Modeling the Dynamic Recrystallization and Flow Curves Using the Kinetics of Static Recrystallization

Shkatov, Valeriy V.; Mazur, Igor P.

doi:10.3390/ma12183024

Cited by 9 publications

(5 citation statements)

References 27 publications

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“…Thus, the application Arrhenius-type model for flow curves and Johnson-Mehl-Avrami-Kolmogorov (JMAK) for recrystallization kinetics are indispensable. JMAK kinetics has a consolidated application in phase transformation of precipitation through nucleation and growth, which gives the content of a new phase as a function of time [5][6][7] . The global kinetics has been applied in the industrial field of hot forging steels because it represents a "semi-empirical" method, the numerical simulation results of the dynamically recrystallized volume fraction and austenitic grain size [8][9][10] .…”

Section: Introductionmentioning

confidence: 99%

Constitutive Modelling of High Temperature Flow Behaviour for a Low Carbon High Silicon Bainitic Steel

et al. 2020

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It is well recognized the importance of the rheological characterization for the development of the steel in thermomechanical treatments, especially for the mechanical properties improvement of bainitic steels in subsequent hot forging optimization. Therefore, the plastic strain behaviour of a low carbon high silicon bainitic steel was studied through isothermal compression tests using a thermomechanical simulator at temperatures of 1123 K-1423 K and strain rates of 0.1-5 s-1. Arrhenius equation was used to obtain the constitutive constants, which represents the material behaviour of flow stress in high temperature. Besides, work hardening, dynamic recovery, and the JMAK model in the dynamic recrystallization (DRX) of the steel parameters were determined. The second part of this research compared two proposed modified models from the literature, which showed the differences in modelled flow curves behaviour when they are applied for high strain levels. The flow curves were modelled in high strain levels for further implementation in numerical simulation, thus allowing an adjustment of parameters in hot forming processes for this bainitic steel. The proposed models presented an agreement with experimental values. However, only the Avrami equation to DRX showed the dynamic recovery mechanism in high strain levels, which has represented physical behaviour during the thermomechanical process.

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Section: Introductionmentioning

confidence: 99%

Constitutive Modelling of High Temperature Flow Behaviour for a Low Carbon High Silicon Bainitic Steel

et al. 2020

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“…The graph in Figure 25 documents the accuracy of Equation (11). The dependence of precipitate size on time and precipitation temperature calculated by Equation ( 11) is shown in Figure 26.…”

mentioning

confidence: 66%

“…Many authors [8][9][10][11] have used microstructure evolution models to design controlled forming regimes. Usually, however, these are models created for strip rolling on the final sequence of (semi)continuous mills at low rolling temperatures, where the SIP effect has already caused, or will soon cause, a slowing down (in the case of continuous mills with short interpass times, a practical stop) of recrystallization.…”

Section: Introductionmentioning

confidence: 99%

“…16, x FOR PEER REVIEW 21 of 2Based on these values of precipitation parameters and the corresponding values o precipitate size, it was possible to develop Equation (11) describing the effect of tempera ture and precipitation time on the size of NbX precipitates: Figure25documents the accuracy of Equation(11). The dependence o precipitate size on time and precipitation temperature calculated by Equation (11) is shown in Figure26.…”

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confidence: 98%

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Analysis of the Microstructure Development of Nb-Microalloyed Steel during Rolling on a Heavy-Section Mill

