Zinc Aluminium Alloy Research Articles

RUNNER ANGLE MODIFICATION FOR ENHANCED MACROSEGREGATION REDUCTION IN ALUMINIUM-ZINC ALLOY

Macro-segregation is an irreversible defect in non-ferrous alloy casts. This can only be significantly minimized by controlling the melt and its flow trajectory during casting. The study identified runner angle inclination as a critical parameter that impacts the development, size and volume of macro-segregation occurrence in binary alloys. The methodology entails variation of runner angles to include 90°, 105°, 120°, 135°, and 150° at a constant casting speed of 100mm/s being the optimum casting speed established in previous study. The casts microstructure was examined using both optical and electron microscopes complemented with energy dispersive spectrometry. Results show that runner position at 120° is the most appropriate for the casting of aluminium-zinc alloy as this gave a highly homogeneous distribution of solute element in the microstructure with corresponding improved mechanical properties

Investigations on microstructure and tensile properties of as-cast ZA-27 metal matrix composite reinforced with zircon sand

Zinc-Aluminum alloys are employed as a bearing material in various machinery. In the present work zircon sand microparticles of size, 100 µm are dispersed in ZA-27 alloy with weight fractions of 1.5 wt%, 3.0 wt%, 4.5 wt%, and 6.0 wt% to synthesize ZA-27 metal matrix composites by stir casting. Microstructure studies using, SEM/EDAX conducted to determine the morphology of the particles and the ZA-27composites. Physical properties like density and porosity of the zircon sand microparticulate reinforced ZA-27 are evaluated and their effect on strength and ductility of the composites are evaluated using the tensile test. dispersion of zircon sand is seen in the SEM micrographs and EDAX confirms the same. The results obtained revealed an increase in tensile strength and yield strength at 3.0 wt%, 4.5 wt and 6.0 wt% at the cost of a reduction in percentage elongation when compared to ZA-27 alloy. The tensile behavior of ZA-27 composites is found to be affected by the dispersion of reinforcement in the matrix arising due to dislocation density.

Mechanical properties analysis of hybrid composites prepared by stir casting approach

Hybrid is the combination of different items to make a single structure; in this study different materials are mixed together to form a high strength composite with enhanced mechanical strength. The correlation of different materials are prepared through stir casting process and it is formed the new composites also improve the strength. This study involved to making a hybrid composites effectively with taken of 50% of Aluminium alloy, 40% Zinc and 10% of copper. From in all casting alloys the toughness is improved by adding of pure zinc of the zinc-aluminium alloy. In the stir casting process 700 rpm of stirring speed is maintained for 8 min to obtain homogeneous mixing. Homogeneous mixtures of the Aluminum alloy- Copper-Zinc are proved the better strength in mechanical test. Newly prepared the homogeneous mixtures of the composites are tested by tensile test and impact test, the wear test also carried out. Mechanical strength of the specimens are evaluated, the result of the test are revealed that the mechanical strength is improved effectively.

Microstructure and properties of arc sprayed Zn-Al alloy coatings

In this study, zinc-aluminum alloy coatings were deposited on low carbon steel substrates by arc thermal spraying with different current and spraying distances. Optical microscope (OM) was used to characterize the deposited coatings. From the experiment, it is found that the samples that use different electric currents and spraying distances result in the different microstructure of the coating surfaces and different mechanical properties. The sample that uses higher current tends to have a higher hardness than the sample with a lower electric current at the same spraying distance.

Effects of thin hard film deposition on fatigue strength of AA7075-T6

Thanks to their favorable strength-to-weight ratio, Aluminum-Zinc alloys are often used in high-performance industrial sectors. These alloys are characterized by poor erosion resistance, which could be increased by the deposition of thin films. For example, PVD (Physical Vapor Deposition) films can reduce wear and ensure appreciable performance in aggressive environments. This paper describes the effects of thin hard film deposition on the strength of AA7075 under cyclic loading. Uncoated samples and samples with a DLC (Diamond-Like Carbon) surface layer were tested with a rotating bending fatigue machine within the range of [Formula: see text]–[Formula: see text] cycles. Two regression models were tested to study the relationship between fatigue strength and number of cycles within the range considered. For the samples without the film, even a linear regression can be suitable. With regard to the fatigue strength of the samples with surface layer, a piecewise linear regression is suggested, although a high scatter of experimental data can be observed. Finite element (FE) modelling was used to calculate the stresses induced by bending moment. The bending stresses were added to the residual stresses induced by the film deposition. The maximum value was found beneath the sample surface. Therefore, crack nucleation is expected under the surface of samples with film. The fatigue cracks initiate at the surface in untreated samples.

