Jyrki Miettinen

Reassessed thermodynamic solution phase data for ternary Fe-Si-C system

Abstract New thermodynamic solution phase data have been optimized for the Fe-Si-C system to improve the correlation between experiments and calculations obtained in an earlier assessment. New values were optimized for a binary Fe-Si interaction parameter of liquid phase and ternary Fe-Si-C interaction parameters of liquid, bcc and fcc phases applying experimental measurements on mixing enthalpies, solute activities, phase equilibria and solute partition.

Thermodynamic description of the Cu-Pb-Sn system at the Cu-Pb side

Thermodynamic description of the ternary Cu–Ni–Sn system at its Cu–Ni side is presented. The thermodynamic parameters of the binary sub-systems, Cu–Ni, Cu–Sn and Ni–Sn, are taken from earlier SGTE-based assessments (modifying the Ni–Sn description slightly) and those of the ternary Cu–Ni–Sn system are optimized in this study by using the experimental data of mixing enthalpy and phase equilibrium. The present ternary description is valid for tin contents up to 38 wt% (xSn ≈ 0.25). In addition, a newdescription is presented for the earlier assessed Cu–P–Sn system, due to the new Cu–Sn description adopted after its appearance (and shown in the present study).

Mathematical simulation of interdendritic solidification of low-Alloyed and stainless steels

A mathematical model for simulating the interdendritic solidification of low-alloyed and stainless steels is presented based on thermodynamic and diffusion calculations made in one volume element in the mushy zone. The method involves the determination of stable phases (ferrite, austenite, liquid, and FeMnS) as well as their fractions and compositions at any temperature during solidification. The model was tested by comparing calculations with experiments, and reasonable agreement was demonstrated. The model also includes a routine for predicting the liquid undercooling caused by solute accumulation ahead of the dendrite tips.

Approximate thermodynamic solution phase data for steels

Abstract Approximate thermodynamic data based on a minimum amount of experiments are optimized for liquid, ferrite and austenite of some iron-based systems not assessed earlier, for a more accurate calculation of phase equilibria between these phases in multicomponent steels. The new data are shown to improve the correlation between calculated and measured liquidus temperature, solute partition and primary phase data in typical stainless steels.

Calculation of thermophysical properties of carbon and low alloyed steels for modeling of solidification processes

Algorithms and a computer software package for calculating thermophysical material properties of carbon and low-alloyed steels, associated with the simulation of solidification processes, have been developed. The earlier studies on kinetic phase transformation modeling are applied and are the base of the present work. The calculation algorithms are based on thermodynamic theory connected to thermodynamic assessment data, as well as on regression formulas of experimental data, and they take into account the temperature, the cooling rate, and the steel composition. The calculation algorithms and some results of calculations are presented in this article.

Thermodynamic reassessment of Fe-Cr-Ni system with emphasis on the iron-rich corner

Abstract Thermodynamic reoptimization has been made for the Fe-Cr-Ni system with emphasis on the iron-rich corner of the system. New ternary substitutional-solution interaction parameters were optimized for the liquid, fcc and bcc phases and a new Gibbs energy expression was suggested for one hypothetical component of the sigma phase. The rest of the data concerning the binary subsystems and the sigma phase were taken from earlier assessed Fe-Cr-Ni descriptions. The calculated results were validated with numerous experiments of phase equilibria, solute partition and component activity. The results were also compared with those of two earlier Fe-Cr-Ni assessments showing improved or equal agreement with most experiments. Only for the liquidus temperatures at high chromium and nickel contents (above 30wt%) is the agreement worse than in the earlier assessments.

Thermodynamic description of the CuAlZn and CuSnZn systems in the copper-rich corner

Thermodynamic descriptions of the ternary CuAlZn and CuSnZn systems in the copper-rich corner are presented. The thermodynamic parameters of the binary sub-systems, CuAl, CuSn, CuZn, AlSn, AlZn and SnZn, are based on earlier SGTE-based assessments and those of the ternary CuAlZn and CuSnZn systems are optimized in this study by using the experimental thermodynamic and phase equilibrium data. The present ternary descriptions are valid for aluminum contents up to xAl=0.33, tin contents up to xSn=0.25 and zinc contents up to xZn=0.7.

IDS: Thermodynamic-kinetic-empirical tool for modelling of solidification, microstructure and material properties

IDS (InterDendritic Solidification) is a thermodynamic-kinetic-empirical tool for simulation of solidification phenomena of steels including phase transformations from melt down to room temperature. In addition, important thermophysical material properties (enthalpy, thermal conductivity, density, etc.) are calculated. The model has been developed in the Laboratory of Metallurgy, Helsinki University of Technology, Finland, since 1984. IDS includes two main modules, the IDS module and the ADC (Austenite DeComposition) module. IDS module simulates the solidification phenomena from liquid down to 1000^oC and ADC the austenite decomposition down to room temperature. Both modules have their own recommended composition ranges. The IDS module is based on the so-called sharp interface concept. The ADC is mainly statistical based on empirical CCT (Continuous Cooling Transformation) diagrams. IDS tool is also coupled with the thermodynamic programmers library, called ChemApp, developed by a German company, GTT-Technologies. This coupled package is used to simulate among other things multiphase inclusions during solidification. The present paper summarises the features of the IDS tool including the coupling with the ChemApp library.

Thermodynamic description of the CuAlFe system at the CuFe side

Abstract Thermodynamic description of the ternary CuAlFe system at the CuFe side is presented. The thermodynamic parameters of the sub-systems, CuAl, CuFe and AlFe, are taken from earlier SGTE-based assessments, and those of the ternary CuAlFe system are optimized in this study by using the experimental phase equilibrium data. The present ternary description is valid for aluminum contents up to 18 wt%.

Thermodynamic solution phase data for binary Mn-based systems

Thermodynamic substitutional solution data of liquid, bcc-A2, fcc-A1, cub-A13 and cbcc-A12 phases are presented for binary Mn-based systems, based both on earlier assessments and optimisations from the present study. The aim is to introduce the most recent, SGTE compatible solution phase database of binary Mn-based systems, to be extended in time to higher-order systems.