2,307 results on '"Short range order"'
Search Results
2. Pressure-induced transformations in a glass: In situ X-Ray diffraction and Raman spectroscopy.
- Author
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Abel da Silveira, Rafael, Evaristo, Leonardo, Soria Pereira, Altair, and Buchner, Silvio
- Subjects
- *
RAMAN spectroscopy , *X-ray diffraction , *DISTRIBUTION (Probability theory) , *DIAMOND anvil cell , *YIELD strength (Engineering) - Abstract
This study investigated the amorphous structure of a soda-lime-silicate glass sample (Na 2 O·2CaO·3SiO 2) utilizing in situ X-ray diffraction and Raman spectroscopy at pressures up to 30.3 GPa. These techniques provided insights into the structure of the glass under high pressure. Analysis of the short-range order of the glass in function of pressure was obtained from the pair distribution function, obtained from the diffractograms, and uncovered the emergence of a new amorphous phase at ∼10 GPa, identifiable through the appearance of new peaks in the data beyond this pressure value. Simultaneous measurements from Raman spectroscopy identified the elastic limit of the material at ∼6 GPa and were used to measure the inter-tetrahedral ∠Si–O–Si angle, which also displayed a ∂θ/∂P discontinuity within the 10 GPa range, due to the new amorphous phase. The study emphasized the potential of utilizing a monolithic glass sample within a diamond anvil cell, highlighting its ability to produce a sufficiently intense diffraction signal for structural analysis of glassy samples, provided that the angular aperture and energy employed are sufficiently high. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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3. Solutions to Complex Material-related Questions via Advanced Material Characterization Techniques.
- Author
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Klünsner, Thomas, Ressel, Gerald, Angerer, Paul, Brandl, Dominik, Bauer, Nicolas, Kosednar-Legenstein, Barbara, Sartory, Bernhard, Hönigmann, Thomas, Pogrielz, Thomas, and Keckes, Jozef
- Abstract
Copyright of BHM Berg- und Hüttenmännische Monatshefte is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)
- Published
- 2024
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4. Correlation of work function and stacking fault energy through Kelvin probe force microscopy and nanohardness in dilute α-magnesium
- Author
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Yiğit Türe, Ali Arslan Kaya, Hüseyin Aydin, Jiang Peng, and Servet Turan
- Subjects
Mg alloys ,Dilute alloys ,Work function ,Stacking fault energy ,Kelvin probe force microscopy ,Short range order ,Mining engineering. Metallurgy ,TN1-997 - Abstract
Electronic interactions of the Group 2A elements with magnesium have been studied through the dilute solid solutions in binary Mg-Ca, Mg-Sr and Mg-Ba systems. This investigation incorporated the difference in the ‘Work Function’ (ΔWF) measured via Kelvin Probe Force Microscopy (KPFM), as a property directly affected by interatomic bond types, i.e. the electronic structure, nanoindentation measurements, and Stacking Fault Energy values reported in the literature. It was shown that the nano-hardness of the solid-solution α-Mg phase changed in the order of Mg-Ca>Mg-Sr>Mg-Ba. Thus, it was shown, by also considering the nano-hardness levels, that SFE of a solid-solution is closely correlated with its ‘Work Function’ level. Nano-hardness measurements on the eutectics and ΔWF difference between eutectic phases enabled an assessment of the relative bond strength and the pertinent electronic structures of the eutectics in the three alloys. Correlation with ΔWF and at least qualitative verification of those computed SFE values with some experimental measurement techniques were considered important as those computational methods are based on zero Kelvin degree, relatively simple atomic models and a number of assumptions. As asserted by this investigation, if the results of measurement techniques can be qualitatively correlated with those of the computational methods, it can be possible to evaluate the electronic structures in alloys, starting from binary systems, going to ternary and then multi-elemental systems. Our investigation has shown that such a qualitative correlation is possible. After all, the SFE values are not treated as absolute values but rather become essential in comparative investigations when assessing the influences of alloying elements at a fundamental level, that is, free electron density distributions. Our study indicated that the principles of ‘electronic metallurgy’ in developing multi-elemental alloy systems can be followed via practical experimental methods, i.e. ΔWF measurements using KPFM and nanoindentation.
- Published
- 2024
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5. Software Tools for Integrating Special Quasirandom Structures and the Cluster Variation Method into the CALPHAD Formalism
- Author
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Samanta, Sayan and van de Walle, Axel
- Published
- 2024
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6. Correlation of work function and stacking fault energy through Kelvin probe force microscopy and nanohardness in dilute α-magnesium.
- Author
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Türe, Yiğit, Kaya, Ali Arslan, Aydin, Hüseyin, Peng, Jiang, and Turan, Servet
- Subjects
KELVIN probe force microscopy ,NANOINDENTATION ,ALKALINE earth metals ,STATISTICAL correlation ,ATOMIC models ,ELECTRON density ,DILUTE alloys - Abstract
• SFE of a solid-solution is closely correlated with its 'Work Function' level. • KPFM measurements give reliable results for correlating SFE and ΔWF levels. • KPFM measurements can show how alloying elements change ΔWF between eutectic phases. • WF difference between eutectic phases indicate the bond strength between them. • Electronic changes due to SRO can be revealed via ΔWF and nanoindentation readings. Electronic interactions of the Group 2A elements with magnesium have been studied through the dilute solid solutions in binary Mg-Ca, Mg-Sr and Mg-Ba systems. This investigation incorporated the difference in the 'Work Function' (ΔWF) measured via Kelvin Probe Force Microscopy (KPFM), as a property directly affected by interatomic bond types, i.e. the electronic structure, nanoindentation measurements, and Stacking Fault Energy values reported in the literature. It was shown that the nano-hardness of the solid-solution α-Mg phase changed in the order of Mg-Ca>Mg-Sr>Mg-Ba. Thus, it was shown, by also considering the nano-hardness levels, that SFE of a solid-solution is closely correlated with its 'Work Function' level. Nano-hardness measurements on the eutectics and ΔWF difference between eutectic phases enabled an assessment of the relative bond strength and the pertinent electronic structures of the eutectics in the three alloys. Correlation with ΔWF and at least qualitative verification of those computed SFE values with some experimental measurement techniques were considered important as those computational methods are based on zero Kelvin degree, relatively simple atomic models and a number of assumptions. As asserted by this investigation, if the results of measurement techniques can be qualitatively correlated with those of the computational methods, it can be possible to evaluate the electronic structures in alloys, starting from binary systems, going to ternary and then multi-elemental systems. Our investigation has shown that such a qualitative correlation is possible. After all, the SFE values are not treated as absolute values but rather become essential in comparative investigations when assessing the influences of alloying elements at a fundamental level, that is, free electron density distributions. Our study indicated that the principles of 'electronic metallurgy' in developing multi-elemental alloy systems can be followed via practical experimental methods, i.e. ΔWF measurements using KPFM and nanoindentation. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
7. Phase stability and the Portevin-Le Chatelier effect in Cr-Mn-Fe-Co-Ni High-Entropy Alloys
- Author
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Bloomfield, Maximilian and Jones, Nicholas Gwilym
- Subjects
Digital image correlation ,Electron microscopy ,High Entropy Alloys ,Mechanical properties ,Phase stability ,Portevin-Le Chatelier effect ,Serrated flow ,Short range order ,CALPHAD - Abstract
High-Entropy Alloys (HEAs) are a new class of metallic materials based on the combination of multiple principal elements, often with the intention to form a concentrated solid solution. It has been suggested that these solid solution phases could offer enhanced mechanical properties, due to fluctuations in their local atomic environments. However, at present, the thermodynamic stability of the solid solution phases which form in HEAs is poorly understood. This study aims to improve our understanding of phase stability in HEAs and investigate possible differences in the mechanical behaviour of dilute and concentrated solid solutions. Firstly, a systematic series of experiments is presented, which establish the effect of Co and Fe on the phase equilibria of the widely studied CrMnFeCoNi system. Both Co and Fe were found to stabilise the A1 matrix relative to the A2 and D8b phases at elevated temperatures but did not prevent the formation of ordered phases at 500°C. Alongside literature data, the results show that stable single-phase alloys are rare in the CrMnFeCoNi system. Secondly, a systematic assessment of the AlxCrFeCoNi alloy system showed that Al promotes the formation of B2, D8b and A2 phases, and improved our understanding of phase stability in this system, which has strong potential for developing alloys with desirable mechanical properties. In each study, experimental observations were used to test the fidelity of thermodynamic predictions from the latest CALPHAD databases. Whilst the predictions generally provided a close approximation of the observed phase equilibria, inaccuracies were common, especially at lower temperatures. Phase stability investigations also served to identify thermodynamically stable alloys, suitable for the investigation of the Portevin-Le Chatelier (PLC) effect - a discontinuous yielding phenomenon widely attributed to the repeated pinning of dislocations by mobile solute atoms over certain regimes of temperature and strain-rate. Under mechanical testing, the effect is generally associated with serrations in the materials flow curve and the localisation of strain into discrete bands. Serrated flow has been observed in several HEAs but the associated strain localisation behaviour has not yet been reported, so it is uncertain whether this behaviour is similar to the PLC effect in other alloy systems. Thus, a series of alloys based on the stable equiatomic quaternary alloy, CrFeCoNi, were selected to investigate the effect of compositional complexity on the PLC effect. Tensile testing, combined with digital image correlation, enabled simultaneous recording of the materials stress and local strain response across a range of temperatures. The results showed close similarities between the alloys at each temperature, indicating that compositional complexity did not have a dominant influence on the PLC effect. This suggested that the dislocation-solute interactions in the complex, concentrated solid solutions were not substantially different from those of more dilute solutions. Calorimetric investigations also revealed evidence of a varying degree of short-range order among the alloys, the influence of which warrants further investigation.
