Regensburg 2002 – scientific programme

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M: Metallphysik

M 28: Wachstum

M 28.1: Fachvortrag

Friday, March 15, 2002, 11:30–11:45, H8

Modeling of dendritic growth under the influence of induced convective flow in undercooled droplets — •Peter Galenko, Dieter M. Herlach, Oliver Funke, and J. Wang — Institut für Raumsimulation, Deutsches Zentrum für Luft- und Raumfahrt DLR, 51170 Köln

In the present report we consider dendritic solidification in liquid droplets within electromagnetic levitation technique. As it has been shown experimentally [1], dendritic growth at small undercoolings in levitated droplets exhibits systematic deviation from theoretical predictions. Convection of the liquid phase during solidification is supposed to play the main role in this deviation. In a levitated droplet convection is attributed to the induced stirring due to electromagnetic Lorenz force and therefore the main focus of the present investigation is dendritic growth with the externally induced liquid flow in levitated droplets.

We introduce a sharp-interface model of steady-state dendritic growth in consideration of forced convection due to thermoelectric magnetohydro-dynamic effects. Within the sharp-interface model we obtain a solution which is consistent with the skin depth approximation. In order to model the details of formation of dendritic pattern we develop a program code based on the phase-field methodology of dendritic growth with induced convection. In order to verify the predictions of the sharp-interface model and phase-field model we use previously obtained experimental data [1] as well as data of additionally performed measurements of dendritic growth at small undercoolings in levitated droplets of pure nickel. The model predictions within the sharp-interface approximation and the phase-field method are compared with the measurements of the dendritic growth velocity versus the amount of undercooling.
This work was performed with support from the Alexander von Humboldt Foundation and DFG Research project He 1601/13.
1. K. Eckler, D.M. Herlach, Mater. Sci. Eng. A178 (1994) 159.