| The wide application of NdFeB magnets leads to the large consumption of precious rare earth elements?especially Nd,Pr,Dy,Tb?.However,the high-abundant rare earth elements represented by La,Ce and Y are overstock,resulting in the unbalanced use of rare earths resources.From the perspective of reducing raw material costs and using national strategic resources effectively,the research and development of high-abundant rare earth permanent magnet materials is imperative.In this paper,nanocrystalline Pr-Nd-Y-Fe-B alloy strips and magnets were prepared by melt quenching and spark plasma sintering?SPS?techniques.The phase composition and magnetic properties of alloys with different Y contents were studied.The influences of fabrication,microstructure and sintering process on the phase composition,magnetic properties and microstructure of the magnets were discussed.Firstly,nanocrystalline[(Pr0.25Nd0.75)1-xYx]13.9Fe80.1B6?x=0-0.5,at.%?ribbons with different Y substitutions were prepared by melt quenching technique.The best magnetic properties were obtained under various belt speeds for samples with different compositions.The effects of different Y substitutions on the phase composition,magnetic properties and microstructure of the alloy were systematically investigated.The results show that an appropriate amount of Y substitution can effectively improve the squareness of the demagnetization curve and inhibit the formation of Fe3B phase.WhentheamountofY-substitutedPrandNdelementsis30%,[(Pr0.25Nd0.75)0.7Y0.3]13.9Fe80.1B6 alloy has the best squareness,and the Curie temperature drops only slightly from 307°C to 302°C.Y element plays a role in grain refinement and the microstructural uniformation.In addition,Y substitution can also enhance the short-range exchange coupling between the main phase grains.Secondly,nanocrystalline[(Pr0.25Nd0.75)0.7Y0.3]13.9Fe80.1B6?at.%?ribbons were prepared.Isotropic nanocrystalline magnets were prepared by spark plasma sintering using the bands as raw materials.The effects of different sintering processes on magnetic properties,phase composition and microstructures of magnets were studied.The results show that the grain shape of the magnet prepared by SPS is rod-like,the average size in the long side direction is 95.2 nm,and the average size in the short side direction is 32.7 nm.The optimum comprehensive magnetic properties were obtained when sintering temperature was 700 C,sintering pressure was 50 MPa and holding time was 5 min:Jr=0.79 T,Hci=818 kA/m,?BH?max=97 kJ/m3.Finally,amorphous[(Pr0.25Nd0.75)0.7Y0.3]13.9Fe80.1B6?at.%?ribbons were prepared,and isotropic nanocrystalline magnets were prepared by SPS equipment.The effects of sintering temperature on magnetic properties,phase composition and microstructure of magnets were studied.The results show that compared with the magnets prepared by nanocrystalline ribbons,the crystalline shape of the magnets prepared by amorphous ribbons is polygonal,and the average grain size is 85.2 nm.In addition,the magnets prepared by amorphous ribbons have better comprehensive magnetic properties than those prepared by nanocrystalline ribbons under the same sintering process at 700C/50 MPa/5 min.The optimum properties of SPS magnets prepared by amorphous ribbons are:Jr=0.79 T,Hci=864 kA/m,?BH?max=102 kJ/m3.In summary,the effect of Y substitution on phase composition,magnetic properties and microstructures of alloys has been studied in this paper.The internal relationship between different sintering processes and magnetic properties,phase composition and microstructures of Pr-Nd-Y-Fe-B magnets has been further explored.The performance differences between nanocrystalline and amorphous magnets have been compared,and the reasons for the differences have been analyzed.This paper shows important academic and pracitical values. |
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