Investigation on Influence of the Cast Part Thickness on Interfacial Mold-Metal Reactions During the Investment Casting of AZ91 Magnesium Alloy

The interfacial mold-metal reactions are the main barrier for the development of the magnesium alloy components through the investment casting route, owing to the higher affinity of the magnesium melt with oxygen. The molds are developed with refractory ceramic oxides mainly in the investment casting process. In the present paper, an attempt was made to investigate the influence of the cast part thickness on interfacial mold-metal reactions during the investment casting of AZ91 magnesium alloy. The thermal profiles during the solidification were recorded using the thermocouples and infrared camera. The reactions on the cast surface were quantified and characterized by image analysis, XRD, SEM-EDX and microhardness profile. It was observed that with the increase in thickness, the interfacial mold-metal reaction increases. The surface hardness was also found to be increased with the increase in thickness of the cast part as a consequence of the oxide formation on the cast surface. The reactions on the casting having connected regions of the varying thickness were observed to be relatively more as compared to the casting with the uniform thickness.