On the transformation kinetics of work-hardened austenite (γ) → pro-eutectoid ferrite (α) of CMn steels

Liu, Z.; Wang, G.; Zhang, Q.

doi:10.1016/0924-0136(94)90039-6

Cited by 2 publications

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References 2 publications

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“…Thorough characterization of the kinetics can enhance the fundamental understanding of the underlying molecular processes, assist in the rational design and development of materials and processes, and address uncertainties regarding the stability of the particular phases. Notable investigations of the kinetics of phase transitions include studies on metals and alloys, ceramics, inorganic compounds, and molecular crystals …”

Section: Introductionmentioning

confidence: 99%

Kinetics of the Solid-State Phase Transformation of Form β to γ of Sulfanilamide Using Time-Resolved Energy-Dispersive X-ray Diffraction

Sheridan

Anwar

1996

Chem. Mater.

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The kinetics of the solid-state phase transformation of form β to γ of sulfanilamide in powdered samples have been investigated using energy-dispersive X-ray diffraction (EDXRD) combined with synchrotron radiation. The β to γ transformation which is relatively fast has been followed in real time, courtesy of the high time resolution of the EDXRD method. The data obtained yield R-time curves of high accuracy and precision. The observed kinetics are atypical in that the transformation does not always proceed to completion but plateaus off, the rate and extent being higher with increasing temperature. This phenomenon suggests a distribution of activation energies in the powdered samples. Despite this complication the data have been analyzed by considering only the fraction transformed. Of the various kinetic models considered, the Avrami-Erofeyev (n ) 3.5) and the Cardew model were found to best describe the data. The data fitting with both of these models, however, was not totally satisfactory. The Avrami-Erofeyev model was found to depart increasingly from the observed data at high R values. The Cardew model, being specific for powdered or polycrystalline samples, was significantly better, but only up to R values of about 0.85. Above this point the Cardew model deviates markedly from the observed data. Direct visual observation using hot-stage microscopy has revealed that the transformation always proceeds from a single nucleation event in each crystallite and that coalescence of growing surfaces and ingestion of potential nuclei are unimportant, which is consistent with the Cardew model. Also, extinction studies using polarized light have shown that the transformation in the crystallites is generally of the type single crystal to single crystal but does not exhibit any orientational relationship. The overall activation energy and the individual nucleation and growth activation energies for the β to γ transformation based on the Cardew model were determined to be 101 ( 7, 142 ( 14, and 70 ( 4 kJ/mol, respectively. The activation energy based on the Avrami-Erofeyev model was 89 ( 8 kJ/mol. These magnitudes are within the expected range for molecular crystals.

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Section: Introductionmentioning

confidence: 99%

Kinetics of the Solid-State Phase Transformation of Form β to γ of Sulfanilamide Using Time-Resolved Energy-Dispersive X-ray Diffraction

Sheridan

Anwar

1996

Chem. Mater.

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“…As for the kinetics of phase transition, several methodologies were proposed, such as phase-field [21][22][23] framework [24] and internal-state variable models [25,26], the Gibbs energy balance model [27,28], the mixed-mode model [29,30], and the Johnson-Mehl-Avrami equation [31]. These methods were applied to medium and high-alloy steel [32] and low-carbon steel [33][34][35]. For example, for medium-carbon microalloy steel, such as high-strength hot-rolled rebar, few experimental studies have focused on the transition kinetics of austenite to ferrite.…”

Section: Introductionmentioning

confidence: 99%

The Kinetics of Phase Transition of Austenite to Ferrite in Medium-Carbon Microalloy Steel

Liu

Zhou

2021

Metals

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To reduce energy and resource consumption, high-strength hot-rolled rebars with yield strengths of ≥400 MPa (HRB500) and ≥500 MPa (HRB600) have been designed and produced in recent years. Optimizing the microstructure in the steel to improve strength necessitates determining the kinetics of the phase transition of austenite to polygonal ferrite. Therefore, in the study, the effect of temperature and holding time on the volume fraction of ferrite is investigated in HRB500 and HRB600 steels. Experimental results show that the ferrite percentage initially increases with an increase in temperature and then decreases as the temperature increases from 600 to 730 °C. The optimum temperature range is 680–700 °C for HRB500 steel and 650–680 °C for HRB600 steel. Based on the Johnson–Mehl–Avrami equation, phase transition kinetic models are established. Model predictions are consistent with the validation data. Thus, this study establishes a reference for studying ferrite formation during cooling.

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On the transformation kinetics of work-hardened austenite (γ) → pro-eutectoid ferrite (α) of CMn steels

Cited by 2 publications

References 2 publications

Kinetics of the Solid-State Phase Transformation of Form β to γ of Sulfanilamide Using Time-Resolved Energy-Dispersive X-ray Diffraction

Kinetics of the Solid-State Phase Transformation of Form β to γ of Sulfanilamide Using Time-Resolved Energy-Dispersive X-ray Diffraction

The Kinetics of Phase Transition of Austenite to Ferrite in Medium-Carbon Microalloy Steel

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