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Sample records for quasicrystalline al-based alloys

  1. Alloy with metallic glass and quasi-crystalline properties

    SciTech Connect

    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.

  2. Self-lubricating, low-friction, wear-resistant Al-based quasicrystalline coatings

    PubMed Central

    Silva Guedes de Lima, Bruno Alessandro; Medeiros Gomes, Rodinei; Guedes de Lima, Severino Jackson; Dragoe, Diana; Barthes-Labrousse, Marie-Geneviève; Kouitat-Njiwa, Richard; Dubois, Jean-Marie

    2016-01-01

    Abstract After gas atomization, a quasicrystalline powder based on aluminium was used to prepare a thick coating by high-velocity oxygen-fuel flame torch spraying. This layer was deposited on top of a bond-coat layer on a steel plate. A post-spraying annealing treatment turned the two layers to their stable state, a γ-brass crystal and an icosahedral quasicrystal, respectively. The projection parameters were selected in such a way that the coating behaved like a self-lubricating material, which offered very good wear resistance (duration of pin-on-disk tests superior to 5 km with negligible material loss) and low friction (µ ≤ 6% against sintered tungsten carbide), in contrast to the state of the art. This property was achieved thanks to, on the one hand, excellent bonding to the substrate via the bound coat, and on the other hand, presence at the boundaries between quasicrystalline flakes of a mixture of both threefold and fourfold coordinated carbon originating from spray processing. Application to hard materials used in mechanical devices is appealing, especially because soft, lubricating additives may not be needed, thus considerably increasing the lifetime of the devices and reducing waste of materials. PMID:27877859

  3. Self-lubricating, low-friction, wear-resistant Al-based quasicrystalline coatings.

    PubMed

    Silva Guedes de Lima, Bruno Alessandro; Medeiros Gomes, Rodinei; Guedes de Lima, Severino Jackson; Dragoe, Diana; Barthes-Labrousse, Marie-Geneviève; Kouitat-Njiwa, Richard; Dubois, Jean-Marie

    2016-01-01

    After gas atomization, a quasicrystalline powder based on aluminium was used to prepare a thick coating by high-velocity oxygen-fuel flame torch spraying. This layer was deposited on top of a bond-coat layer on a steel plate. A post-spraying annealing treatment turned the two layers to their stable state, a γ-brass crystal and an icosahedral quasicrystal, respectively. The projection parameters were selected in such a way that the coating behaved like a self-lubricating material, which offered very good wear resistance (duration of pin-on-disk tests superior to 5 km with negligible material loss) and low friction (µ ≤ 6% against sintered tungsten carbide), in contrast to the state of the art. This property was achieved thanks to, on the one hand, excellent bonding to the substrate via the bound coat, and on the other hand, presence at the boundaries between quasicrystalline flakes of a mixture of both threefold and fourfold coordinated carbon originating from spray processing. Application to hard materials used in mechanical devices is appealing, especially because soft, lubricating additives may not be needed, thus considerably increasing the lifetime of the devices and reducing waste of materials.

  4. Characteristic chemical shifts of quasicrystalline Zn-Mg-Zr alloys studied by EELS and SXES

    NASA Astrophysics Data System (ADS)

    Koshiya, S.; Terauchi, M.; Ohhashi, S.; Tsai, A. P.

    2013-06-01

    Chemical shifts of the constituent atoms of primitive icosahedral quasicrystal (P-QC), face-centred icosahedral quasicrystal (F-QC) and 1/1-approximant (1/1-AP) of F-QC Zn-Mg-Zr alloys were investigated for the first time using high energy-resolution electron energy-loss spectroscopy (EELS) and soft-X-ray emission spectroscopy (SXES). Among Zn M-shell and Mg L-shell excitation EELS spectra of P-QC, F-QC and 1/1-AP alloys, only the quasicrystalline alloys showed a chemical shift towards the larger binding energy side. In Zn-L and Zr-L emission SXES spectra, the P-QC and F-QC alloys showed a chemical shift towards larger binding energy side. The magnitudes of the shifts in the Zn-L emission spectra of the quasicrystalline alloys were almost the same as for ZnO. These results strongly suggest a decrease in valence charge in quasicrystalline states. Therefore, it should be concluded that bonding in quasicrystalline states involves a characteristic increase in covalency compared with bonding in corresponding approximant and standard metal crystals.

  5. Effects in Mg-Zn-based alloys strengthened by quasicrystalline phase

    NASA Astrophysics Data System (ADS)

    Vlček, M.; Čížek, J.; Lukáč, F.; Melikhova, O.; Hruška, P.; Procházka, I.; Vlach, M.; Stulíková, I.; Smola, B.; Jäger, A.

    2016-01-01

    Magnesium Mg-based alloys are promising lightweight structural materials for automotive, aerospace and biomedical applications. Recently Mg-Zn-Y system attracted a great attention due to a stable icosahedral phase (I-phase) with quasicrystalline structure which is formed in these alloys. Positron lifetime spectroscopy and in situ synchrotron X-ray diffraction were used to study thermal stability of I-phase and precipitation effects in Mg-Zn-Y and Mg- Zn-Al alloys. All alloys containing quasicrystalline I-phase exhibit misfit defects characterized by positron lifetime of ∼ 300 ps. These defects are associated with the interfaces between I- phase particles and Mg matrix. The quasicrystalline I-phase particles were found to be stable up to temperatures as high as ∼ 370°C. The W-phase is more stable and melts at ∼ 420°C. Concentration of defects associated with I-phase decreases after annealing at temperatures above ∼ 300°C.

  6. Fabric cutting application of FeAl-based alloys

    SciTech Connect

    Sikka, V.K.; Blue, C.A.; Sklad, S.P.; Deevi, S.C.; Shih, H.R.

    1998-11-01

    Four intermetallic-based alloys were evaluated for cutting blade applications. These alloys included Fe{sub 3}Al-based (FAS-II and FA-129), FeAl-based (PM-60), and Ni{sub 3}Al-based (IC-50). These alloys were of interest because of their much higher work-hardening rates than the conventionally used carbon and stainless steels. The FeAl-based PM-60 alloy was of further interest because of its hardening possibility through retention of vacancies. The vacancy retention treatment is much simpler than the heat treatments used for hardening of steel blades. Blades of four intermetallic alloys and commercially used M2 tool steel blades were evaluated under identical conditions to cut two-ply heavy paper. Comparative results under identical conditions revealed that the FeAl-based alloy PM-60 outperformed the other intermetallic alloys and was equal to or somewhat better than the commercially used M2 tool steel.

  7. Formation of quasicrystalline phase in Al70-x Ga x Pd17Mn13 alloys

    NASA Astrophysics Data System (ADS)

    Yadav, T. P.; Singh, Devinder; Shahi, Rohit R.; Shaz, M. A.; Tiwari, R. S.; Srivastava, O. N.

    2011-07-01

    In the present investigation, the formation and stability of icosahedral phase in Al70- x Ga x Pd17Mn13 alloys has been explored using X-ray diffraction, scanning, transmission electron microscopy and energy dispersive X-ray analysis. Cast alloys and melt-spun ribbons with x = 2.5, 5, 7.5, 10, 12.5, 15 and 20 have been investigated. In both cases, the alloys up to 5 at% Ga exhibit the formation of pure icosahedral phase. However, for x ≥5 at% Ga content, the cast alloy exhibits the formation of multiphase material, consisting of an icosahedral phase along with AlPd-type B2 and ξ‧ crystalline (orthorhombic structure with unit cell a = 23.5 Å, b = 16.6 Å and c = 12.4 Å) phases. In the case of the melt spun ribbon for x = 5 at% Ga, only an icosahedral phase has been found, but for 15 > x > 5 at% Ga, an icosahedral phase is the majority phase with AlPd-type B2 phase being the minority component. For x = 15 at% Ga, a Al3Pd2-type hexagonal phase together with a small amount of quasicrystalline phase is formed. However, for x = 20, only a hexagonal Al3Pd2 phase results.

  8. Melting and casting of FeAl-based cast alloy

    SciTech Connect

    Sikka, V.K.; Wilkening, D.; Liebetrau, J.; Mackey, B.

    1998-11-01

    The FeAl-based intermetallic alloys are of great interest because of their low density, low raw material cost, and excellent resistance to high-temperature oxidation, sulfidation, carburization, and molten salts. The applications based on these unique properties of FeAl require methods to melt and cast these alloys into complex-shaped castings and centrifugal cast tubes. This paper addresses the melting-related issues and the effect of chemistry on the microstructure and hardness of castings. It is concluded that the use of the Exo-Melt{trademark} process for melting and the proper selection of the aluminum melt stock can result in porosity-free castings. The FeAl alloys can be melted and cast from the virgin and revert stock. A large variation in carbon content of the alloys is possible before the precipitation of graphite flakes occurs. Titanium is a very potent addition to refine the grain size of castings. A range of complex sand castings and two different sizes of centrifugal cast tubes of the alloy have already been cast.

  9. Characteristic chemical shift of quasicrystalline alloy Al53Si27Mn20 studied by EELS and SXES

    NASA Astrophysics Data System (ADS)

    Koshiya, S.; Terauchi, M.; Tsai, A. P.

    2011-06-01

    Chemical shifts of all constituent atoms for amorphous (Am), quasicrystalline (QC) and crystalline (Cryst) alloys of Al53Si27Mn20 were investigated for the first time by high energy-resolution electron energy-loss spectroscopy (EELS) and soft-X-ray emission spectroscopy (SXES). Among Al L-shell excitation EELS spectra of Am, QC and Cryst alloys, only QC alloy showed an apparent chemical shift to the larger binding energy side by 0.4 eV. In Al-Kα and Si-Kα emission SXES spectra of these alloys, only QC alloy showed a chemical shift to the larger binding energy side by 4 eV for Al-Kα and 6 eV for Si-Kα. These chemical shift values are comparable to those of corresponding metal oxides. This indicates a smaller amount of valence charge at Al and Si atomic sites in QC alloy. On the other hand, Mn-L SXES spectra did not show any chemical shift. Therefore, the decreased charge from Al and Si sites should be distributed between atomic sites, indicating the presence of covalent bonding nature for QC ordered alloy.

  10. Electron-ion plasma modification of Al-based alloys

    SciTech Connect

    Ivanov, Yurii; Rygina, Mariya; Petrikova, Elizaveta Krysina, Olga Teresov, Anton; Ivanova, Olga Ikonnikova, Irina

    2016-01-15

    The paper reports on the study where we analyzed the surface structure and strength properties of coated Al alloys modified by electron-ion plasma treatment. The Al alloys were deposited with a thin (≈0.5 μm) TiCu film coating (TiCu-Al system) and with a hard TiCuN coating (TiCuN–AlSi system) on a TRIO vacuum setup in the plasma of low-pressure arc discharges. The temperature fields and phase transformations in the film–substrate system were estimated by numerical simulation in a wide range of electron energy densities (5–30 J/cm{sup 2}) and pulse durations (50–200 μs). The calculations allowed us to determine the threshold energy density and pulse duration at which the surface structure of the irradiated Al-based systems is transformed in a single-phase state (solid or liquid) and in a two-phase state (solid plus liquid). The elemental composition, defect structure, phase state, and lattice state in the modified surface layers were examined by optical, scanning, and transmission electron microscopy, and by X-ray diffraction analysis. The mechanical characteristics of the modified layers were studied by measuring the hardness and Young’s modulus. The tribological properties of the modified layers were analyzed by measuring the wear resistance and friction coefficient. It is shown that melting and subsequent high-rate crystallization of the TiCu–Al system makes possible a multiphase Al-based surface structure with the following characteristics: crystallite size ranging within micrometer, microhardness of more than 3 times that in the specimen bulk, and wear resistance ≈1.8 times higher compared to the initial material. Electron beam irradiation of the TiCuN–AlSi system allows fusion of the coating into the substrate, thus increasing the wear resistance of the material ≈2.2 times at a surface hardness of ∼14 GPa.

  11. Formation of the icosahedral quasicrystalline phase in a rapidly solidified Al{sub 52}Cu{sub 25.5}Fe{sub 12.5}Si{sub 1} alloy

    SciTech Connect

    Wang Yan; Zhang Zhonghua . E-mail: zh_zhang@sdu.edu.cn; Geng Haoran; Yang Zhongxi

    2006-04-15

    In the present work, the effect of wheel speed (quenching rate) on the formation of the quasicrystalline phase in a rapidly solidified Al{sub 52}Cu{sub 25.5}Fe{sub 12.5}Si{sub 1} alloy has been investigated using X-ray diffraction (XRD), differential thermal analysis (DTA), differential scanning calorimetry (DSC) and transmission electron microscopy (TEM). The results show that rapid solidification has no effect on the phase constitution of the Al{sub 52}Cu{sub 25.5}Fe{sub 12.5}Si{sub 1} alloy. The addition of Si decreases the stability of the quasicrystalline phase in the conventionally cast Al{sub 52}Cu{sub 25.5}Fe{sub 12.5}Si{sub 1} alloy. The thermal stability of the quasicrystalline phase in the melt-spun alloy depends upon the quenching rate. Moderate-rate rapid solidification can improve the thermal stability of the quasicrystalline phase in the melt-spun alloy. Higher quenching rate instigates the transformation of the quasicrystalline phase into the cubic approximant phase and decreases the stability of the quasicrystalline phase. Furthermore, the transformation temperature decreases with increasing Si addition into the Al{sub (62-x)}Cu{sub 25.5}Fe{sub 12.5}Si{sub x}.

  12. Ni3Al-based alloys for die and tool application

    DOEpatents

    Liu, Chain T.; Bloom, Everett E.

    2001-01-01

    A novel Ni.sub.3 Al-based alloy exhibits strengths and hardness in excess of the standard base alloy IC-221M at temperatures of up to about 1000.degree. C. The alloy is useful in tool and die applications requiring such temperatures, and for structural elements in engineering systems exposed to such temperatures.

  13. Processing, properties, and applications of Ni{sub 3}Al-based alloys

    SciTech Connect

    Sikka, V.K.; Santella, M.L.; Liu, C.T.

    1997-06-01

    The Ni{sub 3}Al-based alloys represent a quantum jump in advanced alloys for structural applications at elevated temperatures. These alloys offer benefits of oxidation, carburization, and chlorination resistance, and significantly higher strength than many commercially used alloys. The commercial applications of the Ni{sub 3}Al-based alloys have begun to occur because of their comprehensive development This paper is to provide a review of. (1) alloy development, (2) melting, casting, and processing of alloys, (3) property data, (4) welding process and weldment properties, and (5) case histories of current applications. It is concluded that the cast alloy IC-221M is on its way to commercialization. 22 refs., 8 figs., 2 tabs.

  14. Investigations of the Electronic Properties and Surface Structures of Aluminium-Rich Quasicrystalline Alloys

    SciTech Connect

    Barrow, Jason A.

    2003-01-01

    equations. Transport behavior is described in terms of charge carriers and the mean-free time between carrier collisions. It is concluded that the mean-free time is much longer in the periodic direction than in the aperiodic direction. This difference produces the observed anisotropy in thermal transport. The third study presented a detailed analysis of the reversible, sputter-induced phase transformation which occurs on the 5-fold surface of an icosahedral Al-Cu-Fe quasicrystal. Reflection high-energy electron diffraction (RHEED), x-ray photoemission spectroscopy (XPS), and ultra-violet photoemission spectroscopy (UPS) data were collected as a function of annealing temperature and were used to probe surface structure, surface composition, and electronic structure, respectively. The composition and structure of the sputtered surface are consistent with a transformation to the β-Al-Cu-Fe cubic structure, and shows a sharp metallic cut-off in the spectral intensity of the electronic structure at the Fermi edge. Upon annealing the surface reverts to a quasicrystalline composition and structure. This transformation has been correlated with a reduction in the spectral intensity of the electronic structure at the Fermi level. This data clearly demonstrates that the observed reduction is intrinsic to a quasicrystalline surface. It is concluded that this is due to the opening of a pseudo-gap in the electronic density of states as the surface reverts from β-Al-Cu-Fe to quasicrystalline.

  15. Mechanisms of cavitation erosion of TiAl-based titanium aluminide intermetallic alloys

    SciTech Connect

    Howard, R.L.; Ball, A.

    1996-08-01

    The modes and controlling mechanisms of cavitation erosion of plasma arc-melted TiAl-based titanium aluminide intermetallic alloys, Ti-52Al (at.%) and Ti-48Al-2Mn-2Nb (at.%) were studied and compared to those of the Ti{sub 3}Al-based alloy, Ti-25Al-10Nb-3V-1Mo (at.%) and other comparative materials. The accumulation of cavitation damage during the initial stages of cavitation erosion was monitored and the work hardening produced in steady state erosion conditions was measured on 5{degree} taper sections. The cavitation erosion resistance of the titanium cavitation erosion resistance of the TiAl-based titanium aluminide alloys compared to Ti-25Al-10Nb-3V-1Mo (at.%) is ascribed to their ability to twin and their greater work hardening ability during cavitation erosion.

  16. Skeletal Ru/Cu catalysts prepared from crystalline and quasicrystalline ternary alloy precursors: characterization by X-ray absorption spectroscopy and CO oxidation.

    PubMed

    Highfield, James; Liu, Tao; Loo, Yook Si; Grushko, Benjamin; Borgna, Armando

    2009-02-28

    The Ru/Cu system is of historical significance in catalysis. The early development and application of X-ray absorption spectroscopy (XAS) led to the original 'bimetallic cluster" concept for highly-immiscible systems. This work explores alkali leaching of Al-based ternary crystalline and quasicrystalline precursors as a potential route to bulk Ru/Cu alloys. Single-phase ternary alloys at 3 trial compositions; Al(71)Ru(22)Cu(7), Al(70.5)Ru(17)Cu(12.5), and Al(70)Ru(10)Cu(20), were prepared by arc melting of the pure metal components. After leaching, the bimetallic residues were characterized principally by transmission XAS, "as-leached" and after annealing in H(2) (and passivation) in a thermobalance. XRD and BET revealed a nanocrystalline product with a native structure of hexagonal Ru. XPS surface analysis of Ru(22)Cu(7) and Ru(17)Cu(12.5) found only slight enrichment by Cu in the as-leached forms, with little change upon annealing. Ru(10)Cu(20) was highly segregated as-leached. XANES data showed preferential oxidation of Cu in Ru(22)Cu(7), implying that it exists as an encapsulating layer. TG data supports this view since it does not show the distinct two-stage O(2) uptake characteristic of skeletal Ru. Cu K-edge EXAFS data for Ru(22)Cu(7) were unique in showing a high proportion of Ru neighbours. The spacing, d(CuRu) = 2.65 A, was that expected from a hypothetical (ideal) solid solution at this composition, but this is unlikely in such a bulk-immiscible system and Ru K-edge EXAFS failed to confirm bulk alloying. Furthermore its invariance under annealing was more indicative of an interfacial bond between bulk components, although partial alloying with retention of local order cannot entirely be ruled out. The XAS and XPS data were reconciled in a model involving surface and bulk segregation, Cu being present at both the grain exterior and in ultra-fine internal pores. This structure can be considered as the 3-dimensional analogue of the classical type

  17. Plasma sprayed ceramic thermal barrier coating for NiAl-based intermetallic alloys

    NASA Technical Reports Server (NTRS)

    Miller, Robert A. (Inventor); Doychak, Joseph (Inventor)

    1994-01-01

    A thermal barrier coating system consists of two layers of a zirconia-yttria ceramic. The first layer is applied by low pressure plasma spraying. The second layer is applied by conventional atmospheric pressure plasma spraying. This facilitates the attachment of a durable thermally insulating ceramic coating directly to the surface of a highly oxidation resistant NiAl-based intermetallic alloy after the alloy has been preoxidized to promote the formation of a desirable Al2O3 scale.

  18. Progress in the Modeling of NiAl-Based Alloys Using the BFS Method

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Ferrante, John; Garg, Anita

    1997-01-01

    The BFS method has been applied to the study of NiAl-based materials to assess the effect of alloying additions on structure. Ternary, quaternary and even pent-alloys based on Ni-rich NiAl with additions of Ti, Cr and Cu were studied. Two approaches were used, Monte Carlo simulations to determine ground state structures and analytical calculations of high symmetry configurations which give physical insight into preferred bonding. Site occupancy energetics for ternary and the more complicated case of quaternary additions were determined, and solubility limits and precipitate formation with corresponding information concerning structure and lattice parameter were also 'observed' computationally. The method was also applied to determine the composition of alloy surfaces and interfaces. Overall, the results demonstrate that the BFS method for alloys is a powerful tool for alloy design and with its simplicity and obvious advantages can be used to complement any experimental alloy design program.

  19. Icosahedral quasicrystalline (Ti₁.₆V₀.₄Ni)₁₀₀₋xScx alloys: Synthesis, structure and their application in Ni-MH batteries

    SciTech Connect

    Hu, Wen; Yi, Jianhong; Zheng, Biju; Wang, Limin

    2013-06-01

    Thanks to the revolutionary discovery of 5-fold symmetry contributed by Shechtman, quasicrystal is now recognized as another solid-state existing form. As the second largest class of quasicrystals, titanium-based icosahedral quasicrystals are very promising for hydrogen storage applications owing to their inherent abundant interstitial sites and favorable hydrogen-metal chemistry. In this context, (Ti₁.₆V₀.₄Ni)₁₀₀₋xScx (x=0.5–6) quaternary icosahedral quasicrystals have been successfully synthesized via arc-melting and subsequent melt-spinning techniques, and then their electrochemical performance toward hydrogen is explored. When the molar ratio of Sc addition is under 1%, a maximum discharge capacity of about 270 mA h g⁻¹ can be delivered. With further increasing Sc amount to 6%, good cycling stability as well as significantly retarded self-discharge rate (capacity retention 94% after 24 h relaxation) is observed. But meanwhile, the discharge capacities fall into 250-240 mA h g⁻¹, and the electrocatalytic activity improvement is highly demanded. - Graphical abstract: Quasicrystalline Ti–V–Ni–Sc hydrogen storage materials: Sc addition into Ti₁.₆V₀.₄Ni alloy forms the icosahedral phase (see picture). With optimal Sc dosage, the anodic cycling stability and self-discharge property are greatly enhanced. - Highlights: • Crystalline disallowed 5-fold symmetry is present in (Ti₁.₆V₀.₄Ni)₁₀₀₋xScx alloys. • Ti-based metastable quasicrystalline alloys can store hydrogen electrochemically. • A maximum discharge capacity of 270 mA h g⁻¹ can be delivered. • Advantageous cycle stability and self-discharge property benefit from Sc addition. • Ti and V dissolution is suppressed by an oxide layer resulting from Sc corrosion.

  20. Development and commercialization status of Fe{sub 3}Al-based intermetallic alloys

    SciTech Connect

    Sikka, V.K.; Viswanathan, S.; McKamey, C.G.

    1993-06-01

    The Fe{sub 3}Al-based intermetallic alloys offer unique benefits of excellent oxidation and sulfidation resistance, limited by poor room-temperature (RT) ductility and low high-temperature strength. Recent understanding of environmental effects on RT ductility of these alloys has led to progress toward taking commercial advantage of Fe{sub 3}Al-based materials. Cause of low ductility appears to be related to hydrogen formed from reaction with moisture. The environmental effect has been reduced in these intermetallic alloys by two methods. The first deals with producing a more hydrogen-resistant microstructure through thermomechanical processing, and the second dealed with compositional modification. The alloys showing reduced environmental effect have been melted and processed by many different methods. Laboratory and commercial heats have been characterized. Tests have been conducted in both air and controlled environments to quantify environmental effects on these properties. These materials were also tested for aqueous corrosion and resistance to stress corrosion cracking. Oxidation and sulfidation data were generated and effects of minor alloying elements on were also investigated. Several applications have been identified for the newly developed iron aluminides. Commercialization status of these alloys is described.

  1. Research into Oil-based Colloidal-Graphite Lubricants for Forging of Al-based Alloys

    SciTech Connect

    Petrov, A.; Petrov, P.; Petrov, M.

    2011-05-04

    The presented paper describes the topical problem in metal forging production. It deals with the choice of an optimal lubricant for forging of Al-based alloys. Within the scope of the paper, the properties of several oil-based colloidal-graphite lubricants were investigated. The physicochemical and technological properties of these lubricants are presented. It was found that physicochemical properties of lubricant compositions have an influence on friction coefficient value and quality of forgings.The ring compression method was used to estimate the friction coefficient value. Hydraulic press was used for the test. The comparative analysis of the investigated lubricants was carried out. The forging quality was estimated on the basis of production test. The practical recommendations were given to choose an optimal oil-based colloidal-graphite lubricant for isothermal forging of Al-based alloy.

  2. Welding and mechanical properties of cast FAPY (Fe-16 at. % Al-based) alloy slabs

    SciTech Connect

    Sikka, V.K.; Goodwin, G.M.; Alexander, D.J.; Howell, C.R.

    1995-08-01

    The low-aluminum-content iron-aluminum program deals with the development of a Fe-Al alloy with aluminum content such as a produce the minimum environmental effect at room temperature. The FAPY is an Fe-16 at. % Al-based alloy developed at the Oak Ridge National Laboratory as the highest aluminum-containing alloy with essentially no environmental effect. The chemical composition for FAPY in weight percent is: aluminum = 8.46, chromium = 5.50, zirconium = 0.20, carbon = 0.03, molybdenum = 2.00, yttrium = 0.10, and iron = 83.71. The cast ingots of the alloy can be hot worked by extrusion, forging, and rolling processes. The hot- worked cast structure can be cold worked with intermediate anneals at 800{degrees}C. Typical room-temperature ductility of the fine-grained wrought structure is 20 to 25% for this alloy. In contrast to the wrought structure, the cast ductility at room temperature is approximately 1% with a transition temperature of approximately 100 to 150{degrees}C, above which ductility values exceed 20%. The alloy has been melted and processed into bar, sheet, and foil. The alloy has also been cast into slabs, step-blocks of varying thicknesses, and shapes. The purpose of this section is to describe the welding response of cast slabs of three different thicknesses of FAPY alloy. Tensile, creep, and Charpy-impact data of the welded plates are also presented.

  3. Templated quasicrystalline molecular layers

    NASA Astrophysics Data System (ADS)

    Smerdon, Joe; Young, Kirsty; Lowe, Michael; Hars, Sanger; Yadav, Thakur; Hesp, David; Dhanak, Vinod; Tsai, An-Pang; Sharma, Hem Raj; McGrath, Ronan

    2014-03-01

    Quasicrystals are materials with long range ordering but no periodicity. We report scanning tunneling microscopy (STM) observations of quasicrystalline molecular layers on five-fold quasicrystal surfaces. The molecules adopt positions and orientations on the surface consistent with the quasicrystalline ordering of the substrate. Carbon-60 adsorbs atop sufficiently-separated Fe atoms on icosahedral Al-Cu-Fe to form a unique quasicrystalline lattice whereas further C60 molecules decorate remaining surface Fe atoms in a quasi-degenerate fashion. Pentacene (Pn) adsorbs at tenfold-symmetric points around surface-bisected rhombic triacontahedral clusters in icosahedral Ag-In-Yb. These systems constitute the first demonstrations of quasicrystalline molecular ordering on a template. EPSRC EP/D05253X/1, EP/D071828/1, UK BIS.

  4. Deformation behavior of NiAl-based alloys containing iron, cobalt, and hafnium

    NASA Technical Reports Server (NTRS)

    Pank, D. R.; Koss, D. A.; Nathal, M. V.

    1989-01-01

    The effects of alloying additions on the mechanical properties of the B2 intermetallic NiAl have been investigated in both the melt-spun ribbon and consolidated, bulk form. The study is based on a matrix of NiAl-based alloys with up to 20 at. pct Co and Fe additions and with reduced Al levels in the range of 30-40 at. pct. Characterization of the melt-spun ribbon by optical and scanning electron microscopy indicates a range of microstructures, including single-phase beta, gamma-prime necklace phase surrounding either martensitic or beta grains, and a mixture of equiaxed martensitic and gamma-prime grains. Bend ductility is present in melt-spun and annealed ribbons exhibiting the gamma-prime necklace structure and in a single-phase beta material containing 20 at. pct Fe. The analysis of compressive flow behavior on consolidated, bulk specimens indicates that the single-phase beta alloys exhibit a continuous decrease in yield stress with increasing temperature and profuse microcracking at grain boundaries. In contrast, multiphase (gamma-prime + either martensite or beta) alloys tend to display a peak in flow stress between 600 and 800 K, with little or no signs of microcracking. In general, heat treatments which convert the martensitic grains to beta + gamma-prime result in improved strength at temperatures above 600 K and better resistance to crack initiation.

  5. Use of Ni{sub 3}Al-based alloys for walking-beam furnaces

    SciTech Connect

    Sikka, V.K.; Dailey, R.E.

    1996-02-01

    This report summarizes the joint work performed by the Oak Ridge National Laboratory (ORNL) and Rapid Technologies, Inc. (the CRADA partner) to determine the potential of Ni{sub 3}Al-based alloys for use in gas-fired walking-beam furnace components. The report identifies tasks to be performed as part of the CRADA and the organization responsible for each task. The work required under each task was completed and is described. The CRADA accomplished the primary goal of utilizing cast Ni{sub 3}Al-based alloy as rails and other components for walking-beam furnaces manufactured by Rapid Technologies. Rapid Technologies, a small business, is implementing on a commercial basis a highly energy efficient rapid-heating technology for use in the metal manufacturing industry. The rapid heating process allows energy savings of up to 95%. Although goals of all of the tasks of this CRADA were met, there is still a need for a material to work in the rapid heating furnaces at temperatures in the range of 1,350 to 1,400 C. Future effort should be focused in fulfilling this need.

  6. Corrosion Mechanisms in Brazed Al-Base Alloy Sandwich Structures as a Function of Braze Alloy and Process Variables

    DTIC Science & Technology

    2013-02-01

    aeration solution for 8 hours. A concentrated Nitric acid (HNO3) dip for 15 seconds removed corrosion products prior to post-exposure SEM imaging [25...32 to -37°C under a liquid nitrogen chill at 11.2 V for one minute [10]. The electropolishing solution was a mixture of 1/3 concentrated Nitric acid ...DATES COVERED (From - To) 03/27/06-12/31/12 4. TITLE AND SUBTITLE Corrosion Mechanisms in Brazed Al-Base Alloy Sandwich Structures as a Function

  7. Dynamic restoration mechanism of a Fe{sub 3}Al based alloy during elevated temperature deformation

    SciTech Connect

    Chen, M.; Shan, A.; Lin, D.

    1995-08-01

    By TEM and metallographic examination, the authors found that dynamic recovery and following continuous recrystallization, which connects with the elevated temperature ductility, takes place in a Fe{sub 3}Al based alloy during elevated temperature deformation. Dynamic restoration consists of the following process: (1) by climbing or cross-slipping, glide dislocations change into dislocation arrays, (2) the dislocation array attracts lattice dislocations, (3) with increasing dislocation density, a non-equilibrium sub boundary forms, which is easy to migrate, slide or rotate under external force, and (4) when the misorientation angle of the sub boundary increases to a critical value, the sub boundary changes into a grain boundary with continuous misfit. By relaxation, the boundary then changes into a grain boundary consisting of periodical structure units.

  8. Processing and Characterization of Mechanically Alloyed NiAl-Based Alloys

    DTIC Science & Technology

    1994-07-20

    50.1 49.9 - - - 0.007 * 5 00 0E 4 CD C o E * 0 0 L 00000i,_ 0 • 4- -. 0 * CCL 6.2 6- Three types of alloys were produced, NiAI with a brittle, Heusler ...16): -e - h where 7’ is the Orowan stress, h is particle height (usually, particle radius), and X is half the mean interparticle spacing. By

  9. Kinetics of Static Strain Aging in Polycrystalline NiAl-based Alloys

    NASA Technical Reports Server (NTRS)

    Weaver, M. L.; Kaufman, M. J.; Noebe, R. D.

    1996-01-01

    The kinetics of yield point return have been studied in two NiAl-based alloys as a function of aging time at temperatures between 300 and 700 K. The results indicate that the upper yield stress increment, Delta sigma(sub u) (i.e., stress difference between the upper yield point and the final flow stress achieved during prestraining), in conventional purity (CP-NiAl) and in high purity carbon-doped (NiAl-C) material first increased with a t(exp 2/3) relationship before reaching a plateau. This behavior suggests that a Cottrell locking mechanism is the cause for yield points in NiAl. In addition, positive y-axis intercepts were observed in plots of Delta sigma(sub u) versus t(exp 2/3) suggesting the operation of a Snoek mechanism. Analysis according to the Cottrell Bilby model of atmosphere formation around dislocations yields an activation energy for yield point return in the range 70 to 76 kJ/mol which is comparable to the activation energy for diffusion of interstitial impurities in bcc metals. It is, thus, concluded that the kinetics of static strain aging in NiAl are controlled by the locking of dislocations by Cottrell atmospheres of carbon atoms around dislocations.

  10. Oxide Dispersion Strengthened Fe(sub 3)Al-Based Alloy Tubes: Application Specific Development for the Power Generation Industry

    SciTech Connect

    Kad, B.K.

    1999-07-01

    A detailed and comprehensive research and development methodology is being prescribed to produce Oxide Dispersion Strengthened (ODS)-Fe3Al thin walled tubes, using powder extrusion methodologies, for eventual use at operating temperatures of up to 1100C in the power generation industry. A particular 'in service application' anomaly of Fe3Al-based alloys is that the environmental resistance is maintained up to 1200C, well beyond where such alloys retain sufficient mechanical strength. Grain boundary creep processes at such high temperatures are anticipated to be the dominant failure mechanism.

  11. Processing and operating experience of Ni{sub 3}Al-based intermetallic alloy IC-221M

    SciTech Connect

    Sikka, V.K.; Santella, M.L.; Orth, J.E.

    1997-05-01

    The cast Ni{sub 3}Al-based intermetallic alloy IC-221M is the most advanced in its commercial applications. This paper presents progress made for this alloy in the areas of: (1) composition optimization; (2) melting process development; (3) casting process; (4) mechanical properties; (5) welding process, weld repairs, and thermal aging response; and (6) applications. This paper also reviews the operating experience with several of the components. The projection for future growth in the applications of nickel aluminide is also discussed.

  12. Rare-earth metals in nickel aluminide-based alloys: III. Structure and properties of multicomponent Ni3Al-based alloys

    NASA Astrophysics Data System (ADS)

    Bazyleva, O. A.; Povarova, K. B.; Kazanskaya, N. K.; Drozdov, A. A.

    2009-04-01

    The possibility of increasing the life of heterophase cast light Ni3Al-based superalloys at temperatures higher than 0.8 T m of Ni3Al is studied when their directional structure is additionally stabilized by nanoprecipitates, which form upon additional alloying of these alloys by refractory and active metals, and using special methods for preparing and melting of an alloy charge. The effect of the method of introducing the main components and refractory reaction-active and surface-active alloying elements into Ni3Al-based cast superalloys, which are thermally stable natural composite materials of the eutectic type, on the structure-phase state and the life of these alloys is studied. When these alloys are melted, it is necessary to perform a set of measures to form particles of refractory oxide cores covered with the β-NiAl phase and, then, γ'prim-Ni3Al phase precipitates during solidification. The latter phase forms the outer shell of grain nuclei, which provides high thermal stability and hot strength of an intermetallic compound-based alloy. As a result, a modified structure that is stabilized by the nanoprecipitates of nickel and aluminum lanthanides and the nanoprecipitates of phases containing refractory metals is formed. This structure enhances the life of the alloy at 1000 °C by a factor of 1.8-2.5.

  13. Effect of CeO{sub 2} addition on the properties of FeAl based alloy produced by mechanical alloying technique

    SciTech Connect

    Khaerudini, Deni S.; Muljadi,; Sardjono, P.; Tetuko, Anggito P.; Sebayang, P.; Ginting, M.

    2013-09-03

    Iron aluminides based on FeAl is notable for their low materials cost, ease of fabrication and good corrosion, suffixation and oxidation resistance. However, the application based on these unique properties still require the development of Fe-Al based alloy since it shows some drawbacks such as a lack of high temperature strength and low ductility. To improve the mechanical properties of FeAl based alloy, ceria (CeO{sub 2}) will be added to this compound. FeAl based alloy produced by the mechanical alloying (MA) technique. The developed specimens then assessed with respect to oxidation behaviour in high temperature, scale microstructure and hardness. The surface morphologies of the alloy evaluated and observed using scanning electron microscopy (SEM) with an energy dispersive X-ray spectroscopy (EDX). The phase structures of oxide scale formed on them were identified by X-ray diffraction (XRD). The results found that the FeAl intermetallic compound containing CeO{sub 2} 0.5 wt.% is less pores and CeO{sub 2} 1.0 wt.% is more homogen in powder and solid form, higher hardness and increase in their resistance to oxidation behaviour in high temperature compared with another percentage of CeO{sub 2}.

  14. Effect of β volume fraction on the dynamic grain growth during superplastic deformation of Ti3Al-based alloys

    NASA Astrophysics Data System (ADS)

    Kim, Ji Sik; Nam, Won Jong; Lee, Chong Soo

    1998-10-01

    The superplastic deformation behavior of Ti3Al based (α 2+β alloy was studied with respect to the volume fraction of α2/β. Three alloys containing 21, 50 and 77% in volume fractions of β exhibited large tensile elongations of over 500% at 970°C with a strain rate of 2.5x10-4 sec-1. The largest elongation was observed in the alloy with 21% of β. As the volume fraction of β phase increased, the flow stress and correspondingly, the strain-rate sensitivity values decreased. Due to the higher diffusivity of Ti in,β phase than in α2 phase, the increase in β volume fraction from 21 % to 77% accelerated the dynamic grain growth, and degraded the superplasticity of the Ti3Al-based alloys. The strain-based grain growth behavior was quantitatively analyzed and incorporated into a constitutive equation. The calculated flow curves are in agreement with the experimental ones in the stable deformation region.

  15. Detection and distribution of lithium in Mg-Li-Al based alloy by ToF-SIMS

    NASA Astrophysics Data System (ADS)

    Kumar, Vinod

    2016-12-01

    Time of Flight-Secondary Ion Mass Spectrometry (ToF-SIMS) is used to investigate the surface as well as bulk microstructural features of novel Mg-Li-Al based alloy namely Mg-9Li-7Al-3Sn-1Zn (LATZ9531). ToF-SIMS study indicates that there are six multi-oxide layers present within the surface film of LATZ9531. Furthermore, The presence of Li containing phase has been qualitatively confirmed based on the high number of Li-ion counts in SIMS, and the same is verified quantitatively by using electron probe microanalysis (EPMA). The novel approach may be useful to determine the chemical composition of the phases in various alloys which has lighter alloying elements such as lithium.

  16. Effect of composition on antiphase boundary energy in Ni3Al based alloys: Ab initio calculations

    NASA Astrophysics Data System (ADS)

    Gorbatov, O. I.; Lomaev, I. L.; Gornostyrev, Yu. N.; Ruban, A. V.; Furrer, D.; Venkatesh, V.; Novikov, D. L.; Burlatsky, S. F.

    2016-06-01

    The effect of composition on the antiphase boundary (APB) energy of Ni-based L 12-ordered alloys is investigated by ab initio calculations employing the coherent potential approximation. The calculated APB energies for the {111} and {001} planes reproduce experimental values of the APB energy. The APB energies for the nonstoichiometric γ' phase increase with Al concentration and are in line with the experiment. The magnitude of the alloying effect on the APB energy correlates with the variation of the ordering energy of the alloy according to the alloying element's position in the 3 d row. The elements from the left side of the 3 d row increase the APB energy of the Ni-based L 12-ordered alloys, while the elements from the right side slightly affect it except Ni. The way to predict the effect of an addition on the {111} APB energy in a multicomponent alloy is discussed.

  17. Effect of extrusion temperature on the microstructure of a powder metallurgy TiAl-based alloy

    SciTech Connect

    Hsiung, L.M.; Nieh, T.G.; Clemens, D.R.

    1997-01-15

    In order to balance low temperature ductility, fracture toughness and high temperature properties of {gamma}-TiAl aluminide alloys, recent developments of the alloys have focused on refining the {gamma}/{alpha}{sub 2} full lamellar (FL) microstructure through advanced processing such as powder metallurgy (P/M). Resulted from a refined FL microstructure (both smaller lamellar grain size and thinner lamellar interface spacing) in the P/M fabricated titanium aluminide alloys, the mechanical properties of the alloys have been demonstrated to be superior to those of the aluminide alloys fabricated by conventional ingot metallurgy (I/M). However, since the microstructure of rapidly-solidified aluminide powder used in P/M process is not in an equilibrium state, the microstructures of P/M aluminide alloys are expected to be sensitive to the processing history. Accordingly, the optimization of microstructure-property of a P/M alloy through an appropriate P/M process control becomes an important issue. The purpose of this investigation is therefore aiming at understanding the effect of extrusion temperature on the microstructure of a P/M titanium aluminide alloy.

  18. Phase Transformation and Residual Stress in a Laser Beam Spot-Welded TiAl-Based Alloy

    NASA Astrophysics Data System (ADS)

    Liu, Jie; Staron, Peter; Riekehr, Stefan; Stark, Andreas; Schell, Norbert; Huber, Norbert; Schreyer, Andreas; Müller, Martin; Kashaev, Nikolai

    2016-12-01

    The microstructure, chemical composition, residual stress, and lattice parameter evolution of the welding zone (WZ) and heat-affected zone (HAZ) of a laser-beam-welded TiAl-based alloy were investigated. It was found that both α 2 and γ phases remain highly restrained in the WZ edge, and the stresses are relieved in the HAZ. A grain refinement mechanism is proposed, which works by heating the material to the β or α + β phase field for a short time. The lamellar colonies are refined by the Nb-enriched segregations.

  19. Experimental and theoretical analyses on the ultrasonic cavitation processing of Al-based alloys and nanocomposites

    NASA Astrophysics Data System (ADS)

    Jia, Shian

    Strong evidence is showing that microstructure and mechanical properties of a casting component can be significantly improved if nanoparticles are used as reinforcement to form metal-matrix-nano-composite (MMNC). In this paper, 6061/A356 nanocomposite castings are fabricated using the ultrasonic stirring technology (UST). The 6061/A356 alloy and Al2O3/SiC nanoparticles are used as the matrix alloy and the reinforcement, respectively. Nanoparticles are injected into the molten metal and dispersed by ultrasonic cavitation and acoustic streaming. The applied UST parameters in the current experiments are used to validate a recently developed multiphase Computational Fluid Dynamics (CFD) model, which is used to model the nanoparticle dispersion during UST processing. The CFD model accounts for turbulent fluid flow, heat transfer and the complex interaction between the molten alloy and nanoparticles using the ANSYS Fluent Dense Discrete Phase Model (DDPM). The modeling study includes the effects of ultrasonic probe location and the initial location where the nanoparticles are injected into the molten alloy. The microstructure, mechanical behavior and mechanical properties of the nanocomposite castings have been also investigated in detail. The current experimental results show that the tensile strength and elongation of the as-cast nanocomposite samples (6061/A356 alloy reinforced by Al2O 3 or SiC nanoparticles) are improved. The addition of the Al2O 3 or SiC nanoparticles in 6061/A356 alloy matrix changes the fracture mechanism from brittle dominated to ductile dominated.

  20. 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.

  1. Directionally Solidified NiAl-Based Alloys Studied for Improved Elevated-Temperature Strength and Room-Temperature Fracture Toughness

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.

    2000-01-01

    Efforts are underway to replace superalloys used in the hot sections of gas turbine engines with materials possessing better mechanical and physical properties. Alloys based on the intermetallic NiAl have demonstrated potential; however, they generally suffer from low fracture resistance (toughness) at room temperature and from poor strength at elevated temperatures. Directional solidification of NiAl alloyed with both Cr and Mo has yielded materials with useful toughness and elevated-temperature strength values. The intermetallic alloy NiAl has been proposed as an advanced material to extend the maximum operational temperature of gas turbine engines by several hundred degrees centigrade. This intermetallic alloy displays a lower density (approximately 30-percent less) and a higher thermal conductivity (4 to 8 times greater) than conventional superalloys as well as good high-temperature oxidation resistance. Unfortunately, unalloyed NiAl has poor elevated temperature strength (approximately 50 MPa at 1027 C) and low room-temperature fracture toughness (about 5 MPa). Directionally solidified NiAl eutectic alloys are known to possess a combination of high elevated-temperature strength and good room-temperature fracture toughness. Research has demonstrated that a NiAl matrix containing a uniform distribution of very thin Cr plates alloyed with Mo possessed both increased fracture toughness and elevated-temperature creep strength. Although attractive properties were obtained, these alloys were formed at low growth rates (greater than 19 mm/hr), which are considered to be economically unviable. Hence, an investigation was warranted of the strength and toughness behavior of NiAl-(Cr,Mo) directionally solidified at faster growth rates. If the mechanical properties did not deteriorate with increased growth rates, directional solidification could offer an economical means to produce NiAl-based alloys commercially for gas turbine engines. An investigation at the NASA Glenn

  2. Surfaces of Al-based complex metallic alloys: atomic structure, thin film growth and reactivity

    PubMed Central

    Ledieu, Julian; Gaudry, Émilie; Fournée, Vincent

    2014-01-01

    We present a review on recent work performed on periodic complex metallic alloy (CMA) surfaces. The electronic and crystallographic structures of clean pseudo-tenfold, pseudo-twofold, sixfold surfaces will be presented along with the recent findings on CMA of lower structural complexity, i.e. with a smaller unit cell. The use of CMA surfaces as templates for thin film growth and the formation of surface alloy will also be introduced. The reactivity of these complex surfaces and their impact in the field of heterogeneous catalysis will be discussed. Finally, common trends among these systems will be highlighted when possible and future challenges will be examined. PMID:27877673

  3. Ni.sub.3 Al-based intermetallic alloys having improved strength above 850.degree. C.

    DOEpatents

    Liu, Chain T.

    2000-01-01

    Intermetallic alloys composed essentially of: 15.5% to 17.0% Al, 3.5% to 5.5% Mo, 4% to 8% Cr, 0.04% to 0.2% Zr, 0.04% to 1.5% B, balance Ni, are characterized by melting points above 1200.degree. C. and superior strengths at temperatures above 1000.degree. C.

  4. Alloying Behavior and Properties of Al-Based Composites Reinforced with Al85Fe15 Metallic Glass Particles Fabricated by Mechanical Alloying and Hot Pressing Consolidation

    NASA Astrophysics Data System (ADS)

    Zhang, Lanxiang; Yang, LiKun; Leng, Jinfeng; Wang, Tongyang; Wang, Yan

    2017-01-01

    In this study, Al85Fe15 metallic glass particles with high onset crystallization temperature (1209 K) were synthesized by a mechanical alloying method. High-quality 6061Al-based composites reinforced with Al85Fe15 metallic glass particles were fabricated by a vacuum hot-pressing sintering technique. The glass particles with flake-like shape are distributed uniformly in the Al matrix. The bulk composites possess high relative density, excellent hardness and strength. The microhardness values of the Al-based bulk composites with the additions of 20 vol.% and 30 vol.% Al85Fe15 particles are 204 MPa and 248 MPa, respectively, which are much higher than that of 6061Al (61 MPa). The compressive yield strength of the 30 vol.% glass-reinforced composite is 478 MPa, which is enhanced by 273% compared with 6061Al. The amorphous characteristic and homogeneous dispersion of glass particles account for the excellent mechanical properties of the Al-based composites. In addition, the corrosion behavior of Al-based composites in a seawater solution has been investigated by electrochemical polarization measurements. Compared to 6061Al, the 30 vol.% glass-reinforced composite shows the lower corrosion/passive current density and larger passive region, indicating the greatly enhanced corrosion resistance.

  5. Quasicrystalline structures and uses thereof

    DOEpatents

    Steinhardt, Paul Joseph; Chaikin, Paul Michael; Man, Weining

    2017-02-14

    This invention relates generally to the field of quasicrystalline structures. In preferred embodiments, the stopgap structure is more spherically symmetric than periodic structures facilitating the formation of stopgaps in nearly all directions because of higher rotational symmetries. More particularly, the invention relates to the use of quasicrystalline structures for optical, mechanical, electrical and magnetic purposes. In some embodiments, the invention relates to manipulating, controlling, modulating and directing waves including electromagnetic, sound, spin, and surface waves, for pre-selected range of wavelengths propagating in multiple directions.

  6. Quasicrystalline structures and uses thereof

    DOEpatents

    Steinhardt, Paul J; Chaikin, Paul Michael; Man, Weining

    2013-12-03

    This invention relates generally to the field of quasicrystalline structures. In preferred embodiments, the stopgap structure is more spherically symmetric than periodic structures facilitating the formation of stopgaps in nearly all directions because of higher rotational symmetries. More particularly, the invention relates to the use of quasicrystalline structures for optical, mechanical, electrical and magnetic purposes. In some embodiments, the invention relates to manipulating, controlling, modulating and directing waves including electromagnetic, sound, spin, and surface waves, for pre-selected range of wavelengths propagating in multiple directions.

  7. Quasicrystalline structures and uses thereof

    DOEpatents

    Steinhardt, Paul Joseph [Princeton, NJ; Chaikin, Paul Michael [New York, NY; Man, Weining [San Francisco, CA

    2011-11-22

    This invention relates generally to the field of quasicrystalline structures. In preferred embodiments, the stopgap structure is more spherically symmetric than periodic structures facilitating the formation of stopgaps in nearly all directions because of higher rotational symmetries. More particularly, the invention relates to the use of quasicrystalline structures for optical, mechanical, electrical and magnetic purposes. In some embodiments, the invention relates to manipulating, controlling, modulating and directing waves including electromagnetic, sound, spin, and surface waves, for a pre-selected range of wavelengths propagating in multiple directions.

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

    SciTech Connect

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

    1989-08-01

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

  9. Welding and mechanical properties of cast FAPY (Fe-16 at. % Al-based) alloy slabs

    SciTech Connect

    Sikka, V.K.; Goodwin, G.M.; Alexander, D.J.; Howell, C.R.

    1995-05-01

    This report deals with the welding procedure development and weldment properties of an Fe-16 at. % Al alloy known as FAPY. The welding procedure development was carried out on 12-, 25-, and 51-mm (0.5-, 1-, and 2-in.) -thick plates of the alloy in the as-cast condition. The welds were prepared by using the gas tungsten arc process and filler wire of composition matching the base-metal composition. The preheat temperatures varied from room temperature to 350{degrees}C, and the postweld heat treatment (PWHT) was limited only for 1 h at 750{degrees}C. The welds were characterized by microstructural. analysis and microhardness data. The weldment specimens were machined for Charpy-impact, tensile, and creep properties. The tensile and creep properties of the weldment specimens were essentially the same as that of the base metal. The Charpy-impact properties of the weldment specimens improved with the PWHT and were somewhat lower than previously developed data on the wrought material. Additional work is required on welding of thicker sections, development of PWHT temperatures as a function of section thickness, and mechanical properties.

  10. The Mechanisms of Dispersion Strengthening and Fracture in Al-based XD (TM) Alloys

    NASA Technical Reports Server (NTRS)

    Aiken, R. M., Jr.

    1990-01-01

    The influence of reinforcement size, volume fraction, and matrix deformation behavior on room and elevated temperature strength, and the fracture toughness of metal matrix composites of both pure aluminum and Al(4 percent)Cu(1.5 percent)Mg with 0 to 15 vol percent TiB2 were examined. Higher TiB2 volume fractions increased the tensile yield strength both at room and elevated temperatures, and reduced the elongation to fracture. Tensile tests also indicate that small particles provided a greater increase in strength for a given volume fraction than larger particles, whereas elongation to fracture appeared to be insensitive to reinforcement size. The fracture toughness of the Al(4 percent)Cu(1.5 percent)Mg alloys decreased rapidly with TiB2 additions of 0 to 5 vol percent and more slowly with TiB2 additions of 5 to 15 vol percent. Fracture toughness appears to be independent of TiB2 particle size. The isothermal-aging response of the precipitation strengthened Al(4 percent)Cu(1.5 percent)Mg alloys was not altered by the presence of TiB2.

  11. Amorphous and nanocrystalline phase formation in highly-driven Al-based binary alloys

    SciTech Connect

    Kalay, Yunus Eren

    2009-01-01

    Remarkable advances have been made since rapid solidification was first introduced to the field of materials science and technology. New types of materials such as amorphous alloys and nanostructure materials have been developed as a result of rapid solidification techniques. While these advances are, in many respects, ground breaking, much remains to be discerned concerning the fundamental relationships that exist between a liquid and a rapidly solidified solid. The scope of the current dissertation involves an extensive set of experimental, analytical, and computational studies designed to increase the overall understanding of morphological selection, phase competition, and structural hierarchy that occurs under far-from equilibrium conditions. High pressure gas atomization and Cu-block melt-spinning are the two different rapid solidification techniques applied in this study. The research is mainly focused on Al-Si and Al-Sm alloy systems. Silicon and samarium produce different, yet favorable, systems for exploration when alloyed with aluminum under far-from equilibrium conditions. One of the main differences comes from the positions of their respective T0 curves, which makes Al-Si a good candidate for solubility extension while the plunging T0 line in Al-Sm promotes glass formation. The rapidly solidified gas-atomized Al-Si powders within a composition range of 15 to 50 wt% Si are examined using scanning and transmission electron microscopy. The non-equilibrium partitioning and morphological selection observed by examining powders at different size classes are described via a microstructure map. The interface velocities and the amount of undercooling present in the powders are estimated from measured eutectic spacings based on Jackson-Hunt (JH) and Trivedi-Magnin-Kurz (TMK) models, which permit a direct comparison of theoretical predictions. For an average particle size of 10 {micro}m with a Peclet number of ~0.2, JH and TMK deviate from

  12. Assembly of quasicrystalline photonic heterostructures

    DOEpatents

    Grier, David G.; Roichman, Yael; Man, Weining; Chaikin, Paul Michael; Steinhardt, Paul Joseph

    2011-07-19

    A method and system for assembling a quasicrystalline heterostructure. A plurality of particles is provided with desirable predetermined character. The particles are suspended in a medium, and holographic optical traps are used to position the particles in a way to achieve an arrangement which provides a desired property.

  13. Assembly of quasicrystalline photonic heterostructures

    DOEpatents

    Grier, David G.; Roichman, Yael; Man, Weining; Chaikin, Paul Michael; Steinhardt, Paul Joseph

    2013-03-12

    A method and system for assembling a quasicrystalline heterostructure. A plurality of particles is provided with desirable predetermined character. The particles are suspended in a medium, and holographic optical traps are used to position the particles in a way to achieve an arrangement which provides a desired property.

  14. Microstructure and wear behavior of quasicrystalline thermal sprayed

    SciTech Connect

    Sordelet, D.J.; Krotz, P.D.; Daniel, R.L.; Smith, M.F.

    1994-12-31

    An Al-Cu-Fe alloy coating which forms a quasicrystalline phase is a potential candidate for replacing electro-deposited chromium on various components in the Space Shuttle Main Engine. Coatings were deposited by air and vacuum plasma spraying and by high-velocity oxygen-fuel spraying. Finer starting powders tended to lose Al during spraying, which affected the phase equilibrium of the coatings. Coatings which retained the starting powder composition were richer in the desired quasicrystalline phase. Ball-on-disk wear tests between 440 C stainless steel ball and the Al-Cu-Fe coatings were performed. Coefficients of friction ranged from 0.60 to 1.2 for the different coatings.

  15. Microstructure and wear behavior of quasicrystalline thermal sprayed coatings

    SciTech Connect

    Sordelet, D.J.; Krotz, P.D.; Daniel, R.L. Jr.; Smith, M.F.

    1995-12-31

    An Al-Cu-Fe alloy coating which forms a quasicrystalline phase is a potential candidate for replacing electro-deposited chromium on various components in the Space Shuttle Main Engine. Coatings were deposited by air and vacuum plasma spraying and by high-velocity oxygen-fuel spraying. Finer starting powders tended to lose Al during spraying, which affected the phase equilibrium of the coatings. Coatings which retained the starting powder composition were richer in the desired quasicrystalline phase. Ball-on-disk wear tests between 440 C stainless steel ball and the Al-Cu-Fe coatings were performed. Coefficients of friction ranged from 0.60 to 1.2 for the different coatings.

