High-strength Copper Alloys Research Articles

AUSTRAL WRIGHT ALLOY B25 (UNS C17200)

Abstract Austral Wright Alloy B25 (UNS C17200) is a wrought beryllium copper alloy. It provides the highest strength of any copper alloy, with electrical conductivity considerably greater than that of other high-strength copper alloys. Since it is heat treated after forming, it provides excellent formability and ductility. This alloy features good stress relaxation resistance and high fatigue strength. This datasheet provides information on composition, physical properties, hardness, elasticity, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, and joining. Filing Code: Cu-943. Producer or source: Austral Wright Metals.

Influence of processing innovations on joint strength improvements in friction stir welded high strength copper alloys

One of the major challenges in welding the Cu–Cr–Zr alloys is that the high welding temperature often causes the coarsening of the precipitates, resulting in lower joint strength. Various strategies were studied to reduce the welding temperature below the aging temperature for limiting the precipitate coarsening. The results showed that great challenges existed in reducing the friction stir welding (FSW) temperature below the peak-aging temperature of Cu–Cr–Zr alloy (420–480 °C) without using coolant. Through softening the Cu–Cr–Zr alloys to the supersaturated solid solution state prior to FSW, the peak temperature during FSW of Cu–Cr–Zr alloy under water was reduced to ∼481 °C, which is close to the aging temperate of the Cu–Cr–Zr alloy. After post-weld aging heat treatment, the stir zone exhibited higher hardness than the peak-aged Cu–Cr–Zr alloy due to the combination of the high density of precipitates 10.5 nm in diameter and refined grains 0.65 μm in diameter, enabling the achievement of high joint strength equal to the peak-aged base metal. In addition, the FSW zone also exhibited a high electrical conductivity of 88.9% IACS, which is higher than that of the peak-aged base material (81.0% IACS).

High Throughput Calculation and Screening of High Strength and High Conductivity Cu-Cr-Sn Copper Alloy

In this paper, based on the first principles, the exchange correlation functional (GGA) and modified functional (PBE) are used for the calculation of Cu-Cr-Sn high strength and high conductivity copper alloy. The cloud high-throughput cloud computing and screening platform such as Matcloud and cluster expansion method are mainly used. Starting from the most basic components of micro atoms, electrons, ions and energy bands, the high-throughput crystal structure modeling and screening optimization algorithm are adopted, The electronic structure, electromigration and diffusivity of the matrix and the second phase of the material were studied. The theoretical criteria for the collaborative optimization and control of the key performance parameters of the matrix and the characteristic microstructure were established. The characteristic microstructure and material component sequences with excellent mechanical, electrical and thermodynamic properties were predicted and screened.

High Strength and High Electrical Conductivity C70250 Copper Alloy with Fibrous Structure Reinforced by High Density, Multi-Scale Nano-Precipitates and Dislocation

High Strength and High Electrical Conductivity C70250 Copper Alloy with Fibrous Structure Reinforced by High Density, Multi-Scale Nano-Precipitates and Dislocation

Additive manufacturing of high strength copper alloy with heterogeneous grain structure through laser powder bed fusion

Laser powder bed fusion (L-PBF) additive manufacturing was utilized to fabricate high-strength copper (Cu) alloys through inoculation of pure Cu powder with cobalt (Co) submicron particles. It was found that when the addition level of Co is lower than its maximum solid solubility in Cu (4.75 wt.%), the microstructure of Cu-Co alloys is characterized by coarse columnar grains. Further addition of Co over 4.75 wt.% led to a heterogeneous grain structure, with large equiaxed grains or columnar grains near the centers of melt pools whereas ultrafine equiaxed grains sitting on the melt pool boundaries. Microstructure characterization showed that the in-situ formed dual phase nanoparticles with Co shell and cobalt oxide (CoO) core acted as heterogeneous nucleation sites of Cu, which allowed ultrafine, equiaxed grains to form. The heterogeneously structured as-built Cu-Co alloy achieved a tensile strength of 381.4 ± 2.9 MPa and an elongation of 31.6 ± 1.3%. Co nanoprecipitation driven by post L-PBF heat treatment further increased the tensile strength of the Cu-Co alloy up to 491.1 ± 12.6 MPa without notably sacrificing the ductility. The combination of high strength and high ductility distinguishes Cu-Co alloys from most conventionally and additively manufactured Cu alloys. This study shows a strategy to produce Cu alloys with high performance through remarkable grain refinement by heterogeneous nucleation.

