Microstructure of selective laser melted AlSi10Mg alloy

Highlights: • The nucleation at the border of melt pool and the columnar to equiaxed transition are responsible for the formation of equiaxed grains. • Fine pseudoeutectic structure was observed in SLMed AlSi10Mg alloy because of the rapid solidification. • The gradient microstructure is caused by the different temperature zones during the heating of laser beam. • Coarse zones are formed by reheating the basic metal to semi-solid state when the temperature is at mushy zone. -- Abstract: The influence of laser power during selective laser melting (SLM) on the grain morphology and texture component in AlSi10Mg alloy has been investigated, using electron backscattered diffraction (EBSD). Both equiaxed and columnar grains were observed. The formation of equiaxed grains was attributed to the huge thermal gradient on the border of melt pool and the columnar to equiaxed transition (CET) occurred in front of the columnar grains. The grain size of low laser power sample was found smaller than that of higher ones. A fine pseudoeutectic structure, in which Si existed as fibrous, was observed because of the high cooling rate. This paper, from a new angle, explained the formations of three different zones across the melt pool, which were differentiated by the morphology of Si phase. The three zones correspond to the three temperature zones, which were divided by liquidus and solidus temperature, during the heating by laser beam. The coarse zones are formed by reheating the basic metal to semi-solid state when the temperature is lower than the liquidus temperature but higher than the solidus temperature.