Rapid solidification of undercooled Al-Cu-Si eutectic alloys |
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Authors: | Ying Ruan BingBo Wei |
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Institution: | (1) Department of Applied Physics, Northwestern Polytechnical University, Xi’an, 710072, China |
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Abstract: | Under the conventional solidification condition, a liquid aluminium alloy can be hardly undercooled because of oxidation.
In this work, rapid solidification of an undercooled liquid Al80.4Cu13.6Si6 ternary eutectic alloy was realized by the glass fluxing method combined with recycled superheating. The relationship between
superheating and undercooling was investigated at a certain cooling rate of the alloy melt. The maximum undercooling is 147
K (0.18T
E). The undercooled ternary eutectic is composed of α(Al) solid solution, (Si) semiconductor and θ(CuAl2) intermetallic compound. In the (Al+Si+θ) ternary eutectic, (Si) faceted phase grows independently, while (Al) and θ non-faceted
phases grow cooperatively in the lamellar mode. When undercooling is small, only (Al) solid solution forms as the leading
phase. Once undercooling exceeds 73 K, (Si) phase nucleates firstly and grows as the primary phase. The alloy microstructure
consists of primary (Al) dendrite, (Al+θ) pseudobinary eutectic and (Al+Si+θ) ternary eutectic at small undercooling, while
at large undercooling primary (Si) block, (Al+θ) pseudobinary eutectic and (Al+Si+θ) ternary eutectic coexist. As undercooling
increases, the volume fraction of primary (Al) dendrite decreases and that of primary (Si) block increases.
Supported by the National Natural Science Foundation of China (Grant Nos. 50121101, 50395105) and the Doctorate Foundation
of Northwestern Polytechnical University (Grant No. CX200419) |
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Keywords: | liquid physics ternary eutectic undercooling crystal nucleation rapid solidification |
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