OBRABOTKAMETALLOV MATERIAL SCIENCE Vol. 24 No. 4 2022 produce parts with uniform structure and properties it is extremely important to prepare the material with the controlled composition which is a difficult task when different-type elementary powders are mixed. In the this paper the method of producing the powder composition by mechanical mixing was estimated to reduce the liability of powder elements to segregation. In the process of mixing finer powder is mixed with coarser one. The process of mechanical mixing suggests a new interesting approach to producing more homogeneous initial powder material which can potentially simplify studying the alloy construction for SLM use and developing new alloy compositions with unique structure. To produce parts with uniform structure and properties it is extremely important to prepare the material with the controlled composition. The structure of SLM produced alloys differs from that of traditionally cast ones in terms of grain size, growth and phase formation morphology due to rapid heating and cooling cycles. Extreme cooling speeds usually result in the formation of finer grains (≪1 µm) in comparison to the normal methods of hardening. The grain sizes in the SLM produced items can be controlled by changing the conditions of the melting process: higher scanning rate and lower resulting energy density allow obtaining finer microstructures. Increase of the scanning speed ensures larger amount of cooling in the molten pool which leads to higher hardening rate and slowing down of grain growth. The results of the study show that the produced powders of magnesium, silicon and aluminum are single-phased. Presence of impurity phases is possible, its proportion does not exceed 5 vol. %. The mechanical alloying of the powder composition (Al – 91 wt. %, Si – 8 wt. %, Mg – 1 wt. %) was conducted with the globe mill during one hour in the protective atmosphere of argon. The powder was made up of aluminum, silicon and magnesium with the particle size of 20–64 µm. Spherical particles were formed in the powder composition in the process of mixing. In the recent years SLM production of the parts was thoroughly studied. The studies concerned the changes in the conditions of the process: laser power, the rate of laser scanning, the beam diameter, the sampling interval. The current research was carried out with the application of the process parameters approaching such optimal melting conditions of preliminary alloyed Al-Si-Mg with the grain-size composition of particles of 20–64 µm. The results of the searching experiments show that the sample made at a speed of 300 mm/s showed the highest strength. The described study shows the possibility of synthesizing products from the powder composition of aluminum, silicon and magnesium by selective laser melting, but to produce samples with improved mechanical properties additional searching experiments are required with varying speed, diameter of the laser beam, changing the scanning strategy. Conclusion The initial powders of aluminum PA-4 (GOST 6058–73), silicon (GOST 2169–69) and magnesium MPF-4 (GOST 60001–79) were studied by the methods of X-ray diffraction and X-ray phase analysis which showed that the powders had single-phase structure. The study of SEM images showed that the aluminum powder consisted of conglomerates of irregular shape particles 1–20 µm in size, and larger particles 30–140 µm in size. The single-phased magnesium powder was a mixture of scaly particles, which size varied within 30–400 µm. The element composition of the powder corresponded to magnesium in the presence of oxygen no more than 2 wt. %. The single-phased silicon powder consisted of conglomerates 0.5–45 µm in size. The proportion of large conglomerates did not exceed 15 vol. %. Besides, it included small amounts of aluminum, titanium, calcium and oxygen (not more than 4%). The powder composition (Al – 91 wt. %, Si – 8 wt. %, Mg – 1 wt. %), which was used for producing the samples, was prepared by mixing the powders in the globe mill during one and two hours. The SEM images of the mixture of aluminum, magnesium and silicon powders after one hour of mechanical activation showed that the powder is presented by spherical and ellipsoidal aluminum particles which sizes vary within the range of 1–40 µm. There are also conglomerates of spherical particles 30 to 50 µm in size. The silicon particles in the powder mixture are presented by irregular agglomerates which sizes vary from 3 to 40 µm. The particles of mag-
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