Alx Alloys Research Articles

Peculiar microstructure with high damping capacity for Al0.5CrFe2Ni medium-entropy alloy

In this paper, the effect of Al mole ratio on phase evolution, damping capacity and mechanical properties of the AlxCrFe2Ni (indicated by Alx, x = 0.3, 0.4, 0.5 and 0.7) medium-entropy alloys (MEAs) was investigated. The results show that the structure of the Alx MEAs changes from the face-centered cubic (FCC) phase dominated by the Al0.3 alloy to the body-centered cubic (BCC) phase dominated by the Al0.7 alloy. As the volume fraction of the BCC phase increases the corresponding grain size of the alloys decreases and then increases, which increases the ferromagnetic properties and decreases interfacial area in the Alx alloys. The high damping capacity of Al0.5 and Al0.7 alloys is corresponding to 0.05545, and 0.05044, respectively, under the synergistic effects of ferromagnetic damping and interfacial damping. The special honeycomb-like morphology of FCC phase distributed in the BCC matrix gives the Al0.5 alloy the highest damping capacity and yield strength.

Unraveling L12 Al3X (X=Ti, Zr, Hf) nano-precipitate evolution in aluminum alloys via multi-scale diffusion simulation

The evolution of L12 Al3X (X = Ti, Zr, Hf) nano-precipitates in Al-X alloys was studied by multi-scale diffusion simulation using a combination of first principles calculation and finite element method. The results show that the diffusion coefficient in Al-X solid-solution phase follows DAl>DZr>DHf>DTi, which are in excellent agreement with available experimental values. On the other hand, the mobility of X atoms in L12 Al3X phases is reversed, following DAlAl3X>DTiAl3Ti>DHfAl3Hf>DZrAl3Zr. The calculated Al and X diffusion coefficients in both Al-X solid-solution and L12 Al3X ordered phases were used to simulate the evolution of L12 nano-precipitate embedded in Al-X solid-solution matrix. It is found that only Zr could promote the formation of nano-precipitates at 650 K, the common heat-treatment temperature for advanced Al alloys. At lower temperature, the sluggish atomic movement hinder the nucleation of L12 phase, while at higher temperature the precipitates redissolve into the Al matrix. The multi-scale diffusion simulation underlines the indispensable role of diffusion in L12 Al3X phases on the nano-precipitate evolution, and also provides a feasible way to the rationally design of precipitate strengthening alloys.

Microstructural, microhardness and electrochemical properties of heat-treated LENS in-situ synthesized Ti–Al-x(Mo, Si) alloys

So as to explore the opportunity of property enhancement of TiAl-based alloys, studies of microstructural evolution after processing with heat treatments are to be expected. Therefore, the objective of this present study is to investigate how additions of silicon (Si) and molybdenum (Mo) as alloying elements affects the microstructure, microhardness, corrosion behaviour, and wear properties of Ti–Al-x(Mo, Si) alloys made from constituent elemental powders through in-situ alloying laser engineered net shaping (LENS) technique. The influence of the feed rate of Si powder (0.1 rpm, 0.2 rpm and 0.3 rpm) on Ti–Al-xMo was studied at 0.1 rpm and 0.2 rpm Mo feed rate, respectively. Heat treatment at 1200 °C for 15, 30, and 60 min was performed after LENS in-situ alloying, and furnace cooling (FC) was the final step. The microstructure of the produced alloys was analyzed via Scanning electron microscopy (SEM) fitted with energy dispersive spectroscopy (EDS). Using a tribometer and a potentiodynamic polarization test, the alloys' wear characteristics and corrosion behaviour were studied. Based on the results, it was noticed that microhardness values decrease after heat treatment for all the samples produced. Owing to the combined effects of Mo and Si, both the βo-TiAl and ζ-Ti5Si3 phases lead to solid precipitation hardening and solution strengthening at the grain boundaries. The XRD analysis confirmed γ, α2, α, βo and ζ-Ti5Si3 phases occurrence in the as-built alloys. The LENS fabricated alloys demonstrated improved wear properties and marginally change in corrosion behavior after heat treatment.

