Pd–Pb nanoscale films as surface modifiers of Pd,Cu alloy membranes used for hydrogen ultrapurification

The purpose of the article is to reveal the role of the thickness of the layer of the lead-palladium alloy deposited on a copper-palladium membrane in the processes of cathodic injection and the anodic extraction of atomic hydrogen.The objects of the study were ~ 4 μm thick copper-palladium film electrodes obtained by magnetron sputtering of a target with a composition of 56 at. % Cu and 44 at. % Pd. The studies were carried out by cyclic voltammetry and double step anodic-cathodic chronoamperometry in a deaerated 0.1 М H2SO4 aqueous solution. The calculation of the parameters of hydrogen permeability for samples of finite thickness was carried out by mathematical modelling.Cathodic injection and anodic extraction of atomic hydrogen were used to study the effect of the surface modification of the foil membrane of a Pd-Cu solid solution on the diffusion and kinetic parameters of hydrogen permeability. It was found that even a small addition of Pd-Pb (a 2 nm thick film) leads to a decrease in the concentration of atomic hydrogen and the diffusion coefficient in the foil. With an increase in the thickness of the coating there is an increase in the diffusion parameters of the hydrogen injection and extraction processes. However, the hydrogen permeability does not reach the level of the unmodified alloy. The main kinetic parameter, the hydrogen extraction rate constant, changes nonlinearly with an increase in the thickness of the coating.

Effect of Al2Ca Addition and Heat Treatment on the Microstructure Modification and Tensile Properties of Hypo-Eutectic Al–Mg–Si Alloys

The current study investigated the microstructure modification in Al–6Mg–5Si–0.15Ti alloy (in mass %) through the minor addition of Ca using Mg + Al2Ca master alloy and heat treatment to see their impact on mechanical properties. The microstructure of unmodified alloy (without Ca) consisted of primary Al, primary Mg2Si, binary eutectic Al–Mg2Si, ternary eutectic Al–Mg2Si–Si, and iron-bearing phases. The addition of 0.05 wt% Ca resulted in significant microstructure refinement. In addition to refinement, lamellar to fibrous-type modification of binary eutectic Al–Mg2Si phases was also achieved in Ca-added (modified) alloy. This modification was related to increasing Ca-based intermetallics/compounds in the modified alloy that acted as nucleation sites for binary eutectic Al–Mg2Si phases. The dendritic refinement with Ca addition was related to the fact that it improves the efficacy of Ti-based particles (TiAl3 and TiB2) in the melt to act as nucleation sites. In contrast, the occupation of oxide bifilms by Ca-based phases is expected to force the iron-bearing phases (as iron-bearing phases nucleate at oxide films) to solidify at lower temperatures, thus reducing their size. The as-cast microstructure of these alloys was further modified by subjecting them to solution treatment at 540 °C for 6 h, which broke the eutectic structure and redistributed Mg2Si and Si phases in Al-matrix. Subsequent aging treatment caused a dramatic increase in the tensile strength of these alloys, and tensile strength of 291 MPa (with El% of 0.45%) and 327 MPa (with El% of 0.76%) was achieved for the unmodified alloy and modified alloy, respectively. Higher tensile strength and elongation of the modified alloy than unmodified alloy was attributed to refined dendritic structure and modified second phases.

Microstructures and Mechanical Properties of Al-2Fe-xCo Ternary Alloys with High Thermal Conductivity

The microstructures, mechanical properties, and thermal conductivity (TC) of Al-2Fe-xCo (x = 0~0.8) alloys in as-cast, homogeneous annealed, and cool rolled states are systematically studied. Results indicate that appropriate Co modification (x ≤ 0.5) simultaneously improves the thermal and mechanical properties of as-cast Al-2Fe alloys. The improvement of TC is attributed to ameliorating the morphology of primary Al3Fe phases from needles to short rods and fine particles, which decreases the scattering probability of free electrons during the electronic transmission. However, further increasing the Co content (x = 0.8) decreases the TC due to the formation of a coarse plate-like Al2FeCo phase. Besides, the thermal conductivity of annealed Al-2Fe-xCo alloys is higher than that of as-cast alloys because of the elimination of lattice defects and spheroidization of Al3Fe phases. After cool rolling with 80 % deformation, thermal conductivity of alloys slightly increases due to the breaking down of Al2FeCo phases. The rolled Al-2Fe-0.3Co alloy exhibits the highest thermal conductivity, which is about 225 W/(m·K), approximately 11 % higher than the as-cast Al-2Fe sample. The ultimate tensile strength (UTS) and elongation (EL) of as-cast Al-2Fe-0.5Co (UTS: 138 MPa; EL: 22.0 %) are increased by 35 % and 69 %, respectively, compared with those of unmodified alloy (UTS: 102 MPa; EL: 13.0 %).

