An investigation of fatigue crack growth in a cast lamellar Ti48Al2Cr2Nb alloy

The results of a study of fatigue crack growth in a lamellar gamma titanium aluminide alloy are presented in this paper. Differences in the fatigue crack growth behavior at 25, 450 and 700°C are shown to be associated with the combined effects of different fracture modes/crack-tip deformation mechanisms and oxide-induced crack closure under cyclic loading. Crack-tip deformation was found to occur by conventional slip at 25°C. At 450 and 700°C, however, crack-tip deformation occurs via a duplex mode of slip and micro-twinning within lamellae. A higher fatigue threshold at 700°C is attributed partly to the effects of oxide-induced crack closure.