Al Solid Solution Research Articles

Hydrogen storage properties of Mg(Al) solid solution alloy doped with LaF3 by ball milling

LaF3 was doped to the Mg(Al) solid solution alloy for enhancing the hydrogen absorption and desorption by ball milling. XRD was used to analyze the phases of the samples and the phase transition induced by hydrogenation and dehydrogenation. The microstructure and phase distribution were investigated by SEM and STEM. The hydrogen storage properties were measured by Sieverts method. For Mg0.93Al0.07-5wt.%LaF3 nanocomposite, the hydrogen storage kinetic properties were significantly improved by reducing the hydriding and dehydriding activation energies to 65 and 78 kJ/mol, respectively, and the dehydriding enthalpy was calculated to be 69.7 kJ/mol. The improved hydrogen storage properties were mainly attributed to the catalytic effects of the in situ formed nanostructure Al11La3 and MgF2 together with the dissolving of Al in Mg lattice.

Nucleation and growth of L12-Al3RE particles in aluminum alloys: A first-principles study

The internal mechanisms of nucleation and growth of L12-Al3RE (RE = Sc, Y, La–Lu) second phases in Al alloys were investigated by combining first-principles calculations with quasi-harmonic approximation (QHA). The calculated results show that the diffusion rate Ds and chemical potential ΔGV increase with the increase of temperature. With the increase of atomic number, the Ds and the strain energy ΔECS increase firstly from Sc to La, and then decreases, while the calculated interface energy γα/β and ΔGV show opposite tendency. Based on above calculated results, the critical nucleation radius R∗ and coarsening rate KLSW are obtained from the classical nucleation theory (CNT) and LSW model of the Ostwald ripening of particles, respectively. With the increase of atomic number, the R∗ increases firstly, and then decreases for all planes at finite temperatures. Whereas the KLSW shows opposite variation to the R∗. From this point of view, it is reasonably speculated that Y and later RE elements can replace the expensive Sc for heat-resistance Al alloys. The solubility c∞ of particles is usually very small at low temperature, and there is obvious solubility only when the temperature reaches 600 K. The surface energies Esur of Al3RE compounds and Al solid solution are respectively larger and smaller than that of pure Al, respectively, except for the surface (001) and (110) of Al3La. For all planes, with the increase of atomic number of RE, Esur decreases firstly from Sc to La, and then increases linearly to Lu. These results are helpful for designing high performance heat-resistance Al alloys.

Investigations on the Microstructure of an Aluminium Nitride Layer and Its Interface with the Aluminium Substrate (Part I)

In principle, the plasma nitriding of Al based substrates is a well-known process, though it remains extremely challenging from both the technological point of view and the aspect of stress loading conditions. In order to improve the latter, a duplex treatment consisting of plasma nitriding and subsequent surface remelting using electron beam technology was employed. The focus of this paper (part I) was on the characterisation of the initial microstructure after plasma nitriding. This should create the basis for a better understanding of the processes taking place or changes in the subsequent duplex treatment. This was done with the help of high-resolution imaging and analysis tools in the scanning and transmission electron microscope as well as XPS analyses. Special attention was paid to the nitriding mechanism at the interface as a function of the local microstructural constituents of the hypereutectic Al alloy substrate (Al solid solution, primary silicon, and intermetallic phases). While the main part of the nitride layer formed consisted of AlN and small fractions of pure Al in the diffusion paths, other nitrides and oxides could also be detected in the area of the interface.

Ultra-rapid and low-temperature soldering of hypereutectic Al-Si alloys by ultrasonic-assisted soldering with In interlayer in air for electronic application

Hypereutectic Al-Si alloys were soldered by an ultrasonic-assisted soldering with In interlayer for only 0.1 s at 160 °C in air. The introduction of ultrasonic vibration into the soldering process promoted the formation of the liquid phase by its acoustic softening effect, ultrasonic cavitation effect and acoustic streaming. The effects of ultrasonic vibration on the formation of Al-In liquid phase were also discussed. The microstructure evolution of solder joint and the migration of Si particles were influenced by ultrasonic vibration. The complex solder joint obtained by the ultrasonic-assisted approach consisted of Si particles and Al-In solid solution. Si particles could be regarded as tracers and reinforced phase. The influence of ultrasonic vibration time, pressure and temperature on the microstructure of the solder joint was investigated. The effect of ultrasonic vibration on shear strength of the joints was also discussed. Image-Pro-Plus Analysis was used to estimate content of Si particles in solder joint. The shear strength of the joints was obtained, when the suitable ultrasonic vibration time, temperature and pressure were chosen.

