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High strength, high conductivity copper alloys that can resist creep at high temperatures are one of the primary candidates for efficient heat exchangers in fusion reactors. Cu–Cr–Nb–Zr (CCNZ) alloys, which were designed to improve the strength and creep life of ITER Cu–Cr–Zr (CCZ) reference alloys, have been found to have comparable electrical conductivity and tensile properties to CCZ alloys. The measured creep rupture times for these improved alloys is about ten times higher than the ITER reference alloys at 90–125 MPa at 500 °C. However, the effects of neutron irradiation on these alloys, and the ensuing material properties, have not been studied; thus, their utility in a fusion reactor environment is not well understood. This study characterizes the room temperature mechanical and electrical properties of a neutron-irradiated CCNZ alloy and compares them to a neutron-irradiated ITER reference heat sink CCZ alloy. Tensile specimens were neutron irradiated in the High Flux Isotope Reactor (HFIR) to 5 dpa between 250 °C and 325 °C. Post-irradiation characterization included electrical resistivity measurements, hardness, and tensile tests. Microstructural evaluation used scanning electron microscopy, energy dispersive x-ray spectroscopy, and atom probe tomography to characterize the irradiation-produced changes in the microstructure and investigate the mechanistic processes leading to post-irradiation properties. Transmutation calculations were validated with composition measurements from atom probe data and used to calculate contributions to the increased electrical resistivity measured after irradiation. Comparisons with CCZ alloys in the same irradiation heat found that the post-irradiated CCNZ and CCZ alloys had comparable electrical resistivity. Although CCNZ alloys suffered more irradiation hardening than CCZ, the overall tensile behavior deviated very little from non-irradiated values in the temperature range studied. [ABSTRACT FROM AUTHOR]

The interfacial bonding characteristics of ceramic reinforced phase and metal matrix in metal matrix composites have a significant impact on their strength. Herein, the interfacial bonding properties and alloy element doping of the Cu/TiC interface in TiC-reinforced Cu matrix composites with a stoichiometric ratio of TiC of 1:1 were investigated by atomistic DFT simulations. The analysis of twelve Cu/TiC interfacial models reveals that the TiC(111) in Cu/TiC interface with C-terminated is more stable than that of TiC(111) interface with Ti-terminated due to the stronger covalent bonds formed by Cu-C. The Cu(110)/TiC(111)-C interface with the highest work of adhesion (2.871 J/m2) is the most stable interface among these Cu/TiC interfaces. Moreover, the Cu-Co/TiC interface has the highest W a d (4.223 J/m2) compared to Cu/TiC, Cu-Ni/TiC, and Cu-Zn/TiC interfaces. And the Cu-Zn/TiC interface has the lowest W a d (2.092 J/m2), which is even lower than that of the Cu/TiC interface (2.306 J/m2). During interfacial tension, the Cu/TiC, Cu-Ni/TiC, and Cu-Zn/TiC interfaces start to fracture either at the interface layer or the sub-interface layer on the Cu side, while the Cu-Co/TiC interface begins to fracture within the Cu slab. The Cu-Co/TiC interface has the highest tensile strength of 20.12 GPa at14 % strain compared to Cu/TiC (14.76 GPa), Cu-Ni/TiC (16.35 GPa), and Cu-Zn/TiC (15.30 GPa) interfaces, which is attributed to the strengthening of both the interface and sub-interface by Co doping. Thus, Co doping in the Cu matrix significantly strengthens the Cu/Ti interfacial bonding, Ni doping has a weaker strengthening effect, and zinc doping weakens the interfacial bonding. [ABSTRACT FROM AUTHOR]

Cu alloys have been widely used in the manufacture of liners because of their high density, good plasticity, and excellent thermal conductivity. In order to achieve excellent jet stability and penetration performance, it is necessary to further improve the mechanical properties of Cu-based liners. Nevertheless, the simultaneous enhancement of strength and ductility of the Cu alloys remains a huge challenge due to the strength–ductility trade-off phenomenon of metals/alloys. In this study, the microstructure evolution of rare earth Nd-modified Cu alloy and its effect on mechanical properties were investigated using OM, SEM, EBSD, and TEM techniques. The results show that the ultimate tensile strength (218 MPa) and elongation (50.7%) of sample 1 without Nd are the lowest. With increasing Nd content; the tensile strength and elongation of the samples increase; and the mechanical properties of sample 4 are the best, with a tensile strength of 278.6 MPa and elongation of 65.2%. In addition, with the increase in Nd content, not only is the grain size of the Cu-Nd alloy refined, but also the strength and plasticity are improved so that the strength–ductility trade-off phenomenon is improved. The strength improvement is mainly attributed to grain refinement strengthening, dispersion strengthening, and strain hardening. The increase in ductility is mainly related to the improvement of the microstructure heterogeneity by the Nd element. [ABSTRACT FROM AUTHOR]

The corrosion behavior of Al/Ni-doped Cu alloys in seawater environments was investigated. Results indicated that increasing immersion temperature significantly worsened the corrosion resistance of Cu alloys in soil simulation and 3.5 wt.% NaCl solution. With the increase of stray current densities, the proportion of CuCl was significantly increased. The presence of stray current seriously destroyed the oxide film on the sample surface, thereby resulting in the deterioration of corrosion resistance. [ABSTRACT FROM AUTHOR]

With the development of modern technology, the construction industry, and navigation technology, the metal Cu alloy has become an important metal material in mainstream industrial applications. As an indispensable basic metal material in the field of science and technology, its problem with corrosion is still a long-term problem that scientists have been working to solve. In this paper, air spraying technology is used to prepare an Al2O3-PDMS composite coating. By adjusting the content of Al2O3, the surface of the Cu alloy can reach different wetting states. The results show that the corrosion potential of the as-prepared superhydrophobic Al2O3-PDMS coating increases by 70 mV compared with the substrate, the corrosion current density decreases by one order of magnitude, and the impedance modulus increases from 2000 to 12,000 Ω⋅cm2, indicating a significantly enhanced corrosion resistance. It also possesses excellent anti-pollution and anti-icing behaviors, thereby allowing them to work in harsh industrial conditions. [ABSTRACT FROM AUTHOR]

