Microstructural effects on the high-cycle fatigue and fracture behaviors of Ti-6Al-4V alloy

In this work, the samples of Ti-6Al-4V alloy are fatigued at room temperature (RT) and 400 degrees C to reveal the effect of microstructure on high-cycle fatigue behaviors. Results show that the RT fatigue strength monotonically increases with increasing primary alpha (alpha(p)) percentage, while a moderate alpha(p) percentage shows slightly higher fatigue strength value at 400 degrees C. Ti-6Al-4V with 45-60% alpha(p) exhibit relatively long fatigue life and small scatter in fatigue data. The crack-initiation sites of RT failed specimens show isolated or contiguous alpha(p) facets. Fatigue steps associated with the multiple crack-initiation are observed in 400 degrees C failed specimens.