Investigation On Microstructure And Magnetic Properties Of Nd₂Fe₁₄B/α-Fe Nanocomposite Magnets

Nd₂Fe₁₄B/α-Fe nanocomposite magnets composed of nanoscaled hard and soft magnetic phases have been attracted consideralbe interest for the highest theoretical maximum energy product and lower cost. Alloy composition, melt-spinning and crystallization process have great effects on the microstructure and magnetic properties. Crystallization with high magnetic field(10T),the additions of refractory and fusible elements and the wheel speed have been investigated. Especially, three dimensional atom probe(3DAP) is employed to map out the distribution of different elemental atoms in a nanometric volume for nanocomposite magnets with different elements added.Effects of melt-spinning speed on the microstructure and magnetic properties of (Nd0.9Dy0.1)9(Fe0.9Co0.1)85.5B5.5 alloys have been investigated. Lower speed was favor for obtaining uniform and fine grains after crystallization treatment, enhancing the interaction coupling of grains and improving the magnetic properties. Nonuniform and coarse grains were found in ribbons with higher melt-spinning speed after crystallization treatment, reducing the magnetic properties. For the ribbons spun with 12m/s wheel speed and annealed within 10T high magnetic field, no [001] texture for Nd2Fe14B phase along the applied magnetic field was found and there was a large amount ofα-Fe phase for the magnetic annealed ribbons, which decreased the magnetic properties.On the basis of the composition of (Nd0.9Dy0.1)9(Fe0.9Co0.1)85.5B5.5 alloy, effects of the additions of refractory and fusible elements, such as Nb, Zr, V, Sn and Cu, on the microstructure an magnetic properties were paid more attention to.The addition of Nb and Zr increased the amorphous formation ability and thermal stability of as-spun ribbons, refining and homogenizing the microstructure and increasing the coercivity of the annealed ribbons. The results of 3DAP analysis showed that: the refractory elements Nb, Zr, V combined with Fe and B elements prefered to form precipitate phases at grain boundary which suppressed the grain...