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工程界有些零部件是用中碳钢制造,并选用回火马氏体组织。有些渗碳件或碳氮共渗件的过渡区或心部组织也是中碳回火马氏作。其中有些零部件由于尺寸大或其它原囚,不能得到单一的回火马氏作组织,往往得到回火马氏体加上少量铁素体的双相组织。已有试验证明,少量铁素体不影响马氏体基体的静拉伸性能。本文选用45Cr钢,研究这种双相组织对裂纹扩展抗力指标:疲劳裂纹扩展门槛值ΔK_(th)和扩展速率(da)/(dN)、断裂韧性K_(IC)的影响。
Some parts of the engineering industry are made of medium carbon steel, and the choice of tempered martensite. Some carburized parts or carbonitriding transition zone or heart tissue is also carbon tempered Markov for. Some of these parts, due to their large size or other prisoners, can not be made of a single tempered martensitic structure and tend to have a duplex structure of tempered martensite with a small amount of ferrite. Experiments have shown that a small amount of ferrite does not affect the static tensile properties of martensite matrix. In this paper, 45Cr steel was used to study the influence of the dual phase microstructure on the crack propagation resistance index: the threshold value of fatigue crack growth ΔK th, the expansion rate da and dN and the fracture toughness K IC.