Multistep nucleation and multi-modification effect of Sc in hypoeutectic Al-Mg-Si alloys

Structure of Al5Mg2SiMn casting alloy with and without of Sc addition, morphology of primary phases and specifically morphology of the Sc-containing intermetallic compounds and nanoscale properties of the α-Al matrix of Al-Mg-Si-Mn alloys were observed. Morphology and chemical composition were investigated by scanning electron microscopy on polished and deep etched microsections. It was found that addition of Sc changes morphology of α-Al, Al-Mg(2)Si eutectic and intermetallic compounds with Mn. α-Al dendrites change their morphology to spherical, lamellar Al-Mg(2)Si eutectic to fine fibrous eutectic. It was found that crystals Al(3)Sc can act as nucleating particles of α-Al grains, as well as Mg(2)Si eutectic fibrous. The mechanisms of nucleation can be attributed to heterogeneous nucleation.