Novel design of weld vector route for dissimilar nonferrous plates laser welding in battery manufacturing for electric vehicles

Abstract

In this research, Al/Cu thicker plates are overlap-joined based on an experimental simulation to improve the metallurgical quality of laser welding the busbar tab to interconnect plate in manufacturing production for electric vehicle battery. The influence of weld vector route on the weld formation, microstructure and mechanical properties has been investigated via stereological microscope, metallographic microscope, material tensile testing machine, scanning electron microscope and energy dispersive spectroscope. Ductility-dip cracking (DDC) easily takes place along fusion zone migrated grain boundaries (MGBs) in local zones of brittle medium-concentrated IMC phases (AlCu+Al3Cu4) of the plain straight weld produced by conventional process, which leads to a maximum load force of only 915 N in tensile shear test. The designed Al/Cu laser welding with novel weld vector route could reduce the level of restraint in the weld metal and the degree of stress relaxation during reheating, which in turn prevents the occurrence of cracks. In tensile shear test, the dummy specimens have achieved an excellent performance with a maximum load force of 1380 N and a prominent plasticity owning a certain degree of dimple-like ductile fracture composition during deformation to break. This novel design of laser welding can successfully improve both the product quality and production efficiency for a green low-carbon manufacturing process, and concurrently reduce the time cost and energy consumption in rework process for nonconforming battery modules. Furthermore, from aspect of failure mode and effects analysis (FMEA), the novel process could enhance the safety and reliability of battery pack in physics and to refrain from potential failures resulting from thermal runaway, vibration, or impact due to pressure and dynamic mechanical loads when electric vehicles are running on the roads.