Al-transition Metal Research Articles

Insights into the complexation and oxidation of quercetin and luteolin in aqueous solutions in presence of selected metal cations

Flavonoids are natural antioxidants that can be used for the chelation of metal ions to treat metal toxicity. Ideal chelators should form stable metal complexes and be resistant to oxidative degradation reactions in aqueous solutions at physiological conditions (pH 7.4 and 37 °C). In this work, the complexation and oxidation of quercetin and luteolin with selected metal cations (i.e. Cr(III), Mn(II), Fe(III), Co(II), Ni(II), Cu(II), Zn(II), and Al(III)) in aqueous solutions at pH 4 and 7.4 is discussed. Using UV–Vis, RP-UHPLC-PDA-MS, ESI-MS and 1H NMR, information about the complexing ability, stoichiometry, and the preferred metal binding sites was obtained. At pH 7.4, all metal ions were complexed by luteolin and quercetin, whereas at pH 4 both flavonoids only formed complexes with the trivalent metal cations (i.e. Cr(III), Fe(III), and Al(III)). No clear preference for any of the complexation sites was observed for quercetin and luteolin. UV–Vis and RP-UHPLC-PDA-MS showed that, at pH 7.4, chelation of quercetin was followed by metal-mediated oxidation resulting in degradation of quercetin. On the contrary, luteolin complexes with metal cations were stable and no oxidative degradation of luteolin was observed. The oxidative degradation pathway of quercetin was investigated by incubation in H218O, which showed that the oxidation occurs via both oxygenation and hydroxylation mechanisms, the latter being the preferred pathway for the trivalent metal ions.Our results indicate that luteolin is a more suitable chelating agent of Al(III) and first-row transition metal cations due to its higher oxidative stability and its ability to form stable complexes in aqueous solutions at pH 7.4.

Metallurgical reactions and tribological properties of self-lubricating Al-WS2 composites: Laser powder bed fusion Vs. spark plasma sintering

Self-lubricating aluminium-based composites reinforced with solid lubricants promise to meet the demand for lightweight materials in green tribological applications. The design advantages granted by additive manufacturing (AM) processes coupled with their capacity for in-situ production of composite materials are yet to be exploited in the realm of Al-transition metal dichalcogenides composites. In this work, laser powder bed fusion (LPBF) was deployed for the in-situ fabrication of Al-WS2 composites for the first time, elucidating the process-structure–property relationships in comparison to reference spark plasma sintering (SPS) samples. The WS2 response to the respective fabrication technique was also firstly investigated through a holistic characterisation. The formation of new phases (W for LPBF, Al5W and Al12W for SPS) provided the potential for microstructural tailoring for optimal tribological performance. For tribological properties, LPBF Al-WS2 exhibited a coefficient of friction (COF) 0.55 ± 0.01 and specific wear rate 3.4 ± 0.3 × 10−3 mm3/N∙m, slightly better than the SPS counterpart (COF 0.57 ± 0.02, specific wear rate 3.6 ± 0.3 × 10−3 mm3/N∙m). Furthermore, a novel methodology for studying the evolution of worn surfaces is proposed and validated, by which a tribo-layer formed at lower friction cycles was observed for the LPBF samples, meaning that AM will also be advantageous for the performance aspect of self-lubricating materials.

The Effect of Al and Ti Transition Metals on the Wear Resistance of Ceramic Based CrN Coatings; Investigation under Ambient Air and Vacuum Conditions

In the present study, CrN, CrAlN and CrAlTiN coatings were deposited using the cathodic arc evaporation technique. The structural investigations of these CrN based coatings were performed by scanning electron microscopy, energy dispersive spectroscopy, atomic force microscopy, X-ray diffractometer. The hardness and adhesion strength values of coatings were determined via Vickers type microhardness tester and progressive load scratch tester, respectively. The wear performance of samples was established at ambient air and vacuum condition. All coatings grew in the “T zone” growth model and had a dense and columnar structure. The XRD patterns presented predominantly (220), (110), and (111) reflections. It was demonstrated that the quaternary coating had a higher texture parameter as 0.68, which was related to the highest thickness and hardness. Also, CrAlTiN coatings with the smallest mean crystallite size of ∼87 nm showed the best hardness, and this ensured relatively high scratch resistance. CrN and CrAlTiN coatings improved wear performance under ambient air condition but were not striking as under vacuum condition. The quaternary coating had a superior performance in the vacuum condition, but due to the high sensitivity of Ti to oxygen, it fell behind the CrN coating under ambient air condition.

