The microstructure of polycrystalline alumina, deformed using hydrostatic pressures at low temperatures, was investigated by means of transmission electron microscopy. It was found that deformation occurred mainly via prism-plane slip and rhombohedral twinning. The introduction of H led to a significant decrease in the yield stress. In large-grained samples, deformed with H, the accommodation of twinning involved dislocation reactions in the twin boundary and in the grains; rather than cracking. Prism-plane dislocations decomposed into basal dislocations by cross-slip; probably due to a decrease in the Peierls stress for basal slip in the presence of H.

Slip and Twinning in Polycrystalline Alumina (α-Al2O3) Deformed under Hydrostatic Pressure between 600 and 1000C. S.L.Korinek, J.Castaing: Journal of the American Ceramic Society, 2003, 86[4], 566-73