Lianxi Hu, Yuping Li, Yuan Yuan
Campus Box 435#, School of Mater, Science and Engineering, Harbin Institute of Technology, Harbin 150001, China.
J Nanosci Nanotechnol. 2009 Jul;9(7):4404-9. doi: 10.1166/jnn.2009.m68.
In order to obtain nano-structured as-disproportionated microstructure in partially Co-substituted NdFeB-type alloys, the Nd14Fe66.9GCo11B7Zr0.1Ga1.0 alloy was disproportionated by room-temperature reactive ball milling in hydrogen, with the mechanical energy serving as the driving force. The reaction progress during milling was examined by hydrogen absorption measurement, and the corresponding microstructure change was characterized by X-ray diffraction (XRD), Mössbauer spectrometry, and transmission electron microscopy (TEM), respectively. The results show that the Nd2(Fe, Co)14B matrix phase in the alloy can be mechanically disproportionated by a two-stage reaction. Firstly, the Nd2(Fe, Co)14B matrix phase in the alloy is hydrogenated into Nd2(Fe, Co)14BH(x), until the value of x achieves about 2.9 when a full hydrogenation is achieved. After that, the Nd2(Fe, Co)14BH(x) phase is gradually disproportionated into alpha-Fe(Co), NdH2.7, and (Fe, Co)2B phases upon further milling in hydrogen. The as-disproportionated phases NdH2.7, (Fe, Co)2B, and alpha-Fe(Co), are typically nano-structured, with an average grain size of about 10 nm, which lays the basis for synthesizing nanocrystalline Nd2(Fe, Co)14B grains via a subsequent desorption-recombination treatment.
为了在部分钴取代的钕铁硼型合金中获得纳米结构的非比例微观结构，通过在氢气中进行室温反应球磨使Nd14Fe66.9GCo11B7Zr0.1Ga1.0合金发生非比例化，其中机械能作为驱动力。通过吸氢测量研究球磨过程中的反应进程，并分别用X射线衍射（XRD）、穆斯堡尔谱和透射电子显微镜（TEM）对相应的微观结构变化进行表征。结果表明，合金中的Nd2(Fe, Co)14B基体相可通过两步反应进行机械非比例化。首先，合金中的Nd2(Fe, Co)14B基体相被氢化为Nd2(Fe, Co)14BH(x)，当完全氢化时x值达到约2.9。之后，在氢气中进一步球磨时，Nd2(Fe, Co)14BH(x)相逐渐非比例化为α-Fe(Co)、NdH2.7和(Fe, Co)2B相。非比例化后的NdH2.7、(Fe, Co)2B和α-Fe(Co)相通常为纳米结构，平均晶粒尺寸约为10 nm，这为通过后续的解吸-重组处理合成纳米晶Nd2(Fe, Co)14B晶粒奠定了基础。
