Journal articles: 'Crystal deformation'

1

Gröschel, Alexander, Hannes Grillenberger, and Andreas Magerl. "Elastic deformations in a perfect bulk Si crystal studied by high-energy X-rays." Journal of Applied Crystallography 42, no. 5 (September 8, 2009): 758–67. http://dx.doi.org/10.1107/s0021889809030349.

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Long-range strain fields induced in highly perfect bulk crystals during the manufacturing process significantly affect the quality and may even lead to spontaneous fracturing. Obviously a quantitative assessment of these deformations is crucial. A possible means is to examine the diffraction of X-rays by strained crystals, as the deformations bear on the diffraction characteristics of such crystals. In this report a quantitative examination of the diffraction characteristics of a perfect silicon bulk crystal with long-range strain fields in a well defined geometry is presented. The experiments were carried out using a high-energy X-ray laboratory source. By simulating the elastic deformation of the crystal by a finite element program the strain fields of the diffracting crystal are accessed. From these, simulated data values for integrated intensities can be derived on the basis of the dynamical diffraction theory for slightly distorted crystals. The theoretical calculations show good agreement with the experimental measured values. The smallest deformation yielding a noticeable change of the integrated intensity can be associated with a bending radius of the diffracting lattice planes of 16 km.

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Romanova, Varvara, Ruslan Balokhonov, Olga Zinovieva, Dmitry Lychagin, Evgeniya Emelianova, and Ekaterina Dymnich. "Mechanical Aspects of Nonhomogeneous Deformation of Aluminum Single Crystals under Compression along [100] and [110] Directions." Metals 12, no. 3 (February 24, 2022): 397. http://dx.doi.org/10.3390/met12030397.

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The deformation behavior of aluminum single crystals subjected to compression along the [100] and [110] directions is numerically examined in terms of crystal plasticity. A constitutive model taking into account slip geometry in face-centered cubic crystals is developed using experimental data for the single-crystal samples with lateral sides coplanar to certain crystal planes. Two sets of calculations are performed using ABAQUS/Explicit to examine the features of plastic strain evolution in perfectly plastic and strain-hardened crystals. Special attention is given to the discussion of mechanical aspects of crystal fragmentation. Several distinct deformation stages are revealed in the calculations. In the first stage, narrow solitary fronts of plastic deformation are alternately formed near the top or bottom surfaces and then propagate towards opposite ends to save the symmetry of the crystal shape. The strain rate within the fronts is an order of magnitude higher than the average strain rate. The first stage lasts longer in the strain-hardened crystals, eventually giving way to an intermediate stage of multiple slips in different crystal parts. Finally, the crystal shape becomes asymmetrical, but no pronounced macroscopic strain localization has been revealed at any deformation stage. The second stage in perfectly plastic crystals relates to abrupt strain localization within a through-thickness band-shaped region, accompanied by macroscale crystal fragmentation. Stress analysis has shown that pure compression took place only in the first deformation stage. Once the crystal shape has lost its symmetry, the compressive stress in some regions progressively decreases to zero and eventually turns tensile.

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Kondou, Ryouji, and Tetsuya Ohashi. "High Density Bands of GN Dislocations Formed by Multi Body Interaction in Compatible Type Multi Crystal Models." Key Engineering Materials 340-341 (June 2007): 187–92. http://dx.doi.org/10.4028/www.scientific.net/kem.340-341.187.

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Slip deformation phenomena in compatible type multi crystal models subjected to tensile load are analyzed by a finite element crystal plasticity analysis code, and accumulation of geometrically-necessary and statistically-stored dislocations (GNDs and SSDs) are evaluated in detail. Crystal orientations for the grains are chosen so that mutual constraint of deformation through grain boundary planes does not take place. We call these models as compatible type multi crystals, because “compatibility requirements” at grain boundaries are automatically maintained by slip deformation only on the primary systems and uniform deformation is expected to occur in each grain. Results of the analysis, however, show non-uniform deformation with high density of GNDs accumulated in a form of band. Growth of such kind of structure of GNDs caused localized accumulation of SSDs at grain boundary triple junctions. Mechanism for the band-shaped accumulation of GNDs in the compatible type multi crystals are discussed from the viewpoint of multi body interactions which arise from shape change of crystal grains after slip deformation.

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Kumar, Ashok V., Chulho Yang, and Vijay B. R. Seelam. "Investigation of Localized Deformation in NiAl Single Crystals." Journal of Engineering Materials and Technology 120, no. 3 (July 1, 1998): 206–11. http://dx.doi.org/10.1115/1.2812344.

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Deformation of NiAl single crystals was studied using finite element analysis to investigate the modes of localized deformation. Constitutive parameters and hardening characteristics of the active slip systems were estimated by comparing numerical simulation results with experimental results. Deformation of tensile specimens of NiAl single crystal was simulated when loaded along different crystal orientations to understand the deformation mechanism that results in various localized modes of deformation. In particular, the formation of shear bands and kink bands was studied and the material and geometric characteristics that influence the formation of such localization were investigated.

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Zhang, Yong, Ning Hou, Liang-Chi Zhang, and Qi Wang. "Elastic-plastic-brittle transitions of potassium dihydrogen phosphate crystals: characterization by nanoindentation." Advances in Manufacturing 8, no. 4 (September 2, 2020): 447–56. http://dx.doi.org/10.1007/s40436-020-00320-3.

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AbstractPotassium dihydrogen phosphate (KDP) crystals are widely used in laser ignition facilities as optical switching and frequency conversion components. These crystals are soft, brittle, and sensitive to external conditions (e.g., humidity, temperature, and applied stress). Hence, conventional characterization methods, such as transmission electron microscopy, cannot be used to study the mechanisms of material deformation. Nevertheless, understanding the mechanism of plastic-brittle transition in KDP crystals is important to prevent the fracture damage during the machining process. This study explores the plastic deformation and brittle fracture mechanisms of KDP crystals through nanoindentation experiments and theoretical calculations. The results show that dislocation nucleation and propagation are the main mechanisms of plastic deformation in KDP crystals, and dislocation pileup leads to brittle fracture during nanoindentation. Nanoindentation experiments using various indenters indicate that the external stress fields influence the plastic deformation of KDP crystals, and plastic deformation and brittle fracture are related to the material’s anisotropy. However, the effect of loading rate on the KDP crystal deformation is practically negligible. The results of this research provide important information on reducing machining-induced damage and further improving the optical performance of KDP crystal components.

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Lu, Chun Peng, Hang Gao, and Xiao Ji Teng. "Tribological Properties of KDP Single Crystal." Applied Mechanics and Materials 490-491 (January 2014): 134–37. http://dx.doi.org/10.4028/www.scientific.net/amm.490-491.134.

