Selective laser melted AlSi10Mg alloy under melting mode transition: Microstructure evolution, nanomechanical behaviors and tensile properties

The effect of the volumetric energy density (VED) on the keyhole formation, microstructural evolution and associated mechanical properties of AlSi10Mg fabricated by selective laser melting (SLM) has been systematically investigated. The results indicated that three melting modes could be distinguished during the laser melting process, corresponding to different VED ranges, i.e. conduction mode (<50 J mm(-3)), transitional mode (similar to 50-65 J mm(-3)), and keyhole mode (>65 J mm(-3)). A high VED not only produced keyhole defects and hydrogen pores, but also generated two types of molten pool, i.e. a general shallow molten pool (GSP) and a keyhole-induced deep molten pool (KDP). The GSP was mainly consisted of an a-Al matrix, with similar to 30 mu m grains size, and enclosed by a similar to 500 nm eutectic Si cellular network. The grain size of the KDP was less than 15 mu m, and it has both a finer Si network (similar to 200 nm) and nano-scale Si particles. No preferential crystallographic orientation could be observed within the KDP, while a strong texture along <111> orientation was exhibited in the GSP. These were responsible for the different mechanical properties of the SLM parts under different melting modes. The related mechanisms of the GSP and the KDP formation are comprehensively discussed and a correlation between the microstructure and the mechanical properties is also outlined. (c) 2021 Elsevier B.V. All rights reserved.

Automated summary

The effect of volumetric energy density (VED) on the fabrication of AlSi10Mg alloy by selective laser melting (SLM) was investigated, revealing different melting modes and resulting in varied microstructural evolution and mechanical properties. Higher VED led to the formation of keyhole defects and two types of molten pools, affecting the grain size, Si network, and mechanical properties of the SLM parts differently.