Resistivity Of Cu Research Articles

Effect of Horizontal Continuous Casting Parameters on Cyclic Macrosegregation, Microstructure, and Properties of High-Strength Cu–Mg Alloy Cast Rod

AbstractThe objective of this paper is to present the effect of horizontal continuous casting parameters on macrosegregation and its effect on microstructures, textures, mechanical properties, and electrical resistivity of Cu–Mg alloy rod. By increasing the pulling distance and intermittent extraction time, chemical macrosegregation was observed along the longitudinal section of the cast rod, which reached a distance of 40 mm. Three areas were identified along the length of the material, especially at high pulling distance: with decreasing, quasi-stable, and increasing Mg concentration area. As the pulling distance increased, the difference in the observed extreme values of Mg concentration increased. Two distinct zones of different grain size were also observed. The first zone was formed of large columnar grains with a preferred direction of solidification $$\langle 100\rangle$$ ⟨ 100 ⟩ inclined to the axis of the wire, followed by a second zone formed of small grains of random texture. Consequently, difference in resistivity occurred from one zone to another and the resistivity increased from 37.5 to 41 nΩm. Likewise, the hardness varied between the values of 90 up and 110 Hv. The most homogenous chemical composition was obtained with up to 6 mm of pulling distance and up to 3 seconds of intermittent extraction time.

Influence of thermomechanical treatment on recrystallization and softening resistance of Cu−6.5Fe−0.3Mg alloy

The recrystallization and softening resistance of a Cu−6.5Fe−0.3Mg (mass fraction, %) alloy prepared by Process 1 (cold rolling heat treatment) and Process 2 (hot/cold rolling heat treatment) were studied using Vickers hardness tests, tensile tests, scanning electron microscopy and transmission electron microscopy. The softening temperature, hardness and tensile strength of the alloy prepared by Process 2 were 110 °C, HV 15 and 114 MPa higher, respectively, than those of the alloy prepared by Process 1 after aging at 300 °C. The recrystallization activation energy of the alloys prepared by Process 1 and Process 2 were 72.83 and 98.11 kJ/mol, respectively. The pinning effects of the precipitates of the two alloys on grain boundaries and dislocations were basically the same. The softening mechanism was mainly attributed to the loss of dislocation strengthening. The higher Fe fiber density inhibited the average free migration path of dislocations and grain boundary migration in the alloy, which was the main reason for higher softening temperature of the alloy prepared by Process 2.

Effect of Citrate-Based Bath pH on Properties of Electrodeposited Cu–Zn Coating on an Aluminum Substrate

In this study, Cu–Zn alloys were deposited in citrate-based electrolytes on aluminum substrate by electrodeposition method. The effect of bath pH variation on the properties of the obtained Cu–Zn alloy coatings was investigated. The electrochemical behavior of the citrate-based baths and the crystalline structure, surface morphology and elemental content, electrical resistivity and thermal behavior of the alloy coatings were analyzed. According to the results of cyclic voltammetry (CV) analysis, increasing bath pH caused a negative shift in the cathodic deposition potential. In addition, the anodic dissolution peaks first shifted to the positive side with increasing pH and then shifted back to the negative direction. According to the results of XRD analysis, the phase structure of Cu–Zn alloys generally consists of α and β′ phases, but according to differential scanning calorimeter (DSC) analysis, it is possible that there is a γ phase in the structure in addition to these phases. In addition, pH increase (4.5 to 6.5) caused a relative increase in crystal grain size (~14 to ~ 25 nm). The Zn content of Cu–Zn coatings first increased (~pct 15 to ~ pct 55) with pH increase, then followed a horizontal trend (~pct 55 to ~ pct 59) with further pH increase and then exhibited a slight decreasing trend (~pct 59 to ~ pct 52). The pH increase significantly affected the surface morphology of the coatings and denser coatings were obtained with increasing pH. While the electrical resistivity of Cu–Zn coatings first increased (0.0408 to 0.0696 µΩcm for 297 K) with increasing pH, it tended to decrease (0.0696 to 0.0479 µΩcm for 297 K) again at higher pH values. In addition, the electrical resistivity of the coatings increased with increasing measurement temperature. According to DSC analysis of the coatings, endothermic peaks were obtained, possibly representing the transformation from γ to β′ phase.Graphical

