Direct fabrication of high-purity magnesium ingot using vacuum distillation technology

Abstract

The conventional vacuum distillation technique for fabricating high-purity Mg faces challenges involving the difficulty of collecting fine Mg crystals and a reduction in purity due to remelting. In this study, a novel apparatus was designed to purify crude Mg and directly fabricate a high-purity Mg ingot, which overcomes the shortcomings of the conventional technique and shortens the process flow. A numerical simulation was conducted to investigate the formation mechanisms of distillates with different morphologies in different crucibles. It was found that Mg vapor could be changed to liquid in the crucibles in the middle part by adjusting the temperature and pressure; thus, a high-purity Mg ingot could be obtained, whereas only Mg crystals could be obtained by changing from vapor to solid in the crucibles in the rear part. Furthermore, the contents of some impurity elements (Mn, Pb, Al, and Ca) in the high-purity Mg ingot first decreased and then increased with an increase in the load temperature, with 973 K being the optimal load temperature. However, the purification of Zn impurities was limited. Finally, a high-purity Mg ingot with a mass greater than 100 g and purity higher than 99.996 % (4N6) was successfully fabricated, with the yield ratio reaching 65 % using the present apparatus. This study provides a new technique for the direct fabrication of high-purity Mg ingots.