WorldWideScience

Sample records for al-si tipo a319

  1. The effects of mischmetal, cooling rate and heat treatment on the eutectic Si particle characteristics of A319.1, A356.2 and A413.1 Al-Si casting alloys

    Energy Technology Data Exchange (ETDEWEB)

    Sebaie, O. El; Samuel, A.M. [Universite du Quebec a Chicoutimi, Chicoutimi, Quebec, G7H 2B1 (Canada); Samuel, F.H. [Universite du Quebec a Chicoutimi, Chicoutimi, Quebec, G7H 2B1 (Canada)], E-mail: fhsamuel@uqac.ca; Doty, H.W. [GM Powertrain Group, Metal Casting Technology, Inc., Milford, NH 03055 (United States)

    2008-05-15

    The effects of mischmetal, cooling rate and heat treatment on the eutectic Si particle characteristics of A319.1, A356.2 and A413.1 Al-Si casting alloys were investigated and recorded for this study. Mischmetal was added to the alloys in the form of Al-20% mischmetal master alloy to produce four levels of mischmetal addition (0, 2, 4 and 6 wt%). The alloys were also modified with strontium ({approx}250 ppm) to study the combined modification effect of Sr and mischmetal at both high and low cooling rates corresponding to dendrite arm spacings of {approx}40 and 120 {mu}m, respectively. The alloys were subjected to solution heat treatment (495 deg. C/8 h for A319.1 and A413.1 alloys, and 540 deg. C/8 h for A356.2 alloy) to investigate its effect on the eutectic Si particle morphology. An optical microscope-image analyzer system was used to measure the characteristics of eutectic Si particles such as area, length, roundness ratio and aspect ratio, in order to monitor the modifying effect of mischmetal, as well as the combined modification effect of mischmetal and Sr. For each alloy sample examined, the Si particle characteristics were measured over an area of 50 fields and the average particle characteristics were thus determined. The eutectic Si particle measurements revealed that partial modification was obtained with the addition of mischmetal while full modification was achieved with the addition of Sr in the as-cast condition, at both high and low cooling rates. The interaction between Sr and mischmetal was observed to weaken the effectiveness of Sr as a Si particle-modifying agent. This effect was particularly evident at the low cooling rate. During solution heat treatment, the eutectic Si particles in the non-modified alloys underwent rapid coarsening, otherwise known as Ostwald ripening, whereas those in the Sr-modified alloys exhibited a high spheroidization rate. The coarsening was evidenced by an increase in the thickness of the Si particles, clearly

  2. Hot Corrosion Behavior of Stainless Steel with Al-Si/Al-Si-Cr Coating

    Science.gov (United States)

    Fu, Guangyan; Wu, Yongzhao; Liu, Qun; Li, Rongguang; Su, Yong

    2017-03-01

    The 1Cr18Ni9Ti stainless steel with Al-Si/Al-Si-Cr coatings is prepared by slurry process and vacuum diffusion, and the hot corrosion behavior of the stainless steel with/without the coatings is studied under the condition of Na2SO4 film at 950 °C in air. Results show that the corrosion kinetics of stainless steel, the stainless steel with Al-Si coating and the stainless steel with Al-Si-Cr coating follow parabolic laws in several segments. After 24 h corrosion, the sequence of the mass gain for the three alloys is the stainless steel with Al-Si-Cr coating steel with Al-Si coating steel without any coating. The corrosion products of the three alloys are layered. Thereinto, the corrosion products of stainless steel without coating are divided into two layers, where the outside layer contains a composite of Fe2O3 and FeO, and the inner layer is Cr2O3. The corrosion products of the stainless steel with Al-Si coating are also divided into two layers, of which the outside layer mainly consists of Cr2O3, and the inner layer is mainly SiO2. The corrosion film of the stainless steel with Al-Si-Cr coating is thin and dense, which combines well with substrate. Thereinto, the outside layer is mainly Cr2O3, and the inside layer is Al2O3. In the matrix of all of the three alloys, there exist small amount of sulfides. Continuous and protective films of Cr2O3, SiO2 and Al2O3 form on the surface of the stainless steel with Al-Si and Al-Si-Cr coatings, which prevent further oxidation or sulfide corrosion of matrix metals, and this is the main reason for the much smaller mass gain of the two alloys than that of the stainless steel without any coatings in the 24 h hot corrosion process.

  3. Quality analysis of the Al-Si-Cu alloy castings

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2007-04-01

    Full Text Available The developed design methodologies both the material and technological ones will make it possible to improve shortly the quality of materials from the light alloys in the technological process, and the automatic process flow correction will make the production cost reduction possible, and - first of all - to reduce the amount of the waste products. Method was developed for analysis of the casting defects images obtained with the X-ray detector analysis of the elements made from the Al-Si-Cu alloys of the AC-AlSi7Cu3Mg type as well as the method for classification of casting defects using the artificial intelligence tools, including the neural networks; the developed method was implemented as software programs for quality control. Castings were analysed in the paper of car engine blocks and heads from the Al-Si-Cu alloys of the AC-AlSi7Cu3Mg type fabricated with the “Cosworth” technological process. The computer system, in which the artificial neural networks as well as the automatic image analysis methods were used makes automatic classification possible of defects occurring in castings from the Al-Si-Cu alloys, assisting and automating in this way the decisions about rejection of castings which do not meet the defined quality requirements, and therefore ensuring simultaneously the repeatability and objectivity of assessment of the metallurgical quality of these alloys.

  4. Laser clad AlSiCuNi functionally graded coatings

    NARCIS (Netherlands)

    Pei, Yutao; de Hosson, J.T.M.; Brebbia, CA

    2001-01-01

    This paper presents an exploration of laser clad AlSiCuNi-alloy FGCs on cast Al-alloy substrates. SEM microstructure observations indicate that, besides Si primary particles, hard Al3Ni2 compounds also exhibits a continuous increase in both particle sizes and volume fractions from the bottom to the

  5. Wettability of AlSi5Mg on Spodumene

    Science.gov (United States)

    Fankhänel, Beate; Stelter, Michael; Voigt, Claudia; Aneziris, Christos G.

    2015-02-01

    The development of new filters for the aluminum industry requires investigations on the wettability of aluminum and its alloys on novel filter materials. The requested filter effects require not only an adequate wetting but also information about the interaction between the filter material and the metal. In the present work the wettability of an AlSi5Mg alloy on spodumene (LiAl[Si2O6]) containing substrates is investigated using the sessile drop technique. These measurements were carried out at 1223 K (950 °C) under vacuum. The spodumene-based substrates showed a completely different wetting behavior compared with an alumina substrate. The contact angel reduced more quickly and leveled out at a lower value (75 ± 2 deg) than in case of a pure alumina substrate (90 ± 1 deg). The reason for this behavior is a reaction between the LiAl(Si2O6) and the alloy droplet which supported deoxidation and formed a silica-rich reaction layer at the droplet/substrate interface.

  6. Crystal structural refinement for NdAlSi

    Institute of Scientific and Technical Information of China (English)

    HE Wei; ZHANG Jiliang; ZENG Lingmin; ZHUANG Yinghong

    2006-01-01

    The compound NdAlSi was studied using X-ray powder diffraction technique and refined by the Rietveld method. The compound NdAlSihas tetragonal α-ThSi2-type structure, space group I41/amd (No.141), Z = 4, and the lattice parameters a = 0.41991(1) nm, c = 1.44916(3) nm. The Smith and Snyder figure of merit FN is F30= 103.1(36). The R-factors of Rietveld refinement are Rp= 0.113 and Rwp= 0.148, respectively. The X-ray powder diffraction data is presented in this article.

  7. Reactive diffusion bonding of SiCp/Al composites by insert layers of mixed Al-Si and Al-Si-SiC powders

    Institute of Scientific and Technical Information of China (English)

    Jihua Huang; Yueling Dong; Yun Wan; Jiangang Zhang; Hua Zhang

    2005-01-01

    Mixed Al-Si and Al-Si-SiC powders were employed as insert layers to reactive diffusion bond SiCp/6063 MMC (metal matrix composites). The results show that SiCp/6063 MMC joints bonded by the insert layer of the mixed Al-Si powder have a dense joining layer with a typical hypoeutectic microstructure. Using the mixed Al-Si-SiC powder as the insert layer, SiCp/6063 MMC can be reactive diffusion bonded by a composite joint. Because of the SiC segregation, however, there are a number of porous zones in the joining layer, which results in the bad shear strength of the joints reactive diffusion bonded by the insert layer of the mixed Al-SiSiC powder, even lower than that of the joints reactive diffusion bonded by the insert layer of the mixed Al-Si powder. Ti and Mg added in the insert layers obviously improve the strength of the joints reactive diffusion bonded by the insert layer of the mixed AlSi-SiC powder, especially, Mg has a more obvious effect.

  8. Effect of NaCl upon an Al-Si casting alloy hipoeutec; Efecto del NaCl sobre una aleacion de Al-Si hipoeutectica vaciada

    Energy Technology Data Exchange (ETDEWEB)

    Martinez Delgado, E.J.; Ortega de la Rosa, R. [Istituto Tecnologico de Zacatecas, Zacatecas (Mexico)]. E-mail: enriquemartinez_1999@yahoo.com; rubin_ortega_2002@yahoo.com.mx; Cisneros Guerrero, M.A. [Instituto Tecnologico de Saltillo, Saltillo, Coahuila (Mexico)]. E-mail: cisneros@its.mx; Haro Rodriguez, S. [Universidad Autonoma de Zacatecas, Zacatecas, Zacatecas (Mexico)]. E-mail: haros907@hotmail.com

    2009-10-15

    This work, comprehends the study about the effect of NaCl kind Halite upon the morphology of eutectic Silicon and porosity in a cast hipoeutectic Al-Si alloy. The melting was carried out in two furnaces, the first to combustion of LP gas in graphite crucible to increase the content of Si in the alloy from 0.13 to 5% wt using metallic silicon with a purity of 99.35% wt, and the second of electric resistances in the same kind of crucible to control the temperature at 750 degrees Celsius. The melting material was casting into molds of sand shell. To add the salt into the metallic bath, two techniques were used; one with injection by means of Argon gas and the other on by gravity, both cases three quantities of salt were used, 0.5, 1.5 and 2.5% wt respectively, powdered and preheated at 150 degrees Celsius during 60 min. The obtained samples were analyzed metallographily evidencing the modification of the eutectic Si, presenting the best results the samples with 1.5 and 2.5% wt of salt added by gravity. Too was obtained effect of Salt upon the degassing of bath metallic, where the simples with 1.5% wt presented the best results. Finally, by means of Scanning Electron Microscopy, the precipitates present were characterized in the samples. [Spanish] Este trabajo comprende el estudio del efecto del NaCl tipo Halita sobre la morfologia del Si eutectico y la porosidad en una aleacion fundida Al-Si hipoeutectica. La fusion se llevo a cabo en dos hornos, el primero a combustion con gas LP en crisol de grafito con la finalidad de incrementar el contenido de Si en la aleacion de 0.13 a 5% en peso, utilizando silicio metalico con una pureza de 99.35%, y el segundo de resistencias electricas en el mismo tipo de crisol para controlar la temperatura a 750 grados Celsios. El material fundido fue vaciado en modelos de arena. La sal se anadio al bano metalico a 0.5, 1.5 y 2.5% en peso, respectivamente, pulverizada y precalentada a 150 grados Celsios durante 60 min, mediante dos

  9. The Effect of Plasma Spraying on the Microstructure and Aging Kinetics of the Al-Si Matrix Alloy and Al-Si/SiC Composites

    Science.gov (United States)

    Altunpak, Yahya; Akbulut, Hatem; Üstel, Fatih

    2010-02-01

    The Al-Si (LM 13)-based matrix alloy reinforced with SiC particles containing 10, 20, and 30 vol.% SiC particles were spray-formed onto Al-Si substrates. The sprayed samples were directly subjected to a standard aging treatment (T551). From the experiments, it was observed that the high rate of solidification resulted in very fine silicon particles which were observed as continuous islands in the matrix and each island exhibited several very fine silicon crystals. Analysis showed that plasma-spraying caused an increased solid solubility of the silicon in the aluminum matrix. DSC measurements in the permanent mold-cast Al-Si matrix alloy and plasma-sprayed Al-Si matrix alloy showed that plasma-spraying causes an increase in the amount of GP-zone formation owing to the very high rate solidification after plasma-spraying. In the plasma-sprayed Al-Si/SiC composites GP zones were suppressed, since particle-matrix interfaces act as a sink for vacancies during quenching from high plasma process temperature. Introduction of SiC particles to the Al-Si age-hardenable alloy resulted in a decrease in the time required to reach plateau matrix hardness owing to acceleration of aging kinetics by ceramic SiC particles.

  10. Heat treatment of AlSi9Mg alloy

    Directory of Open Access Journals (Sweden)

    J. Pezda

    2008-04-01

    Full Text Available Processes of crystallization of alloys have decisive impact on structure of castings, and the same their utility characteristics. Knowledge about those processes constitutes a source of information to development of preparation of liquid metal and control of alloy preparation process within industry. Method of Thermal-Voltage-Derivative Analysis (ATND, developed by Faculty of Chipless Forming Technology enables registration of temperature and voltage curves, on which one can observe thermal and voltage effects being result of crystallization of phases and eutectic mixtures present on these curves in form of characteristic “peaks”. Temperature value read offs for these characteristic points become a basis to taking regression analysis aimed at obtaining of mathematical dependences illustrating effect of changes of these values on change of impact resistance of dispersion hardened AK9 alloy. The paper presents an attempt of implementation of Thermal-Voltage-Derivative Analysis method to determination of temperature of hyperquenching and ageing processes of AK9 (AlSi9Mg silumin. Investigated alloy had undergone typical treatments of refining and modification, and next the heat treatment. Temperature range for the heat treatment has been determined on base of ATND melting curves.

  11. Refining Effect of Boron on Hypoeutectic Al-Si Alloys

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@Several concepts of the grain refinement mechanism of B on hypoeutectic Al-Si alloys have been adopted: the refining effect of B on the α-Al and eutectic Si with the different additions of Al-B master alloys made at 850℃ was investigated; and the Al-B master alloys formed under different temperature conditions have been studied to explore the morphologies of AlB2 particles;slowly cooled sample with addition of Al-B was made to explore the refinement mechanism. AlB master alloy can refine not only α-Al, but eutectic Si. Theoretical analysis indicates that,although AlB2 does not take part directly in the nucleation process in pure Al in the presence of Si, it provides a substrate for precipitation of a small content of Si from which α-Al will grow without any undercooling. When the temperature decreases to eutectic line, AlB2 subsequently nucleates eutectic Si; AlB2 particles appear in two different morphologies, namely, hexagonal platelet and tetradehedron morphology which depend on the processing temperature conditions.

  12. Microstructural development of rapid solidification in Al-Si powder

    Energy Technology Data Exchange (ETDEWEB)

    Jin, Feng [Iowa State Univ., Ames, IA (United States)

    1995-09-26

    The microstructure and the gradient of microstructure that forms in rapidly solidificated powder were investigated for different sized particles. High pressure gas atomization solidification process has been used to produce a series of Al-Si alloys powders between 0.2 μm to 150 μm diameter at the eutectic composition (12.6 wt pct Si). This processing technique provides powders of different sizes which solidify under different conditions (i.e. interface velocity and interface undercooling), and thus give different microstructures inside the powders. The large size powder shows dendritic and eutectic microstructures. As the powder size becomes smaller, the predominant morphology changes from eutectic to dendritic to cellular. Microstructures were quantitatively characterized by using optical microscope and SEM techniques. The variation in eutectic spacing within the powders were measured and compared with the theoretical model to obtain interface undercooling, and growth rate during the solidification of a given droplet. Also, nucleation temperature, which controls microstructures in rapidly solidified fine powders, was estimated. A microstructural map which correlates the microstructure with particle size and processing parameters is developed.

  13. Microstructural Development in Al-Si Powder During Rapid Solidification

    Energy Technology Data Exchange (ETDEWEB)

    Genau, Amber Lynn [Iowa State Univ., Ames, IA (United States)

    2004-01-01

    Powder metallurgy has become an increasingly important form of metal processing because of its ability to produce materials with superior mechanical properties. These properties are due in part to the unique and often desirable microstructures which arise as a result of the extreme levels of undercooling achieved, especially in the finest size powder, and the subsequent rapid solidification which occurs. A better understanding of the fundamental processes of nucleation and growth is required to further exploit the potential of rapid solidification processing. Aluminum-silicon, an alloy of significant industrial importance, was chosen as a model for simple eutectic systems displaying an unfaceted/faceted interface and skewed coupled eutectic growth zone, Al-Si powder produced by high pressure gas atomization was studied to determine the relationship between microstructure and alloy composition as a function of powder size and atomization gas. Critical experimental measurements of hypereutectic (Si-rich) compositions were used to determine undercooling and interface velocity, based on the theoretical models which are available. Solidification conditions were analyzed as a function of particle diameter and distance from nucleation site. A revised microstructural map is proposed which allows the prediction of particle morphology based on temperature and composition. It is hoped that this work, by providing enhanced understanding of the processes which govern the development of the solidification morphology of gas atomized powder, will eventually allow for better control of processing conditions so that particle microstructures can be optimized for specific applications.

  14. Wear resistance of TiAlSiN thin coatings.

    Science.gov (United States)

    Silva, F J G; Martinho, R P; Alexandre, R J D; Baptista, A P M

    2012-12-01

    In the last decades TiAIN coatings deposited by PVD techniques have been extensively investigated but, nowadays, their potential development for tribological applications is relatively low. However, new coatings are emerging based on them, trying to improve wear behavior. TiAlSiN thin coatings are now investigated, analyzing if Si introduction increases the wear resistance of PVD films. Attending to the application, several wear test configurations has been recently used by some researchers. In this work, TiAISiN thin coatings were produced by PVD Unbalanced Magnetron Sputtering technique and they were conveniently characterized using Scanning Electron Microscopy (SEM) provided with Energy Dispersive Spectroscopy (EDS), Atomic Force Microscopy (AFM), Electron Probe Micro-Analyzer (EPMA), Micro Hardness (MH) and Scratch Test Analysis. Properties as morphology, thickness, roughness, chemical composition and structure, hardness and film adhesion to the substrate were investigated. Concerning to wear characterization, two very different ways were chosen: micro-abrasion with ball-on-flat configuration and industrial non-standardized tests based on samples inserted in a feed channel of a selected plastic injection mould working with 30% (wt.) glass fiber reinforced polypropylene. TiAISiN coatings with a small amount of about 5% (wt.) Si showed a similar wear behavior when compared with TiAIN reported performances, denoting that Si addition does not improve the wear performance of the TiAIN coatings in these wear test conditions.

  15. Silicon spheroidization treatment of thixoformed Al-Si-Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ogris, E.; Uggowitzer, P.J. [Eidgenoessische Technische Hochschule, Zurich (Switzerland). Inst. of Metallurgy; Luechinger, H. [SAG-Aluminium Lend GmbH und Co KG and THIXALLOY trademark Components GmbH und Co KG, Lend (Austria)

    2002-07-01

    Al-Si-Mg alloys are commonly used in the automobile industry because of their outstanding mechanical properties and corrosion resistance. The need of lighter and safer cars is the driving force behind research in the area of high strength light metal safety part applications. The strength level can be tuned by varying the amount of alloyed magnesium. Usually if strength is increased, ductility will decrease. Following the demands of the automotive industry, safety parts should have a minimum fracture elongation of 15% and a minimum yield strength of 150 MPa. The huge hurdle is the 15% fracture elongation which can not be reached by sand or die casting, but some relatively new alternative casting technologies, like Thioxocasting or New Rheocasting, yield encouraging ductility values. Recent research activity has focused on increasing strength and ductility, but so far the results have not yet been satisfying. This paper presents investigations on the spheroidization process of eutectic silicon and its positive effect on mechanical properties. It is shown that the spheroidization process is already finished after minutes of exposure to heat treatment. Metallographical and quantitative microstructural analysis is used to describe the growth and spheroidization process of the silicon crystals. Specimens of THIXALLOY trademark 630 (A356) thixocast components were heat treated for varied periods of time, aged and tested. Results show amazing improvements of ductility and strength in comparison to the as cast state. Maximum values of 18% fracture elongation and 230 MPa yield strength are reached. (orig.)

  16. Influence of silicon concentration on linear contraction process of Al-Si binary alloy

    Directory of Open Access Journals (Sweden)

    J. Mutwil

    2008-12-01

    Full Text Available Investigations of shrinkage phenomena during solidification and cooling of aluminium and aluminium-silicon alloys (AlSi5, AlSi7, AlSi9, AlSi11, AlSi12.5, AlSi18, AlSi21 have been conducted. A vertical shrinkage rod casting with circular cross-section (constant or fixed: tapered has been used as a test sample. By constant cross-section a test channel mould was parted and allowed a constrained contraction to examine. No parted test channel mould was tapered and allowed an unconstrained contraction to investigate. In the experiments the dimensions changes of solidifying test bar and the test mould have been registered, what has allowed to explain a mechanism of pre-shrinkage extension of solidifying metals and alloys. Registered time dependence of the test bar and the test mould dimension changes have shown, that so-called pre-shrinkage extension has been by mould thermal extension caused. The investigation results have also shown that time- and temperature dependences of shrinkage of Al-Si alloys have been on silicon concentration depended.

  17. Fabrication of Spherical AlSi10Mg Powders by Radio Frequency Plasma Spheroidization

    Science.gov (United States)

    Wang, Linzhi; Liu, Ying; Chang, Sen

    2016-05-01

    Spherical AlSi10Mg powders were prepared by radio frequency plasma spheroidization from commercial AlSi10Mg powders. The fabrication process parameters and powder characteristics were investigated. Field emission scanning electron microscope, X-ray diffraction, laser particle size analyzer, powder rheometer, and UV/visible/infrared spectrophotometer were used for analyses and measurements of micrographs, phases, granulometric parameters, flowability, and laser absorption properties of the powders, respectively. The results show that the obtained spherical powders exhibit good sphericity, smooth surfaces, favorable dispersity, and excellent fluidity under appropriate feeding rate and flow rate of carrier gas. Further, acicular microstructures of the spherical AlSi10Mg powders are composed of α-Al, Si, and a small amount of Mg2Si phase. In addition, laser absorption values of the spherical AlSi10Mg powders increase obviously compared with raw material, and different spectra have obvious absorption peaks at a wavelength of about 826 nm.

  18. Heat Pipe Embedded AlSiC Plates for High Conductivity - Low CTE Heat Spreaders

    Energy Technology Data Exchange (ETDEWEB)

    Johnson, Matthew (DOE/NNSA Kansas City Plant (United States)); Weyant, J.; Garner, S. (Advanced Cooling Technologies, Inc. (Lancaster, PA (United States)); Occhionero, M. (CPS Technologies Corporation, Norton, MA (United States))

    2010-01-07

    Heat pipe embedded aluminum silicon carbide (AlSiC) plates are innovative heat spreaders that provide high thermal conductivity and low coefficient of thermal expansion (CTE). Since heat pipes are two phase devices, they demonstrate effective thermal conductivities ranging between 50,000 and 200,000 W/m-K, depending on the heat pipe length. Installing heat pipes into an AlSiC plate dramatically increases the plate’s effective thermal conductivity. AlSiC plates alone have a thermal conductivity of roughly 200 W/m-K and a CTE ranging from 7-12 ppm/ deg C, similar to that of silicon. An equivalent sized heat pipe embedded AlSiC plate has effective thermal conductivity ranging from 400 to 500 W/m-K and retains the CTE of AlSiC.

  19. Cell adhesion to cathodic arc plasma deposited CrAlSiN thin films

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Sun Kyu, E-mail: skim@ulsan.ac.kr [School of Materials Science and Engineering, University of Ulsan, Ulsan 680-749 (Korea, Republic of); Pham, Vuong-Hung [Department of Materials Science and Engineering, Seoul National University, Seoul 151-744 (Korea, Republic of); Kim, Chong-Hyun [Department of Food Science, Cornell University, Ithaca, NY 14853 (United States)

    2012-07-01

    Osteoblast cell response (cell adhesion, actin cytoskeleton and focal contact adhesion as well as cell proliferation) to CrN, CrAlSiN and Ti thin films was evaluated in vitro. Cell adhesion and actin stress fibers organization depended on the film composition significantly. Immunofluorescent staining of vinculin in osteoblast cells showed good focal contact adhesion on the CrAlSiN and Ti thin films but not on the CrN thin films. Cell proliferation was significantly greater on the CrAlSiN thin films as well as on Ti thin films than on the CrN thin films.

  20. Bulk Al/SiC nanocomposite prepared by ball milling and hot pressing method

    Institute of Scientific and Technical Information of China (English)

    GU Wan-li

    2006-01-01

    Nano-sized Al/SiC powders were prepared by mechanical alloying method. Two sorts of SiC particle,i.e.,nano-sized and popular micron-sized SiC were utilized. The particle size and microstructure of the milled powder were characterised. Effects of the particle size and agglomerate state of SiC,as well as the microstructure of Al/SiC nanocomposite were studied by SEM and TEM. The results show that nano-sized SiC particles is dispersed in aluminium uniformly after ball milled for only 2 h,whereas the similar process need about 10 h for popular micron-sized SiC particle. The bulk Al/SiC nanocomposite can be fabricated by hot pressing the nano-sized Al/SiC powders at temperature about 723 K under pressure of 100 MPa.

  1. Separation of primary solid phases from Al-Si alloy melts

    Directory of Open Access Journals (Sweden)

    Ki Young Kim

    2014-07-01

    Full Text Available The iron-rich solids formed during solidification of Al-Si alloys which are known to be detrimental to the mechanical, physical and chemical properties of the alloys should be removed. On the other hand, Al-Si hypereutectic alloys are used to extract the pure primary silicon which is suitable for photovoltaic cells in the solvent refining process. One of the important issues in iron removal and in solvent refining is the effective separation of the crystallized solids from the Al-Si alloy melts. This paper describes the separation methods of the primary solids from Al-Si alloy melts such as sedimentation, draining, filtration, electromagnetic separation and centrifugal separation, focused on the iron removal and on the separation of silicon in the solvent refining process.

  2. Tensile property of Al-Si closed-cell aluminum foam

    Institute of Scientific and Technical Information of China (English)

    YU Hai-jun; YAO Guang-chun; LIU Yi-han

    2006-01-01

    Al-Si closed-cell aluminum foams of different densities were prepared by molten body transitional foaming process. The tensile behavior of Al-Si closed-cell aluminum foam was studied and the influence of relative densities on the tensile strength and elastic modulus was also researched. The results show that the fracture surfaces of Al-Si closed-cell aluminum foam display quasi-cleavage fiacture consisting of brittle cleavages and ductile dimples. The tensile strength and elastic modulus are strictly affected by the relative density of Al-Si closed-cell aluminum foam. With increasing relative density, the tensile strength increases and the strain at which the peak strength is measured also increases; in addition, the elastic modulus increases with increasing relative density.

  3. Separation of primary solid phases from Al-Si alloy melts

    Institute of Scientific and Technical Information of China (English)

    Ki Young Kim

    2014-01-01

    The iron-rich solids formed during solidification of Al-Si aloys which are known to be detrimental to the mechanical, physical and chemical properties of the aloys should be removed. On the other hand, Al-Si hypereutectic alloys are used to extract the pure primary silicon which is suitable for photovoltaic cells in the solvent refining process. One of the important issues in iron removal and in solvent reifning is the effective separation of the crystalized solids from the Al-Si aloy melts. This paper describes the separation methods of the primary solids from Al-Si aloy melts such as sedimentation, draining, ifltration, electromagnetic separation and centrifugal separation, focused on the iron removal and on the separation of silicon in the solvent refining process.

  4. Preparation of Al-SiC{sub p} composite coating by plasma thermal spray

    Energy Technology Data Exchange (ETDEWEB)

    Min, J.W. [Chungnam National University, Taejeon (Korea); Yoo, S.E. [Korea Automotive Technology Institute, Chonan (Korea); Kim, Y.J. [Sunmoon University, Asan (Korea); Kim, J.S.; Suhr, D.S. [Chungnam National University, Taejeon (Korea)

    2003-03-01

    Al-SiC{sub p} composite layer was prepared by plasma thermal spray on aluminum substrate using composite powder prepared by mechanical alloying. Mechanically alloyed powder was achieved after 24 h milling, which was used for thermal spray coating. The correlations between process conditions and thickness/porosity were analyzed, and increase of hardness was confirmed. The presence of Al-Si-C-O compound was detected by TEM analysis. (author). 16 refs., 6 tabs., 11 figs.

  5. Modified Mechanism of Eutectic Silicon in Al2O3/Al-Si Alloy

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Al2O3/Al-Si alloy composite was manufactured by squeeze casting. The morphology of the eutectic silicon in the composite was observed by scanning electronic microscope (SEM), and the modified mechanism of eutectic silicon in the composite was approached. The alumina fiber in the composite can trigger twin during the growth of Al-Si eutectic and lead to the modification of eutectic silicon near the fiber.

  6. Towards hard yet self-lubricious CrAlSiN coatings

    Energy Technology Data Exchange (ETDEWEB)

    Qiu, Yuexiu [Central Iron and Steel Research Institute, 76 South Xueyuanlu Rd, Haidan District, Beijing 100081 (China); Advanced Technology and Materials Co., Ltd, 76 South Xueyuanlu Rd, Haidan District, Beijing 100081 (China); Zhang, Sam [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Lee, Jyh-Wei [Department of Materials Engineering, Ming Chi University of Technology, 84 Gung Juan Road, Taishan, Taipei 24301, Taiwan (China); Center for Thin Film Technologies and Applications, Ming Chi University of Technology, 84 Gung Juan Road, Taishan, Taipei 24301, Taiwan (China); Li, Bo [Central Iron and Steel Research Institute, 76 South Xueyuanlu Rd, Haidan District, Beijing 100081 (China); Wang, Yuxi [School of Mechanical and Aerospace Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Zhao, Dongliang [Central Iron and Steel Research Institute, 76 South Xueyuanlu Rd, Haidan District, Beijing 100081 (China); Sun, Deen [School of Materials Science and Engineering, Chongqing University, Chongqing 400044 (China)

    2015-01-05

    Highlights: • Hard yet self-lubricious CrAlSiVN coatings are developed. • Incorporating vanadium into CrAlSiN structure refines crystal grains. • Tribo-oxidized vanadium provides CrAlSiN coatings lubriciousness. - Abstract: CrAlSiN coatings are of high hardness, excellent wear and oxidation resistance but lack of lubriciousness. Vanadium nitride (VN) is easily oxidized to form vanadium oxides and becomes lubricious under stress. Incorporating VN into CrAlSiN to form CrAlSiVN coating renders both hardness and self-lubrication in dry machining. This study investigates the effect of vanadium content on hard yet self-lubricious coating’s mechanical and tribological properties. The coatings are deposited on cemented tungsten carbide and Si wafer (1 0 0) substrates in an in-line magnetron sputtering system. Grazing incidence X-ray diffractometer, scanning electron microscopy, transmission electron microscopy, electron probe micro-analyzer, X-ray photoelectron spectroscopy and energy dispersive X-ray spectroscopy are employed to characterize the microstructures and chemistry. Nanoindentation and ball-on-disc tribo-tester are used in characterization of the mechanical and tribological properties. The coatings demonstrate lubriciousness of coefficient of friction with tungsten carbide from 0.55 down to 0.39 with acceptable loss of hardness (from ∼35 GPa down to ∼30 GPa)

  7. A new method to evaluate the hydraulic activity of Al-Si materials

    Institute of Scientific and Technical Information of China (English)

    LI HuaJian; SUN HengHu; TIE XuChu; XIAO XueJun

    2008-01-01

    Slag, fly ash, gangue and 500℃ calcined gangue are analyzed by using identical coupled plasma optical emission spectroscopy (ICP), X-ray photoelectron spectroscopy (XPS), infrared spectroscopy (IR) and magnetic angle spinning nuclear magnetic resonance (MAS NMR). Research results show that there is a negative linear relationship between the Si 2p and Al 2p binding energies of Al-Si materials and the compressive strength of aluminosilicate based cementitious materials prepared with these Al-Si materials, i.e. the lower the binding energies, the higher the compressive strength. Indeed, the Si 2p and Al 2p binding energies of Al-Si materials can be used to indicate their hydraulic activity. The binding energies of the four examined materials increase in the order of slag, fly ash, 500℃ calcined gangue and untreated gangue. Moreover, the binding energies of Si 2p, Al 2p and O 1s of every Al-Si material have excellent correlation. By using the Al 2p binding energy and 27AI MAS NMR spectra, the coordination number of aluminum in slag is determined to be four, while that in gangue, is six. Based on the aforementioned discoveries, this paper presents a new effective method to evaluate the hydraulic activity of Al-Si materials by using the surface binding energies of silicon and aluminum of Al-Si materials.

  8. A new method to evaluate the hydraulic activity of Al-Si materials

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    Slag,fly ash,gangue and 500℃ calcined gangue are analyzed by using identical coupled plasma optical emission spectroscopy (ICP),X-ray photoelectron spec-troscopy (XPS),infrared spectroscopy (IR) and magnetic angle spinning nuclear magnetic resonance (MAS NMR). Research results show that there is a negative linear relationship between the Si 2p and Al 2p binding energies of Al-Si materials and the compressive strength of aluminosilicate based cementitious materials prepared with these Al-Si materials,i.e. the lower the binding energies,the higher the compressive strength. Indeed,the Si 2p and Al 2p binding energies of Al-Si materials can be used to indicate their hydraulic activity. The binding energies of the four examined materials increase in the order of slag,fly ash,500℃ calcined gangue and untreated gangue. Moreover,the binding energies of Si 2p,Al 2p and O 1s of every Al-Si material have excellent correlation. By using the Al 2p binding energy and 27Al MAS NMR spectra,the coordination number of aluminum in slag is determined to be four,while that in gangue,is six. Based on the aforementioned discoveries,this paper presents a new effective method to evaluate the hydraulic activity of Al-Si materials by using the surface binding energies of silicon and alu-minum of Al-Si materials.

  9. Preparation and study of nanostructured TiAlSiN thin films

    Directory of Open Access Journals (Sweden)

    Jakab-Farkas L.

    2011-12-01

    Full Text Available TiAlSiN thin film coatings were deposited by DC reactive magnetron sputtering of TiAlSi target with 40 at.% Ti, 40 at.% Al and 20 at.% Si, performed in N2-Ar gas mixture. The sputtering power used in these experiments was controlled for 400 W. The bias voltage of the substrates was kept at -20 V DC and the temperature at 500 0C. All the samples were prepared with a constant flow rate of Ar and different nitrogen flow rates, which were selected from 1.25 sccm to 4.0 sccm. Nanostructured TiAlSiN coatings were developed on Si(100 and HSS substrates. Microstructure investigation of the coatings was performed by transmission electron microscopy investigation, structure investigation was performed by XRD analysis, and the mechanical properties of the coatings have been tested by ball-on-disk tribological investigation and micro-Vickers hardness measurements. In this paper will be shown that for optimized nitrogen concentration the microstructure of TiAlSiN coating evolve from a competitive columnar growth to a dendritic growth one with very fine nano-lamellae like morphology. The developed nanostructured TiAlSiN coatingshave hardness HV exceeding 40 GPa and show an increased abrasive wear resistance

  10. Electronic properties and superconductivity of rapidly quenched Al-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Chevrier, J.; Pavuna, D.; Cyrot-Lackmann, F.

    1987-12-15

    We present detailed studies of electronic properties of Al-Si alloys prepared in a nonequilibrium state by means of rapid solidification. The quenched alloys exhibit an enhanced superconducting transition temperature up to 6.2 K in an Al--Si 30 at. % alloy as well as an increased thermal slope of resistivity. Using differential scanning calorimetry, a large enthalpy variation (..delta..H = 4.1 kJ/mole for Al--Si 30 at. %) has been measured during the irreversible transition from the non- equilibrium state to the equilibrium one. This is mainly attributed to the energy difference between the metallic state of silicon atoms trapped in fcc aluminum matrix during quenching and the usual covalent state of silicon precipitates in an equilibrium state. This large energy difference is presented as the origin of a lattice instability which softens the phonon spectrum and gives rise to a stronger electron-phonon coupling. This appears to be a characteristic property of nonequilibrium Al-Si solid solutions, which is associated with the metallic state of silicon atoms. An interpretation of the T/sub c/ enhancement is proposed for both Al-Si and Al-Ge alloys based on the phonon softening in these nonequilibrium crystalline alloys.

  11. Fatigue characteristics and microcosmic mechanism of Al-Si-Mg alloys under multiaxial proportional loadings

    Science.gov (United States)

    Jiang, Xiao-Song; He, Guo-Qiu; Liu, Bing; Zhu, Zheng-Yu; Zhang, Wei-Hua

    2011-08-01

    With the increasing use of Al-Si-Mg alloys in the automotive industry, the fatigue performance of Al-Si-Mg alloy has become a major concern with regard to their reliability. The fatigue characteristics and microcosmic mechanism of an Al-Si-Mg alloy under multiaxial proportional loadings were investigated in this research. As low cycle fatigue life and material strengthening behavior are closely related, the effect of equivalent strain amplitude on the multiaxial fatigue properties was analyzed. Fatigue tests were conducted to determine the influence of equivalent strain amplitude on the multiaxial proportional fatigue properties. The fatigue life exhibits a stable behavior under multiaxial proportional loadings. The dislocation structures of the Al-Si-Mg alloy were observed by transmission electron microscopy (TEM). The dislocation structure evolution of the Al-Si-Mg alloy under multiaxial proportional loadings during low cycle fatigue develops step by step by increasing fatigue cycles. Simultaneously, the dislocation structure changes with the change in equivalent strain amplitude under multiaxial proportional loadings. The experimental evidence indicates that the multiaxial fatigue behavior and life are strongly dependent on the microstructure of the material, which is caused by multiaxial proportional loadings.

  12. Al-Si-Re Alloys Cast by the Rapid Solidification Process / Stopy Al-Si-Re Odlewane Metodą Rapid Solidification

    Directory of Open Access Journals (Sweden)

    Szymanek M.

    2015-12-01

    Full Text Available The aim of the studies described in this article was to present the effect of rare earth elements on aluminium alloys produced by an unconventional casting technique. The article gives characteristics of the thin strip of Al-Si-RE alloy produced by Rapid Solidification (RS. The effect of rare earth elements on structure refinement, i.e. on the size of near-eutectic crystallites in an aluminium-silicon alloy, was discussed. To determine the size of crystallites, the Scherrer X-ray diffraction method was used. The results presented capture relationships showing the effect of variable casting parameters and chemical composition on microstructure of the examined alloys. Rapid Solidification applied to Al-Si alloys with the addition of mischmetal (Ce, La, Ne, Pr refines their structure.

  13. Sn对Al-Si-Mg系合金的时效动力学分析%Effect of Sn on Ageing Kinetics of Al-Si-Mg Alloy

    Institute of Scientific and Technical Information of China (English)

    亓效刚; 刘峰; 王伟民

    2002-01-01

    Sn对Al-Si-Mg系合金的时效过程产生明显的影响,合金中加入Sn,若不进行时效处理,Sn作为夹杂降低合金的力学性能;若合金进行时效处理,Sn抑制Mg2Si沉淀相的聚集、长大,使其弥散分布,因而合金的力学性能有较大幅度的提高.运用Pashley时效动力学模型解释了Al-Si-Mg系合金的时效行为.用Lomer公式,通过计算,Al-Si-Mg系合金中加入微量元素Sn后,合金中的过剩空位浓度约为基体中过剩空位浓度的1/200,正是Sn与空位的较高结合能,抑制了MgSi沉淀相的粗大.

  14. AlSiTiN and AlSiCrN multilayer coatings: Effects of structure and surface composition on tribological behavior under dry and lubricated conditions

    Science.gov (United States)

    Faga, Maria Giulia; Gautier, Giovanna; Cartasegna, Federico; Priarone, Paolo C.; Settineri, Luca

    2016-03-01

    Nanocomposite coatings have been widely studied over the last years because of their high potential in several applications. The increased interest for these coatings prompted the authors to study the tribological properties of two nanocomposites under dry and lubricated conditions (applying typical MQL media), in order to assess the influence of the surface and bulk properties on friction evolution. To this purpose, multilayer and nanocomposite AlSiTiN and AlSiCrN coatings were deposited onto tungsten carbide-cobalt (WC-Co) samples. Uncoated WC-Co materials were used as reference. Coatings were analyzed in terms of hardness and adhesion. The structure of the samples was assessed by X-ray diffraction (XRD), while the surface composition was studied by XPS analysis. Friction tests were carried out under both dry and lubricated conditions using an inox ball as counterpart. Both coatings showed high hardness and good adhesion to the substrate. As far as the friction properties are concerned, in dry conditions the surface properties affect the sliding contact at the early beginning, while bulk structure and tribolayer formation determine the main behavior. Only AlSiTiN coating shows a low and stable coefficient of friction (COF) under dry condition, while the use of MQL media results in a rapid stabilization of the COF for all the materials.

  15. Influence of Nanosized Silicon Carbide on Dimensional Stability of Al/SiC Nanocomposite

    Directory of Open Access Journals (Sweden)

    S. M. Zebarjad

    2008-01-01

    Full Text Available This study concentrated on the role of particle size of silicon carbide (SiC on dimensional stability of aluminum. Three kinds of Al/SiC composite reinforced with different SiC particle sizes (25 μm, 5 μm, and 70 nm were produced using a high-energy ball mill. The standard samples were fabricated using powder metallurgy method. The samples were heated from room temperature up to 500∘C in a dilatometer at different heating rates, that is, 10, 30, 40, and 60∘C/min. The results showed that for all materials, there was an increase in length change as temperature increased and the temperature sensitivity of aluminum decreased in the presence of both micro- and nanosized silicon carbide. At the same condition, dimensional stability of Al/SiC nanocomposite was better than conventional Al/SiC composites.

  16. PREPARATION OF SEMI-SOLID AlSi7Mg ALLOY SLURRY

    Institute of Scientific and Technical Information of China (English)

    Z.D. Zhao; W.M. Mao

    2008-01-01

    In this article, semi-solid AlSi7Mg alloy slurry was prepared by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature and stirring power on the microstructure of the AlSi7Mg alloy slurry were studied. The results showed that the semi-solid AlSi7Mg alloy slurry, 127 mm in diameter, could be prepared by using the low superheat pouring and weak electromagnetic stirring technology and this new technology could save energy and make the pouring process convenient. When the liquid AlSi7Mg alloy was poured at 650°C or 630°C, the solidified microstructure of the AlSi7Mg alloy slurry, prepared by weak electromagnetic stirring, was remarkably improved when compared with that of the slurry prepared without stirring. The primary α-Al grains appeared rosette-like or spherical. When the pouring temperature was decreased, the shape of the primary α-Al grains gradually changed from dendritic-like grains to spherical grains. When the pouring temperature was appropriately increased, that is, raised to a certain superheat, the pouring processbecame easier and an ideal spherical microstructure of the AlSiTMg alloy slurry, prepared by weak electromagnetic stirring, could also be obtained. In this experiment,when the stirring power was 0.36 kW, the optimized pouring temperature parameter was 630°C. When the AISiTMg alloy slurry was prepared by low superheat pouring and weak electromagnetic stirring, the pouring temperature was 630°C. Increasing the stirring power appropriately could gain better spherical primary α-Al grains, but if the stirring power was increased to a certain value, the shape of the primary α-Al grains did not improve further. In this experiment, the optimized stirring power parameter was 0.36 kW.

  17. Creep behaviour of a casting titanium carbide reinforced AlSi12CuNiMg piston alloy at elevated temperatures; Hochtemperaturkriechverhalten der schmelzmetallurgisch hergestellten dispersionsverstaerkten Kolbenlegierung AlSi12CuNiMg

    Energy Technology Data Exchange (ETDEWEB)

    Michel, S.; Scholz, A. [Zentrum fuer Konstruktionswerkstoffe, TU Darmstadt (Germany); Tonn, B. [Institut fuer Metallurgie, TU Clausthal (Germany); Zak, H.

    2012-03-15

    This paper deals with the creep behaviour of the titanium carbide reinforced AlSi12CuNiMg piston alloy at 350 C and its comparison to the conventional AlSi12Cu4Ni2MgTiZr piston alloy. With only 0,02 vol-% TiC reinforcement the creep strength and creep rupture strength of the AlSi12CuNiMg piston alloy are significantly improved and reach the level of the expensive AlSi12Cu4Ni2MgTiZr alloy. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  18. A Novel TiNi/AlSi Composite with High Strength and High Damping Capacity

    Institute of Scientific and Technical Information of China (English)

    Shuwei LIU; Xiuyan LI; Desheng YAN; Haichang JIANG; Lijian RONG

    2008-01-01

    A novel TiNi/AlSi composite with high compressive strength and high damping capacity was obtained by infiltrating Al-12%Si alloy into porous TiNi alloy.It had been found that the high compressive strength (440 MPa) of TiNi/AlSi composite is due to the increase of effective carrying area after infiltrating Al-12%Si alloy,while the high damping capacity is contributed to TiNi carcass,Al-12%Si filling material and micro-slipping at the interface.

  19. Effect of sol gel coating on wettability and interfacial reaction in Al-SiC MMC

    DEFF Research Database (Denmark)

    Liu, Y.L.; Breivik, T.R.; Kindl, B.

    1995-01-01

    The control of the interfacial reaction between the matrix and the SiC reinforcement in Al-SiC metal matrix composites (MMCs) is an important production parameter. The reaction causes degradation of the reinforcement, weakening of the interface and a decrease of the mechanical properties of the p...

  20. Separation Mechanism of Primary Silicon from Hypereutectic Al-Si Melts Under Alternating Electromagnetic Fields

    Science.gov (United States)

    Xue, Haiyang; Lv, Guoqiang; Ma, Wenhui; Chen, Daotong; Yu, Jie

    2015-07-01

    Solar grade silicon (SOG-Si) and hypereutectic Al-Si alloys with low silicon (silicon composition below 25 pct) can be successfully obtained by separation of hypereutectic Al-Si alloy with high silicon (silicon composition above 30 pct) under an alternating electromagnetic field after post-processing. To explore the separation mechanism in detail, experiments were conducted in this study using a high-frequency induction furnace with different pulling conditions of the crucible which is loaded with Al-45 wt pct Si melt. Results demonstrate that the separation of hypereutectic Al-Si alloy is feasible through either a pull-up or drop-down process. The height of each separation interface between the compact and sparse parts of the primary silicon decrease as the pull-up distance rose. When the pulling rate is very low, resultant morphologies of compact primary silicon are rounded and polygonal, allowing for more effective separation of the primary silicon. A novel physical model is presented here based on the experimental results and simulation. The model can be used to effectively describe the separation mechanism of primary silicon from hypereutectic Al-Si melts under alternating electromagnetic fields.

  1. Characteristics and Microstructure of a Hypereutectic Al-Si Alloy Powder by Ultrasonic Gas Atomization Process

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A hypereutectic Al-Si alloy powder was prepared by ultrasonic gas atomization process. The morphologies, microstructure and phase constituent of the alloy powder were studied. The results showed that powder of the alloy was very fine and its rnicrostructure was mainly consisted of Si crystals plus intermetallic compound Al9FeSi3, which were. very fine and uniformly distributed.

  2. Microstructure and abrasive wear studies of laser clad Al-Si/SiC composite coatings

    NARCIS (Netherlands)

    Anandkumar, R.; Colaco, R.; Ocelik, V.; De Hosson, J. Th. M.; Vilar, R.; Gyulai, J; Szabo, PJ

    2007-01-01

    Surface coatings of Al-Si/SiC metal-matrix composites were deposited on Al-7 wt. % Si alloy substrates by laser cladding. The microstructure of the coatings was characterized by optical microscopy, scanning electron microscopy (SEM) and X-ray diffraction (XRD). The microstructure of the coating mate

  3. Microstructure and wear studies of laser clad Al-Si/SiC(p) composite coatings

    NARCIS (Netherlands)

    Anandkumar, R.; Almeida, A.; Colaco, R.; Vilar, R.; Ocelik, V.; De Hosson, J. Th. M.

    2007-01-01

    Coatings of a composite material consisting of an Al-Si matrix reinforced with SiC particles were produced by laser cladding on UNS A03560 cast Al-alloy substrates from mixtures of powders of Al-12 wt.% Si alloy and SiC. The influence of the processing parameters on the microstructure and abrasive w

  4. Laser cladding of Al-Si/SiC composite coatings : Microstructure and abrasive wear behavior

    NARCIS (Netherlands)

    Anandkumar, R.; Almeida, A.; Vilar, R.; Ocelik, V.; De Hosson, J.Th.M.

    2007-01-01

    Surface coatings of an Al-Si-SiC composite were produced on UNS A03560 cast Al-alloy substrates by laser cladding using a mixture of powders of Al-12 wt.% Si alloy and SiC. The microstructure of the coatings depends considerably on the processing parameters. For a specific energy of 26 MJ/m2 the mic

  5. Weld microstructure in cast AlSi9/SiC(p metal matrix composites

    Directory of Open Access Journals (Sweden)

    J. Wysocki

    2009-04-01

    Full Text Available Welded joint in cast AlSi9/SiC/20(p metal matrix composite by manual TIG arc welding using AlMg5 filler metal has been described inhis paper. Cooling curves have been stated, and the influence in distribution of reinforced particles on crystallization and weldmicrostructure. Welded joint mechanical properties have been determined: hardness and tensile.

  6. Study of the Structural and Mechanical Properties of Nanocrystalline TiAlSiN Gradient Coatings

    NARCIS (Netherlands)

    Cholakova, T.; Chitanov, V.; Chaliampalias, D.; Kolaklieva, L.; Kakanakov, R.; Bahchedjiev, Ch.; Petkov, N.; Pashinski, Ch.; Vourlias, G.; Vouroutzis, N.; Polychroniadis, E.; Wang, Y.; Meletis, E. I.

    2014-01-01

    A study of the structural and mechanical properties of nanocrystalline TiAlSiN gradient coatings deposited by cathodic arc deposition techniques at 500 degrees C and post-annealed at 525 degrees C is presented. Analysis of the coatings, chemical composition and microstructure revealed that the coati

  7. Crystallographic Characteristic of Intermetallic Compounds in Al-Si-Mg Casting Alloys Using Electron Backscatter Diffraction

    Institute of Scientific and Technical Information of China (English)

    ZOU Yongzhi; XU Zhengbing; HE Juan; ZENG Jianmin

    2010-01-01

    The Al-Si-Mg alloy which can be strengthened by heat treatment is widely applied to the key components of aerospace and aeronautics. Iron-rich intermetallic compounds are well known to be strongly influential on mechanical properties in Al-Si-Mg alloys. But intermetallic compounds in cast Al-Si-Mg alloy intermetallics are often misidentified in previous metallurgical studies. It was described as many different compounds, such as AlFeSi, Al8Fe2Si, Al5(Fe, Mn)3Si2 and so on. For the purpose of solving this problem, the intermetallic compounds in cast Al-Si alloys containing 0.5% Mg were investigated in this study. The iron-rich compounds in Al-Si-Mg casting alloys were characterized by optical microscope(OM), scanning electron microscope(SEM), energy dispersive X-ray spectrometer(EDS), electron backscatter diffraction(EBSD) and X-ray powder diffraction(XRD). The electron backscatter diffraction patterns were used to assess the crystallographic characteristics of intermetallic compounds. The compound which contains Fe/Mg-rich particles with coarse morphologies was Al8FeMg3Si6 in the alloy by using EBSD. The compound belongs to hexagonal system, space group P2m, with the lattice parameter a=0.662 nm, c=0.792 nm. The β-phase is indexed as tetragonal Al3FeSi2, space group I4/mcm, a=0.607 nm and c=0.950 nm. The XRD data indicate that Al8FeMg3Si6 and Al3FeSi2 are present in the microstructure of Al-7Si-Mg alloy, which confirms the identification result of EBSD. The present study identified the iron-rich compound in Al-Si-Mg alloy, which provides a reliable method to identify the intermetallic compounds in short time in Al-Si-Mg alloy. Study results are helpful for identification of complex compounds in alloys.

  8. In Situ Synthesis of Al-Si-Cu Alloy During Brazing Process and Mechanical Property of Brazing Joint

    Directory of Open Access Journals (Sweden)

    LONG Wei-min

    2016-06-01

    Full Text Available The Al-Si-Cu alloy system is considered to be a promising choice of filler metal for aluminium alloys brazing due to its high strength and low melting point. The greatest obstacle is its lack of plastic forming ability and being difficult to be processed by conventional methods. This disadvantage is ascribed to the considerable amount of brittle CuAl2 intermetallic compound which forms when alloy composition is around the ternary eutectic point. In order to overcome this deficiency, authors of this article proposed to synthesize Al-Si-Cu filler metal by using in situ synthesis method, and the structure and properties of brazing joints were studied. The results show that AlSi alloy is used as the wrap layer, and CuAl alloy is used as the powder core in the composite brazing wire, the two alloys have similar melting points. The machinability of the composite brazing wire is much superior to the traditional Al-Si-Cu filler metal. During the induction brazing of 3A21 alloy, when using AlSi-CuAl composite filler wire, AlSi and CuAl alloys melt almost simultaneously, then after short time holding, Al-Si-Cu braze filler is obtained, the brazing seam has uniform composition and good bonding interface, also, the shearing strength of the brazing joints is higher than the joint brazed by conventional Al-Si-Cu filler metal.

  9. Oxidation of the AlSi6Cu4 alloy and AlSi6Cu4-graphite particles composite at the elevated temperatures

    Directory of Open Access Journals (Sweden)

    J. Pozar

    2009-04-01

    Full Text Available Oxidation process of AlSi6Cu4 alloy as a composite matrix and of AlSi6Cu4 / 8 vol.% graphite particles composite was investigated.Composites were prepared by stirring method for suspension obtaining and by squeeze casting of the suspension. This process wasexamined by testing specimens annealed during up to 1000 hours at 573 K and 673 K in air atmosphere. The average oxidation state, oxidelayer thickness and hardness of examined materials were measured during the annealing time. Obtained results imply the followingconclusions: composite oxidizes faster than matrix alloy at both temperatures what is confirmed by higher weight gains and thicker oxide layer. The rate of oxidation of both materials gradually slows down at both temperatures. At initial stages of annealing at 673 K the rate of oxidation of both materials is much higher than that at 573 K. With increasing time of annealing the ratio of oxidation rate at 673 K to the one at 573 K comes down. Hardness of the composite is lower than that of matrix alloy before and during annealing at both temperatures. Drop in hardness at both 573 K and 673 K is the same for matrix and composite, and after about 100 hours the hardness no longer descents.

  10. Seebeck effect of Fe-Al-Si alloy and low temperature thermoelectric properties; Fe-Al-Si gokin no zebekku koka oyobi teion netsugen netsuden henkan tokusei

    Energy Technology Data Exchange (ETDEWEB)

    Shoda, M.; Kado, M.; Tsuji, T.; Suzuki, R.; Ono, K. [Kyoto University, Kyoto (Japan)

    1998-01-25

    In order to effectively utilize unutilized low heat sources, the Seebeck effect and thermoelectric conversion properties of Fe-Al-Si alloy were investigated. Unutilized low heat sources at temperatures below 600 K have small energy density generally, but their total quantity is huge. High-efficiency electric power conversion utilizing these sources is expected. In order to realize the expectation, thermoelectric power generation is most suitable as a direct energy conversion system of completely stand-still type having no driving components. The Fe-Al-Si based alloy was taken as the object of the investigation because of the following reasons: Al and Si have a wide solid solution range against Fe, and 3p orbit electrons of the respective elements are expected capable of changing the electron state in the vicinity of Fermi surface, which is characteristic to the transition metal, Fe; the alloy has electric conductivity even under low temperatures including subzero temperatures; and the alloy elements are affluently available as natural resources. Measurements were performed on such thermoelectric properties as Seebeck coefficient (thermoelectric capability), electric conductivity and thermal conductivity. As a result, it was made clear that iron-based p-n junction elements in Fe13%Al12%Si(p)-Fe12%Al(n) exhibit highest performance in this alloy system. In addition, the measured thermoelectric properties were used to derive the theoretical surface specific output power of the elements. 9 refs., 10 figs., 1 tab.

  11. Production of Al-Si-SiCp cast composites by injection of low-energy ball-milled Al-SiCp powder into the melt

    Science.gov (United States)

    Ghahremanian, Mohsen; Niroumand, Behzad; Panjepour, Masoud

    2012-02-01

    Al-7wt%Si-10wt%SiCp composite with uniformly distributed reinforcement particles with the average size of about 3 microns was produced by a special compocasting method in which the reinforcement was injected into the melt in the form of particulate Al-SiCp composite powder instead of SiCp. The effects of the reinforcement addition form, the solid fraction of primary alpha-aluminum particles at pouring, and stirring speed on the incorporation of reinforcement particles into the matrix were investigated. Injection of particulate Al-SiCp composite led to improved incorporation and dispersion and reduced size of SiCp. Casting from the semisolid state significantly improved the incorporation of SiCp into the matrix. The optimal solid fraction of primary alpha-aluminum particles to achieve a reasonable combination of reinforcement incorporation and fluidity of the composite slurry was recognized to be about 0.1. The incorporation of SiCp was improved by increasing the stirring speed up to 500 rpm and then gradually decreased.

  12. Optical investigations of AlSi-SiC composites subjected to laser CO 2 annealing

    Science.gov (United States)

    Jaglarz, Janusz; Grabowski, Andrzej

    2010-10-01

    The optical study of the AlSi/SiC composite materials before and after laser annealing has been performed. They concerned total and diffuse reflectance measurements obtained by the means of integrating sphere in the spectral range 250-2500 nm, measurements of intensity of scattered light as a function of scattering angle ( BRDF method) and ellipsometric measurements performed in the range 190-1700 nm. For determination of optical constants, the Kramers-Krönig dispersion relation has been applied. Obtained results had great differences of optical properties alloys before and after laser annealing. For investigated composites roughness and correlation lengths of studied surfaces have been determined. Moreover, optical measurements allowed concluding the light scattering being a result of interaction of light with surface topography and material scattering appeared due to variation of optical constants on surfaces of AlSi/SiC composites.

  13. Solidification, growth mechanisms, and associated properties of Al-Si and magnesium lightweight casting alloys

    Energy Technology Data Exchange (ETDEWEB)

    Hosch, Timothy [Iowa State Univ., Ames, IA (United States)

    2010-01-01

    Continually rising energy prices have inspired increased interest in weight reduction in the automotive and aerospace industries, opening the door for the widespread use and development of lightweight structural materials. Chief among these materials are cast Al-Si and magnesium-based alloys. Utilization of Al-Si alloys depends on obtaining a modified fibrous microstructure in lieu of the intrinsic flake structure, a process which is incompletely understood. The local solidification conditions, mechanisms, and tensile properties associated with the flake to fiber growth mode transition in Al-Si eutectic alloys are investigated here using bridgman type gradient-zone directional solidification. Resulting microstructures are examined through quantitative image analysis of two-dimensional sections and observation of deep-etched sections showing three-dimensional microstructural features. The transition was found to occur in two stages: an initial stage dominated by in-plane plate breakup and rod formation within the plane of the plate, and a second stage where the onset of out-of-plane silicon rod growth leads to the formation of an irregular fibrous structure. Several microstructural parameters were investigated in an attempt to quantify this transition, and it was found that the particle aspect ratio is effective in objectively identifying the onset and completion velocity of the flake to fiber transition. The appearance of intricate out-of-plane silicon instability formations was investigated by adapting a perturbed-interface stability analysis to the Al-Si system. Measurements of silicon equilibrium shape particles provided an estimate of the anisotropy of the solid Si/liquid Al-Si system and incorporation of this silicon anisotropy into the model was found to improve prediction of the instability length scale. Magnesium alloys share many of the benefits of Al-Si alloys, with the added benefit of a 1/3 lower density and increased machinability. Magnesium castings

  14. Preparation of Al/Si functionally graded materials using ultrasonic separation method

    Directory of Open Access Journals (Sweden)

    Zhang Zhongtao

    2008-08-01

    Full Text Available Functionally graded materials (FGM have been widely used in many industries such as aerospace, energy and electronics. In this experimental study of fabricating FGM, an approach was developed to prepare Al/Si FGM using power ultrasonic separation method. Material sample with continuously changing composition and performance/properties was successfully produced. Results showed that the microstructure of the FGM sample transited, from its top to bottom, from the hypereutectic structure with a large quantity of primary Si gradually to the eutectic, and fi nally to the hypoeutectic with numerous primary Al dendrites. The distribution of primary Si and microhardness of the FGM sample also presented graded characteristics, resulting that the wear resistance of the FGM sample decreased from top to bottom. Preliminary discussion was made on the mechanism of the formation of Al/Si FGM.

  15. Preparation of Al/Si functionally graded materials using ultrasonic separation method

    Institute of Scientific and Technical Information of China (English)

    Zhang Zhongtao; LI Tingju; Yue Hongyun; Zhang Jian; Li Jie

    2008-01-01

    Functionally graded materials (FGM) have been widely used in many industries such as aerospace, energy and electronics. In this experimental study of fabricating FGM, an approach was developed to prepare Al/Si FGM using power ultrasonic separation method. Material sample with continuously changing composition and performance/properties was successfully produced. Results showed that the microstructure of the FGM sample transited, from its top to bottom, from the hypereutectic structure with a large quantity of primary Si gradually to the eutectic, and finally to the hypoeutectic with numerous primary AI dendrites. The distribution of primary Si and microhardness of the FGM sample also presented graded characteristics, resulting that the wear resistance of the FGM sample decreased from top to bottom. Preliminary discussion was made on the mechanism of the formation of Al/Si FGM.

  16. Effect of erbium on properties and microstructure of Al-Si eutectic alloy

    Institute of Scientific and Technical Information of China (English)

    XING

    2010-01-01

    Eutectic Al-12.6 wt.%Si alloys with various contents of the rare earth dement Er were prepared by the conventional casting technique.The effect of Er on the microstructure and properties of the eutectic Al-Si alloys was investigated using optical microscopy,scanning electron microscopy as well as the friction and wear tests.It was found that the addition of Er obviously improved the anti-wear properties,and reduced the friction coefficient of the alloys.The appropriate addition of Er would change the size and shape of the eutectic silicon,and thereby refine the microstructure of the Al-Si alloys.The refinement mechanism was also discussed.

  17. Gradual solution heat treatment of AlSiCuMg cast alloys

    Institute of Scientific and Technical Information of China (English)

    WANG Guiqing; BIAN Xiufang; ZHANG Junyan

    2003-01-01

    The microstmcture characteristics of AlSiCuMg cast alloys were studied with different Cu content and the gradual solution treatment by DSC, SEM, TEM and mechanical method. The melting point of α(Al) + Si decreases and polynary eutectic phases with low melting point form with increase of Cu content. Gradual solution treatment includes two steps:solution treating near the melting point of polynary eutectic phase to take it dissolve first, and then increasing solution temperature to take the remainder copper intermetallics dissolved into o(Al). Grain boundaries melting can be avoided by gradual solution treatment, even the maximum solution temperature is above final solidification point, and the age hardening response increases correspondingly.

  18. Solid-state combinatorial chemistry of Eu(2+)-doped Sr-Al-Si-O-N phosphors.

    Science.gov (United States)

    Park, Ji Woong; Han, Bo Yong; Kim, Yang Soo; Sohn, Kee-Sun

    2013-06-01

    Sr-Al-Si-O-N composition space was screened by a solid state combinatorial chemistry. For this sake, powder mixtures of Sr3N2, alpha-Si3N4, AIN and Eu3N2 was fired at 1500 degrees C-1900 degrees C for 2 h under 1.0 Mpa N2 using a gas pressurized sintering (GPS) furnace. The resultant phosphors were phase-identified, and the photo luminescence was examined. The Sr-Al-Si-O-N phosphors are blue-Green and orange in color and emit in the region of 520-630 nm depending on synthesized temperature. Considering an intense excitation band in blue LED and emission band, these materials can be used as novel conversion phosphor for White-LEDs, if the luminance was improved.

  19. Effect of Sc on Precipitation Hardening of AlSi6Mg Alloy

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The effect of Sc on precipitation hardening of AlSi6Mg was studied. Zr was previously reported that it increased the effectiveness of Sc in wrought aluminum in many areas so Zr was also used together with Sc in this study.Different levels of Sc and Zr additions were added to AlSi6Mg before casting in the permanent mold. The samples were precipitation hardened at different aging temperatures and for various aging time before testing for tensile strength and hardness. It was found that Sc addition into Al6SiMg can change its response to age hardening. Additions of Sc and Sc with Zr increased both yield strength and hardness for both aging temperatures. In addition, Sc was found to modify eutectic Si to obtain fibrous morphology. This effect of Sc on eutectic silicon modification has never been reported before.

  20. Low Cost Al-Si Casting Alloy As In-Situ Composite for High Temperature Applications

    Science.gov (United States)

    Lee, Jonathan A.

    2000-01-01

    A new aluminum-silicon (Al-Si) alloy has been successfully developed at NASA- Marshall Space Flight Center (MSFC) that has significant improvement in tensile and fatigue strength at elevated temperatures (500 F-700 F). The alloy offers a number of benefits such as light weight, high hardness, low thermal expansion and high surface wear resistance. In hypereutectic form, this alloy is considered as an in-situ Al-Si composite with tensile strength of about 90% higher than the auto industry 390 alloy at 600 F. This composite is very economically produced by using either conventional permanent steel molds or die casting. The projected material cost is less than $0.90 per pound, and automotive components such as pistons can be cast for high production rate using conventional casting techniques with a low and fully accounted cost. Key Words: Metal matrix composites, In-situ composite, aluminum-silicon alloy, hypereutectic alloy, permanent mold casting, die casting.

  1. Production and mechanical properties of Al-SiC metal matrix composites

    Science.gov (United States)

    Karvanis, K.; Fasnakis, D.; Maropoulos, A.; Papanikolaou, S.

    2016-11-01

    The usage of Al-SiC Metal Matrix Composites is constantly increasing in the last years due to their unique properties such as light weight, high strength, high specific modulus, high fatigue strength, high hardness and low density. Al-SiC composites of various carbide compositions were produced using a centrifugal casting machine. The mechanical properties, tensile and compression strength, hardness and drop-weight impact strength were studied in order to determine the optimum carbide % in the metal matrix composites. Scanning electron microscopy was used to study the microstructure-property correlation. It was observed that the tensile and the compressive strength of the composites increased as the proportion of silicon carbide became higher in the composites. Also with increasing proportion of silicon carbide in the composite, the material became harder and appeared to have smaller values for total displacement and total energy during impact testing.

  2. Optimization of Squeeze Parameters and Modification of AlSi7Mg Alloy

    Directory of Open Access Journals (Sweden)

    A. Zyska

    2013-04-01

    Full Text Available The paper present the examination results concerning mechanical properties of castings made of AlSi7MG alloy in correlation both with the most significant squeeze casting parameters and with the modification treatment. Experiments were planned and held according to the 23 factorial design. The regression equations describing the influence of the squeeze pressure, the mould temperature, and the quantity of strontium modifier on the strength and elongation of the examined alloy were obtained. It was found that the main factor controlling the strength increase is the squeeze pressure, while the plasticity (A5 of the alloy is affected most advantageously by modification. The application of modification treatment in squeeze casting technology enables for production of the slab-type castings made of AlSi7Mg alloy exhibiting strength at the level of 230 MPa and elongation exceeding 14%.

  3. Optimization of Machining Characteristics for Al/SiCp Composites using ANN/GA

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The present work is focused on optimization of machining characteristics of Al/SiCp composites. The machiningcharacteristics such as specific energy, tool wear and surface roughness were studied. The parameters such asvolume fraction of SiC, cutting speed and feed rate were considered. Artificial neural networks (ANN) was usedto train and simulate the experimental data. Genetic algorithms (GA) was interfaced with ANN to optimize themachining conditions for the desired machining characteristics. Validation of optimized results was also performedby confirmation experiments.

  4. Microstructural properties and cavitation behavior of hypereutectic Al-Si alloy obtained by rheocasting process

    OpenAIRE

    Ćosić, Milena; Dojčinović, Marina; Aćimović-Pavlović, Zagorka

    2014-01-01

    The purpose of this study was to investigate possible application of AlSi alloy produced by rheocasting process in cavitation conditions. A rheocasting process was used to refine the as cast microstructure and improve the mechanical properties of Al18wt%Si alloy. Mechanical stirring was applied to the melt for different stirring time: 60,120,180s at different temperatures below the liquidus temperature of the alloy, using different stirring speed values, before pouring into a metallic mould. ...

  5. Effect of electric current on the cast microstructure of Al-Si alloy

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    Effect of electric current on the cast microstructure of Al-Si alloy was investigated. It was found that the microstructure of Al-Si alloy was refined as the electric current was applied during solidification. When DC (Direct Current) was applied in solidification, the eutectic Si flakes are similar to those solidified without current, but its length was shortened and its distribution was changed ,with most of the Si flakes arrange in the radial direction, because of the electromagnetic force that resulted from the DC. On the other hand, when AC (Alternating Current) was applied during the solidification of Al-Si alloy, most of the minute hooks on the silicon flakes that were found under DC or without any applied current were broken into small silicon particles. Through silicon concentration measurement by electron microprobe, it was found that the silicon content in the α-Al matrix increased with the current application during solidification, and the effect is more obvious when AC was applied.

  6. Application of CX-type modifiers in Al-Si alloys

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The modification effect of CX-type (CX means the modifiers that have long effective term) modifiers applied in ZL108and ZL104 Al-Si alloys has been studied in detail. The results show that the morphologies of the eutectic silicon and the primary sili-con can be modified and refined simultaneously. The modification effect acts quickly and can maintain a period of 8 h by the CX-type modifiers. The CX-type modifiers increase the mechanical properties of Al-Si alloys and improve the service properties of ma-chine parts made of Al-Si alloys (such as piston and cylinder etc.). In modifying processes, the amount of the addition of CX-typemodifiers is smaller than that of any other modifiers, and the modifying procedures are simple. There are no smoke, no dust, and noirritant smell in modifying processes using CX-type modifiers. Therefore, the CX-type modifiers have advantages in economy andenvironment protection.

  7. Effects of La and Ce Addition on the Modification of Al-Si Based Alloys

    Directory of Open Access Journals (Sweden)

    Emad M. Elgallad

    2016-01-01

    Full Text Available This study focuses on the effects of the addition of rare earth metals (mainly lanthanum and cerium on the eutectic Si characteristics in Al-Si based alloys. Based on the solidification curves and microstructural examination of the corresponding alloys, it was found that addition of La or Ce increases the alloy melting temperature and the Al-Si eutectic temperature, with an Al-Si recalescence of 2-3°C, and the appearance of post-α-Al peaks attributed to precipitation of rare earth intermetallics. Addition of La or Ce to Al-(7–13% Si causes only partial modification of the eutectic Si particles. Lanthanum has a high affinity to react with Sr, which weakens the modification efficiency of the latter. Cerium, however, has a high affinity for Ti, forming a large amount of sludge. Due to the large difference in the length of the eutectic Si particles in the same sample, the normal use of standard deviation in this case is meaningless.

  8. Influence of Lanthanum on Solidification, Microstructure, and Mechanical Properties of Eutectic Al-Si Piston Alloy

    Science.gov (United States)

    Ahmad, R.; Asmael, M. B. A.

