Dislocation structures around SiO2 Particles in aged Cu-Cr-SiO2

1978 ◽  
Vol 36 (1) ◽  
pp. 594-595
Author(s):  
N.J. Long ◽  
M.H. Loretto ◽  
C.H. Lloyd
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Thin Foil ◽  
Age Hardening ◽  
Dispersion Strengthening ◽  
Accurate Picture ◽  
The Matrix ◽  
Very High ◽  
Good Agreement

IntroductionThere have been several t.e.m. studies (1,2,3,4) of the dislocation arrangements in the matrix and around the particles in dispersion strengthened single crystals deformed in single slip. Good agreement has been obtained in general between the observed structures and the various theories for the flow stress and work hardening of this class of alloy. There has been though some difficulty in obtaining an accurate picture of these arrangements in the case when the obstacles are large (of the order of several 1000's Å). This is due to both the physical loss of dislocations from the thin foil in its preparation and to rearrangement of the structure on unloading and standing at room temperature under the influence of the very high localised stresses in the vicinity of the particles (2,3).This contribution presents part of a study of the Cu-Cr-SiO2 system where age hardening from the Cu-Cr and dispersion strengthening from Cu-Sio2 is combined.

Preparation and Mechanical Properties of Nano-SiCp/Mg Composites by Ultrasonic Dispersion

2010 ◽  
Vol 150-151 ◽  
pp. 792-795 ◽  
Author(s):  
Hong Yan ◽  
Zhi Hu
Keyword(s):  
Mechanical Properties ◽  
Room Temperature ◽  
Ultrasonic Method ◽  
Fracture Morphology ◽  
Dispersion Strengthening ◽  
Ultrasonic Dispersion ◽  
Sic Nanoparticles ◽  
The Matrix ◽  
Dislocation Strengthening ◽  
Magnesium Composites

SiC nanoparticles reinforced AZ61 magnesium composites were fabricated by Ultrasonic method. The distribution of nanoparticles in the matrix and the fracture morphology of the composites were observed by SEM, and the mechanical properties of the composites were tested at room temperature. Experimental shows that SiC nanoparticles were dispersed well in the matrix with the pretreatment method. Compared with the matrix, the tensile strength and hardness of the composites were improved respectively. Meanwhile, the ductility of the composites didn’t be obviously decreased. The enhancement function of nano composites was predicted with the dislocation strengthening and Orowan dispersion strengthening mechanisms. The predicted results coincided well with experimental ones.

Strain Rate Dependence of the Flow Stress and Work-Hardening of Single Crystals of NI3(Al,Hf)B

1994 ◽  
Vol 364 ◽  
Author(s):  
S. S. Ezz ◽  
Y. Q. Sun ◽  
P. B. Hirsch
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Yield Stress ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Controlling Mechanism

AbstractThe strain rate sensitivity ß of the flow stress τ is associated with workhardening and β=(δτ/δln ε) is proportional to the workhardening increment τh = τ - τy, where τy is the strain rate independent yield stress. The temperature dependence of β/τh reflects changes in the rate controlling mechanism. At intermediate and high temperatures, the hardening correlates with the density of [101] dislocations on (010). The nature of the local obstacles at room temperature is not established.

The flow stress of NiAl single crystals below room temperature

2001 ◽  
Vol 319-321 ◽  
pp. 337-341 ◽  
Author(s):  
Dieter Brunner ◽  
Peter Gumbsch
Keyword(s):  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature

Electron effective-mass values in GaxIn1−xSb alloys

1969 ◽  
Vol 47 (6) ◽  
pp. 631-636 ◽  
Author(s):  
Marcel J. Aubin ◽  
Mathew B. Thomas ◽  
Eric H. van Tongerloo ◽  
John C. Woolley
Keyword(s):  
Effective Mass ◽  
High Frequency ◽  
Room Temperature ◽  
Composition Range ◽  
Bridgman Technique ◽  
Scattering Parameter ◽  
Electron Effective Mass ◽  
High Frequency Dielectric Constant ◽  
The Matrix ◽  
Good Agreement

Room-temperature measurements of Faraday rotation, magneto–thermoelectric power, and infrared reflectance have been made on homogeneous coarsely polycrystalline n-type samples of GaxIn1−xSb alloys produced by the horizontal Bridgman technique. Using these data and a Kane equation for the (000) conduction band, values of the bottom of the band effective mass m00* have been determined over the composition range 0 < x < 0.85, i.e. the range in which the subsidiary [Formula: see text] minima make no contribution. The results from the three different techniques show very good agreement. From the data, values are obtained also for the square of the matrix element P2, the high-frequency dielectric constant ε∞, and the scattering parameter s for the various alloy specimens.

