Formulas for the Calculation of Temperatures and Concentrations of Carbon Responsible to the Parar Equilibrium of the Main Phases in Medium Sheet Steels

2019 ◽  
Vol 822 ◽  
pp. 44-52
Author(s):  
Pavel Zhitelev ◽  
Darya Serzhenko
Keyword(s):  
Chemical Composition ◽  
Reference Data ◽  
Calculated Data ◽  
Medium Carbon ◽  
Sheet Steels ◽  
Thermo Calc Software ◽  
Temperature Ranges ◽  
Analytical Formulas ◽  
Equilibrium Concentrations ◽  
Carbon Concentrations

With the help of the Thermo-Calc software package, arrays of calculated data were created for carbon concentrations in ferrite and austenite, corresponding to the para-equilibrium of these phases and their para-equilibrium with cementite, as well as for the corresponding temperatures A1 and A3. Marked arrays were obtained in wide temperature ranges for ranges of carbon concentrations and the most important substitution alloying elements (Mn; Si; Cr; Ni; Mo), covering the respective ranges for medium carbon and moderately alloyed steels. Analytical formulas were developed on the basis of the reference data arrays for calculating para-equilibrium concentrations of carbon in ferrite and austenite (depending on temperature and chemical composition), as well as temperatures A1 and A3 (depending on chemical composition), which allow to reproduce with high accuracy the results obtained using Thermo-Calc.

Point Defect Properties from Metal Diffusion Experiments — What Does the Data Really Tell Us?

1997 ◽  
Vol 469 ◽  
Author(s):  
Srinivasan Chakravarthit ◽  
Scott T. Dunham
Keyword(s):  
Point Defect ◽  
Equilibrium Concentration ◽  
Simulation Software ◽  
Published Data ◽  
Vacancy Diffusion ◽  
Metal Diffusion ◽  
Float Zone ◽  
Equilibrium Concentrations ◽  
Parameter Values ◽  
Carbon Concentrations

Point defect properties, including diffusivities and equilibrium concentrations for both interstitials and vacancies, are commonly extracted from metal diffusion experiments, and these values are widely used in process simulation software. However, in many cases, these parameter values were extracted using oversimplified models which ignore interactions between interstitial and vacancy diffusion mechanisms. Questions about the accuracy of these parameters have come from ab-initio defect calculations which conclude that vacancies diffuse faster than interstitials, in contrast with published reports on metal diffusion which find vacancies diffuse much more slowly than interstitials. We have reanalyzed published data for zinc and platinum diffusion and find that it is possible to match all of the data using fast vacancy diffusivity. The most direct evidence for slow vacancy diffusion (and a high equilibrium concentration) comes from platinum diffusion experiments. However, we are able to reproduce these results with fast V diffusion and carbon/interstitial clustering, using carbon concentrations typical of Czochralski and float zone silicon (1016cm−3). We evaluate the effectiveness of metal diffusion experiments in determining point defect parameters, and find that it is not possible to reliably determine both diffusivities and equilibrium concentrations for both interstitials and vacancies from metal diffusion results.

The Effect of Carbon/Self-Interstitial Clusters on Carbon Diffusion in Silicon Modeled by Kinetic Monte Carlo Simulations

2000 ◽  
Vol 610 ◽  
Author(s):  
R. Pinachoa ◽  
M. Jaraíz ◽  
H. J. Gossmann ◽  
G. H. Gilmer ◽  
J. L. Benton ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Kinetic Monte Carlo ◽  
Carbon Diffusion ◽  
Interstitial Concentration ◽  
Carbon Structures ◽  
Kinetic Monte Carlo Simulations ◽  
Equilibrium Concentrations ◽  
Low Solubility ◽  
Carbon Concentrations ◽  
Diffusion Profiles

AbstractA new model for carbon diffusion in silicon that explains carbon diffusion during annealing at 850°C and 900°C in superlattice carbon structures grown by MBE is implemented using the Monte Carlo atomistic simulator DADOS. Carbon concentrations in the delta layers are 2×1020 cm−3, exceeding by far the solid solubility. The simple kick-out mechanism which incorporates the well established values of the product of diffusivity and equilibrium concentrations of intrinsic point defects and in-diffusion experiments of carbon in silicon does not explain the observed C diffusion profiles. A more detailed analysis of the experiments shows that, in order to fit them, a more unstable Ci is required. Therefore, we include the formation of clusters in the simulations. The formation of carbon/Si self-interstitial clusters promotes the premature break-up of Ci and the increase of the Si self-interstitial concentration in the carbon rich regions and, consequently, provides a better fit to the experiments. The low solubility of carbon in silicon at the annealing temperatures explains why these clusters are formed, even under conditions where the self-interstitial concentration is below the equilibrium value.

scholarly journals Data workflow to incorporate thermodynamic energies from Calphad databases into grand-potential-based phase-field models

