High-resolution electron microscopy study of interfacial structure in TiB₂[sbnd]Ti_0·9W_0·1 C[sbnd]SiC in-situ composite

Abstract

The ultrafine structure of multiphase ceramics TiB₂Ti_0·W_0·C[sbnd]Sic formed by the in-situ reactive hot-pressing process has been characterized using high-resolution electron microscopy (HREM) and analytical electron microscopy. The results reveal that TiB₂ crystallized into plate-like shapes, containing Tic plate precipitates. Three different orientation relationships between Tic precipitates and the TiB₂ matrix were determined and the formation mechanism was proposed. Crystalline intergranular phase containing Fe, Si and Ti elements were formed at grain edge intersections. Along the TiB₂ plates, the intergrowth of 6H-SiC bands were often found. An orientation relationship between the 6H-SiC and TiB₂, in which [1120]_TiB2//[1120]_Sic and (0001)_TiB2//(0001)_SiC, was found and the atomic structures at the TiB₂/6H[sbnd]SiC interface have been investigated by HREM combined with image simulations of several proposed models. Comparison of simulated images and the experimentally observed image resulted into an optimal structure model with Ti[sbnd]B[sbnd]C[sbnd]Si stacking sequence at the interface.