Influence of a Slip Plane Orientation with Respect to the Shear Plane of ECAP on Microstructure of Copper Single Crystal Subject to One Pressing at Room Temperature

2008 ◽  
Vol 584-586 ◽  
pp. 387-392 ◽  
Author(s):  
Soichi Katayama ◽  
Hiroyuki Miyamoto ◽  
Alexei Vinogradov ◽  
Satoshi Hashimoto
Keyword(s):  
Simple Shear ◽  
Crystallographic Orientation ◽  
Room Temperature ◽  
Electron Backscatter Diffraction ◽  
Pure Copper ◽  
Shear Bands ◽  
Large Angle ◽  
Shear Plane ◽  
Deformation Twinning ◽  
Shear Direction

This paper describes the influence of initial crystallographic orientation on the formation of dense shear bands in pure copper single crystals subjected to equal-channel angular pressing (ECAP) for one pass at room temperature. Local orientation change during simple shear by ECAP traced by electron backscatter diffraction (EBSD) indicated that the shear bands were formed when twinning plane and direction become parallel to the macroscopic shear plane and shear direction of simple shear strain, respectively. Orientation splitting associated with shear bands have a twinning relation. The shear bands were delineated by large-angle grain boundaries, having close relation to twinning relation with matrix, suggesting the role of deformation twinning as their nucleation sites. The activation of deformation twinning is suggested and can be rationalized by favorable crystallographic orientation and critical dislocation density as indicated elsewhere by the present authors.

Texture Evolution in Pure Copper Processed by Equal Channel Angular Extrusion with Extended Processing Routes

2010 ◽  
Vol 667-669 ◽  
pp. 271-276 ◽  
Author(s):  
Sai Yi Li ◽  
Hao Li
Keyword(s):  
Simple Shear ◽  
Equal Channel Angular Extrusion ◽  
Texture Evolution ◽  
Pure Copper ◽  
Shear Plane ◽  
Processing Route ◽  
Shear Direction ◽  
Face Centered Cubic ◽  
Wide Range ◽  
Angular Extrusion

An experimental characterization of texture evolution during equal channel angular extrusion (ECAE) of pure copper was conducted up to 8 passes considering an extended range of processing routes. These routes are featured by 0°, 45°, 90°, 135°, and 180° rotation about the billet longitudinal axis after each pass, and were designated as R0, R45, R90, R135, and R180, respectively. They were implemented using new die designs with the cross-section of the die channels as a 24-sided regular convex polygon and with die angle (Φ) of 90° and 120°, respectively. X-ray diffraction measurements show that for both die sets, the textures developed via the different routes all show orientation concentrations along fibers with the {111} planes parallel to the macroscopic simple shear plane and <110> directions parallel to the macroscopic simple shear direction, yet the locations and orientation densities of the main texture components vary significantly with the pass number and the processing route. After 4 to 8 passes, the texture is found to be the weakest via route R180 for both die sets, and strongest via R0 or R45. For a given route and pass number, the texture developed with Φ = 120° is generally weaker than its counterpart with Φ = 90°. These results thus confirm the general tendencies of texture development in face-centered cubic metals with {111}<110> slip as the dominant deformation mechanisms, albeit in a wide range of processing route or deformation history.

Processing of Copper by Equal Channel Angular Pressing (ECAP) – Microstructure Investigations

2015 ◽  
Vol 641 ◽  
pp. 286-293
Author(s):  
Beata Leszczyńska-Madej ◽  
Maria W. Richert ◽  
Agnieszka Hotloś ◽  
Jacek Skiba
Keyword(s):  
Equal Channel Angular Pressing ◽  
Room Temperature ◽  
Subgrain Size ◽  
Pure Copper ◽  
Shear Bands ◽  
Angular Pressing ◽  
Ecap Process ◽  
Transmission Electron ◽  
Different Types ◽  
Diffraction Patterns

The present study attempts to apply Equal-Channel Angular Pressing (ECAP) to 99.99% pure copper. ECAP process was realized at room temperature for 4, 8 and 16 passes through route BC using a die having angle of 90°. The microstructure of the samples was investigated by means both light and transmission electron microscopy. Additionally the microhardness was measured and statistical analysis of the grains and subgrains was performed. Based on Kikuchi diffraction patterns misorientation was determined. There were some different types of bands in the microstructure after deformation. The shear bands, bands and in the submicron range the microshear bands and microbands are a characteristic feature of the microstructure of copper. Also characteristic was increasing of the number of bands with increasing of deformation and mutually crossing of the bands. The intersection of a bands and microbands leads to the formation of new grains with the large misorientation angle. The measured grain/subgrain size show, that the grain size is maintained at a similar level after each stage of deformation and is equal to d = 0.25 – 0.32 μm.

