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1

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

2

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................... .. ....... ... ... 3 Literature Review ......... ...... ..... ... . . 3 Conventional Aluminum Brazing ........ 4 Aluminum Composite Joining ........... 5 Aluminum Joining by Unconventional Methods

Eagar, Thomas W.

3

Dual-nanoparticulate-reinforced aluminum matrix composite materials.  

PubMed

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

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

2012-06-01

4

Self-lubricating aluminum metal-matrix composites dispersed with tungsten disulfide and silicon carbide  

Microsoft Academic Search

This paper describes the synthesis and tribological behavior of self-lubricating aluminum alloy metal-matrix composites (MMCs). The formulations of MMCs comprised of tungsten disulfide (WS) and silicon carbide (SiC) particles dispersed in a commercial aluminum alloy (Al-0.40Si-0.75Mg) matrix. Composites were fabricated by a conventional powder metallurgy route involving blending, compacting and sintering. Friction and wear tests (up to a duration of

S. V. Prasad; K. R. Mecklenburg

1994-01-01

5

Material damping in aluminum and metal matrix composites  

NASA Technical Reports Server (NTRS)

The material damping in beam-like specimens of aluminum and metal matrix composites was measured. A unique apparatus to determine damping by free decay while the specimens are in free fall in a vacuum was used. The specimens tested include 2024-T3 and 6061-T4 aluminum, and unidirectional graphite/metal matrix specimens with P55 and P100 fibers and 6061 Aluminum and AZ91C Magnesium as matrix materials. Tests were conducted to determine the dependence of damping on frequency and stress level. For the aluminum specimens, the material damping followed the Zener model at very low stress levels. Below the Zener relaxation frequency, a strong dependence of damping on stress was found for even moderate stress levels. Damping for the aluminum matrix materials was slightly above that predicted by the Zener model for a homogeneous bar of the matrix aluminum. For the magnesium matrix specimens, damping significantly above the Zener prediction for the homogeneous matrix material was observed.

Crawley, Edward F.; Van Schoor, Marthinus C.

1987-01-01

6

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

NASA Technical Reports Server (NTRS)

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

Olsen, G. C.

1981-01-01

7

Synthesis of In-situ Aluminum Matrix Composite Using a New Activated Powder Injection Method  

Microsoft Academic Search

In the present study, in-situ Al matrix composites containing alumina particles were synthesized by a new method that involved injection of an activated\\u000a powder mixture into the molten aluminum, which was subsequently squeeze cast to minimize its porosity. The activated powder\\u000a mixture was prepared by milling of powders of commercially pure aluminum and zinc oxide for a predetermined time. Milling

A. Maleki; M. Meratian; B. Niroumand; M. Gupta

2008-01-01

8

Hot extruded carbon nanotube reinforced aluminum matrix composite materials.  

PubMed

Carbon nanotube (CNT) reinforced aluminum (Al) matrix composite materials were successfully fabricated by mechanical ball milling followed by powder hot extrusion processes. Microstructural analysis revealed that the CNTs were well dispersed at the boundaries and were aligned with the extrusion direction in the composites obtained. Although only a small quantity of CNTs were added to the composite (1vol%), the Vickers hardness and the tensile strength were significantly enhanced, with an up to three-fold increase relative to that of pure Al. From the fractography of the extruded Al-CNT composite, several shapes were observed in the fracture surface, and this unique morphology is discussed based on the strengthening mechanism. The damage in the CNTs was investigated with Raman spectroscopy. However, the Al-CNT composite materials were not only strengthened by the addition of CNTs but also enhanced by several synergistic effects. The nanoindentation stress-strain curve was successfully constructed by setting the effective zero-load and zero-displacement points and was compared with the tensile stress-strain curve. The yield strengths of the Al-CNT composites from the nanoindentation and tensile tests were compared and discussed. We believe that the yield strength can be predicted using a simple nanoindentation stress/strain curve and that this method will be useful for materials that are difficult to machine, such as complex ceramics. PMID:23011263

Kwon, Hansang; Leparoux, Marc

2012-10-19

9

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

NASA Astrophysics Data System (ADS)

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

Zhang, Gang; Yang, Jianhong

2013-11-01

10

Internal Friction at Elevated Temperatures and Microplasticity of Aluminum Matrix Composites  

Microsoft Academic Search

Aluminum matrix composites (70vol%SiC\\/Al, 55vol%SiC\\/Al, 60vol%Al2O3\\/Al, 70vol%AlN\\/Al, and 30vol%SiC\\/Al) were prepared by the infiltration and the casting methods. The internal friction and the microplasticity of these composites were measured with a Fppel-Pertz torsion pendulum apparatus over the temperature range of 303 to 853 K and the strain range of 310-5 to 310-3. The internal friction of these composites increases with

Katsuhiro Nishiyama; Shigenori Utsumi; Takanobu Nakamura; Hironori Nishiyama

2009-01-01

11

Inertia-friction welding of particulate-reinforced aluminum matrix composites  

SciTech Connect

Aluminum metal-matrix composites (Al-MMC) are rapidly becoming materials of choice for many aerospace, automotive, recreational sports, and microelectronic applications. The attractive features of these materials include high specific strength and stiffness, a low coefficient of thermal expansion and enhanced wear characteristics relative to monolithic aluminum alloys. The effective engineering application of Al-MMC will commonly require their joining beth to themselves, to dissimilar Al-MMC, and to monolithic aluminum alloys. In the present work, dissimilar-alloy inertia-friction welds were produced between a 6061-T6 Al-MMC tube reinforced with l0 v/o Al{sub x}O{sub 3} particles (W6A.l0A-T6) and a modified A356 case MMC bar reinforced with 20 v/o SiC particles (F3S.20S), or a monolithic 6061-T6511 aluminum alloy bar. In Phase I, a fractional-factorial test matrix was statistically designed and performed to evaluate the effects of flywheel speed and axial pressure on the weld integrity, microstructure, hardness, tensile and torsion strengths and fracture behavior. In Phase 2, the effects of pre-weld machining of the solid bar on weld alignment and mechanical properties were evaluated. inertia-friction welding was shown to be effective for the joining of alumina particulate-reinforced composites to monolithic aluminum and to SiC-particulate reinforced aluminum. High-integrity joints exhibiting a defect-free joint interface with varying degrees of base alloy intermixing were produced at optimum parameter settings. Tensile and torsional strength joint efficiencies for the alumina-particulate MMC to monolithic aluminum alloy welds exceeded 80% and 75%, respectively, with tensile strength maximized with high axial pressure and flywheel speed, and torsional strength maximized at both medium and high levels of flywheel speed and axial pressure.

Cola, M.J.; Baeslack, W.A. III; Kou, M.

1994-12-31

12

Modification of cast aluminum-matrix composite materials by refractory nanoparticles  

Microsoft Academic Search

The effect of SiO2 and Al2O3 oxide ceramic nanoparticles on the solidification of model samples based on a commercial D16 alloy is studied. The composite\\u000a samples are fabricated by reaction casting when titanium, nickel, and ceramic powders are mixed with an aluminum melt. The\\u000a grain size in a matrix, the size and shape of Al3Ti intermetallic inclusions, and the interphase

T. A. Chernyshova; L. I. Kobeleva; I. E. Kalashnikov; L. K. Bolotova

2009-01-01

13

Aluminum sulfate (alum; Al2 O) is used as a  

E-print Network

477 Aluminum sulfate (alum; Al2 (SO4 )3 ·14H2 O) is used as a chemical treatment of poultry litter, and pelletizing, the use of chemical amendments, primarily aluminum sulfate (alum, Al2 (SO4 )3 ·14H2 O), alter

Sparks, Donald L.

14

Fabrication and Mechanical Properties of Aluminum Matrix Composite Materials  

Microsoft Academic Search

Aluminum matrix composite materials containing SiC whisker and Saffil alumina short fiber are fabricated by the direct squeeze infiltration method. Optimum processing conditions for preforms and squeeze casting are suggested. For minimum damage of the reinforcements, the relatively low pressure of 25 MPa is applied.

T. Lim; Y. H. Kim; C. S. Lee; K. S. Han

1992-01-01

15

Superconductor covered with reinforced aluminum matrix and method for manufacture thereof  

Microsoft Academic Search

Disclosed herein is a superconductor covered with a reinforced aluminum matrix, which is obtained by cladding a superconductor with an aluminum matrix reinforced with a very small proportion of alumina dispersed therein and subjecting the clad superconductor to integral forming.

K. Koyama; H. Nomura; K. Terao

1981-01-01

16

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

17

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

Microsoft Academic Search

This article presents experimental results of important properties of aluminum-matrix (AA 2014) composite materials reinforced\\u000a with different intermetallics of the Ni-Al system. For the present study, the intermetallics are prepared either by mechanical\\u000a alloying (MA) or by gas atomization (GA). The reinforced composite materials were manufactured by mixing the constituents,\\u000a followed by uniaxial compacting of a preform and subsequent extrusion

C. E. Da Costa; F. Velasco; J. M. Torralba

2002-01-01

18

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  

Microsoft Academic Search

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

Jun Zhu

2008-01-01

19

Investigation of carbon nanotube reinforced aluminum matrix composite materials  

Microsoft Academic Search

We have increased the tensile strength without compromising the elongation of aluminum (Al)carbon nanotube (CNT) composite by a combination of spark plasma sintering followed by hot-extrusion processes. From the microstructural viewpoint, the average thickness of the boundary layer with relatively low CNT incorporation has been observed by optical, field-emission scanning electron, and high-resolution transmission electron microscopies. Significantly, the AlCNT composite

Hansang Kwon; Dae Hoon Park; Jean Franois Silvain; Akira Kawasaki

2010-01-01

20

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

21

Forging limits for an aluminum matrix composite: Part II. Analysis  

NASA Astrophysics Data System (ADS)

Plasticity analysis has been carried out to calculate the forging limits of a particulate-reinforced aluminum matrix composite under various forging conditions. A geometric defect (i.e., variation in cross-sectional area) that can concentrate stresses and strain and accelerate local deformation was assumed to represent all possible defects in this material. Thus, in effect, the local stress concentrations around nondeformable particles, inhomogeneous distribution of particles and grain sizes, porosity and cracked particles, etc., were assumed to be simulated adequately by such a defect factor. The analysis followed a method suggested by Marciniak and Kuczynski (MK) to determine the strain path within the defect region of the composite during multiaxial deformation. A relationship of stress, strain, and strain rate obtained from the uniaxial tension test was used for the calculation of the strains. To terminate the plasticity analysis, a rateindependent fracture criterion was used that is based on Cockcrofts model of a constant work performed by the tensile component of stress. It was found that the calculated results predicted the experimental forging limits for 2014 Al/15 vol pct A12O3 reasonably well. At 400 C and a slow strain rate (0.015 s~), the predicted curve was higher than the experimental result. This was probably because the fracture mechanism, and thus fracture criterion, changed with temperature. The effect of assumed defect factor on predicted forging limits was also studied. It was found that the size of the defect factor did not significantly change the forging limits at 300 C for strain rates from 0.015 s to 0.5 s-1; however, it did have a large effect on the forging limit at 400 C for the lower strain rate of 0.015 s-1.

Syu, D.-G. C.; Ghosh, A. K.

1994-09-01

22

Aluminum (Al) Etch Instructions The CEPSR cleanroom stores Aluminum Etchant Type A, a pre-made product used for  

E-print Network

Aluminum (Al) Etch Instructions The CEPSR cleanroom stores Aluminum Etchant Type A, a pre-made product used for removing or etching away aluminum. This etchant is stored inside the acid or corrosive a specific thickness of aluminum that is desired. Note: Once the bottle is empty or you find that it's etch

Kim, Philip

23

Strengthening behavior of chopped multi-walled carbon nanotube reinforced aluminum matrix composites  

SciTech Connect

Strengthening behavior of the aluminum composites reinforced with chopped multi-walled carbon nanotubes (MWCNTs) or aluminum carbide formed during annealing at 500 C has been investigated. The composites were fabricated by hot-rolling the powders which were ball-milled under various conditions. During the early annealing process, aluminum atoms can cluster inside the tube due to the diffusional flow of aluminum atoms into the tube, providing an increase of the strength of the composite. Further annealing induces the formation of the aluminum carbide phase, leading to an overall drop in the strength of the composites. While the strength of the composites can be evaluated according to the rule of mixture, a particle spacing effect can be additionally imparted on the strength of the composites reinforced with the chopped MWCNTs or the corresponding carbides since the reinforcing agents are smaller than the submicron matrix grains. - Highlights: Strengthening behavior of chopped CNT reinforced Al-based composites is investigated. Chopped CNTs have influenced the strength and microstructures of the composites. Chopped CNTs are created under Ar- 3% H2 atmosphere during mechanical milling. Strength can be evaluated by the rule of the mixture and a particle spacing effect.

Shin, S.E.; Bae, D.H., E-mail: donghyun@yonsei.ac.kr

2013-09-15

24

Self-lubricating aluminum metal-matrix composites dispersed with tungsten disulfide and silicon carbide  

SciTech Connect

This paper describes the synthesis and tribological behavior of self-lubricating aluminum alloy metal-matrix composites (MMCs). The formulations of MMCs comprised of tungsten disulfide (WS{sub 2}) and silicon carbide (SiC) particles dispersed in a commercial aluminum alloy (Al-0.40Si-0.75Mg) matrix. Composites were fabricated by a conventional powder metallurgy route involving blending, compacting and sintering. Friction and wear tests (up to a duration of one million cycles) were performed in a ball-on-disk configuration against a steel counterface. Wear scars on MMC disks and steel balls were analyzed in SEM/EDXS. In a dry nitrogen environment, the steady state friction coefficient of an Al-0.10SiC-0.03WS{sub 2}MMC was 0.05, whereas in laboratory air with relative humidity at approximately 65 percent it was 0.10. In both environments, transfer of aluminum to the steel counterface was absent. 20 refs., 12 figs., 2 tabs.

Prasad, S.V. [Systran Corporation, Dayton, OH (United States); Mecklenburg, K.R.

1994-07-01

25

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

26

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

27

^27Al NMR Study of Molten Aluminum-bearing Oxides  

NASA Astrophysics Data System (ADS)

The chemical structure and internal motions of liquid aluminum-bearing oxides have been examined through use of ^27Al NMR, at temperatures above 1700 Celsius. Compounds studied include aluminum oxide, YAG and rare earth-doped yttrium-aluminum oxide. Samples were levitated in an Ar gas flow and heated to melting ( ~2000 Celsius), using a 138W CO2 laser. Chemical shifts were referenced to dissolved Al(NO_3)_3. FWHM linewidths were ~100 Hz. Spin-lattice and spin-spin relaxation times T1 and T2 were measured directly for the first time in these melts, and were found to be in the range 4-6 ms.

Marzke, Robert F.; Piwowarczyk, Jeremy; McMillan, Paul F.; Wilding, Martin; Weber, Richard

2001-03-01

28

Synthesis of In-situ Aluminum Matrix Composite Using a New Activated Powder Injection Method  

NASA Astrophysics Data System (ADS)

In the present study, in-situ Al matrix composites containing alumina particles were synthesized by a new method that involved injection of an activated powder mixture into the molten aluminum, which was subsequently squeeze cast to minimize its porosity. The activated powder mixture was prepared by milling of powders of commercially pure aluminum and zinc oxide for a predetermined time. Milling for 60 minutes led to optimum activation of the reactant powders. Such activation reduced the reaction temperature from above 1000 C to about 640 C. Microstructural characterization studies revealed the formation of submicron size alumina particles with near equiaxed morphology and good particle/matrix interface. The composite specimen synthesized using the activated powder injection (API) method exhibited higher hardness, greater yield and tensile strengths, and lower elongation when compared to the monolithic specimen of similar composition. This article places particular emphasis on explaining the uniqueness of the processing methodology used in this study for synthesis of in-situ Al/Al2O3 composites.

Maleki, A.; Meratian, M.; Niroumand, B.; Gupta, M.

2008-12-01

29

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

30

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

31

Aluminum Silicon Carbide (AlSiC) For Cost-Effective Thermal Management And Functional Microelectronic Packaging Design Solutions  

Microsoft Academic Search

Aluminum Silicon Carbide (AlSiC) metal matrix composite (MMC) materials have a unique set of material properties that are ideally suited for electronic packaging applications requiring thermal management solutions. The AlSiC coefficient of thermal expansion (CTE) value is compatible with direct IC device attachment for the maximum thermal dissipation (AlSiC thermal conductivity 170 - 200 W\\/mK). The low material density of

Mark A. Occhionero; Robert A. Hay; Richard W. Adams; Kevin P. Fennessy

32

Mechanical characterization of copper coated carbon nanotubes reinforced aluminum matrix composites  

SciTech Connect

In this investigation, carbon nanotube (CNT) reinforced aluminum composites were prepared by the molecular-level mixing process using copper coated CNTs. The mixing of CNTs was accomplished by ultrasonic mixing and ball milling. Electroless Cu-coated CNTs were used to enhance the interfacial bonding between CNTs and aluminum. Scanning electron microscope analysis revealed the homogenous dispersion of Cu-coated CNTs in the composite samples compared with the uncoated CNTs. The samples were pressureless sintered under vacuum followed by hot rolling to promote the uniform microstructure and dispersion of CNTs. In 1.0 wt.% uncoated and Cu-coated CNT/Al composites, compared to pure Al, the microhardness increased by 44% and 103%, respectively. As compared to the pure Al, for 1.0 wt.% uncoated CNT/Al composite, increase in yield strength and ultimate tensile strength was estimated about 58% and 62%, respectively. However, in case of 1.0 wt.% Cu-coated CNT/Al composite, yield strength and ultimate tensile strength were increased significantly about 121% and 107%, respectively. - Graphical Abstract: Copper coated CNTs were synthesized by the electroless plating process. Optimizing the plating bath to (1:1) by wt CNTs with Cu, thickness of Cu-coated CNTs has been reduced to 100 nm. Cu-coated CNTs developed the stronger interfacial bonding with the Al matrix which resulted in the efficient transfer of load. Highlights: Copper coated CNTs were synthesized by the electroless plating process. Thickness of Cu-coated CNTs has been reduced to 100 nm by optimized plating bath. In 1.0 wt.% Cu-coated CNT/Al composite, microhardness increased by 103%. Cu-coated CNTs transfer load efficiently with stronger interfacial bonding. In 1.0 wt.% Cu-coated CNT/Al composite, Y.S and UTS increased by 126% and 105%.

Maqbool, Adnan, E-mail: adnanmaqbool247@gmail.com [Faculty of Materials Science and Engineering, GIK Institute of Engineering Sciences and Technology, Topi 23640, KP (Pakistan); School of Nano and Advanced Material Engineering, Changwon National University, Gyeongnam 641-773 (Korea, Republic of); Hussain, M. Asif; Khalid, F. Ahmad; Bakhsh, Nabi [Faculty of Materials Science and Engineering, GIK Institute of Engineering Sciences and Technology, Topi 23640, KP (Pakistan); Hussain, Ali; Kim, Myong Ho [School of Nano and Advanced Material Engineering, Changwon National University, Gyeongnam 641-773 (Korea, Republic of)

2013-12-15

33

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

Microsoft Academic Search

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

Fan Zhang; Pengfei Sun; Xiaocui Li; Guoding Zhang

2001-01-01

34

Influence of short-term aluminum exposure on demineralized bone matrix induced bone formation  

Microsoft Academic Search

The effects of aluminum exposure on bone formation employing the demineralized bone matrix (DBM) induced bone development model were studied using 4-week-old Sprague-Dawley rats injected with a saline (control) or an aluminum chloride (experimental) solution. After 2 weeks of aluminum treatment, 20-mg portions of rat DBM were implanted subcutaneously on each side in the thoracic region of the control and

Arlen R. Severson; Craig F. Haut; Conrad E. Firling; Thomas E. Huntley

1992-01-01

35

Corrosion characteristics of hybrid Al\\/SiC p \\/MgAl 2O 4 composites fabricated with fly ash and recycled aluminum  

Microsoft Academic Search

The corrosion characteristics of Al\\/SiCp\\/spinel composites fabricated with SiCp, fly ash (FA) and recycled aluminum were experimentally assessed. For type A composites prepared with the alloy Al8Si15Mg (wt.%), the Mg2Si intermetallic precipitated during solidification acted as a microanode coupled to the matrix (in the presence of condensed humidity) and led to catastrophic localized corrosion. Although the potential attack of SiC

R. Escalera-Lozano; C. A. Gutirrez; M. A. Pech-Canul; M. I. Pech-Canul

2007-01-01

36

The Hyperfine Structure of Aluminum Monoxide, AlO  

NASA Astrophysics Data System (ADS)

Small metal-containing molecules were produced in a laser ablation supersonic jet apparatus. The products were investigated by means of millimeter/submillimeter wave spectroscopy and optical spectra were recorded with a high-resolution grating spectrometer (HR2000+, OceanOptics). This method has been applied to study AlO produced from laser ablation of solid aluminum seeded in helium-buffer gas enriched with 2% of nitrogenous oxide. The adiabatically expanding dilute gas mixture is probed by monochromatic radiation of frequencies up to 400 GHz (WR2.8x3,Virginia Diodes Inc.). The measurements reveal the hyperfine structure of a linear molecule in Hund's case b? S due to the nuclear spin of aluminum. With the present measurements, new high accurate line positions for future astronomical observations and more accurate molecular parameters are available. The new data were compared to high level ab initio calculations performed by the group of J. Gauss.

Breier, A.; Bchling, Thomas; Giesen, Thomas; Gauss, Jrgen

2014-06-01

37

Aluminum-matrix composite materials with shungite rock fillers  

Microsoft Academic Search

A method is proposed for the introduction of shungite rocks into aluminum melts by mechanical mixing with carriers, namely,\\u000a aluminum granules and reactive titanium powders taking part in exothermic in situ reactions. The structures of composite materials\\u000a with shungite rock additions are studied, and a stabilizing effect of these additions on dry sliding friction is revealed.

I. E. Kalashnikov; V. V. Kovalevski; T. A. Chernyshova; L. K. Bolotova

2010-01-01

38

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

PubMed

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

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

2010-06-01

39

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

40

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

41

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

42

HIGH TEMPERATURE SULFIDATION BEHAVIOR OF LOW Al IRON-ALUMINUM COMPOSITIONS  

E-print Network

HIGH TEMPERATURE SULFIDATION BEHAVIOR OF LOW Al IRON-ALUMINUM COMPOSITIONS S.W. Banovic, J.N. Du (Received January 5, 1998) (Accepted March 23, 1998) Introduction Iron-aluminum weld overlay coatings, the application of iron-aluminum alloys is currently limited due to hydrogen cracking susceptibility subsequent

DuPont, John N.

43

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

PubMed

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

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

2011-05-01

44

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

NASA Technical Reports Server (NTRS)

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

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

1976-01-01

45

Preparation of Aluminum Metal Matrix Composite with Novel In situ Ceramic Composite Particulates, Developed from Waste Colliery Shale Material  

NASA Astrophysics Data System (ADS)

A novel method is adapted to prepare an in situ ceramic composite from waste colliery shale (CS) material. Heat treatment of the shale material, in a plasma reactor and/or in a high temperature furnace at 1673 K (1400 C) under high vacuum (10-6 Torr), has enabled in situ conversion of SiO2 to SiC in the vicinity of carbon and Al2O3 present in the shale material. The composite has the chemical constituents, SiC-Al2O3-C, as established by XRD/EDX analysis. Particle sizes of the composite range between 50 nm and 200 ?m. The shape of the particles vary, presumably rod to spherical shape, distributed preferably in the region of grain boundaries. The CS composite so produced is added to aluminum melt to produce Al-CS composite (12 vol. pct). For comparison of properties, the aluminum metal matrix composite (AMCs) is made with Al2O3 particulates (15 vol. pct) with size <200 ?m. The heat-treated Al-CS composite has shown better mechanical properties compared to the Al-Al2O3 composite. The ductility and toughness of the Al-CS composite are greater than that of the Al-Al2O3 composite. Fractographs revealed fine sheared dimples in the Al-CS composite, whereas the same of the Al-Al2O3 composite showed an appearance of cleavage-type facets. Abrasion and frictional behavior of both the composites have been compared. The findings lead to the conclusion that the in situ composite developed from the colliery shale waste material has a good future for its use in AMCs.

Venkata Siva, S. B.; Sahoo, K. L.; Ganguly, R. I.; Dash, R. R.; Singh, S. K.; Satpathy, B. K.; Srinivasarao, G.

2013-08-01

46

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

NASA Astrophysics Data System (ADS)

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

Rohatgi, Pradeep K.

1994-11-01

47

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

NASA Technical Reports Server (NTRS)

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

Lee, Jonathan A.

2007-01-01

48

Thermomechanical processing and ambient temperature properties of a 6061 aluminum 10 volume percent alumina metal matrix composite. Master's thesis  

SciTech Connect

Thermomechanical processing was conducted on a cast aluminum-based metal matrix composite. The material studied was 6061 aluminum containing 10 volume percent of alumina (Al2O3) particles, fabricated by casting and subsequently extruded by DURALCAN, Inc. Processing included isothermal rolling of an extruded bar to large strain values. As a result of rolling at 500 C, strength was increased, but with a substantial loss of ductility. Further strengthening was realized by rolling at 350 C and no further ductility loss was seen. Homogeneity of the particle dispersion was considerably improved with no evidence of microstructural damage. Upon subsequent solution heat treatment, ductility of the rolled materials was restored to values greater than obtained in material experiencing only extrusion. Also, the strength of the rolled material exceeded that of material heat treated after extrusion. Upon subsequent aging treatment (aging at 160 C), the increased strength and ductility enhancement persisted.

Schaefer, T.A.

1990-03-01

49

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

50

TRANSCRIPTIONAL ANALYSIS BETWEEN TWO WHEAT NEAR-ISOGENIC LINES CONTRASTING IN ALUMINUM (AL) TOLERANCE UNDER AL STRESS  

Technology Transfer Automated Retrieval System (TEKTRAN)

To understand the mechanisms of aluminum (Al) tolerance and identify genes responsible for Al tolerance in wheat (Triticum aestivum L.), suppression subtractive hybridization (SSH) libraries were constructed from Al-stressed roots for two wheat near- isogenic lines (NILs), Chisholm-T (Al-tolerant) a...

51

Aluminum-matrix composites with embedded Ni-Ti wires by ultrasonic consolidation  

Microsoft Academic Search

[Smart Vehicle Workshop] This paper presents the development of active aluminum-matrix composites manufactured by Ultrasonic Additive Manufacturing (UAM), an emerging rapid prototyping process based on ultrasonic metal welding. Composites created through UAM experience process temperatures as low as 20C, in contrast to current metal-matrix fabrication processes which require fusion of materials and hence reach temperatures of 500C and above. UAM

Ryan Hahnlen; Marcelo J. Dapino; Matt Short; Karl Graff

2009-01-01

52

SiC particle cracking in powder metallurgy processed aluminum matrix composite materials  

Microsoft Academic Search

Particle cracking is one of the key elements in the fracture process of particulate-reinforced metal-matrix composite (MMC)\\u000a materials. The present study quantitatively examined the amount of new surface area created by particle cracking and the number\\u000a fraction of cracked particles in a series of SiC-reinforced aluminum-matrix composite materials. These composite materials\\u000a were fabricated by liquid-phase sintering and contained 9 vol

B. Wang; G. M. Janowski; B. R. Patterson

1995-01-01

53

The aluminum ordering in aluminosilicates: a dipolar 27Al NMR spectroscopy study.  

PubMed

The spatial ordering of aluminum atoms in CsAl(SiO3)2 and 3Al2O3.2SiO2 was probed by 27Al dipolar solid-state NMR spectroscopy. The 27Al response to a Hahn spin-echo pulse sequence in a series of aluminum-containing model crystalline compounds demonstrates that quantitative 27Al homonuclear dipolar second moments can be obtained to within +/-20% of the theoretical values, if evaluation of the spin-echo response curve is limited to short evolution periods (2t1 < or = 0.10 ms). Additionally, selective excitation of the central transition m = 1/2 --> -1/2 is necessary in order to ensure quantitative results. Restriction of spin exchange affecting the dephasing of the magnetization may decelerate the spin-echo decay at longer evolution periods. Considering these restraints, the method was used to probe the spatial distribution of aluminum atoms among the tetrahedral sites in two aluminosilicate materials. Experimental 27Al spin-echo response data for the aluminosilicates CsAl(SiO3)2 (synthetic pollucite) and 3Al2O3.2SiO2 (mullite) are compared with theoretical data based on (I) various degrees of aluminum-oxygen-aluminum bond formation among tetrahedrally coordinated aluminum atoms (Al(T(d) )-O-Al(T(d) )) and (II) the maximum avoidance of Al(T(d) )-O-Al(T(d) ) bonding. Analysis of the second moment values and resulting echo decay responses suggests that partial suppression of spin exchange among aluminum atoms in crystallographically distinct sites may contribute to the 27Al spin echo decay in 3Al2O3.2SiO2, thus complicating quantitative analysis of the data. Silicon-29 and aluminum-27 magic angle spinning (MAS) NMR spectra of 3Al2O3.2SiO2 are consistent with those previously reported. The experimental 27Al spin-echo response behavior of CsAl(SiO3)2 differs from the theoretical response behavior based on the maximum avoidance of Al-O-Al bonding between tetrahedral aluminum sites in CsAl(SiO3)2. A single unresolved resonance is observed in both the silicon-29 and aluminum-27 MAS spectra of CsAl(SiO3)2. PMID:14745814

Gee, Becky A

2004-01-01

54

Aluminum-matrix electrotechnical composite alloys hardened by endogenous nano- and microphases  

NASA Astrophysics Data System (ADS)

A method is developed to manufacture aluminum-matrix composite alloys hardened by endogenous nano- and microphases. The formation of the structure and properties of the composite materials is studied. The experimental results demonstrate that the developed alloys are promising to produce electro-technical wire rods and other electrotechnical products.

Babkin, V. G.; Terent'ev, N. A.; Cherepanov, A. I.

2014-09-01

55

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

Microsoft Academic Search

Continuous fiber silicon carbide\\/titanium and aluminum matrix composite monolayers were tested by means of an indentation technique to measure the interfacial shear strength. Experimental results were interpreted using two analytical models and compared to results of other researches in order to evaluate the interface quality obtained with a vacuum plasma spray fabrication method. The separate contribution of chemical bond and

Valente; JE Masters; T Kevin O'Brien; T Valente

1994-01-01

56

Studies on fiber treatment and fabrication of short ceramic fiber reinforced aluminum matrix composites  

Microsoft Academic Search

Aluminum matrix composites dispersed with the discontinuous reinforcements have been gaining wide acceptance as an important engineering material in automotive and aerospace industries. This is due to their better properties and performance advantage over monolithic alloys. The discontinuous reinforcements used are in the form of particulates, whiskers and short fibers. The short fibers of carbon, silicon carbide and alumina are

T. P. D. Rajan; R. M. Pillai; B. C. Pai

1999-01-01

57

Fabrication of carbon nanofiber-reinforced aluminum matrix composites assisted by aluminum coating formed on nanofiber surface by in situ chemical vapor deposition  

NASA Astrophysics Data System (ADS)

The van der Waals agglomeration of carbon nanofibers (CNFs) and the weight difference and poor wettability between CNFs and aluminum hinder the fabrication of dense CNF-reinforced aluminum matrix composites with superior properties. In this study, to improve this situation, CNFs were coated with aluminum by a simple and low-cost in situ chemical vapor deposition (in situ CVD). Iodine was used to accelerate the transport of aluminum atoms. The coating layer formed by the in situ CVD was characterized using scanning electron microscopy, transmission electron microscopy, x-ray diffraction, Fourier transform-infrared spectroscopy, and x-ray photoelectron spectroscopy. The results confirmed that the CNFs were successfully coated with aluminum. The composites were fabricated to investigate the effect of the aluminum coating formed on the CNFs. The dispersion of CNFs, density, Vickers micro-hardness and thermal conductivity of the composites fabricated by powder metallurgy were improved. Pressure-less infiltration experiments were conducted to fabricate composites by casting. The results demonstrated that the wettability and infiltration were dramatically improved by the aluminum coating layer on CNFs. The aluminum coating formed by the in situ CVD technique was proved to be effective for the fabrication of CNF-reinforced aluminum matrix composites.

Ogawa, Fumio; Masuda, Chitoshi

2015-01-01

58

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

59

In-situ deformation studies of an aluminum metal-matrix composite in a scanning electron microscope  

NASA Technical Reports Server (NTRS)

Tensile specimens made of a metal-matrix composite (cast and extruded aluminum alloy-based matrix reinforced with Al2O3 particulate) were tested in situ in a scanning electron microscope equipped with a deformation stage, to directly monitor the crack propagation phenomenon. The in situ SEM observations revealed the presence of microcracks both ahead of and near the crack-tip region. The microcracks were primarily associated with cracks in the alumina particles. The results suggest that a region of intense deformation exists ahead of the crack and corresponds to the region of microcracking. As the crack progresses, a region of plastically deformed material and associated microcracks remains in the wake of the crack.

Manoharan, M.; Lewandowski, J. J.

1989-01-01

60

Damping properties of aluminum matrixfly ash composites  

Microsoft Academic Search

The damping properties of the hollow sphere fly ash\\/6061Al composites with various reinforcement diameters and with about 40 vol.% porosities (enclosed within the hollow sphere fly ash particles) have been measured by using the forced vibration mode and the bendingvibration mode on the multifunctional internal friction apparatus. The results indicate that the damping capacity of the fly ash\\/6061Al composite with

G. H. Wu; Z. Y. Dou; L. T. Jiang; J. H. Cao

2006-01-01

61

Pressureless Reaction Sintering of AlON using Aluminum Orthophosphate as a Transient Liquid Phase  

Microsoft Academic Search

Use of aluminum oxynitride (AlON) in transparent armor systems has been difficult due to the expense and limitations of the processing methods currently necessary to achieve transparency. Development of a pressureless processing method based on direct reaction sintering of alumina and aluminum nitride powders would reduce costs and provide a more flexible and practical manufacturing method. It may be possible

Michael Bakas; Henry Chu

2009-01-01

62

On the Understanding of Aluminum Grain Refinement by Al-Ti-B Type Master Alloys  

NASA Astrophysics Data System (ADS)

Al-Ti-B type master alloys have been widely used in the grain refinement of aluminum since 1940s. The introduction of Al3Ti and TiB2(AlB2) particles reduces the grain sizes down to about 200 micrometer level and makes aluminum alloys castable. However, the mechanism for the grain refinement is still not clear, though it is believed that TiB2 particles in the presence of Al3Ti nucleate ?-Al grains during solidification. This paper presents our finding on the formation of (Ti,Al)B2 solid solution, which leads to a proposed theory on grain refinement by Al-Ti-B type master alloys that upon addition into aluminum melt stable TiB2 particles react with aluminum slowly and release titanium into the melt. The titanium thus released in combination with titanium in the melt through dissolution of Al3Ti particles maintains a dynamic titanium-rich layer on the surface of (Ti,Al)B2. This layer offers a low crystal mismatch with ?-Al and promotes the nucleation of aluminum grains.

Wang, Xiaoming; Liu, Zhiwei; Dai, Wei; Han, Qingyou

2014-11-01

63

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

64

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

SciTech Connect

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

Schultz, Peter Andrew

2012-04-01

65

Patterned aluminum nanowires produced by electron beam at the surfaces of AlF3 single crystals  

E-print Network

Patterned aluminum nanowires produced by electron beam at the surfaces of AlF3 single crystals C is demonstrated for fabricating patterned aluminum nanowires in AlF3 substrate in a scanning electron microscope nanowires of different sizes. The aluminum nanowires may act as nano- interconnects for nanoelectronics

Wang, Zhong L.

66

Molecular characterization of Atlas 66 derived wheat near-isogenic lines contrasting in Aluminum (Al) tolerance  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aluminum (Al) toxicity is the major limiting factors for wheat growth in acidic soils. Genetic improvement of Al tolerance is one of the most cost-effective solutions to improve wheat productivity. The objective of this study was to identify DNA markers associated with the Al-tolerance in wheat usin...

