Papers by Keyword: Aluminum

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Authors: Michael Pietryga, Johannes Lohmar, Gerhard Hirt
Abstract: Roll bonding is a process to join two or more different materials permanently in a rolling process. A typical industrial application is the manufacturing of aluminum sheets for heat exchangers in cars where the solder is joined onto a base layer by roll bonding. From a modelling point of view the challenge is to describe the bond formation and failure of the different material layers within a FE-process model. Most methods established today either tie the different layers together or treat them as completely separate. The problem for both assumptions is that they are not applicable to describe the influence of tangential stresses that can cause layer shifting and occur in addition to the normal stresses within the roll gap. To overcome these restrictions in this paper a 2D FE-model is presented that integrates an adapted contact formulation being able to join two bodies that are completely separated at the start of the simulation. The contact formulation is contained in a user subroutine that models bond formation by adhesion in dependence of material flow and load. Additionally if the deformation conditions are detrimental already established bonds can fail. This FE-model is then used to investigate the process boundaries of the first passes of a typical rolling schedule in terms of achievable height reductions. The results show that passes with unfavorable height reduction introduce tensile and shear stresses that can lead to incomplete bonding or can even destroy the bond entirely. It is expected that, with adequate calibration, the developed FE-model can be used to identify conditions that are profitable for bond formation in roll bonding prior to production and hence can lead to shorter rolling schedules with higher robustness.
Authors: Ho Sung Lee, Jong Hoon Yoon, Joon Tae Yoo
Abstract: Since solid state welding is formed from an intimate contact between two metals at temperatures below the melting point of the base materials, the structural integrity of welded zone is maintained without presence of foreign materials or temporary liquid phase. This paper provides some of examples for solid state joining of aerospace materials. Diffusion bonding process was developed for a titanium alloy for lightweight sandwich panels. Diffusion bonding of copper and stainless steel was also demonstrated to manufacture a combustion chamber. HIP (Hot Isostatic Press) bonding and friction stir welding process of aluminum alloy was developed in order to study possible application for a large launcher fuel tank. It is shown that solid state joining processes can be successfully applied to various aerospace materials and provide innovative solution for lightweight structures.
Authors: Y.Z. Zhu, Xiao Hui Li, J.C. Li, Wei Long Fan, Cheng Wei Xia, Ran Liu
Abstract: AA1235 aluminum alloys were twin roll cast into a 7.0 mm-thick billet and further rolled into a plate with 70% reduction, followed by annealing at 500 C for 8 h. Abnormal grains were found to be formed on the plate bottom surface. SEM, EBSD, and micro X-ray diffraction were used to analyze the mechanism underlying the abnormal growth of these grains. Results showed that the {100} <001> texture was formed in the surrounding normal grains adjacent to the abnormal grain. The orientation angle between the abnormal grain and its adjacent normal grains was 45°. The {100} <001> texture formed during rolling and annealing accelerated abnormal grain growth. The partially dissolved Fe precipitates were heterogeneously distributed in the plate bottom heterogeneously, which also mainly explained abnormal grain growth.
Authors: Zue Chin Chang, J.Y. Ling, Chien Chon Chen
Abstract: The fabrication processes of nanomaterials adopt semiconductor manufacturing technology mostly, and restrain from mass production due to high vacuity, expensive equipment, and long cycle time. This research offers a relatively simple and convenient fabrication process to improve the manufacturing technology of nanowires. Starting with aluminum film of high purity, this research utilized anodizing to produce the array nanoporous mold, electrochemical deposition to inject ion-state metal, oxidation-reduction method to obtain metal nanowires, and annealing to result the oxidation of metal nanowires. The influence of substrate and oxidation layers was investigated with respect to parameters such as voltage, current, and time. In order to get the best control of array dispersion, diameters, and depth, the influence of temperature over the process is also investigated. A higher anodizing temperature was utilized to stabilize the fabrication process of the array nanoporous mold. The resulted metal nanowires were analyzed with X-ray diffraction, FE-SEM, and TEM, to inspect the morphology and crystallography. The observations are summarized. (a) The preferred orientation of nickel nanowires being annealed at the 600°C pure nitrogen is NiO(111). (b) As the oxidation temperature rises, NiO in pure oxygen or the atmosphere would transfer into Ni2O3 due to the size effect. Nickel nanowires in pure oxygen could oxidize into Ni2O3 at a lower temperature of 500°C. (c) Nickel nanowires both in pure oxygen and in the atmosphere would transfer stably into Ni2O3 at 900°C.
