RII Track-4: NSF: Understanding the Nanoscale Incommensurate Modulated Structure in the Titanium Alloys

该基金支持以新型金属设计策略为重点的基础研究，促进材料科学和技术的进步。金属由于在不同的载荷条件下具有优异的性能而被广泛应用于结构材料。然而，实现金属的高强度和高塑性的协同组合是必要的，但困难的。该项目旨在研究一种新的策略，通过形成具有良好控制的空间不均匀性长度尺度的沉淀物（即，非均相沉淀结构）。该项目将使用尖端的透射电子显微镜来确定纳米结构在钛合金中形成非均匀沉淀结构中的关键作用。该奖学金将允许PI和一名研究生参观美国首屈一指的电子显微镜中心，马萨诸塞州理工学院的麻省理工学院纳米研究设施。该项目将使PI与麻省理工学院建立长期合作。纳米和材料表征的新专业知识，这将对内华达州大学里诺（UNR）的研究能力产生长期影响。PI将为UNR的学生设计新的电子显微镜和材料科学教育模块，并为里诺社区的K-12学生设计外展活动，以影响年轻一代的学习者，特别是那些传统上代表性不足的群体。这个研究基础设施改善轨道-4 EPSCoR研究员（RII轨道-4）项目将提供奖学金，以助理教授和培训研究生在内华达州里诺大学（UNR）。利用纳米结构是调整钛合金中析出相尺寸的有效方法。在这个项目中，PI将使用纳米尺度的无公度调制结构（NIMS）作为一个例子，以确定钛合金中与NIMS相关的局部结构，成分和非均匀沉淀结构之间的相关性。本研究的目的是从根本上了解钛合金热处理过程中的NIMS及其对组织演变的影响。本论文的研究目标有两个：（i）确定合金成分、工艺参数与钛合金中NIMS形成机制之间的关系;（ii）阐明NIMS在钛合金热处理过程中ω和α相析出中的作用。拟议的研究是建立在与世界领先的纳米结构材料科学家和国家首屈一指的电子显微镜中心在马萨诸塞州理工学院的合作。我们将使用像差校正的Themis Z G3 S/TEM来识别NIMS的原子级结构和成分表征，并使用DENS Solution Lightning原位TEM加热保持器来证明NIMS对钛合金中微观结构演化路径的影响。高度先进的前和原位表征工具的集成对于准确描述钛合金中这些复杂的相变是必不可少的。该项目的成功完成将促进对钛合金中纳米结构相关的微观结构演变的基本理解，这对于加速具有新成分和微观结构的钛合金的发现和开发至关重要。该奖项反映了NSF的法定使命，并通过使用基金会的智力价值和更广泛的影响审查标准进行评估，被认为值得支持。

This grant supports the fundamental research focusing a novel metal designing strategy and promotes the progress of materials science and technology. Metals are widely used structural materials because of their excellent performance under different loading conditions. However, to achieve synergetic combination of high strength and ductility in metals is essential but difficult. This project aims to investigate a new strategy to overcome the strength-ductility tradeoff in titanium (Ti) alloys by forming precipitates with a well-controlled length scale of spatial heterogeneities (i.e., heterogeneous precipitate structure). The project will identify the critical roles of nanostructures in forming the heterogeneous precipitate structure in Ti alloys using the cutting-edge transmission electron microscopy. The fellowship will allow the PI and a graduate student to visit the nation’s premier electron microscopy center, the MIT.nano research facilities at Massachusetts Institute of Technology. The project will enable the PI to establish a long-term collaboration with MIT.nano and new expertise in materials characterization, that will lead to a long-lasting impact on the research capability at University of Nevada, Reno (UNR). The PI will design new electron microscopy and materials science education modules for students at UNR and outreach activities for K-12 students in the Reno community to impact a young generation of learners, especially those from groups traditionally underrepresented in. STEM.This Research Infrastructure Improvement Track-4 EPSCoR Research Fellows (RII Track-4) project would provide a fellowship to an Assistant Professor and training for graduate student at the University of Nevada Reno (UNR). Utilizing nanostructures is an effective method to tune the size of precipitates in Ti alloys. In this project, the PI will use nanoscale incommensurate modulated structure (NIMS) as an example to identify the correlations between the local structure, composition and heterogeneous precipitate structure related to NIMS in Ti alloys. The goal of this research is to fundamentally understand the NIMS and its influence on the microstructure evolution during thermal treatment in the Ti alloys. Two specific research aims will be pursued: (i) Identifying the relationship between the alloy composition, processing parameter and the formation mechanism of the NIMS in Ti alloys; and (ii) Demonstrating the role of NIMS in ω and α phase precipitation during heat treatment in Ti alloys. The proposed research is built on the collaboration with the world-leading nanostructured materials scientist and the nation’s premier electron microscopy center at Massachusetts Institute of Technology. We will identify the atomic-level structure and composition characterization of NIMS using the aberration-corrected Themis Z G3 S/TEM and demonstrate the influence of NIMS on microstructure evolution pathways in Ti alloys using the DENS Solution Lightning in-situ TEM heating holder. The integration of highly advanced ex- and in-situ characterization tools is essential for an accurate description of these complex phase transformations in Ti alloys. The successful completion of the proposed project will advance the fundamental understanding of the microstructure evolution related to the nanostructures in Ti alloys, that is critical for accelerating the discovery and development of Ti alloys with a new composition and microstructure.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.