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Home  >  Journal list  >  MATERIALS TRANSACTIONS  >  Vol.42  No.9 (2001)  >  pp.1981-1986

MATERIALS TRANSACTIONS
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Eutectic Solidification Mode in Sodium Modified Al-7 mass%Si-3.5 mass%Cu-0.2 mass%Mg Casting Alloys

Kazuhiro Nogita1), Stuart David McDonald1), Jacob Wesley Zindel2) and Arne Kristian Dahle1)
1) Department of Mining, Minerals and Materials Engineering, The University of Queensland
2) Materials Science Department, Ford Research Laboratory


The influence of sodium (Na) on nucleation and growth of the Al–Si eutectic in a commercial hypoeutectic Al–Si–Cu–Mg foundry alloy has been investigated. The microstructural evolution during eutectic solidification was studied by a quenching technique. By comparing the orientation of the aluminium in the eutectic to that of the surrounding primary aluminium dendrites by EBSD, the eutectic solidification mode could be determined. The results show that the eutectic solidification starts near the mould wall and evolves with front growth opposite the thermal gradient on a macro-scale, and on a micro-scale with independent heterogeneous nucleation of eutectic grains in interdendritic spaces. Na-modified alloys therefore behave significantly differently from those modified by other elemental additions.


Keyword:
aluminium-silicon alloy, sodium, modification, eutectic, solidification, electron back-scatter diffraction, quenching

Received: June 04, 2001
Accepted: July 16, 2001 , Published online: September 06, 2005
Copyright (c) 2005 The Japan Institute of Metals

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