Effect of strain reversals on the processing of high-purity aluminum by high-pressure torsion

High-purity aluminum was processed by high-pressure torsion (HPT) under conventional monotonic (m-HPT) and cyclic (c-HPT) conditions where strain reversals are introduced in c-HPT during processing. Measurements show higher values of the Vickers microhardness in the center regions of all disks but these values are higher when processing by c-HPT by comparison with m-HPT for the same total number of turns. Slightly smaller grain sizes are observed in the c-HPT samples. It is shown that all of the microhardness values correlate with the estimated values of the equivalent strain and the results are consistent with earlier data reported under c-HPT conditions when it is recognized that the variation of hardness with equivalent strain is dependent upon the level of recovery within the material.