STUDY ON THE PEIREL–NABARRO STRESS OF IRON ALUMINIDES

2012 ◽  
Vol 19 (06) ◽  
pp. 1250057 ◽  
Author(s):  
L. X. PANG ◽  
N. F. HAN ◽  
H. SHI ◽  
J. XU ◽  
X. H. HAO ◽  
...  
Keyword(s):  
Domain Boundary ◽  
Antiphase Domain ◽  
Iron Aluminides ◽  
Stress Model ◽  
Theoretical Yield ◽  
Domain Boundaries ◽  
Ordered Intermetallic ◽  
Critical Resolved Shear Stress ◽  
B2 Structure ◽  
Type Crystal

The modified Peirel–Nabarro model of dislocations is not valid for the superdislocation bounded by the antiphase domain boundaries in long-range ordered intermetallic. In this work, a new Peirel–Nabarro Stress model is developed to take into account the critical resolved shear stress of antiphase domain boundary (APDB). Based on it, the Peirel–Nabarro Stress of DO3 structure and B2 structure in iron aluminides are calculated. Comparing the Peirel–Nabarro Stress of dislocations and the crystal theoretical yield strength, the results demonstrate B2-type crystal has good plasticity. It coincides with the experimental results well.

Microdiffraction from out of Phase Domain Boundaries and Stacking Faults

1982 ◽  
Vol 40 ◽  
pp. 698-699
Author(s):  
J. Zhu ◽  
J.M. Cowley ◽  
H.Q. Ye
Keyword(s):  
Electron Beam ◽  
Source Function ◽  
Domain Boundary ◽  
Antiphase Domain ◽  
Step Function ◽  
Phase Object ◽  
Phase Domain ◽  
Domain Boundaries ◽  
The Fourier Transform ◽  
Coherent Source

It has been pointed out1 that any discontinuity at the edge of a crystal or within a crystal may give rise to spot splitting in microdiffraction patterns.The present work gives the basic theory for an antiphase domain boundary in Cu3Au and a twinning boundary in a f.c.c. crystal illuminated by a finite electron beam, which has a diameter of about 15Å. The treatment is based on the weak phase object approximation. These boundaries are planar faults. Multiplying a step function s(x) by the crystal potential expresses the discontinuity in the potential of the sample. When both sides of the boundary in the sample are illuminated by the finite coherent source and the boundary is parallel to the electron beam, the splitting of microdiffraction spots results from the convolution of the Fourier transform of the step function and the finite coherent source function.

The Effect Of Extended Superdislocation / Domain Boundary Interactions in Ordered Intermetallic Compounds

2000 ◽  
Vol 652 ◽  
Author(s):  
Tie-Sheng Rong ◽  
Mark Aindow ◽  
Ian P. Jones
Keyword(s):  
Yield Stress ◽  
Domain Boundary ◽  
Domain Size ◽  
Perfect Crystal ◽  
Boundary Area ◽  
Domain Boundaries ◽  
Ordered Intermetallic ◽  
Additional Domain ◽  
Equilibrium Separation ◽  
Superlattice Structures

ABSTRACTIt has been known for many years that the presence of a distribution of domain boundaries in crystals with ordered superlattice structures can affect both the separation of glissile superpartial dislocations and the yield stress. Based on the details of the interactions between the domain boundaries and glissile extended superdislocations, we incorporate the effects of the thin band of perfect crystal that arises whencoupled superpartial dislocations straddle a domain boundary, and the additional domain boundary area createdonce the whole superdislocation has passed through. If these effects are included then, in an ordered phase containing many domains, we would expect the equilibrium separation of the coupled superpartial dislocations to vary more significantly with domain size than is predicted by previous models. These effects also change the way in which yield stress is predicted to vary with domain size. This variation gives a much better match to published experimental data than existing models.

Phase Transformation Kinetics During Precipitation of an Ordered Intermetallic from a Disordered Matrix -a Computer Simulation

1990 ◽  
Vol 205 ◽  
Author(s):  
Long-Qing Chen ◽  
A.G. Khachaturyan
Keyword(s):  
Computer Simulation ◽  
Diffusion Theory ◽  
Antiphase Domain ◽  
Two Phase ◽  
Domain Boundaries ◽  
Ordered Intermetallic ◽  
Antiphase Domains ◽  
Ordering Transition ◽  
Kinetics Of ◽  
Ordered State

AbstractThe precipitation kinetics of an ordered intermetallic from a disordered matrix, which involves simultaneous ordering and decomposition, is studied by a computer simulation technique based on the microscopic diffusion theory. It is found that the precipitation starts from a congruent ordering transition, which may be continuous or nucleation and growth. This congruent ordering transition transforms the initially disordered state into a single phase nonstoichiometric ordered state with antiphase domains. The next stage is the decomposition which starts from the antiphase domain boundaries and then propagates into the ordered domains. And the final process is the coarsening of the order/disorder two-phase mixture. The predicted kinetics of precipitation is in excellent agreement with recent experimental observations in important alloy systems.

