微波烧结锇的工艺研究及动力学分析

采用微波烧结技术制备锇（Os）烧结体，研究了生坯压制压强和微波烧结主要工艺参数（升温速率、烧结温度和保温时间）对Os烧结体组织结构和相对密度的影响规律，分析了微波烧结致密化的机理。结果表明，1350 ℃微波烧结后Os平均晶粒尺寸约0.22 μm，与粉体颗粒尺寸差别不大；随着烧结温度增加到1500 ℃，晶粒尺寸长大到0.76 μm。1500 ℃烧结时，延长保温时间，Os烧结体的相对密度先快速增加，后缓慢增加。1500 ℃微波烧结60 min后，Os烧结体相对密度为94.3%，平均粒径小于1 μm。烧结动力学分析表明，Os的致密化过程是体积扩散和晶界扩散共同作用的结果，随着烧结温度的升高，扩散机制从晶界扩散逐渐向体积扩散转变。

Process and kinetic analysis of osmium prepared by microwave sintering

Os sintered body was prepared by microwave sintering process. The influences of the green compact pressure and the microwave sintering parameters (heating rate, sintering temperature, and holding time) on the microstructure and relative density of Os sintered bodies were investigated. The densification mechanism of Os microwave sintering was analyzed. The results show that, the average grain size of Os after microwave sintering at 1350 ℃ is about 0.22 μm, which is close to the average particle size of the Os powders. With the increase of the sintering temperature to 1500 ℃, the grain size grows to 0.76 μm. The relative density of the Os sintered body increases rapidly at first and then slowly after prolonging the holding time sintered at 1500 ℃. After microwave sintering at 1500 ℃ for 60 min, the relative density of the Os sintered body is 94.3%, and the average particle size is less than 1 μm. The sintering kinetics analysis shows that the densification process of Os is the result of the combined action of volume diffusion and grain boundary diffusion. With the increase of the sintering temperature, the diffusion mechanism gradually transfers from grain boundary diffusion to volume diffusion.