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摘要
Microstructure of low-temperature bainite steel at different isothermal transformation (IT) temperatures was studied by tests, and the influence of morphology and stability of retained austenite (RA) on mechanical properties and fracture behavior of test steel was studied. The scanning electron microscope(SEM), transmission electron microscope(TEM) and X-Ray diffraction(XRD) were used to characterize the microstructure, tensile and impact fracture morphology of low-temperature bainite steel. The results show that with the increase of IT temperature, the tensile strength of test steel remains above 1500 MPa, the yield strength decreases from 945 MPa to 806 MPa, and the elongation decreases from 14.0% to 9.0%. IT temperature has obvious influence on the morphology and stability of RA of test steel, with the increase of IT temperature, the carbon-rich thin strip RA and film RA turn into carbon-poor blocky RA. In the early stage of plastic deformation, strain induced martensitic transformation of RA with this morphology occurs in quantity and rapidly, which provides a path for crack propagation. Thus the toughness and plasticity of steel are reduced, which makes the ductile transgranular fracture characteristics of the tensile and impact fracture of test steels more obvious. ? 2022, Editorial Board of Journal of Plasticity Engineering. All right reserved.
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