Dependence of tensile deformation behavior of TWIP steels on stacking fault energy, temperature and strain rate

Three experimental high manganese twinning induced plasticity (TWIP) steels were produced based on thermodynamic stacking fault energy (SFE) calculations, following the thermodynamic modeling approach originally proposed by Olson and Cohen (Metall Trans 7A (1976) 1897). At room temperature, the SFE γ SFE of the three materials varied from 20.5 to 42 mJ m −2. In order to study the correlation between the SFE and the mechanical behavior of the TWIP steels, as manifested by the propensity of the material to deformation-induced phase transformations or twinning, tensile tests were performed at temperatures −50 °C ⩽ T ⩽ 80 °C using strain rates varying between 10 −3 s −1 and 1250 s −1. The mechanical behavior of TWIP steels reveals clear temperature dependence, related to the prevailing deformation/strain hardening mechanism, i.e., dislocation slip, deformation twinning or ε-martensite transformation. At high strain rates an increase in temperature due to adiabatic deformation heating also contributes to the SFE, shifting γ SFE either towards or away from the optimum value for twinning.