Papers by Keyword: Copper Alloy

Abstract: CuAgZr alloy is a minor variation of CuAg alloy that is remarkably known for good combination of strength and electrical conductivity. Strengthening and conductivity enhancing of CuAgZr alloy is essentially proficient by the precipitation of Ag precipitates. The behavior of Ag precipitates at high temperature was investigated using in-situ transmission electron microscopy. These nanoscale Ag precipitates are formed in CuAgZr alloy during heating process with the average size of 5 nm. Growth of precipitates at higher temperature can be explained by the consumption of solute diffusing from smaller precipitates. Dislocation looping at high temperature would be the effects of a large lattice strain along matrix/precipitate interface that would retard the dislocation movement.

Abstract: Ultrafine-grained (UFG) pure copper has been in the focus of materials scientists over the last two decades, however ultrafine-grained high-strength copper alloys have scarcely been processed or characterized so far industrially.In this contribution, UFG copper alloys, especially Cu-Ni-Si alloys, being well known as ideal materials for electromechanical connectors, springs and leadframes, are presented. Precipitation hardened Cu-Ni-Si alloys are a well established and technologically important class of materials for a wide range of applications where high strength and good conductivity are required. Yield strength and fatigue properties of metallic alloys can be significantly enhanced by severe plastic deformation methods. In contrast to other strengthening methods such as solid solution hardening, severe plastic deformation leads to a weaker decrease of electrical conductivity and is therefore a means of enhancing strength while maintaining acceptable conductivity for current bearing parts and components. Characterization of these materials after severe plastic deformation by swaging, wire drawing and subsequent aging was carried out using conductivity-, hardness-and tensile tests as well as highly-resolved microstructural characterization methods.The results reveal that UFG low alloyed copper alloys exhibit impressive combinations of properties such as strength, conductivity, high ductility as well as acceptable thermal stability at low and medium temperatures. By a subsequent aging treatment the severely plastically deformed microstructure of Cu-Ni-Si alloys can be further enhanced and thermal stability can profit from grain-boundary pinning by precipitated nanoscale nickel silicides.

Abstract: This paper presents the synthesis of a Cu-0.5wt%Nb alloy via mechanical alloying (MA) and subsequent hot pressing. The evolutions of the density, microstructure, microhardness and electrical conductivity of the alloy as a function of the sintering temperatures were investigated. The results show that the microhardness of the alloy decreases with increasing consolidation temperatures, while the density and the conductivity improve. The alloy, subjected to vacuum hot-pressing sintering under 25 MPa pressure and 800 °C for 2h, has a microhardness of 102 HV and an electrical conductivity of 98% IACS. The as processed alloy is characterized by Nb nanoparticles distributed in the submicron sized Cu grains. The microhardness and electrical conductivity of the alloy are closely related with the microstructure, i.e. Cu grain size, as well as the presence and distribution of Nb nanoparticles.

Abstract: The wear tests of ultrafine-grained Cu-0.68Cr-0.02S energy alloy after equal channel angular pressing followed heat treatment were carried out in alloy-graphite sliding pair system without lubricant at different contact electrical current density. The sutable microstructure, mechanical properties and electrical conductivity of severely deformed alloy have been formed on the samples with different levels of parameters of thermomechanical processing. The microstructure and wear surfaces of the samples have been studied using optical microscope and field emission scanning electron microscope equipped with energy dispersive spectrometer. The results illustrated that the mass loss at wear, wear rate and wear mechanism depend on microstructure, hardness and electrical conductivity of test materials as well as normal pressure stress and electrical current density on the contact surface. The mechanical and physical properties of alloy, testing parameters and their influence on the wear rate as well as wear mechanism are analyzed.

Abstract: Experimental researches that were performed in order to determine the mechanical parameters in the process of joining of materials using the FSW process are presented in this paper. The paper presents the joining of CuETP sheet copper alloy, with thickness of 5 mm, and provides details of the friction stir welding process. Besides that, the influence of tool geometry and the regime of welding on the quality of welded joints, was investigated. Experimental studies are made on the basis of the adopted multifactoral orthogonal plan, with varying of factors on two levels and repetition in the central point of the plan. Parameters varied in the experiment were: welding speed, rotation speed of tool, angle of pin slope, pin diameter and shoulder diameter. The family of tools is provided, based on the adopted geometric parameters. The experiment was carried out in a laboratory at ambient temperature in conditions similar to those in the production. In order to determine the quality of welded joints, mechanical tests were performed in the paper, and tensile strength and impact toughness were determined.

