Zinc In Aluminium Research Articles

Association between Aluminium Levels and Cognitive Decline in Environmentally Exposed Elders

AbstractBackgroundNormal brain functioning depends on metals homeostasis, as imbalances may increase oxidative stress and cause other detrimental intracellular events that lead to cell loss. Furthermore, environmental exposure to toxic metals is hypothesized to induce neuroinflammation and neuropathology, paving the way to neurodegeneration. The aim of this study was to examine whether such Potentially Toxic Elements (PTE) are associated with cognitive performance over time in a sample of elderly individuals of environmentally contaminated regions.MethodA total of 146 elders permanently residing in environmental risk areas were recruited. Participants completed the Mini Mental State Examination (MMSE) for cognitive assessment and were biomonitored for several PTE through hair and urine analysis. After 5 years, the cognitive assessment was repeated.ResultCognitive performance significantly declined from baseline to follow‐up (p < 0.001), with participants scoring on average 4.41 less points on MMSE (Baseline: M = 25.79, SD = 3.520, Md = 27.00; Follow‐up: M = 21.38, SD = 5.343, Md = 21.00). Regression analysis on the relationship between PTE and cognitive performance revealed that Aluminium (β = ‐0.322, p = 0.32) and Zinc (β = ‐0.372, p = 0.15) in hair and Aluminium in urine (β = ‐0.368, p = 0.010) significantly predicted MMSE scores past 5 years of biomonitoring (p = 0.002). Higher contents of these PTE were associated with worse cognitive performance at follow‐up, after controlling the effects of age, education and supplement intake.ConclusionHigher levels of Aluminium significantly predict worse general cognitive performance 5 years after biomonitoring across different biological samples. Environmental exposure to this metal may constitute a risk factor for cognitive decline.

High-Temperature Deformation of Naturally Aged 7010 Aluminum Alloy

This study is focused on the deformation mechanism and behavior of naturally aged 7010 aluminum alloy at elevated temperatures. The specimens were naturally aged for 60 days to reach a saturated hardness state. High-temperature tensile tests for the naturally aged sample were conducted at different temperatures of 573, 623, 673, and 723 K at various strain rates ranging from 5 × 10−5 to 10−2 s−1. The dependency of stress on the strain rate showed a stress exponent, n, of ~6.5 for the low two temperatures and ~4.5 for the high two temperatures. The apparent activation energies of 290 and 165 kJ/mol are observed at the low, and high-temperature range, respectively. These values of activation energies are greater than those of solute/solvent self-diffusion. The stress exponents, n, and activation energy observed are rather high and this indicates the presence of threshold stress. This behavior occurred as a result of the dislocation interaction with the second phase particles that are existed in the alloy at the testing temperatures. The threshold stress decreases in an exponential manner as temperature increases. The true activation energy was computed by incorporating the threshold stress in the power-law relation between the stress and the strain. The magnitude of the true activation energy, Qt dropped to 234 and 102 kJ/mol at the low and high-temperature range, respectively. These values are close to that of diffusion of Zinc in Aluminum and diffusion of Magnesium in Aluminum, respectively. The Zener–Hollomon parameter for the alloy was developed as a function of effective stress. The data in each region (low and high-temperature region) coalescence in a segment line in each region.

Effect of Homogenization on the Structure and Properties of Alloy of the Al – Zn – Mg – Sc – Zr System

The effect of homogenizing regime is studied for continuously cast ingots of alloy of the Al – Zn – Mg – Sc – Zr system on the structure and properties of extruded strips and cold-rolled sheets prepared from them. It is established that the properties of these semiproducts in a thermally strengthened condition depend little on homogenizing regime as a result of constancy of their grain structure, which remains unrecrystallized (polygonized) after heating for hardening. Breakdown of transition metal solid solution present in the alloy, occurring during ingot homogenization affects the recrystallization temperature and kinetics, and also the stability of zinc and magnesium solid solution in aluminum in the semiproducts obtained from ingots.

Abrasive Wear Response of SiC<sub>p</sub> Reinforced ZA-43 Alloy Metal Matrix Composite

Objectives: The objectives of the present study are to synthesize the high aluminium content zinc based alloy and their composites by incorporating 5 and 10 wt% of SiC particles and to assess their two body abrasive wear response. Methods/ Analysis: The matrix alloy and their composites have been synthesized by liquid metallurgy route. High stress abrasive wear examiantion have been conducted on using a pin-on-disc wear tester as per ASTM G132-96 standard. The influence of abrading distance and applied load on the wear behaviour of the test materials have been studied. For understanding the wear mechanism of composite wear rate, friction coefficient and frictional heating have been determined. Findings: The zinc based matrix alloy exhibits dendritic structure comprising of α dendrites surrounded by α + η eutectoid and metastable ∈ phase. in interdendritic regions. The α+η is solid solution of zinc and aluminium in aluminium and zinc respectively are soft and ductile while ∈ phase is quite harder and transmits wear resistance to a slight range. The dispersed SiC particles are considerable harder than the base alloy and enhance the abrasion resistance of the matrix alloy. Increasing abrasive wear rate with test duration could be attributed to greater extent of materiel loss because of the cutting tendency of the abrasive. Higher wear rate with larger load was owing to relatively less deterioration in the cutting efficiency of the abrasive particles spread over fixed track area. Highest frictional heating of the matrix alloy could be because of a greater extent of penetration of the abrasive particles on the samples while dispersion of hard SiC particles reduces the severity of penetration. Higher frictional heating with increasing load may be acribed to a greater extent of penetration by the abrasive particles on the sample surface. The presence of hard SiC particles in the composite reduced the depth of cut by the abrasive leading to increase coefficient of friction than the base alloy. Novelty/Improvements: The present study evaluate the abrasive wear behavior of a lighter zinc-based alloy and their composites in order to substitute as an efficient material system to conventionally used materials in tribiological applications.

New developments on optimizing properties of high-Zn aluminium cast alloys

Foundry alloys with Al-based matrices have a wide range of uses in today's global economy and there is a high demand for castings of Al alloys, including Al-Zn alloys. In this paper, investigations on the grain refinement of high-Zn aluminium cast alloys are presented. Aluminium alloys with relatively high zinc content have a tendency to be coarse-grained, especially in the case of castings with low cooling rates such as are found in sand moulds. The coarse-grained structure degrades the plasticity, specifically the elongation. Therefore, for aluminium alloys of high (10-30 wt.%) zinc content, inoculation is attractive, aiming to break up the primary dendrites of the a-phase solid solution of zinc in aluminium. Such dendrites are the principal microstructural component in these alloys. On the other hand, a finer grain structure usually reduces the damping (e.g. as measured by attenuation of ultrasound) in these alloys. In the present investigations, a binary sand-cast Al-20 wt.% Zn alloy was inoculated with different additions of AlTi3C0.15 (TiCAl) and ZnTi-based master alloys. The sand-cast samples were subjected to mechanical-property measurements (tensile strength and elongation), image analysis to determine grain size, and measurements of the attenuation of 1 MHz ultrasound. It is found that both of the master alloys used cause significant refinement of the a-AlZn primary dendrites and change their morphology from linear-branched to semi-globular, increase the elongation by about 40%, and decrease the attenuation coefficient by about 25% in comparison with the initial alloy without inoculation.

Metal pollution in biotic and abiotic samples of the Büyük Menderes River, Turkey.

The Büyük Menderes River (BMR) is one of the largest rivers in Turkey. This river irrigates efficient farmlands and includes tributaries of other rivers and streams and many populated towns within its limits in the Ege region. Both the estuary and Işıklı Lake serve as a sanctuary for various waterbirds. Therefore, the BMR plays a critical role both for the inhabitants and for the ecosystem organisms in its environs. In the present study, we analyzed levels of metals including iron, barium, zinc, vanadium, cobalt, chromium, cadmium, copper, nickel, aluminum, arsenic, manganese, antimony, silver, selenium, boron, mercury, titanium, and lead in river water, sediment, fish (Cyprinus carpio; common carp), and in various waterbird (Fulica atra, Euroasian coot; Larus michahellis, yellow-legged gull; Ardea cinerea, grey heron; Larus melanocephalus, Mediterranean gull; and Pelecanus crispus, pelican) samples. Analyses were performed using an inductively coupled plasma-mass spectrometry (ICP-MS) instrument after sample preparation. Comparing metal concentrations among different sample types, it was found that barium, aluminum, and zinc are the major metals in river water, and zinc in common carp muscle, while iron, aluminum, and manganese are the major metals in sediments. Iron, zinc, copper, and aluminum were the highest in waterbird muscle tissue. Iron and barium were found to be the major metals in eggshell, while iron and zinc are the major metals in egg samples. A simple "worst-case scenario" model of risk assessment revealed that some of the analyzed metals may pose a risk for human health through consuming fish.