  16. Investigation of Portevin-Le Chatelier effect in 5456 Al-based alloy using digital image correlation

    NASA Astrophysics Data System (ADS)

    Cheng, Teng; Xu, Xiaohai; Cai, Yulong; Fu, Shihua; Gao, Yue; Su, Yong; Zhang, Yong; Zhang, Qingchuan

    2015-02-01

    A variety of experimental methods have been proposed for Portevin-Le Chatelier (PLC) effect. They mainly focused on the in-plane deformation. In order to achieve the high-accuracy measurement, three-dimensional digital image correlation (3D-DIC) was employed in this work to investigate the PLC effect in 5456 Al-based alloy. The temporal and spatial evolutions of deformation in the full field of specimen surface were observed. The large deformation of localized necking was determined experimentally. The distributions of out-of-plane displacement over the loading procedure were also obtained. Furthermore, a comparison of measurement accuracy between two-dimensional digital image correlation (2D-DIC) and 3D-DIC was also performed. Due to the theoretical restriction, the measurement accuracy of 2D-DIC decreases with the increase of deformation. A maximum discrepancy of about 20% with 3D-DIC was observed in this work. Therefore, 3D-DIC is actually more essential for the high-accuracy investigation of PLC effect.

  17. In situ X-ray observations of gas porosity interactions with dendritic microstructures during solidification of Al-based alloys

    NASA Astrophysics Data System (ADS)

    Murphy, A. G.; Browne, D. J.; Houltz, Y.; Mathiesen, R. H.

    2016-03-01

    In situ X-radiography solidification experiments were performed on Al-based alloys, using both synchrotron and laboratory-based X-ray sources, in conjunction with a gradient furnace and a newly developed isothermal furnace, respectively. The effect of gas porosity nucleation and growth within the semi-solid mush during both columnar and equiaxed solidification was thereby observed. In all experimental cases examined, gas porosity was observed to nucleate and grow within the field-of-view (FOV) causing various levels of distortion to the semi-solid mush, and thereafter disappearing from the sample leaving no permanent voids within the solidified microstructure. During columnar growth, a single bubble caused severe remelting and destruction of primary trunks leading to secondary fragmentation and evidence of blocking of the columnar front. Equiaxed solidification was performed under microgravity-like conditions with restricted grain motion in the FOV. The degree to which the nucleated gas bubbles affected the surrounding grain structure increased with increasing solid fraction. However, bubble sphericity remained unaffected by apparent solid fraction or grain coherency.

  18. Flux quantization on quasicrystalline networks

    SciTech Connect

    Behrooz, A.; Burns, M.J.; Deckman, H.; Levine, D.; Whitehead, B.; Chaikin, P.M.

    1986-07-21

    We have measured the superconducting transition temperature T-italic/sub c-italic/(H) as a function of magnetic field for a network of thin aluminum wires arranged in two quasicrystalline arrays, a Fibonacci sequence and the eightfold-symmetric version of a Penrose tiling. The quasicrystals have two periods whose ratio sigma is irrational and are constructed of two tiles with irrationally related areas. We find a series of dips in deltaT-italic/sub c-italic/(H) corresponding to favorable arrangements of the flux lattice on the quasicrystalline substrate. The largest dips are found at sigma/sup n-italic/ and the dips approach the zero-field transition temperature as n-italic increases.

  19. Quasicrystalline structures and uses thereof

    DOEpatents

    Steinhardt, Paul Joseph; Chaikin, Paul Michael; Man, Weining

    2013-08-13

    This invention relates generally to devices constructed from quasicrystalline heterostructures. In preferred embodiments, two or more dielectric materials are arranged in a two- or three-dimensional space in a lattice pattern having at least a five-fold symmetry axis and not a six-fold symmetry axis, such that the quasicrystalline heterostructure exhibits an energy band structure in the space, the band structure having corresponding symmetry, which symmetry is forbidden in crystals, and which band structure comprises a complete band gap. The constructed devices are adapted for manipulating, controlling, modulating, trapping, reflecting and otherwise directing waves including electromagnetic, sound, spin, and surface waves, for a pre-selected range of wavelengths propagating within or through the heterostructure in multiple directions.

  20. Oxide-Dispersion-Strengthened Fe3Al-Based Alloy Tubes: Application-Specific Development for the Power Generation Industry

    SciTech Connect

    Kad, BK

    2001-07-20

    A detailed and comprehensive research and development methodology is being prescribed to produce Oxide Dispersion Strengthened (ODS)-Fe{sub 3}Al thin walled tubes, using powder extrusion methodologies, for eventual use at operating temperatures of up to 1100 C in the power generation industry. A particular ''in service application'' anomaly of Fe{sub 3}Al-based alloys is that the environmental resistance is maintained up to 1200 C, well beyond where such alloys retain sufficient mechanical strength. Grain boundary creep processes at such high temperatures are anticipated to be the dominant failure mechanism. Thus, the challenges of this program are manifold: (1) to produce thin walled ODS-Fe{sub 3}Al tubes, employing powder extrusion methodologies, with (2) adequate increased strength for service at operating temperatures, and (3) to mitigate creep failures by enhancing the as-processed grain size in ODS-Fe{sub 3}Al tubes. Our research progress till date has resulted in the successful batch production of typically 8 Ft. lengths of 1-3/8 inch diameter, 1/8 inch wall thickness, ODS-Fe{sub 3}Al tubes via a proprietary single step extrusion consolidation process. The process parameters for such consolidation methodologies have been prescribed and evaluated as being routinely reproducible. Such processing parameters (i.e., extrusion ratios, temperature, can design etc.) were particularly guided by the need to effect post-extrusion recrystallization and grain growth at a sufficiently low temperature, while still meeting the creep requirement at service temperatures. Static recrystallization studies show that elongated grains (with their long axis parallel to the extrusion axis), typically 200-2000 {micro}m in diameter, and several millimeters long can be obtained routinely, at 1200 C. The growth kinetics are affected by the interstitial impurity content in the powder batches. For example complete recrystallization, across the tube wall thickness, is observed for clean

  1. Oxide Dispersion Strengthened Fe3Al-Based Alloy Tubes: Application Specific Development for the Power Generation Industry

    SciTech Connect

    Kad, B.K.

    2002-02-08

    A detailed and comprehensive research and development methodology is being prescribed to produce Oxide Dispersion Strengthened (ODS)-Fe{sub 3}Al thin walled tubes, using powder extrusion methodologies, for eventual use at operating temperatures of up to 1100% in the power generation industry. A particular ''in service application'' anomaly of Fe{sub 3}Al-based alloys is that the environmental resistance is maintained up to 1200 C, well beyond where such alloys retain sufficient mechanical strength. Grain boundary creep processes at such high temperatures are anticipated to be the dominant failure mechanism. Thus, the challenges of this program are manifold: (1) to produce thin walled ODS-Fe{sub 3}Al tubes, employing powder extrusion methodologies, with (2) adequate increased strength for service at operating temperatures, and (3) to mitigate creep failures by enhancing the as-processed grain size in ODS-Fe{sub 3}Al tubes. Our research progress till date has resulted in the successful batch production of typically 8 Ft. lengths of 1-3/8 inch diameter, 1/8 inch wall thickness, ODS-Fe{sub 3}Al tubes via a proprietary single step extrusion consolidation process. The process parameters for such consolidation methodologies have been prescribed and evaluated as being routinely reproducible. Such processing parameters (i.e., extrusion ratios, temperature, can design etc.) were particularly guided by the need to effect post-extrusion recrystallization and grain growth at a sufficiently low temperature, while still meeting the creep requirement at service temperatures. Static recrystallization studies show that elongated grains (with their long axis parallel to the extrusion axis), typically 200-2000 {micro}m in diameter, and several millimeters long can be obtained routinely, at 1200 C. The growth kinetics are affected by the interstitial impurity content in the powder batches. For example complete recrystallization, across the tube wall thickness, is observed for clean

  2. 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).

  3. Physical, mechanical, and tribological properties of quasicrystalline Al-Cu-Fe coatings prepared by plasma spraying

    NASA Astrophysics Data System (ADS)

    Lepeshev, A. A.; Rozhkova, E. A.; Karpov, I. V.; Ushakov, A. V.; Fedorov, L. Yu.

    2013-12-01

    The physical, mechanical, and tribological properties of quasicrystalline coatings based on the Al65Cu23Fe12 alloy prepared by plasma spraying have been investigated. The specific features of the phase formation due to the competitive interactions of the icosahedral ψ and cubic β phases have been elucidated. A correlation between the microhardness and the content of the icosahedral phase in the coating has been determined. The decisive role of the quasicrystalline phase in the formation of high tribological characteristics of the coatings has been revealed and tested.

  4. Strain accumulation in quasicrystalline solids

    NASA Technical Reports Server (NTRS)

    Nori, Franco; Ronchetti, Marco; Elser, Veit

    1988-01-01

    The relaxation of two-dimensional quasicrystalline elastic networks when their constituent bonds are perturbed homogeneously is studied. Whereas ideal, quasi-periodic networks are stable against such perturbations, significant accumulations of strain in a class of disordered networks generated by a growth process are found. The grown networks are characterized by root mean square phason fluctuations which grow linearly with system size. The strain accumulation observed in these networks also grows linearly with system size. Finally, dependence of strain accumulation on cooling rate is found.

  5. The effect of grain refinement on the room-temperature ductility of as-cast Fe{sub 3}Al-based alloys

    SciTech Connect

    Viswanathan, S.; Andleigh, V.K.; McKamey, C.G.

    1995-08-01

    Fe{sub 3}Al-based alloys exhibit poor room-temperature ductility in the as-cast condition. In this study, the effect of grain refinement of the as-cast alloy on room-temperature ductility was investigated. Small melts of Fe-28 at. % Al-5 at. % Cr were inoculated with various alloying additions and cast into a 50- x 30- x 30-mm graphite mold. The resulting ingots were examined metallographically for evidence of grain refinement, and three-point bend tests were conducted on samples to assess the effect on room-temperature ductility. Ductility was assumed to correlate with the strain corresponding to the maximum stress obtained in the bend test. The results showed that titanium was extremely effective in grain refinement, although it severely embrittled the alloy in contents exceeding 1%. Boron additions strengthened the alloy significantly, while carbon additions reduced both the strength and ductility. The best ductility was found in an alloy containing titanium, boron, and carbon. In order to verify the results of the grain refinement study, vacuum-induction melts of selected compositions were prepared and cast into a larger 25- x 150- x 100-mm graphite mold. Tensile specimens were machined from the ingots, and specimens were tested at room temperature. The results of the tensile tests agreed with the results of the grain refinement study; in addition, the addition of molybdenum was found to significantly increase room-temperature tensile ductility over that of the base alloy.

  6. Effect of directional solidification on the structure and properties of Ni3Al-based alloy single crystals alloyed with W, Mo, Cr, and REM

    NASA Astrophysics Data System (ADS)

    Povarova, K. B.; Drozdov, A. A.; Bondarenko, Yu. A.; Bazyleva, O. A.; Bulakhtina, M. A.; Morozov, A. E.; Antonova, A. V.

    2014-07-01

    The effect of the solidification gradient ( G = 60 and 150°C/cm) at a solidification rate R = 10 mm/min on the structural parameters and the short- and long-term strength characteristics of blade-type single-crystal workpieces made of a heterophase γ' + γ VKNA-1V-type γ'(Ni3Al)-based alloy with low contents of refractory metals is studied. The single crystals have a cellular-dendritic structure: dendrites are heterophase and consist of thin discontinuous nickel-based γ solid solution layers between γ'(Ni3Al)-matrix regions. Primary γ'-phase precipitates are located in the interdendritic space. An increase in solidification gradient G from 60 to 150°C/cm (by a factor of 2.5) at a solidification rate R = 10 mm/min leads to a decrease in the dendrite arm spacing by ˜1.5 times, the size of primary γ'-phase precipitates by 2.5-3 times, and the refinement of γ' regions between γ layers in dendrite arms and at the periphery of dendrites by 2-3 times. The strength characteristics of the single crystals grown at G = 150°C/cm are higher than those of the single crystals grown at G = 60°C/cm by 10%. An increase in gradient G weakly affects the long-term strength of the single crystals. During long-term high-temperature tests under loading, secondary disperse γsec' particles precipitate in the discontinuous γ solid solution layers forming inclusions in two-phase γ' + γ dendrites, and the morphology of the γ layers changes (they become thicker and shorter). The <111> VKNA-1V alloy single crystals grown at G = 150°C/cm and R = 10 mm/min have a set of the required properties, namely, a high high-temperature strength over the entire temperature range, moderate high-temperature plasticity, and the absence of the plasticity drop at 800°C (which is characteristic of single crystals with other crystallographic orientations). These properties make <111> VKNA-1V alloy single crystals promising for working and nozzle gas turbine engine blades, including the blades in

  7. Quasicrystalline tilings with nematic colloidal platelets

    PubMed Central

    Dontabhaktuni, Jayasri; Ravnik, Miha; Žumer, Slobodan

    2014-01-01

    Complex nematic fluids have the remarkable capability for self-assembling regular colloidal structures of various symmetries and dimensionality according to their micromolecular orientational order. Colloidal chains, clusters, and crystals were demonstrated recently, exhibiting soft-matter functionalities of robust binding, spontaneous chiral symmetry breaking, entanglement, shape-driven and topological driven assembly, and even memory imprinting. However, no quasicrystalline structures were found. Here, we show with numerical modeling that quasicrystalline colloidal lattices can be achieved in the form of original Penrose P1 tiling by using pentagonal colloidal platelets in layers of nematic liquid crystals. The tilings are energetically stabilized with binding energies up to 2500 kBT for micrometer-sized platelets and further allow for hierarchical substitution tiling, i.e., hierarchical pentagulation. Quasicrystalline structures are constructed bottom-up by assembling the boat, rhombus, and star maximum density clusters, thus avoiding other (nonquasicrystalline) stable or metastable configurations of platelets. Central to our design of the quasicrystalline tilings is the symmetry breaking imposed by the platelet shape and the surface anchoring conditions at the colloidal platelets, which are misaligning and asymmetric over two perpendicular mirror planes. Finally, the design of the quasicrystalline tilings as platelets in nematic liquid crystals is inherently capable of a continuous variety of length scales of the tiling, ranging over three orders of magnitude in the typical length (from to ), which could allow for the design of quasicrystalline photonics at multiple frequency ranges. PMID:24550269

  8. Quasicrystalline long-range order in an ABC star block copolymer

    NASA Astrophysics Data System (ADS)

    Dotera, Tomonari

    2009-03-01

    We report the formation of a dodecagonal quasicrystal (DDQC) in a lattice Monte Carlo simulation of a star-shaped three component polymeric alloy. We have observed a series of Archimedean and quasicrystalline phases (4.8^2) ->(3^2.4.3.4) ->DDQC ->(4.6.12) with increase of one component of ABC star polymers. This phase behavior can be regarded as a transition from square tiling to triangle tiling via square-triangle tiling. The simulation is associated with the recent striking experimental manifestation of quasicrystalline order: A mesoscopic tiling pattern with twelvefold symmetry in a three-component star polymer system composed of polyisoprene, polystyrene, and poly (2-vinylpyridine). Since, the same kind of quasicrystalline structures have been found for metal alloys, chalcogenides, and liquid crystals, the present result confirms the universal nature of quasicrystalline long-range order over several hierarchical length scales. [4pt] T. Dotera and T. Gemma, Philos. Mag. 86, 1085 (2006).[0pt] T. Dotera, Phil. Mag. 88, 2245 (2008). [0pt] K. Hayashida, et al., Phys. Rev. Lett. 98, 195502 (2007).

  9. Synthesis of Nanostructured GAMMA-TiAl Based Powders and Bulk Alloys Using High Energy Mechanical Milling and Hip

    NASA Astrophysics Data System (ADS)

    Yu, Hongbao; Zhang, Deliang; Chen, Yuyong; Liu, Zhiguang

    The microstructural evolution and powder particle morphology change in the process used to synthesize bulk nanostructured γ-TiAl intermetallic based binary Ti-47Al (in at%) alloy (TA-1) and complex Ti-45Al-2Cr-2Nb-1B-0.5Ta (in at%) alloy (TA-2) have been studied. This process combines high energy mechanical milling of elemental powder mixtures, thermal treatment and HIP. The bulk alloys consist of predominantly TiAl phase and a small fraction of Ti3Al phase, with the average grain sizes of the TiAl and Ti3Al phases being approximately 45nm and 40nm respectively in the bulk TA-1 alloy and being 37nm and 35nm respectively in the bulk TA-2 alloy. The study also shows that addition of a small fraction of hard powder particles such as Nb, Cr, B and Ta powder particles to the starting powder mixture has a significant effect in maintaining a small average particle size during high energy mechanical milling without using PCA and thus significantly enhances the mechanical alloying effect of the milling process.

  10. Effects of composition and heat treatment at 1150{degrees}C on creep-rupture properties of Fe{sub 3}Al-based alloys

    SciTech Connect

    McKamey, C.G.; Maziasz, P.J.; Marrero-Santos, Y.

    1995-08-01

    The effects of composition and heat treatment at 1150{degrees}C on the creep-rupture properties of Fe3Al-based alloys were studied. Tests of alloy FA-180 (Fe-28Al-5Cr-0.5Nb-0.8Mo-0.025Zr-0.05C-0.005B, at.%) with this heat treatment were performed in air using various test temperatures and stresses in order to obtain creep activation energies and constants. An activation energy for creep of approximately 150 kcal/mole was determined, a value which is approximately twice that obtained earlier for the binary alloy heat treated at 750{degrees}C. Tests were also conducted on alloys containing various combinations of Cr, Mo, Nb, Zr, C, and B in order to better understand the effect of composition on the improved creep resistance with heat treating at 1150{degrees}C. The results suggest an interaction of Mo with Zr and Nb to produce increased creep life.

  11. Method of making quasicrystal alloy powder, protective coatings and articles

    DOEpatents

    Shield, J.E.; Goldman, A.I.; Anderson, I.E.; Ellis, T.W.; McCallum, R.W.; Sordelet, D.J.

    1995-07-18

    A method of making quasicrystalline alloy particulates is disclosed wherein an alloy is superheated and the melt is atomized to form generally spherical alloy particulates free of mechanical fracture and exhibiting a predominantly quasicrystalline in the atomized condition structure. The particulates can be plasma sprayed to form a coating or consolidated to form an article of manufacture. 3 figs.

  12. Method of making quasicrystal alloy powder, protective coatings and articles

    DOEpatents

    Shield, Jeffrey E.; Goldman, Alan I.; Anderson, Iver E.; Ellis, Timothy W.; McCallum, R. William; Sordelet, Daniel J.

    1995-07-18

    A method of making quasicrystalline alloy particulates wherein an alloy is superheated and the melt is atomized to form generally spherical alloy particulates free of mechanical fracture and exhibiting a predominantly quasicrystalline in the atomized condition structure. The particulates can be plasma sprayed to form a coating or consolidated to form an article of manufacture.

  13. Effects of Changes in Chemistry on Flex Bending Fatigue Behavior of Al-Based Amorphous Alloy Ribbons

    NASA Astrophysics Data System (ADS)

    Huang, Chun-Kuo; Lewandowski, John J.

    2012-08-01

    The effects of changes in composition on the flow behavior and flex bending fatigue behavior of a series of Al-Gd-Ni- X ( X = Fe or Co) amorphous alloy ribbons have been determined at 1 Hz at room temperature. It has been shown that the addition of Fe, Co, and Fe/Co combination into these materials increases the strength, T g, and T x1 in addition to the activation energy for crystallization. The lowest strength ( i.e., 880 MPa) base alloy Al87Gd6Ni7 exhibited the best low-cycle fatigue (LCF) and worst high-cycle fatigue (HCF) behavior, whereas the higher strength alloys (~1100 MPa) Al85Gd6Ni7Fe2 and Al85Gd6Ni7Fe1Co1 exhibited worse LCF and better HCF behavior. The ratio of the stress amplitude at the fatigue limit at 1 × 106 cycles to uniaxial failure strength ranged from 0.25 to 0.37 (240 to 397 MPa), much higher than conventional aluminum alloys. These results are also compared with those obtained on other amorphous alloy ribbons.

  14. Preliminary Analysis of the General Performance and Mechanical Behavior of Irradiated FeCrAl Base Alloys and Weldments

    SciTech Connect

    Gussev, Maxim N.; Field, Kevin G.; Briggs, Samuel A.; Yamamoto, Yukinori

    2016-09-30

    The iron-based, iron-chromium-aluminum (FeCrAl) alloys are promising, robust materials for deployment in current and future nuclear power plants. This class of alloys demonstrates excellent performance in a range of environments and conditions, including high-temperature steam (>1000°C). Furthermore, these alloys have the potential to have prolonged survival under loss-of-coolant accident (LOCA) conditions compared to the more traditional cladding materials that are either Zr-based alloys or austenitic steels. However, one of the issues associated with FeCrAl alloys is cracking during welding. The present project investigates the possibility of mitigating welding-induced cracking via alloying and precise structure control of the weldments; in the frame work of the project, several advanced alloys were developed and are being investigated prior to and after neutron irradiation to provide insight into the radiation tolerance and mechanical performance of the weldments. The present report provides preliminary results on the post-irradiation characterization and mechanical tests performed during United States Fiscal Year (FY) 2016. Chapter 1 provides a general introduction, and Chapter 2 describes the alloy compositions, welding procedure, specimen geometry and manufacturing parameters. Also, a brief discussion of the irradiation at the High Flux Isotope Reactor (HFIR) is provided. Chapter 3 is devoted to the analysis of mechanical tests performed at the hot cell facility; tensile curves and mechanical properties are discussed in detail focusing on the irradiation temperature. Limited fractography results are also presented and analyzed. The discussion highlights the limitations of the testing within a hot cell. Chapter 4 underlines the advantages of in-situ testing and discusses the preliminary results obtained with newly developed miniature specimens. Specimens were moved to the Low Activation Materials Development and Analysis (LAMDA) laboratory and prepared for

  15. Effect of the method of introduction of Y2O3 into NiAl-based powder alloys on their structure: I. Agitation in a ball mill

    NASA Astrophysics Data System (ADS)

    Povarova, K. B.; Vershinina, T. N.; Skachkov, O. A.; Drozdov, A. A.; Morozov, A. E.; Pozharov, S. V.

    2012-09-01

    The effect of the sintering temperature (1100-1400°C) of NiAl alloy samples with oxide Y2O3 produced by hydrostatic pressing on their structure and phase composition and the distribution of oxide particles in a NiAl-based intermetallic matrix alloyed with ˜0.5 at % Fe is considered. It is found that dispersed oxide particles in the compact material prepared from a mixture of oxide Y2O3 powder and a NiAl alloy (produced by calcium hydride reduction of a mixture of nickel and aluminum oxides) powder in a standard ball mill are nonuniformly distributed in the volume. The morphology of oxides changes during sintering: sintered samples contain rounded particles, which differ strongly from the clearly faceted angular particles of oxide Y2O3 added to a mixture (they represent conglomerates of single crystals). In the sintered samples, large aggregates of oxides are revealed along grain boundaries. Mass transfer is possible at the NiAl/Y2O3 interface in the system: it leads to partial substitution of aluminum and/or iron atoms for yttrium atoms in the Y2O3 lattice and to the formation of submicroscopic particles of (Fe,Al)5Y3O12-type oxides.

  16. Rare-earth metals (REMs) in nickel aluminide-based alloys: II. Effect of a REM on the phase composition of a multicomponent Ni3Al-based alloy

    NASA Astrophysics Data System (ADS)

    Povarova, K. B.; Drozdov, A. A.; Kazanskaya, N. K.; Morozov, A. E.; Kolobov, Yu. R.; Vershinina, T. N.; Kozlov, E. V.

    2008-10-01

    The hardening mechanisms are studied in the cast high-temperature next-generation materials that are based on the intermetallic compound Ni3Al and are low alloyed with refractory (W, Re, Mo, Cr) and reaction- and surface-active (REM, Ti, etc.) metals. The interaction of the main impurities (C, O, Si, S) with three characteristic representatives of the REM group (namely, Y, La, Ce), which can be used for alloying, is analyzed. The reported data on the behavior of some REMs in the alloys based on nickel monoaluminide NiAl are considered. The effect of the REMs on the phase compositions of real multicomponent semicommercial Ni3Al-based VKNA alloys produced by directional solidification is investigated, and the excess phases precipitating upon alloying are revealed. Alloying with refractory metals and REMs is shown to lead to the formation of nanophases that stabilize the dendritic or single-crystal structure of VKNA-type cast alloys and strengthen the interface boundaries in them.

  17. The mechanisms of dispersion strengthening and fracture in Al-based XD(tm) alloys, part 1

    NASA Technical Reports Server (NTRS)

    Aikin, R. M., Jr.

    1990-01-01

    The influence of reinforcement size, volume fraction, and matrix deformation behavior on room and elevated temperature strength; the fracture toughness; and the fatigue crack growth rate of metal matrix composites of Al-4(pct)Cu-1.5(pct)Mg with TiB2 were examined. The influence of reinforcement volume fraction was also examined for pure aluminum with TiB2. Higher TiB2 volume fractions increased the tensile yield strength at both room and elevated temperatures, and reduced the elongation to fracture. Tensile tests also indicate that small particles provided a greater increase in strength for a given volume fraction than larger particles, whereas elongation to fracture appeared to be insensitive to reinforcement size. Interparticle spacing appears to be the factor that controls the strength of these alloys, with the exact nature of the dependence relying on the nature of dislocation slip in the matrix (planar vs. diffuse). The isothermal aging response of the precipitation strengthened Al-4(pct)Cu-1.5(pct)Mg alloys was not accelerated by the presence of TiB2. Cold work prior to artificial aging created additional geometrically necessary dislocations which serve as heterogeneous nucleation sites leading to accelerated aging, a finer precipitate size, and an increase in the strength of the alloy.

  18. Concept of Quasicrystalline Metal Alloys Becoming Clearer.

    ERIC Educational Resources Information Center

    Rawis, Rebecca L.

    1986-01-01

    Reports results of a public opinion survey aimed at measuring the general public's understanding of scientific concepts, and acceptance of scientific paradigms. Assessment and analysis by science and society experts is provided. (JM)

  19. Microstructure characterization and room temperature deformation of a rapidly solidified NiAl-based eutectic alloy containing trace Dy

    NASA Astrophysics Data System (ADS)

    Li, Hutian; Guo, Jianting; Huai, Kaiwen; Ye, Hengqiang

    2006-04-01

    The microstructure and room temperature compressive deformation behavior of a rapidly solidified NiAl-Cr(Mo)-Dy eutectic alloy fabricated by water-cooled copper mold method were studied by a combination of SEM, EDS and compressive tests. The morphology stability after hot isostatic pressing (HIP) treatment was evaluated. Rapid solidification resulted in a shift in the coupled zone for the eutectic growth towards the Cr(Mo) phase, indicating a hypoeutectic composition, hence increasing the volume fraction of primary dendritic NiAl. Meanwhile, significantly refined microstructure and lamellar/rod-like Cr(Mo) transition were observed due to trace rare earth (RE) element Dy addition and rapid solidification effects. Compared with the results in literature [H.E. Cline, J.L. Walter, Metall. Trans. 1(1970)2907-2917; P. Ferrandini, W.W. Batista, R. Caram, J. Alloys Comp. 381(2004)91-98], an interesting phenomenon, viz., NiAl halos around the primary Cr(Mo) dendrites in solidified NiAl-Cr(Mo) hypereutectic alloy, was not observed in this study. This difference was interpreted in terms of their different reciprocal nucleation ability. In addition, it was proposed that the localized destabilization of morphology after HIP treatment is closely related to the presence of primary NiAl dendrites. The improved mechanical properties can be attributed to the synergistic effects of rapid solidification and Dy addition, which included refined microstructure, suppression of the crack development along eutectic grain boundaries, enhancement of density of geometrically necessary dislocations located at NiAl/Cr(Mo) interfaces and the Cr solubility extension in NiAl.

  20. Complex metallic alloys as new materials for additive manufacturing

    PubMed Central

    Kenzari, Samuel; Bonina, David; Marie Dubois, Jean; Fournée, Vincent

    2014-01-01

    Additive manufacturing processes allow freeform fabrication of the physical representation of a three-dimensional computer-aided design (CAD) data model. This area has been expanding rapidly over the last 20 years. It includes several techniques such as selective laser sintering and stereolithography. The range of materials used today is quite restricted while there is a real demand for manufacturing lighter functional parts or parts with improved functional properties. In this article, we summarize recent work performed in this field, introducing new composite materials containing complex metallic alloys. These are mainly Al-based quasicrystalline alloys whose properties differ from those of conventional alloys. The use of these materials allows us to produce light-weight parts consisting of either metal–matrix composites or of polymer–matrix composites with improved properties. Functional parts using these alloys are now commercialized. PMID:27877661

  1. Complex metallic alloys as new materials for additive manufacturing.

    PubMed

    Kenzari, Samuel; Bonina, David; Marie Dubois, Jean; Fournée, Vincent

    2014-04-01

    Additive manufacturing processes allow freeform fabrication of the physical representation of a three-dimensional computer-aided design (CAD) data model. This area has been expanding rapidly over the last 20 years. It includes several techniques such as selective laser sintering and stereolithography. The range of materials used today is quite restricted while there is a real demand for manufacturing lighter functional parts or parts with improved functional properties. In this article, we summarize recent work performed in this field, introducing new composite materials containing complex metallic alloys. These are mainly Al-based quasicrystalline alloys whose properties differ from those of conventional alloys. The use of these materials allows us to produce light-weight parts consisting of either metal-matrix composites or of polymer-matrix composites with improved properties. Functional parts using these alloys are now commercialized.

  2. Complex metallic alloys as new materials for additive manufacturing

    NASA Astrophysics Data System (ADS)

    Kenzari, Samuel; Bonina, David; Dubois, Jean Marie; Fournée, Vincent

    2014-04-01

    Additive manufacturing processes allow freeform fabrication of the physical representation of a three-dimensional computer-aided design (CAD) data model. This area has been expanding rapidly over the last 20 years. It includes several techniques such as selective laser sintering and stereolithography. The range of materials used today is quite restricted while there is a real demand for manufacturing lighter functional parts or parts with improved functional properties. In this article, we summarize recent work performed in this field, introducing new composite materials containing complex metallic alloys. These are mainly Al-based quasicrystalline alloys whose properties differ from those of conventional alloys. The use of these materials allows us to produce light-weight parts consisting of either metal-matrix composites or of polymer-matrix composites with improved properties. Functional parts using these alloys are now commercialized.

  3. Nickel self-diffusion along grain boundaries in Ni{sub 3}Al-base intermetallic alloys

    SciTech Connect

    Zulina, N.P.; Bolberova, E.V.; Razumovskii, I.M.

    1996-09-01

    {sup 63}Ni self-diffusion along grain boundaries (GBs) in intermetallic alloys Ni-25.2Al, Ni-24.9Al-4.8W, Ni-24.2Al-4.7Cr, Ni-19.3Al-4.5Hf and Ni-27.6Al-4.9Co (at.%) has been investigated by the radiotracer technique. The usual darkening in the positions of GBs on the autoradiographs obtained on the parallel and inclined sections of the specimens was observed. The diffusion penetration profiles were measured by the serial sectioning technique. Using the near-surface parts of the profiles which characterize lattice diffusion, the volume diffusion coefficients D were estimated. For pure Ni{sub 3}Al the agreement of the measured high temperature values of D with those of Bronfin et al. is good. By using the D-values and processing the tails of the measured profiles the GB diffusivity P (P = D{prime}{delta}, where D{prime} is the GB diffusion coefficient, {delta} the GB width) was calculated. The obtained P values followed an Arrhenius dependence at high temperatures: Ni-Al, T = 1,273--1,073 K, Q{prime} = 195 kJ/mol, P{sub 0} = 1 {times} 10{sup {minus}12}m{sup 3}/s; Ni-Al-Hf, T = 1,373--1,023 K, Q{prime} = 219 kJ/mol, P{sub 0} = 6.4 {times} 10{sup {minus}12}m{sup 3}/s; Ni-Al-W, T = 1,373--1,023 K, Q{prime} = 217 kJ/mol, P{sub 0} = 3.3 {times} 10{sup {minus}12}m{sup 3}/s; Ni-Al-Co, T = 1,273--1,023 K, Q{prime} = 189 kJ/mol, P{sub 0} = 6.8 {times} 10{sup {minus}13}m{sup 3}/s; Ni-Al-Cr, T = 1,323--1,023 K, Q{prime} = 265 kJ/mol, P{sub 0} = 1.8 {times} 10{sup {minus}9}m{sup 3}/s. By using the obtained D and P values the GB energy {gamma} in Ni{sub 3}Al and its alloys was estimated by the Borisov et al. semiempirical relationship. The {gamma}-values calculated exhibit a strong positive temperature dependence, which is usually revealed in metallic alloys containing elements with a strong tendency to GB segregation.

  4. Characterisation of magnesium oxide and its interface with α-Mg in Mg-Al-based alloys

    NASA Astrophysics Data System (ADS)

    Wang, Y.; Fan, Z.; Zhou, X.; Thompson, G. E.

    2011-08-01

    Magnesium oxide (MgO) films and particles have been collected by pressurised filtration of a Mg-8.6wt%Al-0.67wt%Zn (AZ91D) alloy melt. The morphology of the oxides and their interfaces with the α-Mg phase were investigated by high-resolution transmission electron microscopy. It was found that the oxide films consisted of large numbers of sub-micrometre-sized MgO particles, and that melt shearing can effectively break up the oxide films and disperse the oxide particles. For the first time, orientation relationships (ORs) of OR I: [1 overline 1 1]MgO∼2° from (0 0 0 1)α-Mg and (0 1 1)MgO //[2 overline 1 overline 1 0)α-Mg; and OR II: (overline 1 overline 1 1)MgO//(1 overline 1 0 1)α-Mg and [0 1 1]MgO//[overline 1 2 overline 1 1]α-Mg, were observed between the MgO particles and the α-Mg matrix. The calculated Bramfitt planar disregistries were 5.5% and 2.5% for the two ORs, respectively, indicating good lattice matching between MgO and α-Mg at the interface. With the evidence of grain refinement effect observed in the sheared AZ91D magnesium alloy, the possibility of MgO particles to act as potent nucleants for heterogeneous nucleation of α-Mg grains is discussed in terms of the crystallographic criterion.

  5. Laser-induced breakdown spectroscopy: technique, new features, and detection limits of trace elements in Al base alloy

    NASA Astrophysics Data System (ADS)

    Hegazy, H.; Abdel-Wahab, E. A.; Abdel-Rahim, F. M.; Allam, S. H.; Nossair, A. M. A.

    2014-05-01

    Laser-induced breakdown spectroscopy (LIBS) has proven to be extremely versatile, providing multielement analysis in real time without sample preparation. The principle is based on the ablation of a small amount of target material by interaction of a strong laser beam with a solid target. The laser must have sufficient energy to excite atoms and to ionize them to produce plasma. We aimed to improve the LIBS limit of detection (LOD) and the precision of spectral lines emitted from the produced plasma by optimizing the parameters affecting the LIBS technique. LIBS LOD is affected by many experimental parameters such as interferences, self-absorption, spectral overlap, signal-to-noise ratio, and matrix effects. The plasma in the present study is generated by focusing a 6-ns pulsed Nd-YAG laser at the fundamental wavelength of 1,064 nm onto the Al target in air at atmospheric pressure. The emission spectra are recorded using an SE 200 Echelle spectrometer manufactured by the Catalina Corporation; it is equipped with an ICCD camera type Andor model iStar DH734-18. This spectrometer allows time-resolved spectral acquisition over the whole UV-NIR (200-1,000 nm) spectral range. Calibration curves for Cu, Mg, Mn, Si, Cr, and Fe were obtained with linear regression coefficients around 99 % on the average in aluminum standard alloy samples. The determined LOD has very useful improvements for Cu I at 521.85 nm, Si I at 288.15 nm, Mn I at 482.34 nm, and Cr I at 520.84 nm spectral lines. LOD is improved by 83.8 % for Cu, 49 % for Si, 84.3 % for Mn, and 45 % for Cr lower with respect to the previous works.

  6. Optimization of In-Situ Shot-Peening-Assisted Cold Spraying Parameters for Full Corrosion Protection of Mg Alloy by Fully Dense Al-Based Alloy Coating

    NASA Astrophysics Data System (ADS)

    Wei, Ying-Kang; Luo, Xiao-Tao; Li, Cheng-Xin; Li, Chang-Jiu

    2017-01-01

    Magnesium-based alloys have excellent physical and mechanical properties for a lot of applications. However, due to high chemical reactivity, magnesium and its alloys are highly susceptible to corrosion. In this study, Al6061 coating was deposited on AZ31B magnesium by cold spray with a commercial Al6061 powder blended with large-sized stainless steel particles (in-situ shot-peening particles) using nitrogen gas. Microstructure and corrosion behavior of the sprayed coating was investigated as a function of shot-peening particle content in the feedstock. It is found that by introducing the in-situ tamping effect using shot-peening (SP) particles, the plastic deformation of deposited particles is significantly enhanced, thereby resulting in a fully dense Al6061 coating. SEM observations reveal that no SP particle is deposited into Al6061 coating at the optimization spraying parameters. Porosity of the coating significantly decreases from 10.7 to 0.4% as the SP particle content increases from 20 to 60 vol.%. The electrochemical corrosion experiments reveal that this novel in-situ SP-assisted cold spraying is effective to deposit fully dense Al6061 coating through which aqueous solution is not permeable and thus can provide exceptional protection of the magnesium-based materials from corrosion.

  7. Quasicrystalline Beam Formation in RF Photoinjectors

    SciTech Connect

    Rosenzweig, J. B.; Dunning, M. P.; Hemsing, Erik; Marcus, G.; Marinelli, Agostino; Musumeci, Pietro; Pham, A.; Ferrario, M.

    2009-01-22

    The recent observation of coherent optical transition radiation at the LCLS has raised serious questions concerning the present model of beam dynamics in RF photoinjectors. We present here an analysis of what we term quasicrystalline beam formation. In this scenario, the low longitudinal temperature, in combination with strong acceleration and temporal rearrangement due to bending, allows the longitudinal beam dimension to become more regular, on the microscopic scale of optical wavelengths, than expected from equilibrium statistical properties. This beam distribution then may then display a strong degree of coherence in its optical transition radiation output. We discuss further experimental investigations of this phenomenon.

  8. Vacuum tribological behaviour of self lubricant quasicrystalline composite coatings

    NASA Astrophysics Data System (ADS)

    Garcí de Blas, F. J.; Román, A.; de Miguel, C.; Longo, F.; Muelas, R.; Agüero, A.

    2003-09-01

    High temperature resistant self-lubricant coatings are needed in space vehicles for components that operate at high temperatures and/or under vacuum. Thick composite lubricant coatings containing quasicrystalline alloys (QC) as the hard phase for wear resistance, have been deposited by thermal spray. The coatings also comprise lubricating materials (silver and BaF2-CaF2 eutectic) and NiCr as the tough component. This paper describes the vacuum tribological properties of TH103, a coating belonging to this family, with excellent microstructural quality. The coating was deposited by HVOF and tested under vacuum on a pin-on-disc tribometer. Different loads, linear speeds and pin materials were studied. The pin scars and disc wear tracks were characterized by EDS-SEM. A minimum mean steady friction coefficient of 0.32 was obtained employing a X-750 Ni superalloy pin in vacuum conditions under 10 N load and 15 cm/s linear speed, showing moderate wear of the disc and low wear of the pin.

  9. Structural aspects of the fivefold quasicrystalline Al-Cu-Fe surface from STM and dynamical LEED Studies

    SciTech Connect

    Cai, T.; Shi, F.; Shen, Z.; Gierer, M.; Goldman, A.I.; Kramer, M.J.; Jenks, C.J.; Lograsso, T.A.; Delaney, D.W.; Thiel, P.A.; Van, M.A.

    2001-04-15

    We investigate the atomic structure of the fivefold surface of an icosahedral Al-Cu-Fe alloy, using scanning tunneling microscopy (STM) imaging and a special dynamical low energy-electron diffraction (LEED) method. STM indicates that the step heights adopt (primarily) two values in the ratio of tau, but the spatial distribution of these two values does not follow a Fibonacci sequence, thus breaking the ideal bulk-like quasicrystalline layer stacking order perpendicular to the surface. The appearance of screw dislocations in the STM images is another indication of imperfect quasicrystallinity. On the other hand, the LEED analysis, which was successfully applied to Al-Pd-Mn in a previous study, is equally successful for Al-Cu-Fe. Similar structural features are found for both materials, in particular for interlayer relaxations and surface terminations. Although there is no structural periodicity, there are clear atomic planes in the bulk of the quasicrystal, some of which can be grouped in recurring patterns. The surface tends to form between these grouped layers in both alloys. For Al-Cu-Fe, the step heights measured by STM are consistent with the thicknesses of the grouped layers favored in LEED. These results suggest that the fivefold Al-Cu-Fe surface exhibits a quasicrystalline layering structure, but with stacking defects.

  10. Periodically distributed objects with quasicrystalline diffraction pattern

    SciTech Connect

    Wolny, Janusz Strzalka, Radoslaw; Kuczera, Pawel

    2015-03-30

    It is possible to construct fully periodically distributed objects with a diffraction pattern identical to the one obtained for quasicrystals. These objects are probability distributions of distances obtained in the statistical approach to aperiodic structures distributed periodically. The diffraction patterns have been derived by using a two-mode Fourier transform—a very powerful method not used in classical crystallography. It is shown that if scaling is present in the structure, this two-mode Fourier transform can be reduced to a regular Fourier transform with appropriately rescaled scattering vectors and added phases. Detailed case studies for model sets 1D Fibonacci chain and 2D Penrose tiling are discussed. Finally, it is shown that crystalline, quasicrystalline, and approximant structures can be treated in the same way.

  11. Structures and Electrochemical Hydrogen Storage Properties of the As-Spun RE-Mg-Ni-Co-Al-Based AB2-Type Alloys Applied to Ni-MH Battery

    NASA Astrophysics Data System (ADS)

    Zhang, Yanghuan; Yuan, Zeming; Shang, Hongwei; Li, Yaqin; Qi, Yan; Zhao, Dongliang

    2017-03-01

    In this paper, the La0.8-x Ce0.2Y x MgNi3.5Co0.4Al0.1 (x = 0, 0.05, 0.1, 0.15, 0.2) alloys were synthesized via smelting and melt spinning. The effect of Y content on the structure and electrochemical hydrogen storage characteristics of the as-cast and spun alloys was investigated. The identifications of XRD and SEM demonstrate that the experimental alloys possess a major phase LaMgNi4 and a minor phase LaNi5. The variation of Y content results in an obvious transformation of the phase abundance rather than phase composition in the alloys, namely LaMgNi4 phase increases while LaNi5 phase decreases with Y content growing. Furthermore, the replacement of Y for La causes the lattice constants and cell volume to clearly decrease and markedly refines the alloy grains. The electrochemical tests reveal that these alloys can obtain the maximum values of discharge capacity at the first cycling without any activation needed. With Y content growing, the discharge capacity of the alloys obviously declines, but its cycle stability remarkably improves. Moreover, the electrochemical dynamics of the alloys, involving the high-rate discharge ability, hydrogen diffusion coefficient (D), limiting current density (I L), and charge transfer rate, initially augment and then decrease with rising Y content.

  12. Long-term high-velocity oxidation and hot corrosion testing of several NiCrAl and FeCrAl base oxide dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

    Lowell, C. E.; Deadmore, D. L.; Whittenberger, J. D.

    1982-01-01

    Several oxide dispersion strengthened (ODS) alloys have been tested for cyclic, long-term, high gas-velocity resistance to oxidation at 1100 C and hot corrosion at 900 C. Both nominally Ni-16Cr-4Al and Fe-20Cr-4.5Al ODS alloys were subjected up to about 2500 cycles, where each cycle consisted of 1 hr in a hot, Mach 0.3 combusted gas stream followed by a 3-min quench in an ambient temperature, Mach 0.3 air blast. For comparison to existing technology, a coated superalloy was simultaneously tested. The ODS iron alloy exhibited clearly superior behavior, surviving 3800 oxidation and 2300 hot corrosion cycles essentially unscathed. While the ODS nickel alloys exhibited adequate oxidation resistance, the long-term hot corrosion resistance could be marginal, since the best life for such alloys under these conditions was only about 1100 cycles. However, the hot corrosion resistance of the ODS Ni-base alloys is excellent in comparison to that of traditional superalloys.

  13. Preparation of Al-Cu-Fe-(Sn,Si) quasicrystalline bulks by laser multilayer cladding

    NASA Astrophysics Data System (ADS)

    Feng, Li-ping; Fleury, Eric; Zhang, Guo-sheng

    2012-05-01

    (Al65Cu20Fe15)100- x Sn x ( x=0, 12, 20, 30) and Al57Si10Cu18Fe15 powders were cladded on a medium carbon steel (45# steel) substrate by laser multilayer cladding, respectively. The phases and properties of the produced quasicrystalline bulks were investigated. It was found that the main phases in the Al65Cu20Fe15 sample were crystalline λ-Al13Fe4 and icosahedral quasicrystal together with a small volume fraction of θ-Al2Cu phase. The volume fraction of icosahedral phase decreased as the Sn content in the (Al65Cu20Fe15)100- x Sn x samples increased owing to the formation of β-CuSn phase. The increase of Sn content improved the brittleness of the quasicrystal samples. The morphology of the solidification microstructure in the Al57Si10Cu18Fe15 sample changed from elongated shape to spherical shape due to the addition of Si. The nanohardness of the laser multilayer cladded quasicrystal samples was equal to that of the as-cast sample prepared by vacuum quenching. In terms of hardness, the laser cladded Al57Si10Cu18Fe15 quasicrystalline alloy has the highest value among all the investigated samples.

  14. Fabrication of ten-fold photonic quasicrystalline structures

    SciTech Connect

    Sun, XiaoHong Wu, YuLong; Liu, Wen; Liu, Wei; Han, Juan; Jiang, Lei

    2015-05-15

    Compared to periodic crystals, quasicrystals have higher point group symmetry and are more favorable in achieving complete band-gaps. In this report, a top-cut prism interferometer is designed to fabricate ten-fold photonic quasicrystalline structures. By optimizing the exposing conditions and material characteristics, appropriate quasicrystals have been obtained in the SU8 photoresist films. Atomic Force Microscopy and laser diffraction are used to characterize the fabricated structures. The measurement results show the consistence between the theoretical design and experiments. This will provide guidance for the large-area and fast production of ten-fold quasicrystalline structures with high quality.

  15. Broadband multiple responses of surface modes in quasicrystalline plasmonic structure

    PubMed Central

    Yuan, Haiming; Jiang, Xiangqian; Huang, Feng; Sun, Xiudong

    2016-01-01

    We numerically study the multiple excitation of surface modes in 2D photonic quasicrystal/metal/substrate structure. An improved rigorous coupled wave analysis method that can handle the quasicrystalline structure is presented. The quasicrystalline lattice, which refers to Penrose tiling in this paper, is generated by the cut-and-project method. The normal incidence spectrum presents a broadband multiple responses property. We find that the phase matching condition determines the excitation frequency for a given incident angle, while the depth of the reflection valley depends on the incident polarization. The modes will split into several sub-modes at oblique incidence, which give rise to the appearance of more responses on the spectrum. PMID:27492782

  16. Gamma-resonance study of nanopowders with different dispersion and quasicrystalline phases in the Al-Cu-Fe system

    SciTech Connect

    Frolov, K. V. Mikheeva, M. N.; Lyubutin, I. S.; Nikonov, A. A.; Teplov, A. A.; Shaitura, D. S.; Abuzin, Yu. A.

    2007-11-15

    {sup 57}Fe Moessbauer spectroscopy has been used to monitor synthesis of quasicrystals in the Al-Cu-Fe system and study the influence of the size of quasicrystalline particles in powder samples of the Al{sub 63.1}Cu{sub 25.6}Fe{sub 11.3} alloy on the properties of synthesized materials. Quasicrystalline samples of different dispersion with particle sizes from 0.3 to 15 {mu}m have been studied in the temperature range 80-295 K. It is established that iron atoms in an Al{sub 63.1}Cu{sub 25.6}Fe{sub 11.3} quasicrystals occupy four types of structural positions, which differ in the atomic composition of the nearest environment. The results of the analysis suggest the dependence of the hyperfine-interaction parameters on the degree of sample dispersion. The components corresponding to iron atoms in both the surface layer and bulk of microparticles are isolated in the Moessbauer spectra. No magnetic hyperfine splitting has been found in the Moessbauer spectra in the entire temperature range. This fact suggests that a localized magnetic moment is absent in iron atoms.

  17. Efficient design, accurate fabrication and effective characterization of plasmonic quasicrystalline arrays of nano-spherical particles

    PubMed Central

    Namin, Farhad A.; Yuwen, Yu A.; Liu, Liu; Panaretos, Anastasios H.; Werner, Douglas H.; Mayer, Theresa S.

    2016-01-01

    In this paper, the scattering properties of two-dimensional quasicrystalline plasmonic lattices are investigated. We combine a newly developed synthesis technique, which allows for accurate fabrication of spherical nanoparticles, with a recently published variation of generalized multiparticle Mie theory to develop the first quantitative model for plasmonic nano-spherical arrays based on quasicrystalline morphologies. In particular, we study the scattering properties of Penrose and Ammann- Beenker gold spherical nanoparticle array lattices. We demonstrate that by using quasicrystalline lattices, one can obtain multi-band or broadband plasmonic resonances which are not possible in periodic structures. Unlike previously published works, our technique provides quantitative results which show excellent agreement with experimental measurements. PMID:26911709

  18. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO3 Fe3Al, Co3Al, and Ni3Al based intermetallic phases

    NASA Astrophysics Data System (ADS)

    Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

    2014-11-01

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co, and Ti within the AlNi-based matrix phase. In this paper, we report the results of first-principles calculations of the site preference of ternary alloying additions in DO3 Fe3Al, Co3Al, and Ni3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which correspond to experimental situation, Ti and Fe are found to occupy the α sites, while Co and Ni prefer the γ sites of the DO3 lattice. An important finding is that the magnetic moments of transition metals in Fe3Al and Co3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co is added as a ternary element.

  19. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO3 Fe3Al, Co3Al, and Ni3Al based intermetallic phases

    DOE PAGES

    Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

    2014-11-07

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternarymore » alloying additions in DO3 Fe3Al, Co3Al and Ni3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO3 lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe3Al and Co3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.« less

  20. Dodecagonal quasicrystalline order in a diblock copolymer melt

    PubMed Central

    Gillard, Timothy M.; Lee, Sangwoo; Bates, Frank S.

    2016-01-01

    We report the discovery of a dodecagonal quasicrystalline state (DDQC) in a sphere (micelle) forming poly(isoprene-b-lactide) (IL) diblock copolymer melt, investigated as a function of time following rapid cooling from above the order–disorder transition temperature (TODT = 66 °C) using small-angle X-ray scattering (SAXS) measurements. Between TODT and the order–order transition temperature TOOT = 42 °C, an equilibrium body-centered cubic (BCC) structure forms, whereas below TOOT the Frank–Kasper σ phase is the stable morphology. At T < 40 °C the supercooled disordered state evolves into a metastable DDQC that transforms with time to the σ phase. The times required to form the DDQC and σ phases are strongly temperature dependent, requiring several hours and about 2 d at 35 °C and more than 10 and 200 d at 25 °C, respectively. Remarkably, the DDQC forms only from the supercooled disordered state, whereas the σ phase grows directly when the BCC phase is cooled below TOOT and vice versa upon heating. A transition in the rapidly supercooled disordered material, from an ergodic liquid-like arrangement of particles to a nonergodic soft glassy-like solid, occurs below ∼40 °C, coincident with the temperature associated with the formation of the DDQC. We speculate that this stiffening reflects the development of particle clusters with local tetrahedral or icosahedral symmetry that seed growth of the temporally transient DDQC state. This work highlights extraordinary opportunities to uncover the origins and stability of aperiodic order in condensed matter using model block polymers. PMID:27118844

  1. High-resolution electron microscopy observations of continuous precipitates with Pitsch-Schrader orientation relationship in an Mg-Al based alloy and interpretation with the O-lattice theory.

    PubMed

    Zhou, J P; Zhao, D S; Zheng, O; Wang, J B; Xiong, D X; Sun, Z F; Gui, J N; Wang, R H

    2009-12-01

    High-resolution electron microscopy was applied to analyze the continuous precipitated particles of the gamma-Mg(17)Al(12) phase with Pitsch-Schrader OR in the heat-treated AZ91 alloy at 473 K for 8 h. The existence of a continuous precipitated particle with the Pitsch-Schrader OR including the selection of the habit plane and the growth direction in Mg-Al system is rationalized by the constrained coincidence site lattice/constrained complete pattern shift lattice (CCSL/CDSCL) model and the O-lattice theory.

  2. Crystalline and quasicrystalline allotropes of Pb formed on the fivefold surface of icosahedral Ag-In-Yb

    SciTech Connect

    Sharma, H. R. Smerdon, J. A.; Nugent, P. J.; Ribeiro, A.; McGrath, R.; McLeod, I.; Dhanak, V. R.; Shimoda, M.; Tsai, A. P.

    2014-05-07

    Crystalline and quasicrystalline allotropes of Pb are formed by evaporation on the fivefold surface of the icosahedral (i) Ag-In-Yb quasicrystal under ultra-high vacuum. Lead grows in three dimensional quasicrystalline order and subsequently forms fivefold-twinned islands with the fcc(111) surface orientation atop of the quasicrystalline Pb. The islands exhibit specific heights (magic heights), possibly due to the confinement of electrons in the islands. We also study the adsorption behavior of C{sub 60} on the two allotropes of Pb. Scanning tunneling microcopy reveals that a high corrugation of the quasicrystalline Pb limits the diffusion of the C{sub 60} molecules and thus produces a disordered film, similar to adsorption behavior of the same molecules on the clean substrate surface. However, the sticking coefficient of C{sub 60} molecules atop the Pb islands approaches zero, regardless of the overall C{sub 60} coverage.

  3. Frictional Properties of Single Crystalline and Quasicrystalline Surfaces

    NASA Astrophysics Data System (ADS)

    Gellman, Andrew

    2000-03-01

    The use of ultra-high vacuum surface science methods has been aplied to the problem of studying friction between single srystalline and quasicrystalline metal surfaces. A experimental apparatus has been developed that combines the ability to perform surface preparation and analysis with the ability to make measurements of macroscopic friction forces between surfaces in sliding contact. This UHV chamber allows simultaneous preparation and characterization of two sample surfaces. These are usually single crystalline samples of the same metal and can be either perfectly clean or modified by adsorbed species such as atoms or molecules. Once prepared these two surfaces can be brought into contact under an applied normal load (Fn = 0.001 0.1 N) and sheared relative to one another at constant velocity (vs = 1 100 mm/s). Both normal and shear forces are measured simultaneously enabling one to determine a coefficient of friction. This unique apparatus has been used to study a number of problems in tribology. Adsorbed species on metal surfaces serve as a lubricants and prevent direct metal-metal contact. We have addressed the issue of surface coverage effects on interfacial friction. Surfaces have been prepared with adsorbed species ranging continuously in coverage from zero monolayers to many ( 100) monolayers. These experiments have been performed with pairs of both Ni(100) and Cu(111) surfaces. The interesting observation has been that adsorbed layers of atoms have little or no influence on friction coefficients between the two surfaces at coverages below one monolayer. Adsorbed molecules such as ethanol or trifluoroethanol are more interesting in this regard. They also have little influence on friction when adsorbed at coverages of < 1 monolayer, however, once the coverage exceeds 1 monolayer the coefficient of friction drops substantially. Friction reaches its limit at coverages of 5 10 monolayer. It is quite interesting to note that these metal single crystal surface

  4. Nature-inspired optimization of quasicrystalline arrays and all-dielectric optical filters and metamaterials

    NASA Astrophysics Data System (ADS)

    Namin, Frank Farhad A.

    Quasicrystalline solids were first observed in nature in 1980s. Their lattice geometry is devoid of translational symmetry; however it possesses long-range order as well as certain orders of rotational symmetry forbidden by translational symmetry. Mathematically, such lattices are related to aperiodic tilings. Since their discovery there has been great interest in utilizing aperiodic geometries for a wide variety of electromagnetic (EM) and optical applications. The first thrust of this dissertation addresses applications of quasicrystalline geometries for wideband antenna arrays and plasmonic nano-spherical arrays. The first application considered is the design of suitable antenna arrays for micro-UAV (unmanned aerial vehicle) swarms based on perturbation of certain types of aperiodic tilings. Due to safety reasons and to avoid possible collision between micro-UAVs it is desirable to keep the minimum separation distance between the elements several wavelengths. As a result typical periodic planar arrays are not suitable, since for periodic arrays increasing the minimum element spacing beyond one wavelength will lead to the appearance of grating lobes in the radiation pattern. It will be shown that using this method antenna arrays with very wide bandwidths and low sidelobe levels can be designed. It will also be shown that in conjunction with a phase compensation method these arrays show a large degree of versatility to positional noise. Next aperiodic aggregates of gold nano-spheres are studied. Since traditional unit cell approaches cannot be used for aperiodic geometries, we start be developing new analytical tools for aperiodic arrays. A modified version of generalized Mie theory (GMT) is developed which defines scattering coefficients for aperiodic spherical arrays. Next two specific properties of quasicrystalline gold nano-spherical arrays are considered. The optical response of these arrays can be explained in terms of the grating response of the array

  5. Metasurfaces inner symmetries: from square lattices to quasicrystalline layouts (presentation video)

    NASA Astrophysics Data System (ADS)

    Kruk, Sergey S.; Poddubny, Alexander; Helgert, Christian; Decker, Manuel; Staude, Isabelle; Menzel, Christoph; Etrich, Christoph; Rockstuhl, Carsten; Powell, David A.; Pertsch, Thomas; Neshev, Dragomir N.; Kivshar, Yuri S.

    2014-09-01

    We systematically study both experimentally and theoretically the links between the lattice symmetries of metasurfaces and their optical properties at both normal and oblique illumination. We attribute different symmetry elements to number of polarization phenomena. In particular, we predict analytically and verify experimentally the influence of rotational axes, mirror planes and inversion centres on optical activity, circular dichroism and asymmetric transmission. We fabricate and test nanostructured optical metasurfaces with four different inner structures: square and hexagonal lattices, quasicrystalline layout, and amorphous arrangement. We demonstrate the ability to enhance/suppress particular optical response by appropriate choice of the metasurface's symmetry.

  6. Quasicrystalline Approach to Prediting the Spinel-Nepheline Liquidus: Application to Nuclear Waste Glass Processing

    SciTech Connect

    Jantzen, Carol

    2005-10-10

    The crystal-melt equilibria in complex fifteen component melts are modeled based on quasicrystalline concepts. A pseudobinary phase diagram between acmite (which melts incongruently to a transition metal ferrite spinel) and nepheline is defined. The pseudobinary lies within the Al{sub 2}O{sub 3}-Fe{sub 2}O{sub 3}-Na{sub 2}O-SiO{sub 2} quaternary system that defines the crystallization of basalt glass melts. The pseudobinary provides the partitioning of species between the melt and the primary liquidus phases. The medium range order of the melt and the melt-crystal exchange equilibria are defined based on a constrained mathematical treatment that considers the crystallochemical coordination of the elemental species in acmite and nepheline. The liquidus phases that form are shown to be governed by the melt polymerization and the octahedral site preference energies. This quasicrystalline liquidus model has been used to prevent unwanted crystallization in the world's largest high level waste (HLW) melter for the past three years while allowing >10 wt% higher waste loadings to be processed.

  7. Optimal width of quasicrystalline slabs of dielectric cylinders to microwave radiation transmission contrast

    NASA Astrophysics Data System (ADS)

    Andueza, Ángel; Wang, Kang; Pérez-Conde, Jesús; Sevilla, Joaquín

    2016-08-01

    Light confinement induced by resonant states in aperiodic photonic structures is interesting for many applications. A particular case of these resonances can be found in 2D quasicrystalline arrangements of dielectric cylinders. These systems present a rather isotropic band gap as well as isolated in-gap photonic states (as a result of spatially localized resonances). These states are built by high symmetry polygonal clusters that can be regarded as photonic molecules. In this paper, we study the transmission properties of a slab of glass cylinders arranged in approximants of the decagonal quasicrystalline structure. In particular, we investigate the influence of the slab width in the transmission contrast between the states and the gap. The study is both experimental and numerical in the microwave regime. We find that the best transmission contrast is found for a width of around three times the radiation wavelength. The transmission in the band gap region is mediated by the resonances of the photonic molecules. If the samples are thin enough, they become transparent except around a resonance of the photonic molecule which reflects the incoming light.

  8. Ordering and growth of rare gas films (Xe, Kr, Ar, and Ne) on the pseudo-ten-fold quasicrystalline approximant Al₁₃Co₄(100) surface.

    PubMed

    Petucci, J; Karimi, M; Huang, Y-T; Curtarolo, S; Diehl, R D

    2014-03-05

    Adsorption of the rare gases Kr, Ar, and Ne on the complex alloy surface Al₁₃Co₄(100) was studied using grand canonical Monte Carlo (GCMC) computer simulations. This surface is an approximant to the ten-fold decagonal Al-Ni-Co quasicrystalline surface, on which rare gas adsorption was studied previously. Comparison of adsorption results on the periodic Al₁₃Co₄(100) surface with those of the quasiperiodic Al-Ni-Co surface indicates some similarities, such as layer-by-layer growth, and some dissimilarities, such as the formation of Archimedes tiling phases (Mikhael et al 2008 Nature 454 501, Shechtman et al 1984 Phys. Rev. Lett. 53 1951, Macia 2006 Rep. Prog. Phys. 69 397, Schmiedeberg et al 2010 Eur. Phys. J. E 32 25-34, Kromer et al 2012 Phys. Rev. Lett. 108 218301, Schmiedeberg and Stark 2008 Phys. Rev. Lett. 101 218302). The conditions under which Archimedes tiling phases (ATP) emerge on Al₁₃Co₄(100) are examined and their presence is related to the gas-gas and gas-surface interaction parameters.

  9. Development of ductile Fe{sub 3}Al-based aluminides

    SciTech Connect

    McKamey, C.G.; Sikka, V.K.; Goodwin, G.M.

    1993-07-01

    Iron aluminides based on Fe{sub 3}Al are of interest because of their excellent oxidation and corrosion resistance, especially in sulfur-bearing atmospheres. Work at ORNL has centered on developing Fe{sub 3}Al-based alloys with improved ambient temperature ductilities and increased strengths at temperatures of 600--700C. Ambient temperature brittleness in this system is not ``inherent,`` but is caused by atomic hydrogen which is produced by an environmental reaction between aluminum in the alloy and water vapor in the atmosphere. Great strides have been made in understanding this embrittlement Phenomenon, and the production of alloys with room temperature ductilities of over 10% and tensile yield strengths at 600C of as high as 500 MPa is now possible through modifications in alloy composition and control of thermomechanical processing techniques. Creep rupture lifes of over 200 h at 593C (1100{degrees}F) and 207 MPa (30 ksi) can also be produced through control of alloy composition and microstructure. This paper summarizes our present efforts to improve the tensile and creep rupture properties and gives the status of efforts to commercialize Fe{sub 3}Al-based alloy compositions.

  10. Annealing effect on the dielectric response of novel polymer/nano-quasicrystalline composites

    NASA Astrophysics Data System (ADS)

    Venkatesh, Ch.; Rao, V. V.

    2013-06-01

    In the earlier paper (Ch. Venkatesh et al. Solid State Comm., 2010), a dielectric percolation has been reported in composites of nano-quasicrystalline (nQc) Al-Cu-Fe (filler) and polyvinylidene fluoride (PVDF) (matrix). Though a high value of dielectric constant is observed near to the percolation threshold, these composites show higher dielectric loss values at lower frequencies. An effect of annealing has been investigated on the same composites which lead to decrement in dielectric loss values appreciably. The low dielectric loss values have been attributed due to the formation of thick grain boundaries in polymer matrix which completely surrounds the nQc cluster that weakens the effective tunneling of charge carriers near the filler-polymer interfacial region. Finally, a dielectric constant of 500 with tanδ<1 at 1 KHz is observed which may make the composite useful for low loss capacitive applications.

  11. Precipitates in a quasicrystal-strengthened Al–Mn–Be–Cu alloy

    SciTech Connect

    Zupanič, Franc; Wang, Di; Gspan, Cristian; Bončina, Tonica

    2015-08-15

    In this work, an Al–Mn–Be–Cu alloy was studied containing a primary and eutectic icosahedral quasicrystalline phase in the as-cast microstructure. Special attention was given to a transmission electron microscopy investigation of precipitates formed within the aluminium solid solution (Al{sub ss}) at different temperatures. At 200 °C, only binary Al–Cu precipitates (θ′) were formed. At 300 °C, icosahedral quasicrystalline (IQC) precipitates prevailed with a crystallographic orientation relationship with the Al{sub ss.} The rods of the T-phase (Al{sub 20}Mn{sub 3}Cu{sub 2}) which were precipitated above 400 °C, also had a specific orientation relationship with the Al{sub ss}. The primary and eutectic IQC microstructural constituent started to transform rapidly to the T-phase and Be{sub 4}Al(Mn,Cu) at 500 °C. - Highlights: • In a quasicrystal-strengthened Al-alloy several types of precipitates can form. • At 200 °C, only binary Al–Cu precipitates formed (Al{sub 2}Cu-θ′). • The icosahedral quasicrystalline (IQC) precipitates prevailed at 300 °C. • T-phase (Al{sub 20}Mn{sub 3}Cu{sub 2}) precipitated at temperatures above 400 °C. • The precipitation of different phases did not have a strong effect on hardness.

  12. Icosahedral and Other Quasicrystal Phases in Magnetic Alloy Systems

    DTIC Science & Technology

    1990-09-12

    comoositions at slower wheel speeds we fabrica t ed single-phase quasicrystals with no x-ray evidence of amorphous or crystalline structures present. The...experimental work confirmed that Mn itself shows a larger local moment in quasicrystalline alloys (1.2 - 1.5 IB/Mn, average) than in related crystalline ... structures (0 - 0.5 ItB/Mn), possibly because some of the Mn atoms them occupy the Ih site. The need existed to 1) find QC’s that more readily

  13. Quasicrystalline and crystalline precipitation during isothermal tempering in a 12Cr-9Ni-4Mo maraging stainless steel

    SciTech Connect

    Liu, P.; Stigenberg, A.H.; Nilsson, J.O.

    1995-07-01

    A thorough microstructural investigation has been performed on a high strength maraging steel of the type 12%Cr-9%Ni-4%Mo-2%Cu-1%Ti. The major precipitate formed during isothermal aging at 475 C is a quasicrystalline phase possessing icosahedral symmetry termed R{prime}-phase with a typical chemical composition of 48%Mo-33%Fe-13%Cr-2%Ni-4%Si. At 550 C the major precipitate is trigonal R-phase with a typical composition of 45%Mo-31%Fe-18%Cr-4%Ni-2%Si. At 550 C also Laves phase with a composition of 48%Mo-35%Fe-13%Cr-2%Ni-2%Si could be observed. At both 475 and 550 C an ordered phase termed L-phase precipitated. This minority phase has an ordered face centered cubic (f.c.c.) structure of type L1{sub 0}. Its composition is typically 9%Fe-4%Cr-52%Ni-15%Mo.-16%Ti-4%Al. R{prime}-phase formed at 475 C transformed to R-phase and Laves phase during aging at 550 C. In an analogous manner, R-phase and Laves phase formed at 550 C transformed to R{prime}-phase during subsequent aging at 475 C. This transformation was rationalized by a strong similarity in crystal structure between quasicrystalline R{prime}-phase of icosahedral symmetry and Frank-Kasper phases such as R-phase and Laves phase.

  14. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO{sub 3} Fe{sub 3}Al, Co{sub 3}Al, and Ni{sub 3}Al based intermetallic phases

    SciTech Connect

    Samolyuk, G. D.; Stocks, G. M.; Újfalussy, B.

    2014-11-07

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co, and Ti within the AlNi-based matrix phase. In this paper, we report the results of first-principles calculations of the site preference of ternary alloying additions in DO{sub 3} Fe{sub 3}Al, Co{sub 3}Al, and Ni{sub 3}Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which correspond to experimental situation, Ti and Fe are found to occupy the α sites, while Co and Ni prefer the γ sites of the DO{sub 3} lattice. An important finding is that the magnetic moments of transition metals in Fe{sub 3}Al and Co{sub 3}Al are ordered ferromagnetically, whereas the Ni{sub 3}Al were found to be nonmagnetic unless the Fe or Co is added as a ternary element.

  15. The distribution alloying elements in alnico 8 and 9 magnets: Site preference of ternary Ti, Fe, Co, and Ni additions in DO3 Fe3Al, Co3Al, and Ni3Al based intermetallic phases

    SciTech Connect

    Samolyuk, G. D.; Újfalussy, B.; Stocks, G. M.

    2014-11-07

    Recently, interest in alnico magnetic alloys has been rekindled due to their potential to substitute for rare-earth based permanent magnets provided modest improvements in their coercivity can be achieved without loss of saturation magnetization. Recent experimental studies have indicated that atomic and magnetic structure of the two phases (one AlNi-based, the other FeCo-based) that comprise these spinodally decomposed alloy is not as simple as previously thought. A key issue that arises is the distribution of Fe, Co and Ti within the AlNi-based matrix phase. In our paper we report the results of first-principles calculations of the site preference of ternary alloying additions in DO3 Fe3Al, Co3Al and Ni3Al alloys, as models for the aluminide phase. For compound compositions that are Al rich, which corresponds to experimental situation, Ti and Fe are found to occupy the sites, while Co and Ni prefer the sites of the DO3 lattice. Finally, an important finding is that the magnetic moments of transition metals in Fe3Al and Co3Al are ordered ferromagnetically, whereas the Ni3Al were found to be nonmagnetic unless the Fe or Co are added as a ternary element.

  16. Alloys developed for high temperature applications

    NASA Astrophysics Data System (ADS)

    Basuki, Eddy Agus; Prajitno, Djoko Hadi; Muhammad, Fadhli

    2017-01-01

    Alloys used for high temperatures applications require combinations of mechanical strength, microstructural stability and corrosion/oxidation resistance. Nickel base superalloys have been traditionally the prime materials utilized for hot section components of aircraft turbine engines. Nevertheless, due to their limited melting temperatures, alloys based on intermetallic compounds, such as TiAl base alloys, have emerged as high temperature materials and intensively developed with the main aim to replace nickel based superalloys. For applications in steam power plants operated at lower temperatures, ferritic high temperature alloys still attract high attention, and therefore, development of these alloys is in progress. This paper highlights the important metallurgical parameters of high temperature alloys and describes few efforts in the development of Fe-Ni-Al based alloys containing B2-(Fe,Ni)Al precipitates, oxide dispersion strengthening (ODS) ferritic steels and titanium aluminide based alloys include important protection system of aluminide coatings.

  17. Weak crystallization theory of metallic alloys

    NASA Astrophysics Data System (ADS)

    Martin, Ivar; Gopalakrishnan, Sarang; Demler, Eugene A.

    2016-06-01

    Crystallization is one of the most familiar, but hardest to analyze, phase transitions. The principal reason is that crystallization typically occurs via a strongly first-order phase transition, and thus rigorous treatment would require comparing energies of an infinite number of possible crystalline states with the energy of liquid. A great simplification occurs when crystallization transition happens to be weakly first order. In this case, weak crystallization theory, based on unbiased Ginzburg-Landau expansion, can be applied. Even beyond its strict range of validity, it has been a useful qualitative tool for understanding crystallization. In its standard form, however, weak crystallization theory cannot explain the existence of a majority of observed crystalline and quasicrystalline states. Here we extend the weak crystallization theory to the case of metallic alloys. We identify a singular effect of itinerant electrons on the form of weak crystallization free energy. It is geometric in nature, generating strong dependence of free energy on the angles between ordering wave vectors of ionic density. That leads to stabilization of fcc, rhombohedral, and icosahedral quasicrystalline (iQC) phases, which are absent in the generic theory with only local interactions. As an application, we find the condition for stability of iQC that is consistent with the Hume-Rothery rules known empirically for the majority of stable iQC; namely, the length of the primary Bragg-peak wave vector is approximately equal to the diameter of the Fermi sphere.

  18. Dual-phase glassy/nanoscale icosahedral phase materials in Cu–Zr–Ti–Pd system alloys

    SciTech Connect

    Louzguine-Luzgin, Dmitri V.; Churyumov, A.Yu.

    2014-10-15

    The present work is devoted to an investigation of the formation kinetics, stability and homogeneity area of the nanoscale icosahedral phase formed on heating in the dual-phase glassy/quasicrystalline phase Cu–Zr–Ti–Pd alloys. The data obtained indicate that the Cu–Zr–Ti–Pd icosahedral phase is not a Cu-rich part of the compositional homogeneity area of the Zr–Cu–Pd one. Moreover, Ti, as well as Pd, is found to be an important element stabilizing quasicrystalline phase in the Cu–Zr–Ti–Pd alloys. The formation criteria for Cu- and Zr/Hf-based icosahedral phases are discussed based on the quasilattice constant to average atomic diameter ratio. Deviation from a certain ratio leads to destabilization of the icosahedral phase. By using the isothermal calorimetry traces transformation kinetics above and below the glass-transition region was analyzed. Some difference in the transformation kinetics above and below the glass-transition region allows us to suggest that possible structure changes occur upon glass-transition. - Highlights: • Formation kinetics, stability and homogeneity area of nanoscale icosahedral phase • Cu–Zr–Ti–Pd icosahedral phase is not a Cu-rich part of Zr–Cu–Pd one. • Ti, as well as Pd, is an important element stabilizing quasicrystalline phase. • Difference in transformation kinetics above and below glass-transition region.

  19. Advanced ordered intermetallic alloy deployment

    SciTech Connect

    Liu, C.T.; Maziasz, P.J.; Easton, D.S.

    1997-04-01

    The need for high-strength, high-temperature, and light-weight materials for structural applications has generated a great deal of interest in ordered intermetallic alloys, particularly in {gamma}-based titanium aluminides {gamma}-based TiAl alloys offer an attractive mix of low density ({approximately}4g/cm{sup 3}), good creep resistance, and high-temperature strength and oxidation resistance. For rotating or high-speed components. TiAl also has a high damping coefficient which minimizes vibrations and noise. These alloys generally contain two phases. {alpha}{sub 2} (DO{sub 19} structure) and {gamma} (L 1{sub 0}), at temperatures below 1120{degrees}C, the euticoid temperature. The mechanical properties of TiAl-based alloys are sensitive to both alloy compositions and microstructure. Depending on heat-treatment and thermomechanical processing, microstructures with near equiaxed {gamma}, a duplex structure (a mix of the {gamma} and {alpha}{sub 2} phases) can be developed in TiAl alloys containing 45 to 50 at. % Al. The major concern for structural use of TiAl alloys is their low ductility and poor fracture resistance at ambient temperatures. The purpose of this project is to improve the fracture toughness of TiAl-based alloys by controlling alloy composition, microstructure and thermomechanical treatment. This work is expected to lead to the development of TiAl alloys with significantly improved fracture toughness and tensile ductility for structural use.

  20. Modeling multi-layer effects in passive microwave remote sensing of dry snow using Dense Media Radiative Transfer Theory (DMRT) based on quasicrystalline approximation

    USGS Publications Warehouse

    Liang, D.; Xu, X.; Tsang, L.; Andreadis, K.M.; Josberger, E.G.

    2008-01-01

    The Dense Media Radiative Transfer theory (DMRT) of Quasicrystalline Approximation of Mie scattering by sticky particles is used to study the multiple scattering effects in layered snow in microwave remote sensing. Results are illustrated for various snow profile characteristics. Polarization differences and frequency dependences of multilayer snow model are significantly different from that of the single-layer snow model. Comparisons are also made with CLPX data using snow parameters as given by the VIC model. ?? 2007 IEEE.

  1. Devitrification of Mechanically Alloyed Zr-Ti-Nb-Cu-Ni-Al Glassy Powders Studied by Time-Resolved X-ray Diffraction

    SciTech Connect

    Scudino, S.; Sordelet, D.J.; Eckert, J.

    2009-04-13

    The crystallization of mechanically alloyed Zr{sub 67}Ti{sub 6.14}Nb{sub 1.92}Cu{sub 10.67}Ni{sub 8.52}Al{sub 5.75} glassy powder is investigated by time-resolved X-ray diffraction. The powder displays a multi-step crystallization behavior characterized by the formation of a metastable nanoscale quasicrystalline phase during the first stage of the crystallization process. At higher temperatures, coinciding with the second crystallization event, the amorphous-to-quasicrystalline transformation is followed by the precipitation of the tetragonal Zr{sub 2}Cu phase (space group I4/mmm) and the tetragonal Zr{sub 2}Ni phase (space group I4/mcm). The transformations are gradual and the quasicrystals and the subsequent phases coexist over a temperature interval of about 25K.

  2. Growth morphology of single-crystal grains obtained by directional crystallisation of an Al-Cu-Fe alloy

    NASA Astrophysics Data System (ADS)

    Surowiec, Marian; Bogdanowicz, Wlodzimierz; Krawczyk, Jacek; Formanek, Bolesław; Sozanska, Maria

    2011-07-01

    Quasicrystalline as well as crystalline faceted single grains of four phases were obtained during directional crystallisation of an Al-Cu-Fe alloy by the Bridgman technique. The monoclinic λ phase, Al13(Cu, Fe)4, dominating at high temperatures formed single-crystal lamellae 0.5 mm to 1 mm thick. A second type of attractive morphological form exhibiting flux dissolution terraces was observed on spherical single crystals of β phase Al(Fe, Cu). Rectangular, hexagonal and octagonal shaped dissolution terraces were revealed at the positions of two-, three- and four-fold symmetry axes, respectively. A single quasicrystalline ψ phase, Al6Cu2Fe, exhibited icosahedral symmetry with growth forms of a dodecahedron with pentagonal facets. The flux dissolution of the β phase apparently plays an essential role in a peritectic reaction leading to quasicrystalline ψ phase formation. Polygonal single grains of ω phase Al7Cu2Fe exhibiting tetragonal symmetry formed the fourth type of thermodynamically stable growth forms. Single grains of the ω phase crystallised in the form of pellets with an octagonal cross-section. The growth morphology of the stable phases was investigated by scanning electron microscopy. The chemical composition of the growth forms described was confirmed by X-ray microanalysis using a scanning electron microscope, whereas the phase composition was determined using electron selected area diffraction and X-ray powder diffraction.

  3. Computational study of low-friction quasicrystalline coatings via simulations of thin film growth of hydrocarbons and rare gases

    NASA Astrophysics Data System (ADS)

    Setyawan, Wahyu

    Quasicrystalline compounds (QC) have been shown to have lower friction compared to other structures of the same constituents. The abscence of structural interlocking when two QC surfaces slide against one another yields the low friction. To use QC as low-friction coatings in combustion engines where hydrocarbon-based oil lubricant is commonly used, knowledge of how a film of lubricant forms on the coating is required. Any adsorbed films having non-quasicrystalline structure will reduce the self-lubricity of the coatings. In this manuscript, we report the results of simulations on thin films growth of selected hydrocarbons and rare gases on a decagonal Al73Ni10Co17 quasicrystal (d-AlNiCo). Grand canonical Monte Carlo method is used to perform the simulations. We develop a set of classical interatomic many-body potentials which are based on the embedded-atom method to study the adsorption processes for hydrocarbons. Methane, propane, hexane, octane, and benzene are simulated and show complete wetting and layered films. Methane monolayer forms a pentagonal order commensurate with the d-AlNiCo. Propane forms disordered monolayer. Hexane and octane adsorb in a close-packed manner consistent with their bulk structure. The results of hexane and octane are expected to represent those of longer alkanes which constitute typical lubricants. Benzene monolayer has pentagonal order at low temperatures which transforms into triangular lattice at high temperatures. The effects of size mismatch and relative strength of the competing interactions (adsorbate-substrate and between adsorbates) on the film growth and structure are systematically studied using rare gases with Lennard-Jones pair potentials. It is found that the relative strength of the interactions determines the growth mode, while the structure of the film is affected mostly by the size mismatch between adsorbate and substrate's characteristic length. On d-AlNiCo, xenon monolayer undergoes a first-order structural

  4. Structural, magnetic and electronic transport properties of amorphous and quasicrystalline Al70Pd20Fe10 thin films

    NASA Astrophysics Data System (ADS)

    Barzola-Quiquia, J.; Stiller, M.; Stiehler, M.; Esquinazi, P.; Häussler, P.

    2015-09-01

    We report measurements of transmission electron microscopy, the electrical resistivity, magnetoresistance and Hall effect (HE) in the amorphous and quasicrystalline (QC) phase of {{Al}}70{{Pd}}20{{Fe}}10. The samples are prepared in situ at T≈ 4 K as thin films in the amorphous phase. After preparation, the sample was measured during annealing at different temperatures. The measurements were performed in the temperature range of 1.2-300 K and with fields up to ±8 T. Atomic structure information obtained by transmission electron spectroscopy reveals that the icosahedral local atomic order is already present in the amorphous phase and is improved during annealing to the QC phase. An anomalous contribution in the HE reveals that there is magnetic order present in the amorphous sample, however after annealing the magnetic transition temperature Tc is reduced and finally disappears when the thin films transforms completely into the ordered QC phase. Direct magnetic moment measurements verify the magnetic properties derived from the resistance measurements, such as Curie temperature of 25 K ≤ {T}{{C}} ≤ 150 K upon annealing. The experimental results related to the atomic structure and the electronic transport properties in both phases, can be explained in the framework of electronic stabilized Hume-Rothery phases, where hybridization effects of Al-({{s}},{{p}}) with Fe-{{d}} electrons play an important role.

  5. Microstructure properties and microhardness of rapidly solidified Al64Cu20Fe12Si4 quasicrystal alloy

    NASA Astrophysics Data System (ADS)

    Karaköse, Ercan; Keskin, Mustafa

    2012-04-01

    This paper presents differences in the microstructure and microhardness properties of conventional casting (ingot) and rapidly solidified Al64Cu20Fe12Si4 quasicrystal (QC) alloys. The phases present in the Al64Cu20Fe12Si4 ingot alloy were determined to be icosahedral quasicrystalline (IQC) Ψ-Al65Cu20Fe15, cubic β-AlFe, tetragonal θ-Al2Cu, and monoclinic λ-A13Fe4 phases, whereas only IQC Ψ-Al65Cu20Fe15 and cubic β-AlFe phases were identified in the rapidly solidified alloy. The microhardness value of the melt spun alloy was measured to be approximately 790 kg/mm2. Microhardness increases with increasing solidification rates.

  6. Cost-Effective TiAl based Materials

    NASA Technical Reports Server (NTRS)

    Moxson, V. S.; Sun, Fusheng; Draper, Susan L.; Froes, F. H.; Duz, V.

    2003-01-01

    Because of their inherent low ductility, TiAl-based materials are difficult to fabricate, especially thin gage titanium gamma aluminide (TiAl) sheet and foil. In this paper, an innovative powder metallurgy approach for producing cost-effective thin gage TiAl sheets (with 356 mm long and 235 mm wide, and a thickness of 0.74, 1.09, 1.55, and 2.34 mm, respectively) is presented. The microstructures and tensile properties at room and elevated temperatures of the thin gage TiAl are studied. Results show that these TiAl sheets have a relatively homogenous chemistry, uniform microstructure, and acceptable mechanical properties. This work demonstrates a cost-effective method for producing both flat products (sheet/foil) and complex chunky parts of TiAl for various advanced applications including aerospace and automotive industries.

  7. Synthesis of in-situ TiAl-based composites from elemental powders

    SciTech Connect

    Alman, D.E.; Hawk, J.A.

    1997-02-01

    Alloys and composites based on the intermetallic compound TiAl are emerging as an important class of light-weight, high-temperature structural materials. Recently, it has been recognized that these alloys have applications in industries, such as the automotive industry, where cost is frequently a major concern in materials selection. However, for these alloys to be used in this type of application, new low cost methods for high volume component fabrication are required. One potential fabrication approach is reactive synthesis (also termed combustion synthesis). This technique involves initiating an self-propagating, high-temperature synthesis (SHS) reaction within an intimate mixture of elemental powders. This process has been used to fabricate intermetallics, ceramics and in-situ composites in the form of powders and dense monoliths. SHS reactions tend to initiate at low homologous temperatures of the forming compound (for aluminides near or at the melting point of Al, 660°C), and tend to go to completion in a short period of time (i.e., a few seconds). For some compounds, particularly aluminides, the reaction is ac companied by the formation of transient liquid phases. These factors can reduce the required processing parameters (time, temperature and pressure) needed to produce dense products by reactive synthesis techniques compared to conventional powder metallurgical approaches. This paper characterizes the reactions that occur and resultant microstructures of TiAl based composites fabricated from ternary mixtures of elemental Ti, Al and B or Si powders. Mixtures of the elemental powders were prepared corresponding to TiAl reinforced with 0, 10 25, 60 and 100 vol. pct. Ti5Si3 or TiB2. The powders were consolidated by reactive hot-pressing (at 1000°C and 20 MPa for 1 hr). It was found that the composites produced from Ti, Al and Si powders were dense, and the elemental powders transformed to the target phases of TiAl and Ti5Si3. Whereas, composites produced

  8. Processing and mechanical properties of NiAl-based in-situ composites. Ph. D. Thesis Final report

    SciTech Connect

    Johnson, D.R.

    1994-05-01

    In-situ composites based on the NiAl-Cr eutectic system were successfully produced by containerless processing and evaluated. The NiAl-Cr alloys had a fibrous microstructure while the NiAl-(Cr,Mo) alloys containing 1 at. percent or more molybdenum exhibited a lamellar structure. The NiAl-28Cr-6Mo eutectic displays promising high temperature strength while still maintaining a reasonable room temperature fracture toughness when compared to other NiAl-based materials. The Laves phase NiAlTa was used to strengthen NiAl and very promising creep strengths were found for the directionally solidified NiAl-NiAlTa eutectic. The eutectic composition was found to be near NiAl-15.5Ta (at. percent) and well aligned microstructures were produced at this composition. An off-eutectic composition of NiAl-14.5Ta was also processed, consisting of NiAl dendrites surrounded by aligned eutectic regions. 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. Polyphase in-situ composites were generated by directional solidification of ternary eutectics. The systems investigated were the Ni-Al-Ta-X (X=Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and both the eutectic composition and temperature were determined. Of these ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr,Al)NiTa-Cr eutectic was intermediate between those of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

  9. Processing and Mechanical Properties of NiAl-Based In-Situ Composites. Ph.D. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Johnson, David Ray

    1994-01-01

    In-situ composites based on the NiAl-Cr eutectic system were successfully produced by containerless processing and evaluated. The NiAl-Cr alloys had a fibrous microstructure while the NiAl-(Cr,Mo) alloys containing 1 at. percent or more molybdenum exhibited a lamellar structure. The NiAl-28Cr-6Mo eutectic displays promising high temperature strength while still maintaining a reasonable room temperature fracture toughness when compared to other NiAl-based materials. The Laves phase NiAlTa was used to strengthen NiAl and very promising creep strengths were found for the directionally solidified NiAl-NiAlTa eutectic. The eutectic composition was found to be near NiAl-15.5Ta (at. percent) and well aligned microstructures were produced at this composition. An off-eutectic composition of NiAl-14.5Ta was also processed, consisting of NiAl dendrites surrounded by aligned eutectic regions. 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. Polyphase in-situ composites were generated by directional solidification of ternary eutectics. The systems investigated were the Ni-Al-Ta-X (X=Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and both the eutectic composition and temperature were determined. Of these ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr,Al)NiTa-Cr eutectic was intermediate between those of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

  10. Study of Magnetic Alloys: Critical Phenomena.

    DTIC Science & Technology

    MAGNETIC ALLOYS, TRANSPORT PROPERTIES), ELECTRICAL RESISTANCE, SEEBECK EFFECT , MAGNETIC PROPERTIES, ALUMINUM ALLOYS, COBALT ALLOYS, GADOLINIUM ALLOYS, GOLD ALLOYS, IRON ALLOYS, NICKEL ALLOYS, PALLADIUM ALLOYS, PLATINUM ALLOYS, RHODIUM ALLOYS

  11. Development and Characterization of Carbon Nanotubes (CNTs) and Silicon Carbide (SiC) Reinforced Al-based Nanocomposites

    NASA Astrophysics Data System (ADS)

    Gujba, Kachalla Abdullahi

    Composites are engineered materials developed from constituent materials; matrix and reinforcements, to attain synergistic behavior at the micro and macroscopic level which are different from the individual materials. The high specific strength, low weight, excellent chemical resistance and fatigue endurance makes these composites superior than other materials despite anisotropic behaviors. Metal matrix composites (MMCs) have excellent physical and mechanical properties and alumium (Al) alloy composites have gained considerable interest and are used in multiple industries including: aerospace, structural and automotive. The aim of this research work is to develop an advanced Al-based nanocomposites reinforced with Carbon nanotubes (CNTs) and silicon carbide particulates (SiCp) nanophases using mechanical alloying and advanced consolidation procedure (Non-conventional) i.e. Spark Plasma Sintering (SPS) using two types of aluminum alloys (Al-7Si-0.3mg and Al-12Si-0.3Mg). Different concentrations of SiCp and CNTs were added and ball milled for different milling periods under controlled atmosphere to study the effect of milling time and the distribution of the second phases. Characterization techniques were used to investigate the morphology of the as received monolithic and milled powder using Field Emission Scanning Electron Microscope (FESEM), Energy Dispersive Spectroscopy (EDS), X-Ray Mapping, X-Ray Diffraction (XRD) and Particle Size Analyses (PSA). The results revealed that the addition of high concentrations of SiCp and CNTs in both alloys aided in refining the structure of the resulting powder further as the reinforcement particles acted like a grinding agent. Good distribution of reinforcing particles was observed from SEM and no compositional fluctuations were observed from the EDS. Some degree of agglomerations was observed despite the ethyl alcohol sonication effect of the CNTs before ball milling. From the XRD; continuous reduction in crystallite size and

  12. Alloy materials

    DOEpatents

    Hans Thieme, Cornelis Leo; Thompson, Elliott D.; Fritzemeier, Leslie G.; Cameron, Robert D.; Siegal, Edward J.

    2002-01-01

    An alloy that contains at least two metals and can be used as a substrate for a superconductor is disclosed. The alloy can contain an oxide former. The alloy can have a biaxial or cube texture. The substrate can be used in a multilayer superconductor, which can further include one or more buffer layers disposed between the substrate and the superconductor material. The alloys can be made a by process that involves first rolling the alloy then annealing the alloy. A relatively large volume percentage of the alloy can be formed of grains having a biaxial or cube texture.

  13. Icosahedral quasicrystalline (Ti1.6V0.4Ni)100-xScx alloys: Synthesis, structure and their application in Ni-MH batteries

    NASA Astrophysics Data System (ADS)

    Hu, Wen; Yi, Jianhong; Zheng, Biju; Wang, Limin

    2013-06-01

    Thanks to the revolutionary discovery of 5-fold symmetry contributed by Shechtman, quasicrystal is now recognized as another solid-state existing form. As the second largest class of quasicrystals, titanium-based icosahedral quasicrystals are very promising for hydrogen storage applications owing to their inherent abundant interstitial sites and favorable hydrogen-metal chemistry. In this context, (Ti1.6V0.4Ni)100-xScx (x=0.5-6) quaternary icosahedral quasicrystals have been successfully synthesized via arc-melting and subsequent melt-spinning techniques, and then their electrochemical performance toward hydrogen is explored. When the molar ratio of Sc addition is under 1%, a maximum discharge capacity of about 270 mA h g-1 can be delivered. With further increasing Sc amount to 6%, good cycling stability as well as significantly retarded self-discharge rate (capacity retention 94% after 24 h relaxation) is observed. But meanwhile, the discharge capacities fall into 250-240 mA h g-1, and the electrocatalytic activity improvement is highly demanded.

  14. Optical generation of crystalline, quasicrystalline, and arbitrary arrays of torons in confined cholesteric liquid crystals for patterning of optical vortices in laser beams

    NASA Astrophysics Data System (ADS)

    Ackerman, Paul J.; Qi, Zhiyuan; Smalyukh, Ivan I.

    2012-08-01

    Condensed matter systems with topological defects in the ground states range from the Abrikosov phases in superconductors, to various blue phases and twist grain boundary phases in liquid crystals, and to phases of skyrmion lattices in chiral ferromagnets and Bose-Einstein condensates. In nematic and chiral nematic liquid crystals, which are true fluids with long-range orientational ordering of constituent molecules, point and line defects spontaneously occur as a result of symmetry-breaking phase transitions or due to flow, but they are unstable, hard to control, and typically annihilate with time. Here we describe the optical generation of two-dimensional crystalline, quasicrystalline, and arbitrary ensembles of particlelike structures manifesting both skyrmionlike and Hopf fibration features—dubbed “torons”—composed of looped double twist cylinders and point defects embedded in a uniform director field. In these two-dimensional lattices, we then introduce various dislocations, defects in positional ordering of the torons. We show that the periodic defect lattices with and without dislocation are light- and voltage-tunable reconfigurable two-dimensional diffraction gratings and can be used to generate various controlled phase singularities in the diffracted laser beams. The results of computer simulations of optical images, diffraction patterns, and phase distributions with optical vortices are in a good agreement with the corresponding experimental findings.

  15. Synthesis of nanocrystalline (Co, Ni)Al2O4 spinel powder by mechanical milling of quasicrystalline materials.

    PubMed

    Yadav, T P; Mukhopadhyay, N K; Tiwari, R S; Srivastava, O N

    2007-02-01

    In the present study, attempts have been made to synthesize the nano-crystalline (Co, Ni)Al2O4 spinel powders by ball milling and subsequent annealing. An alloy of Al70Co15Ni15, exhibiting the formation of a complex intermetallic compound known as decagonal quasicrystal is selected as the starting material for mechanical milling. It is interesting to note that this alloy is close to the stoichiometry of aluminum and transition metal atoms required to form the aluminate spinel. The milling was carried out in an attritor mill at 400 rpm for 40 hours with ball to powder ratio of 20 : 1 in hexane medium. Subsequent to this annealing was performed in an air ambience for 10, 20, and 40 h at 600 degrees C in side the furnace in order to oxidize the decagonal phase and finally to form the spinel structure. The X-ray diffraction (XRD) and transmission electron microscopy (TEM) confirmed the formation of nano-sized decagonal phase after milling and then (Co, Ni)Al2O4 spinel type phase after annealing. The XRD studies reveal the lattice parameter to be 8.075 angstroms and the lattice strain as 0.6%. The XRD and TEM explorations of spinel phase indicate the average grain size to be approximately 40 nm.

  16. Quasicrystal-reinforced Mg alloys

    PubMed Central

    Kyun Kim, Young; Tae Kim, Won; Hyang Kim, Do

    2014-01-01

    The formation of the icosahedral phase (I-phase) as a secondary solidification phase in Mg–Zn–Y and Mg–Zn–Al base systems provides useful advantages in designing high performance wrought magnesium alloys. The strengthening in two-phase composites (I-phase + α-Mg) can be explained by dispersion hardening due to the presence of I-phase particles and by the strong bonding property at the I-phase/matrix interface. The presence of an additional secondary solidification phase can further enhance formability and mechanical properties. In Mg–Zn–Y alloys, the co-presence of I and Ca2Mg6Zn3 phases by addition of Ca can significantly enhance formability, while in Mg–Zn–Al alloys, the co-presence of the I-phase and Mg2Sn phase leads to the enhancement of mechanical properties. Dynamic and static recrystallization are significantly accelerated by addition of Ca in Mg–Zn–Y alloy, resulting in much smaller grain size and more random texture. The high strength of Mg–Zn–Al–Sn alloys is attributed to the presence of finely distributed Mg2Sn and I-phase particles embedded in the α-Mg matrix. PMID:27877660

  17. NiAl alloys for structural uses

    NASA Technical Reports Server (NTRS)

    Koss, D. A.

    1991-01-01

    Alloys based on the intermetallic compound NiAl are of technological interest as high temperature structural alloys. These alloys possess a relatively low density, high melting temperature, good thermal conductivity, and (usually) good oxidation resistance. However, NiAl and NiAl-base alloys suffer from poor fracture resistance at low temperatures as well as inadequate creep strength at elevated temperatures. This research program explored macroalloying additions to NiAl-base alloys in order to identify possible alloying and processing routes which promote both low temperature fracture toughness and high temperature strength. Initial results from the study examined the additions of Fe, Co, and Hf on the microstructure, deformation, and fracture resistance of NiAl-based alloys. Of significance were the observations that the presence of the gamma-prime phase, based on Ni3Al, could enhance the fracture resistance if the gamma-prime were present as a continuous grain boundary film or 'necklace'; and the Ni-35Al-20Fe alloy was ductile in ribbon form despite a microstructure consisting solely of the B2 beta phase based on NiAl. The ductility inherent in the Ni-35Al-20Fe alloy was explored further in subsequent studies. Those results confirm the presence of ductility in the Ni-35Al-20Fe alloy after rapid cooling from 750 - 1000 C. However exposure at 550 C caused embrittlement; this was associated with an age-hardening reaction caused by the formation of Fe-rich precipitates. In contrast, to the Ni-35Al-20Fe alloy, exploratory research indicated that compositions in the range of Ni-35Al-12Fe retain the ordered B2 structure of NiAl, are ductile, and do not age-harden or embrittle after thermal exposure. Thus, our recent efforts have focused on the behavior of the Ni-35Al-12Fe alloy. A second parallel effort initiated in this program was to use an alternate processing technique, mechanical alloying, to improve the properties of NiAl-alloys. Mechanical alloying in the

  18. An Introduction to the BFS Method and Its Use to Model Binary NiAl Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Ferrante, J.; Amador, C.

    1998-01-01

    We introduce the Bozzolo-Ferrante-Smith (BFS) method for alloys as a computationally efficient tool for aiding in the process of alloy design. An intuitive description of the BFS method is provided, followed by a formal discussion of its implementation. The method is applied to the study of the defect structure of NiAl binary alloys. The groundwork is laid for a detailed progression to higher order NiAl-based alloys linking theoretical calculations and computer simulations based on the BFS method and experimental work validating each step of the alloy design process.

  19. Processing and Mechanical Properties of Directionally Solidified NiAl/NiAlTa Alloys

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    Promising creep strengths were found for a directionally solidified NiAl-NiAlTa alloy when compared to other NiAl based intermetallics. The directionally solidified alloy had an off-eutectic composition that resulted in microstructures consisting of NiAl dendrites surrounded by aligned eutectic regions. The room temperature toughness of the two phase alloy was similar to that of polycrystalline NiAl even with the presence of the brittle Laves phase NiAlTa. Alloying additions that may improve the room temperature toughness by producing multiphase alloys are discussed.

  20. Casting alloys.

    PubMed

    Wataha, John C; Messer, Regina L

    2004-04-01

    Although the role of dental casting alloys has changed in recent years with the development of improved all-ceramic materials and resin-based composites, alloys will likely continue to be critical assets in the treatment of missing and severely damaged teeth. Alloy shave physical, chemical, and biologic properties that exceed other classes of materials. The selection of the appropriate dental casting alloy is paramount to the long-term success of dental prostheses,and the selection process has become complex with the development of many new alloys. However, this selection process is manageable if the practitioner focuses on the appropriate physical and biologic properties, such as tensile strength, modulus of elasticity,corrosion, and biocompatibility, and avoids dwelling on the less important properties of alloy color and short-term cost. The appropriate selection of an alloy helps to ensure a longer-lasting restoration and better oral health for the patient.

  1. 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.

  2. The effects of layers in dry snow on its passive microwave emissions using dense media radiative transfer theory based on the quasicrystalline approximation (QCA/DMRT)

    USGS Publications Warehouse

    Liang, D.; Xu, X.; Tsang, L.; Andreadis, K.M.; Josberger, E.G.

    2008-01-01

    A model for the microwave emissions of multilayer dry snowpacks, based on dense media radiative transfer (DMRT) theory with the quasicrystalline approximation (QCA), provides more accurate results when compared to emissions determined by a homogeneous snowpack and other scattering models. The DMRT model accounts for adhesive aggregate effects, which leads to dense media Mie scattering by using a sticky particle model. With the multilayer model, we examined both the frequency and polarization dependence of brightness temperatures (Tb's) from representative snowpacks and compared them to results from a single-layer model and found that the multilayer model predicts higher polarization differences, twice as much, and weaker frequency dependence. We also studied the temporal evolution of Tb from multilayer snowpacks. The difference between Tb's at 18.7 and 36.5 GHz can be S K lower than the single-layer model prediction in this paper. By using the snowpack observations from the Cold Land Processes Field Experiment as input for both multi- and single-layer models, it shows that the multilayer Tb's are in better agreement with the data than the single-layer model. With one set of physical parameters, the multilayer QCA/DMRT model matched all four channels of Tb observations simultaneously, whereas the single-layer model could only reproduce vertically polarized Tb's. Also, the polarization difference and frequency dependence were accurately matched by the multilayer model using the same set of physical parameters. Hence, algorithms for the retrieval of snowpack depth or water equivalent should be based on multilayer scattering models to achieve greater accuracy. ?? 2008 IEEE.

  3. VANADIUM ALLOYS

    DOEpatents

    Smith, K.F.; Van Thyne, R.J.

    1959-05-12

    This patent deals with vanadium based ternary alloys useful as fuel element jackets. According to the invention the ternary vanadium alloys, prepared in an arc furnace, contain from 2.5 to 15% by weight titanium and from 0.5 to 10% by weight niobium. Characteristics of these alloys are good thermal conductivity, low neutron capture cross section, good corrosion resistance, good welding and fabricating properties, low expansion coefficient, and high strength.

  4. BRAZING ALLOYS

    DOEpatents

    Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

    1963-02-26

    A brazing alloy which, in the molten state, is characterized by excellent wettability and flowability, said alloy being capable of forming a corrosion resistant brazed joint wherein at least one component of said joint is graphite and the other component is a corrosion resistant refractory metal, said alloy consisting essentially of 20 to 50 per cent by weight of gold, 20 to 50 per cent by weight of nickel, and 15 to 45 per cent by weight of molybdenum. (AEC)

  5. PILOT EVALUATION OF VANADIUM ALLOYS.

    DTIC Science & Technology

    ARCS, SHEETS, ROLLING(METALLURGY), HIGH TEMPERATURE, SCIENTIFIC RESEARCH, COMPRESSIVE PROPERTIES, DUCTILITY, CREEP, OXIDATION, COATINGS , SILICIDES , HARDNESS, WELDING, EXTRUSION, TANTALUM ALLOYS, MOLYBDENUM ALLOYS....VANADIUM ALLOYS, * NIOBIUM ALLOYS, MECHANICAL PROPERTIES, MECHANICAL PROPERTIES, TITANIUM ALLOYS, ZIRCONIUM ALLOYS, CARBON ALLOYS, MELTING, ELECTRIC

  6. Nonswelling alloy

    DOEpatents

    Harkness, S.D.

    1975-12-23

    An aluminum alloy containing one weight percent copper has been found to be resistant to void formation and thus is useful in all nuclear applications which currently use aluminum or other aluminum alloys in reactor positions which are subjected to high neutron doses.

  7. URANIUM ALLOYS

    DOEpatents

    Seybolt, A.U.

    1958-04-15

    Uranium alloys containing from 0.1 to 10% by weight, but preferably at least 5%, of either zirconium, niobium, or molybdenum exhibit highly desirable nuclear and structural properties which may be improved by heating the alloy to about 900 d C for an extended period of time and then rapidly quenching it.

  8. ZIRCONIUM ALLOY

    DOEpatents

    Wilhelm, H.A.; Ames, D.P.

    1959-02-01

    A binary zirconiuin--antimony alloy is presented which is corrosion resistant and hard containing from 0.07% to 1.6% by weight of Sb. The alloys have good corrosion resistance and are useful in building equipment for the chemical industry.

  9. Measurement of the density of liquid aluminum-319 alloy by an x-ray attenuation technique

    SciTech Connect

    Smith, P.M.; Gallegos, G.F.

    1994-11-01

    This study was made for assisting in casting simulations. A relatively simple apparatus was constructed for measuring the density of Al-based alloys in the solid and liquid states up to 900 C. One of the more important physical properties of a casting alloy, solidification shrinkage, was measured for a commercial Al alloy (Al-319). It was found that while the thermal expansion of Al-319 in both solid and liquid phases is similar to that of pure Al, the density of the liquid alloy is lower than estimated by averaging the atomic volumes of the pure liquid components. The densities were measured by x-ray attenuation.

  10. Formation and characterization of Al-Ti-Nb alloys by electron-beam surface alloying

    NASA Astrophysics Data System (ADS)

    Valkov, S.; Petrov, P.; Lazarova, R.; Bezdushnyi, R.; Dechev, D.

    2016-12-01

    The combination of attractive mechanical properties, light weight and resistance to corrosion makes Ti-Al based alloys applicable in many industrial branches, like aircraft and automotive industries etc. It is known that the incorporation of Nb improves the high temperature performance and mechanical properties. In the present study on Al substrate Ti and Nb layers were deposited by DC (Direct Current) magnetron sputtering, followed by electron-beam alloying with scanning electron beam. It was chosen two speeds of the specimen motion during the alloying process: V1 = 0.5 cm/s and V2 = 1 cm/s. The alloying process was realized in circular sweep mode in order to maintain the melt pool further. The obtained results demonstrate a formation of (Ti,Nb)Al3 fractions randomly distributed in biphasic structure of intermetallic (Ti,Nb)Al3 particles, dispersed in α-Al solid solution. The evaluated (Ti,Nb)Al3 lattice parameters are independent of the speed of the specimen motion and therefore the alloying speed does not affect the lattice parameters and thus, does not form additional residual stresses, strains etc. It was found that lower velocity of the specimen motion during the alloying process develops more homogeneous structures. The metallographic analyses demonstrate a formation of surface alloys with very high hardness. Our results demonstrate maximal values of 775 HV [kg/cm2] and average hardness of 673 HV [kg/cm2].

  11. Arsenate uptake by Al nanoclusters and other Al-based sorbents during water treatment.

    PubMed

    Mertens, Jasmin; Rose, Jérôme; Wehrli, Bernhard; Furrer, Gerhard

    2016-01-01

    In many parts of the world, arsenic from geogenic and anthropogenic sources deteriorates the quality of drinking water resources. Effective methods of arsenic removal include adsorption and coagulation with iron- and aluminum-based materials, of which polyaluminum chloride is widely employed as coagulant in water treatment due to its low cost and high efficiency. We compared the arsenic uptake capacity and the arsenic bonding sites of different Al-based sorbents, including Al nanoclusters, polyaluminum chloride, polyaluminum granulate, and gibbsite. Extended X-ray absorption fine structure (EXAFS) spectroscopy revealed that As(V) forms bidentate-binuclear complexes in interaction with all Al-based removal agents. The octahedral configuration of nanoclusters and the distribution of sorption sites remain the same in all types of removal agents consisting of nano-scale Al oxyhydroxide particles. The obtained distances for As(V)-O and As(V)-Al agreed with previously published data and were found to be 1.69 ± 0.02 Å and 3.17-3.21 Å, respectively. Our study suggests that As(V) binds to Al nanoclusters as strongly as to Al oxide surfaces. The As sorption capacity of Al nanoclusters was found to be very similar to that of Al clusters in a polyaluminum chloride. The most efficient Al-based sorbents for arsenic removal were Al nanoclusters, followed by polyaluminum granulate.

  12. PLUTONIUM ALLOYS

    DOEpatents

    Chynoweth, W.

    1959-06-16

    The preparation of low-melting-point plutonium alloys is described. In a MgO crucible Pu is placed on top of the lighter alloying metal (Fe, Co, or Ni) and the temperature raised to 1000 or 1200 deg C. Upon cooling, the alloy slug is broke out of the crucible. With 14 at. % Ni the m.p. is 465 deg C; with 9.5 at. % Fe the m.p. is 410 deg C; and with 12.0 at. % Co the m.p. is 405 deg C. (T.R.H.) l6262 l6263 ((((((((Abstract unscannable))))))))

  13. Aluminum alloy

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  14. BRAZING ALLOYS

    DOEpatents

    Donnelly, R.G.; Gilliland, R.G.; Slaughter, G.M.

    1962-02-20

    A brazing alloy is described which, in the molten state, is characterized by excellent wettability and flowability and is capable of forming a corrosion-resistant brazed joint. At least one component of said joint is graphite and the other component is a corrosion-resistant refractory metal. The brazing alloy consists essentially of 40 to 90 wt % of gold, 5 to 35 wt% of nickel, and 1 to 45 wt% of tantalum. (AEC)

  15. COATED ALLOYS

    DOEpatents

    Harman, C.G.; O'Bannon, L.S.

    1958-07-15

    A coating is described for iron group metals and alloys, that is particularly suitable for use with nickel containing alloys. The coating is glassy in nature and consists of a mixture containing an alkali metal oxide, strontium oxide, and silicon oxide. When the glass coated nickel base metal is"fired'' at less than the melting point of the coating, it appears the nlckel diffuses into the vitreous coating, thus providing a closely adherent and protective cladding.

  16. The effect of hydrogen on ([alpha][sub 2] + [beta])/[beta] transus temperature of super-[alpha][sub 2] alloy

    SciTech Connect

    Liao, B.; Yang, K.; Li, Y.Y. . Liaoning Key Lab. for Materials and Hydrogen); Wang, T.S.; Yuan, H. . Dept. of Materials and Engineering)

    1995-01-15

    Thermochemical processing (TCP) with hydrogen has been proved to be an effective technique to modify the microstructures and enhance the mechanical properties of conventional titanium alloys. In recent years, some effort has also been made to apply this unique method to Ti[sub 3]Al based aluminide alloys in order to improve their properties, especially the room temperature ductilities, through the modification of the microstructures, for the properties have been found to be highly dependent on microstructures of the alloys. However, further investigation on variations of some basic physical parameters of the alloys caused by hydrogen have not been carried on for TCP with hydrogen on this type of alloys, which can result in arbitrary selections of the treatment parameters for processings. Therefore, quantitative investigations on hydrogen behaviors in the alloys can be very important to the optimization of this novel processing technique for Ti[sub 3]Al based aluminide alloys. In the present work, super-[alpha][sub 2], a Ti[sub 3]Al based aluminide alloy, has been chosen to study the effect of hydrogen on ([alpha][sub 2] + [beta])/[beta] transus temperature of the alloy, an important parameter to phase transformation of this type of alloy, in order to provide a preliminary based for the application.

  17. Recent advances in alloy design of Ni{sub 3}Al alloys for structural use

    SciTech Connect

    Liu, C.T.; George, E.P.

