Three high-manganese TWIP steels were produced which had stacking-fault energies that ranged from 20.5 to 42mJ/m2. The materials were tested in tension at temperatures and strain-rates ranging from -50 to 80C and 10-3 to 1250/s, respectively. Due to the temperature dependence of the stacking-fault energy, the mechanical behavior of the TWIP steels revealed a clear temperature dependence; determined by the prevailing deformation mechanism: i.e., dislocation slip, deformation twinning, or ε-martensite transformation. In addition to the so-called ordinary strain-rate sensitivity, an increase in temperature due to adiabatic deformation heating contributed to the stacking-fault energy at high strain rates; shifting the stacking-fault energy towards the dislocation slip regime and thus strongly affecting the mechanical behavior. At stacking-fault energies close to the transition between twinning and ε-martensite transformation, lowering the temperature could ultimately result in entering the ε-martensite transformation regime and perhaps bringing about further ductility.

Effects of Temperature and Strain Rate on the Tensile Properties of TWIP Steels. S.Curtze, V.T.Kuokkala: Revista Materia, 2010, 15[2], 160-6. See also: Acta Materialia, 2010, 58[15], 5129-41