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

金属玻璃由于其高强度和弹性，在结构和生物医学应用中具有作为未来工程材料的潜力，这可以超过最好的可用钢。这些不寻常的性能源于金属键合和玻璃结构的协同效应。尽管具有令人印象深刻的一系列特性，但金属玻璃应用的障碍仍然存在，包括拉伸失效和高材料成本。如果能够理解和控制脆性断裂，金属玻璃的广泛应用就成为可能。这个早期职业教师发展（CAREER）计划研究项目将通过揭示纳米样品中观察到的延展性机制，并利用尺寸减小的优势（降低成本，增强塑性和易于制造）在新的应用中为这些努力做出贡献。研究工作将与综合教育和外联活动相结合。一个新的夏季充实计划，在该地区首次，将提供曝光和工具，以满足特殊需要的学生人口不足，以促进在工程学科的成功职业生涯。该项目的成果和材料将通过基于网络的服务、公共展览、会议和期刊出版物传播。从剪切局部（脆性）到均匀（韧性）变形的尺寸依赖性转变可以消除金属玻璃的根本弱点。然而，这种尺寸效应本身的存在和机制已经难以辨别，由于加工工件（辐射损伤，热历史的变化，和不符合样品的几何形状）和现有的纳米机械测试的低产量。该奖项支持基础研究，以消除样品尺寸和加工对金属玻璃变形的影响。这将通过为无辐射纳米级试样（压缩和拉伸）设计高通量制造和机械测试方法来实现。从这些实验中获得的统计上显著和明确的数据将允许验证和改进现有的模型在纳米级金属玻璃的塑性。尺寸效应的好处将被用于独特的应用，如传感电极，药物输送的微针，扫描探针显微镜的导电尖端。总体研究计划旨在通过展示其对基础科学和应用科学的影响，促进金属玻璃研究从大规模到小规模的范式转变。

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.