A. Sarkissian et A. Karma, ON THE FORMATION OF THE BANDED STRUCTURE IN RAPID SOLIDIFICATION, Materials science & engineering. A, Structural materials: properties, microstructure and processing, 178(1-2), 1994, pp. 153-157
Rapid solidification experiments on metallic alloys over the last deca
de have provided widespread observations of a novel banded structure.
We present the results of numerical and analytical studies of the non-
linear dynamics of the solidifying interface which provide insights in
to the mechanism of formation of this structure. These studies are bas
ed on a model of directional solidification which includes non-equilib
rium effects and consists of a one-dimensional boundary integral equat
ion for the temperature field combined with a boundary-layer approxima
tion for the solute field. Three main ingredients of the banding mecha
nism emerge from these studies: the presence of non-linear oscillation
s of the solidification rate driven by solute trapping, the dramatic e
ffect of latent heat diffusion on the character of these oscillations,
and the propagation of ''optical growth fronts'' connecting collision
-controlled and diffusion-controlled interfacial regions.