Copper-based Alloys Research Articles

Galvanic Series in Seawater as a Function of Temperature, Oxygen Content, and Chlorination

The open-circuit potential is one of the main driving forces of galvanic corrosion when two dissimilar metals are in electrical continuity in an electrolyte. From the existing literature, the galvanic series which provides averaged potential of metallic materials in seawater is generally restricted to ambient/standard conditions or to a limited number of alloys. However, advanced materials have been developed in the last decade and the corrosion potential of any alloy immersed in seawater may be strongly affected by environmental factors. There is a lack of information on these purposes (e.g., effect of dissolved oxygen content, temperatures, chlorination at different levels, or recently developed alloys, etc.). In this work, the open-circuit potential of different stainless steel grades, as well as nickel-based and copper-based alloys, has been systematically measured in seawater under different experimental conditions. In particular, the effect of temperature (from 30°C to 70°C), oxygen content (from 10 ppb to saturation), and chlorination level (from 0 ppm to 0.5 ppm) have been studied. The work can also be used for material selection in terms of risk of bi-metallic corrosion when coupling two materials under these conditions.

The Effect of Al on the Mechanical Properties and Microstructure of Copper-based Metallic Glass

An investigation was carried out into the effect of different amounts of Al on the mechanical properties, and glass-forming ability, of a three component alloy (Cu–Zr–Al). The mechanical properties were studied using a universal materials tester and a Split-Hopkinson bar tester. A series of amorphous alloys with different Al content were subjected to static compression and dynamic high-speed impact tests at 10−1 s−1, 10−2 s−1, and 10−3 s−1 for the static condition and 2000 s−1, 3000 s−1, and 4000 s−1 for the dynamic condition. Experiment showed that the flow stress value and the strain rate sensitivity coefficient of the copper-based amorphous alloys varied with changes of strain and strain rate. An increase in the rate of strain caused the flow stress value and the sensitivity coefficient of the strain rate to rise. When the Al content in an amorphous alloy Cu47.5Zr45.5Al7 was 7%, both the flow stress value and the strain were improved and effectively upgraded the mechanical properties of the material.

Analysis of Compositional Modification of Commercial Aluminum Bronzes to Obtain Functional Shape Memory Properties

In copper-based shape memory alloys (SMAs), some exceptional phenomena, such as the shape memory effect (SME) or superelasticity (SE), are observable. However, commercial aluminum bronzes, Cu3Al-based alloys, do not present these functional properties (SME and/or SE) in their original state. Thus, since one of the main copper-based SMA systems is the Cu-Al-Ni alloy, this paper aims to analyze the modification of these commercial aluminum bronzes to SMA by the addition small amounts of Cu, Al and/or Ni. These modified bronzes were reprocessed by induction melting and injected by centrifugation into a ceramic coating mold. The modifications were made to determine the nominal composition for a Cu-13,0Al-4,0Ni (%wt) SMA. The effectiveness of the modifications was verified by differential scanning calorimetry (DSC) thermal analysis. All modified Cu-Al-Ni bronzes presented DSC peaks of the thermoelastic martensitic phase transformation, showing that SMA behavior was achieved, while the non-modified bronzes revealed no transformation. These results were supported by Vickers hardness (HV), X-ray diffraction (XRD), semi quantitative composition by EDS analysis and optical microscopy.

Cyclic mechanical properties of copper-based shape memory alloys: The effect of strain accommodation at grain boundaries

Fatigue behavior of shape memory alloys depends on deformation mechanisms (e.g., martensitic transformation, variant conversion, slip, and elastic deformation) and how they interact with microstructure. In this paper, we examine fatigue properties of Cu-based shape memory alloys, focusing on the effect of strain accommodation at grain boundaries on fatigue life and fracture mode under various deformation mechanisms in polycrystals. Comparisons with single crystals and static test results are also made. As lack of plastic accommodation at grain boundaries often leads to brittle intergranular fracture, incorporation of a ductile intergranular phase is promising for providing strain accommodation for transformation nearby and improving superelastic fatigue life.

