Growth induced dendritic bending and rosette formation during solidification in a shearing flow

A free boundary model for dendritic growth in a non-stationary fluid is presented. The model is used to evaluate the effect on dendritic growth of fluid flow orthogonal to the principal growth direction. It is found that such a flow causes rotation of the tip due to thermal/solutal advection and that, for small angular deflections, the rotation is a constant per unit length of growth. This rotation is found to be a function of the cross flow and growth Peclet numbers. Results from the dendrite growth model are used in a Cellular Automaton (CA) model of rosette formation. It is found that the predicted bending rates could give rise to rosette formation without any need to invoke mechanical effects. Moreover, the magnitude of the bending parameter defines a maximum size to which a dendritic crystal could grow before being spheroidized. (C) 1999 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.