Study on the microstructure and mechanism of stress relaxation behavior of Cu–Ni–Si alloy by two-stage rolling deformation

In this paper, the effect of the second-stage rolling deformation of Cu–Ni–Si alloy on its stress relaxation resistance was studied, and the mechanism of the change in microstructure and properties before and after stress relaxation was explored. The results show that the tensile strength and yield strength of Two-stage rolling peak aging (TRPA) 43.7 %, TRPA68.8 %, TRPA80.3 % and TRPA96.1 % alloys at 150 °C are close. After stress relaxation, the stress relaxation rates of these alloys are 7.7 %, 11.24 %, 14.69 % and 19.4 %, respectively. It is found that the smaller the second-stage rolling deformation, the better the stress relaxation resistance of the alloy, especially the stress relaxation resistance of the TRPA43.7 % alloy, which is 60.31 % higher than that of the TRPA96.1 % alloy. According to EBSD analysis, it was found that the increase in the number of twins can improve the stress relaxation resistance of the alloy. However, the occurrence of recrystallization reduces the stress relaxation resistance. Additionally, it was determined that the precipitated phase is the δ-Ni2Si phase with an orthogonal structure. Before stress relaxation, the size of the precipitated phase of the alloy with TRPA96.1 % is larger than that of the alloy with TRPA43.7 %, and after stress relaxation, the precipitated phase further grows. The influence of the interface relationship between δ-Ni2Si phase and Cu matrix on the stress relaxation properties of TRPA43.7 % and TRPA96.1 % alloys before and after stress relaxation was investigated using the mismatch theory. In summary, this study reveals that the size of δ-Ni2Si phase, dislocation density and recrystallization are the key factors affecting the stress relaxation resistance of Cu–Ni–Si alloy.

Oxidation behavior of Cu–Ag alloy in-situ manufactured via laser powder bed fusion

The oxidation behavior of copper-silver (Cu–Ag) alloy with the structure of triply periodic minimal surfaces (TPMS) processed by laser powder bed fusion (LPBF) was investigated at 300 °C and 600 °C. The lightweight TPMSs increase surface area, boosting measurement sensitivity in oxidation studies. The presence of silver enhances oxidation resistance of Cu–Ag alloy compared to that of pure copper by slowing down the oxidation process and thinning the oxide layer. This suggests that silver in the alloy potentially suppresses the outward diffusion of copper from the substrate to the oxide layer. This effect is evident in the oxidation rate curves, where the introduction of silver changes the oxidation kinetics from a linear rate in Cu to a parabolic rate in Cu–2 wt.% Ag at 300 °C. Moreover, at 600 °C, silver induces a slower parabolic rate in Cu–2 wt.% Ag compared to Cu.

Friction and wear properties of wide-velocity range high-energy plasma sprayed CuSn–NiCr solid self-lubricating coatings under heavy load

As one of important copper-based solid self-lubricating coatings, the low wear resistance of Cu–Sn coatings greatly limits its application in some heavy-duty cases. In the present work, two types of CuSn–NiCr composite powders designed by electroless plating (E-CN) and mechanical mixing (M − CN) methods, respectively. The friction and wear properties of wide-velocity range high-energy plasma sprayed CuSn–NiCr coatings were studied. The results suggested that, the fracture toughness of E-CN and M − CN coatings increased by 1.38 times and 1.55 times compared with as-sprayed Cu–Sn coatings, and the wear rate decreased by 29 % and 50 % correspondingly. Due to the tribofilm formation and micro-pores storage effect, the M − CN coating with 10 wt% addition ratio of Ni–Cr phase exhibited the lowest friction coefficient and the smallest wear rate. With the increase of Ni–Cr phase, the wear mechanism was transformed from adhesive to abrasive, and accompanied by fatigue step-shaped spallation. Friction and wear model of the CuSn–NiCr coatings was divided into rapid, stable and declining stages.

