Role of particles on microstructure and mechanical properties of the severely processed 7075 aluminium alloy

The 7075-T6 Al alloy was processed by accumulative roll bonding (ARB) up to five passes by a 3:1 thickness reduction per pass at 300, 350 and 400 °C. Microscopical examinations revealed that the particle distribution varies with the processing parameters. As a consequence, the particle pinning effect decreases with increasing processing temperature and the number of ARB passes. For this reason, the evolution of grain structure with the number of passes is different for each processing temperature, and the superplastic properties are determined not only by the microstructural features before deformation, but also by the alloy thermal stability. The best superplastic properties are attained by the sample processed up to three passes at 300 °C, obtaining elongations to failure in excess of 200 %. Finally, ARB processing at high temperature leads to a decrease of hardness with respect to the peak-aged as-received alloy, especially with increasing number of passes and with decreasing processing temperature, due to the variation of the interparticle mean spacing and the amount of solute atoms.