Note: This page contains sample records for the topic aluminum al matrix from Science.gov.
While these samples are representative of the content of Science.gov,
they are not comprehensive nor are they the most current set.
We encourage you to perform a real-time search of Science.gov
to obtain the most current and comprehensive results.
Last update: August 15, 2014.
1

Localized Corrosion Behavior of Al-Si-Mg Alloys Used for Fabrication of Aluminum Matrix Composites  

NASA Astrophysics Data System (ADS)

The relationship between microstructure and localized corrosion behavior in neutral aerated chloride solutions was investigated with SEM/EDAX, conventional electrochemical techniques, and with scanning Kelvin probe force microscopy (SKPFM) for two custom-made alloys with Si/Mg molar ratios of 0.12 and 0.49. In this order, Al3Fe, Al3Mg2, and Mg2Si intermetallics were identified in the first alloy and Al(FeMn)Si and Mg2Si particles in the second one. Anodic polarization curves and corrosion morphology showed that the alloy with higher Si/Mg molar ratio exhibited a better corrosion performance and evidence was shown that it had a more corrosion-resistant passive film. The corrosion process for both alloys in aerated 0.1 M NaCl solutions was localized around the Fe-rich intermetallics. They acted as local cathodes and produced dissolution of the aluminum matrix surrounding such particles. Mg2Si and Al3Mg2 exhibited anodic behavior. SKPFM was successfully used to map the Volta potential distribution of main intermetallics. The localized corrosion behavior was correlated with a large Volta potential difference between the Fe-rich intermetallics and the matrix. After immersion in the chloride solution, such Volta potential difference decreased.

Pech-Canul, M. A.; Giridharagopal, R.; Pech-Canul, M. I.; Coral-Escobar, E. E.

2013-12-01

2

Wetting Behavior of a Novel Al-Si-Ti Active Brazing Filler Metal Foil on Aluminum Matrix Composite  

NASA Astrophysics Data System (ADS)

An active ternary brazing filler metal of Al-12Si-1Ti with a melting temperature range of 851-856 K was developed by adding Ti into Al-Si system alloy to improve the wettability of Al-Si system filler metal on pure aluminum matrix composite reinforced with short alumina fiber (Al2O3sf/Al). The wetting behavior of the developed Al-12Si-1Ti and conventional Al-12Si foils were compared using sessile drop test at 883 K for 300, 900, and 1800 s in flowing argon atmosphere. After shorter retardation periods, the interfacial gaps between Al-12Si-1Ti foil and matrix (M/M) micro-interfaces could disappear more easily than the case of using conventional Al-12Si foil. Moreover, the thickness of residual Al-12Si-1Ti foil also decreased faster than that of conventional Al-12Si foil. Especially, the interfacial gaps between reinforcement and filler metal (R/M) micro-interfaces could be eliminated for the developed Al-12Si-1Ti foil, while for conventional Al-12Si foil the interfacial gaps at R/M micro-interfaces could not be eliminated, although Si atoms could penetrate into the composite through bonded M/M micro-interfaces. These results showed that the Ti addition could not only accelerate the wetting at M/M micro-interfaces, but also eliminate the interfacial gaps at R/M micro-interfaces.

Zhang, Guifeng; Su, Wei; Zhang, Jianxun; Suzumura, Akio

2013-07-01

3

Tensile Properties of Nano AL2O3 Particulate-Reinforced Aluminum Matrix Composites by Mechanical Alloying and Hot Extrusion  

NASA Astrophysics Data System (ADS)

The powder of the micro Al and variant volume fractions of nano Al2O3 were milled by a high energy planetary ball-mill. By milling, a homogenous distribution of nano Al2O3 particles in the metal matrix were developed. Then the milled powder was cold compressed and sintered at 545°C for one hr. The mold and the sintered sample hold in a furnace until the temperature reached 545°C. Then the hot 27mm diameter sample was extruded to 6mm diameter. From the extruded specimens, tensile, hardness and microstructure of the prepared specimens were determined. By these tests the effect of milling time, the percent of nano-particles and the microstructure were evaluated. The hardness and tensile behaviors of aluminum matrix composites reinforced with nano Al2O3 particulate have been found to increase remarkably with the volume fraction of the reinforcement.

Mehdinia, M.; Jenabali Jahromi, S. A.

4

Localized Corrosion Currents from Graphite/Aluminum and Welded SiC/Al Metal Matrix Composites.  

National Technical Information Service (NTIS)

Scanning vibrating electrode techniques (SVET) have been used to study corrosion in Gr/Al and SiC/Al metal matrix composites. This new technique uses vibrating probes to measure localized ionic currents with spatial and current resolutions on the order of...

C. R. Crowe

1985-01-01

5

Hot Extrusion of A356 Aluminum Metal Matrix Composite with Carbon Nanotube/Al2O3 Hybrid Reinforcement  

NASA Astrophysics Data System (ADS)

Over the years, the attention of material scientists and engineers has shifted from conventional composite materials to nanocomposite materials for the development of light weight and high-performance devices. Since the discovery of carbon nanotubes (CNTs), many researchers have tried to fabricate metal matrix composites (MMCs) with CNT reinforcements. However, CNTs exhibit low dispersibility in metal melts owing to their poor wettability and large surface-to-volume ratio. The use of an array of short fibers or hybrid reinforcements in a preform could overcome this problem and enhance the dispersion of CNTs in the matrix. In this study, multi-walled CNT/Al2O3 preform-based aluminum hybrid composites were fabricated using the infiltration method. Then, the composites were extruded to evaluate changes in its mechanical properties. In addition, the dispersion of reinforcements was investigated using a hardness test. The required extrusion pressure of hybrid MMCs increased as the Al2O3/CNT fraction increased. The deformation resistance of hybrid material was over two times that of the original A356 aluminum alloy material due to strengthening by the Al2O3/CNTs reinforcements. In addition, an unusual trend was detected; primary transition was induced by the hybrid reinforcements, as can be observed in the pressure-displacement curve. Increasing temperature of the material can help increase formability. In particular, temperatures under 623 K (350 °C) and over-incorporating reinforcements (Al2O3 20 pct, CNTs 3 pct) are not recommended owing to a significant increase in the brittleness of the hybrid material.

Kim, H. H.; Babu, J. S. S.; Kang, C. G.

2014-05-01

6

Spark plasma sintering of aluminum matrix composites  

NASA Astrophysics Data System (ADS)

Aluminum matrix composites make a distinct category of advanced engineering materials having superior properties over conventional aluminum alloys. Aluminum matrix composites exhibit high hardness, yield strength, and excellent wear and corrosion resistance. Due to these attractive properties, aluminum matrix composites materials have many structural applications in the automotive and the aerospace industries. In this thesis, efforts are made to process high strength aluminum matrix composites which can be useful in the applications of light weight and strong materials. Spark Plasma Sintering (SPS) is a relatively novel process where powder mixture is consolidated under the simultaneous influence of uniaxial pressure and pulsed direct current. In this work, SPS was used to process aluminum matrix composites having three different reinforcements: multi-wall carbon nanotubes (MWCNTs), silicon carbide (SiC), and iron-based metallic glass (MG). In Al-CNT composites, significant improvement in micro-hardness, nano-hardness, and compressive yield strength was observed. The Al-CNT composites further exhibited improved wear resistance and lower friction coefficient due to strengthening and self-lubricating effects of CNTs. In Al-SiC and Al-MG composites, microstructure, densification, and tribological behaviors were also studied. Reinforcing MG and SiC also resulted in increase in micro-hardness and wear resistance.

Yadav, Vineet

7

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  

NASA Astrophysics Data System (ADS)

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 ?-Al grains. Many fine in situ TiAl3 and TiB2 intermetallics were precipitated almost at the grain boundary of ?-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 coating material (Al-12 pctSi alloy), while it reached to 77, 83, and 89 pct by the coating materials of Al-6 pct Si-based mixed with Al-Ti5-B1 master alloy with different percentages 1, 2, and 3 pct, respectively.

El-Labban, Hashem F.; Abdelaziz, M.; Mahmoud, Essam R. I.

2014-05-01

8

Characterization of tribological behaviour of graphitic aluminum matrix composites, grey cast iron, and aluminum silicon alloys  

Microsoft Academic Search

In recent years a number of aluminum-silicon alloys and some graphitic aluminum matrix composites have been fabricated for potential tribological applications in the automotive industry, in particular for lightweight high efficiency internal combustion engines to replace conventional uses of cast iron. This study provides a systematic investigation for wear mechanisms in dry sliding of the graphitic aluminum-matrix composites (A356 Al-10%SiC-4%Gr

Ahmad Reza Riahi

2002-01-01

9

Corrosion Protection of Aluminum Metal-Matrix Composites  

Microsoft Academic Search

Corrosion protection of aluminum metal-matrix composites (MMC) by anodizing treatments was investigated. Electrochemical behavior of MMC without protection also was investigated. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements were used to characterize the properties of protective surface layers. Materials studied were Al 6061\\/SiC, alloy A356\\/SiC, Al 2009\\/SiC, Al 2014\\/AlâOâ and Al 6061\\/AlâOâ with various reinforcement concentrations. The MMC had

H. J. Greene; F. J. Mansfeld

1997-01-01

10

Analysis of Boron Carbide Aluminum Matrix Composites  

Microsoft Academic Search

This study deals with the feasibility of using boron carbide (B4C) as reinforcement for aluminum matrix composites (AMCs) obtained by solid-state processes (powder metallurgy and extrusion). Two different reinforcements were considered: B4C as the object of this study and SiC for direct comparison of results. Aluminum alloy AA6061 was used as matrix in all cases. Comparative analysis between both SiC

L. Gómez; D. Busquets-Mataix; V. Amigó; M. D. Salvador

2009-01-01

11

Effects of AlB2 Particles and Zinc on the Absorbed Impact Energy of Gravity Cast Aluminum Matrix Composites  

NASA Astrophysics Data System (ADS)

The effect of different amounts of boron, in the form of AlB2 particles, as well as zinc concentration in a gravity cast Al-B-Zn composite, was studied and related to the absorbed energy upon fracture during Charpy impact experiments. In addition, the authors correlated the composite Brinell hardness with the quantitative assessment of brittle and ductile fracture areas of the Charpy fractured specimens and found that increasing AlB2 particle concentration resulted in a reduction of absorbed impact energy. Although larger zinc levels produced somewhat similar results, the AlB2 effect was prevalent. The energy absorption upon impact reached a maximum when no particles were present; conversely, the lowest amount of absorbed energy corresponded to a composite with a composition of 15 wt.% Zn and 8% in volume of AlB2, i.e., the highest concentration of AlB2 and zinc studied. Raising the amount of AlB2 as well as zinc, as expected, resulted in higher Brinell hardness. A statistical analysis allowed studying of the particle size distribution, whereas values for crack tip opening displacement were subsequently calculated for the range of particle sizes found and the corresponding AlB2 particle volume percent. Higher porosity values were measured for larger AlB2 volume percent. Finally, analyses of fracture surfaces corroborated that brittle fracture was favored in composites with higher amounts of AlB2 and zinc.

Corchado, Marcos; Reyes, Fernando; Suárez, Oscar Marcelo

2014-04-01

12

Dual-nanoparticulate-reinforced aluminum matrix composite materials  

Microsoft Academic Search

Aluminum (Al) matrix composite materials reinforced with carbon nanotubes (CNT) and silicon carbide nanoparticles (nano-SiC) were fabricated by mechanical ball milling, followed by hot-pressing. Nano-SiC was used as an active mixing agent for dispersing the CNTs in the Al powder. The hardness of the produced composites was dramatically increased, up to eight times higher than bulk pure Al, by increasing

Hansang Kwon; Seungchan Cho; Marc Leparoux; Akira Kawasaki

2012-01-01

13

Corrosion protection of aluminum metal-matrix composites  

SciTech Connect

Corrosion protection of aluminum metal-matrix composites (MMC) by anodizing treatments was investigated. Electrochemical behavior of MMC without protection also was investigated. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements were used to characterize the properties of protective surface layers. Materials studied were Al 6061/SiC, alloy A356/SiC, Al 2009/SiC, Al 2014/Al{sub 2}O{sub 3} and Al 6061/Al{sub 2}O{sub 3} with various reinforcement concentrations. The MMC had similar corrosion (E{sub corr}) and pitting (E{sub pit}) potentials as the matrix alloy. The cathodic current density for oxygen reduction in 0.5% N sodium chloride increased for Al 6061/SiC MMC with reinforcement concentration, which was attributed to electrochemically active interfaces between the matrix and the reinforcement particles. Anodizing and hot-water sealing were less effective for MMC than for the matrix aluminum alloys. The reinforcement particles produced a more porous structure of the anodized layer for MMC. Improved results were noted for dichromate sealing, where chromium (Cr{sup 6+}) in the pores of the outer oxide acted as an inhibitor. The effectiveness of corrosion protection methods decreased with increasing reinforcement concentration and was a function of the matrix alloy but not of the reinforcement material. The observed reduction in corrosion protection was believed to result from corrosion-susceptible interfaces formed between the reinforcement particles and the matrix.

Greene, H.J. [Army Aviation and Troop Command, St. Louis, MO (United States); Mansfeld, F. [Univ. of Southern California, Los Angeles, CA (United States)

1997-12-01

14

Dual-nanoparticulate-reinforced aluminum matrix composite materials.  

PubMed

Aluminum (Al) matrix composite materials reinforced with carbon nanotubes (CNT) and silicon carbide nanoparticles (nano-SiC) were fabricated by mechanical ball milling, followed by hot-pressing. Nano-SiC was used as an active mixing agent for dispersing the CNTs in the Al powder. The hardness of the produced composites was dramatically increased, up to eight times higher than bulk pure Al, by increasing the amount of nano-SiC particles. A small quantity of aluminum carbide (Al(4)C(3)) was observed by TEM analysis and quantified using x-ray diffraction. The composite with the highest hardness values contained some nanosized Al(4)C(3). Along with the CNT and the nano-SiC, Al(4)C(3) also seemed to play a role in the enhanced hardness of the composites. The high energy milling process seems to lead to a homogeneous dispersion of the high aspect ratio CNTs, and of the nearly spherical nano-SiC particles in the Al matrix. This powder metallurgical approach could also be applied to other nanoreinforced composites, such as ceramics or complex matrix materials. PMID:22571898

Kwon, Hansang; Cho, Seungchan; Leparoux, Marc; Kawasaki, Akira

2012-06-01

15

Dual-nanoparticulate-reinforced aluminum matrix composite materials  

NASA Astrophysics Data System (ADS)

Aluminum (Al) matrix composite materials reinforced with carbon nanotubes (CNT) and silicon carbide nanoparticles (nano-SiC) were fabricated by mechanical ball milling, followed by hot-pressing. Nano-SiC was used as an active mixing agent for dispersing the CNTs in the Al powder. The hardness of the produced composites was dramatically increased, up to eight times higher than bulk pure Al, by increasing the amount of nano-SiC particles. A small quantity of aluminum carbide (Al4C3) was observed by TEM analysis and quantified using x-ray diffraction. The composite with the highest hardness values contained some nanosized Al4C3. Along with the CNT and the nano-SiC, Al4C3 also seemed to play a role in the enhanced hardness of the composites. The high energy milling process seems to lead to a homogeneous dispersion of the high aspect ratio CNTs, and of the nearly spherical nano-SiC particles in the Al matrix. This powder metallurgical approach could also be applied to other nanoreinforced composites, such as ceramics or complex matrix materials.

Kwon, Hansang; Cho, Seungchan; Leparoux, Marc; Kawasaki, Akira

2012-06-01

16

Electrometallurgical treatment of aluminum-matrix fuels  

SciTech Connect

The electrometallurgical treatment process described in this paper builds on our experience in treating spent fuel from the Experimental Breeder Reactor (EBR-II). The work is also to some degree, a spin-off from applying electrometallurgical treatment to spent fuel from the Hanford single pass reactors (SPRs) and fuel and flush salt from the Molten Salt Reactor Experiment (MSRE) in treating EBR-II fuel, we recover the actinides from a uranium-zirconium fuel by electrorefining the uranium out of the chopped fuel. With SPR fuel, uranium is electrorefined out of the aluminum cladding. Both of these processes are conducted in a LiCl-KCl molten-salt electrolyte. In the case of the MSRE, which used a fluoride salt-based fuel, uranium in this salt is recovered through a series of electrochemical reductions. Recovering high-purity uranium from an aluminum-matrix fuel is more challenging than treating SPR or EBR-II fuel because the aluminum- matrix fuel is typically -90% (volume basis) aluminum.

Willit, J.L.; Gay, E.C.; Miller, W.E.; McPheeters, C.C.; Laidler, J.J.

1996-08-01

17

Structure of Ascast aluminum matrix composite containing Ni 3 AI-type intermetallic ribbons  

Microsoft Academic Search

An aluminum matrix composite containing rapidly solidified Ni75Al23B1Zr1 (at. pct) ribbons has been fabricated by casting at 700 C, 715 C, 730 C, and 875 C. Microstructural investigation has\\u000a shown that the matrix contains particles with a composition between Al3Ni and eutectic. The interfacial zones composed of several layers with different aluminum and nickel contents are observed\\u000a around the ribbons.

R. A. Varin; M. Metelnick; Z. Wronski

1989-01-01

18

Effects of reinforcements on sliding wear behavior of aluminum matrix composites  

Microsoft Academic Search

Effects of reinforcements on the wear behavior of aluminum matrix composites were investigated by pin-on-disk tests. The matrix materials were 2024 and ADC12 aluminum alloys. The volume fractions of SiC whiskers (Vfw) were 5–29% (MMCw), Al2O3 fibers (Vff) were 3–26% (MMCf), and SiC particles (Vfp) were 2–10% (MMCp). The MMCs were rubbed against a carbon steel pin under a load

T. Miyajima; Y. Iwai

2003-01-01

19

TiB 2\\/Al 2O 3 ceramic particle reinforced aluminum fabricated by spray deposition  

Microsoft Academic Search

Aluminum matrix ceramic particle reinforced composites (AMCs) is a kind of composite with great importance. Aluminum matrix composite reinforced with TiB2\\/Al2O3 ceramic particles was successfully in situ synthesized in Al–TiO2–B2O3 system in this paper, using spray deposition with hot-press treatment technique. Five groups of composites with different reinforcement volume contents were prepared and the comparisons of porosity, ultimate tensile strength

Chen Xing; Yang Chengxiao; Guan Leding; Yan Biao

2008-01-01

20

Cathodoluminescent properties of an Am3+ ion in a matrix of yttrium-aluminum garnet Y3Al5O12  

NASA Astrophysics Data System (ADS)

The luminescent properties of an americium ion are studied. Luminescence spectra of americium in yttrium-aluminum garnet are recorded for the first time. The luminescence bands are identified, and the levels responsible for the observed optical transitions are determined.

Kuznetsova, Ya. V.; Usacheva, V. P.; Zamoryanskaya, M. V.

2014-03-01

21

Aluminum-Alloy-Matrix/Alumina-Reinforcement Composites  

NASA Technical Reports Server (NTRS)

Isotropic composites of aluminum-alloy matrices reinforced with particulate alumina have been developed as lightweight, high-specific-strength, less-expensive alternatives to nickel-base and ferrous superalloys. These composites feature a specific gravity of about 3.45 grams per cubic centimeter and specific strengths of about 200 MPa/(grams per cubic centimeter). The room-temperature tensile strength is 100 ksi (689 MPa) and stiffness is 30 Msi (206 GPa). At 500 F (260 C), these composites have shown 80 percent retention in strength and 95 percent retention in stiffness. These materials also have excellent fatigue tolerance and tribological properties. They can be fabricated in net (or nearly net) sizes and shapes to make housings, pistons, valves, and ducts in turbomachinery, and to make structural components of such diverse systems as diesel engines, automotive brake systems, and power-generation, mining, and oil-drilling equipment. Separately, incorporation of these metal matrix composites within aluminum gravity castings for localized reinforcement has been demonstrated. A composite part of this type can be fabricated in a pressure infiltration casting process. The process begins with the placement of a mold with alumina particulate preform of net or nearly net size and shape in a crucible in a vacuum furnace. A charge of the alloy is placed in the crucible with the preform. The interior of the furnace is evacuated, then the furnace heaters are turned on to heat the alloy above its liquidus temperature. Next, the interior of the furnace is filled with argon gas at a pressure about 900 psi (approximately equal to 6.2 MPa) to force the molten alloy to infiltrate the preform. Once infiltrated, the entire contents of the crucible can be allowed to cool in place, and the composite part recovered from the mold.

Kashalikar, Uday; Rozenoyer, Boris

2004-01-01

22

FRICTION AND WEAR OF ALUMINUM MATRIX COMPOSITES  

Microsoft Academic Search

Aluminum has some beneficial properties: low density, relatively low price, and corrosion resistance in many applications as well as availability in a large quantity. Mechanical properties of aluminum can be improved by alloying with metals as copper, magnesium, silicon etc. Soft metals as tin, lead, cadmium and silver alloyed in aluminum lower the friction and wear rate. At the same

Mihály Kozma

23

Corrosion control of cement-matrix and aluminum-matrix composites  

NASA Astrophysics Data System (ADS)

Corrosion control of composite materials, particularly aluminum-matrix and cement-matrix composites, was addressed by surface treatment, composite formulation and cathodic protection. Surface treatment methods studied include anodization in the case of aluminum-matrix composites and oxidation treatment (using water) in the case of steel rebar for reinforcing concrete. The effects of reinforcement species (aluminum nitride (AIN) versus silicon carbide (SiC) particles) in the aluminum-matrix composites and of admixtures (carbon fibers, silica fume, latex and methylcellulose) in concrete on the corrosion resistance of composites were addressed. Moreover, the effect of admixtures in concrete and of admixtures in mortar overlay (as anode on concrete) on the efficiency of cathodic protection of steel reinforced concrete was studied. For SiC particle filled aluminum, anodization was performed successfully in an acid electrolyte, as for most aluminum alloys. However, for AlN particle filled aluminum, anodization needs to be performed in an alkaline (0.7 N NaOH) electrolyte instead. The concentration of NaOH in the electrolyte was critical. It was found that both silica fume and latex improved the corrosion resistance of rebar in concrete in both Ca(OH)sb2 and NaCl solutions, mainly because these admixtures decreased the water absorptivity. Silica fume was more effective than latex. Methylcellulose improved the corrosion resistance of rebar in concrete a little in Ca(OH)sb2 solution. Carbon fibers decreased the corrosion resistance of rebar in concrete, but this effect could be made up for by either silica fume or latex, such that silica fume was more effective than latex. Surface treatment in the form of water immersion for two days was found to improve the corrosion resistance of rebar in concrete. This treatment resulted in a thin uniform layer of black iron oxide (containing Fesp{2+}) on the entire rebar surface except on the cross-sectional surface. Prior to the treatment, the surface was non-uniform due to rusting. Sand blasting also made the surface uniform, but is an expensive process, compared to the water immersion method. For cathodic protection of steel rebar reinforced concrete, mortar overlay containing carbon fibers and latex needed 11% less driving voltage to protect the rebar in concrete than plain mortar overlay. However, multiple titanium electrical contacts were necessary, whether the overlay contained carbon fibers or not. For the same overlay (containing carbon fibers and latex), admixtures in the concrete also made a significant difference on the effect of cathodic protection; concrete with carbon fibers and silica fume needed 18% less driving voltage than plain concrete and 28% less than concrete containing silica fume.

Hou, Jiangyuan

24

Characterization of tribological behaviour of graphitic aluminum matrix composites, grey cast iron, and aluminum silicon alloys  

NASA Astrophysics Data System (ADS)

In recent years a number of aluminum-silicon alloys and some graphitic aluminum matrix composites have been fabricated for potential tribological applications in the automotive industry, in particular for lightweight high efficiency internal combustion engines to replace conventional uses of cast iron. This study provides a systematic investigation for wear mechanisms in dry sliding of the graphitic aluminum-matrix composites (A356 Al-10%SiC-4%Gr and A356 Al-5%Al2O3-3%Gr) developed for cylinder liner applications. Two eutectic Al-Si alloys (modified with rare earth elements) developed for wear resistant engine blocks were also studied. The tribological behavior of grey cast iron (ASTM A30), which is a traditional material for engine components, was also investigated as reference. For graphitic aluminum matrix composites, a wear mapping approach has been adopted. Three main regimes: ultra mild, mild and severe wear regions were determined in the maps; additionally, a scuffing region was observed. In the ultra mild wear regime the wear resistance was primarily due to the hard particles supporting the load. It was shown that the onset of severe wear in graphitic composites occurred at considerably higher loads compared to A356 aluminum alloy and A356 Al-20% SiC composite. At the onset of severe wear, the surface temperatures and coefficient of friction of the graphitic composites was lower than that of A356 Al-20% SiC. At all testing conditions in the mild wear regime, a protective tribo-layer was formed, which by increasing the speed and load became more continuous, more compact, smoother, and harder. The tribo-layers were removed at the onset of severe wear. An experimental wear map of grey cast iron was constructed; it consisted of three wear regimes: ultra mild, mild and severe wear. In the ultra mild regime a compacted fine iron oxide powder formed on the contact. The onset of severe wear was started with local material transfer to the steel counterface, and continued by increasing the roughness of the counterface. In the mild wear regime the oxide layers on the contact surface controlled the wear. Because of the microstructure of grey cast iron, large size debris formed in the mild regimes, which could promote a transition from mild to severe wear at loading conditions close to the upper limit of the mild regime. The effects of size and morphology of hard phases in eutectic Al-Si alloys on their scuffing and wear resistance was investigated using etching techniques. Scratch tests and sliding wear tests were performed on the Al-Si samples etched to different times. At low loads, the wear rates and scuffing resistance of Al-Si alloys were a strong function of the etching time, surface roughness before etching, and the morphology of the hard phases. In the etched condition, fracture of the hard phases from the roots of the protruded portions of particles caused scuffing; while fracture of the trailing edges of the hard phases controlled the wear rate of the Al-Si alloys.

Riahi, Ahmad Reza

25

Aluminum Metal-Matrix Composites for Automotive Applications: Tribological Considerations  

Microsoft Academic Search

Aluminum alloys possess a number of mechanical and physical properties that make them attractive for automotive applications, but they exhibit extremely poor resistance to seizure and galling. Reinforcement of aluminum alloys with solid lubricants, hard ceramic particles, short fibers and whiskers results in advanced metal-matrix composites (MMC) with precise balances of mechanical, physical and tribological characteristics. Advanced manufacturing technologies such

S. V. Prasad; R. Asthana

2004-01-01

26

Ductile - Ductile Beryllium Aluminum Metal Matrix Composite Manufactured by Extrusion.  

National Technical Information Service (NTIS)

Beryllium-aluminum alloys are unique, in-situ ductile-ductile metal matrix composite alloys. Cast and extruded beryllium-aluminum composite alloys are expected to have a unique combination of properties that are attractive for applications such as ground ...

N. F. Levoy

1994-01-01

27

Mechanical Behavior and Processing of Aluminum Metal Matrix Composites.  

National Technical Information Service (NTIS)

The objectives of the present three year research program were threefold. First the program sought to explore the potential of using spray atomization and deposition to process aluminum metal matrix composites, not only with improved mechanical properties...

E. J. Lavernia F. A. Mohamed

1992-01-01

28

Hot extruded carbon nanotube reinforced aluminum matrix composite materials  

NASA Astrophysics Data System (ADS)

Carbon nanotube (CNT) reinforced aluminum (Al) matrix composite materials were successfully fabricated by mechanical ball milling followed by powder hot extrusion processes. Microstructural analysis revealed that the CNTs were well dispersed at the boundaries and were aligned with the extrusion direction in the composites obtained. Although only a small quantity of CNTs were added to the composite (1 vol%), the Vickers hardness and the tensile strength were significantly enhanced, with an up to three-fold increase relative to that of pure Al. From the fractography of the extruded Al-CNT composite, several shapes were observed in the fracture surface, and this unique morphology is discussed based on the strengthening mechanism. The damage in the CNTs was investigated with Raman spectroscopy. However, the Al-CNT composite materials were not only strengthened by the addition of CNTs but also enhanced by several synergistic effects. The nanoindentation stress-strain curve was successfully constructed by setting the effective zero-load and zero-displacement points and was compared with the tensile stress-strain curve. The yield strengths of the Al-CNT composites from the nanoindentation and tensile tests were compared and discussed. We believe that the yield strength can be predicted using a simple nanoindentation stress/strain curve and that this method will be useful for materials that are difficult to machine, such as complex ceramics.

Kwon, Hansang; Leparoux, Marc

2012-10-01

29

Degradation Mechanisms in Aluminum Matrix Composites: Alumina/Aluminum and Boron/Aluminum. Ph.D. Thesis - North Carolina State Univ. at Raleigh  

NASA Technical Reports Server (NTRS)

The effects of fabrication and long term thermal exposure (up to 10,000 hours at 590 K) on two types of aluminum matrix composites were examined. An alumina/aluminum composite, was made of continuous alpha Al2O3 fibers in a matrix of commercially pure aluminum alloyed with 2.8% lithium. The mechanical properties of the material, the effect of isothermal exposure, cyclic thermal exposure, and fatigue are presented. Two degradation mechanisms are identified. One was caused by formation of a nonstoichiometric alumina during fabrication, the other by a loss of lithium to a surface reaction during long term thermal exposure. The other composite, boron/aluminum, made of boron fibers in an aluminum matrix, was investigated using five different aluminum alloys for the matrices. The mechanical properties of each material and the effect of isothermal and cyclic thermal exposure are presented. The effects of each alloy constituent on the degradation mechanisms are discussed. The effects of several reactions between alloy constituents and boron fibers on the composite properties are discussed.

Olsen, G. C.

1981-01-01

30

Internal Friction at Elevated Temperatures and Microplasticity of Aluminum Matrix Composites  

Microsoft Academic Search

Aluminum matrix composites (70vol%SiC\\/Al, 55vol%SiC\\/Al, 60vol%Al2O3\\/Al, 70vol%AlN\\/Al, and 30vol%SiC\\/Al) were prepared by the infiltration and the casting methods. The internal friction and the microplasticity of these composites were measured with a Föppel-Pertz torsion pendulum apparatus over the temperature range of 303 to 853 K and the strain range of 3×10-5 to 3×10-3. The internal friction of these composites increases with

Katsuhiro Nishiyama; Shigenori Utsumi; Takanobu Nakamura; Hironori Nishiyama

2009-01-01

31

In Situ Synthesis Aluminum Borate Whiskers Reinforced TiB2 Matrix Composites for Application in Aluminum Reduction Cells  

NASA Astrophysics Data System (ADS)

The TiB2 matrix ceramics reinforced by aluminum borate whiskers (Al18B4O33 w) had been prepared by the pressureless sintering method. The mechanical properties and densification behavior of the TiB2 matrix ceramics were investigated. The results showed that Al18B4O33 w was in situ synthesized by the reaction of boehmite (AlOOH) and TiB2 powders during the sintering process. Increasing the sintering temperature had benefited for densification of the TiB2 matrix ceramics. Al18B4O33 w could increase the flexural strength and Vicker's hardness. It is obtained that the maximum value Vicker's hardness with 1.81 GPa and flexural strength with 82 MPa for samples sintered at 1600°C.

Zhang, Gang; Yang, Jianhong

2013-11-01

32

Laser beam welding of SiC-particle-reinforced aluminum metal matrix composite  

Microsoft Academic Search

In this paper, SiC particle reinforced aluminum metal matrix composite (SiCp\\/Al MMC) is welded with high power continuous wave CO2 laser. Microstructure of the laser beam welded SiCp\\/Al MMC is characterized as functions of laser processing parameters (laser power density, welding speed, shielding gas flow direction, etc.). Results show that sound weld with few porosity can be produced by laser

Yong-Lai Chen; A. Shaban; L. G. Yu; Hua Ming Wang

1999-01-01

33

Development and compatibility of magnesium matrix fuel plates clad with 6061 aluminum alloy.  

SciTech Connect

Aluminum (Al) is a commonly used matrix for research reactor fuel plates. It has been found that a reaction between the fuel and the aluminum matrix may reduce or increase the irradiation stability of the fuel. To further understand the contribution of the reaction to the irradiation stability, experiments to develop a non-reacting matrix were performed. The work focused on magnesium (Mg), which is an excellent non-reacting matrix candidate and has a neutron absorption coefficient similar to Al. To avoid the formation of a liquid Al/Mg phase, improvements were made to the roll bonding process to achieve acceptable bonding at 415 C. After these methods were developed, fuel plates were produced with two fuels, uranium (U)-2 w/o molybdenum (Mo) and U-10-w/o Mo with two matrices, Al and Mg. A reaction between the magnesium and the 6061 Al cladding was discovered to take place during the processing at 415 C. To minimize the amount of reaction, methods were successfully developed to roll bond the fuel plates at 275 C. No reaction zone was observed in fuel plates processed at 275 C. Using this method, fuel plates with a Mg matrix are planned to be fabricated and included in the next irradiation matrix for the RERTR high density fuel development program.

Wiencek, T. C.

1998-10-22

34

The role of Metal-Matrix Composite development During Friction Stir Welding of Aluminum to Brass in Weld Characteristics  

NASA Astrophysics Data System (ADS)

The present research aims to investigate the development of brass reinforced aluminum composites during dissimilar friction stir welding of brass and aluminum. Moreover, to probe the effect of such a metal matrix composite on its bed, the cross-sectional properties of joint area are studied in two aspects of corrosion behavior and hardness distribution. Microstructural investigations through optical and electron microscopy show development of lamellar composites within the top site of the stir zone and aluminum surface. The measured iso-hardness contours indicate that evolved composite structures increase the cross-sectional hardness of aluminum locally. Also, the electrochemical assessment of joint area suggests that Al/Br composite structure plays an accelerative role in deterioration of cross-sectional corrosion resistance of aluminum through obstructing passivation and forming microgalvanic cells, where cathodic brass reinforcements intensify the corrosion of anodic aluminum matrix.

Zareie Rajani, H. R.; Esmaeili, A.; Mohammadi, M.; Sharbati, M.; Givi, M. K. B.

2012-11-01

35

Plasma spray joining of Al-matrix particulate reinforced composites  

SciTech Connect

Aluminum matrix composite joints have been produced on both aluminum alloy and metal matrix composite (MMC) substrates using powders containing SiC and Al{sub 2}O{sub 3} particulates. Most of the composite powders were produced by ball milling, but the most effective joints were produced using Osprey composite powders. The results of preliminary joining experiments indicate that the substrate should be preheated to 200 C and a very wide bevel angle should be provided in order to obtain the highest strength joints. Silicon alloy additions to the matrix significantly improved strength but titanium additions had no effect. Heat treatment after spraying significantly improved the bond strength and restored precipitation hardening in the matrix. Significant amounts of Mg were lost from the deposit during spraying while some free silicon was produced by pyrolysis of the SiC powder; hence, further efforts must develop powder compositions that produce the optimum matrix composition in the sprayed deposit. Hot isostatic pressing of the samples to eliminate porosity had only a small effect on the final strength of the joints. No significant amount of Al{sub 4}C{sub 3} was detected in deposits which contained SiC.

Itsukaichi, T.; Eagar, T.W.; Unemoto, M.; Okane, I.

1996-09-01

36

Microstructurally toughened particulate-reinforced aluminum matrix composites  

NASA Astrophysics Data System (ADS)

Silicon carbide particulate-reinforced aluminum matrix composites with dramatically higher energy absorption capability and damage tolerance have been demonstrated. The approach, referred to as microstructurally toughened composites, consists of segregating the composite into particulate-reinforced regions and continuous ductile toughening regions. Composites consisting of silicon carbide particulate-reinforced 6061 Al (SiCp/6061) with monolithic 6061 and commercially pure (CP) titanium toughening regions were fabricated. As much as an order of magnitude increase in notched Charpy impact energy absorption capability was demonstrated relative to conventional SiCp/6061 composites, with the higher values being associated with those samples that deflected the crack front more extensively during failure. The longitudinal tensile strength of the composites was shown to be independent of the scale of the microstructure or the magnitude of the toughening/reinforced region's interfacial strength. The high impact energy 6061 toughened composites displayed low transverse tensile strength values, while the CP titanium toughened composites simultaneously displayed high energy absorption and high transverse tensile strength. A model was also developed to predict the minimum and maximum energy absorption capability of the composites, as well as provide a quantitative estimate of the composite energy absorption based on the measured crack front deflection length in the failed impact samples.

Nardone, Vincent C.; Strife, James R.; Prewo, K. M.

1991-01-01

37

Modeling the Growth of Aluminum Gallium Nitride ((Al)GaN) Films Grown on Aluminum Nitride (AlN) Substrates.  

National Technical Information Service (NTIS)

The goal of this research was to determine if the evolution of dislocations in aluminum gallium nitride (AlGaN) films grown on aluminum nitride (AlN) substrates could be modeled with the goal of determining if there are conditions under which the films ar...

A. J. Ciani I. Batyrev K. A. Jones P. W. Chung

2011-01-01

38

Elevated-temperature deformation and forming of aluminum-matrix composites  

SciTech Connect

Three related studies on the elevated-temperature deformation and forming of aluminum-matrix composites are made. In Part A, isothermal creep deformation of SiC whisker-reinforced 2124Al matrix composites (2124Al-SiCw) and a SiC whisker-reinforced aluminum matrix composite (CMSH A-40) are extensively studied at various applied stresses and temperatures. High stress exponents and activation energies for creep are observed to be general features of these composites creep tension. The anomalously high activation energy for creep observed in 2124Al-SiCw composite is partly attributed to the slightly higher activation energy exhibited by the matrix material. In Part B, thermal-cycling creep deformation of 2124Al-SiCw composites, an Al-Si eutectic alloy, and a CMSH A-40 composite is investigated. Thermal cycling can cause MMC's to creep at much higher strain rates and exhibit very high strain rate sensitivity exponent and very high tensile elongation at failure. Part C explores the possibility of using the unique mechanical properties, (e.g. high-strain-rate sensitivity exponent and high formability), which result from thermal cycling to form useful components from MMC's. Experimental results demonstrate that gas-pressure forming of MMC components via thermal cycling is feasible.

Chen, Yongchin.

1991-01-01

39

Machinability study on a ceramic microsphere-reinforced aluminum matrix composite  

Microsoft Academic Search

When used for engineering applications, metal matrix composites (MMC) are often machined. This paper investigates the machinability of an experimental alumina-containing microsphere using a reinforced 6061 aluminum alloy (Comral 85 composite). The turning data was compared with that obtained for a similar MMC which was reinforced with angular Al2O3 particulates. Tool flank wear, cutting force and workpiece surface finish were

D. Bhattacharyya; G. Murti; J. L. Mihelich; K. Xia; M. J. Couper

1992-01-01

40

Effect of Pin Profile on Friction Stir Welded Aluminum Matrix Composites  

Microsoft Academic Search

To clarify the role of pin profile geometry on some properties of friction stir welded of the considered aluminum matrix composites (Al - 4 wt.% Mg, reinforced with 1 wt.% SiC and 1 wt.% graphite particles) plates of 8 mm thickness were fabricated by compocasting method then annealed at 400°C for 2 hrs. Tools with different pin profiles (square, hexagonal and octagonal) were manufactured to

Adel Mahmood Hassan; Tarek Qasim; Ahmed Ghaithan

2012-01-01

41

Evaluation of dry sliding wear behavior of silicon particles reinforced aluminum matrix composites  

Microsoft Academic Search

This paper reports a study on the wear property of powder metallurgy aluminum matrix composites 9Si\\/Al–Cu–Mg. A ring on rock wear-testing machine is used to evaluate the wear property of the composites, in which a GCrl5 steel ring is used as the counter face material. The wear behavior of the composites under different conditions is studied. The optical microscope and

Sun Zhiqiang; Zhang Di; Li Guobin

2005-01-01

42

Mechanical Response of Al Matrix Syntactic Foams Produced by Pressure Infiltration Casting  

Microsoft Academic Search

Aluminum matrix syntactic foams with low-cost porous ceramic spheres of diameters between 0.25 and 4 mm have been manufactured by pressure infiltration casting. These syntactic foams were homogeneous in structure and had densities as low as half of the density of the Al matrix. The mechanical response of the four types of syntactic foams with different sphere sizes and densities

L. P. Zhang; Y. Y. Zhao

2007-01-01

43

Evaluation of Johnson-Cook model constants for aluminum based particulate metal matrix composites  

NASA Astrophysics Data System (ADS)

High strain rate and high temperature response of three types of aluminum based particulate metal matrix ceramic composites is investigated by performing split Hopkinson pressure bar (SHPB) experiments. The composites are: NGP-2014 (15% SiC), NGT-6061 (15% SiC), and NGU-6061 (15% Al2O3), in which all the reinforcement materials are percentage by volume. Johnson-Cook constitutive model constants are evaluated from the high strain rate/high temperature data and implemented in a two dimensional finite element computer code (EPIC-2D) to simulate the penetration of an ogive nose tungsten projectile (23 grams) at a velocity 1.17 km/sec into the base 6061-T6 aluminum alloy and the composite NGU-6061. The simulated penetrations in the composite and in 6061-T6 aluminum agree with in 2%, in both materials, with the measured values.

Hilfi, H.; Brar, N. S.

1996-05-01

44

Aluminum localization in bone from hemodialyzed patients: Relationship to matrix mineralization  

Microsoft Academic Search

Aluminum localization in bone from hemodialyzed patients: Relationship to matrix mineralization. It has been suggested that in uremic bone, aluminum interferes with normal mineralization. Aluminum content and aluminum localization were studied in iliac crest biopsies of two groups of patients on regular hemodialysis; one group had histologic osteomalacia, and little or no bone resorption (group 1); the other, osteitis fibrosa

Giulia Cournot-Witmer; Johanna Zingraff; Jean Jacques Plachot; Françoise Escaig; Roger Lefèvre; Pierre Boumati; Agnès Bourdeau; Michèle Garabédian; Pierre Galle; Raymond Bourdon; Tilman Drüeke; Sonia Balsan

1981-01-01

45

Control of Defects in Aluminum Gallium Nitride ((Al)GaN) Films on Grown Aluminum Nitride (AlN) Substrates.  

National Technical Information Service (NTIS)

We present efforts aimed at establishing a multiscale approach for simulating dislocations in aluminum gallium nitride ((Al)GaN) semiconductors. We performed quantum mechanical and classical molecular dynamics (MD) simulations to study the electronic and ...

C. Wu I. G. Batyrev K. A. Jones N. S. Weingarten P. W. Chung

2013-01-01

46

Effects of thermal cycling on density, elastic modulus, and vibrational damping in an alumina particulate reinforced aluminum metal matrix composite (Al{sub 2}O{sub 3p}/2014 Al)  

SciTech Connect

The effects of thermal cycling on the mechanical and physical properties, namely, the density, dynamic elastic modulus and vibrational damping, were measured for a particular reinforced metal matrix composite (MMC). The material was made by Duralcan. Specimens were exposed to up thermal cycles from room temperature to 300 C. The density of the material was measured by the Archimedes technique. The dynamic Young`s Modulus and vibrational damping of the material were determined by the piezoelectric ultrasonic composite oscillator technique (PUCOT). The results showed that the density and elastic modulus of the material increased only slightly due to the thermal cycling while the damping increased significantly. An increase in dislocation concentration near the particle/matrix interfaces caused by the thermal cycling could account for the measured results.

Wolfenden, A.; Tang, H.H. [Texas A and M Univ., College Station, TX (United States). Mechanical Engineering Dept.; Chawla, K. [Univ. of Alabama, Birmingham, AL (United States). Dept. of Materials and Mechanical Engineering; Hermel, T. [Univ. of Minnesota, Minneapolis, MN (United States). Dept. of Chemical Engineering and Materials Science

1999-07-01

47

Kinetic energy distributions of sputtered neutral aluminum clusters: Al--Al[sub 6  

Microsoft Academic Search

Neutral aluminum clusters sputtered from polycrystalline aluminum were analyzed by laser postionization time-of-flight (TOF) mass spectrometry. The kinetic energy distributions of Al through Al[sub 6] were measured by a neutrals time-of-flight technique. The interpretation of laser postionization TOF data to extract velocity and energy distributions is presented. The aluminum cluster distributions are qualitatively similar to previous copper cluster distribution measurements

S. R. Coon; W. F. Calaway; M. J. Pellin; G. A. Curlee; J. M. White

1992-01-01

48

Functionally Graded Al Alloy Matrix In-Situ Composites  

NASA Astrophysics Data System (ADS)

In the present work, functionally graded (FG) aluminum alloy matrix in-situ composites (FG-AMCs) with TiB2 and TiC reinforcements were synthesized using the horizontal centrifugal casting process. A commercial Al-Si alloy (A356) and an Al-Cu alloy were used as matrices in the present study. The material parameters (such as matrix and reinforcement type) and process parameters (such as mold temperature, mold speed, and melt stirring) were found to influence the gradient in the FG-AMCs. Detailed microstructural analysis of the composites in different processing conditions revealed that the gradients in the reinforcement modify the microstructure and hardness of the Al alloy. The segregated in-situ formed TiB2 and TiC particles change the morphology of Si particles during the solidification of Al-Si alloy. A maximum of 20 vol pct of reinforcement at the surface was achieved by this process in the Al-4Cu-TiB2 system. The stirring of the melt before pouring causes the reinforcement particles to segregate at the periphery of the casting, while in the absence of such stirring, the particles are segregated at the interior of the casting.

Kumar, S.; Subramaniya Sarma, V.; Murty, B. S.

2010-01-01

49

Infrared spectra of aluminum hydrides in solid hydrogen: Al2H4 and Al2H6.  

PubMed

The reaction of laser-ablated Al atoms and normal-H(2) during co-deposition at 3.5 K produces AlH, AlH(2), and AlH(3) based on infrared spectra and the results of isotopic substitution (D(2), H(2) + D(2) mixtures, HD). Four new bands are assigned to Al(2)H(4) from annealing, photochemistry, and agreement with frequencies calculated using density functional theory. Ultraviolet photolysis markedly increases the yield of AlH(3) and seven new absorptions for Al(2)H(6) in the infrared spectrum of the solid hydrogen sample. These frequencies include terminal Al-H(2) and bridge Al-H-Al stretching and AlH(2) bending modes, which are accurately predicted by quantum chemical calculations for dibridged Al(2)H(6), a molecule isostructural with diborane. Annealing these samples to remove the H(2) matrix decreases the sharp AlH(3) and Al(2)H(6) absorptions and forms broad 1720 +/- 20 and 720 +/- 20 cm(-1) bands, which are due to solid (AlH(3))(n). Complementary experiments with thermal Al atoms and para-H(2) at 2.4 K give similar spectra and most product frequencies within 2 cm(-1). Although many volatile binary boron hydride compounds are known, binary aluminum hydride chemistry is limited to the polymeric (AlH(3))( solid. Our experimental characterization of the dibridged Al(2)H(6) molecule provides an important link between the chemistries of boron and aluminum. PMID:15369378

Wang, Xuefeng; Andrews, Lester; Tam, Simon; DeRose, Michelle E; Fajardo, Mario E

2003-07-30

50

High Temperature Sliding Wear of Spray-Formed Solid-Lubricated Aluminum Matrix Composites  

NASA Astrophysics Data System (ADS)

The present work describes the tribological study of the aluminum metal matrix composite manufactured by the spray atomization and deposition technique. The immiscible element Sn is added in the Al-Si alloy in different proportion to see its effect on wear behavior. The economical mineral zircon sand (8 vol.%) of size range 63-90 ?m has been used as ceramic reinforcement. The microstructural features showed that Sn and reinforced particles were homogeneously dispersed in the matrix phase. The wear experiments were conducted at high temperature on pin-on-disk wear testing machine. The wear debris and worn surfaces are analyzed with the help of scanning electron microscope equipped with energy-dispersive spectroscopy facility. The Al-Si-10Sn/ZrSiO4 composite offers higher wear resistance as compared to base alloy and other composites irrespective of the high temperature conditions of wear tests.

Kaur, Kamalpreet; Pandey, O. P.

2013-10-01

51

Anodic Behavior of Al and the Alloys Al-In and Al-In-Ga in Aluminum-Air Batteries.  

National Technical Information Service (NTIS)

By recording of the polarization characteristics and measurement of the currents of self-dissolution, the anodic behavior of aluminum and the alloys Al-In and Al-In-Ga was tested under the operating conditions of aluminum-air batteries. The tests were con...

D. M. Drazic A. R. Despic S. K. Zecevic

1979-01-01

52

Laser and electron beam welding of SiC[sub p] reinforced aluminum A-356 metal matrix composite  

Microsoft Academic Search

This paper details the results of a comparative study of laser and electron beam welding of a cast aluminum metal-matrix composite (Al-MMC) reinforced with SiC particles (SiC[sub p]). Electron beam welding of 15% SiC[sub p] A356-MMC produces much less deleterious Al[sub 4]C[sub 3] than CO[sub 2] laser beam welding at the same input powers and travel speeds. The advantage of

T. J. Lienert; J. C. Lippold; E. D. Brandon

1993-01-01

53

Evaluation of corrosion-protection methods for aluminum metal-matrix composites (final report). Master's thesis  

SciTech Connect

Corrosion protection of Aluminum Metal Matrix Composites (MMC) using anodizing, chromate conversion coating and polymer coatings was investigated. Electrochemical Impedance Spectroscopy, DC polarization measurements, and Scanning Electron Microscopy (SEM) with Energy Dispersive X-ray Spectroscopy (EDS) were used. The materials studied included 606 1/SiC, A356/SiC, 2009/SiC, 2014/Al203 and 6061/Al203 in various reinforcement concentrations. The electrochemical behavior of the MMCs without protection was also investigated. MMCs were found to have similar corrosion and pitting potentials as the matrix alloy. The cathodic current density were found to be higher for MMCs with the current density increasing with reinforcement concentration. The increased current density is attributed to the interface between the matrix and the reinforcement particles which increases the corrosion rate. Anodizing was performed on both Al alloys and MMCS. A new model is proposed for Al alloys. Anodizing and hot water sealing on MMCs was less effective than on Al. Improved results were noted for dichromate sealing.

Greene, H.J.

1992-07-09

54

Spray-forming monolithic aluminum alloy and metal matrix composite strip  

SciTech Connect

Spray forming with de Laval nozzles is an advanced materials processing technology that converts a bulk liquid metal to a near-net-shape solid by depositing atomized droplets onto a suitably shaped substrate. Using this approach, aluminum alloys have been spray formed as strip, with technoeconomic advantages over conventional hot mill processing and continuous casting. The spray-formed strip had a flat profile, minimal porosity, high yield, and refined microstructure. In an adaptation to the technique, 6061 Al/SiC particulate-reinforced metal matrix composite strip was produced by codeposition of the phases.

McHugh, K.M.

1995-10-01

55

Modulus, strength and thermal exposure studies of FP-Al2O3/aluminum and FP-Al2O3/magnesium composites  

NASA Technical Reports Server (NTRS)

The mechanical properties of FP-Al2O3 fiber reinforced composites prepared by liquid infiltration techniques are improved. A strengthening addition, magnesium, was incorporated with the aluminum-lithium matrix alloy usually selected for these composites because of its good wetting characteristics. This ternary composite, FP-Al2O3/Al-(2-3)Li-(3-5)Mg, showed improved transverse strength compared with FP-Al2O3/Al-(2-3)Li composites. The lower axial strengths found for the FP-Al2O3/Al-(2-3)Li-(3-5)Mg composites were attributed to fabrication related defects. Another technique was the use of Ti/B coated FP-Al2O3 fibers in the composites. This coating is readily wet by molten aluminum and permitted the use of more conventional aluminum alloys in the composites. However, the anticipated improvements in the axial and transverse strengths were not obtained due to poor bonding between the fiber coating and the matrix. A third approach studied to improve the strengths of FP-Al2O3 reinforced composites was the use of magnesium alloys as matrix materials. While these alloys wet fibers satisfactorily, the result indicated that the magnesium alloy composites used offered no axial strength or modulus advantage over FP-Al2O3/Al-(2-3)Li composites.

