HIGH CYCLE FATIGUE OF AN ORTHORHOMBIC TI-22AL-25NB INTERMETALLIC ALLOY

摘要

An evaluation of fatigue behavior of the orthorhombic Ti-22Al-25Nb intermetallic alloy with the duplex microstructure has been carried out with high cycle rotary bending fatigue testing at room temperature (RT), 650°C and 750°C with a test frequency of 50Hz. The testing results show that the fatigue strengths (σ{sub}(-1)) are up to 530MPa at RT, 600MPa at 650°C at or more than 1×10{sup}7 cycles, and 500MPa at 750°C at 8.34×10{sup}6 cycles. Damage mechanisms at crack initiation sites and crack propagation were investigated with the use of scanning electron microscopy. The fatigue failure mechanisms of the duplex microstructure of the present alloy are simply discussed.