2021 ◽  
Author(s):  
Kaveh Dargahi Noubary ◽  
Michael Kellner ◽  
Johannes Hötzer ◽  
Marco Seiz ◽  
Hans J. Seifert ◽  
...  
Keyword(s):  
Gibbs Energy ◽  
Phase Field ◽  
Ternary Eutectic ◽  
Experimental Studies ◽  
Simulation Studies ◽  
Grand Potential ◽  
Material Systems ◽  
Temperature Ranges ◽  
Equilibrium Concentrations ◽  
Direct Generation

Abstract In order to approximate Gibbs energy functions, a semi-automated framework is introduced for binary and ternary material systems, using Calphad databases. To generate Gibbs energy formulations by means of second-order polynomials, the framework includes a precise approach. Furthermore, an optional extensional step enables the modeling of systems in which a direct generation leads to the unsatisfactory results in the representation of the thermodynamics. Furthermore, an optional extensional step enables the modeling of systems, in which a direct generation leads to the unsatisfactory results, when representing the thermodynamics. Within this extension, the commonly generated functions are modified to satisfy the equilibrium conditions in the observed material systems, leading to a better correlation with thermodynamic databases. The generated Gibbs energy formulations are verified by recalculating the equilibrium concentrations of the phases and rebuilding the phase diagrams in the considered concentration and temperature ranges, prior to the simulation studies. For all comparisons, a close match is achieved between the results and the Calphad databases. As practical examples of the method, phase-field simulation studies for the directional solidification of the binary – and the ternary – eutectic systems are performed. Good agreements between the simulation results and the reported theoretical and experimental studies from literature are found, which indicates the applicability of the presented approaches. Graphical Abstract

scholarly journals Study of Phase and Chemical Composition of Bi1-xNdxFeO3 Powders Derived by Pressureless Sintering

2013 ◽  
Vol 58 (4) ◽  
pp. 1371-1376 ◽  
Author(s):  
J. Dzik ◽  
A. Lisinska-Czekaj ◽  
A. Zarycka ◽  
D. Czekaj
Keyword(s):  
Weight Loss ◽  
Chemical Composition ◽  
Structural Phase ◽  
Simultaneous Thermal Analysis ◽  
Orthorhombic Symmetry ◽  
Pressureless Sintering ◽  
Oxide Powders ◽  
Neodymium Concentration ◽  
Temperature Ranges ◽  
Phase And Chemical Composition

Abstract In the present paper studies on Bi1-xNdxFeO3 for x =0.1-0.4 are reported. The mixed oxide method followed with pressureless sintering was employed for ceramics fabrication. Thermal behavior of stoichiometric mixtures of simple oxide powders, viz. Bi2O3, Nd2O3 and Fe2O3 was studied by simultaneous thermal analysis. It was found that with an increase in neodymium content the weight loss increased from 0.75% to 3.16% for x =0.1 and x =0.4, respectively. It was found that weight loss took place mainly within two temperature ranges, namely ΔT1 ≈(300-400)0C and ΔT2 ≈(600-800)°C. Bi1-xNdxFeO3 ceramics was studied in terms of its phase composition (X-ray phase analysis) and chemical composition (EDS method) at room temperature. It was found that Bi1-xNdxFeO3 suffered structural phase transition from rhombohedral to orthorhombic symmetry with an increase in neodymium concentration x within the range x =(0.2-0.3).

When is an outlier not an outlier?

NIR news ◽  
2019 ◽  
Vol 30 (3) ◽  
pp. 9-11 ◽  
Author(s):  
Phil Williams
Keyword(s):  
Chemical Composition ◽  
Chemical Analysis ◽  
Reference Data ◽  
Calibration Development

The tendency of the users of NIRS is to think of the composition particularly in terms of the reference data, for the prediction of which the technique is to be used. The concept and principle of NIRS analysis differ from classical chemical analysis in that NIRS is based exclusively on the spectra. Spectra are of course, derived from the chemical and physical make-up of the material, but the spectra can differ among materials that are reported as having the same chemical composition. This is particularly a factor with growing crops, and is exemplified in the article, which endorses the recommendation to take replicate samples of the same reported composition for calibration development.

Some Regularities of Thermocontact Pyrolysis of Propane

2021 ◽  
Vol 625 (3) ◽  
pp. 25-27
Author(s):  
R. G. Khasanov ◽  
◽  
N. M. Zakharov ◽  
R. R. Gaziev. ◽  
◽  
...  
Keyword(s):  
Kinetic Data ◽  
Thermal Contact ◽  
Reaction System ◽  
Calculated Data ◽  
Equilibrium Thermodynamic ◽  
Preliminary Assessment ◽  
Pyrolysis Products ◽  
Equilibrium Concentrations ◽  
Final Composition ◽  
Calculated Equilibrium

To compare the equilibrium yields of pyrolysis products and real kinetic data, studies on the thermal contact pyrolysis of propane were carried out. To determine the equilibrium yields of pyrolysis products, the method of minimizing the energy of the system was used, the advantage of which is the need to know only the initial and final composition of the components of the reaction system. The possibility of predicting the yields of propane pyrolysis products using calculated equilibrium thermodynamic yields is shown. It is shown that the accuracy of the calculated data depends on the pyrogas components formed during pyrolysis specified at the beginning of the calculation. It is established that the actual concentrations of pyrolysis products in the pyrogas can be both higher and lower than the calculated equilibrium concentrations, which will only indicate that the equilibrium state of the system is reached or not reached during the process. This method can be used for pyrolysis of other hydrocarbons for the purpose of preliminary assessment of the maximum possible yields of products during the process.

