Al In Cu Research Articles

Effect of the Addition of Cu and Al on the Microstructure, Phase Composition and Properties of a Ti-6Al-4V Alloy Obtained by Selective Laser Melting

The present study considers the samples of an Ti-6Al-4V alloy obtained by selective laser melting with the addition of a 10% Cu-Al powder mixture. The microstructure, elemental composition and phase composition, as well as the physico-chemical properties, have been investigated by the methods of electron microscopy, X-ray phase analysis, and bending testing. The obtained samples have a relative density of 98.5 ± 0.1%. The addition of the Cu-Al powder mixture facilitates supercooling during crystallization and solidification, which allows decreasing the size and changing the shape of the initial β-Ti grains. The constant cooling rate of the alloy typical for the SLM technology has been shown to be able to prevent martensitic transformation. The formation of a structure that consists of β-Ti grains, a dispersed eutectoid mixture of α-Ti and Ti2Cu grains, and a solid solution of Al in Cu has been revealed. In the case of doping by the 10% Cu-Al mixture, the physico-mechanical properties are improved. The hardness of the samples amounts to 390 HRC, with the bending strength being 1550 ± 20 MPa and deformation of 3.5 ± 0.2%. The developed alloy can be recommended for applications in the production of parts of jet and car engines, implants for medicine, and corrosion-resistant parts for the chemical industry.

Effect of annealing on the structure and phase composition of Al-Cu laminated metal-matrix composites produced by shear deformation under pressure

This paper presents the data from the study on the effect of annealing of Al-Cu metal-matrix composites, produced by severe plastic deformation via shear under pressure. Three-layer compositions with different alternations of layers (Al-Cu-Al and Cu-Al-Cu) were subjected to deformation by high-pressure torsion, and then annealed at a temperature of 450 °C for 15 minutes. Using X-ray phase analysis and energy-dispersive analysis, we revealed the formation of the Al2Cu, AlCu and Al4Cu9 intermetallic compounds, surrounded by solid solutions of Al in Cu and Cu in Al. Their fraction and distribution in the volume depend on the way of stacking of the layer components. The produced microstructure is an “in situ” composite formed in the process of deformation and annealing.

Microstructure characterization of hypereutectoid aluminium bronze composite coating

Hypereutectoid aluminium bronze coating was deposited onto an E.N. 10503 steel substrate using plasma transferred arc welding (PTA). Microstructure characterisation of the coating and a section near the steel substrate joint was carried out using SEM, EBSD, EDS in conjunction with XRD and depth-sensing nano-indentation. The constituent phases in the coating were identified as: martensitic Cu3Al β1' phase, solid solution of Al in Cu α phase and the intermetallic Fe3Al κ1 phase. The region near the steel substrate was characterised by high hardness, large grains and presence of Cu precipitates. No cracks were observed in this region. The coating has high hardness of 4.9GPa and Young's modulus of 121.7GPa. This is attributed to homogeneous distribution of sub microns size Fe3Al intermetallic phase. The implications of the coating to the engineering application of sheet metal forming are discussed.

Effect of impurities and microstructure of Cu electroplated film on reliability of Cu interconnects using CuAl alloy seed

► The control of the impurities in Cu films is a key issue for Cu interconnects. ► High impurities in electroplated Cu films suppress Al diffusion from CuAl seed. ► This effect improves electro-migration reliability with narrow via. In order to improve reliability of Cu interconnects, Cu–Al alloy seed have been applied. In this paper, the effects of impurities in electroplated Cu (ECP–Cu) film on Cu interconnects have been investigated in detail. It is revealed that high concentration of impurities in ECP–Cu films suppresses the diffusion of Al into ECP–Cu films and confines Al in Cu–Al seed layer. This effect improves via electro-migration (EM) reliability. On the other hand, an ECP–Cu film with high concentration of impurities leads to increase line resistance, due to its small grain size and the existence of impurities in grains. Hence, the control of the impurities in ECP–Cu film is a key issue for the integration of Cu interconnects.

Metal Dusting Resistant Copper-Based Materials

Cu and Cu-based alloy coatings suppress carbon transfer to the metal surface from carbon-supersaturated gaseous environments. The metal dusting resistance of such coatings has been investigated in CO-H2 gas mixtures at temperatures ranging from 450°C to 700°C. Conventional plating and cladding methods have been used to deposit Cu-based materials on the surfaces of commercial materials such as 2.25Cr-0.5Mo steel and carbon steel. In addition to the performance of Cu-based materials under laboratory conditions, the effect of alloying elements such as Sn, Zn, Ni, Si, and Al in Cu on the corrosion process and the coating/substrate interface stability are discussed with particular attention to commercial scale applications.

