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... need copper alloys with medium to high electrical conductivity. For transmission of signals copper alloys with low to medium conductivity are used. It is known that copper alloys of high strength cannot reveal high conductivities like pure or low alloyed solid solution hardened coppers. The chart of electrical conductivity versus yield strength (Fig. 2) gives a first overview about alloying systems of relevance. In case of precipitation hardened low alloyed coppers, Cu-Be-alloys and Corson-type alloys this two-dimensional interdependence is valid for good to fair bend radii r versus strip thicknesses t ratios r:t in the range of 0 to 5. ...
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... The density of twins can be controlled by adjusting the grain size and the stacking fault energy of the alloy: The density of deformation twins decreases with decreasing grain size and the (largely grain-size insensitive) density of recrystallization twins increases with decreasing stacking fault energy (Vöhringer, 1972; Vöhringer, 1976). Figs. 13 and 2). The optimization of the nature, density and location of twins for enhanced mechanical behavior of high performance copper alloys remains a challenging task within grain boundary engineering (Randle, 1999). Fig. 12. OIM (Orientation Imaging Microscopy)-picture (obtained by EBSD) of coarse grained (right) and fine grained CuSn8 (left) ...
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... density of recrystallization twins increases with decreasing stacking fault energy (Vöhringer, 1972; Vöhringer, 1976). Figs. 13 and 2). The optimization of the nature, density and location of twins for enhanced mechanical behavior of high performance copper alloys remains a challenging task within grain boundary engineering (Randle, 1999). Fig. 12. OIM (Orientation Imaging Microscopy)-picture (obtained by EBSD) of coarse grained (right) and fine grained CuSn8 (left) prior to final cold rolling. Cu-type orientation is represented by blue coloured grains, Goss-type by green coloured grains ...
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Citations
... Such metallic components are generally manufactured by forming processes at room temperature, therefore more demands have been made on copper alloy sheets to have not only a high electrical conductivity but also an excellent formability. Moreover, high strength, excellent thermal stability and resistance against fatigue damage are also required [1]. Various parameters influence the mechanical properties of copper alloys, and especially the metallurgical state. ...
Copper alloys are extensively used in the manufacture of electrical and electronic components, which strength depends on the material mechanical properties, which in turn depend on the metallurgical state. Even though the mechanical properties remain within the specifications, the subsequent formability limits may depend strongly on the material batch. Considering the forming stage to manufacture plug-in type connectors made of CuSn6P thin sheets, a crack may appear in the components, in the bent area subject to high strains, when changing the material batch. The aim of this study is to take account of these variations of the mechanical behavior through a probabilistic approach, to predict the formability limit. The mechanical properties of the materials from the two batches were characterized in tension, to highlight the differences. The initial yield stress and the tensile strength are higher for one material, while the maximum equivalent plastic strain at rupture, determined through a hybrid experimental-numerical approach, is lower. And a significant difference in the transverse anisotropy coefficient is evidenced. A 3D parametric finite element model of the forming stage is developed to investigate the role of some mechanical properties and process parameters on the formability limit in bending. The range of the parameter values comes from the experimental data. Their influence is evaluated through a design of experiments, with the aim of highlighting the influence of the variations of the mechanical properties and process parameters on the fracture criterion, using a probabilistic approach with Gauss’s law.
... The main factor that influences the fatigue-crackgrowth behavior is the roughness-induced fatigue crack closure. Li et al. [47] summarized the fatigue behaviors of HEAs and compared them with some traditional alloys, as shown in Fig. 10.39a, b. Figure 10.39a indicates that the range of [46,47,[260][261][262][263][264][265][266][267][268][269][270][271][272] fatigue strength and UTS of HEAs is located between those of Cu alloys and steels, while Fig. 10.39b indicates that the combination fatigue ratio and UTS of HEAs is between those of Cu alloys, Ti alloys, and steels. ...
High-entropy alloys (HEAs) are materials that consist of equimolar or near-equimolar multiple principal components but tend to form single phases, which is a new research topic in the field of metallurgy, and have attracted extensive attention in the past decade. The HEAs families contain the face-centered-cubic (fcc), body-centered-cubic (bcc), and hexagonal-close-packed (hcp)-structured HEAs. On the one hand, mechanical properties, e.g., hardness, strength, ductility, fatigue, and elastic moduli, are essential for practical applications of HEAs. Scientists have explored in this direction since the advent of HEAs. On the other hand, the pursuit of high strength and good plasticity is the critical research issue of materials. Hence, strengthening of HEAs is a crucial issue.
... Despite the insignificance of the displacements, the stresses at the inner points of the conductor are quite large (see Fig. 9). The obtained maximum values of mechanical stresses are of the same order as the short-term strength limit of electrical copper (200-250 MPa [20]) which decreases with increasing temperature. ...
