The Effect of Modulation Ratio of Cu/Ni Multilayer Films on the Fretting Damage Behaviour of Ti-811 Titanium Alloy

PubMed Central

Zhang, Xiaohua; Liu, Daoxin; Li, Xiaoying; Dong, Hanshan; Xi, Yuntao

2017-01-01

To improve the fretting damage (fretting wear and fretting fatigue) resistance of Ti-811 titanium alloy, three Cu/Ni multilayer films with the same modulation period thickness (200 nm) and different modulation ratios (3:1, 1:1, 1:3) were deposited on the surface of the alloy via ion-assisted magnetron sputtering deposition (IAD). The bonding strength, micro-hardness, and toughness of the films were evaluated, and the effect of the modulation ratio on the room-temperature fretting wear (FW) and fretting fatigue (FF) resistance of the alloy was determined. The results indicated that the IAD technique can be successfully used to prepare Cu/Ni multilayer films, with high bonding strength, low-friction, and good toughness, which yield improved room-temperature FF and FW resistance of the alloy. For the same modulation period (200 nm), the micro-hardness, friction, and FW resistance of the coated alloy increased, decreased, and improved, respectively, with increasing modulation ratio of the Ni-to-Cu layer thickness. However, the FF resistance of the coated alloy increased non-monotonically with the increasing modulation ratio. Among the three Cu/Ni multilayer films, those with a modulation ratio of 1:1 can confer the highest FF resistance to the Ti-811 alloy, owing mainly to their unique combination of good toughness, high strength, and low-friction. PMID:28772947

Current Trends of Blanket Research and Deveopment in Japan 4.Blanket Technology Development Using ITER for Demonstration and Commercial Fusion Power Plant

NASA Astrophysics Data System (ADS)

Akiba, Masato; Jitsukawa, Shiroh; Muroga, Takeo

This paper describes the status of blanket technology and material development for fusion power demonstration plants and commercial fusion plants. In particular, the ITER Test Blanket Module, IFMIF, JAERI/DOE HFIR and JUPITER-II projects are highlighted, which have the important role to develop these technology. The ITER Test Blanket Module project has been conducted to demonstrate tritium breeding and power generation using test blanket modules, which will be installed into the ITER facility. For structural material development, the present research status is overviewed on reduced activation ferritic steel, vanadium alloys, and SiC/SiC composites.

Metal alloy identifier

DOEpatents

Riley, William D.; Brown, Jr., Robert D.

1987-01-01

To identify the composition of a metal alloy, sparks generated from the alloy are optically observed and spectrographically analyzed. The spectrographic data, in the form of a full-spectrum plot of intensity versus wavelength, provide the "signature" of the metal alloy. This signature can be compared with similar plots for alloys of known composition to establish the unknown composition by a positive match with a known alloy. An alternative method is to form intensity ratios for pairs of predetermined wavelengths within the observed spectrum and to then compare the values of such ratios with similar values for known alloy compositions, thereby to positively identify the unknown alloy composition.

Hydrogen storage compositions

DOEpatents

Li, Wen; Vajo, John J.; Cumberland, Robert W.; Liu, Ping

2011-04-19

Compositions for hydrogen storage and methods of making such compositions employ an alloy that exhibits reversible formation/deformation of BH.sub.4.sup.- anions. The composition includes a ternary alloy including magnesium, boron and a metal and a metal hydride. The ternary alloy and the metal hydride are present in an amount sufficient to render the composition capable of hydrogen storage. The molar ratio of the metal to magnesium and boron in the alloy is such that the alloy exhibits reversible formation/deformation of BH.sub.4.sup.- anions. The hydrogen storage composition is prepared by combining magnesium, boron and a metal to prepare a ternary alloy and combining the ternary alloy with a metal hydride to form the hydrogen storage composition.

The effect of alloy composition on the mechanism of stress corrosion cracking of titanium alloys in aqueous environments

NASA Technical Reports Server (NTRS)

Boyd, J. D.; Williams, D. N.; Wood, R. A.; Jaffee, R. I.

1972-01-01

The effects of alloy composition on the aqueous stress corrosion of titanium alloys were studied with emphasis on determining the interrelations among composition, phase structure, and deformation and fracture properties of the alpha phase in alpha-beta alloys. Accomplishments summarized include the effects of alloy composition on susceptibility, and metallurgical mechanisms of stress-corrosion cracking.

Size-confined fixed-composition and composition-dependent engineered band gap alloying induces different internal structures in L-cysteine-capped alloyed quaternary CdZnTeS quantum dots

NASA Astrophysics Data System (ADS)

Adegoke, Oluwasesan; Park, Enoch Y.

2016-06-01

The development of alloyed quantum dot (QD) nanocrystals with attractive optical properties for a wide array of chemical and biological applications is a growing research field. In this work, size-tunable engineered band gap composition-dependent alloying and fixed-composition alloying were employed to fabricate new L-cysteine-capped alloyed quaternary CdZnTeS QDs exhibiting different internal structures. Lattice parameters simulated based on powder X-ray diffraction (PXRD) revealed the internal structure of the composition-dependent alloyed CdxZnyTeS QDs to have a gradient nature, whereas the fixed-composition alloyed QDs exhibited a homogenous internal structure. Transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis confirmed the size-confined nature and monodispersity of the alloyed nanocrystals. The zeta potential values were within the accepted range of colloidal stability. Circular dichroism (CD) analysis showed that the surface-capped L-cysteine ligand induced electronic and conformational chiroptical changes in the alloyed nanocrystals. The photoluminescence (PL) quantum yield (QY) values of the gradient alloyed QDs were 27-61%, whereas for the homogenous alloyed QDs, the PL QY values were spectacularly high (72-93%). Our work demonstrates that engineered fixed alloying produces homogenous QD nanocrystals with higher PL QY than composition-dependent alloying.

THERMODYNAMICS AND KINETICS OF PHASE TRANSFORMATIONS IN PLUTONIUM ALLOYS - PART I

DOE Office of Scientific and Technical Information (OSTI.GOV)

Turchi, P A; Kaufman, L; Liu, Z

2004-08-18

In this report we investigate order, stability, and phase transformations for a series of actinide-based alloys. The statics and kinetics of precipitation and ordering in this class of alloys are modeled with a scheme that couples fundamental information on the alloy energetics obtained from experimental and assessed thermo-chemical data to the CALPHAD approach commonly used in industry for designing alloys with engineering specificity with the help of the Thermo-Calc software application. The CALPHAD approach is applied to the study of the equilibrium thermodynamic properties of Pu-based alloys, Pu-X, where X=Al, Fe, Ga. The assessment of the equilibrium phase diagrams inmore » the whole range of alloy composition has been performed with the PARROT module of the Thermo-Calc application software. Predictions are made on the low temperature and Pu-rich side of the phase diagrams of Pu-Ga and Pu-Al for which controversy has been noted in the past. The validity of the assessed thermo-chemical database will be discussed by comparing predicted heats of transformation for pure Pu with measured values from differential scanning calorimetry analysis. An overall picture for the stability properties of Pu-Ga and Pu-Al that reconciles the results of past studies carried out on these alloys is proposed. Results on phase stability in the ternary Fe-Ga-Pu and Al-Fe-Pu alloys are discussed. The information collected in this study is then used to model metastability, long-term stability and aging for this class of alloys by coupling Thermo-Calc with DICTRA, a series of modules that allow the analysis of DIffusion Controlled TRAnsformations. Kinetics information is then summarized in so-called TTT (temperature-time-transformations) diagrams for the most relevant phases of actinide alloys. Specifically, results are presented on kinetics of phase transformations associated with the eutectoid-phase decomposition reaction occurring at low temperature, and with the martensitic transformation that takes place at low Ga content in Pu-Ga alloys. Finally, after a summary of the most salient results, suggestions are made for further studies at the micro- and mesoscales.« less

Finite Element Analysis of Composite Aircraft Fuselage Frame

NASA Astrophysics Data System (ADS)

Dandekar, Aditya Milind

Composites have been introduced in aircraft industries, for their stronger, stiffer, and lighter properties than their metal-alloys counterparts. The general purpose of an aircraft is to transport commercial or military payload. Aircraft frames primarily maintains the shape of fuselage and prevent instability of the structure. Fuselage is similar as wing in construction which consist of longitudinal elements (longerons and stringers), transverse elements (frames and bulkheads) and its external skin. The fuselage is subjected to forces such as the wing reactions, landing gear reaction, empennage reaction, inertia forces subjected due to size and weight, internal pressure forces due to high altitude. Frames also ensure fail-safe design against skin crack propagation due to hoops stress. Ideal fuselage frames cross section is often circular ring shape with a frame cap of Z section. They are mainly made up of light alloy commonly used is aluminium alloys such as Al-2024, Al-7010, Al-7050, Al-7175. Aluminium alloys have good strength to density ratios in compression and bending of thin plate. A high strength to weight ratio of composite materials can result in a lighter aircraft structure or better safety factor. This research focuses on analysis of fuselage frame under dynamic load condition with change in material. Composites like carbon fibre reinforced plastics [CFRP] and glass fibre reinforced plastics [GFRP] are compared with traditional aluminium alloy Al-7075. The frame is subjected to impact test by dropping it at a velocity of 30 ft. / secs from a height of 86 inch from its centre of gravity. These parameters are considered in event of failure of landing gear, and an aircraft is subject to belly landing or gear-up landing. The shear flow is calculated due to impact force which acts in radial direction. The frame is analysed under static structural and explicit dynamic load conditions. Geometry is created in ANSYS Design Modeler. Analysis setup is created using ANSYS Explicit Dynamic (AUTODYN) and ANSYS Composite PrepPost (ACP-Pre) modules. Shear flow and Stress Flow equations are solved by generating a MATLAB code.

Vibrational properties of Ni-Mn-Ga shape memory alloy in the martensite phases

NASA Astrophysics Data System (ADS)

Ener, Semih; Mehaddene, Tarik; Pedersen, Björn; Leitner, Michael; Neuhaus, Jürgen; Petry, Winfried

2013-12-01

Studying the phonon dispersion of the ferromagnetic shape memory alloy system Ni-Mn-Ga gives insight into the mechanism of the martensite transition and the forces driving the transition. Transformation of austenite single crystals under uniaxial stress results in the coexistence of two martensitic variants with perpendicular modulation vector. Here we report on inelastic neutron scattering studies of martensite crystals with off-stoichiometric compositions, varying from non-modulated (NM) to five- (5M) and seven- (7M) layer modulated martensite phases. Both the 5M and 7M crystals show fully commensurate satellite peaks along [\\xi \\bar {\\xi } 0], corresponding to the five- and seven-layer modulation. These superstructure peaks become Γ-points of the modulated structure. Due to the coexistence of two variants within the (001) plane, both new acoustic phonons reflecting the modulation vector [\\xi \\bar {\\xi } 0] and acoustic TA2[ξξ0] phonons corresponding to the non-modulated direction are observed. The latter display a pronounced softening around ξ = 0.2-0.4 when approaching the martensite-austenite transition from above and below, i.e. this soft mode has lowest frequency at the transition temperature. Overall the phonon dispersion of the austenite and martensite phase resemble each other very much. The coexistence of two martensitic variants after uniaxial transformation explains the particular behaviour of the low-energy excitations, in contrast to previous interpretations involving charge-density waves and associated phason modes.

Effects of Stoichiometry on Transformation Temperatures and Actuator-Type Performance of NiTiPd and NiTiPdX High-Temperature Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Bigelow, Glen S.; Gaydosh, Darrell; Garg, Anita; Padula, Santo A., II; Noebe, Ronald D.

2007-01-01

High-temperature shape memory NiTiPd and NiTiPdX (X=Au, Pt, Hf) alloys were produced with titanium equivalent (Ti+Hf) compositions of 50.5, 50.0, 49.5, and 49.0 at.%. Thermo-mechanical testing in compression was used to evaluate the transformation temperatures, transformation strain, work output, and permanent deformation behavior of each alloy to study the effects of quaternary alloying and stoichiometry on high-temperature shape memory alloy behavior. Microstructural evaluation showed the presence of second phases for all alloy compositions. No load transformation temperatures in the stoichiometric alloys were relatively unchanged by Au and Pt substitutions, while the substitution of Hf for Ti causes a drop in transformation temperatures. The NiTiPd, NiTiPdAu and NiTiPdHf alloys exhibited transformation temperatures that were highest in the Ti-rich compositions, slightly lower at stoichiometry, and significantly reduced when the Ti equivalent composition was less than 50 at.%. For the NiTiPdPt alloy, transformation temperatures were highest for the Ti-rich compositions, lowest at stoichiometry, and slightly higher in the Ni-rich composition. When thermally cycled under constant stresses of up to 300 MPa, all of the alloys had transformation strains, and therefore work outputs, which increased with increasing stress. In each series of alloys, the transformation strain and thus work output was highest for stoichiometric or Ti-rich compositions while permanent strain associated with the constant-load thermal cycling was lowest for alloys with Ni-equivalent-rich compositions. Based on these results, basic rules for optimizing the composition of NiTiPd alloys for actuator performance will be discussed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, J. P.; Wang, Y. D.; Hao, Y. L.

Two main explanations exist for the deformation mechanisms in Ti-Nb-based gum metals, i.e. the formation of reversible nanodisturbance and reversible stress-induced martensitic transformation. In this work, we used the in situ synchrotron-based high-energy X-ray diffuse-scattering technique to reveal the existence of a specific deformation mechanism, i.e. deformation-induced spatially confined martensitic transformations, in Ti-24Nb-4Zr-8Sn-0.10O single crystals with cubic 13 parent phase, which explains well some anomalous mechanical properties of the alloy such as low elastic modulus and nonlinear superelasticity. Two kinds of nanosized martensites with different crystal structures were found during uniaxial tensile loading along the [11 0](beta) axis at roommore » temperature and 190 K, respectively. The detailed changes in the martensitic phase transformation characteristics and the transformation kinetics were experimentally observed at different temperatures. The domain switch from non-modulated martensite to a modulated one occurred at 190 K, with its physical origin attributed to the heterogeneity of local phonon softening depending on temperature and inhomogeneous composition in the parent phase. An in-depth understanding of the formation of stress-induced spatially confined nanosized martensites with a large gradient in chemical composition may benefit designs of high-strength and high-ductility alloys. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.« less

Applications of Materials Selection For Joining Composite/Alloy Piping Systems

NASA Technical Reports Server (NTRS)

Crosby, Karen E.; Smith, Brett H.; Mensah, Patrick F.; Stubblefield, Michael A.

2001-01-01

A study in collaboration between investigators at Southern University and Louisiana State University in Baton Rouge, Louisiana and NASA/MSFC is examining materials for modeling and analysis of heat-activated thermal coupling for joining composite to composite/alloy structures. The short-term objectives of this research are to develop a method for joining composite or alloy structures, as well as to study the effects of thermal stress on composite-to-alloy joints. This investigation will result in the selection of a suitable metallic alloy. Al-Li alloys have potential for this purpose in aerospace applications due to their excellent strength-to-weight ratio. The study of Al-Li and other alloys is of significant importance to this and other aerospace as well as offshore related interests. Further research will incorporate the use of computer aided design and rapid prototype hardware for conceptual design and verification of a potential composite piping delivery system.

Effect of Iron Impurity on the Phase Composition, Structure and Properties of Magnesium Alloys Containing Manganese and Aluminum

NASA Astrophysics Data System (ADS)

Volkova, E. F.

2017-07-01

Results of a study of the interaction between iron impurity and manganese and aluminum alloying elements during formation of phase composition in alloys of the Mg - Mn, Mg - Al, Mg - Al - Mn, and Mg - Al - Zn - Mn systems are presented. It is proved that this interaction results in introduction of Fe into the intermetallic phase. The phase compositions of model magnesium alloys and commercial alloys MA2-1 and MA5 are studied. It is shown that both manganese and aluminum may bind the iron impurity into phases. Composite Fe-containing intermetallic phases of different compositions influence differently the corrosion resistance of magnesium alloys.

Strain-Detecting Composite Materials

NASA Technical Reports Server (NTRS)

Wallace, Terryl A. (Inventor); Smith, Stephen W. (Inventor); Piascik, Robert S. (Inventor); Horne, Michael R. (Inventor); Messick, Peter L. (Inventor); Alexa, Joel A. (Inventor); Glaessgen, Edward H. (Inventor); Hailer, Benjamin T. (Inventor)

2016-01-01

A composite material includes a structural material and a shape-memory alloy embedded in the structural material. The shape-memory alloy changes crystallographic phase from austenite to martensite in response to a predefined critical macroscopic average strain of the composite material. In a second embodiment, the composite material includes a plurality of particles of a ferromagnetic shape-memory alloy embedded in the structural material. The ferromagnetic shape-memory alloy changes crystallographic phase from austenite to martensite and changes magnetic phase in response to the predefined critical macroscopic average strain of the composite material. A method of forming a composite material for sensing the predefined critical macroscopic average strain includes providing the shape-memory alloy having an austenite crystallographic phase, changing a size and shape of the shape-memory alloy to thereby form a plurality of particles, and combining the structural material and the particles at a temperature of from about 100-700.degree. C. to form the composite material.

Microstructure Evolution in the Presence of Constraints and Implications on the Properties of Mg - Li and Nb - Al Composites

DTIC Science & Technology

1991-05-30

alloys and composites Solidification experiments with Succinonitrile-acetone system Experimerts with Salol I Directional Solidification of Mg-Li alloys ...Directional Solidification of Mg-Li Composites Microstructural Analysis and Modeling Combustion Synthesis Principles ( theory ) Nb-AI alloys made by...Combustion Synthesis Nb-AI - NbB composites made by Combustion Synthesis Directional Solidification of Nb-AI Alloys Directional Solidification of Nb- Al

Nanostructured calcium phosphate coatings on magnesium alloys: characterization and cytocompatibility with mesenchymal stem cells

PubMed Central

Iskandar, Maria Emil; Aslani, Arash; Tian, Qiaomu

2016-01-01

This article reports the deposition and characterization of nanostructured calcium phosphate (nCaP) on magnesium–yttrium alloy substrates and their cytocompatibility with bone marrow derived mesenchymal stem cells (BMSCs). The nCaP coatings were deposited on magnesium and magnesium–yttrium alloy substrates using proprietary transonic particle acceleration process for the dual purposes of modulating substrate degradation and BMSC adhesion. Surface morphology and feature size were analyzed using scanning electron microscopy and quantitative image analysis tools. Surface elemental compositions and phases were analyzed using energy dispersive X-ray spectroscopy and X-ray diffraction, respectively. The deposited nCaP coatings showed a homogeneous particulate surface with the dominant feature size of 200–500 nm in the long axis and 100–300 nm in the short axis, and a Ca/P atomic ratio of 1.5–1.6. Hydroxyapatite was the major phase identified in the nCaP coatings. The modulatory effects of nCaP coatings on the sample degradation and BMSC behaviors were dependent on the substrate composition and surface conditions. The direct culture of BMSCs in vitro indicated that multiple factors, including surface composition and topography, and the degradation-induced changes in media composition, influenced cell adhesion directly on the sample surface, and indirect adhesion surrounding the sample in the same culture. The alkaline pH, the indicator of Mg degradation, played a role in BMSC adhesion and morphology, but not the sole factor. Additional studies are necessary to elucidate BMSC responses to each contributing factor. PMID:25917827

Nanostructured calcium phosphate coatings on magnesium alloys: characterization and cytocompatibility with mesenchymal stem cells.

PubMed

Iskandar, Maria Emil; Aslani, Arash; Tian, Qiaomu; Liu, Huinan

2015-05-01

This article reports the deposition and characterization of nanostructured calcium phosphate (nCaP) on magnesium-yttrium alloy substrates and their cytocompatibility with bone marrow derived mesenchymal stem cells (BMSCs). The nCaP coatings were deposited on magnesium and magnesium-yttrium alloy substrates using proprietary transonic particle acceleration process for the dual purposes of modulating substrate degradation and BMSC adhesion. Surface morphology and feature size were analyzed using scanning electron microscopy and quantitative image analysis tools. Surface elemental compositions and phases were analyzed using energy dispersive X-ray spectroscopy and X-ray diffraction, respectively. The deposited nCaP coatings showed a homogeneous particulate surface with the dominant feature size of 200-500 nm in the long axis and 100-300 nm in the short axis, and a Ca/P atomic ratio of 1.5-1.6. Hydroxyapatite was the major phase identified in the nCaP coatings. The modulatory effects of nCaP coatings on the sample degradation and BMSC behaviors were dependent on the substrate composition and surface conditions. The direct culture of BMSCs in vitro indicated that multiple factors, including surface composition and topography, and the degradation-induced changes in media composition, influenced cell adhesion directly on the sample surface, and indirect adhesion surrounding the sample in the same culture. The alkaline pH, the indicator of Mg degradation, played a role in BMSC adhesion and morphology, but not the sole factor. Additional studies are necessary to elucidate BMSC responses to each contributing factor.

Platinum-ruthenium-palladium alloys for use as a fuel cell catalyst

DOEpatents

Gorer, Alexander

2002-01-01

A noble metal alloy composition for a fuel cell catalyst, a ternary alloy composition containing platinum, ruthenium and palladium. The alloy shows increased activity as compared to well-known catalysts.

Composite material reinforced with atomized quasicrystalline particles and method of making same

DOEpatents

Biner, S.B.; Sordelet, D.J.; Lograsso, B.K.; Anderson, I.E.

1998-12-22

A composite material comprises an aluminum or aluminum alloy matrix having generally spherical, atomized quasicrystalline aluminum-transition metal alloy reinforcement particles disposed in the matrix to improve mechanical properties. A composite article can be made by consolidating generally spherical, atomized quasicrystalline aluminum-transition metal alloy particles and aluminum or aluminum alloy particles to form a body that is cold and/or hot reduced to form composite products, such as composite plate or sheet, with interfacial bonding between the quasicrystalline particles and the aluminum or aluminum alloy matrix without damage (e.g. cracking or shape change) of the reinforcement particles. The cold and/or hot worked composite exhibits substantially improved yield strength, tensile strength, Young`s modulus (stiffness). 3 figs.

Containerless Measurement of Thermophysical Properties of Ti-Zr-Ni Alloys

NASA Technical Reports Server (NTRS)

Hyers, Robert; Bradshaw, Richard C.; Rogers, Jan C.; Rathz, Thomas J.; Lee, Geun W.; Gangopadhyay, Anup K.; Kelton, Kenneth F.

2004-01-01

The surface tension, viscosity, density, and thermal expansion of Ti-Zr-Ni alloys were measured for a number of compositions by electrostatic levitation methods. Containerless methods greatly reduce heterogeneous nucleation, increasing access to the undercooled liquid regime at finite cooling rates. The density and thermal expansion are measured optically, while the surface tension and viscosity are measured by the oscillating drop method. The measured alloys include compositions which form a metastable quasicrystal phase from the undercooled liquid, and alloys close to the composition of several multi-component bulk metallic glass-forming alloys. Measurements of surface tension show behavior typical of transition metals at high temperature, but a sudden decrease in the deeply undercooled liquid for alloys near the quasicrystal-forming composition range, but not for compositions which form the solid-solution phase first.

High-density interconnect substrates and device packaging using conductive composites

NASA Astrophysics Data System (ADS)

Gandhi, Pradeep; Gallagher, Catherine; Matijasevic, Goran

1998-02-01

High-end printed circuit board manufacturing technology is receiving increasing attention due to higher functionality in smaller form factors. This is evident from the industry efforts to produced reliable microvias and related trace features to pack as much circuit density as possible. Cost, density and performance requirements have prodded entry into a market that was mainly reserved for ceramic and molded packages for the last forty years. To successfully meet the demanding specifications of this market segment, a worldwide effort is underway for the development of new materials, processes and equipment. A novel base technology that is applicable to most of the major packaging and redistribution elements in an electronic module is presented.High density multilayer circuits with landless blind and buried vias can be fabricated by filling the conductor paste into photoimaged dielectrics and thermally processing it at a relatively lower temperature. Via layers are prepared directly on the inherently planarized circuit layer in an identical fashion. Because these composite materials are applied in an additive fabrication method, metal substrates can be employed for high thermal dissipation and excellent CTE control over a wide temperature range. The conductor material is based on interpenetrating polymer and metal networks that are formed in situ from metal particles and a thermosetting flux/binder. The metal network is formed when the alloy particles melt and react with adjacent high melting point metal particle. Interaction also occurs between the alloy particles and pad, lead or previous trace metallizations provided they are solderable by alloys of tin. The new alloy composition created by the interdiffusion process within the bulk material has a higher melting point than the original alloy and thus solidifies immediately upon formation. This metallurgical reaction, known as transient liquid phase sintering, is facilitated by the polymer mixture. INtegration of the polymer and metal networks is maintained by utilizing a thermosetting polymer system that cures simultaneously with the metallurgical reaction. Although similar in concept and performance to cermet inks, these compositions differ in that their process temperatures are compatible with conventional printed wiring board materials and that the polymeric binder remains to provide adhesion and fatigue resistance to the metallurgical network.

Friction and wear of plasma-sprayed coatings containing cobalt alloys from 25 deg to 650 deg in air

NASA Technical Reports Server (NTRS)

Sliney, H. E.; Jacobson, T. P.

1979-01-01

Four different compositions of self-lubricating, plasma-sprayed, composite coatings with calcium fluoride dispersed throughout cobalt alloy-silver matrices were evaluated on a friction and wear apparatus. In addition, coatings of the cobalt alloys alone and one coating with a nickel alloy-silver matrix were evaluated for comparison. The wear specimens consisted of two, diametrically opposed, flat rub shoes sliding on the coated, cylindrical surface of a rotating disk. Two of the cobalt composite coatings gave a friction coefficient of about 0.25 and low wear at room temperature, 400 and 650 C. Wear rates were lower than those of the cobalt alloys alone or the nickel alloy composite coating. However, oxidation limited the maximum useful temperature of the cobalt composite coating to about 650 C compared to about 900 C for the nickel composite coating.

Evolution of the Structure and Phase Composition of Deformable Refractory Nickel Alloys for GTE Discs Upon Complication of Their Alloying

NASA Astrophysics Data System (ADS)

Chabina, E. B.; Filonova, E. V.; Lomberg, B. S.; Morozova, G. I.

2015-07-01

Variation of the phase composition and structure of deformable refractory nickel alloys upon complication of their alloying is considered starting with the ÉI437B pioneer domestic alloy with heterophase hardening and ending with alloy VZh175 used as a material for advanced aircraft engines.

Design of new face-centered cubic high entropy alloys by thermodynamic calculation

NASA Astrophysics Data System (ADS)

Choi, Won-Mi; Jung, Seungmun; Jo, Yong Hee; Lee, Sunghak; Lee, Byeong-Joo

2017-09-01

A new face-centered cubic (fcc) high entropy alloy system with non-equiatomic compositions has been designed by utilizing a CALculation of PHAse Diagram (CALPHAD) - type thermodynamic calculation technique. The new alloy system is based on the representative fcc high entropy alloy, the Cantor alloy which is an equiatomic Co- Cr-Fe-Mn-Ni five-component alloy, but fully or partly replace the cobalt by vanadium and is of non-equiatomic compositions. Alloy compositions expected to have an fcc single-phase structure between 700 °C and melting temperatures are proposed. All the proposed alloys are experimentally confirmed to have the fcc single-phase during materials processes (> 800 °C), through an X-ray diffraction analysis. It is shown that there are more chances to find fcc single-phase high entropy alloys if paying attention to non-equiatomic composition regions and that the CALPHAD thermodynamic calculation can be an efficient tool for it. An alloy design technique based on thermodynamic calculation is demonstrated and the applicability and limitation of the approach as a design tool for high entropy alloys is discussed.

Composite material reinforced with atomized quasicrystalline particles and method of making same

DOEpatents

Biner, Suleyman B.; Sordelet, Daniel J.; Lograsso, Barbara K.; Anderson, Iver E.

1998-12-22

A composite material comprises an aluminum or aluminum alloy matrix having generally spherical, atomized quasicrystalline aluminum-transition metal alloy reinforcement particles disposed in the matrix to improve mechanical properties. A composite article can be made by consolidating generally spherical, atomized quaiscrystalline aluminum-transition metal alloy particles and aluminum or aluminum alloy particles to form a body that is cold and/or hot reduced to form composite products, such as composite plate or sheet, with interfacial bonding between the quasicrystalline particles and the aluminum or aluminum alloy matrix without damage (e.g. cracking or shape change) of the reinforcement particles. The cold and/or hot worked compositehibits substantially improved yield strength, tensile strength, Young's modulus (stiffness).

Effect of SiC Nanoparticles on Hot Deformation Behavior and Processing Maps of Magnesium Alloy AZ91

PubMed Central

Nie, Kaibo; Kang, Xinkai; Deng, Kunkun; Wang, Ting; Guo, Yachao; Wang, Hongxia

2018-01-01

The hot deformation behavior and processing characteristics of AZ91 alloy and nano-SiCp/AZ91 composite were compared at temperature ranges of 523 K–673 K and strain rates of 0.001–1 s−1. Positive impact of SiC nanoparticles on pinning grain boundaries and inhibiting grain growth was not obvious when deformation temperature was below 623 K, but was remarkable when the temperature was above 623 K. By comparing compressive stress-strain curves of AZ91 alloy and nano-SiCp/AZ91 composites, the addition of nanoparticles could improve the deformation ability of a matrix alloy under high-temperature conditions. There was no essential difference of deformation mechanism between AZ91 alloy and the composite, but hot deformation activation energy of the composite was significantly lower than that of the AZ91 alloy. The AZ91 alloy and the composite had the same workability region of 600 K–673 K and 0.001–1 s−1, while instability region for the composite was reduced compared with that of AZ91 alloy at high temperature. PMID:29389888

Characterization of magneto-optical media

NASA Technical Reports Server (NTRS)

Hajjar, Roger A.; Wu, Te-Ho; Mansuripur, M.

1991-01-01

Amorphous rare earth-transition metal (RE-TM) alloys and compositionally modulated TM/TM films were characterized in terms of their magnetic, magneto-optic, and galvanomagnetic properties. The loop tracer, vibrating sample magnetometer (VSM), and Rutherford Backscattering (RBS) facility were used to characterize and analyze the various properties of these magneto-optical storage media. Kerr effect, ellipticity, coercivity, and anisotropy at various temperatures, magnetoresistance, and resistivity are among the properties measured in Co/Pt films, Co/Pd films, and TbFeCo films.

Development of a Hard-Patch Approach for Scarf Repair of Composite Structure

DTIC Science & Technology

2006-06-01

composite skins are bonded to a Ti- 6Al - 4V titanium alloy splice plate. The inboard and outboard ribs are also made of this alloy, as is the root rib which...operation. Options for the patch material include composite laminate, titanium alloy sheet laminate or solid titanium alloy. d) Semi-Hard Patch – The...patch is manufactured from a series of pre-cured composite laminates each containing several plies or titanium sheets, which are interleaved with

Low Cost Al-Si Casting Alloy As In-Situ Composite for High Temperature Applications

NASA Technical Reports Server (NTRS)

Lee, Jonathan A.

2000-01-01

A new aluminum-silicon (Al-Si) alloy has been successfully developed at NASA- Marshall Space Flight Center (MSFC) that has significant improvement in tensile and fatigue strength at elevated temperatures (500 F-700 F). The alloy offers a number of benefits such as light weight, high hardness, low thermal expansion and high surface wear resistance. In hypereutectic form, this alloy is considered as an in-situ Al-Si composite with tensile strength of about 90% higher than the auto industry 390 alloy at 600 F. This composite is very economically produced by using either conventional permanent steel molds or die casting. The projected material cost is less than $0.90 per pound, and automotive components such as pistons can be cast for high production rate using conventional casting techniques with a low and fully accounted cost. Key Words: Metal matrix composites, In-situ composite, aluminum-silicon alloy, hypereutectic alloy, permanent mold casting, die casting.

Microgravity

NASA Image and Video Library

2001-06-05

This scale model depicts the Materials Science Research Rack-1 (MSRR-1) being developed by NASA's Marshall Space Flight Center and the European Space Agency (ESA) for placement in the Destiny laboratory module aboard the International Space Station. The rack is part of the plarned Materials Science Research Facility (MSRF) and is expected to include two furnace module inserts, a Quench Module Insert (being developed by NASA's Marshall Space Flight Center) to study directional solidification in rapidly cooled alloys and a Diffusion Module Insert (being developed by the European Space Agency) to study crystal growth, and a transparent furnace (being developed by NASA's Space Product Development program). Multi-user equipment in the rack is being developed under the auspices of NASA's Office of Biological and Physical Research (OBPR) and ESA. Key elements are labeled in other images (0101754, 0101829, and TBD). This composite is from a digital still camera; higher resolution is not available.

Materials Science Research Rack-1 (MSRR-1)

NASA Technical Reports Server (NTRS)

2001-01-01

This scale model depicts the Materials Science Research Rack-1 (MSRR-1) being developed by NASA's Marshall Space Flight Center and the European Space Agency (ESA) for placement in the Destiny laboratory module aboard the International Space Station. The rack is part of the plarned Materials Science Research Facility (MSRF) and is expected to include two furnace module inserts, a Quench Module Insert (being developed by NASA's Marshall Space Flight Center) to study directional solidification in rapidly cooled alloys and a Diffusion Module Insert (being developed by the European Space Agency) to study crystal growth, and a transparent furnace (being developed by NASA's Space Product Development program). Multi-user equipment in the rack is being developed under the auspices of NASA's Office of Biological and Physical Research (OBPR) and ESA. Key elements are labeled in other images (0101754, 0101829, and TBD). This composite is from a digital still camera; higher resolution is not available.

An evaluation of the benefits of utilizing rapid solidification for development of 2XXX (Al-Cu-Mg) alloys

NASA Technical Reports Server (NTRS)

Paris, H. G.; Chellman, D. J.

1986-01-01

The advantages of rapid solidification processing over ingot metallurgy processing in the development of 2XXX aluminum alloy compositions were evaluated using a similarly processed ingot metallurgy (IM) control alloy. The powder metallurgy (PM) alloy extrusions showed a reduced age-hardening response in comparison with similar IM compositions, with higher tensile properties for naturally aged extrusions but lower properties for artificially aged ones. However, the tensile properties of naturally and artificially aged PM alloy extrusions based on a version of IM 2034 alloy, but containing 0.6 weight percent zirconium, were comparable to those of the IM control extrusions and had significantly superior combinations of strength and toughness. The tensile properties of this PM alloy showed even greater advantage in 6.4-mm (0.25-in.) and 1.8-mm (0.070-in.) plate and sheet, the yield strength being about 68 MPa (10 ksi) greater than reported values for the IM 2034 alloy sheet. An artificially aged PM alloy based on 2219 alloy also showed a strength and strength-toughness combination comparable to those of the PM Al-Cu-Mg-Zr alloy, substantially outperforming the IM 2219 alloy. These results show that rapid solidification offers the flexibility needed to modify conventional IM compositions to produce new alloy compositions with superior mechanical properties.

Improving the corrosion wear resistance of AISI 316L stainless steel by particulate reinforced Ni matrix composite alloying layer

NASA Astrophysics Data System (ADS)

Xu, Jiang; Zhuo, Chengzhi; Tao, Jie; Jiang, Shuyun; Liu, Linlin

2009-01-01

In order to overcome the problem of corrosion wear of AISI 316L stainless steel (SS), two kinds of composite alloying layers were prepared by a duplex treatment, consisting of Ni/nano-SiC and Ni/nano-SiO2 predeposited by brush plating, respectively, and subsequent surface alloying with Ni-Cr-Mo-Cu by a double glow process. The microstructure of the two kinds of nanoparticle reinforced Ni-based composite alloying layers was investigated by means of SEM and TEM. The electrochemical corrosion behaviour of composite alloying layers compared with the Ni-based alloying layer and 316L SS under different conditions was characterized by potentiodynamic polarization test and electrochemical impedance spectroscopy. Results showed that under alloying temperature (1000 °C) conditions, amorphous nano-SiO2 particles still retained the amorphous structure, whereas nano-SiC particles were decomposed and Ni, Cr reacted with SiC to form Cr6.5Ni2.5Si and Cr23C6. In static acidic solution, the corrosion resistance of the composite alloying layer with the brush plating Ni/nano-SiO2 particles interlayer is lower than that of the Ni-based alloying layer. However, the corrosion resistance of the composite alloying layer with the brush plating Ni/nano-SiO2 particles interlayer is prominently superior to that of the Ni-based alloying layer under acidic flow medium condition and acidic slurry flow condition. The corrosion resistance of the composite alloying layer with the brush plating Ni/nano-SiC particles interlayer is evidently lower than that of the Ni-based alloying layer, but higher than that of 316L SS under all test conditions. The results show that the highly dispersive nano-SiO2 particles are helpful in improving the corrosion wear resistance of the Ni-based alloying layer, whereas carbides and silicide phase are deleterious to that of the Ni-based alloying layer due to the fact that the preferential removal of the matrix around the precipitated phase takes place by the chemical attack of an aggressive medium.

Inhomogeneous composition distribution in monolayer transition metal dichalcogenide alloys

NASA Astrophysics Data System (ADS)

Xie, Shuang; Xu, Mingsheng; Huang, Shuyun; Liang, Tao; Wang, Shengping; Li, Hongfei; Iwai, Hideo; Onishi, Keiko; Hanagata, Nobutaka; Fujita, Daisuke; Ma, Xiangyang; Yang, Deren

2017-04-01

Alloying with various compositions is an efficient method to tailor the optoelectronic properties of two-dimensional (2D) transition metal dichalcogenides (TMDs). However, the composition distribution in the monolayer of TMDs alloys lacks detailed investigation. Here, by exploring scanning Auger electron spectroscopy, we investigate the composition distribution in MoS2(1-x)Se2x monolayers with high spatial resolution. Our results demonstrate that inhomogeneous composition distribution exists not only among different nanosheets on a substrate but also within individual nanosheets. Our study would be helpful to develop new methods for controllable synthesis of TMDs alloys and other 2D materials.

Oxidation resistant coating for titanium alloys and titanium alloy matrix composites

NASA Technical Reports Server (NTRS)

Brindley, William J. (Inventor); Smialek, James L. (Inventor); Rouge, Carl J. (Inventor)

1992-01-01

An oxidation resistant coating for titanium alloys and titanium alloy matrix composites comprises an MCrAlX material. M is a metal selected from nickel, cobalt, and iron. X is an active element selected from Y, Yb, Zr, and Hf.

An Undergraduate Experiment Using Differential Scanning Calorimetry: A Study of the Thermal Properties of a Binary Eutectic Alloy of Tin and Lead

ERIC Educational Resources Information Center

D'Amelia, Ronald P.; Clark, Daniel; Nirode, William

2012-01-01

An alloy is an intimate association of two or more metals, with or without a definite composition, which has metallic properties. Heterogeneous alloys, such as tin-lead (Sn/Pb) solders, consist of a mixture of crystalline phases with different compositions. A homogeneous alloy with a unique composition having the lowest possible melting point is…

Interdiffusion in nanometer-scale multilayers investigated by in situ low-angle x-ray diffraction

NASA Astrophysics Data System (ADS)

Wang, Wei-Hua; Bai, Hai Yang; Zhang, Ming; Zhao, J. H.; Zhang, X. Y.; Wang, W. K.

1999-04-01

An in situ low-angle x-ray diffraction technique is used to investigate interdiffusion phenomena in various metal-metal and metal-amorphous Si nanometer-scale compositionally modulated multilayers (ML's). The temperature-dependent interdiffusivities are obtained by accurately monitoring the decay of the first-order modulation peak as a function of annealing time. Activation enthalpies and preexponential factors for the interdiffusion in the Fe-Ti, Ag-Bi, Fe-Mo, Mo-Si, Ni-Si, Nb-Si, and Ag-Si ML's are determined. Activation enthalpies and preexponential factors for the interdiffusion in the ML's are very small compared with that in amorphous alloys and crystalline solids. The relation between the atomic-size difference and interdiffusion in the ML's are investigated. The observed interdiffusion characteristics are compared with that in amorphous alloys and crystalline α-Zr, α-Ti, and Si. The experimental results suggest that a collective atomic-jumping mechanism govern the interdiffusion in the ML's, the collective proposal involving 8-15 atoms moving between extended nonequilibrium defects by thermal activation. The role of the interdiffusion in the solid-state reaction in the ML's is also discussed.

A standards-based method for compositional analysis by energy dispersive X-ray spectrometry using multivariate statistical analysis: application to multicomponent alloys.

PubMed

Rathi, Monika; Ahrenkiel, S P; Carapella, J J; Wanlass, M W

2013-02-01

Given an unknown multicomponent alloy, and a set of standard compounds or alloys of known composition, can one improve upon popular standards-based methods for energy dispersive X-ray (EDX) spectrometry to quantify the elemental composition of the unknown specimen? A method is presented here for determining elemental composition of alloys using transmission electron microscopy-based EDX with appropriate standards. The method begins with a discrete set of related reference standards of known composition, applies multivariate statistical analysis to those spectra, and evaluates the compositions with a linear matrix algebra method to relate the spectra to elemental composition. By using associated standards, only limited assumptions about the physical origins of the EDX spectra are needed. Spectral absorption corrections can be performed by providing an estimate of the foil thickness of one or more reference standards. The technique was applied to III-V multicomponent alloy thin films: composition and foil thickness were determined for various III-V alloys. The results were then validated by comparing with X-ray diffraction and photoluminescence analysis, demonstrating accuracy of approximately 1% in atomic fraction.

Directional Solidification and Mechanical Properties of NiAl-NiAlTa Alloys

NASA Technical Reports Server (NTRS)

Johnson, D. R.; Chen, X. F.; Oliver, B. F.; Noebe, R. D.; Whittenberger, J. D.

1995-01-01

Directional solidification of eutectic alloys is a promising technique for producing in-situ composite materials exhibiting a balance of properties. Consequently, the microstructure, creep strength and fracture toughness of directionally solidified NiAl-NiAlTa alloys were investigated. Directional solidification was performed by containerless processing techniques to minimize alloy contamination. The eutectic composition was found to be NiAl-15.5 at% Ta and well-aligned microstructures were produced at this composition. A near-eutectic alloy of NiAl-14.5Ta was also investigated. Directional solidification of the near-eutectic composition resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The off-eutectic alloy exhibited promising compressive creep strengths compared to other NiAl-based intermetallics, while preliminary testing indicated that the eutectic alloy was competitive with Ni-base single crystal superalloys. The room temperature toughness of these two-phase alloys was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa.

On Nb Silicide Based Alloys: Alloy Design and Selection.

PubMed

Tsakiropoulos, Panos

2018-05-18

The development of Nb-silicide based alloys is frustrated by the lack of composition-process-microstructure-property data for the new alloys, and by the shortage of and/or disagreement between thermodynamic data for key binary and ternary systems that are essential for designing (selecting) alloys to meet property goals. Recent publications have discussed the importance of the parameters δ (related to atomic size), Δχ (related to electronegativity) and valence electron concentration (VEC) (number of valence electrons per atom filled into the valence band) for the alloying behavior of Nb-silicide based alloys (J Alloys Compd 748 (2018) 569), their solid solutions (J Alloys Compd 708 (2017) 961), the tetragonal Nb₅Si₃ (Materials 11 (2018) 69), and hexagonal C14-NbCr₂ and cubic A15-Nb₃X phases (Materials 11 (2018) 395) and eutectics with Nb ss and Nb₅Si₃ (Materials 11 (2018) 592). The parameter values were calculated using actual compositions for alloys, their phases and eutectics. This paper is about the relationships that exist between the alloy parameters δ, Δχ and VEC, and creep rate and isothermal oxidation (weight gain) and the concentrations of solute elements in the alloys. Different approaches to alloy design (selection) that use property goals and these relationships for Nb-silicide based alloys are discussed and examples of selected alloy compositions and their predicted properties are given. The alloy design methodology, which has been called NICE (Niobium Intermetallic Composite Elaboration), enables one to design (select) new alloys and to predict their creep and oxidation properties and the macrosegregation of Si in cast alloys.

On Nb Silicide Based Alloys: Alloy Design and Selection

PubMed Central

Tsakiropoulos, Panos.

2018-01-01

The development of Nb-silicide based alloys is frustrated by the lack of composition-process-microstructure-property data for the new alloys, and by the shortage of and/or disagreement between thermodynamic data for key binary and ternary systems that are essential for designing (selecting) alloys to meet property goals. Recent publications have discussed the importance of the parameters δ (related to atomic size), Δχ (related to electronegativity) and valence electron concentration (VEC) (number of valence electrons per atom filled into the valence band) for the alloying behavior of Nb-silicide based alloys (J Alloys Compd 748 (2018) 569), their solid solutions (J Alloys Compd 708 (2017) 961), the tetragonal Nb5Si3 (Materials 11 (2018) 69), and hexagonal C14-NbCr2 and cubic A15-Nb3X phases (Materials 11 (2018) 395) and eutectics with Nbss and Nb5Si3 (Materials 11 (2018) 592). The parameter values were calculated using actual compositions for alloys, their phases and eutectics. This paper is about the relationships that exist between the alloy parameters δ, Δχ and VEC, and creep rate and isothermal oxidation (weight gain) and the concentrations of solute elements in the alloys. Different approaches to alloy design (selection) that use property goals and these relationships for Nb-silicide based alloys are discussed and examples of selected alloy compositions and their predicted properties are given. The alloy design methodology, which has been called NICE (Niobium Intermetallic Composite Elaboration), enables one to design (select) new alloys and to predict their creep and oxidation properties and the macrosegregation of Si in cast alloys. PMID:29783707

Influence of carbides and microstructure of CoCrMo alloys on their metallic dissolution resistance.

PubMed

Valero-Vidal, C; Casabán-Julián, L; Herraiz-Cardona, I; Igual-Muñoz, A

2013-12-01

CoCrMo alloys are passive and biocompatible materials widely used as joint replacements due to their good mechanical properties and corrosion resistance. Electrochemical behaviour of thermal treated CoCrMo alloys with different carbon content in their bulk alloy composition has been analysed. Both the amount of carbides in the CoCrMo alloys and the chemical composition of the simulated body fluid affect the electrochemical properties of these biomedical alloys, thus passive dissolution rate was influenced by the mentioned parameters. Lower percentage of carbon in the chemical composition of the bulk alloy and thermal treatments favour the homogenization of the surface (less amount of carbides), thus increasing the availability of Cr to form the oxide film and improving the corrosion resistance of the alloy. © 2013.

Oxidation sulfidation resistance of Fe-Cr-Ni alloys

DOEpatents

Natesan, Ken; Baxter, David J.

1984-01-01

High temperature resistance of Fe-Cr-Ni alloy compositions to oxidative and/or sulfidative conditions is provided by the incorporation of about 1-8 wt. % of Zr or Nb and results in a two-phase composition having an alloy matrix as the first phase and a fine grained intermetallic composition as the second phase. The presence and location of the intermetallic composition between grains of the matrix provides mechanical strength, enhanced surface scale adhesion, and resistance to corrosive attack between grains of the alloy matrix at temperatures of 500.degree.-1000.degree. C.

Metal-composite adhesion based on diazonium chemistry.

PubMed

Oweis, Yara; Alageel, Omar; Kozak, Paige; Abdallah, Mohamed-Nur; Retrouvey, Jean-Marc; Cerruti, Marta; Tamimi, Faleh

2017-11-01

Composite resins do not adhere well to dental alloys. This weak bond can result in failure at the composite-metal interface in fixed dental prostheses and orthodontic brackets. The aim of this study was to develop a new adhesive, based on diazonium chemistry, to facilitate chemical bonding between dental alloys and composite resin. Samples of two types of dental alloys, stainless steel and cobalt chromium were primed with a diazonium layer in order to create a surface coating favorable for composite adhesion. Untreated metal samples served as controls. The surface chemical composition of the treated and untreated samples was analyzed by X-ray photoelectron spectroscopy (XPS) and the tensile strength of the bond with composite resin was measured. The diazonium adhesive was also tested for shear bond strength between stainless steel orthodontic brackets and teeth. XPS confirmed the presence of a diazonium coating on the treated metals. The coating significantly increased the tensile and shear bond strengths by three and four folds respectively between the treated alloys and composite resin. diazonium chemistry can be used to develop composite adhesives for dental alloys. Diazonium adhesion can effectively achieve a strong chemical bond between dental alloys and composite resin. This technology can be used for composite repair of fractured crowns, for crown cementation with resin based cements, and for bracket bonding. Copyright © 2017 The Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

Corrosion Behaviour in Human Stimulation Media of a High Entropy Titan-Based Alloy

NASA Astrophysics Data System (ADS)

Ghiban, B.; Popescu, G.; Lazar, C.; Rosu, L.; Constantin, I.; Olaru, M.; Carlan, B.

2018-06-01

The paper presents results on the corrosion behavior of high entropy alloys, commonly called BIOHEA in human physiological simulating media, respectively in the NaCl infusion solution and Ringer’s lactate infusion solution. Corrosion tests were performed by potendiodinamic test using AUTOLAB type potentiostat equipped with specialized corrosion software including the PGSTAT302N, BA and SCAN250 modules. Three entropy alloy systems were investigated: FeTa0.5Nb0.5Ti1.5Zr0.5 (BIOHEA 1), FeMnNb0.5TiZr0.5 (BIOHEA 3), FeTa0.5Nb0.5TiZr0.5 (BIOHEA 4), and BIOHEA alloy 2 was obtained by remelting BIOHEA 1. A comparison of the results obtained in the present tests and the data from the literature shows, on the one hand, that the global results can be compared with the different results from the literature, and, on the other hand, the results are new, in the sense that in any work there are no combinations of alloys studied here or human simulating medians used for testing. The conclusion of the experimental investigations in the present paper is the fact that regardless of the simulation test environment, all the alloys experimental alloys have similar behaviors, there is a difference between the chemical composition of the experimental alloy and the displacement of the corrosion potential values at electropositive values, decreasing of corrosion current, and corrosion rates. The experimental results allow the corrosion resistance of the investigated alloys, alloy BIOHEA 2 having the best corrosion behavior in both test media, with very low corrosion rates (respectivelly 0.067 μm/year in NaCl infusion solution, and 0.021 μm / year in Ringer’s lactate infusion solution).

Formation and corrosion of a 410 SS/ceramic composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, X.; Ebert, W. L.; Indacochea, J. E.

This study evaluates the possible use of alloy/ceramic composite waste forms to immobilize metallic and oxide waste streams generated during the electrochemical reprocessing of spent reactor fuel in a single waste form. A representative composite material AOC410 was made to evaluate the microstructure and corrosion behavior at alloy/ceramic interfaces by reacting 410 stainless steel with Zr, Mo, and a mixture of lanthanide oxides. Essentially all of the Zr reacted with lanthanide oxides to form lanthanide zirconate, which combined with the remaining lanthanide oxides to form a porous ceramic network encapsulated by alloy as a composite puck. Excess alloy formed amore » metal bead on top of the composite. The alloys in the composite and bead were both mixture of martensite grains and ferrite grains with carbide precipitates. FeCrMo intermetallic phases also precipitated in the ferrite grains in the composite part. Ferrite surrounding carbides was sensitized and the least corrosion resistant in electrochemical corrosion tests conducted in an acidic brine electrolyte; ferrite neighboring martensite grains and intermetallics corroded galvanically. The lanthanide oxide domains dissolved chemically, but lanthanide zirconate domains did not dissolve. The presence of oxide phases did not affect corrosion of the neighboring alloy phases. These results suggest the longterm corrosion of a composite waste form can be evaluated by using separate material degradation models for the alloy and ceramic phases.« less

Luminescence of III-IV-V thin film alloys grown by metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Jia, Roger; Zhu, Tony; Bulović, Vladimir; Fitzgerald, Eugene A.

2018-05-01

III-IV-V heterovalent alloys have the potential to satisfy the need for infrared bandgap materials that also have lattice constants near GaAs. In this work, significant room temperature photoluminescence is reported for the first time in high quality III-IV-V alloys grown by metalorganic chemical vapor deposition. Pronounced phase separation, a characteristic suspected to quench luminescence in the alloys in the past, was successfully inhibited by a modified growth process. Small scale composition fluctuations were observed in the alloys; higher growth temperatures resulted in fluctuations with a striated morphology, while lower growth temperatures resulted in fluctuations with a speckled morphology. The composition fluctuations cause bandgap narrowing in the alloys—measurements of various compositions of (GaAs)1-x(Ge2)x alloys reveal a maximum energy transition of 0.8 eV under 20% Ge composition rather than a continuously increasing transition with the decreasing Ge composition. Additionally, luminescence intensity decreased with the decreasing Ge composition. The alloys appear to act as a Ge-like solid penetrating a GaAs lattice, resulting in optical properties similar to those of Ge but with a direct-bandgap nature; a decrease in the Ge composition corresponds to a reduction in the light-emitting Ge-like material within the lattice. An energy transition larger than 0.8 eV was obtained through the addition of silicon to the (GaAs)1-x(Ge2)x alloy. The results indicate significant promise for III-IV-V alloys as potential materials for small bandgap optical devices with previously unachievable lattice constants.

Integral bypass diodes in an amorphous silicon alloy photovoltaic module

NASA Technical Reports Server (NTRS)

Hanak, J. J.; Flaisher, H.

1991-01-01

Thin-film, tandem-junction, amorphous silicon (a-Si) photovoltaic modules were constructed in which a part of the a-Si alloy cell material is used to form bypass protection diodes. This integral design circumvents the need for incorporating external, conventional diodes, thus simplifying the manufacturing process and reducing module weight.

Stabilizing the body centered cubic crystal in titanium alloys by a nano-scale concentration modulation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang, H. L.; Shah, S. A. A.; Hao, Y. L.

It is well-known that the body centered cubic (bcc) crystal in titanium alloys reaches its stability limit as the electron-to-atom (e/a) ratio of the alloy drops down to ~4.24. This critical value, however, is much higher than that of a multifunctional bcc type alloy (e/a = 4.15). Here we demonstrate that a nano-scale concentration modulation created by spinodal decomposition is what stabilizes the bcc crystal of the alloy. Aided by such a nano-scale concentration heterogeneity, unexpected properties from its chemically homogeneous counterpart are obtained. This provides a new strategy to design functional titanium alloys by tuning the spinodal decomposition.

Soil Transport Implement

NASA Technical Reports Server (NTRS)

Dixon, William; Fan, William; Lloyd, Joey; Pham, Nam-Anh; Stevens, Michael

1988-01-01

The design of the Soil Transport Implement (STI) for SKITTER is presented. The purpose of STI is to provide a protective layer of lunar soil for the lunar modules. The objective is to cover the lunar module with a layer of soil approximately two meters thick within a two week period. The amount of soil required to cover the module is roughly 77 dump truck loads or three million earth pounds. A spinning disk is employed to accomplish its task. STI is an autonomous, teleoperated system. The design incorporates the latest advances in composite materials and high strength, light weight alloys to achieve a high strength to weight ratio. The preliminary design should only be used to assess the feasibility of employing a spinning wheel as a soil transport implement. A mathematical model of the spinning wheel was used to evaluate the performance of this design.

Anisotropic thermal transport in van der Waals layered alloys WSe2(1-x)Te2x

NASA Astrophysics Data System (ADS)

Qian, Xin; Jiang, Puqing; Yu, Peng; Gu, Xiaokun; Liu, Zheng; Yang, Ronggui

2018-06-01

Transition metal dichalcogenide (TMD) alloys have attracted great interest in recent years due to their tunable electronic properties and the semiconductor-metal phase transition along with their potential applications in solid-state memories and thermoelectrics among others. However, the thermal conductivity of layered TMD alloys remains largely unexplored despite that it plays a critical role in the reliability and functionality of TMD-enabled devices. In this work, we study the composition- and temperature-dependent anisotropic thermal conductivity of the van der Waals layered TMD alloys WSe2(1-x)Te2x in both the in-plane direction (parallel to the basal planes) and the cross-plane direction (along the c-axis) using time-domain thermoreflectance measurements. In the WSe2(1-x)Te2x alloys, the cross-plane thermal conductivity is observed to be dependent on the heating frequency (modulation frequency of the pump laser) due to the non-equilibrium transport between different phonon modes. Using a two-channel heat conduction model, we extracted the anisotropic thermal conductivity at the equilibrium limit. A clear discontinuity in both the cross-plane and the in-plane thermal conductivity is observed as x increases from 0.4 to 0.6 due to the phase transition from the 2H to the Td phase in the layered alloys. The temperature dependence of thermal conductivity for the TMD alloys was found to become weaker compared with the pristine 2H WSe2 and Td WTe2 due to the atomic disorder. This work serves as an important starting point for exploring phonon transport in layered alloys.

Progress toward a tungsten alloy wire/high temperature alloy composite turbine blade

NASA Technical Reports Server (NTRS)

Ritzert, F. J.; Dreshfield, R. L.

1992-01-01

A tungsten alloy wire reinforced high temperature alloy composite is being developed for potential application as a hollow turbine blade for advanced rocket engine turbopumps. The W-24Re-HfC alloy wire used for these composite blades provides an excellent balance of strength and wire ductility. Preliminary fabrication, specimen design, and characterization studies were conducted by using commercially available W218 tungsten wire in place of the W-24Re-Hfc wire. Subsequently, two-ply, 50 vol pct composite panels using the W-24Re-HfC wire were fabricated. Tensile tests and metallographic studies were performed to determine the material viability. Tensile strengths of a Waspaloy matrix composite at 870 C were 90 pct of the value expected from rule-of-mixtures calculations. During processing of this Waspaloy matrix composite, a brittle phase was formed at the wire/matrix interface. Circumferential wire cracks were found in this phase. Wire coating and process evaluation efforts were performed in an attempt to solve the reaction problem. Although problems were encountered in this study, wire reinforced high temperature alloy composites continue to show promise for turbopump turbine blade material improvement.

Preparation of Pt Ag alloy nanoisland/graphene hybrid composites and its high stability and catalytic activity in methanol electro-oxidation

PubMed Central

2011-01-01

In this article, PtAg alloy nanoislands/graphene hybrid composites were prepared based on the self-organization of Au@PtAg nanorods on graphene sheets. Graphite oxides (GO) were prepared and separated to individual sheets using Hummer's method. Graphene nano-sheets were prepared by chemical reduction with hydrazine. The prepared PtAg alloy nanomaterial and the hybrid composites with graphene were characterized by SEM, TEM, and zeta potential measurements. It is confirmed that the prepared Au@PtAg alloy nanorods/graphene hybrid composites own good catalytic function for methanol electro-oxidation by cyclic voltammograms measurements, and exhibited higher catalytic activity and more stability than pure Au@Pt nanorods and Au@AgPt alloy nanorods. In conclusion, the prepared PtAg alloy nanoislands/graphene hybrid composites own high stability and catalytic activity in methanol electro-oxidation, so that it is one kind of high-performance catalyst, and has great potential in applications such as methanol fuel cells in near future. PMID:21982417

Al-TiH2 Composite Foams Magnesium Alloy

NASA Astrophysics Data System (ADS)

Prasada Rao, A. K.; Oh, Y. S.; Ain, W. Q.; A, Azhari; Basri, S. N.; Kim, N. J.

2016-02-01

The work presented here in describes the synthesis of aluminum based titanium-hydride particulate composite by casting method and its foaming behavior of magnesium alloy. Results obtained indicate that the Al-10TiH2 composite can be synthesized successfully by casting method. Further, results also reveal that closed-cell magnesium alloy foam can be synthesized by using Al-10TiH2 composite as a foaming agent.

Improved oxidation sulfidation resistance of Fe-Cr-Ni alloys

DOEpatents

Natesan, K.; Baxter, D.J.

1983-07-26

High temperature resistance of Fe-Cr-Ni alloy compositions to oxidative and/or sulfidative conditions is provided by the incorporation of about 1 to 8 wt % of Zr or Nb and results in a two-phase composition having an alloy matrix as the first phase and a fine grained intermetallic composition as the second phase. The presence and location of the intermetallic composition between grains of the matrix provides mechanical strength, enhanced surface scale adhesion, and resistance to corrosive attack between grains of the alloy matrix at temperatures of 500 to 1000/sup 0/C.

Synthesis and characterization of a new high entropy composite matrix

NASA Astrophysics Data System (ADS)

Popescu, G.; Matara, M. A.; Csaki, I.; Popescu, C. A.; Truşcă, R.

2016-06-01

Even if high entropy alloys were not reported in a scientific journal till 2003, these new alloys have been investigated since 1995 due to their high temperature properties. In the last years the synthesis of these alloys has been widely investigated. Thus, the present work has been carried out to produce a high entropy composite using an equiatomic AlCrFeMnNi high entropy alloy (HEA) matrix and graphite particles (Gr) as reinforcing material. The high entropy composite was obtained by powder metallurgy route using a planetary ball mill. The mechanically alloyed mixture was investigated by scanning electron microscopy (SEM). Microstructural investigation realized by SEM revealed the homogenous structure of the composite, with multiple phases and decreasing particles size, mostly reaching nanometric scale.

Intermetallic alloy welding wires and method for fabricating the same

DOEpatents

Santella, M.L.; Sikka, V.K.

1996-06-11

Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined. 4 figs.

Intermetallic alloy welding wires and method for fabricating the same

DOEpatents

Santella, Michael L.; Sikka, Vinod K.

1996-01-01

Welding wires for welding together intermetallic alloys of nickel aluminides, nickel-iron aluminides, iron aluminides, or titanium aluminides, and preferably including additional alloying constituents are fabricated as two-component, clad structures in which one component contains the primary alloying constituent(s) except for aluminum and the other component contains the aluminum constituent. This two-component approach for fabricating the welding wire overcomes the difficulties associated with mechanically forming welding wires from intermetallic alloys which possess high strength and limited ductilities at elevated temperatures normally employed in conventional metal working processes. The composition of the clad welding wires is readily tailored so that the welding wire composition when melted will form an alloy defined by the weld deposit which substantially corresponds to the composition of the intermetallic alloy being joined.

Effects of chemical composition on the corrosion of dental alloys.

PubMed

Galo, Rodrigo; Ribeiro, Ricardo Faria; Rodrigues, Renata Cristina Silveira; Rocha, Luís Augusto; de Mattos, Maria da Glória Chiarello

2012-01-01

The aim of this study was to determine the effect of the oral environment on the corrosion of dental alloys with different compositions, using electrochemical methods. The corrosion rates were obtained from the current-potential curves and electrochemical impedance spectroscopy (EIS). The effect of artificial saliva on the corrosion of dental alloys was dependent on alloy composition. Dissolution of the ions occurred in all tested dental alloys and the results were strongly dependent on the general alloy composition. Regarding the alloys containing nickel, the Ni-Cr and Ni-Cr-Ti alloys released 0.62 mg/L of Ni on average, while the Co-Cr dental alloy released ions between 0.01 and 0.03 mg/L of Co and Cr, respectively.The open-circuit potential stabilized at a higher level with lower deviation (standard deviation: Ni-Cr-6Ti = 32 mV/SCE and Co-Cr = 54 mV/SCE). The potenciodynamic curves of the dental alloys showed that the Ni-based dental alloy with >70 wt% of Ni had a similar curve and the Co-Cr dental alloy showed a low current density and hence a high resistance to corrosion compared with the Ni-based dental alloys. Some changes in microstructure were observed and this fact influenced the corrosion behavior for the alloys. The lower corrosion resistance also led to greater release of nickel ions to the medium. The quantity of Co ions released from the Co-Cr-Mo alloy was relatively small in the solutions. In addition, the quantity of Cr ions released into the artificial saliva from the Co-Cr alloy was lower than Cr release from the Ni-based dental alloys.

