Abstract:The cold metal transfer (CMT) butt welding was conducted on AlSi10Mg alloy thin sheets prepared by the powder bed fusion laser beam/metal (PBF-LB/M) technique using two types of filler wires, including ER4043 (Al-Si5) and ER4047 (Al-Si12). The effects of the two wires on weld geometry, porosity, microstructure, and mechanical properties of the welded joints were evaluated. Results indicate that the adding ER4043 wire effectively reduces porosity rate and pore size of the weld metal. In contrast, the ER4047 wire exhibits improved mechanical performance. The ultimate tensile strength of joints welded with ER4047 wire reaches 211.7 MPa, representing a 6.7% increase compared to the 198.4 MPa achieved with ER4043 wire. The average microhardness of the ER4047 weld (76.8 HV) increases by 15.5% compared to that of ER4043 weld. These findings suggest that the higher Si content in ER4047 filler wire is more conducive to achieving superior joint properties. Microstructural analysis attributes this enhancement to a combination of solid solution strengthening, fine grain strengthening, texture strengthening, nanoscale Si precipitation, and the load-bearing contribution of the eutectic Si network.