67

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

68

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

69

Aluminum(III) speciation with acetate and oxalate. A potentiometric and sup 27 Al NMR study  

SciTech Connect

Aluminum (III) hydrolysis and precipitation in the presence of acetic acid and oxalic acid have been studied by combining potentiometric titration and liquid-state {sup 27}Al NMR. The main aluminum species have thus been identified and quantified: unreacted hydrolyzed, complexed monomers, and the Al{sub 13} tridecamer. A solid species appeared when precipitation occurred and was quantified by difference with the other species. The quantitative evolution of these species was followed for pH values up to 5. Acetate forms weak complexes with aluminum. The precipitated phase was hypothesized to be aggregated Al{sub 13}. Oxalate forms strong multiligand complexes to form Al{sub 13} requires higher hydroxyl content. High oxalate contents (L/M > 1) inhibit tridecamer formation and precipitation occurs only at high pH values. With oxalate the precipitated phase seems to be devoid of Al{sub 13} and of a more condensed nature than it is with acetate.

Thomas, F.; Rouiller, J.; Genevrier, F.; Boudot, D. (Univ. Nancy, Vandoeuvre (France)); Masion, A.; Bottero, J.Y. (Centre de Recherches sur la Valorisation des Minerais, Vandoeuvre (France))

1991-09-01

70

Al matrix syntactic foam fabricated with bimodal ceramic microspheres  

Microsoft Academic Search

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

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

2009-01-01

71

Ductile - ductile beryllium aluminum metal matrix composite manufactured by extrusion. Interim report, 1 October1 November 1994  

Microsoft Academic Search

Beryllium-aluminum alloys are unique, in-situ ductile-ductile metal matrix composite alloys. Cast and extruded beryllium-aluminum composite alloys are expected to have a unique combination of properties that are attractive for applications such as ground and space based interceptor and tracking systems that require minimum weight, high stiffness, good damping capacity and thermal stability. Compared with other metal matrix composites, cast and

Levoy

1994-01-01

72

Ductile - ductile beryllium aluminum metal matrix composite manufactured by extrusion. Interim report, 1 November1 December 1994  

Microsoft Academic Search

Beryllium-aluminum alloys are unique, in-situ ductile-ductile metal matrix composite alloys. Cast and extruded beryllium-aluminum composite alloys are expected to have a unique combination of properties that are attractive for applications such as ground and space based interceptor and tracking systems that require minimum weight, high stiffness, good damping capacity and thermal stability. Compared with other metal matrix composites, cast and

Levoy

1994-01-01

73

Fabrication of aluminum based nanomaterials  

Microsoft Academic Search

Structural applications in transportation necessitate materials with high specific strength and stiffness. With its low density, aluminum (Al) is an interesting candidate, but further strengthening would be beneficial. In this work, the benefits and limitations of nanoreinforcements for aluminum strengthening has been assessed through the addition of carbon nanotube (CNTs) and nanometric alumina (n-Al2O3) to an aluminum matrix by powder

Dominique Poirier

2009-01-01

74

Ductile - ductile beryllium aluminum metal matrix composite manufactured by extrusion. Interim report, 1 October-1 November 1994  

SciTech Connect

Beryllium-aluminum alloys are unique, in-situ ductile-ductile metal matrix composite alloys. Cast and extruded beryllium-aluminum composite alloys are expected to have a unique combination of properties that are attractive for applications such as ground and space based interceptor and tracking systems that require minimum weight, high stiffness, good damping capacity and thermal stability. Compared with other metal matrix composites, cast and extruded beryllium-aluminum composites are expected to have the advantages of: (1) lower cost; (2) significantly higher ductility; (3) higher temperature capability; (4) less directionality of properties; (5) applicability of all conventional metal processing techniques; and (6) joining by conventional welding and brazing technology.

Levoy, N.F.

1994-11-01

75

Ductile - ductile beryllium aluminum metal matrix composite manufactured by extrusion. Interim report, 1 November-1 December 1994  

SciTech Connect

Beryllium-aluminum alloys are unique, in-situ ductile-ductile metal matrix composite alloys. Cast and extruded beryllium-aluminum composite alloys are expected to have a unique combination of properties that are attractive for applications such as ground and space based interceptor and tracking systems that require minimum weight, high stiffness, good damping capacity and thermal stability. Compared with other metal matrix composites, cast and extruded beryllium-aluminum composites are expected to have the advantages of: (1) lower cost; (2) significantly higher ductility; (3) higher temperature capability; (4) less directionality of properties; (5) applicability of all conventional metal processing techniques; and (6) joining by conventional welding and brazing technology.

Levoy, N.F.

1994-12-01

76

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

PubMed

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

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

2009-09-30

77

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

NASA Astrophysics Data System (ADS)

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

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

2011-01-01

78

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

SciTech Connect

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

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

2011-01-17

79

Morphology Control for Al2O3 Inclusion Without Ca Treatment in High-Aluminum Steel  

NASA Astrophysics Data System (ADS)

Nozzle blockage is a major problem during continuous casting of Al-containing steel. Herein, we analyzed the thermodynamic equilibrium behavior between aluminum and oxygen in steel at 1873 K (1600 C) and demonstrated that, the dissolved [O] initially decreases with increasing the dissolved [Al] until approximately 0.1 wt pct [Al], and after that, the dissolved [O] increases with dissolved [Al]. Thus, for high-aluminum steel with 1.0 wt pct dissolved [Al], the precipitation of Al2O3 inclusion can be avoided during cooling from deoxidation temperature to the liquidus temperature, if the actual dissolved [O] can be kept from increasing when the dissolved [Al] further increases from 0.1 to 1.0 wt pct. Hence, a method of inclusion control for high-aluminum steel without traditional Ca treatment technology was proposed based on the thermodynamic analysis. Industrial tests confirmed that low-melting point Ca-aluminate inclusions were observed typically through a slag washing with SiO2-minimized high-basicity slag during tapping, accompanied by two-step Al-adding process for production of high-aluminum steel. Moreover, there was no nozzle clogging occurred for five heats of continuous casting.

He, Shengping; Chen, Gujun; Guo, Yintao; Shen, Boyi; Wang, Qian

2015-01-01

80

Structural and optical properties of direct current sputtered zinc aluminum oxides with a high Al concentration  

Microsoft Academic Search

Zinc aluminum oxide films were deposited by reactive dc magnetron sputtering from Zn\\/Al target containing 30 wt.% Al. Sputtering was carried out on glass and Si(100) substrates held at room temperature. The effect of oxygen flow on structural and optical properties was studied. The properties of the films were strongly dependent on oxygen flow. Amorphous, highly transparent and very smooth

S. H. Mohamed; R. Drese

2006-01-01

81

Development of an electronic device quality aluminum antimonide (AlSb) semiconductor for solar cell applications  

DOEpatents

Electronic device quality Aluminum Antimonide (AlSb)-based single crystals produced by controlled atmospheric annealing are utilized in various configurations for solar cell applications. Like that of a GaAs-based solar cell devices, the AlSb-based solar cell devices as disclosed herein provides direct conversion of solar energy to electrical power.

Sherohman, John W; Yee, Jick Hong; Combs, III, Arthur W

2014-11-11

82

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

83

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

84

The Effect of Aluminum Content on the Corrosion Behavior of Fe-Al Alloys in Reducing Environments at 700 C  

E-print Network

The Effect of Aluminum Content on the Corrosion Behavior of Fe-Al Alloys in Reducing Environments with the observance and/or duration of each stage directly related to the aluminum content of the alloy. The first by relatively high corrosion rates. Further decreasing the aluminum content to 5 wt pct and below lead

DuPont, John N.

85

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

86

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 amplitudes below 0.000001. Whereas little variation was observed in the dynamic moduli of specimens with approximately the same fiber content (50 percent), 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. For those few situations where slight deviations from theory were observed, the dynamic data were examined for information concerning microstructural changes induced by composite fabrication and thermal treatment. The 270 C damping peak observed in B/Al (6061) composites after heat treatment above 460 C appears to be the result of a change in the 6061 aluminum alloy microstructure induced by interaction with the boron fibers. The growth characteristics of the damping peak suggest its possible value for monitoring fiber strength degration caused by excess thermal treatment during B/Al (6061) fabrication and use.

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

1979-01-01

87

On the AlF3 and temperature control of an aluminum electrolysis cell  

Microsoft Academic Search

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

Tormod Drengstig; Dag Ljungquist; Bjarne A. Foss

1998-01-01

88

Pressureless Reaction Sintering of AlON using Aluminum Orthophosphate as a Transient Liquid Phase  

SciTech Connect

Use of aluminum oxynitride (AlON) in transparent armor systems has been difficult due to the expense and limitations of the processing methods currently necessary to achieve transparency. Development of a pressureless processing method based on direct reaction sintering of alumina and aluminum nitride powders would reduce costs and provide a more flexible and practical manufacturing method. It may be possible to develop such a processing method using liquid phase sintering; as long as the liquid phase does not remain in the final sample. AlPO4 forms a liquid phase with Al2O3 and AlN at the temperatures required to sinter AlON, and slowly decomposes into P2O5 and alumina. Therefore, it was investigated as a possible transient liquid phase for reaction-sintered AlON. Small compacts of alumina and aluminum nitride with up to of 15wt% AlPO4 additive were pressed and sintered. It was found that AlPO4 formed the requisite transient liquid phase, and it was possible to adjust the process to produce AlON samples with good transmission and densities of 3.66-3.67 g/cc. XRD confirmed the samples formed were AlON, with no trace of any remaining phosphate phases or excess alumina or aluminum nitride. Based on the results, it was concluded that AlPO4 could be utilized as a transient liquid phase to improve the density and transmission of AlON produced by pressureless reaction sintering.

Michael Bakas; Henry Chu

2009-01-01

89

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

90

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

Microsoft Academic Search

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

W. Ames; A. T. Alpas

1995-01-01

91

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

92

The melting behavior of lutetium aluminum perovskite LuAlO3  

E-print Network

DTA measurements with mixtures of aluminum oxide and lutetium oxide around the 1:1 perovskite composition were performed up to 1970 deg. C. A peak with onset 1901 deg. C was due to the melting of the eutectic Lu4Al2O9 (monoclinic phase) and LuAlO3 (perovskite). Neither peritectic melting of the perovskite nor its decomposition in the solid phase could be resolved experimentally. The maximum of the eutectic peak size near x=0.44, on the Lu-rich side of the perovskite, leads to the conclusion that LuAlO3 melts peritectically at ca. 1907 deg. C as proposed by Wu, Pelton, J. Alloys Compd. 179 (1992) 259. Under strongly reducing conditions (oxygen partial pressure <10^{-13} bar) aluminum(III) oxide can be reduced to suboxides or even Al metal. It is shown that under such conditions a new phase field with liquid Al can appear.

Klimm, Detlef

2009-01-01

93

In situ fabrication and properties of AlN dispersion strengthened 2024 aluminum alloy  

NASA Astrophysics Data System (ADS)

Nanoscaled aluminum nitride (AlN) dispersion strengthened 2024 aluminum alloy was fabricated using a novel approach in which Al-Mg-Cu compacts were partially nitrided in flowing nitrogen gas. The compacts were subsequently consolidated by sintering and hot extrusion. The microstructure and mechanical properties of the material were preliminarily investigated. Transmission electron microscopy and X-ray diffraction results revealed that AlN particles were generated by the nitridation of Al-Mg-Cu compacts. The material exhibited excellent mechanical properties after hot extrusion and heat treatment. The ultimate tensile and yield strengths of the extruded samples containing 8.92vol% AlN with the T6 heat treatment were 675 and 573 MPa, respectively.

Yang, Wei-wei; Guo, Zhi-meng; Guo, Lei-chen; Cao, Hui-qin; Luo, Ji; Ye, An-ping

2014-12-01

94

Effects of diffusion on aluminum depletion and degradation of NiAl coatings  

NASA Technical Reports Server (NTRS)

Experiments were performed to critically demonstrate the effects of diffusion on the aluminum depletion and degradation of NiAl coatings on superalloys. Pack aluminized IN 100 and Mar-M200 were diffusion annealed in 0.0005 torr vacuum at 1100 C for 300 hours. Aluminum losses due to oxidation and vaporization were minimal. Metallographic and electron microprobe analyses showed considerable interdiffusion of the coating with the substrate, which caused a large decrease in the original aluminum level of the coating. Subsequent cyclic furnace oxidation tests were performed at 1100 C using 1 hour cycles on pre-diffused and as-coated specimens. The pre-diffusion treatment decreased the oxidation protection for both alloys, but more dramatically for IN 100. Identical oxidation tests of bulk NiAl, where such diffusion effects are precluded, showed no signs of degradation at twice the time needed to degrade the coated superalloys.

Smialek, J. L.; Lowell, C. E.

1973-01-01

95

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

96

Effect of fiber diameter and matrix alloys on impact-resistant boron/aluminum composites  

NASA Technical Reports Server (NTRS)

Efforts to improve the impact resistance of B/Al are reviewed and analyzed. Nonstandard thin-sheet charpy and Izod impact tests and standard full-size Charpy impact tests were conducted on composites containing unidirectional 0.10mm, 0.14mm, and 0.20mm diameter boron fibers in 1100, 2024, 5052, and 6061 Al matrices. Impact failure modes of B/Al are proposed in an attempt to describe the mechanisms involved and to provide insight for maximizing impact resistance. The impact strength of B/Al was significantly increased by proper selection of materials and processing. The use of a ductile matrix and large diameter boron fibers gave the highest impact strengths. This combination resulted in improved energy absorption through matrix shear deformation and multiple fiber breakage.

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

1976-01-01

97

Speciation of hydroxyl-Al polymers formed through simultaneous hydrolysis of aluminum salts and urea  

Microsoft Academic Search

Urea hydrolysis has always been used to prepare alumina gels and little attention has been paid to the reactive polymeric Al species that is formed before alumina solgels occur. Based on the hydrolysis process of aluminum in urea solution at 90C, speciation and transformation of the reactive hydroxyl-Al polymers obtained by urea hydrolysis was investigated with Ferron assay, solution-state and

Chenghong Feng; Qunshan Wei; Shuifeng Wang; Baoyou Shi; Hongxiao Tang

2007-01-01

98

Molecular Characterization of Atlas 66Derived Wheat Near-lsogenic Lines Contrasting in Aluminum (Al) Tolerance  

Microsoft Academic Search

Aluminum (Al) toxicity is the major limiting factor for wheat growth in acidic soils. Genetic improvement of A1 tolerance is one of the most cost-effective solutions to improve wheat productivity. The objective of this study was to characterize near isogenic lines (NILs) contrasting in A1 tolerance derived from Atlas 66 in the backgrounds of Al-sensitive cultivars Chisholm and Century using

Pei-guo GUO; Gui-hua BAI; Rong-hua LI; Carver Brett; Baum Michael

2007-01-01

99

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

Microsoft Academic Search

Optically transparent Al2O3 films has been synthesized, on quartz substrates at 500, 600 and 700C, from 0.02M aluminum acetyl acetonate (Al(acac)3) in ethanol, by using ultrasonic spray pyrolysis technique. The films synthesized at 500, 600 and 700C are amorphous having average particle sizes 276, 183 and 143, respectively. The films are found to be 95% optically transparent in the visible

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

2011-01-01

100

Casting of AlSi hypereutectic aluminum alloy strip using an unequal diameter twin roll caster  

Microsoft Academic Search

Al16%Si and Al20%Si hypereutectic aluminum alloy with wide freezing zone were cast into the strip from low temperature melt using an unequal diameter twin roll caster. The diameter of a lower roll was 1000mm and an upper roll was 250mm. The strip could be cooled on the lower roll after through the roll bite. The strip, which has wide freezing

Toshio Haga; Hideki Inui; Hisaki Watari; Shinji Kumai

2007-01-01

101

Thermal fatigue resistance of discontinuously reinforced cast aluminum-matrix composites  

Microsoft Academic Search

The thermal fatigue resistance of AlSi alloys and discontinuously reinforced Al-matrix composites containing graphite, silicon\\u000a carbide, and fly ash particulates, and short alumina (Saffil) fibers was characterized by measuring the total length of microcracks\\u000a on gravity-cast and squeeze-cast test specimens as a function of number of thermal cycles (10005000 cycles, 270 K amplitude).\\u000a In each thermal cycle, the test specimens

J. Sobczak; N. Sobczak; P. Darlak; Z. Slawinski; R. Asthana; P. Rohatgi

2002-01-01

102

THE ROLE OF SCARF ANGLE IN THE PERFORMANCE OF ALUMINUM MATRIX COMPOSITE JOINTS  

Microsoft Academic Search

The role of geometry on the mechanical performance of scarf joints in Al-matrix composites reinforced with continuous polycrystalline alumina fibers was investigated. Model joints consisting of thin metal interlayers at varying scarf angles between composite sub-elements were designed, manufactured and tested to study the relevant deformation and failure phenomena. Specimens were produced by pressurized infiltration of molten Al-4.5%Mg into fiber

D. D. BRINK; C. G. LEVI; A. C. F. COCKS; F. A. LECKIE

1997-01-01

103

Effect of Al(OH)3 on the hydrogen generation of aluminum-water system  

NASA Astrophysics Data System (ADS)

Many metal oxides effectively modify metallic aluminum (Al) powders to produce hydrogen in neutral water at room temperature. In this study, hydrogen is generated even more rapidly from the reacted solution when the by-product Al(OH)3 (bayerite) is present. The influence of Al(OH)3 on the hydrogen generation during the aluminum/water reaction is highly dependent on the surface area and the crystallinity of Al(OH)3. High surface area and poor crystallinity of Al(OH)3 render the system a rapid hydrogen generation rate. The self-catalytic phenomenon can be explained by the formation of AlO(OH) (boehmite) from the reaction of by-product ?-Al(OH)3 and the surface passive oxide layer Al2O3. Furthermore, by taking advantage of the exothermic heat from the Al/water reaction, hydrogen yield is able to reach 70% within 30min in a common aqueous solution (pH<10) containing fine Al(OH)3. This hydrogen generation technology relies on common, nontoxic, noncorrosive additives and is therefore a very promising system for creating a use-on-demand hydrogen source.

Teng, Hsin-Te; Lee, To-Ying; Chen, Yu-Kuang; Wang, Hong-Wen; Cao, Guozhong

2012-12-01

104

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

PubMed

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

Nowak, Jaroslaw; Friend, Alexander L

2005-02-01

105

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

106

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

NASA Astrophysics Data System (ADS)

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

Singh, S.; Yeh, M. F.

2012-04-01

107

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

SciTech Connect

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

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

1999-08-01

108

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

...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...

2010-10-01

109

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

...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...

2011-10-01

110

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

...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...

2013-10-01

111

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

Code of Federal Regulations, 2014 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...

2014-10-01

112

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

113

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

114

Characterization of the tensile and microstructural properties of an aluminum metal matrix composite  

NASA Technical Reports Server (NTRS)

This study examines a powder metallurgy aluminum alloy in the unreinforced state and with a discontinuous reinforcement of 15 v/o or 30 v/o SiC whisker or 15 v/o SiC particulate. The materials were extruded and then hot-rolled to three plate thicknesses of 6.35, 3.18 and 1.8 mm and were investigated in the as-fabricated and peak aged conditions. The influence of mechanical working on the reinforcement morphology and distribution were examined. A comparison of the mechanical properties was made and the elastic moduli of the reinforced materials were predicted using a micromechanics model. Fractography of tensile specimens revealed that the fracture process was dominated by the presence of microstructural inhomogeneities which were related to both the matrix alloy and to the reinforcement type. An analysis of these microstructural features and a description of the micromechanics model are presented in the paper.

Birt, M. J.; Johnson, W. S.

1990-01-01

115

The Metal-Organic Framework MIL-53(Al) Constructed from Multiple Metal Sources: Alumina, Aluminum Hydroxide, and Boehmite.  

PubMed

Three aluminum compounds, namely alumina, aluminum hydroxide, and boehmite, are probed as the metal sources for the hydrothermal synthesis of a typical metal-organic framework MIL-53(Al). The process exhibits enhanced synthetic efficiency without the generation of strongly acidic byproducts. The time-course monitoring of conversion from different aluminum sources into MIL-53(Al) is achieved by multiple characterization that reveals a similar but differentiated crystallinity, porosity, and morphology relative to typical MIL-53(Al) prepared from water-soluble aluminum salts. Moreover, the prepared MIL-53(Al) constructed with the three insoluble aluminum sources exhibit an improved thermal stability of up to nearly 600?C and enhanced yields. Alumina and boehmite are more preferable than aluminum hydroxide in terms of product porosity, yield, and reaction time. The adsorption performances of a typical environmental endocrine disruptor, dimethyl phthalate, on the prepared MIL-53(Al) samples are also investigated. The improved structural stability of MIL-53(Al) prepared from these alternative aluminum sources enables double-enhanced adsorption performance (up to 206?mg?g(-1) ) relative to the conventionally obtained MIL-53(Al). PMID:25756851

Li, Zehua; Wu, Yi-Nan; Li, Jie; Zhang, Yiming; Zou, Xin; Li, Fengting

2015-04-27

116

Formation of Ge nanocrystals in Al2O3 matrix.  

PubMed

Ge nanocrystals were formed in Al2O3 matrix by implantation of Ge ions into sapphire (alpha-Al2O3) substrates and subsequent annealing. Diagnostic techniques, Raman spectroscopy, XRD, TEM, EDS, and SAED were employed to monitor and study formation of Ge nanocrystals and their evolution during heat treatments. TEM and EDS analysis revealed the diffusion of Ge ions into the substrate during annealing process. While Ge nanocrystals with mean sizes of 15 nm were observed in the heavily implanted region small nanocrystals with mean sizes of 4 nm were identified underneath this region. Some grains of transition aluminas were formed in the implanted region which was amorphized during the implantation. Extensive stress between the transition aluminas and sapphire matrices and its effects on the matrix were detected. The effect of stress on the Raman and XRD spectra of Ge nanocrystals was discussed. PMID:18464402

Yerci, S; Kulakci, M; Serincan, U; Turan, R; Shandalov, M; Golan, Y

2008-02-01

117

Determination of aluminum levels in the kidney, liver, and brain of mice treated with aluminum hydroxide  

Microsoft Academic Search

In the present study, aluminum (Al) accumulation has been examined after aluminum loading in mice. The kidney, liver, and\\u000a brain aluminum levels for mice that had been treated orally with aluminum hydroxide for 105 d and for the control group were\\u000a determined using graphite furnace atomic absorption spectrophotometry (GFAAS) following an acid digestion. Matrix modifier\\u000a consisted of 2% Triton X-100

Gnl ?ahin; I. Varol; A. Temizer; K. Benli; R. Demirdamar; S. Duru

1994-01-01

118

Selection of soldering temperature for ultrasonic-assisted soldering of 5056 aluminum alloy using ZnAl system solders  

Microsoft Academic Search

The conditions for sound butt-joints of 5056 aluminum alloy containing 4.6mass% Mg using ZnxAl (x=5, 13, and 38mass%) solder at the relevant temperatures were investigated. Each solder foil was inserted between faying surfaces of 5056 aluminum rods. Ultrasonic vibration at a frequency of 19kHz was applied to the faying surfaces through an aluminum substrate at soldering temperatures for 4s in

Toru Nagaoka; Yoshiaki Morisada; Masao Fukusumi; Tadashi Takemoto

2011-01-01

119

Photoemission study of the electronic structures of tris-(8-hydroxyquinoline) aluminum/Li2O/Al interfaces  

NASA Astrophysics Data System (ADS)

The electronic structures of tris-(8-hydroquinoline) aluminum (Alq3)/Li2O/Al interfaces were studied using in situ ultraviolet and x-ray photoelectron spectroscopies (UPS and XPS). The UPS and XPS spectra allowed us to evaluate the complete energy level diagrams and to analyze the chemical interactions at the interfaces. Inserting Li2O between Al and Alq3 led to the highest occupied molecular orbital (HOMO) of Alq3 shifting to a higher binding energy compared to that without Li2O, which resulted in an improved electron injection. We also observed that the magnitude of the secondary cutoff shift was almost identical to that of the HOMO shift with the insertion of Li2O. This implies that the energy level alignment depends on the interface dipole and ionization energy of the adsorbate. Additionally, a gap state was observed in the gap of Alq3, which is related to the interfacial reaction. The N 1s spectra revealed that there were destructive chemical reactions between Alq3 and Al, which could be prevented by inserting Li2O between them.

Cho, K.; Cho, S. W.; Whang, C.-N.; Jeong, K.; Kang, S. J.; Yi, Y.

2007-09-01

120

Approach to In-Situ Producing Reinforcing Phase Within an Active-Transient Liquid Phase Bond Seam for Aluminum Matrix Composite  

NASA Astrophysics Data System (ADS)

To optimize the braze composition design route for aluminum matrix composite, the feasibility of in situ producing reinforcing phase within the transient liquid phase bond seam matrix, by adding active melting point increaser (MPI, e.g., Ti) together with general melting point depressant (MPD, e.g., Cu) into the interlayer, was demonstrated. For SiC p /A356 composite, by comparing the wettability, joint microstructure, joint shear strength, and fracture path for the developed Al-19Cu-1Ti, Al-19Cu, Al-33Cu-1Ti, Al-33Cu (wt pct), and commercial Cu foils as interlayer, the feasibility of in situ producing reinforcing phase within the bond seam by adding Ti was demonstrated. Especially for Al-19Cu-1Ti active braze, small and dispersed ternary aluminide of Al-Si-Ti phase was obtained within the bond seam as in situ reinforcement, leading to a favorable fracture path within SiC p /A356, not along the initial interface or within the bond seam. For the formation mechanism of the in situ reinforcing phase of MPI-containing intermetallic compound within the bond seam, a model of repeating concentration-precipitation-termination-engulfment during isothermal solidification is proposed.

Zhang, Guifeng; Liao, Xianjin; Chen, Bo; Zhang, Linjie; Zhang, Jianxun

2015-03-01

121

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

ERIC Educational Resources Information Center

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

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

2008-01-01

122

Composite propellant aluminum agglomeration reduction using tailored Al/PTFE particles  

NASA Astrophysics Data System (ADS)

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

Sippel, Travis R.

123

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

124

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

125

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

PubMed

Nonresonant multiphoton ionization with time-of-flight mass spectrometry has been used to monitor the desorption of aluminum chloride (Al(x)Cl(y)) etch products from the Al(111) surface at 100 and 500 K during low-coverage (<5% monolayer) monoenergetic Cl(2) (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 Cl(2), 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 AlCl(3). Cl(2) sticking probability measurements and Al(x)Cl(y) etch rate measurements show etching even at Cl(2) 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 AlCl(3) 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. PMID:15527367

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

2004-11-01

126

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

127

Effective n-type doping strategy through codoping SiAlFN in aluminum nitride  

NASA Astrophysics Data System (ADS)

Using a first-principles pseudopotential method, we studied an effective n-type doping strategy through codoping SiAlXN (X = F, Cl, Br, and I) in aluminum nitride. Results revealed that the donor ionization energy of the SiAlXN complex is much lower than that of the corresponding isolated SiAl impurity. Theoretically obtained ?(+/0) ionization energies are all near the conduction band minimum (CBM), which is only 1.4 meV below the CBM of the SiAlFN pair. The low ?(+/0) ionization energy of the SiAlXN complex can be explained by the combined repulsion between the X element (X = F, Cl, Br, and I)- and Si donor-induced levels.

Wang, Zhiguo; Li, Jingbo; Qing Fu, Yong

2014-11-01

128

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

129

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

130

Manufacturing of Aluminum Matrix Composites Reinforced with Iron Oxide (Fe3O4) Nanoparticles: Microstructural and Mechanical Properties  

NASA Astrophysics Data System (ADS)

The purpose of this paper is to demonstrate the low-cost manufacturing of aluminum matrix composites reinforced with nano iron oxide as light and efficient materials for engineering applications. It is very desirable to use reinforced aluminum matrix composites in structural applications (automotive, aeronautical, etc.) because of their outstanding stiffness-to-weight and strength-to-weight ratios. In modern industry, it is increasingly important to develop new composites as alternative materials to fabricate multifunctional pieces. Detailed information is presented on the manufacturing process of this composite, and a preliminary study was performed on the cryogenic-cycling behavior to evaluate the interface between the matrix and the reinforcement. Microindentation tests were carried out to evaluate the micromechanical properties of these materials; a simple and practical finite element model is proposed to predict certain parameters related to the composition of the composite.

Bayraktar, Emin; Ayari, Fayza; Tan, Ming Jen; Tosun-Bayraktar, Ayse; Katundi, Dhurata

2014-04-01

131

Thermal fatigue resistance of discontinuously reinforced cast aluminum-matrix composites  

NASA Astrophysics Data System (ADS)

The thermal fatigue resistance of AlSi alloys and discontinuously reinforced Al-matrix composites containing graphite, silicon carbide, and fly ash particulates, and short alumina (Saffil) fibers was characterized by measuring the total length of microcracks on gravity-cast and squeeze-cast test specimens as a function of number of thermal cycles (1000-5000 cycles, 270 K amplitude). In each thermal cycle, the test specimens were heated and stabilized in air at 375 C, water quenched, and air stabilized. In all specimens, the total crack length on a specified region increased with increasing number of thermal cycles. Whereas among monolithic alloys, squeeze-cast Al-12SiCuNiMg alloy exhibited better resistance to thermal cracking than Al-25Si and Al-20SiNi alloys, among the composites, squeeze-cast Al-alumina and Al-fly ash composites exhibited the best thermal fatigue resistance. The theoretical estimates of the thermal fatigue resistance of these composites are consistent with the experimental observations.

Sobczak, J.; Sobczak, N.; Darlak, P.; Slawinski, Z.; Asthana, R.; Rohatgi, P.

2002-12-01

132

Preparation of plate-like nano ?-Al 2O 3 using nano-aluminum seeds by wet-chemical methods  

Microsoft Academic Search

Alumina particles with plate-like shape were prepared successfully by a wet chemical processes with nano-size aluminum additive. The seed-effect of nano-size aluminum and its effect on the final ?-Al2O3 particle size and shape were investigated. TEM, XRD, XPS, Zeta potential and DSC\\/TG were used to observe the microstructure of the ?-Al2O3 particle and analysis this wet chemical processes. It was

Hongxia Lu; Hongwei Sun; Aixia Mao; Huizhi Yang; Hailong Wang; Xing Hu

2005-01-01

133

Aluminum-activated citrate and malate transporters encoded by distinct Al tolerance genes function independently in Arabidopsis  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aluminum (Al) -activated malate and citrate exudation from roots plays an important role in conferring Al tolerance to many plant species. Here, we report on the identification and characterization of AtMATE, the gene encoding an Al-activated root citrate efflux transporter that functions in Arabid...

134

Growth of aluminum catalyzed AlGaAs nanowires on silicon substrate.  

PubMed

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

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

2013-03-01

135

Laser fusion-brazing of aluminum alloy to galvanized steel with pure Al filler powder  

NASA Astrophysics Data System (ADS)

The fusion-brazing connection of the dissimilar metal 5052 aluminum alloy/ST07Z steel was achieved by using the Nd:YAG laser with pure Al filler powder, and the effects of the laser power and powder feeding speed on the formation and mechanical properties of the resultant joints were investigated. The experimental results show that melting-brazing connection of 5052 aluminum alloy/galvanized steel can be successfully achieved, and the zinc plating layer has played the role of flux, assuring the brazing properties. The intermetallic compound layer was generated on the welded brazing interface. The joint exhibited a shear strength of 174 N/mm if the thickness of the intermetallic layer at the interface is about 6-7 ?m.

Liu, Jia; Jiang, Shichun; Shi, Yan; Kuang, Yulin; Huang, Genzhe; Zhang, Hong

2015-03-01

136

PII S0016-7037(98)00136-7 The kinetics of mixed Ni-Al hydroxide formation on clay and aluminum oxide minerals  

E-print Network

PII S0016-7037(98)00136-7 The kinetics of mixed Ni-Al hydroxide formation on clay and aluminum. This finding indicates that the dissolution of clay and aluminum oxide minerals can be promoted by metal ions

Sparks, Donald L.

137

Wear Behavior of Aluminum Alloy 6061-Based Composites Reinforced with SiC, Al2O3, and Red Mud: A Comparative Study  

NASA Astrophysics Data System (ADS)

Metal-matrix composites are widely used in shipping, aerospace, automotive, and nuclear applications. Research attempts have been made in the past to reduce the cost of processing of composites, decrease the weight of the composites, and increase the desired performance characteristics. In this research article, an attempt has been made in using red mud obtained as an industrial waste during the production of aluminum from bauxite ore. This article discusses the novel findings of the experimental study on the dry sliding wear behavior of aluminum alloy 6061-based composites reinforced individually with red mud, SiC, and Al2O3. The microstructural characterization of the composites provides the further insight into the structurewear behavior of the processed composites.

Singla, Yogesh Kumar; Chhibber, Rahul; Bansal, Hitesh; Kalra, Anil

2015-03-01

138

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

139

Characterization of Third Bodies in Self-Lubricating Aluminum Metal-Matrix Composites by Electron Microprobe Analysis  

Microsoft Academic Search

Third bodies play a crucial role in governing the tribological behavior of self-lubricating composites. The present study deals with the characterization of third bodies generated during a two million-cycle wear test of a self-lubricating aluminum metal-matrix composite (MMC). The composite is comprised of five percent by volume of tungsten disulfide (WS2) and 10 vol.% of silicon carbide (SiC) dispersed in

S. V. Prasad; K. R. Mecklenburg

1996-01-01

140

Method using selected carbons to react with Al2O and Al vapors in the carbothermic production of aluminum  

DOEpatents

In a method for recovering Al from an off-gas (3,4) produced during carbothermic reduction of aluminum utilizing at least one smelter (1,2), the off-gas (3,4) is directed to an enclosed reactor (5) which is fed a supply of wood charcoal (7) having a porosity of from about 50 vol. % to 85 vol. % and an average pore diameter of from about 0.05 .mu.m to about 2.00 .mu.m, where the wood charcoal (7) contacts the off-gas (3,4) to produce at least Al.sub.4 C.sub.3 (6), which is passed back to the smelter (1,2).

Fruehan, Richard J.; Li, Yun; Carkin, Gerald

2005-02-01

141

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

142

Elementary surface chemistry during CuO/Al nanolaminate-thermite synthesis: copper and oxygen deposition on aluminum (111) surfaces.  

PubMed

The surface chemistry associated with the synthesis of energetic nanolaminates controls the formation of the critical interfacial layers that dominate the performances of nanothermites. For instance, the interaction of Al with CuO films or CuO with Al films needs to be understood to optimize Al/CuO nanolaminates. To that end, the chemical mechanisms occurring during early stages of molecular CuO adsorption onto crystalline Al(111) surfaces are investigated using density functional theory (DFT) calculations, leading to the systematic determination of their reaction enthalpies and associated activation energies. We show that CuO undergoes dissociative chemisorption on Al(111) surfaces, whereby the Cu and O atoms tend to separate from each other. Both Cu and O atoms form islands with different properties. Copper islanding fosters Cu insertion (via surface site exchange mechanism) into the subsurface, while oxygen islands remain stable at the surface. Above a critical local oxygen coverage, aluminum atoms are extracted from the Al surface, leading to oxygen-aluminum intermixing and the formation of aluminum oxide (?-alumina). For Cu and O co-deposition, copper promotes oxygen-aluminum interaction by oxygen segregation and separates the resulting oxide from the Al substrate by insertion into Al and stabilization below the oxide front, preventing full mixing of Al, Cu, and O species. PMID:25089744

Lanthony, Clo; Guiltat, Mathilde; Ducr, Jean Marie; Verdier, Agnes; Hmeryck, Anne; Djafari-Rouhani, Mehdi; Rossi, Carole; Chabal, Yves J; Estve, Alain

2014-09-10

143

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

PubMed

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

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

2007-06-15

144

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

NASA Astrophysics Data System (ADS)

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

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

2009-09-01

145

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

NASA Astrophysics Data System (ADS)

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

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

2009-02-01

146

Effect of aluminum treatment on proteomes of radicles of seeds derived from Al-treated tomato plants  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aluminum (Al) toxicity is a major constraint to plant growth and crop yield in acid soils. Tomato cultivars are especially susceptible to excessive A1 3+ accumulated in the root zone. In this study, tomato plants were grown in a hydroponic culture system supplemented with 50 uM AlK(SO4)2. Seeds harv...

147

Energy-Saving Melting and Revert Reduction Technology (E-SMARRT): Development of Elevated Temperature Aluminum Metal Matrix Composite (MMC) Alloy and Its Processing Technology  

SciTech Connect

The objective of this project was to provide a production capable cast aluminum metal matrix composite (MMC) alloy with an operating temperature capability of 250-300C. Important industrial sectors as well as the military now seek lightweight aluminum alloy castings that can operate in temperature ranges of 250-300C. Current needs in this temperature range are being satisfied by the use of titanium alloy castings. These have the desired strength properties but the end components are heavier and significantly more costly. Also, the energy requirements for production of titanium alloy castings are significantly higher than those required for production of aluminum alloys and aluminum alloy castings.

Weiss, David C. [Eck Industreis, Inc.] [Eck Industreis, Inc.; Gegal, Gerald A.

2014-04-15

148

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

149

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

150

Interface formation between Al and Ca with tris-(8-hydroxyquinoline) aluminum  

NASA Astrophysics Data System (ADS)

Using x-ray and UV photoemission spectroscopy (XPS and UPS), we have investigated the early stages of the interface formation between metals, namely Al and Ca, and tris-(8- hydroxyquinoline) aluminum (Alq3). Both interfaces show signs of reaction between the metal and Alq3. However, the detailed behaviors of the two interfaces are very different. In the case of Al/Alq3 interface, the metal was found to react preferentially with the quinolate oxygen as soon as it was deposited onto Alq3. No evidence of reaction with the carbon was found. Unlike with Ca, little interaction between Al and nitrogen of the pyridyl was observed. UPS spectra show a quick disappearance of the Alq3 features as early as 0.7 angstrom of Al deposition, and also suggest the formation of a gap state induced by Al. In the case of Ca/Alq3, the interface is characterized by a staged interface reaction: for low Ca coverages, negatively charged Alq3 radical anions are formed by electron transfer from the Ca. The emergence of new states in the energy gap is observed in the UPS spectra. At higher overages, the Ca reacts with the phenoxide oxygen resulting in the decomposition of the Alq3 molecule.

Le, Quoc T.; Mason, M. G.; Yan, Li; Choong-En, Vi; Forsythe, Eric W.; Tang, Ching W.; Gao, Yongli

1999-05-01

151

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

152

Effect of heat treatment on microstructure and interface of SiC particle reinforced 2124 Al matrix composite  

SciTech Connect

The microstructure and interface between metal matrix and ceramic reinforcement of a composite play an important role in improving its properties. In the present investigation, the interface and intermetallic compound present in the samples were characterized to understand structural stability at an elevated temperature. Aluminum based 2124 alloy with 10 wt.% silicon carbide (SiC) particle reinforced composite was prepared through vortex method and the solid ingot was deformed by hot rolling for better particle distribution. Heat treatment of the composite was carried out at 575 C with varying holding time from 1 to 48 h followed by water quenching. In this study, the microstructure and interface of the SiC particle reinforced Al based composites have been studied using optical microscopy, scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDS), electron probe micro-analyzer (EPMA) associated with wavelength dispersive spectroscopy (WDS) and transmission electron microscopy (TEM) to identify the precipitate and intermetallic phases that are formed during heat treatment. The SiC particles are uniformly distributed in the aluminum matrix. The microstructure analyses of AlSiC composite after heat treatment reveal that a wide range of dispersed phases are formed at grain boundary and surrounding the SiC particles. The energy dispersive X-ray spectroscopy and wavelength dispersive spectroscopy analyses confirm that finely dispersed phases are CuAl{sub 2} and CuMgAl{sub 2} intermetallic and large spherical phases are Fe{sub 2}SiAl{sub 8} or Al{sub 15}(Fe,Mn){sub 3}Si. It is also observed that a continuous layer enriched with Cu and Mg of thickness 5080 nm is formed at the interface in between Al and SiC particles. EDS analysis also confirms that Cu and Mg are segregated at the interface of the composite while no carbide is identified at the interface. - Highlights: The composite was successfully heat treated at 575C for 1-48 hrs. A layer of 50-75 nm is formed at interface after heat treatment. No Carbide formation and SiC dissolution is observed at this temperature. MgAl{sub 2}O{sub 4}, CuMgAl{sub 2} phases are segregated at interface of Al-SiC composite. Mg and Cu are also segregated at near to the grain boundary.

Mandal, Durbadal, E-mail: durbadal73@yahoo.co.in [MEF Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Viswanathan, Srinath [Dept of Metallurgical and Materials Engineering, University of Alabama, Tuscaloosa, AL (United States)

2013-11-15

153

Effect of microstructure (particulate size and volume fraction) and counterface material on the sliding wear resistance of particulate-reinforced aluminum matrix composites  

NASA Astrophysics Data System (ADS)

The effects of microstructure (namely, particulate volume fraction and particulate size) and the counterface materials on the dry-sliding wear resistance of the aluminum matrix composites 2014A1-SiC and 6061Al-Al2O3 were studied. Experiments were performed within a load range of 0.9 to 350 N at a constant sliding velocity of 0.2 ms-1. Two types of counterface materials, SAE 52100 bearing steel and mullite, were used. At low loads, where particles act as loadbearing constituents, the wear resistance of the 2014A1 reinforced with 15.8 m diameter SiC was superior to that of the alloy with the same volume fraction of SiC but with 2.4 m diameter. The wear rates of the composites worn against a steel slider were lower compared with those worn against a mullite slider because of the formation of iron-rich layers that act as in situ solid lubricants in the former case. With increasing the applied load, SiC and A12O3 particles fractured and the wear rates of the composites increased to levels comparable to those of unreinforced matrix alloys. The transition to this regime was delayed to higher loads in the composites with a higher volume percentage of particles. Concurrent with particle fracture, large strains and strain gradients were generated within the aluminum layers adjacent to contact surfaces. This led to the subsurface crack growth and delamination. Because the particles and interfaces provided preferential sites for subsurface crack initiation and growth and because of the propensity of the broken particles to act as third-body abrasive elements at the contact surfaces, no improvement of the wear resistance was observed in the composites in this regime relative to unreinforced aluminum alloys. A second transition, to severe wear, occurred at higher loads when the contact surface temperature exceeded a critical value. The transition loads (and temperatures) were higher in the composites. The alloys with higher volume fraction of reinforcement provided better resistance to severe wear. Wearing the materials against a mullite counterface, which has a smaller thermal conductivity than a counterface made of steel, led to the occurrence of severe wear at lower loads.

Alpas, A. T.; Zhang, J.

1994-05-01

154

ACO-zeotype iron aluminum phosphates with variable Al/Fe ratios controlled by F? ions.  

PubMed

Three new iron aluminum phosphates |(C(2)H(10)N(2))(4)|[Fe(8?-?x)Al(x)F(x)(H(2)O)(2?-?x)(PO(4))(8)]2H(2)O (? = 1.64, 1.33, 0.80) with ACO-zeotype structures denoted as FeAPO-CJ66(a), FeAPO-CJ66(b), and FeAPO-CJ66(c), respectively, have been synthesized in the fluoride ion system. Their framework structures are made of double 4-ring (D4R) building units formed by the alternating connection of Fe(Al)O(4)F(O) trigonal bipyramids and PO(4) tetrahedra, which possess 3D intersecting 8-ring channels running along the [001], [010], and [100] directions. Fluoride ions or water molecules reside in the center of D4Rs, and diprotonated ethylenediamine cations and water molecules are occluded in the free space of channels to stabilize the whole structure. Notably, the Al/Fe ratios in the frameworks can be effectively controlled from 1/3.9 to 1/5.0 to 1/9.0 by adjusting the amounts of phosphoric acid and hydrofluoric acid added to the initial reaction mixture. Mo?ssbauer and magnetic measurements show that the Fe ions in the compounds are bivalent and undergo antiferromagnetic ordering at room temperature. PMID:21247084

Wang, Yanyan; Li, Yi; Wang, Lei; Zhang, Jingzhe; Yan, Yan; Li, Jiyang; Yu, Jihong; Wang, Jincheng; Xu, Ruren

2011-03-01

155

Laser cladding of quasicrystal forming AlCuFe on aluminum Krishanu Biswas a  

E-print Network

, Barry L. Mordike b , Kamanio Chattopadhyay a,* a Department of Metallurgy, Indian Institute of Science powder mixture of aluminum, copper and iron on an aluminum substrate. Some of the tracks are remelted

Srivastava, Kumar Vaibhav

156

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

157

Effect of Rhenium Addition on Wear Behavior of Cr-Al2O3 Metal Matrix Composites  

NASA Astrophysics Data System (ADS)

Materials for applications in the automotive industry are required to be strong, stiff, hard, light weight, and wear resistant, which is very difficult to achieve in the case of conventional materials. To meet all these diverse requirements, it is necessary to combine various types of materials (such as metals and ceramics). In the present study, the chromium and chromium-rhenium matrices were reinforced with aluminum oxide to obtain composite materials with improved wear resistance. The composites were fabricated by a powder metallurgy method. The effects of the rhenium addition and volume fraction of aluminum oxide on the wear rate and the friction coefficient of the composites at room temperature were examined in a ball-on-surface apparatus under dry conditions. The worn surfaces and debris were studied by scanning electron microscopy. The final values of the friction coefficient were 0.9 and 0.8 for the Cr-25%Al2O3 and Cr-40%Al2O3 composites, respectively. Alloying Cr matrix with Re improved wear resistance of composite but, at the same time, it caused an increase in its coefficient of friction.

Chmielewski, Marcin; Pi?tkowska, Anna

2015-03-01

158

Transition-metal interactions in aluminum-rich intermetallics Ibrahim Al-Lehyania;b and Mike Widoma  

E-print Network

Transition-metal interactions in aluminum-rich intermetallics Ibrahim Al-Lehyania;b and Mike Widoma GPT to transition-metal TM aluminides produces pair and many-body interactions that allow e cient limitation is a transition- metal over-binding that creates an unrealistic TM-TM attraction at short

Widom, Michael

159

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

160

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

SciTech Connect

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

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

1991-01-01

161

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

SciTech Connect

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

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

1980-06-01

162

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

163

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

Microsoft Academic Search

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

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

1979-01-01

164

Influence of AlAl 2O 3 composite powder on the matrix microstructure in composite casts  

Microsoft Academic Search

The structural characterization is presented of composite casts with an AlMg4 alloy matrix, with the composite powder (AlAl2O3)cp reinforcement obtained in a rotary-vibration mill. On the cross-sections of ingots, metallographic specimens have been made and, by means of quantitative metallographic methods, the grain size distributions have been determined. Statistical tests of the results obtained from the grain plane section area

Anita Olszwka-Myalska; Janusz Szala; Jzef ?leziona; Boles?aw Formanek; Jerzy Myalski

2002-01-01

165

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

166

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

167

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

168

A study of the modifying influence of nanoparticle additives produced by plasma-chemical synthesis on the structure of cast aluminum matrix composite materials  

Microsoft Academic Search

The results of an investigation into the microstructure of composite materials based on an aluminum matrix reinforced by intermetallic\\u000a phases, which are formed by in situ reactions in the presence of nanosize ceramic particles, are presented. The possibility\\u000a of modifying and stabilizing the structure of such composite materials with nanopoweder additives is determined.

T. A. Chernyshova; I. E. Kalashnikov; A. V. Samokhin; N. V. Alekseev; L. K. Bolotova; L. I. Kobeleva

2009-01-01

169

Surface modification of AlZnMg aluminum alloy using the combined process of EDM with USM  

Microsoft Academic Search

This paper presents a novel technique to improve the machined surface of AlZnMg aluminum alloy by a combined machining process of electrical discharge machining (EDM) with ultrasonic machining (USM). In these experiments, SiC particles were added into the dielectric fluid to produce a particle-reinforced mechanism and solid solution strengthened structure to form a modified layer on the machined surface in

Yan Cherng Lin; Biing Hwa Yan; Fuang Yuan Huang

2001-01-01

170

Damage evaluation in discontinuously reinforced aluminum matrix composites subjected to thermal cycling  

Microsoft Academic Search

A comparative study of the damage in the powder metallurgy processed AlCuMg alloySiC (as-extruded and solution-treated) and AlSiC (hot rolled), and in situ cast AlTiC (as-extruded) composites, each with 15vol.% particulate reinforcements, has been carried out. Repeated thermal cycling of the composites between 500 and 0C was followed by evaluation of damage by examination of microstructure using scanning electron microscopy,

Sharmilee Pal; V. V. Bhanuprasad; R. Mitra

2008-01-01

171

Acoustic emission during fatigue crack propagation in SiC particle reinforced Al matrix composites  

SciTech Connect

The acoustic emission (AE) behavior during fatigue propagation in aluminum 6061 and aluminum 6061 matrix composites containing 5, 10, and 20 wt pct SiC particle reinforcement was investigated under tension-tension fatigue loading. The purpose of this investigation was to monitor fatigue crack propagation by the AE technique and to identify the source(s) of AE. Most of the AEs detected were observed at the top of the load cycles. The cumulative number of AE events was found to correspond closely to the fatigue crack growth and to increase with increasing SiC content. Fractographic studies revealed an increasing number of fractured particles and to a lesser extent decohered particles on the fatigue fracture surface as the crack propagation rate (e.g., {Delta}K) or the SiC content was increased.

Niklas, A.; Froyen, L.; Wevers, M.; Delaey, L. [K.U. Leuven (Belgium). Dept. of Metallurgy and Materials Engineering

1995-12-01

172

Mechanical behavior of aluminum matrix composite during extrusion in the semisolid state  

SciTech Connect

Semisolid extrusion experiments have been carried out on SiC particle reinforced aluminum composite. Different die diameters and ram velocities have been used in order to obtain a range of extrusion conditions at a constant temperature of 580 C. The experimental results were fitted to a multiple linear regression to obtain a constitutive equation describing the behavior of the material in these conditions. From the regression equation, it was possible to model the material by finite element analysis. The predicted values of the extrusion force resulting from the numerical analysis are consistent with the experimental values for the different conditions. The flow of primary phase particles through the die observed on micrographs has been compared with the predicted pattern and shows good agreement. These results also justify the use of a frictional stress factor corresponding to a sticking condition at the interface between the billet and the die components.

Turenne, S.; LaPlante, S.; Ajersch, F. [Ecole Polytechnique, Montreal, Quebec (Canada). Dept. de Metallurgie et de Genie des Materiaux; Legros, N. [National Research Council of Canada, Boucherville, Quebec (Canada). Industrial Materials Inst.

1999-04-01

173

Damping mechanisms in alumina borate whisker-reinforced-aluminum matrix composites with or without SnO2 coatings  

NASA Astrophysics Data System (ADS)

SnO2 was successfully coated on the surface of alumina borate whiskers. The pure aluminum matrix composites reinforced with a SnO2-coated alumina borate whisker were fabricated by squeeze casting. The effects of coating contents on the damping properties of the coated composites at various temperatures, frequencies, and strain amplitudes were examined. The microstructures of the coated composites were also investigated through transmission electron microscopy observations. These results indicate that the introduction of Sn at the interface between whisker and matrix in the coated composites during the squeeze casting process alters not only the interface structures but also the dislocation status of the matrices in the vicinity of the interface. The results of damping characterization indicate that the damping capacities of the coated composites strongly depend on the coating contents and strain amplitudes. A damping peak at low temperatures appeared not only in the coated composites but also in the noncoated one, which is related to dislocation motion and interfacial slip caused by Sn. A damping peak at high temperatures appeared only in the coated composites, and the damping mechanisms at high temperature change with the increase in strain amplitudes. Sn played an important role on the damping mechanisms of the coated composites all along.

Hu, J.; Wang, X. F.; Zheng, Z. Z.

2010-01-01

174

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

175

Al2O3 fiber strength degradation in metal and intermetallic matrix composites  

NASA Technical Reports Server (NTRS)

The mechanisms for fiber damage in single crystal Al2O3 fiber-reinforced composites were investigated. Both fiber fragmentation and fiber strength degradation were observed in composites with a variety of matrix compositions. Four mechanisms that may be contributing to the fiber strength loss have been proposed and include matrix reaction, reaction with binders, residual stress-induced damage, and pressure from hot pressing. The effect of matrix reaction was separated from the other three effects by sputter-coating the matrices on cleaned fibers and annealing with a temperature profile that simulates processing conditions. These experiments revealed that Y and Cr in FeCrAlY base alloys and Zr in NiAl alloys reacted with the fiber, and grooves and adherent particles were formed on the fiber surface which were responsible for the strength loss. The effects of the matrix reaction appeared to dominate over the other possible mechanisms, although evidence for reaction with binders was also found. Ridges on the fiber surface, which reflected the grain boundaries of the matrix, were also observed. In order for single-crystal Al2O3 to be used as a fiber in MMC's and IMC's, a matrix or protective coating which minimizes matrix reaction during processing will be necessary. Of the matrices investigated, the Thermo-span(sup TM) alloy was the least damaging to fiber properties.

Draper, S. L.; Locci, I. E.

1994-01-01

176

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

177

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

Microsoft Academic Search

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

M. Aguilar-Frutis; J. Guzmn-Mendoza; T. Alejos; M. Garca-Hiplito; C. Falcony

2003-01-01

178

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

179

PHOSPHORUS AND ALUMINUM INTERACTIONS IN SOYBEAN IN RELATION TO AL TOLERANCE: EXUDATION OF SPECIFIC ORGANIC ACIDS FROM DIFFERENT REGIONS OF THE INTACT ROOT SYSTEM  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aluminum (Al) toxicity and phosphorus (P) deficiency often coexist in acid soils to severely limit crop growth and production. Understanding the mechanisms underlying plant Al and P interactions is necessary to facilitate the development of acid tolerant crops. Here we studied the effects of Al and...

180

Modeling of Interaction Layer Growth Between U-Mo Particles and an Al Matrix  

SciTech Connect

Interaction layer growth between U-Mo alloy fuel particles and Al in a dispersion fuel is a concern due to the volume expansion and other unfavorable irradiation behavior of the interaction product. To reduce interaction layer (IL) growth, a small amount of Si is added to the Al. As a result, IL growth is affected by the Si content in the Al matrix. In order to predict IL growth during fabrication and irradiation, empirical models were developed. For IL growth prediction during fabrication and any follow-on heating process before irradiation, out-of-pile heating test data were used to develop kinetic correlations. Two out-of-pile correlations, one for the pure Al matrix and the other for the Al matrix with Si addition, respectively, were developed, which are Arrhenius equations that include temperature and time. For IL growth predictions during irradiation, the out-of-pile correlations were modified to include a fission-rate term to consider fission enhanced diffusion, and multiplication factors to incorporate the Si addition effect and the effect of the Mo content. The in-pile correlation is applicable for a pure Al matrix and an Al matrix with the Si content up to 8 wt%, for fuel temperatures up to 200 degrees C, and for Mo content in the range of 6 10wt%. In order to cover these ranges, in-pile data were included in modeling from various tests, such as the US RERTR-4, -5, -6, -7 and -9 tests and Koreas KOMO-4 test, that were designed to systematically examine the effects of the fission rate, temperature, Si content in Al matrix, and Mo content in U-Mo particles. A model converting the IL thickness to the IL volume fraction in the meat was also developed.

Yeon Soo Kim; G. L. Hofman; Ho Jin Ryu; Jong Man Park; A. B. Robinson; D. M. Wachs

2013-12-01

181

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

PubMed

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

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

2010-06-15

182

Homocatenation of Aluminum: Alkane-like Structures of Li2 Al2 H6 and Li3 Al3 H8.  

PubMed

A new class of aluminum homocatenated compounds (Lin Aln H2n+2 ) is proposed based on quantum chemical calculations. In these compounds, Al abstracts an electron from Li, becoming valence isoelectronic with C, Si, and Ge, thus mimicking respective structural features of Group?14 hydrides. Using the Coalescence Kick search program coupled with density functional theory calculations, we investigated the potential energy surfaces of Li2 Al2 H6 and Li3 Al3 H6 . Then single-point-energy coupled-cluster calculations were performed for the lowest energy structures found. Indeed, the global minima established for Li2 Al2 H6 and Li3 Al3 H6 contain the Al2 H6 (2-) and Al3 H6 (3-) kernels, which are isostructural with ethane (C2 H6 ), disilane (Si2 H6 ), digermane (Ge2 H6 ) and propane (C3 H8 ), trisilane (Si3 H8 ), trigermane (Ge3 H8 ) molecules, respectively. Structural, energetic, and electronic characteristics of the Li2 Al2 H6 and Li3 Al3 H8 compounds are presented and the viability of their synthesis is discussed. PMID:25704853

Gish, J Tyler; Popov, Ivan A; Boldyrev, Alexander I

2015-03-27

183

Dry sliding wear of Al alloy 2024Al 20 3 particle metal matrix composites  

Microsoft Academic Search

In the present investigation, Al 2024-15vol.%Al203 particulate (average size, 18 ?m) composites were fabricated using the liquid metallurgy route. The wear and friction characteristics of AI alloy 2024 and Al 2024-15vol.%Al203p composite in the as-extruded and peak-aged conditions were studied using a pin-on-disc machine (with a steel disc as the counterface material). The worn surfaces, subsurfaces and the debris were

Manish Narayan; M. K. Surappa; B. N. Pramila Bai

1995-01-01

184

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

NASA Astrophysics Data System (ADS)

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

Gmze, L. A.; Gmze, L. N.; Egsz, .; Ojima, F.

2013-12-01

185

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

NASA Astrophysics Data System (ADS)

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

Caulder, Stanley; Mackey, Joseph; Wilkinson, John

2009-06-01

186

Effects of particle orientation in silicon carbide particulate reinforced aluminum matrix composite extrusions on ultrasonic velocity measurement  

SciTech Connect

In silicon carbide particulate reinforced aluminum matrix composite extrusions, the particles are nonspherical in general and are randomly oriented due to the extrusion process, resulting in sometimes significant anisotropic elastic stiffness. Since the ultrasonic velocity depends upon the elastic stiffness, ultrasonic velocity measurement is employed to characterize the anisotropic elastic stiffness of the composite extrusions. To establish the relationship between the materials` macroscopic response (ultrasonic velocity) and the microstructure, the measured statistical particle orientation distribution has been taken into account in theoretical modeling to predict the velocity of ultrasound that propagates in the composite extrusions, an attempt that has never been made before. The numerically calculated velocity agreed well with the measured velocity. Both numerical calculations and the ultrasonic measurements have shown that the randomly oriented particles have led to a higher velocity (stiffness) in the extrusion plane and a lower velocity (stiffness) in the direction perpendicular to the plane, which are just the manifestation of the nonuniform particle orientation. It has also been shown that satisfactory theoretical modeling requires the consideration of the particle orientation distribution in the composite extrusions. 45 refs.

Lu, Y.; Liaw, P.K. [Univ. of Virginia, Charlottesville, VA (United States)

1995-11-01

187

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

2015-02-01

188

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

189

The Microstructure-Processing-Property Relationships in an Al Matrix Composite System Reinforced by Al-Cu-Fe Alloy Particles  

SciTech Connect

Metal matrix composites (MMC), especially Al matrix composites, received a lot of attention during many years of research because of their promise for the development of automotive and aerospace materials with improved properties and performance, such as lighter weight and better structural properties, improved thermal conductivity and wear resistance. In order to make the MMC materials more viable in various applications, current research efforts on the MMCs should continue to focus on two important aspects, including improving the properties of MMCs and finding more economical techniques to produce MMCs. 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. Microstructures and tensile properties of AYAl-Cu-Fe composites were characterized. 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. Also, the composite samples made from GARS powders show a higher strengthening effect and ductility than the samples made from commercial purity powders. The higher load transfer efficiency and higher strength and ductility may result from an enhanced inter-particle bonding strength, promoted by the ''clean'' interfaces between particles. 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.

Fei Tang

2004-12-19

190

Assistance of Novel Artificial Intelligence in Optimization of Aluminum Matrix Nanocomposite by Genetic Algorithm  

NASA Astrophysics Data System (ADS)

In this article, a genetic algorithm (GA) is used to predict the mechanical properties and to optimize the process conditions of Al nanocomposites. An artificial intelligence method is also implemented as an assisting tool for engineering tasks of GAs. The principle of the survival of the fittest is applied to produce successively superior approximations to a solution. A population of points at each iteration is generated. The population approaches an optimal solution. The next population by computations that involve random choices is selected. The optimal volume percentage of SiC, cooling rate, and temperature gradient are computed to be 2.84 pct, 283 K/s (10 C/s), 1273 K/m (1000 C/m), respectively.

Mazahery, Ali; Shabani, Mohsen Ostad

2012-12-01

191

Effect of Inclusions' Behavior on the Microstructure in Al-Ti Deoxidized and Magnesium-Treated Steel with Different Aluminum Contents  

NASA Astrophysics Data System (ADS)

To clarify the precipitation behavior of beneficial inclusions and mechanism of their effects on microstructure, the effect of aluminum content on inclusion's characteristics and their influence on the refinement of microstructure in Al-Ti complex deoxidized magnesium-treated steels were systematically investigated based on experiment and calculation. The results showed that due to the dual effects of Ti and Mg deoxidation, a large amount of finely dispersed Al2O3-TiO x -MgO inclusions in low aluminum steel with a complex multilayer or mosaic structure were formed, whereas a relatively smaller amount of Al2O3-MgO inclusions with the simple bundle structure were observed in high aluminum steel. The Al2O3-TiO x -MgO core oxides are more conducive to the precipitation of multiple manganese sulfides with thinner thickness on their local surfaces. Thus, the inclusion deformation, which mainly depends on the surface manganese sulfides layer, is smaller in low aluminum steel than that in high aluminum steel. Complex inclusions in low aluminum steel can pin austenite grain boundaries and induce interlocking acicular ferrite effectively. In addition to the small size and chemical composition of inclusions, the complex structure of oxides and the precipitation of multiple MnS on their surface are important to the nucleation of interlocking AFs on inclusions in Ti-deoxidized Mg-treated steel. The AFs quantity is much more, and the grain size is more uniform in low aluminum steel than that in high aluminum steel.

Wu, Zhenhua; Zheng, Wan; Li, Guangqiang; Matsuura, Hiroyuki; Tsukihashi, Fumitaka

2015-02-01

192

Aluminum monocarbonyl and aluminum isocarbonyl Steve S. Wesolowski,a)  

E-print Network

Aluminum monocarbonyl and aluminum isocarbonyl Steve S. Wesolowski,a) T. Daniel Crawford,b) Justin of the aluminum monocarbonyl species AlCO and AlOC have been performed to predict the geometries, fragmentation, Ogden, and Oswald6 first isolated aluminum dicarbonyls in solid krypton and identified the species

Crawford, T. Daniel

193

Pre-Accretionary Distribution of Ca and Al Between Matrix and Chondrules in CV Chondrites  

NASA Astrophysics Data System (ADS)

Ca/Al-ratios in Y-86751 (CV) chondrules are super- and in matrix sub-chondritic. The opposite is true for Allende and Efremovka. Incorporation of spinel in Allende and Efremovka chondrule precursors in a nebular setting can explain this observation.

Hezel, D. C.; Palme, H.

2007-03-01

194

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

NASA Astrophysics Data System (ADS)

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

Mock, Willis; Drotar, Jason T.

2007-12-01

195

Lattice imperfections studied by x-ray diffraction in deformed aluminum-base alloys: Al-Ge alloy  

NASA Astrophysics Data System (ADS)

In the present analysis, which is part of a series on a study that has been undertaken on aluminum-base alloys, a detailed X-ray diffraction study of deformation[1 5] is made on aluminum-base germanium alloys in four different compositions: Al-3.10 at. pct Ge, Al-3.80 at. pct Ge, Al-4.16 at. pct Ge, and Al-4.60 at. pct Ge. The alloys were prepared from spectroscopically pure metals supplied by Johnson-Matthey and Co. Ltd., London, by melting them in graphite crucibles sealed under vacuum in quartz capsules. The alloys were homogenized for 15 days at 400 C in the face-centered cubic phase (Figure 1), and cold working was performed by careful hand filing at room temperature. The diffractometer samples were prepared in the usual manner,[3,4] and X-ray diffraction profiles were recorded in a Siemens Kristalloflex-4 X-ray diffractometer using Cu K? radiation. A portion of the powder obtained by hand filing from each alloy was annealed at 400 C to relieve strain and was taken as standard for line shift, line asymmetry, and line shape analyses in light of recent developments.[3,4,6 8] The microstructural parameters, such as coherent domain size ( D e, microstrain , stacking faults ?' and a" (both intrinsic and extrinsic), deformation twin fault ?, dislocation density ?, and stacking fault energy parameter ?/?, were determined by adopting the same method of analysis and following the same equations that were used before.[3 7

Chattopadhyay, S. K.; Chatterjee, S. K.; Gupta, S. P. Sen

1990-09-01

196

Aluminum catalyzed growth of silicon nanowires: Al atom location and the influence of silicon precursor pressure on the morphology  

NASA Astrophysics Data System (ADS)

We study the growth of silicon nanowires (SiNWs) by chemical vapor deposition (CVD) with aluminum as catalyst. We show that for a growth temperature of 600 C, the silicon precursor partial pressure (SiH4 in this study) is a key parameter for controlling the structural quality of the resulting SiNWs. We find by transmission electron microscopy that at high SiH4 partial pressure, the SiNWs are composed of a monocrystalline core with a high density of surface defects, mainly twins, sheathed by a rough amorphous silicon layer. By contrast, at low SiH4 partial pressure, the SiNWs are monocrystalline with a lower density of surface crystalline defects and a smooth surface. For the low SiH4 partial pressure SiNWs, Al atoms have been detected at the SiNW surface by Auger spectroscopy at level around 3 at% and in the SiNW core by energy dispersive X-ray spectroscopy (EDS) at levels around 1 at%. Interestingly, higher Al concentrations are measured inside the nano-twin domains by EDS (around ten times increase). Two possible explanations are proposed; stacking faults are induced by Al atoms that lower their energy formation, or Al atoms can be trapped inside these stacking faults due to segregation effect during growth. These findings will be important for growing high quality SiNWs using Al as metal catalyst in reduced-pressure CVD tool.

Kohen, David; Cayron, Cyril; De Vito, Eric; Tileli, Vasiliki; Faucherand, Pascal; Morin, Christine; Brioude, Arnaud; Perraud, Simon

2012-02-01

197

Ductile - ductile beryllium aluminum metal matrix composite manufactured by extrusion1. Interim report, 1 December 1994-1 January 1995  

Microsoft Academic Search

The current program is designed to develop a method for extruding a cast beryllium-aluminum composite, establish a basis for estimating the properties that can ultimately be achieved with an optimized process, and produce an extruded structural shape of moderate complexity. Specific technical objectives are as follows: 1. Develop an extrusion process suitable for beryllium-aluminum composites that maximizes product yield, minimizes

Levoy

1995-01-01

198

Effectiveness of metal matrix and ceramic matrix composites as orbital debris shield materials  

NASA Technical Reports Server (NTRS)

The effectiveness of two metal matrix composites and one ceramic matrix material in defeating hypervelocity impacts at about 3.8 km/s are evaluated to determine the potential of these composites as spacecraft shield materials. The metal matrix composites investigated consist of SiC particles (70 percent by volume) in an aluminum matrix and Al2O3 particles (50 percent by volume) in an Al matrix. The ceramic composite consists of ZrB2 platelets in a ZrC matrix. Both the metal matrix and ceramic matrix composites are found to perform as well or better than 6061-T6 aluminum, which is presently used in the Whipple type bumper shield of Space Station Freedom. Test results indicate that the composites tested may have applications as micrometeoroid/orbital debris shield materials.

Mcgill, Preston B.; Mount, Angela R.

1992-01-01

199

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

200

Experimental Research on Ultrasonic Vibration Milling Metal Matrix Composites SiCp/Al  

SciTech Connect

Although particle reinforced metal matrix composites possess excellent physical properties, its machining performance is rather bad because of its specific structure. It is difficult to obtain good cutting effect by traditional machining method. So machining has become the bottleneck which strictly restricts its industry application. This paper mainly focuses on both wear characteristics of different tool materials and material removal mechanism in ultrasonic milling high volume fraction particle reinforced metal matrix composites SiCp/Al. An acoustic device for ultrasonic vibration milling was developed to introduce the ultrasonic vibration into the traditional machining process. Through the contrast experiment of traditional milling and ultrasonic vibration milling SiCp/Al, the mechanism of tool wear and characteristics of surface topography were analyzed. The experimental results showed that the surface integrity and tool life in the ultrasonic vibration milling SiCp/Al were improved.

Gao, G. F.; Zhao, B.; Xiang, D. H.; Zhao, M. L. [School of Mechanical Engineering, Henan Polytechnic University, Jiaozuo (China)

2011-01-17

201

Optimization of electrode size for aluminum-nitride matrix ultrasonic transducers in the frequency range above 200 MHz.  

PubMed

This paper describes an optimization method of the top electrode size for a thin film matrix ultrasonic transducer (M-UT) in the frequency range above 200 MHz. The goal of this work is to design an optimal top electrode size for an M-UT providing the maximal output peak-peak voltage (V(PP)) and the maximal signal-to-noise ratio (SNR) without additional electrical impedance matching. In order to reduce the complexity of the M-UT with more than 1000 elements, an intrinsic matching by electrode size variation is necessary. However, the size of a single element top electrode for an M-UT is related to the number of elements within a targeted sensor area, V(PP) and SNR of the transducer. In this paper, varying the active area of the top electrode from 0.09 to 25 mm(2) shows that for an Al-AlN-Al on silicon wafer configuration connected with a JSR Ultrasonics pulser/receiver (50 ohms), the optimal electrode size is 1 mm(2). With the optimal size electrode, the maximum output V(PP) of 0.08 V and the SNR of 42.93 dB are achieved at the resonance frequency of 225 MHz, and the bandwidth is 16.21 MHz. PMID:23218910

Wei, Yangjie; Herzog, Thomas; Heuer, Henning

2013-03-01

202

Effects of pH, surface finish and thermal treatment on the corrosion of AlFeNi aluminum alloy. Characterization of oxide layers  

NASA Astrophysics Data System (ADS)

The aluminum alloy AlFeNi used as fuel cladding for the Jules Horowitz Reactor (JHR) may undergo corrosion in the reactor environment. In order to qualify the corrosion behavior of the fuel elements of the JHR in accidental conditions, several specimens of AlFeNi have been corroded at 250 C for different durations (9-34 days) in distilled water at various pH (4.9, 5.2 and 5.6) chosen to simulate that currently considered for the JHR. On all specimens, the only crystalline corrosion product formed is boehmite (AlOOH). The corrosion film is composed of three oxide layers which show through thickness chemical composition variations. The iron-nickel precipitates pre-existing in the metal matrix are present in the inner and intermediate oxide layers though oxidized. For long corrosion times, some of the iron and nickel particles are released in the water and some precipitation is observed at the surface of the oxide layer. The effect of surface finish (as received or polished) and thermal treatment (annealed and not annealed) on the oxide growth rate has also been investigated. For durations over 25 days, pH = 5.6 appears to be more favorable than pH = 5.2 and 4.9 in terms of oxide thickness and weight gain limitation. This effect of pH is however reduced on unpolished specimens. The effect of surface finish on the corrosion behavior as measured by optical microscopy appears to be strong, especially for pH = 4.9 where polished samples exhibited an accelerated evolution of the oxide thickness and of the mass gain. This could be due to the combined effect of a strong acid solution (pH = 4.9) and of the local microstructural changes formed at the interface through polishing. The effect of thermal treatment on the behavior of unpolished AlFeNi specimens during corrosion tests in the conditions investigated was found to be small. In this study, microstructural and chemical analyses were performed on the corroded specimens in order to get a better understanding of the corrosion kinetics. The crystallographic nature of the boehmite layers investigated by X-ray diffraction is unaffected by the pH of the solution. Iron precipitates were identified on the oxide surface beyond 34 days of corrosion by Environmental Scanning Electron Microscope (ESEM). Finally, Electron Probe Micro-Analysis (EPMA) was used to determine the chemical composition of the metal matrix and of the different oxide layers and precipitates versus the pH of the solution.

Nabhan, D.; Kapusta, B.; Billaud, P.; Colas, K.; Hamon, D.; Dacheux, N.

