Synthesis of Al₂O₃/TiCN-0.2%Y₂O₃ Composite by Hot Pressing

Al₂O₃/TiCN composites were synthesized by hot pressing. The influences of components and HP temperature on mechanical properties, such as bending strength, breaking tenacity and Vickers hardness were investigated. The results showed that the mechanical properties of Al₂O₃/TiCN composite increased with temperature when hot pressing temperature is below 1650 °C. The mechanical properties reached their maximums when the composites were sintered at 1650 °C for 30 min under hot pressing pressure of 35 MPa, the value of bending strength, breaking tenacity and Vickers hardness was 1015 MPa, 6.89 MPa · m^1/2, and 20.82 MPa, respectively. When hot pressing temperature was above 1650 °C, density decreased because of decomposition with increased temperature, and mechanical properties dropped because of rapid growth of grains in size at high temperature. Microstructure analysis showed that the addition of Y₂O₃ led to the formation of YAG phase so as to inhibit the growth of crystals. This helped to improve breaking tenacity of the composites. TiCN particles with diameters of 1 μm dispersed at Al₂O₃ grain boundaries, inhibited grain growth and enhanced mechanical properties of the composites. SEM study of the propagation of indentation cracks showed that the bridge linking behavior between matrix and strengthening phase might lead to the formation of the coexisted field of crack deflection, branching and bridge linking. The mechanism of this phenomenon was that the addition of Y₂O₃ improved the dispersion of TiCN particles so as to enhance the tenacity of the composites. The breaking tenacity was changed from 5.94 to 6.89 MPa · m^1/2.