Deformation behavior of high-strain-rate superplastic PM 20%SiCp/2124 Al composite was investigated over a wide range of temperature from 643 to 838 K. The entire temperature range of investigation was separated into two regions where grain boundary sliding (high-temperature range from 748 to 838 K: region I) and dislocation climb creep (low-temperature range from 643 to 693 K: region II) dominate the plastic flow, respectively. Determination of true activation energy at a constant value of modulus-compensated effective stress reveals that the energy for region I is considerably higher than that for lattice diffusion in aluminum, Q(L), while the energy for region II is close to Q(L). The composite was shown to be stronger in region II than the unreinforced PM 2124 Al alloy but weaker in region I. The threshold-stress behavior was investigated as a function of temperature. Different behavior was observed between region I and region II. (C) 1999 Elsevier Science S.A. All rights reserved.