Temperature dependent fatigue crack growth in forged TiAl alloys with nearly-lamellar and triplex microstructure

Temperature dependency of fatigue crack growth behavior in 1 containing forged TiAl alloys is investigated. Two kinds of material with nearly-lamellar and triplex microstructures are employed in fatigue crack growth tests at room temperature, 400 degrees C and 760 degrees C. A series of AK increasing and decreasing tests exhibits that at room temperature the fatigue crack growth resistance of triplex microstructure is lower than that of nearly-lamellar microstructure, whereas the resistance of triplex becomes higher at 760 degrees C. This higher resistance of triplex microstructure at high temperature is mainly attributed to the higher volume fraction of ductile p phase. The values of fatigue crack growth threshold in two microstructures show almost comparable at three temperatures, and they reveal the same temperature dependency. The threshold is found to be the highest at 760 degrees C, while the lowest at 400 degrees C. This temperature-dependency of fatigue threshold should be related to the roughness-induced and oxidation-induced crack closure mechanisms.

Automated summary

The study found that at high temperatures, the fatigue crack growth resistance of the triplex microstructure is significantly increased, mainly due to the higher volume fraction of ductile p phase. Meanwhile, the fatigue crack growth threshold in different microstructures and temperatures is almost comparable and shows the same temperature dependency.