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1

Tensile properties of nanometric Al 2O 3 particulate-reinforced aluminum matrix composites  

Microsoft Academic Search

The hardness and tensile behaviors of aluminum matrix composites reinforced with nanometric Al2O3 particulate have been found to increase with the volume fraction of the reinforcement. Above 4vol.% of Al2O3, however, the strengthening effect leveled off because of the clustering of Al2O3. The main strengthening mechanism was Orowan strengthening of effective nano-Al2O3 particles evenly distributed in the matrix.

Yung-Chang Kang; Sammy Lap-Ip Chan

2004-01-01

2

An investigation of laser-assisted machining of Al 2O 3 particle reinforced aluminum matrix composite  

Microsoft Academic Search

Al2O3 particles reinforced aluminum matrix composite (Al2O3p\\/Al) are becoming increasingly used for their excellent physical and chemical properties. However, their poor machinability leads to severe tool wear and to a bad machined surface. In this paper laser heat-assisted machining is adopted in machining Al2O3p\\/Al composite, good results being obtained. The result of the present experiment shows that in machining Al2O3p\\/Al

Y Wang; L. J Yang; N. J Wang

2002-01-01

3

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

NASA Astrophysics Data System (ADS)

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

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

2013-08-01

4

Aluminum Metal Matrix Composites  

SciTech Connect

Metal matrix composites comprise a relatively wide range of materials defined by the metal matrix, reinforcement type, and reinforcement geometry. In the area of the matrix, most metallic systems have been explored for use in metal matrix composites, including Al, Be, Mg, Ti, Fe, Ni, Co, and Ag. By far, the largest usage is in aluminum matrix composites. From a reinforcement perspective, the materials used are typically ceramics since they provide a very desirable combination of stiffness, strength, and relatively low density. Candidate reinforcement materials include SiC, Al2O3, B4C, TiC, TiB2, graphite, and a number of other ceramics. In addition, there has been work on metallic materials as reinforcements, notably W and steel fibers. The morphology of the reinforcement material is another variable of importance in metal matrix composites. The three major classes of reinforcement morphology are continuous fiber, chopped fiber or whisker, and particulate. Typically, the selection of the reinforcement morphology is determined by the desired property/cost combination. Generally, continuous fiber reinforced MMCs provide the highest properties in the direction of the fiber orientation but are the most expensive. Chopped fiber and whisker reinforced materials can produce significant property improvements in the plane or direction of their orientation, at somewhat lower cost. Particulates provide a comparatively more moderate but isotropic increase in properties and are typically available at the lowest cost. By adding to the three variables of metallic matrix, reinforcement material, and reinforcement morphology the further options of reinforcement volume fraction, orientation, and matrix alloy composition and heat treatment, it is apparent that there is a very wide range of available material combinations and resultant properties. This paper will focus on how MMCs have been applied in specific application areas.

Hunt, Warren; Herling, Darrell R.

2004-02-01

5

Corrosion-Resistant Aluminum Matrix for Graphite-Aluminum Composites  

Microsoft Academic Search

Graphite-aluminum (Gr-Al) metal matrix composites (MMC) possess several attractive mechanical and thermal properties, but use of these materials has been limited, partly because they are extremely susceptible to corrosion. Corrosion-resistant Al alloys that contained nonequilibrium concentrations of molybdenum (Mo) were developed as the matrix for G-Al composites using co-sputter deposition. Corrosion testing included potentiodynamic polarization and galvanic coupling of as-sputtered

R. G. Wendt; B. G. Shaw; W. C. Moshier; P. G. Miller; D. L. Olson

1994-01-01

6

Spark plasma sintering of aluminum matrix composites  

NASA Astrophysics Data System (ADS)

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

Yadav, Vineet

7

In Situ ceramic particle-reinforced aluminum matrix composites fabricated by reaction pressing in the TiO 2 (Ti)AlB (B 2 O 3 ) systems  

Microsoft Academic Search

Particulate TiB2 reinforced aluminum-based metal matrix composites (MMCs) were successfully fabricated by means of the reaction processing\\u000a method. TiB2 particulates were formed in situ through the reaction of Ti and B in Ti-Al-B, TiO2 and B in TiO2-Al-B, and TiO2 and B2O3 in TiO2-Al-B2O3 systems. The results showed that in situ TiB2 particulates formed in the Ti-Al-B system had a

Z. Y. Ma; S. C. Tjong

1997-01-01

8

Nonequilibrium Alloying of Graphite-Reinforced Aluminum Metal Matrix Composites  

Microsoft Academic Search

With corrosion behavior superior to pure aluminum (Al), nonequilibrium Al alloys produced by cosputter deposition have great potential for use a s matrix metals in graphite (Gr)-reinforced Al composites. These composites offer enhanced properties as a result of their low density matrix and a high modulus reinforcing fiber. Cosputter-deposited Al alloys provide a means to improve corrosion resistance of Al

T. R. Schrecengost; B. A. Shaw; R. G. Wendt; W. C. Moshier

1993-01-01

9

Galvanic Corrosion of Aluminum-Matrix Composites.  

National Technical Information Service (NTIS)

Galvanic-corrosion rates of Al-matrix composites were high in aerated chloride-containing solutions. Oxygen reduction was found to be the primary cathodic reaction. Aluminum corroded by pitting. The type of noble constituent (i.e., graphite, SiC, or TiB2)...

L. H. Hihara R. M. Latanision

1991-01-01

10

Corrosion-resistant aluminum matrix for graphite-aluminum composites  

SciTech Connect

Graphite-aluminum (Gr-Al) metal matrix composites (MMC) possess several attractive mechanical and thermal properties, but use of these materials has been limited, partly because they are extremely susceptible to corrosion. Corrosion-resistant Al alloys that contained nonequilibrium concentrations of molybdenum (Mo) were developed as the matrix for G-Al composites using co-sputter deposition. Corrosion testing included potentiodynamic polarization and galvanic coupling of as-sputtered (AS) and heat-treated (HT) alloys. Polarization behavior of the AS and HT alloys measured in sodium chloride (NaCl) solutions was improved greatly over that of pure Al and traditional Gr-Al matrix alloys such as type 6061 Al (UNS A96061). Galvanic current density values for as-deposited and HT Al-18% Mo and Al-23% Mo alloys coupled to equal areas of pitch-based graphite from Amoco P75 Gr fibers were found to be up to 3 orders of magnitude lower than for pure sputtered Al-to-Gr couples. Galvanic diagrams for the Al-Mo alloys indicated corrosion was controlled by the anodic reaction irrespective of the cathode-to-anode area ratio.

Wendt, R.G.; Moshier, W.C. (Martin Marietta Astronautics, Denver, CO (United States)); Shaw, B. (Pennsylvania State Univ., University Park, PA (United States)); Miller, P. (Environmental Protection Agency, Washington, DC (United States)); Olson, D.L. (Colorado School of Mines, Golden, CO (United States))

1994-11-01

11

Study of brazeability of aluminum matrix composites  

SciTech Connect

The brazeability of several aluminum matrix composites has been evaluated in the present paper. Tested materials were two different 6061 aluminum alloys, reinforced with 10 and 20% alumina particles, respectively, and a 7005 aluminum alloy containing 10% alumina also in the form of discrete particles. A drop formation test was selected to evaluate the brazeability of the studied composites, using a commercial filler metal (BAlSi4) generally used for brazing of aluminum alloys. Wettability of molten braze on the metal matrix composites (MMCs) was determined by measurement of the solidified contact angle i n sessile drop tests and determination of the spread area. The wettability and spreading increase with the brazing temperature in the studied range (550--625 C, 1,022--1,157 F), and decrease when the reinforcement proportion is increased. Both properties are also influenced by the type of the composite aluminum matrix being enhanced in the Al-Zn-Mg reinforced alloy. This study was completed with the microstructural characterization of the drop test specimens and of real brazed joints made on T-shaped specimens.

Urena, A.; Salazar, J.M.G. de; Escalera, M.D.; Fernandez, M.I. [Univ. Complutense de Madrid (Spain). Dept. de Ciencia de los Materiales e Ingenieria Metalurgica

1997-02-01

12

Fabrication of Aluminum Matrix Hybrid Nanocomposite by Mechanical Milling  

NASA Astrophysics Data System (ADS)

Fabrication and characterization of aluminum matrix composite reinforced by Al2O3-AlB12 particles were investigated. Al2O3-AlB12 composite powder was first synthesized by mechanochemical route starting from Al and B2O3 powder mixture. Then, prepared Al2O3-AlB12 powder was mixed with pure aluminum powder and ball milled in order to produce Al — 20 wt.% (Al2O3-AlB12) composite. The structural evaluation of powders was studied by X-ray diffraction, scanning electron microscopy, and microhardness measurement. The results showed that through ball milling process a homogeneous distribution of Al2O3-AlB12 particles in nanocrystalline Al matrix was obtained. This structure exhibited good thermal stability and high hardness value of 190 HV which is significantly higher than 33 HV for pure Al.

Sharifi, E. Mohammad; Karimzadeh, F.; Enayati, M. H.

13

Corrosion protection of aluminum metal-matrix composites  

SciTech Connect

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

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

1997-12-01

14

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

Microsoft Academic Search

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

Chia Chaw Perng; Jiun Ren Hwang; Ji Liang Doong

1993-01-01

15

INDUSTRIALIZATION OF CAST ALUMINUM MATRIX COMPOSITES (AMCCs)  

Microsoft Academic Search

This paper briefly describes the main research points and activities which have been considered toward industrialization of cast aluminum matrix composites (AMCCs). First, the issues in liquid processing of metal matrix composites are reviewed. The different requirements for successful AMCCs are then described. Post-processingsuch as heat treatment, forming, and machining, which can beperformed on AMCCs, are discussed. The up-to-date, specially

Mohamed A. Taha

2001-01-01

16

Functionally Graded Dual-Nanoparticulate-Reinforced Aluminum Matrix Composite Materials  

NASA Astrophysics Data System (ADS)

Functionally graded carbon nanotubes (CNT) and nano Silicon carbide (nSiC) reinforced aluminum (Al) matrix composite materials were fully densified by a simple ball milling and hot-pressing processes. The nSiC was used as a physical mixing agent to increase dispersity of the CNT in the Al particles. It was observed that the CNT was better dispersed in the Al particles with a nSiC mixing agent compared to without it used. SEM micrograph showed that the interface of the each layers had very tightly adhesion without any serious pores and micro-cracks. This functionally graded dual-nanoparticulate-reinforced Al matrix composite by powder metallurgical approach could also be applied to comples matrix materials.

Kwon, Hansang; Lee, Gil-Geun; Leparoux, Marc; Kawasaki, Akira

2013-03-01

17

Dual-nanoparticulate-reinforced aluminum matrix composite materials  

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

18

Synthesis of germanium nanocrystals in hafnium aluminum oxide matrix  

NASA Astrophysics Data System (ADS)

An examination on the effect of annealing temperature and duration, and the germanium (Ge) concentration on the growth of Ge nanocrystals in hafnium aluminum oxide (HfAlO) matrix, was carried out using a combination of Raman spectroscopy, transmission electron microscopy, and secondary ions mass spectrometry techniques. We found Ge nanocrystals in the HfAlO matrix with a Ge content of 10.5 at. % when annealed at 800 °C. At a relatively higher content of Ge at 23.3 at. % in HfAlO film, a significant outdiffusion of Ge at the film surface or diffusion into the Si substrate occurred, and this imposes a narrow annealing condition for the formation of nanocrystals. We attribute the different nanocrystal formation characteristics in the HfAlO and silicon oxide matrices to the difference crystallization temperatures of HfAlO and silicon oxide films.

Zheng, F.; Chew, H. G.; Choi, W. K.; Zhang, J. X.; Seng, H. L.

2007-06-01

19

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

SciTech Connect

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

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

1993-08-01

20

Nonequilibrium alloying of graphite-reinforced aluminum metal matrix composites  

SciTech Connect

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

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

1993-10-01

21

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

Microsoft Academic Search

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

Chen Xing; Yang Chengxiao; Guan Leding; Yan Biao

2008-01-01

22

A new discontinuously reinforced aluminum MMC: Al+AlB{sub 2} flakes  

SciTech Connect

Development of a novel metal matrix composite based on the Al-B alloy system has been undertaken. Preparation of this discontinuously reinforced material is based on the precipitation of high aspect ratio AlB{sub 2} from an Al-B alloy. This paper describes a number of efforts forced on preparing high volume fractions (> 30 v%) of AlB{sub 2} in aluminum. New insights into the behavior of the Al-B alloys system allowed this effort to be successful.

HALL,AARON C.; ECONOMY,J.

2000-06-08

23

Corrosion control of cement-matrix and aluminum-matrix composites  

NASA Astrophysics Data System (ADS)

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

Hou, Jiangyuan

24

Low Cost Cast Aluminum Metal Matrix Composites Have Arrived  

Microsoft Academic Search

Aluminum metal matrix composites (MMC) have found applications in many industries, from aerospace and automotive to sporting goods and electronics packaging [1-5]. Many of the primary applications have been in military components and structures, where advanced high performance materials are necessary to meet vigorous material challenges. Aluminum MMC are attractive due to their lightweight and high specific stiffness. In addition,

Darrell R. Herling; Warren Hunt

2004-01-01

25

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 (1 vol%), the Vickers hardness and the tensile strength were significantly enhanced, with an up to three-fold increase relative to that of pure Al. From the fractography of the extruded Al-CNT composite, several shapes were observed in the fracture surface, and this unique morphology is discussed based on the strengthening mechanism. The damage in the CNTs was investigated with Raman spectroscopy. However, the Al-CNT composite materials were not only strengthened by the addition of CNTs but also enhanced by several synergistic effects. The nanoindentation stress-strain curve was successfully constructed by setting the effective zero-load and zero-displacement points and was compared with the tensile stress-strain curve. The yield strengths of the Al-CNT composites from the nanoindentation and tensile tests were compared and discussed. We believe that the yield strength can be predicted using a simple nanoindentation stress/strain curve and that this method will be useful for materials that are difficult to machine, such as complex ceramics. PMID:23011263

Kwon, Hansang; Leparoux, Marc

2012-09-26

26

Hot extruded carbon nanotube reinforced aluminum matrix composite materials  

NASA Astrophysics Data System (ADS)

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

Kwon, Hansang; Leparoux, Marc

2012-10-01

27

Effects of T4 treatment on hot rolling behavior and tensile strength of aluminum matrix composite reinforced by aluminum borate whisker with NiO coating  

Microsoft Academic Search

The Al–Si–Cu alloy matrix composite reinforced by aluminum borate whisker with NiO coating was fabricated by squeeze casting. The effects of T4 treatment on the microstructure, tensile strength, and hot rolling behavior of the composite were investigated. During T4 treatment, the NiO coating on whisker surface can react with aluminum matrix in the composite. The ultimate tensile strength of unrolled

W. D. Fei; Z. J. Li; Y. B. Li

2006-01-01

28

Study of Boride-Reinforced Aluminum Matrix Composites Produced via Centrifugal Casting  

Microsoft Academic Search

The redistribution of AlB2 and AlB12 reinforcing particles in functionally graded Al–B–Mg composites was investigated as a function of centrifugal casting time, rotational speed, and pouring temperature of the melt. The microstructure was characterized both qualitatively and quantitatively on four different sections along the main axis (centrifugal force direction) of the cylindrical casting. The resulting aluminum matrix composite showed an

Tunde Kingsley Adelakin; Oscar Marcelo Suárez

2011-01-01

29

Study on the reaction mechanism and mechanical properties of aluminum matrix composites fabricated in an Al–ZrO 2–B system  

Microsoft Academic Search

The in situ composites with reinforcement volume fraction of 30vol.% were fabricated by chemical synthesis method in an Al–ZrO2–B system. The reaction mechanism and mechanical properties of the composites were studied. When the B\\/ZrO2 mole ratio was zero, the reinforcements of the composite consisted of ?-Al2O3 particles and Al3Zr blocks, whose volume fractions were around 8.74vol.% and 21.6vol.%. The ultimate

Heguo Zhu; Yanqun Yao; Jianliang Li; Shi Chen; Jun Zhao; Hengzhi Wang

2011-01-01

30

Material selection and grade optimization applied to aluminum matrix composites  

Microsoft Academic Search

A general model for the optimal use of materials based on structural optimization is derived. The competitiveness of materials\\u000a is assessed with merit parameters. The competition between materials (material selection optimization) and the role of the composition and microstructure for a given material (grade optimization) are analyzed. The model is applied to aluminum matrix composites. The influence of matrix material,

J. Eliasson; R. Sandstroem

1995-01-01

31

Solar array with aluminum foil matrix  

Microsoft Academic Search

A solar array is described which comprises: (a) a first aluminum foil layer having a plurality of spaced apertures therein, (b) a plurality of discrete semiconductor members, each in a corresponding one of the apertures and having a P-type and an N-type region, the N-type region being ohmically bonded to the first aluminum foil, the bond characterized as formed by

J. D. Levine; R. E. Haney; M. J. Jensen

1987-01-01

32

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

SciTech Connect

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

Wiencek, T. C.

1998-10-22

33

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

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

34

Thermally conducting aluminum nitride polymer-matrix composites  

Microsoft Academic Search

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

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

2001-01-01

35

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

National Technical Information Service (NTIS)

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

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

2011-01-01

36

Conversion of Al 13 Keggin ? into Al 30: a reaction controlled by aluminum monomers  

Microsoft Academic Search

In situ 27Al NMR experiments under hydrothermal and room temperature conditions demonstrate that aluminum monomers are the species controlling the Al13 Keggin ? conversion into Al30. New 27Al NMR signatures of Keggin-type aluminum polycation are observed in solution. A chemical pathway is proposed to explain the isomerization process.

Lionel Allouche; Francis Taulelle

2003-01-01

37

Processing of In-Situ Al-AlN Metal Matrix Composites via Direct Nitridation Method.  

National Technical Information Service (NTIS)

The primary objective of this research was to provide a fundamental understanding of the processing science necessary to fabricate the Aluminum Nitride (AlN) reinforced Aluminum (Al) composites via direct nitration of the Al alloy melt. From the thermodyn...

K. S. Shin Y. S. Kim N. J. Kim

1998-01-01

38

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

39

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

Microsoft Academic Search

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

L. P. Zhang; Y. Y. Zhao

2007-01-01

40

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

SciTech Connect

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

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

1991-02-01

41

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

Microsoft Academic Search

High strain rate and high temperature response of three types of aluminum based particulate metal matrix ceramic composites is investigated by performing split Hopkinson pressure bar (SHPB) experiments. The composites are: NGP-2014 (15% SiC), NGT-6061 (15% SiC), and NGU-6061 (15% Al2O3), in which all the reinforcement materials are percentage by volume. Johnson-Cook constitutive model constants are evaluated from the high

H. Hilfi; N. S. Brar

1996-01-01

42

Fabrication and friction drilling of aluminum silicon carbide metal matrix composite  

Microsoft Academic Search

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

G. Somasundaram; S. Rajendra Boopathy

2010-01-01

43

Effect of Pin Profile on Friction Stir Welded Aluminum Matrix Composites  

Microsoft Academic Search

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

Adel Mahmood Hassan; Tarek Qasim; Ahmed Ghaithan

2012-01-01

44

Corrosion of Graphite Aluminum Metal Matrix Composites.  

National Technical Information Service (NTIS)

Several commercial G/Al MMCs have been studied by potentiodynamic polarization in deaerated 0.5 M Na2SO4. The results have been compared with those which were predicted by the mixed electrode theory. The results indicate that processing conditions, especi...

J. F. Chiang L. H. Hihara M. A. Buonanno R. M. Latanision

1991-01-01

45

Material selection and grade optimization applied to aluminum matrix composites  

SciTech Connect

A general model for the optimal use of materials based on structural optimization is derived. The competitiveness of materials is assessed with merit parameters. The competition between materials (material selection optimization) and the role of the composition and microstructure for a given material (grade optimization) are analyzed. The model is applied to aluminum matrix composites. The influence of matrix material, amount of reinforcement, and value of weight savings is studied. Mechanical properties are analyzed with the aid of published experimental data and available models. The Tsai-Halpin model is used to represent the variation of the elastic modulus with the amount of reinforcement. For yield strength the modified shear lag model is applied. It can satisfactorily describe experimental data and the variation with reinforcement for high-strength matrix alloys. For aluminum alloys of medium and lower strength, the observed increase is larger than the predicted one. This can be explained by the help of more recently developed micromechanical models that take into account the changes in microstructure in the matrix. For structural parts, large values of weight savings are usually necessary to make the particulate-reinforced composites competitive with carbon steel or their parent aluminum alloys. In other applications, combinations of properties are important to make the composites competitive.

Eliasson, J.; Sandstroem, R. [Royal Inst. of Tech., Stockholm (Sweden). Materials Science and Engineering

1995-06-01

46

Material selection and grade optimization applied to aluminum matrix composites  

NASA Astrophysics Data System (ADS)

A general model for the optimal use of materials based on structural optimization is derived. The competitiveness of materials is assessed with merit parameters. The competition between materials ( material selection optimization) and the role of the composition and microstructure for a given material ( grade optimization) are analyzed. The model is applied to aluminum matrix composites. The influence of matrix material, amount of reinforcement, and value of weight savings is studied. Mechanical properties are analyzed with the aid of published experimental data and available models. The Tsai-Halpin model is used to represent the variation of the elastic modulus with the amount of reinforcement. For yield strength the modified shear lag model is applied. It can satisfactorily describe experimental data and the variation with reinforcement for high-strength matrix alloys. For aluminum alloys of medium and lower strength, the observed increase is larger than the predicted one. This can be explained with the help of more recently developed micromechanical models that take into account the changes in microstructure in the matrix. For structural parts, large values of weight savings are usually necessary to make the particulate-reinforced composites competitive with carbon steel or their parent aluminum alloys. In other applications, combinations of properties are important to make the composites competitive.

Eliasson, J.; Sandström, R.

1995-06-01

47

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

NASA Astrophysics Data System (ADS)

[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 20°C, in contrast to current metal-matrix fabrication processes which require fusion of materials and hence reach temperatures of 500°C and above. UAM thus creates unprecedented opportunities to develop adaptive structures with seamlessly embedded smart materials and electronic components without degrading the properties that make embedding these materials and components attractive. This research focuses on three aspects of developing UAM Ni-Ti/Al composites which have not been accomplished before: (i) Characterization of the mechanical properties of the composite matrix; (ii) Investigation of Ni-Ti/Al composites as tunable stiffness materials and as strain sensors based on the shape memory effect; and (iii) Development of constitutive models for UAM Ni-Ti/Al composites. The mechanical characterization shows an increase in tensile strength of aluminum UAM builds over the parent material (Al 3003-H18), likely due to grain refinement caused by the UAM process. We demonstrate the ability to embed Ni-Ti wires up to 203 ?m in diameter in an aluminum matrix, compared with only 100 ?m in previous studies. The resulting Ni-Ti/Al UAM composites have cross sectional area ratios of up to 13.4% Ni-Ti. These composites exhibit a change in stiffness of 6% and a resistivity change of -3% when the Ni- Ti wires undergo martensite to austenite transformation. The Ni-Ti area ratios and associated strength of the shape memory effect are expected to increase as the UAM process becomes better understood and is perfected. The Brinson constitutive model for shape memory transformations is used to describe the stiffness and the strain sensing of Ni-Ti/Al composites in response to temperature changes.

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

2009-03-01

48

Aluminum Silicon Carbide (AlSiC) Thermal Management Packaging For High Density Packaging Applications  

Microsoft Academic Search

High-density microelectronics require packaging materials and systems that provide superior thermal management and highly functional interconnection schemes for component performance and reliability. Aluminum Silicon Carbide (AlSiC) metal matrix composite (MMC) packages have a unique set of material properties that are ideally suited to thermal management performance, and a functionality that supports high density interconnection microelectronic packaging applications. Furthermore, the AlSiC

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

49

Aluminum Silicon Carbide (AlSiC) for Advanced Microelectronic Packages  

Microsoft Academic Search

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

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

50

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

Microsoft Academic Search

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

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

1981-01-01

51

Thermal expansion behavior and thermal mismatch stress of aluminum matrix composite reinforced by ?-eucryptite particle and aluminum borate whisker  

Microsoft Academic Search

This paper described a study of the thermal expansion behavior in a new aluminum matrix composite containing both ?-eucryptite particles and aluminum borate whiskers. The results of the measurements of the coefficient of thermal expansion (CTE) showed that the composite had both low thermal expansion coefficient and stringent dimensional stability at a wide temperature range. A simplified model was established

W. D Fei; L. D Wang

2004-01-01

52

Microscopic characteristics of fatigue crack propagation in aluminum alloy based particulate reinforced metal matrix composites  

SciTech Connect

Microscopic characteristics of fatigue crack propagation in two aluminum alloy (A356 and 6061) based particulate reinforced metal matrix composites (MMCs) were investigated by carrying out three point bending fatigue tests. The impedance offered by the reinforcing particles against fatigue crack propagation has been studied by plotting the nominal and actual crack lengths vs number of cycles. Surface observation shows that fatigue cracks tend to develop along the particle-matrix interface. In the case of Al (A356) MMCs, stronger interaction of fatigue crack with Si particles, as compared to SiC particles, was evident. In both MMC materials, particle debonding was more prominent as compared to particle cracking. The attempted application of Davidson's model to calculate [Delta]K[sub th] indicated that for cast MMCs the matrix grain including the surrounding reinforcing particles has to considered as a large hard particle'', and the grain boundary particles themselves behave like a hard egg-shell'' to strengthen the material.

Wang, Zhirui; Zhang, R.J. (Univ. of Toronto, Ontario (Canada). Dept. of Metallurgy and Materials Science)

1994-04-01

53

Elasto-plastic analysis of an aluminum alloy matrix reinforced with silicon carbide fibers  

NASA Astrophysics Data System (ADS)

The micromechanical analysis of a composite with a matrix of an aluminum alloy (Al 6061 T6) reinforced with fibers of silicon carbide was performed using the nonlinear finite element program CALSAP. The fibers were packed in a square array and the fiber volume fraction (V/O) was 36 percent. The matrix was assumed to have elastoplastic material behavior, and the applied load was uniaxial tensile and transverse to the longitudinal axis of the fiber. The computation of the stress-strain distribution, the initiation of plastic yielding, the propagation of plastic zones and prediction of crack initiation within the matrix were performed. The results of the elastoplastic analysis were compared with those obtained using the finite element program MARC, and they are in close agreement.

Gotsis, P. K.; Shabaik, A. H.; Sines, G. H.

1992-05-01

54

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.

2013-05-01

55

Anti-corrosion film on 2024\\/SiC aluminum matrix composite fabricated by microarc oxidation in silicate electrolyte  

Microsoft Academic Search

A corrosion-resistant ceramic film was prepared on the SiC reinforced aluminum matrix composite by microarc oxidation technique in silicate solution. The film with two layer structure consists of mullite, ?-Al2O3, ?-Al2O3 and amorphous SiO2. Analysis of microstructure and composition suggests that only a few SiC particles remain in the film close to the composite\\/film interface and most of SiC reinforcements

Wenbin Xue; Xiaoling Wu; Xijin Li; Hua Tian

2006-01-01

56

Spray-forming monolithic aluminum alloy and metal matrix composite strip  

SciTech Connect

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

McHugh, K.M.

1995-10-01

57

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

PubMed

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

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

2011-02-01

58

Indentation Tests on Al Matrix Syntactic Foams  

Microsoft Academic Search

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

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

59

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

60

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

Microsoft Academic Search

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

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

1979-01-01

61

Interfacial reactions and mechanical properties of 6061Al matrix composites reinforced with alumina-coated Al 18B 4O 33 whiskers  

Microsoft Academic Search

Sol–gel ?-Al2O3 and ?-Al2O3 ceramic coatings were deposited onto surfaces of aluminum borate whiskers to control the spinel reactions between whiskers and matrix alloys. Interface observations, tensile experiments and hardness measurements of the composites were conducted to evaluate the coating effect.By comparison with ?-Al2O3 coating, the ?-Al2O3 coating was found to be more effective in controlling the interfacial reactions, and

D. Y Ding; D. Z Wang; W. L Zhang; C. K Yao; J. C Rao; D. X Li

2000-01-01

62

Modification of cast aluminum-matrix composite materials by refractory nanoparticles  

NASA Astrophysics Data System (ADS)

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 samples are fabricated by reaction casting when titanium, nickel, and ceramic powders are mixed with an aluminum melt. The grain size in a matrix, the size and shape of Al3Ti intermetallic inclusions, and the interphase distances in eutectics are determined with optical and scanning electron microscopes. A certain modifying effect of oxide ceramic nanoparticles on the structure of model CMs during their in situ formation is detected, and the inoculation effect of SiO2 added to a melt on the reaction products is most pronounced.

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

2009-02-01

63

Comparative study of forging parameters on microstructures and properties between Aluminum alloys Al6063 and Al7075  

Microsoft Academic Search

This research were designed and created hot forging moulds of Aluminum alloys to investigate the effect of heating influence on machine qualifications of Aluminum alloys and know the suitable conditions of hot forging. The experimental variable was forging temperature and analyzed the experiment results for determined the suitable condition in hot forging on two types Aluminum alloysAlSi1Mg:Al6063 and AlZn5.5MgCuAl7075. The

S. SOPHA; S. NANSAARNG

2007-01-01

64

Fourier transform microwave spectroscopy of aluminum hydrosulfide, AlSH  

NASA Astrophysics Data System (ADS)

Pure rotational transitions of three isotopic species of aluminum hydrosulfide, AlSH, have been measured with a cavity pulsed jet Fourier transform microwave spectrometer. AlSH was prepared by the reaction of laser ablated Al metal with H2S, and was stabilized in pulsed supersonic free jets of Ar. For each species the transition 101-000 was measured; hyperfine structure due to the nuclear spin of 27Al was observed for the first time and analyzed. For Al32SH and Al32SD, the rotational constants are in excellent agreement with published values. For the third species, Al34SH, this is the first observation, and its rotational constants are consistent with the published geometry. Information on the electronic structure of the molecule has been obtained using the 27Al nuclear quadrupole coupling constants and nuclear spin-rotation constants. The latter have been used to evaluate 27Al NMR shielding parameters, which are compared with those of other 27Al compounds. These shieldings have been found to be in excellent agreement with theoretical predictions. The results should also help facilitate astrophysical searches for the molecule.

Fukushima, Masaru; Gerry, Michael C. L.

2010-07-01

65

Anodic Oxidation of Aluminum by Electron Tunneling through Al/Cadmium-Stearate/Al Structure  

NASA Astrophysics Data System (ADS)

The conduction of the monolayer Langmuir-Blodgett(LB) film consisting of Cadmium-Stearate(CdSt) may be explained by an electron tunneling process. The tunneling current through the Al/CdSt/Al sample showed a great decrease with time when a constant voltage was applied in air. Such a phenomenon seems to result from the growth of an Al2O3 layer by the anodic oxidation of the aluminum electrode enhanced by the electron tunneling.

