On the giga cycle fatigue behaviour of two-phase (α2+γ) TiAl alloy

Fatigue crack initiation behaviour is investigated at room temperature in the (α2-Ti3Al and γ-TiAl) alloy. High cycle fatigue tests ranging up to 1010 cycles are carried out on the powder metallurgy (P/M) bar specimens under different loading conditions with a stress ratio of R=0.1 and R=0.5. Microstructural characterization and fracture surface analysis are also investigated by optical (OM) and scanning electron microscopy (SEM). Ti–Al alloy studied here shows two phases in microstructure (nearly refined lamellar thickness) composed of α2-Ti3Al and γ-TiAl (hereafter called γ+α2 alloys) and fracture mechanism is explained with different plastic incompatibilities between the two phases.