The effect of PEO parameters on the properties of biodegradable Mg alloys: a review

This paper comprehensively reviews recent research carried out in the field of preparation of bioactive coatings on magnesium (Mg)–aluminum (Al)–zinc (Zn) alloys by using the plasma electrolytic oxidation (PEO) method and investigation of factors affecting it. Magnesium–aluminum–zinc alloys (AZ grades) have been developed for use as biodegradation materials because the addition of aluminum and zinc as alloying elements can ameliorate their mechanical properties and increase corrosion resistance over those of pure magnesium alone without decrement in biocompatibility. Among the common methods for improvement of biodegradation, corrosion resistance and biocompatibility of magnesium alloys, surface modification techniques have been more effective. PEO is a relatively novel surface modification technique that provides excellent wear- and corrosion-resistant coatings on lightweight metals, in particular on magnesium and its alloys. The processing parameters of PEO, such as pulse frequencies, applied voltages, oxidation time, electrolyte concentrations and substrate chemical composition, are some of the major factors that determine the quality of the coatings in terms of corrosion resistance and bioactivity in body fluid solutions. Considering the fact that comprehensive review articles on the effect of PEO parameters on the properties of magnesium alloys have not been published in recent years, the aim of the present text is to provide an understanding of all aspects of these process parameters.

HIGH TEMPERATURE AND ELECTROCHEMICAL CORROSION OF Zn0.5Al ALLOY DOPED WITH CALCIUM IN VARIOUS MEDIA

The article presents the results of a study of high-temperature and electrochemical corrosion of Zn0.5Al alloy doped with calcium in the various media. The thermogravimetric method was used to study the interaction of the Zn0.5Al alloy doped with calcium with atmospheric oxygen in the temperature range 523–623 K in the solid state. The kinetic and energy parameters of the process of high-temperature oxidation of alloys are determined. The process of high-temperature oxidation of Zn-Al-Ca alloys system is characterized by a monotonic decrease in the true oxidation rate and an increase in the effective activation energy when the alloying component in the initial Zn0.5Al alloy is up to 1.0 wt% doping with zinc-aluminum alloy 0.5 and 1.0 wt%. Calcium shows a slight increase in the oxidation rate of alloys. It was revealed that the oxidation process of the studied alloys with oxygen of the gas phase obeys the hyperbolic law. It was found that calcium supplements in the range of 0.01 - 0.1 wt%. The oxidizability of the initial Zn0.5Al alloy is reduced significantly, and the oxidation products of the alloys were ZnO, Al2O3, Al2O3 ∙ ZnO, CaO, Al2O3 ∙ CaO. By potentiostatic methods in the potentiodynamic mode with a potential sweep speed of 2 mV/s, it has been shown that for all samples of the Zn0.5Al-Ca alloys system in the acidic, neutral, and alkaline media, electrochemical potentials of corrosion, pitting formation, and repassivation are shifted to the region of negative values. It was revealed that zinc-aluminum alloys doped with calcium are most resistant to pitting corrosion in all studied media, respectively, in acidic (0.01n.), neutral (0.03-, 0.3-, 3.0 wt%) and alkaline (0.01n.) electrolytes of HCl, NaCl and NaOH. It has been established that calcium additions in the range of 0.01 - 0.1 wt.% reduce the corrosion rate of zinc-aluminum alloy Zn0.5Al by a factor of 2–3. Calcium alloys are recommended as anodic coatings and protectors for corrosion protection of steel products and structures operating at high temperatures.

