Refining grain structure and porosity of an aluminium alloy with intensive melt shearing

Intensive melt shearing was achieved using a twin-screw machine to condition an aluminium alloy prior to solidification. The results show that intensive melt shearing has a significant grain-refining effect. In addition, the intensive melt shearing reduces both the volume fraction and the size of porosity. It can reduce the density index from 10.50% to 2.87% and the average size of porosity in the samples solidified under partial vacuum from around 1 mm to 100 mu m. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.