TENSILE CREEP-BEHAVIOR OF A VITREOUS-BONDED ALUMINUM-OXIDE UNDER STATIC AND CYCLIC LOADING

Creep deformation and rupture behavior of a vitreous-bonded aluminum o xide was investigated under uniaxial static and cyclic tensile loading s at 1000 degrees, 1100 degrees, and 1175 degrees C. The material was more creep resistant, i.e., having lower creep strain rates, under cyc lic loading compared to that under static loading, For the same maximu m applied stress, the ratio of steady-state creep rate under static lo ading to that under cyclic loading at 1100 degrees C was approximately 100, However, the value of this ratio decreased to about 10 when the testing temperature was raised to 1175 degrees C or lowered to 1000 de grees C, Under static loading the material had more propensity to deve lop creep damage in the form of micro- and macrocracks, leading to ear ly failure, whereas under cyclic loading the creep damage was more uni formly distributed in the form of cavities confined to the multigrain junctions, Viscous bridging by the grain boundary second phase may be the primary contributor to the lower creep deformation rate and improv ed lifetime under cyclic loading.