Fatigue crack propagation behaviors of a novel high strength Ti-5Al-3Mo-3V-2Zr-2Cr-1Nb-1Fe alloy with equiaxed and lamellar microstructures were systematically investigated. Fatigue crack propagation tests at both increasing and decreasing stress intensity factor range values were carried out with a frequency of 15 HZ and stress radio R of 0.1 by using compact tension samples. The sample with lamellar microstructure displayed the faster fatigue crack propagation rates in near-threshold regime compared to the sample with equiaxed microstructure. The fatigue threshold (ΔK_th) was 2.7 MPa·m^1/2 for lamellar microstructure, and 3.2 MPa·m^1/2 for equiaxed microstructure. The steady state crack growth rate in lamellar microstructure was slightly slower than that in equiaxed microstructure in the Paris regime, while much faster in the rapid growth regime. The interactions between crack path and microstructures as well as the microscopic fracture surface morphology in both microstructures were detected and analyzed by scanning electron microscope (SEM), revealing the different crack propagation behaviors in three regimes. The results showed that the crack propagation behaviors were a result of two contributing factors: interface obstacles and crack front profile. The increased fatigue crack propagation resistance of equiaxed microstructure in near-threshold regime can be attributed to the interface obstacles which dominated over the rougher crack front profile. While the higher fatigue crack growth resistance for lamellar microstructure in Paris regime was attributed to the more positive effect of rougher crack front profile. In the rapid growth regime, the crack in lamellar microstructure was found to be extended along the grain boundary α, which was regarded as a low energy crack path and led to the faster crack propagation rate.

系统研究了具有等轴和层状组织的新型高强度 Ti-5Al-3Mo-3V-2Zr-2Cr-1Nb-1Fe 合金的疲劳裂纹扩展行为。疲劳裂纹扩展测试在增加和减少应力强度因子范围值下进行，频率为 15 HZ，应力无线电 R 为 0.1，使用紧凑拉伸样品。与具有等轴显微组织的样品相比，具有层状显微组织的样品在接近阈值状态下显示出更快的疲劳裂纹扩展速率。层状组织的疲劳阈值（ΔK _th）为2.7 MPa·m ^1/ 2，3.2 MPa·m ^1/2为等轴显微组织。层状微观结构的稳态裂纹扩展速率在巴黎状态下略慢于等轴微观结构中，而在快速增长状态下则快得多。通过扫描电子显微镜 (SEM) 检测和分析裂纹路径与微观结构之间的相互作用以及两种微观结构中的微观断口形貌，揭示了三种状态下不同的裂纹扩展行为。结果表明，裂纹扩展行为是两个影响因素的结果：界面障碍和裂纹前沿轮廓。等轴显微组织在接近阈值状态下增加的疲劳裂纹扩展阻力可归因于界面障碍支配了较粗糙的裂纹前沿轮廓。而在巴黎状态下层状微观结构的更高的疲劳裂纹扩展阻力归因于更粗糙的裂纹前沿轮廓的更积极影响。在快速生长状态下，发现层状组织中的裂纹沿晶界α延伸，这被认为是低能裂纹路径，导致裂纹扩展速度更快。