SusChEM: Collaborative Research: The Role of Surface-Energy on Texture Development in Rare-Earth-Free Auxetic and Magnetostrictive Materials

SusChEM：合作研究：表面能对无稀土拉胀和磁致伸缩材料织构发展的作用

• 批准号: 1310447
• 负责人: Alison Flatau
• 金额: $ 45.4万
• 依托单位: University of Maryland, College Park
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2013
• 资助国家: 美国
• 起止时间: 2013-08-01 至 2016-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1310447&HistoricalAwards=false
• 关键词: SusChEM; Collaborative; Research; Role; Surface

TECHNICAL SUMMARYIn this project, the PIs advance understanding of the mechanisms that lead to grain-boundary mobility differences, texture development and abnormal growth of grains with a preferred texture/grain orientation in polycrystalline metals. They will use this understanding to develop low cost yet high-performance polycrystalline auxetic and/or magnetostrictive materials that are single-crystal-like. Their approach for this research will combine multiple-scale computational simulations, theoretical models and synergistically integrated insights gained from quantitative experimental studies of recrystallization, grain growth and texture development in rolled sheets of Fe-Ga (Galfenol) and Fe-Al (Alfenol) based binary and ternary alloys. Experiments will be used to explore relationships between anneal protocols and surface energy, grain mobility and texture development. Their hypothesis is that surface energy differences are the dominant driving force underlying the ability to selectively develop a grain structure and texture that is single-crystal-like. This hypothesis will be investigated by creating thermodynamic models of grain growth and texture development. In parallel, first-principle-based computational simulations and experimental studies of Galfenol and Alfenol will be conducted to aid in model formulation and validation, and to identify binary and ternary iron alloys with properties that should impart high auxeticity and/or magnetostriction in materials for which surface energy can be used to promote anisotropy development. This research is aligned with the SusChEM initiative through developing methods for processing magnetostrictive alloys that allow earth-abundant, inexpensive and benign chemicals, e.g. Al, Co, Ga, Mn and Sn, to be used as a replacement for expensive critical materials, the rare-earth elements such as Tb and Dy that comprise ~33at.% of Terfenol-D. The PIs will introduce a method for determining the surface energy of metal grains with a specific crystallographic orientation by tracking the contact angle of a drop of liquid gallium on grain surfaces of known orientation. This method overcomes shortcomings of existing methods, such as water-drop methods, that work for glass and polymeric surfaces with low surface energy and high-temperature destructive and/or creep-based methods that work for amorphous solids and samples for which isotropy is a reasonable approximation (e.g. highly polygranular samples).NON-TECHNICAL SUMMARY: This research will lead to the understanding needed to achieve the performance capabilities of costly single-crystal alloys in low-cost polycrystalline alloys. Models of atomic structure and energy-based models of crystal growth processes will be used to gain insights into how to control and target the selective growth of desired crystals at the expense of crystals with less favorable mechanical and/or magnetostrictive properties. The iron-aluminum and iron-gallium alloys that are one focus of this project have been targeted because of preliminary results that suggest they are good candidates for a sustainable alternative to magnetostrictive alloys used in industrial and defense applications that contain rare-earth elements like Terbium and Dysprosium. This research aligns well with the need for advances in the development of sustainable materials, as it focuses on methods for processing magnetostrictive alloys that allow earth-abundant, inexpensive and benign chemicals to be used as a replacement for expensive critical materials, the rare-earth elements that are both significantly more costly and significantly less abundant in the Earth's crust. The iron-aluminum and iron-gallium alloys to be studied are highly-auxetic, a mechanical property that is generally found in polymers but rarely in metals. The potential for high industrial impact of a structural auxetic alloy exists, as studies of non-structural auxetics (i.e. polymers) indicate that auxeticity can be used to enhance resistance to fracture and indentation. This research project will also support the training of postdoctoral, graduate and undergraduate students in modeling and processing anisotropic, rare-earth-free, single-crystal-like materials as well as in developing a new method for the measurement of surface energies of anisotropic solids. Students will disseminate research results in journal publications, conference papers and presentations. The team will mentor underrepresented (minority and women) high-school, undergraduate and graduate students under this project. The PIs will both continue to engage in on-going outreach to K-12 students.

技术总结在这个项目中，PI促进了对导致多晶金属中具有首选织构/颗粒取向的晶界迁移率差异、织构发展和异常生长的机制的理解。他们将利用这一认识来开发低成本但高性能的多晶拉伸和/或磁致伸缩材料，这些材料类似于单晶。他们的研究方法将结合多尺度计算模拟、理论模型和从Fe-Ga(Galfenol)和Fe-Al(Alfenol)基二元和三元合金轧制板材的再结晶、晶粒生长和织构发展的定量实验研究中获得的协同集成的见解。实验将被用来探索退火方案与表面能、颗粒迁移率和织构发展之间的关系。他们的假设是，表面能差异是有选择地形成类似单晶的颗粒结构和纹理的能力背后的主要驱动力。这一假设将通过建立颗粒生长和织构发展的热力学模型来进行研究。同时，将对Galfenol和Alfenol进行基于第一原理的计算模拟和实验研究，以帮助建立和验证模型，并确定具有应在材料中赋予高延展性和/或磁致伸缩性能的二元和三元铁合金，其表面能可用于促进各向异性发展。这项研究与SusChEM倡议保持一致，通过开发处理磁致伸缩合金的方法，允许使用丰富、廉价和无害的化学物质，如Al、Co、Ga、Mn和Sn，作为昂贵的关键材料的替代品，稀土元素如Tb和Dy占Terfenol-D的33at.%。PI将引入一种方法，通过跟踪液镓在已知取向的颗粒表面上的接触角来确定具有特定晶体取向的金属颗粒的表面能。这种方法克服了现有方法的缺点，如水滴法，这些方法适用于低表面能的玻璃和聚合物表面，以及高温破坏性和/或蠕变为基础的方法，适用于非晶态固体和各向同性合理近似的样品(例如，高度多颗粒的样品)。非技术摘要：这项研究将导致对在低成本多晶合金中实现昂贵单晶合金性能所需的理解。原子结构模型和基于能量的晶体生长过程模型将用于深入了解如何控制和定向选择性生长所需的晶体，同时牺牲机械和/或磁致伸缩性能较差的晶体。铁铝和铁镓合金是该项目的重点之一，因为初步结果表明，它们是工业和国防应用中磁致伸缩合金的可持续替代品的良好候选者，这些合金含有Tb和Dy等稀土元素。这项研究与在开发可持续材料方面取得进展的需要很好地一致，因为它侧重于处理磁致伸缩合金的方法，这些方法使地球丰富、廉价和无害的化学物质能够被用作昂贵的关键材料的替代品，而稀土元素在地壳中的成本要高得多，而丰度却要低得多。将要研究的铁-铝和铁-镓合金具有高度的延展性，这种机械性能通常在聚合物中存在，但在金属中很少。由于对非结构材料(即聚合物)的研究表明，结构材料的延展性可用于提高抗断裂和抗压痕能力，因此结构材料具有很高的工业应用潜力。该研究项目还将支持对博士后、研究生和本科生进行建模和处理各向异性、无稀土、类单晶材料以及开发测量各向异性固体表面能的新方法方面的培训。学生将在期刊出版物、会议论文和演讲中传播研究成果。该小组将在该项目下指导代表不足的(少数族裔和妇女)高中生、本科生和研究生。两位督学均会继续为幼稚园至幼稚园的学生提供外展服务。