Abstract
Introducing the temperature dependence of shear modulus and grain size into the rate equation, the values of n and Q in the powder metallurgically processed TiAl intermetallic were established as 2 and 342 kJ/mol at lower strain rates, and 4 and 334 kJ/mol at higher strain rates, respectively. It is postulated that the lower strain rates may correspond to a superplastic region and stress flow in this superplastic region is controlled by a grain boundary sliding mechanism, but the accommodation process remained unclear because of the unspecified value in true activation energy. Whereas at higher strain rates the n value is high at 4 and the rate controlling deformation in this regime seems to be a diffusion controlled dislocation process.
