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Molybdenum disulfide (MoS2)-based transition-metal chalcogenides are considered to be cost-efficient, environmentally-friendly, and stable materials in the application of electrocatalytic hydrogen production.

Designing interfacial structure is an essential but challenging approach to regulating electronic structures to develop favorable bifunctional oxygen electrocatalysts in Zn-air batteries (ZABs). We utilize a facile one-step sintering strategy for preparing Co2P/Co3Fe7 interfacial nanoparticles encapsulated in N-doped carbon nanotubes (Co2P/Co3Fe7@N-C). The obtained Co2P/Co3Fe7@N-C electrocatalyst exhibits significant bifunctional oxygen evolution/reduction reaction (OER/ORR) activity (ΔE = 0.61 V), better than that of Pt/C + Ir/C (ΔE = 0.69 V) and compete with other previously report electrocatalysts. The density functional theory results reveal that the synergistic coupling effect and interfacial electronic interaction between Co2P and Co3Fe7 play a key role in boosting bifunctional ORR/OER efficiency. Remarkably, Co2P/Co3Fe7@N-C-based liquid ZABs exhibit excellent performance with higher power density (152.3 mW cm− 2) and longer cycle stability (1596 cycles) than the Pt/C + Ir/C-based ZABs (105 mW cm− 2; 882 cycles). Interestingly, the connected in series of Co2P/Co3Fe7@N-C-based liquid ZABs can be powered emitting diodes (LEDs) and blue LEDs display panel, indicating the possibility of practical application. It can be predicted that our present work opens a new pathway for rationally designing superior bifunctional oxygen electrocatalysts for rechargeable metal-air batteries through interfacial engineering.

Photonic chip-based continuously tunable lasers are widely recognized as an indispensable component for photonic integrated circuits (PICs). Specifically, mid-infrared (mid-IR) laser sources are of paramount importance in applications such as photonic sensing and spectroscopy. In this article, we theoretically investigate the propagation dynamics of mid-IR Raman soliton in Ge28Sb12Se60 chalcogenide glass waveguide. By carefully engineer the waveguide dispersion and nonlinear interaction, we propose a suspended chalcogenide glass waveguide device that allows an octave-tuning, from 1.96 µm to 3.98 µm, Raman soliton source. The threshold pump energy is in the low pico-Joule range. Our result provides a solution to continuously tunable on-chip mid-IR ultrafast laser sources.

The nonlocal crystal plasticity finite element (CPFE) simulations and extreme value statistics were combined to study the effects of microstructure on the high cycle fatigue (HCF) behavior of dual-phase Ti alloy. A modified Armstrong-Frederick nonlinear kinematic hardening equation accounting for cyclic softening effect was employed in the crystal plasticity constitutive model. Three-dimensional equiaxed microstructure models and two-dimensional duplex microstructure models with real lamellar structure were generated based on Voronoi method, serving as statistical volume elements (SVEs). The effects of morphological and crystallographic features, including grain size, grain orientation, phase volume fraction and lamellae width, on the fatigue performance were investigated. By simulating multiple SVEs, extreme value distributions of the driving force for fatigue crack formation were predicted using Fatemi-Socie (FS) parameter as a fatigue indicator parameter (FIP). Meanwhile, whether the extreme values of geometrically necessary dislocation (GND) density can be taken as a FIP was discussed with compared to FS FIP. The GND density, related to local stress and strain gradient, has considerable potential as a FIP to estimate the fatigue performance of titanium alloys. Based on simulated results, it is suggested that microstructure with small grain size, low volume fraction of primary α grains, and thinner α lamellae width have the lowest probability of crack formation during HCF.

In this work, the effect of pre-deformation in the β phase field on the microstructural characteristics of α phase in a Ti-40Al-8Nb-0.5B alloy (at. %) was investigated. The results showed that the morphology and crystallography of α phase were strongly influenced by the deformation. It was observed that if there was no deformation, α laths which formed strict Burgers orientation relationship with β matrix are predominant (∼81% in number fraction). In contrast, the Burgers α laths are significantly reduced after compression in the β phase field. Meanwhile, an abnormal double-fiber texture, and , is produced. After systematic analysis, we believe that the reduction of Burgers α is attributed to the heterogeneous nucleation of α phase at borides and the breakdown of the boride ribbons during deformation. Moreover, the formation of α texture is a synergetic consequence of β texture and boride texture.

