Si_3N_4 rodlike crystal-reinforced MoSi_2 matrix composites

摘要

A MoSi2-based composite reinforced with 20 vol. percent Si_3N_4 rodlike crystals was fabricated by Spark Plasma Sintering (SPS) process. The microstructure and mechanical properties of the composite were investigated. Relative densities of the monolithic material and composite were above 95 percent. No reactions between Si_3N_4 and MoSi_2 were observed. The composite containing Si_3N_4 rodlike crystal had higher hardness than monolithic MoSi_2. The room-temperature flexural strength increased 60 percent compared to that of pure MoSi_2. Especially the room-temperature fracture toughness of the composites was higher than that of MoSi_2, from 3.6 MPa m~(1/2) for MoSi_2 to 5.1 MPa m~(1/2) for composites with 20 vol. percent Si_3N_4, respectively. Besides, the yield strength at elevated temperature and the low-temperature oxidation resistance for 20 vol. percent Si_3N_4-MoSi_2 composite exhibited considerable improvement over that of monolithic MoSi_2. These results showed that Si_3N_4 rodlike crystal is an effective reinforcement for MoSi_2.