Abstract: The effect of carbide precipitation behavior at different annealing time on microstructure evolution, retained austenite content and mechanical properties for medium manganese steel was investigated by means of ART (Austenite reversed transformation) annealing heat treatment process. The results indicate that the microstructure of experimental steel is composed of ferrite, retained austenite and a small amount of martensite heterogeneous structure after treated by ART process. In the pre-annealing (5 min), the carbide is inhibited by high-density dislocations pinning C and Mn atoms, so that reversed austenite is precipitated before carbides at the boundaries of prior austenite or martensite laths. In the middle of annealing (10 min), the dislocation density decreases rapidly due to recovery, and the diffusion activation energy of C and Mn atoms are increased, which promotes the precipitation of a large amount of carbides. With the annealing time prolonged (30—60 min), the fine carbides are gradually dissolved as the nascent austenite core, and the volume fraction of retained austenite and C content increase. With the precipitation and dissolution of carbides, the yield strength of experimental steel first increase and then decrease, but the elongation and uniform ductility after fracture show a tendency of continuous increased. After 60 min annealing, the elongation after fracture reaches 41.1%, the uniform ductility reaches 34.3%, and the tensile strength reaches 821 MPa. The experimental steel obtaines the production of strength and elongation of up to 33 743 MPa·%.
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