Experimental study of two-phase cryogenic cooling of aluminum stator conductors using a single slot test configuration

An important goal to enable widespread adoption of electric aircraft propulsion is to develop higher power density motors and generators which are at the same time highly efficient. One way to do this is to use conductors that can carry higher currents and/or generate lower losses. One approach to this is the use of superconducting windings. However, here we focus on very low resistance normal state conductors operating at cryogenic temperatures. The resistivity of both aluminum and copper drops quickly with decreasing temperature, such that the resistivity of Cu drops by about a factor of 7, and that of aluminum by 10, by the time we reach 77 K (LN2). OSU and Hyper Tech have teamed to develop a motor with liquid cryogen cooled aluminum windings (LN2 or LNG cooled). It includes a multi-slot stator with direct cryogen cooling. Here we present the results of a simple “single slot” test which explores the temperature rise of a pair of conductors in a slot directly cooled by LN2. These two aluminum bars are made of 1100 commercial purity Al alloy were placed in parallel with a 1.6 mm gap, which behaved as 120 mm long cryogenic flow channel. Current densities up to 75 A/mm2 were explored, with LN2 flow rates ranging from 1.9 g/s to 6.4 g/s. Thermocouples and voltage taps were used to capture temperature and voltage data during the experiment. As a result, we found stable cooling and operation at these flow rates and current densities, and we characterized the temperature gradient which developed along the conductor bars.

High strength and excellent softening resistance Cu–15Ni–8Sn alloy by Ti addition

Cu–15Ni–8Sn alloy is commonly utilized in various applications because of its exceptional strength, elasticity, and softening resistance. Ti microalloying has been employed to enhance the mechanical properties of Cu–15Ni–8Sn alloy. By adding 0.5 wt% Ti, the peak-ageing tensile strength, microhardness, and elastic modulus of the Cu–15Ni–8Sn alloys reach 1401.3 MPa, 479.3 Hv, and 154.7 GPa, respectively, representing the greatest comprehensive performance reported in previous literature. Additionally, the Ti microalloying significantly enhances the softening resistance of Cu–15Ni–8Sn alloys. After ageing at 400 °C for 10 h, the tensile strength of the Cu–15Ni–8Sn-0.5Ti alloy decreases by only around 150 MPa, whereas the alloy without Ti addition experiences a decrease close to 350 MPa. Quantitative analysis reveals that the observed improvements can be attributed to the Ti microalloying inhibiting the dislocation annihilation and the formation of discontinuous precipitation during the ageing process, while simultaneously promoting the precipitation of Ni3Ti. This study provides a theoretical basis for preparing a high-performance Cu–15Ni–8Sn alloy by microalloying.

The growth behavior and kinetics of intermetallic compounds in Cu–Al interface at 600°C–800 °C