Bhatt, R. T.

1981-01-01

56

Effect of Alumina Particle Additions on the Aging Kinetics of 2014-Aluminum Matrix Composites.  

National Technical Information Service (NTIS)

Differential Scanning Calorimetry (DSC) was conducted on 2014 aluminum, 2014 aluminum reinforced with 10 and 15 percent by volume of alumina particles, 2024 aluminum, and a A1/4%Cu alloy. Electrical resistivity and matrix micro-hardness measurements were ...

C. P. Harper

1991-01-01

57

Fabrication and mechanical behaviour of aluminum matrix composite materials  

SciTech Connect

Aluminum matrix composite materials containing SiC whisker and Saffil alumina short fiber are fabricated by the squeeze casting method. It is demonstrated that the direct squeeze casting infiltration method is suitable for discontinuously reinforced metal matrix composites (MMC's) whose volume fractions are in the range of 0.15-0.3; squeeze casting of compounds for the fabrication of discontinuous MMC's with less volume fractions (less than 0.1). Mechanical properties, such as Young's modulus and ultimate tensile strength, are improved up to 80 percent by the addition of reinforcement. Hardness is improved by the incorporation of reinforcement. Optimum aging conditions for MMC's are determined. The peak aging time decreases with increasing the aging temperature and decreasing the volume fraction of reinforcement. Predictions for the elastic moduli and tensile strength are proposed from the transformed laminate analogy, and combinations of modified rule of mixtures and shear lag theory. Wear resistance of the composite is improved. The major wear mechanism of discontinuous MMC's is strongly dependent upon the sliding speed. Weight loss increases linearly with the sliding distance. From fracture surface analyses at room and elevated temperatures, it is found that the failure mode is ductile at the microstructural level and it becomes more ductile as temperature increases. Based on the fracture surface observations and experimental data, the strength reduction at elevated temperatures is due to overaging and softening of the matrix alloy. Failure mechanisms of the as-fabricated composites are summarized.

Lim, Taewon.

1991-01-01

58

Effect on thickness of Al layer in poly-crystalline Si thin films using aluminum(Al) induced crystallization method.  

PubMed

The polycrystalline silicon (poly-Si) thin films were prepared by aluminum induced crystallization. Aluminum (Al) and amorphous silicon (a-Si) layers were deposited using DC sputtering and plasma enhanced chemical vapor deposition method, respectively. For the whole process Al properties of bi-layers can be one of the important factors. In this paper we investigated the structural and electrical properties of poly-crystalline Si thin films with a variation of Al thickness through simple annealing process. All samples showed the polycrystalline phase corresponding to (111), (311) and (400) orientation. Process time, defined as the time required to reach 95% of crystalline fraction, was within 60 min and Al(200 nm)/a-Si(400 nm) structure of bi-layer showed the fast response for the poly-Si films. The conditions with a variation of Al thickness were executed in preparing the continuous poly-Si films for solar cell application. PMID:21456186

Jeong, Chaehwan; Na, Hyeon Sik; Lee, Suk Ho

2011-02-01

59

Role of Al2O3 particulate reinforcements on precipitation in 2014 Al-matrix composites  

NASA Astrophysics Data System (ADS)

Precipitation in commercial aluminum alloy 2014, without and with alumina particulate reinforcements, was studied using microhardness, electrical resistivity, differential scanning calorimetry (DSC), and transmission electron microscopy. The precipitation sequence in 2014 Al was confirmed to be ?ss? ? + GPZ ?? + ?’?a + ?’ + gH?? + ? (AlCuMgSi) + ? (CuAl2). Reinforcement addition decreased the time to peak hardness, but also reduced the peak matrix microhardness. This was traced to a decrease in the amount of ?’ formed in the composites. Further, it was observed that while Guinier-Preston (GP) zone and ?’ formations are accelerated in the composites, ?’ precipitation is decelerated. The acceleration is attributable primarily to enhanced nucleation resulting from an increase in the matrix dislocation density due to coefficient of thermal expansion (CTE) mismatch between the matrix and the reinforcements, whereas the deceleration is associated with a decrease of low-temperature solute diffusivity due to absorption of vacancies at dislocations and interfaces. It was also observed that the degree of overall acceleration in hardening and the reduction in peak matrix microhardness with reinforcement addition decreased with decreasing aging temperatures. The causal relationships of these observations with the associated mechanisms are discussed.

Dutta, I.; Harper, C. P.; Dutta, G.

1994-08-01

60

Indentation Tests on Al Matrix Syntactic Foams  

Microsoft Academic Search

This paper investigates mechanical response of Al matrix syntactic foams manufactured by pressure infiltration casting under\\u000a indentation test. Syntactic foams with ceramic microspheres of three different particle sizes and inner structures were manufactured\\u000a and tested. Because the hollow microspheres are stronger than the porous ones, the syntactic foam with hollow microspheres\\u000a has a higher compressive strength than that of the

X. F. Tao; G. K. Schleyer; Y. Y. Zhao

61

A comparative study on microplastic deformation behavior in a SiCp\\/2024Al composite and its unreinforced matrix alloy  

Microsoft Academic Search

The deformation behaviors below 0.2% offset yield stress in a silicon carbide particulate reinforced aluminum composite (SiCp\\/2024Al) and its unreinforced matrix alloy were investigated experimentally under three typical heat treatment conditions. In the case of annealing, incorporation of SiC particulate into aluminum matrix can enhance the plastic flow stress (PFS) in macroplastic stage, but almost has no effect on PFS

Fan Zhang; Pengfei Sun; Xiaocui Li; Guoding Zhang

2001-01-01

62

Corrosion and wear resistance of titanium- and aluminum-based metal matrix composites fabricated by direct metal laser deposition  

NASA Astrophysics Data System (ADS)

Titanium- and Aluminum-based metal matrix composites (MMC) have shown favorable properties for aerospace applications such as airframes, reinforcement materials and joining elements. In this research, such coatings were developed by direct metal laser deposition with a powder-fed fiber coupled diode laser. The MMC formulations consisted of pure titanium and aluminum matrices with reinforcing powder blends of chromium carbide and tungsten carbide nickel alloy. Two powder formulations were investigated for each matrix material (Ti1, Ti2, Al1 and Al2). Titanium based composites were deposited onto a Ti6Al4V plate while aluminum composites were deposited onto AA 7075 and AA 5083 for Al1 and Al2, respectively. Microstructures of the MMCs were studied by optical and scanning electron microscopy. The hardness and reduced Young's modulus (Er) were assessed through depth-sensing instrumented nanoindentation. microhardness (Vickers) was also analyzed for each composite. The corrosion resistance of the MMCs were compared by monitoring open circuit potential (OCP), polarization resistance (Rp) and potentiodynamic polarization in 0.5 M NaCl to simulate exposure to seawater. The Ti-MMCs demonstrated improvements in hardness between 205% and 350% over Ti6Al4V. Al-MMCs showed improvements between 47% and 79% over AA 7075 and AA 5083. The MMCs showed an increase in anodic current density indicating the formation of a less protective surface oxide than the base metals.

Waldera, Benjamin L.

63

Internal Friction at Elevated Temperatures and Microplasticity of Aluminum Matrix Composites  

NASA Astrophysics Data System (ADS)

Aluminum matrix composites (70vol%SiC/Al, 55vol%SiC/Al, 60vol%Al2O3/Al, 70vol%AlN/Al, and 30vol%SiC/Al) were prepared by the infiltration and the casting methods. The internal friction and the microplasticity of these composites were measured with a Föppel-Pertz torsion pendulum apparatus over the temperature range of 303 to 853 K and the strain range of 3×10-5 to 3×10-3. The internal friction of these composites increases with increasing temperature and increases rapidly over 600 to 800 K, while their shear modulus gradually decrease and rapidly decrease over 600 to 800 K. The internal friction of the composites at elevated temperatures is caused by relaxations due to the interfacial diffusion between a reinforcement phase and Al and due to the plastic flow at grain boundaries. The activation energy of the interfacial diffusion is 40.7-56.7 kJ/mol for SiC/Al, 62.1 kJ/mol for Al2O3/Al, and 27.7 kJ/mol for AlN/Al, respectively. The activation energy of the plastic flow is 42.3-119 kJ/mol. The internal friction of the infiltration composites remarkably depends on strain amplitude rather than that of the casting composites. The Granato-Lücke plots of the composites show a linear relationship, indicating that the increase in internal friction with increasing shear strain is caused by the vibration energy loss due to the dislocation damping mechanism. The dislocation mobility of the infiltration composites is larger than that of the casting composites. The specific damping capacity and Young's modulus of 70vol%SiC are higher than those of 70vol%AlN.

Nishiyama, Katsuhiro; Utsumi, Shigenori; Nakamura, Takanobu; Nishiyama, Hironori

64

Molecular structures and energetics of the neutral aluminum trimethylaluminum complex: an Al Al bonded global minimum?  

NASA Astrophysics Data System (ADS)

From their recent laboratory kinetics studies, Parker and Nelson have proposed a monobridged molecular structure for the aluminum atom-trimethylaluminum system. Here molecular structures and energetics for the neutral aluminum atom-trimethylaluminum complex (AlTMA) are reported from theory. A second distinct minimum was located and characterized, corresponding to an unanticipated H 3C-Al-Al(CH 3) 2 geometry. In addition, the transition state between the two minima was located. The relative energies of these stationary points are also reported, predicting that the monobridged AlTMA structure recently reported is higher in energy than the methylaluminum DMA discovered in this study by about 2 kcal mol -1.

Larkin, Joseph D.; Moran, Damian; Schaefer, Henry F., III

2003-08-01

65

Recycling of aluminum and caustic soda solution from waste effluents generated during the cleaning of the extruder matrixes of the aluminum industry  

Microsoft Academic Search

Anodising industries use a concentrated caustic soda solution to remove aluminum from extruder matrixes. This procedure produces very alkaline effluents containing high amounts of aluminum. The work reported here was focussed on recycling aluminum, as aluminum hydroxide, from these effluents and regenerating an alkaline sodium hydroxide solution. Briefly, the method comprises a dilution step (necessary for reducing the viscosity of

Pieter Tansens; Alberto T. Rodal; Carina M. M. Machado; Helena M. V. M. Soares

2011-01-01

66

In-Situ Synthesis of Alumina Reinforced (Fe,cr)3al Intermetallic Matrix Nanocomposite  

Microsoft Academic Search

In this study, a mixture of chromium oxide, elemental iron and aluminum powders was subjected to high energy ball milling to produce Al2O3 reinforced (Fe,Cr)3Al matrix nanocomposite. The structural changes of powder particles during milling were investigated by X-ray diffractometery. Cross-sectional microstructure of powder particles after different milling times was observed by scanning electron microscopy using back scatter mode. The

S. E. Aghili; M. H. Enayati; F. Karimzadeh

2012-01-01

67

Machinability study on a ceramic microsphere-reinforced aluminum matrix composite  

NASA Astrophysics Data System (ADS)

When used for engineering applications, metal matrix composites (MMC) are often machined. This paper investigates the machinability of an experimental alumina-containing microsphere using a reinforced 6061 aluminum alloy (Comral 85 composite). The turning data was compared with that obtained for a similar MMC which was reinforced with angular Al2O3 particulates. Tool flank wear, cutting force and workpiece surface finish were monitored at regular intervals. Excellent machinability criteria have been achieved for the Comral-85 composite. Using the same type of cutting tool it gave a significantly higher tool life than what is achieved with the other Al2O3 particulate reinforced composite. It is hypothesized that the breakdown of microspheres upon tool contact, the shape, and reinforcement concentration are among the likely causes for this difference.

Bhattacharyya, D.; Murti, G.; Mihelich, J. L.; Xia, K.; Couper, M. J.

1992-09-01

68

Tailoring Microstructure and Properties of Hierarchical Aluminum Metal Matrix Composites Through Friction Stir Processing  

NASA Astrophysics Data System (ADS)

The fabrication of hierarchical aluminum metal matrix composites (MMCs) begins with the cryomilling of inert gas-atomized AA5083 Al powders with B4C particles, which yields agglomerates of nanocrystalline (NC) Al grains containing a uniform dispersion of solidly bonded, submicron B4C particles. The cryomilled agglomerates are size classified, blended with coarse-grain Al (CG-Al) powders, vacuum degassed at an elevated temperature, and consolidated to form the bulk composite. This hierarchical Al MMCs have low weight and high strength/stiffness attributable to the (A) Hall-Petch strengthening from NC-Al (5083) grains, (B) Zener pinning effects from B4C particulate reinforcement and dispersoids in both the NC-Al and CG-Al, (C) the interface characteristics between the three constituents, and (D) a high dislocation density. The hierarchical Al MMCs exhibit good thermal stability and microstructural characteristics that deflect or blunt crack propagation. A significant change in the microstructure of the composite was observed after friction stir processing (FSP) in the thermomechanically affected zone (TMAZ) due to the mechanical mixing, particularly in the advancing side of the stir zone (SZ). The NC-Al grains in the TMAZ grew during FSP. Evidence of CG-Al size reduction was also documented since CG-Al domain was absent by optical observation. Given the proper control of the microstructure, FSP has demonstrated its potential to increase both strength and ductility, and to create functionally tailored hierarchical MMCs through surface modification, graded structures, and other hybrid microstructural design.

Sohn, Y. H.; Patterson, T.; Hofmeister, C.; Kammerer, C.; Mohr, W.; van den Bergh, M.; Shaeffer, M.; Seaman, J.; Cho, K.

2012-02-01

69

Anodic behavior of Al and the alloys Al-In and Al-In-Ga in aluminum-air batteries  

Microsoft Academic Search

The anodic behavior of aluminum and the alloys Al-In and Al-In-Ga was tested under the operating conditions of aluminum-air batteries. The tests were conducted in an aqueous solution of 2 M NaCl, and the results obtained were compared with the results obtained from a special test of these alloys as the anode in a standard electrochemical cell. Significant results and

D. M. Drazic; A. R. Despic; S. K. Zecevic

1979-01-01

70

Control of self-propagating high-temperature synthesis derived aluminum-titanium carbide metal matrix composites  

NASA Astrophysics Data System (ADS)

Self-propagating High-temperature Synthesis (SHS) is a combustion process that can be used to form Metal Matrix Composite (MMC) reinforcing phases in situ. Generally, the kinetic processes in these reactions are poorly understood but are affected by reactant particle size, reactant green density, reactant stoichiometry, reaction preheat temperature, and reaction product cooling rate. These reaction parameters also affect the microstructure of the reaction products because of changes in the rate of heat evolution, reaction rate, surface area available for heterogeneous nucleation, reaction temperature, and the stable phases during and after the reaction. Post-reaction processes affecting the microstructure and properties of the SHS products include densification, melt alloying (SHS reaction products are used as a master alloy), and die casting techniques. Matrix alloy additions should be controlled to prevent unwanted reactions between the matrix and the reinforcement. In the present study, Ti + C + X ? TiC + X (X = Al or TiC) is the SHS reaction system studied, with varying amounts of Al (10-50wt%) or TiC (0-20wt%) added to the reactants as a thermal diluent. Addition of these diluents decreases the reaction temperatures and decreases the TiC reinforcing particle size and interaction during particle growth. A method of direct thermal analysis of the self-heating behavior of diluted SHS reactions is developed and compared to existing methods used to measure the apparent activation energy of single step SHS reactions. The activation energies are used to determine a probable reaction path for Ti + C + Al ? TiC + Al. SHS reaction products of various diluent concentrations are analyzed for TiC particle size and shape. SHS reaction products containing 55v% TiC - 45v% Al are dispersed as a master alloy in aluminum melts; reaction products containing higher concentrations of TiC particles are difficult to disperse. To show compatibility with the TiC reinforcing particles, MMCs with aluminum alloy matrices of pure aluminum, Al-4.5Mg, and Al-4.5Mg-4.5Cu-1Mn-0.25Cr are coupled with TiC particle concentrations of 0, 10, and 20v%. MMC compositions were Thixocast at VForge in Lakewood, CO and squeeze cast at CWRU in Cleveland, OH. A pure aluminum matrix MMC with 55v% TiC was densified after the SHS reaction and thixocast, though the other MMCs with pure aluminum matrices were not thixocast because they lack a semisolid matrix condition required for thixocasting. The cast MMCs are tested for tensile, hardness, wear, and ballistic properties with properties apparently dominated by agglomerated TiC particles.

Garrett, William

71

Reactivity of aluminum cluster anions with ammonia: selective etching of Al11(-) and Al12(-).  

PubMed

Reactivity of aluminum cluster anions toward ammonia was studied via mass spectrometry. Highly selective etching of Al(11)(-) and Al(12)(-) was observed at low concentrations of ammonia. However, at sufficiently high concentrations of ammonia, all other sizes of aluminum cluster anions, except for Al(13)(-), were also observed to deplete. The disappearance of Al(11)(-) and Al(12)(-) was accompanied by concurrent production of Al(11)NH(3)(-) and Al(12)NH(3)(-) species, respectively. Theoretical simulations of the photoelectron spectrum of Al(11)NH(3)(-) showed conclusively that its ammonia moiety is chemisorbed without dissociation, although in the case of Al(12)NH(3)(-), dissociation of the ammonia moiety could not be excluded. Moreover, since differences in calculated Al(n)(-) + NH(3) (n=9-12) reaction energies were not able to explain the observed selective etching of Al(11)(-) and Al(12)(-), we concluded that thermodynamics plays only a minor role in determining the observed reactivity pattern, and that kinetics is the more influential factor. In particular, the conversion from the physisorbed Al(n)(-)(NH(3)) to chemisorbed Al(n)NH(3)(-) species is proposed as the likely rate-limiting step. PMID:19916602

Grubisic, Andrej; Li, Xiang; Gantefoer, Gerd; Bowen, Kit H; Schnöckel, Hansgeorg; Tenorio, Francisco J; Martinez, Ana

2009-11-14

72

PENETRATION ABILITY OF ABRASIVE WATERJETS IN CUTTING OF ALUMINUM-SILICON CARBIDE PARTICULATE METAL MATRIX COMPOSITES  

Microsoft Academic Search

This article presents a set of studies performed on aluminum-silicon carbide particulate metal matrix composites prepared by adding 5, 10, 15 and 20% of SiC in aluminum alloy and processed with abrasive water jets that are formed with garnet and silicon carbide abrasives of 80 mesh size. These studies are essentially meant to assess the penetration ability of abrasive water

S. Srinivas; N. Ramesh Babu

2012-01-01

73

Quantitative analysis of debris clouds from duralumin and SiC-fiber\\/aluminum-matrix composite bumpers  

Microsoft Academic Search

In order to investigate the effect of the macro-structure of metal-matrix composite on impact fragmentation, three kinds of bumper plates, i.e. monolithic duralumin, SiC-fiber\\/pure-aluminum-matrix composite and pure-aluminum lamination were impacted by duralumin projectiles in the velocity range of 2.5–3.7km\\/s. The debris cloud extracting to the rear side of each bumper was taken by soft X-ray radiography, and the constituting fragments

Hideki Tamura; Masamichi Iwawaki; Akira B. Sawaoka

2003-01-01

74

Application of Cast SiC/Al (Silicon Carbide Reinforced Aluminum) to Rotary Engine Components.  

National Technical Information Service (NTIS)

A silicon carbide reinforced aluminum (SiC/Al) material fabricated by Dural Aluminum Composites Corporation was tested for various components of rotary engines. Properties investigated included hardness, high temperature strength, wear resistance, fatigue...

H. M. Stoller J. R. Carluccio J. P. Norman

1986-01-01

75

Fracture toughness of SiC/Al metal matrix composite  

NASA Technical Reports Server (NTRS)

An experimental study was conducted to evaluate fracture toughness of SiC/Al metal matrix composite (MMC). The material was a 12.7 mm thick extrusion of 6061-T6 aluminum alloy with 40 v/o SiC particulates. Specimen configuration and test procedure conformed to ASTM E399 Standard for compact specimens. It was found that special procedures were necessary to obtain fatigue cracks of controlled lengths in the preparation of precracked specimens for the MMC material. Fatigue loading with both minimum and maximum loads in compression was used to start the precrack. The initial precracking would stop by self-arrest. Afterwards, the precrack could be safely extended to the desired length by additional cyclic tensile loading. Test results met practically all the E399 criteria for the calculation of plane strain fracture toughness of the material. A valid K sub IC value of the SiC/Al composite was established as K sub IC = 8.9 MPa square root of m. The threshold stress intensity under which crack would cease to grow in the material was estimated as delta K sub th = 2MPa square root of m for R = 0.09 using the fatigue precracking data. Fractographic examinations show that failure occurred by the micromechanism involved with plastic deformation although the specimens broke by brittle fracture. The effect of precracking by cyclic loading in compression on fracture toughness is included in the discussion.

Flom, Yury; Parker, B. H.; Chu, H. P.

1989-01-01

76

Microstructure and Strength of Al2O3 and Carbon Fiber Reinforced 2024 Aluminum Alloy Composites  

NASA Astrophysics Data System (ADS)

The microstructure and mechanical properties of 2024 aluminum alloy composite materials strengthened with Al2O3 Saffil fibers or together with addition of carbon fibers were investigated. The fibers were stabilized in the preform with silica binder strengthened by further heat treatment. The preforms with 80-90% porosity were infiltrated by direct squeeze casting method. The microstructure of the as-cast specimens consisted mainly of ?-dendrites with intermetallic compounds precipitated at their boundaries. The homogenization treatment of the composite materials substituted silica binder with a mixture of the ? phase and silicon precipitates distributed in the remnants of SiO2 amorphous phase. Outside of this area at the binder/matrix interface, fine MgO precipitates were also present. At surface of C fibers, a small amount of fine Al3C4 carbides were formed. During pressure infiltration of preforms containing carbon fibers under oxygen carrying atmosphere, C fibers can burn releasing gasses and causing cracks initiated by thermal stress. The examination of tensile and bending strength showed that reinforcing of aluminum matrix with 10-20% fibers improved investigated properties in the entire temperature range. The largest increase in relation to unreinforced alloy was observed for composite materials examined at the temperature of 300 °C. Substituting Al2O3 Saffil fibers with carbon fibers leads to better wear resistance at dry condition with no relevant effect on strength properties.

Kaczmar, Jacek W.; Naplocha, Krzysztof; Morgiel, Jerzy

2014-05-01

77

[Relationship among coagulation effect of Al-based coagulant, content and speciation of residual aluminum].  

PubMed

The application of AlCl3, Al2 (SO4)3 and poly-aluminum chloride (PAC) in humic acid-kaolin simulated water was studied in this article. It is intended to discuss the relationship among coagulation effect of Al-based coagulants in humic acid-kaolin simulated water and content and speciation of residual aluminum. It was found that, the turbidity removal efficiency and UV254 removal efficiency could reach about 90% at the tested dosage. At higher dosage, PAC gave better coagulation effect. The residual total aluminum content and residual aluminum ratio of PAC, which was 0.9 mg/L and - 3.0% or so respectively, were greatly lower than those of AlCl3 and Al2 (SO4)3. The residual total dissolved aluminum was the predominant content in the effluent after coagulation and sedimentation by the three Al-based coagulants. For the total dissolved aluminum, the proportion of dissolved organic aluminum was significantly higher than that of other aluminum speciation. With respect to humic acid-kaolin simulated water, the content of residual total aluminum in the effluent after coagulation and sedimentation by PAC decreased obviously compared to AlCl3 and Al2 (SO4)3. PAC could effectively decrease the content of residual dissolved aluminum speciation which has higher toxicity. The content of residual total dissolved aluminum in the effluent after coagulation and sedimentation by PAC was about 0.6 mg/L. PMID:20698270

Yang, Zhong-Lian; Gao, Bao-Yu; Yue, Qin-Yan; Jiang, Yi-Shuai

2010-06-01

78

Corrosion of Continuous Fiber Reinforced Aluminum Metal Matrix Composites (CF-AMCs)  

NASA Astrophysics Data System (ADS)

The first objective of this research is to study the atmospheric corrosion behavior of continuous reinforced aluminum matrix composites (CF-AMCs). The materials used for this research were alumina (Al2O3) and nickel (Ni) coated carbon (C) fibers reinforced AMCs. The major focus is to identify the correlation between atmospheric parameters and the corrosion rates of CF-AMCs in the multitude of microclimates and environments in Hawai'i. The micro-structures of CF-AMCs were obtained to correlate the microstructures with their corrosion performances. Also electrochemical polarization experiments were conducted in the laboratory to explain the corrosion mechanism of CF-AMCs. In addition, CF-AMCs were exposed to seven different test sites for three exposure periods. The various climatic conditions like temperature (T), relative humidity (RH), rainfall (RF), time of wetness (TOW), chloride (Cl- ) and sulfate (SO42-) deposition rate, and pH were monitored for three exposure period. Likewise, mass losses of CF-AMCs at each test site for three exposure periods were determined. The microstructure of the CF-AMCS showed that Al/C/50f MMCs contained a Ni-rich phase in the matrix, indicating that the Ni coating on the C fiber dissolved in the matrix. The intermetallic phases obtained in Al-2wt% Cu/Al 2O3/50f-T6 MMC and Al-2wt%-T6 monolith were rich in Cu and Fe. The intermetallic phases obtained in Al 7075/Al2O3/50f-T6 MMC and Al 7075-T6 monolith also contained traces of Mg, Zn, Ni, and Si. Electrochemical polarization experiment indicated that the Al/Al 2O3/50f Al-2wt% Cu/Al2O3/50f-T6 and Al 7075/Al2O3/50f-T6 MMC showed similar corrosion trends as their respective monoliths pure Al, Al-2wt%-T6 and Al 7075-T6 in both aerated and deaerated condition. Al2O3 fiber, being an insulator, did not have a great effect on the polarization behavior of the composites. Al/C/50f MMCs corroded at a much faster rate as compared to pure Al monolith due to the galvanic effect between C and Al. According to the mass loss data of Al/C/50f MMCs, corrosion rate was high at marine environments (high Cl-) when compared to a tropical rainforest microclimate and low in a test site with a high SO2 and acid rain. Due to presence of conductive C fiber, the galvanic corrosion was a dominating corrosion mechanism. Due to high volume fraction of C, the corrosion phenomenon was cathodically controlled. The galvanic corrosion between C fiber and Al matrix showed a strong positive correlation with Cl - deposition rate. Lower corrosion rate at volcanic test site was attributed to dissolution of Ni rich phase, a potential cathodic site that promotes corrosion of Al/C/50f MMCs. Based on the mass loss data of Al2O3 based CF-AMCs and the monoliths showed maximum corrosion at volcanic test site when compared to any other test site. Due to the small volume fraction of intermetallic phases, the corrosion was anodically controlled. And hence the maximum anodic dissolution was found at volcanic test site (high SO2 and acid rain). The second objective of this thesis is to study the effect localized deformation on the corrosion of CF-AMCs. Corrosion initiation on Al (2 wt% Cu)/Al2O3/60f (60% fiber), Al 6061/Al2O 3/60f, and Al/Al2O3/60f CF-AMCs was studied in an aqueous environment The CF-AMCs and their monolithic alloys were deformed locally using a 1/16" diameter silicon nitride ball and 15-60 Kg load in a Rockwell hardness testing machine. Corrosion initiated at the deformed sites, and after longer exposures, spread over the entire region. Localized mechanical deformation resulted in micro-crevice formations at the fiber matrix interface. When deformed material is exposed to a corrosive solution, the crevices at the fiber matrix interface likely increased the hydrogen ion concentration lowering the pH at those regions, a process that leads to premature corrosion. The copper (Cu) rich CF-AMCs in aqueous solution resulted in dissolution of Cu rich phase and their subsequent deposition and redistribution as Cu over the deformed CF-AMCs surface. The corrosion rates of deformed C

Tiwari, Shruti

79

Strength variability in alumina fiber-reinforced aluminum matrix composites  

SciTech Connect

The strength variability of an Al-2% Cu alloy matrix reinforced with 65 vol.% Nextel-610 Al{sub 2}O{sub 3} fibers has been investigated, with the aim of identifying and separating the contributions associated with the variabilities in both the fiber bundle strength and the fiber volume fraction. Strength distributions have been measured using three test geometries, including three- and four-point flexure and unixaxial tension. The measured distributions are rationalized on the basis of a fiber strength distribution that follows Weibull statistics and a fiber volume fraction distribution characterized by a Gaussian. The fiber bundle strength distribution is found to be extremely narrow, with a Weibull modulus in the range of {approximately}50--60. In addition, the coefficient of variation in the fiber volume fraction distribution is inferred to be {approximately}6%; by comparison, measurements made on relatively large specimens yield a coefficient of variation of {approximately}3%. The differences in these values are attributed to local volume fraction variations which are not detectable by the global measurements. The measured strengths are compared with the predicted values based on the theoretical work of Curtin and co-workers, incorporating the effects of local load sharing between broken fibers and their neighbors. Good correlations are obtained between the experimental data and the model predictions.

Ramamurty, U.; Zok, F.W.; Leckie, F.A. [Univ. of California, Santa Barbara, CA (United States)] [Univ. of California, Santa Barbara, CA (United States); Deve, H.E. [3M Co., Mendota Heights, MN (United States). Metal Matrix Composites Program] [3M Co., Mendota Heights, MN (United States). Metal Matrix Composites Program

1997-11-01

80

Carbon nanofiber reinforced aluminum matrix composite fabricated by combined process of spark plasma sintering and hot extrusion.  

PubMed

Spark plasma sintering and hot extrusion processes have been employed for fabricating carbon nanofiber (CNF)-aluminum (Al) matrix bulk materials. The Al powder and the CNFs were mixed in a mixing medium of natural rubber. The CNFs were well dispersed onto the Al particles. After removal of the natural rubber, the Al-CNF mixture powders were highly densified. From the microstructural viewpoint, the composite materials were observed by optical, field-emission scanning electron, and high-resolution transmission electron microscopies. The CNFs were found to be located on every grain boundary and aligned with the extrusion direction of the Al-CNF bulk materials. Some Al carbides (Al4C3) were also observed at the surface of the CNFs. This carbide was created by a reaction between the Al and the disordered CNF. The CNFs and the formation of Al4C3 play an important role in the enhancement of the mechanical properties of the Al-CNF bulk material. The CNFs can also be used for engineering reinforcement of other matrix materials such as ceramics, polymers and more complex matrices. PMID:21780415

Kwon, Hansang; Kurita, Hiroki; Leparoux, Marc; Kawasaki, Akira

2011-05-01

81

Elastoplastic stress analysis in stainless steel fiber reinforced aluminum metal matrix laminated plates loaded transversely  

Microsoft Academic Search

Metal matrix composites provide new materials with superior properties. They give high strength and stiffness. In this study, a stainless steel fiber reinforced aluminum metal matrix laminated simple supported plate is loaded transversely. Elasto-plastic stress analysis is carried out in the laminated plate by using finite element technique. The expansion of plastic zone and residual stresses are determined in the

O. Sayman

1998-01-01

82

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

PubMed

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). PMID:17320370

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

2008-01-01

83

Carbide coated fibers in graphites-aluminum composites. [(fabrication of metal matrix composites)  

NASA Technical Reports Server (NTRS)

Research activities are described for a NASA-supported program at the Los Alamos Scientific Laboratory to develop graphite fiber-aluminum matrix composites. A chemical vapor deposition apparatus was constructed for continuously coating graphite fibers with TiC. As much as 150 meters of continuously coated fibers were produced. Deposition temperatures were varied from 1365 K to about 1750 K, and deposition time from 6 to 150 seconds. The 6 sec deposition time corresponded to a fiber feed rate of 2.54 m/min through the coater. Thin, uniform, adherent TiC coats, with thicknesses up to approximately 0.1 micrometer were produced on the individual fibers of Thornel 50 graphite yarns without affecting fiber strength. Although coat properties were fairly uniform throughout a given batch, more work is needed to improve the batch-to-batch reproducibility. Samples of TiC-coated Thornel 50 fibers were infiltrated with an aluminum alloy and hot-pressed in vacuum to produce small composite bars for flexure testing. Strengths as high as 90% of the rule-of-mixtures strength were achieved. Results of the examination of the fracture surfaces indicate that the bonding between the aluminum and the TiC-coated fibers is better than that achieved in a similar, commercially infiltrated material made with fibers having no observable surface coats. Several samples of Al-infiltrated, TiC-coated Thornel 50 graphite yarns, together with samples of the commercially infiltrated, uncoated fibers, were heated for 100 hours at temperatures near the alloy solidus. The TiC-coated samples appear to undergo less reaction than do the uncoated samples. Photomicrographs are shown.

Imprescia, R. J.; Levinson, L. S.; Reiswig, R. D.; Wallace, T. C.; Williams, J. M.

1976-01-01

84

The sliding wear resistance behavior of NiAl and SiC particles reinforced aluminium alloy matrix composites  

Microsoft Academic Search

The sliding wear resistance behavior of NiAl and SiC particles reinforced aluminum alloy matrix composites against S46C steel was studied. Experiments were performed within a load range of 3.5 N to 82.7 N at a constant sliding velocity of 0.15 m s1. The sliding distance was 1000 m. Two types of composites, NiAlp\\/Al and SiCp\\/Al with different volume fractions (5

Rong Chen; Akira Iwabuchi; Tomoharu Shimizu; Hyung Seop Shin; Hidenobu Mifune

1997-01-01

85

Numerical study on perforation behavior of 6061-T6 aluminum matrix composite  

Microsoft Academic Search

Explicit finite element code (LS-DYNA3D program) simulation is used to investigate the penetration and perforation behavior of a 6061-T6 aluminum plate and a C12K33 carbon fiber reinforced 6061-T6 aluminum metal-matrix composite plate when impacted by a tungsten projectile. The plate is impacted by the projectile at the angle of incidence of 0° (i.e. in the normal direction), and three impact

Woei-Shyan Lee; Chang-Horng Lai; Su-Tang Chiou

2001-01-01

86

Interfacial shear strength estimates of NiTi-Al matrix composites fabricated via ultrasonic additive manufacturing  

NASA Astrophysics Data System (ADS)

The purpose of this study is to understand and improve the interfacial shear strength of metal matrix composites fabricated via very high power (VHP) ultrasonic additive manufacturing (UAM). VHP-UAM NiTi-Al composites have shown a dramatic decrease in thermal expansion compared to Al, yet thermal blocking stresses developed during thermal cycling have been found to degrade and eventually cause interface failure. Consequently, to improve understanding of the interface and guide the development of stronger NiTi- Al composites, the interface strength was investigated through the use of single ber pullout tests. It was found that the matrix yielded prior to the interface breaking since adhered aluminum was consistently observed on all pullout samples. Additionally, measured pullout loads were utilized as an input to a nite element model for stress and shear lag analysis, which, in turn showed that the Al matrix experienced a peak shear stress near 230 MPa. This stress is above the Al matrix's ultimate shear strength of 150-200 MPa, thus this large stress corroborates with matrix failure observed during testing. The in uence of various ber surface treatments on bond mechanisms was also studied with scanning electron microscopy and energy dispersive X-ray spectroscopy.

Hehr, Adam; Pritchard, Joshua; Dapino, Marcelo J.

2014-03-01

87

Low-cost, fly-ash-containing aluminum-matrix composites  

NASA Astrophysics Data System (ADS)

In recent years there has been considerable activity in the development of metal-matrix composites, especially for aerospace, ground transportation, and the leisure industry. Short-fiber-reinforced pistons and cylinder blocks have been marketed by Japanese companies for several years. It is likely that in the near future cast particulate composites like aluminum-graphite, aluminum-silicon carbide, and aluminum-alumina will find widespread applications as brake rotors, drive shafts, cylinder liners, connecting rods, and wrist pins. The cost of metal-matrix composites has been one of the major barriers toward their widespread application. This paper describes the development of cast aluminum-fly ash particle composites (ash alloy). Incorporation of fly-ash particles, which are a waste by-product of coal-based power generation, reduces the cost of aluminum castings by acting as a filler; decreases their density, and increases their hardness, abrasion resistance, and stiffness. Several prototype castings have been made from aluminum-fly ash composites to demonstrate their castability. With sustained research and the support of manufacturing organizations, these alloys can find widespread applications as low-cost aluminum composite components.

Rohatgi, Pradeep K.

1994-11-01

88

Measurement of interfacial properties for aluminum and titanium matrix alloy composites manufactured by vacuum plasma spray  

SciTech Connect

Continuous fiber silicon carbide/titanium and aluminum matrix composite monolayers were tested by means of an indentation technique to measure the interfacial shear strength. Experimental results were interpreted using two analytical models and compared to results of other researches in order to evaluate the interface quality obtained with a vacuum plasma spray fabrication method. The separate contribution of chemical bond and friction to the mechanical shear strength of the fiber-matrix interface is discussed. For aluminum matrix composites, the interface strength is mainly controlled by frictional force. For titanium matrix composites, chemical bond plays a primary role. The vacuum plasma spray process used needs further optimization work, but it is a very promising fabrication method for continuous fiber reinforced metal matrix composites. 20 refs.

Valente, T. [Rome Univ `La Sapienza`, Rome (Italy)

1994-07-01

89

Fatigue Crack Growth and Retardation Due to Overloads in Metal-matrix Composites Volume I. Fatigue Crack Growth In Boron-Aluminum Metal-Matrix Composites.  

National Technical Information Service (NTIS)

The fatigue crack growth in a Boron-Aluminum metal matrix composite is investigated. The material consists of II plies of diffusion bonded 5.6 mil boron fibers in a 6061 aluminum matrix. In this study, the composite is characterized as an orthotropic elas...

C. T. Sun J. F. Doyle S. Rizzi

1986-01-01

90

Irregular growth of AlSb in solid aluminum-solid antimony diffusion couples  

Microsoft Academic Search

An investigation was made of the growth of the intermediate phase aluminum antimonide (AlSb) in solid aluminum-solid antimony\\u000a diffusion couples, AlSb being the only intermediate phase present in the equilibrum phase diagram. Most diffusion couples\\u000a were assembled from polycrystalline aluminum and antimony, but a few were made from single crystals; the diffusion couple\\u000a surfaces were prepared in a variety of

John E. Lyttle; Peter V. Dembowski; Louis S. Castleman

1971-01-01

91

Applicability of ultrasonic testing for the determination of volume fraction of particulates in alumina-reinforced aluminum matrix composites  

SciTech Connect

An ultrasonic testing technique was employed to determine the volume fraction of alumina particulate reinforcement in 6061 aluminum matrix composites. this study was performed on various composites with Al{sub 2}O{sub 3} nominal volume fractions of 10, 15, and 20%. For comparison, other techniques were employed as well, including the Archimedes method, metallographic image analysis, X-ray diffraction, and acid dissolution. Observations indicated that ultrasonic testing and acid dissolution methods are more reliable than the other techniques, while ultrasonic testing is faster than the acid dissolution method.

Fang, C.K.; Fang, R.L.; Weng, W.P.; Chuang, T.H.

1999-10-01

92

Stir mixing and pressureless infiltration synthesis of aluminum alloy metal matrix nanocomposites  

NASA Astrophysics Data System (ADS)

Pressureless liquid metal infiltration of suitably packed compacts of spherical shaped 47 nm size 70:30 Delta:Gamma Al2O3 mixed with a 7/2 ratio of elemental Al and Mg powders was used to study (i) the kinetics of pressureless infiltration processing of Al2O 3 nanoparticle-A206 alloy composites, (ii) the optimal processing variables to maximize material property responses, (iii) the development of multimodal microstructures in terms of feature size. The major experimental variables included: infiltration temperature (850 to 950°C), infiltration time (1--5 hours), and powder composition (0--50 wt% Al2O 3). All experiments were conducted under UHP nitrogen atmosphere. Under the conditions studied, compacts with a maximum of 20 wt% nanoparticles were successfully infiltrated with A206 alloy aluminum, and the degree of infiltration measured by the percentage of residual porosity depended on infiltration time, temperature and nanoparticle content. By examining responses including percent porosity, and macrohardness, empirical models for correlating processing conditions with material properties and microstructure were developed. The addition of increasing weight percentage of Al2O3 nanoparticles resulted in a decrease in the coefficient of thermal expansion greater than that predicted by the rule of mixtures due to the mechanical constraint of the nanoparticles on the matrix. Likewise, the damping capacity of the 10 wt% and 20 wt% reinforced nanocomposites increased with increasing weight percentage up to 280% greater than the base alloy. The key microstructural observations in the pressureless infiltrated composites include: (1) a bimodal structure of micro-scale grains, exhibiting Al-Cu-Mg precipitates dispersed within the grains; (2) amorphous and crystalline interfaces between the Al-alloy grains and the nanocomposite regions; (3) infiltrated nanoparticle agglomerates having nanoscale channels forming a nanoscale substructure; (4) mixed nanoscale reinforcements of 20 nm Al2MgO4 and ˜2 nm Cu 4O3. Heat treatment of the pressureless infiltrated specimens was not necessary, as Al2CuMg precipitate phases were observed in solution both inside the micro-scale grains and within the composite regions. Remelted and squeeze cast specimens of A206- 1 v% nanosize spinel exhibited a 19% increase in the hardness relative to the base alloy.

Schultz, Benjamin Franklin

93

Comparing addition of ZrO II particles in micron and nano scale on microstructure and mechanical behavior of aluminum-matrix composites produced by vortex route  

NASA Astrophysics Data System (ADS)

Aluminum matrix composites are important engineering materials in automotive, aerospace and other applications because of their low weight, high specific strength and better physical and mechanical properties compared to pure aluminum. ZrO II particles as reinforcement were selected to add aluminum with micron and nano size. Al/ZrO II composites were produced by direct incorporation (vortex method) in different temperatures and 5 volume percents of ZrO II particles. Microstructure of the samples was studied by scanning electron microscopy (SEM). Chemical composition of the phases was studied by XRD. Hardness, and density of these composites were also measured. The microstructure and mechanical properties tests of composites and study the effect of particle size, resulted the better properties compared to matrix aluminum. Homogeneous dispersion of the reinforcement particles in the matrix aluminum was observed. The results show enhancing the composites properties for all samples compared to the monolithic alloy. However there are some differences in results because of particle size of ceramics and therefore differences between particles surface area. Maximum volume percent that can be added to A356 aluminum alloy is 5 vol.%, for nano ZrO II particles, but it seems that is more than 5 vol.% for micron particles. Increasing of viscosity, porosities and much more defects are caused by increasing volume percents and using smaller particles. The casting processing is difficult in these conditions. Furthermore, optimum temperatures of casting for micron and nano zirconia particles are not the same.

Baghchesara, M. A.; Karimi, M.; Abdizadeh, H.; Baharvandi, H. R.

2007-10-01

94

Developing scandium and zirconium containing aluminum boron carbide metal matrix composites for high temperature applications  

NASA Astrophysics Data System (ADS)

The study presented in this thesis focuses on developing castable, precipitation-strengthened Al--B4C metal matrix composites (MMCs) for high temperature applications. In the first part, B4C plates were immersed in liquid aluminum alloyed with Sc, Zr and Ti to investigate the interfacial reactions between B4C and liquid aluminum The influences of Sc, Zr and Ti on the interfacial microstructure in terms of individual and combined additions were examined. Results reveal that all three elements reacted with B4C and formed interfacial layers that acted as a diffusion barrier to limit the decomposition of B4C in liquid aluminum. The interfacial reactions and the reaction products in each system were identified. With the combined addition of Sc, Zr and Ti, most of the Ti was found to enrich at the interface, which not only offered appropriate protection of the B4C but also reduced the consumption of Sc and Zr at the interface. In the second part, Sc and Zr were introduced into Al-15vol.% B 4C composites presaturated by Ti, and eight experimental composites with different Sc and Zr levels were prepared via a conventional casting technique. It was found that Sc was involved in the interfacial reactions with B 4C that partially consume Sc. The Sc addition yielded considerable precipitation strengthening in the as-cast and peak aged conditions. To achieve an equivalent strengthening effect of Sc in binary Al-Sc alloys, approximately double the amount of Sc is required in Al-B4C composites. On the contrary, no major Zr reaction products were found at the interfaces and the major part of Zr remained in the matrix for the precipitation strengthening. The combination of Sc and Zr enhanced sthe precipitation strengthening. Two kinds of nanoscale precipitates, Al3Sc and Al3(Sc, Zr), were found in the as-cast microstructure and contributed to the increase in the matrix hardness. In the third part, all the experimental composites were isothermally aged at 300, 350, 400 and 450°C after a homogenization/solution treatment. Results demonstrate that the addition of Sc generated a considerable precipitation hardening of the matrix of the composites for all aging temperatures applied. The precipitation hardening effect increased when increasing the Sc content and decreased with increase in aging temperature. The combination of alloying Sc and Zr in Al-B4C composites produced a remarkable synergistic effect. The addition of Zr provided not only a strength increase at peak aging but also an improvement of thermal stability. The composites with a high Zr:Sc ratio (?1) showed excellent thermal stability of the strength up to 400°C. The overaging in these materials was delayed by ˜100°C compared with the Zr-free composites at the same Sc level. The precipitate volume fraction, the average radius and the size distribution of nanoscale Al3Sc and Al3(Sc,Zr) precipitates during the aging process were measured. The Al3(Sc,Zr) precipitates generally showed a much better coarsening resistance than the Al3Sc precipitates. In the fourth part, two experimental composites with 0.4wt.% Sc and 0.4wt.% Sc plus 0.24wt.% Zr 0were selected to examine the mechanical properties during long-term exposure (2000h) at elevated temperatures from 250 to 350°C. For long-term thermal stability, the mechanical properties of the Sc and Zr containing composite were stable up to 300°C, while the composite containing only Sc exhibited a good softening resistance up to 250°C. At higher temperatures the strengths of both composites decreased with prolonged annealing time. The reduction of the composites' mechanical properties during long-time annealing at higher temperatures was dominated by the precipitate coarsening. Finally, two experimental composites with 0.58wt.% Sc and 0.58wt.% Sc plus 0.24wt.% Zr, were respectively hot-rolled to a 2 mm thick sheet with a total reduction of 93%. Results indicate that the Sc- and Zr-containing composites possessed a good hot rolling processability. (Abstract shortened by UMI.)

Lai, Jing

95

Strengthening Aluminum Alloys for High Temperature Applications Using Nanoparticles of Al203 and Al3-X Compounds (X= Ti, V, Zr)  

NASA Technical Reports Server (NTRS)

In this paper the effect of nanoparticles A12O3 and A13-X compounds (X= Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their chemical stability and low diffusions rates in aluminum matrix at high temperatures. The strengthening mechanism for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. Samples were prepared from A12O3 nanoparticle preforms, which were produced using ceramic injection molding process and pressure infiltrated by molten aluminum. A12O3 nanoparticles can also be homogeneously mixed with aluminum powder and consolidated into samples through hot pressing and sintering. On the other hand, the Al3-X nanoparticles are produced as precipitates via in situ reactions with molten aluminum alloys using conventional casting techniques. The degree of alloy strengthening using nanoparticles will depend on the materials, particle size, shape, volume fraction, and mean inter-particle spacing.

Lee, Jonathan A.

2007-01-01

96

Corrosion Behavior of Squeeze Cast Aluminum Metal Matrix Composites.  

National Technical Information Service (NTIS)

Corrosion behavior of metal matrix composites (MMC) vary greatly with the reinforcement material type, processing conditions and methods of fabrication into engineering parts. The corrosion susceptibilities for the MMC arise from the segregations of the r...

A. S. Fabiszewski V. S. Agarwala

1991-01-01

97

Combination of hot extrusion and spark plasma sintering for producing carbon nanotube reinforced aluminum matrix composites  

Microsoft Academic Search

Aluminum (Al)\\/carbon nanotube (CNT) composites with nanoscale dispersion and regular orientation of the CNTs were fabricated by a combination of some advanced powder processes. The CNTs were well dispersed onto the Al particles by a nanoscale dispersion method. Moreover, the highly densified CNT composites were prepared by spark plasma sintering and subsequent hot extrusion. Microstructural observations by optical, field-emission scanning

Hansang Kwon; Mehdi Estili; Kenta Takagi; Takamichi Miyazaki; Akira Kawasaki

2009-01-01

98

EFFECT OF EXTRUSION PARAMETERS ON STRUCTURE AND PROPERTIES OF 2124 ALUMINUM ALLOY MATRIX COMPOSITES  

Microsoft Academic Search

Discontinuously reinforced aluminum matrix composites (DRA) have been attracting attention because of their amenability to undergo deformation processing by conventional metalworking techniques. Extrusion is used in processing of DRA composites for consolidation, redistribution of reinforcements, and shape forming. The important parameters that control the extrusion process are temperature and strain rate, which is a function of several equipment\\/extrusion parameters. Vacuum

V. V. Bhanu Prasad; B. V. R. Bhat; Y. R. Mahajan; P. Ramakrishnan

2001-01-01

99

Electron microscopy of barium strontium titanate nanostructures in the aluminum oxide matrix  

NASA Astrophysics Data System (ADS)

Electron microscopy has revealed the mechanism of formation of barium strontium titanate nanostructures during crystallization in the bulk of pores of the aluminum matrix. The nanostructures have the form of nanotubes or nanocolumns 100-200 nm in diameter and a few microns long, which are formed by barium strontium titanate crystals 3-100 nm in size.

Zhigalina, O. M.; Vorotilov, K. A.; Kuskova, A. N.; Sigov, A. S.

2009-07-01

100

Al matrix syntactic foam fabricated with bimodal ceramic microspheres  

Microsoft Academic Search

The energy absorption capability of cellular solids is determined by their plateau strength and onset strain of densification, which in turn are dependent upon their porosity. Metal matrix syntactic foams fabricated with ceramic microspheres of a single size range have a nearly fixed porosity and thus have a limited variability in energy absorption. This paper fabricates Al matrix syntactic foams

X. F. Tao; L. P. Zhang; Y. Y. Zhao

2009-01-01

101

Adiabatic shear failure of high reinforcement content aluminum matrix composites  

Microsoft Academic Search

Dynamic failure behaviors of high reinforcement content TiB2\\/Al composites were experimentally investigated using split Hopkinson pressure bar (SHPB). The TiB2\\/Al composites showed high flow stresses and good plastic deformation ability at high strain rates. Adiabatic temperature\\u000a rise decreased the flow stresses of TiB2\\/Al composites, which was verified by the prediction of Johnson–Cook model. While the predictions by Cowper–Symonds model\\u000a exhibited

G. H. Wu; D. Z. Zhu; G. Q. Chen; L. T. Jiang; Q. Zhang

2008-01-01

102

Role of Al 2 O 3 particulate reinforcements on precipitation in 2014 Al-matrix composites  

Microsoft Academic Search

Precipitation in commercial aluminum alloy 2014, without and with alumina particulate reinforcements, was studied using microhardness,\\u000a electrical resistivity, differential scanning calorimetry (DSC), and transmission electron microscopy. The precipitation sequence\\u000a in 2014 Al was confirmed to be ?ss?? + GPZ ?? + ?’?a + ?’ + gH?? + ? (AlCuMgSi) + ? (CuAl2). Reinforcement addition decreased the time to peak hardness,

I. Dutta; C. P. Harper; G. Dutta

1994-01-01

103

The microstructure-processing-property relationships in an aluminum matrix composite system reinforced by aluminum-copper-iron alloy particles  

NASA Astrophysics Data System (ADS)

Solid state vacuum sintering was studied in tap densified Al powder and in hot quasi-isostatically forged samples composed of commercial inert gas atomized or high purity Al powder, generated by a gas atomization reaction synthesis (GARS) technique. The GARS process results in spherical Al powder with a far thinner surface oxide. The overall results indicated the enhanced ability of GARS-processed Al and Al alloy powders for solid state sintering, which may lead to simplification of current Al powder consolidation processing methods. Elemental Al-based composites reinforced with spherical Al-Cu-Fe alloy powders were produced by quasi-isostatic forging and vacuum hot pressing (VHP) consolidation methods. It was proved that spherical Al-Cu-Fe alloy powders can serve as an effective reinforcement particulate for elemental Al-based composites, because of their high hardness and a preferred type of matrix/reinforcement interfacial bonding, with reduced strain concentration around the particles. Ultimate tensile strength and yield strength of the composites were increased over the corresponding Al matrix values, far beyond typical observations. This remarkable strengthening was achieved without precipitation hardening and without severe strain hardening during consolidation because of the matrix choice (elemental Al) and the "low shear" consolidation methods utilized. This reinforcement effectiveness is further evidenced by elastic modulus measurements of the composites that are very close to the upper bound predictions of the rule of mixtures. The load partitioning measurements by neutron diffraction showed that composite samples made from GARS powders present significantly higher load transfer efficiency than the composites made from commercially atomized powders. Further analysis of the load sharing measurements and the calculated values of the mismatch of coefficient of thermal expansion (CTE) and the geometrically necessary dislocation (GND) effects suggest that these strengthening mechanisms can be combined to predict accurately the strength of the composites. By neutron diffraction measurements, it also was found that the composites consolidated from Al and Al63Cu25Fe12 quasicrystal alloy reinforcement powders have compressive residual stress in the Al matrix, contrary to the tensile residual stress in typical Al/SiC composites. The composites made by the quasi-isostatic forging process exhibited higher tensile strengths and much higher compressive residual stresses than the composites made by the VHP process.

