Copper-clad Aluminum Research Articles

Formation of ultra-fine copper grains in copper-clad aluminum wire

The microstructure formation at the interface in a copper-clad aluminum bimetallic wire has been investigated. Ultra-fine copper grains with sizes of 200 nm are formed near the Cu/Al interface when the wire is drawn after heat treatment. The formation of the ultra-fine copper grains is attributed to low-temperature recrystallization from strain that develops as the copper plastically flows around a broken dispersion of intermetallics at the interface. The ultra-fine copper grains added extra strength to the Cu/Al interface.

Numerical Simulation of Hydrostatic Extruding Cu/Al Bimetal Clad through Equal-Strain Contour Concave Die

A bimetal composite material is a variant of the typical composite that is composed of two materials joined at their interface surface. The advantage of clad material is that the combination of different properties of materials can satisfy both the need of good mechanical properties and the demand of user such as electrical properties simultaneously. This paper is concerned with the hydrostatic extrusion process of copper-clad aluminum rod. The commercially available finite element program ANSYS was used to simulate the process of hydrostatic extrusion for Cu/Al bimetal composite through the equal-strain contour concave dies. The relative slippage between the inner and outer metals under the condition of different friction factors is studied, and the stress-strain distribution in the billet was analyzed. Experiment test was carried out; it was found that the experimental result has good agreement with relative slippage from the finite element analysis.

Extrudability and Bonding Strength of Copper Clad Aluminum Alloy Composites Produced by Indirect Extrusion Process

This paper described extrudability and bonding strength of copper (TPC) clad aluminum alloy (pure Al, Al3003, Al5005, and Al7072) composites produced by indirect extrusion at 350°C with extrusion ratio of 21.39. Conical typed die with semi angle of 30°. Carbon oil was used to reduce the friction between billet/sleeve and billet/die. Maximum extrusion pressure was estimated to 491MPa for the Cu/Al, 714MPa for the Cu/Al3003, 820MPa for the Cu/Al5005, and 743MPa for the Cu/Al7072 alloy composites. No surface fracture was observed. From SEM observation, diffusion layer between the sheath material and the core material of extruded composites is observed and its thickness was measured to about 1.5㎛. The bonding strength was estimated to 65MPa for the Cu/Al, 89.3MPa for the Cu/Al3003, 70MPa for the Cu/Al5005, and 75MPa for the Cu/Al7072 alloy composites.

Microstructure and Mechanical Properties of Copper Clad Aluminium Wire by Drawing at Room Temperature

The microstructure and mechanical properties of pure copper clad Aluminum wires in different diameters by drawing at room temperature were studied in this paper. The results show that the microstructure of the cladding wire by drawing at room temperature is vimineous grain as fibril shape from prime equiaxed grain. The fibril diameter is in inverse proportion to deformation and the fibril length is in direct proportion to square of deformation approximately. The ultimate tensile strength of the cladding wire by drawing at room temperature increases in direct proportion to square root of deformation, and the elongation decreases and fluctuates. Basis of the ultimate tensile strength of prime pure copper and aluminum alloy, the ultimate tensile strength of the cladding wires in different diameters can be doped out by mixed principle of composite material.

A Novel Forming Process of Copper Cladding Aluminum Composite Materials with Core-Filling Continuous Casting

To simplify forming process of cladding materials with high performance, such as copper cladding aluminum composite materials, and to improve the interface quality of cladding materials, a novel forming process called Core-Filling continuous Casting (CFC) for bimetal composite materials is proposed. A conceptual equipment is developed, and the forming of composite bars of copper cladding aluminum is investigated. The basic technique theory of CFC, the reaction and bonded state of interface and the interfacial bonding strength of the cladding materials, as well as the influences of technological parameters are analyzed. The composite bars of copper cladding aluminum with 24mm in diameter of core material and 8mm in thickness of cladding layer are successfully fabricated. The results show that: (i) the proposed CFC process is feasible in principle; (ii) the composite bars of copper cladding aluminum having metallurgical bonding interfaces can be fabricated by CFC process under the conditions of liquid copper temperature of 1250~1300°C, liquid aluminum temperature of about 700°C and drawing velocity of 12~24mm/min; (iii) the copper layer thickness distribution is uniform both in the directions of portrait and circumference and (iv) the interfacial bonding strength is higher than that of core aluminum.

