Slow Bainite: an Opportunity to Determine the Carbon Content of the Bainitic Ferrite during Growth

2011 ◽  
Vol 172-174 ◽  
pp. 111-116 ◽  
Author(s):  
Francisca García Caballero ◽  
Michael K. Miller ◽  
Carlos García-Mateo
Keyword(s):  
Solid Solution ◽  
Carbon Content ◽  
Atom Probe Tomography ◽  
Early Stage ◽  
Bainitic Ferrite ◽  
Atom Probe ◽  
Transformation Kinetics ◽  
Bainite Transformation ◽  
Parent Austenite ◽  
Kinetics Of

The amount of carbon in solid solution in bainitic ferrite at the early stage of transformation has been directly determined by atom probe tomography at 200 °C, taking advantage of the extremely slow transformation kinetics of a novel nanocrystalline steel. Results demonstrated that the original bainitic ferrite retains much of the carbon content of the parent austenite providing strong evidence that bainite transformation is essentially displacive in nature.

scholarly journals Study on Kinetics of Transformation in Medium Carbon Steel Bainite at Different Isothermal Temperatures

Materials ◽  
2021 ◽  
Vol 14 (11) ◽  
pp. 2721
Author(s):  
Wei Pei ◽  
Wei Liu ◽  
Yue Zhang ◽  
Rongjian Qie ◽  
Aimin Zhao
Keyword(s):  
Bainitic Ferrite ◽  
Isothermal Transformation ◽  
Medium Carbon Steel ◽  
Transformation Kinetic ◽  
Transformation Kinetics ◽  
Bainite Transformation ◽  
Medium Carbon ◽  
Microstructure And Properties ◽  
Treatment Processes ◽  
Kinetics Of

Ultra-fine carbide-free bainitic (UCFB) steel, also known as nano-bainite (NB) steel, is composed of bainitic ferrite laths with nanoscale thickness and carbon-rich film-like retained austenite located between laths. The bainite transformation kinetic model can accurately describe the bainite transformation kinetics in conventional austempering (CA) processes based on the shear mechanism combined with the dilatometer test. UCFB steels with medium and high carbon composition are designed in this work to systematically study the transformation kinetics of bainite, and the evolution of its microstructure and properties, and reveal the influence of heat treatment processes on the microstructure and properties the UCFB steels. The results show that the activation energy for BF nucleation decreases during the CA process and isothermal transformation temperature decreases. The bainite transformation is first nucleated at the grain boundaries, and then nucleated at the newly formed bainitic ferrite/austenite interface.

scholarly journals Continuous Cooling Transformation Behaviour and Bainite Transformation Kinetics of 23CrNi3Mo Carburised Steel

Metals ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 48
Author(s):  
Wenjun Song ◽  
Min Lei ◽  
Mingpan Wan ◽  
Chaowen Huang
Keyword(s):  
Phase Transformation ◽  
Volume Fraction ◽  
Austenite Formation ◽  
Steel Matrix ◽  
Transformation Kinetics ◽  
Bainite Transformation ◽  
Continuous Cooling ◽  
The Matrix ◽  
Dimensional Growth ◽  
Kinetics Of

In this study, the phase transformation behaviour of the carburised layer and the matrix of 23CrNi3Mo steel was comparatively investigated by constructing continuous cooling transformation (CCT) diagram, determining the volume fraction of retained austenite (RA) and plotting dilatometric curves. The results indicated that Austenite formation start temperature (Ac1) and Austenite formation finish temperature (Ac3) of the carburised layer decreased compared to the matrix, and the critical cooling rate (0.05 °C/s) of martensite transformation is significantly lower than that (0.8 °C/s) of the matrix. The main products of phase transformation in both the carburised layer and the matrix were martensite and bainite microstructures. Moreover, an increase in carbon content resulted in the formation of lamellar martensite in the carburised layer, whereas the martensite in the matrix was still lath. Furthermore, the volume fraction of RA in the carburised layer was higher than that in the matrix. Moreover, the bainite transformation kinetics of the 23CrNi3Mo steel matrix during the continuous cooling process indicated that the mian mechanism of bainite transformation of the 23CrNi3Mo steel matrix is two-dimensional growth and one-dimensional growth.

Effect of Temperature, Carbon Content and Crystallography on the Lengthening Kinetics of Bainitic Ferrite Laths

2021 ◽  
Author(s):  
Haijiang Hu ◽  
Benrabah Imed-Eddine ◽  
Guang Xu ◽  
Junyu Tian ◽  
Mingxing Zhou ◽  
...  
Keyword(s):  
Carbon Content ◽  
Bainitic Ferrite ◽  
Effect Of Temperature ◽  
Kinetics Of

scholarly journals Effect of Two-Step Austempering Process on Transformation Kinetics of Nanostructured Bainitic Steel

Materials ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 166 ◽  
Author(s):  
Chunhe Chu ◽  
Yuman Qin ◽  
Xuemei Li ◽  
Zhinan Yang ◽  
Fucheng Zhang ◽  
...  
Keyword(s):  
Activation Energy ◽  
Energy Barrier ◽  
Bainitic Ferrite ◽  
Transformation Process ◽  
Transformation Rate ◽  
Bainitic Steel ◽  
Transformation Kinetics ◽  
Activation Energy Barrier ◽  
Quenching Process ◽  
Kinetics Of

The two-step austempering process has been reported to be an effective method to accelerate the bainitic transformation process by introducing martensite (Q-M-B). However, in this study, it was found that the Q-M-B process reduced the incubation time, but the transformation duration remained nearly unchanged. The notably reduced activation energy barrier for nucleation of bainitic ferrite on the preformed martensite should be responsible for the reduced duration time of the Q-M-B process. A process that both of the two steps were above, Ms (Q-B-B), has been demonstrated to increase transformation rate and improve the amount of bainitic ferrite, which probably results from the additional hysteresis free energy provided by the first quenching process.

Atom probe tomography of early stage clustering in Al alloys

2016 ◽  
pp. 187-188
Author(s):  
Stefan Pogatscher ◽  
Phillip Dumitraschkewitz ◽  
Stephan S.A. Gerstl
Keyword(s):  
Atom Probe Tomography ◽  
Early Stage ◽  
Atom Probe ◽  
Al Alloys

Distribution of Dislocations in Nanostructured Bainite

2011 ◽  
Vol 172-174 ◽  
pp. 117-122 ◽  
Author(s):  
J. Cornide ◽  
Goro Miyamoto ◽  
Francisca García Caballero ◽  
Tadashi Furuhara ◽  
Michael K. Miller ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Atom Probe Tomography ◽  
Bainitic Ferrite ◽  
Transformation Strain ◽  
Atom Probe ◽  
Ferrite Plate ◽  
Transmission Electron ◽  
Bainitic Microstructure ◽  
Distribution Of Dislocations ◽  
Very Low Temperature

The dislocation density in ferrite and austenite of a bainitic microstructure obtained by transformation at very low temperature (300 °C) has been determined using transmission electron microscopy. Observations revealed that bainitic ferrite plates consist of two distinctive regions with different substructures. A central region in the ferrite plate is observed with dislocations that may result from lattice-invariant deformation at the earlier stage of bainite growth. As plastic deformation occurs in the surrounding austenite to accommodate the transformation strain as growth progresses, the Ferrite/Austenite interface has also a very distinctive dislocation profile. In addition, atom-probe tomography suggested that dislocation tangles observed in the vicinity of the ferrite/austenite interface might trap higher amount of carbon than single dislocations inside the bainitic ferrite plate.

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