A novel mathematical model describing physical processes during the flow of an aperiodic pulse current with amplitude of 100 kA along a conductor with a circular cross-section is proposed and investigated. It is shown how a short-term electric discharge of an aperiodic shape affects the distribution of the current density in the cross-section of the conductor, causing its nonuniform heating and the appearance of significant thermal forces as well as mechanical stresses and strains. Based on the developed mathematical model, the relation-ship between electromagnetic, thermal and mechanical phenomena is shown, allowing a deeper understanding of the multiphysics processes taking place. The maximum values of the current density are calculated, which on the surface of the conductor reach values of 47 kA/mm2, while the temperature rise of a copper conductor with a diameter of 2.44 mm is no more than 80ºC at high temperature gradients, which causes the appearance of thermal stresses that have value (40–50)% of the value of the short-term strength limit of electrical copper. Utilization of this model allows to more accurately determine the required conductor cross-section based on the characteristics of electromagnetic, thermal and mechanical pro-cesses. It is shown that the simplified model (the condition for the uniform distribution of the current over the cross-section) gives significantly underestimated values of temperatures and does not take into account temperature deformations.
... (a) Fatigue strength-UTS and (b) fatigue ratio-UTS maps of HEAs and some traditional alloys. Figures from Li et al.[46, 47,[264][265][266][267][268][269][270][271][272][273][274][275][276]. ...
High-entropy alloys (HEAs) are materials that consist of equimolar or near-equimolar multiple principal components but tend to form single phases, which is a new research topic in the field of metallurgy, have attracted extensive attention in the past decade. The HEAs families contain the face-centered-cubic (fcc), body-centered-cubic (bcc), and hexagonal-close-packed (hcp)-structured HEAs. On one hand, mechanical properties, e.g. hardness, strength, ductility, fatigue, and elastic moduli, are essential for practical applications of HEAs. Scientists have explored in this direction since the advent of HEAs. On the other hand, the pursuit of high strength and good plasticity is the critical research issue of materials. Hence, strengthening of HEAs is a crucial issue. Recently, many articles are focusing on the strengthening strategies of HEAs[1-14]. In this chapter, we reviewed the recent work on the room-temperature elastic properties and mechanical behavior of HEAs, including the mechanisms behind the plastic deformation of HEAs at both low and high temperatures. Furthermore, the present work examined the strengthening strategies of HEAs, e.g. strain hardening, grain-boundary strengthening, solid-solution strengthening, and particle strengthening. The fatigue, creep, and fracture properties were briefly introduced. Lastly, the future scientific issues and challenges of HEAs were discussed.
... The addition of a small amount of Mg also increases the strength and the stress relaxation resistance by the effect of Mg-atom drag on the dislocation motion [46]. In addition, Mg atoms improve the stress relaxation resistance by solid solution hardening because of the large difference between the atomic radii of Mg and Cu [47,48]. Moreover, Mg also promotes the formation of silicides. ...
High strength and high conductivity (HSHC) Cu alloys are widely used in many fields, such as high-speed electric railway contact wires and integrated circuit lead frames. Pure Cu is well known to have excellent electrical conductivity but rather low strength. The main concern of HSHC Cu alloys is how to strengthen the alloy efficiently. However, when the Cu alloys are strengthened by a certain method, their electrical conductivity will inevitably decrease to a certain extent. This review introduces the strengthening methods of HSHC Cu alloys. Then the research progress of some typical HSHC Cu alloys such as Cu-Cr-Zr, Cu-Ni-Si, Cu-Ag, Cu-Mg is reviewed according to different alloy systems. Finally, the development trend of HSHC Cu alloys is forecasted. It is pointed out that precipitation and micro-alloying are effective ways to improve the performance of HSHC Cu alloys. At the same time, the production of HSHC Cu alloys also needs to comply with the large-scale, low-cost development trend of industrialization in the future.
... Moreover, the presence of inclusions, impurities and porosities in ingots leads to defects in components during plastic deformation of pure copper and has been extensively investigated by many researchers [18][19][20][21][22][23][24][25]. Metallurgical treatments, including the process of deoxygenation, have a significant impact on the microstructure and properties of pure copper castings [10,[26][27][28][29][30]. The use of deoxidizing agents (e.g., phosphorous, magnesium) allows us to acquire copper with very low amounts of gases and other impurities. ...