Visual sensor for automatic weld seam tracking to TIG welding of copper-clad aluminum wire

Aimed at the torch departure from seam in TIG welding of copper-clad aluminum wire,a visual sensor for automatic weld seam tracking system is developed by initiative arc light.The image of copper plate opposite seam is taken 20 mm the front of the torch.In order to decrease the time of video signal processing,analog circuit is applied in the process where video signal is magnified,trimmed and processed into binary by the datum of developing average value.Therefore,the waveform of video signal of copper plate opposite seam is obtained.The method that is used for judging the direction of warp and estimating the value of warp between copper opposite seam and tungsten electrode is established.Results show that the method is feasible to identify copper opposite seam based on visual sensor.A reliable system to real-time tracking seam of copper-clad aluminum wire TIG welding can be provided. The response cycle of this system is no more than 60 ms,and the tracking precision is less than 0.1 mm.

Effects of Core Material on Extrudability of Cu/Pure Al, Cu/Al3003 Clad Composites by Indirect Extrusion

We investigated about the effects of core material(Pure Al, Al3003) on extrudability such as the maximum extrusion ratio and the bonding strength of Copper Clad Aluminum(CCA) by indirect extrusion. As a results of this experiment, the maximum extrusion ratio of Cu/Al3003 was 38, which was larger than 21.39 of Cu/Al(Cu/pure Al). It was because that the difference of flow stress between copper as the sheath material and Al3003 as the core material was smaller than that of between copper and pure aluminum under the same extrusion temperature of 623K. The bonding strength gradually increased when the extrusion ratio increased, on the other hand, the bonding strength of Cu/Al3003 was higher than that of Cu/Al under same extrusion conditions. The diffusion layer thickness that affected bonding strength was not affected by the kind of core material, but it gradually increased when the extrusion ratio increased. It was thought that Cu/Al3003 had a more intimate diffusion layer than Cu/Al had because the extrusion pressure of Cu/Al3003 was higher than that of Cu/Al under the same extrusion conditions.

Fabrication of Copper Clad Aluminum Wire (CCAW) by Indirect Extrusion and Drawing

The optimized extrusion conditions from the present research were the extrusion temperature of 573~623K and the extrusion ratio(A0/A) of 21.39. Above the extrusion temperature of 623K, the fracture of sheath material was observed. It is due to the difference of flow stress between the sheath material and the core material during extrusion process. The bonding strength increased with increasing the extrusion temperature and the extrusion ratio. The bonding strength increased with increasing the annealing temperature. However, over 573K, it decreased abruptly since the thick and brittle intermetallic compounds of larger than 3µm were formed. The electricalconductivity of copper clad aluminum wire was about 70%IACS without annealing.

Finite element simulation of die design for hot extrusion process of Al/Cu clad composite and its experimental investigation

A clad composite material is a variant of the typical composites which is composed of two or more materials joined at their interface surface. The advantage of clad material is that the combination of different properties of materials can satisfy both the need of good mechanical properties and the demand of user such as electrical properties simultaneously. This paper is concerned with the direct and indirect extrusion process of copper-clad aluminum rod. Extrusion of copper-clad aluminum rod was simulated using a commercially available finite element package, DEFORM which can be used to simulate metal forming and heat transfer, welding and machining processes. The simulations were performed for copper-clad aluminum rod to predict the distributions of temperature, effective stress, effective strain rate and mean stress for various sheath thickness, die exit diameters and die temperatures. From the simulations, it was found that the larger the die outlet diameter and the thickness of the sheath material are, the better results can be acquired. It was found that the experimental result for lubricant material with carbon oil has good agreement with extrusion force from finite element analysis.

