OBRABOTKAMETALLOV Vol. 26 No. 1 2024 TECHNOLOGY powder, which resulted in high consolidation with an overall porosity level of less than 1%. There were no cracks in all samples. To refl ect the combined infl uence of laser power, scanning speed, scanning step and layer thickness on the material density the energy input EV was calculated by the following formula [25]: EV = Р/V h S where P is the laser power (W), V is the scanning speed (mm/s), s is the scanning step (mm), h is the thickness of the powder layer (mm). The energy density for obtaining specimens from the powder composition with aluminum measuring 20–64 μm with minimal porosity is 200 J/mm3. Conclusion Thus, the conditions for obtaining a powder composition and processing modes for producing a SLM Al-Si-Mg alloy were systematically studied and the optimal processing SLM range was established. The infl uence of the SLM mode on porosity and microhardness was also studied. The following conclusions can be made. From metal powders that are not suitable for processing by selective laser melting, it is possible to obtain a powder composition with circumspherical particles, recommended for use in SLM units. Powders with the particle size of 20–64 μm were combined in the weight proportion of Al – 91 wt. %, Si – 8 wt. %, Mg – 1 wt. %, and then subjected to mixing in a ball mill for one hour in the protective argon atmosphere to prevent the formation of oxides and the undesirable eff ect of oxygen on the structure and phase composition of the resulting powder. The time of mechanical alloying equal to 40 and 50 minutes is not enough to obtain a circumspherical shape. Analysis of the X-ray diff raction pattern of the powder composition allowed us to identify the phases of aluminum, silicon and magnesium. The phase composition was established as follows: aluminum – 91 %, silicon – 8 % and magnesium – 1 %. SEM images of the powder composition produced after mechanical mixing for one hour showed that spherical particles and irregularly shaped satellites with particle sizes from 1 to 170 μm predominate in the powder. The optimal SLM mode for forming a specimen with the minimal porosity of 0.03 % from an Al-Si-Mg alloy is as follows: laser power of 90 W, scanning speed of 225 mm/s, scanning step S = 0.08 mm, powder layer thickness of 0.025 mm, argon protective medium. The temperature of the working table at the beginning of the SLM cycle was +25 °C. The energy density is 200 J/mm3. The relative density of materials produced in this range exceeds 99.7 %. There are no cracks. The microhardness of the fi nished specimens is in the range from 1.243 to 1.291 MPa. SEM images and distributionmaps of the elements in the specimens produced fromaluminum,magnesium and silicon powders showed that the elements are distributed uniformly over the entire synthesized surface. The specimens annealed under the temperature of 400 ºC for 5 hours have a more dense structure, while the microhardness decrease by almost 50 %. Optimal heat treatment conditions need to be further studied. Studies of the structural-phase state of the specimen using transmission electron microscopy showed that the specimen under study has a dense grain structure. References 1. Bandyopadhyay A., Heer B. Additive manufacturing of multi-material structures. Materials Science and Engineering: R, 2018, vol. 129, pp. 1–16. DOI: 10.1016/j.mser.2018.04.001. 2. DebRoy T., Wei H.L., Zuback J.S., Mukherjee T., Elmer J.W., Milewski J.O., Beese A.M., Wilson-Heid A., De A., Zhang W. Additive manufacturing of metallic components – process, structure and properties. Progress in Materials Science, 2018, vol. 92, pp. 112–224. DOI: 10.1016/j.pmatsci.2017.10.001.
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