High strength, high conductivity copper alloys that can resist creep at high temperatures are one of the primary candidates for efficient heat exchangers in fusion reactors. Cu–Cr–Nb–Zr (CCNZ) alloys, which were designed to improve the strength and creep life of ITER Cu–Cr–Zr (CCZ) reference alloys, have been found to have comparable electrical conductivity and tensile properties to CCZ alloys. The measured creep rupture times for these improved alloys is about ten times higher than the ITER reference alloys at 90–125 MPa at 500 °C. However, the effects of neutron irradiation on these alloys, and the ensuing material properties, have not been studied; thus, their utility in a fusion reactor environment is not well understood. This study characterizes the room temperature mechanical and electrical properties of a neutron-irradiated CCNZ alloy and compares them to a neutron-irradiated ITER reference heat sink CCZ alloy. Tensile specimens were neutron irradiated in the High Flux Isotope Reactor (HFIR) to 5 dpa between 250 °C and 325 °C. Post-irradiation characterization included electrical resistivity measurements, hardness, and tensile tests. Microstructural evaluation used scanning electron microscopy, energy dispersive x-ray spectroscopy, and atom probe tomography to characterize the irradiation-produced changes in the microstructure and investigate the mechanistic processes leading to post-irradiation properties. Transmutation calculations were validated with composition measurements from atom probe data and used to calculate contributions to the increased electrical resistivity measured after irradiation. Comparisons with CCZ alloys in the same irradiation heat found that the post-irradiated CCNZ and CCZ alloys had comparable electrical resistivity. Although CCNZ alloys suffered more irradiation hardening than CCZ, the overall tensile behavior deviated very little from non-irradiated values in the temperature range studied.

With the continuous integration of semiconductor devices, the requirements of the size accuracy and surface quality of etched lead frames are stricter. The etchant is a key factor in the etching process and etched surface quality, while the effects of the difference in etchants on the etched surface morphology of Cu alloy have not been directly studied. In this study, aqua regia, acidic FeCl3 and two CuCl2 solutions were used as etchants, and different CuCrSn specimens were etched and characterized. The results show that the etching rate in aqua regia is high, and the grain orientation, grain boundary (GB) and dislocations have significant influences on the local etching rate. The preferential etching of some atomic planes forms steps between the grains with different orientations, and preferential etching around the GB and dislocation group forms grooves, resulting in high surface roughness. For the surfaces etched by the FeCl3 and CuCl2 etchants, the steps and grooves are blurred; thus, they are less rough. The CuCrSn alloy surface etched by the aqua regia is clean, with little Cr-rich particles, while high-density Cr-rich particles remain on the surfaces etched by the FeCl3 and CuCl2 etchants. For the same kind of etchant, the ion concentration can affect the etching mechanism, rate and the etched surface morphology. [ABSTRACT FROM AUTHOR]

The phase transformation dynamic and electrical conductivity equations of the aged Cu-2.7Ti-2.5Ni-0.8V alloy were established in this work. The microstructure evolution and precipitated phases were characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The mechanical properties were tested using a hardness testing machine and universal test machine, and the electrical conductivity was measured by the eddy conductivity gauge. The results show that NiTi intermetallic compounds are formed during the solidification, and these phases such as Ni3Ti and NiV3 are precipitated after aging treatment. The fracture morphology displays that a large number of shallow and equiaxed dimples occur on the tensile fracture, indicating a typical ductile fracture. After aging treatment at 450°C for 240 min, the hardness, tensile strength, elongation and electrical conductivity of the Cu-2.7Ti-2.5Ni-0.8V alloy are 184 HV, 459 MPa, 6.3% and 28.72% IACS, respectively.

In this study, the ultrafine-grained (UFG) Cu–5Mn alloys were prepared by friction stir processing (FSP) to investigate the influence of short-range ordering (SRO) on the tensile deformation behavior. Due to the dynamic recrystallization, the uniform and equiaxed UFG microstructures were obtained in FSP Cu–5Mn alloys with low density of dislocations, high fraction of high-angle grain boundaries, high Taylor factor and high degree of recrystallization. The introduction of Mn atoms into the Cu matrix cannot change the stacking fault energy apparently but increase the SRO degree. Although the dominant mechanism was still the wavy slip of dislocation, the planar slip of dislocations was motivated and many twin layers were observed in the ultrafine grains of FSP Cu–5Mn alloy. The change of SRO degree can significantly improve the dislocation storage capacity during the tensile deformation process, and promote the improvement of the strain-hardening rate, resulting in an excellent strength-ductility match in FSP UFG Cu–5Mn alloy.

Since Cu exhibits the highest electrical conductivity among base metals and common metals, pure Cu and dilute Cu alloys are widely used as functional materials for electrical components and power transmission materials. It is also expected that in the future, conductive pure Cu and Cu alloys will continue to be used according to the desired properties by understanding inherent characteristics of pure Cu and Cu alloys. This paper reviews factors such as the contribution of lattice defects and solute elements to the electrical conductivity of pure copper, and factors affecting strengthening processes such as precipitation hardening, solid solution hardening, and work hardening in dilute Cu alloys. In precipitation hardening, the type and amount of alloying elements added and the precipitation treatment are adjusted, but softening of the Cu alloy due to overaging must be avoided. In solid solution hardening, the type and amount of alloying elements are also optimized, often in combination with work hardening. Although work hardening generally results in changes in elongation and strength after processing, the decrease in electrical conductivity due to dislocations is small. Therefore, it is effective to combine work hardening with solid solution hardening and other processes. Microstructural characterization using analytical techniques have been conducted to elucidate the electrical conductivity and strengthening mechanisms of these alloys. Their findings are useful in controlling the conductive and mechanical properties of advance Cu alloys. This review also demonstrates the usefulness of these characterization methods. [ABSTRACT FROM AUTHOR]