Novel phase diagram behavior and materials design in heterostructural semiconductor alloys

PubMed Central

Holder, Aaron M.; Siol, Sebastian; Ndione, Paul F.; Peng, Haowei; Deml, Ann M.; Matthews, Bethany E.; Schelhas, Laura T.; Toney, Michael F.; Gordon, Roy G.; Tumas, William; Perkins, John D.; Ginley, David S.; Gorman, Brian P.; Tate, Janet; Zakutayev, Andriy; Lany, Stephan

2017-01-01

Structure and composition control the behavior of materials. Isostructural alloying is historically an extremely successful approach for tuning materials properties, but it is often limited by binodal and spinodal decomposition, which correspond to the thermodynamic solubility limit and the stability against composition fluctuations, respectively. We show that heterostructural alloys can exhibit a markedly increased range of metastable alloy compositions between the binodal and spinodal lines, thereby opening up a vast phase space for novel homogeneous single-phase alloys. We distinguish two types of heterostructural alloys, that is, those between commensurate and incommensurate phases. Because of the structural transition around the critical composition, the properties change in a highly nonlinear or even discontinuous fashion, providing a mechanism for materials design that does not exist in conventional isostructural alloys. The novel phase diagram behavior follows from standard alloy models using mixing enthalpies from first-principles calculations. Thin-film deposition demonstrates the viability of the synthesis of these metastable single-phase domains and validates the computationally predicted phase separation mechanism above the upper temperature bound of the nonequilibrium single-phase region. PMID:28630928

Novel phase diagram behavior and materials design in heterostructural semiconductor alloys.

PubMed

Holder, Aaron M; Siol, Sebastian; Ndione, Paul F; Peng, Haowei; Deml, Ann M; Matthews, Bethany E; Schelhas, Laura T; Toney, Michael F; Gordon, Roy G; Tumas, William; Perkins, John D; Ginley, David S; Gorman, Brian P; Tate, Janet; Zakutayev, Andriy; Lany, Stephan

2017-06-01

Structure and composition control the behavior of materials. Isostructural alloying is historically an extremely successful approach for tuning materials properties, but it is often limited by binodal and spinodal decomposition, which correspond to the thermodynamic solubility limit and the stability against composition fluctuations, respectively. We show that heterostructural alloys can exhibit a markedly increased range of metastable alloy compositions between the binodal and spinodal lines, thereby opening up a vast phase space for novel homogeneous single-phase alloys. We distinguish two types of heterostructural alloys, that is, those between commensurate and incommensurate phases. Because of the structural transition around the critical composition, the properties change in a highly nonlinear or even discontinuous fashion, providing a mechanism for materials design that does not exist in conventional isostructural alloys. The novel phase diagram behavior follows from standard alloy models using mixing enthalpies from first-principles calculations. Thin-film deposition demonstrates the viability of the synthesis of these metastable single-phase domains and validates the computationally predicted phase separation mechanism above the upper temperature bound of the nonequilibrium single-phase region.

Novel phase diagram behavior and materials design in heterostructural semiconductor alloys

DOE PAGES

Holder, Aaron M.; Siol, Sebastian; Ndione, Paul F.; ...

2017-06-07

Structure and composition control the behavior of materials. Isostructural alloying is historically an extremely successful approach for tuning materials properties, but it is often limited by binodal and spinodal decomposition, which correspond to the thermodynamic solubility limit and the stability against composition fluctuations, respectively. We show that heterostructural alloys can exhibit a markedly increased range of metastable alloy compositions between the binodal and spinodal lines, thereby opening up a vast phase space for novel homogeneous single-phase alloys. We distinguish two types of heterostructural alloys, that is, those between commensurate and incommensurate phases. Because of the structural transition around the criticalmore » composition, the properties change in a highly nonlinear or even discontinuous fashion, providing a mechanism for materials design that does not exist in conventional isostructural alloys. The novel phase diagram behavior follows from standard alloy models using mixing enthalpies from first-principles calculations. Furthermore, thin-film deposition demonstrates the viability of the synthesis of these metastable single-phase domains and validates the computationally predicted phase separation mechanism above the upper temperature bound of the nonequilibrium single-phase region.« less

Multicomponent homogeneous alloys and method for making same

DOEpatents

Dutta, Partha S.; Miller, Thomas R.

2003-09-02

The present application discloses a method for preparing a homogeneous ternary or quaternary alloy from a quaternary melt. The method includes providing a family of phase diagrams for the quaternary melt which shows (i) composition/temperature data, (ii) tie lines connecting equilibrium liquid and solid compositions, and (iii) isotherms representing boundaries of a miscibility gap. Based on the family of phase diagrams, a quaternary melt composition and an alloy growth temperature is selected. A quaternary melt having the selected quaternary melt composition is provided and a ternary or quaternary alloy is grown from the quaternary melt at the selected alloy growth temperature. A method for making homogeneous ternary or quaternary alloy from a ternary or quaternary melt is also disclosed, as are homogeneous quaternary single-crystal alloys which are substantially free from crystal defects and which have the formula A.sub.x B.sub.1-x C.sub.y D.sub.1-y, x and y being the same or different and in the range of 0.001 to 0.999.

Effect of platinum substitution on the structural and magnetic properties of Ni2MnGa ferromagnetic shape memory alloy

NASA Astrophysics Data System (ADS)

Singh, Sanjay; D'Souza, S. W.; Nayak, J.; Caron, L.; Suard, E.; Chadov, S.; Felser, C.

2016-04-01

Ni2MnGa exhibits ideal ferromagnetic shape memory properties, however, brittleness and a low-temperature martensite transition hinder its technological applications motivating the search for novel materials showing better mechanical properties as well as higher transition temperatures. In this work, the crystal structure, phase transitions, and the magnetic properties of quaternary Ni2 -xPtxMnGa (0 ≤x ≤1 ) shape memory alloys were studied experimentally by x-ray diffraction, magnetization measurements, and neutron diffraction and compared to ab initio calculations. Compositions within 0 ≤x ≤0.25 exhibit the cubic austenite phase at room temperature. The x ≈0.3 composition exhibits a seven-layer modulated monoclinic martensite structure. Within 0.4 ≤x ≤1 , the system stabilizes in the nonmodulated tetragonal structure. The martensite transition has very narrow thermal hysteresis 0 ≤x ≤0.3 , which is a typical characteristic of a shape memory alloy. By increasing x , the temperature of the martensite transition increases, while that of the magnetic transition decreases. The x =1 composition (NiPtMnGa) in the martensite phase undergoes a para-to-ferrimagnetic transition. The saturation magnetization exhibits a nontrivial behavior with increasing up to x ≈0.25 , above which, it suddenly decreases. Powder neutron diffraction reveals the presence of antisite disorder, with about 17% of the original Ga sites being occupied by Mn. Computations suggest that the antisite disorder triggers an antiferromagnetic coupling between two Mn atoms in different crystallographic positions, resulting into a sudden drop of the saturation magnetization for higher x .

Long-term thermal degradation and alloying constituent effects on five boron/aluminum composites

NASA Technical Reports Server (NTRS)

Olsen, G. C.

1982-01-01

Thermal exposure effects on the properties of five boron/aluminum composite systems were experimentally investigated. The composite systems were 49 volume percent boron fibers (203 micron diameter) in aluminum-alloy matrices 1100 Al, 2024 Al, 3003 Al, 5052 Al, and 6061 Al. Specimens were thermally exposed up to 10,000 hours at 500 K and 590 K, up to 500 hours at 730 K, and up to 10,000 hours at 500 K and 590 K, up to 500 hours at 730 K, and up to 2000 thermal cycles between 200 K and 590 K. Composite longitudinal and transverse tensile strengths, longitudinal compression strength, and in-plane shear strength were determined. None of the systems was severely degraded by exposure at 590 K. The best performing system was B-2024 Al. Effects of matrix alloys on degradation mechanisms were experimentally investigated. Composite specimens and individual fibers were metallurgically analyzed with a scanning electron microscope and an electron microprobe to determine failure characteristics, chemical element distribution, and reaction layer morphology. Alloying constituents were found to be affect the composite degradation mechanisms as follows: alloys containing iron, but without manganese as a stabilizer, caused increased low-temperature degradation; alloys containing magnesium, iron, or manganese caused increased degradation; and alloys containing copper caused increased fiber strength.

A Comparative Study on Permanent Mold Cast and Powder Thixoforming 6061 Aluminum Alloy and Sicp/6061Al Composite: Microstructures and Mechanical Properties.

PubMed

Zhang, Xuezheng; Chen, Tijun; Qin, He; Wang, Chong

2016-05-24

Microstructural and mechanical characterization of 10 vol% SiC particles (SiC p ) reinforced 6061 Al-based composite fabricated by powder thixoforming (PTF) was investigated in comparison with the PTF and permanent mold cast (PMC) 6061 monolithic alloys. The results reveal that the microstructure of the PMC alloy consists of coarse and equiaxed α dendrites and interdendritic net-like eutectic phases. However, the microstructure of the PTF composite, similar to that of the PTF alloy, consists of near-spheroidal primary particles and intergranular secondarily solidified structures except SiC p , which are distributed in the secondarily solidified structures. The eutectics amount in the PTF materials is distinctly lower than that in the PMC alloy, and the microstructures of the former materials are quite compact while that of the latter alloy is porous. Therefore, the PTF alloy shows better tensile properties than the PMC alloy. Owing to the existence of the SiC reinforcing particles, the PTF composite attains an ultimate tensile strength and yield strength of 230 MPa and 128 MPa, representing an enhancement of 27.8% and 29.3% than those (180 MPa and 99 MPa) of the PTF alloy. A modified model based on three strengthening mechanisms was proposed to calculate the yield strength of the PTF composite. The obtained theoretical results were quite consistent with the experimental data.

Combinatorial development of antibacterial Zr-Cu-Al-Ag thin film metallic glasses.

PubMed

Liu, Yanhui; Padmanabhan, Jagannath; Cheung, Bettina; Liu, Jingbei; Chen, Zheng; Scanley, B Ellen; Wesolowski, Donna; Pressley, Mariyah; Broadbridge, Christine C; Altman, Sidney; Schwarz, Udo D; Kyriakides, Themis R; Schroers, Jan

2016-05-27

Metallic alloys are normally composed of multiple constituent elements in order to achieve integration of a plurality of properties required in technological applications. However, conventional alloy development paradigm, by sequential trial-and-error approach, requires completely unrelated strategies to optimize compositions out of a vast phase space, making alloy development time consuming and labor intensive. Here, we challenge the conventional paradigm by proposing a combinatorial strategy that enables parallel screening of a multitude of alloys. Utilizing a typical metallic glass forming alloy system Zr-Cu-Al-Ag as an example, we demonstrate how glass formation and antibacterial activity, two unrelated properties, can be simultaneously characterized and the optimal composition can be efficiently identified. We found that in the Zr-Cu-Al-Ag alloy system fully glassy phase can be obtained in a wide compositional range by co-sputtering, and antibacterial activity is strongly dependent on alloy compositions. Our results indicate that antibacterial activity is sensitive to Cu and Ag while essentially remains unchanged within a wide range of Zr and Al. The proposed strategy not only facilitates development of high-performing alloys, but also provides a tool to unveil the composition dependence of properties in a highly parallel fashion, which helps the development of new materials by design.

Combinatorial development of antibacterial Zr-Cu-Al-Ag thin film metallic glasses

NASA Astrophysics Data System (ADS)

Liu, Yanhui; Padmanabhan, Jagannath; Cheung, Bettina; Liu, Jingbei; Chen, Zheng; Scanley, B. Ellen; Wesolowski, Donna; Pressley, Mariyah; Broadbridge, Christine C.; Altman, Sidney; Schwarz, Udo D.; Kyriakides, Themis R.; Schroers, Jan

2016-05-01

Metallic alloys are normally composed of multiple constituent elements in order to achieve integration of a plurality of properties required in technological applications. However, conventional alloy development paradigm, by sequential trial-and-error approach, requires completely unrelated strategies to optimize compositions out of a vast phase space, making alloy development time consuming and labor intensive. Here, we challenge the conventional paradigm by proposing a combinatorial strategy that enables parallel screening of a multitude of alloys. Utilizing a typical metallic glass forming alloy system Zr-Cu-Al-Ag as an example, we demonstrate how glass formation and antibacterial activity, two unrelated properties, can be simultaneously characterized and the optimal composition can be efficiently identified. We found that in the Zr-Cu-Al-Ag alloy system fully glassy phase can be obtained in a wide compositional range by co-sputtering, and antibacterial activity is strongly dependent on alloy compositions. Our results indicate that antibacterial activity is sensitive to Cu and Ag while essentially remains unchanged within a wide range of Zr and Al. The proposed strategy not only facilitates development of high-performing alloys, but also provides a tool to unveil the composition dependence of properties in a highly parallel fashion, which helps the development of new materials by design.

Combinatorial development of antibacterial Zr-Cu-Al-Ag thin film metallic glasses

PubMed Central

Liu, Yanhui; Padmanabhan, Jagannath; Cheung, Bettina; Liu, Jingbei; Chen, Zheng; Scanley, B. Ellen; Wesolowski, Donna; Pressley, Mariyah; Broadbridge, Christine C.; Altman, Sidney; Schwarz, Udo D.; Kyriakides, Themis R.; Schroers, Jan

2016-01-01

Metallic alloys are normally composed of multiple constituent elements in order to achieve integration of a plurality of properties required in technological applications. However, conventional alloy development paradigm, by sequential trial-and-error approach, requires completely unrelated strategies to optimize compositions out of a vast phase space, making alloy development time consuming and labor intensive. Here, we challenge the conventional paradigm by proposing a combinatorial strategy that enables parallel screening of a multitude of alloys. Utilizing a typical metallic glass forming alloy system Zr-Cu-Al-Ag as an example, we demonstrate how glass formation and antibacterial activity, two unrelated properties, can be simultaneously characterized and the optimal composition can be efficiently identified. We found that in the Zr-Cu-Al-Ag alloy system fully glassy phase can be obtained in a wide compositional range by co-sputtering, and antibacterial activity is strongly dependent on alloy compositions. Our results indicate that antibacterial activity is sensitive to Cu and Ag while essentially remains unchanged within a wide range of Zr and Al. The proposed strategy not only facilitates development of high-performing alloys, but also provides a tool to unveil the composition dependence of properties in a highly parallel fashion, which helps the development of new materials by design. PMID:27230692

Properties of a new type Al/Pb-0.3%Ag alloy composite anode for zinc electrowinning

NASA Astrophysics Data System (ADS)

Yang, Hai-tao; Liu, Huan-rong; Zhang, Yong-chun; Chen, Bu-ming; Guo, Zhong-cheng; Xu, Rui-dong

2013-10-01

An Al/Pb-0.3%Ag alloy composite anode was produced via composite casting. Its electrocatalytic activity for the oxygen evolution reaction and corrosion resistance was evaluated by anodic polarization curves and accelerated corrosion test, respectively. The microscopic morphologies of the anode section and anodic oxidation layer during accelerated corrosion test were obtained by scanning electron microscopy. It is found that the composite anode (hard anodizing) displays a more compact interfacial combination and a better adhesive strength than plating tin. Compared with industrial Pb-0.3%Ag anodes, the oxygen evolution overpotentials of Al/Pb-0.3%Ag alloy (hard anodizing) and Al/Pb-0.3%Ag alloy (plating tin) at 500 A·m-2 were lower by 57 and 14 mV, respectively. Furthermore, the corrosion rates of Pb-0.3%Ag alloy, Al/Pb-0.3%Ag alloy (hard anodizing), and Al/Pb-0.3%Ag alloy (plating tin) were 13.977, 9.487, and 11.824 g·m-2·h-1, respectively, in accelerated corrosion test for 8 h at 2000 A·m-2. The anodic oxidation layer of Al/Pb-0.3%Ag alloy (hard anodizing) is more compact than Pb-0.3%Ag alloy and Al/Pb-0.3%Ag alloy (plating tin) after the test.

Corrosion resistance of sodium sulfate coated cobalt-chromium-aluminum alloys at 900 C, 1000 C, and 1100 C

NASA Technical Reports Server (NTRS)

Santoro, G. J.

1979-01-01

The corrosion of sodium sulfate coated cobalt alloys was measured and the results compared to the cyclic oxidation of alloys with the same composition, and to the hot corrosion of compositionally equivalent nickel-base alloys. Cobalt alloys with sufficient aluminum content to form aluminum containing scales corrode less than their nickel-base counterparts. The cobalt alloys with lower aluminum levels form CoO scales and corrode more than their nickel-base counterparts which form NiO scales.

NASA-UVA Light Aerospace Alloy and Structures Technology Program (LA2ST)

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Scully, John R.; Stoner, Glenn E.; Thornton, Earl A.; Wawner, Franklin E., Jr.; Wert, John A.

1993-01-01

The NASA-UVA Light Aerospace Alloy and Structures Technology (LA2ST) Program continues a high level of activity. Progress achieved between 1 Jan. and 30 Jun. 1993 is reported. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light weight aerospace alloys, composites, and thermal gradient structures in collaboration with NASA-Langley researchers. The following projects are addressed: environmental fatigue of Al-Li-Cu alloys; mechanisms of localized corrosion and environmental fracture in Al-Cu-Li-Mg-Ag alloy X2095 and compositional variations; the effect of zinc additions on the precipitation and stress corrosion cracking behavior of alloy 8090; hydrogen interactions with Al-Li-Cu alloy 2090 and model alloys; metastable pitting of aluminum alloys; cryogenic fracture toughness of Al-Cu-Li + In alloys; the fracture toughness of Weldalite (TM); elevated temperature cracking of advanced I/M aluminum alloys; response of Ti-1100/SCS-6 composites to thermal exposure; superplastic forming of Weldalite (TM); research to incorporate environmental effects into fracture mechanics fatigue life prediction codes such as NASA FLAGRO; and thermoviscoplastic behavior.

Laser-assisted development of titanium alloys: the search for new biomedical materials

NASA Astrophysics Data System (ADS)

Almeida, Amelia; Gupta, Dheeraj; Vilar, Rui

2011-02-01

Ti-alloys used in prosthetic applications are mostly alloys initially developed for aeronautical applications, so their behavior was not optimized for medical use. A need remains to design new alloys for biomedical applications, where requirements such as biocompatibility, in-body durability, specific manufacturing ability, and cost effectiveness are considered. Materials for this application must present excellent biocompatibility, ductility, toughness and wear and corrosion resistance, a large laser processing window and low sensitivity to changes in the processing parameters. Laser deposition has been investigated in order to access its applicability to laser based manufactured implants. In this study, variable powder feed rate laser cladding has been used as a method for the combinatorial investigation of new alloy systems that offers a unique possibility for the rapid and exhaustive preparation of a whole range of alloys with compositions variable along a single clad track. This method was used as to produce composition gradient Ti-Mo alloys. Mo has been used since it is among the few elements biocompatible, non-toxic β-Ti phase stabilizers. Alloy tracks with compositions in the range 0-19 wt.%Mo were produced and characterized in detail as a function of composition using microscale testing procedures for screening of compositions with promising properties. Microstructural analysis showed that alloys with Mo content above 8% are fully formed of β phase grains. However, these β grains present a cellular substructure that is associated to a Ti and Mo segregation pattern that occurs during solidification. Ultramicroindentation tests carried out to evaluate the alloys' hardness and Young's modulus showed that Ti-13%Mo alloys presented the lowest hardness and Young's modulus (70 GPa) closer to that of bone than common Ti alloys, thus showing great potential for implant applications.

Electrocatalyst compositions

DOEpatents

Mallouk, Thomas E.; Chan, Benny C.; Reddington, Erik; Sapienza, Anthony; Chen, Guoying; Smotkin, Eugene; Gurau, Bogdan; Viswanathan, Rameshkrishnan; Liu, Renxuan

2001-09-04

Compositions for use as catalysts in electrochemical reactions are described. The compositions are alloys prepared from two or more elemental metals selected from platinum, molybdenum, osmium, ruthenium, rhodium, and iridium. Also described are electrode compositions including such alloys and electrochemical reaction devices including such catalysts.

Influence of compositional complexity on interdiffusion in Ni-containing concentrated solid-solution alloys

DOE PAGES

Jin, Ke; Zhang, Chuan; Zhang, Fan; ...

2018-03-07

To investigate the compositional effects on thermal-diffusion kinetics in concentrated solid-solution alloys, interdiffusion in seven diffusion couples with alloys from binary to quinary is systematically studied. The alloys with higher compositional complexity exhibit in general lower diffusion coefficients against homologous temperature, however, an exception is found that diffusion in NiCoFeCrPd is faster than in NiCoFeCr and NiCoCr. While the derived diffusion parameters suggest that diffusion in medium and high entropy alloys is overall more retarded than in pure metals and binary alloys, they strongly depend on specific constituents. The comparative features are captured by computational thermodynamics approaches using a self-consistentmore » database.« less

Surface composition of alloys

NASA Astrophysics Data System (ADS)

Sachtler, W. M. H.

1984-11-01

In equilibrium, the composition of the surface of an alloy will, in general, differ from that of the bulk. The broken-bond model is applicable to alloys with atoms of virtually equal size. If the heat of alloy formation is zero, the component of lower heat of atomization is found enriched in the surface. If both partners have equal heats of sublimination, the surface of a diluted alloy is enriched with the minority component. Size effects can enhance or weaken the electronic effects. In general, lattice strain can be relaxed by precipitating atoms of deviating size on the surface. Two-phase alloys are described by the "cherry model", i.e. one alloy phase, the "kernel" is surrounded by another alloy, the "flesh", and the surface of the outer phase, the "skin" displays a deviating surface composition as in monophasic alloys. In the presence of molecules capable of forming chemical bonds with individual metal atoms, "chemisorption induced surface segregation" can be observed at low temperatures, i.e. the surface becomes enriched with the metal forming the stronger chemisorption bonds.

Method of bonding metals to ceramics and other materials

DOEpatents

Gruen, Dieter M.; Krauss, Alan R.; DeWald, A. Bruce; Ju, Chien-Ping; Rigsbee, James M.

1993-01-01

A composite and method of forming same wherein the composite has a non-metallic portion and an alloy portion wherein the alloy comprises an alkali metal and a metal which is an electrical conductor such as Cu, Ag, Al, Sn or Au and forms an alloy with the alkali metal. A cable of superconductors and composite is also disclosed.

Method of bonding metals to ceramics and other materials

DOEpatents

Gruen, D.M.; Krauss, A.R.; DeWald, A.P.; Chienping Ju; Rigsbee, J.M.

1993-01-05

A composite and method of forming same wherein the composite has a non-metallic portion and an alloy portion wherein the alloy comprises an alkali metal and a metal which is an electrical conductor such as Cu, Ag, Al, Sn or Au and forms an alloy with the alkali metal. A cable of superconductors and composite is also disclosed.

Characterization of Magnetic NiFe Nanoparticles with Controlled Bimetallic Composition

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Yan; Chi, Yanxiu; Shan, Shiyao

2014-02-25

The exploration of the magnetic properties of bimetallic alloy nanoparticles for various technological applications requires the ability to control the morphology, composition, and surface properties. In this report, we describe new findings of an investigation of the morphology and composition of NiFe alloy nanoparticles synthesized under controlled conditions. The controllability over the bimetallic composition has been demonstrated by the observation of an approximate linear relationship between the composition in the nanoparticles and in the synthetic feeding. The morphology of the NiFe nanoparticles is consistent with an fcc-type alloy, with the lattice strain increasing linearly with the iron content in themore » nanoparticles. The alloy nanoparticles exhibit remarkable resistance to air oxidation in comparison with Ni or Fe particles. The thermal stability and the magnetic properties of the as-synthesized alloy nanoparticles are shown to depend on the composition. The alloy nanoparticles have also be sown to display low saturation magnetization and coercivity values in comparison with the Ni nanoparticles, in line with the superparamagnetic characteristic. These findings have important implications for the design of stable and controllable magnetic nanoparticles for various technological applications.« less

Magnetic susceptibilities of liquid Cr-Au, Mn-Au and Fe-Au alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ohno, S.; Shimakura, H.; Tahara, S.

The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr{sub 1-c}Au{sub c} with 0.5 ≤ c and Mn{sub 1-c}Au{sub c} with 0.3≤c obeyed the Curie-Weiss law with regard to their dependence of χ on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of χ for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of χ for liquidmore » Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of χ{sub 3d} due to 3d electrons for liquid binary TM-M (M=Au, Al, Si, Sb), and investigated the relationship between χ{sub 3d} and E{sub F} in liquid binary TM-M alloys at a composition of 50 at% TM.« less

Formation and corrosion of a 410 SS/ceramic composite

NASA Astrophysics Data System (ADS)

Chen, X.; Ebert, W. L.; Indacochea, J. E.

2016-11-01

This study addressed the possible use of alloy/ceramic composite waste forms to immobilize metallic and oxide waste streams generated during the electrochemical reprocessing of spent reactor fuel using a single waste form. A representative composite material was made to evaluate the microstructure and corrosion behavior at alloy/ceramic interfaces by reacting 410 stainless steel with Zr, Mo, and a mixture of lanthanide oxides. Essentially all of the available Zr reacted with lanthanide oxides to generate lanthanide zirconates, which combined with the unreacted lanthanide oxides to form a porous ceramic network that filled with alloy to produce a composite puck. Alloy present in excess of the pore volume of the ceramic generated a metal bead on top of the puck. The alloys in the composite and forming the bead were both mixtures of martensite grains and ferrite grains bearing carbide precipitates; FeCrMo intermetallic phases also precipitated at ferrite grain boundaries within the composite puck. Micrometer-thick regions of ferrite surrounding the carbides were sensitized and corroded preferentially in electrochemical tests. The lanthanide oxides dissolved chemically, but the lanthanide zirconates did not dissolve and are suitable host phases. The presence of oxide phases did not affect corrosion of the neighboring alloy phases.

Compositional modulated atomic layer stacking and uniaxial magnetocrystalline anisotropy of CoPt alloy sputtered films with close-packed plane orientation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Saito, Shin, E-mail: ssaito@ecei.tohoku.ac.jp; Nozawa, Naoki; Hinata, Shintaro

An atomic layer stacking structure in hexagonal close packed (hcp) Co{sub 100−x}Pt{sub x} alloy films with c-plane sheet texture was directly observed by a high-angle annular dark-field imaging scanning transmission electron microscopy. The analysis of sequential and/or compositional atomic layer stacking structure and uniaxial magnetocrystalline anisotropy (K{sub u} = K{sub u1} + K{sub u2}) revealed that (1) integrated intensity of the superlattice diffraction takes the maximum at x = 20 at. % and shows broadening feature against x for the film fabricated under the substrate temperature (T{sub sub}) of 400 °C. (2) Compositional separation structure in atomic layers is formed for the films fabricated under T{sub sub} = 400 °C.more » A sequential alternative stacking of atomic layers with different compositions is hardly formed in the film with x = 50 at. %, whereas easily formed in the film with x = 20 at. %. This peculiar atomic layer stacking structure consists of in-plane-disordered Pt-rich and Pt-poor layers, which is completely different from the so-called atomic site ordered structure. (3) A face centered cubic atomic layer stacking as faults appeared in the host hcp atomic layer stacking exists in accompanies with irregularities for the periodicity of the compositional modulation atomic layers. (4) K{sub u1} takes the maximum of 1.4 × 10{sup 7 }erg/cm{sup 3} at around x = 20 at. %, whereas K{sub u2} takes the maximum of 0.7 × 10{sup 7 }erg/cm{sup 3} at around x = 40 at. %, which results in the maximum of 1.8 × 10{sup 7 }erg/cm{sup 3} of K{sub u} at x = 30 at. % and a shoulder in compositional dependence of K{sub u} in the range of x = 30–60 at. %. Not only compositional separation of atomic layers but also sequential alternative stacking of different compositional layers is quite important to improve essential uniaxial magnetocrystalline anisotropy.« less

Influence of chemical composition of zirconium alloy E110 on embrittlement under LOCA conditions - Part 1: Oxidation kinetics and macrocharacteristics of structure and fracture

NASA Astrophysics Data System (ADS)

Nikulin, S. A.; Rozhnov, A. B.; Belov, V. A.; Li, E. V.; Glazkina, V. S.

2011-11-01

Exploratory investigations of the influence of alloying and impurity content in the E110 alloy cladding tubes on the behavior under conditions of Loss of Coolant Accidents (LOCA) has been performed. Three alloys of E110 type have been tested: E110 alloy of nominal composition Zr-1%Nb (E110), E110 alloy of modified composition Zr-1%Nb-0.12%Fe-0.13%O (E110M), E110 alloy of nominal composition Zr-1%Nb with reduced impurity content (E110G). Alloys E110 and E110M were manufactured on the electrolytic basis and alloy E110G was manufactured on the basis of zirconium sponge. The high temperature oxidation tests in steam ( T = 1100 °C, 18% of equivalent cladding reacted (ECR)) have been conducted, kinetics of oxidation was investigated. Quantitative research of structure and fracture macrocharacteristics was performed by means of optical and electron microscopy. The results received were compared with the residual ductility of specimens. The results of the investigation showed the existence of "breakaway oxidation" kinetics and white spalling oxide in E110 and E110M alloys while the specimen oxidation kinetics in E110G alloy was characterized by a parabolic law and specimens had a dense black oxide. Oxygen and iron alloying in the E110 alloy positively changed the macrocharacteristics of structure and fracture. However, in general, it did not improve the resistance to embrittlement in LOCA conditions apparently because of a strong impurity influence caused by electrolytic process of zirconium production.

Cellular Magnesium Matrix Foam Composites for Mechanical Damping Applications

NASA Astrophysics Data System (ADS)

Shunmugasamy, Vasanth Chakravarthy; Mansoor, Bilal; Gupta, Nikhil

2016-01-01

The damping characteristics of metal alloys and metal matrix composites are relevant to the automotive, aerospace, and marine structures. Use of lightweight materials can help in increasing payload capacity and in decreasing fuel consumption. Lightweight composite materials possessing high damping capabilities that can be designed as structural members can greatly benefit in addressing these needs. In this context, the damping properties of lightweight metals such as aluminum and magnesium and their respective composites have been studied in the existing literature. This review focuses on analyzing the damping properties of aluminum and magnesium alloys and their cellular composites. The damping properties of various lightweight alloys and composites are compared on the basis of their density to understand the potential for weight saving in structural applications. Magnesium alloys are observed to possess better damping properties in comparison to aluminum. However, aluminum matrix syntactic foams reinforced with silicon carbide hollow particles possess a damping capacity and density comparable to magnesium alloy. By using the data presented in the study, composites with specific compositions and properties can be selected for a given application. In addition, the comparison of the results helps in identifying the areas where attention needs to be focused to address the future needs.

Characterization of Ternary NiTiPt High-Temperature Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Rios, Orlando; Noebe, Ronald; Biles, Tiffany; Garg, Anita; Palczer, Anna; Scheiman, Daniel; Seifert, Hans Jurgen; Kaufman, Michael

2005-01-01

Pt additions substituted for Ni in NiTi alloys are known to increase the transformation temperature of the alloy but only at fairly high Pt levels. However, until now only ternary compositions with a very specific stoichiometry, Ni50-xPtxTi50, have been investigated and then only to very limited extent. In order to learn about this potential high-temperature shape memory alloy system, a series of over twenty alloys along and on either side of a line of constant stoichiometry between NiTi and TiPt were arc melted, homogenized, and characterized in terms of their microstructure, transformation temperatures, and hardness. The resulting microstructures were examined by scanning electron microscopy and the phase compositions quantified by energy dispersive spectroscopy."Stoichiometric" compositions along a line of constant stoichiometry between NiTi to TiPt were essentially single phase but by any deviations from a stoichiometry of (Ni,Pt)50Ti50 resulted in the presence of at least two different intermetallic phases, depending on the overall composition of the alloy. Essentially all alloys, whether single or two-phase, still under went a martensitic transformation. It was found that the transformation temperatures were depressed with initial Pt additions but at levels greater than 10 at.% the transformation temperature increased linearly with Pt content. Also, the transformation temperatures were relatively insensitive to alloy stoichiometry within the range of alloys examined. Finally, the dependence of hardness on Pt content for a series of Ni50-xPtxTi50 alloys showed solution softening at low Pt levels, while hardening was observed in ternary alloys containing more than about 10 at.% Pt. On either side of these "stoichiometric" compositions, hardness was also found to increase significantly.

Influence of Composition on the Environmental Impact of a Cast Aluminum Alloy

PubMed Central

Gómez, Patricia; Elduque, Daniel; Sarasa, Judith; Pina, Carmelo; Javierre, Carlos

2016-01-01

The influence of alloy composition on the environmental impact of the production of six aluminum casting alloys (Al Si12Cu1(Fe), Al Si5Mg, Al Si9Cu3Zn3Fe, Al Si10Mg(Fe), Al Si9Cu3(Fe)(Zn) and Al Si9) has been analyzed. In order to perform a more precise environmental impact calculation, Life Cycle Assessment (LCA) with ReCiPe Endpoint methodology has been used, with the EcoInvent v3 AlMg3 aluminum alloy dataset as a reference. This dataset has been updated with the material composition ranges of the mentioned alloys. The balanced, maximum and minimum environmental impact values have been obtained. In general, the overall impact of the studied aluminum alloys varies from 5.98 × 10−1 pts to 1.09 pts per kg, depending on the alloy composition. In the analysis of maximum and minimum environmental impact, the alloy that has the highest uncertainty is AlSi9Cu3(Fe)(Zn), with a range of ±9%. The elements that contribute the most to increase its impact are Copper and Tin. The environmental impact of a specific case, an LED luminaire housing made out of an Al Si12Cu1(Fe) cast alloy, has been studied, showing the importance of considering the composition. Significant differences with the standard datasets that are currently available in EcoInvent v3 have been found. PMID:28773536

Influence of Composition on the Environmental Impact of a Cast Aluminum Alloy.

PubMed

Gómez, Patricia; Elduque, Daniel; Sarasa, Judith; Pina, Carmelo; Javierre, Carlos

2016-05-25

The influence of alloy composition on the environmental impact of the production of six aluminum casting alloys (Al Si12Cu1(Fe), Al Si5Mg, Al Si9Cu3Zn3Fe, Al Si10Mg(Fe), Al Si9Cu3(Fe)(Zn) and Al Si9) has been analyzed. In order to perform a more precise environmental impact calculation, Life Cycle Assessment (LCA) with ReCiPe Endpoint methodology has been used, with the EcoInvent v3 AlMg3 aluminum alloy dataset as a reference. This dataset has been updated with the material composition ranges of the mentioned alloys. The balanced, maximum and minimum environmental impact values have been obtained. In general, the overall impact of the studied aluminum alloys varies from 5.98 × 10 -1 pts to 1.09 pts per kg, depending on the alloy composition. In the analysis of maximum and minimum environmental impact, the alloy that has the highest uncertainty is AlSi9Cu3(Fe)(Zn), with a range of ±9%. The elements that contribute the most to increase its impact are Copper and Tin. The environmental impact of a specific case, an LED luminaire housing made out of an Al Si12Cu1(Fe) cast alloy, has been studied, showing the importance of considering the composition. Significant differences with the standard datasets that are currently available in EcoInvent v3 have been found.

A Study on 3-Body Abrasive Wear Behaviour of Aluminium 8011 / Graphite Metal Matrix Composite

NASA Astrophysics Data System (ADS)

Latha Shankar, B.; Anil, K. C.; Patil, Rahul

2016-09-01

Metals and alloys have found their vital role in many applications like structural, corrosive, tribological, etc., in engineering environment. The alloys/composites having high strength to low weight ratio have gained attention of many researchers recently. In this work, graphite reinforced Aluminium 8011 metal matrix composite was prepared by conventional stir casting route, by varying the weight % of reinforcement. Uniform distribution of Graphite in matrix alloy was confirmed by optical micrographs. Prepared composite specimens were subjected to 3-body abrasive testing by varying applied load and time, the silica particles of 400 grit size were used as abrasive particles. It was observed that with the increase of weight% of Graphite the wear resistance of composite was also increasing and on comparison it was found that reinforced composite gives good wear resistance than base alloy.

Grain Refinement and Mechanical Properties of Cu–Cr–Zr Alloys with Different Nano-Sized TiCp Addition

PubMed Central

Zhang, Dongdong; Bai, Fang; Wang, Yong; Wang, Jinguo; Wang, Wenquan

2017-01-01

The TiCp/Cu master alloy was prepared via thermal explosion reaction. Afterwards, the nano-sized TiCp/Cu master alloy was dispersed by electromagnetic stirring casting into the melting Cu–Cr–Zr alloys to fabricate the nano-sized TiCp-reinforced Cu–Cr–Zr composites. Results show that nano-sized TiCp can effectively refine the grain size of Cu–Cr–Zr alloys. The morphologies of grain in Cu–Cr–Zr composites changed from dendritic grain to equiaxed crystal because of the addition and dispersion of nano-sized TiCp. The grain size decreased from 82 to 28 μm with the nano-sized TiCp content. Compared with Cu–Cr–Zr alloys, the ultimate compressive strength (σUCS) and yield strength (σ0.2) of 4 wt% TiCp-reinforced Cu–Cr–Zr composites increased by 6.7% and 9.4%, respectively. The wear resistance of the nano-sized TiCp-reinforced Cu–Cr–Zr composites increased with the increasing nano-sized TiCp content. The wear loss of the nano-sized TiCp-reinforced Cu–Cr–Zr composites decreased with the increasing TiCp content under abrasive particles. The eletrical conductivity of Cu–Cr–Zr alloys, 2% and 4% nano-sized TiCp-reinforced Cu–Cr–Zr composites are 64.71% IACS, 56.77% IACS and 52.93% IACS, respectively. PMID:28786937

Prediction of Contact Fatigue Life of Alloy Cast Steel Rolls Using Back-Propagation Neural Network

NASA Astrophysics Data System (ADS)

Jin, Huijin; Wu, Sujun; Peng, Yuncheng

2013-12-01

In this study, an artificial neural network (ANN) was employed to predict the contact fatigue life of alloy cast steel rolls (ACSRs) as a function of alloy composition, heat treatment parameters, and contact stress by utilizing the back-propagation algorithm. The ANN was trained and tested using experimental data and a very good performance of the neural network was achieved. The well-trained neural network was then adopted to predict the contact fatigue life of chromium alloyed cast steel rolls with different alloy compositions and heat treatment processes. The prediction results showed that the maximum value of contact fatigue life was obtained with quenching at 960 °C, tempering at 520 °C, and under the contact stress of 2355 MPa. The optimal alloy composition was C-0.54, Si-0.66, Mn-0.67, Cr-4.74, Mo-0.46, V-0.13, Ni-0.34, and Fe-balance (wt.%). Some explanations of the predicted results from the metallurgical viewpoints are given. A convenient and powerful method of optimizing alloy composition and heat treatment parameters of ACSRs has been developed.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Holder, Aaron M.; Siol, Sebastian; Ndione, Paul F.

Structure and composition control the behavior of materials. Isostructural alloying is historically an extremely successful approach for tuning materials properties, but it is often limited by binodal and spinodal decomposition, which correspond to the thermodynamic solubility limit and the stability against composition fluctuations, respectively. We show that heterostructural alloys can exhibit a markedly increased range of metastable alloy compositions between the binodal and spinodal lines, thereby opening up a vast phase space for novel homogeneous single-phase alloys. We distinguish two types of heterostructural alloys, that is, those between commensurate and incommensurate phases. Because of the structural transition around the criticalmore » composition, the properties change in a highly nonlinear or even discontinuous fashion, providing a mechanism for materials design that does not exist in conventional isostructural alloys. The novel phase diagram behavior follows from standard alloy models using mixing enthalpies from first-principles calculations. Furthermore, thin-film deposition demonstrates the viability of the synthesis of these metastable single-phase domains and validates the computationally predicted phase separation mechanism above the upper temperature bound of the nonequilibrium single-phase region.« less

Effect of thione primers on adhesive bonding between an indirect composite material and Ag-Pd-Cu-Au alloy.

PubMed

Imai, Hideyuki; Koizumi, Hiroyasu; Shimoe, Saiji; Hirata, Isao; Matsumura, Hideo; Nikawa, Hiroki

2014-01-01

The current study evaluated the effect of primers on the shear bond strength of an indirect composite material joined to a silverpalladium-copper-gold (Ag-Pd-Cu-Au) alloy (Castwell). Disk specimens were cast from the alloy and were air-abraded with alumina. Eight metal primers were applied to the alloy surface. A light-polymerized indirect composite material (Solidex) was bonded to the alloy. Shear bond strength was determined both before and after the application of thermocycling. Two groups primed with Metaltite (thione) and M. L. Primer (sulfide) showed the greatest post-thermocycling bond strength (8.8 and 6.5 MPa). The results of the X-ray photoelectron spectroscopic (XPS) analysis suggested that the thione monomer (MTU-6) in the Metaltite primer was strongly adsorbed onto the Ag-Pd-Cu-Au alloy surface even after repeated cleaning with acetone. The application of either the thione (MTU-6) or sulfide primer is effective for enhancing the bonding between a composite material and Ag-Pd-Cu-Au alloy.

Physical and Mechanical Properties of Composites and Light Alloys Reinforced with Detonation Nanodiamonds

NASA Astrophysics Data System (ADS)

Sakovich, G. V.; Vorozhtsov, S. A.; Vorozhtsov, A. B.; Potekaev, A. I.; Kulkov, S. N.

2016-07-01

The influence of introduction of particles of detonation-synthesized nanodiamonds into composites and aluminum-base light alloys on their physical and mechanical properties is analyzed. The data on microstructure and physical and mechanical properties of composites and cast aluminum alloys reinforced with diamond nanoparticles are presented. The introduction of nanoparticles is shown to result in a significant improvement of the material properties.

Negative electrode composition

DOEpatents

Kaun, Thomas D.; Chilenskas, Albert A.

1982-01-01

A secondary electrochemical cell and a negative electrode composition for use therewith comprising a positive electrode containing an active material of a chalcogen or a transiton metal chalcogenide, a negative electrode containing a lithium-aluminum alloy and an amount of a ternary alloy sufficient to provide at least about 5 percent overcharge capacity relative to a negative electrode solely of the lithium-aluminum alloy, the ternary alloy comprising lithium, aluminum, and iron or cobalt, and an electrolyte containing lithium ions in contact with both of the positive and the negative electrodes. The ternary alloy is present in the electrode in the range of from about 5 percent to about 50 percent by weight of the electrode composition and may include lithium-aluminum-nickel alloy in combination with either the ternary iron or cobalt alloys. A plurality of series connected cells having overcharge capacity can be equalized on the discharge side without expensive electrical equipment.

Fabrication of tungsten wire reinforced nickel-base alloy composites

NASA Technical Reports Server (NTRS)

Brentnall, W. D.; Toth, I. J.

1974-01-01

Fabrication methods for tungsten fiber reinforced nickel-base superalloy composites were investigated. Three matrix alloys in pre-alloyed powder or rolled sheet form were evaluated in terms of fabricability into composite monotape and multi-ply forms. The utility of monotapes for fabricating more complex shapes was demonstrated. Preliminary 1093C (2000F) stress rupture tests indicated that efficient utilization of fiber strength was achieved in composites fabricated by diffusion bonding processes. The fabrication of thermal fatigue specimens is also described.

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

NASA Technical Reports Server (NTRS)

Bhatt, R. T.

1981-01-01

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

Design and development of hot corrosion-resistant

NASA Astrophysics Data System (ADS)

Zhang, J. S.; Hu, Z. Q.; Murata, Y.; Morinaga, M.; Yukawa, N.

1993-11-01

A systematic study of the effects of refractory metals Ti, Ta, and Nb on the microstructures and properties was conducted with a hot corrosion-resistant alloy system Ni-16Cr-9Al-4Co-2W-lMo-(0~4)Ti-(0~4)Ta-(0~4)Nb (in atomic percent) which was selected based on the d-electrons alloy design theory and some basic considerations in alloying features of single-crystal nickel-base superalloys. The contour lines of solidification reaction temperatures and eutectic (γ + γ') volume fraction in the Ti-Ta-Nb compositional triangle were determined by differential thermal analysis (DTA) and imaging analyzer. Compared with the reference alloy IN738LC, in most of the compositional ranges studied, the designed alloys show very low amounts of eutectic (γ + γ') (⪯0.4 vol pct), narrow solidification ranges (⪯65 °C), and wide “heat-treatment windows” (>100 °C). This indicates that the alloys should have the promising microstructural stability, single-crystal castability, and be easier for complete solution treatment. In a wide compositional range, the designed alloys showed good hot corrosion resistance (weight loss less than 20 mg/cm2 after 24 hours kept in molten salt at 900 °C). By summarizing the results, the promising alloy compositional ranges of the alloys with balanced properties were determined for the final step of the alloy design, i.e., to grow single crystal and characterize mechanical properties of the alloys selected from the previously mentioned regions.

Ternary ceramic alloys of ZR-CE-HF oxides

DOEpatents

Becher, Paul F.; Funkenbusch, Eric F.

1990-01-01

A ternary ceramic alloy which produces toughening of zirconia and zirconia composites through the stress transformation from tetragonal phase to monoclinic phase. This alloy, having the general formula Ce.sub.x Hf.sub.y Zn.sub.1-x-y O.sub.2, is produced through the addition of appropriate amounts of ceria and hafnia to the zirconia. Typically, improved toughness is achieved with about 5 to about 15 mol % ceria and up to about 40 mol % hafnia. The preparation of alloys of these compositions are given together with data as to the densities, tetragonal phase content, hardness and fracture toughness. The alloys are useful in preparing zirconia bodies as well as reinforcing ceramic composites.

Synthesis and Magnetic Properties of Fe-Co-Ni/C Nanocomposites

NASA Astrophysics Data System (ADS)

Muratov, D. G.; Kozhitov, L. V.; Karpenkov, D. Yu.; Yakushko, E. V.; Korovin, E. Yu.; Vasil'ev, A. V.; Popkova, A. V.; Kazaryan, T. M.; Shadrinov, A. V.

2018-03-01

Nanoparticles of the Fe-Co-Ni ternary alloy, encapsulated in the carbon matrix of nanocomposites, have been synthesized, The structure, phase composition, and magnetic properties of the obtained materials have been determined with the help of diffractometry and magnetometry. It has been established that nanoparticles of the ternary alloy are formed due to solution of cobalt in the Fe-Ni alloy. The composition of the nanoparticles of the alloy depends on the mass percent ratio of the metas in the precursor. With growth of the iron content, nanoparticles of the ternary alloy with various composition are formed with FCC and BCC crystal lattice structure. As the synthesis temperature and relative iron content are increased, the magnetization of the Fe-Co-Ni/C nanocomposites increases from 26 to 157 A·m2/kg. The coercive force is determined by the synthesis temperature, the size of the nanoparticles, and the composition of the alloy, and its value varies from 330 to 43 Oe.

NiAl-base composite containing high volume fraction of AlN for advanced engines

NASA Technical Reports Server (NTRS)

Hebsur, Mohan (Inventor); Whittenbeger, John D. (Inventor); Lowell, Carl F. (Inventor)

1994-01-01

A particulate reinforced NiAl-AlN composite alloy has a NiAl matrix and greater than about 13 volume percent fine particles of AlN within the matrix. The particles preferably have a diameter from about 15 nanometers to about 50 nanometers. The particulate reinforced NiAl-AlN composite alloy may be prepared by cryomilling prealloyed NiAl in liquid nitrogen using grinding media having a diameter of from about 2 to 6 mm at an impeller speed of from about 450 RPM to about 800 RPM. The cryomilling may be done for a duration of from about 4 hours to about 20 hours to obtain a cryomilled powder. The cryomilled powder may be consolidated to form the particulate reinforced NiAl-AlN composite alloy. The particulate reinforced alloy can further include a toughening alloy. The toughening alloy may include NiCrAlY, FeCrAlY, and FeAl.

Nial-base composite containing high volume fraction of AlN for advanced engines

NASA Technical Reports Server (NTRS)

Hebsur, Mohan G. (Inventor); Whittenberger, John D. (Inventor); Lowell, Carl E. (Inventor)

1997-01-01

A particulate reinforced NiAl-AlN composite alloy has a NiAl matrix and greater than about 13 volume percent fine particles of AlN within the matrix. The particles preferably have a diameter from about 15 nanometers to about 50 nanometers. The particulate reinforced NiAl-AlN composite alloy may be prepared by cryomilling prealloyed NiAl in liquid nitrogen using grinding media having a diameter of from about 2 mm to about 6 mm at an impeller speed of from about 450 RPM to about 800 RPM. The cryomilling may be done for a duration of from about 4 hours to about 20 hours to obtain a cryomilled powder. The cryomilled powder may be consolidated to form the particulate reinforced NiAl-AlN composite alloy. The particulate reinforced alloy can further include a toughening alloy. The toughening alloy may include NiCrAlY, FeCrAY and FeAl.

Solidification processing of monotectic alloy matrix composites

NASA Technical Reports Server (NTRS)

Frier, Nancy L.; Shiohara, Yuh; Russell, Kenneth C.

1989-01-01

Directionally solidified aluminum-indium alloys of the monotectic composition were found to form an in situ rod composite which obeys a lambda exp 2 R = constant relation. The experimental data shows good agreement with previously reported results. A theoretical boundary between cellular and dendritic growth conditions was derived and compared with experiments. The unique wetting characteristics of the monotectic alloys can be utilized to tailor the interface structure in metal matrix composites. Metal matrix composites with monotectic and hypermonotectic Al-In matrices were made by pressure infiltration, remelted and directionally solidified to observe the wetting characteristics of the alloys as well as the effect on structure of solidification in the constrained field of the fiber interstices. Models for monotectic growth are modified to take into account solidification in these constrained fields.

Composite polymer-containing coatings on Mg alloys perspective for industry and implant surgery

NASA Astrophysics Data System (ADS)

Gnedenkov, S. V.; Sinebryukhov, S. L.; Mashtalyar, D. V.; Imshinetskiy, I. M.; Gnedenkov, A. S.; Minaev, A. N.

2017-09-01

In order to improve the corrosion resistance of magnesium alloys the ways of composite protective coating formation were developed by means of plasma electrolytic oxidation (PEO) as well as electrophoretic deposition methods. Electrochemical, corrosion, tribological, and morphological properties of the MAS magnesium alloy composite coatings were studied. The composite polymer-containing coating decrease the corrosion current density values by three orders of magnitude (Ic = 2.0 . 10-10 A/cm2), in comparison with the base PEO-layer. These polymer-containing layers enable one to expand the practical usage area of Mg alloys. The application of such coatings provides the increasing the bioactivity and regulate the corrosion rate of resorbable magnesium implants.

Damage Mechanics Model Development for Monocrystalline Superalloys (PREPRINT)

DTIC Science & Technology

2010-02-01

ferrite , austenite, martensite , and pearlite) colonies in alloy steels [17-20]  the structure of pitch-based carbon foams [21]  the γ-γ...reinforced metal-matrix composites [15, 16]  microstructure (cementite, ferrite , austenite, martensite , and pearlite) colonies in alloy steels [17-20... alloys [11, 12], and Pb-Sn alloys [13, 14]  reinforcement particle for particle -reinforced metal-matrix composites [15, 16] 

Mg-MOF-74/MgF2 Composite Coating for Improving the Properties of Magnesium Alloy Implants: Hydrophilicity and Corrosion Resistance

PubMed Central

Liu, Wei; Yan, Zhijie; Ma, Xiaolu; Geng, Tie; Wu, Haihong

2018-01-01

Surface modification on Mg alloys is highly promising for their application in the field of bone repair. In this study, a new metal–organic framework/MgF2 (Mg-MOF-74/MgF2) composite coating was prepared on the surface of AZ31B Mg alloy via pre-treatment of hydrofluoric acid and in situ hydrothermal synthesis methods. The surface topography of the composite coating is compact and homogeneous, and Mg-MOF-74 has good crystallinity. The corrosion resistance of this composite coating was investigated through Tafel polarization test and immersion test in simulated body fluid at 37 °C. It was found that Mg-MOF-74/MgF2 composite coating significantly slowed down the corrosion rate of Mg alloy. Additionally, Mg-MOF-74/MgF2 composite coating expresses super-hydrophilicity with the water contact angle of nearly 0°. In conclusion, on the basis of MgF2 anticorrosive coating, the introduction of Mg-MOF-74 further improves the biological property of Mg alloys. At last, we propose that the hydrophilicity of the composite coating is mainly owing to the large number of hydroxyl groups, the high specific surface area of Mg-MOF-74, and the rough coating produced by Mg-MOF-74 particles. Hence, Mg-MOF-74 has a great advantage in enhancing the hydrophilicity of Mg alloy surface. PMID:29518933

Mg-MOF-74/MgF₂ Composite Coating for Improving the Properties of Magnesium Alloy Implants: Hydrophilicity and Corrosion Resistance.

PubMed

Liu, Wei; Yan, Zhijie; Ma, Xiaolu; Geng, Tie; Wu, Haihong; Li, Zhongyue

2018-03-07

Surface modification on Mg alloys is highly promising for their application in the field of bone repair. In this study, a new metal-organic framework/MgF₂ (Mg-MOF-74/MgF₂) composite coating was prepared on the surface of AZ31B Mg alloy via pre-treatment of hydrofluoric acid and in situ hydrothermal synthesis methods. The surface topography of the composite coating is compact and homogeneous, and Mg-MOF-74 has good crystallinity. The corrosion resistance of this composite coating was investigated through Tafel polarization test and immersion test in simulated body fluid at 37 °C. It was found that Mg-MOF-74/MgF₂ composite coating significantly slowed down the corrosion rate of Mg alloy. Additionally, Mg-MOF-74/MgF₂ composite coating expresses super-hydrophilicity with the water contact angle of nearly 0°. In conclusion, on the basis of MgF₂ anticorrosive coating, the introduction of Mg-MOF-74 further improves the biological property of Mg alloys. At last, we propose that the hydrophilicity of the composite coating is mainly owing to the large number of hydroxyl groups, the high specific surface area of Mg-MOF-74, and the rough coating produced by Mg-MOF-74 particles. Hence, Mg-MOF-74 has a great advantage in enhancing the hydrophilicity of Mg alloy surface.

Fabrication of a Mo based high temperature TZM alloy by non-consumable arc melting technique

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chakraborty, S.P.; Krishnamurthy, N., E-mail: spc@barc.gov.in

High temperature structural materials are in great demand for power, chemical and nuclear industries which can perform beyond 1000 °C as super alloys usually fail. In this regard, Mo based TZM alloy is capable of retaining strength up to 1500 °C with excellent corrosion compatibility against molten alkali metals. Hence, currently this alloy is considered an important candidate material for high temperature compact nuclear and fusion reactors. Due to reactive nature of Mo and having high melting point, manufacturing this alloy by conventional process is unsuitable. Powder metallurgy technique has limited success due to restriction in quantity and purity. Thismore » paper deals with fabrication of TZM alloy by nonconsumable tungsten arc melting technique. Initially a ternary master alloy of Mo-Ti-Zr was prepared which subsequently by dilution method, was converted into TZM alloy gradually by external addition of Mo and C in various proportions. A number of melting trials were conducted to optimize the process parameters like current, voltage and time to achieve desired alloy composition. The alloy was characterized with respect to composition, elemental distribution profile, microstructure, hardness profile and phase analysis. Well consolidated alloy button was obtained having desired composition, negligible material loss and having microstructure as comparable to standard TZM alloy. (author)« less

Method for producing electricity using a platinum-ruthenium-palladium catalyst in a fuel cell

DOEpatents

Gorer, Alexander

2004-01-27

A method for producing electricity using a fuel cell that utilizes a ternary alloy composition as a fuel cell catalyst, the ternary alloy composition containing platinum, ruthenium and palladium. The alloy shows increased activity as compared to well-known catalysts.

Structure, mechanical property and corrosion behaviors of (HA+β-TCP)/Mg-5Sn composite with interpenetrating networks.

PubMed

Wang, X; Li, J T; Xie, M Y; Qu, L J; Zhang, P; Li, X L

2015-11-01

In this paper, a novel (Hydroxyapatite+β-tricalcium phosphate)/Mg-5Sn ((HA+β-TCP)/Mg-5Sn) composite with interpenetrating networks was fabricated by infiltrating Mg-5Sn alloy into porous HA+β-TCP using suction casting technique. The structure, mechanical property and corrosion behaviors of the composite have been evaluated by means of scanning electron microscopy (SEM), X-ray diffraction (XRD), mechanical testing, electrochemical and immersion test. It is shown that the molten Mg-5Sn alloy has infiltrated not only into the pores but also into the struts of the HA+β-TCP scaffold to forming a compact composite. The microstructure observation also shows that the Mg alloy contacts to the HA+β-TCP closely, and no reaction layer can be found between Mg-5Sn alloy and scaffold. The ultimate compressive strength of the composite is as high as 176MPa, which is about four fifths of the strength of the Mg-5Sn bulk alloy. The electrochemical and immersion tests indicate that the corrosion resistance of the composite is better than that of the Mg-5Sn bulk alloy. The corrosion products on the composite surface are mainly Mg(OH)2, Ca3(PO4)2 and HA. Appropriate mechanical and corrosion properties of the (HA+β-TCP)/Mg-5Sn composite indicate its possibility for new bone tissue implant materials. Copyright © 2015 Elsevier B.V. All rights reserved.

Influence of beta instabilities on the early stages of nucleation and growth of alpha in beta titanium alloys

NASA Astrophysics Data System (ADS)

Nag, Soumya

Microstructural evolution in beta Titanium alloys is an important factor that governs the properties exhibited by them. Intricate understanding of complex phase transformations in these alloys is vital to tailor their microstructures and in turn their properties to our advantage. One such important subject of study is the nucleation and growth of alpha precipitates triggered by the compositional instabilities in the beta matrix, instilled in them during non equilibrium heat treatments. The present work is an effort to investigate such a phenomenon. Here studies have been conducted primarily on two different beta-Titanium alloys of commercial relevance- Ti5553 (Ti-5Al-5Mo-5V-3Cr-0.5Fe), an alloy used in the aerospace industry for landing gear applications and, TNZT (Ti-35Nb-7Zr-5Ta), a potential load bearing orthopedic implant alloy. Apart from the effect of thermal treatment on these alloys, the focus of this work is to study the interplay between different alpha and beta stabilizers present in them. For this, advanced nano-scale characterization tools such as High Resolution STEM, High Resolution TEM, EFTEM and 3D Atom Probe have been used to determine the structure, distribution and composition of the non equilibrium instabilities such as beta' and o, and also to investigate the subsequent nucleation of stable alpha. Thus in this work, very early stages of phase separation via spinodal decomposition and second phase nucleation in titanium alloys are successfully probed at an atomic resolution. For the first time, atomically resolved HRSTEM 'Z'-contrast image is recorded showing modulated structures within the as-quenched beta matrix. Also in the same condition HRTEM results showed the presence of nanoscale alpha regions. These studies are revalidated by conventional selected area diffraction and 3D atom probe reconstruction results. Also TEM dark field and selected are diffraction studies are conducted to understand the effect of quenching and subsequent aging of o precipitates. Using 3D atom probe tomography, the elemental partitioning involved in coarsening of o is investigated in detail. Finally by performing a series of well planned heat treatments, an effort is made to reason out the influence of these instabilities on the morphology, volume fraction and nucleation site of alpha.

Wear studies on plasma-sprayed Al2O3 and 8mole% of Yttrium-stabilized ZrO2 composite coating on biomedical Ti-6Al-4V alloy for orthopedic joint application

PubMed Central

Ganapathy, Perumal; Manivasagam, Geetha; Rajamanickam, Asokamani; Natarajan, Alagumurthi

2015-01-01

This paper presents the wear characteristics of the composite ceramic coating made with Al2O3-40wt%8YSZ on the biomedical grade Ti-6Al-4V alloy (grade 5) used for total joint prosthetic components, with the aim of improving their tribological behavior. The coatings were deposited using a plasma spraying technique, and optimization of plasma parameters was performed using response surface methodology to obtain dense coating. The tribological behaviors of the coated and uncoated substrates were evaluated using a ball-on-plate sliding wear tester at 37°C in simulated body-fluid conditions. The microstructure of both the titanium alloy and coated specimen were examined using an optical microscope and scanning electron microscope. The hardness of the plasma-sprayed alumina–zirconia composite coatings was 2.5 times higher than that of the Ti-6Al-4V alloy, while the wear rate of Ti-6Al-4V alloy was 253 times higher than that of the composite-coated Ti-6Al-4V alloy. The superior wear resistance of the alumina–zirconia coated alloy is attributed to its enhanced hardness and intersplat bonding strength. Wear-track examination showed that the predominant wear mechanism of Ti-6Al-4V alloy was abrasive and adhesive wear, whereas, in the case of alumina–zirconia composite coated alloy, the wear was dominated by microchipping and microcracking. PMID:26491323

Method for preparing homogeneous single crystal ternary III-V alloys

DOEpatents

Ciszek, Theodore F.

1991-01-01

A method for producing homogeneous, single-crystal III-V ternary alloys of high crystal perfection using a floating crucible system in which the outer crucible holds a ternary alloy of the composition desired to be produced in the crystal and an inner floating crucible having a narrow, melt-passing channel in its bottom wall holds a small quantity of melt of a pseudo-binary liquidus composition that would freeze into the desired crystal composition. The alloy of the floating crucilbe is maintained at a predetermined lower temperature than the alloy of the outer crucible, and a single crystal of the desired homogeneous alloy is pulled out of the floating crucible melt, as melt from the outer crucible flows into a bottom channel of the floating crucible at a rate that corresponds to the rate of growth of the crystal.

Effects of compositional complexity on the ion-irradiation induced swelling and hardening in Ni-containing equiatomic alloys

DOE PAGES

Jin, K.; Lu, C.; Wang, L. M.; ...

2016-04-14

The impact of compositional complexity on the ion-irradiation induced swelling and hardening is studied in Ni and six Ni-containing equiatomic alloys with face-centered cubic structure. The irradiation resistance at the temperature of 500 °C is improved by controlling the number and, especially, the type of alloying elements. Alloying with Fe and Mn has a stronger influence on swelling reduction than does alloying with Co and Cr. Lastly, the quinary alloy NiCoFeCrMn, with known excellent mechanical properties, has shown 40 times higher swelling tolerance than nickel.

Tungsten wire-nickel base alloy composite development

NASA Technical Reports Server (NTRS)

Brentnall, W. D.; Moracz, D. J.

1976-01-01

Further development and evaluation of refractory wire reinforced nickel-base alloy composites is described. Emphasis was placed on evaluating thermal fatigue resistance as a function of matrix alloy composition, fabrication variables and reinforcement level and distribution. Tests for up to 1,000 cycles were performed and the best system identified in this current work was 50v/o W/NiCrAlY. Improved resistance to thermal fatigue damage would be anticipated for specimens fabricated via optimized processing schedules. Other properties investigated included 1,093 C (2,000 F) stress rupture strength, impact resistance and static air oxidation. A composite consisting of 30v/o W-Hf-C alloy fibers in a NiCrAlY alloy matrix was shown to have a 100-hour stress rupture strength at 1,093 C (2,000 F) of 365 MN/square meters (53 ksi) or a specific strength advantage of about 3:1 over typical D.S. eutectics.

The Composition and Temperature Effects on the Ultra High Strength Stainless Steel Design

NASA Astrophysics Data System (ADS)

Xu, W.; Del Castillo, P. E. J. Rivera Díaz; van der Zwaag, S.

Alloy composition and heat treatment are of paramount importance to determining alloy properties. Their control is of great importance for new alloy design and industrial fabrication control. A base alloy utilizing MX carbide is designed through a theory guided computational approach coupling a genetic algorithm with optimization criteria based on thermodynamic, kinetic and mechanical principles. The combined effects of 11 alloying elements (Al, C, Co, Cr, Cu, Mo, Nb, Ni, Si, Ti and V) are investigated in terms of the composition optimization criteria: the martensite start (Ms) temperature, the suppression of undesirable phases, the Cr concentration in the matrix and the potency of the precipitation strengthening contribution. The results show the concentration sensitivities of each component and also point out new potential composition domains for further strength increase. The aging temperature effect is studied and the aging temperature industrially followed is recovered.

Grain Refinement and Mechanical Properties of Cu-Cr-Zr Alloys with Different Nano-Sized TiCp Addition.

