Abstract:The behavior of interior dislocation in superplastic deformation of 8090 Al-Li alloy was investigated. TEM observations showed that at initial stage of deformation,  interior dislocation is created at grain boundary ledge and particle and dislocation slip is quite active; at middle stage of deformation the interior dislocanon is created at triple junction of grain boundaries, which is recovered to form subboundary; up to last stage of deformation, dislocation slip becomes again active, which leads to a dislocation pile-up .The interaction between dislocation and voids does not stop untill last stage of deformation. It is indicated that the dislocation slip is a dominant mechanism of deformation at initial stage of deformation, the dynamic recovery and slip of dislo-
canon can all accomodate grain boudary sliding. Furthermore, the immovable helical dislocations formed by the interaction of screw dislocation with voids increase the distortion energy in crystal lattice, and promote the local dynamic recrystallization at middle stage and last stage of deformation.

Key words: dislocations; superplasticity; recovery; recrystallization