Computation of Partial Equilibrium Solidification with Complete Interstitial and Negligible Substitutional Solute Back Diffusion

Abstract

A simple numerical scheme is presented to simulate partial equilibrium solidification with complete interstitial and negligible substitutional solute back diffusion in multi-component and multi-phase systems. Based on this scheme, a computing tool capable of using Thermo-Calc databases directly has been developed for the estimation of solidification behavior of steels and other interstitial-containing alloys. Agreements between calculated and experimental as well as DICTRA results have been obtained on the microsegregation, fraction of eutectic, and freezing range of several steels. This suggests that the partial equilibrium assumption and proposed numerical scheme are reasonable and satisfactory, and confirms that the carbon back diffusion plays a very important role in the solidification of steels.

Modeling Inclusion Formation during Solidification of Steel: A Review

“…The interfacial concentrations are infinite when the solid fraction approaches one, which also limits the application of the Scheil Model, because the final concentrations and solidus temperature are important expectations. To overcome the aforementioned limitations, an improved Scheil Model that considered the back diffusion was proposed [22], which is also termed as the partial equilibrium method [23]. In the partial equilibrium method, the perfect diffusion of interstitial solutes and no diffusion of substitutional solutes in solid steel are accounted.…”

Macrosegregation in Steel Ingots: The Applicability of Modelling and Characterisation Techniques

“…Ueshima et al 150) predicted the start of the peritectic using empirical relationships based on local solid concentrations, whilst Howe et al 151,152) introduced 'carbon equivalents' for alloying elements such that the effect of each partitioned species on the peritectic temperature was accounted for in a pseudo-binary model. More recently the use of thermodynamic databases in steel microsegregation models has become popular [153][154][155][156] and kinetic effects have also been incorporated into models .111,157-163) Nevertheless, adding such complexity into macrosegregation models often comes at great computational expense, and consequently there has been some development of rapid microsegregation models for incorporation into macromodels. 164) For those seeking further details on microsegregation models, the review by Kraft and Chang 165) is a useful starting point.…”

Methodological Progress for Computer Simulation of Solidification and Casting

“…complete interstitial but negligible substututional solute back difuusion in the solid. This is realized in the PE model 66,67) through evening up the chemical potential of the interstitials throughout the solid. In above software packages, the prediction of the solidification path for various alloys is available through coupling with these three models and thermodynamic and kinetic database.…”