Micro-macro model for the transient heat and fluid transport in solidification structure evolution during static casting processes

Abstract

The current work used micro-macro model to study the transient fluid flow patterns, heat transfer and solute segregation during the solidification of eutectic binary Al-4%Cu alloy in a static casting process. Custom codes in the form of user defined functions (UDFs) for Nucleation and growth kinetics, thermo-physical properties, and other transport terms including boundary conditions specifically developed for this study were interfaced to ANSYS Fluent. Solidification kinetics was coupled to macroscopic heat transfer equation through the latent heat evolution. The pressure-velocity coupling in the momentum equations were handled by Semi-Implicit Method for Pressure-Linked Equations Consistent (SIMPLEC). The energy and species conservation equations were also solved with similar algorithm. The transient terms of the transport equations were evaluated using fully implicit scheme. Three cases were simulated to evaluate the effect of cooling conditions on the transient evolution of fluid flow, heat transfer and macro-segregation. The results obtained show significant variations in the pattern of fluid flow, heat transport and solute segregation for the three cases. Different thermal regions were reported for the three cases studied. Thickness of the slurry region was observed to be a function of cooling condition. Severity of macro-segregation varied significantly due to imposed boundary conditions. The results obtained provide evidence that choosing cooling orientations arbitrarily can lead to either overestimation or underestimation of casting defects. Therefore, thermal design and process parameters should be optimized for improved product quality and production output.