CAREER: Understanding of Intrinsic Size-Effects in Deformation of Metallic Glasses

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Metallic glasses have potential as future engineering materials in structural and biomedical applications, due to their high strength and elasticity, which can surpass the best available steels. These unusual properties stem from the synergistic effect of metallic bonding and the glassy structure. Despite the impressive suite of properties, barriers exist to the adoption of metallic glasses into application, including failure in tension and high material cost. Adoption of metallic glasses into wide application could be made possible if brittle fracture could be understood and controlled. This Early Career Faculty Development (CAREER) Program research project will contribute to these efforts by uncovering the mechanism of ductility observed in nanoscale samples and harnessing the advantages of size reduction (lower cost, enhanced plasticity, and ease in fabrication) in novel applications. The research efforts will be integrated with comprehensive education and outreach activities. A new summer-enrichment program, for the first time in the region, will provide exposure and tools to the underserved population of students with special needs, to promote a successful career in engineering disciplines. The results and materials from this project will be disseminated through web-based services, public exhibits, conferences, and journal publications.Size-dependent transitions from shear-localized (brittle) to homogeneous (ductile) deformation can eradicate the fundamental weakness of metallic glasses. However, the existence and the mechanism of such size effects themselves have been difficult to discern due to processing artifacts (irradiation damage, variation in thermal history, and noncompliant sample geometry) and low yield of existing nanomechanical tests. This award supports fundamental research to decouple the effects of sample size and processing on deformation of metallic glasses. This will be achieved by devising high-throughput fabrication and mechanical testing methodologies for irradiation-free nanoscale specimens (compression and tensile). Statistically significant and unambiguous data obtained from these experiments will allow verification and refinement of existing models for plasticity in nanoscale metallic glasses. The benefits of size-effects will be utilized in unique applications such as electrodes for sensing, micro-needles for drug delivery, and conductive tips for scanning probe microscopy. The overall research plan is designed to stimulate a paradigm shift in metallic glass research from bulk to small-scale by demonstrating its impact on the fundamental and applied science.