Effect of forced convection by accelerating crucible rotation on directional solidification

An accelerated crucible rotation (ACR) technique was applied to the Bridgman (B) directional solidification of Al-Cu hypoeutectic and eutectic alloys. For Al-4.5% Cu hypoeutectic alloys. The development of dendrites was prevented and the cellular spacing was reduced by forced convection in the ACR-B process. For the Al-CuAl₂ eutectic alloy, maximum rotation rates of 100, 200, 300 and 400 rpm were adopted, and the growth rate R was varied between 5 and 60 μm/s. The results show that the periodic structure related to the crucible rotation periods occurs when the Reynold's number Re > 500, and that the average eutectic spacing decreases with the increase of Re. It is found that the convection increases the temperature gradient in front of the liquid/solid interface and reduces the depth of the concave interface, depending on Re and R. The convection also changes the solute distribution around the tips of the cells or dendrites or in front of the eutectic growth interface, and therefore influences the growth morphologies in the ACR-B process.