Investigation of Intermetallics Formation and Joint Performance of Laser Welded Ni to Al

In this paper, laser welding Ni to Al using pulsed wave (PW) and continuous wave (CW) lasers was investigated. Weld quality and strength were evaluated in terms of cross-section examination, intermetallic compounds formation, microhardness, shear test and 90-degree peel test. The results show that deep penetration welding Ni to Al causes high melting pool temperature and severe material mixing, which could result in dominant AlNi3 and AlNi intermetallics (IMCs) in the weld. These IMCs could significantly increase the hardness of the welding zone, but could also lead to the formation of defects, as well as reducing the ability to withstand the shear force and peel force applied to the weld. In comparison, using process optimization to maintain a shallow penetration or form a weld-braze joint, low melting pool temperature and minimum material mixing can be achieved. Hence, low-hardness Al3Ni IMCs are prevalent in the weld. This helps generate a defect-free dissimilar weld joint to withstand higher shear force and peel force. The findings show promising applications, such as the battery management system of electric vehicles, in which joining a Ni adaptor to an Al bus bar is required.