Due to the low production cost and light weight, copper-clad aluminum conductors show great potential value in the field of power transmission, while the phase structure and organizational changes at the Cu–Al interface in high-temperature environments have a great impact on the electrical and mechanical properties. In this paper, Cu–Al diffusion couples are prepared to study the diffusion process, microstructure, and growth kinetics of intermetallic compounds (IMCs) in Cu–Al interface during heating from 600 °C to 800 °C, and the mechanical and electrical properties of Cu–Al diffusion couples are discussed. The results show that after heat treatment, IMC layers are formed at the Cu–Al interface and the Al-side is composed of CuAl and CuAl2, in which the CuAl phase transforms from long to thick dendrites with the increase of temperature, and finally grows into a “popcorn” form. The IMCs at the Cu–Al interface from the Cu side to the Al side are in the order of Cu3Al layer, Cu9Al4 layer, Cu3Al2 layer and CuAl layer, among which the Cu3Al2 layer is the thickest (168.42 μm at 700 °C), while the Cu3Al layer is the thinnest (37.32 μm at 700 °C). The kinetic calculations show that the diffusion layer grows up rapidly, which is caused by the generation of liquid-phase during the heating process, leading to the acceleration of the diffusion of Cu and Al. The kinetic factor of the Cu3Al2 layer is the largest (n = 0.69), causing the fastest growth rate of the Cu3Al2 layer, while the Cu3Al layer shows the largest activation energy for diffusion and the smallest diffusion rate (Q = 9.48 kJ/mol, D0 = 2.06 × 10−1 m2/s), therefore its growth rate is the slowest. Based on the thermodynamic calculations and the Cu–Al phase diagram, a growth mechanism of the Cu–Al interface is proposed, the formation sequence of IMCs at the Cu–Al interface is Cu9Al4, CuAl, Cu3Al2 and Cu3Al. The formation of IMCs layer at the Cu–Al interface leads to a significant increase in the hardness of Cu–Al samples (the hardness of the Cu3Al2 is 10 times higher than that of Cu) and an obvious decrease in electrical conductivity (the electrical resistivity of Cu–Al is 5 orders of magnitude higher than that of Cu), affecting its application in the electrical industry.

Aluminum Co-Deposition via DC Magnetron Sputtering for Enhanced Pitting Resistance of Copper–Nickel Alloys

To investigate the improvements in the resistance of Cu–Ni alloys to surface pitting corrosion, Cu–Ni thin films containing Al were fabricated via DC magnetron sputtering. The morphologies of the fabricated samples were obtained using a scanning electron microscopy, which yielded information on the crystal size and sample surface before and after corrosion tests. X-ray diffraction was employed for the structural characterization of the as-deposited films, and vibrational spectroscopy was used to verify the corrosion products. The corrosion behaviors of the Cu–Ni and Cu–Ni–Al samples were examined using electrochemical polarization and cyclic corrosion tests. The Al co-deposited samples showed a refined crystal size as compared to the Cu–Ni sample, suggesting that they are more susceptible to the formation of a passivation film. The corrosion current density of the Cu–Ni–Al was reduced, and the corrosion potential was lower than that without Al content. The negative shift in the corrosion potential of the Al-containing samples indicates that the Al2O3 film suppressed the cathodic reaction, resulting in a decrease in the corrosion rate. These results are consistent with the cyclic corrosion test results, in which no pitting corrosion is observed in the Cu–Ni–Al sample.

The Effect of Cu and Zn Addition on the Intergranular Corrosion Resistance of Al-Mg-Si Alloy

Aluminum alloys are widely used for automobile and aircraft industries because of their good strength-to-weight ratio. In general, Cu improves the strength of Al alloys but reduces localized corrosion resistance. For Al-Mg-Si alloys, it has been reported that Cu decreases intergranular corrosion resistance. In this study, the effect of Cu and Zn on intergranular corrosion resistance was analyzed by electrochemical measurements.As specimens, Cu-free alloy, Cu-added alloy, and Cu- and Zn-added alloy were prepared based on AA6061 composition. The extruded specimens were subjected to T6 heat treatment. Intermetallic compounds were characterized by SEM-EDS and TEM. Open-circuit potentials (OCPs) was measured in 0.1 M NaCl (pH 6.0). To assess the distribution density of the initiation sites of localized corrosion, the size of electrode area was 100 mm2, 9 mm2, or 1 mm2. In the electrochemical measurements, Ag/AgCl (3.33 M KCl) was used as the reference electrode.At the beginning of immersion, OCP was −1.2 V (vs. SHE) for all specimens, and OCP increased with time. After 4000 s, the OCP of Cu-free alloy became −0.5 V, the OCPs of Cu-added alloy and Cu- and Zn-added alloy became −0.4 V. After 3 h immersion, intergranular corrosion was generated on Cu-added alloy and Cu- and Zn-added alloy. In contrast, no intergranular corrosion was observed on Cu-free alloy. Based on intergranular corrosion length, it was shown that intergranular corrosion resistance of Cu- and Zn-added alloy is low compared with the others. This result suggested that Zn promotes the growth of intergranular corrosion. Moreover, the number of intergranular corrosion damages was assessed and found to be less on Cu- and Zn-added alloy than on Cu-added alloy. This result suggested that Zn decrease the number of initiation sites of intergranular corrosion. Additionally, 3-h immersion of Cu-added alloy and Cu- and Zn-added alloy was conducted with the electrode area of 9 mm2 and 1 mm2. For both alloys, intergranular corrosion occurred at 10 sites in 100 mm2 and 1 site in 9 mm2. And no intergranular corrosion occurred in the case of 1 mm2 electrode area. The distribution density of the initiation sites for intergranular corrosion on Cu-added alloy and Cu- and Zn-added alloy was estimated to be approximately 1 site per 9 mm2.