The Reorientation of the Kangâmiut Dike Swarm, West Greenland

1975 ◽  
Vol 12 (2) ◽  
pp. 158-173 ◽  
Author(s):  
A. Escher ◽  
J. C. Escher ◽  
J. Watterson
Keyword(s):  
Simple Shear ◽  
Shear Plane ◽  
Boundary Region ◽  
Ductile Deformation ◽  
Shear Direction ◽  
Average Amount ◽  
Southern Boundary ◽  
Crustal Shortening ◽  
West Greenland ◽  
Simple Shear Deformation

The Nagssugtoqidian belt in West Greenland is formed mainly of Archaean rocks which were strongly reworked during the early Proterozoic. Investigation of the southern boundary region has resulted in a model for the tectonic reworking based on the geometry of homogeneous simple shear deformation. Two differently oriented swarms of mainly pre-kinematic dikes are used as strain indicators at the deformation boundary. Gneiss tectonite fabrics have been used to determine that the shear plane dips northwest at 20–40° and that the shear direction along this plane is towards the southeast. The average amount of simple shear strain (S = 6) has been determined from the degree of dike reorientation. This mechanism has resulted in a ductile overthrusting of the reworked rocks over the Archaean foreland, giving a crustal shortening of ca. 66%. The area investigated represents a deep tectonic level. At higher levels ductile deformation would be expected to give way to thrust and fold nappe development. The displacements demonstrated are those which might be expected in the deformed margins of colliding continental plates.

scholarly journals Crystallographic preferred orientations of ice deformed in direct-shear experiments at low temperatures

2018 ◽  
Author(s):  
Chao Qi ◽  
David J. Prior ◽  
Lisa Craw ◽  
Sheng Fan ◽  
Maria-Gema Llorens ◽  
...  
Keyword(s):  
Shear Strain ◽  
Electron Backscatter Diffraction ◽  
Numerical Models ◽  
Boundary Migration ◽  
Shear Plane ◽  
Equivalent Strain ◽  
Lattice Rotation ◽  
Dislocation Creep ◽  
Shear Direction ◽  
Primary Cluster

Abstract. We sheared synthetic polycrystalline ice at temperatures of −5, −20 and −30 °C, to different shear strains, up to γ = 2.6 (equivalent strain of 1.5). Cryo-electron backscatter diffraction (EBSD) shows that basal intra-crystalline slip planes become preferentially oriented parallel to the shear plane, in all experiments. This is visualized as a primary cluster of crystal c-axes (the c-axis is perpendicular to the basal plane) perpendicular to the shear plane. In all except the two highest-strain experiments at −30 °C, a secondary cluster of c-axes is observed, at an angle to the primary cluster. With increasing strain, the primary c-axis cluster strengthens. With increasing temperature, both clusters strengthen. In the −5 °C experiments, the angle between the two clusters reduces with increasing strain. The c-axis clusters are elongated perpendicular to the shear direction. This elongation increases with increasing shear strain and with decreasing temperature. Highly curved grain boundaries are more prevalent in samples sheared at higher temperatures. At each temperature, the proportion of and irregularity of curved boundaries decreases with increasing shear strain. Subgrains are observed in all samples. Recrystallized grains and subgrains are similar in size and are both smaller than the original grains. Microstructural interpretations and comparisons of the data from experimentally sheared samples with numerical models suggest that the observed crystallographic orientation patterns result from a balance of the rates of lattice rotation (during dislocation creep) and growth of grains by strain-induced grain boundary migration (GBM). GBM is faster at higher temperatures and becomes less important as shear strain increases. These observations and interpretations provide a hypothesis to be tested in further experiments and using numerical models, with the ultimate goal of aiding the interpretation of crystallographic preferred orientations in naturally deformed ice.

scholarly journals Crystallographic preferred orientations of ice deformed in direct-shear experiments at low temperatures

2019 ◽  
Vol 13 (1) ◽  
pp. 351-371 ◽  
Author(s):  
Chao Qi ◽  
David J. Prior ◽  
Lisa Craw ◽  
Sheng Fan ◽  
Maria-Gema Llorens ◽  
...  
Keyword(s):  
Shear Strain ◽  
Electron Backscatter Diffraction ◽  
Numerical Models ◽  
Boundary Migration ◽  
Shear Plane ◽  
Line Length ◽  
Lattice Rotation ◽  
Dislocation Creep ◽  
Shear Direction ◽  
Primary Cluster

