Sequence Of Transformations Research Articles

Discontinuous phase separation, interstitial ordering and recrystallization during nitriding of FeNiCo medium entropy alloy

The sequence of phase transformations triggered as a consequence of inward diffusion of interstitial N during nitriding of FeNiCo medium entropy alloy was investigated. Recrystallized and cold rolled specimens of FeNiCo alloy were nitrided at 580 °C in a flowing ammonia gas atmosphere. Detailed microstructural characterization was carried out using scanning and transmission electron microscopies, X-ray and electron back scattered diffraction and atom probe tomography. Firstly, N supersaturation of about 2 at.% was observed to be established without any nanoscale chemical heterogeneities. Further increase in N-content triggered the occurrence of a discontinuous phase separation reaction, resulting in the formation of alternating Fe+N enriched and Co+Ni enriched phases with a characteristic lamellar morphology and cube-on-cube orientation relationship. The Fe+N enriched lamellae then undergo rapid interstitial N ordering, forming a γ′- Fe4N type nitride phase. The compositional partitioning however is only transient and is followed by a recrystallization of the lamellar microstructure into a compositionally homogeneous γ′-(FeCoNi)4N type matrix. Thermodynamic calculations show that this discontinuous phase separation reaction and subsequent composition homogenization via recrystallization results from isothermally forcing the alloy composition to first enter the metastable miscibility gap in the FeNiCo-N FCC solid solution (at N-supersaturation close to 2 at.%) and then moving out of the miscibility gap at high N contents, beyond 20 at.%. Role of volume misfits, the chemical partitioning and homogenization on the sequential occurrence of different transformations is discussed.

Transformation sequence of Mg-Si precipitates towards a precipitation of Mn and Cr containing phase governed by the high strain-rate collision during magnetic pulse welding of Al-Mg-Si alloy

This paper investigates the transformation of Mg-Si precipitates formed at an interface of an Al-Mg-Si alloy joint, welded by the high strain-rate collision during magnetic pulse impact welding. The Transmission Electron Microscopy (TEM) and Energy dispersive X-Ray (EDX) analysis of the precipitates reveal a nucleation of circular shape AlFeMnSiCr precipitate (size of ∼100 nm) from the dissolution of the native β″ (needle-shaped) precipitate. The AlFeMnSiCr phase can also reach a size up to several microns and grows into diverse shapes (rod-shaped, polygonal-shaped, ovoid-shaped). Based on the microstructural characterizations and on observations available in the literature including relevant data of Lodgaard and Ryum, the transformation sequence due to the high-speed collision can be described as follows: β″-Mg-Si (needle-shaped) → β’-Mg2Si (rod-shaped) ‘u-phase’ → Al(MnCrFe)Si (round-shaped) → Al(MnCrFe)Si +(+: Cr; Cu and/or Ni, rod-shaped, polygonal-shaped, ovoid-shaped). The comparison of samples welded at three different impact conditions (low impact intensity, intermediate impact intensity, high impact intensity) shows that the area fraction of the precipitates decreases with the increase of the impact intensity. The identification of the crystal structure of these different precipitates, from the nucleation to the final complete formation of the precipitation, can further enrich the transformation sequence in this paper. The role of the high strain kinematics on the deformation of the Al lattice and on the diffusion rate of alloying elements is also a perspective that can further explain this new observation of precipitation during magnetic pulse welding.

Utilization of electrolytic manganese residue and bauxite to synthesize zeolite a for pickle liquor adsorption: Characterization, mechanisms and performance

