By aging treatment of a medium manganese lightweight steel at 550℃,the evolution of its microstructure and mechanical properties was analyzed.The results indicate that aging treatment has a significant impact on precipitates.When the aging time is less than 30 minutes,a large number of intra-granular κ'-carbides formed by spinodal decomposition,which distributed dispersedly in the austenite ma-trix.As the aging time increases,besides the intragranular κ'-carbides,intergranular K-carbides are also formed at grain boundaries through eutectoid reactions as a layered structure of α ferrite and κ-carbide.Intragranular κ'-carbides greatly increase the strength,but intergranular K-carbides significantly reduce the ductility of the steel.Compared with long-time aging,the strength of the steel can be significantly in-creased by short-time aging,while the steel still maintains a high elongation with better overall mechani-cal properties.Among them,the good performance is achieved for the steel after aging for 30 minutes,namely a tensile strength of 1031 MPa,yield strength of 784 MPa,an elongation of 41.08％,and a prod-uct of strength and elongation of 42.35 GPa·％.
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