Feeding and Distribution of Porosity in Cast Al-Si Alloys as Function of Alloy Composition and Modification

Niels Skat Tiedje, John A. Taylor, Mark A. Easton

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Abstract

Unmodified, Na-modified, and Sr-modified castings of Al-7 pct Si and Al-12.5 pct Si alloys were cast in molds in which it was possible to create different cooling conditions. It is shown how solidification influences the distribution of porosity at the surface and the center of the castings as a function of modification and Si content in sand- and chill-cast samples. Eutectic modification, Si content, and cooling conditions have a great impact on the distribution of porosity. Unmodified and Na-modified castings are more easily fed with porosity tending to congregate near the centerline of the casting, while Sr-modified castings solidify in a mushy manner that creates a more homogeneous distribution of porosity in the casting. The amount of porosity was highest in the Sr-modified alloys, lower in the Na-modified alloys, and lowest in the unmodified alloys. The size of the porosity-free layer and the effectiveness of the feeders were greater in the castings made with the steel chills due to the increased thermal gradients and consequent increase in the directionality of solidification.
Original languageEnglish
JournalMetallurgical and Materials Transactions A - Physical Metallurgy and Materials Science
Volume43
Issue number12
Pages (from-to)4846-4858
ISSN1073-5623
DOIs
Publication statusPublished - 2012

Bibliographical note

© The Minerals, Metals & Materials Society and ASM International 2012

Cite this

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title = "Feeding and Distribution of Porosity in Cast Al-Si Alloys as Function of Alloy Composition and Modification",
abstract = "Unmodified, Na-modified, and Sr-modified castings of Al-7 pct Si and Al-12.5 pct Si alloys were cast in molds in which it was possible to create different cooling conditions. It is shown how solidification influences the distribution of porosity at the surface and the center of the castings as a function of modification and Si content in sand- and chill-cast samples. Eutectic modification, Si content, and cooling conditions have a great impact on the distribution of porosity. Unmodified and Na-modified castings are more easily fed with porosity tending to congregate near the centerline of the casting, while Sr-modified castings solidify in a mushy manner that creates a more homogeneous distribution of porosity in the casting. The amount of porosity was highest in the Sr-modified alloys, lower in the Na-modified alloys, and lowest in the unmodified alloys. The size of the porosity-free layer and the effectiveness of the feeders were greater in the castings made with the steel chills due to the increased thermal gradients and consequent increase in the directionality of solidification.",
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Feeding and Distribution of Porosity in Cast Al-Si Alloys as Function of Alloy Composition and Modification. / Tiedje, Niels Skat; Taylor, John A.; Easton, Mark A.

In: Metallurgical and Materials Transactions A - Physical Metallurgy and Materials Science, Vol. 43, No. 12, 2012, p. 4846-4858.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - Feeding and Distribution of Porosity in Cast Al-Si Alloys as Function of Alloy Composition and Modification

AU - Tiedje, Niels Skat

AU - Taylor, John A.

AU - Easton, Mark A.

N1 - © The Minerals, Metals & Materials Society and ASM International 2012

PY - 2012

Y1 - 2012

N2 - Unmodified, Na-modified, and Sr-modified castings of Al-7 pct Si and Al-12.5 pct Si alloys were cast in molds in which it was possible to create different cooling conditions. It is shown how solidification influences the distribution of porosity at the surface and the center of the castings as a function of modification and Si content in sand- and chill-cast samples. Eutectic modification, Si content, and cooling conditions have a great impact on the distribution of porosity. Unmodified and Na-modified castings are more easily fed with porosity tending to congregate near the centerline of the casting, while Sr-modified castings solidify in a mushy manner that creates a more homogeneous distribution of porosity in the casting. The amount of porosity was highest in the Sr-modified alloys, lower in the Na-modified alloys, and lowest in the unmodified alloys. The size of the porosity-free layer and the effectiveness of the feeders were greater in the castings made with the steel chills due to the increased thermal gradients and consequent increase in the directionality of solidification.

AB - Unmodified, Na-modified, and Sr-modified castings of Al-7 pct Si and Al-12.5 pct Si alloys were cast in molds in which it was possible to create different cooling conditions. It is shown how solidification influences the distribution of porosity at the surface and the center of the castings as a function of modification and Si content in sand- and chill-cast samples. Eutectic modification, Si content, and cooling conditions have a great impact on the distribution of porosity. Unmodified and Na-modified castings are more easily fed with porosity tending to congregate near the centerline of the casting, while Sr-modified castings solidify in a mushy manner that creates a more homogeneous distribution of porosity in the casting. The amount of porosity was highest in the Sr-modified alloys, lower in the Na-modified alloys, and lowest in the unmodified alloys. The size of the porosity-free layer and the effectiveness of the feeders were greater in the castings made with the steel chills due to the increased thermal gradients and consequent increase in the directionality of solidification.

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JO - Metallurgical and Materials Transactions A - Physical Metallurgy and Materials Science

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