A Weak-Beam Study of the Microstructure of β-CUZN Deformed in the Domain of Flow Stress Anomaly

1988 ◽  
Vol 133 ◽  
Author(s):  
G. Dirras ◽  
P. Beauchamp ◽  
P. Veyssière
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Flow Stress ◽  
Single Crystals ◽  
Room Temperature ◽  
Burgers Vector ◽  
Weak Beam ◽  
Transmission Electron ◽  
Edge Component ◽  
Imaging Conditions

ABSTRACTβ-brass single crystals oriented along <001> were deformed between room temperature and 300°C. The deformation microstructure and dissociation properties were studied by transmission electron microscopy under weak-beam imaging conditions.Whatever the deformation temperature, superdislocations with <111> Burgers vector and strong edge component dominate within the microstructure. In addition, below the temperature of the flow stress peak (≈ 250°C), the density of screw relative to mixed superdislocations decreases as straining temperature increases. Dissociation does not always occur on the slip plane neither does it proceed exclusively by glide, even in samples deformed at 100°C.

EPR Study of VO2+ Doped Diammonium Tricadmium Tetrakis (Sulfate) Pentahydrate [(NH4)2Cd3(SO4)4 ∙ 5H2O] Single Crystals

2010 ◽  
Vol 65 (4) ◽  
pp. 347-352 ◽  
Author(s):  
Ibrahim Kartal ◽  
Bünyamin Karabulut ◽  
Esat Bozkurt
Keyword(s):  
Single Crystals ◽  
Room Temperature ◽  
Epr Spectra ◽  
Spin Hamiltonian ◽  
Axially Symmetric ◽  
Paramagnetic Resonance ◽  
Sulfate Pentahydrate ◽  
Hamiltonian Parameters ◽  
Electron Paramagnetic ◽  
Very High

Electron paramagnetic resonance (EPR) studies are carried out on vanadyl (VO2+) ions in diammonium tricadmium tetrakis (sulfate) pentahydrate single crystals at room temperature. The EPR spectra of a single crystal exhibit resonance signals characteristic to VO2+ ions. The analysis of EPR spectra indicates that the VO2+ ions in single crystals show two magnetically inequivalent VO2+ sites in distinct orientations occupying substitutional positions in the lattice and showing very high angular dependence. They form in octahedral coordination with tetragonal compression with C4v symmetry. The spin Hamiltonian parameters are determined, and these parameters have been used to estimate the bonding coefficients of the VO2+ ion in a diammonium tricadmium tetrakis (sulfate) pentahydrate lattice. The parallel and perpendicular components of axially symmetric g and hyperfine (A) tensors are evaluated and the results are discussed and compared with previous reports.

The Effects Of Environment On The Room Temperature Deformation Of B2-Structured Fe-43Al Single-Crystals

2000 ◽  
Vol 646 ◽  
Author(s):  
I. Baker ◽  
D. Wu ◽  
E. P. George
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Mechanical Behavior ◽  
Single Crystals ◽  
Room Temperature ◽  
Temperature Deformation ◽  
Strain Rates ◽  
Single Slip ◽  
Fracture Surfaces ◽  
Boron Doped

ABSTRACTThe effects of the environment on the room temperature mechanical behavior of Fe-43Al single crystals have been studied. In both single slip and duplex slip crystals, fracture strains greater than 40% were obtained in specimens tested in oxygen, whereas elongations of ∼10% and ∼20% were obtained in air and vacuum, respectively. By comparison, similar elongations were obtained in boron-doped single-slip-oriented single crystals in both air and vacuum, but more ductility was obtained in air at slow strain rate. Fractography showed that testing in different environments produced marked differences in the fracture surfaces. Alternate loading of tensile specimens in air and under vacuum was performed at slow strain rates and showed changes in the flow stress between the two environments. The results are discussed in terms of the effects of moisture-produced hydrogen on the flow and fracture of FeAl.