Effect of Ce Addition and Heat Treatment on Microstructure Evolution and Tensile Properties of Industrial A357 Cast Alloy

The effects of adding different Ce contents (0–0.32 wt.%) on the microstructure, mechanical properties, and fracture morphology of industrial A357 cast alloy in as-cast and T6 heat treatment were studied. The main purpose of this study is to improve the microstructure stability and tensile properties of industrial A357 cast alloy. The microstructural analyses indicate that the addition of Ce causes refinement of the α-Al primary phase for the reason that the formation of intermetallic compounds containing (AlSiCeMg) elements enriches the front of the solid–liquid interface, which causes an increase in constitutional undercooling. Simultaneously, the addition of Ce also affected the characteristics of eutectic Si particles, which make its morphology change from acicular structures into fragmented and spheroidized. This is mainly due to the formation of Ce-rich precipitates during solidification, which increase the constitutional undercooling and suppress the nucleation of the eutectic Si particles, resulting in the change of eutectic Si characteristics. Moreover, the needle-like morphology of a Fe-containing intermetallic is transformed into α(AlSiFeCe) phase containing rare earth Ce when part of the Ce atoms entered β(Al5FeSi) phase compounds. The tensile properties of the modified alloys were improved in the as-cast and T6 heat treatment as a consequence of simultaneous refinement of both secondary dendrite arm spacing and grains and the improvement of eutectic Si particles and Fe-containing intermetallic morphology. The fracture surface of the modified alloy has more dimples than the unmodified alloy, which indicates that the main fracture pattern of the modified alloy is dimple fracture caused by the crack of eutectic Si particles. The optimal percentage of Ce in industrial A357 cast alloy was determined to be 0.16 wt.% according to the change of microstructures structure and mechanical properties. These experimental results provide a new basis for adding rare earth Ce to improve the performance of parts in the actual production of industrial A357 cast alloy.

Surface Plasma Nitriding of Beta-Titanium Alloy Bio-Material

Ti alloys have been intensely used for human implants due to its excellent characteristics, like bio-inertness, low density, and corrosion resistance. However, some alloying elements were found to be toxic for the human body, which restricts the use of some alloys. Furthermore, there are two additional and essential aspects to be considered. The first relates to the young modulus that, despite being lower than other alloys commonly used for this purpose, it is still far over from the human bone modulus. Such high modulus can result in the stress shield phenomena and the consequent implant losing. The second aspect relates to the fact that bio-inertness does not guarantee a complete tissue integration to the implant and, consequently, the expected implant performance. In this context, new low modulus b-Ti alloys containing nontoxic elements have been developed in recent years, and several surface modification processes have been proposed to promote better implant/tissue integration.In the present work, the new b-type Ti-Mo-Zr-Fe alloy has been submitted to a plasma enhanced chemical vapor deposition (PECVD) process in order to form a superficial titanium nitride layer, aiming to produce a satisfactory substrate for the tissue cells growing. In a first step, microstructural characterization and corrosion performance of the modified alloy surface has been evaluated by Electrochemical Impedance Spectrometry and Potentiodynamic testing, and the results compared to the unmodified alloy. It was found that during the plasma nitriding process, that runs at 550°C for 1h, the metastable b microstructure is partially converted into a’ and possibly a” phases, which can impact the young modulus. The 500nm thick TiN layer formed over the alloy surface improved the corrosion behavior of the alloy. These results encourage the continuity of the research, with the future in vitro bio-activity testing of the nitrided surface.

