Thermomechanical Processing, Microstructure, and Mechanical Properties of Medium‐Mn Steel

Medium manganese (M‐Mn) steels have been developed to achieve an excellent combination of strength and ductility for automotive components. This study investigates the microstructural evolution and mechanical properties of hot‐rolled M‐Mn steels subjected to a thermomechanical control process followed by isothermal holding at different subcritical temperatures. M‐Mn steel alloy is fabricated at a laboratory scale and subjected to heat treatments using a deformation dilatometer. After the hot rolling, a fine multiphase structure is obtained after an isothermal holding at 500 °C, 300 °C, and 200 °C for 30 min. Microstructural characterization was examined using light microscope, scanning electron microscope, electron backscatter diffraction, and X‐ray diffraction. The final microstructures have a multiphase structure from different phases: bainite, fresh martensite, tempered martensite, and film‐like retained austenite with no significant M/A islands. Mechanical properties are determined by hardness and tensile tests. The sample held at 300 °C exhibited the best combination of strength and ductility, attributed to its higher bainite and retained austenite content.