Additive Manufacturing of High Strength Copper Alloy With Heterogeneous Grain Structure Through Laser Powder Bed Fusion

The low laser processability of pure copper (Cu) commonly causes high porosity, and therefore low strength of additively manufactured (AMed) Cu parts. The current work reports an effective approach to solve this problem through inoculation of pure Cu powder with cobalt (Co) submicron particles. Co addition enabled increase in laser absorptivity, and therefore dense Cu was fabricated through laser powder bed fusion even though typical AM featured coarse columnar grains were produced when Co addition was 4 wt.% or less. Significant grain refinement with heterogeneous grain structure (HGS) was achieved when the addition level was greater than the maximum solid solubility of Co in Cu (4.75 wt.%), such as 6 and 8 wt.%. HGS is characterized with ultrafine equiaxed grains close to melt pool boundaries and coarser equiaxed grains or columnar grains near centres of melt pools. Heterogenous nucleation of Cu near melt pool boundaries, where were associated with larger thermal undercooling due to faster cooling rate, was responsible for the formation of ultrafine equiaxed grains. In contrast, heterogeneous nucleation near centres of melt pools was suppressed. Detailed substructure examination indicated that heterogenous nucleation occurred on dual phase nanoparticles containing Co shell and cobalt oxide (CoO) core. The higher affinity of Co to oxygen caused formation of CoO. HGS of Cu significantly improved both strength and ductility. After direct ageing at 600°C for one hour, a tensile strength of 491.1±12.6 MPa, elongation of 27.3±2.5% and electrical conductivity of 61.5% IACS (International Annealed Copper Standard) were achieved.

High-temperature deformation behavior of a novel high strength and high elasticity Cu–20Ni–20Mn–0.3Nb–0.3Cr–0.1Zr alloy

The elongation of high-strength copper alloy with tensile strength over 1300 MPa is generally less than 3%. In this paper, a novel Cu–20Ni–20Mn-0.3Nb-0.3Cr-0.1Zr(wt.%) alloy was prepared, of which the tensile strength, elastic modulus and elongation is 1445 MPa, 147 GPa and 6.8%, respectively. The flow stress strain and microstructure evolution during high temperature deformation at different strain temperatures and strain rates are studied to obtain the high temperature deformation law and dynamic recrystallization mechanism of the alloy. The research shows that the flow stress of the design alloy increases rapidly with the increase of the strain during the initial stage of thermal deformation. When the strain rate is higher and the strain temperature is lower, the peak value of flow stress is larger. The thermal activation energy of the designed alloy is 353.31 kJ/mol. When the strain temperature is 650°C–720 °C and the strain rate is 0.1s−1-5s−1, the alloy is in the hot deformation instability zone. The optimal deformation temperature of the alloy is 750°C–850 °C. When the deformation temperature reaches 800 °C, dynamic recrystallization occurs in the alloy structure. When the design alloy is deformed at a temperature of 850 °C, the recrystallization power of the alloy is mainly the deformation stress energy, and the degree of recrystallization mainly depends on the strain rate. At this time, the faster the strain rate is, the more obvious the recrystallization effect is, and even the recrystallization grain growth will occur.

