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Zhou L.,Ames Laboratory | Miller M.K.,Oak Ridge National Laboratory | Lu P.,Sandia National Laboratories | Ke L.,Ames Laboratory | And 11 more authors.
Acta Materialia | Year: 2014

A rare-earth supply crisis has stimulated an intensive search for alternative permanent magnets. Alnico materials, alloys containing Al, Ni, Co and Fe, are functional nanostructured alloys, which show great potential for replacing the best commercial Nd-based rare-earth alloys for applications above 200 °C. However, their coercivity is ∼2-3× below theoretical limits. The coercivity of alnico depends on the nanostructure developed during spinodal decomposition. In this work, atom probe tomography, combined with advanced electron microcopy, indicate that the microstructure of alnico is sensitive to the introduction of alloying elements such as Ti and Cu, as well as the crystallographic orientation of the parent phase with respect to the direction of the imposed magnetic field during spinodal decomposition. The alnico coercivity mechanism involves interplay of size, chemistry and possibly stress at interfaces. Control of these parameters should allow reduction of the spatial dimension of the FeCo-rich precipitates and the interaction between them, which should in term increase the coercivity of alnico alloys. © 2014 Published by Elsevier Ltd.

Palasyuk A.,Iowa State University | Blomberg E.,Iowa State University | Prozorov R.,Iowa State University | Yue L.,University of Nebraska - Lincoln | And 4 more authors.
JOM | Year: 2013

The magnetic domain structure of commercial alnico grades 5-7 and 9 was investigated using a magneto-optical Kerr effect (MOKE) to gain an understanding of their coercivity mechanisms at the micron to millimeter scale. In alnico 5-7, the magnetic domain structure exhibits stripes of alternating high and low induction. Magnetic domains easily cross grain boundaries if neighboring grains have a similar tilt and rotation of their crystallographic axes relative to the magnet body. In contrast for alnico 9, stripe-like magnetic domains are not observed regularly throughout the transverse section; rather, discrete localization of high- and low-induction stripe features are observed. In higher magnification MOKE experiments, i.e., ~100 μm, a zigzag-shaped magnetic domain structure was observed in both alnico 5-7 and 9. The zigzag features are four to five times smaller in size than an average grain of alnico 5-7, implying a pinning mechanism that is caused by structural elements within the grains. Discontinuous and reversible motion on a length scale of a few microns was observed for the zigzag-shaped domains for incremental changes in the applied field of ~10 Oe. Complimentary magnetic force microscopy measurements show that there are domain structures on an even smaller scale, i.e., 2 μm to 100 μm. © 2013 TMS (outside the USA).

Xing Q.,Ames Laboratory | Miller M.K.,Oak Ridge National Laboratory | Zhou L.,Ames Laboratory | Dillon H.M.,Ames Laboratory | And 4 more authors.
IEEE Transactions on Magnetics | Year: 2013

Insight into microstructural features in commercial alnico alloys is revealed through electron microscopy. Significant differences were found in the chemical make-up of the primary phases and their distributions for the different classes of the alloys. Changes in the Co+Fe:Al+Ni and minor alloying elements shift the matrix phase from an ordered B2 phase found in alnico 5-7 to a L2 1 phase found in alnico 8 and 9. The question whether the FeCo-rich phase has a B2 or body-centered cubic structure remains open. The grain-aligned 5-7 alloy shows a well ordered array of prismatic cells of the FeCo-rich phase that is 20-40 nm in width, 100's nm in length and epitaxial with the B2 matrix. Cu is uniformly distributed in the matrix phase for alnico 5-7 whereas for alnico 8 and 9, pure Cu precipitates locate along the phase boundaries. Ti-rich precipitates and non-spinodal FeCo-rich precipitates are observed. © 2013 IEEE.