2015-02-01

203

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

204

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

SciTech Connect

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

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

1994-04-01

205

An Investigation of Micro-Mechanical Properties of Al Matrix in SiC/Al Composite by Indentation Experiments  

NASA Astrophysics Data System (ADS)

With the aid of indentation experiments, the micro-mechanical properties of the matrix of SiC particle-reinforced Aluminum composite were investigated with the load ranging from 80 to 480 mN and the loading speed ranging from 1.94 to 12.91 mN/s at room temperature. The results exhibited that under different loading conditions, the Young's modulus decreased along with the increasing load due to the damage accumulation. As to micro hardness, it reduced with the increasing load, the indentation depth (i.e., indentation size effect), and the decreasing loading speed. Independent of the loading speed, the micro-hardness was not only related to the material elastic property, but also to plastic property with and indenter geometry. The characteristic length was also associated with . The deduced effective strain rates reduced with the increasing load and the decreasing loading speed. According to the experiment results, the energy dissipation maps and the elastic strain map were constructed.

Yuan, Zhanwei; Li, Fuguo; Xue, Fengmei; Zhang, Mingjie; Li, Jiang

2015-02-01

206

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

207

Preparation of Eu-doped ?- and 15R-SiAlONs by ammonia nitridation of the precursor obtained using aluminum glycine gel  

Microsoft Academic Search

Synthesis of Eu-doped ?- and 15R-SiAlONs was studied by the ammonia nitridation of precursors derived from an ?-Si3N4 fine powder dispersed in aluminum glycine gel with various Si\\/Al ratio and post-annealing in a nitrogen pressure furnace. The largest amount of ?-SiAlON was observed in the product at 1750C for Si\\/Al=1\\/1 with small amounts of both ?- and 15R-SiAlON impurities. The

Yuji Masubuchi; Mitsue Yoshikawa; Takashi Takeda; Shinichi Kikkawa

2009-01-01

208

Processing of Carbon Fibers Reinforced Mg Matrix Composites Via Pre-infiltration with Al  

NASA Astrophysics Data System (ADS)

Mg-C composites offer a suitable alternative to Al alloys while allowing for a significant weight reduction, but their production can be impaired by the poor wettability of C substrates by Mg. In this study, a new "liquid" processing route has been investigated. By making use of the well-known effect of a pre-treatment of the C fibers with an aqueous solution of K2ZrF6 in favoring spontaneous wetting of C with Al, C yarns have been pre-impregnated with Al and the feasibility of further using them as reinforcements in Mg matrix composites has been assessed. More particularly, it has thus been shown that the, under the thermal conditions involved in the process, C fibers did not suffer damage due to chemical reaction with Al, and also that special care should be taken to control the surface condition of the pre-infiltrated yarns.

Mertens, A.; Montrieux, H.-M.; Halleux, J.; Lecomte-Beckers, J.; Delannay, F.

2012-05-01

209

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

NASA Astrophysics Data System (ADS)

The problem of uncontrolled oxygen contamination of intermetallic TiAl ingots is considered for the application of crucibles and molds based on traditional oxide ceramics. A synthesized Ti-45.9Al-8Nb (at %) alloy is solidified in alternative oxygen-free crucibles made of high-purity aluminum nitride (99.99% AlN) upon holding at 1670C for 5, 12, and 25 min and subsequent quenching in a high-purity argon atmosphere. The initial material and the solidified ingots are studied by scanning electron microscopy, optical microscopy, X-ray diffraction, electron-probe microanalysis, and gas-content chemical analysis. The key features of the interaction of the TiAl-Nb melt with AlN ceramics are revealed. Partial thermal dissociation of the crucible material according to the reaction AlN ? Al + N and the reaction of atomic nitrogen with the melt lead to the formation of a solid 6.4-?m-thick TiN coating on the ingot surface and provide perfect wettability of the crucible by the melt and easy removal of solidified casting items from the mold. The TiN coating serves as a diffusion barrier that hinders the diffusion of nitrogen and residual oxygen from the pores in the crucible toward the melt. As a result, no oxide particles are detected in the ingots. However, few single microprecipitates of two nitride phases ((Ti,Al) x N y , NbN) are detected in the near-bottom region, 300 ?m thick, in the alloy after holding at 1670C for 25 min. The total oxygen contamination in a two-phase ?2 + ? ingot does not exceed 1100 wt ppm, which is 1.5-2 times lower than that obtained in the experiments performed with modern advanced oxide crucibles made of yttrium ceramics Y2O3. AlN is shown to be a promising crucible material that can be considered as an alternative to oxide ceramics in the metallurgy of TiAl intermetallics.

Kartavykh, A. V.; Cherdyntsev, V. V.

2008-12-01

210

Aluminum-Centered Tetrahedron-Octahedron Transition in Advancing Al-Sb-Te Phase Change Properties  

PubMed Central

Group IIIA elements, Al, Ga, or In, etc., doped Sb-Te materials have proven good phase change properties, especially the superior data retention ability over popular Ge2Sb2Te5, while their phase transition mechanisms are rarely investigated. In this paper, aiming at the phase transition of Al-Sb-Te materials, we reveal a dominant rule of local structure changes around the Al atoms based on ab initio simulations and nuclear magnetic resonance evidences. By comparing the local chemical environments around Al atoms in respective amorphous and crystalline Al-Sb-Te phases, we believe that Al-centered motifs undergo reversible tetrahedron-octahedron reconfigurations in phase transition process. Such Al-centered local structure rearrangements significantly enhance thermal stability of amorphous phase compared to that of undoped Sb-Te materials, and facilitate a low-energy amorphization due to the weak links among Al-centered and Sb-centered octahedrons. Our studies may provide a useful reference to further understand the underlying physics and optimize performances of all IIIA metal doped Sb-Te phase change materials, prompting the development of NOR/NAND Flash-like phase change memory technology. PMID:25709082

Xia, Mengjiao; Ding, Keyuan; Rao, Feng; Li, Xianbin; Wu, Liangcai; Song, Zhitang

2015-01-01

211

Aluminum-centered tetrahedron-octahedron transition in advancing Al-sb-te phase change properties.  

PubMed

Group IIIA elements, Al, Ga, or In, etc., doped Sb-Te materials have proven good phase change properties, especially the superior data retention ability over popular Ge2Sb2Te5, while their phase transition mechanisms are rarely investigated. In this paper, aiming at the phase transition of Al-Sb-Te materials, we reveal a dominant rule of local structure changes around the Al atoms based on ab initio simulations and nuclear magnetic resonance evidences. By comparing the local chemical environments around Al atoms in respective amorphous and crystalline Al-Sb-Te phases, we believe that Al-centered motifs undergo reversible tetrahedron-octahedron reconfigurations in phase transition process. Such Al-centered local structure rearrangements significantly enhance thermal stability of amorphous phase compared to that of undoped Sb-Te materials, and facilitate a low-energy amorphization due to the weak links among Al-centered and Sb-centered octahedrons. Our studies may provide a useful reference to further understand the underlying physics and optimize performances of all IIIA metal doped Sb-Te phase change materials, prompting the development of NOR/NAND Flash-like phase change memory technology. PMID:25709082

Xia, Mengjiao; Ding, Keyuan; Rao, Feng; Li, Xianbin; Wu, Liangcai; Song, Zhitang

2015-01-01

212

Aluminum-Centered Tetrahedron-Octahedron Transition in Advancing Al-Sb-Te Phase Change Properties  

NASA Astrophysics Data System (ADS)

Group IIIA elements, Al, Ga, or In, etc., doped Sb-Te materials have proven good phase change properties, especially the superior data retention ability over popular Ge2Sb2Te5, while their phase transition mechanisms are rarely investigated. In this paper, aiming at the phase transition of Al-Sb-Te materials, we reveal a dominant rule of local structure changes around the Al atoms based on ab initio simulations and nuclear magnetic resonance evidences. By comparing the local chemical environments around Al atoms in respective amorphous and crystalline Al-Sb-Te phases, we believe that Al-centered motifs undergo reversible tetrahedron-octahedron reconfigurations in phase transition process. Such Al-centered local structure rearrangements significantly enhance thermal stability of amorphous phase compared to that of undoped Sb-Te materials, and facilitate a low-energy amorphization due to the weak links among Al-centered and Sb-centered octahedrons. Our studies may provide a useful reference to further understand the underlying physics and optimize performances of all IIIA metal doped Sb-Te phase change materials, prompting the development of NOR/NAND Flash-like phase change memory technology.

Xia, Mengjiao; Ding, Keyuan; Rao, Feng; Li, Xianbin; Wu, Liangcai; Song, Zhitang

2015-02-01

213

Statistical analysis of process parameters in drilling of AL\\/SIC P metal matrix composite  

Microsoft Academic Search

This paper presents a statistical analysis of process parameters for surface roughness in drilling of Al\\/SiCp metal matrix\\u000a composite. The experimental studies were conducted under varying spindle speed, feed rate, drill type, point angle of drill,\\u000a and heat treatment. The settings of drilling parameters were determined by using Taguchi experimental design method. The level\\u000a of importance of the drilling parameters

Gl Tosun

2011-01-01

214

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

215

Investigation on Microstructure and Fatigue Behavior of Al-5Zn- 2Mg High Strength Aluminum Alloy with T5 Heat Treatment  

NASA Astrophysics Data System (ADS)

The low cycle fatigue property of Al-5Zn-2Mg high strength aluminum alloy with T5 heat treatment was tested, and the fatigue damage behaviors were observed by OM, SEM and TEM. The results show that the rolling direction of Al-5Zn-2Mg high strength aluminum alloy is distinct. The separations, such as inclusions, mostly distribute along the rolling direction. The ?? (MgZn2) transitional strengthening phases are precipitated in Al-5Zn-2Mg aluminum alloy, and mostly distributed in grain boundary. The appearance of strengthening phase is ellipsoid. Its diameter of short axis is about 20 nm, and the diameter of long axis is about 40 nm. The cycle fatigue life is 4.22106 cycle in R=0.1, f=8 Hz, and ?max=127-210 MPa. The fatigue crack initiates in surface of Al-5Zn-2Mg aluminum alloy sample, while the fatigue crack come into being and propagate along the rolling direction. The fatigue stress causes the loose microstructure. There have the fatigue striations and shell texture in fatigue crack propagation zone.

Yang, S. L.; Xu, C.; Lin, Q. L.; Ding, B.

216

Electronic structure of the mixed aluminum and sodium cluster Al 2Na  

NASA Astrophysics Data System (ADS)

Electronic structure of Al 2Na was reinvestigated using MP2, CCSD(T) and MRMP2/CASSCF(7,7) calculations with aug-cc-pVnZ ( n = D, T and Q) basis sets. In contrast to a recent report, the triangular Al 2Na has a 2B 1 ground state with a 4B 1- 2B 1 gap of 2.5 kcal/mol, rather than a 2A 1 state (13.7 kcal/mol higher). In addition, Al 2Na + exhibits a linear 1? + ground state with a singlet-triplet gap of -5.2 kcal/mol rather than a cyclic 1A 1 state (6.0 kcal/mol above the linear). Al 2Na - has a triangular 3B 1 ground state and a singlet-triplet gap of 6.9 kcal/mol. We obtained IEa(Al 2Na) = 5.3 0.2 eV and EAa(Al 2Na) = 1.3 0.2 eV.

Lin, Ling; Kita, Yuki; Udagawa, Taro; Sakai, Shogo; Nguyen, Minh Tho

2009-07-01

217

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

NASA Astrophysics Data System (ADS)

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 friction coefficients dropped to below 0.2 when the MMC surface was etched; the stick-slip behavior disappeared. The increase in normal load, the friction coefficients of etched MMC surfaces increased progressively with sliding distance and the rough stick-slip type behavior reappeared. The transition from smooth to rough friction behavior was not observed for the etched surface of the MMC reinforced with 17 percent kaowool fibers even at a normal load of 0.7 N; aluminum transfer to steel was not detected in this case. The results demonstrate the feasibility of producing kaowool and saffil-fiber-reinforced aluminum MMCs by a squeeze infiltration route.

Prasad, S. V.; Mecklenburg, K. R.

1993-04-01

218

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

219

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

220

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

221

Density of Low-Temperature KF-AlF3 Aluminum Baths with Al2O3 and AlPO4 Additives  

NASA Astrophysics Data System (ADS)

The density of the KF-AlF3 melts of various KF and AlF3 ratio with Al2O3 and AlPO4 addition has been measured using the Archimedean method. On the basis of the obtained density data the molar volumes of the melts were calculated. These molar volumes decrease with concentration of Al2O3 or AlPO4. In the system containing AlPO4, the relation between cryolite ratios (CRs) vs slopes of molar volume trend lines was identified with excellent correlation factor of R 2 = 0.9844, while in the system containing Al2O3 a discontinuity at CR = 2.5 can be observed.

Vaskov, Zuzana; Kontrk, Martin; Mlynrikov, Jarmila; Bo?a, Miroslav

2015-02-01

222

Ductile - ductile beryllium aluminum metal matrix composite manufactured by extrusion1. Interim report, 1 December 1994-1 January 1995  

SciTech Connect

The current program is designed to develop a method for extruding a cast beryllium-aluminum composite, establish a basis for estimating the properties that can ultimately be achieved with an optimized process, and produce an extruded structural shape of moderate complexity. Specific technical objectives are as follows: 1. Develop an extrusion process suitable for beryllium-aluminum composites that maximizes product yield, minimizes processing steps, gives good surface finish, and is suited for producing complex shapes. 2.Determine mechanical and physical properties to demonstrate potential. 3. Define potential for property enhancements and cost reductions that could be achieved through continued development of this technology.

Levoy, N.F.

1995-01-01

223

Aluminum alloy  

NASA Technical Reports Server (NTRS)

This invention relates to aluminum alloys, particularly to aluminum-copper-lithium alloys containing at least about 0.1 percent by weight of indium as an essential component, which are suitable for applications in aircraft and aerospace vehicles. At least about 0.1 percent by weight of indium is added as an essential component to an alloy which precipitates a T1 phase (Al2CuLi). This addition enhances the nucleation of the precipitate T1 phase, producing a microstructure which provides excellent strength as indicated by Rockwell hardness values and confirmed by standard tensile tests.

Blackburn, Linda B. (inventor); Starke, Edgar A., Jr. (inventor)

1989-01-01

224

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

225

Fabrication and properties of mechanically milled alumina\\/aluminum nanocomposites  

Microsoft Academic Search

The reinforcement agglomeration in nanocomposites is a key issue that needs to be solved in order to fully benefit of the gain in strength and ductility associated with the decrease in reinforcement size from microscale to nanoscale. In this study, mechanical milling has been used successfully to disperse nanometric alumina (n-Al2O3) in an aluminum matrix. Al2O3\\/Al nanocomposite powders have been

Dominique Poirier; Robin A. L. Drew; Michel L. Trudeau; Raynald Gauvin

2010-01-01

226

Synthesis and structural characterization of a new aluminum oxycarbonitride, Al{sub 5}(O, C, N){sub 4}  

SciTech Connect

A new aluminum oxycarbonitride, Al{sub 5}(O{sub x}C{sub y}N{sub 4-x-y}) (x{approx}1.4 and y{approx}2.1), has been synthesized and characterized by X-ray powder diffraction, transmission electron microscopy and electron energy loss spectroscopy (EELS). The title compound was found to be hexagonal with space group P6{sub 3}/mmc, Z=2, and unit-cell dimensions a=0.328455(6) nm, c=2.15998(3) nm and V=0.201805(6) nm{sup 3}. The atom ratios O:C:N were determined by EELS. The final structural model, which is isomorphous with that of (Al{sub 4.4}Si{sub 0.6})(O{sub 1.0}C{sub 3.0}), showed the positional disordering of one of the three types of Al sites. The maximum-entropy method-based pattern fitting (MPF) method was used to confirm the validity of the split-atom model, in which conventional structure bias caused by assuming intensity partitioning was minimized. The reliability indices calculated from the MPF were R{sub wp}=6.94% (S=1.22), R{sub p}=5.34%, R{sub B}=1.35% and R{sub F}=0.76%. The crystal was an inversion twin. Each twin-related individual was isostructural with Al{sub 5}C{sub 3}N (space group P6{sub 3}mc, Z=2). - Graphical abstract: A new oxycarbonitride discovered in the Al-O-C-N system, Al{sub 5}(O{sub 1.4}C{sub 2.1}N{sub 0.5}). The crystal is an inversion twin, and hence the structure is represented by a split-atom model. The three-dimensional electron density distributions are determined by the maximum-entropy methods-based pattern fitting, being consistent with the disordered structural model. Display Omitted

Inuzuka, Haruya; Kaga, Motoaki; Urushihara, Daisuke [Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Nakano, Hiromi [Cooperative Research Facility Center, Toyohashi University of Technology, Toyohashi 441-8580 (Japan); Asaka, Toru [Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan); Fukuda, Koichiro, E-mail: fukuda.koichiro@nitech.ac.j [Department of Environmental and Materials Engineering, Nagoya Institute of Technology, Nagoya 466-8555 (Japan)

2010-11-15

227

Effects of Cu\\/Al intermetallic compound (IMC) on copper wire and aluminum pad bondability  

Microsoft Academic Search

Copper wire bonding is an alternative interconnection technology that serves as a viable, and cost saving alternative to gold wire bonding. Its excellent mechanical and electrical characteristics attract the high-speed, power management devices and fine-pitch applications. Copper wire bonding can be a potentially alternative interconnection technology along with flip chip interconnection. However, the growth of Cu\\/Al intermetallic compound (IMC) at

Hyoung-Joon Kim; Joo Yeon Lee; Kyung-Wook Paik; Kwang-Won Koh; J. Won; Sihyun Choe; Jin Lee; Jung-Tak Moon; Yong-Jin Park

2003-01-01

228

Wear mechanisms in hybrid composites of graphite-20 pct SiC in A356 aluminum alloy (Al-7 pct Si-0. 3 pct Mg)  

SciTech Connect

The wear behavior of A356 aluminum alloy (Al-7 pct Si-0.3 pct Mg) matrix composites reinforced with 20 vol pct SiC particles and 3 or 10 vol pct graphite was investigated. These hybrid composites represent the merging of two philosophies in tribological material design: soft-particle lubrication by graphite and hard-particle reinforcement by carbide particles. The wear tests were performed using a block-on-ring (SAE 52100 steel) wear machine under dry sliding conditions within a load range of 1 to 441 N. The microstructural and compositional changes that took place during wear were characterized using scanning electron microscopy (SEM), Auger electron spectroscopy (AES), energy-dispersive X-ray spectroscopy (EDXA), and X0ray diffractometry (XRD). The wear resistance of 3 pct graphite-20 pct SiC-A356 hybrid composite was comparable to 20 pct SiC-A356 without graphite at low and medium loads. At loads below 20 N, both hybrid and 20 pct SiC-A356 composites without graphite demonstrated wear rates up to 10 times lower than the unreinforced A356 alloy due to the load-carrying capacity of SiC particles. The wear resistance of 3 pct graphite 20 pct SiC-A356 was 1 to 2 times higher than 10 pct graphite-containing hybrid composites at high loads. However, graphite addition reduced the counterface wear. The unreinforced A356 and 20 pct SiC-A356 showed a transition from mild to severe wear at 95 N and 225 N, respectively. Hybrid composites with 3 pct and 10 pct graphite did not show such a transition over the entire load range, indicating that graphite improved the seizure resistance of the composites.

Ames, W.; Alpas, A.T. (Univ. of Windsor, Ontario (Canada). Dept. of Mechanical Engineering)

1995-01-01

229

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

230

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

231

Size Effect of SiC Particle on Microstructures and Mechanical Properties of SiCp/Al Composites  

E-print Network

matrix composites reinforced with ceramic particles have some attractive properties such as high strengthCp/Al composites were fabricated using aluminum alloy ZL101 as the matrix material, and SiC particles a composite is stretched, most of external load transfers from soft Al matrix to hard SiCp reinforcement

Qin, Qinghua

232

Chemical reactions between aluminum and fly ash during synthesis and reheating of Al-fly ash composite  

Microsoft Academic Search

Thermodynamic analysis indicates that there is the possibility of chemical reactions between aluminum melt and cenosphere\\u000a fly ash particles. These particles contain alumina, silica, and iron oxide, which, during solidification processing of aluminum-fly\\u000a ash composites or during holding of such composites at temperatures above the melting temperature of aluminum, are likely\\u000a to undergo chemical reduction. These chemical reactions between the

R. O. Guo; P. K. Rohatgi

1998-01-01

233

Precipitation behaviors in Al-Cu-Mg and 2024 aluminum alloys  

SciTech Connect

The precipitation behaviors and aging reactions of the pseudobinary Al-Cu-Mg alloy and the commercial 2024 alloy under unstretched and stretched conditions have been investigated in this study by means of conductivity and hardness measurements, differential scanning calorimetry, and transmission electron microscopy (TEM). The morphologies and growth modes of various defects and transition phases as well as the interaction among them were widely discussed. In particular, an electron diffraction ring pattern was found to correspond to the axial growth of the GPB2 zone. This suggested that the atom groups constructing this cylindrical zone are statistically, uniformly arranged in the adjacent {l_brace}100{r_brace}{sub Al} planes and the GPB2 zone is only a partially ordered version of the GPB zone in <001>{sub Al} directions. Moreover, few GPB2 zones can survive long time overaging due to the Gibbs-Thomson effect. As for the S{prime} precipitates, they preferentially nucleate on dislocations. During subsequent growth, they can further coalesce into two morphologies (corrugated sheets and wide plates) for the unstretched specimens. Therefore, the rate of Ostward ripening decreases and the peak hardness becomes flattened. Finally, based on the present analyses, the aging sequence of the two alloys studied could be revised with respect to previous investigations and their isothermal aging reactions can be subdivided into five main stages. These stages correspond to (1) GPB zone precipitation, (2) fast in situ precipitation of GPB2 zones from GPB zones and their subsequent growth, (3) fast nucleation and accelerating growth of the S{prime} phase, (4) decelerating growth of the S{prime} phase, and (5) Ostward ripening of the S{prime} and S phases, respectively.

Shih, H.C.; Ho, N.J.; Huang, J.C. [National Sun Yat-sen Univ., Kaohsiung (Taiwan, Province of China). Inst. of Materials Science and Engineering

1996-09-01

234

Tensile deformation of 2618 and Al-Fe-Si-V aluminum alloys at elevated temperatures  

NASA Technical Reports Server (NTRS)

The present study experimentally characterizes the effects of elevated temperature on the uniaxial tensile behavior of ingot metallurgy 2618 Al alloy and the rapidly solidified FVS 0812 P/M alloy by means of two constitutive formulations: the Ramberg/Osgood equation and the Bodner-Partom (1975) incremental formulation for uniaxial tensile loading. The elastoplastic strain-hardening behavior of the ingot metallurgy alloy is equally well represented by either formulation. Both alloys deform similarly under decreasing load after only 1-5 percent uniform tensile strain, a response which is not described by either constitutive relation.

Leng, Y.; Porr, W. C., Jr.; Gangloff, R. P.

1990-01-01

235

Magnetic properties of nickel nanoparticles embedded in amorphous Al2O3 matrix  

NASA Astrophysics Data System (ADS)

Multilayer thin films consisting of 10 bilayers of (Al2O3+Ni)/Al2O3 were deposited by magnetron sputtering onto Si(100) substrate. Nickel nanoparticles are formed inside amorphous alumina matrix by self-assembly growth process. It was determined by GISAXS measurements that nickel particles are spheroidal with diameter < 3 nm and that they form paracrystal-like body-centered tetragonal lattice. Magnetic properties of the prepared thin films were studied. Due to the nanometer size of nickel particles, their magnetic structure is single domain and they show superparamagnetic behaviour. Anisotropy of magnetic properties was observed when magnetic field is applied parallel or perpendicular to the thin film surface and it was attributed to dipole-dipole interactions between particles. This was confirmed using simulations of the M(H) curve of the 2D superlattice of the identical superparamagnetic particles, which was performed using Monte Carlo method and Metropolis algorithm.

Novosel, Nikolina; Reissner, Michael; Zadro, Kreo; Paji?, Damir; Jer?inovi?, Marko; Buljan, Maja; Radi?, Nikola

2014-12-01

236

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

237

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

238

Fatigue crack growth resistance in SiC particulate and whisker reinforced P\\/M 2124 aluminum matrix composites  

Microsoft Academic Search

Fatigue crack growth is examined in P\\/M 2124 aluminum alloys reinforced with SiC particles (SiCp) and whiskers (SiCw) over a wide spectrum of growth rates from 10?12 to 10?4 m per cycle. Effects of aging treatment, orientation of crack growth direction with respect to the rolling direction, mean stress (or stress ratio), and reinforcement volume percent on the fatigue crack

J. J. Mason; R. O. Ritchie

1997-01-01

239

Fluoride (F) is not taken up by Salmonella typhimurium TA98 (TA98), used for Ames mutagenicity test, unless aluminum (Al) is present  

SciTech Connect

TA98 is commonly used for the Ames test to detect frame-shift mutations. Ames test results for fluoride mutagenicity are controversial. Since Al and F, both present in finished drinking water, form a stable complex, the authors determined the effect of Al on F uptake by TA98 to evaluate any Al effect on Ames test results for F. A known number of TA98 in 0.1M potassium phosphate buffer was incubated with various concentrations of Al, F or aluminum fluoride for 1 hr at 37C in a shaking incubator. The cells were washed twice in potassium phosphate buffer and then resuspended in water. After breaking the cells open by sonication, the resulting supernatant was analyzed for Al by graphite furnace atomic absorption and for F using a F ion-selective electrode. Al accumulated in a concentration-dependent manner to 4.5 ppm then decreased rapidly as the Al was increased to 9 ppm. Intracellular F was below the limit of detection even when the medium contained 590 ppm F. However, F was taken up from media containing greater than 200 ppm F, providing that aluminum was also present. The authors conclude that the Ames test, using TA98, is not suitable for the detection of F mutagenicity.

Ahn, H.W.; Jeffery, E.H. (Univ. of Illinois, Urbana (United States))

1991-03-11

240

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

241

A study of the dielectric characteristics of aluminum oxide thin films deposited by spray pyrolysis from Al(acac) 3  

Microsoft Academic Search

The dielectric characteristics of aluminum oxide thin films deposited by the spray pyrolysis technique are reported. The films were deposited with different molarities from a spraying solution of aluminum acetylacetonate and N,N-dimethylformamide. The films were deposited on silicon substrates at temperatures ranging from 450 to 650C. The addition of water mist during the deposition process led to a remarkable improvement

M. Aguilar-Frutis; M Garcia; C Falcony; G Plesch; S Jimenez-Sandoval

2001-01-01

242

Scanning Electron Microscopy Analysis of Fuel/Matrix Interaction Layers in Highly-Irradiated UMo Dispersion Fuel Plates with Al and AlSi Alloy Matrices  

SciTech Connect

In order to investigate how the microstructure of fuel/matrix-interaction (FMI) layers change during irradiation, different U7Mo dispersion fuel plates have been irradiated to high fission density and then characterized using scanning electron microscopy (SEM). Specifially, samples from irradiated U7Mo dispersion fuel elements with pure Al, Al2Si and AA4043 (~4.5 wt.%Si) matrices were SEM characterized using polished samples and samples that were prepared with a focused ion beam (FIB). Features not observable for the polished samples could be captured in SEM images taken of the FIB samples. For the Al matrix sample, a relatively large FMI layer develops, with enrichment of Xe at the FMI layer/Al matrix interface and evidence of debonding. Overall, a significant penetration of Si from the FMI layer into the U7Mo fuel was observed for samples with Si in the Al matrix, which resulted in a change of the size (larger) and shape (round) of the fission-gas bubbles. Additionally, solid-fission-product phases were observed to nucleate and grow within these bubbles. These changes in the localized regions of the microstructure of the U7Mo may contribute to changes observed in the macroscopic swelling of fuel plates with AlSi matrices.

Dennis D. Keiser, Jr.; Jan-Fong Jue; Brandon D. Miller; Jian Gan; Adam B. Robinson; Pavel Medvedev; James Madden; Dan Wachs; Mitch Meyer

2014-04-01

243

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

244

CHARACTERIZATION AND PROPERTIES OF ALUMINUM COMPOSITE MATERIALS PREPARED BY POWDER METALLURGY TECHNIQUES USING CERAMIC SOLID WASTES  

Microsoft Academic Search

This work provides preliminary results of aluminum metal matrix composites (MMCs) reinforced with granulated slag (GS) and electric arc furnace dust (EAFD). The present work concerns the synthesis and properties of Al\\/GS and Al\\/EAFD composites based on powder metallurgy techniques. The hardness and compressive strength of the sintering compacts were determined to compare the mechanical properties of the composite material

L. Ma. Flores-Vlez; J. Chvez; L. Hernndez; O. Domnguez

2001-01-01

245

Reactions of liquid and solid aluminum clusters with N2: the role of structure and phase in Al114 (+), Al115 (+), and Al117 (+).  

PubMed

Kinetic energy thresholds have been measured for the chemisorption of N2 onto Al114 (+), Al115 (+), and Al117 (+) as a function of the cluster's initial temperature, from around 200 K up to around 900 K. For all three clusters there is a sharp drop in the kinetic energy threshold of 0.5-0.6 eV at around 450 K, that is correlated with the structural transition identified in heat capacity measurements. The decrease in the thresholds corresponds to an increase in the reaction rate constant, k(T) at 450 K, of around 10(6)-fold. No significant change in the thresholds occurs when the clusters melt at around 600 K. This contrasts with behavior previously reported for smaller clusters where a substantial drop in the kinetic energy thresholds is correlated with the melting transition. PMID:25429939

Cao, Baopeng; Starace, Anne K; Judd, Oscar H; Bhattacharyya, Indrani; Jarrold, Martin F

2014-11-28

246

Reactions of liquid and solid aluminum clusters with N2: The role of structure and phase in Al114+, Al115+, and Al117+  

NASA Astrophysics Data System (ADS)

Kinetic energy thresholds have been measured for the chemisorption of N2 onto Al114+, Al115+, and Al117+ as a function of the cluster's initial temperature, from around 200 K up to around 900 K. For all three clusters there is a sharp drop in the kinetic energy threshold of 0.5-0.6 eV at around 450 K, that is correlated with the structural transition identified in heat capacity measurements. The decrease in the thresholds corresponds to an increase in the reaction rate constant, k(T) at 450 K, of around 106-fold. No significant change in the thresholds occurs when the clusters melt at around 600 K. This contrasts with behavior previously reported for smaller clusters where a substantial drop in the kinetic energy thresholds is correlated with the melting transition.

Cao, Baopeng; Starace, Anne K.; Judd, Oscar H.; Bhattacharyya, Indrani; Jarrold, Martin F.

2014-11-01

247

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

248

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

249

Role of Al2O3 intermediate layer for improving the quality of polycrystalline-silicon film in inverted aluminum-induced layer exchange  

NASA Astrophysics Data System (ADS)

A thin Al2O3 intermediate layer prepared by atomic layer deposition was introduced into inverted aluminum-induced layer exchange (inverted-ALILE) to form high-quality polycrystalline silicon (poly-Si) thin layer. It was demonstrated that the continuity and quality of poly-Si were obviously improved by the Al2O3 layer. The fraction of (1 0 0)-oriented crystals reached 93%, and the average grain size of 28 ?m with uniform surface morphology and low defect density were achieved at the optimal Al2O3 thickness of 4 nm. It was also found that an a-AlOx layer always existed at the poly-Si/Al interface after inverted-ALILE process, which is independent on the original surface states. The results suggested that the thin poly-Si layer would be a promising epitaxial template for Si based thin film solar cells.

Duan, Weiyuan; Meng, Fanying; Bian, Jiantao; Yu, Jian; Zhang, Liping; Liu, Zhengxin

2015-02-01

250

Micro-strain Evolution and Toughening Mechanisms in a Trimodal Al-Based Metal Matrix Composite  

NASA Astrophysics Data System (ADS)

A trimodal metal matrix composite (MMC) based on AA (Al alloy) 5083 (Al-4.4Mg-0.7Mn-0.15Cr wt pct) was synthesized by cryomilling powders followed by compaction of blended powders and ceramic particles using two successive dual mode dynamic forgings. The microstructure consisted of 66.5 vol pct ultrafine grain (UFG) region, 30 vol pct coarse grain (CG) region and 3.5 vol pct reinforcing boron carbide particles. The microstructure imparted high-tensile yield strength (581 MPa) compared to a conventional AA 5083 (242 MPa) and enhanced ductility compared to 100 pct UFG Al MMC. The deformation behavior of the heterogeneous structure and the effects of CG regions on crack propagation were investigated using in situ scanning electron microscopy micro-tensile tests. The micro-strain evolution measured using digital image correlation showed early plastic strain localization in CG regions. Micro-voids due to the strain mismatch at CG/UFG interfaces were responsible for crack initiation. CG region toughening was realized by plasticity-induced crack closure and zone shielding of disconnected micro-cracks. However, these toughening mechanisms did not effectively suppress its brittle behavior. Further optimization of the CG distribution (spacing and morphology) is required to achieve toughness levels required for structural applications.

Zhang, Yuzheng; Topping, Troy D.; Yang, Hanry; Lavernia, Enrique J.; Schoenung, Julie M.; Nutt, Steven R.

2015-03-01

251

Effect of mechanical mixing on the microstructure and mechanical properties of Al-based metal matrix composites reinforced with nanocrystalline Al-Ca intermetallics  

NASA Astrophysics Data System (ADS)

Al-based metal matrix composites reinforced with 40 vol.% of nanocrystalline Al- Ca intermetallic particles were synthesized by hot pressing followed by hot extrusion process and the effect of manual blending as well as mechnical mixing on microstructure and mechanical properties was studied. Microstuture reveals that mannual blending leads to the agglomeration of Al-Ca intermetallic particles and on the other hand, the composites prepared by milling display a more homogeneous distribution of the reinforcing particles. Mechanical mixing has a strong impact on the mechanical properties. The strength increases from 112MPa for pure Al to 250 and 415MPa for the composites produced by blending and milling respectively. This behavior is linked to the reduced matrix ligament size characterizing the milled composites.

Chaubey, A. K.; Kumar, Rohit; Sahoo, Tapas

2015-02-01

252

Orientation relationship between ?-Fe precipitate and ?-Al2O3 matrix in iron-implanted sapphire.  

PubMed

Fe ions were implanted into ?-Al2O3 single crystals (sapphire) at room temperature and annealed in a reducing atmosphere. The orientation relationships (ORs) between ?-Fe particles and sapphire matrix were investigated using transmission electron microscopy (TEM). All the ?-Fe particles have the orientation relationship (OR) of (111)?-Fe||(0001)sapphire and [110]?-Fe||[1120]sapphire with sapphire. This OR is predicted precisely by the coincidence of reciprocal lattice points (CRLP) method. The other OR of (110)?-Fe||(0001)sapphire and [111]?-Fe||[5140]sapphire reported before is confirmed by the same method to be one of the secondary preferred orientation relationships in the ?-Fe/sapphire system. PMID:24811987

Wang, Y; Liu, X P; Qin, G W

2014-07-01

253

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

254

Microstructure and texture assessment of AlMnFeSi (3003) aluminum alloy produced by continuous and semicontinuous casting processes  

Microsoft Academic Search

Aluminum sheets are currently produced by the direct-chill process (DC). The need for low-cost aluminum sheets is a challenge\\u000a for the development of new materials produced by the twin roll caster (TRC) process. It is expected that sheets produced from\\u000a these different casting procedures will differ in their microstructure. These differences in microstructure and in the crystallographic\\u000a texture have great

J. P. Martins; A. L. M. Carvalho; A. F. Padilha

2009-01-01

255

Quaternary aluminum silicides grown in Al flux: RE5Mn4Al(23-x)Si(x) (RE = Ho, Er, Yb) and Er44Mn55(AlSi)237.  

