FERROMAGNETIC-LIKE MAGNON DISPERSION IN A FACE-CENTERED CUBIC WITH TYPE-I ANTIFERROMAGNETIC ORDER

1971 ◽  
Vol 32 (C1) ◽  
pp. C1-695-C1-696 ◽  
Author(s):  
J. S. KOUVEL
Keyword(s):  
Antiferromagnetic Order ◽  
Type I ◽  
Face Centered Cubic ◽  
Face Centered

Anti-Twinning in an Ni-Mo-Cr Alloy

2013 ◽  
Vol 203-204 ◽  
pp. 254-257
Author(s):  
Mirosław Wróbel ◽  
Elżbieta Stępniowska ◽  
Stanisław Dymek
Keyword(s):  
Long Range ◽  
The Body ◽  
Type I ◽  
Face Centered Cubic ◽  
The Matrix ◽  
The Face ◽  
Face Centered ◽  
Long Range Ordering ◽  
Mechanical Twins ◽  
Crystallographic Orientations

Two morphological types of mechanical twins occur in the microstructure of cold rolled Ni-Mo-Cr alloy: long – passing over whole grains and micro-twins – confined to individual long range ordered domains. Long mechanical twins were only formed in the disordered alloy. Such twins are typical for metals with the face centered cubic structure with relatively low stacking fault energy. They do not form in the grains with twinning prohibited crystallographic orientations, e.g. {110}. Both types of twins were found in an alloy subjected to prolong annealing at 650 °C. The annealing induces long range ordering reaction leading to the formation of ordered domains with the body centered orthorombic crystal structure (oI8). The twins were of type I, type II, compound twins or pseudo-twins, depending on the crystallographic orientation of the ordered phase in relation to the matrix. It was found that twins of such types were formed even in grains with the {110} orientation and result from the anti-twinning deformation. However, in this orientation they were confined to ordered domains rather than developed into the long form crossing entire grains. On the other hand, the long twins of various types were formed in grains with other twinning favoring crystallographic orientations.

Density functional study of CoFeCrZ (Z=Al, Si, Ga, Ge) quaternary Heusler alloys for phonon spectra

2020 ◽  
Vol 34 (25) ◽  
pp. 2050215
Author(s):  
Muhammad Ahmed ◽  
A. Afaq ◽  
Abu Bakar ◽  
Muhammad Asif
Keyword(s):  
Density Functional ◽  
Phonon Dispersion ◽  
Heusler Alloys ◽  
Dispersion Curves ◽  
Functional Study ◽  
Type I ◽  
Face Centered Cubic ◽  
Phonon Dispersion Curves ◽  
Quaternary Heusler Alloys ◽  
Face Centered

Density Functional Theory (DFT) is used to investigate the phonon properties of CoFeCrZ (Z[Formula: see text]=[Formula: see text]Al, Si, Ga, Ge) equiatomic Quaternary Heusler Alloys. These alloys crystallize in face centered cubic (FCC) structure and have three crystal structures Y-Type I, Y-Type II and Y-Type III on the basis of their atomic positions. For CoFeCrZ (Z[Formula: see text]=[Formula: see text]Al, Si, Ga, Ge), Y-Type I is the most stable structure found in the literature, so phonon dispersion curves for this structure are obtained with the help of norm-conserving pseudo potentials in Quantum ESPRESSO. Absence of negative frequencies in phonon dispersion curves proves the dynamical stability of all these alloys. Phonon dispersion curves are further used to obtain Reststrahlen band, a region where light reflects 100%. The calculated Reststrahlen bands for CoFeCrAl, CoFeCrSi, CoFeCrGa and CoFeCrGe are 4.179 THz ([Formula: see text]m), 4.30 THz ([Formula: see text]m), 3.35 THz ([Formula: see text]m) and 3.05 THz ([Formula: see text]m), respectively. These obtained values of Reststrahlen bands for CoFeCrZ (Z[Formula: see text]=[Formula: see text]Al, Si, Ga, Ge) lie within the far infra-red (FIR) region, and can be used in sensing, imaging and optoelectronic devices.

scholarly journals Cu–Au TYPE STRUCTURES IN THE STAGGERED QUADRUPOLAR REGION OF THE fcc BLUME–EMERY–GRIFFITHS MODEL

2009 ◽  
Vol 20 (10) ◽  
pp. 1617-1632 ◽  
Author(s):  
AYCAN ÖZKAN ◽  
BÜLENT KUTLU
Keyword(s):  
Cellular Automaton ◽  
State Diagram ◽  
Type I ◽  
Face Centered Cubic ◽  
Fcc Lattice ◽  
Face Centered ◽  
Creutz Cellular Automaton ◽  
Beg Model ◽  
Parameter Values ◽  
Made In

The spin-1 Ising Blume–Emery–Griffiths (BEG) model has been simulated using a cellular automaton (CA) algorithm improved from the Creutz cellular automaton (CCA) for a face-centered-cubic (fcc) lattice. The ground state diagram (k, d) of the fcc BEG model has ferromagnetic (F), quadrupolar (Q), and staggered quadrupolar (SQ) structure regions. The simulations have been made in the SQ region for the parameter values in the intervals -24 ≤ d = D/J < 0 and -3 ≤ k = K/J ≤ 0. The phase diagrams on the (kTC/J, d) and the (kTC/J, k) planes have been obtained through k = -3 and d = -4 lines, respectively. The SQ region separates into five regions (A3 B(a), A3 B(f), AB (type-I), AB (type-II), and AB3(f)) which have the different stoichiometric Cu – Au type structures.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

