Al-TiO_2自蔓延高温合成结构宏观动力学分析

The Structural Macrokinetics of The Al—TiO_2 Self-Propagation High Temperature Syntheses

在材料的自蔓延高温合成(SHS)过程中,反应物与产物之间,各种结构层次(宏观、微观、晶体结构等)上的转变过程—结构宏观动力学,对材料制备具有决定意义。本文分别在宏观结构和微观结构两个层次上研究了Al-TiO_2自蔓延高温合成系统的结构宏观动力学。结果表明:在宏观结构上,随着样品尺寸加大,如工艺控制不当会出现三种主要的宏观结构缺陷:气孔增加,偏析加剧、宏观裂纹。材料的显微结构,是由燃烧波内一种非均匀网络状过渡组织转变而来的。

In the process of materials preparation by self-propagation high temperature synthesis (SHS), the structural formation and structural macrokinetics are of great importance. In this paper, the structural macrokinetics in Al-TiO_2 SHS system has been investigated by means of the macrostructural and microstructural examinations. It has been found that with the increase of the dimension of the specimen, the macro-defects increase. There are three main types of macro-defects, pores, compositional segregation and macrocrack. The mechanism of the defect formation have been analyzed. By combustion wave quenching method, the dynamic structure of Al-TiO_2 SHS processes has been maintained. A more detailed description about the microstructure development in this system has been made. The final microstructure of the product results from an intermediary network in the combustion wave.