Copper Joints Research Articles

Tool travel speed effects on the microstructure of friction stir welded aluminum–copper joints

Friction stir welding of aluminum and copper were carried out by varying the tool travel speed from 50mm/min to 90mm/min. The joint properties were evaluated and characterized with respect to the stir zone formation, intermetallics formation and its distribution. Tool traverse speed of 70mm/min and 80mm/min resulted in the optimum range of heat input to form defect free stir zone. The reduced diffusion rate and time prevailing at tool traverse speed of 80mm/min resulted in lower intermetallic thickness of 1.9μm. The continuous nano scaled thin intermetallic layers resulted in higher tensile strength and joint efficiency of 113MPa and 70% respectively. The intermetallics layers were identified and confirmed as Al2Cu, AlCu, Al4Cu9 using transmission electron microscope (TEM), X ray diffraction technique (XRD) and energy diffraction spectrum (EDS). The higher tensile strength is attributed to the dispersion strengthening of the fine Cu particles distributed over the Al material in the stir zone region.

Multi-objective optimization of friction welding parameters in AISI 304L austenitic stainless steel and copper joints

Friction welding is a solid-state joining technique, and joining of dissimilar materials has been witnessing tremendous development in various applications. In this study, friction welding is carried out in dissimilar materials, austenitic stainless steel and copper, which find application in power generators. The parameters such as friction pressure, upset pressure, rotational speed and burn-off length are considered to determine its influence on tensile strength, metal loss and weld time. Taguchi’s L27 orthogonal array is used for experimental design to maximize the tensile strength as well as minimize the metal loss and weld time. Optimal parameters are determined through multiple performance characteristics, and it is found that friction pressure of 22 MPa, upset pressure of 108 MPa, rotational speed of 500 r/min and burn-off length of 1 mm yield good mechanical and metallurgical properties.

Microstructure evolution and mechanical properties of Cu–Al joints by ultrasonic welding

Dissimilar joints of copper to aluminium were produced by high power ultrasonic welding (USW). The interfacial reaction between copper and 6061 aluminium alloy as a function of welding time was studied. The intermetallic compound (IMC) layer is mainly composed of CuAl2 and Cu9Al4. The thickness of the IMC layer increases with the welding time. For a relatively long welding time (0·7 s) in USW, the dendritic solidification microstructure was observed in local regions, owing to the occurrence of the eutectic reaction, α-Al+θ→L, in the welding process. The lap shear load (or strength) of the joints first increases and then decreases with increasing welding time, and the failure of the joints occurred dominantly at the interface. This is mainly attributed to the development of IMC layer at the interface.

Microstructure and Mechanical Properties of Brazed Joints Used in Electronic Devices

The microstructure and mechanical properties of brazed joints of oxygen-free copper and oxygen-free copper, nickel-plated kovar, monel, nickel-plated stainless steel were respectively studied by using AgCu28 and AuCu20 filler metal. Effects of different filler metal on microstructure of the brazed joints were analyzed through metallurgical microscope, SEM, EPMA. The brazed joints tensile strengths were analyzed through tensile test. The results indicate that the brazing process of oxygen-free copper and nickel content alloy used AgCu28 filler metal, nickel element is easy to diffused into AgCu28, AgCu28 filler metal with nickel element wetting spreadability along grain boundary of the oxygen - free copper, resulting in the penetration of the grain boundary of the oxygen-free copper. The joints brazed by AuCu20 filler metal have the better performance than the joints brazed by AgCu28 filler metal.

Experimental Measurement and Numerical Simulation of Temperature Distribution and Thermal History During Friction Stir Welding of Pure Copper Joints

Experimental Measurement and Numerical Simulation of Temperature Distribution and Thermal History During Friction Stir Welding of Pure Copper Joints

Eutectic structures in friction spot welding joint of aluminum alloy to copper

A dissimilar joint of AA5083 Al alloy and copper was produced by friction spot welding. The Al-MgCuAl2 eutectic in both coupled and divorced manners were found in the weld. At a relatively high temperature, mass transport of Cu due to plastic deformation, material flow, and atomic diffusion, combined with the alloy system of AA5083 are responsible for the ternary eutectic melting.

