垂直晶界和倾斜晶界Cu双晶的疲劳开裂行为及其机制

CYCLIC DEFORMATION BEHMIOR AND FATIGUE CRACK INITIATION IN COPPER BICRVSTALS

用扫描电镜（SEM）研究了一种垂直晶界和两种倾斜晶界Cu双晶的疲劳开裂行为及其机制．这三种双晶组元晶体的取向均为[134]．结果表明，沿晶界的疲劳开裂是Cu双晶疲劳破坏的主要形式，但垂直晶界和倾斜晶界双晶疲劳裂纹萌生的机制有所不同．垂直晶界双晶沿晶疲劳裂纹主要由驻留滑移带撞击晶界而产生，而倾斜晶界双晶疲劳裂纹的萌生是由晶界两侧晶粒的滑移台阶而引起的应力集中所致．

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.