Effect of compacting pressure on shape retention during supersolidus liquid phase sintering of Cu base alloys

ABSTRACTThe compacting pressure is one of the key parameters which affects sintering phenomena, such as fragmentation, rearrangement and densification. However, the type of alloy also has a similar significance which should be considered. To demonstrate the effect of the mentioned parameters, two types of copper base alloys, i.e. Cu–9Sn–8Pb and Cu–28Zn, were investigated in the present study. Prealloyed powders were compacted at 100 and 400 MPa, respectively, and sintered in the range of 890–970°C for 20 min. In situ images of the samples were taken at various sintering conditions, and the shapes were recorded. For both materials, in case of compaction at lower pressure, the gravity-induced distortion known as ‘elephant foot’ phenomenon was not observed, and the specimens show shape retention during sintering even at higher temperatures, while samples compacted at 400 MPa showed different responses to the sintering conditions: A-shaped distortion (elephant foot) occurred in the bronze alloy, while in the brass alloy O-shaped distortion was observed.

Damping Capacity of Metallic Materials for Automotive Industry

New requests from the automotive industry suppose to apply new materials with mechanical resistance to heat and vibrations and also with low weight. In order to replace plastic materials with high damping capacity a viable solution can be the metallic materials with sufficient internal friction to transform the external mechanical energy in thermal energy without affecting the microstructure or the mechanical properties of the metallic materials. In automotive applications an important role, especially in low velocity impacts, are the bumper elements. In this article possibility of copper-based shape memory alloys to fulfill the damping necessity of metallic materials is analyzed. Dynamic - mechanical analyze of few copper based shape memory alloys is realized and the results compared to proposed a better solution of Cu-based shape memory alloy for damping materials applications. The damping capacity difference between martensite and austenite like phases is also analyzed.

Stress-Stain State of Pipe Made of Copper-Based Alloy Strengthened with Incoherent Nanoparticles

Stress-Stain State of Pipe Made of Copper-Based Alloy Strengthened with Incoherent Nanoparticles

Experimental evaluation of the temporal effects of paint-based protective films on composite fouling inside admiralty brass and titanium steam surface condenser tubes

Paint-based protective films (PPFs) are inorganic thin coatings currently used in industry to mitigate corrosion and erosion. In this paper the fouling characteristics of one of these PPFs is experimentally investigated using a purpose-built test facility installed at a thermal power plant. Details are provided describing the apparatus which uses actual cooling water from the condenser outlet that passes through six parallel double-pipe heat exchangers. Admiralty brass and titanium tubes are tested simultaneously with and without the same PPF applied, enabling the fouling factor to be measured as a function of exposure time. The predominate fouling mechanisms occurring at this plant are found to be biological, precipitation, and particulate fouling. The results indicate that the PPF fouls identically to the titanium tube and the admiralty brass tube reaches the lowest fouling factor (five times less than all other tubes). The toxicity of the copper ions in the brass with respect to biofilm development is suggested to cause this. Therefore when a new tube alloy is used instead of a copper-based alloy, or when a non-biocidal PPF is employed in conditions liable to biofouling, the water treatment program must be effectively upgraded with respect to its biofouling countermeasures.

Material performance of age-hardened beryllium–copper alloy, CDA-C17200, in a high-pressure, gaseous hydrogen environment

In order to develop safer and more energy-efficient, hydrogen pre-cooling systems for use in hydrogen refueling stations, it is necessary to identify a high-strength metallic material with greater thermal conductivity and lower susceptibility to hydrogen embrittlement, as compared with ordinary, stable austenitic stainless steels. To accomplish this task, the hydrogen compatibility of a precipitation-hardened, high-strength, copper-based alloy was investigated by slow-strain-rate tensile (SSRT), fatigue-life, fatigue-crack-growth (FCG) and fracture toughness tests in 115-MPa hydrogen gas at room temperature. The hydrogen solubility and diffusivity of the alloy were also determined. The hydrogen solubility of the alloy was two or three orders of magnitude lower than that of austenitic stainless steels. The alloy also demonstrated absolutely no hydrogen-induced degradation of its strength properties, a factor which could contribute to the reduction of costs related to the construction and maintenance of hydrogen refueling stations, owing to the downsizing and improved cooling performance of the pre-cooling systems.