Abstract. Synthetic polycrystalline ice was sheared at temperatures of −5, −20 and −30 ∘C, to different shear strains, up to γ=2.6, equivalent to a maximum stretch of 2.94 (final line length is 2.94 times the original length). Cryo-electron backscatter diffraction (EBSD) analysis shows that basal intracrystalline slip planes become preferentially oriented parallel to the shear plane in all experiments, with a primary cluster of crystal c axes (the c axis is perpendicular to the basal plane) perpendicular to the shear plane. In all except the two highest-strain experiments at −30 ∘C, a secondary cluster of c axes is observed, at an angle to the primary cluster. With increasing strain, the primary c-axis cluster strengthens. With increasing temperature, both clusters strengthen. In the −5 ∘C experiments, the angle between the two clusters reduces with strain. The c-axis clusters are elongated perpendicular to the shear direction. This elongation increases with increasing shear strain and with decreasing temperature. Highly curved grain boundaries are more prevalent in samples sheared at higher temperatures. At each temperature, the proportion of curved boundaries decreases with increasing shear strain. Subgrains are observed in all samples. Microstructural interpretations and comparisons of the data from experimentally sheared samples with numerical models suggest that the observed crystallographic orientation patterns result from a balance of the rates of lattice rotation (during dislocation creep) and growth of grains by strain-induced grain boundary migration (GBM). GBM is faster at higher temperatures and becomes less important as shear strain increases. These observations and interpretations provide a hypothesis to be tested in further experiments and using numerical models, with the ultimate goal of aiding the interpretation of crystallographic preferred orientations in naturally deformed ice.

scholarly journals The Relation between Shear Banding, Microstructure and Mechanical Properties in Mg and Mg-Y Alloys

2011 ◽  
Vol 690 ◽  
pp. 202-205 ◽  
Author(s):  
Stefanie Sandlöbes ◽  
Igor Schestakow ◽  
Sang Bong Yi ◽  
Stefan Zaefferer ◽  
Jing Qui Chen ◽  
...  
Keyword(s):  
Mechanical Behaviour ◽  
Room Temperature ◽  
Electron Backscatter Diffraction ◽  
Shear Banding ◽  
Cold Deformation ◽  
Shear Bands ◽  
High Stress ◽  
Temperature Deformation ◽  
Dislocation Slip ◽  
Different Strains

The formation of deformation-induced shear bands plays an important role for the room temperature deformation of both, Mg and Mg-Y alloys, but the formation and structure of shear bands is distinctively different in the two materials. Due to limited deformation modes in pure Mg, the strain is localized in few shear bands leading to an early failure of the material during cold deformation. Contrarily, Mg-RE (RE: rare earth) alloys exhibit a high density of homogeneously distributed local shear bands during deformation at room temperature. A study of the microstructure of the shear bands by electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) at different strains was performed. These investigations give insight into the formation of shear bands and their effects on the mechanical behaviour of pure Mg and Mg-3Y. Since in pure Mg mainly extension twinning and basal <a> dislocation slip are active, high stress fields at grain resp. twin boundaries in shear bands effect fast growth of the shear bands. In Mg-RE alloys additionally contraction and secondary twinning and pyramidal <c+a> dislocation slip are active leading to the formation of microscopic shear bands which are limited to the boundary between two grains. The effects of shear bands on the mechanical behaviour of pure Mg and Mg-RE alloys are discussed with respect to their formation and growth.

scholarly journals Evidence of new twinning modes in magnesium questioning the shear paradigm

2018 ◽  
Vol 51 (3) ◽  
pp. 809-817 ◽  
Author(s):  
Cyril Cayron ◽  
Roland Logé
Keyword(s):  
Habit Plane ◽  
Simple Shear ◽  
Electron Backscatter Diffraction ◽  
Shear Plane ◽  
Deformation Mode ◽  
Crystallographic Analysis ◽  
Hexagonal Close Packed ◽  
Electron Backscatter ◽  
Macroscopic Deformation ◽  
Backscatter Diffraction

Twinning is an important deformation mode of hexagonal close-packed metals. The crystallographic theory is based on the 150-year-old concept of simple shear. The habit plane of the twin is the shear plane; it is invariant. This article presents electron backscatter diffraction observations and crystallographic analysis of a millimetre-size twin in a magnesium single crystal whose habit plane, unambiguously determined both in the parent crystal and in its twin, is not an invariant plane. This experimental evidence demonstrates that macroscopic deformation twinning can be achieved by a mechanism that is not a simple shear. This unconventional twin is often co-formed with a new conventional twin that exhibits the lowest shear magnitude ever reported in metals. The existence of unconventional twinning introduces a shift of paradigm and calls for the development of new crystallographic theories of displacive transformations.

