Weldability and mechanical properties of dissimilar laser welded aluminum alloys thin sheets produced by conventional rolling and Additive Manufacturing

The production of parts involving the combination of different materials has gained a lot of interest in recent years as a strategy for achieving weight reduction. Particular attention has been paid to the joining process of mechanical components obtained with different production processes. This paper aims at studying the feasibility of laser welding to join rolled 6082-T6 thin sheet to A357 sheet produced by Laser-based Powder Bed Fusion (LPBF). The role of welding parameters, LPBF scan strategy and post heat treatment on the weld bead formation has been studied by means of microstructural and mechanical characterization. The results showed that a higher welding speed reduces the porosity in the weld bead obtaining values of about 5% in terms of percentage of fused area, while the post heat treatment of the LPBF sheet has the greatest influence on the final properties of the joint compared to the scanning strategy used. In particular, a complete T6 heat treatment of the additive sheets leads to an ultimate tensile strength of about 200 MPa closes to the reference condition 6082-6082. Hardness measurements showed that a drop in the values occurred at the center of the bead regardless of the treatment conditions while Digital Image Correlation (DIC) strain analysis confirmed that higher deformation occurred in the Fused Zone and in the Heat Affected Zone. SEM-EDS analysis revealed the presence of intergranular precipitates which contain Fe, Si, Mg and Mn in the fused zone.