Formation of nanostructure and abnormal annealing behavior of a Cu–Ag–Zr alloy processed by high-pressuretorsion

A bulk Cu–Ag–Zr alloy was processed by high-pressure torsion (HPT) up to 20 revolutions. The microstructure and microhardness of these deformed samples were studied after annealing. Microstructure refinement and grain growth have been observed at different straining stages. Accordingly, the microhardness increases initially and decreases slightly at extremely high strains. Deformation-induced mechanical alloying has also been detected. When the supersaturated solid solution was annealed at different temperatures, it is found that the microhardness increases slightly at 125 °C and then decreases continuously with increasing the annealing temperature. When the disks processed by HPT for one and five revolutions were annealed at 125 °C, microhardness decreases near the center but increases at the outer region of the disk, and this transition is proposed to be strain-related.