Microstructure and mechanical properties of Al-10Si-0.4Mg alloy fabricated by selective laser melting

Abstract

Microstructure and mechanical properties of Al-10Si-0.4Mg (mass%) alloy (AlSi10Mg alloy) specimens fabricated using selective laser melting (SLM) combined with powder-bed system have been examined. Optical microscope was used to identify the characteristic scalloped microstructure derived from local melting and rapid solidification of alloy powder during SLM process. The results of microscopy observation revealed that columnar α-Al grains subdivided by eutectic fine Si particles were elongated to the solidification direction depending on the radial heat flow caused by SLM process. The observed {100} texture along the building direction was attributed to the preferential [100] growth direction of α-Al phase in liquid. On the basis of the experimental results and thermodynamic analysis, the formation process of microstructure in the fabricated sample was discussed. The tensile strength of the fabricated specimen is 480 MPa, which is independent of the specimen geometry associated with the building direction, whereas the specimen tensile-deformed normal to the building direction exhibits a lower tensile ductility, which would be responsible for the fracture in the vicinity of melt pool (locally melted and rapidly solidified regions) boundaries.