Microstructure and mechanical properties of (γ + β)-based TiAl alloys containing vanadium and niobium

(γ + β)-based TiAl alloys containing V and Nb have been selected for the development of a useful multiphase intermetallic microstructure. The evolution of microstructure was studied by optical microscopy, electron-probe microanalysis (EPMA), scanning electron microscopy (SEM), transmission electron microscopy (TEM). It is indicated that a finer microstructure can be obtained in the TiAl based alloys with a small amount of β (bcc) phase by an appropriate heat treatment. The mechanical properties such as bending strength, plastic strain, creep resistance as well as oxidation resistance were also investigated on the basis of bending tests, compressive creep tests and thermogravimetric analysis (TGA). The results show that the room temperature strength of alloys with this kind of microstructure, particularly those containing 13 to 15 at.% V, can be increased considerably. Also the ductility is obviously improved. However, the introduction of β phase resulted in a poorer creep and oxidation resistance.