Improved hydrogen ab-/desorption performance of Ti–Cr based alloys via dual-effect of oxide reduction and element substitution by minor Al additive

Hysteresis of hydrogen storage alloys essentially hinders the compressibility and operation efficiency of metal hydride hydrogen compressors. In this work, minor Al additive was added into Ti–Cr based hydrogen compression alloys through induction levitation melting, and the apparent hysteresis was successfully ameliorated. The XRD and SEM results indicate homogeneous element distribution of a main C14 Laves phase of Ti0.96Zr0.06Cr1.0Mn0.6Fe0.4Alx (x = 0, 0.01, 0.02, 0.04, 0.08) alloys, and vanishing of a minor oxide phase in case the Al additive is introduced. As Al stoichiometry increases in the alloys, the hydrogenation plateau decreases obviously but the dehydrogenation plateau hardly changes. Meanwhile, the hydrogen capacity ascends initially but descends slightly. Additionally, no severe performance degradation is induced. The mechanism for overall performance improvement can be concluded as dual functions of Al additive: one can be oxide reduction of other elements during melting determined by XPS and ICP, and the other can be partial Al substitution for the B-side elements, leading to relieved deformation energy surrounding the vacant Al-containing interstitials. As to hydrogenation kinetics, the alloys exhibit accelerated hydrogenation rate with increased Al stoichiometry due to decreased activation energy and hydrogenation plateau. Furthermore, the first-principles calculation results indicate random Al substitution for the B-side atoms, and anisotropic expansion of the unit cell can be attributed to Al substitution at 6h sites. This work reveals a simple and effective way to enhance hydrogen storage performance of Ti–Cr based alloys.

Tuning phase structure and electrochemical hydrogen storage properties of A5B19-type La–Y–Ni–Mn-based superlattice alloys by partial Al substitution

Rare earth-based superlattice alloys are essential anodes for high-performance nickel-metal hydride (Ni-MH) batteries. This study aimed to improve the overall electrochemical hydrogen storage properties of (La0.33Y0.67)5Ni18.1-xMn0.9Alx alloys by adjusting the Al content. The alloys predominantly consist of the 2H–Pr5Co19 phase, with Al atoms mainly occupying the 12k2 site at the [AB5]-1/[AB5]-2 boundary and subsequently the 12k1 site at the [A2B4]/[AB5]-1 boundary. As a result, a minimum subunit volume difference of 2.08 Å3 is observed at x = 0.6. Therefore, the Al substitution is responsible for the decrease in the dehydriding plateau pressure and the increase in discharge capacity. Among them, the alloy (La0.33Y0.67)5Ni17.5Mn0.9Al0.6 presents a discharge capacity of 361.2 mAh/g, a higher capacity retention S200 of 69.80 %, and better rate performance owning to the enhanced hydrogen diffusion rate through the multi-phase interface. This work demonstrates the potential of the (La0.33Y0.67)5Ni17.5Mn0.9Al0.6 alloy as high-performance Ni-MH battery anode.

Influence of partial substitution of Cr by Al on microstructure and mechanical behavior of Fe30Ni35Cr35 multi-principal element alloy

Influence of partial substitution of Cr by Al on microstructure and mechanical behavior of Fe30Ni35Cr35 multi-principal element alloy (MPEA) was investigated. In detail, Co-free Fe30Ni35Cr(35-x)Alx (x = 10, 12.5, 13.75 and 15 at.%) MPEAs were prepared by a vacuum arc melting process, subsequently, microstructure and tensile properties of these MPEAs were carefully studied. The as-cast Fe30Ni35Cr(35-x)Alx alloys are composed of face-centered cubic (FCC) and body-centered cubic (BCC) phases with spherical B2 nano-precipitates embedded in the BCC phase and B2 lamellar structure surrounding the BCC phase simultaneously. In particular, Al content strongly influences the solidification process of these alloys; with increasing Al content, the initial morphology varied from columnar dendritic grains (10 < x < 13.75) to equiaxed grains with Widmanstätten structures (x = 15) and resulted in increased tensile strength and hardness with reduced ductility. The as-cast Fe30Ni35Cr21.25Al13.75 alloy exhibits the best mechanical properties in Fe30Ni35Cr(35-x)Alx alloys with an ultimate tensile strength (UTS) of ∼1111.8 ± 11.4 MPa and a total elongation of ∼20.7 ± 2.1%. Furthermore, our study demonstrates outstanding combinations of ductility and strength in multi-phase MPEAs, ascribing to various complementary strengthening mechanisms, such as hetero-deformation induced (HDI) hardening and precipitation strengthening, which influence the work hardening and dislocation movement at different tensile strains.

