Copper-clad Aluminum Research Articles

The growth behavior and kinetics of intermetallic compounds in Cu–Al interface at 600°C–800 °C

Due to the low production cost and light weight, copper-clad aluminum conductors show great potential value in the field of power transmission, while the phase structure and organizational changes at the Cu–Al interface in high-temperature environments have a great impact on the electrical and mechanical properties. In this paper, Cu–Al diffusion couples are prepared to study the diffusion process, microstructure, and growth kinetics of intermetallic compounds (IMCs) in Cu–Al interface during heating from 600 °C to 800 °C, and the mechanical and electrical properties of Cu–Al diffusion couples are discussed. The results show that after heat treatment, IMC layers are formed at the Cu–Al interface and the Al-side is composed of CuAl and CuAl2, in which the CuAl phase transforms from long to thick dendrites with the increase of temperature, and finally grows into a “popcorn” form. The IMCs at the Cu–Al interface from the Cu side to the Al side are in the order of Cu3Al layer, Cu9Al4 layer, Cu3Al2 layer and CuAl layer, among which the Cu3Al2 layer is the thickest (168.42 μm at 700 °C), while the Cu3Al layer is the thinnest (37.32 μm at 700 °C). The kinetic calculations show that the diffusion layer grows up rapidly, which is caused by the generation of liquid-phase during the heating process, leading to the acceleration of the diffusion of Cu and Al. The kinetic factor of the Cu3Al2 layer is the largest (n = 0.69), causing the fastest growth rate of the Cu3Al2 layer, while the Cu3Al layer shows the largest activation energy for diffusion and the smallest diffusion rate (Q = 9.48 kJ/mol, D0 = 2.06 × 10−1 m2/s), therefore its growth rate is the slowest. Based on the thermodynamic calculations and the Cu–Al phase diagram, a growth mechanism of the Cu–Al interface is proposed, the formation sequence of IMCs at the Cu–Al interface is Cu9Al4, CuAl, Cu3Al2 and Cu3Al. The formation of IMCs layer at the Cu–Al interface leads to a significant increase in the hardness of Cu–Al samples (the hardness of the Cu3Al2 is 10 times higher than that of Cu) and an obvious decrease in electrical conductivity (the electrical resistivity of Cu–Al is 5 orders of magnitude higher than that of Cu), affecting its application in the electrical industry.

Research on identification method of transformer winding material based on vibration characteristic

At present, there are shoddy transformers in the market, of which the windings are replaced by aluminum and copper clad aluminum. The commissioning of these transformers may cause poor power supply performance and excessive winding heating. The existing detection methods of windings are complex, time-consuming to operate and destructive. Therefore, a winding material identification method based on vibration characteristics is proposed. Firstly, the vibration accelerations of transformer cores and windings with different winding materials are theoretically derived. Furthermore, through the coupling simulation of magnetic field and structure field of distribution transformers, the calculated vibration characteristics of copper, aluminum, and copper clad aluminum are verified. Finally, by comparing the time domain, the frequency domain and time-frequency domain of acceleration signals, preliminary identification of winding materials is conducted, which lays a theoretical foundation for establishing a precise identification model for winding materials in the future. This work provides guarantee for the safe operation of the distribution network.

Study on the microstructure characteristics of melting marks in copper-clad aluminum wires under overcurrent faults

Study on the microstructure characteristics of melting marks in copper-clad aluminum wires under overcurrent faults

The high‐frequency phenomenon of copper clad aluminum wires which are lower the alternating current resistance than copper solid wires, and the application of copper clad aluminum wires to the electrical equipment

AbstractThe paper is proposed approximate formulas of the ac resistance of lead wires and coils which made by using copper clad aluminum (CCA) wires. There are the frequency range that the ac resistance of CCA wires is lower than it of cupper solid wires for lead wires and coils of an electrical equipment. It is shown that the application of CCA wires is economical as comparing with copper solid wires, if the design is due to successful calculation in the electrical equipment. The measured resistance is compared with the formula. CCA wires is an example of multiple conductors which shall be expected to apply in future.

