Grain boundary evolution and effect on electrical conductivity of Cu-Ti alloys prepared by accumulative roll bonding-diffusion alloying process

Cu-Ti alloys were prepared by accumulative roll bonding-diffusion alloying process. The variation of electrical conductivity was investigated through the analysis of grain boundary evolution during the deformation-aging process, and the intrinsic mechanism was revealed. The results show that annealing twins formed inside the primary deformation-aged alloys, and the twin boundaries are mainly coherent sigma 3 grain boundaries. The density increases after secondary deformation-aging treatment and twin boundaries transform into incoherent ones. The electrical conductivity of 13.1% IACS is obtained for the alloy at a primary aging temperature of 350 degrees C and a secondary aging temperature of 315 degrees C. Higher primary aging temperature provides a driving force for the grain boundary evolution and the formation of coherent sigma 3 grain boundaries. The deformation treatment after primary aging treatment reconfigures the grain boundary strain distribution state and induces migration. The thermal effect of secondary aging process transforms coherent sigma 3 grain boundaries into incoherent ones. Lower secondary aging temperature improves the stability of incoherent I3 grain boundaries, reduces the percentage of random grain boundaries effectively and breaks the network connectivity. It decreases the energy decay degree of electron migration process and improves the electrical conductivity of alloys. The accumulative roll bondingdiffusion alloying process utilizes repetitive deformation and thermal effects to induce grain boundary evolution and regulate the types and content of special grain boundaries. It is an effective way to regulate the electrical conductivity of Cu-Ti alloys.

Automated summary

Cu-Ti alloys were fabricated using the accumulative roll bonding-diffusion alloying process. The change in electrical conductivity was studied by analyzing the evolution of grain boundaries during the deformation-aging process, and the underlying mechanism was revealed. The results showed that annealing twins were formed in the primary deformation-aged alloys, with the twin boundaries primarily consisting of coherent sigma 3 grain boundaries. After secondary deformation-aging treatment, the density increased and the twin boundaries transformed into incoherent ones. An electrical conductivity of 13.1% IACS was achieved for the alloy at a primary aging temperature of 350 degrees C and a secondary aging temperature of 315 degrees C. Higher primary aging temperature facilitated the evolution of grain boundaries and the formation of coherent sigma 3 grain boundaries. Deformation treatment after primary aging treatment reconfigured the distribution and induced migration of grain boundary strain. The thermal effect of secondary aging process transformed coherent sigma 3 grain boundaries into incoherent ones. Lower secondary aging temperature improved the stability of incoherent I3 grain boundaries, reduced the percentage of random grain boundaries effectively, and disrupted the network connectivity. This decreased the degree of energy decay in the electron migration process and improved the electrical conductivity of the alloys. The accumulative roll bonding-diffusion alloying process, which utilizes repetitive deformation and thermal effects to induce grain boundary evolution and regulate the types and content of specific grain boundaries, is an effective method to control the electrical conductivity of Cu-Ti alloys.