Refractory high-entropy alloys present attractive mechanical properties, i.e., high yield strength and fracture toughness, making them potential candidates for structural applications. Understandings of atomic and electronic interactions are important to reveal the origins for the formation of high-entropy alloys and their structure−dominated mechanical properties, thus enabling the development of a predictive approach for rapidly designing advanced materials. Here, we report the atomic and electronic basis for the valence−electron-concentration-categorized principles and the observed serration behavior in high-entropy alloys and high-entropy metallic glass, including MoNbTaW, MoNbVW, MoTaVW, HfNbTiZr, and Vitreloy-1 MG (Zr41Ti14Cu12.5Ni10Be22.5). We find that the yield strengths of high-entropy alloys and high-entropy metallic glass are a power-law function of the electron-work function, which is dominated by local atomic arrangements. Further, a reliance on the bonding-charge density provides a groundbreaking insight into the nature of loosely bonded spots in materials. The presence of strongly bonded clusters and weakly bonded glue atoms imply a serrated deformation of high-entropy alloys, resulting in intermittent avalanches of defects movement. A cluster-and-glue model of atomic arrangements explains the yield strength and mechanical response of high entropy alloys. Inspired by metallic glass, a team led by William Yi Wang at China’s Northwestern Polytechnical University and collaborators in the United States of America used molecular dynamics to build different atomic arrangements of refractory high entropy alloys consisting of four or more elements. Depending on atomic size and the periodic table group of each atom, some atoms organized into clusters while others glued the clusters together. Chemical bonds broke and formed with plastic deformation as the alloys went from one atomic arrangement to another via the glue atoms, causing defect avalanches explaining the serrated mechanical response of high entropy alloys. Taking into account atomic arrangement may thus help us predict the properties of high entropy alloys.

This study reports on the indentation pileup behavior of Ti-6Al-4V alloy. Berkovich nanoindentation was performed on a specimen with equiaxed microstructure. The indented area was characterized by electron backscattered diffraction (EBSD) to obtain the indented grain orientations. Surface topographies of several indents were measured by atomic force microscopy (AFM). The pileup patterns on the indented surfaces show significant orientation dependence. Corresponding nonlocal crystal plasticity finite element (CPFE) simulations were carried out to predict the pileup patterns. Analysis of the cumulative shear strain distributions and evolutions for different slip systems around the indents found that the pileups are mainly caused by prismatic slip. The pileup patterns evolve with the loading and unloading process, and the change in pileup height due to the elastic recovery at unloading stage is significant. The density distributions of geometrically necessary dislocations (GNDs) around the indent were predicted. Simulation of nanoindentation on a tricrystal model was performed.

The cyclic softening behavior of Ti–6Al–4V alloy with three typical microstructures at room temperature has been studied through cyclic deformation experiments at macro-scale and cyclic nanoindentation experiments at micro-scale. Strain control cyclic deformation tests were conducted on specimens with equiaxed, duplex and Widmannstatten microstructure, respectively. Displacement control nanoindentation tests were conducted on the specimen with duplex microstructure. Results show that equiaxed microstructure shows distinct softening since the first cycle, while, duplex and Widmannstatten microstructures exhibit hardening phenomenon at the initial several cycles and then exhibit cyclic softening in subsequent cycles. Cyclic nanoindentation results indicate that both primary and lamellar α phase exhibit cyclic softening phenomenon at micro-scale and the amplitudes of softening vary with grain orientations.

For TA15 Ti-alloy, conventional forging combined with subsequent heat treatment provides a new method to obtain a tri-modal microstructure (consisting of about 20% equiaxed α p , 50–60% lamellar α s and transformed β matrix) possessing attractive comprehensive properties, and it is expected to solve the problems (such as, deformation temperature control, microstructure coarsening, or special requirement for the original microstructure) caused by using the existing method. In this paper, the forming process and principle of obtaining a tri-modal microstructure under conventional forging combined with given subsequent near-β and two-phase field heat treatments (NTH, i.e. 975 °C/30 min/WQ + 930 °C/100 min/AC) were investigated. Meanwhile, taking the volume fraction and morphology of equiaxed α p and lamellar α s as targets, the tri-modal microstructure evolution under different conventional forging conditions (deformation temperatures, deformation degrees, strain rates, cooling modes) and significance of influencing factors were revealed.

Advanced engineering materials (2020). doi:10.1002/adem.201901044, Published by Deutsche Gesellschaft für Materialkunde, Frankfurt, M.

We present a new approach to predict the evolution of anisotropic yield functions by coupling large scale forming simulations with crystal plasticity-spectral based virtual experiments, realizing a multi-scale model for metal forming. Employing a fast spectral method solver enables us to conduct on-the-fly full-field virtual experiments to evolve the yield surface at each integration point of the macroscopic finite element model. As illustrative example, two advanced anisotropic yield functions, namely Yld2000-2D and Yld2004-18p, are used in finite element simulations of deep drawing for a 2090-T3 aluminum alloy sheet. The simulated earing profiles are compared to the experimental ones as well as to simulations with non-evolving yield functions. It is found that the prediction of the earing is improved for the case of the evolving Yld2000-2D yield function. The evolution of the plastic anisotropy during cup drawing is systematically analyzed, showing that the evolution of anisotropy can have considerable effect on the prediction accuracy of the macroscopic simulations.

