GOALI: Exploring In Situ Nanoparticle Synthesis and Redistribution during Solidification of Metal Matrix Nanocomposites

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Automotive and aerospace industries require lightweight, high strength materials to reduce the weight of the machines that move people and goods while maintaining their integrity. Aluminum alloys meet this need because of their high strength-to-weight ratio. The incorporation of nanosized particles in aluminum makes it stronger and more stable at elevated temperatures. These improvements can only be achieved if the nanoparticles do not agglomerate and are uniformly distributed in the aluminum matrix. This Grant Opportunities for Academic Liaison with Industry (GOALI) award aims to provide the fundamental knowledge needed to control the redistribution of particles without agglomeration. By watching the solidification process as it unfolds in real-time, quantifying the motion of the nanoparticles, and developing predictive models, the researchers plan to achieve new understanding on the processing conditions that favor a uniform particle distribution. The research results enable industry to scale-up metal matrix nanocomposite processing to commercial size castings. In addition, stronger and lighter materials enable greater fuel economy. These factors benefit U.S. economy and society. Students gain from collaboration with industry partners on the team. Outreach activities engage female and under-represented minority students in materials research, processing and manufacturing. Industry collaborator North American Die Casting Association disseminates the results to industry.Metal matrix nanocomposites (MMNCs) offer light-weighting, improved strength, wear resistance, and high temperature stability compared to microcomposites and monolithic alloys. However, only with a homogeneous distribution of nanoparticles can the enhanced mechanical properties of MMNCs be fully realized. During solidification of MMNCs, the particles near the freezing front may be pushed or engulfed, thus impacting the final distribution of nanoparticles in the as-solidified microstructure. This project develops a comprehensive understanding of the redistribution of particles during solidification, specifically the interrelationships between particle size, fluid flow, and solidification front velocity and morphology. For this purpose, the team bridges emergent research in melt processing, real-time metrology, and phase field simulation to study in situ nanoparticle synthesis from polymer precursors and their redistribution during solidification of metal matrix nanocomposites. The team studies MMNC samples with a range of particle sizes and shapes provided by industry collaborator Eck Industries; visualizes the interactions between the nanoparticles and the solidification front in these samples via real-time X-ray imaging experiments; and conducts phase field simulations using the experimental data as input to yield detailed insights on the particle pushing-engulfment transition. This integrated effort helps to establish a morphological phase diagram, ultimately enabling precise control of the as solidified microstructure of MMNCs.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.