Electrical Conductance of Bolted Copper Joints for Cryogenic Applications

We present the results of electric contact resistance measurements at low temperatures on copper-to-copper bolted joints. Our accurate and systematic data display a rather small dispersion, and may be a useful tool for cryogenic applications like pulse-tubes, dilution refrigerators and nuclear refrigerators.

Shear strength of copper joints prepared by low temperature sintering of silver nanoparticles

In this work, mechanical properties of Cu-to-Cu joint samples prepared by low temperature sintering of Ag nanoparticle paste have been investigated. The silver nanopaste was prepared by a controlled thermal decomposition of an organometallic precursor. The as-synthesized Ag particles were spherical, with an average diameter of 8.5 nm. The Cu-to-Cu joint samples were made by placing a small amount of Ag nanopaste between two polished Cu plates and sintering at 150°C, 200°C, 220°C and 350°C in air. A normal load was applied to aid sintering. Mechanical properties were measured by imposing a uniform stress across the sample bond area and measuring the corresponding strain. The application of external load was found to have a positive effect on the material’s mechanical properties. Furthermore, interestingly high values of shear strength were observed.

低温焼結接合のための酸化銀および酸化銅混合ペーストを用いた銅継手の接合性評価

低温焼結接合のための酸化銀および酸化銅混合ペーストを用いた銅継手の接合性評価

409 タングステンと銅の接合材の機械的性質及び微細組織におよぼす中性子照射効果(OS4-(2),OS4 オーガナイズドセッション《材料・組織と加工》)

409 タングステンと銅の接合材の機械的性質及び微細組織におよぼす中性子照射効果(OS4-(2),OS4 オーガナイズドセッション《材料・組織と加工》)

Experimental and theoretical investigations on temperature distribution at the joint interface for copper joints using ultrasonic welding

Ultrasonic welding is a solid-state joining process that produces joints by the application of high frequency vibratory energy in the work pieces held together under pressure without melting. Copper and its alloys are extensively used in electrical and electronic industry because of its excellent electrical and thermal properties. This paper mainly focused on temperature distribution and the influence of process parameters at the joint interface while joining copper sheets using ultrasonic welding process. Experiments are carried out using Cu sheets (0.2 mm and 0.3 mm thickness) and the interface temperature is measured using Data Acquisition (DAQ) System (thermocouple) and thermal imager. Numerical and finite element based model for temperature distribution at the interface are developed and solved the same using Finite Difference Method (FDM) and Finite Element Analysis (FEA). The results obtained from FDM and FEA model shows similar trend with experimental results and are found to be in good agreement.

DISSIMILAR METALS CONNECTION THROUGH FRICTION STIR WELDING (CU-AL)

The aim of the paper is to analyze the existing techniques of producing copper and aluminum compounds. The subject matter was to study the possibility of using FSW for producing copper and aluminum compounds. The process of producing the copper and aluminum lap joints is described, welding conditions are discussed. The copper and aluminum overlap joints microstructure is investigated. The factors affecting the strength of copper and aluminum lap joints implemented through FSW are analyzed. The corrugation effect is investigated, and the remaining hole is studied to the strength of the welded joint. Stress distribution diagrams in the copper and aluminum lap joints are shown. The tests to the strength of various lap joints are resulted, the weld cut structure is analyzed, its processibility is estimated, and the joint strength improvement method is presented.

