在不同塑性应变幅下对[233]共面双滑移取向Cu单晶体进行疲劳实验直至循环饱和, 然后在不同温度进行退火处理.利用SEM-ECC和TEM观察疲劳位错结构及其退火后微观结构的变化. 结果表明, 退火温度为300 ℃时, 位错结构均发生了明显的回复, 高应变幅下疲劳样品中甚至出现了部分再结晶. 在500和800 ℃退火, 所有晶体都发生了严重的再结晶, 并且有大量的退火孪晶出现. 随着塑性应变幅和累积塑性应变量的增加, 应变集中程度明显增加, 为再结晶的发生和孪晶的萌生提供了更大的局部应变能, 所以再结晶发生得更为显著, 退火孪晶变得更为粗大且数量增加. 退火孪晶的形成与层错的出现有密切关系. DSC测试分析表明, 再结晶的发生不是突发式的, 而是一个缓慢的过程.

Although comprehensive research findings of the cyclic deformation and dislocation structures of Cu single crystals with various orientations have been well established over the four decades, studies on the thermal stability of dislocation structures in fatigued Cu single crystals are still rarely reported. In the present work, [233] Cu single crystals oriented for coplanar double slip were firstly cyclically deformed at different plastic strain amplitudes γ_pl up to saturation, and then annealed at different temperatures for 30 min.The dislocation structures induced by cyclic deformation as well as the microstructural changes resulting from subsequent annealing treatments were detected by using the electron channeling contrast (ECC) technique in SEM and TEM. It was found that the dislocation structures have undergone an obvious process of recovery at 300 ℃,and the recrystallization even partially takes place in the sample fatigued at highγ_pl. However,at 500 and 800 ℃, the violent recrystallization takes place in all crystals and a large number of annealing twins have appeared. As the plastic strain amplitude and accumulated plastic strain increase, the degree of strain concentration would be significantly aggravated, providing a higher local strain energy for the occurrence of recrystallization and the initiation of twins, so that the recrystallization takes place more noticeably, and annealing twins become coarser and the number of them increases notably. The formation of annealing twins is closely related to the appearance of stacking faults. The DSC measurements demonstrated that the recrystallization process and the formation process of twins should be a gradually-developing process, instead of a suddenly-forming process.