Mathematical Modelling of Isothermal Decomposition of Austenite in Steel

Smoljan, Božo; Iljkić, Dario; Hanza, Sunčana Smokvina; Hajdek, Krunoslav

doi:10.3390/met11081292

Cited by 2 publications

(3 citation statements)

References 15 publications

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“…The derived kinetic equation describes the overall tempering process, encompassing not only the decomposition of M/A but also the transformation of retained austenite (RA) and the bainite matrix during tempering [ 21 ]. Nevertheless, this kinetic equation still describes well the M/A decomposition [ 27 , 36 ]. The kinetic equations for the austempering phase transition can be described using the JMAK equation as follows:

where

is the fraction of new phase generation;

is the reaction rate constant;

is the pre-exponential factor, a constant determined by the material and type of phase transition;

is the phase transition time;

is the Avrami exponent;

is the gas constant (8.314

);

is the thermodynamic temperature; and

is the phase transition activation energy.…”

Section: Resultsmentioning

confidence: 99%

“…The derived kinetic equation describes the overall tempering process, encompassing not only the decomposition of M/A but also the transformation of retained austenite (RA) and the bainite matrix during tempering [21]. Nevertheless, this kinetic equation still describes well the M/A decomposition [27,36]. The kinetic equations for the austempering phase transition can be described using the JMAK equation as follows:…”

Section: Kinetic Equation Of M/a Decompositionmentioning

confidence: 99%

“…Therefore, investigating the kinetic equation of M/A decomposition in ultra-fine nano-bainite steel is crucial for its future application and development. Smoljan et al [ 27 ] conducted mathematical modeling and computer simulations to analyze the isothermal decomposition of austenite in steel, developing kinetic equations that can be used to predict the microstructural composition of hypoeutectoid steels. Differential scanning calorimetry (DSC) has been the preferred technique for measuring kinetic data by numerous researchers because of its speed, dependability, and ease of use.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Kinetics of Martensite/Austenite Decomposition during Tempering of Ultrafine Nano-Bainitic Steels

Qu,

Lei,

Chen

et al. 2024

Materials

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In this study, the decomposition of a martensite/austenite (M/A) microconstituent in bainitic steels was analyzed using differential scanning calorimetry (DSC) data in conjunction with Kissinger’s and Johnson–Mehl–Avrami–Kolmogorov (JMAK)’s formulas. In bainitic steel subjected to austempering heat treatment, the presence of an M/A microstructure adversely affects the mechanical properties. According to the kinetic equations derived, it is observed that after tempering the sample at 600 °C for 4000 s, the generation of each phase reaches its maximum. The SEM images taken before and after tempering reveal extensive decomposition of the M/A constituent in the microstructure. The proportion of the M/A microstructure decreased significantly from about 10% before tempering to less than 1% after. Additionally, the content of residual austenite also reduced nearly to zero. These observations are consistent with the predictions of the kinetic equations.

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where

is the fraction of new phase generation;

is the reaction rate constant;

is the pre-exponential factor, a constant determined by the material and type of phase transition;

is the phase transition time;

is the Avrami exponent;

is the gas constant (8.314

);

is the thermodynamic temperature; and

is the phase transition activation energy.…”

Section: Resultsmentioning

confidence: 99%

“…The derived kinetic equation describes the overall tempering process, encompassing not only the decomposition of M/A but also the transformation of retained austenite (RA) and the bainite matrix during tempering [21]. Nevertheless, this kinetic equation still describes well the M/A decomposition [27,36]. The kinetic equations for the austempering phase transition can be described using the JMAK equation as follows:…”

Section: Kinetic Equation Of M/a Decompositionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Kinetics of Martensite/Austenite Decomposition during Tempering of Ultrafine Nano-Bainitic Steels

Qu,

Lei,

Chen

et al. 2024

Materials

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An Application of Computer Simulation of Austenite Decomposition in Optimization of Hot Rolling of Low Alloyed Steel Bars

Smoljan¹,

Hanza²

2023

IJMMT

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Modern technologies need more and more precise computer design of manufacturing processes. Especially it is visible in thermal processing of steel, such as hot rolling, hot forging, casting, welding, 3D printing, and so on. An application of computer simulation of austenite decomposition in optimization of manufacturing of low alloyed steel bars by hot rolling was studied. For this purpose the mathematical model and computer software for very precise anticipation of TTT diagrams data was developed. The calculation of TTT diagrams data was based on chemical composition of low alloyed steels. The study started with definition mechanisms of austenite decomposition at constant subcritical temperatures. The mechanism of γ→α phase change in steel is not yet been adequately clarified. Methods for calibration of kinetic equations of austenite phase transition at constant subcritical temperatures were developed in this paper. Mathematical modeling of TTT diagrams data consists both, prediction of kinetic of phase transformations and anticipation of steel hardness. It was found out that the hardness of both, microstructural constituents and total hardness of steel mostly depends on the carbon content and temperature of γ→α phase transformation. The model of TTT diagrams data of low alloyed steel was verified in purpose to apply the model of isothermal decomposition of austenite in very precise method for prediction of microstructure composition and hardness of hot rolled steel bars. The verification of developed model was done by comparison of the calculated results of TTT diagrams data with experimentally estimated TTT diagrams data. By the simulation of hardness and microstructural composition of hot rolled steel bar the optimal cooling regime in cooling beds can be designed.

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Mathematical Modelling of Isothermal Decomposition of Austenite in Steel

Cited by 2 publications

References 15 publications

Kinetics of Martensite/Austenite Decomposition during Tempering of Ultrafine Nano-Bainitic Steels

Kinetics of Martensite/Austenite Decomposition during Tempering of Ultrafine Nano-Bainitic Steels

An Application of Computer Simulation of Austenite Decomposition in Optimization of Hot Rolling of Low Alloyed Steel Bars

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