The fatigue and fracture properties of high-purity titanium rods are important factors that determine their service life. Years of research at home and abroad have shown that the fatigue failure mechanism of titanium rods and its relationship with various metallurgical factors is a long-term and arduous task. Because the initial test data is relatively scattered, some substantive issues are not clear enough, and viewpoints are not unified enough, this paper only introduces some representative conclusions.
The fatigue life of most titanium materials is the same as other materials, and it is related to the probability of fatigue crack generation and the growth rate. The research results show that most of the fatigue cracks are formed inside the slip zone and on the surface of the twin boundary, while the Ti-6AI-4V alloy, in the low-stress state, when the force of the slip zone is higher when the slip zone is under high stress.
When the nucleation rate increases, when the temperature of the sample increases, the interface between the phase and the b phase is a weak link. In order to improve the fatigue performance, for the α + β titanium alloy bars, it is generally expected to obtain fine equiaxed α + β. tissue, preferably free beta, to reduce the alpha/beta phase interface area. In addition, the fine-grain sliding is relatively uniform and the free slip time is short, which can alleviate the stress concentration caused by dislocation plugs; meanwhile, the fine-grain has a stronger constraining effect on twinning. On the contrary, the coarse-grained Widmandarin microstructure is prone to nucleation of fatigue cracks, thereby reducing the fatigue strength. Effect of grain size on fatigue properties of Ti-6A1-4V gold smooth and notched specimens.
When the crack is notched and the stress is concentrated, the effect of grain size is reduced, because the fatigue life mainly depends on the crack growth rate at this time, and the experimental results of pure titanium show that the grain size has nothing to do with the crack growth rate.
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