Optimization of microstructure for superplasticity using equalchannel angular pressing

Equal-channel angular (ECA) pressing is a processing procedure which may be used to introduce ultrafine-grained structures into metallic materials. Thus, materials processed by EGA pressing have a potential capability for superplasticity, especially under conditions of very high strain rates. This paper reports an investigation of the thermal stability associated with the ultrafine grain sizes introduced into samples of pure aluminum and several Al-based alloys. It is demonstrated that the stability of these ultrafine grains at elevated temperatures, under the conditions where superplasticity is anticipated, requires the presence of particles to restrict the movement of the grain boundaries.