Cu-10 Wt Research Articles

Mechanical, tribological and electrical properties of ZrB2 reinforced Cu processed via milling and high-pressure hot pressing

The present work investigates the effect of (0–10 wt%) ZrB2 reinforcement on densification, mechanical, tribological and electrical properties of Cu. The consolidation of Cu–ZrB2 samples was carried out using a hot press (temperature: 500 °C, pressure: 500 MPa, time: 30 min, vacuum pressure: 1.3 × 10-2 mbar). The bulk density of the hot-pressed Cu composites decreased from 8.84 g/cc to 8.16 g/cc and the relative density of samples lowered from 98.6% to 92.1% with the addition of ZrB2. The incorporation of hard ZrB2 (up to 10 wt%) improved the hardness of Cu (1.32–2.55 GPa). However, the yield strength and compressive strength of Cu composites increased up to 5 wt% ZrB2, and further addition of ZrB2 lowered its strength. The yield strength of Cu samples varied from 602 to 672 MPa and the compressive strength between ~834 and 971 MPa. On the other hand, the coefficient of friction (COF) (from 0.49 to 0.18) and wear rate (from 49.3 × 10-3 mm3/Nm to 9.1 × 10-3 mm3/Nm) of Cu–ZrB2 samples considerably decreased with the addition of ZrB2. Significantly low wear was observed with Cu-10 wt% ZrB2 (Cu-10Z) samples, which is 5.41 times less than pure Cu. As far as the wear mechanisms are concerned, in pure Cu, continuous chips (wear debris) were formed during sliding wear by plowing. Whereas the major amount of material loss was occurred due to the plowing mechanism with discontinuous and short chip formation for Cu–ZrB2 composites. The electrical conductivity of Cu–ZrB2 samples decreased from 75.7% IACS to 44.1% IACS. In particular, Cu with ZrB2 (up to 3 wt%) could retain the conductivity of 66.8% IACS. This study reveals that the addition of ZrB2 (up to 3 wt%) is advantageous to have a good combination of properties for Cu.

Effect of Adding Nano Ag on Mechanical and Physical Properties of Cu–10% Fe Prepared by Powder Metallurgy Technique

Copper-matrix composites have received a lot of attention and are used widely in various applications, such as electronics, machinery, automobile, military and aerospace; because of their remarkable electrical conductivity, high thermal conductivity and excellent mechanical properties. Among these are copper-iron composites which found many engineering applications due to the role of Fe in enhancing the mechanical properties of these composites beside its low cost. However, Fe addition reduces electrical and thermal conductivity therefore, binary Cu-Fe composites are not suitable for applications where these properties are the main requirement. Many studies have been done to enhance these properties by the addition of alloying elements. The present work aims to study the effect of adding Nano Ag on mechanical and physical properties of Cu-10 wt% Fe composites prepared by powder metallurgy technique. The results showed the effectiveness of Nano Ag in enhancing both mechanical and physical properties of Cu-10 wt% Fe composite. It is found that bulk density, electrical conductivity, and thermal conductivity have been increased by 1.19%, 46%, and 46% respectively on adding 5% Nano Ag. Hardness and compression strength have been increased by 17.3% and 32.8% respectively by adding 4% Nano Ag, while wear rate was reduced by 13.4% by adding 4% Nano Ag.

TEM study on the microstructure of the interface at the scale of nanometer formed between Cu-8 wt.% Ti melt and C/C preform

Carbon/copper composites have been widely used in a variety of fields, for example electrical contact devices by taking advantages of both carbon and Cu simultaneously. However, the interfacial reaction and microstructure of these composites are not well known yet in the nanometer scale, especially involving the interaction between active alloy melt and carbon, which remains an important question in composites technology. In this study, we employ transmission electron microscopy (TEM) to investigate the interfacial microstructures, which are formed in the course of infiltration of carbon/carbon (C/C) composites preform by molten Cu-8 wt.% Ti at 1373 K. The results show that in the short-cut fiber web zone, there are two types of interfaces: (i) the mixture of fine-grained (FG) TiC and nano-sized Cu particles and (ii) a “Cu layer” with a thickness of no more than 500 nm at the pyrolytic carbon (PyC)/coarse-grained (CG) TiC interface. The main bonding mechanisms for the two interfaces are the formation of PyC/TiC and PyC/Cu2O interfaces, and the PyC/Cu2O interface, respectively. In the non-woven cloth zone, only Cu2O layer is found between Cu and PyC without any TiC layer due to the depletion of Ti.

