High-temperature Mechanical Properties and Strengthening Mechanism of New Secondary Hardened Steel 25CrMo3NiTiVNbZr
A novel secondary hardened steel 25CrMo3NiTiVNbZr was developed via optimization the chemical composition of the 25Cr3Mo3NiNbZr steel bymeans of the so called JMatpro and Thermo-Calc software.Then the microstructure,phase composition,morphology of precipitates and mechanical performance at 700℃ of the 25CrMo3NiTiVNbZr steel were characterized by means of transmission elec-tron microscopy(TEM),electron backscattering diffraction(EBSD),while its the high-temperature streng-thening mechanism was also elucidated.The results show that the tensile strength and yield strength of 25CrMo3NiTiVNbZr steel at 700℃ are 543 MPa and 409 MPa,respectively,which are 139 MPa and 123 MPa higher than that of 25Cr3Mo3NiNbZr steel.The high-temperature strengthening of the 25CrMo3NiTiVNbZr steel may mainly ascribed to themechanism,precipitation strengthening.In the pro-cess of being stretched at 700℃,the precipitation strengthening increment derived from the precipitation of the strengthening phase for the 25CrMo3NiTiVNbZr steel reached 367 MPa,which was 147 MPa high-er than that of the 25Cr3Mo3NiNbZr steel.This is mainly due to the higher thermal stability and smaller size(average size at 7.93 nm)of the precipitated strengthening phases in the 25CrMo3NiTiVNbZr steel.After high-temperature stretching,the average size of precipitates remained at 8.14 nm.
metallic materialshigh temperature mechanicsingredient optimizationstrengthening mechanismnanoprecipitated phase
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