Computer Simulation of Vacancy Segregation at Antiphase Domain Boundaries During Coarsening

1993 ◽  
Vol 319 ◽  
Author(s):  
Long-Qing Chen
Keyword(s):  
Computer Simulation ◽  
Vacancy Concentration ◽  
Antiphase Domain ◽  
Atomic Diffusion ◽  
Domain Boundaries ◽  
Order Of Magnitude ◽  
Segregation Profile ◽  
Computer Simulation Technique ◽  
Antiphase Domains ◽  
Coarsening Kinetics

AbstractA computer simulation technique based on the Master Equation Method (MEM) is developed for modeling the spatial distribution of vacancies during ordering and subsequent domain coalescence and coarsening. A vacancy mechanism is assumed for the atomic diffusion and the single-site approximation is employed. It is demonstrated that vacancies strongly segregate into the antiphase domain boundaries (APBs) during coarsening, resulting in the vacancy concentration at APBs more than an order of magnitude higher than that inside the ordered domains. As the antiphase domains coarsen, the vacancy concentration at the APBs continues to increase and its spatial s segregation profile moves accompanying the APB migration. The effect of vacancy concentration on the antiphase domain coarsening kinetics is discussed.

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.

PHASE DIAGRAM OF A DILUTE BINARY SYSTEM

1992 ◽  
Vol 03 (02) ◽  
pp. 297-305 ◽  
Author(s):  
A. SADIQ ◽  
K. YALDRAM ◽  
M. DAD
Keyword(s):  
Phase Diagram ◽  
Computer Simulation ◽  
Binary System ◽  
Vacancy Concentration ◽  
Percolation Transition ◽  
Sharp Drop ◽  
Spin Concentration ◽  
Monte Carlo Computer Simulation ◽  
Metropolis Method ◽  
Computer Simulation Technique

Phase diagram of a binary system with quenched impurities has been studied with Monte Carlo computer simulation technique. Use of Swendsen-Wang algorithm makes it possi-ble to explore the vicinity of percolation transition which was difficult to explore with the traditional Metropolis method. For small vacancy concentration υ(υ=1−p, where p is the spin concentration) the critical temperature, Tc, decreases linearly with υ consistent with earlier results on this system. For larger values of v departure from linearity is observed with Tc decreasing to zero sharply near the percolation threshold. An estimate of the critical exponent describing this sharp drop of Tc is also given.

Effect of Antiphase Domain Boundaries on Prism Slip in Ti3Al Single Crystals

2002 ◽  
Vol 753 ◽  
Author(s):  
Y. Koizumi ◽  
Y. Minamino ◽  
N. Tsuji ◽  
T. Nakano ◽  
Y. Umakoshi
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Yield Stress ◽  
Dislocation Structure ◽  
Antiphase Domain ◽  
Prism Slip ◽  
Domain Boundaries ◽  
Antiphase Domains

ABSTRACTEffect of antiphase domain boundaries (APDBs) on yielding and dislocation structure were investigated in Ti3Al single crystals oriented for prism slip. The yield stress greatly depended on the size of antiphase domains (APDs). The yield stress of Ti3Al with the average APD size of 35nm was about six times higher than that of Ti3Al without APDB. Single dislocations (isolated superpartial dislocations) were observed in the deformed Ti3Al single crystal with APD sizes smaller than 100nm, while superdislocation pairs were observed in those with larger APDs. The mechanism of the interaction between the prism dislocations and APDBs is discussed.

Effect of antiphase domain boundaries on microdiffraction computer simulation

1985 ◽  
Vol 18 (1-4) ◽  
pp. 111-116 ◽  
Author(s):  
Jing Zhu ◽  
H.Q. Ye ◽  
J.M. Cowley
Keyword(s):  
Computer Simulation ◽  
Antiphase Domain ◽  
Domain Boundaries

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
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