Cu-10 Wt Research Articles

Development Of Lead Free Copper Alloy Casting; Mechanical Properties, Castability and Machinability

The regulation for the lead discharge in the environment was strengthened, in Japan, the standards 0.01 mg/I or less has been in force from April 2003. In order to meet the new standard, two technologies for reduction of lead dissolution into the drinking water have been developed in Japan; substitution of lead free copper alloys for lead bearing bronze (JIS-CAC406) and introduction of surface treatment technology. This technological trend was shortly reviewed. For development of lead free copper alloy casting, mechanical properties, castability and machinability of various lead free alloy castings were examined. Trial alloys used were commercially available ones such as the lead free bronze containing Bi, the lead free bronze containing Bi-Se, the lead free bronze containing Bi-Sb and the lead free brass containing Si. Mechanical properties of alloys were dependent on the pouring temperature and castings thickness and were generally less than those of tin bronze castings (JIS-CAC406, Cu-5 wt% Sn-5 wt% Zn-5 wt% Pb). The machinability of the lead free bronze containing Bi and Se was better than that of the lead free bronze castings containing Bi and Bi-Sb. But was still 10 to 15 % less than that of JIS-CAC406. In a lead free alloy substituted by Bi, adjustment of tin, zinc and bismuth contents was attempted and in the Bi-Se system, the adequate adjustment, for bismuth and selenium contents and also for tin, zinc and bismuth contents, was attempted. New alloy in which the mechanical properties sufficiently satisfy the standard for JIS-CAC406 is developed.

Synthesis of Cu-CNTs nanocomposites via double pressing double sintering method

In this research, copper (Cu)-carbon nanotubes (CNTs) nanocomposites were synthesized with different weight percentages of CNTs by double pressing double sintering (DPDS) method as well as conventional sintering method. A planetary ball mill was used to disperse CNTs in Cu matrix. The milled powders were first cold pressed to 450 MPa in a uniaxial stainless-steel die with cylindrical compacts (diameter: 12 mm and height: 5 mm). The effect of CNTs content and the DPDS method on the properties of the nanocomposites were investigated. The microstructure and phase analysis of Cu-CNTs nanocomposite samples were studied by FESEM and X-Ray Diffraction. The electrical conductivity of nanocomposites was measured and compared to both sintering methods. Mechanical properties of Cu-CNTs nanocomposites were characterized using bending strength and micro-hardness measurements. Enhancements of about 32% in bending strength, 31.6% in hardness and 19.5% in electrical conductivity of Cu-1 wt.% CNTs nanocomposite synthesized by DPDS method were observed as compared to Cu-1 wt.% CNTs nanocomposites fabricated under the similar condition by a conventional sintering process.

Modification of the Primary and Peritectic Phases in Directionally Solidified Cu-20 wt.% Sn Alloy by Magnetic Field

Directional solidification experiments on Cu-20 wt.% Sn peritectic alloy were carried out in a direct current magnetic field device to investigate the modification of the primary and peritectic phases. A precipitation of the acicular martensitic structure of peritectic phase was observed below the solid-liquid interface. The magnetic field increased the length of precipitation zone and moved the solid-liquid interface to high temperature side. Solid-state transformation of the peritectic phase was observed below the eutectoid temperature. The magnetic field increased first and then decreased the transformation. A transition of the primary dendrites from arrayed to nonaligned growth under the magnetic field was characterized and analyzed. 3D numerical simulations of the thermoelectric magnetic flows and the thermoelectric magnetic forces were performed. The modification of the primary and peritectic phases under the magnetic field should be attributed to the fluid flows in the liquid and the forces on the solid.

Mechanical properties of HSSS chips reinforced copper-based hybrid composites

Highly strained stainless steel (HSSS) chips and particulates, WC and Cr are reinforced in copper matrix to develop the hybrid composites using the stir-cast technique. The developed copper based hybrid composites are designated as Cu-1 wt.% WC-2 wt.% Cr-x wt.% HSSS (x= 0, 2, 3 and 4 wt.%). SEM and EDAX characterized the developed materials. Densities, Brinell hardness, tensile and compressive strength of the materials were analyzed. The metallographic observations of hybrid composites showed the uniform distribution of WC and HSSS particulates in the matrix. Hardness, tensile and compressive strength of the hybrid composites are higher than its matrix and increases with increasing the HSSS content. However, density of the hybrid composites is lower than its matrix and decreases with increasing of HSSS content. SEM studied the fractured surfaces of developed materials to understand its fracture behaviour.

