Structure-Composition-Magnetostriction Correlations in Strong and Ductile Fe-Based Alloys with large Low-Field Magnetostriction

具有大低场磁致伸缩的强韧性铁基合金的结构-成分-磁致伸缩相关性

• 批准号: 0854166
• 负责人: Sivaraman Guruswamy
• 金额: $ 33万
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-03-15 至 2013-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0854166&HistoricalAwards=false
• 关键词: Structure; Composition; Magnetostriction; Correlations; Strong

TECHNICAL: This work examines the large enhancements in the magnetostriction of Fe with W and Mo additions, and how local atomic environment, short range ordering and structural defects can dramatically influence the magnetostriction in Fe-W, Fe-Mo, FeGa, and other alpha-Fe based magnetostrictive alloy single crystals. PI and co-workers have earlier shown that the addition of Ga to Fe results in a large increase in magnetostriction at low applied magnetic fields and that these alloys are strong and ductile. In a recent work, PI and coworkers have discovered a large increase in magnetostriction with W and Mo additions to Fe. The magnitude of magnetostrictive strain achieved in ductile Fe-4.4% W alloys, on a per atom basis, is comparable to that obtained in Fe-20 at.% Ga and Fe-27.5 at.% Ga alloy single crystals. Ongoing investigations also suggest that internal inhomogeneous strains introduced by the structural changes and defects play a much greater role than has been appreciated in determining the magnetostriction in these alloys. The long-term objectives are to gain an improved understanding of magnetostriction in Fe and Fe alloys and formulate the guidelines for the design of alloys with attractive magnetostrictive and mechanical properties. As a part of this effort, the work will focus on detailed examinations of (a) magnetostriction in bcc phase binary Fe-W and Fe-Mo alloy single crystals and the influence of ternary additions (b) the characterization of local atomic environments that shed light on near-neighbor interatomic distances and how they influence the magnetostriction in Fe alloys (c) how short range order is changed with thermal treatments and how it influences magnetostriction in Fe-W, Fe-Mo and Fe-Ga alloys, and (d) the effect of well-defined crystal defects and their distribution on magnetostriction. The defects to be examined include dislocation structures introduced with controlled single crystal deformation, and coherent second phases introduced through precipitation hardening treatments. The work envisaged involves alloy preparation by vacuum arc-melting, single crystal growth using Bridgman technique, structural evaluation, magnetic and magnetostriction measurements, and structure-composition-property correlations. Transmission electron microscopy will be used to characterize the defects. Extended X-ray absorption Fine Spectrum (EXAFS) measurements using a synchrotron radiation source will be used to probe the local atomic environments and determine the mean inter-atomic distances, coordination number and type of neighboring atom, and mean-square disorder of neighbor distance. Elastic measurements will be made using the resonance ultrasound spectroscopy technique. X-ray diffraction scans, rocking curve scans and X-ray topography measurements will be performed to assess the crystal orientation, short range order and the structural defects. NON-TECHNICAL: The work will further the knowledge that will enable the design and development of a new generation of inexpensive and high performance low-field magnetostrictive alloys for use in sensor and actuator applications. The work will (i) lead to Ph.D. dissertations of two graduate students, (ii) provide research opportunities for undergraduate and high school students, (iii) be used as an educational element to attract undergraduate students to metallurgical engineering, in particular women and underrepresented minority students, and (iv) enhance the undergraduate- and graduate-courses in Magnetic Materials, Metals Processing and Physical Metallurgy. Besides providing a basis for a more scientific understanding of magnetostriction in Fe alloys, this work will lead to the development of inexpensive and high performance alloys for use in acoustic sensors and actuators and magnetomechanical devices that are very rugged and of interest in a wide range of defense and commercial applications that would include nano-positioning devices, MEMS devices, sonar devices, active vibration damping devices, load and torque sensors, and electrical delay lines.

技术：本研究考察了添加W和Mo后Fe的磁致伸缩性能的显著增强，以及局部原子环境、短程有序和结构缺陷如何显著影响Fe-W、Fe-Mo、FeGa和其他α -Fe基磁致伸缩合金单晶的磁致伸缩性能。PI和同事们早些时候已经证明，在低外加磁场下，向Fe中加入Ga会导致磁致伸缩的大幅增加，并且这些合金具有很强的韧性。在最近的一项工作中，PI和他的同事们发现，在铁中加入W和Mo后，磁致伸缩会大大增加。在韧性Fe-4.4% W合金中获得的磁致伸缩应变的大小，在每个原子的基础上，与fe - 20at中获得的大小相当。% Ga和Fe-27.5 at。% Ga合金单晶。正在进行的研究还表明，由结构变化和缺陷引起的内部不均匀应变在确定这些合金的磁致伸缩方面的作用比人们所认识到的要大得多。长期目标是提高对铁和铁合金的磁致伸缩的理解，并制定具有吸引磁致伸缩和机械性能的合金设计指南。作为这项工作的一部分,工作重点是详细的考试(a)磁致伸缩在二进制Fe-W和bcc阶段Fe-Mo合金单晶和三元增加的影响(b)当地原子环境的特征,阐明近邻原子间的距离和它们如何影响铁的磁致伸缩合金(c)短程秩序是如何改变与热疗法,以及它如何影响磁致伸缩,Fe-W Fe-Mo Fe-Ga合金,(d)明确的晶体缺陷及其分布对磁致伸缩的影响。要检测的缺陷包括通过控制单晶变形引入的位错结构和通过沉淀硬化处理引入的相干第二相。设想的工作包括通过真空电弧熔炼制备合金，使用Bridgman技术生长单晶，结构评估，磁性和磁致伸缩测量以及结构-成分-性能相关性。透射电子显微镜将用于表征缺陷。利用同步辐射源的扩展x射线吸收精细光谱（EXAFS）测量将用于探测局部原子环境，确定原子间平均距离、相邻原子的配位数和类型以及相邻距离的均方无序度。弹性测量将使用共振超声光谱技术进行。通过x射线衍射扫描、摇摆曲线扫描和x射线形貌测量来评估晶体取向、近程有序和结构缺陷。非技术：这项工作将进一步的知识，将使设计和开发新一代廉价和高性能的低场磁致伸缩合金用于传感器和执行器的应用。这项工作将(1)促使两名研究生发表博士学位论文，(2)为本科生和高中生提供研究机会，(3)作为教育因素吸引本科生，特别是妇女和代表性不足的少数民族学生，以及(4)加强磁性材料、金属加工和物理冶金的本科和研究生课程。除了为更科学地理解铁合金的磁致伸缩提供基础之外，这项工作还将导致开发廉价和高性能的合金，用于声学传感器和执行器以及非常坚固的磁机械设备，并在广泛的国防和商业应用中感兴趣，包括纳米定位设备，MEMS设备，声纳设备，主动减振设备，负载和扭矩传感器。还有电气延迟线。