Intermetallic Al2Cu Research Articles

Effect of Shoulder Size on Weld Properties of Dissimilar Metal Friction Stir Welds

This article reports a research study that shows the effect of shoulder diameter size on the resulting weld properties of dissimilar friction stir welds between 5754 aluminum alloy (AA) and C11000 copper (Cu). Welds were produced using three different shoulder diameter tools: 15, 18, and 25 mm by varying the rotational speed between 600 and 1200 rpm and the traverse speed between 50 and 300 mm/min to achieve the best result. Each parameter combination was chosen to represent different heat input conditions (low, intermediates and high). The welds were characterized through microstructural evaluation, tensile testing, microhardness measurements, x-ray diffraction analysis, and electrical resistivity. Microstructural evaluation of the welds revealed that the welds produced consisted of all the friction stir welding (FSW) microstructure zones with organized flow lines comprising mixture layers of aluminum (Al) and copper (Cu) at the Stir Zones. The average Ultimate Tensile Strength (UTS) of the welds considered ranged from 178 to 208 MPa. Higher Vickers microhardness values were measured at the joint interfaces of all the welds because of the presence of intermetallic compounds in these regions. The x-ray diffraction analysis revealed the presence of Al4Cu9 and Al2Cu intermetallics at the interfacial regions, and low electrical resistivities were obtained at the joint interfaces. An optimized parameter setting for FSW of Al and Cu was obtained at the weld produced at 950 rpm and 50 mm/min with the 18-mm shoulder diameter tool.

Impact of ac/dc spark anodizing on the corrosion resistance of Al–Cu alloys

An ac/dc spark anodization method was used to deposit an oxide film (6 ± 3 μm in thickness) on the Al–Cu alloy AA2219. The oxide films were formed at 10 mA/cm 2 for 30 min in an alkaline silicate solution, showing three main stages of growth. Scanning electron microscopy and electron microprobe analysis revealed that the oxide films are not uniform and consist of three main layers, an inner Al-rich barrier layer (∼1 μm), an intermediate Al–Si mixed oxide layer (∼2 ± 1 μm), and an outer porous Si-rich layer (∼3 ± 3 μm). In addition, microscopic analysis showed that the Al 2Cu intermetallics present in the alloy have not been excessively oxidized during the anodization process and thus are retained beneath the oxide film, as desired. The coating passivity and corrosion resistance, evaluated using linear sweep voltammetry (LSV) in pH 7 borate buffer solution and electrochemical impedance spectroscopy (EIS) in 0.86 M NaCl solution, respectively, were both significantly improved after spark-anodization.

Surface modification of iron containing aluminum alloys by treatment with copper plasma produced with cathodic arc

In this study, a new approach for modification of surfaces with the help of cathodic arc plasma and its bias voltage dependent interaction with the substrates is described. As an example, alloying and surface modification of aluminium–iron alloys (with iron contents of 0.3 and 1 wt.%) with a cathodic arc plasma of copper is given. The effect of successively applied bias voltages of − 150 V and − 1000 V was investigated on the resulting micro structural surface features of the alloys. Surface modification processes were performed below and above 500 °C. In the experiments conducted below 500 °C, the modified surface predominantly consisted of Al 2Cu intermetallics, accompanied with a small amount of AlCu intermetallics and α-aluminum solid solution. However, in experiments conducted above 500 °C, melting and resolidification of the copper deposited substrate surface took place at − 1000 V and − 150 V bias voltages, respectively. A eutectic-like microstructure, containing α-aluminum, Al 2Cu phases, and iron containing ternary structures were obtained. It was found that the enrichment of iron in the surface took place through the enhanced role of the process on the diffusion of iron from bulk to the surface.

