Crack nucleation mechanism of Ti60 titanium alloy under ultrasonic fatigue loading at different temperatures

Abstract The crack nucleation mechanism of Ti60 titanium alloy under ultrasonic fatigue loading at different temperatures was investigated. The results show that there are two different crack nucleation mechanisms at RT, 300 °C, and 400 °C, i.e., the oversized facet and oxide shedding crack nucleation mechanisms. Almost all fatigue cracks initiate in the form of oversized facets at RT. At 300 °C, the crack initiates at the oversized facet under the low load test, while the crack initiates at the oxide shedding site under the high load test. At 400 °C, all the fatigue cracks initiate at the place where the oxide shedding. Higher temperature and applied stress will help the oxide shedding crack nucleation mechanism to become dominant.