The fatigue and fracture properties of titanium alloy rods occupy a very important position in determining the service life of the alloy. Research has been carried out at home and abroad over the years to investigate the fatigue and fracture mechanisms of titanium alloy rods and their relationship with various metallurgical factors. Due to the complexity of the problem itself and the scattered nature of the initial test data, some of the substantive issues are still not entirely clear and views are not fully unified, so only some representative conclusions are presented here.

The fatigue life of titanium alloy rods, like that of other materials, depends on the chance of fatigue crack nucleation and the rate of crack expansion. According to the study of pure titanium, fatigue cracks are mostly nucleated in the slip zone and at the twin interface, but for Ti-6AI-4V this type of alloy, under low stress conditions, the a-phase and b-phase interface is the weak link of Z. Only at high stress levels, the chance of nucleation in the slip zone increases significantly, and increasing the test temperature has a similar effect In order to improve the fatigue performance of a ten-b titanium alloy rods, it is usually desirable to obtain a fine equiaxial a ten-b organization, and the b-phase is well free, in order to reduce the a/b-phase interface area. In addition, the fine grain slip is more uniform, slip free distance is short, can reduce the stress concentration caused by dislocation plugging; at the same time, the fine crystal on the twin crystal also has a greater restraint effect. On the contrary, the fatigue strength of coarse crystalline Weiss organization is lower due to the easy nucleation of fatigue cracks. The effect of grain size on the fatigue performance of smooth and notched specimens of Ti-6A1-4V alloy.

In the presence of notches and stress concentrations, the effect of grain size decreases, as the fatigue life depends mainly on the crack expansion rate, while experimental results for pure titanium show that the crack expansion rate is not closely related to the grain size.