The Direct Extrusion of Copper Clad Aluminum Composite Materials by Using the Conical Dies

This paper describes experimental investigations in the direct extrusion of copper clad aluminum rods through conical dies. Composite materials consist of two or more different material layers. Copper clad aluminum composite materials are being used fur economic and structural purposes and the development of an efficient production method of copper clad aluminum composite material rods by extrusion is very important, It is necessary to know the conditions in which successful uniform extrusion ,and sound cladding may be carried out without any defects in the direct extrusion. There are several variables that have an influence on determining a sound clad extrusion. In order to investigate the influence of these parameters on the hot direct extrudability of the copper clad aluminum composite material rods, the experimental study have been performed with various extrusion temperatures, extrusion ratios and semi-cone angles of die. Subsequently, the microscopic inspection of interface bonding is carried out for extruded products. By measuring hardness, along extrusion way of products, a variation of hardness has been discussed. Proportional flow state has been considered by measuring radius ratio of Cu sleeve and Al core before and after extrusion.

Scattering of an obliquely incident plane wave from a circular clad rod

The problem of scattering of an obliquely incident plane acoustic wave from an infinite solid elastic clad rod is formulated. Numerical calculations show the effects of the variations of the cladding thickness on both the backscattered pressure spectrum and individual normal modes. It is shown that various resonance frequencies have different levels of sensitivity to variations of the cladding thickness. Experimental measurements are also performed at both normal and oblique incident angles on a copper-clad aluminum rod; good agreement is observed between the calculated and the measured results. These results demonstrate the potential of acoustic resonance scattering procedures for application in nondestructive evaluation (NDE) of clad rods.

A study of the hydrostatic extrusion of copper-clad aluminium tube

This paper is concerned with the hydrostatic extrusion process of copper-clad aluminium tube. In this study, the rigid-plastic finite-element method is used to analyze the steady-state extrusion process of the bimetal tube. Simulations are performed for copper-clad aluminium tube to give the distributions of the effective strain rate, equivalent stress and hardness for some extrusion ratios and die angles. In addition, the interface profile of the bimetal tube is predicted by tracking a particle path at the interface in the Eulerian domain. Experiments are carried out for copper-clad aluminium tube at room temperature. It is found that the finite-element predictions are generally in good agreement with the experimental observations. Detailed comparisons of the extrusion loads and interface profiles by the finite-element method with those from experiment are given.

銅クラッドアルミ導体の異常磁気抵抗

Aluminum stabilizer, which is used in composite superconductors, in external fields at 4.2K prvides a remarkable enhancement of magnetoresistance as compared to predictions by conventional theory. In order to study the cause of this anomalous behavior, we measured the electric resistivities of copper-clad aluminum conductors having rectangular cross-sections in various magnetic fields at 4.2K. The measured values depend on the magnitude and orientation of the applied magnetic field with respect to the sample; the resistivity being several times larger for a parallel field. We calculated the current distributions in the conductors by solving Maxwell's equations, taking the Hall effect into consideration for evaluating resistivities. The predicted resistivities were consistent with our experimental results, leading us to conclude that the current caused by the Hall effect is the main origin of the anomalous magnetoresistance and its anisotropy. Finally, we discussed a method to reduce the anomalous resistivity.

Investigation of aluminium stabilized superconductors

Two types of aluminium stabilized superconducting cables: soldered and pressed have been under investigation. The paper describes cables, manufactured from multifilamentary NbTi/Cu wires in high purity aluminium, or copper-clad aluminium with a cross-section of 4/spl times/9 and 4.6/spl times/37 mm/sup 2/. Dependence of contact resistance on the "superconductor-aluminium matrix" interface, on transport current and magnetic field from 0 to 3 T, have been studied. Contact resistance was varied within the range from 1.4/spl times/10/sup -11/ to 2.2/spl times/10/sup -10/ Ohm/spl times/m. Dependence of contact resistance on the cable construction and electrical and physical characteristics of its components was analysed theoretically and experimentally. Discrepancy between experimental results and classic theory predictions is discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Residual stresses in codeformed composite cylinders

