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Development of a Control Techique for Microstructures in Nd-Fe-B Magnetic Materials produced by HDDR Process

HDDR工艺生产的Nd-Fe-B磁性材料微观结构控制技术的开发

基本信息

批准号：
07555479
负责人：
OKI Kensuke
金额：
$ 3.01万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (A)
财政年份：
1995
资助国家：
日本
起止时间：
1995 至 1997
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-07555479/
关键词：
HDDR process neodymium iron boride anisotropic magnet powder electron microscopy microstructure crystallographic orientation EDX analysis EDX分析

项目摘要

The changes in microstructure of Nd-Fe-B and Nd-Fe-Co-B-Zr alloy powders during the hydrogenation-decomposition-desorption-recombination (HDDR) process have been investigated by X-ray diffraction measurements and transmission electron microscope (TEM) observations, in order to clarify the formation of submicron grains of Nd_2Fe_<14>B and the appearance of the magnetic anisotropy in the HDDR powder. It was found that the microstructural changes in the HDDR process start with the formation of cellular and spherical NdH_2 embedded in alpha-Fe matrices. The hydrogenation-decomposition (HD) reaction in the Nd-Fe-Co-B-Zr alloy progresses slower than the one in Nd-Fe-B ternary system. There is no specific crystallographic orientation relationship between the original Nd_2Fe_<14>B and the decomposed phases ; NdH_2 and alpha-Fe. A large amount of boron is contained in the NdH_2 grain in the early stage of the HD process. As the HD process advances, the NdH_2 grain spews out the boron and consequently Fe_2B grains appear at relatively latter stage. The magnetic anisotropy decreases with the formation of the Fe_2B grains in the decomposed texture. In the desorption-recombination (DR) stage, the rim-like Nd_2Fe_<14>B phase is formed by the recombination at the boundaries between the NdH_2 particles and the alpha-Fe matrix. The rim phase is composed of some fine Nd_2Fe_<14>B grains whose crystallographic orientations are strongly correlated with one another. After further hydrogen desorption, the rim phase grows up to form the recombined Nd_2Fe_<14>B fine grains with a strongly correlated c-aixs. The grain size of the recombined Nd_2Fe_<14>B crystal is related to the size and the number density of the NdH_2 particles. It is thus expected to obtain superfine Nd_2Fe_<14>B crystals if the NdH_2 particle before the HD stage can be controlled smaller in size and dispersed more density in the alpha-Fe inatrix.

通过X射线衍射测量和透射电子显微镜(TEM)观察，研究了Nd-Fe-B和Nd-Fe-Co-B-Zr合金粉末在氢化-分解-解吸-复合(HDDR)过程中微观结构的变化，以阐明Nd_2Fe_<14>B亚微米晶粒的形成以及磁各向异性的表现。 HDDR粉。研究发现，HDDR 工艺中的微观结构变化始于嵌入 α-Fe 基体中的蜂窝状和球形 NdH_2 的形成。 Nd-Fe-Co-B-Zr合金中的氢化分解（HD）反应比Nd-Fe-B三元系中的氢化分解反应进行得慢。原始Nd_2Fe_<14>B与分解相之间不存在特定的晶体取向关系； NdH_2和α-Fe。在HD过程的早期阶段，NdH_2晶粒中含有大量的硼。随着HD过程的进行，NdH_2晶粒喷出硼，因此Fe_2B晶粒在相对较晚的阶段出现。磁各向异性随着分解织构中Fe_2B晶粒的形成而减小。在解吸复合(DR)阶段，NdH_2颗粒与α-Fe基体之间的边界处复合形成轮缘状Nd_2Fe_ 14 B相。边缘相由一些细小的Nd_2Fe_ 14 B晶粒组成，其晶体取向彼此强相关。进一步氢脱附后，边缘相长大形成具有强相关c轴的复合Nd_2Fe_ 14 B细晶粒。复合Nd_2Fe_ 14 B晶体的晶粒尺寸与NdH_2颗粒的尺寸和个数密度有关。因此，如果能够控制HD阶段之前的NdH_2颗粒的尺寸更小并且在α-Fe基体中分散得更高密度，则有望获得超细Nd_2Fe_ 14 B晶体。