The Study On The Melt-spun NdFeB (Co, Nb, Ti, Zr, Cu, P)Nanocrystalline Magnets

Nd Fe B nanocomposite magnet is a new type of magnetic material which compounded of soft and hard magnetic phases. How to further improve its magnetic properties by adjusting the process and optimizing the composition has been a research hotspot. In this article, hard magnetic ribbons with enhanced magnetic properties were produced through to the composition adjustment, Melt spinning process optimization and subsequent annealing treatment, and some instruments like XRD, DSC, VSM, TEM and LTEM were used to characterize the microstructure, magnetic structure and magnetic properties of the ribbons. More details are as follows:1. The changes of microstructure and magnetic properties of the ribbons were studied by elements compound addition on the basis of traditional Nd Fe B alloy. Different elements have different effects on magnetic properties, crystallization mechanism and microstructure of the ribbons. The addition of Co can improve the Br of the material, but reduce the Hc; Nb can obviously improve the Hc; Ti can promote the growth of soft magnetic phase and improve the Hc; Zr mainly improve the Tx of the alloy; Cu can increase nucleation particles of the soft magnetic phase to make it precipitate and grow preferentially; P can also promote the the crystallization and growth of the soft magnetic phase, and has a significant role in promoting of the Br and(BH)max of the ribbons.2. The effects of different elements on the annealed ribbons were also studied in this article. The results showed that microelement addition can general destroy the exchange coupling interaction of the annealed ribbons. Meanwhile, the addition of Co can reduce the Hc and Bs; Zr and Nb can refine the grain size; Ti can significantly promote the the growth of the soft magnetic phase grain.3. Annealed the different crystallization state ribbons with different processes, the magnetic properties changed significantly. When annealed the crystalline state ribbon, the magnetic properties occur varying degrees of deterioration; when annealed the amorphous ribbon, the magnetic properties are much weaker than that of the ribbon prepared at optimum quenching rate. In addition, magnetic annealing can promote the precipitation and growth of the soft magnetic phase, while inhibit the precipitation and growth of the hard magnetic phase, and the deterioration of the magnetic properties is more serious than normal annealing.4. Through the control of wheel speed directly to optimize the quenching rate, as-spun ribbons with different crystallization states were prepared. When the wheel speed is 20~25 m/s, the as-spun ribbons exhibited maximum hard magnetic properties. To gain a deeper understanding of the correlation between magnetic properties and microstructures of the ribbons prepared at different quenching rates, Fe81Nd10Co2Nb1B6 alloy was chosen to observe the grain, domain, and vortex structures. The results show that good hard magnetic properties are correlated to the homogeneous microstructure with appropriate grain size about 20 nm. The intergranular exchange coupling interaction in the nanocomposite ribbon is conductive to the big closed magnetic domains and dense vortex-like magnetization state which results in the large coercivity. It showed that optimization of the quenching rate through the control of wheel speed directly in the absence of any additional treatment after melt spinning can be an easier approach to obtain good magnetic properties and microstructure of nanocomposite magnets.5. Through the comparison of magnetic properties and microstructure of the Nd10Fe84B6 and Nd7Fe90B3 as-spun ribbons, significant changes were observed. With Fe increasing and Nd, B decreasing, the hard magnetic properties of the ribbons reduce gradually while the soft magnetic properties improved. This suggests that direct production of hard magnetic ribbons with excellent properties by controlling cooling rate of melt should also cooperate with the appropriate alloy.