Advances in Magnetic Materials: Rare-earth Lean Permanent Magnets
Sponsored by: TMS Functional Materials Division, TMS: Magnetic Materials Committee
Program Organizers: Jose Maria Porro, BCMaterials; Huseyin Ucar, California Polytechnic University,Pomona; Patrick Shamberger, Texas A&M University; Min Zou, Lab Magnetics, A Quadrant Company; Gaoyuan Ouyang, Ames Laboratory; Alex Leary, NASA Glenn Research Center
Tuesday 8:00 AM
March 21, 2023
Room: 33A
Location: SDCC
Session Chair: Huseyin Ucar, California Polytechnic University, Pomona
8:00 AM Invited
Enhanced Powder-Processed Alnico Magnets by Novel Solid-State Engineering of the Microstructure and Nanostructure: Iver Anderson1; Emily Rinko1; Wei Tang1; Matthew Kramer1; Nicolas Argibay1; 1Iowa State University Ames Laboratory
Alnico rare earth-free magnets have valuable high temperature stability but lack the coercivity and energy product necessary for advanced motors/generators and actuators. Current supply/price pressure on Co motivated this work on abnormal grain growth (AGG), beneficial <001> texturing, and nano-structure alignment in Co-lean alnico. AGG was promoted by engineering a bi-modal starting powder size distribution to enable particle-assisted AGG (PA-AGG), with particles (~500 nm) from residual prior particle boundary oxides. Texturing was encouraged by imposing uniaxial compressive stress during vacuum sintering (1240C, 20h) of samples in an AGG-prone condition (90% dense) that retained grain growth driving force. Nano-structure alignment was attempted by novel tensile annealing during spinodal decomposition to enhance shape anisotropy and magnetic properties, instead of magnetic annealing. Results on grain size, texture evolution, and nanostructure will be reported, along with magnetic properties after standard magnetic annealing and draw cycles. Funded by KC-NSC through Ames Lab contract no. DE-AC02-07CH11358.
8:30 AM
Denitrogenation Process in ThMn12 Nitride by In Situ Neutron Powder Diffraction: Jose Maria Porro1; Alex Aubert2; Ines Puente-Orench3; Sorana Luca4; Jose Javier S. Garitaonandia5; Jose Manuel Barandiaran5; George C. Hadjipanayis6; 1BCMaterials & Ikerbasque; 2TU Darmstadt; 3Institut Laue Langevin; 4Univ. Grenoble Alpes, CEA LITEN; 5University of the Basque Country (UPV/EHU); 6University of Delaware
ThMn12 nitrides are good candidates for high performance permanent magnets. However, one of the remaining challenges is transfering the good properties of the powder into a bulk magnet. Thus, understanding the denitrogenation process of this phase is crucial. We investigate the magnetic and structural stability of (Nd0.75,Pr0.25)1.2Fe10.5Mo1.5Nx compounds (x=0 and 0.85) as function of temperature by neutron powder diffraction. Thermal dependence of the lattice parameters, formation of α-(Fe,Mo), and the nitrogen content in the nitrides are investigated by heating up to 1010 K. The decomposition takes place mainly via the formation of the α-(Fe,Mo) phase, which starts at around 900 K, whereas the nitrogen remains stable in the lattice. Additionally, we show that the magnetic properties of the nitrides are maintained after the thermal treatments up to 900 K. ThMn12 nitrides with Mo as stabilizing element offer good prospects for a bulk magnet provided an adequate processing route is found.
8:50 AM
Enhancing Stability and Magnetism of ThMn12-type Cerium-iron Intermetallics by Site Substitution: Churna Bhandari1; Durga Paudyal1; 1Ames Laboratory
We investigate the lattice stability and electronic, magnetic properties of Ti- or Zr-substituted CeFe12 and CeFe12N. We find negative formation-energy for all compositions in the bulk structure with respect to unaries except for CeFe12. The inclusion of nitrogen in the interstitial sites of CeFe12 improves its chemical stability by reducing the formation energy. The phonon frequencies including 4f-electrons indicate that all compositions are dynamically stable. We demonstrate that cerium exhibits the mixed-valence character in 1:12 materials. The mixed-valency sensibly affects the magneto-crystalline anisotropy (MCA) and magnetic moment. Nitrogen improves the net magnetic moment by influencing the spin-polarization with extra electrons, although it has the opposite effect in the MCA constant, K1. The predicted value confirms all compounds uniaxial along the crystalline c-axis. Especially for CeZrFe11, K1 is the largest in which Ce exhibits Ce3+(S=1/2) and Ce(4f) spin-density contour is elongated towards the uniaxial direction. This work is supported by CMI.