Microstructure and properties of Cu-10 wt%Fe alloy produced by double melt mixed casting and multi-stage thermomechanical treatment

A Cu-10 wt%Fe alloy with high strength and high conductivity was prepared by double melt mixed casting and multi-stage thermomechanical treatment. The microstructure, mechanical property and electrical property evolutions and the strengthening mechanism during the preparation of the alloys were studied. The results showed that there were spherical Fe phase and dendritic Fe phase in the as-cast alloy. After cold rolling, the dendritic Fe phase was elongated along the rolling direction to form fibrous Fe phase, and the spherical Fe phase was flattened along the normal direction of sheet to form ellipsoidal particles after three passes of cold rolling. During aging, a large number of Fe phase particles with a diameter of 20–150 nm precipitated in the alloy. The tensile strength, yield strength and electrical conductivity of the alloys were 608 MPa, 583 MPa and 58% IACS, respectively. The main strengthening mechanism of the alloys was sub-structure strengthening calculated by strengthening model.

Synthesis and investigate the properties of Cu–Al–Ni alloys with Ag addition using powder metallurgy technique

In this study, the samples alloys of Cu-10 wt%Al-4 wt.% Ni with different percentages of Ag (0%, 2%, 4%, 6%) are sintered by powder metallurgy technique. This method is suitable for net-shape and net-shape manufacturing together and is more flexible technique as compared to forging, melting and casting. Homogenous mixing of powder is carried out by using Planetary Ball Mill (PM 200 RETSCH), powder blend is cold compacted under 400 MPa and sintering process is carried out at 850 °C. Heat treatment is carried out under vacuum furnace with heating rate of 5Co/min and is quenched in three different medium (i) water (ii) oil (iii) furnace cooling. Microstructure and mechanical properties of Cu-10 wt%Al-4 wt.%Ni alloys with the addition of silver are investigated using Scanning electron microscopy (SEM), X-rays diffraction (XRD), Rockwell Tester and Universal testing machine (UTM). The results indicate that XRD peaks of Cu, Al, Ni and Ag powders are documented through JCPDS cards. SEM images show structural behavior and differentiated as different quenched samples. Hardness of water-quenched samples is significant higher as compared to oil and furnace cooled samples. Ultimate compression strength of water-quenched samples is much higher than that of oil and furnace cooled samples.

Effects of Mo Concentration on the Structural and Corrosion Properties of Cu–Alloy

Mechanical Alloying (MA) has the ability to extend the solubility limits of immiscible alloys in a solid state. In this work, a Cu-10 wt% Mo alloy was synthesized by mechanical alloying, using a high-energy mill type SPEX. The X-ray diffraction and Rietveld results show a crystallite size of 24 and 22 nm of Cu and Mo, respectively, with an occupation value of Mo inside the Cu structure of 27%, which was identificated by Energy Dispersive X-ray Spectroscopy and High-Resolution Transmission Electron Microscopy analysis. After that, the alloy was sinterized in an oven, heating the alloy to 1000 °C—close to the melting point of Cu (1085 °C). Electrochemical tests were carried out under a saline environment of synthetic seawater. The results show that the polarization curve of the alloy showed a pitting corrosion at about 134.83 mV, as well as a repasivation phenomenon (Erp = 241.47 mV) in the cathodic branch. Finally, three time constants were observed in the Nyquist diagrams: formation of a corrosion product film, load transfer, and diffusion, indicating that the corrosion properties in this alloy were improved compared with other Cu–alloys.

Improving the wettability between liquid Cu and carbon/carbon composite by addition of Ti

The effect of Ti addition on improving the wettability between liquid Cu and carbon/carbon composite was studied by the sessile drop method. The contact angle of a Cu-10 wt%Ti drop on the carbon/carbon composite at 1300 °C for 60 min was measured to be ∼70°, which was less than that of a Cu drop on the composite. TiC was formed at the interface between the drop and substrate by reaction. A higher Ti concentration in the drop near the interface and a copper-rich zone at C/TiC interface were found, thus indicating that the mechanism of improving the wettability by Ti addition was supposed be the higher Ti concentration in the liquid near the interface between liquid Cu and C which resulted in the decrease of interface energy.

A good combination of strength and ductility of ultra-coarse-grained Cu-Al alloy with coarse-grained surface layer via pre-torsional treatment

The trade-off between strength and ductility is a long-standing dilemma in metals and alloys. In this study, we fabricated an ultra-coarse-grained (UCG) Cu-6 wt.%Al alloy with a coarse-grained (CG) surface layer by surface mechanical attrition treatment. Pre-torsional treatment for 45°, 90° and 180° was conducted on the UCG-CG specimens, and the effects of pre-torsional treatment on the microstructures and mechanical properties of the UCG-CG Cu-6 wt.%Al alloy were systematic investigated. It has been shown that the strength and ductility can be simultaneously enhanced via pre-torsional deformation due to the formation of gradient microstructures.

