Microstructure and strength analysis of eutectic Al-Si alloy in-situ manufactured using selective laser melting from elemental powder mixture

Abstract In this study, dense eutectic Al-Si alloys (about 99%) were in-situ fabricated using selective laser melting (SLM) from the powder mixture of Al and Si under argon environment. Compared with the sample obtained from pre-alloyed powder feedstock, a dense eutectic Al-Si alloy manufactured using SLM from powder mixtures needs higher input energy density. The effects of process parameters on microstructure and mechanical properties are investigated with particular emphasis on understanding the in-situ reaction during the SLM process. The microstructural analysis shows that the SLM processed samples present an ultrafine microstructure consisting of supersaturated Al-rich α-Al cellular and nano-sized Si particles. The distribution and morphology of nano-sized Si particles are significantly influenced by laser scanning speed and laser power respectively. The in-situ fabricated eutectic Al-Si alloy present a lower ultimate tensile strength and higher ductility than the sample fabricated from pre-alloyed powder. Moreover, both tensile strength and ductility of SLM processed eutectic Al-Si alloys decrease as the laser scanning speed increases.