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。该工程研究计划（ERI）项目旨在研究一种特殊类型的合金，称为复杂浓缩合金（CCA）。CCA是最近发现的具有上级机械性能的材料。在高温下具有高强度的材料对于许多工程应用是非常期望的。CCA由多个主元素组成，包括高熵合金，其包含五个或更多的主元素。CCA已被研究为用于高温应用的潜在结构合金，例如热交换器、燃气涡轮机和核反应堆。通常，单相面心立方CCA在高温下具有低强度。同时，单相体心立方CCAs在室温下是脆性的。双相（面心立方和体心立方）CCA捕获了最好的特征。它们可以在室温下表现出良好的延展性，在高温下表现出高强度。然而，目前对双相CCA中的力学行为的理解是有限的。本计画旨在研究双相碳纤维复合材料在不同温度下的力学行为，并找出改善其强度的最佳方法。从这个项目中学到的知识可能会导致高温应用的双相CCA的设计。多学科研究将为研究生提供各种工程领域的多样化培训。本项目的目标是从根本上了解界面、微观结构和化学如何影响双相CCA从室温到高温的强度和变形性。具体而言，PI将（1）研究面心立方和体心立方CCAs的温度相关势垒强度之间的相互作用;（2）揭示界面对位错传输和相间塑性传递的作用;（3）阐明位错活动对双相CCAs断裂阻力的影响。为了解决这些科学问题，本项目将采用特定位置的纳米压痕来探测不同温度下双相CCA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。该项目的成果可以提供知识，以减轻脆性破坏的体心立方CCA在室温下通过接口和提高高温强度的双相CCA。该奖项反映了NSF的法定使命，并已被认为是值得支持的评估使用基金会的智力价值和更广泛的影响审查标准。

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.