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Sample records for advanced structural alloys

  1. 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.

  2. 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.

  3. Development of Advanced Aluminum Alloys from Rapidly Solidified Powders for Aerospace Structural Applications

    DTIC Science & Technology

    1980-03-01

    density, compared to Al 7075 -T76, without significant loss in modu- lus, toughness, fatigue behavior , or stress corrosion resistance. Selective... 7075 -T76, without significant loss in modu- lus, toughness, fatigue behavior , or stress corrosion resistance. Selective application of the two advanced...density ratio, when compared to Al 7075 -T76 and without a significant loss in other properties important for structural applications. The program is

  4. Mechanistic Studies Of Combustion And Structure Formation During Combustion Synthesis Of Advanced Materials: Phase Separation Mechanism For Bio-Alloys

    NASA Technical Reports Server (NTRS)

    Varma, A.; Lau, C.; Mukasyan, A.

    2003-01-01

    Among all implant materials, Co-Cr-Mo alloys demonstrate perhaps the most useful balance of resistance to corrosion, fatigue and wear, along with strength and biocompatibility [1]. Currently, these widely used alloys are produced by conventional furnace technology. Owing to high melting points of the main alloy elements (e.g. Tm.p.(Co) 1768 K), high-temperature furnaces and long process times (several hours) are required. Therefore, attempts to develop more efficient and flexible methods for production of such alloys with superior properties are of great interest. The synthesis of materials using combustion phenomena is an advanced approach in powder metallurgy [2]. The process is characterized by unique conditions involving extremely fast heating rates (up to 10(exp 6 K/s), high temperatures (up to 3500 K), and short reaction times (on the order of seconds). As a result, combustion synthesis (CS) offers several attractive advantages over conventional metallurgical processing and alloy development technologies. The foremost is that solely the heat of chemical reaction (instead of an external source) supplies the energy for the synthesis. Also, simple equipment, rather than energy-intensive high-temperature furnaces, is sufficient. This work was devoted to experiments on CS of Co-based alloys by utilizing thermite (metal oxide-reducing metal) reactions, where phase separation subsequently produces materials with tailored compositions and properties. Owing to high reaction exothermicity, the CS process results in a significant increase of temperature (up to 3000 C), which is higher than melting points of all products. Since the products differ in density, phase separation may be a gravitydriven process: the heavy (metallic phase) settles while the light (slag) phase floats. The goal was to determine if buoyancy is indeed the major mechanism that controls phase segregation.

  5. Oxidation of advanced steam turbine alloys

    SciTech Connect

    Holcomb, G.R.; Covino, B.S., Jr.; Bullard, S.J.; Ziomek-Moroz, M.

    2006-03-01

    Advanced or ultra supercritical (USC) steam power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of advanced alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections.

  6. Tensile and toughness assessment of the procured advanced alloys

    SciTech Connect

    Tan, Lizhen; Sokolov, Mikhail A.; Hoelzer, David T.; Busby, Jeremy T.

    2015-09-11

    Life extension of the existing nuclear reactors imposes irradiation of high fluences to structural materials, resulting in significant challenges to the traditional reactor materials such as type 304 and 316 stainless steels. Advanced alloys with superior radiation resistance will increase safety margins, design flexibility, and economics for not only the life extension of the existing fleet but also new builds with advanced reactor designs. The Electric Power Research Institute (EPRI) teamed up with Department of Energy (DOE) to initiate the Advanced Radiation Resistant Materials (ARRM) program, aiming to develop and test degradation resistant alloys from current commercial alloy specifications by 2021 to a new advanced alloy with superior degradation resistance by 2024 in light water reactor (LWR)-relevant environments

  7. 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.

  8. Oxidation of alloys for advanced steam turbines

    SciTech Connect

    Holcomb, Gordon R.; Covino, Bernard S., Jr.; Bullard, Sophie J.; Ziomek-Moroz, M.; Alman, David E.

    2005-01-01

    Ultra supercritical (USC) power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy’s Advanced Power Systems Initiatives include coal generation at 60% efficiency, which would require steam temperatures of up to 760°C. This research examines the steamside oxidation of advanced alloys for use in USC systems, with emphasis placed on alloys for high- and intermediate-pressure turbine sections.

  9. Thermodynamics and Structure of Plutonium Alloys

    SciTech Connect

    Allen, P G; Turchi, P A; Gallegos, G F

    2004-01-30

    The goal of this project was to investigate the chemical and structural effects of gallium and impurity elements, iron and nickel, on the phase behavior and crystallography of Pu-Ga alloys. This was done utilizing a theoretical chemical approach to predict binary and ternary alloy energetics, phase stability, and transformations. The modeling results were validated with experimental data derived from the synthesis of selected alloys and advanced characterization tools. The ultimate goal of this work was to develop a robust predictive capability for studying the thermodynamics and the structure-properties relationships in complex materials of high relevance to the Laboratory and DOE mission.

  10. 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.

  11. Design and screening of nanoprecipitates-strengthened advanced ferritic alloys

    SciTech Connect

    Tan, Lizhen; Yang, Ying; Chen, Tianyi; Sridharan, K.; He, Li

    2016-12-30

    Advanced nuclear reactors as well as the life extension of light water reactors require advanced alloys capable of satisfactory operation up to neutron damage levels approaching 200 displacements per atom (dpa). Extensive studies, including fundamental theories, have demonstrated the superior resistance to radiation-induced swelling in ferritic steels, primarily inherited from their body-centered cubic (bcc) structure. This study aims at developing nanoprecipitates strengthened advanced ferritic alloys for advanced nuclear reactor applications. To be more specific, this study aims at enhancing the amorphization ability of some precipitates, such as Laves phase and other types of intermetallic phases, through smart alloying strategy, and thereby promote the crystalline®amorphous transformation of these precipitates under irradiation.

  12. Development of Advanced Alloys using Fullerenes

    NASA Technical Reports Server (NTRS)

    Sims, J.; Wasz, M.; O'Brien, J.; Callahan, D. L.; Barrera, E. V.

    1994-01-01

    Development of advanced alloys using fullerenes is currently underway to produce materials for use in the extravehicular mobility unit (EMU). These materials will be directed toward commercial usages as they are continually developed. Fullerenes (of which the most common is C(sub 60)) are lightweight, nanometer size, hollow molecules of carbon which can be dispersed in conventional alloy systems to enhance strength and reduce weight. In this research, fullerene interaction with aluminum is investigated and a fullerene-reinforced aluminum alloy is being developed for possible use on the EMU. The samples were manufactured using standard commercial approaches including powder metallurgy and casting. Alloys have been processed having 1.3, 4.0 and 8.0 volume fractions of fullerenes. It has been observed that fullerene dispersion is related to the processing approach and that they are stable for the processing conditions used in this research. Emphasis will be given to differential thermal analysis and wavelength dispersive analysis of the processed alloys. These two techniques are particularly useful in determining the condition of the fullerenes during and after processing. Some discussion will be given as to electrical properties of fullerene-reinforced materials. Although the aluminum and other advanced alloys with fullerenes are being developed for NASA and the EMU, the properties of these materials will be of interest for commercial applications where specific Dual-Use will be given.

  13. Recent advances and developments in refractory alloys

    SciTech Connect

    Nieh, T.G.; Wadsworth, J.

    1993-11-01

    Refractory metal alloys based on Mo, W, Re, Ta, and Nb (Cb) find applications in a wide range of aerospace applications because of their high melting points and high-temperature strength. This paper, presents recent progress in understanding and applications of these alloys. Recent studies to improve the oxidation and mechanical behavior of refractory metal alloys, and particularly Nb alloys, are also discussed. Some Re structures, for extremely high temperature applications (> 2000C), made by CVD and P/M processes, are also illustrated. Interesting work on the development of new W alloys (W-HfC-X) and the characterization of some commercial refractory metals, e.g., K-doped W, TZM, and Nb-1%Zr, continues. Finally, recent developments in high temperature composites reinforced with refractory metal filaments, and refractory metal-based intermetallics, e.g., Nb{sub 3}Al, Nb{sub 2}Be{sub 17}, and MoSi{sub 2}, are briefly described.

  14. NASA-UVA light aerospace alloy and structures technology program

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  15. Investigation of joining techniques for advanced austenitic alloys

    SciTech Connect

    Lundin, C.D.; Qiao, C.Y.P.; Kikuchi, Y.; Shi, C.; Gill, T.P.S.

    1991-05-01

    Modified Alloys 316 and 800H, designed for high temperature service, have been developed at Oak Ridge National Laboratory. Assessment of the weldability of the advanced austenitic alloys has been conducted at the University of Tennessee. Four aspects of weldability of the advanced austenitic alloys were included in the investigation.

  16. Systems study of transport aircraft incorporating advanced aluminum alloys

    NASA Technical Reports Server (NTRS)

    Sakata, I. F.

    1982-01-01

    A study was performed to quantify the potential benefits of utilizing advanced aluminum alloys in commercial transport aircraft and to define the effort necessary to develop fully the alloys to a viable commercial production capability. The comprehensive investigation (1) established realistic advanced aluminum alloy property goals to maximize aircraft systems effectiveness (2) identified performance and economic benefits of incorporating the advanced alloy in future advanced technology commercial aircraft designs (3) provided a recommended plan for development and integration of the alloys into commercial aircraft production (4) provided an indication of the timing and investigation required by the metal producing industry to support the projected market and (5) evaluate application of advanced aluminum alloys to other aerospace and transit systems as a secondary objective. The results of the investigation provided a roadmap and identified key issues requiring attention in an advanced aluminum alloy and applications technology development program.

  17. NASA-UVa light aerospace alloy and structures technology program

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  18. Fine precipitation scenarios of AlZnMg(Cu) alloys revealed by advanced atomic-resolution electron microscopy study Part I: Structure determination of the precipitates in AlZnMg(Cu) alloys

    SciTech Connect

    Liu, J.Z.; Chen, J.H.; Yuan, D.W.; Wu, C.L.; Zhu, J.; Cheng, Z.Y.

    2015-01-15

    Although they are among the most important precipitation-hardened materials for industry applications, the high-strength AlZnMg(Cu) alloys have thus far not yet been understood adequately about their underlying precipitation scenarios in relation with the properties. This is partly due to the fact that the structures of a number of different precipitates involved in electron microscopy in association with quantitative image simulations have to be employed; a systematic study of these hardening precipitates in different alloys is also necessary. In Part I of the present study, it is shown that there are five types of structurally different precipitates including the equilibrium η-phase precipitate. Using two state-of-the-art atomic-resolution imaging techniques in electron microscopy in association with quantitative image simulations, we have determined and clarified all the unknown precipitate structures. It is demonstrated that atomic-resolution imaging can directly suggest approximate structure models, whereas quantitative image analysis can refine the structure details that are much smaller than the resolution of the microscope. This combination is crucially important for solving the difficult structure problems of the strengthening precipitates in AlZnMg(Cu) alloys. - Highlights: Part I: • We determine and verify all the key precipitate structures in AlMgZn(Cu) alloys. • We employ aberration-corrected scanning transmission electron microscopy (STEM). • We use aberration-corrected high-resolution TEM (HRTEM) for the investigations. • We obtain atomic-resolution images of the precipitates and model their structures. • We refine all precipitate structures with quantitative image simulation analysis. Part II: • The hardening precipitates in AlZnMg alloys shall be classified into two groups. • Two precipitation scenarios coexist in the alloys. • The precipitation behavior of such an alloy depends on the alloy's composition. • Very detailed phase/structure

  19. Advanced characterization study of commercial conversion and electrocoating structures on magnesium alloys AZ31B and ZE10A

    DOE PAGES

    Brady, Michael P.; Leonard, Donovan N.; Meyer, III, Harry M.; ...

    2016-03-31

    The local metal-coating interface microstructure and chemistry formed on commercial magnesium alloys Mg–3Al–1Zn (AZ31B) and Mg–1Zn–0.25Zr–<0.5Nd (ZE10A, ZEK100 type) were analyzed as-chemical conversion coated with a commercial hexafluoro-titanate/zirconate type + organic polymer based treatment (Bonderite® 5200) and a commercial hexafluoro-zirconate type + trivalent chromium Cr3 + type treatment (Surtec® 650), and after the same conversion coatings followed by electrocoating with an epoxy based coating, Cathoguard® 525. Characterization techniques included scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and cross-section scanning transmission electron microscopy (STEM). Corrosion behavior was assessed in room temperature saturated aqueous Mg(OH)2 solution with 1 wt.% NaCl. Themore » goal of the effort was to assess the degree to which substrate alloy additions become enriched in the conversion coating, and how the conversion coating was impacted by subsequent electrocoating. Key findings included the enrichment of Al from AZ31B and Zr from ZE10A, respectively, into the conversion coating, with moderate corrosion resistance benefits for AZ31B when Al was incorporated. Varying degrees of increased porosity and modification of the initial conversion coating chemistry at the metal-coating interface were observed after electrocoating. These changes were postulated to result in degraded electrocoating protectiveness. As a result, these observations highlight the challenges of coating Mg, and the need to tailor electrocoating in light of potential degradation of the initial as-conversion coated Mg alloy surface.« less

  20. Advanced characterization study of commercial conversion and electrocoating structures on magnesium alloys AZ31B and ZE10A

    SciTech Connect

    Brady, Michael P.; Leonard, Donovan N.; Meyer, III, Harry M.; Song, Guang -Ling; Kitchen, Kris; Davis, Bruce; Thompson, J. K.; Unocic, K. A.; Elsentriecy, H. H.