Tang, Fei

104

Kinetic energy distributions of sputtered neutral aluminum clusters: Al--Alâ  

Microsoft Academic Search

Neutral aluminum clusters sputtered from polycrystalline aluminum were analyzed by laser postionization time-of-flight (TOF) mass spectrometry. The kinetic energy distributions of Al through Alâ were measured by a neutrals time-of-flight technique. The interpretation of laser postionization TOF data to extract velocity and energy distributions is presented. The aluminum cluster distributions are qualitatively similar to previous copper cluster distribution measurements from

S. R. Coon; W. F. Calaway; M. J. Pellin; G. A. Curlee; J. M. White

1992-01-01

105

Selective aluminum dissolution as a means to observe the microstructure of nanocrystalline intermetallic phases from Al-Fe-Cr-Ti-Ce rapidly solidified alloy.  

PubMed

Rapidly solidified aluminum alloys are promising materials with very fine microstructure. The microscopy observation of these materials is complicated due to overlay of fcc-Al matrix and different intermetallic phases. A possible way to solve this problem is to dissolve the Al matrix. By this process powder formed by single intermetallic phase particles is obtained. In this paper a new aqueous based dissolving agent for Al-based alloy is presented. The influence of oxidation agent (FeCl(3)) concentration on quality of extraction process was studied. PMID:23177792

Michalcová, Alena; Vojt?ch, Dalibor; Novák, Pavel

2013-02-01

106

Effect of thermal treatment on the mechanical and toughness properties of extruded SiC\\/sub w\\/aluminum 6061 metal-matrix composite. Final report  

Microsoft Academic Search

Mechanical, instrumented Charpy V-notch (CVN) energy and plane strain fracture-toughness properties of SiC whisker reinforced 6061 aluminum-metal-matrix composite material from an extruded tube were determined. The effect of thermal treatment and orientation were studied. The mechanical-strength properties are higher than wrought Al 6061 in the T6 condition. CVN energy values, however, were reduced by an order-of-magnitude Kic fracture toughness of

D. F. Hasson; S. M. Hoover; C. R. Crowe

1987-01-01

107

Matrix removal by thermal fluorination in the graphite furnace atomic absorption analysis of high purity aluminum  

NASA Astrophysics Data System (ADS)

A halogen assisted thermal purification method was developed with the use of Ar+1% (v/v) CHF 3 internal furnace gas and applied specifically to the determination of iron impurities in high-purity aluminum. The samples were applied in the form of hydrochloric acid solution, and the alumina formed by hydrolysis from the chloride salt was reacted with the halocarbon in the pyrolysis step to attain a complete volatilization of the matrix without loss of the analyte (Fe). As a result, no interfering background in the 200-340-nm spectral range was observed that was otherwise very intensive without halogenation. The deuterium lamp background correction method was appropriate up to a sample amount of 400 ?g aluminum, resulting in a characteristic concentration of 3.7 ng g -1 (ppb) Fe in the solid aluminum sample.

Scaccia, Silvera; Zappa, Giovanna

2000-08-01

108

Microstructures and thermal properties of aluminum matrix composites based on wood templates  

Microsoft Academic Search

Wood with its rational and magical inner structures was used as a template to fabricate Al\\/C and Al\\/(SiC + C) composites in\\u000a this research. Porous carbon was first pyrolyzed from the wood template. The final composites were then obtained by injecting\\u000a aluminum alloy and silicone resin into the porous carbon. The microstructures, thermal conductivity, and thermal expansions\\u000a of these products were then

Wang Tianchi; Fan Tongxiang; Zhang Di; Zhou Tianle; Zhang Guoding; Xiong Dangsheng

2010-01-01

109

Al NMR study of molten aluminum oxide compounds and mixtures, measured at ultra high temperatures  

Microsoft Academic Search

The technique of ultra high-temperature nuclear magnetic resonance (NMR) has provided insight into the chemical structure and properties of molten aluminum-bearing refractory ceramics, at temperatures in excess of 2000 ^oC. Through application of standard NMR measurements we have studied molten aluminum-bearing ceramics via ^27Al NMR. We have measured spin-lattice (T_1) and spin-spin (T_2) relaxation times, have studied Al-O-P chemical bonding

J. Piwowarczyk; R. F. Marzke; G. H. Wolf; W. T. Petuskey; B. Takulapalli

2002-01-01

110

Effect of Al 3Sc precipitates on the work hardening behavior of aluminum–scandium alloys  

Microsoft Academic Search

The effect of Al3Sc on the flow stress behavior of aluminum–scandium alloy was experimentally verified. The experimental specimens were prepared by quenching to obtain solid solution and then aged to produce Al3Sc phase. One commercial pure aluminum specimen was included for comparison purpose. A specially designed wedge shape was rolled to obtain mechanical deformation up to 75%. Deformation mechanism was

Vikas Jindal; P. K. De; K. Venkateswarlu

2006-01-01

111

First principles predictions of intrinsic defects in aluminum arsenide, AlAs : numerical supplement.  

SciTech Connect

This Report presents numerical tables summarizing properties of intrinsic defects in aluminum arsenide, AlAs, as computed by density functional theory. This Report serves as a numerical supplement to the results published in: P.A. Schultz, 'First principles predictions of intrinsic defects in Aluminum Arsenide, AlAs', Materials Research Society Symposia Proceedings 1370 (2011; SAND2011-2436C), and intended for use as reference tables for a defect physics package in device models.

Schultz, Peter Andrew

2012-04-01

112

Synthesis of mesoporous Al-MCM-41 materials using metakaolin as aluminum source  

Microsoft Academic Search

A novel synthesis route for the preparation of Al-MCM-41 mesoporous materials has been developed using water glass and metakaolin as silica and aluminum sources and surfactant cetyltrimethylammonium bromide as structure template. The Al-MCM-41 samples were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM) and N2 isothermal adsorption–desorption measurement. The experimental results reveal that metakaolin used as aluminum source

Feng Kang; Qiuying Wang; Shouhe Xiang

2005-01-01

113

Damage mechanisms in Ti[sub 3]Al matrix composites  

SciTech Connect

The paper discusses experimental observations and some related theoretical results associated with the mechanical response of two Ti[sub 3]Al matrix composites, subjected to transverse loading. Both composites contain continuous unidirectional fibers; however, there are considerable differences in the composition of the two interfaces. The Ti[sub 3]Al/SCS-6 system contains brittle reaction products around the fibers that degrade the strength of the composite. The second composite consists of a Ti[sub 3]Al matrix reinforced by sapphire fibers that are strongly bonded to the matrix. Experimental observations indicate that the damage mechanisms in the two composites are substantially different. Utilizing elastic analyses of the local stress field, an attempt was made to explain the dependence of the observed damage mechanisms on the residual field and the properties of the interface.

Kouris, D. (Arizona State Univ., Tempe, AZ (United States). Dept. of Mechanical and Aerospace Engineering); Marshall, D. (Rockwell International Science Center, Thousand Oaks, CA (United States))

1994-07-01

114

Oxidative stress is an early symptom triggered by aluminum in Al-sensitive potato plantlets  

Microsoft Academic Search

The objective of this study was to evaluate whether the oxidative stress caused by aluminum (Al) toxicity is an early symptom that can trigger root growth inhibition in Macaca (Al-sensitive) and SMIC148-A (Al-tolerant) potato clones. Plantlets were grown in a nutrient solution (pH 4.00) with 0, 100 and 200mg Al L?1. At 24, 72, 120 and 168h after Al addition,

Luciane Almeri Tabaldi; Denise Cargnelutti; Jamile Fabbrin Gonçalves; Luciane Belmonte Pereira; Gabriel Y Castro; Joseila Maldaner; Renata Rauber; Liana Verônica Rossato; Dilson Antônio Bisognin; Maria Rosa Chitolina Schetinger; Fernando Teixeira Nicoloso

2009-01-01

115

Processing Parameters Effect on Friction Stir Welded Aluminum Matrix Composites Wear Behavior  

Microsoft Academic Search

In the present work, the aluminum matrix composites reinforced with both SiC and graphite particles are joined using a friction stir welding (FSW) process. The wear characteristics of the welded joints were investigated at constant load of 50 N and a rotational speed of 1000 rpm using a pin-on-disk wear testing apparatus. This study focuses on the influences of the FSW processing

Adel Mahmood Hassan; Mohammed Almomani; Tarek Qasim; Ahmed Ghaithan

2012-01-01

116

Matrix infrared spectra of aluminum, gallium, and indium complexes with acetylene  

SciTech Connect

Aluminum, gallium, and indium atoms have been codeposited from thermal sources with C[sub 2]H[sub 2] at high dilution in argon on a 12[plus minus]1 K CsI window. The major products are best characterized as 1/1 [pi] complexes where the metal shares electron density from one acetylene [pi] orbital. Higher reagent concentrations give evidence for 1/2 and 2/1 metal-acetylene complexes. In the case of aluminum, photolysis induces insertion to form HAlC[sub 2]H and AlC[sub 2]H.

Burkholder, T.R.; Andrews, L. (Univ. of Virginia, Charlottesville (United States))

1993-05-26

117

Adsorption of nitrogen on aluminum, Al2O3, and AlN powders at 78 K  

NASA Astrophysics Data System (ADS)

The adsorption of nitrogen on aluminum powders of ASD-4 and UDA grades, aluminum oxide (?-Al2O3), and aluminum nitride is studied at 78 K in the adsorbate relative pressure range ( P a / P 0) of 0 to 1. It is shown that the nature of the chemical bonds and the structure and state of the adsorbent determine the share of the adsorption isotherms and their attribution to a particular type of isotherms. With an increase in the fraction of metal bonds in an adsorbent, the isotherms become more convex, indicating enhancement of the effect of lateral interactions. The specific surfaces of samples are calculated.

Ryabina, A. V.; Kononenko, V. I.; Seleznev, A. S.; Petrov, L. A.

2014-01-01

118

Friction Stir Welding for Aluminum Metal Matrix Composites (MMC's) (Center Director's Discretionary Fund, Project No. 98-09).  

National Technical Information Service (NTIS)

This technical memorandum describes an investigation of using friction stir welding (FSW) process for joining a variety of aluminum metal matrix composites (MMC's) reinforced with discontinuous silicon-carbide (SiC) particulate and functional gradient mat...

J. A. Lee R. W. Carter J. Ding

1999-01-01

119

Effects of microstructure of the behavior of an aluminum alloy and an aluminum matrix composite tested under low levels of superimposed hydrostatic pressure  

Microsoft Academic Search

Experiments have been conducted on an aluminum alloy and an aluminum matrix composite tested in tension under the influence\\u000a of superimposed hydrostatic pressure. Monolithic alloys heat-treated to underaged (UA) and overaged (OA) conditions exhibited\\u000a significant differences in their responses to the superimposition of hydrostatic pressure during tension testing. Significant\\u000a increases in ductility were obtained with moderate increases in confining pressure

D. S. Liu; M. Manoharan; J. J. Lewandowski

1989-01-01

120

Fabrication of in situ TiC reinforced aluminum matrix composites  

Microsoft Academic Search

In the present work, the room and elevated temperature mechanical behavior of Al\\/TiC, high-strength Al-Si\\/TiC and the elevated temperature-resistant Al-Fe(-V-Si)\\/TiC composites has been evaluated. The microstructural characteristics of ingot metallurgy (IM) or rapid solidification (RS) Al-Si\\/TiC and Al-Fe(-V-Si)\\/TiC composites could be thought of as a combination of the related alloy matrix microstructures and the IM or RS Al\\/TiC composites. The

X. C. Tong; A. K. Ghosh

2001-01-01

121

Bonding of Mg and Al with Mg–Al eutectic alloy and its application in aluminum coating on magnesium  

Microsoft Academic Search

Magnesium and aluminum were bonded successfully by using Mg–Al eutectic alloy as the solder under different pressures at 450°C in atmosphere. The microstructures of the Mg\\/Al joints were characterized by SEM, the composition analyzed by EDS, and their bond strengths measured by the bend test. The results show that the bond strength of these Mg\\/Al joints is improved with increasing

Xianrong Li; Wei Liang; Xingguo Zhao; Yan Zhang; Xiaopeng Fu; Fencheng Liu

2009-01-01

122

Aluminum status of synthetic Al–humic substance complexes and their influence on plant root growth  

Microsoft Academic Search

Aluminum (Al)–humus complexes are abundant in the A horizons of non-allophanic Andosols and contribute to the unique properties of volcanic ash soils, such as high reactivity with phosphate ions and a low bulk density. Natural non-allophanic Andosols commonly show Al toxicity to plant roots. There have been very few studies examining the contribution of Al–humus complexes to the Al toxicity

Tadashi Takahashi; Masami Nanzyo; Syuntaro Hiradate

2007-01-01

123

Characterization of Si-added aluminum oxide (AlSiO) films for power devices  

Microsoft Academic Search

Synthesis of Si-added aluminum oxide (AlSiO) films is attempted as an insulating film with both a wide bandgap and a high dielectric constant. Electrical characteristics of AlSiO films are investigated. Leakage current of the AlO film is suppressed by Si addition and is minimized with Si composition ratio of 12%. Capacitance versus voltage (C–V) measurements are carried out for Au\\/AlSiO\\/Si

Naoyoshi Komatsu; Keiko Masumoto; Hidemitsu Aoki; Chiharu Kimura; Takashi Sugino

2010-01-01

124

Calculation-experimental study of the phase composition of Al-Zn-Mg-(Cu)-Ni-Fe aluminum alloys  

NASA Astrophysics Data System (ADS)

To optimize the compositions of new high-strength aluminum ATs7NZh and ATs6N0.5Zh alloys (economically alloyed nikalins), the thermodynamic optimization of the Al-Zn-Mg-Cu-Ni-Fe system is performed via the construction of polythermal sections and the calculation of the chemical composition and volume fraction of phases at characteristic temperatures. The concentrations of the matrix elements (Zn, Mg, Cu) that determine the high level of mechanical properties are shown to be 6-7 wt % Zn, 2-3 wt % Mg, and up to 0.3 wt % Cu. The concentrations of the eutectic-forming elements (Ni, Fe) that ensure the solidification of (Al) + Al9FeNi eutectic are determined. This eutectic favors an increase in the manufacturing properties of the alloys during casting, metal forming, and welding along with a retained high level of the mechanical properties. In general, experimental results confirm the calculated data.

Akopyan, T. K.; Belov, N. A.; Alabin, A. N.; Zlobin, G. S.

2013-07-01

125

Effect of aluminum concentration and boron dopant on environmental embrittlement in FeAl aluminides  

SciTech Connect

The room-temperature tensile properties of FeAl aluminides were determined as functions of aluminum concentration (35 to 43 at. % Al), test environment, and surface (oil) coating. The two lower aluminum alloys containing 35 and 36.5% Al are prone to severe environmental embrittlement, while the two higher aluminum alloys with 40 and 43% Al are much less sensitive to change in test environment and surface coating. The reason for the different behavior is that the grain boundaries are intrinsically weak in the higher aluminum alloys, and these weak boundaries dominate the low ductility and brittle fracture behavior of the 40 and 43% Al alloys. When boron is added to the 40% Al alloy as a grain-boundary strengthener, the environmental effect becomes prominent. In this case, the tensile ductility of the boron-doped alloy, just like that of the lower aluminum alloys, can be dramatically improved by control test environment (e.g. dry oxygen vs air). Strong segregation of boron to the grain boundaries, with a segregation factor of 43, was revealed by Auger analyses. 28 refs., 2 figs., 3 tabs.

Liu, C.T.; George, E.P.

1990-01-01

126

Effect of Variation in Matrix Constitution on the Work Hardening Behavior of a Peak Age Hardened SiC Reinforced Aluminum Based Metal-Matrix Composite  

Microsoft Academic Search

An understanding of the work hardening behavior of particulate reinforced metal -matrix composites is crucial in optimizing the parameters for deformation processing of these materials. In the case of particulate reinforced composites with an age hardenable aluminum alloy matrix, the microstructure and mechanical properties can be altered by a suitable aging treatment as well as by changing the content of

M. Manoharan; M. Gupta

1998-01-01

127

The processing and characterization of sintered metal-reinforced aluminum matrix composites  

NASA Astrophysics Data System (ADS)

Aluminum metal matrix composites are often reinforced with costly ceramic materials. However, porous sintered metal compacts can provide a low-cost alternative. The objective of this investigation was to produce and characterize sintered ferrous metal reinforced 380 aluminum alloy matrix composites, fabricated through a high-pressure casting technique. Tensile, compressive, and rolling contact fatigue tests were used to evaluate the composite properties. During composite fabrication, a non-stoichiometric reaction phase, containing aluminum and iron, formed between the infiltrating molten aluminum and ferrous reinforcement. At high volume fractions, this reaction phase limited composite strength by promoting failure at low stress levels. To minimize the volume fraction of this reaction phase through rapid solidification, the optimum casting conditions were: a metal casting temperature of 675°C, a compact immersion duration of 30 seconds, a maximum punch velocity of 102 cm/min, and a maximum punch dwell pressure of 164 MPa. Superior composite mechanical properties were produced when the compact consisted of relatively large particles (-80 mesh) that contained a sufficient amount of chromium as an alloying element to make the compact stainless. In addition, the strength of the compact and resulting composite was further improved through a high compact relative density and high quality interparticle bonding, which produced a high-strength reinforcing phase. Only the 409 stainless steel compacts exhibited all these properties, and as a result, produced superior composites. The remaining composite types exhibited limited ductility due to the reinforcing ferrous compact having a low relative density and poor interparticle bonding (Delcrome 6347 and HCx) or from a high volume fraction of brittle reaction phase (Anchorsteel 1000). In rolling contact fatigue, each composite type exhibited fatigue lives comparable to the unreinforced 380 aluminum alloy at the same nominal loads. However, when tested at the same normalized loads (applied load divided by the yield strength), only the 409 stainless steel composites exhibited consistently superior fatigue life. The comparatively high fatigue resistance of these composites was attributed to their ability to experience considerable ductility as a result of the properties of the 409 stainless steel compact. Finite element analysis simulation of the tensile and rolling contact mechanical tests on the composite material demonstrated that the majority of the high stress is located in the ferrous reinforcing phase, with stress concentrations present at notches in the ferrous particles. However, high stresses are also generated in the aluminum matrix through elastic constraint. In rolling contact fatigue, these microstructural features can generate high stresses depending upon their orientation with respect to the maximum principal stress axis.

Baron, Richard Paul

128

Synthesis of AlPO4-5 and CrAPO-5 using aluminum dross.  

PubMed

AlPO(4)-5 and its chromium-containing analogue, CrAPO-5, were prepared using aluminum dross in the presence of triethylamine as a structure directing agent; both Al dross powder and an extracted precipitate from Al dross in an alkali solution were used as an aluminum source. These materials were characterized by XRD, BET surface area measurement, SEM, EDX, XRF, ESR, and UV-vis spectroscopy. Their textural properties were found close to those of the corresponding reference samples prepared using pure Al(OH)(3). CrAPO-5 samples prepared from the aluminum dross were tested as a catalyst for liquid phase oxidation of tetralin using t-butyl hydroperoxide as an oxidizing agent, which showed virtually identical catalytic performances to that obtained by a reference CrAPO-5 catalyst. PMID:19442445

Kim, Jun; Biswas, Kalidas; Jhon, Ki-Won; Jeong, Soon-Yong; Ahn, Wha-Seung

2009-09-30

129

Mechanical Properties of Aluminum Matrix Composite Reinforced by Carbothermally Reduced of Fly Ash  

NASA Astrophysics Data System (ADS)

The addition of fly ash into aluminum as reinforcement can potentially reduce the production cost and density of aluminum. However, mechanical properties of aluminum matrix composite reinforced by fly ash (MMC ALFA) have some limitations due to the characteristic of fly ash. In this study, a carbothermal reduction process of fly ash and activated carbon powder with particle size <32 ?m was performed prior to produce MMC ALFA. The process was carried out in a furnace at 1300° C in vacuum condition under argon flow. Synthesis product was analyzed by XRD with Cu-K? radiation. From XRD analysis, it shows that the synthesis process can produce SiC powder. The synthesis product was subsequently used as reinforcement particle. Aluminum powder was mixed with 5, 10 and 15% of the synthesized powder, and then uni-axially compacted at pressure of 300 MPa. The compacted product was sintered for 2 hours in argon atmosphere at temperature variation of 550 and 600° C. Flexural strength, hardness and density of MMC ALFA's product were respectively evaluated using a four point bending test method based on ASTM C1161 standard, Brinell hardness scale and Archimedes method. The result of this study shows that the increase of weight of reinforcement can significantly increase the hardness and flexural strength of MMCs. The highest hardness and flexural strength of the MMC product are 300 kg/mm2 and 107.5 MPa, respectively.

Jamasri; Wildan, M. W.; Sulardjaka; Kusnanto

2011-01-01

130

Mechanical Properties of Aluminum Matrix Composite Reinforced by Carbothermally Reduced of Fly Ash  

SciTech Connect

The addition of fly ash into aluminum as reinforcement can potentially reduce the production cost and density of aluminum. However, mechanical properties of aluminum matrix composite reinforced by fly ash (MMC ALFA) have some limitations due to the characteristic of fly ash. In this study, a carbothermal reduction process of fly ash and activated carbon powder with particle size <32 {mu}m was performed prior to produce MMC ALFA.The process was carried out in a furnace at 1300 deg. C in vacuum condition under argon flow. Synthesis product was analyzed by XRD with Cu-K{sub {alpha}} radiation. From XRD analysis, it shows that the synthesis process can produce SiC powder. The synthesis product was subsequently used as reinforcement particle. Aluminum powder was mixed with 5, 10 and 15% of the synthesized powder, and then uni-axially compacted at pressure of 300 MPa. The compacted product was sintered for 2 hours in argon atmosphere at temperature variation of 550 and 600 deg. C. Flexural strength, hardness and density of MMC ALFA's product were respectively evaluated using a four point bending test method based on ASTM C1161 standard, Brinell hardness scale and Archimedes method. The result of this study shows that the increase of weight of reinforcement can significantly increase the hardness and flexural strength of MMCs. The highest hardness and flexural strength of the MMC product are 300 kg/mm{sup 2} and 107.5 MPa, respectively.

Jamasri [Mechanical and Industrial Engineering Department Gadjah Mada University, Jl. Grafika 2, Yogyakarta, 55281 (Indonesia); Wildan, M. W.; Sulardjaka [Mechanical and Industrial Engineering Department Gadjah Mada University, Jl. Grafika 2, Yogyakarta, 55281(Indonesia); Kusnanto [Engineering Physics Department Gadjah Mada University, Jl. Grafika 2, Yogyakarta, 55281 (Indonesia)

2011-01-17

131

Titanium-Aluminum Phase Diagram. A Review of the Near Ti-50 At.% Al Phase Fields.  

National Technical Information Service (NTIS)

The understanding of the titanium-aluminum (Ti-Al) phase diagram is of great importance to the development of titanium-aluminide alloys and composites for high temperature applications. In this report, the Ti-Al phase diagram near 50 atomic percent (at.%)...

E. S. Chin R. R. Biederman

1992-01-01

132

In-Situ Synthetic TiB2 Particulate Reinforced Metal Matrix Composite Coating on AA2024 Aluminum Alloy by Laser Cladding Technology  

NASA Astrophysics Data System (ADS)

In order to improve the wear resistance of aluminum alloy, in-situ synthesized TiB2 and Ti3B4 peritectic composite particulate reinforced metal matrix composite, formed on a 2024 aluminum alloy by laser cladding with a powder mixture of Fe-coated Boron, Ti and Al, was successfully achieved using 3-KW CW CO2 laser. The chemical composition, microstructure and phase structure of the composite clad coating were analyzed by energy dispersive X-ray spectroscopy (EDX), SEM, AFM and XRD. The typical microstructure of the composite coating is composed of TiB2, Ti3B4, Al3Ti, Al3Fe and ?-Al. The surface hardness of cladding coating increases with the amount of added Fe-coated B and Ti powder which determines the amount of TiB2 and Ti3B4 peritectic composite particulate. The nanohardness and the elastic modulus at the interface of the TiB2 and Ti3B4 peritectic composite particulate/matrix were investigated using the nanoindentation technique. The results showed that the nanohardness and the reduced elastic modulus from the peritectic composite particulate to the matrix is a gradient distribution.

Xu, Jiang; Kan, Yide; Liu, Wenjin

133

Effects of microstructure of the behavior of an aluminum alloy and an aluminum matrix composite tested under low levels of superimposed hydrostatic pressure  

NASA Astrophysics Data System (ADS)

Experiments have been conducted on an aluminum alloy and an aluminum matrix composite tested in tension under the influence of superimposed hydrostatic pressure. Monolithic alloys heat-treated to underaged (UA) and overaged (OA) conditions exhibited significant differences in their responses to the superimposition of hydrostatic pressure during tension testing. Significant increases in ductility were obtained with moderate increases in confining pressure for the OA alloy, while the UA alloy exhibited little effect of pressure. In contrast, significant increases in ductility were obtained for the composites, regardless of the matrix aging condition. The effects of pressure on frature are determined in light of the micromechanisms of fracture in these materials.

Liu, D. S.; Manoharan, M.; Lewandowski, J. J.

1989-11-01

134

Friction Stir Welding of SiC/Aluminum Metal Matrix Composites  

NASA Technical Reports Server (NTRS)

Friction Stir Welding (FSW) is a new solid state process for joining metals by plasticizing and consolidating materials around the bond line using thermal energy producing from frictional forces. A feasibility study for FSW of Metal Matrix Composites (MMC) was investigated using aluminum 6092 alloy reinforced with 17% SiC particulates. FSW process consists of a special rotating pin tool that is positioned to plunge into the MMC surface at the bond line. As the tool rotates and move forward along the bond line, the material at the bond line is heated up and forced to flow around the rotating tip to consolidate on the tip's backside to form a solid state joint. FSW has the potential for producing sound welds with MMC because the processing temperature occurs well below the melting point of the metal matrix; thereby eliminating the reinforcement-to-matrix solidification defects, reducing the undesirable chemical reactions and porosity problems.

Lee, Jonathan A.

1999-01-01

135

Particle combustion rates for mechanically alloyed Al–Ti and aluminum powders burning in air  

Microsoft Academic Search

Mechanically alloyed aluminum-rich powders of Al–Ti (10, 15, 20, and 25 atom% of Ti) were produced and their combustion was compared to that of aluminum and titanium powders of comparable sizes. A laminar lifted-flame aerosol burner developed recently was used in this research. The aerosols were produced and burned in air. Measured flame speeds were higher for the aerosols of

Yuriy L. Shoshin; Edward L. Dreizin

2006-01-01

136

Corrosion behavior of squeeze-cast-aluminum metal-matrix composites. Final report  

SciTech Connect

Corrosion behavior of metal matrix composites (MMC) vary greatly with the reinforcement material type, processing conditions and methods of fabrication into engineering parts. The corrosion susceptibilities for the MMC arise from the segregations of the reinforcement material during fluid flow (extrusion) and/or processing, and from the resulting compositional differences in the alloy, the matrix material. These differences sets-up galvanic cells and cause preferential corrosion. The metal matrix composites studied were Al 6061/Al2O3 and Al 356/SiC. In particular, the effects of near-net-shape processing called squeeze casting (solidification of liquid under pressure) was investigated. The results showed that regions which were clustered with SiC or (Al203)Oi were microstructurally sensitive to preferential corrosion. Electrochemical-potentiodynamic polarization and controlled potential corrosion behavior measurements were made and related to microstructural segregation through metallographic optical microscopic analysis.

Agarwala, V.S.; Fabiszewski, A.S.

1991-12-01

137

Optimization of Al Matrix Reinforced with B4C Particles  

NASA Astrophysics Data System (ADS)

In the current study, abrasive wear resistance and mechanical properties of A356 composite reinforced with B4C particulates were investigated. A center particle swarm optimization algorithm (CenterPSO) is proposed to predict the optimal process conditions in fabrication of aluminum matrix composites. Unlike other ordinary particles, the center particle has no explicit velocity and is set to the center of the swarm at every iteration. Other aspects of the center particle are the same as that of the ordinary particle, such as fitness evaluation and competition for the best particle of the swarm. Because the center of the swarm is a promising position, the center particle generally gets good fitness value. More importantly, due to frequent appearance as the best particle of swarm, it often attracts other particles and guides the search direction of the whole swarm.

Shabani, Mohsen Ostad; Mazahery, Ali

2013-02-01

138

Cast Aluminum Alloys for High Temperature Applications Using Nanoparticles Al2O3 and Al3-X Compounds (X = Ti, V, Zr)  

NASA Technical Reports Server (NTRS)

In this paper, the effect of nanoparticles Al2O3 and Al3-X compounds (X = Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their low cost, chemical stability and low diffusions rates in aluminum at high temperatures. The strengthening mechanism at high temperature for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. For Al2O3 nanoparticles, the test samples were prepared from special Al2O3 preforms, which were produced using ceramic injection molding process and then pressure infiltrated by molten aluminum. In another method, Al2O3 nanoparticles can also be homogeneously mixed with fine aluminum powder and consolidated into test samples through hot pressing and sintering. With the Al3-X nanoparticles, the test samples are produced as precipitates from in-situ reactions with molten aluminum using conventional permanent mold or die casting techniques. It is found that cast aluminum alloy using nanoparticles Al3-X is the most cost effective method to produce high strength aluminum alloys for high temperature applications in comparison to nanoparticles Al2O3. Furthermore, significant mechanical properties retention in high temperature environment could be achieved with Al3-X nanoparticles, resulting in tensile strength of nearly 3 times higher than most 300- series conventional cast aluminum alloys tested at 600 F.

Lee, Jonathan A.

2009-01-01

139

Thermal conductivity of polystyrene–aluminum nitride composite  

Microsoft Academic Search

The thermal conductivity of polymer composites having a matrix of polystyrene (PS) containing aluminum nitride (AlN) reinforcement has been investigated under a special dispersion state of filler in the composites: aluminum nitride filler particles surrounding polystyrene matrix particles. Data for the thermal conductivity of the composites are discussed as a function of composition parameters (aluminum nitride concentration, polystyrene particle size)

Suzhu Yu; Peter Hing; Xiao Hu

2002-01-01

140

On the role of matrix creep in the high temperature deformation of short fiber reinforced aluminum alloys  

Microsoft Academic Search

The present study investigates creep of short fiber reinforced metal matrix composites (MMCs) which were produced by squeeze casting. Two types of aluminum alloys were used as matrix materials with class I (alloy type) and class II (metal type) creep behavior. The creep behavior of the resulting MMCs is similar both in terms of the shape of the individual creep

G. Kausträter; B. Skrotzki; G. Eggeler

2001-01-01

141

On the AlF3 and temperature control of an aluminum electrolysis cell  

Microsoft Academic Search

We propose a control strategy for excess AlF3 and bath temperature of a prebake aluminum electrolysis cell based on analyses of measured data and studies of a simple dynamic model. Model validation indicates that there are dynamics that the model does not capture, and hence, we use real data of excess AlF3 and bath temperature to estimate AlF3 and energy

Tormod Drengstig; Dag Ljungquist; Bjarne A. Foss

1998-01-01

142

Cage Structure Formation of Singly Doped Aluminum Cluster Cations Al n TM + ( TM = Ti, V, Cr)  

NASA Astrophysics Data System (ADS)

Structural information on free transition metal doped aluminum clusters, Al n TM + ( TM = Ti, V, Cr), was obtained by studying their ability for argon physisorption. Systematic size ( n = 5 - 35) and temperature ( T = 145 - 300 K) dependent investigations reveal that bare Al n + clusters are inert toward argon, while Al n TM + clusters attach one argon atom up to a critical cluster size. This size is interpreted as the geometrical transition from surface-located dopant atoms to endohedrally doped aluminum clusters with the transition metal atom residing in an aluminum cage. The critical size, n crit , is found to be surprisingly large, namely n crit = 16 and n crit = 19 - 21 for TM = V, Cr, and TM = Ti, respectively. Experimental cluster-argon bond dissociation energies have been derived as function of cluster size from equilibrium mass spectra and are in the 0.1-0.3 eV range.

Lang, Sandra M.; Claes, Pieterjan; Neukermans, Sven; Janssens, Ewald

2011-09-01

143

On Poisson's ratio for metal matrix composite laminates. [aluminum boron composites  

NASA Technical Reports Server (NTRS)

The definition of Poisson's ratio for nonlinear behavior of metal matrix composite laminates is discussed and experimental results for tensile and compressive loading of five different boron-aluminum laminates are presented. It is shown that there may be considerable difference in the value of Poisson's ratio as defined by a total strain or an incremental strain definition. It is argued that the incremental definition is more appropriate for nonlinear material behavior. Results from a (0) laminate indicate that the incremental definition provides a precursor to failure which is not evident if the total strain definition is used.

Herakovich, C. T.; Shuart, M. J.

1978-01-01

144

Nucleation of Al3Zr and Al3Sc in aluminum alloys: From kinetic Monte Carlo simulations to classical theory  

Microsoft Academic Search

Zr and Sc precipitate in aluminum alloys to form the compounds Al3Zr and Al3Sc which for low supersaturations of the solid solution have the L12 structure. The aim of the present study is to model at an atomic scale this kinetics of precipitation and to build a mesoscopic model based on classical nucleation theory so as to extend the field

Emmanuel Clouet; Maylise Nastar; Christophe Sigli

2004-01-01

145

Effect of deformation temperature on the mechanical behavior and deformation mechanisms of Al-Al[sub 2]O[sub 3] metal matrix composites  

SciTech Connect

Aluminum-alumina (Al-Al[sub 2]O[sub 3]) metal matrix composite (MMC) materials were fabricated using the powder metallurgy (PM) techniques of hot pressing followed by hot extrusion. Different reinforcement weight fractions were used, that is, 0, 2.5, 5, and 10 wt% Al[sub 2]O[sub 3]. The effect of deformation temperature was investigated through hot tensile deformation conducted at different temperatures. The microstructures of the tested specimens were also investigated to characterize the operative softening mechanisms. The yield and tensile strength of the Al-Al[sub 2]O[sub 3] were found to improve as a function of reinforcement weight fraction. With the exception of Al-10wt%Al[sub 2]O[sub 3], the MMC showed better strength and behavior at high temperatures than the unreinforced matrix. The uniform deformation range was found to decrease for the same reinforcement weight fraction, as a function of temperature. For the same deformation temperature, it increases as a function of reinforcement weight fraction. Both dynamic recovery and dynamic recrystallization were found to be operative in Al-Al[sub 2]O[sub 3] MMC as a function of deformation temperature. Dynamic recovery is dominant in the lower temperature range, while dynamic recrystallization is more dominant at the higher range. The increase in reinforcement weight fraction was found to lead to early nucleation of recrystallization. No direct relationship was established as far as the number of grains nucleated due to each reinforcement particle.

Mazen, A.A. (American Univ. in Cairo (Egypt). Dept. of Engineering)

1999-08-01

146

Wear mechanisms in hybrid composites of Graphite20 Pct SiC in A356 Aluminum Alloy (Al7 Pct Si0.3 Pct Mg)  

Microsoft Academic Search

The wear behavior of A356 aluminum alloy (Al-7 Pct Si-0.3 Pct Mg) matrix composites reinforced with 20 vol Pct SiC particles\\u000a and 3 or 10 vol Pct graphite was investigated. These hybrid composites represent the merging of two philosophies in tribological\\u000a material design: soft-particle lubrication by graphite and hard-particle reinforcement by carbide particles. The wear tests\\u000a were performed using a

W. Ames; A. T. Alpas

1995-01-01

147

Fabrication and Characterization of Squeezed Cast Aluminum Matrix Composites Containing Boride Reinforcements  

NASA Astrophysics Data System (ADS)

Aluminum alloys containing 2 and 4 wt.% copper reinforced with aluminum dodecaborides were successfully fabricated by squeeze casting employing pressures up to 62 MPa. The distribution of reinforcements throughout the composites was quantified, whereas the effect of pressure on the composites density and hardness was determined. In addition, the reinforcement chemical stability was examined using high-temperature x-ray diffraction which permitted to confirm the formation of AlB2 phase a result of AlB12 decomposition. The pressure effect on the squeezed composites was investigated by optical microscopy, Vickers microhardness testing, superficial Rockwell hardness testing, and differential thermal analysis. At the highest applied pressures, the castings density increased when the shrinkage porosity was practically eliminated. The composite superficial hardness improved by increasing the applied squeeze. The indirect squeeze cast technique caused Al2Cu phase segregation to upper regions of the specimens, while conversely, the AlB12 reinforcements segregated preferentially at lower regions of the casting.

Olaya-Luengas, L.; Estremera-Pérez, E.; Muñoz, L.; Suárez, O. M.

2010-12-01

148

Optimization of the strength-fracture toughness relation in particulate-reinforced aluminum composites via control of the matrix microstructure  

Microsoft Academic Search

The evolution of the microstructure and mechanical properties of a 17.5 vol. pct SiC particulate-reinforced aluminum alloy 6092-matrix composite has been studied as a function of postfabrication processing and heat treatment. It is demonstrated that, by the control of particulate distribution, matrix grain, and substructure and of the matrix precipitate state, the strength-toughness combination in the composite can be optimized

I. Dutta; T. R. McNelley; R. Nagarajan; F. N. Quiles

1998-01-01

149

Optimization of the strength-fracture toughness relation in particulate-reinforced aluminum composites via control of the matrix microstructure  

Microsoft Academic Search

The evolution of the microstructure and mechanical properties of a 17.5 vol. pct SiC particulate-reinforced aluminum alloy\\u000a 6092-matrix composite has been studied as a function of postfabrication processing and heat treatment. It is demonstrated\\u000a that, by the control of particulate distribution, matrix grain, and substructure and of the matrix precipitate state, the\\u000a strength-toughness combination in the composite can be optimized

I. Dutta; T. R. McNelley; R. Nagarajan; F. N. Quiles

1998-01-01

150

Interaction of Al-Si, Al-Ge, and Zn-Al eutectic alloys with SiC\\/Al discontinuously reinforced metal matrix composites  

Microsoft Academic Search

Interactions between Al-Si, Al-Ge, and Zn-Al eutectic alloys with SiC whisker-reinforced aluminium metal matrix composites were studied as a function of temperature above the eutectic melting temperature. Penetration extended several millimetres into the composite for the Al-Si and Al-Ge alloys but was restricted to a thin surface layer (50 µm) for the Zn-Al alloy. The extent of the penetration zone

W. C. Moshier; J. S. Ahearn; D. C. Cooke

1987-01-01

151

Laser-Induced Fluorescence Studies of the Jet-Cooled Aluminum Acetylide Radical (AlCCH/AlCCD)  

NASA Astrophysics Data System (ADS)

Laser-induced fluorescence and single vibronic level (SVL) emission spectra of the tilde{A}^1? - tilde{X}^1?} system of aluminum acetylide (AlCCH) and its deuterated isotopologue (AlCCD) have been investigated in the region of 350-317 nm. The radicals were produced in a pulsed electric discharge jet using a precursor mixture of trimethyl aluminum or deuterated trimethyl aluminum in high pressure argon. High resolution spectra of the 0_0^0 and 3_0^1 bands of AlCCH have been recorded and the rotational constants determined for both electronic states. SVL emission spectra from several excited state levels were also recorded and the ground state energy levels have been assigned and fitted. The excited state is complicated by a double Renner-Teller effect involving the ?_4 (CCH) and ?_5 (AlCC) bending modes. Our ab initio calculations predict mid?_4mid = 0.833 and mid?_5mid = 0.432 indicating substantial splittings of the bending levels. Progress in assigning the complex vibronic structure in the LIF spectra and fitting it using a Renner-Teller model including both bending modes and the AlC stretching mode will be discussed.

Gharaibeh, Mohammed A.; Clouthier, Dennis J.

2011-06-01

152

Method for embedding optical fibers in an aluminum matrix by ultrasonic consolidation  

NASA Astrophysics Data System (ADS)

The overall aim of the research, part of which is outlined in this paper, was to utilize the ultrasonic consolidation (UC) process for the fabrication of smart metal structures, capable of measuring an external stimulus and responding to this stimulus by adapting its structure accordingly through embedding both active and passive functional elements. This paper presents a fundamental study of embedding methods for the fabrication of optical fibers embedded within aluminum structures. The methods considered in this paper produced embedded optical fiber specimens in which large amounts of plastic flow were observed within the matrix. The matrix material deformed around the fibers, resulting in fully embedded optical fibers capable of transmitting a bright light source and without damaging the fibers. Based on light responses, a general process window was drawn to show the range at which optical fibers can be embedded within aluminum structures using the UC process. The outcomes lay down initial investigative principles for the further development of the technology for embedding or cladding of optical fiber sensors, such as fiber Bragg grating devices, within or on metal structures: for example, the cladding of large free-form metal structures or smart “skinned” metal foam or metal honeycomb structures.

Yen Kong, Choon; Soar, Rupert

2005-10-01

153

The influence of microstructure on the tensile behavior of an aluminum metal matrix composite  

NASA Technical Reports Server (NTRS)

The relationship between tensile properties and microstructure of a powder metallurgy aluminum alloy, 2009 was examined. The alloy was investigated both unreinforced and reinforced with 15 v/o SiC whiskers or 15 v/o SiC particulate to form a discontinuous metal matrix composite (MMC). The materials were investigated in the as-fabricated condition and in three different hot-rolled sheet thicknesses of 6.35, 3.18, and 1.8 mm. Image analysis was used to characterize the morphology of the reinforcements and their distributions within the matrix alloy. Fractographic examinations revealed that failure was associated with the presence of microstructural inhomogeneities which were related to both the matrix alloy and to the reinforcement. The results from these observations together with the matrix tensile data were used to predict the strengths and moduli of the MMC's using relatively simple models. The whisker MMC could be modeled as a short fiber composite and an attempt was made to model the particulate MMC as a dispersion/dislocation hardened alloy.

Birt, Michael J.; Johnson, W. Steven

1990-01-01

154

Modeling stress state dependent damage evolution in a cast Al–Si–Mg aluminum alloy  

Microsoft Academic Search

Internal state variable rate equations are cast in a continuum framework to model void nucleation, growth, and coalescence in a cast Al–Si–Mg aluminum alloy. The kinematics and constitutive relations for damage resulting from void nucleation, growth, and coalescence are discussed. Because damage evolution is intimately coupled with the stress state, internal state variable hardening rate equations are developed to distinguish

M. F. Horstemeyer; J. Lathrop; A. M. Gokhale; M. Dighe

2000-01-01

155

Modeling age hardening kinetics of an Al–Mg–Si–Cu aluminum alloy  

Microsoft Academic Search

In this paper, an Al–Mg–Si–Cu aluminum alloy was exposed to various heat treatment processes and the effect of precipitation hardening on hardness was investigated as a function of time and temperature. It was concluded that the variation in time and temperature can improve the hardness of the alloy. The work revealed that time and temperature play an important role in

A. R. Eivani; A. Karimi Taheri

2008-01-01

156

Irradiation tests for U 3Si-Al dispersion fuels with aluminum cladding  

NASA Astrophysics Data System (ADS)

The HANARO fuel element is made of a cylindrical fuel meat, top and bottom aluminum end plugs and an aluminum cladding with eight longitudinal fins. The fuel meat of each fuel element consists of a dispersion of small particles of a high density uranium silicide (U 3Si) compound in a continuous aluminum matrix. To verify the irradiation performance of the HANARO fuel at a high power and a high burnup, in-pile irradiation tests were performed in the HANARO core. Detailed non-destructive and destructive post-irradiation examinations were conducted. It was verified through the irradiation tests that the HANARO fuel maintains a proper in-pile performance and integrity even at a high power of 121 kW/m and up to a high burnup of 85 at.% U-235.

Chae, H. T.; Kim, H.; Lee, C. S.; Jun, B. J.; Park, J. M.; Kim, C. K.; Sohn, D. S.

2008-02-01

157

Strengthening of aluminum alloy AL25 with a continuous CO 2 -laser  

Microsoft Academic Search

The aim of the present work is a study of hardening mechanisms for aluminum alloy AL25 by means of a continuous CO2-1aser, and developing possibilities for carrying out the process of laser hardening for grooves under compression rings in an internal combustion engine piston made of this alloy. Specimens 105 mm in diameter made of eutectic alloy AL25 (11-13% Si,

A. G. Grigor'yants; A. N. Safonov; N. A. Makusheva

1983-01-01

158

Reactive Atmospheric Plasma Spraying of AlN Coatings: Influence of Aluminum Feedstock Particle Size  

NASA Astrophysics Data System (ADS)

Feedstock powder characteristics (size distribution, morphology, shape, specific mass, and injection rate) are considered to be one of the key factors in controlling plasma-sprayed coatings microstructure and properties. The influence of feedstock powder characteristics to control the reaction and coatings microstructure in reactive plasma spraying process (RPS) is still unclear. This study, investigated the influence of feedstock particle size in RPS of aluminum nitride (AlN) coatings, through plasma nitriding of aluminum (Al) feedstock powders. It was possible to fabricate AlN-based coatings through plasma nitriding of all kinds of Al powders in atmospheric plasma spray (APS) process. The nitriding ratio was improved with decreasing the particle size of feedstock powder, due to improving the nitriding reaction during flight. However, decreasing the particle size of feedstock powder suppressed the coatings thickness. Due to the loss of the powder during the injection, the excessive vaporization of fine Al particles and the completing nitriding reaction of some fine Al particles during flight. The feedstock particle size directly affects on the nitriding, melting, flowability, and the vaporization behaviors of Al powders during spraying. It concluded that using smaller particle size powders is useful for improving the nitriding ratio and not suitable for fabrication thick AlN coatings in reactive plasma spray process. To fabricate thick AlN coatings through RPS, enhancing the nitriding reaction of Al powders with large particle size during spraying is required.

Shahien, Mohammed; Yamada, Motohiro; Yasui, Toshiaki; Fukumoto, Masahiro

2011-03-01

159

Aluminum(III) selective potentiometric sensor based on morin in poly(vinyl chloride) matrix  

Microsoft Academic Search

Al3+ selective sensor has been fabricated from poly(vinyl chloride) (PVC) matrix membranes containing neutral carrier morin as ionophore. Best performance was exhibited by the membrane having composition as morin:PVC:sodium tetraphenyl borate:tri-n-butylphosphate in the ratio 5:150:5:150 (w\\/w, mg). This membrane worked well over a wide activity range of 5.0×10?7 to 1.0×10?1M of Al3+ with a Nernstian slope of 19.7±0.1mV\\/decade of Al3+

Vinod K. Gupta; Ajay K. Jain; Gaurav Maheshwari

2007-01-01

160

Aluminum fractions in root tips of slash pine and loblolly pine families differing in Al resistance.  

PubMed

Aluminum (Al) distribution among several cellular fractions was investigated in root tips of seedlings of one Al-resistant and one Al-sensitive family of slash pine (Pinus elliottii Engelm.) and loblolly pine (Pinus taeda L.) grown in nutrient solution containing 100 microM AlCl3 (pH 4) for 167 h. Aluminum present in 5-mm-long root tips was fractionated into cell-wall-labile (desorbed in 0.5 mM citric acid), cell-wall-bound (retained after filtering disrupted cells through 20-microm mesh) and symplasmic (filtrate following cell disruption) fractions. When averaged across both species, 12% of Al absorbed by root tips appeared in the symplasmic fraction and 88% in the apoplasmic fraction (55% as cell-wall-labile, and 33% as cell-wall-bound). On a fresh mass basis, total Al in root tips was lower in loblolly pine than in slash pine, lower in the Al-resistant slash pine family than in the Al-sensitive slash pine family, and lower in the Al-resistant families than in the Al-sensitive families across species. Although the data support the hypothesis that Al-resistant plants limit Al uptake to root apices, they do not exclude other mechanisms of Al resistance. Differential Al resistance between the species and between slash pine families may also be associated with the size of the total non-labile and cell-wall-labile Al fractions, respectively. We were unable to identify the basis for differential Al resistance in loblolly pine. PMID:15574406

Nowak, Jaroslaw; Friend, Alexander L

2005-02-01

161

Optimization of Abrasive Powder Mixed EDM of Aluminum Matrix Composites with Multiple Responses Using Gray Relational Analysis  

NASA Astrophysics Data System (ADS)

Abrasive powder-mixed electrical discharge machining (APM-EDM), a hybrid manufacturing process involving the use of a dielectric fluid mixed with abrasive powder, combines the benefits of mechanical and thermal interactions. The aim of this article is to use a new approach of performance evaluation, gray relational analysis (GRA), to evaluate the effectiveness of optimizing multiple performance characteristics of APM-EDM of 6061Al/Al2O3p/20p aluminum matrix composites (AMCs). The considered process parameter includes the seven control factors namely pulse current (A), pulse ON time (?s), duty cycle (%), gap voltage (V), time interval of tool lift (s), abrasive powder concentration (g/L), abrasive particle size (?m), and a noise factor, aspect ratio (shape of tool electrode). The combination of L18 (21 × 37) orthogonal array design of experiment with GRA enables to determine the optimal parameters for multiple responses. GRA is used to obtain a single performance index, gray relational grade through gray relational coefficient to optimize the APM-EDM process with lower tool wear rate, surface roughness, and higher material removal rate. In addition, analysis of variance (ANOVA) for the GRC is also utilized.

Singh, S.; Yeh, M. F.

2012-04-01

162

Effects of MgO Nano Particles on Microstructural and Mechanical Properties of Aluminum Matrix Composite prepared via Powder Metallurgy Route  

NASA Astrophysics Data System (ADS)

The objective of the present investigation was to evaluate the microstructural and mechanical properties of Al/nano MgO composite prepared via powder metallurgy method. Pure atomized aluminum powder with an average particle size of 1?m and MgO particulate with an average particle size between 60 to 80 nm were used. Composites containing 1.5, 2.5 and 5 percent of volume fraction of MgO were prepared by powder metallurgy method. The specimens were pressed by Cold Isostatic Press machine (CIP), subsequently were sintered at 575, 600 and 625°C. After sintering and preparing the samples, mechanical properties were measured. The results of microstructure, compression and hardness tests indicated that addition of MgO particulates to aluminum matrix composites improves the mechanical properties.

Baghchesara, Mohammad Amin; Abdizadeh, Hossein; Baharvandi, Hamid Reza

163

A Comparison Between ECAP and Conventional Extrusion for Consolidation of Aluminum Metal Matrix Composite  

NASA Astrophysics Data System (ADS)

In this study, two powder consolidation techniques, equal channel angular pressing (ECAP) and extrusion, were utilized to consolidate attritioned aluminum powder and Al-5 vol.% nano-Al2O3 composite powder. The effect of ECAP and extrusion on consolidation behavior of composite powder and mechanical properties of subsequent compacts are presented. It is found that three passes of ECAP in tube at 200 °C is capable of consolidating the composite to 99.29% of its theoretical density whereas after hot extrusion of the composite the density reached to 98.5% of its theoretical density. Moreover, extrusion needs higher temperature and pressing load in comparison to the ECAP method. Hardness measurements show 1.7 and 1.2 times higher microhardness for the consolidated composite and pure aluminum after ECAP comparing with the extruded ones, respectively. Microstructural investigations and compression tests demonstrate stronger bonds between the particles after three passes of ECAP than the extrusion. Furthermore, the samples after three passes of ECAP show better wear resistance than the extruded ones.

