Journal of Korea Foundry Society (한국주조공학회지)

Korea Foundry Society (한국주조공학회)
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Transformation Behavior of Retained Austenite on Microstructure and Mechanical Properties in Fe-0.7wt%C-2.3wt%Si Steel

Fe-0.7%C-2.3%Si강의 미세조직과 기계적 성질에 미치는 잔류 오스테나이트 변태 거동

  • Son, Je-Young (School of Materials Science and Engineering, Materials Science and Metallurgical Engineering, Graduate School of Kyungpook National University) ;
  • Kwon, Do-Young (School of Materials Science and Engineering, Materials Science and Metallurgical Engineering, Graduate School of Kyungpook National University) ;
  • Kim, Ji-Hun (Small and Medium Business Corporation) ;
  • Kim, Won-Bae (Korean Technology Credit Guarantee Fund) ;
  • Kim, Hak-Jin (Hyundai Steel Company) ;
  • Ye, Byung-Joon (School of Materials Science and Engineering, Materials Science and Metallurgical Engineering, Graduate School of Kyungpook National University)
  • Received : 2012.03.06
  • Accepted : 2011.06.11
  • Published : 2012.06.30
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Abstract

This steel has been synthesized integrating concepts from Austempering Ductile Cast Iron (ADI) technology. While ADI has excellent mechanical and physical properties, the Young's modules of ADI is approximately 20% lower than steel. In addition, the presence of graphite nodules in ADI can be sites of crack initiation, where fracture takes place at graphite matrix interface. Because of this limitations of ADI, there has been a growing interest in austempered steels as structural materials in resent years. In this investigation, a new steel with microstructure composed of ferrite and austenite and with simultaneous high tensile strength (1,150 MPa) and high ductility (33%) was developed. The goal of this investigation is to obtain a better understanding of deformation and transformation behaviour in high carbon retained austenite(${\gamma}_{HC}$) and over-saturated ferrite(${\alpha}$) during the plastic deformation. A detailed study of the microstructure of this steel was carried out by means of X-ray diffraction (XRD) and electron back scattering diffraction (EBSD) technic. In this way it was shown that BCC phase (BCC) took up the larger part of the nominal strain whereas the a part of retained austenite responded to the mechanincal load by partial martensite transformation, and misorientation change in the retained austenite after plastic strain could be attributed to the large elongation.

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References

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