scholarly journals Bicrystallography and Beyond: Example of Group–Subgroup Phase Transformations

Crystals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 560
Author(s):  
Denis Gratias ◽  
Marianne Quiquandon
Keyword(s):  
Phase Transformations ◽  
Grain Boundaries ◽  
The Other ◽  
Permutation Groups ◽  
Global Symmetry ◽  
Simple Link

This paper presents the basic elementary tools for describing the global symmetry obtained by overlapping two or more crystal variants of the same structure, differently oriented and displaced one with respect to the other. It gives an explicit simple link between the concepts used in the symmetry studies on grain boundaries on one side and group–subgroup transformations on the other side. These questions are essentially of the same nature and boil down to the resolution of the same problem: identifying the permutation groups that are images of the corresponding applications. Examples are given from both domains, classical grain boundaries with coincidence lattices and group–subgroup phase transformations that illustrate the profound similarities between the two approaches.

Measurement of the Displacement Across a Coincidence Grain Boundary

1977 ◽  
Vol 35 ◽  
pp. 124-125
Author(s):  
J. W. Matthews ◽  
W. M. Stobbs
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Stacking Fault ◽  
The Other ◽  
Measuring Technique ◽  
High Angle ◽  
Twin Boundaries ◽  
Rigid Displacement ◽  
Cubic Crystals ◽  
Lattice Displacement

Many high-angle grain boundaries in cubic crystals are thought to be either coincidence boundaries (1) or coincidence boundaries to which grain boundary dislocations have been added (1,2). Calculations of the arrangement of atoms inside coincidence boundaries suggest that the coincidence lattice will usually not be continuous across a coincidence boundary (3). There will usually be a rigid displacement of the lattice on one side of the boundary relative to that on the other. This displacement gives rise to a stacking fault in the coincidence lattice.Recently, Pond (4) and Smith (5) have measured the lattice displacement at coincidence boundaries in aluminum. We have developed (6) an alternative to the measuring technique used by them, and have used it to find two of the three components of the displacement at {112} lateral twin boundaries in gold. This paper describes our method and presents a brief account of the results we have obtained.

Determination of the lattice translation across {110} APBs in GaAs

1988 ◽  
Vol 46 ◽  
pp. 600-601
Author(s):  
D.R. Rasmussen ◽  
N.-H. Cho ◽  
C.B. Carter
Keyword(s):  
Grain Boundaries ◽  
Lower Energy ◽  
Antiphase Boundary ◽  
The Other ◽  
Boundary Structure ◽  
Interface Plane ◽  
Inversion Symmetry ◽  
High Angle ◽  
Equilibrium Distance

Domains in GaAs can exist which are related to one another by the inversion symmetry, i.e., the sites of gallium and arsenic in one domain are interchanged in the other domain. The boundary between these two different domains is known as an antiphase boundary [1], In the terminology used to describe grain boundaries, the grains on either side of this boundary can be regarded as being Σ=1-related. For the {110} interface plane, in particular, there are equal numbers of GaGa and As-As anti-site bonds across the interface. The equilibrium distance between two atoms of the same kind crossing the boundary is expected to be different from the length of normal GaAs bonds in the bulk. Therefore, the relative position of each grain on either side of an APB may be translated such that the boundary can have a lower energy situation. This translation does not affect the perfect Σ=1 coincidence site relationship. Such a lattice translation is expected for all high-angle grain boundaries as a way of relaxation of the boundary structure.

scholarly journals Internal melt figures in ice by rapid adiabatic compression

1994 ◽  
Vol 40 (134) ◽  
pp. 132-134
Author(s):  
R.E. Gagnon ◽  
C. Tulk ◽  
H. Kiefte
Keyword(s):  
Phase Transformations ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Adiabatic Compression ◽  
Air Bubbles ◽  
Water Ice ◽  
Deep Focus ◽  
And Behavior ◽  
First Time

AbstractSingle crystals and bicrystals of water ice have been adiabatically pressurized to produce, and clearly illustrate, two types of internal melt figures: (1) dendritic figures that grow from nucleation imperfections on the specimen’s surface, or from air bubbles at grain boundaries, into the ice as pressure is elevated; and (2) compression melt fractures, flat liquid-filled disks, that nucleate at imperfections in the crystal and grow with the application of pressure eventually to sprout dendritic fingers at the periphery. The transparency of the ice permitted visualization of the growth and behavior of the figures, and this could be an important tool in understanding the role of phase transformations in deep-focus earthquakes. Correlation between figure size and pressure is noted for the first time.

