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本文主要采用显微组织研究方法,分析了中碳结构钢(45及42CrMo钢)中位错型板条马氏体和混合马氏体(位错型十孪晶型)的显微裂纹萌生及扩展过程,同时对不同马氏体形态的裂纹萌生及扩展的微观机制提出了初步看法。测定了两种材料不同马氏体形态的断裂韧性(K_(IC))和疲劳裂纹萌生期No,扩展速率da/dN及持久值Nf。研究了不同应力水平下的电镜断口及疲劳断裂特性(裂纹扩展抗力)与组织形态的关系,从而初步探讨了中碳结构钢在不同应力状态下,获得最佳疲劳寿命的合理组织状态。
In this paper, the microstructural research methods are mainly used to analyze the micro-crack initiation and the disaggregated lath martensite and the mixed martensite (dislocated ten-twins) in medium-carbon structural steels (45 and 42CrMo steels) Expansion process, at the same time on the different martensite morphology crack initiation and expansion of the micro-mechanism proposed a preliminary view. The fracture toughness (K_ (IC)) and fatigue crack initiation time No, the expansion rate da / dN and the persistence value Nf of different martensite morphology were measured. The relationship between the fracture of electron microscope and the fatigue fracture (crack propagation resistance) and the morphology of the microstructure under different stress levels was studied. The reasonable microstructure of the medium carbon steel under different stress conditions was obtained.