Preparation of bulk Nd2Fe14B/Fe3B nanocomposite magnets with high rare earth content

Nd6Fe72−xCoxB22 (x = 0, 20) rods with 1 mm diameter have been prepared by suction casting. The Nd6Fe72B22 rod is mainly composed of Nd2Fe23B3, Fe3B and a small amount of amorphous phase, whereas the Nd6Fe52Co20B22 sample is amorphous. Co addition considerably improves the glass-forming ability (GFA) of Nd6Fe72B22, which is believed to result from the large decrease of the eutectic temperature due to Co addition. Co addition promotes the formation of the Nd2Fe14B hard magnetic phase in annealed alloys, which strengthens the exchange coupling action among the magnetic phases and thus leads to a significant enhancement of the magnetic properties of the bulk nanocomposite magnets. For example, the remanence, coercivity, and energy product are increased from 3.9 kG, 1.3 kOe, and 0.9 MGOe for the Co-free alloy to 8 kG, 4.5 kOe, and 6 MGOe after Co addition, respectively.