Enhanced Catalytic Performance and Poison Resistance of Cu–Mn–Ce Ternary Mixed Oxide for Chlorobenzene Oxidation

Enhanced Catalytic Performance and Poison Resistance of Cu–Mn–Ce Ternary Mixed Oxide for Chlorobenzene Oxidation

Printing flexible Cu–Ni traces with high conductivity and high thermal stability by in-situ formed multiscale core–shell structures in inks

Direct printing of flexible Cu traces is one of the most promising additive manufacturing technologies in advanced electronics because it is a cost-effective and environmentally friendly process. However, the low oxidation resistance of Cu is currently a critical issue for the preparation of high-performance metallic inks and the manufacturing of reliable printed traces. Herein, we propose a hybrid ink containing Cu/Ni complexes and Cu particles that can be directly printed onto polyimide substrates to generate high-performance Cu–Ni alloy traces by low-temperature preheating and intense pulsed-light irradiation. The nanoparticles in-situ formed by the decomposition of the complexes effectively bridge the interfaces among Cu particles, allowing the printed traces after subsequent intense pulsed-light irradiation to achieve a low resistivity of 29.4 μΩ·cm and excellent mechanical stability at a bending radius of 7 mm. Strikingly, the obtained Cu–Ni alloy traces achieve multiscale core–shell structures because of the heterogeneous nucleation and passivation of Ni, which enables the printed traces to maintain high conductivity and oxidation resistance even at 250 °C in the air, showing strong potential for use in advanced electronics manufacturing.

Scattering-induced circuit modelling and performance analysis of coupled hybrid Interconnections: Sub-threshold performance evaluation

This paper presents the scattering induced circuit modelling and performance analysis in terms of crosstalk and frequency stability in the newly proposed hybrid interconnects operating in the sub-threshold domain. The electrical performances of hybrid copper carbon-nanotube (HCNT), hybrid copper graphene nanoribbon (HGNR) and hybrid Copper carbon (H Carbon) interconnects are examined and compared with that of copper (Cu), single walled carbon nanotube bundles (SWCNTs) and lithium doped multilayer graphene nanoribbon (MLGNR) interconnects in terms of dynamic and functional crosstalk results by employing the transmission line (TL) analytical model for sub-threshold applications. The impact of the grain-size on the resistivity of Cu and the various scatterings induced mean free path (MFP) on the overall resistance has been analysed in the modelling of HGNR interconnects. The comprehensive analysis of the crosstalk induced delay (dynamic crosstalk), the positive peaks and the time-duration (functional crosstalk) ensures the efficacy of hybrid interconnects, especially H Carbon interconnects in the designing of on-chip interconnects. It has also been observed from the frequency response that the maximum 3-dB bandwidth is obtained in the case of H Carbon hybrid interconnects (approx. 6.7586 × 1010 Hz) at 300 K temperature values. Further, the bandwidth values tend to decrease with the rise in temperature values.

