Research on deposited tracks and microstructures of AlSi10Mg alloy produced by selective laser melting
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Research on deposited tracks and microstructures of AlSi10Mg alloy produced by selective laser melting Sensen Dong1 · Xiaoxun Zhang1 · Fang Ma2 · Juze Jiang1 · Wei Yang1 Received: 14 May 2020 / Accepted: 20 July 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract 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 SLMfabricated 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. Keywords Selective laser melting · AlSi10Mg alloy · Deposited tracks · Microstructure · Transient thermal gradient · Microhardness
1 Introduction Selective laser melting (SLM) is generally performed by a laser selectively melting a layer with a thickness in the microscopic size regime and that is subsequently solidified rapidly with a high cooling rate of approximately 1 03–108 Ks−1 [1]. SLM provides more advantages, including high material utilization and an impressively high degree of shape complexity. AlSi10Mg is one of the most widely used materials in additive manufacturing (AM), because the Si element in the alloy can reduce the quality of alloy, effectively improve powder fluidity and greatly avoid the loose problem and the emergence of hot crack [2]. AlSi10Mg has been widely studied by selective laser melting in terms of microstructure and mechanical properties [3,4]. * Xiaoxun Zhang [email protected] 1
School of Materials Engineering, Shanghai University of Engineering Science, 333 Longteng Rd, Shanghai 201620, China
School of Mechanical and Automotive Engineering, Shanghai University of Engineering Science, 333 Longteng Rd, Shanghai 201620, China
2
In fact, process parameters including laser power, scanning speed, hatch spacing, etc., should be considered to build dense SLM-formed (SLMed) AlSi10Mg parts. The laser energy density (LED, J/mm3), which is defined to represent the laser heat input in unit volume, is adopted to evaluate the combined effect of the process parameters during SLM. The function is given as [5]: LED = p/vhd, where p is the laser power (W), v is the scanning speed (mm/s), h is the hatching space (mm), and d is the layer thickness (mm). The parameters
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