Dissolution Characteristics of Al2Cu and Al-4Cu Thin Films

Although Cu redistribution during dissolution of Al-Cu alloys is thought to have an important influence on susceptibility to localized corrosion, the details of the redistribution process in different environments are still not clear. This work uses in-situ x-ray absorption spectroscopy to follow the oxidation state of Cu in intermetallic Al2Cu and Al-4%Cu thin films during dissolution under potential control, in pH 10 borate and near-neutral Cl- environments. The oxidation state of Cu is observed to change only following significant dissolution of Al at potentials well above open circuit. In borate, formation of Cu (I) and Cu (II) occurs at potentials below the equilibrium potential for Cu/Cu2O, suggesting that the surface Cu is electrically isolated from the matrix. At higher potentials and longer exposure times, Cu ions went into solution, but subsequent re-plating of Cu on the surface was not observed.

Formation of Al2Cu and AlCu intermetallics in Al(Cu) alloy matrix composites by reaction sintering

We report the fabrication and characterization of a series of Al(Cu) alloy-based matrix composites. The composites were produced by sintering and rapid quenching three powder mixtures of Al and Cu with hypoeutectic, eutectic, and hypereutectic compositions. The morphology of the reinforcements formed in the Al(Cu) matrices of these composites was found to be variable. A two-phase Al2Cu–Al(Cu) nanoeutectic, with lamellar spacing of 200–300 nm, was found in the Al(Cu) matrix of the sample having hypoeutectic composition after it was oil-quenched from 1000 °C to room temperature. While oil quenching the sample with eutectic composition, produced single Al2Cu crystals of 2–2.5 μm size, embedded in a lamellar nanoeutectic matrix. As for the hypereutectic alloy, the matrix of the oil-quenched sample consisted mainly of Al2Cu intermetallic, and a secondary phase of AlCu dendrites with dendrite arms spacing of 1–1.5 μm.

Effect of beryllium and non-equilibrium heat treatment on mechanical properties of B319.0 alloy with 1.0%Fe

B319.0 hypoeutectic alloy is a heat treatable Al-Si-Cu-Mg system with nominal composition Al-6Si-3.5Cu-0.3Mg and about 0.1-1.2Fe. The purpose of this study was to determine the influence of Be and non-equilibrium heat treatment on the microstructure and mechanical properties of B319.0 alloys with a higher Fe (1.0 wt-%) content. Results indicate that Be additions can reduce the amount and average length of iron bearing phases, can transform some platelet like shapes (β-Al5FeSi) of iron intermetallic phase to comparatively harmless Chinese-script shapes (α-Al8Fe2Si), and can also refine the eutectic silicon. High temperature solution heat treatment(≥ 510°C) may not only completely dissolve the Al2Cu intermetallics, but may also cause dissolution and fragmentation behaviour in β-phase platelets and consequently reduce their volume fraction. Because the β-phase platelets are smaller in the Be-containing alloy under identical conditions, their dissolution behavior is more obvious than that in Be-free alloy. However, if deterioration of the mechanical properties is to be avoided, the solution temperature should be lower than the interdendritic melting temperature which resulted in an ultrafine eutectic phase on quenching. DSC and electrical conductivity analysis showed that the combined effect of Be additive and non-equilibrium heat treatment caused significant increase in the precipitation kinetics of B319.0 alloy. Fractographic analysis of tensile specimens revealed that fracture processes were mainly initiated by nucleation at β-Al5FeSi platelets as a result of their cracking and decohesion from the matrix. Therefore, adding Be to B319.0 alloy and optimising the solution heat treatment could result in fewer fracture initiating sites and greater precipitation of strengthening phases, with a consequent improvement in tensile properties.

Mechanical and Electrical Properties of Au-Al and Cu-Al Intermetallics Layer at Wire Bonding Interface

Mechanical and electrical properties of the Au-Al intermetallics layer were compared to the Cu-Al intermetallics layer. A thermal aging test was used to expedite the formation and growth of the intermetallics layer. Dynamic hardness, surface hardness, and intermetallic thickness of both bonding systems was compared. Unencapsulated samples were subjected to a ball shear test while encapsulated samples were electrically tested. Results showed that the Cu-Al intermetallics layer is relatively harder than Au-Al. Both intermetallic thicknesses grow linearly at about 18.0 and 0.07 nm/h, respectively, but the Au-Al intermetallic layer is 20 times thicker than Cu-Al before the aging test. The 1.5-μm growth of Au-Al intermetallic thickness acquired an additional shear force of 160 gf. The threshold value of the intermetallics layer thickness for the Au-Al and Cu-Al bonding system is 3.8 and 0.14 μm, respectively, before it shows degradation in shear force. Electrical resistance for the Au-Al system is higher than the Cu-Al system, especially at higher aging readout points.