Impact of hardening law on the FEM prediction of residual stresses in copper-clad aluminum wires

Impact of hardening law on the FEM prediction of residual stresses in copper-clad aluminum wires

Fabrication of a novel high-strength and high-conductivity copper-clad aluminum composite wire

Fabrication of a novel high-strength and high-conductivity copper-clad aluminum composite wire

The High-frequency Phenomenon of Copper Clad Aluminum Wires which are Lower the Alternating Current Resistance than Copper Solid Wires, and the Application of Copper Clad Aluminum Wires to the Electrical Equipment

The paper is proposed approximate formulas of the ac resistance of lead wires and coils which made by using copper clad aluminum (CCA) wires. There are the frequency range that the ac resistance of CCA wires is lower than it of cupper solid wires for lead wires and coils of an electrical equipment. It is shown that the application of CCA wires is economical as comparing with copper solid wires, if the design is due to successful calculation in the electrical equipment. The measured resistance is compared with the formula. CCA wires is an example of multiple conductors which shall be expected to apply in future.

Effect of the annealing process on the formation and growth of intermetallic compounds at the interface of Cu clad Al wire drawn with high area reduction

An increase in the annealing temperature and time increased the thickness of the interface and the θ-Al2Cu, η2-AlCu, and γ-Al4Cu9 layers at the interface of a copper clad aluminum wire (CCAW) drawn with a reduction in area (∼95 %), and their growth followed a linear correlation with the square root of the annealing time. The activation energy for growth of θ, η2, and γ phases was 62.1, 68.3, and 83.5 kJ·mol−1·K−1, respectively, as determined using the Arrhenius equation. The slightly lower activation energies for the intermetallic compared to those reported in previous studies were due to the high dislocation density in CCAW induced by the high area reduction during drawing deformation, thereby generating more vacancies to easily diffuse each atom at the low annealing temperature of 400 °C, according to Kirkendall effects.

A study on electrical resistance and RSW characterizaton of bimetal wire

The objective of this study is to reduce copper consumption in Solenoid of Circuit breaker by using aluminium with copper technically called copper clad aluminium. Aluminium wires with copper clad are widely used, e.g. in telecommunication, power engineering, electronics as a replacement of traditional applied copper wire. The reason is that the properties of these bimetal wires combine the smaller density and low cost. This study investigates the effect of tripping properties in Circuit breaker thru various magnetic testing methods. Magnetic testing and an experiment verified the tripping threshold depends on the Copper and aluminium combination ratio.

Study by nanoindentation of the influence of the manufacturing process on the mechanical properties of Copper-Clad Aluminum wires

We studied the influence of the architecture of Copper-Clad Aluminum (CCA) wires produced by cold-drawing process, on the mechanical properties of materials, and the development of intermetallic compounds at the interface after annealing. Simple and architectured-CCA (A_CCA) rods, fabricated by stacking and re-drawing of original CCA wires, have been characterized before and after a thermal treatment. Nanoindentation tests, performed to map the hardness and the elastic modulus at the microscale, allow to well catch the recrystallization phenomenon, which takes place in both the Cu and the Al subjected to severe plastic deformation, as well as the formation of three intermetallic compounds (IMC) at the interface. Our measures underline that the mechanical properties of all the components involved in the wires, i.e., Cu, Al, and eventually the IMC developing after annealing, are only slightly influenced by the structuration of the wires. IMC developing at the Cu/Al interfaces present a high hardness, and might deteriorate the mechanical properties of the wires, even more for A_CCA wires, which exhibit more interfaces that the traditional CCA samples.

Experimental and Finite Element Analysis of the Tensile Behavior of Architectured Cu-Al Composite Wires.