Investigation of Corrosion Behavior for Copper-Based Shape Memory Alloys in different Media

Copper based shape memory materials was interesting group of metal alloys that have a widespread potential in medical and industrial application due to their characteristics ,the possibility of exhibiting shape memory behavior and lower cost. In this research the alloy (Cu-(15-40) wt%Zn-6wt.%Al) has been prepared by powder metallurgy technique Zn element (15, 20, 25, 30, 35, 40 wt%Zn) and fixed percentage of Al content which is 6.wt%Al then aluminum replaced by (Si, Sn, Ni )element at fixed percentage of 6wt.%, in order to study the effect of these elements on SMA. After samples preparation examination were done by using XRD, SEM technique, DSC, Vickers hardness, Archimedes method to measure the porosity percentage and corrosion rate in different solutions (HCl, NaOH and SEAWATER).The XRD and microstructure results show that all samples with and without additives consist of two phases (β-phase) and (α-phase) at room temperature and the addition of alloying elements in these percentages does not have effect on present phases. the hardness increased with zinc content because the formation of intermetallic compound of CuZn that responsible to hardness while The addition of Si ,Sn and Ni leads to lower the hardness than aluminum. The bulk density increased with the alloys without addition alloying elements(Si, Ni and Sn ) while apparent porosity decreased with it the reason for this phenomenon due to the characterization of alloying elements that addition to the alloy. From the results of corrosion test can be show the alloy with 35wt% Zn have the higher corrosion resistance in all media (HCl, NaOH and sea water) and the addition of alloying element lead to improve the corrosion resistance. Finally, it is observed that the Copper base shape memory alloys with these types of additives are suitable for use in different application.

Plastic Deformation of Copper-Based Alloy Reinforced with Incoherent Nanoparticles

The paper deals with research carried out into plastic deformation of a heavy-wall pipe made of nanoparticle reinforced copper-based alloy. We present an original approach which combines methods of crystal plasticity and deformable solid mechanics, thereby allowing to study the stress-strain state of the heavy-wall pipe strengthened with incoherent nanoparticles using a homogeneous internal pressure. Dependences are constructed for the yielding area and the pressure, the limit of elasto-plastic resistance is obtained for the heavy-wall pipe and its deformation degree is described. It is shown that the particle size has an effect on strength properties of the material.

Microstructural and superficial modification in a Cu-Al-Be shape memory alloy due to superficial severe plastic deformation under sliding wear conditions

Stress induced martensitic transformation in copper-based shape memory alloys has been studied mainly in monocrystals. This limits the use of such results for practical applications as most engineering applications use polycristals. In the present work, a coaxial tribometer developed by the authors was used to characterise the tribological behaviour of polycrystalline Cu-11.5%Al-0.5%Be shape memory alloy in contact with AISI 9840 steel under sliding wear conditions. The surface and microstructure characterization of the worn material was conducted by conventional scanning electron microscopy and atomic force microscopy, while the mechanical properties along the transversal section were measured by means of micro-hardness testing. The tribological behaviour of Cu-Al-Be showed to be optimal under sliding wear conditions since the surface only presented a slight damage consisting in some elongated flakes produced by strong plastic deformation. The combination of the plastically modified surface and the effects of mechanically induced martensitic transformation is well-suited for sliding wear conditions since the modified surface provides the necessary strength to avoid superficial damage while superelasticity associated to martensitic transformation is an additional mechanism which allows absorbing mechanical energy associated to wear phenomena as opposed to conventional ductile alloys where severe plastic deformation affects several tens of micrometres below the surface.

