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

Description: 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.
Date: June 8, 2000
Creator: Hall, Aaron C. & Economy, J.
Partner: UNT Libraries Government Documents Department
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A new active solder for joining electronic components

Description: Electronic components and micro-sensors utilize ceramic substrates, copper and aluminum interconnect and silicon. The joining of these combinations require pre-metallization such that solders with fluxes can wet such combinations of metals and ceramics. The paper will present a new solder alloy that can bond metals, ceramics and composites. The alloy directly wets and bonds in air without the use flux or premetallized layers. The paper will present typical processing steps and joint microstruct… more
Date: May 11, 2000
Creator: Smith, Ronald W.; Vianco, Paul T.; Hernandez, Cynthia L.; Lugscheider, E.; Rass, I. & Hillen, F.
Partner: UNT Libraries Government Documents Department
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Laser welding of automotive aluminum alloys to achieve defect-free, structurally sound and reliable welds

Description: The objective of this program was to seek improved process control and weldment reliability during laser welding of automotive aluminum alloys while retaining the high speed and accuracy of the laser beam welding process. The effects of various welding variables on the loss of alloying elements and the formation of porosity and other geometric weld defects such as underfill and overfill were studied both experimentally and theoretically.
Date: November 17, 2000
Creator: DebRoy, T.
Partner: UNT Libraries Government Documents Department
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Mechanical properties of high strength aluminum alloys formed by pulsed laser deposition

Description: Very high-strength alloys of A1(O) have been formed using a pulsed laser deposition (PLD) system to deposit from alternating targets of A1 and A1{sub 2}O{sub 3}. Ion beam analysis and transmission electron microscopy show that the deposited material is uniform in composition with up to 33 at. % O and has a highly refined microstructure consisting of a fine, uniform dispersion of {approximately}1 nm diameter {gamma}-A1{sub 2}O{sub 3} precipitates. Ultra-low-load indentation testing combined with… more
Date: December 31, 1995
Creator: Knapp, J.A. & Follstaedt, D.M.
Partner: UNT Libraries Government Documents Department
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Processing and Characterizing Alumina/Aluminum Composites with Tailored Microstructures Formed by Reactive Metal Penetration

Description: In industry, the need to maximize energy efficiency depends on the availability of suitable advanced materials. Ceramic composites are exemplary materials for many advanced engineering applications because they exhibit good thermal stability, oxidation resistance and enhanced toughness. Presently, ceramic composite fabrication processes are costly, often requiring high temperatures and pressures to achieve reasonable densities. Our research is focused on developing a processing technique, that … more
Date: January 28, 1999
Creator: Corral, E.; Ellerby, D.; Ewsuk, K.; Fahrenholtz, B. & Loehman, R.
Partner: UNT Libraries Government Documents Department
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Geochemistry of Aluminum in High Temperature Brines

Description: The objective ofthis research is to provide quantitative data on the equilibrium and thermodynamic properties of aluminum minerals required to model changes in permeability and brine chemistry associated with fluid/rock interactions in the recharge, reservoir, and discharge zones of active geothermal systems. This requires a precise knowledge of the thermodynamics and speciation of aluminum in aqueous brines, spanning the temperature and fluid composition rangesencountered in active systems. Th… more
Date: May 18, 1999
Creator: Benezeth, P.; Palmer, D. A. & Wesolowski, D. J.
Partner: UNT Libraries Government Documents Department
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Fabrication, phase transformation studies, and characterization of SiC-AlN-Al{sub 2}OC ceramics. Final report

Description: Principal focus was on phase transformation, microstructure development, and elevated temperature creep, with some effort on room- temperature mechanical properties of selected materials. Fabrication was largely hot pressing, although many of the compositions can be densified by pressureless sintering; hot pressing was to ensure full attainment of density with fine microstructure. Most of the work was on SiC-AlN and AlN-Al{sub 2}OC pseudobinaries.
Date: February 28, 1994
Creator: Virkar, A. V.
Partner: UNT Libraries Government Documents Department
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Energetic-particle synthesis of nanocomposite Al alloys

Description: Ion implantation of O into Al and growth of Al(O) layers using electro-cyclotron resonance plasma and pulsed laser depositions produce composite alloys with a high density of nanometer-size oxide precipitates in an Al matrix. The precipitates impart high strength to the alloy and reduced adhesion during sliding contact, while electrical conductivity and ductility are retained. Implantation of N into Al produces similar microstructures and mechanical properties. The athermal energies of deposite… more
Date: November 26, 1996
Creator: Follstaedt, D. M.; Knapp, J. A.; Barbour, J. C.; Myers, S. M. & Dugger, M. T.
Partner: UNT Libraries Government Documents Department
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Transport in arrays of submicron Josephson junctions over a ground plane

