Fatigue crack propagation behaviour of a TiAl-based alloy

In the present study the fatigue crack propagation resistance of a nearly fully lamellar quaternary TiAl based is investigated at room-temperature. The fatigue crack growth rates material are shown to be highly sensitive on the applied stress intensity factor amplitude. A special attention is also paid to the influence of extrinsic factors. Thus crack-closure is proved to strongly influence the propagation. As regards environmental effects, ambient air induces fatigue crack growth rates two orders of magnitude higher than those measured in vacuum. The role of moisture in this deleterious effect is discussed. (orig.)