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M: Metallphysik

M 23: Phasenumwandlung III

M 23.1: Vortrag

Samstag, 5. März 2005, 14:45–15:00, TU H1058

Phase-field study of the cellular bifurcation in dilute binary alloys — •Mathis Plapp and Esteban Meca — Laboratoire PMC, Ecole Polytechnique, 91128 Palaiseau, Frankreich

In the directional solidification of dilute binary alloys, a planar interface becomes unstable at a critical speed of the solidification front that depends on the alloy concentration and the applied temperature gradient. We investigate the microstructures that form closely above this instability threshold using phase-field simulations in both two and three dimensions. In particular, we study the so-called ’node’ or ’pox’ structures that consist of regular hexagonal arrays of ’holes’ (local depressions of the solidification front) and compare their properties to the ones of the well-known hexagonal cell patterns. The results are compared to the predictions of weakly nonlinear amplitude expansions as well as to experimental findings.