PubMed

Zhang, Dongdong; Bai, Fang; Wang, Yong; Wang, Jinguo; Wang, Wenquan

2017-08-08

The TiC p /Cu master alloy was prepared via thermal explosion reaction. Afterwards, the nano-sized TiC p /Cu master alloy was dispersed by electromagnetic stirring casting into the melting Cu-Cr-Zr alloys to fabricate the nano-sized TiC p -reinforced Cu-Cr-Zr composites. Results show that nano-sized TiC p can effectively refine the grain size of Cu-Cr-Zr alloys. The morphologies of grain in Cu-Cr-Zr composites changed from dendritic grain to equiaxed crystal because of the addition and dispersion of nano-sized TiC p . The grain size decreased from 82 to 28 μm with the nano-sized TiC p content. Compared with Cu-Cr-Zr alloys, the ultimate compressive strength (σ UCS ) and yield strength (σ 0.2 ) of 4 wt% TiC p -reinforced Cu-Cr-Zr composites increased by 6.7% and 9.4%, respectively. The wear resistance of the nano-sized TiCp-reinforced Cu-Cr-Zr composites increased with the increasing nano-sized TiCp content. The wear loss of the nano-sized TiC p -reinforced Cu-Cr-Zr composites decreased with the increasing TiC p content under abrasive particles. The eletrical conductivity of Cu-Cr-Zr alloys, 2% and 4% nano-sized TiCp-reinforced Cu-Cr-Zr composites are 64.71% IACS, 56.77% IACS and 52.93% IACS, respectively.

Reactive Spark Plasma Sintering (SPS) of Nitride Reinforced Titanium Alloy Composites (Postprint)

DTIC Science & Technology

2014-08-15

AFRL-RX-WP-JA-2014-0177 REACTIVE SPARK PLASMA SINTERING (SPS) OF NITRIDE REINFORCED TITANIUM ALLOY COMPOSITES (POSTPRINT) Jaimie S...titanium–vanadium alloys, has been achieved by introducing reactive nitrogen gas during the spark plasma sintering (SPS) of blended titanium and...lcomReactive spark plasma sintering (SPS) of nitride reinforced titanium alloy compositeshttp://dx.doi.org/10.1016/j.jallcom.2014.08.049 0925-8388

STRUCTURE AND HIGH-FIELD PERFORMANCE OF JELLY ROLL PROCESSED Nb{sub 3}Sn WIRES USING Sn-Ta AND Sn-Ti BASED ALLOY SHEET

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tachikawa, K.; Tsuyuki, T.; Hayashi, Y.

Sn-Ta based alloy buttons of different compositions were prepared by the melt diffusion process among constituent metal powders, and then pressed into plates. Meanwhile Sn-Ti based alloy plates were sliced from the melt and cast ingot. Resulting Sn-based alloy plates were rolled into thin sheets. The Sn-based alloy sheet was laminated with a Nb sheet, and wound into a Jelly Roll (JR) composite. The composite was encased in a sheath, and fabricated into a thin wire followed by the heat treatment. The application of hydrostatic extrusion is useful at the initial stage of the fabrication. The JR wires using Sn-Tamore » and Sn-Ti based alloy sheets show a non-Cu J{sub c} of {approx}250 A/mm{sup 2} and {approx}150 A/mm{sup 2} at 20 T and 22 T, respectively, at 4.2 K. It has been found that the Nb impregnates into the Sn-based alloy layers during the reaction, and Nb{sub 3}Sn layers are synthesized by the mutual diffusion between the Nb sheet and the Sn-based alloy sheet without formation of voids. Sn-Ti based alloy sheets are attractive due to their easiness of mass production. Structure and high-field performance of JR processed Nb{sub 3}Sn wires prepared from Sn-based alloy sheets with different compositions are compared in this article.« less

NASA-UVA Light Aerospace Alloy and Structures Technology program (LA2ST)

NASA Technical Reports Server (NTRS)

Starke, Edgar A., Jr.; Gangloff, Richard P.; Herakovich, Carl T.; Scully, John R.; Shiflet, Gary J.; Stoner, Glenn E.; Wert, John A.

1995-01-01

The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light-weight aerospace alloys, composites, and thermal gradient structures in collaboration with NASA-Langley researchers. The general aim is to produce relevant data and basic understanding of material mechanical response, environment/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement and modeling advances; and a pool of educated students for aerospace technologies. Specific technical objectives are presented for each of the following research projects: time-temperature dependent fracture in advanced wrought ingot metallurgy, and spray deposited aluminum alloys; cryogenic temperature effects on the deformation and fracture of Al-Li-Cu-In alloys; effects of aging and temperature on the ductile fracture of AA2095 and AA2195; mechanisms of localized corrosion in alloys 2090 and 2095; hydrogen interactions in aluminum-lithium alloys 2090 and selected model alloys; mechanisms of deformation and fracture in high strength titanium alloys (effects of temperature and hydrogen and effects of temperature and microstructure); evaluations of wide-panel aluminum alloy extrusions; Al-Si-Ge alloy development; effects of texture and precipitates on mechanical property anisotropy of Al-Cu-Mg-X alloys; damage evolution in polymeric composites; and environmental effects in fatigue life prediction - modeling crack propagation in light aerospace alloys.

Understanding the Cu-Zn brass alloys using a short-range-order cluster model: significance of specific compositions of industrial alloys

PubMed Central

Hong, H. L.; Wang, Q.; Dong, C.; Liaw, Peter K.

2014-01-01

Metallic alloys show complex chemistries that are not yet understood so far. It has been widely accepted that behind the composition selection lies a short-range-order mechanism for solid solutions. The present paper addresses this fundamental question by examining the face-centered-cubic Cu-Zn α-brasses. A new structural approach, the cluster-plus-glue-atom model, is introduced, which suits specifically for the description of short-range-order structures in disordered systems. Two types of formulas are pointed out, [Zn-Cu12]Zn1~6 and [Zn-Cu12](Zn,Cu)6, which explain the α-brasses listed in the American Society for Testing and Materials (ASTM) specifications. In these formulas, the bracketed parts represent the 1st-neighbor cluster, and each cluster is matched with one to six 2nd-neighbor Zn atoms or with six mixed (Zn,Cu) atoms. Such a cluster-based formulism describes the 1st- and 2nd-neighbor local atomic units where the solute and solvent interactions are ideally satisfied. The Cu-Ni industrial alloys are also explained, thus proving the universality of the cluster-formula approach in understanding the alloy selections. The revelation of the composition formulas for the Cu-(Zn,Ni) industrial alloys points to the common existence of simple composition rules behind seemingly complex chemistries of industrial alloys, thus offering a fundamental and practical method towards composition interpretations of all kinds of alloys. PMID:25399835

Understanding the Cu-Zn brass alloys using a short-range-order cluster model: Significance of specific compositions of industrial alloys

DOE PAGES

Hong, H. L.; Wang, Q.; Dong, C.; ...

2014-11-17

Metallic alloys show complex chemistries that are not yet understood so far. It has been widely accepted that behind the composition selection lies a short-range-order mechanism for solid solutions. The present paper addresses this fundamental question by examining the face-centered-cubic Cu-Zn α-brasses. A new structural approach, the cluster-plus-glue-atom model, is introduced, which suits specifically for the description of short-range-order structures in disordered systems. Two types of formulas are pointed out, [Zn-Cu 12]Zn 1~6 and [Zn-Cu 12](Zn,Cu) 6, which explain the α-brasses listed in the American Society for Testing and Materials (ASTM) specifications. In these formulas, the bracketed parts represent themore » 1 st-neighbor cluster, and each cluster is matched with one to six 2 nd-neighbor Zn atoms or with six mixed (Zn,Cu) atoms. Such a cluster-based formulism describes the 1 st- and 2 nd-neighbor local atomic units where the solute and solvent interactions are ideally satisfied. The Cu-Ni industrial alloys are also explained, thus proving the universality of the cluster-formula approach in understanding the alloy selections. As a result, the revelation of the composition formulas for the Cu-(Zn,Ni) industrial alloys points to the common existence of simple composition rules behind seemingly complex chemistries of industrial alloys, thus offering a fundamental and practical method towards composition interpretations of all kinds of alloys.« less

Ternary ceramic alloys of Zr-Ce-Hf oxides

DOEpatents

Becher, P.F.; Funkenbusch, E.F.

1990-11-20

A ternary ceramic alloy is described which produces toughening of zirconia and zirconia composites through the stress transformation from tetragonal phase to monoclinic phase. This alloy, having the general formula Ce[sub x]Hf[sub y]Zr[sub 1[minus]x[minus]y]O[sub 2], is produced through the addition of appropriate amounts of ceria and hafnia to the zirconia. Typically, improved toughness is achieved with about 5 to about 15 mol % ceria and up to about 40 mol % hafnia. The preparation of alloys of these compositions are given together with data as to the densities, tetragonal phase content, hardness and fracture toughness. The alloys are useful in preparing zirconia bodies as well as reinforcing ceramic composites. 1 fig.

In vitro degradation, hemolysis, and cytocompatibility of PEO/PLLA composite coating on biodegradable AZ31 alloy.

PubMed

Wei, Zhongling; Tian, Peng; Liu, Xuanyong; Zhou, Bangxin

2015-02-01

Magnesium and its alloys have large potential as degradable and absorbable biomaterials because of their mechanical properties and biocompatibility. However, their corrosion resistance is usually inadequate especially in physiological environment, which limits their broad applications in biomedical areas. In this work, plasma electrolytic oxidized/poly(l-lactide) (PEO/PLLA) composite coating was successfully fabricated on biodegradable AZ31 alloy by combing PEO process and sealing with PLLA. The microstructure, elemental composition, and phase composition of the PEO/PLLA composite coating were investigated. The in vitro degradation of the PEO/PLLA composite coating in simulated body fluid (SBF) was also systematically evaluated. The results revealed that the PEO/PLLA composite coating improved the corrosion resistance of AZ31 alloy significantly. The corrosion potential shifted from -1.663V to more positive position -1.317 V and the corrosion current density was reduced with six-order of magnitude. The Mg(2+) ions, hydrogen release, and pH value change of solution caused by degradation were all decreased significantly. Moreover, the PEO process played a critical role in sustaining the integrity of the implant in long-term service. The result of hemolysis test showed that the PEO/PLLA composite coating vested AZ31 alloy a low hemolysis ratio (0.806 ± 0.771)%, which is much lower than the safe value of 5% according to ISO 10993-4. For the cytocompatibility test, compared with bare AZ31 alloy and PEO coating, MC3T3-E1 cells showed much better adhesion and proliferation on the PEO/PLLA composite coating with nearly 4-fold increase of cells after 7-day cultivation, indicating that the PEO/PLLA composite coating has good biocompatibility for biomedical applications. © 2014 Wiley Periodicals, Inc.

Platinum- and platinum alloy-coated palladium and palladium alloy particles and uses thereof

DOEpatents

Adzic, Radoslav; Zhang, Junliang; Mo, Yibo; Vukmirovic, Miomir Branko

2010-04-06

The present invention relates to particle and nanoparticle composites useful as oxygen-reduction electrocatalysts. The particle composites are composed of a palladium or palladium-alloy particle or nanoparticle substrate coated with an atomic submonolayer, monolayer, bilayer, or trilayer of zerovalent platinum atoms. The invention also relates to a catalyst and a fuel cell containing the particle or nanoparticle composites of the invention. The invention additionally includes methods for oxygen reduction and production of electrical energy by using the particle and nanoparticle composites of the invention.

NASA-UVa light aerospace alloy and structures technology program

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Haviland, John K.; Herakovich, Carl T.; Pilkey, Walter D.; Pindera, Marek-Jerzy; Scully, John R.; Stoner, Glenn E.; Swanson, Robert E.; Thornton, Earl A.; Wawner, Franklin E., Jr.

1991-01-01

The general objective of the NASA-UVa Light Aerospace Alloy and Structures Technology Program was to conduct research on the performance of next generation, light weight aerospace alloys, composites, and associated thermal gradient structures. The following research areas were actively investigated: (1) mechanical and environmental degradation mechanisms in advanced light metals and composites; (2) aerospace materials science; (3) mechanics of materials and composites for aerospace structures; and (4) thermal gradient structures.

Method for fabricating laminated uranium composites

DOEpatents

Chapman, L.R.

1983-08-03

The present invention is directed to a process for fabricating laminated composites of uranium or uranium alloys and at least one other metal or alloy. The laminated composites are fabricated by forming a casting of the molten uranium with the other metal or alloy which is selectively positioned in the casting and then hot-rolling the casting into a laminated plate in or around which the casting components are metallurgically bonded to one another to form the composite. The process of the present invention provides strong metallurgical bonds between the laminate components primarily since the bond disrupting surface oxides on the uranium or uranium alloy float to the surface of the casting to effectively remove the oxides from the bonding surfaces of the components.

Development of graded Ni-YSZ composite coating on Alloy 690 by Pulsed Laser Deposition technique to reduce hazardous metallic nuclear waste inventory.

PubMed

Sengupta, Pranesh; Rogalla, Detlef; Becker, Hans Werner; Dey, Gautam Kumar; Chakraborty, Sumit

2011-08-15

Alloy 690 based 'nuclear waste vitrification furnace' components degrade prematurely due to molten glass-alloy interactions at high temperatures and thereby increase the volume of metallic nuclear waste. In order to reduce the waste inventory, compositionally graded Ni-YSZ (Y(2)O(3) stabilized ZrO(2)) composite coating has been developed on Alloy 690 using Pulsed Laser Deposition technique. Five different thin-films starting with Ni80YSZ20 (Ni 80 wt%+YSZ 20 wt%), through Ni60YSZ40 (Ni 60 wt%+YSZ 40 wt%), Ni40YSZ60 (Ni 40 wt%+YSZ 60 wt%), Ni20YSZ80 (Ni 20 wt%+YSZ 80 wt%) and Ni0YSZ100 (Ni 0 wt%+YSZ 100 wt%), were deposited successively on Alloy 690 coupons. Detailed analyses of the thin-films identify them as homogeneous, uniform, pore free and crystalline in nature. A comparative study of coated and uncoated Alloy 690 coupons, exposed to sodium borosilicate melt at 1000°C for 1-6h suggests that the graded composite coating could substantially reduced the chemical interactions between Alloy 690 and borosilicate melt. Copyright © 2011 Elsevier B.V. All rights reserved.

Tribological properties of self-lubricating fluoride-metal composites to 900 C (1650 F): A review and some new developments

NASA Technical Reports Server (NTRS)

Sliney, H. E.; Graham, J. W.

1974-01-01

The friction and wear behavior of some fluoride-metal, self-lubricating composites are summarized. Fluoride-infiltrated sintered nickel alloy composites and plasma-sprayed, co-deposited fluoride-nickel alloy composites are described. The importance of proper surface-conditioning of the composites is stressed. Performance of fluoride-metal composites in some machine application evaluation is discussed.

Directionally solidified eutectic alloy gamma-beta

NASA Technical Reports Server (NTRS)

Tewari, S. N.

1977-01-01

A pseudobinary eutectic alloy composition was determined by a previously developed bleed-out technique. The directionally solidified eutectic alloy with a composition of Ni-37.4Fe-10.0Cr-9.6Al (in wt%) had tensile strengths decreasing from 1,090 MPa at room temperature to 54 MPa at 1,100 C. The low density, excellent microstructural stability, and oxidation resistance of the alloy during thermal cycling suggest that it might have applicability as a gas turbine vane alloy while its relatively low high temperature strength precludes its use as a blade alloy. A zirconium addition increased the 750 C strength, and a tungsten addition was ineffective. The gamma=beta eutectic alloys appeared to obey a normal freezing relation.

Studies on microstructure and mechanical behaviour of A7075- Flyash/SiC hybrid metal matrix composites

NASA Astrophysics Data System (ADS)

Venkata Reddy, V.; Gopi Krishna, M.; Praveen Kumar, K.; Naga Kishore, B. S.; Babu Rao, J.; Bhargava, NRMR

2018-02-01

Experiments have been performed under laboratory condition to review the mechanical behaviour of the hybrid composites with aluminium matrix A7075 alloy, reinforced with silicon carbide (SiC) and Flyash. This has been possible by fabricating the samples through usual stir casting technique. Scanning electron microscopy was used for microstructure analysis. Chemical characterization of both matrix and composites was performed by using EDAX. Density, hardness, tensile and deformation studies were conceded out on both the base alloy and composites. Enhanced hardness and deformed properties were observed for all the composites. Interestingly improved tensile results were obtained for the composites than alloy. Dispersion of (SiC) and Flyash particles in aluminium matrix enhances the hardness of the composites.

Fusion boundary microstructure evolution in aluminum alloys

NASA Astrophysics Data System (ADS)

Kostrivas, Anastasios Dimitrios

2000-10-01

A melting technique was developed to simulate the fusion boundary of aluminum alloys using the GleebleRTM thermal simulator. Using a steel sleeve to contain the aluminum, samples were heated to incremental temperatures above the solidus temperature of a number of alloys. In alloy 2195, a 4wt%Cu-1wt%Li alloy, an equiaxed non-dendritic zone (EQZ) could be formed by heating in the temperature range from approximately 630 to 640°C. At temperatures above 640°C, solidification occurred by the normal epitaxial nucleation and growth mechanism. Fusion boundary behavior was also studied in alloys 5454-H34, 6061-T6, and 2219-T8. Additionally, experimental alloy compositions were produced by making bead on plate welds using an alloy 5454-H32 base metal and 5025 or 5087 filler metals. These filler metals contain zirconium and scandium additions, respectively, and were expected to influence nucleation and growth behavior. Both as-welded and welded/heat treated (540°C and 300°C) substrates were tested by melting simulation, resulting in dendritic and EQZ structures depending on composition and substrate condition. Orientation imaging microscopy (OIM(TM)) was employed to study the crystallographic character of the microstructures produced and to verify the mechanism responsible for EQZ formation. OIM(TM) proved that grains within the EQZ have random orientation. In all other cases, where the simulated microstructures were dendritic in nature, it was shown that epitaxy was the dominant mode of nucleation. The lack of any preferred crystallographic orientation relationship in the EQZ supports a theory proposed by Lippold et al that the EQZ is the result of heterogeneous nucleation within the weld unmixed zone. EDS analysis of the 2195 on STEM revealed particles with ternary composition consisted of Zr, Cu and Al and a tetragonal type crystallographic lattice. Microdiffraction line scans on EQZ grains in the alloy 2195 showed very good agreement between the measured Cu composition within the interior of the non-dendritic grains and the corresponding value the Scheil equation predicts for the first solid to form upon solidification for a binary Al-Cu alloy with identical Cu composition. In the context of the alloys, compositions and substrate conditions examined a mechanistic model for EQZ zone formation is proposed, helpful in adjusting base metal compositions and/or substrate conditions to control fusion boundary microstructure.

Templated Atom-Precise Galvanic Synthesis and Structure Elucidation of a [Ag24Au(SR)18](-) Nanocluster.

PubMed

Bootharaju, Megalamane S; Joshi, Chakra P; Parida, Manas R; Mohammed, Omar F; Bakr, Osman M

2016-01-18

Synthesis of atom-precise alloy nanoclusters with uniform composition is challenging when the alloying atoms are similar in size (for example, Ag and Au). A galvanic exchange strategy has been devised to produce a compositionally uniform [Ag24Au(SR)18](-) cluster (SR: thiolate) using a pure [Ag25(SR)18](-) cluster as a template. Conversely, the direct synthesis of Ag24Au cluster leads to a mixture of [Ag(25-x)Au(x)(SR)18](-), x=1-8. Mass spectrometry and crystallography of [Ag24Au(SR)18](-) reveal the presence of the Au heteroatom at the Ag25 center, forming Ag24Au. The successful exchange of the central Ag of Ag25 with Au causes perturbations in the Ag25 crystal structure, which are reflected in the absorption, luminescence, and ambient stability of the particle. These properties are compared with those of Ag25 and Ag24Pd clusters with same ligand and structural framework, providing new insights into the modulation of cluster properties with dopants at the single-atom level. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Large-area synthesis of monolayered MoS(2(1-x))Se(2x) with a tunable band gap and its enhanced electrochemical catalytic activity.

PubMed

Yang, Lei; Fu, Qi; Wang, Wenhui; Huang, Jian; Huang, Jianliu; Zhang, Jingyu; Xiang, Bin

2015-06-21

"Band gap engineering" in two-dimensional (2D) materials plays an important role in tailoring their physical and chemical properties. The tuning of the band gap is typically achieved by controlling the composition of the semiconductor alloys. However, large-area preparation of 2D alloys remains a major challenge. Here, we report the large-area synthesis of high-quality monolayered MoS2(1-x)Se2x with a size coverage of hundreds of microns using a chemical vapor deposition method. The photoluminescence (PL) spectroscopy results confirm the tunable band gap in MoS2(1-x)Se2x, which is modulated by varying the Se content. Atomic-scale analysis was performed and the chemical composition was characterized using high-resolution scanning transmission electron microscopy and X-ray photoemission spectroscopy. With the introduction of Se into monolayered MoS2, it leads to enhanced catalytic activity in an electrochemical reaction for hydrogen generation, compared to monolayered MoS2 and MoSe2. It is promising as a potential alternative to expensive noble metals.

Evolution of Primary Fe-Rich Compounds in Secondary Al-Si-Cu Alloys

NASA Astrophysics Data System (ADS)

Fabrizi, Alberto; Capuzzi, Stefano; Timelli, Giulio

Although iron is usually added in die cast Al-Si foundry alloys to prevent die soldering, primary Fe-rich particles are generally considered as "hardspot" inclusions which compromise the mechanical properties of the alloy, namely ductility and toughness. As there is no economical methods to remove the Fe excess in secondary Al-Si alloys at this time, the control of solidification process and chemical composition of the alloy is a common industrial practice to overcome the negative effects connected with the presence of Fe-rich particles. In this work, the size and morphology as well as the nucleation density of primary Fe-rich particles have been studied as function of cooling rate and alloy chemical composition for secondary Al-Si-Cu alloys. The solidification experiments were carried out using differential scanning calorimetry whereas morphology investigations were conducted using optical and scanning electron microscopy. Mcrosegregations and chemical composition of primary Fe-rich particles were examined by energy dispersive spectroscopy.

Solidification and crystal growth of solid solution semiconducting alloys

NASA Technical Reports Server (NTRS)

Lehoczky, S. L.; Szofran, F. R.

1984-01-01

Problems associated with the solidification and crytal growth of solid-solution semiconducting alloy crystals in a terrestrial environment are described. A detailed description is given of the results for the growth of mercury cadmium telluride (HgCdTe) alloy crystals by directional solidification, because of their considerable technological importance. A series of HgCdTe alloy crystals are grown from pseudobinary melts by a vertical Bridgman method using a wide range of growth rates and thermal conditions. Precision measurements are performed to establish compositional profiles for the crystals. The compositional variations are related to compositional variations in the melts that can result from two-dimensional diffusion or density gradient driven flow effects ahead of the growth interface. These effects are discussed in terms of the alloy phase equilibrium properties, the recent high temperature thermophysical data for the alloys and the highly unusual heat transfer characteristics of the alloy/ampule/furnace system that may readily lead to double diffusive convective flows in a gravitational environment.

Composites Strengthened with Graphene Platelets and Formed in Semisolid State Based on α and α/β MgLiAl Alloys

NASA Astrophysics Data System (ADS)

Dutkiewicz, Jan; Rogal, Łukasz; Fima, Przemyslaw; Ozga, Piotr

2018-04-01

MgLiAl base composites strengthened with graphene platelets were prepared by semisolid processing of ball-milled alloy chips with 2% of graphene platelets. Composites strengthened with graphene platelets show higher hardness and yield stress than the cast alloys, i.e., 160 MPa as compared to 90 MPa for as-cast alloy MgLi9Al1.5. Mechanical properties for MgLiAl-based composites were similar or higher than for composites based on conventional AZ91 or WE43 alloys. The strengthening however was not only due to the presence of graphene, but also phases resulting from the reaction between carbon and lithium, i.e., Li2C2 carbide. Graphene platelets were located at globules boundaries resulting from semisolid processing for all investigated composites. Graphene platelets were in agglomerates forming continuous layers at grain boundaries in the composite based on the alloy MgLi4.5Al1.5. The shape of agglomerates was more complex and wavy in the composite based on MgLi9Al1.5 alloy most probably due to lithium-graphene reaction. Electron diffraction from the two-phase region α + β in MgLi9Al1.5 indicated that [001]α and [110]β directions are rotated about 4° from the ideal relationship [001] hex || [110] bcc phases. It showed higher lattice rotation than in earlier studies what is most probably caused by lattice slip and rotation during semisolid pressing causing substantial deformation particularly within the β phase. Raman spectroscopy studies confirmed the presence of graphene platelets within agglomerates and in addition the presence mainly of Li2C2 carbides in composites based on MgLi4.5Al1.5 and Mg9Li1.5Al alloys. From the character of Raman spectra refinement of graphene platelets was found in comparison with their initial size. The graphene areas without carbides contain graphene nanoplatelets with lateral dimension close to initial graphene sample. Electron diffraction allowed to confirm the presence of Li2C2 carbide at the surface of agglomerates found from Raman spectroscopy results.

Composites Strengthened with Graphene Platelets and Formed in Semisolid State Based on α and α/β MgLiAl Alloys

NASA Astrophysics Data System (ADS)

Dutkiewicz, Jan; Rogal, Łukasz; Fima, Przemyslaw; Ozga, Piotr

2018-05-01

MgLiAl base composites strengthened with graphene platelets were prepared by semisolid processing of ball-milled alloy chips with 2% of graphene platelets. Composites strengthened with graphene platelets show higher hardness and yield stress than the cast alloys, i.e., 160 MPa as compared to 90 MPa for as-cast alloy MgLi9Al1.5. Mechanical properties for MgLiAl-based composites were similar or higher than for composites based on conventional AZ91 or WE43 alloys. The strengthening however was not only due to the presence of graphene, but also phases resulting from the reaction between carbon and lithium, i.e., Li2C2 carbide. Graphene platelets were located at globules boundaries resulting from semisolid processing for all investigated composites. Graphene platelets were in agglomerates forming continuous layers at grain boundaries in the composite based on the alloy MgLi4.5Al1.5. The shape of agglomerates was more complex and wavy in the composite based on MgLi9Al1.5 alloy most probably due to lithium-graphene reaction. Electron diffraction from the two-phase region α + β in MgLi9Al1.5 indicated that [001]α and [110]β directions are rotated about 4° from the ideal relationship [001] hex || [110] bcc phases. It showed higher lattice rotation than in earlier studies what is most probably caused by lattice slip and rotation during semisolid pressing causing substantial deformation particularly within the β phase. Raman spectroscopy studies confirmed the presence of graphene platelets within agglomerates and in addition the presence mainly of Li2C2 carbides in composites based on MgLi4.5Al1.5 and Mg9Li1.5Al alloys. From the character of Raman spectra refinement of graphene platelets was found in comparison with their initial size. The graphene areas without carbides contain graphene nanoplatelets with lateral dimension close to initial graphene sample. Electron diffraction allowed to confirm the presence of Li2C2 carbide at the surface of agglomerates found from Raman spectroscopy results.

Microstructure and Elevated Temperature Properties of a Refractory TaNbHfZrTi Alloy

DTIC Science & Technology

2012-01-24

composition of the TaNbHfZrTi alloy produced by vacuum arc melting Composition Ta Nb Hf Zr Ti at.% 19.68 18.93 20.46 21.23 19.7 wt. % 30.04 14.84 30.82 16.34...metallic materials with higher melting points, such as refractory molybdenum (Mo) and niobium ( Nb ) alloys, are examined as alternatives by academic and...creep resistance are the key properties of these alloys, since considerable alloy softening generally occurs at tempera- tures above *0.5 0.6 Tm

Growth and Characterization of Chalcogenide Alloy Nanowires with Controlled Spatial Composition Variation for Optoelectronic Applications

NASA Astrophysics Data System (ADS)

Nichols, Patricia

The energy band gap of a semiconductor material critically influences the operating wavelength of an optoelectronic device. Realization of any desired band gap, or even spatially graded band gaps, is important for applications such as lasers, light-emitting diodes (LEDs), solar cells, and detectors. Compared to thin films, nanowires offer greater flexibility for achieving a variety of alloy compositions. Furthermore, the nanowire geometry permits simultaneous incorporation of a wide range of compositions on a single substrate. Such controllable alloy composition variation can be realized either within an individual nanowire or between distinct nanowires across a substrate. This dissertation explores the control of spatial composition variation in ternary alloy nanowires. Nanowires were grown by the vapor-liquid-solid (VLS) mechanism using chemical vapor deposition (CVD). The gas-phase supersaturation was considered in order to optimize the deposition morphology. Composition and structure were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), and x-ray diffraction (XRD). Optical properties were investigated through photoluminescence (PL) measurements. The chalcogenides selected as alloy endpoints were lead sulfide (PbS), cadmium sulfide (CdS), and cadmium selenide (CdSe). Three growth modes of PbS were identified, which included contributions from spontaneously generated catalyst. The resulting wires were found capable of lasing with wavelengths over 4000 nm, representing the longest known wavelength from a sub-wavelength wire. For CdxPb1-xS nanowires, it was established that the cooling process significantly affects the alloy composition and structure. Quenching was critical to retain metastable alloys with x up to 0.14, representing a new composition in nanowire form. Alternatively, gradual cooling caused phase segregation, which created heterostructures with light emission in both the visible and mid-infrared regimes. The CdSSe alloy system was fully explored for spatial composition variation. CdSxSe1-x nanowires were grown with composition variation across the substrate. Subsequent contact printing preserved the designed composition gradient and led to the demonstration of a variable wavelength photodetector device. CdSSe axial heterostructure nanowires were also achieved. The growth process involved many variables, including a deliberate and controllable change in substrate temperature. As a result, both red and green light emission was detected from single nanowires.

Influence of Sn on the magnetic ordering of Ni-Sn alloy synthesized using chemical reduction method

NASA Astrophysics Data System (ADS)

Dhanapal, K.; Narayanan, V.; Stephen, A.

2016-05-01

The Ni-Sn alloy was synthesized using borohydride assisted chemical reduction method. The composition of the synthesized alloy was determined using atomic absorption spectroscopy which revealed that the observed composition of Sn is high when compared to the initial composition. The ultrafine particles are clearly observed from field emission scanning electron microscope for all the sample. The X-ray diffraction measurement confirmed that the as-synthesized samples are of amorphous like nature while the samples annealed at 773 K showed crystalline nature. The Fourier transform infrared spectroscopy confirmed metallic bond stretching in the alloy samples. The crystallization and phase transition temperature was observed from differential scanning calorimetry. The shift in the crystallization temperature of Ni with increasing percentage of Sn was observed. The vibrating sample magnetometer was employed to understand the magnetic behavior of the Ni-Sn alloy. As-synthesized alloy samples showed paramagnetic nature while the annealed ones exhibit the soft ferromagnetic, antiferromagnetic and paramagnetic nature. The saturation magnetization value and magnetic ordering in the Ni-Sn alloys depend on the percentage of Sn present in the alloy.

Influence of Primary Water Chemistry on Oxides Formed on Alloy 600 and Alloy 690

NASA Astrophysics Data System (ADS)

Devine, Thomas M.

The results of in situ SERS investigations of Alloys' 600 and 690 surface films were combined with the results of a number of ex situ studies conducted by other researchers who used a variety of experimental techniques. Comparing the results of different investigations revealed the surface films' composition and microstructure were most sensitive to alloy composition and the concentrations of aqueous metal cations (especially Fe+2).

Advanced powder metallurgy aluminum alloys and composites

NASA Technical Reports Server (NTRS)

Lisagor, W. B.; Stein, B. A.

1982-01-01

The differences between powder and ingot metallurgy processing of aluminum alloys are outlined. The potential payoff in the use of advanced powder metallurgy (PM) aluminum alloys in future transport aircraft is indicated. The national program to bring this technology to commercial fruition and the NASA Langley Research Center role in this program are briefly outlined. Some initial results of research in 2000-series PM alloys and composites that highlight the property improvements possible are given.

Development and study of chemical vapor deposited tantalum base alloys

NASA Technical Reports Server (NTRS)

Meier, G. H.; Bryant, W. A.

1976-01-01

A technique for the chemical vapor deposition of alloys was developed. The process, termed pulsing, involves the periodic injection of reactant gases into a previously-evacuated reaction chamber where they blanket the substrate almost instantaneously. Formation of alternating layers of the alloy components and subsequent homogenization allows the formation of an alloy of uniform composition with the composition being determined by the duration and relative numbers of the various cycles. The technique has been utilized to produce dense alloys of uniform thickness and composition (Ta- 10 wt % W) by depositing alternating layers of Ta and W by the hydrogen reduction of TaCl5 and WCl6. A similar attempt to deposit a Ta - 8 wt % W - 2 wt% Hf alloy was unsuccessful because of the difficulty in reducing HfCl4 at temperatures below those at which gas phase nucleation of Ta and W occurred.

Transport and breakdown analysis for improved figure-of-merit for AlGaN power devices

NASA Astrophysics Data System (ADS)

Coltrin, Michael E.; Kaplar, Robert J.

2017-02-01

Mobility and critical electric field for bulk AlxGa1-xN alloys across the full composition range (0 ≤ x ≤ 1) are analyzed to address the potential application of this material system for power electronics. Calculation of the temperature-dependent electron mobility includes the potential limitations due to different scattering mechanisms, including alloy, optical polar phonon, deformation potential, and piezoelectric scattering. The commonly used unipolar figure of merit (appropriate for vertical-device architectures), which increases strongly with increasing mobility and critical electric field, is examined across the alloy composition range to estimate the potential performance in power electronics applications. Alloy scattering is the dominant limitation to mobility and thus also for the unipolar figure of merit. However, at higher alloy compositions, the limitations due to alloy scattering are overcome by increased critical electric field. These trade-offs, and their temperature dependence, are quantified in the analysis.

Interface Effects of the Properties and Processing of Graded Composite Aluminum Alloys

DTIC Science & Technology

2015-08-31

diffuse interface. Produced by the Alcoa sequential casting process, the material has a gradient in composition from a stronger, precipitation...strengthened alloy (7055) to a softer, strain-hardenable alloy (5456) [1], [2]. Alcoa donated material, 30x30x2 cm3 in volume. The material was cast, rolled

The kinetics of composite particle formation during mechanical alloying

NASA Technical Reports Server (NTRS)

Aikin, B. J. M.; Courtney, T. H.

1993-01-01

The kinetics of composite particle formation during attritor milling of insoluble binary elemental powders have been examined. The effects of processing conditions (i.e., mill power, temperature, and charge ratio) on these kinetics were studied. Particle size distributions and fractions of elemental and composite particles were determined as functions of milling time and processing conditions. This allowed the deduction of phenomenological rate constants describing the propensity for fracture and welding during processing. For the mill-operating conditions investigated, the number of particles in the mill generally decreased with milling time, indicating a greater tendency for particle welding than fracture. Moreover, a bimodal size distribution is often obtained as a result of preferential welding. Copper and chromium 'alloy' primarily by encapsulation of Cr particles within Cu. This form of alloying also occurs in Cu-Nb alloys processed at low mill power and/or for short milling times. For other conditions, however, Cu-Nb alloys develop a lamellar morphology characteristic of mechanically alloyed two-phase ductile metals. Increasing mill power or charge (ball-to-powder weight) ratio (CR) increases the rate of composite particle formation.

Rheological Behavior and Microstructure of Ceramic Particulate/Aluminum Alloy Composites. Ph.D. Thesis Final Technical Report

NASA Technical Reports Server (NTRS)

Moon, Hee-Kyung

1990-01-01

The rheological behavior and microstructure were investigated using a concentric cylinder viscometer for three different slurries: semi-solid alloy slurries of a matrix alloy, Al-6.5wt percent Si: composite slurries, SiC (sub p) (8.5 microns)/Al-6.5wt percent Si, with the same matrix alloy in the molten state, and composite slurries of the same composition with the matrix alloy in the semi-solid state. The pseudoplasticity of these slurries was obtained by step changes of the shear rate from a given initial shear rate. To study the thixotropic behavior of the system, a slurry was allowed to rest for different periods of time, prior to shearing at a given initial shear rate. In the continuous cooling experiments, the viscosities of these slurries were dependent on the shear rate, cooling rate, volume fraction of the primary solid of the matrix alloy, and volume fraction of silicon carbide. In the isothermal experiments, all three kinds of slurries exhibited non-Newtonian behavior, depending on the volume fraction of solid particles.

The physical metallurgy of mechanically-alloyed, dispersion-strengthened Al-Li-Mg and Al-Li-Cu alloys

NASA Technical Reports Server (NTRS)

Gilman, P. S.

1984-01-01

Powder processing of Al-Li-Mg and Al-Li-Cu alloys by mechanical alloying (MA) is described, with a discussion of physical and mechanical properties of early experimental alloys of these compositions. The experimental samples were mechanically alloyed in a Szegvari attritor, extruded at 343 and 427 C, and some were solution-treated at 520 and 566 C and naturally, as well as artificially, aged at 170, 190, and 210 C for times of up to 1000 hours. All alloys exhibited maximum hardness after being aged at 170 C; lower hardness corresponds to the solution treatment at 566 C than to that at 520 C. A comparison with ingot metallurgy alloys of the same composition shows the MA material to be stronger and more ductile. It is also noted that properly aged MA alloys can develop a better combination of yield strength and notched toughness at lower alloying levels.

Phase composition and corrosion resistance of magnesium alloys

NASA Astrophysics Data System (ADS)

Morozova, G. I.

2008-03-01

The effects of phase composition of castable experimental and commercial alloys based on the Mg-Al, Mg-Al-Mn, Mg-Al-Zn-Mn, and Mg-Zn-Zr systems and of the form of existence of iron and hydrogen admixtures on the rate of corrosion of the alloys in 3% solution of NaCl are studied. The roles of heat treatment in the processes of hydrogen charging and phase formation in alloy ML5pch and of hydrogen in the process of formation of zirconium hydrides and zinc zirconides in alloys of the Mg-Zn-Zr system and their effect on the corrosion and mechanical properties of alloy ML12 are discussed.

Vapor-liquid-solid epitaxial growth of Si 1-xGe x alloy nanowires. Composition dependence on precursor reactivity and morphology control for vertical forests

DOE PAGES

Choi, S. G.; Manandhar, P.; Picraux, S. T.

2015-07-07

The growth of high-density group IV alloy nanowire forests is critical for exploiting their unique functionalities in many applications. Here, the compositional dependence on precursor reactivity and optimized conditions for vertical growth are studied for Si 1- x Ge x alloy nanowires grown by the vapor-liquid-solid method. The nanowire composition versus gas partial-pressure ratio for germane-silane and germane-disilane precursor combinations is obtained at 350°C over a wide composition range (0.05 ≤ x ≤ 0.98) and a generalized model to predict composition for alloy nanowires is developed based on the relative precursor partial pressures and reactivity ratio. In combination with germane,more » silane provides more precise compositional control at high Ge concentrations (x > 0.7), whereas disilane greatly increases the Si concentration for a given gas ratio and enables more precise alloy compositional control at small Ge concentrations (x < 0.3). Vertically oriented, non-kinking nanowire forest growth on Si (111) substrates is then discussed for silane/germane over a wide range of compositions, with temperature and precursor partial pressure optimized by monitoring the nanowire growth front using in-situ optical reflectance. For high Ge compositions (x ≈ 0.9), a “two-step” growth approach with nucleation at higher temperatures results in nanowires with high-density and uniform vertical orientation. Furthermore, increasing Si content (x ≈ 0.8), the optimal growth window is shifted to higher temperatures, which minimizes nanowire kinking morphologies. For Si-rich Si 1- x Ge x alloys (x ≈ 0.25), vertical nanowire growth is enhanced by single-step, higher-temperature growth at reduced pressures.« less

Characteristics of epitaxial garnets grown by CVD using single metal alloy sources. [Chemical Vapor Deposition

NASA Technical Reports Server (NTRS)

Besser, P. J.; Hamilton, T. N.; Mee, J. E.; Stermer, R. L.

1974-01-01

Single metal alloys have been explored as the cation source in the chemical vapor deposition (CVD) of iron garnets. Growth of good quality single crystal garnet films containing as many as five different cations has been achieved over a wide range of deposition conditions. The relationship of film composition to alloy compositions and deposition conditions has been determined for several materials. By proper choice of the alloy composition and the deposition conditions, uncrazed deposits were grown on (111) gadolinium gallium garnet (GGG) substrates. Data on physical, magnetic and optical properties of representative films is presented and discussed.

Electronic modification of Cu-based chalcopyrite semiconductors induced by lattice deformation and composition alchemy

NASA Astrophysics Data System (ADS)

Jiang, F. D.; Feng, J. Y.

2008-02-01

Using first principles calculation, we systematically investigate the electronic modification of Cu-based chalcopyrite semiconductors induced by lattice deformation and composition alchemy. It is shown that the optical band gap Eg is remarkably sensitive to the anion displacement μ, resulting from the opposite shifts of conduction band minimum and valence band maximum. Meanwhile, the dependence of structural parameters of alloyed compounds on alloy composition x is demonstrated for both cation and anion alloying. The d orbitals of group-III cations are found to be of great importance in the calculation. Abnormal changes in the optical band gap Eg induced by anion alloying are addressed.

Fatigue Resistance of Liquid-assisted Self-repairing Aluminum Alloys Reinforced with Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Wright, M. Clara; Manuel, Michele; Wallace, Terryl

2013-01-01

A self-repairing aluminum-based composite system has been developed using a liquid-assisted healing theory in conjunction with the shape memory effect of wire reinforcements. The metal-metal composite was thermodynamically designed to have a matrix with a relatively even dispersion of a low-melting eutectic phase, allowing for repair of cracks at a predetermined temperature. Additionally, shape memory alloy (SMA) wire reinforcements were used within the composite to provide crack closure. Investigators focused the research on fatigue cracks propagating through the matrix in order to show a proof-of-concept Shape Memory Alloy Self-Healing (SMASH) technology for aeronautical applications.

Advanced composite alloys for constructional parts of robots

NASA Astrophysics Data System (ADS)

Issin, D. K.; Zholdubayeva, Zh D.; Neshina, Y. G.; Alkina, A. D.; Khuangan, N.; Rahimova, G. M.

2018-05-01

In recent years all over the world special attention has been paid to the development and implementation of nanostructured materials possessing unique properties and opening fascinating prospects for the development of technical progress in various fields of human activities. A special place can be given to the development of service robots, the market of which is actively developing. There is problem associated mainly with the lack of heat-strengthened alloys which consists in low thermal stability of the alloy properties under the conditions of elevated variable temperatures and loads. The article presents studies to assess the effect of composition, the amounts of refractory nanoscale particles and methods for their introduction into the melt on the structure and properties in nanostructured composite aluminum alloys. The powders of metals, alloys, as well as silicon carbide and aluminum oxide were used to produce the nanostructured powder composite materials. As a result of the research, NPCM compositions containing micro-size particles of transition metals that are carriers of nanosized reinforcing particles and initiators of the formation of an intermetallide of endogenous origin in a melt.

Improvement of chemical composition, structure and mechanical properties of heat-resistant chromium-nickel alloy

NASA Astrophysics Data System (ADS)

Varlamova, S.; Trushnikova, A.; Rumyantsev, B.; Butrim, V.; Simonov, V.

2018-04-01

A thermodynamic analysis of a multicomponent system of the Cr-Ni alloy (Cr-32Ni-1,5W-0,25V-0,5Ti) with small additions of refractory metals was carried out. The microstructure and phase composition of the base alloy (I) and alloy with additional alloying (II) were studied. The effect of additives on the mechanical properties of the Cr-Ni alloy at 20, 900 and 1080 °C was shown. The microstructure of alloys I and II was studied in the fracture zone of samples after tensile tests at different temperatures. We studied the effect of small additives on the microstructure of alloys and changes in the morphology of the structural components (phases) as a function of temperature and degree of deformation.

Microstructure and Mechanical Properties of C/C Composite/TC17 Joints with Ag-Cu-Ti Brazing Alloy

NASA Astrophysics Data System (ADS)

Cao, Xiujie; Zhu, Ying; Guo, Wei; Peng, Peng; Ma, Kaituo

2017-12-01

Carbon/Carbon composite(C/C) was vacuum brazed to titanium alloy (TC17) using Ag-Cu-Ti brazing alloy. The effects of brazing temperature on the interfacial microstructure and joint properties were investigated by energy dispersive spectrometer (EDS), a scanning electron microscope (SEM), X-ray diffraction (XRD) and Gleeble1500D testing machine. Results show that C/C composite and TC17 were successfully brazed using AgCuTi brazing alloy. Various phases including TiC, Ag(s, s), Cu(s, s), Ti3Cu4, TiCu, and Ti2Cu were formed in the brazed joint. The maximum shear strength of the brazed joints with AgCuTi brazing alloy was 24±1 MPa when brazed at 860°C for 15 min.

Indentation creep behaviors of amorphous Cu-based composite alloys

NASA Astrophysics Data System (ADS)

Song, Defeng; Ma, Xiangdong; Qian, Linfang

2018-04-01

This work reports the indentation creep behaviors of two Si2Zr3/amorphous Cu-based composite alloys utilizing nanoindentation technique. By analysis with Kelvin model, the retardation spectra of alloys at different positions, detached and attached regions to the intermetallics, were deduced. For the indentation of detached regions to Si2Zr3 intermetallics in both alloys, very similarity in creep displacement can be observed and retardation spectra show a distinct disparity in the second retardation peak. For the indentation of detached regions, the second retardation spectra also display distinct disparity. At both positions, the retardation spectra suggest that Si elements may lead to the relatively dense structure in the amorphous matrix and to form excessive Si2Zr3 intermetallics which may deteriorate the plastic deformation of current Cu-based composite alloys.

Irradiation-enhanced α' precipitation in model FeCrAl alloys

DOE PAGES

Edmondson, Philip D.; Briggs, Samuel A.; Yamamoto, Yukinori; ...

2016-02-17

We have irradiated the model FeCrAl alloys with varying compositions (Fe(10–18)Cr(10–6)Al at.%) with a neutron at ~ 320 to damage levels of ~ 7 displacements per atom (dpa) to investigate the compositional influence on the formation of irradiation-induced Cr-rich α' precipitates using atom probe tomography. In all alloys, significant number densities of these precipitates were observed. Cluster compositions were investigated and it was found that the average cluster Cr content ranged between 51.1 and 62.5 at.% dependent on initial compositions. Furthermore, this is significantly lower than the Cr-content of α' in binary FeCr alloys. As a result, significant partitioning ofmore » the Al from the α' precipitates was also observed.« less

Comparative Studies on Al-Based Composite Powder Reinforced with Nano Garnet and Multi-wall Carbon Nanotubes

NASA Astrophysics Data System (ADS)

Basariya, M. Raviathul; Srivastava, V. C.; Mukhopadhyay, N. K.

2015-11-01

Effect of mechanical alloying/milling on microstructural evolution and hardness variations of garnet and multi-walled carbon nanotubes (MWCNTs)-reinforced Al-Mg-Si alloy (EN AW6082) composites are investigated. Structural and morphological studies revealed that the composite powders prepared by milling display a more homogenous distribution of the reinforcing particles. Improved nanoindentation hardness viz., 4.24 and 5.90 GPa are achieved for EN AW6082/Garnet and EN AW6082/MWCNTs composites, respectively, and it is attributed to severe deformation of the aluminum alloy powders and embedding of the harder reinforcement particles uniformly into the aluminum alloy matrix. However, enhancement in case of MWCNTs-reinforced composite makes apparent the effect of its nanosized uniform dispersion in the matrix, thereby resisting the plastic deformation at lower stress and increased dislocation density evolved during high-energy ball milling. The results of the present study indicate that carbon nanotubes and garnet can be effectively used as reinforcements for Al-based composites.

NASA-UVA light aerospace alloy and structures technology program

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Haviland, John K.; Herakovich, Carl T.; Pilkey, Walter D.; Pindera, Marek-Jerzy; Stoner, Glenn E.; Swanson, Robert E.; Thornton, Earl A.; Wawner, Franklin E., Jr.; Wert, John A.

1990-01-01

The objective of the Light Aerospace Alloy and Structures Technology Program is to conduct interdisciplinary graduate student research on the performance of next generation, light weight aerospace alloys, composites, and associated thermal gradient structures. Individual technical objectives are established for each project. Efforts aim to produce basic understanding of material behavior, monolithic and composite alloys, processing methods, solid and mechanics analyses, measurement advances, and a pool of educated graduate students. Progress is reported for 11 areas of study.

High-field superconductivity in the Nb-Ti-Zr ternary system

NASA Astrophysics Data System (ADS)

Ralls, K. M.; Rose, R. M.; Wulff, J.

1980-06-01

Resistive critical current densities, critical fields, and normal-state electrical resistivities were obtained at 4.2 °K for 55 alloys in the Nb-Ti-Zr ternary alloy system, excepting Ti-Zr binary compositions. The resistive critical field as a function of ternary composition has a saddle point between the Nb-Ti and Nb-Zr binaries, so that ternary alloying in this system is not expected to result in higher critical fields than the binary alloys.

Low energy milling method, low crystallinity alloy, and negative electrode composition

DOEpatents

Le, Dihn B; Obrovac, Mark N; Kube, Robert Y; Landucci, James R

2012-10-16

A method of making nanostructured alloy particles includes milling a millbase in a pebble mill containing milling media. The millbase comprises: (i) silicon, and (ii) at least one of carbon or a transition metal, and wherein the nanostructured alloy particles are substantially free of crystalline domains greater than 50 nanometers in size. A method of making a negative electrode composition for a lithium ion battery including the nanostructured alloy particles is also disclosed.

Compositional instability of {beta}-phase in Ni-Mn-Ga alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chernenko, V.A.

1999-02-05

The ferromagnetic Heusler alloys of stoichiometric Ni{sub 2}MnGa and nonstoichiometric Ni-Mn-Ga chemical compositions though not containing a noble-metal, indeed, belong to {beta}-alloys which lattice stability is decided by the Hume-Rothery mechanism: electron concentration e/a measuring the decrease of the electron energy due to the pseudogap formation and size factor. The intriguing feature of Ni-Mn-Ga alloys similarly to Ti-Ni, Cu-Al-Be and Ni-Al alloys arises that transformation temperature, M{sub s}, is dramatically dependent on concentration reflecting an extremely high sensitivity of the lattice stability toward the content variation. The main purpose of present paper is an analysis of previous data concerning themore » compositional dependence of M{sub s} from the viewpoint of searching for empirical correlation between the electron concentration and stability of {beta}-phase in Ni-Mn-Ga system. This analysis will provide a confirmation of the feasibility of a reasonable explanation of seemingly random collection of alloys grouped with respect to their M{sub s} values as well as other features. The alloys of compositional range studied previously are added here to a few alloys including ones doped with V and Ge to ensure the decisive role of e/a ratio on M{sub s}. Original results about the temperature dependent resistance behavior are presented as well.« less

Feasibility of producing cast-refractory metal-fiber superalloy composites

NASA Technical Reports Server (NTRS)

Mcintyre, R. D.

1973-01-01

A study was conducted to evaluate the feasibility of direct casting as a practical method for producing cast superalloy tungsten or columbium alloy fiber composites while retaining a high percentage of fiber strength. Fourteen nickel base, four cobalt, and three iron based matrices were surveyed for their degree of reaction with the metal fibers. Some stress-rupture results were obtained at temperatures of 760, 816, 871, and 1093 C for a few composite systems. The feasibility of producing acceptable composites of some cast nickel, cobalt, and iron matrix alloys with tungsten or columbium alloy fibers was demonstrated.

Performance of a Steel/Oxide Composite Waste Form for Combined Waste Steams from Advanced Electrochemical Processes

DOE Office of Scientific and Technical Information (OSTI.GOV)

Indacochea, J. E.; Gattu, V. K.; Chen, X.

The results of electrochemical corrosion tests and modeling activities performed collaboratively by researchers at the University of Illinois at Chicago and Argonne National Laboratory as part of workpackage NU-13-IL-UIC-0203-02 are summarized herein. The overall objective of the project was to develop and demonstrate testing and modeling approaches that could be used to evaluate the use of composite alloy/ceramic materials as high-level durable waste forms. Several prototypical composite waste form materials were made from stainless steels representing fuel cladding, reagent metals representing metallic fuel waste streams, and reagent oxides representing oxide fuel waste streams to study the microstructures and corrosion behaviorsmore » of the oxide and alloy phases. Microelectrodes fabricated from small specimens of the composite materials were used in a series of electrochemical tests to assess the corrosion behaviors of the constituent phases and phase boundaries in an aggressive acid brine solution at various imposed surface potentials. The microstructures were characterized in detail before and after the electrochemical tests to relate the electrochemical responses to changes in both the electrode surface and the solution composition. The results of microscopic, electrochemical, and solution analyses were used to develop equivalent circuit and physical models representing the measured corrosion behaviors of the different materials pertinent to long-term corrosion behavior. This report provides details regarding (1) the production of the composite materials, (2) the protocol for the electrochemical measurements and interpretations of the responses of multi-phase alloy and oxide composites, (3) relating corrosion behaviors to microstructures of multi-phase alloys based on 316L stainless steel and HT9 (410 stainless steel was used as a substitute) with added Mo, Ni, and/or Mn, and (4) modeling the corrosion behaviors and rates of several alloy/oxide composite materials made with added lanthanide and uranium oxides. These analyses show the corrosion behaviors of the alloy/ceramic composite materials are very similar to the corrosion behaviors of multi-phase alloy waste forms, and that the presence of oxide inclusions does not impact the corrosion behaviors of the alloy phases. Mixing with metallic waste streams is beneficial to lanthanide and uranium oxides in that they react with Zr in the fuel waste to form highly durable zirconates. The measured corrosion behaviors suggest properly formulated composite materials would be suitable waste forms for combined metallic and oxide waste streams generated during electrometallurgical reprocessing of spent nuclear fuel. Electrochemical methods are suitable for evaluating the durability and modeling long-term behavior of composite waste forms: the degradation model developed for metallic waste forms can be applied to the alloy phases formed in the composite and an affinity-based mineral dissolution model can be applied to the ceramic phases.« less

Computational-Experimental Processing of Boride/Carbide Composites by Reactive Infusion of Hf Alloy Melts into B4C

DTIC Science & Technology

2015-09-16

AFRL-AFOSR-VA-TR-2015-0314 Computational -Experimental Processing of Boride /Carbide Composites by Reactive Infusion of Hf Alloy Melts into B4C...Computational -Experimental Processing of Boride /Carbide Composites by Reactive Infusion of Hf Alloy Melts into B4C 5a.  CONTRACT NUMBER 5b.  GRANT...with a packed bed of B4C to form boride - carbide precipitates. Although the ultimate goal of the research endeavor is to enhance significantly the

An atomic scale study of surface termination and digital alloy growth in InGaAs/AlAsSb multi-quantum wells.

PubMed

Mauger, S J C; Bozkurt, M; Koenraad, P M; Zhao, Y; Folliot, H; Bertru, N

2016-07-20

An atomic scale study has been performed to understand the influence of the (As,Sb) shutter sequences during interface formation on the optical properties of InGaAs/AlAsSb quantum wells. Our cross-sectional scanning tunneling microscopy results show that the onset of the Sb profile is steep in the Sb-containing layers whereas an appreciable segregation of Sb in the subsequently grown Sb free layers is observed. The steep rise of the Sb profile is due to extra Sb that is supplied to the surface prior to the growth of the Sb-containing layers. No relation is found between the (As,Sb) termination conditions of the Sb-containing layers and the resulting Sb profiles in the capping layers. Correspondingly we see that the optical properties of these quantum wells are also nearly independent on the (As,Sb) shutter sequences at the interface. Digital alloy growth in comparison to conventional molecular beam epitaxy growth was also explored. X-ray results suggest that the structural properties of the quantum well structures grown by conventional molecular beam epitaxy techniques are slightly better than those formed by digital alloy growth. However photoluminescence studies indicate that the digital alloy samples give rise to a more intense and broader photoluminescence emission. Cross-sectional scanning tunneling microscopy measurements reveal that lateral composition modulations present in the digital alloys are responsible for the enhancement of the photoluminescence intensity and inhomogeneous broadening.

Dry sliding wear of heat treated hybrid metal matrix composites

NASA Astrophysics Data System (ADS)

Naveed, Mohammed; Khan, A. R. Anwar

2016-09-01

In recent years, there has been an ever-increasing demand for enhancing mechanical properties of Aluminum Matrix Composites (AMCs), which are finding wide applications in the field of aerospace, automobile, defence etc,. Among all available aluminium alloys, Al6061 is extensively used owing to its excellent wear resistance and ease of processing. Newer techniques of improving the hardness and wear resistance of Al6061 by dispersing an appropriate mixture of hard ceramic powder and whiskers in the aluminium alloy are gaining popularity. The conventional aluminium based composites possess only one type of reinforcements. Addition of hard reinforcements such as silicon carbide, alumina, titanium carbide, improves hardness, strength and wear resistance of the composites. However, these composites possessing hard reinforcement do posses several problems during their machining operation. AMCs reinforced with particles of Gr have been reported to be possessing better wear characteristics owing to the reduced wear because of formation of a thin layer of Gr particles, which prevents metal to metal contact of the sliding surfaces. Further, heat treatment has a profound influence on mechanical properties of heat treatable aluminium alloys and its composites. For a solutionising temperature of 5500C, solutionising duration of 1hr, ageing temperature of 1750C, quenching media and ageing duration significantly alters mechanical properties of both aluminium alloy and its composites. In the light of the above, the present paper aims at developing aluminium based hybrid metal matrix composites containing both silicon carbide and graphite and characterize their mechanical properties by subjecting it to heat treatment. Results indicate that increase of graphite content increases wear resistance of hybrid composites reinforced with constant SiC reinforcement. Further heat treatment has a profound influence on the wear resistance of the matrix alloy as well as its hybrid composites. For all the heat treatment processes studied ice quenching with ageing duration of 6hrs resulted in improved wear resistance of both the unreinforced matrix alloy and its hybrid composites.

Laser Surface Treatment and Modification of Aluminum Alloy Matrix Composites

NASA Astrophysics Data System (ADS)

Abbass, Muna Khethier

2018-02-01

The present work aimed to study the laser surface treatment and modification of Al-4.0%Cu-1.0%Mg alloy matrix composite reinforced with 10%SiC particles produced by stir casting. The specimens of the base alloy and composite were irradiated with an Nd:YAG laser of 1000 mJ, 1064 nm and 3 Hz . Dry wear test using the pin-on -disc technique at different sliding times (5-30 min) at a constant applied load and sliding speed were performed before and after laser treatment. Micro hardness and wear resistance were increased for all samples after laser hardening treatment. The improvement of these properties is explained by microstructural homogenization and grain refinement of the laser treated surface. Modification and refinement of SiC particles and grain refinement in the microstructure of the aluminum alloy matrix (α-Al) were observed by optical and SEM micrographs. The highest increase in hardness was 21.4% and 26.2% for the base alloy and composite sample respectively.

EFFECTS OF COMPOSITION ON THE MECHANICAL PROPERTIES OF NI-CR-MO-CO FILLER METALS.

DTIC Science & Technology

STEEL, WELDING RODS), CHEMICAL ANALYSIS, CARBON ALLOYS , COBALT ALLOYS , CHROMIUM ALLOYS , MOLYBDENUM ALLOYS , NICKEL ALLOYS , MARAGING STEELS...ALUMINUM COMPOUNDS, TITANIUM , NONMETALS, SHIP HULLS, SHIP PLATES, SUBMARINE HULLS, WELDING , WELDS , MECHANICAL PROPERTIES, STATISTICAL ANALYSIS, MICROSTRUCTURE.

DC Electric Arc Furnace Application for Production of Nickel-Boron Master Alloys

NASA Astrophysics Data System (ADS)

Alkan, Murat; Tasyürek, Kerem Can; Bugdayci, Mehmet; Turan, Ahmet; Yücel, Onuralp

2017-09-01

In this study, nickel-boron (Ni-B) alloys were produced via a carbothermic reduction starting from boric acid (H3BO3) with high-purity nickel oxide (NiO), charcoal, and wood chips in a direct current arc furnace. In electric arc furnace experiments, different starting mixtures were used, and their effects on the chemical compositions of the final Ni-B alloys were investigated. After the reduction and melting stages, Ni-B alloys were obtained by tapping from the bottom of the furnace. The samples from the designated areas were also taken and analyzed. The chemical composition of the final alloys and selected samples were measured with wet chemical analysis. The Ni-B alloys had a composition of up to 14.82 mass% B. The phase contents of the final alloys and selected samples were measured using x-ray diffraction (XRD). The XRD data helped predict possible reactions and reaction mechanisms. The material and energy balance calculations were made via the XRD Rietveld and chemical compositions. Nickel boride phases started to form 600 mm below the surface. The targeted NiB phase was detected at the tapping zone of the crucible (850-900 mm depth). The energy consumption was 1.84-4.29 kWh/kg, and the electrode consumption was 10-12 g/kg of raw material charged.

Titanium aluminide intermetallic alloys with improved wear resistance

DOEpatents

Qu, Jun; Lin, Hua-Tay; Blau, Peter J.; Sikka, Vinod K.

2014-07-08

The invention is directed to a method for producing a titanium aluminide intermetallic alloy composition having an improved wear resistance, the method comprising heating a titanium aluminide intermetallic alloy material in an oxygen-containing environment at a temperature and for a time sufficient to produce a top oxide layer and underlying oxygen-diffused layer, followed by removal of the top oxide layer such that the oxygen-diffused layer is exposed. The invention is also directed to the resulting oxygen-diffused titanium aluminide intermetallic alloy, as well as mechanical components or devices containing the improved alloy composition.

Printability of alloys for additive manufacturing

PubMed Central

Mukherjee, T.; Zuback, J. S.; De, A.; DebRoy, T.

2016-01-01

Although additive manufacturing (AM), or three dimensional (3D) printing, provides significant advantages over existing manufacturing techniques, metallic parts produced by AM are susceptible to distortion, lack of fusion defects and compositional changes. Here we show that the printability, or the ability of an alloy to avoid these defects, can be examined by developing and testing appropriate theories. A theoretical scaling analysis is used to test vulnerability of various alloys to thermal distortion. A theoretical kinetic model is used to examine predisposition of different alloys to AM induced compositional changes. A well-tested numerical heat transfer and fluid flow model is used to compare susceptibilities of various alloys to lack of fusion defects. These results are tested and validated with independent experimental data. The findings presented in this paper are aimed at achieving distortion free, compositionally sound and well bonded metallic parts. PMID:26796864

Method of preparing an electrode material of lithium-aluminum alloy

DOEpatents

Settle, Jack L.; Myles, Kevin M.; Battles, James E.

1976-01-01

A solid compact having a uniform alloy composition of lithium and aluminum is prepared as a negative electrode for an electrochemical cell. Lithium losses during preparation are minimized by dissolving aluminum within a lithium-rich melt at temperatures near the liquidus temperatures. The desired alloy composition is then solidified and fragmented. The fragments are homogenized to a uniform composition by annealing at a temperature near the solidus temperature. After comminuting to fine particles, the alloy material can be blended with powdered electrolyte and pressed into a solid compact having the desired electrode shape. In the preparation of some electrodes, an electrically conductive metal mesh is embedded into the compact as a current collector.

NASA-UVA light aerospace alloy and structures technology program (LA(sup 2)ST)

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.; Haviland, John K.; Herakovich, Carl T.; Pilkey, Walter D.; Pindera, Marek-Jerzy; Scully, John R.; Starke, Edgar A., Jr.; Stoner, Glenn E.; Thornton, Earl A.; Wawner, Franklin E., Jr.

1992-01-01

The general objective of the Light Aerospace Alloy and Structures Technology (LA(sup 2)ST) Program is to conduct interdisciplinary graduate student research on the performance of next generation, light weight aerospace alloys, composites, and thermal gradient structures in collaboration with Langley researchers. Specific technical objectives are established for each research project. We aim to produce relevant data and basic understanding of material behavior and microstructure, new monolithic and composite alloys, advanced processing methods, new solid and fluid mechanics analyses, measurement advances, and critically, a pool of educated graduate students for aerospace technologies. Four research areas are being actively investigated, including: (1) Mechanical and Environmental Degradation Mechanisms in Advanced Light Metals and Composites; (2) Aerospace Materials Science; (3) Mechanics of Materials and Composites for Aerospace Structures; and (4) Thermal Gradient Structures.

