The effect of annealing temperature on micro-structure and mechanical properties of C/SiC composites

In this paper, the rare-earth oxide La₂O₃ combined with Al₂O₃ served as sintering additives and low-cost α-SiC powder were exploited successfully to prepare dense short carbon fiber reinforced SiC composites by hot-pressing (HP) sintering. The results of the experiments proved that the combination of Al₂O₃ and La₂O₃ sintering additives system was effective to promote densification of the hot-pressed C_f/SiC composites. The influence of the annealed temperature on the micro-structure and mechanical properties of the C_f/SiC composites was investigated in details. The proper annealed condition is favorable to improve the room temperature mechanical properties. The most interesting phenomenon was observed that silicon carbide nano-whisker structure was formed in the material which was annealed at 1750 °C for 1 h. It is undoubted that nano-whisker structure would promote fracture toughness. The combination of grain bridging, crack deflection and nano-fiber debonding can improve fracture toughness.