    2016-03-31

    The local metal-coating interface microstructure and chemistry formed on commercial magnesium alloys Mg–3Al–1Zn (AZ31B) and Mg–1Zn–0.25Zr–<0.5Nd (ZE10A, ZEK100 type) were analyzed as-chemical conversion coated with a commercial hexafluoro-titanate/zirconate type + organic polymer based treatment (Bonderite® 5200) and a commercial hexafluoro-zirconate type + trivalent chromium Cr3 + type treatment (Surtec® 650), and after the same conversion coatings followed by electrocoating with an epoxy based coating, Cathoguard® 525. Characterization techniques included scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), and cross-section scanning transmission electron microscopy (STEM). Corrosion behavior was assessed in room temperature saturated aqueous Mg(OH)2 solution with 1 wt.% NaCl. The goal of the effort was to assess the degree to which substrate alloy additions become enriched in the conversion coating, and how the conversion coating was impacted by subsequent electrocoating. Key findings included the enrichment of Al from AZ31B and Zr from ZE10A, respectively, into the conversion coating, with moderate corrosion resistance benefits for AZ31B when Al was incorporated. Varying degrees of increased porosity and modification of the initial conversion coating chemistry at the metal-coating interface were observed after electrocoating. These changes were postulated to result in degraded electrocoating protectiveness. As a result, these observations highlight the challenges of coating Mg, and the need to tailor electrocoating in light of potential degradation of the initial as-conversion coated Mg alloy surface.

  1. Aerospace applications of advanced aluminum alloys

    NASA Technical Reports Server (NTRS)

    Chellman, D. J.; Langenbeck, S. L.

    1993-01-01

    Advanced metallic materials within the Al-base family are being developed for applications on current and future aerospace vehicles. These advanced materials offer significant improvements in density, strength, stiffness, fracture resistance, and/or higher use temperature which translates into improved vehicle performance. Aerospace applications of advanced metallic materials include space structures, fighters, military and commercial transport aircraft, and missiles. Structural design requirements, including not only static and durability/damage tolerance criteria but also environmental considerations, drive material selections. Often trade-offs must be made regarding strength, fracture resistance, cost, reliability, and maintainability in order to select the optimum material for a specific application. These trade studies not only include various metallic materials but also many times include advanced composite materials. Details of material comparisons, aerospace applications, and material trades will be presented.

  2. Investigation of austenitic alloys for advanced heat recovery and hot gas cleanup systems

    SciTech Connect

    Swindeman, R.W.; Ren, W.

    1995-08-01

    Alloys for design and construction of structural components needed to contain process streams and provide internal structures in advanced heat recovery and hot gas cleanup systems were examined. Emphasis was placed on high-strength, corrosion-resistant alloys for service at temperatures above 1000 {degrees}F (540{degrees}C). Data were collected that related to fabrication, joining, corrosion protection, and failure criteria. Alloys systems include modified type 310 and 20Cr-25Ni-Nb steels and sulfidation-resistance alloys HR120 and HR160. Types of testing include creep, stress-rupture, creep crack growth, fatigue, and post-exposure short-time tensile. Because of the interest in relatively inexpensive alloys for high temperature service, a modified type 310 stainless steel was developed with a target strength of twice that for standard type 310 stainless steel.

  3. Corrosion performance of structural alloys.

    SciTech Connect

    Natesan, K.

    1999-07-15

    Component reliability and long-term trouble-free performance of structural materials are essential in power-generating and gasification processes that utilize coal as a feedstock. During combustion and conversion of coal, the environments encompass a wide range of oxygen partial pressures, from excess-air conditions in conventional boilers to air-deficient conditions in 10W-NO{sub x} and gasification systems. Apart from the environmental aspects of the effluent from coal combustion and conversion, one concern from the systems standpoint is the aggressiveness of the gaseous/deposit environment toward structural components such as waterwall tubes, steam superheaters, syngas coolers, and hot-gas filters. The corrosion tests in the program described in this paper address the individual and combined effects of oxygen, sulfur, and chlorine on the corrosion response of several ASME-coded and noncoded structural alloys that were exposed to air-deficient and excess-air environments typical of coal-combustion and gasification processes. Data in this paper address the effects of preoxidation on the subsequent corrosion performance of structural materials such as 9Cr-1Mo ferritic steel, Type 347 austenitic stainless steel, Alloys 800, 825, 625, 214, Hastelloy X, and iron aluminide when exposed at 650 C to various mixed-gas environments with and without HCI. Results are presented for scaling kinetics, microstructural characteristics of corrosion products, detailed evaluations of near-surface regions of the exposed specimens, gains in our mechanistic understanding of the roles of S and Cl in the corrosion process, and the effect of preoxidation on subsequent corrosion.

  4. 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.

  5. NASA-UVA light aerospace alloy and structures technology program

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    The report on progress achieved in accomplishing of the NASA-UVA Light Aerospace Alloy and Structures Technology Program is presented. The objective is to conduct interdisciplinary graduate student research on the performance of next generation, light weight aerospace alloys and associated thermal gradient structures in close collaboration with researchers. The efforts will produce basic understanding of material behavior, new monolithic and composite alloys, processing methods, solid and fluid mechanics analyses, measurement advances, and a pool of educated graduate students. The presented accomplishments include: research on corrosion fatigue of Al-Li-Cu alloy 2090; research on the strengthening effect of small In additions to Al-Li-Cu alloys; research on localized corrosion of Al-Li alloys; research on stress corrosion cracking of Al-Li-Cu alloys; research on fiber-matrix reaction studies (Ti-1100 and Ti-15-3 matrices containing SCS-6, SCS-9, and SCS-10 fibers); and research on methods for quantifying non-random particle distribution in materials that has led to generation of a set of computer programs that can detect and characterize clusters in particles.

  6. Periodic Cellular Structure Technology for Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

    Chen, Edward Y.

    2015-01-01

    Shape memory alloys are being considered for a wide variety of adaptive components for engine and airframe applications because they can undergo large amounts of strain and then revert to their original shape upon heating or unloading. Transition45 Technologies, Inc., has developed an innovative periodic cellular structure (PCS) technology for shape memory alloys that enables fabrication of complex bulk configurations, such as lattice block structures. These innovative structures are manufactured using an advanced reactive metal casting technology that offers a relatively low cost and established approach for constructing near-net shape aerospace components. Transition45 is continuing to characterize these structures to determine how best to design a PCS to better exploit the use of shape memory alloys in aerospace applications.

  7. Investigation of austenitic alloys for advanced heat recovery and hot gas cleanup systems

    SciTech Connect

    Swindeman, R.W.; Ren, W.

    1996-08-01

    Materials properties were collected for the design and construction of structural components for use in advanced heat recovery and hot gas cleanup systems. Alloys systems included 9Cr-1Mo-V steel, modified 316 stainless steel, modified type 310 stainless steel, modified 20Cr-25Ni-Nb stainless steel, modified alloy 800, and two sulfidation resistant alloys: HR160 and HR120. Experimental work was undertaken to expand the databases for potentially useful alloys. Types of testing included creep, stress-rupture, creep-crack growth, fatigue, and post-exposure short-time tensile tests. Because of the interest in relatively inexpensive alloys for service at 700{degrees}C and higher, research emphasis was placed on a modified type 310 stainless steel and a modified 20Cr-25Ni-Nb stainless steel. Both steels were found to have useful strength to 925{degrees}C with good weldability and ductility.

  8. Influence of chemical disorder on energy dissipation and defect evolution in advanced alloys

    SciTech Connect

    Zhang, Yanwen; Jin, Ke; Xue, Haizhou; Lu, Chenyang; Olsen, Raina J.; Beland, Laurent K.; Ullah, Mohammad W.; Zhao, Shijun; Bei, Hongbin; Aidhy, Dilpuneet S.; Samolyuk, German D.; Wang, Lumin; Caro, Magdalena; Caro, Alfredo; Stocks, G. Malcolm; Larson, Ben C.; Robertson, Ian M.; Correa, Alfredo A.; Weber, William J.

    2016-08-01

    We report that historically, alloy development with better radiation performance has been focused on traditional alloys with one or two principal element(s) and minor alloying elements, where enhanced radiation resistance depends on microstructural or nanoscale features to mitigate displacement damage. In sharp contrast to traditional alloys, recent advances of single-phase concentrated solid solution alloys (SP-CSAs) have opened up new frontiers in materials research. In these alloys, a random arrangement of multiple elemental species on a crystalline lattice results in disordered local chemical environments and unique site-to-site lattice distortions. Based on closely integrated computational and experimental studies using a novel set of SP-CSAs in a face-centered cubic structure, we have explicitly demonstrated that increasing chemical disorder can lead to a substantial reduction in electron mean free paths, as well as electrical and thermal conductivity, which results in slower heat dissipation in SP-CSAs. The chemical disorder also has a significant impact on defect evolution under ion irradiation. Considerable improvement in radiation resistance is observed with increasing chemical disorder at electronic and atomic levels. Finally, the insights into defect dynamics may provide a basis for understanding elemental effects on evolution of radiation damage in irradiated materials and may inspire new design principles of radiation-tolerant structural alloys for advanced energy systems.

  9. Influence of chemical disorder on energy dissipation and defect evolution in advanced alloys

    DOE PAGES

    Zhang, Yanwen; Jin, Ke; Xue, Haizhou; ...

    2016-08-01

    We report that historically, alloy development with better radiation performance has been focused on traditional alloys with one or two principal element(s) and minor alloying elements, where enhanced radiation resistance depends on microstructural or nanoscale features to mitigate displacement damage. In sharp contrast to traditional alloys, recent advances of single-phase concentrated solid solution alloys (SP-CSAs) have opened up new frontiers in materials research. In these alloys, a random arrangement of multiple elemental species on a crystalline lattice results in disordered local chemical environments and unique site-to-site lattice distortions. Based on closely integrated computational and experimental studies using a novel setmore » of SP-CSAs in a face-centered cubic structure, we have explicitly demonstrated that increasing chemical disorder can lead to a substantial reduction in electron mean free paths, as well as electrical and thermal conductivity, which results in slower heat dissipation in SP-CSAs. The chemical disorder also has a significant impact on defect evolution under ion irradiation. Considerable improvement in radiation resistance is observed with increasing chemical disorder at electronic and atomic levels. Finally, the insights into defect dynamics may provide a basis for understanding elemental effects on evolution of radiation damage in irradiated materials and may inspire new design principles of radiation-tolerant structural alloys for advanced energy systems.« less

  10. 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.

  11. 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.

  12. Exploratory Investigation of Advanced-Temperature Nickel-Base Alloys

    NASA Technical Reports Server (NTRS)

    Freche, John C.; Waters, William J.

    1959-01-01

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

  13. Advanced oxide dispersion strengthened sheet alloys for improved combustor durability

    NASA Technical Reports Server (NTRS)

    Henricks, R. J.

    1981-01-01

    Burner design modifications that will take advantage of the improved creep and cyclic oxidation resistance of oxide dispersion strengthened (ODS) alloys while accommodating the reduced fatigue properties of these materials were evaluated based on preliminary analysis and life predictions, on construction and repair feasibility, and on maintenance and direct operating costs. Two designs - the film cooled, segmented louver and the transpiration cooled, segmented twin Wall - were selected for low cycle fatigue (LCF) component testing. Detailed thermal and structural analysis of these designs established the strain range and temprature at critical locations resulting in predicted lives of 10,000 cycles for MA 956 alloy. The ODs alloys, MA 956 and HDA 8077, demonstrated a 167 C (300 F) temperature advantage over Hastelloy X alloy in creep strength and oxidation resistance. The MA 956 alloy was selected for mechanical property and component test evaluations. The MA 956 alloy was superior to Hastelloy X in LCF component testing of the film cooled, segmented louver design.

  14. Assessment of Titanium Aluminide Alloys for High-Temperature Nuclear Structural Applications

    NASA Astrophysics Data System (ADS)

    Zhu, Hanliang; Wei, Tao; Carr, David; Harrison, Robert; Edwards, Lyndon; Hoffelner, Wolfgang; Seo, Dongyi; Maruyama, Kouichi

    2012-12-01

    Titanium aluminide (TiAl) alloys exhibit high specific strength, low density, good oxidation, corrosion, and creep resistance at elevated temperatures, making them good candidate materials for aerospace and automotive applications. TiAl alloys also show excellent radiation resistance and low neutron activation, and they can be developed to have various microstructures, allowing different combinations of properties for various extreme environments. Hence, TiAl alloys may be used in advanced nuclear systems as high-temperature structural materials. Moreover, TiAl alloys are good materials to be used for fundamental studies on microstructural effects on irradiation behavior of advanced nuclear structural materials. This article reviews the microstructure, creep, radiation, and oxidation properties of TiAl alloys in comparison with other nuclear structural materials to assess the potential of TiAl alloys as candidate structural materials for future nuclear applications.

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

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  16. Structural alloys for high field superconducting magnets

    SciTech Connect

    Morris, J.W. Jr.

    1985-08-01

    Research toward structural alloys for use in high field superconducting magnets is international in scope, and has three principal objectives: the selection or development of suitable structural alloys for the magnet support structure, the identification of mechanical phenomena and failure modes that may influence service behavior, and the design of suitable testing procedures to provide engineering design data. This paper reviews recent progress toward the first two of these objectives. The structural alloy needs depend on the magnet design and superconductor type and differ between magnets that use monolithic and those that employ force-cooled or ICCS conductors. In the former case the central requirement is for high strength, high toughness, weldable alloys that are used in thick sections for the magnet case. In the latter case the need is for high strength, high toughness alloys that are used in thin welded sections for the conductor conduit. There is productive current research on both alloy types. The service behavior of these alloys is influenced by mechanical phenomena that are peculiar to the magnet environment, including cryogenic fatigue, magnetic effects, and cryogenic creep. The design of appropriate mechanical tests is complicated by the need for testing at 4/sup 0/K and by rate effects associated with adiabatic heating during the tests. 46 refs.

