Investigation on the Improvement of Magnetic Properties by Hot Deformation Processes for NdFeB Magnets


Article Preview

Traditionally, NdFeB magnets with high remanent flux density or high energy product could only be manufactured through altering the material compounds. In recent years, studies indicated that the magnet properties of NdFeB magnets could be improved through plastic deformation. These studies pointed out that the degree of plastic deformation is a key factor to improve magnetic properties. However, there are still many other process parameters that could affect the magnetic properties either positively or negatively. In this paper, process parameters such as strain, strain rate, and temperature are studied to illustrate their influences on the magnetic properties of NdFeB magnets. The magnetic property could be greatly improved when the preferred orientation appears on the microstructure of deformed NdFeB magnets. One of the experimental results showed that the energy product value had been increased by 76.7% when the effective strain value had reached 0.65. Experimental results also showed that strain rate is a dominating factor with regard to the flow stress of material. Through a proper combination of these parameters, one can obtain NdFeB magnets with their magnetic properties greatly improved.



Edited by:

Yeong-Maw Hwang and Cho-Pei Jiang




Y. J. Chen et al., "Investigation on the Improvement of Magnetic Properties by Hot Deformation Processes for NdFeB Magnets", Key Engineering Materials, Vol. 626, pp. 317-322, 2015

Online since:

August 2014




* - Corresponding Author

[1] O. Gutfleisch, Controling the properties of high energy density permanent magnetic materials by different processing routes, J. Phys. D: Appl. Phys. 33 (2000) R157–R172.


[2] D. Brown, B.M. Ma, Z.M. Chen, Developments in the processing and properties of NdFeb type permanent magnets, J. Magn. Magn. Mater. 248 (2002) 432-440.


[3] R.W. Lee, Hot-pressed neodymium-iron-boron magnets, Appl. Phys. Lett. 46 (1985) 790-791.


[4] R.K. Mishra, Microstructure of hot-pressed and die-upset NdFeB magnets, J. Appl. Phys. 62 (1987) 967-971.


[5] R.K. Mishra, T.Y. Chu, L.K. Rabenberg, The development of the microstructure of die-upset Nd-Fe-B magnets, J. Magn. Magn. Mater. 84 (1990) 88-94.

[6] R.K. Mishra, V. Panchanathan, J.J. Croat, The microstructure of hot formed neodymium-iron-boron magnets with energy product 48 MGOe, J. Appl. Phys. 73 (1993) 6470-6472.


[7] W. Grunberger, D. Hinz, A. Kirchner, K.H. Muller, L. Schultz, Hot deformation of nanocrystalline Nd-Fe-B alloys, J. Alloy Compd. 257 (1997) 293-301.


[8] S. Liesert, A. Kirchner, W. Grunberger, A. Handstein, P. De Rango, D. Fruchart, L. Schultz, K.H. Muller, Preparation of anisotropic NdFeB magnets with different Nd contents by hot deformation (die-upsetting) using hot-pressed HDDR powders, J. Alloy Compd, 266 (1998).


[9] Y. Li, Y.B. Kim, M.J. Kim, M.S. Song, J.H. Yang, T.K. Kim, C.O. Kim, Anisotropic NdFeB magnet fabricated by single stroke hot deformation, J. Mater. Sci. Technol. 16 (2000) 129-130.

[10] Y. Li, Y.B. Kim, L.S. Wang, M.J. Kim, M.S. Song, J.H. Yang, D.S. Suhr, T.K. Kim, C.O. Kim, Taguchi Parameter Design for the Fabrication Process of Anisotropic NdFeB Magnet by Single Stroke Hot Deformation, J. Magn. 5 (2000) 106-109.


[11] H. Yamada, S. Nakayama, T. Iriyama, Effects of deformation temperature and strain on magnetic properties of hot deformed anisotropic NdFeB magnet material, Denki Seiko 73 (2002) 243-247.


[12] D. Lee, J.S. Hilton, C.H. Chen, M.Q. Huang, Y. Zhang, G.C. Hadjipanayis, S. Liu, Bulk Isotropic and Anisotropic Nanocomposite Rare-Earth Magnets, IEEE. T. Magn. 40 (2004) 2904-2906.


[13] K. Hioki, T. Takano, T. Yamamoto, Influence of process conditions on the magnetic properties for hot deformed magnets, Denki Seiko 79 (2008) 119-125.


[14] H.T. Kim, Y.B. Kim, H.S. Kim, Magnetic properties and texture of NdFeB magnets fabricated by current-applied-pressure-assisted process, J. Magn. Magn. Mater. 224 (2001) 173-179.


[15] Y.L. Huang, Z.W. Liu, X.C. Zhang, H.Y. Yu, X.X. Gao, J. Zhu, D.C. Zeng, Diffusion of Nd-rich phase in the spark plasma sintered and hot deformed nanocrystalline NdFeB magnets, J. Appl. Phys. 111 (2012) 033913.