Welding of additive manufacturing AlSi10Mg alloys using a laser metal deposition process with different heat input

Abstract Welding of AlSi10Mg alloys fabricated by additive manufacturing (AM) has been recently conducted in response to the demands for joining or repairing the AM parts. However, high susceptibility to porosity occurred in the weld metal (WM) poses a significant challenge for fusion welding of AM AlSi10Mg alloys. The laser metal deposition (LMD) process has emerged as a promising welding solution due to its low dilution rate for reducing the porosity. In this study, LMD welding of AM AlSi10Mg alloys was carried out employing different heat input with five and eight tracks. The study systematically assessed the impact of heat input on porosity, microstructure, microhardness, and tensile properties of the welded joints. As a result, the decrease of heat input from 200 to 65 J/mm results in a substantial reduction in porosity from 7.0% to 2.1%. Additionally, this reduction leads to a 29.4% increase in ultimate tensile strength (UTS) and an 11.7% increase in elongation-to-failure (EI). Notably, the upper region of joints with eight tracks possessing low heat input displays lower porosity and superior mechanical properties than the bottom region with relatively high heat input. Furthermore, the WM with eight tracks exhibits a refinement of α-Al cells and Si-rich eutectic phases, improved connectivity of Si-rich networks, increased solid solution strengthening, compared to the five-track joints with higher heat input. In conclusion, low heat input of the upper region in the LMD welded joints has proven effective in minimizing hydrogen pores, enhancing WM microstructure, and improving the mechanical properties of welded joints.