5th International High Manganese Steel Conference - HMNS 2022

In the present work, a metastable Cr-Mn-Ni steel with deformation-induced plasticity was investigated. The influence of martensite formation on the mechanical properties of an Fe-16Cr-6Ni-6Mn (concentrations in wt-%) austenitic stainless steel was studied by tensile tests between -70°C and 300°C. As-quenched martensite formation was observed at temperatures below -30°C. Deformation-induced α' martensite formation, on the other hand, was triggered below 100°C. Subsequently, a microstructure characterization was carried out. The results obtained by a semi empirical thermodynamic-mechanical calculation model were linked to a few experimental results from the tensile tests. The presented model combines chemical energy amounts from thermodynamic databases with mechanical energy amounts obtained by tensile tests with the aid of the conversion rule proposed by Patel and Cohen. The magnitudes of shear strain (γ_0=0.23) and dilatational strain (ε_0=0.023), required for the calculations, were obtained based on the martensite crystallography theory of Wechsler-Lieberman-Read. Thermodynamic calculations were performed using the ThermoCalc software with the database TCFE10. As a result, the Stress-Temperature-Transformation (STT) diagram showing the temperature dependence of proof stress, tensile strength, triggering stress for martensite formation and the associated critical transformation temperatures (M_S, M_d & T_d) is obtained. With the aid of the semi empirical thermodynamic-mechanical model it can be shown, that the mechanical properties and critical temperatures of a metastable austenitic steel can be determined at very low experimental effort.