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Scratch tests on (001) face, doubler face and tripler face of KDP crystals are carried out at room temperature. It shows that the friction ceoffcients of different crystal faces are affected seriously by the crystal oritations, their variation periods of (001) face, doubler face and tripler face are 90o, 180o and 180o, their attitudes of relative anisotropy are 50%, 43.8% and 43.8%, and all of them are less than 0.4. The scratch mechanism of KDP crystal consists of four types: elastic and plastic deformation, ploughing, microchip, and surface damage. Differences between elastic and plastic deformation and ploughing are not obvious due to the soft-brittle nature of KDP crystal.

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Grzegorczyk, Barbara, Wojciech Ozgowicz, and Elżbieta Kalinowska-Ozgowicz. "Influence of the Crystallographic Orientation of CuZn30 Single Crystal on the Portevin-Le Chatelier Effect." Solid State Phenomena 203-204 (June 2013): 406–10. http://dx.doi.org/10.4028/www.scientific.net/ssp.203-204.406.

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Plastic deformation of solid crystals is a complex process, mostly heterogeneous, due to the simultaneous effect of several deformation mechanisms. A dominating deformation mechanism depends on the properties of the material and external coefficients, viz. temperature, stress and strain rate. The applied Bridgman method permitted to obtain single crystal of the CuZn30 alloy adequate for plastic deformation investigations. Single crystal are characterized by selected crystallographic orientations from various areas of the basic triangle. In order to determine the influence of the crystallographic orientation on the Portevin-Le Chatelier effect selected single crystals were compressed at a temperature of 300°C at a strain rate of 10-3 s-1. Experiments confirmed the effect of the crystallographic orientation axis of CuZn30 single crystals on the observed differences in the intensity of stress oscillation on stress-strain curves.

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Sakurada, Eisaku, and Takashi Matsuo. "Change in Stress Axis with Creep Deformation in PST Crystal." Advanced Materials Research 15-17 (February 2006): 858–63. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.858.

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The superiority of creep in Ti-48at%Al alloy with fully transformed lamellar structure to that in Ti-50at%Al alloy with γ single phase is characterized by the extension of transient stage. This extension of the transient stage derives by the retarding effect of α2 plate on the onset of the accelerating stage, through suppressing the dynamically recrystallization which is the main reason of the accelerating stage. This superiority in Ti-48at%Al alloy will become more clear by investigating the creep of the single crystal designated as the PST crystal, because of removing the grain boundaries which is the formation site of dynamic recrystallization. By using the PST crystal, the predominant deformation using primary slip plane of γ plate will continue, because the α2 plate restricts the operation of other slip planes. In PST crystals with the angle between the stress axis and the lamellar plates, designated as φ, less than 45°, the uniform deformation will proceed, because of the decrease in creep rate due to the decreasing in Schmid factor through the monotonous decrease in φ. But these suppositions have not confirmed. In this study, the deformation manner of the PST crystals with φ of less than 45° is investigated by the analyzing of creep curve, macrostructure and inverse pole figure of the PST crystals interrupted the creep tests at 1148K/68.6MPa at the strains of 0.20 and 0.65. Inverse pole figures of PST crystal are obtained using SEM-EBSD method. By accepting the creep deformation, the stress axes of the PST crystals move for [001]-[1, – 11] line with slip system of (111)<1, – 01>, and after reaching at this line, the stress axis turn to [1, – 11] pole position with (111)<1, – 10> slip system. The change in stress axis is not homogeneous in gauge portion accepting small strain, by subjecting the further creep deformation up to the onset of the accelerating stage, this heterogeneous deformation in gauge portion disappeared.

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Магомедов, М. Н. "О хрупкости элементарных полупроводников." Физика твердого тела 65, no. 2 (2023): 212. http://dx.doi.org/10.21883/ftt.2023.02.54292.521.

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It is shown that the brittleness of a single-component covalent crystal (diamond, Si, Ge) is due to the “duplicity” of the paired potential of interatomic interaction for elastic (reversible) and for plastic (irreversible) deformation. This leads to the fact that the specific surface energy during plastic deformation of a covalent crystal is more than two times less than the specific surface energy during elastic deformation. Therefore, with a small deformation of a covalent crystal, it is energetically more advantageous to create a surface by irreversible breaking than by reversible elastic stretching. It is indicated that the brittle-ductile transition in a single-component covalent crystal is accompanied by metallization of covalent bonds on the surface. It is shown that the brittle-ductile transition temperature (TBDT) for single-component covalent crystals under static load has an upper limit: TBDT/Tm < 0.45, where Tm is the melting temperature.

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Dong, Jin Mei, Hong Fa Yu, and Mei Juan Wang. "Influence of Fly Ash on Magnesium Oxychloride Cement Deformation." Materials Science Forum 817 (April 2015): 252–56. http://dx.doi.org/10.4028/www.scientific.net/msf.817.252.

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The inhibition effect of fly ash on the deformation of magnesium oxychloride cement is not obvious. With the increase of fly ash, the deformation of magnesium oxychloride cement decreased at first, and then increased. The smallest deformation is the proportion of FA-35. The fly ash can promote the formation of the 5·1·8 phase crystal and slow the speed of 5·1·8 phase changing into Mg (OH)2. The growing crystals were disordered, like the scattered tree branches. The causes of FA-35 specimen expansion deformation can be explained by the configuration of the crystal.

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Yonenaga, Ichiro, Utako Onose, and Koji Sumino. "Mechanical properties of GaAs crystals." Journal of Materials Research 2, no. 2 (April 1987): 252–61. http://dx.doi.org/10.1557/jmr.1987.0252.

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Mechanical properties of GaAs crystals grown by the liquid encapsulated Czochralski technique and the boat technique are investigated by means of compression tests. Stressstrain characteristics of a GaAs crystal in the temperature range 400°–500°C are very similar to those of a Si crystal in the temperature range 800°–900°C. This seems to reflect the fact that the dislocation mobility in a GaAs crystal in the former temperature range is comparable to that in a Si crystal in the latter temperature range. Dislocations in GaAs crystals are found to be easily immobilized at an intermediate temperature due to gettering of impurities and/or impurity-point defect complexes. In comparison to a Si crystal, the surface of a GaAs crystal seems to involve irregularities that act easily as effective generation centers for dislocations. Thus the magnitude of the yield stress of an aged GaAs crystal is controlled by the surface condition and is not influenced by the density of dislocations involved in the crystal. The socalled steady state of deformation is realized in a GaAs crystal in the deformation stage after the lower yield point as in Si and Ge crystals. Dislocation distributions in a deformed GaAs crystal observed by transmission electron microscopy is very similar to those in deformed Si and Ge crystals.

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12

Noskov, Fedor M., Ludmila I. Kveglis, Artur K. Abkaryan, and Rimma Y. Sakenova. "The Structure of Lenticular Crystals Formed in Plastically Deformed Titanium Nickelide." Crystals 12, no. 2 (January 20, 2022): 145. http://dx.doi.org/10.3390/cryst12020145.

