Interaction of local solidification and remelting during dendrite coarsening - modeling and comparison with experiments

Abstract

The microstructural evolution of dendrite coarsening during isothermal holding is simulated using a quantitative cellular automaton (CA) model involving the mechanisms of both solidification and melting. The present model encompasses the essential aspects of thermodynamics and kinetics, particularly the evolution/influence of composition, temperature, and curvature, leading to valid simulations of simultaneous solidification and melting. Model validation is performed through a comparison of the CA simulations with analytical predictions for a liquid pool migrating in the mushy zone of a SCN–0.3 wt.% ACE alloy due to temperature gradient zone melting. The model is applied to simulate the microstructural evolution of columnar dendrites of a SCN–2.0 wt.% ACE alloy during isothermal holding in a mushy zone. The simulation results are compared with those of a previous CA model that does not include the melting mechanism under otherwise identical conditions. The role of melting for dendrite coarsening is quantified, showing how the melting influences the coarsening process. The present model effectively reproduces the typical dendrite coarsening features as observed in experiments reported in the literature. The simulations reveal how local solidification and melting stimulate each other through the complicated interactions between phase transformation, interface shape variation, and solute diffusion.

Modelling of liquid film migration in Al-Cu alloys

“…The CA model has been validated by comparing the simulation results with analytical predictions [23]. The phenomena of TGZM and dendrite coarsening can be well reproduced by the CA model [23][24][25][26]. In the present study, the CA model is applied for the simulation of LFM in Al-Cu alloys.…”

“…In recent decades, numerical modelling has become a powerful tool to study microstructural evolution in the mushy zone during various types of phase transformations [17][18][19][20]. Phase field (PF) [21,22] and cellular automaton (CA) simulations [23][24][25] have been performed to study microstructural evolution during simultaneous melting and solidification. However, to the knowledge of the present authors, quantitative simulations of microstructural and compositional evolution during LFM have so far not been documented in the literature.…”

“…However, to the knowledge of the present authors, quantitative simulations of microstructural and compositional evolution during LFM have so far not been documented in the literature. We recently proposed a two-dimensional quantitative CA model that incorporates both melting and solidification [23]. It is pertinent to note that (local) melting is often neglected in solidification simulations.…”

A review on the porous medium approaches to model the flow of interdendritic liquid during the solidification of alloys in casting processes: theory and experiments

“…However, new cellular automation methods are now available and represent a powerful numerical tool that should be used in a near future to provide a complete time-dependent description of evolving arbitrarily complex interfacial morphologies. This is illustrated in the recent work of Zhang et al [102], who proposed a cellular automation model allowing the detailed visualization of solution diffusion in 2D under isothermal conditions as well as deeper insight into the coarsening mechanisms observed by Limodin et al [96]. Moreover, 3D phasefield studies must still be performed on representative parts of the mushy zone for technical multicomponent alloys in order to reliably evaluate permeability [7].…”

Modeling of dendrite arm fragmentation and dendrite arm coarsening⋆

“…Cellular automaton (CA) models can simulate various types of solidification microstructures observed in experiments with an acceptable computational efficiency [35][36][37][38][39][40][41][42][43][44][45]. Some of the present authors proposed a CA model involving both solidification and melting mechanisms to study dendrite coarsening of a SCN-ACE alloy under isothermal conditions [45] and dendrite arm migration under a temperature gradient [44].…”