Haghighi, R. Derakhshandeh; Jahromi, S. A. Jenabali; Moresedgh, A.; Khorshid, M. Tabandeh

2012-09-01

164

Formation of a well ordered ultrathin aluminum oxide film on icosahedral AlPdMn quasicrystal  

SciTech Connect

We have exposed the pentagonal surface of icosahedral AlPdMn quasicrystal kept at 700 K to several hundred langmuirs of O{sub 2}, which results in the formation of a 5 A thick, well ordered aluminum oxide film. The local structure of the film resembles that of the oxide layers formed on ordered binary alloys of Al except that the quasicrystalline substrate makes the film consist of five pairs of nanometer-size aluminum oxide domains exposing their nominal (111) faces parallel to the substrate surface and rotated by 72 deg. with respect to each other. The orientational relationship between these domains and the substrate is a consequence of the affinity of the icosahedral structure of AlPdMn to the CsCl structure.

Longchamp, J.-N.; Burkardt, S.; Weisskopf, Y. [Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich (Switzerland); Erbudak, M. [Laboratory for Solid State Physics, ETH Zurich, 8093 Zurich (Switzerland); Department of Physics, Faculty of Arts and Sciences, Bogazici University, 34342 Bebek, Istanbul (Turkey)

2007-09-01

165

Processing of Aluminum-Graphite Particulate Metal Matrix Composites by Advanced Shear Technology  

NASA Astrophysics Data System (ADS)

To extend the possibilities of using aluminum/graphite composites as structural materials, a novel process is developed. The conventional methods often produce agglomerated structures exhibiting lower strength and ductility. To overcome the cohesive force of the agglomerates, a melt conditioned high-pressure die casting (MC-HPDC) process innovatively adapts the well-established, high-shear dispersive mixing action of a twin screw mechanism. The distribution of particles and properties of composites are quantitatively evaluated. The adopted rheo process significantly improved the distribution of the reinforcement in the matrix with a strong interfacial bond between the two. A good combination of improved ultimate tensile strength (UTS) and tensile elongation (?) is obtained compared with composites produced by conventional processes.

Barekar, N.; Tzamtzis, S.; Dhindaw, B. K.; Patel, J.; Hari Babu, N.; Fan, Z.

2009-12-01

166

Interfacial reactions in Al-Mg metal matrix composites reinforced with (Sn/Sb) oxide coated SiC particles  

SciTech Connect

One of the main problems encountered during the fabrication of Al-matrix composites reinforced with SiC particulates is the possible formation of Al{sub 4}C{sub 3}. This compound is very detrimental for the mechanical properties of the composites owing to its hydrophilic character. Moreover the occurrence of the reaction leads to Si rejection in the matrix thus changing also its properties. One way to prevent the formation of Al{sub 4}C{sub 3} during fabrication or subsequent recycling treatment is to use Al-Si alloys as the matrix. However the amount of Si needed to prevent the reaction is temperature dependent and alloys containing 7 to 9 wt% Si can thus be used up to about 750--800 C without Al{sub 4}C{sub 3} formation. The other way which can be employed particularly with wrought Al-alloys is to coat the particulates. Various oxide coatings produced either by a sol-gel or a day mixing technique were tested recently and it was shown that the rate of degradation was significantly decreased as a consequence of the formation of more stable oxides. TiO{sub 2} coating was found particularly efficient in Mg containing Al-alloys owing to the formation of MgO or MgAl{sub 2}O{sub 4}. The aim of this study is to investigate the influence of a complex tin and antimony oxide coating on the rate of degradation of the particles in liquid aluminum. Al-Mg alloys were also used in this work for comparison with previous studies. The presence of Mg allows to follow the reaction rate by making the alloy age hardenable when some Si is rejected as a consequence of Al{sub 4}C{sub 3} formation. However, this technique is only efficient during the first stages of the reaction, becoming ineffective when the Si amount exceeds the solubility limit.

Gonzalez, G.; Salvo, L.; Suery, M. [Institut National Polytechnique de Grenoble, Martin d`Heres (France). Genie Physique et Mecanique des Materiaux] [Institut National Polytechnique de Grenoble, Martin d`Heres (France). Genie Physique et Mecanique des Materiaux; L`Esperance, G. [Ecole Polytechnique de Montreal, Quebec (Canada)] [Ecole Polytechnique de Montreal, Quebec (Canada)

1995-12-15

167

Evidence of aluminum silicate formation during chemical vapor deposition of amorphous Al2O3 thin films on Si(100)  

Microsoft Academic Search

Using narrow nuclear reaction resonance profiling, aluminum profiles are obtained in ~3.5 nm Al2O3 films deposited by low temperature (<400 °C) chemical vapor deposition on Si(100). Narrow nuclear resonance and Auger depth profiles show similar Al profiles for thicker (~18 nm) films. The Al profile obtained on the thin film is consistent with a thin aluminum silicate layer, consisting of

T. M. Klein; D. Niu; W. S. Epling; W. Li; D. M. Maher; C. C. Hobbs; R. I. Hegde; I. J. R. Baumvol; G. N. Parsons

1999-01-01

168

Oxide matrix composite by directional oxidation of a commercial aluminum-magnesium alloy  

SciTech Connect

Oxidation rates of a commercial Al-Mg alloy, Al-5083, were investigated to understand the synthesis of an oxide-based composite. In some experiments, the oxide layer was grown with several platinum wires embedded in the matrix to facilitate transport of electrons. The oxidation rate was not controlled by the rate of transport of the electrons and positive holes through the ceramic oxide layer. In the initial phase of the composite growth, an incubation period was observed due to formation of MgO on the alloy surface. At 1,273 K or higher, the incubation period was followed by a period of sustained oxidation after MgO was converted to a spinel layer. It is demonstrate that, after the initial incubation period, the rate of oxidation is influenced by the rate of transport of ions through the oxide matrix composite.

DebRoy, T.; Bandopadhyay, A.; Roy, R. (Pennsylvania State Univ., University Park, PA (United States). Dept. of Materials Science and Engineering)

1994-05-01

169

Cu precipitation in AlCu-Al{sub 2}O{sub 3} metal matrix composites  

SciTech Connect

Metal matrix composite materials Al-4%Cu reinforced with different volumetric fractions of Al{sub 2}O{sub 3} (Saffil) fibers were produced by ``squeeze casting``. The composites were characterized by thermoelectric power measurements and mechanical spectroscopy measurements, in order to identify the effect of the fibers on the precipitation of Cu and the microstructure of the alloy. The formation of Guinier-Preston zones was found to be hindered by the presence of fibers, while the formation of {theta}{prime} precipitates was favored in the composites. TTT diagrams of Cu precipitation in the composites have been drawn, which characterize well their different response to aging compared with that of the unreinforced matrix. The elastic moduli of the composites were confirmed to be higher than that of the unreinforced alloy.

Parrini, L.; Schaller, R. [Ecole Polytechnique Federale de Lausanne (Switzerland). Inst. de Genie Atomique] [Ecole Polytechnique Federale de Lausanne (Switzerland). Inst. de Genie Atomique

1995-06-01

170

Thermomechanical behavior of TiNi shape memory alloy fiber reinforced 6061 aluminum matrix composite  

Microsoft Academic Search

The processing and thermomechanical behaviors of TiNi shape memory alloy (SMA) fiber-reinforced 6061 Al matrix smart composites\\u000a are investigated experimentally and analytically. Optimum processing conditions of hot pressing temperature and pressure are\\u000a identified. Composite yield stresses are observed to increase with an increase in the volume fraction of TiNi fiber and prestrain\\u000a given to the composites. An analytical model for

K. Hamada; J. H. Lee; K. Mizuuchi; M. Taya; K. Inoue

1998-01-01

171

Analysis of Acoustic Emission During the Melting of Embedded Indium Particles in an Aluminum Matrix: A Study of Plastic Strain Accommodation During Phase Transformation  

NASA Astrophysics Data System (ADS)

Acoustic emission (AE) is used in this article to study melting and solidification of embedded indium particles in the size ranging from 0.2 to 3 ?m in diameter and to show that dislocation generation occurs in the aluminum matrix to accommodate a 2.5 pct volume change. The volume-averaged acoustic energy produced by indium particle melting is similar to that reported for bainite formation upon continuous cooling. A mechanism of prismatic loop generation is proposed to accommodate the volume change, and an upper limit to the geometrically necessary increase in dislocation density is calculated as 4.1 × 109 cm-2 for the Al-17In alloy. Thermomechanical processing is also used to change the size and distribution of the indium particles within the aluminum matrix. Dislocation generation with accompanied AE occurs when the melting indium particles are associated with grain boundaries or upon solidification where the solid-liquid interfaces act as free surfaces to facilitate dislocation generation. AE is not observed for indium particles that require super heating and exhibit elevated melting temperatures. The AE work corroborates previously proposed relaxation mechanisms from prior internal friction studies and that the superheat observed for melting of these micron-sized particles is a result of matrix constraint.

Kuba, Michael M.; Van Aken, David C.

2013-08-01

172

Formation of hexagonal AlN nanotowers and layered nanorods by direct nitridation of aluminum  

NASA Astrophysics Data System (ADS)

Hexagonal AlN nanotowers and layered nanorods with a diameter of hundreds of nanometers and a length of several microns have been successfully synthesized by direct nitridation of aluminum and rice bran mixture compacts in a tube furnace up to 1250 °C under a flow of nitrogen without the addition of extra catalyst. The structure of the nano-AlN products was characterized by XRD and SEM. XRD pattern indicates that the conversion of Al into AlN is complete. The formation of the nanostructures is primarily due to the existence of rich trace elements in the rice bran. The importance of these trace elements and the formation of AlN nanotowers/nanorods have been discussed with the VLS/VS growth mechanisms. The unique morphology of the as-synthesized nanotowers could be useful for investigating fundamental physical phenomena and for fabricating nanodevices.

Zhang, P. G.; Wang, K. Y.; Liang, Jiandong; Guo, S. M.

2011-02-01

173

The aluminum electrode in AlCl3-alkali-halide melts  

NASA Technical Reports Server (NTRS)

Passivation phenomena were observed upon cathodic and anodic polarization of the Al electrode in AlCl3-KCl-NaCl melts between 100 and 160 C. They are caused by formation of a solid salt layer at the electrode surface resulting from concentration changes upon current flow. The anodic limiting currents increased with temperature and with decreasing AlCl3 content of the melt. Current voltage curves obtained on a rotating aluminum disk showed a linear relationship between the anodic limiting current and 1/sq root of 2 pi (rps). Upon cathodic polarization dentrite formation occurs at the Al electrode. The activation overvoltage in AlCl3-KCl-NaCl (57.5-12.5-20 mol%) was determined by galvanostatic current step methods. An apparent exchange current density of 270 mA/cm2 at 130 C and a double layer capacity of 40 plus or minus 10 microfarad/cm2 were measured.

Holleck, G. L.; Giner, J.

1972-01-01

174

The aluminum electrode in AlCl3-alkali-halide melts.  

NASA Technical Reports Server (NTRS)

Passivation phenomena have been observed upon cathodic and anodic polarization of the Al electrode in AlCl3-KCl-NaCl melts between 100 and 160 C. They are caused by formation of a solid salt layer at the electrode surface resulting from concentration changes upon current flow. The anodic limiting currents increased with temperature and with decreasing AlCl3 content of the melt. Current voltage curves obtained on a rotating aluminum disk showed a linear relationship between the anodic limiting current and omega to the minus 1/2 power. Upon cathodic polarization, dendrite formation occurs at the Al electrode. The activation overvoltage in AlCl3-KCl-NaCl was determined by galvanostatic current step methods. An apparent exchange current density of 270 mA/sq cm at 130 C and a double layer capacity of 40 plus or minus 10 microfarad/sq cm were measured.

Holleck, G. L.; Giner, J.

1972-01-01

175

Composite propellant aluminum agglomeration reduction using tailored Al/PTFE particles  

NASA Astrophysics Data System (ADS)

Micron aluminum is widely used in propellants; however, performance could be significantly improved if ignition barriers could be disrupted and combustion tailored. In solid propellants for example, aluminum increases theoretical specific impulse performance, yet theoretical levels cannot be achieved largely because of two-phase flow losses. These losses could be reduced if particles quickly ignited, more gaseous products were produced, and if particle breakup occurred during combustion. To achieve altered aluminum ignition and particle combustion, this work explores the use of low level (10-30 wt.%) fluorocarbon (polytetrafluoroethylene (PTFE) or poly(carbon monofluoride) (PMF)) inclusion inside of aluminum via low or high energy mechanical activation. Aluminum/PTFE particles are found to be amenable to use in binder based energetics, having average particle sizes ranging from 15 to 78 ?m, ~2-7 m2/g, specific surface area, and combustion enthalpies as high as 20.2 kJ/g. Differential scanning calorimetry (DSC) experiments indicate high energy MA reduces both reaction and oxidation onset to ~440 °C that is far below aluminum alone. Safety testing shows these particles have high electrostatic discharge (ESD) (89.9-108 mJ), impact (> 213 cm), and friction (> 360 N) ignition thresholds. The idea of further increasing reactivity and increasing particle combustion enthalpy is explored by reducing fluorocarbon inclusion content to 10 wt.% and through the use of the strained fluorocarbon PMF. Combustion enthalpy and average particle size range from 18.9 to 28.5 kJ/g and 23.0 to 67.5 ?m, respectively and depend on MA intensity, duration, and inclusion level. Specific surface areas are high (5.3 to 34.8 m2/g) and as such, Al/PMF particles are appropriate for energetic applications not requiring a curable liquid binder. Mechanical activation reduces oxidation onset (DSC) from 555 to 480 °C (70/30 wt.%). Aluminum/PMF particles are sensitive to ESD (11.5-47.5 mJ) and some can be ignited via optical flash. Propellant aluminum agglomeration is assessed through replacement of reference aluminum powders (spherical, flake, or nanoscale) with Al/PTFE (90/10 or 70/30 wt.%) particles. The effects on burning rate, pressure dependence, and aluminum ignition, combustion, and agglomeration are quantified. Microscopic imaging shows tailored particles promptly ignite at the burning surface and appear to breakup into smaller particles. Replacement of spherical aluminum with Al/PTFE 70/30 wt.% also increases the pressure exponent from 0.36 to 0.58, which results in a 50% increase in propellant burning rate at 13.8 MPa. Combustion products were quench collected using a liquid-free technique at 2.1 and 6.9 MPa. Sizing of products indicates that composite particles result in nominally 25 ?m coarse products, which are smaller than the original, average particle size and are also 66% smaller in diameter (96% by volume) than the 76 ?m products collected from reference spherical aluminized propellant. Smaller diameter condensed phase products and more gaseous products will likely decrease two-phase flow loss and reduce slag accumulation in solid rocket motors.

Sippel, Travis R.

176

Wire Electrochemical Discharge Machining of Al2O3 Particle Reinforced Aluminum Alloy 6061  

Microsoft Academic Search

The behavior of wire electrochemical discharge machining of Al2O3 particle-reinforced aluminum alloy 6061 was studied. The effects of machining voltage, current, pulse duration, and electrolyte concentration, on material removal rate (MRR) were evaluated in the light of the contribution of the electrical discharge machining (EDM) and electrochemical machining (ECM) actions. The relative strength of the EDM and ECM activities in

J. W. Liu; T. M. Yue; Z. N. Guo

2009-01-01

177

THERMAL STABILITY OF THE ULTRAFINE-GRAINED Al-Cu-Mg-Si ALUMINUM ALLOY  

Microsoft Academic Search

Microstructure and mechanical properties of ultrafine-grained (UFG) samples of the Al- Cu-Mg-Si aluminum alloy processed by high pressure torsion have been investigated. Transmission electron microscopy and electron back scattering diffraction were used for structural investigations. The ultimate tensile strength and ductility were evaluated using tensile tests of small samples. Dynamic dissolution and precipitation in UFG samples has been observed. Special

M. A. Nikitina; R. K. Islamgaliev; A. F. Kamalov

2010-01-01

178

Hydrolysis Studies and Quantitative Determination of Aluminum Ions Using [superscript 27]Al NMR: An Undergraduate Analytical Chemistry Experiment  

ERIC Educational Resources Information Center

This article describes a novel experiment focused on metal ion hydrolysis and the equilibria related to metal ions in aqueous systems. Using [superscript 27]Al NMR, the students become familiar with NMR spectroscopy as a quantitative analytical tool for the determination of aluminum by preparing a standard calibration curve using standard aluminum…

Curtin, Maria A.; Ingalls, Laura R.; Campbell, Andrew; James-Pederson, Magdalena

2008-01-01

179

Sintering Behavior of Hypereutectic Aluminum-Silicon Metal Matrix Composites Powder  

NASA Astrophysics Data System (ADS)

Lightweight materials of Aluminum-Silicon P/M alloys offer the advantage of high-wear resistance, high strength, good temperature resistance, and a low coefficient of thermal expansion. An A359 MMC alloy was mixed together with Alumix 231 in this research. Powders were compacted with compaction pressure up to 700 MPa. Particle size and compaction pressure influenced green density. Compacted powders were sintered in a tube furnace under a flowing nitrogen gas. Sintering temperature, heating rate and sintering time were verified to determine best sintering conditions of the alloys. Chemical composition also contributed to gain higher sintered density. Precipitation strengthening method was used to improve mechanical properties of this materials.T6 heat treatment was carried out to produce fine precipitates to impede movement of dislocation. The chemical composition of this materials allow for the potential formation of several strengthening precipitates including ? (Al2Cu) and ? (Mg2Si).

Rudianto, Haris; Sun, Yang Sang; Jin, Kim Yong; Woo, Nam Ki

180

Analysis of stress-strain, fracture and ductility behavior of aluminum matrix composites containing discontinuous silicon carbide reinforcement  

NASA Technical Reports Server (NTRS)

Mechanical properties and stress-strain behavior for several types of commercially fabricated aluminum matrix composites, containing up to 40 vol % discontinuous SiC whisker, nodule, or particulate reinforcement were evaluated. It was found that the elastic modulus of the composites was isotropic, to be independent of type of reinforcement, and to be controlled solely by the volume percentage of SiC reinforcement present. The yield/tensile strengths and ductility were controlled primarily by the matrix alloy and temper condition. Ductility decreased with increasing reinforcement content, however, the fracture strains observed were higher than those reported in the literature for this type of composite. This increase in fracture strain is attributed to cleaner matrix powder and increased mechanical working during fabrication. Conventional aluminum and titanium structural alloys were compared and have shown that the properties of these low cost, lightweight composites have good potential for application to aerospace structures.

Mcdanels, D. L.

1984-01-01

181

Crystallographic Texture in the Friction-Stir-Welded Metal Matrix Composite Al6061 with 10 Vol Pct Al2O3  

NASA Astrophysics Data System (ADS)

Friction stir welding (FSW) is an important, relatively new joining technology particularly for aluminum alloys and metal matrix composites (MMCs). Metal matrix composites are light weight and have good stiffness and strength—perfect for aerospace and other modern industrial applications. However, MMCs are difficult to join by traditional fusion welding processes due to welding defects and poor joint strength. To better understand the joining process in friction-stir-welded MMCs, investigation of the crystallographic texture of the weld and of the interface between the metal matrix and reinforcing particles is needed. The crystallographic texture and particle-matrix interaction of FSW Al6061-10 vol pct alumina have been studied in this article. Using electron backscatter diffraction (EBSD), the texture gradient of the FSW MMC has been shown to have similar trends to that of an unreinforced Al alloy, but with significantly larger grain size in general. Fracture and redistribution of the reinforcing alumina particles in the weld nugget were also observed.

Root, J. M.; Field, D. P.; Nelson, T. W.

2009-09-01

182

The role of scarf angle in the performance of aluminum matrix composite joints  

SciTech Connect

The role of geometry on the mechanical performance of scarf joints in Al-matrix composites reinforced with continuous polycrystalline alumina fibers was investigated. Model joints consisting of thin metal interlayers at varying scarf angles between composite sub-elements were designed, manufactured and tested to study the relevant deformation and failure phenomena. Specimens were produced by pressurized infiltration of molten Al-4.5%Mg into fiber preforms containing prescribed discontinuities. In this way, matrix continuity through the interlayer was ensured and defects normally introduced in actual joining operations were minimized. Reference composite specimens were produced in the same actual joining operations were minimized. Reference composite specimens were produced in the same manner and exhibited tensile strengths of the order of 700 MPa, compared with a matrix yield strength, {sigma}{sub 0}, of approximately 100 MPa. The strength of the scarf joints with aspect ratios of 17--48 and angles below 45{degree} was relatively constant, {approximately}310 {+-} 10 MPa, but increased at higher angles, reaching over 485 MPa at 75{degree}. Failure of these joints was typically by debonding at the composite-interlayer interface. A simple analytical model suggests that failure occurs when the stress normal to the interlayer reaches a critical value, although the details of the debonding mechanism are still unclear. Conditions leading to a transition from debond failure to plastic collapse in joints of low aspect ratios are also discussed.

Brink, D.D.; Levi, C.G.; Cocks, A.C.F.; Leckie, F.A. [Univ. of California, Santa Barbara, CA (United States)] [Univ. of California, Santa Barbara, CA (United States)

1997-07-01

183

Microstructure and mechanical properties of Al2O3 composites with surface-treated carbon nanotubes (CNTs): dispersibility of modified carbon nanotubes (CNTs) on Al2O3 matrix.  

PubMed

Aluminum oxide (Al2O3) matrix have been reinforced by the multi-walled carbon nanotubes (MWCNTs) to overcome the inherent brittleness of Al2O3 matrix. In order to increase mechanical properties of MWCNTs-Al2O3 composites, MWCNTs need to be well dispersed and individually incorporated in Al2O3 matrix. In this work, aluminum hydroxide (Al(OH)3) used as a Al2O3 precursor and MWCNTs were mixed in an aqueous solution for the homogeneous mixing of hetero-particles, as functions of the content of MWCNTs and the potential hydrogen (pH) of Al(OH)3 suspension. Firstly, MWCNTs were purified and modified by an acid reagent, inducing that the dispersibility of MWCNTs is increased in an aqueous solution by carboxylic group given on the surface of MWCNTs. The modified MWCNTs were added in the Al(OH)3 suspension, and then the mixture was filtered at room temperature. The filtered powders were formed using an uniaxial pressing and then densified by a pressureless heat treatment. As the pH is decreased the Al(OH)3 particles are well dispersed in an aqueous solution, due to the increment of repulsive force between particles with a same surface charge. MWCNTs are individually incorporated into Al2O3 matrix up to 1 vol.% MWCNTs, whereas MWCNTs are aggregated at the composite with 3 vol.% MWCNTs. Therefore, control of the pH and the MWCNTs content are key factors to be considered for the fabrication of MWCNTs-Al2O3 composites with high functional properties. PMID:22629950

Kim, Eun-Hee; Jung, Yeon-Gil; Paik, Ungyu

2012-02-01

184

Growth of aluminum catalyzed AlGaAs nanowires on silicon substrate.  

PubMed

Aluminum catalyzed AlGaAs nanowires were fabricated on Si (111) substrates using metal-organic chemical vapor deposition (MOCVD) technique at a low growth temperature of 450 degrees C. Grown structures were characterized by field emission scanning electron microscope (FE-SEM), energy-dispersive X-ray spectroscopy (EDS) and photoluminescence (PL) techniques. Nanowire clusters were observed all over the substrate. Multiprong root-grown AlGaAs nanowire clusters as well as catalyst particle terminated growth was observed. The growth is explained by Vapor-Solid-Solid (VSS) and Vapor-Solid (VS) growth mechanisms using Al-Si binary phase diagram. EDS and PL measurement confirm the formation of AlGaAs nanowires. PMID:23755616

Bag, R K; Mohan, P; Singh, S; Kumar, A; Tyagi, R; Pandya, D K; Singh, R

2013-03-01

185

Synthesis of Al-catalyzed Si nanowires using the Al remaining after removal of anodic aluminum oxide.  

PubMed

Single-crystal, Al-catalyzed silicon nanowires were grown under atmospheric pressure using the dimpled feature of the Al metal that remained after removal of an anodic aluminum oxide (AAO) template directly formed on a Si substrate. Upon annealing in a hydrogen-rich atmosphere, the dimpled morphology of Al was transformed into a smooth, rounded shape in which Si nanodots were periodically embedded due to Si migration from the substrate. The positions of the nanodots were exactly the same as the positions of sawtooth features on the dimpled surface. Although Al-catalyzed silicon nanowires have been known to grow only under vacuum due to the tendency of Al to oxidize, these silicon nanodots, surrounded by residual AI, showed excellent resistance to oxidation under atmospheric pressure. These nanodots were also capable of acting as catalysts for the growth of nanowires, and played a role in determining the diameter of the nanowires. A thinner residual Al layer made it easier to form Si nanodots while reducing the size of the nanodots, which subsequently led to the growth of nanowires with smaller diameters and better crystalline morphology. PMID:19198343

Jung, Jin-Young; Jee, Sang-Won; Park, Kwang-Tae; Lee, Jung-Ho

2008-11-01

186

First-principle Simulation of Magnesium-aluminum Spinel (MgAl2O4)  

NASA Astrophysics Data System (ADS)

11033768 First-principle Simulation of Magnesium-aluminum Spinel (MgAl2O4) Materials with the spinel crystal structure, AB2O4 are believed to be an important component of Earth's mantle and may be related to density and seismic wave velocity discontinuities at the transition zone from 400km to 660km depth. Using Ab-initio calculations, five phases are predicted to have a stability range at zero temperature: magnesium-aluminum spinel (MgAl2O4), two of its polymorphs, which are of Pbnm and Cmcm space groups, periclase (MgO) and corundum (Al2O3). Pbnm-MgAl2O4 has the calcium-ferrite structure and Cmcm-MgAl2O4 takes the calcium-titanate structure. Calculations are preformed using the PWSCF (Plane-Wave Self-Consistent Field) codes. The free energy of the compressed volume was calculated directly for each of the phases above. Based on the energy-volume results from the calculations, dissolution of MgAl2O4 into MgO + Al2O3 occurs at 12GPa and the mixture (MgO + Al2O3) is expected to recombine to form the calcium-ferrite type phase at about 27GPa. The two phase transition pressures are consistent with experimental results. Cell parameters of the five phases simulated and their bulk modulus derived from the energy-volume curve are also in good agreement with experimental work. But unlike the conclusions drawn from some previous experimental work, the calcium-ferrite type structure (Pbnm-MgAl2O4) did not transform to the calcium-titanate type structure (Cmcm-MgAl2O4) at around 40GPa, which provides the possibility that calcium-ferrite type phase may be stable to even higher pressures (up to100GPa). Derived parameters, bulk modulus and density of each phase are in good agreement with experimental results. The differences are within 4%. Compared to seismic velocity profiles of the earth, these phase transitions pressures match the discontinuity pressures at transition zone 400km (Fd3m- MgAl2O4 -> MgO + Al2O3) and 660km (MgO + Al2O3 -> Pbnm-MgAl2O4) respectively, suggesting that the spinel phase transitions may be partially responsible for the seismic discontinuity at the transition zone. Future calculations will add the energy contribution of phonons which will allow calculations at finite temperature in the first-principle simulations. This is expected to provide more accurate predictions for application to realistic mantle temperature-pressure conditions.

Zhang, W.; Seagle, C. T.; Zhou, H.; Heinz, D. L.

2008-12-01

187

Environment enhanced fatigue of advanced aluminum alloys and metal matrix composites  

NASA Technical Reports Server (NTRS)

The environmental fatigue crack propagation behavior of advanced Al-Li-Cu based alloys and metal matrix composites is being characterized. Aqueous NaCl and water vapor, which produce atomic hydrogen by reactions on clean crack surfaces, are emphasized. The effects of environment sensitive crack closure, stress ratio, and precipitate microstructure are assessed. Mechanistic models are sought for intrinsic crack tip damage processes to enable predictions of cracking behavior outside of the data, metallurgical improvements in material cracking resistance, and insight on hydrogen compatibility.

Slavik, Donald C.; Gangloff, Richard P.

1991-01-01

188

Oxidative stress is an early symptom triggered by aluminum in Al-sensitive potato plantlets.  

PubMed

The objective of this study was to evaluate whether the oxidative stress caused by aluminum (Al) toxicity is an early symptom that can trigger root growth inhibition in Macaca (Al-sensitive) and SMIC148-A (Al-tolerant) potato clones. Plantlets were grown in a nutrient solution (pH 4.00) with 0, 100 and 200mg Al L(-1). At 24, 72, 120 and 168h after Al addition, root length and biochemical parameters were determined. Regardless of exposure time, root length of the Macaca clone was significantly lower at 200mg Al L(-1). For the SMIC148-A clone, root length did not decrease with any Al treatments. Al supply caused lipid peroxidation only in Macaca, in both roots (at 24, 72, 120 and 168h) and shoot (at 120 and 168h). In roots of the Macaca, catalase (CAT) and ascorbate peroxidase (APX) activity decreased at 72 and 120h, and at 24, 72 and 120h, respectively. At 168h, both activities increased upon addition of Al. In roots of the SMIC148-A, CAT activity increased at 72 and 168h, whereas APX activity decreased at 72h and increased at 24, 12 and 168h. The Macaca showed lower root non-protein thiol group (NPSH) concentration at 200mg Al L(-1) in all evaluations, but the SMIC148-A either did not demonstrate any alterations at 24 and 72h or presented higher levels at 120h. This pattern was also observed in root ascorbic acid (AsA) concentration at 24 and 120h. The cellular redox status of these potato clones seems to be affected by Al. Therefore, oxidative stress may be an important mechanism for Al toxicity, mainly in the Al-sensitive Macaca clone. PMID:19570563

Tabaldi, Luciane Almeri; Cargnelutti, Denise; Gonçalves, Jamile Fabbrin; Pereira, Luciane Belmonte; Castro, Gabriel Y; Maldaner, Joseila; Rauber, Renata; Rossato, Liana Verônica; Bisognin, Dilson Antônio; Schetinger, Maria Rosa Chitolina; Nicoloso, Fernando Teixeira

2009-09-01

189

The abrasive wear properties of Al-Mg-Si 3 N 4 metal matrix composites  

Microsoft Academic Search

One kind of three-dimensional network structure, reinforced aluminum magnesium matrix composites, has been prepared by pressure-assisted\\u000a and vacuum-driven infiltration technology. The composites interpenetrated with ceramic have higher wear resistance than the\\u000a metal matrix owing to their special topology structure. The reinforcement volume fraction has a large effect on abrasive wear.\\u000a The wear rate decreases with the increase of the volume

Shou-Ren Wang; Bin Sun; Hao-Ran Geng; Ying-Zi Wang

2006-01-01

190

Low coverage spontaneous etching and hyperthermal desorption of aluminum chlorides from Cl2/Al(111)  

NASA Astrophysics Data System (ADS)

Nonresonant multiphoton ionization with time-of-flight mass spectrometry has been used to monitor the desorption of aluminum chloride (AlxCly) etch products from the Al(111) surface at 100 and 500 K during low-coverage (<5% monolayer) monoenergetic Cl2 (0.11-0.65 eV) dosing. The desorption products in this low-coverage range show predominantly hyperthermal exit velocities under all dosing conditions. For example, with 0.27 eV incident Cl2, the etch product was found to have a most-probable velocity of 517+/-22 m/s at an Al(111) surface temperature of 100 K. This corresponds to 22 times the expected thermal desorption translational energy for AlCl3. Cl2 sticking probability measurements and AlxCly etch rate measurements show etching even at Cl2 coverages of less than 5% monolayer at surface temperatures between 100 and 500 K. These experimental results are consistent with a combination of fast-time-scale surface diffusion and agglomeration of the adsorbed chlorine to form aluminum chlorides and the presence of activated AlCl3 chemisorption states having potential energies above the vacuum level. Density functional theory calculations yield results that are consistent with both our experimental findings and mechanistic descriptions.

Grassman, Tyler J.; Poon, Gary C.; Kummel, Andrew C.

2004-11-01

191

Chemical interactions in the aluminum-carbon and aluminum-silicon carbide systems  

NASA Technical Reports Server (NTRS)

XPS was used to investigate the influence of O2 and H2O on the formation of aluminum carbide at Al-C and Al-SiC interfaces. It was determined that dosing the interfaces with H2O catalyzed the formation of aluminum carbide in both systems. This result is consistent with the oxidation model of carbide formation (developed to understand the kinetics of aluminum carbide formation at graphite-aluminum interfaces). These results imply that the formation of aluminum carbide in graphite- and SiC-reinforced metal-matrix composites, which severely degrades the composite mechanical properties by degrading the fiber and interface strength is catalyzed.

Maruyama, Benji; Ohuchi, Fumio S.; Rabenberg, L.

1990-01-01

192

Measurement of Mercury in Flue Gas Based on an Aluminum Matrix Sorbent  

PubMed Central

The measurement of total mercury in flue gas based on an economical aluminum matrix sorbent was developed in this paper. A sorbent trap consisted of three tubes was employed to capture Hg from flue gas. Hg trapped on sorbent was transferred into solution by acid leaching and then detected by CVAAS. Hg adsorbed on sorbent was recovered completely by leaching process. The 87.7% recovery of Hg in flue gas by tube 1 and tube 2 was obtained on the equipment of coal combustion and sampling in lab. In order to evaluate the ability to recover and accurately quantify Hg0 on the sorbent media, the analytical bias test on tube 3 spiked with Hg0 was also performed and got the average recovery of 97.1%. Mercury measurements based on this method were conducted for three coal-fired power plants in China. The mercury in coal is distributed into bottom ash, electrostatic precipitator (ESP) ash, wet flue gas desulfurization (WFGD) reactant, and flue gas, and the relative distribution varied depending on factors such as the coal type and the operation conditions of plants. The mercury mass balances of three plants were also calculated which were 91.6%, 77.1%, and 118%, respectively. The reliability of this method was verified by the Ontario Hydro (OH) method either in lab or in field.

Wang, Juan; Xu, Wei; Wang, Xiaohao; Wang, Wenhua

2011-01-01

193

Optimization of Tribological Properties in Aluminum Hybrid Metal Matrix Composites Using Gray-Taguchi Method  

NASA Astrophysics Data System (ADS)

This article investigates the optimization of dry sliding performances on the aluminum hybrid metal matrix composites using gray relational analysis in the Taguchi method. Different loads, sliding speeds and varying percentage of molybdenum disulfide are selected as control factors. The multiple responses to evaluate the dry sliding performances are specific wear rate and coefficient of friction. Using a pin-on-disk apparatus, the volume loss and frictional force are measured. Based on gray relational analysis, the optimum level parameters for specific wear rate and coefficient of friction have been identified. An L27 orthogonal array was employed for the experimental design. Analysis of Variance (ANOVA) had given the impact of individual factors and interactions on the specific wear rate as well as the coefficient of friction. The results indicated that the three test parameters had a significant role in controlling the friction and wear behavior of composites. Interaction of the control factors showed the sizable influence on tribological performance. Using Scanning Electron Microscopy (SEM) the wear surface morphology and wear mechanism of the composites have been investigated.

Dharmalingam, S.; Subramanian, R.; Somasundara Vinoth, K.; Anandavel, B.

2011-11-01

194

Aluminum(III) selective potentiometric sensor based on morin in poly(vinyl chloride) matrix.  

PubMed

Al(3+) selective sensor has been fabricated from poly(vinyl chloride) (PVC) matrix membranes containing neutral carrier morin as ionophore. Best performance was exhibited by the membrane having composition as morin:PVC:sodium tetraphenyl borate:tri-n-butylphosphate in the ratio 5:150:5:150 (w/w, mg). This membrane worked well over a wide activity range of 5.0x10(-7) to 1.0x10(-1)M of Al(3+) with a Nernstian slope of 19.7+/-0.1mV/decade of Al(3+) activity and a limit of detection 3.2x10(-7)M. The response time of the sensor is approximately 5s and membrane could be used over a period of 2 months with good reproducibility. The proposed sensor works well over a pH range (3.5-5.0) and demonstrates good discriminating power over a number of mono-, di- and trivalent cations. The sensor can also be used in partially non-aqueous media having up to 20% (v/v) methanol, ethanol or acetone content with no significant change in the value of slope or working activity range. The sensor has also been used in the potentiometric titration of Al(3+) with EDTA and for its determination in zinc plating mud and red mud. PMID:19071785

Gupta, Vinod K; Jain, Ajay K; Maheshwari, Gaurav

2007-06-15

195

Compressive Response of Al Matrix Syntactic Foam Manufactured by Liquid Sintering  

Microsoft Academic Search

Al matrix syntactic foams, with ceramic microspheres embedded in an Al 6082 alloy matrix, were fabricated by a liquid sintering process. The densities of the as-fabricated foams increased from 1.54 to 1.87 g\\/cm3 with increasing volume fraction of Al from 0.4 to 0.7. The mechanical properties of the as-fabricated foams can be adjusted by changing volume fraction of the Al

X. Tao; L. Zhang; Y. Zhao

196

Formation of nanocrystalline h-AlN during mechanochemical decomposition of melamine in the presence of metallic aluminum  

SciTech Connect

Decomposition of melamine was studied by solid state reaction of melamine and aluminum powders during high energy ball-milling. The milling procedure performed for both pure melamine and melamine/Al mixed powders as the starting materials for various times up to 48 h under ambient atmosphere. The products were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results revealed that Al causes melamine deammoniation at the first stages of milling and further milling process leads to the s-triazine ring degradation while nano-crystallite hexagonal aluminum nitride (h-AlN) was the main solid product. Comparison to milling process, the possibility of the reaction of melamine with Al was also investigated by thermal treatment method using differential scanning calorimeter (DSC) and thermo gravimetric analyzer (TGA). Melamine decomposition occurred by thermal treatment in the range of 270-370 Degree-Sign C, but no reaction between melamine and aluminum was observed. - Graphical Abstract: Mechanochemical reaction of melamine with Al resulted in the formation of nanocrystalline AlN after 7 h milling time Highlights: Black-Right-Pointing-Pointer High energy ball milling of melamine and aluminum results decomposition of melamine with elimination of ammonia. Black-Right-Pointing-Pointer Nano-crystalline AlN was synthesized by the mechanochemical route. Black-Right-Pointing-Pointer Milling process has no conspicuous effect on pure melamine degradation. Black-Right-Pointing-Pointer No reaction takes place by heating melamine and aluminum powder mixture in argon.

Rounaghi, S.A., E-mail: s.a.rounaghi@gmail.com [Department of Materials Engineering, Ferdowsi University of Mashhad, P.O. Box No. 91775-1111, Mashhad (Iran, Islamic Republic of); Kiani Rashid, A.R. [Department of Materials Engineering, Ferdowsi University of Mashhad, P.O. Box No. 91775-1111, Mashhad (Iran, Islamic Republic of); Eshghi, H., E-mail: heshghi@ferdowsi.um.ac.ir [Department of Chemistry, Ferdowsi University of Mashhad, P.O. Box No. 91775-1436, Mashhad (Iran, Islamic Republic of); Vahdati Khaki, J. [Department of Materials Engineering, Ferdowsi University of Mashhad, P.O. Box No. 91775-1111, Mashhad (Iran, Islamic Republic of)

2012-06-15

197

Grain refinement and wear properties evaluation of aluminum alloy 2014 matrix-TiB 2 in-situ composites  

Microsoft Academic Search

A salt base exothermic reaction process has been employed to produce aluminum alloy 2014 matrix-TiB2 composites using an exothermic reaction process at 850°C using K2TiF6 and KBF4 salts. The period of exothermic reaction was varied from a minimum of 15min to a maximum of 45min to investigate the relationship between the degree of reaction and the growth behavior of TiB2

C. Mallikarjuna; S. M. Shashidhara; K. I. Parashivamurthy

2011-01-01

198

THERMAL ELASTIC-PLASTIC STRESS ANALYSIS OF STEEL WOVEN REINFORCED ALUMINUM METAL–MATRIX COMPOSITE LAMINATED PLATES  

Microsoft Academic Search

In this study, an elastic-plastic stress analysis is carried out on symmetric cross-ply [0°\\/90°]2 and angle-ply [30°\\/?30°]2, [45°\\/?45°]2, [60°\\/?60°]2 steel woven reinforced aluminum metal–matrix laminated plates under thermal loads varying linearly along the thickness. Laminated composite plates are simply supported and subjected to linear temperature change through the thickness as T0 at the upper and lower surfaces and T at

Numan Behlül Bekta?

2004-01-01

199

Study on tool wear and surface roughness in machining of particulate aluminum metal matrix composite-response surface methodology approach  

Microsoft Academic Search

Metal matrix composites (MMC) have become a leading material among composite materials, and in particular, particle reinforced\\u000a aluminum MMCs have received considerable attention due to their excellent engineering properties. These materials are known\\u000a as the difficult-to-machine materials because of the hardness and abrasive nature of reinforcement element-like silicon carbide\\u000a particles (SiCp). In this study, an attempt has been made to

M. Seeman; G. Ganesan; R. Karthikeyan; A. Velayudham

2010-01-01

200

Analysis of stress-strain, fracture, and ductility behavior of aluminum matrix composites containing discontinuous silicon carbide reinforcement  

Microsoft Academic Search

Mechanical properties and stress-strain behavior were evaluated for several types of commercially fabricated aluminum matrix\\u000a composites, containing up to 40 vol pct discontinuous SiC whisker, nodule, or particulate reinforcement. The elastic modulus\\u000a of the composites was found to be isotropic to be independent of type of reinforcement, and to be controlled solely by the\\u000a volume percentage of SiC reinforcement present.

David L. McDanels

1985-01-01

201

Fatigue crack propagation mechanism for SiC whisker or SiC particle reinforced aluminum matrix composites  

Microsoft Academic Search

Fatigue crack propagation properties and fracture mechanisms were examined for three commercially fabricated aluminum matrix composites containing SiC whiskers (SiCw) and SiC particles (SiCp) under rotating bending condition. Fatigue crack propagation rates for SiCw\\/A2024 and SiCp\\/A356 composites were lower than those for unreinforced alloys at a given stress intensity factor near fatigue threshold, while the fatigue thresholds for those composites

Chitoshi Masuda; Yosihisa Tanaka; Motohiro Yamamoto; Minoru Fukazawa

1994-01-01

202

Phase relations associated with the aluminum blast furnace: Aluminum oxycarbide melts and Al-C-X (X=Fe, Si) liquid alloys  

Microsoft Academic Search

The thermodynamic properties and the phase relations were evaluated and estimated for the Al-O-C, Al-Si-C, and Al-Fe-C systems\\u000a which are important to understand the chemical behavior in an aluminum blast furnace. The mixing properties of binary liquid\\u000a alloys, including metal-carbon systems, were represented by the Redlich-Kister equation. The properties of liquid Al?C and\\u000a Si?C alloys were estimated so as to

Harumi Yokokawa; Masao Fujishige; Seiichi Ujiie; Masayuki Dokiya

1987-01-01

203

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

NASA Astrophysics Data System (ADS)

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.

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

2014-04-01

204

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

NASA Astrophysics Data System (ADS)

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.

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

2014-06-01

205

Synthesis of an aluminum nitride–yttria (AlN–Y 2 O 3 ) composite from nano-sized porous AlN and YCl 3  

Microsoft Academic Search

In order to enhance the thermal conductivity of aluminum nitride (AlN) with sintering additives including yttria (Y2O3), it is necessary to form yttrium aluminate garnet (YAG) and secondary phases both within and around the boundaries of AIN\\u000a drains. Nano-sized porous AlN particles were produced to form YAG and secondary phases within AlN grains, after which a AlN–Y2O3 nano–nano composite was

Jae-Hwan PeeJong-Chul Park; Jong-Chul Park; Kwang-Taek Hwang; SooRyong Kim; Woo-Seok Cho

2010-01-01

206

Matrix-isolated Al2OF6(2-) ion in molten and solid LiF/NaF/KF.  

PubMed

A Raman spectrum consistent with that expected from an Al2OF6(2-) ion was observed when Na2O was dissolved in a eutectic LiF/NaF/KF (FLINAK) melt at 500 degrees C, which contained a low concentration of either AlF3 or Na3AlF6. Furthermore, it was possible to trap the Al2OF6(2-) ion in the frozen solid and to measure its Raman and IR spectra at 25 degrees C. A number of bands have been detected; among those, the two most characteristic bands of the Al2OF6(2-) ion at 494 (polarized) and 265 cm-1 in the FLINAK melt at 500 degrees C, and those at 509 and 268 (Raman) and approximately 780 to approximately 900 (IR) cm-1 for the compound matrix isolated in solid FLINAK at 25 degrees C. In the absence of added oxide, the dissolved aluminum fluoride was in the form of the octahedral AlF6(3-) ion, which has characteristic Raman bands at 542 and 325 cm-1 in the FLINAK melt at 500 degrees C. Whereas alumina, Al2O3, was found to be essentially insoluble in FLINAK melts, it was possible to dissolve sufficient amounts of Na2O to convert most of the AlF6(3-) to the oxyfluoroaluminate, Al2OF6(2-). These solutions appeared to be metastable with respect to formation of insoluble alumina at higher temperatures. The present results can be compared to previous measurements on alumina dissolved in pure molten cryolite at much higher temperatures, where alumina solubility is low and broad bands due to oxide species are difficult to detect due to overlap with bands from AlF6(3-) and AlF4-. PMID:11196946

Brooker, M H; Berg, R W; von Barner, J H; Bjerrum, N J

2000-10-16

207

Properties of Al2O3: nc-Si nanostructures formed by implantation of silicon ions into sapphire and amorphous films of aluminum oxide  

NASA Astrophysics Data System (ADS)

Photoluminescence, infrared Fourier spectroscopy, Raman scattering, transmission electron microscopy, and electron diffraction were used to study the luminescent, optical, and structural properties of aluminum oxide layers (sapphire and films of Al2O3 deposited on silicon) implanted with Si+ to produce silicon nanocrystals. It is established that, in both cases, a high-temperature annealing of heavily implanted samples brings about the formation of silicon nanocrystals. However, the luminescent properties of the nanocrystals are strongly dependent on the type of pristine matrix; namely, nanocrystals in Al2O3 films emit light in the spectral range typical of Si quantum dots (700-850 nm), whereas in sapphire this photoluminescence is not observed. This difference is interpreted as being due to the fact that local stresses arise in the nanocrystal/sapphire system and break chemical bonds at the interface between the phases, whereas in Al2O3 films stresses are relaxed.

Tetelbaum, D. I.; Mikhaylov, A. N.; Belov, A. I.; Ershov, A. V.; Pitirimova, E. A.; Plankina, S. M.; Smirnov, V. N.; Kovalev, A. I.; Turan, R.; Yerci, S.; Finstad, T. G.; Foss, S.

2009-02-01

208

Cast Aluminum Alloys for High Temperature Applications Using Nanoparticles Al2O3 and Al3-X Compounds (X = Ti, V, Zr).  

National Technical Information Service (NTIS)

In this paper, the effect of nanoparticles Al2O3 and Al3-X compounds (X = Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their low co...

J. A. Lee

2009-01-01

209

Formation of nanocrystalline h-AlN during mechanochemical decomposition of melamine in the presence of metallic aluminum  

NASA Astrophysics Data System (ADS)

Decomposition of melamine was studied by solid state reaction of melamine and aluminum powders during high energy ball-milling. The milling procedure performed for both pure melamine and melamine/Al mixed powders as the starting materials for various times up to 48 h under ambient atmosphere. The products were characterized by X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FTIR). The results revealed that Al causes melamine deammoniation at the first stages of milling and further milling process leads to the s-triazine ring degradation while nano-crystallite hexagonal aluminum nitride (h-AlN) was the main solid product. Comparison to milling process, the possibility of the reaction of melamine with Al was also investigated by thermal treatment method using differential scanning calorimeter (DSC) and thermo gravimetric analyzer (TGA). Melamine decomposition occurred by thermal treatment in the range of 270-370 °C, but no reaction between melamine and aluminum was observed.

Rounaghi, S. A.; Kiani Rashid, A. R.; Eshghi, H.; Vahdati Khaki, J.

2012-06-01

210

The effect of oxide film properties on the corrosion behavior of SiC\\/Al metal-matrix composites  

Microsoft Academic Search

Oxide growth on pure aluminum, aluminum alloy 6061, and the aluminum-based metal matrix composite SiC\\/AA6061 was studied, and the properties of the oxides related to the pit-initiation behavior of the materials. The objectives of the work were to identify the effect of alloying elements and SiC reinforcement on the oxide film, and to better understand how the oxide properties control

Golledge

1991-01-01

211

Friction Welding Characteristics of Al-Mg Aluminum Alloy (A5056) and Carbon Steel (S45C)  

Microsoft Academic Search

The possibility of joining composite materials, conventional steel and lighter aluminum alloy, is tested using friction welding that preserves the natural environment greatly. The friction welding of aluminum alloy, Al-Mg (A5056), and carbon steel (S45C) are done under various experimental conditions and the friction welding characteristics are examined. The mechanical property (tensile strength) of the welded specimen has enough strength

Akiyoshi Kobayashi; Michihide Machida; Shigeo Hukaya; Masatoshi Suzuki

2003-01-01

212

Fatigue crack growth and retardation due to overloads in metal-matrix composites Volume I. Fatigue crack growth in boron-aluminum metal-matrix composites. Final report, June 1982December 1985  

Microsoft Academic Search

The fatigue crack growth in a Boron-Aluminum metal matrix composite is investigated. The material consists of II plies of diffusion bonded 5.6 mil boron fibers in a 6061 aluminum matrix. In this study, the composite is characterized as an orthotropic elastic-plastic material using uniaxial test specimens. The constraint effect of the plasticity encountered in specimens with stress gradients is characterized

C. T. Sun; J. F. Doyle; S. Rizzi

1986-01-01

213

Spray pyrolytic deposition of transparent aluminum oxide (Al 2O 3) films  

NASA Astrophysics Data System (ADS)

Optically transparent Al 2O 3 films has been synthesized, on quartz substrates at 500, 600 and 700 °C, from 0.02 M aluminum acetyl acetonate (Al(acac) 3) in ethanol, by using ultrasonic spray pyrolysis technique. The films synthesized at 500, 600 and 700 °C are amorphous having average particle sizes 27 ± 6, 18 ± 3 and 14 ± 3, respectively. The films are found to be 95% optically transparent in the visible region. The optical transparency of the films in the ultraviolet region is found to increase with increase in deposition temperature. The observed increase in optical band gap and decrease in refractive index is attributed to the decrease in particle size with increase in deposition temperature. The stoichiometry and chemical bonding of the amorphous film studied using XPS and FTIR spectroscopy revealed the presence chemisorbed oxygen.

Dhonge, Baban P.; Mathews, Tom; Sundari, S. Tripura; Thinaharan, C.; Kamruddin, M.; Dash, S.; Tyagi, A. K.

2011-11-01

214

On the hot working characteristics of 2014 Al–20 vol% Al 2O 3 metal matrix composite  

Microsoft Academic Search

A simple instability condition based on the Ziegler's continuum principles as applied to large plastic flow, is extended for delineating the regions of unstable metal flow during hot deformation of 2014 Al–20vol% Al2O3 metal matrix composite. The optimum hot working conditions for this material are suggested.

