Onset of sidebranching in directional solidification
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hdl:2117/10936
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Data publicació2010-02-26
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Abstract
We use a computationally efficient phase-field formulation [B. Echebarria et al., Phys. Rev. E 70, 061604
(2004)] to investigate the origin and dynamics of sidebranching in directional solidification for realistic parameters
of a dilute alloy previously studied experimentally [M. Gorgelin and A. Pocheau, Phys. Rev. E 57,
3189 (1998)]. Sidebranching is found to result either from noise amplification or from deterministic oscillations
that exist both in two dimensions and in a three-dimensional thin-sample geometry. The oscillatory
branch of growth solutions bifurcates subcritically from the main steady-state branch of solutions and exists
over a finite range of large array spacings. In contrast, noise-induced sidebranching is associated with a smooth
transition where the sidebranching amplitude increases exponentially with spacing up to nonlinear saturation
due to the overlap of diffusion fields from neighboring cells, as observed experimentally. In the latter case
where sidebranching is noise-induced, we find that increasing the externally imposed thermal gradient reduces
the onset velocity and wavelength of sidebranching, as also observed experimentally. We show that this
counterintuitive effect is due to tip blunting with increasing thermal gradient that promotes noise amplification
in the tip region.
CitacióEchebarria, B.; Karma, A.; Gurevich, S. Onset of sidebranching in directional solidification. "Physical review E: statistical, nonlinear, and soft matter physics", 26 Febrer 2010, vol. 81, núm. 2, p. 021608-1-021608-17.
ISSN1539-3755
Versió de l'editorhttp://link.aps.org/doi/10.1103/PhysRevE.81.021608
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