Mechanical Properties of Fe-Modifie Ll2-Type Al3Ti

1990 ◽  
Vol 213 ◽  
Author(s):  
H. R. P. Inoue ◽  
C. V. Cooper ◽  
L. H. Favrow ◽  
Y. Hamada ◽  
C. M. Wayman
Keyword(s):  
Room Temperature ◽  
Boundary Energy ◽  
Large Population ◽  
Hot Isostatic Pressing ◽  
Antiphase Boundary ◽  
High Resolution Electron Microscopy ◽  
Room Temperature Ductility ◽  
Strain Fracture ◽  
Resolution Electron ◽  
Crystallographic Planes

ABSTRACTThe room temperature ductility of an L12-type A13Ti alloy containing 7.5 at.% Fe has been improved substantially by hot isostatic pressing (HIP) after arc casting. This L12-type alloy can be deformed in compression to 11.4 % at room temperature after HIPing, retaining the original shape of compressive specimens, while compressive specimens without HIPing following heat-treatment for homogenization (HHT) fracture into small pieces when deformed to similar strain. At temperatures higher than 400°C, specimens for both HHTed and HIPed conditions show similar behavior, having strains to failure of greater than 12 % plastic strain. Fracture occurs at room temperature by brittle transgranular cleavage with a smooth surface in HHTed specimens, while in HIPed specimens, fracture occurs by both transgranular and intergranular modes. Transgranularly fractured surfaces in the latter case have rough surfaces with fine structure, indicating ductile fracture as compared with that for HHTed specimens. In both HIPed and HHTed specimens, no fracture surfaces are flat and parallel to any crystallographic planes. High resolution electron microscopy has revealed that a pair of superlattice partial dislocations on a (111) plane have a spacing of approximately 11 nm (2–3 times larger than that for Al-23Ti-6Fe-5V) giving an antiphase boundary energy of 95 mJ/m2. Since this energy is relatively low, the present alloy may be ductile because of its ready emission of dislocations at crack tips, according to the Rice-Thomson criterion. Improvement of room-temperature ductility of this alloy is attributed primarily to the reduction of a large population of cavities formed upon arc casting.

Interpretation of the Contrast of High-Resolution Electron Microscopy Images of Ni4Mo by Means of Simulated Image Maps

1990 ◽  
Vol 48 (1) ◽  
pp. 28-29
Author(s):  
A. Thust ◽  
K. Urban
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Antiphase Boundary ◽  
High Resolution Electron Microscopy ◽  
Foil Thickness ◽  
Order Structure ◽  
Simulated Image ◽  
Resolution Electron ◽  
Fcc Lattice ◽  
Direct Interpretation

The alloy of composition Ni4Mo develops, at temperatures below 860 °C, an ordered Dla-structure which is based on the fcc-lattice. This alloy has been widely investigated with respect to its physical properties and its ordering behaviour. High resolution studies are rare and concentrated mainly on its short-range order structure. The aim of the present work was to develop a detailed understanding of image contrast and to apply the results to antiphase-boundary studies in ordered Ni4Mo by means of a JEOL 4000 EX electron microscope.In high-resolution electron microscopy, depending on defocus and foil thickness, a large variety of different images is obtained. Only a few of these allow a direct interpretation concerning the location and the type of the atoms. By computing a through-focus/through-thickness map (TFTT map) before starting experimental work it is possible to determine the proper conditions at which images can be obtained which are closely related to the projected potential.

scholarly journals Structural and Microanalytical Studies of CrO2 Thin Films on c-Sapphire by High Resolution Electron Microscopy Methods

2008 ◽  
Vol 14 (S3) ◽  
pp. 47-48
Author(s):  
M.I. Ortiz ◽  
P.M. Sousa ◽  
C. Ballesteros ◽  
A.J. Silvestre ◽  
L.F. Cohen ◽  
...  
Keyword(s):  
Room Temperature ◽  
Tunnel Junctions ◽  
High Resolution Electron Microscopy ◽  
Chromium Dioxide ◽  
Recording Industry ◽  
Insulating Layer ◽  
Half Metallic ◽  
Spintronic Devices ◽  
Resolution Electron ◽  
Spin Polarized

Chromium dioxide (CrO2) has been extensively used in the magnetic recording industry. However, it is its ferromagnetic half-metallic nature that has more recently attracted much attention, primarily for the development of spintronic devices. CrO2 is the only stoichiometric binary oxide theoretically predicted to be fully spin polarized at the Fermi level. It presents a Curie temperature of ∼ 396 K, i.e. well above room temperature, and a magnetic moment of 2 mB per formula unit. However an antiferromagnetic native insulating layer of Cr2O3 is always present on the CrO2 surface which enhances the CrO2 magnetoresistance and might be used as a barrier in magnetic tunnel junctions.

