Effects of Temperature on the Fatigue Crack Growth Behavior of Cast Gamma-Based Titanium Aluminides

摘要

This article reports the results of an experimental study of the effects of temperature (25 deg C, 450 deg C, and 700 deg C) on the fatigue crack growth behavior of three near-commercial cast gamma titanium aluminide alloys (Ti-48Al-2Cr-2Nb, Ti-47Al-2Mn-2Nb + 0.8 pct TiB_2, and Ti-45Al-2Mn-2Nb + 0.8 pct TiB_2). 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 oxide-induced crack closure.