Flow behavior and constitutive relationship for elevated temperature compressive deformation of a high Nb containing TiAl alloy with (α_2 + γ) microstructure

摘要

Highlights•A transition in the deformation mechanisms from dislocation creep to GBS of a TiAl alloy compressively deformed is found.•The transition takes place over about one and a half orders of magnitude in diffusion-compensated strain rate.•The transition can be predicted well by constitutive equations for dislocation creep and GBS in an additive manner.•dislocation creep and GBS contribute independently and additively to the strain rate during compressive deformation.AbstractThe isothermal compression of a Ti-43.5Al-8Nb-0.2W-0.2B (at.%) alloy with (α2+γ) microstructure has been examined at temperature range of 950–1050°C under strain rate range of 10−2–10−5s−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.