These are representative sample records from Science.gov related to your search topic.
For comprehensive and current results, perform a real-time search at Science.gov.
1

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

2

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

3

Recycling of aluminum matrix composites  

Microsoft Academic Search

Separation of matrix metals in composites was tried on alumina short fiber-reinforced aluminum and 6061 alloy composites and\\u000a SiC whisker-reinforced 6061 alloy composite for recycling. It is possible to separate molten matrix metals from fibers in\\u000a the composites using fluxes that are used for melt treatment to remove inclusions. About 50 vol pct of the matrix metals was\\u000a separated from

Yoshinori Nishida; Norihisa Izawa; Yukio Kuramasu

1999-01-01

4

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.

2014-10-01

5

Aluminum matrix composites and their superplasticity  

SciTech Connect

This paper introduces in simple terms manufacturing methods associated with aluminum matrix composite materials, superplasticity research as well as its applications, and probes structural faults during the manufacturing of aluminum matrix composite materials. In conjunction with this, it brings together a crossing of subjects to expound on trends in the development of research on aluminum matrix composite material superplasticity and its applications.

Tang, C.; Li, S.; Li, H.

1995-05-26

6

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

7

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

8

The effect of strain rate on the tensile properties of an Al[sub 2]O[sub 3p]\\/6061-T6 aluminum metal-matrix composite at low temperatures  

Microsoft Academic Search

Alumina (Al[sub 2]O[sub 3]) particles reinforced aluminum matrix composites have recently become candidates for structural materials because of their good specific modulus and strength, and are considered to be valuable materials for aerospace and automobile industry applications. In view of such application, they might be processed or applied in high strain rate loading conditions, such as explosive forming, blast loading

Chia Chaw Perng; Jiun Ren Hwang; Ji Liang Doong

1993-01-01

9

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

10

Joining of 6061 Aluminum Matrix-Ceramic Particle Reinforced Composites  

E-print Network

) ) Joining of 6061 Aluminum Matrix-Ceramic Particle Reinforced Composites by R. Kiehn and T. W Appendix B .............. . .. ... ... ........ .. 26 Abstract Thejoining of6061 aluminum reinforced in a suitable thin sheet form, these alloys could produce reliablejoints at lower brazing temperatures

Eagar, Thomas W.

11

The effect of strain rate on the tensile properties of an Al[sub 2]O[sub 3p]/6061-T6 aluminum metal-matrix composite at low temperatures  

SciTech Connect

Alumina (Al[sub 2]O[sub 3]) particles reinforced aluminum matrix composites have recently become candidates for structural materials because of their good specific modulus and strength, and are considered to be valuable materials for aerospace and automobile industry applications. In view of such application, they might be processed or applied in high strain rate loading conditions, such as explosive forming, blast loading and metalworking, etc. Knowledge of the mechanical behavior of the metal matrix composites under high strain rate loading is a prerequisite. However, not much work related to this topic has been done. The objective of this study was to investigate the effect of the strain rate on the tensile properties of the Al[sub 2]O[sub 3p]/6061-T6 composite at low temperatures.

Chia Chaw Perng; Jiun Ren Hwang; Ji Liang Doong (National Central Univ., Taiwan (China))

1993-08-01

12

Nonequilibrium alloying of graphite-reinforced aluminum metal matrix composites  

SciTech Connect

With corrosion behavior superior to pure aluminum (Al), nonequilibrium Al alloys produced by cosputter deposition have great potential for use a s matrix metals in graphite (Gr)-reinforced Al composites. These composites offer enhanced properties as a result of their low density matrix and a high modulus reinforcing fiber. Cosputter-deposited Al alloys provide a means to improve corrosion resistance of Al and to remove a conventional processing step that accelerates degradation of the composite once the Gr fibers are exposed. Additions of tungsten (W) and molybdenum (Mo) were found to enhance the localized corrosion resistance of Al. At concentrations of 19 at.% Mo or 26 at.% W breakdown potentials (E[sub b]) increased by 1,115 mV[sub sce] and 1,245 mV[sub sce] over pure Al, respectively. Heat treatment of these alloys at 400 C. for 1 h did not result in precipitation of a second phase. The alloys maintained excellent resistance to localized attack. Galvanic current diagrams predicted use of these alloys in composite structures would decrease galvanic corrosion rates by at least 2 orders of magnitude. This enhancement in galvanic corrosion resistance was a result of significant improvements in passivity which occurred with the nonequilibrium addition of Mo or W to Al. Galvanic current measurements confirmed the predicted reduction in galvanic corrosion rates.

Schrecengost, T.R. (Elliott Co., Jeannette, PA (United States)); Shaw, B.A. (Pennsylvania State Univ., University Park, PA (United States)); Wendt, R.G.; Moshier, W.C. (Martin Marietta Astronautics Group, Denver, CO (United States))

1993-10-01

13

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

14

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

Mihly Kozma

15

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

16

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

17

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

18

Severe plastic deformation processing and high strain rate superplasticity in an aluminum matrix composite  

SciTech Connect

Metal matrix composites possess an attractive set of properties for structural applications. For example, reinforcement of conventional aluminum alloys with second phase ceramic particulates increases the stiffness, high temperature strength, etc. A drawback of ceramic phase reinforcement is that it makes machining of components difficult. Superplastic forming is quite attractive for hard-to-machine materials like composites. A number of aluminum matrix composites exhibit superplasticity. The most attractive feature of superplasticity in aluminum matrix composite is the high strain rate (10{sup {minus}2}--10{sup 1} s{sup {minus}1}) for optimum ductility. This is significantly higher than the optimum superplastic strain rates of 10{sup {minus}4}--10{sup {minus}3} s{sup {minus}1} in conventional fine grained alloys. The optimum superplasticity in aluminum matrix composites is influenced by the thermo-mechanical processing. In the last five years or so, a number of aluminum alloys have been processes by severe plastic deformation (SePD). Severe plastic deformation processing leads to ultrafine grained aluminum alloys with attractive superplastic properties. In this short paper the authors report on successful processing of an ultrafine grained aluminum matrix composite by severe plastic deformation technique. The SePD processes 2009 Al-SiC{sub 2} composite exhibits high strain rate superplasticity.

Mishra, R.S.; McFadden, S.X.; Mukherjee, A.K. [Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science] [Univ. of California, Davis, CA (United States). Dept. of Chemical Engineering and Materials Science; Valiev, R.Z.; Islamgaliev, R.K. [Ufa State Aviation Technical Univ. (Russian Federation). Inst. of Physics of Advanced Materials] [Ufa State Aviation Technical Univ. (Russian Federation). Inst. of Physics of Advanced Materials

1999-04-23

19

Pathways to a family of low-cost, high-performance, metal matrix composites based on aluminum diboride in aluminum  

NASA Astrophysics Data System (ADS)

The continued development of a new family of metal matrix composites based on the in-situ formation of AlB2 flakes in liquid aluminum is described. First, a new synthesis technique for the preparation of high aspect ratio AlB2 is demonstrated. Borax and B2O 3 were reacted with molten aluminum to prepare high aspect ratio AlB 2. The focus then shifts to further understanding the Al-B alloy system. Work on the Al-B alloy system concentrated on the Al(L) + AlB 2 ? Al(L) + AlB12 peritectic transformation and the growth of AlB2 in aluminum. The equilibrium peritectic transformation temperature was redetermined and found to be 950 +/- 5C. The kinetics of the peritectic transformation were measured and reported for the first time. Cu, Fe, and Si additions were made to the alloy, and their effect on the peritectic reaction was investigated. All three elements shorten the time required for the peritectic reaction to occur. The effect of these three elements on flake growth was also investigated. They each caused a reduction in the size of growing AlB2 flakes. Finally two samples containing more than 30v% AlB2 in aluminum were prepared. Their properties were measured. The sample containing 40v% AlB2 exhibited a flexural strength of 200 MPa. The 35v% sample exhibited a flexural strength of 150 MPa. When the 35v% sample was tested in compression, it exhibited an ultimate strength close to 200 MPa. Its modulus varied from 200--300 GPa depending on the orientation of the loading axis with respect to the flake reinforcement.

Hall, Aaron Christopher

20

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

21

Reactive aluminum metal nanoparticles within a photodegradable poly(methyl methacrylate) matrix  

NASA Astrophysics Data System (ADS)

We report here on new photoreactive core-matrix reactive metal nanoparticles. Poly(methyl methacrylate)-capped aluminum nanoparticles (PMMA-Al NPs) were synthesized and demonstrated air stability on the order of 2 months. Upon exposure of the PMMA-Al NPs to UV radiation the composite reacts more rapidly to release H2 gas from alkaline solution. FTIR spectroscopy indicates that the PMMA cap degrades under UV irradiation, exposing the reactive metal core.

Patel, Ashish; Becic, Jasmin; Buckner, Steven W.; Jelliss, Paul A.

2014-01-01

22

The study of in-situ formed alumina and aluminide intermetallic reinforced aluminum-based metal matrix composites  

Microsoft Academic Search

Aluminum-based metal matrix composites (MMCs) have been widely used as structural materials in the automobile and aerospace industry due to their specific properties. In this thesis, we report the fabrication of in-situ formed alumina and aluminide intermetallic reinforced aluminum-based metal matrix composites by the displacement reactions between Al and selected metal oxides (NiO, CuO and ZnO). These MMCs were produced

Peng Yu

2004-01-01

23

Thermally conducting aluminum nitride polymer-matrix composites  

Microsoft Academic Search

Thermally conducting, but electrically insulating, polymer-matrix composites that exhibit low values of the dielectric constant and the coefficient of thermal expansion (CTE) are needed for electronic packaging. For developing such composites, this work used aluminum nitride whiskers (and\\/or particles) and\\/or silicon carbide whiskers as fillers(s) and polyvinylidene fluoride (PVDF) or epoxy as matrix. The highest thermal conductivity of 11.5W\\/(mK) was

Yunsheng Xu; D. D. L Chung; Cathleen Mroz

2001-01-01

24

Fracture toughness of SiC\\/Al metal matrix composite  

Microsoft Academic Search

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

Y. Flom; B. H. Parker; H. P. Chu

1989-01-01

25

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

26

In situ fabrication of AlTiC Metal Matrix Composites by reactive slag process  

Microsoft Academic Search

The possibility of in situ fabrication of AlTiC composite using reactive slag process is studied in the present paper. Commercial pure aluminum, cryolite, titanium oxide and graphite have been used. Aluminum was melted by an induction furnace and then a mixture of salts powder was added to it. Specimens of aluminum matrix composites containing various percentages of TiCs were prepared.

S. Sheibani; M. Fazel. Najafabadi

2007-01-01

27

Elevated Temperature Strength, Aging Response and Creep of Aluminum Matrix Composites  

Microsoft Academic Search

Aluminum matrix composites with reinforcement of planar-random graphite fibers, SiC whiskers, or alumina particulates have been evaluated for their high temperature performance. The composites were aged at 150 and 200C for up to 500 hours. Microhardness results indicate accelerated aging of the composites in comparison with that of wrought 6061 Al resolutionized and aged under identical conditions. The aging response

Ram B. Bhagat; Maurice F. Amateau; Michael B. House; Kenneth C. Meinert; Paul Nisson

1992-01-01

28

Fabrication and friction drilling of aluminum silicon carbide metal matrix composite  

Microsoft Academic Search

This study investigates the friction drilling process, a nontraditional hole-making technique, for thermal aspects, energy and power in friction drilling of aluminum silicon carbide metal matrix composites (AlSiC MMC). This type of MMC is finding applications in making automotive pats like Engine, brake system and drive shaft. In friction drilling, a rotating conical tool is applied to penetrate work-material and

G. Somasundaram; S. Rajendra Boopathy

2010-01-01

29

Ductility of a continuous fiber reinforced aluminum matrix composite  

NASA Technical Reports Server (NTRS)

The transverse properties of an aluminum alloy metal matrix composite reinforced by continuous alumina fibers have been investigated. The composite is subjected to both mechanical and cyclic thermal loading. The ductility can vary by an order of magnitude according to the operating conditions. For high mechanical and low thermal loading the ductility is small, for low mechanical and high thermal loading the ductility is an order of magnitude higher. Experiments on a beam in bending confirm that the ductility is strongly dependent on the loading conditions. The observations suggest a means of utilizing the inherent ductility of the matrix.

Jansson, S.; Leckie, Frederick A.

1991-01-01

30

Galvanic corrosion of aluminum-matrix composites. Technical report No. 2, 1 Mar-31 Dec 90  

SciTech Connect

Galvanic-corrosion rates of Al-matrix composites were high in aerated chloride-containing solutions. Oxygen reduction was found to be the primary cathodic reaction. Aluminum corroded by pitting. The type of noble constituent (i.e., graphite, SiC, or TiB{sub 2}) also affected galvanic-corrosion rates. For example, results indicated that the galvanic-corrosion rate of Al should be about 30 times greater when coupled to graphite than when coupled to SiC or TiB{sub 2}. In dearated solutions, galvanic corrosion was negligible even if chlorides were present. The galvanic-corrosion rates were determined using the zero-resistance ammeter technique and from potentiodynamic polarization diagrams of ultrapure Al, 6061-T6 Al, graphite fiber, SiC, TiB2, and a commercial graphite fiber/6061-T6 Al metal-matrix composite.

Hihara, L.H.; Latanision, R.M.

1991-02-01

31

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

32

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; Franoise Escaig; Roger Lefvre; Pierre Boumati; Agns Bourdeau; Michle Garabdian; Pierre Galle; Raymond Bourdon; Tilman Dreke; Sonia Balsan

1981-01-01

33

Improvement of the bonding interface in hybrid fiber\\/particle preform reinforced Al matrix composite  

Microsoft Academic Search

The bonding interface between the reinforcement and the matrix alloy in hybrid AZS fiber\\/SiC particle preform based aluminum metal matrix composites (Al MMCs) has been investigated as a function of reinforced particle size and the binder content. It is observed that high binder and large particle will result in a poor bonding interface. This has deleterious effects on the mechanical

Hongwen Zhang; Josh Loukus; Adam Loukus

2009-01-01

34

Superplasticity and superplastic forming of aluminum metal-matrix composites  

SciTech Connect

Superplasticity has been observed in many aluminum metal-matrix composites at extremely high strain rates (approximately 0.1-1/s). These materials generally exhibited a strain-rate sensitivity value of about 0.3 and a maximum elongation of about 300 percent. It is believed that the presence of a liquid phase, or in some cases a low-melting-point region, at the reinforcement/matrix interfaces is responsible for the phenomenon. This phenomenon is not observed in all reinforced composites, despite the fact that they contain fine grain sizes. Thus, a fine matrix grain size is a necessary but insufficient condition for the high-strain-rate superplasticity. 20 refs.

Nieh, T.G.; Wadsworth, J. (Lawrence Livermore National Lab., CA (United States))

1992-11-01

35

ZnAl-based metalmatrix composites with high stiffness and high viscoelastic damping  

Microsoft Academic Search

A maximal product of stiffness and viscoelastic damping (E tan ?), a figure of merit for damping layers, is desirable for structural damping applications. Particulate-reinforced metalmatrix composites were prepared by ultrasonic agitation of the melt and composed of the zincaluminum (ZnAl) alloy Zn80Al20 (in wt%) as the lossy matrix and SiC or BaTiO3 as the particulate reinforcements. ZnAlSiC composites were

T Jaglinski; RS Lakes

2012-01-01

36

Fabrication of Metal Particles Embedded Aluminum Matrix Composite by Friction Stir Processing (FSP)  

NASA Astrophysics Data System (ADS)

Conventional metal matrix composites (MMCs) suffer from the disadvantage of low ductility. In order to overcome this, reinforcing the metal matrix with metal particles can be taken as an alternative approach. However, processing such composites can pose serious challenges as the metal particles can either go in to solution or form undesirable intermetallics during processing through conventional routes. Friction stir processing (FSP) is emerging as a versatile tool for processing and modification of variety of materials. In the present study, metal particulate reinforced aluminum matrix composite was processed by incorporating nickel particles through friction stir processing (FSP) in one step. The microstructure was characterized by scanning electron microscopy (SEM), electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). SEM observations revealed that particles are uniformly dispersed in the aluminum matrix with excellent interfacial bonding. FSP also lead to grain refinement of the matrix as observed by EBSD and TEM analysis. Moreover, no harmful Al-Ni intermetallics formed in the matrix. The mechanical properties were determined by tensile tests to evaluate the effect of metal particulate reinforcement. The novel feature of the composite is that it exhibits a threefold increase in the yield stress (0.2% proof stress) while appreciable amount of ductility is retained.

Yadav, Devinder; Bauri, Ranjit

2011-01-01

37

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

38

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

39

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

40

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

41

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

42

Comparison of the plastic deformation and failure of A359\\/SiC and 6061-T6\\/Al 2O 3 metal matrix composites under dynamic tension  

Microsoft Academic Search

A comparison is presented of the dynamic plastic deformation and tensile failure of two metal-matrix composites (one with a cast alloy matrix and the other with a wrought alloy matrix). The two composites are ceramic particle reinforced aluminum alloys: F3S.20S (A359 aluminum alloy reinforced by 20% SiC particles) and W6A20A (6061-T6 aluminum alloy reinforced by 20% Al2O3 particles). The corresponding

Yulong Li; K. T. Ramesh; E. S. C. Chin

2004-01-01

43

Low cycle fatigue behavior of a SiCp reinforced aluminum matrix composite at ambient and elevated temperature  

SciTech Connect

Based on an investigation of low cycle fatigue life and cyclic stress response characteristics of SiC particulates reinforced pure aluminum and unreinforced matrix aluminum at 298 K and 441 K, the following observations were made. (1) Cyclic stress response of the unreinforced matrix aluminum, in the as-extruded condition, revealed initial cyclic hardening, cyclic stability and second hardening at ambient temperature. With a contrast, the unreinforced aluminum at elevated temperature showed progressively cyclic softening behavior without initial hardening. (2) The cyclic stress response characteristics of the composite were different from that of its unreinforced matrix at room temperature. In spite of the initial hardening, the composite showed progressive softening in most of the fatigue life. At elevated temperature the composite also displayed continuous cyclic softening behavior. The reason for the softening behavior probably was that the dislocation tangles in the composite specimen with a likely work-hardened status was not stable and could be changed under a cyclic loading. (3) The SiCp/Al composite and the unreinforced matrix followed the Coffin-Manson law. The low cycle fatigue resistance of the composite at room temperature was lower than that of the unreinforced matrix. A decrease in the fatigue endurance due to a rise in test temperature was observed for the composite and the unreinforced matrix especially at low cyclic plastic strain ranges. The induction of fatigue life of the unreinforced aluminum was faster than that of the composite, so the fatigue resistance of the composite was stronger than that of the unreinforced aluminum under lower cyclic strain ranges at elevated temperature.

Han, N.L.; Wang, Z.G.; Sun, L.Z. [Academia Sinica, Shenyang (China). Inst. of Metal Research] [Academia Sinica, Shenyang (China). Inst. of Metal Research

1995-06-01

44

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

45

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

46

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

47

The thermal mechanical properties of Al-matrix composite  

SciTech Connect

Thermal effects on the mechanical properties of AC8A aluminum alloy composite reinforced with 12 vol % {delta} Al{sub 2}O{sub 3} short fiber were investigated. The mechanical properties included thermal cycling, fatigue and tensile strength. The results of tensile testing show apparent strength loss for T6 treated composite after thermally cycling between 333{degree}K and 653{degree}K to 50 cycles. However, no additional strength loss was observed when thermal cycling was increased to 1000 cycles. Fractographic analysis indicates no evidence of fiber debonding in thermally cycled composites. The severe degradation in the tensile strength of T6 treated composites after thermal cycling was mainly caused by matrix softening due to thermal effect. However, the composite shows prominent reinforcing effects on fatigue and tensile strength at elevated temperatures as compared with the monolithic AC8A alloy.

Chen, Y.C.; Chen, C.M. [Industrial Technology Research Institute, Hsinchu (Taiwan, Province of China). Materials Research Labs.

1993-12-31

48

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

49

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

50

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

51

X-ray studies of aluminum alloy of the Al-Mg-Si system subjected to SPD processing  

NASA Astrophysics Data System (ADS)

Recently it has been established that during high pressure torsion dynamic aging takes place in aluminum Al-Mg-Si alloys resulting in formation of nanosized particles of strengthening phases in the aluminum matrix, which greatly improves the electrical conductivity and strength properties. In the present paper structural characterization of ultrafine-grained (UFG) samples of aluminum 6201 alloy produced by severe plastic deformation (SPD) was performed using X-ray diffraction analysis. As a result, structure features (lattice parameter, size of coherent scattering domains) after dynamic aging of UFG samples were determined. The size and distribution of second- phase particles in the Al matrix were assessed with regard to HPT regimes. Impact of the size and distribution of the formed secondary phases on the strength, ductility and electrical conductivity is discussed.

Sitdikov, V. D.; Murashkin, M. Yu; Khasanov, M. R.; Kasatkin, I. A.; Chizhov, P. S.; Bobruk, E. V.

2014-08-01

52

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

53

Improving the temperature resistance of aluminum-matrix composites by using an acid phosphate binder  

SciTech Connect

Fabrication of metal-matrix composites by vacuum infiltration of a liquid metal (close to the liquidus temperature) into a SiC-whisker perform under an inert gas pressure was shown to produce SiC-whisker-reinforced aluminum (12-37 vol.%) which was comparable in quality to those produced by powder metallurgy or squeeze casting. The {alpha}-SiC whisker perform (22 vol.%) was made by wet forming using water and a binder. The use of phosphate binders (with Al (OH){sub 3} and H{sub 3}PO{sub 4} as precursors) instead of the widely used silica (SiO{sub 2}) binder resulted in increased tensile strength and temperature resistance of the SiC whisker composites. The excess H{sub 3}PO{sub 4} from the acid phosphate binder reacted with SiC to form SiP{sub 2}O{sub 7}, which strengthened the preform by acting as an in-situ binder. The excess H{sub 3}PO{sub 4} also reacted with Al to form AlP, which strengthened the Al/ binder interface. Upon heating the SiC whisker composites (not the preforms) at 400 or 600 C for 240 h, the tensile strength decreased for composites made with the silica binders, but increased for composites made with the phosphate binders.

Chiou, Jengmaw.

1991-01-01

54

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

55

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

56

Manufacturing of nanostructured Al/WCp metal- matrix composites by accumulative press bonding  

NASA Astrophysics Data System (ADS)

The accumulative press bonding (APB) process used as a novel technique in this study provides an effective alternative method for manufacturing Al/10 vol.% WCp metal matrix composites (MMCs). The results revealed that by increasing the number of APB cycles (a) the uniformity of WC particles in aluminum matrix improved, (b) the porosity of the composite eliminated, (c) the particle free zones decreased. The X-ray diffraction results also showed that nanostructured Al/WCp composite with the average crystallite size of 58.4 nm was successfully achieved by employing 14 cycles of APB technique. The tensile strength of the composites enhanced by increasing the number of APB cycles, and reached to a maximum value of 216 MPa at the end of 14th cycle, which is 2.45 and 1.2 times higher than obtained values for annealed (raw material, 88 MPa) and 14 cycles APB-ed monolithic aluminum (180 MPa), respectively

Amirkhanlou, Sajjad; Ketabchi, Mostafa; Parvin, Nader; Khorsand, Shohreh; Carreo, Fernando

2014-08-01

57

26Al-containing acidic and basic sodium aluminum phosphate preparation and use in studies of oral aluminum bioavailability from foods utilizing 26Al as an aluminum tracer  

NASA Astrophysics Data System (ADS)

We synthesized 26Al-containing acidic and basic (alkaline) sodium aluminum phosphates (SALPs) which are FDA-approved leavening and emulsifying agents, respectively, and used them to determine the oral bioavailability of aluminum incorporated in selected foods. We selected applicable methods from published syntheses (patents) and scaled them down (3000- and 850-fold) to prepare 300-400 mg of each SALP. The 26Al was incorporated at the beginning of the syntheses to maximize 26Al and 27Al equilibration and incorporate the 26Al in the naturally-occurring Al-containing chemical species of the products. Near infrared spectroscopy (NIR) and X-ray powder diffraction (XRD) were used to characterize the two SALP samples and some intermediate samples. Multi-elemental analysis (MEA) was used to determine Na, Al and P content. Commercial products were included for comparison. Satisfactory XRD analyses, near infrared spectra and MEA results confirmed that we synthesized acidic and basic SALP, as well as some of the syntheses intermediates. The 26Al-containing acidic and basic SALPs were incorporated into a biscuit material and a processed cheese, respectively. These were used in oral bioavailability studies conducted in rats in which the 26Al present in blood after its oral absorption was quantified by accelerator mass spectrometry. The results showed oral Al bioavailability from acidic SALP in biscuit was 0.02% and from basic SALP in cheese 0.05%, lower than our previous determination of Al bioavailability from drinking water, 0.3%. Both food and water can appreciably contribute to the Al absorbed from typical human Al intake.

Yokel, Robert A.; Urbas, Aaron A.; Lodder, Robert A.; Selegue, John P.; Florence, Rebecca L.

2005-04-01

58

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

SciTech Connect

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 from our laboratory. In contrast to the steep high energy tails predicted by the single- or multiple- collision models, the measured cluster distributions have high energy power law dependences in the range of E[sup [minus]3] to E[sup [minus]4.5]. Correlated collision models may explain the substantial abundance of energetic clusters that are observed in these experiments. Possible influences of cluster fragmentation on the distributions are discussed.

Coon, S.R.; Calaway, W.F.; Pellin, M.J. (Argonne National Lab., IL (United States)); Curlee, G.A. (Trinity Univ., San Antonio, TX (United States). Dept. of Physics); White, J.M. (Texas Univ., Austin, TX (United States). Dept. of Chemistry and Biochemistry)

1992-01-01

59

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

SciTech Connect

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 from our laboratory. In contrast to the steep high energy tails predicted by the single- or multiple- collision models, the measured cluster distributions have high energy power law dependences in the range of E{sup {minus}3} to E{sup {minus}4.5}. Correlated collision models may explain the substantial abundance of energetic clusters that are observed in these experiments. Possible influences of cluster fragmentation on the distributions are discussed.

Coon, S.R.; Calaway, W.F.; Pellin, M.J. [Argonne National Lab., IL (United States); Curlee, G.A. [Trinity Univ., San Antonio, TX (United States). Dept. of Physics; White, J.M. [Texas Univ., Austin, TX (United States). Dept. of Chemistry and Biochemistry

1992-12-01

60

Mechanical, intergranular corrosion, and wear behavior of aluminum-matrix composite materials reinforced with nickel aluminides  

NASA Astrophysics Data System (ADS)

This article presents experimental results of important properties of aluminum-matrix (AA 2014) composite materials reinforced with different intermetallics of the Ni-Al system. For the present study, the intermetallics are prepared either by mechanical alloying (MA) or by gas atomization (GA). The reinforced composite materials were manufactured by mixing the constituents, followed by uniaxial compacting of a preform and subsequent extrusion without canning or degassing. The present study considered the materials in the extruded state and after T6 heat treatment. Assessments were made from the viewpoint of microstructure (by means of optical and scanning electron microscopy (SEM)) and thermal characteristics (by differential scanning calorimetry (DSC)), with special emphasis on studying the reactions that take place between the matrix and the reinforcement and which produce a highly copper-enriched interphase. A study was also made of the effect of this reactivity on the mechanical properties and wear behavior of the composite materials, as well as the intergranular corrosion resistance of the materials in the extruded state.

da Costa, C. E.; Velasco, F.; Torralba, J. M.

2002-11-01

61

High-Temperature Fatigue of a Hybrid Aluminum Metal Matrix Composite  

NASA Astrophysics Data System (ADS)

An aluminum metal matrix composite (MMC) brake drum was tested in fatigue at room temperature and extreme service temperatures. At room temperature, the hybrid composite did not fail and exceeded estimated vehicle service times. At higher temperatures (62 and 73 pct of the matrix eutectic), fatigue of a hybrid particle/fiber MMC exhibited failure consistent with matrix overloading. Overaging of the A356 matrix coupled with progressive fracture of the SiC particles combined to create the matrix overload condition. No evidence of macro-fatigue crack initiation or growth was observed, and the matrix-particle interface appeared strong with no debonding, visible matrix phases, or porosity. An effective medium model was constructed to test the hypothesis that matrix overloading was the probable failure mode. The measured particle fracture rate was fit using realistic values of the SiC Weibull strength and modulus, which in turn predicted cycles to failure within the range observed in fatigue testing.

Clark, J. T.; Sanders, P. G.

2014-01-01

62

Superplastic deformation mechanisms of particulate reinforced aluminum matrix composites  

Microsoft Academic Search

Superplastic tensile tests of a SiCp reinforced 8090 aluminum alloy composite were carried out at strain rates ranging from 7.25 10?4 to 3.46 10?1 s?1 and at temperatures from 773 to 873 K. A maximum elongation of 300% was obtained at a strain rate of 1.83 10?1 s?1 when tested at a temperature of 848 K which

B. Q. Han; K. C. Chan

1996-01-01

63

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.

2007-07-01

64

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

65

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 450C 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 400C. The overaging in these materials was delayed by 100C 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 350C. For long-term thermal stability, the mechanical properties of the Sc and Zr containing composite were stable up to 300C, while the composite containing only Sc exhibited a good softening resistance up to 250C. 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

66

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 950C), 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

67

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

68

Thermal exposure effects on the mechanical properties of a polycrystalline alumina fiber/aluminum matrix composite  

NASA Technical Reports Server (NTRS)

The effects of thermal exposures and elevated test temperature on the mechanical properties of a unidirectional polycrystalline alumina fiber reinforced aluminum matrix composite were investigated. Test temperatures up to 590 K and 2500 hours exposures at 590 K did not significantly affect fiber dominated properties but did severely degrade matrix dominated properties. Fiber strength, degraded by the fabrication process, was restored by post fabrication thermal exposures. Possible degradation mechanisms are discussed.

Olsen, G. C.

1979-01-01

69

Laser processing of a SiC/Al-alloy metal matrix composite  

NASA Astrophysics Data System (ADS)

Preliminary studies were conducted on the laser processing of SiC/A356-Al alloy metal matrix composite (MMC) for such applications as welding/joining and cutting. The SiC/A356-Al MMC was processed using several different laser specific energies. Microstructural observations after laser processing revealed that the extent of reinforced material (SiC)-matrix (A356-Al) reaction is directly proportional to the laser energy input. As energy input increased, SiC particle dissolution became greater and aluminum carbide formation increased in both size and quantity. It appears possible to control substantial change (physical and chemical) in SiC particles during processing by controlling the amount and mode of energy input.

Dahotre, Narendra B.; McCay, T. Dwayne; McCay, Mary Helen

1989-06-01

70

Aluminum binding to phosphatidylcholine lipid bilayer membranes: 27Al and 31P NMR spectroscopic studies  

Microsoft Academic Search

27Al and 31P nuclear magnetic resonance (NMR) spectroscopies were used to investigate aluminum interactions at pH 3.4 with model membranes composed of 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC). A solution state 27Al NMR difference assay was developed to quantify aluminum binding to POPC multilamellar vesicles (MLVs). Corresponding one-dimensional (1D) fast magic angle spinning (MAS) 31P NMR spectra showed that aluminum induced the appearance of

Neil MacKinnon; Kevin J. Crowell; Andrew K. Udit; Peter M. Macdonald

2004-01-01

71

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

SciTech Connect

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, the cavitation behavior in superplastic metal matrix composites is not well understood. It is important to investigate characteristics of cavitation in metal matrix composites for superplastic forming applications. In this investigation, cavitation in a 20 vol% Si[sub 3]N[sub 4p]/Al-Mg-Si composite, which exhibits superplasticity at high strain rates, has been investigated and the data of the composite have been compared with those of the superplastic 7475 alloy which is a typical superplastic aluminum alloy.

Iwasaki, H.; Takeuchi, M.; Mori, T. (Himeji Inst. of Technology, Hyogo (Japan). Dept. of Materials Science and Engineering); Mabuchi, M. (National Industrial Research Inst. of Nagoya (Japan)); Higashi, K. (Univ. of Osaka Prefecture (Japan). Dept. of Mechanical Systems Engineering)

1994-08-01

72

Role of alloy matrix and dispersoid on corrosion behavior of cast aluminum alloy composites  

SciTech Connect

Observations made during the corrosion of cast aluminum alloys dispersed with graphite/silicon carbide (SiC) particles were analyzed. Corrosion studies were carried out in 3 wt% sodium chloride (NaCl) solution using salt immersion and potentiodynamic techniques. Corresponding base alloys were subjected to identical test conditions to understand the influence of the dispersoid on corrosion behavior. In all cases, the composites exhibited higher corrosion loss over the respective matrix alloy. Weight loss increased with exposure time. The dispersoid/matrix and the precipitate/matrix interfaces were found to be favorable sites for nucleation of corrosion pits. Results were explained with the help of microstructural observations and electrochemical parameters.

Modi, O.P.; Saxena, M.; Prasad, B.K.; Jha, A.K.; Das, S.; Yegneswaran, A.H. [Regional Research Lab., Bhopal (India)

1998-02-01

73

Thermomechanical treatment for high strain rate superplastic aluminum matrix composites  

SciTech Connect

Thermomechanical treatment with hot extrusion is described for a high strain rate superplastic Si{sub 3}N{sub 4p}/6061Al composite. Dynamic precipitation was caused during hot extrusion, which played an important role in grain refinement. As a result, very small grain size of about 1 {mu}m was obtained by hot extrusion.

Mabuchi, Mamoru [Government Industrial Research Institute, Nagoya (Japan); Higashi, Kenji [Univ. of Osaka Prefecture, Sakai (Japan). Dept. of Mechanical Engineering

1993-12-31

74

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

75

Triple-quantum magic angle spinning (27)Al NMR of aluminum hydroxides.  

PubMed

We show that (27)Al triple-quantum magic angle spinning (3Q-MAS) experiments alleviate the second-order quadrupolar broadening to reveal the structure-building units of nonequivalent aluminum octahedra in the most extensively studied aluminum hydroxides, namely, gibbsite, bayerite, and boehmite. Further, aided by ab initio calculations of the electric field gradient tensors, the 3Q-MAS/MAS results are shown to lead to the assignment of (27)Al isotropic resonances to the aluminum positions in their X-ray-determined structures. The present work paves the way for future studies on various structurally transformed materials derived from these basic aluminum hydroxides. PMID:11916391

Damodaran, Krishnan; Rajamohanan, Pattuparambil R; Chakrabarty, Debojit; Racherla, Uday Shankar; Manohar, Venkat; Fernandez, Christian; Amoureux, Jean-Paul; Ganapathy, Subramanian

2002-04-01

76

Particle denuded zones in alumina reinforced aluminum matrix composite weldments  

SciTech Connect

The Welding Institute of Canada (WIC), Ontario, has been studying the weldability of different DURALCAN MMC`s. Research on alumina reinforced (20 vol.%) 6061 Al alloy GTA welds showed satisfactory tensile and yield strengths (0.2% Proof Stress) but the welds failed to pass the bend test requirements with fracture taking place in the relatively brittle heat affected zone (HAZ). Further, the welds were characterized by a region which was devoid of reinforcement particles adjacent to the fusion lines. The present study was undertaken to try and explain the formation of this particle denuded zone (PDZ) at the fusion lines.

Chidambaram, A.; Bhole, S.D. [Univ. of Regina, Saskatchewan (Canada)] [Univ. of Regina, Saskatchewan (Canada)

1996-08-01

77

Part I. Corrosion studies of continuous alumina fiber reinforced aluminum-matrix composites. Part II. Galvanic corrosion between continuous alumina fiber reinforced aluminum-matrix composites and 4340 steel  

NASA Astrophysics Data System (ADS)

Part I. The corrosion performance of continuous alumina fiber reinforced aluminum-matrix composites (CF-AMCs) was investigated in both the laboratory and field environments by comparing them with their respective monolithic matrix alloys, i.e., pure Al, A1-2wt%Cu T6, and Al 6061 T6. The corrosion initiation sites were identified by monitoring the changes in the surface morphology. Corrosion current densities and pH profiles at localized corrosion sites were measured using the scanning-vibrating electrode technique and the scanning ion-selective electrode technique, respectively. The corrosion damage of the materials immersed in various electrolytes, as well as those exposed in a humidity chamber and outdoor environments, was evaluated. Potentiodynamic polarization behavior was also studied. The corrosion initiation for the composites in 3.15 wt% NaCl occurred primarily around the Fe-rich intermetallic particles, which preferentially existed around the fiber/matrix interface on the composites. The corrosion initiation sites were also caused by physical damage (e.g., localized deformation) to the composite surface. At localized corrosion sites, the buildup of acidity was enhanced by the formation of micro-crevices resulting from fibers left in relief as the matrix corroded. The composites that were tested in exposure experiments exhibited higher corrosion rates than their monolithic alloys. The composites and their monolithic alloys were subjected to pitting corrosion when anodically polarized in the 3.15 wt% NaCl, while they passivated when anodically polarized in 0.5 M Na2SO4. The experimental results indicated that the composites exhibited inferior corrosion resistance compared to their monolithic matrix alloys. Part II. Galvanic corrosion studies were conducted on CF-AMCs coupled to 4340 steel since CF-AMCs have low density and excellent mechanical properties and are being considered as potential jacketing materials for reinforcing steel gun barrels. Coupled and uncoupled coupons were immersed in various electrolytes, exposed to a humidity chamber, and exposed at outdoor test sites. Results showed that the corrosion rates of the CF-AMCs increased, while those of the 4340 steel decreased after being coupled together, in most cases. Crevice corrosion was also observed in these exposure experiments. Zero resistance ammeter (ZRA) experiments were conducted to record the galvanic-corrosion rates and potentials of the couples. The CF-AMCs were found to serve as anodes, while the steel was cathodic, in most test conditions. Galvanic performance predicted by polarization experiments was in close agreement with the ZRA results. Key words. Aluminum, metal-matrix composites, alumina fiber, pitting corrosion, galvanic corrosion.

Zhu, Jun

78

Effect of microstructure and notch root radius on fracture toughness of an aluminum metal matrix composite  

NASA Technical Reports Server (NTRS)

Recent results on the effects of matrix aging condition (matrix temper) and notch root radius on the measured fracture toughness of a SiC particulate reinforced aluminum alloy are reviewed. Stress intensity factors at catastrophic fracture were obtained for both underaged and overaged composites reveal. The linear relation found between apparent fracture toughness and the square root of the notch root radius implies a linear dependence of the crack opening displacement on the notch root radius. The results suggest a strain controlled fracture process, and indicate that there are differences in the fracture micromechanisms of the two aging conditions.