Microstructural Assessment of a Multiple-Intermetallic-Strengthened Aluminum Alloy Produced from Gas-Atomized Powder by Hot Extrusion and Friction Extrusion.

An aluminum (Al) matrix with various transition metal (TM) additions is an effective alloying approach for developing high-specific-strength materials for use at elevated temperatures. Conventional fabrication processes such as casting or fusion-related methods are not capable of producing Al–TM alloys in bulk form. Solid phase processing techniques, such as extrusion, have been shown to maintain the microstructure of Al–TM alloys. In this study, extrusions are fabricated from gas-atomized aluminum powders (≈100–400 µm) that contain 12.4 wt % TM additives and an Al-based matrix reinforced by various Al–Fe–Cr–Ti intermetallic compounds (IMCs). Two different extrusion techniques, conventional hot extrusion and friction extrusion, are compared using fabricating rods. During extrusion, the strengthening IMC phases were extensively refined as a result of severe plastic deformation. Furthermore, the quasicrystal approximant IMC phase (70.4 wt % Al, 20.4 wt % Fe, 8.7 wt % Cr, 0.6 wt % Ti) observed in the powder precursor is replaced by new IMC phases such as Al3.2Fe and Al45Cr7-type IMCs. The Al3Ti-type IMC phase is partially dissolved into the Al matrix during extrusion. The combination of linear and rotational shear in the friction extrusion process caused severe deformation in the powders, which allowed for a higher extrusion ratio, eliminated linear voids, and resulted in higher ductility while maintaining strength comparable to that resulting from hot extrusion. Results from equilibrium thermodynamic calculations show that the strengthening IMC phases are stable at elevated temperatures (up to ≈ 600 °C), thus enhancing the high-temperature strength of the extrudates.

Chemical interaction and electronic structure in a compositionally complex alloy: A case study by means of X-ray absorption and X-ray photoelectron spectroscopy

Chemical interaction and changes in local electronic structure of Cr, Fe, Co, Ni and Cu transition metals (TMs) upon formation of an Al8Co17Cr17Cu8Fe17Ni33 compositionally complex alloy (CCA) have been studied by X-ray absorption spectroscopy and X-ray photoelectron spectroscopy. It was found that upon CCA formation, occupancy of the Cr, Co and Ni 3d states changes and the maximum of the occupied and empty Ni 3d states density shifts away from Fermi level (Ef) by 0.5 and 0.6 eV, respectively, whereas the Cr 3d empty states maximum shifts towards Ef by 0.3 eV, compared to the corresponding pure metals. The absence of significant charge transfer between the elements was established, pointing to the balancing of the 3d states occupancy change by involvement of delocalized 4s and 4p states into the charge redistribution. Despite the expected formation of strong Al–TMs covalent bonds, the Al role in the transformation of the TMs 3d electronic states is negligible. The work demonstrates a decisive role of Cr in the Ni local electronic structure transformation and suggests formation of directional Ni–Cr bonds with covalent character. These findings can be helpful for tuning deformation properties and phase stability of the CCA.

Shining Light on Aluminum Nanoparticle Synthesis.

