OBRABOTKAMETALLOV Vol. 26 No. 1 2024 TECHNOLOGY This work is aimed at synthesizing a composite powder of a circumspherical shape Al-Si-Mg (Al – 91 wt. %, Si – 8 wt. %, Mg – 1 wt. %) from powders of PA-4 aluminum (GOST 6058-22), silicon (GOST 216969) and magnesium MPF-4 (GOST 6001-79), which were not originally intended for selective laser melting technology, and optimization of SLM modes to produce an alloy and form three-dimensional specimens with minimal porosity and zero cracking [20]. To achieve this goal, it is necessary to complete the following tasks: to obtain a powder composition from the mixture of single-component powders with circumspherical particles; to determine the structural and phase composition of the resulting composition of powders using scanning electron microscopy, X-ray diff raction and X-ray phase analysis; to form the specimens using selective laser melting technology; to determine the optimal energy density to ensure minimum porosity of the specimens; to anneal the specimens; to determine the microhardness of the specimens before and after annealing; to study the structural-phase composition of the specimen using transmission microscopy. Research methods Single-component aluminum, silicon and magnesium powders were subjected to sieve analysis to obtain the Al-Si-Mg powder composition. Particles with the size of 20–64 μm are optimal for selective laser melting technology. The distribution of the fractional composition of aluminum powder is shown in fi gure 1. Fig. 1. Particle size distribution of PA-4 powder (GOST 6058-22) X-ray structural and X-ray phase analysis were performed on a DRON-7 X-ray diff ractometer (Burevestnik, Russia). Scanning electron microscopy was carried out on a LEO EVO scanning electron microscope at the Nanotech Shared Use Center [20]. Specimens with a size of 10×10×2 mm were produced on a VARISKAF-100MVS 3D printer, which is equipped with a 100 W ytterbium fi ber laser. The scanning speed V was chosen as the fi rst variable factor of SLM: 225, 250, 275, 300 mm/s, the second variable factor was the scanning step S: 0.09, 0.08, 0.07 mm. The power of continuous laser radiation P was 90 W, the thickness of the powder layer h = 0.025 mm, the protective medium was argon, the temperature of the working table at the beginning of the SLM cycle was +25 °C. Then the specimens were subjected to grinding and polishing with diamond pastes, removing the top layer of about 400 μm. Porosity was determined as the average of nine optical images of the polished section surface. The specimens were annealed at a temperature of 400 ºC for 5 hours.
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