An investigation of the effects of temperature on fatigue crack growth behavior of a cast nearly lamellar Ti-47Al-2Cr-2Mn + 0.8 Vol. %TiB₂ gamma titanium alloy

This paper presents the results of a study of the effects of temperature on fatigue crack growth in Ti-47Al-2Cr-2Mn + 0.8 Vol. %TiB₂ gamma titanium aluminide intermetallics. Fatigue crack growth rate data are presented for the cast lamellar microstructure at 25,450 and 750°C. The trends in the fatigue crack growth rate data are explained by considering the combined effects of crack-tip deformation mechanisms and oxide-induced crack closure. Faster fatigue crack growth rates at 450°C are attributed to the high incidence of irreversible deformation-induced twinning, while slower crack growth rates at 700°C are due to increased deformation by slip and the effects of crack-tip shielding provided by oxide-induced wedging, which is analyzed using a modified Dugdale-Barenblatt model.