- Published
- 2022
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8. Vacancy Energetics and Diffusivities in the Equiatomic Multielement Nb-Mo-Ta-W Alloy
- Author
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Zhou, Xinran, He, Sicong, and Marian, Jaime
- Subjects
Engineering ,Materials Engineering ,Nb-Ta-Mo-W ,molecular statics ,vacancy energetics ,diffusivity ,short range order ,Chemical Sciences ,Chemical sciences - Abstract
In this work, we study vacancy energetics in the equiatomic Nb-Mo-Ta-W alloy, especially vacancy formation and migration energies, using molecular statics calculations based on a spectral neighbor analysis potential specifically developed for Nb-Mo-Ta-W. We consider vacancy properties in bulk environments as well as near edge dislocation cores, including the effect of short-range order (SRO) by preparing supercells through Metropolis Monte-Carlo relaxations and temperature on the calculation. The nudged elastic band (NEB) method is applied to study vacancy migration energies. Our results show that both vacancy formation energies and vacancy migration energies are statistically distributed with a wide spread, on the order of 1.0 eV in some cases, and display a noticeable dependence on SRO. We find that, in some cases, vacancies can form with very low energies at edge dislocation cores, from which we hypothesize the formation of stable 'superjogs' on edge dislocation lines. Moreover, the large spread in vacancy formation energies results in an asymmetric thermal sampling of the formation energy distribution towards lower values. This gives rise to effective vacancy formation energies that are noticeably lower than the distribution averages. We study the effect that this phenomenon has on the vacancy diffusivity in the alloy and discuss the implications of our findings on the structural features of Nb-Mo-Ta-W.
- Published
- 2022
9. Role of S/Se replacement on the structure of Ge20Se80-xSx glasses.
- Author
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Elhady, A F, Dongol, M, Ebied, M S, and Mahmoud, S
- Abstract
The effect of S-content on the medium-and short-range order structure of Ge
20 Se80−x Sx x = 0 , 15 , 30 at % , has been investigated by using high-energy X-ray diffraction. Medium-range order changes, as illustrated by the parameters of the first sharp diffraction peak, were discussed in the light of the microcrystalline model. The short-range order parameters have been obtained by the analysis of the first two peaks in the curve of the total radial distribution function. The current results indicate that S-atoms enter the host network of the stiffness composition (Ge20 Se80 ) as compensation of Se-atoms. [ABSTRACT FROM AUTHOR]- Published
- 2023
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10. The analysis of local structural effects in alloys using total scattering and reverse Monte Carlo techniques
- Author
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Owen, Lewis Robert, Stone, Howard J., Playford, Helen Y., and Tucker, Matthew G.
- Subjects
669 ,Short range order ,Alloys ,Pair Distribution Function ,Total Scattering ,Reverse Monte Carlo - Abstract
Over the years `short-range order' (SRO), whereby the local atomic arrangement differs from that of a random distribution, has been used to explain physical phenomena such as thermodynamic discontinuities, increased strength, anomalous electrical resistivity and magnetic variations in a host of alloys. However, due mainly to experimental difficulties and the complexity of the calculations required for the analysis of diffuse scattering, such work has been largely abandoned and hence quantification and assessment of SRO is notably sparse in the literature. The recent development of reverse Monte-Carlo (RMC) methods for the analysis of total scattering data has opened a promising route for the assessment of a material's local environment and has already provided important insights into a host of complex chemical systems, including liquids, network glasses, nano-materials, functional oxides and metal organic frameworks. The work presented in this thesis focuses on the development of a new methodology for the analysis of local structural effects in metallic systems using total scattering, and the first systematic application to the study of alloys. The simulation of total scattering data from a range of model structures is used to show that the information content of total scattering functions, in particular the pair distribution function (PDF), is sufficiently high to allow the assessment of different types and degrees of short-range order. This is supported by a demonstration of how such orders can be quantified from large box models, produced by fitting total scattering data using the RMC algorithm, with the mathematical analyses outlined. This culminates in a proposed methodology for the analysis of SRO in alloys. Having developed this analytical methodology it is subsequently applied to a number of interesting alloy systems. To demonstrate the efficacy of this methodology it was first applied to the study of a sample of Cu$_{3}$Au - the classically cited case example of a system demonstrating SRO prior to an ordering transition. This experiment provides new insight into this well characterised transition, and also demonstrates the significance of data processing errors on the generation of artefacts in large box modelling. The technique is also applied to the study of the industrially important family of nickel superalloys, assessing ordering in the gamma-phase alloy Ni-Cr and the sublattice orderings occurring in L1$_{2}$ alloys. Next, the use of the technique for the analysis of local strains exhibited in a lattice is presented. A series of models is used to demonstrate how the PDF is expected to change under variations in local strain caused by increased concentration of atomic substitution and variation in atomic radii. This is subsequently used to study the characteristic high-entropy alloy (HEA) CrMnFeCoNi. Through analysis of the PDF, it is demonstrated that the level of local strain exhibited in this alloy is not significantly different from those of other related compositionally simpler alloys. This result is highly significant as it challenges one of the core principles of the field - that the lattices of HEAs are necessarily highly strained. Finally, the energetics of ordering reactions are briefly considered and used to justify some of the observed transformations presented in the earlier work. Together, the body of work in this thesis shows how the total scattering technique can be used to provide valuable insight into a host of interesting local phenomena occurring in alloy systems. It is hoped that this will open up a new field of study into these effects, and ultimately guide the creation of new alloys based on these structure-property relationships.
- Published
- 2018
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11. Multi-principal element alloys from the CrCoNi family: outlook and perspectives
- Author
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Francisco G. Coury, Guilherme Zepon, and Claudemiro Bolfarini
- Subjects
High entropy alloys ,Multi-principal element alloys ,Strengthening mechanisms ,Deformation mechanisms ,Short range order ,Alloy design ,Mining engineering. Metallurgy ,TN1-997 - Abstract
A great research effort is being employed in the development of Multi-Principal Element Alloys (MPEAs). The major interest on these alloys lies in the vast compositional field in which they exist, which provides a challenging opportunity for designing alloys with improved combinations of properties. Among the MPEAs produced to date, compositions containing large contents of Cr, Co and Ni, including the recently developed and well-studied Cr33Co33Ni33 alloy (in atomic %), are among the most promising for structural application due to their outstanding combination of strength and ductility. The present work is a critical review of some of the important publications on the topic. First, we give a brief history of the MPEA development in recent years highlighting the importance of CrCoNi alloys. Next, a brief explanation of the phase equilibria in this system is given. The third and major part of this work consists in a compilation followed by critical discussion of the main studies explaining the good mechanical properties of these alloys. This compilation includes what is known about grain refinement, solid solution strengthening, twinning and transformation induced plasticity and short-range ordering. The major controversies on the area are pinpointed as well as directions for future research. Several other CrCoNi alloy properties are also reviewed, including what has been published on wear, fatigue, corrosion, oxidation and hot deformation. High Cr-containing alloys have excellent combinations of strength, ductility, corrosion (in saline environments) and oxidation resistance, surpassing some of the best performing Ni-superalloys.
