Control of Al Content in Mg Melt by Addition of ZrCl₄

Abstract

ZrCl₄ was added into Mg-0.3Al model alloy in order to reduce the Al content in the castings below 0.005 mass%. Amount of ZrCl₄ was determined by thermodynamic calculation. Various Al-Zr intermetallic compounds were formed in the melt at 1013 K. Large intermetallic compounds would be floated to melt surface by Ar bubbling and then removed by skimming before pouring. Smaller ones remained after Ar bubbling and isothermal holding would be partially removed by filter inserted into a mold during pouring. The Al content in the castings was higher than that predicted by thermodynamic calculation due to incomplete removal of Al-Zr intermetallic compounds from the melt.