Quantitative methods for estimating the anisotropy of the strength properties and the phase composition of Mg-Al alloys

NASA Astrophysics Data System (ADS)

Betsofen, S. Ya.; Kolobov, Yu. R.; Volkova, E. F.; Bozhko, S. A.; Voskresenskaya, I. I.

2015-04-01

Quantitative methods have been developed to estimate the anisotropy of the strength properties and to determine the phase composition of Mg-Al alloys. The efficiency of the methods is confirmed for MA5 alloy subjected to severe plastic deformation. It is shown that the Taylor factors calculated for basal slip averaged over all orientations of a polycrystalline aggregate with allowance for texture can be used for a quantitative estimation of the contribution of the texture of semifinished magnesium alloy products to the anisotropy of their strength properties. A technique of determining the composition of a solid solution and the intermetallic phase Al12Mg17 content is developed using the measurement of the lattice parameters of the solid solution and the known dependence of these lattice parameters on the composition.

Experimental Studies on Al (5.7% Zn) Alloy based Hybrid MMC

NASA Astrophysics Data System (ADS)

Shivaprakash, Y. M.; Ramu, H. C.; Chiranjivee; Kumar, Roushan; Kumar, Deepak

2018-02-01

In this investigation, an attempt is made to disperse SiC (20-25 microns) and Gr (15-20 microns) in the aluminium alloy having Zn, Mg and coper as major alloying elements. The composite is further subjected to mechanical testing to determine various properties like hardness, tensile strength and wear resistance. The alloy and composite samples were tested in the un heat treated conditions. All the tests were done at the laboratory conditions as per ASTM standards. The Pin-On-Disc tribometer is used to test the two-body abrasive sliding wear behaviour in dry conditions. The wear pattern is analysed by the optical images of worn surface taken in an inverted metallurgical microscope. The calculated density is found to be reducing as the SiC and Gr quantity is increased in the base alloy. The as cast Al alloy was found to be having highest hardness. The introduction of SiC tend to increase the hardness and UTS, since Gr is also introduced simultaneously which tends to reduce the hardness and UTS of composite. The composite having highest quantity of Gr showed superior wear resistance which is mainly because the Gr particulates provide an inbuilt lubricating properties to composite. The analysis of images of worn surface showed the abrasive and delamination pattern of wear. The composites developed in the present work can be used in the automobile and aerospace parts that are light in weight and require self-lubricating properties to enhance the wear resistance.

A Study of Phase Composition and Structure of Alloys of the Al - Mg - Si - Fe System

NASA Astrophysics Data System (ADS)

Mailybaeva, A. D.; Zolotorevskii, V. S.; Smagulov, D. U.; Islamkulov, K. M.

2017-03-01

The Thermo-Calc software is used to compute the phase transformations occurring during cooling of alloys. Polythermal and isothermal sections of the phase diagram of the Al - Mg - Si - Fe system are plotted. The phase composition and the structure of aluminum alloys in cast condition and after a heat treatment are studied experimentally.

Effects of alloy composition on cyclic flame hot-corrosion attack of cast nickel-base superalloys at 900 deg C

NASA Technical Reports Server (NTRS)

Deadmore, D. L.

1984-01-01

The effects of Cr, Al, Ti, Mo, Ta, Nb, and W content on the hot corrosion of nickel base alloys were investigated. The alloys were tested in a Mach 0.3 flame with 0.5 ppmw sodium at a temperature of 900 C. One nondestructive and three destructive tests were conducted. The best corrosion resistance was achieved when the Cr content was 12 wt %. However, some lower-Cr-content alloys ( 10 wt%) exhibited reasonable resistance provided that the Al content alloys ( 10 wt %) exhibited reasonable resistance provided that the Al content was 2.5 wt % and the Ti content was Aa wt %. The effect of W, Ta, Mo, and Nb contents on the hot-corrosion resistance varied depending on the Al and Ti contents. Several commercial alloy compositions were also tested and the corrosion attack was measured. Predicted attack was calculated for these alloys from derived regression equations and was in reasonable agreement with that experimentally measured. The regression equations were derived from measurements made on alloys in a one-quarter replicate of a 2(7) statistical design alloy composition experiment. These regression equations represent a simple linear model and are only a very preliminary analysis of the data needed to provide insights into the experimental method.

Preparation and characterization of aluminium-silica metal matrix composite

NASA Astrophysics Data System (ADS)

Mallikarjuna, G. B.; Basavaraj, E.

2018-04-01

Aluminum alloys are widely used in aerospace and automobile industries due to their low density and good mechanical properties, better corrosion resistance and wear, low thermal coefficient of expansion as compared to conventional metals and alloys. The excellent properties of these materials and relatively low production cost make them a very attractive for a variety of applications. In this present work, Al alloy LM13-SiO2 composites were produced by stir casting method. The reinforcement SiO2 particle size used for preparation of composites are 106 µm, 150 µm, 250 µm and 355 µm with varying amount of 3 to 12 wt% in steps of 3. The prepared composite specimens were machined as per test standards. Effects of weight percentage of SiO2 particles on wear, tensile strength of Al alloy LM13-SiO2 composites have been investigated. The microstructures of the composites were studied to know the dispersion of the SiO2 particles in matrix. Experimental results shows that there is enhanced mechanical properties, when silica weighing 9% was added to the base aluminium alloy and also similar trend exists in all four different micron size of silica and also it has been observed that addition of SiO2 particles significantly improves wear resistance properties as compared with that of unreinforced matrix.

Nial and Nial-Based Composites Directionally Solidified by a Containerless Zone Process. Ph.D. Thesis

NASA Technical Reports Server (NTRS)

Joslin, Steven M.

1995-01-01

A containerless electromagnetically levitated zone (CELZ) process has been used to directionally solidify NiAl and NiAl-based composites. The CELZ processing results in single crystal NiAl (HP-NiAl) having higher purity than commercially pure NiAl grown by a modified Bridgman process (CP-NiAl). The mechanical properties, specifically fracture toughness and creep strength, of the HP-NiAl are superior to binary CP-NiAl and are used as a base-line for comparison with the composite materials subsequently studied. Two-phase composite materials (NiAl-based eutectic alloys) show improvement in room temperature fracture toughness and 1200 to 1400 K creep strength over that of binary HP-NiAl. Metallic phase reinforcements produce the greatest improvement in fracture toughness, while intermetallic reinforcement produces the largest improvement in high temperature strength. Three-phase eutectic alloys and composite materials were identified and directionally solidified with the intent to combine the improvements observed in the two-phase alloys into one alloy. The room temperature fracture toughness and high temperature strength (in air) serve as the basis for comparison between all of the alloys. Finally, the composite materials are discussed in terms of dominant fracture mechanism observed by fractography.

[The effect of C-SiO2 composite films on corrosion resistance of dental Co-Cr alloy].

PubMed

Huang, Yi; Hu, Jing-Yu; Liu, Yu-Pu; Zhao, Dong-Yuan; Yu, You-Cheng; Bi, Wei

2016-10-01

To study the effect of carbon-silica composite films on corrosion resistance of Co-Cr alloy in simulated oral environment and provide evidences for clinical application of this new material. Co-Cr alloy specimens were cut into appropriate size of 20 mm × 20 mm × 0.5 mm. Then, the carbon-silica composite films were spin-coated onto the specimens. Subsequently, ICP-AES was used to observe the Co, Cr, Mo ion concentrations. Finally, Tafel polarization curves of the specimens were used to measure the electrochemical corrosion resistance by electrochemical workstation. SAS8.0 software package was used for statistical analysis. The results of ICP-AES showed that the ion concentrations of Co, Cr, Mo of specimens coated with composite films in the testing liquid were significantly smaller than that of Co-Cr alloy specimens. Tafel polarization curves showed that in the specimens coated with composite films, the corrosion potential moved in the positive direction and increased from -0.261 V to -0.13 V. At the same time, the corrosion current density decreased from -5.0017μA/cm 2 to -5.3006 μA/cm 2 . Carbon-silica composite films (silica=61.71wt %) can reduce the release of metal ions significantly and improve the corrosion resistance of Co-Cr alloys effectively. Carbon-silica composite films may be a promising dental material.

Spark alloying of VK8 and T15K6 hard alloys

NASA Astrophysics Data System (ADS)

Kuptsov, S. G.; Fominykh, M. V.; Mukhinov, D. V.; Magomedova, R. S.; Nikonenko, E. A.; Pleshchev, V. P.

2015-08-01

A method is developed to restore the service properties of VK hard alloy plates using preliminary carburizing followed by spark alloying with a VT1-0 alloy. The phase composition is studied as a function of the spark treatment time.

Investigation of FeNiCrWMn - a new high entropy alloy

NASA Astrophysics Data System (ADS)

Buluc, G.; Florea, I.; Bălţătescu, O.; Florea, R. M.; Carcea, I.

2015-11-01

The term of high entropy alloys started from the analysis of multicomponent alloys, which were produced at an experimental level since 1995 by developing a new concept related to the development of metallic materials. Recent developments in the field of high-entropy alloys have revealed that they have versatile properties like: ductility, toughness, hardness and corrosion resistance [1]. Up until now, it has been demonstrated that the explored this alloys are feasible to be synthesized, processed and analyzed contrary to the misunderstanding based on traditional experiences. Moreover, there are many opportunities in this field for academic studies and industrial applications [1, 2]. As the combinations of composition and process for producing high entropy alloys are numerous and each high entropy alloy has its own microstructure and properties to be identified and understood, the research work is truly limitless. The novelty of these alloys consists of chemical composition. These alloys have been named high entropy alloys due to the atomic scale mixing entropies higher than traditional alloys. In this paper, I will present the microscopy and the mechanical properties of high entropy alloy FeNiCrWMn.

Low Pt content direct methanol fuel cell anode catalyst: nanophase PtRuNiZr

NASA Technical Reports Server (NTRS)

Whitacre, Jay F. (Inventor); Narayanan, Sekharipuram R. (Inventor)

2010-01-01

A method for the preparation of a metallic material having catalytic activity that includes synthesizing a material composition comprising a metal content with a lower Pt content than a binary alloy containing Pt but that displays at least a comparable catalytic activity on a per mole Pt basis as the binary alloy containing Pt; and evaluating a representative sample of the material composition to ensure that the material composition displays a property of at least a comparable catalytic activity on a per mole Pt basis as a representative binary alloy containing Pt. Furthermore, metallic compositions are disclosed that possess substantial resistance to corrosive acids.

Self-assembly of bimetallic AuxPd1-x alloy nanoparticles via dewetting of bilayers through the systematic control of temperature, thickness, composition and stacking sequence

NASA Astrophysics Data System (ADS)

Kunwar, Sundar; Pandey, Puran; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2018-03-01

Bimetallic alloy nanoparticles (NPs) are attractive materials for various applications with their morphology and elemental composition dependent optical, electronic, magnetic and catalytic properties. This work demonstrates the evolution of AuxPd1-x alloy nanostructures by the solid-state dewetting of sequentially deposited bilayers of Au and Pd on sapphire (0001). Various shape, size and configuration of AuxPd1‑x alloy NPs are fabricated by the systematic control of annealing temperature, deposition thickness, composition as well as stacking sequence. The evolution of alloy nanostructures is attributed to the surface diffusion, interface diffusion between bilayers, surface and interface energy minimization, Volmer-Weber growth model and equilibrium configuration. Depending upon the temperature, the surface morphologies evolve with the formation of pits, grains and voids and gradually develop into isolated semi-spherical alloy NPs by the expansion of voids and agglomeration of Au and Pd adatoms. On the other hand, small isolated to enlarged elongated and over-grown layer-like alloy nanostructures are fabricated due to the coalescence, partial diffusion and inter-diffusion with the increased bilayer thickness. In addition, the composition and stacking sequence of bilayers remarkably affect the final geometry of AuxPd1‑x nanostructures due to the variation in the dewetting process. The optical analysis based on the UV–vis-NIR reflectance spectra reveals the surface morphology dependent plasmonic resonance, scattering, reflection and absorption properties of AuxPd1‑x alloy nanostructures.

Designing and Validating Ternary Pd Alloys for Optimum Sulfur/Carbon Resistance in Hydrogen Separation and Carbon Capture Membrane Systems Using High-Throughput Combinatorial Methods

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lewis, Amanda; Zhao, Hongbin; Hopkins, Scott

2014-12-01

This report summarizes the work completed under the U.S. Department of Energy Project Award No.: DE-FE0001181 titled “Designing and Validating Ternary Pd Alloys for Optimum Sulfur/Carbon Resistance in Hydrogen Separation and Carbon Capture Membrane Systems Using High-Throughput Combinatorial Methods.” The project started in October 1, 2009 and was finished September 30, 2014. Pall Corporation worked with Cornell University to sputter and test palladium-based ternary alloys onto silicon wafers to examine many alloys at once. With the specialized equipment at Georgia Institute of Technology that analyzed the wafers for adsorbed carbon and sulfur species six compositions were identified to have resistancemore » to carbon and sulfur species. These compositions were deposited on Pall AccuSep® supports by Colorado School of Mines and then tested in simulated synthetic coal gas at the Pall Corporation. Two of the six alloys were chosen for further investigations based on their performance. Alloy reproducibility and long-term testing of PdAuAg and PdZrAu provided insight to the ability to manufacture these compositions for testing. PdAuAg is the most promising alloy found in this work based on the fabrication reproducibility and resistance to carbon and sulfur. Although PdZrAu had great initial resistance to carbon and sulfur species, the alloy composition has a very narrow range that hindered testing reproducibility.« less

Compositional redistribution in alloy films under high-voltage electron microscope irradiation

NASA Astrophysics Data System (ADS)

Lam, Nghi Q.; Leaf, O. K.; Minkoff, M.

1983-10-01

The problem of nonequilibrium segregation in alloy films under high-voltage electron microscope (HVEM) irradiation at elevated temperatures is re-examined in the present work, taking into account the damage-rate gradients caused by radial variation in the electron flux. Axial and radial compositional redistributions in model solid solutions, representative of concentrated Ni-Cu, Ni-Al and Ni-Si alloys, were calculated as a function of time, temperature, and film thickness, using a kinetic theory of segregation in binary alloys. The numerical results were achieved by means of a new software package (DISPL2) for solving convection-diffusion-kinetics problems with general orthogonal geometries. It was found that HVEM irradiation-induced segregation in thin films consists of two stages. Initially, due to the proximity of the film surfaces as sinks for point defects, the usual axial segregation (to surfaces) occurs at relatively short irradiation times, and rapidly attains quasi-steady state. Then, radial segregation becomes more and more competitive, gradually affecting the kinetics of axial segregation. At a given temperature, the buildup time to steady state is much longer in the present situation than in the simple case of one-dimensional segregation with uniform defect production. Changes in the alloy composition occur in a much larger zone than the irradiated volume. As a result, the average alloy composition within the irradiated region can differ greatly from that of the unirradiated alloy. The present calculations may be useful in the interpretation of the kinetics of certain HVEM irradiation-induced processes in alloys.

Alloys for hydrogen storage in nickel/hydrogen and nickel/metal hydride batteries

NASA Technical Reports Server (NTRS)

Anani, Anaba; Visintin, Arnaldo; Petrov, Konstantin; Srinivasan, Supramaniam; Reilly, James J.; Johnson, John R.; Schwarz, Ricardo B.; Desch, Paul B.

1993-01-01

Since 1990, there has been an ongoing collaboration among the authors in the three laboratories to (1) prepare alloys of the AB(sub 5) and AB(sub 2) types, using arc-melting/annealing and mechanical alloying/annealing techniques; (2) examine their physico-chemical characteristics (morphology, composition); (3) determine the hydrogen absorption/desorption behavior (pressure-composition isotherms as a function of temperature); and (4) evaluate their performance characteristics as hydride electrodes (charge/discharge, capacity retention, cycle life, high rate capability). The work carried out on representative AB(sub 5) and AB(sub 2) type modified alloys (by partial substitution or with small additives of other elements) is presented. The purpose of the modification was to optimize the thermodynamics and kinetics of the hydriding/dehydriding reactions and enhance the stabilities of the alloys for the desired battery applications. The results of our collaboration, to date, demonstrate that (1) alloys prepared by arc melting/annealing and mechanical alloying/annealing techniques exhibit similar morphology, composition and hydriding/dehydriding characteristics; (2) alloys with the appropriate small amounts of substituent or additive elements: (1) retain the single phase structure, (2) improve the hydriding/dehydriding reactions for the battery applications, and (3) enhance the stability in the battery environment; and (3) the AB(sub 2) type alloys exhibit higher energy densities than the AB(sub 5) type alloys but the state-of-the-art, commercialized batteries are predominantly manufactured using Ab(sub 5) type alloys.

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

DTIC Science & Technology

1998-04-01

to prepare the aluminum melts with desired chemical compositions. Table 1. Chemical compositions of the starting materials. Alloy Mg Fe Cr Si Ni Al...Al 0.001 0.11 0.001 0.04 0.005 bal. Alloy Al Fe Cr Si Ni Mg Mg 0.01 0.12 0.001 0.03 0.006 bal. The ingots were initially cut to chunks with...hours. Figure 26 shows the optical micrographs obtained from the ingots after nitridation reaction of the alloys initially containing Al- 5wt .% Si

Structural, microstructural and thermal analysis of U-(6-x)Zr-xNb alloys (x = 0, 2, 4, 6)

NASA Astrophysics Data System (ADS)

Kaity, Santu; Banerjee, Joydipta; Parida, S. C.; Bhasin, Vivek

2018-06-01

Uranium-rich U-Zr-Nb alloy is considered as a good alternative fuel for fast reactors from the perspective of excellent dimensional stability and desired thermo-physical properties to achieve higher burnup. Detailed investigations related to the structural and microstructural characterization, thermal expansion, phase transformation, microhardness were carried out on U-6Zr, U-4Zr-2Nb, U-2Zr-4Nb and U-6Nb alloys (composition in wt%) where the total amount of alloying elements was restricted to 6 wt%. Structural, microstructural and thermal analysis studies revealed that these alloys undergo a series of transformations from high temperature bcc γ-phase to a variety of equilibrium and intermediate phases depending upon alloy composition, cooling rate and quenching. The structural analysis was carried out by Rietveld refinement. The data of U-Nb and U-Zr-Nb alloys have been highlighted and compared with binary U-Zr alloy.

Tin-silver-bismuth solders for electronics assembly

DOEpatents

Vianco, Paul T.; Rejent, Jerome A.

1995-01-01

A lead-free solder alloy for electronic assemblies composed of a eutectic alloy of tin and silver with a bismuth addition, x, of 0

Tin-silver-bismuth solders for electronics assembly

DOEpatents

Vianco, P.T.; Rejent, J.A.

1995-08-08

A lead-free solder alloy is disclosed for electronic assemblies composed of a eutectic alloy of tin and silver with a bismuth addition, x, of 0

The interaction of hydrogen with metal alloys

NASA Technical Reports Server (NTRS)

Danford, M. D.; Montano, J. W.

1991-01-01

Hydrogen diffusion coefficients were measured for several alloys, and these were determined to be about the same at 25 C for all alloys investigated. The relation of structure, both metallurgical and crystallographic, to the observed hydrogen distribution on charging was investigated, as well as the role of hydride formation in the hydrogen resistance of metal alloys. An attempt was made to correlate the structures and compositions of metal alloys as well as other parameters with the ratios of their notched tensile strengths in hydrogen to that in helium, R(H2/He), which are believed to represent a measure of their hydrogen resistance. Evidence supports the belief that hydrogen permeability and hydrogen resistance are increased by smaller grain sizes for a given alloy composition.

Lattice softening in body-centered-cubic lithium-magnesium alloys

NASA Astrophysics Data System (ADS)

Winter, I. S.; Tsuru, T.; Chrzan, D. C.

2017-08-01

A first-principles investigation of the influence of lattice softening on lithium-magnesium alloys near the body-centered-cubic (bcc)/hexagonal close-packed (hcp) transition composition is presented. Results show that lithium-magnesium alloys display a softening of the shear modulus C11-C12 , and an acoustic phonon branch between the Γ and N high symmetry points, as the composition approaches the stability limit for the bcc phase. This softening is accompanied by an increase in the size of the dislocation core region. Ideal tensile strength calculations predict that ordered phases of lithium-magnesium alloys are intrinsically brittle. Methods to make the alloys more ductile are discussed, and the propensity for these alloys to display gum-metal-like behavior is assessed.

Synthesis of aluminum-based scandium-yttrium master alloys

NASA Astrophysics Data System (ADS)

Bazhin, V. Yu.; Kosov, Ya. I.; Lobacheva, O. L.; Dzhevaga, N. V.

2015-07-01

The preparation technology for an Al-2% Sc-0.5% Y master alloy using aluminum-manganese alloys has been developed and tested. The microstructure of the prepared master alloy is studied and the compositions of intermetallics is determined. The efficient technological parameters of the synthesis are determined. It is shown that varying the compositions of starting reagents and alloying additions and optimizing the process conditions (temperature, mixing, etc.) allow us to forecast the manufacturing and operating characteristics of aluminum-based master alloys. Joint additions of scandium and yttrium oxides to a charge favor a substantial decrease in the grain size of the formed intermetallics; this effect appears to the utmost in the case of microallying with yttrium up to 0.5 wt %.

Pulsed Electrodeposition of Amorphous and Composite Alloys.

DTIC Science & Technology

1983-09-01

lamellar- eutectic composites. A new phenomenon was dis- covered that deposits consisting of alternate layers of the same phase and essentially the...phenomenon will be discussed in connection with the Cu-Zn alloys. The recrystallization kinetics of the Ni-Mo alloys were investigated in order to find...transmission-electron-microscopic examination. The percent of the area which had recrystallized was determined on photographs using a planimeter. From a

Effect of in-situ TiC particulate on the wear resistance of spray-deposited 7075 Al matrix composite

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wang Feng; Liu Huimin; Yang Bin

2005-05-15

TiC reinforced 7075 Al matrix composites have been fabricated by a melt in-situ reaction spray deposition. The microstructures of spray-deposited alloys were studied using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The dry sliding wear behavior of the alloys was investigated using a pin-on-disc machine under four loads, namely 8.9, 17.8, 26.7 and 35.6 N. It has been found that the wear behavior of the alloys was dependent on the TiC content in the microstructure and the applied load. At a lower load (8.9 N), with increasing TiC content, the wear rate of the alloy was decreased. At amore » higher loads (26.7, 35.6 N), a spray-deposited 7075 Al alloy exhibited superior wear resistance to the 7075/TiC composites.« less

Ab initio simulations of molten Ni alloys

NASA Astrophysics Data System (ADS)

Woodward, Christopher; Asta, Mark; Trinkle, Dallas R.; Lill, James; Angioletti-Uberti, Stefano

2010-06-01

Convective instabilities responsible for misoriented grains in directionally solidified turbine airfoils are produced by variations in liquid-metal density with composition and temperature across the solidification zone. Here, fundamental properties of molten Ni-based alloys, required for modeling these instabilities, are calculated using ab initio molecular dynamics simulations. Equations of state are derived from constant number-volume-temperature ensembles at 1830 and 1750 K for elemental, binary (Ni-X, X=Al, W, Re, and Ta) and ternary (Ni-Al-X, X=W, Re, and Ta) Ni alloys. Calculated molar volumes agree to within 0.6%-1.8% of available measurements. Predictions are used to investigate the range of accuracy of a parameterization of molar volumes with composition and temperature based on measurements of binary alloys. Structural analysis reveals a pronounced tendency for icosahedral short-range order for Ni-W and Ni-Re alloys and the calculations provide estimates of diffusion rates and their dependence on compositions and temperature.

Printability of alloys for additive manufacturing

DOE PAGES

Mukherjee, T.; Zuback, J. S.; De, A.; ...

2016-01-22

Although additive manufacturing (AM), or three dimensional (3D) printing, provides significant advantages over existing manufacturing techniques, metallic parts produced by AM are susceptible to distortion, lack of fusion defects and compositional changes. Here we show that the printability, or the ability of an alloy to avoid these defects, can be examined by developing and testing appropriate theories. A theoretical scaling analysis is used to test vulnerability of various alloys to thermal distortion. A theoretical kinetic model is used to examine predisposition of different alloys to AM induced compositional changes. A well-tested numerical heat transfer and fluid flow model is usedmore » to compare susceptibilities of various alloys to lack of fusion defects. These results are tested and validated with independent experimental data. Here, the findings presented in this paper are aimed at achieving distortion free, compositionally sound and well bonded metallic parts.« less

The effect of matrix mechanical properties on (0)8 unidirectional SiC/Ti composite fatigue resistance

NASA Technical Reports Server (NTRS)

Gabb, T. P.; Gayda, J.; Lerch, B. A.; Halford, G. R.

1991-01-01

The relationship between constituent and MMC properties in fatigue loading is investigated with low-cycle fatigue-resistance testing of an alloy Ti-15-3 matrix reinforced with SiC SCS-6 fibers. The fabrication of the composite is described, and specimens are generated that are weak and ductile (WD), strong and moderately ductile (SM), or strong and brittle (SB). Strain is measured during MMC fatigue tests at a constant load amplitude with a load-controlled waveform and during matrix-alloy fatigue tests at a constant strain amplitude using a strain-controlled waveform. The fatigue resistance of the (0)8 SiC/Ti-15-3 composite is found to be slightly influenced by matrix mechanical properties, and the composite- and matrix-alloy fatigue lives are not correlated. This finding is suggested to relate to the different crack-initiation and -growth processes in MMCs and matrix alloys.

Method of preparing copper-dendritic composite alloys for mechanical reduction

DOEpatents

Verhoeven, John D.; Gibson, Edwin D.; Schmidt, Frederick A.; Spitzig, William A.

1988-01-01

Copper-dendritic composite alloys are prepared for mechanical reduction to increase tensile strength by dispersing molten droplets of the composite alloy into an inert gas; solidifying the droplets in the form of minute spheres or platelets; and compacting a mass of the spheres or platelets into an integrated body. The spheres preferably have diameters of from 50 to 2000 .mu.m, and the platelets thicknesses of 100 to 2000 .mu.m. The resulting spheres or platelets will contain ultra-fine dendrites which produce higher strengths on mechanical reduction of the bodies formed therefrom, or comparable strengths at lower reduction values. The method is applicable to alloys of copper with vanadium, niobium, tantalum, chromium, molybdenum, tungsten, iron and cobalt.

Method of preparing copper-dendritic composite alloys for mechanical reduction

DOEpatents

Verhoeven, J.D.; Gibson, E.D.; Schmidt, F.A.; Spitzig, W.A.

1988-09-13

Copper-dendritic composite alloys are prepared for mechanical reduction to increase tensile strength by dispersing molten droplets of the composite alloy into an inert gas; solidifying the droplets in the form of minute spheres or platelets; and compacting a mass of the spheres or platelets into an integrated body. The spheres preferably have diameters of from 50 to 2,000 [mu]m, and the platelets thicknesses of 100 to 2,000 [mu]m. The resulting spheres or platelets will contain ultra-fine dendrites which produce higher strengths on mechanical reduction of the bodies formed therefrom, or comparable strengths at lower reduction values. The method is applicable to alloys of copper with vanadium, niobium, tantalum, chromium, molybdenum, tungsten, iron and cobalt. 3 figs.

Cast B2-phase iron-aluminum alloys with improved fluidity

DOEpatents

Maziasz, Philip J.; Paris, Alan M.; Vought, Joseph D.

2002-01-01

Systems and methods are described for iron aluminum alloys. A composition includes iron, aluminum and manganese. A method includes providing an alloy including iron, aluminum and manganese; and processing the alloy. The systems and methods provide advantages because additions of manganese to iron aluminum alloys dramatically increase the fluidity of the alloys prior to solidification during casting.

Software Package Completed for Alloy Design at the Atomic Level

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo H.; Noebe, Ronald D.; Abel, Phillip B.; Good, Brian S.

2001-01-01

As a result of a multidisciplinary effort involving solid-state physics, quantum mechanics, and materials and surface science, the first version of a software package dedicated to the atomistic analysis of multicomponent systems was recently completed. Based on the BFS (Bozzolo, Ferrante, and Smith) method for the calculation of alloy and surface energetics, this package includes modules devoted to the analysis of many essential features that characterize any given alloy or surface system, including (1) surface structure analysis, (2) surface segregation, (3) surface alloying, (4) bulk crystalline material properties and atomic defect structures, and (5) thermal processes that allow us to perform phase diagram calculations. All the modules of this Alloy Design Workbench 1.0 (ADW 1.0) are designed to run in PC and workstation environments, and their operation and performance are substantially linked to the needs of the user and the specific application.

Low-temperature interface reactions in layered Au/Sb films: In situ investigation of the formation of an amorphous phase

NASA Astrophysics Data System (ADS)

Boyen, H.-G.; Cossy-Favre, A.; Oelhafen, P.; Siber, A.; Ziemann, P.; Lauinger, C.; Moser, T.; Häussler, P.; Baumann, F.

1995-01-01

Photoelectron-spectroscopy methods combined with electrical-resistance measurements were employed to study the effects of intermixing at Au/Sb interfaces at low temperatures. For the purpose of characterizing the growth processes of the intermixed phase on a ML scale, Au/Sb bilayers (layer thicknesses DAu=0.5-75 ML and DSb=150 ML) were evaporated at 77 K and the different in situ techniques allowed a comparison to vapor-quenched amorphous AuxSb100-x alloys. For Au thicknesses between 0.5 and 0.9 ML, a change from a semiconducting to a metallic behavior of the samples has been detected, as indicated by the development of a steplike photoelectron intensity at the Fermi level. Evidence has been found that for Au coverages <= 6 ML chemical reactions at the Au/Sb interface occur, leading to the formation of a homogeneously intermixed amorphous layer with a maximum thickness of about 2.3 nm and Au concentrations as high as x~=80 at. %. This latter value corresponds to the limiting Au content where amorphous alloys can be prepared at low temperature (0 at. % <=x<= 80 at. %). For nominal coverages beyond 6 ML polycrystalline Au films were formed. Consequently, Au/Sb multilayers with sufficiently small modulation lengths, which were prepared at 130 K by ion-beam sputtering, were observed to grow as a homogeneous amorphous phase over a broad range of compositions, as evidenced by in situ resistance measurements and by comparing the obtained crystallization temperatures to those of vapor-quenched amorphous alloys. Variation of the deposition temperature Ts revealed that an amorphous interface layer is only formed for Ts<= 220 K. This is consistent with the fact that for multilayers with large modulation lengths containing unreacted polycrystalline Au and Sb layers, long-range interdiffusion is found to set in at temperatures above 230 K. This interdiffusion, however, results in the formation of polycrystalline Au-Sb alloys.

Oxidation kinetics of some Ni-Cr alloys.

PubMed

Baran, G

1983-01-01

Oxidation kinetics of four Ni-Cr alloys and a high-purity nickel standard was determined under isothermal conditions in an air atmosphere. In addition, weight gains of the alloys were measured during a simulated pre-oxidation treatment. The alloys' behavior suggests that mechanisms of oxidation vary with temperature and alloy composition.

Hf--Co--B alloys as permanent magnet materials

DOEpatents

McGuire, Michael Alan; Rios, Orlando; Ghimire, Nirmal Jeevi

2017-01-24

An alloy composition is composed essentially of Hf.sub.2-XZr.sub.XCo.sub.11B.sub.Y, wherein 0

Conventionally cast and forged copper alloy for high-heat-flux thrust chambers

NASA Technical Reports Server (NTRS)

Kazaroff, John M.; Repas, George A.

1987-01-01

The combustion chamber liner of the space shuttle main engine is made of NARloy-Z, a copper-silver-zirconium alloy. This alloy was produced by vacuum melting and vacuum centrifugal casting; a production method that is currently now available. Using conventional melting, casting, and forging methods, NASA has produced an alloy of the same composition called NASA-Z. This report compares the composition, microstructure, tensile properties, low-cycle fatigue life, and hot-firing life of these two materials. The results show that the materials have similar characteristics.

NASA-UVA Light Aerospace Alloy and Structures Technology Program (LA2ST)

NASA Technical Reports Server (NTRS)

Gangloff, Richard P.

1991-01-01

The general objective of the Light Aerospace Alloy and Structures Technology (LA2ST) Program is to conduct interdisciplinary graduate student research on the performance of next generation, light weight aerospace alloys, composites, and associated thermal gradient structures in close collaboration with Langley researchers. Specific technical objectives are established for each research project. Relevant data and basic understanding of material behavior and microstructure, new monolithic and composite alloys, advanced processing methods, new solid and fluid mechanic analyses, measurement advances, and a pool of educated graduate students are sought.

A Versatile Method for Nanostructuring Metals, Alloys and Metal Based Composites

NASA Astrophysics Data System (ADS)

Gurau, G.; Gurau, C.; Bujoreanu, L. G.; Sampath, V.

2017-06-01

A new severe plastic deformation method based on High Pressure Torsion is described. The method patented as High Speed High Pressure Torsion (HSHPT) shows a wide scope and excellent adaptability assuring large plastic deformation degree on metals, alloys even on hard to deform or brittle alloys. The paper present results obtained on aluminium, magnesium, titan, iron and coper alloys. In addition capability of HSHPT to process metallic composites is described. OM SEM, TEM, DSC, RDX and HV investigation methods were employed to confirm fine and ultrafine structure.

Effect of Cu content on wear resistance and mechanical behavior of Ti-Cu binary alloys

NASA Astrophysics Data System (ADS)

Yu, Feifei; Wang, Hefeng; Yuan, Guozheng; Shu, Xuefeng

2017-04-01

Arc melting with nonconsumable tungsten electrode and water-cooled copper crucible was used to fabricate Ti-Cu binary alloys with different Cu contents in an argon atmosphere. The compositions and phase structures of the fabricated alloys were investigated by glow discharge optical emission spectroscopy (GDOES) and X-ray diffraction (XRD). Nanoindentation tests through continuous stiffness measurement were then performed at room temperature to analyze the mechanical behaviors of the alloys. Results indicated that the composition of each Ti-Cu binary alloy was Ti(100- x) Cu x ( x = 43, 60, 69, and 74 at.%). The XRD analysis results showed that the alloys were composed of different phases, indicating that different Cu contents led to the variations in alloy hardness. The wear tests results revealed that elemental Cu positively affects the wear resistance properties of the Ti-Cu alloys. Nanoindentation testing results showed that the moduli of the Ti-Cu alloys were minimally changed at increasing Cu content, whereas their hardness evidently increased according to the wear test results.

LIBS spectra of multi-component Al, Fe, Cu alloys and composite materials used for selected elements of armament and munition

NASA Astrophysics Data System (ADS)

Ostrowski, R.; Skrzeczanowski, W.; Rycyk, A.; CzyŻ, K.; Sarzyński, A.; Strzelec, M.; Jach, K.; Świerczyński, R.

2017-10-01

Spectral investigations in the UV-VIS range of selected Al, Cu, and Fe alloys and composite materials were performed using LIBS technique. The investigated objects were typical rifle cartridges, mortars, rocket launchers and samples of different type steel, Cu and Al alloys, as well as composite materials of special chemical composition. Two Nd:YAG lasers were applied: a short 4 ns, 60 mJ Brio Quantel/BigSky laser (1064 nm) and a long pulse 200/400 (up to 1000) µs ({ 2/4 up to 10 J) laser (1064 nm) constructed at the Institute of Optoelectronics MUT. This spectrochemical analysis was possible for Al, Cu, and Fe alloys objects for both lasers, and in case of composites only if the samples were irradiated by short laser pulse since in the experiment with the long pulse, all composite materials spectra, in general, were very similar to each other - they imitated a grey/black body spectra. For metal alloys in experiments with a short laser pulse only atomic spectra were observed while for long microsecond laser pulses molecular transitions have been registered for Al alloys. Electron temperatures of plasma created on different materials for short and long laser pulses were found on the base of Boltzmann plots. Temperatures are clearly higher for plasmas generated with a short laser pulse which results from much higher laser power density on the sample surface for short pulse and not from fluence which is 20-40 times larger for long pulse.

Microstructure characterization of the non-modulated martensite in Ni-Mn-Ga alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Han, M.; Bennett, J.C.; Gharghouri, M.A.

2008-06-15

The microstructure of the non-modulated martensite in a Ni-Mn-Ga alloy has been characterized in detail by conventional transmission electron microscopy. Bright field images show that the martensite exhibits an internal substructure consisting of a high density of narrow twins. Using electron diffraction, it is found that the martensite has a tetragonal crystal structure. The lattice correspondence between the parent phase and the non-modulated martensite is investigated. Furthermore, the four twinning elements describing the microtwinning have been graphically and quantitatively determined. The results indicate that the microtwinning within the non-modulated martensite belongs to the compound type.

Metallurgical characterization of new palladium-containing cobalt chromium and nickel chromium alloys

NASA Astrophysics Data System (ADS)

Puri, Raghav

Recently introduced to the market has been an entirely new subclass of casting alloy composition whereby palladium (˜25 wt%) is added to traditional base metal alloys such as CoCr and NiCr. Objectives. The purpose of this study was to evaluate the microstructure and Vickers hardness of two new CoPdCr and one new NiPdCr alloy and compare them to traditional CoCr and NiCr alloys. Methods. The casting alloys investigated were: CoPdCr-A (Noble Crown NF, The Argen Corporation), CoPdCr-I (Callisto CP+, Ivoclar Vivadent), NiPdCr (Noble Crown, Argen), CoCr (Argeloy N.P. Special, Argen), and NiCr (Argeloy N.P. Star, Argen). As-cast cylindrical alloy specimens were mounted in epoxy resin and prepared with standard metallographic procedures, i.e. grinding with successive grades of SiC paper and polishing with alumina suspensions. The alloys were examined with an optical microscope, SEM/EPMA, and XRD to gain insight into their microstructure, composition, and crystal structure. Vickers hardness (VHN) was measured and statistically analyzed by one way ANOVA and Tukey's HSD test (alpha=0.05). Results. Optical microscopy showed a dendritic microstructure for all alloys. The Pd-containing alloys appear to possess a more complex microstructure. SEM/EPMA showed Cr to be rather uniformly distributed in the matrix with palladium tending to be segregated apart from Mo and Ni or Co. Areas of different composition may explain the poor electrochemical results noted in previous studies. XRD suggested the main phase in the Ni-containing solutions was a face centered cubic Ni solid solution, whereas the CoCr exhibited a hexagonal crystal structure that was altered to face centered cubic when Pd was included in the composition. For Vickers hardness, the Co-containing alloys possessed a greater hardness than the Ni-containing alloys. However, the incorporation of Pd in CoCr and NiCr had only a slight effect on microhardness. Conclusion. Overall, the inclusion of palladium increases the microstructural complexity of NiCr and CoCr alloys.

Nonlinear dynamic model for magnetically-tunable Galfenol vibration absorbers

NASA Astrophysics Data System (ADS)

Scheidler, Justin J.; Dapino, Marcelo J.

2013-03-01

This paper presents a single degree of freedom model for the nonlinear vibration of a metal-matrix composite manufactured by ultrasonic additive manufacturing that contains seamlessly embedded magnetostrictive Galfenol alloys (FeGa). The model is valid under arbitrary stress and magnetic field. Changes in the composite's natural frequency are quantified to assess its performance as a semi-active vibration absorber. The effects of Galfenol volume fraction and location within the composite on natural frequency are quantified. The bandwidth over which the composite's natural frequency can be tuned with a bias magnetic field is studied for varying displacement excitation amplitudes. The natural frequency is tunable for all excitation amplitudes considered, but the maximum tunability occurs below an excitation amplitude threshold of 1 × 10-6 m for the composite geometry considered. Natural frequency shifts between 6% and 50% are found as the Galfenol volume fraction varies from 25% to 100% when Galfenol is located at the composite neutral axis. At a modest 25% Galfenol by volume, the model shows that up to 15% shifts in composite resonance are possible through magnetic bias field modulation if Galfenol is embedded away from the composite midplane. As the Galfenol volume fraction and distance between Galfenol and composite midplane are increased, linear and quadratic increases in tunability result, respectively.

Electrochemical synthesis of mesoporous Pt-Au binary alloys with tunable compositions for enhancement of electrochemical performance.

PubMed

Yamauchi, Yusuke; Tonegawa, Akihisa; Komatsu, Masaki; Wang, Hongjing; Wang, Liang; Nemoto, Yoshihiro; Suzuki, Norihiro; Kuroda, Kazuyuki

2012-03-21

Mesoporous Pt-Au binary alloys were electrochemically synthesized from lyotropic liquid crystals (LLCs) containing corresponding metal species. Two-dimensional exagonally ordered LLC templates were prepared on conductive substrates from diluted surfactant solutions including water, a nonionic surfactant, ethanol, and metal species by drop-coating. Electrochemical synthesis using such LLC templates enabled the preparation of ordered mesoporous Pt-Au binary alloys without phase segregation. The framework composition in the mesoporous Pt-Au alloy was controlled simply by changing the compositional ratios in the precursor solution. Mesoporous Pt-Au alloys with low Au content exhibited well-ordered 2D hexagonal mesostructures, reflecting those of the original templates. With increasing Au content, however, the mesostructural order gradually decreased, thereby reducing the electrochemically active surface area. Wide-angle X-ray diffraction profiles, X-ray photoelectron spectra, and elemental mapping showed that both Pt and Au were atomically distributed in the frameworks. The electrochemical stability of mesoporous Pt-Au alloys toward methanol oxidation was highly improved relative to that of nonporous Pt and mesoporous Pt films, suggesting that mesoporous Pt-Au alloy films are potentially applicable as electrocatalysts for direct methanol fuel cells. Also, mesoporous Pt-Au alloy electrodes showed a highly sensitive amperometric response for glucose molecules, which will be useful in next-generation enzyme-free glucose sensors.

Three-dimensional nanometer scale analyses of precipitate structures and local compositions in titanium aluminide engineering alloys

NASA Astrophysics Data System (ADS)

Gerstl, Stephan S. A.

Titanium aluminide (TiAl) alloys are among the fastest developing class of materials for use in high temperature structural applications. Their low density and high strength make them excellent candidates for both engine and airframe applications. Creep properties of TiAl alloys, however, have been a limiting factor in applying the material to a larger commercial market. In this research, nanometer scale compositional and structural analyses of several TiAl alloys, ranging from model Ti-Al-C ternary alloys to putative commercial alloys with 10 components are investigated utilizing three dimensional atom probe (3DAP) and transmission electron microscopies. Nanometer sized borides, silicides, and carbide precipitates are involved in strengthening TiAl alloys, however, chemical partitioning measurements reveal oxygen concentrations up to 14 at. % within the precipitate phases, resulting in the realization of oxycarbide formation contributing to the precipitation strengthening of TiAl alloys. The local compositions of lamellar microstructures and a variety of precipitates in the TiAl system, including boride, silicide, binary carbides, and intermetallic carbides are investigated. Chemical partitioning of the microalloying elements between the alpha2/gamma lamellar phases, and the precipitate/gamma-matrix phases are determined. Both W and Hf have been shown to exhibit a near interfacial excess of 0.26 and 0.35 atoms nm-2 respectively within ca. 7 nm of lamellar interfaces in a complex TiAl alloy. In the case of needle-shaped perovskite Ti3AlC carbide precipitates, periodic domain boundaries are observed 5.3+/-0.8 nm apart along their growth axis parallel to the TiAl[001] crystallographic direction with concomitant composition variations after 24 hrs. at 800°C.

Strain-induced dimensionality crossover of precursor modulations in Ni2MnGa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nie, Zhihua; Wang, Yandong; Shang, Shunli

2015-01-01

Precursor modulations often occur in functional materials like magnetic shape memory alloys, ferroelectrics, and superconductors. In this letter, we have revealed the underlying mechanism of the precursor modulations in ferromagnetic shape memory alloys Ni2MnGa by combining synchrotron-based x-ray diffraction experiments and first-principles phonon calculations. We discovered the precursor modulations along [011] direction can be eliminated with [001] uniaxial loading, while the precursor modulations or premartensite can be totally suppressed by hydrostatic pressure condition. The TA2 phonon anomaly is sensitive to stress induced lattice strain, and the entire TA2 branch is stabilized along the directions where precursor modulations are eliminated bymore » external stress. Our discovery bridges precursor modulations and phonon anomalies, and sheds light on the microscopic mechanism of the two-step superelasticity in precursor martensite.« less

Influence of artificial biological fluid composition on the biocorrosion of potential orthopedic Mg-Ca, AZ31, AZ91 alloys.

PubMed

Gu, X N; Zheng, Y F; Chen, L J

2009-12-01

The electrochemical behavior of potential orthopedic Mg-Ca, AZ31 and AZ91 alloys was studied in Hank's solution, Dulbecco's Modified Eagle's Medium (DMEM) and serum-containing medium (DMEM adding 10% fetal bovine serum (DMEM+FBS)) over a 7 day immersion period. The biocorrosion of the above three alloys for various immersion time intervals was investigated by linear polarization and electrochemical impedance spectroscopy (EIS). After 7 day immersion, potentiodynamic polarization tests were carried out and the surface morphologies of experimental samples were examined by scanning electron microscopy (SEM) observation complemented by energy-disperse spectrometer (EDS) analysis. It was shown that the corrosion of magnesium alloys was influenced by the composition of the solution. The results indicated that chloride ion could reduce the corrosion resistance and the hydrocarbonate ions could induce rapid surface passivation. The adsorbed amino acid on the experimental magnesium alloys' surface increased their polarization resistance and reduced current densities. The influence of the serum protein on corrosion was found to be associated with the magnesium alloy compositions. A Mg-Ca alloy exhibited an increased corrosion rate in the presence of serum protein. An AZ31 alloy showed an increased corrosion rate in DMEM+FBS in the initial 3 day immersion and the corrosion rate decreased thereafter. An AZ91 alloy, with high Al content, showed a reduced corrosion rate with the addition of FBS into DMEM.

Finite element analysis of Al 2024/Cu-Al-Ni shape memory alloy composites with defects/cracks

NASA Astrophysics Data System (ADS)

Kotresh, M.; Benal, M. M., Dr; Siddalinga Swamy, N. H., Dr

2018-02-01

In this work, a numerical approach to predict the stress field behaviour of defect/crack in shape memory alloy (SMA) particles reinforced composite known as the adaptive composite is presented. Simulation is based on the finite element method. The critical stress field approach was used to determine the stresses around defect/crack. Thereby stress amplification issue is being resolved. In this paper, the effect volume % of shape memory alloy and shape memory effect of reinforcement for as-cast and SME trained composites are examined and discussed. Shape memory effect known as training is achieved by pre-straining of reinforcement particles by equivalent changes in their expansion coefficients.

An evaluation of fiber-reinforced titanium matrix composites for advanced high-temperature aerospace applications

NASA Astrophysics Data System (ADS)

Larsen, James M.; Russ, Stephan M.; Jones, J. W.

1995-12-01

The current capabilities of continuous silicon-carbide fiber-reinforced titanium matrix composites (TMCs) are reviewed with respect to application needs and compared to the capabilities of conventional high-temperature monolithic alloys and aluminides. In particular, the properties of a firstgeneration titanium aluminide composite, SCS-6/Ti-24Al-11Nb, and a second-generation metastable beta alloy composite, SCS-6/TIMETAL 21S, are compared with the nickel-base superalloy IN100, the high-temperature titanium alloy Ti-1100, and a relatively new titanium aluminide alloy. Emphasis is given to life-limiting cyclic and monotonie properties and to the influence of time-dependent deformation and environmental effects on these properties. The composite materials offer a wide range of performance capabilities, depending on laminate architecture. In many instances, unidirectional composites exhibit outstanding properties, although the same materials loaded transverse to the fiber direction typically exhibit very poor properties, primarily due to the weak fiber/matrix interface. Depending on the specific mechanical property under consideration, composite cross-ply laminates often show no improvement over the capability of conventional monolithic materials. Thus, it is essential that these composite materials be tailored to achieve a balance of properties suitable to the specific application needs if these materials are to be attractive candidates to replace more conventional materials.

Virtual Parts Engineering Research Center

DTIC Science & Technology

2010-05-20

engineering 10 materials. High strength alloys , composites (polymer composites and metallic composites), and the like cannot merely be replaced by...ceramics, smart materials, shape memory alloys , super plastic materials and nano- structured materials may be more appropriate substitutes in a reverse...molding process using thermosetting Bakelite. For remanufacturing the part in small quantities, machining has been identified as the most economical

Bimetallic alloy electrocatalysts with multilayered platinum-skin surfaces

DOEpatents

Stamenkovic, Vojislav R.; Wang, Chao; Markovic, Nenad M.

2016-01-26

Compositions and methods of preparing a bimetallic alloy having enhanced electrocatalytic properties are provided. The composition comprises a PtNi substrate having a surface layer, a near-surface layer, and an inner layer, where the surface layer comprises a nickel-depleted composition, such that the surface layer comprises a platinum skin having at least one atomic layer of platinum.

Combinatorial assessment of the influence of composition and exposure time on the oxidation behavior and concurrent oxygeninduced phase transformations of binary Ti-x systems

NASA Astrophysics Data System (ADS)

Samimi, Peyman

The relatively low oxidation resistance and subsequent surface embrittlement have often limited the use of titanium alloys in elevated temperature structural applications. Although extensive effort is spent to investigate the high temperature oxidation performance of titanium alloys, the studies are often constrained to complex technical titanium alloys and neither the mechanisms associated with evolution of the oxide scale nor the effect of oxygen ingress on the microstructure of the base metal are well-understood. In addition lack of systematic oxidation studies across a wider domain of the alloy composition has complicated the determination of composition-mechanism-property relationships. Clearly, it would be ideal to assess the influence of composition and exposure time on the oxidation resistance, independent of experimental variabilities regarding time, temperature and atmosphere as the potential source of error. Such studies might also provide a series of metrics (e.g., hardness, scale, etc) that could be interpreted together and related to the alloy composition. In this thesis a novel combinatorial approach was adopted whereby a series of compositionally graded specimens, (Ti-xMo, Ti-xCr, Ti-xAl and Ti-xW) were prepared using Laser Engineered Net Shaping (LENS(TM)) technology and exposed to still-air at 650 °C. (Abstract shortened by ProQuest.).

Preparation of SiC based Aluminium metal matrix nano composites by high intensity ultrasonic cavitation process and evaluation of mechanical and tribological properties

NASA Astrophysics Data System (ADS)

Murthy, N. V.; Prasad Reddy, A.; Selvaraj, N.; Rao, C. S. P.

2016-09-01

Request augments on a worldwide scale for the new materials. The metal matrix nano composites can be used in numerous applications of helicopter structural parts, gas turbine exit guide vane's, space shuttle, and other structural applications. The key mailman to ameliorate performance of composite matrix in aluminium alloy metal reinforces nano particles in the matrix of alloy uniformly, which ameliorates composite properties without affecting limit of ductility. The ultrasonic assisted stir casting helped agitation was successfully used to fabricate Al 2219 metal matrix of alloy reinforced with (0.5, 1, 1.5 and 2) wt.% of nano silicon carbide (SiC) particles of different sizes 50nm and 150nm. The micrographs of scanning electron microscopy of nano composite were investigated it reveals that the uniform dispersion of nano particles silicon carbide in aluminium alloy 2219 matrix and with the low porosity. How the specific wear rate was vary with increasing weight percentage of nano particles at constant load and speed as shown in results and discussions. And the mechanical properties showed that the ultimate tensile strength and hardness of metal matrix nano composite AA 2219 / nano SiC of 50nm and 150nm lean to augment with increase weight percentage of silicon carbide content in the matrix alloy.

Formation of the Structure of a Eutectic Alloy of the Nb - Si System During Directed Crystallization with Liquid-Metal Coolant

NASA Astrophysics Data System (ADS)

Bondarenko, Yu. A.; Echin, A. B.; Kolodyazhnyi, M. Yu.; Surova, V. A.

2017-11-01

Peculiarities of the structure of a refractory eutectic alloy of the Nb - Si system, formed by the method of directed crystallization with liquid-metal coolant, have been studied. Characteristic zones of microstructure of the ingot obtained upon directed crystallization are considered, the alloy composition is analyzed, and volume fractions of phases in the Nb - Si composite are determined.

Microstructures and Grain Refinement of Additive-Manufactured Ti- xW Alloys

NASA Astrophysics Data System (ADS)

Mendoza, Michael Y.; Samimi, Peyman; Brice, David A.; Martin, Brian W.; Rolchigo, Matt R.; LeSar, Richard; Collins, Peter C.

2017-07-01

It is necessary to better understand the composition-processing-microstructure relationships that exist for materials produced by additive manufacturing. To this end, Laser Engineered Net Shaping (LENS™), a type of additive manufacturing, was used to produce a compositionally graded titanium binary model alloy system (Ti- xW specimen (0 ≤ x ≤ 30 wt pct), so that relationships could be made between composition, processing, and the prior beta grain size. Importantly, the thermophysical properties of the Ti- xW, specifically its supercooling parameter ( P) and growth restriction factor ( Q), are such that grain refinement is expected and was observed. The systematic, combinatorial study of this binary system provides an opportunity to assess the mechanisms by which grain refinement occurs in Ti-based alloys in general, and for additive manufacturing in particular. The operating mechanisms that govern the relationship between composition and grain size are interpreted using a model originally developed for aluminum and magnesium alloys and subsequently applied for titanium alloys. The prior beta grain factor observed and the interpretations of their correlations indicate that tungsten is a good grain refiner and such models are valid to explain the grain-refinement process. By extension, other binary elements or higher order alloy systems with similar thermophysical properties should exhibit similar grain refinement.

Powder Metallurgical Synthesis of Biodegradable Mg-Hydroxyapatite Composites for Biomedical Applications

NASA Astrophysics Data System (ADS)

Stüpp, Cesar Augusto; Szakács, Gábor; Mendis, Chamini Lakshi; Gensch, Felix; Müller, Sören; Feyerabend, Frank; Hotza, Dachamir; Fredel, Marcio Celso; Hort, Norbert

Magnesium alloys with acceptable or even controllable corrosion rates, where mechanical properties are not significantly modified or worsened, have been increasingly investigated in the last decade for use as biomaterials. This work shows an approach with a magnesium metal matrix composite (Mg-MMC), composed of ZK60 as base material and hydroxyapatite (HA) particles. The composite was produced by mechanical alloying followed by hot extrusion, as HA in contact with molten magnesium releases toxic gases such as phosphine (PH3). This work will present the influence of different amounts of HA on corrosion behaviour and mechanical properties of the investigated composites. Compared to the ZK60 alloy, corrosion is expected to be delayed, without localized corrosion. The mechanical properties are not expected to be compromised with such composite during tissue's healing period.

Advances in joining newer structural materials; Proceedings of the International Conference, Montreal, Canada, July 23-25, 1990

NASA Astrophysics Data System (ADS)

The present conference on advances in joining novel structural materials encompasses such material types as ceramics, plastics and composites, and new metallic materials. Specific issues addressed include the use of conductor electric explosion to join ceramics, the effects of brazing temperature on joint properties of SiC-fiber-reinforced Al-alloy-matrix composites, the in situ structure control of composite materials, and the weldability of polymeric materials that are heterogeneous as to chemical nature from the standpoint of morphology. Also addressed are the joining of the Al-Li alloy 8090, diffusion bonding of a creep-resistant Fe-ODS alloy, the adhesive bonding of zinc-coated steel sheets, welds in thermoplastic composite materials, and hot-melt joints for carbon-fiber-reinforced composites.

Design of diaphragm actuator based on ferromagnetic shape memory alloy composite

NASA Astrophysics Data System (ADS)

Liang, Yuanchang; Taya, Minoru; Kuga, Yasuo

2003-08-01

A new diaphragm actuator based on the ferromagnetic shape memory alloy (FSMA) composite is designed where the FSMA composite is composed of ferromagnetic soft iron and superelastic grade of NiTi shape memory alloy (SMA). The actuation mechanism for the FSMA composite plate of the actuator is the hybrid mechanism that we proposed previously. This diaphragm actuator is the first design toward designing a new synthetic jet actuator that will be used for active flow control technology on airplane wings. The design of the FSMA composite diaphragm actuator was established first by using both mechanical and ferromagnetic finite element analyses with an aim of optimization of the actuator components. Based on the FEM results, the first generation diaphragm actuator system was assembled and its static and dynamic performance was experimentally evaluated.

Atomically thin layers of B-N-C-O with tunable composition.

PubMed

Ozturk, Birol; de-Luna-Bugallo, Andres; Panaitescu, Eugen; Chiaramonti, Ann N; Liu, Fangze; Vargas, Anthony; Jiang, Xueping; Kharche, Neerav; Yavuzcetin, Ozgur; Alnaji, Majed; Ford, Matthew J; Lok, Jay; Zhao, Yongyi; King, Nicholas; Dhar, Nibir K; Dubey, Madan; Nayak, Saroj K; Sridhar, Srinivas; Kar, Swastik

2015-07-01

In recent times, atomically thin alloys of boron, nitrogen, and carbon have generated significant excitement as a composition-tunable two-dimensional (2D) material that demonstrates rich physics as well as application potentials. The possibility of tunably incorporating oxygen, a group VI element, into the honeycomb sp(2)-type 2D-BNC lattice is an intriguing idea from both fundamental and applied perspectives. We present the first report on an atomically thin quaternary alloy of boron, nitrogen, carbon, and oxygen (2D-BNCO). Our experiments suggest, and density functional theory (DFT) calculations corroborate, stable configurations of a honeycomb 2D-BNCO lattice. We observe micrometer-scale 2D-BNCO domains within a graphene-rich 2D-BNC matrix, and are able to control the area coverage and relative composition of these domains by varying the oxygen content in the growth setup. Macroscopic samples comprising 2D-BNCO domains in a graphene-rich 2D-BNC matrix show graphene-like gate-modulated electronic transport with mobility exceeding 500 cm(2) V(-1) s(-1), and Arrhenius-like activated temperature dependence. Spin-polarized DFT calculations for nanoscale 2D-BNCO patches predict magnetic ground states originating from the B atoms closest to the O atoms and sizable (0.6 eV < E g < 0.8 eV) band gaps in their density of states. These results suggest that 2D-BNCO with novel electronic and magnetic properties have great potential for nanoelectronics and spintronic applications in an atomically thin platform.

Equivalent crystal theory of alloys

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John

1991-01-01

Equivalent Crystal Theory (ECT) is a new, semi-empirical approach to calculating the energetics of a solid with defects. The theory has successfully reproduced surface energies in metals and semiconductors. The theory of binary alloys to date, both with first-principles and semi-empirical models, has not been very successful in predicting the energetics of alloys. This procedure is used to predict the heats of formation, cohesive energy, and lattice parameter of binary alloys of Cu, Ni, Al, Ag, Au, Pd, and Pt as functions of composition. The procedure accurately reproduces the heats of formation versus composition curves for a variety of binary alloys. The results are then compared with other approaches such as the embedded atom and lattice parameters of alloys from pure metal properties more accurately than Vegard's law is presented.

Exploratory Investigation of Advanced-Temperature Nickel-Base Alloys

NASA Technical Reports Server (NTRS)

Freche, John C.; Waters, William J.

1959-01-01

An investigation was conducted to provide an advanced-temperature nickel-base alloy with properties suitable for aircraft turbine blades as well as for possible space vehicle applications. An entire series of alloys that do not require vacuum melting techniques and that generally provide good stress-rupture and impact properties was evolved. The basic-alloy composition of 79 percent nickel, 8 percent molybdenum, 6 percent chromium, 6 percent aluminum, and 1 percent zirconium was modified by a series of element additions such as carbon, titanium, and boron, with the nickel content adjusted to account for the additives. Stress-rupture, impact, and swage tests were made with all the alloys. The strongest composition (basic alloy plus 1.5 percent titanium plus 0.125 percent carbon) displayed 384- and 574-hour stress-rupture lives at 1800 F and 15,000 psi in the as-cast and homogenized conditions, respectively. All the alloys investigated demonstrated good impact resistance. Several could not be broken in a low-capacity Izod impact tester and, on this basis, all compared favorably with several high-strength high-temperature alloys. Swaging cracks were encountered with all the alloys. In several cases, however, these cracks were slight and could be detected only by zyglo examination. Some of these compositions may become amenable to hot working on further development. On the basis of the properties indicated, it appears that several of the alloys evolved, particularly the 1.5 percent titanium plus 0.125 percent carbon basic-alloy modification, could be used for advanced- temperature turbine blades, as well as for possible space vehicle applications.

Model for the Prediction of the Hydriding Thermodynamics of Pd-Rh-Co Ternary Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teter, D.F.; Thoma, D.J.

1999-03-01

A dilute solution model (with respect to the substitutional alloying elements) has been developed, which accurately predicts the hydride formation and decomposition thermodynamics and the storage capacities of dilute ternary Pd-Rh-Co alloys. The effect of varying the rhodium and cobalt compositions on the thermodynamics of hydride formation and decomposition and hydrogen capacity of several palladium-rhodium-cobalt ternary alloys has been investigated using pressure-composition (PC) isotherms. Alloying in the dilute regime (<10 at.%) causes the enthalpy for hydride formation to linearly decrease with increasing alloying content. Cobalt has a stronger effect on the reduction in enthalpy than rhodium for equivalent alloying amounts.more » Also, cobalt reduces the hydrogen storage capacity with increasing alloying content. The plateau thermodynamics are strongly linked to the lattice parameters of the alloys. A near-linear dependence of the enthalpy of hydride formation on the lattice parameter was observed for both the binary Pd-Rh and Pd-Co alloys, as well as for the ternary Pd-Rh-Co alloys. The Pd-5Rh-3Co (at. %) alloy was found to have similar plateau thermodynamics as a Pd-10Rh alloy, however, this ternary alloy had a diminished hydrogen storage capacity relative to Pd-10Rh.« less

High-throughput heterodyne thermoreflectance: Application to thermal conductivity measurements of a Fe-Si-Ge thin film alloy library.

PubMed

d'Acremont, Quentin; Pernot, Gilles; Rampnoux, Jean-Michel; Furlan, Andrej; Lacroix, David; Ludwig, Alfred; Dilhaire, Stefan

2017-07-01

A High-Throughput Time-Domain ThermoReflectance (HT-TDTR) technique was developed to perform fast thermal conductivity measurements with minimum user actions required. This new setup is based on a heterodyne picosecond thermoreflectance system. The use of two different laser oscillators has been proven to reduce the acquisition time by two orders of magnitude and avoid the experimental artefacts usually induced by moving the elements present in TDTR systems. An amplitude modulation associated to a lock-in detection scheme is included to maintain a high sensitivity to thermal properties. We demonstrate the capabilities of the HT-TDTR setup to perform high-throughput thermal analysis by mapping thermal conductivity and interface resistances of a ternary thin film silicide library Fe x Si y Ge 100-x-y (20

High-throughput heterodyne thermoreflectance: Application to thermal conductivity measurements of a Fe-Si-Ge thin film alloy library

NASA Astrophysics Data System (ADS)

d'Acremont, Quentin; Pernot, Gilles; Rampnoux, Jean-Michel; Furlan, Andrej; Lacroix, David; Ludwig, Alfred; Dilhaire, Stefan

2017-07-01

A High-Throughput Time-Domain ThermoReflectance (HT-TDTR) technique was developed to perform fast thermal conductivity measurements with minimum user actions required. This new setup is based on a heterodyne picosecond thermoreflectance system. The use of two different laser oscillators has been proven to reduce the acquisition time by two orders of magnitude and avoid the experimental artefacts usually induced by moving the elements present in TDTR systems. An amplitude modulation associated to a lock-in detection scheme is included to maintain a high sensitivity to thermal properties. We demonstrate the capabilities of the HT-TDTR setup to perform high-throughput thermal analysis by mapping thermal conductivity and interface resistances of a ternary thin film silicide library FexSiyGe100-x-y (20

Composition suitable for use as inert electrode having good electrical conductivity and mechanical properties

DOEpatents

Ray, S.P.; Rapp, R.A.

