Twin Relationship Research Articles

Microstructure and Texture Evolution of Cu-Ni-P Alloy after Cold Rolling and Annealing.

The microstructure and texture evolution of Cu-Ni-P alloy after cold rolling and annealing at 500 °C was studied by electron backscattering diffraction (EBSD). The equiaxed grain is elongated and the dislocation density increases gradually after cold rolling. The grain boundaries become blurred and the structure becomes banded when the reduction in cold rolling reaches 95%. A typical rolling texture is formed with the increase in deformation amount in cold rolling. The deformation structure gradually disappeared and recrystallized new grains were formed after annealing at 500 °C. The recrystallization nucleation mechanism of Cu-Ni-P alloy at 60% reduction is mainly a bow nucleation mechanism. A shear band begins to form after annealing at 80% reduction. The shear band becomes the preferred nucleation location with the increase in reduction. Most adjacent recrystallized grains growing in the shear band have a twin relationship.

In-situ HRTEM observations of intermediate phase transformation in lattice reorientation in HCP rhenium

In-situ high-resolution transmission electron microscopy (HRTEM) is performed to investigate the deformation behavior of hexagonal close-packed rhenium (Re) which is compressed along the 〈11¯00〉 direction. Atomistic simulations are also conducted to better understand the deformation mechanisms. Two types of lattice reorientation are observed during compression. The first type involves the reorientation of one lattice by ∼90° around 〈112¯0〉, which is accomplished by the formation of an intermediate face-center-cubic (FCC) phase at the interface. This transformation sequence can be described as {11¯00}matrix→{111}FCC→(0001)twin. In the second type, a new grain is formed but does not satisfy any known twin relationship with the matrix, and an intermediate FCC phase is also formed. The transformation sequence can be described as {11¯01}matrix→{111}FCC→(0001)grain. Mechanisms responsible for the observed lattice reorientation and sequential phase transitions are analyzed by conducting lattice correspondence analyses on the simulation results. Strain accommodation is also analyzed to explain the mechanisms for lattice reorientation and the intermediate phase transformations. The results provide new insight into the deformation behavior of HCP metals.

A general method for twin element analysis and its application in Cu–Zn–Al shape memory alloys with M18R martensite

Twins play a crucial role in elucidating the structure and deformation characteristics of materials. However, in materials with low-symmetry crystal structures, solving the twin relationships remains a challenging task. In this study, we propose a general method for determining twin elements K1, η1, K2, and η2, which are essential for twin analysis. The proposed method involves three main steps: (1) representing misorientation data measured by electron back-scattered diffraction (EBSD) and transmission electron microscopy (TEM) in matrix form, (2) identifying additional 180° rotation elements related to twin elements K1 or η1 by traversing all symmetrically equivalent misorientations, and (3) using a minimum and crystal structure-dependent uniform shear as the constraint to determine the other twin elements (K2andη2). By combining the experimental data and the proposed method, we systematically analyze the complex twin relationships of Cu–Zn–Al shape memory alloys (SMAs) with monoclinic martensite (M18R). This methodology has been demonstrated to be effective and possesses broad applicability.

Deep Learning-based Knowledge Graph and Digital Twin Relationship Mining and Prediction Modeling

Abstract The era of big data produces massive data, and carrying out data mining can effectively obtain effective information in huge data, which provides support for efficient decision-making and intelligent optimization. The purpose of this paper is to establish a digital twin system, preprocess massive data using random matrix theory, and design the knowledge graph construction process based on digital twin technology. The BERT model, attention mechanism, BiLSTM model, and conditional random field of the joint deep learning technology are used to identify the knowledge entities in the digital twin system, extract the knowledge relations through the Transformer model, and utilize the TransE model for the knowledge representation in order to construct the knowledge graph. Then, the constructed knowledge graph is combined with the multi-feature attention mechanism to build an anomaly data prediction model in the digital twin system. Finally, the effectiveness of the methods in this paper is validated through corresponding experiments. The TransE model is used for knowledge representation. The accuracy of ternary classification is higher than 80% in all cases, and the MR value decreases by up to 64 compared to the TransR model. The F1 composite score of the anomaly data prediction model is 0.911, and the AUC value of the validation of knowledge graph effectiveness is 0.702. Combining deep learning with the knowledge graph, the knowledge information can be realized in the digital twin system’s accurate representation and enhance the data mining ability of the digital twin system.