Fine conductive line printing of high viscosity CuO ink using near field electrospinning (NFES)

Modern printed electronics applications require patterning of fine conductive lines of sufficient thickness. However, the two requirements for pattern width and thickness are a trade-off. To print fine pattern at a micrometer size, the nozzle diameter must be approximately the size of the pattern width, so only low-viscosity inks are used. As a result, the pattern is likely to be very thin and multiple overlapping printing is required for sufficient conductance. In order to use high viscosity ink for fine patterning, near field electrospinning (NFES) is attracting attention because it can print very thin and thick patterns using large nozzles (high-viscosity ink). Until now, silver paste ink has been used for microconductive patterning using electrospinning. However, Ag nanoparticle (NP) inks are expensive. In this study, we report the use of a relatively inexpensive CuO NP ink for electrospinning-based printing. For implementation, the material preparation, printing and post-processing process are discussed. For post-processing, a continuous wave (CW) green laser with a 532 nm wavelength was used to reduce the CuO to Cu and sinter the nanoparticles. After sintering, the 50 μm width and 1.48 μm thick Cu conductive line exhibited a resistivity of 5.46 μΩ·cm, which is 3.25 times of the bulk resistivity of Cu.

Electrical conductivities and mechanical properties of Ti3SiC2 reinforced Cu-based composites prepared by cold spray

In order to improve the wear resistance and oxidation resistance of Cu without compromising the electrical and thermal conductivities, Cu-xTi3SiC2 (x = 0, 10, 20, 30, 40, wt%) composites were prepared by cold spray, which can be used as an additive manufacturing technology. Comparing with Cu, the ultimate tensile strengths (UTS) of as-deposited composites increased significantly, with a slight loss in electrical and thermal conductivities. After annealing at 500 °C and 800 °C for 2 h in vacuum, the composites exhibited brittle and ductile fracture characteristics, respectively. The interface reaction between Cu and Ti3SiC2 was critical to its tensile properties. In these composites, the Cu-20Ti3SiC2 composite annealed at 800 °C possessed optimal overall performances, such as relatively higher UTS (304 MPa) and electrical conductivity (45.4% IACS).

Tailoring the glass forming ability, mechanical properties and corrosion resistance of Cu–Zr–Al bulk metallic glasses by yttrium addition

The effect of yttrium (Y) on the glass-forming ability (GFA), mechanical properties and corrosion of (Cu50Zr43Al7)100-xYx (x = 0, 2 and 4, in at. %) alloys was investigated. The GFA of Cu50Zr43Al7 alloy was improved by the addition of Y, with a GFA of 15 mm in diameter being obtained for (Cu50Zr43Al7)98Y2. In uniaxial compression, the bulk metallic glasses (BMGs) exhibited a limited plastic strain of less than 1%, however compressive fracture strength and Young's modulus of 1787–2006 MPa and 101–122 GPa were achieved, respectively. Fracture surfaces and shear bands were studied via scanning electron microscopy. The corrosion behavior of BMGs was analyzed by potentiodynamic polarization experiments and electrochemical impedance spectroscopy (EIS) in acidic chloride (1 M HCl) and neutral chloride (0.6 M NaCl) environments. As a result of the Y addition, the corrosion resistance of the base BMG was improved.

Mechanically robust antifouling coating with dual-functional antifouling strategy by infiltrating PDMS into plasma-sprayed porous Al2O3-Cu coating