Corrosion Inhibiting by Some Organic Heterocyclic Inhibitors Through Langmuir Adsorption Mechanism on the Al-X (X = Mg/Ga/Si) Alloy Surface: A Study of Quantum Three-Layer Method of CAM-DFT/ONIOM

Corrosion Inhibiting by Some Organic Heterocyclic Inhibitors Through Langmuir Adsorption Mechanism on the Al-X (X = Mg/Ga/Si) Alloy Surface: A Study of Quantum Three-Layer Method of CAM-DFT/ONIOM

CoFeMn0.5Al0.25: A high magnetisation CoFe based soft alloy with reduced Co content

The high cost of CoFe alloys has prevented their widespread use regardless of their promising properties such as high magnetisation, high Curie temperature, as soft magnetic materials for high temperature applications. Here, it is shown that AlMn can be used to create a CoFeMn0.5Alx alloy, which has reduced Co content but comparable soft magnetic properties as CoFe alloys, therefore providing a more economical alternative to pure CoFe soft magnets.

Molecular modelling framework of metal-organic clusters for conserving surfaces: Langmuir sorption through the TD-DFT/ONIOM approach

ABSTRACT The Langmuir adsorption model of some organic inhibitors containing benzotriazole (BTA), 8- hydroxyquinoline (8-HQ), and 2-mercaptobenzothiazole (2-MBT) onto the Al-X (X=Mg, Ga, Si) alloy surface.The ONIOM method has been accomplished with a three-layered step of high level of DFT method using EPR-III, 6-31+G (d,p) and LANL2DZ basis sets. NMR spectroscopy has indeed concentrated on the Al shielding in the intra-atomic interaction with Mg, Ga and Si and meanwhile interatomic interaction with other atoms in BTA, 8-HQ, and 2-MBT compounds. Aluminum-silicon binary alloy with highest changes in the shielding tensors of NMR spectrum produced by intra-atomic interaction directs us to the most penetration in the neighbor atoms created by interatomic reaction. IR computations based on comparing the amounts has exhibited that 2-MBT with high stability based on its active zone of sulfur atoms and high molecular size shows high corrosive inhibition as 2-MBT →Al-Ga>Al-Mg ≈ Al-Si. Furthermore, BTA with nitrogen atom and 8-HQ with oxygen atom can coat the Al-X (X=Mg/Ga/Si) alloys surface through Langmuir adsorption as BTA →Al-Ga>Al-Mg ≈ Al-Si, and 8-HQ →Al-Ga>Al-Mg ≈ Al-Si, respectively. Moreover, it has been observed that the inhibition yield is ordered as: Al-Ga> Al-Mg ≈ Al-Si.

Stability of thermal cycling and high temperature mechanical properties for Ti–V–Al–B lightweight shape memory alloy

The microstructure of the Ti–V–Al shape memory alloy with refined grain and in-situ TiB phase was modified by doping minor Boron (B), which contributes to the superior mechanical performances and strain recovery characteristics. Compared with other quaternary Ti–V–Al-X alloys, the Ti–V–Al–B alloy showed the largest ultimate tensile stress due to the solution strengthening, grain refinement and precipitation strengthening of in-situ TiB phase. Moreover, the Ti–V–Al alloy added 0.1 ​at.%B possessed the maximum yield stress of 701 ​MPa and the largest tensile fracture strain of 27.6% at the temperature of 150 ​°C. Meanwhile, the excellent strain recovery characteristics with fully recoverable strain of 4% could be obtained due to B addition. Besides, B addition suppressed the precipitation of ω phase during thermal cycling and further improved the thermal cycling stability of the Ti–V–Al alloy.

Cathodic Protection of Mild Steel Using Aluminium-Based Alloys.

