United States

thermal stability

nd-fe-b permanent magnets

micromagnetic simulations

microstructure

coercivity

It is our great pleasure to invite you to attend the 26th International Workshop on Rare Earth and Future Permanent Magnets and Their Applications (REPM2021) which will be held virtually on June 7-10, 2021. Please note, this is an updated schedule due to COVID-19 travel restrictions which forced us to postpone the conference from summer of 2020. The REPM workshop takes place every two years and is the premier conference on permanent magnets covering a wide range of topics including:

* Rare earth magnets
* Rare earth-free magnets
* Raw materials, mining and recycling
* Advanced synthesis, processing and characterization techniques
* Theoretical modeling of coercivity
* Fundamental properties of advanced magnetic materials
* Thin film magnets
* Applications of permanent magnets

***Workshop***
The workshop will be chaired by Professor George C. Hadjipanayis, University of Delaware, Newark, DE and Dr. Jinfang Liu, President & COO of Electron Energy Corporation, Landisville, PA.
The objectives of the workshop are to bring together engineers and scientists who work on permanent magnets and their applications to present their latest results and exchange ideas on a wide range of relevant topics including resources, raw materials, recycling, processing, fundamental and hard magnetic properties and applications of rare earth and future magnets.

To regsiter for this event, please follow the link below.

REPM 2021: The 26th International Workshop on Rare-Earth and Future Permanent Magnets and their Applications

Theoretical limit for the thermal stability of coercivity in the Nd-Fe-B based permanent magnets is thermal stability of anisotropic field of Nd2Fe14B phase. However, the temperature dependence of coercivity Hc(T), measured experimentally for anisotropic sintered as well as hot-deformed Nd-Fe-B magnets, does not follow the same linear behavior as HA(T) at the temperature range of 300-500 K but shows concave shape (Fig. 1(a)) [1-3]. Understanding the origin of the deviation of Hc(T) compare to HA(T) in the Nd-Fe-B based permanents can lead to improvement of the thermal stability of coercivity of Nd-Fe-B magnets which is important for the elevated temperature applications. 
We studied the temperature dependence of coercivity of anisotropic Nd-Fe-B magnet from 300-500K, by performing micromagnetic simulations that adapt the temperature dependent magnetic properties of both grain phase and GB phase reported experimentally. It was found that the poor temperature dependence of coercivity in the Nd-Fe-B sintered and hot-deformed magnets and its deviation from HA(T) originates from the temperature dependence of the magnetization of the ferromagnetic grain boundary phase. We demonstrated by micromagnetic simulations that modification of the grain boundary phase from ferromagnetic to non-ferromagnetic phase improves the thermal stability of coercivity (Fig. 2(b)). This was also demonstrated experimentally on the hot-deformed magnets in which modification of the Nd-rich GB phase changes the shape of Hc(T) closer to its theoretical limit which is HA(T) of Nd2Fe14B phase. Moreover, we found the magnetization of the grain boundary phase and its temperature dependence can break the linearity in the fitting of Hc/Ms vs. HA/Ms [4]. Hence, the values of α and Neff achieved in the fitting of experimental data in the Kronmüller equation can vary at different temperature range of 300-500K originating from GB magnetism and its temperature dependence which has been overlooked so far.

[1] H. Kronmüller, K.-D. Durst, M. Sagawa, J. Magn. Magn. Mater. 74 (1988) 291–302.
[2] R. Grössinger, et al. J. Magn. Magn. Mater. 51 (1985) 160–164.
[3] J. Li, X. Tang, H. Sepehri-Amin et al. Acta Mater. 187 (2020) 66–72.
[4] J. Li, X. Tang, H. Sepehri-Amin, et al. Acta Mater. 199 (2020) 288.


On the temperature-dependent coercivities of anisotropic Nd-Fe-B magnets

Structural refinement and magnetic properties of SmCo5-Cu nanocomposites after high pressure torsion

Heat magnetizing method for high-performance neodymium magnets (hot-deformed Nd-Fe-B magnets)

Doping effect of R80Al20 (R= Ce and Dy) alloy powders on the magnetic properties of hot-deformed NdFeB magnet with various reduction ratios

Revealing the mystery of the cases where Nd-Fe-B magnetic like poles attract each other

Short loop recycling process of NdFeB permanent magnets

Grain boundary infiltration in HDDR Nd2Fe14B magnets

Rapid consolidation of Nd-Fe-B-type powders as a useful tool for the manufacture of permanent magnets with additional functionalities

The Effect of Microstructure on the Hydrogen Ductilisation Process (HyDP) for NdFeB Alloys

Nd-Fe-Co-B permanent magnets for high temperature application: intrinsic properties, phase formation, microstructure engineering and coercivity mechanism

Improved coercivity and squreness in bulk hot-deformed magnets by two-step grain boundary diffusion process

poster

https://assets.underline.io/transcript/13885/subtitle/d43f6cbb1f172fe654493a1351863af1.vtt

English (automatic)

On the temperature-dependent coercivities of anisotropic Nd-Fe-B magnets

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Next from REPM 2021: The 26th International Workshop on Rare-Earth and Future Permanent Magnets and their Applications

Structural refinement and magnetic properties of SmCo5-Cu nanocomposites after high pressure torsion

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