ConspectusAluminum in its nanostructured form is generating increasing interest because of its light-harvesting properties, achieved by excitation of its localized surface plasmon resonance. Compared to traditional plasmonic materials, the coinage metals Au and Ag, Al is far more earth-abundant and, therefore, more suitable for large-area applications or where cost may be an important factor. Its optical properties are far more flexible than either Au or Ag, supporting plasmon resonances that range from UV wavelengths, through the visible regime, and into the infrared region of the spectrum. However, the chemical synthesis of Al nanocrystals (NCs) of controlled size and shape has historically lagged far behind that of Au and Ag. This is partially due to the high reactivity of Al precursors, which react readily with O2, H2O, and many reagents used in traditional NC syntheses. The first chemical synthesis of Al NCs was demonstrated by Haber and Buhro in 1998, decomposing AlH3 using titanium isopropoxide (TIP), with a number of subsequent reports refining this protocol. The role of a catalyst in Al NC synthesis is, we believe, unique to this synthetic approach. In 2015, the first synthesis of size controlled Al NCs was published by our group. Since then, we have significantly advanced Al NC synthesis, postsynthetic modifications, and applications of Al nanoparticles (NPs)-NCs with additional surface modifications-in chemical sensing and photocatalysis. Colloidal Al synthesis has its unique challenges, differing markedly from the far more familiar Au and Ag syntheses, which currently appears to present a de facto barrier to broader research activity in this field.The goal of this Account is to highlight developments in controlled synthesis of Al NCs and applications of Al NPs over the last five years. We outline techniques for successful Al NC synthesis and address some of the problems that may be encountered in this synthesis. A mechanistic understanding of AlH3 decomposition using TIP has been developed, while new directions have been discovered for synthetic control. Facet-binding ligands, alternate Al precursors, new titanium-based reduction catalysts, even solvent composition have all been shown to control reaction products while also opening doors to future developments. A variety of postsynthetic modifications to the Al NC native oxide surface, including polymer, MOF, and transition metal island coatings have been demonstrated for applications in molecular sensing and photocatalysis. In this Account, we hope to convey that Al synthesis is more accessible than generally perceived and to encourage new synthetic development based on underlying mechanisms controlling size and shape. High selectivity in particle faceting and twinning, implementation of seeded growth principles for monodisperse samples, and the demonstration of new, practical applications of Al nanoparticles remain primary challenges in the field. As Al nanoparticle synthesis is refined and new applications emerge, colloidal Al will become an accessible and low-cost plasmonic nanomaterial complementary to Au and Ag.

Theoretical investigation of lanthanide and transition metal on Al cathode: Equilibrium potential and atomic radii analysis by a mathematical equation

Partitioning of actinides from the lanthanides is arguably the most difficult separation in radio-chemistry. Since the ionic radii are comparable to that of the trivalent lanthanide ions, the coordination chemistry is similar, resulting in almost no separation option. Meanwhile, due to the radioactivity of actinides and its own dangers, studies of these its theoretical properties are rarely carried out. In this paper, we mainly studied the equilibrium potentials of Al-Ln alloys by cyclic voltammetry and open circuit chronopotentiometry method and established the mathematical equation between the equilibrium potentials of the alloy and the atomic radii by condensation of experimental data. Bold predictions of the equilibrium potential of actinides deposited on Al cathode based on the mathematical equation were made, which shows excellent agreement with previous reports. Meanwhile, the equilibrium potentials of transition metals on Al cathode were tested. It was found that the equilibrium potentials and atomic radii of the Al-transition metal intermetallic compounds accorded with the mathematical equation as well. Hence, the electrochemistry of both lanthanides and actinides as well as transition metal on active cathodes could be reasonably estimated by employing the fitted mathematical equation, which provide a preliminary model and theoretical basis of the behavior of lanthanides elements in electrolysis-based pyroprocessing. From the perspective of development, it provides a unique and rich opportunity to realize both extraction and separation of actinides in spent fuel.

Synthesis of Complex-Alloyed Nickel Aluminides from Oxide Compounds by Aluminothermic Method

This paper deals with the investigation of complex-alloyed nickel aluminides obtained from oxide compounds by aluminothermic reduction. The aim of the work was to study and develop the physicochemical basis for obtaining complex-alloyed nickel aluminides and their application for enhancing the properties of coatings made by electrospark deposition (ESD) on steel castings, as well as their use as grain refiners for tin bronze. The peculiarities of microstructure formation of master alloys based on the Al–TM (transition metal) system were studied using optical, electronic scanning microscopy and X-ray spectral microanalysis. There were regularities found in the formation of structural components of aluminum alloys (Ni–Al, Ni-Al-Cr, Ni-Al-Mo, Ni-Al-W, Ni-Al-Ti, Ni-Cr-Mo-W, Ni-Al-Cr-Mo-W-Ti, Ni-Al-Cr-V, Ni-Al-Cr-V-Mo) and changes in their microhardness, depending on the composition of the charge, which consisted of oxide compounds, and on the amount of reducing agent (aluminum powder). It is shown that all the alloys obtained are formed on the basis of the β phase (solid solution of alloying elements in nickel aluminide) and quasi-eutectic, consisting of the β′ phase and intermetallics of the alloying elements. The most effective alloys, in terms of increasing microhardness, were Al-Ni-Cr-Mo-W (7007 MPa) and Al-Ni-Cr-V-Mo (7914 MPa). The perspective is shown for applying the synthesized intermetallic master alloys as anode materials for producing coatings by electrospark deposition on steel of C1030 grade. The obtained coatings increase the heat resistance of steel samples by 7.5 times, while the coating from NiAl-Cr-Mo-W alloy remains practically nonoxidized under the selected test conditions. The use of NiAl intermetallics as a modifying additive (0.15 wt. %) in tin bronze allows increasing the microhardness of the α-solid solution by 1.9 times and the microhardness of the eutectic (α + β phase) by 2.7 times.