    1996-12-31

    This is a comprehensive review of recent advances in R&D of Ni{sub 3}Al-based alloys for structural use at elevated temperatures in hostile environments. Recent studies indicate that polycrystalline Ni{sub 3}Al is intrinsically quite ductile at ambient temperatures, and its poor tensile ductility and brittle grain-boundary fracture are caused mainly by moisture-induced hydrogen embrittlement when the aluminide is tested in moisture- or hydrogen-containing environments. Tensile ductility is improved by alloying with substitutional and interstitial elements. Among these additives, B is most effective in suppressing environmental embrittlement and enhancing grain-boundary cohesion, resulting in a dramatic increase of tensile ductility at room temperature. Both B-doped and B-free Ni{sub 3}Al alloys exhibit brittle intergranular fracture and low ductility at intermediate temperatures (300-850 C) because of oxygen-induced embrittlement in oxidizing environments. Cr is found to be most effective in alleviating elevated-temperature embrittlement. Parallel efforts on alloy development using physical metallurgy principles have led to development of several Ni{sub 3}Al alloys for industrial use. The unique properties of these alloys are briefly discussed. 56 refs, 15 figs, 3 tabs.

  18. Low-aluminum content iron-aluminum alloys

    SciTech Connect

    Sikka, V.K.; Goodwin, G.M.; Alexander, D.J.

    1995-06-01

    The low-aluminum-content iron-aluminum program deals with the development of a Fe-Al alloy with aluminum content such as a produce the minimum environmental effect at room temperature. The FAPY is an Fe-16 at. % Al-based alloy developed at the Oak Ridge National Laboratory as the highest aluminum-containing alloy with essentially no environmental effect. The chemical composition for FAPY in weight percent is: aluminum = 8.46, chromium = 5.50, zirconium = 0.20, carbon = 0.03, molybdenum = 2.00, yttrium = 0.10 and iron = 83.71. The ignots of the alloy can be hot worked by extrusion, forging, and rolling processes. The hot-worked cast structure can be cold worked with intermediate anneals at 800{degrees}C. Typical room-temperature ductility of the fine-grained wrought structure is 20 to 25% for this alloy. In contrast to the wrought structure, the cast ductility at room temperature is approximately 1% with a transition temperature of approximately 100 to 150{degrees}C, above which ductility values exceed 20%. The alloy has been melted and processed into bar, sheet, and foil. The alloy has also been cast into slabs, step-blocks of varying thicknesses, and shapes. The purpose of this section is to describe the welding response of cast slabs of three different thicknesses of FAPY alloy. Tensile, creep, and Charpy-impact data of the welded plates are also presented.

  19. Quasicrystalline three-dimensional foams

    NASA Astrophysics Data System (ADS)

    Cox, S. J.; Graner, F.; Mosseri, R.; Sadoc, J.-F.

    2017-03-01

    We present a numerical study of quasiperiodic foams, in which the bubbles are generated as duals of quasiperiodic Frank–Kasper phases. These foams are investigated as potential candidates to the celebrated Kelvin problem for the partition of three-dimensional space with equal volume bubbles and minimal surface area. Interestingly, one of the computed structures falls close to (but still slightly above) the best known Weaire–Phelan periodic candidate. In addition we find a correlation between the normalized bubble surface area and the root mean squared deviation of the number of faces, giving an additional clue to understanding the main geometrical ingredients driving the Kelvin problem.

  20. Microstructure and Mechanical Properties of Ultra-Fine Grain Al-Zr Alloy Fabricated by Mechanical Alloying Process.

    PubMed

    Kim, Chung Seok; Kim, Il-Ho

    2015-08-01

    The ultra-fine grain Al-4Zr alloy has been successfully fabricated by a mechanical alloying process. The intermetallic Al3Zr phases strongly enhance the mechanical properties of Al-based alloy and prevent grain growth of alloy. The phase stability and transformation during mechanical alloying process have been investigated. The ultra-fine grain alloy has been successfully obtained. The thin film of Al-4Zr alloy has been observed by a transmission electron microscope. The equivalent grain size of as-milling specimen is 55 nm. After milling process, the specimens were heat treated at 350 °C to 650 °C. The equivalent grain size of heat treated specimens were 80 nm at 350 °C and 130 nm at 650 °C. Some of Zr atoms were dissolved into the Al matrix and most of them reacted with hydrogen produced by decomposition of PCA to form ZrH2 during mechanical alloying process. These ZrH2 hydrides decomposed gradually after the heat treatment. Stable A13Zr with a D023 structure was formed by heat treatment at temperature of 550 °C.

  1. Direct synthesis of nanoporous carbon nitride fibers using Al-based porous coordination polymers (Al-PCPs).

    PubMed

    Hu, Ming; Reboul, Julien; Furukawa, Shuhei; Radhakrishnan, Logudurai; Zhang, Yuanjian; Srinivasu, Pavuluri; Iwai, Hideo; Wang, Hongjing; Nemoto, Yoshihiro; Suzuki, Norihiro; Kitagawa, Susumu; Yamauchi, Yusuke

    2011-07-28

    We report a new synthetic route for preparation of nanoporous carbon nitride fibers with graphitic carbon nitride polymers, by calcination of Al-based porous coordination polymers (Al-PCPs) with dicyandiamide (DCDA) under a nitrogen atmosphere.

  2. Bipolar resistive switching and conduction mechanism of an Al/ZnO/Al-based memristor

    NASA Astrophysics Data System (ADS)

    Gul, Fatih; Efeoglu, Hasan

    2017-01-01

    In this study, a direct-current reactive sputtered Al/ZnO/Al-based memristor device was fabricated and its resistive switching (RS) characteristics investigated. The optical and structural properties were confirmed by using UV-vis spectrophotometry and x-ray diffraction, respectively. The memristive and resistive switching characteristics were determined using time dependent current-voltage (I-V-t) measurements. The typical pinched hysteresis I-V loops of a memristor were observed. In addition, the device showed forming-free, uniform and bipolar RS behavior. The low electric field region exhibited ohmic conduction, while the Schottky emission (SE) was found to be the dominant conduction mechanism in the high electric field region. A weak Poole-Frenkel (PF) emission also appeared. In conclusion, it was suggested that the SE and PF mechanisms were related to the oxygen vacancies in the ZnO.

  3. 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.

  4. Effects of reheating time on microstructure and tensile properties of SiCp/2024 Al-based composites fabricated using powder thixoforming

    NASA Astrophysics Data System (ADS)

    Li, Pu Bo; Chen, Ti Jun; Zhang, Su Qing

    2017-01-01

    The present investigation addresses a new technology, named powder thixoforming, used to fabricate SiCp/2024 Al-based composites. The effects of reheating time on microstructure and mechanical properties have been studied. The results indicated that the quantity of liquid, the coarsening behavior of the primary particles, the subsequent plastic deformation occurring during thixoforging, and thus the resulting microstructural compactness and mechanical properties changed as a function of reheating time. The best comprehensive tensile properties of the composite, that is an ultimate tensile strength of 370 MPa and an elongation of 4.4%, were obtained after reheating for 80 min at 625 °C, which was an increase of 23.3% and a decrease of 57.7%, respectively, compared to the 2024 alloy thixoforged under the same conditions as the composite. The fracturing in the composites occurred through interconnecting cracked SiCp and debonded SiC/Al interfaces caused by a higher concentration of stress and a coalescence of microvoids.

  5. Tensile and fatigue behavior of Al-based metal matrix composites reinforced with continuous carbon or alumina fibers: Part I. Quasi-unidirectional composites

    NASA Astrophysics Data System (ADS)

    Jacquesson, M.; Girard, A.; Vidal-Sétif, M.-H.; Valle, R.

    2004-10-01

    The thermomechanical (dilatometric, tensile, and fatigue) behavior of Al-based metal matrix composites (MMCs) is investigated. These composites are reinforced by quasi-unidirectional (quasi-UD) woven fabric preforms with 90 pct of continuous fibers in the longitudinal direction and 10 pct in the transverse direction. The two composite systems investigated feature a highly ductile matrix (AU2: Al-2Cu wt pct) with a strongly bonded fiber-matrix interface (N610 alumina fibers) and an alloyed, high-strength matrix (A357: Al-7Si-0.6Mg wt pct) with a weak fiber-matrix interface (K139 carbon fibers). Microstructural investigation of the tested specimens has permitted identification of the specific characteristics of these composites: undulation of the longitudinal bundles, presence of the straight transverse bundles, interply shearing, and role of brittle phases. Moreover, simple semiquantitative models ( e.g., interply shearing) have enabled explanation of the specific mechanical behavior of these quasi-UD composites, which exhibit high tensile and fatigue strengths, as compared with the corresponding pure UD composites. Knowledge of the specific characteristics and mechanical behavior of these quasi-UD composites will facilitate the further investigation of the (0, ±45, 90 deg) quasi-UD laminates (Part II). At a more theoretical viewpoint, the specific geometry and behavior of these quasi-UD composites allows exacerbation of fatigue mechanisms, even more intense than in “model” composites.

  6. Thermo-mechanical processing (TMP) of Ti-48Al-2Nb-2Cr based alloys

    SciTech Connect

    Fuchs, G.E.

    1995-02-01

    The effects of heat treatment and deformation processing on the microstructures and properties of {gamma}-TiAl based alloys produced by ingot metallurgy (I/M) and powder metallurgy (P/M) techniques were examined. The alloy selected for this work is the second generation {gamma}-TiAl based alloy -- Ti-48Al-2Nb-2Cr (at %). Homogenization of I/M samples was performed at a variety of temperatures, followed by hot working by isothermal forging. P/M samples were prepared from gas atomized powders, consolidated by both HIP and extrusion and some of the HIPed material was then hot worked by isothermal forging. The effects of processing, heat treatment and hot working on the microstructures and properties will be discussed.

  7. Alloy softening in binary molybdenum alloys

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1972-01-01

    An investigation was conducted to determine the effects of alloy additions of Hf, Ta, W, Re, Os, Ir, and Pt on the hardness of Mo. Special emphasis was placed on alloy softening in these binary Mo alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to Mo, while those elements having an equal number or fewer s+d electrons than Mo failed to produce alloy softening. Alloy softening and hardening can be correlated with the difference in number of s+d electrons of the solute element and Mo.

  8. The shock Hugoniot of the intermetallic alloy Ti-46.5Al-2Nb-2Cr

    SciTech Connect

    Millett, Jeremy; Gray, George T. Rusty III; Bourne, Neil

    2000-09-15

    Plate impact experiments were conducted on a {gamma}-titanium aluminide (TiAl) based ordered intermetallic alloy. Stress measurements were recorded using manganin stress gauges supported on the back of TiAl targets using polymethylmethacrylate windows. The Hugoniot in stress-particle velocity space for this TiAl alloy was deduced using impedance matching techniques. The results in this study are compared to the known Hugoniot data of the common alpha-beta engineering Ti-based alloy Ti-6Al-4V. The results of the current study on the intermetallic alloy TiAl support that TiAl possesses a significantly higher stress for a given particle velocity than the two-phase Ti-6Al-4V alloy. (c) 2000 American Institute of Physics.

  9. Ag-Al based air braze for high temperature electrochemical devices

    SciTech Connect

    Kim, Jin Yong Y.; Hardy, John S.; Weil, K. Scott

    2007-11-01

    Silver-aluminum based air brazing was attempted using an in-situ alloying and brazing process. In this process, layers of foils of aluminum and silver were laid up between alumina plates in alternating fashion to achieve three target compositions representing Ag, Ag3Al, and Ag2Al phases. Each alloy composition revealed different microstructure, mechanical properties and fracture mechanisms. Joints brazed with foils containing 9.8 at% Al formed a long continuous layer parallel to the direction of the original aluminum foil. The fracture occurred through the interface between this long alumina layer and the braze filler, resulting in low bend strength (6 ~ 12 MPa). Joints containing 26.5 at% Al in the braze filler metal experienced the series of phase transformations, leading to cracks in as-brazed specimens. The fracture initiated through these pre-existing cracks, thus the joint strength observed in these specimens was extremely low. The joints prepared using foils with 35.1 at% Al exhibited a good interface even though interfacial alumina particles formed during air brazing. Crack propagation occurred through the interface between the alumina substrate and in-situ formed interfacial alumina particles or directly through these particles and the best bend strength (46 ~ 52 MPa) among Al-added braze compositions was achieved.

  10. Effect of Thermo-Mechanical Processing and Heat Treatment on the Tribological Characteristics of Al Based MMC's

    NASA Astrophysics Data System (ADS)

    Keshavamurthy, R.; Madhu Sudhan, J.; Gowda, Narasimhe; Krishna, R. Ananda

    2016-09-01

    This paper reports on effect of forging and Heat Treatment on Tribological characteristics of aluminium alloy-silicon nitride. Cast aluminium alloy and composite were subjected to open die hot forging process. Alloy and its composites were examined to characteristics hardness and wear test under both primary and secondary processing conditions. Effect of heat treatment on hardness and tribological behaviour were also studied. Microstructure shows even spreading of particles in cast & forged conditions. hot forged alloy and composite shows a noticeable improvement in wear resistance and COF compare to their primary counter parts. Heat treatment has a considerable effect on hardness, friction and wear characteristics of composites.

  11. Mechanical Properties of Iron Alumininides Intermetallic Alloy with Molybdenum Addition

    SciTech Connect

    Zuhailawati, H.; Fauzi, M. N. A.

    2010-03-11

    In this work, FeAl-based alloys with and without molybdenum addition were fabricated by sintering of mechanically alloyed powders in order to investigate the effect of molybdenum on iron aluminide mechanical properties. Bulk samples were prepared by mechanical alloying for 4 hours, pressing at 360 MPa and sintering at 1000 deg. C for 2 hours. The specimens were tested in compression at room temperature using Instron machine. The phase identification and microstructure of the consolidated material was examined by x-ray diffraction and scanning electron microscope correspondingly. Results show that 2.5 wt%Mo addition significantly increased the ultimate stress and ultimate strain in compressive mode due to solid solution hardening. However, the addition of Mo more than 2.5 wt% was accompanied by a reduction in both properties caused by the presence of Mo-rich precipitate particles.

  12. Al-based anti-corrosion and T-permeation barrier development for future DEMO blankets

    NASA Astrophysics Data System (ADS)

    Krauss, W.; Konys, J.; Holstein, N.; Zimmermann, H.

    2011-10-01

    In the Helium-Cooled-Liquid-Lead (HCLL) design of Test-Blanket-Modules (TBM's) for a future fusion power plant Pb-15.7Li is used as liquid breeder which is in direct contact with the structure material, e.g. EUROFER steel. Compatibility testing showed that high corrosion attack appears and that the dissolved steel components form precipitates with a high risk of system blockages. A reliable operation needs coatings as corrosion barriers. The earlier developed Hot-Dip Aluminisation (HDA) process has shown that Al-based scales can act as anti-corrosion as well as T-permeation barriers. Meanwhile two advanced electro-chemically based processes for deposition of Al-scales were successfully developed. The first (ECA = Electro-Chemical Al-deposition) is working with an organic electrolyte and the second one (ECX = Electro-Chemical-X-metal-deposition) is based on ionic liquids. Coatings in the μm-range were deposited homogeneously with exact controllable thicknesses. Metallurgical investigations showed the successful generation of protective scales and compatibility testing demonstrated the barrier function.

  13. Impact Initiation of Pressed Al-Based Intermetallic-Forming Powder Mixture Compacts

    NASA Astrophysics Data System (ADS)

    Du, S. W.; Thadhani, N. N.

    2009-12-01

    Aluminum-based intermetallic forming powder mixtures (Ni-Al, Ta-Al, Nb-Al, Mo-Al and W-Al) were uniaxially pressed into 90% dense pellets, to study the impact initiation of reactions. The pressed pellets were mounted in front of a projectile and impacted onto a steel anvil using a 7.62 mm gas gun, under a 50 millitorr vacuum. Projectiles made of copper, aluminum or poly carbonate, and varying impact velocity (up to 500 m/s) provided different levels of stress, strain, and kinetic energy. The IMACON 200 framing camera was used to observe the transient densification, deformation, and reaction states. AUTODYN 2D was used to simulate the densification and deformation process, and correlate with that observed by high-speed imaging. It was found that the reaction initiates after continued straining following densification of the powder compact, illustrating that neither the kinetic energy and nor the resulting projectile-anvil equilibrated stress are independently controlling the initiation of the intermetallic reaction. Characteristics of threshold conditions for impact-initiated reactions in the various Al-based intermetallic powder-mixture compacts will be presented.

  14. User's manual for the ALS base heating prediction code, volume 2

    NASA Technical Reports Server (NTRS)

    Reardon, John E.; Fulton, Michael S.

    1992-01-01

    The Advanced Launch System (ALS) Base Heating Prediction Code is based on a generalization of first principles in the prediction of plume induced base convective heating and plume radiation. It should be considered to be an approximate method for evaluating trends as a function of configuration variables because the processes being modeled are too complex to allow an accurate generalization. The convective methodology is based upon generalizing trends from four nozzle configurations, so an extension to use the code with strap-on boosters, multiple nozzle sizes, and variations in the propellants and chamber pressure histories cannot be precisely treated. The plume radiation is more amenable to precise computer prediction, but simplified assumptions are required to model the various aspects of the candidate configurations. Perhaps the most difficult area to characterize is the variation of radiation with altitude. The theory in the radiation predictions is described in more detail. This report is intended to familiarize a user with the interface operation and options, to summarize the limitations and restrictions of the code, and to provide information to assist in installing the code.

  15. Photoelectrical, photophysical and photocatalytic properties of Al based MOFs: MIL-53(Al) and MIL-53-NH2(Al)

    NASA Astrophysics Data System (ADS)

    An, Yang; Li, Huiliang; Liu, Yuanyuan; Huang, Baibiao; Sun, Qilong; Dai, Ying; Qin, Xiaoyan; Zhang, Xiaoyang

    2016-01-01

    Two Al based MOFs (MIL-53(Al) and MIL-53-NH2 (Al)) were synthesized, and their photoelectrical, photophysical and photocatalytic properties towards oxygen evolution from water were investigated. Different from the ligand to metal charge transfer process previously reported, we proposes a new photocatalytic mechanism based on electron tunneling according to the results of theoretical calculation, steady state and time resolved fluorescence spectra. The organic linkers absorb photons, giving rise to electrons and holes. Then, the photogenerated electrons tunnel through the AlO6-octahedra, which not only inhibit the recombination of photogenerated charge carriers, but also is a key factor to the photocatalytic activity of Al based MOFs.

  16. 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.

  17. Metallic-covalent bonding conversion and thermoelectric properties of Al-based icosahedral quasicrystals and approximants

    NASA Astrophysics Data System (ADS)

    Takagiwa, Yoshiki; Kimura, Kaoru

    2014-08-01

    In this article, we review the characteristic features of icosahedral cluster solids, metallic-covalent bonding conversion (MCBC), and the thermoelectric properties of Al-based icosahedral quasicrystals and approximants. MCBC is clearly distinguishable from and closely related to the well-known metal-insulator transition. This unique bonding conversion has been experimentally verified in 1/1-AlReSi and 1/0-Al12Re approximants by the maximum entropy method and Rietveld refinement for powder x-ray diffraction data, and is caused by a central atom inside the icosahedral clusters. This helps to understand pseudogap formation in the vicinity of the Fermi energy and establish a guiding principle for tuning the thermoelectric properties. From the electron density distribution analysis, rigid heavy clusters weakly bonded with glue atoms are observed in the 1/1-AlReSi approximant crystal, whose physical properties are close to icosahedral Al-Pd-TM (TM: Re, Mn) quasicrystals. They are considered to be an intermediate state among the three typical solids: metals, covalently bonded networks (semiconductor), and molecular solids. Using the above picture and detailed effective mass analysis, we propose a guiding principle of weakly bonded rigid heavy clusters to increase the thermoelectric figure of merit (ZT) by optimizing the bond strengths of intra- and inter-icosahedral clusters. Through element substitutions that mainly weaken the inter-cluster bonds, a dramatic increase of ZT from less than 0.01 to 0.26 was achieved. To further increase ZT, materials should form a real gap to obtain a higher Seebeck coefficient.

  18. Metallic-covalent bonding conversion and thermoelectric properties of Al-based icosahedral quasicrystals and approximants.

    PubMed

    Takagiwa, Yoshiki; Kimura, Kaoru

    2014-08-01

    In this article, we review the characteristic features of icosahedral cluster solids, metallic-covalent bonding conversion (MCBC), and the thermoelectric properties of Al-based icosahedral quasicrystals and approximants. MCBC is clearly distinguishable from and closely related to the well-known metal-insulator transition. This unique bonding conversion has been experimentally verified in 1/1-AlReSi and 1/0-Al12Re approximants by the maximum entropy method and Rietveld refinement for powder x-ray diffraction data, and is caused by a central atom inside the icosahedral clusters. This helps to understand pseudogap formation in the vicinity of the Fermi energy and establish a guiding principle for tuning the thermoelectric properties. From the electron density distribution analysis, rigid heavy clusters weakly bonded with glue atoms are observed in the 1/1-AlReSi approximant crystal, whose physical properties are close to icosahedral Al-Pd-TM (TM: Re, Mn) quasicrystals. They are considered to be an intermediate state among the three typical solids: metals, covalently bonded networks (semiconductor), and molecular solids. Using the above picture and detailed effective mass analysis, we propose a guiding principle of weakly bonded rigid heavy clusters to increase the thermoelectric figure of merit (ZT) by optimizing the bond strengths of intra- and inter-icosahedral clusters. Through element substitutions that mainly weaken the inter-cluster bonds, a dramatic increase of ZT from less than 0.01 to 0.26 was achieved. To further increase ZT, materials should form a real gap to obtain a higher Seebeck coefficient.

  19. Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations.

    PubMed

    Sato, T; Ramirez-Cuesta, A J; Daemen, L; Cheng, Y-Q; Tomiyasu, K; Takagi, S; Orimo, S

    2016-09-27

    Hydrogen release from Al-based complex hydrides composed of metal cation(s) and [AlH4](-) was investigated using inelastic neutron scattering viewed from vibrational dynamics. The hydrogen release followed the softening of translational and [AlH4](-) librational modes, which was enhanced by vibrational dynamics and the valence(s) of the metal cation(s).

  20. Photoelectrical, photophysical and photocatalytic properties of Al based MOFs: MIL-53(Al) and MIL-53-NH{sub 2}(Al)

    SciTech Connect

    An, Yang; Li, Huiliang; Liu, Yuanyuan; Huang, Baibiao; Sun, Qilong; Dai, Ying; Qin, Xiaoyan; Zhang, Xiaoyang

    2016-01-15

    Two Al based MOFs (MIL-53(Al) and MIL-53-NH{sub 2} (Al)) were synthesized, and their photoelectrical, photophysical and photocatalytic properties towards oxygen evolution from water were investigated. Different from the ligand to metal charge transfer process previously reported, we proposes a new photocatalytic mechanism based on electron tunneling according to the results of theoretical calculation, steady state and time resolved fluorescence spectra. The organic linkers absorb photons, giving rise to electrons and holes. Then, the photogenerated electrons tunnel through the AlO{sub 6}-octahedra, which not only inhibit the recombination of photogenerated charge carriers, but also is a key factor to the photocatalytic activity of Al based MOFs. - Graphical abstract: The photoelectrical, photophysical and photocatalytic properties towards oxygen evolution from water of two Al based MOFs were investigated. A new photocatalytic mechanism was proposed based on electron tunneling according to the results of both theoretical calculation and steady state, time resolved fluorescence spectra. The electron tunneling process not only inhibit the recombination of photogenerated charge carriers, but also is a key factor to the photocatalytic activity of Al based MOFs.

  1. Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations

    DOE PAGES

    Sato, T.; Ramirez-Cuesta, Anibal J.; Daemen, Luke L.; ...

    2016-08-31

    Hydrogen release from Al-based complex hydrides composed of metal cation(s) and [AlH4]– was investigated using inelastic neutron scattering viewed from vibrational dynamics. Here, the hydrogen release followed the softening of translational and [AlH4]– librational modes, which was enhanced by vibrational dynamics and the valence(s) of the metal cation(s).

  2. 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.

  3. Photocatalytic property and structural stability of CuAl-based layered double hydroxides

    SciTech Connect

    Lv, Ming; Liu, Haiqiang

    2015-07-15

    Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) were successfully synthesized by coprecipitation. Powder X-ray diffraction (XRD), inductively coupled plasma atomic emission spectrometry (ICP-AES) and UV–Vis diffuse reflectance spectrum (UV–vis) were used to confirm the formation of as-synthesized solids with good crystal structure. The photocatalytic activity of those LDH materials for CO{sub 2} reduction under visible light was investigated. The experimental results show that CuNiAl-LDHs with narrowest band gap and largest surface areas behave highest efficiency for methanol generation under visible light compared with CuMgAl-LDHs and CuZnAl-LDHs. The CuNiAL-LDH showed high yield for methanol production i.e. 0.210 mmol/g h, which was high efficient. In addition, the influence of the different M{sup 2+} on the structures and stability of the CuMAl-LDHs was also investigated by analyzing the geometric parameters, electronic arrangement, charge populations, hydrogen-bonding, and binding energies by density functional theory (DFT) analysis. The theoretical calculation results show that the chemical stability of LDH materials followed the order of CuMgAl-LDHs>CuZnAl-LDHs>CuNiAl-LDHs, which is just opposite with the photocatalytic activity and band gaps of three materials. - Graphical abstract: The host–guest calculation models and XRD patterns of CuMAl-LDHs: CuMgAl-LDHs (a), CuZnAl-LDHs (b) and CuNiAl-LDHs (c). - Highlights: • Three types of CuMAl layered double hydroxides (LDHs, M=Mg, Zn, Ni) has been synthesized. • CuMgNi shows narrower band gap and more excellent textural properties than other LDHs. • The band gap: CuMgAlAl based on result from UV–vis analysis. • CuMgAl shows the highest stability and lowest photocatalytic activity, while CuNiAl just opposite.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  5. Microstructure study of a severely plastically deformed Mg-Zn-Y alloy by application of low angle annular dark field diffraction contrast imaging

    PubMed Central

    Basha, Dudekula Althaf; Rosalie, Julian M.; Somekawa, Hidetoshi; Miyawaki, Takashi; Singh, Alok; Tsuchiya, Koichi

    2016-01-01

    Microstructural investigation of extremely strained samples, such as severely plastically deformed (SPD) materials, by using conventional transmission electron microscopy techniques is very challenging due to strong image contrast resulting from the high defect density. In this study, low angle annular dark field (LAADF) imaging mode of scanning transmission electron microscope (STEM) has been applied to study the microstructure of a Mg-3Zn-0.5Y (at%) alloy processed by high pressure torsion (HPT). LAADF imaging advantages for observation of twinning, grain fragmentation, nucleation of recrystallized grains and precipitation on second phase particles in the alloy processed by HPT are highlighted. By using STEM-LAADF imaging with a range of incident angles, various microstructural features have been imaged, such as nanoscale subgrain structure and recrystallization nucleation even from the thicker region of the highly strained matrix. It is shown that nucleation of recrystallized grains starts at a strain level of revolution N=1/4 (earlier than detected by conventional bright field imaging). Occurrence of recrystallization of grains by nucleating heterogeneously on quasicrystalline particles is also confirmed. Minimizing all strain effects by LAADF imaging facilitated grain size measurement of 150±25 nm in fully recrystallized HPT specimen after N=5. PMID:27877863

  6. Study of the properties and the choice of alloys for bladed disks (blisks) and a method for their joining

    NASA Astrophysics Data System (ADS)

    Povarova, K. B.; Valitov, V. A.; Obsepyan, S. V.; Drozdov, A. A.; Bazyleva, O. A.; Valitova, E. V.

    2014-09-01

    The choice of materials for the bladed disks (blisks) that are intended for next-generation aviation gas turbine engines is grounded. As blade materials, single crystals of light heterophase γ' + γ VKNA-type alloys based on the γ'(Ni3Al) intermetallic compound with an ordered structure are proposed. The choice of novel deformable EP975-type nickel superalloys, which are intended for operation at 800-850°C, as the disk material is grounded. It is shown that the most effective method for forming one-piece joints of an Ni3Al-based alloy and a high-alloy EP975-type nickel superalloy is the new process of solid-phase pressure welding under conditions of high-temperature superplasticity. Solid-phase joints are formed for heterophase Ni3Al-based alloy single crystals and deformable EK61 and EP975 nickel alloys. The gradient structures in the zone of the solid-phase joints that form under the conditions of low- and high-temperature superplasticity at homologous temperatures of ˜0.6 T m and 0.9 T m are studied. The character and direction of the diffusion processes at the joint of an intermetallic alloy single crystal and a deformable polycrystalline alloy are determined.

  7. Tensile and creep properties of diffusion bonded titanium alloy IMI 834 to gamma titanium aluminide IHI alloy 01A

    SciTech Connect

    Holmquist, M.; Recina, V.; Pettersson, B.

    1999-04-23

    Diffusion bonding of the Ti-alloy Ti-5.8Al-4.0Sn-3.5Zr-0.7Nb-0.5Mo-0.35Se-0.06C (wt%) to the intermetallic {gamma}-based alloy Ti-33Al-2Fe-1.8V-0.1B (wt%) using hot isostatic pressing at 900 C, 200 MPa held for 1 h was studied. Sound joints without any pores or cracks with a width of approximately 5--7 {micro}m could be produced. Tensile testing showed that the strengths of the joints are similar to the strength of the {gamma}-TiAl base material at temperatures between room temperature and 600 C. The fracture occurs either at the joint or in the {gamma}-TiAl material. The fracture initiation process is a competition between initiation in the {gamma}-TiAl base material and initiation at the {gamma}-TiAl/diffusion bond interface. Creep testing showed that most of the creep elongation occurs in the Ti-alloy, but failure is initiated in the joint bond line. Creep causes degradation and pore formation in this line. Interlinkage of these pores creates a crack which grows slowly until the fracture toughness of the {gamma}-TiAl is exceeded and the crack starts to propagate in the {gamma}-TiAl material and terminates creep life.

  8. Reduction in Defect Content in ODS Alloys

    SciTech Connect

    Jones, A.R.; Ritherdon, J.; Prior, D.J.

    2003-04-22

    In order to develop FeCrAl-based ODS alloy tubing with the coarse, high aspect ratio, appropriately oriented grain structures likely to deliver enhanced high temperature (11000C) hoop creep strength compared to conventionally formed ODS alloy tubing, flow forming techniques were explored in a European funded programme. The evolution of microstructure in PM2000 alloy tubing formed by warm flow forming techniques has been the subject of continuing investigation and more detailed study in the current work. The warm flow formed tubes investigated were produced by reverse flow forming using three, 1200 opposed rollers described around a tube preform supported on a driven mandrel. This produced a complex pattern of shape changing deformation, driven from the outer surface of the tube preforms. The grain size and shape together with the pattern of nucleation and growth of secondary recrystallization that developed through the thickness of the tube wall during the subsequent high temperature annealing (13800C) of these warm flow formed samples is described, as are the textures that formed. The unusual pattern and shape of secondary recrystallized grain structures that formed on the outer surfaces of the flow formed tubes closely follows the pattern and pitch of the flow forming rollers. The local texture, grain shape and pattern of misorientation in the surface of warm flow formed tubes that was associated with the development of these outer surface microstructures are described. Parallel studies have continued on the influence of microstructural inhomogeneities on the development of secondary recrystallized grain structures in ODS alloys. As part of this work, a separate variant of PM2000 alloy with additions of 1 wt.% ODS-free Fe powder have been manufactured as extruded bar by Plansee GmbH. The initial recrystallization behavior of the variant has been studied and cross-compared with the recrystallization behavior found in a prototype ODS-Fe3Al alloy, notably where the

  9. Hydrogen release reactions of Al-based complex hydrides enhanced by vibrational dynamics and valences of metal cations

    SciTech Connect

    Sato, T.; Ramirez-Cuesta, Anibal J.; Daemen, Luke L.; Cheng, Yong -Qiang; Tomiyasu, Keisuke; Takagi, Shigeyuki; Orimo, Shin-ichi

    2016-08-31

    Hydrogen release from Al-based complex hydrides composed of metal cation(s) and [AlH4] was investigated using inelastic neutron scattering viewed from vibrational dynamics. Here, the hydrogen release followed the softening of translational and [AlH4] librational modes, which was enhanced by vibrational dynamics and the valence(s) of the metal cation(s).

  10. AL-Base: a visual platform analysis tool for the study of amyloidogenic immunoglobulin light chain sequences

    PubMed Central

    Bodi, Kip; Prokaeva, Tatiana; Spencer, Brian; Eberhard, Maurya; Connors, Lawreen H.; Seldin, David C.

    2014-01-01

    AL-Base, a curated database of human immunoglobulin (Ig) light chain (LC) sequences derived from patients with AL amyloidosis and controls, is described, along with a collection of analytical and graphic tools designed to facilitate their analysis. AL-Base is designed to compile and analyse amyloidogenic Ig LC sequences and to compare their predicted protein sequence and structure to non-amyloidogenic LC sequences. Currently, the database contains over 3000 de-identified LC nucleotide and amino acid sequences, of which 433 encode monoclonal proteins that were reported to form fibrillar deposits in AL patients. Each sequence is categorised according to germline gene usage, clinical status and sample source. Currently, tools are available to search for sequences by various criteria, to analyse the biochemical properties of the predicted amino acids at each position and to display the results in a graphical fashion. The likelihood that each sequence has evolved through somatic hypermutation can be predicted using an automated binomial or multinomial distribution model. AL-Base is available to the scientific community for research purposes. PMID:19291508

  11. New developments on optimizing properties of high-Zn aluminium cast alloys

    NASA Astrophysics Data System (ADS)

    Krajewski, W. K.; Buras, J.; Krajewski, P. K.; Greer, A. L.; Schumacher, P.; Haberl, K.

    2016-07-01

    Foundry alloys with Al-based matrices have a wide range of uses in today's global economy and there is a high demand for castings of Al alloys, including Al-Zn alloys. In this paper, investigations on the grain refinement of high-Zn aluminium cast alloys are presented. Aluminium alloys with relatively high zinc content have a tendency to be coarse-grained, especially in the case of castings with low cooling rates such as are found in sand moulds. The coarse-grained structure degrades the plasticity, specifically the elongation. Therefore, for aluminium alloys of high (10-30 wt.%) zinc content, inoculation is attractive, aiming to break up the primary dendrites of the a-phase solid solution of zinc in aluminium. Such dendrites are the principal microstructural component in these alloys. On the other hand, a finer grain structure usually reduces the damping (e.g. as measured by attenuation of ultrasound) in these alloys. In the present investigations, a binary sand-cast Al-20 wt.% Zn alloy was inoculated with different additions of AlTi3C0.15 (TiCAl) and ZnTi-based master alloys. The sand-cast samples were subjected to mechanical-property measurements (tensile strength and elongation), image analysis to determine grain size, and measurements of the attenuation of 1 MHz ultrasound. It is found that both of the master alloys used cause significant refinement of the a-AlZn primary dendrites and change their morphology from linear-branched to semi-globular, increase the elongation by about 40%, and decrease the attenuation coefficient by about 25% in comparison with the initial alloy without inoculation.

  12. Development of Compositionally Graded Metallic Glass Alloys with Desirable Properties

    DTIC Science & Technology

    2016-06-01

    band towards apparent brittle fracture .24,28,29,30 However, despite their general reputation as brittle materials compared to work-hardenable...engineering alloys, intrinsically “tough” Pd-based and Zr-Cu-Al-based BMGs with surprisingly high resistance to fracture have recently been discov- ered...related to a high Poisson’s ratio (ν) or equivalently, a low ratio of shear modulus to bulk modulus (μ/B).33,34 By plotting the fracture energy versus ν

  13. SUPERCONDUCTING VANADIUM BASE ALLOY

    DOEpatents

    Cleary, H.J.

    1958-10-21

    A new vanadium-base alloy which possesses remarkable superconducting properties is presented. The alloy consists of approximately one atomic percent of palladium, the balance being vanadium. The alloy is stated to be useful in a cryotron in digital computer circuits.

  14. Weldability of intermetallic alloys

    SciTech Connect

    David, S.A. )

    1990-01-01

    Ordered intermetallic alloys are a unique class of material that have potential for structural applications at elevated temperatures. The paper describes the welding and weldability of these alloys. The alloys studied were nickel aluminide (Ni[sub 3]Al), titanium aluminide (Ti[sub 3]Al), and iron aluminide.

  15. DELTA PHASE PLUTONIUM ALLOYS

    DOEpatents

    Cramer, E.M.; Ellinger, F.H.; Land. C.C.

    1960-03-22

    Delta-phase plutonium alloys were developed suitable for use as reactor fuels. The alloys consist of from 1 to 4 at.% zinc and the balance plutonium. The alloys have good neutronic, corrosion, and fabrication characteristics snd possess good dimensional characteristics throughout an operating temperature range from 300 to 490 deg C.

  16. PLUTONIUM-THORIUM ALLOYS

    DOEpatents

    Schonfeld, F.W.

    1959-09-15

    New plutonium-base binary alloys useful as liquid reactor fuel are described. The alloys consist of 50 to 98 at.% thorium with the remainder plutonium. The stated advantages of these alloys over unalloyed plutonium for reactor fuel use are easy fabrication, phase stability, and the accompanying advantuge of providing a means for converting Th/sup 232/ into U/sup 233/.

  17. Separation in Binary Alloys

    NASA Technical Reports Server (NTRS)

    Frazier, D. O.; Facemire, B. R.; Kaukler, W. F.; Witherow, W. K.; Fanning, U.

    1986-01-01

    Studies of monotectic alloys and alloy analogs reviewed. Report surveys research on liquid/liquid and solid/liquid separation in binary monotectic alloys. Emphasizes separation processes in low gravity, such as in outer space or in free fall in drop towers. Advances in methods of controlling separation in experiments highlighted.

  18. Correlating Hardness Retention and Phase Transformations of Al and Mg Cast Alloys for Aerospace Applications

    NASA Astrophysics Data System (ADS)

    Kasprzak, W.; Czerwinski, F.; Niewczas, M.; Chen, D. L.

    2015-03-01

    The methodology based on correlating hardness and phase transformations was developed and applied to determine the maximum temperature of hardness retention of selected Al-based and Mg-based alloys for aerospace applications. The Al alloys: A356, F357, and C355 experienced 34-66% reduction of the initial hardness, in comparison to 4-22% hardness reduction observed in Mg alloys: QE22A, EV31A, ZE41A, and WE43B after the same annealing to 450 °C. For Al alloys the hardness reduction showed a steep transition between 220 and 238 °C. In contrast, Mg alloys showed a gradual hardness decrease occurring at somewhat higher temperatures between 238 and 250 °C. The hardness data were correlated with corresponding phase transformation kinetics examined by dilatometer and electrical resistivity measurements. Although Mg alloys preserved hardness to higher temperatures, their room temperature tensile strength and hardness were lower than Al alloys. The experimental methodology used in the present studies appears to be very useful in evaluating the softening temperature of commercial Al- and Mg-based alloys, permitting to assess their suitability for high-temperature applications.

  19. Influence of homogenization and artificial aging heat treatments on corrosion behavior of Mg-Al alloys

    SciTech Connect

    Beldjoudi, T.; Fiaud, C.; Robbiola, L. . Lab. d'Etudes de la Corrosion)

    1993-09-01

    The influence of heat treatment on corrosion behavior of magnesium-aluminum (Mg-9Al) alloys was investigated by studying the electrochemical properties of Mg-9Al in the solution-treated (T4) and artificially aged (T6) conditions. The alloys' properties were compared to those of pure Mg, the intermetallic Mg[sub 17]Al[sub 12] phase, and different Mg-Al-based alloys (Mg-3Al, AZ91). The Mg-9Al alloy exhibited better corrosion resistance in the T6 condition than in the T4 condition because of the intermetallic Mg[sub 17]Al[sub 12] precipitates present n the T6 alloy. The mechanism responsible for this behavior was attributed to a more protective porous film on the T6 matrix alloy than on the T4 alloy. Addition of zinc did not modify these results. Localized corrosion testing showed the Mg-Al alloys were attacked preferentially in relation to magnesium silicide (Mg[sub 2]Si) precipitates which were characterized clearly using metallurgical examinations.

  20. An overview of the structural capability of available gamma titanium aluminide alloys

    SciTech Connect

    Larsen, J.M.; Worth, B.D.; Balsone, S.J.; Jones, J.W.

    1995-12-31

    TiAl-base, gamma titanium aluminide alloys exhibit high temperature mechanical properties that make them attractive candidates for a variety of applications in advanced turbine engines. This paper presents an overview of the capability of available gamma titanium aluminide alloys in both cast and wrought forms. Emphasis is given to cyclic properties that will govern component life under anticipated usage in gas turbine engines. The roles of fatigue crack initiation and growth are examined, and approaches for life prediction are discussed. An attempt is made to assess the strengths and limitations of these materials with respect to application requirements.

  1. Characterization of novel microstructures in Al-Fe-V-Si and Al-Fe-V-Si-Y alloys processed at intermediate cooling rates

    NASA Astrophysics Data System (ADS)

    Marshall, Ryan

    Samples of an Al-Fe-V-Si alloy with and without small Y additions were prepared by copper wedge-mold casting. Analysis of the microstructures developed at intermediate cooling rates revealed the formation of an atypical morphology of the cubic alpha-Al12(Fe/V)3Si phase (Im 3 space group with a = 1.26 nm) in the form of a microeutectic with alpha-Al that forms in relatively thick sections. This structure was determined to exhibit promising hardness and thermal stability when compared to the commercial rapidly solidified and processed Al-Fe-V-Si (RS8009) alloy. In addition, convergent beam electron diffraction (CBED) and selected area electron diffraction (SAD) were used to characterize a competing intermetallic phase, namely, a hexagonal phase identified as h-AlFeSi (P6/mmm space group with a = 2.45 nm c = 1.25 nm) with evidence of a structural relationship to the icosahedral quasicrystalline (QC) phase (it is a QC approximant) and a further relationship to the more desirable alpha-Al12(Fe/V) 3Si phase, which is also a QC approximant. The analysis confirmed the findings of earlier studies in this system, which suggested the same structural relationships using different methods. As will be shown, both phases form across a range of cooling rates and appear to have good thermal stabilities. Additions of Y to the alloy were also studied and found to cause the formation of primary YV2Al20 particles on the order of 1 microm in diameter distributed throughout the microstructure, which otherwise appeared essentially identical to that of the Y-free 8009 alloy. The implications of these results on the possible development of these structures will be discussed in some detail.

  2. Mechanical properties and dual atmosphere tolerance of Ag-Al based braze

    SciTech Connect

    Kim, Jin Yong; Choi, Jung-Pyung; Weil, K. Scott

    2008-03-14

    Reactive air brazing (RAB) based on the silver-copper oxide system was recently developed for use in sealing high-temperature electrochemical devices such as solid oxide fuel cells. One of the concerns regarding the viability of this joining technique is the long-term stability of silver-based alloys under a high-temperature, dual oxidizing/reducing gas environment. One possible solution to improve the dual atmosphere tolerance of the silver-based system is the addition of elements which can preferentially react with oxygen over hydrogen and minimize the pore formation caused by the reaction of oxygen with hydrogen in the silver matrix. In this paper, the effects of aluminum addition into silver-based air braze filler materials on microstructure, mechanical properties, and high temperature dual atmosphere tolerance were investigated using foils and pastes of aluminum-added braze filler materials. Joints brazed with binary Ag-Al braze foils containing more than 2 at% of Al retained a metallic form of aluminum in the metallic braze filler matrix after brazing at 1000°C in air. The flexural strength of joints prepared with binary Ag-Al braze foils decreased with increase in Al content due to the formation of interfacial aluminum oxide. The existence of metallic aluminum in the braze filler matrix, however, enhanced the high temperature dual atmosphere tolerance of the silver-based braze filler, showing smaller size of porosity after dual reducing/oxidizing atmosphere tests at 800°C for 1000 hrs. The Binary and ternary braze pastes based on the Ag-Al(-Cu) system were also tried as a sealant. Alumina joints brazed with these pastes showed increase in flexural strength with Cu content. However, a braze filler containing 5 at% Al and 8 at% Cu possessed nearly no metallic aluminum in the braze filler matrix after brazing, while the as-brazed sample prepared using a binary braze filler with 5 at% Al kept some metallic Al in the braze matrix. Thus, the addition of copper

  3. Rhenium alloying of tungsten heavy alloys

    SciTech Connect

    German, R.M.; Bose, A.; Jerman, G.

    1989-01-01

    Alloying experiments were performed using rhenium additions to a classic 90 mass % tungsten heavy alloy. The mixed-powder system was liquid phase sintered to full density at 1500 C in 60 min The rhenium-modified alloys exhibited a smaller grain size, higher hardness, higher strength, and lower ductility than the unalloyed system. For an alloy with a composition of 84W-6Re-8Ni-2Fe, the sintered density was 17, 4 Mg/m{sup 3} with a yield strength of 815 MPa, tensile strength of 1180 MPa, and elongation to failure of 13%. This property combination results from the aggregate effects of grain size reduction and solid solution hardening due to rhenium. In the unalloyed system these properties require post-sintering swaging and aging; thus, alloying with rhenium is most attractive for applications where net shaping is desired, such as by powder injection molding.

  4. Materials for Advanced Turbine Engines (MATE): Project 3: Design, fabrication and evaluation of an oxide dispersion strengthened sheet alloy combustor liner, volume 1

    NASA Technical Reports Server (NTRS)

    Henricks, R. J.; Sheffler, K. D.

    1984-01-01

    The suitability of wrought oxide dispersion strengthened (ODS) superalloy sheet for gas turbine engine combustor applications was evaluated. Incoloy MA 956 (FeCrAl base) and Haynes Developmental Alloy (HDA) 8077 (NiCrAl base) were evaluated. Preliminary tests showed both alloys to be potentially viable combustor materials, with neither alloy exhibiting a significant advantage over the other. Both alloys demonstrated a +167C (300 F) advantage of creep and oxidation resistance with no improvement in thermal fatigue capability compared to a current generation combustor alloy (Hastelloy X). MA956 alloy was selected for further demonstration because it exhibited better manufacturing reproducibility than HDA8077. Additional property tests were conducted on MA956. To accommodate the limited thermal fatigue capability of ODS alloys, two segmented, mechanically attached, low strain ODS combustor design concepts having predicted fatigue lives or = 10,000 engine cycles were identified. One of these was a relatively conventional louvered geometry, while the other involved a transpiration cooled configuration. A series of 10,000 cycle combustor rig tests on subscale MA956 and Hastelloy X combustor components showed no cracking, thereby confirming the beneficial effect of the segmented design on thermal fatigue capability. These tests also confirmed the superior oxidation and thermal distortion resistance of the ODS alloy. A hybrid PW2037 inner burner liner containing MA956 and Hastelloy X components was designed and constructed.

  5. Processing and alloying of tungsten heavy alloys

    SciTech Connect

    Bose, A.; Dowding, R.J.

    1993-12-31

    Tungsten heavy alloys are two-phase metal matrix composites with a unique combination of density, strength, and ductility. They are processed by liquid-phase sintering of mixed elemental powders. The final microstructure consists of a contiguous network of nearly pure tungsten grains embedded in a matrix of a ductile W-Ni-Fe alloy. Due to the unique property combination of the material, they are used extensively as kinetic energy penetrators, radiation shields. counterbalances, and a number of other applications in the defense industry. The properties of these alloys are extremely sensitive to the processing conditions. Porosity levels as low as 1% can drastically degrade the properties of these alloys. During processing, care must be taken to reduce or prevent incomplete densification, hydrogen embrittlement, impurity segregation to the grain boundaries, solidification shrinkage induced porosity, and in situ formation of pores due to the sintering atmosphere. This paper will discuss some of the key processing issues for obtaining tungsten heavy alloys with good properties. High strength tungsten heavy alloys are usually fabricated by swaging and aging the conventional as-sintered material. The influence of this on the shear localization tendency of a W-Ni-Co alloy will also be demonstrated. Recent developments have shown that the addition of certain refractory metals partially replacing tungsten can significantly improve the strength of the conventional heavy alloys. This development becomes significant due to the recent interest in near net shaping techniques such as powder injection moldings. The role of suitable alloying additions to the classic W-Ni-Fe based heavy alloys and their processing techniques will also be discussed in this paper.

  6. Tailoring microstructure of Mg–Zn–Y alloys with quasicrystal and related phases for high mechanical strength

    PubMed Central

    Singh, Alok

    2014-01-01

    The occurrence of a stable icosahedral (i-) phase, which is quasicrystalline with an icosahedral (fivefold) symmetry, on the equilibrium phase diagram of Mg–Zn–RE (RE = Y, Gd, Tb, Dy, Ho or Er) alloys opened up an interesting possibility of developing a new series of magnesium alloys for structural applications. Alloys based on the i-phase have been studied for the past 14 years. Ultra-high strengths combined with good ductility have been shown. Here we show two strategies for tailoring microstructures for very high strengths in Mg–Zn–Y alloys. One of them involves strengthening by a fine distribution of rod-like precipitates, where the matrix grain size is not critical. The alloy is solutionized at a high temperature of 480 °C to dissolve a large part of the i-phase, followed by a high temperature extrusion (∼430 °C) and a low temperature ageing to reprecipitate phases with fine size distribution. At first, phase transformations involved in this procedure are described. The closeness of the structure of the precipitates to the i-phase is brought out. By this procedure, tensile yield strengths of over 370 MPa are obtained in grain sizes of 20 μm. In another strategy, the alloys are chill cast and then extruded at low temperatures of about 250 °C. Ultra-fine grains are produced by enhanced recrystallization due to presence of the i-phase. At the same time nano-sized precipitates are precipitated dynamically during extrusion from the supersaturated matrix. Ultra-high tensile strengths of up to 400 MPa are obtained in combination with ductility of 12 to 16%. Analysis of the microstructure shows that strengthening by the i-phase occurs by enhanced recrystallization during extrusion. It produces ultra-fine grain sizes to give very high strengths, and moderate texture for good ductility. Fine distribution of the i-phase and precipitates contribute to strengthening and provide microstructre stability. Ultra-high strength over a very wide range of grain sizes

  7. Tailoring microstructure of Mg-Zn-Y alloys with quasicrystal and related phases for high mechanical strength.

    PubMed

    Singh, Alok

    2014-08-01

    The occurrence of a stable icosahedral (i-) phase, which is quasicrystalline with an icosahedral (fivefold) symmetry, on the equilibrium phase diagram of Mg-Zn-RE (RE = Y, Gd, Tb, Dy, Ho or Er) alloys opened up an interesting possibility of developing a new series of magnesium alloys for structural applications. Alloys based on the i-phase have been studied for the past 14 years. Ultra-high strengths combined with good ductility have been shown. Here we show two strategies for tailoring microstructures for very high strengths in Mg-Zn-Y alloys. One of them involves strengthening by a fine distribution of rod-like [Formula: see text] precipitates, where the matrix grain size is not critical. The alloy is solutionized at a high temperature of 480 °C to dissolve a large part of the i-phase, followed by a high temperature extrusion (∼430 °C) and a low temperature ageing to reprecipitate phases with fine size distribution. At first, phase transformations involved in this procedure are described. The closeness of the structure of the [Formula: see text] precipitates to the i-phase is brought out. By this procedure, tensile yield strengths of over 370 MPa are obtained in grain sizes of 20 μm. In another strategy, the alloys are chill cast and then extruded at low temperatures of about 250 °C. Ultra-fine grains are produced by enhanced recrystallization due to presence of the i-phase. At the same time nano-sized precipitates are precipitated dynamically during extrusion from the supersaturated matrix. Ultra-high tensile strengths of up to 400 MPa are obtained in combination with ductility of 12 to 16%. Analysis of the microstructure shows that strengthening by the i-phase occurs by enhanced recrystallization during extrusion. It produces ultra-fine grain sizes to give very high strengths, and moderate texture for good ductility. Fine distribution of the i-phase and precipitates contribute to strengthening and provide microstructre stability. Ultra-high strength over

  8. Extrusion of aluminium alloys

    SciTech Connect

    Sheppard, T.

    1999-01-01

    In recent years the importance of extruded alloys has increased due to the decline in copper extrusion, increased use in structural applications, environmental impact and reduced energy consumption. There have also been huge technical advances. This text provides comprehensive coverage of the metallurgical, mathematical and practical features of the process. The contents include: continuum principles; metallurgical features affecting the extrusion of Al-alloys; extrusion processing; homogenization and extrusion conditions for specific alloys; processing of 6XXX alloys; plant utilization; Appendix A: specification of AA alloys and DIN equivalents; Appendix B: chemical compositions; and Appendix C: typical properties.

  9. 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.

  10. 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.

  11. Creep Resistant Zinc Alloy

    SciTech Connect

    Frank E. Goodwin

    2002-12-31

    This report covers the development of Hot Chamber Die Castable Zinc Alloys with High Creep Strengths. This project commenced in 2000, with the primary objective of developing a hot chamber zinc die-casting alloy, capable of satisfactory service at 140 C. The core objectives of the development program were to: (1) fill in missing alloy data areas and develop a more complete empirical model of the influence of alloy composition on creep strength and other selected properties, and (2) based on the results from this model, examine promising alloy composition areas, for further development and for meeting the property combination targets, with the view to designing an optimized alloy composition. The target properties identified by ILZRO for an improved creep resistant zinc die-casting alloy were identified as follows: (1) temperature capability of 1470 C; (2) creep stress of 31 MPa (4500 psi); (3) exposure time of 1000 hours; and (4) maximum creep elongation under these conditions of 1%. The project was broadly divided into three tasks: (1) Task 1--General and Modeling, covering Experimental design of a first batch of alloys, alloy preparation and characterization. (2) Task 2--Refinement and Optimization, covering Experimental design of a second batch of alloys. (3) Task 3--Creep Testing and Technology transfer, covering the finalization of testing and the transfer of technology to the Zinc industry should have at least one improved alloy result from this work.

  12. Gamma titanium aluminide alloys

    SciTech Connect

    Yamaguchi, M.; Inui, H.; Kishida, K.; Matsumuro, M.; Shirai, Y.

    1995-08-01

    Extensive progress and improvements have been made in the science and technology of gamma titanium aluminide alloys within the last decade. In particular, the understanding of their microstructural characteristics and property/microstructure relationships has been substantially deepened. Based on these achievements, various engineering two-phase gamma alloys have been developed and their mechanical and chemical properties have been assessed. Aircraft and automotive industries arc pursuing their introduction for various structural components. At the same time, recent basic studies on the mechanical properties of two-phase gamma alloys, in particular with a controlled lamellar structure have provided a considerable amount of fundamental information on the deformation and fracture mechanisms of the two-phase gamma alloys. The results of such basic studies are incorporated in the recent alloy and microstructure design of two-phase gamma alloys. In this paper, such recent advances in the research and development of the two-phase gamma alloys and industrial involvement are summarized.

  13. Weldability of High Alloys

    SciTech Connect

    Maroef, I

    2003-01-22

    The purpose of this study was to investigate the effect of silicon and iron on the weldability of HAYNES HR-160{reg_sign} alloy. HR-I60 alloy is a solid solution strengthened Ni-Co-Cr-Si alloy. The alloy is designed to resist corrosion in sulfidizing and other aggressive high temperature environments. Silicon is added ({approx}2.75%) to promote the formation of a protective oxide scale in environments with low oxygen activity. HR-160 alloy has found applications in waste incinerators, calciners, pulp and paper recovery boilers, coal gasification systems, and fluidized bed combustion systems. HR-160 alloy has been successfully used in a wide range of welded applications. However, the alloy can be susceptible to solidification cracking under conditions of severe restraint. A previous study by DuPont, et al. [1] showed that silicon promoted solidification cracking in the commercial alloy. In earlier work conducted at Haynes, and also from published work by DuPont et al., it was recognized that silicon segregates to the terminal liquid, creating low melting point liquid films on solidification grain boundaries. Solidification cracking has been encountered when using the alloy as a weld overlay on steel, and when joining HR-160 plate in a thickness greater than19 millimeters (0.75 inches) with matching filler metal. The effect of silicon on the weldability of HR-160 alloy has been well documented, but the effect of iron is not well understood. Prior experience at Haynes has indicated that iron may be detrimental to the solidification cracking resistance of the alloy. Iron does not segregate to the terminal solidification product in nickel-base alloys, as does silicon [2], but iron may have an indirect or interactive influence on weldability. A set of alloys covering a range of silicon and iron contents was prepared and characterized to better understand the welding metallurgy of HR-160 alloy.