The North Eastern Baltic has no copper resources of its own, meaning that Cu alloy was imported either as raw material or as finished objects. The north‐eastern coastline of Estonia during the late pre‐Roman and Roman Iron Age was connected to the south by sea to the long‐distance 'amber' trade route and to the east by Russian river systems. This study quantitatively assesses the direction of the Cu alloy supply in the region before and after brass enters circulation at the beginning of the Roman Iron Age. After an initial portable X‐ray fluorescence (pXRF) survey, 18 objects were chosen for Pb isotope analysis. This isotope analysis resolved a group of nine brass artefacts from the Roman Iron Age amongst a 'melting pot' of other Cu alloys. The similarity between the isotope ratios found in the Roman world suggests the presence of the same 'melting pot' in the North Eastern Baltic, possibly created by a large amount of Roman Cu alloy being traded north. No evidence for Cu alloy from Scandinavia or the Ural Mountains could be found. The hypothesis from this small study is that the Cu alloy entering Estonia was dominated by metal from Southern Europe from the late pre‐Roman Iron Age and the Roman period. [ABSTRACT FROM AUTHOR]

In this paper, by adding Cu alloy or Ni‐Au layer to Cu pad surface reduced the occurrence of pseudo welding and improve the rework strength and promoted the product stability and reliability. [ABSTRACT FROM AUTHOR]

Ag and Cu have different advantages and are widely used in key fields due to their typical highly electrical and thermal conductive (HETC) properties. Laser powder bed fusion (LPBF), an innovative technology for manufacturing metallic multi-material components with high accuracy, has expanded the application of Ag–Cu in emerging high-tech fields. In this study, the multi-material sandwich structures of Ag7.5Cu/Cu10Sn/Ag7.5Cu were printed using LPBF, and the formation mechanism, interface characteristics, and molten pool behavior of the Ag7.5Cu/Cu10Sn (A/C) and Cu10Sn/Ag7.5Cu (C/A) interfaces were studied to reveal the influence of different building strategies. At the A/C interface, pre-printed Ag7.5Cu promoted Marangoni turbulence at a relatively low energy density (EA/C = 125 J/mm3). Due to the recoil pressure, the molten pool at the A/C interface transformed from a stable keyhole mode to an unstable keyhole mode. These phenomena promoted the extensive migration of elements, forming a wider diffusion zone and reduced thermal cracking. At the C/A interface, the molten pool was rationed from the conduction mode with more pores to the transition mode with fewer defects due to the high energy density (EC/A = 187.5 J/mm3). This work offers a theoretical reference for the fabrication of HETC multi-material structures via LPBF under similar conditions. [ABSTRACT FROM AUTHOR]

The creep behavior of the CuCrZr alloy, used in the combustion chamber wall of reusable launch vehicles, was investigated at 600-700 K and 150–250 MPa. Results demonstrate significant differences in the creep behavior, microstructure evolution including texture component, dislocation configurations and cavities at 600 K and 700 K, particularly at 250 MPa. At 600 K, the creep life exceeds 400 h, while at 700 K it drops below 0.5 h. The texture components evolved at 600 K-250 MPa are more balanced between hard texture (Brass texture) and soft texture (Goss texture and R-Goss texture). The texture components at 700 K-250 MPa are integrally biased toward the soft texture, implying that it is favorable to accelerate creep strain. The introduced high-density dislocations before creep act as an effective barrier to impede the motion of dislocations at 600 K, inducing long-time dynamic balance of work hardening and recovery softening, while the pre-creep dense dislocations act as an energy supplement at 700 K, promoting that recovery softening dominates the creep process. The dense dislocations can provide energetic support for cavity nucleation. • Creep of CuCrZr was tested at typical service conditions of combustion chamber. • CuCrZr exhibited different creep life between 600 K-250 MPa and 700 K-250 MPa. • Ratio of hard to soft orientation plays important role in creep behavior of CuCrZr. • Pristine dislocations hinder following dislocation move when creep at 600 K. • Pristine dislocations promote recovery softening when creep at 700 K. [ABSTRACT FROM AUTHOR]

This paper investigated the influence of deep cryogenic treatments (DCT) on the tensile strength, elongation to fracture and conductivity of a deformation-processed Cu-Ni-Co-Si alloy. The tensile properties were measured using a mechanical testing machine. The conductivity was evaluated using a low-resistance tester. The microstructure and precipitated phases were analyzed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), an energy dispersive spectrometer (EDS) and an X-ray diffractometer (XRD). The tensile strength, elongation to fracture and conductivity of the Cu-1.34Ni-1.02Co-0.61Si alloy before and after cold rolling at 47% reduction increased with increasing DCT time and tended to be stable at about 36 h. The microstructure became more uniform after the DCT. The grain size was refined and was smallest after DCT for 48 h. The DCT promoted the precipitation of the solid solution elements Ni, Co and Si from the Cu matrix to form many fine and evenly distributed 20–70 nm spherical second-phase particles in the grains and grain boundaries. [ABSTRACT FROM AUTHOR]

The study investigates the effect of heat treatment on the microstructure evolution and properties of an age-hardened ­Cu-3Ti-2Mg alloy. The precipitated Cu2Mg and β'-Cu4Ti phases consequently yield a depletion of the Cu matrix in regards to Ti and Mg solutes, which enhances the electrical conductivity. The Cu2Mg Laves phase and β'-Cu4Ti phase precipitates increase the hardness of the alloy due to the consistency and coherency of the later phase. However, the decrease of hardness is mainly associated with the coarse microstructures, that can be formed due to the phase transformation from metastable β'-Cu4Ti phase to more stable Cu3Ti phase. In the range of experiments, the optimum process is solution treatment at 700°C for 4 h, with subsequent age-hardening at 450°C for 4 h. The electrical conductivity, hardness, tensile strength, and elongation of the Cu-3Ti-2Mg alloy were 15.34 %IACS, 344 HV, 533 MPa, and 12%, respectively.

