Face-centered Cubic Research Articles

In Situ Investigation of Tensile Response for Inconel 718 Micro-Architected Materials Fabricated by Selective Laser Melting.

Topology optimization enables the design of advanced architected materials with tailored mechanical properties and optimal material distribution. This method can result in the production of parts with uniform mechanical properties, reducing anisotropy effects and addressing a critical challenge in metal additive manufacturing (AM). The current study aims to examine the micro-tensile response of Inconel 718 architected materials utilizing the Selective Laser Melting Technique. In this context, three novel architected materials, i.e., Octet, Schwarz Diamond (SD), and hybrid Schwarz Diamond and Face Centered Cubic (FCC), were tested in three different relative densities. The specimens were then subjected to uniaxial quasi-static tensile tests to determine their key mechanical properties, including elastic modulus, yield strength, and ultimate tensile strength (UTS), as well as the scaling laws describing the tensile response of each architected material. In situ Scanning Electron Microscopy (SEM) has been performed to observe the structure and grain morphology of the 3D printed specimens along with the phase transitions (elastic, plastic), the crack propagation, and the overall failure mechanisms. The results highlight the effect of the lattice type and the relative density on the mechanical properties of architected materials. Topologically optimized structures presented a 70-80% reduction in overall strength, while the SD and SD&FCC structures presented higher stretching dominated behavior, which was also verified by the n-value range (1-2) extracted from the identification of the scaling laws.

EFFECT OF STRAIN PATH ON MICROSTRUCTURE AND MECHANICAL PROPERTIES IN COLD - ROLLED [FeNi]69Cr15Mn10Nb6 HIGH - ENTROPY ALLOY

[FeNi]69Cr15Mn10Nb6 high - entropy alloys (HEAs) were subjected to heavy cold-rolling process at ambient temperature through two distinct routes, namely unidirectional cold-rolling (UCR) and multistep cross cold-rolling (MSCCR) routes, to investigate the effect of the strain path on the microstructure and mechanical properties of the alloys. In the MSCCR route, the specimen rotated 90° around the normal direction axis between each cycle. The as-homogenized specimen revealed a two-phase microstructure consisting of FeNiNb - rich dendrites distributed in a nearly homogenous face-centered cubic (FCC) HEA matrix. Here, FeNiNb - rich dendrites were elongated,broken down, and stretched along the rolling direction during both processing routes. In the MSCCR - processed specimen, the dendrites exhibited a smaller average size with a more uniform distribution compared to that of the UCR specimen, which could be mainly ascribed to the elongation mechanisms in the normal and transverse directions during the MSCCR route. These microstructural features, introduced through MSCCR, appeared to be most prone to shear band formation and grain refinement. The MSCCR - processed specimen shows a microhardness of 445 HV, a tensile strength of 1245 MPa, and a remarkable elongation of 16 % at ambient temperature, outperforming the UCR-processed specimen with a microhardness of 418 HV, a tensile strength of 1180 MPa, and an elongation of 14 %. The superior mechanical properties of the MSCCR - processed specimen are attributed to its refined microstructure,increased dislocation density, and uniform distribution of FeNiNb - rich dendrites within the microstructure.

Influence of Mo doping on the structural, Raman scattering, and magnetic properties of NiO nanostructures

In this work, the Ni1-xMoxO, (x = 0.000, 0.025, 0.050, 0.075, 0.100, and 0.150) nanoparticles were prepared employing the coprecipitation method. The X-ray diffraction (XRD) confirmed that all the samples have a face-centered cubic (FCC) structure with no secondary phases by the effect of the Mo-doping. The Mo-dopants yielded smaller crystallites, reaching a size of 9 nm with x = 0.150. The transmission electron microscope (TEM) images revealed agglomerated NiO nanoparticles with nearly spherical shapes varied to elliptical-like shapes upon increasing Mo concentration. The energy dispersive X-ray (EDX) confirmed the purity of the synthesized samples. The XPS analysis confirmed the valence states of the presented elements in the samples as Ni2+, Ni3+, Mo6+, and O2− ions. The XPS detected the reduction of the nickel and oxygen vacancies, by studying the ratio of Ni2+/Ni3+ and lattice oxygen (OL) to vacant oxygen (OV) peaks. The Raman analysis demonstrated the active vibrational modes of NiO, for all the samples, along with stretching Mo = O bonds for the doped samples. The Photoluminescence (PL) spectroscopy was employed to study the near band edge and deep level emissions, giving insight to the defect levels within the band gap. The PL affirmed the decrease of the oxygen vacancies upon Mo-doping. Besides, the magnetic hysteresis measurements at room temperature revealed the superparamagnetic contribution embedded in the antiferromagnetic matrix of NiO. The magnetization was tuned by Mo doping concentration, where it affected the saturation magnetization, coercivity, and remnant magnetization. Mo dopant can modify the magnetic property of NiO nanoparticles and can be a potential candidate in biomedical field and data storage applications.Graphical

