Abstract
Creep of a cast intermetallic TiAl-based alloy with the chemical composition Ti- 46.88Al-1.96W-0.53Si (at.%) was studied in the temperature range from 700 to 800°C and at tensile stresses ranging from 200 to 390 MPa. Analysis of the creep data in the terms of the threshold stress concept and using the stress normalised with respect to the temperature dependence of the shear modulus gives true activation energy for creep of Q = 365 ± 17 kJ/mol and stress exponent of n = 5. This value is close to the activation energy for lattice diffusion of Al in TiAl. Transmission electron microscopy (TEM) investigations revealed that the deformation microstructures are dominated by ordinary dislocations in the ?-matrix. Dislocations are elongated in the screw orientation and frequently pinned along their lengths. Kinetics of the creep deformation within the studied temperature range and applied stresses is controlled by non-conservative motion of ordinary dislocations.

Key words
intermetallics, titanium aluminides, TiAl, creep, deformation microstructure

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