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Samples of Ni51Ti49 alloy subjected to plastic deformation have been studied. The microstructure was studied by transmission electron microscopy and microdifraction on a Hitachi 7700 microscope. The phase composition of the samples was determined by X-ray diffraction in a Bruker diffractometer. Magnetometric measurements were performed in an induction petlescope. Lenticular crystals (of the Ni2Ti3 phase containing bend–extinction contours indicating a significant curvature of the crystal lattice appearing in the localization zones of plastic deformation) were found in the deformation localization zones. It was revealed that the samples are non-magnetic before deformation, but after plastic deformation, they have non-zero magnetization, which is associated with the emergence of new phases. Under conditions of local curvature of the crystal lattice, special structural states arise in zones of increased interatomic distances, which increase the number of degrees of freedom in the deformable solid and thus contribute to the redistribution of the components of the initial solid solution and the appearance of new phases. It was shown that the crystalline structure of lenticular crystals is a phase constructed of a spinel structural type with a crystal lattice parameter of 11.53 ± 0.03 Å.

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Voronin, Vladimir, Valery Fedorov, Sergey Semenikhin, and Yaroslav Berdnikov. "Neutron spin rotation effect at Laue diffraction in a weakly deformed and nonabsorbing crystal with no center of symmetry." EPJ Web of Conferences 219 (2019): 06003. http://dx.doi.org/10.1051/epjconf/201921906003.

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The effect of the neutron spin rotation at Laue diffraction in a weakly deformed noncentrosymmetric and transparent for the neutrons crystal has been theoretically described and experimentally investigated. This effect arises in the deformed crystal because of the curvature of the neutron trajectory in the crystal. A certain type of deformation leads to the escape outside the crystal of one of the two neutron waves excited at Laue diffraction. This two waves propagate in the crystal without a center of symmetry in electric fields with the opposite sign. In this case the spin of the remaining neutron wave will be rotating relative to the original direction due to the interaction of the magnetic moment of the moving neutron with the crystal's intracrystalline electric field. In a perfect undeformed crystal such spin rotation effect is absent. There is only a depolarization of the beam since both waves in opposite electric fields are present with the same amplitudes. A technique for controlled deformation of a perfect single crystal by creating a temperature gradient has been developed. Thus a new possibility to measure the electric fields which act on the neutron in noncentrosymmetric crystals has been realized. There also appeared a way to control these fields in experiments on the study of the neutron fundamental properties.

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Kumar, M. Arul. "Microstructural Modeling of Banding in Single Crystals: 'Stack of Domains' Model." Materials Science Forum 702-703 (December 2011): 200–203. http://dx.doi.org/10.4028/www.scientific.net/msf.702-703.200.

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A rigid-plastic rate-independent crystal plasticity based `stack of domains' model of a single crystal is developed to capture local deformation inhomogeneity and sub-structure formation when subjected to macroscopically homogeneous imposed deformation. This model regards the single crystal as a linear stack of domains with planar shaped domain boundaries. The domains of the model single crystal collectively accommodate the imposed deformation and individual domains maintain velocity and traction continuity with its neighbors. The lattice orientation of individual domains perturbed and that perturbation triggers the inhomogeneity of plastic slip amongst domains. Mobility of domain boundaries relative to the material and a differential hardening law that accounts for the orientational instability of individual domains are also considered in the model. The developed model is applied to predict the formation of banding in initially copper (C), rotated cube (RC) and Goss (G) orientated single crystals when subjected to plane strain deformation and the predictions are compared with the experimental literature.

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Armstrong, Ronald W. "Bertram Hopkinson's pioneering work and the dislocation mechanics of high rate deformations and mechanically induced detonations." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 372, no. 2015 (May 13, 2014): 20130181. http://dx.doi.org/10.1098/rsta.2013.0181.

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Bertram Hopkinson was prescient in writing of the importance of better measuring, albeit better understanding, the nature of high rate deformation of materials in general and, in particular, of the importance of heat in initiating detonation of explosives. This report deals with these subjects in terms of post-Hopkinson crystal dislocation mechanics applied to high rate deformations, including impact tests, Hopkinson pressure bar results, Zerilli–Armstrong-type constitutive relations, shock-induced deformations, isentropic compression experiments, mechanical initiation of explosive crystals and shear banding in metals.

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Kubiak, Marta, Marcel Staar, Ingo Kampen, Anett Schallmey, and Carsten Schilde. "The Depth-Dependent Mechanical Behavior of Anisotropic Native and Cross-Linked HheG Enzyme Crystals." Crystals 11, no. 7 (June 22, 2021): 718. http://dx.doi.org/10.3390/cryst11070718.

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Enzymes are able to catalyze various specific reactions under mild conditions and can, therefore, be applied in industrial processes. To ensure process profitability, the enzymes must be reusable while ensuring their enzymatic activity. To improve the processability and immobilization of the biocatalyst, the enzymes can be, e.g., crystallized, and the resulting crystals can be cross-linked. These mechanically stable and catalytically active particles are called CLECs (cross-linked enzyme crystals). In this study, the influence of cross-linking on the mechanical and catalytic properties of the halohydrin dehalogenase (HheG) crystals was investigated using the nanoindentation technique. Considering the viscoelastic behavior of protein crystals, a mechanical investigation was performed at different indentation rates. In addition to the hardness, for the first time, depth-dependent fractions of elastic and plastic deformation energies were determined for enzyme crystals. The results showed that the hardness of HheG enzyme crystals are indentation-rate-insensitive and decrease with increases in penetration depth. Our investigation of the fraction of plastic deformation energy indicated anisotropic crystal behavior and higher irreversible deformation for prismatic crystal faces. Due to cross-linking, the fraction of elastic energy of anisotropic crystal faces increased from 8% for basal faces to 68% for prismatic crystal faces. This study demonstrates that mechanically enhanced CLECs have good catalytic activity and are, therefore, suitable for industrial use.

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Zhang, Xiaoli, Jinxian He, Zeqiang Ren, Taotao Zhou, Wenjie Cao, and Ben Xu. "Analysis of the Submicrostructural Deformation of Amphibole in a Ductile Shear Zone Based on the TEM Technique." Journal of Nanoscience and Nanotechnology 21, no. 1 (January 1, 2021): 765–71. http://dx.doi.org/10.1166/jnn.2021.18466.

