Anisotropic bonded NdFeB magnets with radial oriented magnetization by 2-step warm compaction process

• Published in: Journal of alloys and compounds 2009-05, Vol.477 (1), p.510-514
• Main Authors: Tao, Siwu, Tian, Jianjun, Lu, Xin, Qu, Xuanhui, Honkura, Y., Mitarai, H., Noguchi, K.
• Format: Article
• Language: English
• Subjects: Anisotropic bonded NdFeB magnets; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Density; Exact sciences and technology; Magnetic properties; Magnetic properties and materials; Permanent magnets; Physics; Radial oriented magnetization; Studies of specific magnetic materials; Warm compaction
• ISSN: 0925-8388; 1873-4669
• DOI: 10.1016/j.jallcom.2008.10.119

Anisotropic bonded NdFeB magnets obviously have better magnetic properties than those of conventional isotropic bonded NdFeB magnets. The anisotropic bonded magnets can be used to make some magnetic devices with special oriented magnetization, such as radial oriented rings. In order to increase the magnetic properties and prolong the life of the molding die, the anisotropic bonded NdFeB magnets with radial oriented magnetization were prepared by 2-step warm compaction molding, which were called the aligning step and densifying step, respectively. In the aligning step, the magnetic powder particles aligned along the radial direction of the magnetic field (1.0 T) and are compressed under 143 MPa at 393 K. (BH) max and density of the magnets were 146 kJ/m 3 and 5.7 g/cm 3, respectively. Then the ring compacts were re-compressed under 800 MPa at 420 K in the densifying step. The density increased to 6.2 g/cm 3 and magnetic properties were: Br = 0.92 T, Hcj = 1020 kA/m, (BH) max = 168 kJ/m 3. SEM micrograph showed that the magnets had excellent microstructure and the magnetic particles were evenly coated by binder.