Interfacial Pattern Formation During Rapid Phase Transformations in a Binary System

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Solidification of alloys often occurs under conditions far from thermal equilibrium. This process of rapid solidification requires special concern beyond the conventional formulations of piecewise linear non-equilibrium thermodynamics. The microstructures and thus the properties of the resulting solids are largely determined by the pattern-forming processes during solidification. Theoretical and experimental work will be performed. Three main topics shall be considered: (i) propagation of several interfaces and their interactions involving also elastic forces, (ii) fast propagation of interfaces under strong non-equilibrium conditions, and (iii) phase separation in the fluid ahead of an advancing liquid-solid interface. We will employ both analytical and numerical methods, including boundary-integral and phase-field methods. The results of theoretical modelling will be compared with results of measurements of the solidification front dynamics and the micro structure evolution from undercooled melts of binary Co-Cu and Cu-Fe alloys, which show a metastable two-phase region in the undercooled melt.