Coupled enthalpy-porosity and front tracking approach to modeling chemical inhomogeneity in solidifying metal alloys
| Autor: | Jerzy Banaszek, Mirosław Seredyński |
|---|---|
| Rok vydání: | 2021 |
| Předmět: |
Fluid Flow and Transfer Processes
Equiaxed crystals Materials science Mechanical Engineering 02 engineering and technology Mechanics 021001 nanoscience & nanotechnology Condensed Matter Physics Tracking (particle physics) 01 natural sciences Casting 010305 fluids & plasmas Dendrite (crystal) Permeability (earth sciences) 0103 physical sciences Polygon mesh 0210 nano-technology Porosity Communication channel |
| Zdroj: | International Journal of Heat and Mass Transfer. 173:121221 |
| ISSN: | 0017-9310 |
| Popis: | Chemical inhomogeneity, developing in a solidifying binary alloy cast and manifesting by spatially distributed heterogeneity of the solute composition and the formation of local highly solute-rich channels, is known a severe defect of casting products. The paper involves the discussion on reliable and efficient multi-scale computer simulations of this phenomenon. The proposed computational model is based on the commonly used enthalpy-porosity approach but combined with the direct tracking of a hypothetical interface separating the stationary columnar dendrites region from the super-cooled alloy melt with fluctuating equiaxed crystals. The model allows the identification of dynamically varying extents of these regions and more precise simulation of melt flow conditions within the whole two-phase zone. The verified and validated model is used to present visible differences between its predicted pictures of channel segregates and the ones got from the enthalpy-porosity method. Next, the simulations have been carried out to study the influence of different permeability laws and various microstructure characteristic lengths on numerically obtained macro-segregation pictures and local channel segregate formations. It is shown that numbers, lengths, widths and directions of the predicted channel segregates is prone to the used control-volume mesh, the applied permeability formula and the assumed size of the dendrite arm spacing. In conclusions, it is indicated that further progress in micro-macroscopic modeling of channel segregates requires more precise semi-empirical permeability models, taking into account the dendritic morphology evolving during the process of solidification, and the model extension to adaptive control volume meshes to better approximate local strong gradients of the solute concentration and velocity in regions where channel segregates develop. |
| Databáze: | OpenAIRE |
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