Typically, steel is protected from corrosion by employing sacrificial anodes or coatings based on Zn, Mg, Al or Cd. However, stricter environmental regulations require new environmentally friendly alternatives to replace Cd. Traditionally, Al-based anodes have been employed to cathodically protect steel in marine applications or as ion vapour deposition (IVD)-Al sacrificial coatings for aerospace applications. However, Al tends to passivate, thus losing its protective effect. Therefore, it is important to identify possible alloys that can provide a constantly sufficient current. In this study, Al-X alloys (X = Ag, Bi, Ca, Cr, Cu, Ga, Gd, In, Mg, Mn, Ni, Sb, Si, Sn, V, Ti, Zn and Zr) were firstly tested for a screening of the sacrificial properties of binary systems. Al-0.5Cr, Al-1Sn, Al-0.2Ga, Al-0.1In, Al-2Si and Al-5Zn alloys were suggested as promising sacrificial Al-based alloys. Suitable heat treatments for each system were implemented to reduce the influence of the secondary phases on the corrosion properties by minimising localised attack. extensive evaluation of the corrosion properties, including galvanic coupling of these alloys to steel, was performed in the NaCl electrolyte. A comparative analysis was conducted in order to choose the most promising alloy(s) for avoiding the passivation of Al and for efficient cathodic protection to steel.

Experimental investigation of diffusion behaviors in γ and γ’ Ni–Al–Co alloys

On the basis of 13 groups of single-phase diffusion couples together with electron probe microanalysis technique, the composition profiles in γ and γ′ Ni–Al–Co systems at 1373–1523 K were measured. Atomic mobilities in γ Ni–Al–Co alloys were directly assessed from 9 groups of concentration profiles by means of HitDIC software. The established atomic mobilities contain only two interaction parameters, and their reliability was verified by comprehensively comparing the model-predicted concentration profiles with the experimental data in the literature and the present work. After that, the composition-dependent interdiffusion coefficients along the entire diffusion path in γ and γ′ Ni–Al–Co alloys were also evaluated at 1373–1523 K by using HitDIC. D˜AlAlNi and D˜CoCoNi in γ Ni-Al-Co alloys were validated by the results obtained by Matano-Kirkaldy method and the corresponding experimental values in Ni-Al and Ni-Co binary alloys. Comprehensive comparisons between the interdiffusion coefficients in the present work and those reported the literature validated the reliability of the presently evaluated interdiffusivities in γ’ Ni-Al-Cr alloys. The influences of Al and X contents on the D˜XXNi in γ Ni-Al-2 at% X (X= Co, Rh, Ta, W, Re, Os, and Ir) alloys and D˜AlAlNi in γ Ni-2 at% Al-X alloys were further discussed.

Structural Evolution and Mechanical and Magnetic Properties of Nonequiatomic CoFe2NiMn0.3Alx (0.25 ≤ x ≤ 1.00) High-Entropy Alloys

CoFe2NiMn0.3Alx (x = 0.25, 0.50, 0.75, 1.00) alloys were prepared using the arc melting method, and their crystal structure, microstructure, and mechanical properties were systematically studied. The results show that a greater Al content beneficially alters the crystal structure of the alloys from a single FCC phase to a mixture of FCC + BCC phases. With increasing Al content, the volume fraction of the BCC phase increases steadily, whereas the volume fraction of the FCC phase substantially decreases. With increasing Al content, the yield strength and hardness of the CoFe2NiMn0.3Alx alloys increases, whereas their ductility gradually decreases. Among the studied alloys, that with x = 0.75 exhibits both high strength and good ductility and its yield strength, fracture strength, and fracture strain are 1100 MPa, 2335 MPa, and 33.24%, respectively. Measurements of magnetic properties indicated that the saturation magnetization increases from 90 emu g−1 for the Al0.25 alloy to 148 emu g−1 for the Al1.00 alloy. The results show that the CoFe2NiMn0.3Alx high-entropy alloys are potential candidates to serve as magnetic materials in industrial applications.

