Microstructure Of Cu Research Articles

Refinement of eutectic structure and precipitates of Cu–20Ag alloy due to Y microalloying

Copper-silver alloy rod with high mechanical properties and stable conductivity are the key materials for the preparation of microfilaments used in endoscopy and other medical fields. In this paper, the microstructure of Cu–20Ag rod was regulated by adding trace rare earth Y in order to improve the comprehensive performance of copper-silver alloy further. and studies the distribution and existence of rare earth Y as well as the influence on the performance of copper-silver alloy rod billet. The results of research show that: rare earth Y mainly exists in the branching nodes of the eutectic organization, so that the alloy in the solidification of constitutional supercooling increases, thus refining the eutectic structure, and make it uniformly distributed. After addition of 0.01 wt%Y, Cu4Y was precipitated in the eutectic structure of the rod. After adding 0.03 wt%Y, the precipitates types increased to trace intermetallic compound AgY and nanoparticles Cu4Y. The increase of the interface between eutectic structure and Cu matrix decreases the electron scattering probability. This is the main factor to lead to the decrease of electrical conductivity. The precipitation hardening of precipitated phase and the increase of interface between eutectic structure and Cu matrix are the main factors for the increase of tensile strength of bar billet. The main factor of the decrease in the conductivity of rod billet is the increase of Ag phase dissolved in eutectic structure and the interface between eutectic structure and Cu matrix.

Effect of Heat Treatment on Some Thermodynamics Analysis, Crystal and Microstructures of Cu-Al-X (X: Nb, Hf) Shape Memory Alloy

Heat treatment is an important technique that can improve the properties of shape memory alloys. In this study the effect of heat treatment at three different temperatures (973 K, 1073 K and 1173 K) on some thermodynamics parameters, crystal structure, and microstructure of Cu_86 Al_12 Nb_2 and Cu_86 Al_12 Hf_2 (mass %) Shape Memory Alloy has been investigated. After heat treatment, the change in the thermal properties of the samples was determined using Differential Scanning calorimetry (DSC). The effect of heat treatment on the crystal and microstructure of the alloy samples were determined at room temperature using X-ray diffraction (XRD), Scanning Electron microscopy (SEM) device. The DSC result showed that in both samples the temperature hysteresis was decreased after heat treatment. Also grain size was decreased by increasing the treatment temperature in both samples. And finally, optical images represented that Hafnium (Hf) is more dissolved in the alloy compared to Niobium (Nb).

Enhanced shear strength and microstructure of Cu–Cu interconnection by low-temperature sintering of Cu nanoparticles

Enhanced shear strength and microstructure of Cu–Cu interconnection by low-temperature sintering of Cu nanoparticles

Synergistic effects of trace silicon, calcium and cerium on the microstructure and properties of a novel Cu–Cr–Nb–Si–Ca–Ce alloy

In this paper, a novel Cu-0.60Cr-0.20Nb-0.05Si-0.02Ca-0.02Ce (CCNSCC, wt.%) alloy is designed. By comparing the differences in the properties and microstructure with the Cu-0.60Cr-0.20Nb (CCN, wt.%) alloy under the same process, the effects of trace Si, Ca, and Ce elements on the CCNSCC alloy are disclosed. After undergoing cold rolling by 80% and aging at 450 °C for 60 min, the CCNSCC alloy exhibits a tensile strength of 524 MPa and a softening temperature of 600 °C. These values represent an increase of 104 MPa and 90 °C respectively compared with the CCN alloy. After a multi-stage combined thermo-mechanical treatment including preaging at 400 °C for 30 min, the tensile strength and electrical conductivity of the CCNSCC alloy reach 618 MPa and 75.2%IACS respectively. Microstructure analysis shows the existence of rod-like and polygonal Cr8Nb3Si particles, as well as globular, ellipsoidal, and crescent-shaped (Ca,Ce)Cu5 particles. During the process of aging, the precipitation of the Cr phase occurs at the phase boundaries of Cr8Nb3Si particles. Additionally, significant quantities of fine Cr particles at the nanoscale surround the Cr8Nb3Si particles, exerting a beneficial influence on the strength and electrical conductivity of the CCNSCC alloy. Besides, the CCNSCC alloy has finer Cr particle size and lower volume fraction of recrystallized grains after aging in comparison to the CCN alloy. This indicates that the addition of trace Si, Ca, and Ce elements significantly inhibits the growth of Cr particles and occurrence of recrystallization. Plenty of dislocations are observed in different states of the CCNSCC alloy, and their interaction with the Cr precipitates is the primary factor contributing to the excellent mechanical properties of the CCNSCC alloy. The findings of this study provide valuable insights for improving the properties and microstructure of Cu–Cr–Nb alloys.