Abstract: With the development of semiconductor technology, the size of complementary metal oxide semiconductor (CMOS) devices has been scaled down to nanoscale dimensions. The technology of copper interconnection is the mainstream technology, so the request of the copper target is more and more rigor. This article analyzes the impact factors on the copper alloy target capability, including oxidation and strength. The aim of this investigation is to set up a bridge between the vendors of copper targets and the foundries of integrated circuit (IC) chip, and the base for the next generation copper targets.

Abstract: High performance rockets are developed using cryogenic technology. High thrust cryogenic rocket engines operating at elevated temperatures and pressures are the backbone of such rockets. The thrust chamber of such engines, which produce the thrust for the propulsion of the rocket, can be considered as structural elements. Often double walled construction is employed for these chambers for better cooling and enhanced performance. The thrust chamber investigated here has its hot inner wall fabricated out of a high conductivity high ductility copper alloy and outer wall made of a ductile stainless steel. The engine is indigenously designed and developed by ISRO and is undergoing hot tests. Inner wall is subjected to high thermal and pressure loads during operation of engine due to which it will be in the plastic regime. Evaluation of tensile properties of the copper alloy and stainless steel up to fracture, at cryogenic, ambient and elevated temperatures in parent metal and welded forms is of paramount importance for its constitutive modelling and thermo structural analysis of the thrust chamber.

Abstract: Cu-Cr-Zr-Ti alloys are widely used for fabrication of thrust chamber in liquid rocket engines, because of their high thermal conductivity and adequate strength. The alloy should be used in peak aged condition to achieve the best combination of strength and conductivity. However, realization of final component involves different stages of forming, intermediate heat treatment and brazing operations, which limit the usage of the alloy in peak aged condition. The formability of material depends on grain size to a large extent. Larger grained metals have better formability, but the roughened surface that results from stretching metal with coarse grain structure results in surface defects like orange peel. Copper alloys on cold working sometimes exhibit a surface pebbling effect termed as ‘orange peel’ or alligator skin’.The plates of this copper alloy, finish hot rolled at 925 to 975°C and annealed at 980±10°C for 10 ±2 min followed by air cooling are subjected to different stages of forming to get the final profile of thrust chamber. During the course of forming of plate for divergent thrust chamber, orange peel defect is observed in areas of higher deformation. Detailed characterization of these formed shells in terms of microstructure, grain size and mechanical property has been carried out to find out the exact cause of this defect. Study revealed that the plate has coarse grain structure, which has resulted in orange peel defect during forming. To overcome this effect, the plates were realized with modifications in finish hot rolling and annealing temperatures, which has shown improvement in grain refinement and mechanical properties. It has suppressed the orange peel defect during forming.

Abstract: Copper alloys are characterized by high plasticity and good resistance to corrosion. They are applied in electrical industry, telecommunication, in transport and machine building, particularly in the production of elements for deep drawing. The scope of investigation enclosed production of testing single crystals, determination of their crystallographic orientation, deformation of selected single crystals by compression in a temperature range from 20 °C to 400 °C, applying strain rate from 10^-5 s^-1 to 10^-1 s^-1 as well as microstructure observations. Typical plastic strain effects were observed in the microstructures of studied single crystals in the form of parallel and intersecting lines and slip bands with locally intensified density in different areas of cross section of examined specimen and the deflection bands with slightly marked slip lines in the primary system.

Abstract: The objective of the study is to conduct experiments to investigate the performance of Electrochemical Micromachining (EMM) process to drill micro-holes on Copper alloy and analyze the parameters to optimize by Taguchi method. An EMM setup developed in-house is used to conduct the experiments. Copper alloy as workpiece, Stainless Steel needle of sharp conical edge as tool and Sodium Nitrate as electrolyte are used. A Pulse generator is used to supply pulsed current. The input parameters analyzed for optimization are Voltage, Pulse on-time and Electrolyte Concentration. The Material Removal Rate (MRR) and Overcut are taken as output parameters to study the process performance. The experiment was designed according to L9 Orthogonal Array (OA) of Taguchi design. The observations have shown that the MRR increases and the accuracy decreases when the level of input value for any parameter is increased. The process parameters are optimized using Taguchi Analysis.