Characterization of Aluminium Metal Matrix Composite Produced by Squeeze Casting Technique

Metal matrix composites play a important role in automobiles, aerospace, sports and marine sector. In the present investigation an attempt has been made to investigate the mechanical properties of Fly Ash particulates reinforced Al-4.5 % Cu alloy composites. Al-4.5 % Cu alloy was used as the base matrix. Fly ash particulates were used as reinforcements. The Al-4.5wt. % Cu alloy was reinforced with constant 3 wt. % of fly ash and 5 wt. % of fly ash The composites were produced by squeeze casting method with a pressure of 120 MPa. Microstructural study was done by using optical microscope to confirm the reinforcement particles in matrix alloy. Further, hardness and tensile properties were evaluated as per ASTM standard. The results showed that the hardness and tensile strength were higher in the case of Al-4.5% Cu-3 wt. % fly ash and 5 wt. % fly ash composites compared to the base alloy.

Modeling the dry sliding wear behavior of Cu-4wt%Ni-TiC composites using response surface methodology

The present paper intends to optimize certain process parameters on the wear and friction properties of Cu-4 wt% Ni- x wt% TiC (x = 0, 2 and 4 wt%) metal matrix composites by using response surface methodology (RSM). The dry sliding wear test was conducted using a pin-on-disc with different process parameters of applied load, weight percentage of TiC particles and sliding distance as process variables. Analysis of variance was applied to check the adequacy of the developed model. Mathematical models were developed to investigate the influence of process parameters on the responses at 95% confidence level. Developed surface and contour plots depicted the effect of main parameters and its interactions on the responses.

Effect of tungsten content on the structure, physical and mechanical properties of silicon bronze (Cu-3 wt%Si)

This research investigated the effect of tungsten content on the structure, physical and mechanical properties of silicon bronze (Cu-3 wt%Si). Tungsten was added in concentrations of 0.1, 0.3, 0.5, 0.8, 1 and 1.5 wt%. The samples were produced using permanent die casting technique, machined and stored for the structural analysis, physical and mechanical tests. The microstructural analysis of the control sample (Cu-3 wt%Si) revealed the presence of dendrite of intermetallic compounds which could be primary silicon and copper silicide (Cu3Si) phases while the alloy doped with tungsten consisted of fine grains of intermetallic compounds evenly dispersed in the copper matrix. The mechanical tests results showed that addition of tungsten to silicon bronze significantly increased the percentage elongation, ultimate tensile strength, hardness and electrical conductivity of the alloy by 174.5%, 741.2%, 98.9% and 14.9% respectively. Maximum percentage elongation, electrical conductivity, ultimate tensile strength and hardness of 25.8%, 61.25% IACS, 286 MPa and 358 BHN respectively were obtained.

Investigation on microstructure and thermal properties of in-situ synthesized Cu–ZrO2 nanocomposites

Abstract Cu–ZrO2 nanocomposites were prepared by an in-situ reactive synthesis of copper nitrate Cu(NO3)2 and zirconium oxychloride ZrOCl2. Zirconia (ZrO2) was added by 2.5, 5 and 10 wt.% to the Cu matrix to assess its effect on thermal conductivity and thermal expansion behavior. The results showed that ZrO2 nanoparticles (30–50 nm) were homogeneously distributed in the copper matrix. The measured thermal conductivity for the Cu–ZrO2 nanocomposites decreased from 372.8 to 94.4 W m−1 K−1 with increasing ZrO2 content from 0 to 10 wt.%. Cu-10 wt.% ZrO2 nanocomposite yields a low thermal conductivity of 94.4 W · m−1 K−1 along with a low coefficient of thermal expansion, 11.47 × 10−6 K−1.

Investigation of thermal and mechanical properties of Cu-Al alloys with silver addition prepared by powder metallurgy

In this study, Cu-10 wt.% Al-X wt.% Ag alloys (X = 0.0, 2.0, 2.5, 3.0, 4.0, 5.0, 5.5, 6.0) were synthesized through Powder Metallurgy. The effect of silver addition on microstructural, thermal and mechanical properties of the prepared alloys were investigated by using Scanning Electron Microscopy (SEM), Energy Dispersion Spectroscopy (EDS), X-rays Diffractometry (XRD), Transient Plane Source method (TPS), Rockwell hardness tester and Universal testing Machines. The XRD result of raw materials such as pure copper, pure aluminum, pure silver were qualified through JCPDS cards, and subsequently quantified. The microstructural analysis of all samples was carried out, with heating rate of 5 ̊C/min and annealed at room temperature. The results indicated that presence of silver in Cu-Al alloy offered better hardness up-to 3%Ag and compression strength increases up to 2%Ag in Cu-10 wt. %Al alloys which shows intermetallic structure in XRD analysis. Thermal conductivity and thermal diffusivity of the prepared alloys are investigated with help of TPS method in this work. It is observed that both thermal conductivity and thermal diffusivity increased with the increase of silver contents in the alloys owing to higher conductive behavior of silver.

