Abstract:High cycle fatigue (HCF) of Ti-600 alloy was tested at a frequency of 120-130 Hz and load ratio R of 0.1. The results show that the HCF strength for the alloy at ambient temperature is 475 MPa, comparable with that of IMI834 alloy. The observed high tensile strength and high HCF strength is attributed to its overlapping fine and thin-plate-like α+β phase microstructure. The propagating region of the fatigue crack for the as-annealed composite is regular and wide, which contribute to its improved HCF strength and prolonged fatigue crack propagation life. The distance between two fatigue stripes for the sample fractured at 8.61′105 cycles is wider than that of the sample failed at 1.78′106 cycles, indicating that their propagation resistance for fatigue cracks is smaller. The average grain size of rare earth phases ranges from several micrometers to 0.2 mm, and no cracks corresponding to rare earth particles are initiated