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

职业：耐火高温合金 (RSA) 的析出途径和变形微观机制

• 批准号: 2141957
• 负责人: James Coakley
• 金额: $ 61.98万
• 依托单位: University of Miami
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-08-15 至 2022-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2141957&HistoricalAwards=false
• 关键词: CAREER; Precipitation; Pathways; Deformation; Micromechanisms

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.

该奖项全部或部分由《2021年美国救援计划法案》（公法117-2）资助。一种高级高温结构材料的破坏性潜力是巨大的，它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，这种材料可以使固定式燃气轮机（占美国全部电力的40%）和航空航天燃气轮机（占人为全球变暖的5%）在更高的温度下运行。更高的发动机温度可以提高发动机效率，提高发电厂和航空的功率输出，在减少温室气体排放的同时促进经济增长，并使军用飞机具有战术优势。最近发现的耐火高熵高温合金（RSAs）在室温和高温下都具有很高的强度和延展性，这是非常有前途的，特别是普通的耐火合金在环境条件下通常是脆性的。拟议的研究确定了关于变形机制、高温下微观结构稳定性的知识空白，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）来解决这些空白。这样的分析和理解对于实现下一代动力装置和航空发动机的加速材料开发至关重要。该项目不仅满足了对先进材料的需求，而且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。这项合作旨在通过整合正在进行的研究和教育举措，提高人们对冶金的认识和兴趣，以及冶金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。第2部分:项目目标是研究难熔高熵高温合金（RSA）的析出、强化和变形机制，具体测试以下假设：(i)淬火时形成的析出是由于spinodal分解，这引起了对两相组织长期稳定性的关注；（ii）优异的机械性能是由于两相通过a111滑移系统的激活而共同变形。鉴于优选的a001{001}机制不满足多晶延展性的标准。应用原位小角x射线和中子散射来确定成分变化的傅里叶变换随时间的变化，从而直接测试spinodal分解，同时在广角探测器中监测相变，这对理解合金中的沉淀途径有重要贡献。弹性加载过程中的原位中子衍射为微观结构演化的相场模拟提供了必要的基础数据（如相刚度）。塑性变形过程中的原位衍射结合TEM位错分析探讨了变形的微观力学，揭示了为什么rsa表现出强度和延展性的结合，而耐火（单相）合金在室温下通常是脆性的。体心立方合金的相演化、spinodal分解和滑移系统的基础研究在多合金体系中具有重要意义，对rsa的发展至关重要，也是推进高温冶金的必要条件。通过研究和教育的紧密结合来解决STEM人才缺口。本科课程的发展提供了与教师和工业工程师一起进行研究的教育机会，增强了南佛罗里达州的材料教育。STEM缺乏多样性是通过一个多步骤的项目来解决的，迈阿密大学理想地位于一个少数民族占多数的城市，并教育了一个高度多样化的学生群体。通过与弗罗斯特科学博物馆建立伙伴关系，提高了对冶金学的认识和了解，在弗罗斯特科学博物馆进行统计调查，监测这些教育和推广活动的成功。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。