Twinning with zero twinning shear

2016 ◽  
Vol 125 ◽  
pp. 73-79 ◽  
Author(s):  
B. Li ◽  
X.Y. Zhang
Keyword(s):  
Twinning Shear

scholarly journals Strain Accommodations among Twin Variants in Ti and Mg

Crystals ◽  
2021 ◽  
Vol 11 (4) ◽  
pp. 453
Author(s):  
Ping Zhou ◽  
Guo-Zhen Zhu
Keyword(s):  
Mechanical Property ◽  
Great Influence ◽  
Local Strain ◽  
Deformation Texture ◽  
Variant Selection ◽  
Slip Systems ◽  
Twinning Shear ◽  
Active Variant ◽  
Shed Light ◽  
Selection Of

The selection of twin variants has a great influence on deformation texture and mechanical property in hcp metals where slip systems are limited and twinning types are abundant during deformation. Local strain accommodations among twin variants are considered to shed light on variant selection rules in Ti and Mg alloys. Five kinds of strain accommodations are discussed in terms of different regions that are affected by the twinning shear of primary twin. These regions contain (I) the whole sample, (II) neighboring grain, (III) adjacent primary twin in neighboring grain, (IV) adjoining primary twin within the same parent grain, and (V) multi-generation of twinning inside the primary twin. For a potentially active variant, its operation needs not only relatively higher resolved shear stress but also easily accommodated strain by immediate vicinity. Many of the non-Schmid behaviors could be elucidated by local strain accommodations that variants with relatively higher SFs hard to be accommodated are absent, while those with relatively lower SFs but could be easily accommodated are present.

Magnetocrystalline Anisotropy and Twinning Stress of 10M and 2M Martensites in Ni-Mn-Ga System

2006 ◽  
Vol 512 ◽  
pp. 195-200 ◽  
Author(s):  
Nariaki Okamoto ◽  
Takashi Fukuda ◽  
Tomoyuki Kakeshita ◽  
Tetsuya Takeuchi
Keyword(s):  
Magnetic Field ◽  
Shear Stress ◽  
Magnetocrystalline Anisotropy ◽  
Anisotropy Constant ◽  
The Other ◽  
Magnetic Shear ◽  
Maximum Value ◽  
Twinning Plane ◽  
Twinning Shear ◽  
The Difference

Ni2MnGa alloy with 10M martensite exhibits rearrangement of martensite variants (RMV) by magnetic field, but Ni2.14Mn0.92Ga0.94 with 2M martensite does not. In order to explain the difference, we measured uniaxial magnetocrystalline anisotropy constant Ku and the stress required for twinning plane movement τreq in these alloys. Concerning the former alloy, the maximum value of magnetic shear stress acting across twinning plane τmag, which is evaluated as |Ku| divided by twinning shear, becomes larger than τr eq. On the other hand, concerning the latter alloy, the maximum of τmag is only one-tenth of τreq at any temperature examined. Obviously, the relation, τmag> τr eq, is satisfied when RMV occurs by magnetic field and vice versa. In this martensite, the large twinning shear of 2M martensite is responsible for small τmag and large τreq.

scholarly journals Determination of sliding and twinning shear stress during microindentation of Hadfield steel single crystals

2020 ◽  
Vol 10 (4) ◽  
pp. 451-456
Author(s):  
Dmitry Lychagin ◽  
Andrey Filippov ◽  
Olga Novitskaya ◽  
Aleksandr Kolubaev
Keyword(s):  
Shear Stress ◽  
Single Crystals ◽  
Hadfield Steel ◽  
Twinning Shear

The theory of the crystallography of deformation twinning

1965 ◽  
Vol 288 (1413) ◽  
pp. 240-255 ◽  
Keyword(s):  
Crystal Structures ◽  
Deformation Twinning ◽  
Type I ◽  
Lattice Structures ◽  
Type Ii ◽  
Orientation Relationships ◽  
Tensor Calculus ◽  
Moving Interface ◽  
Twinning Shear ◽  
Crystallographic Characteristics

The crystallographic characteristics of deformation twinning are derived by considering the atomic movements which occur at the moving interface as a twin propagates. This is facilitated by making use of the notation of the tensor calculus, and general expressions, valid for all crystal structures, are obtained giving the magnitude of the twinning shear and relating the twinning elements for both type I and type II twinning. The atomic shuffles, which in general must accompany the twinning shear in both single and multiple lattice structures, are examined in detail and expressions are derived for their magnitudes and directions for the cases of the four classical orientation relationships associated with deformation twinning. The use of these expressions in predicting operative twinning modes is described and the relations between this theory and other recent theories of the crystallography of deformation twinning are discussed.

scholarly journals Transformation Texture Analysis of BCC and BCT Ferrous Martensite

1993 ◽  
Vol 22 (1) ◽  
pp. 43-51 ◽  
Author(s):  
Hirofumi Miyaji ◽  
Ei-Ichi Furubayashi
Keyword(s):  
Crystal Orientation ◽  
Thin Sheet ◽  
Parent Phase ◽  
External Stress ◽  
Strain Component ◽  
X Ray ◽  
Transformation Texture ◽  
Twinning Shear ◽  
Constraint Stress ◽  
Bain Strain

