| Budget Amount *help |
¥1,300,000 (Direct Cost: ¥1,300,000)
Fiscal Year 1986: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1985: ¥700,000 (Direct Cost: ¥700,000)
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| Research Abstract |
The Oxide which forms on the surface layer of the powder particles has in general harmful effects on the properties of the sintered compacts. Therefore, the suppression of the further oxidation after the pulverization is important for the powder of metals forming hardly reductionable oxide, and the sufficient reduction of the oxide during the sintering of the compact is important for the powders of metals forming reductionable oxide. The handling of powders in the atmosphere of argon gas of temperatures as low as minus 40゜C could reduce the oxidation, compared with the handling in the normal atmosphere. However, the effect was relatively small, contrary to our expectation. Then, the study on the preparation of the sintered compact with low oxygen content as well as ultrafine crystal grain size by using ultrafine metal powders was conducted. It was found that the relative density of the green compact and the heating rate during sintering should be both much lower than those usually set for the normal coarse powders, in order to prepare the sintered compact with full density and almost free from oxygen and that the crystal grain size of the compact was as small as 0.3-1.5 <micro> m which was considerably smaller than that of cast or forged alloy. Next, the study on the preparation of the dispersion-hardened alloy by using ultrafine Cu powder and <Al_2O_3> hardly-reducionable powder was conducted. The result showed that the critical amount of the oxide above which the complete densification of the sintered compact was retarded decreased with decreasing grain size of <Al_2O_3> powder and that the crystal grain size of Cu matrix became finer with increasing amount of oxide.
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