Microstructural and property evolution of Cux(CoCrFeNi)100-x high-entropy alloys during thermo-mechanical processing

High-entropy alloys (HEAs) have emerged as promising candidates for advanced structural and functional applications owing to their unique compositional complexity and outstanding mechanical and tribological properties. However, a comprehensive understanding of the coupled effects of Cu content and severe thermo-mechanical processing on the microstructural evolution, mechanical performance, electrical resistivity, and tribological behavior of CoCrFeNi-based HEAs remains limited. In particular, systematic investigations integrating a wide Cu compositional range with high-reduction cold rolling and subsequent annealing are still scarce. In this study, a series of Cu x (CoCrFeNi) 100-x HEAs with varying Cu contents was fabricated and subjected to cold rolling with reductions of 50% and 75%, followed by annealing at 700 °C for 1 h. The synergistic influences of Cu addition, cold-rolling degree, and annealing treatment on phase constitution, microstructural characteristics, mechanical properties, electrical resistivity, and friction and wear behavior were systematically investigated. The results reveal that cold rolling effectively eliminates casting defects and refines the microstructure, leading to enhanced strength and more uniform wear behavior compared with the as-cast state. Increasing Cu content significantly reduces the wear track width and depth, particularly after 75% cold rolling, which is attributed to the formation of Cu-rich phases and the development of thicker and more stable oxide layers during sliding. The dominant wear mechanisms are identified as abrasive wear and oxidative wear, with their relative contributions strongly dependent on both Cu content and deformation degree. Notably, the HEA containing approximately 30 at.% Cu exhibits an optimal combination of strength and ductility after 75% cold rolling and subsequent annealing, achieving a yield strength of 705.22 MPa, an ultimate tensile strength of 838.86 MPa, and a uniform elongation of 13.47%, while maintaining favorable tribological performance. This work provides new insights into tailoring the mechanical and tribological properties of Cu-containing CoCrFeNi-based HEAs through compositional design and thermo-mechanical processing, offering a viable strategy for optimizing the balance between mechanical robustness and functional performance in engineering applications.