  17. Structure Map for Embedded Binary Alloy Nanocrystals

    SciTech Connect

    Yuan, C.W.; Shin, S.J.; Liao, C.Y.; Guzman, J.; Stone, P.R.; Watanabe, M.; Ager III, J.W.; Haller, E.E.; Chrzan, D.C.

    2008-09-20

    The equilibrium structure of embedded nanocrystals formed from strongly segregating binary-alloys is considered within a simple thermodynamic model. The model identifies two dimensionlessinterface energies that dictate the structure, and allows prediction of the stable structure for anychoice of these parameters. The resulting structure map includes three distinct nanocrystal mor-phologies: core/shell, lobe/lobe, and completely separated spheres.

  18. Investigation of austenitic alloys for advanced heat recovery and hot-gas cleanup systems

    SciTech Connect

    Swindeman, R.W.

    1997-12-01

    Materials properties were collected for the design and construction of structural components for use in advanced heat recovery and hot gas cleanup systems. Alloys systems included 9Cr-1Mo-V steel, modified 316 stainless steel, modified type 310 stainless steel, modified 20Cr-25Ni-Nb stainless steel, and modified alloy 800. Experimental work was undertaken to expand the databases for potentially useful alloys. Types of testing included creep, stress-rupture, creep-crack growth, fatigue, and post-exposure short-time tensile tests. Because of the interest in relatively inexpensive alloys for service at 700 C and higher, research emphasis was placed on a modified type 310 stainless steel and a modified 20Cr-25Ni-Nb stainless steel. Both steels were found to have useful strength to 925 C with good weldability and ductility.

  19. Three-Dimensional Cellular Structures Enhanced By Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

    Nathal, Michael V.; Krause, David L.; Wilmoth, Nathan G.; Bednarcyk, Brett A.; Baker, Eric H.

    2014-01-01

    This research effort explored lightweight structural concepts married with advanced smart materials to achieve a wide variety of benefits in airframe and engine components. Lattice block structures were cast from an aerospace structural titanium alloy Ti-6Al-4V and a NiTi shape memory alloy (SMA), and preliminary properties have been measured. A finite element-based modeling approach that can rapidly and accurately capture the deformation response of lattice architectures was developed. The Ti-6-4 and SMA material behavior was calibrated via experimental tests of ligaments machined from the lattice. Benchmark testing of complete lattice structures verified the main aspects of the model as well as demonstrated the advantages of the lattice structure. Shape memory behavior of a sample machined from a lattice block was also demonstrated.

  20. 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

  1. Steam Oxidation of Advanced Steam Turbine Alloys

    SciTech Connect

    Holcomb, Gordon R.

    2008-01-01

    Power generation from coal using ultra supercritical steam results in improved fuel efficiency and decreased greenhouse gas emissions. Results of ongoing research into the oxidation of candidate nickel-base alloys for ultra supercritical steam turbines are presented. Exposure conditions range from moist air at atmospheric pressure (650°C to 800°C) to steam at 34.5 MPa (650°C to 760°C). Parabolic scale growth coupled with internal oxidation and reactive evaporation of chromia are the primary corrosion mechanisms.

  2. Oxidation-Reduction Resistance of Advanced Copper Alloys

    NASA Technical Reports Server (NTRS)

    Greenbauer-Seng, L. (Technical Monitor); Thomas-Ogbuji, L.; Humphrey, D. L.; Setlock, J. A.

    2003-01-01

    Resistance to oxidation and blanching is a key issue for advanced copper alloys under development for NASA's next generation of reusable launch vehicles. Candidate alloys, including dispersion-strengthened Cu-Cr-Nb, solution-strengthened Cu-Ag-Zr, and ODS Cu-Al2O3, are being evaluated for oxidation resistance by static TGA exposures in low-p(O2) and cyclic oxidation in air, and by cyclic oxidation-reduction exposures (using air for oxidation and CO/CO2 or H2/Ar for reduction) to simulate expected service environments. The test protocol and results are presented.

  3. Forging of Advanced Disk Alloy LSHR

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Gayda, John; Falsey, John

    2005-01-01

    The powder metallurgy disk alloy LSHR was designed with a relatively low gamma precipitate solvus temperature and high refractory element content to allow versatile heat treatment processing combined with high tensile, creep and fatigue properties. Grain size can be chiefly controlled through proper selection of solution heat treatment temperatures relative to the gamma precipitate solvus temperature. However, forging process conditions can also significantly influence solution heat treatment-grain size response. Therefore, it is necessary to understand the relationships between forging process conditions and the eventual grain size of solution heat treated material. A series of forging experiments were performed with subsequent subsolvus and supersolvus heat treatments, in search of suitable forging conditions for producing uniform fine grain and coarse grain microstructures. Subsolvus, supersolvus, and combined subsolvus plus supersolvus heat treatments were then applied. Forging and subsequent heat treatment conditions were identified allowing uniform fine and coarse grain microstructures.

  4. Atomic Structure and Phase Transformations in Pu Alloys

    SciTech Connect

    Schwartz, A J; Cynn, H; Blobaum, K M; Wall, M A; Moore, K T; Evans, W J; Farber, D L; Jeffries, J R; Massalski, T B

    2008-04-28

    Plutonium and plutonium-based alloys containing Al or Ga exhibit numerous phases with crystal structures ranging from simple monoclinic to face-centered cubic. Only recently, however, has there been increased convergence in the actinides community on the details of the equilibrium form of the phase diagrams. Practically speaking, while the phase diagrams that represent the stability of the fcc {delta}-phase field at room temperature are generally applicable, it is also recognized that Pu and its alloys are never truly in thermodynamic equilibrium because of self-irradiation effects, primarily from the alpha decay of Pu isotopes. This article covers past and current research on several properties of Pu and Pu-(Al or Ga) alloys and their connections to the crystal structure and the microstructure. We review the consequences of radioactive decay, the recent advances in understanding the electronic structure, the current research on phase transformations and their relations to phase diagrams and phase stability, the nature of the isothermal martensitic {delta} {yields} {alpha}{prime} transformation, and the pressure-induced transformations in the {delta}-phase alloys. New data are also presented on the structures and phase transformations observed in these materials following the application of pressure, including the formation of transition phases.

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

    NASA Technical Reports Server (NTRS)

    Gangloff, Richard P.

    1991-01-01

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

  6. Advanced Tribological Coatings for High Specific Strength Alloys

    DTIC Science & Technology

    1989-09-29

    Hard Anodised 4 HSSA12 (SHT) Plasma Nitrided 1 HSSA13 (H&G) Plasma Nitrided 2 HSSA14 (SHT) High Temperature Nitrocarburized 1 HSSA15 (H&G) Nitrox 1...HSSA26 ( High Temperature Plasma Nitriding) has recently arrived, and is currently undergoing metallographic examination. The remaining samples are still...Report No 3789/607 Advanced Tribological Coatings For High Specific Strength Alloys, R&D 5876-MS-01 Contract DAJ A45-87-C-0044 5th Interim Report

  7. TEM Examination of Advanced Alloys Irradiated in ATR

    SciTech Connect

    Jian Gan, PhD

    2007-09-01

    Successful development of materials is critical to the deployment of advanced nuclear power systems. Irradiation studies of candidate materials play a vital role for better understanding materials performance under various irradiation environments of advanced system designs. In many cases, new classes of materials have to be investigated to meet the requirements of these advanced systems. For applications in the temperature range of 500 800ºC which is relevant to the fast neutron spectrum burner reactors for the Global Nuclear Energy Partnership (GNEP) program, oxide dispersion strengthened (ODS) and ferritic martensitic steels (e.g., MA957 and others) are candidates for advanced cladding materials. In the low temperature regions of the core (<600ºC), alloy 800H, HCM12A (also called T 122) and HT 9 have been considered.

  8. Advanced Polymer Network Structures

    DTIC Science & Technology

    2016-02-01

    13. SUPPLEMENTARY NOTES 14. ABSTRACT Polymer networks and gels are important classes of materials for defense applications . In an effort to......it is no longer needed. Do not return it to the originator. ARL-TR-7612 ● FEB 2016 US Army Research Laboratory Advanced Polymer

  9. Russian aluminum-lithium alloys for advanced reusable spacecraft

    NASA Astrophysics Data System (ADS)

    Charette, Ray O.; Leonard, Bruce G.; Bozich, William F.; Deamer, David A.

    1998-01-01

    Cryotanks that are cost-affordable, robust, fuel-compatible, and lighter weight than current aluminum design are needed to support next-generation launch system performance and operability goals. The Boeing (McDonnell Douglas Aerospace-MDA) and NASA's Delta Clipper-Experimental Program (DC-XA) flight demonstrator test bed vehicle provided the opportunity for technology transfer of Russia's extensive experience base with weight-efficient, highly weldable aluminum-lithium (Al-Li) alloys for cryogenic tank usage. As part of NASA's overall reusable launch vehicle (RLV) program to help provide technology and operations data for use in advanced RLVs, MDA contracted with the Russian Academy of Sciences (RAS/IMASH) for design, test, and delivery of 1460 Al-Li alloy liquid oxygen (LO2) cryotanks: one for development, one for ground tests, and one for DC-XA flight tests. This paper describes the development of Al-Li 1460 alloy for reusable LO2 tanks, including alloy composition tailoring, mechanical properties database, forming, welding, chemical milling, dissimilar metal joining, corrosion protection, completed tanks proof, and qualification testing. Mechanical properties of the parent and welded materials exceeded expectations, particularly the fracture toughness, which promise excellent reuse potential. The LO2 cryotank was successfully demonstrated in DC-XA flight tests.

  10. Photonic crystal digital alloys and their band structure properties.

    PubMed

    Lee, Jeongkug; Kim, Dong-Uk; Jeon, Heonsu

    2011-09-26

    We investigated semi-disordered photonic crystals (PCs), digital alloys, and made thorough comparisons with their counterparts, random alloys. A set of diamond lattice PC digital alloys operating in a microwave regime were prepared by alternately stacking two kinds of sub-PC systems composed of alumina and silica spheres of the same size. Measured transmission spectra as well as calculated band structures revealed that when the digital alloy period is short, band-gaps of the digital alloys are practically the same as those of the random alloys. This study indicates that the concept of digital alloys holds for photons in PCs as well.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  12. Advanced technology composite aircraft structures

    NASA Technical Reports Server (NTRS)

    Ilcewicz, Larry B.; Walker, Thomas H.

    1991-01-01

    Work performed during the 25th month on NAS1-18889, Advanced Technology Composite Aircraft Structures, is summarized. The main objective of this program is to develop an integrated technology and demonstrate a confidence level that permits the cost- and weight-effective use of advanced composite materials in primary structures of future aircraft with the emphasis on pressurized fuselages. The period from 1-31 May 1991 is covered.

  13. The Effect of Solution Heat Treatment on an Advanced Nickel-Base Disk Alloy

    NASA Technical Reports Server (NTRS)

    Gayda, J.; Gabb, T. P.; Kantzos, P. T.

    2004-01-01

    Five heat treat options for an advanced nickel-base disk alloy, LSHR, have been investigated. These included two conventional solution heat treat cycles, subsolvus/oil quench and supersolvus/fan cool, which yield fine grain and coarse grain microstructure disks respectively, as well as three advanced dual microstructure heat treat (DMHT) options. The DMHT options produce disks with a fine grain bore and a coarse grain rim. Based on an overall evaluation of the mechanical property data, it was evident that the three DMHT options achieved a desirable balance of properties in comparison to the conventional solution heat treatments for the LSHR alloy. However, one of the DMHT options, SUB/DMHT, produced the best set of properties, largely based on dwell crack growth data. Further evaluation of the SUB/DMHT option in spin pit experiments on a generic disk shape demonstrated the advantages and reliability of a dual grain structure at the component level.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  15. 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.

  16. Effective band structure of random alloys.

    PubMed

    Popescu, Voicu; Zunger, Alex

    2010-06-11

    Random substitutional A(x)B(1-x) alloys lack formal translational symmetry and thus cannot be described by the language of band-structure dispersion E(k(→)). Yet, many alloy experiments are interpreted phenomenologically precisely by constructs derived from wave vector k(→), e.g., effective masses or van Hove singularities. Here we use large supercells with randomly distributed A and B atoms, whereby many different local environments are allowed to coexist, and transform the eigenstates into an effective band structure (EBS) in the primitive cell using a spectral decomposition. The resulting EBS reveals the extent to which band characteristics are preserved or lost at different compositions, band indices, and k(→) points, showing in (In,Ga)N the rapid disintegration of the valence band Bloch character and in Ga(N,P) the appearance of a pinned impurity band.

  17. Advanced austenitic alloys for fossil power systems. CRADA final report

    SciTech Connect

    Swindeman, R.W.; Cole, N.C.; Canonico, D.A.; Henry, J.F.

    1998-08-01

    In 1993, a Cooperative Research and Development Agreement (CRADA) was undertaken between Oak Ridge National Laboratory and ABB Combustion Engineering t examine advanced alloys for fossil power systems. Specifically, the use of advanced austenitic stainless steels for superheater/reheater construction in supercritical boilers was examined. The strength of cold-worked austenitic stainless steels was reviewed and compared to the strength and ductility of advanced austenitic stainless steels. The advanced stainless steels were found to retain their strength to very long times at temperatures where cold-worked standard grades of austenitic stainless steels became weak. Further, the steels exhibited better long-time stability than the stabilized 300 series stainless steels in either the annealed or cold worked conditions. Type 304H mill-annealed tubing was provided to ORNL for testing of base metal and butt welds. The tubing was found to fall within range of expected strength for 304H stainless steel. The composite 304/308 stainless steel was found to be stronger than typical for the weldment. Boiler tubing was removed from a commercial boiler for replacement by newer steels, but restraints imposed by the boiler owners did not permit the installation of the advanced steels, so a standard 32 stainless steel was used as a replacement. The T91 removed from the boiler was characterized.

