Creep characterization of a duplex Ti-Al base alloy at 700 and 750 °C

The constant load creep behaviour of a two phase Ti-46Al-2W-0.5Si alloy was investigated at 700 and 750 °C, under stresses ranging from 225 to 370 MPa. The initial microstructure was found to be duplex, consisting of equiaxed primary γ grains and of lamellar γα2 colonies. The minimum creep rate dependence on applied stress was studied by means of the conventional power law equation; the stress exponent was found to vary between five (low stress regime, climb controlled creep) and ten (high stress regime). The transition between the two regimes occurs at stresses close to 300 MPa. The stress exponent, the apparent activation energy as well as the pre-exponential constant are comparable, at least in the low stress regime, with those observed in a Ti-48.7Al-2.2W alloy produced by powder metallurgy.