Insight into austenite reversion and mechanical behavior of quenching and partitioning steel inherited hierarchical structure of martensite

In this paper, the start microstructure of full martensite and dual phases comprising ferrite and martensite were introduced into quenching and partitioning (Q&P) steel to tailor the microstructural characteristics and mechanical behaviors, which was achieved by means of a pre-quenching treatment with various temperatures. It is revealed that the conventional Q&P sample possessed bimodal microstructure with predominantly blocky feature, while gradually changed from combination of blocky and lath structures into individually lath feature in pre-quenched Q&P samples. The reversed austenite presented different variants, which predominantly reproduced the orientation of parent austenite and occasionally possessed twin relationship, low angle misorientation or extraneous with parent austenite. The twin-related austenite included annealing twin and reversed twin, whilst the latter showed twin relationship with both neighbored annealing twin and parent austenite. The variant type of reversed austenite significantly influenced the characteristics of its orientation relationship with neighbored pre-quenched martensite. The pre-quenching treatment was favorable to improve the carbon content of meta-stable austenite before Q&P treatment, while the final carbon content in retained austenite was mainly controlled by the synergistic carbon partitioning of martensite and bainite on basis of thermodynamic calculation, accompanied with the partitioning of Mn and Si elements. Moreover, the pre-quenched martensite deformed coordinately in a unit of martensite packet and was beneficial to retard necking to improve ductility. The optimal mechanical properties were obtained with pre-quenching temperature near Ac3, possessing yielding strength of 623 MPa, ultimate tensile strength of 861 MPa and product of strength and elongation exceeding 28 GPa%, attributing to the positive TRIP effect originating from lath-like retained austenite with high carbon content and multi-level hierarchical microstructure inherited from pre-quenched martensite.

Effect of stacking fault energy on B2 ZrCo phase transition and nanotwins formation in Zr54.5Co33.5Al12 alloy prepared by rapid solidification

Zr–Co–Al alloys are widely used due to their good biocompatibility and high-pressure properties. In the present work, the Zr54.5Co33.5Al12 alloy was prepared by rapid solidification. It has been found that the central region (b region) and the edge region (d region) have obvious changes in the microstructure, with the b region contains a large number of crystalline phases, and the d region can obviously observe the morphology of the amorphous state except a few dendrites. A certain amount of amorphous is contained in the d region as detected by XRD analysis. The fracture strength can undoubtedly reach up to 2031 MPa and the fracture strain is about 1.8 %. TEM analysis revealed the B2-to-B33 phase transition in the deformed alloy, and a significant number of nanotwins with a {111} <121> type of twin relationship were observed in the B33 ZrCo phase. Furthermore, the stacking fault energy (SFE) for varying applied stresses was calculated. From the calculation results, the negative SFE (about −41 mJ/m2) is beneficial to the B2-to-B33 phase transition, and it is known that twin thickness decreases with decreasing SFE.

A new mechanism of lamellar kinking produced by α twins

This study investigated the hot pack rolling of Ti-43Al-1.5Cr-0.5Re (at. %) alloy sheets at 1250 ℃ with a total deformation of 80 %. The results revealed a novel type of lamellar kinking, distinct from conventional lamellar kinking caused by mechanical stress. The kinking interface exhibits a serrated morphology and conformed to the {11-22} <11-2-3> contraction twin relationship. A new lamellar kinking mechanism induced by α twins was proposed, providing a new perspective for understanding the kinking mechanism in TiAl alloys and other anisotropic metallic materials.

Identification of active slip modes in twinned bicrystals of GNS/Cu composite through intragranular misorientation axes analysis

Bicrystals serve as a simplified model system for studying the deformation behavior of polycrystalline materials. In this study, we fabricated graphene nanosheets (GNSs) reinforced copper (Cu) matrix laminated composites using electrophoretic deposition and subsequent vacuum hot-press sintering. Interestingly, the composite exhibited a bicrystal microstructure, with two types of adjacent crystals, i.e., denoted as crystal A (φ1 = 222.06, Φ = 40.54, φ2 = 82.5) and crystal B (φ1 = 141.36, Φ = 43.76, φ2 = 1.94), displaying a twin orientation relationship. To investigate the deformation behavior of the GNS/Cu composite, we conducted interrupted room temperature uniaxial tensile tests combined with Scanning Electron Microscope (SEM) Electron Backscatter Diffraction (EBSD) characterization. To identify the activated slip systems in the composites, we performed trace analysis, applied the Schmid Factor law, analyzed the deformation gradient tensor, and conducted intragranular misorientation axis (IGMA) analysis. The trace analysis revealed that slip systems with high Schmid Factor values were favored during tension. Moreover, the deformation gradient tensor elements of the primary slip systems in the two crystals confirmed the deformation features observed by SEM. However, crystal B exhibited a significant deviation in trace angle. Further IGMA investigation revealed that during tension, some slip systems, which were not favored by the Schmid Factor law, were also activated in crystal B. The activation of these slip systems in crystal B can be attributed to the large deviation in the trace angle. The findings in this work provide valuable insights for exploring the underlying deformation mechanisms in polycrystalline materials.