Effect of applying calcium chloride and three milk supplements to poinsettia ‘Prestige Red’

ABSTRACTSome poinsettia (Euphorbia pulcherrima Willd. ex Klotzsch) cultivars are susceptible to bract calcium (Ca) deficiency in developing bracts. In this study, we evaluated the efficacy of foliar uptake of Ca from milk-based products plus calcium chloride (CaCl2) as a potential Ca source. Weekly foliar applications of 237 mL L−1 whole milk, 80 mL L−1 powdered milk, 30 mL L−1 condensed milk, 0.94 g L−1 CaCl2, or distilled water (used as a control) were applied to runoff of ‘Prestige Red’ for four weeks. The four largest bracts with petioles on three different inflorescences and three leaves with petioles below the transitional leaf per inflorescence were collected per pot. None of the treatments affected bract or leaf Ca concentration. Powdered milk treatments resulted in a higher concentration of zinc (Zn) in bracts and aluminum (Al) in bracts and leaves. White residue remained on the bracts and leaves after treatment with powdered milk, which would reduce marketability.

Sealing Treatment of Aluminum Coating on S235 Steel with Thermal Diffusion of Zinc

The study introduced a thermal diffusion sealing treatment for arc-sprayed aluminum coating on S235 carbon steel. The sprayed aluminum-zinc duplex coating was heated to 420 °C, so that the low-melting-point zinc could diffuse into the pores of the aluminum coating. Optical microscope, microhardness, electron probe microanalysis, and x-ray diffraction were used to evaluate the sealing treatment. The calculated diffusion coefficient for zinc in the arc-sprayed aluminum coating was approximately 7.735 × 10−9 cm2/s. The diffused zinc could increase the compactness and microhardness of the aluminum coating. Nevertheless, adverse interface reactions could destroy the coating if the zinc made contact with the steel substrate. FeZn10 could form initially, and then the heat from the exothermic reactions between zinc and iron would initiate the reactions among iron, aluminum, and zinc. FeAl-Zn x , FeAl2-Zn x , and Fe2Al5-Zn x were generated following FeZn10. The defected structures were mainly composed of Fe2Al5-Zn x and FeZn10. All of these formed tough, brittle, intermetallics that have a negative effect on the coating performance. Thus, the contact between zinc and the steel substrate should be avoided, and the holding time should be restricted to 8.16 × 106 L 2 to prevent the generation of intermetallics.

Fabrication of Porous and Nanoporous Aluminum via Selective Dissolution of Al-Zn Alloys

Porous and nanoporous aluminum have been fabricated via selective dissolution. Al-Zn alloys were dealloyed in an aqueous solution of nitric acid to selectively dissolve zinc. Fast solidification methods permitted to adjust the precursor microstructure of the parent alloy in order to induce supersaturation of zinc in aluminum. An electric potential applied during corrosion affected the final morphology of porosity. Electronic imaging evinced the presence of regions with less than 100 nm diameter pores. This nanoporosity was only present in electrochemically dealloyed samples. We observed two types of porosity in dealloyed samples: a primary porosity resulting from the selective removal of zinc-rich interdendritic phases and a secondary porosity resulting from nanoporosity evolution inside zinc-supersaturated dendrites.

