Influence of in-situ formed Ba-β-Al2O3 on mechanical properties and thermal shock resistance of ZTA/Ba-β-Al2O3 composites

Abstract

To improve the mechanical properties and thermal shock resistance of zirconia toughened alumina (ZTA) composites, barium carbonate (BaCO3) was added to yttria-stabilized zirconia (YSZ) and Al2O3 powders to form ZTA/Ba-β-Al2O3 composites, which were prepared by a solid-state reactive sintering method. As BaCO3 content increased, more Ba-β-Al2O3 was formed, resulting in the decreases in relative density and Vickers hardness. The fracture toughness was enhanced with increasing BaCO3 content and reached a peak at 4 wt% BaCO3. The improved fracture toughness is the result of synergistic toughening effects of martensitic transformation of ZrO2 and crack deflection/bridging. After thermal shock tests, the residual strength of ZTA/Ba-β-Al2O3 composites was higher than that of ZTA. The improvement in thermal shock resistance is mainly ascribed to the formation of elongated Ba-β-Al2O3 with a hexagonal structure, which can dissipate the energy associated with crack propagation during thermal shock.