Current progress and future challenges in rare-earth-free permanent magnets

Jun Cui, Matthew Kramer, Lin Zhou, Fei Liu, Alexander Gabay, George Hadjipanayis, Balamurugan Balasubramanian, David Sellmyer

Research output: Contribution to journalReview article

35 Citations (Scopus)

Abstract

Permanent magnets (PM) are critical components for electric motors and power generators. Key properties of permanent magnets, especially coercivity and remanent magnetization, are strongly dependent on microstructure. Understanding metallurgical processing, phase stability and microstructural changes are essential for designing and improving permanent magnets. The widely used PM for the traction motor in electric vehicles and for the power generator in wind turbines contain rare earth elements Nd and Dy due to their high maximum energy product. Dy is used to sustain NdFeB's coercivity at higher temperature. Due to the high supply risk of rare earth elements (REE) such as Dy and Nd, these elements are listed as critical materials by the U.S. Department of Energy and other international institutes. Other than Dy, finer grain size is also found to have effect on sustaining coercivity at higher temperature. A proper control of phase stability and microstructures has direct impact on mitigating REE supply risk. Compared to rare earth PMs, non-rare earth (non-RE) PMs typically have lower maximum energy products, however, given their small supply risks and low cost, they are being intensively investigated for less-demanding applications. The general goal for the development of non-RE PMs is to fill in the gap between the most cost-effective but low performing hard ferrite magnet and the most expensive but high performing RE PMs. In the past five years great progress has been made toward improving the microstructure and physical properties of non-RE PMs. Several new candidate materials systems were investigated, and some have showed realistic potential for replacing RE PMs for some applications. In this article, we review the science and technology of various types of non-RE materials for PM applications. These materials systems include Mn based, high magnetocrystalline anisotropy alloys (MnBi and MnAl compounds), spinodally decomposing alloys (Alnico), high-coercivity tetrataenite L10 phase (FeNi and FeCo), and nitride/carbide systems (such as α” based, high saturation magnetization Fe16N2 type phase and Co2C/Co3C acicular particle phase). The current status, challenges, potentials as well as the future directions for these candidates non-RE magnet materials are discussed.

Original languageEnglish (US)
Pages (from-to)118-137
Number of pages20
JournalActa Materialia
Volume158
DOIs
StatePublished - Oct 1 2018

Fingerprint

Rare earths
Permanent magnets
Coercive force
Earth (planet)
Rare earth elements
Phase stability
Microstructure
Magnets
Strategic materials
Magnetocrystalline anisotropy
Traction motors
Electric motors
Saturation magnetization
Electric vehicles
Nitrides
Wind turbines
Ferrite
Carbides
Costs
Magnetization

Keywords

  • Alnico
  • CoC
  • CoC
  • FeN
  • HfCo and ZrCo
  • L1 FeCo
  • L1 FeNi
  • MnAl
  • MnBi
  • Permanent magnet
  • Rare-earth-free

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

Cite this

Current progress and future challenges in rare-earth-free permanent magnets. / Cui, Jun; Kramer, Matthew; Zhou, Lin; Liu, Fei; Gabay, Alexander; Hadjipanayis, George; Balasubramanian, Balamurugan; Sellmyer, David.

In: Acta Materialia, Vol. 158, 01.10.2018, p. 118-137.

