On the giga cycle fatigue behaviour of two-phase (?2+?) TiAl alloy

Abstract Fatigue crack initiation behaviour is investigated at room temperature in the (α 2 -Ti 3 Al and γ-TiAl) alloy. High cycle fatigue tests ranging up to 10 10 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 α 2 -Ti 3 Al and γ-TiAl (hereafter called γ+α 2 alloys) and fracture mechanism is explained with different plastic incompatibilities between the two phases.