Microstructural Evolution and Mechanical Properties of Cu-X (X = Sn, Zn) Alloys Processed by High-Pressure Torsion Followed by Short-Time Annealing

High-pressure torsion (HPT) generates ultrafine-grained (UFG) microstructures with high densities of deformation-induced defects, resulting in enhanced mechanical properties but limited thermal stability.In this study CuSn5, CuZn5, and CuZn30 alloys subjected to HPT and subsequent short-time annealing were investigated. ACOM and EDX were used to correlate the grain boundary type with the local distributions of Sn and Zn. The alloys exhibited composition dependent segregation behavior, leading to different degrees of grain boundary stabilization. In CuSn5, Sn segregation occurred at high angle grain boundaries (HAGBs), resulting in stabilization of the microstructure up to 200°C. In CuZn5, the segregation of Zn was deformation-driven, and also stabilized the UFG microstructure, i.e. no grain growth after annealing at 200°C. In the case of CuZn30, the segregation mechanism was reversed and Zn was depleted from the HAGBs. Annealing for several hours resulted in a homogeneous distribution of the alloying elements. These results demonstrate that solute segregation is not only thermally driven but can also be influenced by mechanical deformation. Overall, the segregation of Sn and Zn can enhance the thermal stability of defect rich UFG-Cu alloys.