Cu-Zn Alloy Research Articles

Achieving room temperature superplasticity in the Zn-0.5Cu alloy processed via equal channel angular pressing

The Zn-0.5Cu alloy was investigated in as-cast, homogenized state and after carrying out equal channel angular pressing four times at room temperature via route BC. Microstructure analysis using light microscopy and SEM/EBSD was performed, as well as tensile tests, misorientation angle distribution and texture analysis. The initial microstructure with the average grain size of 560 µm was refined to a grain size of approx. 1 µm. The obtained microstructure consists of uniaxial grains separated mostly by high angle grain boundaries. Mechanical characterization was performed at strain rates from 2 × 10−6 s−1 to 1 s−1 at room temperature. Ultrafine-grained zinc-copper alloy exhibited 510% elongation with the strain rate sensitivity equal 0.31, which was the first observation of room temperature superplasticity in Zn-Cu alloys. Based on the microstructure, misorientation angle and texture analysis, the main operating deformation mechanisms were distinguished for samples deformed at strain rates from 2 × 10−5 s−1 to 10−1 s−1.

Investigation of Color Change in Cu-Zn Alloys by Reflectivity and Color Difference Analysis

Investigation of Color Change in Cu-Zn Alloys by Reflectivity and Color Difference Analysis

Effect of Zn on Pore Characteristics in Lotus-Type Porous Cu.

The effect of Zn on pore characteristics in lotus-type porous Cu alloy was investigated. The lotustype porous Cu-Zn alloys were fabricated with Zn content from 0.01 to 0.1 at% by the centrifugal casting method. The results demonstrated that the porosity was rarely affected by Zn content. However, the average pore diameter and pore number density of the lotus type porous Cu-Zn alloys were significantly affected by the Zn content. The average pore diameter decreased as the Zn content increased up to 0.01 at%, and then increased as the Zn content increased up to 0.1 at%. In contrast, the variations in the pore number density of the lotus-type porous Cu-Zn alloys showed the reversed tendency with respect to that of the average pore diameter. The increase in heterogeneous nucleation sites for pores attributed to the decreased average pore diameter and the increased pore number density.

Compositional ratio effect on the surface characteristics of CuZn thin films

CuZn thin films were fabricated by RF co-sputtering method on p-type Si(100) wafer with various RF powers applied on metallic Cu and Zn targets. This paper aimed to determine the morphological, chemical, and electrical properties of the deposited CuZn thin films by utilizing a surface profiler, atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), UV photoelectron spectroscopy (UPS), and a 4-point probe. The thickness of the thin films was fixed at 200 ± 8 nm and the roughness of the thin films containing Cu was smaller than pure Zn thin films. XRD studies confirmed that the preferred phase changed, and this tendency is dependent on the ratio of Cu to Zn. AES spectra indicate that the obtained thin films consisted of Cu and Zn. The high resolution XPS spectra indicate that as the content of Cu increased, the intensities of Zn2+ decreased. The work function of CuZn thin films increased from 4.87 to 5.36 eV. The conductivity of CuZn alloy thin films was higher than pure metallic thin films.

Transformation stress of shape memory alloy CuZnAl: Non-Schmid behavior

We establish an atomistically-informed model for predicting the non-Schmid behavior of critical stresses for bcc to orthorhombic (L21 to 18R) martensitic transformation in CuZnAl alloys. The interplay between the stacking fault displacements and the applied stress tensor components are shown to be responsible for the variation of the CRSS levels as much as a factor of almost 2.5 (25 MPa–60 MPa) depending on the crystal orientation. The predicted transformation stresses exhibit excellent agreement with the experimental results in this study and the measurements reported in the literature. The possible role of deviations from crystallographic ordering was also investigated illustrating the increase in transformation stress levels upon introduction of local disorder.

