Displacive Transformation Research Articles

1,2‐Dichloroethane‐Assisted Defluorinative Ring‐Opening Reaction of DABCO and Polyfluoroalkyl Peroxides: Synthesis of Fluorinated N‐Ethyl Piperazines

Comprehensive SummaryA catalyst‐free and additive‐free ring‐opening reaction of polyfluoroalkyl peroxides, triethylenediamine (DABCO), and 1,2‐dichloroethane (DCE) has been developed for the defluorinative synthesis of structurally diverse piperazines featuring a fluoroenone framework and a N‐chloroethyl‐substituent with high Z‐stereoselectivity. The success of this three‐component reaction is attributed to the in situ generation of an active 1‐(2‐chloroethyl)‐1,4‐diazabicyclo[2.2.2]octan‐1‐ium (DABCO·DCE) salt, which judiciously acts as a formal N‐(2‐chloroethyl)piperazine equivalent in the defluorinative coupling with less‐studied aliphatic fluorinated substances. Impressively, this reaction accomplishes multi‐activation of robust C(sp3)‐F, C(sp3)‐Cl, C(sp3)‐O, and C(sp3)‐N bonds in a one‐pot process, offering a practical platform for the late‐stage functionalization of complex molecules. Furthermore, the resulting products can not only serve as versatile building blocks for the synthesis of fluorinated heterocycles, but also undergo C—Cl bond displacement transformations with N‐, O‐, and S‐nucleophiles.

Otherness, Belonging, and Production of Space: The Case of Amenity Migration in Fethiye, Türkiye

The article delves into the intricate dynamics of amenity migration and rural gentrification, investigating the challenges that arise when residents and newcomers encounter. Amenity migration, which occurs when individuals relocate to an area in search of desirable features, often leads to rural gentrification. This process involves economic and social changes brought about by the arrival of wealthier residents. While amenity migration can bring economic advantages, it also presents difficulties such as displacement and cultural transformations within the community. The study recognizes the concept of "otherness" is introduced to shed light on potential cultural and social conflicts between amenity migrants and the existing community. With a specific focus on British immigrants in Fethiye, Türkiye, the research aims to unravel how these immigrants establish connections with the place. It explores whether they identify themselves as locals or tourists and examines their sense of belonging within the spatial context. In order to comprehend the relational generation of distinctiveness based on person and place attributes in connection with relevant entities, the decision-tree method is employed. Moreover, an ANOVA matrix is used to recognize the most effective decision mechanisms among spatial and demographic attributes.

Deep Learning for Solar Panels Defect Classification Using Data Augmentation Strategies

The inspection and maintenance of solar panels face significant challenges due to the dangers involved in checking for potential defects in photovoltaic panels. However, the advancement of studies to facilitate this verification is limited by the lack of image datasets for training algorithms that can perform this task. Based on this principle, the use of Convolutional Neural Networks (CNNs) for training and Data Augmentation for creating artificial data from real images is common. With that said, this work aims to explore configurations and models of Data Augmentation for the classification of defects in solar panels using CNNs. The proposed methodology consists of four experimental stages, where the application of Zoom, rotation, horizontal displacement, and vertical displacement transformations are evaluated, followed by filtering the best results and combining them to find the ideal classification model. The performance of the model proved to be most effective when using a 35-degree rotation for creating artificial images, thus achieving an 88% F1-Score and 87.64% accuracy.

