Microstructure Of Cu Research Articles

The evolution of microstructure in Cu–8.0Ni–1.8Si–0.15Mg alloy during aging

The microstructure of precipitates in Cu–8.0Ni–1.8Si–0.15Mg (wt.%) alloy with super-high strength and high electrical conductivity was investigated by transmission electron microscope and selected-area electronic diffraction. The sequence of phase transformation in the alloy with aging time is that: spinodal decomposition + ordering(β-Ni 3Si) → ordering(β-Ni 3Si) + δ-Ni 2Si → δ-Ni 2Si + β-Ni 3Si. And the relationship between the matrix and precipitates is that: ( 1 1 0 ) m / / ( 1 1 0 ) β / / ( 2 1 1 ¯ ) δ , [ 1 1 2 ¯ ] m / / [ 1 1 ¯ 2 ] β / / [ 3 2 4 ] δ . Spinodal decomposition, ordering (β-Ni 3Si) and precipitates (β-Ni 3Si + δ-Ni 2Si) are attributed to the strengthening during aging, whose multiple interactions results in the variation of micro-hardness. After solution treatment at 970 °C for 6 h, cool rolled by 50%, and aged at 450 °C for 180 min, the Cu–8.0Ni–1.8Si–0.15Mg alloy has an average tensile strength of 1005 MPa, 0.2% proof strength of 768 MPa, elongation of 5.6% and an average electrical conductivity of 31.5.0% IACS. The morphology of the fracture surface of the alloy contains shallow dimple and quasi-cleavage pattern.

The Preparation for Cu(Sn) Films of Barrierless Interconnection

In this study, Cu films doped with different Sn concentrations from 0.6-1.4 at.% were prepared by magnetron co-sputtering. The electrical resistivities and microstructures of Cu (Sn) films after annealings were investigated. The results showed that a sharp increase of the resistivity of Cu (1.4 at.% Sn) and Cu (1.1 at.% Sn) films were found after annealing above at 500°C. The existence of 0.6 at.% Sn in the Cu film is in solid solution state. A minimum electrical resistivity value of ~3.2μΩ•cm was obtained after annealing at 600°C for 1h . Even after a annealing at 700°C, the Cu/Si interface of Cu (0.6 at.% Sn) film still remained sharp without any Cu-Si and Cu-Sn compounds. The results confirmed that the lower resistivity and higher stability of Cu films can be achieved by strictly control of the doping concentrations and the existing state (solid solution without compounds and precipitates) of Sn element.

Microstructural evolution and mechanical response of Cu–Al–Be–B shape memory alloy processed by repetitive equal channel angular pressing

Equal channel angular pressing (ECAP) was applied to modify the microstructures of Cu–Al–Be–B shape memory alloys (SMAs). The alloy was greatly refined because of the interaction of the large plastic deformation and physicochemical effects. With an increase of ECAP passes, the specimens showed a change from plastic fracture to brittle fracture, increased proportion of transgranular fracture, and decreased ultimate strength from 460 MPa to 340 MPa. These were caused by the precipitation of the γ 2-phase and the disappearance of thermoelastic martensite. After appropriate heat treatment, the content of thermoelastic martensites increased, while the grain size remained smaller than that of the as-cast alloy. Further tests showed that the ultimate strength of this alloy improved to 703 MPa and the attenuation of shape recovery ratio was alleviated.

Influence of annealing on the elastic properties and microstructure of Cu 58.1Zr 35.9Al 6 bulk metallic glass

The present paper aims to study the crystallization behavior and the elastic properties of Cu 58.1Zr 35.9Al 6 bulk metallic glass using ultrasonic pulse focusing method. It is found that the changes of the elastic properties and microstructure can be classified into three stages corresponding to different temperature regions. Below the glass transition temperature T g, no structural change was observed by X-ray diffraction, and annealing only induced structural relaxation. After annealing at the super-cooled liquid region, the new phase Cu 10Zr 7 formed, meanwhile, some anomalous acoustic and elastic behaviors occurred near T g (490). Above the onset crystallization temperature T x , the elastic properties increased further with the elevated temperature and Cu 8Zr 3 phase was also observed besides Cu 10Zr 7 phase. The annealing has a significant effect on the elastic property and microstructure of Cu 58.1Zr 35.9Al 6 bulk metallic glass, which is closely related to the annihilation of quenched-in free volume and the improvement of the atom order degree.

