Study On Austenite Reversed Transformation Behavior And Microstructure And Properties Of Medium Manganese Steel

The 0.1C-5Mn steel was studied in the present work.The microstructure and element partitioning are studied by warm-rolled annealing.The effect of carbide precipitation behavior on reversed austenite nucleation growth was further studied.The difference in the morphology and tensile properties of different precursors in the coldrolled and hot-rolled steels was explored and elucidated the influence of warm-rolled annealing and carbide evolution behavior on austenite content and stability and work hardening behavior of medium Mn TRIP steel.The results show that the duplex microstructure comprised of ultrafine-grained ferrite and austenite is obtained by means of CR+WR+IA process.The austenite fraction and stability is increased due to more C and Mn enriched locations.The recrystallization progress of deformed martensite is changed.The yield strength is continuously is mainly dependent on whether carbides is dissolved.The ultrahigh strength 1141 MPa and total elongation 23.6% were only obtained after 10 min annealing.The carbide formation is inhibited by high-density dislocations pinning C and Mn atoms,so that reversed austenite first precipitates from martensite laths boundaries.Dislocation density then decreases rapidly due to active recovery,and the diffusion activation energy of C and Mn atoms promotes a large amount of carbides precipitation.For prolonged time,the finer carbides are gradually replaced as fresh austenite core.The PSE value of up to 33.7 GPa·% was obtained with 60 min annealing.The hot-rolled quenched martensite and cold-rolled deformed martensite as precursors are intercritically annealed.The CRA sample is mainly composed of equiaxed submicron grains owing to nearly full recrystallization of deformed martensitic,while the HRA sample still presents lath structure.Metastable austenite fraction and C content in the CRA sample is higher because its precursor enhances austenite stability and C partitioning.The PSE value of both CRA and HRA samples was higher than 30 GPa·%.Figure45;Table5;Reference 115.