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

    NASA Technical Reports Server (NTRS)

    Scully, John R.; Shiflet, Gary J.; Stoner, Glenn E.; Wert, John A.

    1996-01-01

    The NASA-UVA Light Aerospace Alloy and Structures Technology (LA2ST) Program was initiated in 1986 and continues with a high level of activity. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light-weight aerospace alloys, composites and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. We generally aim to produce relevant data and basic understanding of material mechanical response, environmental/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement and modeling advances; and a pool of educated graduate students for aerospace technologies. Three research areas are being actively investigated, including: (1) Mechanical and environmental degradation mechanisms in advanced light metals, (2) Aerospace materials science, and (3) Mechanics of materials for light aerospace structures.

  19. Advances in Solid State Joining of High Temperature Alloys

    NASA Technical Reports Server (NTRS)

    Ding, Jeff; Schneider, Judy

    2011-01-01

    Many of the metals used in the oil and gas industry are difficult to fusion weld including Titanium and its alloys. Solid state joining processes are being pursued as an alternative process to produce robust structures more amenable to high pressure applications. Various solid state joining processes include friction stir welding (FSW) and a patented modification termed thermal stir welding (TSW). The configuration of TSWing utilizes an induction coil to preheat the material minimizing the burden on the weld tool extending its life. This provides the ability to precisely select and control the temperature to avoid detrimental changes to the microstructure. The work presented in this presentation investigates the feasibility of joining various titanium alloys using the solid state welding processes of FSW and TSW. Process descriptions and attributes of each weld process will be presented. Weld process set ]up and welding techniques will be discussed leading to the challenges experienced. Mechanical property data will also be presented.

  20. Report on sodium compatibility of advanced structural materials.

    SciTech Connect

    Li, M.; Natesan, K.; Momozaki, Y.; Rink, D.L.; Soppet, W.K.; Listwan, J.T.

    2012-07-09

    This report provides an update on the evaluation of sodium compatibility of advanced structural materials. The report is a deliverable (level 3) in FY11 (M3A11AN04030403), under the Work Package A-11AN040304, 'Sodium Compatibility of Advanced Structural Materials' performed by Argonne National Laboratory (ANL), as part of Advanced Structural Materials Program for the Advanced Reactor Concepts. This work package supports the advanced structural materials development by providing corrosion and tensile data from the standpoint of sodium compatibility of advanced structural alloys. The scope of work involves exposure of advanced structural alloys such as G92, mod.9Cr-1Mo (G91) ferritic-martensitic steels and HT-UPS austenitic stainless steels to a flowing sodium environment with controlled impurity concentrations. The exposed specimens are analyzed for their corrosion performance, microstructural changes, and tensile behavior. Previous reports examined the thermodynamic and kinetic factors involved in the purity of liquid sodium coolant for sodium reactor applications as well as the design, fabrication, and construction of a forced convection sodium loop for sodium compatibility studies of advanced materials. This report presents the results on corrosion performance, microstructure, and tensile properties of advanced ferritic-martensitic and austenitic alloys exposed to liquid sodium at 550 C for up to 2700 h and at 650 C for up to 5064 h in the forced convection sodium loop. The oxygen content of sodium was controlled by the cold-trapping method to achieve {approx}1 wppm oxygen level. Four alloys were examined, G92 in the normalized and tempered condition (H1 G92), G92 in the cold-rolled condition (H2 G92), G91 in the normalized and tempered condition, and hot-rolled HT-UPS. G91 was included as a reference to compare with advanced alloy, G92. It was found that all four alloys showed weight loss after sodium exposures at 550 and 650 C. The weight loss of the four

  1. 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.

  2. Cast Alloys for Advanced Ultra Supercritical Steam Turbines

    SciTech Connect

    G. R. Holcomb, P. Wang, P. D. Jablonski, and J. A. Hawk,

    2010-05-01

    The proposed steam inlet temperature in the Advanced Ultra Supercritical (A-USC) steam turbine is high enough (760 °C) that traditional turbine casing and valve body materials such as ferritic/martensitic steels will not suffice due to temperature limitations of this class of materials. Cast versions of several traditionally wrought Ni-based superalloys were evaluated for use as casing or valve components for the next generation of industrial steam turbines. The full size castings are substantial: 2-5,000 kg each half and on the order of 100 cm thick. Experimental castings were quite a bit smaller, but section size was retained and cooling rate controlled to produce equivalent microstructures. A multi-step homogenization heat treatment was developed to better deploy the alloy constituents. The most successful of these cast alloys in terms of creep strength (Haynes 263, Haynes 282, and Nimonic 105) were subsequently evaluated by characterizing their microstructure as well as their steam oxidation resistance (at 760 and 800 °C).

  3. Improved Electroformed Structural Copper and Copper Alloys

    NASA Technical Reports Server (NTRS)

    Malone, G. A.; Hudson, W.; Babcock, B.; Edwards, R.

    1998-01-01

    Electroforming offers a superior means for fabricating internally cooled heat exchangers and structures subjected to thermal environments. Copper is deposited from many such applications because of the good thermal conductivity. It suffers from mediocre yield strength as a structural material and loses mechanical strength at intermediate temperatures. Mechanical properties similar to those of electroformed nickel are desired. Phase 1 examined innovative means to improve deposited copper structural performance. Yield strengths as high as 483 MPa (70 ksi) were obtained with useful ductility while retaining a high level of purity essential to good thermal conductivity. Phase 2 represents a program to explore new additive combinations in copper electrolytes to produce a more fine, equiaxed grain which can be thermally stabilized by other techniques such as alloying in modest degrees and dispersion strengthening. Evaluation of new technology - such as the codeposition of fullerness (diamond-like) particles were made to enhance thermal conductivity in low alloys. A test fire quality tube-bundle engine was fabricated using these copper property improvement concepts to show the superiority of the new coppers and fabrications methods over competitive technologies such as brazing and plasma deposition.

  4. Vacuum Plasma Spray of CuCrNb Alloy for Advanced Liquid - Fuel Combustion Chambers

    NASA Technical Reports Server (NTRS)

    Zimmerman, Frank

    2000-01-01

    The copper-8 atomic percent chromium-4 atomic percent niobium (CuCrNb) alloy was developed by Glenn Research Center (formally Lewis Research Center) as an improved alloy for combustion chamber liners. In comparison to NARloy-Z, the baseline (as in Space Shuttle Main Engine) alloy for such liners, CuCrNb demonstrates mechanical and thermophysical properties equivalent to NARloy-Z, but at temperatures 100 C to 150 C (180 F to 270 F) higher. Anticipated materials related benefits include decreasing the thrust cell liner weight 5% to 20%, increasing the service life at least two fold over current combustion chamber design, and increasing the safety margins available to designers. By adding an oxidation and thermal barrier coating to the liner, the combustion chamber can operate at even higher temperatures. For all these benefits, however, this alloy cannot be formed using conventional casting and forging methods because of the levels of chromium and niobium, which exceed their solubility limit in copper. Until recently, the only forming process that maintains the required microstructure of CrNb intermetallics is powder metallurgy formation of a billet from powder stock, followed by extrusion. This severely limits its usefulness in structural applications, particularly the complex shapes required for combustion chamber liners. Vacuum plasma spray (VPS) has been demonstrated as a method to form structural articles including small combustion chambers from the CuCrNb alloy. In addition, an oxidation and thermal barrier layer can be formed integrally on the hot wall of the liner that improve performance and extend service life. This paper discusses the metallurgy and thermomechanical properties of VPS formed CuCrNb versus the baseline powder metallurgy process, and the manufacturing of small combustion chamber liners at Marshall Space Flight Center using the VPS process. The benefits to advanced propulsion initiatives of using VPS to fabricate combustion chamber liners

  5. Application of advanced austenitic alloys to fossil power system components

    SciTech Connect

    Swindeman, R.W.

    1996-06-01

    Most power and recovery boilers operating in the US produce steam at temperatures below 565{degrees}C (1050{degrees}F) and pressures below 24 MPa (3500 psi). For these operating conditions, carbon steels and low alloy steels may be used for the construction of most of the boiler components. Austenitic stainless steels often are used for superheater/reheater tubing when these components are expected to experience temperatures above 565{degrees}C (1050{degrees}F) or when the environment is too corrosive for low alloys steels. The austenitic stainless steels typically used are the 304H, 321H, and 347H grades. New ferritic steels such as T91 and T92 are now being introduced to replace austenitic: stainless steels in aging fossil power plants. Generally, these high-strength ferritic steels are more expensive to fabricate than austenitic stainless steels because the ferritic steels have more stringent heat treating requirements. Now, annealing requirements are being considered for the stabilized grades of austenitic stainless steels when they receive more than 5% cold work, and these requirements would increase significantly the cost of fabrication of boiler components where bending strains often exceed 15%. It has been shown, however, that advanced stainless steels developed at ORNL greatly benefit from cold work, and these steels could provide an alternative to either conventional stainless steels or high-strength ferritic steels. The purpose of the activities reported here is to examine the potential of advanced stainless steels for construction of tubular components in power boilers. The work is being carried out with collaboration of a commercial boiler manufacturer.

  6. Unusual Thermal Stability of High-Entropy Alloy Amorphous Structure

    DTIC Science & Technology

    2012-06-20

    1    REPORT Unusual Thermal Stability of High - Entropy Alloy Amorphous Structure Basic research for AOARD 114009 Award No. FA2386-11-1...stability of high - entropy alloy amorphous structure 5a. CONTRACT NUMBER FA23861114009 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Jien-Wei...at least 3 h. If substrate effect could be eliminated, the crystallization temperature would be higher. 15. SUBJECT TERMS high entropy alloys 16

  7. Advanced textile applications for primary aircraft structures

    NASA Technical Reports Server (NTRS)

    Jackson, Anthony C.; Barrie, Ronald E.; Shah, Bharat M.; Shukla, Jay G.

    1992-01-01

    Advanced composite primary structural concepts were evaluated for low cost, damage tolerant structures. Development of advanced textile preforms for fuselage structural applications with resin transfer molding and powder epoxy materials are now under development.

  8. Advanced textile applications for primary aircraft structures

    NASA Technical Reports Server (NTRS)

    Jackson, Anthony C.; Barrie, Ronald E.; Shah, Bharat M.; Shukla, Jay G.

    1992-01-01

    Advanced composite primary structural concepts have been evaluated for low cost, damage tolerant structures. Development of advanced textile preforms for fuselage structural applications with resin transfer molding and powder epoxy material is now under development.

  9. Alloy Surface Structure:. Computer Simulations Using the Bfs Method

    NASA Astrophysics Data System (ADS)

    Bozzolo, Guillermo; Ferrante, John

    The use of semiempirical methods for modeling alloy properties has proven to be difficult and limited. The two primary approaches to this modeling, the embedded atom method and the phenomenological method of Miedema, have serious limitations in the range of materials studied and the degree of success in predicting properties of such systems. Recently, a new method has been developed by Bozzolo, Ferrante and Smith (BFS) which has had considerable success in predicting a wide range of alloy properties. In this work, we reference previous BFS applications to surface alloy formation and alloy surface structure, leading to the analysis of binary and ternary Ni-based alloy surfaces. We present Monte Carlo simulation results of thin films of NiAl and Ni-Al-Ti alloys, for a wide range of concentration of the Ti alloying addition. The composition of planes close to the surface as well as bulk features are discussed.

  10. Advanced Structures: 2000-2004

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This custom bibliography from the NASA Scientific and Technical Information Program lists a sampling of records found in the NASA Aeronautics and Space Database. The scope of this topic includes technologies for extremely lightweight, multi-function structures with modular interfaces - the building-block technology for advanced spacecraft. This area of focus is one of the enabling technologies as defined by NASA s Report of the President s Commission on Implementation of United States Space Exploration Policy, published in June 2004.

  11. Formation of core-shell structure in high entropy alloy coating by laser cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Wu, Wanfei; He, Yizhu; Li, Mingxi; Guo, Sheng

    2016-02-01

    The formation of core-shell structure is an interesting phenomenon occurring during the solidification process, due to the liquid phase separation. The formation of core-shell structure in high-entropy alloys, a new class of advanced metallic materials, has not been reported previously, and thus constitutes an intriguing scientific question. Here, we firstly report the formation of core-shell structure in one laser cladded high-entropy alloy, where we show the nanosized-Y2O3 powder addition, serves as the catalyst for the liquid phase separation.

  12. Influence of Hold Time on Creep-Fatigue Behavior of an Advanced Austenitic Alloy

    SciTech Connect

    Mark Carroll; Laura Carroll

    2011-09-01

    An advanced austenitic alloy, HT-UPS (high temperature-ultrafine precipitate strengthened), is a candidate material for the structural components of fast reactors and energy-conversion systems. HT-UPS provides improved creep resistance through a composition based on 316 stainless steel (SS) with additions of Ti and Nb to form nano-scale MC precipitates in the austenitic matrix. The low cycle fatigue and creep-fatigue behavior of a HT-UPS alloy has been investigated at 650 C, 1.0% total strain, and an R ratio of -1 with hold times as long as 9000 sec at peak tensile strain. The cyclic deformation response of HT-UPS is compared to that of 316 SS. The cycles to failure are similar, despite differences in peak stress profiles and the deformed microstructures. Cracking in both alloys is transgranular (initiation and propagation) in the case of continuous cycle fatigue, while the primary cracks also propagate transgranularly during creep-fatigue cycling. Internal grain boundary damage as a result of the tensile hold is present in the form of fine cracks for hold times of 3600 sec and longer and substantially more internal cracks are visible in 316 SS than HT-UPS. The dislocation substructures observed in the deformed material are different. An equiaxed cellular structure is observed in 316 SS, whereas tangles of dislocations are present at the nanoscale MC precipitates in HT-UPS and no cellular substructure is observed.

