hardness, and tensile strength were experimentally evaluated. Precise joint alignment was achieved using the Auto Position Alignment (APA) function of the laser scanner. Optical microscopy of the etched cross-sections revealed that both patterns produced sound, fully penetrated weld beads free of internal porosity and hot cracks. Vickers hardness depth profiles indicated that the fusion zone (WZ) exhibited the highest hardness due to rapid-cooling-induced microstructure refinement, with the straight pattern showing higher hardness than the wobble pattern due to its faster cooling rate. Tensile testing demonstrated that the tensile strengths of the straight and wobble patterns reached 84.1% (138.8 MPa) and 77.1% (127.3 MPa) of the base metal, respectively. The straight pattern exhibited a 9.1% higher tensile strength compared to the wobble pattern, which is attributed to the narrower bead width, reduced heat-affected zone (HAZ), and higher joint hardness of the straight path. These experimental findings provide baseline datasets to validate computational fluid dynamics (CFD) melt pool simulations and advance intelligent laser autonomous manufacturing frameworks.