One step electrochemical route to the fabrication of highly ordered array of cylindrical nano porous structure and its electrocatalytic performance toward efficient hydrogen evolution

An efficient and non-precious metal catalyst is a key factor for hydrogen evolution reaction (HER). Here we report that the fabrication of highly ordered porous arrays of Cu-Zn-Ni alloy has been carried out in a one-step electrochemical route at a constant apparent current density of −3 A·cm−2. The optimum film composition and reactivity of the electrodes for catalytic hydrogen evolution reaction were analyzed by using different current densities, deposition time and bath concentration. For this purpose, onset potentials in linear sweep voltammograms (LSV) were compared. The structure and morphology of nanoporous Cu-Zn-Ni and Cu-Zn alloy were characterized by SEM and energy dispersive X-ray (EDS) analysis.The experimental results on the behavior of electrocatalytic activity of prepared alloys showed that the addition of nickel to the alloys improves of the electrocatalytic performance of the electrodes toward HER. In addition, enhancement of electrochemical activity toward hydrogen evolution can be attributed to the large electrochemical active surface area and porous structure of Cu-Zn-Ni alloy. In order to improvement of reaction kinetics, Tafel plots were derived from LSV voltammograms, and the exchange current densities for HER on synthesized electrodes (Cu-Zn and Cu-Zn-Ni alloys) were calculated about 3.2 × 10−5 and 2.1 × 10−3 mA·cm−2, respectively.

An effective method to obtain Cu-35Zn alloy with a good combination of strength and ductility through cryogenic rolling

In the present study, commercial Cu-35Zn α-brass sheets were subjected to cryogenic rolling (CR) to obtain samples with different amounts of deformation in the thickness direction. A self-designed liquid nitrogen cooling system that can simultaneously cool the work rollers and samples was used to ensure an ultra-low temperature condition during the rolling process. The grains, deformation twins, and dislocation density of the samples were studied by optical microscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD). Uniaxial tensile tests and Vickers hardness measurements were conducted to measure the mechanical properties of the samples. The microstructures and mechanical properties of CR samples were apparently improved compared to the room temperature rolling (RTR) samples with increasing deformation amount. As a typical example, when the deformation amount is 90%, the CR sample possesses ultrafine microstructures and demonstrates extraordinary mechanical properties. The average tensile and yield strengths of a 90% deformation CR sample can be improved to 835.3MPa and 711.5MPa, while those of a 90% deformation RTR sample are 718.6MPa and 481.2MPa. The average elongation of the CR sample is 2.9%, which is acceptable compared with the RTR sample whose average elongation is 3.1%. The ultrafine microstructures containing ultrafine grains, high density dislocation, and nanometer scale deformation twins in the 90% deformation CR sample may be the main reason for its extraordinary mechanical properties. Therefore, samples with a good combination of strength and ductility were obtained in the present study. This may be a valuable exploration to fabricate Cu-35Zn alloy sheets with excellent microstructures and mechanical properties.

Structural-Phase Low-Stability States of BCC-Alloys with APB-Complexes in the Course of an Order-Disorder Phase Transition

Using the Monte Carlo method, the influence of the APB-complexes (a pair of shear-induced APBs along the direction and a pair of thermal APBs along the direction) on the low-stability states of β-brass is investigated during an order – disorder phase transition in the CuZn alloy as an example. It is shown that the formation energy of a complex of thermal APBs is higher than that of a complex of shear APBs. The contribution of APBs into disordering is essential up to the temperature of the order – disorder phase transition. The most significant fact for the long-range order in this system is the appearance of a defect in the form of an APB; the difference in the types of APBs and the plane of their occurrence do not exert a significant influence on the long-range order behavior with the temperature variations. The types of antiphase boundaries do affect the structural-energy characteristics of the system at the temperatures below that of the phase transition. It is obvious that a system with structure defects is less ordered than a defect-free system. The presence of a defect in the form of an APB favors the onset of disordering at lower temperatures: reduction of ordering in the alloy begins in the case of thermal APBs at lower temperatures compared to the case of shear APBs. In the CuZn alloy with a complex of thermal APBs along the direction the first distortions of the structural order invariably appear near the Zn–Zn boundary. In the alloy with a complex of shear-induced APBs along the direction the distortions of the structural order are only observed in the regions where the boundaries intersect. The presence of antiphase boundaries influences the alloy stability during heating. The CuZn alloy without distortions of structural defects is more stable than that with APBs. It is shown that the process of disordering is accompanied by the smearing and faceting of the boundaries.

