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For this study, seamless square tubes of aluminum alloys EN AW-6060 and EN AW-6082 were extruded with axial variable wall thickness by applying an axial moveable stepped mandrel. The microstructures in thick-walled and thin-walled sections of these tubes were investigated and correlated to the extrusion conditions. The results for EN AW-6060 revealed fibrous grains at low ram velocity ( v ram = 0.8 mm/s) and thus low strain rate. In these cases, peripheral coarse grains were also observed on the tube surfaces. Applying a higher v ram = 3.3 mm/s lead to a fully recrystallized microstructure. For EN AW-6082 the fibrous microstructure was predominant. This was attributed to the Mn-content of this alloy, which acts as an inhibitor for recrystallization. Only at the highest values of strain, strain rate and temperature a recrystallized microstructure was observed for this alloy. EBSD analyzes of boundary misorientation angles indicate that geometric dynamic recrystallization seems to be the predominant mechanism at low strain rates. The facts that the amount of low angle boundaries significantly decreased as subgrains were removed and the amount of high angle grain boundaries is increased revealed that recrystallization occurred at higher strain rates and strains. Furthermore, the transition areas, where the wall thickness was gradually reduced were investigated. Due to increasing strain and thus increasing strain rate, thin-walled tube segments show lower grain size than thick-walled sections. It was also revealed that the PCG layer thickness remained about constant with increased strain, but since the tube wall thickness was reduced, the recrystallized fraction increased for higher strains. [ABSTRACT FROM AUTHOR]

The objective of this research was to develop a powder metallurgy (PM) counterpart to the wrought aluminum alloy 2618 utilizing press-and-sinter technology. Each starting blend was prepared from a strategic combination of prealloyed aluminum coupled with elemental and master alloy additions and was processed through uni-axial die compaction coupled with controlled atmosphere sintering. All of the PM alloys responded well to sintering with near full theoretical density realized. The most desirable PM product contained minor additions of tin and silicon. Whereas tin imparted enhanced densification, silicon promoted appreciable gains in hardness and tensile properties. It was also determined that the beneficial effects of silicon persevered after prolonged thermal exposure at 260 °C provided that a nominal concentration of 0.2 wt% was maintained. The final press-and-sinter PM product offered mechanical properties and thermal stability that were comparable to the wrought target. [ABSTRACT FROM AUTHOR]

Aluminum-doped zinc oxide (AZO) thin films are prepared by a low temperature (100 °C) aqueous solution deposition method with a subsequent UV post-deposition treatment at 140 °C. Film growth is governed by the retrograde solubility of zinc-ammine complexes at basic conditions (pH 11.4). Aluminum was introduced into the film as a dopant by co-precipitation, either using an aluminum metal foil or aluminum nitrate as a precursor. As the presence of Al ions in the solution influences the film morphology as well as the opto-electronic properties, different profiles of the dopant supply were examined and optimized with respect to the optical and electrical properties of the AZO layer. It was found that independent of the chosen aluminum precursor a linearly increasing dopant concentration in the solution is favorable for achieving dense, highly transparent (<8% absorption between 400 and 900 nm) AZO thin films with a lowest resistivity of 3.4 × 10−3 Ω cm. [ABSTRACT FROM AUTHOR]

The LHC Accelerator Research Program (LARP) is currently developing 4 m long Nb3 Sn quadrupole magnets for a possible upgrade of the LHC Interaction Regions (IR). In order to provide a reliable test bed for the fabrication and test of long Nb,3Sn coils, LARP has started the development of the long racetrack magnet LRS01. The magnet is composed of two 3.6 m long racetrack coils contained in a support structure based on an aluminum shell pre-tensioned with water-pressurized bladders and interference keys. For the phase-one test of the assembly procedure and loading operation, the structure was pre-stressed at room temperature and cooled down to 77 K with instrumented, solid aluminum "dummy coils". Mechanical behavior and stress homogeneity were monitored with strain gauges mounted on the shell and the dummy coils. The dummy coils were replaced with reacted and impregnated Nb3 Sn coils in a second assembly procedure, followed by cool-down to 4.5 K and powered magnet test. This paper reports on the assembly and loading procedures of the support structure as well as the comparison between strain gauge data and 3-D model predictions. [ABSTRACT FROM AUTHOR]