Bridging micro nature with macro behaviors for granular thermal mechanics

The connection between micro-level characteristics and macroscopic properties in granular heat transfer and mechanics is fundamental and crucial. This study proposes a novel discrete element approach incorporating granular heat transfer, contact bonding, and granular stress tensor models to investigate the mechanical and thermal responses of continuum media composed of constituent spheres. Eight benchmark tests were devised to bridge the long-standing gap between micro and macro properties in granular materials. Through these tests, the numerical solutions obtained from discrete element modeling match well with existing analytical or finite element solutions derived from continuum-based theory. This validation underscores the rationality and reliability of the granular heat transfer model, contact bonding model, and granular stress tensor model. Moreover, the study highlights the consistency between continuum-based theory and discontinuum-based theory. A minor distinction between continuum-based models and discrete element models emerges near the boundaries due to variations in the specification of boundary conditions. This discrepancy can be clarified by Saint-Venant's Principle, thus validating the accuracy of the microscale heat transfer and mechanics theory for granular materials. Five mono-disperse packing structures, including simple cubic (SC), body-centered cubic (BCC), face-centered cubic (FCC), hexagonal close packing (HCP), and random packing (Random), were further analyzed to examine their influence on heat transfer performance. Numerical results reveal that higher coordination numbers and solid volume fractions correspond to higher apparent thermal conductivity of granular assemblies, thus elucidating the connection between micro packing configurations and macroscopic heat transfer properties. The apparent thermal conductivity for different crystal configurations follows the sequence: HCP ≒ FCC > BCC ≒ Random > SC. To improve the accuracy and physical relevance of the proposed model, the effect of particle contact area needs to be further incorporated into the granular heat transfer model.

Competitive relationship between the FCC + BCC dual phases in the wear mechanism of laser cladding FeCoCrNiAl0.5Ti0.5 HEAs coating

This work elaborated the microstructure and wear behavior of laser cladding (LC) FeCoCrNiAl0.5Ti0.5 high-entropy alloys (HEAs) coatings on AISI 1045 steel substrates. The microstructure of the HEAs coatings is mainly comprised of a body-centered-cubic (BCC) + face-centered-cubic (FCC) dual-phase structure. Besides, the coating exhibites high hardness. During the friction process, the FCC phase was more prone to deformation and peeling than BCC structure. As the alloying elements (such as Al, Ti, and Cr) tend to form oxide film at high temperatures during friction, the friction process of the LC FeCoCrNiAl0.5Ti0.5 coating was mainly controlled by oxidative wear and adhesive wear mechanisms. Friction test results showed that the coating owned excellent wear resistance and the wear rate of the HEAs coating was only 6.53 % of the wear rate of the steel substrate.

Experimental investigation of heat treatments on the mechanical performance of grade 300 maraging steel strut-based lattices

Lightweight and strong components are essential for reducing energy consumption and enhancing efficiency. Lattice structures are one such geometry utilized to achieve weight reduction. This study investigates the mechanical properties of various lattice structures fabricated from Maraging Steel (EOS MS1) using the Direct Metal Laser Sintering (DMLS) method. The samples include three distinct cellular geometries: body-centered cubic (BCC), face-centered cubic (FCC), and octet truss configurations, which are subjected to tensile and compressive tests. The primary goal of this research is to evaluate the impact of heat treatment on the mechanical properties of cellular architecture under tensile and compressive loading conditions. Destructive, nondestructive testing, and simulation results were also obtained from different heat treatment processes. It was found that the age-hardened specimens performed the best overall in terms of ultimate tensile/compressive strength and elongation. The top-performing topologies in compression and tension were found to be the octet structure, as they were able to withstand the most loading and straining when compared to the other specimens.

