MICROSTRUCTURAL STABILITY OF Ti-46Al-8Ta DURING CREEP

The effect of long-term creep exposure on the microstructure stability of a new cast air-hardenable intermetallic alloy with nominal chemical composition Ti-46Al-8Ta (at .%) was studied. Constat load creep test were performed at the temperature 750°C and at applied stress 250 MPa up to 3479,3 h. The initial gama(TiAl) + alpha2(Ti3Al) microstructure of the alloy is unstable and transforms to alpha2 + gama + tau type. During creep the formation of cavities along the lamellar colony and grain boundaries is observed. The specimens fail by the growth and coalescence of such cavities with intergranular type of fracture