OBRABOTKAMETALLOV Vol. 26 No. 1 2024 TECHNOLOGY Fig. 8. SEM images and distribution maps of elements (Al, Mg, Si) of specimens after annealing a b c d The elemental composition showed that the elements in the specimen are distributed as follows: aluminum – 88.6 wt. % and 88.2 at. %, silicon – 9.9 wt. % and 9.5 at. %, magnesium – 1.5 wt. % and 2.3 at. %. The microhardness of the annealed specimen was 722MPa in the longitudinal section and 710MPa in the cross section. The decrease in microhardness by almost 50 % during the heat treatment strictly depends on the microstructural changes. All the studies reviewed note the decrease in strength after the heat treatment. In all the considered works, there is a decrease in strength after heat treatment, which becomes more intense with increasing temperature or duration of heat treatment. These changes in mechanical behavior follow quite directly from the gradual decrease of the supersaturation of α-Al matrix, rupture of the Si network and continuous growth of relatively large Si particles. Studies of the structural-phase state of the specimen were carried out using a JEOL JEM-2100 transmission electron microscope. It showed that the specimen under study had a grain structure, as can be seen in fi gure 9. Microscopic pores were not detected on the specimen under study in the area accessible for study with the magnifi cations used. The given work showed that pre-prepared non-spherical powder materials can be used for selective laser melting. Formation of three-dimensional specimens with minimal porosity and absence of cracking by the SLM method from aluminum PA-4 (GOST 6058-22), silicon (GOST 2169-69) and magnesium MPF-4 (GOST 6001-79) powders, which were not originally intended for selective laser melting technology, has experimentally proven possible under certain modes. The Al-Si-Mg alloy is well processed using SLM within the established processing modes, where the constructed specimens can reach a material density of more than 99.7 % without cracking during solidifi cation or large metallurgical defects.
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