Metal Dusting Resistant Copper-Based Materials

Copper and Cu-based alloy coatings suppress carbon transfer to the metal surface from carbon-supersaturated gaseous environments. The metal dusting resistance of such coatings has been investigated in CO-H2 gas mixtures at temperatures ranging from 450°C to 700°C. Conventional plating and cladding methods have been employed to deposit Cu-based materials on the surfaces of commercial materials such as 2.25Cr-0.5Mo steel and carbon steel. In addition to the performance of Cu-based materials under laboratory conditions, the effect of alloying elements such as Sn, Zn, Ni and Al in Cu on the corrosion process and the coating/substrate interface stability are discussed with particular attention to commercial scale applications.

Conduction electron scattering and spin-flipping at sputtered Al/Cu Interfaces

We use two different techniques to derive the two parameters describing conduction electron scattering and spin-flipping at sputtered Al/Cu interfaces in the current-perpendicular-to-plane (CPP) geometry. These parameters are: 2ARAl/Cu, twice the interface specific resistance, where A is the area through which the CPP current flows; and δAl/Cu, which gives the probability P of spin-flipping from P = 1 – exp(−δ). A technique involving simple multilayers, and sample temperature not exceeding room temperature, gives 2ARAl/Cu = 2.3 ± 0.2 fΩm2. A technique involving exchange-biased spin-valves (EBSVs), where the sample is annealed briefly to 453 K, gives 2ARAl/Cu = 2.0 ± 0.15 fΩm2. Averaging the two values, but increasing the uncertainty for reasons explained, gives the best estimate of 2ARAl/Cu = 2.15 ± 0.4 fΩm2. This average is comparable to, but smaller than, the published value of 2ARAl/Cu = 3.6 ± 1 fΩm2 derived from thermal conductance measurements, and larger than our calculated values for interface thicknesses up to 6 monolayers (ML). However, it is similar to our calculated values for an interface thickness of 8 ML. Combining extrapolation of higher temperature bulk diffusion data for Al in Cu and vice-versa, with x-ray and transmission electron microscope (TEM) studies of similarly sputtered multilayers, indicates that such interface thicknesses are possible, especially for annealed multilayers. CPP-magnetoresistance (MR) measurements of the EBSV samples give only very small spin-flipping at the Al/Cu interface—δAl/Cu = 0.05−0.05+0.02. Such a small value is consistent with expected small spin-orbit interactions in both Al and Cu. Supplementary studies of CPP-MR of Permalloy (Py)-based EBSVs containing [Cu/Al/Cu] trilayers, show unusual behavior when the central Al layer is at least 10 nm thick, giving a CPP-MR like that for Py/Al, independent of Cu layer thicknesses from 0 to 10 nm. MR, x-ray, and TEM results give some clues as to the origins of this behavior, but a completely satisfactory explanation is not yet available.

Microstructural characterization and properties of Al/Cu/steel diffusion bonded joints

We prepared Al/Cu/steel composite with a gradient structure using a vacuum hot-pressed diffusion method and investigated the Al/Cu/steel interface. The results show that a supersaturated solid solution with a thickness of about 2 um formed in the Cu/steel diffusion zone. Two kinds of intermetallic compounds, Cu9Al4 adjacent to the Cu side and CuAl2 adjacent to the Al side, formed at the interface of the Al/Cu. The thickness of the intermetallic compound layer appeared to greatly affect conductivity and tensile strength. The conductivity and the tensile strength decreased from 36.9 MS/m to 24.2 MS/m, and from 70.9MPa to 40.7MPa, respectively, while the thickness increased from 3.5 um to 23 um. The fractures occurred between a supersaturated solid solution (Al in Cu) and Cu9Al4, or between Cu9Al4 and CuAl2.