Characteristics of laser-offset-TIG hybrid welding of AZ31Mg alloy with 6061Al alloy via Zn filler

This work proposed a laser-offset-TIG hybrid welding method to join AZ31 Mg alloy to 6061 Al alloy with Zn filler in lap configuration. Through the lateral offset of laser and arc, the wettability of filler metal was improved, and the amount of intermetallic compounds (IMCs) was well controlled. The spread width of filler metal increases from 2.13 mm to 3.49 mm and the reaction depth decreases from 0.91 mm to 0.66 mm as the offset distance increases from 0 mm to 2 mm. The major phases formed in joint are Al solid solution, MgZn2 IMCs, Zn solid solution and Mg32(Al,Zn)49 ternary IMCs. At the appropriate offset distance of 2 mm, the coarse MgZn2 grains in fusion zone are refined to (Al)+(Zn)+MgZn2 eutectic, and the brittle Mg32(Al,Zn)49 ternary IMCs in weld corner are eliminated. The maximum joint strength is 1190 N/cm, which is 1.3 times higher than that with normal laser-TIG hybrid welding.

Microstructure and Mechanical Properties of AlN/Al Joints Brazing by a Sputtering Al/Cu Bilayer Film Solder.

This paper presents a magnetron sputtering Al/Cu bilayer film solder to realize the brazing of AlN ceramic and Al metal. The effect of different temperatures on the structure and mechanical properties of brazed joints is studied. The results show that the sputtered Al particles have a sputtering wetting effect on AlN ceramic. The contact angle of molten Al on AlN ceramic with Al film deposited at 700 °C is as low as about 30°. While the contact angle of molten Al on AlN ceramic without Al film deposited at 1000 °C is about 89°. There is a large amount of Cu enrichment in brazed joints at 600 °C. The weld structure is a mixture of Al solid solution and AlCu compound. The shear strength of the brazed joint is only 70.6 MPa, and the joint fracture shows a large number of brittle fracture morphologies. With the increase of brazing temperature, the phenomenon of Cu enrichment in the joint gradually weakens, and the weld structure gradually transforms into a solid solution of Cu in Al. The shear strength of the brazed joint continues to increase, and the joint fracture morphology gradually changes from brittle fracture to furrow-like plastic fracture morphology. When the brazing temperature is increased to 660 °C, the distribution of Cu in the joint is evenly dispersed, and the shear strength of the brazed joint reaches the highest value of 107.8 MPa. The joint fracture is completely furrow-like plastic fracture morphological composition.

The effect of B and Ti–Al intermetallics additions on the microstructure and mechanical properties of hot-pressed B4C

In this work, we studied the microstructure and mechanical properties of hot-pressed B4C, B4C + 5 wt% TiAl, and B4C + B + 5 wt% TiAl. The X-ray diffraction and Raman spectroscopy results showed that the addition of Ti–Al alone did not led to Al doping in B4C, and it did not reduce the degree of amorphization of B4C generated under high shear stresses. In contrast, the co-addition of Ti–Al and B resulted in both B and Al solid solutions in the B4C and effectively mitigated the amorphization of B4C. Electron probe microanalysis (EPMA) and energy dispersive X-ray spectroscopy (EDS) analyses suggested that the co-addition of Ti–Al and B promoted the interdiffusion of lightweight elements such as B, C, Al, Mg, and Si at high temperatures, resulting in a dense body with uniformly distributed second phase. The transmission electron microscopy (TEM) observations of the B4C + B + 5 wt% TiAl sample showed that a nano–core–shell structure with aggregated dislocations in the shells which was generated at TiB2 grains due to the segregation and dissolution-precipitation between TiB2 and B-rich boron carbide. The short-range ordered substitution of B and the disordered doping of Al in B4C led to lattice distortion and expansion, resulting in the formation of high-density defects, including stacking faults and nano-twins, improving the mechanical properties for B4C. The B4C + B + 5 wt% TiAl sample exhibits a combination of fascinating properties, including low density (2.52 g/cm3), high Vickers hardness (35.53 ± 0.83 GPa) and moderate fracture toughness (4.37 ± 0.35 MPa m1/2).

