Globulization mechanism of the primary Al of Al−15Cu alloy during slurry preparation for rheoforming |
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Authors: | J Jayaraj Eric Fleury Ki-Bae Kim Jae-Chul Lee |
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Affiliation: | (1) Division of Materials Science and Engineering, Korea Institute of Science and Technology (KIST), Cheongryang, P.O. Box 131, 130-650 Seoul, Korea;(2) International R & D Academy, KIST-University of Science and Technology, Cheongryang, P.O. Box 131, 130-650 Seoul, Korea;(3) Division of Materials Science and Engineering, Korea University, 1 Anam-dong 5-ga, Seongbuk-gu, 136-701 Seoul, Korea |
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Abstract: | Semisolid slurries of Al-15Cu alloy were produced for rheoforming by a low temperature pouring technique. To investigate the
morphological change of the slurry in terms of the particle mean diameter and the roundness factor, samples were extracted
during the continuous cooling and the isothermal holding stage of the slurry by a simple technique of interrupt quenching.
Results demonstrated that the fine-grained equiaxed dendritic structure, which formed during low temperature pouring, is changed
to a globular structure when held at a semisolid temperature for sufficiently long holding time. With regard to the globulization
mechanism of the primary α-phase, local melting is considered to take place at the neck of equiaxed dendrites, leading to
the separation of small new particles during continuous cooling. These newly formed particles eventually grow during isothermal
holding in the semisolid temperature by obeying theD
3=Kt kinetic law, which suggests coarsening by Ostwald ripening. |
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Keywords: | semisolid rheoforming microstructural evolution local melting coalescence Ostwald ripening |
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