Influence on the Electro-Migration Resistance by Line Width and Average Grain Size along the Longitudinal Direction of Very Narrow Cu Wires

The influence of microstructures of Cu wires on electromigration (EM) resistance has been investigated using Cu wires with various line widths from 50 to 280 nm and line heights of 300 nm or 500 nm. A strong line width dependence of median time to failure was observed as the EM resistance decreases substantially with narrowing of line widths from 280 nm to 50 nm. The activation energies for 50, 80, 100 and 140 nm widths were 0.61, 0.64, 0.68 and 0.71 eV. The EM resistance and activation energy of Cu wires could be represented as a function of the ratio of line length to average grain size, which corresponds to the number of grains along the longitudinal direction, and they both increased as this ratio decreased. The influence of this ratio was particularly significant when the line width was below 100 nm. These results indicate that coarsening of grain sizes in the current flow direction is mandatory to enhance EM resistance and lower resistivity for the very narrow Cu wires.

Effect of equal channel angular pressing and heat treatment on the microstructure of Cu–Al–Be–B shape memory alloy

The combination of equal channel angular pressing (ECAP) and heat treatment was carried out to modify the microstructure of a Cu–Al–Be–B shape memory alloy. Microstructures of the alloy after ECAP and subsequent quenching were investigated by optical microscopy and X-ray diffraction (XRD). The alloy with 8 passes of ECAP at 743 K is characterized with ultra-fine grains (~ 2 μm), but with smaller fraction of martensites which implies the lower shape memory effect (SME). After reheated at 873 K and oil-quenched to room temperature, the grains become coarsen (~ 50 μm) but still finer than that of as-received (100–300 μm), and the fraction and order of martensites were increased simultaneously.

Microstructure and growth mechanism of Cu ramified aggregates on silicone oil surfaces

We study the microstructure and growth mechanism of copper (Cu) ramified aggregates by the optical microscopy and atomic force microscopy. We find that the ramified Cu aggregates exhibit a granular structure with mean size of the single particulate in the range of 30–60 nm. It is interesting that the average width of the ramified aggregates and the mean size of the particulates do not change obviously with the increase of the nominal film thickness. Compared the size distributions of the Cu particulates on the oil surfaces with that of Cu films on glass surfaces, we suggest that the surface morphology and microstructures of Cu aggregates (or films) depend on property of substrates. The interpretation for this phenomenon is also presented.

Microstructure and mechanical properties of Cu–3 at.% Ti alloy aged in a hydrogen atmosphere

The microstructure of Cu–3 at.% Ti alloy aged at 773 K in a hydrogen atmosphere of 0.37 MPa has been investigated, together with hardness and tensile strength. At the early stage of aging, needle-shaped α-Cu 4Ti particles precipitate finely in a similar manner to the case of conventional vacuum-aging. On further aging, some α-Cu 4Ti precipitates are extended, while others are replaced by δ-TiH 2 precipitates. The precipitation of titanium hydride reduces the concentration of Ti in the matrix more efficiently than aging in a vacuum. The yield strength first rises, but falls on further aging. This is due to the microstructural evolution: α-Cu 4Ti particles first form and grow, but then diminish because of the formation of titanium hydrides. Elongation to fracture, as well as the electrical conductivity, is promoted by long-time aging in the hydrogen atmosphere, reflecting the reduced Ti concentration in the matrix.

