Effect of energy per layer on the anisotropy of selective laser melted AlSi12 aluminium alloy

The anisotropy in the tensile properties of AlSi12 alloy fabricated using selective laser melting (SLM) additive manufacturing process was investigated. The tensile samples were printed in three different orientations, horizontal (H - 0°), inclined (I - 45°), and vertical (V - 90°), and found to exhibit yield strength between 225 MPa and 263 MPa, tensile strength between 260 MPa and 365 MPa, and ductility between 1 and 4%, showing distinct fracture patterns. It was established that the build orientation had insignificant effect on the microstructural characteristics of the SLM-printed samples, while XRD phase analysis showed variations in the Al (111) and Al (200) peak intensities. Consequently, the anisotropy in the mechanical properties of the SLM-printed AlSi12 samples was attributed to the differences in their relative density. Although the energy density was kept constant when printing the samples along different orientations, the “energy per layer” was found to be different owing to the variation in the printing area along the build direction. Further investigation on the effect of printing area, and correspondingly energy per layer, on the relative density was carried out. It was found that energy per layer in the range of 504-895 J yielded ≥99.8% relatively dense AlSi12 SLM-printed samples. This study puts forth a new idea that the density of the SLM-printed samples could be controlled using energy per layer as an input process parameter.