Okazaki, Choichiro; Kuniyoshi, Shigekazu; Kudo, Kazuhiro; Tanaka, Kuniaki

1989-11-01

66

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

Microsoft Academic Search

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

S. Srinivas; N. Ramesh Babu

2012-01-01

67

Physical and Mechanical Characterization of a Nano Carbon Infused Aluminum-Matrix Composite.  

National Technical Information Service (NTIS)

A nanocarbon-infused aluminum-matrix composite, termed 'covetic,' has been developed by Third Millennium Metals, LLC, and we have evaluated the enhanced performance prospects for strength and electrical conductivity. This paper examines the effects of the...

D. Forrest J. Wolk L. Brown P. Joyce

2011-01-01

68

[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

69

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

70

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

71

Processing of diamond particle dispersed aluminum matrix composites in continuous solid–liquid co-existent state by SPS and their thermal properties  

Microsoft Academic Search

Diamond-particle-dispersed-aluminum (Al) matrix composites were fabricated in a unique fabrication method where continuous solid–liquid co-existent state of the powder mixture of diamond, pure Al and Al–5mass%Si alloy was designed during spark plasma sintering (SPS) process. Microstructures and thermal properties of the composites fabricated in such a way were investigated. The composites can be well consolidated in the temperature range between

Kiyoshi Mizuuchi; Kanryu Inoue; Yasuyuki Agari; Yoshiaki Morisada; Masami Sugioka; Motohiro Tanaka; Takashi Takeuchi; Jun-ichi Tani; Masakazu Kawahara; Yukio Makino

2011-01-01

72

The mechanism of corrosion and corrosion control of aluminum/graphite metal matrix composites  

SciTech Connect

The mechanism of corrosion and corrosion control of aluminum/graphite metal-matrix composites (MMC) were investigated. Based on the results of salt fog and immersion exposures, anodic and cathodic electrochemical polarizations, and galvanic-coupling experiments of the MMC and their constituents, the rapid disintegration of the composites was found to be unambiguously attributable to oxygen reduction on the graphite fibers. The corrosion mechanism is divided into the three following steps: Stage I-the penetration of the corrosive environment into the interior of the MMC caused by (a) pitting of the foil, (b) mechanical or processing surface defect, or (c) capillary wicking of the solution down exposed fibers; Stage II-galvanic corrosion of the aluminum at the G/Al interface driven by the reduction of oxygen on the graphite fibers; Stage III-corrosion/mechanical rupture of the MMC caused by wedging of the hydrated corrosion products (formed in Stage II) in the confined spaces of the MMC. The kinetics of oxygen reduction on fibers is decreased by silica coatings and silicon-rich surface-modified layers and increased by both copper and nickel coatings. The galvanic corrosion rate is significantly reduced by silica coatings and silicon-rich surface-modified layers on the graphite fibers.

Dash, L.C.

1988-01-01

73

The mechanical response of ceramic microballoon reinforced aluminum matrix composites under compressive loading  

Microsoft Academic Search

An investigation is performed on the mechanical response of a family of ceramic microballoon reinforced aluminum matrix composites under both uniaxial compression and constrained die compression loadings. The key material parameters that are varied are the matrix strength and the ratio of wall thickness t to radius R of the microballoons. Uniaxial compressive failure initiates at relatively small strains (?1–2%)

M. Kiser; M. Y. He; F. W. Zok

1999-01-01

74

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

Microsoft Academic Search

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

O. Sayman

1998-01-01

75

The acoustoelastic measurement of elastic constants in alumina/aluminum metal matrix composites  

SciTech Connect

In this study, acoustoelastic testing is performed on alumina-reinforced aluminum 6061 alloy metal matrix composites. The MMCs consist of an aluminum 6061 matrix containing 0, 10, and 20 volume percentage alumina particulate reinforcements. Since the matrix and reinforcement have such disparate moduli, the second-order elastic constants of the composite should vary with the amount of reinforcement. In addition, the residual stresses that have developed during processing should have a significant effect on higher-order elastic constants. Bulk properties like Young`s and shear modulus are measured, as well as the higher-order elastic constants in an effort to monitor variations as a function of reinforcement.

Leisk, G.G.; Saigal, A. [Tufts Univ., Medford, MA (United States). Dept. of Mechanical Engineering

1995-10-01

76

Structure and mechanical properties of ingots and rolled sections of aluminum alloy based on the Al-Mg-Mn system  

NASA Astrophysics Data System (ADS)

Commercial ingots and hot-pressed rolled sections of Al-Mg-Mn alloy doped with zinc, scandium, zirconium, chromium, and vanadium have been studied using optical microscopy, thermal analysis, electron microscopy, and electron-probe microanalysis. The compositions of the phase constituents and aluminum matrix of the alloy are determined. The sensitivity of the alloy to the formation of complex intermetallic compounds during solidification is revealed. The mechanical properties of ingots and rolled sections are determined.

Ovsyannikov, B. V.; Reznik, P. L.; Zamyatin, V. M.; Doroshenko, N. M.

2013-01-01

77

Dissimilar metal joining of aluminum alloy to galvanized steel with Al–Si, Al–Cu, Al–Si–Cu and Zn–Al filler wires  

Microsoft Academic Search

Aluminum alloy sheets were lap joined to galvanized steel sheets by gas tungsten arc welding (GTAW) with Al–5% Si, Al–12% Si, Al–6% Cu, Al–10% Si–4% Cu and Zn–15% Al filler wires. Different amounts of Si, Cu and Zn were introduced into the weld through different filler wires. The effects of alloying elements on the microstructure in the weld and tensile

Honggang Dong; Wenjin Hu; Yuping Duan; Xudong Wang; Chuang Dong

78

AC losses and critical current in an aluminum stabilized mixed matrix NbTi superconductor composite  

Microsoft Academic Search

AC losses were measured for a twisted (L = 1.57 cm) superconductor wire (0.16 cm O.D.) consisting of 54 NbTi tubular filaments which were filled with high purity aluminum stabilizer and imbedded in a high strength aluminum alloy matrix. The measurements were made at 4.2 ° K in bias fields of zero and five Tesla as a function of ac

G. Wagner; M. Walker; D. Koop; C. Whetstone

1977-01-01

79

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

Microsoft Academic Search

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

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

2001-01-01

80

Effect of aluminum content on the mechanochemical synthesis of in-situ TiN in the Al-Ti-AlN system and subsequent shock consolidation  

NASA Astrophysics Data System (ADS)

To determine the effect of aluminum content on the formation of in-situ TiN in the Al-Ti-AlN system, a mixture of aluminum, titanium and aluminum nitride powders was subjected to high energy milling. Al content of the mixture was changed according to the following stoichiometric reaction: Ti+AlN+XAl?TiN+(1+X)Al. The value of X was varied from 5.35 to 19.65 based on the stoichiometric calculation of the molar mass of each component expected to result in aluminum matrix composite with TiN weights of 30%, 20% and 10%, respectively, in addition to reaction corresponding to X=0(Ti+AlN?TiN+Al). Thermodynamic factors determine that the amount of Al in the mixture plays a key role in the formation of in-situ TiN. XRD and EPMA results showed that at lower Al content (X=0, 5.35), reaction proceed through a gradual mode. By increasing Al content (X=19.65), no mechanochemical reaction occurred between Ti and AlN. Continuation of the milling process allowed acquisition of in-situ TiN in the designed compositions of AlN-TiN, Al-Ti-AlN-30%TiN, and to some extent, of Al-Ti-AlN-20%TiN. A nanocrystalline solid solution evolved by mechanical alloying (MA) was sustained for prolonged milling time. The mean TiN crystallite size obtained was 10 nm for the AlN-TiN composition. The end product milled powder after 40 h of milling time, equating to the Al-Ti-AlN-30%TiN composition was consolidated into bulk compact using the underwater shock compaction method. The milled specimens were characterized by XRD, scanning electron microscopy (SEM), electron probe microanalysis (EPMA) and microhardness testing. The sample had a uniform and fine-grained composite structure with 99% theoretical density and average microhardness of 434 HV0.1. The results confirmed the possibility of fabricating reliable bulk nanostructured materials by imposing shock compaction on submicron sized powders.

Amini Mashhadi, H.; Kennedy, G.; Tanaka, S.; Hokamoto, K.

2011-03-01

81

Method of making solar array with aluminum foil matrix  

Microsoft Academic Search

A method is described forming a solar array comprising the steps of: providing a first aluminum foil, forming apertures in the foil at predetermined locations thereon, providing a spheroid shaped semiconductor particle having a first conductive type opposite the first type center in each of the apertures, each of the particles having a diameter slightly larger than that of the

J. D. Levine; M. J. Jensen; R. E. Haney

1989-01-01

82

Comparing addition of ZrO2 particles in micron and nano scale on microstructure and mechanical behavior of aluminum-matrix composites produced by vortex route  

NASA Astrophysics Data System (ADS)

Aluminum matrix composites are important engineering materials in automotive, aerospace and other applications because of their low weight, high specific strength and better physical and mechanical properties compared to pure aluminum. ZrO2 particles as reinforcement were selected to add aluminum with micron and nano size. Al/ZrO2 composites were produced by direct incorporation (vortex method) in different temperatures and 5 volume percents of ZrO2 particles. Microstructure of the samples was studied by scanning electron microscopy (SEM). Chemical composition of the phases was studied by XRD. Hardness, and density of these composites were also measured. The microstructure and mechanical properties tests of composites and study the effect of particle size, resulted the better properties compared to matrix aluminum. Homogeneous dispersion of the reinforcement particles in the matrix aluminum was observed. The results show enhancing the composites properties for all samples compared to the monolithic alloy. However there are some differences in results because of particle size of ceramics and therefore differences between particles surface area. Maximum volume percent that can be added to A356 aluminum alloy is 5 vol.%, for nano ZrO2 particles, but it seems that is more than 5 vol.% for micron particles. Increasing of viscosity, porosities and much more defects are caused by increasing volume percents and using smaller particles. The casting processing is difficult in these conditions. Furthermore, optimum temperatures of casting for micron and nano zirconia particles are not the same.

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

2007-10-01

83

High-Temperature Fatigue of a Hybrid Aluminum Metal Matrix Composite  

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

84

HTPB\\/AP\\/AL SOLID PROPELLANTS WITH NANOMETRIC ALUMINUM  

Microsoft Academic Search

The effect of aluminum size on solid pro- pellant combustion becomes largely described in the literature. This paper describes the work performed at SNPE Matériaux Energétiques on HTPB propellants containing aluminum nano- particules. First, different forms of nanometric particles are characterized using advanced tech- niques. They differ by their passivation layer and exhibit different reactivity values. Nano aluminum is then

O. Orlandi; J.-F. Guéry; G. Lacroix; S. Chevalier; N. Desgardin

85

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

NASA Astrophysics Data System (ADS)

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

Lai, Jing

86

Metastable pitting of aluminum and Al-Cu alloys  

NASA Astrophysics Data System (ADS)

Metastable pitting behavior and the transition from metastable to stable pitting on high purity aluminum and two Al-Cu alloys (aged Al-2%Cu and AA2024-T3) were investigated. Experiments on pure Al were done potentiostatically, and nominally identical electrodes galvanic coupling experiments were conducted with the Al-Cu alloys. Applied potential, chloride concentration, and exposure time were the variables used to establish the critical potentials for pit stabilization and signature time series of metastable and stable pitting events. A distribution of pitting and repassivation (transition) potentials were observed at each Clsp- concentration. Factors controlling the transition from metastable to stable pitting were identified by comparing the electrochemical behavior of stable pits at elapsed times equal to the mean lifetime of metastable pits. This comparison also provided insight on the origins of statistical distributions of pitting potentials. A key criterion for pit stabilization is that individual pits exceed a threshold of Isbpit/rsbpit > 10sp{-2} A/cm at all times during pit growth. This parameter was linked to pit growth and mass transport conditions leading to the formation of a depassivating pit chemistry. Methods from electrochemical noise analyses were compared using the galvanic coupling time series. Isbpit/rsbpit analysis of the metastable pit current spikes provided a better indication of the transition to stable pitting than the pitting index and electrochemical noise resistance. Power spectral density plots of the current and potential time series provided qualitative information on pit susceptibility. Temporal analyses of the galvanic coupling current time series provided evidence that some correlation may exist between individual metastable pitting events. The metastable pitting events were found to deviate from Poisson behavior with increasing activity. Metastable pitting events may have an influence on subsequent pitting events at higher activity.

Pride, Sheldon Tyrone

87

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

88

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

89

Characterization and defect analysis of high temperature aluminum-based metal matrix composites  

Microsoft Academic Search

There is a need for an aluminum-based material to replace titanium in high temperature aerospace applications. Two powder metallurgy (P\\/M) matrices, RSP Al-8Fe-4Ce and MA Al-9Ti reinforced with 20 volume percent Al2O3 fibers or SiC whiskers or particles were developed for this purpose. Microstructural and mechanical property evaluations of these systems were performed to determine high temperature viability. Elevated temperature

Bayha

1991-01-01

90

Microstructural development in a spray-formed aluminum-silicon carbide based metal-matrix composite. Annual progress report, No. 1  

SciTech Connect

Included in this report are the preliminary findings concerning the investigation on the nature of spray formed aluminum-silicon carbide based metal matrix composite. In light of the fact that grain boundary precipitation (both low-angle and high-angle) is of the utmost importance, we have examined the interaction between grain boundaries and the precipitation of plate-like phases in both Al-based, and other alloys. The results of the investigation are included as a preprint for publication in the conference proceeding 'ALUMINUM ALLOYS: Their Physical and Mechanical Properties'.

Howell, P.R.

1992-05-01

91

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

92

Adiabatic shear failure of high reinforcement content aluminum matrix composites  

Microsoft Academic Search

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

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

2008-01-01

93

Macro-model for Development of Al-Al2O3 Metal Matrix Composite with Vacuum Moulding: Designed Experiments  

NASA Astrophysics Data System (ADS)

Aluminum matrix composites (AMC) have many potential engineering applications. Not much work hitherto has been reported for development of AMC with vacuum moulding (VM). In this work; Al-Al2O3, AMC has been developed with VM. The study highlights the effect of input parameters like: moulding sand, vacuum pressure and component volume on properties of AMC produced by the VM. An approach to macro-model the hardness and dimensional accuracy during development of AMC has been proposed and applied. Relationship between hardness, dimensional accuracy and other parameters have been deduced by using Taguchi technique L9 OA for industrial applications. The comparison with experimental results will also serve as a future validation of the model.

Singh, R.; Singh, J.; Singh, Jagdev

2012-10-01

94

Effect of aluminum content on the mechanochemical synthesis of in-situ TiN in the Al–Ti–AlN system and subsequent shock consolidation  

Microsoft Academic Search

To determine the effect of aluminum content on the formation of in-situ TiN in the Al–Ti–AlN system, a mixture of aluminum, titanium and aluminum nitride powders was subjected to high energy milling. Al content of the mixture was changed according to the following stoichiometric reaction: Ti+AlN+XAl?TiN+(1+X)Al. The value of X was varied from 5.35 to 19.65 based on the stoichiometric

H. Amini Mashhadi; G. Kennedy; S. Tanaka; K. Hokamoto

2011-01-01

95

Al(22)Cl(20).12L (L = THF, THP): the first polyhedral aluminum chlorides.  

PubMed

Aluminum subhalides of the type Al(22)X(20).12L (X = Cl, Br; L = THF, THP) are the only known representatives of polyhedral aluminum subhalides and exhibit interesting multicenter bonding properties. Herein, we report on the synthesis and structural investigation of the first chlorides of this type. Additional investigations applying solid-state (27)Al NMR (MAS), XPS (of Al(4)Cp(4) and Al(22)X(20).12L), and quantum chemical calculations shed more light upon the structure of the molecules and possible Al modifications. PMID:11552817

Klemp, C; Bruns, M; Gauss, J; Häussermann, U; Stösser, G; van Wüllen, L; Jansen, M; Schnöckel, H

2001-09-19

96

Low-Temperature Heat Capacities and Enthalpy of Formation of Aluminum Sulfide (Al 2S3).  

National Technical Information Service (NTIS)

Calorimetric determinations of low-temperature heat capacities and the standard enthalpy of formation were made for aluminum sulfide, Al2S3. The standard entropy (So), enthalpy of formation (delta Gfo), and calculated Gibbs energy of formation (delta Gfo)...

H. C. Ko J. M. Stuve R. R. Brown

1976-01-01

97

Development, growth, and adhesion of Al 2 O 3 on platinum-aluminum alloys  

Microsoft Academic Search

The development, growth, and adhesion of a-Al2O3 scales on platinum-aluminum alloys containing between 0.5 and 6 wt.% aluminum have been studied at temperatures in the interval between 1000 and 1450° C. The morphologies and microstructures of the a-Al2O3 scales were found to be influenced by the temperature, oxygen pressure, and the microstructures of the alloys. The oxidation rates of the

E. J. Felten; F. S. Pettit

1976-01-01

98

Aluminum ammonium sulfate dodecahydrate purified from traditional Chinese medicinal herb Korean monkshood root is a potent matrix metalloproteinase inhibitor.  

PubMed

Matrix metalloproteinases (MMPs) are zinc-dependent endopeptidases and key regulators for many physiological and pathological functions. The MMP inhibitors have been shown to modulate diseases such as cancer, inflammation, and cardiovascular diseases. In this paper we tracked the MMP inhibitory activities of the traditional Chinese medicinal herb Korean Monkshood Root. The purified active ingredient was identified by the elemental analysis, infrared spectrum (IR) and X-ray diffraction as aluminum ammonium sulfate dodecahydrate. This inorganic compound showed inhibitory activities toward a number of MMP family members. In particular, it has a strong inhibitory effect toward MMP-2 and MMP-9, with IC50 values of 0.54 and 0.50 ?M, respectively. Further analysis suggested that the MMP inhibitory activity is mainly due to Al(3+). Cell viability assays using human fibrosarcoma HT1080 cells showed aluminum ammonium sulfate had minimal cyto-toxicity with a concentration up to 500 ?M. However, within 50 ?M, it exhibited significant inhibition of cell invasion. To our knowledge, there has been no previous report of inorganic form of the MMP inhibitor with strong inhibitory activity. Our results for the first time showed that aluminum ammonium sulfate is an inorganic form of MMP inhibitor with high potency, and can be used to interfere with MMP related cellular processes. PMID:22395535

Shen, Yehua; Liu, Sen; Jin, Fenghai; Mu, Tianyang; Li, Cong; Jiang, Kun; Tian, Weihua; Yu, Dahai; Zhang, Yingqi; Fang, Xuexun

2012-03-01

99

Aluminum27 NMR study of some AlCl 3 ?MCl molten systems  

Microsoft Academic Search

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

Francis Taulelle; Alexander I. Popov

1986-01-01

100

Diffusion bonding of Al7075 alloy to titanium aluminum vanadate alloy  

Microsoft Academic Search

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

Abdulaziz Nasser Alhazaa

2010-01-01

101

Precipitation kinetics of Al 3Zr and Al 3Sc in aluminum alloys modeled with cluster dynamics  

Microsoft Academic Search

Precipitation kinetics of Al3Zr and Al3Sc in aluminum supersaturated solid solutions is studied using cluster dynamics, a mesoscopic modeling technique which describes the various stages of homogeneous precipitation by a single set of rate equations. The only parameters needed are the interface free energy and the diffusion coefficient which are deduced from an atomic model previously developed to study the

Emmanuel Clouet; Alain Barbu; Ludovic Laé; Georges Martin

2005-01-01

102

Fatigue behavior of Al 18B 4O 33 whisker-framework reinforced Al matrix composites at high temperatures  

Microsoft Academic Search

The aluminum borate porous ceramic with whisker-framework structure was in situ synthesized and used to manufacture aluminum matrix composites by squeeze casting. The processing technique for the reinforcement was not only non-harmful to the environment and humans, but also relatively cost-effective compared to SiC whiskers. The microstructures were observed and analyzed. The aluminum borate whiskers are uniformly distributed and randomly

S. J Zhu; T Iizuka

2003-01-01

103

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

Microsoft Academic Search

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

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

2010-01-01

104

Properties of single and dual matrix aluminum–carbon nanotube composites processed via spark plasma extrusion (SPE)  

Microsoft Academic Search

The interest in carbon nanotube (CNT) aluminum composites has been growing significantly over the past decade. Most work has focused on the generation of composite materials with homogeneously dispersed carbon nanotubes. On the other hand, the dual matrix composite microstructural design, where the matrix is selectively reinforced in localized regions within the microstructure separated by ductile unreinforced matrix, may present

K. Morsi; A. M. K. Esawi; P. Borah; S. Lanka; A. Sayed; M. Taher

2010-01-01

105

Phase equilibria in aluminum-rich Al-Sc-Si alloys during solidification  

NASA Astrophysics Data System (ADS)

Differential thermal and metallographic analyses are used to study the alloys lying on the sections of the phase diagram opposite to the Al corner and passing across the binary alloy compositions Al-2.5% Sc-Al-7% Si and Al-5% Sc-Al-14% Si. These results are used to plot two vertical sections and part of the liquids surface of the Al-Sc-Si phase diagram from the Al corner to 5% Sc and 14% Si. The character and temperatures of invariant equilibria in aluminum-rich alloys of the Al-Sc-Si system are determined.

Rokhlin, L. L.; Bochvar, N. R.; Rybal'chenko, O. V.; Tarytina, I. E.; Sukhanov, A. V.

2012-07-01

106

Particle denuded zones in alumina reinforced aluminum matrix composite weldments  

SciTech Connect

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

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

1996-08-01

107

Fusion Welding of SiC Particulate-reinforced Aluminum 392 Metal Matrix Composite  

Microsoft Academic Search

SiC particles (SiCp)-reinforced Al?metal matrix composites (Al?MMCs) offer several advantages relative to monolithic Al alloys and SiC. The higher specific strength and specific modulus of the composites compared to Al alloys make them potentially useful as structural materials in aerospace and transportation applications. In addition, these composites exhibit improved high-temperature capabilities as the specific strength and modulus advantages persist to

R. Gürler

1998-01-01

108

Mechanical Properties of Composites Made of an Aluminum Alloy Matrix Reinforced with Titanium Nitride Particles, Consolidated by Powder Extrusion  

Microsoft Academic Search

Metal matrix composite (MMC) rods made of an aluminum alloy matrix with a chemical composition close to AA6061, reinforced\\u000a with 5, 10, and 15 vol pct of titanium nitride particles, were produced by hot extrusion of cold compacted cylindrical forms\\u000a to obtain better mechanical properties than the aluminum alloy itself. Artificial aging by heat treatment makes composites\\u000a have higher increments

J. L. Ortiz; V. Amigó; A. Manzano; M. A. Pérez

2007-01-01

109

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

2009-04-18

110

Solidification behavior of Al-Mg aluminum alloy using double-sided arc welding process  

Microsoft Academic Search

As popular aluminum alloys, the 5xxx Al-Mg series, such as 5050 and 5052, etc., are widely used in applications such as automobile, pressure vessels, armor plate, and components for marine and cryogenic service. In this, as in all non-heat-treatable aluminum alloys, the weld metal zone is considered to be the weakest part of the joint and is the location of

Y. M. Zhang; C. Pan; A. T. Male

2000-01-01

111

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

Microsoft Academic Search

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

Yuriy L. Shoshin; Edward L. Dreizin

2006-01-01

112

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

NASA Astrophysics Data System (ADS)

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

Xu, Jiang; Kan, Yide; Liu, Wenjin

113

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

SciTech Connect

This paper details the results of a comparative study of laser and electron beam welding of a cast aluminum metal-matrix composite (Al-MMC) reinforced with SiC particles (SiC[sub p]). Electron beam welding of 15% SiC[sub p] A356-MMC produces much less deleterious Al[sub 4]C[sub 3] than CO[sub 2] laser beam welding at the same input powers and travel speeds. The advantage of EB welding of 15% SiC[sub p] A356-MMC relative to laser beam welding due to the different mechanisms of energy absorption by the substrate material for the two processes. During laser beam welding, the SiC particles are dissolved into a homogeneous solution of liquid Al, Si, and C at high temperatures, and the Al[sub 4]C[sub 3] subsequently precipitates from this solution on cooling. During EB welding of SiC[sub p] Al-MMCs, neither phase preferentially absorbs the energy of the electrons, and heating is more uniform than with laser beam welding. As a result of the uniform heat transfer to each phase, dissolution and decomposition of the SiC is limited and little Al[sub 4]C[sub 3] is formed. It is recommended that sharp focus of the electron beam and high travel speeds be used to minimize Al[sub 4]C[sub 3] formation. The results of this study can be more broadly interpreted to suggest that other high melting efficiency welding processes that allow for rapid welding cycles and minimal superheating can also be used to join SiC[sub p] Al-MMCs as long as the process is compatible with the material.

Lienert, T.J.; Lippold, J.C. (Edison Welding Inst., Columbus, OH (United States)); Brandon, E.D. (Sandia National Labs., Albuquerque, NM (United States))

1993-06-01

114

The effect of reinforcement stability on composition redistribution in cast aluminum metal matrix composites  

SciTech Connect

The microstructure has been characterized in cast Al-7Si metal matrix composites containing either SiC or B{sub 4}C particulate reinforcement. Also, particulate/matrix interfacial precipitation reactions were extensively examined in these composites. The type of reinforcement was shown to have a profound effect on interfacial precipitation, elemental composition distribution and the as-cast and solution treated and aged microstructure of the matrix alloy. The stability of SiC particulates in the A356 matrix alloy was substantially greater in comparison to highly reactive B{sub 4}C particulates. Electron microprobe (EMP), SEM, and STEM were used to identify and analyze phases associated with the bulk matrix microstructure and the particulate/matrix interfacial reaction zones. Essentially no reaction products were observed at the interface of SiC particulates. In sharp contrast, an extensive reaction products zone was observed at the interface and in regions near the B{sub 4}C reinforcement. The extensive matrix/reinforcement reactions caused selective partitioning of matrix alloying elements, thereby modifying the matrix microstructure in the composites by compositional redistribution in the matrix. Boron carbide significantly modified the matrix microstructure of the composite, whereas the matrix containing silicon carbide particulates remained essentially unchanged. 14 refs., 9 figs., 4 tabs.

Lucas, J.P.; Yang, N.Y.C. (Sandia National Labs., Livermore, CA (USA)); Stephens, J.J.; Greulich, F.A. (Sandia National Labs., Albuquerque, NM (USA))

1990-05-01

115

Al-matrix composite materials reinforced by Al-Cu-Fe particles  

NASA Astrophysics Data System (ADS)

Al-matrix material composites were produced using hot isostatic pressing technique, starting with pure Al and icosahedral (i) Al-Cu-Fe powders. Depending on the processing temperature, the final reinforcement particles are either still of the initial i-phase or transformed into the tetragonal ?-Al00.70Cu0.20Fe0.10 crystalline phase. Compression tests performed in the temperature range 293K - 823K on the two types of composite, i.e. Al/i and Al/?, indicate that the flow stress of both composites is strongly temperature dependent and exhibit distinct regimes with increasing temperature. Differences exist between the two composites, in particul ar in yield stress values. In the low temperatureregime (T <= 570K), the yield stress of the Al/? composite is nearly 75% higher than that of the Al/i composite, while for T > 570K both composites exhibit similar yield stress values. The results are interpreted in terms of load transfer contribution between the matrix and the reinforcement particles and elementary dislocation mechanisms in the Al matrix.

Bonneville, J.; Laplanche, G.; Joulain, A.; Gauthier-Brunet, V.; Dubois, S.

2010-07-01

116

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

117

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

118

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

NASA Astrophysics Data System (ADS)

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

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

2011-09-01

119

Aluminum and silicon diffusion in Fe-Cr-Al alloys  

Microsoft Academic Search

Foils of Fe-Cr-Al alloys containing about 20 wt% Cr, 5 wt% Al and additions of Si and reactive elements like Ce, La, Y, Hf, Zr or Ti are widely used as a substrate in metal-supported automotive catalytic converters. In the present paper the authors report on measurements of Al and Si diffusion in Fe-Cr-Al alloys. Due to a lack of

A. Heesemann; E. Schmidtke; F. Faupel; A. Kolb-Telieps; J. Kloewer

1999-01-01

120

Thermal expansion behaviour of aluminum matrix composites with densely packed SiC particles  

Microsoft Academic Search

The coefficient of thermal expansion (CTE) of Al-based metal matrix composites containing 70vol.% SiC particles (AlSiC) has been measured based on the length change from room temperature (RT) to 500°C. In the present work, the instantaneous CTE(T) of AlSiC is studied by thermo-elastic models and micromechanical simulation using finite element analysis in order to explain abnormalities observed experimentally. The CTE(T)

Tran Huu Nam; Guillermo Requena; Peter Degischer

2008-01-01

121

Aluminum hard mask technique for the fabrication of high quality submicron Nb\\/Al-AlOx\\/Nb Josephson junctions  

Microsoft Academic Search

We have developed a combined photolithography and electron-beam lithography fabrication process for sub-µm to µm-size Nb\\/Al-AlOx\\/Nb Josephson junctions. In order to define the junction size and protect its top electrode during anodic oxidation, we developed and used the new concept of an aluminum hard mask. Josephson junctions of sizes down to 0.5 µm2 have been fabricated and thoroughly characterized. We

Christoph Kaiser; J. M. Meckbach; K. S. Ilin; J. Lisenfeld; R. Schäfer; A. V. Ustinov; M. Siegel

2011-01-01

122

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

123

Theoretical study on aluminum carbide endohedral fullerene-Al4C@C80.  

PubMed

The possibility of a new endohedral fullerene with a trapped aluminum carbide cluster, Al(4)C@C(80)-I( h ), was theoretical investigated. The geometries and electronic properties of it were investigated using density functional theory methods. The Al(4)C unit formally transfers six electrons to the C(80) cage which induces stabilization of Al(4)C@C(80). A favorable binding energy, relatively large HOMO-LUMO gap, electron affinities and ionization potentials suggested the Al(4)C@C(80) is rather stable. The analysis of vertical ionization potential and vertical electron affinity indicate Al(4)C@C(80) is a good electron acceptor. PMID:23160935

Lu, Qi Liang; Song, Wen Jun; Meng, Jun Wei; Wan, Jian Guo

2012-11-17

124

Al-Fe-Ni (Aluminum-Iron-Nickel)  

Microsoft Academic Search

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

V. Raghavan

1994-01-01

125

Investigation on work softening behavior of aluminum and its alloys with iron  

Microsoft Academic Search

Work softening in aluminum and its alloys (Al-2Fe) was investigated at room temperature. Work softening was noticed in aluminum\\u000a with a purity of 99.996 %, in an Al-2Fe alloy with a purity of 99.996 % in the aluminum matrix, and in an Al-2Fe alloy with\\u000a a purity of 99.96% in the aluminum matrix, when the reduction in thickness of samples

F.-Z. Li; Z.-J. Liu; Q. Jin; Z.-M. Yu; E. Liu

1997-01-01

126

Friction and wear behaviour of cast Al 6063 based in situ metal matrix composites  

Microsoft Academic Search

Al 6063 based in situ composites were manufactured from Al–10%Ti and Al–3%B master alloys by liquid metallurgy route. The in situ TiB2 reinforced Al 6063 composites were synthesized through the exothermic reaction between Al–10%Ti and Al–3%B master alloys, which were used in the ratio of 1:2 respectively in Al 6063 matrix alloy. Tribological properties of both Al 6063 matrix alloy

C. S. Ramesh; Abrar Ahamed

2011-01-01

127

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

NASA Astrophysics Data System (ADS)

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

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

2010-12-01

128

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

NASA Astrophysics Data System (ADS)

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

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

1998-04-01

129

High temperature sulfidation behavior of low Al iron-aluminum compositions  

SciTech Connect

Iron-aluminum weld overlay coatings are currently being considered for enhanced sulfidation resistance. The performance of these alloys in reducing atmospheres far exceeds other conventional materials presently used. However, the application of iron-aluminum alloys is currently limited due to hydrogen cracking susceptibility subsequent to welding. A direct correlation between the severity of embrittlement and the amount of aluminum in the alloy has been observed, specifically when the composition resides in the ordered region of the Fe-Al phase diagram (above 10 wt% Al). Higher Al overlays have been deposited, but only with extensive pre-heat and post-weld heat treatments which are not always feasible. In addition to the welding problem, detailed corrosion studies indicating the sulfidation behavior of these binary alloys has not been fully conducted. Previous research has utilized gas compositions and temperatures which would be considered very aggressive (temperatures above 700 C and P{sub S2} {ge} 10{sup {minus}7} atm), especially when compared to industrial boiler environments. Less assaulting conditions could not be found in the open literature. Therefore, research has been initiated to evaluate the sulfidation behavior of weldable iron-aluminum compositions, in the range of 5--10 wt% Al, in moderately reducing environments.

