Mechanical Properties Of Cu Research Articles

Electrical and mechanical properties of Cu–Cr–Zr alloy aged under imposed direct continuous current

The Cu–Cr–Zr alloys were aged at different temperatures for different time with different current densities. The results show that both the electrical conductivity and hardness are greatly improved after being aged with current at a proper temperature. The electrical conductivity increases approximately linearly with increasing current density while the hardness remains constant. The microstructure observation reveals that a much higher density of dislocations and nanosized Cr precipitates appear after the imposition of current, which contributes to the higher electrical conductivity and hardness. The mechanism is related with three factors: 1) Joule heating due to the current, 2) migration of mass electrons, 3) solute atoms, vacancies, and dislocations promoted by electron wind force.

Effect of cryogenic treatment on microstructure and mechanical properties of Cu<sub>40</sub>Zr<sub>44</sub>Ag<sub>8</sub>Al<sub>8</sub> bulk metallic glass composite

The effect of cryogenic treatment on microstructure and mechanical properties of Cu₄₀Zr₄₄Ag₈Al₈ bulk metallic glass composite (BMGC) has been investigated. The microstructure and mechanical properties of BMGC before and after cryogenic treatment were characterized through optical micrograph (OM), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Vickers micro hardness (<italic>H</italic>_v). The results show that the formation of crystalline phase of Cu₄₀Zr₄₄Ag₈Al₈ BMGC can be obtained through the cryogenic treatment with 2 h. The dimension and volume fraction of crystalline phase increases with increasing of the cryogenic treatment duration from 2h to 24 h, which result in the improvement of micro hardness of BMGC. The Cu₁₀Zr₇ and AgZr phases were formed in Cu₄₀Zr₄₄Ag₈Al₈ BMGC after cryogenic treatment. The glass transition temperature of amorphous matrix of BMGC increases with the increase of cryogenic treatment duration. However, the crystallization exothermal heat of BMG decreases with the increasing of the cryogenic treatment duration. The internal stress induced by cryogenic treatment was associated with the microstructure evolution of Cu₄₀Zr₄₄Ag₈Al₈ BMGC.

Effects of particle size, volume fraction, orientation and distribution on the high temperature compression and dynamical recrystallization behaviors of particle-containing alloys

Abstract The high temperature compression and dynamical recrystallization behaviors of particle containing alloys with special particle distribution were examined as a function of strain rate at the temperature of 800 °C. The results show that, the compression behaviors of particle containing alloys significantly depend on the initial microstructure, grain orientation, size, volume fraction and distribution of particles in the alloy matrix. Flow stress changing in the longitudinal compression is greatly different from that in the transverse compression, and peak yield stress is much higher in the longitudinal compression, which correspond to the theoretical results predicted by the critical shear stress model of regular shaped particles, and demonstrates the possibility to further improve mechanical properties of Cu–Al 2 O 3 alloys by controlling particle shape and distribution. The different flow stress changes and microstructure evolution in the longitudinal and transverse compressions have been better explained by grain rotation model. The nucleation and coarsening mechanisms of dynamical recrystallization grains, based on the microstructure evolution, were also established and analyzed.

Effects of Cr addition on glass-forming ability and mechanical properties of Cu–Zr–Al bulk metallic glass

Effects of a small amount addition of Cr on glass-forming ability (GFA) and mechanical properties of Cu–Zr–Al bulk metallic glass were investigated. The GFA of (Cu46Zr46Al8)100−x Cr x (x = 0, 0.25, 0.5, 0.75, and 1 at%) alloys tends to decrease with the increasing Cr content. A good correlation between the GFA and the temperature interval of supercooled liquid region ΔT x or parameter γ exists in these alloys. Addition of an appropriate amount of Cr can significantly improve the plasticity of the alloys. The bulk metallic glass with x = 0.5 exhibits promising mechanical properties with high fracture strength of 1870 MPa and obvious plastic strain of 2.23%.

Effect of post-heat-treatment in ECAP processed Cu–40%Zn brass

This study evaluated the grain refinement and mechanical properties of Cu–40%Zn brass processed by equal channel angular pressing (ECAP). The samples were repeatedly pressed to strains as high as 4 at a temperature of 250°C using route C. Recrystallization heat-treatment was carried out at 350°C for 20min. To evaluate the grain boundary character distributions and mechanical properties of ECAP materials, electron backscattered diffraction, Vickers microhardness, and tensile tests were used. Increased passes in ECAP led to notable grain refinement, from 13μm in the initial sample (350°C/180min heat-treated material) to 300nm after 4 passes. The post-heat-treated material after ECAP also sustained refined grain size (2.4μm in the α phase and 4μm in the β′ phase) than that of initial state, which resulted in an increase in tensile strength with no decrease in elongation. Furthermore, coincidence site lattice boundaries derived from annealing twins were more developed than those of the initial material. This paper discusses the enhancement of mechanical properties in terms of grain boundary character distributions development.

