利用扫描电镜电子通道衬度(SEM--ECC)技术观察了循环变形饱和阶段Cu单晶样品中近表面区域的位错微结构. 在样品边缘一些条带状或斑点状呈黑色的位错组织区, 利用离散位错动力学方法模拟了该区的位错微观结构, 并计算了与此位错微结构相对应的内应力分布. 模拟和计算结果表明, 黑色区是内应力出现最大值区,即应力集中区, 它与驻留滑移带(PSB)中的不均匀变形有关,是疲劳裂纹萌生最可能的位置.模拟和计算结果很好地解释了这一现象.
SEM--ECC technique was employed to observe and characterize the dislocation microstructures during the saturation stage of cyclic deformations in a copper single crystal. Some band--like or spot--like dark zones were found in the dislocation microstructures, which located either at the edge region of the deformed specimen or at the interface between the dislocation matrix and the PSB. To interpret the experiment results, the near surface dislocation microstructure were simulated and the internal stress distributions induced by those dislocations were calculated by using discrete dislocation dynamics method. The simulation results show that near the free surface region, the maximum internal stresses or stress concentration appear at the dark zones which correspond to the interfaces between the PSB and the dislocation matrix or the PSB--matrix--surface interfaces, meaning that fatigue cracks initiate preferentially at these dark zones. The simulated results can well explain the observated ones.
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