Ge Nanoclusters in GeO2: Synthesis and Optical Properties

2005 ◽  
Vol 108-109 ◽  
pp. 83-90 ◽  
Author(s):  
Vladimir A. Volodin ◽  
E.B. Gorokhov ◽  
D.V. Marin ◽  
A.G. Cherkov ◽  
Anton K. Gutakovskii ◽  
...  
Keyword(s):  
Room Temperature ◽  
Blue Shift ◽  
High Resolution Electron Microscopy ◽  
Film Deposition ◽  
Germanium Oxide ◽  
Type I ◽  
Heterophase System ◽  
Raman Scattering Spectroscopy ◽  
Quantum Size ◽  
Resolution Electron

Ge nanocrystals (NCs) in GeO2 films obtained with the use of two methods were studied. The first method is a film deposition from supersaturated GeO vapor with subsequent dissociation of metastable GeO on heterophase system Ge:GeO2. The second method is growth of anomalous thick native germanium oxide layers with chemical composition GeOx(H2O) during catalytically enhanced Ge oxidation. The obtained films were studied with the use of photoluminescence (PL), Raman scattering spectroscopy, high-resolution electron microscopy (HREM). Strong PL signals were detected in GeO2 films with Ge-NCs at room temperature. “Blue-shift” of PL maximum was observed with reducing of Ge excess in anomalous thick native germanium oxide films. Also a correlation between reducing of the NC sizes (estimated from position of Raman peaks) and PL “blue-shift” was observed. The Ge NCs presence was confirmed by HREM data. The optical gap in Ge-NCs was calculated with taking into account quantum size effects and compared with the position of the experimental PL peaks. It can be concluded that a Ge-NC in GeO2 matrix is a quantum dot of type I.

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.

Electrical and Structural Properties of Ti Contacts on an Atomically Clean N-Type GaAs Surface

1992 ◽  
Vol 281 ◽  
Author(s):  
X. W. Lin ◽  
Z. Liliental-Weber ◽  
W. Swider ◽  
T. McCants ◽  
N. Newman ◽  
...  
Keyword(s):  
Structural Properties ◽  
Gaas Substrate ◽  
Room Temperature ◽  
Schottky Barrier Height ◽  
High Resolution Electron Microscopy ◽  
Resolution Electron ◽  
Current Voltage ◽  
Higher Temperature ◽  
Amorphous Interlayer

ABSTRACTUsing current-voltage measurements and high-resolution electron microscopy (HREM), we have studied the electrical and structural properties of Ti contacts on an atomically clean n-type GaAs (110) surface. The Ti/n-GaAs diodes are formed at room temperature in ultrahigh vacuum and in situ isochronally (10 min) annealed at temperatures ranging from 200 to 450°C. We find that the Schottky barrier height of the diodes increases by ≈0.10 eV upon annealing at 200°C and remains basically stable for higher-temperature anneals. HREM investigation reveals that Ti reacts with GaAs in its as-deposited state to form an amorphous interlayer ≈1.5 nm thick. After anneals to 450°C, extensive reactions occur at the interface, resulting in the formation of a layered structure Ti/Ga3Ti2/TiAs/GaAs, with TiAs protruding into the GaAs substrate.

Effect of chromium on properties of Fe3Al

1989 ◽  
Vol 4 (5) ◽  
pp. 1156-1163 ◽  
Author(s):  
C. G. McKamey ◽  
J. A. Horton ◽  
C. T. Liu
Keyword(s):  
Tensile Strength ◽  
Fracture Mode ◽  
Mixed Mode ◽  
Fracture Behavior ◽  
Room Temperature ◽  
Antiphase Boundary ◽  
Transgranular Cleavage ◽  
Room Temperature Ductility ◽  
Wavy Slip ◽  
Strength And Ductility

The effects of the addition of chromium on several properties of Fe3Al, including tensile strength and ductility, fracture behavior, and slip and dislocation characteristics, were studied. Alloying with up to 6 at. % chromium results in an increase in room temperature ductility from approximately 4% to 8–10%. Along with this increase in ductility, the addition of chromium produces a change in fracture mode from transgranular cleavage to a mixed mode of intergranular-transgranular cleavage, and a change in slip behavior from coarse straight slip to fine wavy slip. These phenomena are discussed in terms of the effect of chromium on the antiphase boundary energies and dislocation characteristics.

Microstructure of epitaxial VO2 thin films deposited on (1120) sapphire by MOCVD

1994 ◽  
Vol 9 (9) ◽  
pp. 2264-2271 ◽  
Author(s):  
H. Zhang ◽  
H.L.M. Chang ◽  
J. Guo ◽  
T.J. Zhang
Keyword(s):  
Electron Microscopy ◽  
Thin Films ◽  
Deposition Temperature ◽  
Room Temperature ◽  
High Resolution Electron Microscopy ◽  
Sapphire Substrates ◽  
Resolution Electron ◽  
Initial Nucleation ◽  
Vo2 Thin Films ◽  
Conventional Electron Microscopy

Epitaxial VO2 thin films grown on (1120) sapphire (α-Al2O3) substrates by MOCVD at 600 °C have been characterized by conventional electron microscopy and high resolution electron microscopy (HREM). Three different epitaxial relationships between the monoclinic VO2 films and sapphire substrates have been found at room temperature: I. (200) [010] monoclinic VO2 ‖ (1120) [0001] sapphire, II. (002) [010] monoclinic VO2 ‖ (1120) [0003] sapphire, and III. (020) [102] monoclinic VO2 ‖ (1120) [0001] sapphire. Expitaxial relationships II and III are equivalent to each other when the film possesses tetragonal structure at the deposition temperature; i.e., they can be described as (010) [100] tetragonal VO2 ‖ (1120) [0001] sapphire and (100) [010] tetragonal VO2 ‖ (1120) [0001] sapphire. HREM image shows that the initial nucleation of the film was dominated by the first orientation relationship, but the film then grew into the grains of the second and the third (equivalent to each other at the deposition temperature) epitaxial relationships. Successive 90°transformation rotational twins around the a-axis are commonly observed in the monoclinic films.

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