Presentation Information
[O8-1]Rapidly Quenched Rare Earth Iron Boride Magnets
*DAVID Brown1 (1. University of Birmingham (UK))
Keywords:
rapidly quenched,nanocrystalline,bonded magnet,hit formed magnet
Rapidly quenched Nd-Fe-B magnet materials offer certain advantages over their fully dense anisotropic sintered rivals. This article aims to review the history and current status of nanocrystalline Nd-Fe-B magnetic materials.
It has been over 40 years since the concept of bonded and hot formed nanocrystalline Nd-Fe-B magnets emanated from the General Motors Research Laboratories in Warren, Michigan, USA [1]. Compression moulded magnets prepared from rapidly quenched stoichiometric Nd2Fe14B flakes found many applications in the burgeoning electronics and automation industries. One example was the spindle motor rotor in disc drives. Hot formed anisotropic magnets can be near net-shaped into many forms but found early success as radially aligned rings for automotive and industrial motor applications.
The supply of rapidly quenched NdFeB flake has been pioneered and dominated by Magnequench (China and Thailand). However, the manufacture of bonded magnets is being practiced across the globe, benefiting from the relatively low cost of manufacturing and niche applications that require net-shape formability, high electrical resistivity and bespoke magnetisation profiles.
Daido Electronics and others have pioneered the art of hot forming near net-shaped fully dense, anisotropic magnets from rapidly quenched Nd-Fe-B, and these have found applications where high coercivity and no heavy rare earths elements (Tb, Dy) have been a priority [2].
More recently, rapidly quenched Nd-Fe-B technology has been applied to short-loop recycling of scrap magnetic materials. Direct recycling presents some challenges over and above those of casting primary material, such as repeatable compositional control and contaminants from magnet coatings. However, the versatility of rapid quenching and moulding processes offers certain advantages to recycling scrap rare earth magnets. These advantages can include in-situ compositional adjustments, such as the addition of small amounts of refractory metals to the scrap feed for improved quenchability, grain refinement, flake morphology, powder compactability and ultimate magnet performance. Additionally, lower rare earth compositions can be produced to offer lower cost alternatives [3]. The ultimate challenge remaining for technologies like rapid quenching is the manufacture of exchange-spring nanocomposite structures with greater microstructural refinement than currently possible [4, 5].
[1] J. J. Croat, J.F. Herbst, R. W. Lee and F. E. Pinkerton, ‘Pr-Fe and Nd-Fe based materials: a new class of high-performance permanent magnets.’ J Appl Phys. Vol.55, No.6 (1984), p2078–2082
[2] H. Keiko, ‘High performance hot-deformed Nd-Fe-B magnets (Review).’ Science and Technology of Advanced Materials, Vol. 22, No. 1 (2021), 72–84
[3] S. Hirosawa, H. Kanekiyo, Y. Shigemoto, ‘Materials Properties and Utilization of Fe3B/Nd2Fe14B-Type Nanocomposite Permanent Magnets Based on Nd-Fe-Cr-Co-B.’ MRS Online Proceedings Library. Vol.577, (1999) 141–152
[4] E. F. Kneller, R. Hawig, ‘The exchange-spring magnet: a new material principle for permanent magnets.’ IEEE Trans. Magn., Vol.27 (1991), 3588
[5] R. Skomski and J. M. D. Coey, ‘Giant energy product in nanostructured two-phase magnets.’ Phys. Rev. B Vol.48, (1993), 15812
It has been over 40 years since the concept of bonded and hot formed nanocrystalline Nd-Fe-B magnets emanated from the General Motors Research Laboratories in Warren, Michigan, USA [1]. Compression moulded magnets prepared from rapidly quenched stoichiometric Nd2Fe14B flakes found many applications in the burgeoning electronics and automation industries. One example was the spindle motor rotor in disc drives. Hot formed anisotropic magnets can be near net-shaped into many forms but found early success as radially aligned rings for automotive and industrial motor applications.
The supply of rapidly quenched NdFeB flake has been pioneered and dominated by Magnequench (China and Thailand). However, the manufacture of bonded magnets is being practiced across the globe, benefiting from the relatively low cost of manufacturing and niche applications that require net-shape formability, high electrical resistivity and bespoke magnetisation profiles.
Daido Electronics and others have pioneered the art of hot forming near net-shaped fully dense, anisotropic magnets from rapidly quenched Nd-Fe-B, and these have found applications where high coercivity and no heavy rare earths elements (Tb, Dy) have been a priority [2].
More recently, rapidly quenched Nd-Fe-B technology has been applied to short-loop recycling of scrap magnetic materials. Direct recycling presents some challenges over and above those of casting primary material, such as repeatable compositional control and contaminants from magnet coatings. However, the versatility of rapid quenching and moulding processes offers certain advantages to recycling scrap rare earth magnets. These advantages can include in-situ compositional adjustments, such as the addition of small amounts of refractory metals to the scrap feed for improved quenchability, grain refinement, flake morphology, powder compactability and ultimate magnet performance. Additionally, lower rare earth compositions can be produced to offer lower cost alternatives [3]. The ultimate challenge remaining for technologies like rapid quenching is the manufacture of exchange-spring nanocomposite structures with greater microstructural refinement than currently possible [4, 5].
[1] J. J. Croat, J.F. Herbst, R. W. Lee and F. E. Pinkerton, ‘Pr-Fe and Nd-Fe based materials: a new class of high-performance permanent magnets.’ J Appl Phys. Vol.55, No.6 (1984), p2078–2082
[2] H. Keiko, ‘High performance hot-deformed Nd-Fe-B magnets (Review).’ Science and Technology of Advanced Materials, Vol. 22, No. 1 (2021), 72–84
[3] S. Hirosawa, H. Kanekiyo, Y. Shigemoto, ‘Materials Properties and Utilization of Fe3B/Nd2Fe14B-Type Nanocomposite Permanent Magnets Based on Nd-Fe-Cr-Co-B.’ MRS Online Proceedings Library. Vol.577, (1999) 141–152
[4] E. F. Kneller, R. Hawig, ‘The exchange-spring magnet: a new material principle for permanent magnets.’ IEEE Trans. Magn., Vol.27 (1991), 3588
[5] R. Skomski and J. M. D. Coey, ‘Giant energy product in nanostructured two-phase magnets.’ Phys. Rev. B Vol.48, (1993), 15812