Severe Plastic Deformation of Copper, Binary Cu-Zn Solid-Solution Alloys, and High-Strength Brass by High-Pressure Torsion

Severely-deformed high-strength brasses were investigated by leveraging high-pressure torsion (HPT) processing in order to obtain more enhanced mechanical properties of copper alloys. Pure copper, binary Cu-Zn solid-solution alloys and high-strength brasses including aluminum and manganese additions were selected for experiments. For comparison of these materials, zinc equivalent parameter was used. These materials were subjected to the HPT processing, followed by hardness tests and tensile tests. The maximal hardness value of the nanostructured high-strength brass with β phase matrix was reached 420 HV. The HPT processed high-strength brass with β phase matrix showed significant increase in the yield stress and tensile strength with sacrificing ductility. The tensile specimen of the high-strength brass with β phase matrix was fractured before initiation of necking. It was found that utilizing β phase matrix is also beneficial for controlling enhanced strength of high-strength copper alloys for not only casting process but also severe plastic deformation.

Stress relaxation behaviors and mechanical properties of precipitation strengthening copper alloys

In order to measure cantilever bending stress of elastic alloys during stress relaxation experiment, a homo-made apparatus has been developed. The mechanical properties and stress relaxation resistances of three high strength copper alloys have been investigated. Considering different experimental conditions, the Cu-Ni-Sn alloys exhibit the optimum stress relaxation resistance. The mechanisms of stress relaxation and precipitation strengthening have been discussed. The hardness is recommended to be a critical parameter which can be used to evaluate the stress relaxation resistance simply. Because the interactions between precipitation particles and dislocations which influence the hardness also affect the dynamic recovery of mobile dislocations during stress relaxation. Finally, two effective methods have been proposed to slow down the stress relaxation in the copper alloys.

Microstructure and properties of a novel ultra-high strength, high elasticity and high plasticity Cu–20Ni–20Mn-0.3Nb-0.3Cr-0.1Zr alloy

The elongation of high-strength copper alloy with tensile strength over 1300 MPa is generally less than 3%. In this paper, a novel Cu–20Ni–20Mn-0.3Nb-0.3Cr-0.1Zr (wt.%) alloy with high strength, high elasticity and high plasticity was prepared. Its tensile strength, elastic modulus and elongation is 1445 MPa, 147 GPa and 6.8%, respectively. On the basis of Cu–20Ni–20Mn alloy, microalloying Nb, Cr, Zr elements were added to restrain discontinuous precipitation and improve the properties of the alloys. By matching reasonable heat treatment process, a fine and highly uniform grain structure was obtained, which is the main reason for the increase of elongation. TEM and 3DAP results suggested that a large number of nanoscale NiMn precipitates are the main source of high strength in the alloy. The designed alloy has excellent comprehensive properties, which can be used for the preparation of precision sensing parts, elastic components.

Development of Lead-Free High-Strength Copper Alloy

Development of Lead-Free High-Strength Copper Alloy

Mechanochemical processing of Cu-Y2O3 alloy by MA-HIP for heat sink materials application

Fabricating high-strength copper (Cu) alloys with high conductivity are extremely desirable for a range of applications, such as heat sink materials in fusion reactors. This study reports an in-situ mechanochemical process combining Mechanical Alloying (MA) and Hot Isostatic Pressing (HIP) to prepare Cu-Y2O3 composites. It is found that MA of Cu and Y powders led to formation of a Cu(Y) solid solution, accompanied by lattice expansion, grain refinement, melting point decline, and hardness increase. When the Cu(Y) solid solution powder was milled with CuO powder, reaction between Cu(Y) and CuO occurred, with a shrinkage of the lattice, and increase in both the melting point and hardness. The MA powder was then consolidated by HIP, and the existence of Y2O3 was confirmed by X-ray diffraction. An unexpected decrease of the electrical conductivity of the consolidated bulk material was observed and the reason was analyzed. This study will provide helpful information to optimize the preparation of copper-based materials through process control.