Comparison of Electropolishing Behavior of Two Grades of Brass Alloys

Brasses are widely used in watch manufacturing and jewelry as based materials, thanks to their cost, good mechanical properties and corrosion resistance. These industrial sectors face major changes in substrate composition in particular due to environmental regulations (changes in the grade of lead-free brass substrates) leading to investigate other brass grades. Smooth and bright surfaces are usually obtained by mechanical polishing requiring a succession of manual operations. Electropolishing is an anodic dissolution process currently used in industries to replace mechanical polishing entirely or as a finishing treatment for complex shapes. The first patent for copper polishing in an aqueous orthophosphoric acid solution at high current density, was deposited by Jacquet in the 30s (1). The electropolishing quality depends on the material/electrolyte pair and the operating conditions (potential, time process, temperature…) (2,3). The aim of this work is to observe the impact of alloying composition on polishing quality. Two grades of brass were used CuZn42 which has a diphasic composition, and CuZn37 which has a monophasic composition. They were electropolished in a phosphoric acid solution using a rotating disk electrode. At first, an electrochemical study was performed to investigate the electropolishing mechanism. A kinetic dependence on diffusion following the Levich law, is verified for the two grades of brass. This electrochemical study also allows to determine the best treatment conditions which correspond to the middle of electropolishing current density plateau. The quality of polishing was evaluated by surface characterization which consists of a set of methods (Stylus Profiler, Secondary Electron Microscopy, Atomic Force Microscopy, X-Ray Diffraction). SEM and AFM images highlight a discrepancy between the two grades of brass (Figure 1). Indeed, CuZn37 sample (monophasic composition) shows a smooth surface and grain boundaries are almost not visible, while CuZn42 sample still presents a biphasic composition with a slight level difference between α and β phases. The roughness parameter Ra confirmed this behavior difference. Because CuZn37 sample presents a roughness equal to 42 nm, while CuZn42 is about 10 times rougher. All these characterization results indicate that there is a preferential attack of β phase (richer in Zn) for biphasic materials which induces some difficulties to apply standard conditions for the electropolishing process. 1. Jacquet PA. Electrolytic Method for obtaining Bright Copper Surfaces. Nature. 1935;135:1076. 2. Lin C-C, Hu C-C, Tai-Chou Lee. Electropolishing of 304 stainless steel interactive effects of glycerol content bath temperature and current density on surface roughness and morphology. Surf. Coat. Tech. 2009;448-54. 3. Gabe DR. Electropolishing of copper and copper-based alloys in ortho-phosphoric acid. Corros Sci. 1972;12:113-20. Figure 1

A Study of the Damping Capacity of Mechanically Processed Cu – 9.2Al – 5.3Mn – 0.6Fe Shape Memory Alloys

The effect of deformation on the damping capacity of a copper-base shape memory alloy produced by standard methods is studied. The metallographic analysis is performed with the help of scanning electron microscopy. The internal friction is measured at different temperatures. The damping capacity of the alloy is analyzed and its relation to the mechanical and physical properties is determined.

Oxidation Resistive, CMOS Compatible Copper-Based Alloy Ultrathin Films as a Superior Passivation Mechanism for Achieving 150 °C Cu–Cu Wafer on Wafer Thermocompression Bonding

Surface passivation plays a dual role of protecting copper (Cu) from getting oxidized and reducing the surface roughness of Cu thin film and thus enables low-temperature Cu-Cu bonding. In this paper, we utilized an oxidation resistive, CMOS compatible copper-nickel-based alloy, constantan as a passivation layer, as it does not get oxidized at room temperature and is also CMOS damascene process compatible. Systematically optimized ultrathin, constantan (2 nm) on Cu surface not only protected Cu from oxidation but also reduced the surface roughness to about 0.7 nm, which led to Cu-Cu bonding at a temperature as low as 150 °C at 4 bar pressure. Cross-sectional TEM of bonded Cu layer reveals very significant interdiffusion and grain growth between the Cu films resulting in a zigzag bonding interface and the presence of Cu grains that extend across the entire bonding layer. Furthermore, reliability investigation of passivated Cu bonded structure was demonstrated using current stressing, temperature cycling test, and relative humidity test, which suggest excellent stable bonding without electrical performance degradation. This method of alloy-based passivation is confirmed to be effective and enable low temperature, low-pressure Cu-Cu wafer on wafer bonding for 3-D integration applications.