Constantinides S.,Arnold Magnetic Technologies Corporation
Advances in Powder Metallurgy and Particulate Materials - 2014, Proceedings of the 2014 World Congress on Powder Metallurgy and Particulate Materials, PM 2014 | Year: 2014

Every commercially successful permanent magnet material since 1950 has been manufactured via powder metallurgy. Furthermore, the focus of current research into new magnetic materials is based on processes that require fine particulates at one or more stages of manufacture. Such products include exchange coupled hard and soft magnetic phases, unique metallurgical structures created at the atomic level and interstitial elements that can only be diffused over short distances typical of small particles, small diameter fibers or thin sheets. While forming particulates involves well-established practices, obtaining optimized exchange coupling is proving difficult. An even greater challenge is consolidation of the nanoparticulate into bulk magnetic structures while maintaining the nano-structure and introduction and maintenance of magnetic domain alignment.

Kramer M.J.,Iowa State University | McCallum R.W.,Iowa State University | Anderson I.A.,Iowa State University | Constantinides S.,Arnold Magnetic Technologies Corporation
JOM | Year: 2012

With the advent of high-flux density permanent magnets based on rare earth elements such as neodymium (Nd) in the 1980s, permanent magnet-based electric machines had a clear performance and cost advantage over induction machines when weight and size were factors such as in hybrid electric vehicles and wind turbines. However, the advantages of the permanent magnet-based electric machines may be overshadowed by supply constraints and high prices of their key constituents, rare earth elements, which have seen nearly a 10-fold increase in price in the last 5 years and the imposition of export limits by the major producing country, China, since 2010. We outline the challenges, prospects, and pitfalls for several potential alloys that could replace Nd-based permanent magnets with more abundant and less strategically important elements. © 2012 The Author(s).

Constantinides S.,Arnold Magnetic Technologies Corporation
Materials Research Society Symposium Proceedings | Year: 2013

The 20th century saw rapid and dramatic improvements in permanent magnet materials. It has been 31 years since the discovery of neodymium-iron-boron and numerous companies and laboratories are seeking to produce a new and superior material. Topics discussed herein are material options, economics of selected materials and market drivers in material selection. Market issues include manufacturability by shape, size, and material yield; raw material supply including cost and dependability of the supply chain; raw material and magnet product price stability; development of applications based on commercial needs, government legislation and consumer demand. "Need is the mother of invention" and no discussion would be complete without covering why a new material would be beneficial from an applications point of view especially in energy production and consumption. Therefore, an introduction will be provided for select, major applications using permanent magnets and the growth forecasts for these. © 2013 Materials Research Society.

Victoria P.I.,Rochester Institute of Technology | Yin W.,Arnold Magnetic Technologies Corporation | Gupta S.K.,Rochester Institute of Technology | Constantinides S.,Arnold Magnetic Technologies Corporation
ASME International Mechanical Engineering Congress and Exposition, Proceedings (IMECE) | Year: 2014

Samarium cobalt permanent magnets have been widely used for their excellent intrinsic magnetic properties such as very high Curie temperature, high anisotropy fields and most importantly excellent temperature coefficients of induction and coercivity. These materials have continuing industrial interest especially for applications operating at elevated temperatures and in the presence of high demagnetizing fields, such as particle accelerators, high frequency traveling wave tubes (TWTs), servo-motors and automotive and aerospace applications. An area of opportunity for improving performance of SmCo magnets is increasing magnet toughness-resistance to fracture. Like all other sintered rare earth magnetic materials, SmCo magnets are based on intermetallic compounds which are intrinsically brittle and can crack in the course of fabrication, machine work, and installation in the application. Increased toughness would also reduce handling sensitivity of magnetized magnets. For many years, studies on SmCo magnets have been focused on their magnetic properties, but the mechanical characteristics, strengthening and toughening mechanisms have been rarely reported. Understanding the phase and structural transformations induced in the SmCo magnets during the manufacturing process offers insight into potential modifications-chemical or processing-related. In this study, microstructural characterizations of 1:5 and 2:17 Sm-Co magnets were carried out using optical and scanning electron microscopes. In scanning electron microscopy (SEM), backscattered electron imaging and energy dispersive X-ray (EDX) microanalysis were used to investigate different phases and oxides. Finally, crystal structure of the magnets was studied using an X-ray diffractometer (XRD). The study correlates the microstructure characterization with the thermal processing history of different grades of SmCo magnets. Copyright © 2014 by ASME.

Arnold Magnetic Technologies Corporation | Date: 2013-05-14

Printable flexible plastic and rubber composite magnetic sheets for commercial and industrial use.

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