Manufacturing USA/GOALI: Visualizing Nanoscale Evolution during Aluminum Alloy Melt Processing

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Reducing the weight of vehicles that move people and goods on land, sea and air is critical for improving fuel economy and increasing mission payload. Aluminum alloys are used in the automotive and aerospace industries to meet this need because of their high strength-to-weight ratio. For improved fuel efficiency, however, higher strength and lighter weight alloys are needed, and this can be achieved though the incorporation of nanosized particles in the aluminum matrix. A novel approach to producing the nanoparticles has been developed based on the introduction of gas bubbles directly into the molten aluminum. Blowing nitrogen gas into the melt can produce aluminum nitride particles that are 50 nanometers in size. This Grant Opportunities for Academic Liaison with Industry (GOALI) award supports fundamental research to provide the knowledge needed to control the particle size and shape which lead to optimized mechanical properties and performance. The results from this research will enable industry to scale up this process from small laboratory melts to commercial size ingots, which will enable the development of lightweight alloys for ground, air, and sea transportation, with direct benefit to the U.S. economy. The students involved in this research will have the opportunity to interact with the engineers from industry who are part of the team. An integrated experimental and modeling approach will be utilized, which is forming the new basis for materials engineering education. Outreach activities emphasize the mentoring of women and underrepresented minorities. The incorporation of 50-200 nanometer particles has been shown to improve the strength and high temperature stability of aluminum alloys. However, due to agglomeration of the nanoparticles and insufficient bonding at the nanoparticle-matrix interface, the mechanical properties of the composite material are often degraded. A new approach, in which the reinforcing nanoparticles are generated directly in the molten metal via an in-situ gas-liquid reaction has been shown to produce nanosized, dispersed AlN and TiC particles. In this project, the nano- to micro- structural dynamics governing the process will be investigated. Insights from these fundamental studies will guide the identification of a process condition window for large-scale in-situ aluminum nanocomposite manufacturing, which produces a nanoparticle morphology and distribution with optimum mechanical properties. To examine the nanometer-scale thermodynamic and kinetic processes, in-situ reflection high-energy electron diffraction (RHEED) will be utilized during alloy nitridation in a molecular-beam epitaxy (MBE) system. For in-situ 3D nanoparticle visualization, a mini-melter will be developed and 3D visualization of the nanocomposites will be achieved using synchrotron-based X-ray nanotomography.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.