Nano-mechanical Properties of Grain Boundaries

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NSF Proposal 0625650: Nano-mechanical Properties of Grain BoundariesPI: Md A Haque, the Pennsylvania State University, University Park, PA Abstract: More than 50 years of research on grain boundaries has established their impact on the overall strength of materials, yet experimental studies on their yield strength or Young's modulus are rare in the literature. This is because grain boundaries are random networks of interfaces that are only a few nanometers wide and cannot be isolated and characterized by conventional tensile, bending, indentation tools. This project aims to address this challenge by developing an experimental setup using micro-electro-mechanical (MEMS) force and displacement sensors and in-situ transmission electron microscopy (TEM). Since TEM renders the microstructures visible, the experimental setup will allow simultaneous characterization of crystallographic orientations, crack propagation and plastic deformation mechanisms with atomic resolution. Models based on interfacial fracture mechanics will be developed to extract the grain boundary properties from the experimental data. The fundamental understanding on the interfaces in materials will impact grain boundary engineering, an evolving research direction towards optimized materials design. The project will integrate research and education on mechanics, microscopy and micro/nanotechnology at graduate, undergraduate and K-12 levels while promoting diversity. The research outcomes will be disseminated through conferences and journal articles. One female/minority undergraduate student will be involved through collaboration with the Penn State Minority in Engineering Program. A graduate course titled Mechanics of Nano Materials will be developed and offered. With supplemental funding, two outreach programs will be executed: (1) 'Microscopy for K-12' where local elementary, middle and high school students will operate an electron microscope and (2) Two-week long summer workshop for K-12 teachers.