Investigation of resistance and intermetallic layer formation in laser-welded joints between Copper and AM Aluminium for electrical connections

The increasing electrification of transportation demands the development of more energy-efficient solutions, where additive manufacturing (AM) of electrically conductive components presents new opportunities. The design flexibility of AM enables unique innovations; however, it also introduces challenges due to additional process parameters affecting part production. A key concern in the use of laser powder bed fusion of metal (PBF-LB/M) manufactured parts is their material properties, which are further influenced by part plane orientation during fabrication. Previous research has focused on copper-aluminum dissimilar welding, but the specific challenges posed by AM techniques have not been fully explored. This study investigates the welding behavior concerning resistance and intermetallic layer formation. Nickel-plated copper sheet metal samples were welded to AM aluminium samples using a continuous wave single-mode fiber laser with scanner optics in a lap joint configuration. Before welding, the interface surface of the AM samples was machined to exclude the surface roughness variance effect on the result. During the experiments, the welding´s optical laser power was constant at 2kW and variations were made in welding speed ranging from 1200 mm/s to 400 mm/s in 200 mm/s increments. Electrical resistance measurements were taken using a high-precision micro resistance meter with a 4-wire Kelvin testing method, also hardness testing, tensile testing, and energy dispersive spectroscopy (EDS) analysis were conducted. The results revealed that intermetallic compounds formed during welding, influencing joint properties. At a lower welding speed, more aluminium was mixed with copper which led to the weld solidification cracking. The optimum welding speed was between 800 and 1000 mm/s for this study test setup.