S. V. S. Narayana Murty; B. Nageswara Rao; B. P. Kashyap

2005-01-01

215

Metallurgical factors influencing the corrosion of aluminum, Al-Cu, and Al-Si alloy thin films in dilute hydrofluoric solution  

Microsoft Academic Search

The corrosion behavior of sputter-deposited Al, Al-Cu, and Al-Si alloy thin films in dilute hydrofluoric (HF) acid solution\\u000a was investigated. These materials maintain a thin aluminum oxide film in dilute HF solutions and, consequently, are susceptible\\u000a to localized corrosion. Pit densities increase for the alloys with Cu and, to a lesser extent, Si additions. Open circuit\\u000a potentials (OCP) are more

J. R. Scully; D. E. Peebles; A. D. Romig; D. R. Frear; C. R. Hills

1992-01-01

216

Further characterization of the aluminum peroxide oxide, AlO 2, formed by interfacial reaction between Pt and ?-Al 2O 3  

Microsoft Academic Search

A new metastable aluminum peroxide oxide, AlO2, was recently shown to form by an interfacial reaction in the presence of a kinetic constraint during diffusion-bonding of Pt and ?-Al2O3. Further studies of the properties, bonding, formation kinetics and chemistry of AlO2 are described and the current state of knowledge of the kinetics of its formation is summarized. Raman spectroscopy on

Y.-C. Lu; S. Agnew; R. Dieckmann; S. L. Sass

1995-01-01

217

Colloidal processing of silcon carbide whiskers/aluminum oxide ceramic matrix composites  

NASA Astrophysics Data System (ADS)

By manipulating the interparticle forces of ceramic colloidal systems, suspensions of different dispersing abilities were obtained. Changing the concentration of ionic species, pH, polyelectrolyte and the solution altered the net interparticle force. The zeta potentials of single component suspensions of varying concentration of ionic species, polyelectrolyte addition, pH and solution (electrolyte, ethanol, or a mixture of electrolyte and ethanol) were measured. The stability ratio, W, which measures the effectiveness of the potential barrier in preventing the particles from coagulation, and the interaction between the components were discussed. SiC whisker reinforced Al2O 3 suspensions were slip cast at different processing conditions (SiC whisker volume fraction, solids loading, ball milling, sintering aids, polyelectrolyte and pH). Green specimens were cold-isostatically pressed and pressureless sintered in a flowing nitrogen atmosphere. Homogeneous SiCw/Al2O3 green bodies with densities of 2.55 +/- 0.07 g/cm3 (~65% theoretical density) were obtained. Bulk densities of 3.80 +/- 0.06 g/cm3 (96% theoretical density), 3.79 +/- 0.06 g/cm3 (97% theoretical density), and 3.40 +/- 0.07 g/cm3 (89% theoretical density) were obtained at 1600°C for composite samples containing 5, 10 and 20 vol% SiC whiskers, respectively. Bulk densities of the 10 vol% SiCw/Al2O3 composites were 3.79 +/- 0.06 g/cm3 at PH 11 and 3.66 +/- 0.07 g/cm3 at pH 4, respectively. pH 11 was determined to be the optimum processing pH for SiCw/Al2O3 composites with sintering aids (2 wt% Y2O3 and 0.5 wt% MgO) and 2.5 vol% polyelectrolyte (Ammonia salt of a polymeric carboxylic acid). The final microstructure revealed homogeneous and near fully densified composites. Compositions of the composites were characterized using Energy Dispersive X-ray Spectrum (EDX). The effect of the aspect ratio of SiC whisker, the Y2O 3 content and the choice of polyelectrolyte were examined. The whisker aspect ratio reduction had a more dramatic effect on achieving dense composites in 20 vol% SiC whisker when compared to 5 or 10 vol% SiC whisker composites. High densities with 10 vol% SiC whisker were attainable without aspect ratio reduction. Sintered densities increased with increasing Y2O 3 content. For 10 vol% SiCw/ Al2O3, the densities remained almost constant at Y2O3 additions greater than 0.5 wt% 2.5 vol% polyelectrolyte stabilized the suspension and resulted in high composite densities. However, further addition of polyelectrolyte, past the adsorption saturation limit, served to leave excess polyelectrolyte in suspension. This excess polyelectrolyte lowered the composite density due to depletion flocculation. Sintered densities of 10 vol% SiCw/Al 2O3 composites slip cast from a mixture of ethanol and water were only 2.92 +/- 0.08 g/cm3 (75% theoretical density). The fracture toughness of Al2O3 was remarkably improved with increasing whisker content. The fracture toughness of 20 vol% SiCw/Al2O3 composite was twice the fracture toughness of the unreinforced Al2O3 matrix.

Zhang, Mingli

218

An experimental and analytical study of scuffing in aluminum based metal matrix composites  

NASA Astrophysics Data System (ADS)

Scuffing is a surface damage phenomenon in tribology characterized by the formation of local welds between sliding surfaces. Many previous studies focused on scuffing of ferrous materials due to their extensive use in tribological systems. Information about scuffing behavior of Al metal matrix composites (MMC) is scarce, especially quantitative modeling of the effects of volume percentage, size as well as distribution of reinforcement particles. Therefore, it will broaden our understanding of scuffing in MMC's if the influences of these factors on scuffing behavior are clarified. The objective of this study is to understand when scuffing will occur and the relationships of Al MMC's scuffing resistance with material characteristics and mechanical properties. A new scuffing criterion for particulate reinforced MMG's was proposed in this study based on which an extensive finite element analysis (FEA) on MMC's behavior was carried out. This is the first FEA modeling work in this research field. Various MMC's were tested experimentally in this study including SiC and Alsb{2sb3} ceramic particle reinforcements and Al 356, Al 6061 and Al 2014 matrices. A special ring-on-block reciprocating test apparatus was developed to perform scuffing tests and simulate the interactions between piston ring and engine cylinder bore. Scuffing was detected by an abrupt increase in friction during experiments. Scuffing resistance is represented by scuffing pressure or scuffing initiating time. After scuffing tests, most of the MMC samples were examined with optical and/or scanning electron microscopy (SEM) to obtain information on surface topography changes. The influence of a material's microstructural and mechanical properties (hardness, yield strength, percentage and size of reinforcements), surface finish and lubrication on scuffing were investigated. The conclusions can provide us a guidance in the selection of appropriate materials and machining processes for a tribological system. The major contribution of this study is the finding of an effective method (FEA) to predict scuffing resistance of MMC's quantitatively. The FEA results on scuffing were compared with that from experiments and they show strong correlation.

Bin, Feng

219

Avoidance of stress corrosion susceptibility in high strength aluminum alloys by control of grain boundary and matrix microstructure  

NASA Technical Reports Server (NTRS)

The relation of microstructure to the mechanical strength and stress corrosion resistance of highest strength and overaged tempers of BAR and 7050 aluminum alloys was investigated. Comparison is made with previously studied 7075 aluminum alloy. Optical microscopy, transmission electron microscopy, and differential scanning calorimetry were used to characterize the grain morphology, matrix microstructure, and grain boundary microstructure of these tempers. Grain boundary interparticle spacing was significant to stress corrosion crack propagation for all three alloys; increasing interparticle spacing led to increased resistance to crack propagation. In addition, the fire grain size in Bar and 7050 appears to enhance crack propagation. The highest strength temper of 7050 has a comparatively high resistance to crack initiation. Overall stress corrosion behavior is dependent on environment pH, and evaluation over a range of pH is recommended.

Adler, P.; Deiasi, R.

1974-01-01

220

Optimization of the strength-fracture toughness relation in particulate-reinforced aluminum composites via control of the matrix microstructure  

SciTech Connect

The evolution of the microstructure and mechanical properties of a 17.5 vol. pct SiC particulate-reinforced aluminum alloy 6092-matrix composite has been studied as a function of postfabrication processing and heat treatment. It is demonstrated that, by the control of particulate distribution, matrix grain, and substructure and of the matrix precipitate state, the strength-toughness combination in the composite can be optimized over a wide range of properties, without resorting to unstable, underaged (UA) matrix microstructures, which are usually deemed necessary to produce a higher fracture toughness than that displayed in the peak-aged condition. Further, it is demonstrated that, following an appropriate combination of thermomechanical processing and unconventional heat treatment, the composite may possess better stiffness, strength, and fracture toughness than a similar unreinforced alloy. In the high- and low-strength matrix microstructural conditions, the matrix grain and substructure were found to play a substantial role in determining fracture properties. However, in the intermediate-strength regime, properties appeared to be optimizable by the utilization of heat treatments only. These observations are rationalized on the basis of current understanding of the grain size dependence of fracture toughness and the detailed microstructural features resulting from thermomechanical treatments.

Dutta, I.; Quiles, F.N.; McNelley, T.R.; Nagarajan, R. [Naval Postgraduate School, Monterey, CA (United States). Dept. of Mechanical Engineering

1998-09-01

221

Coagulation behavior of aluminum salts in eutrophic water: significance of Al13 species and pH control.  

PubMed

The coagulation behavior of aluminum salts in a eutrophic source water was investigated from the viewpoint of Al(III) hydrolysis species transformation. Particular emphasis was paid to the coagulation effect of Al13 species on removing particles and organic matter. The coagulation behavior of Al coagulants with different basicities was examined through jar tests and hydrolyzed Al(III) speciation distribution characterization in the coagulation process. The results showed that the coagulation efficiency of Al coagulants positively correlated with the content of Al13 in the coagulation process ratherthan in the initial coagulants. Aluminum chloride (AICl3) was more effective than polyaluminum chloride (PACI) in removing turbidity and dissolved organic matter in eutrophic water because AlCl3 could not only generate Al13 species but also function as a pH control agent in the coagulation process. The solidstate 27Al NMR spectra revealed that the precipitates formed from AlCl3 and PACl were significantly different and proved that the preformed Al13 polymer was more stable than the in situ formed one during the coagulation process. Through regulating Al speciation, pH control could improve the coagulation process especially in DOC removal, and AlCl3 benefited most from pH control. PMID:16433368

Hu, Chengzhi; Liu, Huijuan; Qu, Jiuhui; Wang, Dongsheng; Rut, Jia

2006-01-01

222

Lattice dynamics and Born instability in yttrium aluminum garnet, Y3Al5O12.  

PubMed

We report lattice dynamics calculations of various microscopic and macroscopic vibrational and thermodynamic properties of yttrium aluminum garnet (YAG), Y3Al5O12, as a function of pressure up to 100 GPa and temperature up to 1500 K. YAG is an important solid-state laser material with several technological applications. Garnet has a complex structure with several interconnected dodecahedra, octahedra and tetrahedra. Unlike other aluminosilicate garnets, there are no distinct features to distinguish between intramolecular and intermolecular vibrations of the crystal. At ambient pressure, low energy phonons involving mainly the vibrations of yttrium atoms play a primary role in the manifestations of elastic and thermodynamic behavior. The aluminum atoms in tetrahedral and octahedral coordination are found to be dynamically distinct. Garnet's stability can be discerned from the response of its phonon frequencies to increasing pressure. The dynamics of both octahedral and tetrahedral aluminum atoms undergo radical changes under compression which have an important bearing on their high pressure and temperature properties. At 100 GPa, YAG develops a large phonon bandgap (90-110 meV) and its microscopic and macroscopic physical properties are found to be profoundly different from that at the ambient pressure phase. There are significant changes in the high pressure thermal expansion and specific heat. The mode Grüneisen parameters show significant changes in the low energy range with pressure. Our studies show that the YAG structure becomes mechanically unstable around P = 108 GPa due to the violation of the Born stability criteria. Although this does not rule out thermodynamic crossover to a lower free energy phase at lower pressure, this places an upper bound of P = 110 GPa for the mechanical stability of YAG. PMID:21389366

Goel, Prabhatasree; Mittal, R; Choudhury, N; Chaplot, S L

2010-02-17

223

Interfaces and fracture surfaces in Saffil\\/Al-Mg-Cu metal-matrix composites  

Microsoft Academic Search

The interfacial phases were studied in pressure-cast Saffil\\/Al-4.5Cu-3Mg composite material using a variety of characterization\\u000a techniques. The magnesium- and copper-rich phases were found to segregate near the fibre-matrix interfaces. The major phases\\u000a were identified as MgAl2O4, Al2CuMg and CuAl2. Significant diffusion of silicon from the fibres into the matrix took place during the pressure-casting. A conclusion was\\u000a drawn that solidification

M. Fishkis

1991-01-01

224

Interfaces and fracture surfaces in Saffil\\/Al-Mg-Cu metal-matrix composites  

Microsoft Academic Search

The interfacial phases were studied in pressure-cast Saffil\\/Al-4.5Cu-3Mg composite material using a variety of characterization techniques. The magnesium- and copper-rich phases were found to segregate near the fibre-matrix interfaces. The major phases were identified as MgAl2O4, Al2CuMg and CuAl2. Significant diffusion of silicon from the fibres into the matrix took place during the pressure-casting. A conclusion was drawn that solidification

M. Fishkis

1991-01-01

225

Plastic deformation macrolocalization during serrated creep of an aluminum-magnesium Al-6 wt % Mg alloy  

NASA Astrophysics Data System (ADS)

The nonlinear dynamics of the space-time structure of macrolocalized deformation is studied by a set of high-speed in situ methods under the conditions of serrated creep in an aluminum-magnesium Al-6 wt % Mg alloy at room temperature. Macroscopic deformation jumps with an amplitude of several percent are detected in the creep curve of this alloy. It is found that a complex space-time structure of macrolocalized deformation bands moving in a correlated manner forms spontaneously in the material during the development of a deformation jump. The difference between the observed picture of deformation bands and the well-known Portevin-Le Chatelier classification of deformation bands is discussed.

Shibkov, A. A.; Zolotov, A. E.; Zheltov, M. A.; Denisov, A. A.; Gasanov, M. F.

2014-04-01

226

Atmospheric pressure atomic layer deposition of Al?O? using trimethyl aluminum and ozone.  

PubMed

High throughput spatial atomic layer deposition (ALD) often uses higher reactor pressure than typical batch processes, but the specific effects of pressure on species transport and reaction rates are not fully understood. For aluminum oxide (Al2O3) ALD, water or ozone can be used as oxygen sources, but how reaction pressure influences deposition using ozone has not previously been reported. This work describes the effect of deposition pressure, between ?2 and 760 Torr, on ALD Al2O3 using TMA and ozone. Similar to reports for pressure dependence during TMA/water ALD, surface reaction saturation studies show self-limiting growth at low and high pressure across a reasonable temperature range. Higher pressure tends to increase the growth per cycle, especially at lower gas velocities and temperatures. However, growth saturation at high pressure requires longer O3 dose times per cycle. Results are consistent with a model of ozone decomposition kinetics versus pressure and temperature. Quartz crystal microbalance (QCM) results confirm the trends in growth rate and indicate that the surface reaction mechanisms for Al2O3 growth using ozone are similar under low and high total pressure, including expected trends in the reaction mechanism at different temperatures. PMID:24617608

Mousa, Moataz Bellah M; Oldham, Christopher J; Parsons, Gregory N

2014-04-01

227

Microstructural Characterization of an Al-Li-Cu-Mg Alloy (8090) Metal-Matrix Composite.  

National Technical Information Service (NTIS)

The results of a preliminary investigation into the microstructure of a metal matrix composite (MMC) containing 20 (vol) percent of SiC particles in an Al-Li-Cu-Mg (8090) alloy matrix are described. Transmission electron microscopy and energy dispersive s...

C. J. Gilmore A. W. Bowen

1989-01-01

228

The use of polyimide-modified aluminum nitride fillers in AlN@PI/epoxy composites with enhanced thermal conductivity for electronic encapsulation.  

PubMed

Polymer modified fillers in composites has attracted the attention of numerous researchers. These fillers are composed of core-shell structures that exhibit enhanced physical and chemical properties that are associated with shell surface control and encapsulated core materials. In this study, we have described an apt method to prepare polyimide (PI)-modified aluminum nitride (AlN) fillers, AlN@PI. These fillers are used for electronic encapsulation in high performance polymer composites. Compared with that of untreated AlN composite, these AlN@PI/epoxy composites exhibit better thermal and dielectric properties. At 40?wt% of filler loading, the highest thermal conductivity of AlN@PI/epoxy composite reached 2.03?W/mK. In this way, the thermal conductivity is approximately enhanced by 10.6 times than that of the used epoxy matrix. The experimental results exhibiting the thermal conductivity of AlN@PI/epoxy composites were in good agreement with the values calculated from the parallel conduction model. This research work describes an effective pathway that modifies the surface of fillers with polymer coating. Furthermore, this novel technique improves the thermal and dielectric properties of fillers and these can be used extensively for electronic packaging applications. PMID:24759082

Zhou, Yongcun; Yao, Yagang; Chen, Chia-Yun; Moon, Kyoungsik; Wang, Hong; Wong, Ching-Ping

2014-01-01

229

The use of polyimide-modified aluminum nitride fillers in AlN@PI/Epoxy composites with enhanced thermal conductivity for electronic encapsulation  

NASA Astrophysics Data System (ADS)

Polymer modified fillers in composites has attracted the attention of numerous researchers. These fillers are composed of core-shell structures that exhibit enhanced physical and chemical properties that are associated with shell surface control and encapsulated core materials. In this study, we have described an apt method to prepare polyimide (PI)-modified aluminum nitride (AlN) fillers, AlN@PI. These fillers are used for electronic encapsulation in high performance polymer composites. Compared with that of untreated AlN composite, these AlN@PI/epoxy composites exhibit better thermal and dielectric properties. At 40 wt% of filler loading, the highest thermal conductivity of AlN@PI/epoxy composite reached 2.03 W/mK. In this way, the thermal conductivity is approximately enhanced by 10.6 times than that of the used epoxy matrix. The experimental results exhibiting the thermal conductivity of AlN@PI/epoxy composites were in good agreement with the values calculated from the parallel conduction model. This research work describes an effective pathway that modifies the surface of fillers with polymer coating. Furthermore, this novel technique improves the thermal and dielectric properties of fillers and these can be used extensively for electronic packaging applications.

Zhou, Yongcun; Yao, Yagang; Chen, Chia-Yun; Moon, Kyoungsik; Wang, Hong; Wong, Ching-Ping

2014-04-01

230

The use of polyimide-modified aluminum nitride fillers in AlN@PI/Epoxy composites with enhanced thermal conductivity for electronic encapsulation  

PubMed Central

Polymer modified fillers in composites has attracted the attention of numerous researchers. These fillers are composed of core-shell structures that exhibit enhanced physical and chemical properties that are associated with shell surface control and encapsulated core materials. In this study, we have described an apt method to prepare polyimide (PI)-modified aluminum nitride (AlN) fillers, AlN@PI. These fillers are used for electronic encapsulation in high performance polymer composites. Compared with that of untreated AlN composite, these AlN@PI/epoxy composites exhibit better thermal and dielectric properties. At 40?wt% of filler loading, the highest thermal conductivity of AlN@PI/epoxy composite reached 2.03?W/mK. In this way, the thermal conductivity is approximately enhanced by 10.6 times than that of the used epoxy matrix. The experimental results exhibiting the thermal conductivity of AlN@PI/epoxy composites were in good agreement with the values calculated from the parallel conduction model. This research work describes an effective pathway that modifies the surface of fillers with polymer coating. Furthermore, this novel technique improves the thermal and dielectric properties of fillers and these can be used extensively for electronic packaging applications.

Zhou, Yongcun; Yao, Yagang; Chen, Chia-Yun; Moon, Kyoungsik; Wang, Hong; Wong, Ching-ping

2014-01-01

231

Friction Stir Welding for Aluminum Metal Matrix Composites (MMC's) (Center Director's Discretionary Fund, Project No. 98-09)  

NASA Technical Reports Server (NTRS)

This technical memorandum describes an investigation of using friction stir welding (FSW) process for joining a variety of aluminum metal matrix composites (MMC's) reinforced with discontinuous silicon-carbide (SiC) particulate and functional gradient materials. Preliminary results show that FSW is feasible to weld aluminum MMC to MMC or to aluminum-lithium 2195 if the SiC reinforcement is <25 percent by volume fraction. However, a softening in the heat-affected zone was observed and is known to be one of the major limiting factors for joint strength. The pin tool's material is made from a low-cost steel tool H-13 material, and the pin tool's wear was excessive such that the pin tool length has to be manually adjusted for every 5 ft of weldment. Initially, boron-carbide coating was developed for pin tools, but it did not show a significant improvement in wear resistance. Basically, FSW is applicable mainly for butt joining of flat plates. Therefore, FSW of cylindrical articles such as a flange to a duct with practical diameters ranging from 2-5 in. must be fully demonstrated and compared with other proven MMC joining techniques for cylindrical articles.

Lee, J. A.; Carter, R. W.; Ding, J.

1999-01-01

232

F2Al(mu-eta2:eta2-O2)AlF2: an unusual, stable aluminum peroxo compound.  

PubMed

The oxidation processes in the industrial production of aluminum from cryolite melts are not fully understood. Oxidation of AlOF2- leads initially to AlOF2 radicals. The structure of the AlOF2 dimer and several oxidized and reduced forms of this compound are investigated by theoretical methods and compared to analogous boron and gallium compounds. The thermodynamic stability of these compounds is investigated. It is shown that the dimeric compound of AlOF2 contains a symmetric peroxo bridge and is unexpectedly stable toward decomposition. PMID:14966980

Hammerl, Anton; Welch, Barry J; Schwerdtfeger, Peter

2004-02-23

233

THE PROTOTYPE ALUMINUM - CARBON SINGLE, DOUBLE, AND TRIPLE BONDS: Al - CH3, Al = CH2, AND Al. = CH  

SciTech Connect

Nonempirical quantum mechanical methods have been used to investigate the A{ell}CH{sub 3}, A{ell}CH{sub 2}, and A{ell}CH molecules, which may be considered to represent the simplest aluminum-carbon single, double, and triple bonds. Equilibrium geometries and vibrational frequencies were determined at the self-consistent-field level of theory using double zeta basis set: A{ell}(11s7p/6s4p), C(9s5p/4s2p), H(4s/2s). The {sup 1}A{sub 1} ground state of A{ell}CH{sub 3} has a reasonably conventional A{ell}-C single bond of length 2.013 {angstrom}, compared to 1.96 {angstrom} in the known molecule A{ell}(CH{sub 3}){sub 3}. The CH equilibrium distance is 1.093 {angstrom} and the A{ell}-C-H angle 111.9{sup o}. The structures of three electron states each of A{ell}CH{sub 2} and A{ell}CH were similarly predicted, The interesting result is that the ground state of A{ell}CH{sub 2} does not contain an A{ell}-C double bond, and the ground state of A{ell}CH is not characterized by an A{ell}{triple_bond}C bond. The multiply-bonded electronic states do exist but they lie 21 kcal (A{ell}CH{sub 2}) and 86 kcal (A{ell}CH) above the respective ground states. The dissociation energies of the three ground electronic states are predicted to be 68 kcal (A{ell}CH{sub 3}), 77 kcal (A{ell}CH{sub 2}), and 88 kcal (A{ell}CH), Vibrational frequencies are also predicted for the three molecules, and their electronic structures are discussed with reference to Mulliken populations and dipole moments.

Fox, Douglas J.; Ray, Douglas; Rubesin, Philip C.; Schaefer III, Henry F.

1980-06-01

234

CO sub 2 induced inhibition of the localized corrosion of aluminum, Al-0. 5% Cu, and Al-2% Cu in dilute HF solution  

SciTech Connect

This study presents work on corrosion of aluminum, Al-.5% Cu, and Al-2% Cu. Electrochemical tests were performed in dilute HF solutions both with and without CO{sub 2} sparging. It is suggested that CO{sub 2} or its reaction products interact with the passive film so that exposure of Cu in the oxide-solution interface is minimized. CO{sub 2} is investigated as a corrosion inhibitor. 4 refs. (JDL)

Scully, J.R. (Virginia Univ., Charlottesville, VA (USA). Dept. of Materials Science); Peebles, D.E. (Sandia National Labs., Albuquerque, NM (USA))

1991-01-01

235

Fiber damage and high temperature tensile properties of Al 2O 3 fiber reinforced NiAl-matrix composites with and without hBN-interlayer  

Microsoft Academic Search

The fiber damage caused by thermal residual stress in NiAl-matrix composites reinforced by single-crystal Al2O3 fibers (sapphire) was studied. In the NiAl\\/Al2O3 (Vf=0.3) composites, more fibers were broken into shorter segments because of the larger thermal axial compressive stress exerted on the fibers which was caused by the different thermal expansion coefficients of Al2O3 fibers and NiAl matrix. An increasing

Y. Zhong; H. Chen; W. Hu; G. Gottstein

2007-01-01

236

Particle penetration during spray forming and Co-injection of Ni 3 Al + B\\/Al 2 O 3 intermetallic matrix composite  

Microsoft Academic Search

Intermetallic matrix Ni3Al + B\\/Al2O3 composite, with 11 vol pct of Al2O3 particles incorporated into the matrix, was synthesized using a spray atomization and coinjection method. The penetration\\u000a behavior of ceramic particles into atomized droplets during spray atomization and coinjection of Ni3Al + B\\/Al2O3 composite was investigated experimentally and numerically. It was found that the extent of incorporation of Al2O3

D. E. Lawrynowicz; B. Li; E. J. Lavernia

1997-01-01

237

Mechanical behaviour of the interphase between matrix and reinforcement of Al 2014 matrix composites reinforced with (Ni 3Al) p  

Microsoft Academic Search

The 2XXX series aluminium alloys reinforced with intermetallics present a special behaviour due to the reaction between matrix and reinforcement. This reaction forms an interphase that influences the mechanical and chemical behaviour of the composite, reducing the capability of the material to improve its properties after heat treatment. In this work, an approach is made to the study of this

José M. Torralba; Francisco Velasco; Cesar E. Costa; Isabel Vergara; Daniel Cáceres

2002-01-01

238

Impedance spectroscopy study of aluminum electrocrystallization from basic molten salt (AlCl 3–NaCl–KCl)  

Microsoft Academic Search

Aluminum electrocrystallization is studied by means of electrochemical impedance spectroscopy (EIS). A model based on random birth and deterministic growth of monolayers is proposed, in which the edges are assumed to follow a propagation law. The high frequency impedance data show charge transfer reaction of AlCl4? reduction while the low frequency features signifies the growth mode of deposits. The inductive

M. Jafarian; F. Gobal; I. Danaee; M. G. Mahjani

2007-01-01

239

Failure Modeling of Titanium 6Al-4V and Aluminum 2024-T3 with the Johnson-Cook Material Model.  

National Technical Information Service (NTIS)

Johnson-Cook failure strain parameters were developed for Ti-6Al-4V and 2024-T3 aluminum. The titanium parameters, obtained from simulations of split Hopkinson bar tensile tests, were successfully used to simulate blade fragment impact tests on 0.602, 0.2...

G. Kay

2003-01-01

240

InGaN nanoinclusions in an AlGaN matrix  

SciTech Connect

GaN-based structures with InGaN quantum dots in the active region emitting in the near-ultraviolet region are studied. In this study, two types of structures, namely, with InGaN quantum dots in a GaN or AlGaN matrix, are compared. Photoluminescence spectra are obtained for both types of structures in a temperature range of 80-300 K and at various pumping densities, and electroluminescence spectra are obtained for light-emitting (LED) structures with various types of active region. It is shown that the structures with quantum dots in the AlGaN matrix are more stable thermally due to the larger localization energy compared with quantum dots in the GaN matrix. Due to this, the LED structures with quantum dots in an AlGaN matrix are more effective.

Sizov, V. S., E-mail: sizovviktor@mail.ru; Tsatsul'nikov, A. F.; Lundin, V. V. [Russian Academy of Sciences, Ioffe Physicotechnical Institute (Russian Federation)

2008-07-15

241

Coagulation characteristics of titanium (Ti) salt coagulant compared with aluminum (Al) and iron (Fe) salts.  

PubMed

In this study, the performance of titanium tetrachloride (TiCl(4)) coagulation and flocculation is compared with commonly used coagulants such as aluminum sulfate (Al(2)(SO(4))(3)), polyaluminum chloride (PACl), iron chloride (FeCl(3)), and polyferric sulfate (PFS) in terms of water quality parameters and floc properties. TiCl(4) flocculation achieved higher removal of UV(254) (98%), dissolved organic carbon (DOC) (84%) and turbidity (93%) than other conventional coagulants. Charge neutralization and physical entrapment of colloids within coagulant precipitates and adsorption, seemed to play a significant role during TiCl(4) flocculation, while the main mechanism for conventional coagulants was bridge-aggregation and adsorption. The aggregated flocs after TiCl(4) flocculation showed the fastest growth rate compared to the other coagulants, with the largest floc size (801 ?m) occurring within 8 min. The floc strength factor of PACl, Al(2)(SO(4))(3), PFS, FeCl(3) and TiCl(4) was 34, 30, 29, 26 and 29, respectively, while the floc recovery factor of the TiCl(4) coagulant was the lowest. Based on the results of the above study, it is concluded that the TiCl(4) flocculation can reduce the hydraulic retention time of slow and rapid mixing, however, careful handling of sludge is required due to the low recoverability of the aggregated floc. PMID:21075521

Zhao, Y X; Gao, B Y; Shon, H K; Cao, B C; Kim, J-H

2011-01-30

242

Trace metal characterization of the U-Al matrix by atomic spectroscopy  

Microsoft Academic Search

Uranium-aluminum alloys with a significant enrichment of uranium with ²³³U or ²³⁵U serve as nuclear fuels in research reactors. The quality assurance of this fuel requires, among other things, precise knowledge that all trace metal constituents that affect neutron economy, fuel integrity, and fuel fabrication process parameters are well within the specification limits. Trace metal characterization of ²³⁵U-Al alloy has

A. A. Argekar; S. K. Thulasidas; M. J. Kulkarni; M. K. Bhide; R. Sampathkumar; S. V. Godbole; V. C. Adya; B. A. Dhawale; B. Rajeshwari; N. Goyal

1989-01-01

243

Effect of OH ?\\/Al 3+ and Si\\/Al molar ratios on the coagulation performance and residual Al speciation during surface water treatment with poly-aluminum-silicate-chloride (PASiC)  

Microsoft Academic Search

Coagulation performance, mechanism of poly-aluminum-silicate-chloride (PASiC) and residual Al speciation in the effluent with respect to a specific surface water treatment in China were comprehensively investigated in this study. The impact of OH?\\/Al3+ and Si\\/Al molar ratios on the coagulation performance, mechanism and residual Al speciation of PASiC in surface water treatment was discussed as a function of coagulant dosage.

Zhonglian Yang; Baoyu Gao; Weiying Xu; Baichuan Cao; Qinyan Yue

2011-01-01

244

A comparative study of cavitation characteristics in Si[sub 3]N[sub 4p]\\/Al-Mg-Si composite and 7475 aluminum alloy  

Microsoft Academic Search

Recently, it has been demonstrated that many aluminum matrix composites with discontinuous SiC or Si[sub 3]N[sub 4] show superplastic behavior. In particular, it should be noted that some aluminum matrix composites show superplasticity at high strain rates (> 10[sup [minus]2] s[sup [minus]1]). It is well established that cavitation occurs during superplastic flow in a wide number of metallic materials. However,

H. Iwasaki; M. Takeuchi; T. Mori; M. Mabuchi; K. Higashi

1994-01-01

245

Acoustic emission and microcracking in sapphire, sintered Al{sub 2}O{sub 3}, Al/Al{sub 2}O{sub 3} composite, and aluminum  

SciTech Connect

A range of materials with brittle to ductile behavior (single-crystal and polycrystalline alumina, aluminum-alumina composite, and metallic aluminum) were investigated by acoustic emission (AE) methods for microcracking during hardness indentations or cooling from elevated temperatures (800 C). During indentation, the extent of crack formation (and the AE counts) decreased in the following order: sapphire, sintered alumina, aluminum/alumina composite with no microcracking in metallic aluminum. During cooling from 800 C, polycrystalline alumina exhibited more extensive microcracking than the aluminum/alumina composite, suggesting that the metallic phase in the aluminum/alumina composite absorbs stresses more than the glassy boundary phase in sintered alumina.

Breval, E.; Srikanth, V.; Subbarao, E.C. [Pennsylvania State Univ., University Park, PA (United States). Intercollege Materials Research Lab.

1995-09-01

246

Calorimetric studies of 7000 series aluminum alloys: I. Matrix precipitate characterization of 7075  

Microsoft Academic Search

Both differential scanning calorimetry (DSC) and hot stage transmission electron microscopy were used to characterize the\\u000a solid state reactions accompanying heating of the highest strength (T651) and overaged (T7351) tempers of 7075 aluminum alloy.\\u000a Each of the observed endothermic or exothermic reactions that occurs over the 20 to 500?C temperature range has been ascribed\\u000a to the dissolution or formation of

Deiasi Richard; Philip N. Adler

1977-01-01

247

Spray-forming monolithic aluminum alloy and metal matrix composite strip  

Microsoft Academic Search

Spray forming with de Laval nozzles is an advanced materials processing technology that converts a bulk liquid metal to a near-net-shape solid by depositing atomized droplets onto a suitably shaped substrate. Using this approach, aluminum alloys have been spray formed as strip, with technoeconomic advantages over conventional hot mill processing and continuous casting. The spray-formed strip had a flat profile,

McHugh

1995-01-01

248

Spectrophotometric method free of matrix effects for the sensitive quantitation of aluminum  

Microsoft Academic Search

It is commonly thought that aluminum is a comparatively nontoxic element in its substances. Though it is ubiquitous, most of its naturally occurring compounds e.g. the silicates and oxides, are relatively inert, chemically as well as physically. However, water soluble compounds such as the chloride and nitrate have rat oral LDs0 values of 3.7 (STECHER 1960) and 4.3 g\\/kg (SMYTH

Shane S. Que Hee; James Boyle; Vincent N. Finelli

1979-01-01

249

Al-Cd Alloy Formation by Aluminum Underpotential Deposition from AlCl3+NaCl Melts on Cadmium Substrate  

NASA Astrophysics Data System (ADS)

Aluminum was incorporated into a polycrystalline cadmium electrode surface by underpotential deposition from equimolar AlCl3+ NaCl melt at 473 K, 523 K, and 573 K (200 °C, 250 °C, and 300 °C). The process was studied by linear sweep voltammetry and potentiostatic deposition/galvanostatic striping. The deposits were characterized X-ray diffraction (XRD), Auger electron spectroscopy (AES), and electron probe microanalyzer (EPMA). The electrochemical measurements showed evidence of Cd-Al alloys being formed but they could not be identified. The growth kinetics of the Cd-Al layers of various proportion and depths that depended on temperature and deposition time were described.

Jovi?evi?, Niko; Cvetkovi?, Vesna S.; Kamberovi?, Željko J.; Jovi?evi?, Jovan N.

2013-02-01

250

Fractionation of residual Al in natural water treatment from reservoir with poly-aluminum-silicate-chloride (PASiC): effect of OH/Al, Si/Al molar ratios and initial pH.  

PubMed

An aluminum fractionation study was conducted for a surface reservoir water treatment to understand the performance of poly-aluminum-silicate-chloride (PASiC) in terms of the residual Al fractions as a function of initial pH. The coagulation performance expressed as turbidity and organic matter removal was established as supporting data. Some extra data were evaluated in terms of the residual Al ratio of the composite PASiC coagulant. The main residual Al sources were the Al fractions derived from the use of PASiC. The turbidity and organic matter removal ability was optimal at initial pH 6.00-7.00, while the concentrations of various residual Al species and the residual Al ratio of PASiC were minimal at an initial pH range of 7.00-8.00. Under the conditions of OH/Al molar ratio = 2.00 and Si/Al molar ratio = 0.05, PASiC had superior coagulation performance and comparatively low residual Al concentrations. The Al fraction in the composite PASiC coagulant seldom remained under such conditions. Experimental data also indicated that the suspended (filterable) Al fraction was the dominant species, and organic-bound or organo-Al complex Al was considered to be the major species of dissolved Al in water treated by PASiC coagulation. Additionally, the dissolved inorganic monomeric Al species dominated the dissolved monomeric Al fraction. PMID:23534222

Yang, Zhonglian; Gao, Baoyu; Wang, Yan; Zhao, Yaqin; Yue, Qinyan

2012-01-01

251

Influence of thin porous Al2O3 layer on aluminum cathode to the H? line shape in glow discharge  

NASA Astrophysics Data System (ADS)

The results of the Balmer alfa line shape study in a plane cathode-hollow anode Grimm discharge with aluminum (Al) cathode covered with thin layer of porous Al2O3 are presented. The comparison with same line profile recorded with pure Al cathode shows lack of excessive Doppler broadened line wings, which are always detected in glow discharge with metal cathode. The effect is explained by the lack of strong electric field in the cathode sheath region, which is missing in the presence of thin oxide layer in, so called, spray discharge.

Steflekova, V.; Šišovi?, N. M.; Konjevi?, N.

2009-06-01

252

High Porosity Alumina as Matrix Material for Composites of Al-Mg Alloys  

NASA Astrophysics Data System (ADS)

The sophisticated industry and technologies require higher and higher assumptions against mechanical strength and surface hardness of ceramic reinforced metal alloys and metal matrix composites. Applying the well-known alumina powders by dry pressing technology and some special pore-forming additives and sintering technology the authors have successfully developed a new, high porosity alumina matrix material for composites of advenced Al-Mg alloys. The developed new matrix material have higher than 30% porosity, with homogenous porous structure and pore sizes from few nano up to 2-3 mm depending on the alloys containments. Thanks to the used materials and the sintering conditions the authors could decrease the wetting angles less than 90° between the high porosity alumina matrix and the Al-Mg alloys. Applied analytical methods in this research were laser granulometry, scanning electron microscopy, and X-ray diffraction. Digital image analysis was applied to microscopy results, to enhance the results of transformation.

Gömze, L. A.; Gömze, L. N.; Egész, Á.; Ojima, F.

2013-12-01

253

Partial oxidation of dimethyl ether using the structured catalyst Rh/Al2O3/Al prepared through the anodic oxidation of aluminum.  

PubMed

The partial oxidation of dimethyl ether (DME) was investigated using the structured catalyst Rh/Al2O3/Al. The porous Al2O3 layer was synthesized on the aluminum plate through anodic oxidation in an oxalic-acid solution. It was observed that about 20 nm nanopores were well developed in the Al2O3 layer. The thickness of Al2O3 layer can be adjusted by controlling the anodizing time and current density. After pore-widening and hot-water treatment, the Al2O3/Al plate was calcined at 500 degrees C for 3 h. The obtained delta-Al2O3 had a specific surface area of 160 m2/g, making it fit to be used as a catalyst support. A microchannel reactor was designed and fabricated to evaluate the catalytic activity of Rh/Al2O3/Al in the partial oxidation of DME. The structured catalyst showed an 86% maximum hydrogen yield at 450 degrees C. On the other hand, the maximum syngas yield by a pack-bed-type catalyst could be attained by using a more than fivefold Rh amount compared to that used in the structured Rh/Al2O3/Al catalyst. PMID:22121705

Yu, B Y; Lee, K H; Kim, K; Byun, D J; Ha, H P; Byun, J Y

2011-07-01

254

Particles and Zinc on the Absorbed Impact Energy of Gravity Cast Aluminum Matrix Composites  

NASA Astrophysics Data System (ADS)

The effect of different amounts of boron, in the form of AlB2 particles, as well as zinc concentration in a gravity cast Al-B-Zn composite, was studied and related to the absorbed energy upon fracture during Charpy impact experiments. In addition, the authors correlated the composite Brinell hardness with the quantitative assessment of brittle and ductile fracture areas of the Charpy fractured specimens and found that increasing AlB2 particle concentration resulted in a reduction of absorbed impact energy. Although larger zinc levels produced somewhat similar results, the AlB2 effect was prevalent. The energy absorption upon impact reached a maximum when no particles were present; conversely, the lowest amount of absorbed energy corresponded to a composite with a composition of 15 wt.% Zn and 8% in volume of AlB2, i.e., the highest concentration of AlB2 and zinc studied. Raising the amount of AlB2 as well as zinc, as expected, resulted in higher Brinell hardness. A statistical analysis allowed studying of the particle size distribution, whereas values for crack tip opening displacement were subsequently calculated for the range of particle sizes found and the corresponding AlB2 particle volume percent. Higher porosity values were measured for larger AlB2 volume percent. Finally, analyses of fracture surfaces corroborated that brittle fracture was favored in composites with higher amounts of AlB2 and zinc.

Corchado, Marcos; Reyes, Fernando; Suárez, Oscar Marcelo

2014-06-01

255

Aluminum induces changes in oxidative burst scavenging enzymes in Coffea arabica L. suspension cells with differential Al tolerance.  

PubMed

The accumulation of reactive oxygen species (ROS) and concomitant oxidative stress have been considered deleterious consequences of aluminum toxicity. However, several lines of evidence suggest that ROS can function as important signaling molecules in the plant defense system for protection from abiotic stress and the acquisition of tolerance. The role of ROS-scavenging enzymes was assayed in two different coffee cell suspension lines. We treated L2 (Al-sensitive) and LAMt (Al-tolerant) Coffea arabica suspension cells with 100 ?M AlCl(3) and observed significant differences in catalase activity between the two cell lines. However, we did not observe any differences in superoxide dismutase or glutathione reductase activity in either cell line following Al treatment. ROS production was diminished in the LAMt cell line. Taken together, these results indicate that aluminum treatment may impair the oxidative stress response in L2 cells but not in LAMt cells. We suggest a possible role for Al-induced oxidative bursts in the signaling pathways that lead to Al resistance and protection from Al toxicity. PMID:22099163

Ramírez-Benítez, José Efraín; Muñoz-Sánchez, J Armando; Becerril-Chi, Karen M; Miranda-Ham, María de Lourdes; Castro-Concha, Lizbeth A; Hernández-Sotomayor, S M Teresa

2011-11-01

256

Settling and clustering of silicon carbide particles in aluminum metal matrix composites  

NASA Astrophysics Data System (ADS)

The settling of 14-?m silicon carbide particles in an aluminum-silicon alloy was monitored with an electrical resistance probe to measure the in situ particle voluem fraction. The rate of settling was much greater than expected from hindered settling of single 14-?m particles. From the observed settling rate, an equivalent hydrodynamic diameter and density of clusters of particles were deduced, 38 ?m and 2740 kg/m3, respectively. Other work was analyzed with the same procedure; it was concluded that if the stirring prior to settling were intense, then the clusters would be smaller than with weaker stirring. The implications for foundry practice and mechanical properties are discussed.

Irons, G. A.; Owusu-Boahen, K.

1995-10-01

257

Impact Testing of Aluminum 2024 and Titanium 6Al-4V for Material Model Development  

NASA Technical Reports Server (NTRS)

One of the difficulties with developing and verifying accurate impact models is that parameters such as high strain rate material properties, failure modes, static properties, and impact test measurements are often obtained from a variety of different sources using different materials, with little control over consistency among the different sources. In addition there is often a lack of quantitative measurements in impact tests to which the models can be compared. To alleviate some of these problems, a project is underway to develop a consistent set of material property, impact test data and failure analysis for a variety of aircraft materials that can be used to develop improved impact failure and deformation models. This project is jointly funded by the NASA Glenn Research Center and the FAA William J. Hughes Technical Center. Unique features of this set of data are that all material property data and impact test data are obtained using identical material, the test methods and procedures are extensively documented and all of the raw data is available. Four parallel efforts are currently underway: Measurement of material deformation and failure response over a wide range of strain rates and temperatures and failure analysis of material property specimens and impact test articles conducted by The Ohio State University; development of improved numerical modeling techniques for deformation and failure conducted by The George Washington University; impact testing of flat panels and substructures conducted by NASA Glenn Research Center. This report describes impact testing which has been done on aluminum (Al) 2024 and titanium (Ti) 6Al-4vanadium (V) sheet and plate samples of different thicknesses and with different types of projectiles, one a regular cylinder and one with a more complex geometry incorporating features representative of a jet engine fan blade. Data from this testing will be used in validating material models developed under this program. The material tests and the material models developed in this program will be published in separate reports.

Pereira, J. Michael; Revilock, Duane M.; Lerch, Bradley A.; Ruggeri, Charles R.

2013-01-01

258

Calorimetric studies of 7000 series aluminum alloys. I - Matrix precipitate characterization of 7075. II - Comparison of 7075, 7050, and RX720 alloys  

NASA Technical Reports Server (NTRS)

Correlation between differential scanning calorimetry and high temperature transmission electron microscopy for the characterization of preexisting matrix precipitates in the highest-strength and overaged tempers of 7075 aluminum was demonstrated. The solid state reactions undergone by these tempers in the 20-500 C temperature range were elucidated and expressed in terms of thermodynamic and kinetic parameters. The dissolution parameters for each phase are distinguishable and serve as guidelines for a rapid characterization of the matrix microstructure of these alloys.

Deiasi, R.; Adler, P. N.

1977-01-01

259

Investigation of intermetallics in hypoeutectic Al–Fe alloys by dissolution of the Al matrix  

Microsoft Academic Search

During the non-equilibrium solidification typical of DC (direct chill) castings a range of cooling rates occur from the surface to the casting center, and can cause the formation of metastable intermetallic phases (AlmFe, Al6Fe, etc.) in addition to the stable Al3Fe phase. The extensive presence of the plate-like Al3Fe phase in the as-cast structure adversely influences the mechanical properties of

Pedro R. Goulart; Valentim B. Lazarine; Claudenete V. Leal; José E. Spinelli; Noé Cheung; Amauri Garcia

2009-01-01

260

Failure Modeling of Titanium-6Al-4V and 2024-T3 Aluminum with the Johnson-Cook Material Model  

SciTech Connect

A validated Johnson-Cook model could be employed to perform simulations that conform to FAA standards for evaluating aircraft and engine designs for airworthiness and containment considerations. A previous LLNL report [1] described the motivation for using the Johnson-Cook material model in simulations involving engine containment and the effect of uncontained engine debris on aircraft structures. In that report, experimental studies of the deformation and failure behavior of Ti-6Al-4V and 2024-T3 aluminum at high strain rates and large strains were conducted. The report also describes the generation of material constants for the Johnson-Cook strength model. This report describes the determination and validation of parameters for Ti-6Al-4V and 2024-T3 aluminum that can be used in the failure portion of the Johnson-Cook material.

Kay, G

2002-09-16

261

Effect of clustering on the mechanical properties of SiC particulate-reinforced aluminum alloy 2024 metal matrix composites  

Microsoft Academic Search

Al 2024–SiC metal matrix composite (MMC) powders produced by centrifugal atomization were hot extruded to investigate the effect of clustering on their mechanical properties. Fracture toughness and tension tests were conducted on specimens reinforced with different volume fractions of SiC. A model was proposed to suggest that the strength of the MMCs could be estimated from the load transfer model

Soon-Jik Hong; Hong-Moule Kim; Dae Huh; C. Suryanarayana; Byong Sun Chun

2003-01-01

262

Influence of oxidation conditions on the formation of InAs quantum dots in an aluminum oxide matrix  

Microsoft Academic Search

Raman spectroscopy which provides valuable information on the structural parameters of QDs was used for monitoring of the lateral oxidation of InAs\\/AlAs QD structures and study of the phonon properties of InAs QDs in aluminium oxide matrix. Optical phonons of InAs QDs were found to be affected by both strain and confinement. Raman spectra measured from non-oxidized area reveal asymmetric

D. A. Tenne; O. R. Bajutova; A. K. Bakarov; Aleksandr I. Toropov; A. Milekhin; V. A. Haisler; Dietrich R. T. Zahn

2003-01-01

263

Effect of galvanic corrosion between precipitate and matrix on corrosion behavior of Ascast magnesium-aluminum alloys  

Microsoft Academic Search

In the present study, the corrosion behavior of an as-cast magnesium alloy was studies focusing on the galvanic corrosion\\u000a between a precipitate and Mg-rich matrix. Through immersion and electrochemical tests, the variation of the corrosion behavior\\u000a with the alloy composition and alloy system was discussed in detail. The corrosion rate of an as-cast alloy increased abruptly\\u000a to 9 wt.% Al

Choong Do Lee; Choon Sik Kang; Kwang Seon Shin

2000-01-01

264

Hot deformation behavior of the new Al–Mg–Si–Cu aluminum alloy during compression at elevated temperatures  

Microsoft Academic Search

The hot deformation behavior of the new Al–Mg–Si–Cu aluminum alloy was investigated by compression tests in the temperature range 350°C–550°C and strain rate range 0.005s?1–5s?1 using Gleeble-1500 system, and the associated structural changes were studied by observations of metallographic and TEM. The results show that the true stress–true strain curves exhibit a peak stress at a small strain (<0.15), after

Hui Zhang; Luoxing Li; Deng Yuan; Dashu Peng

2007-01-01

265

Thermodynamics of titanium alloys: II. Titanium and aluminum activities in the Bcc ? phase of the Ti-Al system  

Microsoft Academic Search

Thermodynamic activities have been measured at 1780°K in the bcc ? phase of the Ti-Al system, using three vapor pressure techniques.\\u000a The first technique utilized a conventional Knudsen cell configuration. The sample was placed in the cell and the ratio of\\u000a the aluminum signal to the titanium signal was determined as a function of composition. The data were analyzed with

M. Hoch; R. J. Usell

1971-01-01

266

Grinding of alumina\\/aluminum composites  

Microsoft Academic Search

With the anticipated widespread usage of metal matrix composites (MMCs) in the near future, the machinability of high performance MMCs needs to be understood. This paper reports research results obtained from the grinding of aluminum-based MMCs reinforced with Al2O3 particles using grinding wheels having SiC in a vitrified matrix and diamond in a resin-bonded matrix. The issues discussed are surface

Zhaowei Zhong; Nguyen Phu Hung

2002-01-01

267

Consolidation effects on tensile properties of an elemental Al matrix composite  

Microsoft Academic Search

In a simplified composite design, an unalloyed Al matrix was reinforced by spherical Al–Cu–Fe alloy particles (30vol.%), using either commercial purity (99.7%) or high purity (99.99%) fine powders (diameter < 10?m). This composite material was consolidated by either vacuum hot pressing (VHP) or quasi-isostatic forging. The spatial distribution of reinforcement particles in both VHP and forged samples was shown to

F. Tang; H. Meeks; J. E. Spowart; T. Gnaeupel-Herold; H. Prask; I. E. Anderson

2004-01-01

268

An investigation on the machinability of Al-SiC metal matrix composites using pcd inserts  

Microsoft Academic Search

The paper attempts to study the machinability issues of aluminium-silicon carbide (Al-SiC) metal matrix composites (MMC) in\\u000a turning using different grades of poly crystalline diamond (PCD) inserts. Al-SiC composite containing 15%wt of SiC was used\\u000a as work material for turning and PCD inserts of three different grades were used as cutting tools. Experiments were conducted\\u000a at various cutting speeds, feeds

N. Muthukrishnan; M. Murugan; K. Prahlada Rao

2008-01-01

269

Settling and clustering of silicon carbide particles in aluminum metal matrix composites  

SciTech Connect

The settling of 14-{micro}m silicon carbide particles in an aluminum-silicon alloy was monitored with an electrical resistance probe to measure the in situ particle volume fraction. The rate of settling was much greater than expected from hindered settling of single 14-{micro}m particles. From the observed settling rate, an equivalent hydrodynamic diameter and density of clusters of particles were deduced, 38 {micro}m and 2,740 kg/m{sup 3}, respectively. Other work was analyzed with the same procedure; it was concluded that if the stirring prior to settling were intense, then the clusters would be smaller than with weaker stirring. The implications for foundry practice and mechanical properties are discussed.

Irons, G.A.; Owusu-Boahen, K. [McMaster Univ., Hamilton, Ontario (Canada). Dept. of Materials Science and Engineering

1995-10-01

270

Responses of eucalypt species to aluminum: the possible involvement of low molecular weight organic acids in the Al tolerance mechanism.  