The aim of this paper was to attain defect free, pure copper castings with the highest possible electrical conductivity. In this connection, the effect of magnesium additives on the structure, the degree of undercooling (ΔTα = Tα-Tmin, where Tα - the equilibrium solidification temperature, Tmin - the minimum temperature at the beginning of solidification), electrical conductivity, and the oxygen concentration of pure copper castings have been studied. The two magnesium doses have been investigated; namely 0.1 wt.% and 0.2 wt.%. A thermal analysis was performed (using a type-S thermocouple) to determine the cooling curves. The degree of undercooling and recalescence were determined from the cooling and solidification curves, whereas the macrostructure characteristics were conducted based on a metallographic examination. It has been shown that the reaction of Mg causes solidification to transform from exogenous to endogenous. Finally, the results of electrical conductivity have been shown as well as the oxygen concentration for the used Mg additives.
... Through its high yield strength CuAl21Mn21 exhibts also a high modulus of resilience and can therefore be considered as a material for spring elements. In contrast to low alloyed copper alloys such as Cu-Ni-Si alloys [6,7,8,9], CuAl21Mn21 is not suitable for applications requiring at least moderate electrical or thermal conductivity. ...
The ternary system Cu-Al-Mn is known for its outstanding technological importance. Cu-Al-Mn alloys have experienced widespread applications as functional or smart materials such as Shape-Memory alloys, Heusler alloys for magnetic applications or alloys with high damping capacity.
In the present contribution, results on an ultra high strength Cu-Al-Mn alloy as well as quasi-equiatomic Cu-Al-Mn are outlined and discussed. The microstructure and mechanical properties of CuAl21Mn21 were characterized by scanning electron microscopy, X-ray diffraction as well as indentation and compression tests. Cast as well as isothermally forged conditions were investigated and compared to copper based metallic glass as an ultra high strength benchmark material. Furthermore, the effect of heat treatment on strength and ductility was investigated. The results demonstrate that CuAl21Mn21 is a relatively light and economic ultra high strength copper alloy with excellent high temperature behavior and wear properties. Even higher strength at elevated temperature can be achieved by quasi-equiatomic Cu-Al-Mn composition. Finally, the properties of Cu-Al-Mn alloys as damping materials are outlined briefly and exemplary results are discussed.
... Through its high yield strength CuAl21Mn21 exhibts also a high modulus of resilience and can therefore be considered as a material for spring elements. In contrast to low alloyed copper alloys such as Cu-Ni-Si alloys [6,7,8,9], CuAl21Mn21 is not suitable for applications requiring at least moderate electrical or thermal conductivity. ...
... For an exceptional safety during the lifetime of copper-based electromechanical connectors and springs, the concurrent increase in strength, formability, bending performance, resistance against fatigue and electrical conductivity are the main prerequisites. Kuhn et al. [16] reported that copper-based connectors and springs show good tolerance during bending, push-pull and torsional loading conditions for a repeated cyclic loading of several million cycles. The processing of Cu-Ni-Si alloys through the application of SPD before precipitation hardening process leads to improvement in mechanical properties, thermal stability, electrical conductivity, and fatigue performance [9]. ...
The objective of this study was to examine the influence of grain refinement on fatigue performance of Cu-2.5Ni-0.5Si-0.06Mg alloy (hereinafter referred to as CuNi3Si1Mg). The results indicate that the fatigue strength of the ultrafine-grained (UFG) CuNi3Si1Mg is about 1.6 times higher than the fatigue strength of the coarse-grained (CG) CuNi3Si1Mg. A detailed investigation of the fracture surfaces using scanning electron microscopy (SEM) showed that the initial microstructure affects the fatigue crack nucleation mechanism. In CG CuNi3Si1Mg, the cracks originated from the activated slip bands, while in UFG CuNi3Si1Mg, the cracks nucleated from the slip bands and twin boundaries.
... However, beryllium exposure to humans during the production process causes lung cancer. Therefore, a variety of beryllium-free medium conductive copper alloys are being used nowadays [9]. As an alternative to Cu-Be alloys, much attention has been focused on Cu-Ni-Si alloys [3,5]. ...
The present work points at estimating the effect of grain refinement on transformation kinetics of precipitates and development of both mechanical properties and electrical conductivity of the CuNi3Si1Mg alloy. Mechanical behaviors of the coarse-grained (CG) CuNi3Si1Mg alloy and the ultrafine-grained (UFG) CuNi3Si1Mg alloy were studied during aging at 450°C with analyzing the Avrami-equation of phase transformation kinetics and the Avrami-equation of electrical conductivity. In the UFG and CG CuNi3Si1Mg alloys the required times that the both conditions approach the maximum strength were 6 and 12 hours, respectively. The transformation kinetics curves of the CG and UFG CuNi3Si1Mg alloys indicated that during over aging, reduction in the growth rate of precipitates and their coarsening resulted in the decrease in strength.
