| Budget Amount *help |
¥8,100,000 (Direct Cost: ¥8,100,000)
Fiscal Year 1990: ¥2,300,000 (Direct Cost: ¥2,300,000)
Fiscal Year 1989: ¥5,800,000 (Direct Cost: ¥5,800,000)
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| Research Abstract |
In 1989, an apparatus of shock compaction under magnetic fields were designed and constructed. Since the apparatus was furnished with a velocity-measuring system which was newly developed using optical fibres, high precision and high reproducibility were obtained in the measurements. The maximum velocity obtained were 1.9 km/s for a projectile of 10 g in weight by using gun powder of 60 g and were a capacity of 25 % higher than that designed. On the other hand, in the low velocity range, it was necessary to improve the powder chamber for stable operation. Magnetic field was probably high enough to saturate a magnetic flux in usual materials because of a high energy capacitor bank of 25 kJ.
Ultrafine iron powder, which was supplied by Kantodenka, Co., Ltd., was used as a starting powder. Since the powder was needle-like and had a high aspect ratio of 10 to 30, we obtained only a low packing density of 32 % which led to increase shock temperature too much. A ultrasonic dispersion and sedimentation improved the density upto 41 % which led to compacts with density of 71 % by shock compaction. A multi-stage shock-compression technique using a complex impactor considerably suppressed shock temperature and provided good compacts with density of 92 %. It is necessary to increase more the pasking density in future by per-forming the powder under magnetic field. This technique was expected to improve magnetic properties.
Microstructures of the compacts consisted of nanocrystalline particles without grain growth. We have, therefore, nanocrystalline metallic materials in prospect. In order to improve magnetic properties, however, further experimental investigations, such as surface treatments, effects of additives relations between grain boundaries and magnetic fields, and so on, are required.
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