Phase transformation kinetics in Ti 575 titanium alloy during heat treatment: Role of the initial microstructure during ageing

Phase transformation kinetics were studied of Ti-575 titanium alloy during cooling from solution annealing and subsequent ageing using in-situ high energy X-ray diffraction. Cooling rates of 1.7, 10 and 30 °C·s−1 were applied from Tβ-60 °C therefore generating several microstructures with different size, morphologies or spatial distribution of α precipitates. Isothermal ageing at 500 °C for 1 h on these three microstructures allowed the study of the influence of the initial microstructural state upon phase transformation during ageing. For this purpose, the combined analysis of mass fraction, aβ mean lattice parameter and full width at half maximum is carried out for both cooling and ageing segment and is presented in this study. Displacive and diffusion-controlled transformations were recorded and seem to be cooling rate dependent, particularly with the precipitation of the α″ orthorhombic phase. The chemical and mechanical evolution of these transformation products will influence the phase transformation kinetics during cooling and following ageing hence conditioning the final microstructure and mechanical properties of this alloy.

Effects of Silicon and Aluminum Alloying on Phase Transformation and Microstructure Evolution in Fe–0.2C–2.5Mn Steel: Insights from Continuous–Cooling–Transformation and Time–Temperature–Transformation Diagrams

The impact of silicon and aluminum on phase transformation behavior, particularly bainite, and microstructure evolution in Fe–0.2C–2.5Mn steel are presented. Continuous–cooling–transformation (CCT) and time–temperature–transformation (TTT) diagrams are determined experimentally. An aluminum extended empirical formula is introduced to estimate the martensite start temperature (Ms) with a thorough assessment of existing formulae. Results show that aluminum significantly increases Ms and has a stronger influence on promoting ferritic microstructures than silicon. During continuous cooling, alongside bainite, formation of Widmanstätten structures is induced in aluminum‐alloyed steel at higher cooling rates due to increased prior austenite grain size. Silicon decelerates bainite transformation kinetics by enhancing austenite's chemical stability through carbon enrichment via preventing carbide precipitation and by strengthening austenite against displacive phase transformation via solid solution hardening. Although aluminum has similar effects, incubation time is shortened during isothermal treatment because of the increased driving force, which overcompensates for the retardation effects. A finer carbide‐free bainitic microstructure is achieved in aluminum‐alloyed steel with more pronounced film‐like retained austenite (RA) formation and superior carbon enrichment, improving RA stability and suppressing martensite–austenite island formation. Finally, with the proposed formula, an accurate approximation to experimental Ms is accomplished.

Deformation twinning as a displacive transformation: computational aspects of the phase-field model coupled with crystal plasticity

AbstractSpatially-resolved modeling of deformation twinning and its interaction with plastic slip is achieved by coupling the phase-field method and crystal plasticity theory. The intricate constitutive relations arising from this coupling render the resulting computational model prone to inefficiencies and lack of robustness. Accordingly, together with the inherent limitations of the phase-field method, these factors may impede the broad applicability of the model. In this paper, our recent phase-field model of coupled twinning and crystal plasticity is the subject of study. We delve into the incremental formulation and computational treatment of the model and run a thorough investigation into its computational performance. We focus specifically on evaluating the efficiency of the finite-element discretization employing various element types, and we examine the impact of mesh density. Since the micromorphic regularization is an important part of the finite-element implementation, the effect of the micromorphic regularization parameter is also studied.

Novel multi-degree-of-freedom force–displacement mixed control framework for low loading rate substructure hybrid testing

In substructure hybrid tests, imposing realistic multi-degree-of-freedom (MDOF) displacement and force boundary conditions on a specimen involves controlling several actuators to emulate the MDOF boundary conditions of the experimental substructure. This setup presents significant challenges for decoupling control in MDOF systems. Due to the typically high stiffness of the specimen in the axial direction, force control is preferred over displacement control, which has limited accuracy in this direction. Typically, force control in the axial direction is combined with simultaneous displacement control in the softer direction, forming an MDOF force-displacement mixed control scheme. This scheme transforms force control into displacement control in the inner loop in the axial direction to ensure safe loading. The scheme involves addressing two major challenges: the nonlinear force–displacement transformation and the nonlinear coordinate transformation from the local actuator space (LAS) to the global Cartesian coordinate (GCC) system. To address these challenges, the Modified Newton–Raphson iteration integrated with proportional integral plus feed-forward (MNR-PIFF) and incremental kinematic transformation integrated with proportional integral plus feed-forward (IKT-PIFF) methods are proposed. Based on these methods, a novel MDOF force–displacement mixed control (NMFDC) framework is developed for substructure hybrid testing. A 6-DOF cyclic test simulation using the NMFDC framework was conducted to demonstrate its superiority. Furthermore, a 6-DOF cyclic test and substructure hybrid test at low loading rates were performed to validate the NMFDC framework because of the loading equipment limit. Experimental results and numerical simulations indicate that the NMFDC framework achieves swifter response with lower error levels. For applications in fast and real-time hybrid testing, dynamic loading equipment need to be used, the PIFF controller in the NMFDC framework should be replaced by adaptive time delay compensation in future developments.