  13. Atomic scale modelling of hexagonal structured metallic fission product alloys.

    PubMed

    Middleburgh, S C; King, D M; Lumpkin, G R

    2015-04-01

    Noble metal particles in the Mo-Pd-Rh-Ru-Tc system have been simulated on the atomic scale using density functional theory techniques for the first time. The composition and behaviour of the epsilon phases are consistent with high-entropy alloys (or multi-principal component alloys)-making the epsilon phase the only hexagonally close packed high-entropy alloy currently described. Configurational entropy effects were considered to predict the stability of the alloys with increasing temperatures. The variation of Mo content was modelled to understand the change in alloy structure and behaviour with fuel burnup (Mo molar content decreases in these alloys as burnup increases). The predicted structures compare extremely well with experimentally ascertained values. Vacancy formation energies and the behaviour of extrinsic defects (including iodine and xenon) in the epsilon phase were also investigated to further understand the impact that the metallic precipitates have on fuel performance.

  14. Atomic scale modelling of hexagonal structured metallic fission product alloys

    PubMed Central

    Middleburgh, S. C.; King, D. M.; Lumpkin, G. R.

    2015-01-01

    Noble metal particles in the Mo-Pd-Rh-Ru-Tc system have been simulated on the atomic scale using density functional theory techniques for the first time. The composition and behaviour of the epsilon phases are consistent with high-entropy alloys (or multi-principal component alloys)—making the epsilon phase the only hexagonally close packed high-entropy alloy currently described. Configurational entropy effects were considered to predict the stability of the alloys with increasing temperatures. The variation of Mo content was modelled to understand the change in alloy structure and behaviour with fuel burnup (Mo molar content decreases in these alloys as burnup increases). The predicted structures compare extremely well with experimentally ascertained values. Vacancy formation energies and the behaviour of extrinsic defects (including iodine and xenon) in the epsilon phase were also investigated to further understand the impact that the metallic precipitates have on fuel performance. PMID:26064629

  15. Structure of Al-Ti-C master alloys

    NASA Astrophysics Data System (ADS)

    Popova, E. A.; Brodova, I. G.; Yablonskikh, T. I.; Shirinkina, I. G.; Barbin, N. M.; Bodrova, L. E.; Dolmatov, A. V.; Pastukhov, E. A.; Vatolin, N. A.; Chebykin, V. V.; Chernov, Ya. B.

    2011-06-01

    A binary Al-Ti master alloy of hyperperitectic composition, whose structural characteristics ensure high modifying efficiency, has been prepared by the aluminothermy method. The treatment of the alloy by low-frequency vibrations (LFVs) and its interaction with the carbon emitter of LFVs in the process of crystallization lead to the formation of a ternary Al-Ti-C alloy containing titanium aluminide Al3Ti and titanium carbide TiC. The presence of these phases creates favorable conditions for the formation of solidification nuclei in the aluminum melt when using a ternary master alloy as a modifier. A comparison of the efficiency of the structure refinement when using experimental master alloys and the standard Al-Ti master alloy poured into a metallic chill mold has been performed.

  16. Advanced technology commercial fuselage structure

    NASA Technical Reports Server (NTRS)

    Ilcewicz, L. B.; Smith, P. J.; Walker, T. H.; Johnson, R. W.

    1991-01-01

    Boeing's program for Advanced Technology Composite Aircraft Structure (ATCAS) has focused on the manufacturing and performance issues associated with a wide body commercial transport fuselage. The primary goal of ATCAS is to demonstrate cost and weight savings over a 1995 aluminum benchmark. A 31 foot section of fuselage directly behind the wing to body intersection was selected for study purposes. This paper summarizes ATCAS contract plans and review progress to date. The six year ATCAS program will study technical issues for crown, side, and keel areas of the fuselage. All structural details in these areas will be included in design studies that incorporate a design build team (DBT) approach. Manufacturing technologies will be developed for concepts deemed by the DBT to have the greatest potential for cost and weight savings. Assembly issues for large, stiff, quadrant panels will receive special attention. Supporting technologies and mechanical tests will concentrate on the major issues identified for fuselage. These include damage tolerance, pressure containment, splices, load redistribution, post-buckled structure, and durability/life. Progress to date includes DBT selection of baseline fuselage concepts; cost and weight comparisons for crown panel designs; initial panel fabrication for manufacturing and structural mechanics research; and toughened material studies related to keel panels. Initial ATCAS studies have shown that NASA's Advanced Composite Technology program goals for cost and weight savings are attainable for composite fuselage.

  17. Dual-phase Cr-Ta alloys for structural applications

    DOEpatents

    Liu, Chain T.; Brady, Michael P.; Zhu, Jiahong; Tortorelli, Peter F.

    2001-01-01

    Dual phase alloys of chromium containing 2 to 11 atomic percent tantalum with minor amounts of Mo, Cr, Ti, Y, La, Cr, Si and Ge are disclosed. These alloys contain two phases including Laves phase and Cr-rich solid solution in either eutectic structures or dispersed Laves phase particles in the Cr-rich solid solution matrix. The alloys have superior mechanical properties at high temperature and good oxidation resistance when heated to above 1000.degree. C. in air.

  18. Development of Advanced Oxide Dispersion Strengthened Tungsten Heavy Alloy for Penetrator Application

    DTIC Science & Technology

    2005-09-30

    preparation, sintering, cyclic heat-treatment, swaging , and annealing processes, on microstructures and static/dynamic mechanical properties of ODS tungsten ... tungsten / tungsten contiguity. The swaging and annealing processes of ODS tungsten heavy alloy increase the tensile strength with decreasing the...Final Report for 2nd Year Contract of AOARD 034032 Development of Advanced Oxide Dispersion Strengthened Tungsten Heavy Alloy for

  19. Advances in Nanocarbon Metals: Fine Structure

    DTIC Science & Technology

    2015-03-01

    SUPPLEMENTARY NOTES 14. ABSTRACT This study is an investigation of the structure and some properties of silver, copper, and aluminum alloy covetics...Covetics can incorporate large amounts of carbon (C) in a nanoscale form to alter physical and mechanical properties of the base metal or alloy ...and properties can be obtained. 15. SUBJECT TERMS covetic, nanocarbon silver, aluminum , copper 16. SECURITY CLASSIFICATION OF: 17. LIMITATION

  20. Alloy and structural optimization of a directionally solidified lamellar eutectic alloy

    NASA Technical Reports Server (NTRS)

    Sheffler, K. D.

    1976-01-01

    Mechanical property characterization tests of a directionally solidified Ni-20 percent Cb-2.5 percent Al-6 percent Cr cellular eutectic turbine blade alloy demonstrated excellent long time creep stability and indicated intermediate temperature transverse tensile ductility and shear strength to be somewhat low for turbine blade applications. Alloy and structural optimization significantly improves these off-axis properties with no loss of longitudinal creep strength or stability. The optimized alloy-structure combination is a carbon modified Ni-20.1 percent Cb-2.5 percent Al-6.0 percent Cr-0.06 percent C composition processed under conditions producing plane front solidification and a fully-lamellar microstructure. With current processing technology, this alloy exhibits a creep-rupture advantage of 39 C over the best available nickel base superalloy, directionally solidified MAR M200+ Hf. While improved by about 20 percent, shear strength of the optimized alloy remains well below typical superalloy values.

  1. Fatigue and Creep-Fatigue Deformation of an Ultra-Fine Precipitate Strengthened Advanced Austenitic Alloy

    SciTech Connect

    M.C. Carroll; L.J. Carroll

    2012-10-01

    An advanced austenitic alloy, HT-UPS (high-temperature ultrafine-precipitation-strengthened), has been identified as an ideal candidate material for the structural components of fast reactors and energy-conversion systems. HT-UPS alloys demonstrate improved creep resistance relative to 316 stainless steel (SS) through additions of Ti and Nb, which precipitate to form a widespread dispersion of stable nanoscale metallic carbide (MC) particles in the austenitic matrix. The low-cycle fatigue and creep-fatigue behavior of an HT-UPS alloy have been investigated at 650 °C and a 1.0% total strain, with an R-ratio of -1 and hold times at peak tensile strain as long as 150 min. The cyclic deformation response of HT-UPS is directly compared to that of standard 316 SS. The measured values for total cycles to failure are similar, despite differences in peak stress profiles and in qualitative observations of the deformed microstructures. Crack propagation is primarily transgranular in fatigue and creep-fatigue of both alloys at the investigated conditions. Internal grain boundary damage in the form of fine cracks resulting from the tensile hold is present for hold times of 60 min and longer, and substantially more internal cracks are quantifiable in 316 SS than in HT-UPS. The dislocation substructures observed in the deformed material differ significantly; an equiaxed cellular structure is observed in 316 SS, whereas in HT-UPS the microstructure takes the form of widespread and relatively homogenous tangles of dislocations pinned by the nanoscale MC precipitates. The significant effect of the fine distribution of precipitates on observed fatigue and creep-fatigue response is described in three distinct behavioral regions as it evolves with continued cycling.

  2. Advances in Solid State Joining of High Temperature Alloys

    NASA Technical Reports Server (NTRS)

    Ding, R. Jeff; Schneider, Judy; Walker, Bryant

    2011-01-01

    Many of the metals used in the oil and gas industry are difficult to fusion weld including titanium and its alloys. Thus solid state joining processes, such as friction stir welding (FSWing) and a patented modification termed thermal stir welding (TSWing), are being pursued as alternatives to produce robust structures more amenable to high pressure applications. Unlike the FSWing process where the tool is used to heat the workpiece, TSWing utilizes an induction coil to preheat the material prior to stirring thus minimizing the burden on the weld tool and thereby extending its life. This study reports on the initial results of using a hybrid (H)-TSW process to join commercially pure, 1.3cm thick panels of titanium (CP Ti) Grade 2.

  3. Advanced strategic interceptor composite structures

    SciTech Connect

    Ennis, D.H.; Patty, C.E. Jr.

    1993-12-31

    Launch mass reduction, stiffness increase, and primary bending mode frequency increase remain the prime focus of the US Army Strategic Defense Command (USASDC) advanced composite material development and testing program. The initial activity was directed toward fabrication of a demonstration structure consistent with the Ground-Based Interceptor (GBI) ERIS flight design. The objectives of this phase of the work were three-fold: selection of the optimum composite materials; concurrent bonding and joining technology development; evaluation of the performance of each test structure relative to its metal counterpart and relative to alternative composites. The effort exceeded model predictions. The resin matrix composite structure mass was 52% lower than the metal design. Modal testing demonstrated a 200% increase in stiffness and a 41% gain in first mode bending frequency. Given the demonstrated level of success, an additional element was added to the task focus: cost-effective, mass quantity fabrication techniques. Single step technology has been successfully applied to a relatively simple thermoset based bridge structure. Two step molding and assembly have been demonstrated for a GBI-X class thermoplastic structure. Preliminary testing has been completed to isolate and resolve problems associated with single step fabrication of the more complex GBI-X class structure. Fabrication of an appropriate test article as preparation for modal survey evaluation of the latter is in progress. Results are presented. Future program directions are summarized.

  4. Structural tailoring of advanced turboprops

    NASA Technical Reports Server (NTRS)

    Brown, K. W.; Hopkins, Dale A.

    1988-01-01

    The Structural Tailoring of Advanced Turboprops (STAT) computer program was developed to perform numerical optimization on highly swept propfan blades. The optimization procedure seeks to minimize an objective function defined as either: (1) direct operating cost of full scale blade or, (2) aeroelastic differences between a blade and its scaled model, by tuning internal and external geometry variables that must satisfy realistic blade design constraints. The STAT analysis system includes an aerodynamic efficiency evaluation, a finite element stress and vibration analysis, an acoustic analysis, a flutter analysis, and a once-per-revolution forced response life prediction capability. STAT includes all relevant propfan design constraints.

  5. Pretreatment of Al and Mg Alloys - Structural and Electronic

    DTIC Science & Technology

    2007-05-17

    specific to discussion Applications on structural alloys and castings OEM and depot/repair/rebuild operations Magnesium Alloys Castings – AZ91 , ZE41...in repair/rework – TCP as conversion coating for both Mg and Al?? Needs for Mg Mg specific resin systems for barrier properties – Nonchromate

  6. Production of FR Tubing from Advanced ODS Alloys

    SciTech Connect

    Maloy, Stuart Andrew; Lavender, Curt; Omberg, Ron; Lewandowski, John

    2016-10-25

    Significant research is underway to develop LWR nuclear fuels with improved accident tolerance. One of the leading candidate materials for cladding are the FeCrAl alloys. New alloys produced at ORNL called Gen I and Gen II FeCrAl alloys possess excellent oxidation resistance in steam up to 1400°C and in parallel methods are being developed to produce tubing from these alloys. Century tubing continues to produce excellent tubing from FeCrAl alloys. This memo reports receipt of ~21 feet of Gen I FeCrAl alloy tubing. This tubing will be used for future tests including burst testing, mechanical testing and irradiation testing.