PubMed

Aluminum (Al) tolerance mechanisms in crop plants have been extensively researched, but our understanding of the physiological mechanisms underlying Al tolerance in trees is still limited. To investigate Al tolerance in eucalypts, seedlings of six species (Eucalyptus globulus Labill., Eucalyptus urophylla S.T. Blake, Eucalyptus dunnii Maiden, Eucalyptus saligna Sm., Eucalyptus cloeziana F. J. Muell. and Eucalyptus grandis w. Hill ex Maiden) and seedlings of six clones of Eucalyptus species were grown for 10 days in nutrient solutions containing Al concentrations varying from 0 to 2.5 microM (0 to 648 microM Al3+ activities). Root elongation of most species was inhibited only by high Al3+ activities. Low to intermediate Al3+ activities were beneficial to root elongation of all species and clones. Among the species tested, E. globulus and E. urophylla were more tolerant to Al toxicity, whereas E. grandis and E. cloeziana were more susceptible to Al-induced damage. Although E. globulus seedlings were tolerant to Al toxicity, they were highly sensitive to lanthanum (La), indicating that the tolerance mechanism is specific for Al. Fine roots accumulated more Al and their elongation was inhibited more than that of thick roots. In E. globulus, accumulation of Al in root tips increased linearly with increasing Al concentration in the nutrient solution. The majority of Al taken up was retained in the root system, and the small amounts of Al translocated to the shoot system were found mainly in older leaves. No more than 60% of the Al in the thick root tip was in an exchangeable form in the apoplast that could be removed by sequential citrate rinses. Gas chromatography/mass spectrometry and ion chromatography analyses indicated that root exposure to Al led to a greater than 200% increase in malic acid concentration in the root tips of all eucalypt species. The increase in malate concentration in response to Al treatment correlated with the degree of Al tolerance of the species. A small increase in citric acid concentration was also observed in all species, but there were no consistent changes in the concentrations of other organic acids in response to Al treatment. In all eucalypt species, Al treatment induced the secretion of citric and malic acid in root exudates, but no trend with respect to Al tolerance was observed. Thus, although malate and citrate exudation by roots may partially account for the overall high Al tolerance of these eucalypt species, it appears that tolerance is mainly derived from the internal detoxification of Al by complexation with malic acid. PMID:15339736

Silva, I R; Novais, R F; Jham, G N; Barros, N F; Gebrim, F O; Nunes, F N; Neves, J C L; Leite, F P

2004-11-01

271

Inhibition of corrosion of Al 6061, aluminum, and an aluminum-copper alloy in chloride-free aqueous media. Part 2: Behavior in basic solutions  

SciTech Connect

Electrochemical characteristics of Al 6061 (UNS A96061), Al and an Al-Cu alloy were investigated in aqueous solutions. Inhibition of the corrosion processes in basic solutions was studied using electrochemical impedance spectroscopy (EIS) and polarization techniques. Among a series of inhibitors, molybdate (MoO{sub 4}{sup 2{minus}}) and dichromates (Cr{sub 2}O{sub 7}{sup 2{minus}}) were found effective in passivating the metal or alloy surface. The high inhibition action of Cr{sub 2}O{sub 7}{sup 2{minus}} was traced and discussed. X-ray photoelectron spectroscopy (XPS) of the different electrode materials revealed the presence of Cu peaks on the Al-Cu alloy surface. Immersion of the different electrodes in basic solutions containing the same concentration of Cr{sub 2}O{sub 7}{sup 2{minus}}, MoO{sub 4}{sup 2{minus}}, and sulfate (SO{sub 4}{sup 2{minus}}) anions did not show characteristic peaks of Cr, Mo, or S, which meant the surface layer consisted mainly of aluminum oxide (Al{sub 2}O{sub 3}). Depth profiling experiments up to 6.0-nm thickness showed the Cu peaks of the Al-Cu alloy appeared after etching and that Mo was incorporated in the surface film. The presence of Cu on the Al-Cu surface initiated flawed regions, identified by scanning electron microscopy, which were responsible for increased corrosion rates of this alloy. Effectiveness of the dichromate as a corrosion inhibitor for these materials resulted from its powerful oxidizing properties, which led to formation of a stable passive film.

Al-Kharafi, F.M.; Badawy, W.A. [Univ. of Kuwait, Safat (Kuwait)

1998-05-01

272

Optimal welding parameters for very high power ultrasonic additive manufacturing of smart structures with aluminum 6061 matrix  

NASA Astrophysics Data System (ADS)

Ultrasonic additive manufacturing (UAM) is a recent solid state manufacturing process that combines ad- ditive joining of thin metal tapes with subtractive milling operations to generate near net shape metallic parts. Due to the minimal heating during the process, UAM is a proven method of embedding Ni-Ti, Fe-Ga, and PVDF to create active metal matrix composites. Recently, advances in the UAM process utilizing 9 kW very high power (VHP) welding has improved bonding properties, enabling joining of high strength materials previously unweldable with 1 kW low power UAM. Consequently, a design of experiments study was conducted to optimize welding conditions for aluminum 6061 components. This understanding is critical in the design of UAM parts containing smart materials. Build parameters, including weld force, weld speed, amplitude, and temperature were varied based on a Taguchi experimental design matrix and tested for me- chanical strength. Optimal weld parameters were identi ed with statistical methods including a generalized linear model for analysis of variance (ANOVA), mean e ects plots, and interaction e ects plots.

Wolcott, Paul J.; Hehr, Adam; Dapino, Marcelo J.

2014-03-01

273

Damping mechanisms in alumina borate whisker-reinforced-aluminum matrix composites with or without SnO{sub 2} coatings  

SciTech Connect

SnO{sub 2} was successfully coated on the surface of alumina borate whiskers. The pure aluminum matrix composites reinforced with a SnO{sub 2}-coated alumina borate whisker were fabricated by squeeze casting. The effects of coating contents on the damping properties of the coated composites at various temperatures, frequencies, and strain amplitudes were examined. The microstructures of the coated composites were also investigated through transmission electron microscopy observations. These results indicate that the introduction of Sn at the interface between whisker and matrix in the coated composites during the squeeze casting process alters not only the interface structures but also the dislocation status of the matrices in the vicinity of the interface. The results of damping characterization indicate that the damping capacities of the coated composites strongly depend on the coating contents and strain amplitudes. A damping peak at low temperatures appeared not only in the coated composites but also in the noncoated one, which is related to dislocation motion and interfacial slip caused by Sn. A damping peak at high temperatures appeared only in the coated composites, and the damping mechanisms at high temperature change with the increase in strain amplitudes. Sn played an important role on the damping mechanisms of the coated composites all along.

Hu, J.; Wang, X. F.; Zheng, Z. Z. [School of Materials Science and Engineering, Harbin Institute of Technology, Harbin 150001 (China)

2010-01-15

274

Synthesis and processing of Al{sub 2}O{sub 3}/Al composites by in situ reaction of aluminum and mullite  

SciTech Connect

Al{sub 2}O{sub 3}/Al composites, were formed by reacting molten aluminum metal with dense mullite ceramic preforms. The composites produced by this reactive metal penetration process (RMP) have a two phase, interpenetrating microstructure in which both the ceramic and the metal are continuous in three dimensions. Scanning electron microscopy (SEM) micrographs of composites produced by RMP show a fine microstructure comprised of interlocked metal and ceramic phases, with a feature size of approximately 2 {mu}m. RMP is a relatively rapid process with metal penetration rates of nearly 5 mm/hour at 1100{degrees}C after a short incubation period. An activation energy of 92 kJ/mole was calculated from reaction rate data. Transmission electron microscopy (TEM) micrographs reveal that aluminum metal penetrates along the mullite grain boundaries before reaction with the mullite grains, indicating that diffusion along grain boundaries may be the rate limiting step for the reaction. Thermodynamic information, results of microstructure analyses, and kinetic data indicate that RMP proceeds in 4 stages: (1) Al melting and the formation of a thermodynamically stable metal/ceramic interface; (2) depletion of oxygen from the grain boundaries intersecting the ceramic/metal interface; (3) Al metal penetration into the ceramic preform along grain boundaries; and (4) Al reaction with and conversion of individual mullite grains.

Fahrenholtz, W.G. [Univ. of New Mexico, Albuquerque, NM (United States); Ewsuk, K.G.; Loehman, R.E. [Sandia National Labs., Albuquerque, NM (United States); Tomsia, A.P. [Pask Research and Engineering, Berkeley, CA (United States)

1995-02-01

275

Corrosion Resistance of 2014 Aluminium Matrix Composites Reinforced with Atomised Ni3Al  

Microsoft Academic Search

The corrosion resistance of 2014 aluminium matrix composites has been evaluated. The base alloy was manufactured through mechanical alloying, and reinforced with Ni3Al (manufactured through atomisation). Composite materials were manufactured according to the following procedure: mixing, cold uniaxial compacting, and hot extrusion. All materials were tested as extruded and heat treated (T6 condition). Corrosion tests were carried out following ASTM

P. B. Da Silva-Maia; F. Velasco; N. Antón; C. E. Da Costa; W. C. Zapata

1999-01-01

276

Aluminum oxide thin films deposited on silicon substrates from Al(NO3)3 and an organic solvent by spray pyrolysis  

Microsoft Academic Search

Aluminum oxide thin films were deposited on silicon substrates at temperatures in the range from 500 to 650 °C, from Al(NO3)3 dissolved in N,N-Dimethylformamide and using the spray pyrolysis technique. The films of aluminum oxide resulted stoichiometric, amorphous and optically transparent in the visible spectrum, with a refractive index close to 1.66 when a 0.2 molar solution of Al(NO3)3 was

M. Aguilar-Frutis; J. Guzmán-Mendoza; T. Alejos; M. García-Hipólito; C. Falcony

2003-01-01

277

Structure and properties of the aluminum borates Al(BO2)n and Al(BO2)n(-), (n = 1-4).  

PubMed

The geometrical and electronic structures of Al(BO(2))(n) and Al(BO(2))(n)(-) (n = 1-4) clusters are computed at different levels of theory including density functional theory (DFT), hybrid DFT, double-hybrid DFT, and second-order perturbation theory. All aluminum borates are found to be quite stable toward the BO(2) and BO(2)(-) loss in the neutral and anion series, respectively. Al(BO(2))(4) belongs to the class of hyperhalogens composed of smaller superhalogens, and should possess a large adiabatic electron affinity (EA(ad)) larger than that of its superhalogen building block BO(2). Indeed, the aluminum tetraborate possesses the EA(ad) of 5.6 eV, which, however, is smaller than the EA(ad) of 7.8 eV of the AlF(4) supehalogen despite BO(2) is more electronegative than F. The EA(ad) decrease in Al(BO(2))(4) is due to the higher thermodynamic stability of Al(BO(2))(4) compared to that of AlF(4). Because of its high EA and thermodynamic stability, Al(BO(2))(4) should be capable of forming salts with electropositive counter ions. We optimized KAl(BO(2))(4) as corresponding to a unit cell of a hypothetical KAl(BO(2))(4) salt and found that specific energy and energy density of such a salt are competitive with those of trinitrotoluol (TNT). PMID:22121015

Gutsev, Gennady L; Weatherford, Charles A; Johnson, Lewis E; Jena, Purusottam

2012-02-01

278

Effect of Zr addition on properties of Al–Mg–Si aluminum alloy used for all aluminum alloy conductor  

Microsoft Academic Search

The effects of Zr addition on mechanical property in the aged Al–Mg–Si alloy exposed to thermal-resistant treatment (180–250°C) have been studied by using both Brinell Hardness tests and tensile tests. The softening process at 180°C and 230°C has been investigated by transmission electron microscope (TEM). The Arrhenius Model is introduced to simulate the strength evolution in the thermal-resistant treatment. The

Wuhua Yuan; Zhenyu Liang

2011-01-01

279

Microstructure of multilayer interface in an Al matrix composite reinforced by TiNi fiber.  

PubMed

A multilayer interface was formed in the Al matrix composite which was reinforced by 30% volume fraction of TiNi fiber. The composite was fabricated by pressure infiltration process and the interface between the TiNi fiber and Al matrix was investigated by transmission electron microscopy (TEM) and energy dispersive spectroscopy (EDS). When the TiNi fiber was pre-oxidized in the air at 773K for 1h, three layers have been found and characterized in the interface: TiNi-B2 layer near the TiNi fiber, Ti-Al compound layer with Ti and granular TiO2 near the Al matrix, and Ti-Ni compound layer between TiNi-B2 and Ti-Al compound layers. The effect of the multilayer interface on the mechanical properties of the composite was also discussed. The result showed that the uniaxial tensile strength of the composite at room temperature was 318MPa, which was very close to the theoretical calculation value of 326MPa. Moreover, the composite with good ductility exhibited a typical ductile-fracture pattern. PMID:24981215

Hu, Jie; Wu, Gaohui; Zhang, Qiang; Kang, Pengchao; Liu, Yan

2014-09-01

280

Al:ZnO thin film: An efficient matrix for cholesterol detection  

NASA Astrophysics Data System (ADS)

Al doped ZnO thin film (Al:ZnO) has been realized as a potential matrix for the development of efficient cholesterol biosensor. The correlation between the structural and electrical properties of ZnO thin film with varying Al doping concentration (1% to 5%) and their cyclic voltammetric (CV) response has been studied. 2% Al doped ZnO films were found to give the best CV response and were further utilized for immobilization of cholesterol oxidase (ChOx) to detect cholesterol. Amperometric and photometric studies reveal that the prepared bioelectrode based on 2% Al doped ZnO matrix (ChOx/Al:ZnO/Pt/glass) is highly sensitive (sensitivity = 173 ?AmM-1 cm-2) to the detection of cholesterol in the wide range from 0.6-12.9 mM (25-500 mg/dl). A relatively low value of enzyme's kinetic parameter (Michaelis menten constant, 2.53 mM) indicates enhanced affinity of the immobilized ChOx toward cholesterol. The prepared bioelectrode is found to be exhibiting high shelf life (10 weeks) having negligible interference with the presence of other biomolecules in human serum indicating promising application of Al doped ZnO thin films for cholesterol biosensing.

Batra, Neha; Tomar, Monika; Gupta, Vinay

2012-12-01

281

EELS and EFTEM-investigations of aluminum alloy 6016 concerning the elements Al, Si and Mg  

Microsoft Academic Search

Aluminum alloys are one of the most promising materials concerning high hardness and low weight (important for the use in\\u000a automotive engineering) and consequently low cost in operation (low fuel consumption), and comparatively low costs in fabrication.\\u000a For the investigations done in this work, the aluminum alloy 6016 containing Mg and Si as major elemental additions, have\\u000a been taken into

S. Schwarz; M. Stöger-Pollach

282

Further characterization of the aluminum peroxide oxide, AlO{sub 2}, formed by interfacial reaction between Pt and {alpha}-Al{sub 2}O{sub 3}  

SciTech Connect

A new metastable aluminum peroxide oxide, AlO{sub 2}, was recently shown to form by an interfacial reaction in the presence of a kinetic constraint during diffusion-bonding of Pt and {alpha}-Al{sub 2}O{sub 3}. Further studies of the properties, bonding, formation kinetics and chemistry of AlO{sub 2} are described and the current state of knowledge of the kinetics of its formation is summarized. Raman spectroscopy on AlO{sub 2} gave several peaks in the frequency range characteristic of peroxide ions, providing the strongest evidence yet for their presence. Electron microprobe analysis detected only Al and O, with any other elements, if present, being below the detectability limit of the wavelength dispersive technique. Rutherford backscattering spectroscopy at the carbon resonance energy could detect no carbon within the AlO{sub 2}. Studies of the effect of temperature on the formation of AlO{sub 2} show that it forms after heating for 24 h in the temperature range of 1,200 to 1,400 C, but not at or below 1,100 C. Heating in air at 1,200 causes AlO{sub 2} to first transform to a cubic form of Al{sub 2}O{sub 3}, before finally reverting to {alpha}-Al{sub 2}O{sub 3}. The dielectric constant of AlO{sub 2} is 22.7, approximately twice that of {alpha}-Al{sub 2}O{sub 3} parallel to the c direction, and the hardness of 8.4 GPa is approximately one-half that of {alpha}-Al{sub 2}O{sub 3}.

Lu, Y.C.; Agnew, S.; Dieckmann, R.; Sass, S.L. [Cornell Univ., Ithaca, NY (United States). Dept. of Materials Science and Engineering] [Cornell Univ., Ithaca, NY (United States). Dept. of Materials Science and Engineering

1995-05-01

283

Effect of pH on the coagulation performance of Al-based coagulants and residual aluminum speciation during the treatment of humic acid-kaolin synthetic water.  

PubMed

The fractionation and measurement of residual aluminum was conducted during the treatment of humic (HA)-kaolin synthetic water with Al(2)(SO(4))(3), AlCl(3) and polyaluminum chloride (PAC) in order to investigate the effect of pH on the coagulation performance as well as residual aluminum speciation. Experimental results suggested that turbidity removal performance varied according to the following order: AlCl(3)>PAC>Al(2)(SO(4))(3). HA removal performance of PAC was better than that of AlCl(3) under acidic condition. The optimum pH range for AlCl(3) and Al(2)(SO(4))(3) was between 6.0 and 7.0 while PAC showed stable HA and UV(254) removal capacity with broader pH variation (5.0-8.0). For the three coagulants, majority of residual aluminum existed in the form of total dissolved Al (60-80%), which existed mostly in oligomers or complexes formed between Al and natural organic matter or polymeric colloidal materials. PAC exhibited the least concentration for each kind of residual aluminum species as well as their percentage in total residual aluminum, followed by AlCl(3) and Al(2)(SO(4))(3) (in increasing order). Moreover, PAC could effectively reduce the concentration of dissolved monomeric Al and its residual aluminum ratio was the least among the three coagulants and varied little at an initial pH between 7.0 and 9.0. PMID:20188465

Yang, Zhong Lian; Gao, Bao Yu; Yue, Qin Yan; Wang, Yan

2010-06-15

284

Effect of OH-/Al3+ and Si/Al molar ratios on the coagulation performance and residual Al speciation during surface water treatment with poly-aluminum-silicate-chloride (PASiC).  

PubMed

Coagulation performance, mechanism of poly-aluminum-silicate-chloride (PASiC) and residual Al speciation in the effluent with respect to a specific surface water treatment in China were comprehensively investigated in this study. The impact of OH(-)/Al(3+) and Si/Al molar ratios on the coagulation performance, mechanism and residual Al speciation of PASiC in surface water treatment was discussed as a function of coagulant dosage. It was intended to provide an insight into the relationship between coagulation performance and residual Al. Experimental results revealed that when OH(-)/Al(3+) molar ratio = 2.00 and Si/Al molar ratio = 0.0500 in PASiC coagulant, PASiC exhibited beneficial coagulation property and relatively lower content of residual Al. Surface bridging and entrapment was more effective compared with charge neutralization during the specific surface water treatment. The majority of residual Al in the effluent existed in the form of insoluble suspended or particulate Al. Dissolved organically bound Al was almost the major speciation in dissolved Al and dissolved inorganically bound monomeric Al was the only component in dissolved monomeric Al. Al in PASiC remained abundant at lower dosages and residual Al concentration could be effectively reduced at the dosages of 12.0-15.0mg/L as Al. PMID:21376461

Yang, Zhonglian; Gao, Baoyu; Xu, Weiying; Cao, Baichuan; Yue, Qinyan

2011-05-15

285

The surface tension of molten aluminum and Al-Si-Mg alloy under vacuum and hydrogen atmospheres  

NASA Astrophysics Data System (ADS)

The surface tensions of pure molten aluminum, A356 alloy (Al-7 pct Si-0.3 pct Mg), and strontium-modified A356 alloy have been measured under vacuum and hydrogen atmospheres using the sessile drop technique. The values obtained for pure aluminum at 680 °C and for A356 alloy and modified A356 alloy at 630 °C are 1.007, 0.889, and 0.844 N/m, respectively, when measured under vacuum. The addition of hydrogen gas to the atmosphere of the liquid droplet has no significant effect on the surface tension of the unmodified A356 alloy, while it lowers the surface tension of the modified alloy to 0.801 N/m. This effect is possibly due to the formation of SrH2.

Anson, J. P.; Drew, R. A. L.; Gruzleski, J. E.

1999-12-01

286

Fracture toughness of microsphere Al 2O 3–Al particulate metal matrix composites  

Microsoft Academic Search

The fracture toughness and behaviour of COMRAL-85TM, a 6061 aluminium–magnesium–silicon alloy reinforced with 20vol% Al2O3-based polycrystalline ceramic microspheres, and manufactured by a liquid metallurgy route, have been investigated. Fracture toughness tests were performed using short rod and short bar (chevron-notch) specimens machined from extruded 19mm diameter rod, heat treated to the T6 condition. The fracture toughness in the R–L orientation

B. G. Park; A. G. Crosky; A. K. Hellier

2008-01-01

287

High cycle fatigue behaviour of microsphere Al 2O 3–Al particulate metal matrix composites  

Microsoft Academic Search

The high-cycle stress-life (S–N) curve and fatigue crack growth threshold (?Kth) behaviour of COMRAL-85TM, a 6061 aluminium–magnesium–silicon alloy reinforced with 20vol.% Al2O3-based polycrystalline ceramic microspheres, and manufactured by a liquid metallurgy route, have been investigated for a stress ratio of R=?1 (fully reversed loading). Fatigue testing was conducted on both smooth round bar (S–N) specimens and notched round bar (fatigue

B. G. Park; A. G. Crosky; A. K. Hellier

2008-01-01

288

A theoretical approach to the photochemical activation of matrix isolated aluminum atoms and their reaction with methane.  

PubMed

The photochemical activation of Al atoms in cryogenic matrices to induce their reaction with methane has been experimentally studied before. Here, a theoretical study of the nonadiabatic transition probabilities for the ground ((2)P:3s(2)3p(1)) and the lowest excited states ((2)S:3s(2)4s(1) and (2)D:3s(2)3d(1)) of an aluminum atom interacting with a methane molecule (CH(4)) was carried out through ab initio Hartree-Fock self-consistent field calculations. This was followed by a multiconfigurational study of the correlation energy obtained by extensive variational and perturbational configuration interaction analyses using the CIPSI program. The (2)D state is readily inserted into a C-H bond, this being a prelude to a sequence of avoided crossings with the initially repulsive (to CH(4)) lower lying states (2)P and (2)S. We then use a direct extension of the Landau-Zener theory to obtain transition probabilities at each avoided crossing, allowing the formation of an HAlCH(3) intermediate that eventually leads to the final pair of products H+AlCH(3) and HAl+CH(3). PMID:21054032

Pacheco-Blas, M A; Novaro, O A; Pacheco-Sánchez, J H

2010-11-01

289

Effect of Aluminum Particle Surface Area and Morphology on the Combustion Properties of KClO4/Al Compositions  

NASA Astrophysics Data System (ADS)

Compositions of KClO4/Al are used in military applications as well as the pyrotechnics industry. The reaction rate as well as the ease of initiation depends on metal particle surface area as well as particle morphology. This factor is especially important for metal fuels having a melting point higher than the melting point of the oxidizer component in the energetic composition. Aluminum powder and turnings of various particle sizes were combined with KClO4 to form an energetic composition. The explosives mixtures were combusted in a rapid scanning calorimeter device (RSD). dP/dt and dT/dt results were measured and heats of reaction were calculated. The effect of Al particle surface area and particle morphology on the combustion properties of KClO4/Al is discussed.

Caulder, Stanley; Mackey, Joseph; Wilkinson, John

2009-06-01

290

High-strength powder metallurgy aluminum alloys in glass-forming Al-Ni-Ce-(Ti or Zr) systems  

SciTech Connect

Powder metallurgy (P/M) aluminum alloys with high mechanical strengths have been developed by taking advantage of rapid solidification (RS). The improved strengths result from structural modifications such as reduction of segregation, refinement of grain size and increase in solid solubility limit which mainly depend on the amount of undercooling of melt. To produce crystalline alloys with a refined structure, few approaches are considered: the crystallization of an amorphous alloy, the control of cooling rate from melt and the selection of optimum composition for glass-forming alloys. However, these methods are generally attended with a disadvantage for embrittlement. Recently, it has been found that Al-based amorphous alloys exhibiting high tensile strength and good bending ductility form by liquid quenching in the Al-Ln-TM (Ln: lanthanide metal, TM: transition metal) system. Furthermore, the consolidation of the amorphous alloy powders to a bulk amorphous alloy has also been achieved by warm extrusion. The first aim of this paper is to examine the effect of alloy composition on the strength and ductility of crystalline compacts produced by extrusion of rapidly solidified powders in the Al-Ni-Ce-TM(TM:Ti, Mn, Fe, Co, Cu, Zr) systems where an amorphous phase is formed by melt spinning. The second is to investigate whether or not the structural refinement by using glass-forming alloys is useful to develop high-strength P/M aluminum alloys.

Kawamura, Y.; Inoue, A.; Sasamori, K.; Masumoto, T. (Tohoku Univ., Sendai (Japan))

1993-07-15

291

Synthesis and characterization of lithium aluminum-doped spinel (LiAl x Mn 2? x O 4) for lithium secondary battery  

Microsoft Academic Search

LiAlxMn2?xO4 has been synthesized using various aluminum starting materials, such as Al(NO3)3, Al(OH)3, AlF3 and Al2O3 at 600–800°C for 20h in air or oxygen atmosphere. A melt-impregnation method was used to synthesize Al-doped spinel with good battery performance in this research. The Al-doped content and the intensity ratio of (311)\\/(400) peaks can be important parameters in synthesizing Al-doped spinel which

Yun-Sung Lee; Naoki Kumada; Masaki Yoshio

2001-01-01

292

Elastic–plastic stress analysis and expansion of plastic zone in clamped and simply supported aluminum metal–matrix laminated plates  

Microsoft Academic Search

An elastic–plastic stress analysis and the expansion of plastic zone in layers of stainless steel fiber-reinforced aluminum metal–matrix laminated plates are studied by using Finite Element Method and First-order shear deformation theory for small deformations. The plate is meshed into 64 elements and 289 nodes with simply supported or clamped boundary conditions. Laminated plates of constant thickness are formed by

Cesim Atas; Onur Sayman

2000-01-01

293

49 CFR 178.46 - Specification 3AL seamless aluminum cylinders.  

Code of Federal Regulations, 2013 CFR

...Transportation (Continued) PIPELINE AND HAZARDOUS MATERIALS...Table 1âHeat or Cast Analysis for Aluminum; Similar to... (B) National Gas Taper Thread (NGT...performance of the chemical analyses on each melt or cast...a certified chemical analysis from the material...

2013-10-01

294

Protective Oxides Formed on CoCrAlY (Cobalt, Chromium, Aluminum and Yttrium) Coatings.  

National Technical Information Service (NTIS)

The metallic coatings used to protect the hot-section turbine blades of marine gas turbines are often a mixture of cobalt, chromium, aluminum, and yttrium (CoCrA1Y). Using the surface sensitive technique of x-ray photoelectron spectroscopy, the protective...

L. F. Aprigliano

1986-01-01

295

Effect of aluminum plasma parameters on the physical properties of Ti-Al-N thin films deposited by reactive crossed beam pulsed laser deposition  

NASA Astrophysics Data System (ADS)

This work reports on the preparation and characterization of Ti-Al-N thin films deposited by reactive crossed beam pulsed laser deposition (RCBPLD). The elemental composition, vibrational properties and hardness of the deposited films were investigated as a function of the plasma parameters, that is, the Al+ mean kinetic energy and plasma density. The composition of the thin films was determined from X-ray photoelectron spectroscopy (XPS) measurements as well as by Rutherford backscattering spectroscopy (RBS). The structural modifications of the deposited materials due to Al incorporation were characterized by Raman spectroscopy. The hardness of the deposited films was determined by nanoindentation. It was found that by using this experimental configuration the aluminum content in the deposited films was incorporated in a controlled way, from 2.2 to 31.7 at.% (XPS measurements), by varying the Al+ mean kinetic energy and the plasma density. Raman results suggest that at low aluminum concentrations a solid solution of Ti(Al, N) is produced, whereas at higher aluminum concentrations a nanocomposite formed of TiAlN and AlN is obtained. Ti-Al-N films with hardnesses up to 28.8 GPa, which are suitable for many mechanical applications, were obtained. These results show that the properties of the deposited material are controlled, at least partially, by the aluminum plasma parameters used for thin film growth.

Escobar-Alarcón, L.; Solís-Casados, D. A.; Romero, S.; Fernández, M.; Pérez-Álvarez, J.; Haro-Poniatowski, E.

2013-10-01

296

The quasi-static and cyclic fatigue fracture behavior of 2014 aluminum alloy metal-matrix composites  

Microsoft Academic Search

In this article, the quasi-static and cyclic fatigue fracture behavior of aluminum alloy 2014 discontinuously reinforced with\\u000a fine particulates of aluminum oxide are presented and discussed. The discontinuous particulate-reinforced 2014 aluminum alloy\\u000a was cyclically deformed under fully reversed, tension-compression loading over a range of strain amplitudes, well within the\\u000a plastic domain of the engineering stress-strain curve, resulting in cyclic fatigue

T. S. Srivatsan; R. Annigeri

2000-01-01

297

Corrosion Mechanisms of Steel and Cast Iron by Molten Aluminum  

NASA Astrophysics Data System (ADS)

The corrosion mechanisms by liquid aluminum of three industrial materials have been studied: unalloyed steel (UAS), and ferritic and modified pearlitic cast irons (FCI and PCI, respectively). The behavior of these materials when in contact with liquid aluminum is different. Aluminum diffuses deep into the UAS and forms intermetallic compounds with iron at the surface and in the steel matrix. At the surface, only Fe2Al5 and FeAl3 are found. In the matrix, FeAl2 also is formed in agreement with the equilibrium Fe-Al diagram. From the matrix to FeAl2, the Al content in the ferrite increases progressively until Al saturation is reached. At this step, black elongated precipitates (Al4C3 and/or graphite) appear. Graphite lamellas present in both FCI and PCI constitute an efficient barrier to the Al diffusion. The high silicon content of the FCI leads to the formation of a phase free from Al and saturated in Si. For the PCI, a thin layer rich in Al and Si, which is formed between the matrix and Fe2Al5, limits the diffusion of atoms. The effects of Cr and P added in the PCI also are discussed.

Balloy, David; Tissier, Jean-Charles; Giorgi, Marie-Laurence; Briant, Marc

2010-09-01

298

Evolution of subsequent yield surfaces and elastic constants with finite plastic deformation. Part II: A very high work hardening aluminum alloy (annealed 1100 Al)  

Microsoft Academic Search

Results are presented on the evolution of subsequent yield surfaces with finite deformation in a very high work hardening annealed 1100 aluminum alloy. In Part I [Khan, A.S., Kazmi, R., Stoughton, T., Pandey, A., 2009a. Evolution of subsequent yield surfaces and elastic constants with finite plastic deformation. Part 1: a very low work hardening aluminum alloy (Al-6061–T6511) 25, 1611–1625.] of

Akhtar S. Khan; Amit Pandey; Thomas Stoughton

2010-01-01

299

Dendrite-Free Aluminum Electrodeposition from AlCl3-1-Ethyl-3-Methyl-Imidazolium Chloride Ionic Liquid Electrolytes  

NASA Astrophysics Data System (ADS)

A novel, dendrite-free electrorefining of aluminum scrap alloys (A360) was investigated by using a low-temperature AlCl3-1-ethyl-3-methyl-imidazolium chloride (EMIC) ionic liquid electrolyte on copper/aluminum cathodes. The bulk electrodeposition of aluminum was carried out at a fixed voltage of 1.5 V, temperatures 323 K to 383 K (50 °C to 110 °C), stirring rate (0 to 120 rpm), concentration (molar ratio AlCl3:EMIC = 1.25 to 2.0), and electrode surface modification (modified/unmodified). The study investigated the effect of electrode surface modification, cathode materials, temperature, stirring rate, electrolyte concentration, and deposition time on the deposit morphology of aluminum, cathode current density, and their role in production of dendrite-free aluminum deposit, which is essential for decreasing the production cost. The deposits were characterized using scanning electron microscope (SEM), energy-dispersive spectroscopy (EDS), and X-ray diffraction (XRD). It was shown that electrode surface modification, cathode overpotential, and stirring rate play an important role in dendrite-free deposit. Modified electrodes and stirring (60 rpm) eliminate dendritic deposition by reducing cathode overpotential below critical overpotential ( ?_{{crt}} ? - 0.53V ) for dendrite formation. Pure aluminum (>99 pct) was deposited for all experiments with a current efficiency of 84 to 99 pct and energy consumption of 4.51 to 5.32 kWh/kg Al.

Pradhan, Debabrata; Reddy, Ramana G.

2012-06-01

300

Effect of Aluminum Particle Size on the Impact Initiation of Pressed Ptfe/al Composite Rods  

NASA Astrophysics Data System (ADS)

A gas gun has been used to investigate the impact initiation of rods of a mixture of 72 wt% PTFE (polytetrafluoroethylene) and 28 wt% aluminum powders. The rods were sabot-launched in vacuum into steel anvils at impact velocities ranging from 468 to 969 m/s. A framing camera was used to observe the time sequence of events following impact. At the lowest impact stress of 25 kbar no light was observed. Above the initiation threshold, the initiation time dropped from 74 ?s just above threshold to 14 ?s at 64 kbar. These results are compared with earlier rod impact experiments for a similar material in which the only major difference is a smaller aluminum particle size.

Mock, Willis; Drotar, Jason T.

2007-12-01

301

Kinetics of aluminum lithium alloys  

Microsoft Academic Search

Aluminum lithium alloys are increasingly used in aerospace for their high strength-to-weight ratio. Additions of lithium, up to 4.2 wt% decrease the alloy density while increasing the modulus and yield strength. The metastable, second phase Al3Li or delta' is intriguing, as it remains spherical and coherent with the matrix phase, alpha, well into the overaged condition. Small interfacial strain energy

Ben A. Pletcher

2009-01-01

302

Corrosive wear behavior of 7075 aluminum alloy and its composite containing Al 2 O 3 particles  

Microsoft Academic Search

Corrosive wear behavior of 7075 aluminum alloy and a composite containing 0.10 volume fraction of alumina particles (VFAP)\\u000a has been evaluated. Transient current (TC) generated as a result of impacting a rotating cylindrical electrode immersed in\\u000a a 0.1M NaCl solution with a Vickers diamond hardness indenter has been used to measure the corrosive wear response. Age hardenable\\u000a 7075 alloy shows

S. K. Varma; Gustavo Vasquez

2003-01-01

303

Development of a job-exposure matrix for exposure to total and fine particulate matter in the aluminum industry  

PubMed Central

Increasing evidence indicates that exposure to particulate matter (PM) at environmental concentrations increases the risk of cardiovascular disease, particularly PM with an aerodynamic diameter of less than 2.5?m (PM2.5). Despite this, the health impacts of higher occupational exposures to PM2.5 have rarely been evaluated. In part, this research gap derives from the absence of information on PM2.5 exposures in the workplace. To address this gap, we have developed a job-exposure matrix (JEM) to estimate exposure to two size fractions of PM in the aluminum industry. Measurements of total PM (TPM) and PM2.5 were used to develop exposure metrics for an epidemiologic study. TPM exposures for distinct exposure groups (DEGs) in the JEM were calculated using 8,385 personal TPM samples collected at 11 facilities (1980-2011). For 8 of these facilities, simultaneous PM2.5 and TPM personal monitoring was conducted from 2010-2011 to determine the percent of TPM that is composed of PM2.5 (%PM2.5) in each DEG. The mean TPM from the JEM was then multiplied by %PM2.5 to calculate PM2.5 exposure concentrations in each DEG. Exposures in the smelters were substantially higher than in fabrication units; mean TPM concentrations in smelters and fabrication facilities were 3.86 mg/m3 and 0.76 mg/m3, and the corresponding mean PM2.5 concentrations were 2.03 mg/m3 and 0.40 mg/m3. Observed occupational exposures in this study generally exceeded environmental PM2.5 concentrations by an order of magnitude.

Noth, Elizabeth M.; Dixon-Ernst, Christine; Liu, Sa; Cantley, Linda; Tessier-Sherman, Baylah; Eisen, Ellen A.; Cullen, Mark R.; Hammond, S. Katharine

2014-01-01

304

Characterization of anisotropic elastic constants of silicon-carbide particulate reinforced aluminum metal matrix composites; Part 2: Theory  

SciTech Connect

The effective elastic constants of composite materials contain arbitrarily oriented ellipsoidal fibers were derived using the concept of orientation-dependent average fields and the strain concentration factor tensors. Under the prescribed boundary condition, the concentration factor was evaluated by the Mori-Tanaka method and the Eshelby's equivalent inclusion principle. The fourth-rank tensor expression for the elastic stiffnesses was recast into matrix form for easier numerical computations. The theoretical model developed was applied to the computation of the anisotropic elastic constants of the extruded Al/SiC[sub p] composites considered in Part 1 of this series. Good agreement was found between the model predictions and the ultrasonic measurement results. Comparisons with the Hashin-Shtrikman (H-S) bounds for isotropic composites were also presented. It was found that while the H-S lower bound predicted the out-of-plane properties, it generally gave a poor estimate for the in-plane properties of these composites.

Jeong, H. (Agency for Defense Development, DaeJon (Korea, Republic of)); Hsu, D.K. (Iowa State Univ., Ames, IA (United States). Center for Nondestructive Evaluation); Shannon, R.E. (Westinghouse Science Technology Center, Pittsburgh, PA (United States). Materials Reliability Dept.); Liaw, P.K. (Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering)

1994-04-01

305

Plasticity-improved Zr-Cu-Al bulk metallic glass matrix composites containing martensite phase  

SciTech Connect

Zr{sub 48.5}Cu{sub 46.5}Al{sub 5} bulk metallic glass matrix composites with diameters of 3 and 4 mm were produced through water-cooled copper mold casting. Micrometer-sized bcc based B2 structured CuZr phase containing martensite plate, together with some densely distributed nanocrystalline Zr{sub 2}Cu and plate-like Cu{sub 10}Zr{sub 7} compound, was found embedded in a glassy matrix. The microstructure formation strongly depends on the composition and cooling rate. Room temperature compression tests reveal significant strain hardening and plastic strains of 7.7% and 6.4% before failure are obtained for the 3-mm- and 4-mm-diam samples, respectively. The formation of the martensite phase is proposed to contribute to the strain hardening and plastic deformation of the materials.

Sun, Y.F.; Wei, B.C.; Wang, Y.R.; Li, W.H.; Cheung, T.L.; Shek, C.H. [Research Center for Materials, Department of Materials Science and Engineering, Zhengzhou University, Zhengzhou 450002 (China); National Microgravity Lab, Institute of Mechanics, Chinese Academy of Sciences, Beijing 100080 (China); Department of Physics and Materials Science, City University of Hong Kong, Hong Kong (China)

2005-08-01

306

Processing and interfacial bonding strength of 2014 Al matrix composites reinforced with oxidized SiC particles  

Microsoft Academic Search

The SiC powder with a SiO2 protective layer is used as the reinforcements for 2014Al\\/SiCp composites to suppress the reaction between the Al matrix and the SiC particle. 2014Al\\/SiCp composites were fabricated by vacuum hot pressing (VHP) and subsequent extrusion using 2014Al powders and the SiC particles covered with a SiO2 layer. The interfacial product was found to be Mg

Youngman Kim; Jae-Chul Lee

2006-01-01

307

Trace metal characterization of the U-Al matrix by atomic spectroscopy  

SciTech Connect

Uranium-aluminum alloys with a significant enrichment of uranium with /sup 233/U or /sup 235/U serve as nuclear fuels in research reactors. The quality assurance of this fuel requires, among other things, precise knowledge that all trace metal constituents that affect neutron economy, fuel integrity, and fuel fabrication process parameters are well within the specification limits. Trace metal characterization of /sup 235/U-Al alloy has been carried out by atomic spectrometry. The trace metal constituents of interest are grouped into common metals (silver, boron, calcium, cadmium, cobalt, chromium, copper, iron, magnesium, manganese, molybdenum, sodium, nickel, lead, silicon, tin, titanium, vanadium, tungsten, and zinc) and lanthanides (cerium, dysprosium, europium, gadolinium, holminium, lutetium, samarium, and terbium). The elements yttrium and zirconium are grouped with the latter in view of the chemical separation procedure used. The alloy samples are dissolved in 6 M HCl and evaporated to dryness with nitric acid, and the residue is ignited to oxide. The trace elements are determined by a dc arc emission spectrographic method after chemical separation. Of these, dysprosium, europium, gadolinium, and samarium are determined by inductively coupled plasma-atomic emission spectrometry also. These methods are found to be quite adequate for the requirements of U-Al alloy fuel samples.

Argekar, A.A.; Thulasidas, S.K.; Kulkarni, M.J.; Bhide, M.K.; Sampathkumar, R.; Godbole, S.V.; Adya, V.C.; Dhawale, B.A.; Rajeshwari, B.; Goyal, N. (Bhabha Atomic Research Centre, Bombay (India). Radiochemistry Div.)

1989-02-01

308

Aluminum extraction from aluminum industrial wastes  

NASA Astrophysics Data System (ADS)

Aluminum dross tailings, an industrial waste from the Egyptian Aluminum Company (Egyptalum), was used to produce two types of alums: aluminum sulfate alum (Al2(SO4)3·12H2O) and ammonium aluminum alum {(NH4)2SO4AL2 (SO4)3·24H2O}. This was carried out in two processes. The first involves leaching the impurities using diluted H2SO4 with different solid/liquid ratios at different temperatures to dissolve the impurities present in the starting material in the form of aluminum sulfates. The second process is the extraction of aluminum (as aluminum sulfate) from the purified aluminum dross tailings thus produced. This was carried out in an autoclave. The effects of temperature, time of reaction, and acid concentration on pressure leaching and extraction processes were studied in order to specify the optimum conditions to be applied in the bench scale production as well as the kinetics of leaching process.

Amer, A. M.

2010-05-01

309

Characterization of anisotropic elastic constants of silicon-carbide particulate reinforced aluminum metal matrix composites; Part 1: Experiment  

SciTech Connect

The anisotropic elastic properties of silicon-carbide particulate (SiC[sub p]) reinforced Al metal matrix composites were characterized using ultrasonic techniques and microstructural analysis. The composite materials, fabricated by a powder metallurgy extrusion process, included 2124, 6061, and 7091 Al alloys reinforced by 10 to 30 pct of [alpha]-SiC[sub p] by volume. Results were presented for the assumed orthotropic elastic constants obtained from ultrasonic velocities and for the microstructural data on particulate shape, aspect ratio, and orientation distribution. All of the composite samples exhibited a systematic anisotropy: the stiffness in the extrusion direction was the highest, and the stiffness in the out-of-plane direction was the lowest. Microstructural analysis suggested that the observed anisotropy could be attributed to the preferred orientation of SiC[sub p]. The ultrasonic velocity was found to be sensitive to internal defects such as porosity and intermetallic compounds. It has been observed that ultrasonics may be a useful, nondestructive technique for detecting small directional differences in the overall elastic constants of the composites since a good correlation has been noted between the velocity and microstructure and the mechanical test. By incorporating the observed microstructural characteristics, a theoretical model for predicting the anisotropic stiffnesses of the composites has been developed and is presented in a companion article (Part 2).

Jeong, H. (Agency for Defense Development, DaeJon (Korea, Republic of)); Hsu, D.K. (Iowa State Univ., Ames, IA (United States). Center for Nondestructive Evaluation); Shannon, R.E. (Westinghouse Science Technology Center, Pittsburgh, PA (United States). Materials Reliability Dept.); Liaw, P.K. (Univ. of Tennessee, Knoxville, TN (United States). Dept. of Materials Science and Engineering)

1994-04-01

310

Modeling deformation behavior of Cu-Zr-Al bulk metallic glass matrix composites  

NASA Astrophysics Data System (ADS)

In the present work we prepared an in situ Cu47.5Zr47.5Al5 bulk metallic glass matrix composite derived from the shape memory alloy CuZr. We use a strength model, which considers percolation and a three-microstructural-element body approach, to understand the effect of the crystalline phase on the yield stress and the fracture strain under compressive loading, respectively. The intrinsic work-hardenability due to the martensitic transformation of the crystalline phase causes significant work hardening also of the composite material.

Pauly, S.; Liu, G.; Wang, G.; Das, J.; Kim, K. B.; Kühn, U.; Kim, D. H.; Eckert, J.

2009-09-01

311

Large-scale synthesis of AlN nanofibers by direct nitridation of aluminum  

Microsoft Academic Search

AlN nanopowders and nanofibers were synthesized by direct nitridation of Al and rice bran mixture compacts in a tube furnace up to 1300°C in a nitrogen flow without addition of extra catalyst. The effect of the compaction pressure applied onto the green bodies on the morphology of the final AlN products was investigated. A green body compacting pressure in between

P. G. Zhang; K. Y. Wang; S. M. Guo

2010-01-01

312

Development of aluminum (Al5083)-clad ternary Ag–In–Cd alloy for JSNS decoupled moderator  

Microsoft Academic Search

To develop Ag (silver)–In (indium)–Cd (cadmium) alloy decoupler, a method is needed to bond the decoupler between Al alloy (Al5083) and the ternary Ag–In–Cd alloy. We found that a better HIP condition was temperature, pressure and holding time at 803K, 100MPa and 10min. for small test pieces (?22mm in dia.×6mm in height). Hardened layer due to the formation of AlAg2

M. Teshigawara; M. Harada; S. Saito; K. Oikawa; F. Maekawa; M. Futakawa; K. Kikuchi; T. Kato; Y. Ikeda; T. Naoe; T. Koyama; T. Ooi; S. Zherebtsov; M. Kawai; H. Kurishita; K. Konashi

2006-01-01

313

Wideband characterization of aluminum nitride (AlN) substrates and high frequency application on these substrates  

Microsoft Academic Search

The authors present a method to measure effectively and accurately the dielectric constant of AlN and other ceramic substrates (beryllia and alumina) over a wideband range of frequencies. Measurement results demonstrate the superior performance of AlN substrate material as compared to alumina. It is shown that AlN possesses a dielectric constant on the order of 7.7 in the frequency range

H. Farzanehfard; A. Elshabini-Riad

1990-01-01

314

Time exposure studies on stress corrosion cracking of aluminum 2014-T6, 2219-T87, 2014-T651, 7075-T651, and titanium 6Al-4V  

NASA Technical Reports Server (NTRS)

The effect of a constant applied stress in crack initiation of aluminum 2014-T6, 2219-T87, 2014-T651, 7075-T651 and titanium 6Al-4V has been investigated. Aluminum c-ring specimens (1-inch diameter) and u-band titanium samples were exposed continuously to a 3.5% NaCl solution (pH 7) and organic fluids of ethyl, methyl, and iso-propyl alcohol (reagent purity), and demineralized distilled water. Corrosive action was observed to begin during the first and second day of constant exposure as evidenced by accumulation of hydrogen bubbles on the surface of stressed aluminum samples. However, titanium stressed specimens showed no reactions to its environment. Results of this investigation seems to suggest that aluminum 2014-T6, aluminum 7075-T651 and aluminum 2014-T651 are susceptible to stress corrosion cracking in chloride solution (NaCl), while aluminum 2219-T87 seem to resist stress corrosion cracking in sodium chloride at three levels of stress (25%, 50%, and 75% Y.S.). In organic fluids of methyl, ethyl, and iso-propyl alcohol, 2014-T6 and 7075-T651 did not fail by SCC; but 2014-T651 was susceptible to SCC in methly alcohol, but resistant in ethyl alcohol, iso-propyl alcohol and demineralized distilled water.

Terrell, J.

1973-01-01

315

Study of neutron irradiation on CoS nanoparticles grown on AlMCM-41 matrix.  

PubMed

In this research, cobalt sulfide nanoparticles (NPs) were grown on AlMCM-41 matrix by using ion exchange method. The prepared sample was irradiated by thermalized neutron that emitted from Am-Be source. After that, X-ray diffraction (XRD), UV-vis spectroscopy, Fourier transform infrared (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used for irradiated and non-irradiated samples characterization. The results show the increase of nanoparticles size and aggregation under neutron irradiation. The TEM images show average size of CoS NPs before and after neutron radiation about 20 and 50 nm, respectively. The XRD patterns show that nanoparticles size is increased after neutron radiation. The DRS results show that Co(2+) ions produced after neutron radiation, located in tetrahedral sites in AlMCM-41. The results indicate host materials have important role in decrease of radiation defects (RDs). PMID:22446774

Ochbelagh, D Rezaei; Sohrabnezhad, Sh; Biroon, M Kashefi; Golboos, N Morsali

2012-06-15

316

Characterization of a Pt-core PZT fiber/Al matrix composite  

NASA Astrophysics Data System (ADS)

The objective of this study is to design and characterize a piezoelectric composite and evaluate its suitability for viscosity-measuring applications, i.e., monitoring the coagulation rate of blood. The composite is manufactured of a platinum-core lead zirconate titanate (PZT) fiber inserted into an aluminum matrix. This study characterizes the described composite by testing its impedance, capacitance, voltage sensitivity response to vibrational inputs, and deformation due to electrical input. As actuators, different voltage inputs are fed into the probes and displacement is measured with results on the range of nanometers. As sensors, the devices are used to monitor cantilever beam vibrations. The probe's response is in the mV range and follows the same pattern as an accelerometer. Additional tests in air, water, and deionized water are carried out to evaluate the sensor's suitability for measuring viscosity using two probes: one as an actuator and the other as a sensor. Results of the gain and phase between the two probes indicate that the phase shift may be used as an indicator of viscosity changes. The first significant phase shift was measured as 2.45, 2.77, and 4.065x107Hz, for water, air, and oil, respectively, which is directly proportional to the kinematic viscosity of each fluid.

Richeson, M.; Erturun, U.; Waxman, R.; Mossi, K.; Kunikata, J.; Asanuma, H.

2010-03-01

317

Characterization of disk-laser dissimilar welding of titanium alloy Ti-6Al-4V to aluminum alloy 2024  

NASA Astrophysics Data System (ADS)

Both technical and economic reasons suggest to join dissimilar metals, benefiting from the specific properties of each material in order to perform flexible design. Adhesive bonding and mechanical joining have been traditionally used although adhesives fail to be effective in high-temperature environments and mechanical joining are not adequate for leak-tight joints. Friction stir welding is a valid alternative, even being difficult to perform for specific joint geometries and thin plates. The attention has therefore been shifted to laser welding. Interest has been shown in welding titanium to aluminum, especially in the aviation industry, in order to benefit from both corrosive resistance and strength properties of the former, and low weight and cost of the latter. Titanium alloy Ti-6Al-4V and aluminum alloy 2024 are considered in this work, being them among the most common ones in aerospace and automotive industries. Laser welding is thought to be particularly useful in reducing the heat affected zones and providing deep penetrative beads. Nevertheless, many challenges arise in welding dissimilar metals and the aim is further complicated considering the specific features of the alloys in exam, being them susceptible to oxidation on the upper surface and porosity formation in the fused zone. As many variables are involved, a systematic approach is used to perform the process and to characterize the beads referring to their shape and mechanical features, since a mixture of phases and structures is formed in the fused zone after recrystallization.

Caiazzo, Fabrizia; Alfieri, Vittorio; Cardaropoli, Francesco; Corrado, Gaetano; Sergi, Vincenzo

2013-02-01

318

Friction Welding Characteristics of Al-Mg Aluminum Alloy (A5056) and Carbon Steel (S45C)  

NASA Astrophysics Data System (ADS)

The possibility of joining composite materials, conventional steel and lighter aluminum alloy, is tested using friction welding that preserves the natural environment greatly. The friction welding of aluminum alloy, Al-Mg (A5056), and carbon steel (S45C) are done under various experimental conditions and the friction welding characteristics are examined. The mechanical property (tensile strength) of the welded specimen has enough strength under the friction welding conditions of 1000rpm, the friction pressure of above 20MPa, the friction time of less than 1 second and a quite high upset pressure near the plastic flow pressure of A5056. The macroscopic and microscopic interface structures are also examined in relation to the friction welding conditions in order to clarify the joining mechanism of the interface between different materials by the friction welding. Moreover, the heat quantity during friction welding that relates closely to the generation of the inter-metallic compound and the joining mechanism is also examined. The amount of upset that relates closely to the mechanical properties of the welded specimen is also examined.

Kobayashi, Akiyoshi; Machida, Michihide; Hukaya, Shigeo; Suzuki, Masatoshi

319

Determination of Sulfuric Acid, Oxalic Acid, and Their Matrix Effects in Aluminum Anodizing Solutions by Ion Chromatography.  