Transparent conductive IWO/Cu/IWO (W-doped In2O3) films were deposited on quartz substrates by magnetron sputtering of IWO and Cu in the Ar atmosphere. The X-ray diffraction (XRD) patterns identified the cubic iron&ndash, manganese ore crystal structure of the IWO layers. The influence of the thickness of the intermediate ultra-thin Cu layers on the optical and electrical properties of the multilayer films was analyzed. As the Cu layer thickness increases from 4 to 10 nm, the multilayer resistivity gradually decreases to 4.5 &times, 10&minus, 4 &Omega, &middot, cm, and the optical transmittance in the mid-infrared range increases first and then decreases with a maximum of 72%, which serves as an excellent candidate for the mid-infrared transparent electrode.

In this paper, the effects of subgrain size and static recrystallization on the mechanical performance of polycrystalline material were investigated using a microstructure-based crystal plasticity finite element (CPFE) model. Firstly, polycrystalline microstructures with different mean subgrain sizes were prepared using simple assumption based on experimental observations, and intermediate microstructures during static recrystallization (SRX) were simulated by a cellular automata model adopting curvature driven grain/subgrain growth mechanism. Then, CPFE method was applied to perform stress analysis of plane strain tension on these virtual microstructures. The results show that the subgrains inside pre-existing grains have an effect on the heterogeneity of the stress distributions. The average stress decreases with increasing the mean subgrain radius. As grain/subgrain grows during SRX, the average stress also decreases. It can be deduced that well-defined and finer subgrain structure may strengthen the polycrystalline material, while grain/subgrain growth during SRX process will degrade the strength.

In this paper, we investigated the micromechanical behavior of Ti–6Al–4V by means of nanoindentation experiments performed on a specimen with duplex microstructure. After nanoindentation experiments, electron backscattered diffraction (EBSD) scan was conducted on the nanoindentation region to obtain the crystallographic information. Then the crystal plasticity finite element (CPFE) simulations were carried out using the measured grain orientations. The simulated load–displacement curves match the experimental data well with proper model parameters. It was found that the hardness varied with the grain orientation, and the pileup patterns on the indented surfaces exhibit significant anisotropy and grain orientation dependence. The effects of grain boundary and orientation of Berkovich indenter on the nanoindentation results were discussed.

This study presents a 2D cellular automata simulation of static recrystallization (SRX) arising from the subgrain growth in single-phase material following cold deformation by coupling with a crystal plasticity finite element (CPFE) method. The spatial distribution of the stored deformation energy was obtained by CPFE simulation, based on which the initial deformed microstructure consisting of nonuniformly distributed subgrains was predicted. To simulate grain/subgrain growth during annealing, a curvature-driven mechanism was used, in which the grain/subgrain boundary energy and mobility were misorientation-dependent. On the SRX nucleation, a physically based model using critical subgrain size as criterion was adopted, which could provide better insight into the recrystallization nucleation mechanism involving grain boundary bulging. Simulations under different pre-deformation conditions were performed, and the influence of strain rate and strain on the SRX microstructure evolution and the transformation kinetics were investigated. Results show that deformation at higher strain rate can accelerate the SRX kinetics, and the SRX behavior depends more on the deformation state of individual grain than the nominal strain due to the relatively small computational domain.

A two-dimensional cellular automata model was developed to describe the static recrystallization (SRX) arising from the subgrain growth, the driving force of which is dependent on boundary energy and local curvature. At the same time, the subgrain boundary energy and mobility rely on the boundary misorientation angle. On the basis, a deterministic switch rule was adopted to simulate the subgrain growth and kinetics of recrystallization quantitatively to provide an insight into the grain boundary bulging nucleation mechanism. Microstructure evolutions during SRX in different cases were simulated by the developed model. At the beginning of the simulation, the initial polycrystalline microstructure which contains large number of uniformly distributed subgrains in every pre-existing grain was prepared using simple assumption based on experimental observations. Then, both homogeneous and inhomogeneous subgrain growth phenomena were captured by the simulation with different inter-subgrain misorientation, which showed continuous and discontinuous recrystallization, respectively. The effects of initial mean subgrain radius, distribution of initial subgrains, distribution of inter-subgrain misorientations, and annealing temperature on the recrystallization kinetics were also investigated.

Polycrystalline aggregate models are built based on the theory of Voronoi diagram, then crystal plasticity finite element method (CPFEM) is used to study the relationship of microstructures and stress-strain responses in Ti-6Al-4V alloy during uniaxial tensile tests at room temperature. Stress-strain responses of the Ti-6Al-4V alloy were investigated at different strain rate to study the deformation behavior. Based on the model, the effects of grain size, volume fraction of globular primary αp-phase and strain rate on stress-strain responses are investigated. Results indicate that compared with strain rate and volume fraction of primary αp-phase, grain size show a significant influence on stress-strain responses, the stress has a tendency of increase with the grain refinement. The strain distribution range of aggregates increases with increasing of the strain rate, the stress decreases with increasing of the volume fraction of primary αp-phase.

