Improvement of room-temperature superplasticity in Zn–22 wt.%Al alloy

Zn–22 wt.%Al alloy with sub-micrometer-grained microstructure was prepared by three different processing routes: (1) solid solution treatment + quenching + aging, (2) solid solution treatment + quenching + 8 passes equal channel angular pressing (ECAP) at room temperature (RT), and (3) Route 1 + cryo-rolling at 203 K (with a reduction of 75%). The samples were tested in tension at strain rates range from 1 × 10−4 to 1 × 100 s−1 at room temperature. All the samples processed through these three routes exhibit good superplasticity at room temperature. At the strain rate of 4 × 10−3 s−1, samples processed via Routes 2 and 3 reach a high elongation of 335 and 315%, respectively. At a higher strain rate of 1 × 10−1 s−1, the elongation of samples processed by these two routes is still higher than 220%. Besides the high elongation, at strain rate of 4 × 10−2 s−1, a high value of strain-rate sensitivity (∼0.35) was observed in samples processed by Route 2. A room-temperature grain growth during ECAP was also observed in the alloy.