Abstract:The effect of current pulses on the fracture morphology in the superplastic deformation of 2091 AlLi alloy at two kinds of initial strain rate (ε₁=3.33×10^-3s^-1;.ε₂=3.33×10^-2s^-1) was investigated.Experimental results show that current pulse turns fracture of superplastic deformation at low strain rate from local interior fracture morphology to typical fracture by growth and interlinkage of cavities, and at high strain rate from rough grain boundary surface to smooth grain boundary surface. It is indicated that the characteristic, that current pulse promotes atomic diffusion, maintains an equiaxial grain microstructure at low strain rate, and accelerates the development of diffusional type of cavity and relaxes stress concentration at triple junction of grain boundaries at high strain rate, and makes the superplastic deformation at two kinds of strain
rate show a normal superplastic fracture morphology.

Key words: Al-Li alloy; superplastic deformation; fracture morphology