Nucleation mechanism of the eutectic phases in aluminum–silicon hypoeutectic alloys

A theory is presented to explain the mechanism of formation of the eutectic phases in Al–Si hypoeutectic alloys. Results include optical, scanning and transmission electron microscopy, as well as selected area electron diffraction analysis and elemental X-ray mapping performed on Al–Si hypoeutectic alloy samples. The alloy samples had precisely controlled chemistry and were solidified at various cooling rates. The data presented support the proposed theory with microstructural and crystallographic evidence.