MATERIALS TRANSACTIONS
Online ISSN : 1347-5320
Print ISSN : 1345-9678
ISSN-L : 1345-9678
Determination of Eutectic Solidification Mode in Sr-modified Hypoeutectic Al-Si Alloys by EBSD
Kazuhiro NogitaArne Kristian Dahle
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2001 Volume 42 Issue 2 Pages 207-214

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Abstract

The effect of eutectic modification by strontium on nucleation and growth of the eutectic in hypoeutectic Al–Si foundry alloys has been investigated by electron back-scattering diffraction (EBSD) mapping. Specimens were prepared from three hypoeutectic Al–Si base alloys with 5, 7 and 10 mass%Si and with different strontium contents up to 740 ppm for modification of eutectic silicon. By comparing the orientation of the aluminium in the eutectic to that of the surrounding primary aluminium dendrites, the growth mode of the eutectic could be determined. The mapping results indicate that the eutectic grew from the primary phase in unmodified alloys. When the eutectic was modified by strontium, eutectic grains nucleated separately from the primary dendrites. However, in alloys with high strontium levels, the eutectic again grew from the primary phase. These observed effects of strontium additions on the eutectic solidification mode are independent of silicon content in the range between 5 and 10 mass%Si.

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© 2001 The Japan Institute of Metals and Materials
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