Mechanical properties and microstructure of heat-resistant Mg-Al-Ca alloys formed by thixomolding

Thixomolding is a new process in which the metallic slurry is injected into a die cavity at semi-solid temperatures to form near net-shape products from the solid feed stock in one step. The relationship between the chemical composition and the mechanical properties of heat-resistant Mg-Al-Ca alloys formed by thixomolding was investigated. The effect of a variable such as barrel temperature was also studied. It was found that the addition of Ca is effective in improving the tensile strength and creep resistance of the alloys at elevated temperatures. The ductility is decreased with increasing Ca content. The microstructure of specimens was observed with SEM and TEM. It showed a fine structure consisting of granular primary a Mg solid solution and a network consisting of eutectic a and intermetallic compounds. The morphology of this network varies depending on Ca content.