- Published
- 2021
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12. Atomistic simulations of dislocation plasticity in concentrated VCoNi medium entropy alloys: Effects of lattice distortion and short range order
- Author
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Amin Esfandiarpour, Rene Alvarez-Donado, Stefanos Papanikolaou, and Mikko Alava
- Subjects
non-equiatomic medium entropy alloys ,hybrid MD/MC ,depinning stress ,stress-controlled loading ,mechanical properties ,short range order ,Technology - Abstract
Face-centered cubic (fcc) high and medium entropy alloys (H/MEAs) have been shown to display superior mechanical properties at low temperatures, but significant improvement of their strength at high temperatures is required for industrial applications at extreme conditions. Recently, it has been shown that the breakthrough of the MEAs from equiatomic/near-equiatomic to non-equiatomic ratios leads to strong MEAs with good ductility. To design new H/MEAs, we consider two important factors that may influence strength: the chemical composition and chemical short range order (CSRO). In this study, we investigate the depinning stress (σc) as a criterion of strength of several compositions of VCoNi concentrated solid solution alloys (CSSAs) including V0.33Co0.33Ni0.33, V0.35Co0.2Ni0.45, V0.33Co0.17Ni0.5, and V0.17Co0.33Ni0.5 at 5 K and 300 K, using atomistic simulations. The chosen interatomic potential is shown to be reliable by comparing experimental/ab initio values and calculated parameters such as lattice constant, shear modulus, depinning stress, and temperature variation of stacking fault width for equimolar VCoNi. We find a good agreement between experimental friction stress and the depinning stress extracted from our results for equimolar VCoNi. Also, we find that Vclusters are the main pinning points of dislocations, and With a random distribution of atoms, we find that the alloy composition V0.33Co0.17Ni0.5 displays the largest depinning stress at both 5 and 300 K. Furthermore, to investigate how CSRO affects the strength of these alloys, we design CSRO into the microstructure using two different methods: In the first method, hybrid Molecular-dynamics/Monte-Carlo simulations were employed to simulate annealing at various temperatures. We observe that such simulations create CSRO so that it increases with decreasing annealing temperature. Recently, the CSRO motif and its concentration in an equimolar VCoNi have been determined by experiment. By modeling this experiment, we also implemented the CSRO into microstructure as the second method. By using both methods, the effect of CSRO on the magnitude of the depinning stress is discussed. It was shown that in both methods, CSRO significantly influences the strength of non-equimolar VCoNi alloys.
- Published
- 2022
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13. Thermodynamic calculations using reverse Monte Carlo: convergence aspects, sources of error and guidelines for improving accuracy.
- Author
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Agrahari, Gargi and Chatterjee, Abhijit
- Subjects
- *
MONTE Carlo method , *PHASE diagrams - Abstract
The reverse Monte Carlo (RMC) method has been widely used to gain 3D structural ordering information from experimental scattering data. Recently, we have introduced a novel application of RMC, viz., calculating thermodynamic properties of crystalline materials, construction of phase diagram and rapid estimation of the local structural order [Agrahari and Chatterjee, Physical Review E, 104, 044129 (2021).]. The method has been shown to be accurate and orders-of-magnitude faster than standard Monte Carlo simulations – this makes the approach quite promising. However, the error in RMC has never been systematically quantified. The goal here is to perform a thorough investigation into the types of error in RMC-based thermodynamic calculations, assess the relative magnitude of these errors, and develop strategies to improve the accuracy. Some of the conclusions presented are also relevant to previous experiment-based RMC implementations. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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14. Short and long range ordering on dielectric relaxation of AgI doped glass-ceramic.
- Author
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Poddar, Asmita, Halder, Prolay, Roy, Madhab, and Bhattacharya, Sanjib
- Subjects
- *
DIELECTRIC relaxation , *CHARGE carriers , *DIELECTRICS , *ZINC oxide - Abstract
The dielectric relaxation process of an amorphous glassy system, AgI - CdO -V 2 O 5 -P 2 O 5 - ZnO has been reported here. Electric modulus formalism has been carried out to explore the dielectric behavior of the as-prepared samples and the experimental results have been analyzed in the light of some theoretical models. Study of the nature of peak separation between imaginary components of electric modulus and the complex impedance plots reveals that the present system with lower AgI content should have a tendency to exhibit long range order for the relaxation of charge carriers. On the other hand, the present system with higher AgI content exhibits a relaxation process, dominated by short range order of charge carriers. This relaxation process is found to be Debye type for AgI doping up to x = 0.20 and it becomes non-Debye type beyond that composition range. [ABSTRACT FROM AUTHOR]
- Published
- 2025
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15. Uncovering the origin of unique elemental distribution behaviors of Vanadium in high entropy alloys.
- Author
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Shi, Panhua, Yu, Jianqiao, Yao, Baodian, Si, Jiaxuan, Wu, Lu, Wu, Xiaoyong, and Wang, Yuexia
- Subjects
- *
SOLUTION strengthening , *ENTROPY , *MECHANICAL alloying , *CRYSTAL grain boundaries , *CHARGE transfer , *VANADIUM - Abstract
Owing to the unique elemental character, Vanadium (V) has recently gained growing interest in the field of high entropy alloys. It is known that V benefits in the mechanical strength in alloys, accompanying by the unique elemental distribution behaviors. In this work, we concentrate on the mechanism of V's distribution characters in VFeCoNi, which is similar to that of Cr in CrFeCoNi, by evaluating element inherent electronegativity, charge transfer, atomic volume, Voronoi volume and the atomic stress resulting from the combined effects of these factors. Another unique character of electronic interaction in the t 2g and e g orbitals has been observed, which contributed to the fluctuation of atomic volume, thus enhancing solid solution strengthening. The tensile stress-strain tests show that the chemical ordering of V enhanced mechanical strength, especially for the grain boundary. Our work will provide new insights into the nanoscale distribution of V elements and the related macroscopic mechanical effects. [Display omitted] • V atoms exhibit a preference for sublattice sites. • Negative atomic stress of V atoms leads them tooccupy second-nearest neighboring sites. • V features the d electron flexibility. • Chemical ordering of V enhances mechanical properties. [ABSTRACT FROM AUTHOR]
- Published
- 2024
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16. Role of S/Se replacement on the structure of Ge20Se80-xSx glasses
- Author
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Elhady, A F, Dongol, M, Ebied, M S, and Mahmoud, S
- Published
- 2023
- Full Text
- View/download PDF
17. The effects of vacancy ordering on diffusion: a statistical study.
- Author
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Stotts JC, Tang X, Thompson GB, and Weinberger CR
- Abstract
In this paper we investigate the interconnection between vacancy-ordered phases and vacancy self-diffusion. Here, we investigate three ordered phases on a square lattice with energetics defined by two separate Hamiltonians. In the first case we used a classical antiferromagnetic Ising model Hamiltonian in order to generate a 'checkerboard' type ordered structure. In the second case, we used a modified Ising model with competing influence of second and third nearest-neighbors, which resulted in both 'hatch' and 'labyrinthine' structures, depending on concentration. To understand how vacancy-ordering affects diffusion, we determined the tracer diffusivity using rejection-free kinetic Monte Carlo and compared disordered and ordered structures. Finally, we developed an analytical model describing diffusion in the ordered 'checkerboard' structure and found that it was able to predict apparent activation energies in the ordered and disordered structures. Our results suggest that it is short-range order rather than long-range order that most significantly affects tracer diffusion., (Creative Commons Attribution license.)
- Published
- 2024
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18. Comparative analysis of the short-range order in Al-Ge-Ni and Al-Ge-Fe melts.
- Author
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Roik, Oleksandr, Yakovenko, Oleksiy, Kazimirov, Volodymyr, Sokol'Skii, Volodymyr, and Golovataya, Nataliya
- Subjects
- *
ATOMIC clusters , *COMPARATIVE studies , *MELTING , *LIQUID alloys - Abstract
The comparative analysis of structure in ternary Al-Ge-Fe and Al-Ge-Ni melts has been performed in a wide concentration range using results of X-ray diffraction experiment and RMC simulations. The analysis of total S(Q) and partial SGe-Ge(Q) structure factors has shown that germanium atoms are present in two structural states: in the local environment of Fe(Ni) atoms and as part of clusters with structure of liquid germanium. Formation of these clusters is a result of displacement of Ge atoms outside the nearest environment of Fe(Ni) atoms due to competition effect between Al and Ge atoms. It has been established that ratio between partial nearest neighbour distances R1(Al-Ni)
- Published
- 2021
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19. Local Ordering Tendency in Body-Centered Cubic (BCC) Multi-Principal Element Alloys.