9:10 AM
Development of the Sintered (NdMM)-(FeCo)-B Based Magnets Substituted Nd by Less Critical Rare Earth (MM= La, Ce): Wei Tang1; Harshida Parmar1; Jing Wang1; Xubo Liu1; Ikenna Nlebedim1; Ryan Ott1; Scott McCall2; David Parker3; Jun Cui1; 1Ames National Laboratory; 2Lawrence Livermore National Laboratory; 3Oak Ridge National Laboratory
Replacing critical elements (Nd and Pr) in the RE2Fe14B-type magnet with less critical elements (La or Ce) has been intensively studied in the past ten years. However, the magnetic properties of the sintered magnets containing La or Ce are still much lower than the theoretical values predicted from the intrinsic properties of the La/Ce2Fe14 phase. The magnetic properties of a magnet are predominantly governed by its intrinsic properties and microstructures. In this work, the effects of La and Mischmetal substitution for Nd, on the magnetic properties and microstructures of the sintered (NdMM)-(Fe,Co)-B 2-14-1 typed-magnet (MM=La or Mischmetal) are investigated. PrCu and PrAlCu, as sintering aids, are applied to enhance the coercivity of the magnets by grain boundary diffusion technique. The magnetic property evolution of the magnets with annealing processed are systematically studied as well. The Hc and (BH)max achieved are 10 kOe and 32.4 MGOe, respectively.
9:30 AM Break
9:50 AM Invited
Grain Boundary Engineering for High Performance Heavy Rare-Earth Free Permanent Magnets: Matthew Kramer1; Wei Tang1; Gaoyuan Ouyang1; Jun Cui1; Iver Anderson1; 1Ames Laboratory
Widespread adoption of electric vehicles will require efficient high power density electric drive motors. The most efficient motors are based on permanent magnets (PM), 10 to 15% better than induction machines with comparable power. Meeting the projected demand for these electric vehicles (EV) with current Nd-based PM will require more than 2x increase in production by 2030 and at least 3x by 2040. However, Nd-Fe-B based magnets without heavy rare earth elements (HREE) have poor magnetic properties above 150°C, target operating temperature for most electric vehicles (EV). It is well established that the coercivity is sensitive to grain boundary structure, grain boundary chemistry, and grain size. We will discuss development of grain boundary engineering approaches to produce HREE free Nd-Fe-B magnets include grain boundary diffusion by doping with a low melting point compounds, and grain size reduction and techniques to passivate these fine grain-sized powders to increase operating temperatures.
10:20 AM
Towards One-step Castable Cerium-based Gap Magnet: Andriy Palasyuk1; Arne Swanson1; Matthew Besser1; 1Ames Laboratory
Cerium-based permanent magnets represent an alternative for supply dependent critical rare-earth (RE) magnets. They are domestic, versatile, process effective and less susceptible to supply disruptions. Our experiments show that these magnets easily achieve energy products (BH)max.of 15 – 20 MGOe because of their unique intra-granular coercivity mechanism that does not require typical powder metallurgy. The mechanism is regulated by the 2:7/5:19-type stacking faults and/or intercalated regions that appear in the matrix because of its reduced solubility at low temperatures. This opens potential for simple processing and/or advanced manufacturing. Our casting experiments show that (BH)max. beyond 15 MGOe, with Curie temperatures of >500 oC, remanent magnetizations >8.5 kG and coercivities >5 kOe, are achievable in one-step procedure that includes vacuum induction melting of kg-scale ingots with precisely controlled cooling process.