Microstructural evolution in an Al-6061 alloy processed by high-pressure torsion

Experiments were conducted to evaluate the evolution of hardness and microstructure in a commercial aluminum 6061 alloy processed by high-pressure torsion (HPT). The results show that processing by HPT leads to significant grain refinement with an average grain size of ∼450 nm at the edge of a disk subjected to torsional straining through 5 turns. Hardness measurements show an increase from ∼80 Hv in the solid solution condition to ∼160 Hv after HPT where these values correlate well with the equivalent strain applied to the disk. Quantitative measurements show the grain size decreases and the fraction of high-angle grain boundaries increases with increasing strain.