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 μm was subjected to superplastic investigation at 500–535 °C and a high strain rate of 1 × 10−2 s−1. A maximum elongation of 3250% was achieved at 535 °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.