The sintered Nd_25.5Dy_6.5Co₁₃Fe_balM_1.05B_0.98 magnet (Co13 magnet) and Nd₃₀Dy_1.5Co_0.5Fe_balM_1.05B_0.98 (35SH magnet) were prepared by strip casting (SC), hydrogen decrepitation (HD), jet milling (JM), orienting compression, sintering and annealling. The maximum magnetic energy product (<em>BH</em>)_max and coercivity <em>H</em>_cj of Co13 magnet at room temperature were 30.88 MGOe and 19.01 kOe, which were lower than 35SH magnet. By adding Co and Dy, the remanence temperature coefficient α, curie temperature <em>T</em>_C and max operating temperature <em>T</em>_W were significantly increased form -0.136 %/℃ to -0.065 %/℃ (25~180 ℃), 310 ℃ to 454 ℃ and 160 ℃ to 200 ℃ respectively. Mechanical property test and fracture analysis showed that, due to the high content of Co in the magnet, the proportion of cleavage fracture in the main phase grains was increased, and the bending strength Rbb was reduced compared with 35SH magnets, which was nearly twice that of 2:17 type Sm-Co magnets. The reason for the decrease of Rbb might be that Co element preferentially replaced Fe in the 2:14:1 main phase, which led to lattice distortion and reduced the grain strength of the main phase. The microstructure analysis showed that, there was a high Co region in the grain boundary phase of Co13 magnet, and its composition was close to (Nd,Dy)(Fe,Co)₃, which might be one of the reasons for the decrease of coercivity <em>H</em>_cj.

With the aim of increasing Cu concentration to regulate the distribution of Co in RE-rich phase, the low-melting-point Pr₈₀Cu₂₀ intergranular alloy is introduced into the (Pr,Nd,Dy)_32.2Co₁₃Cu_0.4Fe_balB_0.98M_1.05(M=Al,Ga,Zr) magnet. Compared with the original magnet, the remanence of PrCu-doped magnet is basically unchanged, and the coercivity is increased by approximately 1.3 kOe. Simultaneously, the Curie temperature, remanence temperature coefficient and irreversible flux loss are slightly improved. Microstructural study reveals the coexistence of Co-lean phase and Co-rich phase in the grain boundary in the 2^nd-annealed original magnet. However, for the PrCu-doped magnet, the uniform distribution of Cu and Co in the intergranular phase are evidently improved leading to the elimination of the Co-rich phase. Since the R₂(Fe,Co)₁₇ (R=Pr,Nd,Dy) soft magnetic phase easily coexist with the Co-rich phase and is detrimental to the coercivity, the elimination of Co-rich intergranular phase may be one important reason for the higher coercivity of the 2^nd-annealed PrCu-doped magnet than that of the original magnet.