Interfacial microstructure and defect analysis in Cu(In,Ga)Se([sub]2)-based multilayered film by analytical transmission electron microscopy and focused ion beam

Interfacial microstructures of Cu(In,Ga)Se 2(CIGS)-based multilayered film are closely characterized by TEM (transmission electron microscopy), SEM (scanning electron microscopy) and FIB (focused ion beam). A cross-sectional TEM, energy dispersive X-ray spectroscopy and energy-filtered TEM reveal that a pronounced Cu diffusion occurs across the interface of the CdS/CIGS, which leads to a large amount of Cu rich in the CdS layer and a Cu-deficient sub-surface in the CIGS layer as well as a rough interfacial structure. TEM studies further reveal that the interface microstructures in the multilayered film are dissimilar, both ZnO/CdS and CdS/CIGS interfaces are strongly bonded whereas the CIGS/Mo interface is weakly bonded and interface separation occasionally occurs. Mo back contact layer shows a well adhesion to glass substrate. Detailed observation on defects in the CIGS-based multilayered film is carried out by 3D (3-dimensional) FIB and SEM techniques. Sequential 2D (2-demensional) cross-sectioning shows that dominant growth-defects in the CIGS and top SiO 2 layers are micro-scale crack, appearing as diversified morphologies. The micro-scale crack in the CIGS layer is possibly released by propagating into the adjacent layer while the crack in the SiO 2 layer is relieved usually by forming a small particle behind. It is noted that in the multilayered film the interface frequently acts as crack initiation sites due to distinct thermal expansion coefficients.

Influence of processing on the microstructure of Cu–8Cr–4Nb

The particle-strengthened Cu–8 at.%Cr–4 at.%Nb alloy is processed by consolidation of atomized powders followed by extrusion to obtain bars and rolling to produce sheets. Comparison of copper matrix grain and second-phase particle structures in both extruded and rolled Cu–8Cr–4Nb was performed. Extruded material displayed locally banded arrangements of Cr2Nb particles, while the distribution of particles was more uniform in rolled material. Mean Cr2Nb particle sizes were found to be essentially the same for both processing methods. Non-spherical particles in the extruded alloy showed some preferred orientation, whereas the rolled material displayed a more uniform particle orientation distribution. Extruded material exhibited a dual grain size distribution with smaller grains in banded regions. The mean grain size of 1.36 μm in extruded material was larger than the 0.65 μm grain size of rolled material. A [101] texture was evident in extruded material, whereas the rolled material was only slightly textured along the [001] and [111] directions. The processing differences for the rolled and extruded forms give rise to different microstructures and hence higher creep strength for the extruded material in the temperature range of 773–923 K.

Microstructure and solidification behavior of Cu–Ni–Si alloys

The microstructure and solidification behavior of Cu–Ni–Si alloys with four different Cu contents was studied systematically under near-equilibrium solidification conditions. The microstructures of these Cu–Ni–Si alloys were characterized by SEM and the phase composition was identified by XRD analysis. The phase transition during the solidification process was studied by DTA under an Ar atmosphere. The results show that the microstructure and solidification behavior is closely related to the composition of Cu–Ni–Si alloys. The microstructure of Cu–Ni–Si alloys with higher than 40% Cu content consists of primary phase α-Cu(Ni, Si) and eutectic phase (β 1-Ni 3Si + α-Cu(Ni,Si).When the Cu content is about 40%, only the eutectic phase (β 1-Ni 3Si + α-Cu(Ni,Si)) is present. DTA analysis shows there are three phase transitions during every cooling cycle of alloys with higher than 40% Cu content, but only one for 40% Cu content. Cu–Ni–Si alloy with 40% Cu solidifies by a eutectic reaction, but Cu–Ni–Si alloys with higher than 40% Cu content solidify as a hypoeutectic reaction.

Formation of a Core/Shell Microstructure in Cu–Ni Thin Films

Electrodeposition of Cu–Ni thin films can result in phase separation characterized by the formation of nodular features that exhibit a uniform columnar core/shell structure with a copper-rich core and nickel-rich shell. Here, we show that the core/shell microstructure is the result of differences in the nucleation and growth rates of the two components. In the potential range where the core/shell structure is observed, copper deposition is fast, resulting in the formation of a relatively low density of large hemispherical islands. Nickel deposition is characterized by slower kinetics, resulting in the formation of a high density of small islands surrounding the copper islands. These results provide a basis for understanding the formation of this core/shell microstructure in binary alloy systems.

