Short pulse laser welding of aluminum and copper alloys in dissimilar configuration

The present paper deals with short-pulse laser welding of copper and aluminum alloys in dissimilar configuration. In particular, a 100 W nanosecond-class pulsed fiber laser is exploited as a source for welding lap-joints both with linear and spt strategy. The investigation is aimed at understanding the role of the main process parameters, such as pulse shape, duration and energy, peak power, and welding speed on the weld bead characteristics (width, penetration depth and width at the interface). The SPI laser source exploited in this investigation allows the selection of a wide range of pulse shapes, any of them characterized by specific parameters, which favor different interaction mechanisms with the base material. According to this, the goal is to optimize the use of this kind of source for welding high-reflectivity thin materials. The results pointed out that some of the selectable pulse shapes are very suitable for the welding process and that the very low heat input delivered allows a low mixing of the two base materials and thus limits the occurrence of brittle end hard intermetallic phases. In particular, the wobbling scanning strategy turned to be very flexible, since it allows to fine tune penetration depth and width at the interface and allows a proper fitting of the joint to the desired mechanical characteristics.