Electrolytic manganese residue (EMR) and its pickle liquor are extremely hazardous wastes that can cause significant environmental and biological hazards. In order to solve these problems, this paper used EMR and bauxite (BA) as the main raw materials to synthesize zeolite A (EMRZ), and carried out adsorption and purification of pickle liquor so as to realize the comprehensive utilization of EMR and BA. The study investigated the optimal parameters for the synthesis of zeolite and subsequently characterized the synthesized EMRZ. The characterization results revealed that the synthesized EMRZ exhibited notable attributes such as high purity, high crystallinity, and exceptional ion exchange capabilities. Subsequently, the synthesis mechanism of EMRZ was elucidated using XRD, FTIR, Raman spectroscopy, and MAS NMR techniques. The growth process of EMRZ involved three distinct stages, namely the growth induction period, rapid growth phase, and growth completion stage. More specifically, the transformation sequence was observed as follows: double four-membered rings (D4R) → β cages → α cages → zeolite A crystals. Besides, the migration and transformation of Si and Al in EMR were explored, and the mechanism was further expounded. In addition, the synthesis of EMRZ has been evaluated economically and compared with other zeolites synthesized by different methods. It was discovered that EMRZ has a higher economic value. Moreover, an investigation was conducted on the adsorption effect of EMRZ on impurity ions present in pickle liquor. It was discovered to be effective at removing impurity ions, suggesting that EMRZ is a feasible purification material for pickle liquor. Furthermore, the adsorption mechanism was ion exchange between impurity ions and Na ions, and EMRZ was successfully regenerated. The findings of the study validate the potential of EMRZ as a highly effective adsorbent for the treatment of pickle liquor, thereby offering a viable approach for the comprehensive utilization of EMR.

Total Syntheses of Colletopeptide A and Colletotrichamide A.

The first total syntheses of cyclic depsipeptides colletopeptide A and colletotrichamide A, have been accomplished. The key advanced intermediate, a cyclic tridepsipeptide derivative, was constructed using a sequence of transformations that features asymmetric Brown crotylation, cross metathesis, Yamaguchi esterification, ozonolysis, and macrolactamization. A late-stage incorporation of the mannose fragment completed the synthesis of colletotrichamide A, and the desilylation of the common intermediate gave rise to colletopeptide A, which led to unambiguous confirmation of the absolute stereochemistry of the aforementioned natural products.

Adiabatic deformations of quantum Hall droplets

We consider area-preserving deformations of the plane, acting on electronic wave functions through “quantomorphisms” that change both the underlying metric and the confining potential. We show that adiabatic sequences of such transformations produce Berry phases that can be written in closed form in terms of the many-body current and density, even in the presence of interactions. For a large class of deformations that generalize squeezing and shearing, the leading piece of the phase is a super-extensive Aharonov-Bohm term (\propto N^2∝N2 for NN electrons) in the thermodynamic limit. Its gauge-invariant subleading partner only measures the current, whose dominant contribution to the phase stems from a jump at the edge in the limit of strong magnetic fields. This results in a finite Berry curvature per unit area, reminiscent of the Hall viscosity. We show that the latter is in fact included in our formalism, bypassing its standard derivation on a torus and suggesting realistic experimental setups for its observation in quantum simulators.

Effect of phase transformation sequence on the low cycle fatigue properties of bainitic/martensitic multiphase steels

The three microstructures of bainite-fresh martensite, pre-martensite-bainite and carbide-free bainite were obtained by modulating the phase transformation sequence by the heat treatment process in the medium-carbon multiphase steel. The effects of martensitic and bainitic phase transformation sequences on the low cycle deformation behavior of multiphase steels were investigated. The results showed that the sample of the fresh martensite transformation process (295 °C–15 min) exhibited the best fatigue life among all processes under strain control. The samples of the preformed martensite transformation process (250 °C–295 °C) and the carbide-free bainite transformation process (295 °C–120 min) exhibited similar fatigue life. The sample of 295 °C–15 min possesses good resistance to plastic destabilization, resulting in higher fatigue life. The results of the EBSD crack propagation path analysis demonstrate that high carbon M/A islands block crack propagation in the sample of 295 °C–15 min, and high angular grain boundaries skew the crack propagation path. Fracture scans observed that secondary cracks in the sample of 250 °C–295 °C extend inward with aggregation of voids, which are more likely to form crack sources.

