Effect of strontium and phosphorus on eutectic Al-Si nucleation and formation of beta-Al5FeSi in hypoeutectic Al-Si foundry alloys

Cho, Y.H., Lee, H.-C. and Dahle, A.K. (2008) Effect of strontium and phosphorus on eutectic Al-Si nucleation and formation of beta-Al5FeSi in hypoeutectic Al-Si foundry alloys. Metallurgical and Materials Transactions A - Physical Metallurgy and Materials Science, 39A 10: 2435-2448. doi:10.1007/s11661-008-9580-8


Author Cho, Y.H.
Lee, H.-C.
Dahle, A.K.
Title Effect of strontium and phosphorus on eutectic Al-Si nucleation and formation of beta-Al5FeSi in hypoeutectic Al-Si foundry alloys
Journal name Metallurgical and Materials Transactions A - Physical Metallurgy and Materials Science   Check publisher's open access policy
ISSN 1073-5623
Publication date 2008-07-15
Year available 2008
Sub-type Article (original research)
DOI 10.1007/s11661-008-9580-8
Open Access Status Not yet assessed
Volume 39A
Issue 10
Start page 2435
End page 2448
Total pages 14
Editor Laughlin, D.E.
Place of publication United States
Publisher Springer New York LLC
Language eng
Subject C1
8612 Fabricated Metal Products
091207 Metals and Alloy Materials
Abstract The present investigation was carried out on hypoeutectic Al-Si alloys containing two levels of Fe, 0.5 and 1.1 wt pct, and Sr in the range of 30 to 500 ppm. The addition of Sr in excess of 100 ppm significantly reduced the number of eutectic grains and also resulted in the formation of polygonal-shaped Al2Si2Sr intermetallics. Transmission electron microscopy studies revealed that the Al2Si2Sr phase surrounded the P-rich particles. This may suggest that the otherwise potent nuclei for the Al-Si eutectic, aluminum phosphide (AlP), become poisoned or deactivated by the formation of the Al2Si2Sr phase around the particles. At the high-Fe level (1.1 wt pct Fe), pre-eutectic formation of β-Al5FeSi platelets further reduced the number of eutectic Al-Si nucleation events. It is proposed that both eutectic silicon and β-Al5FeSi are preferentially nucleated on AlP particles. Nucleation of eutectic silicon, therefore, becomes more difficult when it is preceded by the formation of Al2Si2Sr or β-Al5FeSi, because fewer nuclei are available to nucleate silicon. Addition of up to 60 ppm P to the alloys increased the formation temperature of the β-Al5FeSi platelets but did not significantly alter the size, whereas the addition of Sr decreased the β-Al5FeSi nucleation temperature by reducing the potency of the AlP particles.
Q-Index Code C1
Q-Index Status Confirmed Code

 
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Created: Thu, 26 Mar 2009, 21:46:34 EST by Sally Beard on behalf of Materials