Presentation Information
[O12-3]Hot compacted MnAl-type magnets: Bi-bonding and corrosion response
*Semih Ener1, Fernando Maccari1, Konstantin P. Skokov1, Oliver Gutfleisch1 (1. Functional Materials, Technical University of Darmstadt (Germany))
Keywords:
Rare-earth free magnets,Mn-Al
The Mn-Al-C system is a promising candidate for rare-earth-free permanent magnets due to its moderate magnetic performance, relatively low-cost fabrication, and sustainability. However, phase purity, optimization of extrinsic magnetic properties, and ensuring corrosion resistance remain critical challenges to be addressed for practical applications. In this study, we investigate the structural, magnetic, and corrosion properties of Mn-Al-C magnets processed by hot compaction, with an emphasis on their stability and performance under different environmental conditions.
The corrosion behavior was analyzed using voltammetry and aging tests in different media, revealing the sensitivity of Mn-Al-C magnets to alkaline and acidic conditions. Surprisingly, these materials showed significant corrosion resistance in aqueous environments, a promising result for applications where magnetic materials are exposed to moisture or aqueous conditions [1].
In the second part of the study, melt-spun Mn53.3-xAl45C1.7Tix (x = 0-1.5) samples were prepared where Ti doping resulted in an increase of the Curie temperature from 557 K to 600 K. Higher Ti concentrations resulted in an increase in the beta-phase fraction, which negatively affected the phase stability and overall magnetic performance.In addition, Mn-Al-C-Ti magnets consolidated with Bi as the metallic binder achieved coercivities up to 0.33 T while maintaining reasonable remanence. Bi was chosen because of its low melting temperature, which reduces the processing temperature required for consolidation, thereby reducing excessive beta-phase formation. In addition, Bi was considered for its potential to promote the formation of the MnBi phase, which could enhance magnetic properties by introducing magnetically harder grain boundary phases. Microstructural analysis showed that the addition of Bi improved densification without significantly altering the composition of the primary tau-phase; however, no traces of MnBi were observed in the structural analysis [2].
These results reinforce the potential of Mn-Al-C-based magnets for medium-performance applications where corrosion resistance and tunability of magnetic properties are essential. The incorporation of Ti and Bi offers a pathway to optimizing both intrinsic and extrinsic magnetic behavior, although further processing modifications are still necessary to achieve optimal performance as a permanent magnet.
This research was performed within the European Union Horizon 2020 research and innovation programme through the project PASSENGER (Pilot Action for Securing a Sustainable European Next Generation of Efficient RE-free magnets) under grant agreement No 101003914.
[1] U. Rocabert, M.A. Parnicki-Krollik, F. Maccari, N. Tankov, and S. Ener, ACS Omega 10 (2025), 683-691.
[2] J.S. Trujillo Hernández, F. Maccari, J.A. Tabares, K.P. Skokov, G.A. Pérez Alcázar,O. Gutfleisch and S. Ener, J. Magn. Magn. Mater. 610 (2024) 172573
The corrosion behavior was analyzed using voltammetry and aging tests in different media, revealing the sensitivity of Mn-Al-C magnets to alkaline and acidic conditions. Surprisingly, these materials showed significant corrosion resistance in aqueous environments, a promising result for applications where magnetic materials are exposed to moisture or aqueous conditions [1].
In the second part of the study, melt-spun Mn53.3-xAl45C1.7Tix (x = 0-1.5) samples were prepared where Ti doping resulted in an increase of the Curie temperature from 557 K to 600 K. Higher Ti concentrations resulted in an increase in the beta-phase fraction, which negatively affected the phase stability and overall magnetic performance.In addition, Mn-Al-C-Ti magnets consolidated with Bi as the metallic binder achieved coercivities up to 0.33 T while maintaining reasonable remanence. Bi was chosen because of its low melting temperature, which reduces the processing temperature required for consolidation, thereby reducing excessive beta-phase formation. In addition, Bi was considered for its potential to promote the formation of the MnBi phase, which could enhance magnetic properties by introducing magnetically harder grain boundary phases. Microstructural analysis showed that the addition of Bi improved densification without significantly altering the composition of the primary tau-phase; however, no traces of MnBi were observed in the structural analysis [2].
These results reinforce the potential of Mn-Al-C-based magnets for medium-performance applications where corrosion resistance and tunability of magnetic properties are essential. The incorporation of Ti and Bi offers a pathway to optimizing both intrinsic and extrinsic magnetic behavior, although further processing modifications are still necessary to achieve optimal performance as a permanent magnet.
This research was performed within the European Union Horizon 2020 research and innovation programme through the project PASSENGER (Pilot Action for Securing a Sustainable European Next Generation of Efficient RE-free magnets) under grant agreement No 101003914.
[1] U. Rocabert, M.A. Parnicki-Krollik, F. Maccari, N. Tankov, and S. Ener, ACS Omega 10 (2025), 683-691.
[2] J.S. Trujillo Hernández, F. Maccari, J.A. Tabares, K.P. Skokov, G.A. Pérez Alcázar,O. Gutfleisch and S. Ener, J. Magn. Magn. Mater. 610 (2024) 172573