Microstructure and mechanical properties of TC4/oxygen-free copper joint with silver interlayer prepared by diffusion bonding

Diffusion bonding of two dissimilar materials, Ti–6Al–4V (TC4) and oxygen-free copper (OFC), was investigated at low temperature. A 30-µm silver foil was used as interlayer and the bonding was carried out at various bonding temperatures and times. The diffusion bonded joint microstructures were studied using an S-4800 field emission scanning electron microscope, JXA-8100 electron probe micro-analyzer, and Rigaku Ultima II X-ray diffractometer. Joint tensile strengths were measured by tensile tests. The silver interlayer prevented the formation of Ti–Cu compounds, AgTi and AgTi2 were generated at the TC4/Ag interface and a solid solution formed at the Ag/OFC interface. The tensile strength of the TC4/Ag/OFC joint increased first and decreased with bonding temperature or bonding time. The joint bonded at 700°C for 120min at 10MPa showed a maximum tensile strength of 161.9MPa. Fracture morphology showed that ductile fracture initiation and propagation took place at the Ag/OFC interface, which was the weak point of the joint.

Establishing a correlation between interfacial microstructures and corrosion initiation sites in Al/Cu joints by SEM–EDS and AFM–SKPFM

A lap joint of AA3003 and pure copper was produced by friction stir welding and the induced interfaces were investigated. Interfacial regions were characterized by SEM–EDS, AFM, SKPFM, OM and Vickers micro-hardness. Multimodal Gaussian distribution (for characterization of surface potential patterns) showed the formation of multiple compounds. A quantitative correlation between microstructure constituents and Volta potential distribution was recognized and confirmed by corrosion attacked sites observations. It was observed that the Al-rich regions proximate the dispersed Cu particles and Cu–Al intermetallics were most susceptible to corrosion attack initiation due to a galvanic driving force between these surface constituents.

Microstructure characterization and mechanical properties of laser-welded copper and aluminum lap joint

The microstructure in the intermediate layer of a laser-welded Cu–Al lap joint was examined metallographically. Tensile shear test was performed, and fracture surface analysis was also performed using scanning electron microscopy with energy dispersive spectroscopy. Results showed that there were several different zones with diverse characteristics of morphology and composition in the intermediate layer of the weld joint. Banded and cellular structures were observed in the hypereutectic zone; a lamellar structure was found in the eutectic zone which was the narrowest zone with the finest microstructure; a dendritic structure was obtained in the hypoeutectic zone with the coarsest microstructure and widest zone. The joint faulted in the dendritic hypoeutectic zone, under a combination of brittle and shear mode in the fracture surface. The maximum shear load of the Cu–Al joint decreased with increasing primary dendrite arm spacing and the growth of secondary dendrite in the hypoeutectic zone, which was induced by increasing laser power.

Microstructure and Mechanical Properties of Friction Stir Welded Annealed Pure Copper Joints

As a novel technique for joining materials, friction stir welding (FSW) has significant advantages over the conventional welding methods and is widely applied for joining different materials including aluminum, magnesium and copper alloys. In this research, the mechanical and microstructural characteristics of friction stir welded annealed pure copper joints were investigated. The influence of the tool rotation speed, welding speed and applied load was studied. The friction stir welding (FSW) was conducted at welding speed ranged from 30 to 70 mm/ min, rotation speed ranged from 400 to 1200rpm and applied load ranged from 1000 to 1500 kg. After welding process, tensile and Vickers hardness tests were performed. It has been found that increasing the tool rotational speed and/or reducing the welding speed increases heat input and causes grain coarsening in stir zone. High applied load refines the microstructure of NZ and increases the hardness and tensile strength of NZ. An optimum heat input condition was found to reach the best mechanical properties of the joints. The tensile characteristics of the friction stir welded tensile samples depend significantly on the tool rotation speed ,welding speed and applied load.