1984-06-12

An improved inert electrode composition is suitable for use as an inert electrode in the production of metals such as aluminum by the electrolytic reduction of metal oxide or metal salt dissolved in a molten salt bath. The composition comprises one or more metals or metal alloys and metal compounds which may include oxides of the metals comprising the alloy. The alloy and metal compounds are interwoven in a network which provides improved electrical conductivity and mechanical strength while preserving the level of chemical inertness necessary for such an electrode to function satisfactorily. 8 figs.

Composition suitable for use as inert electrode having good electrical conductivity and mechanical properties

DOEpatents

Ray, Siba P.; Rapp, Robert A.

1984-01-01

An improved inert electrode composition is suitable for use as an inert electrode in the production of metals such as aluminum by the electrolytic reduction of metal oxide or metal salt dissolved in a molten salt bath. The composition comprises one or more metals or metal alloys and metal compounds which may include oxides of the metals comprising the alloy. The alloy and metal compounds are interwoven in a network which provides improved electrical conductivity and mechanical strength while preserving the level of chemical inertness necessary for such an electrode to function satisfactorily.

Method of making composition suitable for use as inert electrode having good electrical conductivity and mechanical properties

DOEpatents

Ray, Siba P.; Rapp, Robert A.

1986-01-01

An improved inert electrode composition is suitable for use as an inert electrode in the production of metals such as aluminum by the electrolytic reduction of metal oxide or metal salt dissolved in a molten salt bath. The composition comprises one or more metals or metal alloys and metal compounds which may include oxides of the metals comprising the alloy. The alloy and metal compounds are interwoven in a network which provides improved electrical conductivity and mechanical strength while preserving the level of chemical inertness necessary for such an electrode to function satisfactorily.

Chemical and Phase Composition of Powders Obtained by Electroerosion Dispersion from WC - Co Alloys

NASA Astrophysics Data System (ADS)

Putintseva, M. N.

2004-03-01

The dependence of the chemical and phase composition of dispersed powders on the mode and medium of electroerosion dispersion and the content of cobalt in the initial alloy is considered. It is shown that the dissociation of carbon from tungsten carbide occurs even in dispersion in liquid hydrocarbon-bearing media (kerosene and industrial oils). The phase composition is primarily determined by the dispersion medium and the content of cobalt in the initial alloy. Compound tungsten-cobalt carbides and even a Co7W6 intermetallic are determined in all the powders.

Hydrogen absorption of Pd/ZrO2 composites prepared from Zr65Pd35 and Zr60Pd35Pt5 amorphous alloys

NASA Astrophysics Data System (ADS)

Ozawa, Masakuni; Katsuragawa, Naoya; Hattori, Masatomo; Yogo, Toshinobu; Yamamura, Shin-ichi

2018-01-01

Metal-dispersed composites were derived from amorphous Zr65Pd35 and Zr65Pd30Pt5 alloys and their hydrogen absorption behavior was studied. X-ray diffractograms and scanning electron micrographs indicated that mixtures containing ZrO2, the metallic phase of Pd, and PdO were formed for both amorphous alloys heat-treated in air. In the composites, micron-sized Pd-based metal precipitates were embedded in a ZrO2 matrix after heat treatment at 800 °C in air. The hydrogen temperature-programmed reduction was applied to study the reactivity of hydrogen gas with the oxidized Zr65Pd35 and Zr65Pd30Pt5 materials. Rapid hydrogen absorption and release were observed on the composite derived from the amorphous alloy below 100 °C. The hydrogen pressure-concentration isotherm showed that the absorbed amount of hydrogen in materials depended on the formation of the Pd or Pt-doped Pd phase and its large interface area to the matrix in the nanocomposites. The results indicate the importance of the composite structure for the fabrication of a new type of hydrogen storage material prepared from amorphous alloys.

Cu-Al-Ni-SMA-Based High-Damping Composites

NASA Astrophysics Data System (ADS)

López, Gabriel A.; Barrado, Mariano; San Juan, Jose; Nó, María Luisa

2009-08-01

Recently, absorption of vibration energy by mechanical damping has attracted much attention in several fields such as vibration reduction in aircraft and automotive industries, nanoscale vibration isolations in high-precision electronics, building protection in civil engineering, etc. Typically, the most used high-damping materials are based on polymers due to their viscoelastic behavior. However, polymeric materials usually show a low elastic modulus and are not stable at relatively low temperatures (≈323 K). Therefore, alternative materials for damping applications are needed. In particular, shape memory alloys (SMAs), which intrinsically present high-damping capacity thanks to the dissipative hysteretic movement of interfaces under external stresses, are very good candidates for high-damping applications. A completely new approach was applied to produce high-damping composites with relatively high stiffness. Cu-Al-Ni shape memory alloy powders were embedded with metallic matrices of pure In, a In-10wt.%Sn alloy and In-Sn eutectic alloy. The production methodology is described. The composite microstructures and damping properties were characterized. A good particle distribution of the Cu-Al-Ni particles in the matrices was observed. The composites exhibit very high damping capacities in relatively wide temperature ranges. The methodology introduced provides versatility to control the temperature of maximum damping by adjusting the shape memory alloy composition.

Preparation and corrosion resistance of magnesium phytic acid/hydroxyapatite composite coatings on biodegradable AZ31 magnesium alloy.

PubMed

Zhang, Min; Cai, Shu; Zhang, Feiyang; Xu, Guohua; Wang, Fengwu; Yu, Nian; Wu, Xiaodong

2017-06-01

In this work, a magnesium phytic acid/hydroxyapatite composite coating was successfully prepared on AZ31 magnesium alloy substrate by chemical conversion deposition technology with the aim of improving its corrosion resistance and bioactivity. The influence of hydroxyapatite (HA) content on the microstructure and corrosion resistance of the coatings was investigated. The results showed that with the increase of HA content in phytic acid solution, the cracks on the surface of the coatings gradually reduced, which subsequently improved the corrosion resistance of these coated magnesium alloy. Electrochemical measurements in simulated body fluid (SBF) revealed that the composite coating with 45 wt.% HA addition exhibited superior surface integrity and significantly improved corrosion resistance compared with the single phytic acid conversion coating. The results of the immersion test in SBF showed that the composite coating could provide more effective protection for magnesium alloy substrate than that of the single phytic acid coating and showed good bioactivity. Magnesium phytic acid/hydroxyapatite composite, with the desired bioactivity, can be synthesized through chemical conversion deposition technology as protective coatings for surface modification of the biodegradable magnesium alloy implants. The design idea of the new type of biomaterial is belong to the concept of "third generation biomaterial". Corrosion behavior and bioactivity of coated magnesium alloy are the key issues during implantation. In this study, preparation and corrosion behavior of magnesium phytic acid/hydroxyapatite composite coatings on magnesium alloy were studied. The basic findings and significance of this paper are as follows: 1. A novel environmentally friendly, homogenous and crack-free magnesium phytic acid/hydroxyapatite composite coating was fabricated on AZ31 magnesium alloy via chemical conversion deposition technology with the aim of enhancing its corrosion resistance and bioactivity. The chemical conversion coatings, which are formed through the reaction between the substrate and the environment, have attracted increasing attention owing to the relative low treatment temperature, favorable bonding to substrate and simple implementation process. 2. With the increasing of hydroxyapatite (HA) content, the crack width in the composite coatings and the thickness of the coatings exhibit obviously decreased. The reason is probably that when adding HA into the phytic acid solution, the amount of active hydroxyl groups in the phytic acid are reduced via forming the coordination bond between P-OH groups from phytic acid and P-OH groups from the surface of HA, thus decreasing the coating thickness and hydrogen formation, as well as avoiding coating cracking. 3. By adjusting the HA content to 45 wt.%, a dense and relatively smooth composite coating with ~1.4 μm thickness is obtained on magnesium alloy, and exhibits high corrosion resistance and good bioactivity when compared with the single phytic acid conversion coating.

ALLOY FOR USE IN NUCLEAR FISSION

DOEpatents

Spedding, F.A.; Wilhelm, H.A.

1958-03-11

This patent relates to an alloy composition capable of functioning as a solid homogeneous reactor fuel. The alloy consists of a beryllium moderator, together with at least 0.7% of U/sup 235/, and up to 50% thorium to give increased workability to the alloy.

Phase Diagram of the Al-Ca-Fe-Si System and Its Application for the Design of Aluminum Matrix Composites

NASA Astrophysics Data System (ADS)

Belov, Nikolay A.; Naumova, Evgeniya A.; Akopyan, Torgom K.; Doroshenko, Vitaliy V.

2018-05-01

The phase composition of aluminum alloys in the Al-Ca-Fe-Si system, including the distribution of phases in the solid state and solidification reactions, has been studied. It is shown that the addition of iron and silicon to Al-Ca alloys leads to the formation of ternary Al2CaSi2 and Al10CaFe2 compounds. The equilibrium between these compounds implies the occurrence of the quaternary L → Al + Al4Ca + Al2CaSi2 + Al10CaFe2 eutectic reaction. The alloys near this eutectic have the best structure, which is typical of aluminum matrix composites. It is shown that Al-Ca alloys can have high manufacturability during both shape casting and rolling. This is due to the combination of a narrow temperature range of solidification and a favorable morphology for the eutectic, which has a fine structure. The combination of the mechanical and physical properties of the Al-Ca eutectic-based alloys significantly exceed those of branded alloys based on aluminum-silicon eutectics.

A Fatigue Model for Discontinuous Particulate-Reinforced Aluminum Alloy Composite: Influence of Microstructure

NASA Astrophysics Data System (ADS)

McCullough, R. R.; Jordon, J. B.; Brammer, A. T.; Manigandan, K.; Srivatsan, T. S.; Allison, P. G.; Rushing, T. W.

2014-01-01

In this paper, the use of a microstructure-sensitive fatigue model is put forth for the analysis of discontinuously reinforced aluminum alloy metal matrix composite. The fatigue model was used for a ceramic particle-reinforced aluminum alloy deformed under conditions of fully reversed strain control. Experimental results revealed the aluminum alloy to be strongly influenced by volume fraction of the particulate reinforcement phase under conditions of strain-controlled fatigue. The model safely characterizes the evolution of fatigue damage in this aluminum alloy composite into the distinct stages of crack initiation and crack growth culminating in failure. The model is able to capture the specific influence of particle volume fraction, particle size, and nearest neighbor distance in quantifying fatigue life. The model yields good results for correlation of the predicted results with the experimental test results on the fatigue behavior of the chosen aluminum alloy for two different percentages of the ceramic particle reinforcement. Further, the model illustrates that both particle size and volume fraction are key factors that govern fatigue lifetime. This conclusion is well supported by fractographic observations of the cyclically deformed and failed specimens.

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

NASA Technical Reports Server (NTRS)

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

1992-01-01

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

Direct evidence for stress-induced transformation between coexisting multiple martensites in a Ni-Mn-Ga multifunctional alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, L.; Cong, D. Y.; Wang, Z. L.

2015-07-08

The structural response of coexisting multiple martensites to stress field in a Ni-Mn-Ga multifunctional alloy was investigated by the in situ high-energy x-ray diffraction technique. Stress-induced transformation between coexisting multiple martensites was observed at 110 K, at which five-layered modulated (5M), seven-layered modulated (7M) and non-modulated (NM) martensites coexist. We found that a tiny stress of as low as 0.5 MPa could trigger the transformation from 5M and 7M martensites to NM martensite and this transformation is partly reversible. Besides the transformation between coexisting multiple martensites, rearrangement of martensite variants also occurs during loading, at least at high stress levels.more » The present study is instructive for designing advanced multifunctional alloys with easy actuation.« less

Direct evidence for stress-induced transformation between coexisting multiple martensites in a Ni-Mn-Ga multifunctional alloy

NASA Astrophysics Data System (ADS)

Huang, L.; Cong, D. Y.; Wang, Z. L.; Nie, Z. H.; Dong, Y. H.; Zhang, Y.; Ren, Y.; Wang, Y. D.

2015-07-01

The structural response of coexisting multiple martensites to stress field in a Ni-Mn-Ga multifunctional alloy was investigated by the in situ high-energy x-ray diffraction technique. Stress-induced transformation between coexisting multiple martensites was observed at 110 K, at which five-layered modulated (5M), seven-layered modulated (7M) and non-modulated (NM) martensites coexist. We found that a tiny stress of as low as 0.5 MPa could trigger the transformation from 5M and 7M martensites to NM martensite and this transformation is partly reversible. Besides the transformation between coexisting multiple martensites, rearrangement of martensite variants also occurs during loading, at least at high stress levels. The present study is instructive for designing advanced multifunctional alloys with easy actuation.

Direct evidence for stress-induced transformation between coexisting multiple martensites in a Ni-Mn-Ga multifunctional alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Huang, L.; Cong, D. Y.; Wang, Z. L.

2015-06-03

The structural response of coexisting multiple martensites to stress field in a Ni-Mn-Ga multifunctional alloy was investigated by the in situ high-energy x-ray diffraction technique. Stress-induced transformation between coexisting multiple martensites was observed at 110 K, at which five-layered modulated (5M), seven-layered modulated (7M) and non-modulated (NM) martensites coexist. We found that a tiny stress of as low as 0.5 MPa could trigger the transformation from 5M and 7M martensites to NM martensite and this transformation is partly reversible. Besides the transformation between coexisting multiple martensites, rearrangement of martensite variants also occurs during loading, at least at high stress levels.more » The present study is instructive for designing advanced multifunctional alloys with easy actuation.« less

Behavior of grain boundary chemistry and precipitates upon thermal treatment of controlled purity alloy 690

NASA Astrophysics Data System (ADS)

Angeliu, Thomas M.; Was, Gary S.

1990-08-01

Grain boundary composition and carbide composition and structure were characterized for various microstructures of controlled purity alloy 690. Heat treatments produced varying degrees of grain boundary chromium depletion and precipitate distributions which were characterized via scanning transmission electron microscopy (STEM). Convergent beam electron diffraction revealed that the dominant carbide is M23C6, and energy dispersive X-ray analysis (EDAX) determined that the metallic content was about 90 at. pct chromium. A discontinuous precipitation reaction was observed and is attributed to a high degree of carbon supersaturation. Grain boundary composition measurements confirm that chromium depletion is controlled by volume diffusion of chromium to chromium-rich grain boundary carbides in the temperature range of 873 to 1073 K. Grain boundary chromium levels as low as 18.8 at. pct were obtained by thermal treatment at 873 K for 250 hours and 973 K for 1 hour. A thermodynamic and kinetic model developed for alloy 600 was modified to describe the development of the chromium depletion profile in alloy 690 during thermal treatment. Experimentally measured chromium profiles agree well with the model results for the dependence of the chromium depletion zone width and depth on various input parameters. The establishment of the model for alloy 690 allows the chromium depletion zone width and depth to be computed as a function of alloy composition, grain size, and temperature. The chromium depletion profiles and the precipitate structure and composition of controlled purity 690 are compared to those of controlled purity 600. A thermodynamic analysis of the carbide stability indicates that other factors, such as favorable orientation relationships, play an important role in controlling the precipitation of Cr23C6 in nickel-base alloys.

Evaluation of silicon carbide fiber/titanium composites

NASA Technical Reports Server (NTRS)

Jech, R. W.; Signorelli, R. A.

1979-01-01

Izod impact, tensile, and modulus of elasticity were determined for silicon carbide fiber/titanium composites to evaluate their potential usefulness as substitutes for titanium alloys or stainless steel in stiffness critical applications for aircraft turbine engines. Variations in processing conditions and matrix ductility were examined to produce composites having good impact strength in both the as-fabricated condition and after air exposure at elevated temperature. The impact strengths of composites containing 36 volume percent silicon carbide (SiC) fiber in an unalloyed (A-40) titanium matrix were found to be equal to unreinforced titanium-6 aluminum-4 vanadium alloy; the tensile strengths of the composites were marginally better than the unreinforced unalloyed (A-70) matrix at elevated temperature, though not at room temperature. At room temperature the modulus of elasticity of the composites was 48 percent higher than titanium or its alloys and 40 percent higher than that of stainless steel.

Development of Deployable Elastic Composite Shape Memory Alloy Reinforced (DECSMAR) Structures

DTIC Science & Technology

2006-05-01

battens nest. To mitigate the compromise of deployed performance due to the hinge cross-section, Nitinol SMA wires can be embedded in the composite...proportional limit by slip or conventional plastic deformation. As a logistics example, the particular Nitinol alloy used for proto-typing has...Memory Alloys,” Johnson Matthey, 2004. 10Cross, WB, Kariotis, AH, & Stimler, FJ, “ Nitinol Characterization Study,” NASA CR-1433, 1970. 11Proft, JL

Molybdenum disilicide alloy matrix composite

DOEpatents

Petrovic, John J.; Honnell, Richard E.; Gibbs, W. Scott

1990-01-01

Compositions of matter consisting of matrix matrials having silicon carbide dispersed throughout them and methods of making the compositions. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms.

Molybdenum disilicide alloy matrix composite

DOEpatents

Petrovic, John J.; Honnell, Richard E.; Gibbs, W. Scott

1991-01-01

Compositions of matter consisting of matrix materials having silicon carbide dispersed throughout them and methods of making the compositions. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms.

Acoustic transmission and radiation analysis of adaptive shape-memory alloy reinforced laminated plates

NASA Astrophysics Data System (ADS)

Liang, C.; Rogers, C. A.; Fuller, C. R.

1991-02-01

A theoretical analysis of sound transmission/radiation of shape-memory alloy (SMA) hybrid composite panels is presented. Unlike other composite materials, SMA hybrid composite is dynamically tunable by electrical activation of the SMA fibers and has numerous active control capabilities. Two of the concepts that will be briefly described and utilized in this paper are referred to as active property tuning (APT) and active strain energy tuning (ASET). Tuning or activating the embedded shape-memory alloy fibers in conventional composite materials changes the overall stiffness of the SMA hybrid composite structure and consequently changes natural frequency and mode shapes. The sound transmission and radiation from a composite panel is related to its frequency and mode shapes. Because of the capability to change both the natural frequency and mode shapes, the acoustic characteristics of SMA hybrid composite plates can be changed as well. The directivity pattern, radiation efficiency, and transmission loss of laminated composite materials are investigated based on 'composite' mode shapes in order to derive a basic understanding of the nature and authority of acoustic control by use of SMA hybrid composites.

Development and characterization of laser surface cladding (Ti,W)C reinforced Ni-30Cu alloy composite coating on copper

NASA Astrophysics Data System (ADS)

Yan, Hua; Zhang, Peilei; Yu, Zhishui; Li, Chonggui; Li, Ruidi

2012-07-01

To improve the wear resistance of copper components, laser surface cladding (LSC) was applied to deposit (Ti,W)C reinforced Ni-30Cu alloy composite coating on copper using a cladding interlayer of Ni-30Cu alloy by Nd:YAG laser. The microstructure and phases of the composite coating were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and X-ray energy dispersive microanalysis (EDX). Microhardness tester and pin-on-disc wear tester were employed to evaluate the hardness and dry-sliding wear resistance. The results show that crack-free composite coating with metallurgical bonding to the copper substrate is obtained. Phases identified in the (Ti,W)C-reinforced Ni-30Cu alloy composite layer are composed of TiWC2 reinforcements and (Ni,Cu) solid solution. TiWC2 reinforcements are distributed uniformly in the (Ni,Cu) solid solution matrix with dendritic morphology in the upper region and with particles in the mid-lower region. The microhardness and wear properties of the composite coating are improved significantly in comparison to the as-received copper substrate due to the addition of 50 wt% (Ti,W)C multicarbides.

Generalized Slater--Pauling curve and the role of metalloids in Fe-based amorphous alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sostarich, M.

1990-05-01

A modification of the generalized Slater--Pauling curve so as to consider the concentration dependence of the number of majority-spin {ital sp} electrons per average atom is proposed for amorphous iron-metalloid alloys. In this way an improved matching of the measured magnetic moment dependence on composition is achieved for Fe alloys with B and/or P as metalloids. Comparison of theory with experiment shows that amorphous Fe-P alloys tend to be magnetically rather strong, whereas their Fe-B counterparts are weak itinerant ferromagnets in almost the entire range of compositions.

Thermodynamic analysis of chemical compatibility of several compounds with Fe-Cr-Al alloys

NASA Technical Reports Server (NTRS)

Misra, Ajay K.

1993-01-01

Chemical compatibility between Fe-19.8Cr-4.8Al (weight percent), which is the base composition for the commercial superalloy MA956, and several carbides, borides, nitrides, oxides, and silicides was analyzed from thermodynamic considerations. The effect of addition of minor alloying elements, such as Ti, Y, and Y2O3, to the Fe-Cr-Al alloy on chemical compatibility between the alloy and various compounds was also analyzed. Several chemically compatible compounds that can be potential reinforcement materials and/or interface coating materials for Fe-Cr-Al based composites were identified.

Alloy vapor deposition using ion plating and flash evaporation

NASA Technical Reports Server (NTRS)

Spalvins, T.

1971-01-01

Method extends scope of ion plating technique to include deposition of alloy films without changing composition of plating alloy. Coatings flow with specimen material without chipping or peeling. Technique is most effective vacuum deposition method for depositing alloys for strong and lasting adherence.

Production of small diameter high-temperature-strength refractory metal wires

NASA Technical Reports Server (NTRS)

Petrasek, D. W.; Signorelli, R. A.; King, G. W.

1973-01-01

Special thermomechanical techniques (schedules) have been developed to produce small diameter wire from three refractory metal alloys: colombian base alloy, tantalum base alloy, and tungsten base alloy. High strengths of these wires indicate their potential for contributing increased strength to metallic composites.

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

NASA Technical Reports Server (NTRS)

Olsen, G. C.

1981-01-01

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

Compositional inhomogeneities in AlGaN thin films grown by molecular beam epitaxy: Effect on MSM UV photodetectors

NASA Astrophysics Data System (ADS)

Pramanik, Pallabi; Sen, Sayantani; Singha, Chirantan; Roy, Abhra Shankar; Das, Alakananda; Sen, Susanta; Bhattacharyya, A.

2016-10-01

Ultraviolet (UV) MSM photodetectors (PD) based on AlGaN alloys find many applications, including flame sensing. In this work we investigate the dependence of AlGaN based photodetectors grown by MBE on the kinetics of growth. MSM photodetectors were fabricated in the interdigitated configuration with Ni/Au contacts having 400 μm finger length and 10 μm finger spacing. Bulk Al0.4Ga0.6N films were grown on to sapphire substrates using an AlN buffer layer. A series of PDs were developed using the Al0.4Ga0.6N films grown under different group III/V flux ratios ranging from stoichiometric conditions to much higher than unity. Upon testing, it was observed that the otherwise identical photodetectors show significant decrease in dark current as AlGaN deposition conditions change from stoichiometric to excess group III, due to reduction of unintentional incorporation of oxygen-related point defects. In addition, the intensity and spectral dependence of the photocurrent also change, showing an extended low energy tail for the former and a sharp and prominent excitonic peak for the latter. The optical transmission measurements indicate a variation in Urbach energy with deposition conditions of the AlGaN films, although they have the same absorption edge. While all samples show a single red-shifted photoluminescence peak at room temperature, upon cooling, multiple higher energy peaks appear in the photoluminescence (PL) spectra, indicating that the alloys contain complex compositional inhomogeneities. Two types of alloy fluctuations, determined by the growth conditions, have been identified that modulate the optoelectronic properties of AlGaN by changing the spatial localization of excitons, thereby altering their stability. We identified that growth under stoichiometric conditions leads to compositional inhomogeneities that play a detrimental role in the operation of MSM photodetectors, which reduces the sharpness of the sensitivity edge, while growth under excess metal conditions enhances it.

Unoccupied electronic structure of Ni 2MnGa ferromagnetic shape memory alloy

DOE PAGES

Maniraj, M.; D׳Souza, S. W.; Rai, Abhishek; ...

2015-08-20

Momentum resolved inverse photoemission spectroscopy measurements show that the dispersion of the unoccupied bands of Ni 2MnGa is significant in the austenite phase. Furthermore, in the martensite phase, it is markedly reduced, which is possibly related to the structural transition to an incommensurate modulated state in the martensite phase. Finally, based on the first principle calculations of the electronic structure of Ni–Mn–Ga, we show that the modification of the spectral shape with surface composition is related to change in the hybridization between the Mn 3d and Ni 3d-like states that dominate the unoccupied conduction band.

Unoccupied electronic structure of Ni2MnGa ferromagnetic shape memory alloy

NASA Astrophysics Data System (ADS)

Maniraj, M.; D`Souza, S. W.; Rai, Abhishek; Schlagel, D. L.; Lograsso, T. A.; Chakrabarti, Aparna; Barman, S. R.

2015-11-01

Momentum resolved inverse photoemission spectroscopy measurements show that the dispersion of the unoccupied bands of Ni2MnGa is significant in the austenite phase. In the martensite phase, it is markedly reduced, which is possibly related to the structural transition to an incommensurate modulated state in the martensite phase. Based on the first principle calculations of the electronic structure of Ni-Mn-Ga, we show that the modification of the spectral shape with surface composition is related to change in the hybridization between the Mn 3d and Ni 3d-like states that dominate the unoccupied conduction band.

Magnetic cluster expansion model for random and ordered magnetic face-centered cubic Fe-Ni-Cr alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lavrentiev, M. Yu., E-mail: Mikhail.Lavrentiev@ukaea.uk; Nguyen-Manh, D.; Dudarev, S. L.

A Magnetic Cluster Expansion model for ternary face-centered cubic Fe-Ni-Cr alloys has been developed, using DFT data spanning binary and ternary alloy configurations. Using this Magnetic Cluster Expansion model Hamiltonian, we perform Monte Carlo simulations and explore magnetic structures of alloys over the entire range of compositions, considering both random and ordered alloy structures. In random alloys, the removal of magnetic collinearity constraint reduces the total magnetic moment but does not affect the predicted range of compositions where the alloys adopt low-temperature ferromagnetic configurations. During alloying of ordered fcc Fe-Ni compounds with Cr, chromium atoms tend to replace nickel rathermore » than iron atoms. Replacement of Ni by Cr in ordered alloys with high iron content increases the Curie temperature of the alloys. This can be explained by strong antiferromagnetic Fe-Cr coupling, similar to that found in bcc Fe-Cr solutions, where the Curie temperature increase, predicted by simulations as a function of Cr concentration, is confirmed by experimental observations. In random alloys, both magnetization and the Curie temperature decrease abruptly with increasing chromium content, in agreement with experiment.« less

Investigation on the morphological and optical evolution of bimetallic Pd-Ag nanoparticles on sapphire (0001) by the systematic control of composition, annealing temperature and time.

PubMed

Pandey, Puran; Kunwar, Sundar; Sui, Mao; Bastola, Sushil; Lee, Jihoon

2017-01-01

Multi-metallic alloy nanoparticles (NPs) can offer additional opportunities for modifying the electronic, optical and catalytic properties by the control of composition, configuration and size of individual nanostructures that are consisted of more than single element. In this paper, the fabrication of bimetallic Pd-Ag NPs is systematically demonstrated via the solid state dewetting of bilayer thin films on c-plane sapphire by governing the temperature, time as well as composition. The composition of Pd-Ag bilayer remarkably affects the morphology of alloy nanostructures, in which the higher Ag composition, i.e. Pd0.25Ag0.75, leads to the enhanced dewetting of bilayers whereas the higher Pd composition (Pd0.75Ag0.25) hinders the dewetting. Depending on the annealing temperature, Pd-Ag alloy nanostructures evolve with a series of configurations, i.e. nucleation of voids, porous network, elongated nanoclusters and round alloy NPs. In addition, with the annealing time set, the gradual configuration transformation from the elongated to round alloy NPs as well as size reduction is demonstrated due to the enhanced diffusion and sublimation of Ag atoms. The evolution of various morphology of Pd-Ag nanostructures is described based on the surface diffusion and inter-diffusion of Pd and Ag adatoms along with the Ag sublimation, Rayleigh instability and energy minimization mechanism. The reflectance spectra of bimetallic Pd-Ag nanostructures exhibit various quadrupolar and dipolar resonance peaks, peak shifts and absorption dips owing to the surface plasmon resonance of nanostructures depending on the surface morphology. The intensity of reflectance spectra is gradually decreased along with the surface coverage and NP size evolution. The absorption dips are red-shifted towards the longer wavelength for the larger alloy NPs and vice-versa.

Fatigue design curve of a TiNi/Al shape memory alloy composite for aircraft stringer design

NASA Astrophysics Data System (ADS)

Park, Young-Chul; Jo, Young-Jik; Baek, Seok-Heum; Furuya, Yasubumi

2009-05-01

In this study, a TiNi/Al6061 shape memory alloy (SMA) composite was fabricated by the hot press method, and pressed by a roller for its strength improvement using the shape memory fiber shrinkage phenomenon. These two kinds of specimens were fabricated with 0% and 5% volume ratio and 0%, 10 % and 20% reduction ratio of TiNi alloy fiber, respectively. A fatigue test has been performed to evaluate the fatigue life for the fabricated TiNi/Al SMA composite as an S-N curve. The results from the Goodman diagram is able to illustrate the failure criterion and fatigue limit between tensile and bending fatigue strength in the fatigue characterization of TiNi/Al SMA composites.

High-Performance Metal/Carbide Composites with Far-From-Equilibrium Compositions and Controlled Microstructures

PubMed Central

Hu, Liangfa; O’Neil, Morgan; Erturun, Veysel; Benitez, Rogelio; Proust, Gwénaëlle; Karaman, Ibrahim; Radovic, Miladin

2016-01-01

The prospect of extending existing metal-ceramic composites to those with the compositions that are far from thermodynamic equilibrium is examined. A current and pressure-assisted, rapid infiltration is proposed to fabricate composites, consisting of reactive metallic and ceramic phases with controlled microstructure and tunable properties. An aluminum (Al) alloy/Ti2AlC composite is selected as an example of the far-from-equilibrium systems to fabricate, because Ti2AlC exists only in a narrow region of the Ti-Al-C phase diagram and readily reacts with Al. This kind of reactive systems challenges conventional methods for successfully processing corresponding metal-ceramic composites. Al alloy/Ti2AlC composites with controlled microstructures, various volume ratios of constituents (40/60 and 27/73) and metallic phase sizes (42–83 μm, 77–276 μm, and 167–545 μm), are obtained using the Ti2AlC foams with different pore structures as preforms for molten metal (Al alloy) infiltration. The resulting composites are lightweight and display exceptional mechanical properties at both ambient and elevated temperatures. These structures achieve a compressive strength that is 10 times higher than the yield strength of the corresponding peak-aged Al alloy at ambient temperature and 14 times higher at 400 °C. Possible strengthening mechanisms are described, and further strategies for improving properties of those composites are proposed. PMID:27752106

Bandgap engineering in semiconductor alloy nanomaterials with widely tunable compositions

NASA Astrophysics Data System (ADS)

Ning, Cun-Zheng; Dou, Letian; Yang, Peidong

2017-12-01

Over the past decade, tremendous progress has been achieved in the development of nanoscale semiconductor materials with a wide range of bandgaps by alloying different individual semiconductors. These materials include traditional II-VI and III-V semiconductors and their alloys, inorganic and hybrid perovskites, and the newly emerging 2D materials. One important common feature of these materials is that their nanoscale dimensions result in a large tolerance to lattice mismatches within a monolithic structure of varying composition or between the substrate and target material, which enables us to achieve almost arbitrary control of the variation of the alloy composition. As a result, the bandgaps of these alloys can be widely tuned without the detrimental defects that are often unavoidable in bulk materials, which have a much more limited tolerance to lattice mismatches. This class of nanomaterials could have a far-reaching impact on a wide range of photonic applications, including tunable lasers, solid-state lighting, artificial photosynthesis and new solar cells.

Wear resistance of metals and alloys; Proceedings of the Conference, Chicago, IL, Sept. 24-30, 1988

DOE Office of Scientific and Technical Information (OSTI.GOV)

Kingsbury, G.R.

1988-01-01

Techniques for characterizing and improving the wear properties of metals and composites are discussed in reviews and reports. Topics addressed include the use of interatomic potentials to study the relationship between abrasive wear and other mechanical properties, gas-detonation powder spraying of diamond coatings, a fluidized-bed test method for erosion resistance, the wear behavior of Al and Al-Si-Cu alloys, and abrasive wear of bronze and ZA alloys with and without lubrication. Consideration is given to continuously cast vs sand-cast Zn-Al alloys for bearings, sintered 6061 Al-alloy-based particulate composites with dry lubricants, Cu-based particulate composites, high-temperature friction and wear of X-750 andmore » X-188 superalloys for low-heat-rejection engines, a new metallurgical conception of wear-resistant steels, and the effect of matrix microstructure on the abrasion resistance of high-Cr white cast irons. Extensive graphs and micrographs are provided.« less

Effect of In-Situ Titanium Boride Particle Addition and Friction Stir Processing on Wear Behavior of Aluminum Alloy 2219

NASA Astrophysics Data System (ADS)

Sampath, V.; Rajasekaran, N. R.

There is paucity of data on the effect of in-situ TiB2 particles on the different behavior of 2219 Al alloy. In the present work, therefore, composites with 2219 Al alloy matrix reinforced with in-situ TiB2 particles were produced by flux-assisted synthesis. Different amounts (5 and 10 wt.%) of TiB2 were incorporated. The base alloy and the composites were subjected to friction stir processing to reduce particle clustering. The wear behavior of the materials was studied. The base alloy showed considerable improvement in the wear behavior due to the in-situ particle addition which is attributed to the presence of finer particles with good interfacial bonding and high hardness. Uniform distribution of TiB2 particles and good interface between the matrix and the particles led to reduction in the wear of friction stir processed composites by 30%. The results are analyzed and discussed in detail in the paper.

Novel Method for Making Biomedical Segregation-Free Ti-30Ta Alloy Spherical Powder for Additive Manufacturing

NASA Astrophysics Data System (ADS)

Xia, Yang; Fang, Zhigang Zak; Sun, Pei; Zhang, Ying; Zhu, Jun

2018-03-01

Ti-Ta alloys offer a good combination of high strength and low modulus among Ti-based alloys, and are ideal for biomedical applications. However, making Ti-Ta alloys has always been challenging because they tend to suffer from compositional segregation during melting due to the large difference between the melting points of Ti and Ta. This article describes a novel process for making spherical Ti-30Ta alloy powder through a unique powder metallurgy technique, namely the granulation-sintering-deoxygenation process. The results indicate that the compositional segregation problem can be overcome using this process technology. Combined with use of a deoxygenation process, the critical interstitial element, oxygen, can be controlled to < 400 ppm for powder with particle size < 75 µm. The destabilization effect of Ta on Ti-O solid solutions, and the resulting improved deoxygenation process for Ti-Ta, are discussed, as well as the phase composition and microstructure of the powders.

Zirconium-based alloys, nuclear fuel rods and nuclear reactors including such alloys, and related methods

DOEpatents

Mariani, Robert Dominick

2014-09-09

Zirconium-based metal alloy compositions comprise zirconium, a first additive in which the permeability of hydrogen decreases with increasing temperatures at least over a temperature range extending from 350.degree. C. to 750.degree. C., and a second additive having a solubility in zirconium over the temperature range extending from 350.degree. C. to 750.degree. C. At least one of a solubility of the first additive in the second additive over the temperature range extending from 350.degree. C. to 750.degree. C. and a solubility of the second additive in the first additive over the temperature range extending from 350.degree. C. to 750.degree. C. is higher than the solubility of the second additive in zirconium over the temperature range extending from 350.degree. C. to 750.degree. C. Nuclear fuel rods include a cladding material comprising such metal alloy compositions, and nuclear reactors include such fuel rods. Methods are used to fabricate such zirconium-based metal alloy compositions.

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

NASA Technical Reports Server (NTRS)

Birt, Michael J.; Johnson, W. Steven

1990-01-01

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

Adaptive modulations of martensites.

PubMed

Kaufmann, S; Rössler, U K; Heczko, O; Wuttig, M; Buschbeck, J; Schultz, L; Fähler, S

2010-04-09

Modulated phases occur in numerous functional materials like giant ferroelectrics and magnetic shape-memory alloys. To understand the origin of these phases, we employ and generalize the concept of adaptive martensite. As a starting point, we investigate the coexistence of austenite, adaptive 14M phase, and tetragonal martensite in Ni-Mn-Ga magnetic shape-memory alloy epitaxial films. We show that the modulated martensite can be constructed from nanotwinned variants of the tetragonal martensite phase. By combining the concept of adaptive martensite with branching of twin variants, we can explain key features of modulated phases from a microscopic view. This includes metastability, the sequence of 6M-10M-14M-NM intermartensitic transitions, and the magnetocrystalline anisotropy.

Alloy with metallic glass and quasi-crystalline properties

DOEpatents

Xing, Li-Qian; Hufnagel, Todd C.; Ramesh, Kaliat T.

2004-02-17

An alloy is described that is capable of forming a metallic glass at moderate cooling rates and exhibits large plastic flow at ambient temperature. Preferably, the alloy has a composition of (Zr, Hf).sub.a Ta.sub.b Ti.sub.c Cu.sub.d Ni.sub.e Al.sub.f, where the composition ranges (in atomic percent) are 45.ltoreq.a.ltoreq.70, 3.ltoreq.b.ltoreq.7.5, 0.ltoreq.c.ltoreq.4, 3.ltoreq.b+c.ltoreq.10, 10.ltoreq.d.ltoreq.30, 0.ltoreq.e.ltoreq.20, 10.ltoreq.d+e.ltoreq.35, and 5.ltoreq.f.ltoreq.15. The alloy may be cast into a bulk solid with disordered atomic-scale structure, i.e., a metallic glass, by a variety of techniques including copper mold die casting and planar flow casting. The as-cast amorphous solid has good ductility while retaining all of the characteristic features of known metallic glasses, including a distinct glass transition, a supercooled liquid region, and an absence of long-range atomic order. The alloy may be used to form a composite structure including quasi-crystals embedded in an amorphous matrix. Such a composite quasi-crystalline structure has much higher mechanical strength than a crystalline structure.

Platinum–nickel nanowire catalysts with composition-tunable alloying and faceting for the oxygen reduction reaction

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chang, Fangfang; Yu, Gang; Shan, Shiyao

2017-01-01

The ability to tune the alloying properties and faceting characteristics of bimetallic nanocatalysts is essential for designing catalysts with enhanced activity and stability through optimizing strain and ligand effects, which is an important frontier for designing advanced materials as catalysts for fuel cell applications. This report describes composition-controlled alloying and faceting of platinum–nickel nanowires (PtNi NWs) for the electrocatalytic oxygen reduction reaction. The PtNi NWs are synthesized by a surfactant-free method and are shown to display bundled morphologies of nano-tetrahedra or nanowires, featuring an ultrathin and irregular helix morphology with composition-tunable facets. Using high-energy synchrotron X-ray diffraction coupled with atomicmore » pair distribution function analysis, lattice expansion and shrinking are revealed, with the Pt : Ni ratio of ~3 : 2 exhibiting a clear expansion, which coincides with the maximum electrocatalytic activity for the ORR. In comparison with PtNi nanoparticles (NPs), the PtNi NWs display remarkably higher electrocatalytic activity and stability as a result of the composition dependent atomic-scale alloying and faceting, demonstrating a new pathway to the design of alloy nanocatalysts with enhanced activity and durability for fuel cells.« less

Impact of alloy composition on one-dimensional glide of small dislocation loops in concentrated solid solution alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shi, Shi; Bei, Hongbin; Robertson, Ian M.

2017-06-08

One-dimensional glide of loops during ion irradiation at 773 K in a series of Ni-containing concentrated solid solution alloys has been observed directly during experiments conducted inside a transmission electron microscope. It was found that the frequency of the oscillatory motion of the loop, the loop glide velocity as well as the loop jump distance were dependent on the composition of the alloy and the size of the loop. Loop glide was most common for small loops and occurred more frequently in the less complex alloys, being highest in Ni, then NiCo, NiFe and NiCoFeCr. As a result, no measurablemore » loop glide occurred in the NiCoCr, NiCoFeCrMn and NiCoFeCrPd alloys.« less

Modified ferritic iron alloys with improved high-temperature mechanical properties and oxidation resistance

NASA Technical Reports Server (NTRS)

Oldrieve, R. E.

1975-01-01

An alloy modification program was conducted in which the compositions of two existing Fe-Cr-Al alloys (Armco 18SR and GE-1541) were changed to achieve either improved high-temperature strength or improved fabricability. Only modifications of Armco 18SR were successful in achieving increased strength without loss of fabricability or oxidation resistance. The best modified alloy, designated NASA-18T, had twice the rupture strength of Armco 18SR at 800 and 1000 C. The NASA-18T alloy also had better oxidation resistance than Armco 18SR and comparable fabricability. The nominal composition of NASA-18T is Fe-18Cr-2Al-1Si-1.25Ta. All attempted modifications of the GE-1541 alloy were unsuccessful in terms of achieving better fabricability without sacrificing high-temperature strength and oxidation resistance.

Study on Composition, Microstructure and Wear Behavior of Fe-B-C Wear-Resistant Surfacing Alloys

NASA Astrophysics Data System (ADS)

Zhuang, Minghui; Li, Muqin; Wang, Jun; Ma, Zhen; Yuan, Shidan

2017-12-01

Fe-B-C alloy layers with various microstructures were welded on Q235 steel plates using welding powders/H08Mn2Si and welding wires composite surfacing technology. The relationship existing between the chemical composition, microstructure and wear resistance of the surfacing alloy layers was investigated by scanning electron microscopy, x-ray diffraction, electron backscatter diffraction and wear tests. The results demonstrated that the volume fractions and morphologies of the microstructures in the surfacing alloy layers could be controlled by adjusting the boron and carbon contents in the welding powders, which could further regulate the wear resistance of the surfacing alloy layers. The typical microstructures of the Fe-B-C surfacing alloy layers included dendritic Fe, rod-like Fe2B, fishbone-like Fe2B and daisy-like Fe3(C, B). The wear resistance of the alloy layers with various morphologies differed. The wear resistance order of the different microstructures was: rod-like Fe2B > fishbone-like Fe2B > daisy-like Fe3(C, B) > dendritic Fe. A large number of rod-like Fe2B with high microhardness could be obtained at the boron content of 5.70 5.90 wt.% and the carbon content of 0.50 0.60wt.%. The highest wear resistance of the Fe-B-C alloy layers reached the value of 24.1 g-1, which demonstrates the main microscopic cutting wear mechanism of the Fe-B-C alloy layers.

The dissimilar brazing of Kovar alloy to SiCp/Al composites using silver-based filler metal foil

NASA Astrophysics Data System (ADS)

Wang, Peng; Xu, Dongxia; Zhai, Yahong; Niu, Jitai

2017-09-01

Aluminum metal matrix composites with high SiC content (60 vol.% SiCp/Al MMCs) were surface metallized with a Ni-P alloy coating, and vacuum brazing between the composites and Kovar alloy were performed using rapidly cooled Ag-22.0Cu-15.9In-10.86Sn-1.84Ti (wt%) foil. The effects of Ni-P alloy coating and brazing parameters on the joint microstructures and properties were researched by SEM, EDS, and single lap shear test, respectively. Results show that Ag-Al intermetallic strips were formed in the 6063Al matrix and filler metal layer because of diffusion, and they were arranged regularly and accumulated gradually as the brazing temperature was increased ( T/°C = 550-600) or the soaking time was prolonged ( t/min = 10-50). However, excessive strips would destroy the uniformity of seams and lead to a reduced bonding strength (at most 70 MPa). Using a Ni-P alloy coating, void free joints without those strips were obtained at 560 °C after 20 min soaking time, and a higher shear strength of 90 MPa was achieved. The appropriate interface reaction ( 2 μm transition layer) that occurred along the Ni-P alloy coating/filler metal/Kovar alloy interfaces resulted in better metallurgical bonding. In this research, the developed Ag-based filler metal was suitable for brazing the dissimilar materials of Ni-P alloy-coated SiCp/Al MMCs and Kovar alloy, and capable welding parameters were also broadened.

Preparation of Copper and Chromium Alloyed Layers on Pure Titanium by Plasma Surface Alloying Technology

NASA Astrophysics Data System (ADS)

He, Xiaojing; Li, Meng; Wang, Huizhen; Zhang, Xiangyu; Tang, Bin

2015-05-01

Cu-Cr alloyed layers with different Cu and Cr contents on pure titanium were obtained by means of plasma surface alloying technology. The microstructure, chemical composition and phase composition of Cu-Cr alloyed layers were analyzed by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS) and X-ray diffraction (XRD), respectively. The experimental results demonstrate that the alloyed layers are bonded strongly to pure titanium substrate and consist of unbound Ti, CuTi, Cu3Ti, CuTi3 and Cr2Ti. The thickness of Cu5Cr5 and Cu7Cr3 alloyed layer are about 18 μm and 28 μm, respectively. The antibacterial properties against gram-negative Escherichia coli (E.coli, ATCC10536) and gram-positive Staphylococcus aureus (S. aureus, ATCC6538) of untreated pure titanium and Cu-Cr alloyed specimen were investigated by live/dead fluorescence staining method. The study shows that Cu-Cr alloyed layers exhibit excellent antibacterial activities against both E.coli and S.aureus within 24 h, which may be attributed to the formation of Cu-containing phases.

Effect of Cooling Rate on Microstructure of Two Kinds of High Nb Containing Tial Alloys

NASA Astrophysics Data System (ADS)

Chai, L. H.; Feng, Z. Y.; Xiang, Z. L.; Cui, Y. S.; Zhou, F.; Chen, Z. Y.

2017-09-01

In this paper, high Nb-TiAl alloys with Cr and W additions were prepared by Vacuum induction melting method, and then were heat treated under three different cooling rates of slow cooling, furnace cooling and air cooling. The phase composition of the alloy was analyzed by X ray diffraction, and the microstructure of the alloy was observed by optical microscope (OM), scanning electron microscope (SEM) and energy dispersive analyzer. The results show that the microstructure of Ti45Al8Nb0.2Cr and Ti45Al8Nb0.2W are fully lamellar structure with the main phase composition of α+γ after 3 different heat treatment conditions. The grain size of the two alloys decreases with decreasing of cooling rate, and the grain size of the alloyed with Cr alloy is smaller than that of the alloyed with W alloy. Most of the original massive β phase at grain boundaries and lamellar interfaces dissolved after heat treatment, and the transformation of β phase is easier for Ti45Al8Nb0.2Cr.

Mechanical behaviour of pressed and sintered titanium alloys obtained from master alloy addition powders.

PubMed

Bolzoni, L; Esteban, P G; Ruiz-Navas, E M; Gordo, E

2012-11-01

The fabrication of the workhorse Ti-6Al-4V alloy and of the Ti-3Al-2.5V alloy was studied considering the master alloy addition variant of the blending elemental approach conventionally used for titanium powder metallurgy. The powders were characterised by means thermal analysis and X-ray diffraction and shaped by means of uniaxial pressing. The microstructural evolution with the sintering temperature (900-1400 °C) was evaluated by SEM and EDS was used to study the composition. XRD patterns as well as the density by Archimedes method were also obtained. The results indicate that master alloy addition is a suitable way to fabricate well developed titanium alloy but also to produce alloy with the desired composition, not available commercially. Density of 4.3 g/cm³ can be obtained where a temperature higher than 1200 °C is needed for the complete diffusion of the alloying elements. Flexural properties comparable to those specified for wrought Ti-6Al-4V medical devices are, generally, obtained. Copyright © 2012 Elsevier Ltd. All rights reserved.

High Strength Discontinuously Reinforced Aluminum For Rocket Applications

NASA Technical Reports Server (NTRS)

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

2003-01-01

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

Tribological Behavior of Al-Cr Coating Obtained by Dgpsm and IIP Composite Technology

NASA Astrophysics Data System (ADS)

Luo, Xixi; Yao, Zhengjun; Zhang, Pingze; Zhou, Keyin; Chen, Yu; Tao, Xuewei

An Al-Cr composite alloyed layer composed of an Al enriched layer, a Cr enriched layer and a transition layer from the surface to the bulk along the cross-section was deposited on a 45# steel substrate by composite technology, where Cr was deposited using double glow plasma surface metallurgy (DGPSM), and Al was then implanted by ion implantation (IIP) to achieve higher micro-hardness and excellent abrasive resistance. The composite alloyed layer is approximately 5μm, and as metallurgical adherence to the substrate. The phases are Al8Cr5, Fe2AlCr, Cr23C6, Cr (Al) and Fe (Cr, Al) solid solution. The wear resistance tests were performed under various rotational speed (i.e. 280, 560 and 840r/min) with silicon nitride balls as the counterface material at ambient temperature. The Al-Cr composite alloyed layer exhibits excellent wear resistance when the speed is 280r/min with a friction coefficient as low as 0.3, which is attributed to Al8Cr5 in the Al implanted layer that withstands abrasive wear. Better wear resistance (friction coefficient: 0.254) at 560r/min is resulted from the formation of a high micro-hardness zone, and an oxidation layer with lubrication capacity. In addition, the composite alloyed layer suffers severe oxidative wear and adhesive wear at 840r/min due to the increment of the frictional heating. When compared to the 45# steel substrate, the enhanced wear resistance of the Al-Cr composite alloyed layer demonstrates the viable method developed in this work.

Synthesis and Characterization of Hydroxyapatite-Collagen-Chitosan (HA/Col/Chi) Composite Coated on Ti6Al4V

NASA Astrophysics Data System (ADS)

Charlena; Bikharudin, Ahmad; Wahyudi, Setyanto Tri

2018-01-01

HA-collagen-chitosan (HA/col/chi) composite is developed to increase bioactivity adhesiveness between the metal and the material composite and to improve corrosion resistance. The Ti6Al4V alloy was coated by soaking in HA/col/chi composite at room temperature and then allowed to stand for 5, 6, and 7 days. Diffraction pattern analysis of the coated Ti6Al4V alloy showed that the dominant phase were HA and Ti6Al4V alloy. Corrosion resistance test in media by using 0.9% NaCl showed the corrosion rate at the level of 0.3567 mpy, which was better than that of the uncoated Ti6Al4V alloy (0.4152 mpy). In vitro cytocompatibility assay on endothelial cell of calf pulmonary artery endothelium (CPAE) (ATCC-CCL 209) showed there was no toxicity in the cell culture with the percent inhibition of 33.33% after 72 hours of incubation.

Graphite fiber/copper composites prepared by spontaneous infiltration

NASA Astrophysics Data System (ADS)

Wang, Hongbao; Tao, Zechao; Li, Xiangfen; Yan, Xi; Liu, Zhanjun; Guo, Quangui

2018-05-01

The major bottleneck in developing graphite fiber reinforced copper (GF/Cu) composites is the poor wettability of Cu/graphite system. Alloying element of chromium (Cr) is introduced to improve the wettability of liquid copper on graphite. Sessile drop method experiments illustrate that the contact angle of liquid Cu-Cr (1.0 wt.%) alloy on graphite substrate decreases to 43° at 1300 °C. The improvement of wettability is related to the formation of chromium carbide layer at interface zone. Based on the wetting experiment, a spontaneous infiltration method for preparing GF/Cu composites is proposed. Unidirectional GF preforms are infiltrated by Cu-Cr alloys without external pressure in a tubular furnace. Results reveal that the GF preform can be fully infiltrated by Cu-Cr alloy (8 wt.%) spontaneously when fiber volume fraction is 40%. The coefficient of thermal expansion (CTE) of GF/Cu-Cr (8.0 wt.%) composites is 4.68 × 10-6/K along the longitudinal direction.

Solvothermal synthesis of platinum alloy nanoparticles for oxygen reduction electrocatalysis.

PubMed

Carpenter, Michael K; Moylan, Thomas E; Kukreja, Ratandeep Singh; Atwan, Mohammed H; Tessema, Misle M

2012-05-23

Platinum alloy nanoparticles show great promise as electrocatalysts for the oxygen reduction reaction (ORR) in fuel cell cathodes. We report here on the use of N,N-dimethylformamide (DMF) as both solvent and reductant in the solvothermal synthesis of Pt alloy nanoparticles (NPs), with a particular focus on Pt-Ni alloys. Well-faceted alloy nanocrystals were generated with this method, including predominantly cubic and cuboctahedral nanocrystals of Pt(3)Ni, and octahedral and truncated octahedral nanocrystals of PtNi. X-ray diffraction (XRD) and high angle annular dark field scanning transmission electron microscopy (HAADF-STEM), coupled with energy dispersive spectroscopy (EDS), were used to characterize crystallite morphology and composition. ORR activities of the alloy nanoparticles were measured with a rotating disk electrode (RDE) technique. While some Pt(3)Ni alloy nanoparticle catalysts showed specific activities greater than 1000 μA/cm(2)(Pt), alloy catalysts prepared with a nominal composition of PtNi displayed activities close to 3000 μA/cm(2)(Pt), or almost 15 times that of a state-of-the-art Pt/carbon catalyst. XRD and EDS confirmed the presence of two NP compositions in this catalyst. HAADF-STEM examination of the PtNi nanoparticle catalyst after RDE testing revealed the development of hollows in a number of the nanoparticles due to nickel dissolution. Continued voltage cycling caused further nickel dissolution and void formation, but significant activity remained even after 20,000 cycles.

Diffraction, microstructure and thermal stability analysis in a double phase nanocrystalline Al20Mg20Ni20Cr20Ti20 high entropy alloy

NASA Astrophysics Data System (ADS)

Rameshbabu, A. M.; Parameswaran, P.; Vijayan, V.; Panneer, R.

2017-12-01

An effort has been made to develop a new composition of AlMgNiCrTi high entropy alloy (HEA) with a distinct properties includes squat density, intense strength and hardness, superior corrosion resistance, better oxidation resistance, high temperature resistance, fatigue load and crack resistance to congregate the necessity of aircraft applications. The equivalent atomic percentage for the above defined composition is established using analytical correlation for molar and atom renovation by trial and error method. The alloy is synthesized by powder metallurgy technique through mechanical alloying. Succeeding to mechanical alloying it is elucidated that the metal powder is primarily composed of single BCC solid solution with crystallite magnitude <10 nm. It is also observed that the alloy is thermally stable at prominent temperature about 800°C as it is retained its nanostructure which was revealed using differential scanning caloriemetry (DSC). This alloy powder was consolidated and sintered using spark plasma sintering at 800°C with 50 Mpa pressure to a density of 98.83%. Subsequent to sintering, Titanium carbide FCC phase evolved along with the BCC phase. The alloying behavior and phase transformation were studied using X-ray diffraction (XRD) and scanning electron microscope (SEM). The homogeneity of the composition is confirmed by energy dispersive spectroscopy (EDS). The hardness of the alloy is found to be 710±20 HV. The evolutions of the phases and hardness imply that this alloy is apposite for both high strength and high temperature applications.

Statistical correction of atom probe tomography data of semiconductor alloys combined with optical spectroscopy: The case of Al{sub 0.25}Ga{sub 0.75}N

DOE Office of Scientific and Technical Information (OSTI.GOV)

Rigutti, L., E-mail: lorenzo.rigutti@univ-rouen.fr; Mancini, L.; Hernández-Maldonado, D.

2016-03-14

The ternary semiconductor alloy Al{sub 0.25}Ga{sub 0.75}N has been analyzed by means of correlated photoluminescence spectroscopy and atom probe tomography (APT). We find that the composition measured by APT is strongly dependent on the surface electric field, leading to erroneous measurements of the alloy composition at high field, due to the different evaporation behaviors of Al and Ga atoms. After showing how a biased measurement of the alloy content leads to inaccurate predictions on the optical properties of the material, we develop a correction procedure which yields consistent transition and localization energies for the alloy photoluminescence.

Mechanical properties of as-cast and heat-treated ZA-27 alloy/short glass fiber composites

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharma, S.C.; Girish, B.M.; Satish, B.M.

1998-02-01

This paper reports on the mechanical properties of as-cast and heat-treated ZA-27 alloy composites reinforced with glass fibers from 1 to 5 wt%. The composites were fabricated using the Compocasting method, in which short glass fibers were introduced into the vortex created in the molten alloy through an impeller rotated at 500 rpm. The molten mass was thoroughly stirred and poured into permanent molds and squeezed under pressure. The specimens were heat treated at 320 C for 1, 2, 3, and 4 h. The tests on the as-cast composites revealed that as the glass content in the composites was increased,more » the ultimate tensile strength (UTS), compressive strength, and hardness of the composite increased, while the ductility and impact strength were decreased. Heat treatment was found to improve significantly the ductility, compressive strength, and impact strength, while the hardness and UTS were reduced. This paper discusses the behavior of these composites.« less

Microstructures and Properties of 40Cu/Ag(Invar) Composites Fabricated by Powder Metallurgy and Subsequent Thermo-Mechanical Treatment

NASA Astrophysics Data System (ADS)

Zhang, Xin; Huang, Yingqiu; Liu, Xiangyu; Yang, Lei; Shi, Changdong; Wu, Yucheng; Tang, Wenming

2018-03-01

Composites of 40Cu/Ag(Invar) were prepared via pressureless sintering and subsequent thermo-mechanical treatment from raw materials of electroless Ag-plated Invar alloy powder and electrolytic Cu powder. Microstructures and properties of the prepared composites were studied to evaluate the effect of the Ag layer on blocking Cu/Invar interfacial diffusion in the composites. The electroless-plated Ag layer was dense, uniform, continuous, and bonded tightly with the Invar alloy substrate. During sintering of the composites, the Ag layer effectively prevented Cu/Invar interfacial diffusion. During cold-rolling, the Ag layer was deformed uniformly with the Invar alloy particles. The composites exhibited bi-continuous network structure and considerably improved properties. After sintering at 775 °C and subsequent thermo-mechanical treatment, the 40Cu/Ag(Invar) composites showed satisfactory comprehensive properties: relative density of 99.0 pct, hardness of HV 253, thermal conductivity of 55.7 W/(m K), and coefficient of thermal expansion of 11.2 × 10-6/K.

Micromechanics of composites with shape memory alloy fibers in uniform thermal fields

NASA Technical Reports Server (NTRS)

Birman, Victor; Saravanos, Dimitris A.; Hopkins, Dale A.

1995-01-01

Analytical procedures are developed for a composite system consisting of shape memory alloy fibers within an elastic matrix subject to uniform temperature fluctuations. Micromechanics for the calculation of the equivalent properties of the composite are presented by extending the multi-cell model to incorporate shape memory alloy fibers. A three phase concentric cylinder model is developed for the analysis of local stresses which includes the fiber, the matrix, and the surrounding homogenized composite. The solution addresses the complexities induced by the nonlinear dependence of the in-situ martensite fraction of the fibers to the local stresses and temperature, and the local stresses developed from interactions between the fibers and matrix during the martensitic and reverse phase transformations. Results are presented for a nitinol/epoxy composite. The applications illustrate the response of the composite in isothermal longitudinal loading and unloading, and in temperature induced actuation. The local stresses developed in the composite under various stages of the martensitic and reverse phase transformation are also shown.

Shape memory effect in nanosized Ti2NiCu alloy-based composites

NASA Astrophysics Data System (ADS)

Irzhak, A. V.; Lega, P. V.; Zhikharev, A. M.; Koledov, V. V.; Orlov, A. P.; Kuchin, D. S.; Tabachkova, N. Yu.; Dikan, V. A.; Shelyakov, A. V.; Beresin, M. Yu.; Pushin, V. G.; von Gratowski, S. V.; Pokrovskiy, V. Ya.; Zybtsev, S. G.; Shavrov, V. G.

2017-01-01

The shape memory effect (SME) in alloys with a thermoelastic martensite transition opens unique opportunities for the creation of miniature mechanical devices. The SME has been studied in layered composite microstructures consisting of a Ti2NiCu alloy and platinum. It occurs upon a decrease in the active layer thickness at least to 80 nm. Some physical and technological restrictions on the minimum size of a material with SME are discussed.

Impact of Alloy Fluctuations on Radiative and Auger Recombination in InGaN Quantum Wells

NASA Astrophysics Data System (ADS)

Jones, Christina; Teng, Chu-Hsiang; Yan, Qimin; Ku, Pei-Cheng; Kioupakis, Emmanouil

Light-emitting diodes (LEDs) based on indium gallium nitride (InGaN) are important for efficient solid-state lighting (2014 Nobel Prize in Physics). Despite its many successes, InGaN suffers from issues that reduce the efficiency of devices at high power, such as the green gap and efficiency droop. The origin of the droop has been attributed to Auger recombination, mediated by carrier scattering due to phonons and alloy disorder. Additionally, InGaN exhibits atomic-scale composition fluctuations that localize carriers and may affect the efficiency. In this work, we study the effect of local composition fluctuations on the radiative recombination rate, Auger recombination rate, and efficiency of InGaN/GaN quantum wells. We apply k.p calculations to simulate band edges and wave functions of quantum wells with fluctuating alloy distributions based on atom probe tomography data, and we evaluate double and triple overlaps of electron and hole wave functions. We compare results for quantum wells with fluctuating alloy distributions to those with uniform alloy compositions and to published work. Our results demonstrate that alloy-composition fluctuations aggravate the efficiency-droop and green-gap problems and further reduce LED efficiency at high power. We acknowledge the NSF CAREER award DMR-1254314, the NSF Graduate Research Fellowship Program DGE-1256260, and the DOE NERSC facility (DE-AC02-05CH11231).

Effects of Plasma ZrN Metallurgy and Shot Peening Duplex Treatment on Fretting Wear and Fretting Fatigue Behavior of Ti6Al4V Alloy.

PubMed

Tang, Jingang; Liu, Daoxin; Zhang, Xiaohua; Du, Dongxing; Yu, Shouming

2016-03-23

A metallurgical zirconium nitride (ZrN) layer was fabricated using glow metallurgy using nitriding with zirconiuming prior treatment of the Ti6Al4V alloy. The microstructure, composition and microhardness of the corresponding layer were studied. The influence of this treatment on fretting wear (FW) and fretting fatigue (FF) behavior of the Ti6Al4V alloy was studied. The composite layer consisted of an 8-μm-thick ZrN compound layer and a 50-μm-thick nitrogen-rich Zr-Ti solid solution layer. The surface microhardness of the composite layer is 1775 HK 0.1 . A gradient in cross-sectional microhardness distribution exists in the layer. The plasma ZrN metallurgical layer improves the FW resistance of the Ti6Al4V alloy, but reduces the base FF resistance. This occurs because the improvement in surface hardness results in lowering of the toughness and increasing in the notch sensitivity. Compared with shot peening treatment, plasma ZrN metallurgy and shot peening composite treatment improves the FW resistance and enhances the FF resistance of the Ti6Al4V alloy. This is attributed to the introduction of a compressive stress field. The combination of toughness, strength, FW resistance and fatigue resistance enhance the FF resistance for titanium alloy.

Effects of Plasma ZrN Metallurgy and Shot Peening Duplex Treatment on Fretting Wear and Fretting Fatigue Behavior of Ti6Al4V Alloy

PubMed Central

Tang, Jingang; Liu, Daoxin; Zhang, Xiaohua; Du, Dongxing; Yu, Shouming

2016-01-01

A metallurgical zirconium nitride (ZrN) layer was fabricated using glow metallurgy using nitriding with zirconiuming prior treatment of the Ti6Al4V alloy. The microstructure, composition and microhardness of the corresponding layer were studied. The influence of this treatment on fretting wear (FW) and fretting fatigue (FF) behavior of the Ti6Al4V alloy was studied. The composite layer consisted of an 8-μm-thick ZrN compound layer and a 50-μm-thick nitrogen-rich Zr–Ti solid solution layer. The surface microhardness of the composite layer is 1775 HK0.1. A gradient in cross-sectional microhardness distribution exists in the layer. The plasma ZrN metallurgical layer improves the FW resistance of the Ti6Al4V alloy, but reduces the base FF resistance. This occurs because the improvement in surface hardness results in lowering of the toughness and increasing in the notch sensitivity. Compared with shot peening treatment, plasma ZrN metallurgy and shot peening composite treatment improves the FW resistance and enhances the FF resistance of the Ti6Al4V alloy. This is attributed to the introduction of a compressive stress field. The combination of toughness, strength, FW resistance and fatigue resistance enhance the FF resistance for titanium alloy. PMID:28773345

Incommensurateness in nanotwinning models of modulated martensites

NASA Astrophysics Data System (ADS)

Benešová, Barbora; Frost, Miroslav; Kampschulte, Malte; Melcher, Christof; Sedlák, Petr; Seiner, Hanuš

2015-11-01

We study the formation of modulated martensites in ferromagnetic shape memory alloys by a mathematical model originating from the nanotwinning concept. The results show that the incommensurateness, systematically observed in experiments for the modulated phases, may be understood as a precursor effect of the intermartensitic transitions, and its appearance does not contradict the nanotwinning concept itself. The model sufficiently explains the different levels of incommensurateness reported from different experimental observations for the 14-layered and 10-layered martensites of the Ni-Mn-Ga alloy and outlines the mechanism of formation of faults in the stacking sequences of these materials.