Research output: Contribution to journalReview article

Cui, J, Kramer, M, Zhou, L, Liu, F, Gabay, A, Hadjipanayis, G, Balasubramanian, B & Sellmyer, D 2018, 'Current progress and future challenges in rare-earth-free permanent magnets', Acta Materialia, vol. 158, pp. 118-137. https://doi.org/10.1016/j.actamat.2018.07.049
Cui J, Kramer M, Zhou L, Liu F, Gabay A, Hadjipanayis G et al. Current progress and future challenges in rare-earth-free permanent magnets. Acta Materialia. 2018 Oct 1;158:118-137. https://doi.org/10.1016/j.actamat.2018.07.049
Cui, Jun ; Kramer, Matthew ; Zhou, Lin ; Liu, Fei ; Gabay, Alexander ; Hadjipanayis, George ; Balasubramanian, Balamurugan ; Sellmyer, David. / Current progress and future challenges in rare-earth-free permanent magnets. In: Acta Materialia. 2018 ; Vol. 158. pp. 118-137.
@article{968edf0f20204fe18b03e194166df5dc,
title = "Current progress and future challenges in rare-earth-free permanent magnets",
abstract = "Permanent magnets (PM) are critical components for electric motors and power generators. Key properties of permanent magnets, especially coercivity and remanent magnetization, are strongly dependent on microstructure. Understanding metallurgical processing, phase stability and microstructural changes are essential for designing and improving permanent magnets. The widely used PM for the traction motor in electric vehicles and for the power generator in wind turbines contain rare earth elements Nd and Dy due to their high maximum energy product. Dy is used to sustain NdFeB's coercivity at higher temperature. Due to the high supply risk of rare earth elements (REE) such as Dy and Nd, these elements are listed as critical materials by the U.S. Department of Energy and other international institutes. Other than Dy, finer grain size is also found to have effect on sustaining coercivity at higher temperature. A proper control of phase stability and microstructures has direct impact on mitigating REE supply risk. Compared to rare earth PMs, non-rare earth (non-RE) PMs typically have lower maximum energy products, however, given their small supply risks and low cost, they are being intensively investigated for less-demanding applications. The general goal for the development of non-RE PMs is to fill in the gap between the most cost-effective but low performing hard ferrite magnet and the most expensive but high performing RE PMs. In the past five years great progress has been made toward improving the microstructure and physical properties of non-RE PMs. Several new candidate materials systems were investigated, and some have showed realistic potential for replacing RE PMs for some applications. In this article, we review the science and technology of various types of non-RE materials for PM applications. These materials systems include Mn based, high magnetocrystalline anisotropy alloys (MnBi and MnAl compounds), spinodally decomposing alloys (Alnico), high-coercivity tetrataenite L10 phase (FeNi and FeCo), and nitride/carbide systems (such as α” based, high saturation magnetization Fe16N2 type phase and Co2C/Co3C acicular particle phase). The current status, challenges, potentials as well as the future directions for these candidates non-RE magnet materials are discussed.",
keywords = "Alnico, CoC, CoC, FeN, HfCo and ZrCo, L1 FeCo, L1 FeNi, MnAl, MnBi, Permanent magnet, Rare-earth-free",
author = "Jun Cui and Matthew Kramer and Lin Zhou and Fei Liu and Alexander Gabay and George Hadjipanayis and Balamurugan Balasubramanian and David Sellmyer",
year = "2018",
month = "10",
day = "1",
doi = "10.1016/j.actamat.2018.07.049",
language = "English (US)",
volume = "158",
pages = "118--137",
journal = "Acta Materialia",
issn = "1359-6454",
publisher = "Elsevier Limited",

