Copper Side Research Articles

Microstructure and mechanical properties of dissimilar pure copper/1350 aluminum alloy butt joints by friction stir welding

The dissimilar friction stir welding of pure copper/1350 aluminum alloy sheet with a thickness of 3 mm was investigated. Most of the rotating pin was inserted into the aluminum alloy side through a pin-off technique, and sound welds were obtained at a rotation speed of 1000 r/min and a welding speed of 80 mm/min. Complicated microstructure was formed in the nugget, in which vortex-like pattern and lamella structure could be found. No intermetallic compounds were found in the nugget. The hardness distribution indicates that the hardness at the copper side of the nugget is higher than that at the aluminum alloy side, and the hardness at the bottom of the nugget is generally higher than that in other regions. The ultimate tensile strength and elongation of the dissimilar welds are 152 MPa and 6.3%, respectively. The fracture surface observation shows that the dissimilar joints fail with a ductile-brittle mixed fracture mode during tensile test.

Electrical, Corrosion, and Mechanical Properties of Aluminum-Copper Joints Produced by Explosive Welding

This study investigates the microstructure, electrical, corrosion, and mechanical properties of plate-shaped aluminum-copper couple produced using the explosive welding method. Mechanical tests, including hardness, tensile, tensile-shear, and impact test, concluded that the Al-Cu bimetal had an acceptable joint resistance. In this study, local intermetallic regions formed on the interface of the joint of the aluminum-copper bimetal, produced using the explosive welding technique. However, the formed intermetallic regions had no significant effect on the mechanical properties of the joint, except for increasing its hardness. According to electrical conductivity tests, the Al-Cu bimetal had an average electrical conductivity in comparison to the electrical conductivity of aluminum and copper, which were the original materials forming the joint. According to the results of electro-chemical corrosion test, during which galvanic corrosion formed, the Al side of the Al-Cu bimetal was more anodic due to its high electronegativity; as a result, it was exposed to more corrosion in comparison to the copper side.

Experimental study of diffusion welding/bonding of titanium to copper

In the present study, Ti–6Al–4V alloy was bonded to electrolytic copper at various temperatures of 875, 890 and 900°C and times of 15, 30 and 60min through diffusion bonding. 3MPa uniaxial load was applied during the diffusion bonding. Interface quality of the joints was assessed by microhardness and shear testing. Also, the bonding interfaces were analysed by means of optical microscopy, scanning electron microscopy and energy dispersive spectrometer. The bonding of Ti–6Al–4V to Cu was successfully achieved by diffusion bonding method. The maximum shear strength was found to be 2171N for the specimen bonded at 890°C for 60min. The maximum hardness values were obtained from the area next to the interface in titanium side of the joint. The hardness values were found to decrease with increasing distance from the interface in titanium side while it remained constant in copper side. It was seen that the diffusion transition zone near the interface consists of various phases of βCu4Ti, Cu2Ti, Cu3Ti2, Cu4Ti3 and CuTi.

Weld Quality Improvement with Hybrid FSW Technology Assisted by Preheating for Copper T2/Aluminium 5A06 Dissimilar Materials

Copper and aluminium alloy could be welded by friction stir welding (FSW) but it is quite difficult to achieve a defect-free welding joint for welding dissimilar materials because of the enormous difference of their thermo-physical performances. In this paper, another friction stir tool was applied as a heating source to preheat the copper side to 150~200°C in the welding direction. Preheating temperature can make up the lost heat, improve the temperature of copper plate before the FSW process, achieve the refining grains, and then obtain a high quality welding joint. We concentrated on hybrid heat-source equipments design and procedure optimization in our studies. The microstructure, mechanical properties and phase constituents of FSW joints were studied through mechanical test and metallographic analysis. The results indicated that the hybrid FSW technology with preheating for copper T2/aluminium 5A06 dissimilar materials can not only improve the welding efficiency, but also obtain the high quality welding joint. This special welding technology could solve the welding problems of Al-Cu dissimilar materials and had a good potential for application in aerospace manufacturing.

Microstructure and mechanical properties of friction stir welded joint of Zr 55Cu 30Al 10Ni 5 bulk metallic glass with pure copper

Zr 55Cu 30Al 10Ni 5 bulk metallic glass (BMG) plate and pure copper plates with 2 mm in thickness were successfully joined by friction stir butt welding. Microstructure characterization revealed that a clear interface between the two materials was formed in the stir zone and no crystallization from the amorphous phase can be detected. On the copper side in the stir zone, a transitional microstructure of refined elongated grain structure, refined equiaxial grain structure and coarse equiaxial grain structure was found varying with the distance from the BMG/Cu interface. The welded joint showed lower hardness than that of the base metals and finally fractured on the copper side in tensile tests. The ultimate tensile strength of the joint was about 253 MPa, which reached up to 95% of the pure copper.

