Fatigue Crack Growth Behavior of TA29 Titanium Alloy at Different Temperatures

Abstract

TA29 titanium alloy forging was heated by duplex annealing. The fatigue crack growth behaviour of the alloy at room temperature, 400 °C, 500 °C and 600 °C was studied. The relationship between the fatigue crack growth rate (Da/dN) and the stress intensity factor amplitude (△K) of TA29 alloy at different temperatures was revealed by Paris formula. The fatigue fracture morphology of fatigue crack growth specimens was analysed by scanning electron microscopy (SEM). The results showed that the TA29 titanium exhibited good crack growth resistance at room temperature. With the increase of test temperature, the C value of the Paris formula increased, the m value decreased, and the fatigue crack growth rate increased. From the fatigue fracture morphology of the specimens, it was found that the fractures of fatigue crack growth specimens at different temperatures exhibited typical pre-splitting zone, steady-state expansion zone and rapid expansion zone. As the temperature increased, the range of the pre-cracking zone was larger, the range of the steady-state extension zone and the rapid expansion zone were smaller. At room temperature, there was no obvious fatigue strips in the steady-state expansion zone, and the transient fracture zone exhibited the characteristics of cleavage fracture, while the steady-state expansion zone at high temperature showed obvious fatigue strips and secondary cracks, and the transient fracture zone was a typical ductile fracture mechanism.