Phase morphology and the distribution of the strengthening phase generally have a strong influence on the movement of dislocations. The presence of minor alloying element Mg in Cu–30Fe alloy significantly affects both the morphology and distribution of the strengthening phase. Dendritic α-Fe is transformed into a spherical morphology because of changes in the chemical composition during the solidification process. The presence of Mg leads to the formation of secondary phase-separated Cu within the α-Fe phase and to increasing heterogeneity of the gradient size of the α-Fe phase. The increased volume fraction of α-Fe enhanced by secondary separated Cu, refinement of α-Fe, and the degree of distribution enhanced the yield strength of this alloy by 40% compared with that of Cu–30Fe. This result can be used as a guide to modifying the morphology of Cu–Fe alloys and improve understanding of strengthening mechanism of this system.

This paper focuses on the improvement of hybrid Cu/Al weld performance via a combination of self-reacting brazing mechanism (for stable metallurgical transformation) and process modification approach (for the elimination of tool profile-induced stress-raiser). The modified friction stir clinching-brazing (MFSC-B) and friction stir spot welding-brazing (FSSW-B) of dissimilar AA5083-H321 aluminum and commercially pure Cu alloys are investigated with the use of a thin Zn intermediate layer. The load-bearing capacity, fracture behavior, and microstructure of the respective joints are investigated and compared. The results show that plausible intermetallic phases of Al–Cu (Al2Cu and Al4Cu9) and Cu–Zn are present at the stir zones of all the joints while the brazed zone of the MFSC-B joint is predominated by uniform lamellar eutectic structure due to higher heat input, localized two-fold Zn melting, and frictional-stirring activated eutectic transformation. The increase in the load-bearing area (brazed + stir zones) of the MFSC-B joint improved the fracture resistance of the joint by 59% as the average tensile-shear loads of about 7.0 and 4.4 kN were obtained in the MFSC-B and FSSW-B joints respectively. The use of MFSC-B is thus recommended as a reasonable alternative for improving the weld performance of dissimilar reactive metals.

Ag and Cu have different advantages and are widely used in key fields due to their typical highly electrical and thermal conductive (HETC) properties. Laser powder bed fusion (LPBF), an innovative technology for manufacturing metallic multi-material components with high accuracy, has expanded the application of Ag–Cu in emerging high-tech fields. In this study, the multi-material sandwich structures of Ag7.5Cu/Cu10Sn/Ag7.5Cu were printed using LPBF, and the formation mechanism, interface characteristics, and molten pool behavior of the Ag7.5Cu/Cu10Sn (A/C) and Cu10Sn/Ag7.5Cu (C/A) interfaces were studied to reveal the influence of different building strategies. At the A/C interface, pre-printed Ag7.5Cu promoted Marangoni turbulence at a relatively low energy density (EA/C = 125 J/mm3). Due to the recoil pressure, the molten pool at the A/C interface transformed from a stable keyhole mode to an unstable keyhole mode. These phenomena promoted the extensive migration of elements, forming a wider diffusion zone and reduced thermal cracking. At the C/A interface, the molten pool was rationed from the conduction mode with more pores to the transition mode with fewer defects due to the high energy density (EC/A = 187.5 J/mm3). This work offers a theoretical reference for the fabrication of HETC multi-material structures via LPBF under similar conditions.

With increasing integration of the semiconductor devices, the requirements on size accuracy and surface quality of the lead frame are higher. Cold-rolling and low-temperature aging are usually used in processing of the Cu alloy for lead frame, which generate/eliminate the deformation defects that affect the etched surface morphology and roughness, while the influence mechanisms have not been well revealed. In this study, the CuCrSn alloy was used as the experimental material, which was cold-rolled to different degree and then aged at 450 °C for different time, and the microstructures and etched surfaces of the specimens were characterized. The results show that etched surface morphologies of grains with different orientations in the coarse-grained Cu alloy are different. With increasing cold-rolling deformation, the influences of grain orientation become less obvious, and the dislocation groups on the slip planes result in grooves approximately parallel to the rolling direction, meanwhile the surface uniformity are improved and the surface roughness decreases. For the 80 % cold-rolled Cu alloy, the density of grooves decreases with increasing aging time and elimination of the dislocations, and the etched surface roughness decreases firstly and then tends to be stable. The etched surface changes significantly and the surface roughness increase obviously after recrystallization of the specimen. • The etching behaviors of the cold-rolled and aged CuCrSn were investigated. • The effects of grain orientation decrease with after a large cold-rolling. • The etched surface is more uniform and its roughness decreases after cold-rolling. • Dislocation groups and vacancy defects dominate the etched surface morphology. • A significant change of the etched surface morphology occurs after recrystallization. [ABSTRACT FROM AUTHOR]

Dispersion-strengthened (DS) copper alloys with Y2O3 particles are known as high strength and high thermal conductivity materials having potential for heat sink materials of fusion devices. In the previous study on mechanical alloying (MA) and hot isostatic pressing (HIP) processing of DS-Cu alloys, the MA powders showed various morphology and size distribution which influenced the properties of the MA-HIP samples. In this study, the MA alloyed powders with 3 wt% Y2O3 particles were classified by their size and characterized. The particles ranged from fine particles of under 46 μm to coarse particles of 212 μm over, and a wide particle size distribution was confirmed. The peeled Cu-O fragments from coarser MA powders are the main source of finer grain with 46 μm. The finer grains had oxide-like behavior as microstructural and mechanical properties. On the other hand, the coarser powder having over 212 μm had metal-like behavior as microstructural and mechanical properties. We thought that the classification of the MA powder before HIP process was one of the suitable process to optimize the microstructure and several properties of ODS-Cu alloy.

