The Effects Of Alloy Elements On Properities Of Bulk Nanocrystalline Ndfeynbb Permanent Magnets

In this paper, we adopted the copper mold casting method to fabricate bulk nanocrystalline NdFeYNbB permanent magnets (rod shape,1.5 mm in diameter and 15 mm in length). The magnetic properties, microstructure, antioxidant ability and corrosion behaviour of bulk nanocrystalline NdFeYNbB permanent magnets are investigated.In these Nd10Y1Fe85-xNb3.5Ti0.5Bx (x=14-22) alloys, the magnetic properties of Br、 iHC and (BH)max first rise then fall with increasing B content. The optimal magnetic properties of Br=6.0kG,iHc=7.8kOe and (BH)max=6.7MGOe could be achieved in Nd10Y1Fe69Nb3.5Ti0.5B16 alloy. However, the antioxidant abilities and corrosion resistance of these alloys are increased with increasing B content. With the application of magnetic field during the casting process, the grains are refined, resulting in the increase of magnetic energy product. The optimal magnetic properties of Br=6.3kG, iHc=8.6kOe and (BH)max=7.4MGOe could be achieved in Nd10Y1Fe69Nb3.5Ti0.5B16 alloy. However, the antioxidant ability and corrosion resistance of these alloys become worse, comparing with those alloys without application of magnetic field.In these Nd10Y1Fe69Nb3.5M0.5B16 (M=Ti, Zr, Cr, Mo) alloys, the optimal magnetic properties of Br=6.3kG, iHc=8.2kOe and (BH)max=7.0MGOe are obtained in the Nd10Y1Fe69Nb3.5Zr0.5B16 magnet. While the Mo-doped alloy exhibits the highest coercivity of iHC=8.8 kOe. Among the M-doped alloys, the Zr-doped sample exhibits the best corrosion resistance and the Ti-doped sample exhibits the best antioxidant ability.In these Nd10Y1-xMxFe69Nb3.5Ti0.5B16 (M=Ga、Gd, x=0～1) alloys, while Ga content is 0.5at%, the alloy exhibits the optimal magnetic properties of Br=6.5kG, iHc=8.6kOe and (BH)max=8.3MGOe. While the Ga content is increased to lat%, a soft magnetic phase (Fe3B) is emerged. The existence of Fe3B phase reduces the volume fraction of hard magnetic phase, resulting in the decrease of the coercivity and magnetic energy product. The remanence of alloy is improved with Gd addition, yet rectangularity of demagnetization curve is reduced, leading to the decrease of magnetic energy product. The Ga and Gd additions would deteriorate the antioxidant ability and corrosion resistance of alloys.In these Nd10-xMxY1 Fe69Nb3.5Ti0.5B16 (M=Dy、Pr, x=0～1.5) alloys, the coercivity is increased and the remanence is reduced with increasing Dy and Pr content. The optimal magnetic properties of Br=5.8kG, iHc=9.0kOe and (BH)max=7.1MGOe are achieved in Nd9.5Dy0.5Y1Fe69Nb3.5Tio.5Bi6 alloy. The curie temperature of Nd2Fe14B is slightly increased with increasing Dy content, the curie temperature of Nd2Fe14B is slightly decreased with increasing Pr content. The antioxidant ability of alloy is significantly deteriorated with the Pr addition, while there is not significant change with the Dy addition. Futhermore, The Dy and Pr additions would deteriorate corrosion resistance of alloys.In these Nd10Y1 Fe69-xNb3,5Ti0.5B16Cox (x=0-16) alloys, the grains are refined when the Co content is 4at%, leading to the improvement of magnetic energy product. The optimal magnetic properties of Br= 6.4kG, iHc= 8.4kOe and (BH)=max=7.4MGOe are achieved in Nd10Y1Fe65Nb3.5Ti0.5B16Co4 alloy. The excess Co addition (>8at%) make the grains coarsen, leading to the decrease of magnetic energy product. However, the curie temperatures of Nd2Fe14B and a-Fe phases monotonously increase with increasing Co content. Besides, the corrosion resistance is improved with Co addition.