The present study investigates, experimentally and numerically, the tensile behavior of copper-clad aluminum composite wires. Two fiber-matrix configurations, the conventional Al-core/Cu-case and a so-called architectured wire with a continuous copper network across the cross-section, were considered. Two different fiber arrangements with 61 or 22 aluminum fibers were employed for the architectured samples. Experimentally, tensile tests on the two types of composites show that the flow stress of architectured configurations is markedly higher than that of the linear rule of mixtures’ prediction. Transverse stress components and processing-induced residual stresses are then studied via numerical simulations to assess their potential effect on this enhanced strength. A set of elastic-domain and elastoplastic simulations were performed to account for the influence of Young’s modulus and volume fraction of each phase on the magnitude of transverse stresses and how theses stresses contribute to the axial stress-strain behavior. Besides, residual stress fields of different magnitude with literature-based distributions expected for cold-drawn wires were defined. The findings suggest that the improved yield strength of architectured Cu-Al wires cannot be attributed to the weak transverse stresses developed during tensile testing, while there are compelling implications regarding the strengthening effect originating from the residual stress profile. Finally, the results are discussed and concluded with a focus on the role of architecture and residual stresses.

Optimization of the Indirect Extrusion Process of Copper-Clad Aluminum Rods by Methods of Statistical Experimental Designs and Numerical Analyses

The success of composite extrusion is influenced by multiple process parameters. In order to investigate the significance of specific parameters during indirect extrusion of copper-clad aluminum (CCA) rods, statistical methods were applied and a central composite experimental design was implemented. The runs of the experimental design were modeled with the finite element method based software DEFORM 2D and evaluated with respect to product quality, described by four response variables. Using variance and regression analyses, as well significant linear and quadratic effects of the five investigated process parameters as interactions between them were identified. Based on a statistical model, an overall optimum setting for the process parameters was predicted utilizing the response surface methodology with a desirability approach. By applying the output of the statistical analysis to an extrusion trial, the extrusion of a high quality CCA rod was achieved. Moreover, the results of the statistical analysis could be verified by comparing predicted and experimentally determined values of the investigated quality characteristics.

Microstructure and mechanical properties characterization of architectured copper aluminum composites manufactured by cold-drawing

The present study investigates the mechanical behavior of severely plastic-deformed Cu-Al composite wires with different diameters and heat-treatments. Each composite holds 61 restacked copper-clad aluminum wires. The bimetal composites were cold-worked up to diameters ranging from 1 mm to 3 mm, without any intermediate heat treatment. All the wires contain 61 hexagonal Cu-Al fibers with a continuous copper network extended from the outer surface into the center of the samples. Tensile tests were then performed on the as-drawn and heat treated wires. The latter were treated at 400 °C for 30 min and 6 h. The heat treatments firstly induce recrystallization in both constituents, giving rise to a fine-grained microstructure and secondly prompt the formation of several intermetallics. Without heat treatment after processing, the architectured composites exhibit a ductility value similar to the conventional copper-clad aluminum wires and larger yield stresses compared to them, regardless of the diameter. The intermetallic compounds, forming as a result of heat treatment, affect the yield stress, ductility and strain hardening mechanisms. Finally, the results are discussed in terms of grain size, texture, intermetallics volume fraction and mechanical coupling between the phases.

Geometry of efficient Electromagnetic Linear actuators for flapping wing MAVs

A constraining factor in the development of flapping wing micro air vehicles (MAVs) is the power density and efficiency of actuators. Piezoelectric and rotary electromagnetic actuators have been shown to have functional power densities but can require mechanically complex transmissions to create flapping motion. Electromagnetic Linear actuators (ELAs) have unique characteristics, allowing them to be controlled and implemented similarly to muscles but demonstrated much lower efficiency. This study presents configurations of ELA consisting of multiple coils and magnets that have the potential to improve efficiency. The use of lightweight conductors in the form of copper clad aluminium (CCA) is explored as a method to improve power density. A numerical method of optimising the geometry and mass distribution of the magnetic and conductive material is presented. The results show the power consumption of these actuators can range between 910-260 W/kg. The inclusion of an additional magnet and coil can improve efficiency by up to 3.5 times over typical flapping wing ELAs.

