The influence of impurities with different sizes and number densities on the evolution of the microstructure and mechanical properties of alloys with
different Mg contents has been studied. Phase analysis showed that in the studied alloys, in addition to crystals of a complex alloy solid solution based on aluminum, there are structural components of eutectic or peritectic origin located along the boundaries of dendritic cells. Based on the results of phase analysis and phase morphology, it can be assumed that the phases or structural components of Mg2Si, (Al, Fe, Mn, Ni, Cu), S(Al2CuMg), β(Al3Mg2) should most significantly reduce the mechanical properties and especially the ductility of cast alloys condition).