EBSD Analysis of Friction Stir Welded 7136-T76 Aluminum Alloy

2013 ◽  
Vol 203-204 ◽  
pp. 258-261 ◽  
Author(s):  
Izabela Kalemba ◽  
Krzysztof Muszka ◽  
Mirosław Wróbel ◽  
Stanislaw Dymek ◽  
Carter Hamilton
Keyword(s):  
Grain Size ◽  
Aluminum Alloy ◽  
Grain Boundaries ◽  
Texture Analysis ◽  
Crystallographic Texture ◽  
High Frequency ◽  
The Other ◽  
Ebsd Analysis ◽  
High Angle ◽  
Friction Stir

This research addresses the EBSD analysis of friction stir welded 7136-T76 aluminum alloy. The objectives of this study were to evaluate the grain size and their shape, character of grain boundaries in the stirred and thermo-mechanically affected zones, both on the advancing and retreating side as well as to investigate changes in the crystallographic texture. Results of texture analysis indicate the complexity of the FSW process. The texture gradually weakens on moving from the thermo-mechanically affected zone toward the weld center. The stirred zone is characterized by very weak texture and is dominated by high angle boundaries. On the other hand, the thermo-mechanically affected zone exhibits a high frequency of low angle boundaries.

Dynamical Simulation of the Motion of Curved Grain Boundaries Composed of Pyramidal-Shaped Ledges

1990 ◽  
Vol 193 ◽  
Author(s):  
Re-Jhen Jhan ◽  
P. D. Bristowe
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Boundary Migration ◽  
Model System ◽  
The Other ◽  
Grain Boundary Migration ◽  
Dynamical Simulation ◽  
Atomic Mechanism ◽  
Or Groups

ABSTRACTA dynamical simulation of curved grain boundaries composed of pyramidal-shaped ledges has shown that the boundaries can move by local conservative shuffles of atoms or groups of atoms such that one adjoining crystal grows at the expense of the other. In the model system studied, the shuffles often take the form of correlated rotational displacements about the axis normal to the boundary. The simulations provide support for the atomic mechanism proposed by Babcock and Balluffi to explain their observation of grain boundary migration without the participation of SGBDs.

scholarly journals Pinning Force Scaling Analysis of Polycrystalline MgB2

2020 ◽  
Vol 33 (11) ◽  
pp. 3333-3339
Author(s):  
M. R. Koblischka ◽  
A. Wiederhold ◽  
A. Koblischka-Veneva ◽  
C. Chang
Keyword(s):  
Grain Boundaries ◽  
Flux Pinning ◽  
The Other ◽  
Scaling Analysis ◽  
Pinning Force ◽  
Spark Plasma ◽  
Force Scaling ◽  
Flux Pinning Force

Abstract Flux pinning force scaling $f=F_{p}/F_{p,\max \limits }$ f = F p / F p , max vs. h = Ha/Hirr was performed on a variety of pure MgB2 samples, including a spark plasma sintered (SPS) one and a series of samples sintered at various reaction temperatures ranging between 775 and 950 ∘C. The SPS sample exhibits a well-developed scaling at all temperatures, and also the sintered samples prepared at 950 ∘C; however, the obtained peak positions of the pinning force scalings are distinctly different: The SPS sample reveals dominating pinning at grain boundaries, whereas the dominating pinning for the other one is point-pinning. All other samples studied reveal an apparent non-scaling of the pinning forces. The obtained pinning parameters are discussed in the framework of the Dew–Hughes’ pinning force scaling approach.

Reaction of beta-phase Ni–Al alloys with CrB2

1991 ◽  
Vol 6 (8) ◽  
pp. 1664-1672 ◽  
Author(s):  
Ajay K. Misra
Keyword(s):  
Grain Boundaries ◽  
New Product ◽  
Beta Phase ◽  
Al Alloys ◽  
The Other ◽  
Product Phase ◽  
Other Hand ◽  
Nial Phase

Reaction of Ni–Al alloys within the β-NiAl phase with CrB2 was studied at 1473 K as a function of Al concentration in the alloy. Reaction of 49–50 at. % Al alloys with CrB2 occurred by interdiffusion of Ni into CrB2 and Cr into the alloy without forming a new product phase. On the other hand, a new product phase, rich in Ni and B, formed by the reaction of alloys having Al concentrations 48 at. % or lower with CrB2. The reaction product was observed both at the CrB2/alloy interface and along the alloy grain boundaries.

Phase Analysis of the Precipitates in an Alloy 600/182 Weld

2007 ◽  
Vol 119 ◽  
pp. 111-114 ◽  
Author(s):  
Yun Soo Lim ◽  
Hong Pyo Kim ◽  
Man Kyo Jung ◽  
Joung Soo Kim
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Grain Boundaries ◽  
Phase Analysis ◽  
Fusion Zone ◽  
Base Metal ◽  
The Other ◽  
Alloy 600 ◽  
Other Hand ◽  
Transmission Electron

The precipitates in the base metal and the fusion zone of an Alloy 600/182 weld were characterized through a transmission electron microscopy. Precipitates in the Alloy 600 base metal were identified as Cr7C3. On the other hand, (Nb,Ti)C, Al-rich and Ti-rich oxides were found on the dendritic interfaces, and tiny Cr-rich M23C6 were distributed on the grain boundaries in the Alloy 182 fusion zone.

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