C11000 Copper Research Articles

Corrosion of Cu-5Zn-5Al-1Sn (89% Cu, 5% Zn, 5% Al, 1% Sn) Compared to Copper in Synthetic Perspiration During Cyclic Wetting and Drying: The Fate of Copper

Cu-5Zn-5Al-1Sn (89% Cu, 5% Zn, 5% Al, 1% Sn; wt%) and UNS C11000 copper (Cu) were compared with respect to corrosion rate, film formation, and Cu release. Electrochemical, surface characterization, and solution analysis methods were utilized to track the fate of copper during corrosion of freshly ground alloys exposed to cyclic wetting and drying in a synthetic perspiration droplet. Corrosion behavior was a function of both alloy composition and environment, where cyclic wetting and drying resulted in more severe corrosion behavior compared to full immersion in the same perspiration solution. Throughout the corrosion process, significant concentrations of copper ions were released from both alloys. However, concentration increases were limited by solubility and precipitation reaction but still suggested antimicrobial efficacy.

The Fate of Copper during Corrosion of Cu-5Zn-5Al-1Sn (89% Cu, 5% Zn, 5% Al, 1% Sn) compared to Copper in Synthetic Perspiration Solution

Cu-5Zn-5Al-1Sn (89% Cu, 5% Zn, 5% Al, 1% Sn) and UNS C11000 copper (Cu) were compared with respect to corrosion rate, film formation, and Cu release in two surface conditions pertinent to the use of antimicrobial functional materials. Electrochemical, surface characterization, and solution analysis methods were utilized to track the fate of copper during corrosion in synthetic perspiration solution in a freshly ground condition and after 30-d lab air passivation. Corrosion behavior was a function of both alloy composition and surface condition with slightly lower corrosion rates on Cu-5Zn-5Al-1Sn compared to Cu. Throughout the corrosion process, the majority of Cu was observed to undergo dissolution into the synthetic perspiration solution as copper cations for both materials, at concentrations that would suggest favorable antimicrobial functionality for both Cu-5Zn-5Al-1Sn and Cu, regardless of surface condition. In contrast, oxide films were thinner on Cu-5Zn-5Al-1Sn under all conditions. Hence, the com...

Effects of zinc on static and dynamic mechanical properties of copper-zinc alloy

The effects of adding alloy element zinc on the static and dynamic mechanical properties of copper-zinc alloy were investigated. Tensile and low cycle fatigue behaviors of the C11000 copper and H63 copper-zinc alloy were obtained by using a miniature tester that combined the functions of in situ tensile and fatigue testing. A piezoelectric actuator was adopted as the actuator for the fatigue testing, and the feasibility of the fatigue actuator was verified by the transient harmonic response analysis based on static tensile preload and dynamic sinusoidal load. The experimental results show that the yield strength and tensile strength of the C11000 copper are improved after adding 37% (mass fraction) zinc, and H63 copper-zinc alloy presents more obvious cyclic hardening behavior and more consumed irreversible plastic work during each stress cycle compared with C11000 copper for the same strain controlled cycling. Additionally, based on the Manson-Coffin theory, the strain-life equations of the two materials were also obtained. C11000 copper and H63 copper-zinc alloy show transition life of 16832 and 1788 cycles, respectively.

Friction Stir Spot Welding of AA5052 Aluminum Alloy and C11000 Copper Lap Joint

The article aims to apply a friction stir spot welding for producing the lap joint between AA5052 aluminum alloy and C11000 copper alloy. The dimension of the materials was 100 mm in length, 30 mm in width and 1.0 mm in thickness. The copper plate was set overlap the aluminum plate by 30 mm. The welding parameter was the rotating speed of 2500-4000 rpm, the pin inserting rate of 2-8 mm/min and the holding time of 6 sec. The mechanical properties test and the microstructure investigation were performed to evaluate the lap joint quality. The summarized results are as follows. The friction stir spot welding could produce effectively the lap joint between AA5052 and C11000 copper. Increase of the rotating speed and holding time directly affected to decrease the tensile shear strength of the lap joint. The optimized welding parameters in this study that indicated the tensile shear strength of 864 N was the rotating speed of 3500 rpm, the pin inserting rate of 6 mm/min and the holding time of 4sec. The experimental results also showed that the hardness of the weld metal was lower than that of the base materials.

