Microstructural evolution and mechanical properties of the AA8011 alloy during the accumulative roll-bonding process

The investigation of the microstructure and mechanical properties has been conducted on an AA8011 alloy produced by a novel intense plastic straining process named accumulative roll bonding. The results show that an ultrafine-grained 8011 alloy, having a mean grain (or subgrain) size less than 1 µm, was successfully accumulative roll-bonded (ARB) at room temperature (RT-ARB) and at 200 °C (HT-ARB). The average grain (or subgrain) sizes of the RT-ARB and HT-ARB samples were reduced greatly from about 25.8 µm initially to 650 to 700 nm and 800 to 900 nm, respectively. After several cycles of accumulative roll bonding, most regions of this material were filled with ultrafine grains with high-angle boundaries. The ambient tensile strengths of the RT-ARB and HT-ARB samples increased with equivalent strain only up to the strain of 2.4. After that, the strengths of the RT-ARB samples nearly leveled off, and the strengths of the HT-ARB samples decreased with equivalent strain above the strain of 2.4. Furthermore, the elongation in both the RT-ARB and HT-ARB samples decreased greatly after the first cycle and then increased continuously with strain. The softening behavior happened in HT-ARB samples above a strain of 2.4, which is mainly attributed to the continuous recrystallization, dynamic recovery, and static recovery during and/or after the accumulative roll-bonding process.