Observations of grain boundary structure in submicrometer-grained Cu and Ni using high-resolution electron microscopy

1998 ◽  
Vol 13 (2) ◽  
pp. 446-450 ◽  
Author(s):  
Zenji Horita ◽  
David J. Smith ◽  
Minoru Nemoto ◽  
Ruslan Z. Valiev ◽  
Terence G. Langdon
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
Nonequilibrium State ◽  
High Resolution Electron Microscopy ◽  
High Energy ◽  
Typical Feature ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Resolution Electron

Submicrometer-grained (SMG) structures were produced in Cu and Ni using an intense plastic straining technique, and the grain boundaries and their vicinities were observed by high-resolution electron microscopy. The grain boundaries exhibited zigzag configurations with irregular arrangements of facets and steps, and thus they were found to be in a high-energy nonequilibrium state. A similar conclusion was reached earlier for SMG Al–Mg solid solution alloys which have much lower melting points than Cu and Ni, suggesting that nonequilibrium grain boundaries are a typical feature of metals processed by intense plastic straining.

An investigation of grain boundaries in submicrometer-grained Al-Mg solid solution alloys using high-resolution electron microscopy

1996 ◽  
Vol 11 (8) ◽  
pp. 1880-1890 ◽  
Author(s):  
Zenji Horita ◽  
David J. Smith ◽  
Minoru Furukawa ◽  
Minoru Nemoto ◽  
Ruslan Z. Valiev ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
High Resolution ◽  
Grain Boundaries ◽  
Boundary Migration ◽  
Boundary Energy ◽  
High Resolution Electron Microscopy ◽  
High Energy ◽  
Structural Features ◽  
Resolution Electron

High-resolution electron microscopy was used to examine the structural features of grain boundaries in Al–1.5% Mg and Al–3% Mg solid solution alloys produced with submicrometer grain sizes using an intense plastic straining technique. The grain boundaries were mostly curved or wavy along their length, and some portions were corrugated with regular or irregular arrangements of facets and steps. During exposure to high-energy electrons, grain boundary migration occurred to reduce the number of facets and thus to reduce the total boundary energy. The observed features demonstrate conclusively that the grain boundaries in these submicrometer-grained materials are in a high-energy nonequilibrium configuration.

Grain boundary structure in TiO2-excess barium titanate

1998 ◽  
Vol 13 (12) ◽  
pp. 3449-3452 ◽  
Author(s):  
Takahisa Yamamoto ◽  
Yuichi Ikuhara ◽  
Katsuro Hayashi ◽  
Taketo Sakuma
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
High Resolution Electron Microscopy ◽  
Growth Behavior ◽  
Boundary Structure ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Grain Growth Behavior ◽  
Electron Energy Loss

Grain boundary structure was examined in 0.1 mol% TiO2-excess BaTiO3 by high-resolution electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). Their grain boundaries were mostly faceted with {210} type habit. The faceted boundaries were characterized to be associated with an extra Ti–O2 bond with the rutile-like structure. The grain growth behavior in a small TiO2-excess BaTiO3 is discussed from the viewpoint of grain boundary structure.

Anti-Site Bonds and the Structure of Interfaces in SiC

1990 ◽  
Vol 183 ◽  
Author(s):  
P. Pirouz ◽  
J. Yang
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundary ◽  
Grain Boundaries ◽  
Compound Semiconductors ◽  
High Resolution Electron Microscopy ◽  
High Energy ◽  
Dangling Bonds ◽  
Resolution Electron ◽  
Elemental Semiconductors

AbstractHigh resolution electron microscopy has been used to study the structure of the 3C/6H interface, Σ,=3 {111}and Σ.=3 {112}grain boundaries in 3C-SiC. In SiC, as in other compound semiconductors, anti-site bonds occur in a variety of defects. These are high energy bonds comparable to that of dangling bonds. But, while dangling bonds at the grain boundaries may be eliminated by reconstruction just as in elemental semiconductors, it may not be possible to avoid anti-site bonds.These problems are discussed for the Σ=3 {112} grain boundary, where the structures proposed for Ge and Si are used as starting models for SiC.

Grain boundary structure in Al–Mg and Al–Mg–Sc alloys after equal-channel angular pressing

2001 ◽  
Vol 16 (2) ◽  
pp. 583-589 ◽  
Author(s):  
Keiichiro Oh-ishi ◽  
Zenji Horita ◽  
David J. Smith ◽  
Terence G. Langdon
Keyword(s):  
Grain Boundaries ◽  
Equal Channel Angular Pressing ◽  
High Pressure Torsion ◽  
High Resolution Electron Microscopy ◽  
High Energy ◽  
Boundary Structure ◽  
Angular Pressing ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Before And After

Samples of an Al–3% Mg alloy and an Al–3% Mg–0.2% Sc alloy were subjected to equal-channel angular pressing (ECAP) to reduce the grain size to approximately 0.2–0.3 μm. Some samples of each alloy were also annealed for 1 h at temperatures of either 423 or 673 K, respectively. High-resolution electron microscopy was used to examine the microstructure both before and after annealing. The grain boundaries after ECAP were wavy and faceted and in high-energy nonequilibrium configurations. These results were consistent with earlier observations of materials subjected to severe plastic deformation using high-pressure torsion. In addition, some grain boundaries in the Al–Mg–Sc alloy had a zigzag appearance after annealing at 673 K, where the straight portions of the boundary were identified as low-energy {111} planes. It is suggested these are mobile boundaries lying in a lowest energy configuration where mobility may be restricted by the presence of incoherent Al3Sc particles.

