Gravity and Flow Effects on Coarsening Dynamics in Crystal-Liquid Mixtures

Coarsening of crystals can be driven by cooling, Ostwald ripening, or interfacial kinetics in crystal-liquid mixtures. The relevant phenomena appear in many manufacturing processes involving metals and alloys, or nonmetallic materials. The degree of coarsening determines the size of crystals and microstructural pattern, and thus understanding coarsening dynamics is important in controlling the uniformity of microstructure and properties of the end products. We present a phase-field theoretical framework to investigate coarsening dynamics in symmetric and asymmetric binary systems. The phase transition and microstructure evolution are coupled with fluid flow, trajectory motion of the crystals, thermophysical properties of the materials, interfacial energy, and the relevant heat and mass transport phenomena. Specifically, we focus on crystal morphology and the fluid flow induced by density variation and gravity acceleration. The flow and collective motion of crystals also influence the heat and mass transfer around the interstitial space between crystals and should be resolved simultaneously. The theoretical analysis and 2d computational results based on spectral method will be presented.