Marine biofouling is a worldwide challenge that needs to be solved urgently. Poly(dimethylsiloxane) (PDMS)-based fouling release coatings with low surface free energy (SFE) could effectively inhibit biofouling. Nevertheless, their poor mechanical durability, adhesive strength, and antifouling performance under static conditions significantly limit their applications. Herein, a novel mechanically robust Al2O3-PDMS-Cu composite coating with strong adhesive strength and remarkable antifouling performance was developed. The Al2O3-PDMS-Cu coating loaded with a small amount of Cu was fabricated by infiltrating PDMS into plasma-sprayed micro/nano-scaled porous Al2O3-Cu coating. Results showed that the fabrication of this Al2O3-PDMS-Cu coating did not alter the surface hydrophobicity and SFE of PDMS significantly, thus presenting little influence on its inherent fouling release property. After rigorous abrasion test, the Al2O3-PDMS-Cu coating presented remarkably improved surface hydrophobicity due to the exposure of micro/nano structure, rather than falling off as that of PDMS coating. The combination of excellent abrasion resistance and one order of magnitude higher adhesive strength and hardness than PDMS coating contributed to the outstanding mechanical robustness of Al2O3-PDMS-Cu coating. Additionally, the antifouling assays against marine bacteria adhesion (95% reduction rate for Escherichia coli. (E. coli)) and algae attachment (96% and 94% reduction rates for Chlorella and Phaeodactylum tricornutum (P. tricornutum), respectively after 21 days of incubation) demonstrated the superior antifouling performance of the Al2O3-PDMS-Cu coating. Thus, a high-performance Al2O3-PDMS-Cu antifouling coating with excellent mechanical robustness and long-term antifouling performance was achieved via the combination of mechanical durability of Al2O3 skeleton and the dual-functional antifouling strategy, i.e., the fouling release property of PDMS and fouling resistance of Cu.

Wear behaviour of novel copper alloy as an alternative to copper-beryllium

Copper beryllium age hardenable alloys (Cu–Be) are widely used and appreciated for combining exceptional mechanical and electrical properties. However, the toxicity of these alloys pushes the scientific community to develop alternative alloys. Cu–Ni–Sn alloys are already used in aeronautics and the oil industry to replace Cu–Be when good tribological behaviour is required. Recent studies showed that Cu–Ti alloys, age hardenable, have a higher yield stress and elongation than Cu–Ni–Sn alloys and can approach the mechanical resistance of Cu–Be. In this research work, the wear mechanisms governing the tribological behaviour of a new copper alloy (containing alloying elements such as titanium, nickel or tin) as an alternative to the beryllium containing copper alloys were investigated.Tribological tests under dry conditions were carried out by sliding an alumina ball against three different copper alloys disks applying different loads and during a different number of cycles. Wear volumes were quantified by confocal microscopy while wear morphology and microstructural changes at the surface and subsurface were analysed by SEM and FIB cross-sections. Several wear mechanisms were identified including plastic deformation followed by the build-up of a third body. Friction transitions were measured during sliding as a consequence of the third body formation. The chemical and mechanical properties of the third body were material dependent and determined the wear behaviour of the different copper alloys.

Influence of solution-hardening on the mechanical properties and wear resistance of copper alloys

Solid-solution hardening can increase the wear resistance of metals, involving two factors: the solute 1) pins dislocations, leading to increased hardness of the metals; 2) influences the atomic bond strength and thus Young's modulus, which also affects the resistance to dislocation generation and movement. Solute atoms generally increase hardness of the host metal but may increase or decrease its Young's modulus, which is related to the solute's electron work function (EWF). In this study, Cu (EWF = 4.65 eV) was hardened by solutes, Ni (EWF = 5.15 eV), and Mn (EWF = 4.1 eV), respectively. CuNi (10, 30, 60, 80 wt% Ni) and CuMn (2, 4, 6, 8 wt% Mn) alloys were prepared using an arc furnace. It is demonstrated that with Ni addition, both hardness and Young's modulus increased, while Mn addition led to a decrease in Young's modulus though the hardness was increased. As a result, the effect of Ni on the wear resistance of Cu is underestimated when predicted using the classic Archard equation, while that of Mn is overestimated. Such an issue of under- or over-estimation can be corrected using a wearing energy model, which takes into account the influence of Young's modulus on the wear resistance. The wearing energy model is a modified form of Archard equation, established by including wearing energy consumption via the relationships among atomic bond strength, Young's modulus, and EWF. Density functional theory (DFT) calculations on CuMn and CuNi alloys systems confirm a stronger metallic bond in CuNi with higher overall EWF, compared with that in CuMn showing a lower overall EWF.