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Resource-saving (PrNdCe) 2 Fe 14 B sintered magnets with nominal composition (PrNd) 15−x Ce x Fe 77 B 8 (x = 0-10) were prepared using a dual alloy method by mixing (PrNd) 5 Ce 10 Fe 77 B 8 with (PrNd) 15 Fe 77 B 8 powders. For Ce atomic percent of 1% and 2%, coercivity decreases dramatically. With further increase of Ce atomic percent, the coercivity increases, peaks at 6.38 kOe in (PrNd) 11 Ce 4 Fe 77 B 8 , and then declines gradually. The abnormal dependence of coercivity is likely related to the inhomogeneity of rare earth chemical composition in the intergranular phase, where PrNd concentration is strongly dependent on the additive amount of (PrNd) 5 Ce 10 Fe 77 B 8 powders. In addition, for Ce atomic percent of 8%, 7%, and 6% the coercivity is higher than that of magnets prepared by the conventional method, which shows the advantage of the dual alloy method in preparing high abundant rare earth magnets.

The variation of coercivity with Ce content was investigated in (Pr,Nd)15-xCexFe77B8 (x=0∼10) sintered magnets. The coercivity of magnets largely decreases from 10.22 to 5.4 kOe with increasing x from 0 to 2. The coercivity rises to 7.68 kOe when x=3 and then decreases again with further increasing Ce content. However, both the magnetocrystalline anisotropy and Curie temperature decrease monotonically with increasing Ce content. EDS composition analysis shows that the Ce concentration in the Re2Fe14B main phase is higher than that in the nominal composition when x≤3, but becomes lower when x>3. These results indicate that Ce tends to be expelled from the main phase and segregates at or near the grain boundary regions if Pr-Nd is excessively substituted by Ce. The change of relative solubility of Ce in Re2Fe14B would lead to the change of distributions of Ce and Pr-Nd elements, and thus result in the change of anisotropy at the grain outer layer, contributing to the abnormal behavior of coercivity. These studied results are also expected to provide a guideline for optimizing the composition design of resource-saving permanent magnets.

High energy ball milling (HEBM) is employed to produce nano-sized grains and particles. In this paper, the structure and magnetic properties are investigated in PrCo5 alloy for HEBM in an ethanol milling medium. With the increase of milling time, the grain size reduces and the coercivity increases. For a milling time of less than 30 min, the hysteresis loop of the aligned sample is very different from that of the un-aligned sample and it does not show a large decrease in magnetization slope, indicating a relatively good alignment of easy axes in particles due to the fact that the texture is nearly well preserved. However, when the milling time is further prolonged, the textured structure deteriorates in the powders. Even though exchange coupling exists between grains within the particle, the magnetic properties are exchange-decoupled between particles and the dipolar interaction results in a negative value of δ m in the whole range of the magnetic field.