CAREER: Understanding the Role of Nanoprecipitates in Advanced Metastable Titanium Alloys

非技术总结在材料科学中，强度是衡量一种材料承受载荷或承载重量而不会失败的能力。或者，延展性是一种衡量材料弯曲、拉伸或展开而不会碎成碎片的能力。通常，增加材料的强度会导致延展性降低，反之亦然。该项目支持以钛合金设计为重点的基础研究，通过精心定制所述合金的元素组成来克服这种典型的强度与塑性之间的权衡。这种精心的剪裁控制着金属的特定部分在原子水平上如何排列，以具有一定的化学成分和排列，从而在不降低材料整体弯曲或拉伸能力的情况下增加材料的强度。这种类型的设计被称为亚稳定工程。本项目研究具有相同元素组成和原子结构的钛合金部分如何随着温度和化学成分的变化而变化，以及它们在不同情况下如何变形。为了探索这一行为，使用尖端设备进行实时和“事后”研究，以发现当地化学物质、不同环境和金属中纳米尺寸的非常小的颗粒之间的联系，这些颗粒最近才在钛中被发现。在这个项目中建立的基础知识提高了设计具有高强度和高延展性的轻质钛合金的能力。亚稳态钛合金具有高比强度、抗冲击、抗化学劣化和与生物相容性好等优点，在航空航天、汽车、生物医药和化工等领域具有广阔的应用前景。例如，相对于这些行业中的一个行业，对这些合金的改进可以帮助提高飞机的燃油效率，降低燃油消耗，减少碳排放，最终有利于环境。该项目还为K-12夏令营的学生开发了教育模块，并为内华达州里诺大学的本科生和研究生开发了实验室经验。这两组活动都以高性能显微镜为特色，为来自当地雷诺社区的学生提供接触科学和技术的机会，同时也为妇女和未被充分代表的少数民族提供机会学习材料科学，以发展未来的科学工作。技术总结本项目旨在通过研究亚稳态钛合金的微观结构演变和变形，推进一种名为亚稳工程的新合金设计策略。该项目将确定最近发现的正交纳米沉淀物OPrime(O‘)在钛及其合金的空间受限相变中的关键作用。利用先进的非原位和原位表征技术研究了三种特殊现象：(I)合金成分与O‘纳米析出物之间的关系；(Ii)O’在细化析出相组织中的作用；(Iii)O‘在调节马氏体相变中的作用。使用扫描电子显微镜、透射电子显微镜、扫描电子显微镜和原子探针层析成像技术进行了多尺度的外部和现场实验表征。本研究在实现钛的亚稳合金同时具有高强度和高塑性的能力方面取得了进展。侧重于电子显微镜的教学模块和推广活动创造性地吸引学生参加K-12、本科生和研究生水平的学习。远程控制的透射式电子显微镜和便携式台式扫描电子显微镜加强了教育单元和活动，以捕捉广泛的兴趣并使所有人接触有意义的科学。这些教育活动为邻近社区的学生提供了前所未有的实时接触科学的机会，并为雷诺内华达大学的学生团体提供了一种实用的手段，通过在他们的机构进行先进的表征来加强他们的课堂教学。所有活动都有助于培养未来的STEM劳动力，激发所有年龄段的学生对材料科学的兴趣。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

NON-TECHNICAL SUMMARYIn materials science, strength is the measure of a material’s ability to bear a load or carry weight without failing. Alternatively, ductility is a measure of a material’s ability to bend, stretch or spread without breaking into pieces. Often, increasing the strength of a material results in a decrease of ductility and vice versa. This project supports fundamental research focused on the design of Titanium alloys that overcome this typical strength-to-ductility trade-off by carefully tailoring the elemental make-up of said alloys. This careful tailoring controls how specific parts of the metal are arranged on an atomic level to have a certain chemical composition and arrangement that increases the material’s strength without reducing the material’s overall ability to bend or stretch. This type of design is known as metastability engineering. This project investigates how parts of Titanium alloys having the same elemental makeup and atomic structure change with both temperature and chemical composition and how they deform under various circumstances. To explore this behavior, real-time and “after the fact” studies are performed using cutting edge equipment to discover connections between local chemistry, different environments and very small particles in the metal that are nanometers in size and have only recently been discovered in Titanium. The fundamental knowledge established in this project advances the ability to design lightweight Titanium alloys with both high strength and high ductility. Metastable titanium alloys are desirable for aerospace, automobile, bio-medical and chemical industries, due to their high strength-to-weight ratio, ability to absorb impact, resistance to chemical deterioration and compatibility with biological applications. As an example, relative to just one of these industries, improvements to these alloys can help to increase aircraft fuel efficiency, reduce fuel consumption, lower carbon emissions and ultimately, benefit the environment. This project also develops education modules for students in a K-12 Summer Camp as well as lab experiences for undergraduate and graduate students at the University of Nevada Reno. Both sets of activities feature high powered microscopes providing students from local Reno communities exposure to science and technology while also providing opportunities for women and underrepresented minorities to learn materials science for the purpose of developing the future scientific workforce.TECHNICAL SUMMARYThis project aims to advance a novel alloy designing strategy known as metastability engineering, by studying microstructural evolution and deformation in metastable Titanium alloys. The project will identify the critical role of the recently discovered, orthorhombic nano-precipitate, O prime (O’) in the spatially confined phase transformations of Titanium and its alloys. Advanced ex-situ and in-situ characterization techniques are employed to explore three specific phenomena: (i) The relationship between alloy composition and O’ nano-precipitates; (ii) The role of O’ in refining precipitate microstructure; and (iii) the role of O’ in regulating martensitic transformations. Multiscale ex- and in-situ experimental characterization using scanning electron microscopy, transmission electron microscopy, scanning transmission electron microscopy and atom probe tomography are used. This research progresses the ability to realize metastable alloys of Titanium having both high strength and high ductility. Education modules and outreach activities focused on electron microscopy creatively engage students in K-12, undergraduate and graduate level study. The education modules and activities are enhanced by a remote-controlled transmission electron microscope and a portable desktop scanning electron microscope to capture a wide range of interests and expose all to meaningful science. These education activities provide students in the neighboring community unprecedented access to science in real-time and offers to the student body at the University of Nevada, Reno a practical means of enhancing their in-class instruction with exposure to advanced characterization being performed at their institution. All activities assist with developing a future STEM workforce by generating interest in materials science to students at all ages.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.