Microstructure and mechanical properties of Al2O3-MgB2 composites

The microstructure and mechanical properties of Al2O3-5wt.% MgB2 composites were studied by scanning electron microscopy (SEM) and Vickers hardness measurements. The experiments show that MgO whiskers can grow at temperatures as low as 950 °C. When sintered at 1450 °C, due to the strong vaporization of Mg, MgO and MgAl2O4 appear around Al2O3 grains. The microstructure of the Al2O3-5wt.% MgB2 differs remarkably from Al2O3 sintered at the same temperature. The fracture toughness of the Al2O3-5% MgB2 composite is 4.0 MPa m1/2 which is slightly higher than for pure Al2O3 ceramics.