Development of high-strength corrosion-resistant austenitic TWIP steel
Based on thermodynamic calculations a (C+N) TWIP steel with the nominal composition
Fe-25Mn-12Cr-0.3C-0.4N was developed and produced. Casting, diffusion annealing, hot rolling and water
quenching were performed leading to a fully austenitic structure without ?-ferrite or ?-martensite.
Unidirectional tensile tests were performed, revealing a yield strength of 460 MPa, ultimate tensile strength
of 880 MPa (1700 MPa true strength) and an engineering strain of up to 100% at room temperature.
The plasticity mechanisms were analysed based on the results of the tensile tests and cold work hardening
behaviour, accompanied by microstructural analyses on deformed samples using X-Ray diffraction. Twinning
was found to be an important deformation mechanism, while martensitic transformations do not take place in
these materials. Correlation with predicted values of stacking fault energy (SFE) based on thermodynamic
modelling is also taken into account. Electrochemical corrosion tests show a good extent of passivation in
0.5 M H2SO4 electrolyte. The structure, mechanical properties and corrosion resistance are compared to
conventional TWIP steels such as Fe-25Mn-3Al-3Si and Fe-22Mn-0.6C.