Ultra-high strength stainless steel is widely used in aviation,aerospace and other fields because of its good comprehensive performance.A new type of 2.1 GPa grade ultra-high strength stainless steel was taken as the research object,and the influence law of different solid solution temperature and aging treatment on the mechanical properties of steel was investigated.Scanning electron microscope(SEM),X-ray diffractometer(XRD),transmis-sion electron microscope(TEM)and other means were used to characterize the microstructures of the steel in solid solution and aging state,and an intrinsic correlation was established between the heat treatment-mechanical properties-microstructure.The results show that the solid solution organization of the steel is slat martensite+residual austenite,the size of the original austenite grain increases with the increase of solid solution temperature,the strength shows a decreasing trend with increasing of solid solution temperature,while the impact absorption work increases firstly and then decreases.The strength of the solid solution by 1 050℃ is the highest,but due to the un-dissolved M6C phase disrupts the continuity of matrix organization resulting in low impact absorption work,the strength and the impact absorption work of solid solution by 1 100℃ are lower than the 1 080℃ solid solution.Although the former high austenite content is conducive to improving toughness,coarse grains lead to a reduction in the impact absorption work.After aging,the strength of the steel significantly improved,1 050℃ solid solution+aging has the lowest strength,while 1 080℃ solid solution+aging has the highest strength,the tensile strength is 2 161 MPa and yield strength is 1 784 MPa.Plastic toughness also better than 1 050℃ and 1 100℃,1 080℃ impact absorption work is 37.5 J,which has the best toughness match,and there are a large number of small,dif-fuse Laves phase and M2C phase precipitated in the slat martensite,which is the main reason for obtaining ultra-high strength.In the martensite slat boundary,the thin film austenite is the key to maintain good toughness.The research steel grade is the highest strength level of stainless steel in the international arena currently,and the research results can provide data support to enhance the maturity of its engineering technology.
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