Effect of Zr on Microstructure and Magnetic Properties of Nanocrystalline (Nd, Pr)FeB/α-Fe Composite Alloys

For nanophase （Nd, Pr）FeB/α-Fe composite alloys were prepared by melt spinning, the appreciable addition of Zr reduces their average grain size. Observed by atom force microscopy （AFM）, the average grain diameter of crystallized ribbons on their free surface, reduces from 175 nm of Zr-free alloy to 79 nm of Zr-1at%, by about 55%. If the concentration exceeds 1%, the effects of Zr on fining grain size are evidently weakened. The average grain size on free surface of Zr-1.5at% is 72 nm. With the addition of 1at% Zn, the bonded magnets has the best combination of properties: Br=0.675 T, Hci=616 kA·m-1, （BH）max=77 kJ·m-3. Below 1at%, the coarser grains lead to a lower magnetic property. Beyond 1at%, the layer of Zr-rich intergranular phase will thicken, which results in weakening of the exchange coupling among adjacent grains, and then causes degrading of magnetic properties of magnets.