Analyzing the Variations in the Composition and Properties in Zirconia Alumina Composite Ceramics

Abstract

The effect of unstabilized zirconium dioxide on the processes of formation of composite ceramics from industrial corundum powders heat-treated at temperatures of 1430 and 1580°C, changes in its microstructure and physical and mechanical properties have been investigated. It was shown that due to the rigid corundum matrix, unstabilized ZrO2 is preserved mainly in the tetragonal phase. When ceramics are sintered during heat and self-diffusion, zirconium particles are located along the grain boundary of the corundum matrix and fill the pore space. The sintering effect of amorphous SiO2 also contributes to the increased density of ceramics. A two-stage sintering mode provides a finer-grained microstructure of ceramics. It was shown that due to the presence of a larger number of ZrO2 grains capable of t-m-transformation at the Al2O3 boundaries, the resistance of composite ceramics to mechanical and thermal loads increases. Ceramics obtained at 1580°C and containing 6.0 wt.% t-ZrO2 possesses the maximum hardness of 17 GPa. Dilatometric characteristics and the values of the relative shrinkage of composite samples are given.