Dresden 2009 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 11: Growth
MM 11.4: Vortrag
Montag, 23. März 2009, 15:30–15:45, IFW D
Pattern formation during Diffusion limited Transformations in Solids — •Michael Fleck1, Claas Hüter1, Denis Pilipenko1, Robert Spatschek1,2, and Efim Brener1 — 1Institut für Festkörperforschung, Forschungszentrum 52425 Jülich — 2Interdisciplinary Centre for Advanced Materials Simulation (ICAMS), Ruhr-Universität Bochum
Key feature of many metallurgical procedures to improve materials properties is the formation of very complex microstructures due to solid-solid phase transformation processes.
We develop a description of diffusion limited growth in solid-solid transformations, which are strongly influenced by elastic effects. Density differences and structural transformations provoke stresses at interfaces, which affect the phase equilibrium conditions. We formulate equations for the interface kinetics similar to dendritic growth and study the growth of a stable phase from a metastable solid in both a channel geometry and in free space. We perform sharp interface calculations based on Green's function methods and phase field simulations, supplemented by analytical investigations.
For pure dilatational transformations we find a single growing finger with symmetry breaking at higher driving forces, whereas for shear transformations the emergence of twin structures can be favorable. We predict the steady state shapes and propagation velocities, which can be higher than in conventional dendritic growth.