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

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.

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

Journal of Materials Research ◽

10.1557/jmr.1996.0239 ◽

1996 ◽

Vol 11 (8) ◽

pp. 1880-1890 ◽

Cited By ~ 273

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.

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

Journal of Materials Research ◽

10.1557/jmr.1998.0057 ◽

1998 ◽

Vol 13 (2) ◽

pp. 446-450 ◽

Cited By ~ 132

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.

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Quantitative High Resolution Electron Microscopy of Grain Boundaries and Comparison with Atomistic Simulations

Microscopy and Microanalysis ◽

10.1017/s143192760002729x ◽

2001 ◽

Vol 7 (S2) ◽

pp. 244-245

Author(s):

G.H. Campbell ◽

W.E. King ◽

J.M. Plitzko ◽

J. Belak ◽

S.M. Foiles

Keyword(s):

Electron Microscopy ◽

High Resolution ◽

Grain Boundaries ◽

Atomic Structure ◽

Radiation Effects ◽

Crystal Defects ◽

Boundary Structure ◽

Atomistic Simulations ◽

Simulated Image ◽

Good Test

The technique of high-resolution transmission electron microscopy (HREM) produces images that contain information about the atomic structure of the specimen. Within additional, very stringent, constraints, the HREM image can contain information about atomic structure of crystal defects, including grain boundaries and interfaces. to extract this information from the image it is necessary to compare the experimental image with a simulated image calculated based upon an atomic model of the specimen.2 in this comparison, investigators have been aided by the use of quantitative techniques.Atomistic simulations are often used to predict the atomic structure of crystal defects or to simulate the evolution of dynamic processes in crystals, e.g. radiation effects or dislocation motion and interaction. During the development of new models of interatomic interactions, the predictions of simulations are tested against experimental observations to validate new potentials. Grain boundary structure is a good test because atoms residing in the boundary experience environments (interatomic distances and angles) that are significantly different from those experienced by atoms residing in a perfect crystal lattice site.

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Influence of Annealing Time on Microstructure of Ni-W Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.747-748.613 ◽

2013 ◽

Vol 747-748 ◽

pp. 613-618

Author(s):

Qiao Zhang ◽

Shu Hua Liang ◽

Chen Zhang ◽

Jun Tao Zou

Keyword(s):

Electron Microscopy ◽

Solid Solution ◽

Grain Size ◽

Grain Boundaries ◽

Annealing Time ◽

Single Phase ◽

X Ray Diffraction ◽

X Ray ◽

Average Grain Size ◽

Scanning Electron

The as-cast Ni-W alloys with 15wt%W, 25wt%W and 30wt%W were annealed in hydrogen at 1100. The effect of the annealing time on the microstructure of Ni-W alloys was studied, and the phase constituents and microstructure of annealed Ni-W alloys were characterized by the X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results showed that no any phase changed for Ni-15%W, Ni-25%W and Ni-30%W alloys annealed for 60 min, 90 min and 150 min, which were still consisted of single-phase Ni (W) solid solution. However, microstructure had a significant change after annealing. With increase of annealing time, the microstructure of Ni-15%W alloy became more uniform after annealing for 90 min, and the average grain size was 95μm, whereas the grain size of Ni-15%W alloy increased significantly after annealing for 150 min. For Ni-25%W and Ni-30%W, there was no obvious change on the grain size with increase of annealing time, and the amount of oxides at grain boundaries gradually reduced. After annealing for 150 min, the impurities at grain boundaries almost disappeared. Subsequently, the annealing at 1100 for 150 min was beneficial for the desired microstructure of Ni-25%W and Ni-30%W alloys.

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Anti-Site Bonds and the Structure of Interfaces in SiC

MRS Proceedings ◽

10.1557/proc-183-173 ◽

1990 ◽

Vol 183 ◽

Cited By ~ 11

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.

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High-resolution electron microscopy of nanostructured materials

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100137239 ◽

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.

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

MRS Proceedings ◽

10.1557/proc-639-g3.44 ◽

2000 ◽

Vol 639 ◽

Cited By ~ 1

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.

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