Competition between nucleation and early growth of ferrite from austenite—studies using cellular automaton simulations

Kumar, M.; Sasikumar, R.; Nair, P. Kesavan

doi:10.1016/s1359-6454(98)00243-2

Cited by 88 publications

(53 citation statements)

References 10 publications

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“…These phenomena could be explained via thermodynamics. The volume diffusivities of manganese and carbon in austenite are respectively expressed as following [32,49]: …”

Section: Effect Of Second Phase Region Size On Retained Austenite Retmentioning

confidence: 99%

Microstructure and mechanical properties of strip cast TRIP steel subjected to thermo-mechanical simulation

Xiong

Kostryzhev

Liang

et al. 2016

Materials Science and Engineering: A

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Instead of hot rolling and cold rolling followed by annealing, strip casting is a more economic and environmentally friendly way to produce transformation-induced plasticity (TRIP) steels. According to industrial practice of strip casting, rapid cooling in this work was achieved using a dip tester, and a Gleeble 3500 thermo-mechanical simulator was used to carry out the processing route. A typical microstructure of TRIP steels, which included ~0.55 fraction of polygonal ferrite with bainite, retained austenite and martensite, was obtained. The effects of deformation (0.41 reduction) above non-recrystallisation temperature, isothermal bainite transformation temperature and the size of second phase region on microstructure and mechanical properties were studied. The steel isothermally transformed at 400 °C had the best combination of ultimate tensile strength (UTS) and total elongation (TE), whether deformation was applied or not. The deformation resulted in the improvement of mechanical properties after holding at 400 °C: the UTS increased from 590 to 696 MPa and TE decreased from 0.27 only to 0.26. It was predominantly ascribed to grain size refinement and dislocation strengthening. The studied TRIP steel had comparable mechanical properties with TRIP 690 produced commercially. Abstract: Instead of hot rolling and cold rolling followed by annealing, strip casting is a more economic and environmentally friendly way to produce transformation-induced plasticity (TRIP) steels. According to industrial practice of strip casting, rapid cooling in this work was achieved using a dip tester, and a Gleeble 3500 thermo-mechanical simulator was used to carry out the processing route. A typical microstructure of TRIP steels, which included ~ 0.55 fraction of polygonal ferrite with bainite, retained austenite and martensite, was obtained. The effects of deformation (0.41 reduction) above non-recrystallisation temperature, isothermal bainite transformation temperature and the size of second phase region on microstructure and mechanical properties were studied. The steel isothermally transformed at 400 °C had the best combination of ultimate tensile strength (UTS) and total elongation (TE), whether deformation was applied or not. The deformation resulted in the improvement of mechanical properties after holding at 400 °C: the UTS increased from 590 to 696 MPa and TE decreased from 0.27 only to 0.26. It was predominantly ascribed to grain size refinement and dislocation strengthening. The studied TRIP steel had comparable mechanical properties with TRIP 690 produced commercially.

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“…These phenomena could be explained via thermodynamics. The volume diffusivities of manganese and carbon in austenite are respectively expressed as following [32,49]: …”

Section: Effect Of Second Phase Region Size On Retained Austenite Retmentioning

confidence: 99%

Microstructure and mechanical properties of strip cast TRIP steel subjected to thermo-mechanical simulation

Xiong

Kostryzhev

Liang

et al. 2016

Materials Science and Engineering: A

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“…Similar to the MC simulations 2D CA schemes have been proposed for the austenite-to ferrite transformation. [152][153][154][155] Nucleation and growth models have been incorporated into the CA algorithm and the mixed-mode character of the reaction can be replicated. A number of adjustable parameters, e.g.…”

Section: Meso-scale Modelling Approachesmentioning

confidence: 99%

Computer Simulation of Microstructure Evolution in Low Carbon Sheet Steels

Militzer

2007

ISIJ Int.

