Microstructural Evolution during Partial Remelting of Al-Si Alloys Containing Different Amounts of Magnesium

The effect of magnesium on the microstructures of A356 aluminum alloy in as-cast and semi-solid conditions was investigated. The result showed that magnesium refined the size of primary alpha(Al) phase and eutectic silicon. Magnesium also modified considerably the eutectic silicon and decreased the size of globular alpha(Al) solid phase in the semi-solid processed alloy. Coarsening rate of the solid alpha(Al) phase during partial remelting at semi-solid temperature decreased by adding magnesium, probably due to the decrease of both the solid-liquid interfacial energy and inter-diffusion coefficient of solute atoms.