Research on deposited tracks and microstructures of AlSi10Mg alloy produced by selective laser melting

The selective laser melting (SLM) process parameters significantly affect the bonding of melting powders and the substrate or deposited layer, and the microstructure of end-use components. In this study, single track, double track and cubic sample SLM experiments were carried out to investigate the effect of process parameters on the surface morphology of SLM-fabricated AlSi10Mg alloy. The hierarchical microstructures discriminated by the Si phase are observed in SLM-processed AlSi10Mg samples. The formation mechanism of the hierarchical microstructures is elucidated. The formula proved that the solidification rate (R) increases gradually from the boundary to the center of the melt pool. Coarse zones are formed by the instantaneous existence of an extremely high ratio of thermal gradient (G) and solidification rate at the melt pool boundary, where solidification microstructure grows planar. With the heat propagating, a gradual change of the G/R ratio appears and the microstructure turns to columnar-dendritic growth, creating the fine zones.