    2016-07-01

    The effects of Lanthanum (La) concentration on the solidification parameters of the α-Al, Al-Si, and Al-Cu phases and on the microstructure, tensile, and hardness properties of eutectic Al-Si-Cu-Mg alloy were systematically investigated. The solidification parameters were examined using computer-aided cooling curve thermal analysis (CA-CCTA). The cooling curve and microstructure analysis showed that La altered the Si structure. The nucleation and growth temperatures of eutectic Si decreased when 0.3 wt.% La was added, and a high depression temperature was obtained with 1.0 wt.% La. High amounts of La considerably modified the Si structure and decreased the area and aspect ratio by 69.9 and 51%, respectively. The thermal analysis result recorded a faster freezing time with the La addition and a 36% alteration in the secondary dendrite arm spacing. Two secondary or ternary La-rich intermetallic phases were formed with needle- and plate-like structures. Furthermore, the mechanical properties were investigated by hardness and tensile tests with different La concentrations. The addition of small amounts of La (0.1 wt.%) significantly improved the ultimate tensile strength and quality index of the Al-Si-Cu-Mg alloy. In addition, the hardness value of Al-11Si-Cu increased by 7-8% with the increasing amount of La added.

  9. Hypereutectic AlSi Alloy: Gathering of 3D Microstructure Data

    Science.gov (United States)

    Schaberger-Zimmermann, E.; Mathes, M.; Zimmermann, G.

    2016-08-01

    Hypereutectic and eutectic AlSi-base alloys find frequent application in casting automotive components. The properties of this type of alloy depend significantly on their solidification microstructure, especially the size, shape, and distribution of primary and eutectic silicon. The serial sectioning technique was applied for determining the three-dimensional (3D) microstructure of an Al-18wt.%Si alloy. For clear identification of both the larger primary Si particles grown in the melt and the fine lamellar eutectic Si, a series of two-dimensional equidistant cross sections were metallographically prepared. The microstructure in these cross sections was detected and observed at high resolution using a light microscope. The images were stored in a digital library. The 3D reconstruction of primary Si particles and AlSi eutectic was achieved through the application of various software tools. This provided data about the faceted growth behavior of octahedral Si particles and feathery eutectic Si. The image stack was also imported to hierarchical data format (version 5) (HDF5) open source format, thus, enabling availability of the 3D image data to the wider community. In this way, 3D reconstructions of this kind can contribute to a greater understanding of processing/microstructure property relationships in hypereutectic AlSi alloys.

  10. Investigation of hard gradient PVD (Ti,Al,SiN coating

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2007-10-01

    Full Text Available Purpose: Investigation of gradient coating of (Ti,Al,SiN deposited on the Al2O3+SiC(woxide ceramics substrate by cathodic arc evaporation CAE-PVD method.Design/methodology/approach: Structure of substrate and coating was investigated with use of scanning electron microscopy (SEM. The X-Ray Photoelectron Spectrometry (XPS examination was carried out for proving the gradient character of the (Ti,Al,SiN coating. The investigation includes also microhardness and roughness tests of the deposited coating and used substrate; The Ra surface roughness parameter measurements were made on confocal microscope.Findings: Gradient structure and main properties of the investigated materials were introduced. It has been stated, that properties of the oxide tool ceramic with gradient (Ti,Al,SiN coating increase in comparison with uncoated material.Practical implications: Depositing the wear resistant gradient coating onto the Al2O3+SiC(woxide tool ceramic results in a significant increase of the surface layer microhardness, contributing most probably in this way in machining to the decrease of the wear intensity of cutting tools’ flanks made from the Al2O3+SiC(woxide tool ceramic.Originality/value: Functionally gradient coating form is a new class of structures in which the microstructure and properties vary gradually from the surface to the interior of the material.

  11. The influence of chemical composition on the properties and structure Al-Si-Cu(Mg alloys

    Directory of Open Access Journals (Sweden)

    M. Kaczorowski

    2007-04-01

    Full Text Available The mechanical properties of different chemical composition AlSiCuMg type cast alloys after precipitation hardening are presented. The aim of the study was to find out how much the changes in chemistry of aluminum cast alloys permissible by EN-PN standards may influence the mechanical properties of these alloys. Eight AlSi5Cu3(Mg type cast alloys of different content alloying elements were selected for the study. The specimens cut form test castings were subjected to precipitation hardening heat treatment. The age hardened specimens were evaluated using tensile test, hardness measurements and impact test. Moreover, the structure investigation were carried out using either conventional light Metallography and scanning (SEM and transmission (TEM electron microscopy. The two last methods were used for fractography observations and precipitation process observations respectively. It was concluded that the changes in chemical composition which can reach even 2,5wt.% cause essential differences of the structure and mechanical properties of the alloys. As followed from quantitative evaluation and as could be predicted theoretically, copper and silicon mostly influenced the mechanical properties of AlSi5Cu3(Mg type cast alloys. Moreover it was showed that the total concentration of alloying elements accelerated and intensifies the process of decomposition of supersaturated solid solution. The increase of Cu and Mg concentration increased the density of precipitates. It increases of strength properties of the alloys which are accompanied with decreasing in ductility.

  12. Nano-Crystallization of High-Entropy Amorphous NbTiAlSiWxNy Films Prepared by Magnetron Sputtering

    Directory of Open Access Journals (Sweden)

    Wenjie Sheng

    2016-06-01

    Full Text Available High-entropy amorphous NbTiAlSiWxNy films (x = 0 or 1, i.e., NbTiAlSiNy and NbTiAlSiWNy were prepared by magnetron sputtering method in the atmosphere of a mixture of N2 + Ar (N2 + Ar = 24 standard cubic centimeter per minute (sccm, where N2 = 0, 4, and 8 sccm. All the as-deposited films present amorphous structures, which remain stable at 700 °C for over 24 h. After heat treatment at 1000 °C the films began to crystalize, and while the NbTiAlSiNy films (N2 = 4, 8 sccm exhibit a face-centered cubic (FCC structure, the NbTiAlSiW metallic films show a body-centered cubic (BCC structure and then transit into a FCC structure composed of nanoscaled particles with increasing nitrogen flow rate. The hardness and modulus of the as-deposited NbTiAlSiNy films reach maximum values of 20.5 GPa and 206.8 GPa, respectively. For the as-deposited NbTiAlSiWNy films, both modulus and hardness increased to maximum values of 13.6 GPa and 154.4 GPa, respectively, and then decrease as the N2 flow rate is increased. Both films could be potential candidates for protective coatings at high temperature.

  13. Testing phase changes in Al-Si alloys with application of thermal analysis and differential calorimetric analysis

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2013-10-01

    Full Text Available The paper presents enthalpy of melting and solidification of casting aluminium alloys AlSi6, AlSi12 and AlSi18 during heating and cooling. Calorimetric measurements preceded by tests of thermal analysis ATD were conducted on high-temperature scanning calorimeter multi HTC. A direct method was used for determining parameters of hightemperature processes and enthalpies occurring in phase changes. This method allowed for precise determining of endothermic and exothermic phase changes and, on their basis, the characteristic parameters of solidification necessary to assess the thermal endurance were marked.

  14. Biomorphous SiSiC/Al-Si ceramic composites manufactured by squeeze casting: microstructure and mechanical properties

    Energy Technology Data Exchange (ETDEWEB)

    Zollfrank, C.; Travitzky, N.; Sieber, H.; Greil, P. [Department of Materials Science, Glass and Ceramics, University of Erlangen-Nuernberg (Germany); Selchert, T. [Advanced Ceramics Group, Technical University of Hamburg-Harburg (Germany)

    2005-08-01

    SiSiC/Al-Si composites were fabricated by pressure-assisted infiltration of an Al-Si alloy into porous biocarbon preforms derived from the rattan palm. Al-Si alloy was found in the pore channels of the biomorphous SiSiC preform, whereas SiC and carbon were present in the struts. The formation of a detrimental Al{sub 4}C{sub 3}-phase was not observed in the composites. A bending strength of 200 MPa was measured. The fractured surfaces showed pull-out of the Al-alloy. (Abstract Copyright [2005], Wiley Periodicals, Inc.)

  15. THE INFLUENCE OF HEAT TREATMENT WITH THE LIQUID PHASE ON FORMATION OF A MICROSTRUCTURE OF EUTECTIC Al-Si-ALLOY

    Directory of Open Access Journals (Sweden)

    A. Anikin

    2015-01-01

    Full Text Available The effect of heat treatment on the structure of the eutectic Al-Si-alloy, a theoretical substantiation process based on thermal analyzer and cooked microstructures was presented in this paper.

  16. Microstructures in Centrifugal Casting of SiCp/AlSi9Mg Composites with Different Mould Rotation Speeds

    Institute of Scientific and Technical Information of China (English)

    WANG Kai; SUN Wenju; LI Bo; XUIE Hansong; LIU Changming

    2011-01-01

    Two ingots were produced by centrifugal casting at mould rotational speeds of 600 rpm and 800 rpm using 20 vol% SiCp/AlSi9Mg composite melt, respectively. The microstructure along the radial direction of cross-sectional sample of ingots was presented. SiC particles migrated towards the external circumference of the tube, and the distribution of SiC particles became uniform under centrifugal force. Voids in 20 vol% SiCp/AlSi9Mg composite melt migrated towards the inner circumference of the tube. The quantitative analysis results indicated that not only SiC particles but also primary a phases segregated greatly in centrifugal casting resulting from the transportation behavior of constitutions with different densities in the SiCp/AlSi9Mg composite melt. In addition, the eutectic Si was broken owing to the motion of SiCp/AlSi9Mg composite melt during centrifugal casting.

  17. Molecular Structures of Al/Si and Fe/Si Coprecipitates and the Implication for Selenite Removal.

    Science.gov (United States)

    Chan, Ya-Ting; Kuan, Wen-Hui; Tzou, Yu-Min; Chen, Tsan-Yao; Liu, Yu-Ting; Wang, Ming-Kuang; Teah, Heng-Yi

    2016-04-20

    Aluminum and iron oxides have been often used in the coagulation processes during water purification due to their unique surface properties toward anions. In the presence of silica, the coprecipitation of Al/Si or Fe/Si might decrease the efficiency of wastewater purification and reuse. In this study, surface properties and molecular structures of Al/Si and Fe/Si coprecipitates were characterized using spectroscopic techniques. Also, the selenite removal efficiency of Al/Si and Fe/Si coprecipitates in relation to their surface and structural properties was investigated. While dissolved silicate increased with increasing pH from Fe/Si coprecipitates, less than 7% of silicate was discernible from Al/Si samples over the range from acidic to alkaline conditions. Our spectroscopic results showed that the associations between Al and Si were relatively stronger than that between Fe and Si in coprecipitates. In Al/Si coprecipitates, core-shell structures were developed with AlO6/AlO4 domains as the shells and Si frameworks polymerized from the SiO2 as the cores. However, Si framework remained relatively unchanged upon coprecipitation with Fe hydroxides in Fe/Si samples. The Si core with Al shell structure of Al/Si coprecipitates shielded the negative charges from SiO2 and thereby resulted in a higher adsorption capacity of selenite than Fe/Si coprecipitates.

  18. Molecular Structures of Al/Si and Fe/Si Coprecipitates and the Implication for Selenite Removal

    Science.gov (United States)

    Chan, Ya-Ting; Kuan, Wen-Hui; Tzou, Yu-Min; Chen, Tsan-Yao; Liu, Yu-Ting; Wang, Ming-Kuang; Teah, Heng-Yi

    2016-04-01

    Aluminum and iron oxides have been often used in the coagulation processes during water purification due to their unique surface properties toward anions. In the presence of silica, the coprecipitation of Al/Si or Fe/Si might decrease the efficiency of wastewater purification and reuse. In this study, surface properties and molecular structures of Al/Si and Fe/Si coprecipitates were characterized using spectroscopic techniques. Also, the selenite removal efficiency of Al/Si and Fe/Si coprecipitates in relation to their surface and structural properties was investigated. While dissolved silicate increased with increasing pH from Fe/Si coprecipitates, less than 7% of silicate was discernible from Al/Si samples over the range from acidic to alkaline conditions. Our spectroscopic results showed that the associations between Al and Si were relatively stronger than that between Fe and Si in coprecipitates. In Al/Si coprecipitates, core-shell structures were developed with AlO6/AlO4 domains as the shells and Si frameworks polymerized from the SiO2 as the cores. However, Si framework remained relatively unchanged upon coprecipitation with Fe hydroxides in Fe/Si samples. The Si core with Al shell structure of Al/Si coprecipitates shielded the negative charges from SiO2 and thereby resulted in a higher adsorption capacity of selenite than Fe/Si coprecipitates.

  19. Molecular dynamics study on the nucleation of Al-Si melts on sheet substrates at the nanoscale.

    Science.gov (United States)

    Liu, Sida; Zhou, Xuyan; Wu, Weikang; Zhu, Xiangzhen; Duan, Yunrui; Li, Hui; Wang, Xin

    2016-02-28

    Molecular dynamics (MD) simulations are performed to study the freezing process of Al-Si melts on heterogeneous Si substrates in detail. We highlight the inherent nanostructure of both the Si primary phase and the Al-Si binary phase. It is found for the first time that the primary Si phase displays a "pyramidal configuration" when the Al-Si melt congeals. Experimental measurements could also verify our simulation results. It can be found that the binary Al-Si phase turns into a "Si-Al-Si sandwich construction" during solidification, regardless of freezing on a single substrate or in the restricted space between substrates. This peculiar phenomenon results from the combined effects of the van der Waals potential well and the interatomic interaction between Al and Si. Furthermore, it is also able to control the thickness of the Si atomic shell of the "sandwich construction", resulting in the silicene-like unilaminar Si nanostructure. Our findings provide novel strategies to fabricate desired shaped nanostructures by means of nanocasting in Al-Si melts at the nanoscale.

  20. Improvement in mechanical properties of hypereutectic Al-Si-Cu alloys through sono-solidiifed slurry

    Institute of Scientific and Technical Information of China (English)

    Yoshiki Tsunekawa; Shinpei Suetsugu; Masahiro Okumiya; Naoki Nishikawa; Yoshikazu Genma

    2014-01-01

    For the wider applications, it is necessary to improve the ductility as wel as the strength and wear-resistance of hypereutectic Al-Si-Cu aloys, which are typical light-weight wear-resistant materials. An increase in the amounts of primary silicon particles causes the modiifed wear-resistance of hypereutectic Al-Si-Cu aloys, but leads to the poor strength and ductility. It is known that dual phase steels composed of hetero-structure have succeeded in bringing contradictory mechanical properties of high strength and ductility concurrently. In order to apply the idea of hetero-structure to hypereutectic Al-Si-Cu alloys for the achievement of high strength and ductility along with wear resistance, ultrasonic irradiation of the molten metal during the solidiifcation, which is caled sono-solidiifcation, was carried out from its molten state to just above the eutectic temperature. The sono-solidiifed Al-17Si-4Cu aloy is composed of hetero-structure, which are, hard primary silicon particles, soft non-equilibriuma-Al phase and the eutectic region. Rheo-casting was performed at just above the eutectic temperature with sono-solidiifed slurry to shape a disk specimen. After the rheo-casting with modiifed sono-solidiifed slurry held for 45 s at 570 ºC, the quantitative optical microscope observation exhibits that the microstructure is composed of 18area% of hard primary silicon particles and 57area% of softa-Al phase. In contrast, there exist only 5 area% of primary silicon particles and noa-Al phase in rheo-cast specimen with normaly solidiifed slurry. Hence the tensile tests of T6 treated rheo-cast specimens with modified sono-solidified slurry exhibit improved strength and 5% of elongation, regardless of having more than 3 times higher amounts of primary silicon particles compared to that of rheo-cast specimen with normaly solidiifed slurry.

  1. Melt Processing and Characterization of Al-SiC Nanocomposite, Al, and Mg Foam Materials

    Directory of Open Access Journals (Sweden)

    Ahmed M. Nabawy

    2016-05-01

    Full Text Available In the present work, metallic foams of Al, Mg and an Al-SiC nanocomposite (MMNC have been fabricated using a new manufacturing technique by employing melt infiltration assisted with an electromagnetic force. The aim of this investigation was to study and to develop a reliable manufacturing technique consisting of different types of metallic foams. In this technique, an electromagnetic force was used to assist the infiltration of Al-SiC slurry and of pure liquid metal into a leachable pattern of NaCl, thus providing perfect cellular structures with micro-sized porosities. A high frequency induction coil unit equipped with a vacuum chamber and a hydraulic press was used to manufacture the foam materials. Microstructures of the produced foam materials were explored by using Field Emission Scanning Electron Microscopy (FESEM. The mechanical behavior of the manufactured foams was investigated by applying compression testing. The results indicate a high applicability of the new technique in producing metallic foams of pure metals and of a metal matrix nanocomposite . The produced foam materials displayed isotropic cellular structures with excellent compressive behaviors. Microstructure measurements indicate that the average pore size and strut thickness that can be achieved are in the ranges of 100–500 μm and 50–100 μm, respectively. The produced foam of the Al-SiC nanocomposite material provided the highest strength of 50 MPa prior to the densification stage, which equates to 25 times, and 10 times higher than the strength levels that were obtained by Al, and Mg foams, respectively.

  2. Fluidity and microstructure formation during flow of Al- SiC particle composites

    Science.gov (United States)

    Yarandi, F. M.; Rohatgi, P. K.; Ray, S.

    1993-06-01

    This article presents the results of casting and spiral fluidity in a Al-7 wt% Si alloy reinforced with 10,15, and 20 vol% SiC particles in permanent molds. The fluidity of the Al-SiC slurry increases linearly with temperature up to about 760 °C. Above this temperature, the casting fluidity of the Al-SiC particle slurry does not change significantly with an increase in temperature. In several cases, the fluidity decreased at temperatures above 760 °C. The fluidity of Al-SiC melts containing 9-μm SiC particles decreased with an increase in volume percentage of SiC up to 15 vol% (the range studied), presumably due to an increase in the viscosity of the melt with increasing volume percentage of dispersoid and changes in thermophysical properties of the composite. However, the fluidity of Al-20 vol% SiC of 14-μm particle size is higher than the fluidity of Al-15 vol% SiC 9-μm particles, indicating the role of particle size and surface area in de-creasing fluidity. Composite slurries travel farther in a channel of larger cross sections compared to channels of smaller cross sections under similar conditions. Casting fluidity increases linearly with an in-crease in cross section of the channel. A model has been proposed to calculate the values of fluidity of the composite as a function of particle volume percent, superheat, flow velocity of the melt, and the cross sec-tion of the flow channel. Experimental observations have been compared with the predictions of the model, and some deviations have been attributed to settling and segregation of SiC particles observed through microstructural examination.

  3. Improvement in mechanical properties of hypereutectic Al-Si-Cu alloys through sono-solidified

    Directory of Open Access Journals (Sweden)

    Yoshiki Tsunekawa

    2014-07-01

    Full Text Available For the wider applications, it is necessary to improve the ductility as well as the strength and wear-resistance of hypereutectic Al-Si-Cu alloys, which are typical light-weight wear-resistant materials. An increase in the amounts of primary silicon particles causes the modified wear-resistance of hypereutectic Al-Si-Cu alloys, but leads to the poor strength and ductility. It is known that dual phase steels composed of hetero-structure have succeeded in bringing contradictory mechanical properties of high strength and ductility concurrently. In order to apply the idea of hetero-structure to hypereutectic Al-Si-Cu alloys for the achievement of high strength and ductility along with wear resistance, ultrasonic irradiation of the molten metal during the solidification, which is called sono-solidification, was carried out from its molten state to just above the eutectic temperature. The sono-solidified Al-17Si-4Cu alloy is composed of hetero-structure, which are, hard primary silicon particles, soft non-equilibrium a -Al phase and the eutectic region. Rheo-casting was performed at just above the eutectic temperature with sono-solidified slurry to shape a disk specimen. After the rheo-casting with modified sonosolidified slurry held for 45 s at 570 篊, the quantitative optical microscope observation exhibits that the microstructure is composed of 18area% of hard primary silicon particles and 57area% of soft a -Al phase. In contrast, there exist only 5 area% of primary silicon particles and no a -Al phase in rheo-cast specimen with normally solidified slurry. Hence the tensile tests of T6 treated rheo-cast specimens with modified sono-solidified slurry exhibit improved strength and 5% of elongation, regardless of having more than 3 times higher amounts of primary silicon particles compared to that of rheo-cast specimen with normally solidified slurry.

  4. Evaluating Primary Dendrite Trunk Diameters in Directionally Solidified Al-Si Alloys

    Science.gov (United States)

    Grugel, R. N.; Tewari, S. N.; Poirier, D. R.

    2014-01-01

    The primary dendrite trunk diameters of Al-Si alloys that were directionally solidified over a range of processing conditions have been measured. These data are analyzed with a model based primarily on an assessment of secondary dendrite arm dissolution in the mushy zone. Good fit with the experimental data is seen and it is suggested that the primary dendrite trunk diameter is a useful metric that correlates well with the actual solidification processing parameters. These results are placed in context with the limited results from the aluminium - 7 wt. % silicon samples directionally solidified aboard the International Space Station as part of the MICAST project.

  5. Influence of thermo-derivative analysis conditions on microstructure of the Al-Si-Cu alloy

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2011-04-01

    Full Text Available Microstructure change of the metals and alloys as a result of variable crystallisation conditions also by mind of cooling rate changeinfluence the mechanical properties. In this work there are presented the interdependences between the cooling rate, chemical compositionand microstructure of the cast aluminium alloy Al–Si–Cu as a result of the thermo-derivative analysis, using the UMSA (UniversalMetallurgical Simulator and Analyzer device. An important tool for the microstructure evaluation of the Al type AC-AlSi7Cu3Mg alloywas the light and electron scanning microscopy technique.

  6. Microstructural evolution during friction stir welding of AlSi1MgMn alloy

    Directory of Open Access Journals (Sweden)

    M. Janjić

    2012-01-01

    Full Text Available This paper provides the research of the infl uence of geometric and kinematic parameters on the microstructure and mechanical properties of welded joint of aluminum alloy AlSi1MgMn (6082-T6 obtained through the Friction Stir Welding (FSW process. The experiment parameters were welding speed, rotation speed, angle of pin slope, pin diameter and shoulder diameter. On the obtained welded workpieces the dynamic testing on the impact toughness, and determination of microstructural zones were carried out.

  7. Furnace bottom rise mechanism in preparation of Al-Si alloys by electrothermal process

    Institute of Scientific and Technical Information of China (English)

    1999-01-01

    The experiments of preparation of Al-Si alloys by electrothermal process were carried out respectively in 20 kW, 100 kW and 1 800 kW DC arc furnaces. The mechanism of furnace bottom rise was studied.It was found that the bottom rise can be divided into three types, including the low bottom temperature, abnormal reducing reaction and carbide deposition. The furnace bottom rise is related to the carbon ratio of the briquet, the heating speed of the briquet and the parameters and operation of furnace.

  8. Laser ablation ICP-MS investigation of solute element distributions during Al-Si solidification

    Energy Technology Data Exchange (ETDEWEB)

    Nafisi, Shahrooz [Center for University Research on Aluminum (CURAL), University of Quebec at Chicoutimi, Chicoutimi, QC, G7H 2B1 (Canada); Cox, Richard [Department of Earth Sciences, University of Quebec at Chicoutimi, Chicoutimi, QC, G7H 2B1 (Canada); Ghomashchi, Reza [Center for University Research on Aluminum (CURAL), University of Quebec at Chicoutimi, Chicoutimi, QC, G7H 2B1 (Canada)]. E-mail: rghomash@uqac.ca

    2006-05-18

    During solidification of an alloy, solute elements may pile up ahead of the growing interface due to their lower solubility within the solid material, when the distribution or partition coefficient is less than unity. In this paper, laser ablation inductively coupled plasma mass spectrometry, LA-ICP-MS, as a new method, is used to analyze solute distribution within primary {alpha}-Al particles formed during solidification of hypoeutectic Al-Si alloys. The results are further compared with those obtained from electron probe micro-analysis, EPMA, of the same specimens. There is a good agreement between the results obtained by both techniques.

  9. K-capture by Al-Si based Additives in an Entrained Flow Reactor

    DEFF Research Database (Denmark)

    Wang, Guoliang; Jensen, Peter Arendt; Wu, Hao

    2016-01-01

    A water slurry, consisting of KCl and Al-Si based additives (kaolin and coal fly ash) was fed into an entrained flow reactor (EFR) to study the K-capturing reaction of the additives at suspension-fired conditions. Solid products collected from the reactor were analysed with respect to total...... of KCl to K-aluminosilicate decreased. When reaction temperature increased from 1100 °C to 1450 °C, the conversion of KCl does not change significantly, which differs from the trend observed in fixed-bed reactor....

  10. Development of high plasticity Al-Si alloy and its casting process

    Institute of Scientific and Technical Information of China (English)

    郭国文; 李元元; 陈维平; 张大童; 龙雁

    2002-01-01

    Aiming to meet the challenge of the shape complexity and high plasticity demanded for the upper connective plate(UCP) in motorcycle, a high plasticity Al-Si alloy named HGZL-02 was developed by optimizing the chemical composition and casting process. Premium UCP castings were obtained by using optimized casting process. Results show that fine and dense microstructure are obtained in the UCP castings. An average of 224MPa in ultimate tensile strength, 149MPa in yield strength and 13.2% in elongation are achieved for T6 heat-treated UPS castings.

  11. Anisotropic Mechanical Behavior of AlSi10Mg Parts Produced by Selective Laser Melting

    Science.gov (United States)

    Tang, Ming; Pistorius, Petrus Christiaan

    2017-03-01

    AlSi10Mg cylinders produced by laser powder-bed fusion have somewhat different yield behavior for cylinders with XY orientation and Z orientation. Earlier yielding for Z-oriented samples is likely related to micro-residual stress, resulting from the difference in thermal expansion of the aluminum matrix and cellular silicon. Smaller tensile reduction in area of Z-oriented samples is related to tearing along the softer region at the boundaries of melt pools, where the silicon cell spacing is larger. Indentation measurements confirmed the lower hardness at the edges of melt pools.

  12. Parameter-free calculation of K alpha chemical shifts for Al, Si, and Ge oxides

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper

    2001-01-01

    The chemical shifts of the K alpha radiation line from Al, Si, and Ge ions between their elemental and oxide forms are calculated within the framework of density functional theory using ultrasoft pseudopotentials. It is demonstrated that this theoretical approach yields quantitatively accurate...... results fur the systems investigated, provided that relaxations of the valence electrons upon the core-hole transition are properly accounted for. Therefore, such calculations provide a powerful tool for identification of impurity states based on x-ray fluorescence data. Results for an Al impurity...

  13. Thermodynamics of Fe-C-j (j = Al, Si, P, S) Melts

    Institute of Scientific and Technical Information of China (English)

    WANG Hai-chuan; WANG Shi-jun; ZHOU Yun; DONG Yuan-chi; LI Wen-chao

    2005-01-01

    Based on a proposed method, the mathematical expressions between carbon solubility in Fe-C-j (j=Al, Si, P, S) melts and temperature were obtained. The expressions show the relation of the affecting factors of component j and temperature on carbon solubility, and the activity interaction coefficient of j upon carbon depends on atomic number, covalent radius and electro-negativity. The affecting factors of four elements on carbon solubility are all negative. There is a linear relationship between covalent radius and electro-negativity.

  14. Isothermal section (500  ℃) of phase diagram of Nd-Al-Si ternary system

    Institute of Scientific and Technical Information of China (English)

    龙志林; 周益春; 庄应烘; 陈荣贞; 刘敬旗

    2001-01-01

    The isothermal section of the phase diagram of the ternary system Nd-Al-Si at 500  ℃ (Nd≤50%, mole fraction) has been constructed on the basis of the data obtained by X-ray diffraction analysis, differential thermal analysis, metallographic examination, chemical analysis and electron micro-probe analysis. The obtained diagram consists of 11 single-phase regions, 21 two-phase regions and 11 three-phase regions. There exist two limit solid solutions. The intermetallic compound NdAl1.5Si0.5 has not been found in this section. No evidence of new phase has been observed in this work.

  15. The annealing behavior of hydrogen implanted into Al-Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ogura, Masahiko; Yamaji, Norisuke; Imai, Makoto; Itoh, Akio; Imanishi, Nobutsugu [Kyoto Univ. (Japan). Faculty of Engineering

    1997-03-01

    We have studied effects of not only defects but also an added elements on trap-sites of hydrogen in metals. For the purpose, we observed depth profiles and thermal behaviors of hydrogen implanted into Al-1.5at.%Si alloy samples in an implantation-temperature range of liquid nitrogen temperature (LNT) to 373K at different doses. The results were compared with those for pure aluminum samples. It was found that hydrogen is trapped as molecules in grain boundaries of Al/Si. (author)

  16. Influence exothermical mixtures contents Na or B on elongation and hardness AlSi12 alloy

    Directory of Open Access Journals (Sweden)

    T. Lipiński

    2008-04-01

    Full Text Available The experiments were conducted on alloy AlSi12, following a factor design 23 for 3 independent variables. Mixtures composed of NaNO3, Na2B4O7, and Mg were used for alloy treatment. The amount of a reducing agent (Mg necessary to carry out the process was calculated on the basis of chemical reactions. The mass fraction (weight in weight concentration of individual variables is presented in Table 1. Results of study present by graphical forms. Figures 2-8 present until elongation (A5 and Brinell hardness (HB for each variable, at extreme (lower or higher levels of the other two.

  17. Corrosion behaviour of the AlSi6Cu4 alloy and cast AlSi6Cu4-graphite particles composite

    Directory of Open Access Journals (Sweden)

    S. Holecek

    2009-04-01

    Full Text Available The corrosion behaviour of the AlSi6Cu4 alloy as a composite matrix and of composites with 8% vol. of graphite particles was investigated. The corrosion experiments were performed over a range of elevated temperatures and were carried out in sea water (3.5%NaCl solution. We have focused our attention to the determination of the mode of corrosion attack and to the determination of the rate ofcorrosion and other corrosion characteristics. Both as-cast and annealed matrix and composite specimens were tested, as well as the99.9% as-cast aluminium for comparison. Corrosion behaviour of the materials was assessed by the corrosion potential (Ec and bypotentiodynamic (polarization curves. As expected, composite is less corrosion resistant than the matrix alloy. In addition to pitting,a severe galvanic corrosion occurs as a result of galvanic couple aluminium/graphite formation. Corrosion potentials imply that examinedmaterials would be sufficiently resistant in non or slightly oxidizing solutions without dissolved oxygen. All studied materials corrode very slowly at potentials negative to corrosion potential, while at potentials positive to corrosion potential the corrosion rate goes up by 1 or 2 orders.

  18. Effect of layer thickness on the high temperature mechanical properties of Al/SiC nanolaminates

    Energy Technology Data Exchange (ETDEWEB)

    Lotfian, S. [IMDEA Materials Institute, c/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Mayer, C.; Chawla, N. [Materials Science and Engineering, Arizona State University, Tempe, AZ 85287-6106 (United States); Llorca, J. [IMDEA Materials Institute, c/Eric Kandel 2, 28906 Getafe, Madrid (Spain); Department of Materials Science, Polytechnic University of Madrid, E.T.S. de Ingenieros de Caminos, 28040 Madrid (Spain); Misra, A.; Baldwin, J.K. [Los Alamos National Laboratory, Los Alamos, NM 87545 (United States); Molina-Aldareguía, J.M., E-mail: jon.molina@imdea.org [IMDEA Materials Institute, c/Eric Kandel 2, 28906 Getafe, Madrid (Spain)

    2014-11-28

    Composite laminates on the nanoscale have shown superior hardness and toughness, but little is known about their high temperature behavior. The mechanical properties (elastic modulus and hardness) were measured as a function of temperature by means of nanoindentation in Al/SiC nanolaminates, a model metal–ceramic nanolaminate fabricated by physical vapor deposition. The influence of the Al and SiC volume fraction and layer thicknesses was determined between room temperature and 150 °C and, the deformation modes were analyzed by transmission electron microscopy, using a focused ion beam to prepare cross-sections through selected indents. It was found that ambient temperature deformation was controlled by the plastic flow of the Al layers, constrained by the SiC, and the elastic bending of the SiC layers. The reduction in hardness with temperature showed evidence of the development of interface-mediated deformation mechanisms, which led to a clear influence of layer thickness on the hardness. - Highlights: • The mechanical behavior of Al/SiC nanolaminates was measured between 28 °C and 150 °C. • Room temperature hardness was controlled by the volume fraction of the constituents. • The hardness of all the nanolaminates decreased rapidly with temperature. • Reduction of hardness with temperature increased as the interface density increased.

  19. Role of cerium, lanthanum, and strontium additions in an Al-Si-Mg (A356) alloy

    Energy Technology Data Exchange (ETDEWEB)

    Nabawy, Ahmed M.; Samuel, Agnes M.; Samuel, Fawzy H. [Universite du Quebec, Chicoutimi (Canada). Dept. des Sciences Appliquees; Alkahtani, Saleh A.; Abuhasel, Khaled A. [Salman Bin Abdulaziz Univ., Riyadh (Saudi Arabia). Mechanical Engineering Dept.

    2016-05-15

    The effects of individual and combined additions of cerium (Ce), lanthanum (La), and strontium (Sr) on the eutectic modification and solidification characteristics of an Al-Si-Mg (A356) aluminum alloy were investigated using optical microscopy and thermal analysis techniques. Addition of Ce, La, and Sr resulted in different depression levels of the eutectic nucleation temperature and eutectic growth undercooling, generating modified eutectic structures exhibiting different levels of modification. Microstructural results showed that the best modification levels using individual additions were achieved by Sr which produced a fine fibrous eutectic structure, followed by La, which produced a refined lamellar structure, with Ce providing the lowest level of modification. On the other hand, a combined addition of Ce and Sr provided the highest modification level, with the production of a very fine fibrous eutectic silicon structure. In general, the addition of Sr helped to further increase the refinement obtained in the alloys containing La or Ce + La additions. In the latter alloy, the main intermetallic phases observed were La(Al,Si){sub 2} and Al{sub 20}(La,Ce)Ti{sub 2}Si. The improved modification levels were found to be proportional to the depression in the eutectic nucleation temperature and the eutectic growth undercooling. A high cooling rate also improved the modification level by at least one level.

  20. Wear mechanism for spray deposited Al-Si/SiCp composites under dry sliding condition

    Institute of Scientific and Technical Information of China (English)

    滕杰; 李华培; 陈刚

    2015-01-01

    Al-Si/15%SiCp (volume fraction) composites with different silicon contents were fabricated by spray deposition technique, and typical microstructures of these composites were studied by optical microscopy (OM). Dry sliding wear tests were carried out using a block-on-ring wear machine to investigate the effect of applied load range of 10−220 N on the wear and friction behavior of these composites sliding against SAE 52100 grade bearing steel. Scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDAX) were utilized to examine the morphologies of the worn surfaces in order to observe the wear characteristics and investigate the wear mechanism. The results show that the wear behavior of these composites is dependent on the silicon content in the matrix alloy and the applied load. Al-Si/15%SiCp composites with higher silicon content exhibit better wear resistance in the applied load range. Under lower loads, the major wear mechanisms are oxidation wear and abrasive wear for all tested composites. Under higher loads, severe adhesive wear becomes the main wear mechanisms for Al-7Si/15%SiCp and Al-13Si/15%SiCp composites, while Al-20Si/15%SiCp presents a compound wear mechanism, consisting of oxidation, abrasive wear and adhesion wear.

  1. Fretting Fatigue Experiment and Analysis of AlSi9Cu2Mg Alloy

    Directory of Open Access Journals (Sweden)

    Jun Wang

    2016-12-01

    Full Text Available An investigation was carried out in order to study the fretting fatigue behavior of an AlSi9Cu2Mg aluminum alloy. The fretting fatigue tests of AlSi9Cu2Mg were performed using a specially designed testing machine. The failure mechanism of fretting fatigue was explored by studying the fracture surfaces, fretting scars, fretting debris, and micro-hardness of fretting fatigue specimens using scanning electron microscopy (SEM, energy-dispersive X-ray spectroscopy (EDX, and micro Vickers hardness test techniques. The experimental results show that the fretting fatigue limit (42 MPa is significantly reduced to approximately 47% of the plain fatigue limit (89 MPa under 62.5 MPa contact pressure. Furthermore, the fretting fatigue life decreases with increasing alternating stress and increasing contact pressure. The examination results suggest that the stress concentrates induced by oxidation-assisted wear on the contact interface led to the earlier initiation and propagation of crack under the fretting condition.

  2. The effect of copper concentration on the microstructure of Al-Si-Cu alloys

    Directory of Open Access Journals (Sweden)

    R. Maniara

    2007-04-01

    Full Text Available In the metal casting industry, an improvement of component quality depends mainly on better control over the production parameters. In order to gain a better understanding of how to control the as-cast microstructure, it is important to understand the evaluation of microstructure during solidification and understanding how influence the changes of chemical concentration on this microstructure. In this research, the effect of Cu content on the microstructure and solidification parameters of Al-Si-Cu alloys has been investigated. Thus, the thermal analysis of the alloys is used to control of aluminum casting process. The effect of different Cu content on solidification parameters such: aluminum dendrites nucleation temperature (TLiq, Liquidus temperature, α+β eutectic nucleation temperature (TE(Al+SiN, Cu-rich eutectic nucleation temperature (TAl+Cu, solidus temperature (Tsol, solidification range (ΔTs has been studied in liquidus region. Influence of Cu content on the microstructure has been carried out. The principle observation made from this work ware that as copper concentration is increased the liquidus and solodius temperature decried. In addition to this it was observed that increase a Cu content from 1 to 4 wt % caused reduce of the secondary dendrite arm spacing and increase the grain size.

  3. Research Advance on Magnetocaloric Effect of La-Fe-M(Al, Si) Compounds

    Institute of Scientific and Technical Information of China (English)

    肖素芬; 陈云贵; 郝春; 吴金平; 涂铭旌

    2004-01-01

    Recent research progress on magnetocaloric effect of La-Fe-M(M=Al,Si)compounds was presented.La-Fe-M(M=Al,Si)compounds of high Fe content are excellent soft magnetic materials with NaZn13 structure.The Curie temperature of the compounds can be increased by substituting small amount of Co for Si,Al.The La(Fe1-yCoy)xSi13-x compounds with an appropriate ratio of Co and Si can produce giant magnetocaloric effect comparable to that for Gd5Si2Ge2 at room temperature.The La(FexSi1-x)13 doped with H can also produce giant magnetocaloric effect at room temperature,which is much greater than that for Gd.For La(FexSi1-x)13 compounds with low Si or high Si contents.The nature of phase transition near Curie temperature induced by temperature and magnetic field was described in detail.

  4. Degradation of Al/SiCp composites produced with rice-hull ash and aluminum cans.

    Science.gov (United States)

    Escalera-Lozano, R; Gutiérrez, C A; Pech-Canul, M A; Pech-Canul, M I

    2008-01-01

    The use of recycling aluminum from beverage containers and rice-hull ash (RHA) offers to be an attractive alternative for the economic production of Al/SiCp composites. However, corrosion phenomena in the composites represent technological barriers yet to be resolved before they can be exploited to their full potential. A simple methodology involving characterization by XRD, SEM, EDX, FTIR and ICP was designed in order to investigate the causes of the rapid degradation in a humid environment of Al/SiCp composites produced with RHA and aluminum cans. Results reveal that the use of RHA was beneficial to avoid degradation through the formation and subsequent hydration of the Al4C3 phase. However with condensed moisture acting as an electrolyte, localized corrosion took place with aggressive damage manifested by the disintegration of the composite into a powdery mixture. The relevant corrosion mechanism was mainly attributed to microgalvanic coupling between the Mg2Si intermetallic compound and the matrix (although other phases such as SiC, Si, MgAl2O4 could also work as microcathodes).

  5. Electromagnetic Filtration of Primary Fe-Rich Phases from Al-Si Alloy Melt

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Electromagnetic filtration of primary Fe-rich phases(complex compound of AIFeSiMn)from Al-Si alloy melt containing 1.2 wt pct Fe have been studied by theoretical analysis and on a selfdesigned electromagnetic filtration equipment. The principle of the electromagnetic filtration is that the EMF(electromagnetic force)scarcely acts on the primary Fe-rich phases having low electric conductivity, which are then moved in the direction opposite to that of the EMF.Experimental results show that the primary Fe-rich phases are separated from Al-Si alloy melt and are collected in the filter while the melt is in horizontal flow.The removal efficiency of the primary iron-phases(η)calculated is less as the greatest flow velocity of the melt(uM)and the height of the filter (2h) are larger,while it becomes larger as EMF, operating distance of electromagnetic force (x) and particle size (dp) become larger. lt has been confirmed that the primary iron-phases larger than 20 μm can be removed efficiently by theoretical analysis and experiments. This new technique is high efficient and available for continuously flowing melts as compared with natural settling and filtration methods, which offer a possibility for recycling high quality aluminum alloys.

  6. Discovery of dmisteinbergite (hexagonal CaAlSi O) in the Allende meteorite

    DEFF Research Database (Denmark)

    Ma, C.; Krot, A.N.; Bizzarro, Martin

    2013-01-01

    crystals (100-600 mm in size) in contact with gehlenitic melilite and Al,Ti-diopside, poikilitically enclosing euhedral spinel, and rare anorthite. It is colorless and transparent. The mean chemical composition, determined by electron microprobe analysis, is (wt%) SiO 42.6, AlO 36.9, CaO 20.2, MgO 0.......05, sum 99.75, giving rise to an empirical formula of CaAl SiO. Its electron backscatter diffraction patterns are a good match to that of synthetic CaAl SiO with the P6/mcm structure and the unit cell a = 5.10 Å, c = 14.72 Å, and Z = 2. Dmisteinbergite could have crystallized from a silicate melt at high...... temperature (∼1200-1400 °C) via rapid cooling. Dmisteinbergite in Allende, the first find in a meteorite, is a new member of refractory silicates, among the first solid materials formed in the solar nebula....

  7. Assessment of modification level of hypoeutectic Al-Si alloys by pattern recognition of cooling curves

    Institute of Scientific and Technical Information of China (English)

    CHEN Xiang; GENG Hui-yuan; LI Yan-xiang

    2005-01-01

    Most evaluations of modification level are done according to a specific scale based on an American Foundry Society (AFS) standard wall chart as qualitative analysis in Al-Si casting production currently. This method is quite dependent on human experience when making comparisons of the microstructure with the standard chart. And the structures depicted in the AFS chart do not always resemble those seen in actual Al-Si castings. Therefore, this qualitative analysis procedure is subjective and can introduce human-caused errors into comparative metallographic analyses. A quantization parameter of the modification level was introduced by setting up the relationship between mean area weighted shape factor of eutectic silicon phase and the modification level using image analysis technology. In order to evaluate the modification level, a new method called "intelligent evaluating of melt quality by pattern recognition of thermal analysis cooling curves" has also been introduced. The results show that silicon modification level can be precisely assessed by comparison of the cooling curve of the melt to be evaluated with the one most similar to it in a database.

  8. Wetting of polycrystalline SiC by molten Al and Al-Si alloys

    Science.gov (United States)

    Cong, Xiao-Shuang; Shen, Ping; Wang, Yi; Jiang, Qichuan

    2014-10-01

    The wetting of α-SiC by molten Al and Al-Si alloys was investigated using a dispensed sessile drop method in a high vacuum. In the Al-SiC system, representative wetting stages were identified. The liquid spreading was initially controlled by the deoxidation of the SiC surface and then by the formation of Al4C3 at the interface. The intrinsic contact angle for molten Al on the polycrystalline α-SiC surface was suggested to be lower than 90̊ provided that the oxide films covering the Al and SiC surfaces were removed, i.e., the system is partial wetting in nature. An increase in the Si concentration in liquid Al weakened the interfacial reaction but improved the final wettability. The role of the Si addition on the wetting was presumably attributed to its segregation at the interface and the formation of strong chemical bonds with the SiC surface.

  9. Investigations of linear contraction and shrinkage stresses development in hypereutectic al-si binary alloys

    Directory of Open Access Journals (Sweden)

    J. Mutwil

    2009-07-01

    Full Text Available Shrinkage phenomena during solidification and cooling of hypereutectic aluminium-silicon alloys (AlSi18, AlSi21 have been examined. A vertical shrinkage rod casting with circular cross-section (constant or fixed: tapered has been used as a test sample. Two type of experiments have been conducted: 1 on development of the test sample linear dimension changes (linear expansion/contraction, 2 on development of shrinkage stresses in the test sample. By the linear contraction experiments the linear dimension changes of the test sample and the metal test mould as well a temperature in six points of the test sample have been registered. By shrinkage stresses examination a shrinkage tension force and linear dimension changes of the test sample as well a temperature in three points of the test sample have been registered. Registered time dependences of the test bar and the test mould linear dimension changes have shown, that so-called pre-shrinkage extension has been mainly by mould thermal extension caused. The investigation results have shown that both: the linear contraction as well as the shrinkage stresses development are evident dependent on metal temperature in a warmest region the sample (thermal centre.

  10. Microstructural characteristics of in situ Mg2Si/Al-Si composite by low superheat pouring

    Directory of Open Access Journals (Sweden)

    Wu Xiaofeng

    2013-09-01

    Full Text Available To control the morphology and size of the primary and eutectic Mg2Si phases in in situ Mg2Si/Al-Si composite and achieve a feasible and reliable technique to produce appropriate feedstock for the thixo-casting and rheo-casting of this type of material, three Al-Si matrix composites reinforced by 5wt.%, 9wt.% and 17wt.% Mg2Si with hypoeutectic, eutectic and hypereutectic compositions were prepared by the low superheat pouring (LSP process. The effects of the pouring temperature (superheat on the morphology and size distribution of primary phases (primary α-Al and Mg2Si, binary (α-Al + Mg2Si eutectic cell and eutectic Mg2Si were investigated. The experimental results show that low pouring temperature (superheat not only refines the grain structure of the primary α-Al and binary (α-Al + Mg2Si eutectic cell in three composites and promotes the formation of more non-dendritic structural semi-solid metal (SSM slurry of these phases; but also refines the primary and eutectic Mg2Si phases, which seems to be attributed to the creation of an ideal condition for the nucleation and the acquisition of a high survival of nuclei caused by the LSP process.

  11. Heat treatment of the EN AC-AlSi9Cu3(Fe alloy

    Directory of Open Access Journals (Sweden)

    J. Pezda

    2010-04-01

    Full Text Available Silumins are widely used in automotive, aviation and shipbuilding industries; as having specific gravity nearly three times lower than specific gravity of cast iron the silumins can be characterized by high mechanical properties. Additionally, they feature good casting properties, good machinability and good thermal conductivity. i.e. properties as required for machinery components operating in high temperatures and at considerable loads. Mechanical properties of the silumins can be upgraded, implementing suitably selected heat treatment. In the paper is presented an effect of modification and heat treatment processes on mechanical properties of the EN AC-AlSi9Cu3(Fe alloy. Investigated alloy has undergone typical processes of modification and refining, and next heat treatment. Temperature range of the heat treatment operations was determined on base of curves from the ATD method. Obtained results concern registered melting and solidification curves from the ATD method and strength tests. On base of the performed tests one has determined range of the heat treatment parameters which would assure obtainment of the best possible mechanical properties of the EN AC-AlSi9Cu3(Fe alloy.

  12. Study on in-situ Mg2Si/Al-Si composites with different compositions

    Institute of Scientific and Technical Information of China (English)

    Jing Qingxiu; Zhang Caixia; Huang Xiaodong

    2009-01-01

    Effects of chemical composition and heat treatment on microstructures and mechanical properties of in-situ Mg2Si/Al-Si composites were investigated. It was found that, in the microstructure of an Al-5.7wt% Mg2Si composite with 8.2wt% extra Si, the binary eutectic Mg2Si locates at the grain boundaries with an undeveloped Chinese script-like morphology, and the primary α-Al is formed into a cell structure due to the selective modification effect of the modifiers of mischmetal and Strontium salt; whereas in the composite with a near Al-Mg2Si eutectic composition and little extra Si content, the intercrescence eutectic Mg2Si formed with the binary eutectic a-Al grows into integrated Chinese script-like shape. As Si content increases, the eutectic Mg2Si dendrite becomes coarser in morphology but less in volum e fraction. Hardness and tensile strength of the cast Mg2Si/Al-Si composites do not increase with increasing of Mg content, but they are related to the size and morphology of the eutectic and primary Mg2Si phases. Heat treatment with optimal parameters is an effective way to improve the properties of the in-situ composites.

  13. Laser cutting of an AlSi alloy/SiCp composites: theory and experiments

    Directory of Open Access Journals (Sweden)

    J. Śleziona

    2006-04-01

    Full Text Available Purpose: Discontinuous silicon carbide reinforced aluminium alloy metal matrix composites have proved to be extremely to cutting using conventional cutting tools. Thus, there is a need to introduce new processing method in order to improve both the working conditions and the quality of the products made of metal matrix composites. Laser processing offer the advantages of high processing rates, no tool wear, no contact forces, and relatively high precision. Currently the mechanisms governing the laser cutting process of composites are not fully understood. It is the aim of the authors therefore to investigate the physical processes of laser composite material interactions and the phenomena occurring within the cutting front, viz. the formation of striations, and the effect they have on the resulting cutting quality.Design/methodology/approach: The analysis has taken into the consideration these AlSi alloy/SiCp composites are heterogeneous structural material consisting of two components: a semiconductor and metal alloy that have two different optical absorptions mechanisms to laser radiation. The mathematical model based on energy and mass balance model was used to calculate the maximum cutting depth for fixed cutting speed and laser beam power.Findings: Results indicated that the change in absorptivity magnitude about 0.1 led to a strong increase in power of laser energy absorbed per unit depth in AlSi alloy/SiCp composites.Research limitations/implications: In mathematical modeling the constant values of the effective absorptive parameter describing the energy input from laser to composite and a constant thermophysical properties of composite components are used. During the laser beam scanning the absorptive of the composite surface may changes.Practical implications: The proposed mathematical model is in good agreement with the experimental data obtained for a CO2 laser cut of AlSi alloy/SiCp composites. It is important to understand the

  14. The structure-property relationships of powder processed Fe-Al-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Prichard, Paul D. [Iowa State Univ., Ames, IA (United States)

    1998-02-23

    Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic %). The powder alloys were produced with a high pressure gas atomization (HPGA) process to obtain a high fraction of metal injection molding (MIM) quality powder (D84 < 32 μm). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 μm. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 μm to 104 μm. Mechanical property testing was conducted on both extruded and sintered material using a small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25 to 550 C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase α + DO3 structure. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.

  15. Ce对Al-Si-Cu合金中α(Al)-Al2Cu共晶形貌的影响%Effect of Ce on morphology ofα(Al)-Al2Cu eutectic in Al-Si-Cu alloy

    Institute of Scientific and Technical Information of China (English)

    Maja VONINA; Joef MEDVED; Tonica BONINA; Franc ZUPANI

    2014-01-01

    The effect of Ce addition on the morphology of the α(Al)-Al2Cu eutectic in Al-Si-Cu alloy was investigated using thermal analysis, light microscopy, scanning electron microscopy, focused ion beam and energy dispersive analysis. The results show that the eutectic α(Al)-Al2Cu forms within small space between dendrites, silicon and AlSiFeMn plates. Eutectic Al2Cu is not lamellar but degenerated. However, Al2Cu in Ce-modified alloys is more compact. Ce partially dissolves in Al2Cu, which is a viable reason for the formation of coarser Al2Cu. The addition of Ce also increases the microhardness of theα(Al)-Al2Cu eutectic by almost 10%compared with the basic Al-Si-Cu alloy.%采用热分析、光学显微镜技术、扫描电镜技术、聚焦离子束和能量色散谱分析方法研究Ce对Al-Si-Cu合金中α(Al)-Al2Cu共晶形貌的影响。结果表明,在枝晶、硅和AlSiFeMn之间较小空间内形成了α(Al)-Al2Cu共晶。Al2Cu为非层状的不规则共晶组织。Al2Cu在经Ce改性的合金中更加致密。部分Ce溶解于Al2Cu中,这是粗晶Al2Cu形成的原因。与基体Al-Si-Cu合金相比,Ce的加入能使α(Al)-Al2Cu共晶合金的显微硬度提高约10%。

  16. Neutron absorption of Al-Si-Mg-B{sub 4}C composite

    Energy Technology Data Exchange (ETDEWEB)

    Abdullah, Yusof, E-mail: yusofabd@nuclearmalaysia.gov.my; Yusof, Mohd Reusmaazran [Malaysian Nuclear Agency, 43000, Bangi Selangor (Malaysia); Ibrahim, Anis Syukriah; Daud, Abdul Razak [Department of Applied Physics, Faculty of Science & Technology, National University of Malaysia, 43600, Bangi Selangor (Malaysia)

    2016-01-22

    Al-Si-Mg-B{sub 4}C composites containing 2-8 wt% of B{sub 4}C were prepared by stir casting technique. Homogenization treatment was carried out at temperatures of 540°C for 4 houra and followed by ageing at 180°C for 2 houra. Microstructure and phase identification were studied by scanning electron microscopy (SEM) and X-ray diffraction (XRD) respectively. Neutron absorption study was investigated using neutron source Am/Be{sup 241}. The result indicated that higher B{sub 4}C content improved the neutron absorption property. Meanwhile homogeneity of the composite was increased by ageing processes. This composite is potential to be used as neutron shielding material especially for nuclear reactor application.

  17. In-situ observation of porosity formation during directional solidification of Al-Si casting alloys

    Directory of Open Access Journals (Sweden)

    Zhao Lei

    2011-02-01

    Full Text Available In-situ observation of porosity formation during directional solidification of two Al-Si alloys (7%Si and 13%Si was made by using of micro-focus X-ray imaging. In both alloys, small spherical pores initially form in the melt far away from the eutectic solid-liquid (S/L interface and then grow and coagulate during solidification. Some pores can float and escape from the solidifying melt front at a relatively high velocity. At the end of solidification, the remaining pores maintain spherical morphology in the near eutectic alloy but become irregular in the hypoeutectic alloy. This is attributed to different solidification modes and aluminum dendrite interactions between the two alloys. The mechanism of the porosity formation is briefly discussed in this paper.

  18. Influence of Ultrasound Treatment on Cavitation Erosion Resistance of AlSi7 Alloy

    Directory of Open Access Journals (Sweden)

    Annalisa Pola

    2017-03-01

    Full Text Available Ultrasound treatment of liquid aluminum alloys is known to improve mechanical properties of castings. Aluminum foundry alloys are frequently used for production of parts that undergo severe cavitation erosion phenomena during service. In this paper, the effect of the ultrasound treatment on cavitation erosion resistance of AlSi7 alloy was assessed and compared to that of conventionally cast samples. Cavitation erosion tests were performed according to ASTM G32 standard on as-cast and heat treated castings. The response of the alloy in each condition was investigated by measuring the mass loss as a function of cavitation time and by analyzing the damaged surfaces by means of optical and scanning electron microscope. It was pointed out that the ultrasound treatment increases the cavitation erosion resistance of the alloy, as a consequence of the higher chemical and microstructural homogeneity, the finer grains and primary particles and the refined structure of the eutectic induced by the treatment itself.

  19. Fabrication of ceramic layer on an Al-Si alloy by MAO process

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    The MAO (Micro-Arc Oxidation) process is applied to a eutectic Al-Si alloy (Al-12.0%Si-l.0%Cu-0.9%Mg(mass fraction)). The oxide ceramic layer was fabricated with about 220 μm thickness and 3000 Hv micro-hardness. ByXRD (X-ray diffractometry) and DSC (differential scanning calorimetry) analyses, the oxide layer consists of amorphousAl2O3, which is distinct from the results reported by the other researchers. The SEM photographs of such layer show that thelayer is fixed tightly on the substrate alloy. So this alloy can be used in the high temperature and friction environment after itis treated with such process.

  20. Role of Laser Cladding Parameters in Composite Coating (Al-SiC) on Aluminum Alloy

    Science.gov (United States)

    Riquelme, Ainhoa; Escalera-Rodriguez, María Dolores; Rodrigo, Pilar; Rams, Joaquin

    2016-08-01

    The effect of the different control parameters on the laser cladding fabrication of Al/SiCp composite coatings on AA6082 aluminum alloy was analyzed. A high-power diode laser was used, and the laser control parameters were optimized to maximize the size (height and width) of the coating and the substrate-coating interface quality, as well as to minimize the melted zone depth. The Taguchi DOE method was applied using a L18 to reduce the number of experiments from 81 to only 18 experiments. Main effects, signal-noise ratio and analysis of variance were used to evaluate the effect of these parameters in the characteristics of the coating and to determine their optimum values. The influence of four control parameters was evaluated: (1) laser power, (2) scanning speed, (3) focal condition, and (4) powder feed ratio. Confirmation test with the optimal control parameters was carried out to evaluate the Taguchi method's effectivity.

  1. A solidification model for unmodified, Na-modified and Sr-modified Al-Si alloys

    DEFF Research Database (Denmark)

    Tiedje, Niels Skat; Hattel, Jesper Henri; Taylor, J. A.

    2012-01-01

    and the shape of the Si crystals are modified to a fine fibrous form so that the ductility of the material is increased. In the present work a one-dimensional numerical model is proposed that describes nucleation and growth of both primary dendrites and eutectic grains as a function of cooling conditions...... and modification. The model assumes that dendrites nucleate easily when the liquidus temperature is reached and that they grow as heat is extracted by the mould. Nucleation of the eutectic grains depends on local undercooling and growth is governed by a balance between growth of the eutectic grains and the rate......An addition of small amounts of Na and Sr is commonly used in the industry to modify the eutectic in Al-Si alloys. Both Na and Sr suppress nucleation of the eutectic forcing nucleation and growth to take place at higher undercooling than in the unmodified material. Thus the scale of the eutectic...

  2. Experimental study on directional solidification of Al-Si alloys under the influence of electric currents

    Science.gov (United States)

    Räbiger, D.; Zhang, Y.; Galindo, V.; Franke, S.; Willers, B.; Eckert, S.

    2016-07-01

    The application of electric currents during solidification can cause grain refinement in metallic alloys. However, the knowledge about the mechanisms underlying the decrease in grain size remains fragmentary. This study considers the solidification of Al-Si alloys under the influence of electric currents for the configuration of two parallel electrodes at the free surface. Solidification experiments were performed under the influence of both direct currents (DC) and rectangular electric current pulses (ECP). The interaction between the applied current and its own induced magnetic field causes a Lorentz force which produces an electro-vortex flow. Numerical simulations were conducted to calculate the Lorentz force, the Joule heating and the induced melt flow. The numerical predictions were confirmed by isothermal flow measurements in eutectic GaInSn. The results demonstrate that the grain refining effect observed in our experiments can be ascribed solely to the forced melt flow driven by the Lorentz force.

  3. Study of phase stresses in an Al/SiC metal matrix composite

    Energy Technology Data Exchange (ETDEWEB)

    Levy-Tubiana, R.; Ceretti, M.; Lodini, A. [Laboratoire Leon Brillouin, Centre d' Etudes Nucleaires de Saclay, 91 - Gif-sur-Yvette (France); Baczmanski, A.; Wierzbanowski, K. [Wydzial Fizyki i Techniki Jadrowej, Akademia Gorniczo-Hutnicza, Krakow (Poland); Fitzpatrick, M. [Materials Discipline, Faculty of Technology, Open Univ., Milton Keynes (United Kingdom)

    2000-07-01

    The stress field existing within a polycrystalline material can be described at different scales of interest. Here, the stresses for two different scales are considered: the macro stress which is defined as the average stress over the sample volume containing a large number of polycrystalline grains, i.e. over many millimeters or even centimeters; and the second order stress which is defined as the deviation of the stress for a particular grain from the macroscopic value. The second order stresses vary on the scale of the grain size, or the inter-particle spacing in composite material. In this work the second order stress was predicted using the self-consistent model of elasto-plastic deformation for Al/SiCp composite. The results were verified using neutron diffraction method of stress measurement. (orig.)

  4. Microstructure of AlSi17Cu5 alloy after overheating over liquidus temperature

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2015-01-01

    Full Text Available The paper presents microstructure tests of alloy AlSi17Cu5. In order to disintegrate the primary grain of silicon the so-called time-temperature transformation TTT was applied which was based on overheating the liquid alloy way over the temperature Tliq., soaking in it for 30 minutes and casting it to a casting mould. It was found that such process causes the achievement of fine-crystalline structure and primary silicon crystals take up the form of pentahedra or frustums of pyramids. With the use of X-ray microanalysis and X-ray diffraction analysis the presence of intermetallic phases Al2Cu, Al4Cu9 which are the ingredients of eutectics α - AlCu - β and phase Al9Fe2Si which is a part of eutectic α - AlFeSi - β was confirmed.

  5. Wear behavior and microstructure of hypereutectic Al-Si alloys prepared by selective laser melting

    Science.gov (United States)

    Kang, Nan; Coddet, Pierre; Liao, Hanlin; Baur, Tiphaine; Coddet, Christian

    2016-08-01

    This work investigates the microstructure and wear behavior of hypereutectic Al-Si alloys, in-situ fabricated using selective laser melting of a mixture of eutectic Al-12Si (wt.%) and pure Si powders. The first observation was that the size and morphology of the Si phase are strongly influenced by the laser power. In addition, it was also observed that a high laser power causes serious evaporation of aluminum during the remelting process. Dry sliding wear test and Vickers microhardness measurements were employed to characterize the mechanical properties of the material. The lowest wear rate of about 7.0 × 10-4 mm3 N-1 m-1 was observed for samples having the highest value of relative density (96%) and microhardness (105 Hv0.3).

  6. Al-Si-Mn Alloy Coating on Aluminum Substrate Using Cold Metal Transfer (CMT) Welding Technique

    Science.gov (United States)

    Rajeev, G. P.; Kamaraj, M.; Bakshi, S. R.

    2014-06-01

    The cold metal transfer (CMT) process was explored as a weld overlay technique for synthesizing Al-Si-Mn alloy coating on a commercially pure Al plate. The effect of welding speed on the bead geometry, deposition rate, and the dilution were studied and the best parameter was used to synthesize the coatings. The CMT process can be used to produce thick coatings (>2.5 mm) without porosity and with low dilution levels. The Vickers hardness number of the Al substrate increased from 28 in the bulk to 57 in the coating. It is suggested that the CMT process can be an effective and energy-efficient technique for depositing thick coatings and is useful in weld repair of aluminum alloy components.

  7. Fatigue behavior of press hardened Al-Si coated high strength steel

    Institute of Scientific and Technical Information of China (English)

    Wang Zijian; Gui Zhongxiang; Zhang Yisheng

    2014-01-01

    The fatigue behavior of press hardened Al-Si coated high strength steel has been investigated,and the fatigue strength turns out to be about 1 000 MPa. Surface morphology of fractured and non-fractured speci-men has been observed,and the coating shows significant influence on the fatigue behavior. The difference of elastic modulus between coating and substrate led to the main cracks perpendicular to the loading direction. The coating close to fracture exfoliated thinly,while the coating far away from the fracture kept integrated. Though the specimen was polished to obtain high surface quality,3 types of cracks occurred during the fatigue test. What’s more,inclusion particles were proved to play a crucial role in causing these cracks.

  8. Effect of ring notch radius on the decohesion mode in AlSi alloys

    Directory of Open Access Journals (Sweden)

    J. Pieklo

    2009-04-01

    Full Text Available The article discusses the effect of the, determined by tensile test, non-linear characteristics of AlSi alloys on the value of the shape factor k for the three different sizes of the radius of the ring notch made on round specimens. Applying a numerical solution, the changes of stress in the notch plane were determined in function of the notch configuration and the value of instantaneous load. Tensile tests were carried out on round bars with ring notches. The appearance of fractures was examined on scanning images. Differences in notch effect observed in the linear-elastic and elastic-plastic model of material hardening in a non-linear mode were described.

  9. Analysis and optimization of process parameters in Al-SiCp laser cladding

    Science.gov (United States)

    Riquelme, Ainhoa; Rodrigo, Pilar; Escalera-Rodríguez, María Dolores; Rams, Joaquín

    2016-03-01

    The laser cladding process parameters have great effect on the clad geometry and on dilution in the single and multi-pass aluminum matrix composite reinforced with SiC particles (Al/SiCp) coatings on ZE41 magnesium alloys deposited using a high-power diode laser (HPLD). The influence of the laser power (500-700 W), scan speed (3-17 mm/s) and laser beam focal position (focus, positive and negative defocus) on the shape factor, cladding-bead geometry, cladding-bead microstructure (including the presence of pores and cracks), and hardness has been evaluated. The correlation of these process parameters and their influence on the properties and ultimately, on the feasibility of the cladding process, is demonstrated. The importance of focal position is demonstrated. The different energy distribution of the laser beam cross section in focus plane or in positive and negative defocus plane affect on the cladding-bead properties.

  10. Microstructures and Properties of Ti-Coated SiCp Reinforced Al-Si Alloy Composites

    Science.gov (United States)

    Feng, Yan; Ren, Junpeng; Dong, Cuige; Wang, Richu

    2016-12-01

    A double-layer structure of Ti coating was plated on the surface of SiC particles using a diffusion method in a vacuum reactor, which is a new method to fabricate a Ti-coating layer on the SiC particles. The phase structure of Ti coating on the surface of SiC particles was composed inside of Ti5Si3 and outside of TiC investigated by x-ray diffraction. The Ti5Si3 and TiC double-layer structure realizes the tight chemical bonding between SiC particles and the Ti coating, and significantly promotes the wettability between the aluminum matrix and the Ti-coated SiC particles. The Ti-coated SiCp-reinforced Al-Si composites are prepared by a powder metallurgy method, and express excellent relative densities, desirable mechanical properties and frictional wear resistance.

  11. Effect of Rare Earth Metals on the Microstructure of Al-Si Based Alloys

    Directory of Open Access Journals (Sweden)

    Saleh A. Alkahtani

    2016-01-01

    Full Text Available The present study was performed on A356 alloy [Al-7 wt %Si 0.0.35 wt %Mg]. To that La and Ce were added individually or combined up to 1.5 wt % each. The results show that these rare earth elements affect only the alloy melting temperature with no marked change in the temperature of Al-Si eutectic precipitation. Additionally, rare earth metals have no modification effect up to 1.5 wt %. In addition, La and Ce tend to react with Sr leading to modification degradation. In order to achieve noticeable modification of eutectic Si particles, the concentration of rare earth metals should exceed 1.5 wt %, which simultaneously results in the precipitation of a fairly large volume fraction of insoluble intermetallics. The precipitation of these complex intermetallics is expected to have a negative effect on the alloy performance.

  12. THE APPLICATION OF Ni FOR IMPROVEMENT OF Al-Si-Fe ALLOYS

    Directory of Open Access Journals (Sweden)

    Jozef Petrík

    2009-09-01

    Full Text Available Iron, often present in secondary material (scrap forms brittle and hard needles in Al-Si alloys.These particles decrease the mechanical properties of castings. A reliable and economic method of iron elimination from aluminium alloys has not been well-known yet in metallurgical practice. The influence of nickel as an iron corrector (up to 0.7 % and iron (up to 2.5 % on the fluidity, microstructure and mechanical properties of the Al alloy with 9.75 % Si, 0.2 % Mg was evaluated. The presence of Ni results in shortening of the needles, but the segmentation of ß needles was not observed. Improvement of mechanical properties was observed despite of low affecting of microstructure.

  13. Design, Manufacture and Analysis of Al/SiC MMCs for Connecting Rod

    Science.gov (United States)

    Ramasubramanian, S.; Chandrasekaran, M.; Sridhar, R.; Karunakaran, K.

    2017-03-01

    The Metal matrix composite materials is particularly are widely used in automotive engineering applications. In this work discuss with production of Al/SiC composite and investigate it’s suitability for the application on Connecting Rod. The results were compared with conventional material C70 Steel. The connecting rod is manufactured using the stir casting method. The basic properties were obtained by mechanical testing. The test results were used for FEA. The connecting rod is designed and meshed using solid works and hyper mesh, and then analysis is done used by ANSYS work bench 14.0 software. The results show that the composite connecting rod is more efficient than the conventional ones.

  14. EFFECT OF PROCESS PARAMETERS ON SURFACE ROUGHNESS IN END MILLING OF Al/SiCp MMC

    Directory of Open Access Journals (Sweden)

    K. PALANIRADJA

    2011-01-01

    Full Text Available Metal matrix composites (MMCs have emerged as an important class of materials, which are increasingly being utilized in recent years. These materials are known as the difficult-to-machine materials because of the hardness and abrasive nature of reinforcements. The present work investigate the effect of spindle speed, feed rate, depthof cut and different % wt. of SiCp on surface roughness in end milling of LM25Al/SiCp. Experiments have been conducted on a CNC milling machine according to the principles of Response surface methodology design of experiments (DoE method. Central composite design (CCD was employed in developing an efficient mathematical model for surface roughness. Analysis of variance (ANOVA was used to test the adequacy of the developed mathematical model. The contour plots were generated to study the effect of process parameters aswell as their interactions.

  15. Pressure die cast graphite dispersed Al-Si-Mg alloy matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Pillai, U.T.S. (Regional Research Lab. (CSIR), Trivandrum (India)); Pai, B.C. (Regional Research Lab. (CSIR), Trivandrum (India)); Kelukutty, V.S. (Regional Research Lab. (CSIR), Trivandrum (India)); Satyanarayana, K.G. (Regional Research Lab. (CSIR), Trivandrum (India))

    1993-09-15

    An improvement in casting of aluminium alloy graphite particulate composite synthesized by stir casting is discussed. About 15 wt.% graphite particles were dispersed in Al-Si-Mg (LM 25) alloy by the rheocasting technique. The composite ingots were used as a master alloy and diluted further with LM 25 alloy to obtain a 5 wt.% dispersion of graphite in the matrix. The composite ingots thus processed were subsequently remelted and pressure die cast into plates. Macroscopic and microscopic examination of the plates revealed fewer defects and a fine distribution of particles. The ultimate tensile strength evaluated in this composite was superior (132-136 MPa) to that of gravity die cast (85-95 MPa) composites. The fracture toughness of the composites was in the range 8-10 MPa m[sup 1/2]. (orig.)

  16. Developments in the processing and properties of particulate Al-Si composites

    Science.gov (United States)

    Ejiofor, J. U.; Reddy, R. G.

    1997-11-01

    In the past ten years, materials R&D has shifted from monolithic to composite materials, adjusting to the global need for reduced weight, low cost, quality, and high performance in structural materials. This article reviews developments in the molten processing of particulate Al-Si alloy composites and their respective properties. Existing and emerging processing innovations are discussed, and the reinforcement phases in prominent R&D activities are identified. The vortex (or mixing) method continues to be the most popular processing method in use because of its ease of operation, total production cost, and suitability, while the infiltration, compocasting (or rheocasting), in-situ, and spray atomization and codeposition techniques receive less attention.