Microstructural deformation in fatigued nanotwinned copper alloys

In this study, the uniaxial tension-tension fatigue behavior of fully nanotwinned magnetron sputtered Cu-6wt%Al, Cu-2wt%Al, and Cu-10 wt%Ni is presented. These alloys have average twin thicknesses ranging from 4 to 8 nm, average grain widths from 90 to 180 nm, and tensile strengths from 1 to 1.5 GPa. In the high cycle regime (103 to 107 cycles), the nanotwinned alloys exhibit fatigue strengths ranging from 210 to 370 MPa, which is higher than previously observed in nanotwinned Cu (fatigue strengths between 80 and 200 MPa). Fatigue strengths are normalized by tensile strength for Cu alloys with different microstructures to study the correlation between tensile and fatigue properties. Post-mortem analysis of the materials reveals a newly observed deformation mechanism, where localized detwinning leads to intergranular fracture between columnar grains. Overall, materials displaying detwinning as a deformation mechanism show lower normalized fatigue strengths in comparison to materials that deform with slip band like behavior.

Microstructure and Properties of Cu-ZrO2 Nanocomposites Synthesized by in Situ Processing

In situ chemical reaction method was used to synthesize Cu-ZrO2 nanocomposite powders. The process was carried out by addition of NH4(OH) to certain amount of dispersed Cu(NO3)2·3H2O and ZrOCl2·8H2O solution. Afterwards, a thermal treatment at 650 °C for 1 h was conducted to get the powders of CuO and ZrO2 and remove the remaining liquid. The CuO was then reduced in preferential hydrogen atmosphere into copper. The powders were cold pressed at a pressure of 600 MPa and sintered in a hydrogen atmosphere at 950 °C for 2 h. The structure and characteristics were examined by X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM). The results showed that the nanosized ZrO2 particles (with a diameter of about 30-50 nm) was successfully formed and dispersed within the copper matrix. The density, electrical conductivity, mechanical strength measurements (compression strength and Vickers microhardness) and wear properties of Cu-ZrO2 nanocomposite were investigated. Increment in the weight % of ZrO2 nano-particles up to 10 wt.% in the samples, caused the reduction in the densification (7.2%) and electrical conductivity (53.8%) of the nanocomposites. The highest microhardness (146.5 HV) and compressive strength (474.5 MPa) of the nanocomposites is related to the Cu-10 wt.% ZrO2. Owing to the good interfacial bonding between uniformly dispersed ZrO2 nanoparticles and the copper matrix. The abrasive wear rate of the Cu-ZrO2 nanocomposite increased with the increasing load or sliding velocity and is always lower than that of copper at any load or any velocity.

Effect of Reinforcement Content and Technological Parameters on the Properties of Cu-4 wt.% Ni-TiC Composites

The present study deals with the synthesis and investigation of microstructure, density, and hardness behavior of Cu-4 wt.% Ni-TiC metal matrix composites, produced by high-energy ball milling, followed by compaction and sintering. Matrix of Cu-4 wt.% Ni was used, and different weight percentages (0, 2, 4, 6, and 8) of TiC particles were added. The uniform distribution of TiC particles in the matrix alloy was confirmed by characterizing these composite powders by using scanning electron microscope, energy-dispersive spectroscopy, and x-ray diffraction. Both the density and the hardness of the composite containing 4 wt.% TiC were found to be the highest. The density was found to decrease with increasing TiC content beyond 4 wt.%, and it has been attributed to the agglomeration of TiC particles leading to the formation of pores when added in relatively larger amounts. The compressibility behaviors of the milled powders were studied by using Panelli and Ambrosio Filho equation.

Effects of multiple trace alloying elements on the microstructure and properties of Cu-4 wt% Ti alloys

Effects of multiple trace alloying element Fe and Cr addition on the solid solution-treated Cu-4wt% Ti alloys were studied with respect to microstructure and mechanical properties. It was elucidated that the addition of trace alloying elements results in the formation of intermetallic phase CuTi, lowering the titanium content of Cu solid solution phase, and refining the microstructure. The contributions of different strengthening mechanisms were calculated, which are in good agreement on experimental results. It turns out that the solute solution strengthening in Cu- Ti alloys plays a crucial role, even though the fine grain size and precipitation strengthening mechanism are contributed to the strength of Cu-Ti-Cr -Fe alloys. Therefore, the Cu-Ti-Cr-Fe alloys exhibits lower strength and higher elongation compared with Cu-4wt% Ti alloys. However, Cu-Ti-Cr-Fe alloys show a great potential to balance the mechanical properties and electrical conductivity during aging treatment as the titanium content decreases in the Cu matrix, and the strength is higher than that of others in previous study.