Artificial patina formation onto copper-based alloys: Chloride and sulphate induced corrosion processes

Naturally grown patinas are typically detected onto the surface of modern copper-based artefacts and strictly affect their surface reactivity and appearance. The production of representative patinas is a key issues in order to obtain model systems which can be used for the development and validation of appropriate conservation materials and methods. In this study, we have prepared different artificial representative patinas by using a quaternary Cu-Sn-Zn-Pb alloy with chemical composition and metallurgical features similar to those of valuable modern works of art. In order to produce degradation products usually observed onto their surface, chloride and sulphate species were used to induce corrosion processes. Different patinas were produced by changing the nature of corrosive species and the set-up for the accelerated degradation. The composition and structural properties of the patinas were investigated by attenuated total reflectance Fourier transform infrared spectroscopy, X-ray diffraction, optical microscopy and scanning electron microscopy combined with energy dispersive X-ray spectroscopy. The results allow to identify degradation products and to distinguish copper hydroxychloride polymorphs and copper hydroxysulphates with similar structure. Our findings show that patina composition can be tailored by modifying the degradation procedure and patinas representative of modern artefacts made of quaternary Cu-Sn-Zn-Pb alloy can be obtained.

Crack path and damage in a CuZnAl SMA

Abstract: Pseudo-elastic (PE) materials are an important class of metallic alloy which exhibit unique features with respect to common engineering metals. In particular, due to these properties PEs are able to recover their original shape after high values of mechanical deformations, by removing the mechanical load (PE). From the microstructural point of view shape memory and pseudo-elastic effects are due to a reversible solid state microstructural diffusionless transitions from austenite to martensite, which can be activated by mechanical and/or thermal loads. Copper-based shape memory alloys are preferred for their good memory properties and low cost of production. In this work the main crack initiation and its propagation in a tensile test is analyzed in order to evaluate crack path and its behavior at low and at high values of deformation. Results are also associated both to grains boundary chemical properties and to X-ray diffraction, in order to correlate structural transition involved in an Cu-Zn-Al alloy characterized by a PE behavior.

Влияние энергии дефекта упаковки на накопление дислокаций при пластической деформации поликристаллических сплавов на основе меди

Влияние энергии дефекта упаковки на накопление дислокаций при пластической деформации поликристаллических сплавов на основе меди

Investigation of Magnetic Properties of Phase Transformations in Copper-Based Alloys

In this study, the magnetic properties of both Cu85.41Al9.97Mn4.62 and Cu82.41Mn13.81Al3.78 (wt%) shape memory alloys were studied. The analysis of the magnetization as a function of applied field and temperature was conducted between −10 to 10 T magnetic field ranges at constant temperature. Two alloys were examined using ac magnetic susceptibility measurements. The magnetic saturation values at room temperature were found to be approximately 1 and 70 emu/g for Cu85.41Al9.97Mn4.62 (wt%) and Cu82.41Mn13.81Al3.78 (wt%) alloys, respectively. The magnetic saturation and the coercivity values for the CuAlMn alloy are found smaller than those for the CuMnAl alloy. Moreover, from the magnetization curves, the typical ferromagnetic behavior were observed for both alloys. Details of the morphological properties and chemical composition have been examined by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX), respectively.

Superelasticity and shape memory effect in Cu–Al–Mn–V shape memory alloys

In this study, Cu–Al–Mn–V alloys with bcc phase separation were designed through changing V and Mn contents, resulting in complex microstructure consisted of L21 parent, small amounts of δ(V, Mn) and 2H(γ'1) martensite. The amounts of δ(V, Mn) phase and 2H(γ'1) martensite increase with the increase of V content. The results further show that the stabilization of stress-induced 2H(γ'1) martensite from L21 parent occurs among all Cu–Al–Mn–V alloys during deformation. Thus the same alloy not only exhibits superelasticity, but also shape memory effect after unloading when heated. The superelasticity and shape memory effect are summarized to three situations. Situation I includes Cu63.7Al25.3V1.9Mn9.1 and Cu63.7Al25.8V2.2Mn8.3 alloys (at.%), which have excellent superelasticity strains being up to 5.4% and 3.9% respectively. Cu63.8Al25.4V4.2Mn6.6 and Cu63.0Al26.2V4.7Mn6.1 alloys are situation II, and exhibit good shape memory effects being up to 3.5% and 3.9% respectively. The superelasticity and shape memory effect of Cu62.8Al26.2V2.6Mn8.4 alloy that is situation III are between the above two situations. The obtained results may open an avenue to design copper-based shape memory alloys simultaneously have superelasticity and shape memory effect under the same composition and deformation temperature through applying stress.