One-step fabrication of high-strength, high-conductivity gradient-structured copper terminals by radial plastic flow machining

Copper terminals with high strength and excellent electrical performance are crucial in power systems of electric vehicles. Radial plastic flow machining (RPFM) is an innovative plastic processing technique that utilizes a specially designed forming channel to fabricate high-performance, gradient-structured (GS) copper terminals in a single step. This study systematically investigated the forming mechanism, mechanical properties, and electrical conductivity of GS copper terminals across varying extrusion thicknesses. The study demonstrated that as extrusion thickness increased, the volume of material flowing into the transverse channel also rose. Consequently, the extent of the low-strain zone across the thickness expanded, whereas the proportion of the high-strain zone remained largely constant. Compared to the original pure copper, the mechanical properties exhibited a combined trend of increased hardness, reduced yield strength, and enhanced ductility. Simultaneously, the electrical conductivity reached up to 99.6% IACS (International Annealed Copper Standard), with virtually no loss in performance. The process established a gradient distribution of grains within the terminals, achieving an optimal balance between high strength, high electrical conductivity, and enhanced ductility, thereby overcoming the traditional trade-off dilemma among these three properties. Therefore, the GS copper terminals fabricated by the RPFM process demonstrated significant performance improvements.