Strain hardening behavior of a TRIP/TWIP steel with 18.8% Mn

Tensile tests were carried out to study the strain hardening behavior of a TRIP/TWIP steel with 18.8% manganese. The results indicated that the true stress–strain curve can be divided into 4 stages in tension testing. Material is in an elastic region when the true strain is below 0.06. In the initial stage of the plastic deformation (ɛ = 0.06–0.14), ɛ-martensite was preliminarily formed, and that austenite transformed to α-martensite through the ɛ-martensite formation. When the true strain was between 0.14 and 0.35, the stacking fault energies were elevated by the increase of strain energy, deformation twinning occurred instead of the ɛ-martensite formation. The second derivative of the stress–strain curve satisfied the condition d2σ/dɛ2 > 0. Twinning induced plasticity dominated this stage. In the last plastic deformation stage (ɛ = 0.35–0.45), γ → α transformation occurred at the crossing of twins, and α-martensite grew along the thickness of the twinned regions.