CAREER: Precipitation Pathways and Deformation Micromechanisms of Refractory Superalloys (RSAs)

该奖项全部或部分根据2021年美国救援计划法案（公法117-2）资助。第一部分： 非技术总结高温结构材料的上级类别的破坏性潜力是巨大的，将彻底改变能源部门和航空航天工业，同时推进我们的军事技术。例如，这种材料将使固定式燃气涡轮机（占美国所有电力的40%）和航空航天燃气涡轮机（占人为全球变暖的5%）在更高的温度下运行。更高的发动机温度提供了更高的发动机效率，并提高了动力装置和航空的功率输出，有助于增强经济性，同时减少温室气体排放，并使军用飞机具有战术优势。最近发现的耐热高熵高温合金（RSA）在室温和高温下具有高强度和延展性的优异组合，非常有前途，特别是因为普通耐热合金在环境条件下通常很脆。拟议的研究确定了有关变形机制，高温下微观结构稳定性的知识差距，并通过先进的材料表征，机械测试和模拟，包括国家实验室设施来解决这些差距。这种分析和理解对于加速材料开发以实现下一代动力装置和航空发动机至关重要。该项目不仅满足了对先进材料的需求，还协同减少了科学和工程方面的人才缺口。迈阿密大学工程学院正在与菲利普和帕特里夏·弗罗斯特科学博物馆合作，该博物馆每年接待约70万游客。该合作旨在通过整合正在进行的研究和教育计划，提高人们对冶金及其对降低航空旅行和电力生产的二氧化碳和能源足迹的影响的认识和兴趣。第二部分： 该项目的目标是通过具体测试以下假设来研究耐火高熵高温合金（RSA）的沉淀、强化和变形机制：（i）淬火时形成的沉淀是由于亚稳分解，这引起了对两相微观结构长期稳定性的关注，和（ii）优异的机械性能是由于通过激活A111滑移系统的两相的共同变形，假定优选的A001{001}机制不满足多晶延展性的标准。 原位小角度X射线和中子散射的应用，以确定随时间变化的成分的傅里叶变换，从而直接测试的调幅分解，同时监测在广角检测器的相变，显着有助于合金中的沉淀途径的理解。在弹性加载过程中的原位中子衍射提供了有关微观结构演化的相场模拟所需的基本数据（如相刚度）。在塑性变形过程中的原位衍射结合TEM位错分析探测变形微观力学，并揭示了为什么RSAs表现出强度和延展性的组合，而耐火（单相）合金通常是脆性在环境温度下。体心立方合金中的相演化、旋节分解和滑移系统的基础研究在多个合金系统中具有重要意义，对于RSA的发展至关重要，并且对于推进高温冶金是必要的。 STEM人才缺口通过研究和教育的紧密结合来解决。本科课程的发展，提供了一个教育机会，一起教师和行业工程师进行研究，提高材料教育在南佛罗里达。STEM缺乏多样性是通过一个多步骤计划来解决的。迈阿密地理位置优越，位于一个少数民族占多数的城市，教育着高度多样化的学生群体。通过与弗罗斯特科学博物馆的合作，产生了对冶金学的重要认识和理解，在那里，统计调查监测了这些教育和推广活动的成功。该奖项反映了NSF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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). PART 1: NON-TECHNICAL SUMMARYThe disruptive potential of a superior class of high-temperature structural materials is immense, and would revolutionize the energy sector and aerospace industry while advancing our military technologies. For example, such materials would enable stationary gas turbines (which produce 40% of all U.S. electricity) and aerospace gas turbines (which account for 5% of man-made global warming) to operate at higher temperatures. Higher engine temperatures provide greater engine efficiency and boost power output from powerplants and aviation, contributing to a stronger economy while reducing greenhouse gas emissions and enabling tactical superiority for military aircraft. The recent discovery of refractory high entropy superalloys (RSAs) that possess excellent combinations of high strength and ductility at room-temperature and elevated temperature is extremely promising, especially as normal refractory alloys are typically brittle under ambient conditions. The proposed research identifies knowledge-gaps regarding deformation mechanisms, microstructure stability at high temperatures and addresses these gaps through advanced materials characterization, mechanical testing and simulation, including National Laboratory facilities. Such analysis and understanding are critical for accelerated materials development to realize next-generation powerplants and aerospace engines. This project not only meets demands for advanced materials but synergistically reduces talent gaps in science and engineering. The University of Miami College of Engineering is collaborating with the Phillip and Patricia Frost Museum of Science, which receives approximately 700,000 visitors annually. The collaboration serves to increase awareness and interest in metallurgy, and its impact on lowering CO2 and energy footprints of air travel and electricity production, through integration of ongoing research and education initiatives. PART 2: TECHNICAL SUMMARY The project goal is to study the precipitation, strengthening and deformation mechanisms of refractory high entropy superalloys (RSA) by specifically testing the hypotheses that (i) the precipitation formed on quenching is due to spinodal decomposition, which raises concerns regarding long-term stability of the two-phase microstructure, and that (ii) the excellent mechanical properties are due to co-deformation of both phases via activation of the a111 slip system, given the preferred a001{001} mechanism does not satisfy the criterion for polycrystalline ductility. The application of in-situ small-angle x-ray and neutron scattering to determine the time dependent Fourier transform of the composition variation, and thereby directly test for spinodal decomposition, while simultaneously monitoring for phase transformations in a wide-angle detector, significantly contributes to the understanding of precipitation pathways in alloys. In-situ neutron diffraction during elastic loading provides fundamental data (such as phase stiffnesses) necessary for phase field simulations regarding microstructure evolution. In-situ diffraction during plastic deformation combined with TEM dislocation analysis probes the deformation micromechanics and reveals why RSAs exhibit a combination of strength and ductility, whereas refractory (single-phase) alloys are typically brittle at ambient temperature. The fundamental research regarding phase evolution, spinodal decomposition and slip systems within body-centered cubic alloys is significant across multiple alloy systems, essential for the development of RSAs, and necessary to advance high-temperature metallurgy. The STEM talent gap is addressed through a tight integration of research and education. The development of an undergraduate course that offers an educational opportunity to perform research alongside faculty and industry engineers enhances materials education in South Florida. The lack of diversity in STEM is addressed through a multi-step program, where U. Miami is ideally located in a majority-minority city and educates a highly diverse student body. Significant awareness and understanding in metallurgy is generated through partnership with the Frost Science Museum, where statistical surveys monitor success of these education and outreach activities.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.