Sintering and Mechanical Properties of Alumina-Yttrium Aluminate Composites

Abstract

Yttrium Aluminate (having different mole percent of Y2O3) were prepared by mixing of Al2O3 and Y(NO3)2.6H2O and calcination of powder at 1400oC. The calcined Yttrium Aluminate powder was added to Aluminain different volume fractions (5, 10, 15 and 20 vol%), compacted and sintered at 1650oC. The sintered sample had a relative density (82-90 % of theoretical). The sintered samples were characterised by bulk density, apparent porosity, hardness, strength, toughness and microstructure. The fracture toughness as measured by Indentation Strength in Bending(ISB) method was 2.4 MPavm for pure Alumina and it increased to 4.21 MPavm at 20 vol% Yttrium Aluminate addition. Microstructure showed that the Yttrium Aluminate was inhomogeneously distributed in the Alumina matrix. The crack path of the indented samples indicates that crack bowing takes place in Alumina–Yttrium Aluminate samples. It is concluded that proper densification of the composites could possibly further increase the toughness and strength