Mechanical Properties of Alumina Whisker/Mullite Composite Ceramics

Abstract

Mullite composite ceramics reinforced with 10, 20 and 30vol% a-alumina whiskers were prepared by hotpressing at 1500 to 1800°C under 30 MPa for 30min. The mechanical properties of the hot-pressed bodies were investigated. Considerably dense composites were obtained at 1700°C with a whisker content of up to 30vol%. No change in room temperature bending strength was observed by addition of whiskers. The sintered bodies obtained at 1700°C had the highest room temperature bending strength of around 380 MPa. Although the high temperature strength showed complicated dependence on whisker content, the composite with a whisker content of 30vol% had almost the same high temperature strength as monolithic mullite. Increasing whisker content increased monotonously hardness and elastic modulus. The fracture toughness of a composite with a whisker content of 30vol% was 1.5 times larger than that of monolithic mullite, due to crack deflection by whiskers and to the increase of elastic modulus.