Relationship between powder characteristic and internal oxidation of Al in Cu-Al pre-alloyed powders

Since Cu-Al powder characteristics have important effects on the preparation of Cu/Al 2 O 3 composite, the apparent activation energy of Al internal oxidation reaction in Cu-Al pre-alloyed powders with different characteristics was calculated in the present investigation. The microstructure and properties of the synthesized Cu/Al 2 O 3 were studied. The results show that high-energy milling can obviously promote internal oxidation of Al in Cu-Al powders in the same solid solubility. At the same milling conditions and internal oxidation parameters, the solid solution of Al in Cu either in low or high amount will result in the poor microstructure and properties of the Cu/Al 2 O 3 composite. Subsequently, when high-energy milling and internal oxidation are synchronously used to prepare the Cu/Al 2 O 3 composite, there should be an appropriate solubility and milling effect for the pre-alloyed powders.

Diffusion in Cu(Al) Solid Solution

The solid state diffusion characteristics in the Cu(Al) solid solution phase, was investigated in the temperature range of 1023–1223 K using single phase bulk diffusion couples between pure Cu/Cu- 10 at.% Al. The interdiffusion coefficients, D, were calculated using Boltzmann–Matano method and Hall’s method from the concentration profiles of the couples that were determined using EPMA. The interdiffusion coefficients (D) calculated ranges between 1.39 X 10−14 and 3.97 X 10−13 m2/s in the temperature range of 1023 to 1223 K. The composition and temperature dependence of D were established. The activation energy for interdiffusion varies from 123.1 to 134.2 kJ/mol in the concentration range 1 at. % ≤ CAl ≤ 9 at. %. The impurity diffusion coefficient of Al in Cu is determined by extrapolating the interdiffusion coeffficient values to infinite dilution of the alloy i.e CAl →0 and its temperature dependence was also established. The activation energy for impurity diffusion of Al in Cu was found to be 137.1 kJ/mol.

Comparison of MiM Performance with Various Electrodes and Dieletric in Cu Dual Damascene of CMOS MS/RF Technology

In this paper, we have compared the performance of metal–insulator–metal (MiM) capacitors for different bottom electrode materials including Cu, , and Al in Cu–back-end-of-the-line (BEOL) process. A high-performance and low-defect-density MiM capacitor for mixed-signal and radio frequency (MS/RF) technology based on a complementary metal oxide semiconductor (CMOS) process was demonstrated. Q-factor can achieve for both Cu and Al at with MiM capacitors. showed a low Q-factor due to high resistivity. The process incorporates aluminum electrode into Cu–BEOL for MiM capacitor with a cost-effective process. The roughness of electro-dielectric interface by a thin aluminum electrode is critical for MiM performance due to field enhancement by roughness of a thin aluminum electrode. We have demonstrated a way to eliminate the roughness effect of thin Al and provide a MiM capacitor with high performance and low defect density. In particular, a method is demonstrated to achieve better matching, leakage, electrical breakdown, and temperature coefficient of capacitance performance for MiM capacitors.

Microstructural evolution in the friction stir welded 6061 aluminum alloy (T6-temper condition) to copper

This paper concentrates on the temperature distribution and microstructural evolution of the friction stir welding of 6061 aluminum alloy (T6-temper condition) to copper. The mechanically mixed region in the joining of the dissimilar metals 6061 aluminum alloy and copper weld consists mainly of several intermetallic compounds such as CuAl 2, CuAl, and Cu 9Al 4 together with small amounts of α-Al and the saturated solid solution of Al in Cu. Distributed at the bottom of the weld nugget are numerous deformed copper lamellae with a high solid-solubility of aluminum. An intercalated structure or vertex flow pattern consisting of CuAl 4 and the saturated solid solution of Al in Cu is formed in the Cu-rich regions adjacent to the bottom of the weld by the mechanical integration of aluminum into copper. The measured peak temperature in the weld zone of the 6061 aluminum side reaches 580 °C, which is distinctly higher than the melting points of the Al–Cu eutectic or some of the hypo- and hyper-eutectic alloys. Higher peak temperatures are expected at the near interface regions between the weld metal and the stirred tool pin. The phases present in the welds can be explained from the Al–Cu equilibrium phase diagram with the assumption that a complete phase equilibrium is reached in the liquid state but not during solidification. The primary dendrites of α-Al, CuAl 2, and CuAl, and the eutectic of α-Al/CuAl 2 are formed in the weld nugget during solidification. Distinctly different micro-hardness levels from 136 to 760 HV 0.2 are produced corresponding to various microstructural features in the weld nugget.