Design of quaternary ammonium type-ionic liquids as desiccants for an air-conditioning system

The liquid desiccant air-conditioning system allows reducing energy consumption compared to the conventional compressor-type air conditioners. In order to develop desiccant materials for air conditioners, we have investigated the dehumidification capability of quaternary ammonium Ionic Liquids (ILs) and the equilibrium water vapor pressure of aqueous solutions of these ammonium salts. Among the seven tested types of ILs, 2-hydroxy-N,N,N-trimethylethan-1-aminium dimethylphosphate ([Ch][DMPO4]) displayed the best dehumidification capability and the lowest equilibrium water vapor pressure. Furthermore, the 80% aqueous solution of [Ch][DMPO4] exhibited a less corrosive effect on four types of metals, i.e., steel (hot dip zinc-aluminum alloy plated steel), copper (C1100P), aluminum (A5052), and stainless steel (SUS: SUS304). It should be noted that this [Ch][DMPO4] is not only non-toxic but also exhibits a stable nature; the aqueous solution produced no odor after storing for over 1 year under ambient conditions.

Potentiodynamic Study of the Anodic Behavior of Zn5Al Alloy Doped with Manganese

The widespread use of zinc-aluminum alloys as protective coatings for structures, products, and structures requires studying the effect of various additives in such alloys on their corrosion resistance in various environments. In studying the anode behavior of alloys, potentiodynamic methods are widely used to select methods of protection and increase the stability of anode alloys under given operating conditions. The article presents the results of a potentiodynamic study of the corrosion-electrochemical behavior of Zn5Al alloys doped with manganese in various electrolytes. An increase in the manganese concentration within the studied concentrations leads to a shift in the standard potential and pitting potential to a positive region compared to the initial Zn5Al alloy, which indicates a decrease in the corrosion rate of the studied alloys by 2-2.5 times with respect to the base alloy. An increase in the concentration of chloride ions in the electrolyte leads to a decrease in the electrochemical potentials of corrosion and pitting formation of alloys, which indicates an increase in their anode stability. An increase in the anode stability of the protective coatings of alloys depends on the time spent in an aggressive environment: the longer the time, the lower the rate of anode dissolution.

Design of a rail–road asymmetrical low-pylon cable-stayed bridge with a main span of 588 m

The Shangqiu–Hangzhou high-speed railway is 794.55 km long with a design speed of 350 km/h. The third Wuhu Yangtze River Bridge stands out as the key project of the whole railway. Restricted by the site conditions, the bridge is an asymmetrical low-pylon cable-stayed bridge with a main span of 588 m. To overcome the technical challenges of low stiffness and unfavourable axial force induced by the low pylons, a box-truss type composite section with a strong box at the lower deck and a weak truss above was creatively used in the design of the main girder. In addition, parallel steel wire cables coated with a zinc–aluminium alloy and with a tensile strength of over 2000 MPa were developed to withstand the tremendous axial force in the inclined cables. These two innovative solutions were successfully implemented in the construction of the bridge. This paper describes problem solving through creativity by addressing a few key issues faced by the designers.

Study on the long-lasting Anti-corrosion Construction Technology of Steel Structure of Service Tower in a Coastal Launching Site

In order to realize the long-lasting corrosion protection of the steel structure of service tower in a coastal launch site under C5-M corrosion environment, a five-layer heavy anti-corrosion system with hot spray zinc aluminum alloy as the base, and the supporting process and control requirements are put forward. And this paper studied on the difficult problems encountered in the site construction process, such as the high requirements of pre-treatment of substrate surfaces, difficulty of the protection of finished products and difficulty of coating process control. The actual construction shows that the proposed measures are limited, the coating effect is good, and the research results can guide the anti-corrosion construction.

Cause Analysis for a Corroded 220kV Transmission Tower Legs

In this paper, the corrosion cause of a 220 kV iron tower was analyzed by macroscopic examination, chemical composition analysis, micrustructure observation and finite element analysis. The results showed that the tower was located in a heavy chemical industry park, the sulfur dioxides and other waste gases discharging from the nearby factories resulted in a high content of sulfate in the foundation of the iron tower. Besides, the drainage of the iron tower was very poor, causing the tower legs immersed in highly corrosive sewage. In addition, the thickness of the galvanized layer on the surface of the tower materials was uneven and the thickness and local zinc content did not meet the standard requirements, finally resulting in poor resistance and accelerating the corrosion of the tower materials. At last, it was advised to replace a new tower with zinc aluminum alloy layer for the better sulfur corrosion resistance and connected by high-strength bolts.

