CAREER: Advanced Surface Coating of Metallic Powders by Vibration-Enhanced High-Power Impulse Magnetron Sputtering for Sintering-Based Manufacturing

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Sintering is one of the most practical manufacturing processes in producing density-controlled materials from powder feedstock. However, producing industrially applicable powder alloy precursors is challenging. Although pre-mixing pure metal powders have allowed a wide range of compositions by conventional sintering, rapid heating and cooling in modern sintering techniques inevitably results in new but unwanted chemical gradients, as well as microstructural and property anisotropy. This Faculty Early Career Development (CAREER) award will investigate a high-power impulse magnetron sputtering process as an advanced technology to modify the surface of metallic powders. The deposition of thin films on the powders forming core/shell systems can provide solutions to make different alloys with more homogeneous and controlled microstructures when used as powder feedstock. This new class of powders will enable a reliable supply of raw materials for cost-effective sintering of reproducible components in the aerospace, automotive, energy, and healthcare industries. The integrated educational and outreach activities of this project will broadly concentrate on: 1) educating and training women and underrepresented minorities as the future generation of highly-skilled leaders in advanced manufacturing, 2) establishing a pipeline of diverse undergraduate students to pursue graduate studies in collaboration with James Madison University in Virginia through special summer programs, and 3) implementing an online set of virtual laboratories in advanced materials characterization of core/shell structures as well as materials processing. The overall research objective of this project is to establish the scientific underpinnings for the surface modification of micro- and nano-powders into core/shell systems that promote three-phase transformations in sintering-based processes. The core/shell of various combinations (e.g., aluminum-copper, titanium-copper, copper-chromium and nickel-chromium, etc.) will be the eutectic compositions for modeling because of their industrial relevance, an ability to form precipitation hardening alloys, and excellent high-temperature properties. It is hypothesized that high-power impulse magnetron sputtering combined with the vibrational motions of powder holders can achieve conformal thin films on powders, which are desired to produce favorable microstructures. To test the hypothesis, the project will study sputtering discharges to understand the nucleation and growth mechanism of thin films on complex geometries such as spherical powders when including vibrations. This research also aims to understand the role of powder-film interface in the two-phase core/shell diffusion couple and its effect on the final part microstructure from sintering. The combined strategy of the project will lead to a new method of manufacturing core/shell materials suitable for modern sintering processes.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.