Relationship between microstructure and magnetic domain structure of Nd--Fe--B melt-spun ribbon magnets

Abstract

The relation between the microstructure, observed using an electron probe microanalyzer, and the domain structure, observed using a Kerr microscope, was established to evaluate the effects of hot rolling and the addition of Ti--C on the c-axis orientation and the magnetization process of hot-rolled Nd--Fe--B--Ti--C melt-spun ribbons. The addition of Ti--C promotes the c-axis orientation and high coercivity in the ribbons. Elemental mapping suggests a uniform elemental distribution; however, an uneven distribution of Ti was observed in an enlarged grain with Ti-enriched points inside the grain. The reversal domains that nucleated at the Ti-enriched point inside the grain cause low coercivity.

Keywords

magnetic domain / microstructure / Kerr effect microscope / magneto-optical effect / Nd--Fe--B permanent magnet

References

[1] Hirosawa S, Nishiuchi T, Nozawa N, . Recent efforts toward rare-metal-free permanent magnets in Japan. Proceedings of the 21st Workshop on Rare-Earth Permanent Magnets and their Applications, Bled, 2010, 187–192

[2] Sugimoto S. Recent trend of the researches for reducing dysprosium usage in an Nd–Fe–B sintered magnet. Journal of the Japan Society of Powder and Powder Metallurgy, 2010, 57(6): 395–400

[3] Sepehri-Amin H, Ohkubo T, Nishiuchi T, . Coercivity enhancement of hydrogenation-disproportionation-desorption-recombination processed Nd–Fe–B powders by the diffusion of Nd–Cu eutectic alloys. Scripta Materialia, 2010, 63(11): 1124–1127

[4] Liu M, Sun Y, Han G B, . Dependence of anisotropy and coercivity on microstructure in HDDR Nd–Fe–B magnet. Journal of Alloys and Compounds, 2009, 478(1-2): 303–307

[5] Li W F, Ohkubo T, Hono K, . The role of grain boundaries in the coercivity of hydrogenation disproportionation desorption recombination processed Nd–Fe–B powders. Journal of Applied Physics, 2009, 105: 07A706

[6] Thompson P, Gutfleisch O, Chapman J N, . A comparison of the micromagnetic and microstructural properties of four NdFeB-type materials processed by the HDDR route. Journal of Magnetism and Magnetic Materials, 1999, 202(1): 53–61

[7] Mishra R K, Lee R W. Microstructure, domain walls, and magnetization reversal in hot-pressed Nd–Fe–B magnets. Applied Physics Letters, 1986, 48(11): 733–735

[8] Lee R W, Brewer E G, Schaffel N. Processing of neodymium–iron–boron melt-spun ribbons to fully dense magnets. IEEE Transactions on Magnetics, 1985, 21(5): 1958–1963

[9] Kuji T, O'Handley R C, Grant N J. Magnetic anisotropy of Nd₁₅Fe₇₇B₈ flakes made by twin-roller quenching. Applied Physics Letters, 1989, 54(24): 2487–2489

[10] Kuji T, O'Handley R C, Grant N J. Method for making polycrystalline flakes of magnetic materials having strong grain orientation. US Patent, 5049335, 1991

[11] Takezawa M, Nakanishi Y, Morimoto Y, . Investigation of easy axis orientation of Nd–Fe–B melt-spun ribbons produced by hot rolling and influence of Ti–C addition. Journal of Applied Physics, 2012, 111: 07A703

RIGHTS & PERMISSIONS

Higher Education Press and Springer-Verlag Berlin Heidelberg