The influence of welding speed on geometry, porosity, and microstructure of AlSi10Mg multilayer structures manufactured with arc and powder-based DED

Abstract A novel plasma arc and powder-based Directed Energy Deposition process (DED-Arc-P) demonstrates significant potential for manufacturing high-quality metallic structures. While the process has been validated for steel and titanium alloys, its applicability to aluminum, one of the key industrial metals, remains unexplored. This study is the first to investigate AlSi10Mg processed by DED-Arc-P, focusing on the effect of welding speed and heat input on geometry, process efficiency, porosity, and microstructure to qualify the process for AlSi10Mg. The goal was to establish correlations between process parameters and material properties, and to contribute to the further development of DED-Arc-P. Results demonstrate that increased welding speeds enhance the consistency of layer height and width by minimizing heat input and accumulation. All structures exhibited higher geometric deviations in the bottom region, followed by a stable region, with the stable region achieved earlier at higher speeds due to reduced heat input. The structure produced with the highest speed showed slightly increased porosity (~ 2.7%) compared to the others (~ 2.4%). This was caused by the differences in cooling rates. Pores are primarily situated in the lower regions of all structures, attributed to effective heat dissipation by the substrate plate. The dendrite arm spacing, indicative of microstructure fineness, decreased with reduced welding speeds and higher layers as a result of increased heat accumulation. Additionally, the dendrite growth angle in relation to the build-up direction decreased with higher speeds, attributed to variations in weld pool geometry. SEM and EDS analyses revealed that higher welding speeds refine both the dendritic α-Al structure and eutectic Si particles. Fe-rich intermetallic phases, likely β-Al₅FeSi, were identified in the interdendritic regions.