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Pan J.,Ningbo University | Zhang H.,Ningbo University | Liu X.,Ningbo University | Chen W.,Ningbo Zhaobao Magnet Co. | And 2 more authors.
Xiyou Jinshu Cailiao Yu Gongcheng/Rare Metal Materials and Engineering | Year: 2010

Anisotropic magnets were synthesized by spark plasma sintering Nd11Dy2Gd2Febal Al4.0Nb0.8Zr0.8B6 / Dy2O3 powder. The analyses of microstructure and magnetic property indicate that the sintering temperature determines the distribution of grain boundary phase in the magnets. After spark plasma sintering of 870°C, 12 min (40 MPa) followed by tempering of 970°C, 2 h + 600°C, 1 h, the average density of samples reaches 7.39 g/cm3, residual magnetization is 1.08 T, and intrinsic coercive force is 1181 kA · m-1. The coercivity of the SPSed magnet is smaller than that of traditional sintered magnet with the same compositions, which is attributed to the discontinuous distribution of grain boundary phases, obvious decrease of rare earth relative contents in grain boundary phase because of their loss during the process, and some non-equilibrium structures in them.

Sun Z.-Y.,Ningbo University | Pan J.,Ningbo University | Liu X.-C.,Ningbo University | Chen W.,Ningbo Zhaobao Magnet Co. | And 2 more authors.
Gongneng Cailiao/Journal of Functional Materials | Year: 2011

Nd(Dy, Gd)-Fe(Nb, Zr, Al, Cu)-B powder sintered magnets with 0.8at%Nb+0.9at%Zr or 1.5at%Nb+1.2at%Zr were prepared. The effects of Nb and Zr dopant content on the formation of intergranular phases and the relationship between the intergranular new phases and the coercivity have been investigated on the analysis basis of microstructures, micro-area compositions and magnetic properties of the magnets. The results show that, in the magnets with 0.8at%Nb+0.9at%Zr, a new grey boundary phase with high content of Nb and Zr elements is formed, accordingly the intrinsic coercive force of the magnets is 1900 kA/m. And in the magnets with 1.5at%Nb and 1.2at%Zr, in addition to the new grey boundary phase, a new kind of block NbFe phase with round or polygonal morphology, about 2 μm, appear in magnet boundaries. This makes the intrinsic coercive force of the magnets further increases to 2229.3 kA/m.

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