为了研究组织对疲劳裂纹扩展行为的影响,对3种不同贝氏体组织钢进行了疲劳裂纹扩展实验,并采用SEM和EBSD等方法对裂纹进行了分析.结果表明,板条贝氏体组织在近门槛区和稳定扩展区阻碍裂纹扩展的能力最强,具有最小的裂纹扩展速率.板条贝氏体组织中的大角度晶界使裂纹更容易发生偏折,导致断口表面粗糙度增加,裂纹扩展受到较强的粗糙度诱导裂纹闭合效应的作用.随着ΔK的增大,塑性诱导裂纹闭合效应取代粗糙度诱导裂纹闭合效应开始占据主导作用,是板条贝氏体组织中裂纹扩展速率对ΔK的变化较敏感的原因. In order to study the effect of microstructure on the fatigue crack growth behavior, fatigue crack propagation experiments were carried out on three kinds of bainite steel, SEM and EBSD methods were used to analyze the cracks.The results showed that the bainite Near the threshold area and the stability of the expansion zone impede the crack propagation ability of the strongest, with the smallest crack growth rate of lath bainite in the large-angle grain boundaries make the cracks more prone to deflection, resulting in increased fracture surface roughness, cracks The expansion is affected by the stronger roughness-induced crack closure effect.As the increase of ΔK, the plastic-induced crack closure effect instead of the roughness-induced crack closure effect begins to dominate, which is the effect of the crack propagation rate on the lath bainite The reason for the change of ΔK is more sensitive.