This Small Business Innovation Research (SBIR) Phase I project will demonstrate a new way to produce metal fibers in materials such as titanium and aluminum alloys using a special machining process known as Modulation-Assisted Machining or MAM. The most widely adopted method for producing metal fibers is a multi-step wire drawing process, where small diameter wires are drawn from a metal billet and subsequently cut into discrete lengths. However, this process is limited to materials that can be drawn into wires and the capital equipment costs are high and related infrastructure requirements complex. The MAM process has evolved from research at Purdue University and has demonstrated the potential to radically change the capacity and flexibility of metal fiber production while simultaneously achieving a lower cost. By using the MAM process, fibers can be machined directly from metal bars. The project objectives include: 1) Produce aluminum alloy and titanium fibers using MAM; 2) Characterize the effects of MAM parameters on fiber geometry and microstructure; 3) Measure the strength of fibers produced by MAM; and, 4) demonstrate fiber production scale-up concepts. This is expected to enhance the application of MAM to a viable process for production of metal fibers.
The broader impact/commercial potential of this project is that MAM processes will enable a method for production of metal fibers in virtually any metal alloy system. MAM could offer a new, low-cost method to produce fibers that are difficult or impossible to create using existing technology. The commercial potential for this project lies in the design and development of special modulation devices that adapt MAM technology for fiber-making using a CNC machine tool rather than a complex manufacturing plant. The extension of MAM technology into materials production will increase the market space for M4 Sciences products and increase commercial and research activity in the total market. Increased commercial impact also lies in the development of advanced metal fiber materials produced by MAM. These new metal fibers are expected to lead to commercial opportunities for the company's modulation devices for the production of metal fiber-based products and composite material systems that improve our quality of life. MAM could transform current machining technology from a process traditionally used to produce discrete parts with specific geometry to a process that produces advanced materials. Equally important, the proposed research will further the understanding of the effects of modulation on energy efficiency of machining processes.
Summary of Research This SBIR Phase I project has successfully demonstrated a single-step, machining-based process for large-scale production of non-ferrous metal fibers with reduced process cost, and enhanced energy efficiency. Fibers can be formed directly using MAM in a highly efficient single-step machining process compared to the complex capital intensive multi-step wire drawing method presently available in industry. The results have already been transferred to an industrial production application; however, key technology challenges need to be addressed to realize broad application of the MAM technology, including: rate of production; process capability for diverse material systems; and process/quality controls. In MAM, a controlled modulation is superimposed onto the machining process, causing the otherwise continuous cutting to be divided into a series of discrete chip formation events. With appropriate modulation conditions, the undeformed chip thickness becomes zero during each cycle of modulation resulting in an individual fiber or ‘chip’ (see Fig. 1). The SBIR project emphasized non-ferrous metal fiber production due to the wide range of alloys in this particular segment and their applications in biomedical implant materials, conductive plastics, specialty textiles, filtration and reactive media, friction materials, and structural reinforcements. Currently, both ferrous non-ferrous metal fibers are produced through a complex, multi-step deformation processing protocol referred to as "bundle drawing" which combines a series of rolling and wire drawing processes to achieve a final wire diameter of ~ 20μm to 1mm. This is followed by a cutting operation where the drawn wires are chopped into fibers of desired length. The multi-step protocol bundle drawing is highly energy-intensive and deeply entrenched due to high capital costs. Furthermore, the many intermediate steps necessary to reduce the bulk ingot to wire are the principal cost of the drawn wire. In addition to the high capital costs, the infrastructure and energy requirements are high, process flexibility is limited. Current wire drawing technology is limited by (1) control of fiber size and shape; (2) constraints on the range of metals and alloys that can be processed; and (3) lack of adequate microstructure control, a consequence of the multiple steps of thermo-mechanical processing. Modulation-assisted machining (MAM) offers extraordinary potential for production of metal fibers of controlled size, shape and microstructure, in a single step. The fiber production rate is determined by the modulation frequency, and the shape and size of the fiber are controlled precisely by the modulation and machining conditions. Metal fiber production by MAM can be extended to production of unique metal alloy reinforcements for strength properties in composite materials. Intellectual Merit The ability to produce a wide range of particulate materials, with controlled size and microstructure, is becoming increasingly important in advanced material systems. MAM offers a unique method to produce fibers in virtually any metal alloy system while simultaneously engineering the fiber microstructure through control of the deformation strain. The research has increased the understanding of mechanics of modulation-assisted machining (MAM) processes. The collaboration between M4 Sciences and Purdue University, School of Industrial Engineering has provided engineering students with opportunities to work on scientific tasks, such as measuring performance of the modulation devices; characterization of fibers using optical microscopy techniques, and; developing a simulation of fiber making by MAM. Broader Impacts A new machining method for large-scale production of fiber materials has been demonstrated. MAM processes offer a low-cost method for production of fibers in virtually any metal alloy system, and a process breakthrough to produce fibers that are difficult to create by current technology. The unique sizes, shapes and microstructures created by MAM will enable commercial opportunities in materials processing for production of fiber-based products and composite material systems. The SBIR project has provided graduate students opportunities to be involved in an exciting new industrial machining technology.