Preparation and Characterization of Sr, Ba Filled Type-I Ge Clathrate Single Crystals

2007 ◽  
Vol 336-338 ◽  
pp. 896-899 ◽  
Author(s):  
Ke Feng Cai ◽  
L.C. Zhang ◽  
Q. Lei
Keyword(s):  
Single Crystals ◽  
Room Temperature ◽  
Nominal Composition ◽  
Type I ◽  
Vibrational Modes ◽  
X Ray Diffraction ◽  
X Ray ◽  
Optimum Synthesis ◽  
Good Agreement

Sr or Ba filled type-I Ge clathrate single crystals were prepared using high pure elemental Ga, Ge, and Sr or Ba as the starting materials, and Ga as a flux. Powder X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDS), differential scanning calorimeter (DSC) were used to characterize the crystals, respectively. The results show that large and well-crystallized single crystals can be prepared under optimum synthesis condition. The composition of the crystals is in good agreement with the nominal composition (M8Ga16Ge30, M=Sr, Ba). Raman spectra of the single crystals were studied at room temperature and several of the Raman active vibrational modes in the crystals have been identified.

Tem and Computer Image Simulation Studies on the Dissociation of Superdislocations in Ll2 Al3Ti Alloy

1994 ◽  
Vol 364 ◽  
Author(s):  
Yonghua Rong ◽  
Xiaohua Wu ◽  
Xiaofu Chen ◽  
Shipu Chen ◽  
Gengxiang Hu
Keyword(s):  
Flow Stress ◽  
Low Temperature ◽  
Computer Image ◽  
Room Temperature ◽  
Dislocation Core ◽  
Simulation Studies ◽  
Image Simulation ◽  
Dislocation Core Structure ◽  
Image Simulations ◽  
Good Agreement

AbstractTEM investigation associated with computer image simulations were conducted to determine the dislocation core structure in the Ll2 Al67MnsTi25 alloy deformed at room temperature. It is identified that the a<110> superdislocations dissociated into pairs of a/3<112> superpartials with SISF between them. The theoretical and experimental micrographs are in good agreement under various diffraction conditions. The unusual temperature dependence of flow stress at low temperature can be related to the SISF-type dissociation.

Twinning of Erbium Oxide Single Crystals in the Electron Microscope

1967 ◽  
Vol 25 ◽  
pp. 328-329
Author(s):  
L. E. Murr
Keyword(s):  
Single Crystals ◽  
Room Temperature ◽  
Erbium Oxide ◽  
Flash Evaporation ◽  
Metal Foils ◽  
Individual Crystal ◽  
Transmission Electron ◽  
The Matrix ◽  
Evaporation Technique ◽  
High Beam Intensity

During the course of investigations directed towards the preparation of concentrated solid solutions of rare earth oxides in MgO host crystals, the occasion arose where polycrystalline hep erbium metal foils vapor deposited onto cleaved NaCl substrates at room temperature (in a nominal vacuum prior to vaporization of 10−8-10−9 Torr) were observed by transmission electron microscopy. It was discovered that when an intermittent flash evaporation technique was used in the vaporization of erbium (99.95%) from high purity tungsten boats, tiny single crystals of various prominent surface orientations were formed in association with the erbium matrix, which differed significantly in structure from the matrix. The surface orientations observed for these crystals, which ranged in size from a few hundred Angstroms to a few microns on a side, were (100), (110), and (111). A rather striking feature of these crystals was the fact that if the electron beam was focused on an individual crystal, particularly in (100) orientation, the crystal began to twin from the edges by the apparent motion of “twinning dislocations” in the {110} planes; with subsequent twinning of the entire crystal taking place after a few seconds exposure at high beam intensity.

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