Experimental characterization and modeling of the mechanical properties of Cu–Cu thermocompression bonds for three-dimensional integrated circuits

An analytical model is proposed which relates the bonding temperature, pressure and duration with the integrity of metal–metal thermocompression bonds. Unlike previous models, this approach takes into account the pressure-dependent time evolution of the thermocompression bond formation. The model allows calculation of the true contact area of rough surfaces, based on a creep-dominated plastic deformation. Verification of the model was provided through experiments on Cu–Cu thermocompression bonds of electroplated Cu on diced silicon wafers with chemically/mechanically polished surfaces. The samples were bonded at a range of temperatures, pressures and times. Shear strength measurements were used to characterize the effects of the bonding parameters on the interface bond strength. Calculated true contact area and bond shear strength can be related by a single proportionality factor. The model can be used to predict the thermocompression bond quality for given bonding parameters and process optimization for reliable bonds, thus assisting in the adoption of the Cu thermocompression bond process in three-dimensional integrated circuit applications.

Effect of γ2 phase evolution on mechanical properties of continuous columnar-grained Cu–Al–Ni alloy

Effect of γ2 phase evolution on mechanical properties of Cu–14%Al–3.8%Ni (mass fraction) alloy wires fabricated by continuous unidirectional solidification technology was investigated before and after heat treated at 700–780 °C. Mechanism for the improvement of mechanical properties of the alloy was analyzed. It was found that the alloy retained continuous columnar grains after heat treatment. With the heat treatment temperatures increasing from 700 °C to 770 °C, the coarse dendrite γ2 phase evolved into the fine polygonal, ellipsoidal and spherical particles in the grains, while the long-banding, discontinuous block and ellipsoidal particles at the grain boundaries. The average size of the γ2 phase decreased from 20 μm before heat treatment down to 2 μm, and its amount reduced from 50.0% down to 0.8%. The γ2 phase was full dissolution at 780 °C. The tensile strength of the alloy treated at 700–780 °C ranged from 577 MPa to 710 MPa. The elongation of the alloy ranged from 7.5% to 23.8% and had a peak value at 760 °C. Excellent balance between strength and elongation could be obtained when the spherical γ2 phase was distributed throughout the alloy with the size smaller than 5 μm and the amount in the range of 11.4–16.6%. The nano-hardness and elastic modulus of the γ2 phase decreased gradually with the reduction of the amount, leading to the improvement of mechanical properties.

High glass forming ability and good mechanical properties of Cu–Zr–Al bulk metallic glasses

For developing bulk metallic glasses with high glass forming ability (GFA) and good mechanical properties, Cu92−xZrxAl8 (x = 35–65 at-%) alloys have been studied by means of tilt mould casting method. The largest glassy rod with a critical diameter of 18 mm in this alloy series was obtained for Cu42Zr50Al8 alloy. The Hruby factor is appropriate for evaluating GFA in the cast Zr–Cu–Al bulk glassy alloy. The bulk metallic glasses with high GFA exhibit good mechanical properties, i.e. compressive fracture strength of 1783–2240 MPa, Young’s modulus of 90–123 GPa and plastic strain of 0–0·73%.

Temperature effect on mechanical properties of Cu and Cu alloys

The effect of temperature on the rolling behavior of ultrafine-grained Cu and Cu-alloys with different stacking fault energies (SFEs) is reported. The strength and ductility of the materials increase simultaneously with SFE decreasing by liquid nitrogen temperature (LNT) rolling and room temperature (RT) rolling. Compared with RT-rolled samples with the same low SFE, LNT-rolled ones have a higher strength and better ductility. X-ray diffraction measurements indicate that decreasing SFE leads to a decrease in the average grain size and a concomitant increase in twin density. Special attention should be paid that it is more evident in the LNT-rolled samples. The results show that temperature plays a key role in the rolling process.