Microstructure variation of CuZnAl alloy due to helium ions irradiation

CuZnAl alloy was irradiated at room temperature with helium (He+) ions (50 keV) to doses of 0.1, 1 and 10 displacement per atom (dpa), respectively. X-ray diffraction (XRD) was used to analyze the phase and stress; atomic force microscope and transmission electron microscopy were utilized to characterize roughness and microstructure variation, respectively. The XRD results show that a left shift in the diffraction peaks of irradiated samples was observed due to the tensile stress caused by He+ ions irradiation. The surface roughness of CuZnAl alloy increased first (0.1 and 1 dpa) and then decreased (10 dpa). After He+ ions irradiation at 0.1, 1 and 10 dpa, a large amount of dislocations were formed in the samples, and at a dose of 10 dpa, the sub-grains and helium bubbles were observed. The dislocations at 10 dpa were fewer than those at 0.1 and 1 dpa because high dose can enhance the recombination of interstitial atoms at the defect gathered site and the grain boundaries (GBs) can absorb point defects and defect clusters. Besides, the average diameter of helium bubbles at GBs was slightly larger than that in the grains.

Modification in Cu-Zn Alloy Properties by 2 MeV Ni<sup>+</sup> Ions Irradiation

We investigate the effects of 2 MeV Ni+ ion beam irradiation with various fluence ranging from 15 × 1011 to 60 × 1014 ions/cm2 on the surface, structural and mechanical properties of Cu-Zn alloy. The modification in target properties after irradiation is confirmed by using various characterization techniques viz. SEM, XRD, UTM and Vickers micro-hardness tester. The SEM results illustrate the formation of nano sized craters with different diameters. Their average diameter decreases from 190 nm to 90 nm by increasing ion fluence. The XRD analysis of irradiated targets reveals that Ni+ ion irradiation enhances the growth of (111) phase and its peak position varies due to ion induced tensile stresses in target matrix. Tensile and Vickers micro-hardness tests verify the mechanical properties of Cu-Zn alloy reduce monotonically upon irradiation. Various mechanisms such as generation, recombination, augmentation and annihilation of ion induced defects are responsible for this reduction. Understanding the relationships between various modified properties of irradiated target is essential for growing new advanced material by irradiation.

Orbital-based charge self-consistent Blackman-Esterling-Berk coherent potential approximation approach to substitutional disorder within a pseudopotential framework

We report the development of an ab initio electronic structure method applicable to generic substitutionally disordered real materials. A charge self-consistent orbital-based extension of the coherent potential approximation due to Blackman, Esterling, and Berk (BEB-CPA) is combined with the mixed-basis pseudopotential density functional theory approach. The general formalism in terms of a nonorthogonal basis set including subtleties of the pseudopotential framework is outlined. The BEB-CPA is validated on a binary tight-binding toy model against exact diagonalization of a randomly occupied cluster. Finally, the developed ab initio approach is benchmarked for a binary CuZn alloy, which confirms the robustness of the charge self-consistent procedure with respect to initial conditions.

Electronic structure study of the bimetallic Cu1-xZnx alloy thin films

A series of Zn doped copper materials were investigated upon their crystal and electronic structure with the general formula Cu1-xZnx. CuZn alloys were produced via electrodeposition method. Galvanostatic deposition was preferred for the deposition. Crystal properties of the samples were studied via X-ray diffraction (XRD) patterns and supported by the X-ray absorption fine structure spectroscopy (XAFS) data. According to the crystal structure analysis, crystal geometries of the substituted samples were mainly determined in bcc cubic. The study has revealed that, low amount of Zn substitution (0.1M) are inactive in the molecular interplays and treated as an impurity in fcc copper environment. However, higher Zn concentrations (> 0.1 M) have built bcc structure under the influence of the highly overlapped 4p levels wavefunctions of the neighbouring Cu and Zn atoms. Thus, 0.1 M zinc substitution has been determined as a threshold of the phase transition from fcc to the bcc structure.

