Collaborative Research: Probing Atomic Structure Changes in Deformation of Metallic Glasses: An Experimental and Computational Study

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TECHNICAL SUMMARY:Metallic glasses, or amorphous alloys, are structurally disordered solids without the long-range translational order commonly seen in crystals. The structural disorder originates at the atomic scale from randomly packed atoms in proximity to each other. This disorder leads to some of the most remarkable mechanical properties that their crystalline counterparts can only envy: high strength close to the theoretical value, large elastic strain, and high toughness. Metallic glass covers a wide range of systems including transition metals, refractory metals, rare earth metals, and their alloys. These unique and superb properties make them the perfect candidates for many applications including structural components, durable and high performance equipment, coatings, and miniature devices subject to large loading, wear and corrosive protection, and precision shaping. In the past decade, extensive research and development have been done to utilize metallic glasses, especially their mechanical properties. This collaborative research is focused on probing atomic scale deformation processes and atomic structures. It combines experimental approaches using synchrotron X-ray scattering and neutron scattering, and atomistic simulations using molecular dynamics and first-principle calculations. Specifically, it addresses the following issues: (1) Atomic structures, including short- and medium-range order and their changes caused by deformation; (2) Mechanical responses and their differences for systems with different atomic structures; (3) Atomic scale characterizations of structure-mechanical responses such as free volume, local shear transformation, and local atomic bond changes that cannot be easily captured directly by experimental measurements.NON-TECHNICAL SUMMARY:The ultimate goal of this research is to establish the constitutive relations among stress, strain, strain rate, temperature and various physical, structural properties and compositional changes. Due to the difficulties posed by the structural disorder in metallic glasses, reliable constitutive relations must be built on detailed and accurate understanding of atomic scale processes and mechanisms. This effort contributes critically to the advancement of knowledge in this area. We also expect this effort to contribute a positive step in widening the applications of this marvelous material, thus gaining an edge for US industries in the highly competitive world market. Another integral part of this proposed work is the education and outreach program. The project follows two tracks in this regard: (1) participation in outreach education program for local minority engineering undergraduates and K-12 program for students interested in engineering careers through demonstrations, workshops, and hands-on learning experiences, (2) establishment of a close collaboration and exchange program between experimental and computational work for graduate students in Georgia Tech and University of Tennessee, contributing to a rich education experience for both undergraduates and graduate students.