Work hardening behavior involving the substructural evolution of an austenite–ferrite Fe–Mn–Al–C steel

The strain hardening behavior in relation with the evolving dislocation substructures during uniaxial tensile deformation for an austenite–ferrite Fe–Mn–Al–C steel was investigated in the article. After being solution treated at 1000 °C for 0.5 h and then water quenched, the steel possessed an excellent combination in mechanical properties, with the value of product of tensile strength and elongation over 35 GPa%. The steel exhibited obvious three-stage strain hardening characteristics and austenite showed greater strain hardenability than ferrite. With high Al content included, the stacking fault energy (SFE) of austenite was calculated to be ∼66 mJ/m2. The deformation mode of austenite is dominated by planar glide, relating to dislocation configurations, Taylor lattices and microbands. However, wavy glide in ferrite leads to the formation of dislocation nodes, dislocation cells (DCs) and cell blocks (CBs). The distinct substructural hardening in the duplex phases led to the three-stage strain hardening behavior and eventually considerable combination of mechanical properties. The crush and separation of banded-structure δ-ferrite grains during solution treatment enhanced the deformation coordination and improved the steady plastic deformation ability. Obvious ductile fracture accompanied with many deep dimples was observed in the as-solutionized steel.