Very High Cycle Fatigue Behavior of Ti-6Al-4V Alloy

In order to investigate the fatigue behavior of Titanium Alloy in very high cycle region, fatigue test of Ti-6Al-4V was performed at ambient temperature by using ultrasonic fatigue equipment. Fracture surface morphology was observed by using Scanning Electron Microscope. The results demonstrate that the S-N curve exhibited a continuously descending trend and the fatigue limit was not observed. The fatigue failure still occurred when the loading cycles exceeded 108 cycles. Brittle failure and plastic failure were both observed under ultrasonic loading. Fatigue cracks in high cycles fatigue prefer to initiate from surface and in very high cycle fatigue the crack trend to initiate from subsurface.