High temperature fatigue and creep deformation behavior under static and cyclic loading in ceramics containing a viscous grain boundary phase
Fatigue and creep deformation behavior of a commercial grade of alumina with 6 wt % of grain boundary viscous phase was investigated. Two failure mechanisms were observed at 1000 C under static loading. At high stresses, fracture was dictated by slow growth of a single dominant flaw along the grain boundaries; at low stresses fracture occurred due to the nucleation, growth and linkage of multiple macrocracks. In the stress range used in the fatigue experiments, fracture under cyclic loading was dominated by the slow crack growth of a single dominant crack. In the slow crack growth regime, the lifetime under cyclic loading was greater than that under static loading (for the same maximum stress) by approximately a factor of 30. Extensive crack surface bridging by viscous grain boundary phase behind the crack tip was observed and is believed to be the most important factor for retarding crack growth during cyclic loading.
Engineering, Mechanical, Engineering, Materials Science
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign