CYCLIC DEFORMATION BEHMIOR AND FATIGUE CRACK INITIATION IN COPPER BICRVSTALS
垂直晶界和倾斜晶界Cu双晶的疲劳开裂行为及其机制

The fatigue cracking behavior and mechanisms in three types of 34] iso-axialcopper bicrystals have been studied by using scanning electron microscopy (SEM). One bicrystalcontains a grain boundary (GB) perpendicular to the loading direction and the two others containtilting GBs. The experimental results show that the intergranular fatigue cracking is the mainmode in the fatigue failure for the three types of copper bicrystals. However, the fatigue craCkingmechanisms are different for the perpendicular GB bicrystal and the tilting GB bicrystals. Theintergranular fatigue cracks are mainly formed by impingement of persistent slip bands againstthe GB in the perpendicular GB bicrystal. While the fatigue cracking initiation is predominatelydetermined by the stress concentration resulted from steps for the tilting GB bicrystal. The foregoing difference between the fatigue cracking initiation mechanisms in the two types of bicrystalsis closely related to the specimens geometry with respect to the primary slip systems.