Effect of microstructure on high cycle fatigue behavior of Ti-20Zr-6.5Al-4V alloy

Room temperature fatigue behavior of Ti-20Zr-6.5Al-4V alloy containing equiaxed and lamellar microstructures is investigated. It is found that microstructures significantly affect high cycle fatigue strength. The fatigue strength for equiaxed microstructure at 107 cycles is around 575 MPa, which is lower than that for lamellar microstructure (775 MPa). Opposite scenario is observed at high stress level, especially above 825 MPa. A large scatter in fatigue life for lamellar microstructure is attributed to different crack initiation sites. For both types of microstructures, the pile-up of dislocations in α side of α/β interfaces provides preferable crack nucleation sites due to localized strain. Based on the results, effect of microstructure on high cycle fatigue properties is discussed.