The theoretical prediction of transformation textures, that developed in thin sheet without external stress, was carried out based on the Bain-Strain and Twinning-Shear model, respectively. To examine the validity of the prediction, the experiments were conducted with X-ray pole figure method on Fe-30Ni and Fe-30Ni-0.8C alloy sheets. The results obtained are as follows:(1) Variant selection phenomenon depends on the crystal orientation of the parent phase and on the Bain strain in the martensitic transformation.(2) The effect of the anisotropic constraint stress on the shear deformation involved in the lattice change and on the Bain distortion appears most remarkably in the BCT martensite transformed from the cube textured parent phase.(3) It became clear that such a variant that has the largest Bain strain component to the sheet normal, that is, the variant, of which the Bain distortion is prevented least of all by the anisotropic constraint stress, forms predominantly.

Twinning Shear in Alumina

1983 ◽  
Vol 66 (9) ◽  
pp. c161-c162 ◽  
Author(s):  
William D. Scott
Keyword(s):  
Twinning Shear

Twinning shears in lattices

1968 ◽  
Vol 304 (1476) ◽  
pp. 123-134 ◽  
Keyword(s):  
Deformation Twinning ◽  
Lattice Points ◽  
Contributory Factor ◽  
Subsequent Paper ◽  
Crystalline Materials ◽  
Orientation Relations ◽  
Shear Modes ◽  
Twinning Shear ◽  
Macroscopic Shape ◽  
Small Shear

A generalized theory of twinning in lattices is developed based on the definition that a twinning shear is any shear which restores a lattice in a new orientation. Shears of this kind describe the macroscopic shape deformation associated with deformation twinning which is an important contributory factor in the plastic deformation of many crystalline materials. It is shown that all shears of this kind may be derived from unimodular correspondence matrices satisfying certain simple restrictions. The form of these correspondence matrices is discussed for primitive and centred lattices when all or only a fraction of the lattice points are sheared to correct twin positions. Relations between shear modes associated with closely related matrices are also examined. A convenient method of choosing unimodular matrices which predict twinning modes with small shear strains is then described and a table of such matrices presented. It is then shown that the correspondence matrices describing conven­tional twinning modes, arising from the classical theories of deformation twinning, are identical to their own inverses. However, many other matrices, not having this property but satisfying the conditions of the general theory, exist and must therefore describe non-conventional twinning modes. Certain general characteristics of these modes including various degeneracies are analysed. In particular it is shown that they do not obey the standard orientation relations of classical twinning modes. In addition they are described in general by four irrational twinning elements, whereas classical modes have at least two of the four elements rational. Applications of the theory to specific lattices and examples of these new modes will be presented in a subsequent paper.

On the twinning shear of{101¯2}twins in magnesium – Experimental determination and formal description

2017 ◽  
Vol 134 ◽  
pp. 267-273 ◽  
Author(s):  
Konstantin D. Molodov ◽  
Talal Al-Samman ◽  
Dmitri A. Molodov ◽  
Sandra Korte-Kerzel
Keyword(s):  
Experimental Determination ◽  
Formal Description ◽  
Twinning Shear

Interfacial and twin boundary structures of nanostructured Cu–Ag filamentary composites

2003 ◽  
Vol 18 (9) ◽  
pp. 2194-2202 ◽  
Author(s):  
K. H. Lee ◽  
S. I. Hong
Keyword(s):  
Twin Boundary ◽  
Lattice Misfit ◽  
Longitudinal Section ◽  
Copper Matrix ◽  
Misfit Strain ◽  
Boundary Structure ◽  
Misfit Dislocations ◽  
Transmission Electron ◽  
The Matrix ◽  
Twinning Shear

A high-resolution transmission electron microscope was used to study the interfacial and twin boundary structure of nanostructured Cu–Ag filamentary composites. Copper matrix and silver filaments have the orientation relationship {111}Cu∥{111}Ag and 〈111〉Cu∥〈111〉Ag. In some regions, twin bands propagated through the silver filaments with some boundary steps at the matrix/filament interface, and the silver filament appeared to be kinked in the twin band in the same direction as the twinning shear. This suggests that twins propagated after the formation of silver filament, and twin bands were deformation twins. At the matrix/filament interface, misfit interface dislocations were introduced periodically to relieve the misfit strain. The distance between interfacial misfit dislocations along the matrix/filament interface in the longitudinal section was measured to be 1.88 nm, which is in good agreement with that (1.81 nm) calculated based on lattice misfit. In Cu–Ag nanocomposites, the spacing between Moire fringes was found to be quite close to that between interfacial misfit dislocations.

On the 101¯2 “twinning shear” measured from line deflection

2019 ◽  
Vol 159 ◽  
pp. 133-136 ◽  
Author(s):  
X.Y. Zhang ◽  
B. Li ◽  
Q. Sun
Keyword(s):  
Twinning Shear
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