Characterization of a power bipolar transistor as high-dose dosimeter for 1.9–2.2 MeV electron beams

Results of the characterization studies on a power bipolar transistor investigated as a possible radiation dosimeter under laboratory condition using electron beams of energies from 2.2 to 8.6 MeV and gamma rays from a 60Co source and tested in industrial irradiation plants having high-activity 60Co γ-source and high-energy, high-power electron beam have previously been reported. The present paper describes recent studies performed on this type of bipolar transistor irradiated with 1.9 and 2.2 MeV electron beams in the dose range 5–50 kGy. Dose response, post-irradiation heat treatment and stability, effects of temperature during irradiation in the range from –104 to +22 °C, dependence on temperature during reading in the range 20–50 °C, and the difference in response of the transistors irradiated from the plastic side and the copper side are reported. DLTS measurements performed on the irradiated devices to identify the recombination centres introduced by radiation and their dependence on dose and energy of the electron beam are also reported.

A Kilowatt Radio-Frequency Excited Diffusively Cooled All-Metal Slab Waveguide CO2 Laser

A new type of rf excited diffusively cooled all-metal slab waveguide CO2 laser is presented, in which the waveguide channel is constructed by two copper side walls and two copper electrodes, and the discharge is confined in the slab waveguide channel in terms of the voltage division structure. From this type of structure, over 1 kW laser power is obtained with an efficiency of more than 13%.

Mimicking a Superoxide Dismutase (SOD) Enzyme by copper(II) and zinc(II)-complexes

Mimicking the Superoxide Dismutase Enzyme (SOD), several imidazolato-bridged copper(II)-zinc(II) complexes were prepared, characterised by IR spectroscopy and their SOD enzyme activity was determined. 2,2′-Bipyridine, 2,2′:6′,2″-terpyridine and tris(2-aminoethyl)amine molecules were used on both metal sides, as coordinating ligands. The complex, containing the 2,2′:6′,2″-terpyridine ligand on copper side has the smallest SOD activity, which indicates the importance of the rigidity of the copper complex in SOD activity.

Microstructure and XRD analysis of FSW joints for copper T2/aluminium 5A06 dissimilar materials

Copper (T2) and aluminium alloy (5A06) were welded by friction stir welding (FSW). The microstructure, mechanical properties and phase constituents of FSW joints were studied by metallography, tensile testing machine and X-ray diffraction. The results indicated that the high quality weld joint could be obtained when tool rotational speed is 950 rpm, and travel speed is 150 mm/min. The maximum value of tensile strength is about 296 MPa. The metal Cu and Al close to copper side in the weld nugget (WN) zone showed a lamellar alternating structure characteristic. However, a mixed structure characteristic of Cu and Al existed in the aluminium side of weld nugget (WN) zone. There were no new Cu–Al intermetallic compounds in the weld nugget zone.

Fabrication and characterization of vacuum plasma sprayed W/Cu-composites for extreme thermal conditions

The joining of tungsten to copper and the ongoing search for commercially viable production techniques is one of the challenging issues in the field of composite materials. The reason why this material combination is of essential importance is its ability to withstand erosion and high temperatures on the tungsten side and to remove big quantities of heat on the copper side. Due to the mismatch of thermal expansion and Young’s moduli, the direct joining of these two materials results in high residual and thermal stresses at the interface, ultimately reducing component lifetime. One potential answer to this problem is functionally graded structures of W and Cu, which smoothen the transition of material properties. The present study focuses on vacuum plasma spraying (120 mbar, Ar) of W/Cu-gradients and composites with defined mixing ratios. The influence of the fabrication process and the W:Cu ratio on the microstructure has been investigated and results from thermo-mechanical and thermo-physical results analyses are presented. Finite element modeling has been used to demonstrate the positive effect of gradients on the elastic and elastic–plastic response within two different model-geometries. Partial gradients, ranging from pure tungsten to 75 vol.% tungsten, exhibit the best results and improve the expected life-time performance significantly by reducing the stresses at both interfaces, W/FGM and FGM/Cu, compared to a reference interface between W and Cu.

