Effect of the Intensity of Melt Shearing on the As Cast Structure of Direct Chill Cast 2024 Aluminum Alloy

Intensive melt shearing was achieved by a stator–rotor high-shear unit and was used in the sump during direct chill (DC) casting process to investigate the influence of the rotation speed on the as cast structure of an aluminum alloy. It has been demonstrated that intensive melt shearing has a significant effect on achieving a uniform temperature distribution and obtaining a fine and uniform as cast structure. We also found that the intensity of the melt shearing plays an important role in the effect. As the rotation speed increases, the melt around the high-shear unit transformed from a liquid to a semisolid state. At a rotation speed of 3000 rpm, intensive melt shearing can only increase the nuclei through fragmentation in the region close to the solidification front by forced convection. When the rotation speed increases to 6000 rpm, intensive melt shearing can also evidently increase the number of effective nuclei, mainly by increased fragmentation in a large volume around the high-shear unit.