Ultrafast joule-heating synthesis of FeCoMnCuAl high-entropy-alloy nanoparticles as efficient OER electrocatalysts

High entropy alloys (HEAs), known for their synergistic orbital interactions among multiple elements, have been recognized as promising electrocatalysts for enhancing the sluggish kinetics of oxygen evolution reaction (OER). Despite their potential, the facile and rapid preparation of HEA nanoparticles (NPs) with high electrocatalytic activity remains challenging. Here, we report an ultrafast synthesis of noble-metal-free FeCoMnCuAl HEA NPs loaded on conductive carbon fiber networks using a Joule heating strategy. The prepared HEA NPs exhibited a face-centered cubic (FCC) structure with an average size of approximately 25 ​nm. Synchrotron X-ray absorption fine structure (XAFS) and X-ray photoelectron spectroscopy (XPS) studies were performed to investigate the atomic and electronic structures of the HEA NPs, revealing the co-presence of Fe, Co, Mn, Cu and Al elements as well as their different valences across surface and internal regions. The HEA NPs showed remarkable OER performance, exhibiting an overpotential of 280 ​mV at 10 ​mA ​cm−2 and a low Tafel slope of 76.13 ​mV dec−1 in a 1.0 ​M KOH solution with high electrochemical stability, superior to commercial RuO2 electrocatalysts. This work provides a new approach for synthesizing nanoscale noble-metal-free HEA electrocatalysts for clean energy conversion applications on a large-scale basis for practical commercialization.

The lattice friction stress driven temperature-dependent tensile deformation behaviors of CoNiCr2 eutectic medium-entropy alloy

A heterogeneous CoNiCr2 eutectic medium-entropy alloy (EMEA), comprising soft face-centered cubic (FCC) and hard body-centered cubic (BCC) lamellae, associated with minor acicular hexagonal close-packed (HCP) phase precipitated in BCC phase, was synthesized towards excellent tensile strength and ductility synergy. The tensile mechanical properties demonstrated that this alloy was temperature-dependent, i.e., when the testing temperature reduced from room temperature (RT) to liquid nitrogen temperature (LNT), the yield strength, ultimate strength, and uniform elongation were enhanced from 449 MPa, 821 MPa, and 5.0% to 702 MPa, 1174 MPa, and 8.4%, respectively. The prominent elevation of yield strength at LNT mainly resulted from the dramatically enhanced lattice friction stress (σ0) and the FCC-BCC interfacial strengthening, while the improved ductility was attributed to the superior crack-arrest capability of FCC matrix stemmed from the accumulation of stacking faults (SFs) and enhanced σ0 at LNT. Additionally, although the deformation mechanisms were dominated by planar dislocation glides and SFs at both temperatures, the initiation of premature cracks in the BCC phase due to the inferior deformation capability at LNT constrained the better strength-ductility trade-off. The cracks in the BCC phase tended to propagate along the BCC-HCP interfaces because of the strain incompatibility. Furthermore, the sub-nanoscale L12 particles in the FCC matrix could not only strengthen this alloy but also improve the stacking fault energy leading to no deformation twinning even at LNT. This work may provide a guide for the design of remarkable strength and ductility synergy EMEAs combined with outstanding castability for applications at cryogenic temperatures.

Effect of Laser Energy Density on the Properties of CoCrFeMnNi High-Entropy Alloy Coatings on Steel by Laser Cladding

