Effect of Deformation during Austempering on Bainite Transformation and Retained Austenite in a Medium‐Carbon Bainitic Steel

2019 ◽  
Vol 91 (1) ◽  
pp. 1900353
Author(s):  
Guanghui Chen ◽  
Guang Xu ◽  
Haijiang Hu ◽  
Xin Chen ◽  
Javad Mola
Keyword(s):  
Retained Austenite ◽  
Bainitic Steel ◽  
Bainite Transformation ◽  
Medium Carbon

scholarly journals Effect of two-step ausforming on bainite transformation and retained austenite in a medium-carbon bainitic steel

2020 ◽  
Vol 7 (1) ◽  
pp. 016519 ◽  
Author(s):  
Guanghui Chen ◽  
Guang Xu ◽  
Haijiang Hu ◽  
Junyu Tian ◽  
Qing Yuan ◽  
...  
Keyword(s):  
Retained Austenite ◽  
Bainitic Steel ◽  
Bainite Transformation ◽  
Medium Carbon

scholarly journals Influence of Prior Martensite on Bainite Transformation, Microstructures, and Mechanical Properties in Ultra-Fine Bainitic Steel

Materials ◽  
2019 ◽  
Vol 12 (3) ◽  
pp. 527 ◽  
Author(s):  
Hui Guo ◽  
Xianying Feng ◽  
Aimin Zhao ◽  
Qiang Li ◽  
Jun Ma
Keyword(s):  
Mechanical Properties ◽  
Retained Austenite ◽  
Bainitic Ferrite ◽  
Growth Direction ◽  
Bainitic Transformation ◽  
Bainitic Steel ◽  
Bainite Transformation ◽  
Multiphase Microstructure ◽  
Microstructures And Mechanical Properties ◽  
The Impact

A multiphase microstructure comprising of different volume fractions of prior martensite and ultra-fine bainite (bainitic ferrite and retained austenite) was obtained by quenching to certain temperatures, followed by isothermal bainitic transformation. The effect of the prior martensite transformation on the bainitic transformation behavior, microstructures, and mechanical properties were discussed. The results showed that the prior martensite accelerated the subsequent low-temperature bainite transformation, and the incubation period and completion time of the bainite reaction were significantly shortened. This phenomenon was attributed to the enhanced nucleation ratio caused by the introduced strain in austenite, due to the formation of prior martensite and a carbon partitioning between the prior martensite and retained austenite. Moreover, the prior martensite could influence the crystal growth direction of bainite ferrite, refine bainitic ferrite plates, and reduce the dimension of blocky retained austenite, all of which were responsible for improving the mechanical properties of the ultra-fine bainitic steel. When the content of the prior martensite reached 15%, the investigated steels had the best performance, which were 1800 MPa and 21% for the tensile strength and elongation, respectively. Unfortunately, the increased content of the prior martensite could lead to a worsening of the impact toughness.

scholarly journals Retained Austenite Decomposition and Carbide Precipitation during Isothermal Tempering of a Medium-Carbon Low-Alloy Bainitic Steel

Materials ◽  
2018 ◽  
Vol 11 (8) ◽  
pp. 1441 ◽  
Author(s):  
Seyyed Talebi ◽  
Mohammad Jahazi ◽  
Haikouhi Melkonyan
Keyword(s):  
Electron Microscopy ◽  
Retained Austenite ◽  
Carbide Precipitation ◽  
Austenite Decomposition ◽  
Bainitic Steel ◽  
Tempering Temperature ◽  
Medium Carbon ◽  
Transmission Electron ◽  
Decomposition Behavior ◽  
Isothermal Tempering

The effect of isothermal tempering on retained austenite decomposition and carbide precipitation were investigated in a medium-carbon low-alloy bainitic steel. High-resolution dilatometry was used to perform isothermal tempering at 350 °C, 550 °C and 600 °C for different holding times up to 16 h. The decomposition of retained austenite, morphology and composition of carbides were investigated by analyzing the dilatometric curves and were confirmed through scanning and transmission electron microscopy observations. The decomposition behavior of retained austenite varied significantly as a function of the tempering temperature with a full decomposition observed at 600 °C. It was also found that by increasing the tempering temperature from 550 °C to 600 °C, carbides precipitate approximately twice as fast, and evolve from M3C type to Cr7C3 and Cr23C6 after 16 h of tempering at 600 °C.

Dynamic continuous cooling transformation, microstructure and mechanical properties of medium-carbon carbide-free bainitic steel

2020 ◽  
Vol 39 (1) ◽  
pp. 304-316
Author(s):  
Xi Chen ◽  
Fuming Wang ◽  
Changrong Li ◽  
Jing Zhang
Keyword(s):  
Cooling Rate ◽  
Retained Austenite ◽  
Charpy Impact ◽  
Granular Bainite ◽  
Morphology Evolution ◽  
Bainitic Steel ◽  
Cooling Process ◽  
Medium Carbon ◽  
Continuous Cooling ◽  
Lath Bainite

AbstractThe effects of the cooling rate after hot deformation on phase transformation, the microstructure of the designed nonquenched and tempered medium-carbon carbide-free bainitic steel have been investigated during the dynamic continuous cooling process. The results show that with the increase of the cooling rate, the morphology of the carbide-free bainite of the experimental steel evolves from granular bainite to lath bainite. Meanwhile, the hardness increases, and the amount of the retained austenite decreases with the increase of the cooling rate. Besides, the morphology evolution of the retained austenite from block to film is revealed by EBSD. Moreover, 0.5°C/s is considered to be the favorable cooling rate to obtain the best strength–toughness matching. Furthermore, the semi-industrial experimental results proved that the tensile strength, yield strength and Charpy impact energy were 1,298 MPa, 847 MPa and 38 J, respectively.

The effect of preexisting VC carbides on the bainite transformation in medium-carbon high-alloy steel

2019 ◽  
Vol 34 (15) ◽  
pp. 2695-2704
Author(s):  
Xiaoli Zhao ◽  
Lizhan Han ◽  
Chuanwei Li ◽  
Jianfeng Gu
Keyword(s):  
Alloy Steel ◽  
Bainite Transformation ◽  
High Alloy ◽  
High Alloy Steel ◽  
Medium Carbon ◽  
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