Discontinuous transformation-induced plasticity behaviour in governing the mechanical behaviour in medium-Mn steels

Here, we address the continuing challenges and scientific gaps in obtaining high strength and high elongation in medium-Mn steels. Electron microscopy and X-ray diffraction studies clearly underscored that the discontinuous transformation-induced plasticity played a determining role in impacting high strength-toughness combination in conjunction with the microstructural constituents. The discontinuous TRIP effect during deformation involved stress relaxation, which was responsible for high ductility. An excellent combination of a high tensile strength in the range of 1238-1502 MPa and a total elongation of 25-33.6% was obtained when the steels were subjected to an intercritical hardening in the temperature range of 600-750 degrees C and low tempering at 200 degrees C. The intercritical hardening influenced the co-existence of austenite, ferrite and martensite in a manner such that the deformation behaviour varies with the Mn-content.