Influence of temperature on phase transformation and deformation mechanisms of cast CrMnNi-TRIP/TWIP steel

At different temperatures ranging from -60 degrees C to 200 degrees C a cast CrMnNi-TRIP steel was deformed by uniaxial tension. The resulting microstructure was investigated using XRD, EBSD and LOM. The correlation of the phase transformation with the deformation temperature was examined. Depending on temperature, a transition in the deformation mechanisms was observed. Starting with the generation of deformation bands, accompanied by martensitic phase transformation, followed by twinning, the deformation mechanism turned to conventional dislocation glide with raising temperature. Between -60 degrees C and 20 degrees C the TRIP (TRansformation Induced Plasticity)-effect is the dominating deformation mechanism, whereas between 20 degrees C and 200 degrees C the TWIP (Twinning induced plasticity) effect is observed. The geometrical arrangement of martensite within the microstructure is considered within this study. The amount of alpha'-martensite is mainly responsible for the hardening rate and the resulting mechanical properties.