Pulsed electric current sintering and characterization of ultrafine Al2O3–WC composites

Ultrafine Al2O3 powder mixtures with up to 80 vol% ultrafine WC were prepared and consolidated by pulsed electric current sintering (PECS) for 4 min at 1250–1750 °C under a mechanical pressure of 60 MPa. Fully dense composites with ≤40 vol% WC could be achieved when PECS at 1450 °C for 4 min, whereas 1650 °C was needed for the WC matrix composites. The microstructure, electrical conductivity and mechanical properties of the composites were assessed as a function of the WC content. Microstructural analysis showed that Al2O3 and WC grain growth was significantly suppressed due to secondary phase addition, resulting in ultrafine (<500 nm) microstructures. Excellent mechanical properties, combining a Vickers hardness of 25 GPa, fracture toughness of 4.8 MPa m1/2 and flexural strength of 1000 MPa, as well as electrical conductivity of 1.09E+6 Ω−1 m−1 were obtained for the Al2O3–60 vol% WC composite.