Impurity distribution in preparation of high-purity aluminum by vacuum zone melting

A novel vacuum zone melting process for preparing high-purity Al was proposed. The axial segregation of impurities was investigated by determining the equilibrium distribution coefficient. Theoretical and experimental results showed that impurities (Cu, Si, and Fe) with an equilibrium distribution coefficient k(0)<1 accumulated in the tail of the Al ingot, while Ti (k(0) >1) accumulated at the head end of the ingot. When the molten area moving at 1.5 mm/min and zone melting was performed 15 times, the removal rate of the impurities and the purity of Al were the highest. In the middle of the Al ingot, i.e. 140 mm away from the head end of the sample, the removal rates of Cu, Fe, and Si were higher than 90%, that of Ti was higher than 75%, and the Al content was higher than 99.999%. The purity of the Al samples met the requirements of the commercial 99.999% (5N) high-purity Al standard.