Effect of power ultrasound on solidification of aluminum A356 alloy

The present investigation attempted to evaluate the effect of ultrasonic vibration on the nucleation and growth of aluminum alloy A356 melt. A356 melt was treated at various solid fractions isothermally with ultrasonic vibrations by dipping the acoustic radiator into the melt. Experimental result confirmed that globular grains could be effectively obtained when the melt was ultrasonically treated at the temperature close to its liquidus and subsequently cooled quickly. It further illustrated the difficulty to form globular grains when the specimens were treated at isothermal temperatures in the mushy zone. It may imply that in the given experiments cavitations-induced heterogeneous nucleation plays a more important role than dendrite fragmentation in the formation of globular grains. (C) 2004 Elsevier B.V. All rights reserved.