Effect of Heat Treatment on Microstructural Evolution and Microhardness Change of Al-5Zn-0.03In-1Er Alloy

Adding an appropriate amount of Er element to Al-Zn-In alloys can improve the electrochemical performance of Al alloys; it is convenient to study the electrochemical behavior of the alloy in the rest of our work. However, Er segregation in solid solutions which reduced the comprehensive properties of alloys was difficult to reduce and there was no report on the homogenization of Al-Zn-In alloys. We found that the ultra-high temperature treatment (UHTT) can obviously reduce Er segregation. To explore the better homogenization treatment and the microstructure evolution of Al-5Zn-0.03In-1Er alloy after UHTT, we carried out a series of heat treatments on the alloy and characterized the microstructure of the alloy by optical microscopy (OM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy spectrum analysis (EDS) and transmission electron microscopy (TEM). The results showed that the main element Er of the Al-Zn-In-Er was largely enriched in grain boundaries after UHTT; the distribution Zn and In was almost unchanged. The as-cast Al-Zn-In-Er alloy consisted mainly of α(Al) solid solution and Al3Er phase. As the temperature of UHTT increased and the treatment time prolonged, the precipitated phase dissolved into the matrix, and there were dispersed Al3Er particles in the crystal. The proper UHTT for reducing the interdendritic segregation of the alloy was 615 °C × 32 h, which was properly consistent with the results of the evolution of the statistical amount of interdendritic phase, the line scanning analysis and the microhardness. Moreover, the microhardness of the alloy after treatment of 615 °C × 32 h was obviously higher than that of the as-cast alloy because of the anchoring effect of Al3Er nanoparticles on the movement of dislocations.

Phases and phase equilibria in the Fe–Al–Zr system

AbstractIsothermal sections at 800, 1000, and 1150 °C as well as a tentative partial liquidus surface of the ternary Fe–Al–Zr system were established by means of electron-probe microanalysis, X-ray diffraction, differential thermal analysis, and light-optical as well as scanning electron microscopy. The most prominent features of the ternary phase diagram are the extended homogeneity ranges of the Laves phases. By continuous substitution of Fe by Al, the structure changes three times starting from the cubic C15 structure of Fe2Zr to hexagonal C14 (λ1) back to cubic C15 (λ2) and again to hexagonal C14 (Al2Zr). The various Laves phase fields are separated by very small two-phase fields. Besides the Laves phases λ1and λ2, three more ternary intermetallic phases were found, whose homogeneity ranges have been determined for the first time. In addition, new results concerning the homogeneity ranges of intermetallic phases in the binary subsystems Fe–Al and Al–Zr are reported. The solubilities of the third components in the binary phases are found to be generally very low with the exception of the Laves phases. As a consequence, extended two-phase fields between the Fe(Al) solid solution and Laves phase or between Fe(Al) solid solution and the ternary ThMn12-type phase τ1are formed.

The effect of Ni and Ti additions on the glass forming ability and magnetic properties of Al-Fe-Y alloy prepared by mechanical alloying

Amorphous Al82Fe14Ni2Y2 and Al82Fe14Ti2Y2 alloys were synthesized by mechanical alloying. Morphological and structural characterizations of the powders, milled for different periods of time, were investigated by scanning electron microscopy and X-ray diffraction methods. The dissolution of Ni and Al into the Fe lattice led to the formation of Fe(Ni,Al) solid solutions in Al82Fe14Ni2Y2 alloy after 20 h of milling. A slower dissolution of Ti and Al into the Fe lattice can be observed for Al82Fe14Ti2Y2 after milling 40 h. The fully amorphous structure can be obtained for Al82Fe14Ni2Y2 after 60 h of milling. The amorphization of the Al82Fe14Ti2Y2 sample milled for 100 h was not complete, and a partially nanocrystal phase of Ti was still present. Coercivity (Hc) and the saturation magnetization (Ms) of as-milled powders decreased markedly with increasing milling time. The magnetic properties of the alloys were consistent with the structural changing during milling process. The amorphous phase transforms into fcc-Al and metallic compounds after annealed DSC treatment.