Microstructural characterization of Cu/ZnO/Al2O3 catalysts for methanol steam reforming—A comparative study

Microstructural characteristics of various real Cu/ZnO/Al2O3 catalysts for methanol steam reforming (MSR) were investigated by in situ X-ray diffraction (XRD), in situ X-ray absorption spectroscopy (XAS), temperature programmed reduction (TPR) and electron microscopy (TEM). Structure–activity correlations of binary Cu/ZnO model catalysts were compared to microstructural properties of the ternary catalysts obtained from in situ experiments under MSR conditions. Similar to the binary system, in addition to a high specific copper surface area the catalytic activity of Cu/ZnO/Al2O3 catalysts is determined by defects in the bulk structure. The presence of lattice strain in the copper particles as the result of an advanced Cu–ZnO interface was detected only for the most active Cu/ZnO/Al2O3 catalyst in this study. Complementarily, a highly defect rich nature of both Cu and ZnO has been found in the short-range order structure (XAS). Conventional TPR and TEM investigations confirm a homogeneous microstructure of Cu and ZnO particles with a narrow particle size distribution. Conversely, a heterogeneous microstructure with large copper particles and a pronounced bimodal particle size distribution was identified for the less active catalysts. Apparently, lattice strain in the copper nanoparticles is an indicator for a homogeneous microstructure of superior Cu/ZnO/Al2O3 catalyst for methanol chemistry.

Microstructural Characterizations of Cu Processed by ECAP from 4 to 24 Passes

The microstructures of pure Cu processed by equal channel angular pressing (ECAP) from 4 to 24 passes were investigated. It was found that the microstructures of Cu samples with a small number of ECAP passes (4-8) were not inhomogeneous and the fraction of high-angle grain boundary (HAGB) was low (25~43%). While for the samples with many number of ECAP passes (12-24), the grains became more equiaxed-like and the GB misorientations exhibited double-peak distribution with high fraction (51~64%) of HAGB. It was dislocation cells formed in large grains of the few-pass samples, but subgrains in the many-pass samples. These characterizations suggested that ultrafine-grained (UFG) microstructures in the few-pass samples were not fully accomplished, while it was obtained after many passes (>12). It is believed that dynamic recovery during processing for many passes was attributed to the formation of UFG microstructures.

The microstructure of Cu(In,Ga)S 2 solar cell absorber films prepared using three-stage and two-stage evaporation

The microstructure of three-stage Cu-poor Cu(In,Ga)S 2 solar cell absorbers has been compared with that of two-stage Cu-rich absorbers using high-resolution Transmission Electron Microscopy. It was found that the grains from three-stage evaporation have more stacking faults, and most of the grain boundaries are irregular, such as sawtooth shaped. The grains from two-stage evaporation have less defects, and the grain boundaries are straight. The difference of growth mechanisms between three-stage and two-stage evaporation are discussed and compared to the case of Cu(In,Ga)Se 2.

Influence of Ta-based Diffusion Barriers on the Microstructure of Copper Thin Films

Copper represents the most commonly used interconnect material in ultra large-scale integration (ULSI) technology. Given that the successful implementation of Cu requires the use of underlying diffusion barriers, these studies were focused on the influence of Ta-based barrier layers on the microstructure of physical vapor deposited (PVD) and electrochemically deposited (ECD) Cu thin films. The variation of a-Ta, b-Ta, TaSiN, and TaN as an underlayer caused a modification of the PVD Cu seed-layer texture, which also affected the microstructure of Cu electroplated on top of the seed layer, both before and after recrystallization at room temperature.

Microstructure of Cu–Be alloy triboxidative wear debris

The wear mechanism in disk-on-disk tests of a Cu–Be alloy against AISI D2 steel counterparts changes from metallic to oxidative for increasing loads. At low load the wear debris are made of the Cu–Be alloy, whereas above 50 N the main constituents are copper oxides, with a few residual particles of the copper-base alloy. Despite the lower oxidation state, cuprite (Cu 2O) is the main fraction of the high-load debris, whereas tenorite (CuO) is less than 10%. An analysis of the X-ray diffraction line profile, supported by high-resolution transmission electron microscopy (TEM), shows that cuprite domains are nanocrystalline, with domain sizes distributed about a mean value of 12 ÷ 13 nm, and contain a high density of dislocations (∼5 × 10 16 m −2). The small domain size is considered as a possible stabilization mechanism of cuprite against the higher oxidation state oxide tenorite, whereas the large dislocation content is a consequence of the heavy plastic deformation in the contact area. As a further support to the size-stabilization mechanism, a diffraction measurement repeated on the wear debris after a 6 month aging shows a marked increase in the tenorite fraction. According to line profile analysis, the remaining cuprite fraction is made up of nanocrystalline domains (∼6 nm) smaller than in the as-produced debris, thus supporting the hypothesis that small cuprite grains are more stable than larger ones, which more easily transform to tenorite.

