Effects of temperature and strain rate on the tensile properties of twip steels

Abstract

Three high manganese TWIP steels were produced with stacking fault energies γSFE ranging from 20.5 to 42 mJ/m². The materials were mechanically tested in tension at temperatures and strain rates varying in the ranges of -50°C...80°C and 10-3 s-1...1250 s-1, respectively. Due to the temperature dependence of γSFE, also the mechanical behavior of TWIP steels reveals clear temperature dependence, determined by the prevailing deformation mechanism, i.e., dislocation slip, deformation twinning, or ε-martensite transformation. In addition to the 'ordinary' strain rate sensitivity, an increase in temperature due to adiabatic deformation heating contributes to the stacking fault energy (SFE) at high strain rates, shifting γSFE towards the dislocation slip regime and this way strongly affecting also the mechanical behavior. At stacking fault energies close to the transition between twinning and ε-martensite transformation, lowering the temperature can ultimately result in entering the ε-martensite transformation regime that may bring about further ductility.