Effects Of High Abundance Of Rare Earth On Magnetic Properties And Structures Of Nd-Fe-B Melt-spun Powders

In order to fully balance the application of rare-earth resource in magnetic materials and reduce the cost of permanent magnetic material and promote the sustainable development of the Re-based magnetic materials industry, it becomes a research hotspot in recent years to introduce high abundance of rare earth, such as Ce, La to Nd-Fe-B melt-spun powders. The relationships between annealing process and magnetic properties of melt-spun powders substituted by 24wt% Ce for Nd and Pr had been studied first and then the effects of different Ce-substitution and different ratios of La/Ce-substitution on magnetic properties and microstructure of Pr-Nd-Fe-B melt-spun powders were also resystematically studied. The inexpensive powders with great properties had been manufactured, which will save the cost of magnet and balance the usage of rare-earth. The detailed researches are shown in the following:The melt-spun ribbons of alloy substituted by 24wt% Ce were made first. The orthogonat test of different annealing processes was applied to ribbons manufactured under different rapid-quenching speed. The results showed that the powders prepared under over-optimal speed with succedent optimal heat treatment had the best magnetic properties. By optimizing the annealing temperature and time further, it was founded that the best annealing temperature was 620-650°C when the annealing time was 5min and the best annealing time was 1-7min when the annealing temperature was fixed at 650°C. The cooling rate after annealing had effects on properties of powders with different Ce-content. The higher cooling rate was helpful to improve the properties of powders with low Ce-content, while it was inverse for powders with high Ce-content.The effects of different Ce-content on magnetic properties and structures of Nd-Fe-B melt-spun powders had been studied. Compared with the magnetic properties of as-spun powders with different Ce-content, that of all the powders annealed improved a lot, but thecoercivity was relatively high when the Ce was 24wt% of the total Re. The graphs of SEM and TEM showed that the powders with 24wt% Ce had more uniform structures, smaller grains and obvious intergranular phases, three of which resulted in the result. Finally, the effects of adding La and Ce together to Nd-Fe-B alloy on magnetic properties and microstructures had been studied. It was founded that the size of grains in the powders substituted by La and Ce was smaller than that of grains in the powders substituted only by Ce, which could enhance the Cercivity. At the same time, the enhanced exchange coupling effect made up magnetic dilution effect by La, leading to the almost same remanence of all samples. Besides, there was much more soft magnetic phase in the powders substituted only by Ce, which may also lead to lower coercive force.