Production of Metal Foil and Flat Wire by Single Step Shear-Based Deformation Processing

Thin-gauge foil and flat wire formats of lithium, aluminum and copper are critical to EV markets – especially for power storage performance and light-weighting of motors. Availability of Al and Cu flat wire for winding high-performance electric motors is constrained by manufacturing complexity and cost. A recent web-quote from a major automotive manufacturer “Wire manufacturing technology upstream of the industrial chain needs to be revolutionized” highlights this criticality. In the proposed STTR Phase 1, the thin metal wire and foil production challenge will be addressed by innovative hybrid-cutting extrusion (HCE) technology. The technology – a transformative approach – is structured around high-speed shear-based processing, pioneered by our team. HCE utilizes a well-controlled analogue of machining, with constrained chip formation, to produce metal strip (chip), with fine-grained microstructure and shear textures, in a single-step process. The Phase I project objective is to demonstrate processing of flat-wire and thin gauge Al and Cu, and develop the manufacturing engineering underpinnings for a future production system. HCE technology offers low-cost, flexible manufacturing of foil and wire, optimized for strength and formability. A series of critical HCE experiments will be used to establish a process-properties-performance map. A cost model will be developed to compare production cost by HCE to benchmarked industry rolling processes, along with the first tooling design for production on a computer-controlled machining center. The work will be conducted by an accomplished team with complementary strengths in manufacturing, materials, and advanced process engineering. HCE processing will open new pathways for producing thin-gauge metal alloys (e.g. Li, Cu, Al, Ti). The relatively simple infrastructure and process configuration will enable point of use application (e.g., motor assembly plant), control of the resulting bulk form (e.g., wire size and shape), and enhanced strip product properties. Virtually all commercial metal foil and wire is today produced by multi-stage deformation processing (rolling or drawing), wherein large thickness reductions require multiple (~20) steps of deformation. These highly entrenched manufacturing processes are capable of large-volume production. However, they are multi-step, energy intensive, and inflexible, posing constraints to product design and performance – especially in materials for EV manufacture. Most of the reduction in rolling is accomplished in energy-intensive hot-working steps, where large ingots are preheated to high temperatures to enhance workability. Subsequent cold-rolling, interspersed with annealing, is required to control size and quality. Currently available strip formats can be extremely expensive to produce, and, combined with their limited thickness range, pose challenges for weight and cost reductions in applications. The challenges can be overcome by the more economical HCE that produces metal strip in a single step directly from ingot. A systems analysis has shown that for Al and steel sheet/foil, the HCE specific energy is only 1/3rd that of industrial rolling.