Development of low cost Mg-PSZ with nanostructure and high mechanical strength

Abstract

Magnesia-Partially Stabilized Zirconia (Mg-PSZ) is an attractive ceramic material for engineering applications because it is one of the toughest sintered ceramics. It consists of a cubic zirconia matrix with a dispersion of metastable tetragonal zirconia precipitates when doped with magnesia in the range of 8-10 mol%. It is believed that the high toughness of Mg-PSZ materials is attributed to the tetragonal precipitates which nucleate and grow homogeneously within the cubic grains. Mechanical and thermal properties of Mg-PSZ are improved by controlling the microstructure through heat treatment. The objective of this research was to study the phase transformation and mechanical properties of 8.1 mol% Mg-PSZ specimens. The samples were sintered in a temperature range from 1500 to 1700 degree celsius for 2 hours and heat treated at 1400ํC for 0.5 to 10 hours in air to avoid the prospect of eutectoid decomposition at lower temperature. The bulk density of specimens sintered at 1700 C was 5.78 g/cm3 which was close to the theoretical density. Vickers hardness and bending strength of specimens decreased, but fracture toughness increased with increasing sintering temperature. After heat treatment, Vickers hardness and bending strength drastically decreased. The specimen sintered at lower temperature easily transformed to monoclinic phase. After annealing, many small cracks were generated on the surface. MgO evaporated and condensed on the surface of specimen. These results might be the cause of the decrement of mechanical property of Mg-PSZ.