Characterization of the elevated temperature compressive deformation behavior of high Nb containing TiAl alloys with two microstructures

The elevated temperature compressive deformation behavior of typical β solidifying γ-TiAl alloys with two microstructures was investigated. Combining with the microstructure characterization, the variation of the stress exponent n and the apparent activation energy Q with isothermal compression parameters indicates that a transition of deformation mechanism from dislocation creep to grain boundary sliding (GBS) occurred in both two alloys, but for the (β + γ) alloy, the domination of the compressive deformation by GBS began at a lower temperature and a higher strain rate than (α2 +γ) alloy. The compressive deformation of (α2 +γ) alloy might be mainly controlled by the γ phase lattice diffusion. But for the (β + γ) alloy, in the dislocation creep region it is because of the introduction of β/βo phase lattice diffusion that the Q value of the (β + γ) alloy is below that of the (α2 +γ) alloy. However, in the GBS region the compressive deformation may also be only controlled by the γ lattice diffusion similar with (α2 +γ) alloy, which leads to the rise of the Q value. The constitutive equations considering the compensation of the strain predicts well the flow curves. The power dissipation maps were developed on the basis of the above equations and the dynamic material model (DMM).