Abstract
Alumina composites incorporating with 0, 5, 10 15, 20, and 25 vol pct of TiC were consolidated by the spark plasma sintering at 1673 K (1400 A degrees C). The effects of increasing TiC compositions on electrical and mechanical properties of the composites were investigated at room temperature. The dc electrical conductivity behavior demonstrates a transition from insulator to conductor around 12.5 vol pct of TiC in the framework of percolation theory. The conductivity attains a maximum value of a parts per thousand 230 S/m at 25 vol pct of TiC sufficient to machine the composite by electro discharging machining. The Vickers hardness and fracture toughness of the composites increase with the addition of TiC vol pct, whereas elastic modulus decreases. The results indicate that crack deflection, crack bridging, and crack branching by the TiC particles are responsible for the significantly improved fracture toughness of the composites.