The study investigates the effect of heat treatment on the microstructure evolution and properties of an age-hardened Cu-3Ti-2Mg alloy. The precipitated Cu2Mg and ß'-Cu4Ti phases consequently yield a depletion of the Cu matrix in regards to Ti and Mg solutes, which enhances the electrical conductivity. The Cu2Mg Laves phase and ß'-Cu4Ti phase precipitates increase the hardness of the alloy due to the consistency and coherency of the later phase. However, the decrease of hardness is mainly associated with the coarse microstructures, that can be formed due to the phase transformation from metastable ß'-Cu4Ti phase to more stable Cu3Ti phase. In the range of experiments, the optimum process is solution treatment at 700°C for 4 h, with subsequent age-hardening at 450°C for 4 h. The electrical conductivity, hardness, tensile strength, and elongation of the Cu-3Ti-2Mg alloy were 15.34%I ACS, 344 HV, 533 MPa, and 12%, respectively. [ABSTRACT FROM AUTHOR]

Cu alloys with high durability and high thermal and electric conductivities are the key to achieving a more energetically efficient and eco-friendly future. Noble Zr-added oxide-dispersion-strengthened Cu alloys (ODS-Cu) with high strengths are promising materials for meeting all future service requirements. In this study, three-dimensional atom probe (3D-AP) and transmission electron microscopy (TEM) revealed that the majority of nano-oxide particles in the Zr-added ODS-Cu were novel yttria-stabilized zirconia (YSZ) particles with a diameter of less than 4 nm, which were completely different from Y 2 Zr 2 O 7 and Y 4 Zr 3 O 12 observed in other Zr-added ODS alloys. Multiscale observations including small-angle X-ray scattering (SAXS), 3D-AP, and TEM were performed to clarify the morphology of the oxide particles in the Zr-added ODS-Cu. Further strength enhancement through microstructural homogenization and specific incremental strength values were proposed. • Multiscale observation of oxide particles in Zr-added ODS-Cu was performed using small-angle X-ray scattering, 3D-AP and TEM. • Novel ultrafine YSZ nanoparticles with a diameter of less than 4 nm were confirmed to be mainly dispersed in the ODS-Cu. • Further strength enhancement and the specific incremental value of the ODS-Cu were predicted from the multiscale observation. [ABSTRACT FROM AUTHOR]

This study investigates the age hardening behavior of the cold rolled Cu-3Ti-3Ni-0.5Si alloy upon different deformations. The microstructure and the phase composition after precipitation were characterized by X-ray diffraction, optical microscopy, scanning electron microscopy, and transmission electron microscopy, and the electrical conductivity and mechanical properties of the alloy were tested as well. The as-cast Cu-3Ti-3Ni-0.5Si alloy consists of Ni 2 Ti phase, NiTi phase, and Cu matrix, and Ni 2 Si, Ni 3 Si, and Ni 3 Ti phases precipitated from the Cu matrix after aging treatment. TEM analysis shows that Ni 2 Si phase is coherent with the Cu matrix after 50% deformation and aging at 500 °C for 120 min, with an orientation relationship of [ 2 ¯ 01 ] N i 2 S i / / [ 11 1 ¯ ] C u . However, Ni 2 Si phase loses its coherence with the Cu matrix if the size of the Ni 2 Si phase is above 4.68 nm. Additionally, large deformation promotes most striped precipitates to transform into fine and spherical precipitates, so the appropriate deformation and aging temperature are beneficial for the improvement on the electrical conductivity and hardness. After 90% deformation and aging for 30 min at 500 °C, Cu-3Ti-3Ni-0.5Si alloy has a good combination of tensile strength, elongation, hardness and electrical conductivity, which are 615 MPa, 25.1%, 268 HV and 33.79 %IACS, respectively. The fracture morphology exhibits numerous fine equiaxed dimples with an average size of about 1 μm, and small amounts of large dimples with an average size of about 10 μm, and the assigned failure mechanism of the Cu-3Ti-3Ni-0.5Si alloy is a ductile fracture. • The effect of deformation on the age hardening behavior is clarified. • It gets insights of phase constituents and evolution of the alloy during aging. • It discloses the relation of processing parameters and properties. • A good combination of properties is obtained at the present work. [ABSTRACT FROM AUTHOR]

In the Cu-2.5Fe-0.3Cr-0.3 Mg-0.2Si-0.1Ca-0.1Zr alloy, a double-scale (micro and nano) FeCrSi second phase has been generated. The orientation relationship between nano-precipitates and the matrix is: (111)Cu//(202)Fe x Cr (3- x) Si, 1 1 ¯ 0 Cu// 1 1 ¯ 1 ¯ Fe x Cr (3- x) Si. The influence of the thermomechanical treatment process on the microstructure, mechanical properties and electrical conductivity of the alloy is explored. Results indicate that the final alloy has excellent properties. The hardness, yield strength, tensile strength and electrical conductivity of the final alloy are 204 HV, 635 MPa, 649 MPa and 63.57 %IACS, respectively. The calculations show that precipitation strengthening and dislocation strengthening have essential contributions to the strength of the final alloy. The former mainly comes from the strengthening effect of the FeCrSi nano-precipitates, and the latter is related to the multi-stage thermomechanical treatment process. • A novel high-strength and high-conductivity Cu-2.5Fe-0.2Si-0.3 Mg-0.1Ca-0.3Cr-0.1Zr alloy is designed. • A double-scale (micro and nano) FeCrSi second phase has been generated in the designed alloy. • FeCrSi nano-precipitates have a remarkably significant contribution to the strength of the alloy. • The tensile strength and electrical conductivity are 649 MPa and 63.57 %IACS, respectively. [ABSTRACT FROM AUTHOR]

Owing to good self-lubricating performance, tin bronze is widely used in industrial fields. As tin bronze parts manufactured by powder metallurgy, their tribological performances are influenced by raw powder. In this work, four types of self-lubricating copper alloy composites (CuSn10 (D), CuSn10, CuSn10Pb10 (D) and CuSn10Pb10) were prepared by sintering completely alloyed powder and diffusion alloyed copper tin powder. The morphology, element distribution and microstructure of raw powder and their sintered Cu alloy composites were observed. The tribological properties of Cu alloys were investigated by block-ring friction test under different working conditions and their worn surface and wear debris were analyzed. The results show that the diffusion alloyed powder has an irregular dendritic morphology and its sintered Cu alloy is more likely to produce twin structure which enhances the hardness and the bearing capacity of the material. Compared with completely alloyed powder sintered CuSn10 sample, the wear rate of CuSn10 (D) sintered from diffusion alloyed powder was reduced by 83.96%, 74.39%, and 67.63% under three typical working conditions. Under dry friction conditions, the wear rate of CuSn10 (D) is reduced by 63.64% than CuSn10, and CuSn10Pb10 (D) is 25% lower than CuSn10Pb10. The investigation on the wear tracks and wear debris of Cu alloy composites showed that the diffusion alloyed powder sintered samples are inclined to form a more consecutive and integral third-body layer on wear tracks and which contributes to the better wear resistance.