  17. Thermal description of hypoeutectic Al-Si-Cu alloys using silicon equivalency

    Directory of Open Access Journals (Sweden)

    Mile B. Đurđević

    2012-01-01

    Full Text Available The modeling of casting processes has remained a topic of active interest for several decades, and availability of numerous software packages on the market is a good indication of the interest that the casting industry has in this field. Most of the data used in these software packages are read or estimated from the binary or multi-component phase diagrams. Unfortunately, except for binary diagrams, many of ternary or higher order phase diagrams are still not accurate enough. Having in mind that most of the aluminum binary systems are very well established, it has been tried to transfer a multi-component system into one well known Al-Xi pseudo binary system (in this case the Al-Si phase diagram was chosen as a reference system. The new Silicon Equivalency (SiEQ algorithm expresses the amounts of major and minor alloying elements in the aluminum melts through an 'equivalent' amount of silicon. Such a system could be used to calculate several thermo-physical and solidification characteristics of multi component as cast aluminum alloys. This lends the model the ability to make predictions of solidification characteristics of cast parts, where cooling rates are slow and the solidification process has to be known in great detail in order to avoid problems in the casting. This work demonstrates how the SiEQ algorithm can be used to calculate characteristic solidification temperatures of the multi-component hypoeutectic Al-Si-Cu alloys as well as their latent heats. SA statistical analysis of the results obtained for a wide range of alloy chemical compositions shows a very good correlation with the experimental data and the SiEQ calculations.

  18. Corrosion and protection of heterogeneous cast Al-Si (356) and Al-Si-Cu-Fe (380) alloys by chromate adn cerium inhibitors

    Science.gov (United States)

    Jain, Syadwad

    presence of soluble cerium cations showed that of anodic and cathodic activity was not as strongly inhibited as was observed for chromate ions. Overall cerium conversion coating showed good performance on Al-Si (356) ally, but poor performance on Fe- and Cu-rich alloy (380).

  19. Preparation of Al-Si-Ti Master Alloys by Electrolysis of Silica and Titania in Cryolite-Alumina Melts

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    Aluminum-silicon-titanium master alloys were prepared in the laboratory by electrolysis of silica and titania dissolved in cryolite-alumina melts. Alloys containing up to 12 mass% Si and 2.6 mass% Ti were formed after about 90 min of electrolysis at 950℃. The current efficiency for the preparation of the Al-Si-Ti alloys varied with time, temperature and cathodic current density. It is concluded that this electrolytic method may be an interesting alternative to the direct metal mixing process for formation of Al-Si-Ti master alloys.

  20. Study on selective laser melting process and forming of AlSi10 Mg alloy powder%选择性激光熔化AlSi10 Mg合金粉末的成形工艺

    Institute of Scientific and Technical Information of China (English)

    刘锦辉; 史金光; 李亚

    2015-01-01

    This paper deals with the single-layer single-channel experiment and single-layer multi-channel experiment performed by using different process parameters to study the selective laser melting (SLM) forming process of AlSi10Mg alloy powder. This study consists of analyzing the effects of laser power, laser scanning speed, scanning interval on melting channel width and surface quality;testing the density of SLM AlSi10 Mg samples formed under different parameters and analyzing the relationship be-tween energy density and the sample density; and testing the microstructure and property, and micro-hardness. The results show that the optimal scanning track quality is governed the given process parame-ters:laser power between 240~280 W, scanning speed between 1 000~1 400 mm/s, scanning interval between 0 . 06~0 . 08 mm; SLM-produced AlSi10 Mg parts perform much better than conventionally cast AlSi10 Mg ones .%为了研究AlSi10 Mg合金粉末的选择性激光熔化成形,采用不同的工艺参数,进行了单层单道扫描实验和单层多道扫描实验。分析激光功率、激光扫描速度、扫描间距对激光扫描轨迹宽度和表面质量的影响。检测不同参数下选择性激光熔化成形的AlSi10 Mg合金块的致密度,分析成形件致密度与能量密度的关系,成形件的组织和性能,对成形件进行硬度测试。结果表明:激光功率在240~280 W,扫描速度在1000~1400 mm/s,扫描间距在0.06~0.08 mm时,扫描轨迹成形质量最佳。与传统铸造AlSi10Mg合金零件相比,SLM成形的零件具有更好的性能。

  1. 热处理对Al-Si-Cu-Mg铸造铝合金低周疲劳行为的影响%Influence of Heat Treatment on Low-Cycle Fatigue Behavior of Al-Si-Cu-Mg Alloy

    Institute of Scientific and Technical Information of China (English)

    李锋; 陈巧; 车欣; 陈立佳

    2012-01-01

    为了确定固溶处理及固溶+时效处理对金属型铸造A1-Si-Cu-Mg铝合金低周疲劳行为的影响,在不同外加总应变幅下进行应变控制的室温低周疲劳试验.结果表明:金属型铸造Al-Si-Cu-Mg铝合金可表现为循环应变硬化、循环应变软化和循环稳定;固溶处理及固溶+时效处理可以有效地提高金属型铸造Al-Si-Cu-Mg铝合金的疲劳寿命,且固溶处理对疲劳寿命提高的幅度更大;铸态及固溶态Al-Si-Cu-Mg铝合金的弹性应变幅、塑性应变幅与疲劳断裂时的载荷反向周次之间分别呈直线关系,固溶+时效态Al-Si-Cu-Mg铝合金的弹性应变幅与疲劳断裂时的载荷反向周次之间呈直线关系,但其塑性应变幅与疲劳断裂时的载荷反向周次之间呈双线性关系;不同处理状态的铸造Al-Si-Cu-Mg铝合金的循环应力幅与塑性应变幅之间呈线性关系.%In order to determine the influence of solid-solution and solid-solution plus aging treatments on low-cycle fatigue behavior of permanent-mold cast Al-Si-Cu-Mg alloy, the strain controlled low-cycle fatigue tests were performed at room temperature and different total strain amplitudes. The experimental results show that the permanent-mold cast Al-Si-Cu-Mg alloy exhibits the cyclic strain hardening, softening and stability. The solid-solution and solid-solution plus aging treatments can effectively enhance the fatigue lives of the permanent-mold cast Al-Si-Cu-Mg alloy, and the solid-solution treatment has more significant in enhancing the fatigue lives of the alloy. A single-slope linear relationship between plastic and elastic strain amplitudes as well as reversals to failure is observed for both as-cast and solid-solution treated Al-Si-Cu-Mg alloys. For the permanent-mold cast Al-Si-Cu-Mg alloy subjected to solid-solution plus aging treatment, the relationship between elastic strain amplitude and reversals to failure also shows linear behavior, but a bilinear

  2. Low-cycle Fatigue Behavior of Permanent-mold Cast Al-Si-Cu-Er Alloy%金属型铸造Al-Si-Cu-Er合金的低周疲劳行为

    Institute of Scientific and Technical Information of China (English)

    吴伟; 王爽; 吕伟; 车欣

    2011-01-01

    通过在不同外加总应变幅下进行应变控制的室温低周疲劳试验,探讨了金属型铸造A1-Si-Cu-Er合金的疲劳变形和断裂行为.结果表明,在低周疲劳加载下,金属型铸造Al-Si-Cu-Er合金表现为循环应变硬化、循环稳定;金属型铸造Al-Si-Cu-Er合金的弹性应变幅、塑性应变幅与疲劳断裂时的载荷反向周次之间的关系可分别用Basquin和Coffin-Manson公式描述;金属型铸造Al-Si-Cu-Er合金在低周疲劳加载条件下,裂纹均以穿晶方式萌生于试样表面,并以穿晶方式扩展.%The fatigue deformation and fracture behavior of permanent-mold cast Al-Si-Cu-Er alloy were investigated by low-cycle fatigue test at room temperature under different total strain amplitudes. The results show that permanent-mold cast Al-Si-Cu-Er alloy exhibits cyclic strain hardening and stable cyclic stress response during fatigue deformation, which mainly depend on the imposed total strain. The relation between elastic strain amplitude, plastic strain amplitude and reversals to failure can be described by Coffin-Manson and Basquin equations,respectiveiy. In addition, the fatigue cracks initiate at the free surface of fatigue specimens and propagate in a transgranular mode under low-cycle fatigue.

  3. Optimization of Stir Casting Process Parameters to Minimize the Specific Wear of Al-SiC Composites by Taguchi Method

    Directory of Open Access Journals (Sweden)

    Sadi

    2015-02-01

    Full Text Available The aim of this research is to optimize of stir casting process parameters to minimize the specific wear of Al-SiC composites by Taguchi method. Composite material used in this research was Al- Si aluminum alloy as the matrix and SiC (silicon carbide particles size 400 mesh as the reinforcement. Experimental design used L16 orthogonal arrays Taguchi method standards. Experimental factors used in the making of composite samples were SiC content, melt temperature, rotation speed and stirring duration, each with 4 levels or variations. The microstructures of Al-SiC composite were observed by scanning electron microscope (SEM. Experimental result showed that the optimum of stir casting process parameters are SiC content of 15 wt.%, melt temperature of 740 oC, rotation speed of 300 rpm and stirring duration of 10 minutes. The most significant parameter which affected on specific wear was SiC content which contributes 88.67%. Adding content of SiC from 0 to 15 wt. % can decrease the specific wear of Al-SiC composites about 90.08 %.

  4. Compound fabrication technology of semi-solid billet of Al-Si alloy based on SIMA method

    Institute of Scientific and Technical Information of China (English)

    XUE Ke-min; MI Guang-bao; WANG Qing-rui

    2006-01-01

    Based on SIMA, the Al-Si alloy semi-solid billets were successfully fabricated by means of strain inducement and isothermal treatment for AlSi9Mg poured in the range of near-liquidus. Through orthogonal test, the effects of combination action of near-liquidus casting, strain inducement and isothermal treatment on the morphology of primary α-Al phase of AlSi9Mg close to eutectic point were investigated, and the optimal match relation between the processing parameters of solidification, deformation parameters of strain inducement, processing parameters of isothermal treatment and microstructure parameters of semi-solid alloy was established. The results indicate that compared with the single near-liquidus casting or SIMA, the microstructure of primary α-Al phase in AlSi9Mg alloy prepared by compound fabrication process is more homogeneous, with more globular and finer particles,which has average grain size of 40-50 μm and shape factor of greater than 0.75. After holding at 605 ℃ for 30-40 min under a certain cooling rate, increased deformation volume in SIMA benefits the refinement of the grain and the improvement of the morphology for primary phase.

  5. Analysis of structural properties for AlSi11 alloy with use of thermal derivative gradient analysis TDGA

    Directory of Open Access Journals (Sweden)

    M. Cholewa

    2008-08-01

    Full Text Available In this paper a basis of thermal derivative gradient analysis was shown. Authors presented methodology of the studies, results and analysis. Studies of crystallization kinetics were conducted on non-modified AlSi11 eutectic alloy. Analyzing the results authors proposed some parameters for description of crystallization kinetics and their relation to microstructure and mechanical properties.

  6. Prediction of U-Mo dispersion nuclear fuels with Al-Si alloy using artificial neural network

    Energy Technology Data Exchange (ETDEWEB)

    Susmikanti, Mike, E-mail: mike@batan.go.id [Center for Development of Nuclear Informatics, National Nuclear Energy Agency, PUSPIPTEK, Tangerang (Indonesia); Sulistyo, Jos, E-mail: soj@batan.go.id [Center for Nuclear Facilities Engineering, National Nuclear Energy Agency, PUSPIPTEK, Tangerang (Indonesia)

    2014-09-30

    Dispersion nuclear fuels, consisting of U-Mo particles dispersed in an Al-Si matrix, are being developed as fuel for research reactors. The equilibrium relationship for a mixture component can be expressed in the phase diagram. It is important to analyze whether a mixture component is in equilibrium phase or another phase. The purpose of this research it is needed to built the model of the phase diagram, so the mixture component is in the stable or melting condition. Artificial neural network (ANN) is a modeling tool for processes involving multivariable non-linear relationships. The objective of the present work is to develop code based on artificial neural network models of system equilibrium relationship of U-Mo in Al-Si matrix. This model can be used for prediction of type of resulting mixture, and whether the point is on the equilibrium phase or in another phase region. The equilibrium model data for prediction and modeling generated from experimentally data. The artificial neural network with resilient backpropagation method was chosen to predict the dispersion of nuclear fuels U-Mo in Al-Si matrix. This developed code was built with some function in MATLAB. For simulations using ANN, the Levenberg-Marquardt method was also used for optimization. The artificial neural network is able to predict the equilibrium phase or in the phase region. The develop code based on artificial neural network models was built, for analyze equilibrium relationship of U-Mo in Al-Si matrix.

  7. Rheological behavior of molten Al-SiC slurries and comparison of their behavior with metallic slurries

    Science.gov (United States)

    Heidary, D. Sohrabi Baba; Akhlagh, F.

    2013-07-01

    In this study a new precise rotational viscometer was developed and used to measure the viscosity of molten A356 alloy containing 5, 15, and 25vol.% of 90-106 μm SiC particles at 650 and 690 °C. Three types of typical curves viscosity (η) versus volume fraction of SiC particles, shear time (t), and shear rate (γ) were derived advantage from the results of viscosity measurements. It would present the viscosity got lowered by decreasing particle volume fraction and by increasing the amounts of shear time and shear rate. In the next step, the influence of the number of aggregates on apparent viscosity was studied by the special tests, developed in this research. Also the formation of aggregates in Al-SiC composite slurries was explained and compared with metallic slurries. It concluded that the origin of aggregation in Al-SiC slurries was long range electrical forces while in metallic slurries it was micro welds between particles. it would show the rheological behavior of Al-SiC slurries could be justified according to the nature and the numbers of their aggregates. At the end, the implications of findings in order to predict the gradient of particles in functionally graded Al-SiC composites, produced by casting, were discussed.

  8. Frictional behaviors of some nitrogen ceramics in conformal contact with tin coated Al-Si alloy, steel and MMC

    Science.gov (United States)

    Wang, Q.; Cheng, H. S.; Fine, M. E.

    1994-07-01

    The frictional behavior of certain nitrogen-containing ceramics, such as silicon nitride, alpha sialons, and beta sialons as journal materials were studied in conformal contact with a tin-coated Al-Si alloy (Al-Si/Sn), forged 1141 steel and a cast aluminum matrix composite with silicon carbide reinforcement (cast metal matrix composites (MMC)) as bearing materials while lubricated with SAE 10W30. A case-hardened 1016 steel was also tested with the Al-Si/Sn and cast MMC bearings under the same conditions. The friction values of the ceramic and the steel journal wear pairs were compared and their frictional behaviors were evaluated. Silicon nitride and one of the beta sialons exhibited higher load-supporting capacities than the others when they were in contact with the 1141 steel bearings. The journal surface roughness was found to be very important when the journals were in contact with the Al-Si/Sn bearings. The frictional behavior of the ceramics and cast MMC pairs and the steel and cast MMC pairs were controlled by different wear machanisms, namely for the former, hard particle pull-out and matrix plowing, and for the latter, iron transfer from the journal to the cast MMC bearing surface.

  9. Effect of bias voltage on TiAlSiN nanocomposite coatings deposited by HiPIMS

    Science.gov (United States)

    Ma, Quansheng; Li, Liuhe; Xu, Ye; Gu, Jiabin; Wang, Lei; Xu, Yi

    2017-01-01

    TiAlSiN nanocomposite coatings were deposited onto cemented carbide (WC-10 wt.%, Co) substrates by high power impulse magnetron sputtering (HiPIMS). The effect of substrate bias voltage on plasma discharge characterization of HiPIMS, element concentration, deposition rate, microstructure, surface/cross-sectional morphology, hardness and adhesion strength of coatings were studied. Compared with those deposited with direct current magnetic sputtering (DCMS), HiPIMS-deposited TiAlSiN coatings show improvements in some properties, including the surface roughness, the grain size, the hardness and adhesion strength, but a decrease in the deposition rate. When the bias voltage increases, the discharge current rose up from 118A to 165A. HiPIMS-deposited TiAlSiN coatings show a shift of the preferred crystallographic orientation from (220) to (200) and decreases in surface roughness from 14.1 nm down to 7.4 nm and grain size from 10.5 nm to 7.4 nm. Meanwhile, a change in crystal morphology from columnar to equiaxial and a grain refinement, as well as an increase of hardness from 30 GPa up to 42 GPa of those TiAlSiN coatings were observed with the increasing bias voltage and a decrease in adhesion strength from HF2 to HF5 of those coatings were revealed by indentation adhesion test.

  10. Microstructure of as-fabricated UMo/Al(Si) plates prepared with ground and atomized powder

    Science.gov (United States)

    Jungwirth, R.; Palancher, H.; Bonnin, A.; Bertrand-Drira, C.; Borca, C.; Honkimäki, V.; Jarousse, C.; Stepnik, B.; Park, S.-H.; Iltis, X.; Schmahl, W. W.; Petry, W.

    2013-07-01

    UMo-Al based fuel plates prepared with ground U8wt%Mo, ground U8wt%MoX (X = 1 wt%Pt, 1 wt%Ti, 1.5 wt%Nb or 3 wt%Nb) and atomized U7wt%Mo have been examined. The first finding is that that during the fuel plate production the metastable γ-UMo phases partly decomposed into two different γ-UMo phases, U2Mo and α'-U in ground powder or α″-U in atomized powder. Alloying small amounts of a third element to the UMo had no measurable effect on the stability of the γ-UMo phase. Second, the addition of some Si inside the Al matrix and the presence of oxide layers in ground and atomized samples is studied. In the case with at least 2 wt%Si inside the matrix a Silicon rich layer (SiRL) forms at the interface between the UMo and the Al during the fuel plate production. The SiRL forms more easily when an Al-Si alloy matrix - which is characterized by Si precipitates with a diameter ⩽1 μm - is used than when an Al-Si mixed powder matrix - which is characterized by Si particles with some μm diameter - is used. The presence of an oxide layer on the surface of the UMo particles hinders the formation of the SiRL. Addition of some Si into the Al matrix [7-11]. Application of a protective barrier at the UMo/Al interface by oxidizing the UMo powder [7,12]. Increase of the Mo content or use of UMo alloys with ternary element addition X (e.g. X = Nb, Ti, Pt) to stabilize the γ-UMo with respect to α-U or to control the UMo-Al interaction layer kinetics [9,12-24]. Use of ground UMo powder instead of atomized UMo powder [10,25] The points 1-3 are to limit the formation of the undesired UMo/Al layer. Especially the addition of Si into the matrix has been suggested [3,7,8,10,11,26,27]. It has been often mentioned that Silicon is efficient in reducing the Uranium-Aluminum diffusion kinetics since Si shows a higher chemical affinity to U than Al to U. Si suppresses the formation of brittle UAl4 which causes a huge swelling during the irradiation. Furthermore it enhances the

  11. Role of Al2O3 fiber in eutectic Al-Si alloy composites

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The effects of Al2O3 fiber on wear characteristics of eutectic Al-Si alloy composites were studied using a pin-on-disk tester under dry sliding condition. The results show that the Al2O3 fiber can make matrix grain be fine, specially the eutectic Si be finer and prevent the plastic flow of matrix and prohibit the crack propagation in the wear layer, thereby it can remarkably improve the mechanical property and the wear resistance of the MMCs. Since Al2O3 fiber plays a role of certain framework in protecting the matrix against crash, it can eliminate the severe wear of MMCs with higher φf of fiber from the beginning of test. At mild stage, when φf is in the range of 8%~10%, the wear rates are the lowest. With increasing φf of Al2O3 fiber, the wear mechanism of MMCs can be transformed from adhesive delamination to brittle breakaway.

  12. Microstructure and mechanical properties of hypereutectic Al-Si alloy modified with Cu-P

    Institute of Scientific and Technical Information of China (English)

    ZHANG Henghua; DUAN Haiti; SHAO Guangjie; XU Luoping

    2008-01-01

    The microstructure and mechanical properties of Al-14.6Si castings modified by Cu-P master alloy under different conditions were studied with optical microscope (OM) and mechanical testing and simulation (MTS).The results indicate that the Cu-P master alloy possesses not only obvious modification effect,but also longevity effect with more than 8 h on the hypereutectic Al-Si alloy.It is shown from thermal calculation,scanning electron microscope (SEM),and energy dispersive analysis of X-rays (EDAX) that the modification mechanism of Cu-P on primary silicon in the castings is heterogeneous nucleation around AlP particles.The Cu-P master alloy has no or little modifying effect on eutectic silicon,even though it has obvious modification on primary silicon in the castings.This may be because of the fast transformation of eutectic silicon at a very narrow temperature,which will notably weaken the role of AlP particles as heterogeneous nuclei for eutectic silicon.

  13. New Quality Assessment Criterion of AlSi5Cu1 Alloy

    Directory of Open Access Journals (Sweden)

    M. Wierzbińska

    2007-07-01

    Full Text Available The paper presents the discussion of the results of mechanical testing for aluminium foundry alloy AlSi5Cu1Mg for high-loaded machine elements. Values of yield strength (Rp0.2, tensile strength (Rm, elongation(A5 and hardness (HB are usually considered as the primary quality assessment criterion for a manufacturing process. It was concluded, that this criterion, A5 index particularly, is unsatisfactory to estimate the plasticity of the alloy and its crack resistance in the presence of sharp-pointed stress concentrators or microcracks. More adequate parameter is plane strain fracture toughness KIc. However, size of the samples appeared to be twice as large as would be needed to fulfill requirements of test conditions, and the test itself is laborious and time-consuming that it becomes impractical as a acceptance test. Therefore, substitute test for quality assessment – determination of tensile strength in the presence of a sharp notch kmR was applied. The comparative analysis of kmR/Rp0.2 ratio, as a more enhanced fatigue resistance criterion than kmR and plane strain fracture toughness KIc of the alloy was performed. It was assumed that kmR/Rp0.2 parameter has good correlation with the critical stress intensity factor KIc Thus, under manufacturing process conditions, being unable to carry out KIc test, it may be successfully replaced by kmR test.

  14. Simulation for microstructure evolution of Al-Si alloys in solidification process

    Institute of Scientific and Technical Information of China (English)

    XU Hong; HOU Hua; ZHANG Guo-wei

    2006-01-01

    The numerical simulation for microstructure evolution of Al-Si alloy in solidification process is carried out with phase field model. The phase field model,solution algorithm and the program of dendrite growth are introduced. The definition of initial condition,boundary condition and the stability condition of differential format are all included. The simulation results show that the evolution of dendrite morphology is as follows: the initial circle nucleus transforms to the rectangle one firstly,then its corners develop to the four trunks and from which the secondary side branches are generated and even the third side branches are produced from secondary ones. The dendrite tip radius decreases quickly at the initial stage and changes slowly at the late stage,which is mainly due to the fact that more and more side branches appear and grow up. The comparisons of dendrite morphology between simulated results and investigations by others are also presented. It is proved that the dendrite morphologies are similar in trunks and arms growth,so the developed phase field program is accurate.

  15. Mechanistic Selection and Growth of Twinned Bicrystalline Primary Si in Near Eutectic Al-Si Alloys

    Energy Technology Data Exchange (ETDEWEB)

    Jung, Choonho [Iowa State Univ., Ames, IA (United States)

    2006-01-01

    Morphological evolution and selection of angular primary silicon is investigated in near-eutectic Al-Si alloys. Angular silicon arrays are grown directionally in a Bridgman furnace at velocities in the regime of 10-3 m/sec and with a temperature gradient of 7.5 x 103 K/m. Under these conditions, the primary Si phase grows as an array of twinned bicrystalline dendrites, where the twinning gives rise to a characteristic 8-pointed star-shaped primary morphology. While this primary Si remains largely faceted at the growth front, a complex structure of coherent symmetric twin boundaries enables various adjustment mechanisms which operate to optimize the characteristic spacings within the primary array. In the work presented here, this primary silicon growth morphology is examined in detail. In particular, this thesis describes the investigation of: (1) morphological selection of the twinned bicrystalline primary starshape morphology; (2) primary array behavior, including the lateral propagation of the starshape grains and the associated evolution of a strong <100> texture; (3) the detailed structure of the 8-pointed star-shaped primary morphology, including the twin boundary configuration within the central core; (4) the mechanisms of lateral propagation and spacing adjustment during array evolution; and (5) the thermosolutal conditions (i.e. operating state) at the primary growth front, including composition and phase fraction in the vicinity of the primary tip.

  16. Relationship between Atmospheric Dew Point and Sinterability of Al-Si Based Alloy

    Institute of Scientific and Technical Information of China (English)

    A. Manonukul; A. Salee

    2013-01-01

    Al-Si based alloys are interestingly used to produce automotive components.Fabrication of such components by powder metallurgy (PM) has been developed continuously.During PM,several parameters affect the sinterability of the aluminium powder,including atmospheric dew point which is regarded as one of the crucial parameters.The objective of this work was to investigate the effect of the atmospheric dew point on the sinterability of Al-14.9Si-2.4Cu-0.55Mg by studying the sintering characters obtained under various atmospheric dew points.The aluminium alloy powder was pressed into tensile specimens and subsequently sintered in a nitrogen atmosphere at 560 ℃ for 60 min with varied atmospheric dew points.The results show that as the dew point decreased,the sintered properties were improved.The atmospheric dew point of-38.4 ℃ is sufficient to obtain good sintering characters and it is achievable in a commercial furnace.

  17. Rapid Solidification: Selective Laser Melting of AlSi10Mg

    Science.gov (United States)

    Tang, Ming; Pistorius, P. Chris; Narra, Sneha; Beuth, Jack L.

    2016-03-01

    Rapid movement of the melt pool (at a speed around 1 m/s) in selective laser melting of metal powder directly implies rapid solidification. In this work, the length scale of the as-built microstructure of parts built with the alloy AlSi10Mg was measured and compared with the well-known relationship between cell size and cooling rate. Cooling rates during solidification were estimated using the Rosenthal equation. It was found that the solidification structure is the expected cellular combination of silicon with α-aluminum. The dependence of measured cell spacing on calculated cooling rate follows the well-established relationship for aluminum alloys. The implication is that cell spacing can be manipulated by changing the heat input. Microscopy of polished sections through particles of the metal powder used to build the parts showed that the particles have a dendritic-eutectic structure; the dendrite arm spacings in metal powder particles of different diameters were measured and also agree with literature correlations, showing the expected increase in secondary dendrite arm spacing with increasing particle diameter.

  18. Thermodynamic stability of radiogenic Ba in CsAlSi2O6 pollucite

    Science.gov (United States)

    Jaffe, John; van Ginhoven, Renée; Jiang, Weilin

    2013-03-01

    Pollucite, a zeolite-like nanoporous aluminosilicate structure with nominal composition CsAlSi2O6, has been suggested as a nuclear waste storage form for fission-product radioactive isotopes of cesium, especially 137Cs. One factor affecting the long-term stability of this waste form is the valence change associated with the beta decay that converts Cs into barium. We have used first-principles density functional total energy calculations to evaluate the thermodynamic stability of pollucite with Ba replacing Cs at regular lattice sites with respect to the precipitation of Ba, Cs or their oxides. We included small clusters of substitutional BaCs as well as localized complexes of BaCs with compensating electron donor defects, specifically Cs vacancies and interstitial oxygen. We conclude that Cs-Ba pollucite is thermodynamically stable against precipitation of Cs or its oxide, but that partial precipitation of Ba or BaO may be thermodynamically favored under some conditions. Even this change may be kinetically limited, however. Fuel Cycle Research and Development, U.S. Department of Energy Waste Form Campaign

  19. Mg, Al, Si, Ca, Ti, Fe, and Ni abundance for a sample of solar analogues

    Science.gov (United States)

    López-Valdivia, Ricardo; Bertone, Emanuele; Chávez, Miguel

    2017-01-01

    We report on the determination of chemical abundances of 38 solar analogues, including 11 objects previously identified as super metal-rich stars. We have measured the equivalent widths for 34 lines of 7 different chemical elements (Mg, Al, Si, Ca, Ti, Fe, and Ni) in high-resolution (R ˜ 80 000) spectroscopic images, obtained at the Observatorio Astrofísico Guillermo Haro (Sonora, Mexico), with the Cananea High-resolution Spectrograph. We derived chemical abundances using ATLAS12 model atmospheres and the Fortran code MOOG. We confirmed the super metallicity status of 6 solar analogues. Within our sample, BD+60 600 is the most metal-rich star ([Fe/H]=+0.35 dex), while for HD 166991 we obtained the lowest iron abundance ([Fe/H]=-0.53 dex). We also computed the so-called [Ref] index for 25 of our solar analogues, and we found, that BD+60 600 ([Ref]=+0.42) and BD+28 3198 ([Ref]=+0.34) are good targets for exoplanet search.

  20. Effect of heat treatment on structural changes in metastable AlSi10mg alloy

    Directory of Open Access Journals (Sweden)

    Jordović B.

    2014-01-01

    Full Text Available This paper presents a study on structural changes occurring in a rapidly quenched metastable AlSi10Mg alloy during heating cycles within the temperature range from room temperature to 800 K. Measurement of electrical resistivity of a ribbon showed that structural stabilization takes place at temperatures ranging from 450 K to 650 K. The isotherms of the electrical resistivity measured at temperatures 473 K, 483 K and 498 K revealed two stages of structural stabilization i.e. a kinetic process and diffusion process. Measurement of the thermoelectromotive force of the thermocouple made from the investigated alloy and a copper conductor by a mechanical joining was used to determine relative changes in the electron density of states of the quenched sample after successive heat treatments. The same alloy sample was subjected to successive heat treatments at temperatures up to 503 K, 643 K, 683 K and 763 K. The change in the thermopower suggested that each heating was followed by an increase in free electron density in the alloy. Therefore, the abrupt decline in electrical resistivity was induced by an increase in both the mean free electron path and free electron density during the thermal stabilization of the structure. [Projekat Ministarstva nauke Republike Srbije, br. OI 172057: Controlled synthesis, structure and properties of multifunctional materials

  1. Description of hypoeutectic Al-Si-Cu alloys based on their known chemical compositions

    Directory of Open Access Journals (Sweden)

    Djurdjevic, M. B.

    2013-10-01

    Full Text Available The modeling of casting processes has remained a topic of active interest for several decades, and the availability of numerous software packages on the market is a good indication of the interest that the casting industry has in this field. Most of the data used in these software packages are directly read or estimated from the binary or multi-component phase diagrams. Unfortunately, except for binary diagrams, many of ternary or higher order phase diagrams are still not accurate enough. Having in mind that most of the aluminum binary systems are very well established, it has been tried to transfer multi-component system into one well known Al-Xi pseudo binary system (in this case the Al-Si phase diagram was chosen as a reference system. The new Silicon Equivalency (SiEQ algorithm expresses the amounts of major and minor alloying elements in the aluminum melts through an “equivalent” amount of silicon. Such a system could be used to calculate several thermo-physical and solidification characteristics of multi component as cast aluminum alloys. This provides to the model the capacity to predict the solidification characteristics of cast parts, where cooling rates are slow and the solidification process has to be known in great detail in order to avoid quality problems in the casting. This work demonstrates how the SiEQ algorithm can be used to calculate the characteristic solidification temperatures of the multicomponent Al-Si alloys as well as their latent heats and growth restriction factor. Statistical analysis of the results obtained for a wide range of alloy chemical compositions shows a very good correlation with the experimental data and the SiEQ calculations. The same mathematical approach might be applied for other metallic systems such as iron and magnesium, using carbon equivalency for ferrous systems and aluminum equivalency for magnesium multi-component alloys.La modelización de los procesos de fundición ha sido un tópico de

  2. Changes in Structural Characteristics of Hypoeutectic Al-Si Cast Alloy after Age Hardening

    Directory of Open Access Journals (Sweden)

    Lenka HURTALOVÁ

    2012-09-01

    Full Text Available The contribution describes influence of the age-hardening consist of solution treatment at 515 °C with holding time 4 hours, water quenching at 40 °C and artificial aging at different temperature 150 °C, 170 °C and 190 °C with different holding time 2, 4, 8, 16 and 32 hours on mechanical properties (tensile strength and Brinell hardness and changes in morphology of eutectic Si, Fe-rich and Cu-rich intermetallic phases in secondary (recycled AlSi9Cu3 cast alloy. A combination of different analytical techniques (light microscopy upon black-white and colour etching, scanning electron microscopy (SEM upon deep etching and energy dispersive X-ray analysis (EDX were therefore been used for the identification of the various phases. Quantitative study of changes in morphology of eutectic Si, Cu-rich and Fe-rich phases was carried out using Image Analyzer software NIS-Elements. Mechanical properties were measured in line with EN ISO. Age-hardening led to changes in microstructure include the spheroidization and coarsening of eutectic silicon, gradual disintegration, shortening and thinning of Fe- rich intermetallic phases, the dissolution of precipitates and the precipitation of finer hardening phase (Al2Cu further increase in the hardness and tensile strength in the alloy.DOI: http://dx.doi.org/10.5755/j01.ms.18.3.2430

  3. AN IN SITU SURFACE COMPOSITE AND GRADIENT MATERIALOF Al-Si ALLOY PRODUCED BY ELECTROMAGNETIC FORCE

    Institute of Scientific and Technical Information of China (English)

    Z.M. Xu; T.X. Li; Z.L. Zhu; Y.H. Zhou

    2001-01-01

    Because of the different conductivities between the primary phase (law electric conductivity) and the metal melt, electromagnetic force scarcely acts on the primary phase.Thus, an electromagnetic repulsive force applied by the metal melt exerts on the primary phase when the movement of the melt in the direction of electromagnetic force is limited. As a result, the repulsive force exerts on the primary phase to push them to move in the direction opposite to that of the electromagnetic force when the metal melt with primary phase solidifies under an electromagnetic force field. Based on this,a new method for production of in situ surface composite and gradient material by electromagnetic force is proposed. An in situ primary Si reinforced surface composite of Al-15wt%Si alloy and gradient material of Al-19wt%Si alloy were produced by this method. The microhardness of the primary Si is HV1320. The reinforced phase size is in the range from 40μm to 100μm. The wear resistance of Al-Si alloy gradient material can be more greatly increased than that of their matrix material.``

  4. The Refining Effect of Al-Ti-B-Sr Master Alloy on the Al- Si - Mg Alloy%Al-Ti-B-Sr对Al-Si-Mg合金的变质细化作用

    Institute of Scientific and Technical Information of China (English)

    亓效刚; 王玉厚; 边秀房

    2000-01-01

    用快速凝固和热变形处理的Al-Ti-B-Sr中间合金.对Al-Si-Mg铝轮毂材料进行处理.试验结果表明:Al-Ti-B-Sr中间合金可以对Al-7Si-0.35Mg合金有效地细化与变质;改善Al-Ti-B-Sr的细化与变质效果,Al-Si-Mg合金的抗拉强度和延伸率较Al-Ti-B、Al-Sr两种中间合金分别加入时提高了约10%和25%.

  5. Production and behaviour of aluminium foams with different density by AlSi12 precursor; Fabricacion y comportamiento de espumas de aluminio con diferente densidad a partir de un precursor AlSi12

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez-Vazquez, J. A.; Onoro, J.

    2010-07-01

    Closed cell aluminium foams were prepared by powder metallurgical method in three different ranges of density using AlSi12 precursor. The objective has been to determine by means of tests the effect that has the density of these materials regarding its mechanical behaviour. The used precursor contained 0.4% of foaming agent of titanium hydride (TiH{sub 2}), mixed with aluminum and silicon in appropriate amounts to achieve the commercial composition of the AlSi12 precursor. Once cut the samples thermal treatments of foaming were made of 630 degree centigrade to 750 degree centigrade, by 3 to 20 minutes. The best solidification conditions were determined to avoid the collapse by means of forced air. The samples were prepared with the same weight to different densities, having itself obtained that the best mechanical behaviour was achieved in the high density foams, of 0.70 to 0.81 g/cm{sup 3}. (Author) 26 refs.

  6. 无压浸渗制备Al/SiCp陶瓷基复合材料研究%Study on Pressureless Infiltration Preparation of Al/SiCp Ceramic Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    徐跃; 高霖; 崔崇; 钱凤

    2011-01-01

    The present paper studied the effects of Mg、Si and infiltration time on the preparation and microstructure of Al/SiCp ceramic matrix composites prepared by pressureless infiltration.Increasing fluidity of aluminum alloy liquid, improving the infiltration ability between aluminum alloy and SiC and avoiding the formation of bad Al4C3 on interface were important factors in assuring the scientific preparation of composites.Result indicated that two hours holding of infiltration and aluminum alloy containing 10(wt)% Mg and 15(wt)% Si could infiltrate fully with higher density,which was better technology parameters in preparing Al/SiCp ceramic matrix composites.%采用无压浸渗法,研究Mg、Si、浸渗时间时Al/SiCp陶瓷基复合材料制备及组织的影响.增加铝合金液的流动性,提高铝液同SiC之间的浸润性,防止有害ALC3界面形成,是保证复合材料科学制备的重要因素.研究结果表明,2h保温时间、10%Mg和15%Si铝合金液的实验参数制备的Al/SiCp复合材料浸渗充分,组织致密化程度高,是无压浸渗制备复合材料较好的参数.

  7. Influence of Stored Strain on Fabricating of Al/SiC Nanocomposite by Friction Stir Processing

    Science.gov (United States)

    Khorrami, M. Sarkari; Kazeminezhad, M.; Kokabi, A. H.

    2015-05-01

    In this work, 1050 aluminum (Al) sheets were annealed and severely deformed by 1, 2, and 3 passes of constrained groove pressing process to obtain the various initial stored strain values of 0, 1.16, 2.32, and 3.48, respectively. Friction stir processing (FSP) was then applied using SiC nanoparticles to fabricate Al/SiC nanocomposite with approximately 1.5 vol pct reinforced particles. Microstructural examinations revealed that an increase in the initial stored strain of the base metal led to the formation of finer grain structure after 1 pass of FSP. The finer grain structure occurred in the stir zone where a sufficient amount of nanoparticles with a relatively proper distribution existed. However, the initial stored strain value had a contrary influence in the regions with low volume fraction of nanoparticles. In fact, more stored strain in the base metal provided more driving force for both nucleation and grain growth of newly recrystallized grains at the stir zone. Pinning effect of well-distributed nanoparticles could effectively retard grain growth leading to the formation of very fine grain structure. Also it was observed that the initial stored strain values did not have impressive rule in the microstructural evolutions at the stir zone during the second and third FSP passes signifying that all of the stored energy in the base metal would be released after 1 pass of FSP. The results obtained with microhardness measurement at the stir zone were fairly in agreement with those achieved by the microstructure assessments.

  8. Metallurgical Parameters Controlling the Eutectic Silicon Charateristics in Be-Treated Al-Si-Mg Alloys

    Directory of Open Access Journals (Sweden)

    Mohamed F. Ibrahim

    2016-01-01

    Full Text Available The present work was carried out on Al-7%Si-0.4%Mg-X alloy (where X = Mg, Fe, Sr or Be, where the effect of solidification rate on the eutectic silicon characteristics was investigated. Two solidification rates corresponding to dendrite arm spacings (DAS of 24 and 65 μm were employed. Samples with 24 μm DAS were solution heat-treated at 540 °C for 5 and 12 h prior to quenching in warm water at 65 °C. Eutectic Si particle charateristics were measured using an image analyzer. The results show that the addition of 0.05% Be leads to partial modification of the Si particles. Full modification was only obtained when Sr was added in an amount of 150–200 ppm, depending on the applied solidification rate. Increasing the amount of Mg to 0.8% in Sr-modified alloys leads to a reduction in the effectiveness of Sr as the main modifier. Similar observations were made when the Fe content was increased in Be-treated alloys due to the Be-Fe interaction. Over-modification results in the precipitation of hard Sr-rich particles, mainly Al4SrSi2, whereas overheating causes incipient melting of the Al-Cu eutectic and hence the surrounding matrix. Both factors lead to a deterioration in the alloy mechanical properties. Furthermore, the presence of long, acicular Si particles accelerates the occurrence of fracture and, as a result, yields poor ductility. In low iron (less than 0.1 wt% Al-Si-Mg alloys, the mechanical properties in the as cast, as well as heat treated conditions, are mainly controlled by the eutectic Si charatersitics. Increasing the iron content and, hence, the volume fraction of Fe-based intermetallics leads to a complex fracture mode.

  9. Choice of salts for process of continous sodium modification of Al-Si alloys

    Directory of Open Access Journals (Sweden)

    Białobrzeski A.

    2007-01-01

    Full Text Available Broad application of aluminum cast alloys, silumins first of all, have become to be possible after finding a method of change of solidification form in Al-Si eutectic mixture. By introduction to liquid alloy a slight additive of modifying agent this primary thick, needle-like shape of Si crystals becomes altered into fine and compact structure. Quality of structure modification depends on correct proportioning of the modifying agent, temperature of metal and time elapsing from modification to solidification of the alloy. The sodium is used as one of the modifying agents. The sodium is introduced into metal bath in metallic form or in form of compounds containing sodium. Apart from a form in which modifying agent is introduced to metal bath, however, its action is relatively short (about 15-20 minutes. Prolongation of modifying agent’s action can be accomplished due to technology of continuous introduction of the sodium to metal bath. That technology is based on continuous electrolysis of sodium salt, occurring directly in melting pot with liquid alloy. Sodium salt placed in retort ( immersed in liquid metal undergoes dissociation due to applied voltage, and next electrolysis. Sodium ions arisen during the dissociation of sodium salts and electrolysis are “conveyed” through retort walls made from solid electrolyte. In contact with liquid alloy as cathode, sodium ions pass to atomic state, modifying the alloy. Suitable selection of material for the anode (source of sodium is an important issue. The paper presents results of preliminary research concerning selection of sodium salt, based on predetermined Rm tensile strength and measured voltage drop for the alloy in solid state. Values of those parameters confirm modification effect on tested alloys. Complexity of physical-chemical phenomena occurring in course of the process effects on necessity of further investigation which needs to be performed for optimization of parameters of the

  10. New rheocasting technology of semi-solid AlSi7Mg alloy%半固态AlSi7Mg铝合金的新型流变成形

    Institute of Scientific and Technical Information of China (English)

    毛卫民; 白月龙; 高松福; 汤国兴

    2006-01-01

    采用新型流变成形技术,研究了压射比压与压射速度对半固态AlSi7Mg铝合金流变压铸过程的影响.结果表明:将低过热度浇注与短时弱电磁搅拌相结合,能制备出均匀的半固态AlSi7Mg铝合金浆料,适合流变压铸,流变成型参数范围较宽,有利于提高压铸件的质量.试片的壁厚、压射比压和压射速度都对半固态AlSi7Mg合金浆料的充填性有较大的影响.对于10 mm的试片,压射比压应≥15 MPa,压射速度应≥0.384 m/s;而对于5 mm的试片,压射比压应≥20 MPa,压射速度应≥1.152 m/s.

  11. Electrochemical corrosion behaviour of Mg-Al alloys with thermal spray Al/SiCp composite coatings; Comportamiento a la corrosion electroquimica de aleaciones MgAl con recubrimientos de materiales compuestos Al/SiCp mediante proyeccion termica

    Energy Technology Data Exchange (ETDEWEB)

    Pardo, A.; Feliu Jr, S.; Merino, M. C.; Mohedano, M.; Casajus, P.; Arrabal, R.

    2010-07-01

    The corrosion protection of Mg-Al alloys by flame thermal spraying of Al/SiCp composite coatings was evaluated by electrochemical impedance spectroscopy in 3.5 wt.% NaCl solution. The volume fraction of SiC particles (SiCp) varied between 5 and 30%. The as-sprayed Al/SiCp composite coatings revealed a high number of micro-channels, largely in the vicinity of the SiC particles, that facilitated the penetration of the electrolyte and the subsequent galvanic corrosion of the magnesium substrates. The application of a cold-pressing post-treatment reduced the degree of porosity of the coatings and improved the bonding at the coating/substrate and Al/SiC interfaces. This resulted in improved corrosion resistance of the coated specimens. The effectiveness of the coatings slightly decreased with the addition of 5-30 vol.% SiCp compared with the un reinforced thermal spray aluminium coatings. (Author) 31 refs.

  12. Effect of pattern coating thickness on characteristics of lost foam Al-Si-Cu alloy casting%涂层厚度对消失模铸Al-Si-Cu合金铸件的影响

    Institute of Scientific and Technical Information of China (English)

    Majid KARIMIAN; Ali OURDJINI; Mohd HASBULLAH IDRIS; Hassan JAFARI

    2012-01-01

    An experimental study on lost foam casting of an Al-Si-Cu alloy was conducted.The main objective was to study the effect of pattern coating thickness on casting imperfection and porosity percentage as well as eutectic silicon spacing of the alloy.The results showed that increasing slurry viscosity and flask dipping time influenced the casting integrity and microstructural characteristics.It was found that thinner pattern coating produced improved mould filling,refined microstructure and higher quality castings containing less porosity.%对Al-Si-Cu合金进行消失模铸造,研究涂层厚度对Al-Si-Cu合金铸件缺陷、孔隙率和共晶硅间距的影响.结果表明,提高涂层浆料黏度和延长浸渍时间对铸件的完整性和显微组织有影响.薄的涂层有利于模腔充填性能的改善、显微组织的细化和低孔隙度高质量铸件的获得.

  13. The Influence of Selective Laser Melting Parameters on Density and Mechanical Properties of AlSi10Mg

    Directory of Open Access Journals (Sweden)

    Raus A. A.

    2016-01-01

    Full Text Available Selective Laser Melting (SLM is one of the most effective powder bed technique in the additive Manufacturing (AM which able to fabricate functional metal parts directly from 3D Computer Aided Design (CAD file data. In this paper, the influence of SLM parameters, such as laser power, scanning speed and hatching distance on the density of AlSi10Mg samples are investigated using one factor at a time (OFAT. Furthermore, the optimum results are used to fabricate samples for hardness, tensile strength, and impact toughness test. It is revealed that AlSi10Mg parts fabricated by SLM achieving the best density of 99.13% at the value of 350 watts laser power, 1650 mm/s scanning speed and hatching distance 0.13mm, whereby resulted comparable and even better mechanical properties to those of conventionally HDPC A360F and HDPC A360T6 alloys although without any comprehensive post processing methods.

  14. Experiment and Statistical Analysis of End Milling Parameters for Al/SiC Using Response Surface Methodology

    Directory of Open Access Journals (Sweden)

    Vamsi Krishna M

    2015-12-01

    Full Text Available For industrial applications, the ceramics composites are machined in large scale using end milling. Due the abrasive reinforcement particle, the failure in tool life and surface quality are possible. This research work focuses on developing the mathematical models of cutting force (FR, Metal Removal Rate (MRR and surface roughness (Ra and to optimize it. The Response Surface Methodology (RSM with L31 empirical model was used for conducting the basic trails on Al/SiC composites of various compositions. The XRD, EDS, Optical microscopic images of Al/SiC composites were analysed and the SEM morphology of the machined samples were studied. The models developed for predicting responses were tested by analysis of variance (ANOVA to evaluate its adequacy. The optimal machining configuration was identified which yields 0.5%, 14% and 4% of MRR, Ra and FR respectively compared with experimental results.

  15. AlSi17Cu5Mg alloy as future material for castings of pistons for internal combustion engines

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2015-07-01

    Full Text Available The paper presents chosen properties and microstructure of AlSi17Cu5Mg alloy as future material for casting pistons in automotive industry. Tests were conducted to elaborate technology of preparation, assessment of crystallisation parameters and shaping the primary structure of the silumin with the aim to improve the working parameters and the functioning efficiency in cylinder-piston system. Refinement of Si crystals, achieved due to overheating above the temperature Tliq. causes that the alloy reaches satisfactory properties in working chamber of the engine are optimised. Such condition of material characteristics causes that hypereutectic silumins, for chosen applications in transport, may serve as an alternative to Al - Si alloys of hypoeutectic and near - eutectic type.

  16. Numerical simulation of thermal-mechanical process of Al-Si-Pb alloy treated by high current pulsed electron beam

    Institute of Scientific and Technical Information of China (English)

    L(U) Xiao-xia; LI Rong-guang; AN Jian

    2006-01-01

    The modified microstructure of Al-Si-Pb alloys irradiated by high current electron beam (HCPEB) reveals three distinct regions: a molten zone, an overlapped zone of heat-affected and quasistatic thermal stress-affected zone, and a transition zone followed by the substrate. The hardness and wear properties of the alloys were significantly improved. To better understand these changes in microstructure and properties, the physical model for the simulation of temperature and quasistatic stress fields was established. Based on experimental investigation and physical models, the temperature field and stress field were simulated for Al-Si-Pb alloy. The starting melting position, largest crater depth, melting layer thickness, and quasistatic stress distribution were obtained. These results reveal the mechanism of crater formation on the surface and improvement of hardness and wear resistance.

  17. EFFECT OF SPECIMEN ASPECT RATIO ON FATIGUE LIFE OF CLOSED CELL Al-Si-Ca ALLOY FOAM

    Institute of Scientific and Technical Information of China (English)

    Amkee Kim; Ilhyun Kim

    2008-01-01

    Quasi-static and compressive fatigue tests on the closed cell Al-Si-Ca alloy foam specimens with three different aspect ratios were performed.It turned out that the onset of cyclic shortening of foam with a lower aspect ratio took place earlier and the fatigue strength was lower compared with the specimen with a higher aspect ratio,although aU the dimensions of specimen satisfied the seven times the cell size criterion,while the quasi-static stress-strain curves were almost same having same Young's modulus,yield stress and plateau stress.Therefore,the seven times the cell size criterion for the quasi-static compression behavior was not applicable to the fatigue analysis of Al-Si-Ca alloy foam.

  18. Microstructure and phase constitution near the interface of Cu/3003 torch brazing using Al Si La Sr filler

    Energy Technology Data Exchange (ETDEWEB)

    Yan, Fei; Wang, Chun Ming; Wang, Ya Jun [Huazhong Univ. of Science and Technology, Wuhan (China); Xu, Dao Rong; Wu, S.C.; Sun, Qin De [Heifei Univ. of Technology, Hefei (China)

    2012-12-15

    It has been mainly studied in this paper on brazing of Cu to Al using Al.Si filler metal. The optimized scanning rate of 2.5 mm/s is first obtained through simulating the temperature field of Cu Al brazing process based on ANSYS software. Then the brazing of Cu C11000 to Al 3003 using Al.Si.La.Sr filler is carried out by torch brazing technology. It is found that the brazing seam region is mainly consisted of {alpha} Al solid solution and CuAl2 IMC. Further experimental results also show that the rare earth element La in filler metal can not only refine the grain, but also promote the dispersion of intermetallic compounds into the brazing seam, which significantly improves the brazing seam microstructure and mechanical properties of the joints.

  19. The Microstructures and Properties of SiC/Al2O3/Al-Si Composites Prepared by Reactive Penetration

    Institute of Scientific and Technical Information of China (English)

    ZHOU Xi-ya

    2004-01-01

    The composition, microstructures and properties of SiC /Al2O3/Al-Si composites formed by reactive penetration of the molten aluminum into the preforms of SiO2 and SiC were investigated. The composition of the composites was measured by X-ray diffraction (XRD). The microstructures of the composites were also measured by scanning electron microscopy (SEM) and optical microscopy. In addition, the factors affecting the properties of the composites were discussed.The experiments show that the mechanical properties of the composites depend on their relative densities and the sizes of the fillers"SiC grains".The denser the SiC/Al2O3/Al-Si composites,the higher their bending strength.As the filler "SiC grains" become fine,the bending strength of the composites increases.

  20. Abrasive Wear of AlSi12-Al2O3 Composite Materials Manufactured by Pressure Infiltration

    Directory of Open Access Journals (Sweden)

    Kremzer M.

    2016-09-01

    Full Text Available The aim of this study is to investigate tribological properties of EN AC-AlSi12 alloy composite materials matrix manufactured by pressure infiltration of Al2O3 porous preforms. In the paper, a technique of manufacturing composite materials was described in detail as well as wear resistance made on pin on disc was tested. Metallographic observations of wear traces of tested materials using stereoscopic and confocal microscopy were made. Studies allow concluding that obtained composite materials have much better wear resistance than the matrix alloy AlSi12. It was further proved that the developed technology of their preparation consisting of pressure infiltration of porous ceramic preforms can find a practical application.

  1. Breaking through the strength-ductility trade-off dilemma in an Al-Si-based casting alloy

    Science.gov (United States)

    Dang, B.; Zhang, X.; Chen, Y. Z.; Chen, C. X.; Wang, H. T.; Liu, F.

    2016-08-01

    Al-Si-based casting alloys have a great potential in various industrial applications. Common strengthening strategies on these alloys are accompanied inevitably by sacrifice of ductility, known as strength-ductility trade-off dilemma. Here, we report a simple route by combining rapid solidification (RS) with a post-solidification heat treatment (PHT), i.e. a RS + PHT route, to break through this dilemma using a commercial Al-Si-based casting alloy (A356 alloy) as an example. It is shown that yield strength and elongation to failure of the RS + PHT processed alloy are elevated simultaneously by increasing the cooling rate upon RS, which are not influenced by subsequent T6 heat treatment. Breaking through the dilemma is attributed to the hierarchical microstructure formed by the RS + PHT route, i.e. highly dispersed nanoscale Si particles in Al dendrites and nanoscale Al particles decorated in eutectic Si. Simplicity of the RS + PHT route makes it being suitable for industrial scaling production. The strategy of engineering microstructures offers a general pathway in tailoring mechanical properties of other Al-Si-based alloys. Moreover, the remarkably enhanced ductility of A356 alloy not only permits strengthening further the material by work hardening but also enables possibly conventional solid-state forming of the material, thus extending the applications of such an alloy.

  2. Preparation of semisolid AlSi7Mg alloy slurry through weak traveling-wave electromagnetic stirring

    Institute of Scientific and Technical Information of China (English)

    Zhen-duo Zhao; Wei-min Mao; Sha Li; Rong-mao Zhong

    2009-01-01

    The semisolid AlSi7Mg alloy slurry with large capacity was prepared by low superheat pouring and week traveling-wave electromagnetic stirring. The effects of electromagnetic stirring power and frequency on the shape and distribution of primary α-Al grains in the AlSi7Mg alloy slurry were discussed. The experimental results show that the AlSi7Mg alloy slurry with fine and spherical primary α-Al grains distributed homogeneously can be obtained. Under the condition of low superheat pouring and week traveling-wave electromagnetic stirring, when the pouring temperature is 630°C, raising the stirring power or frequency appropriately can gain a better shape of primary α-Al grains; but if the stirring power or frequency is increased to a certain value (1.72 kW or 10Hz), the shape of primary α-Al grains cannot be obviously improved and spherical primary α-Al grains distributed homogeneously can be still obtained.

  3. Revealing heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys.

    Science.gov (United States)

    Li, Jiehua; Hage, Fredrik S; Liu, Xiangfa; Ramasse, Quentin; Schumacher, Peter

    2016-04-28

    The heterogeneous nucleation of primary Si and eutectic Si can be attributed to the presence of AlP. Although P, in the form of AlP particles, is usually observed in the centre of primary Si, there is still a lack of detailed investigations on the distribution of P within primary Si and eutectic Si in hypereutectic Al-Si alloys at the atomic scale. Here, we report an atomic-scale experimental investigation on the distribution of P in hypereutectic Al-Si alloys. P, in the form of AlP particles, was observed in the centre of primary Si. However, no significant amount of P was detected within primary Si, eutectic Si and the Al matrix. Instead, P was observed at the interface between the Al matrix and eutectic Si, strongly indicating that P, in the form of AlP particles (or AlP 'patch' dependent on the P concentration), may have nucleated on the surface of the Al matrix and thereby enhanced the heterogeneous nucleation of eutectic Si. The present investigation reveals some novel insights into heterogeneous nucleation of primary Si and eutectic Si by AlP in hypereutectic Al-Si alloys and can be used to further develop heterogeneous nucleation mechanisms based on adsorption.

  4. Influence of Milling Time on the Crystallite Size of AlSi5Cu2/SiC Composite Powder

    Directory of Open Access Journals (Sweden)

    Suśniak M.

    2016-06-01

    Full Text Available AlSi5Cu2/SiC nanocrystalline composite powder was successfully obtained by mechanical alloying of AlSi5Cu2 chips with reinforcement of 0, 10, 15, 20 wt. % of silicon carbide. X-ray powder diffraction was used to characterize obtained material. Detailed analyses using transmission and scanning electron microscopy have been conducted in order to collaborate the grain size measurement determined from the XRD analyses. Powders produced in a planetary ball mill with milling time: 1, 5, 10, 15, 20 and 40 hours, have shown shape and size evaluation during mechanical alloying process. It can be seen tendency to decrease the size of the grain as the milling time is increased. It is also noted that the grains of composites (AlSi5Cu2/SiC are smaller than samples prepares without SiC addition. 40 hours of milling lead to formed very small grains of Al phase (20 nm in average in composite powder.

  5. Thermodynamics of open networks: Ordering and entropy in NaAlSiO4 glass, liquid, and polymorphs

    Science.gov (United States)

    Richet, P.; Robie, R.A.; Rogez, J.; Hemingway, B.S.; Courtial, P.; Tequi, C.

    1990-01-01

    The thermodynamic properties of carnegieite and NaAlSiO4 glass and liquid have been investigated through Cp determinations from 10 to 1800 K and solution-calorimetry measurements. The relative entropies S298-S0 of carnegieite and NaAlSiO4 glass are 118.7 and 124.8 J/mol K, respectively. The low-high carnegieite transition has been observed at 966 K with an enthalpy of transition of 8.1??0.3 kJ/mol, and the enthalpy of fusion of carnegieite at the congruent melting point of 1799 K is 21.7??3 kJ/mol. These results are consistent with the reported temperature of the nepheline-carnegieite transition and available thermodynamic data for nepheline. The entropy of quenched NaAlSiO4 glass at 0 K is 9.7??2 J/mol K and indicates considerable ordering among AlO4 and SiO4 tetrahedra. In the liquid state, progressive, temperature-induced Si, Al disordering could account for the high configurational heat capacity. Finally, the differences between the entropies and heat capacities of nepheline and carnegieite do not seem to conform to current polyhedral modeling of these properties ?? 1990 Springer-Verlag.

  6. Magnetic Exchange-Coupled Sm(Co,R)/Cr (R=Al, Si, Ti, Nb, Cu) Series Films for Ultrahigh-Density Longitudinal Recording Media

    Institute of Scientific and Technical Information of China (English)

    王翔; 李佐宜; 李震; 蔡长波; 黄志新; 廖红伟; 王浩敏; 林更琪

    2003-01-01

    SmCoR (R=Al,Si, Ti,Nb, Cu)/Cr series films were fabricated as one kind of promising materials for the ultrahigh density longitudinal magnetic recording media. The Sm(Co,Al, Si)/Cr thin films with coercivity up to 2.36 kOe, squareness ratio S near 0.94 and coercive squareness ratio S* about 0.9 were obtained. The Cr interlayer caused magnetic decoupling in Sm(Co,Al,Si)/Cr/Sm(Co,Al,Si) thin films. High coercivity of 3400-3840 Oe and extremely fine grain size of 5-8 nm for the magnetic layer were examined. Using different substrate bias among the Sm(Co,Al,Si)(deposited with substrate bias of-150 V)/Sm(Co, Al,Si)(deposited with no substrate bias)/Sm(Co,Al, Si)(deposited with substrate bias of-150 V), the multilayer exhibited high coercivity of 2960 Oe and S* of 0.96. Sm(Co,Al, Si)/Sm(Co, Ti, Cu)/Sm(Co,Nb, Cu) trilayer improved matching between the magnetic layer and the Cr underlayer, and led to increasing in-plane anisotropy, high coercivity of 3280 Oe and S* of 0.92. Lattice matching of SmCoR {1121} and Cr {110}, etc. were found under various conditions. The microstructures of these four kinds of medium were also examined. The results suggest that it is possible to produce Sm(Co, Al, Si, Ti, Nb, Cu) multi-layer media with the combined magnetic properties required for the ultrahigh density magnetic recording.

  7. Structure, tribological and electrochemical properties of low friction TiAlSiCN/MoSeC coatings

    Energy Technology Data Exchange (ETDEWEB)

    Bondarev, A.V.; Kiryukhantsev-Korneev, Ph.V.; Sheveyko, A.N.; Shtansky, D.V., E-mail: shtansky@shs.misis.ru

    2015-02-01

    Highlights: • TiAlSiCN/MoSeC coatings for tribological applications. • Doping with MoSeC reduces friction coefficient in humid air from 0.8–0.9 to 0.05. • Doping with MoSeC increases wear resistance by one-two orders of magnitude. • TiAlSiCN/MoSeC coatings demonstrated low friction coefficient in distilled water. • TiAlSiCN/MoSeC coatings showed superior tribological properties at moderate temperatures. - Abstract: The present paper is focused on the development of hard tribological coatings with low friction coefficient (CoF) in different environments (humid air, distilled water) and at elevated temperatures. TiAlSiCN/MoSeC coatings were deposited by magnetron sputtering of four-segment targets consisting of quarter circle TiAlSiCN segments, obtained by self-propagating high-temperature synthesis, and one or two cold pressed segments made of MoSe{sub 2} and C powders in a ratio 1:1 wt%. The structure and phase composition of coatings were investigated by means of X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and Raman spectroscopy. The coatings were characterized in terms of their hardness, elastic modulus, and elastic recovery. The tribological properties of coatings were investigated first at room temperature against Al{sub 2}O{sub 3} and WC–Co balls, after which studied in distilled water and during continuous heating in air in the temperature range of 25–400 °C against Al{sub 2}O{sub 3} counterpart material. To evaluate their electrochemical characteristics, the coatings were tested in 1 N H{sub 2}SO{sub 4} solution. The obtained results show that the coating hardness depends on the amount of MoSeC additives and decreased from 40 to 28 (one MoSeC segment) and 12 GPa (two MoSeC segments). Doping with MoSeC resulted in a significant reduction of CoF values measured in humid air (RH 60 ± 5%) from 0.8–0.9 to 0.05 and an increase of wear resistance by one or two orders of magnitude depending on

  8. Microstructural and mechanical characterization of A357 Al-Si alloy produced by rheocasting; Caracterizacion microestructural y mecanica de la aleacion de Al-Si A357 producida mediante rheocasting

    Energy Technology Data Exchange (ETDEWEB)

    Silva, M. de; Rodriguez-Ibabe, J. M.

    2003-07-01

    In the present work it has been studied the microstructure and the mechanical behaviour of a materials produced by rheocasting, a new semisolid industrial process which introduces important improvements in comparison to conventional routes. the microstructure of the A357 hypoeutectic Al-Si alloys has been analysed before and after material injection. In both cases the microstructure was fine and homogeneous. Tensile tests have been done with specimens machined from real rheocasted components in two conditions, without any heat treatment and after T5 heat treatment. The results were found to be better than those obtained for this alloy when produced by conventional means. (Author) 20 refs.

  9. A novel yellow-emitting SrAlSi4N7:Ce3+ phosphor for solid state lighting: Synthesis, electronic structure and photoluminescence properties

    Science.gov (United States)

    Ruan, Jian; Xie, Rong-Jun; Funahashi, Shiro; Tanaka, Yoshinori; Takeda, Takashi; Suehiro, Takayuki; Hirosaki, Naoto; Li, Yuan-Qiang

    2013-12-01

    Ce3+-doped and Ce3+/Li+-codoped SrAlSi4N7 phosphors were synthesized by gas pressure sintering of powder mixtures of Sr3N2, AlN, α-Si3N4, CeN and Li3N. The phase purity, electronic crystal structure, photoluminescence properties of SrAlSi4N7:Ce3+(Ce3+/Li+) were investigated in this work. The band structure calculated by the DMol3 code shows that SrAlSi4N7 has a direct band gap of 3.87 eV. The single crystal analysis of Ce3+-doped SrAlSi4N7 indicates a disordered Si/Al distribution and nitrogen vacnacy defects. SrAlSi4N7 was identified as a major phase of the fired powders, and Sr5Al5Si21N35O2 and AlN as minor phases. Both Ce3+ and Ce3+/Li+ doped SrAlSi4N7 phosphors can be efficiently excited by near-UV or blue light and show a broadband yellow emission peaking around 565 nm. A highest external quantum efficiency of 38.3% under the 450 nm excitation was observed for the Ce3+/Li+-doped SrAlSi4N7 (5 mol%). A white light LED lamp with color temperature of 6300 K and color rendering index of Ra=78 was achieved by combining Sr0.97Al1.03Si3.997N\\94\\maccounttest14=t0005_18193 7:Ce3+0.03 with a commercial blue InGaN chip. It indicates that SrAlSi4N7:Ce3+ is a promising yellow emitting down-conversion phosphor for white LEDs.

  10. Synthesis of Vertically-Aligned Carbon Nanotubes from Langmuir-Blodgett Films Deposited Fe Nanoparticles on Al2O3/Al/SiO2/Si Substrate.

    Science.gov (United States)

    Takagiwa, Shota; Kanasugi, Osamu; Nakamura, Kentaro; Kushida, Masahito

    2016-04-01

    In order to apply vertically-aligned carbon nanotubes (VA-CNTs) to a new Pt supporting material of polymer electrolyte fuel cell (PEFC), number density and outer diameter of CNTs must be controlled independently. So, we employed Langmuir-Blodgett (LB) technique for depositing CNT growth catalysts. A Fe nanoparticle (NP) was used as a CNT growth catalyst. In this study, we tried to thicken VA-CNT carpet height and inhibit thermal aggregation of Fe NPs by using Al2O3/Al/SiO2/Si substrate. Fe NP LB films were deposited on three typed of substrates, SiO2/Si, as-deposited Al2O3/Al/SiO2/Si and annealed Al2O3/Al/SiO2/Si at 923 K in Ar atmosphere of 16 Pa. It is known that Al2O3/Al catalyzes hydrocarbon reforming, inhibits thermal aggregation of CNT growth catalysts and reduces CNT growth catalysts. It was found that annealed Al2O3/Al/SiO2/Si exerted three effects more strongly than as-deposited Al2O3/Al/SiO2/Si. VA-CNTs were synthesized from Fe NPs-C16 LB films by thermal chemical vapor deposition (CVD) method. As a result, at the distance between two nearest CNTs 28 nm or less, VA-CNT carpet height on annealed Al2O3/Al/SiO2/Si was about twice and ten times thicker than that on SiO2/Si and that on as-deposited Al2O3/Al/SiO2/Si, respectively. Moreover, distribution of CNT outer diameter on annealed Al2O3/Al/SiO2/Si was inhibited compared to that on SiO2/Si. These results suggest that since thermal aggregation of Fe NPs is inhibited, catalyst activity increases and distribution of Fe NP size is inhibited.

  11. Influence of the selected structural parameter on a depth of intergranular corrosion of Al-Si7-Mg0,3 aluminum alloy

    Directory of Open Access Journals (Sweden)

    L. Bernat

    2015-10-01

    Full Text Available The paper presents an influence of the Dendrite Arm Spacing (DAS microstructure parameter on the intergranular corrosion of AlSi7Mg aluminum alloy. The samples were subjected to the corrosion process for: 2,5; 12; 24; 48 and 96 hours in NaCl + HCl + H2O solution. It was noted that the DAS parameter significantly influenced on a distribution and depth of the intergranular corrosion of the hypoeutectic Al - Si - Mg silumin.

  12. Experimental study on new method and automatic system for fast evaluating Al-Si alloy modification effect in front of furnace

    Institute of Scientific and Technical Information of China (English)

    SHI; Dequan; LI; Dayong; GAO; Guili; WANG; Lihua

    2006-01-01

    A new method based on the surface tension measurement for fast evaluating modification effect of Al-Si alloy in front of furnace and an automatic system for fast measuring surface tension of molten Al-Si alloy are introduced. By theoretical analysis the relation between surface tension of molten Al-Si alloy and information parameters △P,N ,φx and T has been established, namely,σe=a·△P+b·N+c·(φx-φ0)+d·T+e . By ex- periments the relationship between surface tension and modification level of Al-Si alloy has been also got thatσe>530 mN/m,400≤σe≤530 mN/m and σe<400mN/m are corresponding with AFS 1-2, AFS 3-4 and AFS 5-6 of Al-Si modification effect. Depending on the conclusions, modification effect can be recognized in a few seconds, which is of practical significance for real-time evaluating modification effect of Al-Si alloy in front of furnace.

  13. Microstructure of interaction interface between Al-Si, Zn-Al alloys and Al2O3p/6061Al composite

    Institute of Scientific and Technical Information of China (English)

    许志武; 闫久春; 吕世雄; 杨士勤

    2004-01-01

    Interaction behaviors between Al-Si, Zn-AI alloys and Al2O3p/6061AI composite at different heating temperatures were investigated. It is found that Al2O3p/6061Al composite can be wetted well by AlSi-1, AlSi-4 and Zn-Al alloys and an interaction layer forms between the alloy and composite during interaction. Little Al-Si alloys remain on the surface when they fully wet the composite and Si element in Al-Si alloy diffuses into composite entirely and assembles in the composite near the interface of Al-Si alloy/composite to form a Si-rich zone. The microstructure in interaction layer with Si penetration is still dense. Much more residual Zn-Al alloy exists on the surface of composite when it wets the composite, and porosities appear at the interface of Zn-Al alloy/composite. The penetration of elements Zn, Cu of Zn-Al alloy into composite leads to the generation of shrinkage cavities in the interaction layer and makes the microstructure of Al2 O3p/6061A1 composite loose.

  14. Tribological Behavior of Aluminum Alloy AlSi10Mg-TiB2 Composites Produced by Direct Metal Laser Sintering (DMLS)

    Science.gov (United States)

    Lorusso, Massimo; Aversa, Alberta; Manfredi, Diego; Calignano, Flaviana; Ambrosio, Elisa Paola; Ugues, Daniele; Pavese, Matteo

    2016-08-01

    Direct metal laser sintering (DMLS) is an additive manufacturing technique for the production of parts with complex geometry and it is especially appropriate for structural applications in aircraft and automotive industries. Aluminum-based metal matrix composites (MMCs) are promising materials for these applications because they are lightweight, ductile, and have a good strength-to-weight ratio This paper presents an investigation of microstructure, hardness, and tribological properties of AlSi10Mg alloy and AlSi10Mg alloy/TiB2 composites prepared by DMLS. MMCs were realized with two different compositions: 10% wt. of microsize TiB2, 1% wt. of nanosize TiB2. Wear tests were performed using a pin-on-disk apparatus on the prepared samples. Performances of AlSi10Mg samples manufactured by DMLS were also compared with the results obtained on AlSi10Mg alloy samples made by casting. It was found that the composites displayed a lower coefficient of friction (COF), but in the case of microsize TiB2 reinforcement the wear rate was higher than with nanosize reinforcements and aluminum alloy without reinforcement. AlSi10Mg obtained by DMLS showed a higher COF than AlSi10Mg obtained by casting, but the wear rate was higher in the latter case.

  15. Formation of hypereutectic silicon particles in hypoeutectic Al-Si alloys under the influence of high-intensity ultrasonic vibration

    Directory of Open Access Journals (Sweden)

    Xiaogang Jian

    2013-03-01

    Full Text Available The modification of eutectic silicon is of general interest since fine eutectic silicon along with fine primary aluminum grains improves mechanical properties and ductilities. In this study, high intensity ultrasonic vibration was used to modify the complex microstructure of aluminum hypoeutectic alloys. The ultrasonic vibrator was placed at the bottom of a copper mold with molten aluminum. Hypoeutectic Al-Si alloy specimens with a unique in-depth profile of microstructure distribution were obtained. Polyhedral silicon particles, which should form in a hypereutectic alloy, were obtained in a hypoeutectic Al-Si alloy near the ultrasonic radiator where the silicon concentration was higher than the eutectic composition. The formation of hypereutectic silicon near the radiator surface indicates that high-intensity ultrasonic vibration can be used to influence the phase transformation process of metals and alloys. The size and morphology of both the silicon phase and the aluminum phase varies with increasing distance from the ultrasonic probe/radiator. Silicon morphology develops into three zones. Polyhedral primary silicon particles present in zone I, within 15 mm from the ultrasonic probe/radiator. Transition from hypereutectic silicon to eutectic silicon occurs in zone II about 15 to 20 祄 from the ultrasonic probe/radiator. The bulk of the ingot is in zone III and is hypoeutectic Al-Si alloy containing fine lamellar and fibrous eutectic silicon. The grain size is about 15 to 25 祄 in zone I, 25 to 35 祄 in zone II, and 25 to 55 祄 in zone III. The morphology of the primary ?Al phase is also changed from dendritic (in untreated samples to globular. Phase evolution during the solidification process of the alloy subjected to ultrasonic vibration is described.