The (γ + γ′ )/γ′ phase boundary in the Ni–Al phase diagram from 600 to 1200 ° C

Abstract The phase boundary separating the γ + γ′ and γ′ regions of the Ni –Al phase diagram (the γ solvus) was established over the temperature range 600– 1200 °C. The γ phase is the Ni –Al solid solution, and γ′ is (non-stoichiometric) Ni3Al. Cast alloys containing 22.0, 22.2, 22.4, 22.6, 22.8 and 23.0 at.% Al, all compositions being within ± 0.03 at.%, were used in the experiments. At temperatures from 1000 to 1200 °C, the γ solvus was determined using aging treatments designed to eliminate the dendritic structure in the as-received castings. At lower temperatures, from 600 to ≈ 900 °C, dissolution experiments were conducted. The method takes advantage of the absence of a barrier to the dissolution of a dispersed phase. Specimens of the supersaturated γ′ phase were aged at low temperatures, 600 or 650 °C, for long times (up to 633 h), to produce fine dispersions of the coherent γ phase precipitates. These specimens were then re-aged at 10 –20 °C intervals of temperature and re-examined to determine whether the γ phase precipitates had dissolved. The absence of the γ phase precipitates enabled the phase boundary to be located to within ± 10 °C for an alloy of known composition, or ± 0.03 at.% at a given temperature, from 600 to 900 °C. The phase boundary generally agrees with the lower end of Al concentrations established in previous research.

Intrinsic Diffusion, Mobility and Correlation Effect in Cu(Al) Solid Solution

Intrinsic Diffusion, Mobility and Correlation Effect in Cu(Al) Solid Solution

Influence of oxygen content on structure, thermal stability, oxidation resistance, and corrosion resistance of arc evaporated (Cr, Al)N coatings

(CrxAl1-x)(OyN1-y)ε coatings with different oxygen fractions were prepared by cathodic arc evaporation through variation of injected oxygen flux, and elaborated concerning structure, mechanical properties, thermal stability, oxidation resistance, and electrochemical properties. A moderate addition of O into (Cr, Al)N coatings generates a (Cr, Al)(O, N) solid solution with a face-centered cubic structure, whereas an additional corundum-structured (Cr, Al)2O3 solid solution is formed with superfluous oxygen introduced. The addition of O effectively improves the thermal stability by retarding the formation of w-AlN as well as the dissociation of the CrN bond, allowing the oxynitride coatings to maintain higher hardness after annealing. Notably, a small fraction of O-addition (e.g. 8 or 21 at.% in non-metal sublattice) enhances significantly the resistance against oxidation to above 1100 °C by facilitating the formation of a protective Al-rich oxide scale. Further incorporation of O gives rise to a development of oxide scale with unity elemental distribution and hence results in inferior oxidation resistance. Nevertheless, the O-rich oxynitride coatings provide better protection against electrochemical corrosion while the N-rich coatings exhibit higher corrosion current as well as lower polarization resistance compared to the CrAlN coating.

Microstructure and properties of Cu-10 wt% Al bronze obtained by high-energy mechanical milling and spark plasma sintering

A fabrication route of Cu-10 wt% Al bronze via high-energy mechanical milling and spark plasma sintering (SPS) is proposed. SPS of the ball-milled powder at 700–800 °C allows obtaining single-phase Cu(Al) solid solution. Vickers hardness measurements and mechanical tests in compression were conducted on the sintered alloys. The electrical conductivity of the alloys was measured by the eddy current method. The alloy sintered at 800 °C shows an attractive set of properties: a hardness of 280 HV1, a proof stress of 760 MPa, a compressive strength of 960 MPa, a deformation at fracture of 5%, and an electrical conductivity of 15% of the International Annealed Copper Standard.

Improving mechanical properties of Cu/Ti3AlC2 composites via in-situ decomposed gradient interfaces

Ti3AlC2 is a promising reinforcement for Cu matrix composites. In this paper, the Cu/20 wt%Ti3AlC2 composites were fabricated using a spark plasma sintering process at various sintering temperatures. The thermodynamic calculation and high-temperature X-ray diffraction results showed that Al element preferred to dissolve from the metastable Ti3AlC2 and diffused into Cu matrix to form Cu(Al) solid solution at temperatures ranging from 600 to 1000 °C. The TiCx→Ti3AlC2→Cu(Al) gradient interface features were in-situ produced in the sintered composites and thus contributed to the improvement of the microhardness and the compressive yield strength. The composite sintered at 1000 °C demonstrated the maximum microhardness of 161.6 HV0.2 and the maximum compressive yield strength of 348 MPa. In-situ tensile test inside SEM revealed that cracks generated from the edge of the specimen and extended along the interface between the Ti3AlC2 reinforcement and the Cu matrix. The present composite interface strategy will provide flexibility to optimize the interface microstructure and the overall properties of the metal matrix composites.