Effect of the Third Element Ni on the Solidification Microstructure of Undercooled Cu-40 wt.% Pb Monotectic Alloy Melt

In this paper, the evolution of solidification microstructure of Cu-40 wt.% Pb monotectic alloy of the third element Ni pair under deep undercooling conditions was studied. By comparing the phenomena of liquid phase separation during deep undercooling and rapid solidification of Cu-40 wt.% Pb monotectic alloy, the melt of the alloy increases with the undercooling, and the solidification structure appears uneven or even stratified. With the addition of the third element Ni, the liquid phase separation can be effectively inhibited by the change of interfacial energy. The solidified structure undergoes the transformation from coarse dendrite to the first kind of granular and refined dendrite in a wide undercooling range. When the undercooling reaches 143 K, the structure begins to show an inhomogeneous trend.

Microstructural Evolution and Mechanical Properties of Heavily Cold-Rolled and Subsequently Annealed Cu-3 wt.%Ti Alloys with Nano-Lamellar Structure

Changes in the microstructure and mechanical properties of Cu-Ti alloy sheets during cold rolling and subsequent annealing were studied with and without Cu-Ti precipitates in the initial microstructures. Pre-existing Cu-Ti precipitates plastically deformed and severely elongated in the rolling direction via cold rolling, accelerating the formation of a nano-lamellar structure. A mean lamellar boundary spacing of 20 nm was achieved at an equivalent strain of 6.7. Vickers hardness increased with decreasing lamellar boundary spacing. Subsequent annealing after cold rolling clearly enhanced the mechanical properties, and a maximum Vickers hardness value of 443 HV (4.35 GPa) was attained in the sample with pre-existing precipitates strained to 6.7. These results suggest that pre-existing precipitates promote microstructural refinement during heavy cold rolling, and that heavily cold-rolled Cu-Ti alloys exhibit anneal hardening behavior, leading to excellent mechanical properties.

Corrosion Properties of Ultra-Fine-Grained Cu-3 wt%Ti Alloy Fabricated by Combination of Hot Rolling and Aging Treatment.

Although deformation and aging treatments of Cu-3 wt%Ti alloys dramatically enhance their mechanical properties, the corrosion behavior of ultra-fine grained (UFG) Cu-3 wt%Ti alloys produced by a combination of hot rolling and artificial aging has not been extensively explored yet. To bridge this gap, we herein probe the corrosion behavior of an UFG Cu-3 wt%Ti alloy produced by cold rolling and artificial aging, revealing that cast sample corrosion preferentially occurs around the β-Cu₄Ti phase. Compared to that of the coarse-grained Cu-3 wt%Ti alloy, the corrosion resistance of its UFG counterpart is remarkably higher, which is ascribed to the effects of grain refinement and enveloping between the α-Cu matrix and β-Cu₄Ti in the absence of pitting corrosion. The development of ultra-fine microstructure upon the introduction of severe deformation is shown to dramatically improve the corrosion resistance of aging-hardened Cu-3 wt%Ti alloys without sacrificing their mechanical properties. Finally, we demonstrate that solid solution treatment of the Cu-3 wt%Ti alloy results in serious mechanical property deterioration, even though the thus treated samples feature the lowest corrosion current density.

Influence of Arc Brazing Parameters on Microstructure and Joint Properties of Electro-Galvanized Steel

Arc brazing of zinc-coated steel (EG, Electro-galvanized steel) using Cu-3 wt%Si filler metal was performed. The influence of arc current and brazing speed on the bonding properties of the joint, such as bead characteristics, arc penetration, joint hardness, and tensile shear strength were evaluated. The microstructural characteristics of the joint were examined by scanning electron microscopy (SEM) and the compositional information was revealed by energy dispersive spectroscopy (EDS). The throat thickness varies inversely with the brazing speed. The EG joint shows the formation of Fe2Si phases, which result in higher microhardness than the base metal. The tensile samples were fractured in base metal, while minor bead cracks developed in the samples brazed at 80 cm/min-80 A, 60 cm/min-70 A, 70 cm/min-70 A.