Enhanced corrosion resistance of Ti[sbnd]Al[sbnd]Mo alloy through solid state transformation driven by rapid solidification

Rapid solidification of undercooled liquid Ti50Al44Mo6 alloy was realized by electromagnetic levitation. Primary (βTi) dendrite grew rapidly from melt with decreasing temperature. As undercooling increased, nucleation rate and growth driving force of primary (βTi) dendrites increased. Growth velocity of primary (βTi) dendrite increased significantly, reaching 13.5 m·s-1 at the maximum undercooling (233 K). After solidification, primary (βTi) dendrite decomposed simultaneously through β→α→α2 transformation and martensite transformation β→γ. Homogeneity of solute distribution in primary (βTi) phase affects the solid-state phase transformation mode. Solid-state phase transition was mainly dominated by diffusion-controlled β→α→α2 transformation at small undercooling. Solid-state phase transition gradually was dominated by displacive martensite transformation at deep undercoolings, and corresponding microstructure was mainly characterized by more refined martensite needles. The refined microstructure and martensite transformation domination contributed to the formation of passivation films with improved corrosion resistance. Moreover, this weakens micro-galvanic effect, significantly reduces size of pits, maintains corrosion scales over pits to effectively alleviate the corrosion process, and consequently enhances corrosion resistance.

Revealing the displacive and diffusional phase transformations in a low-modulus Ti-12Nb alloy

Non-toxic and biocompatible Ti alloys with low modulus are promising biomaterials for implants. Except from the intensely studied metastable β Ti-Nb-based alloys, the α′-type Ti alloys could also present low modulus. But due to the low β stability, the microstructures of these α′ Ti alloys are sensitive to the heat-treatments especially to the cooling rates, which could lead to very different deformation mechanisms and mechanical properties. Thus, the phase transformations and the ‘microstructure–mechanical property’ correlation in the α′ Ti alloys need to be established. In this study, a novel Ti-12Nb wt% alloy was prepared and cooled from the β region temperature to obtain the water-quenched (WQ), air-cooled (AC), and furnace-cooled (FC) samples. Systematic investigations revealed the displacive β → α′ martensitic transformation in the WQ and diffusional β → β + α transformation in the AC and FC samples, in which the α′/α show evident variant selections. The inter-variant orientation relationships (ORs) among the α′/α variants and their ORs with the retained β phase, were found to be agree well with the classical Burgers OR. The high-resolution transmission electron microscope (HRTEM) studies show coherent α′/α′ interfaces in the WQ samples and α/β phase boundaries in the AC and FC samples, the abnormal β nanodomains inside the α′ martensites in WQ samples and the ω nanoparticles in the β phase of AC and FC samples were also presented. The tensile tests show increasing Young's modulus of 61.8 GPa, 77.1 GPa and 108.6GPa in the WQ, AC and FC samples, respectively. The difference in the modulus of these samples was explained by the Nb dependency of Young's modulus in the Ti-Nb alloy. The correlations between the microstructures, deformation mechanisms and mechanical properties were established. The {101¯1}α′ and {101¯2}α′ deformation twins inside the α′ martensites are believed to contribute to the good plasticity in the WQ samples, while the fine α + β structures and severely piled-up dislocations should account for the high yield strength and the poor plasticity in the AC samples. The abundant mobile dislocations in the α bands and deformation-induced ω needles in the surrounding β phase led to the best plasticity in the FC samples among all Ti-12Nb samples. This study systematically studied the displacive and diffusional transformations and the plastic deformation in a Ti-12Nb alloy, the results might pave the way for designing low-modulus biomedical α′ Ti alloy with low content of β stabilizing elements and provide insights into tailoring of the phase transformations and mechanical properties in these Ti alloys.