Deformation behavior and mechanism of p-type (Bi,Sb)2Te3 alloy during three-point bending test at room temperature

In order to improve the machining process to engineer microstructure and defect types so as to further enhance the thermoelectric properties, it is desirable to understand the deformation behavior and mechanism of polycrystalline Bi2Te3 alloys. This work investigated the deformation behavior and mechanism of (Bi,Sb)2Te3 alloy during three-point bending tests using electron backscatter diffraction (EBSD). Results indicated that both dislocation slip and twinning occurred during the bending tests. The twins with the twin orientation relationship of (0001)M//(0001)T were observed. In addition, the nano-grains extruded the coarse grains in such a way that coarse grains assumed an orientation vulnerable to fracture along the basal planes. Slip trace analysis revealed that 13<112¯0> dislocation slipping on basal planes broke the Van der Waals bonds between the basal planes which eventually led grains to fracture. Additionally, a novel model was introduced that first incorporated the bending moment diagram in order to deduce the deformation process.

Fatigue-Induced HCP-to-FCC Phase Transformation Resulting in Two FCC-Zr Variants in Pure Zirconium.

This study utilized transmission electron microscopy (TEM) and on-axis transmission Kikuchi diffraction (TKD) to investigate the fatigue-induced HCP-to-FCC phase transformation in industrial pure zirconium under a stress ratio of R = 0.1. The results show that fatigue damages result from phase deformations during cyclic loadings. The fatigue-induced FCC-Zr phases exhibit a B-type orientation relationship with the HCP-Zr matrix. Notedly, due to the different growth directions of Shockley partial dislocations relative to nucleation points, there are two FCC-Zr variants after the HCP-to-FCC phase transformation. The content of these two variants accounts for 65% and 35% of the total FCC-Zr, respectively, appearing as lamellae morphology embedded parallelly within the matrix. The distribution of the two variants includes isolated distribution and adjacent distribution. For the adjacent distribution, a twinning relationship is observed between the two variants. Meanwhile, as an intermediate transition stage of the HCP-to-FCC phase transformation, stacking faults are observed at the boundaries of the FCC-Zr lamellae. These findings offer insights into the microstructural features and formation mechanisms of fatigue-induced HCP-to-FCC phase transformation.

A nano-twinned structure and tensile properties of a thermally cycled Fe-17Mn alloy

In the present study, the effect of thermal cycling on the microstructure and tensile properties of an Fe-17Mn (wt%) alloy were investigated. The thermal cycling was carried out until 10 times between a lower temperature (TL) of 25 °C and a upper temperature (TU) of 300 °C. A nano-twinned γ structure was observed at TU during thermal cycling through in-situ transmission electron microscopic observation. Many stacking faults, such as intrinsic I1, intrinsic I2, and twin-like T2 stacking faults, were observed in ε martensite at TL. The nano-twinned γ structure was formed by the stacking faults with a localized fcc structure in ε martensite during the ε → γ reverse transformation. Namely, half of the stacking faults with a localized fcc structure had the same crystallographic orientation as an initial γ austenitic phase, while the other half had a twin relationship with the γ austenite. The stacking faults with a twin relationship caused nano-twins during ε → γ reverse transformation. The volume fraction of nano-twins at TU was linearly proportional to that of ε martensite at TL, supporting the result that nano-twins in the γ phase resulted from preexisting stacking faults in ε martensite during ε → γ reverse transformation. Both the yield and ultimate tensile stresses of the γ austenite at TU increased with an increase in the number of thermal cycles, while the elongation decreased. The significant increase in yield stress at TU was due to the increase in dislocations and nano-twins introduced into γ austenite during thermal cycling.

Environmental susceptibility for all: A data-driven approach suggests individual differences in domain-general and domain-specific patterns of environmental susceptibility.