Formation of Deformation Twins and Related Shear Bands in Copper Single Crystals Pressed by ECAP

2010 ◽  
Vol 654-656 ◽  
pp. 1231-1234
Author(s):  
Takumi Ikeda ◽  
Hiroyuki Miyamoto ◽  
Toshiyuki Uenoya ◽  
Satoshi Hashimoto ◽  
Alexei Vinogradov
Keyword(s):  
Shear Band ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Pure Copper ◽  
Shear Bands ◽  
Large Angle ◽  
Deformation Twins ◽  
Crystallographic Feature ◽  
The Matrix ◽  
Copper Single Crystals

The pure copper single crystals with specific crystallographic orientated were subjected to ECAP for one pass at room temperature. Two types of shear bands were observed. Type 1 shear bands were constructed with clusters of distorting micro shear bands and matrix. Micro shear band and matrix were delineated by large-angle grain boundaries, and these two orientations are in a twinning relationship. Parallel sets of deformation twins were observed in the matrix. Type 2 shear bands had no crystallographic feature, and shear band and matrix were considered as low-angle grain boundaries. Deformation twin was not observed both in matrix and the shear bands.

scholarly journals New sights in crenulation geometry developed in anisotropic materials undergoing simple shear deformation

2021 ◽  
Author(s):  
Yuanbang Hu ◽  
Tamara de Riese ◽  
Paul Bons ◽  
Shugen Liu ◽  
Albert Griera ◽  
...  
Keyword(s):  
Structural Geology ◽  
Numerical Simulations ◽  
Shear Deformation ◽  
Simple Shear ◽  
Shear Bands ◽  
Shear Plane ◽  
Initial Orientation ◽  
Mechanical Anisotropy ◽  
Simple Shear Deformation ◽  
Shear Localisation

&lt;p&gt;Deformation of foliated rocks commonly leads to crenulation or micro-folding, with the development of cleavage domains and microlithons. We here consider the effect of mechanical anisotropy due to a crystallographic preferred orientation (CPO) that defines the foliation, for example by of alignment of micas. Mechanical anisotropy enhances shear localisation (Ran, et al., 2018; de Riese et al., 2019), resulting in low-strain domains (microlithons) and high-strain shear bands or cleavage domains. We investigate the crenulation patterns that result from moderate strain simple shear deformation, varying the initial orientation of the mechanical anisotropy relative to the shear plane. &amp;#160;&lt;/p&gt;&lt;p&gt;We use the Viscoplastic Full-Field Transform (VPFFT) crystal plasticity code coupled with the modelling platform ELLE (http://www.elle.ws; Llorens et al., 2017) to simulate the deformation of anisotropic single-phase material with an initial given CPO in dextral simple shear in low to medium strain. Deformation is assumed to be accommodated by glide along the basal, prismatic and pyramidal slip systems of a hexagonal model mineral. An approximately transverse anisotropy is achieved by assigning a small critical resolved shear stress to the basal plane. An initially point-maximum CPO at variable angles to the shear plane defines the initial straight foliation at different angles to the shear plane, limiting ourselves to orientations in which the foliation is in the stretching field. The resulting crenulation geometries strongly depend on the orientation of the foliation and we observe four types of localisation behaviour: (1) synthetic shear bands, (2) antithetic shear bands, (3) initial formation of antithetic shear bands and subsequent development of synthetic shear bands, and (4) distributed, approximately shear-margin parallel strain localisation, but no distinct shear bands.&lt;/p&gt;&lt;p&gt;The numerical simulations not only show the evolving strain-rate field, but also the predicted finite strain pattern of existing visible foliations. We show the results for layers parallel to the foliation, but also cases where the visible layering is at an angle to the mechanical anisotropy (e.g. in case of distinct sedimentary layers and a cleavage that controls the mechanical anisotropy). A wide range of crenulation types form as a function of the initial orientation of the visible layering and mechanical anisotropy (comparable to C, C' and C'' shear bands and compressional crenulation cleavage). Most importantly, some of may be highly misleading and may easily be interpreted as indicating the opposite sense of shear.&lt;/p&gt;&lt;p&gt;Reference&lt;/p&gt;&lt;p&gt;de Riese, T., et al. (2019). Shear localisation in anisotropic, non-linear viscous materials that develop a CPO: A numerical study. Journal of Structural Geology, 124, 81-90. DOI: 10.1016/j.jsg.2019.03.006&lt;/p&gt;&lt;p&gt;Llorens, M.-G., et al. (2017). Dynamic recrystallisation during deformation of polycrystalline ice: insights from numerical simulations. Philosophical Transactions of the Royal Society A, Special Issue on Microdynamics of Ice, 375: 20150346. DOI: 10.1098/rsta.2015.0346.&lt;/p&gt;&lt;p&gt;Ran, H., et al. (2018). Time for anisotropy: The significance of mechanical anisotropy for the development of deformation structures. Journal of Structural Geology, 125, 41-47. DOI: 10.1016/j.jsg.2018.04.019&lt;/p&gt;

