Thin Sample Alloy Solidification in Electromagnetic Driven ConvectionReport as inadecuate

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* Corresponding author 1 Centre for Numerical Modelling and Process Analysis CNMPA 2 Institute of Fluid Dynamics

Abstract : During the directional solidification of Ga-In25%wt., density variations in the liquid cause plumes of solute to be ejected from the interface through natural convection. This can lead to the formation of chimneys during solidification and ultimately freckles. The application of external magnetic fields can be used to suppress these plumes. Two magnetic systems are considered. The first is a rotating magnetic wheel, which provides conditions analogous to forced convection at the solidification interface. The forced convection causes preferential growth of secondary branches and causes the plumes to be transported downstream and back into the bulk. The second is through the application of a static magnetic field that interacts with inherent thermoelectric currents, generating a Lorentz force that drives fluid flow within the inter-dendritic region. However, in the bulk where there are no thermoelectric currents, electromagnetic damping dominates and plumes are stunted. Using a fully coupled transient numerical model each of these systems has been analysed. Comparisons to experiments are given for the cases of natural and forced convection. The experimental setup uses a Hele-Shaw cell with an electric heater and Peltier cooler, allowing for control over the thermal gradient and cooling rate.

Keywords : Gallium Indium Thin Sample Solidification Natural convection Forced convection Thermoelectricmagnetohydrodynamics

Author: A Kao - N Shevchenko - O Roshchupinka - S Eckert - Koulis Pericleous -



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