Realization of exceptionally high elongation at high strain rate in a friction stir processed Al-Zn-Mg-Cu alloy with the presence of liquid phase

Friction stir processed Al-Zn-Mg-Cu alloy with grain size 6.2 mu m was subjected to superplastic investigation at 500-535 degrees C and a high strain rate of 1 x 10(-2) s(-1). A maximum elongation of 3250% was achieved at 535 degrees C, which was just above the incipient melting temperature of the sample. Exceptionally high elongation was attributed to the presence of a liquid phase, which served both to relax the stress concentration and to suppress the appearance of cavities during deformation. (C) 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.