Superplasticity of an isothermal forged TiAl based alloy

Superplastic behavior and microstructural evolution of an isothermal forged Ti-47Al-1Cr-1V-1.5Mo-1.5Nb (atomic fraction, %) alloy were studied. The results show that the strain rate sensitivity m is larger than 0.5 at 900°C, qq5×10-4 s-1 and air and the maximum elongation is 200%. During the superplastic deformation, dynamic recrystallization occurred in γ grains, boundaries and lamellar structures. Dynamic recrystallization released the stress concentration due to grain boundary sliding and provided the microstructural condition for further deformation. {111} ½ [Left angle bracket]110] dislocation slip, {111}[Left angle bracket]101] superlattice dislocation slip and {111}[Left angle bracket]112] twinning took place in γ grains. Slip and twinning acted as both deformation and accommodation mechanisms.