Papers by Keyword: Pure Copper

Abstract: An artificial neural network (ANN) system was created to analyze and simulate the relationship between process parameters of dissimilar weld joints of Aluminum alloy 6061 (AA60061) and pure copper and their resulting mechanical properties. In this study, 2.2 mm thick Aluminum Alloy 6061 and 1.4 mm thick pure copper lap joints are welded using friction stir spot welding (FSSW) process. Tensile-shear tests were performed to evaluate the mechanical characteristics of the lap joints. The welding process parameters are tool speed, plunge depth, and dwell weld time. Optimum friction stir spot welding (FSSW) parameters are identified to achieve the maximum shear load for Aluminum alloy (AA 6061) and pure copper lap joints. This is accomplished at a rotational speed of 2000 rpm for a duration of 20 seconds, with a plunge depth of 0.2 mm. At 15s dwell time and 2000 rpm tool speed, the shear load increases with increasing plunge depth. The best regression neural network that has the least mean squared error of 0.10192 and coefficient of correlation of 0.85033 is the model of 5 neurons in the hidden layer of the system

Abstract: Bidriware is an ancient metal-based object of Art from South India dating back to 14th Century A.D. The base casting in a Bidriware work is made of a Zn-Cu alloy in the ratio of 16:1 while the inlay work is hemmed with pure silver. The black patination obtained on the surface of Bidriware has been a source of mystery and intrigue for a long time. In this work, this black patination has been investigated to understand the chemistry behind it. The patination in Bidriware is actually a combination of Cupric oxide, Cupric chloride and other minute quantities of cuprous oxide, cupric nitrate and Zinc oxide, which are the results obtained from XRD, SEM, Optical microscopy and XRF analysis. We have further found that similar black patination can be obtained on the surfaces of pure copper and yellow brass. Since black oxide layers have multiple applications in many fields for the property of black body, a novel method, based on ancient knowledge, has been suggested here to obtain similar surfaces on pure copper and yellow brass samples.

Abstract: The bulk Cu billets with ultrafine-grained microstructure were successfully processed from full-annealed coarse grained oxygen-free high conductivity (OFHC) Cu by the cyclic extrusion and closed compression (CECC), subsequently annealed at different temperatures. The evolution of the microstructure and mechanical properties was systematically studied. The results show that the effective strain per CECC process is ε=2.77, with further annealing treatment, a high-efficiency grain refinement is realized. After two cycles of CECC process and annealing at 350 °C for 1 h, the grain size refined to ～3 μm, the tensile strength increased to 280 MPa with a high ductility of 54%. Furthermore, a homogeneous structure and mechanical properties in the bulk copper billets for post-forging could be obtained.

Abstract: Friction stir welded lap joints of 5083 aluminum alloy plates with thickness of 2mm and T2 pure copper plates with thickness of 3mm were prepared, and the microstructures and properties of lap joints were investigated. The results showed that Al and Cu interdiffusion occurred at the interface of the lap joints, the grains in the stir zone of Al were refined and the microhardness increased sharply. The joint of Cu can be divided into four parts, including the nugget zone (NZ), thermo-mechanically affected zone (TMAZ), heat affected zone (HAZ) and base metal (BM). Using the optimum welding parameters (rotation speed of 900rpm and welding speed of 100mm/min), the lap joints were well formed. There were fewer welding defects and the average shear tensile force reached 3.155KN. Also, the ductile-brittle hybrid fracture occurred at the transitional zone of the advancing side of the Al plates. XRD results showed that intermetallic compounds (IMCS) mainly composed of Al₂Cu and AlCu₄ were produced in the interface of the lap joints during welding.

Abstract: The effects of rare earth Y addition on microstructure and properties of pure copper were investigated. Mechanical test, electrical test, oxidation resistance test, metalloscope, scanning electronic microscope (SEM) and X-ray difffraction (XRD) were performed to study the properties, microstructure and constitution. The results showed that both the hardness and antioxidant properties obviously increased with the increase of Y, confirmed the successful refinement role of Y. A small amount of Y (less than 0.5 wt.%) could improve the electrical conductivity of pure copper. When the Y content reached 0.2 wt.%, pure coppers obtained optimum electrical conductivity which is 96.8% IACS. However, over-added Y (>0.5 wt.%) resulted in second phase of Cu₇Y coarsening and non-homogeneous microstructures forming, which reduces the conductivity of copper. In addition, Y can effectively purify the organization of molten copper.

