When 10:00 AM - 12:00 PM Aug 04, 2022
Where 1017 H.H. Dow/virtual
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PhD defense: "Visualization and Analysis of Nanoscale Microstructure Evolution of In situ Metal Matrix Composites"

Aaron Gladstein
Taub group

Aluminum and its alloys are increasingly used in automotive, aerospace, and defense industries due to their high strength-to-weight ratio, low cost, and machinability. However, Al alloys suffer from poor thermal stability of mechanical properties, thus limiting their usage for components that operate in elevated temperatures. One possible solution to this problem is the use of Al-based metal matrix nanocomposites (MMNCs), a mixture of aluminum and nanoscale reinforcement, as they have improved mechanical properties at both ambient and elevated temperatures over base Al alloys, without sacrificing the lightweight benefits of Al.

This work is focused on studying of the formation mechanisms of particles and controlling the resulting microstructure of in situ MMNCs made via metal-based polymer pyrolysis (MBPP) and salt-flux reaction synthesis (SFRS). First commercially available precursor polymers are analyzed to inform the best processing parameters for MMNC production, then MBPP is successfully performed to generate Al-based MMNCs with improved mechanical properties. The results of the MBPP experiments demonstrate it as a potential method for in situ MMNC production.

We find that SFSR is a facile technique for generating Al/TiC MMNCs that has the possibility of scaling into industrial production. We use 2D and 3D microstructural analysis techniques to perform a detailed investigation of the MMNCs generated via SFRS and investigate the formation mechanisms of reinforcing TiC particles and intermetallic Al3Ti. We find that the TiC particles are formed first and directly by the SFRS reaction, not through an indirect reaction using Al3Ti, and that their presence in the melt affects the intermetallic morphology in multiple modes. We also investigate the effect of increasing Si content in the Al matrix on the microstructure and properties of the MMNCs. We find that Si affects the microstructure in multiple ways, changing both the intermetallics and the carbides which form, and discuss possible methods which its presence causes these changes. Our analysis and results will assist in forming a more rational approach to processing in situ SFRS MMNCs and is an important step towards scaling up in situ processing methods.