Initiation and growth of short cracks in a nickel-based single crystal were studied by carrying out in-situ fatigue experiments within a scanning electron microscope (SEM). Specimens with two different crystallographic orientations, i.e., [001] and [111], were tested under load-controlled tension fatigue in vacuum. Slip-caused crack initiation was identified at room temperature while initiation of a mode-I crack was observed at 650 °C. Slip traces continuously developed ahead of the crack tip once initiated and acted as nuclei for early-stage crack growth at both room and high temperature (650 °C). These slip traces were caused by accumulated shear deformation of activated octahedral slip systems, which were specifically identified by analysing the surface slip traces and crack-propagation planes. The crack-growth rates were evaluated against stress intensity factor range, revealing the anomaly of slip-controlled short-crack growth. The effects of crystallographic orientations and temperature on fatigue crack growth were subsequently analysed and discussed, including the influence of microstructural features such as carbides and pores.

通过在扫描电子显微镜（SEM）中进行原位疲劳实验，研究了镍基单晶中短裂纹的产生和扩展。具有两种不同晶体学取向的试样，即[001]和[111]在真空中在负荷控制的张力疲劳下进行测试。在室温下确定了由滑移引起的裂纹萌生，而在650°C下观察到了I型裂纹的萌生。滑动痕迹一旦开始就在裂纹尖端之前不断发展，并在室温和高温（650°C）下充当早期裂纹扩展的核。这些滑移痕迹是由活化的八面体滑移系统的累积剪切变形引起的，通过分析表面滑移痕迹和裂纹扩展平面可以明确识别出这些滑移痕迹。针对应力强度因子范围评估了裂纹扩展速率，揭示了滑动控制的短裂纹增长的异常。随后分析和讨论了晶体取向和温度对疲劳裂纹扩展的影响，