In this study, the deformation behavior of a Ti-40Al-10V (at.%) alloy within &beta, single phase field was examined by means of isothermal compression at 1300 &deg, C under strain rates of 2 s&minus, 1, 0.2 s&minus, 1, and 0.02 s&minus, 1, as well as its effect on the subsequent &beta, &rarr, &alpha, transformation. The results showed that the alloy behaved steady-state flow with dislocation creep as the predominant rate-controlling process. Dynamic recrystallization (DRX) evidently occurred during deformation, and its volume fraction was dramatically increased so that at the lowest strain rate (0.02 s&minus, 1), a full-DRX &beta, structure was obtained. The preferentially dynamic migration of grain boundaries with &lt, 100&gt, orientation was demonstrated to be the major DRX mechanism. The texture was characterized by a &lt, + &lt, 111&gt, double-fiber at 2 s&minus, 1, but gradually transformed into a simple rotated cube orientationunder 0.02 s&minus, 1, accompanied by a decreasing texture intensity. During the subsequent &beta, transformation, two types of &alpha, morphology wereproduced with evident variant selection, namely, the Widmannstatten colony and martensitic laths. Texture simulation revealed that the &alpha, texture was solely determined by parent &beta, texture, despite of the variant selections.

To solve the performance changing problem of icing wing of one aircraft, a test method of aerodynamic characteristics and structural characteristics based on flow field and structure field coupled analysis is proposed. The method is used to discretely analyze time-averaged N-S equation of two-dimensional steady incompressible viscous flow by finite element method, and solve droplet trajectory equation by 4-order ronggo-kuta method to determine the degree of pollution. Then coupled analyziz flow field and structure field, and compared with unpolluted wing's aerodynamic characteristics and structural characteristics to determine the optimal position which improve icing wing performance. Practical similar experiment shows that the method can be applied to evaluate performance and optimum design of the icing wing.

In this article, we studied the grain growth kinetics in the presence of second-phase particles by using a 2D cellular automata (CA) model with deterministic rules. The curvature-driven grain growth mechanism was adopted in the CA model and an expanded method for the computation of curvature along a grain boundary was used. Simulations in real time and space were performed for various particle sizes, volume fractions of particles, and initial grain sizes, and their effects on the microstructure evolution and final limiting grain size were discussed. A modified Zener relation was proposed to predict the limiting grain size by introducing two items: one describes the effect of initial grain size and the other describes the effect of the ratio of initial grain size to particle size. The proposed relation shows a good fit to the simulated limiting grain sizes for different cases.

We present a fully embedded implementation of a full-field crystal plasticity model in an implicit finite element (FE) framework, a combination which realizes a multiscale approach for the simulation of large strain plastic deformation. At each integration point of the macroscopic FE model a spectral solver, based on Fast Fourier Transforms (FFTs), feeds-in the homogenized response from an underlying full-field polycrystalline representative volume element (RVE) model which is solved by using a crystal plasticity constitutive formulation. Both, a phenomenological hardening law and a dislocation density based hardening model, implemented in the open source software DAMASK, have been employed to provide the constitutive response at the mesoscale. The accuracy of the FE-FFT model has been benchmarked by one-element tests of several loading scenarios for an FCC polycrystal including simple tension, simple compression, and simple shear. The multiscale model is applied to simulate four application cases, i.e., plane strain deformation of an FCC plate, compression of an FCC cylinder, four-point bending of HCP bars, and beam bending of a dual-phase steel. The excellent capabilities of the model to predict the microstructure evolution at the mesoscale and the mechanical responses at both macroscale and mesoscale are demonstrated.

A methodology is presented to predict yield loci of drawing steels with virtual mechanical tests using (i) the statistical ALAMEL crystal plasticity model (VEF software of KU Leuven) and (ii) an approach based on representative volume elements (RVE's) solved with a spectral numerical Fast Fourier Transform (FFT) technique (DAMASK software of MPIE). In the latter case, the RVE's are defined in the form of a regular mesh of grid points in 3D-space with a crystal orientation assigned to each grid point. The experimental texture is derived from XRD pole figure measurements. Only tensile curves in the rolling direction are used to calibrate the hardening model included in the crystal plasticity models. For an interstitial free steel the predictions are compared to experimental yield loci, as obtained from uniaxial tests, plane strain tests, shear tests and through-thickness compression tests. Analytical FACET yield loci are calibrated to the crystal plasticity (CP) models and these are used in FE simulations of a square cup deep drawing process, validated by experiments.