Effect of microadditions of magnesium and zinc in aluminum upon heating of cold-rolled sheets

Methods of structural investigations, measurements of hardness, temperature, time, and amplitude dependences of internal friction have been used to study processes of polygonization and recrystallization in Al-0.3 at % Mg and Al-0.3 at % Zn alloys. It has been established that the magnesium atoms more efficiently pin dislocations in the aluminum-based alloys as compared to zinc atoms. Therefore, in the alloy with zinc the process of polygonization occurs more intensely and the processes of softening upon recrystallization occur more slowly than those in the alloy with magnesium.

Structural Stability of the High-Aluminium Zinc Alloys Modified with Ti Addition

The subject of the paper is structural stability of the Zn-26 wt.% Al binary alloys doped with 2.2 wt.% Cu or 1.6 wt.% Ti addition. The structural stability of Zn-Al alloys with increased Al content is connected with stability of solid solution of zinc in aluminium α', which is the main component of these alloys microstructure. Such a solution undergoes phase transformations which are accompanied, among others, by changes in dimensions and strength properties. The structural stability of the ZnAL26Cu2.2 and ZnAl26Ti1.6 alloys was investigated using XRD examinations during long term natural ageing after casting, as well as during long term natural ageing after super-saturation and quenching. On the basis of the performed examinations it was stated that small Ti addition to the binary ZnAl25 alloy, apart from structure refinement, accelerates decomposition of the primary α' phase giving stable structure in a shorter period of time in comparison with the alloy without Ti addition. Addition of Ti in amount of 1.6 wt.%, totally replacing Cu, allows obtaining stable structure and dimensions and allows avoiding structural instability caused by the metastable e−CuZn4 phase present in the ZnAl26Cu2.2 alloy.

Analysis of the Solid Solution Microstructure of (HF) Al-Zn Alloys

Rapidly solidified Al-Zn alloys with Zn contents ranging up to 50 wt.% were made under vacuum, by high-frequency (HF) induction melting, from compacted mixture targets of Al and Zn of fine (99.99 % purity) elemental powders. The microstructural characteristics and strengthening mechanisms were investigated. The crystallographic microstructures were characterized by means of X-ray diffraction (XRD) analyses and optical microscopy observations as well as Vickers microhardness testing. Detailed overviews of alloying solubility of zinc in aluminium were given. Extensive solid solutions of CFC Al were found in the (HF) Al-Zn alloys, and a higher Vickers microhardnesses compared to that of pure (HF) aluminium.

Relations between the parameters of grain-boundary diffusion of zinc in aluminum

Experimental results on the grain-boundary diffusion of zinc in aluminum bicrystals containing 〈100〉 and 〈111〉 tilt boundaries at normal and high hydrostatic pressures have been considered. A comparison of the diffusion activation energies and the activation volumes for grain boundaries having the same crystallographic parameters has revealed a linear relation between these kinetic constants. The diffusion activation energy is found to increase with the activation volume. This relation is shown to correspond to the compensation effect well-known in diffusion theory.

Effects of High-Speed Deformation on the Phase Stability and Interdiffusion in Ultrasonically Joined Aluminum and Zinc Foils

ABSTRACTThe effects of high strain-rate deformation on the phase stability and interdiffusion were investigated for Al-Zn welds produced by ultrasonic welding at 513 K. The welds exhibited three distinct regions: a featureless region indicative of local melting on the zinc side, a solidified mushy layer and a layer of fcc grains enriched with zinc. Al-Zn phase diagrams calculated from vacancy-modified Gibbs free energy curves indicate that local melting at the weld interface may result even at 513 K if the vacancy concentrations in the fcc and hcp solutions approach 0.07 as a result of high strain-rate deformation. EDS analysis of the weld interface yielded an interdiffusivity of 1.9 μm2/s, which is five orders of magnitude larger than the normal diffusivity of zinc in aluminum at 513 K. Application of the mono-vacancy diffusion mechanism to the diffusion data also yields a vacancy concentration of 0.07, indicating that such a high vacancy concentration may indeed resulted during the ultrasonic welding at 513 K.

