MECHANICAL-PROPERTIES OF A PARTIALLY SINTERED ALUMINA

An experimental investigation was performed to understand the mechanical properties of alumina with moderate amounts of porosity (similar to 20-40%). Young's modulus, strength and fracture toughness showed similar behavior as a function of the degree of sintering. For low sintering temperatures (<1050 degrees C), the mechanical properties were found to change significantly with only minimal densification, and this was considered to be due to neck growth by surface diffusion. At these temperatures, increases in sintering time resulted in further increases in Young's modulus. The Young's modulus and fracture toughness data agreed well with modifications to a recent theory. The critical crack size in these porous materials calculated from the strength and fracture toughness data was found to increase slightly as the sintering temperature was increased. It was concluded that significant improvements in the mechanical properties of porous ceramics can be obtained by control of the sintering process, and in some cases these improvements can be made with minimal densification.