}

TY - JOUR

T1 - Current progress and future challenges in rare-earth-free permanent magnets

AU - Cui, Jun

AU - Kramer, Matthew

AU - Zhou, Lin

AU - Liu, Fei

AU - Gabay, Alexander

AU - Hadjipanayis, George

AU - Balasubramanian, Balamurugan

AU - Sellmyer, David

PY - 2018/10/1

Y1 - 2018/10/1

N2 - Permanent magnets (PM) are critical components for electric motors and power generators. Key properties of permanent magnets, especially coercivity and remanent magnetization, are strongly dependent on microstructure. Understanding metallurgical processing, phase stability and microstructural changes are essential for designing and improving permanent magnets. The widely used PM for the traction motor in electric vehicles and for the power generator in wind turbines contain rare earth elements Nd and Dy due to their high maximum energy product. Dy is used to sustain NdFeB's coercivity at higher temperature. Due to the high supply risk of rare earth elements (REE) such as Dy and Nd, these elements are listed as critical materials by the U.S. Department of Energy and other international institutes. Other than Dy, finer grain size is also found to have effect on sustaining coercivity at higher temperature. A proper control of phase stability and microstructures has direct impact on mitigating REE supply risk. Compared to rare earth PMs, non-rare earth (non-RE) PMs typically have lower maximum energy products, however, given their small supply risks and low cost, they are being intensively investigated for less-demanding applications. The general goal for the development of non-RE PMs is to fill in the gap between the most cost-effective but low performing hard ferrite magnet and the most expensive but high performing RE PMs. In the past five years great progress has been made toward improving the microstructure and physical properties of non-RE PMs. Several new candidate materials systems were investigated, and some have showed realistic potential for replacing RE PMs for some applications. In this article, we review the science and technology of various types of non-RE materials for PM applications. These materials systems include Mn based, high magnetocrystalline anisotropy alloys (MnBi and MnAl compounds), spinodally decomposing alloys (Alnico), high-coercivity tetrataenite L10 phase (FeNi and FeCo), and nitride/carbide systems (such as α” based, high saturation magnetization Fe16N2 type phase and Co2C/Co3C acicular particle phase). The current status, challenges, potentials as well as the future directions for these candidates non-RE magnet materials are discussed.

AB - Permanent magnets (PM) are critical components for electric motors and power generators. Key properties of permanent magnets, especially coercivity and remanent magnetization, are strongly dependent on microstructure. Understanding metallurgical processing, phase stability and microstructural changes are essential for designing and improving permanent magnets. The widely used PM for the traction motor in electric vehicles and for the power generator in wind turbines contain rare earth elements Nd and Dy due to their high maximum energy product. Dy is used to sustain NdFeB's coercivity at higher temperature. Due to the high supply risk of rare earth elements (REE) such as Dy and Nd, these elements are listed as critical materials by the U.S. Department of Energy and other international institutes. Other than Dy, finer grain size is also found to have effect on sustaining coercivity at higher temperature. A proper control of phase stability and microstructures has direct impact on mitigating REE supply risk. Compared to rare earth PMs, non-rare earth (non-RE) PMs typically have lower maximum energy products, however, given their small supply risks and low cost, they are being intensively investigated for less-demanding applications. The general goal for the development of non-RE PMs is to fill in the gap between the most cost-effective but low performing hard ferrite magnet and the most expensive but high performing RE PMs. In the past five years great progress has been made toward improving the microstructure and physical properties of non-RE PMs. Several new candidate materials systems were investigated, and some have showed realistic potential for replacing RE PMs for some applications. In this article, we review the science and technology of various types of non-RE materials for PM applications. These materials systems include Mn based, high magnetocrystalline anisotropy alloys (MnBi and MnAl compounds), spinodally decomposing alloys (Alnico), high-coercivity tetrataenite L10 phase (FeNi and FeCo), and nitride/carbide systems (such as α” based, high saturation magnetization Fe16N2 type phase and Co2C/Co3C acicular particle phase). The current status, challenges, potentials as well as the future directions for these candidates non-RE magnet materials are discussed.

KW - Alnico

KW - CoC

KW - CoC

KW - FeN

KW - HfCo and ZrCo

KW - L1 FeCo

KW - L1 FeNi

KW - MnAl

KW - MnBi

KW - Permanent magnet

KW - Rare-earth-free

UR - http://www.scopus.com/inward/record.url?scp=85050825065&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85050825065&partnerID=8YFLogxK

U2 - 10.1016/j.actamat.2018.07.049

DO - 10.1016/j.actamat.2018.07.049

M3 - Review article

AN - SCOPUS:85050825065

VL - 158

SP - 118

EP - 137

JO - Acta Materialia

JF - Acta Materialia

SN - 1359-6454

ER -