Properties of Cu–Cr–Zr alloy with ultrafine-grained (UFG) structure produced by equal-channel angular pressing (ECAP) via different routes have been investigated. Special attention was paid to the ...optimization of multi-functional structural, thermal, electrical and mechanical properties of the alloy by aging of UFG one. Multi-pass ECAP via different routes gives rise to the formation of a deformation-induced submicrocrystalline structure with the grain (subgrain) sizes in the range of 200–300nm depending on applied routes which leads to high hardness and strength in the Cu–Cr–Zr alloy with reduced ductility. Amongst the applied routes, route-Bc was found to be the best processing path for achieving the lowest grain size, the highest hardness and strength. Aging of 8Bc-processed UFG samples increases the hardness and strength of Cu–Cr–Zr alloy while retaining an electrical conductivity comparable to that of aged coarse-grained (CG) one. A satisfactory electrical conductivity of 71%IACS without considerable loss of peak hardness was achieved after aging of 8Bc-processed UFG alloy at 425°C for 240min. The precipitation strengthened UFG alloy remains its stable behavior at elevated temperatures up to 450°C.
With the use of electrolytic Cu powder, Zr powder, Si powder and nickel-coated Bsub.4C powder as cladding powders, in-situ synthesized ZrBsub.2-SiC reinforced copper matrix composite coatings were ...prepared by laser cladding on the surface of the copper substrate to improve the surface hardness and wear resistance. Under the condition of a laser energy density at 60 kJ/cmsup.2, the macroscopic surface of the composite coating was continuously flat. The microstructure and phase of the cladding coating were analyzed by means of XRD and SEM. The reinforcements with nano-scale particle and micron-scale needle-like structures were in-situ synthesized in the cladding coating, and the content of the reinforcement phase decreased slightly from the coating surface to the substrate. The phase analysis results showed that the reinforcements included ZrBsub.2 and SiC. When the content of the reinforcement was increased to 30 wt%, microhardness also increased from 48 HVsub.0.2 to 309 HVsub.0.2, which was about 5.6 times that of the copper matrix. The wear resistance of the composite coatings was characterized by current-carrying wear tests. By keeping the sliding speed and load constant, the wear rate decreased with an increase in the reinforcement content, and the wear mechanism changed from adhesive wear to abrasive wear. The wear rate of the composite coating with the current was higher than that without the current due to its electric ablation and high temperature.
•Cu bimetallics are amongst the most promising materials for CO2 electro-reduction.•These materials often give products more deeply reduced than CO/formate.•Products with C–C bonds can also be ...obtained.•Progress in the development of these materials from the last two years is reviewed.•The review focuses on systems producing species more reduced than CO/formate.
Rising levels of carbon dioxide in the atmosphere have precipitated considerable research efforts aimed at generating energy from renewable sources, such that consuming this energy does not lead to further increases in atmospheric CO2. Simultaneously, atmospheric CO2 represents a useful feedstock for the storage of renewably-generated energy, in particular through electroreduction of CO2 powered by renewables to give hydrocarbon fuels that when burned do not increase net CO2 levels in the atmosphere. In order to bring such renewable-powered production of hydrocarbons from CO2 to reality, improved electrocatalysts for carbon dioxide reduction are required. For example, Cu is the only single metal that demonstrates appreciable Faradaic efficiency for CO2 reduction products that are reduced by more than two-electrons, but pure Cu is not an especially active or selective catalyst for this process. Hence there has been considerable interest in making bimetallic catalysts using Cu in combination with other metals in order to find systems that can reduce CO2 to products such as methane, methanol, ethanol and beyond. In this minireview, we give an overview of recent progress in CO2 electroreduction using bimetallic cathodes composed of copper and various other metals in combination, with a particular focus on studies going beyond two-electron reduction products from the last two years.
Solid-solution ternary Pd–Au–Cu nanoparticles (NPs) with broadly tunable compositions (Pd x Au y Cu100–(x+y); where x = 30–70 and y = 15–35) were prepared by a microwave-assisted polyol reduction ...method. Commercially available Pd2+, Au3+, and Cu2+ salts were directly co-reduced by ethylene glycol and NaBH4 in a one-pot process to generate near-monodisperse ternary alloy NPs with mean sizes between 2 and 4 nm. Using the same synthetic approach, the corresponding binary alloy PdCu NPs with similar monodispersities and particle sizes were also prepared. The comparative catalytic performances of PdCu NPs and PdAuCu NPs were assessed for the aqueous-phase reduction of nitrate (NO3 −) anions and were compared to previously published results for analogous binary PdAu NPs. The experimental catalytic results and theoretical studies reveal that the resulting catalytic activity of Pd surface sites are highly sensitive to the relative amounts of Au and Cu also present. We ultimately prove that the hitherto unstudied ternary PdAuCu NPs are highly active and selective as NO2 – reduction catalysts and effectively utilize Cu as an economically viable dilutant metal, without sacrificing the activity or stability of industrially important and well-studied PdAu alloy catalysts. From an economic perspective, the ternary alloy nanocatalysts show superior price-to-activity ratios: the measured turnover rates of Pd63Au22Cu16 NPs (3.353 min–1 $–1) outperform not only monometallic Pd NPs (0.797 min–1 $–1) but also binary PdAu NPs and PdCu NPs of all accessible compositions.