  16. Chemical Changes at the Interface Between Low Carbon Steel and an Al-Si Alloy During Solution Heat Treatment

    OpenAIRE

    2011-01-01

    International audience; The aim of this work was to characterize the chemical changes during solid state solution heat treatment of a metallurgically bonded steel/Al-Si interface. For this purpose, low carbon steel plates covered with the A-S7G03 aluminium alloy (7wt%Si, 0.3wt%Mg analogous to A356) were prepared by dip coating, water-quenching to room temperature and reheating in the solid state at 480-560°C for 3 to 160 hours. Upon reheating at 535 °C, a reaction layer was observed to grow a...

  17. Effect of bariun on the refinement of primary aluminum and eutectics in a hypoeutectic Al-Si alloy

    Institute of Scientific and Technical Information of China (English)

    LI Wei; FAN Hongyuan; ZHANG Xianju; SHEN Baoluo

    2003-01-01

    The effect of barium on the refinement of primary aluminum and on the modification of eutectics in a hypoeutectic aluminm-silicon alloy was investigated. The results indicate that barium not only modifies the eutectic silicon but also refines the primary aluminum and there is a relationship between the retained barium and the second spacing of primary aluminum. Experiments of barium-treated commercial Al-Si hypoeutectic alloy show that barium is a better modifier than sodium when there is a longer holding time.

  18. A planar Al-Si Schottky barrier metal–oxide–semiconductor field effect transistor operated at cryogenic temperatures

    Energy Technology Data Exchange (ETDEWEB)

    Purches, W. E. [School of Physics, UNSW, Sydney 2052 (Australia); Rossi, A.; Zhao, R. [School of Electrical Engineering and Telecommunications, UNSW, Sydney 2052 (Australia); Kafanov, S.; Duty, T. L. [School of Physics, UNSW, Sydney 2052 (Australia); Centre for Engineered Quantum Systems (EQuS), School of Physics, UNSW, Sydney 2052 (Australia); Dzurak, A. S. [School of Electrical Engineering and Telecommunications, UNSW, Sydney 2052 (Australia); Australian Centre of Excellence for Quantum Computation and Communication Technology (CQC2T), UNSW, Sydney 2052 (Australia); Rogge, S.; Tettamanzi, G. C., E-mail: g.tettamanzi@unsw.edu.au [School of Physics, UNSW, Sydney 2052 (Australia); Australian Centre of Excellence for Quantum Computation and Communication Technology (CQC2T), UNSW, Sydney 2052 (Australia)

    2015-08-10

    Schottky Barrier-MOSFET technology offers intriguing possibilities for cryogenic nano-scale devices, such as Si quantum devices and superconducting devices. We present experimental results on a device architecture where the gate electrode is self-aligned with the device channel and overlaps the source and drain electrodes. This facilitates a sub-5 nm gap between the source/drain and channel, and no spacers are required. At cryogenic temperatures, such devices function as p-MOS Tunnel FETs, as determined by the Schottky barrier at the Al-Si interface, and as a further advantage, fabrication processes are compatible with both CMOS and superconducting logic technology.

  19. 浸渗时间对无压浸渗制备Al/SiCp陶瓷基合材料的影响%Infiltration Time Effect of Pressureless Infiltration Preparation of Al/SiCp Ceramic Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    徐跃; 高霖; 崔崇; 钱凤

    2011-01-01

    Microstructure, density and rigidity of Al/SiCp ceramic matrix composites prepared by pressureless infiltration, were investigated in this paper. The result indicates that the infiltration in due course of time made Si and Mg diffusion and interface reaction conducted fully,which increased interface wetting property and decreased interface loose and pore,and advanced the a-luminium alloys infiltration. Holding one hour at proper temperature got full infitration, but poor density and low rigidity, while holding three hours got pulverization so two hours shall be a proper parameter.%本文采用无压浸渗法,研究浸渗时间对Al/SiCp陶瓷基复合材料组织、致密度、硬度的影响.浸渗保温时间1h,能浸透,但致密度差,硬度低.保温时间3h,发生粉化现象.结果表明浸渗保温时间2h是无压浸渗较好的工艺参数.

  20. Mg对无压渗透制备Al/SiCp陶瓷基复合材料的影响%Effect of Mg on Pressureless Infiltration Preparation of Al/SiCp Ceramic Matrix Composites

    Institute of Scientific and Technical Information of China (English)

    徐跃; 高霖; 崔崇; 钱凤

    2011-01-01

    Influence of Mg on preparation and microstructure of SiCp/Al ceramic matrix composites with SiC volume fraction 40% -70% fabricated by pressureless infiltration is discussed in this paper. Result indicated that addition of Mg in aluminium infiltration liquid could improve infiltration ability evidently. Because magnesium diffused and enriched interface of Al and SiC. Interface reaction made Al2O3 film broken to reduce interface strain, that increased liquidity of aluminium alloy liquid. Reaction of Mg and framework air caused negative press that advanced pressureless infiltration process voluntarily.%本文采用无压浸渗法,研究了Mg对Al/SiC.(SiC体积分数为40%-70%)陶瓷基复合材料制备及组织影响.结果表明,Al浸渗液中添加Mg可以显著提高铝液的浸润性,因为Mg扩散并富集于Al/SiCp界面,通过界面反应促使Al2O3膜的破裂降低界面张力,增加了铝合金液的流动性,而且Mg与骨架孔隙内的气氛反应形成负压,促进无压浸渗的自发进行.

  1. New T6 heat treatments for AlSi alloys conformed in semi-solid state; Nuevos tratamientos T6 para aleaciones de AlSi obtenidas por conformacion en estado semisolido

    Energy Technology Data Exchange (ETDEWEB)

    Menargues, S.; Baile, M. T.; Forn, A.

    2013-07-01

    In this work the microstructural changes that occurs during the solution and aging steps of heat treated of AlSi alloys, conformed in semi-solid state, were analysed. The study allowed developing a new T6 heat treatment, with solution times down to 30 min. With this new short heat treatment, the alloy showed better mechanical properties in comparison with the same alloy heat treated in standard conditions (solution times between 6 h and 8 h). This new heat treatment, carried out at 540 degree centigrade, allowed complete magnesium dissolution and, at the same time, minimizes the grain and eutectic silicon growth. Although this experimentation was carried out with A356 and A357 aluminum alloys, conformed by Sub-Liquidus-Casting process, these results may be applicable to components produced with other semi-solid technologies and with others AlSi hard enable alloys that form coherent magnesium precipitates. The characterization of samples was carried out by micrographic analysis, by hardness and ultramicrohardnes tests. (Author)

  2. New insights on pressure, temperature, and chemical stability of CsAlSi5O12, a potential host for nuclear waste

    Science.gov (United States)

    Gatta, G. D.; Brundu, A.; Cappelletti, P.; Cerri, G.; de'Gennaro, B.; Farina, M.; Fumagalli, P.; Guaschino, L.; Lotti, P.; Mercurio, M.

    2016-06-01

    A Cs-bearing polyphase aggregate with composition (in wt%): 76(1)CsAlSi5O12 + 7(1)CsAlSi2O6 + 17(1)amorphous, was obtained from a clinoptilolite-rich epiclastic rock after a beneficiation process of the starting material (aimed to increase the fraction of zeolite to 90 wt%), cation exchange and then thermal treatment. CsAlSi5O12 is an open-framework compound with CAS topology; CsAlSi2O6 is a pollucite-like material with ANA topology. The thermal stability of this polyphase material was investigated by in situ high-T X-ray powder diffraction, the combined P-T effects by a series of runs with a single-stage piston cylinder apparatus, and its chemical stability following the "availability test" ("AVA test") protocol. A series of additional investigations were performed by WDS-electron microprobe analysis in order to describe the P-T-induced modification of the material texture, and to chemically characterize the starting material and the run products. The "AVA tests" of the polyphase aggregate show an extremely modest release of Cs+: 0.05 mg/g. In response to applied temperature and at room P, CsAlSi5O12 experiences an unquenchable and displacive Ama2-to-Amam phase transition at about 770 K, and the Amam polymorph is stable in its crystalline form up to 1600 K; a crystalline-to-amorphous phase transition occurs between 1600 and 1650 K. In response to the applied P = 0.5 GPa, the crystalline-to-amorphous transition of CsAlSi5O12 occurs between 1670 and 1770 K. This leads to a positive Clapeyron slope (i.e., dP/dT > 0) of the crystalline-to-amorphous transition. When the polyphase aggregate is subjected at P = 0.5 GPa and T > 1770 K, CsAlSi5O12 melts and only CsAlSi2O6 (pollucite-like; dominant) and Cs-rich glass (subordinate) are observed in the quenched sample. Based on its thermo-elastic behavior, P-T phase stability fields, and Cs+ retention capacity, CsAlSi5O12 is a possible candidate for use in the immobilization of radioactive isotopes of Cs, or as potential

  3. New insights on pressure, temperature, and chemical stability of CsAlSi5O12, a potential host for nuclear waste

    Science.gov (United States)

    Gatta, G. D.; Brundu, A.; Cappelletti, P.; Cerri, G.; de'Gennaro, B.; Farina, M.; Fumagalli, P.; Guaschino, L.; Lotti, P.; Mercurio, M.

    2016-10-01

    A Cs-bearing polyphase aggregate with composition (in wt%): 76(1)CsAlSi5O12 + 7(1)CsAlSi2O6 + 17(1)amorphous, was obtained from a clinoptilolite-rich epiclastic rock after a beneficiation process of the starting material (aimed to increase the fraction of zeolite to 90 wt%), cation exchange and then thermal treatment. CsAlSi5O12 is an open-framework compound with CAS topology; CsAlSi2O6 is a pollucite-like material with ANA topology. The thermal stability of this polyphase material was investigated by in situ high- T X-ray powder diffraction, the combined P- T effects by a series of runs with a single-stage piston cylinder apparatus, and its chemical stability following the "availability test" ("AVA test") protocol. A series of additional investigations were performed by WDS-electron microprobe analysis in order to describe the P- T-induced modification of the material texture, and to chemically characterize the starting material and the run products. The "AVA tests" of the polyphase aggregate show an extremely modest release of Cs+: 0.05 mg/g. In response to applied temperature and at room P, CsAlSi5O12 experiences an unquenchable and displacive Ama2-to- Amam phase transition at about 770 K, and the Amam polymorph is stable in its crystalline form up to 1600 K; a crystalline-to-amorphous phase transition occurs between 1600 and 1650 K. In response to the applied P = 0.5 GPa, the crystalline-to-amorphous transition of CsAlSi5O12 occurs between 1670 and 1770 K. This leads to a positive Clapeyron slope (i.e., d P/d T > 0) of the crystalline-to-amorphous transition. When the polyphase aggregate is subjected at P = 0.5 GPa and T > 1770 K, CsAlSi5O12 melts and only CsAlSi2O6 (pollucite-like; dominant) and Cs-rich glass (subordinate) are observed in the quenched sample. Based on its thermo-elastic behavior, P- T phase stability fields, and Cs+ retention capacity, CsAlSi5O12 is a possible candidate for use in the immobilization of radioactive isotopes of Cs, or as

  4. Influence of vibrations during crystallization on mechanical properties and porosity of AlSi13Cu2 alloy

    Directory of Open Access Journals (Sweden)

    T.Ciućka

    2010-01-01

    Full Text Available Today’s industry aims at such situation, where number of defective products, so called defects shall approach to zero. Therefore, one introduces a various changes in technology of production, introduces improvements which would help in accomplishment of this objective. Another important factor is introduction of different type of testing, which shall help in assessment which factor has significant effect on quantity of rejects, and which one could be neglected. Existence of casting rejects is unavoidable; therefore a new ideas, technologies and innovations are necessary in the entire widely understood foundry branch, in order to minimize such adverse effect. Performance of tests aimed at unequivocal determination of an effect of vibrations during crystallization on mechanical properties and porosity of the AlSi13Cu2 alloy was the objective of the present work. To do this, there were produced 36 castings from AlSi13Cu2 alloy. All the castings underwent machining operations. Half of the casting was destined to strength tests, the other half served to determination of an effect of vibrations on porosity of the alloy. The specimens were divided into 12 groups, depending on amplitude of vibrations and tilt angle of metal mould during pouring operation.

  5. Evidence for Al/Si tetrahedral network in aluminosilicate glasses from Al K-edge x-ray absorption spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Z. [Laboratoire Pierre Sue, CEA-CNRS CE Saclay, Gif-sur Yvette (France)]|[INFN, Laboratori Nazionali di Frascati, Rome (Italy); Romano, C. [Rome, Univ. `Roma Tre` (Italy). Dip di Scienze Geologiche]|[Univ. Bayreuth (Germany). Bayerishes Geoinstitut; Marcelli, A.; Cibin, G. [INFN, Laboratori Nazionali di Frascati, Rome (Italy); Mottana, A.; Della Ventura, G. [Rome, Univ. `Roma Tre` (Italy). Dip di Scienze Geologiche]|[INFN, Laboratori Nazionali di Frascati, Rome (Italy); Giuli, G. [Florence Univ. (Italy). Dip. Scienze Mineralogiche; Courtial, P.; Dinwell, D.B. [Univ. Bayreuth (Germany). Bayerishes Geoinstitut

    1998-11-01

    The structure of aluminosilicate melts/glasses plays a key role in Earth Sciences for the understanding of rock-forming igneous processes, as well as in the Materials Sciences for their technical applications. In particular, the alkaline earth aluminosilicate glasses are an extremely important group of materials, with a wide range of commercial application, as well as serving as analogue for natural basaltic melts. However, definition of their structure and properties is still controversial, and in particular the role and effect of Al has long been a subject of debate. The paper reports a series of experimental x-ray absorption near-edge structure (XANES) spectra at the Al K edge on a series of synthetic glasses of peralkaline composition in the CaO-Al{sub 2}O{sub 3}-SiO{sub 2} system, together with a general theoretical framework for data analysis based on an ab initio full multiple scattering (MS) theory. It`s proposed an Al/Si tetrahedral network model for aluminosilicate glasses based on distorted polyhedra, with varying both the T-O (T=Al or Si) bond lengths and the T-O-T angles, and with different Al/Si composition. This model achieves a significant agreement between experiments and simulations. in these glasses, experimental data and theoretical results concur to support a model in which Al is network-former with a comparatively well ordered local medium-range order (up to 5 A).

  6. On the Selective Laser Melting (SLM of the AlSi10Mg Alloy: Process, Microstructure, and Mechanical Properties

    Directory of Open Access Journals (Sweden)

    Francesco Trevisan

    2017-01-01

    Full Text Available The aim of this review is to analyze and to summarize the state of the art of the processing of aluminum alloys, and in particular of the AlSi10Mg alloy, obtained by means of the Additive Manufacturing (AM technique known as Selective Laser Melting (SLM. This process is gaining interest worldwide, thanks to the possibility of obtaining a freeform fabrication coupled with high mechanical properties related to a very fine microstructure. However, SLM is very complex, from a physical point of view, due to the interaction between a concentrated laser source and metallic powders, and to the extremely rapid melting and the subsequent fast solidification. The effects of the main process variables on the properties of the final parts are analyzed in this review: from the starting powder properties, such as shape and powder size distribution, to the main process parameters, such as laser power and speed, layer thickness, and scanning strategy. Furthermore, a detailed overview on the microstructure of the AlSi10Mg material, with the related tensile and fatigue properties of the final SLM parts, in some cases after different heat treatments, is presented.

  7. Additive Manufacturing of AlSi10Mg Alloy Using Direct Energy Deposition: Microstructure and Hardness Characterization

    Science.gov (United States)

    Javidani, M.; Arreguin-Zavala, J.; Danovitch, J.; Tian, Y.; Brochu, M.

    2016-12-01

    This paper aims to study the manufacturing of the AlSi10Mg alloy with direct energy deposition (DED) process. Following fabrication, the macro- and microstructural evolution of the as-processed specimens was initially investigated using optical microscopy and scanning electron microscopy. Columnar dendritic structure was the dominant solidification feature of the deposit; nevertheless, detailed microstructural analysis revealed cellular morphology near the substrate and equiaxed dendrites at the top end of the deposit. Moreover, the microstructural morphology in the melt pool boundary of the deposit differed from the one in the core of the layers. The remaining porosity of the deposit was evaluated by Archimedes' principle and by image analysis of the polished surface. Crystallographic texture in the deposit was also assessed using electron backscatter diffraction and x-ray diffraction analysis. The dendrites were unidirectionally oriented at an angle of 80° to the substrate. EPMA line scans were performed to evaluate the compositional variation and elemental segregation in different locations. Eventually, microhardness (HV) tests were conducted in order to study the hardness gradient in the as-DED-processed specimen along the deposition direction. The presented results, which exhibited a deposit with an almost defect free structure, indicate that the DED process can suitable for the deposition of Al-Si-based alloys with a highly consolidated structure.

  8. Evolution of Thermoplastic Shear Localization and Related Microstructures in Al/SiCp Composites Under Dynamic Compression

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    The localized shear deformation in the 2024 and 2124 Al matrix composites reinforced with SiC particles was investigated with a split Hopkinson pressure bar (SHPB) at a strain rate of about 2.0×103 s-1. The results showed that the occurrence of localized shear deformation is sensitive to the size of SiC particles. It was found that the critical strain, at which the shear localization occurs, strongly depends on the size and volume fraction of SiC particles. The smaller the particle size, the lower the critical strain required for the shear localization. TEM examinations revealed that Al/SiCp interfaces are the main sources of dislocations. The dislocation density near the interface was found to be high and it decreases with the distance from the particles. The Al matrix in shear bands was highly deformed and severely elongated at iow angle boundaries. The Al/SiCp interfaces, particularly the sharp corners of SiC particles,provide the sites for microcrack initiation. Eventual fracture is caused by the growth and coalescence of microcracks along the shear bands. It is proposed that the distortion free equiaxed grains with low dislocation density observed in the center of shear band result from recrystallization during dynamic deformation.

  9. The influence of the forced movement of components on the structure in fabricated AlSi/CrxCy composite castings

    Directory of Open Access Journals (Sweden)

    A. Dulęba

    2012-01-01

    Full Text Available Fabrication and microstructure of the AlSi11 matrix composite containing 10 % volume fraction of CrFe30C8 particles were presented in this paper. Composite suspension was manufactured by using mechanical stirring. During stirring process the temperature of liquid metal, time of mixing and rotational speed of mixer were fixed. After stirring process composite suspension was gravity cast into shell mould. The composites were cast, applying simultaneously an electromagnetic field. The aim of the present study was to determine the effect of changes in the frequency of the current power inductor on the morphology of the reinforcing phase in the aluminum matrix. The concept is based on the assumption that a chromium-iron matrix of CrFe30C8 particles dissolves and residual carbide phases will substantially strengthen the composite. The microstructure and interface structure of the AlSi11/CrFe30C8 composite has been studied by optical microscopy, scanning microscopy and X-ray diffraction.

  10. Surface tension of molten Al-Si alloy at temperatures ranging from 92.3 to 112.3 K

    Institute of Scientific and Technical Information of China (English)

    DOU Lei; YUAN ZhangFu; LI JianQiang; LI Jing; WANG XiaoQiang

    2008-01-01

    The surface tension of molten AlSi20 alloy has been measured by using the sessile drop method at 923-1123 K under argon atmosphere in both heating-up and cooling processes. The result shows that the surface tension of this alloy decreases as long as temperature increases. The results of surface tension and contact angles in heating-up process have differences from those obtained in cooling process, because the metal microstructures have some changes at different temperatures based on the metal genetic theory. The surface tension of molten AISi20 alloy and that of molten pure aluminum have been compared as well, and the temperature coefficient of AlSi20 alloy is slightly lower than that of Al. The result has been analyzed by the linear scanning analysis with ESEM. The concentration of silicon in most region of the bulk is lower than that of the surface and the addition of Si to pure Al decreases the surface tension of molten pure Al.

  11. Solidification Sequence and Evolution of Microstructure During Rheocasting of Four Al-Si-Mg-Fe Alloys with Low Si Content

    Science.gov (United States)

    Payandeh, Mostafa; Jarfors, Anders E. W.; Wessén, Magnus

    2016-03-01

    Four Al-Si-Mg-Fe alloys with Si contents varying from 1.6 to 4.5 wt pct were rheocast, using the RheoMetal™ process to prepare slurry and cast in a vertical high-pressure die casting machine. Particle size and Si concentration in the α-Al particles in the slurry and in the as-rheocast component were investigated. A uniform distribution of Si in the globular α 1-Al particles was achieved in the slurry. In the rheocast samples, measurement of the α 1-Al particles showed that these particles did not increase significantly in size during pouring and secondary solidification. The two additional α-Al particles types, α 2-Al particles and α 3-Al particles, were identified as being a result of two discrete nucleation events taking place after slurry production. The Si concentration in the α 2-Al and α 3-Al particles indicated that the larger α 2-Al particles precipitated before the α 3-Al particles. In addition, in the as-rheocast condition, the Si distribution inside the α 1-Al particles showed three distinct zones; an unaffected zone, a transition zone, and in some cases the start of a dendritic/cellular zone. The phenomenon of dendritic growth of globular α 1-Al particles during secondary solidification occurred concomitantly with the final eutectic reaction and increased with increasing amount of the Al-Si eutectic phase.

  12. Fabrication and Characterization of Functionally Graded Al/SiCp Composites Produced by Remelting and Sedimentation Process

    Science.gov (United States)

    Pourmajidian, Maedeh; Akhlaghi, Farshad

    2013-12-01

    A new process termed here as remelting and sedimentation (RAS) was developed to produce functionally graded Al/SiC composites with a smooth concentration gradient of SiC particles along the height of samples, as opposed to a step change. For this purpose, first settling velocities of different-sized SiC particles in aluminum A356 melt were measured, and the results exhibited a reasonably good agreement with those predicted via the modified Stokes law. Then slices of particulate Al/SiC composites with different SiC contents of 5, 10, 15, and 20 vol.% were stacked in a cast iron mold and heated at 650 °C resulting in remelting and unification of the different composite parts. Considering the preliminary settling experiments, the composite slurry was held at this temperature for three different times to investigate the optimum holding time for obtaining a smooth gradient of SiC concentration along the height of the sample. After quenching, the samples were sectioned and subjected to metallographic studies and hardness measurements. The results confirmed that holding the melt for 60 s provides sufficient settling and redistribution of SiC particles and results in successful production of a functionally graded material.

  13. Effect of ultrasonic treatment on formation of iron-containing intermetallic compounds in Al-Si alloys

    Directory of Open Access Journals (Sweden)

    Yu-bo Zhang

    2016-09-01

    Full Text Available Iron is generally regarded as an unavoidable impurity in Al-Si casting alloys. The acicular Al3Fe and β-Al5FeSi (or Al9Si2Fe2 are common iron-containing intermetallic compounds (IMCs in conventional structure which have a detrimental impact on the mechanical properties. In this paper, ultrasonic field (USF was applied to modify acicular iron phases in Al-12%Si-2%Fe and Al-2%Fe alloys. The results show that the USF applied to Al-Fe alloys caused the morphological transformation of both primary and eutectic Al3Fe from acicular to blocky and granular without changes in their composition. In the case of Al-Si-Fe alloys, ultrasonic treatment led to both morphological and compositional conversion of the ternary iron IMCs. When the USF was applied, the acicular β-Al9Si2Fe2 was substituted by star-like α-Al12Si2Fe3. The modification rate of both binary and ternary iron IMCs relates to the USF treatment duration. The undercooling induced by the ultrasonic vibration contributes to the nucleation of intermetallics and can explain the transformation effect.

  14. Electrochemical behavior of TiAlSiN hard coatings synthesized by a multi-plasma immersion ion implantation and deposition technique

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Gengzhu [University of Science and Technology Liaoning, Anshan 114051 (China); Xie, Zhiwen, E-mail: xzw@cigit.ac.cn [University of Science and Technology Liaoning, Anshan 114051 (China); Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 401122 (China); Chen, Tian [Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, Chongqing 401122 (China); Chen, Zhenyu [Key Laboratory of Power Sources, Institute of Power Sources, Tianjin 300381 (China); Song, Xiaohang [Shanghai Aerospace Equipments Manufacturer, Shanghai 401122 (China); Gao, Xu; Yu, Xiaoguang; Song, Hua [University of Science and Technology Liaoning, Anshan 114051 (China)

    2015-06-01

    The TiAlSiN coatings are synthesized by a multi-plasma immersion ion implantation and deposition technique. The microstructure and the electrochemical behavior of the as-deposited coatings are investigated by using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy and electrochemical tests. These studies reveal that huge lattice distortions and dislocations emerge in the coating after introducing a small amount of Al component. These structural defects can facilitate the corrosion process of the TiAlN coating. The TiAlN coating exhibits a worse corrosion resistance performance than the TiN coating. The TiAlSiN coating has a two phase microstructure, nc-TiAlN/a-Si{sub 3}N{sub 4.} The grain size is greatly reduced after introducing Si component, whereas the portion of the a-Si{sub 3}N{sub 4} phase increases as the amount of Si increases in the coating. The reduced grain size and the increased percentage of the a-Si{sub 3}N{sub 4} phase in the TiAlSiN coatings enhance their ability in corrosion resistance. The TiAlSiN coating with a larger amount of Si shows better corrosion resistance performance. This research provides a comprehensive understanding of the relationship between the microstructure and the electrochemical behavior of the TiAlSiN hard coatings. - Highlights: • Microstructure and electrochemical behavior of TiAlSiN coatings are presented. • Al addition induces serious lattice distortions and dislocations. • Si incorporation induces an obvious grain refinement effect. • TiAlN coating shows a higher corrosion rate than the TiN coating. • TiAlSiN coating with higher Si content shows better corrosion resistance.

  15. Colour metallography in commercial Al-Si alloys. Optimization of the microstructural characterization techniques in light optical microscopy; Metalografia a color en aleaciones Al-Si comerciales. Optimizacion de las tecnicas de caracterizacion microestructural mediante microscopia optica de reflexion

    Energy Technology Data Exchange (ETDEWEB)

    Suarez-Pena, B.; Asensio-Lozano, J.; Vander-Voort, G.F.

    2010-07-01

    The present demand on alloy production with improved quality requires the optimization of the metallographic procedures used on its characterization. Traditional etching techniques ommonly employed for phase identification by optical metallography in aluminium alloys are not always suitable for a detailed analysis of existing phases, nor to accurately predict the mechanisms that govern the solidification process in certain detail. This work explores the potential of colour metallography to reveal at its best as-cast microstructures in Al-Si 12 alloys. For this purpose a colour etching technique, specifically developed for aluminium alloys and based on theWeck reagent[1]. The application of such etchant has allowed the qualitative characterization of the microstructure. And it has also shown the advantages of colour metallography over black and white (B&W) etching techniques. (Author).

  16. Study of the removal mechanism of magnesium from Al-Si liquid alloys using silica base minerals injection; Estudio del mecanismo de eliminacion de magnesio de aleaciones Al-Si en estado liquido mediante inyeccion de minerales base silice

    Energy Technology Data Exchange (ETDEWEB)

    Munoz-Arroyo, R.; Escobedo-Bocardo, J. C.; Hernande-Garcia, H. M.; Cortes-Hernandez, D. A.; Terrones-Maldonado, M.; Rodriguez-Pulido, A.; Hernandez-Pinero, J. L.

    2010-07-01

    In order to eliminate magnesium from an A 380 Al-Si alloy at 750 degree centigrade, the submerged powder injection method, using an inert carrier gas (Ar), was applied. The injected powders in the liquid aluminum bath were zeolite, silica and mixtures of zeolite-silica minerals. For each experiment the response variables were: eliminated magnesium versus injection time and quantity of drosses produced. Chemical analysis by atomic absorption spectrometry showed that mixtures of silica-zeolite 66:34 wt% have the best results with regarding to the removal magnesium from 1 to 0.0066 wt%. During the elimination of magnesium complex stoichiometry compounds were formed due to the reactions among zeolite, water steam and liquid aluminum. These compounds were analyzed by XRD, SEM and TEM. The results obtained, along with using the FactSage 6 thermodynamic software, allowed to elucidate the reaction mechanism between the minerals used and liquid aluminum. (Author)

  17. Mechanics and mechanisms of surface damage in Al-Si alloys under ultra-mild wear conditions

    Science.gov (United States)

    Chen, Ming

    Al-Si alloys intended for use in engine components must operate under ultra-mild wear (UMW) conditions to fit an acceptable amount of wear during a typical vehicle life. This study simulated surface damage in a UMW regime on five chemically etched Al-Si alloy surfaces using a pin-on-disc tribometer at low loads (0.5-2.0 N) under boundary lubricated conditions. The five alloys contained 11 to 25 wt.% Si and differed in matrix hardness, silicon particle morphology, and size. The mechanisms leading to the UMW damage and the role that the matrix hardness and microstructure play on said mechanisms were studied. Quantitative measurement methods based on statistical analysis of particle height changes and material loss from elevated aluminum using a profilometer technique were developed and used to assess UMW. The Greenwood and Tripp's numerical model was adapted to analyze the contact that occurred between Al-Si alloys with silicon particles protruding above the aluminum and steel balls. The estimation of the real contact pressure applied to the silicon particles was used to rationalize the damage mechanisms. The UMW mechanisms consisted of (i) abrasive wear on the top of the silicon particle surfaces; (ii) sinking-in of the silicon particles; (iii) piling-up of the aluminium around sunken-in particles and (vi) wear of the aluminium by the counterface, which eventually led to the initiation of UMW-II. Increasing the size or areal density of silicon particles with small aspect ratios delayed the onset of UMW-II by providing resistance against the silicon particles sinking-in and the aluminum piling-up. The UMW wear rates, however, began to decrease after long sliding cycles once an oil residue layer supported by hardened ultra-fine subsurface grains formed on the deformed aluminium matrix. The layer formation depended on the microstructure and applied load. Overall experimental observations suggested that Al-11% Si with small silicon particles exhibited optimal long

  18. The influence of a microgravity environment on the dendritic morphology during directional solidification of hypoeutectic Al-Si alloys

    Science.gov (United States)

    Grugel, Richard N.

    1993-01-01

    NASA grant NAGW-2540 provided the opportunity to evaluate and extend ongoing studies of directionally solidified Al-Si alloys. Microstructural development was further characterized in terms of solidification processing parameters; novel relationships between processing and development of dendrite trunk diameters and tertiary dendrite arm spacings were found. This has resulted in three publications (one in print, one in press, and one in review). Microstructural development under conditions of controlled acceleration during directional solidification has been investigated; this has culminated in a Master's degree and will be submitted for publication. The above work not only contributes to our understanding of solidification phenomena but also defines the processing parameters for a successful microgravity experiment while providing a data base to which mu g samples can be unequivocally compared and evaluated.

  19. Use of sodium salt electrolysis in the process of continuous modification of eutectic EN AC-AlSi12 alloy

    Indian Academy of Sciences (India)

    J Pezda; A Białobrzeski

    2015-04-01

    This paper presents test results concerning the selection of sodium salt for the technology of continuous modification of the EN AC-AlSi12 alloy, which is based on electrolysis of sodium salts, occurring directly in a crucible with liquid alloy. Sodium ions formed as a result of the sodium salt dissociation and the electrolysis are 'transferred' through walls of the retort made of solid electrolyte. Upon contact with the liquid alloy, which functions as a cathode, sodium ions are transformed into the atomic state, modifying the alloy. As a measure of the alloy modification extent, the obtained increase of the tensile strength m and change of metallographic structure are used, confirming obtained modification effect of the investigated alloy.

  20. Influence of the permeability of networked primary Si on the ejection of hypereutectic Al-Si melts by centrifugation

    Science.gov (United States)

    Youn, Ji Won; Jeon, Je-Beom; Park, Jin Man; Seo, Seok Yong; Lim, Jeon Taik; Kim, Suk Jun; Kim, Ki Young

    2017-02-01

    The separation of high purity Si for solar cells from Al-Si alloy melt in the mushy zone was investigated using an advanced centrifugal technique. The efficiency of separating Si, based on the weight ratio of separated Si to Si in alloy melt, was maximized by optimizing the permeability of a porous structure of Si (Si foam.) For the optimization of the permeability, two fundamental microstructure variables, size and the solid fraction of primary Si platelets, were controlled by adjusting the Si content in the melts and the rotation start temperature, respectively. The best separation efficiency (48.3% with 3N purity) was achieved when Si content in melt was 24% and the solid fraction was 8.7%. The melt with 23% Si led to a higher separation efficiency (69.8%) for a solid fraction of 10.4%, but Al sandwiched between the Si platelets resulted in a decrease in the purity to 2N.

  1. Using Atom-Probe Tomography to Understand Zn O ∶Al /SiO 2/Si Schottky Diodes

    Science.gov (United States)

    Jaramillo, R.; Youssef, Amanda; Akey, Austin; Schoofs, Frank; Ramanathan, Shriram; Buonassisi, Tonio

    2016-09-01

    We use electronic transport and atom-probe tomography to study Zn O ∶Al /SiO 2/Si Schottky diodes on lightly doped n - and p -type Si. We vary the carrier concentration in the ZnO ∶Al films by 2 orders of magnitude, but the Schottky barrier height remains nearly constant. Atom-probe tomography shows that Al segregates to the interface, so that the ZnO ∶Al at the junction is likely to be metallic even when the bulk of the ZnO ∶Al film is semiconducting. We hypothesize that the observed Fermi-level pinning is connected to the insulator-metal transition in doped ZnO. This implies that tuning the band alignment at oxide/Si interfaces may be achieved by controlling the transition between localized and extended states in the oxide, thereby changing the orbital hybridization across the interface.

  2. Fabrication of a 2014Al-SiC/2014Al Sandwich Structure Composite with Good Tensile Strength and Ductility

    Science.gov (United States)

    Zhu, Xian; Zhao, Yu-Guang; Wang, Hui-Yuan; Wang, Zhi-Guo; Wu, Min; Pei, Chang-hao; Chen, Chao; Jiang, Qi-Chuan

    2016-09-01

    A sandwich structure laminate composed of a ductile 2014Al inter-layer and two nanoscale SiC reinforced 2014Al (SiC/2014Al) composite outer layers was successfully fabricated through the combination of powder metallurgy and hot rolling. The ductile 2014Al inter-layer effectively improved the processability of the sandwiched laminates. Tensile test revealed that the yield strength and ultimate tensile strength of the sandwiched laminate were 287 and 470 MPa, respectively, compared with 235 and 425 MPa for monolithic 2014Al. The good performance of the sandwiched laminate results from the strong bonding between the SiC/2014Al composites layer and the ductile 2014Al layer. Thus, the sandwich structure with a composite surface and ductile core is effective for increasing the strength and toughness of composite laminates.

  3. Fabrication of a 2014Al-SiC/2014Al Sandwich Structure Composite with Good Tensile Strength and Ductility

    Science.gov (United States)

    Zhu, Xian; Zhao, Yu-Guang; Wang, Hui-Yuan; Wang, Zhi-Guo; Wu, Min; Pei, Chang-hao; Chen, Chao; Jiang, Qi-Chuan

    2016-11-01

    A sandwich structure laminate composed of a ductile 2014Al inter-layer and two nanoscale SiC reinforced 2014Al (SiC/2014Al) composite outer layers was successfully fabricated through the combination of powder metallurgy and hot rolling. The ductile 2014Al inter-layer effectively improved the processability of the sandwiched laminates. Tensile test revealed that the yield strength and ultimate tensile strength of the sandwiched laminate were 287 and 470 MPa, respectively, compared with 235 and 425 MPa for monolithic 2014Al. The good performance of the sandwiched laminate results from the strong bonding between the SiC/2014Al composites layer and the ductile 2014Al layer. Thus, the sandwich structure with a composite surface and ductile core is effective for increasing the strength and toughness of composite laminates.

  4. Corrosion Behavior of AlSi10Mg Alloy Produced by Additive Manufacturing (AM vs. Its Counterpart Gravity Cast Alloy

    Directory of Open Access Journals (Sweden)

    Avi Leon

    2016-06-01

    Full Text Available The attractiveness of additive manufacturing (AM relates to the ability of this technology to rapidly produce very complex components at affordable costs. However, the properties and corrosion behavior, in particular, of products produced by AM technology should at least match the properties obtained by conventional technologies. The present study aims at evaluating the corrosion behavior and corrosion fatigue endurance of AlSi10Mg alloy produced by selective laser melting (SLM in comparison with its conventional counterpart, gravity cast alloy. The results obtained indicate that the corrosion resistance of the printed and cast alloys was relatively similar, with a minor advantage to the printed alloy. The corrosion fatigue endurance of the printed alloy was relatively improved compared to the cast alloy. This was mainly attributed to the significant differences between the microstructure and defect characteristics of those two alloys.

  5. Dimensional Accuracy and Surface Roughness Analysis for AlSi10Mg Produced by Selective Laser Melting (SLM

    Directory of Open Access Journals (Sweden)

    Kamarudin K.

    2016-01-01

    Full Text Available Selective Laser Melting (SLM is an Additive Manufacturing (AM technique that built 3D part in a layer-by-layer method by melting the top surface layer of a powder bed with a high intensity laser according to sliced 3D CAD data. AlSi10Mg alloy is a traditional cast alloy that is broadly used for die-casting process and used in automotive industry due its good mechanical properties. This paper seeks to investigate the requirement SLM in rapid tooling application. The feasibility study is done by examining the surface roughness and dimensional accuracy as compared to the benchmark part produced through the SLM process with constant parameters. The benchmark produced by SLM shows the potential of SLM in a manufacturing application particularly in moulds.

  6. Annealing tests of in-pile irradiated oxide coated U-Mo/Al-Si dispersed nuclear fuel

    Science.gov (United States)

    Zweifel, T.; Valot, Ch.; Pontillon, Y.; Lamontagne, J.; Vermersch, A.; Barrallier, L.; Blay, T.; Petry, W.; Palancher, H.

    2014-09-01

    U-Mo/Al based nuclear fuels have been worldwide considered as a promising high density fuel for the conversion of high flux research reactors from highly enriched uranium to lower enrichment. In this paper, we present the annealing test up to 1800 °C of in-pile irradiated U-Mo/Al-Si fuel plate samples. More than 70% of the fission gases (FGs) are released during two major FG release peaks around 500 °C and 670 °C. Additional characterisations of the samples by XRD, EPMA and SEM suggest that up to 500 °C FGs are released from IDL/matrix interfaces. The second peak at 670 °C representing the main release of FGs originates from the interaction between U-Mo and matrix in the vicinity of the cladding.

  7. Effect of strontium on crystallization of Mg2Si phase in Al-Si-Mg casting alloys

    Institute of Scientific and Technical Information of China (English)

    廖恒成; 丁毅; 孙国雄

    2002-01-01

    Optical microscope and SEM were used to observe the changes of the microstructure of Al-11.6%Si-0.4%Mg alloys with varying strontium additions and the effect of strontium on the crystallization of Mg2Si phase was discussed. It is found that Mg2Si phase nucleates on the surfaces of the eutectic silicon flakes in the unfully modified alloys, growing as meshwork or bamboo-shoot shape, however, very few and fine Mg2Si particles phase are isolated at the boundaries of the eutectic cells in the fully modified alloys. Strontium has an important influence on the crystallization of Mg2Si phase in Al-Si-Mg casting alloys and it is thought to be related to the increase of the amount of dendritic α phase and the modifying degree of eutectic silicon phase.

  8. Al-Si alloy point contact formation and rear surface passivation for silicon solar cells using double layer porous silicon

    Science.gov (United States)

    Moumni, Besma; Ben Jaballah, Abdelkader; Bessais, Brahim

    2012-10-01

    Lowering the rear surface recombination velocities by a dielectric layer has fascinating advantages compared with the standard fully covered Al back-contact silicon solar cells. In this work the passivation effect by double layer porous silicon (PS) (wide band gap) and the formation of Al-Si alloy in narrow p-type Si point contact areas for rear passivated solar cells are analysed. As revealed by Fourier transform infrared spectroscopy, we found that a thin passivating aluminum oxide (Al2O3) layer is formed. Scanning electron microscopy analysis performed in cross sections shows that with bilayer PS, liquid Al penetrates into the openings, alloying with the Si substrate at depth and decreasing the contact resistivity. At the solar cell level, the reduction in the contact area and resistivity leads to a minimization of the fill factor losses.

  9. The influence of material of mould and modification on the structure of AlSi11 alloy

    Directory of Open Access Journals (Sweden)

    M. Łągiewka

    2012-01-01

    Full Text Available The presented work discusses the influence of material of foundry mould on the effect of modification of AlSi11 alloy. For this purpose castings were produced in moulds made of four various materials. Castings of the first type were cast in a metal die, the second ones in the conventional mould of bentonite-bound sand, those of the third type in the sand mould with oil binder, the last ones in a shell mould where phenol-formaldehyde resin was applied as a binder. All the castings were made of AlSi11 alloy modified with strontium. For a purpose of comparison also castings made of the non-modified alloy were produced. The castings were examined with regard to their microstructures. The performed investigations point out that the addition of strontium master alloy results in refining of the alloy structure, particularly of the α-phase, causes some morphological changes in the alloy and the refinement of eutectics. The advantageous influence of modifier on the structure of the examined silumin was observed particularly in the case of alloy cast either in the conventional oil-bound sand mould or in the shell mould. The non-modified alloy cast into a metal die exhibits a structure similar to those of modified alloy solidifying in the other moulds. The improvement in both tensile strength and unit elongation suggests that the modification was carried out correctly. The best mechanical properties were found for the alloy cast in a metal die, both with and without modification treatment.

  10. Thermal and Microstructure Characterization of Zn-Al-Si Alloys and Chemical Reaction with Cu Substrate During Spreading

    Science.gov (United States)

    Berent, Katarzyna; Pstruś, Janusz; Gancarz, Tomasz

    2016-08-01

    The problems associated with the corrosion of aluminum connections, the low mechanical properties of Al/Cu connections, and the introduction of EU directives have forced the potential of new materials to be investigated. Alloys based on eutectic Zn-Al are proposed, because they have a higher melting temperature (381 °C), good corrosion resistance, and high mechanical strength. The Zn-Al-Si cast alloys were characterized using differential scanning calorimetry (DSC) measurements, which were performed to determine the melting temperatures of the alloys. Thermal linear expansion and electrical resistivity measurements were performed at temperature ranges of -50 to 250 °C and 25 to 300 °C, respectively. The addition of Si to eutectic Zn-Al alloys not only limits the growth of phases at the interface of liquid solder and Cu substrate but also raises the mechanical properties of the solder. Spreading test on Cu substrate using eutectic Zn-Al alloys with 0.5, 1.0, 3.0, and 5.0 wt.% of Si was studied using the sessile drop method in the presence of QJ201 flux. Spreading tests were performed with contact times of 1, 8, 15, 30, and 60 min, and at temperatures of 475, 500, 525, and 550 °C. After cleaning the flux residue from solidified samples, the spreadability of Zn-Al-Si on Cu was determined. Selected, solidified solder/substrate couples were cross-sectioned, and the interfacial microstructures were studied using scanning electron microscopy and energy dispersive x-ray spectroscopy. The growth of the intermetallic phase layer was studied at the solder/substrate interface, and the activation energy of growth of Cu5Zn8, CuZn4, and CuZn phases were determined.

  11. Influence of SiC surface polarity on the wettability and reactivity in an Al/SiC system

    Science.gov (United States)

    Shen, Ping; Wang, Yi; Ren, Lihua; Li, Shixin; Liu, Yuhua; Jiang, Qichuan

    2015-11-01

    The wetting of (0 0 0 1) 6H-SiC single crystals by molten Al was investigated using a dispensed sessile drop method in a high vacuum at 973-1173 K. The wettability and reactivity in this system are sensitive to the surface polarity of SiC. The interfacial reaction on the Si-terminated surface is rapid. The formation of a continuous Al4C3 product layer at the interface leads to an equilibrium contact angle of 56 ± 1° at 1173 K. In comparison, the interfacial reaction on the C-terminated surface is sluggish. The interface is only partially covered by discrete Al4C3 platelets even after dwelling at 1173 K for 2 h. The final wettability, however, is much better (θF = 41 ± 1°) than that of the Si-terminated surface which was covered by a dense Al4C3 layer, suggesting that the formation of Al4C3 should not always contribute to the wetting in the Al/SiC system. A plausible explanation is that the clean (i.e., deoxidized) C-terminated surface should be well wetted by molten Al in nature, owing to the strong chemical interactions between liquid Al and the surface atoms of the C-terminated SiC. It is likely that the presence of the oxide film at the surface of the molten Al drop or the SiC substrate and the rapid formation of Al4C3, which prevent the establishment of a real Al/SiC interface, conceal the intrinsic wettability of this system.

  12. Preparation of Al-Si Master Alloy by Electrochemical Reduction of Volcanic Rock in Cryolite Molten Salt

    Science.gov (United States)

    Liu, Aimin; Shi, Zhongning; Xu, Junli; Hu, Xianwei; Gao, Bingliang; Wang, Zhaowen

    2016-06-01

    Volcanic rock found in the Longgang Volcano Group in Jilin Province of China has properties essentially similar to Apollo lunar soils and previously prepared lunar soil simulants, such as Johnson Space Center Lunar simulant and Minnesota Lunar simulant. In this study, an electrochemical method of preparation of Al-Si master alloy was investigated in 52.7 wt.%NaF-47.3 wt.%AlF3 melt adding 5 wt.% volcanic rock at 1233 K. The cathodic electrochemical process was studied by cyclic voltammetry, and the results showed that the cathodic reduction of Si(IV) is a two-step reversible diffusion-controlled reaction. Si(IV) is reduced to Si(II) by two electron transfers at -1.05 V versus platinum quasi-reference electrode in 52.7 wt.%NaF-47.3 wt.%AlF3 molten salt adding 5 wt.% volcanic rock, while the reduction peak at -1.18 V was the co-deposition of aluminum and silicon. In addition, the cathodic product obtained by galvanostatic electrolysis for 4 h was analyzed by means of x-ray diffraction, x-ray fluorescence, scanning electron microscopy and energy dispersive spectrometry. The results showed that the phase compositions of the products are Al, Si, Al5FeSi, and Al3.21Si0.47, while the components are 90.5 wt.% aluminum, 4.4 wt.% silicon, 1.9 wt.% iron, and 0.2 wt.% titanium.

  13. Global Mg/Si and Al/Si Distributions on Lunar Surface Derived from Chang'E-2 X-ray Spectrometer

    CERN Document Server

    Dong, Wu-Dong; Zhu, Meng-Hua; Xu, Aoao; Tang, Zesheng

    2015-01-01

    X-ray fluorescence remote sensing technique plays a significant role in the chemical compositions research of the Moon. Here we describe the data analysis method for China's Chang'E-2 X-ray spectrometer (CE2XRS) in detail and present the preliminary results: the first global Mg/Si and Al/Si maps on the lunar surface. Our results show that the distributions of Mg/Si and Al/Si correlate well with the terrains of the Moon. The higher Mg/Si ratio corresponding to the mare regions while the lower value corresponding to the highland terrains. The map of Al/Si ratio shows a reverse relationship with the map of Mg/Si ratio.

  14. Effects of vacuum annealing treatment on microstructures and residual stress of AlSi10Mg parts produced by selective laser melting process

    Science.gov (United States)

    Chen, Tian; Wang, Linzhi; Tan, Sheng

    2016-07-01

    Selective laser melting (SLM)-fabricated AlSi10Mg parts were heat-treated under vacuum to eliminate the residual stress. Microstructure evolutions and tensile properties of the SLM-fabricated parts before and after vacuum annealing treatment were studied. The results show that the crystalline structure of SLM-fabricated AlSi10Mg part was not modified after the vacuum annealing treatment. Additionally, the grain refinement had occurred after the vacuum annealing treatment. Moreover, with increasing of the vacuum annealing time, the second phase increased and transformed to spheroidization and coarsening. The SLM-produced parts after vacuum annealing at 300∘C for 2 h had the maximum ultimate tensile strength (UTS), yield strength (YS) and elongation, while the elastic modulus decreased significantly. In addition, the tensile residual stress was found in the as-fabricated AlSi10Mg samples by the microindentation method.

  15. Global Mg/Si and Al/Si Distributions on the Lunar Surface Derived from Chang'E-2 X-ray Spectrometer

    Science.gov (United States)

    Dong, Wu-Dong; Zhang, Xiao-Ping; Zhu, Meng-Hua; Xu, Ao-Ao; Tang, Ze-Sheng

    2016-01-01

    The technique of X-ray fluorescence remote sensing plays a significant role in research related to the chemical compositions of the Moon. Here we describe the data analysis method for China's Chang'E-2 X-ray spectrometer in detail and present the preliminary results about the first global Mg/Si and Al/Si maps of the lunar surface. Our results show that the distributions of Mg/Si and Al/Si correlate well with terrains on the Moon. The higher Mg/Si ratio corresponds to the mare regions while the lower value corresponds to the highland terrains. The map of the Al/Si ratio shows a reversed distribution compared with the map of the Mg/Si ratio.

  16. Growth and Device Performance of AlGaN/GaN Heterostructure with AlSiC Precoverage on Silicon Substrate

    Directory of Open Access Journals (Sweden)

    Jae-Hoon Lee

    2014-01-01

    Full Text Available A crack-free AlGaN/GaN heterostructure was grown on 4-inch Si (111 substrate with initial dot-like AlSiC precoverage layer. It is believed that introducing the AlSiC layer between AlN wetting layer and Si substrate is more effective in obtaining a compressively stressed film growth than conventional Al precoverage on Si surface. The metal semiconductor field effect transistor (MESFET, fabricated on the AlGaN/GaN heterostructure grown with the AlSiC layer, exhibited normally on characteristics, such as threshold voltage of −2.3 V, maximum drain current of 370 mA/mm, and transconductance of 124 mS/mm.

  17. Observation of free electron cyclotron resonance in NaAlSi3O8 feldspar: Direct determination of the effective electron mass

    DEFF Research Database (Denmark)

    Poolton, N.R.J.; Nicholis, J.E.; Bøtter-Jensen, L.;

    2001-01-01

    We report the first observation of cyclotron resonances in alkali feldspars, using highly sensitive optical detection methods. In Na-feldspar (NaAlSi3O8). a near isotropic effective electron mass value of m(c)(*) = 0.79m, has been determined. The significance of this measurement in terms of the o......We report the first observation of cyclotron resonances in alkali feldspars, using highly sensitive optical detection methods. In Na-feldspar (NaAlSi3O8). a near isotropic effective electron mass value of m(c)(*) = 0.79m, has been determined. The significance of this measurement in terms...

  18. A Fractional Factorial Design Study of Reciprocating Wear Behavior of Al-Si-SiCp Composites at Lubricated Contacts

    Science.gov (United States)

    Rajeev, V. R.; Dwivedi, D. K.; Jain, S. C.

    2011-04-01

    The lubricated reciprocating wear behavior of two composites A319/15%SiCp and A390/15%SiCp produced by the liquid metallurgy route was investigated by means of an indigenously developed reciprocating friction wear test rig using a fractional factorial-design approach. The main purpose was to study the influence of wear and friction test parameters such as applied load, sliding distance, reciprocating velocity, counter surface temperature and silicon content in composites, as well as their interactions on the wear and friction characteristics of these composites. Two output responses (wear loss and coefficient of friction) were measured. The input parameter levels were fixed through pilot experiment conducted in the newly developed reciprocating friction and wear test rig. The counter surface material used for the wear study was cast iron having Vickers hardness of 244 HVN. It had been demonstrated through established equations that A390/15%SiCp composite is subjected to low wear compared to the A319/15%SiCp composite. The experimental results indicate that the proposed mathematical models suggested could adequately describe the performance indicators within the limits of the factors that are being investigated. The applied load, sliding distance, reciprocating velocity, counter surface temperature, and silicon content in composite are the five important factors controlling the friction and wear characteristics of the composite in lubricated condition. Moreover, the two factor interactions have a strong effect on the wear of composites. The results give a comprehensive insight into the wear of the composites.

  19. TIPO TOTAL DE INJUSTO

    OpenAIRE

    Guimarães, Rodrigo Suzana

    2008-01-01

    Neste estudo, faz-se a releitura do injusto penal com base na teoria dos elementos negativos do tipo, analisando o seu acerto e a necessidade de sua aplicação para o desenvolvimento do Direito Penal brasileiro. A teoria dos elementos negativos do tipo surgiu na Alemanha do século XIX, por obra de Adolf Merkel, como forma de buscar a solução para uma lacuna deixada pelo antigo Código Penal alemão sobre o erro relativo aos pressupostos fáticos de uma causa de justificação. Merkel e seus seguido...

  20. TIPOS DE DISCURSO

    OpenAIRE

    Garcia, Afrânio; UERJ

    2012-01-01

    O professor Adilson Citelli, em seu excelente livro Linguageme persuasão, apresenta cinco tipos de discurso:§ discurso dominante§ discurso autorizado§ discurso polêmico,§ discurso lúdico§ discurso autoritário.

  1. Internally consistent thermodynamic data for aqueous species in the system Na-K-Al-Si-O-H-Cl

    Science.gov (United States)

    Miron, George D.; Wagner, Thomas; Kulik, Dmitrii A.; Heinrich, Christoph A.

    2016-08-01

    A large amount of critically evaluated experimental data on mineral solubility, covering the entire Na-K-Al-Si-O-H-Cl system over wide ranges in temperature and pressure, was used to simultaneously refine the standard state Gibbs energies of aqueous ions and complexes in the framework of the revised Helgeson-Kirkham-Flowers equation of state. The thermodynamic properties of the solubility-controlling minerals were adopted from the internally consistent dataset of Holland and Powell (2002; Thermocalc dataset ds55). The global optimization of Gibbs energies of aqueous species, performed with the GEMSFITS code (Miron et al., 2015), was set up in such a way that the association equilibria for ion pairs and complexes, independently derived from conductance and potentiometric data, are always maintained. This was achieved by introducing reaction constraints into the parameter optimization that adjust Gibbs energies of complexes by their respective Gibbs energy effects of reaction, whenever the Gibbs energies of reactant species (ions) are changed. The optimized thermodynamic dataset is reported with confidence intervals for all parameters evaluated by Monte Carlo trial calculations. The new thermodynamic dataset is shown to reproduce all available fluid-mineral phase equilibria and mineral solubility data with good accuracy and precision over wide ranges in temperature (25-800 °C), pressure (1 bar to 5 kbar) and composition (salt concentrations up to 5 molal). The global data optimization process adopted in this study can be readily repeated any time when extensions to new chemical elements and species are needed, when new experimental data become available, or when a different aqueous activity model or equation of state should be used. This work serves as a proof of concept that our optimization strategy is feasible and successful in generating a thermodynamic dataset reproducing all fluid-mineral and aqueous speciation equilibria in the Na-K-Al-Si-O-H-Cl system within

  2. EBSD Study of the Influence of a High Magnetic Field on the Microstructure and Orientation of the Al-Si Eutectic During Directional Solidification

    Science.gov (United States)

    Li, Xi; Fautrelle, Yves; Gagnoud, Annie; Ren, Zhongming; Moreau, Rene

    2016-06-01

    The effect of a high magnetic field on the morphology of the Al-Si eutectic was investigated using EBSD technology. The results revealed that the application of the magnetic field modified the morphology of the Al-Si eutectic significantly. Indeed, the magnetic field destroyed the coupled growth of the Al-Si eutectic and caused the formation of the divorced α-Al and Si dendrites at low growth speeds (≤1 μm/s). The magnetic field was also found to refine the eutectic grains and reduce the eutectic spacing at the initial growth stage. Moreover, the magnetic field caused the occurrence of the columnar-to-equiaxed transition of the α-Al phase in the Al-Si eutectic. The abovementioned effects were enhanced as the magnetic field increased. This result should be attributed to the magnetic field restraining the interdiffusion of Si and Al atoms in liquid ahead of the liquid/solid interface and the thermoelectric magnetic force acting on the eutectic lamellae under the magnetic field.

  3. Nanostructured Al/SiC-Graphite Composites Produced by Accumulative Roll Bonding: Role of Graphite on Microstructure, Wear and Tensile Behavior

    Science.gov (United States)

    Reihanian, M.; Fayezipour, S.; Lari Baghal, S. M.

    2017-03-01

    Nanostructured Al/SiC composite was fabricated by accumulative roll bonding (ARB). The effect of Gr, as the soft and second reinforcing particle, on the microstructure and deformation behavior of Al/SiC composite was examined. After eight ARB cycles, a homogeneous ultra-fine grained structure with the average grain size of about 710 nm was obtained in the Al/SiC composite. Results showed that Gr could not affect the particle distribution. However, the bonding quality between the layers reduced and the mechanical properties of the composite deteriorated considerably with increasing the Gr content. Compared with the Gr-free composite, the Al/SiC-Gr hybrid composite with the highest Gr content exhibited the lowest bonding quality and the lowest tensile strength. Tensile fracture surface of the composites showed that the number of delaminated layers was increased by increasing the Gr content. The best wear resistance was obtained in the composite whose powder mixture contained 80 SiC and 20 Gr (in wt.%).

  4. Preparation of Semi-solid AlSi30 Billets by SIMA Method%基于SIMA法的AlSi30合金半固态坯料的制备

    Institute of Scientific and Technical Information of China (English)

    薛克敏; 韩国民; 黄科帅; 喻佳; 李晓

    2009-01-01

    引入等径角挤压(ECAP)法替代传统半固态坯料制备方法--应变诱导熔体激活(SIMA)法中的冷、热塑性变形,在正交试验条件下由AlSi30合金粉末制备其半固态坯料,研究了工艺参数对半固态坯料显微组织的影响.结果表明,保温温度是影响初晶硅晶粒大小和圆整程度的主要因素;影响初晶硅晶粒大小的次要因素是保温时间;影响初晶硅圆整度的次要因素是等径角挤压的温度;试验的最佳工艺参数,等径角挤压温度为500 ℃,挤压路径选择A路径,保温温度为605 ℃,保温时间为55 min.

  5. The effects of individual metal contents on isochrones for C, N, O, Na, Mg, Al, Si, and Fe

    CERN Document Server

    Beom, Minje; Ferguson, Jason W; Kim, Y -C

    2016-01-01

    The individual characteristics of C, N, O, Na, Mg, Al, Si, and Fe on isochrones have been investigated in this study. Stellar models have been constructed for various mixtures in which the content of each element is changed up to the extreme value reported in recent studies, and the changes in isochrone shape have been analyzed for the various mixtures. To express the abundance variation of different elements with a single parameter, we have focused on the relative changes in the total number of metal ions. A review of the shape changes revealed that Na, Mg, and Al work the same way in stellar models, as the well-known fact that C, N, and O have the same reactions in the stellar interior. In addition, it was found that in high-metallicity conditions the influence of Si and Fe on the red giant branch becomes smaller than that of Na, Mg, and Al closer to the tip. Furthermore, the influence of Fe on the main sequence is larger than that of Na, Mg, Al, and even Si.

  6. Influence of Vibrations During Crystallization on Mechanical Properties and Porosity of EN AC-AlSi17 Alloy

    Directory of Open Access Journals (Sweden)

    T. Ciućka

    2013-01-01

    Full Text Available Today’s industry aims at such situation, where number of defective products, so called defects shall approach to zero. Therefore, oneintroduces a various changes in technology of production, introduces improvements which would help in accomplishment of this objective.Another important factor is introduction of different type of testing, which shall help in assessment which factor has significant effect on quantity of rejects, and which one could be neglected. Existence of casting rejects is unavoidable; therefore a new ideas, technologies and innovations are necessary in the entire widely understood foundry branch, in order to minimize such adverse effect. Performance of tests aimed at unequivocal determination of an effect of vibrations during crystallization on mechanical properties and porosity of the EN ACAlSi17 alloy was the objective of the present work. To do this, there were produced 36 castings from EN AC-AlSi17 alloy. All the castings underwent machining operations. Half of the casting was destined to strength tests, the other half served to determination of an effect of vibrations on porosity of the alloy. The specimens were divided into 12 groups, depending on amplitude of vibrations and tilt angle of metal mould during pouring operation.

  7. Laser cladding of a Mg based Mg-Gd-Y-Zr alloy with Al-Si powders

    Science.gov (United States)

    Chen, Erlei; Zhang, Kemin; Zou, Jianxin

    2016-03-01

    In the present work, a Mg based Mg-Gd-Y-Zr alloy was subjected to laser cladding with Al-Si powders at different laser scanning speeds in order to improve its surface properties. It is observed that the laser clad layer mainly contains Mg2Si, Mg17Al12 and Al2(Gd,Y) phases distributed in the Mg matrix. The depth of the laser clad layer increases with decreasing the scanning speed. The clad layer has graded microstructures and compositions. Both the volume fraction and size of Mg2Si, Mg17Al12 and Al2(Gd,Y) phases decreases with the increasing depth. Due to the formation of these hardening phases, the hardness of clad layer reached a maximum value of HV440 when the laser scanning speed is 2 mm/s, more than 5 times of the substrate (HV75). Besides, the corrosion properties of the untreated and laser treated samples were all measured in a NaCl (3.5 wt.%) aqueous solution. The corrosion potential was increased from -1.77 V for the untreated alloy to -1.13 V for the laser clad alloy with scanning rate of 2 mm/s, while the corrosion current density was reduced from 2.10 × 10-5 A cm-2 to 1.64 × 10-6 A cm-2. The results show that laser cladding is an efficient method to improve surface properties of Mg-Rare earth alloys.

  8. Accuracy of Ceramic Mould Filling with Liquid AlSi9 Aluminium Alloy in the Process Using Back-pressure

    Directory of Open Access Journals (Sweden)

    A. Karwiński

    2013-01-01

    Full Text Available The paper presents the effect of suction pressure exerted on the liquid AlSi alloy when it is introduced into a ceramic mould made in the investment process and the results compared with data obtained on gravity poured castings.The study used special pattern sets and ceramic moulds made with the alternately applied soluble silicate binder and ethyl silicate.Additionally, self-supported moulds based entirely on the Ekosil binder were used. In the analysis of castings, the following parameters were examined: a linear dimensional accuracy, the state of surface microgeometry and the possibility of metal penetration into a complex ceramic mould, allowing also for the presence of capillary phenomena. In the process of casting with back-pressure, the pressure values of 500 hPa, 600 hPa and 700 hPa were applied in the chamber where the ceramic mould was located, with the temperature of the said mould kept at a level of 150  10C.

  9. The Effect of Technological Parameters on the Microstructure and Mechanical Properties of AlSi17Cu4 Alloy

    Directory of Open Access Journals (Sweden)

    Jaroslaw PIĄTKOWSKI

    2016-09-01

    Full Text Available The mechanical properties (HB, HV, R0.2, Rm and plastic properties (A5, Z of AlSi17Cu4 alloy when exposed to chosen technological processes, such as modification, overheating and rapid cooling, are presented in this paper. The best combination of properties was noticed in alloy overheated for 40 minutes at 920 oC and casted into a metallic mould submerged in liquid nitrogen. Moreover, the technological stability and homogeneity of alloys were evaluated based on spread of results, expressed by standard deviation. It was proven, based on microstructure analysis, that the best effect of refinement was achieved by intensive cooling of alloy preceded by its overheating. The XRD analysis indicated that the intermetallic phases, mainly θ(Al2Cu and γ1(Al4Cu9 caused hardening of the solution, improvement in mechanical properties and technological stability.DOI: http://dx.doi.org/10.5755/j01.ms.22.3.8490

  10. Effects of vibration and grain refiner on microstructure of semisolid slurry of hypoeutectic Al-Si alloy

    Institute of Scientific and Technical Information of China (English)

    ZHAO Jun-wen; WU Shu-sen; XIE Li-zhi; AN Ping; MAO You-wu

    2008-01-01

    The effects of vibration and grain refiner on the microstructure of semisolid slurry of hypoeutectic Al-Si alloy were studied. The impact of vibration on the convection of liquid was conducted by using a system of water-particle tracer. The 356 melt at temperature of 630-660 ℃ with or without grain refiner Al-5%Ti-1%B was poured into a metal cup as the vibrating vessel, then it was cooled to 590-610 ℃ in the semisolid zone and kept for some time, subsequently vibration with different frequencies was applied. The results show that the primary α(Al) particles become finer and rounder with the increase of vibration frequency. The slurry with primary α(Al) equivalent particle diameter(EPD) of about 90 μm and average shape coefficient(ASC) of about 0.5 can be prepared under vibration of 20 Hz. With the combined action of vibration and grain refiner Al-5Ti-B, even smaller and rounder spheroids with EPD of about 85 μm and ASC of about 0.6 are obtained.

  11. A COMBINATORIAL APPROACH TO THE OXIDATION RESISTANCE OF(Ti,Al)N AND Ti-Al-Si-N HARD COATINGS

    Institute of Scientific and Technical Information of China (English)

    R.Cremer; D.Neuschütz

    2002-01-01

    The increasing complexity of modern functional materials leads to the demand of acost efficient tool for the development of new products. One possible approach to thisquestion is the adaptation of combinatorial methods to the specific requirements of ma-terials industry. These methods, originally developed for the pharmaceutical industry,have recently been applied to the screening of superconductive, magnetoresistant andphotoluminescent materials. The principle of these combinatorial approaches is thedeposition of large materials libraries in one process combined with fast methods forthe determination of the resulting properties. In this paper, the deposition and charac-terization of laterally graded materials libraries (composition spread) is presented. Thefilms have been deposited by reactive magnetron sputtering, using two or three metallictargets at a low angle to the substrate surface as well as a system of apertures. Toillustrate the advantages of combinatorial approaches for the development of advancedmaterials, the multicomponent metastable hardcoatings (Ti, Al)N and Ti-Al-Si-N arediscussed with special emphasis on the relations between structure and composition onthe one hand and the oxidation resistance of these coatings on the other. The resultsillustrate that the composition spread approach is a powerful and cost efficient tool forthe development and optimization of new multicomponent functional materials.

  12. Effect of pouring temperature on cooling slope casting of semi-solid Al-Si-Mg alloy

    Institute of Scientific and Technical Information of China (English)

    Prosenjit Das; Sudip K. Samanta; Himadri Chattopadhyay; Pradip Dutta

    2012-01-01

    Present trend of semi-solid processing is directed towards rheocasting route which allows manufacturing of near-net-shape cast components directly from the prepared semi-solid slurry.Generation of globular equi-axed grains during solidification of rheocast components,compared to the columnar dendritic structure of conventional casting routes,facilitates the manufacturing of components with improved mechanical properties and structural integrity.In the present investigation,a cooling slope has been designed and indigenously fabricated to produce semi solid slurry of Al-Si-Mg (A356) alloy and successively cast in a metallic mould.The scope of the present work discusses about development of a numerical model to simulate the liquid metal flow through cooling slope using Eulerian two-phase flow approach and to investigate the effect of pouring temperature on cooling slope semi-solid slurry generation process.The two phases considered in the present model are liquid metal and air.Solid fraction evolution of the solidifying melt is tracked at different locations of the cooling slope,following Schiel's equation.The continuity equation,momentum equation and energy equation are solved considering thin wall boundary condition approach.During solidification of the liquid metal,a modified temperature recovery scheme has been employed taking care of the latent heat release and change of fraction of liquid.The results obtained from simulations are compared with experimental findings and good agreement has been found.

  13. Atomic structure and electronic properties of the two-dimensional (Au ,Al )/Si (111 )2 ×2 compound

    Science.gov (United States)

    Gruznev, D. V.; Bondarenko, L. V.; Matetskiy, A. V.; Tupchaya, A. Y.; Chukurov, E. N.; Hsing, C. R.; Wei, C. M.; Eremeev, S. V.; Zotov, A. V.; Saranin, A. A.

    2015-12-01

    A combination of scanning tunneling microscopy, angle-resolved photoelectron spectroscopy, ab initio random structure searching, and density functional theory electronic structure calculations was applied to elucidate the atomic arrangement and electron band structure of the (Au ,Al )/Si (111 )2 ×2 two-dimensional compound formed upon Al deposition onto the mixed 5 ×2 /√{3 }×√{3 } Au/Si(111) surface. It was found that the most stable 2 ×2 -(Au, Al) compound incorporates four Au atoms, three Al atoms, and two Si atoms per 2 ×2 unit cell. Its atomic arrangement can be visualized as an array of meandering Au atomic chains with two-thirds of the Al atoms incorporated into the chains and one-third of the Al atoms interconnecting the chains. The compound is metallic and its electronic properties can be controlled by appropriate Al dosing since energetic location of the bands varies by ˜0.5 eV during increasing of Al contents. The 2 ×2 -(Au, Al) structure appears to be lacking the C3 v symmetry typical for the hexagonal lattices. The consequence of the peculiar atomic structure of the two-dimensional alloy is spin splitting of the metallic states, which should lead to anisotropy of the current-induced in-plane spin polarization.

  14. Wetting behavior of Al Si Mg alloys on Si3N4/Si substrates: optimization of processing parameters

    Science.gov (United States)

    de La Peña, J. L.; Pech-Canul, M. I.

    2008-06-01

    The wetting behavior of Al Si Mg alloys on Si3N4/Si substrates has been investigated using the sessile drop technique. Based on a Taguchi experiment design, the effect of the following processing parameters on the contact angle (θ) and surface tension (σLV) was studied: processing time and temperature, atmosphere (Ar and N2), substrate surface condition (with and without a silicon wafer), as well as the Mg and Si contents in the aluminium alloy. In nitrogen, non-wetting conditions prevail during the isothermal events while in argon a remarkable non-wetting to wetting transition leads to contact angles θ as low as 11±3° and a liquid surface tension σLV of 33± 10×10-5 kJ/m2. According to the multiple analysis of variance (Manova), the optimum conditions for minimizing the values of θ and σLV are as follows: temperature of 1100 °C, processing time of 90 min, argon atmosphere, no use of a silicon wafer, and the use of the Al-18% Mg-1% Si alloy. A verification test conducted under the optimized conditions resulted in a contact angle of θ=9±3° and a surface tension of σLV=29± 9×10-5 kJ/m2, both indicative of excellent wetting.