Microstructure and mechanical properties of high-temperature free-oxygen rolled Cu/1060Al bimetallic composite materials

In this work, Cu/1060Al bimetallic composite materials manufactured by high-temperature free-oxygen rolling process are reported. The results show that with the increase of rolling passes, the microstructure of Cu and 1060Al gradually extends and elongates in the rolling direction, and the interface that has few compounds is dominated by mechanical bonding. It is worth noting that layered fracture occurs during the tensile process. After annealing, the interface changes from mechanical bonding to metallurgical bonding, and the layered fracture is alleviated under the traction of the interface layer. With the increase of annealing time and temperature, the thickness of the interface compounds gradually increase, and the interface compounds from the copper layer to the aluminum layer are Cu9Al4, CuAl and CuAl2, respectively. Annealing at 350 °C for 2 h exhibits the best comprehensive performance, a tensile strength of 138 MPa and an elongation of 64 %. Tensile behavior in the rolled state and annealed state has been discussed based on failure theory, and compound growth after annealing has been analyzed on account of the theories of dynamics and thermodynamics.

Effect of TiB2 on properties and microstructures of Cu[sbnd]W electrical contact materials

The W skeletons were pressed by the cold isostatic pressing process, and CuW alloys with different TiB2 contents were prepared by the sintering and infiltration method. The effects of TiB2 addition on the microstructures, properties, vacuum breakdown performance, and arc motion characteristics of CuW alloys were investigated. The results show that the conductivity of CuW alloy decreases with the addition of TiB2, while the hardness increases. Compared with CuW alloy, this method improves the breakdown strength, reduces the chopping current and extends the arc life of CuW alloy. The anti-arc erosion performance of CuW alloy with the addition of TiB2 was enhanced. For CuW alloy containing TiB2, the electric breakdown occurs on the TiB2 phase at the edge of the W phase, the cathode spots are split, the arc is effectively scattered, and the ablation area after multiple breakdowns is larger, but the erosion pits are shallow and dispersed.

Triple junction disclinations in severely deformed Cu–0.4%Mg alloys

Stress fields arising from triple junction disclinations (TJDs) play a significant role in the microstructure evolution during the plastic deformation of metals. The calculation of TJD strengths from grain orientation data was developed by Bollmann more than 50 years ago, but so far applied only to collections of a few grains. Developed here is a new methodology for calculating TJD strengths and the associated stress fields in large polycrystalline assemblies using experimental electron back-scattered diffraction (EBSD) maps. The methodology combines Bollmann’s approach with a representation of materials as cell complexes. It is computationally efficient and allows for obtaining the spatial distribution of TJD strengths from EBSD images containing thousands of grains. Analysed are the fraction, distribution, and strengths of TJDs within statistically representative microstructures of Cu–0.4%Mg alloy subjected to severe plastic deformation (SPD) by equal channel angular pressing. It is shown that the formation of low-angle grain boundaries (dislocation walls) during SPD leads to an increasing number of TJDs, whose spatial distribution is progressively more uniform and whose strength distribution remains nearly constant. This result suggests that the SPD reduces the internal stresses associated with disclinations in large regions of the material, as closely situated disclinations screen each other’s fields. Regions with high local stresses can be expected between sparsely distributed TJDs with the highest strengths. The average distance between such TJDs could be considered as a natural length scale in a material.

Effects of Fe content on properties and microstructure of Cu–Ti alloys during aging

In this study, Cu-2.7Ti-0.2Fe (CT-0.2Fe) and Cu-2.7Ti–1Fe (CT-1Fe) alloys were fabricated and underwent multi-stage thermomechanical treatment, and the microstructure and properties evolution of the alloys during aging were investigated. After aging for 60 h at 350 °C, the CT-0.2Fe and CT-1Fe alloys exhibited the yield strength of 1068/935 MPa, tensile strength of 1127/1057 MPa, elongation of 2.54%/2.21%, and electrical conductivity of 20.3/26.4 %IACS, respectively. The relatively higher electrical conductivity of CT-1Fe was primarily attributed to the formation of numerous TiFe particles. Typical modulated structure and β′-Cu4Ti precipitates formed during direct aging in both alloys. However, in the CT-1Fe alloy, the growth of β′-Cu4Ti precipitates was suppressed. During multi-stage thermomechanical treatment, the interaction of the dislocations and precipitates was enhanced, retarding the softening effects of the alloy at the elevated temperatures. The calculation results showed that work hardening and precipitation strengthening significantly contributed to enhancing the mechanical properties of the alloys.

