Magnetic anisotropy in arc-cast Nd-Fe-B-Zr alloys

Magnetically anisotropic ingots with compositions of (Nd2.2Fe14B)100-xZrx were prepared using an arc-melting furnace. The direction perpendicular to the cooling surface Is found to be magnetically hard compared with the parallel direction. The c-axis of each grain is considered to be distributed randomly in the plane parallel to the cooling surface. Zr addition reduces the amount of iron dendrites and makes the anisotropic feature more distinct. After annealing at 1,040 C for 24 hours, very little grain growth In Zr containing ingots is observed in contrast with Zr free ingots. The HDDR (hydrogenation, disproportionation, desorption and recombination) treatment of these ingots shows that higher Zr addition cause a coercivity decrease, however, the anisotropy features are partially preserved after recombination, but only in the annealed ingot