Investigation of thermoelectric magnetic convection and its effect on solidification structure during directional solidification under a low axial magnetic field

Thermoelectric magnetic convection (TEMC) at the scale of both the sample ( L = 3 mm) and the cell/dendrite ( L = 100 μm) was numerically and experimentally examined during the directional solidification of Al–Cu alloy under an axial magnetic field ( B ⩽ 1 T ). Numerical results show that TEMC on th...

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Bibliographic Details
Published in:Acta materialia 2009-04, Vol.57 (7), p.2180-2197
Main Authors: Li, Xi, Gagnoud, Annie, Ren, Zhongming, Fautrelle, Yves, Moreau, Rene
Format: Article
Language:English
Subjects:
Applied sciences
Cellular and dendritic morphology
Engineering Sciences
Exact sciences and technology
Macroscopic interface
Materials
Metals. Metallurgy
Thermoelectric magnetic convection
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Summary:Thermoelectric magnetic convection (TEMC) at the scale of both the sample ( L = 3 mm) and the cell/dendrite ( L = 100 μm) was numerically and experimentally examined during the directional solidification of Al–Cu alloy under an axial magnetic field ( B ⩽ 1 T ). Numerical results show that TEMC on the sample scale increases to a maximum when B is of the order of 0.1 T, and then decreases as B increases further. However, at the cellular/dendritic scale, TEMC continues to increase with increasing magnetic field intensity up to a field of 1 T. Experimental results show that application of the magnetic field caused changes in the macroscopic interface shape and the cellular/dendritic morphology (i.e. formation of a protruding interface, decrease in the cellular spacing, and a cellular–dendritic transition). Changes in the macroscopic interface shape and the cellular/dendritic morphology under the magnetic field are in good agreement with the computed velocities of TEMC at the scales of the macroscopic interface and cell/dendrite, respectively. This means that changes in the interface shape and the cellular morphology under a lower magnetic field should be attributed respectively to TEMC on the sample scale and the cell/dendrite scale. Further, by investigating the effect of TEMC on the cellular morphology, it has been proved experimentally that the convection will reduce the cellular spacing and cause a cellular–dendritic transition.
ISSN:1359-6454
1873-2453
DOI:10.1016/j.actamat.2009.01.016