中文摘要：

通过对焊接接头疲劳断口的观察研究，讨论了控制接头疲劳失效的疲劳机理。实验研究了焊接接头的母材、焊缝及热影响区的微观组织形态。结果发现：母材组织为细小均匀的板条马氏体及弥散分布的第二相粒子，而焊缝区为粗大的板条马氏体及少量的第二相颗粒。组织特征的区别证明母材综合力学性能优于焊缝。

英文摘要：

The fatigue fracture surfaces of welded joints were observed and studied, and accordingly the fatigue mechanisms, governing fatigue failure of welded joints, were discussed. The microstruc- tures on the base metal, the weld seam and the heat-affected zone of welded joints were investigated. It is concluded that the microstructures on the base metal are fine tempered martensite and dispersed secondary phase particles, whereas the ones on the weld seam are coarse lath martensite and few of secondary phase particles. The differences between their microstructures confirm the better mechanical properties of the base metal.