Description: One-dimensional (1D) and two-dimensional (2D) arrays of Al islands linked by submicron Al/Al{sub x}O{sub y}/Al tunnel junctions were fabricated on an insulating layer grown on a ground plane. The arrays were cooled to temperatures as low as 20 mK where the Josephson coupling energy E{sub J} of each junction and the charging energy E{sub C} of each island were much greater than the thermal energy k{sub B}T. The capacitance C{sub g} between each island and the ground plane was much greater than t… more
Date: December 1, 1997
Creator: Ho, Teressa Rae
Partner: UNT Libraries Government Documents Department
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Shock compression of quartz and aluminum powder mixtures

Description: The authors report about the shock-compression response of highly porous (55% and 65% dense) mixtures of 4Al + 3SiO{sub 2} powders having shock-induced phase transitions and chemical reactions. Shock recovery experiments were performed using the CETR/Sawaoka plate-impact system (P = 40 to 100 GPa) and the Sandia Momma Bear A Comp B fixture (P = 22 to 45 GPa). The recovered compacts contained the high pressure stishovite phase, products of chemical reaction, as well as unreacted constituents. Th… more
Date: November 1, 1995
Creator: Joshi, V. S.; Thadhani, N. N.; Graham, R. A. & Holman, G. T., Jr.
Partner: UNT Libraries Government Documents Department
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Low-energy deposition of high-strength Al(0) alloys from an ECR plasma

Description: Low-energy deposition of Al(O) alloys from an electron cyclotron resonance (ECR) plasma offers a scaleable method for the synthesis of thick, high-strength Al layers. This work compares alloy layers formed by an ECR-0{sub 2} plasma in conjunction with Al evaporation to 0-implanted Al (ion energies 25-200 keV); and it examines the effects of volume fraction of A1{sub 2}0{sub 3} phase and deposition temperature on the yield stress of the material. TEM showed the Al(O) alloys contain a dense dispe… more
Date: December 31, 1995
Creator: Barbour, J. C.; Follstaedt, D. M.; Knapp, J. A.; Myers, S. M.; Marshall, D. A. & Lad, R. J.
Partner: UNT Libraries Government Documents Department
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A molecular dynamics study of the {Sigma}11 <1{bar 1}0>/(113)(133) grain boundary in Al and Al-Cu

Description: We present results of molecular dynamics simulation studies of Cu segregation to the {Sigma}11{l_angle}1{bar 1}0{r_angle}/(113)(113) grain boundary (GB) in Al. Simulations were performed with EAM potentials for Al and Al-Cu. Results predict that Cu atoms tend to order along either side of the interface even in the pure symmetrical tilt boundary, forming alternating chains along the {l_angle}{bar 3}{bar 3}2{r_angle} direction. Nucleation of the chains is driven by a change in the local atomic le… more
Date: May 16, 1996
Creator: Huang, H.; Rubia, D. de la & Fluss, M.J.
Partner: UNT Libraries Government Documents Department
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Oxidation dynamics of nanophase aluminum clusters : a molecular dynamics study.

Description: Oxidation of an aluminum nanocluster (252,158 atoms) of radius 100{angstrom} placed in gaseous oxygen (530,727 atoms) is investigated by performing molecular-dynamics simulations on parallel computers. The simulation takes into account the effect of charge transfer between Al and O based on the electronegativity equalization principles. We find that the oxidation starts at the surface of the cluster and the oxide layer grows to a thickness of {approximately}28{angstrom}. Evolutions of local tem… more
Date: January 27, 1998
Creator: Ogata, S.
Partner: UNT Libraries Government Documents Department
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Formation of Chromate Conversion Coatings on Aluminum and Its Alloys: An in Situ Xanes Study.

Description: We used in situ X-ray adsorption near-edge structure (XANES) to investigate the formation of chromate conversion coatings on pure Al, commercial Al alloys (AA 1100, AA2024, and AA7075), and a series of binary Al-Cu alloys. The method employed a new electrochemical cell that can determine the ratio of hexavalent chromium (Cr(VI)) to total chromium (Cr(total)) speciation in conversion coatings as a function of exposure time to a chromate solution. The spectra showed that the initial Cr(VI)/Cr(tot… more
Date: September 2, 2001
Creator: Sasaki, K.; Isaacs, H. S.; Jaffcoate, C. S.; Buchhait, R.; Legat, V.; Lee, H. et al.
Partner: UNT Libraries Government Documents Department
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Studies of hydrogen embrittlement and stress-corrosion cracking in an aluminum-zinc-magnesium alloy. [5. 6 Zn - 2. 6 Mg]

Description: Tensile tests have been carried out on a high-purity A1-5.6 Zn-2.6 Mg alloy hydrogenated by exposure to moist air. Results indicate that internal hydrogen embrittlement occurs by the formation and rupture of a stress-induced hydride at the grain boundaries. The hydride, identified by electron diffraction as A1H/sub 3/, is shown to be unstable in laboratory air, reverting to aluminum. The hydride phase was not detected in specimens failed by SCC, despite evidence that hydrogen is transported ahe… more
Date: January 1, 1980
Creator: Ciaraldi, S. W.; Nelson, J. L.; Yeske, R. A. & Pugh, E. N.
Partner: UNT Libraries Government Documents Department
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Neutron Yield Measurements via Aluminum Activation

