Pure Aluminum Research Articles

Cooling rate calculation of pure aluminum solidified during a novel gas-assisted continuous casting and extrusion process

Gas-assisted continuous casting and extrusion (GAC) process is a novel technique for the continuous preparation of non-equilibrium solidified materials. To evaluate the solidification rate of the melt during GAC, the cooling rate of pure aluminum melt solidified in the wheel groove is calculated, based on the Newtonian heat transfer model and the one-dimensional Fourier heat transfer model. Results show that the cooling rate of the melt during GAC mainly depends on the conduction heat transfer in the wheel groove and the melt thickness. When the thickness of the pure aluminum melt is between 1 and 2.5 mm, the cooling rate can reach 103–104 K s−1, which is much higher than that in CAXTEX (~10 K s−1). It means that GAC is a very effective process in the preparation of non-equilibrium solidification alloys.

Investigations of microstructure and tensile properties of neutron irradiated 6061 aluminum alloys

Effects of neutron irradiation on the microstructure and mechanical properties of CMRR (China Mianyang Research Reactor) structural material pure aluminum and 6061 alloy were studied by scanning/transmission electron microscopy (S/TEM) and tensile tests. The fast neutron (E > 0.1 MeV) fluences of 1.09–2.89 × 1022 n•cm−2 produced damage doses of 1.6–4.2 displacements per atom (dpa). Voids and faulted 1/3<111> dislocation loops were observed in both pure aluminum and 6061 alloy. In particular, voids tended to preferentially aggregate on coarse Cu-rich and fine Mg2Si precipitates which contributes to the higher irradiation tolerance in terms of void formation for 6061 alloy, suggesting that the uniformly distributed precipitates can act as trapping sites for defect clusters during irradiation and thus promote recombination. The size and density of Mg2Si precipitates showed a slight increase and Cu-rich precipitates emerged in 6061 alloy after neutron irradiation. Moreover, radiation-induced segregation was also detected along the grain boundaries. After tensile testing, the pure aluminum showed a lower yield strength and larger uniform elongation than 6061 alloy, where a moderate uniform elongation was still reserved after irradiation to 4.2dpa. The severely reduced ductility in 6061 alloy is supposed to be caused by the transmutation product silicon which contributes to the increase of dispersed multiple precipitates after irradiation. Our results indicate that precipitates especially Mg2Si play a decisive role in void suppression, but are not suitable in diminishing the radiation hardening.

Corrosion Behavior of Pure Aluminum in the Simulated and Real Environments for Use as a Bipolar Plate Component in Polymer Electrolyte Membrane Fuel Cells

Corrosion Behavior of Pure Aluminum in the Simulated and Real Environments for Use as a Bipolar Plate Component in Polymer Electrolyte Membrane Fuel Cells

Structure, mechanical and tribological properties of Ta-xN coatings deposited by reactive HiTUS

This work investigates the structure, mechanical, and tribological properties of Ta-xN coatings deposited using reactive High Target Utilization Sputtering (HiTUS) with a focus on the role of tribological layers formed in the sliding contacts. The scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, and Raman spectroscopy observations revealed that the gradual increase of nitrogen flow results in the transition from textured fcc Ta structure (without nitrogen) toward mixed sub-stoichiometric Ta-Ny/Ta2N/amorphous structures up to near-stoichiometric fcc TaN coatings. The highest hardness HIT ∼37 GPa and indentation modulus EIT ∼375 GPa as well as the lowest coefficients of friction (COF) in the range 0.16–0.36 and wear rates around 3 × 10−7 mm2/N·m were obtained in the layer with Ta2N structure. The unique combination of low COF and high wear resistance combined with high hardness and stiffness were attributed to the shear sliding between Ta2O5-based transfer film in the wear track and pure alumina ball.

Biosynthesis of Al2 O3 and europium-doped Al2 O3 nanoparticle using Cymbopogon citratus (lemongrass) extract and its antibacterial property.