Banovic, S.W.; DuPont, J.N.; Marder, A.R. [Lehigh Univ., Bethlehem, PA (United States). Dept. of Materials Science and Engineering

1998-05-12

130

Aluminum and silicon diffusion in Fe-Cr-Al alloys  

SciTech Connect

Foils of Fe-Cr-Al alloys containing about 20 wt% Cr, 5 wt% Al and additions of Si and reactive elements like Ce, La, Y, Hf, Zr or Ti are widely used as a substrate in metal-supported automotive catalytic converters. In the present paper the authors report on measurements of Al and Si diffusion in Fe-Cr-Al alloys. Due to a lack of suitable radiotracers concentration profiles were obtained by means of electron microprobe analysis. In connection with data evaluation they present numerical calculations assessing the accuracy of the Matano analysis and the thin-film solution of Fick`s 2nd law as function of the thickness of the initial diffusant layer. The results are of general interest, particularly for the evaluation of diffusion measurements involving industrial specimens with given geometry.

Heesemann, A.; Schmidtke, E.; Faupel, F. [Technische Fakultaet der Univ. Kiel (Germany). Lehrstuhl fuer Materialverbunde; Kolb-Telieps, A.; Kloewer, J. [Krupp VDM GmbH, Werdohl (Germany)

1999-02-05

131

Low temperature Aluminum induced crystallization process to get Poly silicon films for thin film transistor application in active matrix displays  

Microsoft Academic Search

The realization of high information-content active matrix flat-panel displays (FPD's) requires low temperature thin film transistor (TFT) process that is compatible with the thermal constraints imposed by common inexpensive glass panels. Aluminum induced crystallization (AIC) has been researched extensively for producing poly-Si from a-Si. In this paper Aluminum- induced crystallization (AIC) in amorphous silicon films deposited by Hot Wire CVD

Hitesh Chelawat; Alka Kumbhar; Subhra Adhikari; Hrishikesk Kelkar; R. O. Dusane

132

Precise determination of aluminum content in AlGaAs  

Microsoft Academic Search

The Al composition of AlGaAs has been determined by four methods: high-resolution transmission electron microscopy (HRTEM), reflection high-energy electron diffraction (RHEED), photoluminescence (PL), and double-crystal x-ray diffraction (DCXRD). HRTEM is direct and the most accurate method because it does not involve any formula or extrapolation. Using the result obtained from HRTEM as a standard, we have calibrated the results from

K. H. Chang; C. P. Lee; J. S. Wu; D. G. Liu; D. C. Liou; M. H. Wang; L. J. Chen; Mario A. Marais

1991-01-01

133

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

NASA Astrophysics Data System (ADS)

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

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

2011-03-01

134

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

135

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

PubMed

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

Goulet, Richard R; Lalonde, Janick D; Munger, Catherine; Dupuis, Suzanne; Dumont-Frenette, Geneviève; Prémont, Stéfane; Campbell, Peter G C

2005-06-01

136

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

NASA Astrophysics Data System (ADS)

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

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

137

Diffusion bonding of Al7075 alloy to titanium aluminum vanadate alloy  

NASA Astrophysics Data System (ADS)

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

Alhazaa, Abdulaziz Nasser

138

Effects of Shot Peening Processing on the Fatigue Behavior of Three Aluminum Alloys and TI-AL-4V.  

National Technical Information Service (NTIS)

The fatigue strength of three shot-peened aluminum alloys (Al 7075- T651, Al 2024-T351 and Al 2014-T6) and a titanium alloy (Ti-6Al-4V) was measured to determine the differences in shot peening quality from three vendors that were given the same shot peen...

J. Campbell

2001-01-01

139

The influence of interphase structure on the kinetics of oxygen reduction on graphite used in aluminum-graphite metal matrix composites  

Microsoft Academic Search

Graphite fibers are used as reinforcement in a number of metal matrix composites. In aluminum-graphite composites this causes severe galvanic corrosion when the material is exposed to a corrosive environment. The graphite fiber surface provides active sites on which the cathodic reaction of oxygen occurs in aqueous solutions. This cathodic reaction causes enhanced aluminum matrix dissolution because of galvanic coupling.

1988-01-01

140

Stability of low level sulfur gases in volatile hydrocarbon matrixes contained in high pressure aluminum cylinders  

SciTech Connect

Recent pollution-monitoring requirements imposed by the US Environmental Protection Agency on the oil and gas industries have generated interest in using high-pressure cylinders containing a known quantity of sulfur gas for calibrating pollution monitors. Because of the difficulties involved in maintaining the sulfur gas's stability in such cylinders, Airco began research on eliminating the sources of this instability. A 2-year evaluation of hydrogen sulfide, carbonyl sulfide, and methyl mercaptan in methane and ethylene matrixes contained in specially treated aluminum cylinders found that use of the proper cylinders, cylinder treatment, and gas-blending procedures could ensure long-term stability in most cases, regardless of cylinder temperature and decreasing pressure.

Kramer, F.J.; Wechter, S.G.

1980-12-01

141

Welding metallurgy and weldability of high strength aluminum alloys  

Microsoft Academic Search

A literature survey was conducted to gather the information available on the welding metallurgy of high strength aluminum alloys, and its effect on their weldability. The report focuses on fusion welding of high strength aluminum alloys. Both conventional high strength aluminum alloys and newer products, e.g., PM aluminum alloys, Al-Li alloys and Al-matrix composites, are included. The survey covers a

Kou

1986-01-01

142

Absorption of pumping radiation by the yttrium aluminum garnet matrix of a neodymium-doped active element  

Microsoft Academic Search

A description is given of a method for the determination of the proportion of the heat evolved in a neodymium-doped active element due to the absorption of pumping radiation in the yttrium aluminum garnet (YAG) matrix. This method is based on a comparison of the evolution of heat from the active rod as a result of pumping with continuously operating

A. A. Shokin

1974-01-01

143

Photocurrent from photocorrosion of aluminum electrode in porphyrin/Al Schottky-barrier cells  

SciTech Connect

Current{endash}voltage characteristics under illumination of monochromatic light for metal-free tetrabenzporphyrin, metal-free triazatetrabenzporphyrin, and metal-free phthalocyanine in (indium{endash}tin{endash}oxide)/porphyrin/Al sandwich cells seem to show high-energy conversion efficiencies of 14{percent}, 7.7{percent}, and 5.5{percent}, respectively. However, according to the simultaneous measurement of both short-circuit photocurrent and transmittance of the aluminum electrode with time, the transmittance of Al linearly increases as the photocurrent flows into the external circuit. It is concluded that all photocurrents in the above cells arise from photoaccelerated corrosion of aluminum electrode and do not originate from conversion of light energy to electrical energy. {copyright} {ital 1997 American Institute of Physics.}

Murata, K.; Ito, S. [Tsukuba Research Laboratory, Nippon Shokubai Co. Ltd., Kannondai, Tsukuba 305 (Japan); Takahashi, K. [Department of Chemistry and Chemical Engineering, Faculty of Engineering, Kanazawa University, Kodatsuno, Kanazawa 920 (Japan); Hoffman, B.M. [Department of Chemistry and Materials Research Center, Northwestern University, Evanston, Illinois 60208-3113 (United States)

1997-08-01

144

The compatibility of pitch-based carbon fibers with aluminum for the improvement of aluminum-matrix composites  

Microsoft Academic Search

The degradation with aluminum of pitch-based carbon fibers of a wide range of Young's moduli has been studied, and changes in the tensile strength of aluminum-coated pitch-based carbon fibers after heat treatment are discussed. The structure parameters and the microstructure of the pitch-based carbon fibers are determined by X-ray diffraction and scanning electron microscopy. Interface analysis is performed with Auger

Takakazu Suzuki

1996-01-01

145

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

146

Heat treatment optimization of alumina/aluminum metal matrix composites using the Taguchi approach  

SciTech Connect

The paper describes the use of the Taguchi approach for optimizing the heat treatment process of alumina-reinforced Al-6061 metal-matrix composites (MMCs). It is shown that the use of the Taguchi method makes it possible to test a great number of factors simultaneously and to provide a statistical data base that can be used for sensitivity and optimization studies. The results of plotting S/N values versus vol pct, solutionizing time, aging time, and aging temperature showed that the solutionizing time and the aging temperature significantly affect both the yield and the ultimate tensile strength of alumina/Al MMCs. 11 refs.

Saigal, A.; Leisk, G. (Tufts University, Medford, MA (United States))

1992-03-01

147

Viscosities of aluminum-rich Al-Cu liquid alloys  

NASA Astrophysics Data System (ADS)

Viscosity data for Al-Cu liquid alloys in the ranges of 0? C L?33.1 wt pct Cu and 1173? T ?973 K are reviewed. It was found that Andrade's equation can be used to represent the variation of viscosity with temperature for a given composition, but that each of the two parameters in Andrade's equation shows no systematic variation with composition of the liquid-alloys. Consequently, arithmetic averages of the parameters were used and assumed to apply to all compositions in the range 0? C L ?33.1 wt pct Cu. Such a procedure implies that the viscosity happens to vary with composition solely because the specific volume varies with composition. In order to establish the predictability of extrapolating such simple behavior, a more complex model was considered. The latter model was recently presented by Kucharski and relates viscosity to the structure and thermodynamics of liquid alloys. Viscosities obtained by interpolating Andrade's equation and Kucharski's model compare closely; furthermore, values obtained by extrapolations to lower temperatures also compare favorably. Finally the simpler model was used to calculate the viscosity of the interdendritic liquid during solidification.

Ganesan, S.; Speiser, R.; Poirier, D. R.

1987-06-01

148

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

NASA Astrophysics Data System (ADS)

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

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

2011-02-01

149

Effect of aluminum content on thermograms of synthesis of intermetallide Ni 3 Al by thermal shock  

Microsoft Academic Search

Thermograms of high-temperature synthesis of nickel aluminide Ni3Al by thermal shock of powder mixtures of pure elements were studied experimentally by varying the proportion of mixture components\\u000a within the single-phase composition of the intermetallic compound. A qualitative analysis of the main thermokinetic parameters\\u000a of the thermal shock versus the aluminum content of the starting powder mixture was made.

V. E. Ovcharenko; E. N. Boyangin

1998-01-01

150

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

151

Electrodeposition of Al–Ni intermetallic compounds from aluminum chloride- N-( n-butyl)pyridinium chloride room temperature molten salt  

Microsoft Academic Search

Electrodeposition of aluminum–nickel intermetallic compounds (particularly Ni3Al) has been carried out onto platinum and mild steel cathodes from a 2:1 (mole ratio) aluminum(III) chloride-N-(n-butyl)pyridinium chloride (BPC) molten bath saturated with nickel(II) chloride at room temperature. A single phase of Al–Ni alloy is difficult to obtain by controlled-potential and controlled-current methods; however, it can be obtained by pulse current plating. The

Muhammad Rostom Ali; Atshushi Nishikata; Tooru Tsuru

2001-01-01

152

Correlation between thermal properties and aluminum fractions in CrAlN layers deposited by PVD technique  

Microsoft Academic Search

The CrAlN coatings are a good alternative to conventional CrN coatings especially for high temperature oxidation-resistance applications. Different CrAlN coatings were deposited on silicon (100) by PVD (Physical vapor deposition) technique from two targets (chromium and aluminum) in a reactive nitrogen atmosphere at aluminum applied negative voltage (?300, ?500, ?700 and ?900V). The composition, structural, mechanical and thermal properties of

B. Tlili; N. Mustapha; C. Nouveau; Y. Benlatreche; G. Guillemot; M. Lambertin

2010-01-01

153

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...

154

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

SciTech Connect

Mechanical, instrumented Charpy V-notch (CVN) energy and plane strain fracture-toughness properties of SiC whisker reinforced 6061 aluminum-metal-matrix composite material from an extruded tube were determined. The effect of thermal treatment and orientation were studied. The mechanical-strength properties are higher than wrought Al 6061 in the T6 condition. CVN energy values, however, were reduced by an order-of-magnitude Kic fracture toughness of the as-received, T6 and degassed + T6 thermal treatments were 50% of the wrought Al 6061 alloy. The effect of orientation showed that the orientation with the least amount of SiC whisker in the crack plane (i.e., greatest mean free path between reinforcements) yields the highest toughness value.

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

1987-01-31

155

Crack growth resistance ( R-curve) behaviour and thermo-physical properties of Al 2O 3 particle-reinforced AlN\\/Al matrix composites  

Microsoft Academic Search

Crack growth resistance behaviour and thermo-physical properties of Al2O3 particle-reinforced AlN\\/Al matrix composites have been studied as a function of AlN volume fraction as well as Al2O3 particle size. The fracture toughness of the composites decreased with increase in vol% AlN and decrease in Al2O3 particle size. All the composites exhibited R-curve behaviour which has been attributed to crack bridging

Srinivasa Rao Boddapati; Jürgen Rödel; Vikram Jayaram

2007-01-01

156

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

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

157

Sliding wear behaviour of aluminum syntactic foam: A comparison with Al–10 wt% SiC composites  

Microsoft Academic Search

The sliding wear behaviour of cenosphere-filled aluminum syntactic foam (ASF) has been studied in comparison with that of 10wt% SiC particle reinforced aluminum matrix composite (AMC) at a load of 3kg and varying sliding speeds under dry and lubricated conditions using a pin-on disc test apparatus. The tribological responses such as the wear rate, the coefficient of friction and the

Nidhi Jha; Anshul Badkul; D. P. Mondal; S. Das; M. Singh

2011-01-01

158

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

159

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

NASA Astrophysics Data System (ADS)

The processing and thermomechanical behaviors of TiNi shape memory alloy (SMA) fiber-reinforced 6061 Al matrix smart composites are investigated experimentally and analytically. Optimum processing conditions of hot pressing temperature and pressure are identified. Composite yield stresses are observed to increase with an increase in the volume fraction of TiNi fiber and prestrain given to the composites. An analytical model for thermomechanical behavior of the composites is developed by utilizing an exponential type of SMA constitutive model. The model predicts an increase in the composite yield stress with an increase in prestrain. It is found that the key parameters affecting the composite yield stress are the fiber volume fraction, prestrain, and matrix heat treatment. The predictions are in a reasonably good agreement with the experimental results.

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

1998-03-01

160

Investigation of the Electrochemical Polarisation Behaviour of SiC/6061 Al Metal Matrix Composites.  

National Technical Information Service (NTIS)

Electrochemical polarization measurements have been made on silicon carbide (SiC), 6061 aluminum metal - silicon carbide metal matrix composite (MMC) and the similarly processed unreinforced alloy in aerated and deaerated 3.5wt% NaCl. The effect of the pH...

A. J. Griffiths A. Turnbull

1992-01-01

161

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

Microsoft Academic Search

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

Harumi Yokokawa; Masao Fujishige; Seiichi Ujiie; Masayuki Dokiya

1987-01-01

162

Pulse laser processing of a SiC/Al-alloy metal matrix composite  

SciTech Connect

The microstructural changes and the tensile behavior of laser processed A356-Al alloy matrix composites reinforced with 10 and 20 vol. % SiC particulates are characterized. The autogenous bead-on-plate welds were made using a pulsed CO{sub 2} laser operating at a peak power level of 3.2 kW. The pulse on-time was constant at 20 ms and the off-time was varied from 20 to 2 msec (duty cycles of 50--91%). The microstructure of the laser melted region was investigated by optical, scanning, and transmission electron microscopy, and x-ray microchemical analysis techniques. The extent of microstructural changes varied directly with duty cycle, i.e., being a maximum for the longest (91%) duty cycles. Pulsed laser processing produced partial to complete dissolution of SiC particles and sometimes resulted in the formation of aluminum carbide. The associated rapid cooling also produced a fine distribution of nonequilibrium complex precipitates. In addition, the laser energy modified the SiC surface both physically and chemically. The results of tensile tests indicated that the modified SiC and the distribution of fine nonequilibrium precipitates enhance the mechanical properties of the laser processed composites. Optimum changes in microstructure and mechanical properties were obtained in the composites processed with intermediate (67 and 74%) duty cycles; therefore pulsed processing appears to be a strong candidate for successful joining of these MMCs.

Dahotre, N.B.; McCay, M.H.; McCay, T.D.; Gopinathan, S. (Center for Laser Applications, The University of Tennessee Space Institute, Tullahoma, Tennessee 37388 (US)); Allard, L.F. (High Temperature Materials Laboratory, Metals and Ceramics Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831 (US))

1991-03-01

163

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

PubMed

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

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

2000-10-16

164

Strengthening of NiAl matrix composites. Annual report, Oct 90-Sep 91  

SciTech Connect

Deformation of titanium boride/nickel aluminum composites at high temperatures exhibit low temperature deformation characteristics, and grain size refinement in these composites could account for the strengthening of the composites. Interfaces of TiB2-NiAl and alpha--aluminum oxides--NiAR in TiB2/NiAl composites have been investigated by analytical electron microscopy. Although no consistent crystallographic orientation relationships have been found between NiAl and TiB2 or Al2O3, semicoherent interfaces between alpha-Al2O3 and NiAl have been observed in areas where the low indexed crystallographic planes of alpha-Al2O3 aligned with that of NiAl. No semicoherent interfaces between NiAl and TiB2 have been observed. Silicon segregation was consistently detected by at the TiB2/NiAl interface region. Segregation has not been detected in the alpha-Al2O3-NiAl interface region. The segregation layer observed at the TiB2-NiAl interface is too thin to absorb any of the thermal residual stress.

Arsenault, R.J.

1991-10-01

165

Al sub 2 S sub 3 Preparation and Use in Electrolysis Process for Aluminum Production.  

National Technical Information Service (NTIS)

A continuous process for producing aluminum sulfide and for electrolyzing the aluminum sulfide to form metallic aluminum in which the aluminum sulfide is produced from aluminum oxide and COS or CS sub 2 in the presence of a chloride melt which also serves...

C. C. Hsu N. P. Yao R. O. Loutfy

1982-01-01

166

Enhancing tensile ductility of a particulate-reinforced aluminum metal matrix composite by lamination with Mg9%Li alloy  

Microsoft Academic Search

A laminated metal composite has been made by press bonding alternating layers of a particulate-reinforced aluminum metal matrix composite (MMC), 6090\\/SiC\\/25p, and a highly ductile Mg-9%Li alloy. The mechanical properties including tensile ductility were evaluated for the 50-50 volume fraction laminated composite. The tensile yield strength of the composite obeyed the rule of averages in agreement with other laminates based

C. K. Syn; D. R. Lesuer; O. D. Sherby

1996-01-01

167

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

Microsoft Academic Search

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

David L. McDanels

1985-01-01

168

Fatigue-life prediction of SiC particulate reinforced aluminum alloy 6061 matrix composite using AE stress delay concept  

Microsoft Academic Search

A study of the residual fatigue life prediction of 6061-T6 aluminum matrix composite reinforced with 15 vol % SiC particulates (SiCp) by using the acoustic emission technique and the stress delay concept has been carried out. Fatigue damages corresponding to 40, 60 and 80% of total fatigue life were stimulated at a cyclic stress amplitude. The specimens with and without

D. Shan; H. Nayeb-Hashemi

1999-01-01

169

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

Microsoft Academic Search

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

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

1997-01-01

170

Effects of the Anisotropic Elastic Modulus of a Boron-Fiber-Reinforced Aluminum-Matrix Composite on Specimens Calibrated for Crack-Length Determination.  

National Technical Information Service (NTIS)

In an investigation undertaken to assess the suitability of the fracture mechanics parameter K sub c for determining the fracture resistance of a boron-fiber-reinforced aluminum-matrix composite, calibration curves designed to measure crack length under l...

A. M. Sullivan J. Stoop

1974-01-01

171

Effect of Thermal Treatment on the Mechanical and Toughness Properties of Extruded Sic sub w/Aluminum 6061 Metal Matrix Composite.  

National Technical Information Service (NTIS)

Mechanical, instrumented Charpy V-notch (CVN) energy and plane strain fracture toughness properties of SiC whisker reinforced 6061 aluminum metal matrix composite material from an extruded tube have been determined. The effect of thermal treatment and ori...

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

1987-01-01

172

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

NASA Astrophysics Data System (ADS)

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

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

2012-06-01

173

Influence of Aluminum on the Formation Behavior of Zn-Al-Fe Intermetallic Particles in a Zinc Bath  

NASA Astrophysics Data System (ADS)

The shape, size, and composition of dross particles as a function of aluminum content at a fixed temperature were investigated for aluminum added to the premelted Zn-Fe melt simulating the hot-dip galvanizing bath by a sampling methodology. In the early stage, less than 30 minutes after Al addition, local supersaturation and depletion of the aluminum concentration occurred simultaneously in the bath, resulting in the nucleation and growth of both Fe2Al5Zn x and FeZn13. However, the aluminum was homogenized continuously as the reaction proceeded, and fine and stable FeZn10Al x formed after 30 minutes. An Al-depleted zone (ADZ) mechanism was newly proposed for the "???+???" phase transformations. The ? phase bottom dross partly survived for a relatively long period, i.e., 2 hours in this work, whereas the ? phase disappeared after 30 minutes. In the early stage of dross formation, both Al-free large particles as well as high-Al tiny particles were formed. The dross particle size decreased slightly with increased reaction time before reaching a plateau. The opposite tendency was observed when the Al content was 0.130 mass pct; with a relatively high Al content, the nucleation of tiny ? phase dross was significantly enhanced because of the high degree of supersaturation. This unstable ? phase dissolved continuously and underwent simple transformation to the stable ? phase. The relationship between nucleation potential and supersaturation ratio of species is discussed based on the thermodynamics of classical nucleation theory.

Park, Joo Hyun; Park, Geun-Ho; Paik, Doo-Jin; Huh, Yoon; Hong, Moon-Hi

2012-01-01

174

Mechanisms of hydrolysis-oligomerization of aluminum alkoxide Al(OC3H7)3.  

PubMed

As one of the representative superinsulating materials, the aluminum trioxypropyl Al(OC(3)H(7))(3) aerogel may be applied in launch vehicles and manned spacecrafts. In this study, the structures and hydrolysis mechanisms of the monomer, dimers, and trimers of Al(OC(3)H(7))(3) in neutral and alkaline environments were studied at the B3LYP/6-31G(d,p) level by using the CPCM solvation model to understand the fundamental chemistry of Al(OC(3)H(7))(3) hydrolysis and oligomerization. Our calculation shows that the first-order hydrolyses of the monomer and oligomers are energetically favorable in both alkaline and neutral solutions. In alkaline solutions, they are more apt to oligomerize than to hydrolyze due to high energy barriers and large binding energies in the formation of anionic species. For the oligomers under neutral condition (1) Al(OC(3)H(7))(3) is linked by four-membered Al-O rings with pentacoordinated bridging and tetracoordinated Al atoms, (2) the hydrolyzed propoxy groups will be expelled by solvent molecules, and (3) partly hydrolyzed species can condense to oligomers with bridging OH groups or O atoms. PMID:21500848

Cheng, Xueli; Liu, Yongjun; Chen, Dairong

2011-04-18

175

Solid-state hot pressing of elemental aluminum and titanium powders to form TiAl (? + ?2) intermetallic microstructure  

NASA Astrophysics Data System (ADS)

The elemental powder metallurgy (EPM) process is used to prepare TiAl-base intermetallics. An EPM process conducted by two-stage solid-state hot pressing was employed to prepare TiAl-base intermetallics and to investigate the resulting microstructural changes. The results showed that the TiAl3 phase forms in the first stage. During the temperature increase to the second sintering stage, lamellar phases start to precipitate in the TiAl3 matrix. Further, the TiAl3 phase transforms to TiAl, and Ti3Al layers develop in the remaining titanium particles. Meanwhile, the lamellar phases grow into ring-type structures between the TiAl matrix and the Ti3 Al layers. After the second stage, the remaining titanium particles are fully reacted, and a microstructure of Ti3Al phases enclosed by fine-grained lamellar rings in the TiAl matrix is developed.

Yang, J. B.; Teoh, K. W.; Hwang, W. S.

1996-10-01

176

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

NASA Astrophysics Data System (ADS)

Zr and Sc precipitate in aluminum alloys to form the compounds Al3Zr and Al3Sc which for low supersaturations of the solid solution have the L12 structure. The aim of the present study is to model at an atomic scale this kinetics of precipitation and to build a mesoscopic model based on classical nucleation theory so as to extend the field of supersaturations and annealing times that can be simulated. We use some ab initio calculations and experimental data to fit an Ising model describing thermodynamics of the Al-Zr and Al-Sc systems. Kinetic behavior is described by means of an atom-vacancy exchange mechanism. This allows us to simulate with a kinetic Monte Carlo algorithm kinetics of precipitation of Al3Zr and Al3Sc. These kinetics are then used to test the classical nucleation theory. In this purpose, we deduce from our atomic model an isotropic interface free energy which is consistent with the one deduced from experimental kinetics and a nucleation free energy. We test different mean-field approximations [Bragg-Williams approximation as well as cluster variation method (CVM)] for these parameters. The classical nucleation theory is coherent with the kinetic Monte Carlo simulations only when CVM is used: it manages to reproduce the cluster size distribution in the metastable solid solution and its evolution as well as the steady-state nucleation rate. We also find that the capillary approximation used in the classical nucleation theory works surprisingly well when compared to a direct calculation of the free energy of formation for small L12 clusters.

Clouet, Emmanuel; Nastar, Maylise; Sigli, Christophe

2004-02-01

177

Al 2 O 3 -TiO 2 composite oxide films on etched aluminum foil fabricated by electrodeposition and anodization  

Microsoft Academic Search

Ti species have been deposited on low-voltage etched aluminum foils by a simple electrochemical method using a Ti anode as\\u000a Ti source in a Ti-free I2-dissolved acetone solution. After annealing at 500–600 °C in air, an Al2O3-TiO2 composite oxide film was formed on the surface of the etched aluminum foil by anodizing galvanostatically in an ammonium\\u000a adipate solution. The effects

JunFu Bu; Lan Sun; Qi Wu; MengYe Wang; ChangJian Lin

178

Reactivity of aluminum cluster anions with ammonia: Selective etching of Al{sub 11}{sup -} and Al{sub 12}{sup -}  

SciTech Connect

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

Grubisic, Andrej; Li Xiang; Gantefoer, Gerd; Bowen, Kit H. [Department of Chemistry, Johns Hopkins University, Baltimore, Maryland 21218 (United States); Schnoeckel, Hansgeorg [Institut fuer Anorganische Chemie, Karlsruhe Universitaet, Karlsruhe 76128 (Germany); Tenorio, Francisco J. [Departamento de Ciencias Exactas y Tecnologia, Centro Universitario de Los Lagos, Universidad de Guadalajara, Jalisco 47460 (Mexico); Martinez, Ana [Departamento de Materia Condensada y Criogenia, Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico, Coyoacan 04510, Distrito Federal (Mexico)

2009-11-14

179

Tensile properties of randomly oriented short ?-Al 2O 3 fiber reinforced aluminum alloy composites: II. Finite element analysis for stress transfer, elastic modulus and stress–strain curve  

Microsoft Academic Search

The tensile properties of aluminum alloy matrix composites containing randomly oriented short ?-Al2O3 fibers were simulated numerically and compared to experimental results. A three-dimensional finite element model based on a representative volume, containing a single fiber was constructed and used for elastic–plastic analysis. Both aligned and tilted fibers were considered in the model. Using this model, the stress transfer between

Guo-Zheng Kang; Qing Gao

2002-01-01

180

Synthesis and structural characterization of a new aluminum oxycarbonitride, Al5(O, C, N)4  

NASA Astrophysics Data System (ADS)

A new aluminum oxycarbonitride, Al5(OxCyN4-x-y) (x˜1.4 and y˜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 P63/mmc, Z=2, and unit-cell dimensions a=0.328455(6) nm, c=2.15998(3) nm and V=0.201805(6) nm3. The atom ratios O:C:N were determined by EELS. The final structural model, which is isomorphous with that of (Al4.4Si0.6)(O1.0C3.0), 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 Rwp=6.94% (S=1.22), Rp=5.34%, RB=1.35% and RF=0.76%. The crystal was an inversion twin. Each twin-related individual was isostructural with Al5C3N (space group P63mc, Z=2).

Inuzuka, Haruya; Kaga, Motoaki; Urushihara, Daisuke; Nakano, Hiromi; Asaka, Toru; Fukuda, Koichiro

2010-11-01

181

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

NASA Astrophysics Data System (ADS)

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

Zhang, Mingli

182

High temperature NMR study of aluminum metal influence on speciation in molten NaF-AlF3 fluorides.  

PubMed

In situ high temperature NMR spectroscopy has been used to characterize the interactions between aluminum metal and cryolitic melts. (27)Al, (23)Na, and (19)F NMR spectra have been acquired in NaF-AlF(3) and NaF-AlF(3)-Al melts over a wide range of compositions. The evolution of the signals evidence a chemical reaction between the metal and the salt. The different samples have been also described after solidification at room temperature by Environmental Scanning Electronic Microscopy, high resolution solid state NMR, and X-ray diffraction. The combination of in situ high temperature NMR characterization of the melts, with experimental description of solidified samples after cooling, evidence an enrichment of the melts with AlF(3) and different reactions with metallic aluminum depending on the initial bath composition. PMID:21413719

Nuta, Ioana; Veron, Emmanuel; Matzen, Guy; Bessada, Catherine

2011-03-17

183

Aluminum hard mask technique for the fabrication of high quality submicron Nb/Al-AlOx/Nb Josephson junctions  

NASA Astrophysics Data System (ADS)

We have developed a combined photolithography and electron-beam lithography fabrication process for sub-µm to µm-size Nb/Al-AlOx/Nb Josephson junctions. In order to define the junction size and protect its top electrode during anodic oxidation, we developed and used the new concept of an aluminum hard mask. Josephson junctions of sizes down to 0.5 µm2 have been fabricated and thoroughly characterized. We found that they have a very high quality, which is witnessed by the IV curves with quality parameters Vm > 50 mV and Vgap = 2.8 mV at 4.2 K, as well as IcRN products of 1.75-1.93 mV obtained at lower temperatures. In order to test the usability of our fabrication process for superconducting quantum bits, we have also designed, fabricated and experimentally investigated phase qubits made of these junctions. We found a relaxation time of T1 = 26 ns and a dephasing time of T2 = 21 ns.