National Technical Information Service (NTIS)

Anodizing and hardcoating (hard anodizing) of aluminum improve corrosion and wear resistance. Acid concentrations (sulfuric, oxalic), pH, and physical plating variables (current, temperature, time) affect oxide coating thickness, porousness, hardness, sol...

S. Sopok

1988-01-01

320

Evaluation of the effects of variations in chemical composition on the quality of Al-Si-Mg, Al-Cu, and Al-Zn-Mg cast aluminum alloys  

Microsoft Academic Search

The effect of slight variations in chemical composition on the quality of cast aluminum alloys from three different major\\u000a alloy systems was evaluated. For the evaluation of the alloy quality, an index Q\\u000a D adjusted to damage tolerance requirements that are currently involved for the design of advanced lightweight structures is\\u000a used. The quality index Q\\u000a D accounts for tensile

N. D. Alexopoulos; Sp. G. Pantelakis

2003-01-01

321

Formation of layered Fe(II)-Al(III)-hydroxides during reaction of Fe(II) with aluminum oxide.  

PubMed

The reactivity of aqueous Fe(II) with aluminum oxide in anoxic solutions was investigated with batch kinetic experiments combined with Fe K edge X-ray absorption spectroscopy measurements to characterize Fe(II) sorption products. Formation of Fe(II)-Al(III)-layered double hydroxides with an octahedral sheet structure similar to nikischerite (NaFe(II)(6) Al(3)(SO(4))(2)(OH)(18) (H(2)O)(12)) was observed within a few hours during sorption at pH 7.5 and aqueous Fe(II) concentrations of 1-3 mM. These Fe(II) phases are composed of brucite-like Fe(II)(OH)(2) sheets with partial substitution of Al(III) for Fe(II), charge balanced by anions coordinated along the basal planes. Their fast rate of formation suggests that these previously unrecognized Fe(II) phases, which are structurally and compositionally similar to green rust, may be an important sink of Fe(II) in suboxic and anoxic geochemical environments, and impact the fate of structurally compatible trace metals, such as Co(II), Ni(II), and Zn(II), as well as redox-reactive species including Cr(VI) and U(VI). Further studies are required to assess the thermodynamics, formation kinetics, and stability of these Fe(II) minerals under field conditions. PMID:22409244

Elzinga, Evert J

2012-05-01

322

Novel silicon/aluminum (Si/Al) alloys for use as cold plate materials in cryogenically cooled solid state lasers  

NASA Astrophysics Data System (ADS)

The issue of heat transfer in high energy lasers has been a serious problem for years. One valid method of mitigating this problem is the use of low quantum defect solid-state materials operated at cryogenic temperatures1. A significant problem exists due to mismatch of coefficient of thermal expansion (CTE) and repeatedly cycling through a temperature range of ~200 K. Other groups, T.Y. Fan et al at MIT Lincoln Laboratory, have used ingenious crystal holders to overcome this problem. In this paper, we suggest the use of silicon/aluminum (Si/Al) alloys produced by Sandvik Osprey Ltd. that can have their CTE altered easily to match the CTE of whatever crystal material is chosen and still have a thermal transfer coefficient suitable for large heat transfer. We show the results of testing three different Si/Al alloys for CTE and thermal conductivity. We further test the material in a flow boil-off cryogenic cooling system that shows that the CE6 alloy material is capable of heat transfer of 21.5KW/m2K , with cold plate temperatures maintained below 110 K. The CE6 material has a CTE that almost exactly matches YAG from 90--300K.

Schill, John F.; Ogilvy, Andrew J. W.

2012-05-01

323

Experimental determination of the phase equilibria of aluminum-rich Al-Li-Cu alloys  

NASA Astrophysics Data System (ADS)

The primary phases, reaction sequences, and temperatures during solidification of Al-rich Al-Li-Cu alloys were studied using optical microscopy, electron probe microanalysis (EPMA), X-ray diffraction (XRD), scanning electron microscopy (SEM), differential thermal analysis (DTA), and chemical analysis. Boron nitride (BN), which was found to be inert to these alloys, was used as the container material. A new liquidus projection is proposed. The temperature and composition of the ternary eutectic, L = ? + T B + T 1, were determined to be 522°C at Al-8.0 at. pct Li-17.9 at. pct Cu.

Chen, Sinn-Wen; Beumler, Howard W.; Chang, Y. Austin

1991-01-01

324

Aluminum Mobility in Crustal Fluids: the Role of Al-Si Complexing  

NASA Astrophysics Data System (ADS)

The low solubility of Al in pure H2O at crustal metamorphic conditions has led to the common assumption that this element is immobile during fluid flow; however, Al-rich minerals in metamorphic veins and segregations suggest otherwise. High fluid fluxes are typically not supported by other data, and alternatives such as H+ metasomatism or complexing with alkalis or halides require special conditions if they are to provide a general explanation for this apparent inconsistency. A more plausible explanation is Al complexing with SiO2 because of its high concentrations in metamorphic pore fluids present in a wide range of crustal lithologies. We investigated this hypothesis via rapid-quench, hydrothermal piston-cylinder experiments on corundum solubility in SiO2-bearing H2O at 700-950° C and 0.5-1.5 GPa. Three sets of runs were conducted at fixed P and T: 1 GPa & 700° C, 1 GPa & 800° C, and 1.5 GPa & 800° C. Corundum solubility increases with SiO2 concentration in each case, signaling Al-Si complexing. Quartz-saturated experiments at 1.5 GPa, 800-950° C, and at 800° C, 0.5-1.5 GPa, show that (1) both Al and Si solubility are enhanced in the presence of corundum+quartz relative to that expected for saturation in a single oxide mineral, and (2) Al and Si solubility enhancements increase with P and T, indicating progressively higher concentrations of Al-Si complexes. The nature of the Al-Si complex(es) can be determined from the solubility patterns. At 800° C, 1 GPa, the predominant Al and Si aqueous species are the neutral Al monomer (AlO1.5(m)) and Si monomer (SiO2(m)) and dimer (Si2O4(d)). Adopting a standard state of unit activity of one mole of the species and assuming ideal mixing, mass balance relations can be coupled with thermodynamic properties of equilibrium between SiO2(m) and Si2O4(d) to obtain the stoichiometry and thermodynamic properties of the homogeneous reaction AlO1.5(m) + nSiO2(m)= AlSinO2n+1.5. We obtain n = 2.01 and logK = 5.1±0.4 (1?). Average deviation from the experimental measurements is 17%. That the best fit value for n corresponds almost exactly to an integer reaction coefficient of 2 strongly suggests that the mechanism for Al interaction with Si is formation of a simple trimer complex at this P and T. In addition, we find that Si>Al at all conditions measured. The results show that, by forming polymeric clusters with silica in solution, Al is readily mobilized in metamorphic fluids simply by H2O equilibration with the major minerals of the crust: quartz, feldspars and micas. Al mobility should thus be expected during fluid-rock interaction in deep crustal settings.

Manning, C. E.; Thomas, R.; Tropper, P.

2012-04-01

325

Short-term aluminum administration in the rat. Effects on bone formation and relationship to renal osteomalacia.  

PubMed Central

Aluminum may be pathogenic in the osteomalacia observed in some patients receiving hemodialysis. To study the early effects of Al on bone growth, bone formation, mineralization, and resorption were measured during short-term Al exposure in the tibial cortex of pair-fed control (C, n = 10), aluminum-treated (AL, n = 9), subtotally nephrectomized control (NX-C, n = 7), and subtotally nephrectomized aluminum-treated (NX-AL, n = 8) rats using double tetracycline labeling of bone. Animals received 2 mg/d of elemental Al intraperitoneally for 5 d/wk over 4 wk. Total bone and matrix (osteoid) formation, periosteal bone and matrix formation, and periosteal bone and matrix apposition fell by 20% in AL from C, P less than 0.05 for all values, and by 40% in NX-AL from NX-C, P less than 0.01 for all values. Moreover, each measurement was significantly less in NX-AL than in AL, P less than 0.05 for all values. Osteoid width did not increase following aluminum administration in either AL or NX-AL. Resorption surface increased from control values in both AL and NX-AL; also, resorptive activity at the endosteum was greater in NX-AL than in NX-C, P less than 0.05. Thus, aluminum impairs new bone and matrix formation but does not cause classic osteomalacia in the cortical bone of rats whether renal function is normal or reduced. These findings may represent either a different response to aluminum administration in cortical bone as contrasted to trabecular bone or an early phase in the development of osteomalacia. Aluminum may increase bone resorption and contribute to osteopenia in clinical states associated with aluminum accumulation in bone.

Goodman, W G; Gilligan, J; Horst, R

1984-01-01

326

Brazing of dispersion-strengthened aluminum  

SciTech Connect

In recent years, the use of rapid solidification powder metallurgy has made it possible to develop a new family of aluminum alloys exhibiting unique properties. One of these materials, dispersion-strengthened (DS) aluminum, is currently being produced for commercial purposes at Raufoss Technology AS, Norway. Dispersion-strengthened aluminum derives its high strength from nanoscale AlN particles embedded in an aluminum matrix. DS Al is expected to be well suited as construction material for high-temperature applications where weight reductions are of particular concern. The present investigation has focused on the wetting behavior of DS aluminum under conditions applicable to brazing. The results from the Sessile drop experiments show that a eutectic Al-Si brazing alloy will completely wet the base metal both under high-vacuum conditions and in controlled argon atmospheres, provided that the partial pressure of oxygen is sufficiently low. The main problem appears to be the stability of the matrix grain structure. In general, the process of grain erosion and coarsening can be controlled by restricting the supply of the brazing alloy so that only a small metal volume is exposed to erosion. In addition, there is a great potential for reducing the thermodynamic driving force of the erosion reaction by proper adjustments of the brazing alloy composition and/or the brazing temperature. Sill, grain boundary liquidation may be a problem which, in turn, may require additions of surface active elements to the filler metal to control the wetting behavior.

Bjoerneklett, B.; Grong, O. [Norwegian Inst. of Technology, Trondheim (Norway). Dept. of Metallurgy; Anisdahl, L. [SINTEF Materials Technology, Oslo (Norway); Hellum, E.; Sande, V. [Raufoss Technology (Norway)

1996-03-01

327

Reregistration Eligibility Decision (RED): AL and MG Phosphide. (Includes RED Facts: Aluminum and Magnesium Phosphide Fact Sheet).  

National Technical Information Service (NTIS)

This document presents the Agency's decision regarding the reregistration eligibility of the registered uses of aluminum and magnesium phosphide. Section I is the introduction. Section II describes aluminum and magnesium phosphide, their uses, data requir...

1998-01-01

328

Mechanisms of Adhesion Failure Between Polymers and Metallic Substrates. Part II. Aluminum 2024-T3 and Titanium 6Al4V with HT424 Adhesive.  

National Technical Information Service (NTIS)

This report describes the continuation of a study of aluminum 2024-T3 alloy and titanium 6Al-4V alloy adherends, adhesively bonded with epoxy HT424 adhesive. The adherend surface properties, after standard preparation treatments, were characterized with a...

T. Smith

1975-01-01

329

Liquid Oxygen LOX Compatibility Evaluations of Aluminum Lithium (Al-Li) Alloys: Investigation of the Alcoa 2090 and MMC Weldalite 049 Alloys.  

National Technical Information Service (NTIS)

The behavior of liquid oxygen (LOX) compatibility of aluminum lithium (Al-Li) alloys is investigated. Alloy systems of Alcoa 2090, vintages 1 to 3, and of Martin Marietta Corporation (MMC) Weldalite 049 were evaluated for their behavior related to the LOX...

R. M. Diwan

1989-01-01

330

Effect of NiCrAlY platelets inclusion on the mechanical and thermal shock properties of glass matrix composites  

Microsoft Academic Search

NiCrAlY platelets modified glass matrix composites were prepared. Their microstructures were characterized, their Young's modulus, fracture strength in bending, Vickers hardness, and indentation toughness were measured, and their thermal shock resistance was studied using quenching-strength and indentation-quench methods. With increasing NiCrAlY content, evident enhancements of the Young's modulus and indentation toughness were obtained. The NiCrAlY alloy inclusion could exert significant

Minghui Chen; Shenglong Zhu; Mingli Shen; Fuhui Wang; Yan Niu

2011-01-01

331

Clarification of isomeric structures and the effect of intermolecular interactions in blue-emitting aluminum complex Alq3 using first-principles 27Al NMR calculations  

NASA Astrophysics Data System (ADS)

We have performed structure analysis of the blue-emitting aluminum complex Alq3 using 27Al NMR and gauge-including projector-augmented wave calculations. The results clearly show that 27Al NMR spectra are insensitive to intermolecular interactions, thus providing a means of carrying out precise intramolecular structure determination. The key determinant of the blue-shifted emission of Alq3 is the facial isomerization.

Suzuki, Furitsu; Nishiyama, Yusuke; Kaji, Hironori

2014-06-01

332

Effects of Al–5Ti–1B on the structure and hardness of a super high strength aluminum alloy produced by strain-induced melt activation process  

Microsoft Academic Search

In this study the effect of Al–5Ti–1B grain refiner on the structural characteristics and hardness of Al–12Zn–3Mg–2.5Cu aluminum alloy has been investigated. The alloy was produced by modified strain-induced melt activation (SIMA) process. Reheating condition to obtain a fine globular microstructure was optimized. The specimens subjected to deformation ratio of 40% (at 300°C) and various heat treatment times (5–40min) and

M. Alipour; M. Emamy

2011-01-01

333

Structure, mechanical and corrosion properties of DC reactive magnetron sputtered aluminum nitride (AlN) hard coatings on mild steel substrates  

Microsoft Academic Search

Aluminum nitride (AlN) coatings of about 2 ?m thick were deposited on mild steel (MS) by means of direct current (DC) reactive\\u000a magnetron sputtering. AlN coatings were prepared in an Ar + N2 gas mixture and their crystal structure, microstructure, and topography were analyzed by X-ray diffractometry (XRD), scanning\\u000a electron microscopy (SEM) and atomic force microscopy (AFM), respectively. XRD revealed that the films

B. Subramanian; K. Ashok; M. Jayachandran

2008-01-01

334

Aluminum oxide formation at Al/La(1-x)Sr(x)MnO3 interface: a computational study for resistance random access memory applications.  

PubMed

Resistance random access memory (ReRAM) is emerging as a next-generation nonvolatile memory. One of the most promising materials for the ReRAM application is a composite of a reactive metal [such as aluminum (Al)] and a mixed-valance manganite [such as La(1-x)Ca(x)MnO3 (LCMO) and La(1-x)Sr(x)MnO3 (LSMO)]. One of the current hypotheses regarding the origin of the resistive switching of such systems is a voltage-controlled reversible formation of a high-resistance aluminum oxide (AlO(x)) layer at the Al/LC(S)MO interface through oxygen migration from LC(S)MO. To validate this hypothesis, quantum mechanics (density functional theory) calculations were carried out on an atomistic model of the resistive-switching phenomena at the Al/LSMO interface (the composite systems of Al/LSMO and AlO(x)/LSMO) as well as on the component materials such as Al, AlO(x), LaMnO3, LaMnO(3-delta), La(1-x)Sr(x)MnO3, and La(1-x)Sr(x)MnO(3-delta). The changes in the structure, energy, and electronic structure of these systems during the oxygen vacancy formation in LSMO, the oxygen migration through the Al/LSMO interface, and the AlO(x) formation were investigated. PMID:21446452

Lee, Nodo; Lansac, Yves; Jang, Yun Hee

2011-01-01

335

Aluminum-fly ash metal matrix composites for automotive parts. [Reports for April 1 to June 30, 1999, and July 1 to September 30, 1999  

SciTech Connect

Some highlights are: (1) During this quarter's field trials, sand mold castings of parts and permanent mold tensile testing bars, K mold bars, and ingots were made from aluminum alloy-fly ash melts. (2) Another objective was met, i.e., to use class ''F'' type precipitator fly ash consisting of particle sizes less than 100 microns. It was possible to pour the composite melt into the sand mold through a filter. (3) Trials were run to determine the required amount of the wetting agent, magnesium, to ensure appropriate mixing of the aluminum alloy and fly ash. The magnesium content required to mix ''F'' fly ash was much lower compared to that required to mix hybrid ''C-F'' fly ash in similar melts. Fly ash particles of less than 100 microns were mixed in aluminum melt. Large scale field trials were undertaken at Eck Industries with the goal of standardizing procedures for producing aluminum-fly ash composite melts and to analyze the structure and properties of the resulting material. Limited testing of tensile properties has been done on pressure die cast parts, and attempts are underway to improve the distribution of fly ash in both sand cast and pressure die cast samples. Eck Industries performed radiographic, heat treatment, and tensile tests on permanent mold cast tensile test bars. After fly ash mixing experiments, the Lanxide high speed-high shear mixer (originally designed for mixing Al-SiC melts) was employed in an attempt to avoid fly ash agglomeration. It led to demixing (instead of deagglomerating) of some fly ash. However, the permanent mold tensile bars poured after high shear mixing displayed good distribution of fly ash in castings. A modified impeller design is being considered for high speed-high shear mixing of aluminum-fly ash melts.

Weiss, David; Purgert, Robert; Rhudy, Richard; Rohatgi, P.

1999-10-15

336

Effects of SiC volume fraction and aluminum particulate size on interfacial reactions in SiC nanoparticulate reinforced aluminum matrix composites  

Microsoft Academic Search

The SiC nanoparticulate reinforced Al–3.0wt.% Mg composites were fabricated by combining pressureless infiltration with ball-milling and cold-pressing technology at 700°C for 2h. The effects of SiC nanoparticulate volume fractions (6%, 10% and 14%) and Al particulate sizes (38?m and 74?m) on interfacial reactions were investigated by SEM, TEM and X-ray diffraction. The results show that the MgO at the interface

Bowen Xiong; Zhifeng Xu; Qingsong Yan; Baiping Lu; Changchun Cai

337

Fully Dense, Aluminum-Rich Al-CuO Nanocomposite Powders for Energetic Formulations  

Microsoft Academic Search

The thermite reaction between Al and CuO is well known and highly exothermic. For a conventional thermite mixture, the reaction is rate limited by a slow heterogeneous mass transfer at the metal and oxide interface. The relatively low reaction rate and ignition difficulty have restricted practical applications for this reaction. For newly developed nanocomposed thermites, the interface area is substantially

Demitrios Stamatis; Zhi Jiang; Vern K. Hoffmann; Mirko Schoenitz; Edward L. Dreizin

2008-01-01

338

Prediction of Thermal Conductivity of Aluminum Nanocluster-Filled Mesoporous Silica (Al/MCM-41)  

NASA Astrophysics Data System (ADS)

MCM-41 consists of a hexagonal array of long, unconnected cylindrical pores with diameters that can be tailored within the range 1.6 nm to 10 nm. As a porous silica nanomaterial, MCM-41 is a promising porous substrate for mesoporous composites with extremely high or low thermal conductivity. In this article, the structural unit of MCM-41 was established first and an equilibrium molecular dynamics simulation was performed to determine the shell thermal conductivity of MCM-41. Then, based on one-dimensional (1D) heat transfer analysis, a mathematical expression for the effective thermal conductivity (ETC) of Al nanocluster-filled mesoporous MCM-41 (Al/MCM-41) was obtained. The effects of porosity and the filling ratio of nanoclusters in the mesochannels were further investigated. As the porosity is greater than 75 %, the ETC of only-air-filling mesoporous MCM-41 in all directions tends to approach the thermal conductivity of air. It seems that Al nanoclusters have negligible effects on the ETC of the composite, except that mesochannels are almost completely filled with Al nanowires.

Huang, Congliang; Feng, Yanhui; Zhang, Xinxin; Li, Jing; Cui, Liu; Wang, Ge; Yang, Mu

2013-12-01

339

Study on Mold Slag with High Al2O3 Content for High Aluminum Steel  

NASA Astrophysics Data System (ADS)

The slag-steel equilibrium reaction between the newly developed mold slag ND-MSL and 20Mn23AlV steel has been studied at high temperatures in the laboratory. The crystal morphology, microanalysis, and phase analysis of the original and final ND-MSL slags were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Results show that, in the final ND-MSL slag, the constitution of SiO2 decreased by 0.7 wt pct and Al2O3 increased by 6.46 wt pct, while the melting temperature, viscosity, and crystallization rate increased by 62 K, 0.66 dPa s, and 15 pct, respectively. NaAlSi3O8 and CaAl2Si2O8 were found to be precipitated in the final ND-MSL slag. Both the original and final ND-MSL slags have a small amount of LiF crystal and good glass form. The ND-MSL slag has little change in the composition and properties compared with the two currently used mold slags.

Wang, Qiang; Sun, Min; Qiu, Shengtao; Tian, Zhiling; Zhu, Guoling; Wang, Longmei; Zhao, Pei

2014-04-01

340

Orientation relationship between ?-Fe precipitate and ?-Al2O3 matrix in iron-implanted sapphire.  

PubMed

Fe ions were implanted into ?-Al2O3 single crystals (sapphire) at room temperature and annealed in a reducing atmosphere. The orientation relationships (ORs) between ?-Fe particles and sapphire matrix were investigated using transmission electron microscopy (TEM). All the ?-Fe particles have the orientation relationship (OR) of (111)?-Fe||(0001)sapphire and [11¯0]?-Fe||[112¯0]sapphire with sapphire. This OR is predicted precisely by the coincidence of reciprocal lattice points (CRLP) method. The other OR of (110)?-Fe||(0001)sapphire and [111]?-Fe||[51¯4¯0]sapphire reported before is confirmed by the same method to be one of the secondary preferred orientation relationships in the ?-Fe/sapphire system. PMID:24811987

Wang, Y; Liu, X P; Qin, G W

2014-07-01

341

Accelerated multiplicative updates and hierarchical ALS algorithms for nonnegative matrix factorization.  

PubMed

Nonnegative matrix factorization (NMF) is a data analysis technique used in a great variety of applications such as text mining, image processing, hyperspectral data analysis, computational biology, and clustering. In this letter, we consider two well-known algorithms designed to solve NMF problems: the multiplicative updates of Lee and Seung and the hierarchical alternating least squares of Cichocki et al. We propose a simple way to significantly accelerate these schemes, based on a careful analysis of the computational cost needed at each iteration, while preserving their convergence properties. This acceleration technique can also be applied to other algorithms, which we illustrate on the projected gradient method of Lin. The efficiency of the accelerated algorithms is empirically demonstrated on image and text data sets and compares favorably with a state-of-the-art alternating nonnegative least squares algorithm. PMID:22168561

Gillis, Nicolas; Glineur, François

2012-04-01

342

Properties of sulfur sorbents containing dispersed nickel in an Al2O3 matrix  

NASA Astrophysics Data System (ADS)

For advanced coal gasification systems, regenerable sorbents are being developed to remove sulfur (S) from the hot product gas prior to its use in gas turbines and high-temperature fuel cells. Whereas zinc (Zn) base sorbents are attractive for these applications, they have limitations in high-temperature capability and in durability. Materials containing dispersed nickel (Ni) in an Al2O3 matrix have the potential to be better in both respects. Their main limitation is that they do not reduce H2S concentrations to the low parts per million (ppm) level. Results are reported here on the second phase of a program on dispersed Ni sorbents. Included are the results of crush strength, thermogravimetric analysis, and fixed-bed reactor experiments. An important conclusion drawn from the results is that chemisorption of H2S plays a major role in reducing its concentration in gas exiting the bed below the levels expected from the Ni-Ni sulfide equilibrium.

Swisher, J. H.; Jhunjhunwala, M.; Gasper-Galvin, L. D.; Gardner, T. H.; Hammerbeck, K.

1996-04-01

343

Time exposure studies on stress corrosion cracking of aluminum 2014-T6, aluminum 7075-T651, and titanium 6Al-4V  

NASA Technical Reports Server (NTRS)

The effect of a constant applied stress in crack initiation of aluminum 2014-T6, 7075-T651 and titanium 6A1-4V has been investigated. Aluminum c-ring specimens (1-inch diameter) and u-band titanium samples were exposed continuously to a 3.5% NaCl solution (pH 6) and organic fluids of ethyl, methyl, and iso-propyl alcohol (reagent purity). Corrosive action was observed to begin during the first and second day of constant exposure as evidenced by accumulation of hydrogen bubbles on the surface of stressed aluminum samples. However, a similar observation was not noted for titanium stressed specimens. Results of this investigation seems to suggest that aluminum 2014-T6, aluminum 7075-T651 are susceptible to stress corrosion cracking in chloride solution (NaCl); while they (both alloys) seem to resist stress corrosion cracking in methyl alcohol, ethyl alcohol, iso-propyl alcohol, and demineralized distilled water. Titanium 6A1-4V showed some evidence of susceptibility to SCC in methanol, while no such susceptibility was exhibited in ethanol, iso-propyl alcohol and demineralized distilled water.

Terrell, J.

1972-01-01

344

A process model for friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites; 2: HAZ microstructure and strength evolution  

SciTech Connect

The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. In Part 2 the heat and material flow models presented in the first paper (Part 1) are utilized for prediction of the HAZ subgrain structure and strength evolution following welding and subsequent natural aging. The modeling is done on the basis of well established principles from thermodynamics, kinetic theory and simple dislocation mechanics. The models are validated by comparison with experimental data, and are illustrated by means of novel mechanism maps. These show the competition between the different process variables that contribute to microstructural changes and strength losses during friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites.

Midling, O.T. (SINTEF, Trondheim (Norway). Div. of Metallurgy); Grong, Oe. (Univ. of Trondheim (Norway). Norwegian Inst. of Tech.)

1994-05-01

345

Process model for friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. Part 2: HAZ microstructure and strength evolution  

NASA Astrophysics Data System (ADS)

The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. In Part 2 the heat and material flow models presented in the first paper (Part 1) are utilized for prediction of the HAZ subgrain structure and strength evolution following welding and subsequent natural aging. The modeling is done on the basis of well established principles from thermodynamics, kinetic theory, and simple dislocation mechanics. The models are validated by comparison with experimental data and are illustrated by means of novel mechanism maps. These show the competition between the different process variables that contribute to microstructural changes and strength losses during friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites.

Midling, O. T.; Grong, O.

1994-05-01

346

In-situ processing of aluminum nitride particle reinforced aluminum alloy composites  

Microsoft Academic Search

Discontinuously reinforced aluminum alloy composites (DRACs) have potential applications in automotive, electronic packaging, and recreation industries. Conventional processing of DRACs is by incorporation of ceramic particles\\/whiskers\\/fibers into matrix alloys. Because of the high cost of ceramic particles, DRACs are expensive. The goal of this work was to develop a low-cost route of AlN-Al DRACs processing through bubbling and reacting nitrogen

Qingjun Zheng

2003-01-01

347

Structural and microstructural characterization of SiB 0.5C 1.5N 0.8Al 0.3 powders prepared by mechanical alloying using aluminum nitride as aluminum source  

Microsoft Academic Search

SiB0.5C1.5N0.8Al0.3 powders were fabricated by mechanical alloying using crystalline silicon (c-Si), hexagonal boron nitride (h-BN), graphite (C) and aluminum nitride (AlN) powders as starting materials. The microstructure of the synthesized SiB0.5C1.5N0.8Al0.3 powders is predominantly amorphous with a very small volume fraction of AlN nano-crystalline phase. The SiB0.5C1.5N0.8Al0.3 powders appeared to possess a structure containing hybridization of several bonds such as

Dan Ye; De-Chang Jia; Zhi-Hua Yang; Xiao-Ming Duan; Yu Zhou

2011-01-01

348

Studies of Orientations of ?? Precipitates in Al-Mg-Si-(Cu) Alloys by Electron Diffraction and Transition Matrix Analysis  

NASA Astrophysics Data System (ADS)

Transition matrix, combine with high-resolution transmission electron microscopy (HRTEM) and stereographic projection, was used in this article to predict and characterize the orientations and electron diffraction patterns of ?? precipitates in Al-Mg-Si-(Cu) alloys. It was found that the ?? phases as the main strengthening precipitates had 12 variants with Al matrix, and the orientation relationships could be expressed as (010) ??//{100}Al, [001] ??//<310>Al, and [100] ??//<230>Al. Further, based on the C-centered monoclinic structure of ?? precipitate, a new diffraction patterns model under the [001]Al zone axis could be established, which was in good agreement with the experiment date. Further, it could be used to explain reasonably some issues (for example, the "cross-shaped" diffraction streaks phenomenon). Simultaneously, we also found that the ?? precipitates had only three different zone axes, [010] ??, [304] ??, and [ {bar{1}06} ]_{{?^' ' } }} , parallel to the [001]Al direction when they were precipitated from the Al matrix, and the ?? precipitate might deviate 1.6 deg from its original orientation because of the lattice relaxation.

Yang, Wenchao; Wang, Mingpu; Jia, Yanlin; Zhang, Ruirong

2011-09-01

349

Synthesis of carbon filament reinforced aluminum-matrix composites. Final report, September 1, 1990December 31, 1993  

Microsoft Academic Search

The objective of this project was to synthesize branched (3D) carbon filaments from natural gas in a graphite tube for subsequent infiltration with aluminum. A deposition reactor was fabricated in which carbon filaments could be grown on the inside surface of net shaped parts. A vertical arrangement of the furnace was found to optimize filament growth. Palladium was found to

L. E. Jones; A. Piotrowski

1994-01-01

350

Wear mechanisms in hybrid composites of Graphite-20 Pct SiC in A356 Aluminum Alloy (Al-7 Pct Si-0.3 Pct Mg)  

NASA Astrophysics Data System (ADS)

The wear behavior of A356 aluminum alloy (Al-7 Pct Si-0.3 Pct Mg) matrix composites reinforced with 20 vol Pct SiC particles and 3 or 10 vol Pct graphite was investigated. These hybrid composites represent the merging of two philosophies in tribological material design: soft-particle lubrication by graphite and hard-particle reinforcement by carbide particles. The wear tests were performed using a block-on-ring (SAE 52100 steel) wear machine under dry sliding conditions within a load range of 1 to 441 N. The microstructural and compositional changes that took place during wear were characterized using scanning electron microscopy (SEM), Auger electron spectroscopy (AES), energy-dispersive X-ray spectroscopy (EDXA), and X-ray diffractometry (XRD). The wear resistance of 3 Pct graphite-20 Pct SiC-A356 hybrid composite was comparable to 20 Pct SiC-A356 without graphite at low and medium loads. At loads below 20 N, both hybrid and 20 Pct SiC-A356 composites without graphite demonstrated wear rates up to 10 times lower than the unreinforced A356 alloy due to the load-carrying capacity of SiC particles. The wear resistance of 3 Pct graphite 20 Pct SiC-A356 was 1 to 2 times higher than 10 Pct graphite-containing hybrid composites at high loads. However, graphite addition reduced the counterface wear. The unreinforced A356 and 20 Pct SiC-A356 showed a transition from mild to severe wear at 95 N and 225 N, respectively. Hybrid composites with 3 Pct and 10 Pct graphite did not show such a transition over the entire load range, indicating that graphite improved the seizure resistance of the composites. Tribolayers, mainly consisting of a compacted mixture of graphite, iron oxides, and aluminum, were generated on the surfaces of the hybrid composites. In the hybrid composites, the elimination of the severe wear (and hence the improvement in seizure resistance) was attributed to the reduction in friction-induced surface heating due to the presence of graphite- and iron-oxide-containing tribolayers.

Ames, W.; Alpas, A. T.

1995-01-01

351

A process model for friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites; 1: HAZ temperature and strain rate distribution  

Microsoft Academic Search

The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. In Part 1 the different components of the model are outlined and analytical solutions presented which provide quantitative information about the HAZ temperature distribution for a wide range

O. T. Midling; Oe. Grong

1994-01-01

352

Process model for friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. Part 1: HAZ temperature and strain rate distribution  

Microsoft Academic Search

The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. In Part 1 the different components of the model are outlined and analytical solutions presented which provide quantitative information about the HAZ temperature distribution for a wide range

O. T. Midling; O. Grong

1994-01-01

353

A process model for friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites; 2: HAZ microstructure and strength evolution  

Microsoft Academic Search

The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. In Part 2 the heat and material flow models presented in the first paper (Part 1) are utilized for prediction of the HAZ subgrain structure and strength evolution

O. T. Midling; Oe. Grong

1994-01-01

354

Process model for friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. Part 2: HAZ microstructure and strength evolution  

Microsoft Academic Search

The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. In Part 2 the heat and material flow models presented in the first paper (Part 1) are utilized for prediction of the HAZ subgrain structure and strength evolution

O. T. Midling; O. Grong

1994-01-01

355

Tribological behaviour of Al 18B 4O 33-whisker-reinforced hypoeutectic Al–Si–Mg-matrix composites under dry sliding conditions  

Microsoft Academic Search

Steady-state friction and wear behaviour of as-cast and T6-treated hypoeutectic Al–Si–Mg-matrix composites reinforced with 19.5 vol.% of Al18B4O33 whiskers dry sliding against 5CrNiMo steel counterface have been investigated as a function of applied load and sliding speed. Owing to the severe interfacial cracking and fracture of whiskers which occurs under higher applied load conditions, the composites exhibited a transition from

J. P Tu; Y. Z Yang

2000-01-01

356

Cryomilled Aluminum Stabilized by Diamondoid Nanoparticles  

NASA Astrophysics Data System (ADS)

Nanocrystalline aluminum powder with an average grain size of 22nm was prepared via cryomilling. Hot Isostatic Pressing was used to consolidate the powder followed by hot extrusion to homogenize the consolidated material. The high homologous temperature processes tend to increase the average grain diameter beyond the nanoscle classification, which is less than 100 nm. Diamantane was added during cryomilling to enhance the thermal stability in nanocrystalline aluminum. The thermal stability test data show that aluminum reinforced with 1 wt% diamantane exhibit two to three fold better thermal stability than non-reinforced aluminum when annealed at 773K (0.84 Tm) for ten hours. A similar trend is shown for the samples consolidated at 693K. This finding is explained through Burke's model for grain growth in materials containing secondary particles to inhibit grain boundary motion. The mechanical properties of cryomilled aluminum stabilized by 0.5 wt% and 1 wt% diamantane particles are compared with cryomilled commercial purity (CP) aluminum with no diamantane after high strain rate deformation (trap extrusion). The grain size of cryomilled CP aluminum is 0.6 to 1.2 times larger than the samples containing diamantane. In contrast to Hall-petch predictions, cryomilled aluminum with diamantane has relatively lower flow stress while demonstrating a 2.7-3.7 time higher ductility compared to cryomilled CP aluminum. Possible reasons for this behavior are suggested in mechnical property section. A combination of higher temperature and pressure resulted in formation of Aluminum tris (Al(C9H6NO)3) precipitates from diamantane in the cryomilled aluminum matrix. The precipitates were formed during trap extrusion process but only seen in samples containing 1 wt% diamantane and HIP'ed at 521°C. Therefore, the HIP'ng temperature plays an important role in formation of these precipitates.

Maung, Khinlay

357

Synthesis and structural characterization of a new aluminum oxycarbonitride, Al{sub 5}(O, C, N){sub 4}  

SciTech Connect

A new aluminum oxycarbonitride, Al{sub 5}(O{sub x}C{sub y}N{sub 4-x-y}) (x{approx}1.4 and y{approx}2.1), has been synthesized and characterized by X-ray powder diffraction, transmission electron microscopy and electron energy loss spectroscopy (EELS). The title compound was found to be hexagonal with space group P6{sub 3}/mmc, Z=2, and unit-cell dimensions a=0.328455(6) nm, c=2.15998(3) nm and V=0.201805(6) nm{sup 3}. The atom ratios O:C:N were determined by EELS. The final structural model, which is isomorphous with that of (Al{sub 4.4}Si{sub 0.6})(O{sub 1.0}C{sub 3.0}), showed the positional disordering of one of the three types of Al sites. The maximum-entropy method-based pattern fitting (MPF) method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The reliability indices calculated from the MPF were R{sub wp}=6.94% (S=1.22), R{sub p}=5.34%, R{sub B}=1.35% and R{sub F}=0.76%. The crystal was an inversion twin. Each twin-related individual was isostructural with Al{sub 5}C{sub 3}N (space group P6{sub 3}mc, Z=2). - Graphical abstract: A new oxycarbonitride discovered in the Al-O-C-N system, Al{sub 5}(O{sub 1.4}C{sub 2.1}N{sub 0.5}). The crystal is an inversion twin, and hence the structure is represented by a split-atom model. The three-dimensional electron density distributions are determined by the maximum-entropy methods-based pattern fitting, being consistent with the disordered structural model. Display Omitted

Inuzuka, Haruya; Kaga, Motoaki; Urushihara, Daisuke [Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Nakano, Hiromi [Cooperative Research Facility Center, Toyohashi University of Technology, Toyohashi 441-8580 (Japan); Asaka, Toru [Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Fukuda, Koichiro, E-mail: fukuda.koichiro@nitech.ac.j [Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

2010-11-15

358

CONDENSED MATTER: STRUCTURAL, MECHANICAL, AND THERMAL PROPERTIES: Mechanical Properties of Ni-Coated Single Graphene Sheet and Their Embedded Aluminum Matrix Composites  

NASA Astrophysics Data System (ADS)

The effects of Ni coating on the mechanical behaviors of single graphene sheet and their embedded Al matrix composites under axial tension are investigated using molecular dynamics (MD) simulation method. The results show that the Young's moduli and tensile strength of graphene obviously decrease after Ni coating. The results also show that the mechanical properties of Al matrix can be obviously increased by embedding a single graphene sheet. From the simulation, we also find that the Young's modulus and tensile strength of the Ni-coated graphene/Al composite is obviously larger than those of the uncoated graphene/Al composite. The increased magnitude of the Young's modulus and tensile strength of graphene/Al composite are 52.27% and 32.32% at 0.01 K, respectively, due to Ni coating. By exploring the effects of temperature on the mechanical properties of single graphene sheet and their embedded Al matrix composites, it is found that the higher temperature leads to the lower critical strain and tensile strength.

Song, Hai-Yang; Zha, Xin-Wei

2010-07-01

359

Precipitation behaviors in Al-Cu-Mg and 2024 aluminum alloys  

Microsoft Academic Search

The precipitation behaviors and aging reactions of the pseudobinary Al-Cu-Mg alloy and the commercial 2024 alloy under unstretched\\u000a and stretched conditions have been investigated in this study by means of conductivity and hardness measurements, differential\\u000a scanning calorimetry, and transmission electron microscopy (TEM). The morphologies and growth modes of various defects and\\u000a transition phases as well as the interaction among them

Han-Cheng Shih; New-Jin Ho; J. C. Huang

1996-01-01

360

THE AGING CHARACTERISTICS OF ALUMINUM ALLOYS. ELECTRON TRANSMISSION STUDIES OF Al-Mg-Si ALLOYS  

Microsoft Academic Search

Transmission electron microscope studies of an Al-- Mg-Si alloy using ; the thin foil technique revealed many interesting features in the quenched and ; aged conditions. The concentration of vacancies annealed out to form dislocation ; loops in quenched specimens was about 3 x 10⁻⁶, and the loop density about ; 10¹⁴\\/cm³. The zones which form first upon aging were

Thomas

1961-01-01

361

Temperature distribution study during the friction stir welding process of Al2024-T3 aluminum alloy  

NASA Astrophysics Data System (ADS)

Heat flux characteristics are critical to good quality welding obtained in the important engineering alloy Al2024-T3 by the friction stir welding (FSW) process. In the present study, thermocouples in three different configurations were affixed on the welding samples to measure the temperatures: in the first configuration, four thermocouples were placed at equivalent positions along one side of the welding direction; the second configuration involved two equivalent thermocouple locations on either side of the welding path; while the third configuration had all the thermocouples on one side of the layout but with unequal gaps from the welding line. A three-dimensional, non-linear ANSYS computational model, based on an approach applied to Al2024-T3 for the first time, was used to simulate the welding temperature profiles obtained experimentally. The experimental thermal profiles on the whole were found to be in agreement with those calculated by the ANSYS model. The broad agreement between the two kinds of profiles validates the basis for derivation of the simulation model and provides an approach for the FSW simulation in Al2024-T3 and is potentially more useful than models derived previously.

Yau, Y. H.; Hussain, A.; Lalwani, R. K.; Chan, H. K.; Hakimi, N.

2013-08-01

362

Deposition of duplex Al 2O 3/aluminum coatings on steel using a combined technique of arc spraying and plasma electrolytic oxidation  

NASA Astrophysics Data System (ADS)

Plasma electrolytic oxidation (PEO) is a cost-effective technique that can be used to prepare ceramic coatings on metals such as Ti, Al, Mg, Nb, etc., and their alloys, but this promising technique cannot be used to modify the surface properties of steels, which are the most widely used materials in engineering. In order to prepare metallurgically bonded ceramic coatings on steels, a combined technique of arc spraying and plasma electrolytic oxidation (PEO) was adopted. In this work, metallurgically bonded ceramic coatings on steels were obtained using this method. We firstly prepared aluminum coatings on steels by arc spraying, and then obtained the metallurgically bonded ceramic coatings on aluminum coatings by PEO. The characteristics of duplex coatings were analyzed by X-ray diffractometer (XRD) and scanning electron microscopy (SEM). The corrosion and wear resistance of the ceramic coatings were also studied. The results show that, duplex Al 2O 3/aluminum coatings have been deposited on steel substrate after the combined treatment. The ceramic coatings are mainly composed of ?-Al 2O 3, ?-Al 2O 3, ?-Al 2O 3 and some amorphous phase. The duplex coatings show favorable corrosion and wear resistance properties. The investigations indicate that the combination of arc spraying and plasma electrolytic oxidation proves a promising technique for surface modification of steels for protective purposes.

Gu, Weichao; Shen, Dejiu; Wang, Yulin; Chen, Guangliang; Feng, Wenran; Zhang, Guling; Fan, Songhua; Liu, Chizi; Yang, Size

2006-02-01

363

Microstructure and mechanical properties of twin-wire arc sprayed Ni-Al composite coatings on 6061-T6 aluminum alloy sheet  

NASA Astrophysics Data System (ADS)

We have systematically studied the microstructure and mechanical properties of Ni-5wt%Al and Ni-20wt%Al composite coatings fabricated on 6061-T6 aluminum alloy sheet by twin-wire arc spraying under different experimental conditions. The abrasive wear behavior and interface diffusion behavior of the composite coatings were evaluated by dry/wet rubber wheel abrasive wear tests and heat treatment, respectively. Experimental results indicate that the composite coatings exhibit features of adhesive wear. Besides, the Vickers microhardness of NiAl and Ni3Al intermetallic compounds is relatively larger than that of the substrate, which is beneficial for enhancing the wear resistance. With the increase of annealing temperature and time, the interface diffusion area between the Ni-Al coating and the substrate gradually expands with the formation of NiAl3 and Ni2Al3 phases, and is controlled by diffusion of aluminum atoms. The grain growth exponent n of diffusion kinetics of the Ni-Al coating, calculated via a high-temperature diffusion model at 400, 480, and 550°C, is between 0.28 and 0.38. This satisfies the cubic law, which is consistent with the general theoretical relationship of high-temperature diffusion.

Wang, Ji-xiao; Liu, Jing-shun; Zhang, Lun-yong; Sun, Jian-fei; Wang, Zhi-ping

2014-05-01

364

Formation mechanism of in situ Al 3Ti in Al matrix during hot pressing and subsequent friction stir processing  

Microsoft Academic Search

In situ Al3Ti\\/Al composites were fabricated by a combination of vacuum hot pressing (VHP) and friction stir processing (FSP). The formation mechanism of the Al3Ti and the effect of VHP and FSP parameters on the resultant microstructure and mechanical properties were investigated. The Al3Ti formed due to the reactive diffusion between Al and Ti during VHP, and the number of

Q. Zhang; B. L. Xiao; D. Wang; Z. Y. Ma

2011-01-01

365

Wear mechanisms in hybrid composites of graphite-20 pct SiC in A356 aluminum alloy (Al-7 pct Si-0. 3 pct Mg)  

SciTech Connect

The wear behavior of A356 aluminum alloy (Al-7 pct Si-0.3 pct Mg) matrix composites reinforced with 20 vol pct SiC particles and 3 or 10 vol pct graphite was investigated. These hybrid composites represent the merging of two philosophies in tribological material design: soft-particle lubrication by graphite and hard-particle reinforcement by carbide particles. The wear tests were performed using a block-on-ring (SAE 52100 steel) wear machine under dry sliding conditions within a load range of 1 to 441 N. The microstructural and compositional changes that took place during wear were characterized using scanning electron microscopy (SEM), Auger electron spectroscopy (AES), energy-dispersive X-ray spectroscopy (EDXA), and X0ray diffractometry (XRD). The wear resistance of 3 pct graphite-20 pct SiC-A356 hybrid composite was comparable to 20 pct SiC-A356 without graphite at low and medium loads. At loads below 20 N, both hybrid and 20 pct SiC-A356 composites without graphite demonstrated wear rates up to 10 times lower than the unreinforced A356 alloy due to the load-carrying capacity of SiC particles. The wear resistance of 3 pct graphite 20 pct SiC-A356 was 1 to 2 times higher than 10 pct graphite-containing hybrid composites at high loads. However, graphite addition reduced the counterface wear. The unreinforced A356 and 20 pct SiC-A356 showed a transition from mild to severe wear at 95 N and 225 N, respectively. Hybrid composites with 3 pct and 10 pct graphite did not show such a transition over the entire load range, indicating that graphite improved the seizure resistance of the composites.

Ames, W.; Alpas, A.T. (Univ. of Windsor, Ontario (Canada). Dept. of Mechanical Engineering)

1995-01-01

366

Friction and wear studies of die cast aluminum alloy-aluminum oxide-reinforced composites  

Microsoft Academic Search

Purpose – Metal matrix composites (MMCs) are engineered materials formed by the combination of metal matrix and reinforcement materials. They have a stiff and hard reinforcing phase in metallic matrix. The matrix includes metals such as aluminum, magnesium, copper and their alloys. The purpose of this paper is to describe the development of an aluminum alloy-aluminum oxide composite using a

M. Kathiresan; T. Sornakumar

2010-01-01

367

Effect of SO 4 2 - \\/ Al 3 + ratio and OH ?\\/Al 3+ value on the characterization of coagulant poly-aluminum-chloride-sulfate (PACS) and its coagulation performance in water treatment  

Microsoft Academic Search

A poly-aluminum-chloride-sulfate (PACS) was prepared at various experimental conditions. It was found that the coagulation performance of PACS in water treatment was affected by the PACS particle size distribution and zeta potential value. The experimental results indicated that the PACS particle size distribution and zeta potential value were highly influenced by SO42-\\/Al3+ molar ratio and bacicities (?,?=[OH]\\/[Al]) value. At a

Baoyu Gao; Qinyan Yue

2005-01-01

368

Precipitation behaviors in Al-Cu-Mg and 2024 aluminum alloys  

SciTech Connect

The precipitation behaviors and aging reactions of the pseudobinary Al-Cu-Mg alloy and the commercial 2024 alloy under unstretched and stretched conditions have been investigated in this study by means of conductivity and hardness measurements, differential scanning calorimetry, and transmission electron microscopy (TEM). The morphologies and growth modes of various defects and transition phases as well as the interaction among them were widely discussed. In particular, an electron diffraction ring pattern was found to correspond to the axial growth of the GPB2 zone. This suggested that the atom groups constructing this cylindrical zone are statistically, uniformly arranged in the adjacent {l_brace}100{r_brace}{sub Al} planes and the GPB2 zone is only a partially ordered version of the GPB zone in <001>{sub Al} directions. Moreover, few GPB2 zones can survive long time overaging due to the Gibbs-Thomson effect. As for the S{prime} precipitates, they preferentially nucleate on dislocations. During subsequent growth, they can further coalesce into two morphologies (corrugated sheets and wide plates) for the unstretched specimens. Therefore, the rate of Ostward ripening decreases and the peak hardness becomes flattened. Finally, based on the present analyses, the aging sequence of the two alloys studied could be revised with respect to previous investigations and their isothermal aging reactions can be subdivided into five main stages. These stages correspond to (1) GPB zone precipitation, (2) fast in situ precipitation of GPB2 zones from GPB zones and their subsequent growth, (3) fast nucleation and accelerating growth of the S{prime} phase, (4) decelerating growth of the S{prime} phase, and (5) Ostward ripening of the S{prime} and S phases, respectively.

Shih, H.C.; Ho, N.J.; Huang, J.C. [National Sun Yat-sen Univ., Kaohsiung (Taiwan, Province of China). Inst. of Materials Science and Engineering

1996-09-01

369

Tensile deformation of 2618 and Al-Fe-Si-V aluminum alloys at elevated temperatures  

NASA Technical Reports Server (NTRS)

The present study experimentally characterizes the effects of elevated temperature on the uniaxial tensile behavior of ingot metallurgy 2618 Al alloy and the rapidly solidified FVS 0812 P/M alloy by means of two constitutive formulations: the Ramberg/Osgood equation and the Bodner-Partom (1975) incremental formulation for uniaxial tensile loading. The elastoplastic strain-hardening behavior of the ingot metallurgy alloy is equally well represented by either formulation. Both alloys deform similarly under decreasing load after only 1-5 percent uniform tensile strain, a response which is not described by either constitutive relation.

Leng, Y.; Porr, W. C., Jr.; Gangloff, R. P.

1990-01-01

370

Aluminum Alloy and Article Cast Therefrom  

NASA Technical Reports Server (NTRS)

A cast article from an aluminum alloy, which has improved mechanical properties at elevated temperatures, has the following composition in weight percent: Silicon 14 - 25.0, Copper 5.5 - 8.0, Iron 0.05 - 1.2, Magnesium 0.5 - 1.5, Nickel 0.05 - 0.9, Manganese 0.05 - 1.0, Titanium 0.05 - 1.2, Zirconium 0.05 - 1.2, Vanadium 0.05 - 1.2, Zinc 0.05 - 0.9, Phosphorus 0.001 - 0.1, and the balance is Aluminum, wherein the silicon-to-magnesium ratio is 10 - 25, and the copper-to-magnesium ratio is 4 - 15. The aluminum alloy contains a simultaneous dispersion of three types of Al3X compound particles (X=Ti, V, Zr) having a LI2, crystal structure, and their lattice parameters are coherent to the aluminum matrix lattice. A process for producing this cast article is also disclosed, as well as a metal matrix composite, which includes the aluminum alloy serving as a matrix and containing up to about 60% by volume of a secondary filler material.

