Phase Distribution Research Articles

Mechanism of thermal exposure on the mechanical properties of microtextured Ti60 alloys

In this study, the mechanism of thermal exposure on the mechanical properties of two Ti60 alloys with different micro-texture regions (MTRs) was systematically investigated through macro- and microstructural characterization. It was found that when the alloy was exposed to prolonged thermal exposure at 600 °C for 100 h, the strength of the no-MTR samples increased significantly and the plasticity decreased sharply. In contrast, the MTR samples showed a sharp decrease in strength and plasticity due to the transmissibility of dislocation slip and crack propagation, resulting in the formation of a continuous brittle cleavage plane on the fracture. Meanwhile, the oxide film formed on the surface promotes the formation of early cracks and cleavage planes, and the oxide film serves as the location of surface crack nuclei and creates a notch effect leading to premature fracture of the alloy. It is further found that the oxide film is mainly composed of alternating nanocrystalline grains of Al2O3 and TiO2, and there is an oxygen-rich layer of Ti3O near the matrix, and these nano-oxides increased the brittleness of the oxide film. The strengthening and embrittlement mechanism of the alloy was revealed based on the deformation characteristics, i.e. the plasticity reduction was attributed to the formation of the oxide film and precipitation of the α2 phase on the surface, whereas the inhomogeneous distribution of the α2 phase in the interior led to the formation of microcracks in the interior. The precipitation of (Ti, Zr)6Si3 phase at grain boundaries hinders the dislocation motion and leads to a significant increase in the strength of No-MTR alloys. This study reveals the effects of interactions between MTRs, oxide films and precipitated phases on the thermal exposure properties of Ti60 alloys, providing theoretical support for the stability of titanium alloy properties at elevated temperatures.

Dynamic thermal performance analysis and experimental study of cascaded packed-bed latent thermal energy storage integrated solar trough collectors

The instability of the renewable energy significantly impacts the thermal performance of solar thermoelectric systems. In this paper, a coupling system consisting of solar trough collector and double-layer cascaded packed-bed latent heat storage system (PLTES) is constructed to investigate thermal performance and operating parameters under dynamic conditions. Additionally, the experimental platform was upgraded to evaluate the dynamic charging/discharging process of the cascaded PLTES. The results show that under dynamic inlet heat flow, the PLTES exhibits only one peak temperature difference, and the average temperature is lower than that in the steady-state. The cascade-packed structure promotes a more uniform temperature and liquid phase distribution, resulting in a longer heat flow output. Higher mass flow rates of the heat flow increase convective heat transfer and reduce the temperature difference, though they have little effect on the energy efficiency. Conversely, an increase in capsule diameter significantly reduces the energy efficiency. Experimental results indicate that under dynamic conditions, the total charge-discharge capacity of the cascade system decreases by 0.5 MJ and 0.9 MJ, and the energy efficiency decreases by 0.15. Nevertheless, the energy efficiency of the cascaded PLTES (0.57) is higher than that of the single layer (0.5).

High-performance sky-blue quasi-2D perovskite light-emitting diodes via synergistic defect passivation and phase narrowing strategies

Quasi-2D perovskite light-emitting diodes (PeLEDs) are considered as one of the most promising candidates for next-generation displays. Yet, the unstable electroluminescent spectra and inferior performance of blue PeLEDs hinder their commercial use. Herein, we demonstrate highly efficient quasi-2D pure bromide (QPB) sky-blue PeLEDs based on an oxygen-rich triethyl 2-acetylcitrate (TEAC) additive. The TEAC additive contains four C = O functional groups, offering several coordination sites to simultaneously passivate multiple bromine vacancy defects. Furthermore, it inhibits the growth of large n (n ≥ 5) phases to achieve narrow phases distribution. As a result, the TEAC-modified PeLEDs show sky-blue emission at 494 nm, with maximum current efficiency and external quantum efficiency up to 29.1 cd/A and 18.5 %, respectively. Moreover, the T50 lifetime of TEAC-modified PeLED is about 25 times higher than that of pristine PeLEDs. Our results provide a reliable approach to realizing high-efficiency blue quasi-2D PeLEDs.