  14. Microstructural evolution and mechanical properties of an Fe-18Ni-16Cr-4Al base alloy during aging at 950°C

    NASA Astrophysics Data System (ADS)

    Wang, Man; Sun, Yong-duo; Feng, Jing-kai; Zhang, Rui-qian; Tang, Rui; Zhou, Zhang-jian

    2016-03-01

    The development of Gen-IV nuclear systems and ultra-supercritical power plants proposes greater demands on structural materials used for key components. An Fe-18Ni-16Cr-4Al (316-base) alumina-forming austenitic steel was developed in our laboratory. Its microstructural evolution and mechanical properties during aging at 950°C were investigated subsequently. Micro-structural changes were characterized by scanning electron microscopy, electron backscatter diffraction, and transmission electron microscopy. Needle-shaped NiAl particles begin to precipitate in austenite after ageing for 10 h, whereas round NiAl particles in ferrite are coarsened during aging. Precipitates of NiAl with different shapes in different matrices result from differences in lattice misfits. The tensile plasticity increases by 32.4% after aging because of the improvement in the percentage of coincidence site lattice grain boundaries, whereas the tensile strength remains relatively high at approximately 790 MPa.

  15. Toxic effects of Al-based coagulants on Brassica chinensis and Raphanus sativus growing in acid and neutral conditions.

    PubMed

    Zhang, Kaisong; Zhou, Qixing

    2005-04-01

    The ecotoxicological effects of aluminum (Al)-based coagulants are of concern because of their wide-ranging applications in wastewater treatment and water purification. As important Al-based coagulants, AlCl(3) and PAC (polyaluminum-chloride) were selected as examples to examine the toxic effects on representative vegetables including the cabbage Brassica chinensis and the radish Raphanus sativus over a range of exposure concentrations in neutral (pH 7.00) and acidic (pH 4.00) conditions, using seed germination and root elongation in the early-growth stage as indicators of toxicity. The results showed that root elongation of the two vegetables was a more sensitive indicator than was seed germination for evaluating the toxicity of Al. As a single influencing factor, H(+) had no significant direct effects on root elongation of Brassica chinensis and Raphanus sativus under the experimental conditions. The toxicity of Al played the main role in inhibiting root elongation and seed germination and was strongly related to changes in pH. There was a markedly positive relationship between the inhibitory rate of root elongation, seed germination, and the concentration of Al at pH 4.00 (p < 0.01). The toxic effect of AlCl(3) on Brassica chinensis was less with a neutral pH than at pH 4.00, but Raphanus sativus was more susceptible to AlCl(3) toxicity at a neutral pH than at pH 4.00. Both Raphanus sativus and Brassica chinensis had a more toxic response to a low concentration (<64 mg . L(-1)) of PAC in a neutral condition than in an acidic condition. Undoubtedly, the Al toxicity caused by Al-based coagulants at a neutral pH is relevant when treatment solids are used in agriculture.

  16. Alloy 10: A 1300F Disk Alloy

    NASA Technical Reports Server (NTRS)

    Gayda, John

    2000-01-01

    Gas turbine engines for future subsonic transports will probably have higher pressure ratios which will require nickel-base superalloy disks with 13000 to 1400 F temperature capability. Several advanced disk alloys are being developed to fill this need. One of these, Allied Signal's Alloy 10, is a promising candidate for gas turbine engines to be used on smaller, regional aircraft. For this application, compressor/turbine disks must withstand temperatures of 1300 F for several hundred hours over the life of the engine. In this paper, three key properties of Alloy 10--tensile, 0.2% creep, and fatigue crack growth--will be assessed at 1300 F.

  17. 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.

  18. Corrosion performance of Fe-Cr-Al and Fe aluminide alloys in complex gas environments

    SciTech Connect

    Natesan, K.; Johnson, R.N.

    1995-05-01

    Alumina-forming structural alloys can offer superior resistance to corrosion in the presence of sulfur-containing environments, which are prevalent in coal-fired fossil energy systems. Further, Fe aluminides are being developed for use as structural materials and/or cladding alloys in these systems. Extensive development has been in progress on Fe{sub 3}Al-based alloys to improve their engineering ductility. In addition, surface coatings of Fe aluminide are being developed to impart corrosion resistance to structural alloys. This paper describes results from an ongoing program that is evaluating the corrosion performance of alumina-forming structural alloys, Fe-Al and Fe aluminide bulk alloys, and Fe aluminide coatings in environments typical of coal-gasification and combustion atmospheres. Experiments were conducted at 650-1000{degrees}C in simulated oxygen/sulfur gas mixtures. Other aspects of the program are corrosion evaluation of the aluminides in the presence of HCl-containing gases. Results are used to establish threshold Al levels in the alloys for development of protective alumina scales and to determine the modes of corrosion degradation that occur in the materials when they are exposed to S/Cl-containing gaseous environments.

  19. Enhanced WWTP effluent organic matter removal in hybrid ozonation-coagulation (HOC) process catalyzed by Al-based coagulant.

    PubMed

    Jin, Xin; Jin, Pengkang; Hou, Rui; Yang, Lei; Wang, Xiaochang C

    2017-04-05

    A novel hybrid ozonation-coagulation (HOC) process was developed for application in wastewater reclamation. In this process, ozonation and coagulation occurred simultaneously within a single unit. Compared with the conventional pre-ozonation-coagulation process, the HOC process exhibited much better performance in removing dissolved organic matters. In particular, the maximal organic matters removal efficiency was obtained at the ozone dosage of 1mgO3/mg DOC at each pH value (pH 5, 7 and 9). In order to interpret the mechanism of the HOC process, ozone decomposition was monitored. The results indicated that ozone decomposed much faster in the HOC process. Moreover, by using the reagent of O3-resistant hydroxyl radical (OH) probe compound, para-chlorobenzoic acid (pCBA), and electron paramagnetic resonance (EPR) analysis, it was observed that the HOC process generated higher content of OH compared with pre-ozonation process. This indicates that the OH oxidation reaction as the key step can be catalyzed and enhanced by Al-based coagulants and their hydrolyzed products in this developed process. Thus, based on the catalytic effects of Al-based coagulants on ozonation, the HOC process provides a promising alternative to the conventional technology for wastewater reclamation in terms of higher efficiency.

  20. Surface alloying of Mg alloys after surface nanocrystallization.

    PubMed

    Zhang, Ming-Xing; Shi, Yi-Nong; Sun, Haiqing; Kelly, Patrick M

    2008-05-01

    Surface nanocrystallization using a surface mechanical attrition treatment effectively activates the surface of magnesium alloys due to the increase in grain boundary diffusion channels. As a result, the temperature of subsequent surface alloying treatment of pure Mg and AZ91 alloy can be reduced from 430 degrees C to 380 degrees C. Thus, it is possible to combine the surface alloying process with the solution treatment for this type of alloy. After surface alloying, the hardness of the alloyed layer is 3 to 4 times higher than that of the substrate and this may significantly improve the wear resistance of magnesium alloys.

  1. Catalyst Alloys Processing

    NASA Astrophysics Data System (ADS)

    Tan, Xincai

    2014-10-01

    Catalysts are one of the key materials used for diamond formation at high pressures. Several such catalyst products have been developed and applied in China and around the world. The catalyst alloy most widely used in China is Ni70Mn25Co5 developed at Changsha Research Institute of Mining and Metallurgy. In this article, detailed techniques for manufacturing such a typical catalyst alloy will be reviewed. The characteristics of the alloy will be described. Detailed processing of the alloy will be presented, including remelting and casting, hot rolling, annealing, surface treatment, cold rolling, blanking, finishing, packaging, and waste treatment. An example use of the catalyst alloy will also be given. Industrial experience shows that for the catalyst alloy products, a vacuum induction remelt furnace can be used for remelting, a metal mold can be used for casting, hot and cold rolling can be used for forming, and acid pickling can be used for metal surface cleaning.

  2. Low activation ferritic alloys

    DOEpatents

    Gelles, David S.; Ghoniem, Nasr M.; Powell, Roger W.

    1986-01-01

    Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

  3. Low activation ferritic alloys

    DOEpatents

    Gelles, D.S.; Ghoniem, N.M.; Powell, R.W.

    1985-02-07

    Low activation ferritic alloys, specifically bainitic and martensitic stainless steels, are described for use in the production of structural components for nuclear fusion reactors. They are designed specifically to achieve low activation characteristics suitable for efficient waste disposal. The alloys essentially exclude molybdenum, nickel, nitrogen and niobium. Strength is achieved by substituting vanadium, tungsten, and/or tantalum in place of the usual molybdenum content in such alloys.

  4. Amorphous metal alloy

    DOEpatents

    Wang, R.; Merz, M.D.

    1980-04-09

    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.

  5. 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.

  6. NICKEL-BASE ALLOY

    DOEpatents

    Inouye, H.; Manly, W.D.; Roche, T.K.

    1960-01-19

    A nickel-base alloy was developed which is particularly useful for the containment of molten fluoride salts in reactors. The alloy is resistant to both salt corrosion and oxidation and may be used at temperatures as high as 1800 deg F. Basically, the alloy consists of 15 to 22 wt.% molybdenum, a small amount of carbon, and 6 to 8 wt.% chromium, the balance being nickel. Up to 4 wt.% of tungsten, tantalum, vanadium, or niobium may be added to strengthen the alloy.

  7. Supersaturated Aluminum Alloy Powders.

    DTIC Science & Technology

    1981-07-15

    shown in Fig. 18 . It .an be clearly seen that most of the iron is concentrated in the precipitates (Fig. 18 ), X-ray mapping immage for the chromium...At 232°C our alloys are comparable to 2� and 2618 in their tensile properties, and except for alloy #1 which at t i temperature has elongation of...demonstrate better yield strength and UTS than the 2219, 2618 and are comparable to the ALCOA alloy. They show however higher ductility than the ALCOA alloy

  8. On the preparation of TiAl alloy by direct reduction of the oxide mixtures in calcium chloride melt

    SciTech Connect

    Prabhat K. Tripathy; Derek J. Fray

    2011-11-01

    In recent years, TiAl-based intermetallic alloys are being increasingly considered for application in areas such as (i) automobile/transport sector (passenger cars, trucks and ships) (ii) aerospace industry (jet engines and High Speed Civil Transport propulsion system) and (iii) industrial gas turbines. These materials offer excellent (i) high temperature properties (at higher than 6000C) (ii) mechanical strength and (iii) resistance to corrosion and as a result have raised renewed interest. The combination of these properties make them possible replacement materials for traditional nickel-based super-alloys, which are nearly as twice as dense (than TiAl based alloys). Since the microstructures of these intermetallic alloys affect, to a significant extent, their ultimate performance, further improvements (by way of alteration/modification of these microstructures), have been the subject matter of intense research investigations. It has now been established that the presence of alloy additives, such as niobium, tantalum, manganese, boron, chromium, silicon, nickel and yttrium etc, in specific quantities, impart marked improvement to the properties, viz. fatigue strength, fracture toughness, oxidation resistance and room temperature ductility, of these alloys. From a number of possible alloy compositions, {gamma}-TiAl and Ti-Al-Nb-Cr have, of late, emerged as two promising engineering alloys/materials. . The conventional fabrication process of these alloys include steps such as melting, forging and heat treatment/annealing of the alloy compositions. However, an electrochemical process offers an attractive proposition to prepare these alloys, directly from the mixture of the respective oxides, in just one step. The experimental approach, in this new process, was, therefore, to try to electrochemically reduce the (mixed) oxide pellet to an alloy phase. The removal of oxygen, from the (mixed) oxide pellet, was effected by polarizing the oxide pellet against a graphite

  9. Final Report for Department of Energy Grant No. DE-FG02-02ER45997, "Alloy Design of Nanoscale Precipitation Strengthened Alloys: Design of a Heat Treatable Aluminum Alloy Useful to 400C"

    SciTech Connect

    Morris E. Fine; Gautam Ghosh; Dieter Isheim; Semyon Vaynman; Keith Knipling; Jefferson Z. Liu

    2006-05-06

    A creep resistant high temperature Al base alloy made by conventional processing procedures is the subject of this research. The Ni-based superalloys have volume fractions of cubic L1{sub 2} phase precipitates near 50%. This is not attainable with Al base alloys and the approach pursued in this research was to add L1{sub 2} structured precipitates to the Al-Ni eutectic alloy, 2.7 at. % Ni-97.3 at. % Al. The eutectic reaction gives platelets of Al{sub 3}Ni (DO{sub 11} structure) in an almost pure Al matrix. The Al{sub 3}Ni platelets give reinforcement strengthening while the L1{sub 2} precipitates strengthen the Al alloy matrix. Based on prior research and the extensive research reported here modified cubic L1{sub 2} Al{sub 3}Zr is a candidate. While cubic Al{sub 3}Zr is metastable, the stable phase is tetragonal, only cubic precipitates were observed after 1600 hrs at 425 C and they hardly coarsened at all with time at this temperature. Also addition of Ti retards the cubic to tetragonal transformation; however, a thermodynamically stable precipitate is desired. A very thorough ab initio computational investigation was done on the stability of L1{sub 2} phases of composition, (Al,X){sub 3}(Zr,Ti) and the possible occurrence of tie lines between a stable L1{sub 2} phase and the Al alloy terminal solid solution. Precipitation of cubic (Al{sub (1-x)}Zn{sub x}){sub 3}Zr in Al was predicted by these computations and subsequently observed by experiment (TEM). To test the combined reinforcement-precipitation concept to obtain a creep resistant Al alloy, Zr and Ti were added to the Al-Ni eutectic alloy. Cubic L1{sub 2} precipitates did form. The first and only Al-Ni-Zr-Ti alloy tested for creep gave a steady state creep rate at 375 C of 8 x 10{sup -9} under 20MPa stress. The goal is to optimize this alloy and add Zn to achieve a thermodynamically stable precipitate.

  10. Oxidation and microstructure evolution of Al-Si coated Ni3Al based single crystal superalloy with high Mo content

    NASA Astrophysics Data System (ADS)

    Tu, Xiaolu; Peng, Hui; Zheng, Lei; Qi, Wenyan; He, Jian; Guo, Hongbo; Gong, Shengkai

    2015-01-01

    A Si modified aluminide (Al-Si) coating was prepared on a Ni3Al based single crystal superalloy with high Mo content by high-activity pack cementation. Cyclic oxidation test at 1150 °C was carried out and the microstructure evolution of the coating was investigated. The results show that the oxidation resistance of the substrate was greatly increased by applying an Al-Si coating. During oxidation, outward diffusion of Mo was effectively blocked due to its high affinity with Si. Besides, a layered structure was formed as a result of the elements inter-diffusion. An obvious degradation of the Al-Si coating was observed after 100 h oxidation. Possible mechanisms related to the oxidation and elements inter-diffusion behaviours were also discussed.

  11. Copper-tantalum alloy

    DOEpatents

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

    1986-07-15

    A tantalum-copper alloy can be made by preparing a consumable electrode consisting of an elongated copper billet containing at least two spaced apart tantalum rods extending longitudinally the length of the billet. The electrode is placed in a dc arc furnace and melted under conditions which co-melt the copper and tantalum to form the alloy.

  12. Ductile transplutonium metal alloys

    SciTech Connect

    Conner, W.V.

    1983-04-19

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as sources of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  13. Neutron Absorbing Alloys

    SciTech Connect

    Mizia, Ronald E.; Shaber, Eric L.; DuPont, John N.; Robino, Charles V.; Williams, David B.

    2004-05-04

    The present invention is drawn to new classes of advanced neutron absorbing structural materials for use in spent nuclear fuel applications requiring structural strength, weldability, and long term corrosion resistance. Particularly, an austenitic stainless steel alloy containing gadolinium and less than 5% of a ferrite content is disclosed. Additionally, a nickel-based alloy containing gadolinium and greater than 50% nickel is also disclosed.

  14. Aluminum battery alloys

    DOEpatents

    Thompson, David S.; Scott, Darwin H.

    1985-01-01

    Aluminum alloys suitable for use as anode structures in electrochemical cs are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

  15. Aluminum battery alloys

    DOEpatents

    Thompson, D.S.; Scott, D.H.

    1984-09-28

    Aluminum alloys suitable for use as anode structures in electrochemical cells are disclosed. These alloys include iron levels higher than previously felt possible, due to the presence of controlled amounts of manganese, with possible additions of magnesium and controlled amounts of gallium.

  16. PLUTONIUM-CERIUM ALLOY

    DOEpatents

    Coffinberry, A.S.

    1959-01-01

    An alloy is presented for use as a reactor fuel. The binary alloy consists essentially of from about 5 to 90 atomic per cent cerium and the balance being plutonium. A complete phase diagram for the cerium--plutonium system is given.

  17. Ductile transplutonium metal alloys

    DOEpatents

    Conner, William V.

    1983-01-01

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as sources of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  18. Ductile transplutonium metal alloys

    DOEpatents

    Conner, W.V.

    1981-10-09

    Alloys of Ce with transplutonium metals such as Am, Cm, Bk and Cf have properties making them highly suitable as souces of the transplutonium element, e.g., for use in radiation detector technology or as radiation sources. The alloys are ductile, homogeneous, easy to prepare and have a fairly high density.

  19. Cesium iodide alloys

    DOEpatents

    Kim, H.E.; Moorhead, A.J.

    1992-12-15

    A transparent, strong CsI alloy is described having additions of monovalent iodides. Although the preferred iodide is AgI, RbI and CuI additions also contribute to an improved polycrystalline CsI alloy with outstanding multispectral infrared transmittance properties. 6 figs.

  20. Alloys in energy development

    SciTech Connect

    Frost, B.R.T.

    1984-02-01

    The development of new and advanced energy systems often requires the tailoring of new alloys or alloy combinations to meet the novel and often stringent requirements of those systems. Longer life at higher temperatures and stresses in aggressive environments is the most common goal. Alloy theory helps in achieving this goal by suggesting uses of multiphase systems and intermediate phases, where solid solutions were traditionally used. However, the use of materials under non-equilibrium conditions is now quite common - as with rapidly solidified metals - and the application of alloy theory must be modified accordingly. Under certain conditions, as in a reactor core, the rate of approach to equilibrium will be modified; sometimes a quasi-equilibrium is established. Thus an alloy may exhibit enhanced general diffusion at the same time as precipitate particles are being dispersed and solute atoms are being carried to vacancy sinks. We are approaching an understanding of these processes and can begin to model these complex systems.

  1. Ultrahigh temperature intermetallic alloys

    SciTech Connect

    Brady, M.P.; Zhu, J.H.; Liu, C.T.; Tortorelli, P.F.; Wright, J.L.; Carmichael, C.A.; Walker, L.R.

    1997-12-01

    A new family of Cr-Cr{sub 2}X based alloys with fabricability, mechanical properties, and oxidation resistance superior to previously developed Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr based alloys has been identified. The new alloys can be arc-melted/cast without cracking, and exhibit excellent room temperature and high-temperature tensile strengths. Preliminary evaluation of oxidation behavior at 1100 C in air indicates that the new Cr-Cr{sub 2}X based alloys form an adherent chromia-based scale. Under similar conditions, Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr based alloys suffer from extensive scale spallation.

  2. Theoretics-directed effect of copper or aluminum content on the ductility characteristics of Al-based (Al3Ti, AlTi, AlCu, AlTiCu2) intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Li, Yong; Ma, Xiao-Juan; Liu, Qi-Jun; Kong, Ge-Xing; Ma, Hai-Xia; Wang, Wen-Peng; Wang, Yi-Gao; Jiao, Zhen; Liu, Fu-Sheng; Liu, Zheng-Tang

    2016-11-01

    First-principle simulations have been applied to investigate the effect of copper (Cu) or aluminum (Al) content on the ductility of Al3Ti, AlTi, AlCu, and AlTiCu2 alloys. The mechanical stable and elastic properties of Al-based intermetallic compounds are researched by density functional theory with the generalized gradient approximation (DFT-GGA). The calculated lattice constants are in conformity with the previous experimental and theoretical data. The deduced elastic constants show that the investigated Al3Ti, AlTi, AlCu, and AlTiCu2 structures are mechanically stable. Shear modulus, Young’s modulus, Poisson’s ratio, and the ratio B/G have also been figured out by using reckoned elastic constants. A further analysis of Young’s modulus and Poisson’s ratio reveals that the third added element copper content has significant effects on the Al-Ti-based ICs ductile character. Project supported by the National Natural Science Foundation of China (Grant Nos. 41674088, 11574254, 11272296, and 11547311), the National Basic Research Program of China (Grant No. 2011CB808201), the Fundamental Research Fund for the Central Universities, China (Grant Nos. 2682014ZT30 and 2682014ZT31), and the Fund of the State Key Laboratory of Solidification Processing in Northwestern Polytechnical University, China (Grant No. SKLSP201511).

  3. The free growth criterion for grain initiation in TiB 2 inoculated γ-titanium aluminide based alloys

    NASA Astrophysics Data System (ADS)

    Gosslar, D.; Günther, R.

    2014-02-01

    γ-titanium aluminide (γ-TiAl) based alloys enable for the design of light-weight and high-temperature resistant engine components. This work centers on a numerical study of the condition for grain initiation during solidification of TiB2 inoculated γ-TiAl based alloys. Grain initiation is treated according to the so-called free growth criterion. This means that the free growth barrier for grain initiation is determined by the maximum interfacial mean curvature between a nucleus and the melt. The strategy presented in this paper relies on iteratively increasing the volume of a nucleus, which partially wets a hexagonal TiB2 crystal, minimizing the interfacial energy and calculating the corresponding interfacial curvature. The hereby obtained maximum curvature yields a scaling relation between the size of TiB2 crystals and the free growth barrier. Comparison to a prototypical TiB2 crystal in an as cast γ-TiAl based alloy allowed then to predict the free growth barrier prevailing under experimental conditions. The validity of the free growth criterion is discussed by an interfacial energy criterion.

  4. Three orthogonal ultrasounds fabricate uniform ternary Al-Sn-Cu immiscible alloy

    PubMed Central

    Zhai, W.; Wang, B. J.; Liu, H. M.; Hu, L.; Wei, B.

    2016-01-01

    The production of Al based monotectic alloys with uniform microstructure is usually difficult due to the large density difference between the two immiscible liquid phases, which limits the application of such alloys. Here, we apply three orthogonal ultrasounds during the liquid phase separation process of ternary Al71.9Sn20.4Cu7.7 immiscible alloy. A uniform microstructure consisting of fine secondary (Sn) phase dispersed on Al-rich matrix is fabricated in the whole alloy sample with a large size of 30 × 30 × 100 mm. The numerical calculation results indicate that the coupled effect of three ultrasounds promotes the sound pressure level and consequently enlarges the cavitation zone within the alloy melt. The strong shockwaves produced by cavitation prevent the (Sn) droplets from coalescence, and keep them suspended in the parent Al-rich liquid phase. This accounts for the formation of homogeneous composite structures. Thus the introduction of three orthogonal ultrasounds is an effective way to suppress the macrosegregation caused by liquid phase separation and produce bulk immiscible alloys with uniform structures. PMID:27841283

  5. Three orthogonal ultrasounds fabricate uniform ternary Al-Sn-Cu immiscible alloy

    NASA Astrophysics Data System (ADS)

    Zhai, W.; Wang, B. J.; Liu, H. M.; Hu, L.; Wei, B.

    2016-11-01

    The production of Al based monotectic alloys with uniform microstructure is usually difficult due to the large density difference between the two immiscible liquid phases, which limits the application of such alloys. Here, we apply three orthogonal ultrasounds during the liquid phase separation process of ternary Al71.9Sn20.4Cu7.7 immiscible alloy. A uniform microstructure consisting of fine secondary (Sn) phase dispersed on Al-rich matrix is fabricated in the whole alloy sample with a large size of 30 × 30 × 100 mm. The numerical calculation results indicate that the coupled effect of three ultrasounds promotes the sound pressure level and consequently enlarges the cavitation zone within the alloy melt. The strong shockwaves produced by cavitation prevent the (Sn) droplets from coalescence, and keep them suspended in the parent Al-rich liquid phase. This accounts for the formation of homogeneous composite structures. Thus the introduction of three orthogonal ultrasounds is an effective way to suppress the macrosegregation caused by liquid phase separation and produce bulk immiscible alloys with uniform structures.

  6. Study of the feasibility of producing Al-Ni intermetallic compounds by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Mohammed, Kahtan S.; Naeem, Haider T.; Iskak, Siti Nadira

    2016-08-01

    Mechanical alloying (MA) was employed to synthesize Al-Zn-Mg-Cu alloys of high weight percentage of the nickel component from the elemental powders of constituents via high-energy ball milling. The mixed powders underwent 15 h of milling time at 350 rpm speed and 10: 1 balls/powder weight ratio. The samples were cold-compacted and sintered thereafter. The sintered compacts underwent homogenization treatments at various temperatures conditions and were aged at 120°C for 24 h (T6). The milled powders and heat-treated Al alloy products were characterized via X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The crystallite sizes and microstrains of the alloyed powder were estimated via measuring the broadening of XRD peaks using the Williamson-Hall equation. The results have revealed that optimum MA time of 15 h has led to the formation of Al-based solid solutions of Zn, Mg, Cu, and Ni. The outcomes showed that the Vickers hardness of the sintered Al-Zn-Mg-Cu compacts of Ni alloys was enhanced following aging at T6 tempering treatments. Higher compression strength of Al-alloys with the addition of 15% nickel was obtained next to the aging treatment.

  7. Three orthogonal ultrasounds fabricate uniform ternary Al-Sn-Cu immiscible alloy.

    PubMed

    Zhai, W; Wang, B J; Liu, H M; Hu, L; Wei, B

    2016-11-14

    The production of Al based monotectic alloys with uniform microstructure is usually difficult due to the large density difference between the two immiscible liquid phases, which limits the application of such alloys. Here, we apply three orthogonal ultrasounds during the liquid phase separation process of ternary Al71.9Sn20.4Cu7.7 immiscible alloy. A uniform microstructure consisting of fine secondary (Sn) phase dispersed on Al-rich matrix is fabricated in the whole alloy sample with a large size of 30 × 30 × 100 mm. The numerical calculation results indicate that the coupled effect of three ultrasounds promotes the sound pressure level and consequently enlarges the cavitation zone within the alloy melt. The strong shockwaves produced by cavitation prevent the (Sn) droplets from coalescence, and keep them suspended in the parent Al-rich liquid phase. This accounts for the formation of homogeneous composite structures. Thus the introduction of three orthogonal ultrasounds is an effective way to suppress the macrosegregation caused by liquid phase separation and produce bulk immiscible alloys with uniform structures.

  8. THORIUM-SILICON-BERYLLIUM ALLOYS

    DOEpatents

    Foote, F.G.

    1959-02-10

    Th, Si, anol Bt alloys where Be and Si are each present in anmounts between 0.1 and 3.5% by weight and the total weight per cent of the minor alloying elements is between 1.5 and 4.5% are discussed. These ternary alloys show increased hardness and greater resistant to aqueous corrosion than is found in pure Th, Th-Si alloys, or Th-Be alloys.

  9. Magnesium silicide intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Li, Gh.; Gill, H. S.; Varin, R. A.

    1993-11-01

    Methods of induction melting an ultra-low-density magnesium silicide (Mg2Si) intermetallic and its alloys and the resulting microstructure and microhardness were studied. The highest quality ingots of Mg2Si alloys were obtained by triple melting in a graphite crucible coated with boron nitride to eliminate reactivity, under overpressure of high-purity argon (1.3 X 105 Pa), at a temperature close to but not exceeding 1105 °C ± 5 °C to avoid excessive evaporation of Mg. After establishing the proper induction-melting conditions, the Mg-Si binary alloys and several Mg2Si alloys macroalloyed with 1 at. pct of Al, Ni, Co, Cu, Ag, Zn, Mn, Cr, and Fe were induction melted and, after solidification, investigated by optical microscopy and quantitative X-ray energy dispersive spectroscopy (EDS). Both the Mg-rich and Si-rich eutectic in the binary alloys exhibited a small but systematic increase in the Si content as the overall composition of the binary alloy moved closer toward the Mg2Si line compound. The Vickers microhardness (VHN) of the as-solidified Mg-rich and Si-rich eutectics in the Mg-Si binary alloys decreased with increasing Mg (decreasing Si) content in the eutectic. This behavior persisted even after annealing for 75 hours at 0.89 pct of the respective eutectic temperature. The Mg-rich eutectic in the Mg2Si + Al, Ni, Co, Cu, Ag, and Zn alloys contained sections exhibiting a different optical contrast and chemical composition than the rest of the eutectic. Some particles dispersed in the Mg2Si matrix were found in the Mg2Si + Cr, Mn, and Fe alloys. The EDS results are presented and discussed and compared with the VHN data.

  10. TUNGSTEN BASE ALLOYS

    DOEpatents

    Schell, D.H.; Sheinberg, H.

    1959-12-15

    A high-density quaternary tungsten-base alloy having high mechanical strength and good machinability composed of about 2 wt.% Ni, 3 wt.% Cu, 5 wt.% Pb, and 90wt.% W is described. This alloy can be formed by the powder metallurgy technique of hot pressing in a graphite die without causing a reaction between charge and the die and without formation of a carbide case on the final compact, thereby enabling re-use of the graphite die. The alloy is formable at hot- pressing temperatures of from about 1200 to about 1350 deg C. In addition, there is little component shrinkage, thereby eliminating the necessity of subsequent extensive surface machining.

  11. Superlubricity in quasicrystalline twisted bilayer graphene

    NASA Astrophysics Data System (ADS)

    Koren, Elad; Duerig, Urs

    2016-05-01

    The unique atomic positions in quasicrystals lead to peculiar self-similarity and fractal-like structural morphology. Accordingly, many of the material properties are supposed to manifest exceptional characteristics. In this Rapid Communication, we explain through numerical simulations the fundamental and peculiar aspects of quasicrystals wearless friction manifested in a 30° twisted bilayer graphene system. In particular, the sliding force exhibits a fractal structure with distinct area correlations due to the natural mixture between both periodic and aperiodic lateral modulations. In addition, zero power scaling of the sliding force with respect to the contact area is demonstrated for a geometric sequence of dodecagonal elements.

  12. Commensurate states in quasicrystalline superconducting networks

    SciTech Connect

    Jing, X. ); Zhang, Z. , P.O. Box 8730, Beijing, China Institute of Physics, Chinese Academy of Sciences, Beijing, China)

    1989-09-01

    By using the theory of de Gennes and Alexander, the commensurate states of the fluxoid configuration on the phase boundaries of superconducting networks with the Fibonacci pattern are studied explicitly for one- and two-strip geometries. The case in which the network contains three tiles with irrational ratios of areas is also studied. Our numerical results strongly indicate that the amplitude of the wave function of a commensurate state has two-cycle self-similar behavior. The locations of the magnetic field where the commensurate states may occur in an {ital M}-strip network are also predicted.

  13. Electrical Resistivity of Ten Selected Binary Alloy Systems.

    DTIC Science & Technology

    1981-04-01

    alloys --* Aluminum Alloys --*Copper alloys --*Gold alloys --*Nickel Alloys --*Silver alloys --*Iron alloys --*Palladium alloys ... aluminum -magnesium, and copper-zinc) are given for 27 compositions: 0 (pure element).* For aluminum -copper, aluninu.-eagnes tur, end copper-zinc alloy ...available data and infor- mation. The ten binary alloy systems selected are the systems of aluminum - copper, aluminum -magnesium, copper-gold,

  14. Microstructure/property relationships in titanium aluminides and alloys; Proceedings of the Symposium, Fall Meeting of the Minerals, Metals, and Materials Society, Detroit, MI, Oct. 7-11, 1990

    SciTech Connect

    Kim, Young-Won; Boyer, R.R. Boeing Commercial Airplane Group, Seattle, WA )

    1991-01-01

    The present symposium on microstructure/property relationships in titanium aluminides and alloys discusses gamma titanium aluminides (ingot metallurgy alloys), gamma titanium aluminides (cast, PM, and XD alloys), alpha-2 titanium aluminides, and structural titanium alloys. Attention is given to phase equilibria in Ti-Al alloys, high-temperature phase stability in the Ti-Al-Ta system, dislocation structure in deformed gamma/alpha-2 titanium aluminides, and the microstructure-property correlation in TiAl-base alloys. Topics addressed include the temperature dependence of the tensile behavior of a gamma titanium aluminide alloy, the plastic flow behavior of a Ti-Al-Nb-Mn alloy at high temperatures, and hydrogen embrittlement in gamma TiAl alloys. Also discussed are microstructure morphology effects on the fracture toughness of a cast near-gamma titanium aluminide alloy, the creep behavior of Ti-24Al-11Nb, the flow behavior of Ti-24Al-11Nb at high strain rates, and the role of hydrogen-assisted cracking in SCC of alpha-beta Ti alloys.

  15. Evaluation of the Transient Liquid Phase (TLP) Bonding Process for Ti3Al-Based Honeycomb Core Sandwich Structure

    NASA Technical Reports Server (NTRS)

    Bird, R. Keith; Hoffman, Eric K.

    1998-01-01

    The suitability of using transient liquid phase (TLP) bonding to fabricate honeycomb core sandwich panels with Ti-14Al-21Nb (wt%) titanium aluminide (T3Al) face sheets for high-temperature hypersonic vehicle applications was evaluated. Three titanium alloy honeycomb cores and one Ti3Al alloy honeycomb core were investigated. Edgewise compression (EWC) and flatwise tension (FWT) tests on honeycomb core sandwich specimens and tensile tests of the face sheet material were conducted at temperatures ranging from room temperature to 1500 F. EWC tests indicated that the honeycomb cores and diffusion bonded joints were able to stabilize the face sheets up to and beyond the face sheet compressive yield strength for all temperatures investigated. The specimens with the T3Al honeycomb core produced the highest FWT strengths at temperatures above 1000 F. Tensile tests indicated that TLP processing conditions resulted in decreases in ductility of the Ti-14Al-21Nb face sheets. Microstructural examination showed that the side of the face sheets to which the filler metals had been applied was transformed from equiaxed alpha2 grains to coarse plates of alpha2 with intergranular Beta. Fractographic examination of the tensile specimens showed that this transformed region was dominated by brittle fracture.

  16. The structure-directed effect of Al-based metal–organic frameworks on fabrication of alumina by thermal treatment

    SciTech Connect

    Liu, Dandan; Dai, Fangna; Tang, Zhe; Liu, Yunqi; Liu, Chenguang

    2015-05-15

    Highlights: • We use Al-MOFs as precursor in the fabrication process of mesoporous alumina by thermal treatment. • The obtained mesoporous alumina has dual pore system and five-fold aluminum. • The aluminum building units in the precursor show structure-directed effect on the formation of alumina. - Abstract: In this work, the block-shaped Al-based metal–organic frameworks (Al-MOFs) MIL-53 have been synthesized by hydrothermal method. To detect the correlation between the structure of Al-MOFs and the formation of alumina, the ligands are eliminated by thermal treatment. MIL-53 and the calcination products were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscope (SEM), transmission electron microscopy (TEM), nitrogen adsorption–desorption and solid-state {sup 27}Al nuclear magnetic resonance ({sup 27}Al NMR). It was found that after calcination, the block-shaped Al-MOFs precursor turns into high-crystallinity mesoporous alumina nanosheets, and the thermal treatment product γ-alumina possesses a dual pore system and a large surface area (146 m{sup 2}/g), with five-fold aluminum. During the thermal treatment process, the structure of MIL-53 and its secondary building units have structure-directed effect in the formation of alumina.

  17. Electroplating on titanium alloy

    NASA Technical Reports Server (NTRS)

    Lowery, J. R.

    1971-01-01

    Activation process forms adherent electrodeposits of copper, nickel, and chromium on titanium alloy. Good adhesion of electroplated deposits is obtained by using acetic-hydrofluoric acid anodic activation process.

  18. Alloy Selection System

    SciTech Connect

    2001-02-01

    Software will Predict Corrosion Rates to Improve Productivity in the Chemical Industry. Many aspects of equipment design and operation are influenced by the choice of the alloys used to fabricate process equipment.

  19. Semiconductor Alloy Theory.

    DTIC Science & Technology

    1986-01-14

    ftoc*o~ow7 and Idenify’ by block nam. bor) Electron mobility , Lattice Relaxation, Bond Length, Bond Energy, Mixing Enthalpies, Band Structure, Core...including: (1) generalization of Brooks’ formula for alloy-scattering limited electron mobility to including multiple bands and indirect gaps, (2...calculation of SiGe alloys band structure, electron mobility and core-exciton binding energy and • :linewidth, (3) comprehensive calculation of bond

  20. PLUTONIUM-URANIUM ALLOY

    DOEpatents

    Coffinberry, A.S.; Schonfeld, F.W.

    1959-09-01

    Pu-U-Fe and Pu-U-Co alloys suitable for use as fuel elements tn fast breeder reactors are described. The advantages of these alloys are ease of fabrication without microcracks, good corrosion restatance, and good resistance to radiation damage. These advantages are secured by limitation of the zeta phase of plutonium in favor of a tetragonal crystal structure of the U/sub 6/Mn type.

  1. Ultrahigh temperature intermetallic alloys

    SciTech Connect

    Brady, M.P.; Zhu, J.H.; Liu, C.T.; Tortorelli, P.F.; Wright, J.L.; Carmichael, C.A.

    1998-11-01

    A new family of Cr-Cr{sub 2}Ta intermetallic alloys based on Cr-(6--10)Ta (at.%) is under development for structural use in oxidizing environments in the 1,000-1,300 C (1,832--2,372 F) temperature range. Development objectives relate to high temperature strength and oxidation resistance and room temperature fracture toughness. The 1,200 C (2,192 F) strength goals have been met: yield and fracture strengths of 275 MPa (40 ksi) and 345 MPa (50 ksi), respectively, were achieved. Progress in attaining reasonable fracture toughness of Cr-Cr{sub 2}Ta alloys has been made; current alloys exhibit room-temperature values of about 10--12 MPa{radical}m (1.1 MPa{radical}m = 1 ksi{radical}in.). Oxidation rates of these alloys at 950 C (1,742 F) in air are in the range of those reported for chromia-forming alloys. At 1,100 C (2,012 F) in air, chromia volatility was significant but, nevertheless, no scale spallation and positive weight gains of 1--5 mg/cm{sup 2} have been observed during 120-h, 6-cycle oxidation screening tests. These mechanical and oxidative properties represent substantial improvement over Cr-Cr{sub 2}Nb and Cr-Cr{sub 2}Zr alloys previously developed.

  2. Microstructural Investigation and Phase Relationships of Fe-Al-Hf Alloys

    NASA Astrophysics Data System (ADS)

    Yildirim, Mehmet; Akdeniz, M. Vedat; Mekhrabov, Amdulla O.

    2014-07-01

    The effect of Hf addition on microstructures, phase relationships, microhardness, and magnetic properties of Fe50Al50- n Hf n alloys for n = 1, 3, 5, 7, and 9 at. pct has been investigated. At all investigated compositions, the ternary intermetallic HfFe6Al6 τ 1 phase forms due to the limited solid solubility of Hf in FeAl phase and tends to develop a eutectic phase mixture with the Fe-Al-based phase. The Hf concentration of the eutectic composition is found to be 7 at. pct from the microstructural examinations and the eutectic phase transition temperature is determined as 1521 K (1248 °C) independent of Hf amount by differential scanning calorimetry measurements. Furthermore, the enthalpies and activation energies (based on Kissinger and Ozawa methods) of eutectic phase transitions are reported. The minimum activation energy is calculated for the fully eutectic composition. Moreover, variation of the microhardness of Fe-Al-based alloys as a function of the Hf content is investigated, and its dependence on the thermal history of the alloys is explained.

  3. Palladium alloys for biomedical devices.

    PubMed

    Wataha, John C; Shor, Kavita

    2010-07-01

    In the biomedical field, palladium has primarily been used as a component of alloys for dental prostheses. However, recent research has shown the utility of palladium alloys for devices such as vascular stents that do not distort magnetic resonance images. Dental palladium alloys may contain minor or major percentages of palladium. As a minor constituent, palladium hardens, strengthens and increases the melting range of alloys. Alloys that contain palladium as the major component also contain copper, gallium and sometimes tin to produce strong alloys with high stiffness and relatively low corrosion rates. All current evidence suggests that palladium alloys are safe, despite fears about harmful effects of low-level corrosion products during biomedical use. Recent evidence suggests that palladium poses fewer biological risks than other elements, such as nickel or silver. Hypersensitivity to palladium alone is rare, but accompanies nickel hypersensitivity 90-100% of the time. The unstable price of palladium continues to influence the use of palladium alloys in biomedicine.

  4. Hot Microfissuring in Nickel Alloy

    NASA Technical Reports Server (NTRS)

    Thompson, R. G.; Nunes, A.

    1984-01-01

    Experiments in intergranular cracking of nickel alloy near solidus temperature discussed in contractor report. Purpose of investigation development of schedule for welding, casting, forging, or other processing of alloy without causing microfissuring.

  5. FY-13 FCRD Milestone M3FT-13OR0202311 Weldability of ORNL Accident Tolerant Fuel Cladding Model Alloys For Thin Walled Tubes

    SciTech Connect

    Field, Kevin G; Gussev, Maxim N; Yamamoto, Yukinori

    2013-07-01

    Ferritic FeCrAl-based alloys show increased oxidation resistance for accident tolerant applications as fuel cladding. This study focuses on investigating the weldability of three model FeCrAl alloys with varying alloy compositions using laser-welding techniques. A detailed study of the mechanical properties of bead-on-plate welds was used to determine the quality of welds as a function of alloy composition. Laser welding resulted in defect free welds devoid of cracking or inclusions. Initial results indicate a reduction in the yield strength of weldments compared to the base material due to distinct changes in the microstructure within the fusion zone. Although a loss of yield strength was observed, there was no significant difference in the magnitude of the tensile property changes with varying Cr or Al content. Also, there was no evidence of embrittlement; the material in the fusion zones demonstrated ductile behavior with high local ductility.

  6. Selective dissolution in binary alloys

    NASA Astrophysics Data System (ADS)

    McCall, Carol Rene

    Corrosion is an important issue in the design of engineering alloys. De-alloying is an aspect of alloy corrosion related to the selective dissolution of one or more of the components in an alloy. The work reported herein focuses on the topic of de-alloying specific to single-phase binary noble metal alloy systems. The alloy systems investigated were gold-silver and gold-copper. The onset of a bulk selective dissolution process is typically marked by a critical potential whereby the more reactive component in the alloy begins dissolving from the bulk, leading to the formation of a bi-continuous solid-void morphology. The critical potential was investigated for the entire composition range of gold-silver alloys. The results presented herein include the formulation of an expression for critical potential as a function of both alloy and electrolyte composition. Results of the first investigation of underpotential deposition (UPD) on alloys are also presented herein. These results were implemented as an analytical tool to provide quantitative measurements of the surface evolution of gold during de-alloying. The region below the critical potential was investigated in terms of the compositional evolution of the alloy surface. Below the critical potential, there is a competition between the dissolution of the more reactive alloying constituent (either silver or copper) and surface diffusion of gold that serves to cover dissolution sites and prevent bulk dissolution. By holding the potential at a prescribed value below the critical potential, a time-dependent gold enrichment occurs on the alloy surface leading to passivation. A theoretical model was developed to predict the surface enrichment of gold based on the assumption of layer-by-layer dissolution of the more reactive alloy constituent. The UPD measurements were used to measure the time-dependent surface gold concentration and the results agreed with the predictions of the theoretical model.

  7. Tissue Response to Base-Metal Dental Alloys.

    DTIC Science & Technology

    RESPONSE(BIOLOGY), *CASTING ALLOYS, *BASE METAL, * DENTAL PROSTHESES, TISSUES(BIOLOGY), COMPATIBILITY, NICKEL ALLOYS, BERYLLIUM, DENTISTRY, CANCER, HISTOLOGY, DENTAL IMPLANTOLOGY , COBALT ALLOYS, CHROMIUM ALLOYS.

  8. Finding the Alloy Genome

    NASA Astrophysics Data System (ADS)

    Hart, Gus L. W.; Nelson, Lance J.; Zhou, Fei; Ozolins, Vidvuds

    2012-10-01

    First-principles codes can nowadays provide hundreds of high-fidelity enthalpies on thousands of alloy systems with a modest investment of a few tens of millions of CPU hours. But a mere database of enthalpies provides only the starting point for uncovering the ``alloy genome.'' What one needs to fundamentally change alloy discovery and design are complete searches over candidate structures (not just hundreds of known experimental phases) and models that can be used to simulate both kinetics and thermodynamics. Despite more than a decade of effort by many groups, developing robust models for these simulations is still a human-time-intensive endeavor. Compressive sensing solves this problem in dramatic fashion by automatically extracting the ``sparse model'' of an alloy in only minutes. This new paradigm to model building has enabled a new framework that will uncover, automatically and in a general way across the periodic table, the important components of such models and reveal the underlying ``genome'' of alloy physics.

  9. Low-temperature superplasticity of submicrocrystalline Ti-48Al-2Nb-2Cr alloy produced by multiple forging

    SciTech Connect

    Imayev, V.M.; Salishchev, G.A.; Shagiev, M.R.; Kuznetsov, A.V.; Imayev, R.M.; Senkov, O.N.; Froes, F.H.

    1998-12-18

    Gamma titanium aluminides are attractive for elevated temperature applications because of their high specific strength, modulus retention, good oxidation and creep resistance. However they are inherently brittle at temperatures below 600 C due to their strong covalent interatomic bonding, which makes fabrication difficult and has restricted commercial applications. In this research work the authors have studied superplastic (SP) forming of a gamma alloy. Grain refinement is the most common method of decreasing the temperature at which superplasticity is observed, while the second approach is applicable only to gamma alloys containing less than 47 at.% Al. In the present work, a low-temperature superplasticity of a gamma TiAl-based alloy was achieved by producing a submicrocrystalline structure via multistep forging. Mechanical behavior and microstructural evolution of the submicrocrystalline gamma titanium aluminide were studied and possible mechanisms of the low-temperature superplasticity were discussed.

  10. Enhancing glass-forming ability via frustration of nano-clustering in alloys with a high solvent content.

    PubMed

    Li, H X; Gao, J E; Wu, Y; Jiao, Z B; Ma, D; Stoica, A D; Wang, X L; Ren, Y; Miller, M K; Lu, Z P

    2013-01-01

    The glass-forming ability (GFA) of alloys with a high-solvent content such as soft magnetic Fe-based and Al-based alloys is usually limited due to strong formation of the solvent-based solid solution phase. Herein, we report that the GFA of soft magnetic Fe-based alloys (with >70 at.% Fe to ensure large saturation magnetization) could be dramatically improved by doping with only 0.3 at.% Cu which has a positive enthalpy of mixing with Fe. It was found that an appropriate Cu addition could enhance the liquid phase stability and crystallization resistance by destabilizing the α-Fe nano-clusters due to the necessity to redistribute the Cu atoms. However, excessive Cu doping would stimulate nucleation of the α-Fe nano-clusters due to the repulsive nature between the Fe and Cu atoms, thus deteriorating the GFA. Our findings provide new insights into understanding of glass formation in general.

  11. Enhancing glass-forming ability via frustration of nano-clustering in alloys with a high solvent content

    NASA Astrophysics Data System (ADS)

    Li, H. X.; Gao, J. E.; Wu, Y.; Jiao, Z. B.; Ma, D.; Stoica, A. D.; Wang, X. L.; Ren, Y.; Miller, M. K.; Lu, Z. P.

    2013-06-01

    The glass-forming ability (GFA) of alloys with a high-solvent content such as soft magnetic Fe-based and Al-based alloys is usually limited due to strong formation of the solvent-based solid solution phase. Herein, we report that the GFA of soft magnetic Fe-based alloys (with >70 at.% Fe to ensure large saturation magnetization) could be dramatically improved by doping with only 0.3 at.% Cu which has a positive enthalpy of mixing with Fe. It was found that an appropriate Cu addition could enhance the liquid phase stability and crystallization resistance by destabilizing the α-Fe nano-clusters due to the necessity to redistribute the Cu atoms. However, excessive Cu doping would stimulate nucleation of the α-Fe nano-clusters due to the repulsive nature between the Fe and Cu atoms, thus deteriorating the GFA. Our findings provide new insights into understanding of glass formation in general.

  12. De-alloyed platinum nanoparticles

    DOEpatents

    Strasser, Peter; Koh, Shirlaine; Mani, Prasanna; Ratndeep, Srivastava

    2011-08-09

    A method of producing de-alloyed nanoparticles. In an embodiment, the method comprises admixing metal precursors, freeze-drying, annealing, and de-alloying the nanoparticles in situ. Further, in an embodiment de-alloyed nanoparticle formed by the method, wherein the nanoparticle further comprises a core-shell arrangement. The nanoparticle is suitable for electrocatalytic processes and devices.

  13. Aluminum alloys with improved strength

    NASA Technical Reports Server (NTRS)

    Deiasi, R.; Adler, P.

    1975-01-01

    Mechanical strength and stress corrosion of new BAR and 7050 alloys that include Zn instead of Cr have been studied and compared with those of 7075 aluminum alloy. Added mechanical strength of new alloys is attributed to finer grain size of 5 to 8 micrometers, however, susceptibility to stress corrosion attack is increased.

  14. PLUTONIUM-URANIUM-TITANIUM ALLOYS

    DOEpatents

    Coffinberry, A.S.

    1959-07-28

    A plutonium-uranium alloy suitable for use as the fuel element in a fast breeder reactor is described. The alloy contains from 15 to 60 at.% titanium with the remainder uranium and plutonium in a specific ratio, thereby limiting the undesirable zeta phase and rendering the alloy relatively resistant to corrosion and giving it the essential characteristic of good mechanical workability.

  15. Semiconductor alloys - Structural property engineering

    NASA Technical Reports Server (NTRS)

    Sher, A.; Van Schilfgaarde, M.; Berding, M.; Chen, A.-B.

    1987-01-01

    Semiconductor alloys have been used for years to tune band gaps and average bond lengths to specific applications. Other selection criteria for alloy composition, and a growth technique designed to modify their structural properties, are presently considered. The alloys Zn(1-y)Cd(y)Te and CdSe(y)Te(1-y) are treated as examples.

  16. The effect of TiB2 reinforcement on the mechanical properties of an Al-Cu-Li alloy-based metal-matrix composite

    NASA Technical Reports Server (NTRS)

    Langan, T. J.; Pickens, J. R.

    1991-01-01

    Weldalite 049, an Al-base Cu-Li-Mg-Ag-Zr alloy, achieves 700 MPa tensile strengths in the near-peak-aged temper in virtue of the nucleation of a T(1)-type platelike strengthening precipitate. Attention is presently given to the possibility that the alloy's modulus could be further increased through the addition of high-modulus TiB2 particles, using the 'XD' process, due to TiB2's good wettability with liquid Al. An 8-percent modulus increase is obtained with 4 vol pct TiB2.

  17. Magnesium and magnesium alloys

    SciTech Connect

    Avedesian, M.; Baker, H.

    1998-12-31

    This new handbook is the most comprehensive publication of engineering information on commercial magnesium alloys under one cover in the last sixty years. Prepared with the cooperation of the International Magnesium Association, it presents the industrial practices currently used throughout the world, as well as the properties of the products critical to their proper application. Contents include: general characteristics; physical metallurgy; melting, refining, alloying, recycling, and powder production; casting; heat treatment; forging, rolling, and extrusion; semisolid processing; forming; joining; cleaning and finishing; selection, application, and properties of grades and alloys; design considerations; mechanical behavior and wear resistance; fatigue and fracture-mechanics; high-temperature strength and creep; corrosion and stress-corrosion cracking; specification.

  18. Hydrogen in titanium alloys

    SciTech Connect

    Wille, G W; Davis, J W

    1981-04-01

    The titanium alloys that offer properties worthy of consideration for fusion reactors are Ti-6Al-4V, Ti-6Al-2Sn-4Zr-2Mo-Si (Ti-6242S) and Ti-5Al-6Sn-2Zr-1Mo-Si (Ti-5621S). The Ti-6242S and Ti-5621S are being considered because of their high creep resistance at elevated temperatures of 500/sup 0/C. Also, irradiation tests on these alloys have shown irradiation creep properties comparable to 20% cold worked 316 stainless steel. These alloys would be susceptible to slow strain rate embrittlement if sufficient hydrogen concentrations are obtained. Concentrations greater than 250 to 500 wppm hydrogen and temperatures lower than 100 to 150/sup 0/C are approximate threshold conditions for detrimental effects on tensile properties. Indications are that at the elevated temperature - low hydrogen pressure conditions of the reactors, there would be negligible hydrogen embrittlement.

  19. A composite of complex and chemical hydrides yields the first Al-based amidoborane with improved hydrogen storage properties.

    PubMed

    Dovgaliuk, Iurii; Jepsen, Lars H; Safin, Damir A; Łodziana, Zbigniew; Dyadkin, Vadim; Jensen, Torben R; Devillers, Michel; Filinchuk, Yaroslav

    2015-10-05

    The first Al-based amidoborane Na[Al(NH2 BH3 )4 ] was obtained through a mechanochemical treatment of the NaAlH4 -4 AB (AB=NH3 BH3 ) composite releasing 4.5 wt % of pure hydrogen. The same amidoborane was also produced upon heating the composite at 70 °C. The crystal structure of Na[Al(NH2 BH3 )4 ], elucidated from synchrotron X-ray powder diffraction and confirmed by DFT calculations, contains the previously unknown tetrahedral ion [Al(NH2 BH3 )4 ](-) , with every NH2 BH3 (-) ligand coordinated to aluminum through nitrogen atoms. Combination of complex and chemical hydrides in the same compound was possible due to both the lower stability of the AlH bonds compared to the BH ones in borohydride, and due to the strong Lewis acidity of Al(3+) . According to the thermogravimetric analysis-differential scanning calorimetry-mass spectrometry (TGA-DSC-MS) studies, Na[Al(NH2 BH3 )4 ] releases in two steps 9 wt % of pure hydrogen. As a result of this decomposition, which was also supported by volumetric studies, the formation of NaBH4 and amorphous product(s) of the surmised composition AlN4 B3 H(0-3.6) were observed. Furthermore, volumetric experiments have also shown that the final residue can reversibly absorb about 27 % of the released hydrogen at 250 °C and p(H2 )=150 bar. Hydrogen re-absorption does not regenerate neither Na[Al(NH2 BH3 )4 ] nor starting materials, NaAlH4 and AB, but rather occurs within amorphous product(s). Detailed studies of the latter one(s) can open an avenue for a new family of reversible hydrogen storage materials. Finally, the NaAlH4 -4 AB composite might become a starting point towards a new series of aluminum-based tetraamidoboranes with improved hydrogen storage properties such as hydrogen storage density, hydrogen purity, and reversibility.

  20. Surface modification of high temperature iron alloys

    DOEpatents

    Park, J.H.

    1995-06-06

    A method and article of manufacture of a coated iron based alloy are disclosed. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700--1200 C to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy. 13 figs.

  1. Surface modification of high temperature iron alloys

    DOEpatents

    Park, Jong-Hee

    1995-01-01

    A method and article of manufacture of a coated iron based alloy. The method includes providing an iron based alloy substrate, depositing a silicon containing layer on the alloy surface while maintaining the alloy at a temperature of about 700.degree. C.-1200.degree. C. to diffuse silicon into the alloy surface and exposing the alloy surface to an ammonia atmosphere to form a silicon/oxygen/nitrogen containing protective layer on the iron based alloy.

