High-Cycle Fatigue of Ultra-fine Grained Commercial Purity Titanium by Combined refining process

Abstract:

Stress-controlled high-cycle fatigue performance of ultra-fine grained commercial purity titanium (UFG CP Ti) was conducted with a loading frequency of 25 Hz and a stress ratio R=-1 at room temperature. The relation between stress amplitude and cycle numbers to failure was fitted, and the fatigue fracture surface of UFG CP Ti specimen was also investigated. The results showed that the fatigue limit of annealed UFG CP Ti specimen at 200℃ for 60 min was 376.5 MPa, which increased 56.5 MPa compared with the unannealed one. Moreover, the fatigue cracks mainly initiated from the surface of fatigue specimen. The annealed UFG CP Ti specimen exhibited the smaller fatigue striation spacing and lower crack propagation rate than the unannealed one, indicating a higher room temperature fatigue performance.

Key words:Combined refining process (ECAP+CR+RS); Ultra-fine grained commercial purity titanium (UFG CP Ti); high-cycle fatigue; fatigue limit; fractography