Effect of element types on the glass forming ability of Al-TM-RE ternary metallic glasses using electron structure guiding

The effect of TM (transition metal, Fe, Co, Ni) and RE (rare earth, La, Ce, Sm, Y, Gd, Er, Pr) element types on the glass forming ability (GFA) of Al86TM9RE5 ternary alloy system has been studied based on the concept of Fermi sphere - Brillouin zone interaction. The effect of TM element is primarily on the electron hybridization between Al atoms and TM atoms, affecting the diameter of the Fermi sphere (2KF). And the effect of RE element is mainly a change in the diameter of the pseudo-Brillouin zone (KP). Their effects on the Fermi level and Brillouin zone size are monitored using spectroscopy experiments. The |δ| = |KP-2KF| criterion was proposed to evaluate the effect of GFA on the TM and RE elements. This criterion guided us to select an optimal GFA element (Al86Ni9Y5) in the Al-TM-RE ternary alloy system and was confirmed by the experimental results.

Anomalously enhanced thermal stability of phosphorene via metal adatom doping: An experimental and first-principles study

Atomically thin black phosphorus, also known as phosphorene, is an emerging two-dimensional (2D) material, which has attracted increasing attention due to its unique electronic and optoelectronic properties. However, the reduced thermal stability of phosphorene limits its suitability for high-temperature fabrication processes, which could be detrimental for the performance of phosphorenebased devices. Here, we investigate the impact of doping by Al and Hf transition metal adatoms on the thermal stability of phosphorene. The formation of Al–P covalent bonds was found to significantly improve the thermal coefficients of the A g 1 , B2g, and A g 2 phonon modes to 0.00044, 0.00081, and 0.00012 cm–1·°C–1, respectively, which are two orders of magnitude lower than those observed for pristine P–P bonds (~0.01 cm–1·°C–1). First-principles calculations within the density functional theory framework reveal that the observed thermal stability enhancement in the Al-doped material reflects a significantly higher Al binding energy, due to the stronger Al–P bonds compared to the weak van der Waals interactions between adjacent P atoms in the undoped material. The present work thus paves the way towards phosphorene materials with improved structural stability, which could be promising candidates for potential nanoelectronic and optoelectronic applications.

Electrodeposition of Al-W Alloy Films from Ionic Liquid and Evaluation of Their Corrosion Resistance and Mechanical Properties

