Structure and chemical compositions of the grain boundary phase in Nd-Fe-B sintered magnets
Structure and chemical compositions of the grain boundary phase in Nd-Fe-B sintered magnets
复制标题
DOI：
10.1016/j.actamat.2016.05.035
复制
发表时间：
2016-08-15
期刊：
影响因子：
9.4
通讯作者：
Hono, K.
中科院分区：
文献类型：
--
作者：
Sasaki, T. T.;Ohkubo, T.;Hono, K.
我们重新审视了商业Nd-Fe-B烧结磁体的显微结构，使用扫描电子显微镜（SEM）和像差校正扫描透射电子显微镜（STEM），以澄清的显微结构特征，是相关的矫顽力。两种类型的薄的富Nd晶界（GB）相被发现：一个是结晶的，另一个是非晶的。晶状富Nd GB相形成于Nd 2Fe 14 B晶粒的c面的平坦表面处，其与在几乎垂直于c面的晶界上形成的非晶GB相相比含有更高量的Nd。这表明烧结Nd-Fe-B磁体中的晶间交换耦合是各向异性的。通过对三相结富Nd相的SEM和STEM分析，发现了五种富Nd相，即：fcc-Nd_2 O_3、hcp-Nd_2 O_3、NdFe_4 B_4、具有fcc结构的金属富Nd相和Ia（3）过棒状结构。金属富Nd相形成于富Nd氧化物和硼化物晶粒的尖锐边缘，薄的富Nd相从所述尖锐边缘沿沿着渗透以形成薄的GB相。未对准的Nd 2Fe 14 B晶粒经常被观察到与Nd 2 O3晶粒直接接触。(C)2016 Acta Materialia Inc.由爱思唯尔有限公司出版。保留所有权利。
We revisited the microstructure of a commercial Nd-Fe-B sintered magnet using scanning electron microscopy (SEM) and aberration corrected scanning transmission electron microscopy (STEM) in order to clarify the microstructure feature that is relevant to the coercivity. Two types of thin Nd-rich grain boundary (GB) phases were found: one is crystalline and the other is amorphous. The crystalline Nd-rich GB phase form at the flat surface of c-plane of the Nd2Fe14B grains, which contains a higher amount of Nd compared to the amorphous GB phase that form on the grain boundaries nearly perpendicular to the c-planes. This indicates that the intergranular exchange coupling in sintered Nd-Fe-B magnets is anisotropic. Correlative SEM and STEM analysis of triple junction Nd-rich phases revealed five types of Nd-rich phases, i.e., fcc-NdO, hcp-Nd2O3, NdFe4B4, metallic Nd-rich phases with the fcc structure and the Ia (3) over bar structure. The metallic Nd-rich phases form at the sharp edges of Nd-rich oxide and boride grains, from which thin Nd-rich phases is infiltrated along grain boundaries to form the thin GB phase. Misaligned Nd2Fe14B grains are often observed in direct contact with the Nd2O3 grains. (C) 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.