Novel in situ device for investigating the tensile and fatigue behaviors of bulk materials

For investigating the static tensile and dynamic fatigue behaviors of bulk materials, a miniaturized device with separate modular tensile and fatigue actuators was developed. The fatigue actuator presented good compatibility with the tensile actuator and mainly consisted of a special flexure hinge and piezoelectric stack. In situ fatigue tests under scanning electron microscope or metallographic microscope could be carried out due to the miniaturized dimensions of the device. A displacement correction method of tensile actuator based on load sensor compliance was investigated, and the feasibility of the method was verified by the comparison tests with a commercial tensile instrument. The application of testing the storage and loss modulus as a function of frequency was explained, and the temperature rises of both the piezoelectric stack and specimen were obtained as a function of frequency. Output characteristics of the fatigue actuator were also investigated. Additionally, the discharge performance of piezoelectric stack based on various initial voltages and fatigue tests on C11000 copper was carried out. This paper shows a modularized example that combines a servo motor with a piezoelectric actuator attached to the specimen grip to realize the in situ fatigue tests.

Optimization of axisymmetric open-die micro-forging/extrusion processes: An upper bound approach

There is a trend towards component miniaturization and strong drive towards cost effective and sustainable metal forming techniques of miniaturized components. This paper presents an upper bound solution for the optimization of open-die forging/extrusion processes in the forming of micro-pins from a sheet metal. Using such an analytical modeling approach, the critical blank thickness, the resulting final part geometry, together with the required forming load were predicted based on the location of the neutral plane under the punch during the process. Based on the phenomenological findings of the process, the geometry size factor, x, was introduced explaining its relative importance to the model. Experimental results obtained from C11000 copper samples using a progressive microforming process was found to agree well with the results predicted by the model. The results were also validated with other results reported before from a similar process.

The effect of tube material, microstructure, and heat treatment on process responses of tube hydroforming without axial force

In this paper, the influence of tube material, microstructure, and heat treatment on process responses of tube hydroforming has been studied. One of the most important parameters in performing a successful tube hydroforming process is the selection of appropriate material for tubes. In the analysis section, effective parameters for the selection of an appropriate tube material for the hydroforming process have been investigated; it was concluded that higher strain hardening exponent (n), elasticity modulus (E), and anisotropy index (R) can enhance formability in this process; and the effects of microstructure and heat treatment on the formability of ASTM C11000 copper and ASTM AA1050 aluminum have been investigated. Consequently, four different heat treatment processes, which had different heating temperatures and durations, were selected, in addition to different cooling methods for each of the materials. In the experimental tests, the effects of these heat treatment methods on maximum bulging height, thickness strains, and final forming pressures were scrutinized. The effects of heat treatment on copper microstructure were also studied through metallographic tests; on the other hand, the effects of microstructure on tube hydroforming process were justified. As a result of these analyses, two heat treatment methods, namely, heating to 450 and 350 °C for 15 min and cooling in water, were recommended for copper and aluminum, respectively. Using these methods and due to their consequent fine and homogenous microstructure, higher mechanical strength and increase in material formability was achieved by attaining higher thickness strain and bulging height values. Finally, after extracting the mechanical properties of the two materials and comparing them with each other, parameters of strength coefficient and strain hardening exponent were reported as two effective factors that would improve tube deformation by tube hydroforming process.

Effects of Aluminum Solids on the under Deposit Corrosion of Copper in Synthetic Potable Water: The Arguments for and against a Semi-Permeable Membrane