Heat Transfer through the Copper Plate of Slab Moulds

In slab moulds the cooling water flows in notches which are machined into the copper body. Therefore, the heat transfer from the hot side of the copper body to the cooling water is two- or three-dimensional. But usually the heat transport is taken to be one-dimensional and is computed using an average value for the copper wall with the water flowing in a slit parallel to the wall. This simplification is not very satisfactory. In the present study the three-dimensional heat flow in a slab mould has been computed with an exact numerical model and the resulting heat transfer coefficient for heat flow from the hot copper side to the bulk of the cooling water is compared with that of three simple engineering equations.

Transient liquid phase bonding of Cu to Cu–W composite using an electron beam energy source

Abstract This paper presents an alternative method for fabricating Cu/Cu–W joints suitable for electrical contacts. The process applied to join the Cu to the Cu–W composite involved using an electron beam welding machine operated in conduction mode to form a transient liquid phase at the interface from the melting of a thin Al foil. Analysis of the microstructure of the joints indicated that for optimized processing conditions, Cu–Al intermetallics were not present in the Cu/Cu–W interfacial region. For the joints with such microstructural characteristics, measurement of the mechanical integrity of the interface between the Cu and Cu–W composite indicated that plastic deformation and fracture occurs at the copper side of the assembly.

Characterization of a continuous CO2 laser-welded Fe-Cu dissimilar couple

Continuous CO2 laser welding of an Fe-Cu dissimilar couple in a butt-weld geometry at different process conditions is studied. The process conditions are varied to identify and characterize the microstructural features that are independent of the welding mode. The study presents a characterization of the microstructure and mechanical properties of the welds. Detailed microstructural analysis of the weld/base-metal interface shows features that are different on the two sides of the weld. The iron side can grow into the weld with a local change in length scale, whereas the interface on the copper side indicates a barrier to growth. The interface is jagged, and a banded microstructure consisting of iron-rich layers could be observed next to the weld/Cu interface. The observations suggest that solidification initiates inside the melt, where iron and copper are mixed due to convective flow. The transmission electron microscopy (TEM) of the weld region also indicates the occasional presence of droplets of iron and copper. The microstructural observations are rationalized using arguments drawn from a thermodynamic analysis of the Fe-Cu system.

Effects of titania content and plasma treatment on the interfacial adhesion mechanism of nano titania-hybridized polyimide and copper system

Nano-titania (TiO 2) incorporated into polyimide (PI) matrix can significantly enhance the adhesion strength for PI/TiO 2 hybrid film and copper system. Surface modifications by various plasma treatments (Ar, Ar/N 2 and Ar/O 2) were also applied in this study to improve the adhesion strength. The Ar/N 2 plasma treatment is regarded as the more effective way in promoting the adhesion strength. The maximum adhesion value of 9.53 N/cm was obtained for the PI/TiO 2–1 wt% hybrid film with Ar/N 2 plasma treatment. It is enhanced about 10 times as large as pristine PI. Furthermore, by Ar/O 2 plasma treatment, a weak boundary of copper oxide was formed at the interlayer between PI/TiO 2 hybrid film and copper which decreases the adhesion strength. The effects of plasma treatment and content of nanosized TiO 2 on the adhesion strength between PI/TiO 2 hybrid film and copper system were studied. Atomic force microscope and contact angle analyses were used to measure the changes in surface morphology and surface energy as a result of plasma treatment. Besides, the interfacial states of peeled-off polymer side and copper side were investigated by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). Based on the result of XPS spectra, the peeled-off failure mode between PI/TiO 2 hybrid film and copper was proposed in this study.

Nd:yttritium–aluminum–garnet laser welding of copper to stainless steel

Systematic laser welding experiments were conducted on dissimilar metal of copper and 300 series stainless steel using a high average power Lumonics JK 701H Nd:yttritium–aluminum–garnet laser. The laser melt penetration depth and width in copper and stainless steel were evaluated as a function of the laser parameters. The results reveal that melting of copper demands much higher average power, shorter pulse duration, and lower welding speed than melting stainless steel. If the laser beam is focused on the interface of the joint or on the stainless steel side, the weld penetration in stainless steel is much deeper than that in copper and the weld formation is poor and solidification cracks emerge. Distributing heat input by positioning the laser beam with respect to the interface of the joint was explored. Good results were achieved while positioning the laser beam 0.4 mm on the copper side. Butt weld penetration can go up to 2.4 mm and fusion zone in both copper and stainless steel is evenly distributed. By adjusting welding parameters, weld defects such as shrinkage, porosity, solidification cracks, etc., can be eliminated. Although isolated hot crack clusters exist along the austenite grain boundary in stainless steel HAZ, the strength of the weld joint is higher than copper and high vacuum tight property can be achieved.

