Thin film brass alloys were galvanostatically electrodeposited from non-cyanide citrate solutions. Aqueous sulphate solutions were used as deposition medium. It was aimed to understand the effect of ultrasonication of the solutions before electrodeposition process. Ultrasonication was not applied during deposition. This method was utilized to change solution characteristics, by applying high energy via cavitation mechanism, which would result in changes in resultant film properties. X-ray diffraction technique was used to investigate phase formation in samples. Moreover X-ray diffractograms were also used to calculate grain size values. Cu and Zn elements were codeposited successfully to form brass alloys. When phase formations in the samples were compared to each other, it was concluded that although there are small differences between X-ray diffractograms of samples, ultrasonic treatment before electrodeposition is not an effective way to alter phase characteristics of CuZn alloy samples, since all samples have shown similar X-ray diffraction graphs. Grain size is found to get smaller with presence of ultrasonication, extending ultrasonication time caused only small random changes in grain size.
Copper zinc alloys were electrodeposited in the form of thin films. Electrodeposition process was carried out in non-cyanide aqueous medium, under constant current. Effect of pre-deposition ultrasonication of solution was investigated. In other words ultrasonic treatment was applied only before the electrodeposition. Solutions were subjected to high-energy ultrasonication for increasing times. Cyclic voltammetry was used to understand changes occurring due to duration of ultrasonication. No ultrasonication was applied during deposition. Atomic composition of resultant films were revealed by MP-AES. It was found that implementation of ultrasonic treatment before electrodeposition affects CV characteristics, when compared to non-ultrasonicated solution. Atomic composition of fabricated samples were found to be close to each other, some of them showing more deviation.
In the present work, Ni-Co alloy coatings were prepared from a modified Watt type electrolyte by direct current. For this purpose, current density was investigated for optimization to obtain high quality coatings on the steel copper substrates. The depositions were controlled to obtain specific thickness (between 50 and 200 μm). The characterization of the coatings was investigated by scanning electron microscopy and X-ray diffraction facilities. The hardness of the resultant coatings was also measured. The effects of the current density on the tribological properties of Ni-Co coatings were investigated. The results showed that although increasing current density showed increasing coating thickness, the wear resistance of the Ni-Co alloys was decreased due to Co depletion in the deposited layer.
Wear resistance of ductile iron can be improved through different surface engineering techniques, each having some limitations and drawbacks. Recently, a new method called pulse plasma technology has been introduced, which through local reinforcement with inserts improves wear resistance of ductile iron without compromising other properties. This paper deals with the improvement of the wear resistance of ductile iron surface modified by pulse plasma technology using a tungsten electrode. The surfaces of the samples were treated by C_3H_8, air, and oxygen gases. The surface morphology and the phase structure in the near surface region of original and treated samples were analyzed with optic microscope, scanning electron microscope and energy-dispersive spectroscopy. The surface properties were evaluated by measuring the microhardness, wear properties and friction coefficient, as well as the elemental depth profiles and chemical composition of the modified layer. It was found that the microhardness of the treated samples was much higher. The tribological resistances were also significantly improved, as confirmed by the reduced friction coefficient and wear track width. This improvement can be attributed to the diffusion of tungsten on the surface layer.
Ferromagnetic FePd L 1_{0} ordered alloys are highly expected as forthcoming high-density recording materials, because they reveal a large perpendicular magnetocrystalline anisotropy [1]. The value of the magnetic anisotropy of FePd alloy strongly depends on the alloy composition, degree of alloy order as well as on the crystallographic grain orientation. In particular, to obtain the perpendicular anisotropy, it is necessary to get the films with (001) texture. One of the successful methods, which allows one to obtain highly ordered alloy, is a subsequent deposition of Fe and Pd layers, followed by an annealing at high temperature. This paper presents the study of the FePd thin alloy film structure changing in the result of high temperature annealing. During the annealing in high vacuum, the measurements of electrical resistance were performed, indicating the regions of different structure evolution. Changes in the crystal structure and surface morphology induced by thermal treatment were investigated by X-ray diffraction, atomic force microscopy, as well as high resolution transmission electron microscopy and then compared with electrical resistivity measurement. The slow thermal annealing of the deposited layers leads to the formation of L 1_{0} ordered FePd alloy with preferred (111) grain orientation. After the annealing at the highest used temperature, the dewetting process was observed, resulting in a creation of well oriented, regular nanoparticles.
As an important surface treatment method, shot peening (SP) is widely used in automotive and aerospace industries in order to improve surface properties. In the present study SP was performed on the α-β titanium alloy Ti6Al4V under various parameters (particle impingement angle, particle acceleration pressure and particle size) by using a specially designed shot peening test rig. It is aimed to optimize surface roughness and hardness of the shot peened Ti6Al4V alloy under various parameters. In order to achieve this goal shot peened samples were investigated in detail by using a non-contact laser optical profilometer and surface hardness of the samples was measured by using a micro-hardness instrument. The surface roughness values, 3D surface morphologies and micro-hardness of the samples were obtained and examined. The results show that particle impingement angle, particle acceleration pressure and particle size dramatically affect the surface properties of the Ti6Al4V alloy.
