Spark plasma sintering of SiC-LaB6 composite

A SiC-LaB6 composite was prepared by the spark plasma sintering (SPS) technique at temperatures of 1600-1880 °C for 300 s at a compaction pressure of 40 MPa, and the densification behaviour, microstructure characteristics and mechanical properties were investigated. The results showed that the maximum relative density of 98.6% belonged to the SiC-LaB6 composite sintered at 1840 °C. Microstructures consisted of equiaxed LaB6 grains and SiC grains, and the average size of LaB6 grains increased from 3.13 to 5.13 μm as the temperature was increased from 1600 to 1880 °C. The SiC and LaB6 grains were atomically abrupt and both crystals were directly bonded. The maximum Vickers hardness and fracture toughness obtained for SiC-LaB6 composite sintered at 1840 °C were 26.5 GPa and 7.15 MPa m1/2, respectively. Crack deflection and crack branching played important roles in the toughening of SiC-LaB6 composite.