Liquid-solid phase transition of Cu-Zr eutectic alloy under microgravity condition

Eutectic phase transition involves the competitive nucleation and coupled growth of two solid phases within one liquid phase. Phase selection especially under unequilibrium condition, may result in novel microstructures and thus affects the performances of eutectic alloys. Liquid Cu-10 wt.% Zr hypoeutectic, Cu-12.27 wt.% Zr eutectic and Cu-15 wt.% Zr hypereutectic alloys are rapidly solidified in the containerless process in a 3 m drop tube. During the experiments, the Cu-Zr alloys are heated by induction heating in an ultrahigh vacuum chamber and further overheated to 200 K above their liquidus temperatures for a few seconds. Then the liquid alloys are ejected out from the small orifice and dispersed into tiny droplets after adding the argon gas flow. The solidified samples are analyzed by Phenom Pro scanning electron microscope and HXD-2000 TMC/LCD microhardness instrument. The competitive nucleation and growth among (Cu) dendrite, Cu9Zr2 dendrite and (Cu+Cu9Zr2) eutectic phase become more and more intensive as droplet diameter decreases. The layer spacing in Cu-12.27 wt.% Zr eutectic alloy decreases when the undercooling increases. And the microstructural transition takes place from lamellar eutectic to anomalous eutectic. The microstructure of Cu-10 wt.% Zr hypoeutectic alloy is characterized by (Cu) dendrite and lamellar eutectic. Whereas the microstructure in Cu-15 wt.% Zr hypereutectic alloy consists of Cu9Zr2 dendrite and lamellar eutectic. For the Cu-10 wt.% Zr hypoeutectic alloy, with the decrease of droplet size, the primary (Cu) phase transforms from coarse dendrites into equiaxed grains, and the volume fraction of (Cu) dendrite becomes larger and larger. As for Cu-15 wt.% Zr hypereutectic alloy, the primary Cu9Zr2 intermetallic compound grows in a band manner, and with the decrease of droplet size and increase of cooling rate, the solidified microstructure transforms from band Cu9Zr2 dendrite plus lamellar eutectic into spherical cell structure. The three alloys reach maximal undercooling at 177 K, 156 K and 204 K, respectively. The Trivedi-Magnin-Kurz and Lipton-Kurz-Trivedi/Boetinger-Coriell-Trivedi models are used to analyze the dendritic and eutectic growth as a function of undercooling. Theoretical analysis indicates that both dendritic growth and eutectic growth are controlled by solute diffusion during liquid-solid phase transition. To further investigate the effects of cooling rate and undercooling on the mechanical properties of Cu-Zr eutectic alloys, the microhardness of each of different phases is determined. The microhardness of the primary (Cu) phase within Cu-10 wt.% Zr hypoeutectic alloy is strengthened with the increase of cooling rate. The microhardness of eutectic within the three alloys also increases with increasing the cooling rate and the initial alloy composition of the alloy.

Effect of Grain Size on the Stress Corrosion Cracking of Ultrafine Grained Cu-10 wt% Zn Alloy in Ammonia

The effect of grain size in the micron to submicron range on the stress corrosion cracking (SCC) of Cu-10 wt% Zn alloys was investigated using constant-load tests in ammonia vapor. The grain size was systematically varied from 4 μm to 0.12 μm by either cold-rolling or equal-channel angular pressing (ECAP), followed by annealing. The time to fracture increased with decreasing grain size above 1 μm but then began to decrease with decreasing grain size into the submicron range. This inverse trend in the submicron range is discussed in terms of a severe plastic deformation- (SPD-) induced ultrafine grain microstructure.

COPPER MATRIX COMPOSITES REINFORCED WITH TITANIUM NITRIDE PARTICLES SYNTHESIZED BY MECHANICAL ALLOYING AND SPARK PLASMA SINTERING

Copper matrix composites containing ceramic particles such as carbides, borides, or nitrides have attracted much attention over the last few years. The increased interest in such materials has mainly been created by their high electrical and thermal conductivity, good mechanical and tribological properties, and microstructural stability. Among other nitrides, the titanium nitride seems to be considered asan attractive reinforcement due to its high hardness, excellent electrical conductivity, and stability at high temperatures. Moreover, its good corrosion resistance proves the uniqueness of the TiN particles above any other nitrides. In this work, Cu-10 wt.% TiN composite powders were produced by mechanical alloying and sintered by the spark plasma sintering (SPS) technique under different temperatures. The morphology and powder particle size after mechanical synthesis were inspected by a scanning electron microscopy (SEM) for all of the powder samples; chemical composition analyses (EDS) were also performed. The hydrostatic method was used to measure the density of the composite samples to analyze the influence of milling time on the process of consolidation in the composite powders.