A top-mounted, chain-driven, bidirectional point absorber type wave energy convertor

The aims of this paper are to introduce the structure of a point absorber type wave energy convertor (WEC) mounted above sea level, to analyze the motion characteristics and power absorptions of such a WEC and to describe the numerous advantages of installing it in the nearshore. The motion equation is solved by representing the excitation force with the dynamic wave pressure and obtaining an approximate system transfer function. The possibility of the buoy becoming airborne or submerged is considered and the power absorption is increased optimally by reshaping the frequency response using a flywheel. The time, phase and spectral averages of power absorptions are presented for offshore waves, nearshore waves and for concentrated nearshore waves using standard wave spectrums and compared. Approximate gains possible with linear and rectangular arrays are also presented. Considering different phase distributions, it is shown that downgrading WECs based on short term power absorptions is not justifiable. With a buoy of radius 2 m, the power absorption of this kind of a WEC is estimated to be about 114 kW in the deep sea and 117 kW in the nearshore, when the energy flux is about 31 kW/m. By concentrating just 13.6 kW/m nearshore waves, it could be increased to 186 kW. If a 3-element longshore in-line array is placed inside the wave concentrator, the total power absorption could be about 556 kW. A 9-element rectangular array would be capable of absorbing about 1 MW by making use of the remaining energy of the down wave.

Gold occurrence in the footwall of the Lappberget Deposit, Garpenberg Mine, Sweden: Implications for recovery efficiency

By-product metals have a significant potential to bring additional economic benefits to mines. However, a detailed characterization of their distribution is generally required to fulfill this potential and should preferably be integrated into a geometallurgical assessment. This contribution presents a detailed mineralogical and textural investigation of gold-bearing phases at the footwall of the Zn–Pb–Ag–(Cu–Au) Lappberget Deposit, Garpenberg Mine, Sweden, using optical microscopy, scanning electron microscope with energy dispersive spectroscopy (SEM-EDS), electron probe microanalysis (EPMA), laser ablation-inductively coupled plasma mass spectrometer (LA-ICPMS), and bulk chemical analysis applied to drill core and Knelson concentrator samples. Gold is a by-product at the Garpenberg mine, but it is unclear how the mineralogy, occurrence, and distribution of gold-bearing phases impact on gold recoveries during mineral processing. Our results show that Au-dominant electrum is the most abundant gold-bearing phase in the footwall of the Lappberget deposit, occurring strongly associated to sulfides in a variety of textures and grain sizes. Electrum grains commonly occur within sulfide borders, as inclusions, intergrowth and overgrowths of chalcopyrite, pyrite, galena, sphalerite, and pyrrhotite. Gangue minerals may also contain disseminated electrum and inclusions. Electrum grain sizes range from ∼5 µm to 300 µm, predominantly below 100 µm. The potential of sulfide lattice-bound invisible gold in the form of solid-solution gold and colloidal gold was also investigated, showing Au depletion within the analyzed sulfide carriers. The analysis of the concentrate samples from the Knelson gravity concentrator showed 584 and 431 ppm of gold content. High degree of liberation is observed among the gold-bearing phases in the concentrate, and gold recovery is highest among fractions coarser than 106 µm mesh. Pyrite and galena are the most abundant minerals in the concentrate samples. The gold-bearing phases were categorized based on its mineralogy, texture, grain size, and association and their influence on gold processing, especially textures and grain size, which implicates its liberation in milling and recovery by the gravity separator.