Manoharan, M.; Lewandowski, J. J.

1989-01-01

79

Lanthanoid Rhenium Aluminides with a High Content of Aluminum: LnRe(2)Al(10) (Ln = Ho-Lu) with a New Structure Type and NdRe(2)Al(10) with CaCr(2)Al(10)-Type Structure.  

PubMed

The title compounds were obtained by reaction of the elemental components with an excess of aluminum after dissolving the matrix in hydrochloric acid. The compounds LnRe(2)Al(10) (Ln = Ho-Lu) crystallize with a new structure type, which was determined from single-crystal X-ray data of LuRe(2)Al(10): Cmcm, a = 929.1(1) pm, b = 1027.7(2) pm, c = 2684.1(5) pm, Z = 12. The two different lutetium atoms of the structure are coordinated by four rhenium and 16 aluminum atoms, while the two rhenium positions are in distorted icosahedral coordination of two lutetium and 10 aluminum atoms. The 12 different aluminum atoms have between 12 and 14 neighbors, of which two are rhenium and one or two are lutetium atoms. The structure may be considered as a stacking variant of the recently determined structure of YbFe(2)Al(10). Both structures are related to that of ThMn(12). They contain hexagonally close-packed, puckered sheets similar to those known from the close-packed TiAl(3)-type structure. In LuRe(2)Al(10) and YbFe(2)Al(10) these sheets of the compositions Re(2)Al(6) and Fe(2)Al(6), respectively, alternate with less densely packed layers of the composition LnAl(4). The crystal structures of YbRe(2)Al(10) (LuRe(2)Al(10) type, a = 930.7(2) pm, b = 1029.3(2) pm, c = 2687.9(5) pm) and NdRe(2)Al(10) (CaCr(2)Al(10) type, a = 1293.7(1) pm, c = 517.4(1) pm) were also refined from single-crystal X-ray data. The refinements of the occupancy factors of these as well as those of 20 other intermetallic compounds with high aluminum content indicate a seemingly slightly lower (on average 2-3%) scattering power for the aluminum positions in all cases. This is ascribed to the differing electron distributions in the free and in the bonded aluminum atoms. The cell volume of YbRe(2)Al(10) indicates a mixed or intermediate +II/+III valence of the ytterbium atoms. PMID:11671070

Fehrmann, Birgit; Jeitschko, Wolfgang

1999-07-12

80

Hydrolysis control of alumina and AlN mixture for aqueous colloidal processing of aluminum oxynitride  

Microsoft Academic Search

AlN powder, surface modified by phosphoric acid treatment was employed for the aqueous colloidal processing of Aluminum Oxynitride (AlON). The hydrolysis of AlN leads to the formation of Al(OH)3 and NH3. On mixing of alumina to the phosphoric acid treated AlN in aqueous medium this reaction reoccurred. The phosphoric acid shield around AlN particles is ruptured by alumina addition thus

R. Senthil Kumar; P. Ramavath; R. Johnson

2011-01-01

81

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

82

1H\\/ 27Al TRAPDOR NMR studies on aluminum species in dealuminated zeolites  

Microsoft Academic Search

Aluminum species in several dealuminated zeolites (ultrastable HY, HZSM-5 and mordenite) were investigated in detail by means of the newly introduced 1H\\/27Al TRAPDOR method in combination with 27Al MAS NMR, and the quadrupole coupling constants (QCCs) for aluminum atoms associated with these species were obtained. A signal at ca. 6.8 ppm, due to water molecules adsorbed on Lewis acid sites,

Feng Deng; Yong Yue; Chaohui Ye

1998-01-01

83

Phytoremediation of effluents from aluminum smelters: A study of Al retention in mesocosms containing aquatic plants  

Microsoft Academic Search

Four mesocosms were exposed to circumneutral and aluminum (Al)-rich wastewater during two successive summers (2000, 2001). The goals of the study were to measure the bioaccumulation of dissolved Al by the aquatic plants Typha latifolia, Lemna minor, Nuphar variegatum and Potamogeton epihydrus, and to evaluate their importance in the retention of Al by the mesocosms. In 2000, inlet concentrations of

Richard R. Goulet; Janick D. Lalonde; Catherine Munger; Suzanne Dupuis; Genevive Dumont-Frenette; Stfane Prmont; Peter G. C. Campbell

2005-01-01

84

Microstructures and Tensile Properties of Hot-Extruded Al Matrix Composites Containing Different Amounts of Al4Sr  

NASA Astrophysics Data System (ADS)

In this investigation, the effect of hot extrusion process has been studied on the microstructure and tensile properties of aluminum matrix composite containing different amounts (10, 15, and 20 wt pct) of Al4Sr intermetallic phase. Microstructural examinations assessed by scanning electron microscopy revealed that hot extrusion breaks large Al4Sr particles and reduces their length tremendously. It was also found that although the addition of Al4Sr content in the composite reduces ultimate tensile strength and elongation values, hot extrusion improves tensile results significantly. Remarkable result of this study was concerned with significant improvement in the toughness of hot-extruded Al-10 wt pct Al4Sr composite in which elongation values raised up to 22 pct. Therefore, optimum amount of Al4Sr intermetallic in the composite was found to be 10 wt pct. Fractographic examinations revealed that hot extrusion encourages ductile mode of fracture by introducing homogeneous distribution of fine dimples on the fracture surface of the composites.

Sharifian, K.; Emamy, M.; Tavighi, K.; Vaziri Yeganeh, S. E.

2014-08-01

85

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

PubMed

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 the effluent and allowing the subsequent filtration) followed by a filtration to eliminate a substantial amount of the insoluble iron. Then, sulphuric acid was added to neutralize the waste solution down to pH 12 and induce aluminum precipitation. The purity of the aluminum salt was improved after washing the precipitate with deionised water. The characterization of the solid recovered, performed by thermogravimetric analysis, Fourier transform infrared spectroscopy and X-ray diffraction, indicated characteristics typical of bayerite. The proposal method allowed recovering 82% of the aluminum present in the wastewater with high purity (99.5%). Additionally, a sufficiently concentrated caustic soda solution was also recovered, which can be reused in the anodising industries. This procedure can be easily implemented and ensures economy by recycling reagents (concentrated caustic soda solution) and by recovering commercial by-products (aluminum hydroxide), while avoiding environmental pollution. PMID:21300435

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

2011-03-15

86

Thermal Conductivity and Thermal Contact Conductance Studies on Al12%Si10wt.%SiCp Metal Matrix Composites  

Microsoft Academic Search

Al12%Si10wt.%SiCp is a metal matrix composite (MMC) which is replacing the traditional metals in automobile industry. This paper describes the detailed investigations carried out for the first time on thermal contact resistance across this MMC contacts and also across the contacts between this MMC and other engineering materials like stainless steel, aluminum and copper, in vacuum at different contact pressures.

V. V. Rao; J. Nagaraju; M. V. Krishna Murthy

2003-01-01

87

Aluminum27 NMR study of some AlCl 3 ?MCl molten systems  

Microsoft Academic Search

Aluminum-27 NMR was used to investigate AlCl3-MCl (M=Li, Na, K, Butylpyridinium) molten mixtures. In AlCl3 rich mixtures, the27Al resonance line was resolved into two components corresponding to the AlCl4- and Al2Cl7- species, which were shown to undergo chemical exchange line broadening. This broadening was found to be cation and temperature dependent.

Francis Taulelle; Alexander I. Popov

1986-01-01

88

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 Gonalves; Luciane Belmonte Pereira; Gabriel Y Castro; Joseila Maldaner; Renata Rauber; Liana Vernica Rossato; Dilson Antnio Bisognin; Maria Rosa Chitolina Schetinger; Fernando Teixeira Nicoloso

2009-01-01

89

Diffusion bonding of Al7075 alloy to titanium aluminum vanadate alloy  

Microsoft Academic Search

The aluminum alloy (Al7075) and titanium alloy (Ti-6Al-4V) are used in a variety of applications in the aerospace industry. However, the high cost of Ti-6Al-4V alloy has been a major factor which has limited its use and therefore, the ability to join Al7075 alloy to Ti-6Al-4V alloy can provide a product that is less costly, but retains the high strength

Abdulaziz Nasser Alhazaa

2010-01-01

90

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

91

Diamond Turning and Grinding of Aluminum-Based Metal Matrix Composites  

Microsoft Academic Search

This paper reports research results obtained from diamond turning and grinding of aluminum-based MMCs reinforced with either SiC or Al2O3 particles. Both polycrystal diamond (PCD) and single crystal diamond (SCD) tools were used for turning the MMCs at depths of cut ranging from 0 to 1.6 um. Diamond grinding wheels were used to grind the MMCs at depths of cut

Zhaowei Zhong; Nguyen Phu Hung

2000-01-01

92

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

93

Chemical synthesis of iron aluminide [FeAl] and iron aluminum carbide [FeAlC{sub 0.5}] nanopowders  

Microsoft Academic Search

Nanopowders of iron aluminide [FeAl] and iron aluminum carbide [FeAlC{sub 0.5}] are prepared by a two-step process involving the reduction of iron chloride [FeCl] with lithium aluminum hydride [LiAlH]. LiAlH serves both as a reducing agent and as a source of aluminum atoms required for the formation of the aluminides. The two-step process involves a solution phase reduction step resulting

Yezdi B. Pithawalla; Sarojini. Deevi

2004-01-01

94

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

95

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

96

Aluminum status of synthetic Alhumic 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 Alhumus complexes to the Al toxicity

Tadashi Takahashi; Masami Nanzyo; Syuntaro Hiradate

2007-01-01

97

Joining 6061 aluminum alloy with AlSiCu filler metals  

Microsoft Academic Search

In this study, brazing of 6061 aluminum alloy was carried out with Al10.8Si10Cu and Al9.6Si20Cu filler metals at 560C. The addition of 10wt.% copper into the Al12Si filler metal lowered the solidus temperature from 586C to 522C, and the liquidus temperature from 592C to 570C. With the addition of 20wt.% copper into the Al12Si filler metal, the liquidus temperature of

S. Y. Chang; L. C. Tsao; T. Y. Li; T. H. Chuang

2009-01-01

98

Wetting and Reaction Characteristics of Al2O3/SiC Composite Refractories By Molten Aluminum and Aluminum Alloy  

SciTech Connect

The reactive wetting behavior in molten aluminum (Al) and Al alloy was investigated for alumina-silicon carbide composite refractory materials using an optimized sessile drop method at 900oC in a purified Ar-4% H2 atmosphere. The time dependent behavior of the contact angle and drop geometry was monitored and the wetting kinetics were determined. The initial contact angle between the liquid Al/Al alloy and the refractory substrates was found to be greater than 90 and to gradually decrease with time. For two of the materials, it was found that the contact angles decreased to and angle less than 90 by the end of the two-hour test. For the third material, the contact angle was still greater than 90 at the conclusion of the two-hour test. The difference in wetting properties among the three types of refractories is attributed to their microstructural and compositional variations. The effect of magnesium in the molten Al alloy drops on the wetting kinetics and the reaction with the refractory substrates are also discussed. The results obtained provide important understanding of the wetting and corrosion mechanisms of alumina and silicon carbide materials in contact with molten aluminum.

Hemrick, James Gordon [ORNL; Xu, Jing [ORNL; Peters, Klaus-Markus [ORNL; Liu, Xingbo [ORNL; Barbero, Ever J [ORNL

2007-01-01

99

Thermal conductivity of polystyrenealuminum 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

100

Effect of volume fraction of AlN particle on superplasticity of AlN/6061 aluminum alloy composite  

SciTech Connect

Ceramic whisker or particulate reinforced aluminum alloy composites which exhibit higher elastic modulus and tensile strength, excellent heat resistance and wear resistance, high thermal conductivity and can produce high strain rate superplasticity (HSRS), are expected to have application in engine and wear resistant components and even in semi-conductor packaging for the automobile and aerospace industries. The purpose of this study is to examine the effect of volume fraction of AlN on HSRS behavior of an AlN particulate reinforced 6061 aluminum alloy composite and the maximum volume fraction by which the HSRS could produce in order to understand the deformation mechanism of the HSRS.

Imai, Tsunemichi [National Industrial Research Inst. of Nagoya (Japan)] [National Industrial Research Inst. of Nagoya (Japan); Kojima, Sumito [Nagoya Municipal Industrial Research Inst. (Japan)] [Nagoya Municipal Industrial Research Inst. (Japan); L`Esperance, G.; Hong, B. [Ecole Polytechnique, Montreal, Quebec (Canada)] [Ecole Polytechnique, Montreal, Quebec (Canada); Jiang, D. [Harbin Inst. of Tech. (China)] [Harbin Inst. of Tech. (China)

1996-11-15

101

Residual stresses in continuous graphite fiber Al metal matrix composites  

NASA Technical Reports Server (NTRS)

The residual stresses in graphite fiber reinforced aluminum (Gr/Al) composites with various thermal histories are measured using X-ray diffraction (XRD) methods. The XRD stress analysis is based on the determination of lattice strains by precise measurements of the interplanar spacings in different directions of the sample. The sample is a plate consisting of two-ply P 100 Gr/Al 6061 precursor wires and Al 6061 overlayers. Prior to XRD measurement, the 6061 overlayers are electrochemically removed. In order to calibrate the relationship between stress magnitude and lattice spacing shift, samples of Al 6061 are loaded at varying stress levels in a three-point bend fixture, while the stresses are simultaneously determined by XRD and surface-attached strain gages. The stresses determined by XRD closely match those determined by the strain gages. Using these calibrations, the longitudinal residual stresses of P 100 Gr/Al 6061 composites are measured for various heat treatments, and the results are presented.

Park, Hun Sub; Zong, Gui Sheng; Marcus, Harris L.

1988-01-01

102

Multinuclear solid-state high-resolution and C-13 -{Al27} double-resonance magic-angle spinning NMR studies on aluminum alkoxides  

Microsoft Academic Search

A combination of Al-27 magic-angle spinning (MAS)\\/multiple quantum (MQ)-MAS, C-13-H-1 CPMAS, and C-13-{Al-27} transfer of population in double-resonance (TRAPDOR) nuclear magnetic resonance (NMR) were used for the structural elucidation of the aluminum alkoxides aluminum ethoxide, aluminum isopropoxide, and aluminum tertiarybutoxide. Aluminum alkoxides exist as oligomers with aluminum in different coordinations. High-resolution 27Al MAS NMR experiments with high-spinning speed distinguished the

Anuji Abraham; Roel Prins; Jeroen A. van Bokhoven; Ernst R. H. van Eck; Arno P. M. Kentgens

2006-01-01

103

Effect of thermal treatment on the aluminum hydroxide nanofibers synthesized by electrolysis of Al plates  

Microsoft Academic Search

Nanofibrous aluminum hydroxides with high specific surface area have been synthesized by a novel process employing electrolysis of aluminum plates, which has the advantages of being very simple and fast. The structural phase transformation has been systemically investigated as a function of thermal treatment. Calcination of the as-prepared boehmite (AlO(OH)) powders produced a series of phase transition that finally transformed

Seunghee Woo; Joong-Hark Park; Chang Kyu Rhee; Jaeyoung Lee; Hasuck Kim

104

Some studies into wire electro-discharge machining of alumina particulate-reinforced aluminum matrix composites  

Microsoft Academic Search

Non-traditional process like wire electro-discharge machining is found to show a promise for machining metal matrix composites.\\u000a However, the machining information for the difficult-to-machine particle-reinforced material is inadequate. This paper is\\u000a focused on experimental investigation to examine the effect of electrical as well as non-electrical machining parameters on\\u000a performance in wire electro-discharge machining of metal matrix composites (Al\\/Al2O3p). Taguchi orthogonal

Nilesh G. Patil; P. K. Brahmankar

2010-01-01

105

Speciation of aqueous mononuclear Al(III)-hydroxo and other Al(III) complexes at concentrations of geochemical relevance by aluminum-27 nuclear magnetic resonance spectroscopy  

Microsoft Academic Search

Aluminum-27 (27Al) nuclear magnetic resonance (NMR) spectroscopy was used to characterize Al(III)-hydroxo complexes, in aqueous solutions with total Al(III) concentrations of 1.010 ?M, using a custom-built NMR probe, coil, and sample bottle with low background aluminum impurities. Published 27Al NMR spectroscopy studies have traditionally used total Al(III) concentrations that are generally outside the range of geochemical interest (total [ Al(III)

Bruce C. Faust; William B. Labiosa; K'o H. Dai; Janet S. MacFall; Bryant A. Browne; Anthony A. Ribeiro; Daniel D. Richter

1995-01-01

106

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

107

Al-Fe-Ni (Aluminum-Iron-Nickel)  

SciTech Connect

[88Ray] reviewed the experimental results on the phase equilibria of this system. The reviewed results were presented as: (1) liquidus and solidus projections for Al-poor Fe-Ni alloys and for compositions near the Al-corner; (2) a reaction sequence for the solidification reactions; (3) isothermal sections at 1250, 950, 850, and 750{degrees}C for Al-poor Fe-Ni compositions; and (4) an isothermal section at 600{degrees}C near the Al-corner.

Raghavan, V.

1994-08-01

108

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

109

Preparation and characterization of thin, well-ordered aluminum oxynitride films on NiAl(001)  

Microsoft Academic Search

We deal with the formation of thin aluminum oxynitride (AlON) layers after adsorption of nitric oxide (or coadsorption of oxygen and ammonia) on NiAl(001) at 75 K and subsequent annealing at 1200 K. The adsorption of NO and formation of the AlON films are investigated by means of high-resolution electron energy loss spectroscopy (HREELS), low-energy electron diffraction (LEED), and Auger

F. Bartolucci; G. Schmitz; P. Gassmann; R. Franchy

1996-01-01

110

Single crystalline AlN film formed by direct nitridation of sapphire using aluminum oxynitride buffer  

Microsoft Academic Search

A noble method forming single crystalline AlN films has been developed as a new substrate for blue\\/UV light emitters. Sapphire substrates have been nitrided by appropriate CON2 gas mixtures saturated with graphite based on the chemical potential diagram of the AlNOC system. The nitrided surface of sapphire consists of consecutive layers of AlN and ?-aluminum oxynitride (?-ALON) with low-level dislocation

Wataru Nakao; Hiroyuki Fukuyama

2003-01-01

111

Solid-state 1H and 27Al NMR studies of amorphous aluminum hydroxides.  

PubMed

Two kinds of amorphous aluminum hydroxides, a sample precipitated from admixing AlCl3 and NaOH aqueous solutions and the commercial product, were measured by 27Al and 1H solid-state NMR spectroscopy. Pentahedral and tetrahedral coordinations, as well as octahedral coordination of oxygen atoms for aluminum, are observed in 27Al magic angle spinning (MAS) spectra of both amorphous samples. In contrast, octahedral coordination is only observed in gibbsite, bayerite, and boehmite. According to 1H MAS-NMR spectra under conditions of high spinning rate (35 kHz) and high field (14.09 T), free waters and OH groups coupled with aluminum for amorphous samples are observed at approximately 5 and approximately 4.5 ppm, respectively, the latter peak being broader. This is consistent with the differential spectra between spin echo and transfer of populations in double resonance. We conclude that the subunits of AlO4, AlO5, and AlO6 in amorphous aluminum hydroxides are bound through hydrogen bonds with a wide distribution of bonding strength. PMID:16256537

Isobe, T; Watanabe, T; d'Espinose de la Caillerie, J B; Legrand, A P; Massiot, D

2003-05-15

112

Retention and release of tritium in aluminum clad, Al-Li alloys  

SciTech Connect

Tritium retention in and release from aluminum clad, aluminum-lithium alloys is modeled from experimental and operational data developed during the thirty plus years of tritium production at the Savannah River Site. The model assumes that tritium atoms, formed by the {sup 6}Li(n,{alpha}){sup 3}He reaction, are produced in solid solution in the Al-Li alloy. Because of the low solubility of hydrogen isotopes in aluminum alloys, the irradiated Al-Li rapidly becomes supersaturated in tritium. Newly produced tritium atoms are trapped by lithium atoms to form a lithium tritide. The effective tritium pressure required for trap or tritide stability is the equilibrium decomposition pressure of tritium over a lithium tritide-aluminum mixture. The temperature dependence of tritium release is determined by the permeability of the cladding to tritium and the local equilibrium at the trap sites. This model is used to calculate tritium release from aluminum clad, aluminum-lithium alloys. 9 refs., 3 figs.

Louthan, M.R. Jr.

1991-01-01

113

Retention and release of tritium in aluminum clad, Al-Li alloys  

SciTech Connect

Tritium retention in and release from aluminum clad, aluminum-lithium alloys is modeled from experimental and operational data developed during the thirty plus years of tritium production at the Savannah River Site. The model assumes that tritium atoms, formed by the {sup 6}Li(n,{alpha}){sup 3}He reaction, are produced in solid solution in the Al-Li alloy. Because of the low solubility of hydrogen isotopes in aluminum alloys, the irradiated Al-Li rapidly becomes supersaturated in tritium. Newly produced tritium atoms are trapped by lithium atoms to form a lithium tritide. The effective tritium pressure required for trap or tritide stability is the equilibrium decomposition pressure of tritium over a lithium tritide-aluminum mixture. The temperature dependence of tritium release is determined by the permeability of the cladding to tritium and the local equilibrium at the trap sites. This model is used to calculate tritium release from aluminum clad, aluminum-lithium alloys. 9 refs., 3 figs.

Louthan, M.R. Jr.

1991-12-31

114

Effect of angleplying and matrix enhancement on impact-resistant boron/aluminum composites  

NASA Technical Reports Server (NTRS)

Efforts to improve the impact resistance of B/Al are reviewed and analyzed. Tensile and dynamic modulus tests, thin sheet Charpy and Izod impact tests, and standard full size Charpy impact tests were conducted on 0.20 mm (8 mil) diameter-B/1100 Al matrix composites. Angleplies ranged from unidirectional to + or - 30 deg. The best compromise between reduced longitudinal properties and increased transverse properties was obtained with + or - 15 deg angleply. The pendulum impact strengths of improved B/Al were higher than that of notched titanium and appear to be enough to warrant consideration of B/Cl for application to fan blades in aircraft gas turbine engines.

Mcdanels, D. L.; Signorelli, R. A.

1976-01-01

115

Al-Cr-Fe (Aluminum-Chromium-Iron)  

SciTech Connect

[88Ray] reviewed the experimental data on this system and presented the reviewed results as: (1) a liquidus projection for alloys near the Al-corner; (2) liquidus and solidus projections for the other regions; (3) isothermal sections for alloys with less than 50 wt.% Al at 1150, 900, 750, 700, 650, and 600{degrees}C; (4) an isothermal section at 600{degrees}C near the Al-corner; (5) a partial reaction sequence; and (6) vertical sections depicting the ordering reactions in Fe{sub 3}Al as a function of Cr content.

Raghavan, V.

1994-08-01

116

Hybrid aluminum and indium conducting filaments for nonpolar resistive switching of Al/AlOx/indium tin oxide flexible device  

NASA Astrophysics Data System (ADS)

The nonpolar resistive switching characteristics of an Al/AlOx/indium tin oxide (ITO) device on a plastic flexible substrate are investigated. By analyzing the electron diffraction spectroscopy results and thermal coefficient of resistivity, it is discovered that the formation of aluminum and indium conducting filaments in AlOx film strongly depends on the polarity of the applied voltage. The metal ions arising from the Al and ITO electrodes respectively govern the resistive switching in corresponding operation polarity. After 104 times of mechanical bending, the device can perform satisfactorily in terms of resistance distribution, read sequence of high and low resistive states, and thermal retention properties.

Yuan, Fang; Wang, Jer-Chyi; Zhang, Zhigang; Ye, Yu-Ren; Pan, Liyang; Xu, Jun; Lai, Chao-Sung

2014-02-01

117

Speciation of aqueous mononuclear Al(III)-hydroxo and other Al(III) complexes at concentrations of geochemical relevance by aluminum-27 nuclear magnetic resonance spectroscopy  

Microsoft Academic Search

Aluminum-27 ( 27 Al) nuclear magnetic resonance (NMR) spectroscopy was used to characterize Al(III)-hydroxo complexes, in aqueous solutions with total Al(III) concentrations of 1.0-10 M, using a custom-built NMR probe, coil, and sample bottle with low background aluminum impurities. Published 27 Al NMR spectroscopy studies have traditionally used total Al(III) concentrations that are generally outside the range of geochemical interest

Bruce C. Faust; William B. Labiosa; Ko H. Dai; Janet S. MacFall; Bryant A. Browne; Anthony A. Ribeiro; Daniel D. Richter

1995-01-01

118

Identification of Aluminum Responsive Genes in Al-Tolerant Soybean Line PI 416937  

PubMed Central

Soybean is one of the most aluminum (Al) sensitive plants. The complex inheritance of Al tolerance trait has so far undermined breeding efforts to develop Al-tolerant soybeans. Discovering the genetic factors underlying the Al tolerance mechanisms would undoubtedly accelerate the pace of such endeavor. As a first step toward this goal, we analyzed the transcriptome profile in roots of Al-tolerant soybean line PI 416937 comparing Al-treated and untreated control plants using DNA microarrays. Many genes involved in transcription activation, stress response, cell metabolism and signaling were differentially expressed. Patterns of gene expression and mechanisms of Al toxicity and tolerance suggest that Cys2His2 and ADR6 transcription activators, cell wall modifying enzymes, and phytosulfokines growth factor play role in soybean Al tolerance. Our data provide insights into the molecular mechanisms of soybean Al tolerance and will have practical value in genetic improvement of Al tolerance trait. PMID:20953355

Duressa, Dechassa; Soliman, Khairy; Chen, Dongquan

2010-01-01

119

Mechanical behavior of a continuous fiber reinforced aluminum matrix composite subjected to transverse and thermal loading  

NASA Technical Reports Server (NTRS)

The transverse properties of an aluminum alloy metal matrix composite reinforced by continuous alumina fibers were investigated. The composite is subjected to both mechanical and cyclic thermal loading. The results of an experimental program indicate that the shakedown concept of structural mechanics provides a means of describing the material behavior. When the loading conditions are within the shakedown region, the material finally responds in an elastic manner after initial plastic response, and for loading conditions outside the shakedown region, the material exhibits a rapid incremental plastic strain accumulation. The failure strain varies by an order of magnitude according to the operating conditions. Hence, for high mechanical and low thermal loading, the failure strains is small; for low mechanical and high thermal loading, the failure strain is large.

Jansson, S.; Leckie, F. A.

1991-01-01

120

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

121

Investigation of Thermo-Mechanical Fatigue Characteristics for Cast Aluminum (AL319-T7)  

NASA Astrophysics Data System (ADS)

In today's transient economy, the demand for new alternative technologies is increasing. Vehicle fuel economy has become the most important phrase in the automotive industry. The ability to achieve optimal fuel economy has many trade-offs. In terms of engine components, this trade-off comes in the form of component reliability. In the past, most engine components were constructed of cast iron. Currently many cast iron components have been replaced by aluminum components to reduce part weight. In parallel with the use of light weight components, higher thermal loadings have been applied to engine components due to the increasing use of fuel saving technologies. Current aluminum reliability concerns have led to a thermal mechanical fatigue (TMF) investigation of the aluminum casting alloy, AL319-T7. This thesis attempts to model TMF behaviour for an AL319-T7 cylinder head using a combined hardening material model, in which the effects of creep and oxidation have been neglected.

Miller, Luke W.

122

Electro-thermo-mechanical coupling analysis of deep drawing with resistance heating for aluminum matrix composites sheet  

NASA Astrophysics Data System (ADS)

Recently, electro-plastic forming to be a focus of attention in materials hot processing research area, because it is a sort of energy-saving, high efficient and green manufacturing technology. An electro-thermo-mechanical model can be adopted to carry out the sequence simulation of aluminum matrix composites sheet deep drawing via electro-thermal coupling and thermal-mechanical coupling method. The first step of process is resistance heating of sheet, then turn off the power, and the second step is deep drawing. Temperature distribution of SiCp/2024Al composite sheet by resistance heating and sheet deep drawing deformation were analyzed. During the simulation, effect of contact resistances, temperature coefficient of resistance for electrode material and SiCp/2024Al composite on temperature distribution were integrally considered. The simulation results demonstrate that Sicp/2024Al composite sheet can be rapidly heated to 400 in 30s using resistances heating and the sheet temperature can be controlled by adjusting the current density. Physical properties of the electrode materials can significantly affect the composite sheet temperature distribution. The temperature difference between the center and the side of the sheet is proportional to the thermal conductivity of the electrode, the principal cause of which is that the heat transfers from the sheet to the electrode. SiCp/2024Al thin-wall part can be intactly manufactured at strain rate of 0.08s-1 and the sheet thickness thinning rate is limited within 20%, which corresponds well to the experimental result.

Zhang, Kaifeng; Zhang, Tuoda; Wang, Bo

2013-05-01

123

Al-Fe-Si (Aluminum-Iron-Silicon)  

SciTech Connect

[88Ray] reviewed the experimental results on the phase equilibria of this system. The reviewed data were presented as: (1) a liquidus surface for the entire composition range with isotherms at 50{degrees}C intervals; (2) a table of the invariant reactions on this liquidus surface; (3) liquidus and solidus projections near the Al-corner; (4) a table of selected crystallographic data on the ternary phases of the systems; (5) a pseudobinary section along the Fe{sub 3}Al-Fe{sub 3}Si line; (6) an isothermal section at 1000{degrees}C covering the entire composition range; (7) isothermal sections near the Al-corner at 560, 550, and 450{degrees}C; and (8) solubility limits of Si and Fe in Al at 577, 500, and 420{degrees}C.

Raghavan, V.

1994-08-01

124

Aluminum diffusion in Al-implanted AISI 321 stainless steel using accelerator-based characterization techniques  

NASA Astrophysics Data System (ADS)

The aluminum diffusion in near-surface layers of Al-implanted AISI 321 austenitic stainless steel (Fe/Cr18/Ni8/Ti) was studied using ion beam analysis techniques. The implanted samples were investigated at temperatures between 450C and 650C (treatment times up to 144 h in vacuum and in air). The Al-profiles were determined by the 992 keV resonance of the 27Al(p,?) 28Si nuclear reaction as well as by 4He +-Rutherford Backscattering Spectrometry (RBS). The experimental diffusion coefficients, obtained during this study using Fick's second law, were compared with corresponding literature concerning the aluminum diffusion in other relevant metallic materials. The determination of the depth profiles contributes to the interpretation of the high temperature oxidation behavior of Al-implanted stainless steel surfaces.

Noli, F.; Misaelides, P.; Bethge, K.

1998-04-01

125

Study of complex formation between aluminum bromide and benzene by 27Al NMR spectroscopy  

Microsoft Academic Search

The reaction of aluminum bromide with benzene in n-hexane was studied by 27Al NMR spectroscopy in the temperature range from 80 to +20 C. The formation of C6H6Al2Br6 (1 : 2) complexes is accompanied by broadening of the resonance line with d 178. No peak splitting following a decrease in the temperature was observed but the temperature dependence of the

V. B. Murachev; A. I. Nesmelov

2001-01-01

126

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

127

Al-Fe-Mn (Aluminum-Iron-Manganese)  

SciTech Connect

[88Ray] reviewed the experimental data on this system. The reviewed results were presented as: (1) liquidus and solidus projections for Fe-rich alloys and for compositions near the Al-corner; and (2) partial isothermal sections at 1200, 1000, 760, and 600{degrees}C.

Raghavan, V.

1994-08-01

128

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

129

Chemical synthesis of iron aluminide [FeAl] and iron aluminum carbide [Fe 3AlC 0.5] nanopowders  

Microsoft Academic Search

Nanopowders of iron aluminide [FeAl] and iron aluminum carbide [Fe3AlC0.5] are prepared by a two-step process involving the reduction of iron chloride [FeCl3] with lithium aluminum hydride [LiAlH4]. LiAlH4 serves both as a reducing agent and as a source of aluminum atoms required for the formation of the aluminides. The two-step process involves a solution phase reduction step resulting in

Yezdi B. Pithawalla; Sarojini Deevi

2004-01-01

130

High-energy - high-rate power processing of aluminum-silicon carbide metal-matrix composites  

SciTech Connect

Discontinuous, silicon-carbide-reinforced, aluminum metal-matrix composite metals were made by consolidating powder constituents using a novel high-energy - high-rate process that employs a fast-rising high-current pulse. The powder mixtures were contained in an insulated die, under pressure, and were rapidly densified during the discharge from a homopolar generator, in a processing time of about one second. Several types of rapidly solidified Al-based powders, X7091, CW67, and 7064, were reinforced with different types and volume fractions of discontinuous SiC. The consolidate materials were evaluated using optical and analytical electron microscopy and Auger spectroscopy to determine the microstructure and to identify the phases evolved. Processing/structure/property interrelationships were established. Energy inputs of 400 kJ/kg to 2500 kJ/kg at applied pressures of 105 to 315 MPa resulted in consolidated forms, having a homogeneous distribution of the SiC particles within the composite. Densities of 95% to 99% of theoretical were obtained with local interparticle melting contributing to densification at the highest energy levels. A direct correlation exists between the density, hardness, and fracture tensile strength, and the specific input energy, indicating that metallurgical bonding and densification scaled with input energy.

Elkabir, G.

1987-01-01

131

Phytoremediation of effluents from aluminum smelters: a study of Al retention in mesocosms containing aquatic plants.  

PubMed

Four mesocosms were exposed to circumneutral and aluminum (Al)-rich wastewater during two successive summers (2000, 2001). The goals of the study were to measure the bioaccumulation of dissolved Al by the aquatic plants Typha latifolia, Lemna minor, Nuphar variegatum and Potamogeton epihydrus, and to evaluate their importance in the retention of Al by the mesocosms. In 2000, inlet concentrations of total monomeric Al were reduced by 56% and 29% at the Arvida and Laterrire mesocosms, respectively, whereas in 2001 inlet dissolved Al concentrations in the inlet decreased by 40% and 33%. L. minor had the highest Al uptake rate (0.8--17 mg Al g(-1)d(-1)). However, because T. latifolia (cattails) yielded the highest biomass, it was responsible for 99% of the Al uptake, largely in its root tissue. In 2001, Al uptake by macrophytes accounted for 2--4% and 15--54% of the total Al retained by the Laterrire and Arvida mesocosms, respectively. In the Laterrire mesocosms, Al uptake by cattails could account for 12% and 18% of the dissolved Al retained by both mesocosms. In contrast, dissolved Al was not significantly reduced in the Arvida enclosures, yet cattails did accumulate Al in their roots. Further research is needed to identify the species community composition that would optimize dissolved Al retention. PMID:15950256

Goulet, Richard R; Lalonde, Janick D; Munger, Catherine; Dupuis, Suzanne; Dumont-Frenette, Genevive; Prmont, Stfane; Campbell, Peter G C

2005-06-01

132

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

133

Diffusion bonding of Al7075 alloy to titanium aluminum vanadate alloy  

NASA Astrophysics Data System (ADS)

The aluminum alloy (Al7075) and titanium alloy (Ti-6Al-4V) are used in a variety of applications in the aerospace industry. However, the high cost of Ti-6Al-4V alloy has been a major factor which has limited its use and therefore, the ability to join Al7075 alloy to Ti-6Al-4V alloy can provide a product that is less costly, but retains the high strength and light weight properties necessary for the transport industry. However, the large difference in the physical properties between these two alloys prevents the use of conventional joining techniques such as fusion welding to join these dissimilar alloys. Therefore, the diffusion bonding technique was used to join Al7075 alloy to Ti-6Al-4V alloy with the objective of minimizing microstructural changes of the two alloys during the bonding process. In this thesis, solid state and liquid phase bonding processes were undertaken. Solid state bonding was employed without interlayers and was successful at 510C and 7 MPa. The bond interface showed an absence of the oxides due to the dissolution of oxygen into the titanium solution. Bonds made using copper interlayers at a temperature sufficient enough to form eutectic liquid formation between copper and aluminum were produced. The intermetallics theta(Al2Cu), S(Al2CuMg) and T(Al2Mg3Zn3) were identified at the aluminum interface while Cu3Ti2 intermetallic was identified at the titanium interface. Bonds made using tin based alloys interlayers and copper coatings were successful and gave the highest shear strength. The eutectic formation on the Al7075 alloy was responsible for joint formation at the aluminum interface while the formation of Sn3Ti5 intermetallic was responsible for the joint formation at titanium interface. The corrosion rate of the bonds decreased with increasing bonding time for joints made using the tin based interlayer in 3% NaCl solution. However, the presence of copper within the joint increased the corrosion rate of the bonds and this was attributed to the corrosive effect of copper in the Al7075 alloy.

Alhazaa, Abdulaziz Nasser

134

The tridecameric aluminum complex as an appropriate precursor for fibrous boehmite: A 27Al NMR study on the partial hydrolysis of aluminum sec-butoxide  

Microsoft Academic Search

The aging of the aluminum tridecamer in acidified aluminum sec-butoxide is studied with 27Al nuclear magnetic resonance. At 20C the tridecamer content passes through a maximum of 19.7% after 133 h of aging to decline subsequently to a final content of approximately 12%. At 90C the tridecamer disappears within 21 h of aging due to clustering. After 91 h colloidal

Roland J. M. J. Vogels; J. Theo Kloprogge; Paul A. Buining; Don Seykens; J. Ben H. Jansen; John W. Geus

1995-01-01

135

49 CFR Appendix C to Part 180 - Eddy Current Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...  

Code of Federal Regulations, 2012 CFR

...for DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 C Appendix C to Part...for DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 1. Examination Procedure...each DOT-3AL cylinder manufactured of aluminum alloy 6351-T6 to be inspected...

2012-10-01

136

49 CFR Appendix C to Part 180 - Eddy Current Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...  

Code of Federal Regulations, 2011 CFR

...DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 C Appendix C to Part 180...DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 1. Examination Procedure...DOT-3AL cylinder manufactured of aluminum alloy 6351-T6 to be inspected must be...

2011-10-01

137

49 CFR Appendix C to Part 180 - Eddy Current Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...  

Code of Federal Regulations, 2010 CFR

...DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 C Appendix C to Part 180...DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 1. Examination Procedure...DOT-3AL cylinder manufactured of aluminum alloy 6351-T6 to be inspected must be...

2010-10-01

138

49 CFR Appendix C to Part 180 - Eddy Current Examination With Visual Inspection for DOT 3AL Cylinders Manufactured of Aluminum...  

Code of Federal Regulations, 2013 CFR

...DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 C Appendix C to Part 180...DOT 3AL Cylinders Manufactured of Aluminum Alloy 6351-T6 1. Examination Procedure...DOT-3AL cylinder manufactured of aluminum alloy 6351-T6 to be inspected must be...

2013-10-01

139

Low cost, SPF aluminum cryogenic tank structure for ALS  

NASA Technical Reports Server (NTRS)

Past production work has shown that cryogenic tank structure for the Shuttle Booster Rockets and the Titan system have very high life cycle costs for the fuel tank structure. The tanks are machined stiffener-skin combination that are subsequently formed into the required contour after machining. The material scrap rate for these configurations are usually high, and the loss of a tank panel due to forming or heat treatment problems is very costly. The idea of reducing the amount of scrap material and scrapped structural members has prompted the introduction of built-up structure for cryogenic tanks to be explored on the ALS program. A build-up structure approach that has shown improvements in life cycle cost over the conventional built-up approach is the use of superplastically formed (SPF) stiffened panels (reducing the overall part count and weight for the tank) resistance spot welded (RSW) to outer tank skin material. The stiffeners provide for general stability of the tank, while the skin material provides hoop direction continuity for the loads.

Anton, Claire E.; Rasmussen, Perry; Thompson, Curt; Latham, Richard; Hamilton, C. Howard; Ren, Ben; Gandhi, Chimata; Hardwick, Dallis

1992-01-01

140

Low cost, SPF aluminum cryogenic tank structure for ALS  

NASA Astrophysics Data System (ADS)

Past production work has shown that cryogenic tank structure for the Shuttle Booster Rockets and the Titan system have very high life cycle costs for the fuel tank structure. The tanks are machined stiffener-skin combination that are subsequently formed into the required contour after machining. The material scrap rate for these configurations are usually high, and the loss of a tank panel due to forming or heat treatment problems is very costly. The idea of reducing the amount of scrap material and scrapped structural members has prompted the introduction of built-up structure for cryogenic tanks to be explored on the ALS program. A build-up structure approach that has shown improvements in life cycle cost over the conventional built-up approach is the use of superplastically formed (SPF) stiffened panels (reducing the overall part count and weight for the tank) resistance spot welded (RSW) to outer tank skin material. The stiffeners provide for general stability of the tank, while the skin material provides hoop direction continuity for the loads.

Anton, Claire E.; Rasmussen, Perry; Thompson, Curt; Latham, Richard; Hamilton, C. Howard; Ren, Ben; Gandhi, Chimata; Hardwick, Dallis

1992-09-01

141

Measurement of mercury in flue gas based on an aluminum matrix sorbent.  

PubMed

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 Hg(0) on the sorbent media, the analytical bias test on tube 3 spiked with Hg(0) 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. PMID:22235178

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

2011-01-01

142

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. PMID:22235178

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

2011-01-01

143

Al-SiC powder preparation for electronic packaging aluminum composites by plasma spray processing  

Microsoft Academic Search

Powders of pure aluminum (Al) with 55 and 75 vol.% SiC particles were ball milled in a conventional rotating ball mill with\\u000a stainless steel and ZrO2 balls for 110 h. The morphology and microstructure of the milled powders have been observed and analyzed by scanning electron\\u000a microscopy (SEM) and energy dispersive x-ray (EDX). The milled powders were plasma sprayed onto

Manchang Gui; Suk Bong Kang; Kwangjun Euh

2004-01-01

144

Dissociation of H2 on carbon doped aluminum cluster Al6C  

NASA Astrophysics Data System (ADS)

The dissociation of H2 molecule is the first step for chemical storage of hydrogen, and the energy barrier of the dissociation is the key factor to decide the kinetics of the regeneration of the storage material. As a light element, aluminum is an important candidate component for storage materials with high gravimetric density. This paper investigates the adsorption and dissociation of H2 on carbon doping aluminum cluster Al6C. The study shows that doping carbon into aluminum cluster can significantly change the electronic structure and increase the stability. Al6C has a few stable isomers with close energies and their structures are quite flexible. The molecular adsorption of H2 on Al6C is very weak, but the H2 molecule can be dissociated easily on this cluster. The stable product of the dissociated adsorption is searched and the different paths for the dissociation are investigated. During the dissociation of H2, the structure of the cluster adjusts accordingly, and strong orbital interaction between the hydrogen and the cluster occurs. The calculated energy barrier for the dissociation is only 0.30 eV, which means the dissociation can take place at moderate temperatures.

Yang, Huihui; Zhang, Yan; Chen, Hongshan

2014-08-01

145

Dissociation of H? on carbon doped aluminum cluster Al?C.  

PubMed

The dissociation of H2 molecule is the first step for chemical storage of hydrogen, and the energy barrier of the dissociation is the key factor to decide the kinetics of the regeneration of the storage material. As a light element, aluminum is an important candidate component for storage materials with high gravimetric density. This paper investigates the adsorption and dissociation of H2 on carbon doping aluminum cluster Al6C. The study shows that doping carbon into aluminum cluster can significantly change the electronic structure and increase the stability. Al6C has a few stable isomers with close energies and their structures are quite flexible. The molecular adsorption of H2 on Al6C is very weak, but the H2 molecule can be dissociated easily on this cluster. The stable product of the dissociated adsorption is searched and the different paths for the dissociation are investigated. During the dissociation of H2, the structure of the cluster adjusts accordingly, and strong orbital interaction between the hydrogen and the cluster occurs. The calculated energy barrier for the dissociation is only 0.30 eV, which means the dissociation can take place at moderate temperatures. PMID:25134566

Yang, Huihui; Zhang, Yan; Chen, Hongshan

2014-08-14

146

Diffusion-reaction of aluminum and oxygen in thermally grown Al2O3 oxide layers  

NASA Astrophysics Data System (ADS)

The diffusion-reaction of aluminum (Al) and oxygen (O), to form thermally grown oxide (TGO) layers in thermal barrier coatings (TBCs), is studied through an analytical model. A nonsymmetrical radial basis function approach is used to numerically solve the mass balance equations that predict the TGO growth. Correct boundary conditions for the Al and O reactions are laid out using scaling arguments. The Damkhler number shows that the O-Al reaction is several orders of magnitude faster than diffusion. In addition, a comparison between aluminum and oxygen diffusivities indicates that TGO growth is governed by aluminum diffusion. The results are compared with experimental measurements on air plasma spray-deposited TBCs treated at 1,373 K with exposure times ranging from 1 to 1700 hours. We found that, for several time decades, the thickness of the thermally grown layer has power law dependence of time with an exponent of , following the diffusion control mechanism. At later times, however, the presence of other oxides and additional kinetics modify the diffusive exponent.

Osorio, Julin D.; Giraldo, Juliana; Hernndez, Juan C.; Toro, Alejandro; Hernndez-Ortiz, Juan P.

2014-04-01

147

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

148

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

149

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

150

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

151

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

152

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

153

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

154

Brazing 6061 aluminum alloy with Al-Si-Zn filler metals containing Sr  

NASA Astrophysics Data System (ADS)

Al-6.5Si-42Zn and Al-6.5Si-42Zn-0.09Sr filler metals were used for brazing 6061 aluminum alloy. Air cooling and water cooling were applied after brazing. Si phase morphologies in the brazing alloy and the brazed joints were investigated. It was found that zinc in the Al-Si filler metals could reduce the formation of eutectic Al-Si phase and lower the brazing temperature at about 520C. Adding 0.09wt% Sr element into the Al-6.5Si-42Zn alloy caused ?-Al phase refinement and transformed acicular Si phase into the finely fiber-like. After water cooling, Zn element dissolved into the Al-Si eutectic area, and ?-Zn phase disappeared in the brazed joints. Tensile strength testing results showed that the Sr-modified filler metal could enhance the strength of the brazed joints by 13% than Al-12Si, while water-cooling further improved the strength at 144 MPa.

Dai, Wei; Xue, Song-bai; Ji, Feng; Lou, Jiang; Sun, Bo; Wang, Shui-qing

2013-04-01

155

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

156

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

157

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

158

Influence of matrix hardness on the dry sliding behaviour of 20 vol.% Al 2O 3-particulate-reinforced 6061 Al metal matrix composite  

Microsoft Academic Search

In the present investigation the wear behaviour of the 6061 Al alloy reinforced with 20 vol. % Al2O3 particles dry sliding against a tool steel counterface was studied as a function of load and with reference to different values of the matrix hardness, obtained by submitting the extruded composite to thermal and forging treatments. The obtained wear rates were interpreted

G. Straffelini; F. Bonollo; A. Molinari; A. Tiziani

1997-01-01

159

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

160

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

161

Synthesis and formation process of Al2CuHx: A new class of interstitial aluminum-based alloy hydride  

NASA Astrophysics Data System (ADS)

Aluminum-based alloy hydride Al2CuHx (x 1) is synthesized by hydrogenating Al2Cu alloy using high-temperature and high-pressure hydrogen atmosphere. Al8Cu square antiprisms in Al2Cu twist around the c axis of a tetragonal unit cell by hydrogenation. The twist enlarges the interstitial spaces for accommodating hydrogen atoms which align linearly parallel to the c axis in Al2CuHx. Thermodynamic stability of Al2CuHx results from the balance of stabilization by H 1s and Al 3sp hybridization and destabilization owing to the Fermi-level lifting upon hydrogenation. The crystal and electronic structures of Al2CuHx illustrate the formation of an interstitial hydride of aluminum-based alloy.

Saitoh, Hiroyuki; Takagi, Shigeyuki; Endo, Naruki; Machida, Akihiko; Aoki, Katsutoshi; Orimo, Shin-ichi; Katayama, Yoshinori

2013-09-01

162

Formation of Al/(Ti, Nb, Ta)-composite oxide films on aluminum by pore filling  

SciTech Connect

Aluminum specimens coated with porous anodic oxide films were dipped in solutions containing Ti{sup 4+}, Nb{sup 5+}, or Ta{sup 5+} ions and heated in air mainly at 400 C to deposit Ti, Nb, or Ta oxide on the inner walls of pores. After 0 to 7 cycles of the dipping and heating process, the specimens were reanodized in a neutral borate solution to fill the pores with Al{sub 2}O{sub 3}. The incorporation of Ti, Nb, or Ta oxide in the anodic oxide films was examined by transmission electron microscopy Rutherford backscattering spectroscopy, and impedance measurements. Incorporation of Ti, Nb, or Ta oxide was found only in the outermost part of the anodic oxide film after reanodizing up to 400 V. The Al/Ti composite oxide films consisted of an outer Al/Ti-composite oxide layer, an intermediate crystalline alumina layer, and an inner amorphous alumina layer, while the Al/Nb- and Al/Ta-composite oxide films consisted of an outer composite oxide layer and an inner amorphous alumina layer. The parallel electric capacitance of Al/Ti-composite oxide film was 40% higher than those of the other two due to its small thickness and high dielectric constant. The formation mechanisms of the composite oxide films during reanodizing are discussed in terms of the ion transport across the oxide film.

Shikanai, M.; Sakairi, M.; Takahashi, H.; Seo, M. [Hokkaido Univ., Sapporo (Japan). Faculty of Engineering; Takahiro, K.; Nagata, S.; Yamaguchi, S. [Tohoku Univ., Sendai (Japan). Inst. for Materials Research

1997-08-01

163

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

164

31P and 27Al NMR studies of aqueous (2-hydroxyethyl) trimethylammonium solutions containing aluminum and phosphorus  

Microsoft Academic Search

Phosphorus-31 and aluminum-27 nuclear magnetic resonance techniques have been used to characterize the distribution of soluble aluminophosphate species in aqueous solutions of (2-hydroxyethyl) trimethylammonium chloride (2-HETMACl), phosphoric acid, and aluminum sulfate. Soluble aluminophosphate cations obtain from reactions of hexaaqua aluminum cations [A1(H2O)6]3+, with phosphate ligands (i.e., H3PO4, H2PO4, and acid dimers H6P2O8 and H5P2O7). 31P NMR and 27Al NMR spectroscopies

Abdolraouf Samadi-Maybodi; S. Karim Hassani Nejad-Darzi; Hamidreza Bijanzadeh

2009-01-01

165

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

NASA Technical Reports Server (NTRS)

An experimental program is underway to develop a consistent set of material property and impact test data, and failure analysis, for a variety of materials that can be used to develop improved impact failure and deformation models. Unique features of this set of data are that all material property information and impact test results are obtained using identical materials, the test methods and procedures are extensively documented and all of the raw data is available. This report describes ballistic impact testing which has been conducted 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.

Pereira, J. Michael; Revilock, Duane M.; Ruggeri, Charles R.; Emmerling, William C.; Altobelli, Donald J.

2012-01-01

166

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

167

Social Network Analysis via Matrix Decompositions: al Qaeda  

Microsoft Academic Search

Social network analysis investigates the structure of human groups using pairwise links among their members. We show how matrix decompositions can be used to extend the standard repertoire of social network and link analysis tools to allow, for example, the inclusion of other information about individuals, and higher-order information about the relationships among them. We show how these extensions can

D. B. Skillicorn

168

Modification of H-ZSM-5 zeolites with phosphorus. 1. Identification of aluminum species by 27Al solid-state NMR and characterization of their catalytic properties  

Microsoft Academic Search

Aluminum species in P-ZSM-5 zeolites were identified and quantified using 27Al MAS and MQMAS NMR methods. Samples containing between 0% and 15% P2O5 were studied after calcination or calcination followed by steaming. In addition to the tetrahedral framework aluminum, Altet-f, and the octahedral aluminum, Aloct, we also observed significant quantities of highly distorted aluminum with tetrahedral coordination, Altet-dis, and octahedrally

S. M. Cabral de Menezes; Y. L. Lam; K. Damodaran; M. Pruski

2006-01-01

169

Development of aluminum beryllium for structural applications  

NASA Astrophysics Data System (ADS)

A newly developed family of Aluminum Beryllium (AlBeMetTM) metal matrix composite materials has been developed for use in satellite structures to address the needs of the designer for lightweight, stiff, thermally stable structures. This paper will present an overview of the development of these metal matrix composites materials and their use in satellite structures. Lightweight and high modulus Aluminum-Beryllium composites offer significant performance advantages over traditional aluminum and organic composite materials. Aluminum-Beryllium composites also can be fabricated using conventional aluminum machining, joining, and coating technologies thereby reducing the cost of the final assembly, and eliminating any special tooling or non destructive testing that is sometimes required when designing and fabricating structures out of fiber reinforced composites. This paper will present the thermal, physical, and mechanical properties of these composites, as well as providing structural test data for satellite components that have utilized Aluminum-Beryllium materials, such as the ORBCOMMsm satellites.

Parsonage, Thomas B.

1997-09-01

170

Damping characteristics of Zn-Al matrix composites  

SciTech Connect

Among high damping materials, Zn-Al alloys are considered to be the most excellent non-ferromagnetic damping alloys due to their attractive properties such as low melting point, low density, good workability and high damping capacity in a broad frequency range. The limitations to high temperature use of these alloys are their poor high temperature mechanical properties and dimensional instability. Recently, various reinforcements have been added to Zn-Al alloys to improve their high temperature properties while to increase their specific strength. Stiffness, wear resistance and to decrease thermal expansion coefficient. However, the effects of these reinforcements on damping behavior of Zn-Al alloys are yet to be elucidated. The present paper is to report some new phenomena found in preliminary damping studies of long graphite fiber, short graphite fiber and silicon carbide whisker reinforced Zn-Al alloy based composites.

Gu, M.; Chen, Z.; Wang, Z.; Jin, Y.; Huang, J.; Zhang, G. (Shanghai Jiao Tong Univ. (China). State Key Lab. of Metal Matrix Composite Materials)

1994-05-15

171

Brazeability of the 6061-T6 aluminum alloy with Al-Si-20Cu-based filler metals  

NASA Astrophysics Data System (ADS)

The bond strength of the 6061-T6 aluminum alloy brazed with Al-12Si, Al-9.6Si-20Cu, and Al-7Si-20Cu-2Sn filer metals at a low temperature of 550C is evaluated. The fractography of these brazements after tensile tests was observed using scanning electron microscopy (SEM). It was found that joints with good integrity can be produced with Al-7Si-20Cu-2Sn filler metal because it can be used in a temperature range of 504 to 526 C, about 70 C lower than the traditional Al-12Si filler metal. It was shown that joints of 6061-T6 aluminum alloy as the base metal, when brazed at 550 C for 60 min using this new filler metal and ward, and after being subjected to a T6 treatment, possessed a high bonding strength of about 121 Mpa.

Tsao, L. C.; Tsai, T. C.; Wu, C. S.; Chuang, T. H.

2001-12-01

172

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

173

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

174

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

175

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

176

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. PMID:24759082

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

2014-01-01

177

High temperature sulfidation behavior of low Al iron-aluminum compositions  

Microsoft Academic Search

Iron-aluminum weld overlay coatings are currently being considered for enhanced sulfidation resistance. The performance of these alloys in reducing atmospheres far exceeds other conventional materials presently used. However, the application of iron-aluminum alloys is currently limited due to hydrogen cracking susceptibility subsequent to welding. A direct correlation between the severity of embrittlement and the amount of aluminum in the alloy

S. W. Banovic; J. N. DuPont; A. R. Marder

1998-01-01

178

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

179

(31)P and (27)Al NMR studies of aqueous (2-hydroxyethyl) trimethylammonium solutions containing aluminum and phosphorus.  

PubMed

Phosphorus-31 and aluminum-27 nuclear magnetic resonance techniques have been used to characterize the distribution of soluble aluminophosphate species in aqueous solutions of (2-hydroxyethyl) trimethylammonium chloride (2-HETMACl), phosphoric acid, and aluminum sulfate. Soluble aluminophosphate cations obtain from reactions of hexaaqua aluminum cations [A1(H(2)O)(6)](3+), with phosphate ligands (i.e., H(3)PO(4), H(2)PO(4)(-), and acid dimers H(6)P(2)O(8) and H(5)P(2)O(7)(-)). (31)P NMR and (27)Al NMR spectroscopies are very powerful techniques for characterization of the species present in the solution. A number of solutions containing different mole ratio of Al/P were prepared. The assignment of the peaks to aluminate connectivities is attempted, clarifying earlier works and producing information on the equilibrium between various aluminum-containing species (different aluminophosphate complexes). At least seven separated resonances were observed by (31)P NMR spectroscopy indicating presence of different complexes in aluminum phosphate solutions. PMID:19041278

Samadi-Maybodi, Abdolraouf; Nejad-Darzi, S Karim Hassani; Bijanzadeh, Hamidreza

2009-03-01

180

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

181

Chemical synthesis of iron aluminide [FeAl] and iron aluminum carbide [Fe{sub 3}AlC{sub 0.5}] nanopowders  

SciTech Connect

Nanopowders of iron aluminide [FeAl] and iron aluminum carbide [Fe{sub 3}AlC{sub 0.5}] are prepared by a two-step process involving the reduction of iron chloride [FeCl{sub 3}] with lithium aluminum hydride [LiAlH{sub 4}]. LiAlH{sub 4} serves both as a reducing agent and as a source of aluminum atoms required for the formation of the aluminides. The two-step process involves a solution phase reduction step resulting in the formation of colloidal mixtures, which when heat treated at temperatures above 550 deg. C undergo solid state reactions to form the aluminides. Presence of ethereal solvents [tetrahydrofuran (THF) and diethyl ether] during the solution phase reduction step predominantly favors the formation of the carbide phase while reduction in a largely aromatic [75/25 volume percent toluene/THF] solvent mixture promotes the formation of the intermetallic FeAl phase in the heat-treated product. In the presence of ethereal solvents, the use of slower heating rates and performing a solvent removal step enhance the formation of the aluminide phase over the carbide phase. When the largely aromatic mixture is used as the solvent the treatments have no effect on the product distribution. Microstructure analysis using SEM and TEM imaging show that both FeAl and Fe{sub 3}AlC{sub 0.5} nanoparticles formed are embedded within aluminum oxide matrices. The average particle size of the FeAl nanoparticles is 4-8 nm.

Pithawalla, Yezdi B. [Research, Development and Engineering Center, Philip Morris USA, Richmond, VA 23261 (United States); Deevi, Sarojini [Research, Development and Engineering Center, Philip Morris USA, Richmond, VA 23261 (United States)]. E-mail: Sarojini.Deevi@pmusa.com

2004-12-02

182

Mechanical behavior of a continuous fiber-reinforced aluminum matrix composite subjected to transverse and thermal loading  

NASA Astrophysics Data System (ADS)

T HE TRANSVERSE properties of an aluminum alloy metal matrix composite reinforced by continuous alumina fibers have been investigated. The composite is subjected to both mechanical and cyclic thermal loading. The results of an experimental program indicate that the shakedown concept of structural mechanics provides a means of describing the material behavior. When the loading conditions are within the shakedown region the material finally responds in an elastic manner after initial plastic response, and for loading conditions outside the shakedown region the material exhibits a rapid incremental plastic strain accumulation. The failure strain varies by an order of magnitude according to the operating conditions. Hence for high mechanical and low thermal loading the failure strain is small, while for low mechanical and high thermal loading the failure strain is large.

Jansson, S.; Leckif, F. A.

183

Interaction of synthetic Alzheimer ? -protein-derived analogs with aqueous aluminum: A low-field 27 Al NMR investigation  

Microsoft Academic Search

Synthetic peptides corresponding to the soluble Alzheimer-protein, i.e., 140 and 6-25, were utilized to investigate the association of aluminum using low-field27Al nuclear magnetic resonance (NMR) spectroscopy and reversed-phase high-performance liquid chromatography (RP-HPLC). Addition of 1-40 or 6-25 to aqueous Al3+ gives rise to a27Al NMR signal corresponding to the association of Al3+ with the peptides; this effect is not easily

Sandip B. Vyas; Lawrence K. Duffy

1995-01-01

184

Matrix metalloproteinases (MMPs) and their tissue inhibitors (TIMPs) in amyotrophic lateral sclerosis (ALS).  

PubMed

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases, responsible for the integrity of the basement membrane (BM) via degradation of extracellular matrix and BM components. These enzymes are presented in central and peripheral nervous system. They are considered to be involved in the pathogenesis of several neurological diseases, including amyotrophic lateral sclerosis (ALS). ALS is a motor neuron disease, leading to muscle atrophy, paralysis and death within 3-5years from diagnosis. Currently, there is no treatment that can substantially prolong life of ALS patients. Despite the fact that MMPs are not specific for ALS, there is also strong evidence that these enzymes are involved in the pathology of ALS. MMPs are able to exert direct neurotoxic effects, or may cause cell death by degrading matrix proteins. The objective of this paper is to provide an updated and comprehensive review concerning the role of MMPs and their tissue inhibitors (TIMPs) in the pathology of ALS with an emphasis on the significance of MMP-2 and MMP-9 as well as their tissue inhibitors as potential biomarkers of ALS. Numerous hypotheses have been proposed regarding the role of selected MMPs and TIMPs in ALS pathogenesis. Moreover, selective MMPs' inhibitors might be potential targets for therapeutic strategies for patients with ALS. However, future investigations are necessary before some of those non-specific for ALS enzymes could finally be used as biomarkers of this disease. PMID:25047909

Lukaszewicz-Zaj?c, Marta; Mroczko, Barbara; S?owik, Agnieszka

2014-11-01

185

Processing stainless steel fibre reinforced NiAl matrix composites by reactive hot pressing  

Microsoft Academic Search

Stainless steel fibres (SSF) were first wound and then plated with electrical nickel film. Alternative layers of these properly\\u000a spaced Ni-coated stainless steel fibres (SSFNi) and aluminum foils were then stacked and diffusion bonded at 500 C, 100\\u000a MPa in vacuum for 10 min to produce an SSFNiAl precursor. Lower-temperature reactive hot pressing (RHP) at 700 C, a process\\u000a employed

SHOU-YI CHANG; SU-JIEN LIN

1997-01-01

186

High temperature dynamic modulus and damping of aluminum and titanium matrix composites  

NASA Technical Reports Server (NTRS)

Dynamic modulus and damping capacity property data were measured from 20 to over 500 C for unidirectional B/Al (1100), B/Al (6061), B/SiC/Al (6061), Al2O3/Al, SiC/Ti-6Al-4V, and SiC/Ti composites. The measurements were made under vacuum by the forced vibration of composite bars at free-free flexural resonance near 2000 Hz and at strain application below 0.000001. The damping of B/Al composites was found at all temperatures to be significantly greater than the damping of the Al2O3/Al and SiC/Ti composites, with little variation observed in the dynamic moduli of specimens having almost the same fiber content. It is concluded that on the practical level, the finding of a damping-strength correlation supports the use of composite damping measurements for the nondestructive evaluation of boron fiber strength in as-fabricated and heat-treated B/Al (6061) composites.

Dicarlo, J. A.; Maisel, J. E.

1979-01-01

187

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; Surez, Oscar Marcelo

2014-06-01

188

Copper matrix SiC and Al 2O 3 particulate composites by powder metallurgy technique  

Microsoft Academic Search

Copper matrix reinforced with either Ni-coated or uncoated SiC and Al2O3 particulate composites were made by means of the powder metallurgy route. The reinforcement particles of SiC and Al2O3 were coated with a thin layer of nickel by electroless method. The coated or uncoated reinforcement particles of either SiC or Al2O3 were added to copper metal powders with nominal loading

S. F Moustafa; Z Abdel-Hamid; A. M Abd-Elhay

2002-01-01

189

Research on laser welding of aluminum matrix composite SiCw\\/6061  

Microsoft Academic Search

Effects of laser welding parameters on strength of welded joint were studied. Mechanism of loss of joint strength was analyzed. It was pointed out that an important factor affecting joint strength is the reaction between matrix and reinforced phase. On the basis of this, the concept of critical Si activity was proposed. In appropriate welding parameters and Si activity, welded

Jitai Niu; Longxiu Pan; Muzhen Wang; Chengbin Fu; Xiaodong Meng

2006-01-01

190

The 1200 C cyclic oxidation behavior of two nickel-aluminum alloys (Ni3AL and NiAl) with additions of chromium, silicon, and titanium  

NASA Technical Reports Server (NTRS)

The alloys Ni3Al and NiAl with and without 1 and 3 atomic percent chromium, silicon, and titanium replacing the aluminum were cyclically oxidized at 1200 C for times to 200 hours, and the results were compared with those obtained with the alloy B-1900 subjected to the same oxidation process. The evaluation was based on metal recession, specific weight change, metallography, electron microprobe analysis, and X-ray diffraction. The oxidation resistance of Ni3Al was improved by Si, unaffected by Ti, and degraded by Cr. The oxidation resistance of NiAl was slightly improved by Ti, unaffected by Si, and degraded by Cr. The oxidation resistance of Ni3Al with 1 atomic percent Si was nearly equal to that of NiAl. Alloy B-1900 exhibited oxidation resistance comparable to that of Ni3Al + Cr compositions.

Lowell, C. E.; Santoro, G. J.

1972-01-01

191

Gas-phase rotational spectroscopy of AlCCH (X?+): A model system for organo-aluminum compounds  

NASA Astrophysics Data System (ADS)

The pure rotational spectrum of AlCCH in its ground electronic state (X?+) has been measured using Fourier transform microwave (FTMW) and mm/sub-mm direct absorption spectroscopy. AlCCH was created in a DC discharge from HCCH and aluminum vapor, either produced by a Broida-type oven, or generated from Al(CH3)3 in a supersonic jet source. Rotational transitions were measured for five isotopologues of AlCCH, with 13C and deuterium substitutions. From these data, rotational and Al and D quadrupole parameters were determined, as well as an accurate structure. AlCCH appears to exhibit an acetylenic arrangement with significant covalent character in the Al-C single bond.

Sun, M.; Halfen, D. T.; Min, J.; Clouthier, D. J.; Ziurys, L. M.

2012-11-01

192

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

193

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

194

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?, eljko J.; Jovi?evi?, Jovan N.

2013-02-01

195

Chemical compatibility of a TiAl-Nb melt with oxygen-free crucible ceramics made of aluminum nitride  

Microsoft Academic Search

The problem of uncontrolled oxygen contamination of intermetallic TiAl ingots is considered for the application of crucibles\\u000a and molds based on traditional oxide ceramics. A synthesized Ti-45.9Al-8Nb (at %) alloy is solidified in alternative oxygen-free\\u000a crucibles made of high-purity aluminum nitride (99.99% AlN) upon holding at 1670C for 5, 12, and 25 min and subsequent quenching\\u000a in a high-purity argon

A. V. Kartavykh; V. V. Cherdyntsev

2008-01-01

196

Observation of four-coordinate aluminum oxynitride (AlO{sub 4-x}N) environments in AlON solids by MAS ²⁷Al NMR at 14 T  

Microsoft Academic Search

The synthesis and magic angle spinning (MAS) [sup 27]Al NMR characterization of a series of aluminum oxynitride powders prepared at various AlN\\/Al[sub 2]O[sub 3] reaction ratios from 16.7 to 88.0 mole percent AlN are reported. The MAS NMR at 14 T reveal the presence of both six-(AlO[sub 6]) and four-coordinate (AlO[sub 4]) sites in lamda-AlON. Also observed were resonances dur

J. J. Fitzgerald; S. D. Kohl; G. Piedra

1994-01-01

197

Speciation of aqueous mononuclear Al(III)-hydroxo and other Al(III) complexes at concentrations of geochemical relevance by aluminum-27 nuclear magnetic resonance spectroscopy  

NASA Astrophysics Data System (ADS)

Aluminum-27 (27Al) nuclear magnetic resonance (NMR) spectroscopy was used to characterize Al(III)-hydroxo complexes, in aqueous solutions with total Al(III) concentrations of 1.0-10 ?M, using a custom-built NMR probe, coil, and sample bottle with low background aluminum impurities. Published 27Al NMR spectroscopy studies have traditionally used total Al(III) concentrations that are generally outside the range of geochemical interest (total [ Al(III) l ? 1000 ?M). In this study, lower Al(III) concentrations (? 10 ?M) were used to more closely approximate natural conditions, while allowing the measurement of mononuclear Al(III) species by 27Al NMR spectroscopy. The sensitivity of the 27Al NMR spectroscopy system, as measured by the signal-to-noise ratio (S/N), is S/N= 5 for 1.0 ?M Al(III) at pH 2.00 and S/N= 3 for 10 ?M Al(III) at pH 5.20. This level of sensitivity is within the range of geochemically relevant Al(III) concentrations found in slightly acidic natural waters. Quantitative models are developed which link observations of NMR chemical shifts and linewidth ratios to the calculated equilibrium speciation of mononuclear Al(III) for 10 ?M Al(III) solutions at pH values 2.00 to 5.20 (prepared by titrating acidic AI(III) solutions with pyridine). Linear-regression best fits of the models to the NMR data are used to determine the intrinsic chemical shifts and linewidths of individual mononuclear Al(III) species. The intrinsic chemical shift of each Al(III) species "i", ?i (ppm), is (1) ?Al3+ ? 0 for Al3+ (defined by convention), (2) ?Al(OH)2+ = 3.5 (SE= 1.3, N = 10) for Al(OH)2+, (3) ?Al(OH)2+ ? 3.7 (SE= 1.4, N = 10) for Al(OH)2+ , and (4) ?Al(OH)4- = 79.9 (SE= 0.03, N = 4) for Al(OH)4-; where positive chemical shifts are "downfield," SE = standard error, and N =number of samples. A convention is delineated in which the linewidth of the Al(III) species/peak of interest is normalized with respect to that of a reference species (Al3+) under the same conditions. Such linewidth ratios are independent of investigation-specific variables such as solution viscosity and temperature. Due to the large sample volume (18.8 mL) used here to achieve increased sensitivity, there is some line broadening caused by magnetic field inhomogeneities; however, this line broadening is constant and reproducible both during and between experimental runs, and it was corrected for in the determination of linewidths of individual Al(III) species. For an absolute linewidth of LWAl3+ = 1.6 Hz for Al3+, the linewidth ratio (ppm/ppm) of each species "i", (LWi)/(LWAl3+), is: (1) (LWAl3+)/(LWAl3+) ? 1for Al3+ (by definition), (2) LWAl(OH)2+/(LWAl3+)= 495 (SE= 11, N = 8) for Al(OH)2+, and (3) (LWAl(OH)2+)/LWAl3+= 450 (SE= 140, N = 10) for Al(OH)2+. The increased sensitivity of this system, and the knowledge of intrinsic 27Al NMR spectroscopic parameters for Al3+, Al(OH)2+, Al(OH)2+, and Al(OH)4-, sets the stage for use of 27Al NMR spectroscopy to characterize these species in natural waters and to study other Al(III) species of geochemical interest.

Faust, Bruce C.; Labiosa, William B.; Dai, K'o. H.; MacFall, Janet S.; Browne, Bryant A.; Ribeiro, Anthony A.; Richter, Daniel D.

1995-07-01

198

Structural Characterization of MAO and Related Aluminum Complexes. 1. Solid-State 27 Al NMR with Comparison to EFG Tensors from ab Initio Molecular Orbital Calculations  

SciTech Connect

Aminato and propanolato aluminum clusters with 3-, 4-, and 6-coordinate aluminum sites are studied with three 27Al NMR techniques optimized for large 27Al Quadrupole coupling constants: field-swept, frequency-stepped, and high-field MAS NMR. The 27Al quadrupole coupling constants and asymmetry parameters of molecular species, both experimental and derived from ab initio molecular orbital calculations, are correlated with structure.

Bryant, Pamela L.; Harwell, Chris; Mrse, Anthony A.; Emery, Earl F.; Gan, Zhedong; Caldwell, Tod; Reyes, Arneil P.; Kuhns, Philip; Hoyt, David W.; Simeral, Larry S.; Hall, Randall W.; Butler, Leslie G.

2001-11-07

199

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

200

Parameter optimization for controlling aluminum loss when laser depositing Ti-6Al-4V  

NASA Astrophysics Data System (ADS)

The ability to predict the mechanical properties of engineering materials is crucial to the manufacturing of advanced products. In the aerospace industry, Ti-6Al-4V is commonly used to build structures. Any deviation from the alloy's standard properties can prove detrimental. Thus, the compositional integrity of the material must be controlled. The ability to directly build and repair large, complicated structures directly from CAD files is highly sought after. Laser Metal Deposition (LMD) technology has the potential to deliver that ability. Before this process can gain widespread acceptance, however, a set of process parameters must be established that yield finished parts of consistent chemical composition. This research aims to establish such a set of parameters. Design of Experiments was utilized to maximize the information gained while minimizing the number of experimental trials required. A randomized, two-factor experiment was designed, performed, and replicated. Another set of experiments (nearly identical to the first) was then performed. The first set of experiments was completed in an open environment, while the second set was performed in an argon chamber. Energy Dispersive X-Ray Spectroscopy (EDS) was then used to perform a quantitative microanalysis to determine the aluminum level in each sample. Regression analysis was performed on the results to determine the factors of importance. Finally, fit plots and response surface curves were used to determine an optimal parameter set (process window). The process window was established to allow for consistent chemical composition of laser deposited Ti64 parts.

Barclay, Richard Charles

201

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

202

Brazing process using'al-Si filler alloy reliably bonds aluminum parts  

NASA Technical Reports Server (NTRS)

Brazing process employs an aluminum-silicon filler alloy for diffusion bonding of aluminum parts in a vacuum or inert gas atmosphere. This process is carried out at temperatures substantially below those required in conventional process and produces bonds of greater strength and reliability.

Beuyukian, C. S.; Johnson, W. R.

1966-01-01

203

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

Ramrez-Bentez, Jos Efran; Muoz-Snchez, J Armando; Becerril-Chi, Karen M; Miranda-Ham, Mara de Lourdes; Castro-Concha, Lizbeth A; Hernndez-Sotomayor, S M Teresa

2011-11-01

204

High strain rate superplasticity of AlN particulate reinforced 1N90 pure aluminum composite  

SciTech Connect

An A1N particulate reinforced aluminum alloy composite exhibits a high elastic modulus and a high thermal conductivity. Moreover, its thermal expansion is similar to silicon so that this composite is expected to apply to semi-conductor packaging in the aerospace structure. In addition, it was also found that the composite could produce superplasticity at high strain rates. But the superplastic characteristics of the aluminum alloy composites has not yet been clear entirely. The purpose of this study is to develop a thermomechanical processing route to produce a fine microstructure and to further produce HSRS in a 1N90 pure aluminum and in a A1N particulate reinforced 1N90 pure aluminum composite. In addition, the superplastic characteristics of the composite and the pure aluminum will also be discussed.

Imai, T. [National Industrial Research Inst., Nagoya (Japan)] [National Industrial Research Inst., Nagoya (Japan); L`Esperance, G.; Hong, B.D. [Ecole Polytechique de Montreal, Quebec (Canada)] [Ecole Polytechique de Montreal, Quebec (Canada); Kojima, S. [Nagoya Municipal Industrial Research Inst. (Japan)] [Nagoya Municipal Industrial Research Inst. (Japan)

1995-10-15

205

Hot deformation behavior of the new AlMgSiCu aluminum alloy during compression at elevated temperatures  

Microsoft Academic Search

The hot deformation behavior of the new AlMgSiCu aluminum alloy was investigated by compression tests in the temperature range 350C550C and strain rate range 0.005s?15s?1 using Gleeble-1500 system, and the associated structural changes were studied by observations of metallographic and TEM. The results show that the true stresstrue strain curves exhibit a peak stress at a small strain (<0.15), after

Hui Zhang; Luoxing Li; Deng Yuan; Dashu Peng

2007-01-01

206

ANALYSIS OF ANISOTROPY IN ELASTIC CONSTANTS OF SiCp/2124 Al METAL MATRIX COMPOSITES  

E-print Network

their properties can be tailored through the addition of selected reinforcements. [1,2] In particular, particulate phases of matrix and reinforcement. The Mori-Tanaka model [8], based on average field theory, has been the anisotropic elastic constants of particulate SiC/Al composites using the Mori-Tanaka model in connection

Hong, Soon Hyung

207

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

208

Observation of four-coordinate aluminum oxynitride (AlO{sub 4-x}N{sub x}) environments in AlON solids by MAS {sup 27}Al NMR at 14 T  

SciTech Connect

The synthesis and magic angle spinning (MAS) [sup 27]Al NMR characterization of a series of aluminum oxynitride powders prepared at various AlN/Al[sub 2]O[sub 3] reaction ratios from 16.7 to 88.0 mole percent AlN are reported. The MAS NMR at 14 T reveal the presence of both six-(AlO[sub 6]) and four-coordinate (AlO[sub 4]) sites in lamda-AlON. Also observed were resonances dur to four-coordinate AlNO[sub 3], AlN[sub 2]O[sub 2], and AlN[sub 3]O sites in the various AlON reaction products, as well as NMR peaks due to the unreacted AlN and Al[sub 2]O[sub 3]. The results of these investigations indicate that sufficient spectral resolution can be obtained via MAS at this field to distinguish and assign four-coordinate aluminum oxynitride moieties in these unique AlON ceramic materials.

Fitzgerald, J.J.; Kohl, S.D.; Piedra, G. [South Dakota State Univ., Brookings, SD (United States)

1994-11-01

209

Stress Corrosion Cracking in Al-Zn-Mg-Cu Aluminum Alloys in Saline Environments  

NASA Astrophysics Data System (ADS)

Stress corrosion cracking of Al-Zn-Mg-Cu (AA7xxx) aluminum alloys exposed to saline environments at temperatures ranging from 293 K to 353 K (20 C to 80 C) has been reviewed with particular attention to the influences of alloy composition and temper, and bulk and local environmental conditions. Stress corrosion crack (SCC) growth rates at room temperature for peak- and over-aged tempers in saline environments are minimized for Al-Zn-Mg-Cu alloys containing less than ~8 wt pct Zn when Zn/Mg ratios are ranging from 2 to 3, excess magnesium levels are less than 1 wt pct, and copper content is either less than ~0.2 wt pct or ranging from 1.3 to 2 wt pct. A minimum chloride ion concentration of ~0.01 M is required for crack growth rates to exceed those in distilled water, which insures that the local solution pH in crack-tip regions can be maintained at less than 4. Crack growth rates in saline solution without other additions gradually increase with bulk chloride ion concentrations up to around 0.6 M NaCl, whereas in solutions with sufficiently low dichromate (or chromate), inhibitor additions are insensitive to the bulk chloride concentration and are typically at least double those observed without the additions. DCB specimens, fatigue pre-cracked in air before immersion in a saline environment, show an initial period with no detectible crack growth, followed by crack growth at the distilled water rate, and then transition to a higher crack growth rate typical of region 2 crack growth in the saline environment. Time spent in each stage depends on the type of pre-crack ("pop-in" vs fatigue), applied stress intensity factor, alloy chemistry, bulk environment, and, if applied, the external polarization. Apparent activation energies ( E a) for SCC growth in Al-Zn-Mg-Cu alloys exposed to 0.6 M NaCl over the temperatures ranging from 293 K to 353 K (20 C to 80 C) for under-, peak-, and over-aged low-copper-containing alloys (<0.2 wt pct) are typically ranging from 80 to 85 kJ/mol, whereas for high-copper-containing alloys (>~0.8 wt pct), they are typically ranging from 20 to 40 kJ/mol for under- and peak-aged alloys, and based on limited data, around 85 kJ/mol for over-aged tempers. This means that crack propagation in saline environments is most likely to occur by a hydrogen-related process for low-copper-containing Al-Zn-Mg-Cu alloys in under-, peak- and over-aged tempers, and for high-copper alloys in under- and peak-aged tempers. For over-aged high-copper-containing alloys, cracking is most probably under anodic dissolution control. Future stress corrosion studies should focus on understanding the factors that control crack initiation, and insuring that the next generation of higher performance Al-Zn-Mg-Cu alloys has similar longer crack initiation times and crack propagation rates to those of the incumbent alloys in an over-aged condition where crack rates are less than 1 mm/month at a high stress intensity factor.

Holroyd, N. J. Henry; Scamans, G. M.

2013-03-01

210

49 CFR 178.46 - Specification 3AL seamless aluminum cylinders.  

Code of Federal Regulations, 2011 CFR

...following conditions: (1) Starting stock must be cast stock or traceable to cast stock. (2) Material with seams, cracks, laminations...will identify the alloy, the aluminum producer's cast number, the solution heat treat batch number...

2011-10-01

211

49 CFR 178.46 - Specification 3AL seamless aluminum cylinders.  

Code of Federal Regulations, 2010 CFR

...following conditions: (1) Starting stock must be cast stock or traceable to cast stock. (2) Material with seams, cracks...will identify the alloy, the aluminum producer's cast number, the solution heat treat batch number...

2010-10-01

212

49 CFR 178.46 - Specification 3AL seamless aluminum cylinders.  

Code of Federal Regulations, 2013 CFR

...following conditions: (1) Starting stock must be cast stock or traceable to cast stock. (2) Material with seams, cracks, laminations...will identify the alloy, the aluminum producer's cast number, the solution heat treat batch number...

2013-10-01

213

49 CFR 178.46 - Specification 3AL seamless aluminum cylinders.  

Code of Federal Regulations, 2012 CFR

...following conditions: (1) Starting stock must be cast stock or traceable to cast stock. (2) Material with seams, cracks, laminations...will identify the alloy, the aluminum producer's cast number, the solution heat treat batch number...

2012-10-01

214

Bulk critical state and fundamental length scales of superconducting nanocrystalline Nb3Al in Nb-Al matrix  

NASA Astrophysics Data System (ADS)

We present the results of magnetization measurements on an as-cast nanocrystalline Nb3Al superconductor embedded in Nb-Al matrix. The typical grain size of Nb3Al ranges from about 2-8 nm with the maximum number of grains at around 3.5 nm, as visualized using transmission electron microscopy. The isothermal magnetization hysteresis loops in the superconducting state can be reasonably fitted within the well-known Kim-Anderson critical-state model. By using the same fitting parameters, we calculate the variation in field with respect to distance inside the sample and show the existence of a critical state over length scales much larger than the typical size of the superconducting grains. Our results indicate that a bulk critical current is possible in a system comprising of nanoparticles. The nonsuperconducting Nb-Al matrix thus appears to play a major role in the bulk current flow through the sample. The superconducting coherence length ? is estimated to be around 3 nm, which is comparable to the typical grain size. The penetration depth ? is estimated to be about 94 nm, which is much larger than the largest of the superconducting grains. Our results could be useful for tuning the current carrying capability of conductors made out of composite materials which involve superconducting nanoparticles.

Mondal, Puspen; Manekar, Meghmalhar; Srivastava, A. K.; Roy, S. B.

2009-07-01

215

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 773 K for 1 h, 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 318 MPa, which was very close to the theoretical calculation value of 326 MPa. 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

216

Investigation on Thermal Properties of Al/SiCp Metal Matrix Composite Based on FEM Analysis  

NASA Astrophysics Data System (ADS)

Computational simulations on the thermal analysis of metal matrix composite (MMC) composed of Al and SiC were performed in extended areas of SiC volume fraction. Due to the experimental limitations, only the narrow range of SiC volume fraction has been examined. Through the simulation, which enables current experimental situation to extend, we attempted to explore the dependencies of thermal and mechanical properties on changing the value of volume fraction (Vf). To calculate the coefficient of thermal expansion (CTE), variables with temperature and Vf were given in a range from 25C to 100C and 0 to 100%, respectively. We obtained quantitative results including CTE as a function of Vf, which are in a good agreement with previous experimental reports. Furthermore, the stress analysis about thermally expanded MMC was performed. At low volume fraction of SiC, the thermal expansion caused the tensile stress at Al near the interface. However, as the volume fraction of SiC was increased, the stress turned to be compressive, it's because the linked SiC particles contracted the expansion of Al. The MMC of Al matrix face centered cubic site SiC particles has more stress evolutions than the MMC of Al matrix simple cubic site SiC particles at same volume fraction.

Yu, Eusun; Sun, Jeong-Yun; Chung, Hee-Suk; Oh, Kyu Hwan

217

Improvement of Mechanical Properties in the Functionally Graded Aluminum Matrix Nanocomposites Fabricated via a Novel Multistep Friction Stir Processing  

NASA Astrophysics Data System (ADS)

In the present study, the functionally graded bulk Al-SiC nanocomposites were successfully fabricated by applying a novel multistep friction stir processing. Microstructural observations by scanning electron microscope indicated a proper distribution of SiC nanoparticles in the Al 6061 matrix. Microhardness profiles descended to 50 from 160 Hv due to the formation of compositionally gradient of SiC nanoparticles along the thickness. The tensile behavior of graded samples revealed a simultaneous enhancement of ultimate tensile strength (44 pct), strain at maximum stress (244 pct), and work of fracture (492 pct) with respect to the homogeneous sample. Furthermore, the graded samples sustained up to 4 pct strain after initiation of primary cracking, while the catastrophic fracture occurred instantly after cracking in the homogenous sample. A dimple-like ductile fracture surface was observed for the graded layers in which an increase in the SiC particle content will result in smaller dimple size.

Salehi, Mojtaba; Farnoush, Hamidreza; Heydarian, Arash; Aghazadeh Mohandesi, Jamshid

2014-09-01

218

Continuous synthesis of high-surface-area aluminum hydroxide methoxide nano- and microparticles in supercritical methanol and their conversion into ?-Al 2O 3  

Microsoft Academic Search

High-surface-area aluminum hydroxide methoxide (CH4Al2O4) nano- and microparticles are synthesized continuously in supercritical methanol (scMeOH). The properties of the particle synthesized in scMeOH are compared with those synthesized in supercritical water (scH2O). The XRD analysis reveals that the particles synthesized in scMeOH retain aluminum hydroxide methoxide crystalline structure while the particles synthesized in supercritical water retain boehmite (AlOOH) crystalline structure.

Bambang Veriansyah; Ratna F. Susanti; Agung Nugroho; Byoung Koun Min; Jaehoon Kim

2011-01-01

219

Aluminum chlorohydrate III: Conversion to aluminum hydroxide.  

PubMed

Bayerite, an aluminum hydroxide polymorph, readily forms when the hydroxyl to aluminum ratio of aluminum chlorohydrate is raised to 3 by titration with sodium hydroxide. Dilution of aluminum chlorhydrate solutions with water leads to the formation of gibbsite, another aluminum hydroxide polymorph. The mechanism of conversion in each instance is related to the structure of the Al13O4(OH)24(H2O)7+(12) complex. PMID:7264935

Teagarden, D L; White, J L; Hem, S L

1981-07-01

220

Effect of reinforcement size on low cycle fatigue behavior of SiC particle reinforced aluminum matrix composites  

SciTech Connect

From the examination of the particle size effect on the cyclic deformation in SiC/Al composites, the authors offer the following conclusions: SiCp/Al composite displayed continuous cyclic softening after initial hardening for any two or three cycles. In contrast, the unreinforced matrix showed initial cyclic hardening, cyclic stability and second hardening. Higher stress in response to a given strain amplitude were observed with the composite with fine (10 {micro}m) SiC particles in comparison with the composite with coarse (32 {micro}m) SiC particles. In addition, the evolution of cyclic softening became faster when the particle size increased. The low cycle fatigue endurance of the composites was generally lower than that of the unreinforced matrix. The decrease in particle size led to a higher fatigue resistance at lower strain amplitudes, but reduced the fatigue life at higher strain amplitudes. The particle size effect on cyclic response behavior can be explained when the difference in interparticle spacing and thus the difference in plastic deformation ability between the coarse and fine particle composites are taken into account. The particle size effect on fatigue-life behavior was explained in terms of the fracture modes.

Han, N.L.; Wang, Z.G.; Sun, L. [Academia Sinica, Shenyang (China). State Key Lab. for Fatigue and Fracture of Materials] [Academia Sinica, Shenyang (China). State Key Lab. for Fatigue and Fracture of Materials

1995-09-01

221

Comparative X-ray and 27Al NMR spectroscopic studies of the speciation of aluminum in aqueous systems: Al(III) complexes of N(CH 2CO 2H) 2(CH 2CH 2OH)  

Microsoft Academic Search

It is recognized that many aspects of the aqueous chemistry of AlIII and FeIII are similar and this might explain how aluminum is able to enter organisms. Since aluminum is potentially toxic, it is important to be able to characterize its speciation in solution. Three major difficulties are the existence of a large number of equilibrium processes, its ready hydrolysis,

Sarah L Heath; Peter A Jordan; Ian D Johnson; Geoffrey R Moore; Annie K Powell; Madeleine Helliwell

1995-01-01

222

Investigation of the structure/property relationship of spray-formed 7XXX series high-strength aluminum alloys and their metal matrix composites  

NASA Astrophysics Data System (ADS)

The purpose of this investigation was to identify the structure/property relationship of spray formed 7XXX series alloys. High solute, ultra-high strength 7XXX series aluminum alloys with solute contents close to equilibrium solid solubility limits of the Al-Zn-Mg-Cu system have been produced by rapid solidification using spray deposition. The process yields massive preforms directly from the liquid state. Various elements, including chromium, manganese, silver, zirconium and scandium, were incorporated to produce a variety of microstructures and mechanical properties. SiC particulate was added to these same alloy compositions to produce metal matrix composites (MMCs). The resulting extruded products in the T6 and T7 conditions were evaluated and compared. Under peak-aged conditions in the unreinforced materials, strengths in excess of 860 MPa were achieved, with one alloy exceeding 900 MPa. Apart from the elongation to failure, the mechanical properties of the composite materials were equal to or superior to those of their unreinforced counterparts. The superior strength properties of the spray formed alloys were attributed to two major substructures with different scale; nanometer sized eta ' metastable precipitates and slightly larger, but finely distributed dispersoids. The large volume fraction of plate-like eta' precipitates (average size 58A, ranging up to 73 A in diameter) were identified as having a hexagonal structure with lattice parameters a = 0.488 nm and c = 1.376. The remarkable strengthening is predominantly attributed to precipitation hardening. The enhanced mechanical properties of the MMC materials are attributed to the increased dislocation density, and thus, a higher concentration of structural particles compared to the unreinforced materials. Higher gas-to-metal ratios of 4.45, as opposed to lower gas-to-metal ratios of 1.95 produced a refined grain structure with an evenly distributed second phase. In both unreinforced and MMC materials, alloys with zinc contents over 12 wt. % attained the highest concentration of structural particles. One alloy displayed high strengths exceeding all others in the study. The superior strength properties were attributed to the addition of scandium, which produced a fine dispersion of the Al3Sc phase. This finely dispersed phase created additional strengthening through, coherency mismatch of Al3Sc and Al3(Sc,Zr) precipitates with the matrix, and ordered particle strengthening. The spray formed extrusions exhibited a loss in fracture resistance (K Q), compared to IM 7075 alloys. Characterization of the fracture surfaces indicated a predominantly intergranular decohesion, possibly facilitated by the presence of incoherent particles at the grain boundary regions and by the large strength differential between the matrix and precipitate zone. The MMC materials displayed a large increase in fatigue strength compared to commercial IM 7075-T6 and -T7 alloys. The enhanced fatigue performance of the spray formed alloys is attributed to low crack growth rates, which are a consequence of inhomogeneous slip. It is believed that the massive presence of coherent and semicoherent (GP zones and eta' phase) particles of reduced dimension in the spray formed alloys allowed a highly inhomogeneous slip behavior, where a slip reverse mechanism was operative.

Sharma-Judd, Malavika M.

223

Friction behavior of ceramic fiber-reinforced aluminum metal-matrix composites against a 440C steel counterface  

Microsoft Academic Search

The friction behavior of short ceramic fiber-reinforced aluminum MMCs against a steel counterface is investigated. The friction coefficients between metallographically polished surfaces of kaowool and saffil fiber-reinforced aluminum MMCs and 44 C steel counterface varied between 0.4 and 0.6. The friction traces were rough with characteristic stick-slip behavior. Transfer of aluminum to steel counterface was observed in all cases. The

S. V. Prasad; K. R. Mecklenburg

1993-01-01

224

X-ray photoelectron spectroscopy study of catalyzed aluminum carbide formation at aluminum-carbon interfaces  

NASA Technical Reports Server (NTRS)

Aluminum carbide may form at aluminum-graphite interfaces during the high-temperature processing of graphite fiber-reinforced aluminum metal matrix composites. The chemical interactions leading to the formation of the aluminum carbide in the solid state involve the breaking of the carbon-carbon bonds within the graphite, the transport of the carbon atoms across the interface, and the reaction with the aluminum to form Al4C3. The aluminum carbide formation process has been followed using X-ray photoelectron spectroscopy of model, thin-film, reaction couples. The overall reaction is shown to be catalyzed by the presence of water vapor. Water at the interface increases reaction kinetics by apparently weakening the bonds between the surface carbon atoms and their substrate. This result is in general agreement with what is known to occur during the oxidation of graphite in air.

Rabenberg, L.; Maruyama, Benji

1990-01-01

225

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. PMID:24022670

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

226

Investigation of the formation of InAs QDs in a AlGaAs matrix  

Microsoft Academic Search

Optical and structural properties of self organized InGaAs quantum dots (QD), deposited in Al0.3Ga0.7As matrix, were investigated. Samples were grown by molecular-beam epitaxy (MBE). It is shown, that deposition of 1.7 - 4 monolayer of InAs on Al0.3Ga0.7As surface results in formation of nanoscale QDs on 1 - 2 monolayer thick wetting layer (Stranski-Krastanov growth mode). Large exciton localization energy

D. S. Sizov; N. V. Kryzhanovskaya; A. G. Gladyshev; Yu B. Samsonenko; G. E. Cirlin; N. K. Polyakov; V. A. Egorov; A. A. Tonkih; Yu G. Musikhin; Anrei F. Tsatsul'nikov; N. N. Ledentsov; Victor M. Ustinov

2003-01-01

227

Fabrication and fracture behavior of metallic fiber reinforced NiAl matrix composites  

SciTech Connect

NiAl intermetallic is recently of considerable interest as the high temperature structure material because of its high melting point, high specific stiffness, better oxidation and creep resistance. However, the low-temperature brittleness of the NiAl intermetallic remained a main reason for its unpopularity for industrial applications. Composite ductile phase toughening approaches have been utilized by many researchers to improve the fracture toughness of intermetallics. In liquid metallurgy, pressure casting or infiltration of molten nickel aluminide into a preform is the usual method for the fabrication of nickel aluminide intermetallic composites. But generally, it is not useful for metallic reinforcements because of the drastic reactions between the molten nickel aluminide and the metallic preform, and the difficulty in sustaining the performance of the metallic preform at a high temperature. In solid metallurgy, this process is based on reactive powder metallurgy and hot pressing, hot extrusion and hot isostatic pressing (HIP). High processing temperature and pressure, generally at a temperature of at least 1,200 C, are necessary conditions for hot pressing, hot extrusion and HIP. Hence the processes require sophisticated manufacturing equipment and considerable energy and render the application of nickel aluminide intermetallic composites unpopular. Work on reactive hot pressing(RHP) at a low temperature near the melting point of aluminum is reconsidered again. Efforts indicated that by combining the spontaneous reaction of the electrically coated nickel film and the aluminum foils, and hot pressing at a temperature about 500 C lower than previously accomplished by HIP, would overcome the fabrication problem of NiAl intermetallic composites reinforced with the uniformly distributed metallic fibers.

Chang, S.Y.; Lin, S.J. [National Tsing Hua Univ., Hsinchu (Taiwan, Province of China). Dept. of Materials Science and Engineering] [National Tsing Hua Univ., Hsinchu (Taiwan, Province of China). Dept. of Materials Science and Engineering

1997-07-01

228

Microstructural development in irradiated U-7Mo\\/6061 Al alloy matrix dispersion fuel  

Microsoft Academic Search

A U-7Mo alloy\\/6061 Al alloy matrix mini-dispersion fuel plate was irradiated in the Advanced Test Reactor and then examined using optical metallography and scanning electron microscopy to characterize the developed microstructure. Results were compared to the microstructure of the as-fabricated dispersion fuel to identify changes that occurred during irradiation. The layer that formed on the surface of the fuel U-7Mo

Dennis D. Keiser Jr.; Adam B. Robinson; Jan-Fong Jue; Pavel G. Medvedev; Daniel M. Wachs; M. Ross Finlay

2009-01-01

229

Experimental analysis of aluminum yield surface for binary Al?Mg alloy sheet samples  

Microsoft Academic Search

In this work, the yield surfaces of binary aluminum-magnesium alloy sheet samples were measured using biaxial compression tests. Sheet samples of a given material were stacked and bonded together with epoxy and cubic compression specimens were machined out of the laminate. The yielding behavior was assumed to be independent of the hydrostatic pressure. In the analysis of the biaxial compression

Y. Maeda; M. Yanagawa; F. Barlat; K. Chung; Y. Hayashida; S. Hattori; K. Matsui; J. C. Brem; D. J. Lege; S. J. Murtha; T. Ishikawa

1998-01-01

230

Matrix grain characterisation by electron backscattering diffraction of powder metallurgy aluminum matrix composites reinforced with MoSi{sub 2} intermetallic particles  

SciTech Connect

Research highlights: Six extruded PM AA6061/MoSi{sub 2}/15p were processed with and without ball milling {yields} EBSD was used to characterise matrix grain size and grain orientation. {yields} Ball milling decreases matrix grain size to submicrometric level. {yields} Ball milling produces a more equiaxed microstructure and larger misorientation. {yields} Increasing milling time produces matrix texture randomization.

Corrochano, J., E-mail: javier.corrochano.flores@gmail.com; Hidalgo, P.; Lieblich, M.; Ibanez, J.

2010-11-15

231

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 600800C 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

232

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-Alarcn, L.; Sols-Casados, D. A.; Romero, S.; Fernndez, M.; Prez-lvarez, J.; Haro-Poniatowski, E.

2013-10-01

233

The Role of Oriented Growth in P Texture Development in Al-Mn-Mg Aluminum Alloy  

NASA Astrophysics Data System (ADS)

The deformation and recrystallization textures in straight-rolled and cross-rolled AA 3105 aluminum alloy were investigated by x-ray diffraction to determine the role of oriented growth in the formation of the P recrystallization texture. A very strong P texture was developed in the straight-rolled sheet after recrystallization annealing. In contrast, the cross-rolled sheet did not develop the P texture on annealing even though the cross-rolling (i.e., rolling along the original transverse direction) texture contained more orientations close to the P orientation than the straight-rolling texture. The formation of the P texture in aluminum alloys requires the presence of the C component, since the P orientation has a 31.1<122> orientation relationship with respect to the C orientation. The recrystallization texture in the cross-rolled sheets was in excellent agreement with the oriented growth theory.

Ma, M.; Wang, W. X.; Zhang, J. X.; Liu, W. C.

2014-09-01

234

Study on bulk aluminum matrix nano-composite fabricated by ultrasonic dispersion of nano-sized SiC particles in molten aluminum alloy  

Microsoft Academic Search

Lightweight metal matrix nano-composites (MMNCs) (metal matrix with nano-sized ceramic particles) can be of significance for automobile, aerospace and numerous other applications. It would be advantageous to produce low-cost as-cast bulk lightweight components of MMNCs. However, it is extremely difficult to disperse nano-sized ceramic particles uniformly in molten metal. This paper presents a new method for an inexpensive fabrication of

Yong Yang; Jie Lan; Xiaochun Li

2004-01-01

235

Synthesis of Al4SiC4 powders from kaolin grog, aluminum and carbon black by carbothermal reaction  

NASA Astrophysics Data System (ADS)

In this paper, the synthesis of Al4SiC4 used as natural oxide materials by carbothermal reduction was investigated in order to explore the synthesis route with low costs. The samples were calcined by using kaolin grog, aluminum and carbon black as raw materials with the selected proportion at the temperature from 1500 to 1800 C for 2 hours under flow argon atmosphere. The phase composition of reaction products were determined by X-ray diffraction. The microstructure and elemental composition of different phases were observed and identified by scanning electron microscopy and energy dispersive spectroscopy. The mechanism of reaction processing was discussed. The results show that Al4SiC4 powders composed of hexagonal plate-like particulates with various sizes and the thickness of less than 20 ?m are obtained when the temperature reaches 1800 C.

Yuan, Wenjie; Yu, Chao; Deng, Chengji; Zhu, Hongxi

2013-12-01

236

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

237

Observation of an elementary cuboctahedron of Xe nanocrystal in an Al matrix.  

SciTech Connect

When a noble gas element such as Xe is implanted in an fcc metal matrix such as Al at room temperature, a fine dispersion of precipitates forms. The precipitates are elementary fcc crystals up to diameters of several nanometers (for Xe in Al, 8-10 rim), above which they are non-crystalline. The precipitates exhibit a cube-on-cube orientation relation with the matrices and have lattice parameters which are much larger than those of the matrices (a{sub Xe} = 1.5a{sub Al}). Thus the interphase interfaces are incommensurate though the lattices are isotactic. The precipitates assume the shape of matrix cavities; for an Al matrix, at equilibrium this is a cuboctahedron, a {r_brace}111{l_brace} octahedron truncated at the corners on {l_brace}100{r_brace}. Fig. 1 is a sketch of a dispersion of such cuboctahedra, viewed approximately along a {l_angle}110{r_angle}. For this study specimens were prepared in the HVEM-Tandem Facility at Argonne National Laboratory by implanting 35 keV Xe to a dose of 4x10{sup 19} m{sup {minus}2} into well-annealed 5N Al discs which had been thinned by jet electropolishing. The range of the implant is approximately 25 nm. Specimens were examined at high resolution in the JEOL ARM-1000 high voltage electron microscope (HVEM) at the High Resolution Beam Station of the National Research Institute for Metals (NRIM), Tsukuba, Japan. The HVEM was operated at 1 MeV with a LaB{sub 6} electron source. A series of studies of electron irradiation effects in this material have been conducted, which have revealed a number of irradiation-induced phenomena including migration within the matrix, changes in shape, faulting, melting, crystallization and coalescence of Xe precipitates. In this presentation, the structure of the smallest possible cuboctahedral Xe nanocrystal will be discussed and its apparently random migration under the influence of the electron irradiation will be demonstrated.

Allen, C. W.; Birtcher, R. C.; Donnelly, S. E.; Furuya, K.; Ryan, E. A.; Song, M.

1999-03-10

238

Microstructural development in irradiated U-7Mo/6061 Al alloy matrix dispersion fuel  

NASA Astrophysics Data System (ADS)

A U-7Mo alloy/6061 Al alloy matrix mini-dispersion fuel plate was irradiated in the Advanced Test Reactor and then examined using optical metallography and scanning electron microscopy to characterize the developed microstructure. Results were compared to the microstructure of the as-fabricated dispersion fuel to identify changes that occurred during irradiation. The layer that formed on the surface of the fuel U-7Mo particles during fuel plate fabrication exhibits stable irradiation performance as a result of the 0.88 wt% Si present in the fuel meat matrix. During irradiation, the pre-formed interaction layer changed very little in thickness and composition. The overall irradiation performance of the fuel plate to moderate power and burnup was considered excellent.

Keiser, Dennis D., Jr.; Robinson, Adam B.; Jue, Jan-Fong; Medvedev, Pavel; Wachs, Daniel M.; Finlay, M. Ross

2009-09-01

239

Vacuum Carbothermic Production of Aluminum and Al-Si Alloys From Kaolin Clay: A Thermodynamic Study  

Microsoft Academic Search

Examination of the thermodynamic constraints for the carbothermic reduction of iron-free kaolinite, Al2Si2O5(OH)4, or of its calcination product mullite, Al6Si2O13, either at atmospheric pressure, or under vacuum of 10 to 10bar, indicates the conditions required at equilibrium to produce either elementary Al or Al-Si alloys. At atmospheric pressure, a very high temperature of 3200K would be required to obtain from

M. Halmann

2012-01-01

240

Stability measurements of aluminum-stabilized NbTi and bronze matrix Nb/sub 3/Sn potted superconducting magnets. Research and development report  

SciTech Connect

Two epoxy-impregnated superconducting test coils, containing 0.635-centimeter electrical heaters imbedded in their windings, have been constructed to measure the minimum energy-to-quench as a function of operating current at various fixed levels of magnetic field strength. One test coil was wound with aluminum-stabilized NbTi superconducting wire and the other coil was wound with bronze matrix Nb/sub 3/Sn superconducting wire. The results of the energy-to-quench measurements are presented for both these test coils, and these results are compared to the previous measurements made for copper-stabilized NbTi test coils.

Waltman, D.J.; Superczynski, M.J.; McDonald, F.E.

1982-03-01

241

In situ SEM thermal fatigue of Al/graphite metal matrix composites  

NASA Technical Reports Server (NTRS)

Several thermal fatigue-induced failure mechanisms are deduced for unidirectional graphite-reinforced 6061 Al-alloy MMCs subjected to in situ thermal cycling. These thermal cycling conditions are representative of MMC service cycles in aerospace environments, where thermal fatigue is primarily associated with changes in the stress states near the interfaces due to coefficient of thermal expansion mismatch between fiber and matrix. This in situ SEM thermal-cycling study clarified such factors affecting MMCs' thermal fatigue as local fiber content and distribution, void volume, fiber stiffness, thermal excursion magnitude, and number of thermal cycles. MMC microfailure modes in thermal fatigue have been deduced.

Zong, G. S.; Rabenberg, L.; Marcus, H. L.

1990-01-01

242

High room-temperature plastic and work-hardening effect of the NiAl-matrix composites reinforced by particulates  

Microsoft Academic Search

The microstructures, interfaces, compression properties and work-hardening effect of the NiAl-matrix composites reinforced by 520wt.% ceramic particulates (Nb2C, NbC and NbB2) fabricated by combustion synthesis and hot pressing (CSHP) have been investigated. The ultimate compression strength and yield strength increase with the increasing content of the ceramic particulates, while the fracture strain and work-hardening capacity (Hc) decrease. The NiAl-matrix composite

Hailong Zhao; Feng Qiu; Shenbao Jin; Qichuan Jiang

2011-01-01

243

Effects of alloying elements on microstructure and protective properties of Al 2O 3 coatings formed on aluminum alloy substrates by plasma electrolysis  

Microsoft Academic Search

Hard alumina coatings were formed on three typical Al alloys using a plasma electrolytic oxidation (PEO) process. The microstructure and protective behavior of the coatings were characterized in the context of the elements alloyed in the substrates. The substrates investigated were three commercial aluminum alloys (Al 6061, 2024, 7075) and various Al?xMg binary alloys with x=0.64.6wt.%. The major portion of

Yong-Jun Oh; Jung-Il Mun; Jung-Hwan Kim

2009-01-01

244

Hardness and tensile strength of zircon particles and TiB 2 reinforced Al-A356.1 alloy matrix composites: comparative study  

NASA Astrophysics Data System (ADS)

Aluminum matrix composites are important engineering materials in automotive, aerospace, thermal, wear, and other applications because of excellent low weight, high specific strength, and better physical and mechanical properties compared to pure aluminum. In this paper, zircon and TiB II ceramic particles with different amounts were incorporated into Al-A356.1 alloy by stir-casting route. The ceramic particles size and adding temperature were 1 micron and 750C respectively. Microstructure of samples has been investigated by scanning electron microscopy (SEM); hence the dispersion of reinforcement was noted. Situation of compounds of composites was examined by XRD. Mechanical tests such as hardness measurement, tensile and physical (density) tests were used. Results showed that the mechanical properties and microstructure behavior of composites have improved compared to monolithic alloy. Microstructures of the composites in as-cast conditions show uniform distribution particles and reveal better bonding in the case of zircon reinforced composite compare to TiB II, but increasing the amount of reinforcement shows better conditions in the case of TiB II reinforced composite. It is observed that TiB II reinforced composites have a better wetting condition compare to zircon reinforced composites.

Shirvani Moghaddam, K.; Abdizadeh, H.; Baharvandi, H. R.; Ehsani, N.; Abdi, F.

2007-07-01

245

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

246

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

247

Dynamic failure mechanisms in a 6061-T6 Al\\/Al 2O 3 metalmatrix composite  

Microsoft Academic Search

The dynamic failure of an alumina particle-reinforced 6061-T6 aluminum alloy composite has been studied using a tension Kolsky bar, and the process of fracture has been investigated using scanning electron microscopy. The failure of a 6061-T6 aluminum alloy was also studied for purposes of comparison. The composite was found to fail in a macroscopically brittle manner in tension, with a

D. R. Chichili; K. T. Ramesh

1995-01-01

248

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

249

Mechanisms of interaction controlling the kinetics of zone formation in metal matrix composites: comparison of the effect of the reinforcement in AlCu and AlMgSi matrix composites  

Microsoft Academic Search

The effects of the presence of ceramic particles in an AlCu alloy and in an AlMgSi alloy on the modification of the kinetics of zone formation are compared. Thermoelectric power measurements, performed on the unreinforced and reinforced alloys, show that the kinetics of GuinierPreston zone formation are significantly retarded in the AlCu matrix composite, while they are only slightly modified

V Massardier; P Merle

1998-01-01

250

Sporadic ALS has compartment-specific aberrant exon splicing and altered cell-matrix adhesion biology  

PubMed Central

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive weakness from loss of motor neurons. The fundamental pathogenic mechanisms are unknown and recent evidence is implicating a significant role for abnormal exon splicing and RNA processing. Using new comprehensive genomic technologies, we studied exon splicing directly in 12 sporadic ALS and 10 control lumbar spinal cords acquired by a rapid autopsy system that processed nervous systems specifically for genomic studies. ALS patients had rostral onset and caudally advancing disease and abundant residual motor neurons in this region. We created two RNA pools, one from motor neurons collected by laser capture microdissection and one from the surrounding anterior horns. From each, we isolated RNA, amplified mRNA, profiled whole-genome exon splicing, and applied advanced bioinformatics. We employed rigorous quality control measures at all steps and validated findings by qPCR. In the motor neuron enriched mRNA pool, we found two distinct cohorts of mRNA signals, most of which were up-regulated: 148 differentially expressed genes (P ? 10?3) and 411 aberrantly spliced genes (P ? 10?5). The aberrantly spliced genes were highly enriched in cell adhesion (P ? 10?57), especially cellmatrix as opposed to cellcell adhesion. Most of the enriching genes encode transmembrane or secreted as opposed to nuclear or cytoplasmic proteins. The differentially expressed genes were not biologically enriched. In the anterior horn enriched mRNA pool, we could not clearly identify mRNA signals or biological enrichment. These findings, perturbed and up-regulated cellmatrix adhesion, suggest possible mechanisms for the contiguously progressive nature of motor neuron degeneration. Data deposition: GeneChip raw data (CEL-files) have been deposited for public access in the Gene Expression Omnibus (GEO), www.ncbi.nlm.nih.gov/geo, accession number GSE18920. PMID:19864493

Rabin, Stuart J.; Kim, Jae Mun 'Hugo'; Baughn, Michael; Libby, Ryan T.; Kim, Young Joo; Fan, Yuxin; Libby, Randell T.; La Spada, Albert; Stone, Brad; Ravits, John

2010-01-01

251

Analysis of electrochemical noise from metastable pitting in aluminum, aged Al-2%Cu, and AA 2024-T3  

SciTech Connect

The authors compare methods of analyzing electrochemical current (ECN) and potential (EPN) noise data associated with metastable pitting and the transition from metastable to stable pitting. Various analysis methods were applied to electrochemical noise data associated with metastable pit events on aluminum, aged Al-2%Cu, and AA 2024-T3 ST. Two experimental approaches were used. High-purity Al, roughly simulating copper-depleted grain boundary zones in aged Al-Cu alloys, was potentiostatically polarized so that current spikes associated with individual pitting events could be analyzed. Second, the coupling current between nominally identical galvanically coupled Al, aged Al-2%Cu, and AA 2024-T3 ST electrodes was recorded in conjunction with couple potential using a saturated calomel reference electrode. Pit stabilization occurred when individual pits exceeded a threshold of I{sub pit}/r{sub pit} > 10{sup {minus}2} A/cm at all times during pit growth as established from potentiostatic measurements. The magnitude of this ratio is linked directly to the concentration of the aggressive solution within pits. Two related statistical pit stabilization factors (I{sub rms}/r{sub pit total} from ECN data and the mean of (I{sub peak}-I{sub ox})/r{sub pit} values from each pit current spike) were obtained from galvanic ECN data containing a large number of pit current spikes. These parameters provided a better indication of the transition to stable pitting than the pitting index or noise resistance but also had shortcomings. Spectral analysis using current and potential spectral power density (SPD) data provided qualitative information on pit susceptibility. However, the transition to stable pitting could not be accurately defined because of a lack of information on pit sizes in spectral data.

Pride, S.T.; Scully, J.R.; Hudson, J.L. [Univ. of Virginia, Charlottesville, VA (United States)

1996-12-31

252

Fabrication of an r-Al2Ti intermetallic matrix composite reinforced with ?-Al2O3 ceramic by discontinuous mechanical milling for thermite reaction  

NASA Astrophysics Data System (ADS)

In this study, a powder mixture with an Al/TiO2 molar ratio of 10/3 was used to form an r-Al2Ti intermetallic matrix composite (IMC) reinforced with ?-Al2O3 ceramic by a novel milling technique, called discontinuous mechanical milling (DMM) instead of milling and ignition of the produced thermite. The results of energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD) of samples with varying milling time indicate that this fabrication process requires considerable mechanical energy. It is shown that Al2Ti-Al2O3 IMC with small grain size was produced by DMM after 15 h of ball milling. Peaks for ?-TiAl as well as Al2Ti and Al2O3 are observed in XRD patterns after DMM followed by heat treatment. The microhardness of the DMM-treated composite produced after heat treatment was higher than Hv 700.

Mosleh, A.; Ehteshamzadeh, M.; Taherzadeh Mousavian, R.

2014-10-01

253

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

254

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

255

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

256

Accelerated Multiplicative Updates and Hierarchical ALS Algorithms for Nonnegative Matrix Factorization  

E-print Network

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 paper, we consider two well-known algorithms designed to solve NMF problems, namely 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 their convergence, based on a careful analysis of the computational cost needed at each iteration. 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 datasets, and compares favorably with a state-of-the-art alternating nonnegative least squares algorithm. Finally, we provide a theoretical argument based on the properties of NMF and its solutions that explains in particular the very ...