PubMed

Four novel intermetallic silicides, RE5Mn4Al(23-x)Si(x) (x = 7.9(9), RE = Ho, Er, Yb) and Er44Mn55(AlSi)237, have been prepared by reaction in aluminum flux. Three RE5Mn4Al(23-x)Si(x) compounds crystallize in the tetragonal space group P4/mmm with the relatively rare Gd5Mg5Fe4Al(18-x)Si(x) structure type. Refinement of single-crystal X-ray diffraction data yielded unit cell parameters of a = 11.3834(9)-11.4171(10) and c = 4.0297(2)-4.0575(4) with volumes ranging from 522.41(5) to 528.90(8) (3). Structure refinements on single-crystal diffraction data show that Er44Mn55(AlSi)237 adopts a new cubic structure type in the space group Pm3n with a very large unit cell edge of a = 21.815(3) . This new structure is best understood when viewed as two sets of nested polyhedra centered on a main group atom and a manganese atom. These polyhedral clusters describe the majority of the atomic positions in the structure and form a perovskite-type network. We also report the electrical and magnetic properties of the title compounds. All compounds except the Ho analogue behave as normal paramagnetic metals without any observed magnetic transitions above 5 K and exhibit antiferromagnetic correlations deduced from the value of their Curie constants. Ho5Mn4Al(23-x)Si(x) exhibits a ferromagnetic transition at 20 K and an additional metamagnetic transition at 10 K, suggesting independent ordering temperatures for two distinct magnetic sublattices. PMID:23931551

Calta, Nicholas P; Kanatzidis, Mercouri G

2013-09-01

256

Critical Experiments with Highly Enriched Uranium and Matrix Elements (Si, Mg, Al, Gd, and Fe)  

SciTech Connect

Scientists at the Los Alamos National Laboratory measured the critical masses of square prisms of highly enriched uranium diluted in various X/{sup 235}U with matrix material and polyethylene. The configuration cores were 22.86 and 45.72 cm square and were reflected with 8.13-cm-thick and 10.16-cm-thick side polyethylene reflectors, respectively. The configurations had 10.16-cm-thick top and bottom polyethylene reflectors. For some configurations, the Rossi-{alpha}, which is an eigenvalue characteristic for a particular configuration, was measured to establish a reactivity scale based on the degree of subcriticality. These experiments provided critical mass data in the thermal energy range for systems containing Si, Mg, Al, Gd, and Fe. The measured k{sub eff} from these experiments was compared with the calculated k{sub eff} from MCNP using ENDF/B-V and ENDF/B-VI cross-section data. The observed biases were +0.005 {delta}k and +0.008 {delta}k for Si, +0.0006 {delta}k and +0.008 {delta}k for Al, +0.0023 {delta}k for Mg, +0.004 {delta}k and +0.01304 {delta}k for Gd, and +0.0123 {delta}k and -0.00106 {delta}k for Fe.

Sanchez, Rene; Loaiza, David; Brunson, Glenn; Kimpland, Robert [Los Alamos National Laboratory (United States)

2004-07-15

257

Chemical reactions between aluminum and fly ash during synthesis and reheating of Al-fly ash composite  

SciTech Connect

Thermodynamic analysis indicates that there is the possibility of chemical reactions between aluminum melt and cenosphere fly ash particles. These particles contain alumina, silica, and iron oxide, which, during solidification processing of aluminum-fly ash composites or during holding of such composites at temperatures above the melting temperature of the aluminum, are likely to undergo chemical reduction. These chemical reactions between the fly ash and molten aluminum have been studied by metallographic examination, differential thermal analysis (DTA), scanning electron microscopy (SEM), energy-dispersive X-ray analysis (EDX) and X-ray analysis after holding the aluminum-fly ash composites for different periods above the liquidus temperature. The experiments indicate that there is progressive reduction of silica and mullite in the fly ash, and formation of alumina with holding time of composites at a temperature of 850 C. The walls of the cenosphere fly ash particles progressively disintegrate into discrete particles as the reaction progresses. The rate of chemical reaction was high at the start of holding the composite at a temperature of 850 C, and then the rate significantly decreased with time. The reaction was almost complete after 10 hours.

Guo, R.Q.; Rohatgi, P.K. [Univ. of Wisconsin, Milwaukee, WI (United States). Dept. of Materials

1998-06-01

258

Melting process of nanometer-sized In particles embedded in an Al matrix synthesized by ball milling  

Microsoft Academic Search

Dispersions of nanometer-sized In particles embedded in an Al matrix (10 wt. % In) have been synthesized by ball milling of a mixture of Al and In powders. The as-milled product was characterized by using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectrometer (EDX), transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HREM), respectively. It

H.W. Sheng; J. Xu; Liguo Yu; X.K. Sun; Z.Q. Hu; K. Lu

1996-01-01

259

Effect of re-melting on particle distribution and interface formation in SiC reinforced 2124Al matrix composite  

SciTech Connect

The interface between metal matrix and ceramic reinforcement particles plays an important role in improving properties of the metal matrix composites. Hence, it is important to find out the interface structure of composite after re-melting. In the present investigation, the 2124Al matrix with 10 wt.% SiC particle reinforced composite was re-melted at 800 C and 900 C for 10 min followed by pouring into a permanent mould. The microstructures reveal that the SiC particles are distributed throughout the Al-matrix. The volume fraction of SiC particles varies from top to bottom of the composite plate and the difference increases with the decrease of re-melting temperature. The interfacial structure of re-melted 2124Al10 wt.%SiC composite was investigated using scanning electron microscopy, an electron probe micro-analyzer, a scanning transmission electron detector fitted with scanning electron microscopy and an X-ray energy dispersive spectrometer. It is found that a thick layer of reaction product is formed at the interface of composite after re-melting. The experimental results show that the reaction products at the interface are associated with high concentration of Cu, Mg, Si and C. At re-melting temperature, liquid Al reacts with SiC to form Al{sub 4}C{sub 3} and AlSi eutectic phase or elemental Si at the interface. High concentration of Si at the interface indicates that SiC is dissociated during re-melting. The X-ray energy dispersive spectrometer analyses confirm that Mg- and Cu-enrich phases are formed at the interface region. The Mg is segregated at the interface region and formed MgAl{sub 2}O{sub 4} in the presence of oxygen. The several elements identified at the interface region indicate that different types of interfaces are formed in between Al matrix and SiC particles. The AlSi eutectic phase is formed around SiC particles during re-melting which restricts the SiC dissolution. - Highlights: Re-melted composite shows homogeneous particle distribution Thick reaction products are observed at the interface Carbide is identified at interface due to SiC dissolution at high temperature Reaction products are also Si enrich phase Mg and Cu segregated and formed MgAl{sub 2}O{sub 4}, CuMgAl{sub 2} phase at grain boundary.

Mandal, Durbadal, E-mail: durbadal73@yahoo.co.in [MEF Division, CSIR-National Metallurgical Laboratory, Jamshedpur 831007 (India); Viswanathan, Srinath [Dept of Metallurgical and Materials Engineering, University of Alabama, Tuscaloosa, AL (United States)

2013-12-15

260

Tensile and compressive test results for metal matrix composites  

NASA Technical Reports Server (NTRS)

Experimental results of the mechanical behavior of two metal matrix composite systems at room temperature are presented. Ultimate stress, ultimate strain, Poisson's ratio, and initial Young's Modulus are documented for BORSIC/Aluminum in uniaxial tension and Boron/Aluminum in uniaxial tension and compression. Poisson's ratio is used for nonlinear stress-strain behavior. A comparison of compression results for B/Al as obtained from sandwich beam compression specimens and IITRI coupon compression specimens is presented.

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

1977-01-01

261

Characterization of reinforcement distribution in Al\\/(Al 2O 3) p composites obtained from composite powder  

Microsoft Academic Search

A composite powder Al(Al2O3)p obtained in a rotary-vibration mill was used as a semifinished component to manufacture particle-reinforced metal matrix composites (PRMMCs) using cast and powder metallurgy technologies. For a quantitative description of the inhomogeneity of Al2O3 particle distributions in the aluminum matrix the following methods were applied: nearest neighbor distance, radial distribution function, influence zone morphology, systematic scanning and

Anita Olszwka-Myalska; Janusz Szala; Jan Cwajna

2001-01-01

262

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

263

Comparison of post-detonation combustion in explosives incorporating aluminum nanoparticles: Influence of the passivation layer  

NASA Astrophysics Data System (ADS)

Aluminum nanoparticles and explosive formulations that incorporate them have been a subject of ongoing interest due to the potential of aluminum particles to dramatically increase energy content relative to conventional organic explosives. We have used time-resolved atomic and molecular emission spectroscopy to monitor the combustion of aluminum nanoparticles within the overall chemical dynamics of post-detonation fireballs. We have studied the energy release dynamics of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) charges incorporating three types of aluminum nanoparticles: commercial oxide-passivated nanoparticles, oleic acid-capped aluminum nanoparticles (AlOA), and nanoparticles in which the oxide shell of the particle has been functionalized with an acrylic monomer and copolymerized into a fluorinated acrylic matrix (AlFA). The results indicate that the commercial nanoparticles and the AlFA nanoparticles are oxidized at a similar rate, while the AlOA nanoparticles combust more quickly. This is most likely due to the fact that the commercial nano-Al and the AlFA particles are both oxide-passivated, while the AlOA particles are protected by an organic shell that is more easily compromised than an oxide layer. The peak fireball temperatures for RDX charges containing 20 wt. % of commercial nano-Al, AlFA, or AlOA were 3900 K, 3400 K, and 4500 K, respectively.

Lewis, W. K.; Rumchik, C. G.; Smith, M. J.; Fernando, K. A. S.; Crouse, C. A.; Spowart, J. E.; Guliants, E. A.; Bunker, C. E.

2013-01-01

264

Thermodynamics of aqueous aluminum: standard partial molar heat capacities of Al/sup 3 +/ from 10 to 55/sup 0/C  

SciTech Connect

The thermodynamic properties of aqueous aluminum species are required over wide ranges of temperature in order to model mineral dissolution and transport in steam injection and combustion processes for the in situ recovery of bitumen. The same data are needed to model aqueous solutions associated with the formation of hydrothermal ore deposits, geothermal power generation, the marine chemistry of deep hydrothermal vents, hydrometallurgy, and the corrosion behavior of aluminum alloys. Apparent molar heat capacities and volumes of Al(NO/sub 3/)/sub 3/ and AlCl/sub 3/ have been measured at 25/sup 0/C in dilute aqueous acid solutions to suppress hydrolysis. Heat capacity results for AlCl/sub 3/ span the range 10-55/sup 0/C. The measurements yield standard partial molar heat capacities, anti C/sub p//sup 0/, and volumes, anti V/sup 0/, for the Al/sup 3 +/ (aq) ion: anti V/sub 298//sup 0/ (Al/sup 3 +/, aq) = -45.3 cm/sup 3/ mol/sup -1/, anti C/sub pT//sup 0/(Al/sup 3 +/, aq) = 566.2 - 1.452% - 27338/(T - 190), where T is the absolute temperature (K). Their result for anti V/sub 298//sup 0/ is consistent with published semi-empirical correlations. The result for anti C/sub p298//sup 0/ is more negative than that predicted from the entropy correspondence principle by 135 J K/sup -1/ mol/sup -1/ and casts doubt upon the correspondence method as a predictive tool. The heat capacities approach born behavior at elevated temperatures and appear to be consistent with the Helgeson-Kirkham-Flowers model for extrapolations to higher temperatures.

Hovey, J.K.; Tremaine, P.R.

1986-03-01

265

Microstructure and Grain Growth of the Matrix of SiCf/Ti-6Al-4V Composites Prepared by the Consolidation of Matrix-Coated Fibers in the ?+ ? Phase Field  

NASA Astrophysics Data System (ADS)

Both the microstructural characteristics and the grain growth of the matrix materials in the SiCf/Ti-6Al-4V composites were investigated by means of experimental tests coupled with theoretical assessment. A very fine matrix microstructure was obtained in the SiCf/Ti-6Al-4V composites that were prepared by the consolidation of matrix-coated fiber (MCF) in the ?+ ? phase field. During a fabrication process through the MCF method, the matrix microstructure after consolidation processing will evolve from the columnar crystals to a fully-lamellar microstructure. The experimental results especially the grain sizes of matrix microstructure were reasonably explained based on theoretical calculations.

Zhao, Guangming; Yang, Yanqing; Zhang, Wei; Luo, Xian; Huang, Bin; Chen, Yan

2015-02-01

266

Maize aluminum tolerance  

Technology Transfer Automated Retrieval System (TEKTRAN)

Maize is one of the most economically important food crops grown on acid soils, where aluminum (Al) toxicity greatly limits crop yields. Considerable variation for Al tolerance exists in maize, and this variation has been exploited for many years by plant breeders to enhance maize Al tolerance. Curr...

267

The crystal structure of aluminum molybdate, Al 2(MoO 4) 3, determined by time-of-flight powder neutron diffraction  

NASA Astrophysics Data System (ADS)

The room temperature crystal structure of aluminum molybdate, Al 2(MoO 4) 3, was refined using time-of-flight powder neutron diffraction data. It is monoclinic, with a = 15.3803(9), b = 9.0443(1) , c = 17.888(1) , and ? = 125.382(3), space group {P2 1}/{a}. It is isostructural with Fe 2(MoO 4) 3 and Cr 2(MoO 4) 3. The application of the Rietveld method to complex structures is discussed.

Harrison, W. T. A.; Cheetham, A. K.; Faber, J.

1988-10-01

268

Analysis of anisotropy in elastic constants of SiC{sub p}/2124 Al metal matrix composites  

SciTech Connect

The present study has attempted to investigate the effect of microstructural parameters on the elastic moduli of SiC particle reinforced 2124 Al matrix composites. Nine elastic-stiffness constants of SiC{sub p}/2124 Al composites have been determined by the RUS measurement method. At the same time, the initial estimates of elastic constants for RUS have been obtained using the Mori-Tanaka theory considering the effective aspect ratio of the SiC particles. The effects of particle size and the volume fraction of SiC particulate reinforcement on the elastic properties of the SiC{sub p}/2124 Al composites have been discussed.

Jung, H.K.; Cheong, Y.M.; Ryu, H.J.; Hong, S.H.

1999-11-19

269

Homocatenation of Aluminum: Alkane-like Structures of Li2 Al2 H6 and Li3 Al3 H8.  

PubMed

Invited for the cover of this issue is Alexander I. Boldyrev and co-workers at Utah State University. The image depicts the magician who symbolizes a chemist synthesizing molecules of "aluminum homocatenated ethane and propane" based on the idea of electronic transmutation. Read the full text of the article at 10.1002/chem.201500298. PMID:25736330

Gish, J Tyler; Popov, Ivan A; Boldyrev, Alexander I

2015-03-27

270

The mechanical properties of a composite coating with a polymer matrix based on sodium carboxymethylcellulose and aluminum powder  

Microsoft Academic Search

The influence of the contents of sodium carboxymethylcellulose, glycerol, Al powder, and its particle size on the mechanical\\u000a strength and relative deformation of the composite coating (CC) made of these components is investigated at various temperatures.\\u000a The regression models describing the interrelation between the mechanical properties of the CC and its composition, which\\u000a allow one to predict the final characteristics

N. M. Antonova

2009-01-01

271

The containment of oil spills in porous media using xanthan/aluminum solutions, gelled by gaseous CO2 or by AlCl3 solutions.  

PubMed

The gelation in situ of polymers may be a method for temporarily containing organic solvents and other petroleum derived products, which may enter the subsurface. In order to create gels that are neither toxic to humans nor to the ecosystem, we have investigated on the use of the biopolymer xanthan gum with aluminum as a crosslinking agent. Firstly we have considered xanthan/sodium aluminate solutions, which upon preparation are strongly basic and do not gel. The gelation takes place in acid solutions so that Al(III) ions are released, and is instantaneous. Therefore, a special technique must be used for generating the gel structure in situ. The un-gelled solution must be injected and an acid must be added afterwards. We have investigated on the gelling reaction induced by gaseous carbon dioxide, which is an acid gas. The insufflation of CO(2) above the solution generates a layer of gel whose thickness progressively increases as CO(2) diffuses in the polymer solution. Secondly we have investigated on the use of aluminum chloride as the source of Al(III) ions. Also in this case, due to the full availability of Al(III) ions, the gelling reaction would be instantaneous. Therefore, the solution of AlCl(3) must be added on the top of the xanthan solution after its injection. For both gelling systems we have studied both theoretically and experimentally the rate of formation of the gel layer which progressively thickens after the insufflation of CO(2) or after the addition of the AlCl(3) solution. PMID:16935417

Gioia, Francesco; Ciriello, Pier Paolo

2006-12-01

272

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

273

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

274

Thermal and mechanical fatigue of laminated 6061 Al - P100 Gr metal matrix composite. Master's thesis  

Microsoft Academic Search

Aluminum-Graphite composite material was tested under thermal and mechanical cyclic loads. Initial thermal cycling experiments of a diffusion bonded, 11 ply composite showed crack nucleation at regions of poor liquid metal infiltration in the fiber tows when heated from room temperature (RT) to 540 C after one cycle. Similar experiments from RT to 100 C did not show similar damage

1990-01-01

275

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

276

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

277

Laser vaporization generation of the SiB and SiAl radicals for matrix isolation electron spin resonance studies; comparison with theoretical  

E-print Network

Laser vaporization generation of the SiB and SiAl radicals for matrix isolation electron spin containing seven valence electrons which have beenrecently studiedby matrix isolation ESR and theoret- ical of this experimental study. The neon matrix mag- netic parameters (MHz) for Si "B are 0=800(2), gll =2.0014(g), g, =2

Morse, Michael D.

278

Lightweight Aluminum/Nano composites for Automotive Drive Train Applications  

SciTech Connect

During Phase I, we successfully processed air atomized aluminum powders via Dynamic Magnetic Compaction (DMC) pressing and subsequent sintering to produce parts with properties similar to wrought aluminum. We have also showed for the first time that aluminum powders can be processed without lubes via press and sintering to 100 % density. This will preclude a delube cycle in sintering and promote environmentally friendly P/M processing. Processing aluminum powders via press and sintering with minimum shrinkage will enable net shape fabrication. Aluminum powders processed via a conventional powder metallurgy process produce too large a shrinkage. Because of this, sinter parts have to be machined into specific net shape. This results in increased scrap and cost. Fully sintered aluminum alloy under this Phase I project has shown good particle-to-particle bonding and mechanical properties. We have also shown the feasibility of preparing nano composite powders and processing via pressing and sintering. This was accomplished by dispersing nano silicon carbide (SiC) powders into aluminum matrix comprising micron-sized powders (<100 microns) using a proprietary process. These composite powders of Al with nano SiC were processed using DMC press and sinter process to sinter density of 85-90%. The process optimization along with sintering needs to be carried out to produce full density composites.

Chelluri, Bhanumathi; Knoth, Edward A.; Schumaker, Edward J.

2012-12-14

279

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

280

Visible photoluminescence in polycrystalline terbium doped aluminum nitride (Tb:AlN) ceramics with high thermal conductivity  

SciTech Connect

Thermal management continues to be one of the major challenges in the development of high powered light sources such as solid state lasers. In particular, the relatively low thermal conductivity of standard photoluminescent (PL) materials limits the overall power output and/or duty cycle. We present a method based on current activated pressure assisted densification for the fabrication of high thermal conductivity PL materials: rare earth doped polycrystalline bulk aluminum nitride. Specifically, the ceramics are translucent and are doped with Tb{sup 3+}, allowing for emission in the visible. Remarkably, the ceramics have a room temperature thermal conductivity of 94 W/(m K) which is almost seven times higher than that of the state of the art host material, Nd-doped yttrium aluminum garnet. These light emitting properties coupled with very high thermal conductivity should enable the development of a wide variety of more powerful light sources.

Wieg, A. T.; Kodera, Y.; Wang, Z.; Garay, J. E. [Department of Mechanical Engineering, Materials Science and Engineering Program, University of California, Riverside, California 92521 (United States); Imai, T. [Department of Materials Chemistry, Ryukoku University, Ohtsu (Japan); Dames, C. [Department of Mechanical Engineering, University of California, Berkeley, California 94720 (United States)

2012-09-10

281

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

282

ZnO:Al cathode for highly efficient, semitransparent 4% organic solar cells utilizing TiOx and aluminum interlayers  

NASA Astrophysics Data System (ADS)

We report on the fabrication of highly efficient, semitransparent bulk heterojunction solar cells comprising poly[[9-(1-octylnonyl)-9h-carbazole-2,7-diyl]-2,5-thiophenediyl-2,1,3-benzothiadiazole-4,7-diyl-2,5-thiophenediyl] (PCDTBT) blended with [6,6]-phenyl-C71-butyric acid methyl (PC71BM) esters as active layer. As semitransparent cathode sputtered aluminum doped ZnO was used in combination with a sputter damage preventing, thin (8 nm) TiOx layer processed from solution and a sputtered aluminum interlayer (ALI). The short circuit current improves for thicker ALIs due to increased reflectance at the cathode leading to average efficiencies of 4.0% for semitransparent solar cells. Comparable results (3.9%) were achieved for devices comprising thick absorbers and thin ALIs.

Bauer, Andreas; Wahl, Tina; Hanisch, Jonas; Ahlswede, Erik

2012-02-01

283

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

284

Utilization of aluminum sludge and aluminum slag (dross) for the manufacture of calcium aluminate cement  

Microsoft Academic Search

Four calcium aluminate cement mixes were manufactured from aluminum sludge as a source of calcium oxide and Al2O3 and aluminum slag (dross) as a source of aluminum oxide with some additions of pure alumina. The mixes were composed of 3550% aluminum sludge, 37.5048.75% aluminum slag (dross) and 12.5016.25% aluminum oxide. The mixed were processed then sintered at different firing temperatures

E. M. M. Ewais; N. M. Khalil; M. S. Amin; Y. M. Z. Ahmed; M. A. Barakat

2009-01-01

285

Effects of Wet Chemical and Trimethyl Aluminum Treatments on the Interface Properties in Atomic Layer Deposition of Al2O3 on InAs  

NASA Astrophysics Data System (ADS)

The reduction of native oxides on an InAs surface using various wet and dry chemical treatments, including hydrochloric acid (HCl) treatment, sulfide treatment, and in situ trimethyl aluminum (TMA) treatment before the atomic layer deposition (ALD) of Al2O3 on InAs is studied. X-ray photoelectron spectrum (XPS) results show that the effect of surface cleaning by TMA was apparent almost after the first pulse but that TMA cleaning is not as effective as wet chemical surface cleaning. The combination of wet chemical treatment and TMA pretreatment is the most effective method for InAs surface cleaning, as indicated by the XPS analysis. Capacitance-voltage (C-V) and current density-voltage (J-V) characteristics on metal-oxide-semiconductor capacitance (MOSCAP) structures were also investigated to evaluate the Al2O3/n-InAs interface quality after different surface treatments, and the results are consistent with the XPS analysis.

Trinh, Hai-Dang; Chang, Edward Yi; Wong, Yuen-Yee; Yu, Chih-Chieh; Chang, Chia-Yuan; Lin, Yueh-Chin; Nguyen, Hong-Quan; Tran, Binh-Tinh

2010-11-01

286

D.D. Luong et al. / Journal of Alloys and Compounds 550 (2013) 412422 412 Development of high performance lightweight aluminum alloy/SiC hollow sphere syntactic foams and compressive  

E-print Network

properties are considerably higher than the existing fly ash cenosphere filled aluminum matrix syntactic Gupta1,* , and Kyu Cho3 1 Composite Materials and Mechanics Laboratory, Department of Mechanical (up to 1520 s-1 ) compressive properties. Such closed cell composite foams, called syntactic foams

Gupta, Nikhil

2013-01-01

287

Aluminum powder metallurgy processing  

SciTech Connect

The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization, commercial inert gas atomization, and gas atomization reaction synthesis (GARS). A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a conventional consolidation process for fabricating aerospace components with aluminum powder and a proposed alternative. The consolidation procedures were compared by evaluating the consolidated microstructures and the corresponding mechanical properties. A low temperature solid state sintering experiment demonstrated that tap densified GARS aluminum powders can form sintering necks between contacting powder particles, unlike the total resistance to sintering of commercial air atomization aluminum powder.

Flumerfelt, J.F.

1999-02-12

288

Strength and Formability Improvement of Al-Cu-Mn Aluminum Alloy Complex Parts by Thermomechanical Treatment with Sheet Hydroforming  

NASA Astrophysics Data System (ADS)

Normally, the strength and formability of aluminum alloys can be increased largely by severe plastic deformation and heat treatment. However, many plastic deformation processes are more suitable for making raw material, not for formed parts. In this article, an experimental study of the thermomechanical treatment by using the sheet hydroforming process was developed to improve both mechanical strength and formability for aluminum alloys in forming complex parts. The limiting drawing ratio, thickness, and strain distribution of complex parts formed by sheet hydroforming were investigated to study the formability and sheet-deformation behavior. Based on the optimal formed parts, the tensile strength, microhardness, grain structure, and strengthening precipitates were analyzed to identify the strengthening effect of thermomechanical treatment. The results show that in the solution state, the limiting drawing ratio of cylindrical parts could be increased for 10.9% compared with traditional deep drawing process. The peak values of tensile stress and microhardness of formed parts are 18.0% and 12.5% higher than that in T6 state. This investigation shows that the thermomechanical treatment by sheet hydroforming is a potential method for the products manufacturing of aluminum alloy with high strength and good formability.

Chen, Yi-Zhe; Liu, Wei; Yuan, Shi-Jian

2015-01-01

289

Formation of ordered films of axially bridged aluminum phthalocyanine [(tBu){sub 4}PcAl]{sub 2}O via magnetic field-induced reaction  

SciTech Connect

The ?-(oxo)bis[tetra-tert-butylphthalocyaninato] aluminum(III) [(tBu){sub 4}PcAl]{sub 2}O films with the crystallites oriented preferably in one direction were obtained via chemical transformation of tetra-tert-butylsubstituted chloroaluminum(III) phthalocyanine (tBu){sub 4}PcAlCl film upon its annealing in magnetic field. A comparative analysis of the influence of post-deposition annealing process without and under applied magnetic field of 1 T, on the orientation and morphology of (tBu){sub 4}PcAlCl and [(tBu){sub 4}PcAl]{sub 2}O films, has been carried out by the methods of UV-vis, Infrared and Raman spectroscopies, XRD as well as atomic force microscopy. The formation of [(tBu){sub 4}PcAl]{sub 2}O films with elongated crystallites having preferential orientation was observed upon heating of the films in magnetic field while annealing without magnetic field under the same conditions does not demonstrate any effect on the structure and morphology of these films. The reasons of the sensitivity of this reaction to the presence of such magnetic field is discussed and studied by electronic paramagnetic resonance spectroscopy.

Basova, Tamara, E-mail: basova@niic.nsc.ru; Berezin, Aleksei; Nadolinny, Vladimir [Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Lavrentiev Pr., 3, 630090 Novosibirsk (Russian Federation)] [Nikolaev Institute of Inorganic Chemistry, Russian Academy of Sciences, Lavrentiev Pr., 3, 630090 Novosibirsk (Russian Federation); Peisert, Heiko; Chass, Thomas [Institute for Physical and Theoretical Chemistry, Auf der Morgenstelle 18, 72076 Tbingen (Germany)] [Institute for Physical and Theoretical Chemistry, Auf der Morgenstelle 18, 72076 Tbingen (Germany); Banimuslem, Hikmat; Hassan, Aseel [Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield S1 1WB (United Kingdom)] [Materials and Engineering Research Institute, Sheffield Hallam University, Sheffield S1 1WB (United Kingdom)

2013-11-28

290

Study on effects of powder and flake chemistry and morphology on the properties of Al-Cu-Mg-X-X-X powder metallurgy advanced aluminum alloys  

NASA Technical Reports Server (NTRS)

A study was conducted: (1) to develop rapid solidification processed (RSP) dispersoid-containing Al-3Cu-2Li-1Mg-0.2Zr alloys as substitutes for titanium alloys and commercial 2XXX aluminum alloys for service to at least 150 C; and (2) to develop RSP Al-4Li-Cu-Mg-Zr alloys as substitutes for high-strength commercial 7XXX alloys in ambient-temperature applications. RSP Al-3Cu-2Li-1Mg-0.2Zr alloys have density-normalized yield stresses at 150 C up to 52% larger than that of 2124-T851 and up to 30% larger than that of Ti-6Al-4V. Strength at 150 C in these alloys is provided by thermally stable delta' (Al3Li), T1 (Al2LiCu), and S' (Al2CuMg) precipitates. Density-normalized yield stresses of RSP Al-3Cu-2Li-1Mg-0.2Zr alloys are up to 100% larger than that of 2124-T851 and equivalent to that of Al-8Fe-4Ce at 260 C. Strength in the RSP alloys at 260 C is provided by incoherent dispersoids and subboundary constituent particles such as T1 and S. The RSP alloys are attractive substitutes in less than or = 100-h exposures for 2xxx and Al-4Fe-Ce alloys up to 260 C and for titanium alloys up to 150 C. RSP Al-4Li-Cu-Mg-Zr alloys have ambient-temperature yield and ultimate tensile stresses similar to that of 7050-T7651, and are 14% less dense. RSP Al-4Li-0.5Cu-1.5Mg-0.2Zr has a 20% higher specific yield stress, 40% higher specific elastic modulus, and superior corrosion resistance compared to the properties of 7050-T7651. Strength in the Al-4Li-Cu-Mg-Zr alloy class is primarily provided by the substructure and delta' precipitates and is independent of Cu:Mg ratio. Improvements in fracture toughness and transverse-orientation properties in both alloy classes depend on improved melt practices to eliminate oxide inclusions which are incorporated into the consolidated forms.

Meschter, P. J.; Lederich, R. J.; Oneal, J. E.

1986-01-01

291

Hot-deformation behaviour of spray-formed 2014 Al + SiC P metal matrix composites  

Microsoft Academic Search

In the present investigation, discontinuous SiC particle reinforced 2014 Al alloy based metal matrix composites have been produced by spray forming process. The composites contained average particle sizes of 17, 30 and 58?m in the range of 511vol.%. The composites were tested for their compressive flow behaviour, in unlubricated condition, at strain rates of 0.01, 0.1 and 1.0s?1 and at

V. C. Srivastava; V. Jindal; V. Uhlenwinkel; K. Bauckhage

2008-01-01

292

Aluminum for plasmonics.  

PubMed

Unlike silver and gold, aluminum has material properties that enable strong plasmon resonances spanning much of the visible region of the spectrum and into the ultraviolet. This extended response, combined with its natural abundance, low cost, and amenability to manufacturing processes, makes aluminum a highly promising material for commercial applications. Fabricating Al-based nanostructures whose optical properties correspond with theoretical predictions, however, can be a challenge. In this work, the Al plasmon resonance is observed to be remarkably sensitive to the presence of oxide within the metal. For Al nanodisks, we observe that the energy of the plasmon resonance is determined by, and serves as an optical reporter of, the percentage of oxide present within the Al. This understanding paves the way toward the use of aluminum as a low-cost plasmonic material with properties and potential applications similar to those of the coinage metals. PMID:24274662

Knight, Mark W; King, Nicholas S; Liu, Lifei; Everitt, Henry O; Nordlander, Peter; Halas, Naomi J

2014-01-28

293

Microstructure and tribological properties of laser clad CaF 2\\/Al 2O 3 self-lubrication wear-resistant ceramic matrix composite coatings  

Microsoft Academic Search

Self-lubrication wear-resistant CaF2\\/Al2O3 ceramic matrix composite coatings were fabricated on substrates of Al2O3 by laser cladding CaF2Al2O3 mixed powder blends. Compared with laser clad monolithic Al2O3 coatings, the CaF2\\/Al2O3 coating has much superior wear resistance and noticeably lower friction coefficient under dry sliding wear test conditions.

H. M. Wang; Y. L. Yu; S. Q. Li

2002-01-01

294

Effect of forging parameters on low cycle fatigue behaviour of Al/basalt short fiber metal matrix composites.  

PubMed

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

295

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

296

Aluminum in Superconducting Magnets Robert J. Weggel  

E-print Network

Aluminum in Superconducting Magnets Robert J. Weggel Magnet Optimization Research Engineering is aluminum, either ultrapure, as quenchstabilization matrix metal, and/or alloyed and coldworked and heat for magnets in which the stresses and strains are modest. The strongest aluminum alloy commercially available

McDonald, Kirk

297

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

298

Influence of shear force on floc properties and residual aluminum in humic acid treatment by nano-Al??.  

PubMed

The impacts of various shear forces on floc sizes and structures in humic acid coagulations by polyaluminum chloride (PACl) and nano-Al13 were comparatively studied in this paper. The dynamic floc size was monitored by use of a laser diffraction particle sizing device. The floc structure was evaluated in terms of fractal dimension, analyzed by small-angle laser light scattering (SALLS). The effect of increased shear rate on residual Al of the coagulation effluents was then analyzed on the basis of different floc characteristics generated under various shear conditions. The results showed that floc size decreased with the increasing shear rate for both Al13 and PACl. Besides, floc strength and re-formation ability were also weakened by the enhanced shear force. Al13 resulted in small, strong and better recoverable flocs than PACl and moreover, in the shear range of 100-300 revolution per minute (rpm) (G=40.7-178.3s(-1)), the characteristics of HA-Al13 flocs displayed smaller scale changes than those of HA-PACl flocs. The results of residual Al measurements proved that with shear increased, the residual Al increased continuously but Al13 presented less sensitivity to the varying shear forces. PACl contributed higher residual Al than Al13 under the same shear condition. PMID:24583809

Xu, Weiying; Gao, Baoyu; Du, Bin; Xu, Zhenghe; Zhang, Yongfang; Wei, Dong

2014-04-30

299

Analysis of the microstructure and reinforcement distribution of an extruded particle-reinforced Al 6061-10 volume percent Al2O3 metal matrix composite. Master's thesis  

SciTech Connect

This research was performed in conjunction with funding by DURALCAN-USA through a Cooperative Research and Development Agreement (CRDA). The program seeks to improve the ductility of cast and extruded Al 6061-Al203 metal matrix composite (MMC) materials. Annealing stages were designed to be introduced into combined extrusion and drawing operations during the processing of the MMCs. This work has included a comprehensive analysis of a composite's microstructure as related to processing strains ranging from zero to 5.32 during extrusion/drawing operations. As the strains were increased, particle clusters present in the as-cast material were dispersed and the particle distribution became more uniform. Strains of greater than 4.0 were required in order to disperse the clusters and substantially eliminate banding of the particle distribution. The recrystallized grain size in the Al matrix decreased as increased processing strain was applied to the material. The grain size appeared to be stable and resistant to coarsening during subsequent solution heat treatment. Quantitative image analysis revealed no change in apparent particle size or aspect ratio indicating no fracturing of the particles during processing. The image analysis revealed no readily measurable feature to be used to assess uniformity of the particle distribution.

Longenecker, F.W.

1993-09-01

300

Melting process of nanometer-sized in particles embedded in an Al matrix synthesized by ball milling  

SciTech Connect

Dispersions of nanometer-sized In particles embedded in an Al matrix (10 wt.{percent} In) have been synthesized by ball milling of a mixture of Al and In powders. The as-milled product was characterized by using x-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive x-ray spectrometer (EDX), transmission electron microscopy (TEM), and high resolution transmission electron microscopy (HREM), respectively. It was found that In and Al are pure components immiscible with each other, with nanometer-sized In particles dispersively embedded in the Al matrix. The melting behavior of In particles was investigated by means of differential scanning calorimeter (DSC). The calorimetric measurements indicate that both the melting point and the melting enthalpy of the In nanoparticles decrease with increasing milling time, or refinement of the In particles. Compared to its bulk melting temperature, a melting point depression of 13.4 K was observed when the mean grain size of In is 15 nm, and the melting point depression of In nanoparticles is proportional to the reciprocal of the mean grain size. The melting enthalpy depression was interpreted according to the two-state concept for the nanoparticles. Melting of the interface was deduced to be an exothermal process due to its large excess energy/volume. {copyright} {ital 1996 Materials Research Society.}

Sheng, H.W.; Xu, J.; Yu, L.G.; Sun, X.K.; Hu, Z.Q.; Lu, K. [State Key Laboratory for RSA, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110015, People`s Republic of (China)

1996-11-01

301

A directionally solidified iron--chromium aluminum--tantalum carbide eutectic alloy. [Fe13. 6 Cr3. 7Al9TaC  

Microsoft Academic Search

A eutectic alloy, Fe--13.6Cr--3.7Al+9TaC, was directionally solidified in a high gradient furnace, producing a microstructure of aligned TaC fibers in an oxidation resistant alpha-iron matrix. Tensile and stress rupture properties, thermal cycling resistance, and microstructures were evaluated. The alloy displays at 1000 C an ultimate tensile strength of 58 MPa and a 100-hour rupture life at a stress of 21

Harf

1977-01-01

302

Wettability of Aluminum on Alumina  

NASA Astrophysics Data System (ADS)

The wettability of molten aluminum on solid alumina substrate has been investigated by the sessile drop technique in a 10-8 bar vacuum or under argon atmosphere in the temperature range from 1273 K to 1673 K (1000 C to 1400 C). It is shown that the reduction of oxide skin on molten aluminum is slow under normal pressures even with ultralow oxygen potential, but it is enhanced in high vacuum. To describe the wetting behavior of the Al-Al2O3 system at lower temperatures, a semiempirical calculation was employed. The calculated contact angle at 973 K (700 C) is approximately 97 deg, which indicates that aluminum does not wet alumina at aluminum casting temperatures. Thus, a priming height is required for aluminum to infiltrate a filter. Wetting in the Al-Al2O3 system increases with temperature.