“Conversations with pigeons”: Capturing Players’ Lived Experience of Perspective Challenging Games

Video games are increasingly designed to provoke reflection and challenge players’ perspectives. Yet we know little about how such perspective-challenging experiences come about in gameplay. In response, we used systematic self-observation diaries and micro-phenomenological interviews to capture players’ (n=15) lived experience of perspective challenges in purposely sampled games including Hatoful Boyfriend, The Stanley Parable, or Papers, Please. We found a sequence of trigger, reflection, and transformation constituting perspective-challenging experiences, matching Mezirow’s model of transformative learning. Most of these were game-related or ‘endo-game’, suggesting that medium self-reflection could be an overlooked part of everyday game reflection and appreciation. Reflections were accompanied by a wide range of emotions, including frequent epistemic emotions, and emotions could change drastically even during short gameplay experiences. Actual perspective change or transformation was rare. We construct a model of granular types of triggers, reflections, and transformations that can aid reflective game design.

Mapping Molecular Hamiltonians into Hamiltonians of Modular cQED Processors.

We introduce a general method based on the operators of the Dyson-Masleev transformation to map the Hamiltonian of an arbitrary model system into the Hamiltonian of a circuit Quantum Electrodynamics (cQED) processor. Furthermore, we introduce a modular approach to programming a cQED processor with components corresponding to the mapping Hamiltonian. The method is illustrated as applied to quantum dynamics simulations of the Fenna-Matthews-Olson (FMO) complex and the spin-boson model of charge transfer. Beyond applications to molecular Hamiltonians, the mapping provides a general approach to implement any unitary operator in terms of a sequence of unitary transformations corresponding to powers of creation and annihilation operators of a single bosonic mode in a cQED processor.

BIOETHYLENE IS A PROMISING SOURCE OF ENERGY AND RAW MATERIALS FOR CHEMICAL INDUSTRY

The modern development of energy, chemical technology and other industrial production sectors is largely focused on processes using renewable raw materials. In the structure of non-traditional energy sources the lion’s share belongs to biomass. The paper provides an prospects assessment for using the available, predominantly solid Ukrainian bioresources, total available amount of which as wood, grain straw and other domestic and industrial organic waste is more than 120 million tons per year, to meet state’s needs both for lubricant and fuel materials and raw materials for chemical industry. A following sequence of transformations for this problem solution were investigated: cellulose of the original raw biomaterial — glucose — bioethanol — ethylene. The option of increasing the effectiveness of the latter stage was considered of obtaining bioethane from bioethanol due to the use of the latest catalysts. The results both physical and computational study of bioethanol dehydration process are given, that allowed to reveal the peculiarities of process kinetics when proposed catalyst using. It is shown that, in addition to reducing energy consumption, the catalyst provides 91 % selectivity for ethylene at ~95 % of the biomethanol conversion rate. The initial data for the design of highly efficient catalytic processes and reactors for the dehydration of bioethanol to ethylene were obtained. Bibl. 20, Fig. 2, Tab. 3.

Фазовые соотношения в системе SrO – GdO1.5 – FeO1.5

The lack of data systematization on the coexistence and stability of compounds formed in the SrO – GdO1.5 – FeO1.5 system at temperatures above 1100°C determines the interest in a more detailed study of this system. The research was focused on studying the stability of phases formed in the pseudobinary section (1-х)GdFeO3 – хSrO in the temperature range 1200- 1400°C in air. The interaction of components in the SrO – GdO1.5 – FeO1.5 system was studied by the method of annealing and quenching followed by physicochemical analysis. The phase composition and sequence of phase transformations were characterized by powder X-ray diffraction. Phase relations results in the SrO – GdO1.5 – FeO1.5 system in air were systematized. The formation of three complex perovskite-like oxides GdSr2FeO5, GdSrFeO4, Gd2SrFe2O7, located on the GdFeO3 – SrO binary section was established. Information on interplanar distances and reflection intensities of the GdSr2FeO5 compound has been supplemented and the existence of a miscibility gap for Gd1-xSrxFeO3-α solid solutions existing in the range 0.05≤x≤0.51 at 1400°C has been shown. Data on thermal stability of complex gadolinium ferrites based on GdO1.5 – SrO – FeO1.5 system has been expanded.

