Collaborative Research: Elucidating High Temperature Deformation Mechanisms in Refractory Multi-Principal-Element Alloys

现代交通、发电、太空进入和国家安全都依赖于能够在高温下保持其形状和强度的材料。镍基高温合金的开发，通常包含十种或更多的元素，用于喷气发动机，可以承受超过1000摄氏度的温度，并允许超过1400摄氏度的气体温度。几十年来，这些高温合金的多代发展已经达到了极限。进一步提高温度将带来更好的燃油效率、更大的推力和最佳性能，但需要新的合金开发方法。使用具有较高熔融温度的耐火材料和制造等原子合金代表了两种有前途的发展方向，但目前对这些新合金在极端温度下如何变形的了解尚缺乏。本研究将先进的计算模型与新颖的超高温实验和详细的电子显微镜相结合，以确定控制这种新型耐火多主元素合金高温强度的变形机制。拟议的合作既能迅速加快合金发现的速度，又能提供有意义的教育和职业发展机会，从而扩大和扩大汽车、航空航天和国防部门的劳动力。技术概述耐火多主元素合金（rmpea）作为结构材料具有巨大的潜力，可以在超高温（UHT）和节能发电、高超音速飞行和空间进入所需的极端环境下工作。传统的高温合金无法满足目标使用温度，目前对rmpea的超高温力学行为的理解仍处于起步阶段，这是实现这类新合金的关键障碍。所提出的研究的科学价值是基于预测、表征和理解rmpea在接近1500℃时的力学响应的变形机制的巨大需求。先进的位错动力学中尺度模型、新颖的亚尺度力学测试和详细的微观结构表征的集成被用于收集急需的超高温拉伸和蠕变数据，以发展对几乎等原子、成分复杂、多组分合金的超高温变形的基本科学描述。参与约翰霍普金斯大学和加州大学圣巴巴拉分校的现有项目为代表性不足的高中生和本科生提供了研究经验，拟议的本科生交换项目具有扩大STEM研究生管道的真正潜力，并及时培养STEM领导者和榜样。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。

NON-TECHNICAL SUMARYModern transportation, power generation, space access, and national security all rely on the availability of materials that can maintain their shape and strength at elevated temperatures. The development of nickel-based superalloys, which often contain ten or more elements, are used in jet engines, can withstand temperatures of over 1,000oC, and allow for gas temperatures in excess of 1,400oC. The development of multiple generations of these superalloys occurred over many decades but is reaching its limit. Further temperature advancements would result in better fuel efficiencies, greater thrust, and optimal performance, but novel approaches to alloy development are required. The use of refractory elements that have higher melting temperatures and the creation of equiatomic alloys represent two promising paths forward, but current understanding of how these new alloys deform at extreme temperatures is currently lacking. This study combines advanced computational modeling with novel ultrahigh temperature experiments and detailed electron microscopy to identify the deformation mechanisms that govern the high temperature strength of this new class of refractory multi-principal-element alloys. The proposed collaboration is both rapidly accelerating the rate of alloy discovery while providing meaningful educational and career advancement opportunities, thus expanding and enlarging the workforce in automotive, aerospace, and national defense sectors.TECHNICAL SUMMARYRefractory-multi-principal-element alloys (RMPEAs) hold tremendous potential for use as structural materials that can operate at ultrahigh temperatures (UHT) and in the extreme environments required for energy efficient power generation, hypersonic flight, and space access. Targeted use temperatures cannot be met with conventional superalloys, and current understanding of the UHT mechanical behavior of RMPEAs is still in its infancy and represents a critical impediment to the realization of this new class of alloys. The scientific merit of the proposed research is predicated on the overwhelming need to predict, characterize, and understand the deformation mechanisms that govern the mechanical response of RMPEAs at temperatures approaching 1500oC. The integration of advanced mesoscale modeling of dislocation dynamics, novel sub-scale mechanical testing, and detailed microstructural characterization are being used to gather much needed UHT tensile and creep data to develop a fundamental scientific description of the ultrahigh temperature deformation of nearly equiatomic, compositionally complex, multicomponent alloys. Participation in established programs at Johns Hopkins University and the University of California, Santa Barbara are providing research experiences for under-represented high school and undergraduate students, and the proposed undergraduate student exchanges hold real potential for expanding the pipeline of STEM graduate students, and in time, STEM leaders and role models.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.