Traditional surface modification obligations, surface coatings, and other methods of surface treatment are used to increase the hardness and mechanical properties of specimen surfaces. But those techniques are limited due to the high equipment cost, and material consumption. Electrolytic plasma technology is a special heat treatment process employing electrolysis in an aqueous solution under particular conditions, for instance voltage, current, electrolyte, duration, and heating-quenching rate. In this study, surface modification of GGG70 cast iron was carried out by using electrolytic plasma treatment. Certain voltage and ampere values were performed to obtain good surface properties. Metallographic studies were carried out with an optical microscope to study the hardened and modified surfaces. The effect of impulse time on surface temperature was investigated and it was observed that the temperature on the workpiece increased with increasing impulse time. It was found that the electrolytic plasma treatment could significantly increase hardness of the cast iron.
Fe-Al single crystals of three different compositions (20, 28 and 40 at.% Al) in single slip orientation were studied. Evolution of their surfaces during deformation at room temperature was observed in situ in atomic force microscope. Atomic force microscopy allows us to investigate slip lines on much finer scale than traditional optical observations. Wavy slip bands in Fe-Al_{20}, cross-slip in Fe-Al_{28} and weak slip line texture in Fe-Al_{40} are described. Post mortem observations of surfaces of Fe-Al_{28} deformed at elevated temperatures (in the range of yield stress anomaly) are presented as well.
The aim of this study was to investigate the effects of two different treatments, as-cast setup and solution heat treatment, on the general electrochemical corrosion resistance of Ti-7Cu alloy samples immersed in a 0.9 wt% NaCl solution at 25°C. The microstructure was examined by scanning electron microscopy and X-ray diffractometry. Corrosion behavior was tested by potentiodynamic polarization curves. Finer α' martensite and Ti_2Cu intermetallic particles were provided by casting and heat treated processes, respectively. The results indicated that only corrosion potential is significantly more noble in the heat treated sample, but other characteristics are only slightly different.
The influence of the Laser Shock Processing (LSP) on the morphology, microstructure and surface layer properties of a Ti6Al4V alloy has been studied. Residual stresses were assessed as well. For the Laser Shock Processing a 1 KW, high-power Q-switched Nd:YAG laser was used. During the process the surface of the investigated material was covered by series of single, partially overlapping impulses. The laser power density was a 1 GW/cm^{2} and a pulse duration of 18 ns. The microstructure and the phases presented in the surface layer of the treated material were analysed by optical, scanning and transmisssion electron microscopy as well as by X-ray diffractometry. The X-ray diffractometry was also use to determine the residual stresses. It has been found that the laser shock processing can cause plastic deformation and generate the compressive residual stresses into the treated surface of a Ti6Al4V alloy.
The corrosion behavior of the bulk glassy samples of Ca₆₅Mg₁₅Zn₂₀ alloy was studied by electrochemical measurements and immersion tests in a simulated body fluid, physiological fluid, and the Ringer solution. The results of immersion show that the volume of H₂ evolved after 2 h in simulated body fluid (29.8 ml/cm²) is the highest in comparison with the results of measurements conducted in physiological fluid (11.3 ml/cm²) and the Ringer solution (7.4 ml/cm²). The electrochemical measurements indicated a shift of the corrosion potential (E_{corr}) from -1.58 V for plate tested in a physiological fluid to -1.56 V and -1.54 V for samples immersed in the Ringer solution and simulated body fluid, adequately. The X-ray diffraction measurements were used to determine composition of corrosion products. The corrosion products were mainly identified to be calcium carbonates and calcium/magnesium hydroxides.
The paper presents results of numerical analysis of AFM images of a surface of sandblasted Ti6Al7Nb alloys before and after wet etching procedure usually used for preparing commercially viable dental implants. Obtained results demonstrate that etching procedure efficiently cleans the implants as it leaves almost pure Ti-Al-Nb surface with trace amounts of alkali metals and increased hydrophobicity. Apart of that, it turned out that simple statistical measures of the height variations (root mean square roughness) only slightly change upon the treatment procedure, especially for scan lengths below 20 μm. On the other hand, correlation analysis exhibits bifractal surface patterns composed of regular residues left on otherwise helical ridges of the base material. Etching leaves its fingerprint in fractal dimension, but not in the corner frequency.
Ab initio calculations of theoretical tensile and compressive strengths in the 〈100〉 direction of a composite having continuous nanofibre reinforcements are performed using pseudopotential approach within density functional theory. Results for iridium or platinum nanofibres in copper or gold matrices, presented as case studies, reveal that the theoretical tensile and compressive strengths almost linearly increase with increasing atomic concentration of the reinforcement exhibiting only slight positive strength deviations from the linearity for Pt-Au and slight negative deviations of the tensile strength for Ir-Cu.
