Equal Channel Angular Extrusion (ECAE) Processing of Tau-MnAl Magnets

Tau-MnAl 磁体的等通道角挤压 (ECAE) 加工

• 批准号: 1852529
• 负责人: Ian Baker
• 金额: $ 41.89万
• 依托单位: Dartmouth College
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2019
• 资助国家: 美国
• 起止时间: 2019-04-01 至 2023-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1852529&HistoricalAwards=false
• 关键词: Equal; Channel; Angular; Extrusion; ECAE

Demand for high-performance permanent magnets is increasing rapidly for applications such as wind turbine generators and motors in both electric and hybrid cars. This market is served by rare earth (RE) magnets based on neodymium-iron-boron and samarium-cobalt. RE magnets are not without issues; they can chip, suffer thermal shock, and can suffer grain boundary corrosion. However, their biggest problems are: price volatility; that China largely controls the RE metals market; and that the extraction of RE metals creates severe environmental degradation. The compound MnAl has been of interest as a permanent magnet since the early 1960s. It has a theoretical energy product (a measure of its magnetic strength) between that of traditional AlNiCo magnets and RE magnets with a value comparable to that of bonded neodymium-iron-boron magnets. Further, it does not suffer from the issues associated with RE magnets, and potentially has the lowest cost per unit energy product of any permanent magnet. The magnetic properties of MnAl are affected by the numerous types of defects present, but how these defects affect the magnetic properties and under what conditions these defects occur is unknown. In this project, we will determine both the conditions under which defects and second phases form during processing of MnAl and how these control the magnetic properties. The expectation is that superior magnetic properties can be obtained by carefully manipulating the defect structure. While the work focuses on MnAl, understanding the relationship between the occurrence of defects, their production and their relationship to the magnetic properties in MnAl will be useful for understanding similar behavior in the related compounds MnBi, MnGa, NiFe, PtFe and CoPt, all of which are of interest as hard magnets. The project includes the training of both a Ph.D. student and several undergraduates in state-of-the-art techniques.Tau-MnAl is a metastable phase that transforms from the high temperature epsilon phase, during which anti-phase boundaries (APBs), twins, stacking faults and dislocations are created. Depending on the processing conditions, the equilibrium beta and gamma 2 phases can also form. The fundamental difficulty with improving the magnetic properties of tau-MnAl is that there is no clear understanding on how they depend on the defect structure. The grain size can also influence the magnetic properties either directly or by affecting the beta and gamma 2 phases arrangement and defect formation. Our aim is to understand both the conditions under which APBs, twins, stacking faults, dislocations and second phases form during processing of tau-MnAl and how these control the magnetic properties. The local chemistry will also be explored at high resolution using atom probe tomography via collaboration with Dr. Baptiste Gault, Max-Planck-Institut fur Eisenforschung, Germany. Our working hypothesis is that we need a strong, c-axis alignment and a low density of APBs, twins and stacking faults (which locally disorder the material) for a high saturation magnetization, while a low density of APBs, twins and stacking faults but a high dislocation density are required for a high coercivity. It is thought that a fine distribution of beta and gamma 2 phases will also contribute to a high coercivity through magnetic domain wall pinning. While the work focuses on MnAl, understanding the relationship between the occurrence of defects, their production and their relationship to the magnetic properties in MnAl will be useful for understanding similar behavior in the related compounds MnBi, MnGa, NiFe, PtFe and CoPt, all of which are of interest as hard magnets. The project will include training of both a Ph.D. student and several undergraduates in state-of-the-art techniques.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.

高性能永久磁铁的需求正在迅速增加，例如电动涡轮机发电机和电动机中的电动机和电动机中的电动机的需求。这个市场由基于新近铁 - 孔子和萨玛群岛的稀土（RE）磁铁服务。磁铁并非没有问题；它们可以芯片，遭受热冲击，并可能遭受晶界腐蚀。但是，他们最大的问题是：价格波动；中国在很大程度上控制着重金属市场； Re金属的提取会造成严重的环境降解。自1960年代初以来，该复合物作为永久磁铁感兴趣。它在传统的Alnico磁铁和RE磁铁之间具有理论能量产物（量度的磁强度），其值与粘合的新近铁磁体磁铁相当。此外，它不会遭受与RE磁铁相关的问题的困扰，并且可能具有任何永久磁铁的每单位能量产品成本最低。 MNAL的磁性特性受到存在的多种缺陷的影响，但是这些缺陷如何影响磁性特性，在什么条件下，这些缺陷发生的情况尚不清楚。在这个项目中，我们将确定在MNAL处理过程中缺陷和第二阶段形成的条件以及它们如何控制磁性特性。期望是可以通过仔细操纵缺陷结构来获得优质磁性。尽管这项工作的重点是MNAL，但了解缺陷的发生之间的关系，它们的产生和与MNAL中的磁性的关系对于理解相关化合物MNBI，MNGA，Nife，PTFE和COPT中的相似行为有用，所有这些行为都作为硬磁铁感兴趣。该项目包括同时培训A博士学位。学生和最先进技术的几个大学生。TAU-MNAL是一个可稳态的阶段，它从高温EPSILON阶段转变为反相边界（APB），双胞胎，双胞胎，堆叠断层和错位。根据处理条件，平衡β和伽马2阶段也可能形成。改善tau-mnal的磁性特性的基本困难是，对它们如何依赖缺陷结构没有明确的了解。晶粒尺寸还可以直接或通过影响β和伽马2相的布置和缺陷形成来影响磁性。我们的目的是了解在tau-mnal加工过程中形成的APB，双胞胎，堆叠断层，位错和第二阶段的条件以及它们如何控制磁性特性。还将通过与德国Max-Planck-Institut Fur Eisenforschung的Baptiste Gault博士合作，使用ATOM探针层析成像在高分辨率上进行局部化学。我们的工作假设是，我们需要强，C轴比对，而高密度的APB，双胞胎和堆叠断层（局部使材料无序）具有高饱和度磁化，而低密度的APB，双胞胎和堆叠断层则需要高脱位密度才能高率高。据认为，β和伽马2阶段的精细分布也将通过磁性域壁钉钉造成高的矫正性。尽管这项工作的重点是MNAL，但了解缺陷的发生之间的关系，它们的产生和与MNAL中的磁性的关系对于理解相关化合物MNBI，MNGA，Nife，PTFE和COPT中的相似行为有用，所有这些行为都作为硬磁铁感兴趣。该项目将包括培训同时的博士学位。该奖项反映了NSF的法定任务，并被认为是值得通过基金会的知识分子优点和更广泛的影响标准来评估值得支持的。

项目成果

Manganese-based permanent magnet materials

• DOI: 10.1016/j.pmatsci.2021.100872
• 发表时间: 2021-09
• 期刊: Progress in Materials Science
• 影响因子: 37.4
• 作者: Thomas Keller;I. Baker

The phase transformation behavior of Mn-Al rare-earth-free permanent magnets

• DOI: 10.1016/j.jmmm.2023.171331
• 发表时间: 2023-09
• 期刊: Journal of Magnetism and Magnetic Materials
• 影响因子: 2.7
• 作者: Thomas Keller;Dylan Barbagallo;Natalya Sheremetyeva;Tushar Kanti Gosh;Katherine S. Shanks;G. Hautier;Ian Baker