Flow behavior and constitutive relationship for elevated temperature compressive deformation of a high Nb containing TiAl alloy with (α₂ + γ) microstructure

The isothermal compression of a Ti-43.5Al-8 Nb-0.2 W-0.2 B (at.%) alloy with (α₂ + γ) microstructure has been examined at temperature range of 950–1050 °C under strain rate range of 10⁻²–10⁻⁵ s⁻¹. The results showed that the value of m (strain rate sensitivity factor) increased from 0.18 through 0.33 to 0.48 with decreasing diffusion compensated strain rates. This indicates a transition of deformation mechanism from dislocation creep to grain boundary sliding (GBS), which was observed in the microstructure characterization. The transition took place over about one and a half orders of magnitude in diffusion-compensated strain rate may also be predicted by employing unified rate constitutive equations for dislocation creep and GBS in an additive manner.