Preparation and Characterization of Nanoporous Copper Films by Chemical Dealloying

Nanoporous Cu (np-Cu) materials can be easily prepared by chemical dealloying of Zn-Cu alloys. Tuning the surface area, the number of defects, the content of the less noble metal, and the mass transport properties of the nanoporous materials allows us to control its chemical, physical and catalytic properties as well as its mechanical properties for different applications. We present how the formation of the np-Cu films is controlled by the annealing temperature and kind of electrolyte. The Zn-Cu alloy films were prepared by electrodeposition of Zn onto a Cu surface. After the thermal annealing at three different temperatures, the Zn-Cu alloy films were dealloyed in acidic and alkaline media. Based on our results obtained from SEM, EDX, XPS and XRD, we correlate the structural changes (ligament size, pore size, composition) with the experimental dealloying conditions (annealing temperature, kind of electrolyte) to better understand the dealloying processes for the np-Cu films.

Differentiating Intrinsic Reactivity of Copper, Copper–Zinc Alloy, and Copper/Zinc Oxide Interface for Methanol Steam Reforming by First-Principles Theory

Identifying the intrinsic activity of the distinct sites which coexist in oxide-supported metal particles is vital but challenging for rational design of catalysts. We treat the challenge here by density functional theory calculations to differentiate unbiasedly the intrinsic reactivity of a variety of sites observed under reaction conditions for methanol steam reforming on Cu/ZnO catalyst. Metallic Cu and CuZn alloy are found to be less active but highly selective toward formaldehyde because water dissociation is demanding, which limits the formation of hydroxyl and subsequent coupling necessary to yield CO2. Cu/ZnO interface is highly active and selective for H2/CO2 because of its superior activity for water and methanol activation. Distinct hydrogen affinity at Cu/ZnO interface also leads to more favorable CO2 production via H2COO, in contrast to via HCOOH at (bi)metallic sites. The distinct reactivity of various structural motifs exposed and the importance of the metal/oxide for selectivity revealed i...

A facile and mild route for fabricating slippery liquid-infused porous surface (SLIPS) on CuZn with corrosion resistance and self-healing properties

In this report, a facile approach combining both galvanic dealloying and chemical vapor deposition is proposed to enable the slippery liquid-infused porous surface (SLIPS) onto CuZn alloy. Firstly, CuZn is dealloyed with CuSO4 aqueous solution, and a porous Cu2O surface is achieved via a dealloying-deposition route. The surface is modified with dodecanethiol to realize the superhydrophobicity. The infusion of oil phase is assisted by the spin coating technique, and SLIPS is finally obtained, showing prominent corrosion inhibition capability with the corrosion current density decreasing to 1/500 of the bare CuZn. Moreover, SLIPS shows high resistance to multiple cycles of electrical field with wide anodic and cathodic window. To external mechanical damage, such as cutting and erosion in seawater, SLIPS behaves good self-healing capability. Even after cutting or drilling the surface for many times, the corrosion inhibition can still be maintained, indicating that the coating constructed by self-healing fluid has high tolerance to external mechanical damage.

Tuning the Ligament Size and the Content of the Foreign Atom of the Nanoporous Copper for the Electrochemical Carbon Dioxide Reduction

