The effect of microstructure on fretting fatigue crack initiation life and crack propagation life of Ti-4.5Al-3V-2Mo-2Fe with Widmanstätten α structure was investigated in comparison with equiaxed α structure in this study. The crack propagation life is more predominant for fretting fatigue compared with the case of plain fatigue in low cycle fatigue life region in both structures. While, the crack initiation life is more predominant for fretting fatigue in high cycle fatigue life region in both structures. The crack propagation resistance of Ti-4.5Al-3V-2Mo-2Fe with Widmanstätten α structure is larger than that of the alloy with equiaxed α structure. The fretting fatigue strength of the alloy with Widmanstätten α structure improves slightly in low cycle fatigue life region. The effect of microstructure on crack deflection is small. The crack propagation rate increases remarkably because of the acceleration of crack propagation due to the frictional force. The fretting fatigue life of the alloy is remarkably lower than its plain fatigue life because of the decrease in crack initiation life and crack propagation life due to the fretting action during crack propagation phase.