scholarly journals Influence of initial preferred orientations on strain localisation and fold patterns in non-linear viscous anisotropic materials

2020 ◽  
Author(s):  
Tamara de Riese ◽  
Paul D. Bons ◽  
Enrique Gomez-Rivas ◽  
Albert Griera ◽  
Maria-Gema Llorens ◽  
...  
Keyword(s):  
Simple Shear ◽  
Shear Bands ◽  
Shear Plane ◽  
Slip Systems ◽  
Full Field ◽  
Deformation Structures ◽  
Single Maximum ◽  
Non Linear ◽  
Very High ◽  
Shear Localisation

&lt;p&gt;Deformation localisation in rocks can lead to a variety of structures, such as shear zones and shear bands that can range from grain to crustal scale, from discrete and isolated zones to anastomosing networks. The heterogeneous strain field can furthermore result in a wide range of highly diverse fold geometries.&lt;/p&gt;&lt;p&gt;We present a series of numerical simulations of the simple-shear deformation of an intrinsically anisotropic non-linear viscous material with a single maximum crystal preferred orientation (CPO) in dextral simple shear. We use the Viscoplastic Full-Field Transform (VPFFT) crystal plasticity code (e.g. Lebensohn &amp; Rollett, 2020) coupled with the modelling platform ELLE (http://elle.ws) to achieve very high strains. The VPFFT-approach simulates viscoplastic deformation by dislocation glide, taking into account the different available slip systems and their critical resolved shear stresses. The approach is well suited for strongly non-linear anisotropic materials (de Riese et al., 2019). We vary the anisotropic behaviour of the material from isotropic to highly anisotropic (according to the relative critical resolved shear stress required to activate the different slip systems), as well as the orientation of the initial single maximum orientation, which we vary from parallel to perpendicular to the shear plane. To visualize deformation structures, we use passive markers, for which we also systematically vary the initial orientation.&lt;/p&gt;&lt;p&gt;At relatively low strains the amount of strain rate localisation and resulting deformation structures highly depend on the initial single maximum orientation in the material in all anisotropic models. Three regimes can be recognised: distributed shear localisation, synthetic shear bands and antithetic shear bands. However, at very high strains localisation behaviour always tends to converge to a similar state, independent of the initial orientation of the anisotropy.&lt;/p&gt;&lt;p&gt;In rocks, shear localisation is often detected by the deflection and/or folding of layers, which may be parallel to the anisotropy (e.g. cleavage formed by aligned mica), or by deflection/deformation of passive layering, such as original sedimentary layers. The resulting fold patterns vary strongly, depending on the original orientation of layering relative to the deformation field. This can even result in misleading structures that seem to indicate the opposite sense of shear. Most distinct deformation structures tend to form when the layering is originally parallel to the shear plane.&lt;/p&gt;&lt;p&gt;&amp;#160;&lt;/p&gt;&lt;p&gt;de Riese, T., Evans, L., Gomez-Rivas, E., Griera, A., Lebensohn, R.A., Llorens, M.-G., Ran, H., Sachau, T., Weikusat, I., Bons, P.D. 2019. Shear localisation in anisotropic, non-linear viscous materials that develop a CPO: A numerical study. J. Struct. Geol. 124, 81-90.&lt;/p&gt;&lt;p&gt;Lebensohn, R.A., Rollett, A.D. 2020. Spectral methods for full-field micromechanical modelling of polycrystalline materials. Computational Mat. Sci. 173, 109336.&lt;/p&gt;

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