Effect of Multi-Scale Thermoelectric Magnetic Convection on Solidification Microstructure in Directionally Solidified Al-Si Alloys Under a Transverse Magnetic Field |
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Authors: | Xi Li Dafan Du Annie Gagnoud Zhongming Ren Yves Fautrelle Rene Moreau |
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Affiliation: | 1. Department of Material Science and Engineering, Shanghai University, Shanghai, 200072, P.R. China 2. SIMAP-EPM-Madylam/CNRS, ENSHMG, BP 38402, St Martin d’Heres Cedex, France
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Abstract: | The influence of a transverse magnetic field (B < 1 T) on the solidification structure in directionally solidified Al-Si alloys was investigated. Experimental results indicate that the magnetic field caused macrosegregation, dendrite refinement, and a decrease in the length of the mushy zone in both Al-7 wt pct Si alloy and Al-7 wt pct Si-1 wt pct Fe alloys. Moreover, the application of the magnetic field is capable of separating the Fe-rich intermetallic phases from Al-7 wt pct Si-1 wt pct Fe alloy. Thermoelectric magnetic convection (TEMC) was numerically simulated during the directional solidification of Al-Si alloys. The results reveal that the TEMC increases to a maximum ( ( u_{rm{max} } ) ) when the magnetic field reaches a critical magnetic field strength ( ( B_{rm{max} } ) ), and then decreases as the magnetic field strength increases further. The TEMC exhibits the multi-scales effects: the ( u_{rm{max} } ) and ( B_{rm{max} } ) values are different at various scales, with ( u_{rm{max} } ) decreasing and ( B_{rm{max} } ) increasing as the scale decreases. The modification of the solidification structure under the magnetic field should be attributed to the TEMC on the sample and dendrite scales. |
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