  15. Selection of heat treatments temperature of AlSi13Cu2Fe silumin on base of ATD method

    Directory of Open Access Journals (Sweden)

    J. Pezda

    2008-08-01

    Full Text Available Nowadays tendency connected with reduction of design structures’ mass effects in growing significance of usage of silumins, which are the most widespread alloys of aluminum. Mechanical and technological properties of machine parts manufactured from Al-Si alloys are determined by their structure. In case of cast parts, structure of alloy is a derivative of properly performed process of melting and pouring, as well as design of the casting and mould. Mechanical properties of alloys destined to machine parts made in casting process can be upgraded by modification. Possible heat treatment performed for a cast products effects in further improvement of their mechanical properties, based on precipitation processes. Selection of proper parameters of heat treatment process impacts directly on reduction of production costs of the castings.The paper presents an attempt of implementation of ATD method to determination of solution heat treatment and ageing treatment of AK132 silumin. Obtained results concern registered curves of ATD method, strength tests and determination of an effect of heat treatment temperatures on Rm tensile strength of modified AK132 silumin. On base of preliminary tests results there was determined an impact of temperature changes of solution heat treatment and ageing treatment on Rm tensile strength of AK132 silumin.

  16. Microstructure and Mechanical Property of 3003 Aluminum Alloy Joint Brazed with Al-Si-Cu-Zn Filler Metal

    Directory of Open Access Journals (Sweden)

    LI Xiao-qiang

    2016-09-01

    Full Text Available Al-Si-Cu-Zn filler metal was developed to braze 3003 aluminum alloy. The microstructure and fracture surface of the joint were analyzed by XRD, SEM and EDS, and the effects of brazing temperature on microstructure and property of the joint were investigated. The results show that good joints are obtained at brazing temperature of 540-580℃ for 10min. The brazed joint consists of α(Al solid solution, θ(Al2Cu intermetallic compound, fine silicon phase and AlCuFeMn+Si phase in the central zone of brazed seam, and α(Al solid solution and element diffusion layers at both the sides of brazed seam, and the base metal. The room temperature (RT shear fracture of the joint occurs at the interface between the teeth shape α(Al in the diffusion layer and the center zone of brazed seam, which is mainly characterized as brittle cleavage. As the brazing temperature increases, α(Al solid solution crystals in the diffusion zone grow up, and the interfacial bonding of the joint is in the form of interdigitation. Brazing at 560℃ for 10min, the RT shear strength of the joint reaches the maximum value of 92.3MPa, which is about 62.7% of the base material.

  17. Influence of Laser Welding Speed on the Morphology and Phases Occurring in Spray-Compacted Hypereutectic Al-Si-Alloys

    Directory of Open Access Journals (Sweden)

    Thomas Gietzelt

    2016-11-01

    Full Text Available Normally, the weldability of aluminum alloys is ruled by the temperature range of solidification of an alloy according to its composition by the formation of hot cracks due to thermal shrinkage. However, for materials at nonequilibrium conditions, advantage can be taken by multiple phase formation, leading to an annihilation of temperature stress at the microscopic scale, preventing hot cracks even for alloys with extreme melting range. In this paper, several spray-compacted hypereutectic aluminum alloys were laser welded. Besides different silicon contents, additional alloying elements like copper, iron and nickel were present in some alloys, affecting the microstructure. The microstructure was investigated at the delivery state of spray-compacted material as well as for a wide range of welding speeds ranging from 0.5 to 10 m/min, respectively. The impact of speed on phase composition and morphology was studied at different disequilibrium solidification conditions. At high welding velocity, a close-meshed network of eutectic Al-Si-composition was observed, whereas the matrix is filled with nearly pure aluminum, helping to diminish the thermal stress during accelerated solidification. Primary solidified silicon was found, however, containing considerable amounts of aluminum, which was not expected from phase diagrams obtained at the thermodynamic equilibrium.

  18. Microstructure and mechanical properties of spray-deposited Al-Si-Fe-Cu-Mg alloy containing Mn

    Institute of Scientific and Technical Information of China (English)

    2003-01-01

    Al-20Si-5Fe-3Cu-lMg alloy was synthesized by the spray atomization and deposition technique. The microstructure and mechanical properties of the spray deposited hypereutectic Al-Si alloy were studied using optical microscopy, scanning electron microscopy, X-ray diffraction, TEM (Transmission Electron Microscope) and HREM (High-resolution Electron Microscope), DSC (Differential Scanning Calorimetry), microhardness measurement, and tensile tests. The effects of Mn on the microstructural evolution of the highsilicon aluminum alloy after extrusion and heat treatment have been examined. The results show that two kinds of phases, i.e. S (Al2CuMg) and σ(Al5Cu6Mg2), precipitated from matrix and improved the tensile strength of the alloy efficiently at both the ambient and elevated temperatures (300℃). The tensile test results indicate that the spray-deposited Al-20Si-SFe-3Cu-1Mg alloy has better strength than the powder metallurgy processed Al-20Si-3Cu-1Mg alloy at elevated temperature.

  19. The Microstructure And Mechanical Properties Of The AlSi17Cu5 Alloy After Heat Treatment

    Directory of Open Access Journals (Sweden)

    Piątkowski J.

    2015-09-01

    Full Text Available In the paper results of the microstructure and mechanical properties (HB, Rm and R0,2 of AlSi17Cu5 alloy, subjected by solution heat treatment (500ºC/6h/woda and aging (200ºC/16h/piec are presented. In next step the alloy was modified and heated significantly above the Tliq temperature (separately and together. It was found that the increase in the strength properties of the tested alloy after heat treatment compared to alloys without solution heat treatment and aging was due to precipitation hardening. The applied aging treatment of ingots (preceded by solution heat treatment, causes not only increase in concentration in α(Al solid solution, but also a favorable change of the primary Si crystals morphology. During stereological measurements significant size reduction and change in the morphology of hypereutectic silicon crystals ware found. This effects can be further enhanced by overheating the alloy to a temperature of 920ºC and rapid cooling before casting of the alloy.

  20. 76 FR 64854 - Airworthiness Directives; Airbus Model A318, A319, A320, and A321 Series Airplanes

    Science.gov (United States)

    2011-10-19

    ..., A319, A320, and A321 Series Airplanes AGENCY: Federal Aviation Administration (FAA), DOT. ACTION... section revision to the airplane flight manual and the installation of a new flight warning computer (FWC... thrust lever configuration and to correct this. For the A320 family of aeroplanes this being IDLE...

  1. Facile synthesis of yellow-emitting CaAlSiN3:Ce3+ phosphors and the enhancement of red-component by co-doping Eu2+ ions

    Science.gov (United States)

    Chen, Jingjing; Zhao, Yang; Li, Guanghao; Mao, Zhiyong; Wang, Dajian; Bie, Lijian

    2017-04-01

    In this paper, facile synthesis of CaAlSiN3:Ce3+ yellow-emitting phosphors under atmospheric pressure at a moderate temperature and their photoluminescent properties are reported. The prepared CaAlSiN3:Ce3+ phosphors exhibit a broad yellow emission band positioned at 580 nm and covering a bandwidth of 150 nm. The thermal stability of CaAlSiN3:Ce3+ phosphors shows obvious superiority than the commercial YAG: Ce3+ phosphor, indicating its promising application prospect in power LEDs. In addition, the enhancement of red-light component for CaAlSiN3:Ce3+ phosphor is demonstrated by co-doping Eu2+ ions. This study offers a facile route to prepare CaAlSiN3:Ce3+ yellow-emitting phosphors, which may be used as a promising candidate for high performance white LEDs.

  2. Acero de alto silicio producido por inmersión en Al-Si y recocido de difusión

    Directory of Open Access Journals (Sweden)

    Ros-Yáñez, Tanya

    2000-10-01

    Full Text Available It is difficult to process steel sheet with a high Si content (>3.5%Si, mainly because of its brittleness and the appearance of cracks during rolling and oxidation. However, there is a market for this steel in electrical applications because of the favourable influence of Si on magnetostriction and electrical resistivity. As an alternative process, 3% Si-steel substrates were coated with hypereutectic Al-Si-alloys in a "hot-dip simulator" using different preheating and dipping times. The obtained layers were characterised by SEM and EDS analysis. Diffusion annealing experiments were performed to obtain sufficient amount of Si in the steel. It was observed that:

    • intermetallic phases appear in the coating layers as according to the ternary Fe-Si-Al diagram
    • with a double dipping primary silicon crystals are formed in the surface layer
    • the ordered DO3 structure is present if the dipping and/or diffusion time is long enough
    • homogeneous silicon gradients in the whole substrate thickness have not yet been achieved
    • theoretic calculations show that Si-gradient, also have beneficial effects on magnetic behaviour


    Es difícil procesar aceros eléctricos de alto contenido en silicio (>3,5 % Si. Esto se debe principalmente, a problemas de fragilidad, aparición de grietas durante la laminación y oxidación. Sin embargo, existe un importante mercado para este tipo de acero en aplicaciones eléctricas debido a la favorable influencia que ejerce el Si sobre la magnetoestricción, las pérdidas eléctricas y la resistividad eléctrica. Como proceso alternativo, se sumergieron substratos de acero con 3 % de silicio en una aleación hipereutéctica Al-25 % Si, en un simulador de recubrimiento por inmersión en caliente. En los ensayos se utilizaron diferentes tiempos de precalentamiento y de inmersión. En la segunda fase de la investigación se llevaron a cabo recocidos de difusión en el

  3. Phase Identification of Nanometric Precipitates in Al-Si-Cu Aluminum Alloy by Hr-Stem Investigations

    Directory of Open Access Journals (Sweden)

    Pawlyta M.

    2016-09-01

    Full Text Available Aluminium recycling is cost-effective and beneficial for the environment. It is expected that this trend will continue in the future, and even will steadily increase. The consequence of the use of recycled materials is variable and difficult to predict chemical composition. This causes a significant reduction in the production process, since the properties of produced alloy are determined by the microstructure and the presence of precipitates of other phases. For this reason, the type and order of formation of precipitates were systematically investigated in recent decades. These studies involved, however, only the main systems (Al-Cu, Al-Mg-Si, Al-Cu-Mg, Al-Mg-Si-Cu, while more complex systems were not analysed. Even trace amounts of additional elements can significantly affect the alloy microstructure and composition of precipitates formed. This fact is particularly important in the case of new technologies such as laser surface treatment. As a result of extremely high temperature and temperature changes after the laser remelting large amount of precipitates are observed. Precipitates are nanometric in size and have different morphology and chemical composition. A full understanding of the processes that occur during the laser remelting requires their precise but also time effectively phase identification, which due to the diversity and nanometric size, is a major research challenge. This work presents the methodology of identification of nanometer phase precipitates in the alloy AlSi9Cu, based on the simultaneous TEM imaging and chemical composition analysis using the dispersion spectroscopy using the characteristic X-ray. Verification is performed by comparing the simulation unit cell of the identified phase with the experimental high-resolution image.

  4. Dependence of dynamic magnetization and magneto-transport properties of FeAlSi films with oblique sputtering studied via spin rectification effect

    Energy Technology Data Exchange (ETDEWEB)

    Soh, Wee Tee; Ong, C. K. [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive 3, Singapore 117551 (Singapore); Zhong, Xiaoxi, E-mail: xiaoxi.zhong@gmail.com [Department of Physics, Center for Superconducting and Magnetic Materials, National University of Singapore, 2 Science Drive 3, Singapore 117551 (Singapore); School of Materials Science and Engineering, Sichuan University, Chengdu 610065 (China)

    2014-09-15

    FeAlSi (Sendust) is known to possess excellent soft magnetic properties comparable to traditional soft magnetic alloys such as NiFe (Permalloy), while having a relatively higher resistance for lower eddy current losses. However, their dynamic magnetic and magneto-transport properties are not well-studied. Via the spin rectification effect, we electrically characterize a series of obliquely sputtered FeAlSi films at ferromagnetic resonance. The variations of the anisotropy fields and damping with oblique angle are extracted and discussed. In particular, two-magnon scattering is found to dominate the damping behavior at high oblique angles. An analysis of the results shows large anomalous Hall effect and anisotropic magneto-resistance across all samples, which decreases sharply with increasing oblique incidence.

  5. Effects of Si Content and the Addition Amount of Al-3B Master Alloy on the Solidification Structures of Hypoeutectic Al-Si Alloys

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Effects of Si content and the addition amount of Al-3B master alloy on the solidification structures of hypoeutectic Al-Si alloys were studied. The addition amounts of the master alloy were 0.2%, 0.4%, 0.7% and 1% (mass fraction, so as the follows), respectively. The Si content of Al-Si binary alloys investigated varied from 1% to 11%. The observation of macrostructures of non-refined samples showed that 3% Si constitutes a transition point at which the minimum grain size can be obtained. It was also found that Al-3B master alloy can shift the transition point towards a higher Si value when its addition amount increases, making this point appear at 4%, 5% and 6% Si as its addition amount increases up to 0.4%, 0.7% and 1%, respectively.

  6. Theoretical Study on the Structure and Stability of Si5X (X = Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl) Clusters

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Density functional theory B3LYP/6-311G* method was used in the geometry optimization and frequency calculation on Si5X (X = Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, S, Cl) clusters. The influence of the doped second and third period element impurities on the structure and stability of Si5X clusters with C2v symmetry has been investigated, and the thermal stability and dynamic activity have also been discussed.

  7. Combustion Synthesis and Photoluminescence Properties of Red-Emitting CaAlSiN3:Eu2+ Phosphor for White-LEDs

    Directory of Open Access Journals (Sweden)

    Shyan-Lung Chung

    2014-12-01

    Full Text Available A combustion synthesis method has been developed for synthesis of Eu2+ doped CaAlSiN3 phosphor and its photoluminescence properties were investigated. Ca, Al, Si, and Eu2O3 powders were used as the Ca, Al, Si and Eu sources. The addition of NaN3, NH4Cl and Si3N4 powders was found to increase significantly the product yield. These powders were mixed and pressed into a compact, which was then wrapped up with an igniting agent (i.e., Mg+Fe3O4. The compact was ignited by electrical heating under a N2 pressure of ≤1.0 MPa. Effects of these experimental parameters on the product yield were investigated and a reaction mechanism was proposed. The synthesized CaAlSiN3:Eu2+ phosphor absorbs light in the region of 200–600 nm and shows a broad band emission in the region of 500–800 nm due to the 4f65d1 → 4f7 transition of Eu2+. The sample doped with Eu2+ at the optimized molar ratio of 0.04 is efficiently excited by the blue light (460 nm and generates emission peaking at ~650 nm with peak emission intensity ~106% of a commercially available phosphor, YAG:Ce3+(P46-Y3.The internal quantum efficiency of the synthesized phosphor was measured to be 71%, compared to 69% of the YAG:Ce3+ (P46-Y3.

  8. Caracterización microestructural y mecánica de la aleación de Al-Si A357 producida mediante rheocasting

    OpenAIRE

    da Silva, M.; Rodríguez-Ibabe, J. M.

    2003-01-01

    In the present work it has been studied the microstructure and the mechanical behaviour of a material produced by rheocasting, a new semisolid industrial process which introduces important improvements in comparison to conventional routes. The microstructure of the A357 hypoeutectic Al-Si alloys has been analysed before and after material injection. In both cases the microstructure was fine and homogeneous. Tensile tests have been done with specimens machined from real rheocasted components i...

  9. High-field magnetization of heusler alloys Fe2 XY ( X = Ti, V, Cr, Mn, Fe, Co, Ni; Y = Al, Si)

    Science.gov (United States)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Belozerova, K. A.; Weber, H. W.

    2015-10-01

    The magnetization curves of ferromagnetic Heusler alloys Fe2 XY (where X = Ti, V, Cr, Mn, Fe, Co, Ni are transition 3 d elements and Y = Al, Si are the s and p elements of the third period of the Periodic Table) have been measured at T = 4.2 K in the field range H ≤ 70 kOe. It has been shown that the high-field ( H ≥ 20 kOe) magnetization is described within the Stoner model.

  10. NaAlSi3O8-hollandite and other high-pressure minerals in the shock melt veins of the Suizhou meteorite

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The Suizhou L6 chondrite contains a few very thin shock melt veins of 0.02-0.09 mm in width. In spite of small width of the veins, shock-induced high-pressure phases, such as coarse-grained NaAlSi3O8-hollandite, ringwoodite, majorite and fine-grained matrix majorite-pyropess have been discovered in these veins. NaAlSi3O8-hollandite, the high-pressure phase of plagioclase, in Suizhou shock veins occurs as a single phase mineral, no silicate glassy phase, such as albitic glass, was incorporated with it. The presence of above-mentioned high-pressure phases constrains the high pressure (up to 23-24 GPa) and high temperature (up to 1900-2000℃) regime in Suizhou shock veins, and indicates that the duration of high-pressure regime in the veins should be long enough (a few seconds) for phase transformation and crystallization of minerals under pressure. The discovery of the first natural single-phase crystalline NaAlSi3O8- hollan-dite in Suizhou meteorite is of important significance in un-derstanding the Earth's mantle geochemistry.

  11. Stability region of K0.2Na0.8AlSi3O8 hollandite at 22 GPa and 2273 K

    Science.gov (United States)

    Zhou, Youmo; Irifune, Tetsuo; Ohfuji, Hiroaki; Shinmei, Toru; Du, Wei

    2017-01-01

    Lingunite (hollandite with Na contents of 80-85 mol%) discovered in the shock veins of strongly shocked meteorites is an important signature of shock metamorphism. To seek the stability region of lingunite, phase relations in the system KAlSi3O8-NaAlSi3O8 have been investigated by multi-anvil experiments at pressures of 20-23 GPa and temperatures of 1873 and 2273 K. Phase assemblages of hollandite + jadeite + stishovite, hollandite + calcium ferrite-type NaAlSiO4 + stishovite and hollandite single phase have been recovered, depending on the pressure-temperature conditions and the compositions of starting materials. Both pressure and temperature have large effects on the solubility of Na in hollandite, and hollandite with 79 mol% Na, similar to the natural lingunite in terms of Na content, has been firstly synthesized at 22 GPa and 2273 K. The stability region of K0.2Na0.8AlSi3O8 hollandite is comparable to the typical pressure-temperature conditions of the shock veins of strongly shocked meteorites (20-25 GPa and 2273-2500 K).

  12. Observaciones microestructurales en el composite Al-SiC-15p obtenido por el procedimiento de compocolado

    Directory of Open Access Journals (Sweden)

    Manzano-Ramírez, A.

    1996-12-01

    Full Text Available In order to study how the processing variables of the compocasting process, such as shear rate and solid fraction, influence the mechanical entrapment of SiCp in the aluminium matrix of the Al-SiC-xxp composite. In the present work, shear rate and solid fraction were varied (γ = 27, 120 and 219 s-1 and fs = 0.3, 0.4 and 0.5, respectively. In addition, the atomic force microscope (AFM was used to investigate the surface topography of the composite, with the purpose of determine, qualitatively, the degree of interfacial bonding between aluminium matrix and reinforcement elements. By using the Chemical facilities of SEM it was attempted to determine the composition of the second phase responsible of bonding between matrix and particulate. The results obtained in the AFM confirmed that the mechanical entrapment of the particles by the solid is more efficient at high solid fractions (fs > 0.4 and high shear rates (γ > 120 s-1. In contrast, at low fs (< 0.3 and low γ (< 27 s-1 such effect is poor. In addition, qualitative evidence, recorded by optical micrographs, illustrate the mechanism of dendritic fragmentation and change (from dendritic to globular of the primary-solid phase in the compocasting process. SEM results suggested that bonding could be established through the silicon phase nevertheless it is considered that more accurate analysis is needed.

    El propósito del presente trabajo es estudiar el efecto de las variables del procedimiento de compocolado (compocasting, velocidad de agitación y fracción de sólido, sobre el atrapamiento mecánico o incorporación de partículas de SiC a la matriz de aluminio del composite Al-SiC-15p. Para ello, se variaron la velocidad de corte, γ, y la fracción de sólido fs, (γ= 27, 120 y 213 s-1 y fs = 0,3, 0,4 y 0,5, respectivamente. Se utilizó el microscopio de fuerza atómica (AFM para observar la topografía del

  13. Doping the Buckminsterfullerene by Substitution: Density Functional Theory Studies of C59X (X = B, N, Al, Si, P, Ga, Ge, and As

    Directory of Open Access Journals (Sweden)

    Hongcun Bai

    2013-01-01

    Full Text Available The heterofullerenes C59X (X = B, N, Al, Si, P, Ga, Ge, and As were investigated by quantum chemistry calculations based on density functional theory. These hybrid cages can be seen as doping the buckminsterfullerene by heteroatom substitution. The geometrical structures, relative stabilities, electronic properties, vibrational frequencies, dielectric constants, and aromaticities of the doped cages were studied systemically and compared with those of the pristine C60 cage. It is found that the doped cages with different heteroatoms exhibit various electronic, vibrational, and aromatic properties. These results imply the possibility to modulate the physical properties of these fullerene-based materials by tuning substitution elements.

  14. From Powders to Dense Metal Parts: Characterization of a Commercial AlSiMg Alloy Processed through Direct Metal Laser Sintering

    Directory of Open Access Journals (Sweden)

    Eleonora Atzeni

    2013-03-01

    Full Text Available In this paper, a characterization of an AlSiMg alloy processed by direct metal laser sintering (DMLS is presented, from the analysis of the starting powders, in terms of size, morphology and chemical composition, through to the evaluation of mechanical and microstructural properties of specimens built along different orientations parallel and perpendicular to the powder deposition plane. With respect to a similar aluminum alloy as-fabricated, a higher yield strength of about 40% due to the very fine microstructure, closely related to the mechanisms involved in this additive process is observed.

  15. Fabricación y comportamiento de espumas de aluminio con diferente densidad a partir de un precursor AlSi12

    Directory of Open Access Journals (Sweden)

    Gutiérrez-Vázquez, J. A.

    2010-06-01

    Full Text Available Closed cell aluminium foams were prepared by powder metallurgical method in three different ranges of density using AlSi12 precursor. The objective has been to determine by means of tests the effect that has the density of these materials regarding its mechanical behaviour. The used precursor contained 0.4% of foaming agent of titanium hydride (TiH2, mixed with aluminum and silicon in appropriate amounts to achieve the commercial composition of the AlSi12 precursor. Once cut the samples thermal treatments of foaming were made of 630 °C to 750 °C, by 3 to 20 minutes. The best solidification conditions were determined to avoid the collapse by means of forced air. The samples were prepared with the same weight to different densities, having itself obtained that the best mechanical behaviour was achieved in the high density foams, of 0.70 to 0.81 g/cm3.

    Se han fabricado espumas de aluminio de poro cerrado, de tres diferentes rangos de densidad, utilizando un precursor AlSi12 producido por pulvimetalurgia. El objetivo ha sido determinar el efecto que tiene la densidad de estos materiales respecto a su comportamiento mecánico. El precursor utilizado contenía un 0,4 % de hidruro de titanio (TiH2 como agente espumante, mezclado con aluminio y silicio en cantidades adecuadas para lograr la composición comercial del precursor AlSi12. Una vez cortadas las muestras, se efectuaron tratamientos térmicos de espumación entre 630 y 750 °C, a tiempos de espumación variables entre 3 y 20 min. Se determinaron las mejores condiciones de solidificación para evitar el colapso mediante aire forzado. Las muestras se prepararon con el mismo peso a diferentes densidades, habiéndose obtenido, que el mejor comportamiento mecánico se lograba en las espumas de mayor densidad, comprendidas entre 0,70 y 0,81 g/cm3.

  16. Nuevos tratamientos T6 para aleaciones de AlSi obtenidas por conformación en estado semisólido

    Directory of Open Access Journals (Sweden)

    Menargues, S.

    2013-08-01

    Full Text Available In this work the microstructural changes that occurs during the solution and aging steps of heat treated of AlSi alloys, conformed in semi-solid state, were analysed. The study allowed developing a new T6 heat treatment, with solution times down to 30 min. With this new short heat treatment, the alloy showed better mechanical properties in comparison with the same alloy heat treated in standard conditions (solution times between 6 h and 8 h. This new heat treatment, carried out at 540 ºC, allowed complete magnesium dissolution and, at the same time, minimizes the grain and eutectic silicon growth. Although this experimentation was carried out with A356 and A357 aluminum alloys, conformed by Sub-Liquidus-Casting process, these results may be applicable to components produced with other semi-solid technologies and with others AlSi hardenable alloys that form coherent magnesium precipitates. The characterization of samples was carried out by micrographic analysis, by hardness and ultramicrohardnes tests.Se estudian los cambios microestructurales que tienen lugar en los tratamientos térmicos de las aleaciones AlSi, conformadas en estado semisólido, durante las etapas de puesta en solución y envejecimiento. El estudio ha permitido proponer nuevos tratamientos T6, con tiempos de puesta en solución inferiores a los 30 min, manteniendo o mejorando las propiedades mecánicas que se obtienen con los actuales procesos de tratamiento de 6 a 8 h. Estos tratamientos de corta duración, realizados a 540 ºC, permiten una completa disolución del magnesio, minimizando al mismo tiempo el crecimiento de los granos y del silicio eutéctico. Si bien la experimentación se ha realizado con componentes producidos por Sub-Liquidus Casting (SLC con aleaciones A356 y A357, se considera que los resultados obtenidos pueden ser aplicables a los componentes producidos en estado semisólido por otras tecnologías, con diferentes aleaciones AlSi que se endurecen por

  17. Study on nanocomposite Ti-Al-Si-Cu-N films with various Si contents deposited by cathodic vacuum arc ion plating

    Energy Technology Data Exchange (ETDEWEB)

    Shi, J. [State Key Laboratory of Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Institute of Materials Engineering, University of Siegen, Paul-Bonatz-Strasse 9-11, Siegen 57076 (Germany); Muders, C.M.; Kumar, A. [Institute of Materials Engineering, University of Siegen, Paul-Bonatz-Strasse 9-11, Siegen 57076 (Germany); Jiang, X., E-mail: xin.jiang@uni-siegen.de [Institute of Materials Engineering, University of Siegen, Paul-Bonatz-Strasse 9-11, Siegen 57076 (Germany); Pei, Z.L.; Gong, J. [State Key Laboratory of Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China); Sun, C., E-mail: csun@imr.ac.cn [State Key Laboratory of Corrosion and Protection, Institute of Metal Research, Chinese Academy of Sciences, 72 Wenhua Road, Shenyang 110016 (China)

    2012-10-01

    Highlights: Black-Right-Pointing-Pointer XRD peaks show a tendency of decreasing intensity with increasing Si content. Black-Right-Pointing-Pointer Ti-Al-Si-Cu-N films present different microstructure with increasing Si content. Black-Right-Pointing-Pointer Films with 6 at.% Si content obtain the highest hardness, elastic modulus and H{sup 3}/E{sup 2}. Black-Right-Pointing-Pointer The wear rate decreases with an increase in hardness. - Abstract: In this study, nanocomposite Ti-Al-Si-Cu-N films were deposited on high speed steel substrates by the vacuum cathode arc ion plating (AIP) technique. By virtue of X-ray diffraction (XRD) analysis, X-ray photoelectron spectroscopy (XPS), and field emission scanning electron microscopy (FESEM), the influence of silicon content on the film microstructure and characteristics was investigated systematically, including the chemical composition, crystalline structure as well as cross-section morphologies. With increasing the silicon content, a deterioration of the preferred orientation and a dense globular structure were detected. In the meanwhile, atomic force microscopy (AFM), nano-indentation, Rockwell indenter and reciprocating test were also utilized to analyze the hardness, elastic modulus, H{sup 3}/E{sup 2}, friction coefficient, adhesive strength and wear rate of the Ti-Al-Si-Cu-N films. The results showed that an optimal silicon content correlated with the best mechanical and tribological properties of the presented Ti-Al-Si-Cu-N films existed. With increasing the silicon content, the hardness, elastic modulus and the ratio H{sup 3}/E{sup 2} first were improved gradually, and then were impaired sharply again. When the silicon content reached to 6 at.%, the film possessed the highest hardness, elastic modulus and ratio H{sup 3}/E{sup 2} of approximately 24 GPa, 218 GPa and 0.31, respectively. Besides, films containing both 6 at.% and 10 at.% Si contents obtained a relatively low friction coefficient and a good adhesive

  18. The antiphase boundary in half-metallic Heusler alloy Co2Fe(Al,Si): atomic structure, spin polarization reversal, and domain wall effects

    Science.gov (United States)

    Nedelkoski, Zlatko; Sanchez, Ana M.; Ghasemi, Arsham; Hamaya, Kohei; Evans, Richard F. L.; Bell, Gavin R.; Hirohata, Atsufumi; Lazarov, Vlado K.

    2016-11-01

    Atomic resolution scanning transmission electron microscopy reveals the presence of an antiphase boundary in the half-metallic Co2Fe(Al,Si) full Heusler alloy. By employing the density functional theory calculations, we show that this defect leads to reversal of the sign of the spin-polarization in the vicinity of the defect. In addition, we show that this defect reduces the strength of the exchange interactions, without changing the ferromagnetic ordering across the boundary. Atomistic spin calculations predict that this effect reduces the width of the magnetic domain wall compared to that in the bulk.

  19. Effect of mixed rare earth oxides and CaCO3 modification on the microstructure of an in-situ Mg2Si/Al-Si composite

    Institute of Scientific and Technical Information of China (English)

    LIU Zheng; LIN Jixing; JING Qingxiu

    2009-01-01

    The effects of mixed rare earth oxides and CaCO3 on the microstructure of an in-situ Mg2Si/Al-Si hypereutectic alloy composite were investigated by optical microscope, scanning electron microscope, and energy dispersive spectrum analysis. The results showed that the morphology of the primary Mg2Si phase particles changed from irregular or crosses to polygonal shape, their sizes decreased from 75 μm to about 25 μm, and the compound of both the oxide and CaCO3 was better than either the single mixed rare earth oxides or CaCO3.

  20. High temperature properties of CrAlN, CrAlSiN and AlCrSiN coatings - Structure and oxidation

    Energy Technology Data Exchange (ETDEWEB)

    Polcar, Tomas, E-mail: polcar@fel.cvut.cz [Department of Control Engineering, Faculty of Electrical Engineering, Czech Technical University in Prague, Technicka 2, Prague 6 (Czech Republic); SEG-CEMUC - Department of Mechanical Engineering, University of Coimbra, Rua Luis Reis Santos, P-3030 788 Coimbra (Portugal); Cavaleiro, Albano [SEG-CEMUC - Department of Mechanical Engineering, University of Coimbra, Rua Luis Reis Santos, P-3030 788 Coimbra (Portugal)

    2011-09-15

    Highlights: {yields} Deposition and structural analysis of CrAln, CrAlSiN and AlCrSiN coatings. {yields} In-situ XRD analysis at high temperature. {yields} AlCrSiN coating showed the highest oxidation resistance and thermal stability. {yields} CrAlN outperformed CrAlSiN film both in oxidation resistance and thermal stability. - Abstract: CrAlN, CrAlSiN and AlCrSiN coatings were deposited by cathodic arc deposition technique from composite targets. Three targets were used: (i) Cr/Al ratio close to 1, (ii) Cr/Al ratio close to 1 with Si addition, and (iii) Cr/Al ratio close to 1/2 and Si addition. Nitrogen flow was kept constant during the depositions. The Cr/Al ratio of the films, measured by electron probe microanalysis (EPMA), was similar to that of the target and the silicon content was in the range 3-4 at.%. The coatings were deposited onto FeCrAl alloy and WC/Co mirror-polished substrates. To analyze the coating structure, X-ray photoelectron (XPS) and X-ray diffraction (XRD) analysis were used. The evolution of the coating structure up to 1000 deg. C was in situ measured in a XRD apparatus equipped with heating plate. The films oxidation behavior was characterized by thermogravimetric analysis (TGA) at two selected temperatures. The annealed coatings were analyzed by XRD and scanning electron microscopy with energy-dispersive X-ray spectroscopy (EDX). CrAlSiN showed low oxidation resistance being partially oxidized at 800 deg. C. Moreover, the film exhibited low thermal stability, since the cubic nitride phases transformed to hexagonal nitrides at relatively low temperatures. CrAlN oxidation behavior was more promising; nevertheless, AlCrSiN showed excellent thermal stability with cubic nitrides observed even after heating to 1300 deg. C. The oxidation of this film at 900 and 1000 deg. C was negligible.

  1. In Situ Synthesis of Al-Si-Cu Alloy During Brazing Process and Mechanical Property of Brazing Joint

    OpenAIRE

    LONG Wei-min; LU Quan-bin; He, Peng; XUE Song-bai; Wu, Ming-Fang; Xue, Peng

    2016-01-01

    The Al-Si-Cu alloy system is considered to be a promising choice of filler metal for aluminium alloys brazing due to its high strength and low melting point. The greatest obstacle is its lack of plastic forming ability and being difficult to be processed by conventional methods. This disadvantage is ascribed to the considerable amount of brittle CuAl2 intermetallic compound which forms when alloy composition is around the ternary eutectic point. In order to overcome this deficiency, authors o...

  2. Structure and Properties of Vacuum Arc Single-Layer and Multiperiod Two-Layer Nitride Coatings Based on Ti(Al:Si Layers

    Directory of Open Access Journals (Sweden)

    V.M. Beresnev

    2017-02-01

    Full Text Available The paper provides an analysis of impact of deposition conditions on structural and phase state and thermal stability of vacuum arc coatings based on Ti(Al:Si layers. We studied single-phase single-layer coatings, and multiperiod bilayer coatings with second phase nitride interlayers of one of the following three metals: Mo, Cr or Zr. It was established that hexagonal and cubic lattices may form in the coatings when transition to the cubic lattice occurs with Al content of about 25 at. %. Presence of second nanoscale (7-8 nm layers in bilayer multiperiod compositions, which consist of one nitride from CrNx, MoNx or ZrNx group, does not change the type of lattice in [Ti(Al:Si]Nx layers. Also, an fcc lattice with a strong or weak texture [111] forms in CrNx and ZrNx layers, while crystallites with hexagonal lattice form in MoNx layers. High-temperature annealing at 700 °С during 40 minutes leads to a significant (by 23 % or up to Н  47.56 GPa increase in microhardness of coating of the [Ti(Al]Nx/ZrNy system due to formation of a nano-size structure with an average size of crystallites of 3.6 nm in [Ti(Al]Nx layers, and 6.3 nm in ZrNx layers.

  3. Effect of overheating degree of molten alloy on material reliability and performance stability of AlSi17CuNiMg silumin castings

    Directory of Open Access Journals (Sweden)

    J. Szymszal

    2010-10-01

    Full Text Available The article discusses the effect of overheating degree (above the casting temperature on material reliability of AlSi17 silumin. Theexamined alloys was poured at temperatures, 760; 870 and 980oC, holding the melt for 40 minutes and casting from the temperature of760oC. The assessment of the impact of the degree of overheating was to analysis the tensile strength. From the results of the static tensile test, the main estimators of the descriptive statistics, and coefficients of variation. Having determined the boundary value sO for Weibull distribution, the value of „m” modulus was computed along with other coefficients of material reliability, proposed formerly by the authors. Basing on the obtained results, a model of Weibull distribution function was developed for the tensile strength with respective graphic interpretation. The time-temperature parameters of the melting and casting technology have been chosen to determine the scatter of resultant parameter (Rm in function of overheating degree. The time-temperature treatment of hypereutectic AlSi17CuNiMg silumin, through its effect on the cluster structure of molten alloy, is shaping the material reliability and performance stability of castings.

  4. Modification of β-Al5FeSi Compound in Recycled Al-Si-Fe Cast Alloy by Using Sr, Mg and Cr Additions

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The effects of Sr, Mg, Cr, Sr/Mg and Sr/Cr combined additions on the Fe-containing intermetallic phase in a recycled Al-Si-Fe cast alloy are investigated. The experimental results show that the additions of Cr and Sr/Cr successfully modified the platelet and flake-like β-AlsFeSi phases (β-compound) into the fibrous α-Al8Fe2Si (α-compound). The additions of Sr and Sr/Mg were less effective to modify the β-compound into the α-compound, while the eutectic Si was fully modified into the fibrous morphology. A small secondary dendrite arm spacing (DAS) was found in the Sr-added, Cr-added and Sr/Cr-added alloys, especially in a steel mold. The Sr, Sr/Cr and Sr/Mg combined additions modify the eutectic Si simultaneously. A sludge phase was found in the addition of Cr-added, Sr/Cr-added and Mg-added alloys, especially in the graphite mold casting. The volume fraction of β-compounds was decreased by the addition of various modifying elements.The Cr and Sr/Cr combined additions are very effective to modify the β-compound for the recycled Al-Si-Fe based alloys.

  5. Structure and properties of selected cemented carbides and cermets covered with TiN/(Ti,Al,SiN/TiN coatings obtained by the cathodic arc evaporation process

    Directory of Open Access Journals (Sweden)

    Leszek A. Dobrzañski

    2005-06-01

    Full Text Available This study presents the results of microstructural examinations, mechanical tests and service performance tests carried out on thin TiN/(Ti,Al,SiN/TiN wear resistance coatings obtained by the CAE process on cermet and cemented carbide substrates. Microstructural examinations of the applied coatings and the substrate were made with an OPTON DSM 940 SEM and a LEICA MEF4A light microscope. Adhesion of the coatings on cemented carbides and cermets was measured using the scratch test. The cutting properties of the materials were determined from service tests in which continuous machining of C45E steel was carried out. The hardness of the substrate and the microhardness of the coatings were determined with a DUH 202 SHIMADZU ultra microhardness tester with a load of 70 mN. Roughness tests were also carried out before applying the coatings and after the PVD process. Cutting tests confirmed the advantages of the TiN/(Ti,Al,SiN/TiN type coatings obtained using the PVD method in the CAE mode on cemented carbides and cermets, as a material that undergoes very low abrasive, thermal and adhesion wear. These coatings extend tool life compared to commercially available uncoated tools with single and multi-layer coatings deposited using PVD/CVD methods.

  6. Heat treatment of EN AC-AlSi13Cu2Fe silumin and its effect on change of hardness of the alloy

    Directory of Open Access Journals (Sweden)

    J. Pezda

    2010-01-01

    Full Text Available Wide application of aluminum casting alloys is connected with their very good physical and technical properties. Within such group of alloys, silumins play important role in automotive and aviation industry, as well as in another branches of technique, because the silumins enable casting of complicated shapes. The most important parameters which predetermine mechanical properties of a material in aspects of suitability for castings of machinery components are: tensile strength (Rm, elongation and hardness. Alloys based on equilibrium system of Al-Si comprise additional constituents (e.g.: Mg, Cu enabling, except modification, improvement of mechanical properties, obtained in result of heat treatment. In the paper are presented results of investigations concerning effect of the heat treatment on change of hardness (HB of the EN AC-AlSi12Cu2Fe alloy. Investigated alloy was melted in an electric resistance furnace. Run of the crystallization was presented with use of the thermal-derivative method (ATD. This method was also implemented to determination of heat treatments temperature range of the alloy. Performed heat treatment gave effect in change of the hardness. Performed investigations have enabled determination of heat treatment parameters range, which conditions suitable hardness of the investigated alloy.

  7. Effects of Ca Content on Formation and Photoluminescence Properties of CaAlSiN3:Eu2+ Phosphor by Combustion Synthesis

    Directory of Open Access Journals (Sweden)

    Shyan-Lung Chung

    2016-03-01

    Full Text Available Effects of Ca content (in the reactant mixture on the formation and the photoluminescence properties of CaAlSiN3:Eu2+ phosphor (CASIN were investigated by a combustion synthesis method. Ca, Al, Si, Eu2O3, NaN3, NH4Cl and Si3N4 powders were used as the starting materials and they were mixed and pressed into a compact which was then wrapped up with an igniting agent (i.e., Mg + Fe3O4. The compact was ignited by electrical heating under a N2 pressure of ≤1.0 MPa. By keeping the molar ratios of Al and Si (including the Si powder and the Si in Si3N4 powder both at 1.00 and that of Eu2O3 at 0.02, XRD (X-ray diffraction coupled with TEM-EDS (transmission electron microscope equipped with an energy-dispersive X-ray spectroscope and SAED (selected area electron diffraction measurements show that AlN:Eu2+ and Ca-α-SiAlON:Eu2+ are formed as the major phosphor products when the Ca molar ratio (denoted by Y is equal to 0.25 and AlN:Eu2+ and Ca-α-SiAlON:Eu2+ could not be detected at Y ≥ 0.75 and ≥1.00, respectively. CASIN (i.e., CaAlSiN3:Eu2+ becomes the only phosphor product as Y is increased to 1.00 and higher. The extent of formation of CASIN increases with increasing Y up to 1.50 and begins to decrease as Y is further increased to 1.68. While the excitation wavelength regions are similar at various Y, the emission wavelength regions vary significantly as Y is increased from 0.25 to 1.00 due to different combinations of phosphor phases formed at different Y. The emission intensity of CASIN was found to vary with Y in a similar trend to its extent of formation. The Ca and Eu contents (expressed as molar ratios in the synthesized products were found to increase roughly with increasing Y but were both lower than the respective Ca and Eu contents in the reactant mixtures.

  8. The Influence of Pressure Die Casting Parameters on Distribution of Reinforcing Particles in the AlSi11/10% SiC Composite

    Directory of Open Access Journals (Sweden)

    A. Pasieka

    2013-07-01

    Full Text Available The method of pressure die casting of composites with AlSi11 alloy matrix reinforced with 10 vol. % of SiC particles and the analysis of the distribution of particles within the matrix is presented. The composite castings were produced at various values of the piston velocity in the second stage of injection, at diverse intensification pressure values, and various injection gate width values. The distribution of particles over the entire cross-section of the tensile specimen is shown. The index of distribution was determined on the basis of particle count in elementary measuring fields. The regression equation describing the change of the considered index was found as a function of the pressure die casting parameters. The conclusion presents an analysis of the obtained results and their interpretation.

  9. The effect of the T6 heat treatment on hardness and microstructure of the en AC-AlSi12CuNiMg alloy

    Directory of Open Access Journals (Sweden)

    J. Pezda

    2014-01-01

    Full Text Available Presented work discusses research results concerning the effect of the T6 heat treatment process, including soaking of the alloy near the solidus temperature, holding in this temperature and next cooling in cold water (20 oC, as well as exposing to the artificial ageing to check the change in HB hardness and microstructure of the EN AC-AlSi12Cu-NiMg (EN AC-48000 alloy modified with strontium and cast into metal moulds. The temperature range of solutioning and ageing treatments was selected on the basis of crystallization curves recorded with the use of thermal-derivative method. Performed investigations enabled to determine the optimal parameters (temperature and time of solutioning and ageing heat treatments and their effect on the change in alloy’s hardness.

  10. Drop Weight Impact Behavior of Al-Si-Cu Alloy Foam-Filled Thin-Walled Steel Pipe Fabricated by Friction Stir Back Extrusion

    Science.gov (United States)

    Hangai, Yoshihiko; Nakano, Yukiko; Utsunomiya, Takao; Kuwazuru, Osamu; Yoshikawa, Nobuhiro

    2017-02-01

    In this study, Al-Si-Cu alloy ADC12 foam-filled thin-walled stainless steel pipes, which exhibit metal bonding between the ADC12 foam and steel pipe, were fabricated by friction stir back extrusion. Drop weight impact tests were conducted to investigate the deformation behavior and mechanical properties of the foam-filled pipes during dynamic compression tests, which were compared with the results of static compression tests. From x-ray computed tomography observation, it was confirmed that the fabricated foam-filled pipes had almost uniform porosity and pore size distributions. It was found that no scattering of the fragments of collapsed ADC12 foam occurred for the foam-filled pipes owing to the existence of the pipe surrounding the ADC12 foam. Preventing the scattering of the ADC12 foam decreases the drop in stress during dynamic compression tests and therefore improves the energy absorption properties of the foam.

  11. Influence of SiC reinforcement particles on the tribocorrosion behaviour of Al-SiC{sub p} FGMs in 0.05M NaCl solution

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, A C; Rocha, L A [Centre for Mechanical and Materials Technologies (CT2M) and Department of Mechanical Engineering, University of Minho, Azurem, 4800-058 Guimaraes (Portugal); Mischler, S, E-mail: catarina.vieira@engmateriais.eng.uminho.pt [Ecole Polytechnique Federale de Lausanne (EPFL), Tribology and Interface Chemistry Group, 1015 Lausanne (Switzerland)

    2011-05-11

    The main aim of this work was to study and understand the influence of SiC particles on the corrosion and tribocorrosion of Al-matrix composite materials. For that, Al-SiC{sub p} functionally graded composites were produced by centrifugal casting and different SiC{sub p} contents were achieved. Their mechanical properties were improved by age-hardening heat treatments. The tribocorrosion behaviour was studied in 0.05M NaCl solutions using a reciprocating motion tribometer involving an alumina ball sliding against the Al-based samples. Above critical SiC particles' content the matrix alloy surface was found to be protected against wear by SiC particles protruding from the surface. Below this threshold content, the SiC reinforcement was inefficient and the wear rate of the composite was the same as the non-reinforced alloy.

  12. Influence of SiC reinforcement particles on the tribocorrosion behaviour of Al-SiCp FGMs in 0.05M NaCl solution

    Science.gov (United States)

    Vieira, A. C.; Rocha, L. A.; Mischler, S.

    2011-05-01

    The main aim of this work was to study and understand the influence of SiC particles on the corrosion and tribocorrosion of Al-matrix composite materials. For that, Al-SiCp functionally graded composites were produced by centrifugal casting and different SiCp contents were achieved. Their mechanical properties were improved by age-hardening heat treatments. The tribocorrosion behaviour was studied in 0.05M NaCl solutions using a reciprocating motion tribometer involving an alumina ball sliding against the Al-based samples. Above critical SiC particles' content the matrix alloy surface was found to be protected against wear by SiC particles protruding from the surface. Below this threshold content, the SiC reinforcement was inefficient and the wear rate of the composite was the same as the non-reinforced alloy.

  13. Optical excitation processes in the near band-edge region of KAlSi3O8 and NaAlSi3O8 feldspar

    DEFF Research Database (Denmark)

    Poolton, N.R.J.; Mauz, B.; Lang, A.;

    2006-01-01

    A complex variety of excitation and relaxation pathways are available for charge in naturally occurring NaAlSi3O8 and KAlpSi(3)O(8) feldspar crystals, when excited with photons in the trans-band-edge energy range 4-12 eV These can involve a mixture of electronic transitions associated with defect...... states, the conduction and valence bands and their associated band-tails. In order to demonstrate that a relationship exists between these processes, combinations of three spectroscopic techniques are deployed in this work: luminescence excitation/emission mapping, energy-resolved photo...... emission in the materials. Luminescence and phosphorescence excitation spectra provide additional, complementary, information regarding the excited states of the blue-emitting defects, including their transition lifetimes and decay paths. Red emission associated with Fe3+ luminescence is mostly isolated...

  14. Al@SiO2 Core-Shell Microflakes as Metal-Based Light Scattering Layer in Dye-Sensitized Solar Cells

    Directory of Open Access Journals (Sweden)

    Chi-Hui Chien

    2011-01-01

    Full Text Available A metal-based light scattering layer (MLSL for dye-sensitized solar cells (DSSCs is formed from Al@SiO2 core-shell microflakes prepared and coated on a thin porous TiO2 electrode (approximately 4 μm thick. The DSSC corresponding to a TiO2 electrode with an MLSL exhibits a low electron transport resistance in the TiO2/electrolyte interface. Electron collection efficiency is greatly improved. Photovoltaic performance measurements indicate that the power conversion efficiency of the DSSC with the MLSL doubled from 1.37% to 2.96% (for an active area of 0.25 cm2, which is better than the 2.1% achieved by a DSSC with a conventional TiO2-based light scattering layer (TLSL obtained under identical experimental conditions.

  15. Crescimento de genótipos de frangos tipo caipira

    Directory of Open Access Journals (Sweden)

    R. C. Veloso

    2015-10-01

    Full Text Available RESUMOObjetivou-se com este trabalho comparar o padrão de crescimento, mediante ajustes das respectivas curvas de crescimento por modelos não lineares, bem como estudar o desenvolvimento de cortes de carcaça em relação ao peso da carcaça em diferentes genótipos de frangos tipo caipira. Foram utilizados 840 pintos de um dia, machos, distribuídos em delineamento inteiramente ao acaso, dos seguintes genótipos da linhagem Redbro: Caboclo, Carijó, Colorpak, Gigante Negro, Pesadão Vermelho, Pescoço Pelado e Tricolor. As aves foram alojadas em 28 boxes, sendo 30 aves/boxe, em galpão de alvenaria com acesso a um piquete de 45m², com quatro repetições. O peso corporal individual dos frangos foi medido ao nascer, aos 14, 28, 42, 56, 70 e 84 dias de idade. Para a determinação das curvas de crescimento do peso corporal das aves, os dados coletados foram avaliados por meio dos modelos não lineares: Brody, Gompertz, Logístico, Richards e von Bertalanffy. Foi empregado o PROC NLIN do SAS, utilizando-se o método interativo de Gauss-Newton. Os critérios usados para escolha do modelo de melhor ajuste da curva de crescimento foram o coeficiente de determinação, o desvio padrão assintótico, o desvio médio absoluto dos resíduos e o índice assintótico. As análises para obtenção dos coeficientes alométricos foram realizadas por meio do PROC GLM do SAS para os genótipos Carijó, Colorpak, Pesadão Vermelho, Pescoço Pelado e Tricolor. Foram avaliados os pesos da carcaça, do peito, das coxas, das sobrecoxas, das pernas e das asas das aves abatidas aos 85 dias de idade. Apenas as equações propostas por Gompertz, von Bertalanffy e Logístico atingiram a convergência, e o modelo proposto por von Bertalanffy foi o mais adequado para descrever o crescimento dos genótipos de frangos caipiras. Todos os cortes avaliados apresentaram crescimento tardio em relação ao peso da carcaça em genótipos de frangos tipo caipira.

  16. Caracterización microestructural y mecánica de la aleación de Al-Si A357 producida mediante rheocasting

    Directory of Open Access Journals (Sweden)

    da Silva, M.

    2003-12-01

    Full Text Available In the present work it has been studied the microstructure and the mechanical behaviour of a material produced by rheocasting, a new semisolid industrial process which introduces important improvements in comparison to conventional routes. The microstructure of the A357 hypoeutectic Al-Si alloys has been analysed before and after material injection. In both cases the microstructure was fine and homogeneous. Tensile tests have been done with specimens machined from real rheocasted components in two conditions, without any heat treatment and after T5 heat treatment. The results were found to be better than those obtained for this alloy when produced by conventional means.

    En el presente trabajo se ha estudiado la microestructura y el comportamiento de material producido mediante rheocasting, una nueva vía de producción industrial, en estado semisólido, que presenta diversas ventajas respecto a los procesos más habituales. Se ha caracterizado microestructuralmente la aleación hipoeutéctica de Al-Si A357, antes y después del proceso de inyección en estado semisólido, observándose en ambos estados una estructura fina y homogénea. Se han realizado ensayos de tracción de probetas mecanizadas de componentes reales producidos mediante rheocasting, tanto sin tratamiento térmico como tras un tratamiento T5. Los resultados, en ambos casos, fueron superiores a los obtenidos, para esta misma aleación, mediante otras vías.

  17. Conformado de aleaciones en estado semisólido. Aplicación a aleaciones hipereutécticas de Al-Si

    Directory of Open Access Journals (Sweden)

    Valer, J.

    1996-08-01

    Full Text Available The processing of alloys in the semi-solid state, known as Rheocasting, Thixoforming, Thixoforging or Thixocasting, is within the new technologies used for the production of materials. This work describes the process as well as the phenomena implied in it. As the forming of alloys in the semisolid state requires of a previous material preparation (in order to obtain a non-dendritic structure the Osprey process or Spray-forming, used in this work, is briefly described. Finally, both the microstructural results obtained from the combination of the two technologies in hypereutectic Al-Si alloys (Al-25%Si-5%Cu, Al-25%Si-5%Cu-2%Mg and Al-30%Si-5%Cu and comparison with microstructures obtained from similar alloys processed by conventional methods are shown.

    Dentro de las nuevas tecnologías utilizadas para la producción de materiales, se encuentra el procesamiento de aleaciones en estado semisólido denominado, en sus distintas versiones, Rheocasting, Thixoforming, Thixoforging o Thixocasting. En este trabajo se describe el proceso, así como los fenómenos implicados en el mismo. Puesto que el conformado de aleaciones en estado semisólido requiere una preparación previa del material (para obtener una microestructura no dendrítica, se describe brevemente el proceso Osprey o Spray-forming, utilizado en este trabajo. Finalmente, se muestran los resultados microestructurales obtenidos mediante la combinación de estas dos tecnologías, en aleaciones hipereutécticas de Al-Si (Al-25%Si-5%Cu, Al-25%Si-5%Cu- 2%Mg y Al-30%Si-5%Cu y su comparación con las microestructuras obtenidas en aleaciones similares procesadas por métodos convencionales.

  18. Effect of ZrO2 Nanoparticles on the Microstructure of Al-Si-Cu Filler for Low-Temperature Al Brazing Applications

    Science.gov (United States)

    Sharma, Ashutosh; Roh, Myung-Hwan; Jung, Do-Hyun; Jung, Jae-Pil

    2016-01-01

    In this study, the effect of ZrO2 nanoparticles on Al-12Si-20Cu alloy has been studied as a filler metal for aluminum brazing. The microstructural and thermal characterizations are performed using X-ray diffraction (XRD), scanning electron microscope (SEM), and differential thermal analysis (DTA). The intermetallic compound (IMC) phases are identified by the energy-dispersive spectroscopy analysis coupled with the SEM. The filler spreading test is performed according to JIS-Z-3197 standard. XRD and SEM analyses confirm the presence of Si particles, the CuAl2 ( θ) intermetallic, and the eutectic structures of Al-Si, Al-Cu, and Al-Si-Cu in the Al matrix in the monolithic and composite samples. It is observed that when the ZrO2 is added in the alloy, the CuAl2 IMCs and Si particles are found to be dispersed uniformly in the Al matrix up to 0.05 wt pct ZrO2. DTA results show that the liquidus temperature of Al-12Si-20Cu filler metal is dropped from ~806.78 K to 804.6 K (533.78 °C to 531.6 °C) with a lowering of 2 K (2 °C) in liquidus temperature, when the amount of ZrO2 is increased up to 0.05 wt pct. It is also shown that the presence of ZrO2 nanoparticles in the filler metal has no deleterious effect on wettability up to 0.05 wt pct of ZrO2. The ultimate tensile strength and elongation percentage are also found to improve with the addition of ZrO2 nanoparticles in the Al-12Si-20Cu alloy.

  19. Study on effects of T6 heat treatment on grain refined A319 alloy with Magnesium and Strontium addition

    Directory of Open Access Journals (Sweden)

    Gopikrishna. S

    2013-10-01

    Full Text Available Effect of heat treatment on A319 alloy with 0.45%wt Magnesium, 0.02%wt Strontium and grain refinement using Titanium has been investigated by hardness measurement and tensile testing. Experiments have been conducted at ageing temperatures 150°C, 160°C and 170°C. Hardness has been estimated up to 24 hours aged samples. The results indicate that hardness of 319 alloy increases with Sr addition and grain refinement. When Mg is added hardness is again found to be increasing progressively up to a maximum value and then varying non – uniformly. The tensile strength and microstructure after Mg modification and heat treatment have been discussed.

  20. Small thermal fatigue crack propagation behavior of sprayed Al-Si/SiCp composite for brake disc%喷射沉积Al-Si/SiCp制动盘材料的热疲劳微裂纹扩展行为

    Institute of Scientific and Technical Information of China (English)

    李微; 陈鼎; 陈振华; 滕杰; 范沧

    2009-01-01

    采用V形缺口试样,研究喷射沉积Al-Si/SiCp复合材料制动盘在25(450 ℃热循环下的热疲劳行为.通过金相显微镜和扫描电镜观察了复合材料的组织和热疲劳裂纹形貌,研究热疲劳裂纹形成与扩展机制.结果表明:热疲劳主裂纹主要从V形缺口处萌生;在同样的热循环次数下,热处理前的试样要比热处理后的试样先出现裂纹,且裂纹扩展的速率较快;裂纹绕过Si颗粒向前扩展以及裂纹穿过Si颗粒向前扩展是裂纹与Si颗粒相互作用的主要机制;SiC颗粒与热疲劳裂纹有明显的交互作用.因此,改善Si相的形态和分布以及加强Al/SiC颗粒间的界面结合有利于提高热疲劳裂纹扩展的抗力.

  1. 75 FR 31282 - Airworthiness Directives; Airbus Model A319-100, A320-200, A321-100, and A321-200 Series Airplanes

    Science.gov (United States)

    2010-06-03

    ...-100, A320-200, A321- 100, and A321-200 Series Airplanes AGENCY: Federal Aviation Administration (FAA... May 12, 2006. The error resulted in an incorrect component maintenance manual number. This AD applies to certain Airbus Model A319-100, A320-200, A321-100, and A321-200 series airplanes. This AD...

  2. en diferentes tipos de matrimonio

    Directory of Open Access Journals (Sweden)

    Mirta Margarita Flores Galaz

    2005-01-01

    Full Text Available En el presente estudio se analizan los estilos de poder y los estilos de negociación del conflicto utilizados por parejas yucatecas, así como la relación entre cada uno de los factores de los estilos de poder y de negociación por tipo de matrimonio, de acuerdo a los ingresos individuales de las esposas y en nivel de trabajo.

  3. 稀土和磷对过共晶Al-Si合金的复合变质作用%Multiplex modification with rare earth elements and P for hypereutectic Al-Si alloys

    Institute of Scientific and Technical Information of China (English)

    欧阳志英; 毛协民; 红梅

    2007-01-01

    The effect of rare earth (RE) elements on the morphologies and sizes of Si phases in the hypereutectic Al-Si alloys modified with P was investigated. The results show that the addition of La element to the hypereutectic Al-Si alloys can enhance the effect of P element on the modification of the primary Si phases. In the multiplex modification of RE-P, the primary Si phase is refiner and the shape of the eutectic Si is changed from long needle-like to short rod-like. Moreover, the agglomeration rate of the primary Si phase is slowed greatly. Even the melt is held for 6 h, the average size of the primary Si phase is still satisfied. The results analyzed by scanning electron microscope (SEM) indicate that La is richer at Al-Si interface than that in α-Al or primary Si phase. The higher the La content in the Al-Si interface, the smaller the primary Si phase.

  4. A novel yellow-emitting SrAlSi{sub 4}N{sub 7}:Ce{sup 3+} phosphor for solid state lighting: Synthesis, electronic structure and photoluminescence properties

    Energy Technology Data Exchange (ETDEWEB)

    Ruan, Jian [Sialon Group, Sialon Unit, Environment and Energy Materials Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Laboratory of Glasses and Nanostructured Functional Materials, 122 Luoshi Road, Wuhan, Hubei 430070 (China); Xie, Rong-Jun, E-mail: Xie.Rong-Jun@nims.go.jp [Sialon Group, Sialon Unit, Environment and Energy Materials Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Funahashi, Shiro [Sialon Group, Sialon Unit, Environment and Energy Materials Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Tanaka, Yoshinori [Green Computational Materials Science Group, Global Research Center for Environment and Energy based on Nanomaterials Science (Green), National Institute for Materials Science (NIMS), 1-2-1 Sengen, Tsukuba, Ibaraki 305-0044 (Japan); Takeda, Takashi; Suehiro, Takayuki; Hirosaki, Naoto [Sialon Group, Sialon Unit, Environment and Energy Materials Division, National Institute for Materials Science, 1-1 Namiki, Tsukuba, Ibaraki 305-0044 (Japan); Li, Yuan-Qiang [Dow Electronic Materials, 201 Washington Road, Princeton, NJ 08540 (United States)

    2013-12-15

    Ce{sup 3+}-doped and Ce{sup 3+}/Li{sup +}-codoped SrAlSi{sub 4}N{sub 7} phosphors were synthesized by gas pressure sintering of powder mixtures of Sr{sub 3}N{sub 2}, AlN, α-Si{sub 3}N{sub 4}, CeN and Li{sub 3}N. The phase purity, electronic crystal structure, photoluminescence properties of SrAlSi{sub 4}N{sub 7}:Ce{sup 3+}(Ce{sup 3+}/Li{sup +}) were investigated in this work. The band structure calculated by the DMol{sup 3} code shows that SrAlSi{sub 4}N{sub 7} has a direct band gap of 3.87 eV. The single crystal analysis of Ce{sup 3+}-doped SrAlSi{sub 4}N{sub 7} indicates a disordered Si/Al distribution and nitrogen vacnacy defects. SrAlSi{sub 4}N{sub 7} was identified as a major phase of the fired powders, and Sr{sub 5}Al{sub 5}Si{sub 21}N{sub 35}O{sub 2} and AlN as minor phases. Both Ce{sup 3+} and Ce{sup 3+}/Li{sup +} doped SrAlSi{sub 4}N{sub 7} phosphors can be efficiently excited by near-UV or blue light and show a broadband yellow emission peaking around 565 nm. A highest external quantum efficiency of 38.3% under the 450 nm excitation was observed for the Ce{sup 3+}/Li{sup +}-doped SrAlSi{sub 4}N{sub 7} (5 mol%). A white light LED lamp with color temperature of 6300 K and color rendering index of Ra=78 was achieved by combining Sr{sub 0.97}Al{sub 1.03}Si{sub 3.997}N/94/maccounttest14=t0005{sub 1}8193 {sub 7}:Ce{sup 3+}{sub 0.03} with a commercial blue InGaN chip. It indicates that SrAlSi{sub 4}N{sub 7}:Ce{sup 3+} is a promising yellow emitting down-conversion phosphor for white LEDs. - Graphical abstract: One-phosphor converted white light-emitting diode (LED) was fabricated by combining a blue LED chip and a yellow-emitting SrAlSi4N7:Ce{sup 3+} phosphor (see inset), which has the color rendering index of 78 and color temperature of 6300 K. - Highlights: • We reported a new yellow nitride phosphor suitable for solid state lighting. • We solved the crystal structure and evidenced a disordered Si/Al distribution. • We fabricated a high color rendering

  5. Influence of Al-Si Master Alloy on Microstructure and Property of Al-Mg-Si Alloy%Al-Si中间合金对Al-Mg-Si系合金组织性能的影响

    Institute of Scientific and Technical Information of China (English)

    张建新; 高爱华

    2011-01-01

    The effects of Al-Si master alloy on microstructure and property of Al-Mg-Si system alloy were studied, and the mechanism of Si in influencing the microstructure and property of the alloy was discussed.The results indicate that Al-Si master alloy with 18% Si can refine the microstmcture of cast aluminum alloy and improve the mechanical properties.The corrosion resistance of Al-Mg-Si system alloy decreases with the increase of Si content in Al-Si master alloy, the corrosion resistance significantly decreases when more than 18%Si in Al-Si master alloy.The tensile strength of Al-Mg-Si system alloy improves with the increase of Si content in Al-Si master alloy, the tensile strength declines when Si content is above 20 %.%研究了Al-Si中间合金对Al-Mg-Si系铝合金组织性能的影响,并分析了Si的作用机理.结果表明:含18%Si的Al-Si中间合金对合金的铸态组织作用效果较好,并能合理改善材料的力学性能;随Al-Si中间合金中Si含量的增加,Al-Mg-Si系合金的耐腐蚀性下降,Si含量高于18%后下降显著;Al-Si中间合金中Si含量的增加,能提高Al-Mg-Si系合金的抗拉强度,Si含量高于20%后其抗拉强度开始下降.

  6. Interlayer states arising from anionic electrons in the honeycomb-lattice-based compounds A e AlSi (A e =Ca , Sr, Ba)

    Science.gov (United States)

    Lu, Yangfan; Tada, Tomofumi; Toda, Yoshitake; Ueda, Shigenori; Wu, Jiazhen; Li, Jiang; Horiba, Koji; Kumigashira, Hiroshi; Zhang, Yaoqing; Hosono, Hideo

    2017-03-01

    We report that the interlayer states common to the compounds A e AlSi (A e =Ca , Sr, Ba) arise from F-center-like electrons arrayed in periodic cavities. The SrPtSb-type intermetallic phases exhibit electrons localized to columns of the trigonal bipyramidal A e3A l2 cages running perpendicular to the honeycomb layers. Ab initio calculations in combination with hard/soft x-ray photoemission spectroscopic measurements reveal that these features correspond to the anionic electrons that hybridize with apical Al 3 pz orbitals from the honeycomb layers above and below. Extra bands with a significant dispersion along the kz direction therefore contribute to the Fermi level in contrast to the apparent two-dimensional connectivity of the bonding in the compounds, and completely account for the presence of interlayer states. Our study demonstrates how the cage centers may serve as electronically important crystallographic sites, and extend the anionic electron concept into honeycomb lattice compounds.

  7. Inhibitive effect by Psidium guajava leaf extract on the corrosion of Al-Si-Mg (SSM-HPDC alloy in simulated seawater environment

    Directory of Open Access Journals (Sweden)

    M. Abdulwahab

    2015-12-01

    Full Text Available The assessment of Psidium guajava leaf extract as corrosion inhibitor for Al-Si- Mg (SSM-HPDC alloy in 3.5%wt NaCl solution using the gravimetric based-mass loss and potentiodynamic polarization techniques was investigated. The gravimetric based mass loss test was carried out at different inhibitor concentration, time and temperature ranges of 0.1-0.5%v/v, 1-5 hrs and 30-70oC, respectively, the results revealed that Psidium guajava leaf extract in 3.5%wt NaCl solution-aluminium environment decreased the corrosion rate at various concentrations considered. Inhibition efficiency (IE as high as 63.17% at 0.5% v/v Psidium guajava leaf extract addition using the gravimetric method was demonstrated in 3.5%wt NaCl solution. The IE of 90.48% was obtained at 0.5%v/v using the potentiodynamic polarization method. The additions of Psidium guajava leaf extract as corrosion inhibitor in the solution indicate higher potential value, IE and polarization resistance with decrease in current density. The two methods used for assessment of the aluminium alloy corrosion behaviour were in agreement and mixed-type corrosion exists which obeyed the Langmuir adsorption isotherm.

  8. Effect of high-intensity ultrasonic irradiation on the modification of solidification microstructure in a Si-rich hypoeutectic Al-Si alloy

    Energy Technology Data Exchange (ETDEWEB)

    Das, A., E-mail: A.Das@swansea.ac.uk [Materials Research Centre, School of Engineering, Swansea University, Singleton Park, Swansea, SA2 8PP (United Kingdom); Kotadia, H.R. [Brunel Centre for Advanced Solidification Technology, Brunel University, Uxbridge, UB8 3PH (United Kingdom)

    2011-02-15

    Effect of high-intensity ultrasound irradiation in modifying complex solidification microstructure is explored in a high Si containing Al-Si alloy and the origin of microstructural changes explained on the basis of nucleation and growth behaviour. Complete suppression of dendritic growth and dramatic refinement to globular morphology were observed for primary {alpha}-Al grains. Strong supportive evidence is presented towards enhanced and prolonged heterogeneous nucleation triggered by cavitation induced increase in the equilibrium melting point and effective dissipation of latent heat at the solidification front. Morphological evolution of eutectic Si and intermetallic particles is found to be dominated by coarsening and spherodisation from strong fluid flow in areas of intense cavitation near the ultrasonic radiator. Outside the region of direct energy transfer, Si particle morphology appears to be controlled predominantly by the imposed cooling conditions. Extremely fine and short Si-platelets observed in the intergranular spaces near the radiator are explained on the basis of probable rapid cooling of final liquid pockets of small volume and large surface area, rather than refinement through ultrasound.

  9. The Mechanical Properties of AlSi17Cu5 Cast Alloy after Overheating and Modification of CuP Master Alloy

    Directory of Open Access Journals (Sweden)

    J. Piątkowski

    2013-07-01

    Full Text Available The paper presents the results of studies on the effect of the AlSi17Cu5 alloy overheating to atemperature of 920°C and modification with phosphorus (CuP10 on the resultingmechanical (HB, Rm, R0.2 and plastic (A5 and Z properties. It has been shown that, so-called, "timethermal treatment" (TTT of an alloy in the liquid state, consisting inoverheating the metal to about 250°C above Tliq,holding at this temperature by 30 minutes improvesthe mechanical properties. It has also been found that overheating of alloy above Tliq.enhances the process of modification, resulting in the formation of fine-grain structure. The primary silicon crystals uniformly distributed in the eutectic and characteristics ofthe α(Al solution supersaturated with alloying elements present in the starting alloy composition (Cu, Fe provide not only an increase of strength at ambient temperature but also at elevated temperature (250°C.

  10. Evolution of the Spectral Emissivity and Phase Transformations of the Al-Si Coating on Usibor® 1500P Steel During Austenitization

    Science.gov (United States)

    Shi, Cangji; Daun, Kyle J.; Wells, Mary A.

    2016-12-01

    Usibor® 1500P coupons are austenitized in a Gleeble 3500 thermomechanical simulator using a two-step heating procedure in an argon atmosphere. Variations in spectral emissivity are measured in-situ using a near infrared spectrometer and ex situ with a Fourier transform infrared reflectometer. Microstructural evolution and surface roughness are investigated using optical microscopy, FE-scanning electron microscopy, and a surface profilometer. A series of phase transformations of Al-Fe-Si intermetallic phases at the coating/steel substrate interface cause the surface phase and surface roughness to change, which in turn influences the spectral emissivity. At the beginning of the first heating step, the coupons have very low spectral emissivity, due to the molten Al-Si coating. Spectral emissivity increases significantly with increasing soak time from 5 to 12 minutes, associated with the surface phase transformation of the coating into Al7Fe2Si intermetallic phase and an increase in surface roughness. Through the second step heating at 1173 K (900 °C), the spectral emissivity shows a gradually decreasing trend with increasing soak time, caused by the surface phase transformation from Al5Fe2 into AlFe intermetallic phase with a decrease in surface roughness.

  11. Elasto-Plastic-Creep Constitutive Equation of an Al-Si-Cu High-Pressure Die Casting Alloy for Thermal Stress Analysis

    Science.gov (United States)

    Motoyama, Yuichi; Shiga, Hidetoshi; Sato, Takeshi; Kambe, Hiroshi; Yoshida, Makoto

    2016-11-01

    Accurate simulation of residual stress and deformation is necessary to optimize the design and lifetime of casting components. Therefore, the recovery and strain-rate dependence of the stress-strain curve have been incorporated into empirical constitutive equations to improve the thermal stress analysis accuracy. Nevertheless, these equations present several difficulties related to the determination of material constants and their physical bases. This study suggested an empirical elasto-plastic-creep constitutive equation incorporating these phenomena. To determine the material parameters used in this constitutive equation, this study investigated tensile test methods to obtain stress-strain curves that most closely resemble those during or immediately after casting for the Al-Si-Cu high-pressure die-casting alloy JIS ADC 12 (A383.0), which exhibits natural aging. Results show that solution heat treatment with subsequent cooling to the test temperature should be applied to obtain stress-strain curves used for the thermal stress analysis of high-pressure die casting process of this alloy. The yield stresses obtained using the conventional heating method were 50-64 pct higher than those of the method described above. Therefore, the conventional method is expected to overestimate the overestimation of the predicted residual stress in die castings. Evaluation of the developed equation revealed that it can represent alloy recovery and strain-rate dependence.

  12. Formation of abrasion-resistant coatings of the AlSiFe{sub x}Mny intermetallic compound type on the AISI 304L alloy

    Energy Technology Data Exchange (ETDEWEB)

    Martinez-Peralez, L. G.; Flores-Valdes, A.; Salinas-Rodriguez, A.; Ochoa-Palacios, R. M.; Toscano-giles, J. A.; Torres-Torres, J.

