Solidification mechanisms of unmodified and strontium-modified hypereutectic aluminium-silicon alloys

Nogita, K., McDonald, S. D. and Dahle, A. K. (2004) Solidification mechanisms of unmodified and strontium-modified hypereutectic aluminium-silicon alloys. Philosophical Magazine, 84 17: 1683-1696. doi:10.1080/14786430310001659803


Author Nogita, K.
McDonald, S. D.
Dahle, A. K.
Title Solidification mechanisms of unmodified and strontium-modified hypereutectic aluminium-silicon alloys
Journal name Philosophical Magazine   Check publisher's open access policy
ISSN 1478-6443
1364-2812
Publication date 2004-01-01
Sub-type Article (original research)
DOI 10.1080/14786430310001659803
Volume 84
Issue 17
Start page 1683
End page 1696
Total pages 14
Editor James L. Smith
Lindsay Greer
Place of publication England
Publisher Taylor & Francis Ltd
Language eng
Subject 291302 Physical Metallurgy
671004 Castings
C1
Abstract The effects of strontium on the solidi. cation mode of hypereutectic aluminium-silicon alloys have been studied. Samples were prepared from an aluminium-17wt% silicon-based alloy and strontium was added at several different concentrations. The development of the microstructure was investigated by cooling curve analysis, interrupted solidi. cation experiments and optical and scanning electron microscopy. It was found that nucleation of primary silicon is suppressed by additions of strontium. The suppressed nucleation results in supersaturation of the liquid prior to nucleation, and an increased growth rate after nucleation. As a result, the silicon crystals become less faceted and more dendritic with increasing strontium additions. Increasing the strontium concentration slightly refined the eutectic spacing and introduced a small amount of fibrous silicon. Electron back-scatter diffraction measurements were performed to determine the crystallographic relation between the primary and eutectic silicon phases. The eutectic silicon in the unmodified alloy does not have any crystallographic relationship with the primary silicon crystals. In contrast, the eutectic silicon crystals in the strontium-modified alloys often share an identical or twin relationship with nearby primary silicon crystals. The incidence of twinning within primary silicon crystals was relatively low and did not appear to increase with strontium additions.
Keyword Materials Science, Multidisciplinary
Mechanics
Metallurgy & Metallurgical Engineering
Physics, Applied
Physics, Condensed Matter
Al-si Alloys
Eutectic Solidification
Growth
Sodium
Q-Index Code C1

Document type: Journal Article
Sub-type: Article (original research)
Collections: Excellence in Research Australia (ERA) - Collection
School of Mechanical & Mining Engineering Publications
 
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Created: Wed, 15 Aug 2007, 13:32:54 EST