Nd5Fe64B23Mo4Y4 bulk nanocomposite permanent magnets produced by crystallizing amorphous precursors

The glass forming ability and magnetic properties of Nd5Fe68 − xB23Mo4Yx (x = 0, 2, 4, 6) alloys prepared by copper mold casting technique have been studied. Amorphous rods with a diameter of 2 mm were obtained in the Nd5Fe64B23Mo4Y4 alloy. After annealing for 10 min at 1013 K, the Nd5Fe64B23Mo4Y4 alloy showed optimal hard magnetic properties with the coercivity of 764.2 kA/m, remanence of 0.6 T and maximum energy product of 57.3 kJ/m3, respectively. The enhanced magnetic properties can be ascribed to the strong exchange coupling among the magnetically soft α-Fe (25–30 nm), Fe3B (30–35 nm) and hard Nd2Fe14B (40–50 nm) grains present in the magnet microstructure. Large size bulk nanocomposite magnets with sound magnetic properties make the Nd–Fe–B–Mo–Y alloy system a promising candidate for industrial applications.

► Synthesis of Nd5Fe68 − xB23Mo4Yx bulk amorphous alloys by copper mold casting method.
► 4 at.% Y addition greatly improves the glass forming ability of the alloy system.
► 2 mm diameter rod permanent nanocomposite magnet was obtained after annealing.
► Optimal magnetic properties were achieved with annealed Nd5Fe64B23Mo4Y4 alloy at 1013 K for 10 min.