Introduction The many useful characteristics of Al, particularly its high oxidation and corrosion resistance, make Al coatings effective in extending the lives of metallic materials. However, if Al is exposed to an environment where chloride ions are present (like seawater), the Al passivation layer is destroyed locally, followed by the creation of small holes on the surface. This form of corrosion is called pitting corrosion, and Al–transition metal alloys are known to exhibit a resistance to pitting corrosion. In particular, sputtered Al–W alloy films are reported to show outstanding pitting corrosion resistance [1-3]. Establishing a method for electrodeposition of Al–W films is of importance for industrial applications, because electrodeposition has advantages over other film formation processes including simple equipment, high film formation speed, and applicability in the case of complex surface shapes. Tsuda et al. reported the electrodeposition of Al–W alloys with a high W content from the 1-ethyl-3-methylimidazolium chloride(EMIC)–AlCl3 ionic liquid containing K3W2Cl9 [4]. However, these Al–W alloys had a powdery morphology when the W content was higher than 3 at%, and did not show significant pitting corrosion resistance. In this study, we formed smooth, dense and adherent Al–W alloy coatings by electrodeposition from the EMIC–AlCl3 ionic liquid with the addition of WCl2, and we investigated the pitting corrosion resistance of the resulting coatings. Furthermore, we evaluated the mechanical properties of the Al–W alloy coatings. Experimental The electrolytic bath was prepared by mixing EMIC with anhydrous AlCl3, and tungsten(II) chloride. The tungsten(II) chloride was prepared by reduction of tungsten(VI) chloride by bismuth. The electrodeposition of Al–W films was conducted under galvanostatic conditions using Cu and Al plates as the cathode and anode, respectively. The bath temperature was 80°C. All electrodeposition experiments were conducted in an argon-filled glove box. The electrodeposited films were analyzed by SEM, EDX, and XRD. Partial current density and current efficiency were determined by ICP-AES. The water content of the electrolytic bath was measured by the coulometric Karl Fischer method. Pitting corrosion potentials were determined by linear sweep voltammetry in a deaerated 3.5 wt% NaCl aqueous solution at room temperature. The mechanical properties of Al–W films were analyzed by the nano-indentation method. Results and Discussion The electrodeposited Al–W films were gray and had a rather smooth appearance. Surface and cross-sectional SEM observation showed that these films were composed of dense globular grains, which is characteristic of amorphous deposit. The average grain size was less than 3 μm. At a fixed concentration of tungsten (II) chloride in the bath, the W content of the films was, typically 15–16 at%, independent of the current density. XRD measurements detected no diffraction peaks from these Al–W films, indicating that the films were amorphous. The current efficiency for the Al–W electrodeposition estimated by ICP-AES was less than 87%, which was lower than that for pure Al electrodeposition. Further, the water content was found to be higher in the electrolytic bath with tungsten(II) chloride than in the bath without it. Therefore, the current loss is attributed to the reduction of water. The pitting corrosion potential of the Al–W alloy film was more positive by >800 mV than that of pure Al, indicating that the Al–W films have a high resistance to the pitting corrosion. Nano-indentation showed that the amorphous Al–W alloy films had high hardness and low elastic modulus compared to a pure Al film. As the alloy films were amorphous, the films contained no grain boundaries and dislocations, and this should be responsible for the excellent hardness and elastic modulus. Conclusion Smooth, dense, and adherent Al–16 at% W alloy films were obtained by electrodeposition. The Al–W alloy films exhibited excellent pitting corrosion resistance and mechanical properties compared with pure Al films. These results sufficiently demonstrate the potential applications of the electrodeposited Al–W alloy as a surface protective material.

Effect of Rare Earth and Transition Metal Elements on the Glass Forming Ability of Mechanical Alloyed Al–TM–RE Based Amorphous Alloys

The present work aims to compare the amorphous phase forming ability of ternary and quaternary Al based alloys (Al86Ni8Y6, Al86Ni6Y6Co2, Al86Ni8La6 and Al86Ni8Y4.5La1.5) synthesized via mechanical alloying by varying the composition, i.e. fully or partially replacing rare earth (RE) and transition metal (TM) elements based on similar atomic radii and coordination number. X-ray diffraction and high resolution transmission electron microscopy study revealed that the amorphization process occurred through formation of various intermetallic phases and nanocrystalline FCC Al. Fully amorphous phase was obtained for the alloys not containing lanthanum, whereas the other alloys containing La showed partial amorphization with reappearance of intermetallic phases attributed to mechanical crystallization. Differential scanning calorimetry study confirmed better thermal stability with wider transformation temperature for the alloys without La.

Origin of catalytic activity in sponge Ni catalysts for hydrogenation of carbonyl compounds

AbstractComputational results are presented from density function theory (DFT) that describe the reactivity of Al and early transition metal doped, sponge Ni catalysts. To develop an understanding of the catalytic activity of these materials, the direct reduction of acetaldehyde has been studied as a test system. Use of the scaling paradigm proposed by Norskov and co-worker shows the influence of dopant atoms upon the atomic adsorption energy of C and O and consequently adsorption energies of reaction intermediates. Construction of a simple kinetic model (parameterized from DFT) demonstrates that the presence of Al improves catalytic performance of carbonyl hydrogenation by increasing the reactivity towards O containing molecules, whilst at the same time decreasing the affinity towards C. Comparison is made to acetylene hydrogenation, where the activity is dependent on the C affinity of the catalysts. It is thus suggested that should one desire to selectively hydrogenate a carbonyl group in the presence o...

