铝热剂反应燃烧合成Al2O3—TiC陶瓷的径向显微组织变化

研究了压坯直径对燃烧合成Al2O3－TiC陶瓷的燃烧速度和温度的影响以及圆柱试样的径向微观组织变化。燃烧合成的圆柱试样轴心区直径1．5μm～5.5μm的圆形颗粒为TiC，具有熔化特征的边长10μm～20μm的多边形为含有少量TiC的刚玉；在二分之一半径处，TiC颗粒和刚玉块的尺寸分别减小为0．1μm～3μm和5μm～15μm；但在靠近合成试样圆周及其圆柱表面，刚玉变成为了晶须，TiC则是0．1μm－0．5μm的微小颗粒组成的团聚体。这是因为试样在燃烧合成过程中沿周向和径向均有热量传递，燃烧过程中径向不同位置温度的显著变化导致了微观组织的变化。

Microstructure Change in the Radial Direction of the Cylindrical Products of the Al_2O_3-TiC Ceramics Combustion-Synthesized by Aluminothermic Reactions

Effect of pellet diameter on the combustion velocity and temperature profile in the combustion synthesis of Al2O3-TiC ceramics and microstructure change in the radial direction of the cylindrical products were investigated. For a cylindrical sample the rounded particles with diameters of 1.5 μm～5.5 μm and the melted polygons with sides about 10 μm～20 μm are TiC particles and corundum with a little TiC in the axial region, respectively. In the region of half-radius, TiC is smaller particles with diameters of 0.1 μm～3 μm and corundum is polygons with sides about 5 μm～15 μm. In the region near the circumference of the fractured sample and on the peripheral surface of the as-combusted sample, however, corundum becomes whiskers and TiC agglomerate actually consisting of fine particles with 0.1 μm～0.5 μm in size.There are heat losses both in axial and radial directions of the sample during combustion synthesis. It has been found that the obvious change of temperature versus profile in the post-combustion stage leads to the microstructure change in the radial direction of the sample.