Positron Annihilation Spectroscopy in the Evaluation of Microstructure of Cast Copper and Copper-Aluminum Alloys during Isochronal Annealing

Isochronal annealing was carried out for cast Cu, Cu-5wt.% Al, Cu-10wt.% Al, and Cu-20Wt.% Al alloys in the range of 423–1173 K. The annealing behavior was followed by positron annihilation lifetime spectroscopy (PALS). Microhardness (H v) has been measured and used for comparison. The microstructure variations were observed by optical and scanning electron microscopy. Three stages were distinguished for all samples in the behavior of average lifetime (τ av) and H v. In the first stage (room temperature to 573 K), τ av and H v reach extremely high values for Cu-20wt.% Al compared with other alloys. The analysis of the first stage indicates anneal softening for cast Cu and Cu-5wt.% Al and anneal hardening for Cu-10wt.% Al and Cu-20wt.% Al. The second stage (573–873 K) is characterized by a maximum of τ av at 673 K followed by a decrease up to the end of the stage for cast Cu, Cu-5wt.% Al (the highest maximum), and Cu-10wt.% Al; a slight change is observed for Cu-20wt.% Al. The change in H v is notable only for Cu-10wt.% Al and Cu-20wt.% Al, and indicates that τ av is sensitive to the change that occurred in the bulk material, while Hv shows the general behavior of the surface of the material. The third stage (873–1173 K) is characterized by near saturation for both τ av and H v, indicating complete recrystallization for cast Cu, Cu-5wt.% Al, and Cu-10wt.% Al and complete softening for Cu-20wt.% Al. Recrystallization is shifted to higher temperatures by increasing the amount of Al in Cu. The analysis of positron lifetime presents evidence of the existence of three-dimensional (3D) defects in addition to one-dimensional defects, so a modification to the simple trapping model is needed when considering inhomogeneous trapping.

Intermetallic Formation in the Aluminum–Copper System

Intermetallic formation at 425°C in the aluminum–copper system has been studied by scanning electron microscopy using welded diffusion couples. Several Al–Cu phases predicted by the equilibrium phase diagram of the elements and voids taking place in the diffusion zone have been detected in the couples. The predominant phases were found to be Al 2 Cu 3 and the solid solution of Al in Cu, α. The growth of the intermetallic layer obeyed the parabolic law.

Failure mechanism of a multilayer (TiN/Al/TiN) diffusion barrier between copper and silicon

The improvement of the diffusion barrier performance for Cu metallization, by inserting a thin Al layer between two TiN layers, has been clearly demonstrated and reported by us. The key idea behind our scheme is “stuffing” of grain boundaries of columnar TiN films by Al2O3. It has been also found that the barrier property is at its best when the Al thickness is 1 nm, but above this value, the barrier performance degrades drastically when the upper TiN film is not preannealed. In this study, why the barrier breaks down at above 1 nm of Al interlayer thickness is investigated. High-resolution transmission electron microscopy, scanning transmission electron microscopy, and energy dispersive spectroscopy analyses revealed that the fast diffusion of Cu in the presence of the free Al is the main reason for the failure of the present diffusion barrier scheme. These results are discussed on the basis of the differences between the movements of Al and Cu through TiN film, and the differences between the solid solubilities of Al in Cu and in Si. Our results show that both Al interlayer thickness and the oxygen content in TiN film should be properly controlled to take full advantage of the present multilayer diffusion barrier scheme.

Dynamics of Phase Transitions in the SHS of a 3Cu–Al Powder Mixture in the Regime of Thermal Explosion

The paper reports results of dynamic x‐ray photography of self‐propagating high‐temperature synthesis of a 3Cu–Al powder mixture in the regime of thermal explosion. The stages of formation of the final product are considered, beginning with the heating of the starting mixture and interaction of its components and ending with phase transitions during cooling of the product — intermetallides Cu9Al4 and Cu3Al, which are the main components of Cu based tribotechnical materials. It is shown that upon heating in the temperature range of 550 – 590°C, the intensity of diffraction lines of Al drops to the background level. The exothermicreaction of synthesis of the intermetallide is initiated at a temperature of 610 – 630°C. In the period of sharp increase in temperature to 1040°C, the presence of the starting copper and the newly formed high‐temperature β′ phase with the Cu9Al4 tructure are detected simultaneously in the combustion wave. When cooled to 300$°C, the material contains two cubic phases — Cu9Al4 and an α‐solid solution of Al in Cu. Further cooling is accompanied by formation and increase of peaks of the Cu3Al phase with an orthorhombic lattice. The phase composition of aluminum bronze produced by SHS with combustion in the regime of thermal explosion is not in equilibrium.

