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Sun B.-Y.,Northeastern University China | Sun B.-Y.,Shenyang General Magnets Co. | Sun B.-Y.,ULVAC Vacuum Furnace Shenyang Co. | Ba D.-C.,Northeastern University China | And 4 more authors.
Gongneng Cailiao/Journal of Functional Materials | Year: 2011

In the article we have done the research on the influence of the annealing treatment on the surface grains' strain, micro-structure, sub-crystallite size and magnetic properties of the thin NdFeB magnet by ordering the SEM scanning electron microscope, X-ray diffraction and magnetic property measurement. The results showed that: firstly, above the three-phase eutectic temperature, 900°C×2 h+490×5 h of annealing treatment can completely eliminate machining strain, stress and defects. Secondly, the capillary action and diffusion of the grain boundary Nd-rich phase uniformly and continuously distributed in the grains and grain boundary around. The Nd-rich phase of this network structure eliminated the grain boundary cracks and defects, and played an important role on the magnetic properties recovery and improvement.

Sun B.,Northeastern University China | Sun B.,ULVAC Vacuum Furnace Shenyang Co. | Ba D.,Northeastern University China | Duan Y.,ULVAC Vacuum Furnace Shenyang Co. | And 4 more authors.
Zhenkong Kexue yu Jishu Xuebao/Journal of Vacuum Science and Technology | Year: 2011

The Al films were deposited by DC magnetron sputtering on surfaces of the NdFeB permanent magnets. The influence of the deposition conditions, including the annealing temperature and time, deposition time, on properties of the films was studied. Its microstructures and corrosion behavior were characterized with salt spray test, palarization curves, and scanning electron microscopy. The results show that the Al coating significantly improves corrosion resistance of the magnets, and that the annealing temperature and time strongly affect the microstructures at the interface of Al films and the magnet. After vacuum annealing at 650°C for 10 min., well-defined Al/NdFeB interface was observed with strong adhesion and high surface corrosion resistance. If annealing temperature is higher than 650°C, the interfacial diffusion resulted in formation of defects and new RNdFeB phase. Moreover, the roughened surface of Al film decreased its corrosion resistance. Possible mechanisms were tentatively discussed.

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