The compatibility of materials deformed simultaneously and homogeneously depends to a great extent on the residual stresses remaining after the forming process is complete. A procedure is described for the calculation of such stresses arising from both the mutual elastic constraints exerted on components and the thermal expansion mismatch resulting from cooling from the forming temperature. The procedure is illustrated by an analysis of the dependence of residual stresses at the interface of coextruded rods of copper-clad aluminum as a function of core volume fraction at constant extrusion ratio and on extrusion ratio at constant core volume fraction. The state of stress can be significantly altered by the choice of composite composition and extrusion ratio.

Contact resistances investigation in aluminium stabilized superconductors

Two types of aluminium stabilized superconducting cables: soldered and pressed have0been under investigation. The paper describes cables, manufactured from multifilamentary NbTi/Cu wires in high purity aluminium, or copper-clad aluminium matrix with a, cross-section of 4×9 and 4.6×37 mm. Dependence of contact resistance on the interface “superconductor-aluminium matrix” on transport current and magnetic field from 0 to 3 T, correspondently have been studied. Contact resistance vary within the range from 1.4×10 −11 to 2.2×10 −10 Ohm×m. Dependance of contact resistance on the cable construction and electrical and physical characteristics of its components was analysed theoreticaly and experimentaly. Discrepancy between experimental results and classic theory predictions is discussed.

Stability tests of module coil (TOKI-MC) wound with an aluminum stabilized superconductor

The module coil TOKI-MC is a twisted solenoid coil wound with an aluminum stabilized superconductor developed as an R&D program for the Large Helical Device (LHD). The TOKI-MC can simulate the conductor and winding structure cooled by pool boiling helium, the twisted winding and the large electromagnetic force of the helical coils for LHD. The TOKI-MC was designed as a cryostable coil at an operating current of 20 kA, but the coil quenched around 17 kA in excitation tests. The cause of quenches was thought to be the result of wire movement. Stability tests were also carried out and the measured recovery current was less than the designed value. The degradation of recovery current was due to the excess magnetoresistivity of the copper clad aluminum stabilizer. The stability of TOKI-MC was evaluated and compared with the data of short sample tests. >

Development of a composite superconductor (Design-M) for research and development programs of the Large Helical Device

The composite superconductor called Design-M for the TOKI-MC has been designed as part of a chain of research and development programs. The conductor must be conductive to the requirements of electrical and mechanical properties. The designed conductor can be divided into three main parts: a five-layered and compacted superconducting cable, four copper-clad 5-nines pure aluminum stabilizers and a half-hard copper sheath. These parts are soldered together. The surface of the copper sheath is coated with copper oxide to assist heat transfer toward liquid helium. The operating current is designed to be 20 kA in a magnetic field of 8 T at a temperature of 4.2 K. The conductor has been manufactured in total lengths of about 900 m, and approximately 2000 kg in weight. Technical improvements have been made and production facilities for assembly have been set up for mass-scale production. Electrical and mechanical properties have been investigated.

The induced transport current investigation in aluminium stabilized superconductors

Two types of aluminium stabilized superconducting cables, soldered and pressed, were investigated. A description is given of cables manufactured from multifilamentary NbTi/Cu wires in high-purity aluminium or a copper-clad aluminium matrix with a cross section of 4*9 and 4.6*37 mm/sup 2/. The dependence of critical current and quench current for two cable samples using a superconducting transformer method was studied. The dependences of contact resistance on the superconductor-aluminium matrix interface on transport current and magnetic field from 0 to 3 T were also studied.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Superconductor for L* detector magnet

A concept of the conductor for the superconducting magnet for the L* detector is presented. Rated current is 50 kA at about 2.5 T. The operation current/critical current ratio is about 0.5. The stabilizer is copper-clad aluminum of 99.995% purity. The superconducting cable is made by transposition of strands around a normal metal core. The conductor is provided with pipes for helium circulation. Manufacturing aspects and conductor behavior during protective discharge are discussed.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>