Gillis, Nicolas

2011-01-01

257

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

258

Characterization of the Structure and Catalytic Behavior of AlF 3? x (OH) x with Aluminum Successively Replaced by Chromium and Magnesium  

Microsoft Academic Search

The calcination of ?-AlF33H2O forms a ?-AlF3phase which is catalytically active for dismutation of C1-hydrocarbons such as dichlorodifluoromethane. The stepwise replacement of aluminum by chromium and magnesium leads to considerable alterations in structure and surface properties of the calcination products. This is accompanied by significant changes in the catalytic activity. The synthesis of the catalysts was carried out by coprecipitation

E. Kemnitz; A. Hess; G. Rother; S. Troyanov

1996-01-01

259

Characterization of framework and extra-framework aluminum species in non-hydrated zeolites Y by 27Al spin-echo, high-speed MAS, and MQMAS NMR spectroscopy at B0 = 9.4 to 17.6 T.  

PubMed

27Al spin-echo, high-speed MAS (nu(rot) = 30 kHz), and MQMAS NMR spectroscopy in magnetic fields of B0 = 9.4, 14.1, and 17.6 T were applied for the study of aluminum species at framework and extra-framework positions in non-hydrated zeolites Y. Non-hydrated gamma-Al2O3 and non-hydrated aluminum-exchanged zeolite Y (Al,Na-Y) and zeolite H,Na-Y were utilized as reference materials. The solid-state 27Al NMR spectra of steamed zeolite deH,Na-Y/81.5 were found to consist of four signals. The broad low-field signal is caused by a superposition of the signals of framework aluminum atoms in the vicinity of bridging hydroxyl protons and framework aluminum atoms compensated in their negative charge by aluminum cations (delta(iso) = 70 +/- 10 ppm, C(QCC) = 15.0 +/- 1.0 MHz). The second signal is due to a superposition of the signals of framework aluminum atoms compensated by sodium cations and tetrahedrally coordinated aluminum atoms in neutral extra-framework aluminum oxide clusters (delta(iso) = 65 +/- 5 ppm, C(QCC) = 8.0 +/- 0.5 MHz). The residual two signals were attributed to aluminum cations (delta(iso) = 35 +/- 5 ppm, C(QCC) = 7.5 +/- 0.5 MHz) and octahedrally coordinated aluminum atoms in neutral extra-framework aluminum oxide clusters (delta(iso) = 10 +/- 5 ppm, C(QCC) = 5.0 +/- 0.5 MHz). By chemical analysis and evaluating the relative solid-state 27Al NMR intensities of the different signals of aluminum species occurring in zeolite deH,Na-Y/81.5 in the non-hydrated state, the aluminum distribution in this material was determined. PMID:16240035

Jiao, Jian; Kanellopoulos, Johanna; Wang, Wei; Ray, Siddharth S; Foerster, Hans; Freude, Dieter; Hunger, Michael

2005-09-01

260

Effect of Aluminum composition on currentvoltage characteristics of AlGaSb/InAs tunnel junction  

E-print Network

tunneling current density, and the large band gap of AlGaSb suppresses offstate current. However effect transistors (TFETs) with staggered band alignment have recently attracted considerable, little experimental study has been done of the band alignment in this material system

261

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

262

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

263

Effect of Hot Rolling on the Properties of In Situ Ti-Aluminide and Alumina-Reinforced Aluminum Matrix Composite  

Microsoft Academic Search

In situ Ti-aluminide and alumina-reinforced aluminium matrix composite were prepared by the melt-cast route by adding 12m sized TiO2 powder particles into molten aluminium at a temperature of 950C. The effects of hot rolling temperature and percentage deformation on the microstructural architecture and mechanical properties (e.g., hardness and tensile strength) of aluminium matrix composite were studied in detail. Presence of

S. Ghosh; S. K. Naskar; A. Basumallick

2007-01-01

264

SEM Characterization of an Irradiated Dispersion Fuel Plate with U-10Mo Particles and 6061 Al Matrix  

Microsoft Academic Search

It has been observed that during irradiation of a dispersion fuel plate, fuel\\/matrix interactions can impact the overall fuel plate performance. To continue the investigation of the irradiation performance of Si-rich fuel\\/matrix interaction layers, RERTR-6 fuel plate V1R010 (U- 10Mo\\/6061 Al) was characterized using scanning electron microscopy. This fuel plate was of particular interest because of its similarities to fuel

D. D. Keiser; J. F. Jue; A. B. Robinson; P. G. Medvedev; M. R. Finlay

2009-01-01

265

Electrical conductivity of aluminum hydride AlH3 at high pressure and temperature  

Microsoft Academic Search

A study of electrophysical and thermodynamic properties of alane AlH3 under multi shock compression has been carried out. The increase in specific electroconductivity of alane at shock compression up to pressure 100 GPa have been measured. High pressures and temperatures were obtained with explosive device, which accelerates the stainless impactor up to 3 km\\/sec. The impact shock is split into

Denis Shakhray; Alexander Molodets; Vladimir Fortov; Aleksei Khrapak

2009-01-01

266

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

267

Effect of alternative aging process on the fracture and interfacial properties of particulate Al 2 O 3 -reinforced Al (6061) metal matrix composite  

Microsoft Academic Search

The effects of different aging processes on ductility, fracture, and interfacial properties in particulate Al2O3-reinforced Al (6061) metal-matrix composite (MMCs) were studied. Tensile tests based on relevant ASTM standards were performed\\u000a to investigate the mechanical responses of specimens under different heat-treatment conditions. Scanning electron microscopy\\u000a (SEM), field-emission SEM (FESEM), and transmission electron microscopy (TEM) studies were carried out to correlate

H. R. Shakeri; Zhirui Wang

2002-01-01

268

A thermodynamic prediction for microporosity formation in aluminum-rich Al-Cu alloys  

NASA Technical Reports Server (NTRS)

A computer model is used to predict the formation and degree of microporosity in a directionally solidified Al-4.5 wt pct Cu alloy, considering the interplay between solidification shrinkage and gas porosity. Macrosegregation theory is used to determine the local pressure within the interdendritic liquid. Results show interdendritic porosity for initial hydrogen contents in the 0.03-1 ppm range, and none below contents of 0.03. An increase in either the thermal gradient or the solidification rate is show to decrease the amount of interdendritic porosity.

Poirier, D. R.; Yeum, K.; Maples, A. L.

1987-01-01

269

Laminated metal matrix composites of ultra-high carbon steel-brass and Al-Al/SiC: Processing and properties. Revision 1  

SciTech Connect

We have fabricated laminated metal composites of (1) ultrahigh carbon steel (1.8%C) and brass (70Cu-30Zn), and (2) aluminum 5182 and aluminum 6061 with 25 vol.% SiCp. The laminates were prepared by hot pressing alternating layers of the component materials in an argon gas atmosphere. The steel was thermo-mechanically processed to produce a fine grained microstructure that exhibited superplasticity. The brass and aluminum materials were obtained from commercial sources and used in the as-received condition. Laminates with different numbers of layers and layer thickness were made. The compressive stress and strain rate were measured during hot pressing, and material flow behavior in the UHCS-brass laminate was found to be rate-controlled by the stronger component rather than by the softer one (brass). Material flow behavior was more complicated in the Al-laminate. Tensile and fracture behavior were determined by tensile tests and by chevron notched fracture toughness tests. Details of processing, microstructure and initial results of mechanical property tests of these laminates are discussed.

Syn, C.K.; Lesuer, D.R.; Cadwell, K.L. [Lawrence Livermore National Lab., CA (United States); Sherby, O.D. [Stanford Univ., CA (United States). Dept. of Materials Science and Engineering; Brown, K.R. [Kaiser Aluminum and Chemical Corp., Pleasanton, CA (United States). Center for Technology

1991-11-01

270

Laminated metal matrix composites of ultra-high carbon steel-brass and Al-Al/SiC: Processing and properties  

SciTech Connect

We have fabricated laminated metal composites of (1) ultrahigh carbon steel (1.8%C) and brass (70Cu-30Zn), and (2) aluminum 5182 and aluminum 6061 with 25 vol.% SiCp. The laminates were prepared by hot pressing alternating layers of the component materials in an argon gas atmosphere. The steel was thermo-mechanically processed to produce a fine grained microstructure that exhibited superplasticity. The brass and aluminum materials were obtained from commercial sources and used in the as-received condition. Laminates with different numbers of layers and layer thickness were made. The compressive stress and strain rate were measured during hot pressing, and material flow behavior in the UHCS-brass laminate was found to be rate-controlled by the stronger component rather than by the softer one (brass). Material flow behavior was more complicated in the Al-laminate. Tensile and fracture behavior were determined by tensile tests and by chevron notched fracture toughness tests. Details of processing, microstructure and initial results of mechanical property tests of these laminates are discussed.

Syn, C.K.; Lesuer, D.R.; Cadwell, K.L. (Lawrence Livermore National Lab., CA (United States)); Sherby, O.D. (Stanford Univ., CA (United States). Dept. of Materials Science and Engineering); Brown, K.R. (Kaiser Aluminum and Chemical Corp., Pleasanton, CA (United States). Center for Technology)

1991-11-01

271

The effect of matrix microstructure on the tensile and fatigue behavior of SiC particle-reinforced 2080 Al matrix composites  

SciTech Connect

The effect of matrix microstructure on the stress-controlled fatigue behavior of a 2080 Al alloy reinforced with 30 pct SiC particles was investigated. A thermomechanical heat treatment (T8) produced a fine and homogeneous distribution of S{prime} precipitates, while a thermal heat treatment (T6) resulted in coarser and inhomogeneously distributed S{prime} precipitates. The cyclic and monotonic strength, as well as the cyclic stress-strain response, were found to be significantly affected by the microstructure of the matrix. Because of the finer and more-closely spaced precipitates, the composite given the T8 treatment exhibited higher yield strengths than the T6 materials. Despite its lower yield strength, the T6 matrix composite exhibited higher fatigue resistance than the T8 matrix composite. The cyclic deformation behavior of the composites is compared to monotonic deformation behavior and is explained in terms of microstructural instabilities that cause cyclic hardening or softening. The effect of precipitate spacing and size has a significant effect on fatigue behavior and is discussed. The interactive role of matrix strength and SiC reinforcement on stress within rogue inclusions was quantified using a finite-element analysis (FEA) unit-cell model.

Chawla, N.; Habel, U.; Shen, Y.L.; Andres, C.; Jones, J.W.; Allison, J.E.

2000-02-01

272

Fabrication of high wear resistant Al\\/Al 3Ti metal matrix composite by in situ hot press method  

Microsoft Academic Search

In this study, hot press method has been used to fabricate Al\\/Al3Ti composite. In situ reacted Al3Ti compound is formed through Al and TiO2 powder blend in order to enhance mechanical properties and mainly wear resistance. After homogeneous blending of Al and TiO2, hot pressing was performed at 580C at different durations and pressures. Scanning electron microscopy was used for

M. Nofar; H. R. Madaah Hosseini; N. Kolagar-Daroonkolaie

2009-01-01

273

Effects of porous carbon on sintered Al-Si-Mg matrix composites  

NASA Astrophysics Data System (ADS)

The influence of microporous particulate carbon char on the mechanical, thermal, and tribological properties of wear-resistant Al-13.5Si-2.5Mg alloy composites was studied. Large increases in surface area due to the formation of micropores in coconut shell chars were achieved by high-temperature activation under CO2 gas flow. Activated char particles at 0.02 V f were used to reinforce the alloy. The composites were fabricated via a double-compaction reaction sintering technique under vacuum at a compaction pressure of 250 MPa and sintering temperature of 600 C. At more than 35% burn-off of the carbon chars at the temperature of activation, 915 C, the total surface area remained virtually unaffected. The ultimate tensile strength and hardness decreased by 23% and 6 %, respectively; with increasing surface area of the reinforcement from 123 to 821 m2g-1. The yield strength and the percentage of elongation decreased by a factor of 2 and 5, respectively. No significant change in sliding wear rate was observed but the coefficient of friction increased by 13 % (0.61 to 0.69). The coefficient of linear thermal expansion was reduced by 16 % (11.7 10-6 to 9.8 10-6 C-1), and remained unaffected at more than 35 % burn-off. Energy-dispersive spectrometry of the particles of the activated chars showed that oxides of potassium and copper coated the open surfaces. Failure at the matrix-char interface was observed, and this was attributed to localized presence of oxides at the interfaces as identified by electron probe microanalysis. Poor wetting of the oxides by magnesium at the sintering conditions resulted in formation of weak matrix-char interface bonds.

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

1997-12-01

274

Effects of porous carbon on sintered Al-Si-Mg matrix composites  

SciTech Connect

The influence of microporous particulate carbon char on the mechanical, thermal, and tribological properties of wear-resistant Al-13.5Si-2.5Mg alloy composites was studied. Large increases in surface area due to the formation of micropores in coconut shell chars were achieved by high-temperature activation under CO{sub 2} gas flow. Activated char particles at 0.02 V{sub f} were used to reinforce the alloy. The composites were fabricated via a double-compaction reaction sintering technique under vacuum at a compaction pressure of 250 MPa and sintering temperature of 600 C. At more than 35% burn-off of the carbon chars at the temperature of activation, 915 C, the total surface area remained virtually unaffected. The ultimate tensile strength and hardness decreased by 23% and 6%, respectively; with increasing surface area of the reinforcement from 123 to 821 m{sup 2} g{sup {minus}1}. The yield strength and the percentage of elongation decreased by a factor of 2 and 5, respectively. No significant change in sliding wear rate was observed but the coefficient of friction increased by 13% (0.61 to 0.69). The coefficient of linear thermal expansion was reduced by 16% (11.7 {times} 10{sup {minus}6} to 9.8 {times} 10{sup {minus}6} C{sup {minus}1}), and remained unaffected at more than 35% burn-off. Energy-dispersive spectrometry of the particles of the activated chars showed that oxides of potassium and copper coated the open surfaces. Failure at the matrix-char interface was observed, and this was attributed to localized presence of oxides at the interfaces as identified by electron probe microanalysis. Poor wetting of the oxides by magnesium at the sintering conditions resulted in formation of weak matrix-char interface bonds.

Ejiofor, J.U. [Shelco Foundries, Inc., Jacksonville, AL (United States); Reddy, R.G. [Univ. of Alabama, Tuscaloosa, AL (United States). Dept. of Metallurgical and Materials Engineering

1997-12-01

275

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 550C, 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

276

High excitation of the species in nitrogen-aluminum plasma generated by electron cyclotron resonance microwave discharge of N2 gas and pulsed laser ablation of Al target  

NASA Astrophysics Data System (ADS)

A reactive nitrogen-aluminum plasma generated by electron cyclotron resonance (ECR) microwave discharge of N2 gas and pulsed laser ablation of an Al target is characterized spectroscopically by time-integrated and time-resolved optical emission spectroscopy (OES). The vibrational and rotational temperatures of N2 species are determined by spectral simulation. The generated plasma strongly emits radiation from a variety of excited species including ambient nitrogen and ablated aluminum and exhibits unique features in optical emission and temperature evolution compared with the plasmas generated by a pure ECR discharge or by the expansion of the ablation plume. The working N2 gas is first excited by ECR discharge and the excitation of nitrogen is further enhanced due to the fast expansion of the aluminum plume induced by target ablation, while the excitation of the ablated aluminum is prolonged during the plume expansion in the ECR nitrogen plasma, resulting in the formation of strongly reactive nitrogen-aluminum plasma which contains highly excited species with high vibrational and rotational temperatures. The enhanced intensities and the prolonged duration of the optical emissions of the combined plasma would provide an improved analytical capability for spectrochemical analysis.

Liang, Peipei; Li, Yanli; Cai, Hua; You, Qinghu; Yang, Xu; Huang, Feiling; Sun, Jian; Xu, Ning; Wu, Jiada

2014-11-01

277

The NICMOS detectors are mounted in a cryogenically cooled well inside of a dewar filled with solid Nitrogen. The cryogenic vessel contains a sparse matrix of an aluminum "sponge" into  

E-print Network

THE DEWAR The NICMOS detectors are mounted in a cryogenically cooled well inside of a dewar filled with solid Nitrogen. The cryogenic vessel contains a sparse matrix of an aluminum "sponge" into which liquid cooling is employed to two shields in the dewar to prolong the cryogen life. On­orbit, the cryogen

Schneider, Glenn

278

Tantalum Aluminum Alkoxide as a Double-Metal Precursor for Metalorganic Chemical Vapor Deposition of Sr2AlTaO6  

NASA Astrophysics Data System (ADS)

We proposed resolving the poor controllability in the metalorganic chemical vapor deposition (MOCVD) of a complex oxide film consisting of a few metal elements, Sr2AlTaO6 (SAT) film, by using a double-metal source, tantalum aluminum isopropoxide TaAl(O-iC3H7)8. It had a melting point as low as 93C and generated suitable vapor pressure for MOCVD at a temperature of 100C. The supply metal ratio, Al/Ta, was 1, because it remained a double-metal structure in the vapor phase. We grew stoichiometric SAT films using it as a metal source.

Zama, Hideaki; Takahashi, Yoshihiro; Tanabe, Keiichi; Morishita, Tadataka

2001-02-01

279

Wetting and interfacial reactions in Al-Li-SiC p metal matrix composites processed by spray atomization and deposition  

Microsoft Academic Search

The present study addresses the wetting and interfacial behaviour in a SiCp reinforced aluminium-lithium alloy processed by spray atomization and deposition. The microstructural characteristics of the spray atomized and deposited Al-Li-SiCp metal matrix composites were investigated as a function of processing history and thermal exposure. The present results show that there was sufficient interfacial activity at the Al-Li\\/SiC interface during

M. Gupta; I. A. Ibrahim; F. A. Mohamed; E. J. Lavernia

1991-01-01

280

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

281

Solid-state hot pressing of elemental aluminum and titanium powders to form TiAl ({gamma} + {alpha}{sub 2}) intermetallic microstructure  

SciTech Connect

The elemental powder metallurgy (EPM) process is used to prepare TiAl-base intermetallics. An EPM process conducted by two-stage solid-state hot pressing was employed to prepare TiAl-base intermetallics and to investigate the resulting microstructural changes. The results showed that the TiAl{sub 3} phase forms in the first stage. During the temperature increase to the second sintering stage, lamellar phases start to precipitate in the TiAl{sub 3} matrix. Further, the TiAl{sub 3} phase transforms to TiAl, and Ti{sub 3}Al layers develop in the remaining titanium particles. Meanwhile, the lamellar phases grow into ring-type structures between the TiAl matrix and the Ti{sub 3}Al layers. After the second stage, the remaining titanium particles are fully reacted, and a microstructure of Ti{sub 3}Al phases enclosed by fine-grained lamellar rings in the TiAl matrix is developed.

Yang, J.B.; Teoh, K.W.; Hwang, W.S. [National Cheng Kung Univ., Tainan (Taiwan, Province of China). Dept. of Materials Science and Engineering

1996-10-01

282

In situ transmission electron microscopy observation of pulverization of aluminum nanowires and evolution of the thin surface Al2O3 layers during lithiation-delithiation cycles.  

PubMed

Lithiation-delithiation cycles of individual aluminum nanowires (NWs) with naturally oxidized Al(2)O(3) surface layers (thickness 4-5 nm) were conducted in situ in a transmission electron microscope. Surprisingly, the lithiation was always initiated from the surface Al(2)O(3) layer, forming a stable Li-Al-O glass tube with a thickness of about 6-10 nm wrapping around the NW core. After lithiation of the surface Al(2)O(3) layer, lithiation of the inner Al core took place, which converted the single crystal Al to a polycrystalline LiAl alloy, with a volume expansion of about 100%. The Li-Al-O glass tube survived the 100% volume expansion, by enlarging through elastic and plastic deformation, acting as a solid electrolyte with exceptional mechanical robustness and ion conduction. Voids were formed in the Al NWs during the initial delithiation step and grew continuously with each subsequent delithiation, leading to pulverization of the Al NWs to isolated nanoparticles confined inside the Li-Al-O tube. There was a corresponding loss of capacity with each delithiation step when arrays of NWs were galvonostatically cycled. The results provide important insight into the degradation mechanism of lithium-alloy electrodes and into recent reports about the performance improvement of lithium ion batteries by atomic layer deposition of Al(2)O(3) onto the active materials or electrodes. PMID:21875099

Liu, Yang; Hudak, Nicholas S; Huber, Dale L; Limmer, Steven J; Sullivan, John P; Huang, Jian Yu

2011-10-12

283

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

284

Identification of the C2?-X2?+ band system of AlO in the ultraviolet galvanoluminescence obtained during aluminum anodization.  

PubMed

The first galvanoluminescence spectrum in the ultraviolet region obtained during anodization of high purity aluminum samples annealed at temperature above 525C is presented. An intense broad peak with the maximum at about 31,900 cm(-1) is assigned to the transitions (some of them heretofore unobserved) between vibrational levels of the C(2)??X(2)?(+) spectral system of AlO, partly overlapped with the A(2)?(+)?X(2)? system of OH. PMID:21795103

Sarvan, Mirjana; Peri?, Miljenko; Zekovi?, Ljubia; Stojadinovi?, Stevan; Bel?a, Ivan; Petkovi?, Marija; Kasalica, Be?ko

2011-10-15

285

Identification of the C 2?-X 2? + band system of AlO in the ultraviolet galvanoluminescence obtained during aluminum anodization  

NASA Astrophysics Data System (ADS)

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 31,900 cm -1 is assigned to the transitions (some of them heretofore unobserved) between vibrational levels of the C 2? ? X 2? + spectral system of AlO, partly overlapped with the A 2? + ? X 2? system of OH.

Sarvan, Mirjana; Peri?, Miljenko; Zekovi?, Ljubia; Stojadinovi?, Stevan; Bel?a, Ivan; Petkovi?, Marija; Kasalica, Be?ko

2011-10-01

286

Atomic layer deposition of Al-doped ZnO films using ozone as the oxygen source: A comparison of two methods to deliver aluminum  

SciTech Connect

Aluminum-doped ZnO films were prepared by atomic layer deposition at 250 deg. C using diethylzinc (DEZ), trimethylaluminum (TMA), and ozone as the precursors. Two deposition methods were compared to assess their impact on the composition, structural, electrical, and optical properties as a function of Al concentration. The first method controlled the Al concentration by changing the relative number of Al to Zn deposition cycles; a process reported in the literature where water was used as the oxygen source. The second method involved coinjection of the DEZ and TMA during each cycle where the partial pressures of the precursors control the aluminum concentration. Depth profiles of the film composition using Auger electron spectroscopy confirmed a layered microstructure for the films prepared by the first method, whereas the second method led to a homogeneous distribution of the aluminum throughout the ZnO film. Beneath the surface layer the carbon concentrations for all of the films were below the detection limit. Comparison of their electrical and optical properties established that films deposited by coinjection of the precursors were superior.

Yuan Hai; Luo Bing; Yu Dan; Cheng, An-jen; Campbell, Stephen A.; Gladfelter, Wayne L. [Department of Electrical and Computer Engineering and Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 and School of Materials Science and Engineering, Northwestern Polytechnical University, Xi'an, Shaan'xi 710025 (China); Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Department of Electrical and Computer Engineering, University of Minnesota, Minneapolis, Minnesota 55455 (United States); Department of Chemistry, University of Minnesota, Minneapolis, Minnesota 55455 (United States)

2012-01-15

287

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

288

Aluminum incorporation in Ti{sub 1-x}Al{sub x}N films studied by x-ray absorption near-edge structure  

SciTech Connect

The local bonding structure of titanium aluminum nitride (Ti{sub 1-x}Al{sub x}N) films grown by dc magnetron cosputtering with different AlN molar fractions (x) has been studied by x-ray absorption near-edge structure (XANES) recorded in total electron yield mode. Grazing incidence x-ray diffraction (GIXRD) shows the formation of a ternary solid solution with cubic structure (c-Ti{sub 1-x}Al{sub x}N) that shrinks with the incorporation of Al and that, above a solubility limit of xapprox0.7, segregation of w-AlN and c-Ti{sub 1-x}Al{sub x}N phases occurs. The Al incorporation in the cubic structure and lattice shrinkage can also be observed using XANES spectral features. However, contrary to GIXRD, direct evidence of w-AlN formation is not observed, suggesting a dominance and surface enrichment of cubic environments. For x>0.7, XANES shows the formation of Ti-Al bonds, which could be related to the segregation of w-AlN. This study shows the relevance of local-order information to assess the atomic structure of Ti{sub 1-x}Al{sub x}N solutions.

Gago, R. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, E-28049 Madrid (Spain); Centro de Micro-Analisis de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Redondo-Cubero, A. [Centro de Micro-Analisis de Materiales, Universidad Autonoma de Madrid, E-28049 Madrid (Spain); Endrino, J. L.; Jimenez, I. [Instituto de Ciencia de Materiales de Madrid, Consejo Superior de Investigaciones Cientificas, E-28049 Madrid (Spain); Shevchenko, N. [Institute of Ion Beam Physics and Materials Research, Forschungszentrum Dresden-Rossendorf, PF-510119, D-01314 Dresden (Germany)

2009-06-01

289

Formation of magnesium aluminate (spinel) in cast SiC particulate-reinforced Al(A356) metal matrix composites  

NASA Astrophysics Data System (ADS)

Transmission (TEM) and scanning electron microscopy (SEM) are employed to study the SiC/Al-alloy interface in a cast SiCp/Al(A356) metal matrix composite (MMC). Magnesium aluminate (spinel), MgAl2O4, was found at the interface as a reaction product after material processing. Comparisons of the crystal structure, structure factor, and interface reaction ther-modynamics between MgAl2O4 and MgO have been carried out. The results from these com-parisons confirm the experimental observation; i.e., the favored interface phase is magnesium aluminate (spinel). Based on the thermodynamic analysis, the presence of oxygen in various forms in the system during processing, such as SiO2, A12O3, and MgO, is believed to be the source which supplies the oxygen for the formation of MgAl2O4.

Wang, Ning; Wang, Zhirui; Weatherly, George C.

1992-05-01

290

Residual microstructure associated with impact crater in Ti-6Al-4V meshes reinforced 5A06Al alloy matrix composite.  

PubMed

In this paper, TC4(m)/5A06Al composite was hypervelocity impacted by 2024 aluminium projectile with the diameter of 2mm and with the impact velocity of 3.5 km/s. The residual microstructure was observed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HREM). The TC4-Al interface before impact was composed of TiAl(3) phase and Ti(3)Al phase. Near the pithead, separation of TC4 fibers and Al matrix occurred along the impact direction. Around the middle of the crater, TC4 fibers were sheared into several sections. Near the bottom of crater, adiabatic shear band (ASB) occurred in TC4 fiber, while the angle between shear plane and cross section was 45. The crack propagated along TC4-Ti(3)Al interface during impact and some Ti(3)Al phase at the TC4-Al interface transformed to amorphous with few nanocrystals after hypervelocity impact. PMID:21852141

Guo, Q; Chen, G Q; Jiang, L T; Hussain, M; Han, X L; Sun, D L; Wu, G H

2012-02-01

291

Effects of Al-5Ti-1B master alloy on the microstructural evaluation of a highly alloyed aluminum alloy produced by SIMA process  

SciTech Connect

This study was undertaken to investigate the influence of Al-5Ti-1B master alloy on the structural characteristics of Al-12Zn-3 Mg-2.5Cu aluminum alloy. The optimum amount of Ti containing master alloy for proper grain refining was selected as 6 wt.%. A modified strain-induced, melt-activated (SIMA) process for semi-solid processing of alloys was proposed. In order to examine the effectiveness of the modified SIMA process, the recrystallized microstructures of the Al alloy (Al-12Zn-3 Mg-2.5Cu) prepared by the modified SIMA processes were macroscopically. The modified SIMA process employed casting, warm multi-forging, recrystallization and partial melting instead of the conventional process. Reheating condition to obtain a fine globular microstructure was optimized. The microstructure evolution of reheated Al-12Zn-3 Mg-2.5Cu aluminum alloy was characterized by SEM (Scanning electron microscopy) and optical microscopy. In this study the relation between the induced strain with size and shape of grain size has been studied. Results indicated that with the increase of strain sphericity of particles, their size decreases and sphericity takes place in less reahiting time.

Alipour, M.; Emamy, M.; Azarbarmas, M.; Karamouz, M. [Center of Excellence for High Performance Materials, School of Metallurgy and Materials, University of Tehran, Tehran (Iran, Islamic Republic of)

2010-06-15

292

Preparing high- and low-aspect ratio AlB2 flakes from borax or boron oxide  

NASA Astrophysics Data System (ADS)

The commercial preparation of aluminum-diboride flakes in aluminum relies on relatively expensive starting materials. A new synthesis has been developed that allows AlB2 to be prepared directly from the reaction of borax (Na2B4O710H2O) or boron oxide (B2O3) with aluminum. Aluminum metal at temperatures higher than 900C has been shown to reduce these boron-containing compounds, producing an Al2O3-containing slag and AlB2. A natural separation occurs, leaving AlB2 in the molten aluminum and Al2O3 as part of a slag that forms at the melt surface. Samples containing up to 10 vol.% AlB2 in an aluminum matrix have been directly prepared using this method.

Hall, A. C.; Economy, J.

2000-02-01

293

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

294

The effect of Al 2 O 3 particulates on the precipitation behaviour of 6061 aluminium-matrix composites  

Microsoft Academic Search

The effect of angular and spherical shaped Al2O3 particulates on the precipitation behaviour of 6061 aluminium-matrix composites has been studied using microhardness testing, differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The evolution of precipitates at each stage of precipitation corresponding to the DSC-peak was monitored through careful TEM observations. Both the formation and dissolution behaviour of the precipitates

T. Das; P. R. Munroe; S. Bandyopadhyay

1996-01-01

295

Geometric, electronic, and optical properties of a boron-doped aluminum cluster of B2Al21-: A density functional theory study  

NASA Astrophysics Data System (ADS)

We present the physicochemical properties for the lowest-energy isomer of a boron-doped aluminum cluster of B2Al21-. The isomer was obtained by basin-hopping minimization based on the density functional theory, starting from a face-sharing bi-icosahedral structure in which two boron atoms were endohedrally doped to each icosahedron. The lowest-energy isomer is a triangular form in which an aluminum cage encapsulates two boron atoms endohedrally. The electronic structure was analyzed by projecting Kohn-Sham orbitals onto the spherical harmonics; occupied and unoccupied frontier orbitals are dominantly G- and H-symmetries, respectively. Optical absorption is mainly assigned to G to H transitions.

Iwasa, Takeshi; Nakajima, Atsushi

2013-09-01

296

Stability measurements of aluminum-stabilized Nb-Ti and bronze matrix Nb/sub 3/Sn potted superconducting magnets  

SciTech Connect

The purpose of the experiments presented here was to measure the stability of two potted test magnets (one would with Nb/sub 3/Sn/Cu-Sn wire and the other would with NbTi/Al wire) and compare the results with previously measured stability characteristics of NbTi/Cu superconducting test coils. Two test coils were constructed; the specifications of their construction are given. the measurements of the energy required to quench their coils show that both these magnets are more stable than coils wound with NbTi/Cu wire. Over an I/I /SUB c/ range of 0.3 to 0.9, the Nb/sub 3/Sn/Cu-Sn test coil required 3 to 10 times the energy to quench than that required by the NbTi/Cu coil; the NbTi/Al test coil required 30 times the energy to quench. Inclusion of possible and known nonuniformities of construction of the two test wires in the calculations could modify these results. A larger data base should be accumulated.

Waltman, D.J.; McDonald, F.E.; Superczynski, M.J.

1982-01-01

297

Synthesis and high-temperature stability of titanium aluminide matrix in situ composites  

NASA Astrophysics Data System (ADS)

A premixture of elemental powders of titanium and aluminum was supplied as a spray material for the direct fabrication of titanium aluminide matrix in situ composites by means of reactive low-pressure plasma spraying with a nitrogen and hydrogen mixed plasma gas. The aluminum content varied from 10 to 63 wt.% in the premixtures. The matrix of sprayed layers consisted of three kinds of titanium aluminidesTi3A1, TiAl, and TiAl3which begin to form on a low-carbon steel substrate immediately after deposition. The formation of nitrides, which act as a reinforcement, occurs both during the flight of liquid droplets and on the substrate. The nitrogen content is approximately 4 to 5 wt.% in the sprayed intermetallic matrix composites, regardless of the aluminum content of the premixtures. The kinds of titanium aluminides and in situ nitrides developed depend on the aluminum content of the premixtures. The homogeneity of the distribution of aluminum and titanium in sprayed intermetallic matrix composites has been improved by vacuum annealing. The predominant TiAl phase that formed in the sprayed intermetallic matrix composites with a Ti-36 wt.% AI premixture increases in quantity through annealing. Although some minor nitrides disappear through annealing, the principal reinforcement, Ti2AlN, does not decompose, but increases in quantity. The hardness of sprayed intermetallic matrix composites varies with aluminum content of the premixtures, but is always greater than that of sprayed titanium aluminides containing no nitrides. Annealing does not reduce the hardness of sprayed intermetallic matrix composites. Sprayed and annealed intermetallic matrix composites with a Ti-36 wt.% Al premixture maintain their hardness of approximately 500 HV up to 800 K. Hence, reactive low-pressure plasma spraying offers a promising fabrication method for titanium aluminide matrix in situ composites, which are expected to excel in wear resistance applications at elevated temperatures.

Tsunekawa, Y.; Gotoh, K.; Okumiya, M.; Mohri, N.

1992-09-01

298

Effect of Forging Parameters on Low Cycle Fatigue Behaviour of Al/Basalt Short Fiber Metal Matrix Composites  

PubMed Central

This paper deals with metal matrix composites (MMCs) of Al 7075 alloy containing different weight percentage (2.5, 5, 7.5, and 10) basalt short fiber reinforcement and unreinforced matrix alloy. The samples were produced by the permanent stir casting technique. The casting ingots were cut into blanks to be forged in single stage and double stage, using MN press and graphite-based lubricant. The microstructures and fatigue properties of the matrix alloy and MMC samples were investigated in the as cast state and in the single and double stage forging operations. The microstructure results showed that the forged sample had a uniform distribution of the basalt short fiber throughout the specimens. Evaluation of the fatigue properties showed that the forged samples had higher values than those of the as cast counterparts. After forging, the enhancement of the fatigue strength of the matrix alloy was so significant and high in the case of 2.5 and 5.0?wt. percentage basalt short fiber reinforced MMC, and there was no enhancement in 7.5 and 10?weight percentages short fiber reinforced MMCs. The fracture damage was mainly due to decohesion at the matrix-fiber interface. PMID:24298207

Karthigeyan, R.; Ranganath, G.

2013-01-01

299

Identification of interfacial parameters in a particle reinforced metal matrix composite Al606110%Al2O3  

E-print Network

­10%Al2O3 by hybrid method and genetic algorithm X.H. Lin, Y.L. Kang *, Q.H. Qin, D.H. Fu School genetic algorithm (GA). A non-continuum four-node interface element is adopted to simulate the interface Science 32 (2005) 47­56 www.elsevier.com/locate/commatsci * Corresponding author. Tel.: +86

Qin, Qinghua

300

Synthesis, quantitative elemental analysis, microstructure characteristics and micro hardness analysis of AA2219 aluminum alloy matrix composite reinforced by in-situ TiB2 and sub-micron ZrB2 particles  

Microsoft Academic Search

Composite material technology has been developed to explore the best advantage of metallic and ceramic material characteristics. Among the various processing route, flex assisted synthesis is a highly potential and low cost method to produce in-situ composites. In-situ aluminum matrix composite has superior performance than the ex-situ composite because of the chemically dispersed reinforcements. In the present work, flex assisted

A. Mahamani; A. Karthik; S. Karthikeyan; P. Kathiravan; Y. P. Kumar

2010-01-01

301

Electronic structure and bonding in four-coordinate organometallic complexes of aluminum. Valence photoelectron spectra of BHT-H, Me sub 3 Al(PMe sub 3 ), and Me sub 2 (BHT)Al(PMe sub 3 )  

SciTech Connect

The He I valence photoelectron spectra of the Lewis acid-base adducts Me{sub 3}Al(PMe{sub 3}) and Me{sub 2}(BHT)Al(PMe{sub 3}) (BHT{minus}H = 2,6-di-tert-butyl-4-methylphenol) have been obtained to characterize the electronic structure and bonding in four-coordinate organometallic complexes of aluminum. To aid in the assignment of the spectrum of Me{sub 2}(BHT)Al(PMe{sub 3}), the spectrum of the free alcohol, BHT-H, was also obtained. The first and second ionizations of the free BHT-H alcohol show vibrational progressions associated with the symmetric C-C phenyl ring stretching modes, consistent with the b{sub 1} and a{sub 2} {pi} ionizations, respectively, of monosubstituted phenyl rings. In the photoelectron spectrum of BHT coordinated to aluminum in Me{sub 2}(BHT)Al(PMe{sub 3}), the corresponding phenoxide a{sub 2} ionization retains the vibrational structure, but the individual vibrational components are lost in the ionization that corresponds most closely with the b{sub 1}. The loss of vibrational fine structure associated with ionization from the phenyl {pi} b{sub 1} orbital in the coordinated phenoxide shows that the phenoxide is involved in a {pi} interaction with the Me{sub 2}Al(PMe{sub 3}) portion of the molecule.

