ERI: Mechanical Behavior of Dualphase Complex Concentrated Alloys at Elevated Temperatures

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。这个工程研究计划（ERI）项目是研究一种特殊类型的合金，称为复杂浓缩合金（CCAs）。cca是最近发现的具有优异机械性能的材料。在高温下具有高强度的材料在许多工程应用中是非常需要的。cca由多个主元素组成，包括高熵合金，它包含五个或更多的主元素。CCAs已被研究为高温应用的潜在结构合金，如热交换器、燃气轮机和核反应堆。一般来说，单相面心立方CCAs在高温下强度较低。同时，单相体心立方CCAs在室温下呈脆性。双相（面心立方和体心立方）cca捕获了最好的特征。它们在室温下具有良好的延展性，在高温下具有较高的强度。然而，目前对双相CCAs力学行为的理解是有限的。本项目旨在研究双相CCAs在不同温度下的力学行为，并找到提高其强度的最佳方法。从这个项目中学到的知识可以引导设计用于高温应用的双相cca。多学科的研究将为研究生提供不同工程领域的多样化训练。该项目还将对代表性不足的群体和工程教育的研究机会产生积极影响。本项目的目的是从根本上了解界面、微观结构和化学成分如何影响双相CCAs从室温到高温的强度和变形能力。具体而言，PI将(1)研究面心立方和体心立方CCAs的温度依赖势垒强度之间的相互作用；(2)揭示了界面在相间位错传递和塑性传递中的作用；(3)阐明位错活动对双相CCAs抗断裂性能的影响。为了解决这些科学问题，该项目将采用特定位点的纳米压痕来探测双相CCAs在不同温度下的力学行为和变形机制，并通过高分辨率扫描探针显微镜和电子显微镜进行详细的表面形貌和微观结构表征。本项目的研究结果可为缓解体心立方cca在室温下通过界面的脆性破坏，提高双相cca的高温强度提供知识。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。

This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2).This Engineering Research Initiative (ERI) project is to study a special type of alloy called complex concentrated alloys (CCAs). CCAs are materials recently found to have superior mechanical properties. Materials that have high strength at high temperature are highly desirable for many engineering applications. CCAs consist of multiple principal elements and include high-entropy alloys, which contain five or more principal elements. CCAs have been researched as potential structural alloys for high temperature applications, such as heat exchangers, gas turbines, and nuclear reactors. Generally, single-phase face-centered cubic CCAs have low strength at high temperatures. Meanwhile, single-phase body-centered cubic CCAs are brittle at room temperature. Dualphase (face-centered cubic and body-centered cubic) CCAs capture the best of the features. They can exhibit both good ductility at room temperature and high strength at high temperatures. However, the current understanding of the mechanical behavior in dualphase CCAs is limited. This project aims to investigate mechanical behaviors and find the best ways to improve the strengths of dualphase CCAs at various temperatures. The knowledge learned from this project could lead to the design of dualphase CCAs for high temperature applications. The multi-disciplinary research will provide graduate students with diverse training in various engineering fields. This project will also positively impact research opportunities of underrepresented groups and engineering education.The objective of this project is to fundamentally understand how interface, microstructure, and chemistry affect the strength and deformability of dualphase CCAs from room temperature to high temperatures. Specifically, the PI will (1) investigate the interplay between temperature-dependent barrier strength of face-centered cubic and body-centered cubic CCAs; (2) reveal the role of interface on dislocation transmission and plasticity transfer between phases; (3) elucidate the effects of dislocation activities on fracture resistance of dualphase CCAs. To address these scientific questions, this project will employ site-specific nanoindentation to probe the mechanical behavior and deformation mechanisms in dualphase CCAs at various temperatures and perform detailed surface morphology and microstructure characterization through high resolution scanning probe microscopy and electron microscopy. The results of this project can provide knowledge to alleviate the brittle failure of body-centered cubic CCAs at room temperature through interfaces and enhance the high temperature strength of dualphase CCAs.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.