Microstructure and magnetic properties of directly quenched Nd₂Fe₁₄B/α-Fe nanocomposite materials at different temperatures

Abstract

Directly quenched Nd_9.5Fe₈₁Zr₃B_6.5 nanocomposite permanent magnets were prepared under different melt treatment conditions, i.e., the melt temperature was varied prior to ejection onto the quenching wheel. The effect of quenching temperature on the microstructure and magnetic properties of the alloys was studied by X-ray diffractometry, transmission electron microscopy and magnetization measurements. It is found that a finer and more uniform microstructure can be obtained directly from the melt quenched at lower temperature. With increasing initial quenching temperature, the optimal quenching speed decreases and the microstructure of the ribbons becomes coarser and more irregular. As a result, the magnetic properties of the alloys are deteriorated. It is believed that the break of the pre-existing Nd₂Fe₁₄B clusters and decrease in number of the developing nuclei of Nd₂Fe₁₄B phase with increase in quenching temperature may be the causes for the change of the microstructure and the magnetic properties of the ribbons.

Keywords

microstructure / nanocomposite magnet / quenching temperature

References

[1] KnellerE F, HawingR. The exchange-spring magnet: A new material principle for permanent magnets [J]. IEEE Trans Magn, 1991, 27: 3588-3692

[2] GabayA M, ZhangY, HadjipanayisG C. Die-upset hybrid Pr-Fe-B nanocomposite magnets [J]. Appl Phys Lett, 2004, 8520: 446-448

[3] HamaddoN, MishimaC, MilaraiH, HonkurnY. Development of NdFeB anisotropic bonded magnet with 27MGOe [J]. IEEE Trans Magn, 2003, 39(5): 2953-2955

[4] LiuY-g, XuL, WangQ-feng. Development of crystal texture in Nd-lean amorphous Nd₉Fe₈₅B₆ under hot deformation [J]. Appl Phys Lett, 2009, 94(17): 2502-2505

[5] LeeD, BauserS, HigginsA, ChenC, LiuS. Bulk anisotropic composite rare earth magnets [J]. J Appl Phys, 2006, 99: 516-518

[6] SchreflT, FischerR, FidlerT. Two- and three-dimensional calculation of remanence enhancement of rare-earth based composite magnets [J]. J Appl Phys, 1994, 76: 7053-7058

[7] SchreflT, FidlerJ, KronmullerH. Remanence and coercivity in the isotropic nanocrystalline permanent magnets [J]. Phys Rev B, 1994, 49: 6100-6104

[8] FidlerT, FidlerJ, KronmullerH. Nucleation field of hard magnetic particles in 2D and 3D micromagnetic calculations [J]. J Magn Magn Mater, 1994, 138: 15-20

[9] XieG Z, YinS L, TianZ J, LiS D, GuB X. Research on the magnetic properties and crystal lattice aberrance of melt-spun Nd₉Fe_85−xMn_xB₆ (x=0–1) [J]. Phys Lett A, 2002, 299: 102-106

[10] BetancourtI, DaviesH A. Influence of Zr and Nb dopant additions on the microstructure and magnetic properties of nanocomposite RE₂(Fe,Co)₁₄B/α-(Fe,Co) (RE=Nd-Pr) alloys [J]. J Magn Magn Mater, 2003, 261: 328-332

[11] ChenZ, SmithB R, BrownD N, MaB M. Effect of Zr substitution for rare earth on microstructure and magnetic properties of melt-spun (Nd_0.75Pr_0.25)_12.5−xZr_xFe₈₂B_5.5 (x=0–3) ribbons [J]. J Appl Phys, 2002, 91: 8168-8170

[12] ChuZ, MaW B, ChenZ, BrownD N. Neutron diffraction analysis of melt spun 2:14:1 type (NdPr)-Fe-B compounds with Ti and Zr additions [J]. J Appl Phys, 2002, 91: 7878-7881

[13] HirosawaS, KanekiyoH, MiyoshiT. Development of high-coercivity nanocomposite permanent magnets based on Nd₂Fe₁₄B and Fe_xB [J]. Journal of Alloys and Compounds, 2006, 408: 260-265

[14] HanitschR, CoeyJ M DRare-earth iron permanent magnets [M], 1996, Oxford, Oxford Scientific Publications: 210-213

[15] PeijieLI, NiktinV I, KandalovaE G. Effect of melt overheating, cooling and solidification rates on Al-16wt%Si alloy structure [J]. Mater Sci Eng A, 2002, A332: 371-374