Authors: Aunyanat Rattanasatitkul, Suksan Prombanpong, Pongsak Tuengsook
Abstract: The anodizing process is an aluminum surface treatment process which an aluminum oxide film forms on an aluminum substrate. Typically, the anodic thickness is a required specification which depends upon current density and anodizing cycle time. In addition, another important factor is ramp time which must be proper set to prevent a burn defect. Thus, this paper investigates a relationship among these three factors to determine the setting condition which minimizes the anodizing cycle time. Moreover, the required thickness must be obtained without increasing the burn defect rate. The experimental design technique is proposed to achieve this goal and it is found that the current of 35 amp, ramp time of 340sec and anodizing time at 1400 sec ensure the obtained anodic thickness greater than 30 micron.
Authors: Peng Fei Wang, Chen Bin Liu, Jin Chuan Jie, Ting Ju Li
Abstract: The 5083 aluminum alloy was prepared and subjected to cryogenic rolling (CR) after heat treatment. The samples were reduced from 15mm to 1.5 mm in the thickness direction and the amount of deformation was 90%. For comparison, samples with the same deformation amount were obtained by room temperature rolling (RTR). The corrosion behavior of CR and RTR samples was measured by electrochemical test, and their microstructures before and after corrosion had been studied through electron scanning microscopy (SEM) and optical microscope (OM). The influence of cryogenic rolling on the corrosion behavior of 5083 aluminum alloys was explored. The experiment results suggested that anti-corrosion ability of 5083 aluminum alloys could be enhanced through cryogenic rolling. The corrosion potential elevated and the corrosion current density reduced according to the electrochemical test. The primary reasons and corresponding mechanism were also discussed.
Authors: Hiromasa Suo, Kazuma Eto, Tomohisa Kato, Kazutoshi Kojima, Hiroshi Osawa, Hajime Okumura
Abstract: The growth of n-type 4H-SiC crystal was performed by physical vapor transport (PVT) growth method by using nitrogen and aluminum (N-Al) co-doping. Resistivity of N-Al co-doped 4H-SiC was as low as 5.8 mΩcm. The dislocation densities of N-Al co-doped substrates were evaluated by synchrotron radiation X-ray topography (SXRT). In addition, epitaxial growth was performed on the N-Al co-doped substrates by chemical vapor deposition (CVD). No double Shockley type stacking fault was observed in the epitaxial layer.
Authors: V.A. Poryazov, K.M. Moiseeva, Aleksey Yu. Krainov
Abstract: The paper presents a mathematical model for combustion of a frozen nanosized aluminum suspension (ALICE), taking into account the combustion of aluminum in water vapor, the motion of combustion products, and the velocity lag of particles compared to gas. The model was formulated based on Belyaev’s approach to modeling the combustion of volatile fuels [1]. The burning rate calculated is in agreement with the experimental data on the ALICE burning rate and its variation with pressure.
Authors: Safwan M.A. Al-Qawabah, Adnan I.O. Zaid, Ahmad Qandil
Abstract: Aluminum and its alloys are widely used materials; they are next to steel in use mainly in the automobile industry due to their high strength – to – weight ratio and corrosion resistance beside its other attractive properties. Against their attractive properties; they have the disadvantage of solidifying in columnar structure which tends to reduce their mechanical characteristics and surface quality. Therefore it became customary to grain refine them either by Ti or Ti+B to overcome this discrepancy. In this paper, comparison between Molybdenum addition to commercially pure aluminum grain refined by Ti and Ti+B on its grain size and mechanical characteristics both in the cast and after pressing by the ECAP process is investigated and the obtained results are presented and discussed.
Authors: Alexey O. Rodin, Nikolai Dolgopolov, Alexander Pomadchik
Abstract: According to different experimental data the grain boundary diffusion the triple product (P) can change in opposite directions after alloying. In this paper the analysis of the effect of alloying for different systems is proposed. It was shown that in Al-based system (Cu diffusion in Al, Zn diffusion in Al) the P value increases with alloying while the solidus temperature according to the phase diagram decreases, in other systems no such tendency can be seen. Estimations based on the segregation factor value demonstrate that some structural effect must be proposed in addition to describe the experimental results.
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