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In Situ Neutron Diffraction Study on Microstructure Evolution During Thermo-Mechanical Processing of Medium Manganese Steel

  • Yoshihiko Nakamura
  • Akinobu Shibata
  • Wu Gong
  • Stefanus Harjo
  • Takuro Kawasaki
  • Atsushi Ito
  • Nobuhiro Tsuji
Conference paper
Part of the The Minerals, Metals & Materials Series book series (MMMS)

Abstract

The microstructure evolution of medium manganese steel (Fe-5Mn-2Si-0.1C (wt%)) during thermo-mechanical processing in ferrite + austenite two-phase region was investigated by in situ neutron diffraction analysis and microstructure observations. When the specimens were isothermally held at a temperature of 700 °C, the fraction of reversely transformed austenite increased gradually with an increase in the isothermal holding time. However, it did not reach the equilibrium fraction of austenite even after isothermal holding for 10 ks. On the other hand, the fraction of reversely transformed austenite increased rapidly after the compressive deformation at a strain rate of 1 s−1 at 700 °C and reached the equilibrium state during subsequent isothermal holding for around 3 ks. Moreover, microstructure observations suggested that the austenite, which was reversely transformed during isothermal holding at 700 °C, exhibited film-like shape and existed between pre-existing martensite laths. In contrast, when the compressive deformation was applied during isothermal holding at 700 °C, most of the reversely transformed austenite had globular shapes with grain sizes less than 1 μm.

Keywords

Medium manganese steel Neutron diffraction Austenite reverse transformation Thermo-mechanical processing 

Notes

Acknowledgements

The neutron experiment at the Materials and Life Science Experimental Facility of the J-PARC was performed under a user program (Proposal No. 2016E0003, 2017E0001, 2017A0129). This study was financially supported by the Elements Strategy Initiative for Structural Materials (ESISM) through the Ministry of Education, Culture, Sports, Science and Technology (MEXT), Japan.

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Copyright information

© The Minerals, Metals & Materials Society 2018

Authors and Affiliations

  • Yoshihiko Nakamura
    • 1
  • Akinobu Shibata
    • 1
    • 2
  • Wu Gong
    • 2
  • Stefanus Harjo
    • 3
  • Takuro Kawasaki
    • 3
  • Atsushi Ito
    • 1
    • 4
  • Nobuhiro Tsuji
    • 1
    • 2
  1. 1.Department of Materials Science and EngineeringKyoto UniversityKyotoJapan
  2. 2.Elements Strategy Initiative for Structural Materials (ESISM)Kyoto UniversityKyotoJapan
  3. 3.J-PARC CenterJapan Atomic Energy Agency (JAEA)IbarakiJapan
  4. 4.Department of Materials and Synchrotron Radiation EngineeringUniversity of HyogoHimejiJapan

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