Plastic Deformation of Fine‐Grained Alumina (Al 2 O 3 ): I, Interface‐Controlled Diffusional Creep

Plastic deformation in fine‐grained alumina polycrystals (grain size 1 to 15 μm) was studied. At least three distinct deformation mechanisms are important: diffusional creep, basal slip, and unaccommodated grain‐boundary sliding. The first and most important of these processes is addressed in this paper. Analysis of the deformation dynamics suggests that both lattice and grain‐boundary diffusion are important in the diffusional creep. Aluminum, rather than oxygen, lattice and grain‐boundary diffusion are rate‐controlling because oxygen diffusion is very slow in the lattice but very rapid in grain boundaries. Significantly, the diffusional creep can become interfacecontrolled at low stresses, causing the often‐reported non‐Newtonian creep behavior of fine‐grained alumina.