Microstructural and wear characterizations of Ultra-Dispersed Diamond (UDD) reinforced Cu-15 wt.% Ti composites fabricated via mechanical alloying and sintering

Microstructural and wear characterizations of Ultra-Dispersed Diamond (UDD) reinforced Cu-15 wt.% Ti composites fabricated via mechanical alloying and sintering

Microstructural evolution and mechanical properties of CuW/CuCr interface with mixed powder interlayers by liquid diffusion bonding technique

Cu-W composites and CuCr alloy were bonded with mixed Cu-Fe powder interlayers using the liquid diffusion bonding technique at 1380 °C for 1 h. Microstructures of the CuW/CuCr joints with Cu-Fe powder interlayers were investigated and compared via field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. Tensile tests were examined to evaluate the resulting joints. The results show that a diffusion solution layer about 2–3 μm width formed at the Cu/W interphase and the interfacial strength can reach up to 400 MPa when Cu-3wt%Fe interlayer is introduced into the interfacial region between Cu-W and CuCr alloy. Furthermore, the interfacial fracture morphology presents more transgranular cleavage fractures of W particles. However, when the content of Fe in the powder interlayers is above 3 wt%, the interfacial strength decreases gradually with the increasing of Fe content. After Cu-15 wt%Fe interlayer was applied, Fe7W6 phase is found in W skeletons and micro-cracks appear at the CuW/CuCr interface. Therefore, the interfacial strength declines to 263 MPa. The fraction of cleavage fracture decreases and the cracks propagate cross different areas of the CuW/CuCr interface.

Microstructure and properties of in-situ synthesized Cu-1 wt%TiC alloy followed by ECAP and post-annealing

A dispersion-strengthened copper alloy with 1wt% TiC for commercial electrical-contact wires was prepared by in-situ reaction casting, grain-ultrafining by equal-channel angular pressing (ECAP) and subsequent annealing with aim to obtain excellent comprehensive performance. The results showed that fine TiC particles were in-situ synthesized in the as-cast Cu matrix and aggregated in clusters, and thus mechanical properties of the as-cast alloy deemed insufficient. Continued ECAP at 473K significantly refined the grains of the as-cast alloy and improved the distribution of TiC particles. Due to multiple strengthening mechanisms, the ECAP-processed alloys maintained good conductivity with obviously enhanced tensile strength and hardness values. After post-ECAP annealing, the elongation and conductivity of the fine-grained copper alloy increased with the adequate tensile strength. The novel combined process endows the alloy appropriate performance to serve current high-frequency electrification railway systems.

Structural Investigations of Nanocrystalline Cu-Cr-Mo Alloy Prepared by High-Energy Ball Milling

Cu-Cr-Mo alloy could be a suitable candidate material for collector electrodes in high-power microwave tube devices. An attempt has been made to synthesize ternary Cu-Cr-Mo alloys by mechanical alloying of elemental Cu, Cr, and Mo powders, to extend the solid solubility of Cr and Mo in Cu, using a commercial planetary ball mill. For the first ternary alloy, a mixture of 80 wt.% Cu, 10 wt.% Cr, and 10 wt.% Mo was mechanically milled for 50 h. For the second ternary alloy, a mixture of 50 wt.% Cr and 50 wt.% Mo was mechanically milled for 50 h to obtain nanocrystalline Cr(Mo) alloy, which was later added to Cu powder and milled for 40 h to obtain Cu-20 wt.%Cr(Mo) alloy. Both nanocrystalline Cu-Cr-Mo ternary alloys exhibited crystallite size below 20 nm. It was concluded that, with addition of nanocrystalline Cr(Mo) to Cu, it was possible to extend the solid solubility of Cr and Mo in Cu, which otherwise was not possible by mechanical alloying of elemental powders. The resulting microstructure of the Cu-20 wt.%Cr(Mo) alloy comprised a homogeneous distribution of fine and hard (Cr, Mo) particles in a copper matrix. Furthermore, Cu-20 wt.%Cr(Mo) alloy showed better densification compared with Cu-10 wt.%Cr-10 wt.%Mo alloy.