An Investigation of The Effects of Temperature on Fatigue Crack Growth Behavior of a Cast Nearly Lamellar Ti-47Al-2Cr-2Mn+0.8 Vol. Percent TiB_2 Gamma Titanium Alloy

摘要

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. Percent TiB_2 gamma titanium aluminide intermetallics. Fatigue crack growth rate data are presented for the cast lamellar microstructure at 25,450 and 750 deg 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 deg C are attributed to the high incidence of irreversible deformation-induced twinning, while slower crack growth rates at 700 deg 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.