Study on the application of ultrafine grained copper to electric materials.

本研究对经ECAP处理的UFG铜进行了疲劳试验，以阐明其疲劳机理。通过实验分析，阐明了光滑试样的疲劳裂纹萌生行为、表面硬度变化与应力疲劳损伤的关系、裂纹扩展行为和扩展机制以及控制其疲劳寿命的表面小裂纹的扩展规律。此外，由于组织不稳定，晶界不平衡，导致长寿命场疲劳强度提高较小，因此采用ecap后退火技术提高长寿命场疲劳强度。结果表明，经180℃后ecap退火的99.9%Cu铜在2 × 10^7次循环时的疲劳强度提高了约1.4倍。

In the present study, the fatigue tests of UFG copper processed by ECAP were conducted to clarify the fatigue mechanism. The experimental analysis was made and the fatigue crack initiation behavior, the relationship between the change in surface hardness and fatigue damage due to stressing, the crack growth behavior and growth mechanism, and the growth law of small surface-cracks which control the fatigue life of smooth specimens, were clarified. In addition, post-ECAP annealing was conducted to improve the fatigue strength in a long-life field because that the less improvement of fatigue strength in long life fields resulted from instability of microstructure with non-equilibrium grain boundaries. Results of copper (99.9%Cu) with post-ECAP annealing at 180℃ showed the enhanced fatigue strength at 2x10^7 cycles (about 1.4 times of as-ECAPed copper with 99.99%Cu).