NON-OXIDATIVE METHANE CONVERSION STUDY ON GRANULATED Mo-CONTAINING ZEOLITE CATALYSTS

The results of the study of the influence of the method of forming granular Mo-containing zeolite catalysts on their physicochemical and catalytic properties in the process of non-oxidative conversion of methane are presented. There is shown a higher catalytic activity of granular catalysts with a hierarchical porous structure, obtained without using binders, compared to a granular catalyst obtained by a conventional method of mixing powdered zeolite with pseudobemite, followed by granulation and calcination. The texture and acid characteristics of granulated zeolites and Mo-containing catalysts based on them have been studied. The effect of dealumination of granular zeolites with a hierarchical porous structure on their texture and acid characteristics, as well as on their catalytic activity in the process of methane conversion is shown. The HRTEM method shows a difference in the distribution of the active Mo-containing phase in the granulated zeolite catalysts depending on the method of their preparation. Particles with a wide size distribution (2-30 nm), which are the crystalline phase of molybdenum carbide (β-Mo2C), and Mo-containing clusters in zeolite channels are present on the surface of granular samples that do not contain a binder. The catalyst prepared with the addition of the binder is micron agglomerates consisting of sub-micron sized zeolite particles and alumina sufficiently uniformly covering the surface of the zeolite. According to elemental mapping using energy dispersive X-ray spectroscopy, it was found that the active component is uniformly distributed over the catalyst surface, but the molybdenum signal on the alumina is significantly higher, which is explained by its higher specific surface area and the availability of particles. It has been found that the method of preparing granular Mo-containing zeolite catalysts has an effect on their catalytic activity, selectivity and stability in the process of non-oxidative conversion of methane to aromatic hydrocarbons. For citation: Stepanov A.A., Korobitsyna L.L., Vosmerikov A.V., Gerasimov E.Yu., Ishkildina A.Kh. Non-oxidative methane conversion study on granulated Mo-containing zeolite catalysts. ChemChemTech [Izv. Vyssh. Uchebn. Zaved. Khim. Khim. Tekhnol.]. 2024. V. 67. N 8. P. 85-94. DOI: 10.6060/ivkkt.20246708.7t.

Partially Ionized Amino Acid Salt Enabling Spatially Vertical n‐Phase Distribution of Quasi‐2D Perovskite for Efficient Deep‐Blue Light‐Emitting Diodes

AbstractThe deep‐blue perovskite light‐emitting diodes (PeLEDs) are of essential and indispensable for the application in full‐gamut display. However, the deep blue emission required large bandgap in small n phase exhibits high surface activity that gives rise to the difficulty of n phase distribution control spatially and proportionally in quasi‐2D perovskite films. Here, the deep‐blue pure‐bromide perovskite films is present that exhibit spatially vertical n phase distribution, owing to the partially ionized amino acid salt of 3‐Ammonium propionic acid bromide (3CBr) modulated crystallization kinetic of perovskite. The strong interaction of 3CBr and perovskite lattice improves the stability of small n phases, showing tunable photoluminescence (PL) emission and enhanced PL quantum yield (PLQY). The achieved champion deep blue PeLED shows a maximum EQE of 3.64% at electroluminescence (EL) emission wavelength of 466 nm, locating at the top rank of the similar devices. This work provides an effective strategy to fabricating efficient deep‐blue perovskite films and devices, promoting the development of perovskite‐based application in display.

Model of Contextual Learning Media in Understanding the Knowledge and Skills of Learners

Abstract The use of teaching methods in accounting education is still rare. This can lead to students having little or no interest, lack of motivation, and learning difficulties in understanding accounting because it is unclear. The importance of this research is to understand the production process of learning media models in accounting. Develop an understanding of knowledge and skills in accounting through learning experiences based on real-world situations. The method used in this study is the use of the research model (4D) developed by Thiagarajan, with definition (interpretation), design phase, development phase and dissemination phase (distribution). The results suggest that interpretation of existing data is not sufficient to support the use of the scientific method. All students are motivated to learn the curriculum in the classroom.

