Coherence of dendritic sidebranching in directional solidificationM. Georgelin, S. Bodea and A. Pocheau
IRPHE, CNRS and Universités Aix-Marseille I and II - 49 rue Joliot-Curie, B.P. 146, Technopôle de Château-Gombert F-13384 Marseille, France
received 16 November 2006; accepted in final form 18 December 2006; published February 2007
published online 6 February 2007
Dendrites stand as the main solidification microstructure of dilute alloys. They are characterized by repetitive emissions of sidebranches on a growing needle form whose regularity conditions the solid structure at micrometric scales. We experimentally evidence here the coherence of this dendritic sidebranching in directional solidification. Sidebranches are found to be emitted by bursts of typically four to fifteen branches. The correlation functions of the signal extracted by cuts of the interface profile reveals a burst distribution that is uncorrelated in length, in time, and in phase of sidebranching, but a sidebranch distribution that is remarkably coherent inside each burst. The former feature may explain the appearance of uncorrelated sidebranching in former experiments and the latter feature reveals a puzzling self-organization of dendrites. Both their origins and mechanisms remain to be understood.
68.70.+w - Whiskers and dendrites (growth, structure, and nonelectronic properties).
81.10.Aj - Theory and models of crystal growth; physics of crystal growth, crystal morphology, and orientation.
81.30.Fb - Solidification.
© Europhysics Letters Association 2007