Eutectic nucleation in Al-Si alloys

Journal Article · Mon Aug 16 04:00:00 EDT 2004 · Acta Materialia

DOI:https://doi.org/10.1016/j.actamat.2004.05.043· OSTI ID:20634749

McDonald, Stuart D; Nogita, Kazuhiro; Dahle, Arne K

In addition to a change in silicon morphology, modification of aluminium-silicon alloys with strontium or sodium increases the size of the eutectic grains. To determine the mechanism responsible, eutectic solidification in commercial purity and ultra-high purity aluminium-silicon alloys, with and without strontium additions, was examined by a quenching technique. In the commercial unmodified alloy, nucleation was prolific while in the high-purity unmodified alloy few eutectic grains nucleated. The addition of strontium to the commercial alloy reduced the number of eutectic grains that nucleated. Addition of strontium to the high-purity alloy did not significantly alter nucleation. It is concluded that commercial purity alloys contain a large number of potent nuclei that are susceptible to poisoning by impurity modification. The flake-to-fibre transition that occurs with impurity modification is shown to be independent of any change in eutectic nucleation mode and frequency.

• OSTI ID: 20634749
• Journal Information: Acta Materialia, Journal Name: Acta Materialia Journal Issue: 14 Vol. 52; ISSN 1359-6454; ISSN ACMAFD
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CASTING
EUTECTICS
IMPURITIES
QUENCHING
SILICON ALLOYS
SODIUM ADDITIONS
SOLIDIFICATION
STRONTIUM ADDITIONS