Preparation of TiC-Ti₃SiC₂ Composites by Mechanical Alloying and Hot-Pressing

Abstract

TiC-Ti₃SiC₂ composites having the microstructure of fine Ti₃SiC₂ grains dispersed in TiC matrix were synthesized by two processes, that is, mechanical alloying of a powder blend of Ti, Si and C followed by hot-pressing (MA-HP process) and hot-pressing of a powder blend of Ti, Si and TiC (MIX-HP process). The microstructure, damage tolerance and 4-point flexural strength of the composites were investigated. It was found that more uniform dispersion of Ti₃SiC₂ grains in TiC matrix was achieved by MA-HP process than by MIX-HP process, while the flexural strength of the composites synthesized by MA-HP process was lower than that by MIX-HP process, which may be attributed to micropores formed in the composites synthesized by MA-HP process. Preferential orientation of Ti₃SiC₂(001) and TiC(111) occurred in the composites synthesized by MA-HP process. We proposed two mechanisms of the preferential orientation. We also found that the dispersion of Ti₃SiC₂ in TiC matrix is effective in improving the damage tolerance of the brittle TiC, evidenced by the fact that no cracks emanated from the corners of Vickers indentations at a load of 9.8 N.