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Deformed amphibole in the plagioclase amphibolite mylonite of the Guandi Complex, Xishan, Beijing, is the research object in this study. The amphibole nanodeformation under the middle crust was analyzed using microstructural analysis and high-resolution transmission electron microscopy (TEM). Microscope observations show that the amphibolite deformations in the plagioclase amphibolite mylonite are δ and σ type porphyroclasts, and the porphyroclast tail is composed of new long-columnar crystals. Using transmission electron microscopy (TEM, and this acronyms would be defined only once), the authors observed the nanodeformation characteristics of the amphibole porphyroclast core and mantle. Dislocation tangles are dominant in the porphyroclast core, and inside the new crystal, there is little or no dislocation. Swelled new crystals surrounded by dislocation can be observed in the transition zone between the porphyroclasts and new crystals. The deformed amphibole microstructure and submicrostructure represent typical brittle–ductile transitional deformation. The deformation process can be divided into two stages: the disordered dislocation increment stage and the dislocation reduction and ordering stage. Crystalline plastic deformation occurs in the amphibole in the plagioclase amphibolite mylonite of the Xishan area, Beijing. The crystalline plastic deformation temperature in amphiboles is higher than that in plagioclase.

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Zhang, Zhen-Wei, Zheng Li, Ying Liu, and Jing-Tao Wang. "Path Dependency of Plastic Deformation in Crystals: Work Hardening, Crystallographic Rotation and Dislocation Structure Evolution." Crystals 12, no. 7 (July 19, 2022): 999. http://dx.doi.org/10.3390/cryst12070999.

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This paper reviewed the research progress of studies on the crystal rotation of single crystals that were deformed by tension and shear and the influences of crystal rotation and dislocation evolution on strain hardening behavior in crystals that were deformed with different initial orientations. The crystal rotation is entirely different depending on whether the single crystal was deformed by tension or shear. A three-stage work hardening behavior, which is not one of the intrinsic properties of materials, is generated when FCC metallic single crystals are deformed by tension along unstable oriFigurFigurentations, but single crystals do not exhibit this three-stage hardening behavior when they are deformed by simple shear at room temperature. Under tension, crystal rotation causes the transition from work hardening stage I to stage II, while the transition from work hardening stage II to III is caused by dislocation evolution. The evolution of the dislocation structure is related to deformation loading and can be classified into three types when a crystal is deformed by tension. Different from tension, shear stress can directly act on one of the 12 slip systems when a crystal is deformed by simple shear. When FCC single crystals are deformed by shear along the (11¯1)[110], (111)[112¯] and (001)[110] orientations, the single slip system, co-planar slip systems and co-directional slip systems are activated, respectively, and the crystals hardly rotate under the shear conditions. The slip direction of [110] forces the crystal to rotate toward the shear direction under simple shear. The dislocation tangles tend to form the dislocation cells and wall structures when multiple slip systems are activated under simple shear.

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LEE, MYOUNG GYU, ROBERT H. WAGONER, and SUNG-JOON KIM. "COMPARATIVE STUDY OF SINGLE CRYSTAL CONSTITUTIVE EQUATIONS FOR CRYSTAL PLASTICITY FINITE ELEMENT ANALYSIS." International Journal of Modern Physics B 22, no. 31n32 (December 30, 2008): 5388–93. http://dx.doi.org/10.1142/s0217979208050541.

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Two sets of single crystal constitutive equations used for the crystal plasticity finite element analysis are comparatively investigated by simulating simple deformation of oriented single crystals. The first of these consists of conventional constitutive equations, which have been adopted for the prediction of deformation texture and their parameters are generally obtained by back-fitting polycrystalline stress-strain response. The other set uses interactions between moving dislocations on the primary slip system and the corresponding forest dislocations. The idealized Orowan hardening mechanism is adopted for the calculation of the critical force, and constitutive parameters are determined by the geometry of dislocations, thus less fitting procedure is involved. The stress-strain curves of copper single crystal are used to demonstrate how the two models work for the orientation dependent stress-strain responses.

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Khosroabadi, Hossein, Lucia Alianelli, Daniel G. Porter, Steve Collins, and Kawal Sawhney. "Cryo-cooled silicon crystal monochromators: a study of power load, temperature and deformation." Journal of Synchrotron Radiation 29, no. 2 (February 8, 2022): 377–85. http://dx.doi.org/10.1107/s160057752200039x.

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Crystal monochromators are often the primary optics in hard X-ray synchrotron beamlines. Management of power load is central to their design. Strict requirements on stability and deformation are to be met, as new-generation synchrotron sources deliver brighter beams of X-rays. This article sets out to illustrate an overall picture of the deformation caused by heat load in a cryo-cooled Si crystal monochromator using first principles. A theoretical model has been developed to predict the temperature distribution and surface deformation by applying intrinsic properties of Si material and the cooling system parameters. The model explains the universal behaviour of crystal slope error versus absorbed power; it has been benchmarked against experimental data and used to interpret finite-element analysis of cryogenically cooled crystals.

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Cao, Xin Ming, Wei Wei Guo, and Xiao Wu Li. "Plastic Deformation Behavior of Differently Oriented Fe-35wt.%Cr Alloy Single Crystals Containing Cr-Rich Precipitates under Uniaxial Compression." Applied Mechanics and Materials 66-68 (July 2011): 1960–65. http://dx.doi.org/10.4028/www.scientific.net/amm.66-68.1960.

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The plastic deformation behavior of the and [014] Fe-35wt.%Cr alloy single crystals containing fine Cr-rich precipitates were investigated under uniaxial compression. The compressive flow behavior is slightly sensitive to the crystallographic orientation. These two oriented crystals exhibit a clear yield plateau in their compressive stress-strain curves, but the yield plateau of the [014] crystal is somewhat shorter than that of the crystal. As the compressive strain is lager than a certain critical value, e.g., ~13% and ~18% for the [014] and crystals, respectively, the work hardening rate for both two orientations decreases obviously, but the decrease in work hardening rate is more remarkable for the [014] crystal rather than the crystal. These phenomena are discussed to be all related to the interactions between moving dislocations and fine Cr-rich precipitates, and the interaction intensity depends strongly on the orientation. Careful observations of slip deformation characteristics and dislocation structures well provide supports for the explanations to the macroscopic compressive plastic flow behavior.

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Thorsteinsson, Throstur. "An analytical approach to deformation of anisotropic ice-crystal aggregates." Journal of Glaciology 47, no. 158 (2001): 507–16. http://dx.doi.org/10.3189/172756501781832124.

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AbstractDeformation rates of single hexagonal crystals, deforming by glide on the basal plane, are described as a function of stress state and crystal orientation. These results are used to infer the deformation rate of crystal aggregates assuming that the stress distribution within the crystal aggregate is homogeneous. Analytical equations for the deformation rate of anisotropic ice aggregates are derived for vertically symmetric girdle fabric. This type of fabric is approximated by a uniform distribution of c-axis orientations between a cone angle and a smaller girdle angle relative to the symmetry axis. For simple shear stress acting on a single-maximum fabric there is a slight de-enhancement for cone angles of 60–90°. In uniaxial compression a maximum enhancement of ∼1.7 occurs at a cone angle of 57°. A pure shear stress state has similar features, with the additional complication that it causes a non-zero transverse strain rate, except for perfect vertical alignment of crystals and isotropic fabric. In combined states of stress the contribution of each stress component to the strain rate depends on fabric. A single enhancement factor is not adequate to describe the effects of anisotropy for complex stress states.

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GAN, YONG X., and XI CHEN. "MACRO- AND MICROSCOPIC APPROACHES TO PLANE STRAIN DEFORMATION STATES OF FACE-CENTERED CUBIC METALS UNDER WEDGE INDENTATION." International Journal of Applied Mechanics 01, no. 01 (March 2009): 41–60. http://dx.doi.org/10.1142/s1758825109000022.

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Face-centered cubic (FCC) metals show active slip under indentation loading. In this work, both macro- and microscopic models are proposed to analyze the deformation behavior of face-centered-cubic (FCC) single crystals under wedge indentation. In the part of macroscopic approach, stress distribution and anisotropic yielding were investigated. Load-displacement relation was obtained to reveal the mechanical responses of the crystals. In the microscopic approach section, an indention induced lattice rotation zone was identified and the deformation behavior was analyzed using the single crystal plasticity theory. The crystal lattice rotation experimental results and slip line trace observations validate the analytical predictions.

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Kaplan, W. D. "The mechanism of crystal deformation." Science 349, no. 6252 (September 3, 2015): 1059–60. http://dx.doi.org/10.1126/science.aac9623.

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Nowak, R., T. Sekino, and K. Niihara. "Surface deformation of sapphire crystal." Philosophical Magazine A 74, no. 1 (July 1996): 171–94. http://dx.doi.org/10.1080/01418619608239696.

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Kandra, J. T., J. Y. Lee, and D. P. Pope. "Deformation of single-crystal Mn3Sn." Materials Science and Engineering: A 145, no. 2 (October 1991): 189–98. http://dx.doi.org/10.1016/0921-5093(91)90248-l.

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Akef, A., and J. H. Driver. "Local Textures in Deformed and Recrystallized Aluminium Crystal." Textures and Microstructures 20, no. 1-4 (January 1, 1993): 141–54. http://dx.doi.org/10.1155/tsm.20.141.

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The recrystallization mechanisms in deformed aluminium single crystals have been investigated by SEM microdiffraction techniques (ECP and EBSP). Aluminium crystals of (001)(uv0) and (001)[011-] orientations were deformed in plane strain compression to a true strain of ~1 to develop different deformation microstructures. Transition bands separating deformation bands were formed by orientation splitting in the (001)(uv0) crystals, but were not observed in the (001)[011-] crystal.During annealing at 250°C and 400°C, recrystallization nuclei are developed in both the deformed matrix and along transition bands. Matrix nucleation appears to occur by a subgrain coalescence mechanism according to which the new grains are misoriented 15-30° from the average as-deformed material. Transition band nucleation gives an orientation spread 20-30° around the original, undeformed crystal orientation. A well-defined cube recrystallization texture is obtained at 400°C after complete recrystallization of the initial cube crystal.

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Liu, Yaping. "Dislocation loops in single-crystal NiAl." Proceedings, annual meeting, Electron Microscopy Society of America 48, no. 4 (August 1990): 942–43. http://dx.doi.org/10.1017/s0424820100177842.

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In the conventional viewpoint, dislocation loops of vacancy type in single crystal NiAl can only exist in Al-rich compositions. Their configurations and their changes when deformation occurs, and their effects on the deformation have not been studied thoroughly.In the present study, nickel-rich NiAl single crystals of 48.1∼48.6 at %A1 were annealed at 1315°C for 50 hours, then cooled at 200°C/hr to permit vacancy condensation. Single-crystal samples cut with an [001] axis then underwent high temperature (850°C) tensile and cyclic deformation. TEM specimens were cut from the undeformed, 0.3% tensile strain, ±0.5 cyclic and 30∼40% tensile deformation samples.Two kinds of dislocations, edge and screw, were found in the undeformed NiAl. Edge dislocations consisted of concentric dislocation loops (Fig. 1) and spiral dislocations (dislocation A in Fig. 2). They lie on cubic planes and have cubic line orientations. Invisibility conditions of g.b=0 and g.b x u=0 show that they have <001> type Burgers vectors normal to the loop planes. The shift in image position on changing the sign of g was used to verify that the loops are vacancy in nature.

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29

Alferova, E., D. Lychagin, and A. Chernyakov. "Research of Stress Field Distribution in FCC-Single Crystal Samples in Compression." Applied Mechanics and Materials 682 (October 2014): 485–90. http://dx.doi.org/10.4028/www.scientific.net/amm.682.485.

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.Theoretical distribution of a stress field in a sample in the form of a rectangular parallelepiped in compression for an isotropic material was calculated using the method of finite elements. Calculations showed that the highest stress is observed at the top and front edges of a sample. There are areas of the tension stress on vertical edges in the area of sample tops. Shift anisotropy was determined by imposing of the distributed tension field in a sample on FCC crystal of a certain crystallographic orientation.Change of shift symmetry in single crystals for different crystallographic orientations of a compression axis was considered. It was established that a shift fragmentation in the parallel octahedral planes in the conditions of plastic deformation determines the process of low-symmetric shift deformation and maintenance of higher single crystal pseudo-symmetry. Connection of the obtained results and test data on heterogeneity of plastic deformation of nickel and aluminum single crystals is discussed.

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Mitsutake, Masaomi, Yoshihiro Terada, and Takashi Matsuo. "Change in Stress Axis with Creep Deformation in Ni-20mass%Cr Single Crystal with Orientation of [011]." Advanced Materials Research 15-17 (February 2006): 870–75. http://dx.doi.org/10.4028/www.scientific.net/amr.15-17.870.

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The features of the creep deformation of γ-single phase single crystals with the composition of Ni-20mass%Cr are characterized by the extended transient stage, which consists of Stage I and Stage II. In the Stage I, the creep rate just after loading remains unchanged, while the creep rate decreases continuously in Stage II. In the single crystals except for the single crystals with the stress axis of [001] and [1, – 11], the predominant creep deformation using the primary slip plane continues. By this deformation, the cross section of specimen turns to elliptical in shape. However, in the single crystals with the angle between stress axis and primary slip plane (111) is more than 45°, the deformation using the primary slip plane does not continue, as a result, the duration of Stage II turn to shorter one. The single crystal with the stress axis of [011] has the largest angle of 55°. In this study, the deformation manner during transient stage of single crystal with the stress axis of [011] orientation is investigated from the two viewpoints. The first one is to clarify the change in deformation manner with decreasing the stress. As a result, with decreasing the stress, the Stage I become clear and strain during Stage I and Stage II become small, furthermore, the decreasing ratio of creep rate with definite strain becomes larger. While, the second viewpoint is to investigate the change in crystallographic orientation of the [011] single crystals with creep deformation using the inverse pole figure obtained by the EBSD method. As a result, at the stress of 29.4 MPa, the spot of stress axis turns from the [011]-[1, – 11] line to the <1, – 01> direction. While, at the stress of 19.6 MPa, the stress axis moves for the [1, – 11] pole along the [011]-[1, – 11] line from the [011] pole. And, it is noteworthy that the spot widely spread from the [011] pole during transient stage. This indicates the large distortion in the primary slip plane and the evidence of heterogeneous deformation.

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31

Sidorenko, Nikolay, Yaakov Unigovski, Zinovi Dashevsky, and Roni Shneck. "A Novel Method to Significantly Improve the Mechanical Properties of n-Type Bi(1−x)Sbx Thermoelectrics Due to Plastic Deformation." Electronic Materials 2, no. 4 (November 2, 2021): 511–26. http://dx.doi.org/10.3390/electronicmat2040036.

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A unique method was developed to significantly improve the strength of Bi(1−x)Sbx single crystals, the most effective thermoelectric (TE) materials in the temperature range from 100 to 200 K due to their plastic deformation by extrusion. After plastic deformation at room temperature under all-round hydrostatic compression in a liquid medium, n-type Bi–Sb polycrystalline solid solutions show a significant increase in mechanical strength compared to Bi–Sb single crystals in the temperature range from 300 to 80 K. The significantly higher strength of extruded alloys in comparison with Bi–Sb single crystals is associated with the development of numerous grains with a high boundary surface as well as structural defects, such as dislocations, that accumulate at grain boundaries. Significant stability of the structure of extruded samples is achieved due to the uniformity of crystal plastic deformation under all-round hydrostatic compression and the formation of the polycrystalline structure consisting of grains with the orientation of the main crystallographic directions close to the original single crystal. The strengthening of Bi–Sb single crystals after plastic deformation allows for the first time to create workable TE devices that cannot be created on the basis of single crystals that have excellent TE properties, but low strength.

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32

Gao, Yipeng, Yunzhi Wang, and Yongfeng Zhang. "Deformation pathway and defect generation in crystals: a combined group theory and graph theory description." IUCrJ 6, no. 1 (January 1, 2019): 96–104. http://dx.doi.org/10.1107/s2052252518017050.

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The generation and motion of crystalline defects during plastic deformation are critical processes that determine the mechanical properties of a crystal. The types of defect generated are not only related to the symmetry of a crystal but also associated with the symmetry-breaking process during deformation. Proposed here is a new mathematical framework to capture the intrinsic coupling between crystal symmetry and deformation-induced symmetry breaking. Using a combination of group theory and graph theory, a general approach is demonstrated for the systematic determination of the types of crystalline defect induced by plastic deformation, through the construction of a crystal deformation group and a deformation pathway graph. The types of defect generated in the deformation of a face-centered cubic crystal are analyzed through the deformation pathway graph and compared with experimental observations.

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33

Gerstein, Gregory, Marc Nowak, Marten Sebastian Bierbaum, Tatjana Zhuravina, Mirko Schaper, and Friedrich Wilhelm Bach. "Increase the Deformability of NiCo Single Crystals Using of Electrical Pulse-Like Currents." Key Engineering Materials 504-506 (February 2012): 143–48. http://dx.doi.org/10.4028/www.scientific.net/kem.504-506.143.

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The effect of short-term electrical pulses on metallic single crystals, with and without the application of external mechanical stresses, was investigated with the aid of deformation reliefs. The nickel-cobalt single crystals were subjected to electrical pulses and subsequently microscopically measured. In doing this, it was established that an electrical pulse without a simultaneously applied mechanical stress, has no influence on the deformation relief. It was possible to show that on loading the single crystal with a mechanical stress, the deformation relief significantly changes even when the stress was markedly below the flow stress.

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34

Lin, T. H., K. K. F. Wong, and N. J. Teng. "Micromechanics of Hysteresis Loops of Fatigue in a Single Crystal." Journal of Applied Mechanics 67, no. 2 (October 1, 1999): 338–43. http://dx.doi.org/10.1115/1.1304917.

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Grain boundaries are susceptible to cause boundary corrosion, cracking, and creep deformation. Single crystals are presently used in turbine engines. A micromechanic analysis is shown to explain the occurrence of highly localized plastic strain in the slip band known as the shear band in metals under a monotonic loading. Based on the prior analyses of fatigue bands in polycrystals, a micromechanic analysis of a single crystal under plane deformation is developed. The Bauschinger effect and hysteresis loops of these single crystals were calculated and shown. The calculated results agree generally with experimental observations. [S0021-8936(00)02202-9]

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35

Minagawa, Hideaki, and Hidetsugu Tsuchida. "Possibility of the existence of a topological defect in dynamic deformation of the free-standing ultrathin silicon wafer during MeV ion irradiation." Journal of Applied Physics 131, no. 8 (February 28, 2022): 085701. http://dx.doi.org/10.1063/5.0077180.

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We study the ion-irradiation-induced deformation of free-standing ultrathin Si wafers with a thickness of 8 [Formula: see text]m. The time-response spectrum of the deformation was measured using a laser displacement meter with a time resolution of 1 ms. The results showed that the deformation appeared during irradiation and disappeared after irradiation. The deformation was composed of a fast deformation with a millisecond time constant and a slow deformation with a second time constant. We performed a model calculation to identify the deformation mechanisms. We found that the fast deformation originated from expansion or shrinkage of crystal lattice caused by beam heating and deduced that the slow deformation resulted from the topological defect formation in Si crystals. The relaxation time of the slow deformation is related to the coordination number of disappeared topological defects. In this experiment, we conclude that the deformation of Si crystals maintains reversible behavior in the formation of topological defects up to the coordination number 5.

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36

Gesenhues, Ulrich. "Structural changes in titanium dioxide nanocrystals during plastic deformation." Journal of Applied Crystallography 38, no. 5 (September 15, 2005): 749–56. http://dx.doi.org/10.1107/s0021889805020418.

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The polygonization of 200 nm rutile crystals during dry ball-milling at 10gwas monitored in detail by means of transmission electron microscopy (TEM) and X-ray diffraction (XRD). The TEM results showed how to modify the Williamson–Hall method for a successful evaluation of crystal size and microstrain from XRD profiles. Macrostrain development was determined from the minute shift of the most intense reflection. In addition, changes in pycnometrical density were monitored. Accordingly, the primary crystal is disintegrated during milling into a mosaic of 12–35 nm pieces where the grain boundaries induce up to 1.2% microstrain in a lower layer of 6 nm thickness. Macrostrain in the interior of the crystals rises to 0.03%. The pycnometrical density, reflecting the packing density of atoms in the grain boundary, decreases steadily by 1.1%. The results bear relevance to our understanding of plastic flow and the mechanism of phase transitions of metal oxides during high-energy milling.

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37

Xiao, B., and J. Feng. "Higher order elastic tensors of crystal structure under non-linear deformation." Journal of Micromechanics and Molecular Physics 04, no. 04 (December 2019): 1950007. http://dx.doi.org/10.1142/s2424913019500073.

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The higher-order elastic tensors can be used to characterize the linear and non-linear mechanical properties of crystals at ultra-high pressures. Besides the widely studied second-order elastic constants, the third- and fourth-order elastic constants are sixth and eighth tensors, respectively. The independent tensor components of them are completely determined by the symmetry of the crystal. Using the relations between elastic constants and sound velocity in solid, the independent elastic constants can be measured experimentally. The anisotropy in elasticity of crystal structures is directly determined by the independent elastic constants.

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38

Saraf, Ravi F., and Roger S. Porter. "Deformation of semicrystalline polymers via crystal–crystal phase transition." Journal of Polymer Science Part B: Polymer Physics 26, no. 5 (May 1988): 1049–57. http://dx.doi.org/10.1002/polb.1988.090260509.

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39

Steglich, Dirk, Stéphane Graff, and Wolfgang Brocks. "Linking Meso- and Macroscale Simulations: Crystal Plasticity of hcp Metals and Plastic Potentials." Materials Science Forum 539-543 (March 2007): 1741–46. http://dx.doi.org/10.4028/www.scientific.net/msf.539-543.1741.

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A crystal plasticity model has been used to simulate channel die experiments on both, pure magnesium single crystals and polycrystalline textured rolled plates. Deformation mechanisms and slip system activity can be identified by FE-analyses of single crystals. The role of twinning can be understood and modeled phenomenologically by an additional slip system. Simulations of polycrystalline aggregates are used to obtain a representation of the material's phenomenological yield function in order to describe the plastic deformation behavior using the framework of continuum mechanics. This allows for accounting for the specific texture and thus for its optimization. The tension- compression asymmetry, which is typical for mechanically processed magnesium material, can be reproduced by means of the crystal plasticity and a phenomenological model.

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40

Alferova, Ekaterina A., and D. V. Lychagin. "Characterization of Deformation Pattern Structure Elements Generated in Uniaxial Compression of Nickel Single Crystals." Applied Mechanics and Materials 379 (August 2013): 66–70. http://dx.doi.org/10.4028/www.scientific.net/amm.379.66.

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Deformation pattern parameters have been studied on the faces of nickel single crystals using microinterferometer NewView 7200. The magnitude of shear displacement in structural elements of the deformation pattern has been determined. As shown, the shear traces transform into accommodation bands, meso- or macrobands as dependent on single crystal orientation with respect to load.

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41

Cheng, Hsien-Chie, Ching-Feng Yu, and Wen-Hwa Chen. "Size, Temperature, and Strain-Rate Dependence on Tensile Mechanical Behaviors of Ni3Sn4Intermetallic Compound Using Molecular Dynamics Simulation." Journal of Nanomaterials 2014 (2014): 1–17. http://dx.doi.org/10.1155/2014/214510.

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This study focuses on exploring the mechanical properties and nonlinear stress-strain behaviors of monoclinic Ni3Sn4single crystals under uniaxial tensile test and also their size, temperature, and strain-rate dependence through constant temperature molecular dynamics (MD) simulation using Berendsen thermostat. The deformation evolution of the Ni3Sn4atomic nanostructure during the tensile test is observed. In addition, the tensile yield strains of various Ni3Sn4single crystals at different strain rates and temperatures are characterized through unloading process. At last, by way of linear regression analysis, the corresponding normal elastic stiffness constants are approximated and then compared with the literature theoretical data. The radial distribution function analysis shows that Ni3Sn4single crystal in a one-dimensional nanowire configuration would become a highly disordered structure after thermal equilibration, thereby possessing amorphous-like mechanical behaviors and properties. The initial elastic deformation of Ni3Sn4single crystal is governed by the reconfiguration of surface atoms, and its deformation evolution after further uniaxial tensile straining is characterized by Ni=Sn bond straightening, bond breakage, inner atomic distortion, cross-section shrinking, and rupture. The calculated normal elastic constants of Ni3Sn4single crystal are found to be consistent with the literature theoretical data.

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42

SELF, R. H., C. P. PLEASE, and T. J. SLUCKIN. "Deformation of nematic liquid crystals in an electric field." European Journal of Applied Mathematics 13, no. 1 (February 2002): 1–23. http://dx.doi.org/10.1017/s0956792501004740.

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The behaviour of liquid crystal materials used in display devices is discussed. The underlying continuum theory developed by Frank, Ericksen and Leslie for describing this behaviour is reviewed. Particular attention is paid to the approximations and extensions relevant to existing device technology areas where mathematical analysis would aid device development. To illustrate some of the special behaviour of liquid crystals and in order to demonstrate the techniques employed, the specific case of a nematic liquid crystal held between two parallel electrical conductors is considered. It has long been known that there is a critical voltage below which the internal elastic strength of the liquid crystal exceeds the electric forces and hence the system remains undeformed from its base state. This bifurcation behaviour is called the Freedericksz transition. Conventional analytic analysis of this problem normally considers a magnetic, rather than electric, field or a near-transition voltage since in these cases the electromagnetic field structure decouples from the rest of the problem. Here we consider more practical situations where the electromagnetic field interacts with the liquid crystal deformation. Assuming strong anchoring at surfaces and a one dimensional deformation, three nondimensional parameters are identified. These relate to the applied voltage, the anisotropy of the electrical permittivity of the liquid crystal, and to the anisotropy of the elastic stiffness of the liquid crystal. The analysis uses asymptotic methods to determine the solution in a numerous of different regimes defined by physically relevant limiting cases of the parameters. In particular, results are presented showing the delicate balance between an anisotropic material trying to push the electric field away from regions of large deformation and the deformation trying to be maximum in regions of high electric field.

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43

Pirouz, P., A. V. Samant, M. H. Hong, A. Moulin, and L. P. Kubin. "On temperature dependence of deformation mechanism and the brittle–ductile transition in semiconductors." Journal of Materials Research 14, no. 7 (July 1999): 2783–93. http://dx.doi.org/10.1557/jmr.1999.0372.

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Recent deformation experiments on semiconductors have shown the occurrence of a break in the variation of the critical resolved shear stress of the crystal as a function of temperature. These and many other examples in the literature evidence a critical temperature at which a transition occurs in the deformation mechanism of the crystal. In this paper, the occurrence of a similar transition in two polytypes of SiC is reported and correlated to the microstructure of the deformed crystals investigated by transmission electron microscopy, which shows evidence for partial dislocations carrying the deformation at high stresses and low temperatures. Based on these results and data in the literature, the explanation is generalized to other semiconductors and a possible relationship to their brittle–ductile transition is proposed.

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44

Jakubowska, D., J. Zdunek, M. Kulczyk, J. Mizera, and K. J. Kurzydłowski. "Microstructure and Texture of Hydrostatic Extrusion Deformed Ni Single Crystals and Polycrystal." Advances in Materials Science and Engineering 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/613839.

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The differences in the microstructure and texture of two Ni single crystals, with different initial orientations (100and110), and of polycrystalline nickel, before and after severe plastic deformation (SPD) produced by hydrostatic extrusion (HE), have been investigated. The crystals were deformed by a two-step HE process with a total deformation value ofε=1.2. The global texture, mechanical properties, and microstructure were examined after the deformation. In every investigated sample, the presence of111fibre texture was noted, while the starting orientation of a100Ni single crystal was preserved in 50% of the volume. The results obtained were compared with the relevant literature data.

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Neels, Antonia, Philippe Niedermann, and Alex Dommann. "Life Time Predictions through X-Ray Defect Analysis of MEMS Devices." Materials Science Forum 584-586 (June 2008): 518–22. http://dx.doi.org/10.4028/www.scientific.net/msf.584-586.518.

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In single crystal silicon (SCSi) MEMS devices, crystalline imperfection is recognized to favor failure. A DRIE etched SCSi structure was built to study the crystal strain profile in dependence of the SCSi deformation by applying a mechanical force. High resolution X-ray diffraction methods such as the rocking curve method and reciprocal space mapping were used to determine the strain as well as the defect concentration in the crystal. The investigations also include the numerical simulation of deformations.

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46

Herring, R. A., W. J. Bruchey, and P. W. Kingman. "Characterization of ballistically deformed tungsten [100]-, [111]-, and [110]-oriented single crystal penetrators by optical metallography, x-ray diffraction and transmission electron microscopy." Journal of Materials Research 19, no. 12 (December 1, 2004): 3451–62. http://dx.doi.org/10.1557/jmr.2004.0464.

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Single-crystal penetrators of tungsten having orientations of [100], [111], and [110] were ballistically deformed into targets of standard armor material and characterized by optical metallography, x-ray diffraction, and transmission electron microscopy (TEM) methods, which showed significant differences in their deformation mechanisms and microstructures corresponding to their deformation performance as measured by the penetration of the target. The [100] single-crystal penetrator, which produced the most energy efficient deformation, provided a new, alternative mechanism for ballistic deformation by forming small single-crystal blocks, defined by {100} oriented cracks, which rotated during extrusion from the interior to the side of the penetrator while maintaining their single crystal integrity. The [111] single-crystal penetrator transferred mass along allowed, high-angle deformation planes to the penetrator’s side where a buildup of mass mushroomed the tip until the built-up mass let go along the sides of the penetrator, creating a wavy cavity. The [110] penetrator, which produced the least energy-efficient deformation, has only two allowed deformation planes, cracked and rotated to invoke other deformation planes.

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47

Kucheyev, S. O., J. E. Bradby, J. S. Williams, C. Jagadish, and M. V. Swain. "Mechanical deformation of single-crystal ZnO." Applied Physics Letters 80, no. 6 (February 11, 2002): 956–58. http://dx.doi.org/10.1063/1.1448175.

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48

Stüwe, H. P. "Crystal Restoration during Severe Plastic Deformation." Materials Science Forum 503-504 (January 2006): 175–78. http://dx.doi.org/10.4028/www.scientific.net/msf.503-504.175.

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Severe plastic deformation of metals leads to changes in microstructure, which in turn are responsible for unusual bulk properties. There are two (interrelated) processes leading to change of microstructure: 1) the production of a very high number of dislocations, leading to a high dislocation density, 2) the “fragmentation” of the original crystal grains into much smaller structural elements leading to what is sometimes called “nanocrystalline” material. Under continued strain neither of these two processes will continue indefinitely. Instead, the microstructure will reach a steady state. Under certain conditions its development may even be reserved. This indicates the operation of restoration mechanisms such as dynamic recovery and recrystallisation. The actual state of art will be discussed on the basis of current experiments.

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49

Lychagin, Dmitry, Andrey Dmitriev, Anton Nikonov, and Ekaterina Alfyorova. "Crystallographic and Geometric Factors in the Shear Development in <001> FCC Single Crystals: Molecular Dynamics Simulation and Experimental Study." Crystals 10, no. 8 (August 2, 2020): 666. http://dx.doi.org/10.3390/cryst10080666.

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An approach to the study of the mechanisms of shear deformation in the bulk of face centered cubic (FCC) single crystals based on molecular dynamics simulation is proposed. Similar shear patterns obtained experimentally, and in simulations, allow consideration of the effect of crystallographic and geometric factors on deformation mechanisms. Deformation of <001> single-crystal samples in the form of tetragonal prisms with {110} and {100} lateral faces and different height-to-width ratios was studied. The simulation showed that the sample vertices are the preferential sites for shear initiation. It was found that the formation of deformation domains and interaction of shear planes are caused by the geometry of shear planes in the bulk of the single crystal, i.e., by their location in relation to basic stress concentrators and by their orientations relative to the lateral faces. The deformation patterns obtained in the simulations were in good agreement with those observed in the experiments. The fractions of sliding dislocations and dislocation barriers were determined for different materials, taking into account the crystallographic and geometric factors.

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Čížek, Jakub, František Lukáč, Marián Vlček, Ivan Procházka, Franziska Traeger, Detlef Rogalla, and Hans Werner Becker. "Diffusivity of Hydrogen in ZnO Single Crystal." Defect and Diffusion Forum 326-328 (April 2012): 459–64. http://dx.doi.org/10.4028/www.scientific.net/ddf.326-328.459.

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Hydrogen diffusivity in ZnO (0001) single crystal was investigated using electrical resistometry and nuclear reaction analysis (NRA). ZnO crystals were covered with a thin Pd over-layer and electrochemically charged with hydrogen. The net concentration of hydrogen determined by NRA was found to be in a reasonable agreement with the value estimated from the transported charge using the Faradays law. The hydrogen diffusion coefficient in ZnO was estimated from in-situ electrical resistivity measurements. Moreover, NRA investigations revealed existence of a subsurface layer with very high concentration of hydrogen (up to 40 at.%). Typical surface modification observed on hydrogen loaded crystal by light microscope indicates hydrogen-induced plastic deformation realized by a slip in the c-direction. Open-volume defects introduced by hydrogen-induced plastic deformation trap diffusing hydrogen and cause an enhancement of hydrogen concentration in the deformed subsurface layer.

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Journal articles on the topic 'Crystal deformation'

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