Accelerating nano-bainite transformation based on a new constructed microstructural predicting model

Yang, Zhinan; Chu, Chunhe; Jiang, Feng; Qin, Yuman; Long, Xiaoyan; Wang, Shuli; Chen, Da; Zhang, Fucheng

doi:10.1016/j.msea.2019.01.061

Cited by 42 publications

(18 citation statements)

References 21 publications

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“…Some of the parameters controlling the final scale of the bainitic ferrite plates have been already identified [ 1 , 8 , 9 , 10 , 11 , 12 ], and the decrease in the scale of the bainitic ferrite plates as transformation temperature T Iso decreases has been correlated to the increase in the yield strength of the parent austenite (

), the driving force for the transformation (

) and the dislocation density (

). Strong austenite or a large driving force results in finer plates, the former because there is a larger resistance to interface motion and the latter because an increased nucleation rate leads to microstructural refinement by impingement between adjacent plates.…”

Section: Introductionmentioning

confidence: 99%

Bainitic Ferrite Plate Thickness Evolution in Two Nanostructured Steels

et al. 2021

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Bainitic ferrite plate thickness evolution during isothermal transformation was followed at the same holding temperatures in two nanostructured steels containing (in wt.%) 1C-2Si and 0.4C-3Si. A dynamic picture of how the bainitic transformation evolves was obtained from the characterization of the microstructure present at room temperature after full and partial transformation at 300 and 350 °C. The continuous change during transformation of relevant parameters influencing the final scale of the microstructure, YS of austenite, driving force of the transformation and evolution of the transformation rate has been tracked, and these variations have been correlated to the evolution of the bainitic ferrite plate. Instead of the expected refinement of the plate predicted by existing theory and models, this study revealed a thickening of the bainitic ferrite plate thickness as the transformation progresses, which is partially explained by changes in the transformation rate through the whole decomposition of austenite into bainitic ferrite.

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), the driving force for the transformation (

) and the dislocation density (

Section: Introductionmentioning

confidence: 99%

Bainitic Ferrite Plate Thickness Evolution in Two Nanostructured Steels

et al. 2021

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“…Gong et al [21,22] also claimed that the dislocation structure introduced in austenite by low temperature ausforming is found to assist bainite transformation with strong variant selection where partial dislocations introduced by ausforming play an important role for bainite transformation. Yang et al [23] also claimed that a two-steps process can be used to shorten the transformation time from over 60 h to nearly 25 h. He et al [24] reported that the kinetics of bainitic transformation depends on the competition between the increase in nucleation rate and the decrease in average volume of bainite sheaf after deformation. The increase in nucleation rate overcomes the decrease in the average volume of bainite sheaf, resulting in the increase in transformation velocity and volume fraction after small deformation.…”

Section: Introductionmentioning

confidence: 99%

Combined Effects of Deformation and Undercooling on Isothermal Bainitic Transformation in an Fe-C-Mn-Si Alloy

Zou

et al. 2019

Metals

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Both ausforming and transformation temperature affect the successive bainitic transformation and microstructure. The individual influence of each case is clear, whereas the combined effects are still unknown. Thermomechanical simulation and metallography were used to investigate the combined effects of ausforming and transformation temperature on bainitic transformation and microstructure. The kinetics of isothermal bainitic transformation in non-deformed and deformed materials was analyzed. A lower transformation temperature can lead to more bainite formation without deformation. However, ausforming with small strains can partially compensate for the decrease of bainite amount caused by the decreased undercooling. The larger the applied strain is, the smaller the difference between the final amounts of bainite with different undercooling. Ausforming at a relatively higher temperature is more favorable to the acceleration of subsequent isothermal bainitic transformation. The results in the present work provide reference for optimizing the fabrication technology of medium-carbon nanobainite steels.

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“…Therefore, a two-phase model, suggested in the literature, was used to illustrate the concentration of oxygen in oxide films and in the adjacent substrate [39,40]. In this model (Figure 2), the concentration of oxygen was assumed to follow a parabolic law, since the diffusion of the element meets the Arrhenius equation for the given temperatures and metallic materials [41][42][43]. As represented in Figure 2, the x axis indicates the distance from the oxide surface; x 0 is the oxide surface and x 1 is the oxide/substrate interface.…”

Section: Model and Calculation Methodsmentioning

confidence: 99%

Calculation of Oxygen Diffusion Coefficients in Oxide Films Formed on Low-Temperature Annealed Zr Alloys and Their Related Corrosion Behavior

Zhang

Chen

Zhao³

et al. 2019

Metals

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The growth of oxide film, which results from the inward oxygen diffusion from a corrosive environment, is a critical consideration for the corrosion resistance of zirconium alloys. This work calculates the oxygen diffusion coefficients in the oxide films formed on zirconium alloys annealed at 400~500 °C and investigates the related corrosion behavior. The annealed samples have a close size for the second-phase particles but a distinctive hardness, indicating the difference in substrate conditions. The weight gain of all samples highly follows parabolic laws. The weight gain of the sample annealed at 400 °C has the fastest increase rate at the very beginning of the corrosion test, but its oxide film has the slowest growth rate as the corrosion proceeds. By contrast, the sample annealed at 500 °C shows the lowest weight gain but the highest corrosion rate constant. Such a corrosion behavior is attributed to the amount of defects existing in the oxide film formed on the annealed samples; fewer defects would provide a lower fraction of short-circuit diffusion in total diffusion, resulting in a lower diffusion coefficient of oxygen in the oxide film, thereby producing better corrosion resistance. This is consistent with the calculated diffusion coefficients of oxygen in the oxide films: 3.252 × 10−11 cm2/s, 3.464 × 10−11 cm2/s and 3.740 × 10−11 cm2/s for the samples annealed at 400 °C, 450 °C, and 500 °C, respectively.

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Accelerating nano-bainite transformation based on a new constructed microstructural predicting model

Cited by 42 publications

References 21 publications

Bainitic Ferrite Plate Thickness Evolution in Two Nanostructured Steels

Bainitic Ferrite Plate Thickness Evolution in Two Nanostructured Steels

Combined Effects of Deformation and Undercooling on Isothermal Bainitic Transformation in an Fe-C-Mn-Si Alloy

Calculation of Oxygen Diffusion Coefficients in Oxide Films Formed on Low-Temperature Annealed Zr Alloys and Their Related Corrosion Behavior

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