Solid Solution Enhanced Synthesis of Multi-Principal Component Alloys via Oxide Reduction

通过氧化物还原固溶强化合成多主成分合金

• 批准号: 2217692
• 负责人: Helen Chan
• 金额: $ 71.91万
• 依托单位: Lehigh University
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2022
• 资助国家: 美国
• 起止时间: 2022-09-01 至 2026-08-31
• 项目状态: 未结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=2217692&HistoricalAwards=false
• 关键词: Solid; Solution; Enhanced; Synthesis; Multi

Non-technical SummaryMulti-principal component alloys (MPCAs) are a radical new class of alloys that consists of approximately equal mixtures of four or more metallic elements. These materials can possess novel and exciting combinations of physical properties. In particular, a sub-group of these alloys, so-called refractory MPCAs exhibit high temperature mechanical properties that surpass those of the alloys currently in use. The application of these new alloys in turbine engines could therefore result in higher efficiency and reduced greenhouse emissions. Current methods used to fabricate refractory MPCAs utilize extremely high temperatures, and can result in compositional variations within the alloy. This program seeks to explore a new process whereby the metallic alloy is produced by reducing a mixture of the metallic oxides. This is achieved by heat-treatment in a hydrogen environment. Not only is this a novel technique, but prior work has shown that it is possible to convert certain oxides that normally would be extremely stable. The research seeks to understand this unexpected aspect of the oxide reduction process. A rationale is suggested whereby the reduction is enhanced by the compositional environment. This model is tested by studying the reduction behavior of a range of MPCAs composed of different elemental combinations. Computer modelling is used to help identify alloy combinations with thermodynamic characteristics that show promise based on the model. These research findings could lead to enhanced processing of tailored MPCA compositions, with potential for significant societal impact in many technological areas, including energy storage and generation, transportation, and medical devices. Outreach activities relating to alloy design and forming focus on encouraging under-represented minorities to pursue opportunities in STEM fields, and to increase awareness of materials engineering amongst middle- and high-school students. Technical SummaryThe aim of this program is to develop a scientific framework for understanding the complex reduction behavior of a mixture of oxide materials, and hence establish composition-based strategies for the processing of technologically important multi-principal component alloys (MPCAs). This research builds on prior work that demonstrated that MPCAs can be fabricated via the reduction of a compacted metal-oxide mixture. Alloys composed of Co, Cr, Fe, Ni and Mn have been successfully synthesized by this route, using relatively mild heat-treatment conditions for which the reduction of MnO would not be expected. A model is proposed whereby the thermodynamic driving force for reduction is enhanced due to the formation of the alloy solid solution. Electronic structure calculations of the enthalpy of mixing guide the selection of elemental combinations for testing. The reduction behavior of these oxide compositions are studied under controlled conditions of temperature and oxygen partial pressure (pO2). The sequence of reactions and phase evolution is revealed by the characterization of partially reduced samples using scanning electron microscopy (SEM) and scanning transmission electron microscopy (STEM) techniques, as well as in-situ x-ray diffraction reduction studies using a synchrotron light source. Identification of the nucleation mechanisms of the metallic phases, role of transient phases, and rate-controlling transport mechanisms is of broad fundamental interest, and benefit related research on catalysis and oxygen looping. The enhanced processing of tailored MPCA compositions, both bulk and powder, is expedited by the development of the solid solution model, since it will help identify the heat treatment and compositional parameters that are critical to the process. The research also benefits the research community by generating Reduction-Composition diagrams for select MPCA elemental combinations. Outreach activities relating to alloy design and forming include CHOICES (Charting Horizons and Opportunities In Careers in Engineering and Science), which is dedicated to encouraging middle-school girls to consider careers in science and engineering, and the ASM Teacher and High School Materials Camps, designed to increase awareness of materials engineering amongst high school students.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.

非技术摘要元素合金合金（MPCAS）是一种根本的新合金，由四个或多个金属元件的大约相等的混合物组成。 这些材料可以具有物理特性的新颖而令人兴奋的组合。 特别是，这些合金，所谓的难治性MPCA的亚组具有高温机械性能，这些特性超过了当前使用的合金。 因此，这些新合金在涡轮发动机中的应用可能会导致更高的效率和降低的温室排放。 用于制造难治性MPCA的当前方法利用了极高的温度，并可能导致合金内的组成变化。 该程序试图探索一个新的过程，从而通过减少金属氧化物的混合物来产生金属合金。 这是通过在氢环境中进行的热处理来实现的。 这不仅是一种新颖的技术，而且先前的工作表明，可以转换某些通常会非常稳定的氧化物。 该研究试图了解氧化物还原过程的这一意外方面。 提出了一个理论，从而通过组成环境增强了还原。 通过研究由不同元素组合组成的一系列MPCA的还原行为来测试该模型。 计算机建模用于帮助识别具有热力学特性的合金组合，这些组合基于模型显示了希望。 这些研究发现可能会导致量身定制的MPCA组成的加工，并在许多技术领域（包括能源存储和发电，运输和医疗设备）中产生重大社会影响。 与合金设计有关的外展活动和构成专注于鼓励代表性不足的少数民族在STEM领域寻求机会，并提高对中学和高中生材料工程的认识。 技术总结该计划的目的是开发一个科学框架，以理解氧化物材料混合物的复杂还原行为，因此建立了基于组成的策略，以处理技术重要的多主体成分合金（MPCAS）。 这项研究基于先前的工作，表明可以通过减少压实的金属氧化物混合物来制造MPCA。 由该途径成功合成了由CO，CR，FE，NI和MN组成的合金，使用了相对温和的热处理条件，预计MNO的降低不会被预期。 提出了一个模型，由于合金固体溶液的形成，热力学驱动力增加了减少。 混合焓的电子结构计算指导测试元素组合的选择。 这些氧化物组成的还原行为是在温度和氧部分压（PO2）的受控条件下研究的。 通过使用扫描电子显微镜（SEM）和扫描透射电子显微镜（STEM）技术以及使用同步体光源的扫描电子显微镜（SEM）技术以及原位X射线衍射还原研究，通过扫描电子显微镜（SEM）和扫描透射电子显微镜（SEM）的样品表征来揭示了反应和相化的序列。 鉴定金属相的成核机制，瞬态相位的作用以及速率控制转运机制具有广泛的基本兴趣，并且对催化和氧气环的益处相关研究。 通过实心溶液模型的开发加快了量身定制的MPCA组成的加工，因为它将有助于识别热处理和对过程至关重要的组成参数。这项研究还通过为精选的MPCA元素组合生成还原组合图来使研究界受益。与合金设计和形成有关的外展活动包括选择（图表范围和工程和科学领域的职业机会），致力于鼓励中学女孩考虑科学和工程学的职业，以及ASM的教师和高中材料营地，旨在通过高中生的材料来提高对材料的认识，以表现出NSF的基础奖励，并反映出NSF的基础知识。更广泛的影响审查标准。