Kaiser, Ch; Meckbach, J. M.; Ilin, K. S.; Lisenfeld, J.; Schäfer, R.; Ustinov, A. V.; Siegel, M.

2011-03-01

184

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

NASA Astrophysics Data System (ADS)

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

Bin, Feng

185

Adhesive wear behaviour of B 4C and SiC reinforced 4147 Al matrix composites (Al\\/B 4C–Al\\/SiC)  

Microsoft Academic Search

Adhesive wear characteristics of 4147Al\\/B4C, 10, 15 and 20wt.% B4C particle and Al\\/SiC metal matrix composites 20wt.% SiC contain produced by liquid metallurgy have been investigated under the dry sliding conditions and their wear behaviours are compared with 4147 Al\\/SiC-reinforced 20wt.% SiC. The results showed that the wear resistance of Al\\/B4C matrix increases considerably with increasing wt.% B4C particle content

R. Ipek

2005-01-01

186

The Fatigue and Impact Resistance of Dual-Matrix Boron-Aluminum Composites.  

National Technical Information Service (NTIS)

The effects of a soft, plastic interface zone and of heat treatments on the axial fatigue resistance and on the Charpy impact behavior of boron-6061 aluminum composites were determined. Interfacial microstructures and composite fatigue resistance were com...

J. R. Hancock G. G. Shaw

1974-01-01

187

Investigation on work softening behavior of aluminum and its alloys with iron  

NASA Astrophysics Data System (ADS)

Work softening in aluminum and its alloys (Al-2Fe) was investigated at room temperature. Work softening was noticed in aluminum with a purity of 99.996 %, in an Al-2Fe alloy with a purity of 99.996 % in the aluminum matrix, and in an Al-2Fe alloy with a purity of 99.96% in the aluminum matrix, when the reduction in thickness of samples after rolling is more than 80 %, 60 %, and 90 %, respectively. Work softening was mainly related to the recovery at room temperature. The addition of iron to aluminum purifies the aluminum matrix. The dispersed second phases formed by aluminum and iron may promote the recovery.

Li, F.-Z.; Liu, Z.-J.; Jin, Q.; Yu, Z.-M.; Liu, E.

1997-04-01

188

Social Network Analysis via Matrix Decompositions: al Qaeda  

Microsoft Academic Search

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

D. B. Skillicorn

189

Fabrication of Al-matrix composites reinforced with amino functionalized boron nitride nanotubes.  

PubMed

Amino functionalized boron nitride nanotubes were used as the reinforcement material for the fabrication of Al-matrix composites using powder metallurgy process. It was found that the mechanical properties of these composites were improved significantly as compared to pure Al composites fabricated under similar conditions. The microhardness of these composites was found to improve by five times and compressive strength by 300% as compared to pure Al composites under similar processing conditions. The enhanced mechanical properties of these composites can be attributed to the proper dispersion of boron nitride nanotubes (BNNTs) in Al matrix and the formation of a strong interfacial bonding between BNNTs and Al matrix under the processing conditions. High-resolution transmission electron microscopy studies revealed the formation of transition layer of AlB2 which might lead to a better load transfer from Al matrix to the BNNTs. Further, these composites are believed to withstand high temperatures as compared to Al matrix composites reinforced with carbon nanotubes and, therefore, can be used for applications where lightweight and high strength materials are desired with stability at elevated temperatures. PMID:21770161

Singhal, Sunil K; Srivastava, Avanish K; Pasricha, Renu; Mathur, Rakesh B

2011-06-01

190

Damping characteristics of Zn-Al matrix composites  

SciTech Connect

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

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

1994-05-15

191

The Interface Between ?? and Matrix in an 8090 Al-Li Alloy Studies by SAXS  

Microsoft Academic Search

A small angle X-ray scattering (SAXS) techniques has been used to characterize the interfaces between the ?? phase and matrix in and 8090 Al-Li alloy aged at 160°C for several times. The results showed that a transition interfacial layer exists between the ?? phase and matrix in the earlier stage of aging, which disappears in the later stage of aging.

Z. G. Chai; Y. Xu; F. L. Meng

1999-01-01

192

Experimental and numerical evaluation of forming limit diagram for Ti6Al4V titanium and Al6061-T6 aluminum alloys sheets  

Microsoft Academic Search

The forming limit diagram (FLD) is a useful concept for characterizing the formability of sheet metal. In this work, the formability, fracture mode and strain distribution during forming of Ti6Al4V titanium alloy and Al6061-T6 aluminum alloy sheets has been investigated experimentally using a special process of hydroforming deep drawing assisted by floating disc. The selected sheet material has been photo-girded

F. Djavanroodi; A. Derogar

2010-01-01

193

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

SciTech Connect

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

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

2004-12-02

194

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

195

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…

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

2008-01-01

196

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

National Technical Information Service (NTIS)

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

G. Kay

2003-01-01

197

High-Temperature Enthalpy and X-Ray Powder Diffraction Data for Aluminum Sulfide (Al2S3).  

National Technical Information Service (NTIS)

High-temperature enthalpy and X-ray power diffraction studies were conducted on aluminum sulfide (Al2 S3) as part of the Bureau of Mines effort to provide new data for the advancement of mineral technology consistent with environmental preservation and en...

M. J. Ferrante R. A. McCune

1981-01-01

198

Aluminum and phosphorus separation: application to preparation of target from brain tissue for 26Al determination by accelerator mass spectrometry  

NASA Astrophysics Data System (ADS)

Acid digested brain containing 4mg added 27Al was ashed at 1000 degC to prepare an Al2O3 target for accelerator mass spectrometry (AMS) analysis of 26Al. A glass-like material usually resulted which was thought to be aluminum (Al) oxyphosphate. The separation of Al and phosphate was investigated. Al, but not phosphate, was bound by a cation exchange resin (AG 50-X8). Hydrofluoric acid eluted the Al from the resin. Removal of phosphate from acid digested brain by this method produced an amorphous material after ashing that was easier to recover from the porcelain crucible and had a higher AMS beam current. This procedure to separate Al from phosphate may have utility in other applications.

Brauer, Russell D.; Robertson, J. David; Sharma, Pankaj; Yokel, Robert A.

1999-04-01

199

Equilibrium and Kinetic Studies of Systems of Hydrogen Isotopes, Lithium Hydrides, Aluminum and LiAlO2  

SciTech Connect

This paper described measurements of (1) the distribution of tritium and helium throughout both phases of irradiated Li-Al alloy, (2) the migration rate of tritium during moderate heating, (3) equilibrium pressures as functions of temperature of H2, D2, or T2 in contact with lithium hydrides + aluminum, Li-Al alloy, or irradiated Li-Al alloy, (4) the equilibrium constant for the reaction as a function of temperature, and (5) extraction rates of tritium from irradiated LiAlO2 targets at elevated temperatures.

Owen, J.H.

2001-10-23

200

The effect of basicity of poly-aluminum macromolecule solution on the properties of ?-Al 2O 3 ceramic membrane  

Microsoft Academic Search

A microporous membrane of ?-Al2O3, with a ceramic plate as substrate was prepared by an in situ graining process. Several important parameters of this ?-Al2O3 ceramic membrane such as the largest pore radius, the distribution of pore-size, and the most probable pore radius were measured. The effect of basicity of the inorganic poly-aluminum (Aln(OH)mCl(3n?m)) solution on the morphology and microstructure

He Weiguang; Lin Shaokun; Zheng Kangcheng; Li Xiaogang; Lin Senshu

1999-01-01

201

High transconductance InAlAs\\/InGaAs double heterostructure MESFETs with in-situ aluminum oxide gate barrier  

Microsoft Academic Search

By incorporating an in-situ aluminum oxide gate barrier in InAlAs\\/InGaAs double heterostructure FETs we have reduced the gate leakage current by more than an order of magnitude. The measured transconductance is 130 mS\\/mm and the device pinches off at -1.5 V. The oxide barrier is prepared by in-situ deposition of 2 nm Al in an MBE system followed by complete

T. Y. Chang; R. E. Behringer; R. E. Howard; A. S. H. Liao; L. D. Jackel; E. A. Caridi; W. J. Skocpol; R. W. Epworth

1984-01-01

202

The effect of particulate loading on the mechanical behaviour of Al2O3\\/Al metal-matrix composites  

Microsoft Academic Search

An investigation was made to determine the effect of particulate loading on the elastic, tensile, compressive and fracture properties of Al2O3\\/Al metal-matrix composites fabricated by a pressureless-liquid-metal-infiltration process. The elastic modulus was found to be strongly affected by the reinforcement content, falling within the Hashin-Shtrikman bounds. The Young's modulus of the most highly loaded composite was 170 GPa; compare with

M. K. Aghajanian; R. A. Langensiepen; M. A. Rocazella; J. T. Leighton; C. A. Andersson

1993-01-01

203

75 FR 44184 - Aluminum tris(O-ethylphosphonate), Butylate, Chlorethoxyfos, Clethodim, et al.; Proposed...  

Federal Register 2010, 2011, 2012, 2013

...EPA-HQ-OPP-2010-0490; FRL-8834-1] Aluminum tris(O-ethylphosphonate), Butylate...propetamphos, and tebufenozide; the fungicides aluminum tris(O-ethylphosphonate) and fenarimol...proposing to revoke the tolerances for aluminum tris(O-ethylphosphonate) on...

2010-07-28

204

The influence on selectivity of the aluminum content in the matrix of FCC catalysts  

Microsoft Academic Search

The influence that both the type of matrix and the interaction between zeolite and matrix have on the selectivity of FCC catalysts was studied by means of the conversion of cyclohexene at 300°C on a large number of samples in which the matrix was changed. Silica\\/alumina matrices had 0, 12 and 25% of alumina, and catalysts were subjected to steaming

Gabriela de la Puente; Eduardo Falabella Sousa-Aguiar; Alexandre Figueiredo Costa; Ulises Sedran

2003-01-01

205

Damping characteristics of Zn-Al matrix composites  

Microsoft Academic Search

Among high damping materials, Zn-Al alloys are considered to be the most excellent non-ferromagnetic damping alloys due to their attractive properties such as low melting point, low density, good workability and high damping capacity in a broad frequency range. The limitations to high temperature use of these alloys are their poor high temperature mechanical properties and dimensional instability. Recently, various

M. Gu; Z. Chen; Z. Wang; Y. Jin; J. Huang; G. Zhang

1994-01-01

206

Aluminum-Metal Reactive Composites  

Microsoft Academic Search

Three binary Al-based reactive composite powders are prepared by mechanical milling. The particles have an aluminum matrix and inclusions of Fe, Ni, or Zn comprising 10 at % of the bulk composition. For additives of Ni and Zn, only short milling times can be used to prepare composites; intermetallic phases form at longer milling. Short milling times yield relatively coarse

Yasmine Aly; Mirko Schoenitz; Edward L. Dreizin

2011-01-01

207

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

Microsoft Academic Search

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

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

1989-01-01

208

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

PubMed

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

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

2010-10-29

209

Internal friction at medium temperature in an Al matrix composite reinforced by SiC particles  

SciTech Connect

The aim of this paper is to present new results showing that a relaxation damping peak associated with the motion of dislocations controlled by point defects, appear at about 450 K in the 6061 Al matrix MMC. For that purpose, mechanical spectroscopy has been measured in a 6061 Al alloy matrix composite reinforced with SiC particulate at low frequencies. In this paper, the damping spectra for the MMC of 6061 Al/SiC{sub p} and unreinforced 6061 Al are presented at first. Secondly, some supplement results are presented. Finally, the origin of the differences between the damping spectra of Al/SiC{sub p} and Al alloy are discussed, and a relaxation model is proposed to explain the damping peak.

Wang, C.; Zhu, Z. [Chinese Academy of Sciences, Hefei (China). Lab. of Internal Friction and Defects in Solids

1998-05-12

210

Improvement in mechanical properties of NiAl matrix composites fabricated by reaction compocasting  

SciTech Connect

With Ni, Al, Fe, Ti and C elemental powders, the NiAl(Fe) matrix composites have been successfully fabricated by the reaction compocasting (RC) technique. The composites consist of three phases, which are {beta}{sup 9} and {gamma}{sup 9} and TiC, respectively. The TiC particles, with the particle size of 0.2{approximately}3{micro}m, tend to be uniformly dispersed in the matrix. The composites not only offer the high elevated temperature strength, but also exhibit the satisfied ambient ductility, which indicates that the shortcomings of the insufficient elevated temperature strength and the poor ambient temperature ductility of stoichiometric NiAl are overcome, and which makes it possible for NiAl(Fe) matrix composites to be used in the high temperature structural applications.

Lu, Y.X. [Beijing Inst. of Aeronautical Materials (China)]|[Harbin Inst. of Tech. (China). School of Materials Science and Engineering; Tao, C.H. [Harbin Inst. of Tech. (China). School of Materials Science and Engineering; Yang, D.Z. [Beijing Inst. of Aeronautical Materials (China)

1996-11-15

211

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

NASA Astrophysics Data System (ADS)

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., †K) or the SiC content was increased.

Niklas, A.; Froyen, L.; Wevers, M.; Delaey, L.

1995-12-01

212

Fatigue testing welded joints for P/M Al-matrix composites  

NASA Astrophysics Data System (ADS)

To meet their need for high stiffness, many bicycles currently rely on aluminum-matrix composites. The highest strength and highest stiffness form of these material, 6092/B4C/15p, is produced by powder metallurgy techniques. The bicycles are tungsten inert-gas welded and fully heat treated after welding. A test technique has been developed to assess the static and fatigue properties of welded joints. This test technique has revealed the increased stiffness and strength of a 6092/B4C/15p-T6P composite tube joint as compared with a 6061-T6 aluminum one. This test technique is currently being used to identify fatigue properties for both tube joints.

Harrigan, William C.

1994-07-01

213

Temperature-dependence mechanism of tensile strength of Si-Ti-C-O fiber-aluminum matrix composites  

SciTech Connect

The mechanism for the temperature dependence of the tensile strength of unidirectional hybrid type Si-Ti-C-O (Tyranno) fiber-reinforced aluminum matrix composite, in which SiC-particles are dispersed in the matrix, is discussed, focusing on the temperature dependencies of the stress concentration arising from broken fibers and critical length and their influences on the composite strength, by means of a shear-lag analysis and a Monte Carlo simulation. The main results are summarized as follows. The softening of the matrix at high temperatures raises the composite strength from the point of decrease in stress concentration, but on the other hand, it also reduces strength from the point of increase in critical length, which reduces the stress-carrying capacity of broken fibers over a long distance. The reason why the measured strength of composite decreased with increasing temperature could be attributed to the predominancy of the latter effect over the former one. The results of the simulation indicated that the hybridization of the composites improved room-temperature and high-temperature strengths through the strengthening of the matrix.

Ochiai, Shojiro; Hojo, Masaki; Osamura, Kozo [Kyoto Univ. (Japan). Faculty of Engineering; Matsunaga, Kenji; Waku, Yoshiharu; Yamamura, Takemi [Ube Industries, Ltd., Yamaguchi (Japan). Corporate Research and Development

1995-03-01

214

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

215

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

Microsoft Academic Search

The settling of 14-?m silicon carbide particles in an aluminum-silicon alloy was monitored with an electrical resistance probe\\u000a to measure thein situ particle voluem fraction. The rate of settling was much greater than expected from hindered settling of single 14-?m particles.\\u000a From the observed settling rate, an equivalent hydrodynamic diameter and density of clusters of particles were deduced, 38\\u000a ?m

G. A. Irons; K. Owusu-Boahen

1995-01-01

216

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

Microsoft Academic Search

A halogen assisted thermal purification method was developed with the use of Ar+1% (v\\/v) CHF3 internal furnace gas and applied specifically to the determination of iron impurities in high-purity aluminum. The samples were applied in the form of hydrochloric acid solution, and the alumina formed by hydrolysis from the chloride salt was reacted with the halocarbon in the pyrolysis step

Silvera Scaccia; Giovanna Zappa

2000-01-01

217

Electric discharge machining of Al–10%SiC P as-cast metal matrix composites  

Microsoft Academic Search

The use of unconventional machining techniques in shaping aluminium metal matrix composites (Al-MMC) has generated considerable interest as the manufacturing of complicated die contours in these hard materials to a high degree of accuracy and surface finish is difficult. Electrical discharge machining (EDM) is an important process for machining difficult-to-machine materials like metal matrix composites. Among the many unconventional processing

P. Narender Singh; K. Raghukandan; M. Rathinasabapathi; B. C. Pai

2004-01-01

218

Fabrication and evaluation of mechanical and tribological properties of boron carbide reinforced aluminum matrix nanocomposites  

Microsoft Academic Search

In this study, fabrication and characterization of bulk Al–B4C nanocomposites were investigated. B4C nanoparticles were mixed with pure Al powder by ball milling to produce Al–B4C powder. Al–B4C powders containing different amounts of B4C (5, 10 and 15wt.%) were subsequently hot pressed to produce bulk nanocomposite samples. Consolidated samples were characterized by hardness, compression and wear tests. Results showed that

E. Mohammad Sharifi; F. Karimzadeh; M. H. Enayati

2011-01-01

219

Tensile/Compressive Fatigue and Interface Characterization of Al2O3 Fiber/Al-2.5% Li Alloy Metal Matrix Composite.  

National Technical Information Service (NTIS)

The fatigue response to cyclic roads of a continuous A12O3 fiber/aluminum-lithium alloy metal matrix composite was successfully characterized at room temperature and 175 C. Low cycle fatigue was dominated by crack propagation perpendicular to the axial fi...

M. M. Buckley J. Homeny

1990-01-01

220

Corrosion of graphite/aluminum metal-matrix composites. Technical report, 1 Mar-31 Dec 90  

SciTech Connect

Several commercial G/Al MMCs have been studied by potentiodynamic polarization in deaerated 0.5 M Na{sub 2}SO{sub 4}. The results have been compared with those which were predicted by the mixed electrode theory. The results indicate that processing conditions, especially the cooling rate, had a strong influence on the corrosion behavior of the G/Al MMCs. Large scale G/Al model MMCs were fabricated at MIT in order to study the corrosion behavior of G/Al galvanic couples with the scanning potential microprobe (SPM). Preliminary results indicate that coating graphite with discontinuous alumina did not reduce the corrosion rate of the G/Al galvanic couple. Ion implanting the surface of G/Al model MMCs with zinc, a cathodic inhibitor, did reduce the corrosion G/Al galvanic couple; however, the protection was incomplete.

Buonanno, M.A.; Latanision, R.M.; Hihara, L.H.; Chiang, J.F.

1991-02-01

221

The influence of Al2O3 particulate reinforcement on cyclic stress response and fracture behavior of 6061 aluminum alloy  

NASA Astrophysics Data System (ADS)

The cyclic stress response characteristics and cyclic fracture behavior of aluminum alloy 6061 discontinuously reinforced with particulates of Al2O3 are presented and discussed. The 6061/Al2O3 composite specimens and the unreinforced 6061 aluminum alloy were cyclically deformed using tension-compression loading under constant total strain amplitude control. Both the composite and the unreinforced alloy exhibited softening to failure from the onset of cyclic deformation. The degree of softening was observed to increase at the elevated test temperature for both the composite and the unreinforced counterpart. The intrisic micromechanisms controlling the stress response characteristics during fully-reversed cyclic straining are highlighted and rationale for the observed behavior is discussed. The cyclic fracture behavior of the composite is discussed in terms of the competing influences of intrinsic microstructural effects, deformation characteristics arising from a combination of mechanical and microstructural contributions, cyclic stress response, and test temperature.

Srivatsan, T. S.; Sriram, S.; Daniels, C.

1995-05-01

222

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

SciTech Connect

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

Kay, G

2002-09-16

223

Welding metallurgy and weldability of high strength aluminum alloys  

SciTech Connect

A literature survey was conducted to gather the information available on the welding metallurgy of high strength aluminum alloys, and its effect on their weldability. The report focuses on fusion welding of high strength aluminum alloys. Both conventional high strength aluminum alloys and newer products, e.g., PM aluminum alloys, Al-Li alloys and Al-matrix composites, are included. The survey covers a wide spectrum of publications, ranging from those using traditional equipment of study to those using more modern analytical instruments, such as electron microscopy and high speed computers. Recommendations of subjects for further research programs are presented. 84 references.

Kou, S.

1986-12-01

224

Mechanical Properties of In-Situ FeAl-TiB2 Intermetallic Matrix Composites  

NASA Astrophysics Data System (ADS)

Intermetallic matrix composites reinforced with ceramic particles have received a great deal of attention. Iron aluminide is known to be a good material for the matrix in such composites. Two processes were used to fabricate FeAl-TiB2 intermetallic matrix composites. One was liquid melt in-situ mixing, and the other was arc melting and suction casting processes. FeAl-TiB2 IMCs obtained by two different methods were investigated to elucidate the influence of TiB2 content. In both methods, the grain size in the FeAl alloy decreased with the presence of titanium diboride. The grain size of in-situ FeAl-TiB2 IMCs became smaller than that of arc FeAl-TiB2 IMCs. Significant increase in fracture stress and hardness was achieved in the composites. The in-situ process gives clean, contamination-free matrix/reinforcement interface which maintained good bonding causing high load bearing capability. This contributed to the increase in the mechanical properties of composites.

Kim, Jonghoon; Park, Bonggyu; Park, Yongho; Park, Ikmin; Lee, Heesoo

225

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

226

Effect of aluminum content on synthesis of Ti 2 AlC and Ti 3 AlC 2 during treatment in a high-energy mill and hot pressing  

Microsoft Academic Search

Treatment of initial powders of titanium, carbon and aluminum in a high-energy mill and pressure sintering are used for synthesizing\\u000a dense and single-phase Ti2AlC and Ti3AlC2 ceramics. The effect of the content of aluminum and of the sintering temperature on the synthesis process is studied. During\\u000a treatment in the high-energy mill the initial Ti, Al and C react and yield

Jianfeng Zhu; Guoquan Qi; Fen Wang; Haibo Yang; Ying Li

2011-01-01

227

Effects of the chromium to aluminum content on the tribology in dry machining using (Cr,Al)N coated tools  

Microsoft Academic Search

The present study investigates the potentials of newly developed (Cr,Al)N coatings compared to uncoated tools. The aim of using chromium-based coatings is to create a thermal barrier and thus redirecting the heat from work piece and tool into the chip. Due to their high resistance for oxidation, CrxAlyN coatings with different chromium to aluminum contents were deposited onto indexed carbide

H. Scheerer; H. Hoche; E. Broszeit; B. Schramm; E. Abele; C. Berger

2005-01-01

228

Static and dynamic hyperpolarizability tensors of aluminum metal clusters, Al4M4 ( M=Li , Na, and K)  

Microsoft Academic Search

Static and dynamic hyperpolarizability calculations have been performed to explore the nonlinear optical properties of aluminum metal clusters Al4M4 ( M=Li , Na, and K). An analytical approach combined with a finite difference technique has been used to evaluate the response properties within the framework of time-dependent density functional theory. Components of the first and second order hyperpolarizability tensors are

Sabyasachi Sen; Prasenjit Seal; Swapan Chakrabarti

2007-01-01

229

Laser peening without coating on aluminum alloy Al-6061-T6 using low energy Nd:YAG laser  

NASA Astrophysics Data System (ADS)

The present study investigates the effect of laser peening without coating on aluminum alloy Al-6061-T6 with a 300mJ infrared laser. The surface topography, microstructure, surface topography, surface residual stress and micro-hardness of peened and unpeened surfaces were studied. The study shows that laser peening without coating can significantly improve surface compressive stress and micro-hardness with trivial increase in surface roughness. Microstructure evaluation confirmed there was no near surface solidification after LPwC.

Sathyajith, S.; Kalainathan, S.; Swaroop, S.

2013-02-01

230

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

NASA Astrophysics Data System (ADS)

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

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

1995-10-01

231

Exploration of Al-based matrix composites reinforced by hierarchically spherical agents  

NASA Astrophysics Data System (ADS)

Al-based composites reinforced with Al-Ti intermetallic compounds/Ti metal hierarchically spherical agents were successfully fabricated by powder metallurgy. This kind of structure produces strongly bonded interfaces as well as soft/hard/soft transition regions between the matrix and reinforced agents, which are beneficial to load transfer during deformation. As expected, the resultant composites exhibit promising mechanical properties at ambient temperature. The underlying mechanism was also discussed in this paper.

Zhang, Li; Wu, Bao-lin; Zhao, Yu-hua; Du, Xing-hao

2013-08-01

232

Corrosion of graphite\\/aluminum metal-matrix composites. Technical report, 1 Mar31 Dec 90  

Microsoft Academic Search

Several commercial G\\/Al MMCs have been studied by potentiodynamic polarization in deaerated 0.5 M NaâSOâ. The results have been compared with those which were predicted by the mixed electrode theory. The results indicate that processing conditions, especially the cooling rate, had a strong influence on the corrosion behavior of the G\\/Al MMCs. Large scale G\\/Al model MMCs were fabricated at

M. A. Buonanno; R. M. Latanision; L. H. Hihara; J. F. Chiang

1991-01-01

233

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

Microsoft Academic Search

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

D. L. Mcdanels; R. A. Signorelli

1976-01-01

234

Fabrication and properties of dispersed carbon nanotube–aluminum composites  

Microsoft Academic Search

Powder metallurgy techniques have emerged as promising routes for the fabrication of carbon nanotube (CNT) reinforced metal matrix composites. In this work, planetary ball milling was used to disperse 2wt% MWCNT in aluminum (Al) powder. Despite the success of ball milling in dispersing CNTs in Al powder, it is often accompanied with considerable strain hardening of the Al powder, which

A. M. K. Esawi; K. Morsi; A. Sayed; A. Abdel Gawad; P. Borah

2009-01-01

235

Reaction of aluminum-on-titanium bilayer with GaN: Influence of the Al:Ti atomic ratio  

Microsoft Academic Search

Backscattering spectrometry, x-ray diffractometry, and scanning electron microscopy have been used to study metallurgically\\u000a the evolution of ?GaN?\\/Ti(40 nm)\\/Al(180 nm) and ?GaN?\\/Ti(80 nm)\\/Al(150 nm) metal contacts before and after annealing for 30\\u000a min in vacuum between 450 and 800C. A slight reaction of the titanium with the aluminum is first observable after annealing\\u000a at 450C. After 550C titanium completely converts

S. M. Gasser; E. Kolawa; M.-A. Nicolet

1999-01-01

236

An analysis of the effect of hydrostatic pressure on the tensile deformation of aluminum-matrix composites  

Microsoft Academic Search

The effect of superposed hydrostatic pressure on the tensile deformation of particle-reinforced Al-matrix composites was analyzed using a self-consistent approximation. The composite was represented in terms of an interpenetrating network of randomly distributed spheres, which stand for the intact and damaged regions in the composite. Each sphere contained an intact or broken ceramic particle at the center, and the model

C González; J Llorca

2003-01-01

237

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

Microsoft Academic Search

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

Choong Do Lee; Choon Sik Kang; Kwang Seon Shin

2000-01-01

238

Accelerated Multiplicative Updates and Hierarchical ALS Algorithms for Nonnegative Matrix Factorization  

Microsoft Academic Search

Nonnegative matrix factorization (NMF) is a data analysis technique used in a great variety of applications such as text mining, image processing, hyperspectral data analysis, computational biology, and clustering. In this letter, we consider two well-known algorithms designed to solve NMF problems: the multiplicative updates of Lee and Seung and the hierarchical alternating least squares of Cichocki et al. We

Nicolas Gillis; François Glineur

2012-01-01

239

Research on the vibration cutting performance of particle reinforced metallic matrix composites SiCp\\/Al  

Microsoft Academic Search

The cutting performance of particle reinforced metallic matrix composites (PRMMCs) SiCp\\/Al in ultrasonic vibration cutting and common cutting (CC) with carbide tools and PCD tools was researched experimentally in this work. The changing rules of chip shape, deformation coefficient, shear angle, surface residual stress and microstructure in ultrasonic vibration cutting are presented. The result shows that when adopting CC, a

B Zhao; C. S Liu; X. S Zhu; K. W Xu

2002-01-01

240

Residual stress effect on impact properties of Gr\\/Al metal matrix composite  

Microsoft Academic Search

The effects of residual stress on the impact properties of the unidirectionally reinforced P 100 Gr\\/6061 Al metal matrix composites with different thermal histories have been investigated using an instrumented impact test method and scanning electron microscopy. The cantilever impact generally causes tensile failure at the notch and compressive loading on the opposite side of the specimen. The specimens with

Ji-Liang Doong; Shyh-Nung S. Lin; H. L. Marcus

1992-01-01

241

Surface treatment of new type aluminum lithium alloy and fatigue crack behaviors of this alloy plate bonded with Ti–6Al–4V alloy strap  

Microsoft Academic Search

Samples consisting of new aluminum lithium alloy (Al–Li alloy) plate developed by the Aluminum Company of America and Ti–6Al–4V alloy (Ti alloy) plate were investigated. Plate of 400mm×140mm×2mm with single edge notch was anodized in phosphoric solution and Ti alloy plate of 200mm×20 (40) mm×2mm was anodized in alkali solution. Patterns of two alloys were studied at original\\/anodized condition. And

Zhen-Qi Sun; Ming-Hui Huang; Guo-Huai Hu

242

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

243

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

PubMed

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

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

2011-11-25

244

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

Microsoft Academic Search

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

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

2006-01-01

245

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

SciTech Connect

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

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

1995-10-01

246

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

247

Effect of mechanical alloying time and carbon nanotube (CNT) content on the evolution of aluminum (Al)–CNT composite powders  

Microsoft Academic Search

One of the major obstacles to the effective use of carbon nanotubes as reinforcements in metal matrix composites is their\\u000a agglomeration and poor distribution\\/dispersion within the metallic matrix. In the present work, we use mechanical alloying\\u000a (MA) to mechanically mix CNT (2 and 5 wt.%) with Al powders. These powders would be used as precursors for subsequent consolidation\\u000a to generate bulk

K. Morsi; A. Esawi

2007-01-01

248

Corrosion protection of Al alloys and Al-based metal-matrix composites by chemical passivation  

SciTech Connect

Chemical passivation by immersion of aluminium alloys and aluminium 6061/ silicon carbide and aluminium 6061/graphite metal-matrix composites in cerium chloride solution produces very corrosion-resistant surfaces. Aluminium 6061 and aluminium 7075-T6 that had been immersed in 1000 ppm cerium chloride for one week did not suffer from pitting corrosion during immersion in acerated 0.5 N NaCl for three weeks. For aluminium 7075-T7l3 some improvement of the corrosion resistance was also achieved, but to a much lesser extent. Chemical passivation in cerium chloride was also successful for aluminium/silicon carbide and Allgraphite.

