+ National Industrial Research Institute of Nagoya, Hirate-cho, Kita-ku, Nagoya 462, Japan
# College of Engineering, Department of Mechanical Systems Engineering, Osaka Prefecture University, Gakuen-cho, Sakai, Osaka 593, Japan
Abstract:
The activation energy for superplastic flow in a variety of Si3N4/Al composites exhibiting high-strain-rate superplasticity was analyzed. The activation energy in a solid state including no liquid was in agreement with the one for lattice self-diffusion. However, the activation energy was increased by the presence of a liquid phase. The behaviors of the Al-Cu-Mg(2124) alloy composites were different from those of the Al-Mg(5052), AI-Mg-Si(6061) and Al-Zn-Mg(7064) alloy composites. This is probably because partial melting occurred at a temperature lower than the apparent partial melting temperature determined by the DSC investigation, however, the volume of liquid was too small to be measured by the DSC investigations for the Al-Cu-Mg composites.