Abstract: The activated slip systems in the α-phase of the superplastically deformed Ti-6Al-4V alloy were analyzed by systematic operation method with TEM.The results show that the dominately activated slip systems in the α-phase are{01(?)0}〈2(?)0〉and{01(?)}2(?)0〉, The{0001}〈2(?)0〉system as well as the c+a dislocalions of b=[1/3]〈11(?)3〉will be acti- vated when the deformation temperature is lowered.Large amounts of TEM observations in- dicate that the dislocations in the α-phase were mainly activated near the triple grain bounda- ry junctions,α/α grain boundaries and α/β interlaces.

Key words: titanium alloy, superplastic deformation, dislocation