Elucidating the ball-milling-induced crystallization mechanism of amorphous NbCo1.1Sn via atomic-scale compositional analysis

NbCoSn-based half-Heusler is a promising thermoelectric material candidate due to its outstanding advantages. The recently introduced nanostructure tailoring via an amorphous precursor has greatly reduced thermal conductivity. Although the nanocrystallization of amorphous NbCo1.1Sn has been observed during ball milling, its mechanism remains unclear even though it affects the microstructure of the milled powder, which is important for optimizing the final microstructure after sintering. In this study, the crystallization mechanism of the amorphous matrix induced by ball milling was investigated and the phase transformation sequence of amorphous NbCo1.1Sn–NbCo2Sn full-Heusler was verified. In the ball milling process, the introduction of oxygen and the formation of niobium oxide were observed. Through the oxygen content comparison experiment and atomic-scale compositional research, i.e., atom probe tomography, it was proven that the introduced oxygen concentration determines whether the amorphous matrix crystallizes into NbCo2Sn full-Heusler or simply transforms into a Co-rich amorphous region. Furthermore, a ball milling-induced crystallization mechanism based on atomic diffusion and free volume theories in amorphous materials was suggested. In this mechanism, the free volumes become localized and some exceed the volume of the near constituent atom. Then, atomic diffusion occurs with different diffusivities depending on the atomic radius. In the Nb-depleted region originated by oxidation, the more dominant Co diffusion than Sn induces the Co-saturated region and relative Sn-depleted region. If this region reaches the chemical composition of NbCo2Sn, it transforms into NbCo2Sn full-Heusler via polymorphous crystallization through the ordering reaction in order to reach thermodynamical stability. The suggested crystallization mechanism deepens the understanding of the nature of the ball-milled feedstock and provides insight for optimizing the process to develop an ideal microstructure for realizing reduced thermal conductivity.

Research Progress on Cu-15Ni-8Sn Alloys: The Effect of Microalloying and Heat Treatment on Microstructure and Properties.

Cu-15Ni-8Sn alloy is the best choice to replace beryllium bronze alloy. This alloy has unparalleled application value in aerospace, ocean engineering, electronic information, equipment manufacturing, and other fields. However, the application of Cu-15Ni-8Sn alloy is challenged and limited because of a series of problems in its preparation and processing, such as easy segregation, difficult deformation, and discontinuous precipitation. It is an effective way to improve the comprehensive properties of Cu-15Ni-8Sn alloy using alloying design and process optimization to control the as-cast, deformed, and heat-treated microstructures. At present, it is a hot spot for scholars to study. In this paper, the grade generation, system evolution, and preparation technology development of Cu-15Ni-8Sn alloy are comprehensively reviewed. The phase transformation sequence of the Cu-15Ni-8Sn alloy is discussed. The influence of the type, amount, and existing form of alloying elements on the strength of Cu-15Ni-8Sn alloy and its mechanism are systematically summarized. Furthermore, the latest research progress on the effects of solid solution, cold deformation, and aging on the phase structure transformation and mechanical properties of Cu-15Ni-8Sn alloy is summarized. Finally, the future development trend of the Cu-15Ni-8Sn alloy is projected. The research results of this paper can provide a reference for the control of the microstructure and properties of high-performance Cu-15Ni-8Sn alloys used in key fields, as well as the optimization of the preparation process and alloy composition.