Small-scale characterisation of irradiated nuclear materials: Part I – Microstructure

DOE PAGES

Edmondson, P. D.; London, A.; Xu, A.; ...

2014-11-26

The behaviour of nanometre-scale precipitates in oxide dispersion strengthened (ODS) ferritic alloys and tungsten-rhenium alloys for nuclear applications has been examined by atom probe tomography (APT). Low Re content tungsten alloys showed no evidence of Re clustering following self-ion irradiation whereas the 25 at.% Re resulted in cluster formation. The size and composition of clusters varied depending on the material form during irradiation (pre-sharpened needle or bulk). Lastly, these results highlight the care that must be taken in interpreting data from ion irradiated pre-sharpened needles due to the presence of free surfaces. Self-ion irradiation of the ODS ferritic alloy resultedmore » in a change in the composition of the clusters, indicating a transition from a near-stoichiometric Y 2Ti 2O 7 composition towards a Ti 2YO 5.« less

A-15 Superconducting composite wires and a method for making

DOEpatents

Suenaga, Masaki; Klamut, Carl J.; Luhman, Thomas S.

1984-01-01

A method for fabricating superconducting wires wherein a billet of copper containing filaments of niobium or vanadium is rolled to form a strip which is wrapped about a tin-alloy core to form a composite. The alloy is a tin-copper alloy for niobium filaments and a gallium-copper alloy for vanadium filaments. The composite is then drawn down to a desired wire size and heat treated. During the heat treatment process, the tin in the bronze reacts with the niobium to form the superconductor niobium tin. In the case where vanadium is used, the gallium in the gallium bronze reacts with the vanadium to form the superconductor vanadium gallium. This new process eliminates the costly annealing steps, external tin plating and drilling of bronze ingots required in a number of prior art processes.

Wrapping process for fabrication of A-15 superconducting composite wires

DOEpatents

Suenaga, M.; Klamut, C.J.; Luhman, T.S.

1980-08-15

A method for fabricating superconducting wires wherein a billet of copper containing filaments of niobium or vanadium is rolled to form a strip which is wrapped about a tin-alloy core to form a composite. The alloy is a tin-copper alloy for niobium filaments and a gallium-copper alloy for vanadium filaments. The composite is then drawn down to a desired wire size and heat treated. During the heat treatment process, the tin in the bronze reacts with the niobium to form the superconductor niobium tin. In the case where vanadium is used, the gallium in the gallium bronze reacts with the vanadium to form the superconductor vanadium gallium. This new process eliminates the costly annealing steps, external tin plating and drilling of bronze ingots required in a number of prior art processes.

Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

DOE PAGES

Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; ...

2015-07-14

The Fe Cr Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe Cr Al alloys has not been fully established. In this study, a series of Fe Cr Al alloys with 10 18 wt % Cr and 2.9 4.9 wt % Al were neutron irradiated at 382 C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition.more » Dislocation loops with Burgers vector of a/2 111 and a 100 were detected and quantified. Results indicate precipitation of Cr-rich is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. Furthermore, a structure property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α' precipitates at sufficiently high chromium contents after irradiation.« less

Low-melting elemental metal or fusible alloy encapsulated polymerization initiator for delayed initiation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hermes, Robert E.

2017-08-15

An encapsulated composition for polymerization includes an initiator composition for initiating a polymerization reaction, and a capsule prepared from an elemental metal or fusible alloy having a melting temperature from about 20.degree. C. to about 200.degree. C. A fluid for polymerization includes the encapsulated composition and a monomer. When the capsule melts or breaks open, the initiator is released.

Molybdenum disilicide alloy matrix composite

DOEpatents

Petrovic, J.J.; Honnell, R.E.; Gibbs, W.S.

1991-12-03

Compositions of matter consisting of matrix materials having silicon carbide dispersed throughout them and methods of making the compositions are disclosed. A matrix material is an alloy of an intermetallic compound, molybdenum disilicide, and at least one secondary component which is a refractory silicide. The silicon carbide dispersant may be in the form of VLS whiskers, VS whiskers, or submicron powder or a mixture of these forms. 3 figures.

Method of making composition suitable for use as inert electrode having good electrical conductivity and mechanical properties

DOEpatents

Ray, S.P.; Rapp, R.A.

1986-04-22

An improved inert electrode composition is suitable for use as an inert electrode in the production of metals such as aluminum by the electrolytic reduction of metal oxide or metal salt dissolved in a molten salt bath. The composition comprises one or more metals or metal alloys and metal compounds which may include oxides of the metals comprising the alloy. The alloy and metal compounds are interwoven in a network which provides improved electrical conductivity and mechanical strength while preserving the level of chemical inertness necessary for such an electrode to function satisfactorily. 8 figs.

Characterizing Semiconductor Alloys for Infrared Sensors

NASA Technical Reports Server (NTRS)

Lehoczky, B. S. L.; Szofran, F. R.; Martin, B. G.

1986-01-01

Report presents results of continuing program aimed at characterizing mercury/cadmium/tellurium alloys and eventually developing improved methods of preparing alloys for use as infrared sensors. Work covered by report includes series of differential thermal analysis (DTA) measurements of alloy compositions with x varied from 9 to 1 in 0.1 increments.

Bombardment-induced segregation and redistribution

NASA Astrophysics Data System (ADS)

Lam, N. Q.; Wiedersich, H.

During ion bombardment, a number of processes can alter the compositional distribution and microstructure in near-surface regions of alloys. The relative importance of each process depends principally on the target composition, temperature, and ion characteristics. In addition to displacement mixing leading to a randomization of atomic locations, and preferential loss of alloying elements by sputtering, which are dominant at relatively low temperatures, several thermally-activated processes, including radiation-enhanced diffusion, radiation-induced segregation and Gibbsian adsorption, also play important roles. At elevated temperatures, nonequilibrium point defects induced by ion impacts become mobile and tend to anneal out by recombination and diffusion to extended sinks, such as dislocations, grain boundaries and free surfaces. The high defect concentrations, far exceeding the thermodynamic equilibrium values, can enhance diffusion-controlled processes, while persistent defect fluxes, originating from the spatial non-uniformity in defect production and annihilation, give rise to local redistribution of alloy constituents because of radiation-induced segregation. Moreover, when the alloy is maintained at high temperature, Gibbsian adsorption, driven by the reduction in free energy of the system, occurs even without irradiation; it involves a compositional perturbation in a few atom layers near the alloy surface. The combination of these processes leads to the complex development of a compositionally-modified layer in the subsurface region. Considerable progress has been made recently in identifying and understanding the relative contributions from the individual processes under various irradiation conditions. In the present paper, selected examples of these different phenomena and their synergistic effects on the evolution of the near-surface compositions of alloys during sputtering and ion implantation at elevated temperatures are discussed.

Ultralight monolithic photovoltaic modules of amorphous silicon alloys

NASA Astrophysics Data System (ADS)

Hanak, J. J.

A process has been developed for fabrication of roll-up, monolithic, photovoltaic (PV) modules made of amorphous silicon (a-Si) alloys. They consist of tandem-junction solar cells deposited by a continuous, roll-to-roll process onto thin, foil substrates of bare metal, high temperature resin, or metal coated with insulators. They have the following characteristics: size, up to 71 cm x 30.5 cm; total thickness, 8 to 50 microns, power-to-weight and power-to-volume ratios at AM1, 2.4 kW/kg and 6.5 MW/cu m, respectively. Cells of a-Si alloys are up to 100 times as tolerant to irradiation with 1 MeV protons than crystalline cells and the damage is easily annealable. The modules have high power density and stability, they are portable, stowable, deployable, retractable, tolerant to radiation and meteorite or projectile impact, and attractive for terrestrial and aerospace applications.

Ultralight amorphous silicon alloy photovoltaic modules for space and terrestrial applications

NASA Astrophysics Data System (ADS)

Hanak, J. J.; Fulton, C.; Myatt, A.; Nath, P.; Woodyard, J. R.

This paper gives a review and an update on recently developed ultralight photovoltaic modules based on amorphous silicon (a-Si) alloys. They consist of tandem-junction solar cells deposited by a continuous, roll-to-roll process onto thin, foil substrates of bare metal, high temperature resin or metal coated with insulators. They have the following features: size, up to 71 cm x 30.5 cm; total thickness, 8 to 50 microns; power-to-weight at AM1, 2.4 kW/kg; and power-to-volume ratio 6.5 MW/cu m. Cells of a-Si alloys are over 50 times more tolerant to irradiation with 1 MeV and with 200 keV protons than crystalline cells and the damage is easily annealable. The modules have high power density and stability, they are portable, stowable, deployable, retractable, tolerant to radiation and meteorite or projectile impact and attractive for terrestrial and aerospace applications.

Mechanical properties of neutron-irradiated model and commercial FeCrAl alloys

NASA Astrophysics Data System (ADS)

Field, Kevin G.; Briggs, Samuel A.; Sridharan, Kumar; Howard, Richard H.; Yamamoto, Yukinori

2017-06-01

The development and understanding of the mechanical properties of neutron-irradiated FeCrAl alloys is increasingly a critical need as these alloys continue to become more mature for nuclear reactor applications. This study focuses on the mechanical properties of model FeCrAl alloys and of a commercial FeCrAl alloy neutron-irradiated to up to 13.8 displacements per atom (dpa) at irradiation temperatures between 320 and 382 °C. Tensile tests were completed at room temperature and at 320 °C, and a subset of fractured tensile specimens was examined by scanning electron microscopy. Results showed typical radiation hardening and embrittlement indicative of high chromium ferritic alloys with strong chromium composition dependencies at lower doses. At and above 7.0 dpa, the mechanical properties saturated for both the commercial and model FeCrAl alloys, although brittle cleavage fracture was observed at the highest dose in the model FeCrAl alloy with the highest chromium content (18 wt %). The results suggest the composition and microstructure of FeCrAl alloys plays a critical role in the mechanical response of FeCrAl alloys irradiated near temperatures relevant to light water reactors.

Corrosion-induced release of the main alloying constituents of manganese-chromium stainless steels in different media.

PubMed

Herting, Gunilla; Wallinder, Inger Odnevall; Leygraf, Christofer

2008-09-01

The main focus of this paper is the assessment of release rates of chromium, nickel, iron and manganese from manganese-chromium stainless steel grades of low nickel content. The manganese content varied between 9.7 and 1.5 wt% and the corresponding nickel content between 1 and 5 wt%. All grades were exposed to artificial rain and two were immersed in a synthetic body fluid of similar pH but of different composition and exposure conditions. Surface compositional studies were performed using X-ray photoelectron spectroscopy (XPS) in parallel to correlate the metal release process with changes in surface oxide properties. All grades, independent of media, revealed a time-dependent metal release process with a preferential low release of iron and manganese compared to nickel and chromium while the chromium content of the surface oxide increased slightly. Manganese was detected in the surface oxide of all grades, except the grade of the lowest manganese bulk content. No nickel was observed in the outermost surface oxide. Stainless steel grades of the lowest chromium content (approximately 16 wt%) and highest manganese content (approximately 7-9 wt%), released the highest quantity of alloy constituents in total, and vice versa. No correlation was observed between the release rate of manganese and the alloy composition. Released main alloy constituents were neither proportional to the bulk alloy composition nor to the surface oxide composition.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Okumus, S. Cem, E-mail: cokumus@sakarya.edu.tr; Karslioglu, Ramazan, E-mail: cokumus@sakarya.edu.tr; Akbulut, Hatem, E-mail: cokumus@sakarya.edu.tr

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

Tribological Behavior of Aluminum Alloy AlSi10Mg-TiB2 Composites Produced by Direct Metal Laser Sintering (DMLS)

NASA Astrophysics Data System (ADS)

Lorusso, Massimo; Aversa, Alberta; Manfredi, Diego; Calignano, Flaviana; Ambrosio, Elisa Paola; Ugues, Daniele; Pavese, Matteo

2016-08-01

Direct metal laser sintering (DMLS) is an additive manufacturing technique for the production of parts with complex geometry and it is especially appropriate for structural applications in aircraft and automotive industries. Aluminum-based metal matrix composites (MMCs) are promising materials for these applications because they are lightweight, ductile, and have a good strength-to-weight ratio This paper presents an investigation of microstructure, hardness, and tribological properties of AlSi10Mg alloy and AlSi10Mg alloy/TiB2 composites prepared by DMLS. MMCs were realized with two different compositions: 10% wt. of microsize TiB2, 1% wt. of nanosize TiB2. Wear tests were performed using a pin-on-disk apparatus on the prepared samples. Performances of AlSi10Mg samples manufactured by DMLS were also compared with the results obtained on AlSi10Mg alloy samples made by casting. It was found that the composites displayed a lower coefficient of friction (COF), but in the case of microsize TiB2 reinforcement the wear rate was higher than with nanosize reinforcements and aluminum alloy without reinforcement. AlSi10Mg obtained by DMLS showed a higher COF than AlSi10Mg obtained by casting, but the wear rate was higher in the latter case.

Pre-irradiation testing of actively cooled Be-Cu divertor modules

DOE Office of Scientific and Technical Information (OSTI.GOV)

Linke, J.; Duwe, R.; Kuehnlein, W.

1995-09-01

A set of neutron irradiation tests is prepared on different plasma facing materials (PFM) candidates and miniaturized components for ITER. Beside beryllium the irradiation program which will be performed in the High Flux Reactor (HFR) in Petten, includes different carbon fiber composites (CFQ) and tungsten alloys. The target values for the neutron irradiation will be 0.5 dpa at temperatures of 350{degrees}C and 700{degrees}C, resp.. The post irradiation examination (PIE) will cover a wide range of mechanical tests; in addition the degradation of thermal conductivity will be investigated. To determine the high heat flux (HHF) performance of actively cooled divertor modules,more » electron beam tests which simulate the expected heat loads during the operation of ITER, are scheduled in the hot cell electron beam facility JUDITH. These tests on a selection of different actively cooled beryllium-copper and CFC-copper divertor modules are performed before and after neutron irradiation; the pre-irradiation testing is an essential part of the program to quantify the zero-fluence high heat flux performance and to detect defects in the modules, in particular in the brazed joints.« less

Kinetics and Equilibrium of Age-Induced Precipitation in Cu-4 At. Pct Ti Binary Alloy

NASA Astrophysics Data System (ADS)

Semboshi, Satoshi; Amano, Shintaro; Fu, Jie; Iwase, Akihiro; Takasugi, Takayuki

2017-03-01

Transformation kinetics and phase equilibrium of metastable and stable precipitates in age-hardenable Cu-4 at. pct Ti binary alloy have been investigated by monitoring the microstructural evolution during isothermal aging at temperatures between 693 K (420 °C) and 973 K (700 °C). The microstructure of the supersaturated solid solution evolves in four stages: compositional modulation due to spinodal decomposition, continuous precipitation of the needle-shaped metastable β'-Cu4Ti with a tetragonal structure, discontinuous precipitation of cellular components containing stable β-Cu4Ti lamellae with an orthorhombic structure, and eventually precipitation saturation at equilibrium. In specimens aged below 923 K (650 °C), the stable β-Cu4Ti phase is produced only due to the cellular reaction, whereas it can be also directly obtained from the intergranular needle-shaped β'-Cu4Ti precipitates in specimens aged at 973 K (700 °C). The precipitation kinetics and phase equilibrium observed for the specimens aged between 693 K (420 °C) and 973 K (700 °C) were characterized in accordance with a time-temperature-transformation (TTT) diagram and a Cu-Ti partial phase diagram, which were utilized to determine the alloy microstructure, strength, and electrical conductivity.

Search for promising compositions for developing new multiphase casting alloys based on Al-Cu-Mg matrix using thermodynamic calculations and mathematic simulation

NASA Astrophysics Data System (ADS)

Zolotorevskii, V. S.; Pozdnyakov, A. V.; Churyumov, A. Yu.

2012-11-01

A calculation-experimental study is carried out to improve the concept of searching for new alloying systems in order to develop new casting alloys using mathematical simulation methods in combination with thermodynamic calculations. The results show the high effectiveness of the applied methods. The real possibility of selecting the promising compositions with the required set of casting and mechanical properties is exemplified by alloys with thermally hardened Al-Cu and Al-Cu-Mg matrices, as well as poorly soluble additives that form eutectic components using mainly the calculation study methods and the minimum number of experiments.

Composition design for Laves phase-related body-centered cubic-V solid solution alloys with large hydrogen storage capacities.

PubMed

Wang, H B; Wang, Q; Dong, C; Yuan, L; Xu, F; Sun, L X

2008-03-19

This paper analyzes the characteristics of alloy compositions with large hydrogen storage capacities in Laves phase-related body-centered cubic (bcc) solid solution alloy systems using the cluster line approach. Since a dense-packed icosahedral cluster A(6)B(7) characterizes the local structure of AB(2) Laves phases, in an A-B-C ternary system, such as Ti-Cr (Mn, Fe)-V, where A-B forms AB(2) Laves phases while A-C and B-C tend to form solid solutions, a cluster line A(6)B(7)-C is constructed by linking A(6)B(7) to C. The alloy compositions with large hydrogen storage capacities are generally located near this line and are approximately expressed with the cluster-plus-glue-atom model. The cluster line alloys (Ti(6)Cr(7))(100-x)V(x) (x = 2.5-70 at.%) exhibit different structures and hence different hydrogen storage capacities with increasing V content. The alloys (Ti(6)Cr(7))(95)V(5) and Ti(30)Cr(40)V(30) with bcc solid solution structure satisfy the cluster-plus-glue-atom model.

Effect of gallium alloying on the structure, the phase composition, and the thermoelastic martensitic transformations in ternary Ni-Mn-Ga alloys

NASA Astrophysics Data System (ADS)

Belosludtseva, E. S.; Kuranova, N. N.; Marchenkova, E. B.; Popov, A. G.; Pushin, V. G.

2016-04-01

The effect of gallium alloying on the structure, the phase composition, and the properties of quasibinary Ni50Mn50- z Ga z (0 ⩽ z ⩽ 25 at %) alloys is studied over a wide temperature range. The influence of the alloy composition on the type of crystal structure in high-temperature austenite and martensite and the critical martensitic transformation temperatures is analyzed. A general phase diagram of the magnetic and structural transformations in the alloys is plotted. The temperature-concentration boundaries of the B2 and L21 superstructures in the austenite field, the tetragonal L10 (2 M) martensite, and the 10 M and 14 M martensite phases with complex multilayer crystal lattices are found. The predominant morphology of martensite is shown to be determined by the hierarchy of the packets of thin coherent lamellae of nano- and submicrocrystalline crystals with planar habit plane boundaries close to {011} B2. Martensite crystals are twinned along one of the 24 24{ {011} }{< {01bar 1} rangle _{B2}} "soft" twinning shear systems, which provides coherent accommodation of the martensitic transformation-induced elastic stresses.

Effect of in-situ formed Al3Ti particles on the microstructure and mechanical properties of 6061 Al alloy

NASA Astrophysics Data System (ADS)

Gupta, Rahul; Chaudhari, G. P.; Daniel, B. S. S.

2018-03-01

In this study, in situ Titanium-tri-aluminide (Al3Ti) particles reinforced Al 6061 alloy matrix composites were fabricated by the reaction of potassium hexafluorotitanate (K2TiF6) inorganic salt with molten Al 6061 alloy via liquid metallurgy route. The development of in-situ Al3Ti particles and their effects on the mechanical properties such as yield strength (YS), ductility, ultimate tensile strength (UTS) and hardness, and microstructure of Al 6061 alloy were studied. It was observed from the results that in-situ formed Al3Ti particles were blocky in morphology whose average size was around 2.6 ± 1.1 μm. Microstructure studies showed that grain size of Al matrix was reduced due to the nucleating effect of Al3Ti particles. It was observed from the mechanical properties analysis that when the volume fraction of Al3Ti particles was increased, the hardness, UTS and YS of the composites were also increased as compared to that of Al 6061 alloy. An improvement in ductility was observed with the dispersion of Al3Ti particles in base alloy which is contrary to many other composites.

Synthesis, Characterization and Cold Workability of Cast Copper-Magnesium-Tin Alloys

NASA Astrophysics Data System (ADS)

Bravo Bénard, Agustín Eduardo; Martínez Hernández, David; González Reyes, José Gonzalo; Ortiz Prado, Armando; Schouwenaars Franssens, Rafael

2014-02-01

The use of Mg as an alloying element in copper alloys has largely been overlooked in scientific literature and technological applications. Its supposed tribological compatibility with iron makes it an interesting option to replace Pb in tribological alloys. This work describes the casting process of high-quality thin slabs of Cu-Mg-Sn alloys with different compositions by means of conventional methods. The resulting phases were analyzed using X-ray diffraction, scanning electron microscopy, optical microscopy, and energy dispersive X-ray spectroscopy techniques. Typical dendritic α-Cu, eutectic Cu2Mg(Sn) and eutectoid non-equilibrium microstructures were found. Tensile tests and Vickers microhardness show the excellent hardening capability of Mg as compared to other copper alloys in the as-cast condition. For some of the slabs and compositions, cold rolling reductions of over 95 pct have been easily achieved. Other compositions and slabs have failed during the deformation process. Failure analysis after cold rolling reveals that one cause for brittleness is the presence of casting defects such as microshrinkage and inclusions, which can be eliminated. However, for high Mg contents, a high volume fraction of the intermetallic phase provides a contiguous path for crack propagation through the connected interdendritic regions.

Analysis of 2D Transport and Performance Characteristics for Lateral Power Devices Based on AlGaN Alloys

DOE PAGES

Coltrin, Michael E.; Baca, Albert G.; Kaplar, Robert J.

2017-10-26

In this paper, predicted lateral power device performance as a function of alloy composition is characterized by a standard lateral device figure-of-merit (LFOM) that depends on mobility, critical electric field, and sheet carrier density. The paper presents calculations of AlGaN electron mobility in lateral devices such as HEMTs across the entire alloy composition range. Alloy scattering and optical polar phonon scattering are the dominant mechanisms limiting carrier mobility. Due to the significant degradation of mobility from alloy scattering, at room temperature Al fractions greater than about 85% are required for improved LFOM relative to GaN using a conservative sheet chargemore » density of 1 × 10 13 cm –2. However, at higher temperatures at which AlGaN power devices are anticipated to operate, this “breakeven” composition decreases to about 65% at 500 K, for example. For high-frequency applications, the Johnson figure-of-merit (JFOM) is the relevant metric to compare potential device performance across materials platforms. At room temperature, the JFOM for AlGaN alloys is predicted to surpass that of GaN for Al fractions greater than about 40%.« less

Analysis of 2D Transport and Performance Characteristics for Lateral Power Devices Based on AlGaN Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Coltrin, Michael E.; Baca, Albert G.; Kaplar, Robert J.

In this paper, predicted lateral power device performance as a function of alloy composition is characterized by a standard lateral device figure-of-merit (LFOM) that depends on mobility, critical electric field, and sheet carrier density. The paper presents calculations of AlGaN electron mobility in lateral devices such as HEMTs across the entire alloy composition range. Alloy scattering and optical polar phonon scattering are the dominant mechanisms limiting carrier mobility. Due to the significant degradation of mobility from alloy scattering, at room temperature Al fractions greater than about 85% are required for improved LFOM relative to GaN using a conservative sheet chargemore » density of 1 × 10 13 cm –2. However, at higher temperatures at which AlGaN power devices are anticipated to operate, this “breakeven” composition decreases to about 65% at 500 K, for example. For high-frequency applications, the Johnson figure-of-merit (JFOM) is the relevant metric to compare potential device performance across materials platforms. At room temperature, the JFOM for AlGaN alloys is predicted to surpass that of GaN for Al fractions greater than about 40%.« less

Effects of Precipitant and pH on Coprecipitation of Nanosized Co-Cr-V Alloy Powders.

PubMed

Chen, Xiaoyu; Li, Yongxia; Huang, Lan; Zou, Dan; Wu, Enxi; Liu, Yanjun; Xie, Yuanyan; Yao, Rui; Liao, Songyi; Wang, Guangrong; Zheng, Feng

2017-09-21

Nanosized Co-Cr-V alloy powders were synthesized via coprecipitation method. Effects of precipitants ((NH₄)₂C₂O₄·H₂O and Na₂CO₃) and pH were investigated by X-ray diffraction (XRD), Zeta potential analyzer, thermogravimetry-differential scanning calorimetry (TG-DSC), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and scanning electron microscopy (SEM). Co-Cr-V alloy powders were consisted of major face-centered cubic Co (fcc Co) and minor hexagonal close-packed Co (hcp Co). Grain sizes of precursors and Co-Cr-V alloy powders were increased with pH value (7-10) within the ranges of 3~39 and 39~66 nm, respectively. Rod-like or granular Co-Cr-V alloy particles were assembled by interconnected nanograins. At pH = 7, Na₂CO₃ precipitant was found to be beneficial to maintain the desirable composition of Co-Cr-V powders. It was also found that lower pH favors the maintenance of pre-designed composition, while grain coarsens at higher pH. Effects of variation for precipitant and pH on the morphology and composition of Co-Cr-V alloy powder were discussed in detail and relevant mechanism was further proposed.

Metal- and intermetallic-matrix composites for aerospace propulsion and power systems

NASA Technical Reports Server (NTRS)

Doychak, J.

1992-01-01

The requirements for high specific strength refractory materials of prospective military, civil, and space propulsion systems are presently addressed in the context of emerging capabilities in metal- and intermetallic-matrix composites. The candidate systems encompass composite matrix compositions of superalloy, Nb-Zr refractory alloy, Cu-base, and Ti-base alloy types, as well as such intermetallics as TiAl, Ti3Al, NiAl, and MoSi2. The brittleness of intermetallic matrices remains a major consideration, as does their general difficulty of fabrication.

From chemistry to mechanics: bulk modulus evolution of Li-Si and Li-Sn alloys via the metallic electronegativity scale.

PubMed

Li, Keyan; Xie, Hui; Liu, Jun; Ma, Zengsheng; Zhou, Yichun; Xue, Dongfeng

2013-10-28

Toward engineering high performance anode alloys for Li-ion batteries, we proposed a useful method to quantitatively estimate the bulk modulus of binary alloys in terms of metallic electronegativity (EN), alloy composition and formula volume. On the basis of our proposed potential viewpoint, EN as a fundamental chemistry concept can be extended to be an important physical parameter to characterize the mechanical performance of Li-Si and Li-Sn alloys as anode materials for Li-ion batteries. The bulk modulus of binary alloys is linearly proportional to the combination of average metallic EN and atomic density of alloys. We calculated the bulk moduli of Li-Si and Li-Sn alloys with different Li concentrations, which can agree well with the reported data. The bulk modulus of Li-Si and Li-Sn alloys decreases with increasing Li concentration, leading to the elastic softening of the alloys, which is essentially caused by the decreased strength of constituent chemical bonds in alloys from the viewpoint of EN. This work provides a deep understanding of mechanical failure of Si and Sn anodes for Li-ion batteries, and permits the prediction of the composition dependent bulk modulus of various lithiated alloys on the basis of chemical formula, metallic EN and cell volume (or alloy density), with no structural details required.

Choosing An Alloy For Automotive Stirling Engines

NASA Technical Reports Server (NTRS)

Stephens, Joseph R.

1988-01-01

Report describes study of chemical compositions and microstructures of alloys for automotive Stirling engines. Engines offer advantages of high efficiency, low pollution, low noise, and ability to use variety of fuels. Twenty alloys evaluated for resistance to corrosion permeation by hydrogen, and high temperature. Iron-based alloys considered primary candidates because of low cost. Nickel-based alloys second choice in case suitable iron-based alloy could not be found. Cobalt-based alloy included for comparison but not candidate, because it is expensive strategic material.

Measuring 3D Alloy Composition Profiles at Surfaces

NASA Astrophysics Data System (ADS)

Hannon, James

2006-03-01

A key challenge in thin-film growth is controlling structure and composition. Of particular importance is understanding how and why atomic-scale heterogeneity develops during growth. We have used low-energy electron microscopy (LEEM) to measure how the three-dimensional composition of an alloy film evolves with time at the nanometer length scale. By quantitatively analyzing the reflected electron intensity in LEEM, we determine the alloy composition and structure, layer by layer near a surface, with 9 nm lateral spatial resolution. As an example, we show that heterogeneity during the growth of Pd on Cu(001) arises naturally from a generic step-overgrowth mechanism that is likely to be relevant in many growth systems. This work was performed in collaboration with Jiebing Sun (UNH), Karsten Pohl (UNH), and Gary Kellogg (Sandia Labs).

Inert electrode composition having agent for controlling oxide growth on electrode made therefrom

DOEpatents

Ray, S.P.

1986-04-15

An improved inert electrode composition is suitable for use as an inert electrode in the production of metals such as aluminum by the electrolytic reduction of metal oxide or metal salt dissolved in a molten salt bath. The composition comprises one or more metal alloys and metal compounds which may include oxides of the metals comprising the alloy. The alloy and metal compounds are interwoven in a network which provides improved electrical conductivity and mechanical strength while preserving the level of chemical inertness necessary for such an electrode to function satisfactorily. The electrode composition further includes a metal compound dopant which will aid in controlling the thickness of a protective oxide layer on at least the bottom portion of an electrode made therefrom during use. 12 figs.

Model forecasting of phase composition of electrolytic alloys Co-Ni-Mn (part 1)

NASA Astrophysics Data System (ADS)

Schmidt, V. V.; Zhikhareva, I. G.

2018-03-01

With the help of four criteria for phase formation, a model forecasting of the phase composition of electrolytic alloy Co-Ni-Mn was carried out; the expected phases were calculated. The boundaries of the chemical content of the metal-solvent (Co) in these phases are determined, depending on the ratio of metal ions in the electrolyte of deposition. Model forecasting of the phase composition of Co-Ni-Mn alloys makes it possible to predict the type and number of Co phases (hexagonal close-packed - HCP-α-Co, face-centered cubic - FCC-β-Co) depending on the mole fraction of the solvent metal (Co). In the first approximation, the forecast allows one to determine the phase and chemical composition of the coating, which corresponds to the specified operational properties.

Inert electrode composition having agent for controlling oxide growth on electrode made therefrom

DOEpatents

Ray, Siba P.

1986-01-01

An improved inert electrode composition is suitable for use as an inert electrode in the production of metals such as aluminum by the electrolytic reduction of metal oxide or metal salt dissolved in a molten salt bath. The composition comprises one or more metal alloys and metal compounds which may include oxides of the metals comprising the alloy. The alloy and metal compounds are interwoven in a network which provides improved electrical conductivity and mechanical strength while preserving the level of chemical inertness necessary for such an electrode to function satisfactorily. The electrode composition further includes a metal compound dopant which will aid in controlling the thickness of a protective oxide layer on at least the bottom portion of an electrode made therefrom during use.

Nuclear fuel element

DOEpatents

Armijo, Joseph S.; Coffin, Jr., Louis F.

1980-04-29

A nuclear fuel element for use in the core of a nuclear reactor is disclosed and has an improved composite cladding comprised of a moderate purity metal barrier of zirconium metallurgically bonded on the inside surface of a zirconium alloy tube. The metal barrier forms a shield between the alloy tube and a core of nuclear fuel material enclosed in the composite cladding. There is a gap between the cladding and the core. The metal barrier forms about 1 to about 30 percent of the thickness of the composite cladding and has low neutron absorption characteristics. The metal barrier serves as a preferential reaction site for gaseous impurities and fission products and protects the alloy tube from contact and reaction with such impurities and fission products. Methods of manufacturing the composite cladding are also disclosed.

One-piece, composite crucible with integral withdrawal/discharge section

DOEpatents

Besser, Matthew; Terpstra, Robert L.; Sordelet, Daniel J.; Anderson, Iver E.; Hartman, Alan D.; Argetsinger, Edward R.; Hansen, Jeffrey S.; Paige, Jack I.; Turner, Paul C.

2002-07-30

A one-piece, composite open-bottom casting mold with integral withdrawal section is fabricated by thermal spraying of materials compatible with and used for the continuous casting of shaped products of reactive metals and alloys such as, for example, titanium and its alloys or for the gas atomization thereof.

Growth of amorphous and epitaxial ZnSiP 2–Si alloys on Si

DOE PAGES

Martinez, Aaron D.; Miller, Elisa M.; Norman, Andrew G.; ...

2018-01-30

ZnSiP 2is a wide band gap material lattice matched with Si, with potential for Si-based optoelectronics. Here, amorphous ZnSiP 2–Si alloys are grown with tunable composition. Films with Si-rich compositions can be crystallized into epitaxial films.

Crystallization kinetics of Mg–Cu–Yb–Ca–Ag metallic glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsarkov, Andrey A., E-mail: tsarkov@misis.ru; WPI Advanced Institute for Materials Research, Tohoku University, Katahira 2-1-1, Aoba-Ku, Sendai 980-8577; Zanaeva, Erzhena N.

The paper presents research into a Mg–Cu–Yb system based metallic glassy alloys. Metallic glasses were prepared using induction melting and further injection on a spinning copper wheel. The effect of alloying by Ag and Ca on the glass forming ability and the kinetics of crystallization of Mg–Cu–Yb system based alloys were studied. The differential scanning calorimeter and X-ray diffractometer were used to investigate the kinetics of crystallization and the phase composition of the samples. An indicator of glass forming ability, effective activation energy of crystallization, and enthalpy of mixing were calculated. An increase of the Ca and Ag content hasmore » a positive effect on the glass forming ability, the effective activation energy of crystallization, and the enthalpy of mixing. The highest indicators of the glass forming ability and the thermal stability were found for alloys that contain both alloying elements. The Ag addition suppresses precipitation of the Mg{sub 2}Cu phase during crystallization. A dual-phase glassy-nanocrystalline Mg structure was obtained in Mg{sub 65}Cu{sub 25}Yb{sub 10} and Mg{sub 59.5}Cu{sub 22.9}Yb{sub 11}Ag{sub 6.6} alloys after annealing. Bulk samples with a composite glassy-crystalline structure were obtained in Mg{sub 59.5}Cu{sub 22.9}Yb{sub 11}Ag{sub 6.6} and Mg{sub 64}Cu{sub 21}Yb{sub 9.5}Ag{sub 5.5} alloys. A thermodynamic database for the Mg–Cu–Yb–Ca–Ag system was created to compare the process of crystallization of alloys with polythermal sections of the Mg–Cu–Yb–Ca–Ag phase diagram. - Highlights: • New alloy compositions based on Mg–Cu–Yb system were developed and investigated. • Increasing content of Ag and Ca leads to improving GFA. • Bulk samples with a composite glassy-crystalline structure were obtained. • Thermodynamic database for Mg–Cu–Yb–Ca–Ag system was created.« less

On the origin of bulk glass forming ability in Cu-Hf, Zr alloys

NASA Astrophysics Data System (ADS)

Ristić, Ramir; Zadro, Krešo; Pajić, Damir; Figueroa, Ignacio A.; Babić, Emil

2016-04-01

Understanding the formation of bulk metallic glasses (BMG) in metallic systems and finding a reliable criterion for selection of BMG compositions are among the most important issues in condensed-matter physics and material science. Using the results of magnetic susceptibility measurements performed on both amorphous and crystallized Cu-Hf alloys (30-70 at% Cu) we find a correlation between the difference in magnetic susceptibilities of corresponding glassy and crystalline alloys and the variation in the glass forming ability (GFA) in these alloys. Since the same correlation can be inferred from data for the properties associated with the electronic structure of Cu-Zr alloys, it seems quite general and may apply to other glassy alloys based on early and late transition metals. This correlation is plausible from the free-energy considerations and provides a simple way to select the compositions with high GFA.

Estimation of Transformation Temperatures in Ti-Ni-Pd Shape Memory Alloys

NASA Astrophysics Data System (ADS)

Narayana, P. L.; Kim, Seong-Woong; Hong, Jae-Keun; Reddy, N. S.; Yeom, Jong-Taek

2018-03-01

The present study focused on estimating the complex nonlinear relationship between the composition and phase transformation temperatures of Ti-Ni-Pd shape memory alloys by artificial neural networks (ANN). The ANN models were developed by using the experimental data of Ti-Ni-Pd alloys. It was found that the predictions are in good agreement with the trained and unseen test data of existing alloys. The developed model was able to simulate new virtual alloys to quantitatively estimate the effect of Ti, Ni, and Pd on transformation temperatures. The transformation temperature behavior of these virtual alloys is validated by conducting new experiments on the Ti-rich thin film that was deposited using multi target sputtering equipment. The transformation behavior of the film was measured by varying the composition with the help of aging treatment. The predicted trend of transformational temperatures was explained with the help of experimental results.

Hot corrosion of four superalloys - HA-188, S-57, IN-617, and TD-NiCrAl

NASA Technical Reports Server (NTRS)

Santoro, G. J.

1979-01-01

Cyclic oxidation and hot corrosion tests of two cobalt-base and two nickel-base alloys are reported. The alloys were exposed to maximum temperatures of 900 and 1000 C in a Mach 0.3 burner rig whose flame was doped with various concentrations of sea salt and sodium sulfate for hot corrosion tests. The test data were subjected to a regression analysis for the development of model equations relating corrosion to temperature and for the effects of salt concentration and composition on corrosion. The corrosion resistance varied with temperature, sea salt concentration, and salt composition, concluding that the S-57 cobalt-base alloy was the most hot corrosion-resistant alloy, and the TD-NiCrAl nickel-base alloy was the least resistant. However, under straight oxidation conditions, the TD-NiCrAl was most resistant, while S-57 was the least resistant alloy.

Preparation of TbCu7-type Sm-Fe powders by low-temperature HDDR treatment

NASA Astrophysics Data System (ADS)

Takagi, Kenta; Jinno, Miho; Ozaki, Kimihiro

2018-05-01

Low-temperature hydrogen-disproportionation-desorption-recombination (HDDR) treatment of Sm-Fe alloy powder was conducted to prepare a metastable TbCu7 type Sm-Fe alloy powder with a grain size of more than a few hundreds of nanometers. While a treatment temperature above 700 °C produced the familiar Th2Zn17 type alloy, one below 600 °C resulted in successful synthesis of the TbCu7 type Sm-Fe alloy with submicron-size grains. This TbCu7 type alloy powder, however, showed no significant improvement in magnetic properties compared to the Th2Zn17 type, as its composition was estimated to be near SmFe8.5 and thus did not achieve the expected Fe-rich composition. Therefore, cross-sectional transmission electron microscope observation of the unfinished TbCu7 type alloy powder was conducted in order to explore means of forming the Fe-rich phase.

Ductile long range ordered alloys with high critical ordering temperature and wrought articles fabricated therefrom

DOEpatents

Liu, Chain T.; Inouye, Henry

1979-01-01

Malleable long range ordered alloys having high critical ordering temperatures exist in the V(Fe, Co).sub.3 and V(Fe, Co, Ni).sub.3 systems. These alloys have the following compositions comprising by weight: 22-23% V, 14-30% Fe, and the remainder Co or Co and Ni with an electron density no more than 7.85. The maximum combination of high temperature strength, ductility and creep resistance are manifested in the alloy comprising by weight 22-23% V, 14-20% Fe and the remainder Co and having an atomic composition of V(Fe .sub.0.20-0.26 C Co.sub.0.74-0.80).sub.3. The alloy comprising by weight 22-23% V, 16-17% Fe and 60-62% Co has excellent high temperature properties. The alloys are fabricable into wrought articles by casting, deforming, and annealing for sufficient time to provide ordered structure.

Hydrogen-isotope permeation barrier

DOEpatents

Maroni, Victor A.; Van Deventer, Erven H.

1977-01-01

A composite including a plurality of metal layers has a Cu-Al-Fe bronze layer and at least one outer layer of a heat and corrosion resistant metal alloy. The bronze layer is ordinarily intermediate two outer layers of metal such as austenitic stainless steel, nickel alloys or alloys of the refractory metals. The composite provides a barrier to hydrogen isotopes, particularly tritium that can reduce permeation by at least about 30 fold and possibly more below permeation through equal thicknesses of the outer layer material.

Life cycle assessment of metal alloys for structural applications

NASA Astrophysics Data System (ADS)

Malovrh Rebec, K.; Markoli, B.; Leskovar, B.

2018-03-01

The study compared environmental footprints of two types of Al-alloys: well-known 5083 aluminium alloy with magnesium and traces of manganese and chromium in its composition. This material is highly resistant to seawater corrosion and the influence of industrial chemicals. Furthermore, it retains exceptional strength after welding. The comparisons were made to an innovative alloy where the aluminium based matrix is reinforced by metastable quasicrystals (QC), thus avoiding magnesium in its composition. Furthermore, we checked other aluminium ingots’ footprints and compared European average and Germany country specific production data. Environmental footprints were assessed via cradle to gate life cycle assessment. Our findings normalized to 1 m2 plate suggest, that newly proposed alloy could save around 50 % in value of parameters abiotic resources depletion of fossil fuels, acidification, eutrophication, global warming potential and photochemical ozone creation potential if we compare Qc5 to 6 mm 5083 alloy plate. Only abiotic resources depletion of elements and ozone depletion parameters increase for Qc5 compared to 6 mm 5083 alloy plate.

Corrosion Performance of Fe-Based Alloys in Simulated Oxy-Fuel Environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zeng, Zuotao; Natesan, Ken; Cai, Zhonghou

The long-term corrosion of Fe-based alloys in simulated oxy-fuel environment at 1023 K (750 A degrees C) was studied. Detailed results are presented on weight change, scale thickness, internal penetration, microstructural characteristics of the corrosion products, and the cracking of scales for the alloys after exposure at 1023 K (750 A degrees C) for up to 3600 hours. An incubation period during which the corrosion rate was low was observed for the alloys. After the incubation period, the corrosion accelerated, and the corrosion process followed linear kinetics. Effects of alloy, CaO-containing ash, and gas composition on the corrosion rate weremore » also studied. In addition, synchrotron nanobeam X-ray analysis was employed to determine the phase and chemical composition of the oxide layers on the alloy surface. Results from these studies are being used to address the long-term corrosion performance of Fe-based alloys in various coal-ash combustion environments and to develop methods to mitigate high-temperature ash corrosion.« less

Strain-induced dimensionality crossover of precursor modulations in Ni{sub 2}MnGa

DOE Office of Scientific and Technical Information (OSTI.GOV)

Nie, Zhihua, E-mail: zhihua-nie@yahoo.com, E-mail: ydwang@neu.edu.cn; Wang, Yandong, E-mail: zhihua-nie@yahoo.com, E-mail: ydwang@neu.edu.cn; Shang, Shunli

2015-01-12

Precursor modulations often occur in functional materials like magnetic shape memory alloys, ferroelectrics, and superconductors. In this letter, we have revealed the underlying mechanism of the precursor modulations in ferromagnetic shape memory alloys Ni{sub 2}MnGa by combining synchrotron-based x-ray diffraction experiments and first-principles phonon calculations. We discovered the precursor modulations along [011] direction can be eliminated with [001] uniaxial loading, while the precursor modulations or premartensite can be totally suppressed by hydrostatic pressure condition. The TA{sub 2} phonon anomaly is sensitive to stress induced lattice strain, and the entire TA{sub 2} branch is stabilized along the directions where precursor modulationsmore » are eliminated by external stress. Our discovery bridges precursor modulations and phonon anomalies, and sheds light on the microscopic mechanism of the two-step superelasticity in precursor martensite.« less

On the causes of compositional order in the Ni sub c Pt sub (1-c) alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gyorffy, B.L.; Pinski, F.J.; Ginatempo, B.

1991-01-01

We review, briefly, the arguments which gave rise to the current controversy concerning the origin of compositional order in Ni{sub c}Pt{sub 1-c} alloys. We note that strain fluctuations play an important role in determining the state of compositional order in this system and outline a theoretical framework that takes account of them. 29 refs., 4 figs.

USSR and Eastern Europe Scientific Abstracts, Materials Science and Metallurgy, Number 56.

DTIC Science & Technology

1978-10-05

metals and materials, coatings, composites , metal corrosion, extraction and refining, forming, instrumentation, lubricants, mechanical and physical...Aluminum and Its Alloys 1 Analysis and Testing 5 Beryllium • > • 1 Coatings • 8 Composite Materials 9 Conferences • 15 Corrosion 18 Graphite...alloys, consisting in changing the chemi- cal composition of the surface layer, which plays an important role in corrosion processes. The content of

Composite construction for nuclear fuel containers

DOEpatents

Cheng, Bo-Ching [Fremont, CA; Rosenbaum, Herman S [Fremont, CA; Armijo, Joseph S [Saratoga, CA

1987-01-01

An improved method for producing nuclear fuel containers of a composite construction having components providing therein a barrier system for resisting destructive action by volatile fission products or impurities and also interdiffusion of metal constituents, and the product thereof. The composite nuclear fuel containers of the method comprise a casing of zirconium or alloy thereof with a layer of copper overlying an oxidized surface portion of the zirconium or alloy thereof.

Nanocrystal dispersed amorphous alloys

NASA Technical Reports Server (NTRS)

Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

2001-01-01

Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

The effect of heat treatment on microstructure evolution in artificially aged carbon nanotube/Al2024 composites synthesized by mechanical alloying

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pérez-Bustamante, R.

Although carbon nanotubes/aluminum (CNT/Al) composites are promising materials in the production of structural components, their mechanical behavior under overaging conditions has not been considered. In this paper the effect of CNTs on the microstructural and mechanical behavior of a 2024 aluminum alloy (Al2024) synthesized by mechanical alloying (MA) and powder metallurgy routes is discussed, as well as the effect of aging heat treatments at different temperatures and aging times. The mechanical behavior of composites was screened by hardness measurements as function of aging time. After 96 h of aging time, composites showed mechanical stability in their hardness performance. Images frommore » transmission electron microscopy showed that the mechanical stability of composites was due to a homogeneous dispersion of CNTs in the aluminum matrix and a subsequent alteration in the kinetics of precipitation is due to their presence in the aluminum matrix. Even though strengthening precipitation took place during aging, this was not the main strengthening mechanism observed in composites. - Highlights: • Dispersion of carbon nanotubes during mechanical alloying • Microstructural evolution observed by HRTEM. • Mechanical performance evaluated through micro-hardness test. • Increased mechanical performance at high working temperatures • Acceleration of kinetics of precipitation due to CNTs, and milling conditions.« less

LSP/MAO composite bio-coating on AZ80 magnesium alloy for biomedical application.

PubMed

Xiong, Ying; Hu, Qiang; Song, Renguo; Hu, Xiaxia

2017-06-01

A composite bio-coating was fabricated on AZ80 magnesium (Mg) alloy by using micro-arc oxidation (MAO) under the pretreatment of laser shock peening (LSP) in order to improve the bio-corrosion resistance and the mechanical integrity. LSP treatment could induce grain refinement and compressive residual stress field on the surface of material. MAO bio-coating was grown in alkaline electrolyte with hydroxyapatite (HA, Ca 10 (PO4) 6 (OH) 2 ) to improve the biological properties of the material. The microstructure, element and phase composition for untreated based material (BM) and treated samples (LSP layer, MAO bio-coating and LSP/MAO composite bio-coating) were investigated by transmission electron microscopy (TEM), scanning electron microscope (SEM), energy dispersion spectroscopy (EDS) and X-ray diffraction (XRD). Electrochemical tests and slow strain rate tensile (SSRT) tests were used to evaluate the corrosion resistance and the stress corrosion susceptibility in simulated body fluid (SBF). The results indicated that LSP/MAO composite bio-coating can not only improve the corrosion resistance of Mg alloy substrate evidently but also increase the mechanical properties in SBF compared to LSP layer and MAO bio-coating. Mg alloy treated by LSP/MAO composite technique should be better suited as biodegradable orthopedic implants. Copyright © 2017 Elsevier B.V. All rights reserved.

Thermal treatment, grain boundary composition and intergranular attack resistance of Alloy 690

DOE Office of Scientific and Technical Information (OSTI.GOV)

Smith, A.J.; Stratton, R.P.

1992-12-31

Commercial Alloy 690 PWR steam generator tubes and experimentally produced alloys with varying amounts of carbon, aluminium and titanium have been examined. After simulated mill annealing and thermal treatment, the microstructure and corrosion behaviour in corrosion tests have been investigated. Stress corrosion resistance of selected alloy 690 tubes and experimental alloys has been examined with environments based on pure water, sodium hydroxide and sodium hydroxide + sodium sulphate solutions. Effects of aluminium content and the thermal treatments on the susceptibility to intergranular attack have been examined, although they appear not to be very significant to the amounts of IGA. Samplesmore » used in thermal treatments have been further examined with a dedicated scanning transmission electron microscope to show compositional changes at grain boundaries.« less

Dendritic Ag-Fe nanocrystalline alloy synthesized by pulsed electrodeposition and its characterization

NASA Astrophysics Data System (ADS)

Santhi, Kalavathy; Revathy, T. A.; Narayanan, V.; Stephen, A.

2014-10-01

Synthesis of dendrite shaped Ag-Fe alloy nanomaterial by pulsed electrodeposition route was investigated. The alloy samples were deposited at different current densities from electrolytes of different compositions to study the influence of current density and bath composition on metal contents in the alloy, which was determined by ICP-OES analysis. The XRD studies were carried out to determine the structure of these samples. Magnetic characterization at room temperature and during heating was carried out to understand their magnetic behaviour and to confirm the inferences drawn from the XRD results. The XPS spectra proved the presence of Fe and Ag in the metallic form in the alloy samples. The FESEM and TEM micrographs were taken to view the surface morphology of the nanosized particles.

Calculations of hydrogen diffusivity in Zr-based alloys: Influence of alloying elements and effect of stress

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yu, J.; Jiang, C.; Zhang, Y.

This report summarizes the progress on modeling hydrogen diffusivity in Zr-based alloys. The presence of hydrogen (H) can detrimentally affect the mechanical properties of many metals and alloys. To mitigate these detrimental effects requires fundamental understanding of the thermodynamics and kinetics governing H pickup and hydride formation. In this work, we focus on H diffusion in Zr-based alloys by studying the effects of alloying elements and stress, factors that have been shown to strongly affect H pickup and hydride formation in nuclear fuel claddings. A recently developed accelerated kinetic Monte Carlo method is used for the study. It is foundmore » that for the alloys considered here, H diffusivity depends weakly on composition, with negligible effect at high temperatures in the range of 600-1200 K. Therefore, the small variation in compositions of these alloys is likely not a major cause of the very different H pickup rates. In contrast, stress strongly affects H diffusivity. This effect needs to be considered for studying hydride formation and delayed hydride cracking.« less

Microscopy of Alloy Formation on Arc Plasma Sintered Oxide Dispersion Strengthen (ODS) Steel

NASA Astrophysics Data System (ADS)

Bandriyana, B.; Sujatno, A.; Salam, R.; Dimyati, A.; Untoro, P.

2017-07-01

The oxide dispersed strengthened (ODS) alloys steel developed as structure material for nuclear power plants (NPP) has good resistant against creep due to their unique microstructure. Microscopy investigation on the microstructure formation during alloying process especially at the early stages was carried out to study the correlation between structure and property of ODS alloys. This was possible thanks to the arc plasma sintering (APS) device which can simulate the time dependent alloying processes. The ODS sample with composition of 88 wt.% Fe and 12 wt.% Cr powder dispersed with 1 wt.% ZrO2 nano powder was mixed in a high energy milling, isostatic compressed to form sample coins and then alloyed in APS. The Scanning Electron Microscope (SEM) with X-ray Diffraction Spectroscopy (EDX) line scan and mapping was used to characterize the microstructure and elemental composition distribution of the samples. The alloying process with unification of each Fe and Cr phase continued by the alloying formation of Fe-Cr by inter-diffusion of both Fe and Cr and followed by the improvement of the mechanical properties of hardness.

Effect of Composition and Pre-Ageing on the Natural Ageing and Paint-Baking Behaviour of Al-Mg-Si Alloys

NASA Astrophysics Data System (ADS)

Rometsch, Paul A.; Gao, Sam X.; Couper, Malcolm J.

Two 6xxx series aluminium alloys were designed to have the same total solute content but very different Mg/Si ratios. An excess Mg alloy (Al-1.2Mg-0.5Si) and an excess Si alloy (Al-0.5Mg-1.2Si) were cast and rolled to 1 mm thick sheet. Both were naturally aged for 30 days and then artificially aged for 0.5 h at 170°C to simulate an automotive body panel paint-baking cycle. In order to improve the paint-bake response, pre-ageing treatments of 20 s at 200°C and 2 h at 100°C were tested and evaluated using atom probe tomography, transmission electron microscopy and hardness testing. The results show that the excess Mg alloy tends to have coarser clusters/precipitates than the excess Si alloy, and that the Mg/Si ratio of the smaller clusters is closer to the alloy composition than that of the larger clusters and precipitates. Depending on the pre-ageing treatment, both alloys can give good paint-baking responses.

Structure and Tribological Properties of B83 Babbit-Based Composite Rods and the Coatings Produced from Them by Arc Surfacing

NASA Astrophysics Data System (ADS)

Bolotova, L. K.; Kalashnikov, I. E.; Kobeleva, L. I.; Katin, I. E.; Kolmakov, A. G.; Mikheev, R. S.; Kobernik, N. V.; Podymova, N. B.

2018-01-01

Surfacing composite rods based on a B83 babbit alloy reinforced by silicon carbide and boron carbide particles are fabricated by extrusion. The structure and the tribological properties of the rods are studied. Extrusion allowed us to introduce and to uniformly distribute reinforcing fillers and to change the size and the morphology of the intermetallic phases in the matrix alloy. The wear resistance of the rods made of the B83 babbit + 5 wt % SiC composite material is shown to be higher than that of commercial B83 alloy samples by a factor of 1.2. Arc surfacing is used to deposit antifriction coatings, which are made of the surfacing composite rods based on B83 babbit reinforced by boron carbide or silicon carbide particles, onto steel substrates. The deposited layers exhibit good adhesion to the substrates: the melting line is continuous and does not contain discontinuities. The structure and the tribological properties of the deposited coatings are studied. The wear resistance of the composite coatings is higher than that of the B83 alloy-based coating by 30%.

Understanding the effect of compositions on electronegativity, atomic radius and thermal stability of Mg-Ni-Y amorphous alloy

NASA Astrophysics Data System (ADS)

Deshmukh, A. A.; Kuthe, S. A.; Palikundwar, U. A.

2018-05-01

In the present paper, the consequences of variation in compositions on the electronegativity (ΔX), atomic radius difference (δ) and the thermal stability (ΔTx) of Mg-Ni-Y bulk metallic glasses (BMGs) are evaluated. In order to understand the effect of variation in compositions on ΔX, δ and ΔTx, regression analysis is performed on the experimentally available data. A linear correlation between both δ and ΔX with regression coefficient 0.93 is observed. Further, compositional variation is performed with δ and then it is correlated to the ΔTx by deriving subsequent equations. It is observed that concentration of Mg, Ni and Y are directly proportional to the δ with regression coefficients 0.93, 0.93 and 0.50 respectively. The positive slope of Ni and Y stated that ΔTx will increase if it has more contribution from both Ni and Y. On the other hand negative slope stated that composition of Mg should be selected in such a way that it will have more stability with Ni and Y. The results obtained from mathematical calculations are also tested by regression analysis of ΔTx with the compositions of individual elements in the alloy. These results conclude that there is a strong dependence of ΔTx of the alloy on the compositions of the constituting elements in the alloy.

Characterization of B4C-composite-reinforced aluminum alloy composites

NASA Astrophysics Data System (ADS)

Singh, Ram; Rai, R. N.

2018-04-01

Dry sliding wear tests conducted on Pin-on-disk wear test machine. The rotational speed of disc is ranging from (400-600rpm) and under loads ranging from (30-70 N) the contact time between the disc and pin is constant for each pin specimen of composites is 15 minute. In all manufacturing industries the uses of composite materials has been increasing globally, In the present study, an aluminum 5083 alloy is used as the matrix and 5% of weight percentage of Boron Carbide (B4C) as the reinforcing material. The composite is produced using stir casting technique. This is cost effective method. The aluminum 5083 matrix can be strengthened by reinforcing with hard ceramic particles like silicon carbide and boron carbide. In this experiment, aluminum 5083 alloy is selected as one of main material for making parts of the ship it has good mechanical properties, good corrosion resistance and it is can welded very easily and does have good strength. The samples are tested for hardness and tensile strength. The mechanical properties like Hardness can be increased by reinforcing aluminum 5083alloy 5% boron carbide (B4C) particles and tensile strength. Finally the Scanning Electron Microscope (SEM) analysis and EDS is done, which helps to study topography of composites and it produces images of a sample by scanning it with a focused beam of electrons and the presence of composition found in the matrix.

Aluminum-Alloy-Matrix/Alumina-Reinforcement Composites

NASA Technical Reports Server (NTRS)

Kashalikar, Uday; Rozenoyer, Boris

2004-01-01

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

Creating ligand-free silicon germanium alloy nanocrystal inks.

PubMed

Erogbogbo, Folarin; Liu, Tianhang; Ramadurai, Nithin; Tuccarione, Phillip; Lai, Larry; Swihart, Mark T; Prasad, Paras N

2011-10-25

Particle size is widely used to tune the electronic, optical, and catalytic properties of semiconductor nanocrystals. This contrasts with bulk semiconductors, where properties are tuned based on composition, either through doping or through band gap engineering of alloys. Ideally, one would like to control both size and composition of semiconductor nanocrystals. Here, we demonstrate production of silicon-germanium alloy nanoparticles by laser pyrolysis of silane and germane. We have used FTIR, TEM, XRD, EDX, SEM, and TOF-SIMS to conclusively determine their structure and composition. Moreover, we show that upon extended sonication in selected solvents, these bare nanocrystals can be stably dispersed without ligands, thereby providing the possibility of using them as an ink to make patterned films, free of organic surfactants, for device fabrication. The engineering of these SiGe alloy inks is an important step toward the low-cost fabrication of group IV nanocrystal optoelectronic, thermoelectric, and photovoltaic devices.

Structure and phase composition of ultrafine-grained TiNb alloy after high-temperature annealings

NASA Astrophysics Data System (ADS)

Eroshenko, Anna Yu.; Glukhov, Ivan A.; Mairambekova, Aikol; Tolmachev, Alexey I.; Sharkeev, Yurii P.

2017-12-01

The paper presents the experimental data observed in the microstructure and phase composition of ultrafine-grained Ti-40 mass % Nb (Ti40Nb) alloy after high-temperature annealings. The ultrafine-grained Ti40Nb alloy is produced by severe plastic deformation (SPD). This method includes multiple abc-pressing and multi-pass rolling followed by further pre-recrystallizing annealing which, in its turn, enhances the formation of ultrafine-grained structures with mean size of 0.28 µm involving stable β- and α-phase and metastable nanosized ω-phase in the alloy. It is shown that annealing at 500°C preserves the ultrafine-grained structure and phase composition. In cases of annealing at 800°C the ultrafine-grained state transforms into the coarse-grained state. The stable β-phase and the nanosized metastable ω-phase have been identified in the coarse-grained structure.

Determination of Thermodynamic Properties of Alkaline Earth-liquid Metal Alloys Using the Electromotive Force Technique

PubMed Central

Nigl, Thomas P.; Smith, Nathan D.; Lichtenstein, Timothy; Gesualdi, Jarrod; Kumar, Kuldeep; Kim, Hojong

2017-01-01

A novel electrochemical cell based on a CaF2 solid-state electrolyte has been developed to measure the electromotive force (emf) of binary alkaline earth-liquid metal alloys as functions of both composition and temperature in order to acquire thermodynamic data. The cell consists of a chemically stable solid-state CaF2-AF2 electrolyte (where A is the alkaline-earth element such as Ca, Sr, or Ba), with binary A-B alloy (where B is the liquid metal such as Bi or Sb) working electrodes, and a pure A metal reference electrode. Emf data are collected over a temperature range of 723 K to 1,123 K in 25 K increments for multiple alloy compositions per experiment and the results are analyzed to yield activity values, phase transition temperatures, and partial molar entropies/enthalpies for each composition. PMID:29155770

Abrasive wear behavior of in-situ RZ5-10wt%TiC composite

NASA Astrophysics Data System (ADS)

Mehra, Deepak; Mahapatra, M. M.; Harsha, S. P.

2018-05-01

RZ5 Magnesium alloys containing zinc, rare earth and zirconium are well-known to have high specific strength, good creep resistance widely used in aerospace components. The incorporation of hard ceramic strengthens RZ5 mg alloy. The RZ5-10wt%TiC composite has been fabricated in situ using RZ5 mg alloy as matrix and TiC as reinforcement by self propagating high temperature synthesis (SHS) technique. This paper investigates the abrasive wear behavior of RZ5-10wt%TiC. Tests were performed using pin-on-disc apparatus against 600 grit abrasive paper by varying the sliding distance and applied load. The results showed improvement in the wear resistance of testing composite as compared to the unreinforced RZ5 Mg alloy. The coefficient of friction and weight loss increased linearly as applied load and sliding distance increased. The field emission scanning electron microscopic (FESEM) showed dominate wear mechanisms: abrasion, ploughing grooves.

Developing Gradient Metal Alloys through Radial Deposition Additive Manufacturing

PubMed Central

Hofmann, Douglas C.; Roberts, Scott; Otis, Richard; Kolodziejska, Joanna; Dillon, R. Peter; Suh, Jong-ook; Shapiro, Andrew A.; Liu, Zi-Kui; Borgonia, John-Paul

2014-01-01

Interest in additive manufacturing (AM) has dramatically expanded in the last several years, owing to the paradigm shift that the process provides over conventional manufacturing. Although the vast majority of recent work in AM has focused on three-dimensional printing in polymers, AM techniques for fabricating metal alloys have been available for more than a decade. Here, laser deposition (LD) is used to fabricate multifunctional metal alloys that have a strategically graded composition to alter their mechanical and physical properties. Using the technique in combination with rotational deposition enables fabrication of compositional gradients radially from the center of a sample. A roadmap for developing gradient alloys is presented that uses multi-component phase diagrams as maps for composition selection so as to avoid unwanted phases. Practical applications for the new technology are demonstrated in low-coefficient of thermal expansion radially graded metal inserts for carbon-fiber spacecraft panels. PMID:24942329

The effect of nanobioceramic reinforcement on mechanical and biological properties of Co-base alloy/hydroxyapatite nanocomposite.

PubMed

Bahrami, M; Fathi, M H; Ahmadian, M

2015-03-01

The goal of the present research was to fabricate, characterize, and evaluate mechanical and biological properties of Co-base alloy composites with different amounts of hydroxyapatite (HA) nanopowder reinforcement. The powder of Co-Cr-Mo alloy was mixed with different amounts of HA by ball milling and it was then cold pressed and sintered. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used. Microhardness measurement and compressive tests were also carried out. Bioactivity behavior was evaluated in simulated body fluid (SBF). A significant decrease in modulus elasticity and an increase in microhardness of the sintered composites were observed. Apatite formation on the surface of the composites showed that it could successfully convert bioinert Co-Cr-Mo alloy to bioactive type by adding 10, 15, and 20wt.% HA which have lower modulus elasticity and higher microhardness. Copyright © 2014 Elsevier B.V. All rights reserved.