- Author
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Zhao, Shijun
- Subjects
- *
ALLOYS , *MONTE Carlo method , *CRYSTAL lattices , *ELASTICITY - Abstract
The recent development of high-entropy alloys (HEAs) has opened a new avenue for alloy design by incorporating multiple principal elements into a simple crystal lattice. In HEAs, short-range chemical ordering may arise due to the different mixing properties of various constituent elements. In this work, we explore the trend of elemental arrangement in five typical body-centered cubic (BCC) multi-principal element alloys (MPEAs), including CrFeV, HfNbZr, TaVW, NbTaV, and TaTiV. Combining the Monte Carlo method and density-functional theory calculations, we calculated the evolution of short-range order (SRO) parameters in these alloys at 500 K. Our results demonstrated that all these MPEAs might develop a certain degree of SRO, depending on the mixing properties of different element pairs. Using a modified quasi-chemical model, we show that the SRO values in these MPEAs can be accurately predicted as long as the mixing enthalpy values between different atomic pairs are known. The presence of SRO has a profound impact on the local structure of MPEAs, which further alters the electronic and elastic properties of MPEAs. Our results provide a theoretical understanding of the basic alloy structure of novel MPEAs, which is an essential step toward tailoring their properties. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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20. Metal Nanocatalysts
- Author
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Li, Yuanyuan, Frenkel, Anatoly I., Iwasawa, Yasuhiro, editor, Asakura, Kiyotaka, editor, and Tada, Mizuki, editor
- Published
- 2017
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21. Ion distribution models for defect fluorite ZrO2 - AO1.5 (A = Ln, Y) solid solutions: I. Relationship between lattice parameter and composition.
- Author
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Bukaemskiy, Andrey A., Vinograd, Victor L., and Kowalski, Piotr M.
- Subjects
- *
SOLID solutions , *LATTICE constants , *FLUORITE , *LINEAR equations , *IONS - Abstract
The composition dependence of the lattice constant, a , in A x B 1- x O 2-0.5 x V 0.5 x , fluorite-type solid solutions (B = Zr, A = {Nd-Yb, Y}, V = oxygen vacancy) is characterized by changes in slope at x ~ 1/3, which cannot be described by existing models. Moreover, over the range of 0.15 ≤ x ≤ 1/3 the a vs. x data on all systems can be fitted with a linear equation, a = q + rx , with the same intercept, q , however, over the range of 1/3 ≤ x ≤ 1/2 the data bifurcate requiring different intercepts for A={Nd-Gd] and for A={Dy-Yb,Y} systems, implying steeper slopes for the first group. An adequate description is achieved via close-packing models involving two anion species, O2- and V, and three combinations of cation species, namely 8A, 7B, 8B (0 ≤ x ≤ 1/3), 7A, 8A, 7B (1/3 ≤ x ≤ 1/2) and 8A, 6B, 7B (1/3 ≤ x ≤ 1/2), that take into an account the constraint on the average coordination number, K (x), of K (x) = 8 – 2 x and two additional short-range order (SRO) constrains referring to vacancy-vacancy avoidance and vacancy-to-Zr association. The consistent fit to a vs. x data with these models requires the effective size of the oxygen vacancy to be larger than the radius of the oxygen anion by ~11%. The latter observation seems to play an important role in the understanding of structure-property relationships in A x B 1- x O 2-0.5 x V 0.5 x systems. Average coordination numbers of A and B cations in A x B 1- x O 2-0.5 x solid solutions (B = Zr; A = Ln , Y) deviate from the total average coordination number, K = 8 − 2 x , due to cation-vacancy association effects. Two contrasting solutions to the total average seem to exist within the range of 1/3 < x < 2/3. Image, graphical abstract [ABSTRACT FROM AUTHOR]
- Published
- 2021
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22. A Review on Developments in Magnesium Alloys
- Author
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A. Arslan Kaya
- Subjects
magnesium alloys ,doping of magnesium ,dilute alloys ,short range order ,LPSO phases ,rare earth alloys ,Technology - Abstract
In order to facilitate the understanding of the current research efforts and directions, this article first introduces the anomalous/problematic features of magnesium (Mg) and presents the recent approach of stacking fault energy (SFE)–based alloying element selection to lessen or eliminate this problem. Stacking fault energy computations via ab initio techniques necessitate an understanding of the free electron density distribution around atoms in a solid solution. Therefore, the assessment of the role of atoms by also considering the possibility of short range order (SRO) formation rather than a random solid solution has been revisited. Two possible types of SRO have been indicated. The relevant electronic interactions between the host Mg and the alloying element atoms are more clearly incorporated in a generally less known model by Miedema based on atomic-level thermodynamics rather than in Hume–Rothery rules. This more successful approach has also been addressed here. An evaluation founded on these premises, introducing the relatively more recent Mg alloy systems, has been given in terms of their achievements toward healing the problematic features of Mg alloys. The spectrum of alloy systems discussed ranges from doping of Mg to dilute alloy systems and to some rich alloy systems that offer remarkable properties. Among the first category, an unorthodox addition, doping with oxygen, and its implications, has been presented. The dilute alloy systems and their compositional design based on SRO and SFE together with their potentials have been reviewed. Among the rich alloy compositions, the most interesting precipitate systems, that is, the ones involving order and intermetallic formations, long-period stacking order phases, and quasi-crystals, have been discussed. Among all the alloying elements, one that deserves particular attention, calcium, with its implications such as being economical, offering environmentally friendly Mg metallurgy, and remedial effects on the shortcomings of engineering properties, and a closely related issue of calcium oxide (CaO) addition have been scrutinized. This article also makes an attempt to point out the future directions throughout the text, whenever possible.
- Published
- 2020
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23. ePDFpy: A Python-based interactive GUI tool for electron pair distribution function analysis of amorphous materials.
- Author
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Kim, Minhyo, Kim, Pilsung, Bassiri, Riccardo, Prasai, Kiran, Fejer, Martin M., and Lee, Kyung-ha
- Abstract
ePDFpy is an interactive analysis program with a graphical user interface (GUI), designed to process the electron Pair Distribution Function (PDF) analysis of diffraction patterns from Transmission Electron Microscope (TEM), to identify the local atomic structure of amorphous materials. The program offers a user-friendly Python-based interface, providing a straightforward and adaptable workflow for PDF analysis. Various optimization and fitting processes were implemented to accurately reduce the electron diffraction data, including center-fitting and elliptical correction of diffraction data. An improved parameter-estimation feature is available to enhance the efficiency of the fitting process, along with an interactive GUI. ePDFpy will be freely distributed for academic purposes, with additional features, including a beam mask drawing module. Program Title: ePDFpy CPC Library link to program files: https://doi.org/10.17632/sym3sfnh7w.1 Developer's repository link: https://github.com/GWlab-SKKU/ePDFpy Licensing provisions: GNU GPLv3 Programming language: Python Nature of problem: The general process of pair distribution function analysis consists of two major steps: image process on diffraction pattern and fitting appropriate parameters. Both of the procedures are affected by the user's proficiency, which can be responsible for producing inconsistent results and inefficiency. Thus, accurate calculation methods along with fully automated feature are required to enhance the quality of the analysis result. Solution method: ePDFpy offers an unbiased automated image process based on a computer vision algorithm to produce the consistent output of intensity profiles from diffraction patterns. In addition, converting the data structures into a multi-dimensional array enables efficient multi-parameter fitting features by performing parallel computation. All of these features are accomplished using various open-source libraries in the Python community, along with an interactive GUI. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
24. Structural and electrical properties of Bi2YSnVO9 ceramic.
- Author
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Gupta, Prabhasini, Mahapatra, P.K., Choudhary, R.N.P., and Acharya, Truptimayee
- Subjects
- *
FREQUENCY spectra , *HYSTERESIS loop , *ELECTRIC impedance , *RAMAN spectroscopy , *X-ray spectra , *DIELECTRIC relaxation - Abstract
In the present communication, the structural, microstructural, dielectric, and electrical (impedance, conductivity, polarization) characteristics of a new member of the Aurivillius family (Bi 2 YSnVO 9), processed through a high-temperature solid-state reaction method, have been reported. The formation and content of the compound at room temperature have been analyzed by using X-ray diffraction, Raman spectra, and energy dispersive X-ray spectrum. Analysis of frequency and temperature dependence of impedance and electrical modulus spectroscopic data and Nyquist plots has shown the contributions of grains and grain boundaries to the electrical properties of the prepared material. Detailed dielectric characterizations carried out in a broad spectrum of temperature and frequency have helped to explain the polarization and relaxation mechanism of the sample. The appearance of a hysteresis loop at room temperature and an increasing trend of dielectric constant with temperature to get expected peak at high temperature suggests the existence of ferroelectricity in the material, as of other members of the family. The activation energy of the sample is estimated as 1.19 eV which implies the activation of doubly ionized oxygen vacancy and the electrons released conduct via correlated barrier hopping mechanism. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
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25. Solid solution softening in a Al0.1CoCrFeMnNi high-entropy alloy.
