Creep of a beta phase-containing TiAl alloy

The creep properties of a powder-metallurgy Ti–46.5Al–2Cr–2Nb–0.8Mo–0.2W–0.2Si (at%) alloy containing beta phase were investigated. Tensile creep experiments were performed in air at 705, 760 and 815°C at stresses ranging from 35 to 414 MPa. Stress exponent and activation energy were both measured. Data indicated that the creep of the alloy can be divided into two regimes, depending upon the applied stress. Microstructures before and after deformation were examined using X-ray diffraction, scanning and transmission electron microscopy techniques. Efforts were made to correlate creep properties with microstructures. Possible deformation mechanisms in the two creep regimes were discussed. The creep resistance of the present alloy was also compared with other alloys without beta phase. It is concluded that the presence of beta phase reduces the creep resistance of TiAl.