HIGH-TEMPERATURE MECHANICAL-BEHAVIOR OF POROUS OPEN-CELL AL2O3

Crushing strength and fracture toughness values have been determined for open-cell Al2O3 of density less than 30% of the theoretical density for temperatures up to 1500°C. Room temperature crushing strengths as a function of relative density were found to obey approximately a model for mechanical properties based on bending of individual struts within a cell. Fracture toughness values showed some deviation from the model, which was attributed to the presence of closed cells and microstructural inhomogeneities. Strength and toughness increased at about 900-1100°C but declined above 1200°C. Compressive creep of the open-cell Al2O3 has been measured for temperatures of 1200-1500°C. Creep occured by diffusional flow for strain rates between 10-8 and 10-6 s-1 for stresses in the range 20-100 kPa. The activation energy for steady state creep was 504 kJ mol-1, which is typical for creep of dense Al2O3. The onset of tertiary creep was associated with the formation of creep cracks in the struts subjected to bending. © 1990.