Effects of Zr addition on the liquid phase separation and the microstructures of Cu–Cr ribbons with 18–22 at.% Cr

Cu 77Cr 23 − X Zr X ( X = 1, 2, 3) and Cu 82 − X Cr 18Zr X ( X = 6, 10) (at.%) ribbons were prepared by melt spinning in order to obtain finer Cr particles in Cu–Cr contact materials. Microstructural analyses reveal that the Cr particles from liquid phase separation can be refined to 50 nm when Cr content is in a range of 18–22 at.% and Zr addition is more than 3%. Meanwhile, Cu 5Zr precipitations in nano-scale were observed in the ribbons. The thermodynamic analyses indicate that Zr addition has reduced the large positive mixing heat between Cu and Cr, which resulted in the liquid phase separation occurring at a lower temperature and a smaller nucleation driving force. Therefore, Zr addition can partly restrain the liquid phase separation of Cu–Cr alloy during rapid cooling and then Cr particles have been refined.

Fatigue and martensitic transitions in Cu–Zn–Al and Cu–Al–Ni single crystals: mechanicalbehaviour, defects and diffusive phenomena

The effects of the repeated stress-induced transformation (pseudoelastic fatigue)on the mechanical behaviour and microstructure of Cu–Zn–Al and Cu–Al–Nisingle crystals are presented. Several microstructural changes occur duringcycling at temperatures above the martensitic transformation temperatureMs in Cu–Zn–Al alloys. Bulk defects consisting of dislocation bands with retained martensiteand intrusion–extrusion types of surface defects are observed. The fine characteristics of thedefects, such as nucleation, density, as well as other microstructural features, depend on theworking temperature, alloy composition, applied stresses and number of cycles. Thepresence of these defects alters the shape of the stress–strain curves in the pseudoelasticrange for Cu–Zn–Al. Also diffusive phenomena strongly affect the mechanical behaviourof these alloys both in the parent and martensite phases, even for tests carriedout slightly above room temperature. In turn, the kinetics of these diffusionalprocesses has been found to depend on the density of bulk defects. Details of theseprocesses are discussed and a simple model that describes the main characteristicsof the mechanical behaviour evolution is considered. The interaction betweenthe mechanical behaviour, density of defects and diffusion is discussed. In thecase of Cu–Al–Ni, bulk defects are also shown to occur but the system is lessprone to diffusion effects that could affect the mechanical behaviour. The defectsgenerated during pseudoelastic cycling lead, however, to the inhibition of theγ′ phase when a transition between the bcc parent phase and a mixture of two martensitic structuresγ′ (2H)and β′ (18R) is involved at the beginning of the cycling process.

The effect of added oversized elements on the microstructure of binary alloy nanoparticles

Molecular dynamics simulations are used to investigate the microstructures of Cu–Ninanoparticles with different concentrations of oversized atoms added to them. A manybody second moment tight binding approximation potential is adopted to model theinteratomic interactions. The Honeycutt–Anderson (HA) pair analysis technique is adoptedto analyse in detail the transformation between local structures at different temperatures.From the simulation results, at temperatures higher than the melting point, thenanoparticles are in a liquid state and an icosahedral local structure is most frequentlyfound inside the nanoparticles. At temperatures beneath the melting point, the fraction ofFCC local structure increases with decreasing concentrations of the larger size atoms,whereas a larger fraction of amorphous structure still remains in the solid state for higherconcentrations of oversized atoms. This is because the effects of distortion and misfit aremore significant for a nanoparticle having a higher concentration of oversizedatoms.