In-situ formation and ablation mechanism of dense and multilayered ZrB2-ZrSi2-MoSi2 ultra-high temperature ceramic composite coating on Ta-W alloy under plasma blame beyond 2000 ℃

A dense and three-layered ZrB2-ZrSi2-MoSi2 composite coating with continuous interlayer interfaces and a thickness of ∼270 μm was in-situ prepared on Ta-10 W alloy by plasma spraying and pack cementation. Subjected to plasma ablation at 9.8 MW/m² for 1000 seconds, the coating with a mass ablation rate of 0.0002 mg/s undergoes oxidation to form a skeleton-structured ZrO2 and liquid self-sealing SiO2. During the ablation, the over-diffused silicon top layer of the coating with high silicon content and uniform phase distribution can produce relatively adequate SiO2 to withstand the consumption for up to 1000 seconds, yielding excellent ablation resistance above 2000 ℃.

Modifying the Characteristics of the Electrical Arc Generated during Hot Switching by Reinforcing Silver and Copper Matrices with Carbon Nanotubes

Switching elements are crucial components in electrical and electronic systems that undergo severe degradation due to the electrical arc that is generated during breaking. Understanding the behavior of the electrical arc and modifying its characteristics via proper electrode design can significantly improve durability while also promoting optimal performance, reliability, and safety in circuit breakers. This work evaluates the feasibility of carbon nanotube (CNT)-reinforced silver and copper metal matrix composites (MMCs) as switching electrodes and the influence of CNT concentration on the characteristics of the arcs generated. Accordingly, three different concentrations per MMC were manufactured via powder metallurgy. The MMCs and reference materials were subjected to a single break operation and the electrical arcs generated using 100 W and 200 W resistive loads were analyzed. The proposed MMCs displayed promising results for application in low-voltage switches. The addition of CNTs improved performance by maintaining the arc’s energy in the silver MMCs and reducing the arc’s energy in the copper MMCs. Moreover, a CNT concentration of at least 2 wt.% is required to prevent unstable arcs in both metallic matrices. Increased CNT content further promotes the splitting of the electrical arc due to a more complex phase distribution, thereby reducing the arc’s spatial energy density.

Microstructure and performance of AlCoCrFeNiCu(CeO2)X high-entropy alloy coatings by plasma cladding

AlCoCrFeNiCu(CeO2)X (x=0 wt%, 0.3 wt%, 0.6 wt%, 0.9 wt%, and 1.2 wt%) HEA coatings were applied via plasma cladding technology to a 35CrMo steel surface in this investigation. Electron back-scattering diffraction (EBSD), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and X-ray diffraction (XRD) were used to analyze the phase composition and microstructure of the coatings. A microhardness meter, a nanoindenter, a wear test machine, and an electrochemical station were used to assess the coating performance. The findings demonstrate that the phase composition of the coatings is unaffected by the addition of CeO2, with all coatings consisting of FCC and BCC phases. CeO2 was added to the coatings to refine their grain size and increase their proportion of high angle grain boundaries (HAGBs), BCC phase content, and geometrically necessary dislocation (GND) density. These improvements led to significant increases in the microhardness and wear resistance of the coatings. The 0.3 wt% CeO2 coating has the best corrosion resistance, which is caused by a number of factors including the element distribution, grain size, content of each phase, and phase distribution of the coatings. The corrosion resistance of the coating increases and then decreases nonlinearly with increasing CeO2 content.

Enhanced amplified spontaneous emission performance through effective regulation of phase distribution in Ruddlesden-Popper perovskite films.

Ruddlesden-Popper (RP) perovskites promise next-generation gain media for laser devices. However, most RP perovskite lasers are still suffering from inferior performance characteristics, such as inadequate energy transfer, unstable emission, and short lifetime. To address the above problems, high crystalline quality, compact, and smooth PEA2FA2Pb3Br10 films with uniform phase distribution were successfully prepared by ionic liquid (IL) methylammonium acetate (MAAc) in an air environment. Compared with the PEA2FA2Pb3Br10 film prepared by the traditional solvent dimethyl sulfoxide (DMSO), an enhanced amplified spontaneous emission (ASE) with a lower threshold of 58 µJ·cm-2 from the MAAc-treated film was obtained under nanosecond laser excitation. The transient absorption (TA) spectroscopy revealed that a uniform phase distribution and more efficient energy transfer processes were achieved in the PEA2FA2Pb3Br10-MAAc film, leading to an enhanced band-to-band spontaneous emission process. Furthermore, the films exhibited better stability, showing no signs of degradation under the 120 min pulsed laser pumping in air and stability of ASE spectra at even 95% humidity conditions. This study provides an important foundation for achieving high-performance optically pumped lasers based on the unique RP perovskites.