  7. Steam Oxidation Behavior of Advanced Steels and Ni-Based Alloys at 800 °C

    NASA Astrophysics Data System (ADS)

    Dudziak, T.; Boroń, L.; Deodeshmukh, V.; Sobczak, J.; Sobczak, N.; Witkowska, M.; Ratuszek, W.; Chruściel, K.

    2017-02-01

    This publication studies the steam oxidation behavior of advanced steels (309S, 310S and HR3C) and Ni-based alloys (Haynes® 230®, alloy 263, alloy 617 and Haynes® 282®) exposed at 800 °C for 2000 h under 1 bar pressure, in a pure water steam system. The results revealed that all exposed materials showed relatively low weight gain, with no spallation of the oxide scale within the 2000 h of exposure. XRD analysis showed that Ni-based alloys developed an oxide scale consisting of four main phases: Cr2O3 (alloy 617, Haynes® 282®, alloy 263 and Haynes® 230®), MnCr2O4 (alloy 617, Haynes® 282® and Haynes® 230®), NiCr2O4 (alloy 617) and TiO2 (alloy 263, Haynes® 282®). In contrast, advanced steels showed the development of Cr2O3, MnCr2O4, Mn7SiO12, FeMn(SiO4) and SiO2 phases. The steel with the highest Cr content showed the formation of Fe3O4 and the thickest oxide scale.

  8. Steam Oxidation Behavior of Advanced Steels and Ni-Based Alloys at 800 °C

    NASA Astrophysics Data System (ADS)

    Dudziak, T.; Boroń, L.; Deodeshmukh, V.; Sobczak, J.; Sobczak, N.; Witkowska, M.; Ratuszek, W.; Chruściel, K.

    2017-03-01

    This publication studies the steam oxidation behavior of advanced steels (309S, 310S and HR3C) and Ni-based alloys (Haynes® 230®, alloy 263, alloy 617 and Haynes® 282®) exposed at 800 °C for 2000 h under 1 bar pressure, in a pure water steam system. The results revealed that all exposed materials showed relatively low weight gain, with no spallation of the oxide scale within the 2000 h of exposure. XRD analysis showed that Ni-based alloys developed an oxide scale consisting of four main phases: Cr2O3 (alloy 617, Haynes® 282®, alloy 263 and Haynes® 230®), MnCr2O4 (alloy 617, Haynes® 282® and Haynes® 230®), NiCr2O4 (alloy 617) and TiO2 (alloy 263, Haynes® 282®). In contrast, advanced steels showed the development of Cr2O3, MnCr2O4, Mn7SiO12, FeMn(SiO4) and SiO2 phases. The steel with the highest Cr content showed the formation of Fe3O4 and the thickest oxide scale.

  9. Cellular Shape Memory Alloy Structures: Experiments & Modeling (Part 1)

    DTIC Science & Technology

    2012-08-01

    AFOSR  Grant  #FA9550-­‐08-­‐1-­‐0313 Cellular  Shape  Memory   Alloy  Structures:   Experiments  &  Modeling J.  Shaw  (UM...2012 4. TITLE AND SUBTITLE Cellular Shape Memory Alloy Structures: Experiments & Modeling (Part 1) 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c...dense,  0.37  g/cc) Combine benefits of light-weight cellular structures with Shape Memory Alloy (SMA) adaptive behavior CombinaKon •Amplified

  10. 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.

  11. 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.

  12. Al-Ti-Zr master alloys: Structure formation

    NASA Astrophysics Data System (ADS)

    Popova, E. A.; Shubin, A. B.; Kotenkov, P. V.; Pastukhov, E. A.; Bodrova, L. E.; Fedorova, O. M.

    2012-05-01

    The effects of the composition of ternary Al-Ti-Zr master alloys, the overheating of their melts with respect to liquidus, and exposure to low-frequency vibrations on the structure formation in them are studied. It is shown that complex aluminide Al3(Zr x Ti1 - x ) with a metastable L12-type cubic lattice coinciding with the structure type of α Al primarily precipitates during the crystallization of Al-Ti-Zr melts under certain conditions. This fact makes such master alloys promising for modifying aluminum alloys.

  13. Weldability and joining techniques for advanced fossil energy system alloys

    SciTech Connect

    Lundin, C.D.; Qiao, C.Y.P.; Liu, W.; Yang, D.; Zhou, G.; Morrison, M.

    1998-05-01

    The efforts represent the concerns for the basic understanding of the weldability and fabricability of the advanced high temperature alloys so necessary to affect increases in the efficiency of the next generation Fossil Energy Power Plants. The effort was divided into three tasks with the first effort dealing with the welding and fabrication behavior of 310HCbN (HR3C), the second task details the studies aimed at understanding the weldability of a newly developed 310TaN high temperature stainless (a modification of 310 stainless) and Task 3 addressed the cladding of austenitic tubing with Iron-Aluminide using the GTAW process. Task 1 consisted of microstructural studies on 310HCbN and the development of a Tube Weldability test which has applications to production welding techniques as well as laboratory weldability assessments. In addition, the evaluation of ex-service 310HCbN which showed fireside erosion and cracking at the attachment weld locations was conducted. Task 2 addressed the behavior of the newly developed 310 TaN modification of standard 310 stainless steel and showed that the weldability was excellent and that the sensitization potential was minimal for normal welding and fabrication conditions. The microstructural evolution during elevated temperature testing was characterized and the second phase particles evolved upon aging were identified. Task 3 details the investigation undertaken to clad 310HCbN tubing with Iron Aluminide and developed welding conditions necessary to provide a crack free cladding. The work showed that both a preheat and a post-heat was necessary for crack free deposits and the effect of a third element on the cracking potential was defined together with the effect of the aluminum level for optimum weldability.

  14. Multilayer relaxation and surface structure of ordered alloys

    NASA Technical Reports Server (NTRS)

    Kobistek, Robert J.; Bozzolo, Guillermo; Ferrante, John; Schlosser, Herbert

    1993-01-01

    Using BFS, a new semiempirical method for alloys, we study the surface structure of fcc ordered binary alloys in the Ll(sub 2) structure (Ni3Al and Cu3Au). We show that the surface energy is lowest for the mixed composition truncation of the low-index faces of such systems. Also, we present results for the interlayer relaxations for planes close to the surface, revealing different relaxations for atoms of different species producing a rippled surface layer.

  15. Synthesis of alloys with controlled phase structure

    DOEpatents

    Guthrie, Stephen Everett; Thomas, George John; Bauer, Walter; Yang, Nancy Yuan Chi

    1999-04-20

    A method for preparing controlled phase alloys useful for engineering and hydrogen storage applications. This novel method avoids melting the constituents by employing vapor transport, in a hydrogen atmosphere, of an active metal constituent, having a high vapor pressure at temperatures .apprxeq.300 C. and its subsequent condensation on and reaction with the other constituent (substrate) of an alloy thereby forming a controlled phase alloy and preferably a single phase alloy. It is preferred that the substrate material be a metal powder such that diffusion of the active metal constituent, preferably magnesium, and reaction therewith can be completed within a reasonable time and at temperatures .apprxeq.300 C. thereby avoiding undesirable effects such as sintering, local compositional inhomogeneities, segregation, and formation of unwanted second phases such as intermetallic compounds.

  16. Synthesis of alloys with controlled phase structure

    DOEpatents

    Guthrie, S.E.; Thomas, G.J.; Bauer, W.; Yang, N.Y.C.

    1999-04-20

    A method is described for preparing controlled phase alloys useful for engineering and hydrogen storage applications. This novel method avoids melting the constituents by employing vapor transport, in a hydrogen atmosphere, of an active metal constituent, having a high vapor pressure at temperatures {approx_equal}300 C and its subsequent condensation on and reaction with the other constituent (substrate) of an alloy thereby forming a controlled phase alloy and preferably a single phase alloy. It is preferred that the substrate material be a metal powder such that diffusion of the active metal constituent, preferably magnesium, and reaction therewith can be completed within a reasonable time and at temperatures {approx_equal}300 C thereby avoiding undesirable effects such as sintering, local compositional inhomogeneities, segregation, and formation of unwanted second phases such as intermetallic compounds. 4 figs.

  17. Advanced investment cast processing for gamma titanium aluminide alloys

    SciTech Connect

    Larsen, D.; Govern, C.

    1995-12-31

    Investment casting of gamma titanium aluminide alloys has become the near-term process of choice for component manufacture. This is largely due to its near-net shape processing capabilities which allow cast gamma components to be manufactured at a lower cost when compared to wrought or powder methods. Many papers have been published discussing the effect of heat treatment on the microstructure of HIP processed samples. However, the relationship between casting parameters and resultant microstructures has not been widely discussed. An L9 DOE casting experiment was performed to examine mold preheat, furnace atmosphere, shell type and gating design parameters. It was determined that mold preheat had a very significant effect on as-cast and as-HIP processed microstructures. Mold preheats of 70 F and 750 F produced HIP Processed microstructures containing 80 to >90% equiaxed gamma grains and 2,100 F mold preheats produced structures containing 10--30% equiaxed gamma grains. The results of this experiment will be presented, including optical microstructures and microprobe analysis.

  18. Advanced powder metallurgy aluminum alloys via rapid solidification technology

    NASA Technical Reports Server (NTRS)

    Ray, R.

    1984-01-01

    Aluminum alloys containing 10 to 11.5 wt. pct. of iron and 1.5 to 3 wt. pct. of chromium using the technique of rapid solidification powder metallurgy were studied. Alloys were prepared as thin ribbons (.002 inch thick) rapidly solidified at uniform rate of 10(6) C/second by the melt spinning process. The melt spun ribbons were pulverized into powders (-60 to 400 mesh) by a rotating hammer mill. The powders were consolidated by hot extrusion at a high reduction ratio of 50:1. The powder extrusion temperature was varied to determine the range of desirable processing conditions necessary to yield useful properties. Powders and consolidated alloys were characterized by SEM and optical metallography. The consolidated alloys were evaluated for (1) thermal stability, (2) tensile properties in the range, room temperature to 450 F, and (3) notch toughness in the range, room temperature to 450 F.

  19. Advanced Gas Cooled Nuclear Reactor Materials Evaluation and Development Program: Topical report I, selection of candidate alloys. Volume 3. Selection of surface coating/substrate systems for screening creep and structural stability studies

    SciTech Connect

    Not Available

    1980-06-20

    Considering the high temperature, low O/sub 2/, high C environment of operation in the Very High Temperature Reactor (VHTR) Systems, the utilization of coatings is envisaged to hold potential for extending component lifetimes through the formation of stable and continuous oxide films with enhanced resistance to C diffusion. A survey of the current state of technology for high temperature coatings has been performed. The usefulness of these coatings on the Mo, Ni, and Fe base alloys is discussed. Specifically, no coating substitute was identified for TZM other than the well known W-3 (pack silicide) and Al/sub 2/O/sub 3/ forming coatings were recommended for the Fe and Ni base structural materials. Recommendations as to coating types and processng have been made based on the predicted VHTR component size, shape, base metal and operational environment. Four tests designed to evaluate the effects of selected combinations of coatings and substrate matrices are recommended for consideration.

  20. Structural materials challenges for advanced reactor systems

    NASA Astrophysics Data System (ADS)

    Yvon, P.; Carré, F.

    2009-03-01

    Key technologies for advanced nuclear systems encompass high temperature structural materials, fast neutron resistant core materials, and specific reactor and power conversion technologies (intermediate heat exchanger, turbo-machinery, high temperature electrolytic or thermo-chemical water splitting processes, etc.). The main requirements for the materials to be used in these reactor systems are dimensional stability under irradiation, whether under stress (irradiation creep or relaxation) or without stress (swelling, growth), an acceptable evolution under ageing of the mechanical properties (tensile strength, ductility, creep resistance, fracture toughness, resilience) and a good behavior in corrosive environments (reactor coolant or process fluid). Other criteria for the materials are their cost to fabricate and to assemble, and their composition could be optimized in order for instance to present low-activation (or rapid desactivation) features which facilitate maintenance and disposal. These requirements have to be met under normal operating conditions, as well as in incidental and accidental conditions. These challenging requirements imply that in most cases, the use of conventional nuclear materials is excluded, even after optimization and a new range of materials has to be developed and qualified for nuclear use. This paper gives a brief overview of various materials that are essential to establish advanced systems feasibility and performance for in pile and out of pile applications, such as ferritic/martensitic steels (9-12% Cr), nickel based alloys (Haynes 230, Inconel 617, etc.), oxide dispersion strengthened ferritic/martensitic steels, and ceramics (SiC, TiC, etc.). This article gives also an insight into the various natures of R&D needed on advanced materials, including fundamental research to investigate basic physical and chemical phenomena occurring in normal and accidental operating conditions, lab-scale tests to characterize candidate materials

  1. Development of Advanced Carbide for Nickel-Based Alloy Machining for Turbine Engines

    DTIC Science & Technology

    2006-06-20

    based alloys such as Inconel 718 with 40% higher machining productivity. 15. SUBJECT TERMS NCDMM; Success Stories; Kennametal, Inc.; Inconel 718 ...Inc. involved developing an advanced coated carbide cutting tool for turning nickel-based alloys such as Inconel 718 with 40% higher machining...nd DOC constant for the ng of six (6) cutting tools t 180 and 250 SFM led to l performance goal. It was r resulting from premature e in Inconel

  2. Advanced Corrosion-Resistant Zr Alloys for High Burnup and Generation IV Applications

    SciTech Connect

    Arthur Motta; Yong Hwan Jeong; R.J. Comstock; G.S. Was; Y.S. Kim

    2006-10-31

    The objective of this collaboration between four institutions in the US and Korea is to demonstrate a technical basis for the improvement of the corrosion resistance of zirconium-based alloys in more extreme operating environments (such as those present in severe fuel duty,cycles (high burnup, boiling, aggressive chemistry) andto investigate the feasibility (from the point of view of corrosion rate) of using advanced zirconium-based alloys in a supercritical water environment.

