Microband-induced plasticity in a high Mn–Al–C light steel

Room temperature tensile behavior of a high Mn–Al–C steel in the solid solution state was correlated to the microstructures developed during plastic deformation in order to clarify the dominant deformation mechanisms. The steel was fully austenitic with a fairly high stacking fault energy of ∼85 mJ/m2. The tensile behavior of the steel was manifested by an excellent combination of strength and ductility over 80,000 MPa% in association with continuous strain hardening to the high strain. In addition, the austenite phase was very stable during deformation. The high stacking fault energy and firm stability of austenite were attributed to the high Al content. In spite of the high stacking fault energy, deformed microstructures exhibited the planar glide characteristics, seemingly due to the glide plane softening effect. In the process of straining, the formation of crystallographic microbands and their intersections dominantly occurred. Microbands consisting of geometrically necessary dislocations led to the high total dislocation density state during deformation, resulting in continuous strain hardening. This microband-induced plasticity is to be the origin of the enhanced mechanical properties of the steel.