Rare earth concentration in the primary Si crystal in rare earth added Al-21 wt. % Si alloy

Journal Article · Fri Jul 03 04:00:00 EDT 1998 · Scripta Materialia

DOI:https://doi.org/10.1016/S1359-6462(98)00168-7· OSTI ID:634755

Chang, J Y; Kim, G H ^[1]; Moon, I G; Choi, C S ^[2]

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1. Korea Inst. of Science and Technology, Seoul (Korea, Republic of)
2. Yonsei Univ., Seoul (Korea, Republic of). Dept. of Metallurgical Engineering

Al-Si alloys containing more than about 12 wt. % Si exhibit a hypereutectic microstructure, normally consisting of a primary silicon phase in an eutectic matrix. The primary silicon in normal hypereutectic alloys is usually very coarse and thus leads to poor properties to these alloys. Therefore, alloys with a predominantly coarse primary silicon crystal must be modified to ensure adequate mechanical strength and ductility. Further improvement of mechanical properties of these alloys can be achieved by the modification of eutectic microstructure. Therefore, development of a modifier or refiner that can produce both fine primary and eutectic Si is a major factor which can lead to significant enhancement of mechanical properties in hypereutectic Al-Si alloys. Refinement of primary silicon is usually achieved by the addition of phosphor to the melt. On the other hand, it is reported that the rare earth (RE) elements are capable of modifying the eutectic structure of cast Al-Si alloys. According to the literature, Phosphor acts as a heterogeneous nucleation site of Si crystal by forming AlP intermetallic particles at high temperature, i.e., above liquidus temperature of Al-Si alloy. Unlike phosphor, RE was not known to form a stable compound with Al that can act as a nucleation site at high temperature. Therefore, the role of RE as a refiner should be considered by examining the behavior of RE as a solute in the melt. The distribution of RE within the primary Si and in the matrix of the alloy will provide a clue to the role of RE on the modification of primary Si during solidification.

• OSTI ID: 634755
• Journal Information: Scripta Materialia, Journal Name: Scripta Materialia Journal Issue: 3 Vol. 39; ISSN 1359-6462; ISSN SCMAF7
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
ALUMINIUM ALLOYS
CONCENTRATION RATIO
EUTECTICS
GRAIN REFINEMENT
RARE EARTHS
SILICON ALLOYS