Abstract: The absorptivity of La in pure copper and the effects of La microalloying on microstructure evolution of pure copper were studied by adding different La contents to pure copper under vacuum condition. The microstructure of copper ingots with different La contents were synthetically analyzed by means of optical microscope (OM) and scanning electron microscope (SEM), and the content of La in ingots was tested using inductively coupled plasma-atomic emission spectrometry (ICP-AES). The results showws that the absorptivity of La in pure copper was more than 90% under vacuum condition and the burning rate was mainly determinated by autoxidation of La and the reaction with impurity elements in copper. The microstructure of copper ingot was refined with La addition. The columnar to equiaxed transition (CET) occured with 0.14% La addition and the microstructure of copper ingot was full equiaxed grains when La content was 0.16%. The CET mechanism was that the constitutional supercooling in copper melt was increased with La addition. The tensile strength of copper alloys could be improved slightly, while the elongation was decreased a little after La alloying.

Abstract: Microstructural and mechanical properties of powder metallurgy (PM) with carbon nanotube (CNTs) dispersed copper (Cu) composites were investigated in detail. Pure copper powder was coated with un-bundled CNTs by using the zwitterionic surfactant solution containing CNTs. The powder rolling process was applied to increase the powder surface area to be coated with CNTs. The total rolling reduction of Cu-CNT composite powder by 5 steps rolling was about 75%. With increasing the number of rolling steps, the content of CNTs coated on the Cu powder surface increased because of the increment of the flat surface area of flaky Cu rolled powder. As a result, the CNT content was 0.67mass% after 5 steps powder rolling. It was about twice as that of as-coated Cu-CNT composite powder without rolling. The grain size of PM extruded Cu-CNT composite was about one fifth of that of the extruded monolithic Cu material without CNT. Yield stress of the extruded Cu-CNT composite via the rolling process was 192 MPa, which is about twice that of the extruded monolithic Cu material (88 MPa). CNTs distributed at primary particle boundaries were effective to prevent the grain coarsening by their pinning effects, and this grain refinement was the main strengthening factor of the Cu-CNT composite via rolling process.

Abstract: The deformation characteristics of pure copper have been investigated by compression tests in the temperature range of 20 °C~900 °C and strain rate range of 0.001 s^-1~1 s^-1. The results showed that the flow stress of pure copper increased with increasing strain rate and decreasing deformation temperature. Three types of strain-contained flow stress prediction models were developed. The flow stress prediction models based on parameters such as α, Q, lnA and n were related to deformation temperature, strain rate and strain, the prediction accuracy of the flow stress was deeply influenced by the cumulative error of multi-parameter fitting. The flow stress prediction model based on σ, , ε and T constitutive relations and the flow stress prediction model based on GA+BP possessed less correlation with microscopic deformation mechanism, proving to have high prediction accuracy, in which GA+ BP-based flow stress prediction model is in very good agreement with true stress curve, which is of significance to the guidance of hot working of pure copper.

Abstract: Oxidizing agent of ferric nitrate was added into Sodium thiosulfate chemical coloring liquid. The influence of components concentration and process parameters on the film was analysed. The results indicated that colored film was mainly composed of CuS, the colored film was obtained by the method of combining oxidation and sulfidation, and it had a better adhesion with the substrate, the best optimal process condition were that the temperature was 70°C and the concentration of ferric nitrate and thiosulfate were 9.5g/L and 45g/L respectively.

Abstract: The main aims of this study is to produce copper reinforced metal matrix composite (MMC) using micron sized chromium particles via friction stir processing (FSP) in order to studying effects of adding Cr particles to copper based matrix by FSP.Microstructures, microhardness and wear properties have been studied in order to evaluate the microstructures and mechanical properties of fabricated composites. the microstructure properties are evaluated by optical microscopy (OM) and field emission scanning electron microscopy (FESEM). The mechanical behaviors of the samples are determined by microhardness and wear tests. The results showed that the grain size of fabricated composite reduced. also it is indicated that in comparison to base copper microhardness of FSPed composites in stir zone (SZ) have been increased significantly. the results of wear test showed that in comparison with specimen with traverse speed of 80 mm/min , higher traverse speed of 160 mm/min increase wear rate of cylindrical pins.