Processing of fully dense and high conductivity W[sbnd]20Cu composite via copper melt infiltration into a pressed tungsten wire skeleton

The current study proposed melt infiltration into entangled pressed wire as a proper method for rapid and energy-efficient production of tungsten‑copper composites. The process includes wire packing through different strategies, pressing, and infiltration steps. First, a predesigned wire structure through different strategies of simple, spiral, cylindrical, and spherical is packed and pressed to form a permeable tungsten skeleton. Then, by infiltrating molten copper under a dry hydrogen atmosphere into the porous preforms, the W20Cu composite is fabricated and characterized. An almost fully dense sample with excellent hardness of 238.1 HV1 and high conductivity of 58.64% IACS in W20Cu composite was achieved. These values are almost 25% and 50% higher than that from the conventional melt infiltration method, respectively. It was seen that the packing strategy is so effective in achieving the best properties where the processed composite by spherical packing strategy exhibits better density, conductivity, and hardness than the sample produced via the other three packing strategies. However, all the properties of the melt infiltration into entangled pressed wire processed composite via all packing strategies are higher than those processed via conventional methods. These excellent properties could be attributed to the mostly bonded tungsten phase, high purity, pore-free, and suitable distribution of tungstens which are a result of this process characteristics. Besides, lower cycle time and energy consumption are other advantages of the new process compared to conventional melt infiltration via powder metallurgy. This approach presents a promising prospect for future industrial applications.

Electron Microscopic Analysis of the Nb<sub>5</sub>Si<sub>3</sub>/NBC/NbSi<sub>2</sub> Composite Structure

The method of aluminothermic self-propagating high-temperature synthesis was used to obtain a composite material based on Nb-Si-C. The study of this system is of interest from the point of view of obtaining high-temperature materials of a new generation for gas turbine engine building, capable of replacing heat-resistant nickel alloys, as well as the potential possibility of forming MAX-phases (phases Mn + 1AXn where n = 1, 2, 3, ...; M is transitional d-metal, A – p-element, X – carbon). The resulting Nb-Si-C composite were studied by X-ray diffraction, scanning electron microscopy, and X-ray spectral microanalysis. It is shown that NbC carbide and silicides γ-Nb5Si3 and NbSi2 are formed in the sample. A detailed analysis of the morphological distribution of the constituent phases has been carried out.

The influence of microstructure on the oxidation behavior of a TaTiCr refractory complex concentrated alloy

This work explores the effect of microstructure on the oxidation behavior of an equiatomic TaTiCr RCCA after 24 h of exposure at 800°C, 1000°C, 1200°C, and 1400°C. Two microstructural conditions, both containing a bcc matrix with C15 Laves precipitates, with one condition having coarser precipitates (∼10.9 µm diameter) and one condition having finer precipitates (∼2.9 µm diameter) were studied. At all oxidation temperatures except 800°C, the finer-scale (TaTiCr-F) condition experienced more rapid oxidation kinetics, higher mass gains, and thicker oxide scales and internal reaction zones. However, at 800°C, the microstructure containing coarser precipitates (TaTiCr-C) formed a thicker oxide scale. Continuous, protective Cr2O3 layers were only observed in the coarse precipitate condition and correlations between Cr2O3 layer thickness, subsequent formation of complex refractory oxides, and the initial Laves precipitate size are described. It is proposed that the formation of continuous Cr2O3 is highly dependent on the size and distribution of the Cr-rich Laves phase and only mildly dependent on phase fraction. Oxidation mechanisms for each condition are discussed relative to the initial microstructures, observed oxide species, and related alloy systems.

