低碳马氏体不锈钢的TRIP 效应

Different processes of cryogenic treatment + tempering were applied to a low-carbon martensitic stainless steel. The microstructure and properties of the tested steel were characterized by using scanning electron microscope (SEM),transmission electron microscope (TEM),electron backscatter diffraction (EBSD),X-ray diffraction (XRD),and tensile tests. The law of transformation-induced plasticity (TRIP)effect occurring in retained austenite with different contents and morphological characteristics during the tensile process,as well as its effect on strength and plasticity,were investigated. The results show that during the tensile process,most of the retained austenite undergoes martensitic transformation when the strain is less than 1. 5%,with the transformation amount reaching 75%. After the strain exceeds 1. 5%,the transformation continues as the deformation increases,but the transformation rate slows down. When the strain exceeds 4. 0%,almost all the retained austenite is transformed into martensite. The TRIP effect during the tensile process effectively improves the strain hardening capacity and tensile strength of the steel. The formation of a greater number of film-like retained austenite in the matrix after double cryogenic treatment + tempering is conducive to the further improvement of plasticity. Compared with the specimen treated by single cryogenic treatment + tempering,the specimen treated by double cryogenic treatment + tempering,which contain,a higher content of retained austenite,exhibits higher yield strength,tensile strength,and percentage total extension at fracture,with the values reaching 1444 MPa, 1901 MPa,and 12. 8%,respectively.