Microstructure and mechanical property of (TiB2-SiC) agglomerate-toughened B4C-TiB2-SiC composites

摘要

B4C-TiB2-SiC composites toughened by (TiB2-SiC) agglomerates were prepared via reactive hot pressing with B4C and TiSi(2)as raw materials. Phase composition, microstructure, and mechanical properties of the fabricated composites were investigated. The function of (TiB2-SiC) agglomerates was analyzed, and the strengthening and toughening mechanism were also discussed. Results indicated that some of the in situ formed TiB(2)and SiC were interlocked to form special (TiB2-SiC) agglomerates in the matrix. The good comprehensive performances of 510 MPa flexural strength, 5.84 MPa center dot m(1/2)fracture toughness, and 31.93 GPa hardness were obtained in the composites fabricated with 30 wt TiSi2. The in situ introduced fine TiB(2)and SiC grains refined the grains of B4C due to the pinning effect, which enhanced the strength. The special (TiB2-SiC) agglomerates and the existing toughening phenomena such as crack deflection, branching, and microcrack regions induced by the mismatch of thermal expansion coefficients, had cumulative effects on improving the fracture toughness.