Properties and mechanism of Cu(OH)2 nanoarray reinforced cement composites

This experiment investigates the effect of Cu(OH)2 nanoarray on the properties of cementitious materials. Cu(OH)2 nanoarray is a novel nanomaterial with excellent electrical conductivity and chemical stability. At present, the interaction mechanism between Cu(OH)2 nanoarray and cementitious materials has not been explored. In this paper, the effect of Cu(OH)2 nanoarray on the properties of cement mortar was investigated by testing the mechanical strength and electrical conductivity of Cu(OH)2 nanoarray. The microstructure of Cu(OH)2 nanoarray cement mortar and the development of hydration products were analyzed using XRD, SEM, EDS and MIP tests. The results showed that when 0.5% Cu(OH)2 nanoarray was added, the 28d compressive strength and flexural strength of the cement mortar increased by 50.29% and 41.28%, respectively, and its electrical resistivity decreased by 50%. The Cu(OH)2 nanoarray optimized the mechanical strength and workability of the cement mortar by modulating the hydration products and improving the microstructure.

In Situ Study on Cu-to-Cu Thermal Compression Bonding

Cu-to-Cu thermal compression bonding (TCB) has emerged as a promising solution for ultrafine pitch packaging in 3D integrated circuit technologies. Despite the progress made by conventional Cu-to-Cu TCB methods in achieving good mechanical strength of the Cu bonds, the bonding processes generally require high temperature and high pressure, which may degrade the performance and reliability of the device. Therefore, it is imperative to investigate the processing parameters to understand the bonding mechanism and achieve effective TCB at a low temperature and low pressure. Here, we developed an in situ TCB technique inside a scanning electron microscope. The in situ TCB method enables a real-time observation of bonding development, which provides critical insights into how the texture and microstructure of Cu bumps may influence the creep and surface diffusion during the bonding process. This work features a strategy to advance our understanding of the bonding mechanisms and provides insight into tailoring the microstructure of Cu for bonding at a low temperature and low pressure.

Heterogeneity of microstructures in a Cu–Zr based amorphous alloy composite reinforced by crystalline phases

Amorphous alloy composites (AACs) comprising reinforcing crystalline phases exhibit far better mechanical properties than their base amorphous alloy counterparts, and Cu–Zr based alloys consisting of B2 phase particles embedded in an amorphous matrix are well-researched AACs in this respect. Traditionally, the B2 particles in Cu–Zr based AACs may appear to be homogeneously crystalline (without any amorphous phase inside), the glassy matrix homogeneously amorphous, and their interfaces atomically sharp. Yet, such a picture would pose difficulties in understanding how crystallization can happen in the glassy matrix, since the crystallized product is denser than but iso-stoichiometric with the matrix. The present work provides insights into this puzzle, by using electron microscopy, nanoindentation and molecular dynamics (MD) simulations to investigate the structures and mechanical properties of the crystalline and amorphous phases, and their interfaces in a Cu62Zr34.5Al3Nb0.5 AAC. Surprisingly, in this AAC, the superficially crystalline particles with tens to hundreds of microns large are found to be heterogeneous at the sub-micron scale, comprising nano-crystallites embedded in a glassy matrix, and the amorphous phase outside also exhibits a gradient in free volume content towards the interface. Smaller particles containing only B2 nano-crystallites are found to be softer than the amorphous matrix, while larger particles are harder than the amorphous phase due to martensitic transformation into the B19’ phase. MD simulations indicate that the B2 phase is marginally more stable than the glassy state, and on crystallization the densification leads to free-volume generation in the surrounding glassy matrix as observed experimentally. Mechanics analysis indicates that the strain energy in the glassy matrix associated with free-volume generation scales with the volume of the crystallization, as would be the crystallization energy itself. Hence, crystallization in the AAC leading to a two-phase structure is a spontaneous but kinetically limiting process arising from the net energy difference between the crystallization energy and free-volume energy produced in the glassy matrix. This work provides a detailed understanding of the heterogeneity in the microstructures in Cu–Zr based AACs, to shed light on the crystallization of the iso-stoichiometric B2 phase from the amorphous phase.

