Effects of Mold Materials on the Interfacial Reaction between Magnesium Alloy and Ceramic Shell Mold during Investment Casting

In order to suppress the interfacial reaction between the ceramic shell mold and the magnesium molten alloy during the investment casting process, a mold material with a high thermodynamic stability based on alkaline zirconium sol (CH4NO3Zr) binder and corundum (Al2O3) powder was prepared. The effects of the mold materials and casting thicknesses on the interfacial reaction were investigated by an optical microscope, X-ray diffraction, a scanning electron microscope, and an energy dispersive spectroscope analysis. The results suggested that the casting poured by the conventional ZrSiO4 mold has a serious reaction on the surface, and the reaction was more severe when the casting thickness was increased. The oxidation layer was approximately 300 μm in some severe areas of 45 mm thickness. The XRD and EDS results showed that the reaction interface mainly contains MgO and Mg2Si. While the casting poured by the Al2O3 mold provides a light and smooth surface, the reaction layer was only 1.5 μm on average. The reaction interface mainly contains MgO and Mg2F.