Research of Superplasticity Deformation Behavior about Coarse-Grain Ti-22Al-25Nb Alloy

This study investigates the superplastic deformation mechanism of coarse-grain materials .Superplasticity deformation behavior of Ti-22Al-25Nb alloy with 200~410μm coarse grain has been investigated through tensile test at 940~990°C and 3.3× (10-2~10-4) s-1 strain rate. Results prove coarse-grain Ti-22Al-25Nb alloy primary depends on slipping of crystal planes between two phases to achieve superplasticity. Transformation from lath O phase to ring equiaxed O phase occurs as temperature rises and its volume percent falls, but percentage of recrystallized B2 phase increases. Dislocation can move round ring equiaxed O phase. Good plasticity can be preserved because O phase can flow as solid particle in semisolid slurry in B2 grain.