Grain Boundary Migration in Alumina

2000 ◽  
Vol 652 ◽  
Author(s):  
Jeffrey K. Farrer ◽  
N. Ravishankar ◽  
Joseph R. Michael ◽  
C. Barry Carter
Keyword(s):  
Grain Boundary ◽  
Small Angle ◽  
Electron Backscatter Diffraction ◽  
Boundary Migration ◽  
Liquid Films ◽  
Grain Boundary Migration ◽  
Sintering Process ◽  
Orientation Relationships ◽  
Electron Backscatter ◽  
Backscatter Diffraction

ABSTRACTThe sintering process of ceramics involves grain-boundary migration (GBM) that is accompanied by mass transport across an interface. In this study, electron backscatter diffraction (EBSD) has been used to examine grain-boundary migration in alumina bicrystals with liquid films at the interface. EBSD patterns, taken near the sintered interface, have been used to study the effects of crystallography on GBM and to study the orientation relationships within the migrated regions of the crystal. Results indicate that the direction of migration is not always the same as that predicted by the current theories on GBM. It was also found that there may be small-angle misorientations in the migrated regions.

scholarly journals Texture and Shape Analysis of Quartzite Mylonites of the Metamorphic Sole of the Samail Ophiolite (Oman): Evidence for Syn- and Post-Obduction Deformation

Geosciences ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 111
Author(s):  
Peter Hallas ◽  
Wilfried Bauer
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Boundary Migration ◽  
Arabian Plate ◽  
Grain Boundary Migration ◽  
Main Role ◽  
Subgrain Rotation ◽  
Shear Sense ◽  
Subduction System ◽  
Backscatter Diffraction

The metamorphic sole, tectonically welded to the base of the Samail ophiolite in a supra-subduction system, is assumed to play the main role in strain accumulation during later thrusting onto the Arabian Plate (i.e., during obduction). The present study deals with five quartzite samples representative of the upper amphibolite and lower greenschist facies parts of the sole. Whole-rock textures obtained by neutron time-of-flight technique were coupled with microstructural observation using electron backscatter diffraction analyses. The quartz microstructural fabrics and textures in the upper and lower parts of the sole represent grain boundary migration and [c]-in-Y textures and subgrain rotation recrystallization and {r}-in-Z textures, respectively. The shear sense in these samples points to top-to-the-SW to SSW shear. One sample of the upper part, yielding a higher calcite amount, is later overprinted by bulging and displays top-to-the-NNE shear. We postulate to differentiate two main deformation steps. The first is the overall present subgrain rotation and grain boundary migration recrystallization combined to top ~SW shear is related to the sole accretion to the ophiolite and the eventually following thrusting onto the Arabian Plate. The second is correlated to a post-obduction extensional top-to-the-NNE shearing, which is associated with tectonic thinning of the ophiolite and mainly documented in the underlying autochthonous units.

scholarly journals Microstructural Evidence for Grain Boundary Migration and Dynamic Recrystallization in Experimentally Deformed Forsterite Aggregates

Minerals ◽  
2018 ◽  
Vol 9 (1) ◽  
pp. 17
Author(s):  
Caroline Bollinger ◽  
Billy Nzogang ◽  
Alexandre Mussi ◽  
Jérémie Bouquerel ◽  
Dmitri Molodov ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Dynamic Recrystallization ◽  
Grain Boundaries ◽  
Driving Forces ◽  
Electron Backscatter Diffraction ◽  
Boundary Migration ◽  
Large Strains ◽  
Grain Boundary Migration ◽  
Mapping Techniques ◽  
Von Mises