How we are influenced by our environment is a fundamental question in developmental science. Theories and empirical research have claimed that some individuals are susceptible to environmental influences and others are much less susceptible. The present study addressed four questions: (1) Is environmental susceptibility a continuous or categorical construct? (2) Is environmental susceptibility unidimensional (i.e., domain general) or multidimensional (i.e., domain specific)? (3) Are there genetic contributions to individual differences in environmental susceptibility? (4) What are the temperamental characteristics of different environmental susceptibility patterns? We used child- and mother-report data from a sample of 11-year-old twins (N = 1,507) and applied a novel data-driven approach to assess an environmental susceptibility space, based on simultaneous associations between multiple environmental exposures (18 measures relating to parenting, parent, peer, and twin relationships) and developmental outcomes (10 measures relating to empathy, prosocial behavior, aggression, and self-esteem). The results suggest that the environmental susceptibility space we assessed is better conceptualized as continuous and multidimensional. Different children showed susceptibility to different contexts and variation in domain-general versus domain-specific patterns. A comparison of distances between monozygotic and dizygotic twins within the space demonstrated genetic contributions. Finally, susceptibility patterns could not be differentiated based on a specific temperament trait, but rather related to temperament profiles.

Two Peas in a Pod? Development of Twin Relationships in Light of Twins’ Temperament Differences

This study examines the hypothesis that temperamental (dis)similarity is associated with twin relationship quality. In a longitudinal study that followed 322 monozygotic twins (who share close to 100% of their genes) and 1199 dizygotic twins (who on average, share 50% of their segregating genes) throughout childhood, mothers ( N = 1547) and fathers ( N = 536) reported on their twins’ relationships on at least one of four measurement points when the twins were between 3 and 8–9 years of age. Mothers also reported on the twins’ temperament. Negative associations were found between reports by both parents on the twins’ closeness and their temperament difference throughout childhood, while positive associations were found between twins’ conflict and their temperament difference in late childhood. Latent growth modeling indicated that the association between temperament differences and the twins’ mother-reported closeness was evident beyond the effect of zygosity. A different pattern was found for twin conflict: the more the twins differed in their temperament (specifically negative emotionality) with age, the more the conflict between them increased. Our findings support the hypothesis that personality similarities can contribute to positive relationships from early childhood, and vice versa, beyond the effect of genetic similarity.

Coherent twin-oriented Al3Sc-based precipitates in Al matrix

Al3(Sc,Zr,Ti) nanoparticles with an ideal twin-type orientation relationship to Al host matrix were found in cold-rolled and subsequently annealed Al-based alloy. Atomic-scale investigations using high-resolution scanning transmission electron microscopy identified particles that form prominent coherent (111) twin-type interfaces along their longer facets and semi-coherent twin interfaces on their shorter facets. Ab-initio calculations showed that a coherent Al/Al3Sc twin-like phase boundary corresponds to a local energy minimum. A model is proposed explaining the formation of the twin orientation relationship of an Al3Sc nanoparticle with the Al host matrix.

Room-temperature plastic deformation modes of cubic ZnS crystals

Light environment drastically alters the plasticity of zinc sulfide (ZnS) single crystals: they exhibit ductility in darkness while brittleness in lights. This study investigated their microscopic deformation modes of the light-environment-dependent plasticity, by using synchrotron X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning TEM (STEM) measurements. The XRD analyses disclosed that the ZnS crystals originally have two domains with almost the same volume fraction with a twin relationship and plastically deform in darkness, accompanying changes in the domain volume ratio (namely extinction of twins). It was also observed that the domain volume ratios become constant to be 0.2 at more than 10% plastic strains. The STEM analyses indicated that the deformation mode in darkness switches at around 10% plastic strain from slip deformation by glide of isolated partial dislocations to by simultaneous glide of paired partials inside the major domains. Although ZnS single crystals exhibited only a few percent of plastic strains in lights, localized glide of isolated partials and the resultant changes in domain volume ratios similar to in darkness were confirmed. That is, the deformation modes of ZnS at the initial stage were similar regardless of light environments although the macroscopic deformation behaviors were quite different.

A 3D characterization of equiaxed grains induced by mediated nucleation in additively manufactured Inconel 718

In additive manufacturing of Ni-based alloy IN718, what causes Icosahedral Short-Range Order (ISRO) or iQC mediated nucleation of equiaxed grains is still not understood. In order to have a better comprehension of the microstructure formation, a more comprehensive characterization both on grain structure and chemical heterogeneities must be achieved. In this work, a scanning electron microscope equipped with a focused ion beam (FIB) allowed to perform a 3D EDS chemical analysis and EBSD orientation mapping of the volume in an equiaxed grain zone. After the 3D reconstruction of the equiaxed grains has been performed, grain-to-grain orientation analysis allowed to analyze multiple twin boundaries orientation relationships in a volume containing hundreds of grains. Chemical mapping using EDS allowed to identify TiC inclusions from which a five-fold symmetry axis seem to emerge, indicating a potential nucleation site. Such areas were analyzed in transmission electron microscopy (TEM) to investigate the different present phases. The nucleation sequence and potential origin of mediated nucleation are further discussed, opening new prospects for grain refinement in additively manufactured nickel-based alloys.