Phase equilibria and solidified microstructure in Cu–Cr–La ternary system via experimental investigation and thermodynamic calculation

Phase equilibria and solidified microstructure in Cu–Cr–La ternary system via experimental investigation and thermodynamic calculation

Combined effect of Cu partitioning and nano-size precipitates on improving strength-ductility balance of Cu bearing Q&P steel

Cu was intentionally added to the traditional Q&P steel for further improving comprehensive mechanical properties through Cu partitioning, nano-size precipitates and microstructural refinement. Substantial enrichment of C, Mn, Cu and Ni atoms in newly formed austenite during intercritical annealing effectively inhibited the formation of bainite during the partitioning stage. The final microstructure of Cu bearing Q&P steel (Cu-QP steel) was significantly refined because of the refined prior austenite grains. Moreover, the modified constrained carbon equilibrium (CCE) model considering intercritical ferrite, Cu partitioning and the refinement effect of grain size was newly developed to better predict retained austenite (RA) fractions at different annealing temperatures in Cu-QP steel and Cu free Q&P steel (base steel). Both experiments and modeling results indicated that Cu-QP steel exhibited stronger austenite retention ability. The discrepancy of solid solubility between α and γ phases resulted in 14–18 nm Cu-rich precipitates randomly dispersed at the grain boundaries and in the interior of tempered martensite and intercritical ferrite after partitioning holding. The outstanding mechanical properties with ultra-high yield strength of 706–962 MPa, tensile strength of 1065–1139 MPa, and total elongation of 22–26% were obtained after the intercritical Q&P process. More volume fraction of tempered martensite and/or fresh martensite was formed in Cu-QP steel as a substitute for softer bainite, which remarkably improved the tensile strength. High density of nano-size Cu-rich precipitates and the refined microstructure enabled an appreciable increase of yield strength, while larger-fraction of ultrafine RA with higher stability contributed to better ductility. • Multi-element synergistic partitioning inhibited the formation of bainite. • The partitioning process facilitated carbon partitioning and Cu-rich precipitation. • The modified CCE model was newly developed to better predict RA fractions. • Multi-scale RA with various morphologies was beneficial to stronger TRIP effect.

Formation of a nanoscale two-phase microstructure in Cu–Zn( Al) samples with macroscopic concentration gradient

In binary Cu Zn and ternary Cu–Zn–Al with 1.5 wt% Al, the formation of a nanoscale two-phase α + ordered β 2 microstructure is observed after quenching samples with a macroscopic solute concentration gradient from 875 °C in iced brine. The two-phase microstructure has formed from high temperature β phase and is located at higher Zn contents, after the concentration invariant massive or martensitic transformation, respectively. Its occurrence further substantiates the high competition between different types of solid-state reactions in brass. The nanoscopic α + β 2 microstructure was investigated by a combination of EBSD and TEM. Experimentally measured Kikuchi patterns were correlated with dynamically simulated ones by a pattern deconvolution which compensates the limitation of existing commercial EBSD software. The employed combination of methods revealed changing phase fractions of α and β 2 along the Zn gradient. Cellular reaction, coupled growth and spinodal decomposition were discussed as possible mechanisms for the formation of the nanoscale structure, with coupled growth identified as the most likely. • Combination of state-of-the-art EBSD and (HR)TEM analysis for phase identification • Determination of c-dependent phase fractions by a comparative study of measured and dynamically simulated Kikuchi patterns • Observation of nanoscopic α + β 2 microstructure in α/β brass in direct competition with massive/martensitic transformation • Classification of competitive solid state reactions depending on the level of undercooling classification of competitive solid state reactions depending on the level of undercoolings

Improvement of Microstructure and Properties of Cu Coatings Prepared with Cold Spraying by Plasma Heating

To improve the microstructure and properties of Cu coating prepared by cold spraying, the plasma heating is used during the cold spraying process. The models of Cu particles deposited on a Cu substrate during cold spraying process without/with plasma heating are established and calculated, and the results are compared. The calculated results show that the plasma heating causes copper particles and substrates to produce greater plastic deformation during deposition. The microstructure of Cu coating prepared by cold spraying with plasma heating is experimentally investigated. Plasma heating can effectively reduce the porosity of the copper coating, improve the binding between the coating and the substrate, and reduce the grain size of the coating, which is due to the greater deformation of the copper particles under plasma heating. The experimental results are consistent with the calculation results. The results of the coating immersion experiments show that the corrosion rate of the Cu coating prepared by plasma‐assisted low‐pressure cold spraying is reduced from 1.5 to 0.094 mg cm−2 h compared with the samples prepared without plasma heating under the same conditions, which is due to the reduced porosity of the coating.

