Effect of the melt cooling rate on the structural-phase state of the Al – Si alloy doped with metals

The paper presents the results of a study of the microstructure, elemental and phase compositions of the eutectic alloy Al – 12.5 wt. % Si – 0.8 wt. % Mg – 0.4 wt. % Mn – 0.7 wt. % Fe – 0.9 wt. % Ni – 1.8 wt. % Cu. A comparison of the microstructure of the alloy obtained at melt cooling rates of 102 and 105 K/s is made. It is shown that an increase in the melt cooling rate leads to refinement of structural components, a decrease in the volume fraction of primary α-Al dendrites, an increase in the volume fraction of a mixture of eutectic silicon and aluminum, and a decrease in the silicon concentration in the interdendritic space from 23 to 13 wt. %. Using X-ray spectrum microanalysis and X-ray diffraction analysis, it was revealed that inclusions of intermetallic compounds Mg5Si6, Al17(FeMn)Si2, Al3(CuNi)2 are formed at melt cooling rates of 102 and 105 K/s. A mechanism of the formation of a layered microstructure of a eutectic alloy is proposed. An explanation for the formation of X-ray amorphous nanosized particles in the foil layer adjacent to the mold is given.