Lee, Jonathan A. (Inventor); Chen, Po-Shou (Inventor)

2003-01-01

371

Influence of high-temperature annealing with the melting of the aluminum matrix on the properties of SAP materials  

Microsoft Academic Search

At present the following technique is employed to obtain semiproducts from SAP materials: cold compacting of aluminum powder at a specific pressure of about 35 kg\\/mm2, sintering of the compacts at a temperature of 620~ with a holding period of 20-30 h, and hot re-pressing of the sintered compacts at a temperature of 500~ and a specific pressure of 40-50

V. S. Kurbatov; V. A. Shelamov; Yu. V. Shmakov

1967-01-01

372

Fatigue crack growth resistance in SiC particulate and whisker reinforced P\\/M 2124 aluminum matrix composites  

Microsoft Academic Search

Fatigue crack growth is examined in P\\/M 2124 aluminum alloys reinforced with SiC particles (SiCp) and whiskers (SiCw) over a wide spectrum of growth rates from 10?12 to 10?4 m per cycle. Effects of aging treatment, orientation of crack growth direction with respect to the rolling direction, mean stress (or stress ratio), and reinforcement volume percent on the fatigue crack

J. J. Mason; R. O. Ritchie

1997-01-01

373

Chemical reactions between aluminum and fly ash during synthesis and reheating of Al-fly ash composite  

Microsoft Academic Search

Thermodynamic analysis indicates that there is the possibility of chemical reactions between aluminum melt and cenosphere\\u000a fly ash particles. These particles contain alumina, silica, and iron oxide, which, during solidification processing of aluminum-fly\\u000a ash composites or during holding of such composites at temperatures above the melting temperature of aluminum, are likely\\u000a to undergo chemical reduction. These chemical reactions between the

R. O. Guo; P. K. Rohatgi

1998-01-01

374

Precipitation behaviors in Al-Cu-Mg and 2024 aluminum alloys  

NASA Astrophysics Data System (ADS)

The precipitation behaviors and aging reactions of the pseudobinary Al-Cu-Mg alloy and the commercial 2024 alloy under unstretched and stretched conditions have been investigated in this study by means of conductivity and hardness measurements, differential scanning calorimetry, and transmission electron microscopy (TEM). The morphologies and growth modes of various defects and transition phases as well as the interaction among them were widely discussed. In particular, an electron diffraction ring pattern was found to correspond to the axial growth of the GPB2 zone. This suggested that the atom groups constructing this cylindrical zone are statistically, uniformly arranged in the adjacent {100}A1 planes and the GPB2 zone is only a partially ordered version of the GPB zone in <001>Al, directions. Moreover, few GPB2 zones can survive long time overaging due to the Gibbs-Thomson effect. As for the S' precipitates, they preferentially nucleate on dislocations. During subsequent growth, they can further coalesce into two morphologies (corrugated sheets and wide plates) for the unstretched specimens. However, for the stretched specimens, this coalescing process does not occur until a long time of overaging due to more introduced dislocations. Therefore, the rate of Ostward ripening decreases and the peak hardness becomes flattened. Finally, based on the present analyses, the aging sequence of the two alloys studied could be revised with respect to previous investigations and their isothermal aging reactions can be subdivided into five main stages. These stages correspond to (1) GPB zone precipitation, (2) fast in situ precipitation of GPB2 zones from GPB zones and their subsequent growth, (3) fast nucleation and accelerating growth of the S' phase, (4) decelerating growth of the S' phase, and (5) Ostward ripening of the S' and S phases, respectively.

Shih, Han-Cheng; Ho, New-Jin; Huang, J. C.

1996-09-01

375

Effects of particle size on the fracture toughness of SiC p\\/Al alloy metal matrix composites  

Microsoft Academic Search

The influences of the SiC particles, constituents and precipitates on the fracture toughness of SiCp\\/Al alloy metal matrix composites have been investigated through both modeling and experimental studies. It has been shown that the model predictions are in reasonable agreement with the experimental data when testing on SiCp\\/Al–Cu–Mg composites. The fracture toughness of the composites decreases with the increase in

Min Song; Baiyun Huang

2008-01-01

376

The effect of sulfate on aluminum concentrations in natural waters: some stability relations in the system Al2O3-SO3-H2O at 298 K  

USGS Publications Warehouse

While gibbsite and kaolinite solubilities usually regulate aluminum concentrations in natural waters, the presence of sulfate can dramatically alter these solubilities under acidic conditions, where other, less soluble minerals can control the aqueous geochemistry of aluminum. The likely candidates include alunogen, Al2(SO4)3 ?? 17H2O, alunite, KAl3(SO4)2(OH)6, jurbanite, Al(SO4)(OH) ?? 5H2O, and basaluminite, Al4(SO4)(OH)10 ?? 5H2O. An examination of literature values shows that the log Ksp = -85.4 for alunite and log Ksp = -117.7 for basaluminite. In this report the log Ksp = -7.0 is estimated for alunogen and log Ksp = -17.8 is estimated for jurbanite. The solubility and stability relations among these four minerals and gibbsite are plotted as a function of pH and sulfate activity at 298 K. Alunogen is stable only at pH values too low for any natural waters (<0) and probably only forms as efflorescences from capillary films. Jurbanite is stable from pH < 0 up to the range of 3-5 depending on sulfate activity. Alunite is stable at higher pH values than jurbanite, up to 4-7 depending on sulfate activity. Above these pH limits gibbsite is the most stable phase. Basaluminite, although kinetically favored to precipitate, is metastable for all values of pH and sulfate activity. These equilibrium calculations predict that both sulfate and aluminum can be immobilized in acid waters by the precipitation of aluminum hydroxysulfate minerals. Considerable evidence supports the conclusion that the formation of insoluble aluminum hydroxy-sulfate minerals may be the cause of sulfate retention in soils and sediments, as suggested by Adams and Rawajfih (1977), instead of adsorption. ?? 1982.

Nordstrom, D. K.

1982-01-01

377

Gd(1.33)Pt(3)(Al,Si)(8) and Gd(0.67)Pt(2)(Al,Si)(5): two structures containing a disordered Gd/Al layer grown in liquid aluminum.  

PubMed

Gd(1.33)Pt(3)Al(8) was synthesized by the combination of Gd and Pt in excess liquid aluminum. Addition of silicon resulted in the incorporation of a small amount of this element into the material to form the isostructural Gd(1.33)Pt(3)Al(7)Si. Both compounds grow as rodlike crystals with hexagonal cross section. The structures were refined in the rhombohedral space group R(-)3m, with cell parameters a = 4.3359(6) A and c = 38.702(8) A for the ternary and a = 4.3280(8) A and c = 38.62(1) A for the quaternary compound. The structure is comprised of stuffed arsenic-like PtAl(2) layers and disordered Gd/Al layers. Analysis of the hk0 zone reflections indicate the presence of an a = radical 3a supercell, but the structure is not ordered along c, as revealed by the highly diffuse reflections in the 0kl zone photos. Therefore, the compounds are disordered variants of the Gd(4)Pt(9)Al(24) type. Magnetic susceptibility studies reveal antiferromagnetic transitions at 15 K for the ternary and 7 K for the quaternary compound. Variation of the reactant ratio produces a different structure comprised of the same structural blocks, including the disordered Gd/Al layer. Gd(0.67)Pt(2)Al(5) and its quaternary analogue Gd(0.67)Pt(2)Al(4)Si form in the hexagonal system P6(3)/mmc with cell parameters a = 4.2907(3) A and c = 16.388(2) A for the ternary and a = 4.2485(6) A and c = 16.156(3) A for the quaternary compound. PMID:12377043

Latturner, S E; Kanatzidis, M G

2002-10-21

378

Aluminum alloy  

NASA Technical Reports Server (NTRS)

This invention relates to aluminum alloys, particularly to aluminum-copper-lithium alloys containing at least about 0.1 percent by weight of indium as an essential component, which are suitable for applications in aircraft and aerospace vehicles. At least about 0.1 percent by weight of indium is added as an essential component to an alloy which precipitates a T1 phase (Al2CuLi). This addition enhances the nucleation of the precipitate T1 phase, producing a microstructure which provides excellent strength as indicated by Rockwell hardness values and confirmed by standard tensile tests.

Blackburn, Linda B. (inventor); Starke, Edgar A., Jr. (inventor)

1989-01-01

379

Effects of acute and chronic coingestion of AlCl3 with citrate or polyphenolic acids on tissue retention and distribution of aluminum in rats.  

PubMed

Aluminum (Al) is toxic to certain biological systems and has been implicated as a neurotoxic agent in the pathogenesis of Alzheimer's disease. Intestinal absorption of Al is very low (0.1%), but many organic dietary components are potential chelators of Al and may enhance its absorption and tissue distribution. We examined the effects of acute and chronic coingestion of AlCl3 with different polyphenolic acids on Al retention and compared to citrate in rats. In experiment 1, animals fasted for 14 h were dosed orally with demineralized water, Al chloride, Al chloride plus sodium citrate, or Al chloride plus a polyphenol acid. Blood samples were taken before and 2 h after the gavage and animals were killed 6 h later. In experiment 2, the rats were adapted on a purified diet for 1 wk and received the following for 4 wk in their experimental diets: AlCl3, except group 1, plus citrate or a polyphenol acid, except groups 1 and 2. Animals were killed and blood and tissues were sampled. In experiment 1, citrate highly enhanced Al absorption and its tissue retention. Gallic and chlorogenic acids significantly increased tibia and kidney Al levels compared to the Al group. In experiment 2, Al levels in the urine were significantly increased in all the Al groups compared to the control group. Significantly higher Al levels in the tibia, kidney, and brain were observed in the citrate group and a significant increase in brain Al level was also noted in the chlorogenic acid group compared to AlCl3 group. This may suggest a possible relation structure-activity of polyphenol acids. However, further studies are necessary to better understand the influence of polyphenol acids on Al metabolism, in particular that of chlorogenic acid. PMID:11049223

Deng, Z; Coudray, C; Gouzoux, L; Mazur, A; Rayssiguier, Y; Pépin, D

2000-09-01

380

Microstructural characterization of U-7Mo/Al-Si alloy matrix dispersion fuel plates fabricated at 500 °C  

NASA Astrophysics Data System (ADS)

The starting microstructure of a dispersion fuel plate will impact the overall performance of the plate during irradiation. To improve the understanding of the as-fabricated microstructures of U-Mo dispersion fuel plates, particularly the interaction layers that can form between the fuel particles and the matrix, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses have been performed on samples from depleted U-7Mo (U-7Mo) dispersion fuel plates with either Al-2 wt.% Si(Al-2Si) or AA4043 alloy matrix. It was observed that in the thick interaction layers, U(Al, Si)3 and U6Mo4Al43 were present, and in the thin interaction layers, (U, Mo) (Al, Si)3, U(Al, Si)4, U3Si3Al2, U3Si5, and possibly USi-type phases were observed. The U3Si3Al2 phase contained some Mo. Based on the results of this investigation, the time that a dispersion fuel plate is exposed to a relatively high temperature during fabrication will impact the nature of the interaction layers around the fuel particles. Uniformly thin, Si-rich layers will develop around the U-7Mo particles for shorter exposure times, and thicker, Si-depleted layers will develop for the longer exposure times.

Keiser, Dennis D., Jr.; Jue, Jan-Fong; Yao, Bo; Perez, Emmanuel; Sohn, Yongho; Clark, Curtis R.

2011-05-01

381

Resonant Waveguiding and Lasing in Structures with InAs Submonolayers in an AlGaAs Matrix.  

National Technical Information Service (NTIS)

This work studies optical properties III-V structures with SML InAs insertions in an AlGaAs matrix. Lasing under photoexcitation is demonstrated for the structure without external optical confinement. Lasing occurs on a low energy side of the exciton reso...

A. F. Tsatsul'nikov A. Y. Egorov B. V. Volovik M. V. Maximov N. N. Ledentsov

1998-01-01

382

Effect of aluminum addition on ductility and yield strength of Fe/sub 3/Al alloys with 0. 5 wt % TiB/sub 2/  

SciTech Connect

Studies have been conducted of the mechanical properties of Fe/sub 3/Al alloys containing 24 to 30 at. % Al, to which 0.5 wt % TiB/sub 2/ was added for grain refinement. In tensile tests conducted at room temperature, it has been found that, as the aluminum content is increased, the yield strength decreases sharply from 760 to 310 MPa. The decrease in yield strength is accompanied by a four-fold increase in room-temperature ductility. Ordered iron aluminides (containing no disordered ..cap alpha.. phase) showed a clear increase in yield strength with temperature above 300/sup 0/C. Their strength reached a maximum around 600/sup 0/C, above which it decreased sharply. All these results are discussed and correlated with stability of superlattice dislocations as a function of aluminum content.

McKamey, C.G.; Horton, J.A.; Liu, C.T.

1986-12-01

383

The Effects of Al2O3 Amount on the Microstructure and Properties of Fe-Cr Matrix Composites  

NASA Astrophysics Data System (ADS)

Iron based matrix composites reinforced with 5 to 25 wt pct of Al2O3 particles were fabricated using the powder metallurgy method. The samples were prepared by mixing at 250 rpm for 30 minutes, uniaxially pressing at 750 MPa and sintering in a vacuum furnace at a temperature of 1373 K (1100 °C) for 2 hours with 10 °C/min heating rate. The optimum amount of reinforcement was determined by evaluating the microstructure, relative density, total porosity, micro Vickers hardness, and wear resistance of the composites. The results and analysis revealed that the micro Vickers hardness and wear resistance of the composites were better after increasing the reinforcement up to 20 wt pct. Increasing the Al2O3 particles to 25 wt pct resulted in a decrease in mechanical properties due to agglomeration of the particles in the matrix, which lowers the interaction between the matrix and reinforcement.

Shamsuddin, Saidatulakmar; Jamaludin, Shamsul Baharin; Hussain, Zuhailawati; Ahmad, Zainal Arifin

2010-12-01

384

Preparation and Characterization of Nicotine–Magnesium Aluminum Silicate Complex-Loaded Sodium Alginate Matrix Tablets for Buccal Delivery  

Microsoft Academic Search

Nicotine (NCT) buccal tablets consisting of sodium alginate (SA) and nicotine–magnesium aluminum silicate (NCT–MAS) complexes\\u000a acting as drug carriers were prepared using the direct compression method. The effects of the preparation pH levels of the\\u000a NCT–MAS complexes and the complex\\/SA ratios on NCT release, permeation across mucosa, and mucoadhesive properties of the tablets\\u000a were investigated. The NCT–MAS complex-loaded SA tablets

Sopaphan Kanjanabat; Thaned Pongjanyakul

2011-01-01

385

Identification of the C 2?–X 2? + band system of AlO in the ultraviolet galvanoluminescence obtained during aluminum anodization  

Microsoft Academic Search

The first galvanoluminescence spectrum in the ultraviolet region obtained during anodization of high purity aluminum samples annealed at temperature above 525°C is presented. An intense broad peak with the maximum at about 31,900cm?1 is assigned to the transitions (some of them heretofore unobserved) between vibrational levels of the C2??X2?+ spectral system of AlO, partly overlapped with the A2?+?X2? system of

Mirjana Sarvan; Miljenko Peric; Ljubiša Zekovi?; Stevan Stojadinovic; Ivan Belca; Marija Petkovic; Becko Kasalica

2011-01-01

386

Comparison of the Booster Interface Temperature in Stainless Steel (SS) V-Channel Versus the Aluminum (Al) Y-Channel Primer Chamber Assemblies (PCAs). Volume 2; Appendices  

NASA Technical Reports Server (NTRS)

NASA's Technical Fellow for Propulsion, requested a technical assessment of the performance improvement achieved by the introduction of the stainless steel (SS) V-channel compared to the aluminum (Al) Y-channel Primer Chamber Assembly (PCA) design. The SS V-channel PCA was developed for NASA's Mars Science Laboratory (MSL) Project. The principle focus of the assessment was to measure the transient temperature at the booster interface with both designs. This document contains the Appendices to the Volume I main report.

Garcia, Roberto; Saulsberry, Regor L.

2011-01-01

387

Brazability of dissimilar metals tungsten inert gas butt welding–brazing between aluminum alloy and stainless steel with Al–Cu filler metal  

Microsoft Academic Search

Dissimilar metals tungsten inert gas butt welding–brazing between 5A06 aluminum alloy and SUS321 stainless steel was carried out using Al–Cu6 filler metal and non-corrosive flux. A thin intermetallic compound layer has formed in welded seam\\/steel interface and the average thickness of the whole layer is 3–5?m, which is less than the limited value of 10?m. The intermetallic compound layer consists

S. B. Lin; J. L. Song; C. L. Yang; C. L. Fan; D. W. Zhang

2010-01-01

388

Development of low-cost, high-strength hot-corrosion-resistant iron aluminum-base alloys. Final report. [Fe--Al--Mo  

Microsoft Academic Search

The report describes attempts to prepare Fe--Al--Mo alloys with sufficient high-temperature strength to be competitive with stainless steels for oxidizing and\\/or hot-corrosive environments and to provide competitive alternatives to superalloys based on domestically produced alloying elements. An 8 percent aluminum alloy, which exhibited good room-temperature ductility, had superior strength at 815C and oxidation resistance equivalent to type 321 stainless steel.

E. R. Duffy; J. F. Nachman

1976-01-01

389

Refractory calcium-aluminum-rich inclusions and aluminum-diopside-rich chondrules in the metal-rich chondrites Hammadah al Hamra 237 and Queen Alexandra Range 94411  

Microsoft Academic Search

The metal-rich chondrites Hammadah al Hamra 237 (HH 237), and QUE 94411 (QUE), paired with QUE 94627, contain relatively rare (< 1 vol%) Ca, Al-rich inclusions (CAIs) and Al-diopside-rich chondrules. Forty CAIs and CAI fragments and 7 Al-diopside-rich chondrules were identified in HH 237 and QUE. The CAIs, ~50-400 mum in apparent diameter, include: (a) 22 (56%) pyroxene-spinel melilite [+forsterite

Alexander N. Krot; Kevin D. McKeegan; Sara S. Russell; Anders Meibom; Michael K. Weisberg; Jutta Zipfel; Tatiana V. Krot; Timothy J. Fagan; Klaus Keil

2001-01-01

390

F/Cl-exchange on AlCl(3)-pyridine adducts: synthesis and characterization of trans-difluoro-tetrakis-pyridine-aluminum-chloride, [AlF2(Py)4]+Cl-.  

PubMed

Whereas liquid CCl3F reacts with solid AlCl3 exothermically under chlorine-fluorine-exchange already above -20 degrees C, no reaction takes place between CCl3F and the pyridine complexes of AlCl3 (AlCl3.Py, AlCl3.2Py, or AlCl3.3Py) up to 100 degrees C. The desired chlorine by fluorine substitution on the monomer AlCl3-pyridine adducts occurs, however, easily using Me3SiF as fluorinating agent. By reacting AlCl3.3Py with Me3SiF (even up to 10-fold stoichiometric excess) in pyridine as a solvent, only two of the three Cl atoms can be substituted by fluorine, leading in good yield to the new "mixed aluminum halide", AlF2Cl.4Py. Actually, it represents the first example of a stable solid donor-acceptor adduct of an aluminum-III halide with two different halogens of defined stoichiometry. It was characterized by multinuclear solid-state NMR (27Al and 19F), IR spectroscopy, as well as single-crystal structure analysis. The new compound has an ionic solid-state structure with helical trans-octahedral [(Py)4AlF2]+ cations and isolated Cl- anions. The comparison of its 27Al MAS solid-state NMR spectra with those of a compound bearing the analogous [(Py)4AlCl2]+ cation reveals an extreme increase in the quadrupolar coupling constants, from 0.24 MHz in case of the chlorine cation to about 16 MHz in case of the new [(Py)4AlF2]+ cation. PMID:17173440

Dimitrov, Anton; Heidemann, Detlef; Kemnitz, Erhard

2006-12-25

391

Effects of isothermal and cyclic exposures on interface structure and mechanical properties of FPalpha-Al2O3/aluminum composites. [polycrystaline alumina fibers  

NASA Technical Reports Server (NTRS)

The microstructural and interface stability of FPalpha-Al203/Al-Li composites are investigated as a function of isothermal exposure at 500 C or thermal cycling between 140 and 500 C with hold time at Tmax. Interfacial morphology, growth kinetics, crystal structure, and composition of interfacial reaction products are characterized. Strength is monitored in the transverse orientation, and fracture mechanics is analyzed in terms of interface reaction products. The interfacial reaction product in FP/Al is Li2O.5Al2O3. Significant fiber-matrix reaction occurs during fabrication. The number of thermal cycles rather than total time at Tmax is the determining factor in strength degradation, thermal cycling giving rise to voids at the fiber-matrix interface. Extensive interface failures occur at composite fracture stresses below about 128 MPa; above this stress level failure is attributed to ductile matrix fracture.

Kim, W. M.; Koczak, M. J.; Lawley, A.

1979-01-01

392

Liquid oxygen LOX compatibility evaluations of aluminum lithium (Al-Li) alloys: Investigation of the Alcoa 2090 and MMC weldalite 049 alloys  

NASA Technical Reports Server (NTRS)

The behavior of liquid oxygen (LOX) compatibility of aluminum lithium (Al-Li) alloys is investigated. Alloy systems of Alcoa 2090, vintages 1 to 3, and of Martin Marietta Corporation (MMC) Weldalite 049 were evaluated for their behavior related to the LOX compatibility employing liquid oxygen impact test conditions under ambient pressures and up to 1000 psi. The developments of these aluminum lithium alloys are of critical and significant interest because of their lower densities and higher specific strengths and improved mechanical properties at cryogenic temperatures. Of the different LOX impact tests carried out at the Marshall Space Flight Center (MSFC), it is seen that in certain test conditions at higher pressures, not all Al-Li alloys are LOX compatible. In case of any reactivity, it appears that lithium makes the material more sensitive at grain boundaries due to microstructural inhomogeneities and associated precipitate free zones (PFZ). The objectives were to identify and rationalize the microstructural mechanisms that could be relaxed to LOX compatibility behavior of the alloy system in consideration. The LOX compatibility behavior of Al-Li 2090 and Weldalite 049 is analyzed in detail using microstructural characterization techniques with light optical metallography, scanning electron microscopy (SEM), electron microprobe analysis, and surface studies using secondary ion mass spectrometry (SIMS), electron spectroscopy in chemical analysis (ESCA) and Auger electron spectroscopy (AES). Differences in the behavior of these aluminum lithium alloys are assessed and related to their chemistry, heat treatment conditions, and microstructural effects.

Diwan, Ravinder M.

1989-01-01

393

Synthesis and Characterization of Aluminum-Nanodiamond Composite Powders by High Energy Ball Milling.  

National Technical Information Service (NTIS)

High-energy ball milling was studied for the ex situ strengthening of aluminum (Al) with nanodiamond (ND). Al-ND metal matrix composite powders with 5 wt% and 10 wt% nanodiamond were synthesized by high-energy ball milling of the blended component powders...

B. D. Sneed

2011-01-01

394

CHARACTERIZATION AND PROPERTIES OF ALUMINUM COMPOSITE MATERIALS PREPARED BY POWDER METALLURGY TECHNIQUES USING CERAMIC SOLID WASTES  

Microsoft Academic Search

This work provides preliminary results of aluminum metal matrix composites (MMCs) reinforced with granulated slag (GS) and electric arc furnace dust (EAFD). The present work concerns the synthesis and properties of Al\\/GS and Al\\/EAFD composites based on powder metallurgy techniques. The hardness and compressive strength of the sintering compacts were determined to compare the mechanical properties of the composite material

L. Ma. Flores-Vélez; J. Chávez; L. Hernández; O. Domínguez

2001-01-01

395

Load partitioning in aluminum syntactic foams containing ceramic microspheres  

Microsoft Academic Search

Syntactic foams were fabricated by pressure-infiltrating liquid aluminum (commercial purity and 7075-Al) into a packed preform of silica–mullite hollow microspheres. These foams were subjected to a series of uniaxial compression stresses while neutron or synchrotron X-ray diffraction measurements of elastic strains in the matrix and the microspheres were obtained. As for metal matrix composites with monolithic ceramic reinforcement, load transfer

Dorian K. Balch; David C. Dunand

2006-01-01

396

Investigation of an efficient YbF 3\\/Al cathode for tris-(8-hydroxyquinoline)aluminum-based small molecular organic light-emitting diodes  

Microsoft Academic Search

Efficient tris-(8-hydroxyquinoline)aluminum (Alq3)-based organic light-emitting diodes (OLEDs) using YbF3 as the electron injection layer have been investigated. With an YbF3 (3.0nm)\\/Al cathode, the device with Alq3 as the emitting layer achieved a better performance than the control device with a LiF (0.5nm)\\/Al cathode. The release of the low-work-function metal Yb is responsible for the performance enhancement. From the analysis by

Yang Li; Lian Duan; Qian Liu; Rui Zhang; Deqiang Zhang; Liduo Wang; Juan Qiao; Yong Qiu

2008-01-01

397

Adhesive strength of nano-size particles filled thermoplastic polyimides. Part-II: Aluminum nitride (AlN) nano-powder–polyimide composite films  

Microsoft Academic Search

Adhesive properties of thermoplastic polyimides (PI) filled with aluminum nitride (AlN) nano-powder are investigated. Two PIs, one amorphous (oxydiphthalic anhydride (ODPA)\\/3,4?-oxydianiline (3,4?-ODA)\\/phthalic anhydride (PA)) and the other a semi-crystalline (3,3?,4,4?-biphenyltetracarboxylic dianhydride (BPDA)\\/3,4?-ODA\\/PA) are synthesized via two-step method involving formation of poly(amide acid) (PAA) followed by thermal or chemical imidization to obtain PI in film or powder forms, respectively. AlN in

M. B. Saeed; Mao-Sheng Zhan

2007-01-01

398

Aluminum reference electrode  

DOEpatents

A stable reference electrode is described for use in monitoring and controlling the process of electrolytic reduction of a metal. In the case of Hall cell reduction of aluminum, the reference electrode comprises a pool of molten aluminum and a solution of molten cryolite, Na[sub 3]AlF[sub 6], wherein the electrical connection to the molten aluminum does not contact the highly corrosive molten salt solution. This is accomplished by altering the density of either the aluminum (decreasing the density) or the electrolyte (increasing the density) so that the aluminum floats on top of the molten salt solution. 1 fig.

Sadoway, D.R.

1988-08-16

399

Aluminum reference electrode  

DOEpatents

A stable reference electrode for use in monitoring and controlling the process of electrolytic reduction of a metal. In the case of Hall cell reduction of aluminum, the reference electrode comprises a pool of molten aluminum and a solution of molten cryolite, Na.sub.3 AlF.sub.6, wherein the electrical connection to the molten aluminum does not contact the highly corrosive molten salt solution. This is accomplished by altering the density of either the aluminum (decreasing the density) or the electrolyte (increasing the density) so that the aluminum floats on top of the molten salt solution.

Sadoway, Donald R. (Belmont, MA)

1988-01-01

400

Characterization of tool wear and weld optimization in the friction-stir welding of cast aluminum 359+20% SiC metal-matrix composite  

Microsoft Academic Search

Tool wear for threaded steel pin tools declines with decreasing rotation speed and increasing traverse or weld speeds for the friction-stir welding (FSW) of Al 359+20% SiC metal-matrix composite (MMC). Less than 10% tool wear occurs when the threaded tool erodes to a self-optimized shape resembling a pseudo-hour glass at weld traverse distances in excess of 3 m. There is

G. J. Fernandez; L. E Murr

2004-01-01

401

Deformation and fracture behavior of beams composed of aluminum foam core and ceramic Al2O3 under monolithic bending  

NASA Astrophysics Data System (ADS)

Deformation and fracture mechanisms of sandwich and multilayer beams composed of aluminum foam core and ceramic face sheets under four-point bending condition were investigated in situ by surface displacement analysis (SDA) software. The toughening mechanism of the beams was discussed and a model was given for the computation of the fracture energy of the beams. Beams containing foam core with 5-, 10-, and 20-mm thickness and Al2O3 face sheets of 0.5-and 1-mm thickness were prepared. The results show that collapse of the beams is by two basic modes, indentation (ID) and face plate failure (PF). The SDA results illustrated that indentation is localized compression on the portion of the beam adjacent to the loading rollers, where displacement and strain are at the maximum. In PF, the beam entirely bends. It is also found that before collapse of the beams with pure PF mode, the foam core undergoes uniform compressive deformation, which contributes most to the fracture energy of the beams. As for the beams with ID characteristic, the localized compressive deformation plays a key role rather than the uniform compressive deformation in the fracture energy of the beam. The total fracture energy W of a beam under bending condition is proposed as W= W UC+ W LC+ W CB+ W PF where W UCis the energy of uniform compressive deformation of the foam core, W LCis the energy of localized compression of the foam core and W CBand W PFare the bending fracture energy of the monolithic foam core and ceramic face sheet, respectively. For the beams with pure PF mode, W LCis zero. The estimated values of the fracture energy are in good agreement with the measured fracture energy of the beams.

Sha, J. B.; Yip, T. H.

2005-03-01

402

Elastic modulus of Al-Si/SiC metal matrix composites as a function of volume fraction  

NASA Astrophysics Data System (ADS)

Aluminum alloy matrix composites have emerged as candidate materials for electronic packaging applications in the field of aerospace semiconductor electronics. Composites prepared by the pressureless infiltration technique with high volume fractions in the range 0.41-0.70 were studied using ultrasonic velocity measurements. For different volume fractions of SiC, the longitudinal velocity and shear velocity were found to be in the range of 7600-9300 m s-1 and 4400-5500 m s-1, respectively. The elastic moduli of the composites were determined from ultrasonic velocities and were analysed as a function of the volume fraction of the reinforcement. The observed variation is discussed in the context of existing theoretical models for the effective elastic moduli of two-phase systems.

Santhosh Kumar, S.; Bai, V. Seshu; Rajkumar, K. V.; Sharma, G. K.; Jayakumar, T.; Rajasekharan, T.

2009-09-01

403

Functional, structural and phylogenetic analysis of domains underlying the Al sensitivity of the aluminum-activated malate/anion transporter, TaALMT1.  

PubMed

Triticum aestivum aluminum-activated malate transporter (TaALMT1) is the founding member of a unique gene family of anion transporters (ALMTs) that mediate the efflux of organic acids. A small sub-group of root-localized ALMTs, including TaALMT1, is physiologically associated with in planta aluminum (Al) resistance. TaALMT1 exhibits significant enhancement of transport activity in response to extracellular Al. In this study, we integrated structure-function analyses of structurally altered TaALMT1 proteins expressed in Xenopus oocytes with phylogenic analyses of the ALMT family. Our aim is to re-examine the role of protein domains in terms of their potential involvement in the Al-dependent enhancement (i.e. Al-responsiveness) of TaALMT1 transport activity, as well as the roles of all its 43 negatively charged amino acid residues. Our results indicate that the N-domain, which is predicted to form the conductive pathway, mediates ion transport even in the absence of the C-domain. However, segments in both domains are involved in Al(3+) sensing. We identified two regions, one at the N-terminus and a hydrophobic region at the C-terminus, that jointly contribute to the Al-response phenotype. Interestingly, the characteristic motif at the N-terminus appears to be specific for Al-responsive ALMTs. Our study highlights the need to include a comprehensive phylogenetic analysis when drawing inferences from structure-function analyses, as a significant proportion of the functional changes observed for TaALMT1 are most likely the result of alterations in the overall structural integrity of ALMT family proteins rather than modifications of specific sites involved in Al(3+) sensing. PMID:24188189

Ligaba, Ayalew; Dreyer, Ingo; Margaryan, Armine; Schneider, David J; Kochian, Leon; Piñeros, Miguel

2013-12-01

404

A process model for friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites; 1: HAZ temperature and strain rate distribution  

SciTech Connect

The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. In Part 1 the different components of the model are outlined and analytical solutions presented which provide quantitative information about the HAZ temperature distribution for a wide range of operational conditions. Moreover, a general procedure for modeling the HAZ strain rate distribution has been developed by introducing a series of kinematically admissible velocity equations which describe the material flow fields in the radial, the rotational, and the axial direction, respectively. Calculations performed for both types of materials show that the effective strain rate may exceed 1,000 s[sup [minus]1] in positions close to the contact section due to the high rotational velocities involved. Application of the model for evaluation of the response of Al-Mg-Si alloys and Al-SiC metal matrix composites to the imposed heating and plastic deformation is described in an accompanying paper (Part 2).

Midling, O.T. (SINTEF, Trondheim (Norway). Div. of Metallurgy); Grong, Oe. (Univ. of Trondheim (Norway). Norwegian Inst. of Tech.)

1994-05-01

405

Process model for friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. Part 1: HAZ temperature and strain rate distribution  

NASA Astrophysics Data System (ADS)

The present investigation is concerned with the development of an overall process model for the microstructure and strength evolution during continuous drive friction welding of Al-Mg-Si alloys and Al-SiC metal matrix composites. In Part 1 the different components of the model are outlined and analytical solutions presented which provide quantitative information about the HAZ temperature distribution for a wide range of operational conditions. Moreover, a general procedure for modeling the HAZ strain rate distribution has been developed by introducing a series of kinematically admissible velocity equations which describe the material flow fields in the radial, the rotational, and the axial direction, respectively. Calculations performed for both types of materials show that the effective strain rate may exceed 1000 s(exp -1) in positions close to the contact section due to the high rotational velocities involved. Application of the model for evaluation of the response of Al-Mg-Si alloys and Al-SiC metal matrix composites to the imposed heating and plastic deformation is described in an accompanying paper (Part 2).

Midling, O. T.; Grong, O.

1994-05-01

406

Laser-induced spallation of aluminum and Al alloys at strain rates above 2x10{sup 6} s{sup -1}  

SciTech Connect

Material microstructure is a significant determinant of the tensile stress at which materials fail. Using a high-energy laser to drive shocks in thin slabs, we have explored the role material microstructure plays on the spall strength of high-purity and alloyed aluminum at strain rates of (2-7.5)x10{sup 6} s{sup -1}. Slabs of pure recrystallized Al and recrystallized or cold worked Al+3 wt % Mg were shock driven using the Z-Beamlet Laser at Sandia National Laboratories. Velocity interferometer measurements determined the spall strength of the materials, and postshot target analysis explored the microscopic fracture morphology. We observed the greatest spall strength for large-grained, recrystallized high-purity aluminum, with the dominant failure mode being ductile and transgranular. We observe for the first time at these strain rates fracture features for a fine-grained Al+3 wt % Mg that were a combination of brittle intergranular and ductile transgranular fracture types. Postshot analysis of target cross sections and hydrocode simulations indicate that this mixed-mode failure results from spall dynamics occurring on spatial scales on the order of the grain size. Differences in spall strength between these Al samples were experimentally significant and correlate with the damage morphologies observed.

Dalton, D. A.; Bernstein, A. C.; Grigsby, W.; Milathianaki, D.; Ditmire, T. [Texas Center for High Intensity Laser Science, Department of Physics, University of Texas, Austin, Texas 78712 (United States); Brewer, J. L. [Stress Engineering Services Inc., Houston, Texas 77041 (United States); Jackson, E. D.; Taleff, E. M. [Department of Mechanical Engineering, University of Texas, Austin, Texas 78712 (United States); Adams, R. G.; Rambo, P.; Schwarz, J.; Edens, A.; Geissel, M.; Smith, I. [Z-Backlighter Facility, Sandia National Laboratories, Albuquerque, New Mexico, 87185 (United States)

2008-07-01

407

Interface structure in carbon and graphite fiber reinforced 2014 aluminum alloy processed with active fiber cooling  

Microsoft Academic Search

The fiber\\/matrix interfaces developed in continuous carbon fiber (CF) and graphite fiber (GRF) reinforced 2014 aluminum matrix composites were characterized using scanning and transmission electron microscopy (TEM). The as-cast CF\\/2014 Al and GRF\\/2014 Al composite specimens were processed by pressure infiltration of continuous fiber bundles preheated at 500°C, while the fiber reinforcements were externally cooled during infiltration by exposing fiber

H. G. Seong; H. F. Lopez; D. P. Robertson; P. K. Rohatgi

2008-01-01

408

In-situ processing of aluminum nitride particle reinforced aluminum alloy composites  

NASA Astrophysics Data System (ADS)

Discontinuously reinforced aluminum alloy composites (DRACs) have potential applications in automotive, electronic packaging, and recreation industries. Conventional processing of DRACs is by incorporation of ceramic particles/whiskers/fibers into matrix alloys. Because of the high cost of ceramic particles, DRACs are expensive. The goal of this work was to develop a low-cost route of AlN-Al DRACs processing through bubbling and reacting nitrogen and ammonia gases with aluminum alloy melt in the temperature range of 1373--1523 K. Thermodynamic analysis of AlN-Al alloy system was performed based on Gibbs energy minimization theory. AlN is stable in aluminum, Al-Mg, Al-Si, Al-Zn, and Al-Li alloys over the whole temperature range for application and processing of DRACs. Experiments were carried out to form AlN by bubbling nitrogen and ammonia gases through aluminum, Al-Mg, and Al-Si alloy melts. Products were characterized with XRD, SEM, and EDX. The results showed that in-situ processing of AlN reinforced DRACs is technically feasible. Significant AlN was synthesized by bubbling deoxidized nitrogen and ammonia gases. When nitrogen gas was used as the nitrogen precursor, the AlN particles formed in-situ are small in size, (<10 mum). The formation of AlN is strongly affected by the trace oxygen impurities in the nitrogen gas. The deleterious effect of oxygen impurities is due to their inhibition to the chemisorption of nitrogen gas at the interface. In comparison with nitrogen gas, bubbling ammonia led to formation of AlN particles in smaller size (about 2 mum or less) at a significantly higher rate. Ammonia is not stable and dissociated into nitrogen and hydrogen at reaction temperatures. The hydrogen functions as oxygen-getter at the interface and benefits chemisorption of nitrogen, thereby promoting the formation of AlN. The overall process of AlN formation was modeled using two-film model. For nitrogen bubbling gas, the whole process is controlled by chemisorption of nitrogen molecules at the gas bubble - aluminum melt interface. For ammonia precursor, the rate of the overall process is limited by the mass transfer of nitrogen atoms in the liquid boundary layer. The models agree well with the experimental results.

Zheng, Qingjun

409

Synthesis and atomic-level characterization of Ni nanoparticles in Al2O3 matrix  

Microsoft Academic Search

Single domain magnetic nickel nanocrystals were embedded in alumina matrix using a pulsed-laser deposition technique. Structural characterization carried out at the atomic level using scanning transmission electron microscopy with atomic number contrast (STEM-Z) in conjunction with electron energy loss spectroscopy have revealed that the Ni particles are well separated and have interfaces with the host matrix that are atomically sharp

D. Kumar; S. J. Pennycook; A. Lupini; G. Duscher; A. Tiwari; J. Narayan

2002-01-01

410

Reliability in room-temperature negative differential resistance characteristics of low-aluminum content AlGaN/GaN double-barrier resonant tunneling diodes  

NASA Astrophysics Data System (ADS)

AlGaN/GaN resonant tunneling diodes (RTDs), consisting of 20% (10%) aluminum-content in double-barrier (DB) active layer, were grown by metal-organic chemical vapor deposition on freestanding polar (c-plane) and nonpolar (m-plane) GaN substrates. RTDs were fabricated into 35-?m-diameter devices for electrical characterization. Lower aluminum content in the DB active layer and minimization of dislocations and polarization fields increased the reliability and reproducibility of room-temperature negative differential resistance (NDR). Polar RTDs showed decaying NDR behavior, whereas nonpolar ones did not significantly. Averaging over 50 measurements, nonpolar RTDs demonstrated a NDR of 67 ?, a current-peak-to-valley ratio of 1.08, and an average oscillator output power of 0.52 mW.

Bayram, C.; Vashaei, Z.; Razeghi, M.

2010-11-01

411

Irradiation performance of U-Mo-Ti and U-Mo-Zr dispersion fuels in Al-Si matrixes  

NASA Astrophysics Data System (ADS)

Performance of U-7 wt.%Mo with 1 wt.%Ti, 1 wt.%Zr or 2 wt.%Zr, dispersed in an Al-5 wt.%Si alloy matrix, was investigated through irradiation tests in the ATR at INL and HANARO at KAERI. Post-irradiation metallographic features show that the addition of Ti or Zr suppresses interaction layer growth between the U-Mo and the Al-5 wt.%Si matrix. However, higher fission gas swelling was observed in the fuel with Zr addition, while no discernable effect was found in the fuel with Ti addition as compared to U-Mo without the addition. Known to have a destabilizing effect on the ?-phase U-Mo, Zr, either as alloy addition or fission product, is ascribed for the disadvantageous result. Considering its benign effect on fuel swelling, with slight disadvantage from neutron economy point of view, Ti may be a better choice for this purpose.

Kim, Yeon Soo; Hofman, G. L.; Robinson, A. B.; Wachs, D. M.; Ryu, H. J.; Park, J. M.; Yang, J. H.

2012-08-01

412

Closo-alanes (Al4H4, AlnHn+2, 4 aluminum hydride chemistry.  

PubMed

Anion photoelectron spectroscopy and density functional theory were employed to study aluminum hydride clusters, AlnHm- (4 Al4H4, Al4H6, and a family of species with general formula AlnHn+2 (5 aluminum versions of hypothetical diprotonated closo-borane dianions (BnHn2- + 2H+). In addition, Al4H4 assumes a closo-tetrahedral geometry, while Al4H6 takes on a distorted tetrahedral (D2d) structure with two counter-positioned bridging hydrogen atoms and has the largest HOMO-LUMO gap (1.9 eV) of all the alanes we studied. All of these species can be understood in terms of underlying polyhedral skeletal electron pair theory (PSEPT) concepts. Although, the herein studied alanes do not have direct borane analogues, the ability to understand their structures in terms of the Wade-Mingos rules and the underlying PSEPT concepts suggests that they can be considered as borane analogues, thereby opening a new chapter in aluminum hydride chemistry. PMID:17439121

Grubisic, A; Li, X; Stokes, S T; Cordes, J; Ganteför, G F; Bowen, K H; Kiran, B; Jena, P; Burgert, R; Schnöckel, H

2007-05-01

413

Extrusion and mechanical properties of mixed powder and spray co-deposited Al 2014\\/SiC metal matrix composites  

Microsoft Academic Search

Al 2014\\/SiCp metal matrix composites have been produced by a powder metallurgy route that included mixing, canning, degassing and hot extrusion (300°C, 16:1). Two types of SiC (12 and 4 µm), two SiC contents (~ 10 vol. % and ~ 15 vol. %) and three different degassing temperatures (350, 400, 500 °C) were used. The degassing temperature was found to

M. H. Carvalho; T. Marcelo; H. Carvalhinhos; C. M. Sellars

1992-01-01

414

Hot-deformation behaviour of spray-formed 2014 Al + SiC P metal matrix composites  

Microsoft Academic Search

In the present investigation, discontinuous SiC particle reinforced 2014 Al alloy based metal matrix composites have been produced by spray forming process. The composites contained average particle sizes of 17, 30 and 58?m in the range of 5–11vol.%. The composites were tested for their compressive flow behaviour, in unlubricated condition, at strain rates of 0.01, 0.1 and 1.0s?1 and at

V. C. Srivastava; V. Jindal; V. Uhlenwinkel; K. Bauckhage

2008-01-01

415

Nondestructive evaluation of damage in SiC/Al metal matrix composite using x ray tomographic microscopy  

SciTech Connect

A fundamental understanding of damage evolution will be required before metal matrix composites (MMC) can be utilized safely for structural applications. Although macroscopic mechanical response to cyclic loading has been monitored in many mechanical and thermal test programs, little is known about the nucleation and growth of damage in MMC's. The goal of the present work is to improve the understanding of damage accumulation in SiC/Al using a new microscopic non-destructive volume-imaging technique, X-ray Tomographic Microscopy (XTM), which has resolution comparable to optical microscopy. Correlation of damage initiation and accumulation mechanisms and the macroscopic mechanical response of samples are discussed for continuous fiber SiC/Al MMC's. A series of mechanical tests were performed on a continuous, aligned fiber SiC/Al MMC, and the ensuing three-dimensional damage state was nondestructively characterized using XTM to map the x-ray absorptivity within the sample. The types of damage detected include: fiber fracture (SiC sheath, and C core), fiber-matrix interface microcracking, intra-ply matrix voids, and cracks. Quantitative three-dimensional measurements of damage are reported in as-fabricated, monotonically loaded and mechanically fatigue loaded SiC/Al. The XTM results indicate that increases in observed macroscopic structural stiffness during monotonic loading and the first few fatigue cycles of an MMC coupon correspond to elimination of processing-related matrix porosity and to displacement of the fibers from a somewhat irregular arrangement into a more nearly hexagonal array. The XTM of monotonically loaded samples also show that the carbon cores begin to fracture at or below 828 MPa, that is, at loads far less than those for fracture of the entire fiber. The fracture of the SiC sheath appears to be significantly affected by the fracture of the C cores.

Breunig, T.M.

1992-01-01

416

Chemical reactions between aluminum and fly ash during synthesis and reheating of Al-fly ash composite  

SciTech Connect

Thermodynamic analysis indicates that there is the possibility of chemical reactions between aluminum melt and cenosphere fly ash particles. These particles contain alumina, silica, and iron oxide, which, during solidification processing of aluminum-fly ash composites or during holding of such composites at temperatures above the melting temperature of the aluminum, are likely to undergo chemical reduction. These chemical reactions between the fly ash and molten aluminum have been studied by metallographic examination, differential thermal analysis (DTA), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and X-ray analysis after holding the aluminum-fly ash composites for different periods above the liquidus temperature. The experiments indicate that there is progressive reduction of silica and mullite in the fly ash, and formation of alumina with holding time of composites at a temperature of 850 C. The walls of the cenosphere fly ash particles progressively disintegrate into discrete particles as the reaction progresses. The rate of chemical reaction was high at the start of holding the composite at a temperature of 850 C, and then the rate significantly decreased with time. The reaction was almost complete after 10 hours.

Guo, R.Q.; Rohatgi, P.K. [Univ. of Wisconsin, Milwaukee, WI (United States). Dept. of Materials

1998-06-01

417

Microstructure and high-temperature oxidation resistance of TiN\\/Ti3Al intermetallic matrix composite coatings on Ti6Al4V alloy surface by laser cladding  

Microsoft Academic Search

A high-temperature oxidation resistant TiN embedded in Ti3Al intermetallic matrix composite coating was fabricated on titanium alloy Ti6Al4V surface by 6kW transverse-flow CO2 laser apparatus. The composition, morphology and microstructure of the laser clad TiN\\/Ti3Al intermetallic matrix composite coating were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to

Xiaowei Zhang; Hongxi Liu; Chuanqi Wang; Weihua Zeng; Yehua Jiang

2010-01-01

418

Effects of tool geometry and welding rates on the tool wear behavior and shape optimization in friction stir welding of aluminum alloy 6061 + 20% aluminum oxide MMC  

Microsoft Academic Search

FSW is a new solid-state process currently being investigated for joining aluminum alloys that are difficult to weld, where there is no perceptible wear of the pin tool throughout the experiment. The present report investigates and examines tool wear in the friction-stir welding of Al 6061-T6 and Al 6061-T6 containing 20% (volume) Al2O3 particles, a metal matrix composite (MMC), in

Rafael Arcangel Prado

2005-01-01

419

The Chemical Nature of Aluminum Corrosion. I. Activation of Aluminum Surfaces by Aluminum Salts.  

National Technical Information Service (NTIS)

The activation of aluminum surfaces (alloys 1199-H14 and 7075-T6) by solutions of Al(NO3)3, AlBr3, AlCl3, Al2' SO4)2, Al(ClO4)3, AlI3, and NaCl of various concentrations has been measured. Experiments were also conducted in saturated solutions of aluminum...

K. Sotoudeh R. T. Foley B. F. Brown

1979-01-01

420

In-situ scanning electron microscope studies of crack growth in an aluminum metal-matrix composite  

NASA Technical Reports Server (NTRS)

Edge-notched specimens of a cast and extruded Al alloy-based, alumina particulate-reinforced composite in the annealed condition were tested in situ in a SEM apparatus equipped with a deformation stage permitting the direct observation of crack growth phenomena. Fracture in this composite is seen to proceed by initiation of microcracks ahead of the macrocrack; as deformation proceeds, the microcracks lengthen, and crack propagation occurs when the region of intense plastic straining becomes comparable to the macrocrack-microcrack distance. The sequence is then repeated.

Manoharan, M.; Lewandowski, J. J.

1990-01-01

421

Comparison of post-detonation combustion in explosives incorporating aluminum nanoparticles: Influence of the passivation layer  

NASA Astrophysics Data System (ADS)

Aluminum nanoparticles and explosive formulations that incorporate them have been a subject of ongoing interest due to the potential of aluminum particles to dramatically increase energy content relative to conventional organic explosives. We have used time-resolved atomic and molecular emission spectroscopy to monitor the combustion of aluminum nanoparticles within the overall chemical dynamics of post-detonation fireballs. We have studied the energy release dynamics of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) charges incorporating three types of aluminum nanoparticles: commercial oxide-passivated nanoparticles, oleic acid-capped aluminum nanoparticles (AlOA), and nanoparticles in which the oxide shell of the particle has been functionalized with an acrylic monomer and copolymerized into a fluorinated acrylic matrix (AlFA). The results indicate that the commercial nanoparticles and the AlFA nanoparticles are oxidized at a similar rate, while the AlOA nanoparticles combust more quickly. This is most likely due to the fact that the commercial nano-Al and the AlFA particles are both oxide-passivated, while the AlOA particles are protected by an organic shell that is more easily compromised than an oxide layer. The peak fireball temperatures for RDX charges containing 20 wt. % of commercial nano-Al, AlFA, or AlOA were ~3900 K, ~3400 K, and ~4500 K, respectively.

Lewis, W. K.; Rumchik, C. G.; Smith, M. J.; Fernando, K. A. S.; Crouse, C. A.; Spowart, J. E.; Guliants, E. A.; Bunker, C. E.

2013-01-01

422

Effect of manganese supersaturation on texture and earing behavior of aluminum alloys. [Al alloys 5005, 5050, and 3004  

Microsoft Academic Search

Using the strip and ingot cast aluminum alloys 5005, 5050 and 3004, the rolling and annealing texture development is studied from the cast to the final sheet condition. The effects of the degree of supersaturation, of precipitate particles and the rolling temperature in the evolution of textures has been revealed.

T. C. Sun; J. G. Morris; H. D. Merchant

2008-01-01

423

Precipitation hardening processes in an Al–0.4%Mg–1.3%Si–0.25%Fe aluminum alloy  

Microsoft Academic Search

Aluminum alloys containing Mg and Si as the major solutes are strengthened by precipitation of the metastable precursors of the equilibrium ? (Mg2Si) phase in one or more sequences. There are several metastable particles that can form during ageing, but the strengthening potential of these particles relative to one another is not extensively studied. In this paper, the precipitation and

A. K. Gupta; D. J. Lloyd; S. A. Court

2001-01-01

424

High-strength powder metallurgy aluminum alloys in glass-forming Al-Ni-Ce-(Ti or Zr) systems  

Microsoft Academic Search

Powder metallurgy (P\\/M) aluminum alloys with high mechanical strengths have been developed by taking advantage of rapid solidification (RS). The improved strengths result from structural modifications such as reduction of segregation, refinement of grain size and increase in solid solubility limit which mainly depend on the amount of undercooling of melt. To produce crystalline alloys with a refined structure, few

Y. Kawamura; A. Inoue; K. Sasamori; T. Masumoto

1993-01-01

425

Experimental Investigations of Material Models for Ti-6Al-4V Titanium and 2024-T3 Aluminum.  

National Technical Information Service (NTIS)

The report describes studies of the deformation and failure behavior of Ti-6A1-4V titanium and 2024-T3 aluminum. This work was accomplished by the Lawrence Livermore National Laboratory under an Interagency Agreement between the Federal Aviation Administr...

D. R. Lesuer

2000-01-01

426

The containment of oil spills in porous media using xanthan/aluminum solutions, gelled by gaseous CO2 or by AlCl3 solutions.  

PubMed

The gelation in situ of polymers may be a method for temporarily containing organic solvents and other petroleum derived products, which may enter the subsurface. In order to create gels that are neither toxic to humans nor to the ecosystem, we have investigated on the use of the biopolymer xanthan gum with aluminum as a crosslinking agent. Firstly we have considered xanthan/sodium aluminate solutions, which upon preparation are strongly basic and do not gel. The gelation takes place in acid solutions so that Al(III) ions are released, and is instantaneous. Therefore, a special technique must be used for generating the gel structure in situ. The un-gelled solution must be injected and an acid must be added afterwards. We have investigated on the gelling reaction induced by gaseous carbon dioxide, which is an acid gas. The insufflation of CO(2) above the solution generates a layer of gel whose thickness progressively increases as CO(2) diffuses in the polymer solution. Secondly we have investigated on the use of aluminum chloride as the source of Al(III) ions. Also in this case, due to the full availability of Al(III) ions, the gelling reaction would be instantaneous. Therefore, the solution of AlCl(3) must be added on the top of the xanthan solution after its injection. For both gelling systems we have studied both theoretically and experimentally the rate of formation of the gel layer which progressively thickens after the insufflation of CO(2) or after the addition of the AlCl(3) solution. PMID:16935417

Gioia, Francesco; Ciriello, Pier Paolo

2006-12-01

427