Effect of Prior Creep Strain on High Cycle Fatigue Life of Ti 834

Room-temperature fatigue tests were conducted on Ti 834 with prior creep strains accumulated under constant load at 550°C and 600°C, respectively. Microstructural and fractographic examinations on specimens with prior creep strain > 3% revealed the failure process consisting of multiple surface crack nucleation and internal void generation by creep, followed by fatigue crack propagation in coalescence with the internally distributed damage, leading to the final fracture. The amount of prior creep damage increased with creep strain. The fatigue life of Ti 834 was significantly reduced by prior creep straining. The behavior is rationalized with the integrated creep-fatigue theory.