5th International Conference on Advances in Solidification Processes (ICASP-5) 5th International Symposium on Cutting Edge of Computer Simulation of Solidification, Casting and Refining (CSSCR-5)

Modelling of non-equilibrium solidification is of singular importance in microstructure control, which however owing to the complex systems with complex additional constraints is still an open problem. In this work, the thermodynamic extremal principle was applied to solve the complex additional constraints self-consistently in thermodynamics for both binary and multi-component alloys. Consequently, short-range solute redistribution and long-range solute diffusion that share the same mobility are integrated naturally into the solute diffusion equations, thus avoiding the introduction of additional kinetic coefficients (e.g. interface permeability) to describe solute redistribution. Under non-equilibrium conditions, solute trapping as well as solute drag happens and at the critical interface velocity that is equal to the maximal solute diffusion velocity in liquid, abruptly concurrent occurrence of diffusionless solidification and absence of solute drag happens, thanks to the adoption of effective mobilities for non-equilibrium solute diffusion. Under equilibrium conditions, the interface and bulk contributions are completely decoupled, indicating that the current model might be preferred for simulations not only because of its simplest form of evolution equations but also its feasibility to increase the simulation efficiency by the “thin interface limit” analysis.