Diffusionless rotator-crystal transitions in colloidal truncated cubes.

Upon osmotic compression, rotationally symmetric faceted colloidal particles can form translationally ordered, orientationally disordered rotator mesophases. This study explores the mechanism of rotator-to-crystal phase transitions where orientational order is gained in a translationally ordered phase, using rotator-phase forming truncated cubes as a testbed. Monte Carlo simulations were conducted for two selected truncations (s), one for s = 0.527 where the rotator and crystal lattices are dissimilar and one for s = 0.572 where the two phases have identical lattices. These differences set the stage for a qualitative difference in their rotator-crystal transitions, highlighting the effect of lattice distortion on phase transition kinetics. Our simulations reveal that significant lattice deviatoric effects could hinder the rotator-to-crystal transition and favor arrangements of lower packing fraction instead. Indeed, upon compression, it is found that for s = 0.527, the rotator phase does not spontaneously transition into the stable, densely packed crystal due to the high lattice strains involved but instead transitions into a metastable solid phase to be colloquially referred to as "orientational salt" for short, which has a similar lattice as the rotator phase and exhibits two distinct particle orientations having substitutional order, alternating regularly throughout the system. This study paves the way for further analysis of diffusionless transformations in nanoparticle systems and how lattice-distortion could influence crystallization kinetics.

New tetragonal phases of titanium under shock loading - Predicted by molecular dynamics and ab initio calculations

Based on molecular dynamics simulations of the long-term evolution of polycrystalline titanium structures under shock waves, a novel phase (ζ) has been identified to emerge at shock pressures of approximately 20 GPa. This phase originates from the initial HCP phase and the disordered structure induced by the shock. The energy change characteristics during this phase transition are explained based on the Helmholtz free energy under volume constraints. The ζ phase comprises framework atoms (F-atoms) with fixed positions and unfixed interstitial atoms (I-atoms), exhibiting incomplete symmetry. Validation of this phase structure using ab initio simulations and machine learning potentials supports its existence as a metastable structure. The transformation from the initial α phase to ζ phase is diffusional transformation, while the reverse transformation is multistage displacive transformation.

Modeling of martensitic phase transformation accounting for inertia effects

As a diffusionless phase transformation, martensite evolves at the speed close to sound, with its kinetics and morphology dominated by the mechanical energy. However, the mechanism of martensitic phase transformation with the consideration of inertia is rarely investigated. This paper presents a multiphase-field model, where the transformation strain in martensite performs as the mechanical wave source, and in return the kinetic energy contributes to the driving force for phase transformation. As a result, the mechanical fields, i.e., the stress and the velocity, are derived according to the increment of the transformation strain. The propagation direction of the mechanical wave is corrected by considering the growth of the martensitic nucleus. With the 1D and 2D analysis, as well as the comparison against 2D static case, the mechanism of martensitic phase transformation is investigated, and the advantage of mechanical model accounting for inertia effects is illustrated.