Cu結晶の(111)面転位ピットの形態変化について

Dislocation etch pits on the (111) surface of Cu crystals have been observed to study the effects of the composition, stirring rate and temperature of etchants and the small addition of Al in Cu. The etchants are Young’s solutions containing (NH4)2S2O8, NH4OH and NH4Br. The dislocation etch pit morphology strongly depends on the composition of the etchants. It is shown that the pit size varies with the concentration of the etchant and the pit shape varies with the ratio of each components in the etchant. At a ratio (NH4)2S2O8:NH4OH:NH4Br nearly equal to 1∼1.5:6:0.3, the triangular pyramid pits surrounded with 〈110〉 sides are produced, while, off this ratio, the etch pits tend to become more or less rounded. On the other hand, the stirring of the etchant increases the pit size remaining its shape unchanged. Such a tendency is also indicated with an increase of etchant temperature from 260 to 300 K, except a slight rounding of etch pit at 300 K. Moreover, with the addition of Al, the etch pits become small and rounded, though the straight-sided pits are revealed when etched with etchant containing high concentration of (NH4)2S2O8. Some discussions about the effects of the etching condition are given in connection with the kink nucleation and motion at the surface steps.

Dislocation structures in fatigued copper-aluminum alloys

Low-temperature (1.5–30 K) thermal conductivity measurments are used for a nondestructive determination of dislocation structures generated by cyclic deformation in two copper-aluminum alloys (1 and 15 at.% Al in Cu). A torsional strain mode is adopted with an amplitude of a few percent. Fatigue life is estimated to be approximately 1000 cycles. In both alloys the change in lattice thermal resistivity due to deformation follows a T−2 dependence above 10 K, and a T−1 dependence below 2 K. At intermediate temperatures it is found to be composed of a T−2 and a T−3 term. This temperature variation is interpreted as due to phonon scattering by dislocations and by dislocation structures. Electron microscope observations by others indicate that these structures form cell walls in the lower-concentration alloy, and dislocation bands in the higher-concentration alloy. A dipole wall model of these substructures is proposed, and the corresponding lattice thermal resistivity calculated using a simple extension of Klemens’s theory of phonon scattering by the various lattice defects. These calculations give reasonable agreement with the experimental results. Dislocation densities are estimated to be of the order of 1012 cm−2 in the substructures, and of the order of 1010 cm−2 in the crystal matrix. It is found that dislocation substructures are formed during the first quarter -cycle of straining. Subsequent strain reversal tends to ’’condense’’ dislocations into cell walls and dislocation bands. As a result, there is a vary rapid saturation of dislocations in the substructures, which is almost complete after two cycles of deformation.

Contribution of s-d Interaction to the Internal Magnetic Field in Heusler Alloys

Spin echoes and their external magnetic field effects have been observed on Heusler alloys, Cu 2 MnAl, Cu 2 MnIn and Cu 2 MnSn at 4.2°K. The sign of the internal magnetic field at nuclei of the constituent elements has been determined to be negative, and on the basis of the R-K-K-Y interaction semiquantitative agreement between calculated and observed internal magnetic fields has been obtained in Cu 2 MnAl, Cu 2 MnIn and Cu 2 MnSn. The spectra for Cu, Mn and Sn in Cu 2 MnSn, In in Cu 2 MnIn and Al in Cu 2 MnAl have been observed for the first time.

Nuclear-Magnetic-Resonance and X-Ray Study of Solute Loss by Internal Oxidation in Comminuted and Vaccum-Annealed Cu-Mn Alloys

It is shown that Cu-Mn alloys lose part of their solute Mn during comminution and vacuum annealing. X-ray measurements indicate that the solute loss occurs by the mechanism of internal oxidation, the dominant oxide formed being MnO (manganosite). NMR and x-ray measurements have been correlated in terms of loss of solute Mn from the Cu lattice. The results indicate that physical measurements on both annealed and unannealed samples of powdered Cu-Mn alloys can lead to errors in interpretation, if measured parameters are correlated with solute concentrations obtained directly from chemical analysis. Similar effects were observed with solutes of Ti, Fe, and Al in Cu.