The effect of technological parameters on the microstructure and properties of the AlSiMg alloy obtained by selective laser melting

Introduction. The development of additive technologies is aimed at the synthesis of new powder compositions for selective laser melting plants, the study of the effect of mode parameters on the stable quality of products. The purpose of this work is to study the effect of the scanning strategy on the microstructure, elemental composition, porosity and density of specimens obtained by selective laser melting from non-spherical powders (Al — 91 wt. %, Si — 8 wt. %, Mg — 1 wt. %), subjected to special preparation to determine the optimal conditions for selective laser melting. The research methods are methods of X-ray diffraction and X-ray phase analysis, transmission electron microscopy. The paper examines specimens formed using four different scanning strategies. Results and discussions. A promising aluminum alloy AlSi8Mg is developed for selective laser melting. The material has good manufacturability and low powder cost. The technological parameters of melting make it possible to form a thin structure with a low level of porosity. The mechanism of influence of the scanning strategy on porosity, surface morphology, relative density and microstructure is investigated. A specimen from the AlSi8Mg powder composition with a high relative density of 99.97 % is produced by selective laser melting with an energy density of 200 J/mm3, a specimen scanning circuit when the direction of laser movement changes by an angle of 90° each odd layer. It is proved that the density of the AlSiMg alloy depends on the scanning strategy used. The calculated density of the specimen was 2.5 g/cm3, which corresponds to the density of silumin. Analysis of SEM images and maps of the distribution of elements (Al, Mg, Si) of the specimens showed that different specimen formation strategies do not affect the nature of silicon distribution. A unique grain structure is observed in the resulting AlSi8Mg alloy. The melt pool consists of small grains along the border and large grains in the center. The formation of fine grains is explained by the addition of Si and the high cooling rate during selective laser melting.