Mechanical properties of copper to titanium joined by friction welding

This paper describes a fundamental investigation of friction welding pure copper to titanium. Friction welding was performed using a brake type friction welder. The effect of friction time and upset pressure on the mechanical and metallurgical properties were evaluated. Under constant upset pressure, the tensile strength made little difference with an increase in friction time, whereas at the constant friction time, the tensile strength increased with increasing upset pressure. Thus, the upset pressure plays a major role over the friction time and friction pressure on tensile strength. Though Cu3Ti intermetallic compound is formed at the copper/titanium interface during welding, the tensile strength of welded joint is not affected. It may be due to the thickness of intermetallic compound layer at interface being very thin and scattered. The tensile fracture of the welded joint occurred in copper side near the interface.

Investigation of micro-crack occurrence conditions in diffusion bonded Cu-304 stainless steel couple

Kirkendall effect has been used for calculation of intrinsic diffusion coefficients at the interface of diffusion bonded 304 stainless steel and electrolytic copper. Welding conditions have been chosen at temperatures in the range 700–900 °C for times of up to 30 min and pressures of up to 12 MPa. Microstructure of samples has been assessed using metallography, tensile testing, and scanning electron microscopy (SEM). Diffusion distance, and concentration distribution have been detected by using SEM and EDS analysis. Moreover, Heumann and Darken methods have been used in calculations of intrinsic and chemical diffusion coefficients. Under optimum bonding conditions, it was observed that the conditions giving the quotient ( D Cu/ D Fe+Cr+Ni) is different than unit propagated micro-voids at copper side in grain boundaries.

破壊力学 異種接合材中を伝ぱする疲労き裂の伝ぱ経路の等価試験片によるシミュレーション

A method of simulating the behavior of fatigue cracks propagating in bonded dissimilar materials by using equivalent specimens made of single constituent material was proposed. The equivalent specimens reproduced the same elastic characteristics with those of the bonded dissimilar materials by replacing the effect of elastic constant by that of the specimen thickness, and removed the effect of weakened strength of the bonded interface. Using the proposed equivalent specimens, experiments were conducted simulating fatigue crack paths propagating near or across the slant (15° and 45°) interface of bonded steel-copper specimens. When the cracks propagated from the thick (equivalent to steel) side to the thin (copper) side, they grew almost straight across the interface, while the initial cracks were in the thin (copper) side, they propagated along the interface without penetrating into the thick (steel) side. These behaviors were quite similar to the actual ones directly observed with the real bonded steel-copper specimens. The proposed concept of the equivalent specimen was confirmed to be useful in simulating the behavior of fatigue cracks in bonded dissimilar materials.

反応性インサート材を用いた５０５２アルミニウム合金‐純銅異種材の低電流スポット溶接

A reduced-current resistance spot welding technique, which utilizes the heat of reaction from reactive inserts together with the Joule heat, has been applied to join aluminum alloy A5052–H34 sheets to pure copper C1100–O sheets. Employing elemental powder mixtures of Ti–Al and Ti–Mn binary systems as the reactive inserts, well balanced tensile shear load and bonded area are obtained by the latter insert especially in a composition of Ti–75Mn. Since expulsion causes damage to the joint strength strongly, welding conditions are investigated to prevent the strength decrease. Application of a F-type electrode in the aluminum side is effective to avoid the surface expulsion by chilling the melted zone formed through the thickness of the aluminum alloy sheets during welding. As the mating electrode in the copper side, a CF-type one with a tip diameter just larger than that of the melted zone is effective to prevent the inter-layer expulsion by its forging effect. When a welding current of 12 kA is applied for 0.2 s with Ti–75Mn insert and welding force of 1 kN to join aluminum alloy sheets of 1 mm and 2 mm in thickness to copper sheet of 1 mm in thickness, tensile shear loads over 1.5 kN and 1.9 kN are achieved by the use of an electrode pair of CFφ6(Cu)/F(Al), respectively.

E.P.R. study of an imidazolate-bridged Cu-Zn complex of glycylglycine

An imidazolate-bridged heterometallic binuclear copper–zinc complex Na[(glygly)Cu–im–Zn(glygly)], where H 2glygly is glycylglycine and imH is imidazole, has been synthesized. X-band e.p.r. spectra of the complex at different pH values in frozen solution (50% DMSO, 77 K) suggest that the imidazolate bridged complex is stable in the pH range 7–10. At lower pH (<7) the imidazolate bridge breaks on the copper side. At higher pH (>10), the e.p.r. changes suggest either hydroxylation of the copper centre or breaking of the imidazolate bridge on the zinc side.