Microstructural evolution in a two-phase alloy processed by high-pressure torsion

Experiments were conducted to evaluate the microstructural evolution occurring in the Zn–22% Al eutectoid alloy when processed by high-pressure torsion (HPT) over a range of experimental conditions. Processing by HPT reduces the grain size and at the edges of the disks it produces agglomerates of Zn-rich and Al-rich grains lying in bands delineating the torsional straining. Unlike most metals processed by HPT, the measured hardness values are lower than in the initial annealed condition. This is due to a significant reduction during processing in the distribution of Zn precipitates which are visible within the Al-rich grains in the annealed condition. It is shown that all of the hardness measurements are mutually consistent when plotted against the calculated equivalent strain.