A Kinetics Model of Isothermal Ferrite and Pearlite Transformations under Applied Stress

Ye, J. S.; Chang, Hongbing; Hsu, T.Y.

doi:10.2355/isijinternational.44.1079

Cited by 6 publications

(3 citation statements)

References 11 publications

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“…Therefore, it is necessary to study the effect of stress on microstructures development during the non-isothermal process. Until now, some studies have been concentrated on the effect of stress on phase transformation behaviors, such as isothermal ferrite and pearlite transformations [11], austenite decomposition [12], martensitic phase transformations [13], bainitic phase transformation [14] and so on. However, to our best knowledge, there is still no research concerning on the microstructural transformation, and especially the cementite precipitation behaviors of GCr15 bearing steel during the non-isothermal process under applied stress.…”

Section: Introductionmentioning

confidence: 99%

Accelerating Cementite Precipitation during the Non-Isothermal Process by Applying Tensile Stress in GCr15 Bearing Steel

et al. 2018

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In this work, the non-isothermal process of GCr15 bearing steel after quenching and tempering (QT) under different tensile stress (0, 20, 40 MPa) was investigated by kinetic analysis and microstructural observation. The Kissinger method and differential isoconversional method were employed to assess the kinetic parameters of the microstructural evolution during the non-isothermal process with and without applied stress. It is found that the activation energy of retained austenite decomposition slightly increases from 109.4 kJ/mol to 121.5 kJ/mol with the increase of tensile stress. However, the activation energy of cementite precipitation decreases from 179.4 kJ/mol to 94.7 kJ/mol, proving that tensile stress could reduce the energy barrier of cementite precipitation. In addition, the microstructural observation based on scanning and transmission electron microscopy (SEM and TEM) shows that more cementite has formed for the specimens with the applied tensile stress, whereas there is still a large number of ε carbides existing in the specimens without stress. The results of X-ray diffraction (XRD) also verify that carbon in martensite diffuses more and participates in the formation of cementite under the applied tensile stress, which thus are in good agreement with the kinetic analysis. The mechanisms for the differences in cementite precipitation behaviors may lie in the acceleration of carbon atoms migration and the reduction of the nucleation barrier by applying tensile stress.

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Section: Introductionmentioning

confidence: 99%

Accelerating Cementite Precipitation during the Non-Isothermal Process by Applying Tensile Stress in GCr15 Bearing Steel

et al. 2018

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“…It is clear that the temperatures of the points in contact with the punch (points 1-5) are almost equal, and the same conditions also exist for the points in contact with the die (points [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. According to the slight temperature differences in each of these two regions, in order for reducing calculations, the thermal histories of the points P and D (1 and 26) were considered as the representatives of those of other points in contact with the punch and die, respectively, for the final calculations of the microstructure predictions.…”

Section: Simulation Resultsmentioning

confidence: 92%

“…Previous studies show that the stored plastic deformation energy in austenite has different effects on several austenite transformations. It raises the transformation rate of austenite to ferrite and pearlite (Ref 9,10,(15)(16)(17)(18)(19)(20) ) models are the most known. However, these models have limitations and problems ( Ref 10,12,19), which one of the most important ones can be the existence of empirical parameters in their equations requiring fitting equations to experimental data.…”

Section: Introductionmentioning

confidence: 99%

Prediction of Proper Temperatures for the Hot Stamping Process Based on the Kinetics Models

Samadian

Parsa

Mirzadeh

2014

J. of Materi Eng and Perform

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Nowadays, the application of kinetics models for predicting microstructures of steels subjected to thermomechanical treatments has increased to minimize direct experimentation, which is costly and time consuming. In the current work, the final microstructures of AISI 4140 steel sheets after the hot stamping process were predicted using the Kirkaldy and Li kinetics models combined with new thermodynamically based models in order for the determination of the appropriate process temperatures. In this way, the effect of deformation during hot stamping on the Ae 3 , Acm, and Ae 1 temperatures was considered, and then the equilibrium volume fractions of phases at different temperatures were calculated. Moreover, the ferrite transformation rate equations of the Kirkaldy and Li models were modified by a term proposed by Å kerström to consider the influence of plastic deformation. Results showed that the modified Kirkaldy model is satisfactory for the determination of appropriate austenitization temperatures for the hot stamping process of AISI 4140 steel sheets because of agreeable microstructure predictions in comparison with the experimental observations.

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Prediction of Temperatures of Austenite Equilibrium Transformations in Steels During Thermomechanical Processing

Samadian

Parsa

Nili‐Ahmadabadi

et al. 2014

J. of Materi Eng and Perform

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A Kinetics Model of Isothermal Ferrite and Pearlite Transformations under Applied Stress

Cited by 6 publications

References 11 publications

Accelerating Cementite Precipitation during the Non-Isothermal Process by Applying Tensile Stress in GCr15 Bearing Steel

Accelerating Cementite Precipitation during the Non-Isothermal Process by Applying Tensile Stress in GCr15 Bearing Steel

Prediction of Proper Temperatures for the Hot Stamping Process Based on the Kinetics Models

Prediction of Temperatures of Austenite Equilibrium Transformations in Steels During Thermomechanical Processing

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