Analysis of Surface and Bulk Behavior in Ni-Pd Alloys

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Noebe, Rondald D.

2003-01-01

The most salient features of the surface structure and bulk behavior of Ni-Pd alloys have been studied using the BFS method for alloys. Large-scale atomistic simulations were performed to investigate surface segregation profiles as a function of temperature, crystal face, and composition. Pd enrichment of the first layer was observed in (111) and (100) surfaces, and enrichment of the top two layers occurred for (110) surfaces. In all cases, the segregation profile shows alternate planes enriched and depleted in Pd. In addition, the phase structure of bulk Ni-Pd alloys as a function of temperature and composition was studied. A weak ordering tendency was observed at low temperatures, which helps explain the compositional oscillations in the segregation profiles. Finally, based on atom-by-atom static energy calculations, a comprehensive explanation for the observed surface and bulk features will be presented in terms of competing chemical and strain energy effects.

Aluminium-gold reference material for the k0-standardisation of neutron activation analysis

NASA Astrophysics Data System (ADS)

Ingelbrecht, C.; Peetermans, F.; De Corte, F.; De Wispelaere, A.; Vandecasteele, C.; Courtijn, E.; D'Hondt, P.

1991-05-01

Gold is an excellent comparator material for the k0-standardisation of neutron activation analysis because of its convenient and well defined nuclear properties. The most suitable form for a reference material is a dilute aluminium-gold alloy, for which the self-shielding effect for neutrons is small. Castings of composition Al-0.1 wt.% Au were prepared by crucible-less levitation melting, which gives close control of ingot composition with minimal contamination of the melt. The alloy composition was checked using induction-coupled plasma source emission spectrometry. The homogeneity of the alloy was measured by neutron activation analysis and a relative standard deviation of the gold content of 0.30% was found (10 mg samples). Metallography revealed a homogeneous distribution of AuAl 2 particles. The alloy was certified as Reference Material CBNM-530, with certified gold mass fraction 0.100±0.002 wt.%.

Recycling of Aluminum Alloy with Dimox and Rheocasting Functionalize High Performance Structural Foam Composite

NASA Astrophysics Data System (ADS)

Rabeeh, Bakr Mohamed

Great efforts aiming towards the synthesis and the development of structural composite materials. Direct metal oxidation, DIMOX introduced for hybrid composite processing. However, oxidation temperatures around 1100°C lead to the formation of porous ceramic materials. To utilize this porosity intentionally for foam production, a new approach based on synergetic effect of alloying elements, DIMOX and semisolid (rheocsting) processing is developed. A semisolid reaction, rheocasting is introduced to control porosity shape and size. Aluminum alloy 6xxx (automobile scrap pistons) is recycled for this objective and DIMOX at 1100°C for 30 min, then rheocasting, at 750°C for 30 minutes. The effect of α-Fe powder, Mg powder, and Boric acid powder established for the objective of a hybrid structural metal matrix composite in bulk foam matrix. The kinetic of formation of hybrid metal matrix foam composite is introduced. Microstructural and mechanical characterization established for high performance Aluminum foam hybrid composite materials.

Investigations on Mechanical Behaviour of Micro Graphite Particulates Reinforced Al-7Si Alloy Composites

NASA Astrophysics Data System (ADS)

Nagaraj, N.; Mahendra, K. V.; Nagaral, Madeva

2018-02-01

Micro particulates reinforced metal matrix composites are finding wide range of applications in automotive and sports equipment manufacturing industries. In the present study, an attempt has been made to develop Al-7Si-micro graphite particulates reinforced composites by using liquid melt method. 3 and 6 wt. % of micro graphite particulates were added to the Al-7Si base matrix. Microstructural characterization was done by using scanning electron microscope and energy dispersive spectroscope. Mechanical behaviour of Al-7Si-3 and 6 wt. % composites were evaluated as per ASTM standards. Scanning electron micrographs revealed the uniform distribution of micro graphite particulates in the Al-7Si alloy matrix. EDS analysis confirmed the presence of B and C elements in graphite reinforced composites. Further, it was noted that ultimate tensile and yield strength of Al-7Si alloy increased with the addition of 3 and 6wt. % of graphite particulates. Hardness of graphite reinforced composites was lesser than the base matrix.

The effect of Cr, Co, Al, Mo and Ta on a series of cast Ni-base superalloys on the stability of an aluminide coating during cyclic oxidation in Mach 0.3 burner rig

NASA Technical Reports Server (NTRS)

Zaplatynsky, I.; Barrett, C. A.

1986-01-01

The influence of varying the content of Co, Cr, Mo, Ta, and Al in a series of cast Ni-based gamma/gamma'superalloys on the behavior of aluminide coatings was studied in burner rig cyclic oxidation tests at 1100 C. The alloys had nominally fixed levels of Ti, W, Cb, Zr, C, and B. The alloy compositions were based on a full 2(sup 5)-fractional statistical design supplemented by 10 star point alloys and a center point alloy. This full central composite design of 43 alloys plus two additional alloys with extreme Al levels allowed a complete second degree estimating equation to be derived from the 5-compositional variables. The weight change/time data for the coated samples fitted well to the paralinear oxidation model and enabled a modified oxidation attack parameter, K'(sub a) to be derived to rank the alloys and log K' (sub a ) to be used as the dependent variable in the estimating equation to determine the oxidation resistance of the coating as a function of the underlying alloy content. The most protective aluminide coatings are associated with the highest possible base ally contents of CR and Al and at a 4 percent Ta level. The Mo and Co effects interact but at fixed levels of 0, 5, or 10% Co. A 4% Mo level is optimum.

The Effects of Composition and gamma'/gamma Lattice Parameter Mismatch on the Critical Resolved Shear Stresses for Octahedral and Cube Slip in NiAlCrX Alloys

NASA Technical Reports Server (NTRS)

Miner, R. V.

1997-01-01

Prototypical single-crystal NiAlCrX superalloys were studied to examine the effects of the common major alloying elements, Co, Mo, Nb, Ta, Ti, and W, on yielding behavior. The alloys contained about 10 at. pct Cr, 60 vol pct of the gamma' phase, and about 3 at. pct of X in the gamma'. The critical resolved shear stresses (CRSSs) for octahedral and primary cube slip were measured at 760 C, which is about the peak strength temperature. The CRSS(sub oct) and CRSS(sub cube) are discussed in relation to those of Ni, (Al, X) gamma' alloys taken from the literature and the gamma'/gamma lattice mismatch. The CRSS(sub oct) of the gamma + gamma' alloys reflected a similar compositional dependence to that of both the CRSS(sub cube) of the gamma' phase and the gamma'/gamma lattice parameter mismatch. The CRSS(sub cube) of the gamma + gamma' alloys also reflected the compositional dependence of the gamma'/gamma mismatch, but bore no similarity to that of CRSS(sub cube) for gamma' alloys since it is controlled by the gamma matrix. The ratio of CRSS(sub cube)/CRSS(sub oct) was decreased by all alloying elements except Co, which increased the ratio. The decrease in CRSS(sub cube)/CRSS(sub oct) was related to the degree in which elements partition to the gamma' rather than the gamma phase.

Design of a biomimetic self-healing superalloy composite

NASA Astrophysics Data System (ADS)

Files, Bradley Steven

1997-10-01

Use of systems engineering concepts to design technologically advanced materials has allowed ambitious goals of self-healing alloys to be realized. Shape memory alloy reinforcements are embedded in an alloy matrix to demonstrate concepts of stable crack growth and matrix crack closure. Computer methods are used to design thermodynamically compatible iron-based alloys using bio-inspired concepts of crack bridging and self-healing. Feasibility of crack closure and stable crack growth is shown in a prototype system with a Sn-Bi matrix and TiNi fibers. Design of Fe-Ni-Co-Ti-Al alloys using thermodynamic models to determine stabilities and phase equilibria allows for a methodical system designing compatible multicomponent alloys for composite systems. Final alloy computations for this project led to the alloy Fe-27.6Ni-18.2Co-4.1Ti-1.6Al as a compatible shape memory a with a 650sp°C 90 minute heat treatment leading to martensite and austenite start temperatures (Msbs and Asbs) near room temperature. Thin slices of this alloy were able to fully recover at least 5% strain upon unloading heating. Composites made from the designed shape memory alloy and a compatible Fe-based B2 matrix were used to test self-healing concepts in the superalloy system. Diffusion couple experiments verified thermodynamic compatibility between matrix and reinforcement alloys at the solution treatment temperature of 1100sp°C. Concepts of stable crack growth and crack bridging were demonstrated in the composite, leading to enhanced toughness of the brittle matrix. However, healing behavior in this system was limited by intergranular fracture of the reinforcement alloy. It is believed that use of rapidly solidified powders could eliminate intergranular fracture, leading to greatly enhanced properties of toughening and healing. Crack clamping and stable crack growth were achieved in a feasibility study using a Sn-Bi matrix reinforced with TiNi fibers. Tensile specimens with less than 1% fibers showed an ability upon heating to recover over 80% of the plastic deformation induced during a tensile test. Further straining proved that stable crack growth can be realized in this system due to crack bridging of the shape memory fibers. Macroscopic cracks were clamped shut after heating of the material above the TiNi reversion temperature.

Ballistic impact velocity response of carbon fibre reinforced aluminium alloy laminates for aero-engine

NASA Astrophysics Data System (ADS)

Mohammed, I.; Abu Talib, A. R.; Sultan, M. T. H.; Saadon, S.

2017-12-01

Aerospace and other industries use fibre metal laminate composites extensively due to their high specific strength, stiffness and fire resistance, in addition to their capability to be tailored into different forms for specific purposes. The behaviours of such composites under impact loading is another factor to be considered due to the impacts that occur in take-off, landing, during maintenance and operations. The aim of the study is to determine the specific perforation energy and impact strength of the fibre metal laminates of different layering pattern of carbon fibre reinforced aluminium alloy and hybrid laminate composites of carbon fibre and natural fibres (kenaf and flax). The composites are fabricated using the hand lay-up method in a mould with high bonding polymer matrix and compressed by a compression machine, cured at room temperature for one day and post cure in an oven for three hours. The impact tests are conducted using a gun tunnel system with a flat cylindrical bullet fired using a helium gas at a distance of 14 inches to the target. Impact and residual velocity of the projectile are recorded by high speed video camera. Specific perforation energy of carbon fibre reinforced aluminium alloy (CF+AA) for both before and after fire test are higher than the specific perforation energy of the other composites considered before and after fire test respectively. CF +AA before fire test is 55.18% greater than after. The same thing applies to impact strength of the composites where CF +AA before the fire test has the highest percentage of 11.7%, 50.0% and 32.98% as respectively compared to carbon fibre reinforced aluminium alloy (CARALL), carbon fibre reinforced flax aluminium alloy (CAFRALL) and carbon fibre reinforced kenaf aluminium alloy (CAKRALL), and likewise for the composites after fire test. The considered composites in this test can be used in the designated fire zone of an aircraft engine to protect external debris from penetrating the engine shield due to higher values of impact strength and specific perforation energy as highlighted by the test results.

NREL/industry interaction: Amorphous silicon alloy research team formation

NASA Astrophysics Data System (ADS)

Luft, Werner

1994-06-01

The low material cost and proven manufacturability of amorphous silicon (a-Si) alloy photovoltaic technology make it ideally suited for large-scale terrestrial applications. The present efficiency of a-Si alloy modules is, however, much lower than the 15% stable efficiency that would lead to significant penetration of the electric utility bulk-power market. The slow progress in achieving high stabilized a-Si alloy module efficiencies may in part be attributed to the fact that only in the last few years did we emphasize stable efficiencies. A mission-focused integrated effort among the a-Si PV industry, universities, and the National Renewable Energy Laboratory (NREL) would help. To foster research integration, NREL has established four research teams with significant industry participation. In the 11 months since the research team formation, a close interaction among the a-Si PV industry, universities, and NREL has been achieved and has resulted in mission-directed research.

NREL/industry interaction: Amorphous silicon alloy research team formation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luft, W.

1994-06-30

The low material cost and proven manufacturability of amorphous silicon (a-Si) alloy photovoltaic technology make it ideally suited for large-scale terrestrial applications. The present efficiency of a-Si alloy modules is, however, much lower than the 15% stable efficiency that would lead to [ital significant] penetration of the electric utility bulk-power market. The slow progress in achieving high stabilized a-Si alloy module efficiencies may in part be attributed to the fact that only in the last few years did we emphasize stable efficiencies. A mission-focused integrated effort among the a-Si PV industry, universities, and the National Renewable Energy Laboratory (NREL) wouldmore » help. To foster research integration, NREL has established four research teams with significant industry participation. In the 11 months since the research team formation, a close interaction among the a-Si PV industry, universities, and NREL has been achieved and has resulted in mission-directed research.« less

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)

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

2010-11-01

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.

Growth Kinetics of Magnesio-Aluminate Spinel in Al/Mg Lamellar Composite Interface

NASA Astrophysics Data System (ADS)

Fouad, Yasser; Rabeeh, Bakr Mohamed

The synthesis of Mg-Al2O3 double layered interface is introduced via the application of hot isostatic pressing, HIPing, in Al-Mg foils. Polycrystalline spinel layers are grown experimentally at the interfacial contacts between Al-Mg foils. The growth behavior of the spinel layers along with the kinetic parameters characterizing interface motion and long-range diffusion is established. Low melting depressant (LMD), Zn, and alloying element segregation tends to form micro laminated and/or Nano structure interphase in a lamellar composite solid state processing. Nano composite ceramic interphase materials offer interesting mechanical properties not achievable in other materials, such as superplastic flow and metal-like machinability. Microstructural characterization, mechanical characterization is also established via optical microscopy scanning electron microscopy, energy dispersive X-ray spectroscopy and tensile testing. Chemical and mechanical bonding via inter diffusion processing with alloy segregation are dominant for interphase kinetics. Mechanical characterization with interfacial shear strength is also introduced. HIPing processing is successfully applied on 6082 Al-alloy and AZ31 magnesium alloy for either particulate or micro-laminated interfacial composite processing. The interphase kinetic established through localized micro plasticity, metal flow, alloy segregation and delocalized Al oxide and Mg oxide. The kinetic of interface/interphase induce new nontraditional crack mitigation a long with new bridging and toughening mechanisms.

Low void content autoclave molded titanium alloy and polyimide graphite composite structures.

NASA Technical Reports Server (NTRS)

Vaughan, R. W.; Jones, R. J.; Creedon, J. F.

1972-01-01

This paper discusses a resin developed for use in autoclave molding of polyimide graphite composite stiffened, titanium alloy structures. Both primary and secondary bonded structures were evaluated that were produced by autoclave processing. Details of composite processing, adhesive formulary, and bonding processes are provided in this paper, together with mechanical property data for structures. These data include -65 F, room temperature, and 600 F shear strengths; strength retention after aging; and stress rupture properties at 600 F under various stress levels for up to 1000 hours duration. Typically, shear strengths in excess of 16 ksi at room temperature with over 60% strength retention at 600 F were obtained with titanium alloy substrates.

Corrosion resistance and adhesion strength of a spin-assisted layer-by-layer assembled coating on AZ31 magnesium alloy

NASA Astrophysics Data System (ADS)

Zhao, Yan-Bin; Liu, Han-Peng; Li, Chang-Yang; Chen, Yong; Li, Shuo-Qi; Zeng, Rong-Chang; Wang, Zhen-Lin

2018-03-01

A polyvinylpyrrolidone (PVP)/polyacrylic acid (PAA) layer-by-layer (LbL) assembled composite coating with a multilayer structure for the corrosion protection of AZ31 magnesium alloy was prepared by a novel spin-casting method. The microstructure and composition of this coating were investigated by means of SEM, XRD and FT-IR measurements. Moreover, electrochemical, immersion and scratch tests in vitro were performed to measure the corrosion performance and the adhesion strength. These results indicated that the (PVP/PAA)10 composite coating with defect-free, dense and uniform morphologies could be successfully deposited on the surface of magnesium alloy. The coating had excellent corrosion resistance and adhesion strength.

Surface Modifications with Laser Synthesized Mo Modified Coating

NASA Astrophysics Data System (ADS)

Sun, Lu; Chen, Hao; Liu, Bo

2013-01-01

Mg-Cu-Al was first used to improve the surface performance of TA15 titanium alloys by means of laser cladding technique. The synthesis of hard composite coating on TA15 titanium alloy by laser cladding of Mg-Cu-Al-B4C/Mo pre-placed powders was investigated by means of scanning electron microscope, energy dispersive spectrometer and high resolution transmission electron microscope. Experimental results indicated that such composite coating mainly consisted of TiB2, TiB, TiC, Ti3Al and AlCuMg. Compared with TA15 alloy substrate, an improvement of wear resistance was observed for this composite coating due to the actions of fine grain, amorphous and hard phase strengthening.

Mechanical properties of neutron-irradiated model and commercial FeCrAl alloys

DOE PAGES

Field, Kevin G.; Briggs, Samuel A.; Sridharan, Kumar; ...

2017-03-28

The development and understanding of the mechanical properties of neutron-irradiated FeCrAl alloys is increasingly a critical need as these alloys continue to become more mature for nuclear reactor applications. This study focuses on the mechanical properties of model FeCrAl alloys and of a commercial FeCrAl alloy neutron-irradiated to up to 13.8 displacements per atom (dpa) at irradiation temperatures between 320 and 382 °C. Tensile tests were completed at room temperature and at 320 °C, and a subset of fractured tensile specimens was examined by scanning electron microscopy. Results showed typical radiation hardening and embrittlement indicative of high chromium ferritic alloysmore » with strong chromium composition dependencies at lower doses. At and above 7.0 dpa, the mechanical properties saturated for both the commercial and model FeCrAl alloys, although brittle cleavage fracture was observed at the highest dose in the model FeCrAl alloy with the highest chromium content (18 wt %). Finally, the results suggest the composition and microstructure of FeCrAl alloys plays a critical role in the mechanical response of FeCrAl alloys irradiated near temperatures relevant to light water reactors.« less

[Influence of different types of posts and cores on color of IPS-Empress 2 crown].

PubMed

Li, Dong-fang; Yang, Jing-yuan; Yang, Xing-mei; Yang, Liu; Xu, Qiang; Guan, Hong-yu; Wan, Qian-bing

2007-10-01

To evaluate the influence of different types of posts and cores on the final color of the IPS-Emperss 2 crown. Five types of posts and cores (Cerapost with Empress cosmo, Cerapost with composite resin, gilded Ni-Cr alloy, gold alloy and Ni-Cr alloy) were made. The shifts in color of three points of IPS-Empress 2 crown surface (cervical, middle and incisal) with different posts and cores was measured with a spectroradiometer (PR-650). The L* a* b* values of zirconium oxide and gilded Ni-Cr alloy posts and cores with ceramic crown were the highest. The L* a* values of zirconium oxide posts composite cores were higher while the b* values were lower. The L* a* b* values of Ni-Cr alloy were lower than that of gold alloy and were the lowest. In combination with IPS-Empress 2 crown, zirconium oxide posts are suitable for routine use in the anterior dentition, and gilded Ni-Cr alloy and gold alloy posts and cores can be recommended for clinical practice. Ni-Cr alloy posts and cores can not be recommended for clinical practice.

Shaping bronze by heat and hammer: An experimental reproduction of Minoan Copper alloy forming techniques.

NASA Astrophysics Data System (ADS)

Nerantzis, Nerantzis

The compositions of copper-base tools, weapons, ornaments and ceremonial metalwork from numerous Late Bronze Age Aegean sites reveal a pattern of specific alloy combinations for the fabrication of certain classes of objects. Thus the majority of weapons and tools were made of high tin bronze whereas bronze statuettes, tripods and cauldrons contain small amounts of lead and in some cases tin is present in low amounts. Such diversity reflects the direct relationship between the compositions of prehistoric bronze objects and the art of their fabrication, because both the alloy additions and the impurities exert a pronounced effect on the forming capacity of alloys. In order to understand the correlation between composition and formability of Minoan bronzes, replica compositions with varying tin and lead contents were experimentally reproduced and their forming capacities were tested. Deformation and heat treatment of five tin and two leaded tin bronze alloys was attempted in order to replicate the forming stages for the shaping of cutting tools and bronze sheet for vessels and cauldrons. The amount of cold-working and annealing intervals, required to test the effects of workability on alloy properties, has been reflected as hardness values and transformations of the structural characteristics for each sample. It has been shown through the course of the experiment that high tin bronzes could be formed by frequent, short annealing stages at 600˚C and that it is possible to work-harden leaded bronze as long as time and temperatures are closely monitored.

Effect of chemical composition of Ni-Cr dental casting alloys on the bonding characterization between porcelain and metal.

PubMed

Huang, H-H; Lin, M-C; Lee, T-H; Yang, H-W; Chen, F-L; Wu, S-C; Hsu, C-C

2005-03-01

The purpose of this study was to investigate the influence of chemical composition of Ni-Cr dental casting alloys on the bonding behaviour between porcelain and metal. A three-point bending test was used to measure the fracture load of alloy after porcelain firing. A scanning electron microscope, accompanied by an energy dispersion spectrometer, was used to analyse the morphology and chemical composition of the fracture surface. An X-ray photoelectron spectrometer and glow discharge spectrometer were used to identify the structure and cross-sectional chemical composition, respectively, of oxide layers on Ni-Cr alloys after heat treatment at 990 degrees C for 5 min. Results showed that the oxide layers formed on all Ni-Cr alloys contained mainly Cr2O3, NiO, and trace MoO3. The Ni-Cr alloy with a higher Cr content had a thicker oxide layer, as well as a weaker bonding behaviour of porcelain/metal interface. The presence of Al (as Al2O3) and Be (as BeO) on the oxide layer suppressed the growth of the oxide layer, leading to a better porcelain/metal bonding behaviour. However, the presence of a small amount of Ti (as TiO2) on the oxide layer did not have any influence on the bonding behaviour. The fracture propagated along the interface between the opaque porcelain and metal, and exhibited an adhesive type of fracture morphology.

Corrosion resistance and antibacterial properties of polysiloxane modified layer-by-layer assembled self-healing coating on magnesium alloy.

PubMed

Zhao, Yanbin; Shi, Liqian; Ji, Xiaojing; Li, Jichen; Han, Zhuangzhuang; Li, Shuoqi; Zeng, Rongchang; Zhang, Fen; Wang, Zhenlin

2018-04-18

Magnesium (Mg) alloys have shown great potential in biomedical materials due to their biocompatibility and biodegradability. However, rapid corrosion rate, which is an inevitable obstacle, hinders their clinical applications. Besides, it is necessary to endow Mg alloys with antibacterial properties, which are crucial for temporary implants. In this study, silver nanoparticles (AgNPs) and polymethyltrimethoxysilane (PMTMS) were introduced into AZ31 Mg alloys via layer-by-layer (LbL) assembly and siloxane self-condensation reaction. The characteristics of the composite films were investigated by SEM, UV-vis, FT-IR, and XRD measurements. Corrosion resistance of the samples was measured by electrochemical and hydrogen evolution tests. Antibacterial activities of the films against Staphylococcus aureus were evaluated by plate-counting method. The results demonstrated that the composite film with smooth and uniform morphologies could enhance the corrosion resistance of Mg alloys owing to the physical barrier and the self-healing functionality of polysiloxane. Moreover, the composite coating possessed antibacterial properties and could prolong the release of assembled silver ions. Copyright © 2018 Elsevier Inc. All rights reserved.

Nanophase diagram of binary eutectic Au-Ge nanoalloys for vapor-liquid-solid semiconductor nanowires growth

NASA Astrophysics Data System (ADS)

Lu, Haiming; Meng, Xiangkang

2015-06-01

Although the vapor-liquid-solid growth of semiconductor nanowire is a non-equilibrium process, the equilibrium phase diagram of binary alloy provides important guidance on the growth conditions, such as the temperature and the equilibrium composition of the alloy. Given the small dimensions of the alloy seeds and the nanowires, the known phase diagram of bulk binary alloy cannot be expected to accurately predict the behavior of the nanowire growth. Here, we developed a unified model to describe the size- and dimensionality-dependent equilibrium phase diagram of Au-Ge binary eutectic nanoalloys based on the size-dependent cohesive energy model. It is found that the liquidus curves reduce and shift leftward with decreasing size and dimensionality. Moreover, the effects of size and dimensionality on the eutectic composition are small and negligible when both components in binary eutectic alloys have the same dimensionality. However, when two components have different dimensionality (e.g. Au nanoparticle-Ge nanowire usually used in the semiconductor nanowires growth), the eutectic composition reduces with decreasing size.

Assessment of exposures and potential risks to the US adult population from wear (attrition and abrasion) of gold and ceramic dental restorations.

PubMed

Richardson, G Mark; Clemow, Scott R; Peters, Rachel E; James, Kyle J; Siciliano, Steven D

2016-01-01

Little has been published on the chemical exposures and risks of dental restorative materials other than from dental amalgam and composite resins. Here we provide the first exposure and risk assessment for gold (Au) alloy and ceramic restorative materials. Based on the 2001-2004 US National Health and Nutrition Examination Survey (NHANES), we assessed the exposure of US adults to the components of Au alloy and ceramic dental restorations owing to dental material wear. Silver (Ag) is the most problematic component of Au alloy restorations, owing to a combination of toxicity and proportional composition. It was estimated that adults could possess an average of four tooth surfaces restored with Au alloy before exceeding, on average, the reference exposure level (REL) for Ag. Lithium (Li) is the most problematic component of dental ceramics. It was estimated that adults could possess an average of 15 tooth surfaces restored with ceramics before exceeding the REL for Li. Relative risks of chemical exposures from dental materials decrease in the following order: Amalgam>Au alloys>ceramics>composite resins.

Development of ODS FeCrAl for compatibility in fusion and fission energy applications

DOE PAGES

Pint, Bruce A.; Dryepondt, Sebastien N.; Unocic, Kinga A.; ...

2014-11-15

In this paper, oxide dispersion strengthened (ODS) FeCrAl alloys with 12–15% Cr are being evaluated for improved compatibility with Pb-Li for a fusion energy application and with high temperature steam for a more accident-tolerant light water reactor fuel cladding application. A 12% Cr content alloy showed low mass losses in static Pb-Li at 700°C, where a LiAlO 2 surface oxide formed and inhibited dissolution into the liquid metal. All the evaluated compositions formed a protective scale in steam at 1200°C, which is not possible with ODS FeCr alloys. However, most of the compositions were not protective at 1400°C, which ismore » a general and somewhat surprising problem with ODS FeCrAl alloys that is still being studied. More work is needed to optimize the alloy composition, microstructure and oxide dispersion, but initial promising tensile and creep results have been obtained with mixed oxide additions, i.e. Y 2O 3 with ZrO 2, HfO 2 or TiO 2.« less

The effect of alloying on gamma and gamma prime in nickel-base superalloys

NASA Technical Reports Server (NTRS)

Dreshfield, R. L.; Wallace, J. F.

1972-01-01

An investigation was conducted to determine the compositional limits of gamma and gamma prime phases in nickel-base superalloys. Fifty-one nickel-base alloys were melted under vacuum and heat treated for 4 hours at 1190 C followed by 1008 hours at 850 C. The alloys had the following composition ranges: A1 4.0 to 13 atomic percent, Cr 6.5 to 20.5 percent, Ti 0.25 to 4.75 percent, Mo 0.0 to 6.0 percent, and W 0.0 to 4.0 percent. The residues from the ammonium sulfate electrolytic extraction for the two-phase alloys were analyzed chemically and by X-ray diffraction. The results of the investigation were used to assemble a mathematical model of the gamma-gamma prime region of the Ni-Al-Cr-Ti-Mo-W system. A computer program was written to analyze the model of the phase diagram. Some of these results are also presented graphically. The resulting model is capable of satisfactorily predicting the compositions of conjugate gamma-gamma prime phases in the alloys investigated and twelve of fifteen commercial superalloys studied.

Cytotoxicity of dental alloys, metals, and ceramics assessed by millipore filter, agar overlay, and MTT tests.

PubMed

Sjögren, G; Sletten, G; Dahl, J E

2000-08-01

Biocompatibility of dental materials is dependent on the release of elements from the materials. In addition, the composition, pretreatment, and handling of the materials influence the element release. This study evaluated the cytotoxicity of dental alloys, metals, and ceramics, with specific emphasis on the effects of altering the composition and the pretreatment. By using cells from a mouse fibroblast cell line and the agar overlay test, Millipore filter test, and MTT test, cytotoxicity of various metals, metal alloys, and ceramics for dental restoration were studied. Effects of altering the composition of a high noble gold alloy and of pretreatment of a ceramic-bonding alloy were also studied. In addition, the release of elements into the cell culture medium by the materials studied was measured using an inductively coupled plasma optical emission spectrophotometer. The results of the MTT test were analyzed statistically using ANOVA and Scheffé test at a significance level of P <.05. Specimens manufactured from materials intended for dental restorations and handled in accordance with the manufacturers' instructions were ranked from "noncytotoxic" to "mildly cytotoxic" according to the agar overlay and Millipore filter tests. For the MTT test, no significant differences were observed between these materials and controls, with the exception of JS C-gold and unalloyed titanium. The modified materials were ranked from "mildly cytotoxic" to "moderately cytotoxic" in the agar overlay and Millipore filter tests and from "noncytotoxic" to "moderately cytotoxic" in the MTT test. Thus, cytotoxicity was related to the alloy composition and treatment. The release of Cu and Zn seemed to be important for the cytotoxic effect. Alterations in the composition and the pretreatment can greatly influence the cytotoxicity, and the results stress the importance of carefully following the manufacturers' instructions when handling dental materials.

High damping Al-Fe-Mo-Si/Zn-Al composites produced by rapidly solidified powder metallurgy process

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, P.Y.; Dai, S.L.; Chai, S.C.

2000-05-10

The metallic materials commonly used in aircraft and aerospace fields, such as aluminum and titanium alloys, steels, etc., show extremely low damping capacity (usually of the order of or less than 10{sup {minus}3}). Thus, some problems related to vibration may emerge and influence the reliability, safety and life of airplanes, satellites, etc. It has been reported that almost two thirds of errors for rockets and satellites are related to vibration and noise. One effective way to solve these vibration-related problems is to adopt high damping metallic materials. Conventional high damping alloys exhibit damping capacity above 10{sup {minus}2}, however, their densitiesmore » are usually great than 5 x 10{sup 3} kg m{sup {minus}3}, or their strengths are less than 200 MPa (for alloys based on dislocation damping), making them impossible to be applied to aircraft and aerospace areas. Recently, some low-density high-damping metal/metal composites based on aluminum and high damping alloys have been developed in Beijing Institute of Aeronautical Materials (BIAM) by the rapidly solidified power metallurgy process. This paper aims to report the properties of the composites based on a high temperature Al-Fe-Mo-Si alloy and a high damping Zn-Al alloy, and compare them with that of 2618-T61 alloy produced by the ingot metallurgy process.« less

Choosing the optimal Pareto composition of the charge material for the manufacture of composite blanks

NASA Astrophysics Data System (ADS)

Zalazinsky, A. G.; Kryuchkov, D. I.; Nesterenko, A. V.; Titov, V. G.

2017-12-01

The results of an experimental study of the mechanical properties of pressed and sintered briquettes consisting of powders obtained from a high-strength VT-22 titanium alloy by plasma spraying with additives of PTM-1 titanium powder obtained by the hydride-calcium method and powder of PV-N70Yu30 nickel-aluminum alloy are presented. The task is set for the choice of an optimal charge material composition of a composite material providing the required mechanical characteristics and cost of semi-finished products and items. Pareto optimal values for the composition of the composite material charge have been obtained.

Composition-Tunable Optical Properties of Zn x Cd(1 - x)S Quantum Dot-Carboxymethylcellulose Conjugates: Towards One-Pot Green Synthesis of Multifunctional Nanoplatforms for Biomedical and Environmental Applications

NASA Astrophysics Data System (ADS)

Mansur, Alexandra A. P.; Mansur, Herman S.; Caires, Anderson J.; Mansur, Rafael L.; Oliveira, Luiz C.

2017-07-01

Quantum dots (QDs) are colloidal semiconductor nanocrystals with unique properties that can be engineered by controlling the nanoparticle size and chemical composition by doping and alloying strategies. However, due to their potential toxicity, augmenting their biocompatibility is yet a challenge for expanding to several biomedical and environmentally friendly applications. Thus, the main goal of this study was to develop composition-tunable and biocompatible Zn x Cd1 - x S QDs using carboxymethylcellulose polysaccharide as direct capping ligand via green colloidal aqueous route at neutral pH and at room temperature for potential biomedical and environmental applications. The ternary alloyed QDs were extensively characterized using UV-vis spectroscopy, photoluminescence spectroscopy (PL), transmission electron microscopy (TEM), X-ray diffraction (XRD), electron energy loss spectroscopy (EELS), and X-ray photoelectrons spectroscopy (XPS). The results indicated that Zn x Cd(1 - x)S QDs were surface stabilized by carboxymethylcellulose biopolymer with spherical morphology for all composition of alloys and narrow sizes distributions ranging from 4 to 5 nm. The XRD results indicated that monophasic ternary alloyed Zn x Cd1 - x S nanocrystals were produced with homogenous composition of the core as evidenced by EELS and XPS analyses. In addition, the absorption and emission optical properties of Zn x Cd1 - x S QDs were red shifted with increasing the amount of Cd2+ in the alloyed nanocrystals, which have also increased the quantum yield compared to pure CdS and ZnS nanoparticles. These properties of alloyed nanomaterials were interpreted based on empirical model of Vegard's law and chemical bond model (CBM). As a proof of concept, these alloyed-QD conjugates were tested for biomedical and environmental applications. The results demonstrated that they were non-toxic and effective fluorophores for bioimaging live HEK293T cells (human embryonic kidney cells) using confocal laser scanning fluorescence microscopy. Moreover, these conjugates presented photocatalytic activity for photodegradation of methylene blue used as model organic industrial pollutant in water. Hence, composition-tunable optical properties of ternary Zn x Cd1 - x S ( x = 0-1) fluorescent alloyed QDs was achieved using a facile eco-friendly aqueous processing route, which can offer promising alternatives for developing innovative nanomaterials for applications in nanomedicine and environmental science and technology.

Sealing glasses for titanium and titanium alloys

DOEpatents

Brow, Richard K.; Watkins, Randall D.

1992-01-01

Glass compositions containing CaO, Al.sub.2 O.sub.3, B.sub.2 O.sub.3, SrO and BaO of various combinations of mole % are provided. These compositions are capable of forming stable glass-to-metal seals with titanium and titanium alloys, for use in components such as seals for battery headers.

Sealing glasses for titanium and titanium alloys

DOEpatents

Brow, R.K.; Watkins, R.D.

1988-01-21

Glass compositions containing CaO, Al/sub 2/O/sub 3/, B/sub 2/O/sub 3/, SrO and BaO of various combinations of mole % are provided. These compositions are capable of forming stable glass-to-metal seals with titanium and titanium alloys, for use in components such as seals for battery headers.

AN INVESTIGATION OF THE IMPACT OF ALLOY COMPOSITION AND PH ON THE CORROSION OF BRASS IN DRINKING WATER

EPA Science Inventory

A better understanding of brass corrosion may provide information and guidance on the use of the safest materials for the production of plumbing fixtures, and optimization of corrosion control treatments. The effect of alloy composition and pH on the metal leached from six differ...

Gold-nickel-titanium brazing alloy

DOEpatents

Mizuhara, Howard

1995-01-03

A brazing alloy in accordance with this invention has the following composition, by weight: 91 to 99 gold, 0.5 to 7% nickel; 0.10 to 2% titanium. Alternatively, with palladium present, the composition is as follows, by weight: 83 to 96% gold; 3 to 10% palladium; 0.5 to 5% nickel; 0.10 to 2% titanium.

Gold-nickel-titanium brazing alloy

DOEpatents

Mizuhara, Howard

1990-07-03

A brazing alloy in accordance with this invention has the following composition, by weight: 91 to 99% gold, 0.5 to 7% nickel; 0.10 to 2% titanium. Alternatively, with palladium present, the composition is as follows, by weight: 83 to 96% gold; 3 to 10% palladium; 0.5 to 5% nickel; 0.10 to 2% titanium.

Bimetallic Platinum-Rhodium Alloy Nanodendrites as Highly Active Electrocatalyst for the Ethanol Oxidation Reaction.

PubMed

Bai, Juan; Xiao, Xue; Xue, Yuan-Yuan; Jiang, Jia-Xing; Zeng, Jing-Hui; Li, Xi-Fei; Chen, Yu

2018-06-13

Rationally designing and manipulating composition and morphology of precious metal-based bimetallic nanostructures can markedly enhance their electrocatalytic performance, including selectivity, activity, and durability. We herein report the synthesis of bimetallic PtRh alloy nanodendrites (ANDs) with tunable composition by a facile complex-reduction synthetic method under hydrothermal conditions. The structural/morphologic features, formation mechanism, and electrocatalytic performance of PtRh ANDs are investigated thoroughly by various physical characterization and electrochemical methods. The preformed Rh crystal nuclei effectively catalyze the reduction of Pt 2+ precursor, resulting in PtRh alloy generation due to the catalytic growth and atoms interdiffusion process. The Pt atoms deposition distinctly interferes in Rh atoms deposition on Rh crystal nuclei, resulting in dendritic morphology of PtRh ANDs. For the ethanol oxidation reaction (EOR), PtRh ANDs display the chemical composition and solution pH co-dependent electrocatalytic activity. Because of the alloy effect and particular morphologic feature, Pt 1 Rh 1 ANDs with optimized composition exhibit better reactivity and stability for the EOR than commercial Pt nanocrystals electrocatalyst.

Wear Mechanism Maps for Magnesium Alloy AM60 and Composite AM60-9% (Al2O3)f

NASA Astrophysics Data System (ADS)

Ullah Khan, Muhammad Zafar

The purpose of this work was to study the tribological behaviour of squeeze cast Mg alloy AM60 and its composite AM60-9% (Al2O3) f. Dry sliding wear tests were performed on specimens of these materials using a block-on-ring tribometer which was equipped with a COF and temperature measurement system. Wear, COF and temperature maps were constructed to illustrate the effect of temperature and COF on the wear behaviour of the Mg alloy and it's composite. Four wear regimes namely low, mild, transient and severe wear were identified. The transition from mild to severe wear regime was found to be dependent on the bulk temperature of the specimen. Oxidational wear prevailed in low and mild wear whereas plastic deformation induced wear and melt wear controlled the wear rates in transient and severe wear regimes, respectively. This study shows that the incorporation of Al2O3 fibres in AM60 alloy improved the wear resistance of the resulting composite by delaying the transition from mild to severe wear.

Composite construction for nuclear fuel containers

DOEpatents

Cheng, B. C.; Rosenbaum, H. S.; Armijo, J. S.

1987-04-21

Disclosed is an improved method for producing nuclear fuel containers of a composite construction having components providing therein a barrier system for resisting destructive action by volatile fission products or impurities and also interdiffusion of metal constituents, and the product thereof. The composite nuclear fuel containers of the method comprise a casing of zirconium or alloy thereof with a layer of copper overlying an oxidized surface portion of the zirconium or alloy thereof. 1 fig.

Friction Stir Processing of Particle Reinforced Composite Materials

PubMed Central

Gan, Yong X.; Solomon, Daniel; Reinbolt, Michael

2010-01-01

The objective of this article is to provide a review of friction stir processing (FSP) technology and its application for microstructure modification of particle reinforced composite materials. The main focus of FSP was on aluminum based alloys and composites. Recently, many researchers have investigated this technology for treating other alloys and materials including stainless steels, magnesium, titanium, and copper. It is shown that FSP technology is very effective in microstructure modification of reinforced metal matrix composite materials. FSP has also been used in the processing and structure modification of polymeric composite materials. Compared with other manufacturing processes, friction stir processing has the advantage of reducing distortion and defects in materials. The layout of this paper is as follows. The friction stir processing technology will be presented first. Then, the application of this technology in manufacturing and structure modification of particle reinforced composite materials will be introduced. Future application of friction stir processing in energy field, for example, for vanadium alloy and composites will be discussed. Finally, the challenges for improving friction stir processing technology will be mentioned.

Zinc alloy enhances strength and creep resistance

DOE Office of Scientific and Technical Information (OSTI.GOV)

Machler, M.

1996-10-01

A family of high-performance ternary zinc-copper-aluminum alloys has been developed that provides higher strength, hardness, and creep resistance than the traditional zinc-aluminum alloys Zamak 3, Zamak 5, and ZA-8. Designated ACuZinc, mechanical properties comparable to those of more expensive materials make it suitable for high-load applications and those at elevated temperatures. This article describes the alloy`s composition, properties, and historical development.

Effects of recasting on the biocompatibility of a Ni-Cr alloy.

PubMed

Zhang, Chang Yuan; Cheng, Hui; Lin, Dong Hong; Zheng, Ming; Ozcan, Mutlu; Zhao, Wei; Yu, Hao

2012-01-01

To evaluate the effects of recasting on the biocompatibility of a commercially available Ni-Cr alloy. The alloy tested was cast and subsequently recast four more times. For each cast condition, 24 disk shaped specimens were fabricated (5 mm in diameter, 0.5 mm in thickness). All the recasting was performed without adding new alloy. After the first cast and following each recast, the surface composition and microstructure of the alloy were determined using an X-ray fluorescence spectrometer and optical microscope, respectively. The in vitro cytotoxicity and in vivo mucous irritation potential of the cast and recast Ni-Cr alloy were investigated. The results were statistically analysed at the significance level of 0.05. Recasting neither yielded to cytotoxicity or to changes in the surface composition of the Ni-Cr alloy tested. However, an increase in impurities and porosity of the surface structure was observed with recasting. Also, the segregation of the impurities to grain boundaries was evident after multiple castings. After the fourth recast, the alloys showed significantly greater mucosal irritation than the control. After fourth recast, the alloy of this type may contribute to mucosal inflammation. Furthermore, there is a need for diverse methods addressing different biological endpoints for the evaluation of dental alloys.

Design of Modern High Nb-Content gamma-gamma' Ni-Base Superalloys

NASA Astrophysics Data System (ADS)

Antonov, Stoichko

Certain elemental additions to Ni-base superalloys can significantly improve properties when added in high contents, but can quickly deteriorate the high temperature structural integrity and stability of the alloy, when solubility limits are exceeded and secondary phases are formed. Improved understanding of solubility limits of various elements in high refractory content Ni-base supralloys is therefore essential to improved alloy design. The morphology, formation, and composition of precipitate phases in a number of experimental alloys spanning a broad range of compositions were explored and compositional relationships were developed. The effect of increasing Nb alloying additions on formation and long term stability of topologically close packed (TCP) phases, as well as assessment of grain boundary phase compositions and local segregation along it before and after a 1000 hour thermal exposure at 800°C, was studied via electron microscopy and atom probe tomography (APT). Beneficial secondary phase precipitation, such as carbides and borides, was also studied through B, Hf and C doping. Elemental boron was observed to segregate to the grain boundary and phase interfaces, but did not form borides. APT studies on MC carbides of the alloys revealed the formation kinetics and morphological differences between NbC and Hf doped NbC, which were further explained using density functional theory (DFT) calculations of the formation energies of different facets of the MC carbide. Detailed electron microscopy and APT techniques were then used to systematically quantify the chemical and morphological instabilities that occur during aging of polycrystalline γ-γ' Ni-base superalloys containing elevated levels of refractory alloying additions. The morphological changes and splitting phenomenon associated with the secondary γ' precipitates were related to the discrete chemical compositions of the secondary and tertiary γ' along with the phase compositions of the γ matrix and the γ precipitates that form within the secondary γ' particles. In addition, compositions of the constituent phases were measured in four high Nb-content γ-γ' Ni-base superalloys and the results were compared to thermodynamic database models from Thermo-Calc. Results were also used to predict the solid solution strength behavior of the four alloys. Finally, creep behavior of high Nb-content γ-γ' Ni-Based superalloys was related to the formation of secondary phases mainly at grain boundaries. As secondary phases form, their brittle nature leads to crack formation, which can propagate under the tensile load and lead to premature failure of the alloy.

Effect of Composition of Alloys of Tin-Sodium Systems on Surface Tension

NASA Astrophysics Data System (ADS)

Alchagirov, B. B.; Kyasova, O. Kh.

2018-07-01

The results are presented from investigating the surface tensions of tin-sodium systems, along with original experimental data on the concentration dependences of the surface tensions of 19 tin-based sodium alloys obtained for samples of enhanced purity in a range of compositions with contents of 0.06 to 5.00 at % Na at T = 573 K. It is established that adding small amounts of sodium to tin greatly reduces the surface tensions of the studied melts. Calculations of sodium adsorption in alloys with tin show there is a maximum on the adsorption curve that corresponds to alloys with contents of around 1.5 at % Na in Sn.

Phase Composition and Hardening of Castable Al - Ca - Ni - Sc Alloys Containing 0.3% Sc

NASA Astrophysics Data System (ADS)

Belov, N. A.; Naumova, E. A.; Bazlova, T. A.; Doroshenko, V. V.

2017-05-01

The phase composition of aluminum alloys of the Al - Ca - Ni - Sc system containing 0.3 wt.% Sc is studied. It is shown that the aluminum solid solution may be in equilibrium not only with binary phases (Al4Ca, Al3Sc and Al3Ni) but also with a ternary Al9NiCa compound. The temperature of attainment of maximum hardening due to precipitation of nanoparticles of phase Al3Sc is determined for all the alloys studied. Principal possibility of creation of castable alloys based on an (Al) + Al4Ca + Al9NiCa eutectic, the hardening heat treatment of which does not require quenching, is substantiated.

Fe-based long range ordered alloys

DOEpatents

Liu, Chain T; Inouye, Henry; Schaffhauser, Anthony C.

1980-01-01

Malleable long range ordered alloys having high critical ordering temperatures exist in the V(Co,Fe).sub.3 and V(Co,Fe,Ni).sub.3 system having the composition comprising by weight 22-23% V, 35-50% Fe, 0-22% Co and 19-40% Ni with an electron density no greater than 8.00. Excellent high temperature properties occur in alloys having compositions comprising by weight 22-23% V, 35-45% Fe, 0-10% Co, 25-35% Ni; 22-23% V, 28-33% Ni and the remainder Fe; and 22-23% V, 19-22% Ni, 19-22% Co and the remainder Fe. The alloys are fabricable by casting, deforming and annealing for sufficient time to provide ordered structure.

Carbon fibers coated with graphene reinforced TiAl alloy composite with high strength and toughness.

PubMed

Cui, Sen; Cui, Chunxiang; Xie, Jiaqi; Liu, Shuangjin; Shi, Jiejie

2018-02-05

To meet the more rigorous requirement in aerospace industry, recent studies on strengthening and toughening TiAl alloys mostly focus on high Nb addition, which inevitably bring in an increasing of density. In this study, a carbon fibers coated with graphene reinforced TiAl alloy composite was fabricated by powder metallurgy, melt spun and vacuum melting. This composite got remarkable mechanical properties combined with a prominent density reduction. In contrast with pure TiAl ingots, this sample exhibits an average fracture strain from 16% up to 26.27%, and an average strength from 1801 MPa up to 2312 MPa. Thus, we can achieve a new method to fabricate this low-density, good mechanical performance TiAl composite which could bring in more opportunities for application in aerospace industry.

An Evaluation on the Smart Composite Damaged by Thermal Shock

NASA Astrophysics Data System (ADS)

Lee, Jin Kyung; Lee, Sang Pill; Park, Young Chul; Lee, Joon Hyun

A shape memory alloy (SMA) as part of some products and system has been used to keep their shape at any specified temperature. By using this characteristic of the shape memory alloy it can be solved the problem of the residual stress by difference of coefficients of thermal expansion between reinforcement and matrix within composite. In this study, TiNi/Al6061 shape memory alloy composite was fabricated through hot press method, and the optimal fabrication condition was created. The bonding effect of the matrix and the reinforcement within the SMA composite was strengthened by cold rolling. The SMA composite can be applied as the part of airplane and vessel, and used under tough condition of repetitive thermal shock cycles of high and low temperatures. Therefore, the thermal shock test was performed for the SMA composite, and mechanical properties were evaluated. The tensile strength of the SMA composite showed a slight decline with the thermal shock cycles. In addition, acoustic emission (AE) technique was used to quantify the microscopic damage behavior of cold rolled TiNi/Al6061 shape memory alloy composite that underwent thermal shock cycles. The damage degree on the specimen that underwent thermal shock cycles was discussed. Actually AE parameters such as AE event, count and energy was analyzed, and these parameters was useful to evaluate the damage behavior and degree of the SMA composite. The waveform of the signal caused by debonding was pulse type, and showed the frequency range of 160 kHz, however, the signal by the fiber fracture showed the pulse type of high magnitude and frequency range of 220 kH.

[Microanalytical determinations of gold alloys for fixed dentures].

PubMed

Lotito, M; Negri, P; Fraschini, M

1993-01-01

In this work the authors analyse gold alloys for fixed prosthesis by X-ray spectrometry in energy dispersion (EDS). The results of this analysis, given in graphic and table form, show remarkable differences in alloy composition. For this reason recommended dentists are to be attentive and severe in the control of gold alloys for fixed prosthesis.

Study on erosion behaviour of hybrid aluminium composite

NASA Astrophysics Data System (ADS)

Vishwas, D. K.; Chandrappa, C. N.; Venkatesh, Shreyas

2018-04-01

The origin of the light metals, as compared to other metals in this century, is noticeable and an exciting area of expansion for innovation. Light metals, are need of the day in engineering, among them application of aluminium and its alloys is enormous. we observe that these metals tend to have a progressive loss of metal from having contact surface with other metals. Erosion is one such wear process, where damage occurs by the repeated application of high localised stresses. Erosion due to impact of solid particle, is a significant problem. In the present work, the erosion behaviour of hybrid aluminium composite is studied. AL 6061 is used as the base alloy. AL 6061 alloy has excellent corrosion resistance but poor wear resistance. So, in order to have improved properties, it is reinforced with Tungsten Chromium Nickel powder in varied proportions by the method of stir casting. The results are compared with the as-cast Al-alloy to determine the improvement in mechanical properties. The tests were conducted in ASTM G76 setup, to determine solid particle erosion behaviour and the results of the hybrid composite were compared with that of as-cast AL 6061 alloy. It was evident that mass loss was maximum at 300 inclinations, which is a characteristic of ductile materials. It was observed that upon increasing the percentages of reinforcement (wt.%), the wear resistance of the hybrid composite increased significantly. It was also observed that the inclusion of tungsten-chromium-nickel powder increased the hardness of the hybrid composite significantly.

Evaluation of two dual-functional primers and a tribochemical surface modification system applied to the bonding of an indirect composite resin to metals.

PubMed

Yanagida, Hiroaki; Tanoue, Naomi; Ide, Takako; Matsumura, Hideo

2009-07-01

We evaluated the effects of two dual-functional primers and a tribochemical surface modification system on the bond strength between an indirect composite resin and gold alloy or titanium. Disk specimens (diameter, 10 mm; thickness, 2.5 mm) were cast from type 4 gold alloy and commercially pure titanium. The specimens were wetground to a final surface finish using 600-grit silicone carbide paper. The specimens were then air-dried and treated using the following four bonding systems: (1) air-abrasion with 50-70 mum alumina, (2) system 1 + alloy primer, (3) system 1 + metal link primer, and (4) tribochemical silica/silane coating (Rocatec). A light-polymerizing indirect composite resin (Ceramage) was applied to each metal specimen and polymerized according to the manufacturer's specifications. Shear bond strengths (MPa) were determined both before and after thermocycling (4 degrees C and 60 degrees C for 1 min each for 20 000 cycles). The values were compared using analysis of variance, post hoc Scheffe tests, and Mann-Whitney U tests (alpha = 0.05). The strengths decreased after thermocycling for all combinations. For both gold alloy and titanium, the bond strength with air-abrasion only was statistically lower than that with the other three modification methods after thermocycling. Titanium exhibited a significantly higher value (13.4 MPa) than gold alloy (10.5 MPa) with the air. abrasion and alloy primer system. Treatment with the tribochemical system or air abrasion followed by treatment with dual-functional priming agents was found to be effective for enhancement of the bonding between the indirect composite and gold alloy or titanium.

Synthesis of Amorphous Powders of Ni-Si and Co-Si Alloys by Mechanical Alloying

NASA Astrophysics Data System (ADS)

Omuro, Keisuke; Miura, Harumatsu

1991-05-01

Amorphous powders of the Ni-Si and Co-Si alloys are synthesized by mechanical alloying (MA) from crystalline elemental powders using a high energy ball mill. The alloying and amorphization process is examined by X-ray diffraction, differential scanning calorimetry (DSC), and scanning electron microscopy. For the Ni-Si alloy, it is confirmed that the crystallization temperature of the MA powder, measured by DSC, is in good agreement with that of the powder sample prepared by mechanical grinding from the cast alloy ingot products of the same composition.

Evaluation on the Effect of Composition on Radiation Hardening and Embrittlement in Model FeCrAl Alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, Kevin G.; Briggs, Samuel A.; Edmondson, Philip

2015-09-18

This report details the findings of post-radiation mechanical testing and microstructural characterization performed on a series of model and commercial FeCrAl alloys to assist with the development of a cladding technology with enhanced accident tolerance. The samples investigated include model alloys with simple ferritic grain structure and two commercial alloys with minor solute additions. These samples were irradiated in the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) up to nominal doses of 7.0 dpa near or at Light Water Reactor (LWR) relevant temperatures (300-400 C). Characterization included a suite of techniques including small angle neutron scatteringmore » (SANS), atom probe tomography (APT), and transmission based electron microscopy techniques. Mechanical testing included tensile tests at room temperature on sub-sized tensile specimens. The goal of this work was to conduct detailed characterization and mechanical testing to begin establishing empirical and/or theoretical structure-property relationships for radiation-induced hardening and embrittlement in the FeCrAl alloy class. Development of such relationships will provide insight on the performance of FeCrAl alloys in an irradiation environment and will enable further development of the alloy class for applications within a LWR environment. A particular focus was made on establishing trends, including composition and radiation dose. The report highlights in detail the pertinent findings based on this work. This report shows that radiation hardening in the alloys is primarily composition dependent due to the phase separation in the high-Cr FeCrAl alloys. Other radiation induced/enhanced microstructural features were less dependent on composition and when observed at low number densities, were not a significant contributor to the observed mechanical responses. Pre-existing microstructure in the alloys was found to be important, with grain boundaries and pre-existing dislocation networks acting as defect sinks, resulting in variations in the observed microstructures after irradiation. Dose trends were also observed, with increasing radiation dose promoting changes in the size and number density of the Cr-rich α' precipitates. Based on the microstructural analysis, performed tensile testing, and prior knowledge from FeCr literature it was hypothesized that the formation of the Cr-rich α' precipitates could lead to significant radiation-induced embrittlement in the alloys, and this could be composition dependent, a result which would mirror the trends observed for radiation-induced hardening. Due to the limited database on embrittlement in the FeCrAl alloy class after irradiation, a series of radiation experiments have been implemented. The overarching point of view within this report is the radiation tolerance of FeCrAl is complex, with many mechanisms and factors to be considered at once. Further development of the FeCrAl alloy class for enhanced accident tolerant applications requires detailed, single (or at least limited) variable experiments to fully comprehend and predict the performance of this alloy in LWRs. This report has been submitted as fulfillment of milestone M2FT-15OR0202321 titled, Summary report on the effect of composition on the irradiation embrittlement of Gen 1 ATF FeCrAl for the Department of Energy Office of Nuclear Energy, Advanced Fuel Campaign of the Fuel Cycle R&D program.« less

Computational Thermodynamic Study to Predict Complex Phase Equilibria in the Nickel-Base Superalloy Rene N6

NASA Technical Reports Server (NTRS)

Copland, Evan H.; Jacobson, Nathan S.; Ritzert, Frank J.

2001-01-01

A previous study by Ritzert et al. on the formation and prediction of topologically closed packed (TCP) phases in the nickel-base superalloy Rene' N6 is re-examined with computational thermodynamics. The experimental data on phase distribution in forty-four alloys with a composition within the patent limits of the nickel-base superalloy Rene' N6 provide a good basis for comparison to and validation of a commercial nickel superalloy database used with ThermoCalc. Volume fraction of the phases and partitioning of the elements are determined for the forty-four alloys in this dataset. The baseline heat treatment of 400 h at 1366 K was used. This composition set is particularly interesting since small composition differences lead to dramatic changes in phase composition. In general the calculated values follow the experimental trends. However, the calculations indicated no TCP phase formation when the experimental measurements gave a volume percent of TCP phase less than 2 percent. When TCP phases were predicted, the calculations under-predict the volume percent of TCP phases by a factor of 2 to 8. The calculated compositions of the gamma and gamma' phases show fair agreement with the measurements. However, the calculated compositions of the P Phase do not agree with those measured. This may be due to inaccuracies in the model parameters for P phase and/or issues with the microprobe analyses of these phases. In addition, phase fraction diagrams and sigma and P phase solvus temperatures are calculated for each of the alloys. These calculations indicate that P phase is the primary TCP phase formed for the alloys considered here at 1366 K. Finally, a series of isopleths are calculated for each of the seven alloying elements. These show the effect of each alloying element on creating TCP phases.

Investigation on the morphological and optical evolution of bimetallic Pd-Ag nanoparticles on sapphire (0001) by the systematic control of composition, annealing temperature and time

PubMed Central

Pandey, Puran; Kunwar, Sundar; Sui, Mao; Bastola, Sushil

2017-01-01

Multi-metallic alloy nanoparticles (NPs) can offer additional opportunities for modifying the electronic, optical and catalytic properties by the control of composition, configuration and size of individual nanostructures that are consisted of more than single element. In this paper, the fabrication of bimetallic Pd-Ag NPs is systematically demonstrated via the solid state dewetting of bilayer thin films on c-plane sapphire by governing the temperature, time as well as composition. The composition of Pd-Ag bilayer remarkably affects the morphology of alloy nanostructures, in which the higher Ag composition, i.e. Pd0.25Ag0.75, leads to the enhanced dewetting of bilayers whereas the higher Pd composition (Pd0.75Ag0.25) hinders the dewetting. Depending on the annealing temperature, Pd-Ag alloy nanostructures evolve with a series of configurations, i.e. nucleation of voids, porous network, elongated nanoclusters and round alloy NPs. In addition, with the annealing time set, the gradual configuration transformation from the elongated to round alloy NPs as well as size reduction is demonstrated due to the enhanced diffusion and sublimation of Ag atoms. The evolution of various morphology of Pd-Ag nanostructures is described based on the surface diffusion and inter-diffusion of Pd and Ag adatoms along with the Ag sublimation, Rayleigh instability and energy minimization mechanism. The reflectance spectra of bimetallic Pd-Ag nanostructures exhibit various quadrupolar and dipolar resonance peaks, peak shifts and absorption dips owing to the surface plasmon resonance of nanostructures depending on the surface morphology. The intensity of reflectance spectra is gradually decreased along with the surface coverage and NP size evolution. The absorption dips are red-shifted towards the longer wavelength for the larger alloy NPs and vice-versa. PMID:29253017

High strength alloys

DOEpatents

Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub

2012-06-05

High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.

High strength alloys

DOEpatents

Maziasz, Phillip James [Oak Ridge, TN; Shingledecker, John Paul [Knoxville, TN; Santella, Michael Leonard [Knoxville, TN; Schneibel, Joachim Hugo [Knoxville, TN; Sikka, Vinod Kumar [Oak Ridge, TN; Vinegar, Harold J [Bellaire, TX; John, Randy Carl [Houston, TX; Kim, Dong Sub [Sugar Land, TX

2010-08-31

High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

Bond-strength inversion in (In,Ga)As semiconductor alloys

NASA Astrophysics Data System (ADS)

Eckner, Stefanie; Ritter, Konrad; Schöppe, Philipp; Haubold, Erik; Eckner, Erich; Rensberg, Jura; Röder, Robert; Ridgway, Mark C.; Schnohr, Claudia S.

2018-05-01

The atomic-scale structure and vibrational properties of semiconductor alloys are determined by the energy required for stretching and bending the individual bonds. Using temperature-dependent extended x-ray absorption fine-structure spectroscopy, we have determined the element-specific In-As and Ga-As effective bond-stretching force constants in (In,Ga)As as a function of the alloy composition. The results reveal a striking inversion of the bond strength where the originally stiffer bond in the parent materials becomes the softer bond in the alloy and vice versa. Our findings clearly demonstrate that changes of both the individual bond length and the surrounding matrix affect the bond-stretching force constants. We thus show that the previously used common assumptions about the element-specific force constants in semiconductor alloys do not reproduce the composition dependence determined experimentally for (In,Ga)As.

Thermodynamic modeling and experimental validation of the Fe-Al-Ni-Cr-Mo alloy system

DOE Office of Scientific and Technical Information (OSTI.GOV)

Teng, Zhenke; Zhang, F; Miller, Michael K

2012-01-01

NiAl-type precipitate-strengthened ferritic steels have been known as potential materials for the steam turbine applications. In this study, thermodynamic descriptions of the B2-NiAl type nano-scaled precipitates and body-centered-cubic (BCC) Fe matrix phase for four alloys based on the Fe-Al-Ni-Cr-Mo system were developed as a function of the alloy composition at the aging temperature. The calculated phase structure, composition, and volume fraction were validated by the experimental investigations using synchrotron X-ray diffraction and atom probe tomography. With the ability to accurately predict the key microstructural features related to the mechanical properties in a given alloy system, the established thermodynamic model inmore » the current study may significantly accelerate the alloy design process of the NiAl-strengthened ferritic steels.« less

Method for joining carbon-carbon composites to metals

DOEpatents

Lauf, Robert J.; McMillan, April D.; Moorhead, Arthur J.

1997-01-01

A method for joining carbon-carbon composites to metals by brazing. Conventional brazing of recently developed carbon-bonded carbon fiber (CBCF) material to a metal substrate is limited by the tendency of the braze alloy to "wick" into the CBCF composite rather than to form a strong bond. The surface of the CBCF composite that is to be bonded is first sealed with a fairly dense carbonaceous layer achieved by any of several methods. The sealed surface is then brazed to the metal substrate by vacuum brazing with a Ti-Cu-Be alloy.

Method for joining carbon-carbon composites to metals

DOEpatents

Lauf, R.J.; McMillan, A.D.; Moorhead, A.J.

1997-07-15

A method for joining carbon-carbon composites to metals by brazing. Conventional brazing of recently developed carbon-bonded carbon fiber (CBCF) material to a metal substrate is limited by the tendency of the braze alloy to ``wick`` into the CBCF composite rather than to form a strong bond. The surface of the CBCF composite that is to be bonded is first sealed with a fairly dense carbonaceous layer achieved by any of several methods. The sealed surface is then brazed to the metal substrate by vacuum brazing with a Ti-Cu-Be alloy. 1 fig.

van der Waals epitaxial two-dimensional CdSxSe(1-x) semiconductor alloys with tunable-composition and application to flexible optoelectronics.

PubMed

Xia, Jing; Zhao, Yun-Xuan; Wang, Lei; Li, Xuan-Ze; Gu, Yi-Yi; Cheng, Hua-Qiu; Meng, Xiang-Min

2017-09-21

Despite the substantial progress in the development of two-dimensional (2D) materials from conventional layered crystals, it still remains particularly challenging to produce high-quality 2D non-layered semiconductor alloys which may bring in some unique properties and new functions. In this work, the synthesis of well-oriented 2D non-layered CdS x Se (1-x) semiconductor alloy flakes with tunable compositions and optical properties is established. Structural analysis reveals that the 2D non-layered alloys follow an incommensurate van der Waals epitaxial growth pattern. Photoluminescence measurements show that the 2D alloys have composition-dependent direct bandgaps with the emission peak varying from 1.8 eV to 2.3 eV, coinciding well with the density functional theory calculations. Furthermore, photodetectors based on the CdS x Se (1-x) flakes exhibit a high photoresponsivity of 703 A W -1 with an external quantum efficiency of 1.94 × 10 3 and a response time of 39 ms. Flexible devices fabricated on a thin mica substrate display good mechanical stability upon repeated bending. This work suggests a facile and general method to produce high-quality 2D non-layered semiconductor alloys for next-generation optoelectronic devices.

