应用电子及光学显微术对45钢及55钢中的马氏体形态、亚结构等特征进行了研究。结果表明,中碳铁基合金中马氏体的形貌是以板条状为主的混合马氏体形态,其典型的马氏体惯析面为{225}_y,随着奥氏体中碳浓度微区的波动,亦可发现{111}_y马氏体。{225}_y马氏体中的亚结构随马氏体的碳含量高低而变,有的以位错为主,有的则以孪晶为主。作者认为这种{225}_y马氏体是一种形态介于板条状和片状马氏体之间的一种特殊过渡形态马氏体。 The characteristics of martensite morphology and substructure in 45 steel and 55 steel were studied by electron and optical microscopy. The results show that the morphology of martensite in medium-carbon iron-based alloys is a lath-shaped mixed martensite morphology with a typical martensite inertial plane of {225} _y, Carbon concentration in the micro-area fluctuations, but also found {111} _y martensite. The substructure of {225} _y martensite changes with the carbon content of martensite, some of them are mainly dislocations and others are twins. The authors believe that this {225} _y martensite is a special transitional form of martensite in the shape of laths and lamellar martensite.