A rotating disk study of impurity segregation in aluminum alloy solidification

Abstract

The presence of impurities during the solidification of aluminum alloys can be detrimental to alloy properties and performance. As aluminum manufacturers aim to increase the amount of recycled scrap in direct-chill cast aluminum ingots, they face rising levels of impurities that threaten the quality of the aluminum alloys produced. The harmful effects of impurities are exacerbated by convection-induced macrosegregation of impurities within ingots, which leads to local regions of accumulation or depletion of impurity-containing intermetallic compounds. A small-scale rotating disk experimental approach was used to study the segregation of iron, the most common impurity in aluminum alloys, in the presence of forced convection. Applying forced convection was found to deplete iron from solidified aluminum, and evidence for the entrainment of iron within fluid flow streamlines was observed. The rotating disk system is shown to be a promising experimental approach for further research in the solidification of aluminum alloys.