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

2002 ◽  
Vol 43 (7) ◽  
pp. 1561-1565 ◽  
Author(s):  
Tsuyoshi Watanabe ◽  
Hidehiro Yoshida ◽  
Yuichi Ikuhara ◽  
Taketo Sakuma ◽  
Hiroyuki Muto ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Boundary Sliding ◽  
Atomic Structures ◽  
Symmetric Tilt ◽  
Boundary Sliding

Grain Boundary Characters and Sliding of [0001] Symmetric Tilt Boundaries in Alumina

2003 ◽  
Vol 778 ◽  
Author(s):  
Katsuyuki Matsunaga ◽  
Hitoshi Nishimura ◽  
Hiroyuki Muto ◽  
Takahisa Yamamoto ◽  
Yuichi Ikuhara
Keyword(s):  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Creep Tests ◽  
Open Spaces ◽  
Atomic Structures ◽  
Transmission Electron ◽  
Symmetric Tilt ◽  
Tilt Boundaries ◽  
Boundary Sliding ◽  
Boundary Core

AbstractBicrystal experiments were performed to investigate atomic structures and high-temperature creep properties of [0001] symmetric tilt grain boundaries in Al2O3. Al2O3 bicrystals with Σ7, Σ31 and Σ39 boundaries were fabricated by a diffusion bonding technique, and their atomic arrangements at the grain boundary cores were analyzed by high-resolution transmission electron microscopy (HRTEM), in combination with static lattice calculations based on two-body ionic potentials. Compressive creep tests were also conducted to examine the behavior of grain boundary sliding for the above bicrystals. It was found that the behavior of grain boundary sliding depends on the grain boundary characters, whereas the trend of grain boundary sliding was not related to their Σ values. In contrast, HRTEM observations showed that the Σ31 boundary exhibiting the highest sliding rate has open spaces at the boundary core. Since grain boundary diffusion is expected to accommodate strains at grain boundary cores during sliding, it is likely that such open spaces give rise to high diffusivity at the grain boundary core, which results in the rapid grain boundary sliding of Σ31.

Research on Micro-Mechanism of Nanocomposite Ceramic in Two-Dimensional Ultrasound Grinding

2007 ◽  
Vol 359-360 ◽  
pp. 344-348 ◽  
Author(s):  
Bo Zhao ◽  
Yan Wu ◽  
Guo Fu Gao ◽  
Feng Jiao
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Deformation Mechanism ◽  
Ground Surface ◽  
Grain Boundary Sliding ◽  
Second Phase ◽  
Two Dimensional ◽  
Composite Ceramics ◽  
Nano Composite ◽  
Boundary Sliding

Surface microstructure of nano-composite ceramics prepared by mixed coherence system and machined by two-dimensional ultrasonic precision grinding was researched using TEM, SEM, XRD detector and other equipments. Structure, formation mechanism and characteristic of metamorphic layer of ground surface of nano-composite ceramics were researched. The experiment shows micro deformation mechanism of ceramic material in two-dimensional ultrasound grinding is twin grain boundary and grain-boundary sliding for Al2O3, and it is crystal dislocation of enhanced phase, matrix grain boundary sliding, coordination deformation of intergranular second phase as well as its deformation mechanism for nano-composite ceramics. The fracture surfaces of nano-composite materials with different microscopic structure were observed using TEM and SEM. Research shows that ZrO2 plays an important influence on the generation and expansion of crack, and enhances the strength of grain boundaries. When grain boundaries is rich in the ZrO2 particles, the crack produced in grinding process will be prevented, and the surface with plastic deformation will be smooth. The results shows nanoparticles dispersed in grain boundary prevents crack propagation and makes materials fracture transgranularly which makes the processed surface fine.

scholarly journals Hierarchical creep cavity formation in an ultramylonite and implications for phase mixing

Solid Earth ◽  
2017 ◽  
Vol 8 (6) ◽  
pp. 1193-1209 ◽  
Author(s):  
James Gilgannon ◽  
Florian Fusseis ◽  
Luca Menegon ◽  
Klaus Regenauer-Lieb ◽  
Jim Buckman
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Finite Strain ◽  
Grain Boundary Sliding ◽  
Large Strains ◽  
Cavity Formation ◽  
Phase Mixing ◽  
Transient Phenomena ◽  
Boundary Sliding

