J. Mater. Sci. Technol. ›› 2015, Vol. 31 ›› Issue (2): 199-204.DOI: 10.1016/j.jmst.2014.07.010

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Tempering Behavior of Ductile 1700 MPa Mn-Si-Cr-C Steel Treated by Quenching and Partitioning Process Incorporating Bainite Formation

Guhui Gao1, Han Zhang2, Xiaolu Gui1, Zhunli Tan1, Bingzhe Bai1, 3   

  1. 1 Materials Science & Engineering Research Center, Beijing Jiaotong University, Beijing 100044, China; 2 Max-Planck-Institut für Eisenforschung, Max-Planck-Str. 1, Düsseldorf 40237, Germany; 3 Key Laboratory of Advanced Materials, Department of Material Science & Engineering, Tsinghua University, Beijing 100084, China
  • Received:2014-02-12 Online:2015-02-20 Published:2015-07-23
  • Contact: Corresponding author. Ph.D.; Tel.: +86 10 51685495; Fax: +86 10 51685461.E-mail address: gaogh@bjtu.edu.cn (G. Gao).
  • Supported by:
    This work was financially supported by the National Natural Science Foundation of China (No. 51301012).

Abstract: We obtained a good combination of strength and ductility in a 0.4C-2.0Mn-1.7Si-0.4Cr (wt%) steel, namely, ~1.7 GPa of ultimate tensile strength and ~26% of elongation, by conducting a Q-P-T (quenching-partitioning-tempering) process incorporating the formation of carbide-free bainite. The tempering behavior of this steel was discussed by using experimental finding (scanning electron microscopy, X-ray diffraction (XRD), transmission electron microscopy and dilatometer) and CCE (constrained carbon equilibrium) modeling. The XRD results combined with CCE calculation prove that carbon partitioning from martensite to austenite occurs during tempering. Consequently, the thermodynamic stability of retained austenite is enhanced. This idea can be utilized to design novel Q-P-T processes in future.

Key words: Bainite, Quenching and partitioning, Tempering, Microstructure evolution, Mechanical properties