The threshold effect of public debt on the twin imbalances: Evidence from MENA countries

ABSTRACT The study explains the non-linear relationship between total public debt and twin imbalances, across a panel of 15 countries in the MENA (Middle East and North Africa) region from 2003 to 2019. A panel data threshold model with fixed effects proposed by Hansen (1999) estimates two debt-to-GDP thresholds (36.71% and 72.99%), which determine three debt-to-GDP intervals in the twin relationship. Our findings show two interesting results. First, if the level of public debt to GDP is less than 36.71%, the model determines a negative relationship between the budget balance and the current account. Twin deficits are confirmed exclusively if debt-to-GDP is in the interval between 36.71% and 72.99%. A twin divergence is also confirmed if public debt-to-GDP is more than 72.99% (e.g. as in Egypt and Lebanon). The results of this study show that there is not a single debt threshold applicable to all MENA countries, and the regression results are robust for different specifications and estimation techniques. As a result, policymakers may be able to adjust the current account deficit by lowering the public-debt ratio, reducing government-funded sterile programs, and implementing appropriate austerity measures to mitigate the effects of the financial crisis.

Identification of a coherent twin relationship in functional perovskites from high-resolution reciprocal-space maps

Identification of a coherent twin relationship in functional perovskites from high-resolution reciprocal-space maps

Brazilian portuguese version of twin relationship questionnaire (TRQ-BR): Evidence of validity

Our aim was to adapt and validate a Brazilian Portuguese version of the Twin Relationship Questionnaire developed by Fortuna et al. (2010) and validated by H. Segal and Knafo-Noam (2019) in Israel. The respondents were 862 Brazilian mothers of twins ( N = 1724 twins) with mean age of 35 years (SD = 6.1). The majority of the sample lived in the Southeast (61.8%) or in the South (24.5%) of Brazil. We conducted a Multilevel Confirmatory Factor Analysis with the pair of twins as second level variable, and the five-factor structure (closeness, dependence, conflict, dominance, and rivalry) proposed by the original validation study of H. Segal and Knafo-Noam (2019) was confirmed. The final model retained 15 items out of 22 proposed in the original version of the questionnaire. Although the TRQ-BR has fewer items, the accuracy compared to the original questionnaire was maintained. Mixed Model Analysis (LMM) of TRQ scores were used to investigate twins’ relationships as a function of zygosity, age groups, and sex in order to provide evidence of convergent validity of the instrument. As expected, mothers perceived monozygotic twins (MZ) as more depedent than dizygotic twins (DZ). Furthermore, male twin pairs were considered more conflictive when compared to female twins. The present study showed that TRQ-BR is an adequate instrument for research purposes in the Brazilian population. It can also be useful for applied areas such as clinical and educational fields.

An atomistic study of self-accommodation martensite morphologies and microstructure evolution during forward and reverse martensitic transformations in single crystal and bicrystal NiTi alloys

The forward and reverse martensitic transformations in NiTi alloys with different crystallography conditions, in terms of [100]-oriented and [110]-oriented single crystal models as well as a bicrystal model possessing twist grain boundary, are studied deeply using molecular dynamics simulations. An atomic tracing method is proposed to identify the specific numbers of B19′ martensite variants, hence the self-accommodation martensite morphologies and microstructure evolution during cooling and heating are clearly demonstrated at the atomic scale. The triangular self-accommodation morphology consisted of three correspondence variants (CVs) possessing {1¯1¯1}M type I twin relationships is formed in the NiTi single crystals at the beginning of the martensitic transformation, and stays settled till the end of the transformation. Whereas three types of self-accommodation morphologies including triangular, “herring-bone” and mixed morphologies are formed in the bicrystal, due to the geometrical constraint induced by the grain boundary. The mixed self-accommodation morphology is unstable, which occurs briefly during martensitic transformation and thus evolves into “herring-bone” morphology ultimately. During reverse transformation, B2 austenite phase nucleates preferentially at the triple-junctions of the triangular self-accommodation morphology in NiTi single crystals, and propagates along the junction plane rather than the (001)M compound twin boundaries in the bicrystal alloy.