Semisolid Casting of Hypereutectic Al-Si-Cu Alloy with Sono-Solidified Slurry

Abstract:

Hypereutectic Al-Si-Cu alloys which are typical light-weight wear-resistant materials, are required to improve the ductility as well as the strength and wear-resistance for the wider applications. Increase in amounts of primary silicon particles causes the modified wear-resistance of hypereutectic Al-Si-Cu alloys, however, it leads to the poor strength and ductility. It is known that dual phase steels composed of hetero-structure have succeeded to bring contradictory mechanical properties of high strength and ductility concurrently. In order to apply the idea of hetero-structure to hypereutectic Al-Si-Cu alloys for the achievement of high strength and ductility along with wear resistance, ultrasonic irradiation to molten metal during the solidification, which is named sono-solidification, was carried out from its molten state to just above the eutectic temperature. The sono-solidified Al-17Si-4Cu alloy is composed of hetero-structure, that is, hard primary silicon particles, soft non-equilibrium α-Al phase and eutectic region. Rheocasting was performed at just above the eutectic temperature with sono-solidified slurry to shape a disk specimen. After the rheocasting with modified sono-solidified slurry held for 45s at 570^oC, the quantitative optical microscope observation exhibits that the microstructure is composed of 18area% of hard primary silicon particles and 57area% of soft α-Al phase, in contrast there exist only 5area% of primary silicon particles and no α-Al phase rheocast with normally solidified slurry. Hence the tensile tests of T6 treated rheocast specimens with modified sono-solidified slurry exhibit the improved strength and 5% of elongation, regardless of more than 3 times higher amounts of primary silicon particles compared to that rheocast with normally solidified slurry.

• Periodical: Key Engineering Materials (Volumes 622-623)
• Pages: 804-810
• DOI: https://doi.org/10.4028/www.scientific.net/KEM.622-623.804
• Online since: September 2014
• Authors: Yoshiki Tsunekawa*, Shinpei Suetsugu, Masahiro Okumiya, Yuichi Furukawa, Naoki Nishukawa, Yoshikazu Genma
• Keywords: Hetero-Structure, Hypereutectic Aluminum Alloy, Primary Silicon, Semisolid Casting, Slurry, Sono-Solidification, Ultrasonic Vibration, α-Al Solid Solution

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