PHASE FORMATION BEHAVIOR ON MECHANICALLY ACTIVATED ANNEALING OF Al-RICH PERITECTIC Al-Cr COMPOSITIONS

The formation of phases in the Al rich peritectic compositions of Al - Cr system was investigated under mechanical milling (MM) and subsequent annealing. MM led to the formation of nanocrystalline Al (Cr) solid solution and also caused carbon contamination originating from the organic process control agent (PCA). Al11Cr4 and AlCr2 phases were formed on annealing instead of the equilibrium peritectic compounds. Additionally, AlCr2C phase was also detected after annealing of Al-16 to 33Cr whereas Al-13Cr did not produce any intermetallic compound. The generation of the intermetallic phases was attributed to classical theories of nucleation and growth.

Schottky barrier in Si-M structures of solid-state lithium-ion batteries

The results of measuring the charge-discharge characteristics of solid-state thin-film lithium-ion batteries with a nanocomposite anode based on the a-Si(Al) solid solution are presented. The charging characteristics of batteries have a feature in the form of a step on the gentle branch of the U(t) curve. It has been suggested and substantiated that the appearance of the step is related to the gradual compensation and change of the a-Si(Al) hole conductivity to electronic one as the lithium concentration increases. As a result, the a-Si(Al)|Ti ohmic contact becomes rectifying, and the electrons participating in the Faraday process have to overcome the Schottky barrier. The potential growth required to maintain the galvanostatic charge regime manifests itself as a step on the charge curve. Keywords: thin film solid-state lithium-ion battery, amorphous silicon, solid solution, sp3 hybridization, lithiation, Schottky barrier.

Барьер Шоттки в структурах Si-M твердотельных литий-ионных аккумуляторов

The results of measuring the charge-discharge characteristics of solid-state thin-film lithium-ion batteries with a nanocomposite anode based on a-Si(Al) solid solution are presented. The charging characteristics of batteries have a feature in the form of a step on the gentle branch of the curve. It has been suggested and substantiated that the appearance of the step is related to the gradual compensation and change of the a-Si(Al) hole conductivity to electronic one as the lithium concentration increases. As a result, the a-Si(Al)|Ti ohmic contact becomes rectifying, and the electrons participating in the Faraday process are forced to overcome the Schottky barrier. The potential growth required to maintain the galvanostatic charge regime appears as a step on the charge curve.

Features of the current-voltage characteristic of the Ti-Si@O@Al junction Ti-Si@O@Al

The results on measuring the I--V characteristics of the metal-semiconductor transition within the Ti (200 nm)|Si@O@Al (180 nm)|Ti (203 nm) test structure are presented. The basis of the Si@O@Al nanocomposite is a solid solution of Al in amorphous silicon a-Si(Al). The I--V of the test structure has a form characteristic of a reverse-biased ohmic contact between a metal and a p-type semiconductor, which implies that a-Si(Al) is a substitutional solid solution. It is shown that the I--V fits well the framework of the metal-semiconductor transition model and the varistor effect of the nanocomposite. Within the framework of the percolation model, it is shown that the I--V give values of the Si@O@Al resistivity, which are overestimated with respect to the resistance of the a-Si(Al) solid solution. Keywords: nanocomposite, amorphous silicon, solid solution, Schottky barrier, nonlinear conductor, dangling bonds.

Особенности вольт-амперной характеристики перехода Ti-Si@O@Al

The results on measuring the I-V characteristics of the metal-semiconductor transition within the Ti(200nm)|Si@O@Al(179nm)|Ti(203nm) test structure are presented. The basis of the Si@O@Al nanocomposite is a solid solution of Al in amorphous silicon a-Si(Al). The I–V of the test structure has a form characteristic of a reverse-biased ohmic contact between a metal and a p-type semiconductor, which implies that a-Si(Al) is a substitutional solid solution. It is shown that the I-V fits well the framework of the metal-semiconductor transition model and the varistor effect of the nanocomposite. Within the framework of the percolation model, it is shown that the I–V give values of the Si@O@Al resistivity, which are overestimated with respect to the resistance of the a-Si(Al) solid solution.