中文摘要：

对ф16mm三元复合稀土钨电极垂熔烧结时所产生的烧结分层现象进行了研究。采用SEM、XRD方法对垂熔坯条的形貌和物相组成进行了分析,并对第二相粒子进行了EDAX定点能谱分析。用ICP-AES方法分析了坯条不同区域稀土氧化物的百分含量,利用电子探针（EPMA）对稀土元素在坯条断口上的分布进行了探测。根据烧结坯条的显微组织及不同区域成分的差异,探讨了稀土元素在这种大坯条烧结工艺制度下的扩散与挥发过程。结果表明：稀土元素在坯条截面上分布不均匀;同时稀土第二相粒子多分布在钨基体晶粒的晶界上;边缘和中心稀土第二相及钨晶粒大小、数目不一,稀土元素的挥发扩散不仅造成了烧结坯条断面成分不均,而且进一步加重了温度梯度引起的组织不均匀性,最终造成了分层现象的发生。

英文摘要：

The captioned research was conducted with a tertiary RE-W electrode nun. The morphologies and phases of the sintered billets were investigated with a diameter of 16 by SEM and XRD, respectively. The composition of the second phase particles was analyzed by EDAX. The percentages of rare earth oxides in different regions were detected by ICEP-AES. The distribution of RE elements at the fracture was detected by EPMA. According to the different microstructures and compositions in different regions, the diffusing and volatilizing behaviors of the RE elements during sintering were investigated. The results show that the distribution of RE elements across the fracture section is not uniform; the second phase particles are mostly distributed at grain boundaries ; the number and grain size of the second phase particles of RE elements and tungsten particles are different between the center and the edge. It is found out that the diffusion and volatilization of RE elements not only lead to the non-uniform composition but also aggravate the non-uniformity of the structure the lamination phenomenon finally.