High strain rate superplastic deformation behavior of powder metallurgy (PM) processed 17 vol. pct SiCp/2024 Al composite sheet after heat treatment was investigated over a range of temperature from 753 to 833 K. At 813 K,a maximum elongation of 259% was discovered at a strain rate of 10-1 s-1. The activation energy was closed to that for lattice diffusion of Al and increased at temperature upon incipient melting temperature. The mechanism of superplastic deformation for present composites was attributed to lattice diffusion controlled grain boundary sliding.