Grain Boundary Sliding and Atomic Structures in Alumina Bicrystals with [0001] Symmetric Tilt Grain Boundaries

Abstract

Orientation controlled alumina bicrystals were fabricated by a hot joining technique at 1773 K in air to obtain [0001] symmetric tilt boundaries including coincidence grain boundaries. The grain boundary energies were measured by the thermal grooving technique, and they were found to strongly depend on the grain boundary character. Atomic structures of those grain boundaries were observed by high-resolution electron microscopy (HREM). It was found that the atomic structures did not always correlate with the grain boundary energies. This finding indicates that the grain boundary energy originates not only from the atomic bonding on the grain boundary but also from the strain of the grain interior in the vicinity of the boundary. The grain boundary sliding was also investigated by the high-temperature creep test. As the results, the grain boundaries with the same energy showed different sliding behavior. The occurrence of grain boundary sliding is considered to depend on the atomic bonding of a grain boundary.

Al2O3 Grain Boundary Segregation in a Thermal Barrier Coating on a Ni-Based Superalloy

“…Combining all the segregating elements, the total interfacial excess at the grain boundaries decreased from 8.5 atoms/nm 2 near the topcoat to 1.8 atoms/nm 2 at about the middle of the TGO layer with a minimum interfacial excess of 1.5 atoms/nm 2 found at 1.2 μm beneath the top-coat. No obvious dependence between solute segregation and grain boundary character was noted, which may not be surprising considering all the grain boundaries analyzed in this work were large-angle random boundaries (Watanabe et al, 2002). For such boundaries, the solute saturation level was reported to be 9 atoms/nm 2 for Y-doped α-Al 2 O 3 (Gülgün et al, 2002), which is above the cumulative excesses measured in this study.…”

Direct Evidence of Dopant‐Enhanced Grain‐Boundary Sliding in Yttria‐Stabilized Zirconia Bicrystals

“…Bicrystal studies in ceramics have focused on the characterization of atomic structures and energies of specific grain boundaries, such as boundaries according to the coincidence site lattice (CSL) theory and the low‐angle tilt boundaries 18–27 . Accordingly, a limited number of mechanical tests using bicrystals have been reported for ceramic materials 28–31 . Thus far, Yoshida et al 31 .…”

“…[18][19][20][21][22][23][24][25][26][27] Accordingly, a limited number of mechanical tests using bicrystals have been reported for ceramic materials. [28][29][30][31] Thus far, Yoshida et al 31 systematically investigated creep behavior for zirconia bicrystals with [110] tilt grain boundaries and found that the creep behavior strongly depended on the grain-boundary characters. These results indicate that the grain-boundary geometry is one of the important factors for grain-boundary sliding in zirconia.…”

Dopant Effect on the High-Temperature Grain Boundary Sliding in Alumina

“…However, it is not clear whether the doped cations affect the grain boundary sliding itself or influence the accommodation process for sliding. More recently, we have started to investigate the grain boundary sliding behavior using Al 2 O 3 bicrystals in order to make clear the effect of cation segregation on grain boundary sliding directly [12][13][14]. This paper aims to show the dopant effect on the grain boundary sliding in Al 2 O 3 ceramics.…”