Influences of different prior heat treatments on the microstructural and mechanical properties of Cu–Fe filamentary composites

Cu–6 wt.% Fe and Cu–12 wt.% Fe filamentary composites were prepared by casting and cold drawing. And a different heat treatment of quenching and aging or homogenizing was introduced before cold drawing process, respectively. The microstructure was observed and the tensile strength measured for the composites at different drawing strains. The quenching and aging or homogenizing prior to drawing deformation refine the as-cast microstructure and result in the increase in interface density in the drawn microstructure. The drawn alloys with the homogenizing treatment show smaller filament spacing than those with the quenching and aging treatment because homogenizing results in smaller and more dispersive primary Fe dendrites before drawing deformation. The heat treatments can improve the strength of the composites by increasing precipitation strengthening and interface strengthening levels. With the reduction in filament spacing during drawing deformation, the strength of the alloys with smaller initial size of Fe dendrites increases more obviously.

Effect of Al and Ag addition on phase formation, thermal stability, and mechanical properties of Cu–Zr-based bulk metallic glasses

Abstract

Influence of Carbon on Mechanical Properties of Cu bearing Extra Low Carbon Steel Sheets

AbstractThis paper examines the effect of carbon (C) on solid solution strengthening, bake hardening and anti‐strain aging property for copper (Cu) bearing extra low carbon (ELC) steel sheets. For this purpose, five ELC steels that contain different content of C were selected. We have investigated the effect of C on mechanical properties and microstructures for the continuous annealed ELC steel sheets. Mechanical properties and microstructures were analyzed as well using uni‐axial tensile test and electron back‐scattered diffraction (EBSD) technique following pilot rolling and continuous annealing. It has been found that the addition of C increases the solid solution strengthening as well as 19.9MPa per 0.0010wt%C in yield strength. What is more, the addition of C increases the bake hardenability (BH) as well as 18.7MPa per 0.0010wt%C. In addition, the addition of C delays the recrystallization during continuous annealing process. From an industrial standpoint, it is possible to control both a stable anti‐strain aging property and high bake hardenability for the ELC steel sheets without Ti and Nb addition.

Effect of Compression with Oscillatory Torsion Processing on Structure and Properties of Cu

In this study, commercial Cu was subjected to plastic deformation by compression with oscillatory torsion. Different deformation parameters were adopted to study their effects on the microstructure and mechanical properties of Cu. The deformed microstructure was characterized by using scanning electron microscopy (SEM) equipment with electron backscattered diffraction (EBSD) facility and scanning transmission electron microscopy (STEM). The mechanical properties were determined on an MTS QTest/10 machine equipped with digital image correlation. Can be found, that process performed at high compression rate and high torsion frequency is recommended for the refining grain size. The size of structure elements: average grain size (D) and subgrain size (d) reached 0.42 m and 0.30 m respectively, and the fraction of high angle boundaries was 35%, when the sample was deformed at a torsion frequency f= 1.6 Hz and compression rate v=0.04 mm/s. Deformation at these parameters leads to an improvement in strength properties. The strength properties are about two times greater than the initial state.

Microstructure and mechanical properties of Cu and Cu–Zn alloys produced by equal channel angular pressing

Ultrafine-grained (UFG) Cu and Cu–Zn alloy were prepared using equal-channel angular pressing (ECAP) to investigate the effects of stacking fault energy (SFE) on microstructure evolution and mechanical properties. Combining with the previous researches, the grain refinement process of ECAP is divided into three stages based on the variation of tensile strength and plasticity. According to the influences of defects on strength and ductility during plastic deformation, the three stages are discussed in detail by considering the dislocation density, grain and twin boundaries. Besides, the impact of SFE on the strength and ductility of the UFG Cu–Zn alloys are evaluated, indicating that these two mechanical properties can be improved simultaneously in the whole ECAP process either through slightly or widely adjusting the SFE. This significant effect of SFE reflects in two aspects, one is in the microstructure evolution during ECAP processing and the other is in the subsequent tensile plastic deformation, both of which can be achieved through regulating the dislocation motion via changing the SFE.

Effect of Si addition on glass-forming ability and mechanical properties of Cu–Zr–Al bulk metallic glass

The effect of Si addition on the glass-forming ability (GFA) and mechanical properties of (Cu 50Zr 43Al 7) 100− x Si x ( x = 0, 0.5, 1, 1.5 and 2 at.%) alloys were investigated. The GFA of Cu 50Zr 43Al 7 alloy is improved by addition of a small amount of Si, and the critical diameter for glass formation increases from 10 mm for the alloy with x = 0–12 mm for the alloy with x = 1 when prepared using copper mold casting. Different criteria are used to evaluate the influence of Si content on the GFA, and the possible mechanisms involved in the achievement of this GFA are also discussed. In the uniaxial compression, the bulk glassy alloys exhibit a limited plastic strain of less than 1%, but the compressive fracture strength and Young's modulus were obtained in high values of 1969–2129 MPa and 101–144 GPa, respectively. Fracture surface and shear bands of samples were studied by using scanning electron microscopy (SEM).

