Multiscale hierarchical Fe–Cu composites manufactured from recycled machining chips

The direct recycling of metallic machining chips through solid-state processing offers an attractive route for sustainable manufacturing; however, simultaneously achieving strong interfacial bonding, near-full densification, and controlled heterogeneous microstructures in dissimilar metal systems remains a significant challenge. In particular, the limited mutual solubility and distinct deformation behaviors of Fe and Cu hinder the development of high-performance recycled Fe–Cu composites. To address this challenge, a ball milling-assisted spark plasma sintering (SPS) route was developed to engineer a hierarchical heterogeneous Fe–Cu architecture directly from recycled machining chips. SPS at 750 °C under 40 MPa enabled rapid densification to a relative density of ∼99.73% within an 8 min holding time. The consolidated composite exhibited strong Cu–Cu, Fe–Fe, and Cu–Fe bonding together with a multiscale heterogeneous microstructure comprising coarse recrystallized Cu grains (∼100 μm) and heterogeneous Fe grains with coarse chip-core regions (∼12.7 μm) and refined interfacial domains (∼2.76 μm). This architecture resulted in ultimate tensile strengths of 775–810 MPa with elongation exceeding 10%, while maintaining an electrical conductivity of 69.25% International Annealed Copper Standard (IACS). The proposed strategy demonstrates an effective pathway for manufacturing multifunctional Fe–Cu composites from recycled feedstock through hierarchical microstructural engineering.