Influence of high-pressure torsion on microstructural evolution in an Al–Zn–Mg–Cu alloy

A commercial age-hardenable Al-7136 alloy was successfully processed by high-pressure torsion (HPT) at room temperature through 1/8 to 4 turns. Microhardness measurements showed significant hardening even after 1/8 turn with the average hardness value reaching a maximum after 1 turn and then slowly decreasing. Higher hardness values were attained by processing the alloy through one pass of equal-channel angular pressing in a supersaturated condition at room temperature and then applying HPT for 1 or 2 turns. Microstructural observations revealed the possibility of achieving true nanometer grain sizes of <100 nm after processing at room temperature. There were variations in hardness with imposed strain due to the fragmentation and subsequent growth of precipitates during processing.