The elemental and phase composition, the state of the defective substructure of eutectic silumin used for engineering were studied by the methods of scanning and transmission electron microscopy. The findings of the study show that silumin is a multiphase material and comprises, along with phases based on solid solutions of aluminum and silicon, intermetallic compounds of different composition. Particles of silicon and intermetallics have diverse forms and as a consequence they can both reinforce the material or cause microcracks in the process of product operation.