In this paper, the effects of hydrogen content and temperature on the fatigue crack initiation and propagation behavior of Zircaloy-4 are investigated by in-situ scanning electron microscope observation. The results show that, at room temperature, with the increase of hydrogen content, the tensile strength increases and the elongation decreases, but the fatigue lifetime (fatigue crack initiation lifetime and fatigue failure lifetime) first increases and then decreases. The cut-off point is at about 200 ppm hydrogen content. The fatigue crack growth rate increases with the increase of hydrogen content. At 300 °C, with the increase of the hydrogen content, tensile strength, elongation and fatigue lifetime of Zircaloy-4 alloys exhibit the same variations as those at room temperature. However, the fatigue crack growth rate is less affected by the hydrogen content. The results also show that, with the same hydrogen content, the fatigue lifetime at 300 °C is longer than that at room temperature, and the fatigue crack growth threshold at 300 °C is lower than that at room temperature. The fatigue crack propagation path is strongly affected by the hydride and grain boundaries. The hydrogen content has a significant effect on the fatigue crack initiation mechanism. For the un-hydrided sample, the fatigue cracks initiate at the sub-surface. With the increase of hydrogen content, the fatigue cracks tend to initiate at the surface of the sample.

本文通过原位研究了氢含量和温度对Zircaloy-4疲劳裂纹萌生和扩展行为的影响。扫描电子显微镜观察。结果表明，在室温下，随着氢含量的增加，抗拉强度增加，伸长率降低，但疲劳寿命（疲劳裂纹萌生寿命和疲劳破坏寿命）先增加后降低。临界点是约200ppm的氢含量。疲劳裂纹扩展速率随着氢含量的增加而增加。在300°C下，随着氢含量的增加，Zircaloy-4合金的拉伸强度，伸长率和疲劳寿命与室温下的变化相同。但是，疲劳裂纹扩展速度受氢含量的影响较小。结果还表明，在相同氢含量下，300°C的疲劳寿命比室温长。300℃的疲劳裂纹扩展阈值低于室温。疲劳裂纹扩展路径受到氢化物和晶界的强烈影响。氢含量对疲劳裂纹萌生机理具有重要影响。对于未水合的样品，疲劳裂纹始于次表面。随着氢含量的增加，疲劳裂纹倾向于在样品表面开始。