Advanced Magnetic Materials for Energy and Power Conversion Applications: Developments in Rare-earth Free Permanent Magnets
Sponsored by: TMS Functional Materials Division, TMS: Magnetic Materials Committee
Program Organizers: Daniel Salazar, BCMaterials; Alex Leary, NASA Glenn Research Center; Markus Chmielus, University of Pittsburgh; Ryan Ott, Ames Laboratory; Arcady Zhukov, University of the Basque Country
Wednesday 2:00 PM
February 26, 2020
Room: Del Mar
Location: Marriott Marquis Hotel
Session Chair: Thomas Schrefl, Danube University Krems; Cajetan Ikenna Nlebedim, AMES Laboratory
2:00 PM Invited
A Brief Review of MnBi-based Hard Magnetic Materials: Jun Cui1; 1Iowa State University
The MnBi low temperature phase (LTP) is a promising permanent magnet material with theoretical maximum energy product (BH)Max 20 MGOe. The intrinsic coercivity (Hci) of LTP-MnBi exceeded 12 kOe and 26 kOe at 300 K and 523 K, respectively. LTP-MnBi has limitations. Obtaining with pure LTP-MnBi powders is difficult because of the drastic Mn-Bi peritectic reaction; Consolidating bulk magnet with high texture and full dense is difficult because of the 535K eutectic reaction of Bi and MnBi. Moreover, the saturation magnetization of MnBi is relatively low, less than 9 kG and 7 kG at 300 K and 523 K, respectively. To date, a bulk magnet with 11 MGOe and a composite film with 25 MGOe at 300 K have been fabricated. This talk reviews these efforts and highlights the important achievement, the key barrier that remains to be overcome, and possible approaches to optimize the properties for commercial applications.
2:30 PM Cancelled
Magnetic Properties, Microstructure and Phase Formation in Rare Earth Free MnAl-C Alloys: Thomas G. Woodcock1; 1IFW Dresden
The need to diversify the permanent magnets market with rare earth free alternatives is becoming more urgent as the wind power and hybrid/electric vehicle sectors expand. MnAl-C magnets, based on the τ-phase, have the potential to achieve energy products which would enable them to replace Nd-Fe-B bonded magnets, thus contributing to the long-term sustainability of rare earth magnet production. In order to estimate the upper limits for the energy product of MnAl-C magnets, the intrinsic magnetic properties of the t-phase must be known in detail. Recent results using high-field magnetometry will be presented. Achieving high energy products in Mn-Al-C alloys requires understanding and control of the microstructure. The various crystalline defects commonly observed in MnAl-C materials influence the magnetic properties and recent advances in defect characterisation will be presented along with an analysis of the change in magnetic properties and defect population at various processing steps.
3:00 PM
The Effect of Ti and Zr Additions on the Magnetic Properties and Microstructure of MnAl-C Alloys: Feng Le1; Kornelius Nielsch1; Thomas Woodcock1; 1Leibniz IFW Dresden
The intrinsic magnetic properties of the τ-phase in MnAl-C alloys show strong potential as a rare earth free permanent magnet. Previous works have indicated that Ti and Zr additions may enhance the magnetic properties of melt-spun MnAl and MnAl-C ribbons. The aim of this work is to investigate the effect of Ti and Zr additions on bulk MnAl-C samples in the homogenised, as-transformed and hot-deformed states. The samples were characterised with scanning and transmission electron microscopy and magnetometry. TiC or ZrC precipitates were shown to form and the effect of these on the chemical composition of the τ-phase, its magnetic properties and the flow stress during hot deformation was investigated.
3:20 PM
Investigation of the Long-Term Thermal Stability of the L10 Phase in Ternary Mn-Al-Ga Alloys: Torsten Mix1; Thomas Woodcock1; 1Leibniz IFW Dresden
The intrinsic magnetic properties of the ferromagnetic L10 phase in Mn-Al and Mn-Ga alloys make them promising candidates for rare earth free permanent magnets. In the Mn-Al system, the L10 phase is metastable and therefore high temperatures lead to decomposition. In the Mn-Ga system the L10 phase is thermodynamically stable; however, the global supply of Ga is critical and the raw materials costs are high. A possible solution to these problems may be offered by ternary Mn-Al-Ga alloys.Researches on the ternary alloys showed the possibility to form the L10 phase in a wide composition range with intrinsic magnetic properties comparable to the binary systems. The thermal stability of the L10 phases was investigated at 700°C in a series of heat treatments up to 14 days, showing that the thermal stability of the L10 phase in the Mn-Al system can be improved with small additions of Ga.