High-entropy alloys (HEAs) have emerged as a novel class of materials with exceptional mechanical and corrosion properties, offering promising applications in various engineering fields. However, optimizing their performance through advanced manufacturing techniques, like laser cladding, remains an area of active research. This study investigated the effects of laser energy density on the mechanical and electrochemical properties of CoCrFeMnNi HEA coatings applied to Q235 substrates. Utilizing X-ray diffraction (XRD), this study confirmed the formation of a single-phase face-centered cubic (FCC) structure in all coatings. The hardness of the coatings peaked at 210 HV with a laser energy density of 50 J/mm2. Friction and wear tests highlighted that a coating applied at 60 J/mm2 exhibited the lowest wear rate, primarily due to adhesive and oxidative wear mechanisms, while the 55 J/mm2 coating showed increased hardness but higher abrasive wear. Electrochemical testing revealed superior corrosion resistance for the 60 J/mm2 coating, with a slow corrosion rate and minimal passivation tendency in contrast to the 55 J/mm2 coating. The comprehensive evaluation indicates that the HEA coating with an energy density of 60 J/mm2 exhibits exceptional wear and corrosion resistance.

Fabrication, catalytic activity, metal sensing ability and electrochemical evaluation of nano silver particles for supercapacitor applications

In this work, stable, spherical silver nanoparticles (MAgNp) were prepared via a green synthesis method using flowers of Myristica fragrans (nutmeg). This flower is abundant in phytochemicals such as saponins that can be utilized as reductants to produce silver nanoparticles. The synthesized nanoparticles were examined using a variety of physico-chemical methods, including transmission electron microscopy (TEM), Dynamic light scattering (DLS), elemental dispersive X-ray spectroscopy (EDX), powder X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), and UV–VIS spectrometer. EDX study confirmed the crystalline and face-centered cubic (FCC) structure of AgNP. The majority of particles are present with a higher percentage intensity at an average size of 58.77 nm as revealed in the TEM image, PDI was found to be 0.055. MAgNPs demonstrated perfect activity in the catalytic degradation of methylene blue dye (88 %) and para-nitrophenol (98 %), both anthropogenic pollutants. These nanoparticles were further used as plasmonic sensors to detect heavy metals like Fe(II) and Hg(II) in an aqueous solution. The minimum detection limit was found to be 0.2 mM for Hg(II) and 10 μM for Fe(II) with good linearity. The electrochemical properties of MAgNPs were studied using a carbon supercapacitor electrode coated with MAgNPs. Results from cyclic voltammetry were also determined, and they showed a high specific capacitance of 41 F/gm at 5 mV/s scan rate.

Microstructure, hardness, and tribological properties of Ni-Co/ SiO2 nanocomposite coating produced through pulsed current electrodeposition

This study investigates the development of Ni-Co/SiO2 nanocomposite coatings on mild steel surface using pulsed-current electrodeposition method. The effects of incorporating SiO2 nanoparticle and varying its concentration on the coatings' microstructure, microhardness, wear resistance, and frictional properties were assessed using field-emission electron microscopy, X-ray diffraction, Vickers microhardness testing, and dry sliding wear tests. The results indicated that the coatings exhibited two-phases of Ni-Co solid solution (α) with a face-centered cubic (FCC) crystal structure and hexagonal Co, a refined crystallite size of approximately 31 nm for Ni-Co and about 25 nm for Ni-Co/SiO2, along with a colony-like morphology that did not show any preferred growth direction. The amount of Ni-Co solid solution increased with the addition of SiO2 nanoparticles. The composite coatings demonstrated enhanced microhardness of 581 HV, which is 52 % greater than that of the Ni-Co coating, as well as improved wear resistance and a reduced friction coefficient compared to the unreinforced alloy coating. However, higher SiO2 content adversely impacted the tribological properties due to nanoparticle agglomeration. Analysis of the worn surfaces revealed a transition from abrasive wear to oxidative wear with increasing applied force for the coatings.

Phase stability of precipitate-hardened CoCrFeNiTi high entropy alloys fabricated via laser-directed energy deposition under high-temperature irradiation

This study investigated the irradiation response of precipitate-hardened CoCrFeNiTi high entropy alloys (HEAs) fabricated by laser-directed energy deposition (LDED). These HEAs were in-situ irradiated with 1 MeV krypton ions (Kr2+) at 400 °C and 600 °C up to 10 displacements per atom (dpa) at the IVEM-Tandem Facility at Argonne National Laboratory. Transmission electron microscopy (TEM) characterized precipitate stability and defect evolution under irradiation. At 400 °C and 10 dpa, precipitates showed high phase stability, while irradiation at 600 °C caused intense dissolution mainly due to its annealing effect. A high density of faulted dislocation loops formed at 400 °C. The annihilation rate of dislocation loops seemed higher at 600 °C. Increasing the dose increased the number and size of voids in the face-centered cubic (FCC) matrix.

