Contribution Oral Presentation
MULTISCALE MODELING OF DENDRITIC ALLOY MICROSTRUCTURES
This talk will review recent progress to bridge the gap between phase-field modeling on the microstructure scale and grain structure modeling. While phase-field modeling has been used successfully to model quantitatively dendritic alloy microstructures, only volumes up to about a millimeter cube (or even smaller for concentrated alloys) can be simulated even on today’s massively parallel computer architectures . On a much larger scale, Cellular Automata coupled with Finite Elements (CAFE) models have yielded impressive predictions of grain structures of castings in both two and three dimensions . However, those models do not resolve dynamical interactions between branches of hierarchical dendritic networks, which can strongly influence both intra-grain microstructure selection and the growth competition of different grains . This talk will discuss efforts to overcome this limitation by using phase-field simulations to inform the choice of CAFE model parameters , thereby improving their predictions, or by developing coarse-grained models that can simulate dendritic microstructures on much larger length and time scales than phase-field models and that can be integrated into CAFE models. Among such approaches, the ones most explored and tested to date include the dendritic needle network (DNN) model that tracks the dynamical evolution of the hierarchical dendritic network on scale larger than the dendrite tip radius , and a mesoscopic model that approximates the complex dendritic morphology by its envelope . Examples will be given that illustrate how those approaches have been used to model columnar and equiaxed microstructures, and transitions between them. Advantages and limitations of those approaches will be discussed to highlight ongoing challenges in scale-bridging and to provide an outlook for future developments.
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