    2016-05-01

    The α-Al{sub 9}FeMnSi and α-Al{sub 9}FeMn{sub 2}Si intermetallics formed by reactive sintering of Al, Si, Mn, Fe, Cr and Ni powders have been used in AISI 304L steels to enhance microhardness. Processing variables of the reactive sintering treatment were temperature (600, 650, 700, 750 and 800 degree centigrade), pressure (5, 10 y 20 MPa) and holding time (3600, 5400 y 7200 seconds). Experimental results show that temperature is the most important variable affecting the substrate/coating formation, while pressure does not appear to have a significant effect. The results show the optimum conditions of the reactive sintering that favor the substrate/coating formation are 800 degree centigrade, 20 MPa and 7200 seconds. Under these conditions, the reaction zone between the substrate and coating is more compacted and well-adhered, with a microhardness of 1300 Vickers. The results of SEM and X-Ray diffraction confirmed the formation of β-Al{sub 9}FeMnSi and β-Al{sub 9}FeMn{sub 2}Si intermetallics in the substrate/coating interface as well as the presence of Cr and Ni, indicating diffusion of these two elements from the substrate to the interface. (Author)

  13. Influence of Melt Superheat, Sr Modifier, and Al-5Ti-1B Grain Refiner on Microstructural Evolution of Secondary Al-Si-Cu Alloys

    Science.gov (United States)

    Rakhmonov, Jovid; Timelli, Giulio; Bonollo, Franco

    2016-11-01

    The role of impurity elements and melt superheat on the efficiency of Sr modification, grain refinement with Al-Ti-B and the precipitation behavior of intermetallic phases in a secondary Al-7Si-3Cu-0.3Mg alloy were investigated. Metallographic and thermal analysis techniques were used to quantitatively examine the macro- and microstructural changes occurring with modifier and grain refiner additions at various pouring temperatures. The results indicate how the Sr modification and grain refinement with Al-Ti-B can be effective enough despite the presence of impurity elements in the material and the variation of pouring temperature. A slight poisonous effect of impurities, in particular, Zr and V, in the grain refinement efficiency can be eventually induced due to their action in promoting the formation of primary AlSiTi compounds. Moreover, grain refiner addition exerted a pronounced influence on the precipitation sequence of Fe-rich phases. The TiB2 particles appeared to promote the formation of Al5FeSi during solidification by acting as a favorable nucleation site.

  14. Reciprocating Wear Behaviour of 7075Al/SiC and 6061Al/Al2O3 Composites: A study of Effect of Reinforcement, Stroke and Load

    Directory of Open Access Journals (Sweden)

    J. Lakshmipathy

    2014-06-01

    Full Text Available The wear behaviour comparison of Al/SiC and Al/Al2O3 composites prepared by stir casting technique is investigated to find out the effects of weight percentage of SiC/Al2O3, load and the number of strokes on a reciprocating wear testing machine. The MMC pins are prepared with different weight percentage of SiC and Al2O3 (10, 15 and 20 %. The tests are carried out with different load conditions (25, 50 and 75 N and different number of strokes (420,780 and 1605 strokes. Wear surfaces of tested samples are examined in Scanning Electron Microscope (SEM. Hardness test and impact test are also carried out on the MMC samples. The experimental results shows that hardness of composites increases with increase in SiC and Al2O3 particle and the impact strength decreases with increase in SiC and Al2O3 content. The volume loss of MMC specimens are less than that of the matrix alloy. The temperature rise near the contact surface of the MMC specimens increases with increase in wt% of SiC and Al2O3, load and number of strokes. The coefficient of friction decreases with increase in the number of strokes. The WVAS (Wireless Vibration Acquisition System interfaced with MAT Lab software is used to record the amplitudes during the test.

  15. Research on semi-solid slurry of a hypoeutectic Al-Si alloy prepared by low superheat pouring and weak electromagnetic stirring

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    The semi-solid slurry of a hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature and stirring power on the semi-solid slurry were investigated. The results indicated that the semi-solid slurry to satisfy rheocasting can be manufactured by low superheat pouring and weak electromagnetic stirring. The pouring temperature (or superheat) and the stirring power remarkably affected the morphology of primary α-Al and the size of primary α-Al, and there is no obvious effect of stirring time on primary α-Al. Compared with the samples made by low superheat pouring with no stirring, the nucleation rate, particle morphology and grain size of primary α-Al in A356 were markedly improved by low superheat pouring and weak electromagnetic stirring. On the condition of weak electromagnetic stirring, the pouting temperature with low superheat can be suitably raised to reach the effectiveness obtained from the lower pouring temperature without stirring.

  16. Manufacture technique of semi-solid slurry of hypoeutectic Al-Si alloy by low superheat pouring and weak electromagnetic stirring

    Institute of Scientific and Technical Information of China (English)

    LIU Zheng; MAO Wei-ming; ZHAO Zheng-duo

    2006-01-01

    The semi-solid slurry of hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature and stirring power on the semi-solid slurry making process were investigated. The results indicate that the semi-solid slurry to satisfy rheocasting requirement can be made by a combination of low superheat pouring and weak electromagnetic stirring. The pouring temperature (or superheat) and the stirring power significantly affect the morphology and the size of primary α-Al, while there is no obvious effect of the stirring time on primary α-Al. Compared with the samples made by low superheat pouring without stirring, the nucleation rate,particle morphology and grain size of primary α-Al in A356 Al alloy are markedly improved by a process of applying both low superheat pouring and weak electromagnetic stirring. Under the condition of weak electromagnetic stirring applied, the pouring temperature with low superheat can be equivalerttly to reach the effectiveness obtained from the even lower pouring temperature without stirring.

  17. Manufacture technique of semi-solid slurry of hypoeutectic Al-Si alloy by low superheat pouring and weak electromagnetic stirring

    Directory of Open Access Journals (Sweden)

    LIU Zheng

    2006-05-01

    Full Text Available The semi-solid slurry of hypoeutectic Al-Si alloy was manufactured by low superheat pouring and weak electromagnetic stirring. The effects of pouring temperature and stirring power on the semi-solid slurry making process were investigated. The results indicate that the semi-solid slurry to satisfy rheocasting requirement can be made by a combination of low superheat pouring and weak electromagnetic stirring. The pouring temperature (or superheat and the stirring power significantly affect the morphology and the size of primary α-Al, while there is no obvious effect of the stirring time on primary α-Al. Compared with the samples made by low superheat pouring without stirring, the nucleation rate, particle morphology and grain size of primary α-Al in A356 Al alloy are markedly improved by a process of applying both low superheat pouring and weak electromagnetic stirring. Under the condition of weak electromagnetic stirring applied, the pouring temperature with low superheat can be equivalently to reach the effectiveness obtained from the even lower pouring temperature without stirring.

  18. Three-dimensional visualization and characterization of morphology and internal microstructural features of primary silicon crystals in a cast Al-Si base alloy

    Science.gov (United States)

    Singh, H.; Gokhale, A. M.; Mao, Y.; Tewari, A.; Sachdev, A. K.

    2009-09-01

    Primary Si crystals are usually present in the cast microstructures of near-eutectic, eutectic, and hyper-eutectic Al-Si base alloys. Three-dimensional digital images of individual primary Si crystals present in a permanent mold cast unmodified Al-12 wt% Si-1 wt% Ni base alloy are reconstructed using a combination of montage serial sectioning and three-dimensional digital image processing techniques. Octahedral, prismatic, and plate-like three-dimensional morphologies of the primary Si crystals are present in the microstructure. Some of the primary Si crystals contain interior regions/islands of Al-alloy that are completely enclosed in the corresponding Si crystals indicating certain variations in the crystal growth velocities during the evolution of these crystals. The boundaries of these interior regions/islands are non-faceted smooth and curved indicating re-melting of the Al-rich islands and re-dissolution of some Si near these internal boundaries in the Al-alloy as a result of the heat generated by liquid-to-solid transformation of Si away from the islands.

  19. Swelling of U(Mo)-Al(Si) dispersion fuel under irradiation - Non-destructive analyses of the LEONIDAS E-FUTURE plates

    Science.gov (United States)

    Van den Berghe, S.; Parthoens, Y.; Charollais, F.; Kim, Y. S.; Leenaers, A.; Koonen, E.; Kuzminov, V.; Lemoine, P.; Jarousse, C.; Guyon, H.; Wachs, D.; Keiser, D., Jr.; Robinson, A.; Stevens, J.; Hofman, G.

    2012-11-01

    In the framework of the elimination of High-Enriched Uranium (HEU) from the civil circuit, the search for an appropriate fuel to replace the high-enriched research reactor fuel in those reactors that currently still require it for their operation has led to the development of a U-7 wt.%Mo alloy based dispersion fuel with an Al-Si matrix. The European LEONIDAS program, joining SCK•CEN, ILL, CEA and AREVA-CERCA, is aimed at the qualification of such a fuel for the use in high power conditions. The first experiment of the program, designated E-FUTURE, was performed to select the appropriate matrix Si concentration and fuel plate post-production heat treatment parameters for further qualification. It consisted of the irradiation of four distinct (4% and 6% Si, 3 different heat treatments) full size, flat fuel plates in the BR2 reactor. The irradiation conditions were relatively severe: 470 W/cm2 peak BOL power, with a ˜70% 235U peak burnup.

  20. Wetting behavior of Al-Si-Mg alloys on Si{sub 3}N{sub 4}/Si substrates: optimization of processing parameters

    Energy Technology Data Exchange (ETDEWEB)

    Pena, J.L. de la; Pech-Canul, M.I. [Centro de Investigacion y de Estudios Avanzados Unidad Saltillo, Saltillo, Coahuila (Mexico)

    2008-06-15

    The wetting behavior of Al-Si-Mg alloys on Si{sub 3}N{sub 4}/Si substrates has been investigated using the sessile drop technique. Based on a Taguchi experiment design, the effect of the following processing parameters on the contact angle ({theta}) and surface tension ({sigma}{sub LV}) was studied: processing time and temperature, atmosphere (Ar and N{sub 2}), substrate surface condition (with and without a silicon wafer), as well as the Mg and Si contents in the aluminium alloy. In nitrogen, non-wetting conditions prevail during the isothermal events while in argon a remarkable non-wetting to wetting transition leads to contact angles {theta} as low as 11{+-}3 and a liquid surface tension {sigma}{sub LV} of 33{+-}10 x 10{sup -5} kJ/m{sup 2}. According to the multiple analysis of variance (Manova), the optimum conditions for minimizing the values of {theta} and {sigma}{sub LV} are as follows: temperature of 1100 C, processing time of 90 min, argon atmosphere, no use of a silicon wafer, and the use of the Al-18% Mg-1% Si alloy. A verification test conducted under the optimized conditions resulted in a contact angle of {theta}=9{+-}3 and a surface tension of {sigma}{sub LV}=29{+-} 9 x 10{sup -5} kJ/m{sup 2}, both indicative of excellent wetting. (orig.)

  1. Evolution of the Spectral Emissivity and Phase Transformations of the Al-Si Coating on Usibor® 1500P Steel During Austenitization

    Science.gov (United States)

    Shi, Cangji; Daun, Kyle J.; Wells, Mary A.

    2016-08-01

    Usibor® 1500P coupons are austenitized in a Gleeble 3500 thermomechanical simulator using a two-step heating procedure in an argon atmosphere. Variations in spectral emissivity are measured in-situ using a near infrared spectrometer and ex situ with a Fourier transform infrared reflectometer. Microstructural evolution and surface roughness are investigated using optical microscopy, FE-scanning electron microscopy, and a surface profilometer. A series of phase transformations of Al-Fe-Si intermetallic phases at the coating/steel substrate interface cause the surface phase and surface roughness to change, which in turn influences the spectral emissivity. At the beginning of the first heating step, the coupons have very low spectral emissivity, due to the molten Al-Si coating. Spectral emissivity increases significantly with increasing soak time from 5 to 12 minutes, associated with the surface phase transformation of the coating into Al7Fe2Si intermetallic phase and an increase in surface roughness. Through the second step heating at 1173 K (900 °C), the spectral emissivity shows a gradually decreasing trend with increasing soak time, caused by the surface phase transformation from Al5Fe2 into AlFe intermetallic phase with a decrease in surface roughness.

  2. Analysis by numerical calculations of the depth and dynamics of the penetration of ordered cellular structure made by casting from AlSi10Mg eutectic alloy

    Directory of Open Access Journals (Sweden)

    M. Małysza

    2011-07-01

    Full Text Available Owing to high plastic deformability while maintaining stress values constant and relatively low, ordered cellular structures arecharacterised by excellent properties and the ability to dissipate the impact energy. Due to the low weight, structures of this type can beused, among others, for different parts of motor vehicles. For tests, a trapezoidal ordered cellular structure of 50.8 x 50.8 x 25.4 (mmoverall dimensions was selected. It was made as an investment casting from AlSi9Mg eutectic alloy by the method of Rapid Prototyping(RP. During FEM computations using an Abaqus programme, it was assumed that the material is isotropic and exhibits the features of anelastic – plastic body, introducing to calculations the, listed in a table, values of the stress-strain curve obtained in tensile tests performedon a MTS testing machine (10T. The computations used Johnson - Cook model, which is usually sufficiently accurate when modelling thephenomena of penetration of an element by an object of high initial velocity. The performed numerical calculations allowed identification

  3. DOE applied to study the effect of process parameters on silicon spacing in lost foam Al-Si-Cu alloy casting

    Science.gov (United States)

    Shayganpour, A.; Idris, M. H.; Izman, S.; Jafari, H.

    2012-09-01

    Lost foam casting as a relatively new manufacturing process is extensively employed to produce sound complicated castings. In this study, an experimental investigation on lost foam casting of an Al-Si-Cu aluminium cast alloy was conducted. The research was aimed in evaluating the effect of different pouring temperatures, slurry viscosities, vibration durations and sand grain sizes on eutectic silicon spacing of thin-wall castings. A stepped-pattern was used in the study and the focus of the investigations was at the thinnest 3 mm section. A full two-level factorial design experimental technique was used to plan the experiments and afterwards identify the significant factors affecting casting silicon spacing. The results showed that pouring temperature and its interaction with vibration time have pronounced effect on eutectic silicon phase size. Increasing pouring temperature coarsened the eutectic silicon spacing while the higher vibration time diminished coarsening effect. Moreover, no significant effects on silicon spacing were found with variation of sand size and slurry viscosity.

  4. A study of Al/Si{sub 3}N{sub 4}/ultrathin Si/GaAs structures by DLTS and C-V measurements

    Energy Technology Data Exchange (ETDEWEB)

    Pincik, E.; Bartos, J.; Brunner, R.; Ivanco, J

    2003-06-02

    We present a study on electrical properties of Al/Si{sub 3}N{sub 4}/Si/GaAs structure studied by deep level transient spectroscopy and capacitance-voltage technique. Here, the Si means an ultrathin silicon layer with thickness of approximately 2 nm. We have modelled the presented structure, while emissions from deep levels at Si/GaAs interface, traps in the bulk of GaAs and from a quantum well (QW) possibly formed by the Si interlayer, were taken into the account. Four deep traps were identified in the structure with the following thermal activation energies: 0.04, 0.19, 0.40 and 0.68 eV. The energy levels 0.4 and 0.68 are related with As defects, while the energy levels 0.04 and 0.19 are associated with the presence of the Si interlayer. Based on the emission behaviour, an existence of the QW is not probable (can be excluded). Rather, parameters of the Si-related energy levels suggest the levels are induced by {delta}-doping of GaAs.

  5. Microstructural features associated with the effect of temperature on the dimensional stability of an automotive Al-A319 alloy

    Directory of Open Access Journals (Sweden)

    Hugo F. Lopez

    2016-05-01

    Full Text Available In this work an automotive Al-A319 was given a solid solution heat treatment (T4 at 753 K (480 °C for 4.5 hours and an ageing treatment (T7 at 513 K (240 °C for various times up to 3.0 h. The alloy in the T4 condition was dilatometrically tested at various temperatures in order to measure its relative dimensional changes. It was found that the dimensional changes are due to both, alloy thermal expansion and nucleation and growth of second phases. In addition, in the T7 condition the alloy strength and ductility were determined as a function of ageing times. Ageing promoted alloy strength but at the expenses of a rather poor alloy ductility (down to 1%. Apparently, Cu rich intermetallic phases and regions provided a brittle path for fracturing. In particular, microstructural characterization using high resolution transmission electron microscopy indicated that not all the Cu in the matrix was dissolved during the T4 treatment. Hence, after ageing (T7 these Cu-rich regions seemed to coarsen into spherical particles.

  6. Effects Of T6 Heat Treatment With Double Solution Treatment On Microstructure, Hardness And Corrosion Resistance Of Cast Al-Si-Cu Alloy

    Directory of Open Access Journals (Sweden)

    Wiengmoon A.

    2015-06-01

    Full Text Available Effects of T6 heat treatment with double solution treatment on microstructure, hardness and corrosion resistance of a cast A319 (Al-4.93wt%Si-3.47wt%Cu alloy were investigated. The T6 heat treatment comprised of the first solution treatment at 500±5°C for 8 h, the second solution treatment in the temperature range of 510 to 530±5°C for 2 h followed by water quenching (80°C, and artificial aging at 170°C for 24 h followed by water quenching (80°C. Microstructure of the alloy was studied by optical microscopy and electron microscopy, Rockwell hardness was measured, and corrosion resistance in 0.1 M NaCl aqueous solution was determined by a potentiodynamic technique. The results revealed that the T6 heat treatment with double solution treatment led to an improvement in corrosion resistance and comparable macrohardness as compared to those obtained from the case of single solution treatment. The second solution treatment at 520°C is the optimum leading to relatively low corrosion current density without substantial drawbacks on breakdown potential or the width of passive range.

  7. Formation of abrasion-resistant coatings of the AlSiFexMny intermetallic compound type on the AISI 304L alloy

    Directory of Open Access Journals (Sweden)

    Martínez-Perales, Laura G.

    2016-03-01

    Full Text Available The α-Al9FeMnSi and β-Al9FeMn2Si intermetallics formed by reactive sintering of Al, Si, Mn, Fe, Cr and Ni powders have been used in AISI 304L steels to enhance microhardness. Processing variables of the reactive sintering treatment were temperature (600, 650, 700, 750 and 800 °C, pressure (5, 10 y 20 MPa and holding time (3600, 5400 y 7200 seconds. Experimental results show that temperature is the most important variable affecting the substrate/coating formation, while pressure does not appear to have a significant effect. The results show the optimum conditions of the reactive sintering that favor the substrate/coating formation are 800 °C, 20 MPa and 7200 seconds. Under these conditions, the reaction zone between the substrate and coating is more compacted and well-adhered, with a microhardness of 1300 Vickers. The results of SEM and X-Ray diffraction confirmed the formation of α-Al9FeMnSi and β-Al9FeMn2Si intermetallics in the substrate/coating interface as well as the presence of Cr and Ni, indicating diffusion of these two elements from the substrate to the interface.Los intermetálicos α-Al9FeMnSi y β-Al9FeMn2Si formados por sinterización reactiva de polvos Al, Si, Mn, Fe, Cr, Ni se han utilizado en aceros AISI 304L para mejorar la microdureza. Las variables de procesamiento de sinterización reactiva fueron temperatura (600, 650, 700, 750, y 800 °C, presión (5, 10 y 20 MPa y el tiempo de retención (3600, 5400 7200 segundos. Los resultados experimentales muestran que la temperatura es la variable más importante que afecta a la formación del sustrato/recubrimiento, mientras que la presión no parece tener un efecto significativo una influencia significativa. Los resultados muestran las condiciones óptimas de la sinterización reactiva que favorecen la formación del sustrato/recubrimiento a 800 °C, 20 MPa y 7200 segundos. En estas condiciones, la zona de reacción entre el sustrato y el recubrimiento es más compacta y bien

  8. Microstructure and mechanical properties of Al-Si-Ni-Ce alloys prepared by gas-atomization spark plasma sintering and hot-extrusion

    Energy Technology Data Exchange (ETDEWEB)

    Wang, E.R. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Hui, X.D., E-mail: xdhui@ustb.edu.cn [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China); Wang, S.S.; Zhao, Y.F.; Chen, G.L. [State Key Laboratory for Advanced Metals and Materials, University of Science and Technology Beijing, Beijing 100083 (China)

    2011-07-15

    Highlights: {yields} There are distinct microstructures in the as-atomized powders with different size. {yields} The morphology of Al{sub 11}Ce{sub 3} crystals is related to the Ni content. {yields} Tiny Al{sub 3}Ni precipitated from the supersaturated matrix after SPS process. {yields} Hot-extrusion leads to the improved microstructures. {yields} This kind of alloy exhibits high comprehensive mechanical properties. - Abstract: Al-Si-Ni-Ce alloys with the composition of Al{sub 78.5}Si{sub 19}Ni{sub 2}Ce{sub 0.5}, Al{sub 76}Si{sub 19}Ni{sub 4}Ce{sub 1} and Al{sub 73}Si{sub 19}Ni{sub 7}Ce{sub 1} were atomized and then sintered by using spark plasma method. The microstructure of the as-atomized powders, sintered and hot-extruded samples was analyzed. The influences of granularity and sintering parameters including time and temperature on the density of sintered alloy were also discussed. It is shown that the atomized powders are composed of Si, Al{sub 11}Ce{sub 3}, Al{sub 3}Ni and alpha Al. Tiny Al{sub 3}Ni particles precipitate from supersaturated matrix near the powder boundaries during SPS. Hot-extrusion process leads to the layer structure and more homogeneous distribution of precipitates. These alloys exhibit high comprehensive mechanical properties with combination of high Vicker's micro-hardness, moderate tensile properties and elongation, which provide a novel kind of promising engineering materials.

  9. Processing and Characterization of Functionally Graded Aluminum (A319)—SiCp Metallic Composites by Centrifugal Casting Technique

    Science.gov (United States)

    Jayakumar, E.; Jacob, Jibin C.; Rajan, T. P. D.; Joseph, M. A.; Pai, B. C.

    2016-08-01

    Functionally graded materials (FGM) are successfully adopted for the design and fabrication of engineering components with location-specific properties. The present study describes the processing and characterization of A319 Aluminum functionally graded metal matrix composites (FGMMC) with 10 and 15 wt pct SiCp reinforcements. The liquid stir casting method is used for composite melt preparation followed by FGMMC formation by vertical centrifugal casting method. The process parameters used are the mold preheating temperature of 523 K (250 °C), melt pouring temperature of 1013 K (740 °C), and mold rotation speed of 1300 rpm. The study analyzes the distribution and concentration of reinforcement particles in the radial direction of the FGMMC disk along with the effects of gradation on density, hardness, mechanical strength, the variation in coefficient of thermal expansion and the wear resistance properties at different zones. Microstructures of FGMMC reveal an outward radial gradient distribution of reinforcements forming different zones. Namely, matrix-rich inner, transition, particles-rich outer, and chill zone of a few millimeters thick at the outer most periphery of the casting are formed. From 10-FGM, a radial shift in the position of SiCp maxima is observed in 15-FGM casting. The mechanical characterization depicts enhanced properties for the particle-rich zone. The hardness shows a graded nature in correlation with particle concentration and a maximum of 94.4 HRB has been obtained at the particle-rich region of 15-FGM. In the particle-rich zone, the lowest CTE value of 20.1 µm/mK is also observed with a compressive strength of 650 MPa and an ultimate tensile strength of 279 MPa. The wear resistance is higher at the particle-rich zone of the FGMMC.

  10. Creep Properties of the As-Cast Al-A319 Alloy: T4 and T7 Heat Treatment Effects

    Science.gov (United States)

    Erfanian-Naziftoosi, Hamid R.; Rincón, Ernesto J.; López, Hugo F.

    2016-08-01

    In this work, the creep behavior of a commercial Al-A319 alloy was investigated in the temperature range of 413 K to 533 K (140 °C to 260 °C). Tensile creep specimens in the as-cast condition and after heat treating by solid solution (T4) and by aging (T7) were tested in a stress range varying from 60 to 170 MPa. It was found that steady-state creep strain rate was significantly low in the T7 condition when compared with either the T4 or as-cast alloy conditions. As a result, the time to failure behavior considerably increased. The experimentally determined creep exponents measured from the stress-strain curves were 4 for the as-cast alloy, 7.5 in the solid solution, and 9.5 after aging. In particular, after solid solution a grain substructure was found to develop which indicated that creep in a constant subgrain structure was active, thus accounting for the n exponent of 7.5. In the aged condition, a stress threshold is considered to account for the power law creep exponent n of 9.5. Moreover, It was found that the creep activation energy values were rather similar for the alloys in the as-cast (134 kJ/mol) and T4 (146 kJ/mol) conditions. These values are close to the one corresponding to pure Al self-diffusion (143 kJ/mol). In the aged alloy, the apparent creep activation energy (202 kJ/mol) exceeded that corresponding to Al self-diffusion. This deviation in activation energy is attributed to the effect of temperature on the alloy elastic modulus. Microstructural observations using transmission electron microscopy provided further support for the various dislocation-microstructure interactions exhibited by the alloy under the investigated creep conditions and implemented heat treatments.

  11. Synthesis and photoluminescence properties of Eu{sup 2+}-doped Ca{sub 2}AlSi{sub 3}O{sub 2}N{sub 5} green phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Cai Chao; Xie Wenjie; Hao Luyuan [Chinese Academy of Sciences Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei Anhui 230026 (China); Xu Xin, E-mail: xuxin@ustc.edu.cn [Chinese Academy of Sciences Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei Anhui 230026 (China); Agathopoulos, Simeon [Materials Science and Engineering Department, University of Ioannina, GR-451 10 Ioannina (Greece)

    2012-05-15

    Highlights: Black-Right-Pointing-Pointer We successfully produced a novel Ca{sub 2}AlSi{sub 3}O{sub 2}N{sub 5}:Eu{sup 2+} phosphors. They have a single intense broad green band centered at c.a. 500 nm and the excitation spectra match well with the emission of UV LED chips (350-410 nm), these qualify them for consideration in potential use as green phosphors in UVLED-based white LED. Black-Right-Pointing-Pointer The phosphors can be prepared in lower temperature than the other sialon-based materials, although they have excellent optical properties. Black-Right-Pointing-Pointer We studied impact factors on the photoluminescence behavior of the produced phosphors, and found we could tune the intensity and the emission spectra with these characteristic. - Abstract: Novel Eu{sup 2+}-doped Ca{sub 2}AlSi{sub 3}O{sub 2}N{sub 5} phosphors with a general formula of Eu{sub x}Ca{sub 2-x}AlSi{sub 3}O{sub 2}N{sub 5} were successfully prepared via a solid-state reaction method under a nitrogen atmosphere. The produced phosphors were effectively excited by UV-vis light in the wavelength range between 250 and 400 nm, and featured an intense green emission band which peaked at about 500 nm. The emission spectra featured a red-shift over increasing Eu{sup 2+} content and the temperature of heat treatment. The maximum intensity of emission was obtained for x = 0.014 and heat treatment at 1450 Degree-Sign C. The photoluminescence properties of the produced Ca{sub 2}AlSi{sub 3}O{sub 2}N{sub 5}:Eu{sup 2+} phosphors qualify them for consideration in potential use as green phosphors in UVLED-based white LED.

  12. Au12M(M=Na,Mg,Al,Si,P,S,Cl)团簇的结构、稳定性和电子性质%Geometries, Stabilities and Electronic Properties of Au12M (M=Na, Mg, Al, Si, P, S, Cl) Clusters

    Institute of Scientific and Technical Information of China (English)

    赵高峰; 王银亮; 孙建敏; 王渊旭

    2012-01-01

    The geometries,stabilities,and electronic properties of Au12M (M=Na,Mg,Al,Si,P,S,Cl)clusters were systematically investigated by using first-principles calculations based on density functional theory (DFT).For each cluster,the average binding energy,the embedding energy,the vertical ionization potential,the energy gap between the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO),the natural charge population analysis,and the natural bond orbital analysis (NBO) were calculated.The lowest-energy structures of Au12M (M=Na,Mg,Al)clusters are cages with M encapsulated in the center,while structures of Au12M (M=Si,P,S,Cl) clusters are pyramidal with M at the apex.The Au12S cluster,having the full closed-shells,is the most stable.Furthermore,from the natural population analysis,it follows that charges transfer from Au to M in all the clusters.The NBO and HOMO analyses reveal that hybridization occurs between the Au s-d orbitals and the M p orbitals.%采用基于密度泛函理论的第一性原理方法系统地研究了Au12M (M=Na,Mg,Al,Si,P,S,Cl)团簇的结构、稳定性和电子性质.对团簇的平均结合能、镶嵌能、垂直离化势、最高占据分子轨道(HOMO)和最低未占据分子轨道(LUMO)的能级差、电荷布居分析、自然键轨道(NBO)进行了计算和讨论.对于Au12M(M=Na,Mg,Al)团簇,它们形成了内含M原子的最稳定的笼状结构.然而对于Au12M (M=Si,P,S,Cl)团簇,它们却形成了以M元素为顶点的稳定锥形结构.在这些团簇中发现Au12S团簇相对是最稳定的,这是由于Au12S团簇形成了稳定的满壳层的电子结构.自然电荷布居分析表明:对于所有的Au12M (M=Na,Mg,Al,Si,P,S,Cl)团簇电荷总是从Au原子转向M原子.自然键轨道和HOMO分析表明Au12M团簇中发生了Au原子的s-d轨道和M原子的p轨道间的杂化现象.

  13. Evaluación del efecto de modificadores y refinadores en el comportamiento mecánico y magnitud del rechupe de aleaciones Al-Si-Mg. // Modifier and refiners effect evaluation in the magnitude and mechanical shrinkage behavior of Al-Si-Mg alloys.

    Directory of Open Access Journals (Sweden)

    V. Lavaert

    2002-05-01

    Full Text Available Se estudia la influencia del Na, Sr y Ti y sus combinaciones (Na-Ti y Sr-Na en las propiedades mecánicas y el rechupe(superior y lateral de la aleación hipoeutéctica AlSi7Mg Aunque todos estos elementos y combinaciones tienden aneutralizar la formación del rechupe substancialmente, el Sr se presenta como el más eficaz para disminuir el rechupesuperior mientras la combinación Na-Ti llevó a la menor formación de rechupe lateral.Se observó una acción modificadora excelente para 0.02% de Sr y 0.02% de Na, pero a diferencia del Sr, el efectomodificador del Na comienza a desvanecerse después de 30 min afectando el alargamiento notablemente. El estroncio, sinembargo, mostró un efecto de la modificación muy duradero (aproximadamente 3 h. Otro hallazgo interesante es laexistencia de un cierto periodo de incubación de aproximadamente 90 minutos después de agregar Sr. Contrariamente a loesperado el uso de titanio no mejoró las propiedades mecánicas a pesar de un eficaz refinamiento de grano.Palabras claves: Rechupe superior, acción modificadora, propiedades mecánicas, metalurgia no ferrosa._________________________________________________________________________AbstractThe influence of Na, Sr and Ti and their combinations (Na-Ti and Sr-Na on the mechanical properties and the shrinkage(top macro shrinkage and lateral macro shrinkage of hypoeutectic aluminium-silicon alloys (AlSi7xMg has been studied.Although all these elements and combinations tend to counteract substantially the shrinkage formation, Sr appeared to bethe most effective to decrease top macro shrinkage whereas the combination Na-Ti led to the least formation of lateralmacro shrinkage. An excellent modifying action was observed for 0.02% Sr and 0.02% Na, but unlike Sr the modifyingeffect provided by Na started fading after 30 min of holding which affected the elongation markedly. However, strontiumshowed a very lasting modification effect (about 3 h. Another interesting

  14. Un problema tipo bin-packing

    Directory of Open Access Journals (Sweden)

    Geovanni Figueroa Mata

    2011-09-01

    Full Text Available Se presentan dos algoritmos heurísticos para resolver un problema de tipo binpacking en el cual se quiere guardar objetos de n tipos diferentes (en donde la demanda del objeto de tipo i-ésimo está dada por d1 en m tipos de recipientes con capacidades no necesariamente iguales; todos los recipientes de tipo j =1,2,...,m deben tener la misma distribución de los objetos. El objetivo es minimizar el costo de los recipientes por utilizar, donde el costo de cada tipo de recipiente está dado por wj (j =1,2,...,m. Para cada recipiente de tipo j =1,2,...,m se deben encontrar el número de repeticiones xj del recipiente, así como el número de copias aij del objeto i-ésimo que se deben almacenar en el recipiente j-ésimo (j =1,2,...,m.

  15. Influence of the Sr and Mg Alloying Additions on the Bonding Between Matrix and Reinforcing Particles in the AlSi7Mg/SiC-Cg Hybrid Composite

    Directory of Open Access Journals (Sweden)

    Dolata A. J.

    2016-06-01

    Full Text Available The aim of the work was to perform adequate selection of the phase composition of the composite designated for permanent - mould casting air compressor pistons. The hybrid composites based on AlSi7Mg matrix alloy reinforced with mixture of silicon carbide (SiC and glassy carbon (Cg particles were fabricated by the stir casting method. It has been shown that the proper selection of chemical composition of matrix alloy and its modification by used magnesium and strontium additions gives possibility to obtain both the advantageous casting properties of composite suspensions as well as good bonding between particles reinforcements and matrix.

  16. Comportamiento a la corrosión electroquímica de aleaciones MgAl con recubrimientos de materiales compuestos Al/SiCp mediante proyección térmica

    Directory of Open Access Journals (Sweden)

    Pardo, A.

    2010-04-01

    Full Text Available The corrosion protection of Mg-Al alloys by flame thermal spraying of Al/SiCp composite coatings was evaluated by electrochemical impedance spectroscopy in 3.5 wt.% NaCl solution. The volume fraction of SiC particles (SiCp varied between 5 and 30%. The as-sprayed Al/SiCp composite coatings revealed a high number of micro-channels, largely in the vicinity of the SiC particles, that facilitated the penetration of the electrolyte and the subsequent galvanic corrosion of the magnesium substrates. The application of a cold-pressing post-treatment reduced the degree of porosity of the coatings and improved the bonding at the coating/substrate and Al/SiC interfaces. This resulted in improved corrosion resistance of the coated specimens. The effectiveness of the coatings slightly decreased with the addition of 5-30 vol.% SiCp compared with the unreinforced thermal spray aluminium coatings.

    Se estudia, mediante espectroscopía de impedancia electroquímica en solución 3,5 % NaCl, la protección frente a la corrosión de aleaciones Mg-Al recubiertas por proyección térmica con materiales compuestos Al/SiCp. Se varió la fracción de volumen de las partículas de SiC (SiCp entre 5 y 30 %. Los recubrimientos efectuados por proyección térmica revelan un elevado número de microcanales, en la vecindad de las partículas de SiC, que facilitan la penetración del electrolito originando procesos de corrosión galvánica en los substratos de las aleaciones de magnesio. Un tratamiento posterior mediante la aplicación de una presión en frío reduce el grado de porosidad de los recubrimientos y mejora la unión, tanto entre el substrato y el recubrimiento como entre las partículas de aluminio y SiC, mejorando la resistencia a la corrosión de las aleaciones recubiertas. La efectividad de los recubrimientos disminuye ligeramente con la adición de SiCp cuando se comparan con los mismos recubrimientos de aluminio sin refuerzo.

  17. Selective laser melting Al-Si aluminum alloy and the crack formation mechanism%选区激光熔化成形Al-Si合金及其裂纹形成机制研究

    Institute of Scientific and Technical Information of China (English)

    王梦瑶; 朱海红; 祁婷; 张虎; 曾晓雁

    2016-01-01

    To get Al-Si alloy parts with high performance , the formation and cracking behaviors of Al-Si alloy parts fabricated by selective laser melting were studied .The relationship between process parameters and fabrication densification , and the mechanism of crack formation were revealed .The results show that the density of the fabricated samples increases at first and then decreases with the increase of laser power density .The cold cracks are formed in most of the samples which expand along the cladding layer .Its formation mechanism is that a large number of eutectic Si is formed during the process and eutectic Si reduces crack resistance strength of Al-Si aluminum alloy , and crack resistance cannot be enough to resist the high temperature gradient during the forming process , and the generated residual stress is the cause of cold cracks .By improving the process parameters , Al-Si alloy parts with high performance and without cracks could be formed .%为了得到性能良好的Al-Si合金零件,对选区激光熔化成形Al-Si合金的成形特性以及成形试样中裂纹进行了研究,得到了成形样致密度和工艺参量的关系以及裂纹的形成机制. 在合适的工艺区间内,随着激光能量密度的增大,致密度先上升后下降;大部分试样底部存在沿熔覆层扩展的冷裂纹;其形成机制是Al-Si合金粉末成形过程中,生成大量共晶Si相,使材料的抗裂性能不足以抵抗成形过程中的高温度梯度导致的残余应力所致. 结果表明,通过调整成形工艺参量,可以得到无裂纹的性能良好的成型零件.

  18. Grain refinement of gravity die cast secondary AlSi7Cu3Mg alloys for automotive cylinder heads%重力铸造汽车气缸盖用AlSi7Cu3Mg 二次合金的晶粒细化

    Institute of Scientific and Technical Information of China (English)

    Giordano CAMICIA; Giulio TIMELLI

    2016-01-01

    The effects of AlTi5B1 grain refinement and cooling rate on the microstructure and mechanical properties of a secondary AlSi7Cu3Mg alloy were reported. Metallographic and image analysis techniques have been used to quantitatively examine the macrostructural and microstructural changes occurring with the addition of grain-refining agent at different cooling rates by using a step casting die. The results indicate that the addition of AlTi5B1 produces a fine and uniform grain structure throughout the casting and this effect is more pronounced in the slowly solidified regions. Increasing the cooling rate, lower amount of grain refiner is necessary to produce a uniform grain size throughout the casting. On the other hand, the initial contents of Ti and B, present as impurity elements in the supplied secondary alloy, are not sufficient to produce an effective grain refinement. The results from the step casting geometry were applied to investigate a gasoline 16V cylinder head, which was produced by gravity semi-permanent mould technology. The grain refinement improves the plastic behaviour of the alloy and increases the reliability of the casting, as evidenced by the Weibull statistics.%研究了 AlTi5B1晶粒细化和冷却速率对 AlSi7Cu3Mg 二次合金显微组织和力学性能的影响。采用阶梯铸模在不同冷却速率下制备添加晶粒细化剂的合金,并利用金相和图像分析技术定量研究了合金的宏观组织和显微组织。研究结果表明,添加 AlTi5B1后,整个铸件具有细小均匀的晶粒组织,且在慢速凝固区域效果更显著。当冷却速率增加时,少量细化剂就可使铸件获得细小均匀组织。另外,原材料中的 Ti 和 B 以杂质的形式存在,不足以形成有效的晶粒细化效果。利用阶梯铸造法的研究结果研究了重力半固模铸造16V 汽油发动机气缸盖。Weibull 统计结果表明,晶粒细化改善了合金的塑形变形行为,提高了铸件的可靠性。

  19. Single-crystal elastic properties of (Cs,Na)AlSi2O6.H2O pollucite: A zeolite with potential use for long-term storage of Cs radioisotopes

    Science.gov (United States)

    Sanchez-Valle, Carmen; Chio, Chi-Hong; Gatta, G. Diego

    2010-11-01

    The single-crystal and aggregate elastic properties of the zeolite pollucite (Cs,Na)AlSi2O6ṡH2O, a potential host for Cs radionucleides in geological repositories, have been determined by Brillouin scattering spectroscopy at ambient conditions. The three nonzero individual elastic constants of cubic pollucite are: C11=105.0(1.3) GPa, C44=27.0(3) GPa, and C12=25.7(6) GPa. The Voigt-Reuss-Hill average of the aggregate bulk, shear modulus, Young's modulus and Poisson's ratio are KS=52.2(1.0) GPa, G=31.5(7) GPa, E=78.6(1.0) GPa, and ν =0.248(4), respectively. The bulk modulus of pollucite is 12.7% lower than that of the all-Na isotypic mineral analcime NaAlSi2O6ṡH2O whereas the shear moduli G are identical within mutual uncertainties. The higher compressibility of pollucite results from the weaker Cs-O bonds compared to Na-O bonds, suggesting strong control of the nature and configuration of the extraframework content on the behavior of the structure. The elastic properties of pollucite reported here will help in the prediction of its behavior as a geological barrier and in the modeling of the short-term and long-term safety of the Cs-repositories.

  20. Algunos tipos de preferencias no transitivas

    OpenAIRE

    Carmen Vázquez

    2010-01-01

    Este trabajo ofrece una visión sobre la modelación de las relaciones de preferencias del consumidor diferente a la clásica, pues prescindimos de la hipótesis de transitividad. Concretamente, analizamos dos tipos de relaciones de preferencias no transitivas, las acíclicas y las asimétricas, que bajo ciertas condiciones, admiten tipos de representación numérica distintos. Justificamos la aceptación de las mismas mediante ejemplos prácticos y vemos también resultados que garantizan la existencia...

  1. Estrutura temporal dos tipos de xuro

    OpenAIRE

    Reboredo Nogueira, Juan Carlos

    2013-01-01

    Esta unidade didáctica forma parte do curso de Análise Económica dos Mercados Financeiros I que se imparte no primeiro cuadrimestre do Máster en Economía: Organización Industrial e Mercados Financeiros. Esta unidade ten como obxectivo analizar a estrutura temporal dos tipos de xuro, é dicir a relación existente entre os tipos de xuro a diferentes prazos. En particular, estudarase a curva cupón cero, a súa utilidade no proceso de valoración dos activos financeiros e os diferentes mé...

  2. Luminescence properties of blue La1-xCexAl(Si6-zAlz)(N10-zOz) (z˜1) oxynitride phosphors and their application in white light-emitting diode

    Science.gov (United States)

    Takahashi, Kohsei; Hirosaki, Naoto; Xie, Rong-Jun; Harada, Masamichi; Yoshimura, Ken-ichi; Tomomura, Yoshitaka

    2007-08-01

    This letter reports blue oxynitride phosphors of La1-xCexAl(Si6-zAlz)(N10-zOz) (z˜1) (termed JEM crystal phase) and their application for the white light-emitting diodes (LEDs). The JEM phosphor can be excited by 405nm light efficiently, and its spectrum can be tuned widely by changing the Ce concentration. The emission spectrum of this phosphor is as wide as 110nm in full width at half maximum, which is convenient to solid state lighting. The preparation of white LED was attempted by using a 405nm InGaN chip and oxynitride phosphors in this work. High color rendering index >95 was achieved in white LED with various correlated color temperatures, indicating the suitability of the JEM phosphor in solid-state lightings.

  3. The effect of the interlayer element on the exfoliation of layered Mo2AC (A = Al, Si, P, Ga, Ge, As or In) MAX phases into two-dimensional Mo2C nanosheets

    Science.gov (United States)

    Khazaei, Mohammad; Arai, Masao; Sasaki, Taizo; Estili, Mehdi; Sakka, Yoshio

    2014-02-01

    The experimental exfoliation of layered, ternary transition-metal carbide and nitride compounds, known as MAX phases, into two-dimensional (2D) nanosheets, is a great development in the synthesis of novel low-dimensional inorganic systems. Among the MAX phases, Mo-containing ones might be considered as the source for obtaining Mo2C nanosheets with potentially unique properties, if they could be exfoliated. Here, by using a set of first-principles calculations, we discuss the effect of the interlayer ‘A’ element on the exfoliation of Mo2AC (A = Al, Si, P, Ga, Ge, As or In) MAX phases into the 2D Mo2C nanosheets. Based on the calculated exfoliation energies and the elastic constants, we propose that Mo2InC with the lowest exfoliation energy and the highest elastic constant anisotropy between C11 and C33 might be a suitable compound for exfoliation into 2D Mo2C nanosheets.

  4. Proton induced K X-ray production cross sections of the elements Al, Si, Ti, Fe, and Ni in the 0.7–2.0 MeV energy range

    Energy Technology Data Exchange (ETDEWEB)

    Bertol, Ana Paula Lamberti [Programa de Pós Graduação em Física, PPGFis, Universidade Federal do Rio Grande do Sul, UFRGS, Porto Alegre, RS (Brazil); Hinrichs, Ruth [PPGFis and Instituto de Geociências, UFRGS (Brazil); Vasconcellos, Marcos A.Z. [PPGFis and Instituto de Física, UFRGS (Brazil)

    2015-12-15

    Proton induced K-shell ionization cross sections were obtained for the elements Al, Si, Ti, Fe, and Ni in the 0.7–2.0 MeV energy range. The accuracy of these fundamental parameters is essential for PIXE analysis and the data in the literature present a considerable spread, mainly for Al and Si. The values obtained for Ti, Fe and Ni are compatible with the current theories and the experimental results reported in the literature. However, Al and Si cross sections present important differences from theoretical and experimental data. We propose values for the fluorescent yields of Al and Si that are compatible with recent results and can be incorporated in the computations of K X-ray production cross sections.

  5. Electronic Origins of the Variable Efficiency of Room-Temperature Methane Activation by Homo- and Heteronuclear Cluster Oxide Cations [XYO2](+) (X, Y = Al, Si, Mg): Competition between Proton-Coupled Electron Transfer and Hydrogen-Atom Transfer.

    Science.gov (United States)

    Li, Jilai; Zhou, Shaodong; Zhang, Jun; Schlangen, Maria; Weiske, Thomas; Usharani, Dandamudi; Shaik, Sason; Schwarz, Helmut

    2016-06-29

    The reactivity of the homo- and heteronuclear oxide clusters [XYO2](+) (X, Y = Al, Si, Mg) toward methane was studied using Fourier transform ion cyclotron resonance mass spectrometry, in conjunction with high-level quantum mechanical calculations. The most reactive cluster by both experiment and theory is [Al2O2](•+). In its favorable pathway, this cluster abstracts a hydrogen atom by means of proton-coupled electron transfer (PCET) instead of following the conventional hydrogen-atom transfer (HAT) route. This mechanistic choice originates in the strong Lewis acidity of the aluminum site of [Al2O2](•+), which cleaves the C-H bond heterolytically to form an Al-CH3 entity, while the proton is transferred to the bridging oxygen atom of the cluster ion. In addition, a comparison of the reactivity of heteronuclear and homonuclear oxide clusters [XYO2](+) (X, Y = Al, Si, Mg) reveals a striking doping effect by aluminum. Thus, the vacant s-p hybrid orbital on Al acts as an acceptor of the electron pair from methyl anion (CH3(-)) and is therefore eminently important for bringing about thermal methane activation by PCET. For the Al-doped cluster ions, the spin density at an oxygen atom, which is crucial for the HAT mechanism, acts here as a spectator during the course of the PCET mediated C-H bond cleavage. A diagnostic plot of the deformation energy vis-à-vis the barrier shows the different HAT/PCET reactivity map for the entire series. This is a strong connection to the recently discussed mechanism of oxidative coupling of methane on magnesium oxide surfaces proceeding through Grignard-type intermediates.

  6. Characterization of cylinder liners produced with hypereutectic Al-Si alloys and investigation of corrosion behaviour in synthetic automotive condensed solution; Caracterizacao de camisas de cilindro em ligas Al-Si hipereuteticas e investigacao do comportamento de corrosao em meio de condensado sintetico automotivo

    Energy Technology Data Exchange (ETDEWEB)

    Santos, Hamilta de Oliveira

    2006-07-01

    In the present study four hypereutectic Al-Si alloys, three produced by spray forming and one by casting, were characterized for microhardness, roughness, microstructure, texture and corrosion resistance in a synthetic automotive condensed solution (SACS). Two of the spray formed alloys tested were obtained from cylinder liners and the other was laboratory made. Spray forming involves alloy atomization and droplets deposition on a substrate, previous to the solidification of all of the droplets. This process favours the production of materials with a fine microstructure free of macrosegregation that is related to improved hot workability. The microstructure characterization of the four alloys revealed the presence of porosities in the laboratory made alloy. All the three alloys produced by spray forming showed a homogeneous distribution of primary precipitates. The microstructure of one of the alloys showed eutectic microstructure, indicating that this alloy was fabricated by casting. In the cylinder liners, the surface roughness was measured and the microhardness of all the alloys was also evaluated. Furthermore, the laboratory made alloy was hot and cold rolled. Texture determinations were carried out to investigate the correlation between the alloy type and their fabrication process. The texture investigation indicated that the fine distribution of primary silicon phase in the alloy hindered the development of texture typical of aluminium alloys deformation, even after severe mechanical work, such as those used in the conversion of pre-formed in cylinder liners. The surface roughness results indicated typical characteristics of the surface finishing used, honing or chemical etching. The microhardness results were dependent on the fabrication process used, with higher microhardness associated to the eutectic alloy comparatively to the spray formed ones. All hypereutectic alloys were tested for corrosion resistance using electrochemical impedance spectroscopy in

  7. Neodesarrollismo y el tipo de cambio competitivo

    Directory of Open Access Journals (Sweden)

    Alejandro Fiorito

    2015-01-01

    Full Text Available En este trabajo se intenta mostrar que las modificaciones en los tipos de cambio tienen efectos limitados en el aumento del producto, mientras que, inversamente, esos cambios impactan especialmente en la distribución del ingreso al incidir en los precios domésticos. Se analizan y muestran múltiples referencias de la literatura internacional que cuestionan este "consenso de tipos de cambio competitivos". Se realizan correlaciones que muestran resultados distintos de los obtenidos en Rodrik (2008 con los mismos datos utilizados, aunque simplemente cambiando la metodología de datos de panel y usando en cambio una más convencional de series de tiempo.

  8. Tipos e mitos do pensamento brasileiro

    Directory of Open Access Journals (Sweden)

    Ianni Octavio

    2002-01-01

    Full Text Available No pensamento brasileiro são freqüentes os "tipos ideais" elaborados por diferentes autores e que se tornam emblemáticos, notáveis ou mesmo definitivos, podendo, às vezes, figurar como mitos. Esse é o caso do bandeirante, do gaúcho, do Jeca Tatu, do Macunaíma, do homem cordial e outros. Vale a pena refletir sobre este aspecto da cultura e do pensamento brasileiros.

  9. Ataxia espinocerebelar tipo 6: relato de caso

    Directory of Open Access Journals (Sweden)

    Bianca Simone Zeigelboim

    2014-10-01

    Full Text Available O objetivo deste estudo foi verificar as alterações vestibulococleares observadas em um caso de ataxia espinocerebelar tipo 6. O caso foi encaminhado do Hospital de Clínicas para o Laboratório de Otoneurologia de uma Instituição de Ensino e foi submetido aos seguintes procedimentos: anamnese, inspeção otológica, avaliações audiológica e vestibular. O caso retrata uma paciente com diagnóstico genético de ataxia espinocerebelar tipo 6, do sexo feminino, com 57 anos de idade, que referiu desequilíbrio à marcha com tendência a queda para a esquerda, disartria e disfonia. Na avaliação audiológica apresentou configuração audiométrica descendente a partir da frequência de 4kHz e curva timpanométrica do tipo "A" com presença dos reflexos estapedianos bilateralmente. No exame vestibular observou-se na pesquisa da vertigem posicional presença de nistagmo vertical inferior e oblíquo, espontâneo e semiespontâneo múltiplo com características centrais (ausência de latência, paroxismo, fatigabilidade e vertigem, nistagmooptocinético abolido e hiporreflexia à prova calórica. Constataram-se alterações labirínticas que indicaram afecção do sistema vestibular central evidenciando-se a importância dessa avaliação. A existência da possível relação entre os achados com os sintomas vestibulares apresentados pela paciente apontou a relevância do exame labiríntico neste tipo de ataxia uma vez que a presença do nistagmo vertical inferior demonstrou ser frequente neste tipo de patologia.

  10. Error de tipo y el conocimiento del hecho

    OpenAIRE

    Palacios Riquetti, Damián Patricio

    2013-01-01

    Lo que busco es establecer la diferencia entre el error de tipo y el error de prohibición, para luego tratar sobre el conocimiento que debe tener el autor, sobre los elementos del tipo legal, para que se configure un error de tipo, y determinar si el error de tipo es evitable o inevitable, lo que en cada caso llevará a la gradación y a la imposición o no de una pena; trataré sobre el error de los elementos normativos integrados en el tipo penal, comentaré del error sobre el curso causa...

  11. Coating of 6028 Aluminum Alloy Using Aluminum Piston Alloy and Al-Si Alloy-Based Nanocomposites Produced by the Addition of Al-Ti5-B1 to the Matrix Melt

    Science.gov (United States)

    El-Labban, Hashem F.; Abdelaziz, M.; Mahmoud, Essam R. I.

    2014-10-01

    The Al-12 pctSi alloy and aluminum-based composites reinforced with TiB2 and Al3Ti intermetallics exhibit good wear resistance, strength-to-weight ratio, and strength-to-cost ratio when compared to equivalent other commercial Al alloys, which make them good candidates as coating materials. In this study, structural AA 6028 alloy is used as the base material. Four different coating materials were used. The first one is Al-Si alloy that has Si content near eutectic composition. The second, third, and fourth ones are Al-6 pctSi-based reinforced with TiB2 and Al3Ti nano-particles produced by addition of Al-Ti5-B1 master alloy with different weight percentages (1, 2, and 3 pct). The coating treatment was carried out with the aid of GTAW process. The microstructures of the base and coated materials were investigated using optical microscope and scanning electron microscope equipped with EDX analyzer. Microhardness of the base material and the coated layer were evaluated using a microhardness tester. GTAW process results in almost sound coated layer on 6028 aluminum alloy with the used four coating materials. The coating materials of Al-12 pct Si alloy resulted in very fine dendritic Al-Si eutectic structure. The interface between the coated layer and the base metal was very clean. The coated layer was almost free from porosities or other defects. The coating materials of Al-6 pct Si-based mixed with Al-Ti5-B1 master alloy with different percentages (1, 2, and 3 pct), results in coated layer consisted of matrix of fine dendrite eutectic morphology structure inside α-Al grains. Many fine in situ TiAl3 and TiB2 intermetallics were precipitated almost at the grain boundary of α-Al grains. The amounts of these precipitates are increased by increasing the addition of Al-Ti5-B1 master alloy. The surface hardness of the 6028 aluminum alloy base metal was improved with the entire four used surface coating materials. The improvement reached to about 85 pct by the first type of

  12. Estudio del mecanismo de eliminación demagnesio de aleaciones Al-Si en estado líquido mediante inyección de minerales base sílice

    Directory of Open Access Journals (Sweden)

    Muñoz-Arroyo, R.

    2010-08-01

    Full Text Available In order to eliminate magnesium from an A 380 Al-Si alloy at 750°C, the submerged powder injection method, using an inert carrier gas (Ar, was applied. The injected powders in the liquid aluminum bath were zeolite, silica and mixtures of zeolite-silica minerals. For each experiment the response variables were: eliminated magnesium versus injection time and quantity of drosses produced. Chemical analysis by atomic absorption spectrometry showed that mixtures of silica-zeolite 66:34 wt% have the best results with regarding to the removal magnesium from 1 to 0.0066 wt%. During the elimination of magnesium complex stoichiometry compounds were formed due to the reactions among zeolite, water steam and liquid aluminum. These compounds were analyzed by XRD, SEM and TEM. The results obtained, along with using the FactSage 6 thermodynamic software, allowed to elucidate the reaction mechanism between the minerals used and liquid aluminum.

    Se empleó el método de inyección sumergida de polvos por medio de un gas de arrastre inerte (Ar con el fin de eliminar el magnesio de la aleación Al-Si A380 a 750 °C. Los polvos inyectados al baño de metal fundido fueron zeolita mineral, arena sílice y mezclas de ambas. Las variables de respuesta medidas fueron el contenido de magnesio en el baño metálico respecto al tiempo de inyección y las mermas de metal al final de cada experimento. En el análisis de resultados, la mezcla sílice:zeolita 66:34 % e.p. obtuvo la mayor eficiencia, lográndose una disminución en el contenido de magnesio en el baño metálico de 1 a 0.0066 % e.p. Los productos de reacción se analizaron por difracción de rayos-X, microscopía electrónica de barrido y de transmisión. Los resultados de estos análisis y el empleo del paquete termodinámico FactSage, versión 6, permitieron justificar el mecanismo de reacción entre los minerales y el aluminio líquido.

  13. O oraloma da diabetes melitos tipo 1 vs diabetes melitos tipo 2 - um estudo comparativo

    OpenAIRE

    2013-01-01

    A Diabetes Melitos é uma doença de grande prevalência a nível mundial e os seus mecanismos fisiopatológicos não são ainda totalmente conhecidos. Actualmente, a terapêutica seguida em casos de Diabetes Melitos é eminentemente sintomática consistindo na administração de insulina nos casos de Diabetes Melitos tipo 1 ou quando se verifica a falência das células beta do pâncreas de pacientes com Diabetes Melitos tipo 2, ou no controlo da glicemia nos casos de Diabetes Melitos ...

  14. Glaucoma secundario a neurofibromatosis tipo-1

    Directory of Open Access Journals (Sweden)

    Anay Martínez Díaz

    2012-02-01

    Full Text Available Paciente de 59 años de edad, con antecedentes de neurofibromatosis tipo 1 y trauma contuso del ojo derecho desde hace años. Acudió a consulta de oftalmología refiriendo disminución lenta de la visión; al examen físico se constató una agudeza visual de 0.6 en ambos ojos, así como disminución concéntrica del campo visual en la perimetría por confrontación. El examen objetivo mostró en los anexos una pingüécula en ojo derecho y pterigion grado II en ojo izquierdo; en segmento anterior, múltiples nódulos de Lisch en el iris de ambos ojos, y en el ojo derecho, pupila ligeramente midriática, pero reactiva. Se le realizó gonoscopia, oftalmoscopia y perimetría Humphry; en esta última se halló un escotoma arqueado en ojo derecho, y un defecto superior arqueado en el ojo izquierdo. Se concluyó el caso con los diagnósticos de catarata presenil incipiente y glaucoma secundario a neurofibromatosis tipo 1.

  15. The effect of the interlayer element on the exfoliation of layered Mo2AC (A = Al, Si, P, Ga, Ge, As or In MAX phases into two-dimensional Mo2C nanosheets

    Directory of Open Access Journals (Sweden)

    Mohammad Khazaei

    2014-01-01

    Full Text Available The experimental exfoliation of layered, ternary transition-metal carbide and nitride compounds, known as MAX phases, into two-dimensional (2D nanosheets, is a great development in the synthesis of novel low-dimensional inorganic systems. Among the MAX phases, Mo-containing ones might be considered as the source for obtaining Mo2C nanosheets with potentially unique properties, if they could be exfoliated. Here, by using a set of first-principles calculations, we discuss the effect of the interlayer 'A' element on the exfoliation of Mo2AC (A = Al, Si, P, Ga, Ge, As or In MAX phases into the 2D Mo2C nanosheets. Based on the calculated exfoliation energies and the elastic constants, we propose that Mo2InC with the lowest exfoliation energy and the highest elastic constant anisotropy between C11 and C33 might be a suitable compound for exfoliation into 2D Mo2C nanosheets.

  16. Effect of Al{sub 2}Cu precipitates size and mass transport on the polarisation behaviour of age-hardened Al-Si-Cu-Mg alloys in 0.05 M NaCl

    Energy Technology Data Exchange (ETDEWEB)

    Vieira, A.C., E-mail: catarina.vieira@engmateriais.eng.uminho.p [University of Minho, Centre for Mechanics and Materials Technologies (CT2M), 4800-058 Guimaraes (Portugal); Pinto, A.M.; Rocha, L.A. [University of Minho, Centre for Mechanics and Materials Technologies (CT2M), 4800-058 Guimaraes (Portugal); Mischler, S. [Ecole Polytechnique Federale de Lausanne (EPFL), Tribology and Interface Chemistry Group, 1015 Lausanne (Switzerland)

    2011-04-15

    Research highlights: {yields} Influence of the size distribution of Al-Cu phases on the electrochemical behaviour of well defined alloys under controlled mass transport conditions (RDE). {yields} Oxygen reduction occurs only the Al{sub 2}Cu phases. {yields} Thinner Al-Cu grains the oxygen reduction current deviates at high rotation rates from the Levich behaviour. - Abstract: The electrochemical behaviour of age-hardened Al-Si-Cu-Mg alloys was investigated in a 0.05 M NaCl solution under controlled mass transport conditions using a rotating disk electrode. This work aimed at getting better understanding of the effect of the alloy microstructure, in particular the size distribution of Al{sub 2}Cu phase, on the corrosion behaviour of the alloy. Three different size distributions of the Al{sub 2}Cu phase were obtained through appropriate heat treatments. The cathodic reduction of oxygen was found to occur mainly on the Al{sub 2}Cu phases acting as preferential cathodes. Small sized Al{sub 2}Cu phases were found to promote at high rotation rates a transition from a 4 electron to a 2 electron dominated oxygen reduction mechanisms.

  17. Degradation processes in Al/SiC{sub p}/MgAl{sub 2}O{sub 4} composites prepared from recycled aluminum with fly ash and rice hull ash

    Energy Technology Data Exchange (ETDEWEB)

    Pech-Canul, M.I.; Escalera-Lozano, R.; Rendon-Angeles, J.C.; Lopez-Cuevas, J. [Cinvestav Saltillo, Carr. Saltillo-Mty. Km. 13, Saltillo, Coah, Mexico 25900 (Mexico); Pech-Canul, M.A. [Cinvestav Merida, Km. 6 Antigua Carr. a Progreso Apdo. Postal 73, Cordemex. Merida, Yuc., Mexico 97310 (Mexico)

    2007-11-15

    The degradation characteristics of Al/SiC{sub p}/spinel composites prepared with fly ash (FA) and rice hull ash (RHA) under environmental conditions were investigated. Composite specimens were prepared with recycled aluminum via reactive infiltration in the temperature range 1050-1150 C for 50-70 min and, in argon atmosphere at a pressure slightly above that of the atmospheric pressure. Results reveal that although both FA and RHA help in preventing SiC{sub p} dissolution and the subsequent chemical degradation of the composites, due to the interaction of native carbon in FA with liquid aluminum, FA-composites are susceptible to corrosion via Al{sub 4}C{sub 3}. Moreover, this phase accelerates the degradation process and increases the damage severity. The primary corrosion mechanism in both types of composites is attributed to microgalvanic coupling between the intermetallic Mg{sub 2}Si and the matrix. Accordingly, an appropriate control of the Si/(Si + Mg) molar ratio in the aluminum alloy hinders the Mg{sub 2}Si corrosion mechanism in both types of composites and a proper FA calcination prevents chemical degradation in FA composites. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  18. Bulk modulus of basic sodalite, Na8[AlSiO4]6(OH)2·2H2O, a possible zeolitic precursor in coal-fly-ash-based geopolymers

    KAUST Repository

    Oh, Jae Eun

    2011-01-01

    Synthetic basic sodalite, Na8[AlSiO4] 6(OH)2•2H2O, cubic, P43n, (also known as hydroxysodalite hydrate) was prepared by the alkaline activation of amorphous aluminosilicate glass, obtained from the phase separation of Class F fly ash. The sample was subjected to a process similar to geopolymerization, using high concentrations of a NaOH solution at 90 °C for 24 hours. Basic sodalite was chosen as a representative analogue of the zeolite precursor existing in Na-based Class F fly ash geopolymers. To determine its bulk modulus, high-pressure synchrotron X-ray powder diffraction was applied using a diamond anvil cell (DAC) up to a pressure of 4.5 GPa. A curve-fit with a truncated third-order Birch-Murnaghan equation of state with a fixed K\\'o = 4 to pressure-normalized volume data yielded the isothermal bulk modulus, K o = 43 ± 4 GPa, indicating that basic sodalite is more compressible than sodalite, possibly due to a difference in interactions between the framework host and the guest molecules. © 2010 Elsevier Ltd.

  19. Wetting and reaction characteristics of crystalline and amorphous SiO2 derived rice-husk ash and SiO2/SiC substrates with Al-Si-Mg alloys

    Science.gov (United States)

    Bahrami, A.; Pech-Canul, M. I.; Gutiérrez, C. A.; Soltani, N.

    2015-12-01

    A study of the wetting behavior of three substrate types (SiC, SiO2-derived RHA and SiC/SiO2-derived RHA) by two Al-Si-Mg alloys using the sessile drop method has been conducted, using amorphous and crystalline SiO2 in the experiment. Mostly, there is a transition from non-wetting to wetting contact angles, being the lowest θ values achieved with the alloy of high Mg content in contact with amorphous SiO2. The observed wetting behavior is attributed to the deposited Mg on the substrates. A strong diffusion of Si from the SiC/Amorphous RHA substrate into the metal drop explains the free Si segregated at the drop/substrate interface and drop surface. Although incorporation of both SiO2-derived RHA structures into the SiC powder compact substrates increases the contact angles in comparison with the SiC substrate alone, the still observed acute contact angles in RHA/SiC substrates make them promising for fabrication of composites with high volume fraction of reinforcement by the pressureless infiltration technique. The observed wetting characteristics, with decrease in surface tension and contact angles is explained by surface related phenomena. Based on contact angle changes, drop dimensions and surface tension values, as well as on the interfacial elemental mapping, and XRD analysis of substrates, some wetting and reaction pathways are proposed and discussed.

  20. 杭州维修基地自行改装A319/A320/A321液压式飞机牵引杆

    Institute of Scientific and Technical Information of China (English)

    贾杰; 方坚

    2007-01-01

    本文参考空客AMM手册和GROUND EQUIPMENT MANUAL-A319/A320/A321 TOWBAR手册的要求,自行加工改装组件,对现有A319/A320/A321液压式牵引杆进行了改装,这对延长牵引杆使用寿命,提高设备可用率,降低工作者劳动强度,以及降低杭州维修基地工具设备维修成本,都具有重要的现实意义。

  1. Estereótipos e mulheres na cultura marroquina

    OpenAIRE

    Sadiqi,Fatima

    2008-01-01

    Estereótipos sobre as mulheres no Marrocos podem ser caracterizados como crenças culturais incompletas e inexatas mantidas por algumas pessoas e que se encontram inscritos em expressões lingüísticas ou em discursos subliminares. A cultura popular marroquina emprega representações poderosas para transmitir e sustentar tais estereótipos. Embora existam alguns estereótipos positivos, a maioria dos estereótipos sobre as mulheres no Marrocos é negativa e reflete ditames patriarcais subliminares qu...

  2. Ejemplares tipo de Asteraceae (= Compositae de A. L. Cabrera

    Directory of Open Access Journals (Sweden)

    Susana E. Freire

    2000-01-01

    Full Text Available Freire, S. E. & Iharlegui, L. 2000. Ejemplares tipo de Asteraceae (= Compositae de A. L.Cabrera. Darwiniana 38(3-4: 307-364.El presente trabajo representa un catálogo de los ejemplares tipo de 426 especies y 82 variedades deAsteraceae descriptas por A. L. Cabrera entre los años 1931 y 1999. Los taxones se presentan en ordenalfabético. Para cada taxón se indica: diagnosis original, tipo nomenclatural, categoría del tipo, herbario,etiqueta original y nombre actualizado

  3. Effects of T6 heat treatment on mechanical, abrasive and erosive-corrosive wear properties of eutectic Al-Si alloy%T6热处理对共晶Al-Si合金力学性能、耐磨和抗蚀性能的影响

    Institute of Scientific and Technical Information of China (English)

    A. K. GUPTA; B. K. PRASAD; R. K. PAJNOO; S. DAS

    2012-01-01

    对共晶Al-Si合金的耐磨、抗蚀性能进行研究.通过控制T6热处理参数来改变共晶Al-Si合金的组织,研究组织变化对合金的硬度、强度和拉伸性能的影响,以及对抗冲蚀和腐蚀性能的影响.采用Al-Si合金制备了一典型的农机零部件.并将Al-Si合金与常用的农机用铝材的性能进行比较.结果表明,合金的化学成分、显微组织、载荷、滑动距离和试验环境对材料的耐磨、抗冲蚀和腐蚀性能有很大的影响.铸态Al-Si合金的性能要明显优于传统的铝材,而且T6热处理能够改善Al-Si合金的性能.因此,可采用Al-Si合金来替代传统的铝材制造农机.%The abrasive and erosive-corrosive properties of eutectic Al-Si (LM6) alloy were studied.Microstructural features of the alloy were altered by controlling the T6 heat treatment parameter,and their influence on hardness,strength and elongation,and response of the samples in erosion-corrosion and abrasion conditions were studied.Characteristics of the Al-Si alloy samples were compared with those of Al conventionally used in agricultural machineries.Fabrication of a typical component using the Al-Si alloy was also explored in order to understand the feasibility of using the alloy system for the envisaged applications.The study suggests the response of the samples in different conditions to be greatly influenced by parameters like chemical composition,microstructural features and applied load,traversal distance and test environment.The performance of even the as cast Al-Si alloy is far superior to that of the conventional Al samples,while the T6 heat treated Al-Si alloy shows improved performance.Accordingly,the as-cast as well as T6 heat treated Al-Si alloy has potential for applications in agriculture as a replacement for the conventionally used Al.

  4. 铁定千元机 索尼Xperia Tipo/Tipo Dual

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    除了XperiaMiro,还有另外一对因为疯狂点击而早产的双胞胎——XperiaTipo和XperiaTipoDual。两机外观上一摸一样。前者共有白、黑、蓝、红四色可选,后者仅有银、黑两色。Tipoi两兄弟都内置800MHz高通处理器、512MBRAM以及320万像素摄像头,屏幕再度缩减为3.2英寸HVGA级别。具备抗刮划的能力。其中,TipoDual还是一部支持双卡双待的产品.非常符合国内运营商千元机的定制标准。

  5. Miocardiopatía tipo Takotsubo

    Directory of Open Access Journals (Sweden)

    Juan José Ramírez Chaves

    2014-06-01

    Full Text Available La miocardiopatía adquirida de tipo Takotsubo ha sido descrita desde 1991 en pacientes principalmente del género feme­nino, post menopáusicas, quienes posterior a un evento estresante físico o psicológico asocian clínica de dolor precordial, con cambios electrocardiográficos, alteraciones transitorias de contractilidad de predominio anteroapical del ventrículo izquierdo (VI y elevación de los biomarcadores cardiacos, en ausencia de una enfermedad arterial coronaria (EAC aguda como mecanismo desencadenante del cuadro. La fisiopatología no ha sido completamente dilucidada pero existe con­senso sobre la acción tóxica de las catecolaminas sobre el miocardio. El pronóstico es variable y va desde dolor, insuficien­cia cardiaca, choque cardiogénico hasta, la muerte; por lo tanto, constituye un desafío en el diagnóstico diferencial de las causas no ateroescleróticas generadoras de un síndrome coronario agudo (SCA.

  6. Influence of Age Hardening Parameters on the Microstructure and Properties of the AlSi7Mg Sand Cast Alloy / Wpływ Parametrów Utwardzania Wydzieleniowego Na Strukturę I W Łaściwości Stopu Alsi7mg

    Directory of Open Access Journals (Sweden)

    Poloczek Ł.