Aluminum solids promote under deposit pitting of UNS C11000 copper. The possible roles that aluminum solids (i.e., Al(OH)3) play to promote copper pitting were examined by various characterization methods followed by diagnostic chemical/electrochemical methods in Edwards synthetic drinking water (ESDW). Cathodic polarization scans indicated that aluminum solids did not affect the intrinsic cathodic half-cell kinetics on an isolated copper electrode. Cyclic potentiodynamic polarization (CPP) experiments showed that the pitting potential (EPit) of copper was decreased by the presence of gelatinous aluminum solids deposited on the surface. Multi-electrode arrays (MEAs) with various surface deposition treatments were tested in ESDW under both driven and natural conditions. Lower pitting potentials were found under driven conditions on copper electrodes containing aluminum deposits. Pitting events also occurred on copper electrodes containing aluminum deposits with the presence of 5 ppm Cl2 under freely corroding conditions. MEAs were also tested with an inert Delrin crevice former. In this case, a lower EPit and greater number of pitting events were found outside the crevice former. The drop in EPit was not as severe as in the case of deposited Al(OH)3, pointing to effects besides geometrically occluded sites, produced by inert crevice formers. Preferential sorption/transport of selected anions (OH−, HCO3−, SO42−, and Cl−) through gelatinous Al(OH)3 was studied. Plausible explanations for the detrimental effects of Al(OH)3 were given.

Application of simulated annealing method to pressure and force loading optimization in tube hydroforming process

The most important parameters in success of tube hydroforming process are internal pressure and axial force loading paths. Theoretical calculations and finite element trial-and-error simulations to find the optimum loading paths are so time-consuming and costly. In this paper, pressure and force loading paths in tube hydroforming process are investigated and optimized using Simulated Annealing optimization method. The final aim is to obtain the optimal loading paths for tube hydroforming of axisymmetric geometries under a failure criterion based on the maximum allowable thinning and von-Mises stress. Simulated Annealing algorithm is directly incorporated into the non-linear structural finite element code ANSYS/LS-DYNA to analyze the forming parameters. This novel approach is validated by experiments on ASTM C11000 copper tubes. The results are also compared and verified with another literature, in which a good correlation is obtained. Less thinning and better shape conformation is attained using the optimized parameters.

Effect of Shoulder Size on Weld Properties of Dissimilar Metal Friction Stir Welds

This article reports a research study that shows the effect of shoulder diameter size on the resulting weld properties of dissimilar friction stir welds between 5754 aluminum alloy (AA) and C11000 copper (Cu). Welds were produced using three different shoulder diameter tools: 15, 18, and 25 mm by varying the rotational speed between 600 and 1200 rpm and the traverse speed between 50 and 300 mm/min to achieve the best result. Each parameter combination was chosen to represent different heat input conditions (low, intermediates and high). The welds were characterized through microstructural evaluation, tensile testing, microhardness measurements, x-ray diffraction analysis, and electrical resistivity. Microstructural evaluation of the welds revealed that the welds produced consisted of all the friction stir welding (FSW) microstructure zones with organized flow lines comprising mixture layers of aluminum (Al) and copper (Cu) at the Stir Zones. The average Ultimate Tensile Strength (UTS) of the welds considered ranged from 178 to 208 MPa. Higher Vickers microhardness values were measured at the joint interfaces of all the welds because of the presence of intermetallic compounds in these regions. The x-ray diffraction analysis revealed the presence of Al4Cu9 and Al2Cu intermetallics at the interfacial regions, and low electrical resistivities were obtained at the joint interfaces. An optimized parameter setting for FSW of Al and Cu was obtained at the weld produced at 950 rpm and 50 mm/min with the 18-mm shoulder diameter tool.

Effect of Chlorine Concentration on Natural Pitting of Copper as a Function of Water Chemistry

The cathodic reduction reaction kinetics of free chlorine and oxygen on UNS C11000 copper microelectrodes were investigated in Edwards synthetic drinking water. increases cathodic reaction rates and thus raises open-circuit potential (OCP) toward pitting potentials. An increase in both the mass-transport factor (where ) for chlorine reduction (HOCl and ) and OCP was observed as pH was increased from 8.5 to 9.5, and free chlorine levels were raised. Natural pitting was investigated using coupled multielectrode copper (UNS C11000) arrays exposed under the same conditions from pH 6 to 10 with various residual free chlorine concentrations (0–5 ppm). An empirical equation that forecasts the OCP as a function of pH and concentration was developed. This enabled an assessment of the pitting susceptibility of various waters based on the comparison of OCPs to critical pitting potentials. Pits formed when the OCP rose above repassivation potential and stopped growing once the OCP dropped below . Pitting severity, as determined by calculated pitting factors, increased with free chlorine concentration and was highest at pH 9.