Bonding characteristics and site occupancies of alloying elements in Zr3Al2 compound from first principles

The bonding characteristics and site occupancies of the intermetallic compound Zr3Al2 alloyed by Ti, V and Cr elements have been investigated using first-principles methods based on density functional theory. By calculating the impurity formation energy, the alloying elements Ti, V, and Cr prefer to occupy the Zr3 site in Zr3Al2 compound. The lattice parameter and bond length after alloying at Al site are also discussed. The results showed that alloying elements Ti, V, and Cr are beneficial to improve the internal atomic forces of Zr3Al2. The bonding characteristics and mechanism of site preference in pure and alloyed Zr3Al2 are analyzed with differential electron density as well as density of states. It can be concluded that the bonding charge accumulation at the Zr3 site is along X–Al (X=Ti, V and Cr) directions while the bonding charge depletion is along X–Zr3 directions by analyzing the differential electron density of (110) plane after replacing Al with Ti, V and Cr. Total and partial density of states analysis showed that there is a strong hybridization between Al 3s-states and transition metal d-states.

Direct observations of local electronic states in an Al-based quasicrystal by STEM-EELS.

Most quasicrystals (QCs) reveal pseudogaps in their density of states around Fermi level, and hence the stability of QCs have been discussed in terms of energetic gains in electron systems. In fact, many QCs have been discovered by tuning valence electron density based on Hume-Rothery rule. Therefore, understanding electronic structures in QCs may provide an important clue for their stabilization mechanism. Generally, it has been frequently discussed based on an interaction between Fermi surface and Brillouin zone boundary within the framework of nearly free electron model, which is believed to be an underlying physics of a Hume-Rothery's empirical criteria. However the hybridization effect also stabilize electron system, particularly in Al-transition metal system, in which a lot of quasicrystalline phases were discovered. Therefore, the electronic structures of QCs have not yet been fully understood, whereas their atomic structures have been studied well in terms of configuration entropy by scanning transmission electron microscopy (STEM) [1]. In the present work, we investigate local electronic states in Al-based QCs using electron energy loss spectroscopy (EELS) combined with STEM, by which EELS spectra with sub-Å probe and atomic structure can be obtained simultaneously. We report STEM-EELS results on AlCuIr decagonal phases [2].jmicro;63/suppl_1/i17-a/DFU069F1F1DFU069F1Fig. 1.Core-loss edges obtained from cluster-centers and cluster-edges. Al L1 (left) Ir O23, Ir N67 (center) and Cu L23 (right). Principal components analysis clearly shows up the atomic-site dependence of plasmon loss spectra in a two-dimensional map. Qualitatively, there seems to be certain correlations between the plasmon peaks and the core-loss edges, Al L1, Ir O23, Ir N67 and Cu L23, all of which reveal different behaviors at the cluster centers and the edges (Fig. 1). All results indicate the cluster centers have metallic states and the cluster edges have covalent states in comparison. First-principles calculations confirm the unusual electronic state. On the basis of the calculated DOS and charge-density map, we conclude Al-Ir pairs, which are mainly located at the cluster edges, hybridize their orbitals and Cu atoms are localized at cluster center without hybridization. We analyze a distribution of the hybridized orbitals by Fourier transformation of electron localization function. The distribution seems like a 10-fold standing wave with Fermi wave length. It suggests that the Hume-Rothery mechanism works even when hybridization effect mainly contributes to pseudogap formation. In other words, global distribution of hybridized orbitals is important to stabilize structures whereas usually only local atomic configurations are discussed. Moreover, in the 10-fold standing wave, no distinct peak appears at the cluster centers. It means hybridized orbitals located at cluster centers are unable to contribute to the Hume-Rothery mechanism. It may be the reason why the metallic regions appear at the cluster centers.

Electrodeposition of Al-W-Mn Alloy from Lewis Acidic AlCl3−1-Ethyl-3-Methylimidazolium Chloride Ionic Liquid