During the electrochemical reduction reaction of carbon dioxide (CO2RR) on metallic copper surfaces several C1 and C2 products can be formed. The reaction mechanisms and kinetics, yet, are unclear to date. Different reaction mechanisms for CO2RR are postulated.1-3 For instance, the adsorption of negatively charged intermediates at the catalytically active surface might play a very important role in the formation of C2 products.3 Further critical issues for the CO2RR are addressed: (i) high overpotentials of up to 1 V, (ii) broad product distribution, (iii) fast degradation by catalyst poisoning and (iv) competition reaction at high cathodic potentials, referred to as hydrogen evolution reaction. Thus, tailoring the structure, morphology and chemical composition of Cu-based materials by adding other metals is one of the promising strategies to control the catalytic activity and product distribution during the CO2RR.4-5 In our study, we investigated the catalytic properties of a novel nanoporous copper film (np-Cu) for the CO2RR. The np-Cu films were prepared by de-alloying process of the less noble metal (Zn) from a Zn-Cu alloy. This technique allows us to tailor the ligament and pore size as well as the content of the Zn in the np-Cu. For the characterization of the np-Cu we used SEM, TEM, EDX, XRD and XPS. The catalytic performance of different np-Cu materials for the CO2RR was evaluated by linear sweep voltammetry and chronoamperometry. To correlate the measured current during the CO2RR polarization curves, the formed products were quantified by using gas chromatography and ion chromatography. Our results show how the ligament structure and the Zn content of the np-Cu have an effect on the activity and selectivity during the CO2RR. Depending on the experimental conditions, the dealloying in alkaline media largely forms copper oxide with very low content of Zn. In contrast, after dealloying in acidic media the ligament size and pore distribution of np-Cu are more uniform and contains a higher amount of Zn. The polarization curves for both np-Cu materials showed higher activity for the CO2RR compared to that for a flat Cu surface. We showed that a high content of Zn at the surface promotes the formation of hydrogen, while the copper oxide leads to higher selectivity to C2 products. Based on our results, we provide a deeper insight into the mechanism and kinetics for the CO2RR on np-Cu materials. 1. K. P. Kuhl, E. R. Cave, D. N. Abram, and T. F. Jaramillo, Energy Environ. Sci., 7050-7059, 5 (2012) 2. A. A. Peterson, F. Abild-Pedersen, F. Studt, J. Rossmeisl, and J. K. Nørskov, Energy Environ. Sci., 1311-1315, 3 (2010) 3. R. Kortlever, J. Shen, K. J. P. Schouten, F. Calle-Vallejo, and M. F. M. Koper, J. Phys. Chem. Lett., 4073-4082, 6 (2015) 4. R. Reske, M. Duca, M. Oezaslan, K. J. P. Schouten, M. T. M. Koper, and P. Strasser, J. Phys. Chem. Lett., 2410-2413, 4 (2013) 5. A. Dutta, M. Rahaman, N. C. Luedi, M. Mohos, and P. Broekmann, ACS Catal., 2804-2814, 6 (2016)

Phase Formation in Electrodeposited Cu-Zn Alloy Films Produced from Ultrasonicated Solutions

Phase Formation in Electrodeposited Cu-Zn Alloy Films Produced from Ultrasonicated Solutions

Preparation and Characterization of Nanoporous Copper Films By (electro)Chemical Dealloying