Cymbopogon citratus-mediated pure aluminium oxide (Al2 O3 ) and europium (Eu)-doped Al2 O3 with different amounts of metal ion were prepared using a green synthesis method. Synthesised nanoparticles were characterised by ultraviolet (UV)-visible spectroscopy, photoluminescence (PL), Fourier-transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM). Synthesis of nanoparticles is confirmed by using UV-visible spectroscopy showing maximum absorption at 411 and 345 nm for Al2 O3 and Eu-doped Al2 O3 , respectively. The antibacterial activity of prepared nanoparticles was evaluated against Pseudomonas aeruginosa, Streptococcus aureus, Escherichia coli and Klebsiella pneumoniae using a well-diffusion technique. The effect of pure Al2 O3 and Eu-doped nanoparticles shows excellent results against P. aeruginosa, S. aureus, E. coli and K. pneumoniae.

Statistical Comparison of Substructures in Pure Aluminum Before and After Creep Deformation, Based on EBSD Image Data.

Electron backscatter diffraction (EBSD) images of extruded pure aluminum were statistically analyzed to investigate creep-induced subgrain structures after applying two different levels of creep stress, corresponding to the power law (PL) and power-law breakdown (PLB) regimes. Kernel average misorientation analysis of EBSD measurements revealed 2D morphologies, which were subdivided by a multi-step segmentation procedure into subgranular arrangements. Various descriptors were employed to characterize the "subgrains" quantitatively, including their size, shape, spatial arrangement, and crystallographic orientation. In particular, the analysis of the orientations of subgrains was conducted by neglecting rotations around the loading axis. This approach facilitated the individual investigation of the {001} and {111} subgrain families with respect to the loading axis for two investigated stress levels plus a reference specimen. For the PL regime, the statistical analysis of subgrain descriptors computed from segmented image data revealed a similar degree of strain accumulation for {111} and {001} subgrains. In contrast, for the PLB regime, the analyzed descriptors indicate that {111} subgrains tend to accumulate significantly more strain than {001} ones. These observations suggest that the mechanisms leading to PLB may be associated with strain localization dependent on intergranular stress, hindering the recovery process within {111} grains.

The effect of post heat treatment and TiO2 addition on tribological and electrochemical performances of thermally sprayed alumina

ABSTRACT The heat treatment of alumina ceramics is a fundamental process for controlling the physical, mechanical and thermal properties of these components during industrial operations. The problem statement in this case is about the effects of TiO2 addition and post heat-treatment on the expansion behaviour of alumina coating. For that alumina (Al-99) and alumina-titania coatings 5% wt. TiO2 (AT-5) and 15% wt. TiO2 (AT-15) were formed onto E335 substrate steel via the flame spraying technique. The samples were heat-treated (1000°C for 2 h in Air) and their wear and electrochemical behaviour was compared with the as-sprayed samples. The X-ray diffraction (XRD) patterns reveal a change in the phase composition of the heat-treated coatings compared to the as-sprayed coatings, as alpha alumina matrix but with different ratio. The heat-treated coatings exhibit higher values to as-sprayed coating. At the same time, the addition of TiO2 present hardness twice than pure alumina coating (Al-99). The tribological properties show that the deposits after heat treatment have low wear values compared to the as-sprayed coatings, the lowest specific wear rate was obtained for the heat-treated AT-5 composite coatings. The heat treatment had a positive effect on the corrosion resistance.

Effect of TiO2 addition on the microstructure and electrical properties of Al2O3 ceramics

The resistivity of the dielectric layer material of a Johnsen–Rahbek (J–R) electrostatic chuck is generally between E8 and E12 Ω⋅cm, while that of pure alumina ceramic is more than E15 Ω⋅cm. Therefore, it is necessary to regulate the resistivity of the alumina ceramic for use as a dielectric layer material for a J–R-type electrostatic chuck. An electrostatic chuck requires a uniform and controllable surface temperature on the silicon wafer. Therefore, there is a certain requirement for the thermal conductivity of the dielectric layer.In this experiment, Al2O3 ceramics with different TiO2 contents (ranging from 0.08 to 3.6 wt%) were used as the research system and sintered at 1550 °C in a reducing sintering atmosphere. The obtained samples showed electrical resistivity from E9 to E14 Ω⋅cm and thermal conductivity from 26 to 37 W/m·K. The effects of Al2O3 ceramics with TiO2 on the phase composition, microstructure, relative density, electrical conductivity, and thermal conductivity were systematically studied, along with the relationship between the temperature and electrostatic adsorption force J–R and the resistivity of the sample. The addition of 1.2 wt% TiO2 gave the Al2O3 sample better overall performance; its relative density was up to 97.88 %, resistivity was reduced to 7.09 × 109 Ω cm, thermal conductivity was 27.211 W/m·K, and the electrostatic adsorption forces at 300 and 500 V/mm were up to 119 and 331 gf/cm2, respectively. The samples were primarily used as dielectric layers of the electrostatic chuck. By simulating the electrostatic adsorption between the dielectric layer and silicon wafer under an external voltage, the J–R force of stable adsorption between the electrostatic chuck and the silicon wafer was realised.

