Grain Boundary Structures and High Temperature Deformations in Alumina Bicrystals

Abstract

Alumina bicrystals were successfully fabricated by hot joining technique at 1500°C in air to obtain two kinds of [0001] symmetrical tilt grain boundaries, i.e., Σ7 and Σ31. Their atomic structures and high-temperature deformation behaviors were investigated by high resolution transmission electron microscopy (HRTEM) and compressive creep tests, respectively. HRTEM observation revealed that grain boundaries in the alumina bicrystals were directly bonded without any amorphous phases, and that the atomic structure of ∑7 was different from that of Σ31 due to their geometrical misorientation and grain boundary planes. It was also found that grain boundary sliding rate in Σ7 was much smaller than that in Σ31. These results indicate that grain boundary sliding strongly depends on geometrical coherency and atomic structure of grain boundaries.