Multi-material processing in selective laser melting using a novel approach, by the separation of two different materials within a single dispensing coating system was investigated. 316L stainless ...steel and UNS C18400 Cu alloy multi-material samples were produced using selective laser melting and their interfacial characteristics were analyzed using focused ion beam, scanning electron microscopy, energy dispersive spectroscopy and electron back scattered diffraction techniques. A substantial amount of Fe and Cu element diffusion was observed at the bond interface suggesting good metallurgical bonding. Quantitative evidence of good bonding at the interface was also obtained from the tensile tests where the fracture was initiated at the copper region. Nevertheless, the tensile strength of steel/Cu SLM parts was evaluated to be 310±18MPa and the variation in microhardness values was found to be gradual along the bonding interface from the steel region (256±7HV0.1) to the copper region (72±3HV0.1).
•Multi-material processing was successfully implemented and demonstrated in SLM.•Bi-metallic laminates of steel/Cu were successfully produced with the SLM process.•A substantial amount of Fe and Cu diffusion was observed at the bond interface.•Good metallurgical bonding was obtained at the interface of the steel/Cu laminates.•Highly refined microstructure was obtained due to rapid solidification in SLM.
Monodisperse bimetallic Pd–Cu nanoparticles with controllable size and composition were synthesized by a one‐step multiphase ethylene glycol (EG) method. Adjusting the stoichiometric ratio of the Pd ...and Cu precursors afforded nanoparticles with different compositions, such as Pd85–Cu15, Pd56–Cu44, and Pd39–Cu61. The nanoparticles were separated from the solution mixture by extraction with non‐polar solvents, such as n‐hexane. Monodisperse bimetallic Pd–Cu nanoparticles with narrow size‐distribution were obtained without the need for a size‐selection process. Capping ligands that were bound to the surface of the particles were removed through heat treatment when the as‐prepared nanoparticles were loaded onto a Vulcan XC‐72 carbon support. Supported bimetallic Pd–Cu nanoparticles showed enhanced electrocatalytic activity towards methanol oxidation compared with supported Pd nanoparticles that were fabricated according to the same EG method. For a bimetallic Pd–Cu catalyst that contained 15 % Cu, the activity was even comparable to the state‐of‐the‐art commercially available Pt/C catalysts. A STEM‐HAADF study indicated that the formation of random solid‐solution alloy structures in the bimetallic Pd85–Cu15/C catalysts played a key role in improving the electrochemical activity.
Army of two: Supported bimetallic Pd–Cu nanoparticles, which were synthesized by a one‐step multiphase method, showed enhanced electrocatalytic activity towards MeOH oxidation, comparable to the state‐of‐the‐art commercially available Pt/C catalysts.
Utilizing the extra-ordinary properties of carbon nanotube (CNT) in metal matrix composite (MMC) for macroscopic applications is still a big challenge for science and technology. Very few successful ...attempts have been made for commercial applications due to the difficulties incorporating CNTs in metals with up-scalable processes. CNT reinforced copper and copper alloy (bronze) composites have been fabricated by well-established hot-press sintering method of powder metallurgy. The parameters of CNT–metal powder mixing and hot-press sintering have been optimized and the matrix materials of the mixed powders and composites have been evaluated. However, the effect of shape and size of metal particles as well as selection of carbon nanotubes has significant influence on the mechanical and electrical properties of the composites. The hardness of copper matrix composite has improved up to 47% compared to that of pure copper, while the electrical conductivity of bronze composite has improved up to 20% compared to that of the pure alloy. Thus carbon nanotube can improve the mechanical properties of highly-conductive low-strength copper metals, whereas in low-conductivity high-strength copper alloys the electrical conductivity can be improved.
The electrical resistivity, magnetic, and galvanomagnetic properties of the cast and rapid melt quenched Mn.sub.3Al Heusler alloy have been studied. Rapid melt quenching was found to result in ...changing the microstructure of the Mn.sub.3Al alloy, which leads to substantial changes in its electronic transport and magnetic properties. It was suggested that for the cast and rapid melt quenched Mn.sub.3Al alloy frustrated antiferromagnetic and almost compensated ferrimagnetic state could appear, respectively. It is shown that the preparation and treatment of the Mn.sub.3Al compound plays a substantial role in the formation of its electronic and magnetic characteristics.
To investigate the thermal and mechanical behavior of casting wheel, a two-dimensional thermo-elastic-plastic finite element model was used to predict the temperature, stress and distortion ...distribution of the casting wheel during the wheel and belt continuous casting process. The effects of grinding thickness and casting speed on the thermal and mechanical behaviors of the center of the hot face of the casting wheel were discussed in detail. In each rotation, the casting wheel passes through four different spray zones. The results show that the temperature distribution of the casting wheel in different spray zones is similar, the temperature of the hot face is the highest and the temperature reaches the peak in the spray zone III. The stress and distortion depend on the temperature distribution, and the maximum stress and distortion of the hot face are 358.2 MPa and 1.82 mm, respectively. The temperature at the center of the hot face decreases with increasing grinding thickness and increases with increasing casting speed.
The research focuses on alloy design, powder production, and laser powder bed fusion (LPBF) of copper alloys. Copper and its alloys play a fundamental role for modern industrial applications due to ...their excellent thermal and electric conductivity in conjunction with considerable mechanical strength, for example, as welding electrodes and nozzles. By precipitation hardening, the hardness of low-alloyed copper, like CuCr1Zr, can be increased significantly. A combination of the geometry freedom of additive manufacturing with a tailor-made alloy design during powder production offers the opportunity to develop new alloy systems with a focus on the respective application. Experimental results regarding gas atomization, LPBF, property investigations, and property optimization of CuCr1Zr are presented. Powder particles and LPBF parts were analyzed with respect to phase and precipitate formation and compared to benchmark experiments of conventionally cast copper alloys. The microstructure differs significantly. Furthermore, the relative density of the LPBF parts reaches a value of 99.8%.
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