Mechanical properties and microstructural evolution of alumina–zirconia nanocomposites by microwave sintering

Microwave sintering has emerged in recent years as a novel method for sintering a variety of materials that have shown significant advantages against conventional sintering procedures. This work involved an investigation of microwave hybrid fast firing of alumina–zirconia nanocomposites using commercial alumina powder and monoclinic nanometric zirconia. The suspensions were prepared separately in order to obtain 5, 10 and 15 vol% of ZrO2 in the alumina matrix. The samples were sintered in a monomode microwave furnace at 2.45 GHz in air at different temperatures in the range 1200–1400 °C with 10 min of dwelling time and 200 °C/min of heating rate. The effect of sintering temperature in densification, mechanical properties and microstructure behavior of the composites was investigated. Higher density, hardness and Young׳s modulus, excellent fracture toughness properties and homogeneous microstructure were achieved by microwave sintering in comparison to conventional heating. Microstructure analysis showed that the alumina grains had not grown significantly, indicating that the zirconia particles provided a hindering effect on the grain growth of alumina.