Study of Forming Parameters in Hydroforming of a Thin-Walled ASTM C11000 Copper Tube

Tube hydroforming technology is still considered a new technique growing fast in automotive and aircraft industries. Many researches on all aspects of this process are still required. Contact friction is one of the most effective parameters on tube wall thinning. To successfully fulfill the process without any common defects, it is very important to determine the proper internal pressure and axial feeding loading paths. In this paper, the effect of lubrication on tube wall thinning on ASTM C11000 copper alloy is discussed as well as the effect of internal pressure and axial feeding. An axisymmetric bulged tube is investigated using theoretical, numerical and experimental methods. Improved linear and non-linear pressure and feeding loading paths are applied and the predicted results are experimentally proved. It is observed that non-linear pressure application gives smoother results. Also proper lubrication plays an important role in success of the process.

Use of Coupled Multielectrode Arrays to Elucidate the pH Dependence of Copper Pitting in Potable Water

Natural pitting was investigated using coupled multielectrode arrays (CMEAs) constructed from flush mounted, close-packed UNS C11000 copper wires exposed in chlorinated and aerated Edwards synthetic drinking waters (ESDWs) [ J. C. Rushing and M. Edwards , Corros. Sci. , 46 , 3069 (2004) ]. Tests were conducted in ESDWs with pH adjusted from 6 to 10 and containing 5 ppm . The CMEA method detected the formation of persistent anodes (pitting) in synthetic waters compared to switchable anodes at pH 6 (uniform corrosion). Local maximum and minimum open-circuit potentials (OCPs) were analyzed before, during, and after pitting events and were compared to pitting and repassivation potentials. Natural pitting was found to occur on a small percentage of electrodes once the OCP rose above determined in upward/downward scans. Pits stopped growing once the OCP dropped below . Pitting factors, determined as a function of pH, increased with pH from 7 to 9. However, a further increase in pH to 10 reduced pitting, which could not be determined from other test methods. This drop in pitting factor could be ascertained from arrays but not from a comparison of OCPs to pitting potentials seen in upward scans. The cathodic capacity of adjacent cathodic sites as a function of water chemistry and the nature of the cathodic sites were factored into this analysis.

Passivity and Pit Stability Behavior of Copper as a Function of Selected Water Chemistry Variables

The electrochemical pitting behavior of UNS C11000 copper was investigated in a synthetic potable water found to cause pitting. Tests were also conducted in several other HCO3-, SO42- and Cl- containing-waters. Studies of the effect of water chemistry on passivity, uniform corrosion, and pitting were accomplished using the cyclic voltammetry method. Certain water chemistry concentrations promote pitting. High [SO42-]/[OH-],[SO42-]/[HCO3-] and [Cl-]/[HCO3-] ratios lower pitting potentials while an increase in alkalinity improves passivity and raises pitting potentials. HCO3-/CO32- can protect copper surfaces by forming carbonate containing minerals. However, carbonated species are less beneficial towards passivity compared to OH- with respect to passivation efficiency. Empirical equations that forecast pitting and repassivation potentials as a function of selected water chemistry variables were developed by linear regression analysis based on experimental pitting and repassivation potential trends with HCO3-, Cl- and SO42- content. The origins of the trends with water chemistry variables are discussed.

Passivity and Pit Stability Behavior of Copper as a Function of Selected Water Chemistry Variables

The electrochemical pitting behavior of UNS C11000 copper was investigated in a synthetic potable water found to cause pitting. Tests were also conducted in several other , , and containing waters with systematic variations in concentrations of these species. Studies of the effect of water chemistry on passivity, uniform corrosion, and pitting were accomplished using the cyclic voltammetry method complemented by various diagnostic methods. Certain water chemistry concentrations promote pitting. Critical pitting potentials for copper pitting are decreased by certain water chemistry variables. High /, /, and / ratios lower pitting potentials while an increase in alkalinity (increasing or /) improves passivity and raises pitting potentials. / can protect copper surfaces by forming carbonate containing minerals. However, carbonated species are less beneficial toward passivity compared to with respect to passivation efficiency. Empirical equations that forecast pitting and repassivation potentials as a function of selected water chemistry variables were developed by linear regression analysis based on experimental pitting and repassivation potential trends with , , and content. The origins of the trends with water chemistry variables are discussed.