Thermomigration of Zinc in Aluminium and Al-Zn Alloy

Thermomigration of Zinc in Aluminium and Al-Zn Alloy

Erratum to Beam focusing characteristics and alloying element effects on high-intensity electron beam welding

Effects of focusing characteristics of the beam as well as concentrations of a volatile alloying element in the workpiece on the shape of the cavity produced by a high-energy beam are systematically and quantitatively investigated. The energy flux of the focused energy beam is independently specified by the convergence angle, the energy distribution parameter at the focal spot, and the focal spot location relative to the workpiece surface. Energy flux at any cross section of the beam is a Gaussian distribution. The geometry of the cavity is determined by satisfying interfacial energy and momentum balances. By accounting for beam focusing characteristics, the cavity surface temperatures, depths of penetration, and cavity shapes are found to agree with experimental data. The opening diameter and depth of the cavity depend primarily upon the energy distribution parameter at the workpiece surface for a surface-focused weld t increase in the content of the volatile alloying element zinc in aluminum exhibits a pronounced influence on the shape of the cavity.

Low temperature volume diffusion of zinc in aluminium

The low temperature volume diffusion coefficients of zinc in aluminium have been measured over the temperature range from 180° to 235° C by determining the zinc concentraton profiles across grain boundaries more or less perpendicular to the surface of the extending across thick foils of aluminium which were chemically coatted with zinc and anneleed for times greater than that necessary to attain a steady state flow of zinc along the boundaries from one side of the foils to the other. The zinc concentrations were determined by energy dispersive X-ray analysis of thin foils in a transmission electron microscope and were fitted with the constant source of the diffusion equation in order to determine the diffusion coefficients. The diffusivities obtained agreed well with an extrapolation of the high temperature values of Hilliard et al. and yielded values of 0.018 cm 2·s −1 and 112 kJ·mol −1 for the preexponential factor D 0 and the activation energy Q, respectively.

Beam focusing characteristics and alloying element effects on high-intensity electron beam welding

Effects of focusing characteristics of the beam as well as concentrations of a volatile alloying element in the workpiece on the shape of the cavity produced by a high-energy beam are systematically and quantitatively investigated. The energy flux of the focused energy beam is independently specified by the convergence angle, the energy distribution parameter at the focal spot, and the focal spot location relative to the workpiece surface. Energy flux at any cross section of the beam is a Gaussian distribution. The geometry of the cavity is determined by satisfying interfacial energy and momentum balances. By accounting for beam focusing characteristics, the cavity surface temperatures, depths of penetration, and cavity shapes are found to agree with experimental data. The opening diameter and depth of the cavity depend primarily upon the energy distribution parameter at the workpiece surface for a surface-focused weld t increase in the content of the volatile alloying element zinc in aluminum exhibits a pronounced influence on the shape of the cavity.

Investigation of the decomposition behaviour in supersaturated Al-Zn alloys

The decomposition behaviour in supersaturated Al + (1–6.4) at % Zn has been investigated using electrical resistivity and microhardness measurements in the temperature range from room temperature to ∼500° C. The experimental results showed that (i) both the temperature coefficient of resistivity and the relaxation time of the free electrons diminish as the concentration of Zn increases in the alloy; (ii) the early stage decomposition of the supersaturated alloys via Guinier-Preston zone formation is accompanied by an appreciable increase in the microhardness of about 80 MPa per 1 at % Zn; (iii) the obtained activation energy of 0.41 eV for the precipitation process of the dissolved zinc atoms is close to the migration energy of zinc in aluminium which indicates that the precipitation mechanism is characterized by the migration and coalescence of zinc atoms.

Effect of scandium on the decomposition of aluminium-zinc alloys

The effect of scandium on the hardness, structure and heat evolution of an aluminium-40% zinc alloy was investigated. It was found that contrary to its action in other aluminium-based alloys, scandium does not raise the maximum hardness during an ageing treatment. This may be explained by insufficient scandium redissolution at the rather low temperature necessary for achieving a solid solution of zinc in aluminium. Differential scanning calorimetry studies show a similar heat evolution in both alloys upon linear heating, starting with the reversion of modulated structures. An exothermal effect appears only in the scandium-bearing alloy due to increased heterogeneous precipitation of α′r, and β on Al3Sc particles. Above 200 °C, the dissolution of the α′r and β phases starts, followed by the monotectoid reaction.