Metal release rate from AISI 316L stainless steel and pure Fe, Cr and Ni into a synthetic biological medium--a comparison.

PubMed

Herting, G; Wallinder, I Odnevall; Leygraf, C

2008-09-01

Metal release rates from stainless steel grade 316L were investigated in artificial lysosomal fluid (ALF), simulating a human inflammatory cell response. The main focus was placed on release rates of main alloying elements using graphite furnace atomic absorption spectroscopy, and changes in surface oxide composition by means of X-ray photoelectron spectroscopy. To emphasise that alloys and pure metals possess totally different intrinsic properties, comparative studies were performed on the pure alloying constituents: iron, nickel and chromium. Significant differences in release rates were observed due to the presence of a passive surface film on stainless steel. Iron and nickel were released at rates more than 300 times lower from the 316L alloy compared with the pure metals whereas the release rate of chromium was similar. Iron was preferentially released compared with nickel and chromium. Immersion in ALF resulted in the gradual enrichment of chromium in the surface film, a small increase of nickel, and the reduction of oxidized iron with decreasing release rates of alloy constituents as a result. As expected, released metals from stainless steel grade 316L were neither in proportion to the bulk alloy composition nor to the surface film composition.

In vitro degradation of MAO/PLA coating on Mg-1.21Li-1.12Ca-1.0Y alloy

NASA Astrophysics Data System (ADS)

Zeng, Rong-Chang; Qi, Wei-Chen; Song, Ying-Wei; He, Qin-Kun; Cui, Hong-Zhi; Han, En-Hou

2014-12-01

Magnesium and its alloys are promising biomaterials due to their biocompatibility and osteoinduction. The plasticity and corrosion resistance of commercial magnesium alloys cannot meet the requirements for degradable biomaterials completely at present. Particularly, the alkalinity in the microenvironment surrounding the implants, resulting from the degradation, arouses a major concern. Micro-arc oxidation (MAO) and poly(lactic acid) (PLA) composite (MAO/PLA) coating on biomedical Mg-1.21Li-1.12Ca-1.0Y alloy was prepared to manipulate the pH variation in an appropriate range. Surface morphologies were discerned using SEM and EMPA. And corrosion resistance was evaluated via electrochemical polarization and impedance and hydrogen volumetric method. The results demonstrated that the MAO coating predominantly consisted of MgO, Mg2SiO4 and Y2O3. The composite coating markedly improved the corrosion resistance of the alloy. The rise in solution pH for the MAO/PLA coating was tailored to a favorable range of 7.5-7.8. The neutralization caused by the alkalinity of MAO and Mg substrate and acidification of PLA was probed. The result designates that MAO/PLA composite coating on Mg-1.21Li-1.12Ca-1.0Y alloys may be a promising biomedical coating.

Effects of Precipitant and pH on Coprecipitation of Nanosized Co-Cr-V Alloy Powders

PubMed Central

Chen, Xiaoyu; Li, Yongxia; Huang, Lan; Zou, Dan; Wu, Enxi; Liu, Yanjun; Xie, Yuanyan; Yao, Rui; Liao, Songyi; Wang, Guangrong

2017-01-01

Nanosized Co-Cr-V alloy powders were synthesized via coprecipitation method. Effects of precipitants ((NH4)2C2O4·H2O and Na2CO3) and pH were investigated by X-ray diffraction (XRD), Zeta potential analyzer, thermogravimetry-differential scanning calorimetry (TG-DSC), inductively coupled plasma-atomic emission spectrometry (ICP-AES) and scanning electron microscopy (SEM). Co-Cr-V alloy powders were consisted of major face-centered cubic Co (fcc Co) and minor hexagonal close-packed Co (hcp Co). Grain sizes of precursors and Co-Cr-V alloy powders were increased with pH value (7–10) within the ranges of 3~39 and 39~66 nm, respectively. Rod-like or granular Co-Cr-V alloy particles were assembled by interconnected nanograins. At pH = 7, Na2CO3 precipitant was found to be beneficial to maintain the desirable composition of Co-Cr-V powders. It was also found that lower pH favors the maintenance of pre-designed composition, while grain coarsens at higher pH. Effects of variation for precipitant and pH on the morphology and composition of Co-Cr-V alloy powder were discussed in detail and relevant mechanism was further proposed. PMID:28934147

Precipitation Strengthenable NiTiPd High Temperature Shape Memory Alloys

NASA Technical Reports Server (NTRS)

Bigelow, Glen; Garg, Anita; Benafan, Othmane; Noebe, Ronald; Gaydosh, Darrell; Padula, Santo, II

2017-01-01

In binary NiTi alloys, it has long been known that Ni-rich alloys can be heat treated to produce precipitates which both strengthen the matrix against dislocations and improve the behavior of the material under thermal and mechanical cycling. Within recent years, the same effect has been observed in Ni-rich NiTiHf high temperature shape memory alloys and heat treatment regimens have been defined which will reliably produce improved properties. In NiTiPd alloys, precipitation has also been observed, but studies are still underway to define reliable heat treatments and compositions which will provide a balance of strengthening and good thermomechanical properties. For this study, a series of NiTi-32 at.Pd alloys was produced to determine the effect of changing nickeltitanium content on the transformation behavior and heat treatability of the material. Samples were aged at temperatures between 350C and 450C for times up to 100 hours. Actuation type behavior was evaluated using uniaxial constant force thermal cycling (UCFTC) to determine the effect of composition and aging on the material behavior. TEMSEM was used to evaluate the microstructure and determine the types of precipitates formed. The correlation between composition, heat treat, microstructure, and thermomechanical behavior will be addressed and discussed.

Size, shape, and compositional effects on the order-disorder phase transitions in Au-Cu and Pt-M (M = Fe, Co, and Ni) nanocluster alloys.

PubMed

Kaatz, Forrest H; Bultheel, Adhemar

2018-08-24

Au-Cu and Pt-M (M = Fe, Co, and Ni) nanocluster alloys are currently being investigated world-wide by many researchers for their interesting catalytic and nanophase properties. The low temperature behavior of the phase diagrams is not well understood for alloys with nanometer sizes and shapes. We consider two models for low temperature ordering in the phase diagrams of Au-Cu and Pt-M nanocluster alloys. These models are valid for sizes ∼5 nm and approach bulk values for sizes ∼20 nm. We study the phase transitions in nanoclusters with cubic, octahedral, and cuboctahedral shapes, covering the compositions of interest. These models are based on studying the melting temperatures in nanoclusters using the regular solution, mixing model for alloys. From our data, experiments on nanocubes about 5 nm in size, of stoichiometric AuCu and PtM composition, could help differentiate between the models. Dispersion data shows that for the three shapes considered, octahedra have the highest percentage of surface atoms for the same relative diameter. We summarize the effects of structural ordering on the catalytic activity and suggest a method to avoid sintering during annealing of Pt-M alloys.

Compositional Control of the Mixed Anion Alloys in Gallium-Free InAs/InAsSb Superlattice Materials for Infrared Sensing (Postprint)

DTIC Science & Technology

2015-08-28

AFRL-RX-WP-JA-2016-0251 COMPOSITIONAL CONTROL OF THE MIXED ANION ALLOYS IN GALLIUM -FREE InAs/InAsSb SUPERLATTICE MATERIALS FOR...ANION ALLOYS IN GALLIUM -FREE InAs/InAsSb SUPERLATTICE MATERIALS FOR INFRARED SENSING (POSTPRINT) 5a. CONTRACT NUMBER FA8650-07-D-5800-0006 5b...proceedings.spiedigitallibrary.org doi: 10.1117/12.2186188 14. ABSTRACT (Maximum 200 words) Gallium (Ga)-free InAs/InAsSb superlattices (SLs) are being actively explored for

Synthesis of high T.sub.C superconducting coatings and patterns by melt writing and oxidation of metallic precursor alloys

DOEpatents

Gao, Wei; Vander Sande, John B.

1998-01-01

A method is provided for fabrication of superconducting oxides and superconducting oxide composites and for joining superconductors to other materials. A coating of a molten alloy containing the metallic elements of the oxide is applied to a substrate surface and oxidized to form the superconducting oxide. A material can be contacted to the molten alloy which is subsequently oxidized joining the material to the resulting superconducting oxide coating. Substrates of varied composition and shape can be coated or joined by this method.

Synthesis of high {Tc} superconducting coatings and patterns by melt writing and oxidation of metallic precursor alloys

DOEpatents

Gao, W.; Vander Sande, J.B.

1998-07-28

A method is provided for fabrication of superconducting oxides and superconducting oxide composites and for joining superconductors to other materials. A coating of a molten alloy containing the metallic elements of the oxide is applied to a substrate surface and oxidized to form the superconducting oxide. A material can be contacted to the molten alloy which is subsequently oxidized joining the material to the resulting superconducting oxide coating. Substrates of varied composition and shape can be coated or joined by this method. 5 figs.

Elastic anomalies in Fe-Cr alloys

NASA Astrophysics Data System (ADS)

Zhang, Hualei; Wang, Guisheng; Punkkinen, Marko P. J.; Hertzman, Staffan; Johansson, Börje; Vitos, Levente

2013-05-01

Using ab initio alloy theory, we determine the elastic parameters of ferromagnetic and paramagnetic Fe1-cCrc (0 ≤ c ≤ 1) alloys in the body centered cubic crystallographic phase. Comparison with the experimental data demonstrates that the employed theoretical approach accurately describes the observed composition dependence of the polycrystalline elastic moduli. The predicted single-crystal elastic constants follow complex anomalous trends, which are shown to originate from the interplay between magnetic and chemical effects. The nonmonotonic composition dependence of the elastic parameters has marked implications on the micro-mechanical properties of ferrite stainless steels.

Effect of Low-Melting Metals (Pb, Bi, Cd, In) on the Structure, Phase Composition, and Properties of Casting Al-5% Si-4% Cu Alloy

NASA Astrophysics Data System (ADS)

Yakovleva, A. O.; Belov, N. A.; Bazlova, T. A.; Shkalei, I. V.

2018-01-01

The effect of low-melting metals (Pb, Bi, Cd, In) on the structure, phase composition, and properties of the Al-5% Si-4% Cu alloy was studied using calculations. Polythermal sections have been reported, which show that the considered systems are characterized by the presence of liquid regions and monotectic reactions. The effect of low-melting metals on the microstructure and hardening of base alloy in the cast and heat-treated states has been studied.

Ni-P/Zn-Ni compositionally modulated multilayer coatings - Part 1: Electrodeposition and growth mechanism, composition, morphology, roughness and structure

NASA Astrophysics Data System (ADS)

Bahadormanesh, Behrouz; Ghorbani, Mohammad

2018-06-01

The Ni-P/Zn-Ni compositionally modulated multilayer coatings CMMCs were electrodeposited from a single bath by switching the cathodic current density. The composition, surface morphology, roughness, layers growth pattern as well as the phase structure of deposits were extensively studied via SEM, EDS, AFM and XRD analysis. Effects of bath ingredients on the electrodeposition behavior were analyzed through cathodic linear sweep voltammetry. Although the concentration of Zn2+ in bath was 13 times higher than Ni2+, the Zn-Ni deposition potential was much nearer to Ni deposition potential rather than that of Zn. Addition of NaH2PO2 to the Ni deposition bath considerably raised the current density and shifted the crystallization potential of Ni to more nobble values. Codeposition of P with Zn-Ni alloy lead to crack formation in the monolayer that was deposited in 60 mA/cm2. However, the cracks were not observed in the Zn-Ni layers of multilayers. Zn-Ni layers in CMMCs exhibited a three-dimensional pattern of growth while that of Ni-P layers was two-dimensional. Also, the Ni-P deposits tends to fill the discontinuities in Zn-Ni layers and performed leveling properties and lowered the surface roughness of Zn-Ni layers and CMMCs. Structural analysis demonstrated that Ni-P layers were amorphous and the Zn-Ni layers exhibited crystallite phase of Zn11Ni2. Thus, the Ni-P/Zn-Ni CMMCs comprised of alternate layers of amorphous Ni-P and nanocrystalline Zn Ni.

In situ synthesized TiB-TiN reinforced Ti6Al4V alloy composite coatings: microstructure, tribological and in-vitro biocompatibility.

PubMed

Das, Mitun; Bhattacharya, Kaushik; Dittrick, Stanley A; Mandal, Chitra; Balla, Vamsi Krishna; Sampath Kumar, T S; Bandyopadhyay, Amit; Manna, Indranil

2014-01-01

Wear resistant TiB-TiN reinforced Ti6Al4V alloy composite coatings were deposited on Ti substrate using laser based additive manufacturing technology. Ti6Al4V alloy powder premixed with 5wt% and 15wt% of boron nitride (BN) powder was used to synthesize TiB-TiN reinforcements in situ during laser deposition. Influences of laser power, scanning speed and concentration of BN on the microstructure, mechanical, in vitro tribological and biological properties of the coatings were investigated. Microstructural analysis of the composite coatings showed that the high temperature generated due to laser interaction with Ti6Al4V alloy and BN results in situ formation of TiB and TiN phases. With increasing BN concentration, from 5wt% to 15wt%, the Young's modulus of the composite coatings, measured by nanoindentation, increased from 170±5GPa to 204±14GPa. In vitro tribological tests showed significant increase in the wear resistance with increasing BN concentration. Under identical test conditions TiB-TiN composite coatings with 15wt% BN exhibited an order of magnitude less wear rate than CoCrMo alloy-a common material for articulating surfaces of orthopedic implants. Average top surface hardness of the composite coatings increased from 543±21HV to 877±75HV with increase in the BN concentration. In vitro biocompatibility and flow cytometry study showed that these composite coatings were non-toxic, exhibit similar cell-materials interactions and biocompatibility as that of commercially pure titanium (CP-Ti) samples. In summary, excellent in vitro wear resistance, high stiffness and suitable biocompatibility make these composite coatings as a potential material for load-bearing articulating surfaces towards orthopaedic implants. © 2013 Elsevier Ltd. All rights reserved.

Metastable high-entropy dual-phase alloys overcome the strength-ductility trade-off.

PubMed

Li, Zhiming; Pradeep, Konda Gokuldoss; Deng, Yun; Raabe, Dierk; Tasan, Cemal Cem

2016-06-09

Metals have been mankind's most essential materials for thousands of years; however, their use is affected by ecological and economical concerns. Alloys with higher strength and ductility could alleviate some of these concerns by reducing weight and improving energy efficiency. However, most metallurgical mechanisms for increasing strength lead to ductility loss, an effect referred to as the strength-ductility trade-off. Here we present a metastability-engineering strategy in which we design nanostructured, bulk high-entropy alloys with multiple compositionally equivalent high-entropy phases. High-entropy alloys were originally proposed to benefit from phase stabilization through entropy maximization. Yet here, motivated by recent work that relaxes the strict restrictions on high-entropy alloy compositions by demonstrating the weakness of this connection, the concept is overturned. We decrease phase stability to achieve two key benefits: interface hardening due to a dual-phase microstructure (resulting from reduced thermal stability of the high-temperature phase); and transformation-induced hardening (resulting from the reduced mechanical stability of the room-temperature phase). This combines the best of two worlds: extensive hardening due to the decreased phase stability known from advanced steels and massive solid-solution strengthening of high-entropy alloys. In our transformation-induced plasticity-assisted, dual-phase high-entropy alloy (TRIP-DP-HEA), these two contributions lead respectively to enhanced trans-grain and inter-grain slip resistance, and hence, increased strength. Moreover, the increased strain hardening capacity that is enabled by dislocation hardening of the stable phase and transformation-induced hardening of the metastable phase produces increased ductility. This combined increase in strength and ductility distinguishes the TRIP-DP-HEA alloy from other recently developed structural materials. This metastability-engineering strategy should thus usefully guide design in the near-infinite compositional space of high-entropy alloys.

The microstructure and precipitation effects in Inconel alloy 690

NASA Astrophysics Data System (ADS)

Smith, Alan J.

Failure of Alloy 600 steam generator tubing in Pressurised Water Reactors (PWRs) has prompted the investigation of alloy 690 as an alternative material. Six commercially produced tubes and ten experimentally produced alloys have been examined with varying amounts of carbon, aluminium and titanium. Alloy compositions have been selected to investigate the individual and combined effects of these elements on the microstructure and corrosion behaviour in the environments of corrosion tests and simulated PWR conditions. Alloys were subjected to simulated mill annealing treatments at varied temperatures. Microstructural characterisation using optical and electron microscopy has demonstrated the effects of composition and thermal treatment in controlling grain size and carbide precipitation together with the interdependence between these structural details. Stress corrosion resistance of selected alloy 690 tubes has been examined with samples in an autoclave at fixed temperatures with environments based on pure water, sodium hydroxide and sodium hydroxide + sodium sulphate solutions. Susceptibility to intergranular attack has been related to aluminium contents of the alloy and to thermal treatments given. Results suggest a decreased resistance to IGA when aluminium is increased. Thermal treatments given to the samples appear not to be very significant to the amounts of IGA. The compositions and heat treatments used in the corrosion study were further examined on a dedicated scanning transmission electron microscope in order to correlate the effects of, chromium depletion, nickel enrichment and impurity segregation at grain boundaries, with corrosion characteristics. These results have shown the effect of varying the special thermal treatment temperature and time on the degree of enrichment / depletion / segregation and the corrosion resistance of the alloy. The mechanism of protection afforded by the special thermal treatment can thus be elucidated.

Metastable high-entropy dual-phase alloys overcome the strength-ductility trade-off

NASA Astrophysics Data System (ADS)

Li, Zhiming; Pradeep, Konda Gokuldoss; Deng, Yun; Raabe, Dierk; Tasan, Cemal Cem

2016-06-01

Metals have been mankind’s most essential materials for thousands of years; however, their use is affected by ecological and economical concerns. Alloys with higher strength and ductility could alleviate some of these concerns by reducing weight and improving energy efficiency. However, most metallurgical mechanisms for increasing strength lead to ductility loss, an effect referred to as the strength-ductility trade-off. Here we present a metastability-engineering strategy in which we design nanostructured, bulk high-entropy alloys with multiple compositionally equivalent high-entropy phases. High-entropy alloys were originally proposed to benefit from phase stabilization through entropy maximization. Yet here, motivated by recent work that relaxes the strict restrictions on high-entropy alloy compositions by demonstrating the weakness of this connection, the concept is overturned. We decrease phase stability to achieve two key benefits: interface hardening due to a dual-phase microstructure (resulting from reduced thermal stability of the high-temperature phase); and transformation-induced hardening (resulting from the reduced mechanical stability of the room-temperature phase). This combines the best of two worlds: extensive hardening due to the decreased phase stability known from advanced steels and massive solid-solution strengthening of high-entropy alloys. In our transformation-induced plasticity-assisted, dual-phase high-entropy alloy (TRIP-DP-HEA), these two contributions lead respectively to enhanced trans-grain and inter-grain slip resistance, and hence, increased strength. Moreover, the increased strain hardening capacity that is enabled by dislocation hardening of the stable phase and transformation-induced hardening of the metastable phase produces increased ductility. This combined increase in strength and ductility distinguishes the TRIP-DP-HEA alloy from other recently developed structural materials. This metastability-engineering strategy should thus usefully guide design in the near-infinite compositional space of high-entropy alloys.

Comparison of the tensile bond strength of high-noble, noble, and base metal alloys bonded to enamel.

PubMed

Sen, D; Nayir, E; Pamuk, S

2000-11-01

Although the bond strengths of various resin composite luting materials have been reported in the literature, the evaluation of these systems with various cast alloys of different compositions has not been completely clarified. To evaluate the tensile bond strength of sandblasted high-noble, noble, and base metal alloys bonded to etched enamel by 2 different bonding agents of different chemical composition: Panavia-Ex (BIS-GMA) and Super-Bond (4-META acrylic). Flat enamel surfaces were prepared on buccal surfaces of 60 extracted noncarious human incisors. Teeth were divided into 3 groups of 20 each. Twenty circular disks of 5 mm diameter were prepared for casting for each group. Group I was cast with a high-noble, group II with a noble, and group III with a base metal alloy. The surfaces of the disks were sandblasted with 250 microm Al(2)O(3). Ten disks of each group were bonded to exposed enamel surfaces with Super-Bond and 10 disks with Panavia-Ex as recommended by the manufacturer. The tensile bond strength was measured with an Instron universal testing machine with a crosshead speed of 0.5 mm/min until failure occurred. Two-way ANOVA was used to evaluate the results. The differences in bond strengths of Super-Bond and Panavia-Ex with different alloys were not significant. The highest bond strengths were obtained in base metal alloys, followed by noble and high-noble alloys. These results were significant. Panavia-Ex and Super-Bond exhibited comparable tensile bond strengths. For both luting agents, the highest bond strengths were achieved with base metal alloys and the lowest with high-noble alloys.

Tailoring nanostructured, graded, and particle-reinforced Al laminates by accumulative roll bonding.

PubMed

Göken, Mathias; Höppel, Heinz Werner

2011-06-17

Accumulative roll bonding (ARB) is a very attractive process for processing large sheets to achieve ultrafine-grained microstructure and high strength. Commercial purity Al and many Al alloys from the 5xxx and the precipitation strengthened 6xxx alloy series have been successfully processed by the ARB process into an ultrafine-grained state and superior ductility have been achieved for some materials like technical purity Al. It has also been shown that the ARB process can be successfully used to produce multi-component materials with tailored properties by reinforcement or grading, respectively. This allows optimizing the properties based on two or more materials/alloys. For example, to achieve high corrosion resistance and good visual surface properties it is interesting to produce a composite of two different Al alloys, where for example a high strength alloy of the 5xxx series is used as the core material and a 6xxx series alloy as the clad material. It has been shown that such a composite achieves more or less the same strength as the core material although 50% of the composite consists of the significant softer clad alloy. Furthermore, it has been found, that the serrated yielding which typically appears in 5xxx series alloys and limits applications as outer skin materials completely disappears. Moreover, the ARB process allows many other attractive ways to design new composites and graded material structures with unique properties by the introduction of particles, fibres and sheets. Strengthening with nanoparticles for example is a very attractive way to improve the properties and accelerate the grain refining used in the severe plastic deformation process. With an addition of only 0.1 vol.-% Al2O3 nanoparticles a significantly accelerated grain refinement has been found which reduces the number of ARB passes necessary to achieve the maximum in strength. The paper provides a short review on recent developments in the field of ARB processing for producing multicomponent ultrafine-grained sheet materials with tailored properties.

Fabrication and characterization of a flow-through nanoporous gold nanowire/AAO composite membrane.

PubMed

Liu, L; Lee, W; Huang, Z; Scholz, R; Gösele, U

2008-08-20

The fabrication of a composite membrane of nanoporous gold nanowires and anodic aluminum oxide (AAO) is demonstrated by the electrodeposition of Au-Ag alloy nanowires into an AAO membrane, followed by selective etching of silver from the alloy nanowires. This composite membrane is advantageous for flow-through type catalytic reactions. The morphology evolution of the nanoporous gold nanowires as a function of the diameter of the Au-Ag nanowire 'precursors' is also investigated.

Method for forming nuclear fuel containers of a composite construction and the product thereof

DOEpatents

Cheng, Bo-Ching; Rosenbaum, Herman S.; Armijo, Joseph S.

1984-01-01

An improved method for producing nuclear fuel containers of a composite construction having components providing therein a barrier system for resisting destructive action by volatile fission products or impurities and also interdiffusion of metal constituents, and the product thereof. The composite nuclear fuel containers of the method comprise a casing of zirconium or alloy thereof with a layer of copper overlying an oxidized surface portion of the zirconium or alloy thereof.

Raman Scattering Study of Lattice Vibrations in the Type-II Superlattice InAs /InAs1 -xSbx

NASA Astrophysics Data System (ADS)

Liu, Henan; Zhang, Yong; Steenbergen, Elizabeth H.; Liu, Shi; Lin, Zhiyuan; Zhang, Yong-Hang; Kim, Jeomoh; Ji, Mi-Hee; Detchprohm, Theeradetch; Dupuis, Russell D.; Kim, Jin K.; Hawkins, Samuel D.; Klem, John F.

2017-09-01

The InAs /InAs1 -xSbx superlattice system distinctly differs from two well-studied superlattice systems GaAs /AlAs and InAs /GaSb in terms of electronic band alignment, common elements at the interface, and phonon spectrum overlapping of the constituents. This fact leads to the unique electronic and vibrational properties of the InAs /InAs1 -xSbx system when compared to the other two systems. In this work, we report a polarized Raman study of the vibrational properties of the InAs /InAs1 -xSbx superlattices (SLs) as well as selected InAs1 -xSbx alloys, all grown on GaSb substrates by either MBE or metalorganic chemical vapor deposition (MOCVD) from both the growth surface and cleaved edge. In the SL, from the (001) backscattering geometry, an InAs-like longitudinal optical (LO) mode is observed as the primary feature, and its intensity is found to increase with increasing Sb composition. From the (110) cleaved-edge backscattering geometry, an InAs-like transverse optical (TO) mode is observed as the main feature in two cross-polarization configurations, but an additional InAs-like "forbidden" LO mode is observed in two parallel-polarization configurations. The InAs1 -xSbx alloys lattice matched to the substrate (xSb˜0.09 ) grown by MBE are also found to exhibit the forbidden LO mode, implying the existence of some unexpected [001] modulation. However, the strained samples (xSb˜0.35 ) grown by MOCVD are found to behave like a disordered alloy. The primary conclusions are (1) the InAs-like LO or TO mode can be either a confined or quasiconfined mode in the InAs layers of the SL or extended mode of the whole structure depending on the Sb composition. (2) InAs /InAs1 -xSbx and InAs /GaSb SLs exhibit significantly different behaviors in the cleaved-edge geometry but qualitatively similar in the (001) geometry. (3) The appearance of the forbidden LO-like mode is a universal signature for SLs and bulk systems resulting from the mixing of phonon modes due to structural modulation or symmetry reduction.

Raman Scattering Study of Lattice Vibrations in the Type-II Superlattice InAs / InAs 1 - x Sb x

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Henan; Zhang, Yong; Steenbergen, Elizabeth H.

The InAs/InAs 1-xSb x superlattice system distinctly differs from two well-studied superlattice systems GaAs / AlAs and InAs/GaSb in terms of electronic band alignment, common elements at the interface, and phonon spectrum overlapping of the constituents. This fact leads to the unique electronic and vibrational properties of the InAs/InAs 1-xSb x system when compared to the other two systems. Here, we report a polarized Raman study of the vibrational properties of the InAs/InAs 1-xSb x superlattices (SLs) as well as selected InAs 1-xSb x alloys, all grown on GaSb substrates by either MBE or metalorganic chemical vapor deposition (MOCVD) frommore » both the growth surface and cleaved edge. In the SL, from the (001) backscattering geometry, an InAs-like longitudinal optical (LO) mode is observed as the primary feature, and its intensity is found to increase with increasing Sb composition. From the (110) cleaved-edge backscattering geometry, an InAs-like transverse optical (TO) mode is observed as the main feature in two cross-polarization configurations, but an additional InAs-like “forbidden” LO mode is observed in two parallel-polarization configurations. The InAs 1-xSb x alloys lattice matched to the substrate (x Sb ~ 0.09) grown by MBE are also found to exhibit the forbidden LO mode, implying the existence of some unexpected [001] modulation. However, the strained samples (x Sb ~ 0.35) grown by MOCVD are found to behave like a disordered alloy. The primary conclusions are (1) the InAs-like LO or TO mode can be either a confined or quasiconfined mode in the InAs layers of the SL or extended mode of the whole structure depending on the Sb composition. (2) InAs/InAs 1-xSb x and InAs/GaSb SLs exhibit significantly different behaviors in the cleaved-edge geometry but qualitatively similar in the (001) geometry. (3) The appearance of the forbidden LO-like mode is a universal signature for SLs and bulk systems resulting from the mixing of phonon modes due to structural modulation or symmetry reduction.« less

Structure and Properties of High-Temperature Multilayer Hybrid Material Based on Vanadium Alloy and Stainless Steel

NASA Astrophysics Data System (ADS)

Nechaykina, Tatyana A.; Nikulin, Sergey A.; Rozhnov, Andrey B.; Khatkevich, Vladimir M.; Rogachev, Stanislav O.

2017-03-01

The present work is devoted to the development of new structural composite material having the unique complex of properties for operating in ultrahard conditions that combine high temperatures, radiation, and aggressive environments. A new three-layer composite tube material based on vanadium alloy (V-4Ti-4Cr) protected by stainless steel (Fe-0.2C-13Cr) has been obtained by co-extrusion. Mechanism and kinetics of formation as well as structure, composition, and mechanical properties of "transition" area between vanadium alloy and stainless steel have been studied. The transition area (13- to 22- µm thick) of the diffusion interaction between vanadium alloy and steel was formed after co-extrusion. The microstructure in the transition area was rather complicated comprising different grain sizes in components, but having no defects or brittle phases. Tensile strength of the composite was an average 493 ± 22 MPa, and the elongation was 26 ± 3 pct. Annealing at 1073 K (800 °C) increased the thickness of transition area up to 1.2 times, homogenized microstructure, and slightly changed mechanical properties. Annealing at 1273 K (1000 °C) further increased the thickness of transition area and also lead to intensive grain growth in steel and sometimes to separation between composite components during tensile tests. Annealing at 1073 K (800 °C) is proposed as appropriate heat treatment after co-extrusion of composite providing balance between diffusion interaction thickness and microstructure and monolithic-like behavior of composite during tensile tests.

Corrosion behavior of high-nickel and chromium alloys in natural Baltic seawater

DOE Office of Scientific and Technical Information (OSTI.GOV)

Birn, J.; Janik-Czachor, M.; Wolowik, A.

Effect of Cl{sup {minus}} ion concentration (O M sodium chloride [NaCl] to 2 M NaCl) and temperature (25 C to 75 C) on stability of the passive state of high-Ni and Cr alloys: NI-1 ({approximately} 16% Mo), CR-2 ({approximately} 6.2% Mo), and NI-3 (3.5% Mo) were investigated in acidic and neutral electrolytes in strictly controlled electrochemical conditions. The anodic behavior of the alloys appeared to depend mostly upon Mo content in the alloy. Thus, the NI-1 was the most stable alloy under the applied experimental conditions. The other alloys were also quite resistant, undergoing pitting only at elevated temperatures, atmore » high anodic potentials, and at a chloride concentration not lower than 1 M. In natural Baltic seawater, these alloys did not exhibit any tendency to pitting, in qualitative agreement with the accelerated electrochemical tests. Complementary microscopic and surface analytical (AES) investigations were carried out to correlate the anodic and corrosion behavior of these materials with their composition and structure, and the composition of the passivating films formed at their surfaces.« less

In-situ investigation of stress-induced martensitic transformation in Ti–Nb binary alloys with low Young's modulus [In-situ high-energy X-ray diffraction investigation on stress-induced martensitic transformation in Ti-Nb binary alloys

DOE PAGES

Chang, L. L.; Wang, Y. D.; Ren, Y.

2015-11-04

Microstructure evolution, mechanical behaviors of cold rolled Ti-Nb alloys with different Nb contents subjected to different heat treatments were investigated. Here, optical microstructure and phase compositions of Ti-Nb alloys were characterized using optical microscopy and X-ray diffractometre, while mechanical behaviors of Ti-Nb alloys were examined by using tension tests. Stress-induced martensitic transformation in a Ti-30. at%Nb binary alloy was in-situ explored by synchrotron-based high-energy X-ray diffraction (HE-XRD). The results obtained suggested that mechanical behavior of Ti-Nb alloys, especially Young's modulus was directly dependent on chemical compositions and heat treatment process. According to the results of HE-XRD, α"-V1 martensite generated priormore » to the formation of α"-V2 during loading and a partial reversible transformation from α"-V1 to β phase was detected while α"-V2 tranformed to β completely during unloading.« less

Liquid-liquid phase separation and core-shell structure of ternary Al-In-Sn immiscible alloys

NASA Astrophysics Data System (ADS)

Zhao, Degang; Bo, Lin; Wang, Lin; Li, Shanshan

2018-04-01

In this study, the liquid-liquid phase separation of four kinds of ternary immiscible Al-In-Sn melts was investigated with resistivity and thermodynamics method. The nonlinear changes in ρ-T and DSC curves of Al-In-Sn immiscible alloys above monotectic reaction temperature revealed the occurrence of liquid-liquid phase separation of Al-In-Sn melts. The monotectic temperature, liquid phase separation temperature and immiscible gap of ternary Al-In-Sn alloys were lower than those of binary Al-In alloy. With the Al content decreasing, the immiscible gap of Al-In-Sn alloy decreased. The composition of Al80In10Sn10, Al70In15Sn15, Al60In20Sn20 and Al50In25Sn25 was located in the immiscible zone of Al-In-Sn system. Due to the differences of Stokes effect, Marangoni convection and immiscible gap, the solidification morphology of four kinds of Al-In-Sn monotectic alloy was different. The core–shell structure of Al-In-Sn monotectic alloy can form within a certain range of composition.

Microstructure and Mechanical Properties of Laves Phase-strengthened Fe-Cr-Zr Alloys

DOE PAGES

Tan, Lizhen; Yang, Ying

2014-12-05

Laves phase-reinforced alloys have shown some preliminary promising performance at room temperatures. This paper aims at evaluating mechanical properties of Laves phase-strengthened alloys at elevated temperatures. Three Fe-Cr-Zr alloys were designed to favor the formation of eutectic microstructures containing Laves and body-centered cubic phases with the aid of thermodynamic calculations. Microstructural characterization was carried out on the alloys in as-processed and aged states using optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The effect of thermal aging and alloy composition on microstructure has been discussed based on microstructural characterization results. Mechanical properties have been evaluated by meansmore » of Vickers microhardness measurements, tensile testing at temperatures up to 973.15 K (700.15 °C), and creep testing at 873.15 K (600.15 °C) and 260 MPa. Alloys close to the eutectic composition show significantly superior strength and creep resistance compared to P92. Finally, however, their low tensile ductility may limit their applications at relatively low temperatures.« less

Quantitative analysis of interfacial chemistry in TiC/Ti composite using electron-energy-loss spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Gu, M.; Jiang, W.; Zhang, G.

Due to titanium carbide`s physical and elastic properties, titanium carbide particles are widely used as a reinforcement in titanium-alloy-based composites. Previous studies have shown that no obvious reaction products were detected on the interface region in TiC/Ti alloy systems; instead, a nonstoichiometric region in the TiC particle between the Ti{sub 6}Al{sub 4}V alloy and the stoichiometric TiC was found. However, the nature and the extent of the nonstoichiometric zone have not been quantitatively described. The present communication reports some results of a parallel electron-energy-loss spectroscopy (PEELS) study on a 10 vol pct TiC-particle-reinforced IMI-829 metal-matrix composite.

Solid Modeling of Crew Exploration Vehicle Structure Concepts for Mass Optimization

NASA Technical Reports Server (NTRS)

Mukhopadhyay, Vivek

2006-01-01

Parametric solid and surface models of the crew exploration vehicle (CEV) command module (CM) structure concepts are developed for rapid finite element analyses, structural sizing and estimation of optimal structural mass. The effects of the structural configuration and critical design parameters on the stress distribution are visualized, examined to arrive at an efficient design. The CM structural components consisted of the outer heat shield, inner pressurized crew cabin, ring bulkhead and spars. For this study only the internal cabin pressure load case is considered. Component stress, deflection, margins of safety and mass are used as design goodness criteria. The design scenario is explored by changing the component thickness parameters and materials until an acceptable design is achieved. Aluminum alloy, titanium alloy and an advanced composite material properties are considered for the stress analysis and the results are compared as a part of lessons learned and to build up a structural component sizing knowledge base for the future CEV technology support. This independent structural analysis and the design scenario based optimization process may also facilitate better CM structural definition and rapid prototyping.

Amorphous metal alloy and composite

DOEpatents

Wang, Rong; Merz, Martin D.

1985-01-01

Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

PLUTONIUM-ZIRCONIUM ALLOYS

DOEpatents

Schonfeld, F.W.; Waber, J.T.

1960-08-30

A series of nuclear reactor fuel alloys consisting of from about 5 to about 50 at.% zirconium (or higher zirconium alloys such as Zircaloy), balance plutonium, and having the structural composition of a plutonium are described. Zirconium is a satisfactory diluent because it alloys readily with plutonium and has desirable nuclear properties. Additional advantages are corrosion resistance, excellent fabrication propenties, an isotropie structure, and initial softness.

Aluminum and its light alloys

NASA Technical Reports Server (NTRS)

Merica, Paul D

1920-01-01

Report is a summary of research work which has been done here and abroad on the constitution and mechanical properties of the various alloy systems with aluminum. The mechanical properties and compositions of commercial light alloys for casting, forging, or rolling, obtainable in this country are described.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Field, Kevin G.; Briggs, Samuel A.; Sridharan, Kumar

The development and understanding of the mechanical properties of neutron-irradiated FeCrAl alloys is increasingly a critical need as these alloys continue to become more mature for nuclear reactor applications. This study focuses on the mechanical properties of model FeCrAl alloys and of a commercial FeCrAl alloy neutron-irradiated to up to 13.8 displacements per atom (dpa) at irradiation temperatures between 320 and 382 °C. Tensile tests were completed at room temperature and at 320 °C, and a subset of fractured tensile specimens was examined by scanning electron microscopy. Results showed typical radiation hardening and embrittlement indicative of high chromium ferritic alloysmore » with strong chromium composition dependencies at lower doses. At and above 7.0 dpa, the mechanical properties saturated for both the commercial and model FeCrAl alloys, although brittle cleavage fracture was observed at the highest dose in the model FeCrAl alloy with the highest chromium content (18 wt %). Finally, the results suggest the composition and microstructure of FeCrAl alloys plays a critical role in the mechanical response of FeCrAl alloys irradiated near temperatures relevant to light water reactors.« less

Development and property evaluation of nuclear grade wrought FeCrAl fuel cladding for light water reactors

DOE PAGES

Yamamoto, Yukinori; Pint, Bruce A.; Terrani, Kurt A.; ...

2015-10-19

Development of nuclear grade, iron-based wrought FeCrAl alloys has been initiated for light water reactor (LWR) fuel cladding to serve as a substitute for zirconium-based alloys with enhanced accident tolerance. Ferritic alloys with sufficient chromium and aluminum additions can exhibit significantly improved oxidation kinetics in high-temperature steam environments when compared to zirconium-based alloys. In the first phase, a set of model FeCrAl alloys containing 10–20Cr, 3–5Al, and 0–0.12Y in weight percent, were prepared by conventional arc-melting and hot-working processes to explore the effect of composition on the properties of FeCrAlY alloys. It was found that the tensile properties were insensitivemore » to the alloy compositions studied; however, the steam oxidation resistance strongly depended on both the chromium and the aluminum contents. The second phase development focused on strengthening Fe-13Cr-5Al with minor alloying additions of molybdenum, niobium, and silicon. Combined with an optimized thermo-mechanical treatment, a thermally stable microstructure was produced with improved tensile properties at temperatures up to 741°C.« less

Influence of composition and heat treatment on damping and magnetostrictive properties of Fe–18%(Ga + Al) alloys

DOE PAGES

Golovin, I. S.; Palacheva, V. V.; Zadorozhnyy, V. Yu.; ...

2014-07-16

The structure, magnetostriction and damping properties of Fe 82Ga (18–x)Al x (x = 0, 5, 8, 12) alloys were analyzed. The anelastic response of Fe–18(Ga + Al) alloys was studied as a function of temperature (from 0 to 600 °C), frequency (from 0.01 to 200 Hz) and amplitude (from 0.0004% to 0.2%) of forced vibrations. The origin of the relatively high damping capacity of Fe–Ga–Al alloy at room temperature was determined by applying a magnetic field and different heat treatment regimes. The substitution of Ga by Al in Fe–18% Ga alloys was found to decrease magnetostriction and damping. The heatmore » treatment of alloys influences the damping capacity of alloys more than variations of their chemical compositions. Thermally activated frequency and temperature-dependent anelastic effects in Fe–Ga–Al alloys were analyzed and the corresponding activation parameters for relaxation processes were evaluated. Internal friction effects caused by structural transformations were recorded and were found to be consistent with the A2 → D0 3 → L1 2 reaction. Thus, the physical mechanisms for all anelastic effects are discussed.« less

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

NASA Technical Reports Server (NTRS)

Starke, E. A., Jr.

1993-01-01

This report on the NASA-UVa Light Aerospace Alloy and Structure Technology Program Supplement: Aluminum-Based Materials for High Speed Aircraft covers the period from January 1, 1992 to June 30, 1992. The objective of the research is to develop aluminum alloys and aluminum matrix composites for the airframe which can efficiently perform in the HSCT environment for periods as long as 60,000 hours (certification for 120,000 hours) and, at the same time, meet the cost and weight requirements for an economically viable aircraft. Current industry baselines focus on flight at Mach 2.4. The research covers four major materials systems: (1) ingot metallurgy 2XXX, 6XXX, and 8XXX alloys, (2) powder metallurgy 2XXX alloys, (3) rapidly solidified, dispersion strengthened Al-Fe-X alloys, and (4) discontinuously reinforced metal matrix composites. There are ten major tasks in the program which also include evaluation and trade-off studies by Boeing and Douglas aircraft companies.

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

NASA Technical Reports Server (NTRS)

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

1995-01-01

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

A CALPHAD Study on the Thermodynamic Stability of Calcium-, Zinc-, and Yttrium-Doped Magnesium in Aqueous Environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Kaisheng

2011-12-15

Magnesium has attracted the attention of the biomaterials community as a potential biodegradable metallic candidate for use in stents and orthopedic applications. Alloying of Mg with metals such as Ca, Y and Zn, etc., to form alloy precursors is important to optimize its corrosion rate in electrolytic and aqueous environments to understand the alloy response in body fluid environments. In the current study, the chemical reactions of Mg–Me alloys (Me = Ca, Y, and Zn) with pure water have been investigated using the CALPHAD technique. A qualitative agreement between CALPHAD and first-principles results has been obtained. The CALPHAD method hasmore » also been employed to study the reactions of Mg alloys in the human blood fluid environment. The effects of alloying elements and compositions on the reaction enthalpies, reaction products, amount of gas release and gas compositions as well as the pH of the fluids have been systematically discussed and reported.« less

A CALPHAD study on the thermodynamic stability of calcium-, zinc-, and yttrium-doped magnesium in aqueous environments

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Kaisheng; Dogan, Omar N.; Velikokhatnyl, Oleg I.

2011-12-15

Magnesium has attracted the attention of the biomaterials community as a potential biodegradable metallic candidate for use in stents and orthopedic applications. Alloying of Mg with metals such as Ca, Y and Zn, etc., to form alloy precursors is important to optimize its corrosion rate in electrolytic and aqueous environments to understand the alloy response in body fluid environments. In the current study, the chemical reactions of Mg–Me alloys (Me = Ca, Y, and Zn) with pure water have been investigated using the CALPHAD technique. A qualitative agreement between CALPHAD and first-principles results has been obtained. The CALPHAD method hasmore » also been employed to study the reactions of Mg alloys in the human blood fluid environment. The effects of alloying elements and compositions on the reaction enthalpies, reaction products, amount of gas release and gas compositions as well as the pH of the fluids have been systematically discussed and reported.« less

Surface Segregation in Multicomponent Systems: Modeling of Surface Alloys and Alloy Surfaces

NASA Technical Reports Server (NTRS)

Bozzolo, Guillermo; Ferrante, John; Noebe, Ronald D.; Good, Brian; Honecy, Frank S.; Abel, Phillip

1999-01-01

The study of surface segregation, although of great technological importance, has been largely restricted to experimental work due to limitations associated with theoretical methods. However, recent improvements in both first-particle and semi-empirical methods are opening, the doors to an array of new possibilities for surface scientists. We apply one of these techniques, the Bozzolo, Ferrante and Smith (BFS) method for alloys, which is particularly suitable for complex systems, to several aspects of the computational modeling of surfaces and segregation, including alloy surface segregation, structure and composition of alloy surfaces, and the formation of surface alloys. We conclude with the study of complex NiAl-based binary, ternary and quaternary thin films (with Ti, Cr and Cu additions to NiAl). Differences and similarities between bulk and surface compositions are discussed, illustrated by the results of Monte Carlo simulations. For some binary and ternary cases, the theoretical predictions are compared to experimental results, highlighting the accuracy and value of this developing theoretical tool.

Improved microstructure and mechanical properties in gas tungsten arc welded aluminum joints by using graphene nanosheets/aluminum composite filler wires.

PubMed

Fattahi, M; Gholami, A R; Eynalvandpour, A; Ahmadi, E; Fattahi, Y; Akhavan, S

2014-09-01

In the present study, different amounts of graphene nanosheets (GNSs) were added to the 4043 aluminum alloy powders by using the mechanical alloying method to produce the composite filler wires. With each of the produced composite filler wires, one all-weld metal coupon was welded using the gas tungsten arc (GTA) welding process. The microstructure, mechanical properties and fracture surface morphology of the weld metals have been evaluated and the results are compared. As the amount of GNSs in the composition of filler wire is increased, the microstructure of weld metal was changed from the dendritic structure to fine equiaxed grains. Furthermore, the tensile strength and microhardness of weld metal was improved, and is attributed to the augmented nucleation and retarded growth. From the results, it was seen that the GNSs/Al composite filler wire can be used to improve the microstructure and mechanical properties of GTA weld metals of aluminum and its alloys. Copyright © 2014 Elsevier Ltd. All rights reserved.

The isothermal fatigue behavior of a unidirectional SiC/Ti composite and the Ti alloy matrix

NASA Technical Reports Server (NTRS)

Gayda, John, Jr.; Gabb, Timothy P.; Freed, Alan D.

1989-01-01

The high temperature fatigue behavior of a metal matrix composite (MMC) consisting of Ti-15V-3Cr-3Al-3Sn (Ti-15-3) matrix reinforced by 33 vol percent of continuous unidirectional SiC fibers was experimentally and analytically evaluated. Isothermal MMC fatigue tests with constant amplitude loading parallel to the fiber direction were performed at 300 and 550 C. Comparative fatigue tests of the Ti-15-3 matrix alloy were also conducted. Composite fatigue behavior and the in-situ stress state of the fiber and matrix were analyzed with a micromechanical model, the Concentric Cylinder Model (CCM). The cyclic stress-strain response of the composite was stable at 300 C. However, an increase in cyclic mean strain foreshortened MMC fatigue life at high strain ranges at 550 C. Fatigue tests of the matrix alloy and CCM analyses indicated this response was associated with stress relaxation of the matrix in the composite.

Large moments in bcc FexCoyMnz ternary alloy thin films

NASA Astrophysics Data System (ADS)

Snow, R. J.; Bhatkar, H.; N'Diaye, A. T.; Arenholz, E.; Idzerda, Y. U.

2018-02-01

The elemental magnetic moments and the average atomic moment of 10-20 nm thick single crystal bcc (bct) FexCoyMnz films deposited on MgO(001) have been determined as a function of a broad range of compositions. Thin film epitaxy stabilized the bcc structure for 80% of the available ternary compositional space compared to only a 23% stability region for the bulk. The films that display ferromagnetism represent 60% of the available compositional possibilities compared to 25% for the bulk. A maximum average atomic moment of 3.25 ± 0.3 μB/atom was observed for a bcc Fe9Co62Mn29 film (well above the limit of the Slater-Pauling binary alloy curve of 2.45 μB/atom). The FexCoyMnz ternary alloys that exhibit high moments can only be synthesized as ultrathin films since the bcc structure is not stable in the bulk for those compositions.

Nonlinear structure-composition relationships in the Ge 1-ySn y/Si(100) (y<0.15) system

DOE PAGES

Beeler, R.; Roucka, R.; Chizmeshya, A. V. G.; ...

2011-07-26

The compositional dependence of the cubic lattice parameter in Ge 1-ySn y alloys has been revisited. Large 1000-atom supercell ab initio simulations confirm earlier theoretical predictions that indicate a positive quadratic deviation from Vegard's law, albeit with a somewhat smaller bowing coefficient, θ = 0.047 Å, than found from 64-atom cell simulations (θ = 0.063 Å). On the other hand, measurements from an extensive set of alloy samples with compositions y < 0.15 reveal a negative deviation from Vegard's law. The discrepancy with earlier experimental data, which supported the theoretical results, is traced back to an unexpected compositional dependence ofmore » the residual strain after growth on Si substrates. The experimental bowing parameter for the relaxed lattice constant of the alloys is found to be θ = -0.066 Å. Possible reasons for the disagreement between theory and experiment are discussed in detail.« less

Superconducting properties of Nb-Cu nano-composites and nano-alloys

DOE Office of Scientific and Technical Information (OSTI.GOV)

Parab, Pradnya, E-mail: pradnyaprb@gmail.com; Kumar, Sanjeev; Bhui, Prabhjyot

The evolution of the superconducting transition temperature (T{sub c}) in nano-composite and nano-alloys of Nb-Cu, grown by DC magnetron co-sputtering are investigated. Microstructure of these films depends less strongly on the ratio of Nb:Cu but more on the growth temperature. At higher growth temperature, phase separated granular films of Nb and Cu were formed which showed superconducting transition temperatures (T{sub c}) of ~ 7.2±0.5 K, irrespective of the composition. Our results show that this is primarily influenced by the microstructure of the films determined during growth which rules out the superconducting proximity effect expected in these systems. At room temperaturemore » growth, films with nano-scale alloying were obtained at the optimal compositional range of 45-70 atomic% (At%) of Nb. These were also superconducting with a T{sub c} of 3.2 K.« less

Preparation and characterization of Ni-P/Ni3.1B composite alloy coatings

NASA Astrophysics Data System (ADS)

Wang, Yurong; He, Jiawei; Wang, Wenchang; Shi, Jianhua; Mitsuzaki, Naotoshi; Chen, Zhidong

2014-02-01

The preparation of Ni-P/Ni3.1B composite alloy coating on the surface of copper was achieved by co-deposition of Ni3.1B nanoparticles with Ni-P coating during electroless plating. Ni-P-B alloy coating was obtained by heat-treating the as-plated Ni-P/Ni3.1B composite coating. The effect of the concentration of sodium alginate, borax, thiourea, Ni3.1B, temperature, and pH value on the deposition rate and B content were investigated and determined to be: 30 g L-1, 10 g L-1, 2 mg L-1, 20 mg L-1, 70 °C and 9.0 , respectively. Sodium alginate and thiourea were played as surfactant for coating Ni3.1B nanoparticles and stabilizer for the plating bath, respectively. Ni-P/Ni3.1B composite coating had good performance such as corrosion resistance and solderability.

Design of membrane actuators based on ferromagnetic shape memory alloy composite for the synthetic jet actuator

NASA Astrophysics Data System (ADS)

Liang, Yuanchang; Taya, Minoru; Kuga, Yasuo

2004-07-01

A new membrane actuator based on our previous diaphragm actuator was designed and constructed to improve the dynamic performance. The finite element analysis was used to estimate the frequency response of the composite membrane which will be driven close to its resonance to obtain a large stroke. The membrane is made of ferromagnetic shape memory alloy (FSMA) composite including a ferromagnetic soft iron pad and a superelastic grade of NiTi shape memory alloy (SMA). The actuation mechanism for the FSMA composite membrane of the actuator is the hybrid mechanism that we proposed previously. This membrane actuator is designed for a new synthetic jet actuator package that will be used for active flow control technology on airplane wings. Based on the FEM results, the new membrane actuator system was assembled and its static and dynamic performance was experimentally evaluated including the dynamic magnetic response of the hybrid magnet.

Predictions and Experimental Microstructural Characterization of High Strain Rate Failure Modes in Layered Aluminum Composites

NASA Astrophysics Data System (ADS)

Khanikar, Prasenjit

Different aluminum alloys can be combined, as composites, for tailored dynamic applications. Most investigations pertaining to metallic alloy layered composites, however, have been based on quasi-static approaches. The dynamic failure of layered metallic composites, therefore, needs to be characterized in terms of strength, toughness, and fracture response. A dislocation-density based crystalline plasticity formulation, finite-element techniques, rational crystallographic orientation relations and a new fracture methodology were used to predict the failure modes associated with the high strain rate behavior of aluminum layered composites. Two alloy layers, a high strength alloy, aluminum 2195, and an aluminum alloy 2139, with high toughness, were modeled with representative microstructures that included precipitates, dispersed particles, and different grain boundary (GB) distributions. The new fracture methodology, based on an overlap method and phantom nodes, is used with a fracture criteria specialized for fracture on different cleavage planes. One of the objectives of this investigation, therefore, was to determine the optimal arrangements of the 2139 and 2195 aluminum alloys for a metallic layered composite that would combine strength, toughness and fracture resistance for high strain-rate applications. Different layer arrangements were investigated for high strain-rate applications, and the optimal arrangement was with the high toughness 2139 layer on the bottom, which provided extensive shear strain localization, and the high strength 2195 layer on the top for high strength resistance. The layer thickness of the bottom high toughness layer also affected the bending behavior of the roll-boned interface and the potential delamination of the layers. Shear strain localization, dynamic cracking and delamination were the mutually competing failure mechanisms for the layered metallic composite, and control of these failure modes can be optimized for high strain-rate applications. The second major objective of this investigation was the use of recently developed dynamic fracture formulations to model and analyze the crack nucleation and propagation of aluminum layered composites subjected to high strain rate loading conditions and how microstructural effects, such as precipitates, dispersed particles, and GB orientations affect failure evolution. This dynamic fracture approach is used to investigate crack nucleation and crack growth as a function of the different microstructural characteristics of each alloy in layered composites with and without pre-existing cracks. The zigzag nature of the crack paths were mainly due to the microstructural features, such as precipitates and dispersed particles distributions and orientations ahead of the crack front, and it underscored the capabilities of the fracture methodology. The evolution of dislocation density and the formation of localized shear slip contributed to the blunting of the propagating crack. Extensive geometrical and thermal softening due to the localized plastic slip also affected crack path orientations and directions. These softening mechanisms resulted in the switching of cleavage planes, which affected crack path orientations. Interface delamination can also have an important role in the failure and toughening of the layered composites. Different scenarios of delamination were investigated, such as planar crack growth and crack penetration into the layers. The presence of brittle surface oxide platelets in the interface region also significantly influenced the interface delamination process. Transmission Electron Microscopy (TEM), Scanning Electron Microscopy (SEM) and Optical Microscopy (OM) characterization provided further physical insights and validation of the predictive capabilities. The inherent microstructural features of each alloy play a significant role in the dynamic fracture, shear strain localization, and interface delamination of the layered metallic composite. These microstructural features, such as precipitates, dispersed particles, and GB orientations and distributions can be optimized for desired behavior of metallic composites.

[The design of Co-Cr-Mo alloy combining the framework with porcelain fused to metal restorations and determination of the mechanical properties].

PubMed

Chao, Yong-lie; Lui, Chang-hong; Li, Ning; Yang, Xiao-yu

2005-02-01

To investigate a kind of Co-Cr-Mo alloys used for both porcelain fused to metal (PFM) restorations and casting framework of removable partial dentures. The Co-Cr-Mo alloy underwent the design for elementary compositions of the alloys and the production from the raw materials by means of a vacuum melt furnace. The strength, hardness, plasticity and casting ability of the alloy were examined with metal tensile test. Vickers hardness test and grid casting were examined respectively. The microstructure of the Co-Cr-Mo alloy was also inspected by scanning electron microscope and X-ray diffraction analysis. The elementary composition of DA9-4 alloy mainly consisted of Co 54%-67%, Cr 21%-26%, Mo 5%-8%, W 5%-8%, Si 1%-3%, Mn 0.1%-0.25% and trace elements. The yield strength of the alloy was 584 MPa, while the tensile strength was 736 MPa. The coefficient of expansion was 15.0%, the Vickers hardness reached 322, and the casting ratio exibited 100%. The DA9-4 Co-Cr-Mo alloy used for PFM and framework shown in this paper can meet the clinical demands and have reached the objects of the experiment plan.

ZnxCd1-xSe alloy nanowires covering the entire compositional range grown by metalorganic chemical vapor deposition

NASA Astrophysics Data System (ADS)

Shan, C. X.; Liu, Z.; Ng, C. M.; Hark, S. K.

2005-07-01

We show that preferentially oriented, single-crystalline ZnxCd1-xSe alloy nanowires can be grown on GaAs (100) surface using Au as a catalyst over the entire compositional range in a metalorganic chemical vapor deposition system. The composition of the alloy nanowires can be simply adjusted through the ratio of the flow rates of group-II precursors. Electron microscopy shows that the nanowires are smooth and uniform in shape; their diameters range from 20 to 80 nm and lengths exceed a few micrometers. Nanowires containing more than 13% Zn are zinc blende structured and grow along the ⟨110⟩ direction. Those containing less Zn are wurtzite structured and grow along the ⟨210⟩ direction. Compared with the bulk alloy, the change from zinc blende to wurtzite structure in nanowires occurs at far smaller x. The preferred orientation and the persistence of the zinc blende structure both reflect the influence of the substrate on the growth of the nanowires. Photoluminescence measurements identify a strong near-band-edge emission for all samples and show that its peak energy tracks the band gap of ZnxCd1-xSe epilayer for x>0.13. The growth of alloy nanowires at many compositions opens up the possibility of realizing quasi-one-dimensional heterojunctions.

Grain boundary engineering to control the discontinuous precipitation in multicomponent U10Mo alloy

DOE PAGES

Devaraj, Arun; Kovarik, Libor; Kautz, Elizabeth; ...

2018-03-30

Here, we demonstrate here that locally stabilized structure and compositional segregation at grain boundaries in a complex multicomponent alloy can be modified using high temperature homogenization treatment to influence the kinetics of phase transformations initiating from grain boundaries during subsequent low temperature annealing. Using aberration-corrected scanning transmission electron microscopy and atom probe tomography of a model multicomponent metallic alloy —uranium-10 wt% molybdenum (U-10Mo) a nuclear fuel, that is highly relevant to worldwide nuclear non-proliferation efforts, we demonstrate the ability to change the structure and compositional segregation at grain boundary, which then controls the subsequent discontinuous precipitation kinetics during sub-eutectoid annealing.more » A change in grain boundary from one characterized by segregation of Mo and impurities at grain boundary to a phase boundary with a distinct U 2MoSi 2C wetting phase precipitates introducing Ni and Al rich interphase complexions caused a pronounced reduction in area fraction of subsequent discontinuous precipitation. The broader implication of this work is in highlighting the role of grain boundary structure and composition in metallic alloys on dictating the fate of grain boundary initiated phase transformations like discontinuous precipitation or cellular transformation. This work highlights a new pathway to tune the grain boundary structure and composition to tailor the final microstructure of multicomponent metallic alloys.« less

Grain boundary engineering to control the discontinuous precipitation in multicomponent U10Mo alloy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Devaraj, Arun; Kovarik, Libor; Kautz, Elizabeth

Here, we demonstrate here that locally stabilized structure and compositional segregation at grain boundaries in a complex multicomponent alloy can be modified using high temperature homogenization treatment to influence the kinetics of phase transformations initiating from grain boundaries during subsequent low temperature annealing. Using aberration-corrected scanning transmission electron microscopy and atom probe tomography of a model multicomponent metallic alloy —uranium-10 wt% molybdenum (U-10Mo) a nuclear fuel, that is highly relevant to worldwide nuclear non-proliferation efforts, we demonstrate the ability to change the structure and compositional segregation at grain boundary, which then controls the subsequent discontinuous precipitation kinetics during sub-eutectoid annealing.more » A change in grain boundary from one characterized by segregation of Mo and impurities at grain boundary to a phase boundary with a distinct U 2MoSi 2C wetting phase precipitates introducing Ni and Al rich interphase complexions caused a pronounced reduction in area fraction of subsequent discontinuous precipitation. The broader implication of this work is in highlighting the role of grain boundary structure and composition in metallic alloys on dictating the fate of grain boundary initiated phase transformations like discontinuous precipitation or cellular transformation. This work highlights a new pathway to tune the grain boundary structure and composition to tailor the final microstructure of multicomponent metallic alloys.« less

Improvements to the strength and corrosion resistance of aluminum-magnesium-manganese alloys of near-AA5083 chemistry

NASA Astrophysics Data System (ADS)

Carroll, Mark Christopher

Aluminum alloys of the 5000 series (AI-Mg-Mn) are extremely popular in a wide range of applications that call for a balance of moderately high strength, good corrosion resistance, and light weight, all at a moderate cost. One of the most popular 5000 series alloys is designated A1-5083, containing, in addition to aluminum, approximately 4 wt% magnesium and 0.7 wt% manganese. In order to increase the range of versatility of this particular alloy, a number of modifications have been examined that will potentially improve the strength and corrosion resistance characteristics while maintaining a chemical composition that is very close to the proven 5083 alloy. The strength of the 5083-based alloys under study are investigated with two goals in mind---to maximize the potential strength characteristics in a "standard" 5083 form through changes in minor processing parameters or through minor alloying additions. Increasing the standard alloy's potential is possible through improved efficiency of "preprocessing" heat treatments that maximize the homogeneous dispersion of secondary manganese-based particles. For the modified alloy study, additions of scandium and zirconium are shown to improve strength not only by forming secondary particles in the alloy, but also through substitutional solid solution strengthening, even when added at very small levels. Corrosion resistance of these 5083-based alloys is investigated once again through minor alloying additions; specifically zinc, copper, and silver. Zinc is particularly effective in that it changes the corrosion-susceptible binary aluminum-magnesium phase that would otherwise form on grain boundaries following exposure to moderately elevated temperatures for extended periods of time to a ternary aluminum-magnesium-zinc phase. This chemical composition of this ternary phase that forms following zinc additions can be further altered through minor additions of copper and silver. By determining threshold levels for these modifications while maintaining a chemical composition that is very near that of standard Al-5083, it can be shown that even minor modifications to processing and alloying parameters can have a favorable effect on the final bulk properties of the alloy. The increased range of strength and corrosion resistance of these lightly modified alloys make them more attractive in a broadened range of potential applications.

Research and Development of High-Strength of Al-Zn-Mg-Cu Alloys

NASA Astrophysics Data System (ADS)

Vakhromov, R. O.; Antipov, V. V.; Tkachenko, E. A.

The paper is focused on high-strength alloys (UTS=600-650 MPa, specific strength (UTS/density) 220-230 kN•m/kg) which will allow one to retain aluminum's predominant position during the next 15-20 years as applied in advanced aircraft primary structures. Parameters of microstructure (dispersoids, precipitates, degree of recrystallisation, grain size) and properties of semiproducts were studied in dependence on content of base alloying elements in chemical compositions of alloys (total sum of Zn+Mg+Cu — higher than 10 % mass). Contribution of minor additions (Zr, Sc, Ag) to strengthening and creation of improved combination of service properties was investigated. Evolution of phase composition and properties was studied as a dependence of different aging treatments.

Effect of graphenenano-platelets on the mechanical properties of Mg/3wt%Al alloy-nanocomposite

NASA Astrophysics Data System (ADS)

Kumar, Pravir; Kujur, MilliSuchita; Mallick, Ashis; Sandar Tun, Khin; Gupta, Manoj

2018-04-01

The bulk Mg/3%Al/0.1%GNP alloy-nano composite was fabricated using powder metallurgy route assisted with microwave sintering and followed by hot extrusion. The microstructural and Raman spectroscopy studies were performed to characterize the graphene nano-platelet(GNP).EDX tests confirmed the presence and the homogeneous distribution of Al and graphene nano-platelets in the magnesium alloy-nanocomposite. The addition of 3 wt% Al and 0.1wt%GNP to the Mg changed Vicker hardness, ultimate tensile strength and failure strain by +46.15%,+17.6% and -5% respectively. The fabricated composite offers higher resistance to the local deformation than monolithic Mg and Mg/3%Al alloy, revealed by the load/unload-indentation depth curve.