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MM: Fachverband Metall- und Materialphysik
MM 3: Microstructure and Phase Transformations
MM 3.1: Talk
Monday, March 16, 2015, 10:15–10:30, H 0106
Phase field simulations of grain boundary wetting and melting kinetics — •Venkata Sai Pavan Kumar Bhogireddy1, Claas Hüter1, Jörg Neugebauer1, Oleg Shchyglo2, Ingo Steinbach2, and Robert Spatschek1 — 1Max Planck Institute for Iron Research, Düsseldorf, Germany — 2Interdisciplinary Center for Advanced Materials Simulation, Ruhr-University Bochum, Bochum, Germany
Grain boundary premelting is known as the phenomenon that a thin melt layer can appear between two grains already below the bulk melting point, which can cause material failure. It results from a short-ranged structural interaction between the nearby solid-melt interfaces, which are induced by the overlap of the crystal structures in the sandwiched melt. The classical prediction for the transition between wetting and non-wetting states at the melting point is 2σsl = σgb, where σsl is the solid-melt interface energy and σgb the dry grain boundary energy. Here we report on theoretical and numerical investigations of this phenomenon using a multi-order parameter phase field model based on obstacle potentials. We find that the premelting transition is in agreement with the classical expectation, and the short-ranged interactions are predicted.
Beyond this static perspective we report on the kinetics of grain boundary melting along dry and overheated low angle grain boundaries. A steady state regime for the diffusion limited growth is found in the phase field simulations, and the melting velocity depends on the aforementioned short-ranged structural interactions. The velocities are qualitatively in agreement with a sharp interface theory.