scholarly journals Quantitative characterization of mns inclusions in S355 steel regarding to solidification rate

2013 ◽  
Vol 67 (2) ◽  
pp. 331-336
Author(s):  
Aida Mahmutovic
Keyword(s):  
Chemical Composition ◽  
Special Interest ◽  
Electron Probe ◽  
Solidification Rate ◽  
Equilibrium Phase ◽  
Casting Surface ◽  
Electron Probe Microanalyzer ◽  
Metallic Inclusions ◽  
Thermo Calc Software ◽  
Liquidus Temperatures

A practice of special interest for metallurgical steelmaking is the relationship between redistribution of solute elements and dendrite microsegregation that occurs during solidification. These phenomena have a significant impact on the final properties of cast and forged products. In this paper, a calculation of the characteristic chemical phases in S355 steel using a software program Thermo-Calc is presented. Also, the paper presents experimental measurements of the dendrites size and non-metallic inclusions using optical and electron probe microanalyzer, as well as the calculation of the local solidification rate on the particular example. These phenomena are of special interest when it comes to thin castings and higher cooling rates. Thin castings require higher quality of casting surface, corresponding distribution, and character than those of non-metallic inclusions. Thermo-calc software was used for calculation of equilibrium phases, temperature ranges of solidification of tested material, and temperature range for developing characteristic equilibrium phase. It was found that during solidification and cooling processes manganese sulphide inclusions were formed. Additionally, accurate values for solidus and liquidus temperatures, which coincide with the values of solidus and liquidus temperatures obtained by the Thermo Calc, were calculated. Using optical and electron probe microanalyzer, the type of inclusions were confirmed, whereas chemical composition and size measurement of dendrites, and formed non-metallic inclusions were determined. Mapping and Linescan methods were used to examine the size and exact chemical composition of sulphides in atomic percents. Using secondary dendrites local solidification rate was calculated (for casting surface area solidification rate was 5 K/s). This paper gives contribution to better understanding the influence of cooling rate on casting microstructure formation and dendrites, which essentially determine the size of non-metallic inclusions and their redistribution.

scholarly journals Estimating sulfide capacities for ternary systems with limited solubility

2012 ◽  
Vol 48 (2) ◽  
pp. 219-226 ◽  
Author(s):  
L.J. Wang ◽  
Q.Y. Liu ◽  
K.C. Chou
Keyword(s):  
Thermophysical Properties ◽  
Boundary Data ◽  
Molten Slag ◽  
Reference Data ◽  
Calculated Data ◽  
Sulfide Capacity ◽  
Ternary Systems ◽  
Optical Basicity ◽  
Current Work ◽  
Good Agreement

In view of successful application of mass triangle model in thermophysical properties, in the current work, the mass triangle model was extended to evaluate sulfide capacities of ternary systems with limited homogeneous region. Four ternary systems of Al2O3-FeO-SiO2, FeO-CaO-SiO2, CaO-CaCl2-CaF2 and CaO-CaF2-SiO2 were chosen to calculate iso-sulfide capacity based on the limited boundary data. The good agreement between reference data and calculated data indicated that this model is feasible and will play an indispensable role in the future. Compared with optical basicity model, the results obtained by mass triangle model are still competitive when containing Cl- and F- in the molten slag due to lacking the optical basicity values.

scholarly journals Correlations for calculating the transport and thermodynamic properties of lead-bismuth eutectic

2020 ◽  
Vol 6 (2) ◽  
pp. 125-130
Author(s):  
Igor A. Chusov ◽  
Vladimir G. Pronyaev ◽  
Grigory Ye. Novikov ◽  
Nikolay A. Obysov
Keyword(s):  
Experimental Studies ◽  
Calculated Data ◽  
Statistical Processing ◽  
Least Square Method ◽  
Least Square ◽  
Temperature Ranges ◽  
State Corporation ◽  
Density Dynamic ◽  
Data Estimation ◽  
Local Speed

The paper presents recommended correlations for calculating the thermodynamic and transport properties of Pb-Bi eutectic (44.5% Pb + 55.5% Bi), namely: density, dynamic viscosity, specific heat, thermal conductivity, surface tension, specific electrical resistance, and local speed of sound as a function of temperature. These correlations are based on calculated data presented in 39 experimental studies performed in our country and abroad and published during the period from 1923 to 2015. The authors had information on 1103 experimental points; however, a direct assessment was performed on 1076 points. The main difficulty in processing the data was that the experiments considered in the work were performed at different times using a variety of measurement methods, non-unified methods of statistical processing, varying degrees of eutectic purity, etc. The basis of the data estimation technique was the modified least square method, which made it possible to take into account the errors of the experimental data involved. The paper gives the error values of the proposed correlations and the temperature ranges of their applicability. The paper was prepared based on the results of the work of the Thermodynamic Data Center (TDC INPE NRNU MEPhI) of Rosatom State Corporation.

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