It is well-known that Al-W alloy prepared by non-equilibrium alloying methods, e.g., RF sputtering deposition, show the most superior chloride-induced pitting corrosion potential among Al-transition metal binary alloys. If the W content exceeds 10 atomic percent (at %), the pitting potential is capable of extending the passive region more than 2600 mV against pure Al.1 Recently we have established the electrodeposition process of the binary Al-W alloy from the Lewis acidic 66.7-33.3 percent mole fraction (mol %) AlCl3–[C2mim]Cl ionic liquid.2 Depending on the electrodeposition conditions, it was possible to prepare Al-W alloys with W content approaching 96 at %. However, Al-W alloys with a high chloride pitting potential comparable to those produced by other non-equilibrium methods were not obtained because of their powdery morphology and fragile nature. Current challenge faced by Al-W alloy electrodeposition is to find out a new approach to form a smooth and dense layer onto a metal substrate possibly leading to higher chloride-induced pitting potential. In this study, we examined ternary Al-W-Mn alloy electrodeposition from the Lewis acidic 66.7-33.3 mol % AlCl3–[C2mim]Cl with both K3[W2Cl9] and MnCl2 because the addition of Mn to binary Al-transition metal alloys often gives a favorable chloride pitting potential.3 The procedures used for the preparation and purification of the AlCl3−[C2mim]Cl IL were identical to those described in previous articles.2-4 All the electrochemical experiments were conducted using a three-electrode cell. A Teflon® sheathed platinum rotating disk electrode was employed for the working electrode. A coil of 1.00 mm diameter aluminum wire was used for the counter electrode. The reference electrode was an aluminum wire immersed in a neat 66.7-33.3 mol % AlCl3–[C2mim]Cl, but was separated from the bulk IL by porosity E glass frits. All experiments were carried out in an Ar gas-filled glove box with O2 and H2O < 1 ppm. Alloy samples were deposited from the 66.7-33.3 m/o AlCl3−[C2mim]Cl with K3[W2Cl9] and MnCl2 onto Teflon®-sheathed 2.0-mm-diameter copper cylinder electrodes.Cyclic voltammograms were recorded at a Pt stationary disk electrode in the 66.7 mol % AlCl3–[C2mim]Cl before and after addition of K3[W2Cl9] and/or MnCl2 (Figure 1). In the neat melt, Al deposition/stripping occurred at 0 V vs. Al(III)/Al by the electrochemical reactions of the [Al2Cl7]-. After addition of K3[W2Cl9] or MnCl2 to the neat IL, the Al deposition/stripping behavior altered as reported in previous articles.2,3 Interestingly the electrochemical behavior varied significantly after addition of both K3[W2Cl9] and MnCl2. Three unknown oxidation peaks related to Al alloy stripping appeared. The main oxidation peak observed at ca. 0.73 V was more positive than those in the K3[W2Cl9] or the MnCl2 solutions. Based on this, the Al-W-Mn alloy was prepared on Cu substrates rotated at a fixed rate of 1000 rpm by a dc galvanostatic method at 353 K. As is the case for binary Al-W alloy electrodeposition in the 66.7 mol % AlCl3–[C2mim]Cl,2 the W content in the ternary Al-W-Mn alloys decreased with increasing the applied current density independently of the K3[W2Cl9] and MnCl2 concentration in the IL. The Mn content greatly varied with the solution composition and the applied current density. X-ray diffraction patterns of the samples are shown in Figure 2. As we expected, XRD pattern for Al92.1W0.2Mn7.7 suggested an amorphous phase formation, which is usually signaled by the disappearance of the fcc Al reflections and the development of a broad reflection centered at about 2θ = 41°, due to the high Mn content. Surprisingly the pattern for Al88.6W3.6Mn7.8 did not show the broad reflection while the Mn content in these two samples is about the same. It is difficult to explain this unexpected result; however, there is no doubt that W atoms in the alloys prevent an amorphous phase formation in Al-W-Mn alloy system. This result is very similar to the fact found during the electrodeposition of Al-Mo-Ti alloy.4 The chloride-induced pitting potential of the Al-W-Mn alloys produced in this study exceeded that for Al-W and Al-Mn binary alloy electrodeposits. Thus, the Mn addition to Al-W alloy electrodeposits is a highly effective approach in the improvement of surface morphology and chloride-induced pitting potential.

Structure of an Al&amp;ndash;Cu&amp;ndash;Co Decagonal Quasicrystal Studied by &lt;i&gt;C&lt;/i&gt;s-Corrected STEM