Bao, Sarina; Tang, Kai; Kvithyld, Anne; Tangstad, Merete; Engh, Thorvald Abel

2011-12-01

303

Aluminum carboxymethyl cellulose-rice bran microcapsules: enhancing survival of Lactobacillus reuteri KUB-AC5.  

PubMed

This research aimed to enhance the survival of Lactobacillus reuteri KUB-AC5 from heat conditioning by using microencapsulation with aluminum carboxymethyl cellulose-rice bran (AlCMC-RB) composites of different weight ratios of 1:0, 1:1, and 1:1.5. The cell/polymer suspension was crosslinked with aluminum chloride at different agitation speeds of 1200, 1500, and 2100 rpm. The AlCMC microcapsules had significantly higher encapsulation efficiency, but lower microcapsule yield than the AlCMC-RB microcapsules (p?0.05). Scanning electron microscopy revealed the complexation between AlCMC and RB. Fourier transform infrared spectroscopy showed hydrogen bondings between AlCMC, RB, and cells. The AlCMC-RB microcapsules had significantly lower aluminum ion and moisture contents than the AlCMC ones. After heat exposure, the viability of non-encapsulated and microencapsulated cells in the AlCMC matrix dramatically declined, while that of microencapsulated cells in the AlCMC-RB matrix was about 8 log CFU/g. The results showed the promising potential of the AlCMC-RB composite microcapsules for the protection of probiotics against heat. PMID:24751013

Chitprasert, Pakamon; Sudsai, Polin; Rodklongtan, Akkaratch

2012-09-01

304

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

305

'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

306

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 ...

307

Aluminum anode for aluminum-air battery - Part I: Influence of aluminum purity  

NASA Astrophysics Data System (ADS)

2N5 commercial grade aluminum (99.5% purity) leads to the lower aluminum-air battery performances than 4N high pure grade aluminum (99.99% purity) due to impurities itself and formed impurity complex layer which contained Fe, Si, Cu and others. The impurity complex layer of 2N5 grade Al declines the battery voltage on standby status. It also depletes discharge current and battery efficiency at 1.0V which is general operating voltage of aluminum-air battery. However, the impurity complex layer of 2N5 grade Al is dissolved with decreasing discharge voltage to 0.8V. This phenomenon leads to improvement of discharge current density and battery efficiency by reducing self-corrosion reaction. This study demonstrates the possibility of use of 2N5 grade Al which is cheaper than 4N grade Al as the anode for aluminum-air battery.

Cho, Young-Joo; Park, In-Jun; Lee, Hyeok-Jae; Kim, Jung-Gu

2015-03-01

308

Microstructure and wear properties of Al2O3-CeO2/Ni-base alloy composite coatings on aluminum alloys by plasma spray  

NASA Astrophysics Data System (ADS)

Al2O3 and CeO2 particles reinforced Ni-base alloy composite coatings were prepared on aluminum alloy 7005 by plasma spray. The microstructure, microhardness, fracture toughness, critical bonding force and the wear behavior and mechanisms of the composite coatings were investigated. It is found that CeO2 particles can refine crystal grains, reduce porosity and unmelted Al2O3 particles in the composite coatings. The microhardness, fracture toughness, critical bonding force and wear resistance of the composite coatings are enhanced due to synergistic strengthening effects of Al2O3 and CeO2 particles. The friction coefficients and wear losses increase as loads increase. At the loads of 3-6 N, the composite coatings experience local plastic deformation and micro-cutting wear. At the loads in the range of 9-12 N, the calculated maximum contact stress and maximum tensile stress on friction surfaces increase leading to plastic deformation induced working hardening. The wear mechanisms change into micro-brittle fracture wear and slight oxidative wear.

He, Long; Tan, Yefa; Wang, Xiaolong; Xu, Ting; Hong, Xiang

2014-09-01

309

MICROSTRUCTURE EVOLUTION MODELING FOR SOLUTION TREATMENT OF ALUMINUM ALLOYS  

SciTech Connect

The microstructure evolution during solution treatment plays an important role in mechanical properties of heat-treated aluminum alloys. In this paper, models were reviewed that can predict the microstructure evolution during the solutionizing process of the aging heat treatment of aluminum alloys. The dissolution of Mg2Si particles has been modeled as a diffusion process of Mg in the -Al matrix. The evolution of volumetric fraction of fragmented silicon as a function of time and temperature was also considered. The growth and coarsening of silicon particles during the heat treatment was considered. It was found that constitutive equations and required property data for most of the phenomena that need to be considered are available. Several model parameters that need to be obtained from material characterization were identified. Pending the availability of these model parameters, this comprehensive model can be used to describe the microstructure evolution of aluminum alloys in order to optimize the solutionizing heat treatment for energy savings.

Yin, Hebi [ORNL; Sabau, Adrian S [ORNL; Skszek, Timothy [Vehma International of American, Inc.; Niu, X [Magna Cosma International, Promatek Research Centre

2013-01-01

310

Hydrothermal Transformation of the Calcium Aluminum Oxide Hydrates CaAl2O4 . 10H2O and Ca2Al2O. 8H2O to Ca3Al2(OH)12 Investigated by In Situ Synchrotron X-ray Powder Diffraction  

SciTech Connect

The hydrothermal transformation of calcium aluminate hydrates were investigated by in situ synchrotron X-ray powder diffraction in the temperature range 25 to 170 C. This technique allowed the study of the detailed reaction mechanism and identification of intermediate phases. The material CaAl{sub 2}O{sub 4}{center_dot}10H{sub 2}O converted to Ca{sub 3}Al{sub 2}(OH){sub 12} and amorphous aluminum hydroxide. Ca{sub 2}Al{sub 2}O{sub 5}{center_dot}8H{sub 2}O transformed via the intermediate phase Ca{sub 4}Al{sub 2}O{sub 7}{center_dot}13H{sub 2}O to Ca{sub 3}Al{sub 2}(OH){sub 12} and gibbsite, Al(OH){sub 3}. The phase Ca{sub 4}Al{sub 2}O{sub 7}{center_dot}19H{sub 2}O reacted via the same intermediate phase to Ca{sub 3}Al{sub 2}(OH){sub 12} and mainly amorphous aluminum hydroxide. The powder pattern of the intermediate phase is reported.

Jensen,T.; Christensen, A.; Hanson, J.

2005-01-01

311

Synthesis and atomic-level characterization of Ni nanoparticles in Al2O3 matrix  

E-print Network

in alumina matrix using a pulsed-laser deposition technique. Structural characterization carried out field data and experimentally using STEM-Z which indicates the absence of any magnetically dead layers to the transition to a single domain magnetic structures. While constant efforts are rou- tinely being made

Pennycook, Steve

312

Prediction of tribological behavior of aluminumcopper based composite using artificial neural network  

Microsoft Academic Search

The potential of using neural network in prediction of wear loss quantities of some aluminumcoppersilicon carbide composite materials has been studied in the present work. Effects of addition of copper as alloying element and silicon carbide as reinforcement particles to Al4wt.%Mg metal matrix have been investigated. Different AlCu alloys and composites were subjected to dry sliding wear test using pin-on-disk

Mohammed Hayajneh; Adel Mahamood Hassan; Abdalla Alrashdan; Ahmad Turki Mayyas

2009-01-01

313

Production of aluminum metal by electrolysis of aluminum sulfide  

DOEpatents

Production of metallic aluminum by the electrolysis of Al.sub.2 S.sub.3 at 700.degree.-800.degree. 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, Nguyen Q. (Woodridge, IL); Loutfy, Raouf O. (Tucson, AZ); Yao, Neng-Ping (Clarendon Hills, IL)

1984-01-01

314

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

315

Microstructure/mechanical property relationships for various thermal treatments of Al-Cu-Mg-X PM aluminum alloys  

NASA Technical Reports Server (NTRS)

The thermal response and aging behavior of three 2XXX-series powder metallurgy aluminum alloys have been investigated, using Rockwell B hardness measurements, optical and electron microscopy, and energy-dispersive chemical analysis, in order to correlate microstructure with measured mechanical properties. Results of the thermal response study indicated that an increased solution heat treatment temperature was effective in resolutionizing large primary constituents in the alloy bearing more copper but had no apparent effect on the microconstituents of the other two. Aging studies conducted at room temperature and at 120, 150, and 180 C for times ranging up to 60 days indicated that classic aging response curves, as determined by hardness measurements, occurred at lower aging temperatures than were previously studied for these alloys, as well as at lower aging temperatures than are commonly used for ingot metallurgy alloys of similar compositions. Microstructural examination and fracture surface analysis of peak-aged tension specimens indicated that the highest tensile strengths are associated with extremely fine and homogeneous distributions of theta-prime or S-prime phases combined with low levels of both large constituent particles and dispersoids. Examination of the results suggest that refined solution heat treatments and lower aging temperatures may be necessary to achieve optimum mechanical properties for these 2XXX series alloys.

Blackburn, L. B.

1986-01-01

316

Electric discharge machining of AlSiC metal matrix composites using rotary tube electrode  

Microsoft Academic Search

The machining characteristics of SiC\\/6025 Al composite using rotary electro-discharge machining (EDM) with a tube electrode were investigated in this study. Brass was used as the electrode material to EDM SiC\\/6025 Al composites. Three observed values: material removal rate (MRR), electrode wear rate (EWR) and surface roughness (SR) are adopted to evaluate the machinability. Peak current, polarity, volume fraction of

B. Mohan; A. Rajadurai; K. G. Satyanarayana

2004-01-01

317

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

318

Durability of nickel-metal hydride (Ni-MH) battery cathode using nickel-aluminum layered double hydroxide/carbon (Ni-Al LDH/C) composite  

NASA Astrophysics Data System (ADS)

We report the durability of the optimized nickel-aluminum layered double hydroxide/carbon (Ni-Al LDH/C) composite prepared by liquid phase deposition (LPD) as cathode active materials in nickel metal hydride (Ni-MH) secondary battery. The positive electrode was used for charge-discharge measurements under two different current: 5mA for 300 cycles in half-cell conditions, and 5.8mA for 569 cycles in battery regime, respectively. The optimized Ni-Al LDH/C composite exhibits a good lifespan and stability with the capacity retention above 380mAhgcomp-1 over 869 cycles. Cyclic voltammetry shows that the ?-Ni(OH)2/?-NiOOH redox reaction is maintained even after 869 cycles, and the higher current regime is beneficial in terms of materials utilization. X-ray diffraction (XRD) patterns of the cathode after charge and discharge confirms that the ?-Ni(OH)2/?-NiOOH redox reaction occurs without any intermediate phase.

Blk, Alexis Bienvenu; Higuchi, Eiji; Inoue, Hiroshi; Mizuhata, Minoru

2014-02-01

319

Characterization of molecular disorder in vapor-deposited thin films of aluminum tris(quinoline-8-olate) by one-dimensional 27Al NMR under magic angle spinning  

NASA Astrophysics Data System (ADS)

Aluminum tris (quinoline-8-olate) (Alq3) is used as an electron-transport layer in organic light-emitting diodes. The material can be obtained in a wide range of different solid phases, both crystalline and amorphous, by deposition from the vapor phase or from solution under controlled conditions. While the structure of the crystalline polymorphs of Alq3 has been investigated thoroughly by x-ray diffraction as well as solid-state NMR, very little information is currently available on the amount of structural disorder in the amorphous forms of Alq3. In the present contribution, we report the use of Al27 NMR spectroscopy in the solid state under magic angle spinning to extract such information from amorphous vapor deposits of Alq3. The NMR spectra obtained from these samples exhibit different degrees of broadening, reflecting distributions of the electric-field gradient tensor at the site of the aluminum ion. These distributions can be obtained from the NMR spectra by solving the corresponding inverse problem. From these results, the magnitude of structural disorder in terms of molecular geometry has been estimated by density-functional theory calculations. It was found that the electric-field gradient anisotropy ? follows a bimodal distribution. Its majority component is centered around ? values comparable to the meridianal ? crystal polymorph and has a width of about 10%, corresponding to distortions of the molecular geometry of a few degrees in the orientation of the ligands. Alq3 samples obtained at higher deposition rates exhibit higher degrees of disorder. The minor component, present at about 7%, has a much smaller anisotropy, suggesting that it may be due to the facial isomer of Alq3.

Utz, Marcel; Nandagopal, Magesh; Mathai, Mathew; Papadimitrakopoulos, Fotios

2006-01-01

320

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

SciTech Connect

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. [National Aeronautics and Space Administration, Cleveland, OH (United States). Lewis Research Center; Tiwari, R.; Tewari, S.N. [Cleveland State Univ., OH (United States). Dept. of Chemical Engineering

1995-08-01

321

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

SciTech Connect

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.; Babenkov, S. V. [Deutsches Elektronen-Synchrotron DESY, Notkestrae 85, 22607 Hamburg (Germany); Aristova, I. M. [Institute of Solid State Physics of Russian Academy of Sciences, Chernogolovka 142432 (Russian Federation); Vilkov, O. V. [Helmholtz-Zentrum Berlin (HZB) fr Materialien und Energie, Albert-Einstein-Strae 15, 12489 Berlin (Germany); Aristov, V. Yu., E-mail: aristov@issp.ac.ru [Deutsches Elektronen-Synchrotron DESY, Notkestrae 85, 22607 Hamburg (Germany); Institute of Solid State Physics of Russian Academy of Sciences, Chernogolovka 142432 (Russian Federation); Institut fr Theoretische Physik, Universitt Hamburg, Jungiusstrae 9, D-20355 Hamburg (Germany)

2014-04-28

322

Abrasive Wear Behavior of In Situ TiC Reinforced with Al-4.5%Cu Matrix  

NASA Astrophysics Data System (ADS)

The present work deals with the investigation on weight loss and coefficient of friction of TiC reinforced Al-4.5%Cu in situ metal matrix composites. Experiments were conducted using pin-on-disc apparatus against abrasive paper by varying the applied load, sliding distance, and weight percentage of TiC. The results indicated significant improvement in the mechanical properties and wear resistance of experimental composites as compared to the parent metal matrix. The percentage of porosity though increased with increasing TiC reinforcement. The variation of weight loss of composites increased linearly with increasing applied load and sliding distance, whereas decreased with increasing weight percentage of TiC reinforcement. The coefficient of friction decreased linearly with increasing applied load and TiC reinforcement. SEM micrographs of worn surfaces show a well compacted transfer layer of wear debris along with wear track over the sliding surface. Grooves, delamination, and crack propagation were also observed in all test samples. The effective depth of penetration and size of debris was seen to reduce with increasing wt.% of TiC reinforcement in metal matrix.

Kumar, Anand; Jha, P. K.; Mahapatra, M. M.

2014-03-01

323

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

324

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

325

Trimethyl-aluminum and ozone interactions with graphite in atomic layer deposition of Al2O3  

NASA Astrophysics Data System (ADS)

A study of the chemical interactions between the atomic layer deposition (ALD) Al2O3 precursors trimethlyaluminum (TMA) and ozone (TMA/O3) and sp2 carbon surfaces is presented. In-situ x-ray photoelectron spectroscopy is used to study these interactions, while ex-situ atomic force microscopy (AFM) is used to monitor the surface morphology. Ozone functionalization of the sp2 carbon surface is discussed and the dependence of TMA/O3 reactions over a range of ALD process conditions is examined. The utilization of a 6-cycle room temperature TMA/O3 ALD seed layer to nucleate the conformal growth of Al2O3 by TMA/H2O at 200 C as well as the quality of such films is discussed. Two stages of ozone reactions are observed: first the ozone appears to remove adsorbed species from the graphite surface before reacting with the surface. The deposition of Al2O3 is found to be strongly dependant on the N2 purge time as well as the precursor pulse sequence. It is shown that the quality of these low temperature deposited films can easily be improved by removal of carbon containing species through an 300 C anneal.

McDonnell, Stephen; Pirkle, Adam; Kim, Jiyoung; Colombo, Luigi; Wallace, Robert M.

2012-11-01

326

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

327

Preparation of aluminum(III) (bis(amido)pyridine)(thiolate) complexes: unexpected transmetalation mediated by LiAlH(4).  

PubMed

Treatment of an unsymmetrical bis(imino)pyridyl-thiolate zinc(II) complex [Zn(II)(LN(3)S)(OTf)] (1) with LiAlH(4) results in the double reduction of the two imino groups in the ligand backbone, and at the same time causes a rare transmetalation reaction to occur. The products formed in this reaction are two novel aluminium(III) bis(amido)pyridyl-thiolate complexes [(R,S/S,R-[Al(III)(LH(2)N(3)S)(THF)] (2a) and [(R,R/S,S-[Al(III)(LH(2)N(3)S)(THF)] (2b), which are diastereomers of each other. These complexes have been characterized by single-crystal X-ray diffraction and (1)H NMR spectroscopy. Single crystal X-ray structure analysis shows that the Al(III) ion is bound in an almost idealized square pyramidal geometry in 2a, while being held in a more distorted square pyramidal geometry in 2b. The major difference between 2a and 2b arises in the orientation of the terminal methyl groups of the ligand backbone in relation to the Al(III)N(3)S plane. These two complexes are crystallized at different temperatures (room temperature vs -35 C), allowing for their separate isolation. Structural analysis shows that these complexes are reduced by the formal addition of one hydride ion to each imino group, resulting in a deprotonated bis(amido)pyridyl-thiolate ligand. A detailed analysis of metrical parameters rules out the possibility of pure one- or two-electron reduction of the ?-conjugated bis(imino)pyridine framework. (1)H NMR spectra reveal a rich pattern in solution indicating that the solution state structures for 2a and 2b match those observed in the solid-state crystal structures, and reveal that both complexes are severely conformationally restricted. Direct organic synthetic methods failed to produce the reduced bis(amino)pyridyl-thiol ligand in pure form, but during the course of these efforts an unusual unsymmetrical aminopyridyl ketone, 1-(6-(1-(2,6-diisopropylphenylamino)ethyl)pyridin-2-yl)ethanone was synthesized in good yield and can be used as a possible precursor for further ligand development. PMID:22345823

Badiei, Yosra M; Jiang, Yunbo; Widger, Leland R; Siegler, Maxime A; Goldberg, David P

2012-03-15

328

Review Article Aluminum-Induced Entropy in Biological Systems  

E-print Network

Review Article Aluminum-Induced Entropy in Biological Systems: Implications for Neurological years, mining, smelting, and refining of aluminum (Al) in various forms have increasingly exposed living of the Al toxicants to which we are being exposed. 1. Introduction Aluminum (Al) is the most common metal

Seneff, Stephanie

329

Improved performance of U-Mo dispersion fuel by Si addition in Al matrix.  

SciTech Connect

The purpose of this report is to collect in one publication and fit together work fragments presented in many conferences in the multi-year time span starting 2002 to the present dealing with the problem of large pore formation in U-Mo/Al dispersion fuel plates first observed in 2002. Hence, this report summarizes the excerpts from papers and reports on how we interpreted the relevant results from out-of-pile and in-pile tests and how this problem was dealt with. This report also provides a refined view to explain in detail and in a quantitative manner the underlying mechanism of the role of silicon in improving the irradiation performance of U-Mo/Al.

Kim, Y S; Hofman, G L [Nuclear Engineering Division

2011-06-01

330

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

SciTech Connect

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 melt; and (3) the industrial-size field test was successful in that sand mold castings and permanent mold castings of tensile bars, K mold bars, and ingots were made from aluminum alloy 535-fly ash mix. Use of aluminum alloy 535 containing 7% magnesium precluded the need to introduce additional magnesium into the melt. The third round of sand mold castings as well as permanent mold castings produced components and ingots of alloy 535 instead of alloy 356. The ingots will be remelted and cast into parts to assess the improvement of flyash distribution which occurs through reheating and the solidification wetting process. Microstructure analysis continues on sand and permanent mold castings to study particle distribution in the components. A prototype sand cast intake manifold casting was found to be pressure tight which is a major performance requirement for this part. Another heat of pressure die cast brackets of A380-classified fly ash will be made to examine their strength and fly ash distribution. Ingots of A356-fly ash have been made at Eck for remelting at Thompson Aluminum for squeeze casting into motor mounts.

Weiss, David; Purgert, Robert; Rhudy, Richard; Rohatgi, Pradeep

2000-04-21

331

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

332

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

333

Li.sub.2 O-Al.sub.2 O.sub.3 -SiO.sub.2 glass ceramic-aluminum containing austenitic stainless steel composite body and a method of producing the same  

DOEpatents

The present invention relates to a hermetically sealed Li.sub.2 O-Al.sub.2 O.sub.3 -SiO.sub.2 glass ceramic-aluminum containing stainless steel composite body and a method of producing the body. The composite body includes an oxide interfacial region between the glass ceramic and metal, wherein the interfacial region consists essentially of an Al.sub.2 O.sub.3 layer. The interfacial Al.sub.2 O.sub.3 region includes constituents of both the metal and glass ceramic.

Cassidy, Roger T. (Monroe, OH)

1990-05-01

334

Physical and Microstructure Properties of MgAl2C2 Matrix Composite Coating on Titanium  

NASA Astrophysics Data System (ADS)

This work is based on the dry sliding wear of the MgAl2C2-TiB2-FeSi composite coating deposited on a pure Ti using a laser cladding technique. Scanning electron microscope images indicate that the nanocrystals and amorphous phases are produced in such coating. X-ray diffraction result indicated that such coating mainly consists of MgAl2C2, Ti-B, Ti-Si, Fe-Al, Ti3SiC2, TiC and amorphous phases. The high resolution transmission electron microscope image indicated that the TiB nanorods were produced in the coating, which were surrounded by other fine precipitates, favoring the formation of a fine microstructure. With increase of the laser power from 0.85 kW to 1.00 kW, the micro-hardness decreased from 1350 1450 HV0.2 to 1200 1300 HV0.2. The wear volume loss of the laser clad coating was 1/7 of pure Ti.

Li, Peng

2014-12-01

335

Modification of Cast Al-Mg2Si Metal Matrix Composite by Li  

NASA Astrophysics Data System (ADS)

The effects of both Li modification and cooling rate on the microstructure and tensile properties of an in-situ prepared Al-15 pct Mg2Si composite were investigated. Adding 0.3 pct Li reduced the average size of Mg2Si primary particles from ~30 to ~6 ?m. The effect of cooling rate was investigated by the use of a mold with different section thicknesses from 3 to 9 mm. The results show a refinement of primary particle size as a result of both Li additions and cooling rate increases, and their effects are additive. Similarly, both effects increased ultimate tensile stress (UTS) and elongation values. The thin sections show somewhat unexpectedly low and scattered tensile results attributed to the casting defects observed in fracture surfaces. The Li-modified alloy displays serrated yielding behavior that is not fully explained here. The refinement by Li and enhanced cooling rate is explained in terms of an analogy with the effect of Sr and cooling rate in Al-Si alloys, and is ultimately attributed to the effect of the alkali and alkaline earth metals deactivating oxide double films (bifilms) suspended in Al melts as favored substrates for intermetallics.

Hadian, R.; Emamy, M.; Campbell, J.

2009-12-01

336

Aluminum-Based Cast In Situ Composites: A Review  

NASA Astrophysics Data System (ADS)

In situ composites are a class of composite materials in which the reinforcement is formed within the matrix by reaction during the processing. In situ method of composite synthesis has been widely followed by researchers because of several advantages over conventional stir casting such as fine particle size, clean interface, and good wettability of the reinforcement with the matrix and homogeneous distribution of the reinforcement compared to other processes. Besides this, in situ processing of composites by casting route is also economical and amenable for large scale production as compared to other methods such as powder metallurgy and spray forming. Commonly used reinforcements for Al and its alloys which can be produced in situ are Al2O3, AlN, TiB2, TiC, ZrB2, and Mg2Si. The aim of this paper is to review the current research and development in aluminum-based in situ composites by casting route.

Pramod, S. L.; Bakshi, Srinivasa R.; Murty, B. S.

2015-02-01

337

Effect of thermal exposure, forming, and welding on high-temperature, dispersion-strengthened aluminum alloy: Al-8Fe-1V-2Si  

NASA Technical Reports Server (NTRS)

The feasibility of applying conventional hot forming and welding methods to high temperature aluminum alloy, Al-8Fe-1V-2Si (FVS812), for structural applications and the effect of thermal exposure on mechanical properties were determined. FVS812 (AA8009) sheet exhibited good hot forming and resistance welding characteristics. It was brake formed to 90 deg bends (0.5T bend radius) at temperatures greater than or equal to 390 C (730 F), indicating the feasibility of fabricating basic shapes, such as angles and zees. Hot forming of simple contoured-flanged parts was demonstrated. Resistance spot welds with good static and fatigue strength at room and elevated temperatures were readily produced. Extended vacuum degassing during billet fabrication reduced porosity in fusion and resistance welds. However, electron beam welding was not possible because of extreme degassing during welding, and gas-tungsten-arc welds were not acceptable because of severely degraded mechanical properties. The FVS812 alloy exhibited excellent high temperature strength stability after thermal exposures up to 315 C (600 F) for 1000 h. Extended billet degassing appeared to generally improve tensile ductility, fatigue strength, and notch toughness. But the effects of billet degassing and thermal exposure on properties need to be further clarified. The manufacture of zee-stiffened, riveted, and resistance-spot-welded compression panels was demonstrated.

Kennedy, J. R.; Gilman, P. S.; Zedalis, M. S.; Skinner, D. J.; Peltier, J. M.

1991-01-01

338

In Situ Observation of Solidification Conditions in Pulsed Laser Welding of AL6082 Aluminum Alloys to Evaluate Their Impact on Hot Cracking Susceptibility  

NASA Astrophysics Data System (ADS)

The influence of laser pulse parameters on solidification conditions and hot crack formation in pulsed laser welding of Al6082 aluminum alloys was studied with the aid of high-speed cameras capturing visible and infrared radiation. Hot cracking was evaluated with respect to strain rate, strain, and metallurgical outcome. The strain rate was approximated by the product of interface velocity and temperature gradient at the interface. The temperature gradient decreases during the course of solidification and followed a specific course. The interface velocity was therefore used as an indicator for the strain rate, which increased in a logarithmic manner with respect to the slope of the laser pulse's cooling time. The accumulated strain was calculated by measuring the spot weld deformation during solidification. Within the heat-conduction welding regime, hot cracking can be reduced by lowering the interface velocity leading to a reduced strain rate and enhanced permeability of the dendritic microstructure. An over-proportional increase of the accumulated strain was observed for keyhole welding, which led to a high susceptibility to hot cracking regardless of the interface velocity. At low interface velocities, hot cracking was induced by extensive hydrogen diffusion at the solid-liquid interface, which promotes crack initiation.

von Witzendorff, Philipp; Kaierle, Stefan; Suttmann, Oliver; Overmeyer, Ludger

2015-04-01

339

Aluminum Boats  

NSDL National Science Digital Library

Test the buoyancy of an aluminum foil boat and an aluminum foil ball. Why does the same material in different shapes sink or float? This activity explores the fact that the amount of water pushed aside by an object equals the force of water pushing upward on the object.

Reuben H. Fleet Science Center

1999-01-01

340

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

341

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

342

The adhesion strength of the composition coating with a polymer matrix based on sodium carboxymethylcellulose with a metallic filler made from aluminum powder  

Microsoft Academic Search

In order to interpret the adhesion regularities, a way to make coagulants from fine fractions of aluminum powder on the microroughness\\u000a of steel surface, providing the adhesion strength of coating due to the van der Waals interaction forces, is suggested. The\\u000a role of the plasticizer as a factor increasing the adhesion strength of coatings via decreasing the internal stresses in

N. M. Antonova; V. I. Kulinich; V. Yu. Dorofeev

2008-01-01

343

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

344

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

345

Immunotoxicity of aluminum.  

PubMed

Aluminum (Al) is present in the daily life of all humans. With the incidence of Al contamination increased in recent years, the toxicity of Al on the immune function has attracted more attention. Even with this increased attention, the mechanism of Al immunotoxicity still remains unclear. The mechanism of Al immunotoxicity reviewed herein focused on the effects of Al on the splenic trace elements, the status of ?-naphthyl acetate esterase (ANAE) cells, cytokines, complement and immunoglobulins, as well as macrophages. The studies in the literature showed that Al decreased splenic iron (Fe) and zinc (Zn) levels, but the effects of Al on splenic copper (Cu) level was ambiguous and controversial. Al exposure inhibited levels of ANAE(+) cells, the production of interleukin (IL)-2 and the functions of macrophages. With respect to other key cytokines, studies showed that Al suppressed the production of tumor necrosis factor (TNF)-? in vitro; effects of Al on TNF-? formation in vivo were less overt. Al exposure reduced complement 3 (C3) level, but effects of Al exposure on complement 4 (C4) level were not as clear-cut. Lastly, the effects of Al exposure on the IgG, IgM and IgA levels were conflicting. Taken in totality, the results of several studies in the literature demonstrated that Al could impart adverse effects on immune function. PMID:24287266

Zhu, Yanzhu; Li, Yanfei; Miao, Liguang; Wang, Yingping; Liu, Yanhuan; Yan, Xijun; Cui, Xuezhe; Li, Haitao

2014-06-01

346

Detoxification of endotoxin by aluminum hydroxide adjuvant  

Microsoft Academic Search

Langmuir adsorption isotherms of endotoxin and aluminum-containing adjuvants at pH 7.4 and 25C revealed that aluminum hydroxide adjuvant has a greater adsorption capacity (283 ?g\\/mg Al) and adsorption coefficient (1.3104 ml\\/?g) than aluminum phosphate adjuvant (3.0 ?g\\/mg Al, 0.20 ml\\/?g). The difference in endotoxin adsorption was related to two adsorption mechanisms: electrostatic attraction and covalent bonding. The isoelectric point (iep)

Yi Shi; Harm HogenEsch; Fred E. Regnier; Stanley L. Hem

2001-01-01

347

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

NASA Astrophysics Data System (ADS)

Mechanical alloying of Ti-Al-graphite 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 morphology from a flattened shape (10 h) to a highly coarsened spherical one (15 h) and, eventually, to a fine, equiaxed and uniform one (above 25 h). The prepared TiC/Ti(Al) composite powder was nanocrystalline, with the estimated average crystallite size of 12 nm and of 7 nm for Ti(Al) and TiC, respectively. Formation mechanisms behind the microstructural development of powders were elucidated. The Ti(Al) solid solution is formed through a gradual and progressive solution of Al into Ti lattice. The formation of TiC is through an abrupt, exothermic, and self-sustaining reaction between Ti and C elements. Selective Laser Melting (SLM) of as-prepared TiC/Ti(Al) composite powder was performed. The TiC particle reinforced TiAl 3 (a major phase) and Ti 3AlC 2 (a minor phase) matrix composite part was obtained after SLM. Although a slight grain growth occurred as relative to as-milled powder, the SLM processed composites still exhibited a refined microstructure.

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

2009-08-01

348

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

Diffusion-bonded NiAl-Al[sub 2]O[sub 3] and Ni[sub 3]Al-Al[sub 2]O[sub 3] couples were thermally fatigued at 900 C for 1500 and 3500 cycles. The fiber-matrix interface weakened after 3500 cycles for the Saphikon fibers, while the Altex, PRD-166, and FP fibers showed little, if any, degradation. Diffusion bonding of fibers to Nb matrix is being studied. Coating the fibers slightly increases the tensile strength and has a rule-of-mixtures effect on elastic modulus. Push-out tests on Sumitomo and FP fibers in Ni aluminide matrices were repeated. Al[sub 2]O[sub 3] was evaporated directly from pure oxide rod onto acoustically levitated Si carbide particles, using a down-firing, rod-fed electron beam hearth; superior coatings were subsequently produced using concurrent irradiation with 200-eV argon ion-assist beam. The assist beam produced adherent films with reduced tensile stresses. In diffusion bonding in B-doped Ni[sub 3]Al matrices subjected to compressive bonding at 40 MPa at 1100 C for 1 hr, the diffusion barriers failed to prevent catastrophic particle- matrix reaction, probably because of inadequate film quality. AlN coatings are currently being experimented with, produced by both reactive evaporation and by N[sup +]-ion enhanced deposition. A 3-kW rod-fed electron-beam-heated evaporation source has been brought into operation.

Grummon, D.S.

1993-01-21

349

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. Progress summary report, June 1, 1993--May 31, 1994  

SciTech Connect

Diffusion-bonded NiAl-Al{sub 2}O{sub 3} and Ni{sub 3}Al-Al{sub 2}O{sub 3} couples were thermally fatigued at 900 C for 1500 and 3500 cycles. The fiber-matrix interface weakened after 3500 cycles for the Saphikon fibers, while the Altex, PRD-166, and FP fibers showed little, if any, degradation. Diffusion bonding of fibers to Nb matrix is being studied. Coating the fibers slightly increases the tensile strength and has a rule-of-mixtures effect on elastic modulus. Push-out tests on Sumitomo and FP fibers in Ni aluminide matrices were repeated. Al{sub 2}O{sub 3} was evaporated directly from pure oxide rod onto acoustically levitated Si carbide particles, using a down-firing, rod-fed electron beam hearth; superior coatings were subsequently produced using concurrent irradiation with 200-eV argon ion-assist beam. The assist beam produced adherent films with reduced tensile stresses. In diffusion bonding in B-doped Ni{sub 3}Al matrices subjected to compressive bonding at 40 MPa at 1100 C for 1 hr, the diffusion barriers failed to prevent catastrophic particle- matrix reaction, probably because of inadequate film quality. AlN coatings are currently being experimented with, produced by both reactive evaporation and by N{sup +}-ion enhanced deposition. A 3-kW rod-fed electron-beam-heated evaporation source has been brought into operation.

Grummon, D.S.

1993-01-21

350

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

351

Suppression of activation energy and superconductivity by the addition of Al2O3 nanoparticles in CuTl-1223 matrix  

NASA Astrophysics Data System (ADS)

Low anisotropic (Cu0.5Tl0.5)Ba2Ca2Cu3O10-? (CuTl-1223) high Tc superconducting matrix was synthesized by solid-state reaction and Al2O3 nanoparticles were prepared separately by co-precipitation method. Al2O3 nanoparticles were added with different concentrations during the final sintering cycle of CuTl-1223 superconducting matrix to get the required (Al2O3)y/CuTl-1223, y = 0.0, 0.5, 0.7, 1.0, and 1.5 wt. %, composites. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray, and dc-resistivity (?) measurements. The activation energy and superconductivity were suppressed with increasing concentration of Al2O3 nanoparticles in (CuTl-1223) matrix. The XRD analysis showed that the addition of Al2O3 nanoparticles did not affect the crystal structure of the parent CuTl-1223 superconducting phase. The suppression of activation energy and superconducting properties is most probably due to weak flux pinning in the samples. The possible reason of weak flux pinning is reduction of weak links and enhanced inter-grain coupling due to the presence of Al2O3 nanoparticles at the grain boundaries. The presence of Al2O3 nanoparticles at the grain boundaries possibly reduced the number of flux pinning centers, which were present in the form of weak links in the pure CuTl-1223 superconducting matrix. The increase in the values of inter-grain coupling (?) deduced from the fluctuation induced conductivity analysis with the increased concentration of Al2O3 nanoparticles is a theoretical evidence of improved inter-grain coupling.

Jabbar, Abdul; Qasim, Irfan; Mumtaz, M.; Zubair, M.; Nadeem, K.; Khurram, A. A.

