等径弯曲通道制备的超细晶铜的疲劳性能

研究了等径弯曲通道(ECAP)变形后的超细晶T3铜在恒应力幅控制条件下的疲劳寿命和循环形变行为.通过扫描电镜观察了疲劳试样表面的滑移带,并利用电子背散射技术观察了疲劳前、后晶粒尺寸的变化.结果表明,超细晶T3铜具有较高的疲劳极限(σ-1=153 Mpa),是粗晶铜疲劳极限的2倍.在低周疲劳域内表现出疲劳软化,而在高周疲劳域内表现比较稳定的疲劳行为,甚至出现疲劳硬化.类似驻留滑移带(PSB)的剪切带与最后一次挤压的剪切面一致,剪切带的形成和晶界滑移是疲劳裂纹形核和疲劳断裂的主要原因.

Fatigue Property of Ultrafine-grained Copper Produced by ECAP

The fatigue life and cyclic deformation behavior of ultrafine-grained (UFG) T3 copper produced by equal channel angular pressing (ECAP) were studied and the changes of the grain size and the development of slip bands are observed by means of electron back scattering and SEM, respectively. The result shows that the fatigue limit of the UFG T3 copper corresponding to 107 cycles is 153 MPa which is the double of fatigue limit of the coarse grained (CG) copper. Cyclic softening occurs in the low-cycle fatigue region whereas stable cyclic behavior, even cyclic hardening, occurs in the high-cycle region. Persistent slip bands (PSB)-like shear bands (SBs) are approximately parallel to the shear plane at the last pressing. The formation of SBs and grain boundary sliding are the main factor causing crack nucleation as well as fatigue failure.