Characterization and Wear Behavior of Nano ZrO2 Reinforced Copper-Zinc Alloy Composites

In the present investigation, an endeavor has been made to create copper-zinc-nano ZrO2 particulates strengthened composites by utilizing liquid stir technique. 4, 8 and 12 wt. % of nano ZrO2 particulates were added to the Cu-10 wt. % Zn base grid. Microstructural studies were finished by utilizing SEM and EDS examinations. Wear behavior of Cu-Zn-4, 8, 12 wt. % of nano ZrO2 composites were assessed according to ASTM G99 benchmarks. Scanning electron micrographs uncovered the uniform dispersion of nano ZrO2 particulates in the copper zinc composite network. EDS examination affirmed the nearness of Zr and O components in nano ZrO2 strengthened composites. The experiments were conducted at a constant speed of 400rpm and sliding distance of 3000m over a varying load of 1, 2, 3 and 4 kg. Similarly, at a constant load of 4 kg and sliding distance of 3000m over a varying sliding speed of 100, 200, 300 and 400rpm. The results showed that the wear resistance of Cu-Zn-4, 8% and 12% ZrO2 nano composites were superior than the as cast alloy. As load and speed increased the height loss in the composites and alloy was increased. Worn surface morphology was studied by using SEM.

Experimental study on tribological properties of Cu–Al2O3 nanocomposite hybridized by graphene nanoplatelets

Mechanical and tribological properties of Cu–Al2O3 nanocomposite hybridized by silver (Ag) coated graphene nanoplatelets (GNPs) were studied. Four different GNPs content, 0.3, 0.6, 0.9 and 1.2 wt% were considered to highlight its influence on the properties of the produced hybrid nanocomposite. The synthesis of hybrid nanocomposites involves ball milling and hot pressing. Microstructural observations showed homogenous distribution of both Al2O3 and GNPs. The results showed significant hardness improvement with increasing GNPs content reaching 55.2% compared to the pure Cu due to the grain refinement, high strength of GNPs and the reinforcing of grain boundaries by the precipitation of GNPs. Moreover, the wear resistance is increased while the coefficient of friction is decreased by increasing GNPs content. Among the all manufactured samples, Cu-10 wt% Al2O3 +1.2 wt% GNPs shows the highest mechanical and the wear resistance. Additionally, it shows the lowest coefficient of friction highlighting its importance for tribological applications.

Study of Dry Sliding Wear Behavior of Hot-Rolled and Mushy-State Rolled Al-4.5Cu-5TiB2 In-Situ Composite with Analysis of Work Hardening and Subsurface Microstructure-Microtexture Evolution Using EBSD

The response of the Al-4.5 wt pct Cu-5 wt pct TiB2 in-situ composite in the as-cast, hot-rolled, mushy-state rolled, or pre-cold rolled mushy-state rolled conditions to dry sliding wear tests at 1 m/s linear speed under 20N load has been examined. Further, microstructures and chemical compositions were simultaneously studied by scanning electron microscopy and energy dispersive X-ray spectroscopy, respectively, whereas the microtexture was quantified by electron backscattered diffraction (EBSD) analysis. An effort has been made to understand the relationship of CuAl2 and TiB2 particle distribution, microtexture, and hardness obtained through the aforementioned rolling processes with wear rates and post-wear surface profile. Additionally, the amount and depth of work hardening as a result of wear has been correlated with the subsurface microtexture evolution. Among the investigated wear-tested samples, the pre-cold rolled mushy-state rolled composite (PCMRC) has shown the best wear resistance due to high hardness being contributed by the highest low-angle boundary (LABs; misorientation angles 15 deg due to considerable strain accumulation near TiB2 particles or particle-stimulated nucleation by dynamic recrystallization due to flash heat generation. Furthermore, a remarkable increase in the post-wear microhardness of the subsurface locations has been used to confirm that significant work hardening is caused by severe plastic deformation of the composite matrix during wear, which is in great coherence with the results of EBSD analysis.

Phase transitions in copper–silver alloys under high pressure torsion

AbstractThe influence of high pressure torsion (HPT) on the formation and decomposition of solid solutions in the copper–silver system has been studied. The investigated Cu-8 wt.% Ag alloy was annealed at two different temperatures, 500 and 650°C, and quenched. The samples consisted of (Cu) solid solution in the matrix with (Ag) precipitates. During HPT a steady-state value of torsion torque was reached after about 1.5 anvil rotations. After HPT (5 anvil rotations) the composition of the (Cu) solid solution in both samples had become equal. In other words, the concentration of silver in the (Cu) matrix annealed at 650°C decreased and in the sample annealed at 500°C increased. Moreover, a similar process took place in (Ag) precipitates as well. The concentration of copper in (Ag) particles in the sample annealed at 650°C decreased and in the sample annealed at 500°C increased. Thus, the composition of (Cu) and (Ag) solid solutions reached at steady-state during HPT does not depend on that before HPT. The composition of the (Cu) and (Ag) solid solutions after HPT is as high as if the samples were annealed at a certain intermediate temperature about 600 ± 20°C.