Plastic deformation of peridotites in the mantle involves large strains. Orthorhombic olivine does not have enough slip systems to satisfy the von Mises criterion, leading to strong hardening when polycrystals are deformed at rather low temperatures (i.e., below 1200 °C). In this study, we focused on the recovery mechanisms involving grain boundaries and recrystallization. We investigated forsterite samples deformed at large strains at 1100 °C. The deformed microstructures were characterized by transmission electron microscopy using orientation mapping techniques (ACOM-TEM). With this technique, we increased the spatial resolution of characterization compared to standard electron backscatter diffraction (EBSD) maps to further decipher the microstructures at nanoscale. After a plastic strain of 25%, we found pervasive evidence for serrated grain and subgrain boundaries. We interpreted these microstructural features as evidence of occurrences of grain boundary migration mechanisms. Evaluating the driving forces for grain/subgrain boundary motion, we found that the surface tension driving forces were often greater than the strain energy driving force. At larger strains (40%), we found pervasive evidence for discontinuous dynamic recrystallization (dDRX), with nucleation of new grains at grain boundaries. The observations reveal that subgrain migration and grain boundary bulging contribute to the nucleation of new grains. These mechanisms are probably critical to allow peridotitic rocks to achieve large strains under a steady-state regime in the lithospheric mantle.

Examination of the Orientation Relationships between the Main Phases of Duplex Stainless Steel by EBSD

2007 ◽  
Vol 537-538 ◽  
pp. 297-302
Author(s):  
Tibor Berecz ◽  
Péter János Szabó
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Stainless Steels ◽  
Electron Backscatter Diffraction ◽  
Duplex Stainless Steels ◽  
Alloying Elements ◽  
Orientation Relationships ◽  
Σ Phase ◽  
Electron Backscatter ◽  
Backscatter Diffraction

Duplex stainless steels are a famous group of the stainless steels. Duplex stainless steels consist of mainly austenitic and ferritic phases, which is resulted by high content of different alloying elements and low content of carbon. These alloying elements can effect a number of precipitations at high temperatures. The most important phase of these precipitation is the σ-phase, what cause rigidity and reduced resistance aganist the corrosion. Several orientation relationships have been determined between the austenitic, ferritic and σ-phase in duplex stainless steels. In this paper we tried to verify them by EBSD (electron backscatter diffraction).

scholarly journals Coupling Automated Electron Backscatter Diffraction with Transmission Electron and Atomic Force Microscopies

2000 ◽  
Vol 6 (S2) ◽  
pp. 940-941
Author(s):  
A.J. Schwartz ◽  
M. Kumar ◽  
P.J. Bedrossian ◽  
W.E. King
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Thermomechanical Processing ◽  
Electron Backscatter Diffraction ◽  
Grain Boundary Character Distribution ◽  
Atomic Force ◽  
Transmission Electron ◽  
Electron Backscatter ◽  
Network Engineering ◽  
Backscatter Diffraction

Grain boundary network engineering is an emerging field that encompasses the concept that modifications to conventional thermomechanical processing can result in improved properties through the disruption of the random grain boundary network. Various researchers have reported a correlation between the grain boundary character distribution (defined as the fractions of “special” and “random” grain boundaries) and dramatic improvements in properties such as corrosion and stress corrosion cracking, creep, etc. While much early work in the field emphasized property improvements, the opportunity now exists to elucidate the underlying materials science of grain boundary network engineering. Recent investigations at LLNL have coupled automated electron backscatter diffraction (EBSD) with transmission electron microscopy (TEM)5 and atomic force microscopy (AFM) to elucidate these fundamental mechanisms.An example of the coupling of TEM and EBSD is given in Figures 1-3. The EBSD image in Figure 1 reveals “segmentation” of boundaries from special to random and random to special and low angle grain boundaries in some grains, but not others, resulting from the 15% compression of an Inconel 600 polycrystal.

Crystallographic orientation of ilmenite inclusions in amphibole – an electron backscatter diffraction study

2020 ◽  
Vol 235 (4-5) ◽  
pp. 105-116
Author(s):  
Chang Xu ◽  
Shanrong Zhao ◽  
Jiaohua Zhou ◽  
Xu He ◽  
Haijun Xu
Keyword(s):  
Crystallographic Orientation ◽  
Electron Backscatter Diffraction ◽  
Reduction Reaction ◽  
Formation Temperature ◽  
Orientation Relationships ◽  
Ultra High Pressure ◽  
Electron Backscatter ◽  
Metamorphic Terrane ◽  
Backscatter Diffraction ◽  
Group 1

