Role of Diffusion-Induced Grain Boundary Migration in Alloy Oxidation

非技术总结抗氧化性仍然是许多关键领域（如能源、运输和航空航天）中高温材料应用的关键要求。几十年的研究已经产生了关于如何提高结构材料抗氧化性的重要知识，其策略包括使用合金元素，涂层和表面处理。然而，这些策略背后的许多机制仍然难以捉摸，限制了我们设计性能更好的合金的能力。在这种情况下，该项目解决了变形和小晶粒尺寸对选定的结构合金的氧化反应的影响。这项工作特别侧重于阐明扩散的关键作用沿着移动晶界供应元素的合金表面形成的氧化物层。这种普遍存在的机制在很大程度上被忽视，因此在合金氧化的背景下未被探索;然而，它可以解释表面变形和小晶粒尺寸对合金系统氧化行为的影响。该计划有助于对扩散条件下晶体材料中普遍存在的机制--沿沿着移动晶界的扩散--的一般科学理解，并增加了我们对材料在扩散条件下的机械理解。极端环境对新合金和微结构的开发产生影响，特别是在先进制造工艺的背景下。由于其重点是极端环境下的材料，特别是高温氧化，拟议的研究影响了工业和国家重要性的关键领域，包括交通，能源和航空航天。除了其科学和技术的影响，该计划还有助于招聘，保留和培训先进的研究方法和技术的多样化的学生团体和劳动力通过其研究活动。该项目还包括在课堂、实验室和校园范围内提高多样性、公平性、包容性和无障碍意识的活动和实践。技术总结抗氧化性仍然是许多关键领域（能源、交通、航空航天）中高温应用的关键要求。虽然改善结构材料的抗氧化性的途径，即，合金化、涂层和表面处理是常用的，但这些策略背后的许多机制仍然难以理解，限制了我们设计性能更好的合金的能力。该项目提出了扩散诱导晶界迁移（DIGM）在合金氧化中普遍存在的假设，并独特地解释了表面变形和晶粒细化对合金系统氧化行为的影响。为了支持这一假设，该项目使用了一系列越来越复杂的合金，从模型镍合金到多主元素合金，其中扩散动力学一直是争论的对象。该计划量化DIGM合金氧化过程中，产生的观察，实验数据，并分析必要的增加我们的溶质运输和相变的理解，不仅氧化建模和缓解，但也为任何传统的和复杂的集中合金扩散条件下，在中间温度下，DIGM可能发生的DIGM过程中的影响。该方法结合了系统的系列实验，使用最先进的表征技术，将微米尺度的观察与原子机制联系起来，为材料基因组计划中的未来建模和计算方法建立了知识基础。该奖项反映了NSF的法定使命，并被认为值得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来支持。

NON-TECHNICAL SUMMARYOxidation resistance remains a critical requirement for materials applications at medium to hightemperatures in many key sectors such as energy, transportation, and aerospace. Decades of studies have generated significant knowledge about how to improve the oxidation resistance of structural materials, with strategies including the use of alloying elements, coatings, and surface treatments. However, many of the mechanisms behind these strategies remain elusive limiting our ability to design better performing alloys. In this context, the project addresses the impact of deformation and small grain sizes on the oxidation response of selected structural alloys. The work specifically focuses on elucidating the key role of diffusion along moving grain boundaries supplying elements to the alloy surface to form an oxide layer. This ubiquitous mechanism has been largely ignored and therefore unexplored in the context of alloy oxidation; yet it can explain the impacts of surface deformation and small grain sizes on the oxidation behavior of alloy systems.This program contributes to the general scientific understanding of diffusion along moving grain boundaries as a ubiquitous mechanism in crystalline materials under diffusive conditions and increases our mechanistic understanding of materials under extreme environments with impact on the development of new alloys and microstructures, particularly in the context of advanced manufacturing processes. Because of its focus on materials under extreme environments and specifically high temperature oxidation, the proposed research impacts key areas of industrial and national importance, including transportation, energy, and aerospace. In addition to its scientific and technological impacts, the program also contributes to the recruitment, retention, and training in advanced research methods and techniques of a diverse student body and workforce through its research activities. The project also includes activities and practices focusing on increasing diversity, equity, inclusion, and accessibility awareness in the classroom, laboratories, and campus wide.TECHNICAL SUMMARYOxidation resistance remains a critical requirement for applications at medium to high temperatures in many key sectors (energy, transportation, aerospace). While avenues to improve the oxidation resistance of structural materials, i.e., alloying, coating, and surface treatments, are commonly used, many of the mechanisms behind these strategies remain elusive limiting our ability to design better performing alloys. The project addresses the hypothesis that diffusion-induced grain boundary migration (DIGM) is ubiquitous in alloy oxidation and uniquely explains the impacts of surface deformation and grain refinement on the oxidation behavior of alloy systems. To support this hypothesis, this project uses a series of increasingly complex alloys, from model Ni alloys to multi principal element alloys for which diffusion kinetics have been the object of debate. The program quantifies DIGM during alloy oxidation, generating observations, experimental data, and analyses necessary to increase our understanding of solute transport and phase transformation during DIGM with implications for not only oxidation modeling and mitigation but also for any conventional and complex concentrated alloy under diffusive conditions at intermediate temperatures where DIGM can occur. The approach combines systematic series of experiments using state-of-the-art characterization techniques tying micron scale observations to atomistic mechanisms, establishing the knowledge base for future modeling and computational approaches within the Materials Genome Initiative.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.