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M: Metallphysik

M 32: Poster TU B (Symposium Tomographic Methods in Materials Research M-32.32-55)

M 32.12: Poster

Montag, 7. März 2005, 14:30–16:30, Poster TU B

Phase-field model for binary alloys solidifying under stress — •Bo Liu and Klaus Kassner — Institut für Theoretische Physik, Otto-von-Guericke Universität Magdeburg Postfach 4120, D-39016, Germany

A phase-field approach is developed to investigate the effect of compositionally-genarated elastic stresses on the morphological instability during directional solidification of a binary alloy. We present a detailed thermodynamic derivation of the model with antitrapping solute current in the mass convervation relation[A. Karma, Phys. Rev. Lett 87, 115701 (2001)]. This antitrapping current counterbalances the physical, albeit artificially large, solute trapping effect generated when a mesoscopic interface thickness is used to simulate the interface evolution on experimental length and time scales. Furthermore, all spurious effects that scale with this thinkness can be suppressed after we introduce the different diffusivity of concentation evolution and elastic field evolution. The asymptotic analysis of the model recovers previous Gibbs-Thomson condition with compositionally-genarated elastic stresses [ B.J. Spencer et.al, Acta metall. mater. 40, 1599 (1992)]. The performance of the model is demonstrated by calculating accurately for the first time within a phase-field approach the oscillatory instability of a planar interface.