Transmission electron microscopy investigations on the twinning suppression attributes in a Fe-Mn-Al-C steel and the associated strain hardening

Abstract

• A fine-grain (∼5 µm) high-Mn steel is investigated under uniaxial tension. • Nearly stable high strain hardening ∼ 2 GPa was observed until failure. • Deformation twinning was largely suppressed. • Dislocation substructures dominate the plasticity. • Twinning induced plasticity is overestimated in high-Mn steels. Suppression of twinning in a tensile deformed fine-grained (∼5 μm) Fe-Mn-Al-C steel is reported from transmission electron microscopy investigations. A high stable strain hardening ∼ 2 GPa was observed until 0.30 true strain despite twinning being largely suppressed, but seldom observed in regions devoid of dislocation substructure. Dislocation dipole and Taylor lattice were observed at low strains that transformed to dislocation cell structure at large strains. The twin deficiency could not be interpreted on the basis stacking fault energy of the steel, but the dislocation substructures in the matrix offered a preventive environment for twinning. The effect of cross-slip induced dislocation substructures on strain hardening in a twinning suppressed condition is discussed.