    2015-12-01

    Full Text Available Aluminium alloys are characterized by a low density, acceptable mechanical properties and good technological properties. This unique connection of features made aluminium alloys perfect structural material for the transportation industry. Also, due to their good electrical conductivity they also found application in energy production industry. High mechanical properties and electrical conductivity of the Al-Si alloys with Mg addition may be achieved by heat treatment. However, the highest mechanical properties are achieved in the early stages of age hardening - due to precipitation of coherent phases, while high electrical conductivity may be achieved only by prolonged aging, during precipitation of semi-coherent or fully noncoherent, coarse phases. Carefully heat treated AlSi7Mg alloy may exhibit both fairly high electrical conductivity and slightly increased mechanical properties. The following article present results of the research of influence of heat treatment on the properties and microstructure of sand cast AlSi7Mg alloy. Microstructure observations were performed using light microscopy, scanning electron and scanning-transmission electron microscopy. Hardness and electrical conductivity of the AlSi7Mg alloy were investigated both in as-cast condition and after heat treatment. Maximum hardness of the alloy is achieved after solutioning at 540°C for 8h, followed by 72h of aging at 150°C, while maximal electrical conductivity after solutioning at 540°C for 48h, followed by 96h of aging at 180°C. Increase of the electrical conductivity is attributed to increasing distance between Si crystals and precipitation of semi coherent phases.

  7. Doença cerebrovascular tipo "moyamoya"

    Directory of Open Access Journals (Sweden)

    Reynaldo A. Brandt

    1976-09-01

    Full Text Available É relatado o caso de um paciente masculino, branco, 34 anos, que apresentou hemorragia meníngea sem sinais de comprometimento cerebral. A carotidoangiografia direita mostrou as alterações típicas do "moyamoya", com estenose da artéria carótida interna ao nível do sifão, acima da origem da artéria comunicante posterior; há uma rede vascular angiomatosa anormal projetando-se na base do cérebro, da qual nascem as artérias cerebrais anterior e média, sendo as artérias comunicante e cerebral posterior hipertrofiadas e de trajeto tortuoso; há anastomoses meningo-corticiais, sendo as artérias meníngeas hipertrofiadas. A carotidoangiografia esquerda mostrou hipertrofia das artérias carótidas comum e interna, com contrastação de ambas as artérias cerebrais anteriores e médias a partir deste lado; a artéria comunicante anterior é do tipo fetal e há a presença anômala da artéria cerebral anterior mediana do corpo caloso. Estes dados apoiam a teoria segundo a qual a doença constitui anomalia do desenvolvimento vascular encefálico, não tendo sido encontrado outro caso na literatura com hipertrofia vicariante da artéria carótida interna contralateral à da lesão típica do "moyamoya".

  8. Die Casting Technology of Hypereutectic Al-Si Alloy Clutch Gear with High Strength and Wear Resistance%高强耐磨过共晶铝合金离合器齿轮的压铸技术

    Institute of Scientific and Technical Information of China (English)

    万里; 杨剑霞; 刘后尧; 吴湛方; 陈国强; 赖沛基

    2012-01-01

    Aiming at die casting thick-walled ADC automobile clutch gear, P-Cu modification on hypereu-tectic Al-Si alloy suitable for die casting was conducted. Die casting scheme for clutch gear was designed and simulated, meanwhile, vacuum die casting and local pressurization technology were developed. The results show that with 0. 1 % P addition, ADC14 exhibits good modification effects with 6 h modification time, where primary Si phase in the alloy reaches 20~40 μm with uniform distribution, and the depth of Si particle depletion zone on surface of the castings is in the range of 0. 18~0. 20 mm. At given injecting parameters, the mechanical vacuum valve is superior to zig-zag valve in vacuum effects, and the rejected rate with gas hole is decreased by 10%. Shrinkage porosity (hole) at thick-wall of the gear can be effectively eliminated by optimized local pressurization, the quality of the gear is improved, and qualification rate of mass-production is more than 95%.%针对压铸成形的ADCl4汽车离合器齿轮厚壁部件,研究了适于压铸的过共晶Al-Si合金的P-Cu变质处理工艺.设计并模拟了齿轮的压铸工艺方案,开发了真空压铸及局部加压技术.结果表明,当P的加入量为0.1%时,ADC14的变质效果好,变质时间可达6h.铸件中初生Si尺寸为20~40 μm,分布均匀;铸件表面的Si贫乏区深度在0.18~0.20 mm范围内.在相同压射参数下,采用机械式真空阀比搓衣板式排气阀的真空效果好,铸件的气孔缺陷废品率下降10%以上.优化后的局部加压技术消除了厚壁部位的缩松缺陷,提高了铸件内部质量.批量生产合格率达95%以上.

  9. The ammonium ion in a silicate under compression: infrared spectroscopy and powder X-ray diffraction of NH4AlSi3O8—buddingtonite to 30 GPa

    Science.gov (United States)

    E. Vennari, Cara; O'Bannon, Earl F.; Williams, Quentin

    2017-02-01

    The behavior of the ammoniated feldspar buddingtonite, NH4AlSi3O8, has been studied using infrared (IR) spectroscopy up to 30 GPa and using synchrotron powder X-ray diffraction to 10 GPa at room temperature. We examine the bonding of the ammonium ion under pressure and in particular whether hydrogen bonding is enhanced by compaction, as well as probe how the ammonium ion affects the elasticity and behavior of the aluminosilicate framework at pressure. Powder diffraction data yield a bulk modulus of 49 GPa for a pressure derivative of 4, implying that the ammonium ion substitution may induce a modest softening of the feldspar lattice relative to the potassium ion. Under compression, the N-H vibrations are remarkably insensitive to pressure throughout the pressure range of these experiments. However, the vibrations of the aluminosilicate framework of buddingtonite undergo changes in their slope at 13 GPa, implying that a change in compressional mechanism occurs near this pressure, but the vibrational modes of the ammonium molecule show little response to this change. These results show that (1) there is little, if any, enhancement of hydrogen bonding between the ammonium ion and the oxygen ions of the silica and aluminum tetrahedral framework under pressure, as manifested by the slight (and mostly positive) shifts in the N-H stretching vibrations of the ammonium ion; (2) ordering of the ammonium ion is not observed under compression, as no changes in peak width or in the general appearance of the spectra are observed under compression; and (3) structural changes induced by pressure in the aluminosilicate framework do not produce significant changes in the bonding of the ammonium ion. Hence, it appears that the ammonium ion interacts minimally with its surrounding lattice, even at high pressures: Its behavior is compatible with it being, aside from Coulombic attraction to the oxygen-dominated matrix, a largely non-interactive guest molecule within the silicate

  10. Microstructure of laser-welded joints of Fe-Mn-Al-Si TRIP/TWIP steels%Fe-Mn-Al-Si系TRIP/TWIP钢激光焊接接头的微观组织研究

    Institute of Scientific and Technical Information of China (English)

    谢盼; 伍翠兰; 艾倍倍; 陈汪林; 陈燕; 陈亚

    2013-01-01

    采用光纤激光器对两种锰含量分别为20wt.%和29wt.%的Fe-Mn-Al-Si系TRIP/TWIP钢进行激光焊接.利用扫描电子显微镜(SEM)、能谱仪(EDS)、电子背散射衍射仪(EBSD)和透射电子显微镜(TEM)对接头的显微组织进行研究.结果表明:靠近熔合线的焊缝组织以柱状晶为主,而焊缝心部为细小的等轴晶且出现大量AlN纳米颗粒;焊缝组织的孪晶界比例比母材的大幅度降低,但仍然达到了15.8%;熔合线宽1 μm,富Fe、Mn而贫Al、Si;焊缝在凝固过程中,先形成γ-奥氏体,当遇到应力集中时发生局部ε-马氏体的相变来缓解应力,避免裂纹形成.%Two types of Fe-Mn-Al-Si TRIP/TWIP steels with different Mn concentrations,which are respectively 20 wt% and 29 wt%,were welded by fiber laser welding technique.The microstructures of the weld joints were investigated using scanning electron microscope (SEM),X-ray energy disperse spectroscopy (EDS),electron backscatter diffraction technology (EBSD) and transmission electron microscopy (TEM).The results show that the fusion zone (FZ) adjacent to the fusion lines was made up of columnar grains while the centre of the FZ consisted of equiaxed grains,in which a great deal of AlN nano-particles were formed.The fraction of twin boundaries of FZ is about 15.8% although the twin boundaries have decreased greatly compared with that of the base materials.The fusion lines are rich in Fe and Mn but lack of Al and Si.In the process of solidification of the FZ,the austenite first formed and some austenite transformed into ε-martensite at the stress concentration regions,which can relieve some stress and prevent formation cracks.

  11. Fenótipo Rett em paciente com cariótipo XXY: relato de caso

    Directory of Open Access Journals (Sweden)

    SCHWARTZMAN JOSÉ SALOMÃO

    1998-01-01

    Full Text Available Relatamos o caso de um menino com cariótipo XXY que apresenta desordem neurológica progressiva com início por volta dos 11 meses de idade, com estagnação do desenvolvimento seguida de regressão. A criança apresenta, ainda, movimentos estereotipados de mãos, apraxia manual e microcefalia. Investigações não constataram presença de qualquer condição neurológica ou sistêmica definida que pudesse ser apontada como possível etiologia para o quadro descrito. Trata-se de menino com alterações fenotípicas muito similares àquelas consideradas típicas para a síndrome de Rett que, associadas com a alteração cromossômica constatada (cariótipo XXY, constituem quadro de evidente interesse científico.

  12. Genética de la diabetes mellitus tipo 2

    OpenAIRE

    Carmen Carrillo; Arturo Panduro Cerda

    2001-01-01

    Factores genéticos predisponen a la diabetesmellitus (DM) tipo 2 y el desarrollo de la enfermedad depende en gran parte de la alimentación y actividad física (factores ambientales).Existen familias cuyos miembros presentan DMtipo 2 solamente o bien diferentes tipos de diabetes. En general se presenta un patrón de herencia multifactorial, rara vez autosómico dominante o mitocondrial. El riesgo que tienen losfamiliares de pacientes con DM tipo 2 se establece con el valor lambda el cual depende ...

  13. Primeiro caso de botulismo tipo F, em Portugal

    OpenAIRE

    Saraiva, Margarida; Lopes, Teresa Teixeira; Militão, André; Ribeiro, Rosa Santos; Coelho, Adelaide; Moura, Isabel Bastos; Pena, Cláudia; Bonito, Conceição Costa; Cunha, Isabel Campos; Sousa, Isabel; Toscano, Maria Manuel; Gomes, Carlos Orta; Soares, Elsa; Tavares, António; Calhau, Maria Antónia

    2016-01-01

    A nível mundial, estão descritos poucos casos de botulismo tipo F em humanos. Em julho de 2016 foi identificado o primeiro caso de botulismo tipo F, em Portugal. Foi detetada toxina botulínica tipo F (BoNT/F) nas fezes de um doente com quadro clínico típico de botulismo e isolada a estirpe de Clostridium botulinum produtora de BoNT/F. Worldwide few cases of type F botulism are described in humans. In July 2016 the first case of type F botulism in Portugal was identified. ...

  14. Tipos de interés de los productos bancarios

    OpenAIRE

    Gonzalo Aguado, David

    2016-01-01

    EI trabajo analiza los tipos de interes que las entidades financieras establecen en sus productos. Se configura en tres bloques: Operaciones de Activo, Operaciones de Pasivo y Otras Operaciones. Se puede comprobar que tienen dos opciones : Aplicar un tipo de interés fijo, con el que desde el primer momento conocemos la totalidad de lo que vamos a pagar. La otra opción es aplicar un tipo de interés variable, normalmente aplicando el Euribor más una parte fija. Dentro de cada producto bancario,...

  15. Nuevo tipo de apoyos y articulaciones

    Directory of Open Access Journals (Sweden)

    Andrä, Fritz Leonhardt

    1963-11-01

    of theoretical and technical difficulties inherent in these bearings: they also express acknowledgement to German individuals and institutions, for their contribution to this investigation.Las tendencias actuales son funciones que dependen directamente de la presencia creciente y mejorada de los materiales de construcción que se ofrecen al comercio. En el campo de los materiales cabe una marcada subdivisión en naturales y preparados o sintéticos; estos últimos constituyen la preocupación de los autores para su aprovechamiento y adecuada aplicación. De entre ellos, las resinas sintéticas o caucho artificial, dentro de las distintas especies de la extensa familia han gozado de un lugar preferente en este estudio de nuevos tipos de apoyos que presentan los notables ingenieros alemanes Wolfhart Andrä y Fritz Leonhardt. En los ensayos de laboratorio y a escala natural, las variedades comerciales de estas resinas, conocidas con los nombres de «neopreno» y «Teflon», han sido elegidas por presentar, por lo menos actualmente, características marcadamente apropiadas a la finalidad perseguida en este estudio, del que se confía ulterior desarrollo y mejor acogida, por las importantes aplicaciones que de él se derivan en el campo de la ingeniería y construcción. Los autores estudian con detenimiento y sobrado rigor para las aplicaciones prácticas las deformaciones que de estos materiales se espera al someterlos a fuerzas de gran concentración. En los apoyos juega particular interés la distribución de la carga siempre concentrada en superficies relativamente pequeñas, lo que exige elevadas cargas unitarias y, con ello, la utilización de materiales extremadamente nobles para resistirlas con la resistencia que las deformaciones instantáneas requieren para recobrar rápidamente la posición de estabilidad perdida momentáneamente. La fatiga en el ciclo de deformaciones relaja los materiales, y ha de tenerse presente al considerar las características que los

  16. Tipo de alimentación en pacientes con diabetes mellitus tipo 2: una muestra de Monterrey (México)

    OpenAIRE

    Samaniego Garay, Rafael Armando; Universidad Autónoma de Zacatecas; Álvarez Bermúdez, Javier; Universidad Autónoma de Nuevo León

    2013-01-01

    El presente trabajo tuvo el propósito de realizar un análisis descriptivo de la frecuencia y tipo de alimentos que se consumen en un grupo de personas con este padecimiento. Se describen los resultados obtenidos en 94 pacientes con diabetes tipo 2 que asistían a un hospital universitario, encontrándose que el tipo de dieta que realizan no es la apropiada, que este recurso es menos utilizado que otras actividades de tratamiento para el control de la diabetes y que el nivel de glucemia en ayuna...

  17. Parâmetros de desempenho e carcaça de genótipos de frangos tipo caipira

    OpenAIRE

    Veloso,R.C.; PIRES, A. V.; R.A. Torres Filho; Pinheiro,S.R.F.; Winkelstroter,L.K.; Alcântara,D.C.; Cruz,C.C.D.C.S.

    2014-01-01

    Objetivou-se com este trabalho avaliar as características de desempenho e de carcaça de sete genótipos de frangos tipo caipira da linhagem Redbro. Foram utilizados 840 pintos de um dia, machos, distribuídos em delineamento inteiramente ao acaso, dos seguintes genótipos: Caboclo, Carijó, Colorpak, Gigante Negro, Pesadão Vermelho, Pescoço Pelado e Tricolor. Os frangos foram alojados em 28 boxes, sendo 30 frangos por boxe, em galpão de alvenaria com a...

  18. Algunos swaps de tipos de interés

    OpenAIRE

    Fernández, Pablo

    2013-01-01

    Empresa A firmó, el 27 de febrero de 2008, un contrato de crédito de 800.000 euros por el que pagaría a Banco B el tipo euríbor más un 1% anual (véase la Figura 1 del caso). La empresa A invertía en plantas de energía solar fotovoltaica. Con este crédito, Empresa A tiene lo que se denomina "riesgo de tipo de interés", que es incertidumbre en el tipo de interés que pagará. El tipo de interés a pagar será alto (grande) si el euríbor sube, y bajo (pequeño) si el euríbor desciende.

  19. Experimental Study of Selective Laser Melted AlSi12%铝合金粉末选择性激光熔化成形工艺优化试验研究

    Institute of Scientific and Technical Information of China (English)

    张骁丽; 齐欢; 魏青松

    2013-01-01

    选择性激光熔化技术(Selective Laser Melting,SLM)是最近十几年发展起来的一种先进快速成形技术,利用高能激光束熔化金属粉末,逐层堆积,直接成形高性能复杂金属零部件.SLM可成形的粉末材料广泛,其中铝合金作为轻金属材料有优良的物理、化学和机械性能,在很多领域获得了广泛应用,但是铝合金自身的特性(如易氧化,高反射性和导热性等)增加了选择性激光熔化制造的难度.研究使用AlSi12铝合金粉末对SLM成形工艺优化做了一系列试验研究,利用金相显微(OM)、电镜扫描(SEM)等方法分析了扫描轨迹和成形件的组织性能.采用不同工艺参数组合,在铝合金基板上进行铝合金粉末单道熔化实验,研究了激光功率、扫描速度对单熔化道形貌和宽度的影响规律;最终单道实验得出的优化工艺窗口,要求线能量密度在0.17~0.36 J/mm范围内.在优化的工艺窗口内,实施单层多道扫描,分析扫描间距和搭接率对单层形貌的影响规律,并进一步优化激光功率和扫描速度参数,得到较优工艺参数是激光功率140~180W,扫描速度700~1 000 mm/s,扫描间距0.04~0.05 mm.最后,实施块体成形,分析了成形件致密度与线能量密度的关系,并对成形件的性能作了微观表征,从粉末特性和工艺参数两方面分析孔隙的成因.

  20. Os distúrbios alimentares na diabetes mellitus tipo 1

    OpenAIRE

    Pereira, Inês Sofia Soares

    2013-01-01

    Introdução: A diabetes mellitus tipo 1 e os distúrbios alimentares são doenças frequentes na adolescência. Em ambas as condições, os pacientes dão uma grande importância ao peso corporal e à dieta. Assim, estima-se que os pacientes com diabetes mellitus tipo 1 tenham uma grande vulnerabilidade para o desenvolvimento de distúrbios alimentares (incluindo a diabulimia, um comportamento compensatório particular), que podem ter repercussões significativas na sua qualidade de vida. Os objectivos de...

  1. CARACTERIZAÇÃO PÓS-COLHEITA E SENSORIAL DE GENÓTIPOS DE BANANEIRAS TIPO PRATA

    Directory of Open Access Journals (Sweden)

    ARIANE CASTRICINI

    2015-03-01

    Full Text Available RESUMO O norte de Minas Gerais é grande produtor de banana ‘Prata-Anã’ irrigada, cultura altamente suscetível ao Mal-do-Panamá. O uso de genótipos resistentes é uma alternativa, mas os frutos devem apresentar características pós-colheita o mais próximo possível da ‘Prata-Anã’, para melhor aceitação pelos consumidores. O objetivo do trabalho foi caracterizar frutos em pós-colheita, identificar a preferência e a intenção de compra de diferentes genótipos de bananeira tipo Prata. Os genótipos Prata-Anã, BRS Platina e Fhia-18. foram caracterizados no ponto de colheita (verdes e maduros (estádio seis de maturação, por avaliações químicas, físicas e sensoriais. Quando verde, ‘BRS Platina’ apresentou maior massa fresca e tamanho que ‘Fhia-18’ e ‘Prata-Anã’. ‘Fhia-18.’ teve a tonalidade verde da casca mais intensa que a dos demais genótipos. Madura, ‘BRS Platina’ foi mais firme, mas com a mesma resistência ao despencamento que ‘Fhia-18’ e superior à ‘Prata-Anã’. ‘Fhia-18’ apresentou cor da casca com amarelo mais clara e tão brilhante quanto da ‘Prata-Anã’, mas ‘BRS Platina’ teve a tonalidade de amarelo mais intensa. Bananas ‘Fhia-18’ foram mais ácidas, ‘BRS Platina’, com menor acidez titulável, e ‘Prata-Anã’, o maior teor de sólidos solúveis. Os genótipos Prata-Anã e BRS Platina tiveram maior preferência e intenção de compra pelos consumidores, sendo as bananas ‘Prata-Anã’ em dedos e ‘BRS Platina’ e ‘Fhia-18’ em dedos, buquê e penca, as mais preferidas. Entretanto, a maioria compraria bananas ‘Prata-Anã’ em buquê e ‘BRS Platina’ e ‘Fhia-18’ em penca. Enquanto verdes, os genótipos foram semelhantes à ‘Prata-Anã’, e maiores diferenças químicas e físicas ocorreram quando maduros.

  2. Vaciamiento gástrico y diabetes mellitus tipo 2

    Directory of Open Access Journals (Sweden)

    Camilo Andrés Quintero-Cadavid

    2015-04-01

    Full Text Available El adecuado control de la diabetes mellitus tiene una gran importancia desde muchos puntos de vista. En los últimos años, se ha destacado el impacto que tienen los niveles de la glucemia postprandial sobre el manejo y las complicaciones de esta enfermedad. Controlar la hiperglucemia postprandial y, por lo tanto, su participación en el deterioro clínico de los pacientes con diabetes puede conseguirse retardando el vaciamiento gástrico y estimulando el efecto incretina, los cuales se pueden promover utilizando los análogos del péptido similar al glucagón tipo 1 (GLP-1. En este artículo se revisa el concepto del efecto incretina y la utilidad de los análogos GLP-1 en el control de la glicemia en los pacientes con diabetes mellitus tipo 2.

  3. Sobre la localidad tipo de Eunectes notaeus Cope (Serpentes: Boidae

    Directory of Open Access Journals (Sweden)

    Waller, Tomás

    2000-02-01

    Full Text Available Todas las revisiones han pasado por alto el hecho de que el mismo de la descripción, al detallar el catálogo de la colección realizada durante la expedición conducida por el Capitán T. J. Page en los ríos Paraná, Paraguay, Bermejo y Uruguay, E. D. Cope especifica claramente el lugar de procedencia del especimen tipo: "...No. 4707. Taken in the Paraguay River about thirty miles south of Fort Coimbra, Brazil, near lat. 20°S" (Cope, 1862b: 350. En definitiva, esta última debería ser considerada la localidad tipo de E. notaeus.

  4. Efectos del tipo funcional de entrenamiento sobre el ajuste lector

    OpenAIRE

    Rosalinda Arroyo Hernández; Guadalupe Mares Cárdenas

    2009-01-01

    El presente trabajo tuvo por objetivo evaluar los efectos de entrenar cinco tipos de contacto con las relaciones entre objetos y sus elaboraciones lingüísticas sobre el ajuste lector de estudiantes universitarios. Primeramente los participantes fueron expuestos a una evaluación de ajuste lector, consistente en preguntas de diferente complejidad funcional, para posteriormente ser asignados aleatoriamente a uno de cinco grupos experimentales diferenciados por el nivel de complejidad funcional d...

  5. TC4合金基体上激光熔敷钛、铝、二氧化硅碳粉末的显微组织%Microstructure of laser clad Ti+Al+SiO2+C powders on Ti6Al4V alloy

    Institute of Scientific and Technical Information of China (English)

    母久方; 胡芳友; 回丽; 何雪浤; 赵金

    2006-01-01

    Laser cladding experiment of Ti + Al + SiO2 + C was carried out on Ti6Al4V alloy substrate, thenthe microstructure of the clad layer was analyzed with SEM and its Anti - oxidation function was discussed.Analyses microstructure show that the clad coating can be divided into three zones along the depth direction:clad, binding and heat - affected zones. Ti5Si3 in the clad zone exists in the form of fine dendrites, TiAl matrix filling among Ti5Si3 dendrites plays a role of connecting the Ti5Si3 with the TiAl3 and transferring load,so the clad coating has been strengthened obviously.

  6. Research on the melt flow of aluminum alloy in the process of AlSiC infiltration%基于铝基碳化硅材料压力浸渍过程中的铝液流动性研究

    Institute of Scientific and Technical Information of China (English)

    邓星; 杨尔卫; 高永昌

    2015-01-01

    针对铝基碳化硅压力浸渍过程中铝液的流动性问题,采用ANSYS软件对铝合金熔液的注入和冷却过程进行了分析,计算表明将400 g铝合金熔液注入模腔中,铝液在注入后6.8 s内处于流动性较好的状态,随后流动性逐渐减弱。设计相同尺寸工装进行压力浸渍试验,结果表明铝液在注入6.8s内呈现比较好的流动状态,与计算结果相符;此时采用活塞加压实现了碳化硅基材的浸渍,获得了性能良好的铝基碳化硅复合材料。%Aiming at the problem of melt flow in the process of pressure infiltration for the preparation of AlSiC composite materials , it simulates the pouring and cooling process of aluminum alloy melt based on APDL program of ANSYS software.The numerical results show that the melt flow performance is excellent within 6.8seconds af-ter 400 g aluminum alloy poured to mould cavity , and then the flow performance become weak with time subse-quently .It designs the same size tooling for pressure infiltration experiment .The experiment results show that the melt flow performance is excellent with 7 seconds after aluminum alloy melt poured to mould cavity , the numerical experimental results agree with each other .It obtains AlSiC composite materials with excellent performance from the piston pressure infiltration of SiC base .

  7. Metalografía a color en aleaciones Al-Si comerciales. Optimización de las técnicas de caracterización microestructural mediante microscopía óptica de reflexión

    Directory of Open Access Journals (Sweden)

    Vander-Voort, G. F.

    2010-10-01

    Full Text Available The present demand on alloy production with improved quality requires the optimization of the metallographic procedures used on its characterization. Traditional etching techniques commonly employed for phase identification by optical metallography in aluminium alloys are not always suitable for a detailed analysis of existing phases, nor to accurately predict the mechanisms that govern the solidification process in certain detail. This work explores the potential of colour metallography to reveal at its best as-cast microstructures in Al-Si 12 alloys. For this purpose a colour etching technique, specifically developed for aluminium alloys and based on the Weck reagent. The application of such etchant has allowed the qualitative characterization of the microstructure. And it has also shown the advantages of colour metallography over black and white (B&W etching techniques.La demanda de aleaciones con calidades optimizadas conlleva la mejora continua de estas calidades, lo que viene suscitando la necesidad de mejora y optimización permanentes de las técnicas de caracterización metalográfica. Las técnicas de ataque tradicionales, utilizadas en la observación microscópica de las aleaciones de aluminio, no permiten un análisis detallado de la evolución microestructural de las fases presentes ni de parte de los mecanismos que rigen la solidificación. En el presente trabajo, se explora el potencial de la metalografía en color aplicada a las estructuras de solidificación de aleaciones Al-Si 12. Se ha utilizado un procedimiento de ataque en color, basado en un reactivo desarrollado porWeck para aleaciones de aluminio. El empleo de esta técnica ha permitido la evaluación cualitativa de la microestructura. La técnica ha permitido revelar características microestructurales que los métodos de ataque en blanco-negro no revelan.

  8. A IDENTIFICAÇÃO DE TIPOS DE LIDERANÇA A PARTIR DE ARQUÉTIPOS

    Directory of Open Access Journals (Sweden)

    Adriana Nunes Lacerda e Prestupa

    2009-09-01

    junguianos analisados por Moore e Gillette (1993 foram relacionados com características de líderes dentro do contexto organizacional. Desta forma foi possível apresentar uma tipologia rica e aplicável, onde o individuo pode se identificar e também entender o processo e a maturação das características dos arquétipos estudados para melhor desempenho dentro das organizações.

  9. Qualidade sanitária de grãos de soja tipo alimento

    OpenAIRE

    Ronaldo, Adilson Bizzeto; Universidade Estadual de Londrina; Levy, Mauricio; Universidade Estadual de Londrina; Homechin, Martin; Universidade Estadual de Londrina; Destro, Deonisio; Universidade Estadual de Londrina; Miranda, Lilian Azevedo; Universidade Estadual de Londrina

    1996-01-01

    O objetivo foi quantificar a incidência de fungos em grãos de soja (Glycine max ( L.) Merrill) provenientes de cruzamentos de soja tipo alimento com soja tipo grão. A soja tipo alimento inclui a soja com sementes grandes, com peso de cem sementes (PCS) igual ou maior que 20 gramas (soja tipo hortaliça) e a soja com sementes pequenas, com PCS menor que 10 gramas (soja para consumo na forma de brotos ou "natto"). A soja tipo grão tem sementes de tamanho médio, com PCS entre 10 e 19 gramas, e é ...

  10. Síndrome de Waardenburg tipo I: relato de caso

    Directory of Open Access Journals (Sweden)

    Patricia Capua Vieira da Silva

    2011-06-01

    Full Text Available A síndrome de Waardenburg tipo I é uma desordem auditivo-pigmentária que inclui, entre outros, perda auditiva neurossensorial congênita não progressiva, telecanto, distúrbios pigmentares de íris, cabelo e pele. Indivíduos afetados podem ter maior risco de: defeitos no tubo neural, fendas labial e palatina, anormalidades nos membros e doença de Hirschsprung. O diagnóstico é clínico, sendo necessários dois critérios maiores ou um maior e dois menores. PAX3 é o único gene conhecido associado à síndrome, sendo, entretanto, mais usado no aconselhamento genético. Quanto ao diagnóstico diferencial, podemos citar: outras causas de perda auditiva neurossensorial congênita não progressiva, outros tipo de síndrome de Waardenburg, piebaldismo, albinismo, vitiligo e síndrome de Teitz. Neste trabalho, apresenta-se um paciente masculino de 11 anos com diagnóstico de síndrome de Waardenburg tipo I. Ressalta-se a importância do oftalmologista no auxílio do diagnóstico deste raro quadro sistêmico, uma vez que inclui algumas alterações oftalmológicas. O diagnóstico precoce da síndrome permite estimulação adequada para a perda auditiva, assim como medidas preventivas em caso de gestantes afetadas no aconselhamento genético.

  11. Actividad física y diabetes mellitus tipo 2

    OpenAIRE

    Blanca Estela Bastidas Ramírez; Jesús Javier García Bañuelos; Ana Rosa Rincón Sánchez; Arturo Panduro Cerda

    2001-01-01

    Los efectos del ejercicio sobre el metabolismode la glucosa y los lípidos han sido plenamentecomprobados, por lo que se debería considerarcomo medida terapéutica y preventiva de la diabetes mellitus tipo 2. El ejercicio produce unefecto inmediato sobre la captación de glucosa, que perdura hasta por 2 hrs, provocado porla translocación de receptores GLUT4 a la membrana plasmática de músculo esquelético, pormecanismos diferentes a los desencadenadospor insulina. Además, se presenta un efecto ta...

  12. Manejo nutricio del adulto con diabetes mellitus tipo 2

    OpenAIRE

    Claudia Hunot Alexander

    2001-01-01

    El manejo nutricio del adulto con diabetes tipo2, es la parte angular en el tratamiento de esta enfermedad. Es un proceso que requiere de unconocimiento profundo de nutrición y alimenta-ción, en donde el profesional de la salud recibeun entrenamiento a profundidad en esta áreacon la finalidad de transmitir esta información alos pacientes. El establecimiento de un plan decuidado nutricio, implementado a través del pro-ceso de terapia médico nutrimental, involucrael trabajo multidisciplinario d...

  13. Tratamiento de la diabetes mellitus tipo 2. Actualidades

    OpenAIRE

    J. Miguel Escalante Pulido

    2001-01-01

    La diabetes mellitus tipo 2 es un grupo de trastornos con complejas anormalidadesmetabólicas. Estas incluyen: elevada producciónde glucosa por el hígado, deficiente secreciónde insulina por el páncreas y una pobre respuestadel organismo hacia la insulina, referido comoresistencia a la insulina. Por lo tanto, una correcta selección de los diferentes fármacos actuales es necesaria para modificar favorablemente los diferentes trastornos de esta enfermedad. Los hipoglucemiantes actuales modifican...

  14. Tipos de humor en la publicidad impresa en Colombia

    OpenAIRE

    Carolina María Cifuentes

    2005-01-01

    Una de las herramientas frecuentemente utilizadas por los publicistas para persuadir es el humor. De ahí el creciente interés por estudiar su influencia en el procesamiento, actitudes y comportamiento de los individuos. Se realizó una revisión de investigaciones sobre humor publicitario y sus efectos en la persuasión, atención, comprensión, actitudes y memoria, así como estudios sobre humor y factores culturales, de audiencia, medios masivos y tipos de producto. Se pre...

  15. Sarcopenia en pacientes con diabetes mellitus tipo 2.

    OpenAIRE

    Vergara Ruiz, José Carlos

    2015-01-01

    El riesgo de discapacidad es mayor en pacientes con diabetes mellitus tipo 2 (DM2). Buena parte del mismo se debe al envejecimiento del músculo esquelético o sarcopenia. El déficit de fuerza muscular asociado a la edad tiene mayor asociación con la pérdida de funcionalidad que el mismo proceso cuando afecta a la masa muscular esquelética, y no ocurren de forma paralela ni proporcional. Recientemente se ha propuesto el término dinapenia para referirse a ésta pérdida de fuerza muscular, con ind...

  16. Alteraciones salivares en pacientes con diabetes tipo 2

    OpenAIRE

    Carda Batalla, María del Carmen; Mosquera Lloreda, Nezly; Salom, Lucas; Gómez de Ferraris, María Elsa; Peydró Olaya, Amando

    2006-01-01

    La diabetes mellitus tipo 2 es el desorden metabólico más frecuente, siendo además causante de una importante morbi-mortalidad. En estos pacientes se han descrito alteraciones estructurales de la parotida (sialosis) que podrían comportar modificaciones en la composición salivar, así como un incremento de patología dental y periodontal. Objetivos: establecer las alteraciones bioquímicas de la saliva y su posible correlación con los hallazgos morfológicos. Diseño del estudio: se realizo u...

  17. INSULINA Y ENFERMEDAD DE ALZHEIMER: UNA DIABETES TIPO 3?

    Directory of Open Access Journals (Sweden)

    Andrés Jagua Gualdrón

    2007-03-01

    Full Text Available La enfermedad de Alzheimer es un trastorno degenerativo del sistema nervioso central cuya incidencia probablemente aumentará en los próximos años. Los resultados de investigaciones recientes relacionan esta enfermedad con trastornos en la señal de la insulina a nivel de las neuronas. ¿Es la Enfermedad de Alzheimer una diabetes tipo 3? En este documento presentamos una reseña breve de las evidencias que se levantan en torno a este modelo de la enfermedad.

  18. "The Shield": un tipo de policía diferente

    OpenAIRE

    García-Martínez, A.N. (Alberto Nahum)

    2013-01-01

    No hay ficción televisiva que se abra y se cierre mejor que The Shield. El primer asalto es salvaje: una crochet de realismo sucio y adrenalina en la jungla de asfalto, una hora que castiga el hígado hasta noquearte. «Lo del poli bueno y el poli malo se acabó por hoy. Yo soy un tipo de policía diferente», clama Vic Mackey antes de partirle los dientes a un pederasta en la sala de interrogación. Como el protagonista, The Shield (FX, 2002-08) también es un relato diferente, arriesgado, que...

  19. Sistemas de tipos en lenguajes lógico-funcionales

    OpenAIRE

    2013-01-01

    La programación lógico-funcional es un paradigma de programación declarativa muy expresivo, fruto de la combinación de la programación funcional y la programación lógica. Entre sus principales características destacan la posibilidad de de1nir funciones indeterministas, los patrones de orden superior y el uso de variables libres que se ligan a valores adecuados durante el cómputo. Desde el punto de vista de tipos, los sistemas lógico-funcionales han adoptado demaneradirectaelsistemadetiposdeDa...

  20. INTEGRACION DE UNA CELULA FLEXIBLE DE MECANIZADO, DE TIPO DOCENTE

    OpenAIRE

    2007-01-01

    Este trabajo trata sobre la integración de una célula flexible de mecanizado de tipo docente, compuesta por una fresadora didáctica CNC, marca Denford, un brazo robótico articulado de seis ejes, modelo Scorbot -ER Vplus  y un riel deslizante; todos pertenecientes al Laboratorio de Manufactura Integrada por Computador, de la Escuela de Ingeniería Mecánica de la Universidad de Talca. Las tareas que realiza esta célula flexible son controladas por un PC director  a través de un  programa, utiliz...

  1. Memoria larga en el tipo de cambio nominal: evidencia internacional

    Directory of Open Access Journals (Sweden)

    Héctor F. Salazar Núnez

    2015-01-01

    Full Text Available En este trabajo se examina la dinámica del tipo de cambio con respecto del dólar americano para varias economías, desarrolladas y en vías de desarrollo, con el fin de encontrar evidencia de memoria larga durante el periodo 1971-2012. Para ello se aplican lassiguientes pruebas: coeficiente de Hurst, correlograma, gráfico de la varianza, Geweke y Porter-Hudak, así como estimador local de Whittle de Robinson. Al respecto, Chile, China, Islandia, Israel, México y Turquía presentaron evidencia de memoria larga de acuerdo con pruebas consistentes y, en consecuencia, se estimó para ellos un modelo Autorregresivo Fraccionalmente Integrado con Medias Móviles en los dominios del tiempo y la frecuencia. En el dominio del tiempo se empleó el método de máxima verosimilitud (Sowell, 1992, y en el dominio de la frecuencia se utilizó la técnica de Fox y Taqqu (1986. Los resultados del modelo Autorregresivo Fraccionalmente Integrado con Medias Móviles muestran que Chile, China, Islandia y México presentan evidencia de memoria larga en el tipo de cambio; el método de estimación que presenta el mejor ajuste a la curva original es el método de máxima verosimilitud exacta de acuerdo con el criterio de información de Akaike.

  2. Ocorrência de Staphylococcus aureus em queijo tipo "frescal"

    Directory of Open Access Journals (Sweden)

    Almeida Filho Edvaldo Sampaio de

    2000-01-01

    Full Text Available OBJETIVO: Verificar a ocorrência de Staphylococcus aureus em uma amostra de queijo tipo Minas "frescal" comercializado na cidade de Poços de Caldas, MG, de modo a obter subsídios que permitam avaliar o risco potencial que este produto pode representar para a saúde da população consumidora. MÉTODOS: Foi investigada a presença e o número de cepas de Staphylococcus aureus em 80 amostras de queijo tipo Minas "frescal" produzido artesanalmente e comercializado na cidade de Poços de Caldas, MG, Brasil. RESULTADOS: Os resultados obtidos evidenciaram a presença de S. aureus em 40 (50,0% amostras, cujas contagens revelaram valores médios em torno de 10(5/g. CONCLUSÕES: Tais achados parecem ser extremamente preocupantes, pois além de se situarem acima do limite máximo de 10³/g estabelecido pelo Ministério da Saúde, estes valores mostraram-se muito próximos dos requeridos para a produção de enterotoxinas em quantidades suficientes para a ocorrência de surtos de intoxicação alimentar estafilocócica.

  3. 浆态床合成二甲醚用CuZnAlSi催化剂的完全液相法制备及表征%Complete liquid phase preparation and characterization of CuZnAlSi catalysts for DME synthesis in slurry reactor

    Institute of Scientific and Technical Information of China (English)

    李志红; 黄伟; 樊金串; 左志军; 谢克昌

    2009-01-01

    采用完全液相法制备了不同SiO_2含量的二甲醚(DME)合成CuZnAlSi双功能催化剂,并在浆态床反应器中评价其催化反应活性,通过in-situ XPS、XRD、BET、NH_3-TPD等方法对其物理化学性能进行研究.结果表明,CuZnAl催化剂中加入SiO_2组分,能够促进活性组分Cu的分散,并通过与AlOOH的作用调变催化剂的孔结构和表面酸性,从而提高催化剂在DME合成反应中的活性.准原位 XPS表征结果显示,还原后的催化剂表面Cu0和ZnO共同构成DME合成反应中的甲醇合成活性中心.SiO_2的加入可能导致Cu、Zn和Al组分间的相互作用减弱,催化剂稳定性降低.%A series of CuZnAlSi bifunctional catalysts with different SiO_2 contents were prepared by a complete liquid phase method, and the catalysts were characterized by using in-situ XPS, XRD, BET and NH_3-TPD. The catalytic performance was evaluated in a slurry reactor. Based on these results, it was deduced that SiO_2 in the CuZnAlSi catalyst could interact with A1OOH resulting in the change of some physicochemical properties, such as the pore structure and surface acidity, thus the catalytic activity for DME synthesis has got improved. It was found from the in-situ XPS characterization that the surface active species for the methanol synthesis in the process of DME production is composed by the reduced Cu~0 species and ZnO. However, the stability of the catalyst decreased owing to the introduction of SiO_2, which may due to a lower interaction among the components of Cu, Zn and Al.

  4. A ultra-sonografia do pâncreas é eficaz em diagnosticar o diabete melito tipo 1 e tipo 2?

    Directory of Open Access Journals (Sweden)

    Pimenta Walkyria de Paula

    2002-01-01

    Full Text Available Este trabalho foi realizado para verificar se a ultra-sonografia do pâncreas oferece dados auxiliares na classificação de diabéticos adultos dos tipos 1 e 2. O tamanho e a ecogenicidade do pâncreas foram determinados pela ultra-sonografia em 81 diabéticos, sendo 20 do tipo 1 e 61 do tipo 2 (53 obesos e oito não-obesos. Os pacientes tipo 2 obesos diferiram dos demais por apresentarem área total e diâmetro ântero-posterior do corpo do pâncreas significativamente maiores. Quanto à ecogenicidade pancreática, esta estava aumentada com maior freqüência nos diabéticos tipo 2 obesos que nos diabéticos tipo 1. Consideramos, assim, que a ultra-sonografia do pâncreas constitui metodologia auxiliar na classificação de diabéticos entre os tipo 1 e 2, sendo menos eficaz quando os últimos não são obesos.

  5. A ultra-sonografia do pâncreas é eficaz em diagnosticar o diabete melito tipo 1 e tipo 2?

    Directory of Open Access Journals (Sweden)

    Walkyria de Paula Pimenta

    2002-07-01

    Full Text Available Este trabalho foi realizado para verificar se a ultra-sonografia do pâncreas oferece dados auxiliares na classificação de diabéticos adultos dos tipos 1 e 2. O tamanho e a ecogenicidade do pâncreas foram determinados pela ultra-sonografia em 81 diabéticos, sendo 20 do tipo 1 e 61 do tipo 2 (53 obesos e oito não-obesos. Os pacientes tipo 2 obesos diferiram dos demais por apresentarem área total e diâmetro ântero-posterior do corpo do pâncreas significativamente maiores. Quanto à ecogenicidade pancreática, esta estava aumentada com maior freqüência nos diabéticos tipo 2 obesos que nos diabéticos tipo 1. Consideramos, assim, que a ultra-sonografia do pâncreas constitui metodologia auxiliar na classificação de diabéticos entre os tipo 1 e 2, sendo menos eficaz quando os últimos não são obesos.

  6. Biopirataria: reflexões sobre um tipo penal

    OpenAIRE

    Ivanira Pancheri

    2013-01-01

    O foco do presente Doutorado cinge-se ao tema Biopirataria reflexionando sob a criação de um respectivo tipo penal. Não obstante a ausência de uma conceituação jurídica uníssona sobre Biopirataria parte-se da concepção primordial de um acesso irregular ao Patrimônio Genético e ainda, aos Conhecimentos Tradicionais associados. Não se olvide todavia que, ao lado destes dois grandes nortes, comportamentos outros igualmente conformam a problemática, demandando coibição, ad exemplum, a não reparti...

  7. Terapêutica da diabetes mellitus tipo 1

    OpenAIRE

    Antunes, Ana Luisa Lopes

    2009-01-01

    Introdução: Diabetes Mellitus (DM) é uma doença metabólica de etiologia múltipla caracterizada por hiperglicemia crónica com distúrbios no metabolismo dos hidratos de carbono, lípidos e proteínas, por deficiências na secreção e/ou acção da insulina. A descoberta da insulina em 1921, foi um grande marco na sua terapêutica, aumentando a esperança e qualidade de vida dos doentes, nomeadamente na DM tipo 1. Tornou-se um fármaco salvador de vidas (life saving). A primeira a ser comercializad...

  8. COMPORTAMENTO HIGROSCÓPICO DA LINGUIÇA TIPO CALABRESA

    OpenAIRE

    Piaia, Julio Cesar Zanchet; Quadri,Marintho Bastos; Bolzan, Ariovaldo

    2012-01-01

    O presente trabalho teve como objetivo a obtenção de isotermas de dessorção de umidade da linguiça tipo calabresa cozida e defumada. As isotermas foram obtidas em três temperaturas (20, 30, e 40 °C) em condições de dessorção, através do método gravimétrico estático, com soluções de ácido sulfúrico. Os dados experimentais foram ajustados a quatro modelos matemáticos da literatura (Henderson, Oswin, GAB e BET modificado) e determinou-se o valor do conteúdo de umidade da monocamada. O produto ap...

  9. Cirurgia metabólica: cura para diabete tipo 2

    OpenAIRE

    Zeve,Jorge Luiz de Mattos; Tomaz, Carlos Alberto Bezerra

    2011-01-01

    INTRODUÇÃO: O diabete melito tipo 2 é doença metabólica caracterizada por hiperglicemia crônica que está associada com dano e insuficiência de vários órgãos. A evolução da doença é a causa mais comum de cegueira, amputações e insuficiência renal em adultos no ocidente, além de aumentar a incidência de infarto agudo do miocárdio e acidente vascular cerebral, com maior mortalidade dos pacientes. A associação dele com obesidade é relevante. Os pacientes obesos diabéticos quando submetidos ao tra...

  10. formales o categorías tipo interfase?

    Directory of Open Access Journals (Sweden)

    Julio Alfonso Piña López

    2011-01-01

    Full Text Available Se analiza la relación entre los fenómenos básicos y los fenómenos del desarrollo y la personalidad, en términos de si los primeros deberían concebirse como condición de existencia necesaria y suficiente de los segundos, y, a su vez, si los unos y los otros lo son de los últimos. Se concluye que dependiendo de cómo se plantee dicha relación, es que eventualmente tendrá sentido la construcción de teorías formales sobre el desarrollo y la personalidad, o bien caracterizar ambos fenómenos como categorías tipo interfase con fines de predicción.

  11. Tipos de socialización y desesperanza aprendida

    Directory of Open Access Journals (Sweden)

    Sandro Macassi

    1988-12-01

    Full Text Available Las nociones de alienación, falta de poder y desesperanza aprendida son revisadas. Sesenta obreros de una empresa limeña fueron evaluados en términos del tipo de socialización dominante (SD y desesperanza aprendida (DA en sus tres áreas: falta de motivación, falta de control y expectativas de no-control en el futuro. Las escalas SD y DA resultaron consistentes. El análisis de regresión múltiple con las variables grado de división del trabajo, el grado de instrucción y –en migrantes- edad de arribo y permanencia en la capital, evidenció que el único predictor de DA es el grado de instrucción, correlacionándose negativamente. Los resultados se discuten a la luz de la realidad peruana.

  12. Una propuesta de tipo investigativo - interventivo para construir resiliencia

    Directory of Open Access Journals (Sweden)

    Sandra Liliana Aya Angarita

    2012-01-01

    Full Text Available Este artículo continúa con las reflexiones planteadas en la tesis magistral “Procesos de construcciónnarrativa que organizan experiencias resilientes enfamilias en situación de desplazamiento, en la interaccióninstitución familia” (articulada a la Maestríade Psicología Clínica y de Familia de la Universidad Santo Tomás, en las que se pretende comprender losprocesos de construcción narrativa y el interventivo busca movilizar dichos procesos hacia la emergenciade experiencias resilientes. El texto muestra algunos resultados de la intención interventiva, definiendola resiliencia desde diversas perspectivas, para luego conectar dichos significados con los procesos de construcción narrativa. Finalmente se proponenideas acerca de cómo en un escenario conversacional de tipo reflexivo es posible movilizar procesos haciala construcción de experiencias resilientes.

  13. Estudo clinico da epilepsia catamenial: tipos clinicos das crises epilepticas

    Directory of Open Access Journals (Sweden)

    Arthur Oscar Schelp

    1983-06-01

    Full Text Available Foram atendidas 431 pacientes epilépticas com idades acima de 10 anos, no período de fevereiro a julho de 1981 no ambulatório de neurologia do H.C.F.M.R.P. Destas, foram selecionadas 119 pacientes com idade de 13 a 45 anos e/ou fluxo menstrual periódico e pelo menos uma crise epiléptica ao mês. As pacientes foram separadas em dois grupos, o primeiro constituído de 36 pacientes com diagnóstico de epilepsia catamenial e o segundo com 83 pacientes que apresentavam epilepsia não catamenial. Determinamos um coeficiente de prevalência de 105,9/1000 para a epilepsia catamenial. Classificamos os tipos clínicos de crises epilépticas ocorridas em pacientes com epilepsia catamenial e comparamos com as ocorridas em pacientes na menacme.

  14. Todo tipo de relacionamento consumidor-marca é eficiente?

    Directory of Open Access Journals (Sweden)

    Eliane Cristine Francisco-Maffezzolli

    2014-03-01

    Full Text Available O objetivo neste estudo foi investigar a existência de diferentes perfis de relacionamento consumidor-marca e sua respectiva eficiência na relação comercial. Três construtos da teoria de relacionamento com marcas foram avaliados: autoconexão, intimidade e interdependência com a marca. Foi realizado um survey com 441 casos. Os dados foram analisados por técnicas de cluster, fatorial e ANOVA. Três diferentes perfis foram encontrados: o relacionamento por inércia (RI, o qual sugere uma relação superficial e com menor poder de diferenciação sobre a marca; o relacionamento moderado (RM, o qual registrou avaliações intermediárias em todas as variáveis; o relacionamento verdadeiro (RV, o qual demonstra maior proximidade e conexão com a marca. Para verificar a eficiência desses tipos, foram avaliados os índices de satisfação, confiança, comprometimento e lealdade. Consumidores do tipo RI tendem a trocar de marca tão logo percebam vantagens maiores em outros concorrentes. Já os RM demonstram certa tendência de atitudes positivas em relação à marca, dependendo de seu contexto e oferta. O grupo RV demonstra maior tendência à continuidade do relacionamento. Do ponto de vista gerencial, perceber diferentes intensidades de relacionamento permite reconhecer que nem todo relacionamento é eficiente.

  15. Tipos (Guía de programación de C#)

    OpenAIRE

    MSDN, Microsoft

    2015-01-01

    C# es un lenguaje fuertemente tipado. Todas las variables y constantes tienen un tipo, al igual que toda expresión que da como resultado un valor.Cada firma de método especifica un tipo para cada parámetro de entrada y para el valor devuelto.La biblioteca de clases .NET Framework define un conjunto de tipos numéricos integrados y tipos más complejos que representan una amplia variedad de construcciones lógicas, como el sistema de archivos, conexiones de red, colecciones y matrices de objetos ...

  16. EMISSÕES SOLARES TIPO-U E TIPO-J DECIMÉTRICAS REGISTRADAS PELO BRAZILIAN SOLAR SPECTROSCOPE (BSS

    Directory of Open Access Journals (Sweden)

    José Augusto S. S. Dutra

    2013-09-01

    Full Text Available Neste trabalho são apresentados os resultados da análise de cinco emissões solares tipo-U e tipo-J registradas pelo rádio espectrógrafo “Brazilian Solar Spectroscope” (BSS em frequências decimétricas (1,0 – 2,5 GHz, entre junho de 2000 e outubro de 2001. As características espectro-temporais das emissões foram medidas a partir dos espectros dinâmicos. Considerando a emissão de plasma no segundo harmônico, foram inferidos os seguintes parâmetros da fonte emissora: densidade de fluxo inferior a 20 – 80 u.f.s.; comprimento dos arcos magnéticos da ordem de (0,3 – 5,1 ´ 1010 cm; velocidade dos feixes de elétrons de (0,47 – 1,16 ´ 105 km/s; densidade máxima dos feixes de elétrons de (0,56 - 1,95 ´ 105 cm-3; máximo de (2,53 – 7,37 ´ 1031 elétrons no feixe; temperatura do topo dos arcos magnéticos de (2,5 – 15,5 ´ 106 K; e limite inferior para a intensidade do campo magnético na região do plasma confinado de 7 – 22 G. Os resultados são comparados com determinações publicadas na literatura.

  17. Foaming behaviour of Al-Si-Cu-Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kim, A. [Kongju National University (Korea). Dept. of Mechanical Engineering; Cho, S.S. [Chungnam National University, Daejeon (Korea). School of Materials Engineering; Lee, H.J. [Hanbat National University, Daejeon (Korea). Dept. of Building Service Engineering

    2004-12-15

    The powder metallurgical route was utilised to obtain the Al-5Si-4Cu-4Mg (alloy 544) and Al-3Si-2Cu-2Mg (alloy 322) foams. Various steps such as centrifugal atomisation, mixing alloy powder and foaming agent (1 wt-%TiH{sub 2}), cold compaction of mixture, hot extrusion and foaming in a preheated furnace were performed. Foaming behaviour of the alloys was investigated by digital microscopy, image analysis, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) mapping in this study. It was found that alloy 544 takes a shorter period of time to initiate pore nucleation than alloy 322. Alloy 544 had a higher pore growth rate than alloy 322 at the same pre-set furnace temperature. In both alloys, crack-like pore nucleation occurred between aluminium alloy powders elongated in a direction parallel to the extrusion direction. Both alloys showed the same foaming sequence of crack-like pore nucleation, spherical pore growth, coalescence of neighbouring pores and collapse of pores adjacent to the free surface of specimen. The time required to start pore nucleation decreased with the increase of foaming temperature. The cell walls of both alloys consisted of {alpha}-Al phase and eutectic phase. (author)

  18. Microstructural Characterization of Beryllium Treated Al-Si Alloys

    Directory of Open Access Journals (Sweden)

    M. F. Ibrahim

    2015-01-01

    Full Text Available The present study was carried out on B356 and B357 alloys using the thermal analysis technique. Metallographic samples prepared from these castings were examined using optical microscopy and FESEM. Results revealed that beryllium causes partial modification of the eutectic Si, similar to that reported for magnesium additions. Addition of 0.8 wt.% Mg reduces the eutectic temperature by ~10°C. During solidification of alloys containing high levels of Fe and Mg, but no Sr, formation of a Be-Fe phase was detected at 611°C, close to that of α-Al. The Be-Fe phase precipitates in script-like form at or close to the β-Al5SiFe platelets. A new reaction, composed of fine particles of Si and π-Fe phase, was observed to occur near the end of solidification in high Mg-, high Fe-, and Be-containing alloys. The amount of this reaction decreased with the addition of Sr. Occasionally, Be-containing phase particles were observed as part of the reaction. Addition of Be has a noticeable effect on decreasing the β-Al5FeSi platelet length; this effect may be enhanced by addition of Sr. Beryllium addition also results in precipitation of the β-Al5FeSi phase in nodular form, which lowers its harmful effects on the alloy mechanical properties.

  19. Demencia tipo Alzheimer, deterioro cognitivo y toma de decisiones

    Directory of Open Access Journals (Sweden)

    Aurora Moreno

    2011-04-01

    Full Text Available El objetivo de este trabajo es el de conocer cómo es la toma de decisiones en la Demencia Tipo Alzheimer (DTA en situaciones de incertidumbre, si se manifiesta la tendencia al riesgo o no, y la relación que guarda la ejecución con el status cognitivo en cada una de las áreas evaluadas por los test de cribado del deterioro cognitivo propios de las demencias. Participaron 10 pacientes con DTA, y comparados con 10 sujetos controles. Se utilizó la Prueba Cartas (basada en la Iowa Gambling Task, donde los sujetos deben elegir entre varias opciones que entrañan más o menos riesgo, y una batería de cribado del deterioro cognitivo. Los resultados reflejaron que los sujetos con DTA en etapas iniciales presentan cierta tendencia al riesgo en las decisiones que toman y no desarrollan patrones estratégicos de elección. Parece que el deterioro cognitivo y el grado de afectación en las distintas áreas se relaciona con la forma en que toman decisiones.

  20. Solid state reaction synthesis of Ba{sub 0}.75Sr{sub 0}.25AlSi{sub 2}O{sub 8} - Al{sub 2}O{sub 3} ceramic composites from mechanically activated precursor mixtures

    Energy Technology Data Exchange (ETDEWEB)

    Ramos-Ramirez, M. V.; Lopez-Cuevas, J.; Rodriguez-Galicia, J. L.; Rendon-Angeles, J. C.

    2014-10-01

    Ceramic composites with Ba{sub 0}.75Sr{sub 0}.25AlSi{sub 2}O{sub 8} (SBAS)/Al{sub 2}O{sub 3} mass ratios of: 1) 90/10, 2) 70/30, and 3) 50/50, were in situ synthesized at 900-1500 degree centigrade/5 h from mixtures of fly ash, BaCO{sub 3}, SrCO{sub 3} and Al{sub 2}O{sub 3}. The green mixtures were mechanically activated for 0, 4 and 8 h in an attrition mill. As a result, the solid state reactions were faster and occurred at lower temperatures. Only the SBAS and Al{sub 2}O{sub 3} phases were obtained at 1300-1500 degree centigrade, with the SBAS present in composition 1 achieving full conversion from its hexagonal (Hexacelsian) into its monoclinic (Celsian) form, with or without milling. The higher nominal SBAS content of composition 1 facilitated in it the mentioned conversion, in comparison with the other two studied compositions, which required to be mechanically activated for times that increased with increasing Al{sub 2}O{sub 3} content, in order to attain in them similarly high Hexacelsian to Celsian conversions. The mechanical properties of the synthesized materials increased with increasing milling time, sintering temperature and Al{sub 2}O{sub 3} content. Thus, the best mechanical properties were obtained for composition 3 milled for 8 h and sintered at 1500 degree centigrade. (Author)

  1. Tipo de parto: expectativas das mulheres Tipo de parto: expectativas de las mujeres Childbirth types: women's expectations

    Directory of Open Access Journals (Sweden)

    Sonia Maria Junqueira Vasconcellos de Oliveira

    2002-10-01

    Full Text Available Estudo descritivo e exploratório, realizado mediante entrevista com 221 puérperas que tiveram parto em maternidades públicas estaduais, localizadas no município de São Paulo. Teve como objetivos: 1. identificar o tipo de parto esperado pelas mulheres, considerando a via vaginal ou cesariana, e sua justificativa; 2. verificar a ocorrência do tipo de parto, segundo as expectativas dessas mulheres; 3. comparar a indicação médica da cesariana com o entendimento das mulheres sobre justificativa dessa intervenção. Os dados revelam que 74,7% tinham expectativa de que o parto fosse normal, e 25,3%, de que fosse cesárea. O parto normal, esperado por 165 entrevistadas, ocorreu em 66,1% dessas mulheres. A justificativa mais citada pelas mulheres para esperar o parto normal foi a recuperação pós-parto mais rápida e, para a cesárea, ter tido cesárea anterior. As justificativas apresentadas por 61 mulheres para a realização da cesariana não era coincidente com a indicação médica em 47,5% dos casos.Estudio descriptivo y exploratorio, realizado mediante entrevista con 221 puerperas que tuvieron el parto en maternidades públicas de en la ciudad de São Paulo. La investigación tuvo como objetivos: 1. identificar el tipo de parto esperado por las mujeres, considerando la vía vaginal o cesárea y su justificación; 2. verificar la ocurrencia del tipo de parto, según las expectativas de esas mujeres; 3. comparar la indicación médica da la cesárea con la comprensión de las mujeres sobre la justificación para esa intervención. Los datos muestran que 74,7% de las mujeres tenían la expectativa de que el parto fuese normal y 25,3% que fuese cesárea. El parto normal, esperado por 165 entrevistadas, ocurrió en 66,1% de estas mujeres. La justificativa más utilizada por las mujeres para esperar el parto normal fue la recuperación postparto más rápida y para la cesárea, haber tenido la cesárea anterior. La justificación presentada

  2. Implantes inmediatos transalveolares tipo IMETI®. Reporte de un caso

    Directory of Open Access Journals (Sweden)

    Joyce Barrios Mejía

    2013-10-01

    Full Text Available ResumenHoy en día existen avances en el concepto de mantenimiento y regeneración ósea. Es bien conocido en el ámbito de la odontología que tras una exodoncia se produce una reabsorción del alveolo residual dentro del mismo proceso de cicatrización y remodelación gingival y ósea, pero para evitar estos inconvenientes se plantean los implantes inmediatos insertados en el mismo acto quirúrgico en el cual se extrae el diente a sustituir. Con respecto a los implantes diferidos, tienen precisamente la ventaja de disminuir la continua reabsorción ósea del alveolo postextracción, acortar el tiempo de tratamiento rehabilitador y evitar segundas cirugías de implantación. El objetivo de este artículo es caracterizar a través de un caso el éxito de esta técnica quirúrgica con la convencional utilizando los implantes tipo IMETI ®. (Duazary 2007; 1: 45 - 51AbstractNow a days exists an advance in the maintenance concept and bony regeneration. is very well-known that after an exodontic a reabsorption of the residual alveolus takes place inside the same scaring process and gingival remodeling and bony, to avoid these inconveniences, it is thought about the immediate implant inserted in the same surgical act in which the tooth to substitute is extracted. With regard the differed implants; they have the advantage of diminishing the continuous bony reabsorption of the alveolus post-extraction, to shorten the time of rehabilitative treatment and to avoid second implantation surgeries. The objective of the present case, is to characterize the success of this surgical technique with the conventional used the IMETI ® implants.Key Words: Extraction; Implant; Alveolus; IMETI ®

  3. O uso de politetrafluoroetileno expandido em tireoplastia tipo I

    Directory of Open Access Journals (Sweden)

    Mello-Filho Francisco Veríssimo de

    2003-01-01

    Full Text Available A paralisia unilateral de prega vocal (PUPV em abdução é uma alteração que produz grande desconforto ao paciente, principalmente pelos distúrbios fonatórios causados. Atualmente dispomos de uma variedade de métodos para seu tratamento. OBJETIVO: Verificar a eficiência, vantagens e desvantagens do uso da fita de politetrafluoretileno expandido (PTFE-e, na medialização de prega vocal (PV paralisada, em abdução. FORMA DE ESTUDO: Coorte Longitudinal. MATERIAL E MÉTODOS: Foram estudados quatro pacientes com diagnóstico clínico-laringoscópico de disfonia por PPVU, em abdução há pelo menos um ano. Os pacientes foram submetidos a avaliação fonoaudiológica e a tireoplastia tipo I para medialização da PV com fita de PTFE-e. Durante o seguimento pós-operatório procedeu-se videolaringoscopia, tomografia computadorizada e fonoterapia. RESULTADOS: Todos os pacientes estão satisfeitos com a qualidade vocal, apresentam medialização estável da PV com a fonocirurgia e bons resultados à avaliação fonoaudiológica. Um paciente apresentou extrusão intra-operatória da fita de PTFE-e, sendo feito um segundo procedimento, sem complicações, seis meses depois. CONCLUSÃO: Na opinião dos autores a fita de PTFE-e se presta com eficiência ao tratamento da PUPV, sem apresentar riscos importantes.

  4. COMPOSTOS FENÓLICOS E ATIVIDADE ANTIOXIDANTE DE GENÓTIPOS DE CIRIGUELAS (SPONDIA PURPUREA L.

    Directory of Open Access Journals (Sweden)

    Quésia Jemima da SILVA

    2012-01-01

    Full Text Available Com o objetivo de determinar em frutos de 11 genótipos de cirigueleiras o teor de fenólicos totais e o potencial antioxidante foram preparados extratos hidrometanólicos e hidroacetônicos por extração sequencial. A ação antioxidante foi analisada utilizando dois ensaios: sequestro do radical DPPH● (1,1-difenil-2-picrilhidrazil e do radical ABTS+• (2,2’-azino-bis-(3-etilbenzotiazolina-6- acido sulfônico. O extrato obtido do genótipo IPA-10 apresentou maior teor de fenólicos totais (862,31mg EAG.g-1 de polpa, superando, estatisticamente, os extratos dos demais genótipos. Em relação ao percentual de sequestro do radical DPPH●, os extratos dos frutos de todos os genótipos apresentaram forte capacidade antioxidante, tendo em vista que os valores determinados foram superiores a 70%. O comportamento cinético dos extratos dos frutos dos genótipos IPA-2, IPA-3, IPA-4, IPA-5, IPA-6, IPA-7, IPA-8, IPA- 10 e IPA-11 foram classificados como rápidos (TEC50<5 minutos, no entanto, apenas o genótipo IPA-7 apresentou eficiência antirradical super alta. Com relação ao radical ABTS+• todos os genótipos apresentaram apreciável ação antioxidante com destaque para o extrato do genótipo IPA- 10 que demonstrou uma ação superior aos demais genótipos(6.633,87μM TEAC.g-1.

  5. Seleção de protótipos: combinando auto-geração de protótipos e mistura de gaussianas

    OpenAIRE

    de Santana Pereira, Cristiano

    2008-01-01

    Seleção de protótipos é uma técnica de aprendizagem de máquina cujo objetivo é a escolha ou produção de instâncias de dados que consigam a melhor representação para os dados do problema realçando as fronteiras de decisão e mantendo a separação entre as classes. A idéia é reduzir a quantidade de dados e ainda assim obter um conjunto de protótipos que minimize o erro de classificação. As estratégias baseadas em protótipos têm sido bastante utilizadas em aplicações reais nos mais diversos domíni...

  6. Estudos comparativos do ciclo de regeneração de diferentes tipos de silicoaluminofosfatos

    OpenAIRE

    Chellappa, Thiago

    2013-01-01

    Diferentes tipos de catalisadores heterogêneos do tipo silicoaluminofosfático, (SAPO-5, SAPO-11, SAPO-31, SAPO-34 e SAPO-41), peneiras moleculares com estrutura: AFI, AEL, ATO, CHA e AFO, respectivamente, foram sintetizados pelo método hidrotérmico. Utilizando-se de fontes como à alumina hidratada (pseudobohemita), ácido fosfórico, sílica gel, água e diferentes tipos de direcionadores estruturais orgânicos, tais como o: brometo de cetiltrimetilamônio (CTMABr), di-isopropilamina (DIPA), di-n-p...

  7. Déficit hídrico em tipos de crescimento da soja

    OpenAIRE

    Machado Júnior, Carlos Sebastião

    2015-01-01

    Estudos envolvendo o impacto do déficit hídrico na fisiologia da soja são abundantes, mas os que envolvam os tipos de crescimento determinado e indeterminado são escassos. Considerando que as respostas do tipo de crescimento para com o déficit hídrico podem ser de grande valor para o aperfeiçoamento de programas de melhoramento promovendo a resistência à seca, o objetivo deste trabalho foi avaliar as diferenças fisiológicas e de biomassa de cultivares de soja do tipo de crescim...

  8. Influencia del contacto precoz, nacionalidad, tipo de parto y prematuridad en la lactancia materna

    OpenAIRE

    Ana Belén Laviña Castan

    2015-01-01

    Conocer si en el HUMS existe asociación entre lactancia materna y nacionalidad, prematuridad, tipo de parto, contacto precoz piel con piel. Estudio de cohortes, en una muestra de 541 puérperas del HUMS en octubre-noviembre 2011. Las variables: nacionalidad, tipo de parto, contacto precoz, parto prematuro e inicio lactancia materna se recogieron antes del alta hospitalaria mediante cuestionario. A los dos meses postparto se contactó telefónicamente con las madres para conocer el tipo de lactan...

  9. Distintos tipos de células fotosensibles del sistema visual humano

    OpenAIRE

    Gómez García, Olga

    2016-01-01

    Existen en la retina dos tipos de células fotosensibles ampliamente conocidos, estos son los conos y los bastones. Hay tres tipos diferentes de conos, sensibles a distintas longitudes de onda, y un solo tipo de bastón, sensible a otra longitud de onda diferente. Los conos son los encargados de la visión en color y los bastones son altamente sensibles en luminancias bajas. Estos fotorreceptores, además de la generación y trasmisión de la información visual consciente, intervienen en la a...

  10. Endocardite bacteriana em paciente com diabetes mellitus tipo 2

    Directory of Open Access Journals (Sweden)

    Alcinda Aranha Nigri

    2016-10-01

    Full Text Available Introdução: A endocardite infecciosa é uma infecção microbiana da superfície do endocárdio. Acomete sobretudo valvas cardíacas, em geral, a mitral. Etiologias comuns são: uso de drogas injetáveis, infecção oral, hemodiálise a longo prazo e diabetes mellitus (DM. O diagnóstico é realizado por meio dos Critérios de Duke. Objetivos: Relatar caso de endocardite de paciente do Hospital Santa Lucinda (HSL. Metodologia: As informações foram obtidas pelo exame clínico, prontuário da paciente, relato da equipe médica e revisão de literatura. Relato de Caso: Paciente L.F.P.L., F., 54 anos, DM tipo 2, hipertensa, com insuficiência renal crônica não-dialítica, com úlceras de membros inferiores (MMII. Foi realizado debridamento e uso de antibiótico (ATB. Posteriormente, procurou hospital com queixa de dispneia. Diagnosticada com pneumonia (sic, usou ATB. A posteriori, apresentou anasarca e febre. Não houve leucocitose provavelmente devido ao uso de ATB. Constatou-se sopro mitral; no ecocardiograma: insuficiência mitral e tricúspide e vegetação em valva mitral, indicando endocardite infecciosa. Encaminhada ao HSL para cirurgia, apresentou na admissão: derrame pleural, hemo- e leucograma (LEU sem alterações, ureia 142, glicose 256 (mg/dL e albumina 2,6 (g/dL. Após 6 dias, foi inserida a prótese biomitral e cerclagem de valva tricúspide. Realizou-se transfusões sanguíneas pós-cirúrgicas. Manifestou parada cardiorrespiratória (PCR, realizada ressuscitação cardiopulmonar. Após 10 dias, apresentou arritmia, PCR, sepse e foi a óbito. Conclusões: O manejo adequado do DM pode evitar complicações, como úlceras de MMII, evitando, consequentemente, a disseminação via hematogênica e o quadro de endocardite. Deve-se considerar o uso prévio de ATB ao se analisar o LEU do paciente.

  11. CRESCIMENTO INICIAL DE KIWANO EM DIFERENTES TIPOS DE SUBSTRATOS

    Directory of Open Access Journals (Sweden)

    Omar Schmildt

    2012-12-01

    Full Text Available The kiwano (Cucumis metuliferus is an exotic species, belonging to the Cucurbitaceae family, possessing a great potential for commercialization. This study aimed to learn more about the culture of kiwanothrough its initial growth on different substrates, since there are few works related to this culture. The study was carried out in a greenhouse in Alegre-ES, a completely randomized design with four replications. The treatmentsconsisted of the following substrates: Plantmax®, composed of legume Acacia sp; composed of rice husk carbornized + humus, composed of corn stover + manure and compost humus + vermiculite. At 28 days after sowing wereevaluated height, fresh weight and dry weight of seedlings. The substrate Plantmax® was more effective in the initial spread of the kiwano, with statistically higher in those variables and is therefore suitable for the production ofseedlings of this crop.O kiwano (Cucumis metuliferus é uma espécie exótica, pertencente à família das Cucurbitáceas, possuindo um grande potencial para comercialização. Este trabalho teve como objetivo conhecer mais sobre a cultura do kiwano, através do seu crescimento inicial em diferentes tipos de substratos, visto que são poucos os trabalhos relacionados com esta cultura. O trabalho foi realizado em casa de vegetação, em Alegre-ES, num delineamento inteiramente casualizado com quatro repetições. Os tratamentos utilizados foram constituídos dos seguintes substratos: Plantmax®; composto de leguminosa Acacia sp; composto de casca de arroz carbonizada + húmus; composto de palha de milho + esterco; e composto de vermiculita + húmus. Aos 28 dias após a semeadura foram avaliadas a altura, a massa de matéria fresca e a massa de matéria seca das plântulas. O substrato Plantmax®se mostrou mais eficiente na propagação inicial do kiwano, apresentando médias estatisticamente superiores para asvariáveis analisadas, sendo, portanto indicado para a produção de

  12. Interação genótipo x ambiente em genótipos de feijão-caupi semiprostrado via modelos mistos

    Directory of Open Access Journals (Sweden)

    Francisco Eduardo Torres

    2015-01-01

    Full Text Available A metodologia de modelos mistos (REML/BLUP tem sido empregada para estudar os efeitos da interação genótipo x ambiente (G x E em várias culturas, como: arroz, feijão, cana-de-açúcar, cajueiro e eucalipto, porém ainda não foi aplicada em feijão-caupi. Assim, o objetivo deste trabalho foi selecionar simultaneamente genótipos de feijão-caupi semiprostrado cultivados no Estado do Mato Grosso do Sul, via modelos mistos, que reúnam alta adaptabilidade, estabilidade e produtividade de grãos. Foram conduzidos quatro ensaios de valor de cultivo e uso com genótipos de genótipos de feijão-caupi nos anos de 2005 e 2006 em Aquidauana, Chapadão do Sul e Dourados. O delineamento experimental utilizado foi o de blocos completos casualizados, com 20 genótipos e 4 repetições. Os parâmetros genéticos foram estimados pela metodologia REML/BLUP, e a seleção baseou-se no método da média harmônica do desempenho relativo dos valores genéticos (MHPRVG, em três estratégias: seleção com base no valor genético predito, tendo-se considerado o desempenho médio dos genótipos em todos os ambientes (sem efeito de interação ou o desempenho em cada ambiente (com efeito da interação; e seleção simultânea quanto à produtividade de grãos, estabilidade e adaptabilidade. Os genótipos BRS Paraguaçu, MNC99-542F-5 e MNC99-508G-1 podem ser cultivados em vários ambientes, pois reúnem alta produtividade de grãos, adaptabilidade e estabilidade. A herdabilidade da média dos genótipos apresentou magnitude variando de moderada a alta, fato que indica excelentes possibilidades para a seleção, permitindo acurácia seletiva de 82%.

