Abstract:A new viscous-rheologic superplastic technique for TiAl based alloy has been explored successfully, which can be divided into three stages: accelerated deformation at large load, viscous-rheologic deformation at low load and final deformation at increasing load. In above three stages, three respective deformation mechanisms exist: coerced grain boundary movement, grain boundary viscous-rheologic sliding, grain boundary sliding aided by sliding inside grains. The damage of recrystallization and neck shrinkage on superplasticity can be avoided in this technique.

Key words: TiAl based alloy　superplasticity　deformation　mechanism