Experimental investigation into lock-in characteristics of the composite hydrofoils

Abstract This study experimentally investigates the lock-in characteristics of structural vibration of hydrofoils made of CFRP composite material. The synchronous experimental measurement system constituted of high-speed framing camera, LDV, velocity and pressure regulation systems are set up. It can be found that the Com+45° hydrofoil accelerates the cavitation inception, and the Com-45° hydrofoil defers it. The evolution of the dominant vibration frequency and cloud cavity shedding frequency are semblable. As the cavitation evolution gradually develops, the larger dominant frequency reduces, while the lower frequency remains unchanged. The scope of frequency lock-in meets the magnitude relationship Com+45° hydrofoil> Com-45° hydrofoil> Com0° hydrofoil. The wavelet transformation of structural vibration displacement and non-dimensional cavity area shows that both f shed and f shed,lock-in exist in the lock-in condition.

Ferroelectric polymorphic phenomena in the layered antiferromagnet Cu(OH)2

Ferroic orders and their associated structural phase transitions are paramount in the understanding of a multitude of unconventional condensed matter phenomena. On this note, our investigation focuses on the polymorphic ferroelectric (FE) phase transitions of Copper(II) hydroxide, Cu(OH)2, considering an antiferromagnetic ground state. By employing the first-principles studies and group theory analysis, we have provided a systematic theoretical investigation of vibrational properties in the hypothetical Cmcm high-symmetry phase to unveil the symmetry-allowed ferroic phases. We identified a non-polar to polar ( Cmc21 ) phase transition, in which the displacive transformation is primarily responsible for the phase change induced by two B1u ( i.e. Γ2− ) phonon modes within the centrosymmetric phase. We also observed the existence of two polar structures with the same space group and different degrees of polarization ( i.e. Ps = 3.06 µC·cm−2 and Ps = 42.41 µC·cm−2), emerging from the high symmetry non-polar structure. According to the structural analysis the FE order, of a geometric nature, is driven by the Γ2− mode in which the O- and H-sites displacements lead the polar distortion with a minor contribution from the Cu-sites. Interestingly, the 3d 9:Cu2+ Jahn–Teller distortion coupled with the orientational shifts of O–H atoms enhances the polarization.

Expanded Stability of Layered SnSe-PbSe Alloys and Evidence of Displacive Phase Transformation from Rocksalt in Heteroepitaxial Thin Films.

Bulk PbSnSe has a two-phase region, or miscibility gap, as the crystal changes from a van der Waals-bonded orthorhombic 2D layered structure in SnSe-rich compositions to the related 3D-bonded rocksalt structure in PbSe-rich compositions. This structural transition drives a large contrast in the electrical, optical, and thermal properties. We realize low temperature direct growth of epitaxial PbSnSe thin films on GaAs via molecular beam epitaxy using an in situ PbSe surface treatment and show a significantly reduced two-phase region by stabilizing the Pnma layered structure out to Pb0.45Sn0.55Se, beyond the bulk limit around Pb0.25Sn0.75Se at low temperatures. Pushing further, we directly access metastable two-phase films of layered and rocksalt grains that are nearly identical in composition around Pb0.50Sn0.50Se and entirely circumvent the miscibility gap. We present microstructural and compositional evidence for an incomplete displacive transformation from a rocksalt to layered structure in these films, which we speculate occurs during the sample cooling to room temperature after synthesis. In situ temperature-cycling experiments on a Pb0.58Sn0.42Se rocksalt film reproduce characteristic attributes of a displacive transition and show a modulation in electronic properties. We find well-defined orientation relationships between the phases formed and reveal unconventional strain relief mechanisms involved in the crystal structure transformation using transmission electron microscopy. Overall, our work adds a scalable thin film integration route to harness the dramatic contrast in material properties in PbSnSe across a potentially ultrafast crystalline-crystalline structural transition.

A Mode Sensitivity Enhancement Method for Beam Bridge Using High-Density Strain Feedback

Abstract Closed-loop damage diagnosis method has attracted some attention in recent years; however, for lack of sufficient measuring points, it is difficult to achieve robust control of large structures cause the output dimension is not enough to meet the demand of system controllability and observability. On this basis, a mode sensitivity enhancement method for beam bridge using high-density strain feedback is proposed, in which high density dynamic strain measurements of the girder structure can be collected by distributed fiber sensor. Utilizing strain–displacement transformation relationship of the girder structure, the dynamic displacements can be obtained and used as output with high dimension to achieve the feedback control for eigenvalue sensitivity enhancement. To verify the proposed method, a series of numerical case studies of a beam bridge structure are performed, and it is demonstrated that the eigenvalue sensitivity can be enhanced effectively.

