Optimizing the procedure of equal-channel angular pressing for maximum superplasticity

The imposition of severe plastic straining on an Al-3% Mg-0.2% Sc alloy through equal-channel angular pressing (ECAP) reduces the grain size to ca. 0.2 mum and provides an opportunity to achieve superplastic elongations at high strain rates. Experiments were conducted to evaluate the procedure for optimizing the ECAP process in order to attain maximum superplastic ductilities. The results show that: (i) high elongations are achieved only after each sample has been subjected to a sufficiently high strain to establish a homogeneous array of grains separated by high angle boundaries and (ii) elongations are a maximum when using processing route B-C in which the sample is rotated by 90 degrees in the same sense between each consecutive pressing through the ECAP die. (C) 2001 Elsevier Science B.V. All rights reserved.