The effect of Sr and Fe additions on the microstructure and mechanical properties of a direct squeeze cast Al-7Si-0.3Mg alloy

Journal Article · Sat May 01 00:00:00 EDT 1999 · Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science

DOI:https://doi.org/10.1007/s11661-999-0283-6· OSTI ID:363993

Dong, J X; Karnezis, P A; Durrant, G; Cantor, B ^[1]

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1. Univ. of Oxford (United Kingdom). Dept. of Materials

This article describes the results of an investigation into the microstructure and mechanical properties of a gravity die cast and direct squeeze cast LM25 alloy (Al-7Si-0.3Mg-0.3Fe). The direct squeeze cast LM25 alloy has superior mechanical properties compared to the gravity die cast LM25 alloy, especially with regard to ductility, which is increased from {approximately}1.7 pct for the gravity die cast LM25 alloy to {approximately}8.0 pct for the direct squeeze cast LM25 alloy in the T6 heat-treated conditions. This increase in ductility is due to (1) the removal of porosity, (2) a decrease in Si particle size, and (3) a refinement of the Fe-Si-aluminide particles. High cooling rates in direct squeeze casting result in quench modification of the Si particles, such that chemical modification with Sr or Na may not be required. In addition, direct squeeze casting is more tolerant of Fe impurities in the alloy, due to the formation of smaller Fe-Si-aluminide particles than those in gravity die cast material. The direct squeeze cast LM25 + Fe alloy (Al-7Si-0.3Mg-1.0Fe) has a ductility of {approximately}6.5 pct, compared to that of {approximately}0.5 pct for the gravity die cast LM25 + Fe alloy in the T6 heat-treated condition. This increase in tolerance to Fe impurities can lead to a substantial reduction in manufacturing costs due to (1) reduced raw-material costs, (2) reduced die sticking, and (3) improved die life.

• Sponsoring Organization: USDOE
• OSTI ID: 363993
• Journal Information: Metallurgical and Materials Transactions. A, Physical Metallurgy and Materials Science, Vol. 30, Issue 5; Other Information: PBD: May 1999
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
MICROSTRUCTURE
MECHANICAL PROPERTIES
ALUMINIUM ALLOYS
SILICON ALLOYS
MAGNESIUM ADDITIONS
IRON ADDITIONS
STRONTIUM ADDITIONS
METALLURGICAL EFFECTS
PRECIPITATION
INTERMETALLIC COMPOUNDS