Effect of Temperature on High Cycle Fatigue Behaviour of Ti-6Al-4V Alloy

Ti–6Al–4V alloy is widely used in aerospace applications for its high strength-to-weight ratio and outstanding resistance to corrosion. It also ensures better high temperature specific strength. Aerospace components are often confronted with cyclic stresses throughout their operating lives. The fatigue behaviour of Ti-6Al-4V alloy was studied at room temperature (RT) and moderately high temperature (150 ℃) at a stress ratio (R) of 0.7. The specimens were subjected to high cycle fatigue (HCF) loading at 78Hz on the RUMUL TESRONIC resonance system. Fractographic investigations were carried out on the tested specimens. HCF results indicate that, this alloy exhibited a decrease in fatigue strength by 50 MPa upon increasing the temperature from RT to 150 °C. The lower crack initiation resistance behaviour at increased temperatures provides a rationale for the decrease in fatigue strength. Findings from fractographic studies for RT tests reveal that the crack initiation region was observed to originate from the surface. Samples from specimens tested at 150 ℃ reveal that the cracks initiated from the interior.