Preparation and Property Evalution of Ultrafinegrained Materials by Ultra-High Pressure Sintering

研究了Fe、Co、Ni、Fe-Co、Fe-Ni、Fe-Ni、Go-Ni、Fe-Co-Ni等超细晶系超细粉末完全致密化的热压工艺条件(研究一)、烧结体的平均晶粒度和硬度(研究二)。获得的结果如下。研究一：(1)以400 Mpa为例，Fe+Co+Ni混合粉末的完全致密化温度比Fe、Co和Ni粉末的完全致密化温度(500-800K)高约200-300K，比Co+Ni、Fe+Co和Fe+Ni粉末的完全致密化温度高约100K。(2)Co-Ni和Fe-Co-Ni烧结体的最小晶粒度分别为0.18和0.12微米，在相同的热压条件下，晶粒度随着组元个数的增加而减小，与组元均一化温度和致密化温度的变化趋势一致。(3)Co-Ni和Fe-Co-Ni烧结体的最大硬度分别为600和800Hv。研究II；(1)在较高的测试温度下，合金体系中在室温下观察到的Hv的顺序总体上没有变化。(2)Fe细晶压坯的Hv在500K左右急剧下降，远低于3.5um粗晶压坯的Hv(约800K)。这归因于细晶压块即使在如此低的温度下也很容易发生蠕变变形。

The hot-pressing condition for complete densification of Co+Ni and Fe+Co+Ni mixed ultrafine powders (0.02 ; mum), the average crystal grain size and hardness (Hv) of the sintered compacts were investigated (Research I) and the effect of test temperature on the hardness (Hv) of ultrafinegrained sintered compacts with the average crystal grain size of 0.10 0.35mum was investigated for Fe, Co, Ni, Fe-Co, Fe-Ni, Go-Ni and Fe-Co-Ni systems (Research II). The results obtained were as follows. Research I ; (1) The complete densification temperatures for Fe+Co+Ni mixed powders, for example at 400 MPa, was about 200-300K higher than those (500-800K) of Fe, Co and Ni powders, and about 100K higher than those of Co+Ni, Fe+Co and Fe+Ni powders. (2) The minimum crystal grain size of the Co-Ni and Fe-Co-Ni sintered compacts were 0.18 and 0.12 um respectively ; the crystal grain size under the same hot-pressing condition tended to decrease with the number of components, in accordance with the tendencies of both the homogenization temperature of the components and the densification temperature. (3) The maximum hardness of Co-Ni and Fe-Co-Ni sintered compacts were about 600 and 800 Hv. Research II ; . (1) The order of Hv observed at room temperature among the alloy systems did not change in general at the higher test temperatures. (2) The Hv of Fe fine-grained compacts decreased sharply at about 500K, which was much lower than that (about 800K) for coarse-grained compacts of 3.5um. This was attributed to the fact that creep deformation easily occurs even at such low temperatures for fine-grained compacts.