- Author
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Cheng, Q., Xu, X.D., Li, X.Q., Li, Y.P., Nieh, T.G., and Chen, M.W.
- Subjects
- *
SOLUTION strengthening , *ALLOYS , *SOLID solutions - Abstract
Solute effects on high-entropy alloys of equiatomic proportions are scientifically intriguing because there is no such well-defined "solute" and "solvent" atoms compared to those of conventional single principal element alloys. To date, most of the face-centered cubic alloys exhibit solid solution strengthening rather than softening due to the interactions between dislocations and solute atoms. Here, we present the careful experimental measurements and demonstrate solid solution softening, albeit weak, in a single phase CoCrFeMnNi through the minor addition of 2. at.% Al. This softening effect is mostly related to the decreased Peierl's stress by Al addition. Image, graphical abstract [ABSTRACT FROM AUTHOR]
- Published
- 2020
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26. Quantitative Analysis of DEPES Distributions of Pt(111).
- Author
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Kruk, K. and Morawski, I.
- Subjects
- *
QUANTITATIVE research , *ELECTRON spectroscopy , *SPHERICAL projection , *ELECTRON scattering , *CRYSTAL structure - Abstract
Directional elastic peak electron spectroscopy (DEPES) was used to reveal a short range order within the near-surface region of Pt(111). Experiments were performed at primary electron beam energies in the range from 0.9 keV to 1.8 keV. DEPES signal was recorded for a wide range of polar θ and azimuthal ø angles and then transformed to two-dimensional DEPES maps using stereographic projection. Theoretical DEPES distributions were obtained with the application of the multiple scattering (MS) theory. In MS calculations, the following parameters were varied: the inelastic mean free path λ, the radius around the emitter Rmax and the cones of smoothing M. The comparison of experimental and theoretical DEPES maps was performed by an R-factor analysis in order to find the best correspondence between the recorded and calculated distributions. The absolute minimum of the R-factor was found at rather small values of the radius around the emitter and large inelastic mean free paths. However, the obtained minimum was very shallow and took the form of a characteristic band in the Rmax(l) plots. Thus, other Rmax and λ values corresponding to the local R-factor minimum can also be to some extent used in computations. The cone of smoothing, which reflects the spread of primary beam directions before it strikes the sample, decreases at larger electron energies which scales with better electron focusing at larger Ep values. The discussion concerns the computation time associated with the mentioned parameters and the convergence of theoretical data. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
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27. БЛИЖНІЙ ПОРЯДОК ТА КОНФІҐУРАЦІЙНА ЕНТРОПІЯ ПРОМІЖНИХ ФАЗ У РІДКОМУ СТАНІ.
- Author
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Олійник, З. М., Королишин, А. В., Мудрий, С. І., and Коваль, І. З.
- Subjects
- *
GAS distribution , *IDEAL gases , *ATOMIC structure , *ATOMIC interactions , *ENTROPY - Abstract
The configurational entropy of mixing was calculated on the basis of the experimental diffraction data of melts of intermediate phases of Cu-In, Bi-Te, Fe-Ge, Ni-In and Bi-Tl systems. The entropy determined in such a way is the difference between the entropy of the melt and the one of an ideal gas of the same atoms being a measure of the degree of ordering of the melt. This value is in fact the excess entropy and differs from the classical definition of configurational entropy for crystals, defined as the difference between total entropy and its vibrational contribution. This approach was used to calculate such a configurational contribution to entropy in the case of one-component melts, but we tried to use it to study two-component melts too, replacing them by effective one-component liquids. Configuration entropy indicates the deviation of the topology of the real atomic distribution from the distribution in the gas of the same atoms, and in the case of binary melts, we have calculated the degree of deviation of the structural state of the melt from the structure of an ideal atomic solution. For a melt with an average atomic distribution, the excess configuration entropy is close to zero, and in the case of significant changes in the atomic distribution during the formation of the melt, it will be different. The transformation of the structure during the melt formation is accompanied by both a change in the interparticle interaction and the topology of the atomic distribution in comparison with the pure components, and these changes will be displayed in the experimental pair correlation function and hence in the configurational entropy of mixing. The concentration dependence of the excess configurational entropy within the concentration range corresponding to the existence of intermediate phases of the studied systems is characterized by minimal values and increases within concentration intervals in which eutectics and atomic solutions exist, that is the evidence of its correlation with equilibrium diagrams of the studied systems. [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
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28. An ab initio molecular dynamics exploration of associates in Ba-Bi liquid with strong ordering trends.
- Author
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Ma, Jianbo, Shang, Shun-Li, Kim, Hojong, and Liu, Zi-Kui
- Subjects
- *
MOLECULAR dynamics , *POLYHEDRA , *LIQUIDS , *CRYSTAL structure , *ENTHALPY - Abstract
Fictive associates are widely used to describe and model liquid phases with strong ordering trends. However, little evidence is known about the assumed associates in most cases. In the present work, an ab initio molecular dynamics (AIMD) study is employed to investigate the characters of the Ba-Bi liquid, in which associates have been assumed in existing thermodynamic modeling. It is found that in the Ba rich melt, the Bi atoms are almost completely surrounded by Ba atoms. The Bi-centered coordination polyhedrons are strongly associated to crystalline structures of Ba 5 Bi 3 and Ba 4 Bi 3 with a longer lifetime than other polyhedrons during the AIMD simulations. In addition, these Bi-centered polyhedrons in Ba rich melt connect with each other through vertex, edge, face, and/or bipyramid sharing to form medium range orders (MRO). In the Bi rich melt, the Ba-centered polyhedrons also form MROs, but they are both structurally and compositionally diverse with a shorter lifetime. These findings from AIMD study provide evidences that there exist a strongly ordering Ba 4 Bi 3 associate and a weakly ordering BaBi 3 associate in the Ba-Bi liquid. The predicted enthalpy of mixing in the liquid agrees well with the results by the CALPHAD modeling in the literature. Snapshots of AIMD configurations for some connected Bi- and Ba-centered coordination polyhedrons in molten Ba 1- x Bi x with x = 0.025 (a), 0.05 (b), 0.10 (c), 0.90 (d), 0.95 (e), and 0.975 (f). The green and purple spheres represent Ba and Bi atoms, respectively. Image, graphical abstract [ABSTRACT FROM AUTHOR]
- Published
- 2020
- Full Text
- View/download PDF
29. Structure and Properties of Refractory High-Entropy Alloys
- Author
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Maiti, Soumyadipta, Steurer, Walter, and The Minerals, Metals & Materials Society
- Published
- 2016
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30. Creep Behaviour of Mg Binary Solid Solutions
- Author
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Abaspour, Saeideh, Cáceres, C. H., Hort, Norbert, editor, Mathaudhu, Suveen Nigel, editor, Neelameggham, Neale R., editor, and Alderman, Martyn, editor
- Published
- 2016
- Full Text
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31. Bounds to Hardening by Solid Solution, Precipitation and Short Range Order in Mg Binary Alloys
- Author
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Cáceres, C. H., Abaspour, Saeideh, Hort, Norbert, editor, Mathaudhu, Suveen Nigel, editor, Neelameggham, Neale R., editor, and Alderman, Martyn, editor