Effect of EDTA-modified alumina composite abrasive on the CMP performance of sapphire substrate

Sapphire is one of the most widely used substrate materials for semiconductor lighting. With the improvement of chemical mechanical polishing (CMP) processing technology for sapphire substrate, mass production, and cost control requires faster polishing efficiency and better surface quality. In CMP, alumina abrasive is widely used for its high polishing rate, but it also has the disadvantages of easy agglomeration and poor polishing quality. Therefore, ethylenediamine tetraacetic acid (EDTA)-grafted alumina composite abrasives were produced by a two-step process for the sapphire substrate CMP. As demonstrated by time of flight secondary ion mass spectrometry and fourier transform infrared spectroscopy, EDTA has been successfully grafted onto the surface of alumina particles. As shown by the scanning electron microscope, particle size distribution, and zeta potential analyses, the modified alumina composite abrasives exhibit superior dispersion properties than pure alumina particles. CMP experiment results show that the material removal rate (MRR) of the alumina composite abrasives can reach up to 2.6 μm/h, and the surface roughness (Sa) of the sapphire substrate can be reduced to 0.89 nm, which is 53 % higher and 66 % lower than pure alumina, respectively. According to X-ray photoelectron spectroscopy, the chemical etch of modified abrasive particles was strengthened, and the complex reaction occurred throughout the CMP process to generate the C–O–Al structural compound. Meanwhile, the friction coefficient test and contact angle test were combined to create the contact wear model. It shows that the addition of EDTA expands the contact area between the composite abrasives and the surface of substrates, improving the mechanical interaction during CMP. The chemical reaction and mechanical action combine and promote each other to enhance the CMP performance.

TWO TYPES OF GALLIUM EXPOSURE TO ALUMINUM

The effect of gallium on aluminum during their fusion is investigated. The corrosion rate of aluminum alloys with 1, 2 and 5 at % gallium content was experimentally determined, which was 0.001, 0.00101 and 0.00062 g/m2 · h, respectively, which is less than that of pure grade A99 aluminum – 0.0016 g/m2 · h. The rate of dissolution of these alloys in acidic and alkaline media is determined. X-ray phase analysis showed the homogeneity of the alloys under consideration. The morphology of aluminum alloys with gallium was studied, after exposure to an aggressive environment – a solution of hydrochloric acid. The possibility of obtaining hydrogen and nanoscale alumina by decomposition of water by activated gallium aluminum alloy is shown. Activation of the aluminum surface by gallium alloy occurs according to the Rebinder effect and the article presents a micrograph of the surface of aluminum treated with Ga-Sn alloy, clearly demonstrating this effect. When using metallic gallium in contact with aluminum, the interaction requires heating to a temperature above 30°C (the melting point of gallium is 29.7°C), the melting point of the eutectic composition 92Ga–8Sn is 20.0°C, which allows the interaction to begin at room temperature. At temperatures of about 4°C, activated aluminum can be stored for a long time. The quality of hydrogen obtained by decomposition of water should be higher than that obtained by cracking, and the cost is close to a well-developed technology of electrolysis of water and no more than 2 times the cost of its synthesis via cracking of hydrocarbons. Gallium and its liquid alloys are non-toxic, almost do not interact with water, activate aluminum, preventing the formation of a protective oxide film, penetrate into the intergranular space and aluminum easily interacts with water, forming hydrogen and aluminum hydroxide.