Effect of Erbium Addition on the Microstructure and Mechanical Properties of Aluminium Alloy

The effect of rare earth metal erbium (Er) modification on the microstructure and mechanical properties of aluminium alloys (A380) were investigated using Optical Microscope (OM), Scanning Electronic Microscope (SEM) attached with Electron Dispersive Scanning (EDS), Vicker’s hardness test and Ultimate Tensile Test (UTS). The results show that the addition of Er reduces the size of the silicon particle and improve mechanical properties of the aluminium alloy. In addition, by adding 0.1 wt. % of Er, the mean area (μm2) and aspect ratio value decreased. The coarse plate like existed in the unmodified alloy transformed into fine particle and short rod. The mechanical properties were investigated by using tensile test and Vicker’s hardness test. The ultimate tensile strength test shows that the tensile and the elongation increased 1.32 % and 9.1 % with 0.1 wt. % Er content of the aluminium alloys, respectively. The hardness improved from the addition of 0.1% Er aluminium A380 alloy.

Effect of Structural Modification on Corrosion Behavior of Hypo Eutectic Al-Si Alloy

Al-Si eutectic cast alloys are widely used in aeronautical and automobile industries where significantly high strength, toughness and wear resistance are required. This class of cast alloys exhibit relatively low corrosion resistance in brine environments. The mechanical properties of the alloy system mainly depend upon the shape of Si rich eutectic phase, which mainly has acicular geometry. In present research, the effect of modified microstructure of 12 wt. % Si-Al alloy on corrosion behavior was studied. The needle like Si rich eutectic phase was modified to disperse spherical structure using rare earth metal halides. The corrosion rate and pitting behavior of modified and unmodified alloy were evaluated in 3.5% NaCl solution by general corrosion for calculated time. It was observed that the corrosion rate and pitting tendency of modified alloy had been appreciably reduced as compare to unmodified alloy. The improvement of corrosion properties were the attributes of changed morphology and distribution of Si rich eutectic phase.

Grain Refinements of Cu6Sn5 in Sn-3wt%Ag-5wt%Cu High Temperature Solder Alloys

This paper investigated the effect of trace addition of Al and Mg on the grain refinements of Cu6Sn5in Sn-3wt%Ag-5wt%Cu high temperature solder alloys. Furthermore, the effect of Al and Mg addition on the Sn/Ag3Sn eutectic were also investigated. It was found that the addition of both Al and Mg successfully refined the Cu6Sn5in Sn-3wt%Ag-5wt%Cu solder alloy. In addition, Al suppresses the formation of Ag3Sn in the Sn/Ag3Sn eutectic; while Mg promotes the formation of fine Sn/Ag3Sn eutectic microstructure. The refinement of Cu6Sn5is believed to be due to heterogeneous nucleation by Al and Mg rich intermetallic particles respectively. Effect of Al and Mg addition on the undercooling of the Sn/Ag3Sn eutectic was found to be similar, both reducing undercooling effectively at a low addition rate of 0.025wt%. The addition of Al and Mg have mixed effect on the nucleation temperature of Cu6Sn5. It is found that the nucleation temperature of Cu6Sn5is increased with 0.025wt% Al and 0.1wt% Mg addition to the unmodified alloy, while the nucleation temperature slowly decreases again as the trace element addition rate increases.

Influence of Neodymium on Wear Resistance of Hypereutectic Al-Si Alloy

The morphology of eutectic and primary silicon phases was analyzed by OM and SEM. OM and SEM results show that pure Nd can significantly refine both eutectic and primary silicon of hypereutectic Al-20%Si alloy. Morphology of primary silicon is transformed from star-shaped and irregular morphology to fine polyhedral and grain size of primary silicon is refined from 80~120 μm to 20~50 μm. Friction and wear resistance tests show that friction coefficient of Al-20%Si alloy reduces after Nd modification. Wear resistance of Al-20%Si alloy after modification is significantly improved as compared to the initial sample. The dominant wear mechanism for 0.3% Nd modified alloy is abrasive wear, adhesive wear and oxidative wear mechanism, but wear mechanism for unmodified alloy is abrasive wear and adhesive wear mechanism.

Analysis of the Antimony and Strontium Cross-Effects in Al-Si Foundry Alloys

In this work we show the effect of various concentrations of strontium and antimony on the level of modification in the Al-Si alloy. The scale of the modification rate was determined in two ways: thermal analysis was performed and the images of the samples. The eutectic temperature registered during the analysis were compared to the eutectic temperature of the unmodified alloy and on the basis of them was determined which samples are registered as modified, which are not. On the basis of the results of the cooling curves the partially modified category was introduced, if the ΔT value is less than 9°C and more than 7.5°C. The samples made of the alloys were examined with a computer image analysis and the samples were grouped on the basis of the size of the eutectic silicon phases. The aim of our research work was the examination of cross-effects of strontium and antimony.