An evaluation of Al 2O 3–ZrO 2 composites produced by coprecipitation method

Abstract

The objective of this work is to produce Al 2O 3–ZrO 2 composite from nano-sized powders processed by coprecipitation method. Al 2O 3 and mixture of Al 2O 3 + 10 wt.% ZrO 2 precipitated successfully by chemical route from aluminum sulfate and zirconium sulfate were pressed under uniaxial compression of 170 MPa and sintered at 1600 °C for 1 h. SEM investigations revealed that, pure alumina sample has a microstructure with coarse grains which anisotropically grown up to 30–40 μm in size. In alumina–zirconia composite, the structure consists of very fine equiaxed grains of typically 2 μm in which zirconia precipitates were uniformly dispersed. By adding zirconia to alumina, hardness and indentation fracture toughness were increased from 11.6 GPa to 16.8 GPa and from 3.2 MPa m 1/2 to 4.9 MPa m 1/2, respectively. Improvement in fracture toughness was attributed to bridging effects of zirconia particles as well as transformation toughening.