Mechanical properties of Ce-TZP/Al₂O₃ ceramic composites as a function of sintering parameters

Abstract

Ceramic composites based on Ce-TZP/Al₂O₃/H6A were sintered in order to promote grain growth and to study the effects of ZrO₂ grain size on the properties of this material. A mixture of ZrO₂-CeO₂-Al₂O₃ powders was sintered at 1450 °C-2 h, following the manufacturer’s recommendations. Then, the samples were further treated at 1500 or 1600 °C, for 0, 2, 8, or 24 h. The sintered specimens were characterized by X-ray diffraction, relative density, and grain size distribution. Vickers nanohardness, Young’s modulus (E), and fracture toughness were measured. The materials showed complete densification for all sintering conditions studied. t-ZrO₂, α-Al₂O₃, and cerium hexaluminate (H6A) were observed. The alumina and hexaluminate grains had average grain sizes of 0.7 and 4.5 μm (AR>3), respectively, without significant variations during the additional heat treatments. However, significant growth took place for the ZrO₂ grains with increasing temperature and holding time, increasing the average grain size from 0.6~1.4 μm, when sintered at 1500 °C-2 h to 1600 °C-24 h, respectively. The materials exhibited Vickers nanohardness of 1800 HV and E=241±15 GPa. On the other hand, the considerable grain growth of the ZrO₂ grains as a function of holding time reflected in a reduction of the fracture toughness, which decreased from 8.5 to 5.7 MPa.m^1/2 for samples sintered at 1500 °C-2 h to 1600 °C-24 h, respectively.

Keywords:
Ce-TZP/Al₂O₃/H6A composites; densification; grain growth; mechanical properties