Microstructural Dependence of the Impact Toughness of TP316H Stainless Steel Exposed to Thermal Aging and Room-Temperature Electrolytic Hydrogenation.

This work deals with the effects of two individual isothermal aging experiments (450 °C/5000 h and 700 °C/2500 h) and the subsequent room-temperature electrolytic hydrogen charging of TP316H stainless steel on its Charpy V-notch (CVN) impact toughness and fracture behavior at room temperature. Microstructural analyses revealed that aging at 700 °C resulted in the abundant precipitation of intermediary phases, namely, the Cr23C6-based carbide phase and Fe2Mo-based Laves phase, whereas aging at 450 °C resulted in much less pronounced precipitation of mostly intergranular Cr23C6-based carbides. The matrix phase of 700 °C-aged material was completely formed of austenitic solid solution with a face-centered cubic (FCC) crystal structure, whereas an additional formation of ferritic phase with a base-centered cubic (BCC) structure was detected in 450 °C-aged material. The performed microstructure observations correlated well with the obtained values of CVN impact toughness, i.e., a sharp drop in the impact toughness was observed in the material aged at 700 °C, whereas negligible property changes were observed in the material aged at 450 °C. The initial, solution-annealed (precipitation-free) TP316H material exhibited a notable hydrogen toughening effect after hydrogen charging, which has been attributed to the hydrogen-enhanced twinning-induced plasticity (TWIP) deformation mechanism of the austenitic solid solution. In contrast, both aging expositions resulted in significantly lowered hydrogen embrittlement resistance, which was likely caused by hydrogen trapping effects at the precipitate/matrix interfaces in thermally aged materials, leading to a reduced TWIP effect in the austenitic phase.

Preparation of magnetite nanoparticles and their application in the removal of methylene blue dye from wastewater

Wastewater is discharged in large amounts from different industries; thus, wastewater treatment is currently one of the main concerns, advanced oxidation is a promising technique for wastewater treatment. This research aims to synthesize magnetite nanoparticles and study their application in wastewater treatment via adsorption and advanced oxidation processes. Magnetite nanoparticles were synthesized via coprecipitation technique between ferric and ferrous sulfate at a molar ratio of 2:1. The prepared sample was characterized using FTIR, XRD, TEM, BET surface area, zeta potential, VSM, and UV‒visible spectroscopy. XRD confirmed the formation of a single face-centered cubic (FCC) spinel structure of Fe3O4. TEM revealed an average particle size of 29.2 nm and a BET surface area of 70.1 m2 g−1. UV‒visible spectroscopy revealed that the UV–visible peak of the sample was obtained at 410 nm. VSM confirmed the attraction of the sample to a magnet with a magnetization of 60 (emu/g). The removal efficiency of methylene blue was studied using adsorption and advanced oxidation methods. For adsorption, the studied parameters were dye concentration 2–10 ppm, 3–10 pH, and 50:300 mg Fe3O4/L. For advanced oxidation, peroxide was used with nanomagnetite as a catalyst, and the studied parameters were pH 2–11, magnetite dose 20–200 PPM, and peroxide dose 500–2000 PPM. The removal efficiency by adsorption reached 95.11% by adding 50 mg of Fe3O4/L and 10 ppm dye conc at 6.5 pH; on the other hand, in advanced oxidation, it reached 98.5% by adding 110 PPM magnetite and 2000 ppm H2O2 at pH 11. The magnetite nanoparticles were reused for ten cycles of advanced oxidation, for a 10% reduction in removal efficiency at the tenth cycle.