Influence of Die Surface Topography and Lubrication on the Product Quality during Indirect Extrusion of Copper-Clad Aluminum Rods

Copper-clad aluminum rods are usually fabricated using hydrostatic extrusion, since during direct and indirect extrusion fracture of the copper sleeve is difficult to avoid. In this study, different die surface topographies and lubrication conditions were applied to improve the material flow during indirect extrusion of copper-clad aluminum rods. Thus, conic dies with different roughness (polished and sandblasted) and surfaces shapes (fine and coarse grooves) were tested. Additionally, the effects of a wax-graphite-based lubricant as well as a graphite-like carbon (GLC) coating of the die conic surfaces were investigated. The composite billets were made of aluminum EN AW-1080A cores and copper CW004A sleeves with an equivalent copper cross section of 0.24 of the total billet cross section. For all trials, an extrusion ratio of 14.8:1 and a conic die angle of 2α = 90° were chosen. Non-isothermal extrusion trials were carried out using a container at 330 °C and billet and tools at room temperature to reduce the flow stress ratio σCu/σAl. The extruded composite rods’ integrity, surface quality, interface integrity, and equivalent copper cross section were analyzed. In addition, a visual inspection of the sleeve-die contact surface was performed. The results showed that the GLC coating proved to be unsuitable due to a lack of lubrication, which causes accumulated sleeve fractures and longitudinal grooves on the extruded rods. The best results were achieved with the combination of the sandblasted die surface and the wax-graphite-based lubricant, observing a uniform material flow without sleeve fractures.

Numerical Investigations on Material Flow During Indirect Extrusion of Copper-Clad Aluminum Rods

In the extrusion of clad composites materials with different flow stresses are usually used. This causes an inhomogeneous material flow which can induce sleeve or core fracture. In the present study, the material flow during indirect extrusion of copper-clad aluminum rods was analyzed by means of experimental and numerical investigations throughout the process. In order to provide material models for the numerical analysis hot compression tests of the aluminum alloy EN AW-1080A and the copper alloy CW004A were carried out. The indirect extrusion was performed using a conical die with a semi die angle of 45 ° and an extrusion ratio of 14.8:1. The container was heated to 330 °C, while billet, die and ram were kept at room temperature. The extrusion trial was then modeled with the FEM based software DEFORM 2D. Cross sections were taken from the extruded rod and compared to the corresponding sections of the simulation with regard to the development of the equivalent copper cross section. As a result, the development of extrusion force and equivalent copper cross section could be clarified. The numerical investigations indicated a higher flow velocity for the aluminum core than for the copper sleeve at the bearing channel. Therefore, high tensile stresses and fractures of the copper sleeve were induced. Additionally, the validated numerical analysis made possible to determine the conditions for a successful co-extrusion of the analyzed copper-clad aluminum rod.

An investigation on micro-hardness, micro-structure and ductility of clad layer in copper clad aluminum wire under multi stage–NCWD

The copper clad aluminum (CCA) wire was fabricated by roll forming of copper foil around the aluminum wire rode. Non-continuous wire drawing (NCWD) was employed to study the effect of wire drawing parameters on ductility, micro-hardness and microstructure of the copper clad layer. The NCWD process continued without intermediate annealing until cracks were observed on the copper clad layer. The cracks appeared after a 78% reduction in the cross-section. The micro-tensile test was performed on specimens with transverse curvature to determine elongation. A modified correction factor was introduced to correct the effect of curvature size on elongation. The introduced correction factor proportional to the sample characteristics was between 0.7 and 1.4. Moreover, variations in the hardness and microstructure of the copper clad layer were investigated in the base metal and at the welding zone. Before beginning the wire drawing process for the annealed CCA wire with a diameter of 10.1mm and a Cu clad thickness of 0.48mm , the hardness, ductility, UTS and grain size of the clad layer were 87HV, 43%, 103MPa and 80 μm, respectively. At the end of NCWD for 10° and the 20% reduction ratio of the die, the diameter of CCA wire reached 4.7mm with a 0.22mm thickness of Cu clad. The hardness, ductility, UTS and grain size of the clad layer were 157HV, 2.9%, 325MPa and 8 μm, respectively.

