Structure Formation in the Melt-Quenched Al–12.2Si–0.2Fe Alloys

The microstructure, the phase composition, the component distribution, and the grain structure of the commercial eutectic Al–12.2 Si–0.2 Fe (at %) silumins formed at cooling rates of 10 2 and 10 5 K/s are studied. Three phases are detected in the alloy after solidification at both cooling rates: α-aluminum, silicon, and an iron-containing phase. The bulk samples have a heterogeneous dendritic structure with large dendrites of an aluminum-based solid solution, and a eutectic lamellar mixture of aluminum and silicon filling the interdendritic space. The melt-quenched foils are characterized by a homogeneous microstructure over the thickness; however, they have a layered structure. The rapidly solidified foils also have a homogeneous granular structure through the thickness and no pronounced texture. The mechanisms of solidification and microstructure formation are proposed for both the bulk samples and the melt-quenched foils.