Comparative investigation on single laser beam and dual laser beam for lap welding of aluminum alloy

Aluminum alloy is considered to be one of the ideal materials for light-weighting on aerospace and new energy automotive. Laser welding without a filler wire is an efficient way for weight reduction. The common defects in laser welding of aluminum alloys are porosities and cracks, resulting in poor mechanical performances and short service life of joints. In order to investigate the methods to suppress defects, 1 mm thick automotive aluminum alloy AA6014 was performed for single and dual-beam laser lap welding in this study. The effects of two welding processes on microstructure, cracks, and mechanical properties were investigated. The results showed that the welding adaptability of dual laser beam lap welding was much better than single laser beam lap welding. Well-formed weld could be obtained in a suitable line energy range by both welding processes. The dual beam with an energy ratio of 1:1 was at an angle along the welding direction, which could increase the molten pool area and stir the weld pool more sufficiently. Thus, dual laser beam lap welding could significantly increase the welding speed and alleviate collapse caused by single laser beam welding. The gaps of lap welding tended to be crack sources and generate cracks, while dual-beam laser welding was advantageous for reducing such cracks. This research is of great significance to improve the laser welding quality of all-aluminum automotive bodies, increase production efficiency, and further reduce the weight of the automotive.