Prediction of phase and tensile properties of selective laser melting manufactured high entropy alloys by machine learning

Selective laser melting (SLM) for high entropy alloys (HEAs) holds significant promise in commercial applications, and substantial experimental research efforts have been directed toward this domain. To take advantage of the reported experimental data of SLM manufactured (SLM-ed) HEAs and reduce unnecessary experimentation, this study incorporates machine learning (ML) techniques for the phase and tensile properties prediction of SLM-ed HEAs, thus presenting a novel avenue for accelerating the discovery of new SLM-ed HEAs. Through the adjustment of material descriptors and ML models, a model has been developed with an impressive accuracy of 81.58 % in distinguishing between face-centered cubic (FCC), body-centered cubic (BCC), and dual-phase (FCC+BCC) of SLM-ed HEAs. Additionally, optimized models have been devised for the prediction of tensile properties of SLM-ed HEAs, namely ultimate tensile strength (UTS) and yield strength (YS), achieving noteworthy MAPEs (mean absolute percentage errors) of 20.43 % and 20.25 %, respectively. Furthermore, several HEAs were fabricated using SLM, and the experimental outcomes exhibited a favorable alignment with the predicted results. These efforts carry significant implications in advancing the utilization of SLM for HEAs.

Green Synthesis of Silver Nanoparticle Using Parmotrema parmutatum Extract and its Application in Colorimetric Sensing and Photolytic Degradation of Organic Dye

Background: Silver nanoparticles possess distinctive characteristics, including chemical stability, high thermal and electrical conductivity, and linear optical properties, making them unique and fascinating. The rise of green synthesis methods for silver nanoparticles is garnering significant interest among researchers, surpassing traditional chemical and physical approaches due to the environmentally friendly, cost-effective, and convenient nature of synthesis. This approach stands as a viable alternative across various sectors, encompassing research, industry, and environmental safety initiatives. Method: Parmotrema permutatum was utilized in the synthesis of silver nanoparticles, followed by their characterization using ultraviolet-visible spectroscopy, Fourier-transformed infrared spectroscopy, X-ray diffraction, energy dispersive X-ray analysis, and scanning electron microscopy. These nanoparticles are subsequiently employed for detecting methylene blue, formaldehyde, and hazardous mercury metal ions as well as photocatalytically degrading methylene blue. objective: Green Synthesis of Silver Nanoparticle Using Parmotrema parmutatum Extract and Its Application in Colorimetric Sensing Results: The silver nanoparticle synthesized was confirmed by a color change and the maximum peak of the SPR band was at 420 nm in the UV spectrum. The crystal has face-centered cubic (FCC) structure with an average size of 12.78 nm. The lichen extract contains polyphenolic groups which act as capping agents. synthesized silver nanoparticles were used to detect formaldehyde and hazardous Hg2+ ions separately. A color change was observed. The detection limit of Hg2+ was 600 μL. Likewise, silver nanoparticles were used to degrade methylene blue. The blue color of methylene blue disappeared. The efficiency of silver nanoparticles was found to be 72% in 4 hours and 87.82% in 24 hours. Conclusion: Parmotrema permutatum has the potential to reduce Ag2+ to Ago and acts as a capping and stabilizing agent, it can be used to biosynthesize silver nanoparticles and can detect formaldehyde, and Hg2+ ions, in addition, it also degrades methylene blue photolytically.

Unveiling the precipitation behavior and mechanical properties in G-phase strengthened CrFe2Ni2Ti0.2Six multi-principal element alloys

In order to develop Co-free CrFeNi based multi-principal element alloys (MPEAs) with good synergies between strength and plasticity, the effects of Si content on the microstructures and mechanical properties of CrFe2Ni2Ti0.2Six (x = 0, 0.125, 0.25, 0.375, 0.5 and 0.625) MPEAs are studied in this work. The results show that the addition of Si induces a phase transformation from a single-phase face-centered cubic (FCC) structure to a dual-phase structure, comprising an FCC solid solution phase and G-phase. The outcomes from phase formation theory and phase diagram calculations (CALPHAD) also confirm that CrFe2Ni2Ti0.2Six MPEAs are prone to form dual-phase structures. With increasing Si content, the yield strength and hardness of the alloys increase by 47.2 % and 57.3 %, respectively, while still maintaining a strain of 34.2 %, which is indicative of commendable overall mechanical properties. This is ascribed to the coherence between FCC matrix and G-phase, enabling an enhancement in strength concurrently with the retention of considerable plasticity. Moreover, grain boundary strengthening and precipitation strengthening play a dominant role in the strengthening of CrFe2Ni2Ti0.2Six MPEAs. The present work offers new insights for the further development of high-performance non-metallic MPEAs, so as to achieve a combination of targeted microstructures and excellent properties.