Nanostructured materials are of great interest in different fields such as solar cells, batteries, fuel cells and sensors.1-3 The chemical and physical properties of nanostructured materials strongly differ from those of the corresponding bulk materials. For instance, with decreasing size, quantum-physical effects get more relevant.2 Nanoporous materials offer not only new chemical and physical properties by nano-sizing but also very high surface area and good mass transport properties through the pores.3 A promising synthetic approach to prepare nanoporous copper (np-Cu) materials is the (electro)chemical dealloying process.4 Dealloying is the dissolution of the less noble metal (Zn) from a Cu-based alloy. The Cu-based alloys are prepared by electrodeposition of Zn on a Cu surface followed by thermal annealing step in an inert atmosphere. We showed that by modifying the dealloying conditions, np-Cu films with tuneable structure (e.g. ligament size and shape) and chemical composition (e.g. the residual content of the foreign atom and surface oxides) can be produced. For the characterization, a broad combination of microscopic and spectroscopic techniques was used: XPS, XRD, EDX, SEM and XANES/EXAFS. Our study shows the relationship between the dealloying parameters such as temperature, electrolyte, concentration etc. and the material properties of the np-Cu such as ligament size and shape, pore distribution and content of the foreign atom. First, the annealing temperature controls the crystal phase and the degree of alloying of the Zn-Cu film. The crystalline phase and chemical surface composition of the master alloy have a strong influence on the resulting structure after the dealloying step. In particular, with higher annealing temperature, the dealloying proceeds slower and the ligament-pore size ratio increases. Furthermore, the variation of the dealloying conditions (electrolyte concentration and time) leads to different structures of the np-Cu films, indicating that the mechanism and kinetics of the dealloying significantly change. One of the critical parameters is the effect of the supporting electrolyte. For instance, in HCl, a homogeneous ligament structure is formed, whereas in NaOH solution the dealloying mainly proceeds at the grain boundaries of the Zn-Cu alloy and forms cracks. Large ligament sizes and strong oxidized surfaces with very low content of Zn was observed. Moreover, the temperature during the dealloying can be used to tune the ligament and pore size. For example, using a HCl solution with the same concentration, the ligament size can be adjusted from 30 to 300 nm in a temperature range between 10 and 70 °C. Another observation is that by increasing dealloying time, the Zn content further decreases. In basic solutions, the absence of Zn leads to an increased formation of copper oxide at the surface. The aim of our work is to better understand the formation mechanism and kinetics of the np-Cu. The next step is the rational design of various np-Cu materials as electrocatalysts for the electrochemical carbon dioxide reduction reaction (CO2RR). 1. A. S. Aricò, P. Bruce, B. Scrosati, J. Tarascon, and W. van Schalkwijk, Nature Materials, 366-377, 4 (2005) 2. W. A. Badawy, Journal of Advanced Research, 123-132, 6(2) (2015) 3. M. Oezaslan, M. Heggen, and P. Strasser, J. Am. Chem. Soc., 514-524, 134(1) (2012) 4. Z. Zhang, Y. Wang, Z. Qi, W. Zhang, J. Qin, and J. Frenzel, J. Phys. Chem. C, 12629-12636, 113 (2009)

Improvement of Structural Characteristics for CuZn Alloy through Heat Treatments

The paper presents aspects of structure modifications and properties for a CuZn alloy, after the appliance of heat treatments, at their specific parameters. The samples subjected to analysis, coming from cast bar, from which have been taken standard samples, with specific dimensions for experiments.Nonferrous alloys are subject frequently to annealing, quenching and tempering. The annealing follows the homogenization of structure after casting. The quenching followed by tempering is a spectacular modality to modify the mechanical properties for numerous nonferrous alloys.The characteristics of alloys have highlighted by experiments, using standard samples specific to the requests. The determination of alloying elements was made on optical spectrometer. The researches by SEM and optical microscopy, confirm the improvement of properties by obtaining uniform structures according to the applied thermal processing.

Structural-Phase Features of the Order – Disorder Transition in an Fcc-Alloy with В2 Superstructure in the Presence of a Complex of Thermal Antiphase Boundaries

Using the Monte Carlo method, it is shown that the presence of a dual defect in the form of a pair of thermal antiphase boundaries in an ordered FCC-alloy with В2 supersructure (CuZn alloy taken as an example) gives rise to considerable structural-phase variations in the system during the order – disorder transition compared to the defect-free system. The availability and character of the observed peculiarities largely depend both on the temperature and the distance between thermal antiphase boundaries. It is underlined that the boundaries of the Cu–Cu and Zn–Zn types differ both in linear dimensions and in the degree of ordering of near-theboundary regions. For a boundary of the Cu–Cu type, this region is smaller and less ordered in contrast to linear dimensions and ordering degree of the Zn–Zn type boundary. At low temperatures, linear dimensions of the near-the-boundary disordered regions increase with the temperature, while the overall order in the system decreases. In the range of low-stability states of the system, the dimensions of the near-the-boundary disordered regions are maintained at approximately 10 interplanar distances for a boundary of the Cu–Cu type and about 12 interplanar distances for a boundary of the Zn–Zn type. It is noted that ordering degrees in these regions become similar, antiphase boundaries become smeared and get faceted; the first disordered regions invariably appear in the vicinity of the Zn–Zn type boundary.