CAREER: New Solid State Metal Foams Using Oxide Reduction and Intraparticle Expansion

事业：利用氧化物还原和颗粒内膨胀的新型固态金属泡沫

• 批准号: 1555016
• 负责人: Mark Atwater
• 金额: $ 50.24万
• 依托单位: Millersville University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2016
• 资助国家: 美国
• 起止时间: 2016-06-01 至 2020-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1555016&HistoricalAwards=false
• 关键词: CAREER; New; Solid; State; Metal

Nontechnical DescriptionMetals are useful materials, as they are durable and easy to manufacture, but they have characteristically high densities which make them inefficient in many weight-sensitive applications. Their density can be reduced by introducing porosity, but porosity is also useful for increasing surface area, enhancing energy absorption, assisting bone ingrowth and more. Methods used to "foam" metals often require high temperatures, high pressures and/or complex processes, which limit the availability and cost-effectiveness of these materials. A new method has been developed to enhance porosity in metals at modest temperatures using simple, well-established powder metallurgy processes. The fundamental difference is that pores are developed within individual powder particles in the solid state, and this expandable metal powder can be incorporated into current, state-of-the-art foaming processes to enhance the level of porosity, or it can be used as a stand-alone process. This unique approach to creating porous metals may allow for cost reduction, the development of new metals and alloys for solid state foaming and the overall improvement of solid state foam processing. Both the fundamental mechanisms and commercial potential of this technology will be investigated to create a holistic understanding of the process and resulting materials. This technology can result in more fuel-efficient transit, safer vehicles, reduced emissions and much more. Through this work, educational awareness and career opportunities will be developed in partnership with the local community. This will involve establishing, promoting and expanding undergraduate research initiatives and promoting diversity in materials research and nanoscale technologies. Technical DescriptionA new method in the solid state foaming of metals has been developed using standard powder metallurgy processing. The technique involves two steps: (1) disperse oxides in a metal powder and (2) reduce oxides at a temperature sufficient to allow expansion. In general, mechanical milling can be used to create an oxide dispersion-strengthened (ODS) metal which is later foamed under hydrogen at elevated temperature via the formation of steam at oxide sites. The conditions under which this process is achieved depend on the oxide and matrix composition but are expected to be modest when compared to current foaming processes. This fundamentally different approach will allow for advances on three major fronts: (1) the ability to make metal foams with new compositions, (2) enhanced ability to control the structure and properties of the metal foam, and (3) the ability to combine this process with established powder metallurgy foaming methods to significantly increase the resulting porosity.This work will help to elucidate the fundamental mechanisms of this new method and has the potential to alleviate some of the critical issues plaguing solid state foaming. These issues include the complexity of processing, the lack of diversity in foamed metals and alloys and the modest porosities and/or mechanical properties achieved using current solid-state foaming methods. A number of fundamental research questions will be addressed, including: What is the influence of process variables, including reduction temperature, oxide chemistry, content and character, the microstructural properties of the matrix, and quantity and chemistry of process gas(es) on the pore formation process? What is the reduction and pore expansion behavior of multi-element systems, especially in which the elements possess greatly differing oxidation potentials? And what is the fundamental behavior of the ODS powder feedstock during bulk processing? A process map will be produced for creating metallic foams of a given porosity while independently controlling pore size, morphology and interconnectedness.This work will be conducted in a multi-scale manner, and an understanding of the nano- and micro-scale phenomena will be leveraged to inform processing decisions and methods by which to incorporate this feedstock into current, state-of-the-art methodologies. Educational initiatives will impact the university and community through increased collaboration internally and engaging local organizations to provide new opportunities for students to develop professionally. Expanded programs and opportunities in undergraduate research will be developed through this work, and outreach in the community will be conducted to help inform others of advanced materials and manufacturing as well as to inspire the future generation toward science and engineering.

金属是有用的材料，因为它们耐用且易于制造，但它们具有高密度的特点，这使得它们在许多重量敏感的应用中效率低下。它们的密度可以通过引入多孔性来降低，但多孔性也可用于增加表面积，增强能量吸收，辅助骨长入等。用于“发泡”金属的方法通常需要高温、高压和/或复杂的工艺，这限制了这些材料的可用性和成本效益。一种新的方法已经开发出来，以提高孔隙率的金属在适当的温度下使用简单，完善的粉末冶金工艺。根本区别在于，孔隙在固态的单个粉末颗粒内形成，并且这种可膨胀金属粉末可以被并入当前最先进的发泡工艺中以提高孔隙率水平，或者它可以用作独立的工艺。这种产生多孔金属的独特方法可以降低成本，开发用于固态发泡的新金属和合金，以及整体改进固态泡沫加工。这项技术的基本机制和商业潜力将被调查，以创造一个整体的理解过程和所得材料。这项技术可以带来更省油的运输，更安全的车辆，减少排放等等。通过这项工作，将与当地社区合作，提高教育意识和发展就业机会。这将涉及建立，促进和扩大本科研究计划，并促进材料研究和纳米技术的多样性。技术说明采用标准粉末冶金工艺开发了一种金属固态发泡的新方法。该技术包括两个步骤：（1）将氧化物分散在金属粉末中，（2）在足以允许膨胀的温度下还原氧化物。通常，机械研磨可用于产生氧化物分散强化（ODS）金属，其随后在高温下在氢气下通过在氧化物位点形成蒸汽而发泡。实现该方法的条件取决于氧化物和基质组成，但与当前的发泡方法相比，预期是适度的。这种根本不同的方法将在三个主要方面取得进展：（1）制造具有新组成的金属泡沫的能力，（2）控制金属泡沫的结构和性能的增强的能力，以及（3）将联合收割机与现有的粉末冶金发泡方法相结合，显著增加所得孔隙率的能力。这项工作将有助于阐明这种新的方法，并有可能减轻一些关键问题，固态发泡。这些问题包括加工的复杂性、泡沫金属和合金缺乏多样性以及使用当前固态发泡方法实现的适度孔隙率和/或机械性能。一些基本的研究问题将得到解决，包括：什么是工艺变量的影响，包括还原温度，氧化物化学，内容和字符，基体的微观结构特性，以及工艺气体的数量和化学（ES）上的孔隙形成过程？多元素体系的还原和孔扩张行为是什么，特别是在元素具有非常不同的氧化电位的情况下？耗氧物质粉末原料在批量加工过程中的基本行为是什么？将制作一个工艺图，用于制造给定孔隙率的金属泡沫，同时独立控制孔径、形态和互连性。这项工作将以多尺度方式进行，并将利用对纳米和微米尺度现象的理解来告知加工决策和方法，通过这些决策和方法将这种原料纳入当前最先进的方法中。教育举措将通过加强内部合作和让当地组织参与为学生提供专业发展的新机会来影响大学和社区。通过这项工作，将开发本科研究的扩展计划和机会，并将在社区中开展外联活动，以帮助向其他人介绍先进材料和制造，并激励下一代走向科学和工程。