Mansfeld, F.; Lin, S.; Sim, S.; Shih, H.

1989-08-01

249

Nature and acidity of aluminum species in AlMCM-41 with a high aluminum content (Si\\/Al = 1.25)  

Microsoft Academic Search

A series of low-silica (Si\\/Al=1.25) [H,Na]AlMCM-41 with H\\/Na ratios comprised between 0 and 1 has been obtained by ionic exchange with ammonium nitrate followed by calcination. Standard procedures starting from a calcined [Na]-precursor could not be applied; some of the Na+ species were not accessible and treatments in water led to a significant dealumination and to a gradual collapse of

Yongrui Wang; Natacha Lang; Alain Tuel

2006-01-01

250

Avoidance of Stress Corrosion Susceptibility in High Strength Aluminum Alloys by Control of Grain Boundary and Matrix Microstructure.  

National Technical Information Service (NTIS)

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 9previously studied 7075 aluminum alloy. Optical m...

P. Adler R. Deiasi

1974-01-01

251

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

Microsoft Academic Search

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

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

2008-01-01

252

Dynamic mechanical analysis of prestrained Al 2 O 3 \\/Al metal-matrix composite  

Microsoft Academic Search

The effect of prestraining on the elastic modulus,E, and damping capacity, tanf, of 10 and 20 vol% Al2O3 particle-reinforced composites has been investigated as function of temperature using dynamic mechanical analysis. Both elastic modulus and damping capacity were found to increase with volume fraction. At 10 vol% the modulus and damping were relatively insensitive to prestrain. However, at 20 vol%

S. Elomari; R. Boukhili; M. D. Skibo; J. Masounave

1995-01-01

253

Surface-modified anodic aluminum oxide membrane with hydroxyethyl celluloses as a matrix for bilirubin removal.  

PubMed

Microporous anodic aluminum oxide (AAO) membranes were modified by 3-glycidoxypropyltrimethoxysilane to produce terminal epoxy groups. These were used to covalently link hydroxyethyl celluloses (HEC) to amplify reactive groups of AAO membrane. The hydroxyl groups of HEC-AAO composite membrane were further modified with 1,4-butanediol diglycidyl ether to link arginine as an affinity ligand. The contents of HEC and arginine of arginine-immobilized HEC-AAO membrane were 52.1 and 19.7mg/g membrane, respectively. As biomedical adsorbents, the arginine-immobilized HEC-AAO membranes were tested for bilirubin removal. The non-specific bilirubin adsorption on the unmodified HEC-AAO composite membranes was 0.8mg/g membrane. Higher bilirubin adsorption values, up to 52.6mg/g membrane, were obtained with the arginine-immobilized HEC-AAO membranes. Elution of bilirubin showed desorption ratio was up to 85% using 0.3M NaSCN solution as the desorption agent. Comparisons equilibrium and dynamic capacities showed that dynamic capacities were lower than the equilibrium capacities. In addition, the adsorption mechanism of bilirubin and the effects of temperature, initial concentration of bilirubin, albumin concentration and ionic strength on adsorption were also investigated. PMID:23290920

Xue, Maoqiang; Ling, Yisheng; Wu, Guisen; Liu, Xin; Ge, Dongtao; Shi, Wei

2012-11-02

254

Aluminum chlorohydrate III: Conversion to aluminum hydroxide.  

PubMed

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

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

1981-07-01

255

In situ reacted titanium nitride-reinforced aluminum alloy composite  

Microsoft Academic Search

In this paper, an aluminum matrix containing titanium nitride particles was fabricated by an in situ process in which nitrogen gas reacts with titanium in the liquid melt to form TiN. The tensile and yield strength increased by up to 20% after the formation of TiN particles in the Al alloy matrix, whilst the hardness increased by up to 27%.

R. F Shyu; F. T Weng; C. T Ho

2002-01-01

256

Metal Matrix Composites  

SciTech Connect

Metal matrix composites have found selected application in areas that can cost-effectively capitalize on improvements in specific stiffness, specific strength, fatigue resistance, wear resistance, and coefficient of thermal expansion. Metal matrix composites comprise a relatively wide range of materials defined by the metal matrix, reinforcement type, and reinforcement geometry. In the area of the matrix, most metallic systems have been explored, including aluminum, beryllium, magnesium, titanium, iron, nickel, cobalt, and silver. However, aluminum is by far the most preferred. For reinforcements, the materials are typically ceramics, which provide a very beneficial combination of stiffness, strength, and relatively low density. Candidate reinforcement materials include SiC, Al2O3, B4C, TiC, TiB2, graphite, and a number of other ceramics. In addition, metallic materials such as tungsten and steel fibers have been considered.

Hunt, Warren; Herling, Darrell R.

2004-02-01

257

Effect of Aluminum Content on Plasma-Nitrided Al x CoCrCuFeNi High-Entropy Alloys  

Microsoft Academic Search

High-entropy alloys (HEAs) Al\\u000a x\\u000a CoCrCuFeNi with different aluminum contents (x = 0 to 1.8) were plasma nitrided at 525 °C for 45 hours with an aim to develop wear-resistant structural parts. The nitrided\\u000a layer comprises a well-nitrided dendrite phase and an un-nitrided Cu-rich interdendrite phase. Surface hardening is a result\\u000a of the formation of various nitrides in the nitrided dendrite: CrN, Fe4N, and

Wei-Yeh Tang; Jien-Wei Yeh

2009-01-01

258

Fracture mechanism of FeAl matrix composites with discontinuous ceramic reinforcements  

Microsoft Academic Search

The fracture mechanism of Fe-40at.%Al matrix composites with ceramic particles, whiskers and short fibers fabricated by reactive hot-pressing was investigated in air and in oil bath at ?300 K. The loading rate was varied in the range of 10?2–10 MPa m1\\/2 s?1 to characterize the sensitivity for environmental embrittlement. The fracture resistance of the composites basically depends on the stress

Masahiro Inoue; Katsuaki Suganuma; Koichi Niihara

1999-01-01

259

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

Gül Tosun

2011-01-01

260

Experimental evidence for a structural unit model of quasiperiodic grain boundaries in aluminum. [AL  

Microsoft Academic Search

This paper presents a geometrical description of aperiodic grain boundaries within the framework of a quasiperiodic lattice. Experimental evidence is given in support of a structural unit model of quasiperiodic (100)45° twist and (100)45° twist plus tilt grain boundaries in aluminum.

P. A. Deymier; M. Shamsuzzoha; J. D. Weinberg

1991-01-01

261

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

NASA Astrophysics Data System (ADS)

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

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

2013-10-01

262

COMPARATIVE MAPPING OF ALTSB, A NOVEL ALUMINUM TOLERANCE GENE IN SORGHUM BICOLOR (L.) MOENCH, REVEALS INTER-TRIBE SYNTENY AMONG AL TOLERANCE GENES IN THE POACEAE  

Technology Transfer Automated Retrieval System (TEKTRAN)

When soil pH declines below pH 5, aluminum (Al) is released into the soil solution in ionic forms that are highly toxic to plant roots. Because of the widespread extent of acid soils, Al toxicity is a major constraint to crop production worldwide. Thus, there is considerable interest in elucidating ...

263

Reinforcement stresses during deformation of sphere- and particulate-reinforced Al-matrix composites  

SciTech Connect

Recent experimental results showed that reinforcement fracture is very often the dominant damage mechanism during ambient temperature deformation of discontinuously reinforced Al-matrix composites (DRAC). The reinforcements are broken by cracks perpendicular to the loading axis, and the fraction of broken reinforcements increases during plastic deformation as the load transferred from the matrix to the ceramic particulates increases. This process continues until a criteria fraction of broken reinforcements is reached, and then fracture takes place suddenly by a ductile mechanism involving localized necking of the intervoid matrix. The rate of reinforcement fracture depends on the strength of the ceramic reinforcements and on the stresses acting on them, and the modeling of the processes of damage accumulation in DRAC requires the knowledge of both. In particular, the stresses acting on the reinforcements during monotonic tensile deformation are a function of the applied strain, of the matrix and reinforcement properties, and of the volume fraction and shape of the ceramic reinforcements. A parametrical study is presented in this article of the influence of these factors on the stress acting on the reinforcements. The numerical results covered the whole range of matrix strengths which are typical in DRAC and were fitted to simple analytical expressions to facilitate their use by other researchers.

Justice, I. [Oxford Univ. (United Kingdom). Dept. of Materials; Poza, P.; Martinez, J.L.; Llorca, J. [Polytechnic Univ. of Madrid (Spain). Dept. of Materials Science

1996-02-01

264

Study on the effect of the surface treatment on the residual stress gradient in silicon carbide (SiC) reinforced aluminum metal matrix composites  

Microsoft Academic Search

In this work, the residual stresses induced on SiC-reinforced MMCs by the manufacturing processes (machining, surface finishing, and surface treatment) were investigated using an incremental hole-drilling method to measure the macroscopic residual stress gradient in depth and X-ray diffraction method to study the surface residual stresses in matrix. Three aluminum matrices (2024, 2124, and 6061) with different proportions of SiC

J. Lu; B. Miege; J. Flavenot; S. Thery

1990-01-01

265

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

Microsoft Academic Search

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

Cesim Atas; Onur Sayman

2000-01-01

266

Corrosion Mechanisms of Steel and Cast Iron by Molten Aluminum  

NASA Astrophysics Data System (ADS)

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

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

2010-09-01

267

Preparation and characterization of SiAlON matrix composites reinforced with combustion synthesis rod-like SiAlON particles  

Microsoft Academic Search

SiAlON matrix composites were prepared from a precursor reaction mixture of ?-Si3N4, AlN, Al2O3 and Y2O3 powders and reinforced with different proportions of elongated SiAlON particles obtained by combustion synthesis. Green cylindrical specimens were consolidated by slip casting from well dispersed suspensions. The dried samples were densified by hot pressing at 1650 and 1700°C and then characterized for density, phase

V. X. Lima Filho; J. P. Davim; C. A. Cairo; J. M. F. Ferreira

2009-01-01

268

Influence of the starting aluminum salt on the surface and acid properties of AlPO/sub 4/ catalysts precipitated with ammonium hydroxide  

SciTech Connect

In this paper, the influence of the starting aluminum salt (chloride, nitrate, or sulfate) and the pretreatment temperature (773-1273 K) on textural properties, crystal structure, and surface acidity of AlPO/sub 4/ (Al/P = 1) catalysts was studied in order to learn how preparation conditions affect catalyst activity in organocationic reactions. The catalysts were characterized using nitrogen adsorption, X-ray diffraction, infrared spectroscopy, and thermogravimetric analyses. The surface acid properties were determined using a dynamic method that consists of determining the AlPO/sub 4/'s catalytic activity in cyclohexene skeletal isomerization (CSI), a reaction that requires the presence of strong surface acid sites. Catalytic activity (as apparent rate constants), activation energies, and selectivities to 1-methylcyclopentene (1-MCP) were calculated in terms of Bassett-Habgood's kinetic model for first-order processes in which the surface reaction is the controlling step and the partial pressure of the reactant is low. Significant differences in structure, texture, surface acidity, and catalytic activity in CSI were found, showing that the aluminum starting salt plays an important role in the final properties of AlPO/sub 4/ (Al/P molar ratio = 1) catalysts. Thus, aluminum nitrate yielded material with higher surface area and low activity for CSI while aluminum sulfate resulted in higher surface acidity, and hence catalytic activity for CSI, although the sample is highly crystalline exhibiting low surface area. Aluminum chloride produces porous catalysts although they are less acidic.

Campelo, J.M.; Garcia, A.; Luna, D.; Marinas, J.M.

1988-05-01

269

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

270

Characterization of aluminum metal-matrix composite (MMC) for lightweight space optics application: a study of thermal expansion behavior of MMC in simulated space thermal environment  

NASA Astrophysics Data System (ADS)

Application of advanced composite material for lightweight mirror for space optics needs to know the exact thermal expansion behavior of the composite in space thermal environment. In this paper, thermal expansion behaviors of plasma thermal sprayed and powder metallurgy processed ceramic particulate reinforced aluminum metal-matrix composites in simulated space thermal environment were studied. Thermal cycling was found to cause hysteresis and non-linear thermal expansion responses to the composites when the thermal stress within the composite exceeds the yield strength of the matrix, and subsequently causes matrix plastic flow. High matrix yield strength is necessary for MMC to have linear, stable and repeatable thermal expansion response in severe space thermal environment. The study lays out a fundamental for choosing existed or developing a new MMC for lightweight mirror application.

Jiang, Xin X.; Nikanpour, Darius

2000-10-01

271

Investigations on NiAl composites fabricated by matrix coated single crystalline Al 2 O 3 -fibers with and without hBN interlayer  

Microsoft Academic Search

The intermetallic compound NiAl has excellent potential for high temperature structural applications but suffers from low\\u000a temperature brittleness and insufficient high temperature strength. One way to remove these deficiencies is the reinforcement\\u000a by high strength ceramic fibers. Such intermetallic matrix composites can be conveniently fabricated by the hot pressing of\\u000a matrix coated fibers. Al2O3 single crystal fibers show excellent chemical

Weiping Hu; Hao Chen; Yunlong Zhong; Jia Song; Günter Gottstein

2008-01-01

272

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

Microsoft Academic Search

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

S. V. Prasad; K. R. Mecklenburg

1993-01-01

273

Kinetics of aluminum lithium alloys  

Microsoft Academic Search

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

Ben A. Pletcher

2009-01-01

274

Microstructure and Mechanical Properties of 6063 Aluminum Alloy Brazed Joints with Al-Si-Cu-Ni-RE Filler Metal  

NASA Astrophysics Data System (ADS)

A new low melting point filler metal, Al-Si-Cu-Ni-RE, was developed for the furnace brazing of aluminum alloy 6063. Flux-assisted brazing was conducted at 560 °C using the new filler metal and AlF3-CsF-KF flux. Microstructure of the brazed joints were studied by means of SEM, TEM, and EDS. Shear strength and micro-Vickers hardness of joints had been tested. Results show that sound joints could be obtained with the filler metal and the flux. Microstructure characterization of the brazed joint shows dendritic CuAl2 phase was distributed evenly and Si-phase was spheroidized and refined, which was embedded in CuAl2 dendrites with modification of rare-earth element. Shear strength test results show that the joints with Al-Si-Cu-Ni-RE filler metal achieved average shear strength of 62.5 MPa, 14.5% more than the shear strength of brazed joints with Chinese HL401 filler metal. The micro-Vickers hardness of joint after T6 treatment is about 83 HV. The hardness of the joints after just brazing and after solution treatment was higher than the hardness of the base metal.

Zhang, Guowei; Bao, Yefeng; Jiang, Yongfeng; Zhu, Hong

2011-11-01

275

Influence of Natural Organic Matter (NOM) on the Speciation of Aluminum during Water Treatment  

Microsoft Academic Search

Natural organic matter (NOM) is a term collectively used to describe the complex matrix of organic material present in natural waters. The impact of NOM on the speciation of aluminum at Buffalo Pound water treatment plant was evaluated in the present study using fulvic acid. The first stage of the study was to conduct aluminum (Al) speciation experiments (using background

P. T. Srinivasan; T. Viraraghavan

2004-01-01

276

The effect of Al3Ti capping layers on electromigration in single-crystal aluminum interconnects  

NASA Astrophysics Data System (ADS)

Studies of accelerated electromigration were conducted on passivated Al single-crystal interconnects fabricated on oxidized Si, and capped with Al3Ti overlayers. The capping layers were formed by the reaction of the single-crystal Al films with Ti overlayers. The activation energy for electromigration-induced failure was determined to be 0.94+/-0.05 eV. Previous work on Al single-crystal interconnects without Al3Ti overlayers gave an activation energy of 0.98+/-0.2 eV and lifetimes of similar magnitude [Y.-C. Joo and C. V. Thompson, J. Appl. Phys. 81, 6062 (1997)]. The similarity of these results suggests that either the rate-limiting mechanism for electromigration-induced failure of single-crystal Al interconnects is not diffusion along the interface of the Al with the surrounding oxide and overlayer, or that, surprisingly, the diffusivity of Al along the Al/Al3Ti interface is approximately the same as, or lower than, the diffusivity of Al along the Al/AlOx interface.

Srikar, V. T.; Thompson, C. V.

1998-05-01

277

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

2012-11-19

278

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

SciTech Connect

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

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

1999-03-10

279

Effect of Aluminum Level on Boron Clustering in Ni3 Al.  

National Technical Information Service (NTIS)

In alloys containing 0.24% boron, atom-probe field-ion microscopy (APFIM) revealed the presence of boron clusters in Ni-25 at. % Al and Ni-26 Al but not in Ni-24 Al. The observed boron clusters generally consisted of two to three boron atoms with a maximu...

J. A. Horton M. K. Miller C. T. Liu E. P. George J. Bentley

1988-01-01

280

A STUDY OF IRON-ALUMINUM ALLOYS IN THE FeâAl REGION OF COMPOUND FORMATION  

Microsoft Academic Search

Iron alloys containing 9 to 16 wt% Al were prepared by vacuum fusion in ; an induction furnace. The hardness, hot hardness, linear expansion coefficient, ; and electrical resistance were measured as a function of the Al content. ; Microstructural analyses on quenched and annealed samples showed the absence of ; any changes due to transformations of Fe3Al. All the

R. S. Mints; N. N. Samsonova

1962-01-01

281

Tensile flow properties of Al-based matrix composites reinforced with a random planar network of continuous metallic fibers  

SciTech Connect

Squeeze casting was used for processing two new types of composites: pure Al matrix composites reinforced with fibers of Inconel 601, and AS13 (Al-12% Si) matrix composites reinforced with fibers of Inconel 601 or stainless steel 316L. The fibers are continuous with a diameter of 12 {micro}m and their volume fraction in the composites varied from 20 to 80%. The processing conditions were such that no trace of interfacial reaction compound or of matrix precipitate resulting from the dissolution of elements of the fibers could be detected. The quality of the process was attested by Young`s modulus and electrical conductivity measurements. Tensile tests were carried out from room temperature up to 300 C. The composites with the pure Al matrix present a remarkable tensile ductility. They thus constitute convenient materials for assessing continuum plasticity models for composites. Properties of composites with the AS13 matrix are much affected by interface adhesion strength.

Boland, F.; Salmon, C.; Delannay, F. [Univ. Catholique de Louvain, Louvain-la-Neuve (Belgium). Dept. de Sciences des Materiaux et des Procedes; Colin, C. [Ecole Nationale Superieure des Mines de Paris, Evry (France)

1998-11-20

282

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

SciTech Connect

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

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

2005-08-01

283

Microstructural Development in Irradiated U-7Mo/6061 Al Alloy Matrix Dispersion Fuel  

SciTech Connect

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

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

2009-09-01

284

Aluminum extraction from aluminum industrial wastes  

NASA Astrophysics Data System (ADS)

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

Amer, A. M.

2010-05-01

285

Effects of SiC particulates on the fatigue behaviour of an Al-alloy matrix composite  

Microsoft Academic Search

In this study, the fatigue behaviour of aluminium matrix–silicon carbide (SiC) particulate reinforced composite specimens was investigated in comparison to the matrix aluminium alloy containing 12wt% Si. Three different weight percentages of SiC particulates: 5, 10, and 15 in the size range of 40–60?m were injected into the melt. Mg was also added to improve the wettability of Al-alloy matrix

Cevdet Kaynak; Suha Boylu

2006-01-01

286

Plasma joining of metal-matrix composites. Interin report, October-November 1985  

SciTech Connect

Aluminum-reactive metal-matrix alloys for Al-SiC composite filler metals are described. Preliminary process modeling studies on constituent vaporization effects, thermochemical stability of surface oxide films, and dissolved gas evolution in-plasma are described.

Reynolds, G.H.; Yang, L.

1985-12-01

287

Hybrid Effect on Whisker Orientation Dependence of Composite Strength of Aluminum Cast Alloy Reinforced by Al2O3 Whiskers and SiC Particles  

NASA Astrophysics Data System (ADS)

The hybrid effect on the orientation dependence of the composite strength of an aluminum cast alloy reinforced by Al2O3 whiskers and SiC particles is studied experimentally and numerically. Two types of specimens are prepared for monotonic bending tests. The longitudinal specimen orientation (maximum stress direction) is parallel to or normal to randomly oriented whiskers in plane. The monotonic strength is 18% higher when the hybrid metal matrix composite (MMC) is subjected to an external load parallel to the random whisker orientation in plane than when the load is perpendicular to the whisker orientation. The whisker orientation dependence of composite strength in hybrid composite is weaker than that in whisker-reinforced composite. On the fracture surface of the specimen loaded along the direction parallel to the random whisker orientation in plane, most whiskers are broken while many de-bonded interfaces between the whiskers and matrix are observed on the fracture surface of the specimen loaded along the direction perpendicular to the whisker orientation. To characterize the hybrid effect on the whisker orientation dependence of composite strength, a three-dimensional hybrid composite unit cell model including one whisker and a few particles under a periodic boundary condition is developed using the finite element method. The hybrid composites have higher whisker stress than whisker-reinforced composite when subjected to an external load parallel to the whisker orientation if these composites have the same total volume fraction of reinforcement and the particles are distributed randomly. Under an external load perpendicular to the whisker orientation, the interface stress of hybrid composites is lower than that of whisker-reinforced composite. As a result, the strength difference for parallel and perpendicular loading conditions of the hybrid composites is smaller than that of whisker-reinforced composite. Thus, the weak whisker orientation effect in the hybrid composites is due to a change in microscopic stress distribution induced by interaction between whiskers and particles.

Md, Rafiquzzaman; Arai, Yoshio

288

Microstructural evolution and hardness of TiAl3 and TiAl2 phases on Ti-45Al-2Nb-2Mn-1B by plasma pack aluminizing  

NASA Astrophysics Data System (ADS)

Plasma pack aluminizing of Ti-45Al-2Nb-2Mn-1B forms TiAl3 and TiAl2 phases.The TiAl3 and TiAl2 phases contain Cu, Nb and Mn.TiAl3 and TiAl2 appear as blocky, needle type and round particles in a matrix of aluminum alloy.Microhardness of TiAl3 and TiAl2 phases is higher than the substrate.

Rastkar, Ahmad Reza; Parseh, Pejman; Darvishnia, Naser; Hadavi, Seyed Mohammad Mehdi

2013-07-01

289

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

290

Aluminum nanocomposites for elevated temperature applications  

NASA Astrophysics Data System (ADS)

Aluminum casting alloys conventionally used in the automotive and aerospace industries (i.e., Al-Zn-Mg, and Al-Cu-Mg systems) are able to achieve excellent tensile strength at room temperature. At high temperatures, such alloys lose dimensional stability and their mechanical properties rapidly degrade. Aluminum-based nanocomposites show the potential for enhanced performance at high temperatures. The manufacturing process, however, is difficult; a viable and effective method for large-scale applications has not been developed. In the current study, an innovative and cost-effective approach has been adopted to manufacture Al/AlN composites. A nitrogen-bearing gas is injected into the melt and AlN particles synthesize in-situ via chemical reaction. In a preliminary stage, a model able to predict the amount of reinforcement formed has been developed. AlN dispersoids have been succesfully synthesized in the matrix and the model has been experimentally validated.

Borgonovo, C.; Apelian, D.; Makhlouf, M. M.

2011-02-01

291

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 1670°C 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 1670°C 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

292

Matrix of rectangular pores obtained by AFM nanoindentation and electrolytic oxidation of Al  

NASA Astrophysics Data System (ADS)

AFM nanoindentation is used for pretexturing of Al sample intended for anodic oxidation in porous film-forming electrolytes. The rectangular quadratic and non-quadratic matrices of nanoindents were made by means of an AFM with diamond tip. The period of the 2D array of nanoindented concaves ranged from ˜50 to ˜370 nm. The pitch of the holes ranged from 13 to 170 nm. After anodization in water solutions of three different acids (0.3 M sulfuric, 0.3 M oxalic and 0.3 M phosphoric) at voltages chosen according to matrix period (20, 30 and 160 V), the well-arranged matrices of rectangular pores were obtained. The rectangular symmetry of the pretextured Al surface almost ideally transferred on porous alumina matrix, maintaining the highly ordered arrangement of the pores and rectangular cross section trough the whole film thickness with high pore depth to aperture size aspect ratio. During prolonged anodization in phosphoric acid, standard cells on the boundary of nanoindented area disturbed the arrangement and shape of quadratic cells.

Belca, I. D.; Petkovic, M.; Stojadinovic, S.; Kasalica, B.; Belca, J. S.; Zekovic, Lj. D.

2010-11-01

293

Matrix of rectangular pores obtained by AFM nanoindentation and electrolytic oxidation of Al  

NASA Astrophysics Data System (ADS)

AFM nanoindentation is used for pretexturing of Al sample intended for anodic oxidation in porous film-forming electrolytes. The rectangular quadratic and non-quadratic matrices of nanoindents were made by means of an AFM with diamond tip. The period of the 2D array of nanoindented concaves ranged from ˜50 to ˜370 nm. The pitch of the holes ranged from 13 to 170 nm. After anodization in water solutions of three different acids (0.3 M sulfuric, 0.3 M oxalic and 0.3 M phosphoric) at voltages chosen according to matrix period (20, 30 and 160 V), the well-arranged matrices of rectangular pores were obtained. The rectangular symmetry of the pretextured Al surface almost ideally transferred on porous alumina matrix, maintaining the highly ordered arrangement of the pores and rectangular cross section trough the whole film thickness with high pore depth to aperture size aspect ratio. During prolonged anodization in phosphoric acid, standard cells on the boundary of nanoindented area disturbed the arrangement and shape of quadratic cells.

Belca, I. D.; Petkovic, M.; Stojadinovic, S.; Kasalica, B.; Belca, J. S.; Zekovic, Lj. D.

2011-07-01

294

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

National Technical Information Service (NTIS)

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

S. Sopok

1988-01-01

295

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

SciTech Connect

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

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

2010-11-15

296

Tensile deformation and fracture behavior of spray-deposition 7075/15SiC{sub p} aluminum matrix composite sheet at elevated temperatures  

SciTech Connect

The tensile deformation and fracture behavior of spray-deposition 7075/15SiC{sub p} (15 vol.% SiC particle) aluminum matrix composite sheet were studied by uniaxial tension tests at temperatures ranging from 300 deg. C to 450 deg. C and strain rates of 0.001-0.1 s{sup -1}, and the fracture surfaces were examined by using a scanning electron microscopy. The results show that strain softening is present up to the point of failure and the flow stress level increases with increasing strain rate but decreases with increasing temperature. The total elongation to fracture increases with increasing temperature and with decreasing strain rate. The maximum strain rate sensitivity exponent is 0.24 which is much lower than that of typical superplastic materials. The apparent activation energy is calculated to be approximately 379 kJ/mol which is much higher than its unreinforced counterpart. The fracture surface morphology shows a large amount of localized plastic deformation in the aluminum matrix and numerous large cavities around the reinforcement. The absence of strain accommodation by interface sliding might have caused premature failure at the reinforcement/matrix interface.

Zhang Hui [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China)], E-mail: zhanghui63hunu@163.com; He Yusong; Li Luoxing [College of Materials Science and Engineering, Hunan University, Changsha 410082 (China)

2008-08-15

297

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

298

Corrosion of Aluminum-Uranium Alloys in Water Vapor at 200\\260C  

SciTech Connect

Coupons of aluminum-uranium alloys at 10 and 18 weight percent were exposed to a saturated water vapor condition at 200 degrees C up to about 1500 hours and compared to previous results for aluminum 1100. The aluminum-uranium materials exhibited a range of initial corrosion rates and approached similar rates with the formation of a passive film of boehmite (Al2O3oH2O). The cast and extruded 10 percent uranium, having a primary aluminum-eutectic microstructure, was more corrosion resistant than the 18% cast and extruded. The initial corrosion rates of the aluminum-uranium materials were one to four times higher than that for aluminum 1100. It is postulated that a micro-galvanic coupling between the large UAl4 particles and the aluminum matrix has caused the variation. Sectioning the exposed specimens shows different characteristics of the oxide layers. In the case of the cast and extruded Al-10 percent U alloy, small uranium aluminide particles can be seen in the boehmite matrix and do not seem to be corroded. The oxide film of the Al-18 percent U alloy appears to have two distinct oxide layers. The outer layer has mass aggregates formed in the aluminum oxide matrix, while the inner layer contains UAl4 particles as in the case of Al-10 percent U

Lam, P.S.

1998-11-25

299

Electromagnetic interfering shielding of aluminum alloy–cenospheres composite  

Microsoft Academic Search

Fly-ash cenosphere particles were used as mixture in aluminum matrix composite by squeeze casting method [1]. The electromagnetic interfering shielding effectiveness (EMISE) was investigated in the frequency range from 0.03 MHz to\\u000a 1.5 GHz. It showed the SE value of Al2024\\/cenospheres composite (ACC) is higher than that of aluminum alloy, and comparative\\u000a to traditional material 1J50. Unlike 1J50, the mechanism of EMI

Gaohui Wu; Xiaoli Huang; Zuoyong Dou; Su Chen; Longtao Jiang

2007-01-01

300

Effect of Thermal Exposure, Forming, and Welding on High-Temperature, Dispersion-Strengthened Aluminum Alloy: Al-8Fe-1V-2Si.  

National Technical Information Service (NTIS)

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) s...

