Internal cooling to produce aluminium alloy slurries for rheocasting

Rheocasting is becoming the choice of the casting industry which relies on the semi-solid processing for high integrity structural parts. It is thus of great technological interest to identify simple methods to prepare slurries at reduced cost. The potential of internal cooling to produce slurries for rheocasting was investigated in the present work for several aluminium casting alloys which are technologically important for aluminium foundries. Alloys quenched directly from the liquid state were predominantly dendritic while the slurry samples quenched after an initial fraction of solid phase was first formed, were dominated by alpha-Al rosettes and globules. The solidification of the remaining liquid phase occurred through the growth of the alpha-Al rosettes and globules which have formed during internal cooling before quenching. (C) 2009 Elsevier B.V. All rights reserved.