Full Field Strain Measurement in Compression and Tensile Split Hopkinson Bar Experiments

The 3D image correlation technique is used for full field measurement of strain (and strain rate) in compression and tensile split Hopkinson bar experiments using commercial image correlation software and two digital high-speed cameras that provide a synchronized stereo view of the specimen. Using an array of 128 × 80 (compression tests) and 258 × 48 (tensile tests) pixels, the cameras record about 110,000 frames per second. A random dot pattern is applied to the surface of the specimens. The image correlation algorithm uses the dot pattern to define a field of overlapping virtual gage boxes, and the 3-D coordinates of the center of each gage box are determined at each frame. The coordinates are then used for calculating the strains throughout the surface of the specimen. The strains determined with the image correlation method are compared with those determined from analyzing the elastic waves in the bars, and with strains measured with strain gages placed on the specimens. The system is used to study the response of OFE C10100 copper. In compression tests, the image correlation shows a nearly uniform deformation which agrees with the average strain that is determined from the waves in the bars and the strains measured with strain gages that are placed directly on the specimen. In tensile tests, the specimen geometry and properties affect the outcome from the experiment. The full field strain measurement provides means for examining the validity and accuracy of the tests. In tests where the deforming section of the specimen is well defined and the deformation is uniform, the strains measured with the image correlation technique agree with the average strain that is determined from the split Hopkinson bar wave records. If significant deformation is taking place outside the gage section, and when necking develops, the strains determined from the waves are not valid, but the image correlation method provides the accurate full field strain history.

Stress Corrosion Cracking of Tough Pitch Copper in a Bolting Application

Stress corrosion cracking was observed in C11000 and C10200 copper electrical feedthrough pins used in a bolting application. The component provided the balancing tensile stress required for compression of a gasket seal of a refrigeration compressor. The component, as designed, had functioned without failure for years of production and thousands of units. The fractures were mixed brittle intergranular with ductile microvoid dimples. An extensive analysis of actual failed samples as well as a process of elimination methodology indicated that the fractures were due to SCC by an unidentified chemical species within the sealed compressor chamber. A unique combination of applied stress, residual stress, a stress riser, and fine-grain size isolated the failure mechanism to a single production lot of material.

Use of Coupled Electrode Arrays to Elucidate Copper Pitting as a Function of Potable Water Chemistry

The electrochemical pitting behavior of UNS C11000 copper was investigated in synthetic potable water and several other HCO3- , SO42- and Cl- containing waters using microelectrodes and coupled multi-electrode arrays. Studies were systematically conducted (pH from 6 to 10, [Cl2] (as NaOCl) from 1-5 ppm, and with or without Al(OH)3 additions). Studies of the effect of water chemistry on electrochemical properties of copper were accomplished using the cyclic voltammetry and cathodic polarization methods. Critical potentials for copper pitting are observed to be brought about and decreased by certain water chemistry variables. High [SO42-]/[HCO3-] and [Cl-]/ [HCO3-] lower pitting potentials (EPit) while high [HCO3-] and pH raise EPit. ClO- increases cathodic reaction rates and thus raises OCPs towards EPit. Certain water chemistries (pH from 8 to 10, [Cl2] > 2 ppm and with Al(OH)3) are found to promote pitting conditions where strong, persistent anodes developed at certain sites and pitting factor was raised.

Pulse shaping techniques for testing brittle materials with a split hopkinson pressure bar

We present pulse shaping techniques to obtain compressive stress-strain data for brittle materials with the split Hopkinson pressure bar apparatus. The conventional split Hopkinson pressure bar apparatus is modified by shaping the incident pulse such that the samples are in dynamic stress equilibrium and have nearly constant strain rate over most of the test duration. A thin disk of annealed or hard C11000 copper is placed on the impact surface of the incident bar in order to shape the incident pulse. After impact by the striker bar, the copper disk deforms plastically and spreads the pulse in the incident bar. We present an analytical model and data that show a wide variety of incident strain pulses can be produced by varying the geometry of the copper disks and the length and striking velocity of the striker bar. Model predictions are in good agreement with measurements. In addition, we present data for a machineable glass ceramic material, Macor, that shows pulse shaping is required to obtain dynamic stress equilibrium and a nearly constant strain rate over most of the test duration.