High-Temperature Compression Deformation Behavior of Fine-Grained Carbon-Bonded Alumina

Carbon-bonded alumina with 33 wt% residual carbon was tested in compression at room temperature and at temperatures between 700 degrees C and 1500 degrees C in quasi-static tests, creep tests, and stress relaxation tests. Therefore, a new high-temperature test set up with inert gas chamber and inductive heating was used. The tests were accomplished by investigations of microstructure and Young's modulus. At room temperature, the results exhibit a pronounced hysteresis for the first loading cycle, which almost completely disappeared in subsequent cycles. The creep tests showed characteristic curves for compression whereas primary and secondary (stationary) creep occurred. Above 1000 degrees C, a strong increase in creep rate was detected, whereas almost no creep was observed below this temperature. All creep curves were approximated with the models of logarithmic and Andrade creep. The activation energy for creep was found to be 263 kJ/mol above 1150 degrees C. The resistance against stress relaxation showed an anomaly with a minimum between 1000 degrees C to 1200 degrees C and a maximum between 1300 degrees C and 1400 degrees C.