A study of interface sliding at F.C.C.-B.C.C. boundaries in a Cu-Zn alloy

1978 ◽  
Vol 36 (1) ◽  
pp. 422-423
Author(s):  
F. Monchoux ◽  
A. Rocher ◽  
J.L. Martin
Keyword(s):  
Face Centered Cubic ◽  
Creep Tests ◽  
High Voltage Electron Microscopy ◽  
Diffusion Treatment ◽  
Voltage Electron ◽  
The Face ◽  
Face Centered ◽  
Interface Sliding ◽  
Zn Alloy ◽  
Made In

Interphase sliding is an important phenomenon of high temperature plasticity. In order to study the microstructural changes associated with it, as well as its influence on the strain rate dependence on stress and temperature, plane boundaries were obtained by welding together two polycrystals of Cu-Zn alloys having the face centered cubic and body centered cubic structures respectively following the procedure described in (1). These specimens were then deformed in shear along the interface on a creep machine (2) at the same temperature as that of the diffusion treatment so as to avoid any precipitation. The present paper reports observations by conventional and high voltage electron microscopy of the microstructure of both phases, in the vicinity of the phase boundary, after different creep tests corresponding to various deformation conditions.Foils were cut by spark machining out of the bulk samples, 0.2 mm thick. They were then electropolished down to 0.1 mm, after which a hole with thin edges was made in an area including the boundary

Microstructure of Electro-Eroded Cemented Carbide Surfaces

1968 ◽  
Vol 26 ◽  
pp. 284-285
Author(s):  
V. N. Filimonenko ◽  
M. H. Richman ◽  
J. Gurland
Keyword(s):  
Surface Layer ◽  
Cobalt Content ◽  
Cemented Carbides ◽  
Face Centered Cubic ◽  
X Ray Diffraction ◽  
Metallographic Examination ◽  
Standard Procedures ◽  
Face Centered ◽  
Diamond Paste ◽  
Plastic Carbon

The high temperatures and pressures that are found in a spark gap during electrical discharging lead to a sharp phase transition and structural transformation in the surface layer of cemented carbides containing WC and cobalt. By means of X-ray diffraction both W2C and a high-temperature monocarbide of tungsten (face-centered cubic) were detected after electro-erosion. The W2C forms as a result of the peritectic reaction, WC → W2C+C. The existence and amount of the phases depend on both the energy of the electro-spark discharge and the cobalt content. In the case of a low-energy discharge (i.e. C=0.01μF, V = 300v), WC(f.c.c.) is generally formed in the surface layer. However, at high energies, (e.g. C=30μF, V = 300v), W2C is formed at the surface in preference to the monocarbide. The phase transformations in the surface layer are retarded by the presence of larger percentages of cobalt.Metallographic examination of the electro-eroded surfaces of cemented carbides was carried out on samples with 5-30% cobalt content. The specimens were first metallographically polished using diamond paste and standard procedures and then subjected to various electrical discharges on a Servomet spark machining device. The samples were then repolished and etched in a 3% NH4OH electrolyte at -0.5 amp/cm2. Two stage plastic-carbon replicas were then made and shadowed with chromium at 27°.

Faceted antiphase boundaries in GaAs grown on Ge

1987 ◽  
Vol 45 ◽  
pp. 314-315
Author(s):  
N.-H. Cho ◽  
S. McKernan ◽  
C.B. Carter ◽  
K. Wagner
Keyword(s):  
Cross Section ◽  
Atomic Resolution ◽  
Face Centered Cubic ◽  
Electrical Behavior ◽  
Sphalerite Structure ◽  
Antiphase Boundaries ◽  
Transmission Electron ◽  
Face Centered ◽  
Quality Material ◽  
Simulated Images

Interest has recently increased in the possibility of growing III-V compounds epitactically on non-polar substrates to produce device quality material. Antiphase boundaries (APBs) may then develop in the GaAs epilayer because it has sphalerite structure (face-centered cubic with a two-atom basis). This planar defect may then influence the electrical behavior of the GaAs epilayer. The orientation of APBs and their propagation into GaAs epilayers have been investigated experimentally using both flat-on and cross-section transmission electron microscope techniques. APBs parallel to (110) plane have been viewed at the atomic resolution and compared to simulated images.Antiphase boundaries were observed in GaAs epilayers grown on (001) Ge substrates. In the image shown in Fig.1, which was obtained from a flat-on sample, the (110) APB planes can be seen end-on; the faceted APB is visible because of the stacking fault-like fringes arising from a lattice translation at this interface.

Electron diffraction detection of ordliking in annealed PbTe thin film

1990 ◽  
Vol 48 (4) ◽  
pp. 1018-1019
Author(s):  
Karimat El-Sayed
Keyword(s):  
Thin Film ◽  
Electron Diffraction ◽  
Lead Telluride ◽  
Structural Basis ◽  
Face Centered Cubic ◽  
X Ray ◽  
Polycrystalline Thin Films ◽  
Stage Process ◽  
Diffraction Patterns ◽  
Face Centered

Lead telluride is an important semiconductor of many applications. Many Investigators showed that there are anamolous descripancies in most of the electrophysical properties of PbTe polycrystalline thin films on annealing. X-Ray and electron diffraction studies are being undertaken in the present work in order to explain the cause of this anamolous behaviour.Figures 1-3 show the electron diffraction of the unheated, heated in air at 100°C and heated in air at 250°C respectively of a 300°A polycrystalline PbTe thin film. It can be seen that Fig. 1 is a typical [100] projection of a face centered cubic with unmixed (hkl) indices. Fig. 2 shows the appearance of faint superlattice reflections having mixed (hkl) indices. Fig. 3 shows the disappearance of thf superlattice reflections and the appearance of polycrystalline PbO phase superimposed on the [l00] PbTe diffraction patterns. The mechanism of this three stage process can be explained on structural basis as follows :

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