Plastic recovery and strength retention of cryogenic rolled pure Cu via high density electropulsing

The matching of strength and plasticity is the key to realize the service of materials under complex stress fields. Due to the inherent low strength of pure Cu, the tensile strength (UTS) of the original pure Cu plate was significantly increased from 187.5 MPa to 378.6 MPa by cryogenic rolling (CR), but the work hardening induced by this process greatly reduced the plasticity of the material. In order to coordinate this contradiction, this paper first introduces high-density crystal defects into the material matrix through CR, and further uses high density electropulsing treatment to regulate the microstructure and optimize the comprehensive properties of the materials. The experimental results show that the yield strength (YS) of the electropulsing treatment after cryogenic rolling (CR + EPT) sample is 323.5 MPa, the UTS is 353.7 MPa, and the elongation (EL) is 10.3%. Compared with CR sample, the strength loss is less than 9%, while the EL is increased by about 98%, which achieves excellent control of the strength-plastic matching of pure Cu. Microstructure analysis revealed the relative uniformity of the distribution of texture components in the CR + EPT sample. The degree of dislocation tangle is alleviated, the proportion of Σ3 twin boundaries has increased. The in-depth analysis indicates that the introduction of electropulsing effectively retains the multi-level defect synergistic strengthening system generated by cryogenic rolling. At the same time, the intervention of electropulsing treatment provides additional driving force for the movement of partial dislocations, which reduces the overall free energy of the system.