An Al-2wt%Cu alloy was subjected to accumulative roll bonding (ARB) process up to a strain of 4.8. The two kinds of different microstructures, i.e, solution treated (ST) one and 190°C pre-aged for 30 min (Aged), were prepared as the starting structures for the ARB process. The microstructures were studied by transmission electron microscope (TEM) and electron backscattering diffraction (EBSD). The results showed that the fine precipitates having the average particle size of 16 nm were formed after aging process. On the other hand, the mean grain size of the ST-ARB and the Aged-ARB specimens reached to 650 nm and 420 nm, respectively. Study of the fracture surfaces were carried out by scanning electron microscope (SEM). The results indicated that at 0-cycle ARB, the specimens show dimples indicating the micro-void coalescence (MVC) mechanism of ductile fracture. The average size of dimples was larger in the ST-ARB specimen compared to the Aged-ARB specimen. The fracture mode was transgranular cleavage fracture in the Aged-specimen. At 3- cycle and 6-cycle ARB, also the specimens showed cleavage facets and river lines, that the river lines or the stress lines are steps between cleavage or parallel planes, which are always converged in the direction of local crack propagation.

Abstract A Cu–6.0 Ni–1.0 Si–0.5 Al (wt%) alloy was fabricated, and its phase transformation behavior in the early stages of aging treatment were studied systematically, including the mechanical properties, type of precipitates, formation heat of precipitates, elastic strain energy, crystal orientation relationships, and spatial distribution of elements. The experimental results demonstrate that a B2 ordering structured β-NiAl precipitate formed in the matrix as the supersaturation solid solution (SSS) was aged at 400 °C; δ-Ni 2 Si, a L1 2 ordering structured β-Ni 3 Si, and L1 2 structured γ′-Ni 3 Al were precipitated from the matrix aged at 450 °C; and discontinuous δ-Ni 2 Si precipitates occurred in the matrix aged at 500 °C and above. Atom probe results revealed that Ni and Si formed clusters with a size of 1–2 nm, and Al tended to segregate around these clusters as the SSS was aged at 450 °C. The ultimate tensile strength of the studied alloy was 1080.2 ± 20.4 MPa for the sample aged at 450 °C for 1 h, and the electrical conductivity was 25.4% IACS. Sketch maps of the crystal orientation relationships between the matrix and precipitates were also established. Graphical Abstract Unlabelled Image Highlights • δ-Ni 2 Si, β-Ni 3 Si, γ′-Ni 3 Al were precipitated from the matrix aged at 450 °C. • Ni and Si formed clusters with a size of 1–2 nm, and Al tended to segregate around these clusters. • The ultimate tensile strength and the electrical conductivity of the studied alloy were 1080.2 ± 20.4 MPa and 25.4% IACS. • Sketch maps of the crystal orientation relationships between the matrix and precipitates were established. [ABSTRACT FROM AUTHOR]

Equal channel angular extrusion (ECAE) is considered as an advanced extrusion process, where metal billets are plastically deformed without reducing its cross-sectional area. In this study, a die was designed and fabricated with channel angle and diameter of 110° and 12.44 mm, respectively, for extruding aluminum and copper alloys via ECAE process. The die and punches were made from EN-31 steel and were heat-treated to achieve hardness of 45 HRC. The heat treatment cycle for the die and punch consisted of austenitizing them at 840 °C for 1.5 h, followed by quenching in oil to form martensite, and tempering at 450 °C for 1 h, followed by air cooling to room temperature. The inner surface of channel in the die was electroplated with hard chrome. Aluminum and copper alloys were successfully extruded by ECAE process at room temperature. Aluminum and brass samples were subjected to single pass, whereas copper sample was subjected to double pass during ECAE processing. Microstructures of ECAE-processed aluminum and copper samples were examined under optical microscope, and hardness was measured. Microstructural examination shows significant grain refinement in ECAE-processed samples as compared to as-received billets. The hardness of ECAE-processed samples was significantly greater than that of as-received billet. [ABSTRACT FROM AUTHOR]

In this study, we investigated the color transition mechanism of Cu-5Al-5Zn-1Sn (in wt%) alloy during cold-rolling and annealing processing by analyzing the correlation between microstructural characteristics and optical transition behavior. Single-phase Cu alloys have limited solubility which restrict on controlling their optical properties. Therefore, we propose a novel strategy for modulating the optical properties of single-phase Cu alloys. Cu alloys with low stacking fault energy (SFE) exhibit highly dense twin defects and dislocations when subjected to severe plastic deformation. In addition, annealed low SFE samples contain unique grain boundary structure, with different energies according to atomic structure and misorientation angle, which influences the density of states and electronic structure of the alloys. Consequently, the optical transition energy of the samples is affected by the grain boundary energy, which this influence to the chromaticity of the samples. These findings provide a new approach for adjusting the color of the alloys. [Display omitted] • The high density of LAGB influence to electric band structure and optical transition energy. • The process of this study could induce increasing of hardness and maintain chromaticity of alloy at the same time. • Tailoring technology of Grain boundary character can be applied on new color transition method of alloy. [ABSTRACT FROM AUTHOR]

The surface generation mechanism of the Cu alloys in ultra-precision diamond turning is investigated by both simulation and experimental methods, where the effects of the cutting parameters on the surface characteristics are explored, including the workpiece spindle speed, the cutting depth, the feed rate and the nose radius of the diamond tool. To verify the built model, the cutting experiments are conducted at selected parameters, where the causes of the error between the simulation and the machining results are analyzed, including the effects of the materials microstructure and the diamond tool wear. In addition, the nanometric surface characteristics of the Cu alloys after the diamond turning are identified, including the finer scratching grooves caused by the tool wear, the formation of the surface burs and the adhesion of graphite. The results show that the built model can be basically used to predict the surface topography for the selection of the appropriate machining parameters in the ultra-precision diamond turning process.