Effect of Tempering Time on Carbide Evolution and Mechanical Properties of a Nb-V-Ti Micro-Alloyed Steel

The evolution of the microstructure, the precipitation behavior, and the mechanical performances of Nb-V-Ti micro-alloyed steel prepared under different tempering time were studied using transmission electron microscopy (TEM), X-ray diffraction (XRD), and mechanical tests. It was found that the width of the martensite laths increases with the increasing tempering time. Several kinds of carbides, including M3C, M2C, M23C6, M7C3, and MC particles, were identified after tempering. The MC carbides remain stable during tempering, but the transformation behavior of other carbides was identified. The transformation sequence can be summarized as: M3C → M2C → M7C3 → M23C6. The strength decreases and the Charpy impact toughness increases gradually with the increase in the tempering time. The ultimate strength (UTS) decreases from 1231 to 896 MPa, and the yield strength (YS) decreases from 1138 to 835 MPa. The −40 °C Charpy impact toughness increases from 20 to 61 J as the tempering time increases from 10 min to 100 h. The evolution of carbides plays an important role in their mechanical performances.

Liquid matrix SHS manufacturing and heat treatment of Al–Mg composites reinforced with fine titanium carbide

Aluminum matrix composites reinforced with ultra-fine refractory titanium carbide feature a unique combination of properties. They are promising structural materials. Self-propagating high-temperature synthesis (SHS) is an affordable and energy-saving composite making process. It involves the exothermic reaction between titanium and carbon (or their compounds) directly in the melt. We studied the properties of SHS composites based on the AMg2 and AMg6 commercially available alloys reinforced with 10 wt.%TiC. We investigated the macroand microstructure of the samples with XRD and EDS analysis. It was found that the β-phase is separated from α-solid solution of aluminum as early as the air cooling stage. We conducted experiments aimed at studying the effects of additional heating on the sample structure and properties and found the optimal temperature and time values. We also proposed a phenomenological model of the structural transformation sequence. We compared the physical, mechanical, and manufacturing properties and corrosion resistance of the original cold-hardened AMg2N and AMg6N alloys and the composites before and after heat treatment. It was found that additional heating reduces porosity and maintains electrical conductivity. It was also found that the compressive strength and relative strain of the composite based on the AMg2 alloy change insignificantly, while for the AMg6-based composite the reduction is more significant. Heat treatment increases the composite hardness while maintaining sufficient plastic deformation. It is confirmed by the measured values of the relative strain and the reduction ratio close to that of the original matrix alloys. It was also found that the composites retain high resistance to carbon dioxide and hydrogen sulfide corrosion.

Infrastructure-Based Vehicle Localization through Camera Calibration for I2V Communication Warning.

In recent years, the research on object detection and tracking is becoming important for the development of advanced driving assistance systems (ADASs) and connected autonomous vehicles (CAVs) aiming to improve safety for all road users involved. Intersections, especially in urban scenarios, represent the portion of the road where the most relevant accidents take place; therefore, this work proposes an I2V warning system able to detect and track vehicles occupying the intersection and representing an obstacle for other incoming vehicles. This work presents a localization algorithm based on image detection and tracking by a single camera installed on a roadside unit (RSU). The vehicle position in the global reference frame is obtained thanks to a sequence of linear transformations utilizing intrinsic camera parameters, camera height, and pitch angle to obtain the vehicle's distance from the camera and, thus, its global latitude and longitude. The study brings an experimental analysis of both the localization accuracy, with an average error of 0.62 m, and detection reliability in terms of false positive (1.9%) and missed detection (3.6%) rates.

The welch-gong stream cipher - evolutionary path

This survey presents the rich history of the Welch-Gong (WG) Stream cipher family. It has been a long journey that lead the WG stream ciphers to become practical. The evolutionary path is a combination of mathematical endeavour and engineering striving to transfer pure mathematical functions to practical encryption algorithms for various applications. This path began as the pioneering work on WG transformation sequences with 2-level autocorrelation, leading to important breakthroughs in the early 2000’s, such as the submission of the first WG stream cipher to the eSTREAM competition in 2005 and the subsequent introduction of the WG stream cipher family WG(m, l), followed by extensive work on particular instances proposed for various (mostly lightweight) applications. A recent construction using a WG permutation is the authenticated encryption WAGE, submitted to the NIST LWC competition in 2019. The story of the WG stream cipher is by far not finished. The future opens numerous possibilities for WG stream ciphers and WAGE, with applications in both lightweight environments and in high-performance computing. We conclude the survey with new ideas and open problems.

