Studies of the microstructure, phase composition, component distribution, and grain structure of industrial technical eutectic silumin with composition Al–12.2Si–0.2Fe (at %) obtained at cooling rates of 102 and 105 K/s. At both cooling rates, the alloys are characterized by three phases: α-aluminum, silicon, and iron-containing phase. Massive samples are characterized by a heterogeneous dendritic structure representing large dendrites of a solid solution based on aluminum, and a eutectic lamellar mixture of aluminum and silicon filling the interdendritic spacing. The rapidly solidified foils are characterized by a uniform microstructure, however, they have a thickness layering. The rapidly solidified foils are also distinguished by the homogeneity of the grain structure in thickness and the absence of any pronounced texture. The mechanisms of solidification and the formation of a microstructure are proposed, both for massive samples and for rapidly solidified foils.