Effect of Pr<sub>80</sub>Cu<sub>20</sub> grain boundary addition on microstructure and magnetic properties of (Pr, Nd, Dy)<sub>32.2</sub>Co<sub>13</sub>Cu<sub>0.4</sub>Fe<sub>bal</sub>B<sub>0.98</sub><i>M</i><sub>1.05</sub> magnet

Abstract

With the aim of increasing Cu concentration to regulate the distribution of Co elements in RE-rich phase, the low-melting-point Pr<sub>80</sub>Cu<sub>20</sub> intergranular alloy is introduced into the (Pr, Nd, Dy)<sub>32.2</sub>Co<sub>13</sub>Cu<sub>0.4</sub>Fe<sub>bal</sub>B<sub>0.98</sub><i>M</i><sub>1.05</sub> (<i>M</i> = Al, Ga, Zr) magnet. Comparing 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 that the Co-lean phase and the Co-rich phase coexist in the grain boundary in the 2<sup>nd</sup>-annealed original magnet. However, for the PrCu-doped magnet, the uniform distribution of Cu and Co elements in the intergranular phase are evidently improved, resulting in the elimination of the Co-rich phase. Since the <i>R</i><sub>2</sub>(Fe, Co)<sub>17</sub> (<i>R</i> = Pr, Nd, Dy) soft magnetic phase easily coexist with the Co-rich phase and are detrimental to the coercivity, the elimination of Co-rich intergranular phase may be an important reason for the higher coercivity of the 2<sup>nd</sup>-annealed PrCu-doped magnet than that of the original magnet.