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EFFECT OF GRAIN-BOUNDARY AND INTERPHASE STRUCTURES ON MECHANICAL PROPERTIES OF STRUCTURAL MATERIALS

晶界和相间结构对结构材料力学性能的影响

基本信息

批准号：
02452235
负责人：
YOSHINAGA Hideo
金额：
$ 5.06万
依托单位：
KYUSHU UNIVERSITY
依托单位国家：
日本
项目类别：
Grant-in-Aid for General Scientific Research (B)
财政年份：
1990
资助国家：
日本
起止时间：
1990 至 1992
项目状态：
已结题

项目摘要

Grain boundaries of single phase materials and interphase boundaries of composite materials are often responsible for the degradation of mechanical properties. In the present investigation, for molybdenum which has problems of grain boundary brittleness, ceramics of Si_3N_4, SiC and TiC which are hopeful as high-temperature structural materials, and micro-bonded Au-Al which is important in the IC industry, the grain boundary structure and interphase boundary structure have been observed by means of high-resolution transmission electron microscopy. Their boundary strength is discussed in connection with the boundary structure.Symmetric tilt-boundary in Molybdenum: The fracture strength strongly depends on the grain boundary character in molybdenum. SIGMA 1 low angle and near SIGMA 3 coincidence boundaries have a good coherency, whereas the boundaries of misorientation angle around 30ﾟ are poor in coherency. However, the structure in those boundaries was found to be described by the grain-boundary dislocation model, It is considered that the grain boundary structure in molybdenum with a high covalency in bonding is not greatly different from that in normal metals.Grain boundary structure of Si_3N_4, SiC and TiC: An amorphous-like layer was observed at grain boundaries in Si_3N_4 and SiC. That layer in SiC was analyzed by EELS using a micro beam technique. It is clarified that the layer is neither sintering aids nor impurity layer but a relaxed structure. A grain boundary layer such as observed in Si_3N_4 and SiC was not observed in TiC where the boundary structure was metal like.Interphase boundary of micro-bonded Au-Al: In the foils prepared with a ultra-microtome no amorphous phase was observed, whereas in the foils prepared by ion milling a large part of the intermetallic compound formed on the interface was amorphous. Using the foils prepared with the microtome, the contamination effect on the bonding was clarified.

单相材料的晶界和复合材料的相间边界通常是导致机械性能下降的原因。本研究针对存在晶界脆性问题的钼、有望作为高温结构材料的Si_3N_4、SiC、TiC陶瓷以及在IC工业中重要的微结合Au-Al，利用高分辨率透射电子显微镜观察了晶界结构和相间界面结构。它们的边界强度是结合边界结构来讨论的。钼中的对称倾斜边界：断裂强度很大程度上取决于钼中的晶界特征。 SIGMA 1低角度和SIGMA 3附近重合边界具有良好的相干性，而定向误差角30°左右的边界相干性较差。然而，发现这些晶界的结构是用晶界位错模型描述的，认为高共价键合钼的晶界结构与普通金属的晶界结构没有太大区别。 Si_3N_4、SiC和TiC的晶界结构：在Si_3N_4和SiC的晶界处观察到非晶态层。使用微束技术通过 EELS 分析了 SiC 中的该层。表明该层既不是烧结助剂也不是杂质层，而是松弛结构。 TiC中没有观察到Si_3N_4和SiC中观察到的晶界层，其边界结构是金属状的。微结合Au-Al的界面：在超薄切片机制备的箔中没有观察到非晶相，而在离子铣削制备的箔中，界面上形成的金属间化合物大部分是非晶的。使用切片机制备的箔片，阐明了污染对粘合的影响。