The structure of an Al­Cu­Co decagonal quasicrystal (DQC) with two quasiperiodic planes in an annealed Al64Cu22Co14 alloy has been studied by spherical aberration (Cs)-corrected scanning transmission electron microscopy (STEM) with high-angle annular detector dark-field (HAADF) and annular bright-field (ABF) techniques. The observed HAADF-STEM images taken with the incident beam parallel to the periodic axis clearly represent individual transition-metal (TM) Cu/Co atoms and mixed sites (MSs) of Al and TM atoms as separated bright dots, and consequently arrangements of TM atoms and MSs on the two quasiperiodic planes can be directly determined. The TM atoms on the two quasiperiodic planes are arranged in pentagonal tiling with an edge-length of 0.76nm, and also the TM atoms and MSs are located at vertices of Penrose tiling with an edge-length of 0.25nm, and so they are arranged with a bond orientational order (BOO). Pentagonal frames with definite directions in the pentagonal tiling of TM atoms are also arranged in ¸ 2 -inflated pentagonal tiling with an edge-length of 2nm. Arrangements of TM atoms derived from the observed HAADF-STEM image are placed in ideal pentagonal Penrose tiling with an edge-length of 2nm, which is generated by the projection of five-dimensional (5D) hyper-cubic lattice, and are projected on occupation domains (ODs) in the perpendicular space. The arrangement of Al atoms and TM atoms and MSs in a well-symmetric region is interpreted from the observed HAADF- and ABFSTEM images. [doi:10.2320/matertrans.M2014008]

Aluminum Alloying Effects on Lattice Types, Microstructures, and Mechanical Behavior of High-Entropy Alloys Systems

The crystal lattice type is one of the dominant factors for controlling the mechanical behavior of high-entropy alloys (HEAs). For example, the yield strength at room temperature varies from 300 MPa for the face-centered-cubic (fcc) structured alloys, such as the CoCrCuFeNiTix system, to about 3,000 MPa for the body-centered-cubic (bcc) structured alloys, such as the AlCoCrFeNiTix system. The values of Vickers hardness range from 100 to 900, depending on lattice types and microstructures. As in conventional alloys with one or two principal elements, the addition of minor alloying elements to HEAs can further alter their mechanical properties, such as strength, plasticity, hardness, etc. Excessive alloying may even result in the change of lattice types of HEAs. In this report, we first review alloying effects on lattice types and properties of HEAs in five Al-containing HEA systems: AlxCoCrCuFeNi, AlxCoCrFeNi, AlxCrFe1.5MnNi0.5, AlxCoCrFeNiTi, and AlxCrCuFeNi2. It is found that Al acts as a strong bcc stabilizer, and its addition enhances the strength of the alloy at the cost of reduced ductility. The origins of such effects are then qualitatively discussed from the viewpoints of lattice-strain energies and electronic bonds. Quantification of the interaction between Al and 3d transition metals in fcc, bcc, and intermetallic compounds is illustrated in the thermodynamic modeling using the CALculation of PHAse Diagram method.

Corrosion behaviour of Al–29at%Co alloy in aqueous NaCl

Microstructure and corrosion behaviour of a binary Al–29 at%Co alloy have been studied. The alloy was prepared by arc-melting of Al and Co in high purity Ar and rapidly solidified on a water-cooled Cu mould. The alloy chemical composition and microstructure were characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray diffraction. Furthermore, the corrosion behaviour was studied by potentiodynamic polarization in aqueous NaCl (0.6 mol dm −3 ) at room temperature. The alloy was found to consist of three phases: hexagonal Al 5 Co 2 , Z-phase and AlCo (β). The corrosion resistance of different intermetallic phases is characterized. The results are compared to previously published results of Al–TM (TM = transition metal) alloys.

Effect of upset forging on microstructure and tensile properties in a devitrified Al–Ni–Co–Y Alloy

Devitrified Al—transition metal—rare earth alloys offer routes to obtain higher volume fractions of dispersed strengthening phases than conventional precipitation routes. Here, we report a study of the microstructure–property relationships of an Al–Ni–Co–Y alloy processed by gas atomization and consolidated/devitrified by warm extrusion. Microstructural characterization by electron microscopy and serial section FIB tomography show that the alloy comprises an FCC Al matrix and 44 % by volume of elongated Al19(Ni,Co)5Y3 plates with the Al19Ni5Gd3 structure. The plates are aligned with the extrusion direction in the as-extruded alloy, and tensile data show a distinct anisotropy in yield strength and strain to failure. These data are consistent with the alloy acting more like a unidirectional short-fiber-reinforced metal–matrix composite than a conventional precipitation-hardened alloy. During axial upset forging, the ternary plates do not break up, but instead they rotate, until at large upset strains they lie perpendicular to their original orientation with corresponding changes in the tensile properties. The materials exhibit yield strengths of up to 713 MPa and tensile elongations of up to 5 %. Thus, such systems could form the basis for truly deformable high-strength low-density metal–matrix composites.