Sauer

Fabík²,

Schindler

et al. 2022

Materials

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It is not realistic to optimize the roll pass design of profile rolling mills, which typically roll hundreds of profiles, using physical modelling or operational rolling. The use of reliable models of microstructure evolution is preferable here. Based on the mathematical equations describing the microstructure evolution during hot rolling, a modified microstructure evolution model was presented that better accounts for the influence of strain-induced precipitation (SIP) on the kinetics of static recrystallization. The time required for half of the structure to soften, t0.5, by static recrystallization was calculated separately for both situations in which strain-induced precipitation occurred or did not occur. On this basis, the resulting model was more sensitive to the description of grain coarsening in the high-rolling-temperature region, which is a consequence of the rapid progress of static recrystallization and the larger interpass times during rolling on cross-country and continuous mills. The modified model was verified using a plain strain compression test (PSCT) simulation of rolling a 100-mm-diameter round bar performed on the Hydrawedge II hot deformation simulator (HDS-20). Four variants of simulations were performed, differing in the rolling temperature in the last four passes. For comparison with the outputs of the modified model, an analysis of the austenite grain size after rolling was performed using optical metallography. For indirect comparison with the model outputs, the SIP initiation time was determined based on the NbX precipitate size distribution obtained by TEM. Using the PSCT and the outputs from the modified microstructure evolution model, it was found that during conventional rolling, strain-induced precipitation occurs after the last pass and thus does not affect the austenite grain size. By lowering the rolling temperature, it was possible to reduce the grain size by up to 56 μm, while increasing the mean flow stress by a maximum of 74%. The resulting grain size for all four modes was consistent with the operating results.

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“…The sintering of nanomaterials is a technologically important process and has been studied by both experimental researchers [10][11][12][13] and those conducting model works [14][15][16][17]. First of all, various kinetic aspects of the sintering process related to the change in the structure of nanomaterials and the growth of nanoparticles were examined [6,[18][19][20][21]. To describe the sintering process, the concept of residual dispersion was introduced [22].…”

Section: Introductionmentioning

confidence: 99%

Thermodynamics of Iron Ammonia Synthesis Catalyst Sintering

Arabczyk,

Pelka,

Jasińska

et al. 2024

Crystals

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The sintering of iron ammonia synthesis catalysts (nanocrystalline iron promoted with: Al2O3, CaO and K2O) was studied under a hydrogen atmosphere, in a temperature range of 773 to 973 K to obtain stationary states. The catalysts were characterized by measuring the nitriding reaction rate under an ammonia atmosphere at 748 K to obtain steady states and the measurement of specific surface area. Chemical processes were conducted in a tubular differential reactor enabling thermogravimetric measurements and the chemical composition analysis of a gas phase under conditions allowing experiments to be carried out in the kinetic region of chemical reactions. An extended model of the active surface of the iron ammonia synthesis catalyst was presented, taking into account the influence of the gas phase composition and process temperature. The surface of iron nanocrystallites was wetted using promoters in an exothermic process associated with the formation of the surface Fes-O- bond and the change in the surface energy of iron nanocrystallites. Promoters formed on the surface of iron nanocrystallites with different structures of chemisorbed dipoles, depending on the composition of the gas phase. The occupied sites stabilized the structure, and the free sites were active sites in the process of adsorption of chemical reagents and in sintering. Based on the bonding energy of the promoter oxides and the difference in surface energy between the covered and uncovered surfaces, the wetting abilities of promoters, which can be arranged according to the order K2O > Fe3O4 > Al2O3 > CaO, were estimated. By increasing the temperature in the endothermic sintering process, the degree of surface coverage with dipoles of promoters decreased, and thus the catalyst underwent sintering. The size distribution of nanocrystallites did not change with decreasing temperature. Only the equilibrium between the glass phase and the surface of iron nanocrystallites was then established.

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Modeling the Dynamic Recrystallization and Flow Curves Using the Kinetics of Static Recrystallization

Cited by 9 publications

References 27 publications

Constitutive Modelling of High Temperature Flow Behaviour for a Low Carbon High Silicon Bainitic Steel

Constitutive Modelling of High Temperature Flow Behaviour for a Low Carbon High Silicon Bainitic Steel

Analysis of the Microstructure Development of Nb-Microalloyed Steel during Rolling on a Heavy-Section Mill

Thermodynamics of Iron Ammonia Synthesis Catalyst Sintering

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