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Models of microstructure evolution in steels are reviewed. The emphasis of the review is on low carbon sheet steels both hot-rolled and cold-rolled and annealed. First the state-of-the-art on industrial microstructure process models is presented. The individual model concepts for grain growth, recrystallization, precipitation and phase transformations are briefly discussed. The development from empirically-based models to physically-based models is identified as a key issue to have increased predictive capabilities for these models over a wider range of steel grades and operational conditions. The challenges in the development of the next generation of models are delineated. In particular, new aspects of microstructure evolution associated with novel processing routes and advanced high strength steels are evaluated. Further, the majority of the currently employed models are on the macro-scale but future microstructure models will increasingly be meso-scale models that predict actual microstructures rather than a number of average parameters (e.g. grain size, fraction transformed) to describe microstructure evolution.KEY WORDS: mathematical model; microstructure; steel; hot rolling; annealing; grain growth; recrystallization; precipitation; phase transformation. © 2007 ISIJ Reviewvates the development of advanced microstructure models that provide an increased insight into the underlying physical metallurgy principles. Further, AHSS are frequently produced as cold-rolled annealed and/or coated sheets. Here, the intercritical annealing step assumes a crucial role to obtain the desired complex, multi-phase microstructures. Intercritical annealing constitutes a paradigm shift from annealing of conventional steels where no cycling through the transformation region occurs. The added complexity of the annealing routes for AHSS requires the development of novel annealing models that also address austenite formation which has received comparatively little attention in process models.Currently available microstructure models for the production of sheet and other steels are usually formulated on the macro-scale, i.e. the microstructure is described with a number of so-called internal state variables such as grain size, fraction recrystallized and fraction transformed. However, the advances in computer technology make it now feasible to routinely conduct modelling of the microstructure on the meso-scale if not on the atomistic level. In particular the meso-scale approach appears to open a new era of modelling the microstructure evolution in sheet steels. In this methodology actual microstructures can be predicted rather than mean values which have traditionally been used to characterize microstructures. The significance of these new modelling strategies is also fueled by the realization that material properties may markedly depend on morphology and spatial distributions of microstructure constituents. [22][23][24] In this paper, first the models proposed for hot strip rolling are reviewed. Special attention is given to the ...

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“…With the recent development of numerical models, simulations using different methods, such as the phase field (PF) method [6,7], the Monte Carlo (MC) method [8,9] and the cellular automaton (CA) method [10][11][12][13], can provide insight into the microstructure evolution and solute diffusion during the ferrite-austenite transformation. The present authors proposed a two-dimensional (2-D) CA model to simulate the ferrite (α)-austenite (γ) transformation and carbon diffusion during different heat treatment processes [14].…”

Section: Introductionmentioning

confidence: 99%

Cellular automaton simulation of ferrite-austenite transformation in low-carbon steels

Pan

et al. 2015

IOP Conf. Ser.: Mater. Sci. Eng.

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Abstract.A two-dimensional (2-D) cellular automaton (CA) model is adopted to simulate ferrite (α)-austenite (γ) transformation in low-carbon steels. In the model, the preferential nucleation sites of austenite, the driving force of phase transformation coupled with thermodynamic parameters, solute partition at the α/γ interface, and carbon diffusion in both the α and γ phases are taken into consideration. The model is able to simulate the ferrite-toaustenite transformation during isothermal heating in the ferrite-austenite two-phase region, and the austenite-to-ferrite transformation during continuous cooling. The influences of cooling rate and α grain size on the final carbon concentration field are investigated. The results show that after isothermal heating at 815°C for 300 s, the carbon concentration in both the α and γ phases reach the respective equilibrium values. The simulated microstructures compare well with the SEM images. After cooling to room temperature, the carbon distribution is more uniform when cooled at 1.2°C/s than at 7°C/s. The carbon distributions for different α grain sizes cooled at 1.2°C/s are similar. The simulation results are used to understand the mechanisms of the experimental phenomena of an enameling steel.

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Competition between nucleation and early growth of ferrite from austenite—studies using cellular automaton simulations

Cited by 88 publications

References 10 publications

Microstructure and mechanical properties of strip cast TRIP steel subjected to thermo-mechanical simulation

Microstructure and mechanical properties of strip cast TRIP steel subjected to thermo-mechanical simulation

Computer Simulation of Microstructure Evolution in Low Carbon Sheet Steels

Cellular automaton simulation of ferrite-austenite transformation in low-carbon steels

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