Full-Potential KKR Calculations for Interaction Energies in Al-Rich AlX (X = H～Sn) Alloys: I. Fundamental Features and Thermal Electronic Contribution due to Fermi-Dirac Distribution

We presented systematical ab-initio calculations for the n-body (n = 1-4) interaction energies (IEs) in Al-rich AlX (X = H～Sn) alloys, by using the full-potential Korringa-Kohn- Rostoker Green's function (FPKKR) method, and clarified the fundamental features and the thermal electronic contribution due to the Fermi Dirac (FD) distribution for these IEs. We show the calculated results for the IEs: (1) the 2-body IEs of the X = 3d and 4d impurities are strongly repulsive at the 1st-nearest neighbor (nn) and show the oscillating behavior with the interatomic distance; (2) the 1st-nn 2-body IEs of the X = Ne, Ar, and Kr (inert gas elements) impurities are strongly attractive; (3) the 1st-nn 2-body IEs around X = N (2sp element) are repulsive and relatively high; (4) the thermal electronic contribution due to the FD distribution is considerably high for the X = d impurities, while very low for the X = sp impurities; (5) the n-body (n = 1-4) IEs of the X = 3d and 4d impurities in Al and the thermal electronic contribution for these n-body IEs may be in general lower and lower with the increase in n. It is also discussed that the fundamental features (attraction or repulsion) of the calculated 2-body IEs may be understood by considering the strength differences among the X−X, Al−X, and Al−Al interactions.

Microstructure, Mechanical Properties, Electric and Thermal Conductivity of the As-Extruded Al-x(1.0 wt.% Zn + 0.5 wt.% Cu) Alloys (x = 1, 2 and 4).

In this research, effects of Zn and Cu content on microstructure, mechanical properties, electric and thermal conductivity of the as-extruded Al-x(Zn+0.5Cu) alloys were investigated. As the content of Zn and Cu increased, the area ratio of Al₂Cu intermetallic compounds increased. After homogenization treatment and extrusion process, most of Al₂Cu intermetallic compounds was disappeared due to solution in Al matrix of Cu atoms. As the (Zn+0.5Cu) content increased from 1 to 2 wt.%, the average grain size decreased remarkably from 645 to 227 μm due to the dynamic recrystallization caused by the solute Zn and Cu atoms during the extrusion. With increasing Zn and Cu additions, the thermal conductivity was decreased from 225 (x = 1) to 208 (x = 2) and 183 W/mK (x = 4) due to electric scattering by solute Zn and Cu atoms. The ultimate tensile strength (UTS) of the as-extruded Al-x(1Zn+0.5Cu) alloys improved remarkably from 77 (x = 1) to 142 MPa (x = 4) as Zn and Cu content increased, and the elongation increased from 30 to 33%. This improvement in the strength resulted from the grain refinement and solid solution strengthening due to the solute Zn and Cu atoms. The Zn and Cu addition in Al alloy played an important role in thermal conductivity and mechanical properties.

Novel Al-X alloys with improved hardness

In this study, our goal is to design solid solution strengthened aluminum alloys for manufacturing technologies that involve high cooling rates. This investigation starts with an analysis of solid solution strengthening using first principles calculations to determine elastic property changes and local lattice distortions from the introduction of different elements into a host aluminum lattice. These results, coupled with both equilibrium and non-equilibrium solubility data, leads to the selection of cerium and cobalt as the primary candidate alloying elements. Alloys of AlCe and AlCo at concentrations of 0.5, 1.0, and 3.0 at. % are then synthesized and subjected to laser glazing to produce non-equilibrium microstructures. The microstructure and solid solution characteristics are determined using a combination of scanning electron microscopy and transmission electron microscopy. Furthermore, nanoindentation is used to measure the hardness showing that both candidate systems harden significantly after glazing. In addition, Al-1.0Co at. % achieves a hardness comparable to Al6061-T6. These results conclusively show that cerium and cobalt are promising elements in the next generation aluminum alloys which make use of non-equilibrium processing conditions such as additive manufacturing.

