Microstructure and Mechanical Properties of Hot-Rolled and Cold-Rolled Medium-Mn TRIP Steels

This study investigated the microstructure and mechanical properties of hot-rolled and cold-rolled medium-Mn transformation-induced plasticity (TRIP) steel. The experimental steel, processed by quenching and tempering (Q & T) heat treatment, exhibited excellent mechanical properties for hot-rolled and Q & T steels (strength of 1050-1130 MPa and ductility of 16-34%), as well as for cold-rolled and Q & T steels (strength of 878-1373 MPa and ductility of 18-40%). The mechanical properties obtained after isothermal holding at 775 degrees C for one hour for cold-rolled/Q & T steel were superior to that of hot-rolled/Q & T steel. Excellent mechanical properties were attributed to the large amount of retained austenite, which produced a discontinuous TRIP effect. Additionally, the differences in mechanical properties correlated with the morphology, stability and content of retained austenite. The cold-rolled sample, quenched from 650 degrees C (CR 650 degrees C) had extensive TRIP effects in the middle and late stages of the deformation, leading to better mechanical properties. The fracture modes of the hot-rolled sample, quenched from 650 degrees C, and the cold-rolled sample quenched from 650 degrees C, were ductile fractures, resulting in excellent ductility.