The Influence of Grain Boundary Structure on Strain-Induced Grain Growth During Superplastic Deformation

1990 ◽  
Vol 196 ◽  
Author(s):  
H. J. Frost ◽  
R. Raj
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Superplastic Deformation ◽  
Boundary Migration ◽  
Forced Migration ◽  
Grain Boundary Sliding ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Diffusional Flow ◽  
Boundary Sliding

ABSTRACTA model is presented to explain the grain growth that is often observed during superplastic deformation. The atomic structure of grain boundaries leads to a coupling between boundary sliding and boundary migration. There is a similar coupling between the absorption or emission of vacancies from a boundary and boundary migration. Because of these couplings, the grain boundary sliding and diffusional flow of superplastic deformation produce extensive boundary migration. We propose that this forced migration leads to random changes in the sizes of grains, and that this evolution of the grain size distribution leads to grain growth.

Grain Boundary Structure and Sliding of Alumina Bicrystals

1999 ◽  
Vol 601 ◽  
Author(s):  
Y. Ikuhara ◽  
T. Watanabe ◽  
T. Yarnamoto ◽  
T. Saito ◽  
H. Yoshida ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Small Angle ◽  
Boundary Energy ◽  
High Resolution Electron Microscopy ◽  
Grain Boundary Sliding ◽  
Boundary Structure ◽  
Grain Boundary Energy ◽  
Grain Boundary Structure ◽  
Boundary Sliding

AbstractAlumina bicrystals were fabricated by a hot joining technique at 1500°C in air to obtain ten kinds of [0001] symmetric tilt grain boundaries which included small angle, CSL and high angle grain boundaries. Their grain boundary structures were investigated by high-resolution electron microscopy (HREM), and the respective grain boundary energies were systematically measured by a thermal grooving technique. It was found that grain boundary energy strongly depended on the grain boundary characters, e.g., there were large energy cusps at low Σ CSL grain boundaries. But, main part of grain boundary energy is likely to be due to the strain energy around the grain boundary, and the contribution of atomic configuration is not so large. Small angle grain boundaries were consisted of an array of partial dislocation with Burgers vector of 1/3[1100] to form the stacking faults between the dislocations. The behavior of grain boundary sliding was also investigated for typical grain boundaries by high-temperature creep test at 1400°C. As the result, the occurrence of grain boundary sliding was found to depend on the grain boundary atomic structure.

Superplastic Deformation Mechanisms in a Fine-Grained, Yttria-stabilized Tetragonal Zirconia Polycrystal (Y-TZP)

1990 ◽  
Vol 196 ◽  
Author(s):  
T. G. Nieh ◽  
J. Wadsworth
Keyword(s):  
Grain Boundary ◽  
Strain Rate ◽  
Grain Growth ◽  
Strain Rate Sensitivity ◽  
Superplastic Deformation ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Boundary Triple ◽  
Sliding Mechanism ◽  
Boundary Sliding

ABSTRACTConcurrent grain growth, and in particular, dynamic grain growth, was observed to take place during superplastic deformation of Y-TZP. As a result of this concurrent grain growth, the measured strain rate sensitivity was found to be lower than that measured under constantstructure conditions. In the present paper, data obtained from the superplastic deformation of YTZP under constant-structure conditions are presented. It is demonstrated that the strain rate sensitivity values are generally higher than 0.5, when measured from the grain size-compensated data; this result suggests a grain boundary sliding mechanism. Microstructures from samples prior to and after superplastic deformation reveal grains which are essentially equiaxed; this observation is also consistent with a grain boundary sliding mechanism. Both high-resolution images of grain boundary triple points using transmission electron microscopy, and fracture surface studies using Auger electron spectroscopy and X-ray photoelectron spectroscopy indicate that there is no evidence for the presence of glassy phases at grain boundaries in Y-TZP.

scholarly journals Grain Growth and Mechanical Behaviour of Polar Ice

1985 ◽  
Vol 6 ◽  
pp. 79-82 ◽  
Author(s):  
P. Duval
Keyword(s):  
Crystal Growth ◽  
Grain Boundary ◽  
Grain Growth ◽  
Boundary Migration ◽  
Grain Boundary Sliding ◽  
Dislocation Creep ◽  
Polar Ice ◽  
Dislocation Glide ◽  
Ice Caps ◽  
Polar Snow

Crystal size in polar ice caps increases with depth from the snow surface down to several hundred meters. Data on crystal growth in isothermal polar snow and ice show the same linear relationship between the size of crystals and their age. This paper reviews the mechanical behavior of polar ice which exhibits grain growth. Grain boundary migration associated with grain growth appears to be an efficient accomodation process for grain boundary sliding and dislocation glide. For grain growth to occur, strain energy must always be lower than the free energy of boundaries. The sintering of ice particles in polar firn is energized by the pressure due to the overburden of snow. Dislocation creep must be taken into account to explain the densification rate in the intermediate and final stage Constants of power law creep should depend on the crystal growth rate.

scholarly journals Grain and Grain Boundary Structure Evolution Without Texture Changes During Normal Grain Growth in 2-D Al Strips

1999 ◽  
Vol 32 (1-4) ◽  
pp. 187-195 ◽  
Author(s):  
V. Sursaeva ◽  
U. Czubayko ◽  
A. Touflin
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Columnar Structure ◽  
Boundary Structure ◽  
Structure Evolution ◽  
Grain Boundary Character Distribution ◽  
Grain Boundary Character ◽  
Grain Boundary Structure ◽  
Texture Change ◽  
Character Distribution

Changes of the grain boundary character distribution and texture during normal grain growth have been investigated using the SAC-SEM based method and a 4 circle X-ray texture goniometer on A1 strips with columnar structure. The microstructure of the strips consists of regions with oriented (clusters) and randomly oriented grains. All changes of microstructure are outside the clusters during normal grain growth and consequently no texture change was observed.

Recrystallization and Grain Growth in Rocks and Minerals

2004 ◽  
Vol 467-470 ◽  
pp. 545-550 ◽  
Author(s):  
David J. Prior ◽  
Michel Bestmann ◽  
Angela Halfpenny ◽  
Elisabetta Mariani ◽  
Sandra Piazolo ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
Grain Boundary Sliding ◽  
Data Sets ◽  
Nucleation Process ◽  
Ebsd Data ◽  
Boundary Sliding ◽  
And Migration

Misorientation analysis, using EBSD data sets, has enabled us to constrain better recrystallization mechanisms in rocks and minerals. Observed microstructures are not explicable in terms of recovery, boundary bulging and migration alone. We have to invoke either a nucleation process (physics unknown) or grain rotations that are not related to grain or boundary crystallography. Such rotations can occur by diffusion accommodated grain boundary sliding and this mechanism explains best the microstructure and texture of recrystallized grains in some rocks.

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