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

1991-01-01

301

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

PubMed Central

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

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

2010-01-01

302

Synthesis and hydrodesulfurization properties of NiW catalyst supported on high aluminum content, highly ordered, and hydrothermally stable Al-SBA-15  

Microsoft Academic Search

Highly ordered mesoporous Al-SBA-15 with high aluminum content and high hydrothermal stability has been synthesized by a new pH-adjusting and high-temperature hydrothermal treatment approach. Thus prepared samples were characterized by X-ray fluorescence spectroscopy, X-ray powder diffraction, 27Al nuclear magnetic resonance spectroscopy, N2 adsorption-desorption, temperature-programmed desorption of ammonia, Fourier transformed infrared spectroscopy with pyridine adsorption, temperature-programmed reduction with hydrogen, and high-resolution

Yang Li; Dahai Pan; Chengzhong Yu; Yu Fan; Xiaojun Bao

303

Crack propagation behaviour during three-point bending of polymer matrix composite\\/Al 2O 3\\/polymer matrix composite laminated composites  

Microsoft Academic Search

The crack propagation behaviour during three-point bending of a monolithic Al2O3 and PMC\\/Al2O3\\/PMC (where PMC denotes polymer matrix composite) laminated composites have been investigated. The laminated composites were fabricated by bonding two PMC layers on both sides of an Al2O3 plate. Carbon-epoxy and aramid-epoxy composites with two different stacking sequences, i.e. carbon(0\\/90)4 (C(0\\/90)), carbon(+45\\/?45)4 (C(+45\\/?45)), aramid(0\\/90)4 (A(0\\/90)) and aramid(+45\\/?45)4 (A(+45\\/?45)),

S. H. Hong; H. Y. Kim; J. R. Lee

1995-01-01

304

Effect of the aluminum content on the behavior of mechanochemical reactions in the WO 3–C–Al system  

Microsoft Academic Search

In order to produce tungsten carbide from its oxide through mechanochemical process, a mixture of tungsten oxide, carbon and aluminum powders was subjected to high energy milling. Excess carbon addition was made in expense of aluminum, so that carbon acts not only as a carbide former agent but also as a reductant. Aluminum and carbon contents of the mixture were

M. Sakaki; M. Sh. Bafghi; J. Vahdati Khaki; Q. Zhang; J. Kano; F. Saito

2009-01-01

305

Aluminum levels and stores in patients with total hip endoprostheses from TiAlV or TiAINb alloys  

Microsoft Academic Search

Aluminum ranks as a potentially hazardous agent. Pathologic findings in different organs show that it can accumulate in brain, muscle, liver and bone. Therefore, we investigated whether patients with cementless total hip endoprostheses made out of titanium alloys containing aluminum are at risk. In order to determine the complete aluminum body loading in patients who have had their hip replacement

D.-D. Dittert; G. Warnecke; H.-G. Willert

1995-01-01

306

Melt-processed Ni[sub 3]Al matrix composites reinforced with TiC particles  

SciTech Connect

TiC-reinforced Ni[sub 3]Al metal matrix composites have been investigated. The composites were prepared by in situ precipitation of either 0.01, 0.05, or 0.1 vol fraction TiC in molten Ni[sub 3]Al. These precipitates are thermodynamically stable in the Ni[sub 3]Al at 1,000 C up to 50 hours. Although almost ideal precipitate distribution was achieved at low volume fraction of TiC, at higher volume fraction, there was a tendency toward agglomeration. Room- and high-temperature mechanical testing showed significant improvement in modulus, yield strength, and ultimate tensile strength, while still maintaining a 2.5 pct elongation at 0.1 vol. fraction TiC and 500 C. The density of precipitates (number/m[sup 3]) is strongly dependent on the fraction of TiC, on temperature, and on the holding time at that temperature. The critical nucleation temperature for these precipitates was determined to be at 1,475 C. Experimentally evaluated growth rate constants indicate a diffusion-controlled coarsening mechanism along with coalescence and multiparticle interaction at higher volume fractions of TiC. This is in accordance with either the Lifshitz Slyozov Encounter Modified (LSEM) model or with the Voorhess and Glicksman (VG) model.

Sen, S.; Stefanescu, D.M. (Univ. of Alabama, Tuscaloosa, AL (United States). Dept. of Metallurgical Engineering); Dhindaw, B.K. (IIT Kharagpur (India). Dept. of Metallurgical Engineering)

1994-11-01

307

Effect of Reinforcement Size and Matrix Microstructure on the Fracture Properties of an Aluminum Metal Matrix Composite. (Reannouncement with New Availability Information).  

National Technical Information Service (NTIS)

The effects of microstructural changes on the fracture toughness of SiC reinforced aluminum alloy composites were determined. Reinforcement sizes of 5 um and 13 um were utilized at both the 15 and 20 volume percent level. Heat treatments were designed to ...

M. Manoharan J. J. Lewandowski

1992-01-01

308

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

NASA Astrophysics Data System (ADS)

Diffusion-bonded NiAl-Al2O3 and Ni3Al-Al2O3 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. Al2O3 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 Ni3Al 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(+)-ion enhanced deposition. A 3-kW rod-fed electron-beam-heated evaporation source has been brought into operation.

Grummon, D. S.

1993-01-01

309

Crystal structure of the metastable form of aluminum trifluoride ?-AlF3 and the gallium and indium homologs  

NASA Astrophysics Data System (ADS)

The crystal structure of the metastable phase ?-AlF3, which is related to the hexagonal tungsten bronze structure, has been solved by X-ray powder and single-crystal diffraction methods. The crystal habit is pseudo-hexagonal with systematic twinning (rotation of 120° around the c axis), but the true symmetry is orthorhombic with space group Cmcm, Z = 12, a = 6.931(3), b = 12.002(6), c = 7.134(2), Å (R = 0.044 and Rw = 0.051) from 929 independent reflections). The network is built from very regular AlF6 octahedra rotated by approximately 7.2° from the positions of the ideal HTB structure. A similar network, with the same propagation of the tilting, was observed in the compound (H2O)0.33FeF3 and in the metastable polymorphs of CrF3 and of VF3. Our reinvestigation of the structures of ?-GaF3 and ?-InF3 using powder data shows that they are isotypic with the aluminum compound, with a = 7.210(1), b = 12.398(2), c = 7.333(1) and a = 7.875(2), b = 13.499(4), c = 7.956(2), Å, respectively.

Le Bail, A.; Jacoboni, C.; Leblanc, M.; de Pape, R.; Duroy, H.; Fourquet, J. L.

1988-11-01

310

Effect of alloying elements in the brazing sheet on the bonding strength between Al{sub 2}O{sub 3} and aluminum  

SciTech Connect

Ceramics have several outstanding mechanical properties especially at high temperatures, but a difficulty in machining has been hindering the cost-effective use. Hence, bonding between ceramics and metals has become an important technology. Among many bonding techniques such as brazing, diffusion bonding, frictional bonding and so forth, brazing is one of the most promising methods for practical applications. There are several bonding parameters such as temperature, time, pressure and atmosphere. In this work, Al{sub 2}O{sub 3}/aluminum bonding using an aluminum alloy as a filler sheet is dealt with, and the effects of some parameters on the bonding strength are mainly discussed.

Kobashi, M.; Ninomiya, T.; Kanetake, N.; Choh, T. [Nagoya Univ. (Japan)

1996-02-01

311

Fully Dense, Aluminum-Rich Al-CuO Nanocomposite Powders for Energetic Formulations  

Microsoft Academic Search

The thermite reaction between Al and CuO is well known and highly exothermic. For a conventional thermite mixture, the reaction is rate limited by a slow heterogeneous mass transfer at the metal and oxide interface. The relatively low reaction rate and ignition difficulty have restricted practical applications for this reaction. For newly developed nanocomposed thermites, the interface area is substantially

Demitrios Stamatis; Zhi Jiang; Vern K. Hoffmann; Mirko Schoenitz; Edward L. Dreizin

2008-01-01

312

Study on Mold Slag with High Al2O3 Content for High Aluminum Steel  

NASA Astrophysics Data System (ADS)

The slag-steel equilibrium reaction between the newly developed mold slag ND-MSL and 20Mn23AlV steel has been studied at high temperatures in the laboratory. The crystal morphology, microanalysis, and phase analysis of the original and final ND-MSL slags were studied by scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), and X-ray diffraction (XRD). Results show that, in the final ND-MSL slag, the constitution of SiO2 decreased by 0.7 wt pct and Al2O3 increased by 6.46 wt pct, while the melting temperature, viscosity, and crystallization rate increased by 62 K, 0.66 dPa s, and 15 pct, respectively. NaAlSi3O8 and CaAl2Si2O8 were found to be precipitated in the final ND-MSL slag. Both the original and final ND-MSL slags have a small amount of LiF crystal and good glass form. The ND-MSL slag has little change in the composition and properties compared with the two currently used mold slags.

Wang, Qiang; Sun, Min; Qiu, Shengtao; Tian, Zhiling; Zhu, Guoling; Wang, Longmei; Zhao, Pei

2013-08-01

313

Prediction of Thermal Conductivity of Aluminum Nanocluster-Filled Mesoporous Silica (Al/MCM-41)  

NASA Astrophysics Data System (ADS)

MCM-41 consists of a hexagonal array of long, unconnected cylindrical pores with diameters that can be tailored within the range 1.6 nm to 10 nm. As a porous silica nanomaterial, MCM-41 is a promising porous substrate for mesoporous composites with extremely high or low thermal conductivity. In this article, the structural unit of MCM-41 was established first and an equilibrium molecular dynamics simulation was performed to determine the shell thermal conductivity of MCM-41. Then, based on one-dimensional (1D) heat transfer analysis, a mathematical expression for the effective thermal conductivity (ETC) of Al nanocluster-filled mesoporous MCM-41 (Al/MCM-41) was obtained. The effects of porosity and the filling ratio of nanoclusters in the mesochannels were further investigated. As the porosity is greater than 75 %, the ETC of only-air-filling mesoporous MCM-41 in all directions tends to approach the thermal conductivity of air. It seems that Al nanoclusters have negligible effects on the ETC of the composite, except that mesochannels are almost completely filled with Al nanowires.

Huang, Congliang; Feng, Yanhui; Zhang, Xinxin; Li, Jing; Cui, Liu; Wang, Ge; Yang, Mu

2011-09-01

314

Numerical and experimental investigations of the global and local behaviour of an Al(6061)\\/Al2O3 metal matrix composite under low cycle fatigue  

Microsoft Academic Search

The deformation behaviour of an Al(6061)\\/Al2O3 metal matrix composite was experimentally and numerically investigated under low cycle fatigue. The deformation behaviour,fatigue damage initiation and development are studied on the specimen surface and in the bulk material. The three-dimensional FE model based on tomographic data has been created and loaded step by step up to 100 cycles.For the simulation of the

Y. Schneider; E. Soppa; C. Kohler; R. Mokso; E. Roos

2011-01-01

315

TEM study of the interface in ceramic-reinforced aluminum-based composites  

Microsoft Academic Search

The microstructure and interfaces of aluminum matrix composites were studied using conventional and high-resolution transmission electron microscopy (HREM). Also convergent-beam electron diffraction (CBED) was used. Two kinds of Al-based ceramic-reinforced composites (Al–TiC and Al–TiB2) were studied. Transmission electron microscopy (TEM) revealed the presence of a relatively high dislocation density in the matrix of both kinds of investigated composites. The dislocation

A. Kostka; J. Lel; M. Gigla; H. Morawiec; A. Janas

2003-01-01

316

Effects of SiC volume fraction and aluminum particulate size on interfacial reactions in SiC nanoparticulate reinforced aluminum matrix composites  

Microsoft Academic Search

The SiC nanoparticulate reinforced Al–3.0wt.% Mg composites were fabricated by combining pressureless infiltration with ball-milling and cold-pressing technology at 700°C for 2h. The effects of SiC nanoparticulate volume fractions (6%, 10% and 14%) and Al particulate sizes (38?m and 74?m) on interfacial reactions were investigated by SEM, TEM and X-ray diffraction. The results show that the MgO at the interface

Bowen Xiong; Zhifeng Xu; Qingsong Yan; Baiping Lu; Changchun Cai

317

Relation between mechanical properties and microstructure of cast aluminum alloy AlSi9Cu3  

Microsoft Academic Search

One common material for engine applications is the AlSi9Cu3 alloy. This alloy has a good castability, excellent machinability,\\u000a medium strength, and low specific weight. The study was focused on the investigation of the effect of the solution heat treatment\\u000a on the microstructure and mechanical properties of the alloy (strength-Rm, hardness-HBS). The temperatures of the solution heat treatment were 505°C, 515°C,

M. Panušková; E. Tillová; M. Chalupová

2008-01-01

318

Efficiency of light emission in high aluminum content AlGaN quantum wells  

Microsoft Academic Search

High quality multiple quantum well Al0.35Ga0.65N active layers with narrow wells designed for ultraviolet (UV) light-emitting diodes using the phonon engineering approach are characterized using quasi-steady-state and time-resolved photoluminescence spectroscopy. The photoluminescence intensity decrease with temperature increasing from 10 to 300 K was very small, and the upper limit of the internal quantum efficiency (IQE) of up to 70% was

Max Shatalov; Jinwei Yang; Wenhong Sun; Robert Kennedy; Remis Gaska; Kai Liu; Michael Shur; Gintautas Tamulaitis

2009-01-01

319

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

320

Microstructure, tensile properties and fracture behaviour of Al2O3 particulate-reinforced aluminium alloy metal matrix composites  

Microsoft Academic Search

The tensile deformation and fracture behaviour of aluminium alloy 2014 discontinuously-reinforced with particulates of Al2O3 was studied with the primary objective of understanding the influence of reinforcement content on composite microstructure, tensile properties and quasi-static fracture behaviour. Results reveal that elastic modulus and strength of the metal-matrix composite increased with reinforcement content in the metal matrix. With increase in test

T. S. Srivatsan

1996-01-01

321

Temperature distribution study during the friction stir welding process of Al2024-T3 aluminum alloy  

NASA Astrophysics Data System (ADS)

Heat flux characteristics are critical to good quality welding obtained in the important engineering alloy Al2024-T3 by the friction stir welding (FSW) process. In the present study, thermocouples in three different configurations were affixed on the welding samples to measure the temperatures: in the first configuration, four thermocouples were placed at equivalent positions along one side of the welding direction; the second configuration involved two equivalent thermocouple locations on either side of the welding path; while the third configuration had all the thermocouples on one side of the layout but with unequal gaps from the welding line. A three-dimensional, non-linear ANSYS computational model, based on an approach applied to Al2024-T3 for the first time, was used to simulate the welding temperature profiles obtained experimentally. The experimental thermal profiles on the whole were found to be in agreement with those calculated by the ANSYS model. The broad agreement between the two kinds of profiles validates the basis for derivation of the simulation model and provides an approach for the FSW simulation in Al2024-T3 and is potentially more useful than models derived previously.

Yau, Y. H.; Hussain, A.; Lalwani, R. K.; Chan, H. K.; Hakimi, N.

2013-08-01

322

RE2MAl6Si4 (RE = Gd, Tb, Dy; M = Au, Pt): layered quaternary intermetallics featuring CaAl2Si2-type and YNiAl4Ge2-type slabs grown from aluminum flux.  

PubMed

Six new intermetallic aluminum silicides--Gd(2)PtAl(6)Si(4), Gd(2)AuAl(6)Si(4), Tb(2)PtAl(6)Si(4), Tb(2)AuAl(6)Si(4), Dy(2)PtAl(6)Si(4), and Dy(2)AuAl(6)Si(4)--have been obtained from reactions carried out in aluminum flux. The structure of these compounds was determined by single-crystal X-ray diffraction. They form in space group Rthremacr;m with cell constants of a = 4.1623(3) A and c = 51.048(5) A for the Gd(2)PtAl(6)Si(4) compound. The crystal structure is comprised of hexagonal nets of rare earth atoms alternating with two kinds of layers that have been observed in other multinary aluminide intermetallic compounds (CaAl(2)Si(2) and YNiAl(4)Ge(2)). All six RE(2)MAl(6)Si(4) compounds show antiferromagnetic transitions at low temperatures (T(N) < 20 K); magnetization studies of the Dy compounds show metamagnetic behavior with reorientation of spins at 6000 G. Band structure calculations indicate that the AlSi puckered hexagonal sheets in this structure are electronically distinct from the other surrounding structural motifs. PMID:14632514

Latturner, Susan E; Bilc, Daniel; Mahanti, S D; Kanatzidis, Mercouri G

2003-12-01

323

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

Microsoft Academic Search

Transmission (TEM) and scanning electron microscopy (SEM) are employed to study the SiC\\/Al-alloy interface in a cast SiCp\\/Al(A356) metal matrix composite (MMC). Magnesium aluminate (spinel), MgAl2O4, was found at the interface as a reaction product after material processing. Comparisons of the crystal structure, structure\\u000a factor, and interface reaction ther-modynamics between MgAl2O4 and MgO have been carried out. The results from

Ning Wang; Zhirui Wang; George C. Weatherly

1992-01-01

324

Surface modification of titanium alloy with laser cladding RE oxides reinforced Ti 3Al–matrix composites  

Microsoft Academic Search

Ti3Al–matrix composites were prepared by laser cladding of the Al3Ti\\/TiB2\\/Al2O3 pre-placed powders on the Ti–6Al–4V alloy, which can improve the wear resistance of the substrate. With addition of the proper content of RE oxides (nano-Y2O3), this composite coating exhibited finer microstructure and better wear resistance. Nevertheless, excessive RE oxides could lead to the production of the micro-crack, and also decrease

Jianing Li; Chuanzhong Chen; Diangang Wang

325

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

326

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

SciTech Connect

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

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

1991-11-01

327

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

SciTech Connect

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

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

1991-11-01

328

Immersed nano-sized Al dispersoids in an Al matrix: effects on the structural and mechanical properties by molecular dynamics simulations  

Microsoft Academic Search

We used molecular dynamics simulations based on a potential model, in analogy to the tight binding scheme in the second moment approximation, to simulate the effects of aluminium icosahedral grains (dispersoids) on the structure and the mechanical properties of an aluminium matrix. First we validated our model by calculating several thermodynamic properties referring to the bulk Al case and we

H Chamati; M S Stoycheva; G A Evangelakis

2004-01-01

329

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

NASA Astrophysics Data System (ADS)

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

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

2001-02-01

330

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

331

Electron spin resonance g tensors for complexes of Ne and Ar with AlO: Theoretical studies related to the large matrix effect observed for AlO  

NASA Astrophysics Data System (ADS)

For Nen-AlO (n=2, 4, 6, 8, 10) and Arn-AlO clusters (n=2, 4, 6, 8), the perpendicular (relative to AlO) component of the g tensor was calculated by second-order perturbation theory, using multireference configuration-interaction wave functions. The rare-gas (Rg) atoms were placed axially and/or off axially (one or two rings of four Rg atoms each), and the distance of the Rg atoms from the Al and O atoms, or from the AlO axis, was varied from 4 to 12 bohrs. Rg atoms placed axially mostly increase g?, whereas off-axially placed ones lower it below the gas-phase value of AlO. The largest deviations from g? of isolated AlO occur at Ne-Al,O distances of 5-6 bohrs, and Ar-Al,O distances of 6-9 bohrs, with maximal lowerings of about 1600 ppm for Ne and about 2200 ppm (estimated) for Ar in the case of two axial and eight off-axial Rg atoms. Electron spin resonance studies by Knight and Weltner found large matrix effects for AlO, with downshifts of g? observed to be about 450 and 1150 ppm in Ne and Ar matrices, respectively.

Grein, Friedrich

2005-03-01

332

Gd(1.33)Pt(3)(Al,Si)(8) and Gd(0.67)Pt(2)(Al,Si)(5): two structures containing a disordered Gd/Al layer grown in liquid aluminum.  

PubMed

Gd(1.33)Pt(3)Al(8) was synthesized by the combination of Gd and Pt in excess liquid aluminum. Addition of silicon resulted in the incorporation of a small amount of this element into the material to form the isostructural Gd(1.33)Pt(3)Al(7)Si. Both compounds grow as rodlike crystals with hexagonal cross section. The structures were refined in the rhombohedral space group R(-)3m, with cell parameters a = 4.3359(6) A and c = 38.702(8) A for the ternary and a = 4.3280(8) A and c = 38.62(1) A for the quaternary compound. The structure is comprised of stuffed arsenic-like PtAl(2) layers and disordered Gd/Al layers. Analysis of the hk0 zone reflections indicate the presence of an a = radical 3a supercell, but the structure is not ordered along c, as revealed by the highly diffuse reflections in the 0kl zone photos. Therefore, the compounds are disordered variants of the Gd(4)Pt(9)Al(24) type. Magnetic susceptibility studies reveal antiferromagnetic transitions at 15 K for the ternary and 7 K for the quaternary compound. Variation of the reactant ratio produces a different structure comprised of the same structural blocks, including the disordered Gd/Al layer. Gd(0.67)Pt(2)Al(5) and its quaternary analogue Gd(0.67)Pt(2)Al(4)Si form in the hexagonal system P6(3)/mmc with cell parameters a = 4.2907(3) A and c = 16.388(2) A for the ternary and a = 4.2485(6) A and c = 16.156(3) A for the quaternary compound. PMID:12377043

Latturner, S E; Kanatzidis, M G

2002-10-21

333

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

334

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

SciTech Connect

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

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

1996-10-01

335

The mechanical properties of Al-TiC metal matrix composites fabricated by a flux-casting technique  

Microsoft Academic Search

Metal matrix composites have been made by the addition of 10 ?m diameter TiC particles to molten aluminium by a proprietary process. The resultant reinforcement distribution in commercial purity Al and 2xxx alloy matrices is reasonably homogeneous and extensive grain refinement is observed. The elastic modulus increases per volume percent of reinforcement added, are greater for Al-TiC composites than they

A. E. Karantzalis; S. Wyatt; A. R. Kennedy

1997-01-01

336

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

PubMed

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

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

2011-09-01

337

Efficiency of light emission in high aluminum content AlGaN quantum wells  

NASA Astrophysics Data System (ADS)

High quality multiple quantum well Al0.35Ga0.65N active layers with narrow wells designed for ultraviolet (UV) light-emitting diodes using the phonon engineering approach are characterized using quasi-steady-state and time-resolved photoluminescence spectroscopy. The photoluminescence intensity decrease with temperature increasing from 10 to 300 K was very small, and the upper limit of the internal quantum efficiency (IQE) of up to 70% was estimated based on this temperature dependence. Carrier lifetime measurements yielded the lower bound of the IQE to be ~35% under optical pumping, whereas IQE of ~25% was estimated from the measured external quantum efficiency and the light extraction efficiency calculated by ray tracing. The observed photoluminescence features and the high IQE are interpreted as a consequence of strong carrier (exciton) localization.

Shatalov, Max; Yang, Jinwei; Sun, Wenhong; Kennedy, Robert; Gaska, Remis; Liu, Kai; Shur, Michael; Tamulaitis, Gintautas

2009-04-01

338

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

NASA Astrophysics Data System (ADS)

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

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

1997-12-01

339

Microstructural Characterization of U-7Mo/Al-Si Alloy Matrix Dispersion Fuel Plates Fabricated at 500°C  

SciTech Connect

The starting microstructure of a dispersion fuel plate will impact the overall performance of the plate during irradiation. To improve the understanding of the as-fabricated microstructures of U–Mo dispersion fuel plates, particularly the interaction layers that can form between the fuel particles and the matrix, scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analyses have been performed on samples from depleted U–7Mo (U–7Mo) dispersion fuel plates with either Al–2 wt.% Si(Al–2Si) or AA4043 alloy matrix. It was observed that in the thick interaction layers, U(Al, Si)3 and U6Mo4Al43 were present, and in the thin interaction layers, (U, Mo) (Al, Si)3, U(Al, Si)4, U3Si3Al2, U3Si5, and possibly USi-type phases were observed. The U3Si3Al2 phase contained some Mo. Based on the results of this investigation, the time that a dispersion fuel plate is exposed to a relatively high temperature during fabrication will impact the nature of the interaction layers around the fuel particles. Uniformly thin, Si-rich layers will develop around the U–7Mo particles for shorter exposure times, and thicker, Si-depleted layers will develop for the longer exposure times.

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

2011-05-01

340

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

SciTech Connect

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

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

2000-02-01

341

Influence of high-temperature annealing with the melting of the aluminum matrix on the properties of SAP materials  

Microsoft Academic Search

At present the following technique is employed to obtain semiproducts from SAP materials: cold compacting of aluminum powder at a specific pressure of about 35 kg\\/mm2, sintering of the compacts at a temperature of 620~ with a holding period of 20-30 h, and hot re-pressing of the sintered compacts at a temperature of 500~ and a specific pressure of 40-50

V. S. Kurbatov; V. A. Shelamov; Yu. V. Shmakov

1967-01-01

342

A Patch-Clamp Study on the Physiology of Aluminum Toxicity and Aluminum Tolerance in Maize. Identification and Characterization of Al3+-Induced Anion Channels1  

PubMed Central

The presence of Al3+ in the rhizosphere induces citrate efflux from the root apex of the Al-tolerant maize (Zea mays) hybrid South American 3, consequently chelating and reducing the activity of toxic Al3+ at the root surface. Because citrate is released from root apical cells as the deprotonated anion, we used the patch-clamp technique in protoplasts isolated from the terminal 5 mm of the root to study the plasma membrane ion transporters that could be involved in Al-tolerance and Al-toxicity responses. Acidification of the extracellular environment stimulated inward K+ currents while inhibiting outward K+ currents. Addition of extracellular Al3+ inhibited the remaining K+ outward currents, blocked the K+ inward current, and caused the activation of an inward Cl? current (anion efflux). Studies with excised membrane patches revealed the existence of Al-dependent anion channels, which were highly selective for anions over cations. Our success in activating this channel with extracellular Al3+ in membrane patches excised prior to any Al3+ exposure indicates that the machinery required for Al3+ activation of this channel, and consequently the whole root Al3+ response, is localized to the root-cell plasma membrane. This Al3+-activated anion channel may also be permeable to organic acids, thus mediating the Al-tolerance response (i.e. Al-induced organic acid exudation) observed in intact maize root apices.

Pineros, Miguel A.; Kochian, Leon V.

2001-01-01

343

Damage development of Al\\/SiC metal matrix composite under fatigue, creep and monotonic loading conditions  

Microsoft Academic Search

A consolidation of powders using the KOBO method at elevated temperature was elaborated for production of Al\\/SiC metal matrix composite (MMC). The observations of the mean strain and inelastic strain range during the force controlled high cycle fatigue (HCF) tests identified the ratcheting mechanism combined with mechanism characterized by cyclic plasticity. Damage parameters were calculated on the basis of strain

A. Rutecka; Z. L. Kowalewski; K. Pietrzak; L. Dietrich; K. Makowska; J. Wo?niak; M. Kostecki; W. Bochniak; A. Olszyna

2011-01-01

344

Effect of aluminum content on the decomposition kinetics of supersaturated solid solution in Mg-Al-alloys  

Microsoft Academic Search

For correct selection of aging schedules providing the optimum mechanical properties for magnesium alloys containing aluminum it is important to know how the solid solution decomposition rate can be varied depending on its concentration. There are very little data in the literature. The aim of the present work is to establish the dependence of solid solution decomposition kinetics for aluminum

L. L. Rokhlin; A. A. Oreshkina

1989-01-01

345

Reinforcement shape effects on the fracture behavior and ductility of particulate-reinforced 6061-Al matrix composites  

SciTech Connect

Particle shape effects on the fracture and ductility of a spherical and an angular particulate-reinforced 6061-Al composite containing 20 pct vol Al{sub 2}O{sub 3} were studied using scanning electron microscopy (SEM) fractography and modeled using the finite element method (FEM). The spherical particulate composite exhibited a slightly lower yield strength and work hardening rate but a considerably higher ductility than the angular counterpart. The SEM fractographic examination showed that during tensile deformation, the spherical composite failed through void nucleation and linking in the matrix near the reinforcement/matrix interface, whereas the angular composite failed through particle fracture and matrix ligament rupture. The FEM results indicate that the distinction between the failure modes for these two composites can be attributed to the differences in the development of internal stresses and strains within the composites due to particle shape.

Song, S.G.; Shi, N.; Gray, G.T. III; Roberts, J.A. [Los Alamos National Lab., NM (United States)

1996-11-01

346

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

SciTech Connect

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

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

2009-06-01

347

Neutron activation analysis of aluminum in Mg2SiO4  

NASA Astrophysics Data System (ADS)

An investigation of the role of aluminum in the enhancement of the near infrared lasing properties of chromium doped forsterite (Cr:Mg2SiO4) has led to the development of a neutron activation analysis (NAA) procedure for the trace analysis of aluminum in a silicon-containing matrix. After the initial analysis of a set of standards, this method requires only one irradiation per sample and relies upon the inherent nuclear properties of the silicono isotopes 28Si and 29Si. The 28Al signal produced by the activation reaction 27Al(n, ?)28Al, is interfered by the competing fast neutron reaction 28Si(n, p)28Al. Activation of an aluminum-free silicate will produce a constant ratio of 28Al and 29Al signals due to the 28Si(n, p)28Al and 29Si(n, p)29Al fast neutron reactions. Activation of an aluminum-doped sasmple will result in an increase in the 28Al signal due to the 27Al(n, ?)28Al thermal neutron reaction but have no effect on the 29Al signal. Therefore, any increase of the 28Al/29Al ratio in the doped silicate is due to the presence of aluminum. The subtraction of the 28Al/29Al ratio of the undoped sample from the 28Al/29Al ratio of the doped sample gave the portion of the 28Al signal resulting from the 27Al(n, ?)28Al reaction. Three forsterite single crystals with varying ratios of chromium to aluminum were grown for this study by the floating zone method using sol-gel derived feedstocks. Their compositions were determined by NAA using the correction procedure described above.

Mass, J. L.; Burlitch, J. M.; McGuire, S. C.; Hossain, T. Z.; Demiralp, R.

1994-12-01

348

Brazability of dissimilar metals tungsten inert gas butt welding–brazing between aluminum alloy and stainless steel with Al–Cu filler metal  

Microsoft Academic Search

Dissimilar metals tungsten inert gas butt welding–brazing between 5A06 aluminum alloy and SUS321 stainless steel was carried out using Al–Cu6 filler metal and non-corrosive flux. A thin intermetallic compound layer has formed in welded seam\\/steel interface and the average thickness of the whole layer is 3–5?m, which is less than the limited value of 10?m. The intermetallic compound layer consists

S. B. Lin; J. L. Song; C. L. Yang; C. L. Fan; D. W. Zhang

2010-01-01

349

Hybrid Effect on Whisker Orientation Dependence of Composite Strength of Aluminum Cast Alloy Reinforced by Al2O3 Whiskers and SiC Particles  

Microsoft Academic Search

The hybrid effect on the orientation dependence of the composite strength of an aluminum cast alloy reinforced by Al2O3 whiskers and SiC particles is studied experimentally and numerically. Two types of specimens are prepared for monotonic bending tests. The longitudinal specimen orientation (maximum stress direction) is parallel to or normal to randomly oriented whiskers in plane. The monotonic strength is

Yoshio Arai

2010-01-01

350

Kinetic Spectrophotometric Determination of Trace Aluminum by Catalytic Activity of Al 3+ on the Oxidation of Methylene Blue by Hydrogen Peroxide  

Microsoft Academic Search

A novel kinetic spectrophotometry for the determination of trace aluminum is described based on the catalytic activity of Al 3+ on the redox reaction between methylene blue (MB) and hydrogen peroxide in acetate buffer (pH 3.8). The reaction is monitored spectrophotometrically by measuring the decrease in absorbance of the dye at the maximum absorption wavelength of 670?nm. The variables that

Ren-Min Gong; Qiu-Yi Chen; Zhi-Li Liu

2003-01-01

351

Synthesis and Characterization of Aluminum-Nanodiamond Composite Powders by High Energy Ball Milling.  

National Technical Information Service (NTIS)

High-energy ball milling was studied for the ex situ strengthening of aluminum (Al) with nanodiamond (ND). Al-ND metal matrix composite powders with 5 wt% and 10 wt% nanodiamond were synthesized by high-energy ball milling of the blended component powders...