For plasma-facing components of ITER, tritium (T) transport into the coolant by permeation through CuCrZr heat sink will raise T safety and recovery issues. In the present work, hydrogen isotope permeation and retention in copper (Cu) materials have been experimentally studied. Deuterium (D) gas-driven permeation (GDP) experiments have been performed to evaluate the permeability and diffusion coefficients. Meanwhile, D retention properties in these Cu materials are compared by gas absorption and subsequent thermal desorption spectroscopy (TDS). Finally, low energy (several eV) plasma-driven permeation (PDP) of D through Cu and its alloys has been demonstrated. Significant enhancement in D permeation flux compared with that of GDP has been measured. [ABSTRACT FROM AUTHOR]

Grain refinement by elemental addition has been extensively investigated within the last decades in Al or Mg alloys. In contrast, in the Cu system, the role of solute on grain size is less investigated. In this study, the grain refinement potency of several alloying elements of the Cu system was examined. To predict grain size depending on the growth restriction factor Q, grain size modelling was performed. The results obtained by the grain size model were compared to variations in the grain size of binary Cu alloys with increasing solute content under defined cooling conditions of the TP-1 grain refiner test of the Aluminium Association©. It was found that the experimental results differed significantly from the predicted grain size values for several alloying elements. A decreasing grain size with increasing alloy concentration was observed independently of the growth restriction potency of the alloying elements. Furthermore, excessive grain coarsening was found for several solutes beyond a transition point. It is assumed that contradictory variations in grain size result from a change in the nucleating particle density of the melt. Significant decreases in grain size are supposed to be due to the in-situ formation of potent nucleation sites. Excessive grain coarsening with increasing solute content may occur due to the removal of nucleating particles. The model shows that the difference in the actual number of particles before and beyond the transition point must be in the range of several orders of magnitude. [ABSTRACT FROM AUTHOR]

The growth restriction factorQof the alloying elements of the Cu-system was determined using thermodynamic software tools to obtain accurateQ-values. A comprehensive list was given for a nominal solute content of 1 wt-%. Based on the calculations, melting experiments were carried out under defined casting conditions given by the TP-1 test to evaluate the correlation betweenQand grain size in Cu alloys. [ABSTRACT FROM PUBLISHER]

High strength and high electrically conductivity Cu-Ni-Si alloys are important candidate materials for extending the life of currently used elastic-conductor materials. Phase transformation behaviors and properties of a synthesized Cu-6.0Ni-1.0Si-0.5Al-0.15Mg-0.1Cr alloy were investigated systematically. After homogenized for 4 h at 940 °C, hot rolled by 80% at 850 °C, solution treated for 6 h at 970 °C, cold rolled by 50%, and annealed for 60 min at 450 °C, the studied alloy approached physical properties of 1097.5 MPa in tensile strength and 26.4%IACS in electrical conductivity. Transmission electron microscope observations showed that four precipitation phases including δ-Ni 2 Si, β-Ni 3 Si, β-NiAl, and γ′-Ni 3 Al were formed in the studied alloy, which was subjected to different annealing temperatures. A detailed diagram for isothermal decompositions has been established. The high strength of the studied alloy was primarily attributed to the Orowan precipitation strengthening, and secondary attributed to the solid solution strengthening, the Hall-Petch type grain boundary strengthening, and the work hardening. Multi-precipitation phases of Ni 2 Si, γ′-Ni 3 Al, β-Ni 3 Si played significantly into the strengthening effects, and the low electron diffraction influence of Mg and Cr contributed to both solution strengthening and maintaining a high electrical conductivity. Multi-phase precipitation strengthening and using trace amount alloying elements for solution strengthening will be a new strategy to develop high strength and high electrical conductivity copper alloys. [ABSTRACT FROM AUTHOR]

The kinematic contribution to the hardening of ultra-thin metallic sheets characterized by monotonic and reversed simple shear tests is of high interest in the sheet metal forming industry, because of its influence on the accurate prediction of springback. However, ultra-thin sheets are very sensitive to buckling when submitted to shear stress because of the large gauge width to thickness ratio, the stress perturbations induced by the clamping and the alignment of sample, which thus limit the attainable strain levels using conventional simple shear devices. In this paper, a new simple shear test dedicated to ultra-thin metallic sheets is proposed through the development of a specific support. A transparent glass part enables the application of a normal tightening force to prevent the out-of-plane buckling of the sheets whilst also allowing full field strain measurements to be taken. Firstly, the capabilities of the device are shown by comparing the mechanical behavior in a simple shear test on an austenitic stainless steel with and without the support. A good reproducibility of the flow curves is observed with the support and large shear strains are reached without buckling. Secondly, the influence of friction due to the contact between the sample and the support is checked by finite elements simulations and shown to be negligible compared to the shearing force. Finally, monotonic and reversed shear tests on a pure copper sheet with a thickness of 0.1 mm were performed up to rupture without buckling, these were not previously conceivable on such a low thichness, and demonstrate the potential of the proposed device. [ABSTRACT FROM AUTHOR]

The dependence of the grain boundary character distribution for a Cu-4 at. % Ti polycrystal alloy (average grain size: 100 βm) on the nucleation of cellular discontinuous precipitates was systematically investigated. In an alloy over-aged at 723 K, cellular discontinuous precipitates consisted of a terminal Cu solid solution and a stable β-Cu4Ti lamellae nucleated at grain boundaries. Electron backscatter diffraction analysis revealed that the discontinuous precipitation reaction preferentially occurred at random grain boundaries with a Σ value of more than 21 according to the coincidence site lattice theory. On the other hand, few cellular discontinuous precipitates nucleated at low-angle and low-Σ boundaries, particularly twin (Σ 3) boundaries. These findings suggest that the nucleation of discontinuous precipitates is closely correlated with grain boundary character and structure, and hence energy and/or diffusibility. It should therefore be possible to suppress the discontinuous precipitation reaction through control of the alloy's grain boundary energy, by means of texture control and third elemental addition. [ABSTRACT FROM AUTHOR]