  13. Diabetes tipo 2 en niños. Serie de casos

    OpenAIRE

    Manrique-Hurtado, Helard; Aro-Guardia, Pedro; Pinto-Valdivia, Miguel

    2015-01-01

    Objetivos: Describir las características clínicas y bioquímicas de un grupo de niños y adolescentes con diagnóstico reciente de diabetes tipo 2. Material y métodos: Estudio descriptivo, retrospectivo, tipo de serie de casos. Se definió caso al niño o adolescente con glucosa plasmática en ayunas mayor a 126 mg/dl, ausencia de antiGAD y péptido C mayor a 1,5 ng/dl. Se excluyeron a los pacientes con diagnóstico previo de diabetes mellitus tipo 1, diabetes tipo MODY o diabetes secundaria a uso de...

  14. Estudo do cronótipo de um grupo de trabalhadores em turnos

    Directory of Open Access Journals (Sweden)

    Milva Maria Figueiredo de Martino

    Full Text Available Neste estudo, os objetivos foram descrever as características de matutinidade/vespertinidade de um grupo de trabalhadores em turnos de uma indústria química e identificar possíveis associações entre cronótipo e turno de trabalho. A pesquisa foi realizada em uma indústria química do interior do estado de São Paulo. Os trabalhadores lotados nesta seção eram distribuídos em dois turnos: matutino e vespertino. A amostra constituiu-se de 44 trabalhadores, dos sexos feminino e masculino, que trabalhavam em ambos os turnos. Os dados foram coletados com a versão brasileira do questionário de identificação de indivíduos matutinos e vespertinos que foi elaborado por Horne & Östberg (1976. Foi verificado o predomínio do cronótipo "moderadamente matutino" - MM (n = 21 ou 47,73% -, seguido pelo tipo "Indiferente" - IN (n = 12 ou 27,27% - e pelo tipo "definitivamente matutino" - DM (n = 10 ou 22,73%. Somente um indivíduo foi classificado como "definitivamente vespertino" - DV (2,27%. Entre os trabalhadores estudados houve predomínio do cronótipo "moderadamente matutino" seguido do tipo "indiferente" e do tipo "definitivamente matutino". Não foram verificadas associações estatisticamente significativas entre o cronótipo e as características individuais neste estudo.

  15. La victimología como ciencia : tipos de víctimas

    OpenAIRE

    Liñares Lobón, Pablo

    2013-01-01

    El tratamiento de los diversos tipos de víctimas ha sido objeto de estudio de la perspectiva psicológica desde los últimos años. En este sentido, es tan vital conocer bien los tipos de víctimas como las herramientas metodológicas que son utilizadas en los programas de intervención que aporten soluciones reales al problema

  16. Tipos de propiedad y comportamiento estratégico de la empresa

    OpenAIRE

    2001-01-01

    Esta tesis tiene como principal objetivo profundizar en el entendimiento de los efectos de diferentes tipos de propietarios como factor determinante de los objetivos y de las decisiones empresariales en presencia de problemas informativos. La investigacion trata de explicar algunas de las consecuencias que tiene en el comportamiento estrategico de las empresas participadas, la existencia de distintos tipos de inversores estables, bien informados y con capacidad de control, como son los grupos...

  17. Material tipo de insectos en el Laboratorio de Sanidad Vegetal, SENASA, Lima, Perú

    Directory of Open Access Journals (Sweden)

    Pedro W. Lozada

    2013-05-01

    Full Text Available Se presenta la lista de material tipo de Insecta depositado en la colección del Laboratorio de Sanidad Vegetal, Servicio Nacional de Sanidad Agraria (SENASA, Lima, Perú, comprendiendo 21 especies de Psylloidea (Hemiptera, 4 de Cicadellidae (Hemiptera, 4 de Curculionidae (Coleoptera y 2 de Tachinidae (Diptera, todas provenientes de localidades peruanas. Los tipos de Tachinidae descritos por Charles Townsend no han sido incluidos en esta relación.

  18. Nuevas estrategias terapéuticas en diabetes mellitus tipo 1

    OpenAIRE

    Barajas, M. (Miguel); Príncipe, R.M. (R.M.); Escalada, J.; Prosper, F. (Felipe); J. Salvador

    2008-01-01

    El principal determinante del riesgo de complicaciones derivadas de la diabetes mellitus tipo 1 se debe a los altos niveles de glucosa en sangre mantenidos durante largo tiempo. Para conseguir un beneficio terapéutico en pacientes con diabetes mellitus es necesario desarrollar tratamientos que permitan de manera segura, efectiva y estable mantener la normoglucemia. Lamentablemente, el tratamiento de la diabetes mellitus tipo 1 mediante el aporte exógeno de insulina no ...

  19. 76 FR 27863 - Airworthiness Directives; Airbus Model A318-112, A319-111, A319-112, A319-115, A319-132, A319-133...

    Science.gov (United States)

    2011-05-13

    ... been detected on terminal modules Part Number (P/N) NSA 937901M1604, manufactured by Deutsch, due to an... on terminal modules Part Number (P/N) NSA 937901M1604, manufactured by Deutsch, due to an... Number (P/N) NSA 937901M1604, manufactured by Deutsch, due to an insufficient crimping of the...

  20. Genótipos de haptoglobina e hipertensão refratária em pacientes com diabete melito tipo 2

    Directory of Open Access Journals (Sweden)

    Vânia Pereira Albuquerque Wobeto

    2011-10-01

    Full Text Available FUNDAMENTO: Tem sido sugerido que o polimorfismo da haptoglobina pode influenciar na patogênese das complicações microvasculares e macrovasculares em pacientes diabéticos. OBJETIVO: O objetivo principal deste estudo transversal foi de realizar uma investigação da existência ou não de uma associação entre os genótipos de haptoglobina e a prevalência de eventos isquêmicos cardiovasculares (angina estável, angina instável e infarto agudo do miocárdio, hipertensão arterial sistêmica, hipertensão refratária, obesidade e dislipidemia em 120 pacientes com diabete melito tipo 2, seguidos no Hospital Universitário da Unicamp, em Campinas, Estado de São Paulo. MÉTODOS: A genotipagem da haptoglobina foi realizada por reações em cadeia da polimerase alelo-específicas. As frequências dos genótipos de haptoglobina foram comparadas com a presença/ausência de doença cardiovascular, hipertensão arterial sistêmica, hipertensão refratária, obesidade e dislipidemia; medições de pressão arterial sistólica e diastólica; glicemia, colesterol (total, lipoproteínas de alta densidade - HDL e lipoproteínas de baixa densidade - LDL e triglicerídeos; assim como níveis de creatinina sérica. RESULTADOS: Embora nenhuma associação entre o genótipo de haptoglobina e a presença de doença cardiovascular tenha sido identificada, encontramos um excesso significativo de pacientes com o genótipo Hp2-1 entre as pessoas com hipertensão refratária, que também apresentavam uma maior pressão arterial sistólica e diastólica e níveis de colesterol total e LDL. CONCLUSÃO: Nossos resultados sugerem que os pacientes com diabete melito tipo 2 com o genótipo Hp2-1 podem apresentar uma maior chance de desenvolver hipertensão refratária. Estudos adicionais em populações diabéticas são necessários para confirmar esses achados.

  1. Resistência de genótipos de feijoeiro a Bemisia tabaci biótipo B Resistance of bean genotypes to Bemisia tabaci biotype B

    Directory of Open Access Journals (Sweden)

    Lucas Castro Torres

    2012-01-01

    Full Text Available O estudo de genótipos de feijoeiro resistentes à mosca-branca Bemisia tabaci (Genn. biótipo B (Hemiptera: Aleyrodidae é de grande importância devido aos danos ocasionados por essa praga à cultura. Neste trabalho, foram estudados a atratividade para adultos, a preferência para oviposição em testes com e sem chance de escolha, o ciclo ovo-adulto e o tipo e número de tricomas presentes nos folíolos. Os experimentos foram realizados em casa de vegetação avaliando-se, inicialmente, cem genótipos de feijoeiro. A resistência do tipo não-preferência para alimentação e/ou antibiose foi observada nos genótipos ARC-3, IAC-Alvorada e Canário 101, sendo a emergência de adultos fortemente influenciada pelos genótipos. Também se observou correlação negativa moderada entre o número de ovos e o número de tricomas glandulares, e correlação positiva muito forte entre o número de ovos e o número de tricomas tectores unciformes.The study of bean genotypes resistant to the whitefly Bemisia tabaci (Genn. B biotype (Hemiptera: Aleyrodidae has been of great importance due to the damage caused by this pest. In this research, bean genotypes were evaluated regarding attractiveness to whitefly adults, the preference for oviposition in free-choice and non choice tests, egg-to-adult development time and characterized for the presence, type and number of trichomes. The experiments were carried out under greenhouse conditions initially evaluating 100 bean genotypes. The non-preference type of resistance for feeding and/or antibiosis was observed in the genotypes ARC-3, IAC-Alvorada and Canário 101, and the emergence of adults was strongly influenced by the genotypes. It was also observed a moderate negative correlation between the number of eggs and the number of glandular trichomes, as well as a very strong positive correlation between the number of eggs and the number of unciform non-glandular trichomes.

  2. El cambio en la designación general de material (DGM de las AACR a las RDA: Definición de los atributos tipo de contenido, tipo de medio y tipo de soporte

    Directory of Open Access Journals (Sweden)

    Paola Andrea Picco Gómez

    2012-04-01

    Full Text Available Se aborda el estudio de los atributos tipo de contenido, tipo de medio y tipo de soporte definidos por el código de catalogación Resource Description and Access (RDA para solucionar los problemas que presentaba la lista de términos utilizadas para registrar la designación general de material (DGM en las Anglo American Cataloging Rules (AACR. Los términos eran ambiguos combinando aspectos referidos al contenido y clase de material del recurso. Se parte de una exhaustiva revisión bibliográfica y del estudio de los documentos que se generaron en el proceso de elaboración del nuevo código. Se menciona el trabajo conjunto entre el Joint Steering Committee (JSC y el estándar ONIX para el establecimiento de criterios que permitieron definir estos tres atributos, así como el aporte del modelo FRBR en la definición de los mismos. Se presentan ejemplos de registros bibliográficos donde se utilizan estos tres atributos en formato MARC21, ISBD consolidada a partir de la definición del área 0 y en el esquema de metadatos Dublin Core. Se finaliza destacando la necesidad de continuar con investigaciones que permitan concluir sobre la adecuación de estos tres atributos a las necesidades de los catalogadores, usuarios y a la realidad tecnológica

  3. Resgate vegetativo por alporquia de genótipos adultos de urucum (Bixa orellana L.

    Directory of Open Access Journals (Sweden)

    Nilton César Mantovani

    2010-09-01

    Full Text Available Este trabalho teve por objetivos avaliar a técnica de alporquia visando ao resgate vegetativo de genótipos de urucum (Bixa orellana L. e a obtenção de plantas fornecedoras de propágulos para processos de propagação clonal. Foram utilizadas dez plantas matrizes de urucum, com 12 anos de idade, obtidas partindo do cruzamento artificial entre os genótipos "Fruto Verde Piloso" X "Fruto Vermelho Liso". Os alporques foram realizados em ramos de 1 a 2 cm de diâmetro, utilizando-se como substrato uma mistura de vermiculita e musgo. Foi avaliado o efeito (1 do tipo de anelamento da casca dos ramos (total ou parcial, com 1 cm de comprimento, (2 do AIB (ácido indol-3-butírico a 0 e 4,92 mM aplicado em papel filtro e (3 do tipo de proteção dos alporques (filmes plásticos transparente ou preto ou tecido tencel, no enraizamento de alporque dos dez genótipos. A técnica de alporquia proporcionou o enraizamento de ramos dos dez genótipos avaliados, com eficiência variável de 20 a 100%, havendo efeito do genótipo sobre a frequência de enraizamento. A sobrevivência desses alporques foi de 100% após o plantio quando estes foram produzidos com anelamento total, tratados com AIB e protegidos com plástico transparente. Em casa de vegetação os alporques desenvolveram ramos partindo da brotação de gemas caulinares constituindo estoques de explantes apropriados para serem utilizados como estacas ou como fontes de segmentos nodais para a propagação in vitro desta espécie.

  4. Autoinmunidad y receptores tipo Toll = Autoimmunity and toll-like receptors

    Directory of Open Access Journals (Sweden)

    Ossa Giraldo, Ana Claudia

    2012-07-01

    Full Text Available La respuesta inmune innata está conformada por un conjunto de mecanismos que permiten reconocer los componentes propios del organismo y diferenciarlos de los microorganismos invasores para generar una primera línea de defensa. Este reconocimiento está mediado por diferentes receptores presentes en la superficie y en el interior de células inmunes y no inmunes; entre ellos se encuentran los siguientes: receptores tipo Toll (RTT, receptores de lectinas tipo C, receptores tipo GIR (genes inducibles por ácido retinoico y receptores tipo Nod y NALP, que reconocen patrones moleculares asociados a microorganismos (PMAM. Gracias a esta capacidad de discriminación, adquirida evolutivamente por la inmunidad innata, se ha aceptado tradicionalmente que los procesos autoinmunes no están relacionados con esta sino con la inmunidad adquirida. Sin embargo, varios estudios han demostrado que esa teoría no es totalmente cierta y que algunos mecanismos efectores de la inmunidad innata participan en la generación de las enfermedades autoinmunes o en la potenciación de su fisiopatología. En esta revisión se estudia la contribución de la inmunidad innata a la autoinmunidad con énfasis en el papel de los receptores tipo Toll.

  5. Plutón La Costa, una expresión de magmatismo tipo-s en el sector noreste de la Sierra de Velasco, Sierras Pampeanas

    Directory of Open Access Journals (Sweden)

    P.H. Alasino

    2006-06-01

    Full Text Available Estudios combinados de petrología, química mineral y geoquímcia de roca total revelan la presencia de dos unidades graníticas peraluminosas con minerales aluminosos magmáticos tales como granate y mica blanca y la presencia distintiva de turmalina. Las evidencias aquí presentadas indican que estas dos facies, Anillaco y Anjullón, junto a la unidad peraluminosa Santa Cruz estudiada en trabajos previos, constituyen una serie de rocas co-sanguíneas, emplazadas en niveles someros de la corteza y las cuales conforman una unidad ígnea mayor denominada aquí plutón La Costa, la cual aflora en el sector noreste de la sierra de Velasco. La asociación mineral, la química mineral y la geoquímica de roca total permiten definir al plutón La Costa como un clásico granitoide tipo-S, derivado de una roca fuente de composición esencialmente pelítica. Diferentes estudios demuestran que la generación de granitoides tipo-S requiere de un alto gradiente geotérmico, por lo cual el plutón La Costa indica que la corteza en esta región soportó un notable calentamiento durante la generación del magma. Sin embargo, la ausencia de datos geocronológicos impide definir el evento tectomagmático que produjo el magma primordial de este plutón.

  6. Effect of composition of Al-Si welding wires on welded joint characteristics of copper and aluminum by CMT welding%铝硅焊丝成分对铜铝异种金属CMT焊接接头特征的影响

    Institute of Scientific and Technical Information of China (English)

    孟凡玲; 吕曜晨; 武小娟; 孙焕焕

    2016-01-01

    采用冷金属过渡(CMT)焊对异种金属T2和1060Al进行焊接,选用S301、ER4043、ER4047 3种焊丝作为填充材料,研究在适当工艺参数下,焊丝成分对焊接接头组织、相组成、界面化合物形态及硬度的影响.结果表明:3种焊丝焊接的接头均由焊缝区、结合区、熔合区组成,且靠Cu侧的焊缝结合区均生成了较厚的界面化合物层.结合区的组织主要为(α-Al+ CuAl2)共晶和CuAl2金属间化合物相,当采用含Si量12.0%的ER4047焊接时结合区还析出了块状Si.焊丝中添加Si元素,抑制了靠Cu侧焊缝区界面化合物生长,并改变了化合物形态.同时,界面化合物生成,也导致3种焊缝均在靠Cu侧出现显微硬度的高峰区.%Cold metal transfer (CMT) welding was employed to weld the dissimilar metallic sheets of T2 and 1060 aluminum.S301,ER4043 and ER4047 welding wires were used as filler materials,respectively.The effects of composition of Al-Si welding wires on the characteristics of Cu-Al welded joints obtained by using suitable CMT welding parameters were studied.The results show that the three welded joints are composed of weld zone,bonding zone,fusion zone,and the thick interface compounds are generated at the bonding zone near the copper sheets.The microstructure of the three bonding zones is mainly (α-Al + CuAl2) eutectic and CuAl2 intermetallics.Moreover,the massive Si phases are found at the bonding zones of the welded joint that produced by using ER4047 welding wire with 12.0% Si.These results indicate that Si element in the welding wires can restrain the growth of the interface compounds in the weld near the copper sheet,and the morphology of the compounds also can be changed by Si element as changing their contents in welding wires.The microhardness peak zones are formed in the copper side of the joint interface because of these interface compounds.

  7. Menzerite-(Y) a New Species {(Y REE)(Ca Fe2plus)2}[(Mg Fe2plus)(Fe3plus Al)](Si3)O12 from a Felsic Granulite Parry Sound Ontario and a New Garnet End-member (Y2Ca)Mg2(SiO4)3

    Energy Technology Data Exchange (ETDEWEB)

    E Grew; J Marsh; M Yates; B Lazic; T Armbruster; A Locock; S Bell; M Dyar; H Bernhardt; O Medenbach

    2011-12-31

    Menzerite-(Y), a new mineral species, forms reddish brown cores, n = 1.844 (20), up to 70 {micro}m across, rimmed successively by euhedral almandine containing up to 2.7 wt% Y{sub 2}O{sub 3} and by K-feldspar in a felsic granulite on Bonnet Island in the interior Parry Sound domain, Grenville Orogenic Province, Canada. It is named after Georg Menzer (1897-1989), the German crystallographer who solved the crystal structure of garnet. Single-crystal X-ray-diffraction results yielded space group Ia3d, a = 11.9947(6) {angstrom}. An electron-microprobe analysis of the grain richest in Y (16.93 wt% Y{sub 2}O{sub 3}) gave the following formula, normalized to eight cations and 12 oxygen atoms: {l_brace}Y{sub 0.83}Gd{sub 0.01}Dy{sub 0.05}Ho{sub 0.02}Er{sub 0.07}Tm{sub 0.01}Yb{sub 0.06}Lu{sub 0.02}Ca{sub 1.37}Fe{sub 0.49}{sup 2+}Mn{sub 0.07}{r_brace} [Mg{sub 0.55}Fe{sub 0.42}{sup 2+}Fe{sub 0.58}{sup 3+}Al{sub 0.35} V{sub 0.01}Sc{sub 0.01}Ti{sub 0.08}](Si{sub 2.82}Al{sub 0.18})O{sub 12}, or {l_brace}(Y,REE)(Ca,Fe{sup 2+}){sub 2}{r_brace}[(Mg,Fe{sup 2+})(Fe{sup 3+},Al)](Si{sub 3})O{sub 12}. Synchrotron micro-XANES data gave Fe{sup 3+}/{Sigma}Fe = 0.56(10) versus 0.39(2) calculated from stoichiometry. The scattering power refined at the octahedral Y site, 17.68 epfu, indicates that a relatively light element contributes to its occupancy. Magnesium, as determined by electron-microprobe analyses, would be a proper candidate. In addition, considering the complex occupancy of this site, the average Y-O bond length of 2.0244(16) {angstrom} is in accord with a partial occupancy by Mg. The dominance of divalent cations with Mg > Fe{sup 2+} and the absence of Si at the octahedral Y site (in square brackets) are the primary criteria for distinguishing menzerite-(Y) from other silicate garnet species; the menzerite-(Y) end-member is {l_brace}Y{sub 2}Ca{r_brace}[Mg{sub 2}](Si{sub 3})O{sub 12}. The contacts of menzerite-(Y) with almandine are generally sharp and, in places, cuspate. It is

  8. Tipos y uso de argumentos escépticos en Hume

    Directory of Open Access Journals (Sweden)

    Plínio Junqueira Smith

    2010-12-01

    Full Text Available La intención del presente artículo es mostrar que Hume distingue dos tipos de argumentos escépticos. El tipo antiguo, basado en el método de antinomias, es considerado muy débil por Hume. Él desarrolla un tipo nuevo de argumento escéptico a partir de su ciencia empírica de la naturaleza humana. Del otro lado, Hume distingue entre dos usos de los argumentos escépticos: el primero, que él llama pirrónico, tiene como finalidad la suspensión del juicio, lo que es imposible, porque la naturaleza nos obliga a creer; el segundo, el uso académico, pone límites a nuestro conocimiento, aceptando las creencias naturales, la ciencia empírica y las matemáticas.

  9. Comercio, tipo de cambio real y crecimiento económico

    OpenAIRE

    Enrique R. Casares.

    2007-01-01

    Se desarrolla un modelo de crecimiento endógeno con tres bienes, exportable, importado y no-comerciable. Se estudia la respuesta del tipo de cambio real y de la tasa de crecimiento de la economía a una disminución de la tasa arancelaria. Se muestra que una liberalización comercial debe ir acompañada de una depreciación del tipo de cambio real. Se deduce que la tasa de crecimiento de la economía se incrementa en el largo plazo. Se argumenta que la economía mexicana no siguió este comportamient...

  10. Diabetes Tipo 2 y Depresión en Guadalajara, México. 2005

    OpenAIRE

    Colunga-Rodríguez, Cecilia; García de Alba, Javier E.; José G. Salazar-Estrada; Ángel-González, Mario

    2008-01-01

    Objetivo Determinar la prevalencia de depresión y comparar indicadores sociodemográficos, metabólicos y clínicos, en personas con diabetes tipo 2 deprimidas y no deprimidas. Material y métodos Se realizó un estudio transversal comparativo en una muestra de 450 personas con diabetes tipo 2, mayores de 30 años, con más de un año de diagnóstico y sin determinación de psicopatología. Aplicamos escala de Zung modificada y encuesta sociodemográfica, evaluamos Hemoglobina glucosilada, índice de masa...

  11. Percepción de la insulinoterapia en pacientes con diabetes mellitus tipo 2 descontrolada

    OpenAIRE

    Rafael Leyva Jiménez; Gustavo Hernández Zambrano; Silvia Ibarra Maldonado; Carlos Tomás Ibarra Ramírez

    2016-01-01

    Objetivo: Conocer la percepción de la insulinoterapia en los pacientes con diabetes mellitus tipo 2 descontrolada tratados con hipoglucemiantes orales o con insulina. Diseño: Transversal comparativo prospectivo. Emplazamiento: Unidad de Medicina Familiar número 53 de la Delegación Guanajuato del Instituto Mexicano del Seguro Social. Participantes: Pacientes de 40 a 80 años afectos de diabetes tipo 2, descontrolados, en tratamiento con insulina o hipoglucemiantes orales. Mediciones...

  12. Manifestaciones orales en pacientes diabéticos tipo 2 y no diabéticos.

    OpenAIRE

    Rafaela del Toro Ávalos; María Guadalupe Aldrete Rodríguez; Álvaro Cruz González; Víctor Manuel Ramírez Anguiano; Patricia Lorelei Mendoza Roaf; José Luis Vázquez Castellanos; Carlos E. Bracamontes Campoy

    2004-01-01

    El propósito de esta investigación fue analizar el estado de higiene bucal, caries, enfermedad periodontal, presencia de candidiasis e infección post-extracción en pacientes diabéticos tipo 2 en comparación con pacientes no diabéticos. De 226 pacientes, 180 eran no diabéticos y 46 diabéticos tipo 2, todos con resultados recientes de hemoglobina glucosilada y glicemia. Se les realizó un examen clínico evaluando el índice de higiene bucal simplificado, dientes cariados, la presencia de candidia...

  13. La transformación de los tipos residenciales tradicionales como motor del proyecto de arquitectura

    OpenAIRE

    Abaurre Delgado, Blanca

    2015-01-01

    El trabajo realizado ha consistido en el análisis de los tipos arquitectónicos básicos de la construcción de la ciudad histórica de Sevilla, Casas Patio, Corrales de Vecinos y la Casa Vecinal, para estudiar como esos tipos pueden construir unas bases, mediante su concepción como estructura espacial, y ser utilizadas como material para la concepción de la arquitectura contemporánea de la ciudad. Grado en Fundamentos de Arquitectura

  14. EVIDENCIA DE UN TIPO INVESTIGACIÓN QUE ABORDE DE MILES Y SNOW EN BRASIL

    OpenAIRE

    Vanderlei Vieira; Roberto Klosowski Machado; Nathanael Kusch Brey; Carlos Ricardo Rossetto

    2012-01-01

    El objetivo de este trabajo es analizar las referencias utilizadas en las publicaciones de las conferencias nacionales que las tipologías actuales de gestión desarrolladas por Miles y Snow. El método utilizado en el estudio fue de tipo descriptivo, con abordaje cuantitativo, y el estudio bibliométrico tipo. En la selección de artículos, se tomó como base la existencia del término "Miles y Snow" en el título, resumen o palabras clave, la observación de la literatura mencionada en los artículos...

  15. Influencia del contacto precoz, nacionalidad, tipo de parto y prematuridad en la lactancia materna

    Directory of Open Access Journals (Sweden)

    Ana Belén Laviña Castan

    2015-01-01

    Full Text Available Conocer si en el HUMS existe asociación entre lactancia materna y nacionalidad, prematuridad, tipo de parto, contacto precoz piel con piel. Estudio de cohortes, en una muestra de 541 puérperas del HUMS en octubre-noviembre 2011. Las variables: nacionalidad, tipo de parto, contacto precoz, parto prematuro e inicio lactancia materna se recogieron antes del alta hospitalaria mediante cuestionario. A los dos meses postparto se contactó telefónicamente con las madres para conocer el tipo de lactancia en ese momento. El 70,32 % iniciaron la lactancia materna en las dos primeras horas postparto y el 55,58% daban Lactancia materna exclusiva (LME a los dos meses. Influyen en la lactancia materna el tipo de parto, contacto precoz y parto prematuro. La probabilidad de lactancia materna es 3,65 veces más alta si se ha realizado contacto precoz (RR 3,65; IC 95% 2,72-4,88; p=0,001. El inicio de lactancia materna en las 2 primeras horas y la nacionalidad española influye positivamente en la LME a los 2 meses. Las prácticas hospitalarias en el postparto deben promover el contacto precoz madre-recién nacido y el inicio de lactancia materna en las dos primeras horas, principalmente en las cesáreas.

  16. Control predictivo basado en modelo de un campo de colectores solares tipo acurex

    OpenAIRE

    Flor Unda, Omar Cristóbal

    2013-01-01

    El presente trabajo, presenta los resultados del control de un sistema de colectores solares tipo ACUREX, aplicando control predictivo basado en modelo como una técnica que aporta criterios para su estudio y mejoramiento. Se ha empleado el simulador creado para entorno Simulink, trabajo de (Camacho, et al., 1997).

  17. Quebrando estereótipos e rompendo preconceitos na sala de aula

    Directory of Open Access Journals (Sweden)

    Daniela Jakubaszko

    2015-04-01

    Full Text Available Este texto se preocupa em contribuir para a reflexão que torna possível a identificação e ruptura dos estereótipos sociais que dão origem a preconceitos e ações discriminatórias. Com base nos estudos de Walter Lippann, Agnes Heller, Adam Shaff e Eclea Bosi, pretende-se discutir os conceitos de estereótipo e preconceito, buscando entender o que são e porque se formam. Para entender melhor o estereótipo temos que refletir sobre três elementos que a ele se ligam: a linguagem, o cotidiano e o senso comum. É no plano da linguagem - do diálogo e das práticas de linguagem - que se deve estudar e se pode romper e desconstruir os estereótipos, tomando consciência da própria formação discursiva. O texto oferece, ainda, algumas sugestões para trabalhar o conceito na sala de aula e para ampliar o repertório de textos e referências a serem debatidas com os alunos.

  18. CORRELACION ENTRE DISTINTOS TIPOS HISTOLOGICOS DE CANCER DE MAMA Y RECEPTORES ESTROGENICOS

    OpenAIRE

    Schiaffino O.,Rodrigo; Ibarra P.,Andrés; González A.,Raúl; Urrutia M.,Julio

    2002-01-01

    Se presentan los resultados de 140 muestras histológicas tomadas en pacientes con cáncer de mama para determinar su concentración de receptores de estrógenos. Destaca la importancia, frecuencia de positividad para receptores de estrógenos en todos los tipos histológicos

  19. Tipo de tratamiento farmacológico y deterioro de la función pulmonar en pacientes con diabetes tipo 2

    OpenAIRE

    Vargas Diaz, Henry Alexander; Dennis Verano, Rodolfo José

    2013-01-01

    Antecedentes: En la actualidad no es clara la relación de la DM 2 con respecto al deterioro de la función pulmonar y menos aún si el tipo de tratamiento modifica parámetros espirométricos e inflamatorios. Objetivo: Comparar la función pulmonar de pacientes con DM 2 tratados con metformina vs secretagogos y la combinación con insulinas. Establecer el nivel de biomarcadores inflamatorios entre los grupos de tratamiento. Metodología: Estudio observacional analítico de corte transversal 495 pacie...

  20. Control predictivo de canales de riego utilizando modelos de predicción de tipo Muskingum (primer orden) y de tipo Hayami (segundo orden)

    OpenAIRE

    Alvarez Brotons, Xavier

    2004-01-01

    En el desarrollo de los algoritmos de control predictivo a aplicar en la gestión de canales de riego, es necesario considerar un modelo simplificado que represente la dinámica hidráulica del canal. En esta tesina se pretende comparar el rendimiento de diferentes algoritmos de control basados en modelos hidráulicos de la dinámica del canal, en particular un modelo de primer orden, como el modelo de Muskingum de tipo hidrológico y basado en la ecuación de continuidad y una relación de almacenam...

  1. Una función apotropaica de los amuletos de tipo egipcio en el mundo prerromano hispánico

    OpenAIRE

    2003-01-01

    En este articulo tratamos sobre la identificación en la costa mediterránea ibérica del uso apotropaico de los amuletos de tipo egipcio, revisando brevemente los principales hallazgos de este tipo en la esteras coloniales griegas y fenicio, así como en el ambiente indígena peninsular.

  2. Metodología y clasificación de tipos de paisaje en Galicia

    Directory of Open Access Journals (Sweden)

    Augusto Pérez-Alberti

    2014-12-01

    Full Text Available En el presente artículo se exponen los resultados de las investigaciones llevadas a cabo con el fin de caracterizar los diferentes tipos de paisaje existentes en Galicia (Noroeste de España. Se ha considerado el paisaje como resultado de un sistema dinámico en que interaccionan elementos estructurales y texturales. El resultado ha sido la caracterización de 6 grupos de paisaje, en función del dominio de la dinámica natural o antrópica y 28 tipos de paisaje sobre los que incidir de forma directa de cara a su protección, gestión y ordenación.

  3. Papel da vitamina D na susceptibilidade para a diabetes mellitus tipo 1

    OpenAIRE

    2010-01-01

    A diabetes mellitus tipo 1 é uma doença crónica auto-imune, caracterizada pela destruição selectiva das células nos ilhéus pancreáticos, resultando numa perda lenta e progressiva da secreção de insulina e para a qual contribuem factores ambientais e factores de predisposição genética. Vários estudos epidemiológicos e experimentais sugerem que a vitamina D tem um efeito protector contra o desenvolvimento da diabetes mellitus tipo 1, através da modulação da resposta do siste...

  4. Aposentadoria e as mudanças de vida das pessoas com diabetes tipo 2

    OpenAIRE

    Ma. Laura Ruiz Paloalto

    2007-01-01

    Trata-se de um estudo qualitativo, que teve como objetivo compreender as mudanças de vida das pessoas aposentadas com diabete tipo 2. Primeiramente se caracteriza a população com diabetes tipo 2 da Clínica Hospital ISSSTE Celaya - México, onde extraiu-se uma amostra de 56 pacientes do quais 39,28% estão entre 60 e 69 anos de idade, 53,6% pertencem ao sexo feminino, 69,6% são casados, 35,7% são do lar, 41% têm nível básico de estudos, 92,8% vivem com algum familiar, 28,57% têm entre 1 e 5 anos...

  5. Distribución de marcadores discursivos en distintos tipos de discurso

    Directory of Open Access Journals (Sweden)

    María Teresa Poblete Bennett

    1999-09-01

    Full Text Available Partiendo de supuestos de Bolívar (1995, se establece que la entrevista semiformal es una clase de texto donde se dan distintos tipos de discurso, y se comprueba la ocurrencia de tres clases de marcadores discursivo-conversacionales en distintos tipos de discurso: expositivo, narrativo y argumentativo. El corpus analizado se obtuvo de dieciocho entrevistas, nueve hombres y nueve mujeres, divididas en tres estratos sociales y tres grupos etarios que conforman una muestra representativa de los hablantes de Valdivia urbano (Cepeda et al., 1988:56-66. Los resultados indican, por una parte, que la distribución de los relacionantes supraoracionales está condicionada por el tipo de discurso donde ocurren y al cual le contribuyen en el logro de su objetivo comunicativo básico. Por otra parte, la distribución de los marcadores interactivos y de modalidad covaría más con las variables sociales que con el tipo de discurso en que ocurren. (Bolívar's (1995 assumptions concerning kinds of texts and types of discourse have been taken into account for the study of the distribution of three groups of discourse markers in three types of discourse: expository, narrative and argumentative.The data was taken from 18 semiformal interviews to nine women and nine men divided according to social strata, sex and age who belong to a representative sample of Valdivian speakers (Cepeda, et al., 1988: 55-66. The results show, on the one hand, that the distribution of suprasentential connectors is conditioned by the type of discourse where they occur, and that this distribution contributes to the achievement of the communicative objective of each type of discourse. On the other hand, the distribution of interactive and modality markers varies according to social variables rather than the type of discourse where they occur.

  6. Los diferentes tipos de hidroxiapatita y sus aplicaciones en cirugía bucal

    OpenAIRE

    Sánchez Garcés, Ma. Ángeles; Berini Aytés, Leonardo; Gay Escoda, Cosme

    1993-01-01

    Se describe las aplicaciones actuales de los diferentes tipos de hidroxiapatita en las técnicas quirúrgicas bucales practicadas con anestesia local que consisten en técnicas de tunelización subperióstica y el relleno de los defectos óseos y su aplicación combinada con implantes endo-óseos y las membranas de regeneración tisular guiada.

  7. Nuovi approcci terapici in modelli murini di neurodegenerazione di tipo Alzheimer

    OpenAIRE

    Kleiner, Giulio

    1982-01-01

    La demenza di tipo Alzheimer (AD) rappresenta una delle principali patologie che affliggono la nostra società. Purtroppo, i trattamenti terapeutici oggi disponibili non sono in grado di bloccare l’inesorabile esito della malattia, ma solo di rallentarlo. Pertanto, lo studio di nuove strategie terapiche e la successiva validazione delle stesse sono obiettivi prioritari della ricerca, con robuste analisi da effettuare su modelli animali affidabili. Attualmente, nessuno dei modelli sperimentali ...

  8. Tipos de edentulismo parcial tratados con prótesis parcial removible

    OpenAIRE

    Nogueras Clemente, Joaquin; Vela, X.; Samsó Manzanedo, Jorge; Peraire Ardèvol, Maria; Anglada Cantarell, José María; Salsench Cabré, Juan

    1994-01-01

    Nuestro estudio se ha llevado a cabo sobre una muestra compuesta por 60 modelos para la confección de una PPR, en los cuales estudiamos las ausencias dentales y la clasificación según el tipo de edentación. Las ausencias dentales son el 45,6% del total y la clase I de Kennedy predomina en la arcada inferior, mientras que la clase II lo hace en la superior.

  9. Inibidores da fosfodiesterase do tipo 5 e perda auditiva neurossensorial súbita

    Directory of Open Access Journals (Sweden)

    Monique Antunes de Souza Chelminski Barreto

    2013-12-01

    Full Text Available O uso de inibidores da fosfodiesterase do tipo 5 como sildenafil, vardenafil e tadalafil tem aumentado atualmente e alguns destes pacientes vêm apresentando perda auditiva neurossensorial súbita. OBJETIVO: Apresentar dois casos de pacientes que apresentaram surdez súbita em uso eventual do medicamento e revisar estudos sobre o uso de inibidores da fosfodiesterase do tipo 5 e surdez súbita. MÉTODO: Estudo analítico de dois casos e revisão sobre o tema no banco de dados da Pubmed/ MedLine e Bireme utilizando as palavras-chave inibidores da fosfodiesterase e surdez súbita e seus correlatos na língua inglesa. RESULTADOS: Os pacientes analisados são jovens, sem comorbidades, em uso de inibidores da fosfodiesterase do tipo 5 e após terapia combinada para o tratamento da surdez súbita, apenas um deles obteve melhora auditiva. Nove estudos científicos foram encontrados. Estudos pré-clínicos e clínicos, transversais e prospectivos foram revisados. CONCLUSÃO: O aumento da ocorrência na prática clínica e relatos científicos na literatura sugerem que o uso de inibidores da fosfodiesterase do tipo 5 seja encarado como fator de risco para surdez súbita. Novos estudos com amostras maiores e grupo controle são necessários para investigar esta associação.

  10. Sobre el buen planteamiento de una ecuación del tipo r-BO bidimensional

    OpenAIRE

    2015-01-01

    En este trabajo tratamos el buen planteamiento en los espacios de Sobolev Hs (R2) del problema de Cauchy asociado a la ecuación del tipo r-BO bidimensional [Fórmula Matemátiva] donde u(x, y, t) es real si x, y, t ∈ R. También, estableceremos resultados sobre la continuación única, para esta ecuación.

  11. PREJUÍZOS COGNITIVOS EM IDOSOS COM DIABETES MELLITUS TIPO 2

    Directory of Open Access Journals (Sweden)

    Regina Maria Fernandes Lopes

    2009-01-01

    Full Text Available El avance en las condiciones de salud propicia el progresivo aumento de la esperanza de vida. Estudios han identificado la existencia de una conexión entre la Diabetes Mellitus (DM y demencia. La hiperglicemia podría ser un factor importante en la incidencia de la enfermedad de Azheimer, la cual puede ser una causa secundaria de demencia. La diabetes mellitus tipo 2 (DM2 está asociada con déficits cognitivos y funcionales, y el WCST es una de las herramientas que puede ser utilizada para evaluar funcionamiento ejecutivo. El objetivo de este estudio fue evaluar los déficits cognitivos de ancianos con diabetes mellitus tipo 2. Los participantes fueron 254 ancianos de ambos sexos, mayores de 60 años; 44 de ellos diagnosticados de DM2 y 210 en un grupo control de población general. El diseño fue un estudio cuantitativo transversal. Los instrumentos utilizados fueron: datos sociodemográficos, WCST, MMSE, BDI, BAI, GD, junto a las Sub pruebas de: Vocabulario, códigos, números y Cubos del WAIS-III. Los resultados mostraron una diferencia significativa en el desempeño de los ancianos con diabetes tipo 2 en comparación con el grupo control en cuatro descriptores de WCST que indicaban un deterioro. Igualmente los ancianos con diabetes tipo 2 mostraron una intensidad de síntomas depresivos y de ansiedad estadísticamente mayor que el grupo control

  12. Compactones, soluciones de ecuaciones no lineales con estructura tipo esferas duras

    Directory of Open Access Journals (Sweden)

    Máximo Agüero Granados

    2001-01-01

    Full Text Available Se estudian ciertas soluciones de ecuaciones no lineales que modelan procesos físicos, que tienen semejanzas con estructuras coherentes del tipo de esferas duras, modelo de partículas muy usado en varias ramas de la física. Estas soluciones compactas (gotas, kinks, etcétera. interactúan entre sí sólo a cortas distancias, porque no poseen colas infinitas como los solitones clásicos.

  13. Epidemiología de la diabetes mellitus en la infancia y adolescencia: tipo 1, tipo 2 y ¿diabetes "doble"?

    Directory of Open Access Journals (Sweden)

    Ingrid M. Libman

    2009-09-01

    Full Text Available Durante las últimas décadas, el aporte de la epidemiología a través de la estandarización de los métodos y las definiciones y la colaboración internacional ha permitido una mejor estimación de la incidencia y prevalencia de la diabetes mellitus (DM en la infancia y la adolescencia, así como la detección de probables factores de riesgo para los distintos tipos de la enfermedad, lo que orientaría al desarrollo de medidas preventivas y terapéuticas y la mayor comprensión de la magnitud del problema. Se ha observado un aumento global y amplias diferencias entre distintas regiones en la incidencia de la diabetes tipo 1 (DM1, al igual que un incremento en la frecuencia de la diabetes tipo 2 (DM2 en ciertas etnias asociado a un aumento de la obesidad. Se ha descripto la existencia de la llamada DM "doble" o "híbrida", caracterizada por la asociación de un fenotipo de DM2 (obesidad, acantosis nigricans con manifestaciones de autoinmunidad anti células beta.During the last decades, the contribution of epidemiology through the standardization of methods and definitions and international collaboration allowed a better estimation of the incidence and prevalence of DM in children and adolescents, as well as the detection of likely risk factors for the different types of the disease, which would allow the development of preventive and therapeutic measures and a better understanding of the magnitude of the problem. A global increase and wide differences in the incidence of type 1 diabetes have been observed among regions, as well as an increase in the frequency of type 2 diabetes in some ethnic groups, associated to a growing prevalence of obesity. The existence of what has been named "double" or "hybrid" DM has also been described, characterized by a phenotype of DM2 (obesity and acantosis nigricans associated with manifestations of autoimmunity.

  14. El automanejo de los pacientes con diabetes tipo 2: una revisión narrativa

    Directory of Open Access Journals (Sweden)

    N. Campo Guinea

    2013-12-01

    Full Text Available Según la Organización Mundial de la Salud para el año 2030 la cifra de personas con diabetes mellitus alcanzará valores cercanos a 366 millones en el mundo, ocupando su mayor proporción la diabetes mellitus tipo 2. Las estrategias actuales de Cronicidad y de la Diabetes presentes en España abogan por un adecuado automanejo del paciente por medio de programas y/o intervenciones apropiadas para ello. Sin embargo, existen unos conocimientos y actitudes inadecuadas que limitan la asociación paciente-profesional que las estrategias de automanejo implican. A través de esta revisión bibliográfica se pretende mostrar las necesidades reales no cubiertas que los pacientes con diabetes mellitus tipo 2 tienen a la hora de automanejar la enfermedad. Así, se asentarán las bases para el desarrollo de futuros programas efectivos que se implementen ayudando al profesional sanitario a dirigir su trabajo diario hacía su principal objetivo, la persona con diabetes mellitus tipo 2 y sus necesidades.

  15. Determinantes del tipo de cambio real en Colombia. Un modelo neokeynesiano

    Directory of Open Access Journals (Sweden)

    Moreno Rivas, Álvaro Martín

    2002-12-01

    Full Text Available Este artículo presenta un modelo de tipo de cambio real siguiendo los desarrollos de la escuela neokeynesiana. Se estima econométricamente de acuerdo con la metodología de la escuela inglesa de econometría. El modelo empírico incorpora una dinámica interesante y respeta las restricciones de equilibrio de largo plazo entre el tipo de cambio real y los fundamentales macroeconómicos. Se encuentra que el ritmo de apreciación o depreciación del tipo de cambio real está determinado por los cambios en los términos de intercambio, la apertura de la economía, los flujos de capitales y la aceleración de la devaluación nominal. El incremento del gasto público no es significativo a los niveles convencionales de confianza estadística. Finalmente se evalúa si la devaluación cumple con los requisitos de exogeneidad débil, exogeneidad fuerte y superexogeneidad.

  16. Tipos de Ativismo Digital e Ativismo Preguiçoso no Mapa Cultural

    Directory of Open Access Journals (Sweden)

    Gabriela Bezerra Lima

    2012-08-01

    Full Text Available Este artigo se propõe a elencar os tipos de ativismo digital desenvolvidos por instituições e indivíduos e que estimulam o compartilhamento de suas mensagens nas redes sociais digitais. A partir da classificação dos tipos de ativismo digital (VEGH, 2003, propomos uma subclassificação do ativismo de ‘organização e mobilização’ e das ações de “ativismo preguiçoso” (MOROZOV, 2010 dos internautas. Para exemplificar os tipos de ativismo digital, este artigo observa as ações desenvolvidas na internet pela Fundação SOS Mata Atlântica. Nosso objetivo é analisar como os contratos de comunicação (CHARAUDEAU, 2006 de ativismo digital são percebidos e quais são seus níveis de contestação ao status quo no Mapa Cultural (DOUGLAS, 1998.

  17. Efecto incretina en el tratamiento de la diabetes mellitus tipo 2

    Directory of Open Access Journals (Sweden)

    Manuel de Jesús Díaz Pérez

    2015-02-01

    Full Text Available El efecto incretina está dado por las funciones del polipéptido insulinotrópico dependiente de glucosa y un péptido similar a glucagón sobre la hiperglucemia en el organismo humano. Desde su descubrimiento ha cobrado un papel cada vez más significativo en la elaboración de nuevos fármacos normoglucemiantes, que logren el control metabólico de los pacientes con diabetes mellitus tipo 2. El objetivo de esta revisión es actualizar la información sobre el efecto incretina, su relación con la diabetes mellitus tipo 2, los fármacos cuyo mecanismo de acción se basa en este fenómeno fisiológico, así como las perspectivas para el futuro inmediato en este tema. Para ello se realizó una revisión bibliográfica, empleando servicios disponibles desde la red Infomed, específicamente: SciELO, Hinari, PubMed y EBSCO. Se resumen aspectos del sustrato fisiológico y fisiopatológico del efecto incretina y su aplicación en la terapéutica de los pacientes con diabetes mellitus tipo 2, así como los resultados positivos que se han logrado hasta el momento en este campo

  18. RELACIÓN ENTRE EL TIPO DE APOYO Y EL ESTILO DE AMOR EN PAREJAS

    Directory of Open Access Journals (Sweden)

    Sergio Daniel Solares Barbosa

    2011-01-01

    Full Text Available Debido al incremento en el índice de divorcios en México, esta investigación tuvo como objetivo determinar la relación que existe entre el tipo de apoyo y el estilo de amor en parejas casadas mediante la aplicación del Inventario de Estilos de Amor y el Cuestionario de Tipo de Apoyo en Parejas. Se realizó una correlación de Pearson entre los estilos de amor y los tipos de apoyo, hallándose que el estilo de amor amistoso se presenta con mayor frecuencia y tiene una relación positiva con el apoyo expresado, mientras que el amor lúdico es menos frecuente y se vincula con el apoyo negativo. Para las mujeres es muy importante que exista un sentimiento de amistad para percibir un apoyo positivo de la pareja, mientras que en los hombres la relación pasional es aquella en la que se percibe el apoyo. En hombres y mujeres el estilo de amor lúdico es el que menos apoyo positivo encuentra.

  19. Identificação molecular de Mycoplasma mycoides subesp. mycoides tipo SC ioslado do conduto auditivo externo de caprinos clinicamente saudáveis

    Directory of Open Access Journals (Sweden)

    Pereira Lucieri Olegário

    2003-01-01

    Full Text Available O trabalho relata a presença de Mycoplasma mycoides subesp. mycoides Tipo SC, biótipo bovino, em caprinos clinicamente saudáveis no Estado do Rio de Janeiro, Brasil, identificado por PCR.

  20. Efecto de los factores socioculturales en la capacidad de autocuidado del paciente hospitalizado con diabetes tipo 2

    OpenAIRE

    Mireya Gricelia Galindo-Martínez; Laura Rico-Herrera; Nicolás Padilla-Raygoza

    2014-01-01

    Introducción: la diabetes tipo 2 es considerada como un problema de salud pública por su creciente prevalencia e incidencia. Obje- tivo: describir el efecto de los factores socioculturales en la capacidad de autocuidado del paciente hospitalizado con diabetes tipo 2 en el Hospital General de Tecomán, Colima, México. Método: estudio transversal, observacional. Se trabajó con 68 pacientes hospitalizados con diabetes tipo 2; se utilizó un instrumento que midió el efecto de los factores sociocult...

  1. Lipoperóxidos, actividad antioxidante y factores prooxidantes en adultos mayores con diabetes mellitus tipo 2

    OpenAIRE

    Ricardo Blanco Hernández; Mirna Ruíz Ramos; Martha A. Sánchez Rodríguez; Víctor Manuel Mendoza Núñez

    2004-01-01

    Antecedentes: La diabetes mellitus tipo 2 (DM) es una enfermedad crónico-degenerativa de alta prevalencia durante el envejecimiento que ha sido asociada con el estrés oxidativo (EOx), sin embargo las evidencias científicas no son del todo concluyentes. Objetivo: Determinar la relación de los niveles plasmáticos de lipoperóxidos (LPO), actividad antioxidante y factores pro-oxidantes con la DM tipo 2 en adultos mayores. Material y métodos: Se llevó a cabo un estudio de tipo transversal, compara...

  2. Gestión del riesgo de tipo de cambio: caso de la inversión en bolsa

    OpenAIRE

    2014-01-01

    RESUMEN: El análisis y la gestión del riesgo de tipo de cambio es un aspecto muy importante a la hora de realizar operaciones en el exterior. Por ello, en el trabajo que se presenta a continuación estudiaremos desde un punto de vista teórico la evolución del sistema monetario internacional, así como la definición del tipo de cambio y del riesgo del tipo de cambio, englobados dentro del mercado de divisas. Además, propondremos alternativas para la cobertura de dicho riesgo: el forward y los co...

  3. Intensyviosios insulino terapijos naujovės gydant 1 ir 2 tipo cukrinį diabetą

    OpenAIRE

    Varanauskienė, Eglė; Čeponienė, Indrė; Čeponis, Jonas

    2006-01-01

    Sergančiųjų 1 ir 2 tipo cukriniu diabetu pagrindinis gydymo tikslas – pasiekti ir palaikyti gerą glikemijos kontrolę (glikuotas hemoglobinas – HbA1c≤7,0 proc. pagal ADA (angl. American Diabetes Association – Amerikos diabeto asociacija) ir ≤6,5 proc. pagal IDF (angl. International Diabetes Federation – Tarptautinė diabeto federacija) taip sumažinant cukrinio diabeto komplikacijų riziką. Insulinoterapija būtina sergantiesiems 1 tipo cukriniu diabetu. Sergančiųjų 2 tipo cukriniu diabetu gydymas...

  4. OS EFEITOS DO EXERCÍCIO AERÓBICO NO TRATAMENTO DO DIABETES MELLITUS TIPOS 1 E 2

    OpenAIRE

    da Silva Neto, João Henrique; Ex-aluno do Centro Universitário La Salle; Marques Toigo, Adriana

    2013-01-01

    O objetivo desse estudo foi revisar na literatura os efeitos do exercício aeróbico (especialmente na modalidade de dança) no tratamento do diabetes mellitus tipo 1 e tipo 2, apresentando resultados obtidos em pesquisa nacionais e internacionais. Inicialmente foram abordados aspectos conceituais sobre o diabetes mellitus tipos 1 e 2. Em seguida, verificou-se como o exercício aeróbico vem sendo utilizado como tratamento do diabetes e quais são seus benefícios em relação aos índices glicêmicos e...

  5. Epidemiología de la diabetes mellitus en la infancia y adolescencia: tipo 1, tipo 2 y ¿diabetes "doble"?

    OpenAIRE

    Libman, Ingrid M.

    2009-01-01

    Durante las últimas décadas, el aporte de la epidemiología a través de la estandarización de los métodos y las definiciones y la colaboración internacional ha permitido una mejor estimación de la incidencia y prevalencia de la diabetes mellitus (DM) en la infancia y la adolescencia, así como la detección de probables factores de riesgo para los distintos tipos de la enfermedad, lo que orientaría al desarrollo de medidas preventivas y terapéuticas y la mayor comprensión de la magnitud del prob...

  6. SOMATÓTIPO E IMAGEM CORPORAL EM PESSOAS VIVENDO COM HIV/AIDS

    Directory of Open Access Journals (Sweden)

    Danielle Coutinho de Medeiros

    2016-02-01

    Full Text Available RESUMO Introdução: A terapia antirretroviral de alta atividade (HAART está associada ao surgimento de diversos efeitos adversos na população com HIV/Aids, dentre as quais, a lipodistrofia. Caracterizada pela reorganização anormal de gordura pelo corpo, é um dos efeitos mais relevantes, envolvendo riscos cardiometabólicos e prejuízos na imagem corporal. Objetivo: Analisar a somatotipia e a imagem corporal em pessoas vivendo com HIV/AIDS. Métodos: A amostra foi composta por cinco mulheres (47,8 ± 6,53 anos em uso da HAART e fisicamente ativas. Foi realizada uma intervenção com o treinamento concorrente e aconselhamento dietético e avaliou-se a conformação corporal pelo somatótipo e a imagem corporal pela escala de silhuetas. Resultados: Não houve diferença na classificação do somatótipo, entretanto, os resultados apontaram diferença significativa para a análise da distância de dispersão entre somatótipos (DDS na 1ª semana (DDS = 2,63 e 16ª semana de intervenção (DDS = 2,96, quando avaliado pelas médias; e quando avaliado individualmente, verificou-se diferença significativa tanto na DDS quanto na distância espacial entre somatótipos (DES nos casos 1, na 8ª semana (DDS = 3,20 e DES = 1,01 e 16.a semana (DDS = 2,73; e caso 3, na 1ª semana (DDS = 9,25 e DES = 1,44 e 16ª semana (DDS = 8,06 e DES = 1,37. Quanto à imagem corporal, observou-se a aproximação da imagem atual à imagem ideal (imagem atual inicial = 6; imagem atual final = 5; e imagem ideal inicial e final = 3. Conclusão: O programa de treinamento concorrente associado à orientação nutricional produziu resultados positivos tanto no somatótipo quanto na percepção da imagem corporal das participantes, comprovando sua eficácia no controle da lipodistrofia e na satisfação da imagem corporal do grupo avaliado.

  7. Los ejemplares tipo de Cicadellinae y Gyponinae (Hemiptera: Auchenorrhyncha: Cicadellidae depositados en el Museo de La Plata, Argentina

    Directory of Open Access Journals (Sweden)

    Susana L. PARADELL

    2010-01-01

    Full Text Available En la presente contribución, se realizó un relevamiento de los ejemplares tipo de Cicadellidae, depositados en la colección de la División Entomología del Museo de La Plata (MLP. Fueron examinados y listados 86 ejemplares tipo pertenecientes a 32 especies: siete Cicadellinae y 25 Gyponinae, las que fueron descriptas por los siguientes autores: Berg, DeLong, DeLong & Freytag, DeLong & Martinson, Spångberg , Tesón y Young. Para cada ejemplar tipo se brinda información acerca del nombre específico, referencia bibliográfica, categoría de tipo y procedencia.

  8. Factores asociados al auto-cuidado de la salud en pacientes diabéticos tipo 2

    OpenAIRE

    MB Amador-Díaz; FG Márquez-Celedonio; AS. Sabido-Sighler

    2007-01-01

    Objetivo: Cuantificar la prevalencia y los factores asociados al autocuidado de la salud en pacientes con diabetes tipo 2. Material y métodos. Mediante muestreo probabilistico fueron seleccionados 200 pacientes diabeticos tipo 2 a quienes se aplico una encuesta transversal analitica. Se aplico un cuestionario relacionado con el autocuidado de la salud; se investigo ademas el nivel de glucemia, factores sociodemograficos, culturales y psicologicos, analizados a traves de la razon de momios de ...

  9. Nuevas estrategias terapéuticas en diabetes mellitus tipo 1 New therapeutic strategies for type 1 diabetes mellitus

    OpenAIRE

    Barajas, M. (Miguel); Príncipe, R.M. (R.M.); Escalada, J.; Prósper, F; J. Salvador

    2008-01-01

    El principal determinante del riesgo de complicaciones derivadas de la diabetes mellitus tipo 1 se debe a los altos niveles de glucosa en sangre mantenidos durante largo tiempo. Para conseguir un beneficio terapéutico en pacientes con diabetes mellitus es necesario desarrollar tratamientos que permitan de manera segura, efectiva y estable mantener la normoglucemia. Lamentablemente, el tratamiento de la diabetes mellitus tipo 1 mediante el aporte exógeno de insulina no es capaz de conseguir ni...

  10. Resistência de biótipos de arroz-vermelho aos herbicidas imazapyr + imazapic e alternativas de controle

    Directory of Open Access Journals (Sweden)

    Rafael Salles Rubin

    2014-10-01

    Full Text Available O uso intenso de herbicidas com o mesmo mecanismo de ação na cultura do arroz (Oryza sativa L. tem selecionado biótipos resistentes, como, por exemplo, o arroz-vermelho (planta daninha resistente aos herbicidas imidazolinonas. Por essa razão, este trabalho foi desenvolvido com o objetivo de avaliar a resistência de arroz-vermelho ao herbicida imazapyr + imazapic, na região sul do Rio Grande do Sul, e o controle do biótipo resistente de arroz-vermelho com os herbicidas alternativos clethodim e glyphosate. Foram realizados três experimentos, em delineamento casualizado, arranjados em esquema fatorial. No primeiro experimento, o fator A testou biótipos de arroz-vermelho [ORYSA 184 (resistente e ORYSA 188 (susceptível], o fator B comparou herbicidas (imazapyr + imazapic, clethodim e glyphosate e o fator C avaliou doses dos herbicidas (0; 0,5; 1; 2; 4; 8; 16 e 32 vezes a dose recomendada. No segundo, compararam-se biótipos de arroz-vermelho e doses do herbicida imazapyr + imazapic (0; 0,5; 1; 2; 4; 8; 16; 32 e 64 vezes a dose recomendada. No terceiro, testaram-se biótipos de arroz-vermelho e doses diferentes do herbicida imazapyr + imazapic para cada biótipo. O biótipo ORYSA 184 é resistente ao imazapyr + imazapic, quando aplicada a dose máxima de registro e estádio indicado. Os herbicidas clethodim e glyphosate, detentores de mecanismos de ação alternativos, controlam o biótipo resistente ORYSA 184 de arroz-vermelho.

  11. Adaptabilidade, estabilidade e resistência a patógenos em genótipos de feijoeiro

    Directory of Open Access Journals (Sweden)

    Cleber Vinicius Giaretta Azevedo

    2015-10-01

    Full Text Available Resumo:O objetivo deste trabalho foi avaliar a resistência de genótipos de feijoeiro aos principais patógenos da cultura, bem como a adaptabilidade e a estabilidade de produção de grãos desses genótipos. Avaliaram-se 26 genótipos de feijoeiro quanto à resistência a Colletotrichum lindemuthianum, Fusarium oxysporum f. sp. phaseolie Xanthomonas axonopodis pv. phaseoli, por meio de inoculação, em laboratório, e em 19 ensaios de valor de cultivo e uso (VCU, em diferentes locais do Estado de São Paulo, nas safras das "águas", "seca" e "inverno", durante os anos agrícolas 2011, 2012 e 2013. Dezoito genótipos foram considerados resistentes: sete deles a C. lindemuthianum, sete a F. oxysporumf. sp. phaseolie quatro a X. axonopodispv. phaseoli. A reação de resistência aos patógenos está associada à estabilidade dos genótipos. Por meio das análises GGE biplot, foi possível identificar genótipos com adaptabilidade e estabilidade superiores às das testemunhas, nos dois grupos de tegumento avaliados, em todas as épocas de semeadura.

  12. Variación de la actividad cognitiva en diferentes tipos de pruebas de fluidez verbal.

    Directory of Open Access Journals (Sweden)

    Julián C. Marino

    2009-12-01

    Full Text Available En esta investigación se aplicaron diez pruebas de fluidez verbal del tipo fonológico, categorial, gramatical y combinadas a 259 adultos argentinos (15 a 70 años con el fin de conocer su correlación con la actividad ejecutiva, semántica y atencional. Se indagó sobre la estructura teórica de cada prueba de fluidez verbal, a fines de determinar la lógica de sus variaciones. El objetivo final de la investigación fue aportar al desarrollo de un explorador neuropsicológico en fluidez verbal, que sea útil para hacer evaluaciones breves y sencillas, incluyendo situaciones difíciles como pacientes hospitalizados, y tratando de extraer la máxima información posible de la actividad cognitiva. RESULTADOS: se realizaron análisis descriptivos sobre las pruebas de fluidez verbal, análisis factorial sobre las variables de la actividad cognitiva y análisis de regresión múltiples, ingresando como variables independientes las variables cognitivas y como dependientes cada una de las pruebas de fluidez verbal. CONCLUSIONES: los modelos predictivos hallados indican variaciones sistemáticas en relación al compromiso cognitivo entre los tipos de pruebas de fluidez verbal. También se hallaron variaciones dentro de cada tipo. Esto indica que el explorador en fluidez verbal puede ser una herramienta útil para evaluar diferentes capacidades y funciones cognitivas.

  13. Qualidade do leite cru tipo C e refrigerado em sistemas leiteiros tradicionais do sudoeste goiano

    Directory of Open Access Journals (Sweden)

    Aurélio Ferreira Melo

    2013-12-01

    Full Text Available Objetivou-se avaliar a qualidade do leite cru tipo C e cru refrigerado de sistemas leiteiros pouco tecnificados do Sudoeste Goiano, e verificar se o leite produzido atende às exigências previstas na instrução normativa 62/2011. Coletou-se 49 amostras de leite cru tipo C e leite cru refrigerado, em condições assépticas, utilizando frascos de 40 mL, contendo conservante Azidiol® para análise da CBT e Bronopol® para determinação da CCS e composição química. As análises eletrônicas foram realizadas no Laboratório de Qualidade do Leite do Centro de Pesquisa em Alimentos da Escola de Veterinária e Zootecnia da Universidade Federal de Goiás. Para comparação das médias entre os tratamentos utilizou-se o teste de Tukey a 5% de probabilidade. Os resultados de gordura e CCS evidenciaram que a maior ocorrência de mastite no leite proveniente de refrigeração tem relação direta com o aumento do teor de gordura do leite. A contagem bacteriana total do leite tipo C e refrigerado foram mais elevadas que o limite estabelecido pela legislação brasileira de qualidade do leite, e indicou a necessidade de maior atenção à higiene durante a obtenção e estocagem do leite.

  14. Pipe type poles in transmission power lines; Postes tipo tubo en lineas de transmision

    Energy Technology Data Exchange (ETDEWEB)

    Cervantes E, Mario; Becerril A, Armando [Luz y Fuerza del Centro, Mexico, D. F. (Mexico)

    1997-12-31

    The first supports for transmission power lines were relatively small structures, of simple configuration, to save reduced clearances to resist load in accordance with its need; with the technical development, gradually appeared higher and higher electric tensions and greater obstacles to overcome, consequently the design of the supports had to be adapted to the new conditions. This gave rise to the development of a specific technique that would adequate and incorporate the continuous engineering advances. In this document the initial considerations on the design poles pipe type are examined; within these considerations mention is made of: the design, the manufacture, the prototype tests, installation, quality control and foundations. The type tube pole is portrayed, as well as the steel reinforcement, finally the types of precast foundations are shown [Espanol] Los primeros soportes para lineas de transmision fueron estructuras relativamente pequenas, de configuracion simple, para salvar claros reducidos y resistir cargas proporcionales a sus necesidades, con el desarrollo de la tecnica, fueron apareciendo tensiones electricas cada vez mas elevadas y obstaculos mayores que vencer, por lo que el diseno de los soportes tuvo que adaptarse a las nuevas condiciones. Esto dio origen al desenvolvimiento de una tecnica especifica que fuese adecuando e incorporando los continuos avances de la ingenieria. En este documento se tratan las consideraciones iniciales del diseno de los postes tipo tubo; dentro de estas consideraciones se citan: el diseno, la fabricacion, las pruebas de prototipo, montajes, control de calidad y cimentaciones. Se ilustra el poste tipo tubo, al igual que el armado del poste, por ultimo se muestra los tipos de cimentaciones precoladas

  15. CONTROL PREDICTIVO DE UN ROBOT TIPO SCARA PREDICTIVE CONTROL OF A SCARA ROBOT

    Directory of Open Access Journals (Sweden)

    Oscar Andrés Vivas Albán

    2006-08-01

    Full Text Available Este artículo presenta una aplicación eficiente de un control por modelo de referencia sobre un robot de tipo SCARA. El control estudiado es un control predictivo funcional, el que hace uso de un modelo dinámico simplificado del robot. Los ensayos simulados se realizan sobre un robot de cuatro grados de libertad, tipo SCARA. Con el fin de comparar diferentes estrategias de control, se diseña un controlador clásico tipo PID y dos controladores basados en el modelo de referencia. En este último caso el sistema se linealiza y se desacoplada por realimentación, lo que transforma el sistema a controlar en un simple par de integradores. Al sistema lineal y desacoplado resultante se le aplica el control por par calculado y el control predictivo funcional. Los tres controladores estudiados se simulan sobre el robot SCARA con valores numéricos reales. Las pruebas permiten valorar las respuestas de estos controladores en seguimiento de trayectoria, rechazo de perturbaciones y presencia de errores en el modelado con consignas complejas similares a las utilizadas en procesos de fabricación.This paper describes an efficient approach for model based control, applied on a SCARA robot. The studied control is the predictive functional control which uses a simplified dynamical model of the robot. The simulated tests are made on a SCARA type robot, with four DOF. To compare several control strategies, a classical PID control and two model based controllers are designed. In the last case, the model is first linearized and decoupled by feedback, transforming the system into a double set of integrators. Computed torque control and predictive functional control are applied to the linear and decoupled system. The three studied controllers are simulated on the SCARA robot with real numerical values. Tracking performance, disturbance rejection and model robot mismatch are enlightened, using complex machining tasks trajectories and error presence in the modelling

  16. El coste de la diabetes tipo 2 en España: El estudio CODE-2

    Directory of Open Access Journals (Sweden)

    Mata M.

    2002-01-01

    Full Text Available Objetivo: Estimar el coste de la atención sanitaria al paciente diabético tipo 2, diferenciando el gasto derivado del control de la enfermedad, de la atención de sus complicaciones y de otros costes directos asociados. Métodos: Recogida retrospectiva del consumo de recursos a partir de la historia clínica y la entrevista personal en 29 centros de atención primaria de todo el territorio nacional de una muestra de pacientes seleccionados de forma aleatoria a partir del registro de diabéticos de cada centro. Resultados: Se evaluó a 1.004 pacientes (561 mujeres con una media de edad de 67,42 años y una media de evolución de la enfermedad de 10,07 años. El 50,9% no presentaba complicaciones, el 17,7% sólo macrovasculares, el 19,5% sólo microvasculares y el 11,9% ambas. El coste anual sanitario por paciente fue de 1.305,15 euros. De este coste el 28,6% (373,27 euros estaba relacionado directamente con el control de la diabetes, el 30,51% (398,20 euros con sus complicaciones y el 40,89% (533,68 euros no estaba relacionado. El coste medio de un paciente sin complicaciones fue de 883 euros frente a 1.403 de un paciente con complicaciones microvasculares, 2.022 cuando existían complicaciones macrovasculares y 2.133 cuando coexistían ambos tipos de complicaciones. Conclusiones: El elevado coste del tratamiento de la diabetes tipo 2 y sus complicaciones, sugiere la posibilidad de que la mejora del control de la enfermedad pueda no sólo mejorar la supervivencia y la calidad de vida, sino reducir los costes asociados con las complicaciones crónicas.

  17. Tipo de cambio, exportaciones e importaciones: El caso de la economía boliviana

    OpenAIRE

    2000-01-01

    Recientemente, como resultado de las salidas de capitales de las economías emergentes, ha vuelto la preocupación por los elevados déficit comerciales y el retorno a políticas cambiarias más activas. En el caso de Bolivia, debido a los saldos comerciales deficitarios que le caracterizan, surge la preocupación por el papel de la política cambiaria para tratar dichos déficit y la interrogante es ¿cuán elásticas son las exportaciones y las importaciones a las variaciones en el tipo de cambio real...

  18. Indicadores de neuropatia autonômica cardiovascular em pacientes com diabetes tipo 1

    OpenAIRE

    Lucianne Righeti Monteiro Tannus

    2014-01-01

    A Neuropatia autonômica cardiovascular (NAC), apesar de ter sido apontada como fator de risco independente para doença cardiovascular (DCV) em pacientes com diabetes tipo 1 (DM1), permanece subdiagnosticada. Os objetivos do trababalho foram determinar a prevalência de NAC e seus indicadores clínicos e laboratoriais em pacientes com DM1 e a associação com outras complicações crônicas do diabetes, além de avaliar a concordância entre os critérios diagnósticos da NAC determinados pelos parâmetro...

  19. Patrón de conducta tipo A y pautas educativas

    OpenAIRE

    Castro Fornieles, Josefina

    1993-01-01

    [spa] A finales de la década de los años cincuenta, dos cardiólogos, M. Friedman y R.H. Rosenman (1959), identificaron una serie de actitudes y comportamientos en sus pacientes coronarios que consideraron favorecían la aparición de problemas coronarios. Al conjunto de estas características le dieron el nombre de patrón de conducta tipo A (PCTA). Sus elementos principales son: estilo duro y competitivo, impaciencia y ritmo acelerado y además una excesiva implicación laboral con actividad inces...

  20. ¿Conviene flexibilizar el tipo de cambio para mejorar la competitividad?

    OpenAIRE

    Guadalupe Mántey

    2013-01-01

    En este artículo se investigan los efectos de una devaluación cambiaria en la dinámica exportadora de los países en desarrollo. En oposición a la teoría convencional, se muestra que el efecto negativo de esa medida en las hojas de balance de las empresas exportadoras, por su elevada dolarización de pasivos, anula la posible ganancia en competitividad. Con base en los resultados de la investigación empírica, se argumenta que el establecimiento de un tipo de cambio real competitivo y estable, p...