Formation of bulk material of metastable phase by solid-state reaction of complex ultra fine powders.

本研究对超细粉体的烧结进行了两年的研究。该研究的特点是超细粉体从生产到烧结在一个连续设备中处理。特别是采用本项目所获得的惰性气体净化系统，可使烟气中的O_2和水分含量保持在较低的状态。得到的主要结果如下：1。惰性气体清洗系统、O_2和H_2O探测器均安装在格罗夫箱上，该格罗夫箱与超细粉体生产系统直接相连。超细粉体的直径随着腔室压力的减小和物料给粉速率的减小而减小。相同烧结温度下有压烧结的超细粉体密度高于相同烧结温度下无压烧结。在相同烧结密度下，烧结温度比无压力烧结温度低200K，有压力（300MPa）烧结温度比无压力烧结温度低200K。烧结后的超细粉末硬度随烧结的进行而增大，随晶粒长大而减小。获得的最大硬度Ni为50OHv， Cu为25OHv，分别比铸件高7倍和4倍。烧结后的超细粉末的硬度与晶粒尺寸的-1/2次方成正比，这表明存在Hall-Petch关系。从理论上考虑了晶粒尺寸对烧结速率和晶粒长大速率的影响，结果表明，随着晶粒尺寸的减小，烧结速率高、晶粒长大速率低的温度区域增大。用超声波设备对各种粉体生产后的不同超细粉体进行了混合试验。然而，由于聚集的原因，没有实现微尺度的混合。为了获得均匀的混合，考虑了在蒸汽条件下混合材料的最佳方法。设计了一种新型双等离子体触摸超细粉体生产系统。少

In the present investigation the sintering of matal ultra fine powders have been studied for two years. This study was characterized by the fact that the ultra fine powders were handled in one continuous equipment from production to sintering. Especially using the inert gas cleaning system obtained by the present grant, the O_2 and moisture content was kept in quite low state. The main results obtained were as follows.1. The inert gas cleaning system, O_2 and H_2O detectors were censer attached to the grove box and this grove box was directly connected with the ultra fine powder producing system.2. The diamer of ultra fine powder was reduced with reducing the chamber pressure and the material powder feeding rate.3. The density of sintered ultra fine powder at the same sintering temperature was higher when sintered under the pressure than that without pressure at the same sintering temperature. The sintering temperature which gives the same sintering density was 200K lower when sintered … More for that under pressure (300MPa) than that without pressure.4. The hardness of sintered ultra fine powder increases with the progress of sintering and decrease with the progress of grain growth. The maximum hardness obtained was 50OHv for Ni and 25OHv for Cu, which were 7 and 4 nines larger than those of casted.5. The hardness of sintered ultra fine powders was proportional to -1/2 power of the grain size and this indicates that the Hall-Petch relation is held.6. The theoretical consideration of the effect of grain size to the sintering rate and grain growth rate indicates that the temperature region where sintering rate is high and grain growth rate is low increases with the decrease in grain size.7. The mixing of different ultra fine powders after production of each powder was tried using ultrasonic equipment. However microscale mixing was not achieved because of the aggregation. To obtain uniform mixing the best method wascon sidered to mix the material in the vapor condition. A new type double plasma touch ultra fine powder production system was designed. Less