Young's Modulus of Elasticity of Carbon-Bonded Alumina Materials up to 1450°C

Investigating Young's modulus at elevated temperatures supports the understanding of microstructural changes as a function of application temperature. A sintered alumina and three carbon-bonded alumina materials with carbon contents of 20 and 30wt% and alumina grain size of 0.6-3mm were investigated. Young's modulus was measured in a temperature range from 25 degrees C to 1450 degrees C by the impulse excitation technique. The Young's modulus of carbon-bonded materials increases up to 140% at 1450 degrees C. After one cycle, a decrease of the Young's modulus up to 50% is registered at room temperature. There is a strong hysteresis behavior during one cycle. Thermal expansion measurements show highest expansion for the highest graphite content material. The expansion of alumina grains and graphite flakes, resulting in microcrack generation during cooling and microcrack healing during heating, is reflected in the registered values of the Young's modulus as a function of the temperature. It is assumed, that higher graphite amounts as well as coarse grains lead to lower sintering effects of the microstructure at elevated temperatures and as a result lower values of the Young's modulus have been registered.