Abstract   We provide a convenient recipe for fabricating reliable superconducting microbolometers as acoustic phonon detectors with sub-nanosecond response, using image-reversal optical lithography and dc-magnetron sputtering, and our recipe requires no chemical or plasma etching. Our approach solves the traditional problem for granular aluminium bolometers of unreliable (i.e., non-Ohmic) electrical contacts by sequentially sputtering the granular aluminium film and then a palladium capping layer. We use dc calibration data, the method of Danilchenko et al. (Acta Phys. Pol. A 103(4):325, [2003]) and direct nanosecond-pulsed photoexcitation to obtain the microbolometer’s characteristic current, thermal conductance, characteristic relaxation time, and heat capacity. We also demonstrate the use of the deconvolution algorithm of Edwards et al. (J. Phys. E Sci. Instrum. 22:582, [1989]) to obtain the phonon flux in a heat pulse experiment with nanosecond resolution. [ABSTRACT FROM AUTHOR]

Abstract: Chemical etching is employed as micromachining manufacturing process to produce micron-size components. The process applies a strong chemical etchant solution to remove unwanted part in the workpiece material. It is basically a corrosion-controlled process. Chemical etching process has a long history and accepted one of the important nontraditional machining processes during the last half century. The method is widely applied to machine geometrically complex parts from thin and flat of any material. It is also used to reduce weight of the workpiece materials. In this study, aluminium was machined by well-known chemical etchant, ferric chloride (FeCl3) at different etching temperature. The effects of selected chemical etching parameters on depth of etch and surface finish quality were investigated. It was observed that FeCl3 was very useful chemical etching for aluminium etching. [Copyright &y& Elsevier]

Abstract: A solid electrolyte type nitrogen oxides (NO x ) gas sensor was fabricated by applying an Al3+ cation conducting solid electrolyte with the KNO3-doped (Gd0.4Nd0.6)2O3 solid solution and Al metal as the auxiliary sensing electrode and the reference electrode, respectively. A rapid, reproducible and continuous sensor response was obtained with obeying the theoretical Nernst relationship for NO and NO2 gases at the temperature as low as 250°C, one of typical temperature of emitted gases. [Copyright &y& Elsevier]

Hot deformation of 7050 aluminium alloy with coarse elongated grains has been investigated by tensile tests conducted at 340 and 460°C and the strain rate of 10 × 10–4–10 × 10–1 s–1. When the 7050 aluminium alloy was conducted at 460°C and 10 × 10–2 s–1, the maximum elongation of 273% is achieved and large plastic deformation was carried out at an almost constant stress. The microstructure evolution under the deformation condition is characterised using OM, SEM, EBSD and TEM in detail. The results show that the microstructure evolution is realised by continuous dynamic recrystallisation in coarse grains. The increase in misorientation is proportional to the increase in the true strain, and the k value, the increasing rate of average misorientation angle, is 157°. The primary hot deformation mechanisms of the 7050 aluminium alloy are localised grain boundary sliding and dislocation gliding, which can increase the grain boundary misorientation continuously. [ABSTRACT FROM AUTHOR]

Abstract: The HANARO fuel element is made of a cylindrical fuel meat, top and bottom aluminum end plugs and an aluminum cladding with eight longitudinal fins. The fuel meat of each fuel element consists of a dispersion of small particles of a high density uranium silicide (U3Si) compound in a continuous aluminum matrix. To verify the irradiation performance of the HANARO fuel at a high power and a high burnup, in-pile irradiation tests were performed in the HANARO core. Detailed non-destructive and destructive post-irradiation examinations were conducted. It was verified through the irradiation tests that the HANARO fuel maintains a proper in-pile performance and integrity even at a high power of 121kW/m and up to a high burnup of 85at.% U-235. [Copyright &y& Elsevier]

Abstract: Most polymeric tribological components are inherently insulative, resulting in susceptibility to failure from frictional heating at the PV limit, which is typically reported as a product of the heat flux terms pressure (P) and sliding speed (V). This letter reports on the design of a tribological composite for increased thermal conductivity and PV limit. The control sample is an unfilled compositionally graded sample, consisting of a PEEK bulk with an integral PEEK/PTFE tribological solid lubricant surface layer. One composite sample is a compositionally graded PEEK bulk containing 10vol.% aluminum foam, and the other is a 10vol.% indium filled PEEK/PTFE bulk sample. Tribological experiments are conducted on a thrust washer tribometer instrumented with 13 thermocouples. At failure, the unfilled sample had a temperature rise of 170K. Under the same conditions, the aluminum and indium filled samples had temperature rises of 37K and 115K, respectively. They also had 250% and 40% higher PV limits, respectively than the unfilled sample. As designed, the continuity of the aluminum foam was found to be substantially more effective than the particle dispersion of the indium at dissipating thermal energy. [Copyright &y& Elsevier]