Nucleation of Disorder in Fe3Al Alloys

1967 ◽  
Vol 25 ◽  
pp. 312-313
Author(s):  
P. R. Swann ◽  
W. R. Duff ◽  
R. M. Fisher
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Annealing Temperature ◽  
Antiphase Domain ◽  
Effect Of Temperature ◽  
Domain Structures ◽  
Transmission Electron ◽  
Domain Boundaries ◽  
Higher Temperature ◽  
The One

Recently we have investigated the phase equilibria and antiphase domain structures of Fe-Al alloys containing from 18 to 50 at.% Al by transmission electron microscopy and Mössbauer techniques. This study has revealed that none of the published phase diagrams are correct, although the one proposed by Rimlinger agrees most closely with our results to be published separately. In this paper observations by transmission electron microscopy relating to the nucleation of disorder in Fe-24% Al will be described. Figure 1 shows the structure after heating this alloy to 776.6°C and quenching. The white areas are B2 micro-domains corresponding to regions of disorder which form at the annealing temperature and re-order during the quench. By examining specimens heated in a temperature gradient of 2°C/cm it is possible to determine the effect of temperature on the disordering reaction very precisely. It was found that disorder begins at existing antiphase domain boundaries but that at a slightly higher temperature (1°C) it also occurs by homogeneous nucleation within the domains. A small (∼ .01°C) further increase in temperature caused these micro-domains to completely fill the specimen.

Antiphase Boundaries in Ordered Ni3FE Crystals

1969 ◽  
Vol 27 ◽  
pp. 62-63
Author(s):  
Y. H. Liu
Keyword(s):  
Domain Size ◽  
Antiphase Domain ◽  
X Ray Diffraction ◽  
X Ray ◽  
Hardening Mechanism ◽  
Superlattice Structure ◽  
Disordered Phase ◽  
Domain Boundaries ◽  
Atomic Scattering ◽  
The Difference

Ordered Ni3Fe crystals possess a LI2 type superlattice similar to the Cu3Au structure. The difference in slip behavior of the superlattice as compared with that of a disordered phase has been well established. Cottrell first postulated that the increase in resistance for slip in the superlattice structure is attributed to the presence of antiphase domain boundaries. Following Cottrell's domain hardening mechanism, numerous workers have proposed other refined models also involving the presence of domain boundaries. Using the anomalous X-ray diffraction technique, Davies and Stoloff have shown that the hardness of the Ni3Fe superlattice varies with the domain size. So far, no direct observation of antiphase domain boundaries in Ni3Fe has been reported. Because the atomic scattering factors of the elements in NijFe are so close, the superlattice reflections are not easily detected. Furthermore, the domain configurations in NioFe are thought to be independent of the crystallographic orientations.

The observation of solutions in Ni3Nb

1988 ◽  
Vol 46 ◽  
pp. 540-541
Author(s):  
Z.M. Wang ◽  
J.P. Zhang
Keyword(s):  
Electron Microscopy ◽  
High Resolution ◽  
Phase Modulation ◽  
High Resolution Electron Microscopy ◽  
Antiphase Domain ◽  
Boundary Area ◽  
Matrix Type ◽  
Resolution Electron ◽  
Domain Boundaries ◽  
Kontorova Model

High resolution electron microscopy reveals that antiphase domain boundaries in β-Ni3Nb have a hexagonal unit cell with lattice parameters ah=aβ and ch=bβ, where aβ and bβ are of the orthogonal β matrix. (See Figure 1.) Some of these boundaries can creep “upstairs” leaving an incoherent area, as shown in region P. When the stepped boundaries meet each other, they do not lose their own character. Our consideration in this work is to estimate the influnce of the natural misfit δ{(ab-aβ)/aβ≠0}. Defining the displacement field at the boundary as a phase modulation Φ(x), following the Frenkel-Kontorova model [2], we consider the boundary area to be made up of a two unit chain, the upper portion of which can move and the lower portion of the β matrix type, assumed to be fixed. (See the schematic pattern in Figure 2(a)).

scholarly journals Robust long-range magnetic correlation across antiphase domain boundaries in Sr2CrReO6

2021 ◽  
Vol 103 (6) ◽  
Author(s):  
Bo Yuan ◽  
Subin Kim ◽  
Sae Hwan Chun ◽  
Wentao Jin ◽  
C. S. Nelson ◽  
...  
Keyword(s):  
Long Range ◽  
Antiphase Domain ◽  
Magnetic Correlation ◽  
Domain Boundaries

MBE Growth and Characterization of SxGe1−x Multilayer Structures on Si (100) for Use as a Substrate for GaAs Heteroepitaxy

1991 ◽  
Vol 220 ◽  
Author(s):  
J. B. Posthill ◽  
D. P. Malta ◽  
R. Venkatasubramanian ◽  
P. R. Sharps ◽  
M. L. Timmons ◽  
...  
Keyword(s):  
Molecular Beam ◽  
Lattice Mismatch ◽  
Antiphase Domain ◽  
Multilayer Structures ◽  
Si Substrate ◽  
Mbe Growth ◽  
Etch Pit ◽  
Layer Structures ◽  
Domain Boundaries

ABSTRACTInvestigation has continued into the use of SixGe1−x multilayer structures (MLS) as a buffer layer between a Si substrate and a GaAs epitaxial layer in order to accommodate the 4.1% lattice mismatch. SixGe1−x 4-layer and 5-layer structures terminating in pure Ge have been grown using molecular beam epitaxy. Subsequent GaAs heteroepitaxy has allowed evaluation of these various GaAs/SixGe1−xMLS/Si (100) structures. Antiphase domain boundaries have been eliminated using vicinal Si (100) substrates tilted 6° off-axis toward [011], and the etch pit density in GaAs grown on a 5-layer SixGe1−x MLS on vicinal Si (lOO) was measured to be 106 cm−2.

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