Aluminium alloys - their physical and mechanical properties: Grain formation in AlSi7Mg0.35 foundry alloy at low superheat

Dahle, A. K., St John, D. H., Attavanich, P. and Taopetch, P. (2000) Aluminium alloys - their physical and mechanical properties: Grain formation in AlSi7Mg0.35 foundry alloy at low superheat. Materials Science Forum, 331-337 : 271-276.


Author Dahle, A. K.
St John, D. H.
Attavanich, P.
Taopetch, P.
Title Aluminium alloys - their physical and mechanical properties: Grain formation in AlSi7Mg0.35 foundry alloy at low superheat
Journal name Materials Science Forum   Check publisher's open access policy
Publication date 2000
Sub-type Article
Volume number 331-337
ISBN 0-87849-853-2
ISSN 0255-5476
Start page 271
End page 276
Total pages 6
Editor G. E. Murch
F. H. Wohlbier
Place of publication Switzerland
Publisher Trans Tech Publications
Collection year 2000
Language eng
Subject C1
671004 Castings
0912 Materials Engineering
Abstract Hypoeutectic AI-Si alloys represent the most widely used alloy system for cast aluminium applications. This system has a unique behaviour with respect to grain formation where an increase in silicon content results in a transition to larger grain sizes after a minimum at an intermediate concentration. As a result of the already large solute content, grain refinement by solute additions is inefficient and nucleant particles from the common aluminium grain refiners are not as effective as in wrought alloys. However, casting conditions, such as a low pouring temperature, that promote the formation of wall crystals tie. crystals nucleated in the thermally undercooled layer at or next to mould walls) are very effective in yielding a small grain size. This paper presents results of an investigation of the effect of low superheat and mould preheat temperature on grain size. It was found that pouring temperature controls the effectiveness of the wall mechanism while mould preheat has little effect until high preheat temperatures at which a large increase in grain size occurs. The observed changes in grain size are explained in terms of the balance between nucleation rate and survival rate of crystal nuclei resulting from changes in superheat and mould temperature.
Keyword Materials Science, Multidisciplinary
Al-si Alloy
Casting
Grain Refinement
Nucleation
Solidification
Superheat
Al-si Alloys
Q-Index Code C1

Document type: Journal Article
Sub-type: Article
Collection: School of Mechanical & Mining Engineering Publications
 
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Created: Mon, 13 Aug 2007, 11:54:42 EST