Effect of cryogenic rolling on the microstructure and properties of C70250 copper alloy

Abstract

The application of cryogenic rolling technology serves to enhance the strength of a material by increasing the density of dislocations and refining the grain size. However, a high density of dislocations can lead to a reduction in its ductility. In this study, cryogenic rolling at low strain followed by subsequent aging treatment at temperatures between 450 and 550 ℃ was employed to introduce deformation twins into C70250 Cu alloys, aiming to balance both strength and electrical conductivity. The microstructural evolution and property changes of the alloy were examined throughout the cryogenic rolling and aging process using SEM, TEM, XRD, and various mechanical and electrical property tests. The results indicate that alloys subjected to cryogenic rolling and aging exhibit significantly improved strength compared to those treated at room temperature. The introduction of twinning through cryogenic rolling significantly enhances the efficiency of dislocation multiplication during rolling. This high dislocation density facilitates the nucleation of precipitated phases during the subsequent aging process, leading to superior mechanical properties. Within the integrated cryogenic rolling and aging treatment, the precipitated phases, dislocations, and twin boundaries collectively exert a synergistic reinforcing effect, resulting in exceptional yield and tensile strengths, reaching up to 685MPa and 744MPa, respectively. The findings in this study contribute to the development of novel methods for fabricating high-strength, high-conductivity copper alloys.