形变热处理对低碳Co-Cr-Mo-Ni合金钢组织性能的影响

In order to improve the strength of low-carbon high-alloy steels, the influence of deformation of thermo-mechanical treatment on microstructure evolution and mechanical properties was studied. The results show that the microstructures of the steel after processing by thermo-mechanical treatment with deformation in the range of 20%-60%, cryogenic treatment and tempering contain the complex phases with tempered martensite, retained austenite and a few carbides. Compared with the conventional quenching and tempering sample, the strength of steel decreases with the elongation increase due to the thicker tempered martensite and a higher fraction of retained austenite after the thermo-mechanical treatment with the deformation of 20%. With deformation increasing from 20% to 60%, the dislocation density increases, the width of tempered martensite lath and the fraction of retained austenite decreases simultaneously, which leads to an improvement in the strength and a decrease in ductility. When the deformation reaches to 60%, the yield strength is higher by about 13% than that of the un-deformed quenching-tempering specimen, and the yield strength, ultimate tensile strength and elongation of the steel are 1547MPa, 1810MPa and 17%, respectively, achieving a good strength-ductility matching.