Microstructure of die-upset Nd-Fe-Co-Ga-B magnet was investigated with a scanning electron microscopy (SEM), high resolution and analytical transmission electron microscopy (HRTEM and ATEM). Inside the original melt-spun flakes in the magnet, the typical texture consists of fine platelet Nd 2(Fe,Co) 14B grains surrounded continuously by a thin grain boundary (GB) phase with 2-3nm in thickness. The GB phase has an amorphous structure of which the chemical composition is Nd 44Fe 39Co 10Ga 7. It was found that high fluidity of the Nd- and Ga-rich GB phase contributes to produce a high crystallographic c-axis alignment of Nd 2(Fe,Co) 14B grains. Near the interfaces of the original flakes, morphology of the Nd 2(Fe,Co) 14B grains changes from platelet to globular involving the deterioration of c-axis alignment. Many Nd-oxide (NdO and fcc-(Nd,Fe)O x) grains and a large amount of fine Nd 3Co precipitates are formed near the interfaces, and then the composition of GB phase changes to Nd 36Fe 50Co 9Ga 5. The insufficiency of Nd in the GB phase and the existence of Nd-oxide particles prevent the anisotropic growth of Nd 2(Fe,Co) 14B grains, and then lead to the inhomogeneous GB phase and the low c-axis alignment.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering