Types Of Twins Research Articles

Simultaneous enhancement of strength and ductility in friction stir welded AZ31 alloy via multi-pass hot-rolling and subsequent annealing

Friction stir welding (FSW) is a new solid-state joining process for joining light metals, such as magnesium (Mg) alloys. However, the texture-induced softening mechanism (in stir zone, SZ) tends to cause the worsening of mechanical properties in FSW Mg alloys. In this work, multi-pass hot-rolling and subsequent annealing is used to ameliorate the FSW AZ31 alloy plate. The results show that multi-pass hot-rolling leads to the c-axes of most grains in the SZ approximately perpendicular to the normal direction (ND) transforming into these almost parallel to the ND, accompanied with multiple twin types. After subsequent annealing, twins, as nucleation sites, promote the formation of new grains with off-basal texture, resulting in the weak basal texture. Compared with the FSW plate and the initial plate, the rolled-annealed FSW plate exhibits a relatively uniform hardness distribution and a “strength-ductility” synergy, which are mainly attributed to an appropriate texture feature and a homogeneous grain structure. This work provides a new idea for the development of new high-performance FSW Mg alloys.

Loading-direction dependence of interaction types between different twin variants in AZ31 alloy

ABSTRACT In this research, Loading-direction dependence of interaction types between different twin variants in AZ31 alloy was investigated. The microstructure, twin evolution, and the deformation mechanisms of samples were characterised by quasi-in-situ electron backscatter diffraction. The result showed that during rolling direction (RD)-pre-compression and re-compression, the grains with co-zone twin–twin interaction (Type I) are in the majority, while during RD-pre-compression and transverse direction (TD)-re-compression, the grains with non-cozone twin–twin interaction (Type II) are dominant. Furthermore, the effect of different types of twin–twin interaction on subsequent microstructure evolution is clarified. Our experimental results may provide insights for tailoring different types of twin–twin interaction.

An On-Station Analysis of Factors Affecting Growth Traits of Pure Red Maasai and Dorper Sheep Breeds under an Extensive Production System.

This comparative study aimed to evaluate genetic and environmental factors' effects on the growth traits of lambs in Dorper and Red Maasai (RedM) sheep breeds. The data analyzed contained the following measurements: birth weight (Bwt), weaning weight (Wwt), yearling weight (Ywt), birth type (single or twins), and details on each lamb's dam (dam ID and age) and sire. Except for the RedM, whose birth weight decreased with time, both breeds generally showed an increase in other growth weights across the study period, with yearly variations affecting both breeds. Additionally, analysis by a linear mixed model with restricted maximum likelihood (REML) showed that only breed as a factor significantly (p < 0.05) influenced birth weight; breed, sex, and birth type all significantly (p < 0.05) influenced weaning weight, whereas season, sex, and dam age significantly (p < 0.05) influenced yearling weight. The RedM breed outperformed the Dorper breed in post-weaning growth rate, demonstrating early resilience and adaptation to local environmental factors independent of maternal influence. Breed and non-genetic factors play a vital role in the growth of lambs, and the results of this study offer an opportunity for improved farm management under an extensive production system and selection for the conservation of the indigenous Red Maasai breed.

ICONOSTASIS OF THE LORD TRANSFIGURATION MONASTERY CATHEDRAL: APPROACHING IN DETAIL

The article describes the results of digitization of the iconostasis of the Transfiguration of the Savior Cathedral in Perm and describes the experience of digitalization of cultural heritage using 3D laser scanning methods. Two types of digital twins of the iconostasis were created: a highly detailed one for display and a web model for smartphone screens. The analysis of the obtained results allows further improvement of digitalization approaches for a wide range of different cultural artifacts.

Double Diffraction or ω-Fe Diffraction in Body-Centered Cubic {112}<111>-Type Twinned Martensite

The martensitic substructure in steels plays a major role in understanding the nature of martensite transformation and improving mechanical properties. However, the substructure in the quenched martensite of carbon steel, particularly in high carbon martensite, has not been clarified yet. Local crystal structure in martensite has been characterized by means of transmission electron microscope (TEM). A specimen tilting experiment in TEM is a practical method to simply confirm that the electron diffraction spots are caused by either double diffraction effect or a second crystalline phase. By tilting the TEM specimen containing Fe–C twinned martensite structure, the so-called double diffraction spots of {112}<111>-type twin are still visible even after the diffraction spots from the twinned crystals become invisible. This experimental result is the direct evidence that the so-called twinning double diffraction spots come from a second crystalline phase (ω-phase), which is distributed in the body-centered cubic (BCC){112}<111>-type twinning boundary region. An ideal BCC {112}<111>-type twin is just a model, which has not been reported yet in any experiment.

Polysynthetic Twinning of Diopsides in the Niewang and Tatliksu Nephrite Deposits, Xinjiang, China

Diopside, an important component of the crustal and upper mantle, plays an important role in the formation of nephrite. Polysynthetic twinning in natural diopside, especially from skarns, has rarely been systematically researched. Here, the polysynthetic twinning of natural diopside was investigated in two skarn-type nephrite deposits (Niewang and Tatliksu) in Qiemo, Xinjiang, China. Petrographic observations revealed periodic alternations of dark–light lamellae under cross-polarized light and parallel striations under plane-polarized light, whereas backscattered electron images indicated high homogeneity, which suggested a type of mechanical polysynthetic twinning. According to the optical indicatrix, twins were predominantly oriented as a (100)[100] system. Raman spectra and chemical data show that pyroxenes in nephrite are close to the Di end-member with 0.90–1.04 a.p.f.u. Mg and 0.98–1.05 a.p.f.u. Ca. Both diopside and tremolite from Tatliksu contain slightly higher Fe than those from Niewang. Given the seismic origin of mechanical clinopyroxenes twins, twins of studied diopsides are likely to be attributed to Paleozoic-Mesozoic paleoearthquakes in the Altyn Mountain. A shear stress ≥ 140 MPa and a differential stress greater than 280 MPa are suggested as conditions linked to generation of the twinning of diopsides in the nephrite deposits. The replacement of diopside by tremolite along its twin planes highlights the potential gemological implications, as such replacement by tremolite probably facilitated the formation of dense, fine fibre textures in the nephrites.

Effect of rolling reduction on deformation mechanism and twinning behavior of WE43 magnesium alloy

The effect of rolling reduction of the last pass on the dislocation slip and twinning behavior during direct hot rolling of a cast WE43 magnesium alloy at 480 °C was investigated. The results showed that prismatic 〈a〉 slip was always the main deformation mode during rolling at 480 °C. In addition, the activated twinning type was associated with rolling reduction. The extension twinning was activated at a slight rolling reduction (2%), while compression twinning and - double twinning were activated at larger rolling reduction (12% and 20%). Schmid factor calculation showed that the activation of extension twin variants followed the Schmid Law, whereas the activation of compression twin variants did not follow it. Even if the rolling reduction reached 20%, almost no dynamic recrystallization (DRX) grains were found, presumably because the amount of deformation required for DRX to occur was not reached.

Twin and dislocation induced grain subdivision and strengthening in laser shock peened Ti

A significantly refined microstructure with high twin and dislocation densities is a common feature in the Ti surface layers subjected to laser shock peening (LSP). In this study, in order to develop a detailed understanding of the different twin variants and accurate estimation of twin and dislocation densities that result from LSP, electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM) were performed at different depths below the peened surfaces of single and triple LSP impacted Ti. To overcome challenges associated with characterization of the nano-sized LSP-induced twins during the conventional EBSD analysis, a novel data mining strategy is developed to identify the characteristic straight twin boundary traces from the band contrast maps. Results show five types of twins, whose total density initially increases and then monotonically decreases with increasing distance from the LSP treated surface. The intersection of the primary and secondary type twins subdivides the grains and leads to grain refinement. In contrast, the dislocation density is highest at the LSP treated surface but decreases monotonically with the increasing depth. A similar trend in the variation of microhardness as a function of the depth indicates that LSP-induced strengthening is dominated by the dislocations and grain refinement. Further analysis reveals that the former's contribution is more pronounced than that of the latter. The understanding developed in this work can be useful for the design of the alloys and the LSP process for improved mechanical performance.

Improved strength and plasticity of magnesium matrix nanocomposites reinforced by carbonaceous nanoplatelets and micro-clusters

The uniform distribution of carbonaceous nanomaterials in a magnesium matrix composite can dramatically improve the strength without sacrificing ductility. In this work, graphene oxide (GO) reinforced AZ31 magnesium alloy matrix composites were fabricated using friction stir processing to achieve higher strength, toughness, and plasticity compared with the unreinforced condition. The composite microstructure consisted of individual GO nanoplatelets and GO micro-clusters, having different effects on the deformation behavior of the matrix. Texture analysis revealed that adding GO led to the activation of different twin types and variants during tensile deformation. In contrast, only one extension twin variant was dominant in the case of the unreinforced condition. In spite of the GO micro-clusters, the individual GO nanoplatelets cannot hinder the growth of twins. The GO micro-clusters inhibit twin growth, change the stress state in the parent grains, and provide a driving force for twin nucleation. The extensive twinning occurrence was followed by twin intersections and significantly enhanced the plasticity of the alloy by providing easy orientations for further basal slip.

Construction Project Management with Digital Twin Information System

The current stage in the development of the construction industry is its digitalization, which requires the transformation of processes and models based on the use of digital platforms and twins. Datasets in a construction project accumulates quickly and becomes difficult to store and process due to the large file sizes of CAD,GIS and BIM technologies. Managing such datasets is a complex problem, since the usefulness of such data lies in ensuring that it is available and used as needed by all participants in a construction project. The article proposes to develop an information system for creating digital twins of construction project management as an integrator of digital tools based on Big Data Analytics and BIM technology, which is already the standard for the digitalization of the construction industry. The study describes four types of digital twins and ten properties of Big Data required for construction project. Conceptual model of Big Data domains for construction project and BIM-model of Big Data exchange and information transfer for construction project digital twin are considered. The authors propose a framework for creating digital twins of construction project management that uses three main components: BIM-models, Big Data Analytics and Knowledge Base. The results of the study are structure of information system of creating digital twin of territory urban planning project for Design Company and example using a BIMoriented software product. Keywords—BIM-model, Big Data, digital twin, construction projectmanagement, digital construction

Identification of Active Slip Mode and Calculation of Schmid Factors in Magnesium Alloy

Four types of slip systems (basal &lt;a&gt;, prismatic &lt;a&gt;, pyramidal &lt;a&gt;, and pyramidal &lt;a + c&gt;) and two types of twinning (extension twinning {101–2} and contraction twinning {101–1}) could be identified in magnesium alloys using scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD). In addition, the Schmid factors (SF) of these slip systems were systematically calculated on the basis of the Euler angle which was obtained in EBSD. The identification of slip systems and calculation of SF can help us to understand the contribution made by each type of slip in the plastic deformation of the material, which is important for understanding the deformation mechanism.

Effect of Al addition and annealing on the microstructure evolution of Mg-3Sn Mg alloy subjected to high-speed rolling

The microstructure evolution of Mg-3Sn, Mg-3Sn-3Al-Zn (ATZ331), and Mg-3Sn-6Al-Zn (ATZ631) alloys during high-speed rolling (HSR) and annealing was studied. High-speed rolling was carried out on the three alloys at a rolling speed of 1100 m/min, a rolling temperature of 400 °C, and a reduction of 40% during a single pass. The results showed that the microstructure of the samples after HSR contained many twins and was dominated by {10−12} extension twins (ETs) and supplemented by {10−11} contraction twins (CTs) and {10−11}-{10−12} double twins (DTs). After adding Al, the content of these different types of twins was reduced. The twinning fraction decreased significantly with 3 wt% Al addition, while the twinning fraction decreased slightly with 6 wt% Al addition. The high-speed rolled alloys were annealed at 370 °C for 1 min, 2 min, 3 min, 5 min, and 8 min. When the annealing time was 1 min, the recrystallization fraction of the ATZ631 alloy was low, indicating that increasing the Al content to 6 wt% inhibited recrystallization. When the annealing time increased to 3 min, the recrystallized grains in the ATZ631 alloy grew, indicating that the grain growth progressed faster in this alloy. When the annealing time was 8 min, the grain size of the three alloys grew. The electron backscattered diffraction (EBSD) results of the alloy annealed for 8 min showed that the twin fraction in the annealed state was lower than that after high-speed rolling. In addition with the increase in Al content, the twin fraction decreased. During high-speed rolling, the maximum intensity also increased with an increase in Al content, were 22.72, 25.09, and 26.35, and the texture of the annealed alloy was weakened. The Al addition also increased the maximum intensity.

Mineral Texture Identification Using Local Binary Patterns Equipped with a Classification and Recognition Updating System (CARUS)

In this paper, a rotation-invariant local binary pattern operator equipped with a local contrast measure (riLBPc) is employed to characterize the type of mineral twinning by inspecting the texture properties of crystals. The proposed method uses photomicrographs of minerals and produces LBP histograms, which might be compared with those included in a predefined database using the Kullback–Leibler divergence-based metric. The paper proposes a new LBP-based scheme for concurrent classification and recognition tasks, followed by a novel online updating routine to enhance the locally developed mineral LBP database. The discriminatory power of the proposed Classification and Recognition Updating System (CARUS) for texture identification scheme is verified for plagioclase, orthoclase, microcline, and quartz minerals with sensitivity (TPR) near 99.9%, 87%, 99.9%, and 96%, and accuracy (ACC) equal to about 99%, 97%, 99%, and 99%, respectively. According to the results, the introduced CARUS system is a promising approach that can be applied in a variety of different fields dealing with classification and feature recognition tasks.

Effects of deformation twins on microstructure evolution, mechanical properties and corrosion behaviors in magnesium alloys - A review

Due to lattice reorientation, grain segmentation, induced recrystallization, twins play a very important role in regulating texture, refining grains, improving mechanical properties and corrosion resistance, and has received more extensive attention. Numerous studies have shown that {10-12}<10-11> tensile twins (TTWs) are easily activated in large quantities due to the lower critical resolve shear stresses (CRSS). Introduction of TTWs under uniaxial compression improved the strength, ductility, and formability of magnesium (Mg) alloys. Moreover, TTWs produced by multi-directional impact forging (MDIF) can optimize the microstructure by dividing grains and promoting recrystallization, resulting in significant improvement of mechanical properties. Although {10-11}<10-12> compressive twins (CTWs) and {10-11}-{10-12} double twins (DTWs) can promote dynamic recrystallization (DRX), they are also favorable nucleation sites for cracks. In addition, the type and volume fraction of twins can affect the corrosion resistance, and they also play different roles in the corrosion process of different Mg alloys. Twins have shown great potential for improving structure and properties, but a comprehensive and critical discussion of twins in Mg alloys is still lacking. Therefore, based on previous studies, this article reviews the common types and variants of twins in Mg alloys, influencing factors, and their effects on the microstructure, mechanical properties and corrosion resistance. In addition, some interesting ideas are being proposed for further research.

Study on the Twinning/De-twining Behavior of Different Types of Twin–Twin Interaction via Experiments and Molecular Dynamics Simulation

Study on the Twinning/De-twining Behavior of Different Types of Twin–Twin Interaction via Experiments and Molecular Dynamics Simulation

Critical resolved shear stress for twinning and twinning-induced plasticity in single crystals of the CoCrFeNiMo0.2 high-entropy alloy

The effect of alloying with Mo atoms 4 at.% on the twinning deformation, critical resolved shear stresses (CRSS) for slip τcrsl and twinning τcrtw and plasticity was studied in [1‾11]-, [1‾44]- and [001]- oriented crystals of the Co24Cr24Fe24Ni24Mo4 (at.%) high-entropy alloy (HEA) under tension at 296 and 77 K. The stacking fault energy of the Co24Cr24Fe24Ni24Mo4 HEA, measured in the present paper on the triple dislocation nodes, is equal to 0.027 J/m2. It is shown that initial yield behavior along studied orientations is governed by dislocation slip and the CRSS for slip are independent of crystal orientation. Under tensile strain, twinning develops in the [1‾11]- and [1‾44]- oriented crystals only at 77 K and is not detected in the [001]-oriented crystals. Two types of twins are found in the [1‾11]- and [1‾44]-oriented crystals (thin nanotwins and macrotwins). Nanotwins develop after a low slip deformation of 5–10% and are observed only by transmission electron microscopy. Macrotwins are detected after a significant slip deformation of 20 and 60% and are determined metallographically and X-ray by the precession of the crystal axis, respectively, in the [1‾11]- and [1‾44]-oriented crystals. In the [1‾11]- oriented crystals, there is no precession of the crystal axis due to the development of slip simultaneously in several systems. It is shown that CRSS for nano- and macrotwins are dependent on the crystal orientation. In the [1‾44]-oriented crystals, τcrtw = 212 MPa for nanotwinning and τcrtw = 400 MPa for macrotwinning. In the [1‾11]-oriented crystals, τcrtw = 250 MPa for nanotwinning and τcrtw = 335 MPa for macrotwinning. For the transition to deformation by macrotwinning, it is necessary that the effective stacking fault energy γef is approaching to zero and the condition τcrtw <τcrsl is satisfied. Deformation by macrotwinning suppresses slip multiplicity and shifts the formation of the neck formation according to the Considère condition to higher stress levels. This increases plasticity from 72% at 296 K to 108% at 77 K in [1‾44]-oriented crystals and from 48% at 296 K to 57% at 77 K in [1‾11]-oriented crystals.

Twinning during recrystallization and its correlation with the deformation microstructure

The formation of annealing twins during recrystallization in a cold-rolled copper single crystal has been studied. A new method is proposed to classify annealing twins according to their orientation relationship with the surrounding deformed matrix. A statistical analysis based on the new classification method shows that during growth of a recrystallized grain, twinning occurs more frequently on twinning planes close to one of the {111} planes of the deformation microstructure, and most frequently when the {111} plane is the dominant slip plane of the deformed matrix for the present single crystal. The differences in morphology for different types of twins are discussed based on growth selection criteria. The study highlights the importance of the local deformation microstructure on the formation of annealing twins.

Amino acid meat composition of the Edilbaev breed lambs born in single and double litters

The article presents data on the amino acid composition of the meat of Edilbaev rams of different types of birth. The content of essential and non-essential amino acids was studied; the ratio of the group of essential amino acids to the group of non-essential amino acids is 0.67-0.69, with the recommended norm of a balanced diet of 0.56-0.67. The studies were carried out in SPO "Kamyshinskoye" of the Kamyshinsky district of the Volgograd region on lambs of the Edilbaev breed of single and twin birth types.

DIGITAL TWINS IN PRODUCTION AS ONE OF THE DIRECTIONS OF DIGITAL TRANSFORMATION OF THE ECONOMY

The article describes one of the areas of digital transformation of the economy, namely digital twins in manufacturing. The meaning of the concept "digital twin" is considered, as well as a diagram of the application of this technology is presented. Different types of digital twins are given according to two classification criteria. The article also contains information about the constraining and stimulating factors for the development of the digital twins market. The main suppliers of technology are highlighted, as well as examples of the use of digital twins in domestic practice.

Twinning character and texture origination in the randomly-oriented AZ31B magnesium alloy during cold-rolling

Based on generalized Schmid factor (G-SF) calculation, the twinning character and texture development in the rolling plate of randomly-oriented AZ31B magnesium alloy were investigated in this work. The results showed that when the rolling reduction/nip angle is low, the twin type selection is independent of crystal orientation or G-SF due to the significant difference of critical resolved shear stress (CRSS) between extension twinning and contraction twinning. The twin variant selection does not intimately follow the Schmid criterion. In comparison, the extension twin variant selection departs more from the G-SF prediction than the contraction twin variant selection. The orientations of the matrix grains develop gradually tending to distribute around the normal direction (ND), which promote the activation of contraction twinning. The basal texture results only from the orientation development of the matrix grains, depending on the basal <a> slip and the pyramidal <c+a> slip, which was explained in terms of a crystal rotation by the dislocation interactions.