Effect of microstructure on low-cycle fatigue property of Ti6321 alloy

The low-cycle-fatigue behavior of Ti6321 alloy with bimodal and lamellar microstructure have been investigated by analyzing of strain-cycles curve under different stress amplitudes. The results show that under the stress amplitude of 600 MPa, the fatigue life of lamellar microstructure is 6644 times, and the fatigue life of bimodal microstructure is 16252, which is more than twice that of the former. What's more, two dislocation models of initiation and growth of cracks were demonstrated by analysis of fatigue fracture. The bimodal microstructure have the higher dislocation density and the shorter effective dislocation slip distance, which could hinder the initiation and propagation of fatigue cracks. The findings of low-cycle-fatigue property can provide data support and theoretical guidence for the safety assessment of titanium alloy pressure structures.