  2. Progress on Numerical Modeling of the Dispersion of Ceramic Nanoparticles During Ultrasonic Processing and Solidification of Al-Based Nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhang, Daojie; Nastac, Laurentiu

    2016-12-01

    In present study, 6061- and A356-based nano-composites are fabricated by using the ultrasonic stirring technology (UST) in a coreless induction furnace. SiC nanoparticles are used as the reinforcement. Nanoparticles are added into the molten metal and then dispersed by ultrasonic cavitation and acoustic streaming assisted by electromagnetic stirring. The applied UST parameters in the current experiments are used to validate a recently developed magneto-hydro-dynamics (MHD) model, which is capable of modeling the cavitation and nanoparticle dispersion during UST processing. The MHD model accounts for turbulent fluid flow, heat transfer and solidification, and electromagnetic field, as well as the complex interaction between the nanoparticles and both the molten and solidified alloys by using ANSYS Maxwell and ANSYS Fluent. Molecular dynamics (MD) simulations are conducted to analyze the complex interactions between the nanoparticle and the liquid/solid interface. The current modeling results demonstrate that a strong flow can disperse the nanoparticles relatively well during molten metal and solidification processes. MD simulation results prove that ultrafine particles (10 nm) will be engulfed by the solidification front instead of being pushed, which is beneficial for nano-dispersion.

  3. Effect of post-pattern annealing on the grain structure and reliability of Al-based interconnects

    SciTech Connect

    Kang, S.H.; Kim, C.; Morris, J.W. Jr. |; Genin, F.Y.

    1996-06-01

    The possibility is addressed of improving the electromigration resistance of Al and Al{endash}Cu thin-film conductors with {open_quote}{open_quote}quasi-bamboo{close_quote}{close_quote} structures by post-pattern anneals that decrease the maximum polygranular segment length. Pure Al, Al{endash}2Cu, and Al{endash}2Cu{endash}1Si lines were patterned and annealed at temperatures high enough to stimulate grain growth. Appropriate anneals led to predominantly bamboo structures with short polygranular segments. These grain structures had a high median time to failure with a relatively low deviation of the time to failure. Metallographic analyses showed that polygranular segment length was a dominant factor in determining the failure site. Post-pattern annealing promotes a preferential shortening of the relatively long polygranular segments that cause early failures. However, even after annealing, failure occurred at the longest residual polygranular segments, even when these were significantly shorter than the {open_quote}{open_quote}Blech length{close_quote}{close_quote} under the test conditions. Statistical analysis of the failure of alloy lines revealed a simple exponential relation between the failure time and the longest polygranular segment length within a line, which is functionally identical to that previously found for lines tested in the as-patterned condition.

  4. The Melt-Dilute Treatment of Al-Base Highly Enriched DOE Spent Nuclear Fuels: Principles and Practices

    SciTech Connect

    Adams, T.M.

    1998-11-25

    The melt-dilute treatment technology program is focused on the development and implementation of a treatment technology for diluting highly enriched (>20 percent 235U) aluminum spent nuclear fuel to low enriched levels (<20 percent 235U) and qualifying the LEU Al-SNF form for geologic repository storage. In order to reduce the enrichment of these assemblies prior to ultimate geologic repository disposal, the melt-dilute technology proposes to melt these SNF assemblies and then dilute with additions of depleted uranium. The benefits accrued from this treatment process include the potential for significant volume reduction, reduced criticality potential, and the potential for enhanced SNF form characteristics. The emphasis within the development program to date has been on determining the process metallurgy and off-gas system design for the treatment of all types of Al SNF (UAlx, Al-U3O8, and Al-U3Si2). In determining the process metallurgy a wide range of alloys, representative of those expected in the Al-SNF form, have been fabricated and their product characteristics, namely microstructure, homogeneity, phase composition, and "ternary" constituent effects have been analyzed. As a result of the presence of species within the melt which will possess significant vapor pressures in the desired operating temperature range an off-gas system is necessary. Of the volitile species the one of greatest concern is 137Cs.

  5. High temperature creep behaviour of Al-rich Ti-Al alloys

    NASA Astrophysics Data System (ADS)

    Sturm, D.; Heilmaier, M.; Saage, H.; Aguilar, J.; Schmitz, G. J.; Drevermann, A.; Palm, M.; Stein, F.; Engberding, N.; Kelm, K.; Irsen, S.

    2010-07-01

    Compared to Ti-rich γ-TiAl-based alloys Al-rich Ti-Al alloys offer an additional reduction of in density and a better oxidation resistance which are both due to the increased Al content. Polycrystalline material was manufactured by centrifugal casting. Microstructural characterization was carried out employing light-optical, scanning and transmission electron microscopy and XRD analyses. The high temperature creep of two binary alloys, namely Al60Ti40 and Al62Ti38 was comparatively assessed with compression tests at constant true stress in a temperature range between 1173 and 1323 K in air. The alloys were tested in the cast condition (containing various amounts of the metastable phases Al5Ti3 and h-Al2Ti) and after annealing at 1223 K for 200 h which produced (thermodynamically stable) lamellar γ-TiAl + r-Al2Ti microstructures. In general, already the as-cast alloys exhibit a reasonable creep resistance at 1173 K. Compared with Al60Ti40, both, the as-cast and the annealed Al62Ti38 alloy exhibit better creep resistance up to 1323 K which can be rationalized by the reduced lamella spacing. The assessment of creep tests conducted at identical stress levels and varying temperatures yielded apparent activation energies for creep of Q = 430 kJ/mol for the annealed Al60Ti40 alloy and of Q = 383 kJ/mol for the annealed Al62Ti38 material. The latter coincides well with that of Al diffusion in γ-TiAl, whereas the former can be rationalized by the instability of the microstructure containing metastable phases.

  6. Microstructure and mechanical properties of zirconium doped NiAl/Cr(Mo) hypoeutectic alloy prepared by injection casting

    NASA Astrophysics Data System (ADS)

    Sheng, L. Y.; Du, B. N.; Guo, J. T.

    2017-01-01

    NiAl based materials has been considered as most potential candidate of turbine blade, due to its excellent high-temperature properties. However the bad room-temperature properties handicap its application. In the present paper, the zirconium doped NiAl/Cr(Mo) hypoeutectic alloy is fabricated by conventional casting and injection casting technology to improve its room-temperature properties. The microstructure and compressive properties at different temperatures of the conventionally-cast and injection-cast were investigated. The results exhibit that the conventionally-cast alloy comprises coarse primary NiAl phase and eutectic cell, which is dotted with irregular Ni2AlZr Heusler phase. Compared with the conventionally-cast alloy, the injection-cast alloy possesses refined the primary NiAl, eutectic cell and eutectic lamella. In addition, the Ni2AlZr Heusler phase become smaller and distribute uniformly. Moreover, the injection casting decrease the area fraction of primary NiAl phase at the cell interior or cell boundaries. The compressive ductility and yield strength of the injection-cast alloy at room temperature increase by about 100% and 35% over those of conventionally-cast alloy, which should be ascribed to the microstructure optimization.

  7. Erosion of a TiAl intermetallic alloy under conditions simulating plasma disruptions

    NASA Astrophysics Data System (ADS)

    Kalin, B. A.; Yakushin, V. L.; Polsky, V. I.; Dzhumaev, P. S.; Fedotov, V. T.; Sevryukov, O. N.; Golikov, M. Yu.; Zolotarev, M. V.

    2009-04-01

    Radiation erosion and thermal stability of TiAl-based intermetallic alloys produced by vacuum-arc melting, compacting of microcrystal powders with binder and impregnantion by melt, and their brazed joints with bronze have been investigated under irradiation by high-temperature pulsed hydrogen plasma flows (the flow energy density Q = 0.2-0.9 MJ/m 2, the pulse duration 15 μs, the number of pulses 1-21) which simulate the expected plasma disruptions in a fusion reactor. It has been found that the erosion coefficients and thermal stability of alloys are determined by the way of their fabrication, and compacted intermetallides have a higher thermal stability in comparison with the cast ones. The brazed joints of the intermetallic compound with bronze under irradiation by pulsed hydrogen plasma up to the energy density Q = 0.75 MJ/m 2 have a high thermal stability and formation of cracks was not observed.

  8. Quinary metallic glass alloys

    DOEpatents

    Lin, X.; Johnson, W.L.

    1998-04-07

    At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10{sup 3}K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf){sub a}(Al,Zn){sub b}(Ti,Nb){sub c}(Cu{sub x}Fe{sub y}(Ni,Co){sub z}){sub d} wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d{hor_ellipsis}y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.

  9. Quinary metallic glass alloys

    DOEpatents

    Lin, Xianghong; Johnson, William L.

    1998-01-01

    At least quinary alloys form metallic glass upon cooling below the glass transition temperature at a rate less than 10.sup.3 K/s. Such alloys comprise zirconium and/or hafnium in the range of 45 to 65 atomic percent, titanium and/or niobium in the range of 4 to 7.5 atomic percent, and aluminum and/or zinc in the range of 5 to 15 atomic percent. The balance of the alloy compositions comprise copper, iron, and cobalt and/or nickel. The composition is constrained such that the atomic percentage of iron is less than 10 percent. Further, the ratio of copper to nickel and/or cobalt is in the range of from 1:2 to 2:1. The alloy composition formula is: (Zr,Hf).sub.a (Al,Zn).sub.b (Ti,Nb).sub.c (Cu.sub.x Fe.sub.y (Ni,Co).sub.z).sub.d wherein the constraints upon the formula are: a ranges from 45 to 65 atomic percent, b ranges from 5 to 15 atomic percent, c ranges from 4 to 7.5 atomic percent, d comprises the balance, d.multidot.y is less than 10 atomic percent, and x/z ranges from 0.5 to 2.

  10. Microporosity in casting alloys.

    PubMed

    Lewis, A J

    1975-06-01

    Three series of tensile test pieces were produced using a nickel base partial denture casting alloy. For the first series induction heating was employed, for the second a resistance crucible, and for the third an oxy-acetylene torch. Samples from each series were sectioned longitudinally, mounted, polished and examined microscopically for evidence of microporosity.

  11. Superplasticity in aluminum alloys

    SciTech Connect

    Nieh, T. G.

    1997-12-01

    We have characterized in the Al-Mg system the microstructure and mechanical properties of a cold-rolled Al-6Mg-0.3Sc alloy. The alloy exhibited superplasticity at relatively high strain rates (about 10-2 s-1). At a strain rate of 10-2 s-1 there exists a wide temperature range (475-520`C) within which the tensile elongation is over 1000%. There also exists a wide strain rate range (10-3 - 10-1 s-1) within which the tensile elongation is over 500%. The presence of Sc in the alloy results in a uniform distribution of fine coherent Al3SC precipitates which effectively pin grain and subgrain boundaries during static and continuous recrystallization. As a result, the alloy retains its fine grain size (about 7 micron), even after extensive superplastic deformation (>1000%). During deformation, dislocations Mg with a high Schmidt factor slip across subgrains but are trapped by subgrain boundaries, as a result of the strong pining of Al3Sc. This process leads to the conversion of low-angled subgrain boundaries to high-angled grain boundaries and the subsequent grain boundary sliding, which produces superelasticity. A model is proposed to describe grain boundary sliding accommodated by dislocation glide across grains with a uniform distribution of coherent precipitates. The model predictions is consistent with experimental observations.

  12. Shape Memory Alloy Actuator

    NASA Technical Reports Server (NTRS)

    Baumbick, Robert J. (Inventor)

    2002-01-01

    The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

  13. Shape Memory Alloy Actuator

    NASA Technical Reports Server (NTRS)

    Baumbick, Robert J. (Inventor)

    2000-01-01

    The present invention discloses and teaches a unique, remote optically controlled micro actuator particularly suitable for aerospace vehicle applications wherein hot gas, or in the alternative optical energy, is employed as the medium by which shape memory alloy elements are activated. In gas turbine powered aircraft the source of the hot gas may be the turbine engine compressor or turbine sections.

  14. Mechanical alloying of brittle materials

    NASA Astrophysics Data System (ADS)

    Davis, R. M.; McDermott, B.; Koch, C. C.

    1988-12-01

    Mechanical alloying by high energy ball milling has been observed in systems with nominally brittle components. The phases formed by mechanical alloying of brittle components include solid solutions (Si + Ge → SiGe solid solution), intermetallic compounds (Mn + Bi → MnBi), and amorphous alloys (NiZr2 + Ni11Zr9 → amorphous Ni50Zr50). A key feature of possible mechanisms for mechanical alloying of brittle components is the temperature of the powders during milling. Experiments and a computer model of the kinetics of mechanical alloying were carried out in order to esti-mate the temperature effect. Temperature rises in typical powder alloys during milling in a SPEX mill were estimated to be ≤350 K using the kinetic parameters determined from the computer model. The tempering response of fresh martensite in an Fe-1.2 wt pct C alloy during milling was consistent with the maximum results of the computer model, yielding temperatures in the pow-ders of ≤575 K i.e., ΔT ≤ 300 K). Thermal activation was required for mechanical alloying of Si and Ge powder. No alloying occurred when the milling vial was cooled by liquid nitrogen. The pos-sible mechanisms responsible for material transfer during mechanical alloying of brittle components are considered.

  15. Grindability of dental magnetic alloys.

    PubMed

    Hayashi, Eisei; Kikuchi, Masafumi; Okuno, Osamu; Kimura, Kohei

    2005-06-01

    In this study, the grindability of cast magnetic alloys (Fe-Pt-Nb magnetic alloy and magnetic stainless steel) was evaluated and compared with that of conventional dental casting alloys (Ag-Pd-Au alloy, Type 4 gold alloy, and cobalt-chromium alloy). Grindability was evaluated in terms of grinding rate (i.e., volume of metal removed per minute) and grinding ratio (i.e., volume ratio of metal removed compared to wheel material lost). Solution treated Fe-Pt-Nb magnetic alloy had a significantly higher grinding rate than the aged one at a grinding speed of 750-1500 m x min(-1). At 500 m x min(-1), there were no significant differences in grinding rate between solution treated and aged Fe-Pt-Nb magnetic alloys. At a lower speed of 500 m x min(-1) or 750 m x min(-1), it was found that the grinding rates of aged Fe-Pt-Nb magnetic alloy and stainless steel were higher than those of conventional casting alloys.

  16. Tungsten carbide laser alloying of a low alloyed steel

    NASA Astrophysics Data System (ADS)

    Cojocaru, Mihai; Taca, Mihaela

    1996-10-01

    Laser alloying is a way to change the composition of metal surfaces in order to improve their corrosion-resistance, high-temperature strength and hardness. The results of a structural and phase analysis of a tungsten carbide based surface layer prepared by laser alloying of a low carbon steel substrate are presented. Structure, phase composition and microhardness of surface alloyed layers have been investigated. The surface of the samples exhibited a thin layer with a different chemical and phase composition. An increase in alloyed surface hardness and wear-resistance was observed.

  17. Filler metal alloy for welding cast nickel aluminide alloys

    DOEpatents

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

    1998-03-10

    A filler metal alloy used as a filler for welding cast nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and cast in copper chill molds. 3 figs.

  18. Filler metal alloy for welding cast nickel aluminide alloys

    DOEpatents

    Santella, Michael L.; Sikka, Vinod K.

    1998-01-01

    A filler metal alloy used as a filler for welding east nickel aluminide alloys contains from about 15 to about 17 wt. % chromium, from about 4 to about 5 wt. % aluminum, equal to or less than about 1.5 wt. % molybdenum, from about 1 to about 4.5 wt. % zirconium, equal to or less than about 0.01 wt. % yttrium, equal to or less than about 0.01 wt. % boron and the balance nickel. The filler metal alloy is made by melting and casting techniques such as are melting the components of the filler metal alloy and east in copper chill molds.

  19. Development and Processing of Nickel Aluminide-Carbide Alloys

    NASA Technical Reports Server (NTRS)

    Newport, Timothy Scott

    1996-01-01

    With the upper temperature limit of the Ni-based superalloys attained, a new class of materials is required. Intermetallics appear as likely candidates because of their attractive physical properties. With a relatively low density, high thermal conductivity, excellent oxidation resistance, high melting point, and simple crystal structure, nickel aluminide (NiAl) appears to be a potential candidate. However, NiAl is limited in structural applications due to its low room temperature fracture toughness and poor elevated temperature strength. One approach to improving these properties has been through the application of eutectic composites. Researchers have shown that containerless directional solidification of NiAl-based eutectic alloys can provide improvement in both the creep strength and fracture toughness. Although these systems have shown improvements in the mechanical properties, the presence of refractory metals increases the density significantly in some alloys. Lower density systems, such as the carbides, nitrides, and borides, may provide NiAl-based eutectic structure. With little or no information available on these systems, experimental investigation is required. The objective of this research was to locate and develop NiAl-carbide eutectic alloys. Exploratory arc-melts were performed in NiAl-refractory metal-C systems. Refractory metal systems investigated included Co, Cr, Fe, Hf, Mo, Nb, Ta, Ti, W, and Zr. Systems containing carbides with excellent stability (i.e.,HfC, NbC, TaC, TiC, and ZrC) produced large blocky cubic carbides in an NiAl matrix. The carbides appeared to have formed in the liquid state and were randomly distributed throughout the polycrystalline NiAl. The Co, Cr, Fe, Mo, and W systems contained NiAl dendrites with a two-phase interdendritic microconstituent present. Of these systems, the NiAl-Mo-C system had the most promising microstructure for in-situ composites. Three processing techniques were used to evaluate the NiAl-Mo-C system

  20. DESIGN DATA STUDY FOR COATED COLUMBIUM ALLOYS

    DTIC Science & Technology

    ANTIOXIDANTS, * COATINGS , * NIOBIUM ALLOYS, *REFRACTORY COATINGS , *SILICON COATINGS , ALLOYS, ALUMINUM, DEFORMATION, ELASTIC PROPERTIES, HIGH...TEMPERATURE, OXIDATION, PLASTIC PROPERTIES, REENTRY VEHICLES, REFRACTORY MATERIALS, SHEETS, SILICIDES , VACUUM APPARATUS, VAPOR PLATING, ZIRCONIUM ALLOYS

  1. Materials data handbook, Inconel alloy 718

    NASA Technical Reports Server (NTRS)

    Sessler, J.; Weiss, V.

    1967-01-01

    Materials data handbook on Inconel alloy 718 includes data on the properties of the alloy at cryogenic, ambient, and elevated temperatures and other pertinent engineering information required for the design and fabrication of components and equipment utilizing this alloy.

  2. Two phase titanium aluminide alloy

    DOEpatents

    Deevi, Seetharama C.; Liu, C. T.

    2001-01-01

    A two-phase titanic aluminide alloy having a lamellar microstructure with little intercolony structures. The alloy can include fine particles such as boride particles at colony boundaries and/or grain boundary equiaxed structures. The alloy can include alloying additions such as .ltoreq.10 at % W, Nb and/or Mo. The alloy can be free of Cr, V, Mn, Cu and/or Ni and can include, in atomic %, 45 to 55% Ti, 40 to 50% Al, 1 to 5% Nb, 0.3 to 2% W, up to 1% Mo and 0.1 to 0.3% B. In weight %, the alloy can include 57 to 60% Ti, 30 to 32% Al, 4 to 9% Nb, up to 2% Mo, 2 to 8% W and 0.02 to 0.08% B.

  3. TERNARY ALLOY-CONTAINING PLUTONIUM

    DOEpatents

    Waber, J.T.

    1960-02-23

    Ternary alloys of uranium and plutonium containing as the third element either molybdenum or zirconium are reported. Such alloys are particularly useful as reactor fuels in fast breeder reactors. The alloy contains from 2 to 25 at.% of molybdenum or zirconium, the balance being a combination of uranium and plutonium in the ratio of from 1 to 9 atoms of uranlum for each atom of plutonium. These alloys are prepared by melting the constituent elements, treating them at an elevated temperature for homogenization, and cooling them to room temperature, the rate of cooling varying with the oomposition and the desired phase structure. The preferred embodiment contains 12 to 25 at.% of molybdenum and is treated by quenching to obtain a body centered cubic crystal structure. The most important advantage of these alloys over prior binary alloys of both plutonium and uranium is the lack of cracking during casting and their ready machinability.

  4. Dynamic mechanical analyze of superelastic CuMnAl shape memory alloy

    NASA Astrophysics Data System (ADS)

    (Dragoș Ursanu, A. I.; Stanciu, S.; Pricop, B.; Săndulache, F.; Cimpoeșu, N.

    2016-08-01

    A new shape memory alloy was obtain from high purity Cu, Mn and Al elements using a induce furnace. The intelligent material present negative transformation temperatures and an austenite like state at room temperature. The austenite state of CuMnAl shape memory alloy present superelasticity property. Five kilograms ingot was obtain of Cu10Mn10Al alloy. From the base material (melted state) were cut samples with 6 mm thickness using a mechanical saw. After an homogenization heat treatment the samples were hot rolled through four passes with a reduction coefficient of 20%. Experimental lamellas were obtained with 1.5 mm thickness and 90x10 mm length and width. After the hot rolled treatment the materials were heat treated at 800°C for 20 minutes and chilled in water. Four samples, one just laminated and three heat treated by aging, were analyzed with a Netzsch DMA equipment to establish the elastic modulus and the internal friction values of the materials. Metallic materials microstructure was analyzed using a scanning electron microscope Vega Tescan LMH II type. After the aging heat treatment a decrease of internal friction is observed on the entire analyze range which is assigned to formation of Al-based precipitates that block the internal movement of the alloy characteristic phases.

  5. High strain rate superplasticity in an Al-Mg alloy containing scandium

    SciTech Connect

    Komura, Shogo; Horita, Zenji; Nemoto, Minoru; Berbon, P.B.; Langdon, T.G.; Furukawa, Minoru

    1998-05-12

    Superplastic forming is a well-established industrial process for the fabrication of complex shapes in sheet metals. It has been suggested that it may be possible to achieve superplasticity at high strain rates in conventional materials by making a substantial reduction in the grain size. This may be achieved by using a process such as equal-channel angular (ECA) pressing, where the sample is subjected to intense plastic straining in simple shear, because it is well established that ECA pressing leads to significant grain refinement in large-grained polycrystalline materials down to the submicrometer or even the nanometer level. High strain rate superplasticity (HSR SP) has been widely documented in a range of metal matrix composites, mechanically alloyed materials and in alloys fabricated using powder metallurgy procedures and very recently there was a report of HSR SP in commercial cast Al-based alloys after ECA pressing. The present investigation was initiated in order to evaluate the potential for achieving HSR SP in an Al-3% Mg alloy containing a scandium addition. Scandium was selected for use in this investigation because it is well established that dilute amounts of scandium in the Al-Mg system lead to a considerable enhancement in both the strength and the thermal stability of the material.

  6. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

    PubMed Central

    Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

    2016-01-01

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications. PMID:26892834

  7. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths.

    PubMed

    Jiao, Z B; Luan, J H; Miller, M K; Yu, C Y; Liu, C T

    2016-02-19

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. The co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.

  8. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

    DOE PAGES

    Jiao, Z. B.; Luan, J. H.; Miller, M. K.; ...

    2016-02-19

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for twomore » interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. Lastly, the co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.« less

  9. Group precipitation and age hardening of nanostructured Fe-based alloys with ultra-high strengths

    SciTech Connect

    Jiao, Z. B.; Luan, J. H.; Miller, M. K.; Yu, C. Y.; Liu, C. T.

    2016-02-19

    The precipitation of nanoparticles plays a key role in determining the properties of many structural materials, and the understanding of their formation and stabilization mechanisms has been a long standing interest in the material field. However, the critical issues involving the group precipitation of various nanoparticles and their cooperative hardening mechanism remain elusive in the newly discovered Fe-based alloys with nanostructures. Here we quantitatively elucidate the nucleation mechanism, evolution kinetics and hardening effects of the group-precipitated nanoparticles in the Fe-Cu-Ni-Al-based alloys by atom probe tomography together with both first-principles and thermodynamic calculations. Our results provide the compelling evidence for two interesting but complex group precipitation pathways of nanoparticles, i.e., the Cu-rich and NiAl-based precipitations. Lastly, the co-existence of the two precipitation pathways plays a key role in age hardening kinetics and ultimately enhances the hardening response, as compared to the single particle type of strengthening, therefore providing an effective new approach for strengthening materials for structural applications.

  10. Titanium-tantalum alloy development

    SciTech Connect

    Cotton, J.D.; Bingert, J.F.; Dunn, P.S.; Butt, D.P.; Margevicius, R.W.

    1996-04-01

    Research has been underway at Los Alamos National Laboratory for several years to develop an alloy capable of containing toxic materials in the event of a fire involving a nuclear weapon. Due to their high melting point, good oxidation resistance, and low solubility in molten plutonium, alloys based on the Ti-Ta binary system have been developed for this purpose. The course of the alloy development to-date, along with processing and property data, are presented in this overview.

  11. Characterization Techniques for Amorphous Alloys

    NASA Astrophysics Data System (ADS)

    Carow-Watamura, U.; Louzguine, D. V.; Takeuchi, A.

    This document is part of Part 2 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from B-Be-Fe to Co-W-Zr' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter '2 Characterization Techniques for Amorphous Alloys' with the content:

  12. 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.

  13. Machine Casting of Ferrous Alloys.

    DTIC Science & Technology

    possible today. Extensive work was conducted on casting of semi-solid alloys when highly fluid (’ Rheocasting ’) and when thixotropically gelled...Thixocasting’). In initial phases of the program, copper base alloys and cast iron alloys were prepared with special non-dendritic Rheocast structure by batch...processing. Compatibility studies were carried out to select materials suitable for preparing cast iron with the Rheocast structure. Design

  14. Surface Segregation in Ternary Alloys

    NASA Technical Reports Server (NTRS)

    Good, Brian; Bozzolo, Guillermo H.; Abel, Phillip B.

    2000-01-01

    Surface segregation profiles of binary (Cu-Ni, Au-Ni, Cu-Au) and ternary (Cu-Au-Ni) alloys are determined via Monte Carlo-Metropolis computer simulations using the BFS method for alloys for the calculation of the energetics. The behavior of Cu or Au in Ni is contrasted with their behavior when both are present. The interaction between Cu and Au and its effect on the segregation profiles for Cu-Au-Ni alloys is discussed.

  15. Alloy Interface Interdiffusion Modeled

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo H.; Garces, Jorge E.; Abel, Phillip B.

    2003-01-01

    With renewed interest in developing nuclear-powered deep space probes, attention will return to improving the metallurgical processing of potential nuclear fuels so that they remain dimensionally stable over the years required for a successful mission. Previous work on fuel alloys at the NASA Glenn Research Center was primarily empirical, with virtually no continuing research. Even when empirical studies are exacting, they often fail to provide enough insight to guide future research efforts. In addition, from a fundamental theoretical standpoint, the actinide metals (which include materials used for nuclear fuels) pose a severe challenge to modern electronic-structure theory. Recent advances in quantum approximate atomistic modeling, coupled with first-principles derivation of needed input parameters, can help researchers develop new alloys for nuclear propulsion.

  16. Shape memory alloy actuator

    DOEpatents

    Varma, Venugopal K.

    2001-01-01

    An actuator for cycling between first and second positions includes a first shaped memory alloy (SMA) leg, a second SMA leg. At least one heating/cooling device is thermally connected to at least one of the legs, each heating/cooling device capable of simultaneously heating one leg while cooling the other leg. The heating/cooling devices can include thermoelectric and/or thermoionic elements.

  17. Duct and cladding alloy

    DOEpatents

    Korenko, Michael K.

    1983-01-01

    An austenitic alloy having good thermal stability and resistance to sodium corrosion at 700.degree. C. consists essentially of 35-45% nickel 7.5-14% chromium 0.8-3.2% molybdenum 0.3-1.0% silicon 0.2-1.0% manganese 0-0.1% zirconium 2.0-3.5% titanium 1.0-2.0% aluminum 0.02-0.1% carbon 0-0.01% boron and the balance iron.

  18. 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.

  19. Radiation Effects in Refractory Alloys

    NASA Astrophysics Data System (ADS)

    Zinkle, Steven J.; Wiffen, F. W.

    2004-02-01

    In order to achieve the required low reactor mass per unit electrical power for space reactors, refractory alloys are essential due to their high operating temperature capability that in turn enables high thermal conversion efficiencies. One of the key issues associated with refractory alloys is their performance in a neutron irradiation environment. The available radiation effects data are reviewed for alloys based on Mo, W, Re, Nb and Ta. The largest database is associated with Mo alloys, whereas Re, W and Ta alloys have the least available information. Particular attention is focused on Nb-1Zr, which is a proposed cladding and structural material for the reactor in the Jupiter Icy Moons Orbiter (JIMO) project. All of the refractory alloys exhibit qualitatively similar temperature-dependent behavior. At low temperatures up to ~0.3TM, where TM is the melting temperature, the dominant effect of radiation is to produce pronounced radiation hardening and concomitant loss of ductility. The radiation hardening also causes a dramatic decrease in the fracture toughness of the refractory alloys. These low temperature radiation effects occur at relatively low damage levels of ~0.1 displacement per atom, dpa (~2×1024 n/m2, E>0.1 MeV). As a consequence, operation at low temperatures in the presence of neutron irradiation must be avoided for all refractory alloys. At intermediate temperatures (0.3 to 0.6 TM), void swelling and irradiation creep are the dominant effects of irradiation. The amount of volumetric swelling associated with void formation in refractory alloys is generally within engineering design limits (<5%) even for high neutron exposures (>>10 dpa). Very little experimental data exist on irradiation creep of refractory alloys, but data for other body centered cubic alloys suggest that the irradiation creep will produce negligible deformation for near-term space reactor applications.

  20. Fracture behavior of a B2 Ni-30Al-20Fe-0.05Zr intermetallic alloy in the temperature range 300 to 1300 K

    NASA Technical Reports Server (NTRS)

    Raj, S. V.

    1992-01-01

    The fracture behavior of a B2 Ni-30Al-20Fe-0.05Zr (at. pct) alloy was investigated using results of tensile tests conducted in the temperature range 300-1300 K under initial strain rates that varied between 10 exp -6 and 10 exp -3/sec, together with results of deformation measurements reported by Raj et al. (1992). Microstructural observations revealed that the alloy had failed by transgranular cleavage fracture below 873 K and by ductile fracture, power-law cavitation, triple point cracking, and rupture above this temperautre. The fracture map constructed using fracture results is compared with those for other classes of materials, showing that the atomic bonding plays a significant role in the low-temperature ductility of NiAl-based alloys.

  1. PLUTONIUM-CERIUM-COPPER ALLOYS

    DOEpatents

    Coffinberry, A.S.

    1959-05-12

    A low melting point plutonium alloy useful as fuel is a homogeneous liquid metal fueled nuclear reactor is described. Vessels of tungsten or tantalum are useful to contain the alloy which consists essentially of from 10 to 30 atomic per cent copper and the balance plutonium and cerium. with the plutontum not in excess of 50 atomic per cent.

  2. Shape memory alloy thaw sensors

    DOEpatents

    Shahinpoor, Mohsen; Martinez, David R.

    1998-01-01

    A sensor permanently indicates that it has been exposed to temperatures exceeding a critical temperature for a predetermined time period. An element of the sensor made from shape memory alloy changes shape when exposed, even temporarily, to temperatures above the Austenitic temperature of the shape memory alloy. The shape change of the SMA element causes the sensor to change between two readily distinguishable states.

  3. 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.

  4. 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.

  5. Heat storage in alloy transformations

    NASA Technical Reports Server (NTRS)

    Birchenall, C. E.; Gueceri, S. I.; Farkas, D.; Labdon, M. B.; Nagaswami, N.; Pregger, B.

    1981-01-01

    The feasibility of using metal alloys as thermal energy storage media was determined. The following major elements were studied: (1) identification of congruently transforming alloys and thermochemical property measurements; (2) development of a precise and convenient method for measuring volume change during phase transformation and thermal expansion coefficients; (3) development of a numerical modeling routine for calculating heat flow in cylindrical heat exchangers containing phase change materials; and (4) identification of materials that could be used to contain the metal alloys. Several eutectic alloys and ternary intermetallic phases were determined. A method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation from data obtained during one continuous experimental test. The method and apparatus are discussed and the experimental results are presented. The development of the numerical modeling method is presented and results are discussed for both salt and metal alloy phase change media.

  6. Mo-Si alloy development

    SciTech Connect

    Liu, C.T.; Heatherly, L.; Wright, J.L.

    1996-06-01

    The objective of this task is to develop new-generation corrosion-resistant Mo-Si intermetallic alloys as hot components in advanced fossil energy conversion and combustion systems. The initial effort is devoted to Mo{sub 5}-Si{sub 3}-base (MSB) alloys containing boron additions. Three MSB alloys based on Mo-10.5Si-1.1B (wt %), weighing 1500 g were prepared by hot pressing of elemental and alloy powders at temperatures to 1600{degrees}C in vacuum. Microporosities and glassy-phase (probably silicate phases) formations are identified as the major concerns for preparation of MSB alloys by powder metallurgy. Suggestions are made to alleviate the problems of material processing.

  7. DEVELOPMENT OF PROTECTIVE COATINGS FOR TANTALUM-BASE ALLOYS

    DTIC Science & Technology

    PHASE STUDIES, PHYSICAL PROPERTIES, REFRACTORY MATERIALS, SILICIDES , SILICON COATINGS , SILICON COMPOUNDS, TANTALUM, TENSILE PROPERTIES, TITANIUM COMPOUNDS, TUNGSTEN ALLOYS, VANADIUM ALLOYS, VAPOR PLATING, ZINC COATINGS ....TANTALUM ALLOYS, ALLOYS, ALUMINUM COATINGS , ALUMINUM COMPOUNDS, BORON COMPOUNDS, CERAMIC COATINGS , CHROMIUM COMPOUNDS, COATINGS , FLAME SPRAYING...HAFNIUM ALLOYS, HAFNIUM COMPOUNDS, HARDNESS, HEAT RESISTANT ALLOYS, INTERMETALLIC COMPOUNDS, METAMATHEMATICS, NIOBIUM ALLOYS, OSCILLOGRAPHS, OXIDES

  8. Wedlable nickel aluminide alloy

    DOEpatents

    Santella, Michael L.; Sikka, Vinod K.

    2002-11-19

    A Ni.sub.3 Al alloy with improved weldability is described. It contains about 6-12 wt % Al, about 6-12 wt % Cr, about 0-3 wt % Mo, about 1.5-6 wt % Zr, about 0-0.02 wt % B and at least one of about 0-0.15 wt % C, about 0-0.20 wt % Si, about 0-0.01 wt % S and about 0-0.30 wt % Fe with the balance being Ni.

  9. Lightweight Disk Alloy Development

    DTIC Science & Technology

    1991-04-01

    2001 (1982). 45. K C. Russell and J. W Eddington , JI Mat. Sci., 6, 20 (1972). 46. M. J. Lequeux, Ph.D. Thesis, Univ. de Paris-Sud (1979). 47. P S ...AD-A237 064 UGHTWEIGHT DISK ALLOY DEVELOPMENT S . M. Russel, C. C. Law and M. J. Blackburn Uted Te lowkles Corpoaton Prat & Whtney Govnment Enes...Space Propulo P. 0. Box 109600 West Palm Beach, FL 33410-9600 P. C. Clapp and D. M. Pease Istitute of Materials Science 9 ELECT Fg AW 11il S E Final

  10. Thermomechanical treatment of alloys

    DOEpatents

    Bates, John F.; Brager, Howard R.; Paxton, Michael M.

    1983-01-01

    An article of an alloy of AISI 316 stainless steel is reduced in size to predetermined dimensions by cold working in repeated steps. Before the last reduction step the article is annealed by heating within a temperature range, specifically between 1010.degree. C. and 1038.degree. C. for a time interval between 90 and 60 seconds depending on the actual temperature. By this treatment the swelling under neutron bombardment by epithermal neutrons is reduced while substantial recrystallization does not occur in actual use for a time interval of at least of the order of 5000 hours.

  11. Stable palladium alloys for diffusion of hydrogen

    NASA Technical Reports Server (NTRS)

    Patapoff, M.

    1973-01-01

    Literature search on hydrogen absorption effect on palladium alloys revealed existence of alloy compositions in which alpha--beta transition does not take place. Survey conclusions: 40 percent gold alloy of palladium should be used in place of palladium; alloy must be free of interstitial impurities; and metallic surfaces of tube must be clean.

  12. Interaction Of Hydrogen With Metal Alloys

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    Report describes experiments on interaction of hydrogen with number of metal alloys. Discusses relationship between metallurgical and crystallographic aspects of structures of alloys and observed distributions of hydrogen on charging. Also discusses effect of formation of hydrides on resistances of alloys to hydrogen. Describes attempt to correlate structures and compositions of alloys with their abilities to resist embrittlement by hydrogen.

  13. THEORY OF DIFFUSION IN ORDERING ALLOYS

    DTIC Science & Technology

    interstitial atoms through the interstices Diffusion of interstitial atoms in alloys with a body - centered cubic lattice Diffusion of...sites of the alloy The case of an alloy with body - centered cubic lattic structure The case of an alloy with a face-centered cubic lattic

  14. Oxidation resistant alloys, method for producing oxidation resistant alloys

    DOEpatents

    Dunning, John S.; Alman, David E.

    2002-11-05

    A method for producing oxidation-resistant austenitic alloys for use at temperatures below 800.degree. C. comprising of: providing an alloy comprising, by weight %: 14-18% chromium, 15-18% nickel, 1-3% manganese, 1-2% molybdenum, 2-4% silicon, 0% aluminum and the balance being iron; heating the alloy to 800.degree. C. for between 175-250 hours prior to use in order to form a continuous silicon oxide film and another oxide film. The method provides a means of producing stainless steels with superior oxidation resistance at temperatures above 700.degree. C. at a low cost

  15. Oxidation resistant alloys, method for producing oxidation resistant alloys

    DOEpatents

    Dunning, John S.; Alman, David E.

    2002-11-05

    A method for producing oxidation-resistant austenitic alloys for use at temperatures below 800 C. comprising of: providing an alloy comprising, by weight %: 14-18% chromium, 15-18% nickel, 1-3% manganese, 1-2% molybdenum, 2-4% silicon, 0% aluminum and the balance being iron; heating the alloy to 800 C. for between 175-250 hours prior to use in order to form a continuous silicon oxide film and another oxide film. The method provides a means of producing stainless steels with superior oxidation resistance at temperatures above 700 C. at a low cost

  16. Joint properties of cast Fe-Pt magnetic alloy laser welded to gold alloys.

    PubMed

    Watanabe, Ikuya; Nguyen, Khoi; Benson, P Andrew; Tanaka, Yasuhiro

    2006-01-01

    This study investigated the joint properties of a cast Fe-Pt magnetic alloy (Fe-36 at % Pt) laser welded to three gold alloys. The gold alloys used were ADA Type II and Type IV gold alloys, and an Ag-based (Ag-Au) gold alloy. Cast plates (0.5 x 3.0 x 10 mm) were prepared for each alloy. After the cast Fe-Pt plates were heat treated, they were butted against each of the three alloys and then laser welded with Nd:YAG laser at 200 V. Homogeneously welded specimens were also prepared for each alloy. Tensile testing was conducted at a crosshead speed of 1 mm/min. Failure load (N) and elongation (%) were recorded. After tensile testing, the fractured surfaces were examined with the use of SEM. The failure-load values of the group of alloys welded homogeneously were ranked in the order of: Ag-Au alloy > Type IV alloy > Type II alloy > Fe-Pt alloy. The Type IV alloy welded to Fe-Pt alloy had the highest failure-load value among the three alloys tested. The elongation results tended to follow a similar pattern. The results of this study indicated that Type IV gold alloy is a suitable alloy for metal frameworks to which cast Fe-Pt magnetic alloy is laser welded.

  17. High performance alloy electroforming

    NASA Technical Reports Server (NTRS)

    Malone, G. A.; Winkelman, D. M.

    1989-01-01

    Electroformed copper and nickel are used in structural applications for advanced propellant combustion chambers. An improved process has been developed by Bell Aerospace Textron, Inc. wherein electroformed nickel-manganese alloy has demonstrated superior mechanical and thermal stability when compared to previously reported deposits from known nickel plating processes. Solution chemistry and parametric operating procedures are now established and material property data is established for deposition of thick, large complex shapes such as the Space Shuttle Main Engine. The critical operating variables are those governing the ratio of codeposited nickel and manganese. The deposition uniformity which in turn affects the manganese concentration distribution is affected by solution resistance and geometric effects as well as solution agitation. The manganese concentration in the deposit must be between 2000 and 3000 ppm for optimum physical properties to be realized. The study also includes data regarding deposition procedures for achieving excellent bond strength at an interface with copper, nickel-manganese or INCONEL 718. Applications for this electroformed material include fabrication of complex or re-entry shapes which would be difficult or impossible to form from high strength alloys such as INCONEL 718.

  18. DISPERSION STRENGTHENED NICKEL-BASE ALLOYS.

    DTIC Science & Technology

    The swaged cone of extruded Nichrome-thoria alloys prepared by the thermal decomposition of thorium nitrate onto alloy powder indicated descreased... swaging of these dispersion-strengthened Nichrome alloys was dependent on the presence of a mild steel jacket on the alloy rod as a result of the canned...extrusion practice. Efforts to cold swage the alloy materials without this jacket were unsuccessful. (Author)

  19. Heat storage in alloy transformations

    NASA Technical Reports Server (NTRS)

    Birchenall, C. E.

    1980-01-01

    The feasibility of using metal alloys as thermal energy storage media was investigated. The elements selected as candidate media were limited to aluminum, copper, magnesium, silicon, zinc, calcium, and phosphorus on the basis of low cost and latent heat of transformation. Several new eutectic alloys and ternary intermetallic phases were determined. A new method employing X-ray absorption techniques was developed to determine the coefficients of thermal expansion of both the solid and liquid phases and the volume change during phase transformation. The method and apparatus are discussed and the experimental results are presented for aluminum and two aluminum-eutectic alloys. Candidate materials were evaluated to determine suitable materials for containment of the metal alloys. Graphite was used to contain the alloys during the volume change measurements. Silicon carbide was identified as a promising containment material and surface-coated iron alloys were also evaluated. System considerations that are pertinent if alloy eutectics are used as thermal energy storage media are discussed. Potential applications to solar receivers and industrial furnaces are illustrated schematically.

  20. Mechanically Alloyed High Entropy Composite

    NASA Astrophysics Data System (ADS)

    Popescu, G.; Adrian, M. M.; Csaki, I.; Popescu, C. A.; Mitrică, D.; Vasile, S.; Carcea, I.

    2016-08-01

    In the last years high entropy alloys have been investigated due to their high hardness, high temperature stability and unusual properties that make these alloys to have significant interest. In comparison with traditional alloys that are based on two or three major elements, this new generation alloys consists at least of 5 principal elements, with the concentration between 5 and 35 at.%. The present paper reports synthesis of high entropy alloys (HEA) and high entropy composites (HEC) synthesized by mechanical alloying (MA). The equiatomic AlCrFeNiMn matrix was used for creating the HEA matrix, starting from elemental powders and as reinforcing material for composites was used pure graphite. The mechanical alloying process was carried out at different duration, in a high energy planetary ball mill, under argon atmosphere. The elemental powders alloying began after '5 hours of milling and was complete after 40 hours. The mechanical alloyed matrix and composite was pressed and heat treated under argon protection. The elemental powers were investigated for physical - technological properties, and by X-ray diffraction and scanning electron microscopy. Phase pressing operation was realized with a hydraulic press and the applied pressure was progressive. The sintering process was carried out at 850°C for 2 h. The X-ray diffraction revealed that the MA process resulted in solid solutions formation and also revealed body- centred cubic (BCC) and face-centred cubic (FCC) structures with average grain size around 40 nm. In addition, nanoscale particles were highlighted by scanning electron microscopy, as well as the homogeneity of the chemical composition of the matrix and composite that was confirmed by EDX microanalysis. It was noted that HEA matrix and HEA composites were processed with a high degree of compaction and with a quite large capacity of mixed powder densification (around 70%).

  1. Development of powder metallurgy 2XXX series Al alloys for high temperature aircraft structural applications

    NASA Technical Reports Server (NTRS)

    Chellman, D. J.

    1984-01-01

    The objective of the present investigation was to improve the strength and fracture toughness combination of P/M 2124 Al alloys in accordance with NASA program goals for damage tolerance and fatigue resistance. Two (2) P/M compositions based on Al-3.70 Cu-1.85 Mg-0.20 Mn with 0.12 and 0.60 wt. pct. Zr were selected for investigation. The rapid solidification rates produced by atomization were observed to prohibit the precipitation of coarse, primary Al3Zr in both alloys. A major portion of the Zr precipitated as finely distributed, coherent Al3Zr phases during vacuum preheating and solution heat treatment. The proper balance between Cu and Mg contents eliminated undissolved, soluble constituents such as Al2CuMg and Al2Cu during atomization. The resultant extruded microstructures produced a unique combination of strength and fracture toughness. An increase in the volume fraction of coherent Al3Zr, unlike incoherent Al20Cu2Mn3 dispersoids, strengthened the P/M Al base alloy either directly by dislocation-precipitate interactions, indirectly by a retardation of recrystallization, or a combination of both mechanisms. Furthermore, coherent Al3Zr does not appear to degrade toughness to the extent that incoherent Al20Cu2Mn3 does. Consequently, the addition of 0.60 wt. pct. Zr to the base alloy, incorporated with a 774K (935 F) solution heat treatment temperature, produces an alloy which exceeds all tensile property and fracture toughness goals for damage tolerant and fatigue resistant applications in the naturally aged condition.

  2. Modeling dissolution in aluminum alloys

    NASA Astrophysics Data System (ADS)

    Durbin, Tracie Lee

    2005-07-01

    Aluminum and its alloys are used in many aspects of modern life, from soda cans and household foil to the automobiles and aircraft in which we travel. Aluminum alloy systems are characterized by good workability that enables these alloys to be economically rolled, extruded, or forged into useful shapes. Mechanical properties such as strength are altered significantly with cold working, annealing, precipitation-hardening, and/or heat-treatments. Heat-treatable aluminum alloys contain one or more soluble constituents such as copper, lithium, magnesium, silicon and zinc that individually, or with other elements, can form phases that strengthen the alloy. Microstructure development is highly dependent on all of the processing steps the alloy experiences. Ultimately, the macroscopic properties of the alloy depend strongly on the microstructure. Therefore, a quantitative understanding of the microstructural changes that occur during thermal and mechanical processing is fundamental to predicting alloy properties. In particular, the microstructure becomes more homogeneous and secondary phases are dissolved during thermal treatments. Robust physical models for the kinetics of particle dissolution are necessary to predict the most efficient thermal treatment. A general dissolution model for multi-component alloys has been developed using the front-tracking method to study the dissolution of precipitates in an aluminum alloy matrix. This technique is applicable to any alloy system, provided thermodynamic and diffusion data are available. Treatment of the precipitate interface is explored using two techniques: the immersed-boundary method and a new technique, termed here the "sharp-interface" method. The sharp-interface technique is based on a variation of the ghost fluid method and eliminates the need for corrective source terms in the characteristic equations. In addition, the sharp-interface method is shown to predict the dissolution behavior of precipitates in aluminum

  3. Superior Ballistic Impact Resistance Achieved by the Co-Base Alloy Haynes 25

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.; Noebe, Ronald D.; Revilock, Duane M.

    2003-01-01

    The fan case in a jet engine is required to contain a fan blade in the rare event of a blade loss during operation. Because of its function, the fan case is the largest structural component in high-bypass-ratio turbofan engines used in commercial aircraft. Therefore, the use of lighter and stronger materials would be advantageous in most engines and is practically a necessity in the latest generation of high-bypass engines. Small panels, 7 in. wide by 7 in. long, of a number of metallic alloys were impact tested at room temperature with a 0.50-caliber blunt-nose titanium alloy projectile at the NASA Glenn Research Center (ref. 1). These metallic systems included several high-strength aluminum (Al) alloys, Al-based laminates, aluminum metal matrix composites (Al-MMCs), nickel-base superalloys (Inconel 718 and 625), several titanium (Ti) alloys in different heat treated conditions, 304L stainless steel, a stainless-steel-based laminate, and a high strength steel (Nitronic 60). It was determined that a simple Co-base alloy (Haynes 25) had the best impact resistance on an areal weight basis. Haynes 25 was at least 10 percent better than IMI 550, the best titanium alloy tested to date, and it was far superior to other metals, especially at higher impact velocities (greater than 1100 ft/sec). Because this material could be ideal for fan containment applications in supersonic aircraft as a replacement for titanium, impact tests were also conducted at 371 oC and compared with results from alloys tested at elevated temperature under previous programs (i.e., Inconel 718, Ti-6242, M-152, Timetal 21S, and Aeromet 100). Although cobalt-base alloys are used in some high-temperature engine applications, to our knowledge they are not used in any containment systems. Advantages of cobalt over titanium include lower cost, easier processing, better high-temperature strength, and no fire hazard if tip rub occurs. Future plans include testing of lightweight sandwich panels with Haynes

  4. Alloy design for intrinsically ductile refractory high-entropy alloys

    NASA Astrophysics Data System (ADS)

    Sheikh, Saad; Shafeie, Samrand; Hu, Qiang; Ahlström, Johan; Persson, Christer; Veselý, Jaroslav; Zýka, Jiří; Klement, Uta; Guo, Sheng

    2016-10-01

    Refractory high-entropy alloys (RHEAs), comprising group IV (Ti, Zr, Hf), V (V, Nb, Ta), and VI (Cr, Mo, W) refractory elements, can be potentially new generation high-temperature materials. However, most existing RHEAs lack room-temperature ductility, similar to conventional refractory metals and alloys. Here, we propose an alloy design strategy to intrinsically ductilize RHEAs based on the electron theory and more specifically to decrease the number of valence electrons through controlled alloying. A new ductile RHEA, Hf0.5Nb0.5Ta0.5Ti1.5Zr, was developed as a proof of concept, with a fracture stress of close to 1 GPa and an elongation of near 20%. The findings here will shed light on the development of ductile RHEAs for ultrahigh-temperature applications in aerospace and power-generation industries.

  5. Mechanical alloying of biocompatible Co-28Cr-6Mo alloy.

    PubMed

    Sánchez-De Jesús, F; Bolarín-Miró, A M; Torres-Villaseñor, G; Cortés-Escobedo, C A; Betancourt-Cantera, J A

    2010-07-01

    We report on an alternative route for the synthesis of crystalline Co-28Cr-6Mo alloy, which could be used for surgical implants. Co, Cr and Mo elemental powders, mixed in an adequate weight relation according to ISO Standard 58342-4 (ISO, 1996), were used for the mechanical alloying (MA) of nano-structured Co-alloy. The process was carried out at room temperature in a shaker mixer mill using hardened steel balls and vials as milling media, with a 1:8 ball:powder weight ratio. Crystalline structure characterization of milled powders was carried out by X-ray diffraction in order to analyze the phase transformations as a function of milling time. The aim of this work was to evaluate the alloying mechanism involved in the mechanical alloying of Co-28Cr-6Mo alloy. The evolution of the phase transformations with milling time is reported for each mixture. Results showed that the resultant alloy is a Co-alpha solid solution, successfully obtained by mechanical alloying after a total of 10 h of milling time: first Cr and Mo are mechanically prealloyed for 7 h, and then Co is mixed in for 3 h. In addition, different methods of premixing were studied. The particle size of the powders is reduced with increasing milling time, reaching about 5 mum at 10 h; a longer time promotes the formation of aggregates. The morphology and crystal structure of milled powders as a function of milling time were analyzed by scanning electron microscopy and XR diffraction.

  6. Research on Si-Al based catalysts prepared by complete liquid-phase method for DME synthesis in a slurry reactor

    NASA Astrophysics Data System (ADS)

    Li, Zhihong; Zuo, Zhijun; Huang, Wei; Xie, Kechang

    2011-01-01

    A series of Si-Al based DME synthesis catalysts were prepared by complete liquid-phase method and characterized by in situ XPS, XRD, N 2 adsorption and NH 3-TPD analyses. Based on the results, the addition of Si could adjust the pore structure and surface acidity of catalyst, exhibiting a strong promoting effect on the CO conversion and DME selectivity. However, when Si/Al ratio is higher, Si would cover active sites and increase the amount of strong acidity sites, causing the reduction in catalytic activity. It was found from in situ XPS characterization that Cu 0 is the active center of methanol synthesis in DME production, and the addition of Si changes the chemical surroundings of active components and weaken the interaction between Cu, Zn and Al, which maybe give rise to the decrease in catalyst stability.

  7. Metallic alloy stability studies

    NASA Technical Reports Server (NTRS)

    Firth, G. C.

    1983-01-01

    The dimensional stability of candidate cryogenic wind tunnel model materials was investigated. Flat specimens of candidate materials were fabricated and cryo-cycled to assess relative dimensional stability. Existing 2-dimensional airfoil models as well as models in various stages of manufacture were also cryo-cycled. The tests indicate that 18 Ni maraging steel offers the greatest dimensional stability and that PH 13-8 Mo stainless steel is the most stable of the stainless steels. Dimensional stability is influenced primarily by metallurgical transformations (austenitic to martensitic) and manufacturing-induced stresses. These factors can be minimized by utilization of stable alloys, refinement of existing manufacturing techniques, and incorporation of new manufacturing technologies.

  8. High strength ferritic alloy

    DOEpatents

    Hagel, William C.; Smidt, Frederick A.; Korenko, Michael K.

    1977-01-01

    A high-strength ferritic alloy useful for fast reactor duct and cladding applications where an iron base contains from about 9% to about 13% by weight chromium, from about 4% to about 8% by weight molybdenum, from about 0.2% to about 0.8% by weight niobium, from about 0.1% to about 0.3% by weight vanadium, from about 0.2% to about 0.8% by weight silicon, from about 0.2% to about 0.8% by weight manganese, a maximum of about 0.05% by weight nitrogen, a maximum of about 0.02% by weight sulfur, a maximum of about 0.02% by weight phosphorous, and from about 0.04% to about 0.12% by weight carbon.

  9. Manufacturing of High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Jablonski, Paul D.; Licavoli, Joseph J.; Gao, Michael C.; Hawk, Jeffrey A.

    2015-07-01

    High entropy alloys (HEAs) have generated interest in recent years due to their unique positioning within the alloy world. By incorporating a number of elements in high proportion they have high configurational entropy, and thus they hold the promise of interesting and useful properties such as enhanced strength and phase stability. The present study investigates the microstructure of two single-phase face-centered cubic (FCC) HEAs, CoCrFeNi and CoCrFeNiMn, with special attention given to melting, homogenization and thermo-mechanical processing. Large-scale ingots were made by vacuum induction melting to avoid the extrinsic factors inherent in small-scale laboratory button samples. A computationally based homogenization heat treatment was applied to both alloys in order to eliminate segregation due to normal ingot solidification. The alloys fabricated well, with typical thermo-mechanical processing parameters being employed.

  10. Technical Seminar "Shape Memory Alloys"

    NASA Video Gallery

    Shape memory alloys are a unique group of materials that remember their original shape and return to that shape after being strained. How could the aerospace, automotive, and energy exploration ind...

  11. Casting Characteristics of Aluminum Die Casting Alloys

    SciTech Connect

    Makhlouf M. Makhlouf; Diran Apelian

    2002-02-05

    The research program investigates the casting characteristics of selected aluminum die casting alloys. Specifically, the alloys' tendencies towards die soldering and sludge formation, and the alloys' fluidity and machinability are evaluated. It was found that: When the Fe and Mn contents of the alloy are low; caution has to be taken against possible die soldering. When the alloy has a high sludge factor, particularly a high level of Fe, measures must be taken to prevent the formation of large hardspots. For this kind of alloy, the Fe content should be kept at its lowest allowable level and the Mn content should be at its highest possible level. If there are problems in die filling, measures other than changing the alloy chemistry need to be considered first. In terms of alloy chemistry, the elements that form high temperature compounds must be kept at their lowest allowable levels. The alloys should not have machining problems when appropriate machining techniques and machining parameters are used.

  12. Shape memory alloy thaw sensors

    DOEpatents

    Shahinpoor, M.; Martinez, D.R.

    1998-04-07

    A sensor permanently indicates that it has been exposed to temperatures exceeding a critical temperature for a predetermined time period. An element of the sensor made from shape memory alloy changes shape when exposed, even temporarily, to temperatures above the austenitic temperature of the shape memory alloy. The shape change of the SMA element causes the sensor to change between two readily distinguishable states. 16 figs.