Investigation on microstructure and mechanical properties of multiphase ZrSn1.5Alx alloy with simultaneous enhance of strength and plasticity

Abstract There are many means and mechanisms to strengthen alloys, but often at the cost of plasticity. Strength or plasticity? In practice, the two often appear as contradictory relationships. In the current work, the ZrSn1.5Alx (x = 6, 8, 10, 12, 14 at. %) alloy obtained by controlling the Al content was smelted and hot-rolled at 890 °C, and then immediately quenched to obtain an alloy containing α + β + AlZr3 multiphase structure. Compared with ZrSn1.5Al6 alloy, ZrSn1.5Al14 alloy reaches a high ultimate tensile strength (1080.84 MPa) and a large elongation at fracture (28.59%) at room temperature, an increase of 27.6% and 86.3%, respectively. The formation of AlZr3 particles pins dislocations, promotes cross-sliding of dislocations, and improves the dislocation nucleation rate by changing the dislocation sliding mode, which increases the dislocation density and promotes uniform plastic deformation, enhance the strain-hardening ability of the alloys, thereby improve its plasticity and strength simultaneously. Optical microscopy (OM) and scanning electron microscope (SEM) were used to observe the metallographic structure and tensile fracture morphology. The transmission electron microscope bright field (TEM-BF) image and scanning transmission electron microscope high-angle annular dark field (STEM-HAADF) image of the sample were observed for detailed analysis. The samples were taken in the rolling direction and the mechanical properties were evaluated by uniaxial tensile tests at room temperature. In summary, the machining process is simple, the cost is low, and it is suitable for large-scale industrial-grade applications. It may have reference significance to other alloy systems.

Hydrogen storage performances, kinetics and microstructure of Ti1.02Cr1.0Fe0.7-xMn0.3Alx alloy by Al substituting for Fe

For achieving good economic and environmental benefit, capacity of hydrogen storage alloys plays an important role in high-pressure-metal-hydride system of refueling station. Hydrogen storage characteristics of Ti1.02Cr1.0Fe0.7-xMn0.3Alx (0 ≤ x ≤ 0.1) alloys with main C14 structure were analyzed by Pressure-Composition-Temperature, XRD, HRTEM, SEM, EDS, ICP and XPS measurements, which were prepared by plasma arc melting and subsequent heat treatment. When Al content is lower than 0.05, it can improve the hydrogen reversible storage capacity from 1.58 to 1.65 wt% at 233 K. The pulverization resistances are enhanced by addition of Al (Al content: 0.05, 0.1), and the ductile fractures appear on the particle surfaces. Based on kinetic analysis, the dehydrogenation rates are fast with low activation energies between 7.4 and 9.9 kJ/mol. The mechanism for Al effecting the capacity is that, the big size effect dominates the capacity increase as Al content less than 0.05. Otherwise, higher Al2O3 content covering on the particles surface deteriorate hydrogen storage capacity as Al content exceeding 0.05. Among them, Ti1.02Cr1.0Fe0.68Mn0.3Al0.02 alloy has the best comprehensive properties for high-pressure metal hydride system in hydrogen refueling station. How to utilize the alloy to assemble the compressor and measure the toxicity resistance to impurity gas in H2 may be the future work.

Effects of solute segregation on surface properties of dilute Al-X (X = Li, Sn) alloys from first-principles calculations

Considering the interactions between solute atom (Li or Sn) and various surfaces, along with the ones between solute atoms in the surfaces, this work applies the first-principles method to investigate the influences of solute atoms on the surface energy of dilute Al alloys at room temperature, and further predicts the nano-crack nucleation along different surfaces. The statistical ordered surface configurations are depicted for ensuring the maximum surface concentrations of solute-atom segregations. The Gaussian-Like distribution (GLD) model is introduced to describe the distribution of solute atoms. Results indicate that the nano-crack nucleation may occur along the (1¯10) surface in the region of dilute Li atom less than 0.016%, but along the (1¯11) surface in the region of high concentration exceeding 0.016%. While Sn atom has a fairly stronger effect on reducing the surface energy than Li atom, especially in the (001) surface, suggesting that the nano-cracks are likely to nucleate along (001) surface under the action of Sn atom. This work provides a valuable guidance for theoretical and experimental study of the nano-crack nucleation in Al alloys.

Full-Potential KKR Calculations for Interaction Energies in Al-Rich AlX (X = H∼Sn) Alloys: I. Fundamental Features and Thermal Electronic Contribution due to Fermi-Dirac Distribution

Full-Potential KKR Calculations for Interaction Energies in Al-Rich AlX (X = H∼Sn) Alloys: I. Fundamental Features and Thermal Electronic Contribution due to Fermi-Dirac Distribution