Microstructure, mechanical properties and fracture mechanisms of ZrB2 ceramic reinforced A7075 composites fabricated by stir casting

In the present work, 7075 aluminum–zinc alloy is strengthened with blends of ZrB2 particles using the stir casting technique. The reinforcements were added to the base alloy at weight percentages of 5, 10, and 15. An attempt was made to establish a correlation among microstructure, physical, and mechanical properties such as density, hardness, strength, and electrical resistivity. A linear relationship between the concentration of reinforcement of ZrB2 and electrical resistivity was observed. When compared with the base alloy, the hardness and density of the composites were considerably improved. A significant difference was observed in the mechanical properties such as the ultimate tensile strength, elastic modulus, and yield stress. With the current processing sequence, the composite with 15 wt. % exhibited an enhancement of about 34 % in tensile strength compared to base alloy. The tensile tested fracture surface and XRD imaging comprised and gave the evidence for weak linkage of the phases, which lead to fracture. The evidence for the strength properties was revealed in the Electron backscatter diffraction (EBSD) observations. The microstructure and the interfacial binding of various phases in the specimens were observed in the high resolution Transmission Electron Microscopy (HR-TEM) graphs.

Study of the Corrosion Behavior of Zinc-Aluminum Alloy Matrix Composite Reinforced with Nanosilica Produced by Stir Casting

In this investigation, Zn-Al alloy metal-matrix nano composites that reinforced via various weight percentages (2%, 4%, 6%, and 8%) of nanosilica (SiO2) particles were fabricated applying the technique of stir casting. Behaviors of the corrosion of the unreinforced alloy and reinforced composites were measured utilizing a potentiostat test in a (3.5 wt.% NaCl) salt solution. The optical microscopy was employed to investigate the surface microstructure of the composite. Microstructure analysis manifested that the uniform distributions of the reinforcing particles in the composites are alike, consisting of a dendritic structure of the zinc alloy matrix with an excellent reinforcing particles steady dispersion. The improved results of the corrosion resistance for the metal matrix composites showed an excellent resistance to corrosion than the matrix in the (3.5 wt.% NaCl) solution. Raising the weight percentage of the reinforcement particulates of nansilica (SiO2) reduced the composites rate of corrosion.

Wire Laser Arc Additive Manufacture of aluminium zinc alloys

Aluminium zinc alloys are widely used in the aerospace industry due to their high strength. However, only a few studies have been reported on the additive manufacture of aluminium zinc alloys. This rarity is due to the difficulties occurring during the fusion processing of these alloys and to the lack of available raw material. This paper presents an alternative process used for the deposition of aluminium zinc alloys. In this study, a Wire Laser Arc Additive Manufacture (WLAAM) system was used. This consisted of a gas metal arc power source, used to generate the melt pool, and a laser beam applied to control the melt pool size. By using this approach, it was possible to produce an elongated melt pool and feed zinc into it with a cold wire without compromising the process stability. A welding camera along with a system measuring the arc voltage and current was used to monitor the process. Different process parameters and configurations were investigated along with their effect on process stability and deposited material microstructure. A very high zinc concentration was achieved in the deposited material without macro-segregation.

Structure Modification of a Rheocast Aluminum–Zinc Alloy by Friction Stir Butt Welding: Microstructural Evolution

In this study, friction stir butt welding was applied to weld an aluminum–zinc alloy produced by semi-solid method (rheocasting). For this aim, the effect of tool rotational and traverse speeds on the microstructure was investigated. The microstructures of the processed materials were studied using optical microscopy, scanning electron microscopy equipped with energy dispersive spectroscopy, and X-ray diffraction. The Vickers hardness test was used to evaluate the hardness of the joints. The results showed that the friction stir welding using optimum parameters improved the structure of the rheocast alloy. The porosities were eliminated due to severe plastic deformation induced to the material, which caused filling the voids. Friction stir welding lead to replacement of the semi-solid structure by finer equiaxed grains, which are formed by continuous dynamic recrystallization mechanism. High rotational speeds and low traverse speeds (high heat inputs) caused formation of larger grains, due to grain growth at higher temperatures. On the other hand, at high heat inputs the eutectic phases were more scattered throughout the microstructure, and super saturated solid solution was formed. Because of this behavior, the relationship between the hardness and grain size of the joints did not follow the classical Hall–Petch equation.