Development of a new class of high strength copper alloy using immiscibility route in Cu-Fe-Si system: Evolution of hierarchical multi-scale microstructure

In this paper, a new high strength copper based alloy (Cu-20 at%Fe-5 at% Si) in Cu-Fe-Si system is reported that is designed by accessing submerged liquid miscibility gap of the Cu-Fe system and ternary addition of Si for a hierarchical design of microstructure. The alloy was synthesized by suction casting of the melt into a copper mould. This paper further elucidates the sequence of evolution of metastable phases in the microstructure due to non-equilibrium solidification through detailed characterizations of the microstructure of the alloy using transmission electron microscopy. The microstructure containing particles with globular morphology of the Fe-rich DO3 ordered phase suggests its origin in the liquid state consistent with the expectation of a metastable liquid immiscibility. The solute rejection process during the later stage of solidification and the solid state cooling results in the evolution of Fe rich nano sized fully coherent ordered particles in the Cu-rich matrix. This particular alloy has achieved an excellent mechanical strength both at room temperature and at elevated temperature. The correlations between microstructure and mechanical behavior have been discussed in details.

Transient Liquid Phase Bonding of Cu-Cr-Zr-Ti Alloy Using Ni and Mn Coatings: Microstructural Evolution and Mechanical Properties

High-strength copper alloys are used extensively in the regenerative cooling parts of aerospace structures. Transient liquid phase (TLP) bonding of a Cu-Cr-Zr-Ti alloy was attempted in the present study using thin layers of elemental Ni and Mn coatings applied by electroplating. One of the base metals was given a Ni coating of 4 µm followed by a Mn coating of 15 µm, while the other base metal was given only the Ni coating (4 µm). The bonding cycle consisted of the following: TLP stage—heating to 1030 °C and holding for 15 min; homogenization stage—furnace cooling to 880 °C and holding for 2 h followed by argon quenching to room temperature. Detailed microscopy and electron probe microanalysis analysis of the brazed joints were carried out. The braze metal was found to undergo isothermal solidification within the 15 min of holding time at 1030 °C. At the end of TLP stage, the braze metal showed a composition of Cu-17Ni-9Mn (wt.%) at the center of the joint with a steep gradient in Ni and Mn concentrations from the center of the braze metal to the base metal interfaces. After holding for 2 h at 880 °C (homogenization stage), the compositional gradients were found to flatten significantly and the braze metal was found to develop a homogeneous composition of Cu-11Ni-7Mn (wt.%) at the center of the joint. In lap-shear tests, failures were always found to occur in the base metal away from the brazed region. The copper alloy base metal was found to undergo significant grain coarsening due to high-temperature exposure during brazing and, consequently, suffer considerable reduction in yield strength.

Ultrafine-Grained High Strength Cu-Ni-Si Alloys

Ultrafine-grained (UFG) pure copper has been in the focus of materials scientists over the last two decades, however ultrafine-grained high-strength copper alloys have scarcely been processed or characterized so far industrially.In this contribution, UFG copper alloys, especially Cu-Ni-Si alloys, being well known as ideal materials for electromechanical connectors, springs and leadframes, are presented. Precipitation hardened Cu-Ni-Si alloys are a well established and technologically important class of materials for a wide range of applications where high strength and good conductivity are required. Yield strength and fatigue properties of metallic alloys can be significantly enhanced by severe plastic deformation methods. In contrast to other strengthening methods such as solid solution hardening, severe plastic deformation leads to a weaker decrease of electrical conductivity and is therefore a means of enhancing strength while maintaining acceptable conductivity for current bearing parts and components. Characterization of these materials after severe plastic deformation by swaging, wire drawing and subsequent aging was carried out using conductivity-, hardness-and tensile tests as well as highly-resolved microstructural characterization methods.The results reveal that UFG low alloyed copper alloys exhibit impressive combinations of properties such as strength, conductivity, high ductility as well as acceptable thermal stability at low and medium temperatures. By a subsequent aging treatment the severely plastically deformed microstructure of Cu-Ni-Si alloys can be further enhanced and thermal stability can profit from grain-boundary pinning by precipitated nanoscale nickel silicides.