Ce10Cl4Ga5 and Ln3ClGa4 (Ln: La, Ce): Reduced Halides or Oxidized Intermetallics?

AbstractFor Abstract see ChemInform Abstract in Full Text.

Ce10Cl4Ga5 and Ln3ClGa4 (Ln = La, Ce): reduced halides or oxidized intermetallics?

The compounds Ce(10)Cl(4)Ga(5) and Ln(3)ClGa(4) (Ln = La, Ce) were synthesized from stoichiometric mixtures of Ln, LnCl(3), and Ga under Ar atmosphere in sealed Ta ampules at 910-1020 degrees C for 25-26 days. Ce(10)Cl(4)Ga(5) is isostructural to La(10)Cl(4)Ga(5) (space group I4/mcm, No. 140) with lattice constants a = 7.9546(11) A, c = 31.793(6) A. Ln(3)ClGa(4) represents a new structural type, also in the space group I4/mcm, with a = 8.1955(8) and 8.1123(11) A, c = 11.363(2) and 11.229(2) A, respectively, for Ln = La and Ce. Ce(10)Cl(4)Ga(5) features building blocks of Ga-centered Ce(6) trigonal prisms and distinctive two-dimensional intermetallic CuAl(2) and U(3)Si(2) type nets. Its electronic structure falls within the realm of reduced rare-earth halides. Ln(3)ClGa(4) also contains the intermetallic CuAl(2) type nets, but the interstitials are inverted: The building blocks are Cl-centered Ln(6) octahedra. Its electronic structure is characterized by strong peripheral Ln-Ga bonding stabilizing the Ln(6)Cl octahedron which normally would have its Ln-Ln antibonding orbitals filled with electrons from interstitials beyond chalcogen. Magnetic susceptibility and conductivity measurements confirm the metallic nature of all three compounds.

Electron Energy-Loss Near-Edge Structure Studies of a Cu/(11-20)?-Al2O3 Interface

Electron energy-loss near-edge structure (ELNES) studies were employed to determine the bonding mechanisms and electronic structure of a Cu/(1120)α-Al 2 O 3 interface prepared by molecular beam epitaxy. The existence of an interfacial ELNES component at the Al-L 2,3 edge reveals that the Al atoms participate in the bonding and change their local coordination compared to bulk Al 2 O 3 . At the interfacial O-K ELNES some pre-edge intensity appears, indicating the presence of deep-level O-2p states hybridised with Cu-3d and/or Al-3p states. The interfacial Cu-L 2,3 ELNES shows a chemical shift of the edge onset to higher energy-loss values and the existence of unoccupied Cu-3d states. The shape and edge onset are similar to the Cu-L 2,3 edge measured in an intermetallic CuAl 2 compound. Image simulations of the experimental high-resolution transmission electron microscopic images were carried out assuming Cu-Al bonds at the Cu/(1120)Al 2 O 3 interface as found by the ELNES studies. The derived structural model for the atomistic arrangement at the interface contains a mixed monolayer of Cu and Al atoms that exhibits a projected bonding distance of (0.15 ± 0.02) nm to the first O-layer of the Al 2 O 3 substrate.

