Enhanced Thermal Stability of Nd–Fe–B Sintered Magnets by Intergranular Doping Y₇₂Co₂₈ Alloys

Abstract

The intergranular addition process using Y 72 Co 28 eutectic alloy powders has been applied to (Pr, Nd) 27 Dy 4 Fe 67.65 Cu 0.15 Al 0.2 B 1 (wt.%) sintered magnets, resulting in an enhanced thermal stability. It was found that the coercivity of magnets at 100°C increased while the addition of Y 72 Co 28 is 1 wt.%, whereas the magnetic properties decreased slightly at room temperature due to lower magnetocrystalline anisotropy field (H A ) of Y 2 Fe 14 B. The temperature coefficient of remanence (α) and coercivity (β) for the magnets improved significantly. Microstructure observation indicated that Y atoms prefer to enter into the 2-14-1 phase and form a core-shell structure with an outer layer of (Nd, Dy, Y) 2 (Fe, Co) 14 B. Magnetic domain and intrinsic properties analysis suggested that the improved thermal stability resulted from the modified grain boundaries and the introduction of Y in matrix phases.

Study on Microstructure and Coercivity of Thermally Processed Nd-Fe-B–type HDDR Material

“…It would be desirable, therefore, to use a fine grain structured material like HDDR-treated Nd-Fe-B-type powder as starting material for fabrication of bulk magnet with high coercivity because the HDDR-treated Nd-Fe-B-type material inherently possesses fine Nd 2 Fe 14 B grain structure. Several attempts have been made to exploit the HDDR powder as a starting material for consolidated bulk magnet with the intention of achieving high coercivity, but with little success [5][6][7][8]. As consolidation of powder material commonly requires thermal processing, insight into the influence of thermal heating on the coercivity of the Nd-Fe-B-type HDDR material can hint at finding the best way for preparing high coercivity magnet.…”

Effect of Cathodic Hydrogen Evolution on the Coercivity and Thermal Stability of Sintered NdFeB Magnets

“…The coercivity and thermal stability are in close relation with the composition and microstructure of magnets. Additions including Ce [12] , Ho 63.4 Fe 36.6 [13] , DyH x [14] , Y 72 Co 28 [15] , Dy 82.3 Co 17.7 [16] and Zr [17] etc. were used to enhance the coercivity and thermal stability by composition and microstructure optimization.…”