From coated fibers to fully dense alloys: Introducing entangled coated fiber plasma sintering for Cu–Fe systems

In this study, Entangled Coated Fiber Plasma Sintering (ECFPS) is proposed for the first time as a novel processing route for the fabrication of dense Cu–Fe alloy with improved mechanical performance while maintaining high electrical conductivity. Commercially pure copper fibers were mechanically crumpled to form a three-dimensional entangled architecture and subsequently coated with a thin iron layer using arc physical vapor deposition. The Fe-coated Cu fibers were then cold compacted and consolidated via spark plasma sintering, enabling rapid densification and effective metallurgical bonding. Microstructural analysis revealed that the initially continuous Fe coating undergoes controlled fragmentation during compaction and plasma-assisted sintering, facilitating direct Cu–Cu contact, diffusion-driven bonding, and near-complete elimination of porosity. As a result, the Cu–Fe alloy produced by ECFPS achieved an exceptionally high relative density of approximately 99.93 %, significantly exceeding densities reported for conventionally processed Cu–Fe alloy. Mechanical testing demonstrated substantial increases in yield strength, ultimate tensile strength, and hardness compared to annealed copper, albeit with a reduction in ductility. Despite the presence of iron, the alloy retained a high electrical conductivity of 90.9 % International Annealed Copper Standard (IACS), attributed to the preservation of a continuous three-dimensional Cu-rich conductive network and limited Fe solid-solution formation. The ECFPS approach introduced in this work establishes a fundamentally new strategy for designing high-density copper-based material that combine structural integrity with functional electrical performance.