Phase composition and magnetization curves of the soft magnetic composites, fabricated by compaction of several kinds of powders mixed in various proportions, have been investigated by means of conversion electron Mössbauer spectroscopy and an alternating gradient force magnetometry. The results point to significant quantity of iron oxides - hematite and magnetite - at the surface of the samples. After the rubbing of thin surface layer, the relative content of oxides was distinctly reduced. Magnetic measurements revealed very similar characteristics of hysteresis curves for all the investigated materials.
The effects of the thermal cycles on the microstructures and properties of ductile iron modified by electrolytic plasma treatment were investigated. Microstructure changes occurring in the modified surface were characterized with scanning electron microscopy, X-ray diffractometry techniques. Martensitic structure evolved in the heat affected zone and ledeburite structure was produced in the molten zone of the ductile iron. Microhardness of the treated specimens improved considerably as compared to the original sample. X-ray diffraction clearly revealed the formation of a martensite phases in the modified zone.
This article describes the study of corrosion resistance of tin coatings deposited onto aluminum alloy substrates using the low pressure cold spraying and electroplating methods. The chemical corrosion resistance was examined using the Kesternich and cyclic salt spray tests inside SO₂ and NaCl climate chambers, respectively. The selected tests allowed simulation of the conditions of the coatings during service. The results were satisfactory for low pressure cold spraying coatings. Coatings produced by electroplating exhibit substantial corrosive losses due to their method of application and low thickness. Evaluation of corrosion were carried out by analyzing changes in the microstructure. Additionally, the physicochemical tests were carried out using X-ray diffraction to verify corrosion changes on the coatings surface.
The atomic structure and morphology of ultrathin Pb layers deposited on the Ni(001) face in ultrahigh vacuum at the substrate temperature, ranging from 145 K to 900 K, were investigated with the use of the Auger electron spectroscopy and low-energy electron diffraction. The analysis of the Auger electron spectroscopy measurements indicates that the Volmer-Weber growth of the Pb takes place for substrate temperature T < 300 K. Between 300 and 600 K, the Stranski-Krastanov growth mode is observed. For 600 K ≤ T ≤ 700 K, only first two-dimensional Pb layer formation is found. Above 700 K desorption of lead atoms from the first layer is observed. The ordered low-energy electron diffraction patterns corresponding to p(1×1) and c(2×2) structures are observed.
This study is concerned with the research and development in the field of materials science, leading to the industrial applications especially for the development of materials by moulding process. The purpose of this study was to determine the influence of vanadium on microstructural, mechanical and electrochemical properties of gray cast iron with lamellar graphite EN-FGL250. We investigated the effect of adding element (vanadium), during the casting of the metal in the mould, in a powder form having a particle size of 0.5 mm with the amounts of 1%, 3% and 5% in weight percent on microstructural and mechanical properties of gray cast iron with lamellar graphite. The originality of this work is the addition of the vanadium powder during the last stage of cooling of the melted gray cast iron EN-FGL250. These additions have a significant impact on the solidification phenomenon since the deposited vanadium powder into the sand moulds creates the new sites of nucleation and absorbs a lot of heat leading to the fast cooling. From the experimental results, we can confirm that the cooling rate directly affects the microstructural, mechanical and electrochemical behavior of the cast gray iron treated with vanadium. As result, it was observed that there is a slight decrease of the elasticity modulus of the work pieces, and a reduction of the maximum tensile resistance R_{m}. Finally, the addition of vanadium considerably reduces the corrosion current of gray cast iron treated with vanadium.
Series of Al₂O₃(0001)/Pt/(Fe/Pt)ₙ/Pt multilayers with variable number of bilayers n and thicknesses of individual layers were grown using molecular beam epitaxy to investigate influence of buffer layer structure, number of bilayers, and individual layer thickness on their structural and magnetic properties. Both columnar and monocrystalline 10 nm Pt (111) buffer layers were used in the experiment. Structure of Pt buffer layer determined the roughness of Fe/Pt interfaces and consequently magnetic properties of the multilayers. When multilayers were deposited on columnar Pt buffer layer, we observed increase of Fe/Pt interfaces roughness with increasing number of bilayers to values exceeding the nominal Fe/Pt bilayer thickness in the upper part of the sample volume, which resulted in the increment of coercivity in the sample with n=15 determined from hysteresis loops measured for perpendicular orientation of magnetic field. When Fe/Pt multilayers were deposited on monocrystalline Pt buffer layer, Fe/Pt interfaces were smooth regardless the number of bilayers. All samples, despite of the quality of buffer layer, number of bilayers, and individual layer thickness revealed easy magnetisation axis oriented in the sample plane.
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