Atomic Scale Deformation Mechanisms in New Ductile Cu-Based Bulk Metallic Glasses with High Manufacturability

大块金属玻璃（bmg）是一类相当新的高级材料，具有非结晶（玻璃状）内部结构。它们不像金属中常见的那样含有与晶体有关的缺陷。这种特殊的结构使bmg具有许多优于许多金属的性能（例如，强度、硬度、回弹性、耐磨损和耐腐蚀）。这种差异创造了潜力，大大提高了许多金属的性能，广泛应用于几个工程应用。然而，bmg面临的一个重大挑战是其弯曲和拉伸能力有限。即使断裂，bmg在断裂前也没有明显的拉伸或弯曲迹象。一些bmg已经显示出良好的延展性，但它们通常很难大尺寸制造，或者需要昂贵、有毒和/或难以找到的元素。设计延展性好、可大规模生产、不使用有毒或难以获得的元素的bmg是该领域的一个突出问题。该项目通过研究最近由首席研究员发现的铜基bmg的原子尺度变形机制来解决这一挑战。这些cu基bmg具有高强度，良好的延展性，优异的可制造性和工程友好的组合。了解这些bmg弯曲、拉伸和最终失效的方式，将有助于未来发现其他同样或更出色的bmg，这些bmg将更好地满足社会对高性能材料的需求，而不是我们目前使用的材料。该项目让多名研究生和本科生参与直接研究，并为他们未来在学术界或工业界从事与材料相关的职业做好准备。通过一个完善的暑期项目，该项目还涉及K-12学生，特别是来自服务欠缺地区和群体的学生，培养他们对材料科学的好奇心和兴趣，同时促进STEM教育的多样性、公平性和包容性。研究成果被用来丰富俄勒冈州立大学的本科材料科学导论课程。该项目还有助于美国成为bmg研究的领先之地，bmg是一种具有重要战略意义的材料，也是未来国防和航空航天应用中潜在的游戏规则改变者。在各种类型的材料中，延展性（或塑性）经常与强度相冲突。此外，可制造性和成分的工程友好性是工程材料的另一个常见权衡。大块金属玻璃（BMG）面临着这两方面的挑战。在不牺牲材料强度、可制造性和工程友好性的前提下，通过合金设计实现良好的塑性是该领域的核心问题。这些挑战的一个重要障碍是缺乏对BMG中原子尺度特征（键、元素）如何控制其宏观变形以及如何通过设计元素组成来控制这些影响的理解。本项目结合实验和计算方法，研究了最近发现的一系列具有高强度、良好延展性、优异的可制造性和工程友好成分的cu基bmg的原子销售变形机制。利用同步加速器束流线和扫描电子显微镜对不同应力应变水平下新型bmg的原子键和剪切带行为进行了原位协调应变跟踪，探讨了成分变化对其变形行为的影响（通过原子键和剪切带）。然后使用分子动力学模拟和有限元建模来分析和解释实验数据。该项目预计将确定主要负责弹性变形的原子键，并确定主要负责塑性变形和延性的原子键的强度。通过这种方式，研究人员正在阐明这种新型bmg中强度和延性不寻常组合的根本起源，并揭示合金成分如何影响应力驱动的原子键行为和宏观变形。这些知识对于设计具有良好延展性和其他性能的理想组合的未来bmg是需要的。该项目还推进了极端应力下材料塑性领域的基础材料科学，这是普通金属、陶瓷或聚合物材料无法探索的。该项目支持的研究生将有机会学习材料宏观变形和原子尺度行为，掌握重要的实验和计算技术，并为未来在材料相关领域的职业生涯做好准备。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYBulk metallic glasses (BMGs) are a fairly new class of advanced material that has a non-crystalline (glassy) inner structure. They do not contain crystal-related defects as are common in metals. This special structure gives BMGs a host of properties (e.g., strength, hardness, resilience, wear- and cor-rosion-resistance) that can be superior to many metals. This difference creates the potential to dras-tically improve upon the performance of many metals widely used in several engineering applica-tions. However, one significant challenge facing BMGs is their limited ability to bend and stretch. Even when they break, BMGs do not show evidence of significant stretching or bending before failure. A few BMGs have demonstrated good ductility but they are often very difficult to make in large sizes or require elements that are either expensive, toxic and/or hard to find. Designing BMGs with good ductility, that can be manufactured at scale and which do not use toxic or hard to acquire elements is an outstanding question in the field. This project addresses this challenge by investigating the atomic-scale deformation mechanisms in Copper-based BMGs that were recently discovered by the principal investigator. These Cu-based BMGs possess an exceptional combination of high strength, good ductility, excellent manufacturability, and engineering-friendly compositions. Understanding the way these BMGs bend, stretch and ultimately fail, will help future discovery of other equally or more remarkable BMGs that will better serve the societal needs of high performance materials than the materials we currently use. This project engages multiple graduate and undergraduate students in direct research and prepares them for future materials-related careers in academia or industry. Through a well-established summer program, the project also involves K-12 students, particularly from underserved areas and groups, to cultivate curiosity and interest in materials science while promoting diversity, equity and inclusion in STEM education for all. Research findings are used to enrich an undergraduate Introduction to Materials Science course taught at Oregon State University. This project also aids the U.S. in being a place for leading research for BMGs which are a strategically important class of materials and a potential game changer in future defense and aerospace applications.TECHNICAL SUMMARYDuctility (or plasticity) often conflicts with strength in various types of materials. In addition, manufacturability and engineering-friendliness of composition is an additional common trade-off for engineering materials. Bulk metallic glasses (BMG) are challenged by both. Achieving good ductility in BMGs by alloy design without sacrificing strength, manufacturability and engineering-friendliness of composition are central issues in the field. A significant barrier to these challenges is the lack of understanding relative to how atomic-scale features (bonds, elements) in a BMG govern their macroscopic deformation and how to control these effects by design of their elemental compositions. This project combines experimental and computational methods to investigate atomic-sale deformation mechanisms in a recently discovered family of Cu-based BMGs which possess exceptional combinations of high strength, good ductility, excellent manufacturability and engineering-friendly compositions. Coordinated in-situ straining via a synchrotron beamline and a scanning electron microscope are used to track the behavior of the atomic bonds and shear bands in the new BMGs at different levels of stress and strain to probe the effects of changing composition on their deformation behavior (through atomic bonds and shear bands). Molecular dynamics simulations and finite element modeling are then used to analyze and interpret the experimental data. The project is expected to identify the atomic bonds primarily responsible for elastic deformation and determine the strength of those bonds chiefly responsible for plastic deformation and ductility. In this way, investigators are elucidating the fundamental origin of the unusual combination of strength and ductility in this new class of BMGs as well as revealing how alloy composition influences stress-driven atomic bond behavior and macroscopic deformation. Such knowledge is needed for the design of future BMGs with good ductility and ideal combinations of additional properties. This project also advances fundamental materials science in the area of materials plasticity at extreme stresses which cannot be explored with common metallic, ceramic or polymeric materials. Graduate students supported by the project experience a unique opportunity to learn about materials macroscopic deformatiion and atomic-scale behavior, master important experimental and computational techniques, and prepare for future careers in materials-related fields.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.