High-temperature fatigue property of Ti46Al8Nb alloy with the fully lamellar microstructure

The high-cycle fatigue behavior of Ti46Al8Nb cast alloy with fully lamellar microstructure has been studied at room temperature, 400 °C, 600 °C and 750 °C. The result shows that temperature has great influence on the fatigue strength of Ti46Al8Nb alloy. Compared with that at room temperature, fatigue strength is significantly reduced at 400 °C. However, at 600 °C the fatigue strength is slightly improved. A further increasing of temperature up to 750 °C gives rise to larger scatter of fatigue life and produces a more flat S-N (stress amplitude versus number of cycles to failure) curve. Fractographic observations indicate that fatigue cracks initiate at the interior casting defects and the lamellar colonies near the surface. Mixed modes of delamination, translamellar fracture and stepwise fracture are observed on the fracture surfaces at all temperatures.