3:40 PM Break
4:00 PM Invited
Mn-based Permanent Magnets: from Thin Film Micromagnets to Bulk Magnets Obtained by Hot-pressing of Gas-atomized Powder: Carla Muñoz-Rodríguez1; Melek Villanueva1; Le Feng2; Elena H. Sánchez3; Javier Rial1; Julio Camarero1; Cristina Navío1; Ester M. Palmero1; Torsten Mix2; Thomas Woodcock2; Peter S. Normile3; José A. De Toro3; Alberto Bollero1; 1IMDEA Nanociencia; 2IFW Dresden, Institute of Metallic Materials; 3Instituto Regional de Investigación Científica Aplicada (IRICA) and Departamento de Física Aplicada, Universidad de Castilla-La Mancha
MnAl and MnBi are considered interesting permanent magnets (PMs) for several applications (energy, transport...). This presentation will show first the possibility of controlling the orientation of the magnetic anisotropy (perpendicular/parallel to the film plane) in high-coercive MnBi thin films [1] and, moreover, exploring the growth of single-crystal MnBi micromagnets. The second part will focus on tuning PM properties in MnAl(C) synthesized by gas-atomization and ultrafast-milling (30-270s) [2]. The resulting powder was used to produce polymer/PM composites for 3D-printing in the shape of high-quality continuous wire [3]. A different approach (hot-pressing) allowed us to prepare isotropic magnets (density: 94-98%) starting from ε-phase and managing, in a single-step, the ε-to-τ transformation and compaction. Both approaches will be discussed. [1] Villanueva, AIP Advances. 9, 035325 (2019) [2] Rial, Acta Mater. 157, 42 (2018) & Engineering. In press (2019)[3] Palmero, Sci. Technol. Adv. Mater. 19, 465 (2018)
4:30 PM Invited
Development of Enhanced Magnetic and Mechanical Properties of Alnico as a Rare Earth-free Permanent Magnet by Final-shape Powder Processing: Iver Anderson1; Emily Rinko1; Emma White1; Aaron Kassen2; Wei Tang1; Lin Zhou1; Timothy Prost1; Matthew Kramer1; 1Iowa State University / Ames Laboratory; 2Carpenter Technology Corporation
A lack of useful coercivity in alnico (Al-Ni-Co-Fe) magnets currently limits application in automotive traction drive motors, despite high temperature stability. Using enhanced alnico magnets to replace rare earth magnets, can decrease motor cooling needs and increase the motor’s efficiency. Conventional alnico magnet production involves directionally-solidified casting into special chill molds (high-cost/limited production) to achieve good second quadrant squareness, but insufficient coercivity limits their energy product at 180˚C to about 50% of Nd-Dy-Fe-B magnets for existing traction drives. Alternatively, full density pre-alloyed powder processed alnico magnets are mass production capable with increased coercivity, but have so-far achieved reduced energy products as isotropic fine-grained magnets, insufficient for drive motors. However, current results have shown that aligned microstructures with enhanced properties are accessible in alnico magnets by novel approaches during final shaping by compression molding and stress-biased secondary sintering. Funded by USDOE-EERE-VT-EDT program and USDOE-OTT-TCF program through Ames Lab contract no. DE-AC02-07CH11358.
5:00 PM Invited
Processing and Calorimetry of Alnico in High Magnetic Fields: Michael Kesler1; Xubo Liu2; Ikenna Nlebedim2; Matthew Kramer2; Orlando Rios1; Michael Mcguire1; 1Oak Ridge National Laboratory; 2Ames Laboratory
We have investigated the effects of thermomagnetic processing on directionally solidified alnico magnet materials in magnetic fields up to 9 T. The work employed large superconducting magnet systems fitted with induction furnaces and a custom calorimetry insert. Calorimetry measurements of alnico magnets were performed to study the effect of high magnetic fields and heating/cooling rates on thermal signatures of phase transformations, including solutionizing and spinodal decomposition, by cycling in the temperature range between 400 C and 1300 C at magnetic fields between zero and 9 T. Based on these results, heat treatments were performed (solutionizing, quenching, spinodal decomposition, and draw) in high magnetic fields to observed the effects on the resulting permanent magnet properties and microstructures as determined by magnetization measurements and electron microscopy.