Coupled toughening of a low carbon medium manganese heavy steel plate investigated by electron back–scattered diffraction (EBSD)

• The high toughness has been achieved by the combinations of microstructure refinement and austenite.
• Nearly full fine ferrite microstructure and fine ferrite plus austenite dual phase microstructure have been obtained.
• The orientation relationship between ferrite and austenite was analyzed.

Nearly full fine ferrite microstructure (d=2.7±0.5 µm) and fine ferrite (d=2.4±0.3 µm) plus ~8.9% retained austenite with relatively good stability were produced. The upper shelf energy increases by ~30 J and the CVN impact energy increases by ~60 J at −100 °C by introducing ~8.9% retained austenite. The high toughness (263 J at −40 °C and 191 J at −100 °C) has been achieved by grain refinement and retained austenite.

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