Effect of Aging on Fatigue-Crack Growth Behavior of a High-Temperature Titanium Alloy

摘要

The effects of aging on the fatigue-crack growth (FCG) behavior of a newly developed high-temperature titanium alloy (Ti-6Al-4.8Sn-2Zr-lMo-0.4Si-lNd) with bimodal and lamellar microstructures were investigated at room temperature. The results indicate that aging had a more pronounced effect on the lamellar than on the bimodal microstructure. The effect is weakened with prolonged aging time especially for lamellar microstructure. TEM and SEM studies of microstructures and fracture surfaces were performed to gain insight into the deformation characteristics and crack propagation mechanisms of these microstructures. The differences in FCG behavior in different aging conditions were interpreted in terms of the effect of aging time on the microstructure, the crack path tortuosity and crack closure. The dependence of FCG behavior on aging condition can be attributed to the precipitation of the α_2 phase based on Ti_3Al from the two microstructures, and the silicide was found to play a limited role in the present investigation.