Prediction of mechanical properties in friction stir welds of pure copper

This research was carried out to predict the mechanical properties of friction stir welded pure copper joints. Response surface methodology based on a central composite rotatable design with three parameters, five levels, and 20 runs, was used to conduct the experiments and to develop the mathematical regression model by using of Design-Expert software. The three welding parameters considered were rotational speed, welding speed, and axial force. Analysis of variance was applied to validate the predicted models. Microstructural characterization and fractography of joints were examined using optical and scanning electron microscopes. Also, the effects of the welding parameters on mechanical properties of friction stir welded joints were analyzed in detail. The results showed that the developed models were reasonably accurate. The increase in welding parameters resulted in increasing of tensile strength of the joints up to a maximum value. Elongation percent of the joints increased with increase of rotational speed and axial force, but decreased by increasing of welding speed, continuously. In addition, hardness of the joints decreased with increase of rotational speed and axial force, but increased by increasing of welding speed. The joints welded at higher heat input conditions revealed more ductility fracture mode.

Metallurgical and mechanical examinations of steel–copper joints arc welded using bronze and nickel-base superalloy filler materials

The paper presents metallurgical and mechanical examinations of joints between dissimilar metals viz. copper (UNSC11000) and alloy steel (En31) obtained by Shielded Metal Arc Welding (SMAW) using two different filler materials, bronze and nickel-base super alloy. The weld bead of the joint with bronze-filler displayed porosity, while that with nickel-filler did not. In tension tests, the weldments with bronze-filler fractured in the centre of the weld, while those with nickel-filler fractured in the heat affected zone (HAZ) of copper. Since the latter exhibited higher strength than the former, all the major tests were undertaken over the joints with nickel-filler alone. Scanning Electron Microscopy (SEM) coupled with Energy Dispersive Spectroscopy (EDS) indicated corrugated weld interfaces and favorable elemental diffusions across them. X-ray diffraction (XRD) studies around the weld interfaces did not reveal any detrimental intermetallic compounds. Transverse bending tests showed that flexural strengths of the weldments were higher than the tensile strengths. Transverse side bend tests confirmed good ductility of the joints. Shear strength of the weld-interface (Cu–Ni or Ni–steel) was higher than the yield strength of weaker metal. Microhardness and Charpy impact values were measured at all the important zones across the weldment.

Evaluation of Mechanical and Metallurgical Properties of Dissimilar Materials by Friction Welding

Friction welding has been widely used to metals with dissimilar materials due to solid state joining process and shows good mechanical properties. In this study, the effect of mechanical and metallurgical properties of austenitic stainless steel (304L) and copper were experimentally investigated by tensile and hardness test while the metallurgical properties of optical, scanning electron microscopy and atomic force microscopy was used to analyze the microstructure of the welded joint. The joints were also examined with EDX line in order to understand the phases formed during welding. The material is evaluated by tensile test and their strength is determined and the hardness test measurements are examined in base metal and heat affected zone. The bonded materials of austenitic stainless steel and copper joint were produced by varying the friction pressure, upset pressure and rotational speed through Taguchi's orthogonal array. The highest tensile strength obtained in friction welded joint was 2.52% higher than parent material of copper. The effects of metallurgical characterization are discussed based on the microstructural studies.

Microstructure Evolution and Bonding Strength of Brazed Joint of Stainless Steel and Copper

The joining behaviour between stainless steel and copper has an importance in scientific and engineering applications such as high energy ring vacuum chambers and International Thermonuclear Fusion Experiment Reactor (ITER). In this research, the rapidly solidified foils of nominal composition 50Cu-40Mn-10Ni (C50) are used as a filler alloy for brazing between stainless steel (304 SS) and copper (Cu) plates. It is examined that C50 foil makes a good contact joint between two dissimilar metal plates of different thermal conductivities. The brazed region is mostly free from any porosities and intermetallic compounds, emphasizing on the distribution of solid solution phases. It causes high bonding strength of 304 SS-Cu butt joint at low brazing O temperature (B =920 C) with a fracture at the joint area. On the other hand, the fracture occurs at Cu base T metal for B = 980°C. The fractography also shows the presence of several dimples at Cu substrate and T severely deformed region at stainless steel substrate, representing a good quality bonding between 304SS and Cu plates.