As-cast and heat treated ternary alloys containing 44.2～47at.%A1 and 0～8at.% Nb were investigated for oxidation resistance at 900°C and crack propagation behavior during thermal fatigue test between 900°C and 15°C. It was found that alloys with about 5at.% Nb content show the best balance of properties. An alloy based on Ti-46.5 Al-5Nb was then prepared and its mechanical and fatigue properties were evaluated. For the fully lamellar microstructure, the alloy typically exhibits fracture toughness of about 30 MPam~(1/2) and creep strains less than 0.1% under the test condition of 80MPa at 800°C for 100 h. High cycle fatigue test shows that the alloy has excellent fatigue performance and the ratio of fatigue strength to yield strength was about 1.14. The thermal-mechanical fatigue behavior of the alloy was studied using smooth bar samples under synchronized temperature and load control. Triangular and trapezoidal wave forms were used for 200～600°C and 300～700°C cycling in air, respectively. Slightly better fatigue life was found under the trapezoidal test condition than the triangular. The fatigue strength of the alloy was estimated at about 350MPa under the trapezoidal test condition and 340MPa under the triangular test condition. An engine component was cast from the alloy, and initial ground test of the component has been successful.
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