Improving the absorption of copper for near-infrared laser beams to optimize laser spot welding quality of copper to aluminum

Laser spot welding of copper-aluminum has gained significant attention thanks to the unique properties of these metals in addition to the capabilities of laser welding. Applying the laser on the aluminum side in an overlap configuration is well-studied in the literature however, directing the beam from the copper may bring some advantages to better control the final microstructure of the weld and minimize the formation of intermetallic compounds. The issue to be addressed is the considerable reflectivity of copper surfaces for well-established near-infrared laser sources. In this paper, the absorption of copper is improved by implementing laser-based surface structuring. The absorption of copper is tracked with online temperature measurement and offline microscopic observation. In addition, the mechanical performance (shear load) of welded copper-aluminum samples with different copper surface conditions and laser powers was considered to explain the absorption of the laser beam and optimize the microstructure of the weld zone regarding the formation of intermetallic compounds.