  3. Creep crack growth behavior of several structural alloys

    NASA Astrophysics Data System (ADS)

    Sadananda, K.; Shahinian, P.

    1983-07-01

    Creep crack growth behavior of several high temperature alloys, Inconel 600, Inconel 625, Inconel X-750, Hastelloy X, Nimonic PE-16, Incoloy 800, and Haynes 25 (HS-25) was examined at 540, 650, 760, and 870 °C. Crack growth rates were analyzed in terms of both linear elastic stress intensity factor and J*-integral parameter. Among the alloys Inconel 600 and Hastelloy X did not show any observable crack growth. Instead, they deformed at a rapid rate resulting in severe blunting of the crack tip. The other alloys, Inconel 625, Inconel X-750, Incoloy 800, HS-25, and PE-16 showed crack growth at one or two temperatures and deformed continuously at other temperatures. Crack growth rates of the above alloys in terms ofJ* parameter were compared with the growth rates of other alloys published in the literature. Alloys such as Inconel X-750, Alloy 718, and IN-100 show very high growth rates as a result of their sensitivity to an air environment. Based on detailed fracture surface analysis, it is proposed that creep crack growth occurs by the nucleation and growth of wedge-type cracks at triple point junctions due to grain boundary sliding or by the formation and growth of cavities at the boundaries. Crack growth in the above alloys occurs only in some critical range of strain rates or temperatures. Since the service conditions for these alloys usually fall within this critical range, knowledge and understanding of creep crack growth behavior of the structural alloys are important.

  4. NASA-UVA light aerospace alloy and structures technology program (LA2ST)

    NASA Technical Reports Server (NTRS)

    Gangloff, Richard P.

    1992-01-01

    The NASA-UVa Light Aerospace Alloy and Structure Technology (LAST) Program continues to maintain a high level of activity, with projects being conducted by graduate students and faculty advisors in the Departments of Materials Science and Engineering, Civil Engineering and Applied Mechanics, and Mechanical and Aerospace Engineering at the University of Virginia. This work is funded by the NASA-Langley Research Center under Grant NAG-1-745. Here, we report on progress achieved between January 1 and June 30, 1992. The objectives of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of the next generation, light weight aerospace alloys, composites and thermal gradient structures in collaboration with Langley researchers. Technical objectives are established for each research project. We aim to produce relevant data and basic understanding of material mechanical response, corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement advances; and critically, a pool of educated graduate students for aerospace technologies. The accomplishments presented in this report cover topics including: (1) Mechanical and Environmental Degradation Mechanisms in Advance Light Metals and Composites; (2) Aerospace Materials Science; (3) Mechanics of Materials and Composites for Aerospace Structures; and (4) Thermal Gradient Structures.

  5. Advanced ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

    Dryepondt, Sebastien N; Unocic, Kinga A; Hoelzer, David T; Pint, Bruce A

    2014-09-01

    ODS FeCrAl alloys are being developed with optimum composition and properties for accident tolerant fuel cladding. Two oxide dispersion strengthened (ODS) Fe-15Cr-5Al+Y2O3 alloys were fabricated by ball milling and extrusion of gas atomized metallic powder mixed with Y2O3 powder. To assess the impact of Mo on the alloy mechanical properties, one alloy contained 1%Mo. The hardness and tensile properties of the two alloys were close and higher than the values reported for fine grain PM2000 alloy. This is likely due to the combination of a very fine grain structure and the presence of nano oxide precipitates. The nano oxide dispersion was however not sufficient to prevent grain boundary sliding at 800 C and the creep properties of the alloys were similar or only slightly superior to fine grain PM2000 alloy. Both alloys formed a protective alumina scale at 1200 C in air and steam and the mass gain curves were similar to curves generated with 12Cr-5Al+Y2O3 (+Hf or Zr) ODS alloys fabricated for a different project. To estimate the maximum temperature limit of use for the two alloys in steam, ramp tests at a rate of 5 C/min were carried out in steam. Like other ODS alloys, the two alloys showed a significant increase of the mas gains at T~ 1380 C compared with ~1480 C for wrought alloys of similar composition. The beneficial effect of Yttrium for wrought FeCrAl does not seem effective for most ODS FeCrAl alloys. Characterization of the hardness of annealed specimens revealed that the microstructure of the two alloys was not stable above 1000 C. Concurrent radiation results suggested that Cr levels <15wt% are desirable and the creep and oxidation results from the 12Cr ODS alloys indicate that a lower Cr, high strength ODS alloy with a higher maximum use temperature could be achieved.

  6. VAMAS tests of structural materials on aluminum alloy and composite material at cryogenic temperatures

    SciTech Connect

    Ogata, T.; Evans, D.

    1997-06-01

    A Technical Working Area 17, cryogenic structural materials, has been organized in the Versailles Project on Advanced Materials and Standards (VAMAS) to promote the prestandardization program on material properties tests of glass fiber reinforced polymer (GFRP) composite materials and alloys at liquid helium temperature. A series of international interlaboratory comparisons of both tensile and fracture toughness tests for aluminum alloy 2219 and compression and shear tests for composite material G-10CR were performed. Nine research institutes from seven nations have participated in this project. The results prove that there are few problems in cryogenic tensile tests for alloy materials. In compression and shear tests, the amount of data scatter was identified and further experiments are planned. This paper presents the program details and interim results of round robin tests.

  7. Relations between the modulus of elasticity of binary alloys and their structure

    NASA Technical Reports Server (NTRS)

    Koster, Werner; Rauscher, Walter

    1951-01-01

    A comprehensive survey of the elastic modulus of binary alloys as a function of the concentration is presented. Alloys that form continuous solid solutions, limited solid solutions, eutectic alloys, and alloys with intermetallic phases are investigated. Systems having the most important structures have been examined to obtain criteria for the relation between lattice structure, type of binding, and elastic behavior.

  8. Advanced nickel base alloys for high strength, corrosion applications

    DOEpatents

    Flinn, J.E.

    1998-11-03

    Improved nickel-base alloys of enhanced strength and corrosion resistance, produced by atomization of an alloy melt under an inert gas atmosphere and of composition 0--20Fe, 10--30Cr, 2--12Mo, 6 max. Nb, 0.05--3 V, 0.08 max. Mn, 0.5 max. Si, less than 0.01 each of Al and Ti, less than 0.05 each of P and S, 0.01--0.08C, less than 0.2N, 0.1 max. 0, bal. Ni. 3 figs.

  9. Advanced nickel base alloys for high strength, corrosion applications

    DOEpatents

    Flinn, John E.

    1998-01-01

    Improved nickel-base alloys of enhanced strength and corrosion resistance, produced by atomization of an alloy melt under an inert gas atmosphere and of composition 0-20Fe, 10-30Cr, 2-12Mo, 6 max. Nb, 0.05-3 V, 0.08 max. Mn, 0.5 max. Si, less than 0.01 each of Al and Ti, less than 0.05 each of P and S, 0.01-0.08C, less than 0.2N, 0.1 max. 0, bal. Ni.

  10. Nanostructured Fe-Cr Alloys for Advanced Nuclear Energy Applications

    SciTech Connect

    Scattergood, Ronald O.

    2016-04-26

    We have completed research on the grain-size stabilization of model nanostructured Fe14Cr base alloys at high temperatures by the addition of non-equilibrium solutes. Fe14Cr base alloys are representative for nuclear reactor applications. The neutron flux in a nuclear reactor will generate He atoms that coalesce to form He bubbles. These can lead to premature failure of the reactor components, limiting their lifetime and increasing the cost and capacity for power generation. In order to mitigate such failures, Fe14Cr base alloys have been processed to contain very small nano-size oxide particles (less than 10 nm in size) that trap He atoms and reduce bubble formation. Theoretical and experimental results indicate that the grain boundaries can also be very effective traps for He atoms and bubble formation. An optimum grain size will be less than 100 nm, ie., nanocrystalline alloys must be used. Powder metallurgy methods based on high-energy ball milling can produce Fe-Cr base nanocrystalline alloys that are suitable for nuclear energy applications. The problem with nanocrystalline alloys is that excess grain-boundary energy will cause grains to grow at higher temperatures and their propensity for He trapping will be lost. The nano-size oxide particles in current generation nuclear alloys provide some grain size stabilization by reducing grain-boundary mobility (Zener pinning – a kinetic effect). However the current mitigation strategy minimizing bubble formation is based primarily on He trapping by nano-size oxide particles. An alternate approach to nanoscale grain size stabilization has been proposed. This is based on the addition of small amounts of atoms that are large compared to the base alloy. At higher temperatures these will diffuse to the grain boundaries and will produce an equilibrium state for the grain size at higher temperatures (thermodynamic stabilization – an equilibrium effect). This would be preferred compared to a kinetic effect, which is not

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

    NASA Technical Reports Server (NTRS)

    Gangloff, Richard P.; Starke, Edgar A., Jr.; Kelly, Robert G.; Scully, John R.; Shiflet, Gary J.; Stoner, Glenn E.; Wert, John A.

    1997-01-01

    The NASA-UVA Light Aerospace Alloy and Structures Technology (LA2ST) Program was initiated in 1986 and continues with a high level of activity. Here, we report on progress achieved between July I and December 31, 1996. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light-weight aerospace alloys, composites and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. We generally aim to produce relevant data and basic understanding of material mechanical response, environmental/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement and modeling advances; and a pool of educated graduate students for aerospace technologies. The accomplishments presented in this report are summarized as follows. Three research areas are being actively investigated, including: (1) Mechanical and Environmental Degradation Mechanisms in Advanced Light Metals, (2) Aerospace Materials Science, and (3) Mechanics of Materials for Light Aerospace Structures.

  12. Structural properties of bismuth-bearing semiconductor alloys

    NASA Technical Reports Server (NTRS)

    Berding, M. A.; Sher, A.; Chen, A.-B.; Miller, W. E.

    1988-01-01

    The structural properties of bismuth-bearing III-V semiconductor alloys InPBi, InAsBi, and InSbBi were studied theoretically. Bond energies, bond lengths, and strain coefficients were calculated for pure AlBi, GaBi, and InBi compounds and their alloys, and predictions were made for the mixing enthalpies, miscibility gaps, and critical metastable-to-stable material transition temperatures. Miscibility calculations indicate that InSbBi will be the most miscible, and the InPBi will be the the most difficult to mix. However, calculations of the hardness of the Bi compounds indicate that, once formed, the InPBi alloy will be harder than the other Bi alloys and substantially harder than the currently favored narrow-gap semiconductor HgCdTe.

  13. Welding of unique and advanced alloys for space and high-temperature applications: welding and weldability of iridium and platinum alloys

    SciTech Connect

    David, Stan A.; Miller, Roger G.; Feng, Zhili

    2016-08-31

    Advances have been made in developing alloys for space power systems for spacecraft that travel long distances to various planets. The spacecraft are powered by radioisotope thermoelectric generators (RTGs) and the fuel element in RTGs is plutonia. For safety and containment of the radioactive fuel element, the heat source is encapsulated in iridium or platinum alloys. Ir and Pt alloys are the alloys of choice for encapsulating radioisotope fuel pellets. Ir and Pt alloys were chosen because of their high-temperature properties and compatibility with the oxide fuel element and the graphite impact shells. This review addresses the alloy design and welding and weldability of Ir and Pt alloys for use in RTGs.

  14. Welding of unique and advanced alloys for space and high-temperature applications: welding and weldability of iridium and platinum alloys

    DOE PAGES

    David, Stan A.; Miller, Roger G.; Feng, Zhili

    2016-08-31

    Advances have been made in developing alloys for space power systems for spacecraft that travel long distances to various planets. The spacecraft are powered by radioisotope thermoelectric generators (RTGs) and the fuel element in RTGs is plutonia. For safety and containment of the radioactive fuel element, the heat source is encapsulated in iridium or platinum alloys. Ir and Pt alloys are the alloys of choice for encapsulating radioisotope fuel pellets. Ir and Pt alloys were chosen because of their high-temperature properties and compatibility with the oxide fuel element and the graphite impact shells. This review addresses the alloy design andmore » welding and weldability of Ir and Pt alloys for use in RTGs.« less

  15. Advanced Thermal-Barrier Bond Coatings for Alloys

    NASA Technical Reports Server (NTRS)

    Secura, Stephen

    1987-01-01

    New and improved bond coatings developed for use in thermal-barrier systems on Ni, Co-, and Fe-base alloy substrates. Use of these new bond coatings, containing ytterbium instead of yttrium, significantly increased lives of resultant thermal-barrier systems. Uses include many load-bearing applications in high-temperature, hostile environments.

