5th International High Manganese Steel Conference - HMNS 2022

With an increasing demand for high-strength steel with lean-alloyed composition, the medium-Mn steels containing ~3-12 wt.% Mn and ~0.05-0.4 wt.% C have garnered significant attention as next-generation advanced high-strength steels. The α′ martensite microstructure could be observed after hot and cold rolling of the corresponding steel, and it turns to the two-phase microstructure of α ferrite plus γR retained austenite or tempered α′ plus γR after reversion treatment at intercritical temperature region of the steels. The large fraction of metastable γR triggers the transformation-induced plasticity (TRIP) and twinning-induced plasticity (TWIP) during plastic loading, leading to a remarkable combination of strength (< ~1400 MPa) and ductility (< ~50%). Interestingly, two different microstructural morphology could be obtained in the medium-Mn steels; hot-rolled steel reveals a nanolaminate morphology and cold-rolled steel shows a nanoscale globular morphology after annealing. The various mechanical responses such as tensile property, impact absorbed energy, hydrogen embrittlement resistance, and fatigue resistance are greatly influenced by the morphology characteristics. Here, we summarized the relation between microstructural morphology and mechanical responses in medium-Mn steel to derive the optimum microstructure for improved mechanical properties.