Copper selective separation and nanoporous copper oxide preparation from waste copper-clad aluminum scraps

Waste copper-clad aluminum (CCA) scraps are secondary resources that are rich in Cu and Al, with biosafety disposal that bears considerable strategic significance in promoting CCA. A process comprising NH3 leaching, NH3 distillation, and roasting was proposed to separate Cu from waste CCA scraps and prepare nanoporous CuO. First, NH3 leaching was performed to separate Cu from scraps. The effects of initial Cu2+ concentration, NH3 concentration, and air flow rate on Cu leaching speed were assessed. Over 99% Cu could be selectively leached, whereas nearly no Al reacted in optimum conditions. Leaching mechanism was analyzed by combining the changes in the potential and pH of the entire NH3 leaching process. Subsequently, NH3 distillation of the leach liquor was carried out to prepare a precursor, which was confirmed to be CuCO3·Cu(OH)2 by X-ray powder diffraction (XRD) analysis. Finally, CuCO3·Cu(OH)2 was roasted, and the effect of roasting temperature on roasted product composition and properties was investigated by thermogravimetry–differential scanning calorimetry, XRD, scanning electron microscopy, and N2 adsorption–desorption. Results indicated that nanoporous CuO (purity, >99%; Brunauer–Emmett–Teller surface area, 44.38 m2/g; pore volume, 0.2690 cm3/g) was successfully prepared. In the entire process, 96.70% NH3 and 98% Cu were recovered via analytical calculation.

Effect of Severe Plastic Deformation on the Conductivity and Strength of Copper-Clad Aluminium Conductors

Aluminium rods with different copper sheath thicknesses were processed by severe plastic deformation at room temperature and then annealed, to join the constituent metals and produce a nanocrystalline microstructure. A study of the effects of the deformation parameters, copper cladding thickness and annealing temperature on the electrical conductivity and hardness of the conductors is reported. It is shown that an interface forms between constituents because of intermixing in the course of severe shear deformation under high hydrostatic pressure and diffusion during the subsequent annealing. The effective conductivity of the aluminium copper-clad conductor dropped after deformation, but was recovered during annealing, especially during short annealing at 200 °C, to a level exceeding the theoretically predicted one. In addition, the annealing resulted in increased hardness at the interface and copper sheath.

Analyzing Handling Effects on Performance Parameters of Ethernet Cables using the Feature Selective Validation Method and Kolmogorov-Smirnov Test

The use of Ethernet cables is a vital, if under- discussed element of the infrastructure for the internet of things (IOT). While there are many cable types on the market, one worrying trend is the wide availability of copper clad aluminum (CCA) cables, which are widely considered unsuitable for infrastructure deployment. The availability of these copper clad aluminum (CCA) cables frequently disguised as compliant Ethernet communication cables calls for a method of assessing their performance, as this is crucial to ensuring quality of service delivery. This paper presents a method of analyzing the measured return loss and impedance profile due to handling stress. In this research, four Ethernet cables of which one of them was copper CCA cable were subjected to three rounds of coiling and uncoiling tests to represent stress from handling during installation. The Feature Selective Validation (FSV) method and Kolmogorov-Smirnov (KS) tests were used to quantify the variations between the tests. The results indicate that the CCA cable has the lowest resilience to physical stress with high potential for degradation.