2014-05-01

352

Aluminum Zintl anion moieties within sodium aluminum clusters  

SciTech Connect

Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have established that aluminum moieties within selected sodium-aluminum clusters are Zintl anions. Sodiumaluminum cluster anions, Na{sub m}Al{sub n}{sup ?}, were generated in a pulsed arc discharge source. After mass selection, their photoelectron spectra were measured by a magnetic bottle, electron energy analyzer. Calculations on a select sub-set of stoichiometries provided geometric structures and full charge analyses for both cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra), and fragment molecular orbital based correlation diagrams.

Wang, Haopeng; Zhang, Xinxing; Ko, Yeon Jae; Grubisic, Andrej; Li, Xiang; Gantefr, Gerd; Bowen, Kit H., E-mail: AKandalam@wcupa.edu, E-mail: kiran@mcneese.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Schnckel, Hansgeorg [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany)] [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany); Eichhorn, Bryan W. [Department of Chemistry, University of Maryland at College Park, College Park, Maryland 20742 (United States)] [Department of Chemistry, University of Maryland at College Park, College Park, Maryland 20742 (United States); Lee, Mal-Soon; Jena, P. [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)] [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Kandalam, Anil K., E-mail: AKandalam@wcupa.edu, E-mail: kiran@mcneese.edu, E-mail: kbowen@jhu.edu [Department of Physics, West Chester University of Pennsylvania, West Chester, Pennsylvania 19383 (United States); Kiran, Boggavarapu, E-mail: AKandalam@wcupa.edu, E-mail: kiran@mcneese.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 (United States)] [Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 (United States)

2014-02-07

353

Synthesis of high-surface-area ?-Al2O3 from aluminum scrap and its use for the adsorption of metals: Pb(II), Cd(II) and Zn(II)  

NASA Astrophysics Data System (ADS)

Several types of alumina were synthesized from sodium aluminate (NaAlO2) by precipitation with sulfuric acid (H2SO4) and subsequently calcination at 500 C to obtain ?-Al2O3. The precursor aluminate was derived from aluminum scrap. The various ?-Al2O3 synthesized were characterized by Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), adsorption-desorption of N2 (SBET) and scanning electron microscopy (SEM). XRD revealed that distinct phases of Al2O3 were formed during thermal treatment. Moreover, it was observed that conditions of synthesis (pH, aging time and temperature) strongly affect the physicochemical properties of the alumina. A high-surface-area alumina (371 m2 g-1) was synthesized under mild conditions, from inexpensive raw materials. These aluminas were tested for the adsorption of Cd(II), Zn(II) and Pb(II) from aqueous solution at toxic metal concentrations, and isotherms were determined.

Asencios, Yvan J. O.; Sun-Kou, Mara R.

2012-10-01

354

Dependence of the properties of a carbon-aluminum composite material on its carbide phase content  

Microsoft Academic Search

To ensure that the necessary bond strength at fiber\\/matrix interfaces is attained during the manufacture of a carbon-aluminum composite such as that investigated in this work, the degree of chemical reaction between the components must be strictly controlled, the optimum amount of the reaction product (Al4C3) being 23%. For matrices of other compositions and fibers of other types, the optimum

K. I. Portnoi; N. I. Timofeeva; A. A. Zabolotskii; V. N. Sakovich; B. F. Trefilov; M. Kh. Levinskaya; N. N. Polyak

1981-01-01

355

Laser Welding of Aluminum and Aluminum Alloys  

E-print Network

.. ) Laser Welding of Aluminum and Aluminum Alloys Welds made with sharp bevel-groove weld aluminum and by aluminum alloy 5456 have been studied. The results indicate that initial absorption varies of the most dramatic illustrations of the differences in beam characteristics occurs when welding aluminum

Eagar, Thomas W.

356

Study on stainless steel electrode based on dynamic aluminum liquid corrosion mechanism.  

PubMed

Scanning electrion microscope (SEM) was performed for investigations on the corrosion mechanism of stainless steel electrode in dynamic melting aluminum liquid. Microstructures and composition analysis was made by electron probe analysis (EPA) combined with metallic phase analysis. It can be concluded that the corrosion process is mainly composed of physical corrosion (flowing and scouring corrosion) and chemical corrosion (forming FeAl and Fe2Al5) and the two mechanisms usually exist simultaneously. The corrosion interface thickness is about 10 ?m, which is different to usual interface width of hundreds ?m in the static melting Al with iron matrix. PMID:25084422

Hou, Hua; Yang, Ruifeng

2009-01-01

357

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

358

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

359

Crystallographic study of grain refinement in aluminum alloys using the edge-to-edge matching model  

SciTech Connect

The edge-to-edge matching model for describing the interfacial crystallographic characteristics between two phases that are related by reproducible orientation relationships has been applied to the typical grain refiners in aluminum alloys. Excellent atomic matching between Al{sub 3}Ti nucleating substrates, known to be effective nucleation sites for primary Al, and the Al matrix in both close packed directions and close packed planes containing these directions have been identified. The crystallographic features of the grain refiner and the Al matrix are very consistent with the edge-to-edge matching model. For three other typical grain refiners for Al alloys, TiC (when a = 0.4328 nm), TiB{sub 2} and AlB{sub 2}, the matching only occurs between the close packed directions in both phases and between the second close packed plane of the Al matrix and the second close packed plane of the refiners. According to the model, it is predicted that Al{sub 3}Ti is a more powerful nucleating substrate for Al alloy than TiC, TiB{sub 2} and AlB{sub 2}. This agrees with the previous experimental results. The present work shows that the edge-to-edge matching model has the potential to be a powerful tool in discovering new and more powerful grain refiners for Al alloys.

Zhang, M.-X. [Division of Materials, School of Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia)]. E-mail: m.zhang@minmet.uq.edu.au; Kelly, P.M. [Division of Materials, School of Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia); Easton, M.A. [School of Physics and Materials Engineering, Monash University, Clayton, VIC 3800 (Australia); Taylor, J.A. [Division of Materials, School of Engineering, University of Queensland, St. Lucia, QLD 4072 (Australia)

2005-03-01

360

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.

361

Electrochemical study of Aluminum-Fly Ash composites obtained by powder metallurgy  

SciTech Connect

In this paper, two different ASTM C 618 Class C fly ashes (FA) were used for the production of aluminum metal matrix composites (MMCs) using powder metallurgy (PM) technology. Calcareous FAs were sampled from the electrostatic precipitators of two different lignite-fired power stations: from Megalopolis, Southern Greece (MFA) and from Kardia, Northen Greece (KFA), under maximum electricity load. FAs were milled in order to reduce the mean particle diameter and Aluminum-FA composites containing 10% and 20% of FA were then prepared and compacted. The green products were sintered for 2 h at 600 Degree-Sign C. Sintered Al-FA MMCs showed increased hardness and wear resistance suggesting their possible use in industrial applications for example in covers, casings, brake rotors or engine blocks. As most possible industrial applications of MMCs not only require wear resistance, but also corrosion resistance in different mild aggressive medias, this paper aims to study the electrochemical behavior of FA MMCs in order to evaluate their corrosion resistance. The morphology and chemical composition of the phases in the Aluminum-FA composite samples were investigated using Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDXS). Moreover, topographic and Volta potential maps were acquired by Scanning Kelvin Probe Force Microscopy (SKP-FM). Volta potential maps provide information about the electrochemical behavior of the different phases in absence of electrolyte. The electrochemical behavior was investigated by Open Circuit Potential measurements and potentiodynamic polarization, while the corrosion mechanisms were studied by SEM observations after different times of immersion in a mild corrosive medium. In all cases it could be stated that the addition of the FA particles into the Al matrix might cause an increase of the hardness and mechanical properties of the pure aluminum but deteriorates the corrosion resistance. The degradation phenomena occurring on the FA containing samples might be related to the following mechanisms: 1) Partial detachment or dissolution of the FA soluble phases, in particular based on Si, Fe and Ca; 2) dissolution of the Al matrix surrounding the FA particles due to crevice corrosion; 3) Al localized dissolution due to galvanic coupling between the Fe-rich intermetallics and the matrix. - Highlights: Black-Right-Pointing-Pointer Aluminum metal matrix composites containing two types of fly ashes have been characterized. Black-Right-Pointing-Pointer The microstructure and the electrochemical behavior have been studied using different techniques. Black-Right-Pointing-Pointer The addition of FA deteriorates the corrosion resistance of the aluminum. Black-Right-Pointing-Pointer Degradation mechanisms: galvanic coupling, crevice corrosion, detachment of FA particles.

Marin, E. [Department of Chemistry, Physics and Environment, University of Udine, Via Cotonificio 108, 33100, Udine (Italy); Lekka, M., E-mail: maria.lekka@uniud.it [Department of Chemistry, Physics and Environment, University of Udine, Via Cotonificio 108, 33100, Udine (Italy); Andreatta, F.; Fedrizzi, L. [Department of Chemistry, Physics and Environment, University of Udine, Via Cotonificio 108, 33100, Udine (Italy); Itskos, G. [School of Chemical Engineering, National Technical University of Athens, Iroon Polytechneiou 9, Zografou 15780, Athens (Greece); Centre for Research and Technology Hellas/Institute for Solid Fuels Technology and Applications, Mesogeion Avenue 357-359, Halandri 15231, Athens (Greece); Moutsatsou, A. [School of Chemical Engineering, National Technical University of Athens, Iroon Polytechneiou 9, Zografou 15780, Athens (Greece); Koukouzas, N. [Centre for Research and Technology Hellas/Institute for Solid Fuels Technology and Applications, Mesogeion Avenue 357-359, Halandri 15231, Athens (Greece); Kouloumbi, N. [School of Chemical Engineering, National Technical University of Athens, Iroon Polytechneiou 9, Zografou 15780, Athens (Greece)

2012-07-15

362

Structure of framework aluminum Lewis sites and perturbed aluminum atoms in zeolites as determined by 27Al{1H} REDOR (3Q) MAS NMR spectroscopy and DFT/molecular mechanics.  

PubMed

Zeolites are highly important heterogeneous catalysts. Besides Brnsted SiOHAl acid sites, also framework AlFR Lewis acid sites are often found in their H-forms. The formation of AlFR Lewis sites in zeolites is a key issue regarding their selectivity in acid-catalyzed reactions. The local structures of AlFR Lewis sites in dehydrated zeolites and their precursors--"perturbed" AlFR atoms in hydrated zeolites--were studied by high-resolution MAS NMR and FTIR spectroscopy and DFT/MM calculations. Perturbed framework Al atoms correspond to (SiO)3AlOH groups and are characterized by a broad (27)Al NMR resonance (?i = 59-62?ppm, CQ = 5?MHz, and ? = 0.3-0.4) with a shoulder at 40?ppm in the (27)Al?MAS?NMR spectrum. Dehydroxylation of (SiO)3AlOH occurs at mild temperatures and leads to the formation of AlFR Lewis sites tricoordinated to the zeolite framework. Al atoms of these (SiO)3Al Lewis sites exhibit an extremely broad (27)Al?NMR resonance (?i ? 67?ppm, CQ ? 20?MHz, and ? ? 0.1). PMID:25393612

Brus, Ji?; Kobera, Libor; Schoefberger, Wolfgang; Urbanov, Martina; Klein, Petr; Sazama, Petr; Tabor, Edyta; Sklenak, Stepan; Fishchuk, Anna V; D?de?ek, Ji?

2015-01-01

363

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

364

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

365

Complexation of aluminum with DNA.  

PubMed

The extent of complexation of aluminum(III) with DNA (Calf thymus, Sigma type I) was estimated by means of two experimental techniques: potentiometric titration with a fluoride selective indicator electrode and dialysis followed by aluminum determination by graphite furnace AAS. Both types of experiments indicate that aluminum(III) is bound to DNA. The data are treated by assuming an ion exchange reaction with the phosphate diester groups. Using Rt to denote the concentration of these groups the values of log [AlMn-3R]/(Rt-3[AlMn-3R])[Al3+] decrease from approx. 7.6 to 5.6 when the concentration of sodium chloride is increased from 1 to 100 mM. In the pH range 4.5-5.5 the ion exchange constant increases approximately 0.5 log units. Dialysis gives lower values for the complex formation constant than potentiometry. PMID:3559548

Dyrssen, D; Haraldsson, C; Nyberg, E; Wedborg, M

1987-01-01

366

Microstructural Evolution and Mechanical Properties of Nanointermetallic Phase Dispersed Al65Cu20Ti15 Amorphous Matrix Composite Synthesized by Mechanical Alloying and Hot Isostatic Pressing  

NASA Astrophysics Data System (ADS)

The structure and mechanical properties of nanocrystalline intermetallic phase dispersed amorphous matrix composite prepared by hot isostatic pressing (HIP) of mechanically alloyed Al65Cu20Ti15 amorphous powder in the temperature range 573 K to 873 K (300 C to 600 C) with 1.2 GPa pressure were studied. Phase identification by X-ray diffraction (XRD) and microstructural investigation by transmission electron microscopy confirmed that sintering in this temperature range led to partial crystallization of the amorphous powder. The microstructures of the consolidated composites were found to have nanocrystalline intermetallic precipitates of Al5CuTi2, Al3Ti, AlCu, Al2Cu, and Al4Cu9 dispersed in amorphous matrix. An optimum combination of density (3.73 Mg/m3), hardness (8.96 GPa), compressive strength (1650 MPa), shear strength (850 MPa), and Young's modulus (182 GPa) were obtained in the composite hot isostatically pressed ("hipped") at 773 K (500 C). Furthermore, these results were compared with those from earlier studies based on conventional sintering (CCS), high pressure sintering (HPS), and pulse plasma sintering (PPS). HIP appears to be the most preferred process for achieving an optimum combination of density and mechanical properties in amorphous-nanocrystalline intermetallic composites at temperatures ?773 K (500 C), while HPS is most suited for bulk amorphous alloys. Both density and volume fraction of intermetallic dispersoids were found to influence the mechanical properties of the composites.

Roy, D.; Mitra, R.; Ojo, O. A.; Lojkowski, W.; Manna, I.

2011-08-01

367

A STRUCTURAL STUDY OF ALUMINUM-CHLORHYDRATE  

Microsoft Academic Search

The structure of the antiperspirant aluminum chlorhydrate was determined to be the {Al(,13)O(,4)(OH)(,24)(H(,2)O)(,12)}('+7)Cl(,7). This structure is composed of a central aluminum in a tetrahedral configuration surrounded by twelve aluminum in a octahedral configuration. The structure is essentially spherical with a +7 charge equally distributed on the surface. Chloride ions act essentially as counterions.^ Chloride activity measurements indicated that the chloride

DIRK LOWELL TEAGARDEN

1980-01-01

368

Methemoglobinemia in aluminum phosphide poisoning  

Microsoft Academic Search

Introduction. Acute aluminum phosphide (AlP) poisoning is one of the most common causes of acute pesticide poisoning in Iran. Hydrogen phosphide or phosphine gas is produced following reaction of AlP with water even at ambient humidity. Methemoglobinemia is a rare finding following phosphine poisoning. In this paper, two cases of fatal AlP poisoning complicated by methemoglobinemia are reported. Case Report.

Shahin Shadnia; Kambiz Soltaninejad; Hossein Hassan ian-Moghadam; Anahaita Sadeghi; Hormat Rahimzadeh; Nasim Zamani; Alireza Ghasemi-Toussi; Mohammad Abdollahi

2011-01-01

369

Thermal imaging of nickel-aluminum and aluminum-polytetrafluoroethylene impact initiated combustion  

NASA Astrophysics Data System (ADS)

Combustion temperatures from impact initiated nickel-aluminum (NiAl) and aluminum-polytetrafluoroethylene (Al-PTFE) materials have been measured using a high-speed two-camera imaging pyrometer. The materials were launched with a nominal velocity of 1700 m/s into a sealed chamber. Upon impact into a steel anvil chemical reactions were initiated and a flame propagated through the chamber. The measured temperature after impact was 3600 K (NiAl) and 3300 K (Al-PTFE).

Densmore, John M.; Biss, Matthew M.; Homan, Barrie E.; McNesby, Kevin L.

2012-10-01

370

Aluminum Cans  

NSDL National Science Digital Library

In this data analysis activity students investigate data in connection with recyclable materials and develop plans to help the environment. Students collect data about aluminum can usage and graph that data in a line plot. The lesson includes student worksheet and extension suggestions.

2008-01-01

371

Aluminum Pannier  

USGS Multimedia Gallery

This aluminum pannier was made for the storage of meat, vegetables and other food products. The pannier could be buried in the ground or placed in water in order to keep the contents cool. It was designed by Dr. J. D. Love and made for him in 1945. For transportation, this pannier, along with two re...

372

Evaluation of aluminum tolerance in grapevine rootstocks  

Technology Transfer Automated Retrieval System (TEKTRAN)

Aluminum (Al) toxicity is a major worldwide agricultural problem. At low pH, Al speciates into the soluble and phyto-toxic form Al3+, causing inhibition of root growth and affecting plant development. In Brazil, agriculture in acidic soils regions with elevated concentration of Al has significantly ...

373

Thermodynamic Modeling of Aqueous Aluminum Chemistry and Solid-Liquid Equilibria to High Solution Concentration and Temperature. I. The Acidic H-Al-Na-K-Cl-H 2 O System from 0 to 100?C  

Microsoft Academic Search

In this paper, we describe the development of a thermodynamic model that calculates solute\\/solvent activities and solid-liquid\\u000a equilibria in the acidic aluminum system, H-Al3+-Na-K-Cl-H2O, to high molality from 0? to ?100?C. The model incorporates the concentration-dependent, specific interaction equations\\u000a for aqueous solutions of Pitzer (Activity Coefficients in Electrolyte Solutions, 2nd edn., pp.75153, CRC Press, Boca Raton,1991). Parameterization of this model

Christomir Christov; Andrew G. Dickson; Nancy Moller

2007-01-01

374

Method of forming aluminum oxynitride material and bodies formed by such methods  

DOEpatents

Methods of forming aluminum oxynitride (AlON) materials include sintering green bodies comprising aluminum orthophosphate or another sacrificial material therein. Such green bodies may comprise aluminum, oxygen, and nitrogen in addition to the aluminum orthophosphate. For example, the green bodies may include a mixture of aluminum oxide, aluminum nitride, and aluminum orthophosphate or another sacrificial material. Additional methods of forming aluminum oxynitride (AlON) materials include sintering a green body including a sacrificial material therein, using the sacrificial material to form pores in the green body during sintering, and infiltrating the pores formed in the green body with a liquid infiltrant during sintering. Bodies are formed using such methods.

Bakas, Michael P. (Ammon, ID) [Ammon, ID; Lillo, Thomas M. (Idaho Falls, ID) [Idaho Falls, ID; Chu, Henry S. (Idaho Falls, ID) [Idaho Falls, ID

2010-11-16

375

Development of damped metal-matrix composites for advanced structural applications. Technical report  

SciTech Connect

The development of damped metal matrix composite structures for advanced applications has been investigated by the use of two different approaches: (1) the development of metal matrix composites with high intrinsic damping compared to that of the matrix material, and (2) the development of coated metal matrix composites with high structural damping compared to that of the composite substrates. The two different approaches are analyzed in terms of their potential for improved damping and feasibility for structural applications. Damping was measured by the transverse vibration of free-free beams using the bandwidth technique by a laser vibrometer under ambient conditions. The damping measurements were made over a wide range of frequencies (.7 kHz to 25.6 kHz) at low strain amplitudes (10 to the -10 power to 10 to the -7 power). Materials investigated for their tensile stiffness, strength, and damping performance include mechanically alloyed (MA) Aluminum-Magnesium, SiC(p)/Aluminum-Copper (MA), SiC(p)/AL, AL2O3(p)/AL, SiC(W)/AL, planar random Gr/AL, unidirectional Gr/AL and unidirectional SiC(Nicalon)/AL composites. The effects of coatings of high damping metals (nitinol and incramute) on 6061-T6 AL and AL2O3(p)/AL substrates have also been studied. The AL-Mg (MA), SiC(p)/AL (MA), SiC(W)/AL and th AL2O3(p)/AL composites show no significant improvement in damping compared with that of the 6061-T6 AL.

Updike, C.A.; Bhagat, R.B.

1990-04-01

376

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

377

Transmission electron microscopy characterization of microstructural features in aluminum-lithium-copper alloys  

NASA Technical Reports Server (NTRS)

A transmission electron microscopy (TEM) examination of aluminum-lithium-copper alloys was conducted. The principal purpose is to characterize the nature, size, and distribution of stringer particles which result from the powder metallurgy (P/M) processing of these alloys. Microstructural features associated with the stringer particles are reported that help explain the stress corrosion susceptibility of the powder metallurgy-processed Al-Li-Cu alloys. In addition, matrix precipitaton events are documented for a variety of heat treatments and process variations. Hot rolling is observed to significantly alter the nature of matrix precipitation, and the observations are correlated with concomitant mechanical property variations.

Avalos-Borja, M.; Larson, L. A.; Pizzo, P. P.

1984-01-01

378

Redistribution of Ti and Al in deuterium charged TiAl  

SciTech Connect

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. 10 refs.

Legzdina, D.; Robertson, I.M.; Birnbaum, H.K. (Illinois, University, Urbana (United States))

1992-06-01

379

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

380

Extrusion of spark plasma sintered aluminum-carbon nanotube composites at various sintering temperatures.  

PubMed

The combined processes of spark plasma sintering and hot extrusion were used to fabricate a multi-walled carbon nanotube (MWCNT) reinforced aluminum (Al) matrix composite. The structural defects of carbon nanotubes (CNT) at various sintering temperatures were investigated by Raman spectroscopy. A small amount of Al liquid phase was generated and it reacted with disordered CNTs, even during the solid-state spark plasma sintering process. The influence of Al carbides generated by the reaction between Al and disordered CNTs is discussed from a microstructural viewpoint and in relation to tensile strength. We conclude that structurally controlled CNTs could potentially be attractive for metal matrix applications, and could significantly improve the mechanical properties of AI-CNT composites. PMID:19908562

Kwon, Hansang; Kawasaki, Akira

2009-11-01

381

Hydrothermal transformation of the calcium aluminum oxide hydrates CaAl{sub 2}O{sub 4}.10H{sub 2}O and Ca{sub 2}Al{sub 2}O{sub 5}.8H{sub 2}O to Ca{sub 3}Al{sub 2}(OH){sub 12} investigated by in situ synchrotron X-ray powder diffraction  

SciTech Connect

The hydrothermal transformation of calcium aluminate hydrates were investigated by in situ synchrotron X-ray powder diffraction in the temperature range 25 to 170 deg. C. This technique allowed the study of the detailed reaction mechanism and identification of intermediate phases. The material CaAl{sub 2}O{sub 4}.10H{sub 2}O converted to Ca{sub 3}Al{sub 2}(OH){sub 12} and amorphous aluminum hydroxide. Ca{sub 2}Al{sub 2}O{sub 5}.8H{sub 2}O transformed via the intermediate phase Ca{sub 4}Al{sub 2}O{sub 7}.13H{sub 2}O to Ca{sub 3}Al{sub 2}(OH){sub 12} and gibbsite, Al(OH){sub 3}. The phase Ca{sub 4}Al{sub 2}O{sub 7}.19H{sub 2}O reacted via the same intermediate phase to Ca{sub 3}Al{sub 2}(OH){sub 12} and mainly amorphous aluminum hydroxide. The powder pattern of the intermediate phase is reported.

Jensen, Torben R. [Interdisciplinary Nanoscience Center, Department of Chemistry, University of Aarhus, Langelandsgade 140, DK-8000 Aarhus C (Denmark)]. E-mail: trj@chem.au.dk; Christensen, Axel Norlund [Hojkolvej 7, DK-8210 Arhus V (Denmark); Hanson, Jonathan C. [Chemistry Department, Brookhaven National Laboratory, Upton, NY 11973, USA (United States)

2005-12-15

382

Processing and response of aluminum-lithium alloy composites reinforced with copper-coated silicon carbide particulates  

SciTech Connect

Lithium-containing aluminum alloys have shown promise for demanding aerospace applications because of their light weight, high strength, and good damage tolerance characteristics. Additions of ceramic reinforcements to an aluminum-lithium alloy can significantly enhance specific strength, and specific modulus while concurrently offering acceptable performance at elevated temperatures. The processing and fabrication of aluminum-lithium alloy-based composites are hampered by particulate agglomeration or clustering and the existence of poor interfacial relationships between the reinforcing phase and the matrix. The problem of distribution of the reinforcing phase in the metal matrix can be alleviated by mechanical alloying. This article presents the results of a study aimed at addressing and improving the interfacial relationship between the host matrix and the reinforcing phase. Copper-coated silicon carbide particulates are introduced as the particulate reinforcing phase, and the resultant composite mixture is processed by conventional milling followed by hot pressing and hot extrusion. The influence of extrusion ration and extrusion temperature on microstructure and mechanical properties was established. Post extrusion processing by hot isostatic pressing was also examined. Results reveal the increase in elastic modulus of the aluminum-lithium alloy matrix reinforced with copper-coated SiC to be significantly more than the mechanically alloyed Al-Li/SiC counterpart. This suggests the possible contributions of interfacial strengthening on mechanical response in direct comparison with a uniform distribution of the reinforcing ceramic particulates.

Khor, K.A.; Cao, Y.; Boey, F.Y.C. [Nanyang Technological Univ. (Singapore). School of Mechanical and Production Engineering] [Nanyang Technological Univ. (Singapore). School of Mechanical and Production Engineering; Hanada, K.; Murakoshi, Y. [AIST, Tsukuba (Japan). Mechanical Engineering Lab.] [AIST, Tsukuba (Japan). Mechanical Engineering Lab.; Sudarshan, T.S. [Materials Modification Inc., Fairfax, VA (United States)] [Materials Modification Inc., Fairfax, VA (United States); Srivatsan, T.S. [Univ. of Akron, OH (United States). Dept. of Mechanical Engineering] [Univ. of Akron, OH (United States). Dept. of Mechanical Engineering

1998-02-01

383

Suppression of activation energy and superconductivity by the addition of Al{sub 2}O{sub 3} nanoparticles in CuTl-1223 matrix  

SciTech Connect

Low anisotropic (Cu{sub 0.5}Tl{sub 0.5})Ba{sub 2}Ca{sub 2}Cu{sub 3}O{sub 10??} (CuTl-1223) high T{sub c} superconducting matrix was synthesized by solid-state reaction and Al{sub 2}O{sub 3} nanoparticles were prepared separately by co-precipitation method. Al{sub 2}O{sub 3} nanoparticles were added with different concentrations during the final sintering cycle of CuTl-1223 superconducting matrix to get the required (Al{sub 2}O{sub 3}){sub y}/CuTl-1223, y?=?0.0, 0.5, 0.7, 1.0, and 1.5?wt.?%, composites. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy, energy dispersive X-ray, and dc-resistivity (?) measurements. The activation energy and superconductivity were suppressed with increasing concentration of Al{sub 2}O{sub 3} nanoparticles in (CuTl-1223) matrix. The XRD analysis showed that the addition of Al{sub 2}O{sub 3} nanoparticles did not affect the crystal structure of the parent CuTl-1223 superconducting phase. The suppression of activation energy and superconducting properties is most probably due to weak flux pinning in the samples. The possible reason of weak flux pinning is reduction of weak links and enhanced inter-grain coupling due to the presence of Al{sub 2}O{sub 3} nanoparticles at the grain boundaries. The presence of Al{sub 2}O{sub 3} nanoparticles at the grain boundaries possibly reduced the number of flux pinning centers, which were present in the form of weak links in the pure CuTl-1223 superconducting matrix. The increase in the values of inter-grain coupling (?) deduced from the fluctuation induced conductivity analysis with the increased concentration of Al{sub 2}O{sub 3} nanoparticles is a theoretical evidence of improved inter-grain coupling.

Jabbar, Abdul; Qasim, Irfan; Mumtaz, M.; Zubair, M.; Nadeem, K. [Materials Research Laboratory, Department of Physics, FBAS, International Islamic University (IIU) Islamabad, Islamabad 44000 (Pakistan); Khurram, A. A. [Experimental Physics Labs, National Centre for Physics, Islamabad (Pakistan)

2014-05-28

384

HYDROGEN IN TITANIUM-ALUMINUM ALLOYS  

Microsoft Academic Search

The effects of hydrogen on the properties of binary Ti-Al alloys ; cortaining 2.5, 5, and 7% aluminum and arnary alloys of the same compositions ; with added interstitial elements oxygen, nitrogen, and carbon were studied. ; Aluminum increases the apparent hydrogen solubility of the alpha -phase, ; resulting in a mankind increase in resistance to impact embrittlement. In the

L. W. Berger; D. N. Williams; R. I. Jaffee

1958-01-01

385

A theoretical and experimental investigation of surface generation in diamond turning of an Al6061\\/SiC p metal matrix composite  

Microsoft Academic Search

In this paper, the surface generation in ultra-precision diamond turning of Al6061\\/15SiCp metal-matrix composites was investigated based on different analytical approaches which include parametric analysis, cutting mechanic analysis, finite element method (FEM) analysis and power spectrum analysis. Parametric analysis was performed to explore the in situ inter-relationships between the process parameters and the surface roughness. The surface properties of the

K. C Chan; C. F Cheung; M. V Ramesh; W. B Lee

2001-01-01

386

Analysis of the adhesion strength of the composite coating based on a sodium carboxymethylcellulose polymer matrix with a fine-dispersed aluminum filler  

Microsoft Academic Search

The formation of coagulates from the fine fractions of an Al powder on the microroughnesses of the steel surface was investigated\\u000a via scanning electron microscopy. The coagulates improve the adhesion strength of coatings due to the van der Waals interaction.\\u000a It is shown that a plasticizer increases the adhesion strength of coatings because its addition decreases internal stresses\\u000a in the

N. M. Antonova; V. I. Kulinich

2008-01-01

387

Microstructure of SiC-Si-Al2O3 composites derived from silicone resin - metal aluminum filler compounds by low temperature reduction process  

NASA Astrophysics Data System (ADS)

Concentrated slurry of a silicone resin with low carbon content, 3 ?m aluminum particles and ethanol were prepared. After casting, addition of cross-linking agent and drying, silicone resin-aluminum composite with thick sheet form was obtained. The prepared sheet was heat-treated at 933 or 1073K with various holding times to characterize formed phases during the heat treatments. XRD patterns and FT-IR spectra revealed free Si formation and existence of Si-O-Si bond at 933K. The Si-O-Si bond, however, disappeared and silicon carbide was formed at 1073K. SEM observation indicated formation of cracks bridged with a number of tiny struts at 933K and conversion to wholly porous structure at 1073K.

Narisawa, M.; Abe, Y.

2011-06-01

388

Aluminum Carbothermic Technology  

SciTech Connect

This report documents the non-proprietary research and development conducted on the Aluminum Carbothermic Technology (ACT) project from contract inception on July 01, 2000 to termination on December 31, 2004. The objectives of the program were to demonstrate the technical and economic feasibility of a new carbothermic process for producing commercial grade aluminum, designated as the ''Advanced Reactor Process'' (ARP). The scope of the program ranged from fundamental research through small scale laboratory experiments (65 kW power input) to larger scale test modules at up to 1600 kW power input. The tasks included work on four components of the process, Stages 1 and 2 of the reactor, vapor recovery and metal alloy decarbonization; development of computer models; and economic analyses of capital and operating costs. Justification for developing a new, carbothermic route to aluminum production is defined by the potential benefits in reduced energy, lower costs and more favorable environmental characteristics than the conventional Hall-Heroult process presently used by the industry. The estimated metrics for these advantages include energy rates at approximately 10 kWh/kg Al (versus over 13 kWh/kg Al for Hall-Heroult), capital costs as low as $1250 per MTY (versus 4,000 per MTY for Hall-Heroult), operating cost reductions of over 10%, and up to 37% reduction in CO2 emissions for fossil-fuel power plants. Realization of these benefits would be critical to sustaining the US aluminum industries position as a global leader in primary aluminum production. One very attractive incentive for ARP is its perceived ability to cost effectively produce metal over a range of smelter sizes, not feasible for Hall-Heroult plants which must be large, 240,000 TPY or more, to be economical. Lower capacity stand alone carbothermic smelters could be utilized to supply molten metal at fabrication facilities similar to the mini-mill concept employed by the steel industry. Major accomplishments for the program include definition of the system thermo-chemistry, demonstration of reactor stage 1, development of reactor stage 2 critical components in a 500 kW module, experimental determination of the vapor recovery reactor fundamentals, detailed design and installation of an advanced stage 1/vapor recovery reactor, feasibility of efficient separation of Al-C metal alloy product, updated capital and operating cost estimates, and development of computer models for all steps of the Advanced Reactor Process.

Bruno, Marshall J.

2005-03-31

389

Mobilizing aluminum in crustal and mantle fluids Craig E. Manning  

E-print Network

Mobilizing aluminum in crustal and mantle fluids Craig E. Manning Department of Earth and Space December 2005 Available online 9 March 2006 Abstract Aluminum is a major rock-forming element, but its low by formation of polynuclear Na­Al­Si­O clusters and/or polymers. Aluminum should not be assumed to be immobile

Manning, Craig

390

Characterization of molecular disorder in vapor-deposited thin films of aluminum tris(quinoline-8-olate) by one-dimensional 27Al NMR under magic angle spinning  

Microsoft Academic Search

Aluminum tris (quinoline-8-olate) (Alq3) is used as an electron-transport layer in organic light-emitting diodes. The material can be obtained in a wide range of different solid phases, both crystalline and amorphous, by deposition from the vapor phase or from solution under controlled conditions. While the structure of the crystalline polymorphs of Alq3 has been investigated thoroughly by x-ray diffraction as

Marcel Utz; Magesh Nandagopal; Mathew Mathai; Fotios Papadimitrakopoulos

2006-01-01

391

Formation of ettringite, Ca 6Al 2(SO 4) 3(OH) 1226H 2O, AFt, and monosulfate, Ca 4Al 2O 6(SO 4)14H 2O, AFm-14, in hydrothermal hydration of Portland cement and of calcium aluminum oxidecalcium sulfate dihydrate mixtures studied by in situ synchrotron X-ray powder diffraction  

NASA Astrophysics Data System (ADS)

In the hydration of calcium aluminum oxide-gypsum mixtures, i.e., Ca 3Al 2O 6, Ca 12Al 14O 33 and CaSO 42H 2O, the reaction products can be ettringite, Ca 6Al 2(SO 4) 3(OH) 1226H 2O, monosulfate, Ca 4Al 2O 6(SO 4)14H 2O, or the calcium aluminum oxide hydrate, Ca 4Al 2O 719H 2O. Ettringite is formed if sufficient CaSO 42H 2O is present in the mixture. Ettringite is converted to monosulfate when all CaSO 42H 2O is consumed in the synthesis of ettringite. The reactions were investigated in the temperature range 25-170C using in situ synchrotron X-ray powder diffraction. This technique allows the study of very fast chemical reactions that are observed here under hydrothermal conditions. A new experimental approach was developed to perform in situ mixing of the reactants during X-ray data collection.

Christensen, Axel Nrlund; Jensen, Torben R.; Hanson, Jonathan C.

2004-06-01

392

Tribocorrosion Behavior of Aluminum\\/Alumina Composite Manufactured by Anodizing and ARB Processes  

Microsoft Academic Search

In the present work, tribocorrosion behavior of Al\\/Al2O3 composite strips manufactured by anodizing and accumulative roll bonding (ARB) processes was investigated. The alumina quantity\\u000a was 0.48, 1.13, and 3.55vol.% in the aluminum matrix. Tribocorrosion experiments were conducted using a ball-on-plate tribometer,\\u000a where the sliding contact was fully immersed in 1wt.% NaCl solution. The composite sample served as a working electrode

Roohollah Jamaati; Mohammad Reza Toroghinejad; Jerzy A. Szpunar; Duanjie Li

393

Recycling of automotive aluminum  

Microsoft Academic Search

With the global warming of concern, the secondary aluminum stream is becoming an even more important component of aluminum production and is attractive because of its economic and environmental benefits. In this work, recycling of automotive aluminum is reviewed to highlight environmental benefits of aluminum recycling, use of aluminum alloys in automotive applications, automotive recycling process, and new technologies in

Jirang CUI; Hans J. ROVEN

2010-01-01

394

Structural Evaluation and Mechanical Properties of Aluminum/Tungsten Carbide Composites Fabricated by Continual Annealing and Press Bonding (CAPB) Process  

NASA Astrophysics Data System (ADS)

In the present work, a novel technique is introduced called continual annealing and press bonding (CAPB) for the manufacturing of a bulk aluminum matrix composite dispersed with 10 vol pct tungsten carbide particles (Al/WCp composite). The microstructural evolution and mechanical properties of the Al/WCp composite during various CAPB cycles were examined by scanning electron microscopy (SEM), wavelength dispersive X-ray spectroscopy (WDX), and tensile testing. The microstructure of the fabricated composite after fourteen cycles of CAPB showed homogenous distribution of the WC particles in the aluminum matrix and strong bonding between the various layers. According to WDX analysis, the manufactured Al/WCp composite did not evidence the presence of additional elements. 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 the fourteenth cycle, which was 1.6 times 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 process, it increased significantly during the final cycles. SEM observation of fracture surfaces showed that the rupture mode in the CAPB-processed Al/WCp composite was of the shear ductile rupture type.