Abstract: The present study demonstrates different approaches towards MIC identification in three real cases of technological equipment failures. In the first case the failure of carbon steel heat exchanger as a result of tubes, lids, tube sheets, and connection pipes clogging was investigated. Chemical analysis of cooling water and precipitates, as well laboratory screening of deposits for bacteria, revealed that activity of iron-oxidizing bacteria present in cooling water led to heat exchanger blockage. The second case is related to MIC detection on floating roofs made of magnesium–aluminum alloy following a 3-weeks hydro-test. Corrosion tests carried out on the original and sterilized water used in hydro-test confirmed MIC process. In the third case the potential of MIC occurrence in engine cooling system made of cast aluminum alloy and filled with 20% ethylene glycol coolant solution was evaluated. The simulation tests allowed determining the real causes of the severe corrosion attack of examined system, including MIC high probability. [Copyright &y& Elsevier]

Abstract: Dry machining and high speed machining are increasingly attempted because of their impact on manufacturing cost. However, these processes generate dust that can be harmful. Environmental regulations require that manufacturers reduce manufacturing hazards, hence the need to develop environmentally conscious processes and cutting strategies that will help them to achieve that goal. This work investigates the turning of the 6061-T6 aluminium alloy, and 1018 and 4140 steels, using carbide cutting tools. The cutting tool geometry and the cutting speed are varied and their effect on dust formation and chip formation studied. The size of the dust particle investigated is 2.5μm and under (PM2.5). A new dust unit, which can be used as an ecological factor, is introduced to compare the dust emissivity of the tested materials. This dust unit is then related to the cutting conditions, and experimental models are developed. A correlation is established between the chip formation, the tool lead angle, the cutting speed, and the dust emission, in order to determine the conditions required for minimal dust emission. [Copyright &y& Elsevier]

Abstract: A kinetic study of dissolution reaction of Al can waste was conducted for the synthesis of aluminum isopropoxide (AIP). With the used Al can and isopropyl alcohol (IPA) as reactants, the reaction was examined at the condition of 3molIPA/mol Al of stoichiometric ratio, adding 10−3 molHgI2/mol Al for catalyst and no agitation at the reaction temperature ranging from 70 to 82°C. After 17h, the reaction gave a 75% yield. A two-stage dissolution mechanism was proposed in which the dissolution rate is determined first by a chemical reaction and then by ash layer diffusion. On the basis of the shrinking core model with the shape of flat plate, the first dissolution rate of Al can was controlled by chemical reaction. The concentration of isopropyl alcohol was added to the reaction at the stoichiometric ratio, then it was largely changed through the dissolution reaction. Therefore, since the conversion rate of isopropyl alcohol varies greatly depending on the reaction time, it was included as an integral term of the reaction time. By using the Arrhenius expression, the apparent activation energy of the first chemical reaction step was determined to be 92.4kJmol−1. In the second stage, the dissolution rate is controlled by diffusion control through the ash layer. The apparent activation energy of the second step was determined to be 174.9kJmol−1. [Copyright &y& Elsevier]

Abstract: The praseodymium-aluminium perovskite–praseodymium oxide, PrAlO3–Pr2O3, and praseodymium-aluminium perovskite–praseodymium hexaluminate, PrAlO3–PrAl11O18, eutectics have been recently obtained by the micro-pulling down method. The aim of this work was determination of the chemical composition and electronic structure examination of the above-mentioned eutectics. [Copyright &y& Elsevier]

