Effect of carbon powder on grain refinement of an AZ91E magnesium alloy

Abstract

Grain refinement of cast magnesium alloys containing Al is attained by the well established technique of adding carbon materials. However, C2Cl6 as a grain refiner generates dioxin. Therefore, it is impossible to use grain refiners containing chloride. This study was performed to investigate grain refinement by adding carbon powder instead of harmful C2Cl6. Carbon is an important element for grain refining of commercial AZ91 magnesium alloy. Pure carbon powder was blown into the molten AZ91E magnesium alloy of 99.9% purity argon gas. Fine grains were obtained by adding the carbon powder. Foreign substances that functioned as nucleants could be observed in the center of each grain. The result of electron microprobe analysis indicated that the foreign substances were composed of Al, C and O.