Lichtenberger, D.L.; Hogan, R.H. (Univ. of Arizona, Tucson (USA)); Healy, M.D.; Barron, A.R. (Harvard univ., Cambridge, MA (USA))

1990-04-25

302

{sup 27}Al and {sup 23}Na MAS NMR and powder x-ray diffraction studies of sodium aluminate speciation and the mechanistics of aluminum hydroxide precipitation upon acid hydrolysis  

SciTech Connect

{sup 27}Al and {sup 23}Na MAS NMR, powder X-ray diffraction, and infrared spectroscopic investigations of freeze-dried sodium aluminates and aluminum hydroxides formed through acid hydrolysis have been undertaken, with OH/Al hydrolysis ratios between 5.3 and 2.8 being analyzed. Numerous {sup 27}AlNMR resonances were observed, the intensities of which vary as a function of OH/Al ratio, and these have been assigned to four-, five-, and six-coordinate aluminum species constituting a variety of structural moieties. The dominant species at an OH/Al ratio above 4.4 appears to be a Q{sup o}Na[Al(OH);{sub 4}] salt, as indicated by a {sup 27}Al resonance at 86.6 ppm. In addition, a second, broader resonance at 71.3 ppm demonstrates the simultaneous existence of further four-coordinate aluminum species linked thorough oxo bonds to other four-coordinate aluminums (e.g., Q{sup 2} [Al(OH);{sub 2}(OAl){sub 2}];{sup x-}). At an OH/Al ratio between 4.4 and 4.1, a water-soluble phase forms that contains both four- and six-coordinate aluminum. At OH/Al ratios fo 4.0 and below, a water-soluble phase forms that contains both four-and six-coordinate aluminum. AT OH/Al ratios of 4.0 and below, a water-insoluble phase exists possessing four-, five-, and six-coordinate aluminum. At OH/Al{le}3.9 range exhibits {sup 27}Al chemical shifts similar to those reported for transitional aluminas such as {gamma}-, {eta}-, and 0-Al{sub 2}O{sub 3} and an infrared spectrum similar to pseudo-spinel gels, suggesting that a pseudo-spinel intermediate is the first phase involved in the crystallization of gibbsite. The resonance assigned to five-coordinate aluminum probably results from species involved in the transformation of the pseudo-spinal phase to pseudo-boehmite. The formation of gibbssite on the acid hydrolysis of alkaline sodium aluminate solutions thus appears to follow the pathway pseudo-spinel {r_arrow} pseudo-boehmite {r_arrow} bayerite {r_arrow} gibbsite. 82 refs., 7 figs., 3 tabs.

Bradley, S.M.; Hanna, J.V. [Univ. of New South Wales, Sydney (Australia)

1994-08-24

303

Aqueous solution-chemical derived Nisbnd Al2O3 solar selective absorbing coatings. 2. Wetting agents and spreading of aqueous solutions on aluminum substrate  

NASA Astrophysics Data System (ADS)

Wettability of aluminum substrate by the aqueous solutions containing ethoxylated alcohol nonionic surfactants C12En- or Triton X-series was studied using dynamic contact angle measurements. The efficiency of wetting was found to strongly depend on the length of polyoxyethylene (POE) chain of C12En- or Triton X surfactants. For C12E4 that has a very short POE chain, it hardly made the aqueous solution spreading over aluminum. The others with a long POE chain were indeed very efficient in promoting the solution spreading. Moreover, all the spreading process could be completed within 10 s. The single-layer Nisbnd Al2O3 coatings were fabricated from the precursor solutions containing C12En- or Triton X surfactants and the reflectance spectra were measured by a UV/vis spectrophotometer equipped with an integrating sphere. The results indicated that the precursor solution with a long POE chain surfactant as wetting agent favored to fabricate a uniform film on the aluminum substrate and therefore to get a high solar absorptance.

Li, Zhenxiang; Zhao, Jianxi

2013-03-01

304

Parametric analysis and optimization of Nd:YAG laser micro-grooving of aluminum titanate (Al 2 TiO 5 ) ceramics  

Microsoft Academic Search

Pulsed Nd:YAG Laser offers an excellent role for various micro-machining operations of a wide range of engineering materials\\u000a such as ceramics, composites, diamond etc. The micro-machining of ceramics are highly demanded in the present industry because\\u000a of its wide and potential uses in various field such as automobile, electronic, aero-space, and bio-medical engineering applications\\u000a etc. Aluminum titanate (Al2TiO5) has tremendous

D. Dhupal; B. Doloi; B. Bhattacharyya

2008-01-01

305

Broadband Emitting Superluminescent Diodes With InAs Quantum Dots in AlGaAs Matrix  

Microsoft Academic Search

Superluminescent diodes were fabricated by using InAs-AlGaAs self-assembled quantum dots (QDs) as the active region. The ultrawide emitting spectrum of 142 nm was achieved. The short migration length of indium adatoms on AlGaAs surface increases the size dispersion of InAs QDs, resulting in the broadening of optical gain spectrum.

X. Q. Lv; N. Liu; P. Jin; Z. G. Wang

2008-01-01

306

Sporadic ALS has compartment-specific aberrant exon splicing and altered cell-matrix adhesion biology  

Microsoft Academic Search

Amyotrophic lateral sclerosis (ALS) is a fatal neurodegenerative disease characterized by progressive weak- ness from loss of motor neurons. The fundamental pathogenic mechanisms are unknown and recent evidence is implicating a significant role for abnormal exon splicing and RNA processing. Using new comprehensive genomic technologies, we studied exon splicing directly in 12 sporadic ALS and 10 control lumbar spinal cords

Stuart J. Rabin; Jae Mun; Michael Baughn; Ryan T. Libby; Young Joo Kim; Yuxin Fan; Randell T. Libby; Albert La Spada; Brad Stone; John Ravits

2009-01-01

307

High strain rate constitutive equation for aluminium metal matrix composites  

SciTech Connect

In this paper, high strain rate constitutive equations are presented for two different types of Al Metal Matrix Composite materials. Simple dynamic compression test results in conjunction with a numerical technique are used to determine the constants of this equation. For comparison, tests were also conducted on pure aluminum. Finally, some important issues relevant to the constitutive models for MMC are outlined.

Hamouda, A.M.S.; Hashmi, M.S.J. [Dublin City Univ. (Ireland). Advance Materials Processing Centre

1993-12-31

308

Optical reflection from the Bragg lattice of AsSb metal nanoinclusions in an AlGaAs matrix  

SciTech Connect

The optical properties of metal-semiconductor metamaterials based on an AlGaAs matrix are studied. The specific feature of these materials is that there are As and AsSb nanoinclusion arrays which modify the dielectric properties of the material. These nanoinclusions are randomly arranged in the medium or form a Bragg structure with a reflectance peak at a wavelength close to 750 nm, corresponding to the transparency region of the matrix. The reflectance spectra are studied for s- and p-polarized light at different angles of incidence. It is shown that (i) As nanoinclusion arrays only slightly influence the optical properties of the medium in the wavelength range 700-900 nm, (ii) chaotic AsSb nanoinclusion arrays cause strong scattering of light, and (iii) the spatial periodicity in the arrangement of AsSb nanoinclusions is responsible for Bragg resonance in the optical reflection.

Ushanov, V. I.; Chaldyshev, V. V., E-mail: chald.gvg@mail.ioffe.ru [Russian Academy of Sciences, Ioffe Physical-Technical Institute (Russian Federation); Preobrazhenskii, V. V.; Putyato, M. A.; Semyagin, B. R. [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation)] [Russian Academy of Sciences, Institute of Semiconductor Physics, Siberian Branch (Russian Federation)

2013-08-15

309

Preparation and Characteristics of Al Matrix Composites Reinforced with ZnWO4 Coated (WO3p + ABOw) Hybrid Reinforcements  

NASA Astrophysics Data System (ADS)

In this article, a ZnWO4 coating was prepared successfully on the surfaces of WO3 particulates and Al18B4O33 whiskers by a chemical precipitation method. Then the Al matrix composite with coated reinforcements was fabricated by a squeeze casting technique. Scanning electronic microscope analysis shows that a thin coating is coated on the surfaces of reinforcements. Differential thermal analysis and x-ray diffraction (XRD) results show that the Zn(OH)2 decomposes at 248C and that the ZnWO4 is produced by reaction WO3 with ZnO at 716C. Transmission electronic microscope and XRD analysis show that the coating of ZnWO4 is effective to prevent interfacial reaction between the WO3 particle and the Al matrix. The mechanical property testing shows that the ultimate tensile strength, elastic modulus, and elongation of the hybrid composites with coated reinforcements are improved greatly by introduction of ZnWO4 coating.

Feng, Y. C.; Cao, G. J.; Fan, G. H.; Wang, L. P.; Geng, L.

2013-02-01

310

High Strength Discontinuously Reinforced Aluminum For Rocket Applications  

NASA Technical Reports Server (NTRS)

This study presents results on the development of a new aluminum alloy with very high strength and ductility. Five compositions of Al-Mg-Sc-Gd-Zr alloy were selected for this purpose. These alloys were also reinforced with 15 volume percent silicon-carbide and boron-carbide particles to produce Discontinuously Reinforced Aluminum (DRA) materials. Matrix alloys and DRA were processed using a powder metallurgy process. The helium gas atomization produced very fine powder with cellular-dentritic microstructure. The microstructure of matrix alloys showed fine Al3Sc based precipitate which provides significant strengthening in these alloys. DRA showed uniform distribution of reinforcement in aluminum matrix. DRA materials were tested at -320 F, 75 F in air and 7S F in gaseous hydrogen environments and matrix alloys were tested at 75 F in air. DRA showed high strengths in the range of 89-111 ksi (614-697 MPa) depending on alloy compositions and test environments. Matrix alloys had a good combination of strength, 84-89 ksi (579-621 MPa) and ductility, 4.5-6.5%. The properties of these materials can further be improved by proper control of processing parameters.

Pandey, A. B.; Shah, S. R.; Shadoan, M.

2003-01-01

311

High Strength Aluminum Alloy For High Temperature Applications  

NASA Technical Reports Server (NTRS)

A cast article from an aluminum alloy has improved mechanical properties at elevated temperatures. The cast article has the following composition in weight percent: Silicon 6.0-25.0, Copper 5.0-8.0, Iron 0.05-1.2, Magnesium 0.5-1.5, Nickel 0.05-0.9, Manganese 0.05-1.2, Titanium 0.05-1.2, Zirconium 0.05-1.2, Vanadium 0.05-1.2, Zinc 0.05-0.9, Strontium 0.001-0.1, 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 containing up to about 60% by volume of a secondary filler material.

Lee, Jonathan A. (Inventor); Chen, Po-Shou (Inventor)

2005-01-01

312

Boron-carbide-aluminum and boron-carbide-reactive metal cermets. [B/sub 4/C-Al  

DOEpatents

Hard, tough, lighweight boron-carbide-reactive metal composites, particularly boron-carbide-aluminum composites, are produced. These composites have compositions with a plurality of phases. A method is provided, including the steps of wetting and reacting the starting materials, by which the microstructures in the resulting composites can be controllably selected. Starting compositions, reaction temperatures, reaction times, and reaction atmospheres are parameters for controlling the process and resulting compositions. The ceramic phases are homogeneously distributed in the metal phases and adhesive forces at ceramic-metal interfaces are maximized. An initial consolidated step is used to achieve fully dense composites. Microstructures of boron-carbide-aluminum cermets have been produced with modules of rupture exceeding 110 ksi and fracture toughness exceeding 12 ksi..sqrt..in. These composites and methods can be used to form a variety of structural elements.

Halverson, D.C.; Pyzik, A.J.; Aksay, I.A.

1985-05-06

313

Development and Processing Improvement of Aerospace Aluminum Alloys-Development of AL-Cu-Mg-Ag Alloy (2139)  

NASA Technical Reports Server (NTRS)

This final report supplement in presentation format describes a comprehensive multi-tasked contract study to continue the development of the silver bearing alloy now registered as aluminum alloy 2139 by the Aluminum Association. Two commercial scale ingots were processed into nominal plate gauges of two, four and six inches, and were extensively characterized in terms of metallurgical and crystallographic structure, and resulting mechanical properties. This report includes comparisons of the property combinations for this alloy and 2XXX and 7XXX alloys more widely used in high performance applications. Alloy 2139 shows dramatic improvement in all combinations of properties, moreover, the properties of this alloy are retained in all gauge thicknesses, contrary to typical reductions observed in thicker gauges of the other alloys in the comparison. The advancements achieved in this study are expected to result in rapid, widespread use of this alloy in a broad range of ground based, aircraft, and spacecraft applications.

Cho, Alex; Lisagor, W. Barry; Bales, Thomas T.

2007-01-01

314

Electron microscopy investigation of AlMg6 aluminum alloy surface defects caused by microorganisms extracted in space stations  

Microsoft Academic Search

The surfaces of AMg6 (aluminum-magnesium) alloy samples that have passed accelerated biocorrosion tests have been investigated\\u000a in a Quanta-3D scanning electron microscope. The alloy samples have been treated with the Ulocladium botrytis Preuss fungus, which is an active destructive fungus and was previously extracted on surfaces of the International Space Station.\\u000a Biocorrosion pits 210 ?m in diameter, cavities the depths

T. A. Alekhova; V. Ya. Shklover; N. A. Zagustina; N. V. Shvyndina; A. D. Plotnikov; A. L. Vasilev

2010-01-01

315

Tungsten wire/FeCrAlY matrix turbine blade fabrication study  

NASA Technical Reports Server (NTRS)

The objective was to establish a viable FRS monotape technology base to fabricate a complex, advanced turbine blade. All elements of monotape fabrication were addressed. A new process for incorporation of the matrix, including bi-alloy matrices, was developed. Bonding, cleaning, cutting, sizing, and forming parameters were established. These monotapes were then used to fabricate a 48 ply solid JT9D-7F 1st stage turbine blade. Core technology was then developed and first a 12 ply and then a 7 ply shell hollow airfoil was fabricated. As the fabrication technology advanced, additional airfoils incorporated further elements of sophistication, by introducing in sequence bonded root blocks, cross-plying, bi-metallic matrix, tip cap, trailing edge slots, and impingement inserts.

Melnyk, P.; Fleck, J. N.

1979-01-01

316

Fabrication of near net-shaped Al-based intermetallics matrix composites  

Microsoft Academic Search

Intermetallic compounds based on aluminium with Ni, Fe or Ti offer new opportunities for developing superior\\/advanced structural alloys for applications as diversified as biomedical and aerospace-aircraft industries. Aluminides have the attractive characteristics of low density, high strength, good corrosion and oxidation resistance, non-strategic elements and relatively low cost.There are several techniques for synthesizing the intermetallics and intermetallic matrix composites (IMCs),

M. R Ghomashchi

2001-01-01

317

Structure-property relationships in the heat affected zone of friction welded Al-SiC metal matrix composites  

SciTech Connect

The present investigation is concerned with the development of an overall process model for the microstructure evolution during continuous drive friction welding of Al-SiC metal matrix composites. The process model is composed of three components, i.e., a heat flow model, a mass flow model and a structural (kinetic) model, and is validated by comparison with experimental data. Computer simulations show that a narrow width of the heat affected zone (HAZ) requires the use of high friction pressure in combination with a short duration heating cycle, in agreement with general experience.

Midling, O.T. [SINTEF, Trondheim (Norway). Division of Metallurgy; Grong, O. [Norwegian Institute of Technology, Trondheim (Norway). Dept. of Metallurgy

1993-12-31

318

Impact loading of an aluminum/alumina composite  

SciTech Connect

The combined demands of increased strength and reduced weight in modern dynamic structural applications require improved understanding of composite materials subject to impact conditions. In order to isolate and identify individual contributions to composite material behavior under these conditions, an experimental and theoretical program was undertaken to examine dynamic behavior of an aluminum/alumina composite consisting of a 6061-T6 aluminum matrix containing elastic, spherical Al{sub 2}O{sub 3} inclusions (10 percent by volume, average diameter {approximately}25 microns). Parallel impact experiments are conducted on these composites and on pure 6061-T6 aluminum samples. This combination provides a direct and immediate qualitative picture of the effect of Al{sub 2}O{sub 3} inclusions the dynamic response of the composite in compression, release, and spallation. Additional experimental information is provided by post-shock reload tests of shock-recovered samples at quasi-static and intermediate strain rates.

Johnson, J.N.; Hixson, R.S.; Gray, G.T. III

1994-02-01

319

Development of Ta-matrix Nb3Al Strand and Cable for High-Field Accelerator Magnet  

SciTech Connect

Research and development of Nb{sub 3}Al strands and cables for a high field accelerator magnet is ongoing under the framework of the CERN-KEK collaboration. In this program, new Ta-matrix Nb{sub 3}Al strands were developed and their mechanical properties and superconducting properties were studied. The non-Cu J{sub c} values of these strands were 750 {approx} 800 A/mm{sup 2} at 15 T and 4.2 K. Using these strands, test fabrication of 27-strand Rutherford cable was carried out in collaboration with NIMS and Fermilab. The properties of the strands extracted from the cable were examined and it was found that there was no degradation of the superconducting properties of the strands. In this paper, we report the fabrication of the strands and the cable in brief and present some of the results obtained by studying their properties.

Tsuchiya, K.; Ghosh, A.; Kikuchi, A.; Takeuchi, T.; Banno, N.; Iijima, Y.; Nimori, S.; Takigawa, H.; Terashima, A.; Nakamoto, T.; Kuroda, Y.; Maruyama, M.; Takao, T.; Tanaka, K.; Nakagawa, K.; Barzi, E.; Yamada, R.; Zlobin, A.

2011-08-03

320

SEM Characterization of an Irradiated Dispersion Fuel Plate with U-10Mo Particles and 6061 Al Matrix  

SciTech Connect

It has been observed that during irradiation of a dispersion fuel plate, fuel/matrix interactions can impact the overall fuel plate performance. To continue the investigation of the irradiation performance of Si-rich fuel/matrix interaction layers, RERTR-6 fuel plate V1R010 (U- 10Mo/6061 Al) was characterized using scanning electron microscopy. This fuel plate was of particular interest because of its similarities to fuel plate R1R010, which had U-7Mo particles dispersed in 6061 Al. Both fuel plates were irradiated as part of the RERTR-6 experiment and saw very similar irradiation conditions. R1R010 was characterized in another study and was observed to form relatively uniform Si-rich layers during fabrication that remained stable during irradiation. Since U-10Mo does not interact as much with 6061 Al at high temperatures to form layers, it was of interest to characterize a fuel plate with these particles since it would allow for a comparison of fuel plates with different amounts of preirradiation interaction zone formation, which were then exposed to similar irradiation conditions. This paper demonstrates how the lower amount of interaction layer development in V1R010 during fabrication appears to impact the overall performance of the fuel plate, such that it does not behave as well as R1R010 in terms of interaction layer stability. Additionally, the results of this study are applied to improve the understanding of fuel/cladding interactions in monolithic fuel plates that consist of U-10Mo foils encased in 6061 Al cladding.

D. D. Keiser; J. F. Jue; A. B. Robinson; P. G. Medvedev; M. R. Finlay

2009-11-01

321

Quasicrystalline particulate reinforced aluminum composite  

SciTech Connect

Particulate reinforced aluminum and aluminum alloy composites are rapidly emerging as new commercial materials for aerospace, automotive, electronic packaging and other high performance applications. However, their low processing ductility and difficulty in recyclability have been the key concern. In this study, two composite systems having the same aluminum alloy matrix, one reinforced with quasicrystals and the other reinforced with the conventional SiC reinforcements were produced with identical processing routes. Their processing characteristics and tensile mechanical properties were compared.

Anderson, I.E.; Biner, S.B.; Sordelet, D.J.; Unal, O.

1997-07-01

322

Experimentally measured thermal transport properties of aluminumpolytetrafluoroethylene nanocomposites with graphene and carbon nanotube additives  

Microsoft Academic Search

Reactive materials such as aluminum (Al) and polytetrafluoroethylene (Teflon) are used for energy generation applications and specifically in ordnance technologies. With the advent of nanotechnology various nano-scale additives have become incorporated into reactive material formulations with the hope of enhanced performance. An important component to the study of energy generation is an examination of energy transport through a reactant matrix.

Keerti Kappagantula; Michelle L. Pantoya

323

Molecular aspects of aluminum toxicity  

Microsoft Academic Search

The focus in this review is directed to molecular aspects of aluminum toxicity in animal and plant cells. Unique thermodynamic features of Al(lII) ions impart biological specificity which may form the biochemical basis of aluminum interactions with cellular constituents. Current knowledge about aluminum?specific, molecular interactions is rather scanty. Al(III) ions may coordinate with nucleotides or complex to phospholipids resulting in

Alfred Haug; Charles E. Foy

1984-01-01

324

Influence of Cr and W alloying on the fiber-matrix interfacial shear strength in cast and directionally solidified sapphire NiAl composites  

NASA Technical Reports Server (NTRS)

Sapphire-reinforced NiAl matrix composites with chromium or tungsten as alloying additions were synthesized using casting and zone directional solidification (DS) techniques and characterized by a fiber pushout test as well as by microhardness measurements. The sapphire-NiAl(Cr) specimens exhibited an interlayer of Cr rich eutectic at the fiber-matrix interface and a higher interfacial shear strength compared to unalloyed sapphire-NiAl specimens processed under identical conditions. In contrast, the sapphire-NiAl(W) specimens did not show interfacial excess of tungsten rich phases, although the interfacial shear strength was high and comparable to that of sapphire-NiAl(Cr). The postdebond sliding stress was higher in sapphire-NiAl(Cr) than in sapphire-NiAl(W) due to interface enrichment with chromium particles. The matrix microhardness progressively decreased with increasing distance from the interface in both DS NiAl and NiAl(Cr) specimens. The study highlights the potential of casting and DS techniques to improve the toughness and strength of NiAl by designing dual-phase microstructures in NiAl alloys reinforced with sapphire fibers.

Asthana, R.; Tiwari, R.; Tewari, S. N.

1995-01-01

325

Crystal structures and properties of europium aluminum oxynitride Eu2AlO(3.75)N(0.1) and europium aluminum oxide EuAl2O4.  

PubMed

The reactions among Eu2O3, AlN, and Al2O3 with the ratios Eu:Al = 2:1 and 1:2 at 1200 C for 10 h yielded Eu2AlO(3.75)N(0.1) and EuAl2O4, respectively. The powder X-ray diffraction pattern of the new oxynitride could be indexed as a monoclinic structure with the space group I2 (No. 5) (a = 3.7113(2) , b = 3.6894(2) , c = 12.3900(8) , and ? = 90.6860(5)). This structure was found to be a novel distorted Ruddlesden-Popper type. For EuAl2O4, isostructural with monoclinic SrAl2O4 (space group P2(1), No. 4), a structural refinement was performed, indicating that the cell parameters were a = 8.44478(11) , b = 8.82388(12) , c = 5.15643(7) , and ? = 93.1854(12). (151)Eu Mssbauer spectra revealed that the divalent and trivalent Eu ions coexisted in Eu2AlO(3.75)N(0.1), while Eu ions were in the divalent state in EuAl2O4. A photoluminescent mechanism due to 4f(7) ((8)S(7/2)) ? 4f(6)5d(1) of europium in EuAl2O4 was proposed on the basis of the calculated band structure, the band gap obtained from UV-vis diffuse reflectance spectra, and the photoluminescence spectra. PMID:24191631

Tezuka, Keitaro; Tokuhara, Yoshimi; Wakeshima, Makoto; Shan, Yue Jin; Imoto, Hideo; Hinatsu, Yukio

2013-11-18

326

Microstructure and high-temperature oxidation resistance of TiN/Ti3Al intermetallic matrix composite coatings on Ti6Al4V alloy surface by laser cladding  

NASA Astrophysics Data System (ADS)

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 evaluate the high-temperature oxidation resistance of the composite coatings and the titanium alloy substrate, isothermal oxidation test was performed in a conventional high-temperature resistance furnace at 600C and 800C respectively. The result shows that the laser clad intermetallic composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like, and dendrites), and uniformly distributed in the Ti3Al matrix. It indicates that a physical and chemical reaction between the Ti powder and AlN powder occurred completely under the laser irradiation. In addition, the microhardness of the TiN/Ti3Al intermetallic matrix composite coating is 844HV0.2, 3.4 times higher than that of the titanium alloy substrate. The high-temperature oxidation resistance test reveals that TiN/Ti3Al intermetallic matrix composite coating results in the better modification of high-temperature oxidation behavior than the titanium substrate. The excellent high-temperature oxidation resistance of the laser cladding layer is attributed to the formation of the reinforced phase TiN and Al2O3, TiO2 hybrid oxide. Therefore, the laser cladding TiN/Ti3Al intermetallic matrix composite coating is anticipated to be a promising oxidation resistance surface modification technique for Ti6Al4V alloy.

Zhang, Xiaowei; Liu, Hongxi; Wang, Chuanqi; Zeng, Weihua; Jiang, Yehua

2010-11-01

327

High-temperature discontinuously reinforced aluminum  

NASA Astrophysics Data System (ADS)

High-temperature discontinuously reinforced aluminum (HTDRA) composites have been developed for elevated-temperature applications by incorporating SiC particulate reinforcement into a rapidly solidified, high-temperature Al-Fe-V-Si (alloy 8009) matrix. HTDRA combines the superior elevated-temperature strength, stability and corrosion resistance of the 8009 matrix with the excellent specific stiffness and abrasion resistance of the discontinuous SiC particulate reinforcement. On a specific stiffness basis, HTDRA is competitive with Ti-6-Al-4V and 17-4 PH stainless steel to temperatures approaching 480C. Potential aerospace applications being considered for HTDRA include aircraft wing skins, missile bodies, and miscellaneous engine, spacecraft and hypersonic vehicle components.

Zedalis, M. S.; Bryant, J. D.; Gilman, P. S.; Das, S. K.

1991-08-01

328

Growth and characterization of quaternary AlInGaN multiple quantum wells with different aluminum composition  

NASA Astrophysics Data System (ADS)

Quaternary AlInGaN multiple quantum well structures with (Al)InGaN wells were grown on sapphire substrates by metalorganic chemical vapor deposition. The structural and optical properties of the samples were investigated by means of high-resolution X-ray diffraction (HRXRD) and photoluminescence (PL). The shift of satellite peaks in HRXRD shows the fact that the Al composition increases and In composition decreases with increasing Al precursor flow rate during the growth process of quaternary AlInGaN wells or barriers. The PL intensity could be enhanced by optimizing Al composition in the barrier layers and further improved by adding Al atoms into InGaN wells due to the reduction in the quantum-confined Stark effect, even if the surface morphology is degraded when using AlInGaN as well layers observed from atomic force microscopy images. The reasons for the improvement are attributed to the reduced polarization mismatch and the enhanced carrier localization effect induced by Al composition increasing.

Liu, Tong; Jiao, Shujie; Wang, Dongbo; Zhao, Liancheng; Yang, Tianpeng; Xiao, Zhiguo

2014-05-01

329

Fatigue crack propagation in aerospace aluminum alloys  

Microsoft Academic Search

This article reviews fracture mechanics-based, damage tolerant characterizations and predictions of fatigue crack growth in aerospace aluminum alloys. The results of laboratory experimentation and micromechanical modeling are summarized in the areas of 1) the wide range crack growth rate response of conventional aluminum alloys, 2) fatigue crack closure, 3) the fatigue behavior of advanced monolithic aluminum alloys and metal matrix

Richard P. Gangloff; Robert S. Piascik; Dennis L. Dicus; James C. Newman Jr.

1994-01-01

330

Micromechanisms of low load wear in an Al18.5% Si alloy  

Microsoft Academic Search

Hypereutectic aluminumsilicon (AlSi) alloys are being used for engine block applications. Wear mechanisms at low loads in these alloys require further study to establish correlations between microstructure and wear resistance. Previous work showed that at 0.5N the A390 (Al18.5% Si) alloy operated in the ultra-mild wear (UMW) regime, with no damage to the aluminum matrix and very limited damage on

S. K. Dey; T. A. Perryb; A. T. Alpas

2009-01-01

331

Electron microscopy characterization of an as-fabricated research reactor fuel plate comprised of U-7Mo particles dispersed in an Al-2Si alloy matrix  

SciTech Connect

To understand the microstructural development of nuclear fuel plates during irradiation, it is imperative to know the microstructure of a fuel plate after all the fabrication steps have been completed and before it is inserted into the reactor. To this end, a U-7 wt.% Mo alloy research reactor dispersion fuel plate with Al-2 wt.% Si matrix was destructively examined using scanning and transmission electron microscopy to characterize the developed microstructure after fabrication. Of particular interest for this study was how the Si that was added to the fuel matrix partitioned between the various fuel plate phases during fabrication. Si was added to the matrix so that the microstructure that developed during fuel fabrication would exhibit good irradiation behavior. SEM analysis was used to identify the representative microstructure, the compositions of the various phases, and the partitioning behavior of the fuel and matrix constituents. TEM analysis was employed to definitively identify the phases in the U-7Mo alloy and the phases that formed due to diffusional interactions between the fuel particles and matrix during fuel plate fabrication. The TEM results are the first reported for an as-fabricated U-7 wt.% Mo dispersion fuel plate with an Al alloy matrix. SEM results showed that a significant portion of the original {gamma}-(U-Mo) fuel particles had transformed to a lamellar microstructure, comprised of {alpha}-U and either {gamma} or {gamma}' phases, and the fuel/matrix interaction layers were enriched in Si. TEM analysis identified an ordered fcc (U-Mo)(Al-Si){sub 3} type of phase, which formed at the decomposed U-7Mo/matrix interface and extended into the lamellar microstructure. Some regions of the U-7Mo particles retained the single-phase {gamma}-(U-Mo). Small precipitate phases were observed in the fuel meat matrix that contained Fe, Al, and Si. The Si that is added to the matrix of a U-Mo dispersion fuel plate to improve irradiation performance appears to result in the creation of a Si-rich (U-Mo)(Al-Si){sub 3} type of fuel/matrix interaction layer during fabrication that appears to exhibit favorable behavior during irradiation compared to the behavior of the layers that form in U-Mo dispersion fuel plates without Si in the matrix. - Research Highlights: {yields}Si seems to positively affect the microstructure of an as-fabricated fuel plate. {yields}Si modifications to the fuel plate exhibit favorable performance during irradiation. {yields}Si interdiffuses faster than Al.

Keiser, Dennis D., E-mail: Dennis.Keiser@inl.gov [Idaho National Laboratory, P. O. Box 1625, Scoville, ID 83415-6188 (United States); Gan, J.; Jue, J.F. [Idaho National Laboratory, P. O. Box 1625, Scoville, ID 83415-6188 (United States); Miller, B.D. [University of Wisconsin, Madison, WI 53706 (United States); Clark, C.R. [Idaho National Laboratory, P. O. Box 1625, Scoville, ID 83415-6188 (United States)

2010-11-15

332

Formation of adiabatic shear band in Al-SiC{sub w} metal matrix composites  

SciTech Connect

Ballistic impact accompanying high strain rate plastic deformation caused adiabatic shear bands to form in 2124 Al-SiC{sub w} composites. It is tried to interpret the formation behavior of the adiabatic shear bands in terms of microstructure of the composites including the volume fraction and distribution of SiC whiskers. Higher volume fraction of SiC whiskers prevented the formation of adiabatic shear bands more effectively. Shear bands were blocked by SiC whiskers, thereby changing their propagation path to the extrusion direction running through the whisker depleted zone. Cracks formed within the shear band induce loss of load carrying capacity and thus failure of the composites.

Cho, K.M.; Park, I.M. [Pusan National Univ. (Korea, Republic of); Lee, S. [Pohang Institute of Science and Technology (Korea, Republic of). Center for Advanced Aerospace Materials; Choi, W.B. [Agency for Defense and Development, Daejeon (Korea, Republic of)

1993-12-31

333

Synthesis, microstructure, and mechanical properties of aluminum/granulated-slag composites  

NASA Astrophysics Data System (ADS)

The present work provides results of aluminum metal matrix composites reinforced with granulated slag (GS). The study concerns the synthesis and properties of Al/GS composites based on powder metallurgy techniques. Dilatometry, differential thermal analysis, and scanning electron microscopy were employed to track the reactions between the aluminum matrix and the granulated slag during the sintering treatment. Thermal analysis results revealed an exothermic reaction at 640 C, leading to the formation of the intermetallic compound Al3Fe. The hardness and compressive strength of the sintering compacts were determined as a function of the GS content. The best results were achieved with the aluminum composites with 15 wt.% GS, reaching compressive strengths up to 372 MPa.

Torres, A.; Cruz, J.; Hernndez, L.; Domnguez, O.; Flores-Vlez, L. Ma.

2002-02-01

334

Effect of heat treatment on strength and abrasive wear behaviour of Al6061SiC p composites  

Microsoft Academic Search

In recent years, aluminum alloy based metal matrix composites (MMC) are gaining importance in several aerospace and automobile\\u000a applications. Aluminum 6061 has been used as matrix material owing to its excellent mechanical properties coupled with good\\u000a formability and its wide applications in industrial sector. Addition of SiCp as reinforcement in Al6061 alloy system improves its hardness, tensile strength and wear

N. R. Prabhu Swamy; C. S. Ramesh; T. Chandrashekar

2010-01-01

335

Effect of alternative aging process on the fracture and interfacial properties of particulate Al2O3-reinforced Al (6061) metal matrix composite  

NASA Astrophysics Data System (ADS)

The effects of different aging processes on ductility, fracture, and interfacial properties in particulate Al2O3-reinforced Al (6061) metal-matrix composite (MMCs) were studied. Tensile tests based on relevant ASTM standards were performed to investigate the mechanical responses of specimens under different heat-treatment conditions. Scanning electron microscopy (SEM), field-emission SEM (FESEM), and transmission electron microscopy (TEM) studies were carried out to correlate fracture mechanism(s) with microstructural features. Based on the experimental results, the overall effect of heat treatment on tensile properties is similar to that in the monolithic alloy, however, the rate of recovery in fracture-related properties, such as elongation to fracture, is lower in the overaged condition for the MMC samples. To explain this low recovery behavior of overaged MMCs, the following observations have been taken into account: (1) a shift of the materials behavior from particle fracture to interface (or near-interface) debonding fracture, when moving from the underaged to overaged regime, and (2) more frequent observations of interfacial reaction products (spinel) on the fracture surface of overaged specimens. The presence/formation of spinel phase at the interface was recognized as the main cause of this behavior. Although spinel products mainly form during material processing, they may continue to form in the solid state as well. As a result, the surface morphology of the spinel phase in the underaged specimens is different from that in the overaged specimens.

Shakeri, H. R.; Wang, Zhirui

2002-06-01

336

Growth of aluminum-free porous oxide layers on titanium and its alloys Ti-6Al-4V and Ti-6Al-7Nb by micro-arc oxidation.  

PubMed

The growth of oxides on the surfaces of pure Ti and two of its ternary alloys, Ti-6Al-4V and Ti-6Al-7Nb, by micro-arc oxidation (MAO) in a pH 5 phosphate buffer was investigated. The primary aim was to form thick, porous, and aluminum-free oxide layers, because these characteristics favor bonding between bone and metal when the latter is implanted in the human body. On Ti, Ti-6Al-4 V, and Ti-6Al-7Nb, the oxides exhibited breakdown potentials of about 200 V, 130 V, and 140 V, respectively, indicating that the oxide formed on the pure metal is the most stable. The use of the MAO procedure led to the formation of highly porous oxides, with a uniform distribution of pores; the pores varied in size, depending on the anodizing applied voltage and time. Irrespective of the material being anodized, Raman analyses allowed us to determine that the oxide films consisted mainly of the anatase phase of TiO2, and XPS results indicated that this oxide is free of Al and any other alloying element. PMID:24907769

Duarte, Las T; Bolfarini, Claudemiro; Biaggio, Sonia R; Rocha-Filho, Romeu C; Nascente, Pedro A P

2014-08-01

337

Effect of Si3N4 powder reactivity on the preparation of the Si2N2O-Al2O3 silicon aluminum oxynitride solid solution  

NASA Technical Reports Server (NTRS)

Dense high-purity silicon aluminum oxynitride was prepared by reactive hot-pressing of an Si3N4-Al2O3-SiO2 mixture. The formation of a single-phase material was found to be critically dependent on the Si3N4 powder in the starting mixture. It is suggested that evolution of a chlorine- and nitrogen-containing species may enhance the reactivity of Si3N4 in this reaction. Densities of O prime sialons are very similar to that of Si2N2O, the widely quoted value in the ceramics literature of 3.1 g/cu cm for the density of Si2N2O being incorrect.

Sekercioglu, I.; Wills, R. R.

1979-01-01

338

Electrodeposition studies of aluminum on tungsten electrode from DMSO[sub 2] electrolytes: Determination of Al[sup III] species diffusion coefficients  

SciTech Connect

DMSO[sub 2] possesses a number of attractive features that suggest technological applications as electrolyte for rechargeable cells. These features include high conductivity, good thermal stability, ability to dissolve numerous metallic salts and weak or no coordination with metallic cations. Moreover, cathode materials such as V[sub 2]O[sub 5] or MnO[sub 2] have shown to be reversibly reduced in DMSO[sub 2] based electrolytes. However, there is a lack of information about the anode compounds that can be used in the presence of DMSO[sub 2] since previous studies of this nature were limited to lithium. Aluminum electrodeposition from mixtures of AlCl[sub 3]/LiCl/DMSO[sub 2] [dimethylsulfone (CH[sub 3])[sub 2]SO[sub 2

Legrand, L.; Tranchant, A.; Messina, R. (CNRS, Thiais (France). Lab. d'Electrochimie Catalyse et Synthese Organique)

1994-02-01

339

'Forbidden' reflections in resonant diffraction of synchrotron radiation in yttrium aluminum garnet Y{sub 3}Al{sub 5}O{sub 12}  

SciTech Connect

The purely resonant Bragg reflections (13, 13, 0) and (14, 0, 0) in yttrium aluminum garnet Y{sub 3}Al{sub 5}O{sub 12} at energies near the K absorption edge of yttrium have been studied experimentally and theoretically. The anisotropic tensor atomic factor of yttrium corresponding to dipole-dipole resonance transitions depends on three independent parameters changing with energy. The intensities of the reflections (14, 0, 0) and (13, 13, 0) are shown to depend on the parameter difference f{sub 1}(E) - f{sub 2}(E) and the parameter f{sub 3}(E), respectively, which are attributable to distortions of the wave functions of the excited atoms and change greatly with photon energy E. Studying various reflections has allowed one to determine the various components of the tensor atomic factor and to compare them with the results of numerical calculations.

Mukhamedzhanov, E. Kh.; Kovalchuk, M. V.; Borisov, M. M. ['Kurchatov Institute' Russian Research Center (Russian Federation); Ovchinnikova, E. N., E-mail: ovtchin@gmail.com; Oreshko, A. P. [Moscow State University (Russian Federation); Dmitrienko, V. E. [Russian Academy of Sciences, Shubnikov Institute of Crystallography (Russian Federation)

2011-01-15

340

Characterization of tool wear and weld optimization in the friction-stir welding of cast aluminum 359+20% SiC metal-matrix composite  

SciTech Connect

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 only a 7% reduction in the SiC mean particle size in the weld zone for self-optimized pin tools with no threads as compared with a 25% variation for threaded tools wearing significantly at the start of welding. The weld zone becomes more homogeneous for efficient welding with self-optimized tools, and there is a reduction in the weld zone grain size due to dynamic recrystallization, which facilitates the solid-state flow. Transmission electron microscopy shows little difference in the dislocation density from the base material to the weld zone, but there is a propensity of dislocation loops in the weld zone. The weld zone is observed to harden by as much as 30%, in contrast to the base material, as a consequence of the recrystallized grain size reduction and the SiC particles distributed therein.

