Dresden 2011 – scientific programme
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MM: Fachverband Metall- und Materialphysik
MM 31: Postersitzung II
MM 31.23: Poster
Wednesday, March 16, 2011, 17:15–18:45, P5
Phase-field study of needle crystal fragmentation — •Marius Kist1, Abhik Choudhury1, and Britta Nestler1,2 — 1Institute of Materials and Processes, Karlsruhe University of Applied Sciences, Moltkestr.30, 76133 Karlsruhe, Germany — 2Institute of Reliability of Components and Systems(IZBS), Karlsruher Institut für Technologie, Haid-und-Neu-Str.7, 76131 Karlsruhe, Germany
We investigate the melting process of a single solid phase in contact with its liquid for the case of a binary alloy at near to equilibrium conditions by two and three dimensional simulations based on a phase-field method. In particular, we study the effect of surface energy anisotropy on the melting behavior. In 2D, for the case of isotropic surface energies, the solid phase melts continuously keeping its shape intact. For the case of anisotropic surface energy giving rise to elliptical needle crystals, we observe a discontinuous melting behavior where, beyond a critical aspect ratio (major axis/minor axis), the needle splits into two fragments while melting. We investigate this phenomenon, and suggest a mechanism for its occurrence. In 3D, the classical Rayleigh-Plateau-Instability is known to cause a break up of a cylindrical surface into a row of droplets through surface energy minimization. This instability is an additional contribution to the splitting behavior of needle crystals. We study the interplay of the mechanisms of needle breaking in 2D and analyze the effect of Rayleigh Instability in the presence of bulk diffusion in 3D. From the phase-field simulations, we derive the time exponent for the kinetics of the needle crystal fragmentation.