Here we report an "intragranular ultra-nano precipitation" strategy to strongly plasticizing and simultaneously strengthen polycrystalline Cu alloys. Our strategy relies on a high density (more than 1023 m−3) and uniform dispersion of extremely fine Fe nanoprecipitates (5.0 ± 2.7 nm) with minimal lattice misfit (theoretically 0.69%) inside Cu grains. The intragranular dispersion of ultra-nano particles not only considerably enhance tensile ductility of a plasticity-poor tin bronze alloy more than 2 times, but also elevate tensile strength above 20% in the meantime, arising from more stable and greater work hardening. The superb plasticizing and hardening of this class of Cu alloy are based on minimal lattice misfit to achieve maximal precipitate dispersion and durable intragranular nanoprecipitation-dislocation interactions (i.e., dislocations cut through fully-coherent Fe nanoprecipitates and hence produce plastic deformation), and we envisage that this intragranular ultra-nano precipitation strategy may be applied to many other metallic alloys. [Display omitted] [ABSTRACT FROM AUTHOR]

Sintered materials are commonly used in industrial equipment, including bearing components. These materials include bimetals consisting of steel backed sintered bronze lined bushings. In particular, 90Cu-10Sn (mass%) bronze is widely used in bearing components. Lead bronze, in which the lead serves as a solid lubricant, is being replaced with other materials, among which are sulfide-dispersed bronzes. In sulfide-dispersed bronze, sulfides instead of lead play the role of solid lubricant. However, the sulfides in the bronze may be subject to chemical reduction during sintering, especially when this is carried out under a reducing atmosphere containing hydrogen gas. In this study, we investigate the effect of the sulfides on the bronze, with a focus on the hardness of the bronze matrix and the reaction between sulfides and hydrogen gas. Water-atomized powders were prepared for comparison of the sintering behavior. The sintering temperature in the tests was 1123 K. From the phase diagram of the Cu-Sn system, the liquid phase starts to form into bronze containing 20 mass% Sn at approximately 1123 K; thus, some conditions undergo liquid-phase sintering. Sulfides are observed to disappear from sintered bronze surfaces under a reducing atmosphere. However, the sulfides that are not in a solid solution do not affect the hardness of the bronze matrix, which does, however, depend on the tin content.

Cu alloys such as bronze have long been used as bearing materials because of their good run-in properties for steels used as mating materials. These Cu alloys are also suitable for various applications: High-strength brass castings and phosphorus bronze castings are used for their ability to obtain higher strengths, whereas Pb-bronze castings are used for anti-seizure applications. To prevent scoring and seizure, base materials such as Cu alloys were often combined with a solid lubricant. In this study, the tribological properties of sulfide-dispersed bronze were investigated. Friction tests were conducted under dry conditions for bronze with/without sulfides. It was found that seizure was prevented in sulfide-bronze systems only under certain test conditions. It was estimated that the dispersed sulfide restricted the transfer of the Cu alloy elements to the mating steel surface. Moreover, the addition of Si to a Cu-Fe-S system and to sulfide-dispersed bronze resulted in crystallization of Fe-Si compounds. The hardness and anti-wear properties of the compounds were also improved. [ABSTRACT FROM AUTHOR]

The kinetics of W precipitation in dilute Cu-W alloys during room temperature irradiation is investigated using in situ electrical resistivity measurements and transmission electron microscopy. For a series of alloys with W concentrations varying from ∼1 at.% to 6 at.%, resistivity measurements show that high dose irradiation leads to steady-state solubility values which are concentration dependent, while electron microscopy shows that the precipitate structures are stabilized at high doses at a size of about 2 nm. These steady states are independent of the initial alloy microstructure: whether it is a solid solution or it contains large W precipitates within the Cu matrix. The effective tracer impurity diffusion coefficient of W in Cu in energetic displacement cascades is determined by in situ electrical resistivity measurements on multilayer structures of alternating Cu/W layers, yielding a value of 2.1 nm 2 /dpa. These multilayer structures are observed to undergo significant interfacial roughening during irradiation, showing signs of transforming from a 2-dimensional to 3-dimensional structure under prolonged irradiation. A model based on a dynamical competition between recoil mixing and thermal spike diffusion is proposed to explain these various results; it is implemented in kinetic Monte Carlo simulations. [ABSTRACT FROM AUTHOR]

The microstructural evolution and characterization of discontinuous precipitates in a Cu-4.3 Ni-2.2 Si (in at.%) alloy were studied, and compared with those of continuous precipitates in the same alloy. During prolonged aging, coarse cellular components containing fiber-shaped δ -Ni 2 Si and copper solid-solution phases nucleate and grow quickly but discontinuously at the grain boundaries, accompanied by the consumption of fine δ -Ni 2 Si particles formed by continuous precipitation. In terms of the crystal structure, all the precipitates are of the same type of orthorhombic δ -Ni 2 Si. However, in terms of the crystallographic features, the δ -Ni 2 Si discontinuous precipitates have micro-scale fibers that are aligned with the orientation relationship of ⟨100⟩ δ //⟨110⟩ Cu and (013) δ //( 1 1 ̅ 1 ) Cu , and with a preferential extending direction on the (111) Cu plane, which differs from the fine δ -Ni 2 Si continuous precipitates at the early stages of aging. The evolution of the discontinuous precipitates can be explained by the existing classical theories of phase transformation, as discussed by Hu et al. regarding the subsequence of the continuous precipitates. In this study, we also confirmed that the development of coarse δ -Ni 2 Si discontinuous precipitates of the cellular components leads to a serious drop in the strength in the later stages of aging. [ABSTRACT FROM AUTHOR]