Achieving microstructures prone to superplastic deformation in an Al - Zn - Mg - Cu alloy by equal channel angular pressing

An Al-Zn-Mg-Cu alloy without Sc or Zr additions was subjected to overaging and processing by equal channel angular pressing, obtaining a grain size of ∼160 nm and a fraction of high-angle boundaries of 56%. The high elongations attained at high strain rate (10-10 s) and low test temperature (250-300 oC) are attributed to the formation of new recrystallized grains, ∼500 nm in size, during heating at test temperature. The presence of equiaxed grains and texture randomization in the gauge length confirms that grain boundary sliding is the operative deformation mechanism in the mentioned range of testing conditions.