Carbon nanotubes/aluminum interface structure and its effects on the strength and electrical conductivity of aluminum

The contradiction between strength and electrical conductivity of pure aluminum (Al) hinders its wide applications in electrical engineering. In this study, an attempt was made to overcome this limitation by adding carbon nanotubes (CNTs) into Al matrix using friction stir processing (FSP) method. The results showed that CNTs were singly distributed in Al matrix and strong bonded CNTs/Al interfaces without chemical reaction as well as impurity contamination were formed. Interestingly, it was found that the axis of CNTs tended to be parallel to Al (111) planes, which provided a geometric basis for the formation of semi-coherent CNTs/Al interfaces. These semi-coherent CNTs/Al interfaces possessed an extremely low electrical resistivity, which weakened the total electron scattering generated by all CNT/Al interfaces. Meanwhile, strong bonded CNTs/Al interfaces effectively hindered dislocations movement, inducing an improvement of 84 % and 50 % in yield strength and tensile strength of Al respectively. As a result, the strength of Al was significantly improved without losing its electrical conductivity. This study provides a new strategy for breaking through the contradiction between strength and electrical conductivity of Al and then producing CNTs/Al nanocomposites with high strength and high electrical conductivity.

Effect of Al–Ti–B master alloy on microstructure and properties of aluminum-air battery anode materials

This study investigates the effects of Al–5Ti–B master alloy addition on the electrochemical properties and discharge performance of commercial pure aluminum (1060Al) in 4 M NaOH solution. The results show that the coarse branch-like α-Al grains are transformed into finer and smaller equiaxed grains, and the iron-rich phase are changed from long rod-like to small spherical grains. TiB2 particles introduce more heterogeneous nucleation sites in the α-Al crystals, resulting in an increased amount of grain boundaries in the aluminum matrix. There are more crystal defects at the grain boundaries than in the interior of α-Al grains, which provids more channels and energy for the reactions. This significantly increases the electrochemical activity of the aluminum alloy, causing the negative shifts for both the open circuit potential and the corrosion potential. The reduction in the size and change in the morphology of the iron-rich phase decreased the contact area between the iron-rich phase and the aluminum matrix, weakening the galvanic action between them. Meanwhile, the refinement of the α-Al grains decreased the potential difference between the interior and exterior of the grains, resulting in a reduction in the material corrosion current and an improvement in its corrosion resistance. Therefore, compared to the method of adding high hydrogen evolution potential elements to suppress hydrogen evolution reaction, the refinement of α-Al grains and the changes in the size and morphology of iron-rich phases due to the presence of TiB2 particles are the main reasons for improving the corrosion resistance and discharge performance of aluminum-air batteries in NaOH solution.

Optimizing the strength and ductility of pure aluminum laminate via tailoring coarse/ultrafine grain layer thickness ratio

Ultrafine-grained (UFG) materials typically exhibit high strength but disappointingly low ductility due to the limited dislocation accumulation. To evade the strength-ductility tradeoff of UFG pure aluminum (Al), four kinds of UFG/coarse-grained (CG)/UFG sandwich-structured pure Al laminates were designed via extrusion and cold rolling. Microstructure characterization displayed that the grain size of the CG in the four designed laminates always remained ∼5 times that of UFG, indicating significant grain size heterogeneity between the constituent layers. The finite element analysis indicated that as the CG/UFG layer thickness ratio increased, the distribution of residual stress between the constituent layers was inhomogeneous and became more pronounced near the interface, which reduced the tensile ductility of the laminates. Tensile tests indicated that when the CG:UFG layer thickness ratio was 1:3, the laminate obtained a desirable strength and ductility compared to other laminates and UFG sample, with a yield strength of 150 MPa and a tensile ductility of 13.5 %. The optical microscope (OM)-digital image correlation (DIC) results revealed that the significant strain gradient near the layer interface caused by the heterogeneous deformation contributed to hetero-deformation induced (HDI) strengthening and HDI strain hardening, thereby strengthening and toughening the laminate.

The effect of subgrain mobility on recrystallization kinetics: phase-field simulation study

The influence of grain boundary mobility on the recrystallization process (ReX) was investigated in this study using the phase-field approach. In accordance with the Read-Shockley equation, for the interfacial mobility as a function of the misorientation angle, the resulting microstructural evolution was studied. It was observed that the disappearance of low-angle grain boundaries (LAGBs) during the ReX process caused high-angle grain boundaries to move faster during the subsequent ReX stages. For materials with high stacking energy, such as aluminum, LAGBs were additionally found to play a significant role in the ReX process. The kinetics of the ReX process, coupled with grain growth, showed the typical behavior observed in fine-grained structures of pure aluminum.