- Published
- 2016
- Full Text
- View/download PDF
32. Magnetic properties and reminiscent rare earth-cobalt coupling in RCo3B2 compounds.
- Author
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Burzo, Emil and Vlaic, Petru
- Subjects
- *
MAGNETIC properties , *MAGNETIC measurements , *CURIE temperature , *RARE earth metals , *COBALT , *ELECTRONIC measurements - Abstract
[Display omitted] • Magnetic and electronic properties of RCo 3 B 2 compounds (R = heavy rare earth or yttrium) are investigated. • Small cobalt magnetizations, antiparallel coupled with those of the heavy rare earth elements, are evidenced. • Exchange interactions between R and Co moments are mediated by the rare earth R5d band polarization. • Effective cobalt moments are in the range 1.34 ÷ 1.84 μ B /Co atom, being rather little dependent on the rare earth partner. • Reminiscent R5d-Co3d interactions are present above the Curie points in compounds with R=Tb, Dy and Ho. The magnetic properties of RCo 3 B 2 compounds, with heavy rare earth elements were investigated using magnetic measurements and electronic structure calculations. The cobalt sublattice magnetizations are very small and antiparallel oriented to heavy rare earth moments. The contributions of cobalt moments to the Curie constants are also shown. The magnetic behavior of cobalt has been analyzed in the spin fluctuations model. The presence of short-range order above the Curie temperatures in RCo 3 B 2 compounds with R = Tb, Dy, and Ho has been attributed to reminiscent R5d-Co3d interactions. [ABSTRACT FROM AUTHOR]
- Published
- 2024
- Full Text
- View/download PDF
33. The Athermal Component of the Strength of Binary Mg Solid Solutions
- Author
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Abaspour, Saeideh, Cáceres, C. H., Alderman, Martyn, editor, Manuel, Michele V., editor, Hort, Norbert, editor, and Neelameggham, Neale R., editor
- Published
- 2016
- Full Text
- View/download PDF
34. Phase stability and the Portevin-Le Chatelier effect in Cr-Mn-Fe-Co-Ni High-Entropy Alloys
- Author
-
Bloomfield, Maximilian
- Subjects
Short range order ,CALPHAD ,Phase stability ,Digital image correlation ,Electron microscopy ,Mechanical properties ,Portevin-Le Chatelier effect ,High Entropy Alloys ,Serrated flow - Abstract
High-Entropy Alloys (HEAs) are a new class of metallic materials based on the combination of multiple principal elements, often with the intention to form a concentrated solid solution. It has been suggested that these solid solution phases could offer enhanced mechanical properties, due to fluctuations in their local atomic environments. However, at present, the thermodynamic stability of the solid solution phases which form in HEAs is poorly understood. This study aims to improve our understanding of phase stability in HEAs and investigate possible differences in the mechanical behaviour of dilute and concentrated solid solutions. Firstly, a systematic series of experiments is presented, which establish the effect of Co and Fe on the phase equilibria of the widely studied CrMnFeCoNi system. Both Co and Fe were found to stabilise the A1 matrix relative to the A2 and D8b phases at elevated temperatures but did not prevent the formation of ordered phases at 500°C. Alongside literature data, the results show that stable single-phase alloys are rare in the CrMnFeCoNi system. Secondly, a systematic assessment of the AlxCrFeCoNi alloy system showed that Al promotes the formation of B2, D8b and A2 phases, and improved our understanding of phase stability in this system, which has strong potential for developing alloys with desirable mechanical properties. In each study, experimental observations were used to test the fidelity of thermodynamic predictions from the latest CALPHAD databases. Whilst the predictions generally provided a close approximation of the observed phase equilibria, inaccuracies were common, especially at lower temperatures. Phase stability investigations also served to identify thermodynamically stable alloys, suitable for the investigation of the Portevin-Le Chatelier (PLC) effect - a discontinuous yielding phenomenon widely attributed to the repeated pinning of dislocations by mobile solute atoms over certain regimes of temperature and strain-rate. Under mechanical testing, the effect is generally associated with serrations in the materials flow curve and the localisation of strain into discrete bands. Serrated flow has been observed in several HEAs but the associated strain localisation behaviour has not yet been reported, so it is uncertain whether this behaviour is similar to the PLC effect in other alloy systems. Thus, a series of alloys based on the stable equiatomic quaternary alloy, CrFeCoNi, were selected to investigate the effect of compositional complexity on the PLC effect. Tensile testing, combined with digital image correlation, enabled simultaneous recording of the materials stress and local strain response across a range of temperatures. The results showed close similarities between the alloys at each temperature, indicating that compositional complexity did not have a dominant influence on the PLC effect. This suggested that the dislocation-solute interactions in the complex, concentrated solid solutions were not substantially different from those of more dilute solutions. Calorimetric investigations also revealed evidence of a varying degree of short-range order among the alloys, the influence of which warrants further investigation.
- Published
- 2023
- Full Text
- View/download PDF
35. Improved optoelectronic properties in CdSexTe1−x through controlled composition and short-range order.
- Author
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Dumre, B.B., Szymanski, N.J., Adhikari, V., Khatri, I., Gall, D., and Khare, S.V.
- Subjects
- *
DENSITY functionals , *DENSITY functional theory , *ABSORPTION coefficients , *PHASE transitions , *LIGHT absorption , *PHOTOELECTROCHEMICAL cells , *PHASE diagrams - Abstract
• In computed phase diagram of CdSe x Te 1−x , consolute temperature = 325 K. • In CdSe x Te 1−x alloy, zincblende-wurtzite phase transition seen at x = 0.5–0.6. • Band gap lowest at 45% Se concentration to be around 1.41 eV due to bowing. • Significant clustering effects are observed in the Te/Se sublattice of CdSe 0.5 Te 0.5. • Negative bowing in effective hole mass contributing to high photo-current. We employ first principles methods based on density functional theory and beyond to study CdSe x Te 1−x alloys in the zincblende and wurtzite structures. From the cluster expansion formalism, we provide a detailed phase diagram showing a consolute temperature of 325 K, above which miscibility may be achieved. In the random solid solution, a zincblende-to-wurtzite phase boundary is found to range from Se concentrations of x = 0.5–0.6, in agreement with experiment, owing to increasing ionic character of the Cd-anion bonds. Disordered CdSe x Te 1−x configurations are modeled using special quasirandom structures, for which optoelectronic properties are computed with the hybrid HSE06 functional. Alloying is shown to cause strong bowing effects in the band gap and effective electron/hole masses, which we attribute to local structural distortions as illustrated by analysis of bond length distributions. Downward bowing in the band gap and effective hole mass of the zincblende structure is highlighted for its potential benefits in photovoltaics through increased net photocurrent. Absorption coefficients and reflectivity are also reported, showing promising results in zincblende CdSe x Te 1−x as indicated by substantial optical absorption throughout all Se concentrations. Lastly, we identify the presence of short-range order in CdSe x Te 1−x characterized by clustering among like atoms in order to minimize strain. The degree of clustering, which may be tuned by temperature, also controls the magnitude of the band gap. Therefore, we propose both composition and short-range order as effective tools to be utilized in the design and synthesis of improved solar cell absorber layer materials. [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
36. Directional Auger and elastic peak electron spectroscopies: Versatile methods to reveal near-surface crystal structure.
- Author
-
Morawski, I. and Nowicki, M.
