Hamburg 2001 – wissenschaftliches Programm

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M: Metallphysik

M 3: Symposium Unterkühlte Metallschmelzen III

M 3.6: Fachvortrag

Montag, 26. März 2001, 16:30–16:45, S8

Dendritic growth at small undercoolings: a test for existing models — •Peter Galenko and Dieter M. Herlach — Institut für Raumsimulation, Deutsches Zentrum für Luft- und Raumfahrt, D-51170 Köln

As it has been stated by means of the electromagnetic levitation technique [1], the dendritic crystal growth in metallic systems exhibit systematic deviations of the growth velocities obtained experimentally and in the theoretical predictions at low undercoolings. It was concluded that during dendritic growth at small undercoolings, convective flow of the liquid melt plays an important role and it can be included into the existing theoretical models [1,2]. In the present report we consider two different possibilities for convective flow that can be stated as follows: (i) natural convection due to Earth’s gravity and the thermal gradient estabished by liberation of the latent heat at the solid-liquid interface, and (ii) forced convection due to thermoelectric magnetohydrodynamic effects acting in the experiments on the electromagnetic levitation facility. We analyze the existing models with the including both the natural and forced convection applicable for the sluggish dendritic growth. We estimate various regimes of convective flow with using the dimensional analysis and compare it with the calculated and experimental growth velocities. It allows us to estimate an influence of the natural or forced convection on the dendritic growth at small undercoolings.
This work was made possible due to support from the Alexander von Humboldt Foundation, No. IV RUS 1068584.
1. D.M. Herlach, Mater. Sci. Eng. R12 (1994) 177.
2. K. Eckler, D.M. Herlach, Mater. Sci. Eng. A178 (1994) 159.