Microstructure evolution and mechanical behavior of a new microalloyed high Mn austenitic steel during compressive deformation

To study the microstructural and mechanical behavior of a new microalloyed transformation-twinning induced plasticity steel, the compression tests were conducted from 25 to 1000 °C. Five different categories of true stress-true strain curve, exhibiting distinctive strain hardening/strain softening and stress fluctuation, have been characterized in the range of deformation temperature. The experimental steel exhibits the strength of about 1.28 GPa after straining to 0.6 along with an outstanding strain hardening rate (~2000 MPa) during compression at 25 °C. This excellent combination of mechanical properties is attributed to the occurrence of strain-induced martensite transformation. The martensitic transformation continues occurring up to temperatures as high as 150 °C, while mechanical twinning is considered as the chief deformation mechanism in the temperature range of 150-600 °C. Furthermore, a banded-like structure is observed in the temperature range of 600-1000 °C as a result of precipitate formation. This banded structure is mainly composed of planar slip as well as deformation twins with misorientation of about 59°.