scholarly journals Plesiotwinsversusdiperiodic twins

2018 ◽  
Vol 74 (4) ◽  
pp. 332-344 ◽  
Author(s):  
Massimo Nespolo
Keyword(s):  
Coincidence Site Lattice ◽  
Twin Plane ◽  
Relative Orientation ◽  
Small Deviations ◽  
Site Lattice ◽  
Low Degree

Plesiotwins and diperiodic twins have in common the fact of being characterized by a low degree of lattice restoration. Plesiotwins differ from twins by the fact that the relative orientation of the individuals is obtained by a non-crystallographic rotation about the normal to the composition plane, whereas for twins this rotation is crystallographic, apart from possible small deviations coming from metric pseudosymmetries. In the case of plesiotwins, the low degree of lattice restoration comes from a large coincidence site lattice (CSL) in the composition plane. Diperiodic twins, instead, have a small CSL in the composition plane but the second plane of the same family contributing to the overall lattice restoration is too far away from the composition plane to be considered significant. It is shown that plesiotwins can occur as reflection twins if the composition plane is not parallel to the twin plane, and as rotation twins in the case of parallel hemitropy. Diperiodic twins can in principle occur in any category, but either the metric conditions to obtain a diperiodic twin are actually in contrast with the metric pseudosymmetry required for twinning or the result is actually a hybrid twin. This justifies why no confirmed examples of diperiodic twins are known to date.

Plesiotwinning: oriented crystal associations based on a large coincidence-site lattice

1999 ◽  
Vol 214 (7) ◽  
Author(s):  
M. Nespolo ◽  
G. Ferraris ◽  
H. Takeda ◽  
Y. Takéuchi
Keyword(s):  
Crystal Lattice ◽  
Coincidence Site Lattice ◽  
Oriented Crystal ◽  
Site Lattice ◽  
Low Degree ◽  
Point Groups ◽  
Definition Of

AbstractOriented crystal associations with a low degree of restoration of lattice nodes are discussed and it is shown that they are based on a large coincidence-site lattice (CSL). In this type of associations the oriented crystals are related by symmetry or pseudo-symmetry elements expressed by high indices in the crystal lattice. The relative orientations of the crystals correspond to rotations belonging to non-crystallographic point groups. In spite of the low number of common lattice nodes, these associations are not uncommon, especially in layer compounds. Since this kind of associations does not enter either in the definition of twinning or in that of cell-twinning, we propose to introduce the definition of

Dissociated Σ=27 boundaries in silicon

1988 ◽  
Vol 46 ◽  
pp. 624-625
Author(s):  
A. Garg ◽  
W.A.T. Clark ◽  
J.P. Hirth
Keyword(s):  
Electron Diffraction ◽  
Local Minimum ◽  
Boundary Energy ◽  
Coincidence Site Lattice ◽  
Boundary Plane ◽  
Low Energy ◽  
Theoretical Understanding ◽  
Site Lattice ◽  
Kikuchi Pattern ◽  
Analysis Techniques

In the last twenty years, a significant amount of work has been done in the theoretical understanding of grain boundaries. The various proposed grain boundary models suggest the existence of coincidence site lattice (CSL) boundaries at specific misorientations where a periodic structure representing a local minimum of energy exists between the two crystals. In general, the boundary energy depends not only upon the density of CSL sites but also upon the boundary plane, so that different facets of the same boundary have different energy. Here we describe TEM observations of the dissociation of a Σ=27 boundary in silicon in order to reduce its surface energy and attain a low energy configuration.The boundary was identified as near CSL Σ=27 {255} having a misorientation of (38.7±0.2)°/[011] by standard Kikuchi pattern, electron diffraction and trace analysis techniques. Although the boundary appeared planar, in the TEM it was found to be dissociated in some regions into a Σ=3 {111} and a Σ=9 {122} boundary, as shown in Fig. 1.

Coincidence-Site-Lattice Twist Boundaries in Bicrystalline α-Fe2O3 Nanoblades

2014 ◽  
Vol 118 (11) ◽  
pp. 5796-5801 ◽  
Author(s):  
Yiqian Wang ◽  
Chao Wang ◽  
Lu Yuan ◽  
Rongsheng Cai ◽  
Xuehua Liu ◽  
...  
Keyword(s):  
Coincidence Site Lattice ◽  
Site Lattice ◽  
Twist Boundaries

scholarly journals Molecular Dynamics Study on Deformation Mechanism of Grain Boundaries in Magnesium Crystal: Based on Coincidence Site Lattice Theory

2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Ken-ichi Saitoh ◽  
Kohei Kuramitsu ◽  
Tomohiro Sato ◽  
Masanori Takuma ◽  
Yoshimasa Takahashi
Keyword(s):  
Molecular Dynamics ◽  
Deformation Mechanism ◽  
Coincidence Site Lattice ◽  
Md Simulations ◽  
Uniaxial Tensile ◽  
High Angle ◽  
Site Lattice ◽  
Embedded Atom ◽  
Significant Difference ◽  
Eam Potential

As for magnesium (Mg) alloys, it has been noted that they are inferior to plastic deformation, but improvement in the mechanical properties by further refinement of grain size has been recently suggested. It means the importance of atomistic view of polycrystalline interface of Mg crystal. In this study, to discuss the deformation mechanism of polycrystalline Mg, atomistic grain boundary (GB) models by using coincidence site lattice (CSL) theory are constructed and are simulated for their relaxed and deformatted structures. First, GB structures in which the axis of rotation is in [11¯00] direction are relaxed at 10 Kelvin, and the GB energies are evaluated. Then, the deformation mechanism of each GB model under uniaxial tensile loading is observed by using the molecular dynamics (MD) method. The present MD simulations are based on embedded atom method (EAM) potential for Mg crystal. As a result, we were able to observe atomistically a variety of GB structures and to recognize significant difference in deformation mechanism between low-angle GBs and high-angle GBs. A close scrutiny is made on phenomena of dislocation emission processes peculiar to each atomistic local structure in high-angle GBs.

scholarly journals Microstructure and Impact Toughness of Local-Dry Keyhole Tungsten Inert Gas Welded Joints

Materials ◽  
2019 ◽  
Vol 12 (10) ◽  
pp. 1638 ◽  
Author(s):  
Shuwan Cui ◽  
Zhiyong Xian ◽  
Yonghua Shi ◽  
Baoyi Liao ◽  
Tao Zhu
Keyword(s):  
Impact Toughness ◽  
Weld Metal ◽  
Welded Joint ◽  
Coincidence Site Lattice ◽  
Random Phase ◽  
Inert Gas ◽  
Phase Boundaries ◽  
Site Lattice ◽  
Underwater Welding ◽  
The Impact

In this paper, the microstructure and impact toughness of a S32101 duplex stainless steel underwater local-dry keyhole tungsten inert gas welded joint were studied. The impact toughness value of the underwater weld metal reached 78% of the onshore weld metal, which is in accordance with the underwater welding standards. The proportion of austenite in the underwater weld metal was 0.9% lower than that of the onshore weld metal. The proportion of the Σ3 coincidence site lattice boundaries and random phase boundaries in the underwater weld metal, which significantly influence the impact toughness of the weld metal, were smaller than that of the onshore weld metal.

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