The fatigue and fracture properties of titanium alloy rods play an important role in determining the service life of alloys. The fatigue and fracture mechanism of titanium alloy bars and their relationship with various metallurgical factors have been studied at home and abroad for many years. Due to the complexity of the problem itself, some substantive issues are still unclear and opinions are not completely unified due to the scattered data of the initial test. Here only some representative conclusions are introduced.
The fatigue life of titanium alloy rod, like other materials, depends on the probability of fatigue crack nucleation and crack growth rate. According to the study of pure titanium, most fatigue cracks within the slip zone and the twin boundary surface nuclear, but for this ai Ti - 6, 4 v type alloy, under the condition of low stress, a and b phase interface is the weakest link, just in a high stress level, slip band endogenous nuclear risk increased significantly, improve test temperature has a similar effect, in order to improve the fatigue performance, to a 10 b type of titanium alloy rods, usually get fine equiaxed hope a 10 b group, and b is the best in the free state, in order to reduce a/b phase interface area. In addition, fine grain slip is uniform and free slip distance is short, which can reduce the stress concentration caused by dislocation plug deposition. At the same time, the fine crystal has a great restraint effect on the twin. On the contrary, the fatigue strength of coarse crystal weissner structure is low because of the easy nucleation of fatigue crack. Effect of grain size on fatigue properties of smooth specimens and notched specimens of Ti - 6A1-4V alloy.
In the case of notch and stress concentration, the influence of grain size decreases, because the fatigue life at this time mainly depends on the crack growth rate, while the experimental results of pure titanium show that the crack growth rate is not closely related to grain size.