Solid State Reactions in Transition Metal Diboride-Based Materials
Solid State Reactions in Transition Metal Diboride-Based Materials
复制标题
过渡金属二硼化物基材料中的固态反应
DOI：
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发表时间：
2001
期刊：
影响因子：
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通讯作者：
W. Mader
中科院分区：
文献类型：
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作者：
C. Schmalzried;R. Telle;B. Freitag;W. Mader
摘要 采用高分辨率透射电子显微镜（HRTEM）和电子过滤透射电子显微镜（EFTEM）研究了准三元体系TiB2-WB2-CrB2沉淀退火陶瓷中过渡金属硼化物层状结构的各种微观结构特征。这些方法的组合可以解析各种沉淀物的结构和成分。起始硼化物与 (Ti, W, Cr)B2 固溶体相的反应可以分析为跨晶粒或相间边界的扩散固态反应。退火产生部分反应的样品，其显示出由未反应的 TiB2 核和 (Ti, W, Cr)B2 固溶体相壳组成的微观结构，其中由于晶格之间的失配而产生的高应力通过在界面中形成位错而得到缓解。厚度仅为一个晶格常数的 β-WB 型相板状析出物可以通过电子能谱成像 (ESI) 进行化学表征，并通过 HRTEM 鉴定其结构。 ESI 和电子衍射证明了在两相场退火期间基体相的旋节线分解。固溶体相和具有 W2B5 结构的 WB2 相中经常出现的堆垛层错可以通过 HRTEM 进行结构表征。
Abstract The variety of microstructural features of the layered structures of transition metal borides in precipitation-annealed ceramics in the quasi-ternary system TiB2–WB2 –CrB2 have been investigated by high-resolution transmission electron microscopy (HRTEM) and electron-filtering transmission electron microscopy (EFTEM). The combination of the methods allows to resolve structure and composition of various precipitates. The reaction of the starting borides to the (Ti, W, Cr)B2 solid-solution phase could be analysed to be a diffusive solid state reaction across the grain or interphase boundaries. The annealing leads to a partly reacted specimen which shows a microstructure consisting of unreacted TiB2 cores with a shell of the (Ti, W, Cr)B2 solid solution phase, where high stress due to the misfit between the lattices is relaxed by formation of dislocations in the interface. Plate-shaped precipitates of a β-WB-type phase with thickness of only one lattice constant could be characterised chemically by electron spectroscopic imaging (ESI) and their structure was identified by HRTEM. Spinodal decomposition of the matrix phase during annealing in the two-phase field was proven by ESI and electron diffraction. Frequently occurring stacking faults in the solid solution phase and in the WB2 phase with W2B5 structure could be structurally characterised with HRTEM.