Temperature-Rate Conditions of Deformation and Structure-Forming Processes in Nickel during High-Pressure Torsion

Abstract—Scanning and transmission electron microscopy has been used to investigate the nickel structure formed by high pressure torsion deformation at temperatures of 100–250°C. The relationship between the structure and temperature–rate conditions of deformation, which is characterized by the Zener–Hollomon parameter (Z), has been found. A change in the temperature–rate conditions of deformation has been shown to alter the dominant structure-forming process and to change the resultant structure. We have identified ln Z ranges where these processes occurred, namely, dynamic recovery at ln Z > 25, dynamic recrystallization at 21 < ln Z < 25, and dynamic polygonization at ln Z < 21.