Through an innovative fatigue test design, the initiation and propagation of fatigue cracks were observed with a microscope in real time, and the effects of surface nanocrystallization on the fatigue properties of pure Zr were systematically studied in the work. The results showed that the fatigue limit of pure Zr treated by ultrasonic shot peening (USSP) for 45 min was up to 11.2% higher than that of the original pure Zr. Both the initiation life and propagation life of fatigue cracks could be increased after USSP treatment. When the cyclic stress was set as 225 MPa, the initiation life and propagation life of fatigue cracks in the 45-min USSP-treated pure Zr were 3.1 times and 1.48 times those of the original samples, respectively. The lower the cyclic stress was, the more obvious the improvement in the initiation life of the fatigue cracks. This improvement in initiation life was the main reason for the promotion in the overall fatigue life of the USSP-treated samples. The results of the fatigue fracture analysis showed that a large number of secondary cracks and dimples appeared in both the original and the USSP-treated samples. However, the fatigue bands in the original pure Zr were disorderly, whereas those in the USSP-treated pure Zr were parallel to each other and perpendicular to the direction of crack propagation.

通过创新的疲劳测试设计，使用显微镜实时观察疲劳裂纹的萌生和扩展，并在工作中系统地研究了表面纳米晶对纯Zr疲劳性能的影响。结果表明，经超声波喷丸处理（USSP）处理45分钟的纯Zr的疲劳极限比原始纯Zr的疲劳极限高11.2％。经过USSP处理后，疲劳裂纹的起始寿命和扩展寿命都可以增加。当循环应力设定为225 MPa时，经USSP处理45分钟的纯Zr的疲劳裂纹的起始寿命和扩展寿命分别是原始样品的3.1倍和1.48倍。循环应力越低，疲劳裂纹萌生寿命的改善越明显。初始寿命的这种改善是提高USSP处理的样品的整体疲劳寿命的主要原因。疲劳断裂分析的结果表明，原始样品和USSP处理过的样品中均出现大量次要裂纹和凹痕。但是，原始纯Zr中的疲劳带是无序的，而经USSP处理的纯Zr中的疲劳带彼此平行且垂直于裂纹扩展的方向。