  13. Alloy dissolution in argon stirred steel

    NASA Astrophysics Data System (ADS)

    Webber, Darryl Scott

    Alloying is required for the production of all steel products from small castings to large beams. Addition of large quantities of bulk alloys can result in alloy segregation and inconsistent alloy recovery. The objective of this research was to better understand alloy dissolution in liquid steel especially as it relates to Missouri S&Ts' patented continuous steelmaking process. A 45-kilogram capacity ladle with a single porous plug was used to evaluate the effect of four experimental factors on alloy dissolution: alloy species, alloy size or form, argon flow rate, and furnace tap temperature. Four alloys were tested experimentally including Class I low carbon ferromanganese, nickel and tin (as a surrogate for low melting alloys) and Class II ferroniobium. The alloys ranged in size and form from granular to 30 mm diameter lumps. Experimental results were evaluated using a theoretically based numerical model for the steel shell period, alloy mixing (Class I) and alloy dissolution (Class II). A CFD model of the experimental ladle was used to understand steel motion in the ladle and to provide steel velocity magnitudes for the numerical steel shell model. Experiments and modeling confirmed that smaller sized alloys have shorter steel shell periods and homogenize faster than larger particles. Increasing the argon flow rate shortened mixing times and reduced the delay between alloy addition and the first appearance of alloy in the melt. In addition, for every five degree increase in steel bath temperature the steel shell period was shortened by approximately four percent. Class II ferroniobium alloy dissolution was an order of magnitude slower than Class I alloy mixing.

  14. Microstructures and Mechanical Properties of Ultrafine Grained Ti-47Al-2Cr (at %) Alloy Produced Using Powder Compact Forging

    NASA Astrophysics Data System (ADS)

    Nadakuduru, Vijay N.; Zhang, Deliang; Cao, Peng; Gabbittas, Brian

    Development of innovative techniques to produce gamma TiAl based alloys, with good mechanical properties, while still maintaining ultra fine grain size can be rewarding, but also is a great challenge. In the present study study a Ti-47Al-2Cr (at %) alloy has been synthesized by directly forging green powder compacts of a Ti/Al/Cr composite powder produced by high energy mechanical milling of a mixture of elemental Ti, Al, Cr powders. It has been found that the density of the bulk consolidated alloy sample after forging decreases from 95% of the theoretical density in the central region to 84% in the periphery region. The microstructure of the bulk alloy consisted of several Ti rich regions, which was expected to be mainly due to initial powder condition. The room temperature tensile strength of the samples produced from this process was found to be in the range of 115 - 130 MPa. The roles of canning and green powder compact density in determining the forged sample porosity level and distribution are discussed.

  15. Research and Development on Titanium Alloys

    DTIC Science & Technology

    1949-10-31

    svmym lIfe. Th~e rAnge of cOmposila Ivwstpted in the bin"rtniaum-stiver sistems was extended to 5% snw an M~an~Ajmm loy cntprn 0.1 Is beryllium were...extended to 5,0 per cent silverl and titanium- beryllium alloys containing 0.1 to-1.0 per cent berylliuma were inveitiga~ted. None of~ these alloys had...of: 1. Binary titanium-germanium alloys. 2. Binary titanium-nickel alloys. 3, Binary titanium-silver alloys. 4. Binary titanium- beryllium alloys. 5

  16. 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.

  17. Ni{sub 3}Al aluminide alloys

    SciTech Connect

    Liu, C.T.

    1993-10-01

    This paper provides a brief review of the recent progress in research and development of Ni{sub 3}Al and its alloys. Emphasis has been placed on understanding low ductility and brittle fracture of Ni{sub 3}Al alloys at ambient and elevated temperatures. Recent studies have resulted in identifying both intrinsic and extrinsic factors governing the fracture behavior of Ni{sub 3}Al alloys. Parallel efforts on alloy design using physical metallurgy principles have led to properties for structural use. Industrial interest in these alloys is high, and examples of industrial involvement in processing and utilization of these alloys are briefly mentioned.

  18. Effects of Microalloying on the Microstructures and Mechanical Properties of Directionally Solidified Ni-33(at.%)Al-31Cr-3Mo Eutectic Alloys Investigated

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel; Raj, Sai V.; Locci, Ivan E.; Salem, Jonathan A.

    2002-01-01

    Despite nickel aluminide (NiAl) alloys' attractive combination of oxidation and thermophysical properties, their development as replacements for superalloy airfoils in gas turbine engines has been largely limited by difficulties in developing alloys with an optimum combination of elevated-temperature creep resistance and room-temperature fracture toughness. Alternatively, research has focused on developing directionally solidified NiAl-based in situ eutectic composites composed of NiAl and (Cr,Mo) phases in order to obtain a desirable combination of properties a systematic investigation was undertaken at the NASA Glenn Research Center to examine the effects of small additions of 11 alloying elements (Co, Cu, Fe, Hf, Mn, Nb, Re, Si, Ta, Ti, and Zr) in amounts varying from 0.25 to 1.0 at.% on the elevated-temperature strength and room-temperature fracture toughness of directionally solidified Ni-33Al-31Cr-3Mo eutectic alloy. The alloys were grown at 12.7 mm/hr, where the unalloyed eutectic base alloy exhibited a planar eutectic microstructure. The different microstructures that formed because of these fifth-element additions are included in the table. The additions of these elements even in small amounts resulted in the formation of cellular microstructures, and in some cases, dendrites and third phases were observed. Most of these elemental additions did not improve either the elevated-temperature strength or the room-temperature fracture toughness over that of the base alloy. However, small improvements in the compression strength were observed between 1200 and 1400 K when 0.5 at.% Hf and 0.25 at.% Ti were added to the base alloy. The results of this study suggest that the microalloying of Ni-33Al-31Cr-3Mo will not significantly improve either its elevatedtemperature strength or its room-temperature fracture toughness. Thus, any improvements in these properties must be acquired by changing the processing conditions.

  19. Structural and dynamical properties of liquid Al-Au alloys

    NASA Astrophysics Data System (ADS)

    Peng, H. L.; Voigtmann, Th.; Kolland, G.; Kobatake, H.; Brillo, J.

    2015-11-01

    We investigate temperature- and composition-dependent structural and dynamical properties of Al-Au melts. Experiments are performed to obtain accurate density and viscosity data. The system shows a strong negative excess volume, similar to other Al-based binary alloys. We develop a molecular-dynamics (MD) model of the melt based on the embedded-atom method (EAM), gauged against the available experimental liquid-state data. A rescaling of previous EAM potentials for solid-state Au and Al improves the quantitative agreement with experimental data in the melt. In the MD simulation, the admixture of Au to Al can be interpreted as causing a local compression of the less dense Al system, driven by less soft Au-Au interactions. This local compression provides a microscopic mechanism explaining the strong negative excess volume of the melt. We further discuss the concentration dependence of self- and interdiffusion and viscosity in the MD model. Al atoms are more mobile than Au, and their increased mobility is linked to a lower viscosity of the melt.

  20. High-Temperature Oxidation-Resistant and Low Coefficient of Thermal Expansion NiAl-Base Bond Coat Developed for a Turbine Blade Application

    NASA Technical Reports Server (NTRS)

    2003-01-01

    Many critical gas turbine engine components are currently made from Ni-base superalloys that are coated with a thermal barrier coating (TBC). The TBC consists of a ZrO2-based top coat and a bond coat that is used to enhance the bonding between the superalloy substrate and the top coat. MCrAlY alloys (CoCrAlY and NiCrAlY) are currently used as bond coats and are chosen for their very good oxidation resistance. TBC life is frequently limited by the oxidation resistance of the bond coat, along with a thermal expansion mismatch between the metallic bond coat and the ceramic top coat. The aim of this investigation at the NASA Glenn Research Center was to develop a new longer life, higher temperature bond coat by improving both the oxidation resistance and the thermal expansion characteristics of the bond coat. Nickel aluminide (NiAl) has excellent high-temperature oxidation resistance and can sustain a protective Al2O3 scale to longer times and higher temperatures in comparison to MCrAlY alloys. Cryomilling of NiAl results in aluminum nitride (AlN) formation that reduces the coefficient of thermal expansion (CTE) of the alloy and enhances creep strength. Thus, additions of cryomilled NiAl-AlN to CoCrAlY were examined as a potential bond coat. In this work, the composite alloy was investigated as a stand-alone substrate to demonstrate its feasibility prior to actual use as a coating. About 85 percent of prealloyed NiAl and 15 percent of standard commercial CoCrAlY alloys were mixed and cryomilled in an attritor with stainless steel balls used as grinding media. The milling was carried out in the presence of liquid nitrogen. The milled powder was consolidated by hot extrusion or by hot isostatic pressing. From the consolidated material, oxidation coupons, four-point bend, CTE, and tensile specimens were machined. The CTE measurements were made between room temperature and 1000 C in an argon atmosphere. It is shown that the CTE of the NiAl-AlN-CoCrAlY composite bond coat

  1. Alloy hardening and softening in binary molybdenum alloys as related to electron concentration

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1972-01-01

    An investigation was conducted to determine the effects of alloy additions of hafnium, tantalum, tungsten, rhenium, osmium, iridium, and platinum on hardness of molybdenum. Special emphasis was placed on alloy softening in these binary molybdenum alloys. Results showed that alloy softening was produced by those elements having an excess of s+d electrons compared to molybdenum, while those elements having an equal number or fewer s+d electrons that molybdenum failed to produce alloy softening. Alloy softening and alloy hardening can be correlated with the difference in number of s+d electrons of the solute element and molybdenum.

  2. High strength forgeable tantalum base alloy

    NASA Technical Reports Server (NTRS)

    Buckman, R. W., Jr.

    1975-01-01

    Increasing tungsten content of tantalum base alloy to 12-15% level will improve high temperature creep properties of existing tantalum base alloys while retaining their excellent fabrication and welding characteristics.

  3. Imprinting bulk amorphous alloy at room temperature

    PubMed Central

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; Lograsso, Thomas A.; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-01-01

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. Our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment. PMID:26563908

  4. Imprinting bulk amorphous alloy at room temperature

    SciTech Connect

    Kim, Song-Yi; Park, Eun-Soo; Ott, Ryan T.; Lograsso, Thomas A.; Huh, Moo-Young; Kim, Do-Hyang; Eckert, Jürgen; Lee, Min-Ha

    2015-11-13

    We present investigations on the plastic deformation behavior of a brittle bulk amorphous alloy by simple uniaxial compressive loading at room temperature. A patterning is possible by cold-plastic forming of the typically brittle Hf-based bulk amorphous alloy through controlling homogenous flow without the need for thermal energy or shaping at elevated temperatures. The experimental evidence suggests that there is an inconsistency between macroscopic plasticity and deformability of an amorphous alloy. Moreover, imprinting of specific geometrical features on Cu foil and Zr-based metallic glass is represented by using the patterned bulk amorphous alloy as a die. These results demonstrate the ability of amorphous alloys or metallic glasses to precisely replicate patterning features onto both conventional metals and the other amorphous alloys. In conclusion, our work presents an avenue for avoiding the embrittlement of amorphous alloys associated with thermoplastic forming and yields new insight the forming application of bulk amorphous alloys at room temperature without using heat treatment.

  5. MATE (Materials for Advanced Turbine Engines) Program, Project 3. Volume 2: Design, fabrication and evaluation of an oxide dispersion strengthened sheet alloy combustor liner

    NASA Technical Reports Server (NTRS)

    Bose, S.; Sheffler, K. D.

    1988-01-01

    The suitability of wrought oxide dispersion strengthened (ODS) superalloy sheet for gas turbine engine combustor applications was evaluated. Two yttria (Y2O3) dispersion strengthened alloys were evaluated; Incoloy MA956 and Haynes Development Alloy (HDA) 8077 (NiCrAl base). Preliminary tests showed both alloys to be potentially viable combustor materials, with neither alloy exhibiting a significant advantage over the other. MA956 was selected as the final alloy based on manufacturing reproducibility for evaluation as a burner liner. A hybrid PW2037 inner burner liner containing MA956 and Hastelloy X components and using a louvered configuration was designed and constructed. The louvered configuration was chosen because of field experience and compatibility with the bill of material PW2037 design. The simulated flight cycle for the ground based engine tests consisted of 4.5 min idle, 1.5 min takeoff and intermediate conditions in a PW2037 engine with average uncorrected combustor exit temperature of 1527 C. Post test evaluation consisting of visual observations and fluorescent penetrant inspections was conducted after 500 cycles of testing. No loss of integrity in the burner liner was shown.

  6. Precipitation Sequence of a SiC Particle Reinforced Al-Mg-Si Alloy Composite

    NASA Astrophysics Data System (ADS)

    Shen, Rujuan; Wang, Yihan; Guo, Baisong; Song, Min

    2016-11-01

    In this study, the precipitation sequence of a 5 vol.% SiC particles reinforced Al-1.12 wt.%Mg-0.77 wt.%Si alloy composite fabricated by traditional powder metallurgy method was investigated by transmission electron microscopy and hardness measurements. The results indicated that the addition of SiC reinforcements not only suppresses the initial aging stage but also influences the subsequent precipitates. The precipitation sequence of the composite aged at 175 °C can be described as: Guinier-Preston (G.P.) zone → β″ → β' → B', which was confirmed by high-resolution transmission electron microscopy. This work might provide the guidance for the design and fabrication of hardenable automobile body sheet by Al-based composites with enhanced mechanical properties.

  7. Shape memory alloys. Ultralow-fatigue shape memory alloy films.

    PubMed

    Chluba, Christoph; Ge, Wenwei; Lima de Miranda, Rodrigo; Strobel, Julian; Kienle, Lorenz; Quandt, Eckhard; Wuttig, Manfred

    2015-05-29

    Functional shape memory alloys need to operate reversibly and repeatedly. Quantitative measures of reversibility include the relative volume change of the participating phases and compatibility matrices for twinning. But no similar argument is known for repeatability. This is especially crucial for many future applications, such as artificial heart valves or elastocaloric cooling, in which more than 10 million transformation cycles will be required. We report on the discovery of an ultralow-fatigue shape memory alloy film system based on TiNiCu that allows at least 10 million transformation cycles. We found that these films contain Ti2Cu precipitates embedded in the base alloy that serve as sentinels to ensure complete and reproducible transformation in the course of each memory cycle.

  8. Tarnish of dental alloys by oral microorganisms.

    PubMed

    Vaidyanathan, T K; Vaidyanathan, J; Linke, H A; Schulman, A

    1991-11-01

    Five dental alloys, on exposure to blood and chocolate media with and without inoculated microorganisms, showed varying degrees of tarnish. The results indicated a composition-dependent tarnish behavior of alloys in microorganism-inoculated media, indicating a potential role for the oral microorganisms in inducing clinically observed tarnish of dental alloys. Actinomyces viscosus and periodontal pocket specimens show a similarity in their activity to induce tarnish in base metal-containing dental alloys.

  9. Nickel aluminide alloys with improved weldability

    DOEpatents

    Santella, Michael L.; Goodwin, Gene M.

    1995-05-09

    Weldable nickel aluminide alloys which are essentially free, if not entirely free, of weld hot cracking are provided by employing zirconium concentrations in these alloys of greater than 2.6 wt. % or sufficient to provide a substantial presence of Ni--Zr eutectic phase in the weld so as to prevent weld hot cracking. Weld filler metals formed from these so modified nickel aluminide alloys provide for crack-free welds in previously known nickel aluminide alloys.

  10. Nickel aluminide alloys with improved weldability

    DOEpatents

    Santella, M.L.; Goodwin, G.M.

    1995-05-09

    Weldable nickel aluminide alloys which are essentially free, if not entirely free, of weld hot cracking are provided by employing zirconium concentrations in these alloys of greater than 2.6 wt. % or sufficient to provide a substantial presence of Ni--Zr eutectic phase in the weld so as to prevent weld hot cracking. Weld filler metals formed from these so modified nickel aluminide alloys provide for crack-free welds in previously known nickel aluminide alloys. 5 figs.

  11. HEAT TREATED U-Nb ALLOYS

    DOEpatents

    McGeary, R.K.; Justusson, W.M.

    1959-11-24

    A fuel element for a nuclear reactor is described comprising an alloy containing uranium and from 7 to 20 wt.% niobium, the alloy being substantially in the gamma phase and having been produced by working an ingot of the alloy into the desired shape, homogenizing it by annealing it at a temperature in the gamma phase field, and quenching it to retain the gamma phase structure of the alloy.

  12. Contact dermatitis from beryllium in dental alloys.

    PubMed

    Haberman, A L; Pratt, M; Storrs, F J

    1993-03-01

    An increasing number of metals with the potential to cause allergic contact dermatitis have found their way into dental alloys for economic and practical reasons. 2 patients are reported who developed gingivitis adjacent to the Rexillium III alloy in their dental prostheses. Patch testing demonstrated positive reactions to beryllium sulfate, a component of the alloy. Components of dental alloys and the mechanism of the contact dermatitis are discussed.

  13. Self-disintegrating Raney metal alloys

    DOEpatents

    Oden, Laurance L.; Russell, James H.

    1979-01-01

    A method of preparing a Raney metal alloy which is capable of self-disintegrating when contacted with water vapor. The self-disintegrating property is imparted to the alloy by incorporating into the alloy from 0.4 to 0.8 weight percent carbon. The alloy is useful in forming powder which can be converted to a Raney metal catalyst with increased surface area and catalytic activity.

  14. HIGH-TEMPERATURE OXIDATION PROTECTIVE COATINGS FOR VANADIUM-BASE ALLOYS

    DTIC Science & Technology

    SILICIDES , SILICON COATINGS , THIN FILM STORAGE DEVICES, TITANIUM ALLOYS, VAPOR PLATING, YTTRIUM COMPOUNDS, ZINC ALLOYS, ZINC COATINGS ....ANTIOXIDANTS, *METAL COATINGS , *REFRACTORY COATINGS , *VANADIUM ALLOYS, ALUMINUM ALLOYS, CERAMIC COATINGS , CHROMIUM ALLOYS, CLADDING, FLAME SPRAYING...HIGH TEMPERATURE, INTERMETALLIC COMPOUNDS, IODINE COMPOUNDS, IRON ALLOYS, MAGNESIUM ALLOYS, NICKEL ALLOYS, NICKEL COMPOUNDS, NIOBIUM ALLOYS, OXIDES

  15. Oxidation of low cobalt alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.

    1982-01-01

    Four high temperature alloys: U-700, Mar M-247, Waspaloy and PM/HIP U-700 were modified with various cobalt levels ranging from 0 percent to their nominal commercial levels. The alloys were then tested in cyclic oxidation in static air at temperatures ranging from 1000 to 1150 C at times from 500 to 100 1 hour cycles. Specific weight change with time and X-ray diffraction analyses of the oxidized samples were used to evaluate the alloys. The alloys tend to be either Al2O3/aluminate spinel or Cr2O3/chromite spinel formers depending on the Cr/Al ratio in the alloy. Waspaloy with a ratio of 15:1 is a strong Cr2O3 former while this U-700 with a ratio of 3.33:1 tends to form mostly Cr2O3 while Mar M-247 with a ratio of 1.53:1 is a strong Al2O3 former. The best cyclic oxidation resistance is associated with the Al2O3 formers. The cobalt levels appear to have little effect on the oxidation resistance of the Al2O3/aluminate spinel formers while any tendency to form Cr2O3 is accelerated with increased cobalt levels and leads to increased oxidation attack.

  16. Superconducting compounds and alloys research

    NASA Technical Reports Server (NTRS)

    Otto, G.

    1975-01-01

    Resistivity measurements as a function of temperature were performed on alloys of the binary material system In sub(1-x) Bi sub x for x varying between 0 and 1. It was found that for all single-phase alloys (the pure elements, alpha-In, and the three intermetallic compounds) at temperatures sufficiently above the Debye-temperature, the resistivity p can be expressed as p = a sub o T(n), where a sub o and n are composition-dependent constants. The same exponential relationship can also be applied for the sub-system In-In2Bi, when the two phases are in compositional equilibrium. Superconductivity measurements on single and two-phase alloys can be explained with respect to the phase diagram. There occur three superconducting phases (alpha-In, In2Bi, and In5Bi3) with different transition temperatures in the alloying system. The magnitude of the transition temperatures for the various intermetallic phases of In-Bi is such that the disappearance or occurrence of a phase in two component alloys can be demonstrated easily by means of superconductivity measurements.

  17. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites.

    PubMed

    Wang, Z; Georgarakis, K; Nakayama, K S; Li, Y; Tsarkov, A A; Xie, G; Dudina, D; Louzguine-Luzgin, D V; Yavari, A R

    2016-04-12

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

  18. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    NASA Astrophysics Data System (ADS)

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-04-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses.

  19. Microstructure and mechanical behavior of metallic glass fiber-reinforced Al alloy matrix composites

    PubMed Central

    Wang, Z.; Georgarakis, K.; Nakayama, K. S.; Li, Y.; Tsarkov, A. A.; Xie, G.; Dudina, D.; Louzguine-Luzgin, D. V.; Yavari, A. R.

    2016-01-01

    Metallic glass-reinforced metal matrix composites are an emerging class of composite materials. The metallic nature and the high mechanical strength of the reinforcing phase offers unique possibilities for improving the engineering performance of composites. Understanding the structure at the amorphous/crystalline interfaces and the deformation behavior of these composites is of vital importance for their further development and potential application. In the present work, Zr-based metallic glass fibers have been introduced in Al7075 alloy (Al-Zn-Mg-Cu) matrices using spark plasma sintering (SPS) producing composites with low porosity. The addition of metallic glass reinforcements in the Al-based matrix significantly improves the mechanical behavior of the composites in compression. High-resolution TEM observations at the interface reveal the formation of a thin interdiffusion layer able to provide good bonding between the reinforcing phase and the Al-based matrix. The deformation behavior of the composites was studied, indicating that local plastic deformation occurred in the matrix near the glassy reinforcements followed by the initiation and propagation of cracks mainly through the matrix. The reinforcing phase is seen to inhibit the plastic deformation and retard the crack propagation. The findings offer new insights into the mechanical behavior of metal matrix composites reinforced with metallic glasses. PMID:27067824

  20. PREPARATION OF URANIUM-ALUMINUM ALLOYS

    DOEpatents

    Moore, R.H.

    1962-09-01

    A process is given for preparing uranium--aluminum alloys from a solution of uranium halide in an about equimolar molten alkali metal halide-- aluminum halide mixture and excess aluminum. The uranium halide is reduced and the uranium is alloyed with the excess aluminum. The alloy and salt are separated from each other. (AEC)

  1. High-temperature nickel-brazing alloy

    NASA Technical Reports Server (NTRS)

    Powell, A. H.; Thompson, S. R.

    1970-01-01

    Gold-nickel brazing alloy, with 5 percent indium added to depress the melting point, is used for brazing of nickel-clad silver electrical conductors which operate at temperatures to 1200 deg F. Alloy has low resistivity, requires no flux, and is less corrosive than other gold-nickel, gold-copper alloys.

  2. High-niobium titanium aluminide alloys

    SciTech Connect

    Huang, S.C.

    1992-02-18

    This patent describes an aged niobium modified titanium aluminum alloy, the alloy consisting essentially of titanium, aluminum, and niobium in the following atomic ratio: Ti{sub 48-37}Al{sub 46-49}Nb{sub 6-14}, the alloy having been prepared by ingot metallurgy.

  3. 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.

  4. 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.

  5. Post-soldering of nonprecious alloys.

    PubMed

    Saxton, P L

    1980-05-01

    A repeatable post-soldering technique for a nonprecious alloy has been described. With proper metal design, nonprecious alloy crowns can be soldered in a standard vacuum porcelain furnace. Scanning electron micrographs and EDXA confirm that a good union has taken place between the gold solder and nickel alloy.

  6. High strength uranium-tungsten alloy process

    DOEpatents

    Dunn, Paul S.; Sheinberg, Haskell; Hogan, Billy M.; Lewis, Homer D.; Dickinson, James M.

    1990-01-01

    Alloys of uranium and tungsten and a method for making the alloys. The amount of tungsten present in the alloys is from about 4 wt % to about 35 wt %. Tungsten particles are dispersed throughout the uranium and a small amount of tungsten is dissolved in the uranium.

  7. High strength uranium-tungsten alloys

    DOEpatents

    Dunn, Paul S.; Sheinberg, Haskell; Hogan, Billy M.; Lewis, Homer D.; Dickinson, James M.

    1991-01-01

    Alloys of uranium and tungsten and a method for making the alloys. The amount of tungsten present in the alloys is from about 4 wt % to about 35 wt %. Tungsten particles are dispersed throughout the uranium and a small amount of tungsten is dissolved in the uranium.

  8. Improved thermal treatment of aluminum alloy 7075

    NASA Technical Reports Server (NTRS)

    Cocks, F. H.

    1968-01-01

    Newly developed tempering treatment considerably increases the corrosion resistance of 7075-T6 alloy and concomitantly preserves its yield strength. The results of tests on samples of the alloy subjected to the above treatments show that when the overaging period is 12 hours /at 325 degrees F/, the alloy exhibits a yield strength of 73,000 psi.

  9. NiAl-based Polyphase in situ Composites in the NiAl-Ta-X (X = Cr, Mo, or V) Systems

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    Polyphase in situ composites were generated by directional solidification of ternary eutectics. This work was performed to discover if a balance of properties could be produced by combining the NiAl-Laves phase and the NiAl-refractory metal phase eutectics. The systems investigated were the Ni-Al-Ta-X (X = Cr, Mo, or V) alloys. Ternary eutectics were found in each of these systems and the eutectic composition, temperature, and morphology were determined. The ternary eutectic systems examined were the NiAl-NiAlTa-(Mo, Ta), NiAl-(Cr, Al) NiTa-Cr, and the NiAl-NiAlTa-V systems. Each eutectic consists of NiAl, a C14 Laves phase, and a refractory metal phase. Directional solidification was performed by containerless processing techniques in a levitation zone refiner to minimize alloy contamination. Room temperature fracture toughness of these materials was determined by a four-point bend test. Preliminary creep behavior was determined by compression tests at elevated temperatures, 1100-l400 K. Of the ternary eutectics, the one in the NiAl-Ta-Cr system was found to be the most promising. The fracture toughness of the NiAl-(Cr, Al)NiTa-Cr eutectic was intermediate between the values of the NiAl-NiAlTa eutectic and the NiAl-Cr eutectic. The creep strength of this ternary eutectic was similar to or greater than that of the NiAl-Cr eutectic.

  10. Effect of a ductility layer on the tensile strength of TiAl-based multilayer composite sheets prepared by EB-PVD

    SciTech Connect

    Zhang, Rubing; Zhang, Yaoyao; Liu, Qiang; Chen, Guiqing; Zhang, Deming

    2014-09-15

    TiAl/Nb and TiAl/NiCoCrAl laminate composite sheets with a thickness of 0.4–0.6 mm and dimensions of 150 mm × 100 mm were successfully fabricated by electron beam physical vapor deposition. The microstructures of the sheets were examined, and their mechanical properties were compared with those of TiAl monolithic sheet produced by electron beam physical vapor deposition. Tensile testing was performed at room temperature and 750 °C, and the fracture surfaces were examined by scanning electron microscopy. Among the three microlaminate sheets, the TiAl/NiCoCrAl micro-laminate sheet had the best comprehensive properties at room temperature, and the TiAl/Nb micro-laminate sheet showed the ideal high-temperature strength and plasticity at 750 °C. The result was discussed in terms of metal strengthening mechanism. - Highlights: • TiAl-based multilayer foils was fabricated successfully by using EB-PVD method; • The tensile properties and micro-fracture morphologies of the sheet were investigated; • The deformation behavior of the multilayer foils was discussed.

  11. Co{sub 2}FeAl based magnetic tunnel junctions with BaO and MgO/BaO barriers

    SciTech Connect

    Rogge, J.; Schmalhorst, J.; Hütten, A.; Hetaba, W.

    2015-07-15

    We succeed to integrate BaO as a tunneling barrier into Co{sub 2}FeAl based magnetic tunnel junctions (MTJs). By means of Auger electron spectroscopy it could be proven that the applied annealing temperatures during BaO deposition and afterwards do not cause any diffusion of Ba neither into the lower Heusler compound lead nor into the upper Fe counter electrode. Nevertheless, a negative tunnel magnetoresistance (TMR) ratio of -10% is found for Co{sub 2}FeAl (24 nm) / BaO (5 nm) / Fe (7 nm) MTJs, which can be attributed to the preparation procedure and can be explained by the formation of Co- and Fe-oxides at the interfaces between the Heusler and the crystalline BaO barrier by comparing with theory. Although an amorphous structure of the BaO barrier seems to be confirmed by high-resolution transmission electron microscopy (TEM), it cannot entirely be ruled out that this is an artifact of TEM sample preparation due to the sensitivity of BaO to moisture. By replacing the BaO tunneling barrier with an MgO/BaO double layer barrier, the electric stability could effectively be increased by a factor of five. The resulting TMR effect is found to be about +20% at room temperature, although a fully antiparallel state has not been realized.

  12. The investigation of Ni-Al and Co-Al based layered double hydroxides and their derived mixed oxides thin films deposited by pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Birjega, R.; Matei, A.; Filipescu, M.; Stokker-Cheregi, F.; Luculescu, C.; Colceag, D.; Zavoianu, R.; Pavel, O. D.; Dinescu, M.

    2013-08-01

    Layered Double Hydroxides (LDHs) are host-guest materials consisting of positively charged metal/hydroxides sheets with intercalated anions and water molecules. LDHs can be described by the generic formula [[ṡmHO and their structure is formed by layers containing divalent cations (M2+: Mg, Zn, Ni, Co,…) and trivalent cations (M3+: Al, Ga, Cr,…) with an octahedral coordination. LDH films with well-oriented structure and controlled thickness are needed for numerous applications like sensors, protective coatings, catalysts, components for optoelectronics etc. In this work, we report on the deposition of Ni-Al and Co-Al based LDHs and their derived mixed oxides by pulsed laser deposition as a new approach to fabricate oriented LDHs or highly dispersed metallic mixed oxides. The influence of the laser characteristics, such as wavelength and fluence, on the films properties was studied. The films investigation techniques were X-Ray Diffraction, Atomic Force Microscopy, Scanning Electron Microscopy combined with energy dispersive X-ray analysis, and Secondary Ions Mass Spectrometry.

  13. METHOD OF DISSOLVING REFRACTORY ALLOYS

    DOEpatents

    Helton, D.M.; Savolainen, J.K.

    1963-04-23

    This patent relates to the dissolution of alloys of uranium with zirconium, thorium, molybdenum, or niobium. The alloy is contacted with an anhydrous solution of mercuric chloride in a low-molecular-weight monohydric alcohol to produce a mercury-containing alcohol slurry. The slurry is then converted to an aqueous system by adding water and driving off the alcohol. The resulting aqueous slurry is electrolyzed in the presence of a mercury cathode to remove the mercury and produce a uranium-bearing aqueous solution. This process is useful for dissolving irradiated nuclear reactor fuels for radiochemical reprocessing by solvent extraction. In addition, zirconium-alloy cladding is selectively removed from uranium dioxide fuel compacts by this means. (AEC)

  14. Method for calculating alloy energetics

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John; Smith, John R.

    1992-01-01

    A semiempirical method for the computation of alloy energies is introduced. It is based on the equivalent-crystal theory of defect-formation energies in elemental solids. The method is both simple and accurate. Heats of formation as a function of composition are computed for some binary alloys of Cu, Ni, Al, Ag, Pd, Pt, and Au using the heats of solution in the dilute limit as experimental input. The separation of heats into strain and chemical components helps in understanding the energetics. In addition, lattice-parameter contractions seen in solid solutions of Ag and Au are accurately predicted. Good agreement with experiment is obtained in all cases.

  15. Alloy 718 for Oilfield Applications

    NASA Astrophysics Data System (ADS)

    deBarbadillo, John J.; Mannan, Sarwan K.

    2012-02-01

    Alloy 718 (UNS N07718) was developed for use in aircraft gas turbine engines, but its unique combination of room-temperature strength and aqueous corrosion resistance made it a candidate for oilfield fasteners, valves, drill tools, and completion equipment. As well environments became more severe, stress corrosion and hydrogen embrittlement failures in production equipment drove the evolution of the composition and microstructure that distinguish today's oilfield-grade 718 from aerospace grades. This paper reviews the development of the grade and its applications and describes some of its unique characteristics, testing, and manufacturing methods as well as newer alloys designed for high-pressure high-temperature (HPHT) conditions.

  16. High strength, tough alloy steel

    DOEpatents

    Thomas, Gareth; Rao, Bangaru V. N.

    1979-01-01

    A high strength, tough alloy steel is formed by heating the steel to a temperature in the austenite range (1000.degree.-1100.degree. C.) to form a homogeneous austenite phase and then cooling the steel to form a microstructure of uniformly dispersed dislocated martensite separated by continuous thin boundary films of stabilized retained austenite. The steel includes 0.2-0.35 weight % carbon, at least 1% and preferably 3-4.5% chromium, and at least one other substitutional alloying element, preferably manganese or nickel. The austenite film is stable to subsequent heat treatment as by tempering (below 300.degree. C.) and reforms to a stable film after austenite grain refinement.

  17. PROCESS OF DISSOLVING ZIRCONIUM ALLOYS

    DOEpatents

    Shor, R.S.; Vogler, S.

    1958-01-21

    A process is described for dissolving binary zirconium-uranium alloys where the uranium content is about 2%. In prior dissolution procedures for these alloys, an oxidizing agent was added to prevent the precipitation of uranium tetrafluoride. In the present method complete dissolution is accomplished without the use of the oxidizing agent by using only the stoichiometric amount or slight excess of HF required by the zirconium. The concentration of the acid may range from 2M to 10M and the dissolution is advatageously carried out at a temperature of 80 deg C.

  18. [Microbiological corrosion of aluminum alloys].

    PubMed

    Smirnov, V F; Belov, D V; Sokolova, T N; Kuzina, O V; Kartashov, V R

    2008-01-01

    Biological corrosion of ADO quality aluminum and aluminum-based construction materials (alloys V65, D16, and D16T) was studied. Thirteen microscopic fungus species and six bacterial species proved to be able to attack aluminum and its alloys. It was found that biocorrosion of metals by microscopic fungi and bacteria was mediated by certain exometabolites. Experiments on biocorrosion of the materials by the microscopic fungus Alternaria alternata, the most active biodegrader, demonstrated that the micromycete attack started with the appearance of exudate with pH 8-9 on end faces of the samples.

  19. Protective claddings for high strength chromium alloys

    NASA Technical Reports Server (NTRS)

    Collins, J. F.

    1971-01-01

    The application of a Cr-Y-Hf-Th alloy as a protective cladding for a high strength chromium alloy was investigated for its effectiveness in inhibiting nitrogen embrittlement of a core alloy. Cladding was accomplished by a combination of hot gas pressure bonding and roll cladding techniques. Based on bend DBTT, the cladding alloy was effective in inhibiting nitrogen embrittlement of the chromium core alloy for up to 720 ks (200hours) in air at 1422 K (2100 F). A significant increase in the bend DBTT occurred with longer time exposures at 1422 K or short time exposures at 1589 K (2400 F).

  20. Liquid metal ion source and alloy

    DOEpatents

    Clark, Jr., William M.; Utlaut, Mark W.; Behrens, Robert G.; Szklarz, Eugene G.; Storms, Edmund K.; Santandrea, Robert P.; Swanson, Lynwood W.

    1988-10-04

    A liquid metal ion source and alloy, wherein the species to be emitted from the ion source is contained in a congruently vaporizing alloy. In one embodiment, the liquid metal ion source acts as a source of arsenic, and in a source alloy the arsenic is combined with palladium, preferably in a liquid alloy having a range of compositions from about 24 to about 33 atomic percent arsenic. Such an alloy may be readily prepared by a combustion synthesis technique. Liquid metal ion sources thus prepared produce arsenic ions for implantation, have long lifetimes, and are highly stable in operation.

  1. ZIRCONIUM-TITANIUM-BERYLLIUM BRAZING ALLOY

    DOEpatents

    Gilliland, R.G.; Patriarca, P.; Slaughter, G.M.; Williams, L.C.

    1962-06-12

    A new and improved ternary alloy is described which is of particular utility in braze-bonding parts made of a refractory metal selected from Group IV, V, and VI of the periodic table and alloys containing said metal as a predominating alloying ingredient. The brazing alloy contains, by weight, 40 to 50 per cent zirconium, 40 to 50 per cent titanium, and the balance beryllium in amounts ranging from 1 to 20 per cent, said alloy having a melting point in the range 950 to 1400 deg C. (AEC)

  2. Alloy softening in binary iron solid solutions

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1976-01-01

    An investigation was conducted to determine softening and hardening behavior in 19 binary iron-alloy systems. Microhardness tests were conducted at four temperatures in the range 77 to 411 K. Alloy softening was exhibited by 17 of the 19 alloy systems. Alloy softening observed in 15 of the alloy systems was attributed to an intrinsic mechanism, believed to be lowering of the Peierls (lattice friction) stress. Softening and hardening rates could be correlated with the atomic radius ratio of solute to iron. Softening observed in two other systems was attributed to an extrinsic mechanism, believed to be associated with scavenging of interstitial impurities.

  3. Nd:YAG laser welding aluminum alloys

    SciTech Connect

    Jimenez, E. Jr.

    1992-02-01

    Autogenous Nd:YAG laser welding wrought 4047, 1100, 3003, 2219, 5052, 5086, 5456, and 6061 and cast A356 aluminum alloys to cast A356 aluminum alloy in restrained annular weld joints was investigated. The welds were 12.7 mm (0.375 in.) and 9.5 mm (0.375 in.) diameter with approximately 0.30 mm (0.012 in.) penetration. This investigation determined 4047 aluminum alloy to be the optimum alloy for autogenous Nd:YAG laser welding to cast A356 aluminum alloy. This report describes the investigation and its results.

  4. Semiempirical Analysis of Surface Alloy Formation

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John; Ibanez-Meier, Rodrigo

    1995-01-01

    The BFS method for alloys is applied to the study of surface alloy formation. This method was previously used to examine the experimental STM observation of surface alloying of Au on Ni(110) for low Au coverages by means of a numerical simulation. In this work, we extend the study to include other cases of surface alloying for immiscible as well as miscible metals. All binary combinations of Ni, Au, Cu, and Al are considered and the simulation results are compared to experiment when data is available. The driving mechanisms of surface alloy formation are then discussed in terms of the BFS method and the available results.

  5. Alloy softening in binary iron solid solutions

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R.

    1976-01-01

    An experimental study was conducted to determine whether alloy softening in Fe alloys is dependent on electron concentration and to provide a direct comparison of alloy softening and hardening in several binary Fe alloy systems having the same processing history. Alloy additions to Fe included the elements in the Periods 4-6 and the Groups IV-VIII with the exception of technetium. A total of 19 alloy systems was investigated, and hardness testing was the primary means of evaluation. Testing was carried out at four temperatures over a homologous temperature range of 0.043-0.227 times the absolute melting temperature of unalloyed Fe. Major conclusions are that the atomic radius ratio of solute-to-Fe is the key factor in controlling low-temperature hardness of the binary Fe alloys and that alloy softening rates at 77 K and alloy hardening rates at 411 K are correlated with this atomic radius ratio for 15 of the binary alloy systems. Mechanisms of alloy softening and hardening are proposed.

  6. Environmental fatigue in aluminum-lithium alloys

    NASA Technical Reports Server (NTRS)

    Piascik, Robert S.

    1992-01-01

    Aluminum-lithium alloys exhibit similar environmental fatigue crack growth characteristics compared to conventional 2000 series alloys and are more resistant to environmental fatigue compared to 7000 series alloys. The superior fatigue crack growth behavior of Al-Li alloys 2090, 2091, 8090, and 8091 is due to crack closure caused by tortuous crack path morphology and crack surface corrosion products. At high R and reduced closure, chemical environment effects are pronounced resulting in accelerated near threshold da/dN. The beneficial effects of crack closure are minimized for small cracks resulting in rapid growth rates. Limited data suggest that the 'chemically small crack' effect, observed in other alloy system, is not pronounced in Al-Li alloys. Modeling of environmental fatigue in Al-Li-Cu alloys related accelerated fatigue crack growth in moist air and salt water to hydrogen embrittlement.

  7. Passive Corrosion Behavior of Alloy 22

    SciTech Connect

    Rebak, R B; Payer, J H

    2006-01-10

    Alloy 22 (N06022) was designed to stand the most aggressive industrial applications, including both reducing and oxidizing acids. Even in the most aggressive environments, if the temperature is lower than 150 F (66 C) Alloy 22 would remain in the passive state having particularly low corrosion rates. In multi-ionic solutions that may simulate the behavior of concentrated ground water, even at near boiling temperatures, the corrosion rate of Alloy 22 is only a few nanometers per year because the alloy is in the complete passive state. The corrosion rate of passive Alloy 22 decreases as the time increases. Immersion corrosion testing also show that the newer generation of Ni-Cr-Mo alloys may offer a better corrosion resistance than Alloy 22 only in some highly aggressive conditions such as in hot acids.

  8. Passive Corrosion Behavior of Alloy 22

    SciTech Connect

    R.B. Rebak; J.H. Payer

    2006-01-20

    Alloy 22 (NO6022) was designed to stand the most aggressive industrial applications, including both reducing and oxidizing acids. Even in the most aggressive environments, if the temperature is lower than 150 F (66 C) Alloy 22 would remain in the passive state having particularly low corrosion rates. In multi-ionic solutions that may simulate the behavior of concentrated ground water, even at near boiling temperatures, the corrosion rate of Alloy 22 is only a few nano-meters per year because the alloy is in the complete passive state. The corrosion rate of passive Alloy 22 decreases as the time increases. Immersion corrosion testing also show that the newer generation of Ni-Cr-Mo alloys may offer a better corrosion resistance than Alloy 22 only in some highly aggressive conditions such as in hot acids.

  9. Informatics Aided Design for Alloys

    DTIC Science & Technology

    2009-02-28

    different conditions. Figure 5 shows some preliminary results for developing new Ti alloys with desired phase transformation ( martensitic transformation from...h representing the extracted factors from that information. The dark yellow circle suggests the range for martensitic transformation from ß to cc...high temperature structural applications. b) Discovery of new structure-property correlations in high temperature multicomponent oxides and nitrides

  10. Machine Casting of Ferrous Alloys

    DTIC Science & Technology

    1976-11-01

    ii TABLE OF CONTENTS ABSTRACT .......................... Introduction ........................ Continuous Rheocasting ...ferrous alloys is fully and reliably operational. The Continuous Rheocaster works dependably in production runs in which typically up to 500 pounds... Rheocast stainless steel and the initiation of large scale Thixocasting runs to test actual die life. More than 3000 pounds of Rheocast stainless

  11. Machine Casting of Ferrous Alloys

    DTIC Science & Technology

    1978-05-01

    produce porosity-free parts and to evaluate the Rheocasting and Thixocasting processes from both a technical and economical point of view. Analytical...and computer models were developed for solutionizing of Rheocast and conventional cast (dendritic) alloys. The predictions were compared with

  12. Machine Casting of Ferrous Alloys

    DTIC Science & Technology

    1977-01-01

    months of the contract period were modified and improved. A new technique was developed for the production of Rheocast ingots of low temperature alloys...important variables in a continuous slurry producer, a Rheocasting apparatus, were identified and the relationship between these variables and the

  13. Introduction to hydrogen in alloys

    SciTech Connect

    Westlake, D.G.

    1980-01-01

    Substitutional alloys, both those that form hydrides and those that do not, are discussed, but with more emphasis on the former than the latter. This overview includes the following closely related subjects: (1) the significant effects of substitutional solutes on the pressure-composition-temperature (PCT) equilibria of metal-hydrogen systems, (2) the changes in thermodynamic properties resulting from differences in atom size and from modifications of electronic structure, (3) attractive and repulsive interactions between H and solute atoms and the effects of such interactions on the pressure dependent solubility for H, (4) H trapping in alloys of Group V metals and its effect on the terminal solubility for H (TSH), (5) some other mechanisms invoked to explain the enhancement (due to alloying) of the (TSH) in Group V metals, and (6) H-impurity complexes in alloys of the metals Ni, Co, and Fe. Some results showing that an enhanced TSH may ameliorate the resistance of a metal to hydrogen embrittlement are presented.

  14. Recent developments in light alloys

    NASA Technical Reports Server (NTRS)

    Woodward, R W

    1920-01-01

    This report is intended to cover the progress that has been made in both the manufacture and utility of light alloys in the United States since the first part of 1919. Duralumin is extensively discussed both as to manufacture and durability.

  15. Alloys formation upon hypervelocity impacts

    NASA Astrophysics Data System (ADS)

    Mandeville, J. C.; Perrin, J. M.; Vidal, L.; Vidal, A.

    Satellite materials exposed to the space environment are indeed valuable detectors for cosmic and man-made solid particles Many investigations have been made to deduce the geometric size shape and dynamic incidence angle parameters of these projectiles from the morphology of the impact features Furthermore the chemical analysis of remnants when they are found inside craters can provide valuable information about the nature and the origin of these particles However interpretation difficulties have made necessary laboratory hypervelocity impact tests A number of impacts with well defined angles of incidence and velocities using calibrated projectiles have been performed on various targets Alloys obviously formed from projectile and targets components are found We have studied the links between the morphologies the physical and chemical properties of these alloys and those of the incident particles and the targets When projectiles and targets are made of pure materials such as in laboratory tests we have found a clear connection between the composition of the alloys and the kinetic energy of the projectiles Explanations using phase diagrams are given An extrapolation to complex materials such as those used in solar arrays is presented Further modelling of the alloys formation upon hypervelocity impacts is proposed

  16. Effect of solution properties, competing ligands, and complexing metal on sorption of tetracyclines on Al-based drinking water treatment residuals.

    PubMed

    Punamiya, Pravin; Sarkar, Dibyendu; Rakshit, Sudipta; Datta, Rupali

    2015-05-01

    In the current batch study, we investigated the effect of solution properties, competing ligands (phosphate (P(V)) and sulfate), and complexing metal (calcium (Ca(2+))) on tetracycline (TTC) and oxytetracycline (OTC) sorption by Al-based drinking water treatment residuals (Al-WTR). The sorption behavior for both TTC and OTC on Al-WTR was pH dependent. The sorption in absence of competing ligands and complexing metal increased with increasing pH up to circum-neutral pH and then decreased at higher pH. The presence of P(V) when added simultaneously had a significant negative effect (p < 0.001) on the sorption of TTC and OTC adsorbed by Al-WTR at higher TTC/OTC:P ratios. However, when P(V) was added after the equilibration of TTC and OTC by Al-WTR, the effect was minimal and insignificant (p > 0.1). The presence of sulfate had a minimal/negligible effect on the sorption of TCs by Al-WTR. A significant negative effect (p < 0.001) on the adsorption of TCs by Al-WTR was observed in the pH range below 5 and at higher TCs:Ca(2+) ratios, probably due to TCs-Ca(2+) complex formation. Fourier transform infrared (FTIR) analysis indicated the possibility of inner-sphere-type bonding by the functional groups of OTC/TTC on Al-WTR surface. Results from the batch sorption study indicate high affinity of Al-WTR for TCs in the pH range 4-8 (majorly encountered pH in the environment) in the presence of competing ligands and complexing metal.

  17. New developments in hardfacing alloys

    SciTech Connect

    Menon, R.

    1996-02-01

    The hardfacing industry has matured substantially since its inception in the early 1920s. Numerous welding alloys have been developed and field proven. By developing a strong working knowledge of available alloys, wear conditions and the specific wear situation, the goal of selecting the proper alloy to prolong service life and fight wear is now more attainable than ever. Hardfacing is the process in which a coating or cladding is applied to a substrate for the main purpose of reducing wear or loss of material by abrasion, impact, erosion, galling and cavitation. Most service environments involve a combination of these factors. The choice of an alloy system depends to a great degree on the nature of the wear process encountered. This can range from a simple low-stress condition to a very complex situation that involves abrasion combined with a corrodant and high temperature. The list of possible wear conditions is outlined below: (1) low-stress abrasion, (2) high-stress abrasion, (3) impact, (4) metal-to-metal wear, (5) erosion, and (6) cavitation erosion. In general, service conditions involve a combination of several of the conditions listed above. In addition to the type of wear, three other factors are also important as far as the severity of the wear condition is concerned. These are: (1) type of abradant, (2) service temperature, and (3) service environment. It is clear that in terms of the nature of the wear process as well as the environmental conditions, service conditions are extremely complex. They are, therefore, difficult to simulate in the laboratory. The selection of hardfacing alloys for an application is based primarily on actual field experiences and these are refined with data gathered with time.

  18. Rare-earth metals (REMs) in nickel aluminide-based alloys: I. Physicochemical laws of interaction in the Ni-Al-REM and Ni x Al y -REM-AE (alloying element) systems

    NASA Astrophysics Data System (ADS)

    Povarova, K. B.; Kazanskaya, N. K.; Drozdov, A. A.; Morozov, A. E.

    2008-02-01

    The data on the Ni-Al- R ( R = REM Sc, Y, La, lanthanides) binary and ternary systems and the interactions of three rare-earth metals (yttrium, lanthanum, cerium) with the main alloying elements (Ti (Zr, Hf), Cr (Mo, W) that are introduced into Ni3Al-based VKNA alloys are analyzed. The binary aluminides of REMs in the Ni-Al- R ternary systems are shown to be in equilibrium with neither NiAl nor Ni3Al. The solid solution of aluminum in RNi5, which penetrates deep into these ternary systems, is the most stable phase in equilibrium with Ni3Al. In the NiAl (Ni3Al)-AE- R systems, REM precipitation (segregation) on various defects and interfaces in nickel aluminides is likely to be the most probable, and REMs are thought to interact with the most active impurities in real alloys (C, O, N), since REMs have a large atomic radius and, thus, are virtually undissolved in nickel, aluminum, and nickel aluminides.

  19. CORROSION OF HIGH-TEMPERATURE ALLOYS

    SciTech Connect

    John P. Hurley; John P. Kay

    1999-10-01

    Five alloys were tested in the presence of water vapor and water vapor with HCl for 1000 hours using simulated combustion gas. Samples were removed at intervals during each test and measured for determination of corrosion rates. One sample of each alloy was examined with a SEM after the completion of each test. Cumulative corrosion depths were similar for the superstainless alloys. Corrosion for Alloy TP310 roughly doubled. Corrosion for the enhanced stainless alloys changed dramatically with the addition of chlorine. Corrosion for Alloy RA85H increased threefold, whereas Alloy TP347HFG showed an eightfold increase. SEM examination of the alloys revealed that water vapor alone allowed the formation of chromium oxide protective layers on the superstainless alloys. The enhanced stainless alloys underwent more corrosion due to greater attack of sulfur. Iron-rich oxide layers were more likely to form, which do not provide protection from further corrosion. The addition of chlorine further increased the corrosion because of its ability to diffuse through the oxide layers and react with iron. This resulted in a broken, discontinuous, and loose oxide layer that offered less protection. Niobium, although added to aid in creep strength, was found to be detrimental to corrosion resistance. The niobium tended to be concentrated in nodules and was easily attacked through sulfidation, providing conduits for further corrosion deep into the alloy. The alloys that displayed the best corrosion resistance were those which could produce chromium oxide protective layers. The predicted microstructure of all alloys except Alloy HR3C is the same and provided no further information relating to corrosion resistance. No correlation can be found relating corrosion resistance to the quantity of minor austenite-or ferrite-stabilizing elements. Also, there does not appear to be a correlation between corrosion resistance and the Cr:Ni ratio of the alloy. These alloys were tested for their

  20. Method of producing superplastic alloys and superplastic alloys produced by the method

    NASA Technical Reports Server (NTRS)

    Troeger, Lillianne P. (Inventor); Starke, Jr., Edgar A. (Inventor); Crooks, Roy (Inventor)

    2002-01-01

    A method for producing new superplastic alloys by inducing in an alloy the formation of precipitates having a sufficient size and homogeneous distribution that a sufficiently refined grain structure to produce superplasticity is obtained after subsequent PSN processing. An age-hardenable alloy having at least one dispersoid phase is selected for processing. The alloy is solution heat-treated and cooled to form a supersaturated solid solution. The alloy is plastically deformed sufficiently to form a high-energy defect structure useful for the subsequent heterogeneous nucleation of precipitates. The alloy is then aged, preferably by a multi-stage low and high temperature process, and precipitates are formed at the defect sites. The alloy then is subjected to a PSN process comprising plastically deforming the alloy to provide sufficient strain energy in the alloy to ensure recrystallization, and statically recrystallizing the alloy. A grain structure exhibiting new, fine, equiaxed and uniform grains is produced in the alloy. An exemplary 6xxx alloy of the type capable of being produced by the present invention, and which is useful for aerospace, automotive and other applications, is disclosed and claimed. The process is also suitable for processing any age-hardenable aluminum or other alloy.

  1. Alloy substantially free of dendrites and method of forming the same

    DOEpatents

    de Figueredo, Anacleto M.; Apelian, Diran; Findon, Matt M.; Saddock, Nicholas

    2009-04-07

    Described herein are alloys substantially free of dendrites. A method includes forming an alloy substantially free of dendrites. A superheated alloy is cooled to form a nucleated alloy. The temperature of the nucleated alloy is controlled to prevent the nuclei from melting. The nucleated alloy is mixed to distribute the nuclei throughout the alloy. The nucleated alloy is cooled with nuclei distributed throughout.

  2. EFFECT OF JP-5 SULFUR CONTENT ON HOT CORROSION OF SUPER ALLOYS IN MARINE ENVIRONMENT.

    DTIC Science & Technology

    SULFUR, AVIATION FUELS), (*NICKEL ALLOYS , CORROSION), (*COBALT ALLOYS , CORROSION), (*CORROSION, AVIATION FUELS), ENVIRONMENTAL TESTS, SEA WATER...GAS TURBINE BLADES, AIRCRAFT ENGINES, CORROSION RESISTANT ALLOYS , COMBUSTION PRODUCTS, CHROMIUM ALLOYS , MOLYBDENUM ALLOYS , TUNGSTEN ALLOYS , ALUMINUM... ALLOYS , ALUMINUM COATINGS, ANALYSIS OF VARIANCE, TITANIUM ALLOYS , EXPERIMENTAL DATA, STATISTICAL ANALYSIS

  3. Fatigue-crack propagation in gamma-based titanium aluminide alloys at large and small crack sizes

    SciTech Connect

    Kruzic, J.J.; Campbell, J.P.; Ritchie, R.O.

    1999-07-01

    Most evaluations of the fracture and fatigue-crack propagation properties of {gamma}+{alpha}{sub 2} titanium aluminide alloys to date have been performed using standard large-crack samples, e.g., compact-tension specimens containing crack sizes which are on the order of tens of millimeters, i.e., large compared to microstructural dimensions. However, these alloys have been targeted for applications, such as blades in gas-turbine engines, where relevant crack sizes are much smaller ({lt}500 {micro}m) and where the small-crack fatigue threshold may be the most relevant design parameter. In this study, the authors compare and contrast the cyclic crack-growth behavior of both large (a {gt} 5 mm) and (c {approximately} 25--300 {micro}m) cracks in a {gamma}-TiAl based alloy, of composition Ti-47Al-2Nb-2Cr-0.2B (at.%), specifically for duplex (average grain size {approximately}17 {micro}m) and refined lamellar (average colony size {approximately}150 {micro}m) microstructures. It is found that, whereas the lamellar microstructure displays far superior fracture toughness and fatigue-crack growth resistance in the presence of large cracks, in small-crack testing the duplex microstructure exhibits a better combination of properties. The reasons for such contrasting behavior are examined in terms of the intrinsic and extrinsic (i.e., crack bridging) contributions to cyclic crack advance.

  4. Enhancing glass-forming ability via frustration of nano-clustering in alloys with a high solvent content

    PubMed Central

    Li, H. X.; Gao, J. E.; Wu, Y.; Jiao, Z. B.; Ma, D.; Stoica, A. D.; Wang, X. L.; Ren, Y.; Miller, M. K.; Lu, Z. P.