Abstract. Establishing models for the formation of well-mixed polyphase domains in ultramylonites is difficult because the effects of large strains and thermo-hydro-chemo-mechanical feedbacks can obscure the transient phenomena that may be responsible for domain production. We use scanning electron microscopy and nanotomography to offer critical insights into how the microstructure of a highly deformed quartzo-feldspathic ultramylonite evolved. The dispersal of monomineralic quartz domains in the ultramylonite is interpreted to be the result of the emergence of synkinematic pores, called creep cavities. The cavities can be considered the product of two distinct mechanisms that formed hierarchically: Zener–Stroh cracking and viscous grain-boundary sliding. In initially thick and coherent quartz ribbons deforming by grain-size-insensitive creep, cavities were generated by the Zener–Stroh mechanism on grain boundaries aligned with the YZ plane of finite strain. The opening of creep cavities promoted the ingress of fluids to sites of low stress. The local addition of a fluid lowered the adhesion and cohesion of grain boundaries and promoted viscous grain-boundary sliding. With the increased contribution of viscous grain-boundary sliding, a second population of cavities formed to accommodate strain incompatibilities. Ultimately, the emergence of creep cavities is interpreted to be responsible for the transition of quartz domains from a grain-size-insensitive to a grain-size-sensitive rheology.

scholarly journals Diffusion-Accommodated Grain Boundary Sliding in a Polycrystal

1990 ◽  
Vol 196 ◽  
Author(s):  
P. M. Hazzledine ◽  
J. H. Schneibel
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Grain Boundary Sliding ◽  
Diffusional Creep ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Material Deposition ◽  
Two Dimensional Model ◽  
Boundary Sliding ◽  
Coble Creep

ABSTRACTA two-dimensional model for diffusional creep (Coble creep) and diffusionaccommodated grain boundary sliding in polycrystals has been developed. The results obtained for small symmetrical clusters of grains reproduce Spingam and Nix's work [Acta Metall. 2M, 1389 (1978)]. For clusters of irregularly shaped grains the material deposition and removal rates, the fluxes along the grain boundaries, the grain boundary tractions as well as the grain boundary sliding rates are irregular and can all be calculated.

Atomistic simulation of sliding of [1010] tilt grain boundaries in Mg

2009 ◽  
Vol 24 (11) ◽  
pp. 3446-3453 ◽  
Author(s):  
Hao Zhang
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Twin Boundary ◽  
Boundary Migration ◽  
Rigid Motion ◽  
Grain Boundary Sliding ◽  
Normal Displacement ◽  
Tangential Displacement ◽  
Boundary Sliding ◽  
Shear Motion

A series of molecular dynamics simulations was performed to study grain boundary sliding of three types of [101¯0] tilt grain boundaries in a magnesium bicrystal. In particular, a near Σ11 twin boundary, an asymmetric near Σ11 twin boundary, and a θ = 40.3° general [101¯0] tilt grain boundary were studied. Simulations showed that grain boundary sliding (a rigid motion of two grains relative to each other along boundary plane) did not occur over the stress range applied; instead, coupled shear motion (grain boundary sliding induced boundary migration) was dominant. Although the measured coupling coefficient, the ratio of boundary tangential displacement to boundary normal displacement, was in good agreement with theoretical prediction, the detailed shear behavior was different, depending on types of grain boundary, magnitude of applied shear stress, and temperature. It was also noted that grain boundary twining was the predominant mechanism that allowed the coupled shear motion to occur in hexagonal close-packed (HCP) magnesium.

Transient creep in fine-grained polycrystalline Al2O3 with Lu3+ ion segregation at the grain boundaries

2001 ◽  
Vol 16 (3) ◽  
pp. 716-720 ◽  
Author(s):  
Hidehiro Yoshida ◽  
Yuichi Ikuhara ◽  
Taketo Sakuma
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Testing Temperature ◽  
Grain Boundary Sliding ◽  
Transient Creep ◽  
Transient Time ◽  
Fine Grained ◽  
Boundary Sliding ◽  
The Difference ◽  
Good Agreement

The creep deformation in fine-grained polycrystalline Al2O3 is highly suppressed by the addition of 0.1 mol% LuO1.5. The transient creep behavior in Lu-doped Al2O3 was examined at the testing temperature of 1250–1350 °C, and the data were analyzed in terms of the effect of stress and temperature on the extent of transient time and strain. The experimental data on the transient creep in Lu-doped Al2O3 showed good agreement with the prediction from a time function of the transient and the steady-state creep associated with grain boundary sliding as well as an undoped one. The difference in the transient creep between Lu-doped and undoped Al2O3 can also be explained by the retardation of grain boundary diffusion due to the Lu3+ ions segregation in the grain boundaries.

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