Fernandez, G.J.; Murr, L.E

2004-03-15

341

Tribological Properties of Al-SiC Metal Matrix Composites: A Comparison Between Sand Cast and Squeeze Cast Techniques  

NASA Astrophysics Data System (ADS)

Tribological behaviour of Al-SiC metal matrix composites prepared using two different fabrication techniques, viz. sand cast and squeeze cast techniques are studied in a multi- tribotester (TR-25, DUCOM, India) under dry sliding conditions and ambient atmosphere for varying volume fraction of reinforcement, applied load and sliding speed. Friction increases with increase in applied load and sliding speed and volume fraction of reinforcement. Wear test results show increased wear rates at higher load and speed, while increase in SiC volume fraction yields decrease in wear rate. Corrosion study conducted in 3.5 % NaCl solution shows that squeeze cast composites have better corrosion resistance than sand cast composites. Vickers's microhardness test shows improved hardness properties for squeeze cast composites compared to sand cast ones. The microstructure study of wear tracks reveals domination of abrasive wear with minor traces of adhesive wear.

Ghosh, S.; Sahoo, P.; Sutradhar, G.

2014-10-01

342

Short-term aluminum administration in the rat: reductions in bone formation without osteomalacia  

SciTech Connect

Aluminum may be a pathogenic factor in dialysis-associated osteomalacia. To study the early effects of Al on bone, cortical bone growth was measured in pair-fed rats given Al and control rats over two consecutive intervals of 28 (period I) and 16 (period II) days, respectively, using tetracycline labeling of bone. Al (2 mg elemental Al per rat) was administered intraperitoneally for 5 days each week, except for the first week of study, when an incremental dose of Al was given. Control rats received saline vehicle only. For the entire 44-day study, bone and matrix formation were reduced from control values in rats given Al. Although bone and matrix formation remained at control levels during period I in rats given Al, both measurements decreased from control values during period II. During Al exposure, bone and matrix apposition at the periosteum were reduced from control levels in period II, but not in period I. Neither osteoid width nor mineralization front width increased from control values in rats given Al. These findings indicate that Al reduces bone and matrix formation early in the course of Al exposure and prior to the development of histologic osteomalacia. Rather than acting as an inhibitor of mineralization, the early effect of Al on bone is the suppression of matrix synthesis. Our results suggest that the state of low bone formation seen in dialysis-associated osteomalacia may be the consequence of a direct toxic effect of Al on the cellular activity of osteoblasts. 29 references, 3 tables.

Goodman, W.G.

1984-05-01

343

Micromechanic of Al{sub 2}O{sub 3} matrix composites toughened by metallic phases  

SciTech Connect

Ceramic materials toughened by dispersion of a ductile metallic phase can be a solution for high temperature applications where corrosion and mechanical resistance are requested in severe conditions. Alumina based composites are studied for this purpose from the micromechanic point of view; combining the microstructure characterization with numerical simulations a better study Dan design of these materials can be performed. Al{sub 2}O{sub 3} reinforced with Ni second phase composites were prepared and characterized by SEM, TEM and XRD techniques; the measured mechanical properties were compared with numerical simulation based on the microstructure analysis and the results can be used to design a better microstructure. In particular, using some microstructure characteristics as design parameters, the mechanical properties of the composite can be optimized by numerical simulations.

Lutterotti, L.; Di Maggio, R.; Gialanella, S.; Orsini, P.G. [Univ. di Trento, Mesiano (Italy). Dept. di Ingegneria dei Materiali

1996-10-01

344

Spatial Inhomogeneity of Aluminum Content in Air-Bridged Lateral Epitaxially Grown AlGaN Ternary Alloy Films Probed by Cross-Sectional Scanning Near-Field Optical Microscopy  

NASA Astrophysics Data System (ADS)

We systematically studied spatial inhomogeneity of aluminum content in air-bridged lateral epitaxially grown (ABLEG) AlGaN ternary alloy films by high-resolution photoluminescence mapping probed with cross-sectional scanning near-field optical microscopy (SNOM). We observed the content changes along the vertical <0001> and the horizontal <11bar 20> growth directions in AlGaN films with four different mask widths. The spatial inhomogeneity was determined by considering the following factors: the different growth rates of the lateral and vertical directions, the aluminum and gallium adatom supplies from a gas that depend on mask width, and the aluminum and gallium adatom diffusions on the (0001) and (11bar 20) facets.

Ishibashi, Akihiko; Murotani, Hideaki; Yokogawa, Toshiya; Yamada, Yoichi

2012-03-01

345

Potentiometric and 19F nuclear magnetic resonance spectroscopic study of fluoride substitution in the GaAl 12 polyoxocation: implications for aluminum (hydr)oxide mineral surfaces  

NASA Astrophysics Data System (ADS)

Fluoride replacement of oxygens in the GaO 4Al 12(OH) 24(H 2O)127+(aq) molecule [GaAl 12] was studied via 19F nuclear magnetic resonance (NMR) at 4 < pH < 5 and 278 K in order to elucidate similar reactions at the surfaces of clays. Peaks are identified in the 19F-NMR spectra that correspond to both terminal and bridging fluorides on the GaAl 12 molecule, with relative peak positions similar to those previously identified in fluoridated aluminum (hydr)oxide mineral surfaces (Nordin, J. P., Sullivan, D. J., Phillips, B. L., and Casey, W. H. [1999], "Mechanisms for fluoride-promoted dissolution of bayerite [?-Al(OH) 3(s)] and boehmite [?-AlOOH(s)]- 19F-NMR spectroscopy and aqueous surface chemistry," Geochim. Cosmochim. Acta63, 3513-3524). Fluoride substitutes for oxygen at three different sites in the GaAl 12 molecule, but at dramatically different rates. The kinetics of fluoride substitution follow a rate law that includes parallel and reversible transfer of fluoride from nonbridging sites to the two bridging sites. The essential features of the rate law are as follows: (1) fluoride replaces bound water molecules (?-OH 2) within minutes at 278 K at rates that are quantitatively similar to fluoride uptake by Al(H 2O)63+(aq) to form AlF 2+(aq) at similar conditions; (2) fluoride substitutes onto the two topologically distinct ? 2-OH sites at different rates, as was previously observed for oxygen exchange, but here, the reaction is complete in hours to days at 278 K. Most importantly, rates of fluoride substitution onto ? 2-OH sites are 10 2 times more rapid than the corresponding rates of oxygen exchange with bulk waters, indicating that fluoride considerably labilizes the molecule, as is also observed at the surfaces of minerals. The largest cause of this labilization is the reduced molecular charge on the GaAl 12 upon replacement of bound waters by fluoride, which for mineral surfaces corresponds to a reduction in surface charge density.

Yu, Ping; Lee, Alasdair P.; Phillips, Brian L.; Casey, William H.

2003-03-01

346

Aluminum avoids the central position in AlB9- and AlB10-: photoelectron spectroscopy and ab initio study.  

PubMed

The structures and the electronic properties of two Al-doped boron clusters, AlB(9)(-) and AlB(10)(-), were investigated via joint photoelectron spectroscopy and high-level ab initio study. The photoelectron spectra of both anions are relatively broad and have no vibrational structure. The geometrical structures were established by unbiased global minimum searches using the Coalescence Kick method and comparison between the experimental and calculated vertical electron detachment energies. The results show that both clusters have quasi-planar structures and that the Al atom is located at the periphery. Chemical bonding analysis revealed that the global minimum structures of both anions can be described as doubly (?- and ?-) aromatic systems. The nona-coordinated wheel-type structure of AlB(9)(-) was found to be a relatively high-lying isomer, while a similar structure for the neutral AlB(9) cluster was previously shown to be either a global minimum or a low-lying isomer. PMID:21800920

Li, Wei-Li; Romanescu, Constantin; Galeev, Timur R; Wang, Lai-Sheng; Boldyrev, Alexander I

2011-09-29

347

Impulse plasma deposition of aluminum oxide layers for Al 2O 3\\/Si, SiC, GaN systems  

Microsoft Academic Search

Nanocrystalline Al2O3 layers were produced by means of impulse plasma deposition (IPD) technique on Si and SiC substrates. Morphology, microstructure and chemical composition of films and film\\/substrate interfaces were investigated using SEM and SIMS methods. After depositing on top of the layers metal (Al) dot contacts also CV and IV measurements of so produced metal-insulatorsemiconductor structures were performed in order

A. Werbowy; K. Zdunek; E. Dusi?ski; J. Szmidt; M. Elert

2003-01-01

348

Crack Propagation During Sustained-Load Cracking of Al-Zn-Mg-Cu Aluminum Alloys Exposed to Moist Air or Distilled Water  

NASA Astrophysics Data System (ADS)

Intergranular sustained-load cracking of Al-Zn-Mg-Cu (AA7xxx series) aluminum alloys exposed to moist air or distilled water at temperatures in the range 283 K to 353 K (10 C to 80 C) has been reviewed in detail, paying particular attention to local processes occurring in the crack-tip region during crack propagation. Distinct crack-arrest markings formed on intergranular fracture faces generated under fixed-displacement loading conditions are not generated under monotonic rising-load conditions, but can form under cyclic-loading conditions if loading frequencies are sufficiently low. The observed crack-arrest markings are insensitive to applied stress intensity factor, alloy copper content and temper, but are temperature sensitive, increasing from ~150 nm at room temperature to ~400 nm at 313 K (40 C). A re-evaluation of published data reveals the apparent activation energy, E a for crack propagation in Al-Zn-Mg(-Cu) alloys is consistently ~35 kJ/mol for temperatures above ~313 K (40 C), independent of copper content or the applied stress intensity factor, unless the alloy contains a significant volume fraction of S-phase, Al2CuMg where E a is ~80 kJ/mol. For temperatures below ~313 K (40 C) E a is independent of copper content for stress intensity factors below ~14 MNm-3/2, with a value ~80 kJ/mol but is sensitive to copper content for stress intensity factors above ~14 MNm-3/2, with E a , ranging from ~35 kJ/mol for copper-free alloys to ~80 kJ/mol for alloys containing 1.5 pct Cu. The apparent activation energy for intergranular sustained-load crack initiation is consistently ~110 kJ/mol for both notched and un-notched samples. Mechanistic implications are discussed and processes controlling crack growth, as a function of temperature, alloy copper content, and loading conditions are proposed that are consistent with the calculated apparent activation energies and known characteristics of intergranular sustained-load cracking. It is suggested, depending on the circumstances, that intergranular crack propagation in humid air and distilled water can be enhanced by the generation of aluminum hydride, AlH3, ahead of a propagating crack and/or its decomposition after formation within the confines of the nanoscale volumes available after increments of crack growth, defined by the crack arrest markings on intergranular fracture surfaces.

Holroyd, N. J. Henry; Scamans, G. M.

2011-12-01

349

Aluminum Hydroxide  

MedlinePLUS

Aluminum hydroxide is used for the relief of heartburn, sour stomach, and peptic ulcer pain and to ... Aluminum hydroxide comes as a capsule, a tablet, and an oral liquid and suspension. The dose and ...

350

Aluminum dodecatungstophosphate (AlPW 12O 40) as a non-hygroscopic Lewis acid catalyst for the efficient FriedelCrafts acylation of aromatic compounds under solvent-less conditions  

Microsoft Academic Search

Stable and non-hygroscopic aluminum dodecatungstophosphate (AlPW12O40), which is prepared easily from cheap and commercially available compounds was found to be an effective catalyst for FriedelCrafts acylation reactions using carboxylic acids, acetic anhydride and benzoyl chloride in the absence of solvent under mild reaction conditions.

Habib Firouzabadi; Nasser Iranpoor; Farhad Nowrouzi

2004-01-01

351

Aluminum-fly ash metal matrix composites for automotive parts. [Reports for April 1 to June 30, 1999, and July 1 to September 30, 1999  

Microsoft Academic Search

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

David Weiss; Robert Purgert; Richard Rhudy; P. Rohatgi

1999-01-01

352

Aluminum-fly ash metal matrix composites for automotive parts. [Reports for October 1 to December 31, 1999, and January 1 - to March 31, 2000  

Microsoft Academic Search

The highlights of this report are: (1) fly ash classified by less than 100 microns in size was mixed into a 300 lb melt of alloy 535 without the need of a magnesium additive; (2) a vibratory feeder fitted with a sieve was used as the means to minimize particle clustering while introducing fly ash into the aluminum alloy 535

David Weiss; Robert Purgert; Richard Rhudy; Pradeep Rohatgi

2000-01-01

353

Microstructure characterization of as-fabricated and 475 Degrees C annealed U7 wt.% Mo dispersion fuel in AlSi alloy matrix  

SciTech Connect

High-density uranium (U) alloys with an increased concentration of U are being examined for the development of research and test reactors with low enriched metallic fuels. The U-Mo fuel alloy dispersed in Al-Si alloy has attracted particular interest for this application. This paper reports our detailed characterization results of as-fabricated and annealed (475 Degrees C for 4 h) U-Mo dispersion fuels in Al-Si matrix with a Si concentration of 2 and 5 wt.%, named as As2Si, As5Si, An2Si, An5Si accordingly. Techniques employed for the characterization include scanning electron microscopy and transmission electron microscopy with specimen prepared by focused ion beam in situ lift-out. Fuel plates with Al-5 wt.% Si matrix consistently yielded thicker interaction layers developed between U-Mo particles and Al-Si matrix, than those with Al-2 wt.% Si matrix, given the same processing parameters. A single layer of interaction zone was observed in as-fabricated samples (i.e., As2Si, As5Si), and this layer mainly consisted of U3Si3Al2 phase. The annealed samples contained a two-layered interaction zone, with a Si-rich layer near the U-Mo side, and an Al-rich layer near the Al-Si matrix side. The U3Si5 appeared as the main phase in the Si-rich layer in An2Si sample, while both U3Si5 and U3Si3Al2 were identified in sample An5Si. The Al-rich layer in sample An2Si was amorphous, whereas that in sample An5Si mostly consisted of crystalline U(Al,Si)3, along with a small fraction of U(Al,Si)4 and U6Mo4Al43 phases. The influence of Si on the diffusion and reaction in the development of interaction layers in U(Mo)/Al(Si) is discussed in the light of growth-controlling mechanisms and irradiation performance.

Bo Yao; Emmanuel Perez; Dennis D. Keiser, Jr.; Jan-Fong Jue; Curtis R. Clark; Nicolas Woolstenhulme; Yongho Sohn

2011-09-01

354

Morphology and properties of a hybrid organic-inorganic system: Al nanoparticles embedded into CuPc thin film  

NASA Astrophysics Data System (ADS)

The evolution of the morphology and the electronic structure of the hybrid organic-inorganic system composed of aluminum nanoparticles (NPs) distributed in an organic semiconductor matrixcopper phthalocyanine (CuPc)as a function of nominal aluminum content was studied by transmission electron microscopy and by photoemission spectroscopy methods. The aluminum atoms deposited onto the CuPc surface diffuse into the organic matrix and self-assemble to NPs in a well-defined manner with a narrow diameter distribution, which depends on the amount of aluminum that is evaporated onto the CuPc film. We find clear evidence of a charge transfer from Al to CuPc and we have been able to determine the lattice sites where Al ions sit. The finally at high coverage about 64 the formation of metallic aluminum overlayer on CuPc thin film takes place.

Molodtsova, O. V.; Aristova, I. M.; Babenkov, S. V.; Vilkov, O. V.; Aristov, V. Yu.

2014-04-01

355

Synthesis, processing and characterization of NiAl-AlN-Al(2)O(3) composites  

NASA Astrophysics Data System (ADS)

A hybrid composite based on nickel aluminide (NiAl) was developed, which contains both aluminum nitride (AlN) dispersoids and short alumina (Alsb2Osb3) fibers, with the strategy being the combination of the two different strengthening mechanisms, one microscopic and the other macroscopic, to provide a synergistic improvement in the mechanical properties. The AlN dispersion strengthened NiAl was synthesized by mechanical alloying of nickel and aluminum elemental powders in a nitrogen atmosphere and the alumina fibers were added during consolidation. The microstructure of the NiAl-(AlN)sb{Dispersion}-(Alsb2Osb3)sb{Fiber} composites showed a fine grain sized, near-stoichiometric NiAl matrix, submicron size AlN particles and randomly oriented Alsb2Osb3 fibers dispersed homogeneously in the matrix. The thermal residual stresses in the composites were measured at room temperature as well as at high temperatures using neutron diffraction and Rietveld refinement. The residual stresses in the as-processed composites were tensile in the NiAl matrix and compressive in the AlN and Alsb2Osb3 reinforcements. Upon heating these stresses relaxed at temperatures that are lower than the processing temperature due to the creep in the matrix. A simple finite element analysis was used to estimate the residual stress in the composites and showed reasonable agreement with the experimental results. The compressive strength of these composites was characterized both at 300K and 1300K and showed a significant strengthening compared with the base material at both temperatures. The relationship between the microstructure, residual stress and the mechanical properties was studied and the strengthening mechanisms were identified.

Choo, Hahn

356

The effect of simulated space thermal environment on damping capacity of metal matrix composites  

NASA Astrophysics Data System (ADS)

Damping capacity is one of important parameters that engineers need to consider when they select materials for space structure applications. The materials studied in this paper are high performance SiC particulate reinforced aluminum and Al2O3 woven fabric reinforced aluminum composites. Changes in damping capacity of the materials in simulated space thermal environment were studied using Dynamic Mechanical Analyzer (DMA). Comparing to the conventional aluminum alloy, the composites have significantly higher damping capacity. The experiment demonstrated that thermal cycling to sub-ambient temperature can significantly affects the damping capacity of metal matrix composites. The long-term effects of space thermal cycling on the composites were also discussed.

Jiang, X.; Ouellet, L.; Nikanpour, Darius; Lo, J.

2003-09-01

357

Aluminum and bone disorders: with specific reference to aluminum contamination of infant nutrients.  

PubMed

Aluminum (Al) impairment of bone matrix formation and mineralization may be mediated by its direct effect on bone cells or indirectly by its effect on parathyroid hormone and calcium metabolism. Its toxic effects are proportional to tissue Al load. Al contamination of nutrients depends on the amount of Al present naturally in chemicals or from the manufacturing process. Intravenous calcium, phosphorus, and albumin solutions have high Al (greater than 500 micrograms/L), whereas crystalline amino acid, sterile water, and dextrose water have low Al (less than 50 micrograms/L) content. Enteral nutrients including human and whole cow milk have low Al, whereas highly processed infant formulas with multiple additives, such as soy formula, preterm infant formula, and formulas for specific disorders are heavily contaminated with Al. Healthy adults are in zero balance for Al. The gastrointestinal tract excludes greater than 95% of dietary Al, and kidney is the dominant organ for Al excretion. However, even with normal renal function, only 30-60% of an Al load from parenteral nutrition is excreted in the urine, resulting in tissue accumulation of Al. The risk for Al toxicity is greatest in infants with chronic renal insufficiency, recipients of long term parenteral nutrition, i.e., no gut barrier to Al loading, and preterm infants with low Al binding capacity. The rapid growth of the infant would theoretically potentiate Al toxicity in all infants, although the critical level of Al loading causing bone disorders is not known. To minimize tissue burden, Al content of infant nutrients should be similar to "background" levels, i.e., similar to whole milk (less than 50 micrograms/L). PMID:3292633

Koo, W W; Kaplan, L A

1988-06-01

358

Production of aluminum metal by electrolysis of aluminum sulfide  

DOEpatents

Metallic aluminum may be produced by the electrolysis of Al/sub 2/S/sub 3/ at 700 to 800/sup 0/C in a chloride melt composed of one or more alkali metal chlorides, and one or more alkaline earth metal chlorides and/or aluminum chloride to provide improved operating characteristics of the process.

Minh, N.Q.; Loutfy, R.O.; Yao, N.P.

1982-04-01

359

Study of the phase compositions of Al-Se-Ge alloys for designing solders for aluminum alloys  

NASA Astrophysics Data System (ADS)

Alloys based on the Al-Si-Ge system are studied in order to design solders with a liquidus temperature lower than 570C. Electron-probe microanalysis, differential scanning calorimetry, and X-ray diffraction analysis are used to optimize the solder composition and the process of solder production. Quantitative phase analysis methods, which are based on an experimental determination of the lattice parameters of the phases and their diffraction line intensities, are developed for these alloys.

Osintsev, O. E.; Betsofen, S. Ya.; Konkevich, V. Yu.; Betsofen, M. S.; Stepanov, V. V.

2009-06-01

360

Binding and Electrostatic Attraction of Lanthanum (La 3+ ) and Aluminum (Al 3+ ) to Wheat Root Plasma Membranes  

Microsoft Academic Search

. A general model for the sorption of trivalent cations to wheat-root (Triticum aestivum L cv. Scout 66) plasma membranes (PM) has been developed and includes the first published coefficients for La3+ and Al3+ binding to a biological membrane. Both ions are rhizotoxic, and the latter ion is the principal contributor to the toxicity\\u000a of acidic soils around the world.

U. Yermiyahu; G. Rytwo; D. K. Brauer; T. B. Kinraide

1997-01-01

361

Development and characterization of Powder Metallurgy (PM) 2XXX series Al alloy products and Metal Matrix Composite (MMC) 2XXX Al/SiC materials for high temperature aircraft structural applications  

NASA Technical Reports Server (NTRS)

The results of a series of material studies performed by the Lockheed Aeronautical Systems Company over the time period from 1980 to 1991 are discussed. The technical objective of these evaluations was to develop and characterize advanced aluminum alloy materials with temperature capabilities extending to 350 F. An overview is given of the first five alloy development efforts under this contract. Prior work conducted during the first five modifications of the alloy development program are listed. Recent developments based on the addition of high Zr levels to an optimum Al-Cu-Mg alloy composition by powder metallurgy processing are discussed. Both reinforced and SiC or B4C ceramic reinforced alloys were explored to achieve specific target goals for high temperature aluminum alloy applications.

Chellman, D. J.; Gurganus, T. B.; Walker, J. A.

1992-01-01

362

In-situ TiC particle reinforced TiAl matrix composites: Powder preparation by mechanical alloying and Selective Laser Melting behavior  

Microsoft Academic Search

Mechanical alloying of TiAlgraphite elemental powder mixture was performed to synthesize nanocomposite powder with Ti(Al) solid solution matrix reinforced by in-situ formed TiC particles. The evolutions in phases, microstructures, and compositions of milled powders with the applied milling times were investigated. It showed that with increasing the milling time, the starting irregularly shaped powder underwent a successive change in its

Dongdong Gu; Zhiyang Wang; Yifu Shen; Qin Li; Yufang Li

2009-01-01

363

Modeling shear instability and fracture in dynamically deformed Al/W granular composites  

NASA Astrophysics Data System (ADS)

Aluminum/Tungsten granular composites are materials which combine high density and strength with bulk distributed fracture of Al matrix into small particles under impact or shock loading. They are processed using cold and hot isostatic pressing of W particles/rods in the matrix of Al powder. Numerical models were used to elucidate the dynamic behavior of these materials under dynamic conditions simulating low velocity high energy impact in drop weight test (10 m/s). It was demonstrated that arrangement of W components and bonding between Al particles dramatically affect the samples shear localization and mode of fracture of the Al matrix in agreement with experiments.

Olney, Karl; Benson, David; Nesterenko, Vitali F.

2012-03-01

364

Stress Corrosion Cracking of Al-Mg and Mg-Al Alloys  

SciTech Connect

Aluminum and magnesium based alloys are being used for reducing the weight of automobiles. For structural applications they must have adequate stress corrosion resistance and yet, under some circumstances, stress corrosion cracking can occur in both alloy systems. Precipitation of the Mg rich Beta-phase (Al3Mg2) at grain boundaries of Al-Mg alloys and the Beta-phase (Mg17Al12) at grain boundaries of the Mg-Al alloys are critical factors in their stress corrosion performance. In Mg-Al, the Beta-phase is cathodic to the matrix while in the Al-Mg case, the Beta-phase is anodic to the matrix. These phases produce localized galvanic induced-corrosion that leads to intergranular stress corrosion cracking and cracking growth rates of 5 and 103 times faster than the solution treated condition, for Al-Mg and Mg-Al, respectively.

Jones, Russell H.; Vetrano, John S.; Windisch, Charles F.

2004-12-01

365

Improved Irradiation Performance of Uranium-Molybdenum/Aluminum Dispersion Fuel by Silicon Addition in Aluminum  

SciTech Connect

Uranium-molybdenum fuel particle dispersion in aluminum is a form of fuel under development for conversion of high-power research and test reactors from highly enriched to low-enriched uranium in the U.S. Global Threat Reduction Initiative program (also known as the Reduced Enrichment for Research and Test Reactors program). Extensive irradiation tests have been conducted to find a solution for problems caused by interaction layer growth and pore formation between U-Mo and Al. Adding a small amount of Si (up to [approximately]5 wt%) in the Al matrix was one of the proposed remedies. The effect of silicon addition in the Al matrix was examined using irradiation test results by comparing side-by-side samples with different Si additions. Interaction layer growth was progressively reduced with increasing Si addition to the matrix Al, up to 4.8 wt%. The Si addition also appeared to delay pore formation and growth between the U-Mo and Al.

Yeon Soo Kim; G. L. Hofman; A. B. Robinson; D. M. Wachs

2013-10-01

366

A mathematical model to predict thrust force in drilling hybrid metal matrix composites  

Microsoft Academic Search

This paper presents the development of mathematical model to correlate the drilling parameters with thrust force. The results indicate that the developed model is suitable for prediction of thrust forces in drilling of hybrid metal matrix composites. Materials used for the present investigation are Al 356-aluminum alloy reinforced with silicon carbide of size 25 microns and mica of size 45

T. Rajmohan; K. Palanikumar

2010-01-01

367

Recycling of aluminum matric composites  

Microsoft Academic Search

Separation of matrix metals in composites was tried on alumina short fiber-reinforced aluminum and 6061 alloy composites and\\u000a SiC whisker-reinforced 6061 alloy composite for recycling. It is possible to separate molten matrix metals from fibers in\\u000a the composites using fluxes that are used for melt treatment to remove inclusions. About 50 vol pct of the matrix metals was\\u000a separated from

Yoshinori Nishida; Norihisa Izawa; Yukio Kuramasu

1999-01-01

368

The aluminum content of biological products containing aluminum adjuvants: determination by atomic absorption spectrometry.  

PubMed

Aluminum compounds are used as adjuvants in certain types of vaccines, toxoids and allergenic extracts for human use. The most common Al compounds used in biological products to enhance the immune response are aluminum potassium sulphate (alum), aluminum hydroxide and aluminum phosphate. This study describes an atomic absorption spectrometric method for the determination of the Al content of Al adsorbed toxoid preparations and allergenic extracts at levels of less than 0.85 mg of Al per half millilitre human dose. Aliquots of the samples which contained Al suspensions were acid digested with nitric and sulphuric acid and analysed in the nitrous oxide-acetylene flame of an atomic absorption spectrometer. The 396.2 nm Al line was used for analysis. The Al content of the National Bureau of Standards (NBS) Standard Reference Material No. 1075a aluminum 2- ethylhexanoate was determined to within 1% of the NBS certificate value by this method. Atomic absorption results for the Al content of tetanus toxoids containing aluminum potassium sulphate and aluminum phosphate were compared with polarographic and inductively coupled argon plasma (ICP) emission spectrometry results. Reproducibility and recovery data for Al are tabulated for a variety of biological products containing aluminum phosphate, aluminum potassium sulphate and aluminum hydroxide adjuvants. In addition, ICP has been used to characterize the Al and P compositions of the precipitates and supernatant solutions which resulted from centrifuging toxoid suspensions that contained the three different Al adjuvants. PMID:6736048

May, J C; Progar, J J; Chin, R

1984-01-01

369

Charge storage behavior of nanostructures based on SiGe nanocrystals embedded in Al2O3 matrix  

NASA Astrophysics Data System (ADS)

The charge storage behavior of nanostructures based on Si1- x Ge x (0 ? x ? 1) nanocrystals (NCs) in an Al2O3 matrix was investigated. The structures have been grown by RF magnetron sputtering and subsequently annealed at temperatures ranging from 700 C to 1000 C for 30 min in nitrogen ambient. The stoichiometry of the SiGe NCs and the alumina crystalline structure were found to be significantly dependent on the RF power and the annealing temperature. The sizes of the SiGe NCs and their distribution were investigated by grazing incidence small angle X-ray scattering (GISAXS). The capacitance-voltage ( C- V) and conductance-voltage ( G- V) measurements were performed to investigate the charge trapping characteristics of the memory structures. The C- V hysteresis width depends on variations in the crystalline structure resulting from different annealing temperatures. It is also shown that charge injection is governed by the Fowler-Nordheim tunnel mechanism for higher electric fields.

Vieira, Eliana M. F.; Levichev, Sergey; Dias, Carlos J.; Igreja, Rui; Buljan, Maja; Bernstorff, Sigrid; Conde, Olinda; Chahboun, Adil; Rolo, Anabela G.; Gomes, Maria J. M.

2013-07-01

370

Properties of sulfur sorbents containing dispersed nickel in an Al{sub 2}O{sub 3} matrix  

SciTech Connect

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 Al{sub 2}O{sub 3} matrix have the potential to be better in both respects. Their main limitation is that they do not reduce H{sub 2}S 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 H{sub 2}S 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. [Southern Illinois Univ., Carbondale, IL (United States); Gasper-Galvin, L.D.; Gardner, T.H. [Dept. of Energy, Morgantown, WV (United States). Morgantown Energy Technology Center; Hammerbeck, K. [Oak Ridge Associated Universities, TN (United States)

1996-04-01

371

High temperature stability, interface bonding, and mechanical behavior in (beta)-NiAl and Ni3Al matrix composites with reinforcements modified by ion beam enhanced deposition  

NASA Astrophysics Data System (ADS)

In preparation for experiments with surface modified Al2O3 reinforcements in (beta)NiAl, diffusion bonding experiments were conducted. FP alumina fibers were prepared with ion sputtered surface films (Al2O3, Al, Ni) and then composited with (beta)NiAl slabs and hot pressed. After 70 thermal cycles, interfacial shear strength was measured. A roughness mechanism is proposed for the observed increased strength of the coated fibers. Creep in Ni3Al was studied.

Grummon, D. S.

1992-01-01

372

Composite aluminum conductor for high current density applications at cryogenic temperatures  

NASA Astrophysics Data System (ADS)

Electrical resistivity of high purity aluminum decreases by several order of magnitude below a temperature of approximately 25 K and consequently it can be for high current density applications at these low temperatures. However, high-purity aluminum does not have the requisite strength to withstand magnetic forces produced by the high currents. A composite conductor consisting of high purity aluminum filaments supported in a high strength powder metallurgy processed Al-Fe-Ce alloy matrix has been successfully fabricated to meet these requirements by a combination of hot extrusion through streamline dies followed by cold drawing to wire gauges. Effects of hot extrusion and cold drawings as well as the influence of superimposed hydrostatic stresses during cold working on the filament shape are considered in terms of deformation principles. Results of microstructural observations and theoretical analyses of diffusional contamination of the high purity aluminum filaments during processing are presented.

Premkumar, M. K.; Billman, F. R.; Chakrabarti, D. J.; Dawless, R. K.; Austen, A. R.

373

Orientation relationship between {beta}-Mn and L2{sub 1} matrix in a Cu{sub 2}MnAl alloy  

SciTech Connect

In the as-quenched condition, the microstructure of the Cu{sub 2}MnAl alloy was L2{sub 1} phase containing extremely fine L-J precipitates. This result is different from that reported by other workers in the as-quenched Cu{sub 2}MnAl alloy. When the as-quenched alloy was aged at 350 C, {gamma}-brass precipitates started to appear within the L2{sub 1} matrix. The orientation relationship between the {gamma}-brass and the L2{sub 1} matrix was determined to be cubic to cubic. This result is consistent with that observed by other workers in the aged Cu-Mn-Al alloy. When the alloy was aged at 460 C, the {gamma}-brass precipitates disappeared and platelike {beta}-Mn precipitates occurred within the L2{sub 1} matrix. As the aging temperature was increased to 560 C, the morphology of the {beta}-Mn precipitates changed from platelike to granular shape. Electron diffraction examinations indicated that in spite of the morphology change the same orientation relationship between the {beta}-Mn and the L2{sub 1} matrix is maintained, and it could be best stated as follows: (210){sub {beta}-Mn}{parallel}(100){sub m}, ({bar 1}20){sub {beta}-Mn}{parallel}(010){sub m}, (001){sub {beta}-Mn}{parallel}(001){sub m}. This result is in disagreement with that reported by Kuzobski et al. in the aged Cu{sub 2}MnAl alloy. In their study, it was concluded that both the morphology of the {beta}-Mn precipitates and the orientation relationship between the {beta}-Mn and the L2{sub 1} matrix would vary with the aging temperature.

Chu, K.C.; Liu, T.F. [National Chiao Tung Univ. (Taiwan, Province of China). Dept. of Materials Science and Engineering

1999-07-01

374

TEM study of {beta} Prime precipitate interaction mechanisms with dislocations and {beta} Prime interfaces with the aluminium matrix in Al-Mg-Si alloys  

SciTech Connect

The interaction mechanisms between dislocations and semi-coherent, needle-shaped {beta} Prime precipitates in Al-Mg-Si alloys have been studied by High Resolution Transmission Electron Microscopy (HRTEM). Dislocation loops appearing as broad contrast rings around the precipitate cross-sections were identified in the Al matrix. A size dependency of the interaction mechanism was observed; the precipitates were sheared when the longest dimension of their cross-section was shorter than approximately 15 nm, and looped otherwise. A more narrow ring located between the Al matrix and bulk {beta} Prime indicates the presence of a transition interface layer. Together with the bulk {beta} Prime structure, this was further investigated by High Angle Annular Dark Field Scanning TEM (HAADF-STEM). In the bulk {beta} Prime a higher intensity could be correlated with a third of the Si-columns, as predicted from the published structure. The transition layer incorporates Si columns in the same arrangement as in bulk {beta} Prime , although it is structurally distinct from it. The Z-contrast information and arrangement of these Si-columns demonstrate that they are an extension of the Si-network known to structurally connect all the precipitate phases in the Al-Mg-Si(-Cu) system. The width of the interface layer was estimated to about 1 nm. - Highlights: Black-Right-Pointing-Pointer {beta} Prime is found to be looped at sizes larger than 15 nm (cross section diameter). Black-Right-Pointing-Pointer {beta} Prime is found to be sheared at sizes smaller than 15 nm (cross section diameter). Black-Right-Pointing-Pointer The recently determined crystal structure of {beta} Prime is confirmed by HAADF-STEM. Black-Right-Pointing-Pointer Between {beta} Prime and the Al-matrix a transition layer of about 1 nm is existent. Black-Right-Pointing-Pointer The {beta} Prime /matrix layer is structurally distinct from bulk {beta} Prime and the aluminium matrix.

Teichmann, Katharina [Norwegian University of Science and Technology, Trondheim (Norway)] [Norwegian University of Science and Technology, Trondheim (Norway); Marioara, Calin D.; Andersen, Sigmund J. [SINTEF Materials and Chemistry, Trondheim (Norway)] [SINTEF Materials and Chemistry, Trondheim (Norway); Marthinsen, Knut, E-mail: knut.marthinsen@material.ntnu.no [Norwegian University of Science and Technology, Trondheim (Norway)] [Norwegian University of Science and Technology, Trondheim (Norway)

2013-01-15

375

Effect of processing cycles on aluminum/tungsten carbide composites prepared by continual annealing and press bonding process  

NASA Astrophysics Data System (ADS)

In the present work, a novel technique is introduced called CAPB (continual annealing and press bonding) for the manufacturing of a bulk aluminum matrix composite dispersed with 10 vol.% WC particles (Al/WCp). The microstructure of the fabricated composite after fourteen cycles of CAPB showed an excellent and homogenous distribution of the WC particles in the aluminum matrix and strong bonding between the various layers. The results indicated that the tensile strength of the composites increased with the number of CAPB cycles, and reached a maximum value of 140 MPa at the end of fourteenth cycle, which was 1.6 time higher than the obtained value for annealed aluminum (raw material, 88 MPa). Even though the elongation of the Al/WCp composite was reduced during the initial cycles of CAPB-ing, it increased significantly during the final cycles.

Amirkhanlou, Sajjad; Ketabchi, Mostafa; Parvin, Nader; Khorsand, Shohreh; Carreo, Fernando

2014-08-01

376

Damage of aluminum borate whisker reinforced 6061 aluminum composite under impact of hypervelocity projectiles  

Microsoft Academic Search

An aluminum borate whisker reinforced 6061 aluminum composite (AlBOw\\/6061Al) semi-infinite target was impacted by hypervelocity projectiles with velocity of 2.1 km s?1. The results showed that a columned crater with hemispherical bottom was formed. The crater formed on the AlBOw\\/6061Al composite is much smaller than that on the 6061 aluminum alloy target. Spallation occurred along the edge of the crater

H. T Li; W. D Fei; D. Z Yang

2002-01-01

377

The influence of Si and Mg rich phases on the mechanical properties of 6061 Al-matrix composites reinforced with Al 2 O 3  

Microsoft Academic Search

Besides altering the kinetics of precipitation, the reinforcements with alumina particles appear to alter the relative proportions of the various phases formed in the matrix alloy during ageing. Alumina also seems to reduce the volume fractions of hardening phase in these materials, especially at higher contents. One reason for this effect could be the dislocation relief of the matrix strain

J. M. Gmez De Salazar; M. I. Barrena

2002-01-01

378

Solid-State NMR Detection, Characterization, and Quantification of the Multiple Aluminum Environments in US-Y Catalysts by Al-27 MAS and MQMAS Experiments at Very High Field  

SciTech Connect

The detection of all of the aluminum present in steamed zeolite H-Y catalysts by (27)Al MAS NMR at 14.4 T (600 MHz for (1)H) and 18.8T (800 MHz for (1)H) is reported. Further, it is shown that it is possible by (27)Al MAS and MQMAS NMR measurements to clearly identify four separate aluminum environments which are characteristic of these materials and to unambiguously assign their coordinations. Average chemical shift and quadrupolar coupling parameters are used to accurately simulate the (27)Al MAS NMR spectra at 9.4 T (400 MHz for (1)H), 14.4 T (600 MHz for (1)H) and 18.8 T (800 MHz for (1)H) in terms of these four aluminum environments. In addition, these average chemical shift and quadrupolar coupling parameters are used to calculate peak positions in the (27)Al MQMAS isotropic dimension that are in good agreement with the experimental data acquired at 9.4 and 18.8 T.

