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 (epsilon=0.06-0.14), epsilon-martensite was preliminarily formed, and that austenite transformed to alpha-martensite through the epsilon-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 epsilon-martensite formation. The second derivative of the stress-strain curve satisfied the condition d(2)sigma/d epsilon(2)>0. Twinning induced plasticity dominated this stage. In the last plastic deformation stage (epsilon = 0.35-0.45), gamma ->alpha a transformation occurred at the crossing of twins, and alpha-martensite grew along the thickness of the twinned regions. (C) 2010 Elsevier B.V. All rights reserved.