Effect of Cast Part Geometry and Face Coat Materials on Mold Metal Reactions during Investment Casting of Az91d Magnesium Alloy

Abstract

Recently, global attention is on the development of cast magnesium alloys due newlineto the higher strength-to-weight ratio. The inherent castability of magnesium newlineAZ91D alloy along with excellent mechanical properties draws significant attention newlineamong all other magnesium alloys. The magnesium alloy investment castings newlinehave greater potential for automobile, aircraft, and biomedical applications newlinebecause of the excellent performance of magnesium alloys and the capability of newlinethe investment casting process to produce near net shape complex castings. The newlineinterfacial mold-metal reactions is the main barrier for the development of the newlinemagnesium alloy components through the investment casting route, due to the newlinehigher affinity of the magnesium melt with oxygen. The reactions during the newlineinvestment casting of magnesium alloy hinder the successful production of quality newlinecastings. newlineThe uniform mold development and experimental conditions (i.e., melting, newlinehandling, and pouring practice) are desirable while studying interfacial mold-metal newlinereactions. The integrity of the primary coating determines the surface quality of the newlinecasting. The reactions occur at the interface between the primary coat and liquid newlinemetal. Therefore, the effect of slurry composition and mixing time on mold surface newlinefinish were studied and selected accordingly. Similarly, the effect of secondary newlinestucco size and the number of coatings on mold permeability and strength were newlinestudied and selected accordingly. The melting, handling, and pouring were carried newlineout in the presence of protective gas 3% SF6 + CO2 to prevent excessive burning newlineand oxidation. newlineIn the present work, the investigation was carried out to assess the influence newlineof the cast part thickness on interfacial mold-metal reactions during the investment newlinecasting of AZ91D magnesium alloy. The reactions were studied for the cast parts newlinewith uniform thickness and with varying thickness having adjoining sections. The newlinethermal profiles during the solidification were recorded using the thermocouples newlineand infrared camera. The r