Abstract: When bubbles collapse near solid surfaces, cavitation damage can occur. Two are the already known erosion mechanisms: liquid micro-jets impingement and shock waves. These micro-jets and shock waves are responsible for material loss from the surface, basically by wear failure. In the rotating disk device, a disk with cavitation inducers and specimens fixed on it rotates inside a water chamber to provide cavitating flow. In this work, a new concept of the horizontal rotating disk device is presented and discussed, as well as some preliminary results obtained from its operation. This new compact apparatus is tested with the aim to observe its performance in generating bubbles and to cause erosion. The damage in the specimens is measured by mass loss and surface observations by photographs of the tested specimen surface obtained by scanning electronic microscope, which are shown and discussed. After 15h working in cavitating conditions, pure aluminum and brass were eroded by the cavitation phenomenon, resulting in pitting formation and mass loss. Also, 1020 mild steel specimen was investigated for 5h. The new presented version of the equipment is cheaper and more compact than the preceding ones, resulting in advantages related to initial costs and losses in power transmission. The specimens of aluminum, brass and steel, were eroded by cavitation although in the aluminum the mass loss was lower than expected. The brass specimen was eroded as expected. The erosion mechanism is possibly due to bubbles collapse and water jet impact perpendicular to the specimen surface, producing circular erosion craters. Burned circular craters were also seen in the aluminum specimen. [Copyright &y& Elsevier]

Abstract: Both gravity casting and squeeze casting were carried out previously on an aluminium alloy (LM6) and a zinc alloy (ZA3) with different casting temperatures. Tensile, impact and density measurement were conducted. It was found that generally, samples taken from the bottom of the squeeze casting mould gave higher tensile strength, higher impact strength and higher density values. This study was carried out to determine the effect of solidification time on the mechanical properties of the castings. Two analytical methods were used: a steady-state heat flow model and Garcia''s virtual model. It was found that similar results were obtained with both analytical methods. Casting samples taken from the lower part of the squeeze casting mould were found to have a significantly shorter solidification time. For both types of alloys, it was found that generally the shorter the solidification time of the casting, the higher is its density, impact energy, yield strength and ultimate tensile strength (UTS). This study had therefore contributed to a better understanding of the mechanical properties obtained previously from different casting processes. [Copyright &y& Elsevier]

Abstract: A new method for micropatterning of metallic patterns on porous anodic oxide film of aluminium is described. The porous anodic oxide film was impregnated with organic dye and palladium ions before the hydrothermal pore-sealing. The surface layers formed during the pore-sealing, i.e. outer acicular hydroxide layer and a compact intermediate sub-layer trap the palladium ion underneath the layers. Exposing the palladium enriched area by the help of laser beam followed by electroless nickel deposition results the deposition of nickel on the laser-exposed part. Thickness of the deposits can be up to about 2–3μm, after about the 20min of immersion in electroless nickel plating bath. The metallic micropatterns, formed by the method are crack free, smooth and uniform over extended length. [Copyright &y& Elsevier]

Abstract: We studied the aluminum-induced early alteration of cultured diatom frustules in a series of laboratory experiments. Ashed frustules of the diatom Thalassiosira punctigera were exposed to natural seawater at varying dissolved aluminum (Al) concentrations (without addition, 100 nM and 500 nM Al) for periods of up to 6 months both in batch incubations and in flow-through chambers. These Al concentrations are representative of levels commonly found in pore waters in the marine environment. In general, the aluminum content of the frustules increased with time of exposure. A maximum increase of the aluminum to silicon mole ratio from 1.23×10−3 (day 0) to 3.14×10−3 was observed after 14 days of incubation at 500 nM Al. Time series with incubation times from 1 to 21 days at 100 nM Al confirm that the aluminum is rapidly associated with the diatom frustule. The uptake of Al during incubation goes along with a shift in pore structure towards smaller pores. The structural association of aluminum and silicon in biogenic silica was investigated using X-ray absorption spectroscopy at the Al–K-edge. Al–K-edge X-ray adsorbtion near edge spectra (XANES) of incubated diatom frustules demonstrate that most aluminum is present in tetrahedral coordination regardless of the Al concentration of the seawater and the duration of exposure. Al–K-edge EXAFS spectroscopy indicates the structural incorporation of aluminum into the Si framework. The results from X-ray absorption spectroscopy at the Al–K-edge, the textural changes of diatom frustules during incubation and wet chemical data are all consistent with the formation of an aluminosilicate phase on the surface of the diatom frustules. The precipitation this surface phase occurred under experimental conditions mimicking those prevailing at the sediment–water interface. We propose that the documented reaction pathway contributes to the rapid post-mortem aluminum enrichment of diatom frustules at the sediment–water interface. [Copyright &y& Elsevier]