The segregation of copper and silicon in Al-Si-Cu alloy during electromagnetic centrifugal solidification

Abstract

The present paper investigates the segregation of copper and silicon in an Al–lwt%Cu–lwt%Si alloy solidified under the co-action of centrifugal and electromagnetic forces. The reasons for the solute segregation and the effect of electromagnetic force on segregation are discussed. Tubular samples cut from the solidified alloy are analyzed, the results showing that the segregation of copper and silicon occurs along the normal direction of the samples and that the electromagnetic field has a remarkable influence on the segregation of both copper and silicon. As the exciting current increases, the segregation of copper decreases, while the segregation of silicon first increases and then decreases. The migration of solute atoms in the melt depends not only on the density difference between the solute and aluminum atoms, but also on the strength of the electromagnetic force. The magnetic force changes the rotation velocity of the melt, reduces the migration velocity of copper and causes the reduction of copper segregation. Because of the difference of the electrical conductivity between the solute and the aluminum melt, the reductions of velocity are not equal.