HIGH TEMPERATURE DAMAGE ACCUMULATION IN HOT PRESSED ALUMINA.

The development of grain-boundary cavitation in hot-pressed Al//2O//3 both during flexural creep and tress-free annealing in air has been studied. Creep damage accumulation in driven both by the applied stress, and by internal gas pressure in the cavities. The internal pressure results from gas trapped during hot pressing, and from gas-generating chemical reactions active during testing. At machined surfaces, a damage-resistant skin about 15-20 mu m thick overlies a heavily cavitated region.