- Subjects
- *
ELECTRON spectroscopy , *ADSORBATES , *LOW energy electron diffraction , *AUGER electron spectroscopy , *CRYSTAL structure , *CRYSTALS - Abstract
A review of directional Auger (DAES) and directional elastic peak electron spectroscopy (DEPES) for investigations of the short range order within a near-surface region, similar to XPD, is presented. The application of these techniques requires nothing more than a retarding field analyser (RFA), commonly applied for the observation of low energy electron diffraction (LEED) patterns and Auger electron spectroscopy (AES) measurements, for in depth structural investigations associated with the short range order within a near-surface region. The physical principles, experimental set-up, as well as examples of experimental and theoretical results, the latter obtained with the use of single scattering cluster (SSC) and multiple scattering (MS) calculations adopted for primary electron plane wave, are shown. The scattering geometry and details concerning the scattering events of primary electrons in crystalline solids described by SSC and MS approximations are presented. Furthermore, some issues related to computation parameters such as: maximal scattering order, the maximum radius around the emitter, the number of cluster layers, and the averaging range considered in the calculations are also addressed. The presentation of the data obtained for clean and covered substrates in the form of polar profiles and stereographic intensity distributions enables the straightforward identification of the crystalline structure within the first few sample layers. The data presented in the form of anisotropy maps enable the identification of interatomic axes formed between substrate and adsorbate atoms at the interface. The contribution of different sample layers to the final DEPES signal is discussed. The comparison of DAES results with those obtained by means of x-ray photoelectron diffraction (XPD) is also presented. The qualitative and quantitative data analysis, the latter achieved by the comparison of experimental data with theoretical results by means of an R-factor analysis, is shown. The application of DAES and DEPES enables the characterization of the crystalline structure of adsorption systems from one monolayer (1 ML) up to thicknesses of the adsorbate limited by the inelastic mean free path of the registered electrons. Exemplary results are presented for adsorption systems, where the adsorbate and the substrate crystallize in the same (Ag/Cu, Pt/Cu, Cu/Pt) and in different (Cu/Ru) structures. The influence of the large unit cell of graphene formed on Ru(0001) on measured DEPES intensities is also shown. The detailed analysis of these results enables an identification of the short range order of atoms within the near-surface region, of adsorbate domains exhibiting different orientation with respect to the crystalline substrate, the determination of the domain populations, the relaxation and termination of the surface, the specific adsorption sites of adsorbed atoms, as well as the positions of atoms within a unit cell and their bond lengths (e.g. O / R u (10 1 ¯ 0) ). [ABSTRACT FROM AUTHOR]
- Published
- 2019
- Full Text
- View/download PDF
37. Structure of the interlayer between Au thin film and Si-substrate: Molecular Dynamics simulations
- Author
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V Plechystyy, I Shtablavyi, S Winczewski, K Rybacki, S Mudry, and J Rybicki
- Subjects
thin film ,diffusion process ,phase formation ,contact melting ,eutectic alloys ,short range order ,Materials of engineering and construction. Mechanics of materials ,TA401-492 ,Chemical technology ,TP1-1185 - Abstract
Interaction between 2, 3, 5 and 7 atomic layers of gold and a (111) silicon surface was investigated with the molecular dynamics simulation method. The simulation of the diffusion interaction between gold and silicon in the temperature range 425–925 K has been carried out. The peculiarities of the concentration changes of the interacting components and the atomic density at the boundary of two phases in the direction perpendicular to the crystalline surface were established. By means the formalism of quasi two dimensional partial pair correlation functions the atomic structure of the diffusion region was analyzed. The formation of the alloy of eutectic composition within the gold-silicon interlayer was established. It was shown that the inter-phase mixing in various temperature intervals occurred according to different diffusion mechanisms.
- Published
- 2020
- Full Text
- View/download PDF
38. Quantitative Phase Analysis: Method Developments
- Author
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Lutterotti, Luca, Kolb, Ute, editor, Shankland, Kenneth, editor, Meshi, Louisa, editor, Avilov, Anatoly, editor, and David, William I.F, editor
- Published
- 2012
- Full Text
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39. A Comparison Study of Electrical Resistivity, Vickers Hardness, and Microstructures of Alloy 625 Prior and Posterior to Rolling
- Subjects
Materials science ,Condensed matter physics ,Mechanics of Materials ,Electrical resistivity and conductivity ,Lattice defects ,Materials Chemistry ,Metals and Alloys ,Short range order ,Condensed Matter Physics - Published
- 2021
- Full Text
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40. The coordination of unprotonated peptide tertiary structure as a metric of pMHC–TCR functional avidity
- Author
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Georgios S.E. Antipas and Anastasios E. Germenis
- Subjects
pMHC–TCR interaction ,Atomic pair correlation ,Short range order ,Cumulative coordination ,Functional avidity ,Structure–function relationship ,Computer applications to medicine. Medical informatics ,R858-859.7 ,Science (General) ,Q1-390 - Abstract
The coordination difference between the unprotonated tertiary structures of a native (Tax) peptide and a number of its variants – all peptides presented by HLA-A201 and bound to the human A6 T cell receptor-was discovered to constitute a metric of pMHC–TCR functional avidity. Moreover, increasing coordination deviations from the index were found to flag correspondingly weakening immunological outcomes of the variant peptides. The prognostic utility of the coordination difference of unprotonated tertiary structure was established to operate strictly on the peptide scale, seizing to be of relevance either to the immediate peptide environment (i.e. within the realm of peptide short range order, within 7 Å of any peptide atom) or over the entirety of the pMHC–TCR complex. Additionally, the imprint of peptide immunological identity was expressed both by the total coordination as well as by its C–C partial.
- Published
- 2015
- Full Text
- View/download PDF
41. A Procedure to Quantify the Short Range Order of Disordered Phases
- Author
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Pardo, Luis Carlos, Rovira-Esteva, Muriel, Tamarit, Josep Lluis, Veglio, Nestor, Bermejo, Francisco Javier, Cuello, Gabriel Julio, Rzoska, Sylwester, editor, Drozd-Rzoska, Aleksandra, editor, and Mazur, Victor, editor
- Published
- 2010
- Full Text
- View/download PDF
42. Neutron Diffraction as a Tool to Explore the Free Energy Landscape in Orientationally Disordered Phases
- Author
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Rovira-Esteva, Muriel, Pardo, Luis C., Tamarit, Josep LL., Bermejo, F. Javier, Rzoska, Sylwester, editor, Drozd-Rzoska, Aleksandra, editor, and Mazur, Victor, editor
- Published
- 2010
- Full Text
- View/download PDF
43. Local structures and optical properties of As-Se-Te(S) chalcogenide glasses.
- Author
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Alekberov, R.I., Isayev, A.I., Mekhtiyeva, S.I., and Fábián, M.
- Subjects
- *
OPTICAL properties of chalcogenide glass , *NEUTRON diffraction , *MONTE Carlo method , *COORDINATION number (Chemistry) , *ARSENIC , *LIGHT transmission - Abstract
Abstract The partial, total and average coordination number of atoms and, their neighbor distributions have been determined by the neutron diffraction method and application of the Reverse Monte Carlo modeling for experimental data in As 40 Se 60 , As 40 Se 30 S 30 and As 40 Se 30 Te 30 chalcogenide glasses. The total coordination number of the arsenic and chalcogen atoms is 3 and 2 for all compounds. The average coordination number is 2.4, i.e. the 8-N rule is performed and main structural element is AsSe 3 type pyramids, where depending on the chemical composition Se atom is replaced by S or Te atoms. The proportion of homopolar bonds is significant in As 40 Se 60 and As 40 Se 30 S 30 compositions, but sharply decreases in As 40 Se 30 Te 30. In all compositions the neighbor distances between arsenic and selenium atoms are the same within error: 2.35 Å (Se Se); 2.45 Å (As As) and 2.40 Å (As Se). The existence of medium range order (MRO) is proved by the analysis of the total and partial pair structural factors and correlation functions in above mentioned compositions. The geometric dimensions of the MRO area, i.e. the quasi-periodicity of density fluctuations in the MRO area and the size of nano-voids have determined within Elliott's void-based model. The change of the optical parameters by variation of the chemical composition has been established from the analysis of the optical transmission spectra. Highlights • Local structure of As-Se-Te and As-Se-S glasses was investigated. • The main role in the formation of the MRO region belongs to the Se Se bonds. • The neutron diffraction and optical studies show correlation between the optical band gap (Eg) and local structure. • The existence of medium range order (MRO) is proved by the analysis of the total and partial pair structural factors and correlation functions. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
44. Composition dependence of the short range order structures in 0.2Na2O + 0.8[xBO3/2 + (1-x)GeO2] mixed glass formers.
- Author
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Curtis, Brittany, Hynek, David, Kaizer, Sydney, Feller, Steve, and Martin, Steve W.