Strengthening mechanism of ultra-high strength Cu–20Ag alloy wire induced by cumulative strain

This study deals with the evolution of strength and microstructure in Cu–20Ag alloy during wire drawing from an initial diameter of 7.84 mm–0.02 mm. The final wire had a strength of 1670 MPa and 53.8% of the conductivity of international annealed copper standard (IACS). Electron backscattering diffraction (EBSD) and transmission electron microscope (TEM) were used for microstructural characterization in the later stages of deformation, we found that many boundaries resulting from the lamellar structures and the occurrence of nano-twins formed in the lamellar improved the strength of the wire. When the wire diameter is less than 2.95 mm，with an essentially constant dislocation density, the strength can be related solely to strengthening boundaries by a grain size refinement. The strengthening mechanism of the wire during cumulative strain is discussed.

Improvements in Li deposition and stripping induced by Cu (111) nanotwinned columnar grains

How to depress the dendrite growth, promote the coulombic efficiency, and improve the cycling stability of Li plating/stripping on Cu foils is a strict challenge in the lithium metal-free batteries (LMfBs). Here, the Cu substrates with the (111)-preferred orientation and the (111)-nanotwinned lamella grains are compared for the performance of Li deposition/stripping in 1 M lithium hexafluorophosphate/ethylene carbonate-dimethyl carbonate (LiPF6/EC-DMC with EC:DMC=50:50 vol.%). The presence of twin boundaries in the Cu foil does decrease the total interfacial energy of the copper surface, favoring the formation of the LiF-amorphous matrix solid electrolyte interphase (SEI) to provide fast Li-ion pathways and inducing the growth of UPD (underpotential deposition) Li. As a result, the (111)-nanotwinned copper foil significantly reduces the nucleation overpotential of Li plating, uniforms the lithium deposit, improves the coulombic efficiency, and ameliorates the cycling stability of Li plating/stripping. The microstructures of Cu foils with the (111)-preferred orientation and the (111)-nanotwinned lamella grains have been confirmed by the X-ray diffraction (XRD), scanning electron microscopy (SEM), and high-resolution transmission electron microscopy (HRTEM).

Manipulating the microstructure of Cu from direct current electrodeposition without additives to overcome the strength-ductility trade-off

The attainment of both high strength and ductility has been a long-standing quest for most metallic materials in engineering. However, these properties were generally mutually exclusive. In this study, columnar nanotwinned Cu (col-nt-Cu) with a hexagonal pyramid surface morphology was fabricated using direct current (DC) electrodeposition in an additive-free electrolyte. The formation mechanism of col-nt-Cu was studied from the perspective of surface morphology, and the results indicated that both nanotwins and hexagonal pyramids were the result of screw dislocation-driven growth. This unique microstructure is at the basis of excellent mechanical properties, including a high ultimate tensile strength up to 443 MPa and superior elongation to failure (∼21%), thereby overcoming the strength-ductility trade-off. This unusual strengthening is caused by the synergy of multiple deformation mechanisms, including dislocation transfer across twin boundaries (TBs) and threading dislocation gliding in the confined twin lamella. In particular, the interaction between dislocations and TBs exhibited variability in the spatial distribution of col-nt-Cu. The TBs in the top grains dominate the strength of the sample, whereas the grain boundaries (GBs) in the core grains dominate the ductility of the sample. These results not only provide new insight to overcome the strength-ductility trade-off, but also steer the way for optimization of mechanical properties through the design of nanotwinned structures in spatial distribution.

The Effect of the RMACREO Process Applying Remarkable Torsional Distortion on the Aging Behavior and Microstructure of Cu–Cr–Zr Alloy

The Effect of the RMACREO Process Applying Remarkable Torsional Distortion on the Aging Behavior and Microstructure of Cu–Cr–Zr Alloy

Effect of boron on aging strengthened phase and properties of Cu–Cr–Zr alloy

The effect of trace B on the properties and microstructure of Cu–Cr–Zr alloy was investigated in this work. Aging precipitation phases in Cu matrix were analyzed by transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). It was found that Cr is the main precipitation phase and its precipitation process is affected by B. Boron can increase the precipitation rate of the precipitation phase and promote the precipitation of the precipitation phase. After Cu–Cr–Zr alloy aged at 480 °C for 2 h, nanosized Cr particles were coherent with the Cu matrix and formed coherent G.P zones. In Cu–Cr–Zr alloy with 0.03wt% B addition, the aging precipitation process was accelerated, resulting in most of the aging precipitate being bcc Cr. Effect of trace B on hardness and electrical conductivity of Cu–Cr–Zr alloy was tested. It is indicated that B addition improves the hardness and electrical conductivity of the alloy and 0.03wt% B corresponds to the peak value of conductivity and hardness of Cu–Cr–Zr–B alloy.