Design, Fabrication, and Test of a High-Strength Uniform Pressure Actuator

Electromagnetic forming using a uniform pressure actuator (UPA) has advantages for forming many components, such as car door pockets, cell phone cases, and fuel cell panels. However, how to generate magnetic pressures on sheet metal with enough high uniformity and high strength is a challenging issue. To improve the strength of the coil, current UPAs were machined out of a solid block of high-strength copper alloy, but its strength was still limited. In this paper, the design idea of pulsed high-field magnets has been applied to improve the coil's strength in a better way. A UPA with high strength has been designed, fabricated, and tested. A series of simulation analysis and experiments have been done; it has been found that the uniformity of the magnetic force on sheet would be increased with the decrease of the wire spacing and the wire width. In addition, the experiment results show that sheets with a thickness of 1 mm can be effectively deformed with a maximum of 14.6 mm under 2.88-kJ energy and the deformation of the sheet is in high uniformity along the direction perpendicular to the wire.

強度と導電性に優れた車載端子用固溶型銅合金「MSP<sup>®</sup>5」の開発

強度と導電性に優れた車載端子用固溶型銅合金「MSP<sup>®</sup>5」の開発

Applicability of Scheil–Gulliver solidification model in real alloy: a case study with Cu-9wt%Ni-6wt%Sn alloy

The present work explores the possibilities of the application of Scheil–Gulliver equation in modelling the solidification of a real alloy. For this study, Cu-9 wt%Ni-6 wt%Sn alloy was chosen which exhibits profuse micro-segregation during solidification, and hence easy to quantify experimentally. Also, this alloy is spinodally strengthened high strength copper alloy and has industrial importance. In this study, thermodynamic assessment using Scheil–Gulliver solidification model was carried out. Subsequently, the assessed result was compared with the experimentally obtained results from energy-dispersive X-ray spectroscopy analysis, and a good agreement was observed between these results. Therefore, it could be concluded that the solidification of this particular alloy system can be modelled using Scheil–Gulliver equation.

Ultrafine-Grained Precipitation Hardened Copper Alloys by Swaging or Accumulative Roll Bonding

There is an increasing demand in the industry for conductive high strength copper alloys. Traditionally, alloy systems capable of precipitation hardening have been the first choice for electromechanical connector materials. Recently, ultrafine-grained materials have gained enormous attention in the materials science community as well as in first industrial applications (see, for instance, proceedings of NANO SPD conferences). In this study the potential of precipitation hardened ultra-fine grained copper alloys is outlined and discussed. For this purpose, swaging or accumulative roll-bonding is applied to typical precipitation hardened high-strength copper alloys such as Corson alloys. A detailed description of the microstructure is given by means of EBSD, Electron Channeling Imaging (ECCI) methods and consequences for mechanical properties (tensile strength as well as fatigue) and electrical conductivity are discussed. Finally the role of precipitates for thermal stability is investigated and promising concepts (e.g. tailoring of stacking fault energy for grain size reduction) and alloy systems for the future are proposed and discussed. The relation between electrical conductivity and strength is reported.

Material properties of high-strength beryllium-free copper alloys

High strength copper alloys can be produced either by generating very fine grained low alloyed single phased or precipitation hardened copper alloys or by highly alloyed precipitation hardened copper alloys. The latter process requires special processing methods such as spray forming in order to achieve a sufficiently homogeneous microstructure. Systematic investigations on the aging behaviour of the highly alloyed nickel-manganese bronze CuNi20Mn20 demonstrate that fully crystalline copper alloys with hardness exceeding 500 HV can be produced. In addition to age hardening, swaging or severe plastic surface deformation can be used for additional grain refinement and strain hardening before precipitation hardening. In contrast to CuMn20Ni20, the low-alloyed precipitation hardened copper alloy CuNi3Si1Mg exhibits excellent thermal and electrical conductivity while maintaining acceptable strength after swaging and precipitation hardening. Finally, a systematic comparison between spray-formed or precipitation high strength hardened copper alloys and classical well-known materials such as steels or aluminium alloys was carried out by using material property charts (Ashby-maps) and highlighting the fields of application and unique property combinations of copper alloys.