Microstructure characterization and high-temperature wear mechanism of high-entropy alloy matrix composite coating fabricated by laser cladding

The development of diecasting technology requires hot die steels with high-temperature resistance. In this study, a high-entropy alloy (HEA) was combined with ceramic particles to generate a CoCrFeNiMo0.2Nb0.2/WC composite coating via laser cladding. The coating consisted of a face-centered cubic (FCC) matrix with unmelted WC particles, eutectics and nanoscale (Mo)NbC phases. With the strong lattice distortion caused by the sequestration of W atoms, a nanoscale amorphous layer existed between the Laves and HEA matrix phases. A transition layer with the same structure as the Laves phase was facilitated between the WC particles and the HEA matrix. Due to the hard phases in the HEA matrix and their interfaces, the composite coating with a high proportion of WC exhibited excellent wear resistance under high-temperature dry friction conditions. When the WC was 60 wt%, a minimum wear rate reached to 0.74 × 10−5 mm3/(N·m) at 600 ℃ and 1.46 × 10−5 mm3/(N·m) at 800 ℃. The destruction pattern of the composite coating at 600 ∼ 800 °C was due to the interaction of the adhesive, oxidative and abrasive wear. The composite coatings fabricated in this study provide a route to enhance the high-temperature wear resistance of die-casting molds.

On the plastic deformation mechanism of Al0.6CoCrFeNi high entropy alloy: In-situ EBSD study and crystal plasticity modeling

In this study, in-situ tensile tests with electron back-scattered diffraction (EBSD) were conducted to reveal the microstructural effects on the plastic deformation behavior of dual-phase Al0.6CoCrFeNi high entropy alloys (HEAs). The in-situ EBSD results demonstrated a uniform distribution of dislocation density in the fine grain (FG) samples, whereas high dislocation density was predominantly localized near body-centered cubic (BCC) phases in the coarse grain (CG) samples. The difference in mechanical properties between face-centered cubic (FCC) and BCC phases caused stress concentration and cracking at the boundaries during tension. The FCC phase within FG samples exhibited excellent plasticity, effectively impeding the propagation and coalescence of microcracks emanating from the BCC phase into longer cracks. For CG samples, brittle cracks formed in BCC phases are easy to merge, thus evolving into long cracks. Crystal plasticity finite element analysis revealed that as the strain increases, stress distribution in FG samples tended to become more homogeneous, whereas for CG samples high stress concentration consistently occurred within BCC phases. The deformation characteristics of FG were attributed to the synergistic effect generated by the FCC phase with heterogeneous grain size and the BCC phase characterized by small grain size.

Three-dimensional step potential electrochemical spectroscopy (SPECS) simulations of porous pseudocapacitive electrodes

This study validates the step potential electrochemical spectroscopy (SPECS) method and refines the associated analysis for differentiating the contributions of electrical double layer (EDL) formation and Faradaic reactions to the total charge storage in three-dimensional porous pseudocapacitive electrodes. The modified Poisson–Nernst–Planck (MPNP) model coupled with the Frumkin–Butler–Volmer theory were used to numerically reproduce experimental data obtained from the SPECS method accounting for interfacial, transport, and electrochemical phenomena in porous electrodes consisting of monodisperse spherical nanoparticles ordered in face-centered cubic (FCC) packing. The fitting analysis of the SPECS method was modified for the Faradaic current. The new model can accurately predict the individual contributions of EDL formation and Faradaic reactions to the total current. Moreover, the contributions of EDL formation at the electrode surface or at the electrode/electrolyte interface within the porous electrode can be identified. Similarly, the Faradaic reactions due to surface-controlled or diffusion-controlled mechanisms can be distinguished. Furthermore, the capacitance associated with EDL formation obtained from SPECS was in good agreement with that obtained from cyclic voltammetry. Finally, cyclic voltammograms were reconstructed using the multiple potential step chronoamperometry (MUSCA) method, and the integral capacitance associated with each charge storage mechanism was calculated for a range of scan rates.