Amirkhanlou, Sajjad; Ketabchi, Mostafa; Parvin, Nader; Drummen, G. P. C.

2014-12-01

395

Friction properties of Al1.5 Pct Mg\\/SiC particulate metal-matrix composites  

Microsoft Academic Search

With the advent of A1-SiC metal matrix composites (MMCs), research has been devoted to enhance the production, processing, and properties of these composites. u] The low cost of production of cast composites is an added benefit over other methods of production. By optimizing the dispersion of SiC particles in the matrix, conventionally cast products become comparably superior to other methods.

Farid Rana; D. M. Stefanescu

1989-01-01

396

Method of winning aluminum metal from aluminous ore  

DOEpatents

Aluminous ore such as bauxite containing alumina is blended with coke or other suitable form of carbon and reacted with sulfur gas at an elevated temperature. For handling, the ore and coke can be extruded into conveniently sized pellets. The reaction with sulfur gas produces molten aluminum sulfide which is separated from residual solid reactants and impurities. The aluminum sulfide is further increased in temperature to cause its decomposition or sublimation, yielding aluminum subsulfide liquid (AlS) and sulfur gas that is recycled. The aluminum monosulfide is then cooled to below its disproportionation temperature to again form molten aluminum sulfide and aluminum metal. A liquid-liquid or liquid-solid separation, depending on the separation temperature, provides product aluminum and aluminum sulfide for recycle to the disproportionation step.

Loutfy, Raouf O. (Naperville, IL); Keller, Rudolf (Naperville, IL); Yao, Neng-Ping (Clarendon Hills, IL)

1981-01-01

397

Aluminum Coprecipitates with Fe (hydr)oxides: Does Isomorphous Substitution of Al3plus for Fe3plus in Goethite Occur  

SciTech Connect

Iron (hydr)oxides are common in natural environments and typically contain large amounts of impurities, presumably the result of coprecipitation processes. Coprecipitation of Al with Fe (hydr)oxides occurs, for example, during alternating reduction-oxidation cycles that promote dissolution of Fe from Fe-containing phases and its re-precipitation as Fe-Al (hydr)oxides. We used chemical and spectroscopic analyses to study the formation and transformation of Al coprecipitates with Fe (hydr)oxides. In addition, periodic density functional theory (DFT) computations were performed to assess the structural and energetic effects of isolated or clustered Al atoms at 8 and 25 mol% Al substitution in the goethite structure. Coprecipitates were synthesized by raising the pH of dilute homogeneous solutions containing a range of Fe and Al concentrations (100% Fe to 100% Al) to 5. The formation of ferrihydrite in initial suspensions with {<=}20 mol% Al, and of ferrihydrite and gibbsite in initial suspensions with {>=}25 mol% Al was confirmed by infrared spectroscopic and synchrotron-based X-ray diffraction analyses. While base titrations showed a buffer region that corresponded to the hydrolysis of Fe in initial solutions with {<=}25 mol% Al, all of the Al present in these solutions was retained by the solid phases at pH 5, thus indicating Al coprecipitation with the primary Fe hydroxide precipitate. In contrast, two buffer regions were observed in solutions with 30 mol% Al (at pH {approx}2.25 for Fe{sup 3+} and at pH {approx}4 for Al{sup 3+}), suggesting the formation of Fe and Al (hydr)oxides as two separate phases. The Al content of initial coprecipitates influenced the extent of ferrihydrite transformation and of its transformation products as indicated by the presence of goethite, hematite and/or ferrihydrite in aged suspensions. DFT experiments showed that: (i) optimized unit cell parameters for Al-substituted goethites (8 and 25 Mol% Al) in clustered arrangement (i.e., the formation of diaspore-like clusters) were in good agreement with available experimental data whereas optimized unit cell parameters for isolated Al atoms were not, and (ii) Al-substituted goethites with Al in diaspore-like clusters resulted in more energetically favored structures. Combined experimental and DFT results are consistent with the coprecipitation of Al with Fe (hydr)oxides and with the formation of diaspore-like clusters, whereas DFT results suggest isomorphous Al for Fe substitution within goethite is unlike at 8 mol% Al substitution.

E Bazilevskaya; D Archibald; M Aryanpour; J Kubicki; C Martinez

2011-12-31

398

Fabrication of Al3 Wt pct Mg matrix composites reinforced with Al 2 O 3 and SiC particulates by the pressureless infiltration technique  

Microsoft Academic Search

In Al-3 wt pct Mg\\/Al2O3p\\u000a (or SiC\\u000a p\\u000a ) composites fabricated by the pressureless infiltration method, the infiltration behavior of molten metal, the mechanical\\u000a properties, and the interfacial reactions were investigated. The spontaneous infiltration of the molten Al-3 wt pct Mg alloy\\u000a into the powder bed occurred at a relatively low temperature (700 C for 1 hour under a nitrogen

Kon Bae Lee; Youn Su Kim; Hoon Kwon

1998-01-01

399

Aluminum Alloys for High Temperatures  

NASA Technical Reports Server (NTRS)

New Al/Li alloys processed by rapid solidification show greatly improved strength-to-density ratios. Alloys suitable substitutes for heavier titanium alloys and weaker aluminum alloys in high-performance aircraft, bombers, and transports. Also suitable for use in high-performance-aircraft structures heated by engines and normally constructed from titanium alloys.

Meschter, Peter J.; Lederich, Richard J.; O'Neal, James E.

1987-01-01

400

Molecular Structure of Aluminum bromide  

NSDL National Science Digital Library

Aluminum bromide is hygroscopic and appears as white to yellow-red lumps. It is corrosive and causes severe burns. It should be stored in a cool, dry and well ventilated place. AlBr3 reacts violently with water and evolves HBr, and also reacts quickly with alcohols and acids.

2002-10-09

401

Effect of aluminum exposure on pteridine metabolism  

Microsoft Academic Search

Occupational and environmental aluminum (Al) exposure cause serious health problems by interaction with biological systems.\\u000a Al is one of the most documented metals because its cellular targets are unclear biochemical processes and membranes of organisms.\\u000a The major aim of the present study was to investigate the alteration of serum and urine aluminum in occupational exposure\\u000a and to observe whether the

T. Baydar; A. B. Engin; A. Aydin; G. Sahin

2005-01-01

402

Mechanical behavior of Al-Al{sub 2}O{sub 3} MMC manufactured by PM techniques. Part 1: Scheme 1 processing parameters  

SciTech Connect

Metal matrix composites (MMC) were manufactured using hot pressing followed by hot extrusion of aluminum (Al) powder reinforced by alumina (Al{sub 2}O{sub 3}) particles. Under tensile as well as compressive loads, a strength improvement of 64 to 100% compared to the matrix material strength was obtained. The percent elongation to fracture ranged from 20 to 30%, which indicates good ductility as compared to the ductility of MMC manufactured by other techniques. Optical as well as scanning electron microscopy (SEM) examinations were used for characterization of the material microstructure and fracture behavior. Porosity retained in the microstructure was very limited in the case of pure aluminum billets. Microstructural examination revealed uniform distribution of Al{sub 2}O{sub 3} particles in the Al-matrix. Under tensile loads, voids opened by decohesion between the matrix and reinforcement. Such behavior led to a decrease in strength properties of the MMC as a function of reinforcement volume fraction. The fracture surface is dominated by the ductile fracture features, that is, dimples. Voids were found to initiate at retained porosity sites at the Al/Al{sub 2}O{sub 3} interface or in the matrix close to the interface due to stress concentration. The SEM revealed the formation of a complex fine subgrain structure. Such a polygonized structure is a major source of strengthening.

Mazen, A.A.; Ahmed, A.Y. [American Univ., Cairo (Egypt). Mechanical Engineering Dept.] [American Univ., Cairo (Egypt). Mechanical Engineering Dept.

1998-06-01

403

Compressive strength of a B2 matrix NiAl-Nb intermetallic at 1200 and 1300 K  

NASA Technical Reports Server (NTRS)

The effect of a large Nb addition to a NiAl, to a final composition 43.5Ni-45.2Al-0.8Fe-10.5Nb (in at. pct), on the high-temperature compressive strength of NiAl was investigated using cylindrical samples which were compression tested in air at 1200 K and 1300 K under constant-velocity conditions. The compressive strength of the Ni-45Al-10.5Nb was compared to data from all known solid solution-strengthened and/or precipitation-strengthened NiAl-based materials. It was found that, for strain rates higher than 5 x 10 to the -6th/sec, the Ni-45Al-10.5Nb is stronger than NiAl. However, this advantage disappears at lower strain rates. A comparison of NiAl-based materials indicated that a NiAl+TiB2 composite containing 20 vol pct 1-micron-diam particles has a strength superiority over all the solid solution and precipitation-hardened aluminides at strain rates below 10 to the -7th/sec.

Whittenberger, J. Daniel; Westfall, L. J.; Nathal, M. V.

1989-01-01

404

Subsurface Aluminum Nitride Formation in Iron-Aluminum Alloys  

NASA Astrophysics Data System (ADS)

Transformation-induced plasticity (TRIP) steels containing higher amounts of aluminum than conventional steels are ideal for structural automotive parts due to their mechanical properties. However, the aluminum tends to react with any processing environment at high temperatures and therefore presents significant challenges during manufacturing. One such challenge occurs during secondary cooling, reheating, and hot-rolling and is caused by a reaction with nitrogen-rich atmospheres wherein subsurface aluminum nitride forms in addition to internal and external oxides. The nitrides are detrimental to mechanical properties and cause surface cracks. It is important to understand how these nitrides and oxides form and their consequences for the quality of steel products. This study looks at model iron-aluminum (up to 8 wt.% aluminum) alloys and uses confocal laser scanning microscopy, x-ray diffraction, scanning electron microscopy with energy dispersive x-ray spectrometry, and transmission electron microscopy to study the effect of various conditions on the growth and development of these precipitates in a subsurface oxygen-depleted region. By using model alloys and controlling the experimental atmosphere, this study is able to understand some of the more fundamental materials science behind aluminum nitride formation in aluminum-rich iron alloys and the relationship between internal nitride and oxide precipitation and external oxide scale morphology and composition. The iron-aluminum alloys were heated in N2 atmospheres containing oxygen impurities. It was found that nitrides formed when bulk aluminum content was below 8 wt.% when oxygen was sufficiently depleted due to the internal oxidation. In the samples containing 1 wt.% aluminum, the depth of the internal oxide and nitride zones were in agreement with a diffusion-based model. Increasing aluminum content to 3 and 5 wt% had the effects of modifying the surface-oxide scale composition and increasing its continuity, which gradually decreased the internal precipitation zones with increasing aluminum content. In samples containing 8 wt.% aluminum, a thick continuous oxide scale formed and prevented nitrogen and oxygen penetration into the bulk of the sample, thus preventing the formation of any internal precipitates. The effect of modifying the heating rate in pure N2 atmospheres was examined. Samples were heated over the course of 1, 10, or 100 minutes. Faster heating rates increased the aluminum content in the oxide scale on all samples. Additionally, these rapid heating rate samples had either had lower internal precipitation depths or no internal precipitates. Experiments were conducted in N2--2.5% H2/H 2O mixtures with varying dew points to lower the oxygen potential of the reaction gas and prevent the formation of external iron oxide scales. In the 3 and 5 wt.% Al alloys, this produced an internal aluminum-rich oxide band which inhibited further internal precipitation. Samples treated in atmospheres to simulate the reheat furnace combustion atmosphere experienced dramatically increased external oxidation in addition to inward growth of the oxide scale and internal precipitation of oxides and nitrides within the metal. The most important scientific findings of this dissertation are the dramatic effect of heating rate on modifying the external scale of the alloys presented and the presence of continuous internal oxide bands in several samples throughout the study. Oxidation studies typically occur for longer times and in higher oxygen contents than the present results, so the influence of heating rate is either largely unnoticed or is overcome by oxide growth at long times. Oxide bands have been observed in literature, but few aluminum oxide bands have been seen before this study. vi.

Bott, June H.

405

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

406

Mechanical Properties of Squeeze Infiltrated AS52 Magnesium Matrix Composites  

NASA Astrophysics Data System (ADS)

Aluminum borate whisker (9(Al2O3)(B2O3)) reinforced AS52(with and without strontium modification) metal matrix composites (MMC) were fabricated by the squeeze infiltration method. Creep rupture test was carried out at 150C and 100 MPa condition. Results showed that Alborex reinforcement and modified polygonal shape Mg2Si phase contributed to the enhancement of mechanical properties and creep resistance. Creep rupture time was increased 11% and minimum creep rate was decreased 17% in the composite. At the Alborex/matrix interface, uniform thin layer of MgO was formed. The initiation of micro-voids at the reinforcement/matrix or Mg2Si/matrix interface was followed by their growth and coalescence to macro-cracks.

Park, Yong-Ha; Park, Yong-Ho; Park, Ik-Min; Cho, Kyung-Mox; Oak, Jeong-Jung; Kimura, Hisamichi

407

Ignition of Aluminum Particles and Clouds  

SciTech Connect

Here we review experimental data and models of the ignition of aluminum (Al) particles and clouds in explosion fields. The review considers: (i) ignition temperatures measured for single Al particles in torch experiments; (ii) thermal explosion models of the ignition of single Al particles; and (iii) the unsteady ignition Al particles clouds in reflected shock environments. These are used to develop an empirical ignition model appropriate for numerical simulations of Al particle combustion in shock dispersed fuel explosions.

Kuhl, A L; Boiko, V M

2010-04-07

408

High conductivity, low cost aluminum composite for thermal management  

SciTech Connect

In order to produce an inexpensive packaging material that exhibits high thermal conductivity and low CTE, Technical Research Associates, Inc. (TRA) has shown in Phase I the feasibility of incorporating natural flake graphite in an aluminum matrix. TRA has developed a proprietary coating technique where graphite flakes have been coated with a thin layer of molybdenum/molybdenum carbide (approximately 0.2 microns). This barrier coating can protect the graphite flake from chemical reaction and high temperature degradation in molten aluminum silicon alloys. Methods to successfully vacuum infiltrate coated flake with molten aluminum alloys were developed. The resulted metal matrix composites exhibited lower CTE than aluminum metal. The CTE of the composites were significantly lower than aluminum and its alloys. The CTE can potentially be tailored for specific applications. The in plane thermal conductivity was higher than the aluminum matrix alloy. The thermal conductivity and CTE of the composite may be significantly improved by improving the bond strength of the molybdenum coating on the graphite flake. The flake can potentially be incorporated in the molten aluminum and pressure die cast to align the flakes within the aluminum matrix. By preferentially aligning high conductivity graphite flakes within a plane or direction, the thermal conductivity of the resulting composite will be above pure aluminum in the alignment direction.

Sommer, J.L.

1997-04-01

409

/Al-Si Composites Fabricated by Reaction Hot Pressing  

NASA Astrophysics Data System (ADS)

Three in situ formed Al2O3/Al-Si composites with a different volume fraction of 10, 20, and 30 vol pct were fabricated using low energy ball milling and reaction hot pressing. The effect of reinforcement volume fraction on the microstructure and mechanical properties were studied. When the volume fraction was 30 vol pct, a massive primary Si (~130 m) along with an increase of Al2O3 (~2 m) was observed. The YS, UTS, and Brinell hardness of the composites were significantly higher than the aluminum matrix. Mechanisms governing the tensile fracture process are discussed.

Mokhnache, El Oualid; Wang, G. S.; Geng, L.; Huang, L. J.

2014-12-01

410

Mixed domain models for the distribution of aluminum in high silica zeolite SSZ-13.  

PubMed

High silica zeolite SSZ-13 with Si/Al ratios varying from 11 to 17 was characterized by aluminum-27 and silicon-29 NMR spectroscopy. Aluminum-27 MAS and MQMAS NMR data indicated that in addition to tetrahedral aluminum sites, a fraction of aluminum sites are present in distorted tetrahedral environments. Although in samples of SSZ-13 having high Si/Al ratios all aluminum atoms are expected to be isolated, silicon-29 NMR spectra revealed that in addition to isolated aluminum atoms (Si(1Al)), non-isolated aluminum atoms (Si(2Al)) exist in the crystals. To model these contributions of the various aluminum atoms, a mixed-domain distribution was developed, using double-six membered rings (D6R) as the basic building units of SSZ-13. A combination of different ideal domains, one containing isolated and the other with non-isolated aluminum sites, has been found to describe the experimental silicon-29 NMR data. PMID:23830719

Prasad, Subramanian; Petrov, Maria

2013-01-01

411

Metallography of a pulsed Nd:YAG laser weld in a RS/PM Al-8Fe-2Mo alloy  

SciTech Connect

This paper reports the microstructure of a pulsed Nd:YAG laser weld in a rapid solidification/powder metallurgy (RS/PM) Al-8.0 wt.% Fe-2.3 wt.% Mo (Al-8Fe-2Mo) alloy investigated using light microcopy, canning electron microscopy (SEM) and transmission electron microscopy (TEM) techniques. This analysis revealed significant microstructure variations across the weld fusion zone (FZ). Near the fusion boundary, a light-etching FZ microstructure was observed to contain submicron dispersoids entrapped in a matrix of fine-sized dendritic alpha aluminum. At the center of the FZ, the presence of relatively coarse-sized intermetallic particles that served as growth centers for coarser dendritic alpha aluminum promoted a dark-etching microstructure. In the boundary between successive melt zones, both a heat-affected zone (HAZ) containing acicular dispersoids and a fusion boundary region (FBR) containing irregular-shaped particles in a coarse-grained dendritic alpha aluminum matrix were observed.

Krishnaswamy, S.; Baeslack, W.A. III (Ohio State Univ., Columbus, OH (USA). Dept. of Welding Engineering)

1990-06-01

412

Stacking faults in SiC particles and their effect on the fracture behavior of a 15 vol pct SiC/6061-Al matrix composite  

SciTech Connect

Mechanical tests and microstructural examinations performed on a SiC-particle-reinforced 6061-Al matrix composite indicate that particle cracking during mechanical testing significantly affects the failure mechanisms of the composite. Microcracks were observed to nucleate and propagate on stacking faults and interfaces between the 4H (or 3C) and 6H hexagonal phases within the SiC particle reinforcements. These planar defects were the predominant defects seen in the SiC particles. Partial dislocations, having a 1/3 <10{bar 1}0> Burgers vector, were also observed bounding the stacking faults in the reinforcement phase.

Song, S.G.; Vaidya, R.U.; Zurek, A.K.; Gray, G.T. III [Los Alamos National Lab., NM (United States)

1996-02-01

413

Aluminum chloride formation on Space Shuttle aluminum oxide  

NASA Technical Reports Server (NTRS)

Samples of particulates collected from the exhaust of Space Shuttle launches STS-1, -4, -5, -6, and -7 were analyzed. Scanning electron microscopy and X-ray diffractometry of these samples indicated that the particulates were spherical and predominantly composed of aluminum oxide. The water-soluble weight fraction, pH, acid-soluble weight fraction, and insoluble weight fraction were determined for each sample. Water-soluble weight fractions averaged about 7 percent of the total sample weight, were generally very acidic, and contained significantly elevated concentrations of chloride and aluminum (III) ion. The high concentrations of soluble aluminum (III) and chloride ions observed suggested that aluminum chlorides and/or oxychlorides had formed on the surface of the alumina particulates. More than 72 percent by weight of each sample was insoluble in either water or strong mineral acid, and was identified as alpha-Al2O3. The results from these analyses suggest that the surface of Space Shuttle exhaust alumina particulates will be highly acidic and heavily chlorided, and that a substantial amount of the surface chloride may be chemically associated with aluminum (III) ions rather than just physically adsorbed as HCl.

Cofer, W. R., III

1984-01-01

414

Simulated Desorption of Aluminum and Oxide Covered Aluminum  

NASA Astrophysics Data System (ADS)

There is evidence that laser or electron stimulated nonthermal desorption from aluminum can proceed through plasmon excitation processes. Arakawa et al. observed this phenomenon with Al films and Kim et al. observed it with direct laser irradiation. (E.T. Arakawa, I. Lee and T.A. Callcott in Laser Ablation, J.C. Miller and R.F. Haglund Eds., Springer-Verlag, NY, 82 (1991).; H. S. Kim and H. Helvjian, J. Phys. Chem. 95, 6623 (1991).) Dreyfus et al. found nonthermal Al neutral species from laser irradiation of Al_2O_3, Schildbach et al. measured nonthermal Al ions from a well characterized sapphire (1120) sample, and Pedraza et al. showed that for laser irradiation of both alumina and sapphire there is a change in the degree of oxidation of the surface Al.(R.W. Dreyfus, R. Kelly and R.E. Walkup, Appl. Phys. Lett. 49, 1478 (1986);M.A. Schildbach and A.V. Hamza, Phys. Rev. B. 45, 6197 (1992); Pedraza et al., AIP Proc., Vol. 288 (1993) pg. 329.) These experiments show that oxygen on Al does not quench the nonthermal desorption. We will present measurements of the Al yield and K. E. w.r.t. oxygen coverage and laser fluence. This stimulated desorption work has environmental relevance to the storage of oxidized Al clad nuclear fuel rods.

Helvajian, Henry

1998-03-01

415

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

416

Evaluation of precipitates used in strainer head loss testing : Part II. precipitates by in-situ aluminum alloy corrosion.  

SciTech Connect

Vertical loop head loss tests were performed with 6061 and 1100 aluminum (Al) alloy plates immersed in borated solution at pH = 9.3 at room temperature and 60 C. The results suggest that the potential for corrosion of an Al alloy to result in increased head loss across a glass fiber bed may depend on its microstructure, i.e., the size distribution and number density of intermetallic particles that are present in Al matrix and FeSiAl ternary compounds, as well as its Al release rate. Per unit mass of Al removed from solution, the WCAP-16530 aluminum hydroxide (Al(OH){sub 3}) surrogate was more effective in increasing head loss than the Al(OH)3 precipitates formed in situ by corrosion of Al alloy. However, in choosing a representative amount of surrogate for plant specific testing, consideration should be given to the potential for additional head losses due to intermetallic particles and the apparent reduction in the effective solubility of Al(OH){sub 3} when intermetallic particles are present.

Bahn, C.; Kasza, K. E.; Shack, W. J.; Natesan, K. (Nuclear Engineering Division)

2011-05-01

417

A comparative wear study on Al-Li and Al-Li/SiC composite  

SciTech Connect

Aluminum-lithium based unreinforced (Al-8090) alloy and Al-8090/SiCp/17 vol.% metal matrix composite produced by extrusion after spray co-deposition. A dry ball-on disk wear test was carried out for both alloy and composite. The tests were performed against an Al{sub 2}O{sub 3} ball, 10 mm in diameter, at room temperature and in laboratory air conditions with a relative humidity of 40-60%. Sliding speed was chosen as 1.0 ms{sup ?1} and normal loads of 1.0, 3.0 and 5.0 N were employed at a constant sliding distance of 1000 m. The wear damage on the specimens was evaluated via measurement of wear depth and diameter. Microstructural and wear characterization was carried out via scanning electron microscopy (SEM). The results showed that wear loss of the Al-8090/SiC composite was less than that of the Al-8090 matrix alloy. Plastic deformation observed on the wear surface of the composite and the matrix alloy, and the higher the applied load the greater the plastic deformation. Scanning electron microscopy examinations of wear tracks also reveal that delamination fracture was the dominant wear mechanism during the wear progression. Friction coefficient was maximum at the low applied load in the case of the Al-8090/SiC composite while a gradual increase was observed with applied load for the matrix alloy.

Okumus, S. Cem, E-mail: cokumus@sakarya.edu.tr; Karslioglu, Ramazan, E-mail: cokumus@sakarya.edu.tr; Akbulut, Hatem, E-mail: cokumus@sakarya.edu.tr [Sakarya University Engineering Faculty, Department of Metallurgical and Materials Engineering, Esentepe Campus, 54187, Sakarya (Turkey)

2013-12-16

418

A comparative wear study on Al-Li and Al-Li/SiC composite  

NASA Astrophysics Data System (ADS)

Aluminum-lithium based unreinforced (Al-8090) alloy and Al-8090/SiCp/17 vol.% metal matrix composite produced by extrusion after spray co-deposition. A dry ball-on disk wear test was carried out for both alloy and composite. The tests were performed against an Al2O3 ball, 10 mm in diameter, at room temperature and in laboratory air conditions with a relative humidity of 40-60%. Sliding speed was chosen as 1.0 ms-1 and normal loads of 1.0, 3.0 and 5.0 N were employed at a constant sliding distance of 1000 m. The wear damage on the specimens was evaluated via measurement of wear depth and diameter. Microstructural and wear characterization was carried out via scanning electron microscopy (SEM). The results showed that wear loss of the Al-8090/SiC composite was less than that of the Al-8090 matrix alloy. Plastic deformation observed on the wear surface of the composite and the matrix alloy, and the higher the applied load the greater the plastic deformation. Scanning electron microscopy examinations of wear tracks also reveal that delamination fracture was the dominant wear mechanism during the wear progression. Friction coefficient was maximum at the low applied load in the case of the Al-8090/SiC composite while a gradual increase was observed with applied load for the matrix alloy.

Okumus, S. Cem; Karslioglu, Ramazan; Akbulut, Hatem

2013-12-01

419

Residual microstructure and damage geometry associated with high speed impact crater in Al{sub 2}O{sub 3} and TiB{sub 2} particles reinforced 2024 Al composite  

SciTech Connect

The resistance of Al{sub 2}O{sub 3} + TiB{sub 2}/2024Al composite to hypervelocity impact was tested by a two-stage light gas gun. The impact damage behaviors of the Al{sub 2}O{sub 3} + TiB{sub 2}/2024Al composite by different-sized Al projectiles with a velocity of 2.49 km/s and the residual microstructures associated with the crater impacted by a 1.2 mm aluminum projectile were investigated by transmission electron microscopy and high-resolution transmission electron microscopy. Both the diameters of craters at front face and spalling areas at back face increased with the aluminum projectile diameter. The diameter of perforation on the 2 mm thick Al{sub 2}O{sub 3} + TiB{sub 2}/Al composite target was zero when impacted by 1.2 mm aluminum projectile and it increased to 2.4 mm when the projectile diameter was 1.5 mm, indicating that the critical perforation diameter of the aluminum projectile was between 1.2 mm and 1.5 mm when the 2 mm thick Al{sub 2}O{sub 3} + TiB{sub 2}/Al composite target was impacted by 2.49 km/s aluminum projectiles. The diameter of perforation increases with the diameter of Al projectile. In addition, under each impact condition, the diameters of craters at front face were smaller than that of spalling areas at back face. Microstructure observations by transmission electron microscopy demonstrated four characteristics: stacking faults around TiB{sub 2} particle and dislocations within the TiB{sub 2} particle; twins in the Al{sub 2}O{sub 3} particle; recrystal grains in 2024 Al matrix; and mixture of amorphous microstructure and nanograins in the matrix. - Highlights: Black-Right-Pointing-Pointer Stacking faults were produced around the edge of TiB{sub 2} particle after impact. Black-Right-Pointing-Pointer Twins with the twin plane of (2{sup Macron }112) were observed in Al{sub 2}O{sub 3} particle after impact. Black-Right-Pointing-Pointer Recrystal grains with size of 100 nm were formed in aluminum matrix after impact. Black-Right-Pointing-Pointer Mixture of amorphous microstructure and nanograins was also found in matrix.

Guo, Q.; Sun, D.L., E-mail: sdl602@hit.edu.cn; Jiang, L.T.; Wu, G.H.; Chen, G.Q.

2012-04-15

420

High-velocity-oxidation performance of metal-chromium-aluminum (MCrAl), cermet, and modified aluminide coatings on IN-100 and type VIA alloys at 1093 C  

NASA Technical Reports Server (NTRS)

Cermet, MCrAl, and modified aluminide types of coatings applied to IN-100 and NASA-TRW-VIA alloy specimens were cyclically oxidation tested in a high velocity (Mach 1) gas flame at 1093 C. Several coating compositions of each type were evaluated for oxidation resistance. The modified aluminide coating, Pt-Al, applied to alloy 6A proved to be the best, providing oxidation protection to approximately 750 hours based on weight change measurements. The second best, a CoCrAlY coating applied to 6A, provided protection to 450 hours. The third best was a cermet + aluminide coating on 6A with a protection time to 385 hours.

Deadmore, D. L.

1974-01-01

421

Characterization of Metal Matrix Composites  

NASA Technical Reports Server (NTRS)

Experimental methods were developed, adapted, and applied to the characterization of a metal matrix composite system, namely, silicon carbide/aluminim (SCS-2/6061 Al), and its constituents. The silicon carbide fiber was characterized by determining its modulus, strength, and coefficient of thermal expansion. The aluminum matrix was characterized thermomechanically up to 399 C (750 F) at two strain rates. The unidirectional SiC/Al composite was characterized mechanically under longitudinal, transverse, and in-plane shear loading up to 399 C (750 F). Isothermal and non-isothermal creep behavior was also measured. The applicability of a proposed set of multifactor thermoviscoplastic nonlinear constitutive relations and a computer code was investigated. Agreement between predictions and experimental results was shown in a few cases. The elastoplastic thermomechanical behavior of the composite was also described by a number of new analytical models developed or adapted for the material system studied. These models include the rule of mixtures, composite cylinder model with various thermoelastoplastic analyses and a model based on average field theory. In most cases satisfactory agreement was demonstrated between analytical predictions and experimental results for the cases of stress-strain behavior and thermal deformation behavior at different temperatures. In addition, some models yielded detailed three-dimensional stress distributions in the constituents within the composite.

Daniel, I. M.; Chun, H. J.; Karalekas, D.

1994-01-01

422

SCIENCE CAREER Al nanoclusters in coagulants and granulates: application  

E-print Network

aluminum hydroxide complexes with 1 nm diameter and 12 nm length. Al13 is a cluster of four Al trimers suitable for arsenic removal. The aluminum nanocl- usters Al13 (AlO4Al12(OH)24H2O12 7? ) and Al30 (Al2O8Al properties of aluminum nanoclusters and their efficiency for water treatment, particularly for arsenic

Wehrli, Bernhard

423

The viability of aluminum Zintl anion moieties within magnesium-aluminum clusters  

SciTech Connect

Through a synergetic combination of anion photoelectron spectroscopy and density functional theory based calculations, we have investigated the extent to which the aluminum moieties within selected magnesium-aluminum clusters are Zintl anions. Magnesium-aluminum cluster anions were generated in a pulsed arc discharge source. After mass selection, photoelectron spectra of Mg{sub m}Al{sub n}{sup ?} (m, n = 1,6; 2,5; 2,12; and 3,11) were measured by a magnetic bottle, electron energy analyzer. Calculations on these four stoichiometries provided geometric structures and full charge analyses for the cluster anions and their neutral cluster counterparts, as well as photodetachment transition energies (stick spectra). Calculations revealed that, unlike the cases of recently reported sodium-aluminum clusters, the formation of aluminum Zintl anion moieties within magnesium-aluminum clusters was limited in most cases by weak charge transfer between the magnesium atoms and their aluminum cluster moieties. Only in cases of high magnesium content, e.g., in Mg{sub 3}Al{sub 11} and Mg{sub 2}Al{sub 12}{sup ?}, did the aluminum moieties exhibit Zintl anion-like characteristics.

Wang, Haopeng; Jae Ko, Yeon; Zhang, Xinxing; Gantefoer, Gerd; Bowen, Kit H., E-mail: kiran@mcneese.edu, E-mail: akandalam@wcupa.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Schnoeckel, Hansgeorg [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany)] [Institute of Inorganic Chemistry, Karlsruhe Institute of Technology, 76128 Karlsruhe (Germany); Eichhorn, Bryan W. [Department of Chemistry, University of Maryland, College Park, Maryland 20742 (United States)] [Department of Chemistry, University of Maryland, College Park, Maryland 20742 (United States); Jena, Puru [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States)] [Department of Physics, Virginia Commonwealth University, Richmond, Virginia 23284 (United States); Kiran, Boggavarapu, E-mail: kiran@mcneese.edu, E-mail: akandalam@wcupa.edu, E-mail: kbowen@jhu.edu [Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 (United States)] [Department of Chemistry, McNeese State University, Lake Charles, Louisiana 70609 (United States); Kandalam, Anil K., E-mail: kiran@mcneese.edu, E-mail: akandalam@wcupa.edu, E-mail: kbowen@jhu.edu [Department of Physics, West Chester University, West Chester, Pennsylvania 19383 (United States)

2014-03-28

424

Effects of Effective Dendrite Size on Tensile Deformation Behavior in Ti-Based Dendrite-Containing Amorphous Matrix Composites Modified from Ti-6Al-4V Alloy  

NASA Astrophysics Data System (ADS)

Five composite sheets having different thicknesses were fabricated by varying cooling rates after a vacuum arc melting of a Ti-based amorphous matrix composite fabricated by adding alloying elements of Ti, Zr, V, Ni, Al, and Be into a Ti-6Al-4V alloy. These composite sheets contained 72 to 75 vol. pct of dendrites sized by 9 to 27 ?m, and showed excellent tensile properties of yield strength of 1.3 GPa and elongation up to 6.5 pct. According to the observation of tensile deformation behavior of the 3-mm-thick composite sheet, many deformation bands were formed inside dendrites in several directions, and deformation bands met crossly each other to form widely deformed areas. Since the wide and homogeneous deformation in this sheet beneficially worked for the tensile strength and elongation simultaneously, the optimum effective dendrite size (12.1 ?m) and sheet thickness (3 mm) were determined for the Ti-based amorphous matrix composite. The finite element method (FEM) analysis based on real microstructures was also conducted to theoretically explain the enhanced elongation in terms of effective dendrite size. The shape and location of deformation bands estimated from the FEM simulations were well matched with the experimental observations.

Jeon, Changwoo; Lee, Hyungsoo; Kim, Choongnyun Paul; Joo, Soo-Hyun; Kim, Hyoung Seop; Lee, Sunghak

2015-01-01

425

Studies of aluminum in rat brain  

SciTech Connect

The effects of high aluminum concentrations in rat brains were studied using /sup 14/C autoradiography to measure the uptake of /sup 14/C 2-deoxy-D-glucose (/sup 14/C-2DG) and microbeam proton-induced x-ray emission (microPIXE) with a 20-..mu..m resolution to measure concentrations of magnesium, aluminum, potassium, and calcium. The aluminum was introduced intracisternally in the form of aluminum tartrate (Al-T) while control animals were given sodium tartrate (Na-T). The /sup 14/C was administered intravenously. The animals receiving Al-T developed seizure disorders and had pathological changes that included cerebral cortical atrophy. The results showed that there was a decreased uptake of /sup 14/C-2DG in cortical regions in which increased aluminum levels were measured, i.e., there is a correlation between the aluminum in the rat brain and decreased brain glucose metabolism. A minimum detection limit of about 16 ppM (mass fraction) or 3 x 10/sup 9/ Al atoms was obtained for Al under the conditions employed. 14 refs., 4 figs., 1 tab.

Lipman, J.J.; Brill, A.B.; Som, P.; Jones, K.W.; Colowick, S.; Cholewa, M.

1985-01-01

426

Impact of aluminum concentration and magnesium doping on the effect of electron injection in p-Al xGa 1- xN  

NASA Astrophysics Data System (ADS)

The impact of electron injection on the minority carrier diffusion length was studied at various temperatures in p