Microstructure and Mechanical Properties of a Combination Interface between Direct Energy Deposition and Selective Laser Melted Al-Mg-Sc-Zr Alloy

Selective laser melting (SLM) and direct energy deposition (DED) are two widely used technologies in additive manufacturing (AM). However, there are few studies on the combination of the two technologies, which can synthetically combine the advantages of the two technologies for more flexible material design. This paper systematically studies the Al-Mg-Sc-Zr alloy by combination of SLM and DED with emphasis on its bonding properties, microstructure, and metallurgical defects. It is found that the aluminum alloy prepared by the two methods achieves a good metallurgical combination. The microstructure of aluminum alloy prepared by DED is composed of equiaxed crystals, and there are a large number of Al3(Sc, Zr) precipitated phase particles rich in Sc and Zr. The microstructure of SLM aluminum alloy is composed of equiaxed crystals and columnar crystals, and there is a fine-grained area at the boundary of the molten pool. With the decrease of laser volumetric energy density (VED), the width and depth of the molten pool at the interface junction gradually decrease. The porosity gradually increases with the decrease of VED, and the microhardness shows a downward trend. Tensile strength and elongation at fracture of the SLM printed sample at 133.3 J/mm3 are about 400 MPa and 9.4%, while the direct energy depositioned sample are about 280 MPa and 5.9%. Due to the excellent bonding performance, this research has certain guiding significance for SLM–DED composite aluminum alloy.