Microstructure and Mechanical Properties of Mg-Al-La-Mn Composites Reinforced by AlN Particles.

The Mg-Al-RE series heat-resistant magnesium alloys are applied in automotive engine and transmission system components due to their high-temperature performance. However, after serving at a high temperature for a long time, the Al11RE3 phase coarsened and even decomposed, while the Mg17Al12 phase grew and dissolved, which limits the service temperature of Mg-Al-RE series heat-resistant magnesium alloys to a maximum of 175 °C. In this study, a new preparation method for in situ AlN particles was presented. The AlN/Mg-4Al-4La-0.3Mn composites were prepared by a master alloy and casting method. The effects of various contents of AlN (0.5-3.0 wt.%) on the microstructure and mechanical properties of the Mg-4Al-4La-0.3Mn (AE44) alloy at room (25 °C) and high temperatures (150-250 °C) were investigated. Microstructure analysis revealed that the inclusion of AlN led to a reduction in both the grain size and second phase size in the AE44 alloy, while also improving the distribution of the second phase. The average grain size, Al11La3 phase, Al2La phase, and Al3La phase of the 2.0 wt.% AlN/AE44 composite were 135.7, 9.6, 1.9, and 12.6 μm, respectively, which were significantly lower than those of the AE44 matrix alloy (179.8, 12.6, 3.3, 17.8 μm). The refinement was attributed to the ability of AlN particles to serve as heterogeneous nucleation cores for α-Mg and, at the same time, impede the growth of the solid-liquid interface, eventually leading to grain refinement. With the increase in the AlN content, the mechanical properties of composites initially exhibited an increase at both room and high temperatures, followed by a subsequent decrease. When the AlN content was 2.0 wt.%, the composite exhibited optimal strength and plasticity matching. At room temperature, the TYS, UTS, and EL values of the 2.0 wt.% Mg-4Al-4La-0.3Mn composite were 96 MPa, 175 MPa, and 7.0%, respectively, which were increased by 26 MPa, 27 MPa, and 0.7% when compared with the base alloy. The TYS of the 2.0 wt.% Mg-4Al-4La-0.3Mn composite at 150 °C, 200 °C, and 250 °C were 17 MPa, 14 MPa, and 22 MPa higher than those of the matrix alloy, respectively. The main strengthening mechanisms were second phase strengthening, load transfer strengthening, and thermal mismatch strengthening. At elevated temperatures, AlN particles effectively pinned the grain boundaries, inhibiting their migration, and hindered dislocation climbing, resulting in excellent mechanical properties of the composites at high temperatures. This study contributes to the advancement of in situ AlN particle preparation methods and the exploration of effects of AlN on the properties and microstructure of Mg-Al-RE alloys at high temperatures (150-250 °C).

Over 18.2% efficiency of layer–by–layer all–polymer solar cells enabled by homoleptic iridium(III) carbene complex as solid additive

The vertical phase distribution of active layers plays a vital role in balancing exciton dissociation and charge transport for achieving efficient polymer solar cells (PSCs). The layer–by–layer (LbL) PSCs are commonly prepared by using sequential spin–coating method from donor and acceptor solutions with distinct solvents and solvent additives. The enhanced exciton dissociation is expected in the LbL PSCs with efficient charge transport in the relatively neat donor or acceptor layers. In this work, a series of LbL all–polymer solar cells (APSCs) were fabricated with PM6 as donor and PY–DT as acceptor, and triplet material m–Ir(CPmPB)3 is deliberately incorporated into PY–DT layer to prolong exciton lifetimes of active layers. The power conversion efficiency (PCE) of LbL APSCs is improved to 18.24% from 17.32% by incorporating 0.3 wt% m–Ir(CPmPB)3 in PY–DT layer, benefiting from the simultaneously enhanced short–circuit current density (JSC) of 25.17 mA cm−2 and fill factor (FF) of 74.70%. The enhancement of PCE is attributed to the efficient energy transfer of m–Ir(CPmPB)3 to PM6 and PY–DT, resulting in the prolonged exciton lifetime in the active layer and the increased exciton diffusion distance. The efficient energy transfer from m–Ir(CPmPB)3 to PM6 and PY–DT layer can be confirmed by the increased photoluminescence (PL) intensity and the prolonged PL lifetime of PM6 and PY–DT in PM6 + m–Ir(CPmPB)3 and PY–DT + m–Ir(CPmPB)3 films. This study indicates that the triplet material as solid additive has great potential in fabricating efficient LbL APSCs by prolonging exciton lifetimes in active layers.

