利用光学显微镜、扫描电镜、电子背散射衍射及透射电镜观察了40Cr钢等温淬火形成的下贝氏体组织形貌,并分析了下贝氏体与马氏体、回火索氏体的差异。结果表明:下贝氏体组织形貌与马氏体、回火索氏体均有明显差异,且下贝氏体的硬度高于回火索氏体;下贝氏体针状组织密集排列成束,方向感强,侵蚀后呈彩色,组织内部细密的碳化物沉淀在铁素体板条上,碳化物排列整齐,且与铁素体长轴夹角呈60°。

The morphology of lower bainite formed by isothermal quenching of 40Cr steel was observed by optical microscope, scanning electron microscope, electron backscatter diffraction and transmission electron microscope, and the differences with martensite and tempered sorbite were analyzed. The results show that the morphology of lower bainite was obviously different from that of martensite and tempered sorbite, and the hardness of lower bainite was higher than that of tempered sorbate. The needle like structure of lower bainite was densely arranged in bundles, with strong sense of direction and color after erosion. The inside of the structure was fine carbide precipitated on the ferrite lath. The carbides were arranged in order, and the included angle with the long axis of ferrite was 60°.