B. D. Sneed

2011-01-01

352

Fabrication of metal matrix composites of  

Microsoft Academic Search

Fine fibrous titanium carbide (TiC) was processed through the self-propagating high-temperature synthesis (SHS) method and employed to fabricate aluminum matrix composites. Two consol-idation methods were investigated: (1) combustion synthesis of TiC fiber\\/Al composites directly using titanium powders and carbon fibers ignited simultaneously with varying amounts of the matrix metal powder and (2) combustion synthesis of TiC using titanium powders and

Y. Choi; M. E. Mullins; K. Wijayatilleke; J. K. Lee

1992-01-01

353

Load partitioning in aluminum syntactic foams containing ceramic microspheres  

Microsoft Academic Search

Syntactic foams were fabricated by pressure-infiltrating liquid aluminum (commercial purity and 7075-Al) into a packed preform of silica–mullite hollow microspheres. These foams were subjected to a series of uniaxial compression stresses while neutron or synchrotron X-ray diffraction measurements of elastic strains in the matrix and the microspheres were obtained. As for metal matrix composites with monolithic ceramic reinforcement, load transfer

Dorian K. Balch; David C. Dunand

2006-01-01

354

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

355

High-temperature behavior of silicon carbide fibers in a Si-Al-Ca-O-N ceramic matrix  

SciTech Connect

A Nicalon SiC fiber-reinforced Si-Al-Ca-O-N composite was fabricated by a slurry infiltration process followed by hot pressing at 1,600 C. A carbon-rich interfacial layer ({approximately} 100 nm) as well as a crystalline silicon-rich layer ({approximately} 15 nm) was observed between the fiber and matrix. Based on this interfacial phenomenology, the following behavior of SiC fibers in the matrix was proposed: fine SiC grains (diameter of {approximately} 1.7 nm in as-received fibers) decomposed at fiber surfaces (SiC {yields} C + Si), followed by silicon migration into the glassy phase of the matrix. The glassy phase was interpreted to play a key role as a silicon consumer in fostering the formation of the carbon-rich layer. The presence of silicon implied that the oxygen activity in the matrix was low enough to avoid SiC oxidation.

Shin, Hyunho [Georgia Inst. of Tech., Atlanta, GA (United States). School of Materials Science and Engineering

1995-11-01

356

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

2011-07-23

357

In-situ Deformation Studies of an Aluminum Metal-Matrix Composite in a Scanning Electron Microscope.  

National Technical Information Service (NTIS)

Metal-matrix composites have been developed in recent years to fulfill the need for materials with high specific strength and stiffness. Fiber reinforced composites provide the highest improvements in strength and stiffness in the reinforcement direction....

M. Manoharan J. J. Lewandowski

1989-01-01

358

Study on the effect of the surface treatment on the residual stress gradient in silicon carbide (SiC) reinforced aluminum metal matrix composites  

SciTech Connect

In this work, the residual stresses induced on SiC-reinforced MMCs by the manufacturing processes (machining, surface finishing, and surface treatment) were investigated using an incremental hole-drilling method to measure the macroscopic residual stress gradient in depth and X-ray diffraction method to study the surface residual stresses in matrix. Three aluminum matrices (2024, 2124, and 6061) with different proportions of SiC fiber were tested, and the effects of the heat treatment, machining, and shot-peening treatment on the residual stress distribution of the materials were analyzed and compared. Results show that it is possible to optimize the residual stress distribution of MCC materials with adequate posttreatment. 14 refs.

Lu, J.; Miege, B.; Flavenot, J.; Thery, S. (Centre Technique des Industries Mecaniques, Senlis (France) Groupe Usinor Sacilor, Firminy (France))

1990-01-01

359

Preparation and Characterization of Nicotine–Magnesium Aluminum Silicate Complex-Loaded Sodium Alginate Matrix Tablets for Buccal Delivery  

Microsoft Academic Search

Nicotine (NCT) buccal tablets consisting of sodium alginate (SA) and nicotine–magnesium aluminum silicate (NCT–MAS) complexes\\u000a acting as drug carriers were prepared using the direct compression method. The effects of the preparation pH levels of the\\u000a NCT–MAS complexes and the complex\\/SA ratios on NCT release, permeation across mucosa, and mucoadhesive properties of the tablets\\u000a were investigated. The NCT–MAS complex-loaded SA tablets

Sopaphan Kanjanabat; Thaned Pongjanyakul

2011-01-01

360

Aluminum reference electrode  

DOEpatents

A stable reference electrode for use in monitoring and controlling the process of electrolytic reduction of a metal. In the case of Hall cell reduction of aluminum, the reference electrode comprises a pool of molten aluminum and a solution of molten cryolite, Na.sub.3 AlF.sub.6, wherein the electrical connection to the molten aluminum does not contact the highly corrosive molten salt solution. This is accomplished by altering the density of either the aluminum (decreasing the density) or the electrolyte (increasing the density) so that the aluminum floats on top of the molten salt solution.

Sadoway, Donald R. (Belmont, MA)

1988-01-01

361

Aluminum reference electrode  

DOEpatents

A stable reference electrode is described for use in monitoring and controlling the process of electrolytic reduction of a metal. In the case of Hall cell reduction of aluminum, the reference electrode comprises a pool of molten aluminum and a solution of molten cryolite, Na[sub 3]AlF[sub 6], wherein the electrical connection to the molten aluminum does not contact the highly corrosive molten salt solution. This is accomplished by altering the density of either the aluminum (decreasing the density) or the electrolyte (increasing the density) so that the aluminum floats on top of the molten salt solution. 1 fig.

Sadoway, D.R.

1988-08-16

362

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

363

Cu\\/N ?3Al METAL MATRSLKOMPOZTN KURU KAYMA AINMA DAVRANILARININ ARATIRILMASI AN INVESTIGATION OF DRY SLIDE BEHAVIORS OF Cu\\/Ni 3Al METAL MATRIX COMPOSITE  

Microsoft Academic Search

In this work, the dry sliding wear behaviour of cupper matrix composites reinforced with Ni 3Al was investigated. The samples were obtained using P\\/M routes. Dry sliding wear tests were performed using pin on ring apparatus with constant sliding speed and distance for different load (83N,100N and 150N) on the composite samples having three vol.% of reinforcement (5,10,15 wt.% Ni

Mehtap Muratolu; Mehtap Demirel

364

Investigation of alloying effects in aluminum dispersion strengthened with Al$sub 2$O$sub 3$  

SciTech Connect

Two types of alloying elements were investigated to determine if the room-temperature strength could be improved and if, through lowering the oxide content, the high-temperature ductility could be improved. Mg was investigated for its solid solution strengthening in one type alloy. The other type alloy involved further dispersion strengthening through adding Fe, Mo, Zr, Cr, V, and Ti which form highly stable intermetallic compounds with Al. Fabrication techniques were developed which produced uniform and reproducible rods for testing. Prealloyed powders were produced by atomizing the molten alloys and collecting the powders in water. This procedure produced uniform powders with a very fine distribution of the intermetallic compounds. Fabrication into rods then included ball-milling, vacuum hot pressing, vacuum heat treating, and hot extrusion. Mg additions improved strengths up to 200$sup 0$C with little effect above that temperature. Room-temperature tensile strengths up to 77,000 psi were obtained which are comparable to the strengths obtained in conventional aluminum alloys. The additional dispersion strengthening of the intermetallic compounds is additive to that of the oxide from room temperature to 450$sup 0$C. No significant improvements in ductility are obtained by reducing the oxide content since even at very low ball-milling times (i.e., low oxide contents) the uniform elongation at 450$sup 0$C is typically 0.5 percent. Good combinations of strength and ductility at 450$sup 0$C were obtained in some of the alloys containing intermetallic compounds with no ball-milling. Typical properties at this temperature were tensile strengths of 7,000 psi, uniform elongation of 3 percent, and total elongation of 35 percent. (21 tables, 33 fig, 43 references) (auth)

Copeland, G.L.

1975-10-01

365

Corrosion behavior of aluminum-alumina composites in aerated 3.5 percent chloride solution  

Microsoft Academic Search

Aluminum based metal matrix composites are finding many applications in engineering. Of these Al-Al2O3 composites appear to have promise in a number of defense applications because of their mechanical properties. However, their corrosion behavior remains suspect, especially in marine environments. While efforts are being made to improve the corrosion resistance of Al-Al2O3 composites, the mechanism of corrosion is not well

Paul Omar Acevedo Hurtado

2010-01-01

366

Studies on the mechanism of hydrolysis and polymerization of aluminum salts in aqueous solution: correlations between the “Core-links” model and “Cage-like” Keggin-Al 13 model  

Microsoft Academic Search

Two conflicting models describe the mechanism of aluminum (Al) hydrolysis and polymerization in aqueous solution, namely, the “Core-links” model and the “Cage-like” Keggin-Al13 model. For the sake of simplicity, the expressions of Al13 in the “Core-links” model and the “Cage-like” model are termed as C-Al13 and K-Al13, respectively. The two models have co-existed for almost 50 years, but describe differences

Shuping Bi; Chenyi Wang; Qing Cao; Caihua Zhang

2004-01-01

367

The interface between {delta}{prime} and matrix in an 8090 Al-Li alloy studies by SAXS  

SciTech Connect

A small angle X-ray scattering (SAXS) techniques has been used to characterize the interfaces between the {delta}{prime} phase and matrix in and 8090 Al-Li alloy aged at 160 C for several times. The results showed that a transition interfacial layer exists between the {delta}{prime} phase and matrix in the earlier stage of aging, which disappears in the later stage of aging. The existence of a transition interfacial layer indicated that the phase precipitates by spinodal decomposition. This mechanism is thought to be the cause of the deviation of {delta}{prime} phase coarsening from the LSW coarsening rate law.

Chai, Z.G. [Jilin Univ., Changchun (China). Inst. of Materials Science]|[Air Force Flying Coll. in Changchun (China); Xu, Y.; Meng, F.L. [Jilin Univ., Changchun (China)

1999-01-01

368

In-situ processing of aluminum nitride particle reinforced aluminum alloy composites  

NASA Astrophysics Data System (ADS)

Discontinuously reinforced aluminum alloy composites (DRACs) have potential applications in automotive, electronic packaging, and recreation industries. Conventional processing of DRACs is by incorporation of ceramic particles/whiskers/fibers into matrix alloys. Because of the high cost of ceramic particles, DRACs are expensive. The goal of this work was to develop a low-cost route of AlN-Al DRACs processing through bubbling and reacting nitrogen and ammonia gases with aluminum alloy melt in the temperature range of 1373--1523 K. Thermodynamic analysis of AlN-Al alloy system was performed based on Gibbs energy minimization theory. AlN is stable in aluminum, Al-Mg, Al-Si, Al-Zn, and Al-Li alloys over the whole temperature range for application and processing of DRACs. Experiments were carried out to form AlN by bubbling nitrogen and ammonia gases through aluminum, Al-Mg, and Al-Si alloy melts. Products were characterized with XRD, SEM, and EDX. The results showed that in-situ processing of AlN reinforced DRACs is technically feasible. Significant AlN was synthesized by bubbling deoxidized nitrogen and ammonia gases. When nitrogen gas was used as the nitrogen precursor, the AlN particles formed in-situ are small in size, (<10 mum). The formation of AlN is strongly affected by the trace oxygen impurities in the nitrogen gas. The deleterious effect of oxygen impurities is due to their inhibition to the chemisorption of nitrogen gas at the interface. In comparison with nitrogen gas, bubbling ammonia led to formation of AlN particles in smaller size (about 2 mum or less) at a significantly higher rate. Ammonia is not stable and dissociated into nitrogen and hydrogen at reaction temperatures. The hydrogen functions as oxygen-getter at the interface and benefits chemisorption of nitrogen, thereby promoting the formation of AlN. The overall process of AlN formation was modeled using two-film model. For nitrogen bubbling gas, the whole process is controlled by chemisorption of nitrogen molecules at the gas bubble - aluminum melt interface. For ammonia precursor, the rate of the overall process is limited by the mass transfer of nitrogen atoms in the liquid boundary layer. The models agree well with the experimental results.

Zheng, Qingjun

369

Elimination of aluminum adjuvants.  

PubMed

In vitro dissolution experiments although perhaps not at typical body concentrations and temperatures demonstrated that the alpha-hydroxycarboxylic acids present in interstitial fluid (citric acid, lactic acid, and malic acid) are capable of dissolving aluminum-containing adjuvants. Amorphous aluminum phosphate adjuvant dissolved more rapidly than crystalline aluminum hydroxide adjuvant. Intramuscular administration in New Zealand White rabbits of aluminum phosphate and aluminum hydroxide adjuvants, which were labelled with 26Al, revealed that 26Al was present in the first blood sample (1 h) for both adjuvants. The area under the blood level curve for 28 days indicated that three times more aluminum was absorbed from aluminum phosphate adjuvant than aluminum hydroxide adjuvant. In vivo studies using 26Al-labelled adjuvants are relatively safe because accelerator mass spectrometry (AMS) can quantify quantities of 26Al as small as 10(-17) g. A similar study in humans would require a whole-body exposure of 0.7 microSv per year compared to the natural background exposure of 3000 microSv per year. The in vitro dissolution and in vivo absorption studies indicate that aluminum-containing adjuvants which are administered intramuscularly are dissolved by alpha-hydroxycarboxylic acids in interstitial fluid, absorbed into the blood, distributed to tissues, and eliminated in the urine. PMID:12184363

Hem, Stanley L

2002-05-31

370

Laser-induced spallation of aluminum and Al alloys at strain rates above 2x10{sup 6} s{sup -1}  

SciTech Connect

Material microstructure is a significant determinant of the tensile stress at which materials fail. Using a high-energy laser to drive shocks in thin slabs, we have explored the role material microstructure plays on the spall strength of high-purity and alloyed aluminum at strain rates of (2-7.5)x10{sup 6} s{sup -1}. Slabs of pure recrystallized Al and recrystallized or cold worked Al+3 wt % Mg were shock driven using the Z-Beamlet Laser at Sandia National Laboratories. Velocity interferometer measurements determined the spall strength of the materials, and postshot target analysis explored the microscopic fracture morphology. We observed the greatest spall strength for large-grained, recrystallized high-purity aluminum, with the dominant failure mode being ductile and transgranular. We observe for the first time at these strain rates fracture features for a fine-grained Al+3 wt % Mg that were a combination of brittle intergranular and ductile transgranular fracture types. Postshot analysis of target cross sections and hydrocode simulations indicate that this mixed-mode failure results from spall dynamics occurring on spatial scales on the order of the grain size. Differences in spall strength between these Al samples were experimentally significant and correlate with the damage morphologies observed.

Dalton, D. A.; Bernstein, A. C.; Grigsby, W.; Milathianaki, D.; Ditmire, T. [Texas Center for High Intensity Laser Science, Department of Physics, University of Texas, Austin, Texas 78712 (United States); Brewer, J. L. [Stress Engineering Services Inc., Houston, Texas 77041 (United States); Jackson, E. D.; Taleff, E. M. [Department of Mechanical Engineering, University of Texas, Austin, Texas 78712 (United States); Adams, R. G.; Rambo, P.; Schwarz, J.; Edens, A.; Geissel, M.; Smith, I. [Z-Backlighter Facility, Sandia National Laboratories, Albuquerque, New Mexico, 87185 (United States)

2008-07-01

371

Study on the Mechanical Properties of Cast 6063 Al Alloy Using a Mixture of Aluminum Dross and Green Sand as Mold  

NASA Astrophysics Data System (ADS)

The mechanical characteristics of 6063 aluminum alloy cast in a mixture of aluminum dross and silica sand as mold have been examined. The amount of dross in the green silica sand was varied in the range of 0-80% with bentonite as binder. In all, 40 samples were cast, and 8 of these were left in the as-cast condition for control while 32 were first homogenized at 470°C for 6 h and then rolled in a two-high mill at ambient temperature to 10% reduction in one pass. The rolled samples were solution heat treated at 515°C for 8 h followed by normalizing, annealing, and quench tempering, respectively. The samples were then simulated and tensile behavior coupled with the evaluation of microhardness and microstructures developed. The results obtained demonstrate significant improvement in mechanical properties from 50% to 80% dross in the mold. Tensile strength increased to 177 MPa and 15% elongation compared with conventional 6063-T5 aluminum alloy with 145 MPa tensile strength and 8% elongation. The improvement in mechanical properties by the quench-tempered samples can be attributed to the inducement of fine and coherent Mg2Si crystals within the matrix. Furthermore, the overall analysis of the proportion of dross to the size of cast show that about 64% of dross generated can be utilized as mold material.

Adeosun, S. O.; Sekunowo, O. I.; Balogun, S. A.; Obembe, O. O.

2012-08-01

372

Irradiation performance of U-Mo-Ti and U-Mo-Zr dispersion fuels in Al-Si matrixes  

NASA Astrophysics Data System (ADS)

Performance of U-7 wt.%Mo with 1 wt.%Ti, 1 wt.%Zr or 2 wt.%Zr, dispersed in an Al-5 wt.%Si alloy matrix, was investigated through irradiation tests in the ATR at INL and HANARO at KAERI. Post-irradiation metallographic features show that the addition of Ti or Zr suppresses interaction layer growth between the U-Mo and the Al-5 wt.%Si matrix. However, higher fission gas swelling was observed in the fuel with Zr addition, while no discernable effect was found in the fuel with Ti addition as compared to U-Mo without the addition. Known to have a destabilizing effect on the ?-phase U-Mo, Zr, either as alloy addition or fission product, is ascribed for the disadvantageous result. Considering its benign effect on fuel swelling, with slight disadvantage from neutron economy point of view, Ti may be a better choice for this purpose.

Kim, Yeon Soo; Hofman, G. L.; Robinson, A. B.; Wachs, D. M.; Ryu, H. J.; Park, J. M.; Yang, J. H.

2012-08-01

373

Structure, thermochemical properties, and growth sequence of aluminum-doped silicon clusters Si(n)Al(m) (n = 1-11, m = 1-2) and their anions.  

PubMed

A systematic examination of the aluminum doped silicon clusters, Si(n)Al(m) with n = 1-11 and m = 1-2, in both neutral and anionic states, is carried out using quantum chemical calculations. Lowest-energy equilibrium structures of the clusters considered are identified on the basis of G4 energies. High accuracy total atomization energies and thermochemical properties are determined for the first time using the G4 and CCSD(T)/CBS (coupled-cluster theory with complete basis set up to n = 3) methods. In each size, substitution of Si atoms at different positions of a corresponding pure silicon clusters by Al dopants invariably leads to a spectrum of distinct binary structures but having similar shape and comparable energy content. Such an energetic degeneracy persists in the larger cluster sizes, in particular for the anions. The equilibrium growth sequences for Al-doped Si clusters emerge as follows: (i) neutral singly doped Si(n)Al clusters favor Al atom substitution into a Si position in the structure of the corresponding cation Si(n+1)(+), whereas the anionic Si(n)Al(-) has one Si atom of the isoelectronic neutral Si(n+1) being substituted by the Al impurity; and (ii) for doubly doped Si(n)Al2(0/-) clusters, the neutrals have the shape of Si(n+1) counterparts in which one Al atom substitutes a Si atom and the other Al adds on an edge or a face of it, whereas the anions have both Al atoms substitute two Si atoms in the Si(n+2)(+) frameworks. The Al dopant also tends to avoid high coordination position. PMID:23837568

Tam, Nguyen Minh; Tai, Truong Ba; Ngan, Vu Thi; Nguyen, Minh Tho

2013-07-24

374

Laser surface coating of Mo–WC metal matrix composite on Ti6Al4V alloy  

Microsoft Academic Search

Laser surface alloying of Mo, WC and Mo–WC powders on the surface of Ti6Al4V alloys using a 2kW Nd-YAG laser was performed. The dilution effect upon the microstructure, microhardness and wear resistance of the surface metal matrix composite (MMC) coating was investigated. With a constant thickness of pre-placed powder, the dilution levels of the alloyed layers were found to increase

W. Pang; H. C. Man; T. M. Yue

2005-01-01

375

Chemical reaction in Al matrix composite reinforced with SiC p coated by SnO 2  

Microsoft Academic Search

Reducing the extent of interfacial reaction in Al matrix composite reinforced with SiC particles during remelt-recycling is critical to its commercialization and sustainable-development. In this article, the remelting behavior of the composite with SnO2 coating on SiC particles during the remelting was investigated by Differential Scanning Calorimeter (DSC) and the thermodynamic calculations. The results showed that SnO2 coating could reduce

Guang Yang; Tongxiang Fan; Di Zhang

2004-01-01

376

Deposition of Co nano-particles in a CoO\\/Al 2O 3 matrix by magnetron sputtering  

Microsoft Academic Search

We have explored the use of sequential sputtering as an alternative way of growing Co clusters inside an antiferromagnetic matrix of CoO. The samples are composed of 10 bi- or tri-layers and have been deposited by direct magnetron sputtering of Co, CoO and Al2O3 targets. Transmission electron microscopy and impedance spectroscopy measurements show that the direct deposition of Co over

M. Gamino; J. T. D. de Oliveira; C. R. dos Santos; F. Bohn; L. F. Schelp; J. C. Denardin

2008-01-01

377

Deposition of Co nano-particles in a CoO\\/Al2O3 matrix by magnetron sputtering  

Microsoft Academic Search

We have explored the use of sequential sputtering as an alternative way of growing Co clusters inside an antiferromagnetic matrix of CoO. The samples are composed of 10 bi- or tri-layers and have been deposited by direct magnetron sputtering of Co, CoO and Al2O3 targets. Transmission electron microscopy and impedance spectroscopy measurements show that the direct deposition of Co over

M. Gamino; J. T. D. de Oliveira; C. R. Dos Santos; F. Bohn; L. F. Schelp; J. C. Denardin

2008-01-01

378

Glow discharge excitation and matrix effects in the Zn–Al–Cu system in argon and neon  

Microsoft Academic Search

Matrix effects and other deviations from the standard model of glow discharge optical emission spectroscopy (GD-OES) have been investigated in the Zn–Al–Cu system in a Grimm-type discharge in argon and neon. In ionic spectra of the elements that can be ionized by asymmetric charge transfer with ions of the discharge gas, most observed deviations from the standard model can be

Zdenek Weiss

2007-01-01

379

Microstructure and mechanical properties of Cr3C2 particulate reinforced Al2O3 matrix composites  

Microsoft Academic Search

Al2O3 matrix with three grades of Cr3C2 particle size (0.5, 1.5 and 7.5 µm) composites were fabricated by a hot-pressing technique. Fully dense compacts with Cr3C2 content up to 40 vol % can be acquired at 1400 °C under 30 MPa pressure for 1 h. The flexural strength increases from 595 to 785 Mpa for fine Cr3C2 particle (0.5 µm)

Chen-Tsu Fu; Jenn-Ming Wu; Ai-Kang Li

1994-01-01

380

Properties of Wear-Resistant Metal Matrix Composite and It's Applications.  

National Technical Information Service (NTIS)

Metal matrix composite (MMC), consisting of aluminum alloy matrix reinforced with fibers or powders of SiC or Al2O3, exhibits not only superior specific strength and specific rigidity but also high resistance to wear and heat. As such, it is expected to b...

H. Kashiwaya T. Nishimura M. Kikuchi

1989-01-01

381

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

382

Formation of Small Blocky Al3Ti Particles via Direct Reaction Between Solid Ti Powders and Liquid Al  

NASA Astrophysics Data System (ADS)

The evolution of titanium powders in the pure aluminum melt at a lower temperature was studied in our research. The process involved some titanium powders being added into the pure aluminum melt at 1003 K (730 °C), and then the melt was cast into an ingot after 5 minutes. A reaction layer composed of some loose Al3Ti particles was formed on the solid Ti surface due to the reactive diffusion between titanium and aluminum. In-situ blocky Al3Ti particles smaller than 5 ?m were produced in the aluminum matrix. A reaction-peeling model was suggested to illustrate the formation mechanism of Al3Ti particles, and a simple approach for fabricating in-situ Al3Ti/Al-alloy composites was proposed as well.

Liu, Z. W.; Han, Q.; Li, J. G.

2012-12-01

383

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 CaF2–Al2O3 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

384

Understanding the Co-Poisoning Effect of Zr and Ti on the Grain Refinement of Cast Aluminum Alloys  

NASA Astrophysics Data System (ADS)

The “co-poisoning” effect between Zr and Ti (derived from Al-Zr and Al-Ti-B master alloy additions) on the grain refinement of cast aluminum alloys is studied from a crystallographic atom matching viewpoint. The edge-to-edge matching (E2EM) model has been used to investigate the possible “poisoning” phase containing Zr/Ti, Al, and Fe in commercial grade aluminum alloys. The results show that Al3Ti is the most likely constituent to be poisoned due to the formation of an Al8Fe4Zr coating on its surface, since the Al8Fe4Zr phase has good crystallographic atom matching with Al3Ti, but not with the aluminum matrix. Meanwhile, the partial dissolution of Al3Zr nucleant particles to compensate for the loss of solute Zr aggravates the poisoning phenomenon. This proposed mechanism is consistent with most previous experimental observations and with existing practical solutions employed in the foundry.

Qiu, D.; Taylor, J. A.; Zhang, M.-X.

2010-12-01

385

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

Microsoft Academic Search

A high-temperature oxidation resistant TiN embedded in Ti3Al intermetallic matrix composite coating was fabricated on titanium alloy Ti6Al4V surface by 6kW transverse-flow CO2 laser apparatus. The composition, morphology and microstructure of the laser clad TiN\\/Ti3Al intermetallic matrix composite coating were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to

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

2010-01-01

386

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

387

Reaction synthesis of Ni-Al based particle composite coatings  

SciTech Connect

Electrodeposited metal matrix/metal particle composite (EMMC) coatings were produced with a nickel matrix and aluminum particles. By optimizing the process parameters, coatings were deposited with 20 volume percent aluminum particles. Coating morphology and composition were characterized using light optical microscopy (LOM), scanning electron microscopy (SEM), and electron probe microanalysis (EPMA). Differential thermal analysis (DTA) was employed to study reactive phase formation. The effect of heat treatment on coating phase formation was studied in the temperature range 415 to 1,000 C. Long-time exposure at low temperature results in the formation of several intermetallic phases at the Ni matrix/Al particle interfaces and concentrically around the original Al particles. Upon heating to the 500--600 C range, the aluminum particles react with the nickel matrix to form NiAl islands within the Ni matrix. When exposed to higher temperatures (600--1,000 C), diffusional reaction between NiAl and nickel produces ({gamma})Ni{sub 3}Al. The final equilibrium microstructure consists of blocks of ({gamma}{prime})Ni{sub 3}Al in a {gamma}(Ni) solid solution matrix, with small pores also present. Pore formation is explained based on local density changes during intermetallic phase formation and microstructural development is discussed with reference to reaction synthesis of bulk nickel aluminides.

SUSAN,DONALD F.; MISIOLEK,WOICECK Z.; MARDER,ARNOLD R.

2000-02-11

388

Influence of the temperature of aluminum oxide micropowder modification with Al2O3 nanopowders on the optical properties and radiation resistance of coatings manufactured on their basis  

NASA Astrophysics Data System (ADS)

Influence of the temperature of aluminum oxide micropowder modification with Al2O3 nanopowders in the interval 200-1000°C on the granulometric composition, diffusion reflection spectra in the wavelength range 360-2100 nm, and integral solar radiation absorption coefficient of coatings fabricated on the basis of these powders as well as on changes of these parameters upon exposure to electrons is investigated. It is demonstrated that with increase in the modification temperature, the average powder particle size decreases, the negative action is intensified, and the radiation resistance of coatings increases.

Mikhailov, M. M.; Lapin, A. N.

2011-04-01

389

Aqueous solution-chemical derived NiAl2O3 solar selective absorbing coatings. 2. Wetting agents and spreading of aqueous solutions on aluminum substrate  

NASA Astrophysics Data System (ADS)

Wettability of aluminum substrate by the aqueous solutions containing ethoxylated alcohol nonionic surfactants C12En- or Triton X-series was studied using dynamic contact angle measurements. The efficiency of wetting was found to strongly depend on the length of polyoxyethylene (POE) chain of C12En- or Triton X surfactants. For C12E4 that has a very short POE chain, it hardly made the aqueous solution spreading over aluminum. The others with a long POE chain were indeed very efficient in promoting the solution spreading. Moreover, all the spreading process could be completed within 10 s. The single-layer NiAl2O3 coatings were fabricated from the precursor solutions containing C12En- or Triton X surfactants and the reflectance spectra were measured by a UV/vis spectrophotometer equipped with an integrating sphere. The results indicated that the precursor solution with a long POE chain surfactant as wetting agent favored to fabricate a uniform film on the aluminum substrate and therefore to get a high solar absorptance.

Li, Zhenxiang; Zhao, Jianxi

2013-03-01

390

Influence of additives on the microstructure and tensile properties of near-eutectic Al–10.8%Si cast alloy  

Microsoft Academic Search

The continuing quest for aluminum castings with enhanced mechanical properties for applications in the automotive industries has intensified the interest in aluminum–silicon alloys. In Al–Si alloys, the properties are influenced by the shape and distribution of the eutectic silicon particles in the matrix, as also by the iron intermetallics and copper phases that occur upon solidification. The detailed microstructure and

A. M. A. Mohamed; A. M. Samuel; F. H. Samuel; H. W. Doty

2009-01-01

391

Experimental Investigations of Material Models for Ti-6Al-4V Titanium and 2024-T3 Aluminum.  

National Technical Information Service (NTIS)

The report describes studies of the deformation and failure behavior of Ti-6A1-4V titanium and 2024-T3 aluminum. This work was accomplished by the Lawrence Livermore National Laboratory under an Interagency Agreement between the Federal Aviation Administr...

D. R. Lesuer

2000-01-01

392

An Examination of Wire Electrical Discharge Machining (WEDM) of Al2O3 Particulate Reinforced Aluminum Based Composites  

Microsoft Academic Search

The material removal mechanism in wire electrical discharge machining of an alumina particulate reinforced aluminum based composite and the related machined surface morphologies were investigated. Under the two cutting conditions of this study, fine and coarse cuttings, the surface roughness measurements on the machined surfaces of the composite material did not show a significant difference, but their corresponding surface topographies

T. M. Yue; Y. Dai; W. S. Lau

1996-01-01

393

Thermal compatibility studies of unirradiated uranium silicide dispersed in aluminum  

SciTech Connect

Powder metallurgy dispersions of uranium silicides in an aluminum matrix have been developed by the international Reduced Enrichment for Research and Test Reactors program as a new generation of proliferation-resistant fuels. A major issue of concern is the compatibility of the fuel with the matrix material and the dimensional stability of this fuel type. A total of 45 miniplate-type fuel plates were annealed at 400/sup 0/C for up to 1981 h. A data base for the thermal compatibility of unirradiated uranium silicide dispersed in aluminum was established. No tested modification of a standard fuel plate showed any significant reduction in plate swelling. The cause of thermal growth of silicide fuel plates was determined to be a two-step process: (a) the reaction of the uranium silicide with aluminum to form U(AlSi)/sub 3/ and (b) the release of hydrogen and subsequent creep and pillowing of the fuel plate.

Wiencek, T.C.; Domagala, R.F.; Tresh, H.R.

1985-12-01

394

LETTER TO THE EDITOR: Electron-impact ionization of Al2+ ions: a unified R-matrix calculation  

NASA Astrophysics Data System (ADS)

The cross section for electron-impact ionization of Al2+ in the energy range 60-100 eV has been calculated using a unified R-matrix method which describes both direct and indirect processes in a consistent manner. The direct ionization (DI), excitation autoionization (EA), resonant excitation double-autoionization (REDA) and resonant excitation auto-double-ionization (READI) processes are included in the present work. By including seven bound target states, five pseudo states and thirty-two autoionizing states in the R-matrix expansion, completely convergent results for the total cross section have been obtained. The calculated total cross sections are in very good agreement with the recent experimental results of Thomason and Peart (1998 J. Phys. B: At. Mol. Opt. Phys. 31 L201) and the pseudo state R-matrix calculation of Badnell et al (1998 J. Phys. B: At. Mol. Opt. Phys. 31 911). In particular, the present calculation predicts the existence of resonances due to READI process and reproduces very well the experimental non-resonant and resonant features observed by Thomason and Peart. The remaining discrepancy between theory and experiment is discussed.