Enhanced thermal stability in Cu-40 wt% Zn/WC nanocomposite

A major challenge for alloy applications is to achieve thermal stability of phase transitions and anti-oxidation properties. Given the stability of ceramic nanoparticles, we propose the incorporation of WC nanoparticles as a novel way to tune the thermal stability of Cu-40 wt% Zn, which is an important alloy known as naval brass. In situ XRD and DSC results confirmed the enhanced thermal stability of Cu-40 wt% Zn/10 vol% WC nanocomposites at higher temperatures were observed for both phase transitions and oxidation. The underlying mechanisms behind Zn diffusion during phase change and oxygen contact are discussed to understand the phenomena. Optical profiles along with SEM and FIB images reveal the morphologies and microstructures of different stages and give supporting information for the above argument. Due to the kinetic and dynamic impedance on Zn diffusion and the intrinsic stability of WC, the higher thermal stability in Cu-40 wt% Zn/WC is achieved. This study provides an effective way to tune thermal stability of alloys, control phase change, and vary post-oxidation morphology.

Hardening Cu-Ag composite by doping with Sc

The microstructure and properties of Cu-Ag can be tuned by doping with Sc. To strengthen Cu-Ag while keeping cost low and electrical conductivity high, we lowered Ag content and added Sc. After aging treatment, our doped Cu-3 wt%Ag-0.3 wt%Sc contained exclusively continuous Ag precipitates, as opposed to exclusively discontinuous Ag precipitates in non-doped Cu-3 wt%Ag. After deformation at a low level of strain, electrical conductivity was almost the same in doped and non-doped samples, but Sc doping significantly improved hardness by suppressing formation of discontinuous Ag precipitates.

Sliding Wear Behavior of Spark Plasma-Sintered Cu–6 Wt Pct Cr Alloy at Room and Elevated Temperatures

Although dilute Cu-Cr alloys are frequently used for applications involving sliding contacts, their wear mechanism at elevated temperatures has rarely been explored. We fabricated a bulk Cu-6 wt pct Cr alloy using high-energy ball milling and spark plasma sintering, and systematically investigated its dry sliding wear behavior against 440C stainless steel at room temperature and 300 °C. The alloy had a heterogeneous microstructure consisting of coarse-grained Cu (average grain size: 1.5 µm) distributed into a nanocrystalline Cu-Cr matrix (average Cu grain size: 77 nm; Cr-rich precipitate size: 18 nm), which gave high strength and plasticity (ultimate compressive strength: 1020 MPa; strain-to-failure: 26.0 pct) at room temperature. At 300 °C, the strength was significantly reduced, the coefficient of friction and wear rate increased, and the dominant wear mode switched from adhesive wear to oxidative/abrasive wear. Uniformly distributed nanoscale Cr-rich and Cr oxide precipitates hindered severe plastic deformation near the sliding surface during wear at room temperature; at 300 °C, severe plastic deformation was observed, with elongated Cu grains and uniformly dispersed Cr-rich and Cr oxide nanoparticles. Formation of a discontinuous glaze layer consisting of equiaxed nanograins of Cu, Cu oxides, and Cr oxides resulted in severe abrasion-assisted wear, and reduced the wear resistance at 300 °C.

Synergetic strengthening effects on copper matrix induced by Al2O3 particle revealed from micro-scale mechanical deformation and microstructure evolutions

Abstract The micro-scale effect of Al 2 O 3 particle on the deformation behaviors of the copper matrix was investigated using nanoindentation. Moderate strengthening effects were produced by the Al 2 O 3 as indicated from the mechanical deformation evolutions. Specifically, the displacement recovery ratio and elastic work ratio is 6% and 9% higher for the Cu-5 wt% Al 2 O 3 (C5A) composite material compared with that of the pure copper (PC) material, respectively. While for the indentation hardness and indentation modulus, the increment is 36% and 75%, respectively. Notably, the moderate strengthening effects were quantitatively illuminated from the power law index m for the C5A indent (1.2) and PC indent (1.1–1.3). In addition, synergetic strengthening effects were proposed from the microstructure evolutions in the C5A composite material. Specifically, the increment in yield strength deduced from the grain refinement is 120 MPa, which is 67% higher than that of the Al 2 O 3 particle dispersion strengthening. The synergetic strengthening effects revealed from the microstructure evolutions are expected to provide new strengthening approaches for the ceramic particle reinforced metal matrix composite materials.