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| THERMAL ANALYSIS AND DOMAIN OBSERVATION OF Nd-Fe-B MAGNET |
| LUO Yang; ZHANG Ning; SU Xiujin (Central Iron and Steel Research Institute; Ministry of Metallurgical Industry; Beijing) (Manuscript received 27 June; 1985; revised manuscript 15 January; 1986) |
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Cite this article:
LUO Yang; ZHANG Ning; SU Xiujin (Central Iron and Steel Research Institute; Ministry of Metallurgical Industry; Beijing) (Manuscript received 27 June; 1985; revised manuscript 15 January; 1986). THERMAL ANALYSIS AND DOMAIN OBSERVATION OF Nd-Fe-B MAGNET. Acta Metall Sin, 1987, 23(2): 136-244.
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Abstract Curie temperature of Nd-Fe-B magnet was determined with a DSC set and thermal demagnetization curve (σ-T curve) was drawn with a magnetic balance High-temperature metallography was used for direct observation of the variation of domains with temperature. Melting process of Nd-rich phase and oxidation of the specimens were observed as well. The results show that the Curie temperature of Nd_2Fe_(14)B phase is 307.5±1℃ and the melting point of Nd-rich phase is approximately 600℃.The domain structure in Nd_2Fe_(14)B phase is that of strong uniaxial anisotropy. Instead of transverse closure domains, certain amount of cone-like reverse domians would appear on the surface when the domain spacing becomes wide enough. The magnetic contrast of domains decreases continuously with the increase of temperature, but neither local migration nor partial regulation of the domains can be found until Curie temperature. During cooling, renucleation of domains in the thermal-demagnetized specimens, which have to fit in with crystal orientation, still shows some randomness. Consequently, the domains in same grain look substantially identical before and after thermal demagnetization but with minor difference.
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Received: 18 February 1987
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1 Sagawa M, Fujimura S, Togawa N, Yamamoto H, Matsuura Y. JAppl Phys 1984; 55: 2083
2 罗阳,马黛,苏秀锦,李岫梅,孙立,王振琴.金属学报,1984;20:A416
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4 Kittel C. Rev Mod Phys 1949; 21: 541
5 Morrish A H. The Physical Principles of Magnetism. New York: Wiley, 1965, 265
6 Sagawa M, Fujimura S, Yamamoto H, Matsuura Y, Hiraga K. IEEE Trans Magn 1984; MAG20． 1584 |
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