AbstractOrientated ilmenite inclusions have been discovered in amphibole of hornblendite from the Zhujiapu area, Dabie ultra-high-pressure (UHP) metamorphic terrane, China. In order to characterize the crystallographic orientation relationships between ilmenite inclusions and amphibole host and reconstruct the mechanism of their formation, we present an electron backscatter diffraction (EBSD) analysis combined with energy dispersive spectroscopy (EDS) analysis and electron microprobe analysis (EPMA) for ilmenite inclusions and amphibole host. The inclusions can be subdivided into four groups: (1) 60.2% of ilmenites have the crystallographic orientation {0001}Ilm // {100}Amp, (101̅0)Ilm // {010}Amp, [112̅0]Ilm // <001> Amp and [112̅0]Ilm // <012 > Amp. (2) 16.5% of ilmenites have <0001> Ilm // <001> Amp, (101̅0)Ilm // {010}Amp, (112̅0)Ilm // {100}Amp and [3̅031]Ilm // <012> Amp. (3) 13.8% of ilmenites have <0001> Ilm // <012> Amp, (112̅0)Ilm // {100}Amp and [3̅031]Ilm // <001> Amp. (4) 9.5% of ilmenites have <0001> Ilm // [1̅12]Amp, (101̅0)Ilm // {201}Amp, [112̅0]Ilm // [1̅12]Amp and ${[11\overline {21} ]_{Ilm}}$// <010> Amp. By comparing the lattice relationship between ilmenite inclusions and amphibole hosts, it is shown that the frequency of the ilmenite inclusions in different groups is related to the lattice coherency and oxygen packing. Group-1 of the ilmenite inclusions was most likely be formed via a solid-state exsolution process by cooling of the hornblendite after the intrusion was emplaced. The other three groups of ilmenite inclusions were probably formed via reduction reaction in an open system. The formation temperature of the ilmenite inclusions is estimated by using the TiO2 solubility geothermeter in amphibole. The minimum formation temperature of the ilmenite inclusions is about 1025 °C, and the maximum formation temperature of the ilmenite inclusions is about 1126 °C.

Application of Electron Backscatter Diffraction to Grain Boundaries

2010 ◽  
Vol 160 ◽  
pp. 39-46 ◽  
Author(s):  
Valerie Randle
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Experimental Methodology ◽  
Polycrystalline Materials ◽  
Grain Boundary Engineering ◽  
Network Characteristics ◽  
Grain Boundary Plane ◽  
Electron Backscatter ◽  
Measurement Strategies ◽  
Backscatter Diffraction

The technique of electron backscatter diffraction (EBSD) is ideal for the characterisation of grain boundary networks in polycrystalline materials. In recent years the experimental methodology has evolved to meet the needs of the research community. For example, the capabilities of EBSD have been instrumental in driving forward the topic of ‘grain boundary engineering’. In this paper the current capabilities of EBSD for grain boundary characterisation will be reviewed and illustrated by examples. Topics are measurement strategies based on misorientation statistics, determination of grain boundary plane distributions and grain boundary network characteristics.

Micromechanisms Involved in Grain Boundary Engineering

2005 ◽  
Vol 495-497 ◽  
pp. 1225-1230
Author(s):  
Andre Luiz Pinto ◽  
Carlos Sergio da Costa Viana ◽  
Luiz Henrique de Almeida
Keyword(s):  
Grain Boundary ◽  
Electron Backscatter Diffraction ◽  
Boundary Migration ◽  
Coincidence Site Lattice ◽  
Inconel 625 ◽  
Grain Boundary Engineering ◽  
Inconel 600 ◽  
Special Boundaries ◽  
Deformation Step ◽  
Backscatter Diffraction

Grain boundary engineering has been applied to different materials in order to increase properties particularly sensitive to intergranular phenomena. This work analyses the micromechanisms that allow the control of the amount of special boundaries which respect coincidence site lattice theory. α-brass, a lead alloy, Inconel 625 and Inconel 600 were submitted to different thermomechanical treatments and were analyzed via electron backscatter diffraction in order to characterize their grain boundaries. The occurrence of thin twins in some crystal directions during the deformation step seems to determine the results obtained as well as strain induced boundary migration.

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