材料期刊网

用DSC仪测定了Nd-Fe-B磁体的Curie点,以磁称法绘制了热退磁曲线.并用高温金相显微镜直接观察了Nd-Fe-B畴结构随温度的变化.对Nd-Fe-B磁体畴结构的特点作了初步讨论.同时观察了富Nd相的熔融和试样表面的氧化过程。

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.