Finding the Right Problems: Some HREM Applications to Interfaces

1984 ◽  
Vol 42 ◽  
pp. 376-379
Author(s):  
D. Cherns
Keyword(s):  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Boundary Structure ◽  
Atomic Structures ◽  
Grain Boundary Structure ◽  
Resolution Electron ◽  
Point To Point ◽  
The Right ◽  
New Generation ◽  
Better Than

The use of high resolution electron microscopy (HREM) to determine the atomic structure of grain boundaries and interfaces is a topic of great current interest. Grain boundary structure has been considered for many years as central to an understanding of the mechanical and transport properties of materials. Some more recent attention has focussed on the atomic structures of metalsemiconductor interfaces which are believed to control electrical properties of contacts. The atomic structures of interfaces in semiconductor or metal multilayers is an area of growing interest for understanding the unusual electrical or mechanical properties which these new materials possess. However, although the point-to-point resolutions of currently available HREMs, ∼2-3Å, appear sufficient to solve many of these problems, few atomic models of grain boundaries and interfaces have been derived. Moreover, with a new generation of 300-400kV instruments promising resolutions in the 1.6-2.0 Å range, and resolutions better than 1.5Å expected from specialist instruments, it is an appropriate time to consider the usefulness of HREM for interface studies.

High-resolution EM study of submicrometer-grained Al-Mg solid solution alloys

1995 ◽  
Vol 53 ◽  
pp. 524-525
Author(s):  
Z. Horita ◽  
D. J. Smith ◽  
M. Furukawa ◽  
M. Nemoto ◽  
R. Z. Valiev ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Solid Solution ◽  
High Resolution ◽  
Grain Boundaries ◽  
Energy State ◽  
High Energy ◽  
Grain Structure ◽  
Boundary Structure ◽  
Solid Solution Alloy ◽  
Average Grain Size

It is possible to produce metallic materials with submicrometer-grained (SMG) structures by imposing an intense plastic strain under quasi-hydrostatic pressure. Studies using conventional transmission electron microscopy (CTEM) showed that many grain boundaries in the SMG structures appeared diffuse in nature with poorly defined transition zones between individual grains. The implication of the CTEM observations is that the grain boundaries of the SMG structures are in a high energy state, having non-equilibrium character. It is anticipated that high-resolution electron microscopy (HREM) will serve to reveal a precise nature of the grain boundary structure in SMG materials. A recent study on nanocrystalline Ni and Ni3Al showed lattice distortion and dilatations in the vicinity of the grain boundaries. In this study, HREM observations are undertaken to examine the atomic structure of grain boundaries in an SMG Al-based Al-Mg alloy.An Al-3%Mg solid solution alloy was subjected to torsion straining to produce an equiaxed grain structure with an average grain size of ~0.09 μm.

High-resolution electron microscopy of nanostructured materials

1995 ◽  
Vol 53 ◽  
pp. 172-173
Author(s):  
M. José-Yacamán
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
Nanostructured Materials ◽  
High Resolution Electron Microscopy ◽  
Hrem Image ◽  
Small Particles ◽  
Resolution Electron ◽  
Nanophase Materials

Electron microscopy is a fundamental tool in materials characterization. In the case of nanostructured materials we are looking for features with a size in the nanometer range. Therefore often the conventional TEM techniques are not enough for characterization of nanophases. High Resolution Electron Microscopy (HREM), is a key technique in order to characterize those materials with a resolution of ~ 1.7A. High resolution studies of metallic nanostructured materials has been also reported in the literature. It is concluded that boundaries in nanophase materials are similar in structure to the regular grain boundaries. That work therefore did not confirm the early hipothesis on the field that grain boundaries in nanostructured materials have a special behavior. We will show in this paper that by a combination of HREM image processing, and image calculations, it is possible to prove that small particles and coalesced grains have a significant surface roughness, as well as large internal strain.

Interaction Between Basal Stacking Faults and Prismatic Inversion Domain Boundaries in GaN

2000 ◽  
Vol 639 ◽  
Author(s):  
Philomela Komninou ◽  
Joseph Kioseoglou ◽  
Eirini Sarigiannidou ◽  
George P. Dimitrakopulos ◽  
Thomas Kehagias ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Stacking Faults ◽  
High Resolution Electron Microscopy ◽  
High Energy ◽  
Low Energy ◽  
Inversion Domain ◽  
Resolution Electron ◽  
Domain Boundaries ◽  
Inversion Domain Boundaries

ABSTRACTThe interaction of growth intrinsic stacking faults with inversion domain boundaries in GaN epitaxial layers is studied by high resolution electron microscopy. It is observed that stacking faults may mediate a structural transformation of inversion domain boundaries, from the low energy types, known as IDB boundaries, to the high energy ones, known as Holt-type boundaries. Such interactions may be attributed to the different growth rates of adjacent domains of inverse polarity.

scholarly journals Analysis of Stresses and Strains around Dislocations at Grain Boundaries by Quantitative High-Resolution Electron Microscopy

2006 ◽  
Vol 12 (S02) ◽  
pp. 894-895
Author(s):  
M Hytch ◽  
J-L Putaux ◽  
J Thibault
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Grain Boundaries ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron

Extended abstract of a paper presented at Microscopy and Microanalysis 2006 in Chicago, Illinois, USA, July 30 – August 3, 2006

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