淬火回火低碳合金钢的疲劳形变与断裂的电镜观察

FATIGUE DEFORMATION AND FRACTURE IN QUENCH-TEMPERED LOW-CARBON STEEL

应用透射电子显微术研究了淬火并400℃和600℃回火钢中疲劳位错结构随循环加载周数的增加所发生的变化。钢中出现具有循环显微硬化与循环显微软化的位错结构形式。前者主要是形成位错缠结,后者主要是粗大疲劳变形带的萌生和扩展,在扩展过程中萌生显微疲劳裂纹。

The variation of fatigue dislocation structures in quench-400℃ tempered 12CrMo steel with incresing cyclic loading numbers have been investigated by using transmis-sion electron microscopy.The dislocation structure styles showing cyclic micro-hardeningand softening occur in the steel.It was found that the former is the formation of dislocationtangles,and the latter is initiation and propagation of thick fatigue deformation bands.The fatigue dislocation structure and the fatigue crack initiation in quench-600℃tempere 12 CrMo steel have been investigated by using transmission electron microscopy.The variation of fatigue dislocation structures can be divided into three stages:the firststage—occurence of the dislocation structure possessing fatigue feature,the second stage-formation of microscopic fatigue slip bands,and the third stage-initiation and propaga-tion of the thick fatigue deformation bands.The microscopic fatigue cracks are formed inpropagation of the thick fatigue deformation bands.