Fyfe, Colin A.(8998) [8998; Bretherton, Jeremy L.(8998) [8998; Lam, Lau Y.(University of British Columbia) [University of British Columbia

2001-06-06

379

Pitting corrosion of aluminum  

Microsoft Academic Search

This review describes the experiments performed during the last few decades which enhance knowledge of the pitting of aluminum. Specifically, metastable and stable pits, pit chemistry and the effect of intermetallics on pitting are discussed. The properties of metastable alloys and inhibition of Al are also discussed.

Z Szklarska-Smialowska

1999-01-01

380

Carbon nanotube reinforced aluminum nanocomposite via plasma and high velocity oxy-fuel spray forming.  

PubMed

Free standing structures of hypereutectic aluminum-23 wt% silicon nanocomposite with multiwalled carbon nanotubes (MWCNT) reinforcement have been successfully fabricated by two different thermal spraying technique viz Plasma Spray Forming (PSF) and High Velocity Oxy-Fuel (HVOF) Spray Forming. Comparative microstructural and mechanical property evaluation of the two thermally spray formed nanocomposites has been carried out. Presence of nanosized grains in the Al-Si alloy matrix and physically intact and undamaged carbon nanotubes were observed in both the nanocomposites. Excellent interfacial bonding between Al alloy matrix and MWCNT was observed. The elastic modulus and hardness of HVOF sprayed nanocomposite is found to be higher than PSF sprayed composites. PMID:17450788

Laha, T; Liu, Y; Agarwal, A

2007-02-01

381

Mechanisms of Aluminum Tolerance  

Microsoft Academic Search

\\u000a Aluminum (Al) toxicity limits agricultural productivity over much of the worlds arable land by inhibiting root growth and\\u000a development. Affected plants have difficulty in acquiring adequate water and nutrition from their soil environments and thus\\u000a have stunted shoot development and diminished yield. Al toxicity is due to soil acidity and is largely a natural problem;\\u000a however, it can also result

Owen A. Hoekenga; Jurandir V. Magalhaes

382

Benefits of Residual Aluminum in Ductile Iron  

NASA Astrophysics Data System (ADS)

Two main chemistry systems of micro-inclusions can be identified in ductile iron: Ca-S-X and Mg-Si-O-X with the majority of the inclusions regardless of treatment type and location being of the second type, silicates. Laboratory investigations have shown that simple silicates were present in the matrix, while more complex silicates were present in conjunction with graphite, probably acting as graphite nucleation sites. In these more complex silicates, elevated levels of Al, Ca, Ce and La were typical. Comparing micro-particles embedded in iron matrix and graphite nodules of iron treated with pure Mg-metal and iron treated with MgFeSi alloy showed a higher amount of complex silicates with elevated Al-levels in the iron treated with MgFeSi. Further laboratory investigation was undertaken to explore which source of Al and which range of residual Al would have a favorable impact on the graphite nucleation in ductile iron. The work showed that a residual aluminum of 0.005 to 0.020 wt.% appears to be beneficial for improving ductile iron solidification characteristics without the incidence of pinholes. Greatest benefits were achieved when introducing the Al into the iron via an inoculant late during processing or via a pre-conditioner to the base iron. Al added via the MgFeSi provided less benefit. Some case studies illustrating the effect of Al in ductile iron are also presented, as Al-containing pre-conditioner or/and Al-bearing, FeSi inoculant application.

Riposan, Iulian; Chisamera, Mihai; Stan, Stelian; Toboc, Pavel; Grasmo, Geir; White, Douglas; Ecob, Chris; Hartung, Cathrine

2011-02-01

383

High temperature stability, interface bonding, and mechanical behavior in. beta. -NiAl and Ni sub 3 Al matrix composites with reinforcements modified by ion beam enhanced deposition  

SciTech Connect

In preparation for experiments with surface modified Al{sub 2}O{sub 3} reinforcements in {beta}NiAl, diffusion bonding experiments were conducted. FP alumina fibers were prepared with ion sputtered surface films (Al{sub 2}O{sub 3}, Al, Ni) and then composited with {beta}NiAl slabs and hot pressed. After 70 thermal cycles, interfacial shear strength was measured. A roughness mechanism is proposed for the observed increased strength of the coated fibers. Creep in Ni{sub 3}Al was studied. 3 figs, 1 tab. (DLC)

Grummon, D.S.

1992-01-22

384

Comparison of the Booster Interface Temperature in Stainless Steel (SS) V-Channel versus the Aluminum (Al) Y-Channel Primer Chamber Assemblies (PCAs). Volume 1; Technical Assessment Report  

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 findings of the assessment.

Garcia, Roberto; Saulsberry, Regor L.

2011-01-01

385

Regeneration of aluminum hydride  

DOEpatents

The present invention provides methods and materials for the formation of hydrogen storage alanes, AlH.sub.x, where x is greater than 0 and less than or equal to 6 at reduced H.sub.2 pressures and temperatures. The methods rely upon reduction of the change in free energy of the reaction between aluminum and molecular H.sub.2. The change in free energy is reduced by lowering the entropy change during the reaction by providing aluminum in a state of high entropy, by increasing the magnitude of the change in enthalpy of the reaction or combinations thereof.

Graetz, Jason Allan (Mastic, NY); Reilly, James J. (Bellport, NY)

2009-04-21

386

Regeneration of aluminum hydride  

DOEpatents

The present invention provides methods and materials for the formation of hydrogen storage alanes, AlH.sub.x, where x is greater than 0 and less than or equal to 6 at reduced H.sub.2 pressures and temperatures. The methods rely upon reduction of the change in free energy of the reaction between aluminum and molecular H.sub.2. The change in free energy is reduced by lowering the entropy change during the reaction by providing aluminum in a state of high entropy, and by increasing the magnitude of the change in enthalpy of the reaction or combinations thereof.

Graetz, Jason Allan; Reilly, James J; Wegrzyn, James E

2012-09-18

387

Corrosion behavior of AlZn\\/Al 2O 3 and AlZnX\\/Al 2O 3 (X = Cu, Mn) composites synthesized by mechanicalthermal treatment  

Microsoft Academic Search

The development of ceramic particulate reinforced aluminum metal matrix composites (MMCs) has resulted in advanced engineering materials for potential use in structural applications in automobile and marine industries. In the present work we have analyzed the corrosion behavior of AlZnAl2O3 MMCs with minor alloying additions of Cu and Mn. The composites have been prepared via reaction sintering of partially reacted

T. G. Durai; Karabi Das; Siddhartha Das

2008-01-01

388

Distribution of aluminum species in the hydrosphere--I Aluminum in the ocean  

Microsoft Academic Search

This paper attempts to solve the apparent controversy concerning the concentration of dissolved aluminum in ocean water and furthermore to present some information on the kinds and the distribution of various species in natural waters. The aluminum was determined fluorimetrically using Pontachrome Blue-Black R. Aluminum in sea water was subdivided into the following categories: Coarse, particulate Al; retained on a

W. Sackett; G. Arrhenius

1962-01-01

389

Application of modern aluminum alloys to aircraft  

Microsoft Academic Search

Aluminum alloys have been the primary material of choice for structural components of aircraft since about 1930. Although polymer matrix composites are being used extensively in high-performance military aircraft and are being specified for some applications in modern commercial aircraft, aluminum alloys are the overwhelming choice for the fuselage, wing, and supporting structure of commercial airliners and military cargo and

E. A. Starke; J. T. Staley

1996-01-01

390

Aluminum-fly ash metal matrix composites for automotive parts. [Reports for October 1 to December 1998, and January 31 to March 31, 1999  

SciTech Connect

Some highlights are: (1) Material development, process development, and part validation are occurring simultaneously on a fast track schedule. (2) Prior project activity has resulted in a program emphasis on three components--manifolds, mounting brackets, and motor mounts; and three casting techniques--squeeze casting, pressure die casting, and sand casting. (3) With the project focus, it appears possible to offer manifolds and mounting brackets for automotive qualification testing on a schedule in line with the PNGV Year 2004 goal. (4) Through an iterative process of fly ash treatment, MMC ingot preparation, foundry process refinement, and parts production, both foundries (Eck Industries and Thompson Aluminum Casting Company) are addressing the pre-competitive issues of: (a) Optimum castability with fly ash shapes and sizes; (b) Best mechanical properties derived from fly ash shapes and sizes; (c) Effective fly ash classification processes; (d) Mechanical properties resulting from various casting processes and fly ash formulations. Eck and TAC continued experiments with batch ingot provided by both Eck and the University of Wisconsin at Milwaukee. Castings were run that contained varying amounts of fly ash and different size fractions. Components were cast using cenosphere material to ascertain the effects of squeeze casting and to determine whether the pressure would break the cenospheres. Test parts are currently being machined into substandard test bars for mechanical testing. Also, the affect of heat treatments on ashalloy are being studied through comparison to two lots, one heat treated and one in the ''as cast'' condition.

Weiss, David; Purgert, Robert; Rhudy, Richard; Rohatgi, P.

1999-04-21

391

Characterization of ultradispersed aluminum  

SciTech Connect

Samples of ultradispersed Al were received, which were produced by electrically exploding Al wires in argon. These samples comprised very small particles that were not significantly oxidized and that were stable in air. Particle morphology were studied with SE, micropycnometry, and gas adsorption surface area. Composition were determined using various techniques, as were thermal stability and reaction exotherms. The inexplicable reports of an Al-Ar compound and of an exothermic reaction were not confirmed. The material is a stable, nonoxidized, small-particle, highly reactive form of aluminum that is of interest in energetic materials formulations.

Simpson, R.L.; Maienschein, J.L.; Swansiger, R.W.; Garcia, F.; Darling, D.H.

1994-12-08

392

Aluminum Analysis.  

ERIC Educational Resources Information Center

Presents three problems based on the price of aluminum designed to encourage students to be cooperative and to use an investigative approach to learning. Students collect and synthesize information, analyze results, and draw conclusions. (AIM)

Sumrall, William J.

1998-01-01

393

Processing and structure of in situ Fe-Al alloys produced by gas tungsten arc welding  

SciTech Connect

Iron aluminide weld overlays are being investigated for corrosion and erosion protection of boiler tubes in low NOx burners. The primary objective of the research is to identify overlay compositions which can be deposited in a crack-free condition and provide corrosion protection in moderately reducing environments. In the current phase of work, Fe-Al alloy weld overlays were produced by depositing commercially pure aluminum wire on to low carbon steel substrates using Gas Tungsten Arc Welding. A systematic variation of the wire feed speed and current, two major factors affecting dilution, resulted in a variation in aluminum contents of the welds ranging from 3--42 wt% aluminum. The aluminum content was observed to increase with wire feed speed and a decrease in the current. The aluminum content was also found to affect the cracking susceptibility of the overlays. At 10wt% aluminum, few to no cracks were observed in the deposits. Above this value, cracking was prevalent throughout the weld. In addition, two types of microstructures were found correlating to different concentrations of aluminum. A homogeneous matrix with second phase particles consisting of coarse columnar grains was found for low aluminum concentrations. With higher aluminum contents, a two-phase constituent was observed to surround primary dendrites growing from the substrate. The transition of the microstructures occurred between 24 and 32 wt% Al.

Banovic, S.W.; DuPont, J.N.; Marder, A.R. [Lehigh Univ., Bethlehem, PA (United States). Energy Research Center

1997-02-14

394

Microstructural evolution in laser and electron beam welds on SiC-reinforced A356 aluminum  

Microsoft Academic Search

A comparative study of laser beam welding (LBW) and electron beam welding (EBW) of cast A356\\/SiC\\/15p aluminum metal matrix composite (Al-MMC) has been completed. Laser and electron beam welds have been made at identical powers, rapid travel speeds (up to 200 ipm) and focusing conditions to allow direct comparison of the effects of the welding process characteristics with the resulting

Thomas Joseph Lienert

1998-01-01

395

Sr effect on the microstructure and tensile properties of A357 aluminum alloy and Al{sub 2}O{sub 3}/SiC-A357 cast composites  

SciTech Connect

The effect of strontium as a modifier on the microstructures and tensile properties of two castable particulate metal matrix composites has been studied. The particulate metal matrix composites had similar matrix alloy (A357) but different reinforcing fine particles (silicon carbide and alumina). Results showed that the addition of 0.03% strontium makes a modest improvement to the yield strength, ultimate tensile strength and elongation percentage values, and the scatter of these properties, but makes a significant improvement to minimum strength and elongation results. Microstructural examinations by scanning electron microscope and energy dispersive spectroscopy analysis of metal matrix composites showed segregation of strontium on both the silicon carbide and alumina particles. Further results showed that the addition of higher strontium levels contributes to the over-modification of the eutectic silicon and promotes the formation of an Al-Si-Sr intermetallic compound on the particle/matrix interface.

Razaghian, A. [Imam Khomeini International University, Qazvin (Iran, Islamic Republic of); Emamy, M., E-mail: Emamy@ut.ac.ir [Center of Excellence for High Performance Materials, School of Metallurgy and Materials, University of Tehran, Tehran (Iran, Islamic Republic of); Najimi, A.A.; Ebrahimi, S.H. Seyed [Center of Excellence for High Performance Materials, School of Metallurgy and Materials, University of Tehran, Tehran (Iran, Islamic Republic of)

2009-11-15

396

Preparation of micro/nano-structure superhydrophobic film on aluminum plates using galvanic corrosion method.  

PubMed

A simple and novel approach has been developed to obtain a microporous film with compound nanoparticles on the surface of aluminum alloy substrate using the galvanic corrosion method. The wettability of the surface changes from hydrophilicity to superhydrophobicity after chemical modification with stearic acid (SA). The water contact angle (WCA) and sliding angle (WSA) of superhydrophobic aluminum alloy surface (SAAS) are 154 degrees and 9 degrees, respectively. The roughness of the aluminum substrate increases after the oxidation reaction. The porous aluminum matrix surface is covered with irregularly shaped holes with a mean radius of about 15 microm, similar to the surface papillae of natural Lotus leaf, with villus-like nanoparticles array on pore surfaces. The superhydrophobic property is attributed to this special surface morphology and low surface energy SA. X-ray powder diffraction (XRD) pattern and Energy Dispersive X-Ray Spectroscopy (EDS) spectrum indicate that Al2O3, Al(OH)3 and AIO(OH) has been formed on the surface of aluminum substrate after the oxidation reaction. The Raman spectra indicate that C-H bond from SA and the Al-O are formed on the SAAS. The as-formed SAAS has good stability. PMID:24245140

Wu, Ruomei; Chao, Guang Hua; Jiang, Haiyun; Pan, Anqiang; Chen, Hong; Yuan, Zhiqing; Liu, Qilong

2013-10-01

397

Superplasticity in powder metallurgy aluminum alloys and composites  

SciTech Connect

Superplasticity in powder metallurgy Al alloys and composites has been reviewed through a detailed analysis. The stress-strain curves can be put into 4 categories: classical well-behaved type, continuous strain hardening type, continuous strain softening type and complex type. The origin of these different types of is discussed. The microstructural features of the processed material and the role of strain have been reviewed. The role of increasing misorientation of low angle boundaries to high angle boundaries by lattice dislocation absorption is examined. Threshold stresses have been determined and analyzed. The parametric dependencies for superplastic flow in modified conventional aluminum alloys, mechanically alloyed alloys and Al alloy matrix composites is determined to elucidate the superplastic mechanism at high strain rates. The role of incipient melting has been analyzed. A stress exponent of 2, an activation energy equal to that for grain boundary diffusion and a grain size dependence of 2 generally describes superplastic flow in modified conventional Al alloys and mechanically alloyed alloys. The present results agree well with the predictions of grain boundary sliding models. This suggests that the mechanism of high strain rate superplasticity in the above-mentioned alloys is similar to conventional superplasticity. The shift of optimum superplastic strain rates to higher values is a consequence of microstructural refinement. The parametric dependencies for superplasticity in aluminum alloy matrix composites, however, is different. A true activation energy of superplasticity in aluminum alloy matrix composites, however, is different. A true activation energy of 313 kJ/mol best describes the composites having SiC reinforcements. The role of shape of the reinforcement (particle or whisker) and processing history is addressed. The analysis suggests that the mechanism for superplasticity in composites is interface diffusion controlled grain boundary sliding.

Mishra, R.S. [Defence Metallurgical Research Lab., Hyderabad (India)] [Defence Metallurgical Research Lab., Hyderabad (India); Bieler, T.R. [Michigan State Univ., East Lansing, MI (United States). Dept. of Materials Science and Mechanics] [Michigan State Univ., East Lansing, MI (United States). Dept. of Materials Science and Mechanics; Mukherjee, A.K. [Univ. of California, Davis, CA (United States). Dept. of Mechanical, Aeronautical and Materials Engineering] [Univ. of California, Davis, CA (United States). Dept. of Mechanical, Aeronautical and Materials Engineering

1995-03-01

398

Processing, microstructure evolution and properties of nanoscale aluminum alloys  

NASA Astrophysics Data System (ADS)

In this project, phase transformations and precipitation behavior in age-hardenable nanoscale materials systems, using Al-Cu alloys as model materials, were first studied. The Al-Cu nanoparticles were synthesized by a Plasma Ablation process and found to contain a 25 nm thick adherent aluminum oxide scale, which prevented further oxidation. On aging of the particles, a precipitation sequence consisting of, nearly pure Cu precipitates to the metastable theta' to equilibrium theta was observed, with all three forming along the oxide-particle interface. The structure of theta' and its interface with the Al matrix has been characterized in detail. Ultrafine Al-Cu nanoparticles (525 nm) were also synthesized by inert gas condensation (IGC) and their aging behavior was studied. These particles were found to be quite stable against precipitation. Secondly, pure Al nanoparticles were prepared by the Exploding Wire process and their sintering and consolidation behavior were studied. It was found that nanopowders of Al could be processed to bulk structures with high hardness and density. Sintering temperature was found to have a dominant effect on density, hardness and microstructure. Sintering at temperatures >600C led to breakup of the oxide scale, leading to an interesting nanocomposite composed of 100200 nm Al oxide dispersed in a bimodal nanometer-micrometer size Al matrix grains. Although there was some grain growth, the randomly dispersed oxide fragments were quite effective in pinning the Al grain boundaries, preventing excessive grain growth and retaining high hardness. Cold rolling and hot rolling were effective methods for attaining full densification and high hardness. Thirdly, the microstructure evolution and mechanical behavior of Al-Al 2O3 nanocomposites were studied. The composites can retain high strength at elevated temperature and thermal soaking has practically no detrimental effect on strength. Although the ductility of the composite remains quite low, there was substantial evidence for high localized plasticity. The strengthening mechanisms of the composite include: Orowan strengthening, grain size strengthening and Forest strengthening. Finally, the microstructure evolution and mechanical behavior of 2024Al-Al 2O3 nanocomposites were studied. This 2024Al-Al2O 3 composite exhibits similar thermal stability and high strength at elevated temperature as Al-Al2O3. On aging, the matrix of 2024Al-Al2O3 composites revealed a precipitation sequence of: alphaAl ? GP/GPB ? theta'/S' ? theta/S. The strengthening mechanisms of the 2024Al-Al2O3 composites include precipitation strengthening, Orowan strengthening, grain size strengthening and Forest strengthening.

Han, Jixiong

399

NASA-UVa light aerospace alloy and structures technology program supplement: Aluminum-based materials for high speed aircraft  

NASA Technical Reports Server (NTRS)

This report on the NASA-UVa light aerospace alloy and structure technology program supplement: Aluminum-Based Materials for High Speed Aircraft covers the period from July 1, 1992. The objective of the research is to develop aluminum alloys and aluminum matrix composites for the airframe which can efficiently perform in the HSCT environment for periods as long as 60,000 hours (certification for 120,000 hours) and, at the same time, meet the cost and weight requirements for an economically viable aircraft. Current industry baselines focus on flight at Mach 2.4. The research covers four major materials systems: (1) Ingot metallurgy 2XXX, 6XXX, and 8XXX alloys, (2) Powder metallurgy 2XXX alloys, (3) Rapidly solidified, dispersion strengthened Al-Fe-X alloys, and (4) Discontinuously reinforced metal matrix composites. There are ten major tasks in the program which also include evaluation and trade-off studies by Boeing and Douglas aircraft companies.

Starke, E. A., Jr. (editor)

1995-01-01

400

Thermo-piezo-electro-mechanical simulation of AlGaN (aluminum gallium nitride) / GaN (gallium nitride) High Electron Mobility Transistors  

NASA Astrophysics Data System (ADS)

Due to the current public demand of faster, more powerful, and more reliable electronic devices, research is prolific these days in the area of high electron mobility transistor (HEMT) devices. This is because of their usefulness in RF (radio frequency) and microwave power amplifier applications including microwave vacuum tubes, cellular and personal communications services, and widespread broadband access. Although electrical transistor research has been ongoing since its inception in 1947, the transistor itself continues to evolve and improve much in part because of the many driven researchers and scientists throughout the world who are pushing the limits of what modern electronic devices can do. The purpose of the research outlined in this paper was to better understand the mechanical stresses and strains that are present in a hybrid AlGaN (Aluminum Gallium Nitride) / GaN (Gallium Nitride) HEMT, while under electrically-active conditions. One of the main issues currently being researched in these devices is their reliability, or their consistent ability to function properly, when subjected to high-power conditions. The researchers of this mechanical study have performed a static (i.e. frequency-independent) reliability analysis using powerful multiphysics computer modeling/simulation to get a better idea of what can cause failure in these devices. Because HEMT transistors are so small (micro/nano-sized), obtaining experimental measurements of stresses and strains during the active operation of these devices is extremely challenging. Physical mechanisms that cause stress/strain in these structures include thermo-structural phenomena due to mismatch in both coefficient of thermal expansion (CTE) and mechanical stiffness between different materials, as well as stress/strain caused by "piezoelectric" effects (i.e. mechanical deformation caused by an electric field, and conversely voltage induced by mechanical stress) in the AlGaN and GaN device portions (both piezoelectric materials). This piezoelectric effect can be triggered by voltage applied to the device's gate contact and the existence of an HEMT-unique "two-dimensional electron gas" (2DEG) at the GaN-AlGaN interface. COMSOL Multiphysics computer software has been utilized to create a finite element (i.e. piece-by-piece) simulation to visualize both temperature and stress/strain distributions that can occur in the device, by coupling together (i.e. solving simultaneously) the thermal, electrical, structural, and piezoelectric effects inherent in the device. The 2DEG has been modeled not with the typically-used self-consistent quantum physics analytical equations, rather as a combined localized heat source* (thermal) and surface charge density* (electrical) boundary condition. Critical values of stress/strain and their respective locations in the device have been identified. Failure locations have been estimated based on the critical values of stress and strain, and compared with reports in literature. The knowledge of the overall stress/strain distribution has assisted in determining the likely device failure mechanisms and possible mitigation approaches. The contribution and interaction of individual stress mechanisms including piezoelectric effects and thermal expansion caused by device self-heating (i.e. fast-moving electrons causing heat) have been quantified. * Values taken from results of experimental studies in literature.

Stevens, Lorin E.

401

Influence of Whisker Toughening and Microstructure on the Wear Behavior of Si3N4- and Al2O3-Matrix Composites  

SciTech Connect

A comparative study of the influence of randomly-oriented SiC whiskers on the abrasive wear behavior of several commercially-produced Si3N4- and Al2O3-based ceramics suggested that the residual stress states present within the materials can be important in predicting their wear resistance. The addition of SiC whiskers to the Si3N4 matrix created residual tensile stresses at the whisker-matrix interfaces which led to enhanced bulk fracture toughness, but which degraded the fracture toughness at the microstructural level, and thus the abrasive wear resistance, by promoting easier whisker debonding and removal by the abrasive particles. The addition of SiC whiskers to an alumina matrix, on the other hand, led to the creation of residual compressive stresses at whisker-matrix interfaces, producing a locally tougher interface that was more able to withstand the rigors of the abrasive wear environment. These results indicate that in brittle materials, improved bulk mechanical properties do not always translate directly to improved performance in a tribological environment.

Dogan, Cynthia P.; Hawk, Jeffrey A.

2000-12-01

402

Effect of matrix on the metal poisoning of REY catalysts  

SciTech Connect

The effect of matrix on the resistance of vanadium and nickel poisoning of the REY zeolite has been investigated by X-ray diffraction, nitrogen adsorption, and n-hexane cracking reaction. Alumina (Al{sub 2}O{sub 3}), magnesia-alumina (MgO-Al{sub 2}O{sub 3}), alumina-aluminum phosphate (AAP), and magnesia-alumina-aluminum phosphate (MgAAP) were used as matrices of REY. The presence of matrix can increase the resistance of REY to steam deactivation. AAP has a better hydrothermal stability than the other matrics. MgO-Al{sub 2}O{sub 3} matrix demonstrates the highest ability to capture vanadium due to the basicity of magnesia. There is an interaction between vanadium and nickel. This interaction inhibits the destruction of REY structure caused by vanadium. AAP has a strong interaction with nickel. The stronger the nickel-matrix interaction, the less poison effect of nickel. In addition, the strong interaction leads to the decrease in nickel`s ability to retard the destruction of REY structure by vanadium.

Yang, S.J.; Chen, Y.W. [National Central Univ., Chungli (Taiwan, Province of China). Dept. of Chemical Engineering; Li, C. [Chinese Petroleum Corp., Chiayi (Taiwan, Province of China). Refining and Manufacturing Research Inst.

1995-04-01

403

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

2014-08-01

404

Redistribution of Ti and Al in deuterium charged TiAl  

NASA Technical Reports Server (NTRS)

The redistribution of titanium and aluminum in a single-phase TiAl alloy that has been exposed to a high pressure of deuterium gas at high temperature is studied. The microstructure in the as-received, uncharged condition consisted of single-phase gamma TiAl grains and a random distribution of precipitates. Precipitates were distributed throughout the matrix and along the grain boundaries. The chemistry of the precipitates varied considerably; some were rich in Al, while other were mostly Ti with some Si and Al. The dislocation density in most grains was low, although in a few grains a high dislocation density was observed. FCC deuterides with a lattice parameter of 0.45 nm form in a Ti-52.1Al-2.1Ta (at. pct) alloy after exposure to 1.38 MPa of deuterium gas at 650 C for 213 hr. The structure and lattice parameter are consistent with the formation of Ti(l)D2. The deuterides that form in this alloy are enriched in Ti and deficient in Al and Ta compared to the deuteride-free matrix. Regions of the matrix contiguous with the deuterides have a correspondingly enhanced aluminum and tantalum concentration.

Legzdina, D.; Robertson, I. M.; Birnbaum, H. K.

1992-01-01

405

Possibility of inverse manufacturing of coated aluminum product  

Microsoft Academic Search

The retrieving of metallic aluminum (Al) was tested from Al composite products, such as foils, laminated films and beverage cans which consist of metallic Al and organic materials including paint. In this paper, the possibility of a new aluminum retrieving method for Al products with organic materials or paints attached is considered using an example of beverage can recycling. Without

H. H. Uchida; Y. Ozu; S. Ohga; M. Ohga

1999-01-01

406

Effect of Al2O3 nanocrystals on the structural and electrical studies of lithium titanate phosphate glass ceramic matrix  

NASA Astrophysics Data System (ADS)

A series of lithium phosphate glass ceramics dispersed with Al2O3 nanocrystals were synthesized via high energy ball milling technique. The milling of Al2O3 powder at room temperature for different milling times is 0, 5, 10, 20, 30, 40, 50 and 60 h. The mean particle size distribution was measured using the Scherrer formula for a half width of the diffraction peaks vary from micrometers to 24 nm for the milling time at 40 h. The details of compositions chosen for the present study of investigation are given in the general formula: (100-x) [0.4Li2O-0.1TiO2-0.6P2O5]+x 40 h ball milled Al2O3 (where x=0, 2, 4, 6, 8, 10 and 12 mol% ) and labeled as LTPAx (where x is the mole% of 40 h ball milled Al2O3). The average crystallite size of Al2O3 nanoparticles was measured to be 22 nm by transmission electron microscopy (TEM) images, which is in good agreement with the crystallite size calculated from X-ray diffraction (XRD) (24 nm) measurements using Scherrer's formula. The frequency dependent conductivity was explained in the light of conducting nanocrystalline phases such as AlPO4, LiTi2(PO4)3, LiAl2P3O7 precipitated in the LTPA samples.

Krishna Kishore Reddy, Ch.; Rao, R. Balaji; Ramana Reddy, M. V.

2013-08-01

407

Conversion of aluminum chlorohydrate to aluminum hydroxide  

Microsoft Academic Search

aluminum hydroxide. X-ray, IR, and 27A1 NMR spectroscopic data indicate that aluminum chlorohydrate is composed of a central aluminum in tetrahedral configuration surrounded by 12 aluminums each in octahedral configuration. This highly .charged complex is neutralized by 7 chloride counterions. In contrast, aluminum hydroxide has a polymer-like structure whose basic unit is a ring of six aluminums in octahedral configuration

DIRK L. TEAGARDEN; STANLEY L. HEM

408

Damage evolution in SiC particle reinforced Al alloy matrix composites by X-ray synchrotron tomography  

Microsoft Academic Search

Metal matrix composites (MMCs) have a combination of high strength, high stiffness, and low density. The damage behavior of MMCs has been studied extensively by a combination of traditional mechanical testing, microstructural characterization, and post-experiment fractographic analysis. X-ray tomography is an excellent technique that eliminates destructive cross-sectioning, and allows for superior resolution and image quality with minimal sample preparation. In

J. J. Williams; Z. Flom; A. A. Amell; N. Chawla; X. Xiao; F. De Carlo

2010-01-01

409

Effects of irradiation on the microstructure of U-7Mo dispersion fuel with Al-2Si matrix  

NASA Astrophysics Data System (ADS)

The Reduced Enrichment for Research and Test Reactor (RERTR) program is developing low-enriched uranium U-Mo dispersion fuels for application in research and test reactors around the world. As part of this development, fuel plates have been irradiated in the Advanced Test Reactor and then characterized using optical metallography (OM) and scanning electron microscopy (SEM) to determine the as-irradiated microstructure. To demonstrate the irradiation performance of U-7Mo dispersion fuel plates with 2 wt.% Si added to the matrix, fuel plates were tested to moderate burnups at intermediate fission rates as part of the RERTR-6 experiment. Further testing was performed to higher fission rates as part of the RERTR-7A experiment, and very aggressive testing (high temperature, high fission density, and high fission rate) was performed in the RERTR-9A, RERTR-9B, and AFIP-1 experiments. As-irradiated microstructures were compared to those observed after fabrication to determine the effects of irradiation on the microstructure. Based on comparison of the microstructural characterization results for each irradiated sample, some general conclusions can be drawn about how the microstructure evolves during irradiation: there is growth during irradiation of the fuel/matrix interaction (FMI) layer created during fabrication; Si diffuses from the FMI layer to deeper depths in the U-7Mo particles as the irradiation conditions are made more aggressive; lowering of the Si content in the FMI layer results in an increase in the size of the fission gas bubbles; as the FMI layer grows during irradiation, more Si diffuses from the matrix to the FMI layer/matrix interface; and interlinking of fission gas bubbles in the fuel plate microstructure that may indicate breakaway swelling is not observed.

Keiser, Dennis D.; Jue, Jan-Fong; Robinson, Adam B.; Medvedev, Pavel; Gan, Jian; Miller, Brandon D.; Wachs, Daniel M.; Moore, Glenn A.; Clark, Curtis R.; Meyer, Mitchell K.; Ross Finlay, M.

2012-06-01

410

Hot deformation and processing maps of a particulate reinforced 2618\\/Al 2O 3\\/20p metal matrix composite  

Microsoft Academic Search

The mechanical response of a AA2618 aluminium based metal matrix composite was investigated by means of hot compression tests. The flow stress curves were obtained in the temperature and strain rate ranges of 350500 C and 110?3 s?1, respectively in order to obtain the processing and stability maps of the studied material following the Dynamic Material Model. All the zones

P. Cavaliere; E. Cerri; P. Leo

2004-01-01

411

The effect of structural defects in SiC particles on the static & dynamic mechanical response of a 15 volume percent SiC/6061-Al matrix composite  

SciTech Connect

Static and Dynamic mechanical tests, and microstructural examinations performed on a SiC particle reinforced 6061-Al matrix composite indicated that particle cracking significantly affected the strength, strain hardening, and failure mechanism of the composite. Cracks were observed to nucleate and propagate on stacking faults and interfaces between the various phases within the reinforcing SiC particles. Planar defects were the predominant artifacts seen in the SiC particles. Partial dislocations were also observed bounding the stacking faults within the reinforcement phase.

Vaidya, R.U.; Song, S.G.; Zurek, A.K.; Gray, G.T. III

1995-09-01

412

Mesoporous aluminum phosphite  

NASA Astrophysics Data System (ADS)

High surface area pure mesoporous aluminum-phosphorus oxide-based derivatives have been synthesized through an S +I - surfactant-assisted cooperative mechanism by means of a one-pot preparative procedure from aqueous solution and starting from aluminum atrane complexes and phosphoric and/or phosphorous acids. A soft chemical extraction procedure allows opening the pore system of the parent as-prepared materials by exchanging the surfactant without mesostructure collapse. The nature of the pore wall can be modulated from mesoporous aluminum phosphate (ALPO) up to total incorporation of phosphite entities (mesoporous aluminum phosphite), which results in a gradual evolution of the acidic properties of the final materials. While phosphate groups in ALPO act as network building blocks (bridging Al atoms), the phosphite entities become basically attached to the pore surface, what gives practically empty channels. The mesoporous nature of the final materials is confirmed by X-ray diffraction (XRD), transmission electron microscopy (TEM) and N 2 adsorption-desorption isotherms. The materials present regular unimodal pore systems whose order decreases as the phosphite content increases. NMR spectroscopic results confirm the incorporation of oxo-phosphorus entities to the framework of these materials and also provide us useful information concerning the mechanism through which they are formed.

El Haskouri, Jamal; Prez-Cabero, Mnica; Guillem, Carmen; Latorre, Julio; Beltrn, Aurelio; Beltrn, Daniel; Amors, Pedro

2009-08-01

413

Aluminum compounds used as adjuvants in vaccines.  

PubMed

The structure of nine commercially manufactured aluminum-containing adjuvants was investigated by X-ray diffraction, infrared spectroscopy, transmission electron micrography, and energy dispersive spectrometry. Seven samples which were labeled as aluminum hydroxide were identified as boehmite, a crystalline aluminum oxyhydroxide [AlO(OH)]. However, the degree of crystallinity varied between the samples. Two samples which were labeled as aluminum phosphate were found to be amorphous aluminum hydroxyphosphate. Buffer anions and sulfate anions substitute for hydroxyls in the amorphous aluminum hydroxide formed by the in situ alum precipitation method. Finally, the aluminum-containing adjuvant in diphtheria and tetanus toxoid, U.S.P., produced by three manufacturers was characterized. PMID:2095567

Shirodkar, S; Hutchinson, R L; Perry, D L; White, J L; Hem, S L

1990-12-01

414

Structural change and mineralogical transformation mechanism of aluminum hydroxide gels from forced hydrolysis Al(III) solutions containing AlO 4 Al1 2 (OH) 24 (H 2 O) 12 7+ polyoxycation during aging  

Microsoft Academic Search

The structural change and mineralogy of Al gel during aging time were investigated by using spectroscopy techniques. The results\\u000a indicated that: 1) the aggregation extent of solution-gel system increases with aging time, and the structure of amorphous\\u000a gel becomes more short-ordered; 2) after six months, the gel formats nordstrandite and little gibbsite; 3) a marked decrease\\u000a in the number of

Jing Liu; Fenghua Zhao

2010-01-01

415

Kinetics of aluminum uptake by excised roots of aluminum-tolerant and aluminum-sensitive cultivars of Triticum aestivum L  

Microsoft Academic Search

Uptake of aluminum (Al) by excised roots of two Al-tolerant cultivars and two Al-sensitive cultivars of Triticum aestivum L. (wheat) was biphasic, with a rapid phase of uptake in the first 30 minutes followed by a linear phase of uptake up to 180 minutes. At the end of the uptake period, higher concentrations of Al were found in roots of

Guichang Zhang; G. J. Taylor

1989-01-01

416

Nanoclusters of MoO3-x embedded in an Al2O3 matrix engineered for customizable mesoscale resistivity and high dielectric strength  

NASA Astrophysics Data System (ADS)

We have synthesized a material consisting of conducting metal oxide (MoO3-x) nanoclusters embedded in a high-dielectric-strength insulator (Al2O3) matrix. The resistivity of this material can be customized by varying the concentration of the MoO3-x nanoclusters. The Al2O3 protects the MoO3-x from stoichiometry change, thus conserving the number of carriers and maintaining a high dielectric strength. This composite material is grown by atomic layer deposition, a thin film deposition technique suitable for coating 3D structures. We applied these atomic layer deposition composite films to our 3D electron-optical micro electrical mechanical systems devices and greatly improved their performance.

Tong, William M.; Brodie, Alan D.; Mane, Anil U.; Sun, Fuge; Kidwingira, Franoise; McCord, Mark A.; Bevis, Christopher F.; Elam, Jeffrey W.

2013-06-01

417

Aluminum-air battery for automotive propulsion  

Microsoft Academic Search

Research on the development of aluminum-air batteries which will be used in energy efficient, economical electric vehicles is reviewed with information on the research strategy, performance characteristics of aluminum-air cells, vehicle design, and the net energy required and energy costs for producing and operating Al-air batteries. The aluminum-air battery is being developed to provide a propulsion source for a general-purpose

J. F. Cooper; E. Behrin

1980-01-01

418

Aluminum-air batteries for military applications  

Microsoft Academic Search

The authors review the basic characteristics of