A comparative investigation on cathodic protections of three sacrificial anodes on chloride-contaminated reinforced concrete

This paper aims to evaluate the cathodic protections of zinc alloy, magnesium alloy and aluminum alloy as sacrificial anodes on chloride-contaminated reinforced concrete by a comparative experiment. For simulating the real condition, the large concrete slab with steel-mesh (size: 1.0 m × 1.0 m × 0.06 m) was fabricated. The measurements of half-cell potentials, anode stimulation current, electrochemical impedance spectroscopy (EIS) and the titration analyses of chloride irons contents in the concrete slabs at different times were carried out. The results indicate that the aluminum alloy anode cannot provide enough cathodic protection to the steel due to the loss of activity in the long term. Both zinc alloy and magnesium alloy have a good electrochemical activity and stability as a sacrificial anode. In comparison with zinc alloy, the magnesium alloy anode has the better ability of cathodic protection on the reinforcing steel. The cathodic protection effects for three anodes can be verified by the shift of characteristic frequency corresponding to the maximum value of the phase angle in the Bode plot of EIS. The chloride migration contributes to the effect of cathodic protection.

Effect of sintering temperature on pore ratio and mechanical properties of composite structure in nano graphene reinforced ZA27 based composites

Nano graphene platelet (Gr) reinforced nano composites with a zinc-aluminum alloy (ZA27) matrix were produced by powder metallurgy at four different mass ratios (0.5wt%, 1.0wt%, 2.0wt% and 4.0wt%) and three different sintering temperatures (425, 450, and 475°C). In order to investigate the effect of sintering temperatures and nano graphene reinforcement materials on the composite structure, the microstructures of the composite samples were investigated and their densities were determined with a scanning electron microscope. Hardness, transverse rupture, and abrasion wear tests were performed to determine the mechanical properties. According to the test results, the porosity increased and the mechanical strength of the nano composites decreased as the amount of nano graphene reinforcement in ZA27 increased. However, when the composites produced in different reinforcement ratios were evaluated, the increase in sintering temperature increased the mechanical structure by positively affecting the composite structure.

Comparative Surface Morphology of Machined Hybrid and Unhybrid Zinc-Aluminum Alloy-Based Metal Matrix Composites

Abstract The present article reveals the surface characteristics of zinc-aluminum alloy (ZA43) reinforced with silicon carbide (SiC) particulate conventional composite and SiC+Graphite dual reinforced hybrid metal matrix composites. Both the composites were prepared using a liquid metallurgy technique. A base alloy of metal matrix composites (MMC) containing zinc—57 %, aluminum—43 % was reinforced with SiC (5 %) with an average particle size of 60 μm and hybrid composite with 5 % SiC and 5 % graphite. The coated carbide tool SNMG was used to machine the two varieties of composites under dry condition. Machining parameters were considered at three different levels, keeping a constant depth of cut. It was observed from the results that the surface finish was greatly influenced by cutting speed and feed. Unhybridized composites exhibit (without graphite) higher roughness values than composites with graphite during the machining trials. The reasons for higher roughness values include particle pullout, particle fracture, and built-up edge formation on the cutting tool during the machining process.

Through-Glass-Via Based Microstrip Band-Pass Filters Fabricated with Wafer-Level Low-Melting-Point Alloy Micro-Casting

Through-glass-via based X-band microstrip band-pass filters are wafer-level fabricated by casting molten zinc-aluminum alloy into micromachined glass substrate. Instead of using time-consuming electroplating to form a via based GHz microstrip filter, where seed-layer deposition, plating and seed-layer removal process cycle should be repeated for several times, herein the metal parts of filter, including the resonators, the large-area ground and the metal plug in through-glass-via are all formed in one-step liquid-alloy filling in the pre-micromachined mold within only 5min for a whole wafer. This process is much quicker and simpler compared to those electroplating based approaches for microstrip filters. The micro-casting fabricated filter has a center frequency of 8.6GHz with 800MHz bandwidth. The measured insertion loss is −2.1dB, and the return loss is lower than −10dB within the passband. Good agreement is achieved between the measured results and the simulated ones. This technique can also be widely used for fabricating various RF devices.