    2013-01-01

    The glass-forming ability (GFA) of alloys with a high-solvent content such as soft magnetic Fe-based and Al-based alloys is usually limited due to strong formation of the solvent-based solid solution phase. Herein, we report that the GFA of soft magnetic Fe-based alloys (with >70 at.% Fe to ensure large saturation magnetization) could be dramatically improved by doping with only 0.3 at.% Cu which has a positive enthalpy of mixing with Fe. It was found that an appropriate Cu addition could enhance the liquid phase stability and crystallization resistance by destabilizing the α-Fe nano-clusters due to the necessity to redistribute the Cu atoms. However, excessive Cu doping would stimulate nucleation of the α-Fe nano-clusters due to the repulsive nature between the Fe and Cu atoms, thus deteriorating the GFA. Our findings provide new insights into understanding of glass formation in general. PMID:23760427

  5. PERFORMANCE IMPROVEMENT OF CREEP-RESISTANT FERRITIC STEEL WELDMENTS THROUGH THERMO-MECHANICAL TREATMENT AND ALLOY DESIGN

    SciTech Connect

    Yamamoto, Yukinori; Babu, Prof. Sudarsanam Suresh; Shassere, Benjamin; Yu, Xinghua

    2016-01-01

    Two different approaches have been proposed for improvement of cross-weld creep properties of the high temperature ferrous structural materials for fossil-fired energy applications. The traditional creep strength-enhanced ferritic (CSEF) steel weldments suffer from Type IV failures which occur at the fine-grained heat affected zone (FGHAZ). In order to minimize the premature failure at FGHAZ in the existing CSEF steels, such as modified 9Cr-1Mo ferritic-martensitic steels (Grade 91), a thermo-mechanical treatment consisting of aus-forging/rolling and subsequent aus-aging is proposed which promotes the formation of stable MX carbonitrides prior to martensitic transformation. Such MX remains undissolved during welding process, even in FGHAZ, which successfully improves the cross-weld creep properties. Another approach is to develop a new fully ferrtic, creep-resistant FeCrAl alloy which is essentially free from Type IV failure issues. Fe-30Cr-3Al base alloys with minor alloying additions were developed which achieved a combination of good oxidation/corrosion resistance and improved tensile and creep performance comparable or superior to Grade 92 steel.

  6. In-Situ Observation of Directional Solidifications of Al-Cu Alloys During Parabolic Flight Campaigns

    NASA Astrophysics Data System (ADS)

    Abou-Khalil, L.; Salloum-Abou-Jaoude, G.; Reinhart, G.; Pickmann, C.; Zimmermann, G.; Houltz, Y.; Li, J.; Janson, O.; Nguyen-Thi, H.

    2015-09-01

    It is well known that the final properties of materials are strongly related to the microstructures formed during growth and to the accompanying segregation, both being very sensitive to the natural hydrodynamic movements in the melt induced by gravity. Therefore, a deeper understanding of gravity effects on the solidification microstructure is of great importance for industrial applications. In the framework of the ESA-MAP project entitled XRMON (in-situ X-Ray MONitoring of advanced metallurgical processes under microgravity and terrestrial conditions), directional solidification experiments with in situ X-ray radiography were carried out during the 60th and 61st ESA — PF campaigns onboard the Airbus A300 operated by Novespace. Parabolic flights offer several successions of periods with normal gravity between two parabolas, and hyper gravity and microgravity during each parabola, which allows the impact of gravity level variations on the solidification microstructures to be investigated. For this purpose, a dedicated apparatus was designed and developed in collaboration with SSC (Swedish Space Corporation). XRMON-PFF (Parabolic Flight Facility) includes a Bridgman furnace dedicated to the solidification of Al-based alloys with an X-ray device that enables in situ characterization. Columnar and/or equiaxed growth of refined and non-refined Al2Owt.%Cu alloys were investigated and X-ray radiography was successfully used to assess the effect of periodic variations of the gravity level on the solidification microstructure formation. Preliminary results confirmed the strong influence of gravity on the solidification microstructure development.

  7. Development of a Brazing Alloy for the Mechanically Alloyed High Temperature Sheet Material INCOLOY Alloy MA 956.

    DTIC Science & Technology

    1981-09-01

    well established that joining these alloys by conventional fusion welding techniques has presented problems, especially in achieving good quality high...temperature joint properties, mainly because of agglomeration of the dispersoid in the weld bead. Brazing, diffusion bonding and transient liquid...produced mechanically alloyed iron based sheet material, INQ)LOY alloy MA956, has excellent high temperature strength and corrosion resistance and has

  8. Status of Testing and Characterization of CMS Alloy 617 and Alloy 230

    SciTech Connect

    Ren, Weiju; Santella, Michael L; Battiste, Rick; Terry, Totemeier; Denis, Clark

    2006-08-01

    Status and progress in testing and characterizing CMS Alloy 617 and Alloy 230 tasks in FY06 at ORNL and INL are described. ORNL research has focused on CMS Alloy 617 development and creep and tensile properties of both alloys. In addition to refurbishing facilities to conduct tests, a significant amount of creep and tensile data on Alloy 230, worth several years of research funds and time, has been located and collected from private enterprise. INL research has focused on the creep-fatigue behavior of standard chemistry Alloy 617 base metal and fusion weldments. Creep-fatigue tests have been performed in air, vacuum, and purified Ar environments at 800 and 1000 C. Initial characterization and high-temperature joining work has also been performed on Alloy 230 and CCA Alloy 617 in preparation for creep-fatigue testing.

  9. Micro-Structures of Hard Coatings Deposited on Titanium Alloys by Laser Alloying Technique

    NASA Astrophysics Data System (ADS)

    Li, Wei; Yu, Huijun; Chen, Chuanzhong; Wang, Diangang; Weng, Fei

    2013-01-01

    This work is based on micro-structural performance of the Ti-B4C-C laser alloying coatings on Ti-6Al-4V titanium alloy. The test results indicated that laser alloying of the Ti-B4C-C pre-placed powders on the Ti-6Al-4V alloy substrate can form the ceramics reinforced hard alloying coatings, which increased the micro-hardness and wear resistance of substrate. The test result also indicated that the TiB phase was produced in alloying coating, which corresponded to its (101) crystal plane. In addition, yttria has a refining effect on micro-structures of the laser alloying coating, and its refinement mechanism was analyzed. This research provided essential experimental and theoretical basis to promote the applications of the laser alloying technique in manufacturing and repairing of the aerospace parts.

  10. Progress in ODS Alloys: A Synopsis of a 2010 Workshop on Fe- Based ODS Alloys

    SciTech Connect

    Kad, Bimal; Dryepondt, Sebastien N; Jones, Andy R.; Vito, Cedro III; Tatlock, Gordon J; Pint, Bruce A; Tortorelli, Peter F; Rawls, Patricia A.

    2012-01-01

    In Fall 2010, a workshop on the role and future of Fe-based Oxide Dispersion Strengthened (ODS) alloys gathered together ODS alloy suppliers, potential industrial end-users, and technical experts in relevant areas. Presentations and discussions focused on the current state of development of these alloys, their availability from commercial suppliers, past major evaluations of ODS alloy components in fossil and nuclear energy applications, and the technical and economic issues attendant to commercial use of ODS alloys. Significant progress has been achieved in joining ODS alloys, with creep resistant joints successfully made by inertia welding, friction stir welding and plasma-assisted pulse diffusion bonding, and in improving models for the prediction of lifetime components. New powder and alloy fabrication methods to lower cost or improve endproduct properties were also described. The final open discussion centered on challenges and pathways for further development and large-scale use of ODS alloys.

  11. Aluminum Alloys--Industrial Deformable, Sintered and Light Aluminum Alloys

    DTIC Science & Technology

    1974-10-30

    thin film on the particles of the highly dispersed aluminum powder when it is ground in spherical mills in a nitrogen atmosphere in which the...principal elements, certain small admixtures are introduced into the alloys, which have a considerable effect on the decay kinetics of the oversaturated...strengthened by the insoluble dispersed alumina particles. Fine grinding of the original powder provides the dispersion of the oxide films and particles

  12. Evolution of microstructure and defect structure in manganese-aluminum-based permanent magnet alloys

    NASA Astrophysics Data System (ADS)

    Yanar, Cagatay

    In this study, the transformation behavior of MnAl-based ferromagnetic alloys was investigated. The low-cost and availability of the Mn-Al base metals along with their high mechanical strength, machineability and high magnetic energy product (BH) per unit weight make these materials attractive candidates for permanent magnet applications. These alloys derive their magnetic properties from the metastable L10 tau-phase, which generally appears towards the Mn-rich side of the near equiatomic composition. The magnetic properties of these materials are strongly influenced by the microstructure and characteristic defect structure of the tau-phase. The tau-phase exhibits a unique defect structure, which includes twins, stacking faults, anti-phase domain boundaries and dislocations. Understanding the true nature of defect generation is necessary in order to be able to develop processing techniques to enhance and optimize the properties of these materials. The tau-phase derives from a phase mixture of ε(hcp) and ε '(B19) phases through various heat treatment processes. Controversial mechanisms are reported in the literature regarding the nature of the ε + ε' → tau transformation. Phase transformation mechanisms that are displacive and those involving a massive transformation have been reported. In this study, the true nature of the tau-phase formation was investigated experimentally by utilizing techniques such as transmission electron microscopy (TEM), high-resolution electron microscopy (HREM) and in-situ TEM heating experiments. It was shown that both of the transformation modes, i.e. massive and displacive mechanisms, can operate and result in tau-phase formation. The atomic nature of the displacive transformation was studied in detail to elucidate the viability of transformation of a two-phase mixture into a single phase through a shear transformation. In the absence of stress, the massive mode was shown to dominate microstructural evolution in bulk materials

  13. First principles theory of disordered alloys and alloy phase stability

    SciTech Connect

    Stocks, G.M.; Nicholson, D.M.C.; Shelton, W.A.

    1993-06-05

    These lecture notes review the LDA-KKR-CPA method for treating the electronic structure and energetics of random alloys and the MF-CF and GPM theories of ordering and phase stability built on the LDA- KKR-CPA description of the disordered phase. Section 2 lays out the basic LDA-KKR-CPA theory of random alloys and some applications. Section 3 reviews the progress made in understanding specific ordering phenomena in binary solid solutions base on the MF-CF and GPM theories of ordering and phase stability. Examples are Fermi surface nesting, band filling, off diagonal randomness, charge transfer, size difference or local strain fluctuations, magnetic effects; in each case, an attempt is made to link the ordering and the underlying electronic structure of the disordered phase. Section 4 reviews calculations of electronic structure of {beta}-phase Ni{sub c}Al{sub 1-c} alloys using a version of the LDA-KKR-CPA codes generalized to complex lattices.

  14. Nickel aluminide alloy suitable for structural applications

    DOEpatents

    Liu, Chain T.

    1998-01-01

    Alloys for use in structural applications based upon NiAl to which are added selected elements to enhance room temperature ductility and high temperature strength. Specifically, small additions of molybdenum produce a beneficial alloy, while further additions of boron, carbon, iron, niobium, tantalum, zirconium and hafnium further improve performance of alloys at both room temperature and high temperatures. A preferred alloy system composition is Ni--(49.1.+-.0.8%)Al--(1.0.+-.0.8%)Mo--(0.7.+-.0.5%)Nb/Ta/Zr/Hf--(nearly zero to 0.03%)B/C, where the % is at. % in each of the concentrations. All alloys demonstrated good oxidation resistance at the elevated temperatures. The alloys can be fabricated into components using conventional techniques.

  15. Magnesium alloy applications in automotive structures

    NASA Astrophysics Data System (ADS)

    Easton, Mark; Beer, Aiden; Barnett, Matthew; Davies, Chris; Dunlop, Gordon; Durandet, Yvonne; Blacket, Stuart; Hilditch, Tim; Beggs, Peter

    2008-11-01

    The use of magnesium alloys in structural applications has great potential for the lightweighting of transportation vehicles. Research within the CAST Cooperative Research Centre has tackled some of the important issues related to the use of magnesium in structural applications. To this end, a new alloy with extrudability and properties similar to 6000 series aluminum alloys has been developed. Furthermore, a method of laser heating magnesium alloys before self-piercing riveting has enabled high-integrity joining between magnesium components or between magnesium and dissimilar metals. In this paper, new technologies and improved understanding of the deformation behavior of wrought magnesium alloys are discussed in light of key metallurgical features such as alloy composition, grain size, and work hardening rate.

  16. Nickel aluminide alloy suitable for structural applications

    DOEpatents

    Liu, C.T.

    1998-03-10

    Alloys are disclosed for use in structural applications based upon NiAl to which are added selected elements to enhance room temperature ductility and high temperature strength. Specifically, small additions of molybdenum produce a beneficial alloy, while further additions of boron, carbon, iron, niobium, tantalum, zirconium and hafnium further improve performance of alloys at both room temperature and high temperatures. A preferred alloy system composition is Ni--(49.1{+-}0.8%)Al--(1.0{+-}0.8%)Mo--(0.7 + 0.5%)Nb/Ta/Zr/Hf--(nearly zero to 0.03%)B/C, where the % is at. % in each of the concentrations. All alloys demonstrated good oxidation resistance at the elevated temperatures. The alloys can be fabricated into components using conventional techniques. 4 figs.

  17. A lightweight shape-memory magnesium alloy

    NASA Astrophysics Data System (ADS)

    Ogawa, Yukiko; Ando, Daisuke; Sutou, Yuji; Koike, Junichi

    2016-07-01

    Shape-memory alloys (SMAs), which display shape recovery upon heating, as well as superelasticity, offer many technological advantages in various applications. Those distinctive behaviors have been observed in many polycrystalline alloy systems such as nickel titantium (TiNi)-, copper-, iron-, nickel-, cobalt-, and Ti-based alloys but not in lightweight alloys such as magnesium (Mg) and aluminum alloys. Here we present a Mg SMA showing superelasticity of 4.4% at -150°C and shape recovery upon heating. The shape-memory properties are caused by reversible martensitic transformation. This Mg alloy includes lightweight scandium, and its density is about 2 grams per cubic centimeter, which is one-third less than that of practical TiNi SMAs. This finding raises the potential for development and application of lightweight SMAs across a number of industries.

  18. Magnetic Characteristics of Two Metglas Alloys

    NASA Astrophysics Data System (ADS)

    Blatnik, Marie; SNS nEDM Collaboration

    2016-09-01

    Magnetic shielding is gaining greater significance as precision experiments become more sensitive, such as for the Spallation Neutron Source nEDM [neutron electric dipole moment] measurement. Targeting a sensitivity of 10-28 e-cm, the SNS nEDM collaboration minimizes magnetic shield gradients and magnetic noise with a superconducting lead shield and several shield layers that include using a Metglas layer as a primary component. Metglas is a thin ribbon of proprietary engineered alloy that comes in many varieties. One alloy with high (as cast) permeability is Metglas alloy 2705M, which is primarily composed of Cobalt. However, this alloy will activate under neutron radiation and is therefore unsuitable. However, another high-performance Metglas alloy, 2826 MB, contains only trace amounts of Cobalt. A study of the shielding characteristics of the two alloys was performed, paying close attention to field oscillation frequency and magnitude.

  19. 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.

  20. Annealing behavior of high permeability amorphous alloys

    SciTech Connect

    Rabenberg, L.

    1980-06-01

    Effects of low temperature annealing on the magnetic properties of the amorphous alloy Co/sub 71/ /sub 4/Fe/sub 4/ /sub 6/Si/sub 9/ /sub 6/B/sub 14/ /sub 4/ were investigated. Annealing this alloy below 400/sup 0/C results in magnetic hardening; annealing above 400/sup 0/C but below the crystallization temperature results in magnetic softening. Above the crystallization temperature the alloy hardens drastically and irreversibly. Conventional and high resolution transmission electron microscopy were used to show that the magnetic property changes at low temperatures occur while the alloy is truly amorphous. By imaging the magnetic microstructures, Lorentz electron microscopy has been able to detect the presence of microscopic inhomogeneities in this alloy. The low temperature annealing behavior of this alloy has been explained in terms of atomic pair ordering in the presence of the internal molecular field. Lorentz electron microscopy has been used to confirm this explanation.

  1. The influence of chromium on structure and mechanical properties of B2 nickel aluminide alloys. Ph.D. Thesis - Florida Univ., 1991 Final Report

    NASA Technical Reports Server (NTRS)

    Cotton, James Dean

    1992-01-01

    Major obstacles to the use of NiAl-based alloys and composites are low ductility and toughness. These shortcomings result in part from a lack of sufficient slip systems to accommodate plastic deformation of polycrystalline material (von Mises Criterion). It has been reported that minor additions of chromium to polycrystalline NiAl cause the predominant slip system to shift from the usual. If true, then a major step toward increasing ductility in this compound may be realized. The purpose of the present study was to verify this phenomenon, characterize it with respect to chromium level and Ni to Al ratio, and correlate any change in slip system with microstructure and mechanical properties. Compression and tensile specimens were prepared from alloys containing 0 to 5 percent chromium and 45 to 55 percent aluminum. Following about one percent strain, transmission electron microscopy foils were produced and the slip systems determined using the g x b = 0 invisibility criterion. Contrary to previous results, chromium was found to have no effect on the preferred slip system of any of the alloys studied. Possible reasons for the inconsistency of the current results with previous work are considered. Composition-structure-property relationships are discerned for the alloys, and good correlation are demonstrated in terms of conventional strengthening models for metallic systems.

  2. 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.

  3. Alloying Solid Solution Strengthening of Fe-Ga Alloys: A First-Principle Study

    DTIC Science & Technology

    2006-01-01

    effect from alloying additions of Nb, Mo, V, Cr and Co in cubic solid solution of Fe-Ga alloys. Mayer bond order "BO" values were used to evaluate the...that transition metal Nb achieves the best strengthening effect in Fe-Ga alloys. The solid solution strengthening follows a trend from larger to

  4. [Composition and morphology of oxides on porcelain fused to Ni-Cr alloys. Be containing alloys].

    PubMed

    Watanabe, T

    1989-06-01

    Bonding strength between porcelain and Ni-Cr alloy for the porcelain fused-to metal crown in which Be is contained in the alloy is known to be higher than those in which Be is not contained. Since, bonding between porcelain and alloy is the reaction of oxides and porcelain, the bonding is thought to be influenced by the quality the oxides film which forms on the alloy surface. The purpose of this study was to determine the composition and morphology of the oxides formed on both Be containing and non-Be contained Ni-Cr alloys. The oxides analysis was done using an EPMA and Auger analysis. Also, the Porcelain/Ni-Cr alloy interface was observed by a scanning electron microscope (SEM). The following results are indicated from this investigation: 1. The oxides from the alloys not containing Be are corundum type Cr2O3 and spinel type NiCr2O4. These oxide layers are uniform, thick and porous and the adhesion to alloy is poor. 2. The oxides from alloy containing Be is BeO only. The BeO is uniform, thin and condensed. The adhesion to the alloy is good. 3. The oxide layer formed when the porcelain is fused to alloy containing Be is thin (1 micron average) and has good adhesion to alloy. 4. Be is selectively oxidized and controlled the form of Cr2O3 and NiO.

  5. Properties and microstructures for dual alloy combinations of three superalloys with alloy 901

    NASA Technical Reports Server (NTRS)

    Harf, F. H.

    1985-01-01

    Dual alloy combinations have potential for use in aircraft engine components such as turbine disks where a wide range of stress and temperature regimes exists during operation. Such alloy combinations may directly result in the conservation of elements which are costly or not available domestically. Preferably, a uniform heat treatment yielding good properties for both alloys should be used. Dual alloy combinations of iron rich Alloy 901 with nickel base superalloys Rene 95, Astroloy, or MERL 76 were not isostatically pressed from prealloyed powders. Individual alloys, alloy mixtures, and layered alloy combinations were given the heat treatments specified for their use in turbine disks or appropriate for Alloy 901. Selected specimens were overaged for 1500 hr at 650 C. Metallographic examinations revealed the absence of phases not originally present in either alloy of a combination. Mechanical tests showed adequate properties in combinations of Rene 95 or Astroloy with Alloy 901 when given the Alloy 901 heat treatment. Combinations with MERL 76 had better properties when given the MERL 76 heat treatment. The results indicate that these combinations are promising candidates for use in turbine disks.

  6. Magnesium-titanium alloys for biomedical applications

    NASA Astrophysics Data System (ADS)

    Hoffmann, Ilona

    Magnesium has been identified as a promising biodegradable implant material because it does not cause systemic toxicity and can reduce stress shielding. However, it corrodes too quickly in the body. Titanium, which is already used ubiquitously for implants, was chosen as the alloying element because of its proven biocompatibility and corrosion resistance in physiological environments. Thus, alloying magnesium with titanium is expected to improve the corrosion resistance of magnesium. Mg-Ti alloys with a titanium content ranging from 5 to 35 at.-% were successfully synthesized by mechanical alloying. Spark plasma sintering was identified as a processing route to consolidate the alloy powders made by ball-milling into bulk material without destroying the alloy structure. This is an important finding as this metastable Mg-Ti alloy can only be heated up to max. 200C° for a limited time without reaching the stable state of separated magnesium and titanium. The superior corrosion behavior of Mg 80-Ti20 alloy in a simulated physiological environment was shown through hydrogen evolution tests, where the corrosion rate was drastically reduced compared to pure magnesium and electrochemical measurements revealed an increased potential and resistance compared to pure magnesium. Cytotoxicity tests on murine pre-osteoblastic cells in vitro confirmed that supernatants made from Mg-Ti alloy were no more cytotoxic than supernatants prepared with pure magnesium. Mg and Mg-Ti alloys can also be used to make novel polymer-metal composites, e.g., with poly(lactic-co-glycolic acid) (PLGA) to avoid the polymer's detrimental pH drop during degradation and alter its degradation pattern. Thus, Mg-Ti alloys can be fabricated and consolidated while achieving improved corrosion resistance and maintaining cytocompatibility. This work opens up the possibility of using Mg-Ti alloys for fracture fixation implants and other biomedical applications. KEYWORDS: Magnesium, titanium, corrosion

  7. Damping in Ferrous Shape Memory Alloys

    DTIC Science & Technology

    1993-08-01

    time it has been proposed that the solution lies in the approach of energy dissipation by using metallic structural materials which have inherent...and automotive manufacturing plants, has never achieved commercial producton . 1-b. Ferromagnetic alloys, such as Fe-Cr alloys High damping Fe-Cr alloys...Pre-exsiring mar~en-si,ýe worms orwie treenred orieL a ion ! A Lr cow s SL AL 14- L AL Figure 26. Schematic illustration of various processes involved

  8. Cobalt-Base Alloy Gun Barrel Study

    DTIC Science & Technology

    2014-07-01

    Cobalt -Base Alloy Gun Barrel Study by William S. de Rosset and Jonathan S. Montgomery ARL-RP-0491 July 2014 A reprint...21005-5069 ARL-RP-0491 July 2014 Cobalt -Base Alloy Gun Barrel Study William S. de Rosset and Jonathan S. Montgomery Weapons and Materials...DATE (DD-MM-YYYY) July 2014 2. REPORT TYPE Reprint 3. DATES COVERED (From - To) October–November 2013 4. TITLE AND SUBTITLE Cobalt -Base Alloy

  9. Development of Lightweight Titanium Base Alloys

    DTIC Science & Technology

    1989-04-15

    program on Development of Lightweight Titanium Base Alloys was to develop new titanium alloys with 10% lower density, 50% higher elastic modulus, and...program. permitted the cvaluation of a low-dc-isity. dislicrsion-strengthcnicd 02 + y titanium aluminide , which has excellent high temperature strength...713e alloy has significantly higher strength than the titanium aluminides . The limited data for ’i-34AI-4Be show it to be very strong above 7(X)°C

  10. Processing of 2090 Aluminum Alloy for Superplasticity

    DTIC Science & Technology

    1988-06-01

    behavior has now been extensively documented in Al-Mg alloys, with elongations in excess of 1,000 percent obtained in many cases in these alloys. The...crucial. Characteristics of superplastic behavior include a fine grain size (two to five microns), a strain rate sensitivity coefficient m > 0.3, 1 I| and...seven to eight percent less and demonstrates ten percent higher stiffness than 7075 aluminum, an alloy it was designed to replace. This is due to the

  11. Nanotechnology Corrosion Pretreatment for Magnesium Alloys

    DTIC Science & Technology

    2012-08-29

    Pretreatment for Magnesium Alloys AMS-SAE-M-3171, Type IV Replacement on AZ91D Glycolic Nitrate Pickle (GNP) (1 min) PT-60 (3 min) 0 hr SST 1 4 3 2...Nanotechnology Corrosion Pretreatment for Magnesium Alloys Mr. Jules F. Senske and Mr. Daniel Schmidt Army Research Development and...SUBTITLE Nanotechnology Corrosion Pretreatment for Magnesium Alloys 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d

  12. PREPARATION OF ACTINIDE-ALUMINUM ALLOYS

    DOEpatents

    Moore, R.H.

    1962-09-01

    BS>A process is given for preparing alloys of aluminum with plutonium, uranium, and/or thorium by chlorinating actinide oxide dissolved in molten alkali metal chloride with hydrochloric acid, chlorine, and/or phosgene, adding aluminum metal, and passing air and/or water vapor through the mass. Actinide metal is formed and alloyed with the aluminum. After cooling to solidification, the alloy is separated from the salt. (AEC)

  13. 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.

  14. High toughness-high strength iron alloy

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Witzke, W. R. (Inventor)

    1980-01-01

    An iron alloy is provided which exhibits strength and toughness characteristics at cryogenic temperatures. The alloy consists essentially of about 10 to 16 percent by weight nickel, about 0.1 to 1.0 percent by weight aluminum, and 0 to about 3 percent by weight copper, with the balance being essentially iron. The iron alloy is produced by a process which includes cold rolling at room temperature and subsequent heat treatment.

  15. Carcinogenicity of Embedded Tungsten Alloys in Mice

    DTIC Science & Technology

    2007-03-01

    out a two-year protocol in mice based upon NTP guidelines. The uses the B6C3F1 hybrid mouse , a strain commonly used in carcinogenicity and toxicity...the same percentages present in the alloys). Aim 2: Sacrifice mice at various times after alloy implantation to detect early signs of tumor...Alloys in Mice PRINCIPAL INVESTIGATOR: David E. McClain, Ph.D. CONTRACTING ORGANIZATION: Henry M. Jackson Foundation for the

  16. Composition Dependence of Bulk Alloy Properties

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John

    1994-01-01

    We introduce an approximate expression for the direct calculation of properties of alloys in terms of the pure components. This rule can be obtained as a particular case from the Bozzolo-Ferrante-Smith (BFS) method, a recently developed semiempirical method for alloys. In particular, we examine the application of this rule to several examples of the concentration dependence of the lattice parameter of binary and ternary alloys.

  17. The oxidation and corrosion of ODS alloys

    NASA Technical Reports Server (NTRS)

    Lowell, Carl E.; Barrett, Charles A.

    1990-01-01

    The oxidation and hot corrosion of high temperature oxide dispersion strengthened (ODS) alloys are reviewed. The environmental resistance of such alloys are classified by oxide growth rate, oxide volatility, oxide spalling, and hot corrosion limitations. Also discussed are environmentally resistant coatings for ODS materials. It is concluded that ODS NiCrAl and FeCrAl alloys are highly oxidation and corrosion resistant and can probably be used uncoated.

  18. Alloy nanoparticle synthesis using ionizing radiation

    DOEpatents

    Nenoff, Tina M.; Powers, Dana A.; Zhang, Zhenyuan

    2011-08-16

    A method of forming stable nanoparticles comprising substantially uniform alloys of metals. A high dose of ionizing radiation is used to generate high concentrations of solvated electrons and optionally radical reducing species that rapidly reduce a mixture of metal ion source species to form alloy nanoparticles. The method can make uniform alloy nanoparticles from normally immiscible metals by overcoming the thermodynamic limitations that would preferentially produce core-shell nanoparticles.

  19. Modelling of zirconium alloy hydrogenation

    NASA Astrophysics Data System (ADS)

    Zaika, Yury V.; Rodchenkova, Natalia I.

    2016-11-01

    Zirconium alloys are the construction materials for critical elements in active zones of nuclear power reactors. During the operation of reactors such materials are subject to hydrogenation. Hydrogenation results in a decrease of alloy plasticity and cracking resistance. The formation of brittle hydrides at crack tips can result in severe embrittlement. One of the most important requirements for the reactor's active zone materials is low hydrogen absorptivity. The mathematical model of hydride layer formation and growth is developed. The problem is to determine the dynamics of the free boundary of phase interface and the distributions of hydrogen concentration in hydride and in solution. Iterative computational algorithm for solving the nonlinear boundary-value problem with the Stefan condition based on implicit difference schemes is developed.

  20. Digital Alloy Absorber for Photodetectors

    NASA Technical Reports Server (NTRS)

    Hill, Cory J. (Inventor); Ting, David Z. (Inventor); Gunapala, Sarath D. (Inventor)

    2016-01-01

    In order to increase the spectral response range and improve the mobility of the photo-generated carriers (e.g. in an nBn photodetector), a digital alloy absorber may be employed by embedding one (or fraction thereof) to several monolayers of a semiconductor material (insert layers) periodically into a different host semiconductor material of the absorber layer. The semiconductor material of the insert layer and the host semiconductor materials may have lattice constants that are substantially mismatched. For example, this may performed by periodically embedding monolayers of InSb into an InAsSb host as the absorption region to extend the cutoff wavelength of InAsSb photodetectors, such as InAsSb based nBn devices. The described technique allows for simultaneous control of alloy composition and net strain, which are both key parameters for the photodetector operation.

  1. 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.

  2. Direct Cast Titanium Alloy Strip

    DTIC Science & Technology

    1990-08-01

    alloys: copper, yellow brass, molybdenum, Grade H-13 steel and plasma sprayed molybdenum on copper. Seven additional substrates were used for experiments...chromium on copper, electroplated chromium on steel and copper oxide. The chill roll dimensions were 190 mm (7.5 in) diameter by 50 mm (2 in) wide. The...Silver was electro-plated on a copper chill roll that was threaded on the circumference. Chromium was electroplated on a Cl0 copper and Grade H-13 steel

  3. 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.

  4. 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.

  5. Machine Casting of Ferrous Alloys

    DTIC Science & Technology

    1977-06-01

    During this year the basic Rheocasting system, which was fully operational at the beginning of the year, was improved in various ways to increase...graphite inserts at the bottom of the Rheocaster to eliminate ’hot spots’. Large quantities of 304 and 440C stainless steel alloys were cast during this...period (approximately 800 pounds of 304 and 2000 pounds of 440C) and smaller quantities of other materials were also Rheocast including M2 tool steel, and

  6. Melt Spinning of Crystalline Alloys.

    DTIC Science & Technology

    1980-01-01

    manufactoring iron-based amorphous alloys for magnetic appli- cations (2). Liebermann and Graham (3) and Kavesh (-)’have discussed the effect of melt spinning...and Mn. The main objectige was to determine whether the conclusions of Liebermann and Graham and Kavesh can be applied over a wide range of materials...length, width and thickness, p is density (2.71.103 Kgm-3 ), and W is the measured weight. Liebermann and Graham (3) applied Bernoulli’s equation

  7. The Fatigue of Powder Metallurgy Alloys.

    DTIC Science & Technology

    1982-01-08

    characteristics of an ingot metallurgy product, 7075 -T76. In all alloys high closure levels are observed atR=0.05 in the near threshold region, an...of two aluminum P/M alloys, X7090 and X7091. For comparison purposes, the ingot metallurgy (I/M) alloy 7075 -76 has also been tested. The results of...described in this report were obtained in extruded form from L Alcoa via Lockheed-California Company. These alloys are: P/M X7090-T6 P/M X7091-T7E69 I/M 7075

  8. Surface alloying of silicon into aluminum substrate.

    SciTech Connect

    Xu, Z.

    1998-10-28

    Aluminum alloys that are easily castable tend to have lower silicon content and hence lower wear resistance. The use of laser surface alloying to improve the surface wear resistance of 319 and 320 aluminum alloys was examined. A silicon layer was painted onto the surface to be treated. A high power pulsed Nd:YAG laser with fiberoptic beam delivery was used to carry out the laser surface treatment to enhance the silicon content. Process parameters were varied to minimize the surface roughness from overlap of the laser beam treatment. The surface-alloyed layer was characterized and the silicon content was determined.

  9. Design and discovery of heterostructural alloys

    NASA Astrophysics Data System (ADS)

    Holder, Aaron; Siol, Sebastian; Ndione, Paul; Peng, Haowei; Zakutayev, Andriy; Lany, Stephan; Matthews, Bethany; Tate, Janet; Gorman, Brian; Gordon, Roy; Schelhas, Laura; Toney, Mike

    The tailoring of materials properties by alloying is routinely utilized to design materials for targeted technological applications. Despite the great successes of alloying in isostructural systems, heterostructural alloying remains a fundamentally unexplored area. In heterostructural alloys, the crossover between different crystal structures enables a new parameter for control over structure and properties by variation of the composition. Here, we present a complementary theoretical and experimental investigation of novel semiconducting metal chalcogenide alloys to develop design principles and approaches for utilizing heterostructural alloying as a materials design strategy. We use ab initio methods to predict the structural and electronic properties of novel alloys with commensurate and incommensurate lattice symmetries. Non-equilibrium deposition methods are employed to overcome thermodynamic solubility limits and produce metastable thin-film samples across the entire alloy composition range. The prediction, theory-guided combinatorial synthesis, and characterization of heterostructural alloys demonstrate the design and discovery of functional metastable materials. Our approach establishes a new route for the control of structure-property and composition-structure relationships by accessing non-equilibrium phase space to develop new materials with uniquely tailored properties.

  10. Hardfacing with cobalt and nickel alloys

    SciTech Connect

    Wu, J.B.C. ); Redman, J. , Los Angles, CA )

    1994-09-01

    The use of cobalt or nickel alloys for added wear resistance was initiated in the early 1900s with the development of the cobalt-chromium-tungsten family of alloys. The cobalt alloys were called the Stellite'' because of their bright, shiny, nontarnished appearance. Further development and characterization of this alloy system established its usage in unlubricated metal-to-metal contact or erosion by high-velocity fluid or solid particulate impingement. Initially, the alloys were used as solid castings but later were applied by welding to tougher or more ductile substrates, hence the birth of the hardfacing industry. Many of the original Stellite compositions are still in use, but many others, including the nickel and iron alloys, have been developed for special applications or for use by newer application procedures. Examining the microstructural features and wear properties of these families of hardfacing alloys can help in choosing the right alloy for the job. Various cobalt and nickel alloys, their available product forms and the corresponding hardfacing methods, are reviewed in this article.

  11. Liquid metal corrosion considerations in alloy development

    SciTech Connect

    Tortorelli, P.F.; DeVan, J.H.

    1984-01-01

    Liquid metal corrosion can be an important consideration in developing alloys for fusion and fast breeder reactors and other applications. Because of the many different forms of liquid metal corrosion (dissolution, alloying, carbon transfer, etc.), alloy optimization based on corrosion resistance depends on a number of factors such as the application temperatures, the particular liquid metal, and the level and nature of impurities in the liquid and solid metals. The present paper reviews the various forms of corrosion by lithium, lead, and sodium and indicates how such corrosion reactions can influence the alloy development process.

  12. Solution for Depositing an Electroless Cobalt Alloy.

    DTIC Science & Technology

    SOLUTIONS(MIXTURES), *ELECTROLESS PLATING), (*PATENTS, ELECTROLESS PLATING), (*COBALT ALLOYS, ELECTROLESS PLATING), ADDITIVES, SODIUM COMPOUNDS... TUNGSTATES , POTASSIUM COMPOUNDS, NICKEL COMPOUNDS, SULFATES, THIOUREA, MAGNETIC PROPERTIES

  13. The physical properties of some alternative alloys.

    PubMed

    Johnson, L N

    1983-03-01

    Over the past 30 years the 'traditional' gold alloy systems have been modified by reducing the percentage of gold and other noble metals to the point where the 'non-precious metal' alloys have no noble metal content. These include the nickel-based alloys, cobalt-based alloys and certain experimental alloys, all suitable for porcelain application. This application demands castability, compatibility with investments, suitable finishing properties, appropriate thermal expansion, chemical bonding with porcelain, solderability and biocompatibility. Recent research into these functional requirements has (1) confirmed the role of Cr in corrosion resistance; (2) related high fusion temperatures to surface roughness and inaccurate fit; (3) demonstrated the importance of casting size and thickness; (4) related castability to the choice of investment for a particular alloy; (5) provided a method for controlling the deposition of oxide film upon the casting; and (6) shown that the re-use of base metal alloy has an adverse effect upon the mechanical properties of the casting. The expense of manipulating the base metal alloys to some extent offsets their cost-benefit advantage over traditional gold alloys. It is possible that Cr will not remain freely available, in which case its price too will soar.

  14. Corrosion of austenitic alloys in aerated brines

    SciTech Connect

    Heidersbach, R.; Shi, A.; Sharp, S.

    1999-11-01

    This report discusses the results of corrosion exposures of three austenitic alloys--3l6L stainless steel, UNS N10276, and UNS N08367. Coupons of these alloys were suspended in a series of brines used for processing in the pharmaceutical industry. The effects of surface finish and welding processes on the corrosion behavior of these alloys were determined. The 316L coupons experienced corrosion in several environments, but the other alloys were unaffected during the one-month exposures of this investigation. Electropolishing the surfaces improved corrosion resistance.

  15. Transient oxidation of multiphase Ni-Cr base alloys

    SciTech Connect

    Baran, G.; Meraner, M.; Farrell, P.

    1988-06-01

    Four commercially available Ni-Cr-based alloys used with porcelain enamels were studied. Major alloying elements were Al, Be, Si, B, Nb, and Mo. All alloys were multiphase. During heat treatments simulating enameling conditions, phase changes occurred in most alloys and were detected using hardness testing, differential thermal analysis (DTA), and microscopy. Oxidation of these alloys at 1000/degrees/C for 10 min produced an oxide layer consisting principally of chromium oxide, but the oxide morphology varied with each alloy depending on the alloy microstructure. Controlling alloy microstructure while keeping the overall composition unchanged may be a means of preventing wrinkled poorly adherent scales from forming.

  16. Nonstochastic magnetic reversal in artificial quasicrystalline spin ice

    SciTech Connect

    Farmer, B.; Bhat, V. S.; Woods, J.; Teipel, E.; Smith, N.; De Long, L. E.; Sklenar, J.; Ketterson, J. B.; Hastings, J. T.

    2014-05-07

    We have measured the isothermal DC magnetization of Penrose P2 tilings (P2T) composed of wire segments of permalloy thin film. Micromagnetic simulations reproduce the coercive fields and “knee anomalies” observed in experimental data and show magnetic shape anisotropy constrains segments to be single-domain (Ising spins) at low fields, similar to artificial spin ice (ASI). Mirror symmetry controls the initial reversal of individual segments oriented parallel to the applied field, followed by complex switching of multiple adjacent segments (“avalanches”) of various orientations such that closed magnetization loops (“vortices”) are favored. Ferromagnetic P2T differ from previously studied ASI systems due to their aperiodic translational symmetry and numerous inequivalent pattern vertices, which drive nonstochastic switching of segment polarizations.

  17. Covalent bonds in AlMnSi icosahedral quasicrystalline approximant

    PubMed

    Kirihara; Nakata; Takata; Kubota; Nishibori; Kimura; Sakata

    2000-10-16

    Electron density distributions were obtained using the maximum entropy method with synchrotron radiation powder data. In the metallic Al12Re, metallic bonding was observed for the icosahedral Al12 cluster with central Re atom. In the nonmetallic alpha-AlMnSi 1/1 approximant, covalent bonds were found in the electron density distribution of the Mackay icosahedral cluster without central atom. Rather than the Hume-Rothery mechanism, the covalency of Al (Si) icosahedron and that between Al (Si) and Mn atoms is considered to be the origin of the pseudogap and nonmetallic behavior of alpha-AlMnSi.

  18. Alloy NASA-HR-1

    NASA Technical Reports Server (NTRS)

    Chen, Po-Shou; Mitchell, Michael

    2005-01-01

    NASA-HR-1 is a high-strength Fe-Ni-base superalloy that resists high-pressure hydrogen environment embrittlement (HEE), oxidation, and corrosion. Originally derived from JBK-75, NASA-HR-1 has exceptional HEE resistance that can be attributed to its gamma-matrix and eta-free (Ni3Ti) grain boundaries. The chemistry was formulated using a design approach capable of accounting for the simultaneous effects of several alloy additions. This approach included: (1) Systematically modifying gamma-matrix compositions based on JBK-75; (2) Increasing gamma (Ni3(Al,Ti)) volume fraction and adding gamma-matrix strengthening elements to obtain higher strength; and (3) Obtaining precipitate-free grain boundaries. The most outstanding attribute of NASA-HR-1 is its ability to resist HEE while showing much improved strength. NASA-HR-1 has approximately 25% higher yield strength than JXK-75 and exhibits tensile elongation of more than 20% with no ductility loss in a hydrogen environment at 5 ksi, an achievement unparalleled by any other commercially available alloy. Its Cr and Ni contents provide exceptional resistance to environments that promote oxidation and corrosion. Microstructural stability was maintained by improved solid solubility of the gamma-matrix, along with the addition of alloying elements to retard eta (Ni3Ti) precipitation. NASA-HR-1 represents a new system that greatly extends the compositional ranges of existing HEE-resistant Fe-Ni-base superalloys.

  19. Pack cementation coatings for alloys

    SciTech Connect

    He, Yi-Rong; Zheng, Minhui; Rapp, R.A.

    1996-08-01

    The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on a Cr-Cr{sub 2}Nb alloy in a single processing step. The morphology and composition of the coating depended both on the composition of the pack and on the composition and microstructure of the substrate. Higher Ge content in the pack suppressed the formation of CrSi{sub 2} and reduced the growth kinetics of the coating. Ge was not homogeneously distributed in the coatings. In cyclic and isothermal oxidation in air at 700 and 1050{degrees}C, the Ge-doped silicide coating protected the Cr-Nb alloys from significant oxidation by the formation of a Ge-doped silica film. The codeposition and diffusion of aluminum and chromium into low alloy steel have been achieved using elemental Al and Cr powders and a two-step pack cementation process. Sequential process treatments at 925{degrees}C and 1150{degrees}C yield dense and uniform ferrite coatings, whose compositions are close to either Fe{sub 3}Al or else FeAl plus a lower Cr content, when processed under different conditions. The higher content of Al in the coatings was predicted by thermodynamic calculations of equilibrium in the gas phase. The effect of the particle size of the metal powders on the surface composition of the coating has been studied for various combinations of Al and Cr powders.

  20. Irradiation-assisted stress corrosion cracking in HTH Alloy X-750 and Alloy 625

    SciTech Connect

    Bajaj, R.; Mills, W.J.; Lebo, M.R.; Hyatt, B.Z.; Burke, M.G.

    1995-12-31

    In-reactor testing of bolt-loaded compact tension specimens was performed in 360 C water to determine the irradiation-assisted stress corrosion cracking (IASCC) behavior of HTH Alloy X-750 and direct-aged Alloy 625. New data confirm previous results showing that high irradiation levels reduce SCC resistance in Alloy X-750. Heat-to-heat variability correlates with boron content, with low boron heats showing improved IASCC properties. Alloy 625 is resistant to IASCC, as no cracking was observed in any Alloy 625 specimens. Microstructural, microchemical and deformation studies were performed to characterize the mechanisms responsible for IASCC in Alloy X-750 and the lack of an effect in Alloy 625. The mechanisms under investigation are: boron transmutation effects, radiation-induced changes in microstructure and deformation characteristics, and radiation-induced segregation. Irradiation of Alloy X-750 caused significant strengthening and ductility loss that was associated with the formation of cavities and dislocation loops. High irradiation levels did not cause significant segregation of alloying or trace elements in Alloy X-750. Irradiation of Alloy 625 resulted in the formation of small dislocation loops and a fine body-centered-orthorhombic phase. The strengthening due to the loops and precipitates was apparently offset by a partial dissolution of {gamma}{double_prime} precipitates, as Alloy 625 showed no irradiation-induced strengthening or ductility loss. In the nonirradiated condition, an IASCC susceptible HTH heat containing 28 ppm B showed grain boundary segregation of boron, whereas a nonsusceptible HTH heat containing 2 ppm B and Alloy 625 with 20 ppm B did not show significant boron segregation. Transmutation of boron to helium at grain boundaries, coupled with matrix strengthening, is believed to be responsible for IASCC in Alloy X-750, and the absence of these two effects results in the superior IASCC resistance displayed by Alloy 625.

  1. Iron-based amorphous alloys and methods of synthesizing iron-based amorphous alloys

    DOEpatents

    Saw, Cheng Kiong; Bauer, William A.; Choi, Jor-Shan; Day, Dan; Farmer, Joseph C.

    2016-05-03

    A method according to one embodiment includes combining an amorphous iron-based alloy and at least one metal selected from a group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel phosphorous, yttrium, and alloys thereof to form a mixture, wherein the at least one metal is present in the mixture from about 5 atomic percent (at %) to about 55 at %; and ball milling the mixture at least until an amorphous alloy of the iron-based alloy and the at least one metal is formed. Several amorphous iron-based metal alloys are also presented, including corrosion-resistant amorphous iron-based metal alloys and radiation-shielding amorphous iron-based metal alloys.

  2. Influence of alloying elements on structure and some physical properties of quenched Sn-Sb alloy

    NASA Astrophysics Data System (ADS)

    Kamal, M.; El-Bediwi, A. B.; El-Shobaki, M. R.

    2006-09-01

    We study the influence of ternary and quaternary alloying elements (Pb, Cd, Cu or Cu-Pb and Cu-Cd) on structural, electrical, hardness and other mechanical properties of Sn-Sb alloys (using an X-ray diffractometer and optical microscope, the double bridge method, Vickers hardness tester and the dynamic resonance method) to produce the best alloy for bearing applications. Adding Cu or Pb to Sn-Sb alloys improves their bearing properties, such as the mechanical properties (elastic modulus, internal friction, hardness and fracture strain) and thermal conductivity. Also, adding Cu, Pb or Cu-Pb to Sn-Sb alloys makes them excellent in their bearing applications and environmental hazards when compared with the Pb88Sn10Cu2 alloy for automotive applications (FIAT Normalizzazione) and the lead-based Babbitt bearing alloy.

  3. Role of alloying elements in adhesive transfer and friction of copper-base alloys

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1978-01-01

    Sliding friction experiments were conducted in a vacuum with binary-copper alloy riders sliding against a conventional bearing-steel surface with normal residual oxides present. The binary alloys contained 1 atomic percent of various alloying elements. Auger spectroscopy analysis was used to monitor the adhesive transfer of the copper alloys to the bearing-steel surface. A relation was found to exist between adhesive transfer and the reaction potential and free energy of formation of the alloying element in the copper. The more chemically active the element and the more stable its oxide, the greater was the adhesive transfer and wear of the copper alloy. Transfer occurred in all the alloys except copper-gold after relatively few (25) passes across the steel surface.

  4. Mathematical Modeling of Wear Characteristics of 6061 Al-Alloy-SiCp Composite Using Response Surface Methodology

    NASA Astrophysics Data System (ADS)

    Mandal, Nilrudra; Roy, H.; Mondal, B.; Murmu, N. C.; Mukhopadhyay, S. K.

    2012-01-01

    In the light of attractive wear characteristics as well as high strength to weight ratio, extensive research on Al-based Metal Matrix Composite (MMC) have been carried out globally in the last two decades. However, very limited research has been pursued on tribological behavior of Al-based MMC under combined action of rolling and sliding. This study investigates the wear behavior of 6061 Al-alloy/SiC with 10 vol.% SiCp against hardened and tempered AISI 4340 steel under combined rolling-sliding conditions. 23 factorial design of experiments have been carried out to see the effect of few parameters, i.e., contact stress, speed and duration with respect to wear. The interaction effect has also been studied by 3D graphical contours. A mathematical model is developed using regression analysis technique for prediction of wear behavior of the MMC and adequacy of the model has been validated using analysis of variance (ANOVA) techniques. Finally, the optimization of parameter has also been done using Design Expert software. The results have shown that Response Surface Methodology (RSM) is an effective tool for prediction of wear behavior under combined sliding and rolling action. It is also found that the wear of MMC is much lower than hardened; tempered AISI 4340 steel and rolling speed has the maximum influence in wear of both materials under investigation.

  5. Magnetic properties of metastable Fe Pd alloys by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Yabe, Hiromasa; O'Handley, Robert C.; Kuji, Toshiro

    2007-03-01

    Metastable Fe-Pd powder samples with various Pd content were synthesized by mechanical alloying. Their fundamental properties, i.e., structure, magnetization and coercive fore are discussed. The saturation magnetizations of the metastable Fe-Pd powders gradually decreases with increasing Pd content. The coercive forces observed in as-milled samples are all less than 40 Oe. However, some of the heat-treated samples, notably, Pd content around 55 at% with L1 0 structure, shows Hc up to 1589 Oe.

  6. Environmental effects on orthorhombic alloy Ti-22Al-25Nb in air between 650 and 1,000 C

    SciTech Connect

    Leyens, C. |

    1999-12-01

    The environmental behavior of an orthorhombic titanium-aluminide alloy, Ti-22Al-25Nb, was studied in dry and humid air between 650 and 1,000 C by scanning electron microscopy, energy dispersive spectroscopy, and X-ray diffraction. Microhardness measurements were performed after exposure to gage hardening due to nitrogen and oxygen ingress. The parabolic rate constant of Ti-22Al-25Nb was of the same order as conventional titanium alloys and Ti{sub 3}Al-based titanium aluminides at and below 750 C. Between 800 and 1,000 C, the oxidation resistance of Ti-22Al-25Nb was as good as {gamma}-TiAl base aluminides; however, the growth rate changed from parabolic to linear after several tens of hours at 900 and 1,000 C. The mixed oxide scale consisted of TiO{sub 2}, AlNbO{sub 4}, and Al{sub 2}O{sub 3} with TiO{sub 2} being the dominant oxide phase. Underneath the oxide scale, a nitride layer formed in the temperature range investigated and, at 1,000 C, internal oxidation was observed below this layer. In all cases, oxygen diffused deeply into the subsurface zone and caused severe embrittlement. Microhardness measurements revealed that Ti-22Al-25Nb was hardened in a zone as far as 300 {micro}m below the oxide scale when exposed to air at 900 C for 500 hr. The peak hardness depended on exposure time and reached five times the average hardness of the bulk material under the above conditions.

  7. Weldable aluminum alloy has improved mechanical properties

    NASA Technical Reports Server (NTRS)

    Westerlund, R. W.

    1966-01-01

    Weldable aluminum alloy has good resistance to stress-corrosion cracking, shows unchanged strength and formability after storage at room temperature, and can be pre-aged, stretched, and aged. Since toxic fumes of cadmium oxide are evolved when the new alloy is welded, adequate ventilation must be provided.

  8. Heats of formation in transition intermetallic alloys

    SciTech Connect

    Pasturel, A.; Colinet, C.; Hicter, P.

    1984-07-01

    The heats of formation in intermetallic alloys are calculated within a tight-binding scheme for the d band. The difference in bandwidth between the metals and the difference between their energy levels are two dominant effects in determination of the formation energy. The influence of charge transfer on alloy formation is studied.

  9. Braze alloys for high temperature service

    NASA Technical Reports Server (NTRS)

    Lindberg, R. A.; Mckisson, R. L.; Erwin, G., Jr.

    1973-01-01

    Two groups of refractory metal compositions have been developed that are very useful as high temperature brazing alloys for sealing between ceramic and metal parts. Each group consists of various compositions of three selected refractory metals which, when combined, have characteristics required of good braze alloys.

  10. Heats of formation of bcc binary alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John; Smith, John R.

    1991-01-01

    The method of Bozzolo, Ferrante and Smith is applied for the calculation of alloy energies for bcc elements. The heat of formation of several alloys is computed with the help of the Connolly-Williams method within the tetrahedron approximation. The dependence of the results on the choice of different sets of ordered structures is discussed.

  11. Machining of uranium and uranium alloys

    SciTech Connect

    Morris, T.O.

    1981-12-14

    Uranium and uranium alloys can be readily machined by conventional methods in the standard machine shop when proper safety and operating techniques are used. Material properties that affect machining processes and recommended machining parameters are discussed. Safety procedures and precautions necessary in machining uranium and uranium alloys are also covered. 30 figures.

  12. Tantalum modified ferritic iron base alloys

    NASA Technical Reports Server (NTRS)

    Oldrieve, R. E.; Blankenship, C. P. (Inventor)

    1977-01-01

    Strong ferritic alloys of the Fe-CR-Al type containing 0.4% to 2% tantalum were developed. These alloys have improved fabricability without sacrificing high temperature strength and oxidation resistance in the 800 C (1475 F) to 1040 C (1900 F) range.

  13. Plasma deposition of amorphous metal alloys

    DOEpatents

    Hays, Auda K.

    1986-01-01

    Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

  14. Castable nickel aluminide alloys for structural applications

    DOEpatents

    Liu, C.T.

    1992-04-28

    The specification discloses nickel aluminide alloys which include as a component from about 0.5 to about 4 at. % of one or more of the elements selected from the group consisting of molybdenum or niobium to substantially improve the mechanical properties of the alloys in the cast condition. 4 figs.

  15. Castable nickel aluminide alloys for structural applications

    DOEpatents

    Liu, Chain T.

    1992-01-01

    The specification discloses nickel aluminide alloys which include as a component from about 0.5 to about 4 at. % of one or more of the elements selected from the group consisting of molybdenum or niobium to substantially improve the mechanical properties of the alloys in the cast condition.

  16. TERNARY ALLOYS OF URANIUM, COLUMBIUM, AND ZIRCONIUM

    DOEpatents

    Foote, F.G.

    1960-08-01

    Ternary alloys of uranium are described which are useful as neutron- reflecting materials in a fast neutron reactor. They are especially resistant to corrosion caused by oxidative processes of gascous or aqueous origin and comprise uranium as the predominant metal with zirconiunn and niobium wherein the total content of the minor alloying elements is between 2 and 8% by weight.

  17. Bonding titanium to Rene 41 alloy

    NASA Technical Reports Server (NTRS)

    Scott, R. W.

    1972-01-01

    Pair of intermediate materials joined by electron beam welding method welds titanium to Rene 41 alloy. Bond is necessary for combining into one structure high strength-to-density ratio titanium fan blades and temperature resistant nickel-base alloy turbine-buckets in VTOL aircraft lift-fan rotor.

  18. Heats of formation of bcc binary alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John

    1992-01-01

    The method of Bozzolo, Ferrante and Smith is applied for the calculation of alloy energies for bcc elements. The heat of formation of several alloys is computed with the help of the Connolly-Williams method within the tetrahedron approximation. The dependence of the results on the choice of different sets of ordered structures is discussed.

  19. Alloys of clathrate allotropes for rechargeable batteries

    SciTech Connect

    Chan, Candace K; Miller, Michael A; Chan, Kwai S

    2014-12-09

    The present disclosure is directed at an electrode for a battery wherein the electrode comprises clathrate alloys of silicon, germanium or tin. In method form, the present disclosure is directed at methods of forming clathrate alloys of silicon, germanium or tin which methods lead to the formation of empty cage structures suitable for use as electrodes in rechargeable type batteries.

  20. Study of stress corrosion in aluminum alloys

    NASA Technical Reports Server (NTRS)

    Brummer, S. B.

    1967-01-01

    Mechanism of the stress corrosion cracking of high-strength aluminum alloys was investigated using electrochemical, mechanical, and electron microscopic techniques. The feasibility of detecting stress corrosion damage in fabricated aluminum alloy parts by nondestructive testing was investigated using ultrasonic surface waves and eddy currents.