scholarly journals High-Resolution Electron Microscopy Studies of the Precipitation of Copper Under Neutron Irradiation in An Fe-1.3Wt%Cu Alloy

1998 ◽  
Vol 540 ◽  
Author(s):  
A. C. Nicol ◽  
M. L. Jenkins ◽  
M. A. Kirk
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Neutron Irradiation ◽  
High Resolution Electron Microscopy ◽  
High Energy ◽  
Model Alloy ◽  
Cu Alloy ◽  
Energy Cascades ◽  
Resolution Electron ◽  
Previous Assumption

AbstractWe have studied by electron microscopy the copper-rich precipitates in an Fe-1.3wt%Cu model alloy irradiated with neutrons to doses of 8.61 × 10−3dpa and 6.3×10−2 dpa at a temperature of-270°C. In the lower dose material a majority (ca. 60%) of the precipitates visible in high-resolution electron microscopy were twinned 9R precipitates of size ∼ 2−4 nm, whilst ca. 40 % were untwinned. In the higher dose material, a majority (ca. 75%) of visible precipitates were untwinned although many still seemed to have a 9R structure. The average angle α between the herring-bone fringes in the twin variants was measured as 1250, not the 1290 characteristic of precipitates in thermally-aged and electron-irradiated material immediately after the bcc-→9R martensitic transformation. We argue that these results imply that the bcc-→9R transformation of small (< 4 nm) precipitates under neutron irradiation takes place at the irradiation temperature of 270°C rather than after subsequent cooling. Preliminary measurements showed that precipitate sizes did not depend strongly on dose, with a mean diameter of 3.4 ± 0.7 nm for the lower dose material, and 3.0 ± 0.5 rim for the higher dose material. This result agrees with the previous assumption that the lack of coarsening in precipitates formed under neutron irradiation is a consequence of the partial dissolution of larger precipitates by high-energy cascades.

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.

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.

Dissolution of Copper Precipitates in An Fe−1·3Wt%Cu Alloy Under Fe+ Ion Irradiation

1998 ◽  
Vol 540 ◽  
Author(s):  
A. C. Nicol ◽  
M. L. Jenkins ◽  
N. Wanderka ◽  
C. Abromeit
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
High Resolution ◽  
Room Temperature ◽  
Ion Irradiation ◽  
High Resolution Electron Microscopy ◽  
Cu Alloy ◽  
Transmission Electron ◽  
Resolution Electron ◽  
The Stability

AbstractThe stability of Cu precipitates in an Fe-1.3wt%Cu alloy under 300 keV Fe+ion irradiation has been investigated using transmission electron microscopy and high-resolution electron microscopy. The irradiations were carried out between room temperature and 550°C at displacement rates of 103 to 10−2 dpa(s)−1 to fluences of up to 30 dpa. Copper precipitates were found to keep their shape but decrease in size under all irradiation conditions. The results are discussed within the framework of a competitive process between irradiation induced ballistic destruction of precipitates by cascades and irradiation-enhanced precipitation.

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.

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.

High Resolution Electron Microscopy of Semiconductor Defects

1981 ◽  
Vol 39 ◽  
pp. 120-123 ◽  
Author(s):  
J.C.H. Spence
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Spatial Resolution ◽  
High Spatial Resolution ◽  
Structural Information ◽  
High Resolution Electron Microscopy ◽  
High Energy ◽  
High Energy Resolution ◽  
Resolution Electron ◽  
The Individual

Any attempt to study the relationship between the electronic and atomic struc ture of isolated defects in semiconductors by high resolution electron microscopy must deal with the following difficulties: (i) The limited point reso lution of modern TEM instruments, which has fallen by about 1Å from 3.8Å to 2.8Å (with tilt) over the last decade. This is still not sufficient to resolve the individual atomic columns in any semiconductor. (ii) The fundamental difficulties in obtaining both high spatial resolution structural information and high energy resolution spectroscopic data from the same, isolated, defect. (iii) The considerable difficulties in extracting chemical, or atomic number information from electron scattering and imaging experiments with high spatial resolution. Among other problems, the separation of composition variation effects from those of thickness is an important problem. Some of our recent approaches to these problems are outlined below.

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