Mechanical behaviour of heavily deformed CuAgZr conductor materials

The mechanical properties of Cu–7m.%Ag–0.05m.%Zr-alloys have been improved by optimised thermo-mechanical treatments. After processing the conductor material shows an ultimate tensile strength of more than 1.1 GPa, a yield strength of about 1 GPa, a plastic strain of 0.7%, and a conductivity of 60 %IACS (at room temperature). The yield strength of a cold deformed Cu – 7m.%Ag – 0.05m.%Zr-alloy has been assessed on the basis of different hardening mechanisms: solid solution, grain boundary, precipitation and dislocation hardening. The critical shear stress which is determined from the experimentally observed critical shear strength by Schmid's law is between a linear and a quadratic superposition of its individual contributions and hence is in good agreement with the theoretical prediction.

Effect of grain refinement on the mechanical properties of Cu–Al–Be–B shape memory alloy

In this work, the mechanical properties of equal channel angular processing (ECAP)-processed fine- and coarse-grained Cu–11.42Al–0.35Be–0.18B shape memory alloys (wt.%) were evaluated using tensile testing. After eight passes of ECAP and subsequently quenching from 600 °C to RT, the mean grain diameter was refined from 227 μm to 42 μm with grain boundaries purified. The fine-grained alloy exhibited good mechanical properties with a high tensile strength (703 MPa) and featured deeper and closer dimples on its fracture surface. The micro cracks were more refined, and the cracks extension along the grain boundaries was improved in the fine-grained alloy. These changes can be attributed to improvement of martensite morphology, structural refinement and grain boundary purification.

Improvement of elevated temperature mechanical properties of Cu–Ni–Sn–Pb alloys

Cu–Ni–Sn alloys with Pb additions exhibit high mechanical strength at room temperature coupled with good machinability but experience a significant ductility loss above the melting point of lead. We explore here the influence of minor additions of Al, Mn, Zr, B or P to the copper alloy CuNi9Sn6Pb1 on its tensile properties at 400 °C and 10 −2 s −1. Only boron and phosphorous additions have a clear beneficial effect. Unlike other elements tested, these form intermetallic particles; it is proposed that the improvement results from a combination of capillary pinning and mechanical shielding by these particles of the molten lead inclusions in the alloy.

Effect of Powder Type and Composition on Structure and Mechanical Properties of Cu + Al2O3 Coatings Prepared by using Low-Pressure Cold Spray Process

Powder type and composition have a very important role in the production of metallic and metallic-ceramic coatings by using the low-pressure cold spray process. Furthermore, structure and mechanical properties of Cu and Cu + Al2O3 coatings are strongly influenced by powder characteristics of Cu particles. The aim of this study was to evaluate the effect of different particle types of Cu powder and different compositions of added Al2O3 particles on the microstructure, fracture behavior, denseness, and mechanical properties, i.e., hardness and bond strength. Spherical and dendritic Cu particles were tested together with 0, 10, 30, and 50 vol.% Al2O3 additions. Coating denseness and particle deformation level increased with the hard particle addition. Furthermore, hardness and bond strength increased with increasing Al2O3 fractions. In the comparison between different powder types, spherical Cu particles led to the denser and less oxide-contenting coating structure due to the highly deformed particles.

Molecular dynamics simulation study of thermodynamic and mechanical properties of the Cu–Pd random alloy

Molecular dynamics (MD) simulations have been performed to investigate the thermodynamic and mechanical properties of Cu– x% Pd (at%) random alloy, as well as those of the Cu 3Pd and CuPd 3 ordered alloys, in the temperature range from 200 K up to the melting point. The quantum Sutton-Chen (Q-SC) many-body interatomic potentials have been used to describe the energetics of the Cu and Pd pure metals, and a standard mixing rule has been employed to obtain the potential parameters for the mixed (alloy) states. We have computed the variation of the melting temperature with the concentration of Pd. Furthermore, the variation of the cohesive energy, the order parameter, the thermal expansion coefficient, the density, the isobaric heat capacity, the bulk modulus, and the elastic stiffness constants were also calculated at different temperatures and concentrations for these materials. The computed variations of the thermodynamic and mechanical properties with temperature are fitted to a polynomial function. Our computed results show good agreement with other computational simulations, as well as with the experimental results where they have been available.