Bulls-Eye: Active Few-Shot Learning Guided Logic Synthesis

Generating sub-optimal synthesis transformation sequences (“synthesis recipe”) is an important problem in logic synthesis. Manually crafted synthesis recipes have poor quality. State-of-the art machine learning (ML) works to generate synthesis recipes do not scale to large netlists as the models need to be trained from scratch, for which training data is collected using time consuming synthesis runs. We propose a new approach, Bulls-Eye, that fine-tunes a pre-trained model on past synthesis data to accurately predict the quality of a synthesis recipe for an unseen netlist. Our approach achieves 2x-30x run-time improvement and generates synthesis recipes achieving close to 95% quality-of-result (QoR) compared to conventional techniques using actual synthesis runs. We show our QoR beat state-of-the-art approaches on various benchmarks.

Darboux integrability for diagonal systems of hydrodynamic type

We prove that (1) diagonal systems of hydrodynamic type are Darboux integrable if and only if the corresponding systems for commuting flows are Darboux integrable, (2) systems for commuting flows are Darboux integrable if and only if the Laplace transformation sequences terminate, (3) Darboux integrable systems are necessarily semihamiltonian. We give geometric interpretation for Darboux integrability of such systems in terms of congruences of lines and in terms of solution orbits with respect to symmetry subalgebras, discuss known and new examples.

Reconceptualizing Archaeological Perspectives on Long-Term Political Change

In archaeology, along with a large sector of other social sciences, comparative approaches to long-term political change over the last two centuries have been underpinned by two big ideas, classification and evolution, which often have been manifest as cultural history and progress. Despite comparative archaeology's agenda to explain change, the conceptual core of these frames was grounded in the building of stepped sequences of transformation with expectations drawn from synchronic empirical snapshots in time. Nevertheless, especially over the last 70 years, archaeology has seen the generation and analysis of unprecedented volumes of data collected along multiple dimensions and a range of spatial scales. Compilation and comparison of these data reveal significant diversity along various dimensions, which have begun to create dissonance with key tenets, assumptions, and even the aims of extant, long-held approaches. Expanded conceptual framing with a shift toward a focus on explaining variation and change is necessary.

Phase stability and physical property for off-stoichiometric Ni-Mn-Sb alloys including 4O phase

Large magnetic field-induced strains can only be found in modulated martensite for Ni-Mn-Sb alloys, but the theoretical research on this alloy which is generally concentrated in the austenite and non-modulated martensite (NM) ignores the modulated martensite. Therefore, in this paper, we systematically study the relationship between phase stability, physical property and composition in the full series Ni-Mn-Sb Heusler alloys (Ni24+xMn12-xSb12, Ni24+xMn12Sb12-x, Ni24-xMn12+xSb12, Ni24Mn12+xSb12-x) including four-layered orthorhombic modulated martensite (4O) by the first principles calculations. For phase stability, we determined that the critical components of 4O for Ni24+xMn12-xSb12, Ni24+xMn12Sb12-x and Ni24Mn12+xSb12-x is × = 6, x = 6 and × = 4, respectively. There is no 4O phase within the concentration range considered for Ni24-xMn12+xSb12. Moreover, the martensitic transformation sequences are also determined. As for physical properties, the transformation temperatures from austenite to 4O and NM phases are predicted respectively. Meanwhile, the ternary magnetic moment diagram of austenite, 4O and NM phases is constructed. The maximum value of total magnetic moment is distributed in the Ni-excess Sb-deficient system, while the minimum value of that is distributed in the Mn-excess Sb-deficient system. The origin of the above observations is explained by the competition between the Jahn-Teller effect in the electronic structure and the strength of the covalent bond. The results in this paper are expected to provide information for the composition design and performance optimization of Ni-Mn-Sb alloy.