Development of Formation Technique and Chracterization of Nanocrystal Material form Ultra Fine Powder and MA Process

本研究的目的是利用超细粉体或机械合金化法制备超细粉体材料，并利用超细粉体的特性开发功能材料。主要研究结果如下：1.等离子体粉末法制备的超细粉体的粒径随着反应室压力和送粉速率的降低而减小.结果表明，在低温高压条件下烧结超细粉体，可以制备出晶粒尺寸为50nm的块体材料。这种块体材料的硬度比具有普通晶粒尺寸的常规材料高4至6倍。然而，当对纯金属元素的粉末进行烧结时，即使在低温下也会发生晶粒生长.当Cu和AlN的混合超细粉被烧结时，得到了静态晶粒尺寸为0.4 μ m的超细晶材料。研究表明，未固溶于基体的第二相的钉扎作用对超细晶组织起到了很好的稳定作用. Al-Ni-Ti系二元合金粉末经机械合金化处理后，根据化学成分不同，产生了非晶相、过饱和固溶体相或金属间化合物相.机械合金化粉末在放热量较大时烧结良好。烧结材料的晶粒尺寸非常小，通常约为0.1 μ m。采用机械合金化（MA）细化晶粒，得到了Sm_2Fe_3和NdMo_2Fe_3的氮化物。<17><10>观察到这些材料的晶粒尺寸约为50nm，并认为获得了单磁畴结构。该材料的结晶度比常规铸造或快速凝固工艺的结晶度高。

The purpose of this research was to make nanocrystal materials using ultra fine powder or powder produced by mechanical alloying process and to develop functional material using the characteristics of nanocrystal. The main results obtained were as follows :1. The particle size of the ultra fine powder produced by plasma-powder process was decreased with the decrease in chamber pressure and powder feeding rate.2. It was shown to be possible to produce bulk materials with 50nm in grain size by sintering Ultra fine powder under the condition of low temperature and high pressure. Such bulk materials exhibited the hardness of 4 to 6 times higher than the regular materials with ordinary grain size. However, when sintering is carried out for the powder of a puremetal element, grain growth occurred even at low temperature.3. When the mixed ultra fine powder of Cu and AIN was sintered, Ultra fine grained material with the stationally grain size of 0.4mum was produced. It was made clear that the pinning effect of the second phase which does not dissolve into matrix works well to stabilize the ultra fine grained structure.4. When the powders of the binary alloys in Al-Ni-Ti system were mechanically alloyed, phases of amorphous, super saturated solid solution or intermetallic compounds were produced depending on the chemical compositions.5. Mechanically alloyed powder was well sintered when the amount of exothermic heat was large. The grain size of Sintered material was extremely small and usually about 0.1mum.6. By applying the grain refinement by MA, nitrides of Sm_2Fe_<17> and NdMo_2Fe_<10> were produced. The grain size of these materials were observed to be about 50nm and it was considered that the single magnetic domain structure was obtained. The coercivity of the above material was measured to be higher that those obtained by regular casting or repid solidification process.