Teng, Huaguo

2000-08-01

395

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

Microsoft Academic Search

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

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

2009-01-01

396

Study on luminescence properties of Eu2+ in BaAl12O19 matrix.  

PubMed

Eu(2+)-doped BaAl12O19 phosphors were prepared using the sol-gel method, and their structure and luminescence properties were characterized by X-ray diffraction (XRD) analysis and fluorescence spectrometry. The results showed that a single hexagonal BaAl12O19 crystal structure was synthesized and the emission spectrum of BaAl12O19:Eu exhibited a broad asymmetric band from 375 to 600 nm, which was composed of three emission peaks at 438, 462, and 511 nm. The effects of crystallization temperature, Eu2+ concentration, and Al3+ content on the occupation of Eu2+ in three crystallographic positions were investigated. The emission intensity of 438 nm increased with increasing crystallization temperature, while the emission intensity of 462 and 511 nm increased with the increase of Eu2+ concentration and Al3+ content. PMID:20355640

Xiao, Linjiu; He, Mingrui; Tian, Yanwen; Chen, Yongjie; Karaki, Tomoaki; Li, Wenze; Xie, Ying; Zhang, Liqing

2010-03-01

397

Thermal expansion studies of prestrained Al{sub 2}O{sub 3}/Al metal matrix composite  

SciTech Connect

The present study was undertaken to investigate the effect of prestraining on the coefficient of thermal expansion (CTE) of 10 and 20 volume percent (v/o) Al{sub 2}O{sub 3} particle-reinforced composite over various temperature ranges using thermal mechanical analysis (TMA). The CTE of the composite was shown to be dependent on the volume fraction of the broken particle, plastic yielding and flow, and other transformation processes occurring at elevated temperatures. The experimentally measured values of the CTE were found to be in good agreement with Schapery`s model at various values of plastic prestrain (0--10%) and with a modified Kerner`s equation, at high prestraining ({epsilon}{sub p} > 4%) for a wider temperature range.

Elomari, S.; Boukhili, R. [Ecole Polytechnique de Montreal, Quebec (Canada). Dept. de Genie Mecanique; Lloyd, D.J. [Alcan International Ltd., Kingston, Ontario (Canada)

1996-05-01

398

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

399

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

Microsoft Academic Search

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

G. F. Gao; B. Zhao; D. H. Xiang; M. L. Zhao

2011-01-01

400

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

Microsoft Academic Search

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

G. F. Gao; B. Zhao; D. H. Xiang; M. L. Zhao

2011-01-01

401

MAS-NMR studies of lithium aluminum silicate (LAS) glasses and glass-ceramics having different Li2O/Al2O3 ratio  

NASA Astrophysics Data System (ADS)

Emergence of phases in lithium aluminum silicate (LAS) glasses of composition (wt%) xLi2O-71.7SiO2-(17.7-x)Al2O3-4.9K2O-3.2B2O3-2.5P2O5 (5.1?x?12.6) upon heat treatment were studied. 29Si, 27Al, 31P and 11B MAS-NMR were employed for structural characterization of both LAS glasses and glass-ceramics. In glass samples, Al is found in tetrahedral coordination, while P exists mainly in the form of orthophosphate units. B exists as BO3 and BO4 units. 27Al NMR spectra show no change with crystallization, ruling out the presence of any Al containing phase. Contrary to X-ray diffraction studies carried out, 11B (high field 18.8 T) and 29Si NMR spectra clearly indicate the unexpected crystallization of a borosilicate phase (Li,K)BSi2O6, whose structure is similar to the aluminosilicate virgilite. Also, lithium disilicate (Li2Si2O5), lithium metasilicate (Li2SiO3) and quartz (SiO2) were identified in the 29Si NMR spectra of the glass-ceramics. 31P NMR spectra of the glass-ceramics revealed the presence of Li3PO4 and a mixed phase (Li,K)3PO4 at low alkali concentrations.

Ananthanarayanan, A.; Kothiyal, G. P.; Montagne, L.; Revel, B.

2010-01-01

402

Effect of Aluminum Content on Microstructure and Mechanical Properties of Al x CoCrFeMo0.5Ni High-Entropy Alloys  

NASA Astrophysics Data System (ADS)

High-entropy alloys Al x CoCrFeMo0.5Ni with varied Al contents (x = 0, 0.5, 1.0, 1.5, and 2.0) have been designed based on the Al x CoCrCuFeNi system to improve mechanical properties for room and elevated temperatures. They have been investigated for microstructure and mechanical properties. As the aluminum content increases, the as-cast structure evolves from face-centered cubic dendrite + minor ?-phase interdendrite at x = 0 to B2 dendrite with body-centered cubic (bcc) precipitates + bcc interdendrite with B2 precipitates at x = 2.0. This confirms the strong bcc-forming tendency of Al. The room-temperature Vickers hardness starts from the lowest, HV 220, at x = 0, attains to the maximum, HV 720, at x = 1.0, and then decreases to HV 615 at x = 2.0. Compared with the base alloy system, the current alloy system has a superior combination of hardness and fracture toughness. In addition, Al x CoCrFeMo0.5Ni alloys except x = 0 display a higher hot hardness level than those of Ni-based superalloys, including In 718 and In 718 H, up to 1273 K and show great potential in high-temperature applications.

Hsu, Chin-You; Juan, Chien-Chang; Sheu, Tsing-Shien; Chen, Swe-Kai; Yeh, Jien-Wei

2013-09-01

403

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

404

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

405

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

406

Aluminum coprecipitates with Fe (hydr)oxides: Does isomorphous substitution of Al 3+ for Fe 3+ in goethite occur?  

NASA Astrophysics Data System (ADS)

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 ˜2.25 for Fe 3+ and at pH ˜4 for Al 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 unlikely at ?8 mol% Al substitution.

Bazilevskaya, Ekaterina; Archibald, Douglas D.; Aryanpour, Masoud; Kubicki, James D.; Martínez, Carmen Enid

2011-08-01

407

Effect of magnesium on the aging behavior of Al-Zn-Mg-Cu/Al2O3 metal matrix composites  

NASA Astrophysics Data System (ADS)

The effect of magnesium content on the aging behavior of Al-Zn-Mg-Cu alloy reinforced with alumina (A12O3) was studied by using the differential scanning calorimetry (DSC) technique and hardness measurement. The magnesium contents were studied in the range from 1.23 to 2.97 wt pct. The addition of magnesium was found to increase the coherent Guinier-Preston (GP) zones in com-posites. The apparent formation enthalpy of GP zones of composites (0.1 V f) was 0.932 cal/g for 1.23 wt pct magnesium content and 1.375 cal/g for 2.97 wt pct magnesium content. The precipitation time to achieve the maximum hardness in the composites depends on the magnesium content. The time changed from 12 to 48 hours as the magnesium content increased from 1.23 to 2.97 wt pct. Both Vickers microhardness and Rockwell hardness increased with increasing magnesium content. The maximum hardness occurred in the composites that contained maximum amounts of GP zones and ?' precipitates. However, the microhardness of the composites was always lower than that of monolithic alloys due to the alumina fibers which caused the suppression of GP zones and ?' for-mation in the composites.

Chou, Ming-Chun; Chao, Chuen-Guang

1996-07-01

408

Ageing behaviour of spray-deposited 18Ni(250) maraging steel + 10 vol.% Al 2O 3 particulate-reinforced metal matrix composites  

Microsoft Academic Search

The ageing behaviour of spray-deposited 18Ni(250) maraging steel+10 vol.% Al2O3 particulate-reinforced metal matrix composites (MMCs) was investigated by microhardness and nanoindentation techniques. Compared to the control steel, the composite material showed an accelerated ageing kinetics. Nanoindentation investigation revealed observable gradient distribution of elastic modulus and hardness around Al2O3 particulates inside the plastic zone in the matrix. Around a reinforcement particulate,

J. S. Zhang; X. J. Liu; H. Cui; X. J. Duan; Z. Q. Sun; G. L. Chen

1997-01-01

409

Tensile and fatigue behavior of Al-based metal matrix composites reinforced with continuous carbon or alumina fibers: Part I. Quasi-unidirectional composites  

Microsoft Academic Search

The thermomechanical (dilatometric, tensile, and fatigue) behavior of Al-based metal matrix composites (MMCs) is investigated.\\u000a These composites are reinforced by quasi-unidirectional (quasi-UD) woven fabric preforms with 90 pct of continuous fibers\\u000a in the longitudinal direction and 10 pct in the transverse direction. The two composite systems investigated feature a highly\\u000a ductile matrix (AU2: Al-2Cu wt pct) with a strongly bonded

M. Jacquesson; A. Girard; M.-H. Vidal-Sétif; R. Valle

2004-01-01

410

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

411

Dry sliding wear of Al\\/Saffil\\/C hybrid metal matrix composites  

Microsoft Academic Search

Tribological behaviour of Al\\/Saffil\\/C hybrid composites with various amounts of graphite and alumina fibres, produced by the squeeze casting method, was studied. Preforms with about 6.5–15.0% (all the percentages v\\/v) of Al2O3 fibres (Saffil) and 1.5–12.0% of graphite were infiltrated under the pressure of 75MPa. The effects of the applied load, form of graphite, and the reinforcement volume fraction on

K. Naplocha; K. Granat

2008-01-01

412

Tribocorrosion Studies in Centrifugally Cast Al-Matrix SiCp-reinforced Functionally Graded Composites  

Microsoft Academic Search

The present work reports results obtained from a series of preliminary experiments aiming at complementing the current knowledge about the wear behaviour of centrifugally-cast FGM Al\\/SiCp composites, through concurrent corrosion processes. Precursor MMC's were prepared by rheocasting, using 118.8 µm SiC particles and an Al-10Si-2.2 Mg alloy. Those MMC's were then molten and centrifugally cast in order to produce cylindrical

Alexandre Velhinho; José D. Botas; E. Ariza; J. R. Gomes; L. A. Rocha

2004-01-01

413

Effects of mercury on thermally sprayed aluminum coatings  

SciTech Connect

The quantification of liquid metal embrittling effects of mercury on thermally sprayed aluminum was investigated. The program consisted of heat treatments at 250 and 300 C of thermally sprayed (aluminum on lead) cylinders with mercury additions of 0.25, 0.50, 1.00, and 3.00 wt.%. The cylinders were then tested to determine the adhesion/cohesion strength of the thermally sprayed bond. The Pb/Al interfaces were evaluated using energy dispersive spectroscopy (EDS). The results of the testing indicate that there was no noticeable embrittling effects of the mercury, up to 3.0 wt.% Hg in the Pb matrix.

Czajkowski, C.J.; Usmani, S.; Greene, G.A.

1999-09-01

414

Indium-silicon co-doping of high-aluminum-content AlGaN for solar blind photodetectors  

Microsoft Academic Search

We report on an indium-silicon co-doping approach for high-Al-content AlGaN layers. Using this approach, very smooth crack-free n-type AlGaN films as thick as 0.5 mum with Al mole fraction up to 40% were grown over sapphire substrates. The maximum electron concentration in the layers, as determined by Hall measurements, was as high as 8×1017 cm-3 and the Hall mobility was

V. Adivarahan; G. Simin; G. Tamulaitis; R. Srinivasan; J. Yang; M. Asif Khan; M. S. Shur; R. Gaska

2001-01-01

415

A new phase in the system lithium-aluminum: Characterization of orthorhombic Li{sub 2}Al  

SciTech Connect

Investigation of the Li rich part of the binary Li-Al system revealed the existence of a new phase, orthorhombic Li{sub 2}Al, which is isostructural to Li{sub 2}Ga and Li{sub 2}In. The crystal structure was determined from single crystal X-ray diffraction data (Cmcm, a=4.658(2) A, b=9.767(4) A, c=4.490(2) A, Z=4). Refinement of atomic position site occupancies yielded a composition Li{sub 1.92}Al{sub 1.08} (64 at% Li) indicating a small homogeneity range, Li{sub 2-x}Al{sub 1+x}. Li{sub 2}Al is the peritectic decomposition product of the stoichiometric compound Li{sub 9}Al{sub 4}, which is stable below 270{+-}2 {sup o}C. Li{sub 2}Al itself decomposes peritectically to Li{sub 3}Al{sub 2} and Li rich melt at 335{+-}2 {sup o}C. The discovery of Li{sub 2}Al (Li{sub 2-x}Al{sub 1+x}) settles a long standing inconsistency in the Li-Al phase diagram which was based on the assumption that Li{sub 9}Al{sub 4} possesses a high temperature modification. - Graphical abstract: A new phase, Li{sub 2}Al, has been discovered in the binary Li-Al system. The structure of orthorhombic Li{sub 2}Al is closely related to that of the established monoclinic phase Li{sub 9}Al{sub 4}.

Puhakainen, Kati [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Bostroem, Magnus [Sandvik Materials Technology, S-881 81 Sandviken (Sweden); Groy, Thomas L. [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States); Haeussermann, Ulrich, E-mail: Ulrich.Haussermann@asu.ed [Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604 (United States)

2010-11-15

416

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

SciTech Connect

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

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

2011-08-03

417

Application of Finite Element Model and Artificial Neural Network in Characterization of Al Matrix Nanocomposites Using Various Training Algorithms  

NASA Astrophysics Data System (ADS)

In this research, the effect of the volume fraction of the alumina nanoparticles on the mechanical properties of the Al-Si matrix composites was studied. The yield strength and tensile strength increase, but the elongation decreases with the increase in the volume fraction of the particles, indicating that increasing the volume fraction of the Al2O3 particles can improve the strength but degrade the plasticity of the composites. The mechanical properties modeling was carried out using an artificial neural network (ANN) and finite element model (FEM). The neural network was trained using different training algorithms, hidden layers, and neuron numbers in hidden layers in order to check the system accuracy of each training algorithm at the end of learning.

Shabani, Mohsen Ostad; Mazahery, Ali

2012-06-01

418

Microstructure and abrasive wear behaviour of B 4 C particle reinforced 2014 Al matrix composites  

Microsoft Academic Search

In this study, the microstructure and abrasive wear properties of varying volume fraction of particles up to 12% B4C particle reinforced 2014 aluminium alloy metal matrix composites produced by stircasting method was investigated. The density,\\u000a porosity and hardness of composites were also examined. Wear behaviour of B4C particle reinforced aluminium alloy composites was investigated by a block-on-disc abrasion test apparatus

A. Canakci

2011-01-01

419

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

SciTech Connect

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

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

2009-11-01

420

Aluminum Fluidity in Casting  

NASA Astrophysics Data System (ADS)

The understanding and control of fluidity is, and has been, a major aspect of foundry technology development. This paper reviews the progress made in this area over the years as it applies to aluminum castings. As a result of this development, thin-wall, high-integrity aluminum castings which were previously not thought possible have been produced. Further work in this area is expected to allow metal-matrix composites to fulfill their technical and economic promise.

Mollard, Francois R.; Flemings, Merton C.; Niyama, Eisuke F.

1987-11-01

421

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

422

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 600°C and 800°C 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

423

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

Microsoft Academic Search

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

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

2010-01-01

424

Microstructural, mechanical and electrochemical corrosion properties of sputtered titanium–aluminum–nitride films for bio-implants  

Microsoft Academic Search

The effect of aluminum (Al) addition to titanium nitride (TiN) matrix on the structural, mechanical and corrosion resistance properties of titanium–aluminum–nitride was studied. Ti1?xAlxN where x=0, 0.5 and 1 films were coated onto substrates like Si wafer, AISI 316L stainless steel and low carbon steel by a direct current magnetron sputtering process. The layers were sputtered in pure Argon with

Balasubramanian Subramanian; Ramadoss Ananthakumar; Muthirulandi Jayachandran

2010-01-01

425

Synthesis and structural characterization of Al7C3N3-homeotypic aluminum silicon oxycarbonitride, (Al7-xSix)(OyCzN6-y-z) (x˜1.2, y˜1.0 and z˜3.5)  

NASA Astrophysics Data System (ADS)

A new aluminum silicon oxycarbonitride, (Al5.8Si1.2)(O1.0C3.5N1.5), has been synthesized and characterized by X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), energy dispersive X-ray spectroscopy (EDX) and electron energy loss spectroscopy (EELS). The title compound is hexagonal with space group P63/mmc and unit-cell dimensions a=0.322508(4) nm, c=3.17193(4) nm and V=0.285717(6) nm3. The atom ratios of Al:Si and those of O:C:N were, respectively, determined by EDX and EELS. The initial structural model was successfully derived from the XRPD data by the direct methods and further refined by the Rietveld method. The crystal is most probably composed of four types of domains with nearly the same fraction, each of which is isotypic to Al7C3N3 with space group P63mc. The existence of another new oxycarbonitride (Al6.6Si1.4)(O0.7C4.3N2.0), which must be homeotypic to Al8C3N4, has been also demonstrated by XRPD and TEM.

Urushihara, Daisuke; Kaga, Motoaki; Asaka, Toru; Nakano, Hiromi; Fukuda, Koichiro

2011-08-01

426

21 CFR 73.1010 - Alumina (dried aluminum hydroxide).  

Code of Federal Regulations, 2010 CFR

...Specifications. Alumina (dried aluminum hydroxide) shall conform to the...more than 1 part per million. Aluminum oxide (Al2 O3 ), not less than...restrictions. Alumina (dried aluminum hydroxide) may be safely...

2010-04-01

427

21 CFR 73.1010 - Alumina (dried aluminum hydroxide).  

Code of Federal Regulations, 2010 CFR

...Specifications. Alumina (dried aluminum hydroxide) shall conform to the...more than 1 part per million. Aluminum oxide (Al2 O3 ), not less than...restrictions. Alumina (dried aluminum hydroxide) may be safely...

2009-04-01

428

Fatigue crack growth resistance of SiC p reinforced Al alloys: Effects of particle size, particle volume fraction, and matrix strength  

Microsoft Academic Search

The main aim of this work was to study the effects of particle size, particle volume fraction, and matrix strength on the\\u000a long fatigue crack growth resistance of two different grades of Al alloys (Al2124-T1 and Al6061-T1) reinforced with SiC particles.\\u000a Basically, it was found that an increase in particle volume fraction and particle size increases the fatigue crack growth

M. T. Milan; P. Bowen

2004-01-01

429

Oxyfluorides and Basic Fluorides of Aluminum.  

National Technical Information Service (NTIS)

Aluminum oxyfluorides ranging from AlOF to Al2OF4 have been prepared by reacting aluminum oxybromide with bromine trifluoride at room temperature, then heating the initially formed product at 350 degrees in vacuo. These aluminum oxyfluorides are sparingly...

B. Siegel R. L. Johnson

1966-01-01

430

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

SciTech Connect

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

Goodman, W.G.

1984-05-01

431

Influence of processing variables and aluminum content on the microstructure and mechanical properties of cast Mg-Al alloys  

Microsoft Academic Search

Using statistical design of experiments, a variety of industrially relevant Mg-Al microstructures were developed and characterized by investigating casting variables such as; Al content, solidification rate, grain refinement, gas content, HIPing, and post-casting thermal treatment. The microstructures were microscopically characterized and the statistical results not only exemplified the power of experimental design but also generated a wealth of knowledge concerning

Blair Edward Carlson

1997-01-01

432

Conventional and Micro-XRD Study of a New Ternary Zirconium, Titanium, Aluminum Alloy--Zr2TiAl  

NASA Astrophysics Data System (ADS)

Zr3Al is a cubic intermetallic compound whereas Ti3Al has a hexagonal structure. Crystallography and microstructure study of an alloy containing all three components is, therefore, interesting to study. A nominal Zr2TiAl alloy was prepared by arc melting and subsequently vacuum annealing at 1050° C for 30 days. Scanning Electron Microscopy and Energy Dispersive Spectrometry showed three phases in the material. Among the three phases the major phase was the stoichiometric alloy Zr2TiAl. Of the two minor phases present in the specimen, one was rich in Ti and the other rich in Al. In an SEM micrograph the major phase grains varied in size from 10 ?m to 50?m. Conventional XRD shows peaks due to all three phases with considerable proximity and overlap. In order to identify peaks due to individual phases micro-beam XRD was carried out and the major phase was identified.

Sornadurai, D.; Flemming, Roberta L.; Sastry, V. S.

2011-07-01

433

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

SciTech Connect

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

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

1994-02-01

434

Ultrathin aluminum oxide films: Al-sublattice structure and the effect of substrate on ad-metal adhesion  

SciTech Connect

First principles density-functional slab calculations are used to study 5 {angstrom} (two O-layer) Al{sub 2}O{sub 3} films on Ru(0001) and Al(111). Using larger unit cells than in a recent study, it is found that the lowest energy stable film has an even mix of tetrahedral (t) and octahedral (o) site Al ions, and thus most closely resembles the {kappa}-phase of bulk alumina. Here, alternating zig-zag rows of t and o occur within the surface plane, resulting in a greater average lateral separation of the Al-ions than with pure t or o. A second structure with an even mix of t and o has also been found, consisting of alternating stripes. These patterns mix easily, can exist in three equivalent directions on basal substrates, and can also be displaced laterally, suggesting a mechanism for a loss of long-range order in the Al-sublattice. While the latter would cause the film to appear amorphous in diffraction experiments, local coordination and film density are little affected. On a film supported by rigid Ru(0001), overlayers of Cu, Pd, and Pt bind similarly as on bulk truncated {alpha}-Al{sub 2}O{sub 3}(0001). However, when the film is supported by soft Al(111), the adhesion of Cu, Pd, and Pt metal overlayers is significantly increased: Oxide-surface Al atoms rise so only they contact the overlayer, while substrate Al metal atoms migrate into the oxide film. Thus the binding energy of metal overlayers is strongly substrate dependent, and these numbers for the above Pd-overlayer systems bracket a recent experimentally derived value for a film on NiAl(110).

JENNISON,DWIGHT R.; BOGICEVIC,ALEXANDER

2000-03-06

435

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

NASA Astrophysics Data System (ADS)

We systematically studied spatial inhomogeneity of aluminum content in air-bridged lateral epitaxially grown (ABLEG) AlGaN ternary alloy films by high-resolution photoluminescence mapping probed with cross-sectional scanning near-field optical microscopy (SNOM). We observed the content changes along the vertical < 0001> and the horizontal < 11\\bar{2}0> growth directions in AlGaN films with four different mask widths. The spatial inhomogeneity was determined by considering the following factors: the different growth rates of the lateral and vertical directions, the aluminum and gallium adatom supplies from a gas that depend on mask width, and the aluminum and gallium adatom diffusions on the (0001) and (11\\bar{2}0) facets.

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

2012-03-01

436

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

SciTech Connect

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

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

2010-11-15

437

Enthalpies of formation in the systems tantalum-sulfur and tantalum-aluminum. [Ta/sub 2/Al/sub 3/, Ta/sub 2/Al, Ta/sub 4/Al, TaAl/sub 3/  

SciTech Connect

The enthalpies of formation of selected intermediate phases in the binary systems Ta-S and Ta-Al were determined via thermochemical measurements at greater than or equal to 1000/sup 0/C. The measurements of partial pressures of sulfur species were accomplished by the mass loss variation of the Knudsen effusion method and led to the following ..delta..H/sup 0//sub f,298/ values: Ta/sub 2/S: -41.8 kcal/mole, Ta/sub 6/S: -48.6. Partial pressures of Al over condensed Ta-Al phases were obtained by the coupled mass loss-mass spectrometric version of Knudsen effusion, resulting in enthalpies of formation of: TaAl/sub 3/: -22.7 kcal/mole, Ta/sub 2/Al/sub 3/: -22.6, Ta/sub 2/Al: -8.2, Ta/sub 4/Al: -10.4. Estimated error is +-0.7 kcal/mol atoms in all cases. Data analysis leading to these values demonstrated agreement with the Neumann-Kopp rule for heat capacities of solid compounds in the Ta-Al system but not for Ta-S phases. In the latter case, a derived set of free energy function values for Ta-S, required for agreement of 2nd law and 3rd law determinations of reaction enthalpies, was assessed as physically reasonable when compared to values for the component elements. Enthalpies of atomization for phases in each system were compared to those of chemically similar phases and were seen to be consistent with composition. Comparisons between the two systems suggest that Ta-S interactions are stronger than Ta-Al interactions in energetic terms. Evaluations of bond strengths and stabilities in transition metal sulfides and aluminides in general were based on features of the models proposed by Brewer and Engel and by Miedema. The relevance and adequacy of these models are discussed as applied to the systems in question, and reasons for deviations from predictions by the models are proposed. 57 refs., 20 figs., 13 tabs.

Schmidt, S.R.

1985-04-01

438

Analysis of laser shock waves and resulting surface deformations in an Al-Cu-Li aluminum alloy  

NASA Astrophysics Data System (ADS)

Laser shock processing is now a recognized surface treatment for improving fatigue or corrosion behaviour of metallic materials through the generation of a compressive stress field. In turn, the analysis of shock wave propagation is of primary importance to predict numerically morphological and mechanical surface modifications. Considering experimental and numerical analyses of shock wave propagation, and surface deformations induced by single impacts, a 2050 aluminum alloy having different microstructures was investigated under laser-shock loading. In a first step, the evolution of shock wave attenuation and elastic precursor amplitude was correctly reproduced by finite element simulations, and in a second step, surface deformations induced by 1-6 local impacts were also compared satisfactorily with experiments. This allowed us to validate mechanical loading and materials' constitutive law, but did not allow accurate determination of residual stress fields on a single impact.

Peyre, P.; Berthe, L.; Vignal, V.; Popa, I.; Baudin, T.

2012-08-01

439

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

SciTech Connect

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

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

2004-12-01

440

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

Microsoft Academic Search

We have fabricated laminated metal composites of (1) ultrahigh carbon steel (1.8%C) and brass (70Cu-30Zn), and (2) aluminum 5182 and aluminum 6061 with 25 vol.% SiCp. The laminates were prepared by hot pressing alternating layers of the component materials in an argon gas atmosphere. The steel was thermo-mechanically processed to produce a fine grained microstructure that exhibited superplasticity. The brass

C. K. Syn; D. R. Lesuer; K. L. Cadwell; O. D. Sherby; K. R. Brown

1991-01-01

441

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

Microsoft Academic Search

We have fabricated laminated metal composites of (1) ultrahigh carbon steel (1.8%C) and brass (70Cu-30Zn), and (2) aluminum 5182 and aluminum 6061 with 25 vol.% SiCp. The laminates were prepared by hot pressing alternating layers of the component materials in an argon gas atmosphere. The steel was thermo-mechanically processed to produce a fine grained microstructure that exhibited superplasticity. The brass

C. K. Syn; D. R. Lesuer; K. L. Cadwell; O. D. Sherby; K. R. Brown

1991-01-01

442

Electrolysis of Aluminum Sulfide in Molten Chlorides.  

National Technical Information Service (NTIS)

A laboratory-scale investigation of the production of aluminum by the electrolysis of aluminum sulfide in molten salt electrolytes has been carried out at Argonne National Laboratory. The solubility, electrochemical behavior, and electrolysis of Al sub 2 ...

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

1982-01-01

443

Role of carbon nanotube dispersion in fracture toughening of plasma sprayed aluminum oxide-carbon nanotube nanocomposite coating  

Microsoft Academic Search

Aluminum oxide (Al2O3, or alumina) is a conventional ceramic known for applications such as wear resistant coatings, thermal liners, heaters, crucibles, dielectric systems, etc. However applications of Al 2O3 are limited owing to its inherent brittleness. Due to its excellent mechanical properties and bending strength, carbon nanotubes (CNT) is an ideal reinforcement for Al2O3 matrix to improve its fracture toughness.

Kantesh Balani

2007-01-01

444

The effect of aluminum content on the corrosion behavior of FeAl alloys in reducing environments at 700 °C  

Microsoft Academic Search

The high-temperature corrosion behavior of monolithic Fe-Al alloys, with 0 to 20 wt pct Al, was investigated at 700 C in\\u000a a reducing atmosphere (p(S2) = 10?4 atm, p(O2) = 10?25 atm) for up to 100 hours. Postexposure characterization of the corrosion reaction products consisted of surface and cross-sectional\\u000a microscopy, in combination with energy dispersive spectroscopy, electron probe microanalysis, and

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

2000-01-01

445

The effects of discontinuation of aluminum exposure on aluminum–induced osteomalacia  

Microsoft Academic Search

The effects of discontinuation of aluminum exposure on aluminum–induced osteomalacia. Studies in patients on dialysis have shown that aluminum (Al) accumulation in bone plays a major role in the pathogenesis of osteomalacia. It has been suggested that deferoxamine (DFO) may be beneficial in the treatment of aluminum–induced osteomalacia. The present studies were performed in four groups of uremic rats to

Jane Lewis Finch; Michele Bergfeld; Kevin J Martin; Steven Teitelbaum; Eduardo Slatopolsky

1986-01-01

446

Elevated Temperature Aluminum-Titanium Alloy.  

National Technical Information Service (NTIS)

This abstract discloses an aluminum-titanium alloy and a process of making it. The alloy consist essentially of aluminum, 4-6 wt. % titanium, 1-2 wt. % carbon, and 0.1-0.2 WT. % oxygen. The alloy is an aluminum matrix supersaturated with titanium, and hav...

W. E. Frazier M. J. Koczak

1988-01-01

447

Herstellung eines federelastischen Spangutes geringer Dichte als Matrix für Schüttdämmstoffe, für plattenförmige Dämmstoffe und leichte Spanplatten  

NASA Astrophysics Data System (ADS)

Klimaschutz und die ständig steigenden Energiekosten erfordern eine kontinuierliche Verbesserung der Dämmstoffe. Eine Alternative zur relativ kostenaufwändigen Wärmedämmung durch Platten bzw. Matten auf Basis von mineralischen Stoffen, ist der Einsatz von schütt-bzw. einblasbaren Dämmstoffpartikeln. Späne aus Holz und andere Dämmstoffe aus nachwachsenden Rohstoffen waren schon vor dem ersten Weltkrieg die gebräuchlichsten Dämmstoffe überhaupt. Seit etwa fünfzehn Jahren werden u.a. für den Holzhausbau im zunehmenden Maße auch Fräs-, Säge und Hobelspäne für Wärmedämmzwecke eingesetzt [1], [2], [3]. Hervorzuheben ist der ökologische Aspekt dieser Dämmstoffe durch die Bindung von CO2 und den sinkenden Heizenergiebedarf. Die bisherige Philosophie bei der Gewinnung von Dämmstoffspänen beruhte darauf, anfallendes Spangut stofflich weiter zu nutzen. Die Recyclingspäne sollten dabei sowohl die Setzungssicherheit als auch eine möglichst gute Wärmedämmung gewährleisten.

Tröger, Johannes; Groß, Lucia

448