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

Abstract

Welding of AlSi10Mg alloys fabricated by additive manufacturing (AM) has been recently conducted to meet the demands for joining or repairing them. However, high susceptibility to porosity occurring in 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 inputs with five and eight tracks. The study systematically assessed the impact of heat input on porosity, microstructure, and mechanical properties of the welded joints. The results show that the decrease of heat input from 180 to 75 J/mm results in a substantial reduction in porosity from 7.0 to 2.1%. This reduction leads to a 29.4% increase in ultimate tensile strength (UTS) and an 11.7% increase in elongation index (EI). Furthermore, 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. The WM with eight tracks exhibits refined α-Al cells and Si-rich eutectic phases, improved connectivity of Si-rich networks, and increased solid solution strengthening, compared to the five-track joints with higher heat input. As a result, low heat input of the upper region in the LMD welded joints has been effective in minimizing hydrogen pores, enhancing WM microstructure, and improving the mechanical properties of welded joints in AM AlSi10Mg alloys.