Blue Laser Conduction Welding of Dissimilar Cu and Al Sheets

Abstract

Joining Cu-Al with 0.6 mm is important for the high-power density battery in the new energy field. Low laser absorptivity is a challenge in Cu-Al welding with conventional infrared laser at around 1000 nm wavelength, where keyhole welding is necessary. It is difficult to control welding qualities in keyhole welding due to the intense flow and violently changing absorption rate. At 450 nm wavelength, Cu and Al have high laser absorptizzvity which has the potential to implement stable conduction welding. Therefore, this work adopted a blue laser welding system, and for the first time, realized the conduction welding of 0.6 mm Cu and 0.6 mm Al sheets. The welding process, surface appearance, mechanical properties, and electrical properties were investigated. The results showed that high-power (1950 W) could effectively realize stable Cu-Al conduction welding without spatters, and the welding speed could reach 40 mm/s. Compared with an infrared laser, the blue laser could weld Cu-Al using the form of Cu on top and Al on bottom, which was beneficial for a wide process window and stable welding process. A larger bead width and more consistent intermetallic compound thickness resulting from the blue laser were conducive to performance improvement. In addition, the relationship between welding parameters, molten pool characteristics, and process qualities was built. It provided a possibility to control the welding quality under the influence of strong heat accumulation and high thermal conductivity. This work demonstrated that blue laser has great potential in joining Cu-Al for new energy applications.