Effective chloride ion resistance of aluminum powder through interface electric field designing

Pure aluminium (Al) powder is widely used in aerospace fields as fuel while its corrosion mechanisms and anti-corrosion strategies are not thoroughly studied. Herein, corrosion mechanisms of Al nanoparticles are revealed by density functional theory (DFT) and experiments. Moreover, by utilizing the behaviour of ions moving in the electric field, an interfacial electric field is designed to endow spherical aluminium powder (sAl) with high anti-corrosion for chloride ions (Cl−). Because TiO2 presents lower electrostatic potential than Al2O3 which is on the surface of sAl, the prepared core@shell structural material (sAl@TiO2) holds an interfacial electric field and its direction is from TiO2 to Al2O3. The electric field repels the Cl− adsorption on the surface of sAl@TiO2, bringing about superior Cl− anti-corrosion.

Influence of α-Al2O3 Ceramic Nanoparticles on the Microstructure and Mechanical Properties of Pure Aluminium Based Nanocomposites

Influence of α-Al2O3 Ceramic Nanoparticles on the Microstructure and Mechanical Properties of Pure Aluminium Based Nanocomposites

Anodik Polarizasyon ve Kayma Aşınmasının Gemi İnşa Alüminyum Alaşımı 5083'ün Çukurcuk Korozyonu Davranışına Etkisi

This study aimed to characterize the pitting corrosion and simultaneous wear-corrosion (tribocorrosion) mechanisms of shipbuilding aluminum alloy 5083 under sliding wear and different anodic polarization conditions in simulated seawater. A tribocorrosion experimental setup was provided for the study under a 3 N load and different anodic potentials in a 3.5% NaCl solution. In the study, many grooves, parallel scratches and transverse cracks were determined on the wear track surface due to the low hardness of the test material. Chloride ions played a decisive role in the corrosion and tribocorrosion behavior of AA 5083. The dissolution of AA5083 increased from open circuit potential to higher anodic potentials. A half-cube mechanism, similar to the pitting corrosion of pure aluminum, and an intergranular pitting corrosion mechanism were observed under high anodic potentials.

Strengthening Effect of Decreased Dislocation Density After Annealing in Pure Aluminum or Copper

Strengthening Effect of Decreased Dislocation Density After Annealing in Pure Aluminum or Copper

Direct Writing of Reactive Inks Based on Electroless Nickel Deposition on Pure Aluminium Powders

Direct Writing of Reactive Inks Based on Electroless Nickel Deposition on Pure Aluminium Powders

Tribological and corrosion characteristics of tetra hybrid particulate-reinforced aluminum composites for aerospace and automotive applications

This study investigates Hybrid Particulate-Reinforced Aluminum Matrix Composites (HPRAMCs), a material class known for exceptional physico-mechanical, tribological, and corrosion resistant properties. The research synthesizes HPRAMCs using SiC, Al2O3, graphite (Gr), and sugar cane bagasse ash (SCBA) reinforcements through a powder metallurgy process, followed by sintering at 550°C for 3 h. Comprehensive tests include X-ray diffraction (XRD) for phase analysis, physico-mechanical assessments, tribological evaluations, and corrosion resistance analyses. Notably, secondary reinforcements significantly reduce porosity, with AS4 HPRAMC exhibiting a 0.53% porosity, while AS1 HPRAMC has 1.446%. AS4 HPRAMC displays a remarkable 209.76% increase in compressive strength and a 446.40% boost in material hardness compared to pure aluminum. Secondary reinforcements also improve tribological performance, reducing wear loss by 60.27% and the coefficient of friction by 89.89%. Exceptional corrosion resistance, with an inhibition efficiency of 99.691%, is observed in the AS4 HPRAMC sample, confirmed by scanning electron microscopy (SEM). These findings underline the substantial potential of HPRAMC materials, positioning them as promising candidates for aerostructural components, aircraft systems, automobiles, spacecraft, and high-performance engineering applications.