- Subjects
- *
GLASS analysis , *MAGNETIC resonance microscopy , *BORON , *GERMANIUM oxide films , *ATOMIC structure - Abstract
Abstract The atomic level structures of ternary 0.2Na 2 O + 0.8[xBO 3/2 + (1-x)GeO 2 ] glasses have been carefully examined for the first time using a combination of Raman, infrared (IR) and 11B magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopies. It was found that, like in other mixed glass former (MGF) systems, there is an unequal sharing of the sodium oxide between the two glass formers, B and Ge, across this series 0 < x < 1. It is found that for all x > 0, the Na 2 O preferentially reacts with boron to create a larger number of tetrahedral boron, BO 4/2 −1 ≡ B4, units than would be found for a binary sodium borate glass of the same mole fraction, 0.20, of Na 2 O. In addition to this higher than expected fraction of B4 units as determined by the 11B MAS-NMR measurements, the Raman spectra further suggest the presence of high concentrations of octahedrally coordinated GeO 6/2 −2, Ge6, units in the GeO 2 rich end of this compositional series, x ≤ 0.2. Across this series, it is found that there are at most five short range order (SRO) structural units present in these glasses, BO 3/2 (B3), B4, GeO 6/2 −2 (Ge6), GeO 3/2 O−1 (Ge3), and GeO 4/2 (Ge4), where the superscript gives the number of bridging oxygens (BOs) bonded to the central atom. The composition, x, dependence of all of these SRO structural units were determined by combining the results all of these spectral techniques and requiring that the total sum of all the negatively charged SRO units balance the positive (+0.4) charges from the Na+ ions and that the total amount of B balance to 0.8×, the total amount of Ge balance to 0.8*(1-x), and the total amount of oxygen balance to1.8–0.4× as required by the stoichiometry of this compositional series. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
45. On the chemical effects in molten Ni1−xMx alloy.
- Author
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Ma, Jianbo, Dai, Yongbing, Zhang, Jiao, Chen, Shihao, Yang, Jian, Xing, Hui, Dong, Qing, Han, Yanfeng, and Sun, Baode
- Subjects
- *
NICKEL alloys , *MOLECULAR dynamics , *ELECTRONIC density of states , *PERIODIC table of the elements , *PARTITION coefficient (Chemistry) - Abstract
A study of molten Ni 1−x M x (M = Ta, W, Re, Os, Nb, Mo, Ru, Ti or Cr) at 1773 K was carried out by ab initio molecular dynamics simulation. Static structure factors, pair correlation functions and bond-angle distribution functions were calculated. Chemical short range order, the structure of coordination short range order (SRO), compactness of coordination shell and electronic density of states were studied. Hetero-coordination is preferred in molten Ni 1−x M x (M = Ta, W, Re, Nb, Mo, Ti or Cr), while, self-coordination is preferred in molten Ni 1−x Os x and Ni 1−x Ru x . The affinity between unlike species in molten Ni 1−x M x is decreasing with solute species shifting to the right in the periodic table. The structure difference between M- and Ni-centered coordination SROs is narrowed when solute species shifts to the right in the periodic table. With an increase of solute concentration, the affinity between bonding Ni-M and Ni-Ni atomic pairs both decrease, the solute and solvent centered coordination shells both become looser, in general. The structures of locally favored coordination SROs in molten Ni 1−x M x are diversified and independent of the structure of crystal state. Few FCC- and HCP-type coordination SROs are found in these melts. No BCC type coordination SRO is detected. For these melts, the compactness difference of solute- and solvent-centered coordination shells is correlated with the equilibrium partition coefficients, k 0 , of solute elements. Namely, when the solute centered coordination shell is averagely denser than the Ni centered one, k 0 < 1, vice versa. Our findings shed light on understanding the nature of segregation from the aspect of molten structure at atomic scale. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
46. The effect of short range order on the thermal output and gage factor of Ni3FeCr strain gages.
- Author
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Kieffer, T. P. and Peters, K. J.
- Subjects
- *
CRYSTAL structure , *ALLOYS , *MAGNETISM , *STRENGTH of materials , *ELECTRIC resistance , *STRAINS & stresses (Mechanics) - Abstract
The ability of alloy 70Ni-27.5Fe-2.5Cr to form an ordered crystalline structure upon application of elevated temperature and the resulting effects on a variety of physical properties such as magnetism, strength, electrical resistance, and specific heat are well known. This paper demonstrates that strain gages made with 70Ni-27.5Fe-2.5Cr foil with an ordered crystalline structure have both high gage factors and high thermal outputs. The thermal output for strain gages made of 70Ni-27.5Fe-2.5Cr foil is demonstrated to be about 1,374 μΩ/Ω/K. The gage factor is nonlinear ranging in magnitude from about 5.0 to 3.6 for applied strains of 300 and 1,300 μE, respectively. The magnitude of gage factor and thermal output correspond with transformation of the crystalline structure from a state of disorder to a state of order. Comparisons to strain gages made with 36Ni-57Fe-7Cr foil are provided because of its use in the manufacturing of metal foil strain gages and their demonstrated high gage factors and high thermal outputs. Practical application for 70Ni-27.5Fe-2.5Cr strain gages is demonstrated by dead-weight loading of shear-beam load cells at low applied strain levels to minimise the effect of nonlinear gage factor; and Wheatstone bridge cancellation of high thermal output. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
47. Influence of glass insulation on the structure and magnetic properties of Co-Si-B microwires.
- Author
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Kutseva, N., Bashev, V., Delov, V., and Larin, V. S.
- Subjects
- *
CRYSTALLIZATION , *MAGNETIC properties , *GRAIN size , *MICROSTRUCTURE , *HEAT treatment - Abstract
Investigations of the effect of glass insulation on the structure of Co67,7Fe4,3Cr3B15Si10 glass-coated microwire are carried out. It is shown that in initial MW the average distance between metal atoms and the average number of Co neighbors are 0.253 nm and 10.2, respectively. Heat treatments influence considerably on the structural parameters of amorphous microwires. In microwires, an increase in the height of the first maximum of the structure factor is observed, but in glass-coating microwires this increasing is more significant. Such structure changes indicate the beginning of crystallization processes. The crystallization of amorphous microwires occurs in two stages. At the first stage of crystallization primary α-Co crystallites are formed in residual amorphous matrix at the temperature 495 - 498°C. At the second stage the residual B and Si enriched amorphous phase transforms into Co2Si phase and the metastable phase Co3B through eutectic crystallization in the temperature range 510-550°C. The mean grain size and crystallized volume fraction of α-Co crystals are 20 nm and 7%, respectively. Additional internal stresses arising from the presence of glass insulation accelerate the crystallization processes (crystallized volume fraction and the mean grain size of Co crystals increases up to 12%, and 30 nm, respectively). The nanocrystalline structure cased a decrease of coercivity from 130 A/m in initial state to 60 A/m at the annealing 495°C. [ABSTRACT FROM AUTHOR]
- Published
- 2018
- Full Text
- View/download PDF
48. Functional Nanostructured Thin Films
- Author
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Krishna, Hare, Kalyanaraman, Ramki, Lockwood, David J., editor, and Seal, Sudipta, editor
- Published
- 2008
- Full Text
- View/download PDF
49. Static Displacements and Short-Range Order in Ni-14 at. % Ir Alloy
- Author
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Khorgolkhuu Odbadrakh, Lkhamsuren Enkhtur, V. M. Silonov, Tsenddavaa Amartaivan, Tsedendorj Gantulga, and Galbadrakh Ragchaa
- Subjects
Materials science ,Alloy ,Physics::Atomic and Molecular Clusters ,Short range order ,engineering ,General Materials Science ,engineering.material ,Composite material ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics - Abstract
In this paper, we are proposing a novel method to estimate static displacements of atoms caused by size effects in fcc substitutional binary polycrystalline solid solutions. Fourier transforms of static displacements of the atoms on every considered shell were calculated using the equations that include dynamical matrix and Fourier transform of interatomic forces. Short-range order parameters on the first seven shells of Ni-14 at. % Ir alloy have been identified from X-ray diffuse scattering intensity by accounting microscopic static displacements of atoms on a particular shell. Pairwise interatomic potentials on the considered shells and critical temperature of disorder-order phase transition were calculated using values of short-range order parameters.
- Published
- 2021
- Full Text
- View/download PDF
50. Calculation of Pairwise Effective Potentials in the Disordered Ni-22.5at.%Fe Alloy Using Model Potential Method with Account of Size Effect
- Author
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Lkhamsuren Enkhtor and V. M. Silonov
- Subjects
Materials science ,Alloy ,engineering ,Short range order ,Thermodynamics ,General Materials Science ,Potential method ,Pairwise comparison ,engineering.material ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics - Abstract
Pairwise effective potentials in first seventeen shells of the Ni-22.5at.%Fe alloy are calculated using model potential method with account of the linear size effect. Using obtained values of pairwise effective potentials, the short range order parameters on the first seventeen shells of alloy are calculated by Krivoglaz-Clapp-Moss method. The calculated values of the short-range order parameters were fitted to the experimental values by varying the parameters of static atomic displacements. Reliable value of critical temperature of order-disorder phase transition in Ni-22.5at.%Fe alloy was calculated using obtained meanings of pairwise effective potentials.
- Published
- 2021
- Full Text
- View/download PDF
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