Phase-Field Simulation of Precipitation and Grain Boundary Segregation in Fe-Cr-Al Alloys under Irradiation.

A phase-field model for the precipitation of Fe-Cr-Al alloy is established incorporating grain boundary (GB) effects and irradiation-accelerated diffusion. The radiation source and grain boundary effect are incorporated to broaden the applicability of the Fe-Cr-Al precipitated phase-field model. The model is firstly employed to simulate the precipitation of the Cr-rich α' phase in a single-crystal alloy. The precipitation rate and the size distribution of the precipitated phase were analyzed. Subsequently, the model is utilized to simulate segregation at GBs in a double-crystal system, analyzing the enrichment of Cr and depletion of Al near these boundaries. The simulation results are consistent with experimental observations reported in the references. Finally, the model is applied to simulate the precipitation in a polycrystalline Fe-Cr-Al system. The simulated results revealed that the presence of GBs induces the formation of localized regions with enhanced Cr and Al content as well as depleted zones adjacent to these boundaries. GBs also diminish both the quantity and precipitation rate of the formed phase within the grains.

Mechanical properties of AlCoCrFeNi2.1 EHEA controlled via the coherent nano-precipitated phase during hot rolling

In the present work, the AlCoCrFeNi2.1 EHEA was hot rolled in multiple passes at different temperatures and reductions. The L12/B2 lamellar eutectic structure of the as-cast alloy disappeared after hot rolling and evolved into an irregular distribution of FCC and B2 phases resembling a heterogeneous structure. Combined with SEM and TEM microscopic characterization, it is evident that the nanoprecipitates in both the FCC and B2 phases simultaneously maintain a highly coherent relationship with their matrix structure, with the ordered L12 nanoprecipitates in FCC phase rich in Al and Ni, and the disordered BCC nanoprecipitates in B2 phase rich in Cr. The strength of the alloy can be greatly improved through microstructure evolution which can be directly derived from the back stress effect in the heterogeneous structure. The tensile fracture morphology and fracture mechanism were analyzed to further study this effect. More importantly, this work examined the effects of changes in the mean-free path of the dislocation induced by the morphology evolution and density of the nanoprecipitates on the mechanical properties. As a result, the microstructure and mechanical properties of hot rolled AlCoCrFeNi2.1 EHEA can be controlled to a certain extent.

Characterizing PEM fuel cell catalyst layer properties from high resolution three-dimensional digital images, part I: A numerical procedure for the ionomer distribution reconstruction

In this work, a numerical approach is presented to reconstruct the ionomer three-dimensional distribution in the microstructure of the cathode catalyst layer (CCL) of a polymer electrolyte membrane fuel cell (PEMFC) from a 3D segmented image of the CCL obtained by focused ion beam-scanning electron microscopy (FIB-SEM). Three forms of ionomer are distinguished: the ionomer filaments, the coating ionomer and the inter-carbon grains ionomer. The ionomer filaments are identified by applying a filtering procedure to the size distribution in the segmented solid phase obtained via a maximum sphere inscription algorithm. The coating ionomer is reconstructed via a filtering procedure of the curvature distribution computed over the interface between the two segmented phases from the consideration that concave regions are preferential ionomer accumulation zones during the drying step of the CCL fabrication procedure. This procedure of coating controlled by the local curvature is applied until a desired value of coverage is reached. In a last step, catalyst nanoparticles, also not visible in the FIB-SEM image, are reconstructed in the image.