MMORF—FSL’s MultiMOdal Registration Framework

Abstract We present MMORF—FSL’s MultiMOdal Registration Framework—a newly released nonlinear image registration tool designed primarily for application to magnetic resonance imaging (MRI) images of the brain. MMORF is capable of simultaneously optimising both displacement and rotational transformations within a single registration framework by leveraging rich information from multiple scalar and tensor modalities. The regularisation employed in MMORF promotes local rigidity in the deformation, and we have previously demonstrated how this effectively controls both shape and size distortion, leading to more biologically plausible warps. The performance of MMORF is benchmarked against three established nonlinear registration methods—FNIRT, ANTs, and DR-TAMAS—across four domains: FreeSurfer label overlap, diffusion tensor imaging (DTI) similarity, task-fMRI cluster mass, and distortion. The evaluation is based on 100 unrelated subjects from the Human Connectome Project (HCP) dataset registered to the Oxford-MultiModal-1 (OMM-1) multimodal template via either the T1w contrast alone or in combination with a DTI/DTI-derived contrast. Results show that MMORF is the most consistently high-performing method across all domains—both in terms of accuracy and levels of distortion. MMORF is available as part of FSL, and its inputs and outputs are fully compatible with existing workflows. We believe that MMORF will be a valuable tool for the neuroimaging community, regardless of the domain of any downstream analysis, providing state-of-the-art registration performance that integrates into the rich and widely adopted suite of analysis tools in FSL.

Phase stability of a eutectic high entropy alloy under extremes of pressures and temperatures

Additively manufactured high-entropy alloys are of interest because of their unique combination of high yield strength and large ductility achieved with far-from-equilibrium crystalline phases and micro/nanostructure morphology. We report on the phase transformation and thermal equation of state of the eutectic high-entropy alloy (EHEA) Al18Co20Cr10Fe10Ni40W2, produced by laser powder-bed fusion (L-PBF). The EHEA was studied in a large-volume Paris–Edinburgh cell using energy-dispersive x-ray diffraction to a pressure of 5.5 GPa and a temperature of 1723 K. Static compression studies in diamond anvil cells using angle-dispersive x-ray diffraction extended the high-pressure structural data to 317 GPa at ambient temperature. The initial dual-phase nanolamellar face-centered cubic (FCC) and body-centered cubic (BCC) structure of Al18Co20Cr10Fe10Ni40W2 transforms into a single FCC phase under high pressure, with the BCC-to-FCC phase transformation completing at 9 ± 2 GPa. The FCC phase remained stable up to the highest pressure of 317 GPa. The measured thermal equation of state for the FCC phase of Al18Co20Cr10Fe10Ni40W2 is presented up to 5.5 GPa and 1473 K. We observed melting of the EHEA at 1698 ± 25 K at a pressure of 5.5 GPa, and the recrystallized sample shows an increased fraction of the CsCl-type (B2) phase at ambient conditions following release from the high-pressure high-temperature state. The BCC-to-FCC phase transition completion pressure is correlated with the nanolamellae thickness of the BCC layer in this diffusion-less transformation at ambient temperature.

Deformation twinning as a displacive transformation: computational aspects of the phase-field model coupled with crystal plasticity

Deformation twinning as a displacive transformation: computational aspects of the phase-field model coupled with crystal plasticity

Математична модель вимірювального перетворення віброзміщення ємнісним сенсором в часовий інтервал

Математична модель вимірювального перетворення віброзміщення ємнісним сенсором в часовий інтервал