Description: Neutron activation of aluminum may occur by several neutron capture reactions. Four such reactions are described here: {sup 27}Al + n = {sup 28}Al, {sup 27}Al(n,{alpha}){sup 24}Na, {sup 27}Al(n, 2n){sup 26}Al and {sup 27}Al(n,p){sup 27}Mg. The radioactive nuclei {sup 28}Al, {sup 24}Na, and {sup 27}Mg, which are produced via the {sup 27}Al + n = {sup 28}Al, {sup 27}Al(n,{alpha}){sup 24}Na and {sup 27}Al(n,p){sup 27}Mg neutron reactions, beta decay to excited states of {sup 28}Si, {sup 24}Mg and … more
Date: December 8, 1999
Partner: UNT Libraries Government Documents Department
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Hollow-anode plasma source for molecular beam epitaxy of gallium nitride

Description: GaN films have been grown by molecular beam epitaxy (MBE) using a hollow-anode nitrogen plasma source. The source was developed to minimize defect formation as a result of contamination and ion damage. The hollow-anode discharge is a special form of glow discharge with very small anode area. A positive anode voltage drop of 30--40 V and an increased anode sheath thickness leads to ignition of a relatively dense plasma in front of the anode hole. Driven by the pressure gradient, the ``anode`` pl… more
Date: September 1, 1995
Creator: Anders, A.; Newman, N.; Rubin, M.; Dickinson, M.; Thomson, A.; Jones, E. et al.
Partner: UNT Libraries Government Documents Department
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A method for treating electrolyte to remove Li{sub 2}O

Description: Electrorefining has been used in processes for recovering uranium and plutonium metals from spent nuclear fuel. The electrorefining is performed in an electrochemical cell in which the chopped fuel elements from the reactor forms the anode, the electrolyte, preferably, is the fused eutectic salt of the LiCl-KCl which contain UCl{sub 3} and PuCl{sub 3}. Purified metal collected at the cathode collects at the bottom of the cell. This invention provides a method for removing lithium oxide from the… more
Date: April 1, 1998
Creator: Tomczuk, Z.; Miller, W. E.; Johnson, G. K. & Willit, J. L.
Partner: UNT Libraries Government Documents Department
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Measurement of the density of liquid aluminum-319 alloy by an x-ray attenuation technique

Description: This study was made for assisting in casting simulations. A relatively simple apparatus was constructed for measuring the density of Al-based alloys in the solid and liquid states up to 900 C. One of the more important physical properties of a casting alloy, solidification shrinkage, was measured for a commercial Al alloy (Al-319). It was found that while the thermal expansion of Al-319 in both solid and liquid phases is similar to that of pure Al, the density of the liquid alloy is lower than … more
Date: November 1, 1994
Creator: Smith, P.M. & Gallegos, G.F.
Partner: UNT Libraries Government Documents Department
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Die Soldering in Aluminium Die Casting

Description: Two types of tests, dipping tests and dip-coating tests were carried out on small steel cylinders using pure aluminum and 380 alloy to investigate the mechanism of die soldering during aluminum die casting. Optical and scanning electron microscopy were used to study the morphology and composition of the phases formed during soldering. A soldering mechanism is postulated based on experimental observations. A soldering critical temperature is postulated at which iron begins to react with aluminum… more
Date: March 15, 2000
Creator: Han, Q.; Kenik, E.A. & Viswanathan, S.
Partner: UNT Libraries Government Documents Department
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The Effect of Surface Contamination on Adhesive Forces as Measured by Contact Mechanics

Description: The contact adhesive forces between two surfaces, one being a soft hemisphere and the other being a hard plate, can readily be determined by applying an external compressive load to mate the two surfaces and subsequently applying a tensile load to peel the surfaces apart. The contact region is assumed the superposition of elastic Hertzian pressure and of the attractive surface forces that act only over the contact area. What are the effects of the degree of surface contamination on adhesive for… more
Date: December 18, 2000
Creator: Emerson, John A.; Giunta, Rachel K.; Miller, Gregory V.; Sorensen, Christopher R. & Pearson, Raymond A.
Partner: UNT Libraries Government Documents Department
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Surface alloying of silicon into aluminum substrate.

Description: Aluminum alloys that are easily castable tend to have lower silicon content and hence lower wear resistance. The use of laser surface alloying to improve the surface wear resistance of 319 and 320 aluminum alloys was examined. A silicon layer was painted onto the surface to be treated. A high power pulsed Nd:YAG laser with fiberoptic beam delivery was used to carry out the laser surface treatment to enhance the silicon content. Process parameters were varied to minimize the surface roughness fr… more
Date: October 28, 1998
Creator: Xu, Z.
Partner: UNT Libraries Government Documents Department
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