Incipient melting of Al5Mg8Si6Cu2 and Al2Cu intermetallics in unmodified and strontium-modified Al–Si–Cu–Mg (319) alloys during solution heat treatment

The present work was performed on seven alloys containing in common Al–6.5 wt%Si–3.5 wt%Cu, with magnesium in the range 0.04–0.45 wt%, and strontium in the range 0–300 p.p.m. The alloys were cast in the form of tensile test bars, solution heat treated in the temperature range 480–540°C for times up to 24 h. Two types of solution heat treatment were applied: (i) single-stage, where the test bars were solution treated at a certain temperature for 12 h prior to quenching in hot water (60°C); (ii) two-stage, where the test bars were solution treated for 12 h/510°C+12 h/T°C (T=510, 520, 530, 540°C), followed by quenching in hot water. In the low-magnesium alloys (i.e. with Mg∼0.04 wt%), melting of the Al2Cu phase commenced at 540°C. Increasing the magnesium content to ∼0.5 wt% reduced the incipient melting temperature of the Al5Mg8Si6Cu2 phase to 505°C. The mechanism of incipient melting and its effect on the tensile properties have been discussed in detail. © 1998 Chapman & Hall

Nanocomposite Microstructure in a melt spun Al-Cu-Zr Alloy

Rapid solidification of a ternary Al-Cu-Zr alloy results in a nanocomposite microstructure. In this study, melt spinning a Al82Cu15Zr3 alloy has resulted in the combined occurrence of, (a) 0.5 mu m sized grains of Al solid solution and (b) fine grains (10-20 nm) of intermetallic Al2Cu (theta) and alpha-Al, along side each other. The larger alpha-Al grains contain nanometric GP zones, with the Zr addition resulting in a grain refinement. In the other type of microstructure Zr promotes simultaneous nucleation of nanosized grains of the two equilibrium phases, Al2Cu and alpha-Al. Both these lead to a very high hardness of similar to 540 VHN for this alloy and can be used as a candidate for a high strength alloy with good ductility at a low strain rate.

非晶質Ｃｕ‐Ｔｉ粒子を含有するアルミニウム粉末の押出し加工

Mixture of aluminum and amorphous Ti-43at%Cu powders was mechanically alloyed to produce aluminum powder with a dispersion of amorphous particles. Microstructural changes in the both particles during the mechanical alloying and influence of heating on the structure of alloyed powder were investigated by using X-ray diffraction and differential thermal analysis. In the powder mechanically alloyed for prolong milling period than 14.4ks, intermetallic Al2Cu phase is formed by the heating at 600K and the Al3Ti and Al2Cu3 phases are formed at 800K. The forming temperature of Al3Ti and Al2Cu3 phases decreases with the increasing of milling period. Crystallization of AITi from t1he amorphous phase begins at about 700K. Extrusion of the mechanically alloyed powder was carried out at 573K, the amorphous structure of Ti-43at%Cu particle was unchanged during the heating at that temperature. The hardness of the extruded alloy increases with increasing of the mechanical alloying period and the heating temperature.

Ａｌ‐Ｃｕ‐Ｔｉ混合粉末の機械的合金化

Mixture of aluminum, copper and titanium powders was mechanically alloyed and then the powder was heat-treated at various temperature. A change of structure of the powder with milling period was investigated by using XRD, DTA, SEM and EPMA. In the early stage of mechanical alloying, particles of Cu and Ti are deformed and dispersed in Al matrix, but degree of deformation of Ti particle is smaller than that of Cu particle.Particles of Cu and Ti become finer with the increasing of milling period, and they disperse homogeneously as the milling period reaches to 72.0ks. Intermetallic Al2Cu phase was observed in the powder mechanically alloyed for 21.6ks. In the powder heattreated at 773K intermetallic Al3Ti and AlCu phases were observed. The forming temperature of Al3Ti and AlCu phase decrease with the increasing of milling period.Intermetallic AlTi phase was observed at low temperature in the powder mechanically alloyed for 72.0ks.

Thermal desorption study of catalytic systems. 17. Reaction of carbon monoxide with water on the surface of skeletal copper

1. The absence of intermetallic Cu-Al compounds in skeletal copper alters the state of the surface, resulting in the presence of selective competition of CO with CO2, increased adsorptive capacity of the surface with respect to CO2, the absence of the stably adsorbed form of CO, and a decrease in the catalytic activity. 2. Adsorption of CO in bridge and linear forms takes place on copper. Intermetallic Cu-Al compounds are the adsorption centers for the stably bound form of CO.