  16. Advanced TEM characterization of oxide nanoparticles in ODS Fe–12Cr–5Al alloys

    DOE PAGES

    Unocic, Kinga A; Hoelzer, David T; Pint, Bruce A

    2016-01-01

    For oxide nanoparticles present in three oxide-dispersion-strengthened (ODS) Fe–12Cr–5Al alloys containing additions of (1) Y2O3 (125Y), (2) Y2O3 + ZrO2 (125YZ), and (3) Y2O3 + HfO2 (125YH), were investigated using transmission and scanning transmission electron microscopy. Furthermore, in all three alloys nano-sized (<3.5 nm) oxide particles distributed uniformly throughout the microstructure were characterized using advanced electron microscopy techniques. In the 125Y alloy, mainly Al2O3 and yttrium–aluminum garnet (YAG) phases (Y3Al5O12) were present, while in the 125YZ alloy, additional Zr(C,N) precipitates were identified. The 125YH alloy had the most complex precipitation sequence whereby in addition to the YAG and Al2O3 phases,more » Hf(C,N), Y2Hf2O7, and HfO2 precipitates were also found. The presence of HfO2 was mainly due to the incomplete incorporation of HfO2 powder during mechanical alloying of the 125YH alloy. The alloy having the highest total number density of the oxides, the smallest grain size, and the highest Vickers hardness was the 125YZ alloy indicating, that Y2O3 + ZrO2 additions had the strongest effect on grain size and tensile properties. Finally, high-temperature mechanical testing will be addressed in the near future, while irradiation studies are underway to investigate the irradiation resistance of these new ODS FeCrAl alloys.« less

  17. Copper alloys for high heat flux structure applications

    SciTech Connect

    Zinkle, S.J.; Fabritsiev, S.A.

    1994-09-01

    The mechanical and physical properties of copper alloys are reviewed and compared with the requirements for high heat flux structural applications in fusion reactors. High heat flux structural materials must possess a combination of high thermal conductivity and high mechanical strength. The three most promising copper alloys at the present time are oxide dispersion-strengthened copper (Cu-Al{sub 2}O{sub 3}) and two precipitation-hardened copper alloys (Cu-Cr-Zr and Cu-Ni-Be). These three alloys are capable of room temperature yield strengths >400 MPa and thermal conductivities up to 350 W/m-K. All of these alloys require extensive cold working to achieve their optimum strength. Precipitation-hardened copper alloys such Cu-Cr-Zr are susceptible to softening due to precipitate overaging and recrystallization during brazing, whereas the dislocation structure in Cu-Al{sub 2}O{sub 3} remains stabilized during typical high temperature brazing cycles. All three alloys exhibit good resistance to irradiation-induced softening and void swelling at temperatures below 300{degrees}C. The precipitation-strengthened allows typically soften during neutron irradiation at temperatures above about 300{degrees}C and therefore should only be considered for applications operating at temperatures <300{degrees}C. Dispersion-strengthened copper may be used up to temperatures in excess of 500{degrees}C. Based on the available data, dispersion-strengthened copper (Cu-Al{sub 2}O{sub 3}) is considered to be the best candidate for high heat flux structural applications.

  18. CHARACTERIZATION OF AN ADVANCED GADOLINIUM NEUTRON ABSORBER ALLOY BY MEANS OF NEUTRON TRANSMISSION

    SciTech Connect

    Gregg W. Wachs

    2007-09-01

    Neutron transmission experiments were performed on samples of an advanced nickel-chromium-molybdenum-gadolinium (Ni-Cr-Mo-Gd) neutron absorber alloy. The primary purpose of the experiments was to demonstrate the thermal neutron absorbing capability of the alloy at specific gadolinium dopant levels. The new alloy is to be deployed for criticality control of highly enriched DOE SNF. For the transmission experiments, alloy test samples were fabricated with 0.0, 1.58 and 2.1 wt% natural gadolinium dispersed in a Ni-Cr-Mo base alloy. The transmission experiments were successfully carried out at the Los Alamos Neutron Science Center (LANSCE). Measured data from the neutron transmission experiments were compared to calculated results derived from a simple exponential transmission formula using only radiative capture cross sections. Excellent agreement between the measured and calculated results demonstrated the expected strong thermal absorption capability of the gadolinium poison and in addition, verified the measured elemental composition of the alloy test samples. The good agreement also indirectly confirmed that the gadolinium was dispersed fairly uniformly in the alloy and the ENDF VII radiative capture cross section data were accurate.

  19. Elevated temperature crack growth in advanced powder metallurgy aluminum alloys

    NASA Technical Reports Server (NTRS)

    Porr, William C., Jr.; Gangloff, Richard P.

    1990-01-01

    Rapidly solidified Al-Fe-V-Si powder metallurgy alloy FVS0812 is among the most promising of the elevated temperature aluminum alloys developed in recent years. The ultra fine grain size and high volume fraction of thermally stable dispersoids enable the alloy to maintain tensile properties at elevated temperatures. In contrast, this alloy displays complex and potentially deleterious damage tolerant and time dependent fracture behavior that varies with temperature. J-Integral fracture mechanics were used to determine fracture toughness (K sub IC) and crack growth resistance (tearing modulus, T) of extruded FVS0812 as a function of temperature. The alloy exhibits high fracture properties at room temperature when tested in the LT orientation, due to extensive delamination of prior ribbon particle boundaries perpendicular to the crack front. Delamination results in a loss of through thickness constraint along the crack front, raising the critical stress intensity necessary for precrack initiation. The fracture toughness and tensile ductility of this alloy decrease with increasing temperature, with minima observed at 200 C. This behavior results from minima in the intrinsic toughness of the material, due to dynamic strain aging, and in the extent of prior particle boundary delaminations. At 200 C FVS0812 fails at K levels that are insufficient to cause through thickness delamination. As temperature increases beyond the minimum, strain aging is reduced and delamination returns. For the TL orientation, K (sub IC) decreased and T increased slightly with increasing temperature from 25 to 316 C. Fracture in the TL orientation is governed by prior particle boundary toughness; increased strain localization at these boundaries may result in lower toughness with increasing temperature. Preliminary results demonstrate a complex effect of loading rate on K (sub IC) and T at 175 C, and indicate that the combined effects of time dependent deformation, environment, and strain aging

  20. Process Simulation and Modeling for Advanced Intermetallic Alloys.

    DTIC Science & Technology

    1994-06-01

    Alloys Alloy Tauperaturo(K) _____________BeUating Cooling F Tri-44A1 1390 Ti-44Al-4V 1373 1383 Ti-44A1-7V 1378 1373 Ti-44&l-15V 1358 11376 40 17 TABLE 4 ...N. ~ 04 to 14 tie ttS 04 1100 tt~m ~ ir no 4 st lb m ti tim 300 T330 1’ 17 t~m S Ci t SqJC Figure~ ~~~~~~~~~~~~~~~I 3. Throrm f()Ti4A-N-M n etn,()T-81...a peritectic y--- 4 3 + L reaction. The varying TiB2 morphologies observed as a function of both solidification rate and volume percent TiB2 show that

  1. Electronic structure and phase equilibria in ternary substitutional alloys

    SciTech Connect

    Traiber, A.J.S.; Allen, S.M.; Turchi, P.E.A.; Waterstrat, R.M.

    1996-04-26

    A reliable, consistent scheme to study phase equilibria in ternary substitutional alloys based on the tight-binding approximation is presented. With electronic parameters from linear muffin-tin orbital calculations, the computed density of states and band structures compare well with those from more accurate {ital ab}{ital initio} calculations. Disordered alloys are studied within the tight-binding coherent-potential approximation extended to alloys; energetics of ordered systems are obtained through effective pair interactions computed with the general perturbation method; and partially ordered alloys are studied with a novel simplification of the molecular coherent-potential approximation combined with the general perturbation method. The formalism is applied to bcc-based Zr-Ru-Pd alloys which are promising candidates for medical implant devices. Using energetics obtained from the above scheme, we apply the cluster- variation method to study phase equilibria for particular pseudo- binary alloys and show that results are consistent with observed behavior of electronic specific heat coefficient with composition for Zr{sub 0.5}(Ru, Pd){sub 0.5}.

  2. NASA-UVA light aerospace alloy and structures technology program (LA2ST)

    NASA Technical Reports Server (NTRS)

    Gangloff, Richard P.; Starke, Edger A., Jr.

    1996-01-01

    This progress report covers achievements made between January 1 and June 30, 1966 on the NASA-UVA Light Aerospace Alloy and Structures Technology (LA2ST) Program. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light-weight aerospace alloys, composites and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. . The accomplishments presented in this report are: (1) Mechanical and Environmental Degradation Mechanisms in Advanced Light Metals, (2) Aerospace Materials Science, and (3) Mechanics of Materials for Light Aerospace Structures. Collective accomplishments between January and June of 1996 include: 4 journal or proceedings publications, 1 NASA progress report, 4 presentations at national technical meetings, and 2 PhD dissertations published.

  3. Polyphase alloys as rechargeable electrodes in advanced battery systems

    NASA Technical Reports Server (NTRS)

    Huggins, Robert A.

    1987-01-01

    The rechargeability of electrochemical cells is often limited by negative electrode problems. These may include loss of capacity, increased impedance, macroscopic shape change, dendrite growth, or a tendency for filamentary or whisker growth. In principle, these problems can be reduced or eliminated by the use of alloys that undergo either displacement or insertion reactions at reactant species activities less than unity, rather than pure elements. The fundamental reasons for some of these problems with elemental electrodes, as well as the basic principles involved in the different behavior of alloys, are briefly discussed. More information is now available concerning the thermodynamic and kinetic properties of a number of alloys of potential interest for use as electrodes in elevated temperature lithium battery systems. Recent results have extended these results down to ambient temperatures, indicating that some such materials may be of interest for use with new low temperature molten salt electrolytes, or with organic solvent electrolytes. The all solid mixed conductor matrix concept is also reviewed.

  4. Structural and magnetic properties of nanocrystalline Fe-Co-Ni alloy processed by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Raanaei, Hossein; Eskandari, Hossein; Mohammad-Hosseini, Vahid

    2016-01-01

    In this present work, a nanostructured iron-cobalt-nickel alloy with Fe50Co30Ni20 composition has been processed by mechanical alloying. The structural and magnetic properties have been investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and vibrating sample magnetometer. It is shown that the crystallize size reaches to about 18.7 nm after 32 h milling time. A remarkable decrease in coercivity after 16 h milling time and also a continuous increase in remanent magnetization during the mechanical alloying process are observed. Heat treatment of the samples milled at 32 and 48 h demonstrates the crystalline constituent elements and also Fe3O4 crystalline phase.

  5. Protection of Advanced Copper Alloys With Lean Cu-Cr Coatings

    NASA Technical Reports Server (NTRS)

    Greenbauer-Seng, L. (Technical Monitor); Thomas-Ogbuji, L.

    2003-01-01

    Advanced copper alloys are used as liners of rocket thrusters and nozzle ramps to ensure dissipation of the high thermal load generated during launch, and Cr-lean coatings are preferred for the protection of these liners from the aggressive ambient environment. It is shown that adequate protection can be achieved with thin Cu-Cr coatings containing as little as 17 percent Cr.

  6. X-Ray Absorption Fine Structure Study for Fe60Ni40 Alloy

    SciTech Connect

    Yang, Dong-Seok; Oh, Kyuseung; Na, Wonkyung; Kim, Nayoung; Yoo, Yong-Goo; Min, Seung-Gi; Yu, Seong-Cho

    2007-02-02

    Fe60Ni40 alloys were fabricated by the mechanical alloying process with process periods of 1, 2, 4, 6, 12 and 24 hours, respectively. The formation of alloy and the structural evolution of the alloy were examined by X-ray diffraction and extended X-ray absorption fine structure methods. With increase of alloying time the BCC phase of iron was changed significantly during the mechanical alloying process. The alloying was activated in about 6 hours and completed in about 24 hours.

  7. Development of Advanced Wear and Corrosion Resistant Systems Through Laser Surface Alloying and Materials Simulations

    SciTech Connect

    R. P. Martukanitz and S. Babu

    2007-05-03

    Laser surfacing in the form of cladding, alloying, and modifications are gaining widespread use because of its ability to provide high deposition rates, low thermal distortion, and refined microstructure due to high solidification rates. Because of these advantages, laser surface alloying is considered a prime candidate for producing ultra-hard coatings through the establishment or in situ formation of composite structures. Therefore, a program was conducted by the Applied Research Laboratory, Pennsylvania State University and Oak Ridge National Laboratory to develop the scientific and engineering basis for performing laser-based surface modifications involving the addition of hard particles, such as carbides, borides, and nitrides, within a metallic matrix for improved wear, fatigue, creep, and corrosion resistance. This has involved the development of advanced laser processing and simulation techniques, along with the refinement and application of these techniques for predicting and selecting materials and processing parameters for the creation of new surfaces having improved properties over current coating technologies. This program has also resulted in the formulation of process and material simulation tools capable of examining the potential for the formation and retention of composite coatings and deposits produced using laser processing techniques, as well as positive laboratory demonstrations in producing these coatings. In conjunction with the process simulation techniques, the application of computational thermodynamic and kinetic models to design laser surface alloying materials was demonstrated and resulted in a vast improvement in the formulation of materials used for producing composite coatings. The methodology was used to identify materials and to selectively modify microstructures for increasing hardness of deposits produced by the laser surface alloying process. Computational thermodynamic calculations indicated that it was possible to induce the

  8. Electron Beam Freeform Fabrication of Titanium Alloy Gradient Structures

    NASA Technical Reports Server (NTRS)

    Brice, Craig A.; Newman, John A.; Bird, Richard Keith; Shenoy, Ravi N.; Baughman, James M.; Gupta, Vipul K.

    2014-01-01

    Historically, the structural optimization of aerospace components has been done through geometric methods. A monolithic material is chosen based on the best compromise between the competing design limiting criteria. Then the structure is geometrically optimized to give the best overall performance using the single material chosen. Functionally graded materials offer the potential to further improve structural efficiency by allowing the material composition and/or microstructural features to spatially vary within a single structure. Thus, local properties could be tailored to the local design limiting criteria. Additive manufacturing techniques enable the fabrication of such graded materials and structures. This paper presents the results of a graded material study using two titanium alloys processed using electron beam freeform fabrication, an additive manufacturing process. The results show that the two alloys uniformly mix at various ratios and the resultant static tensile properties of the mixed alloys behave according to rule-of-mixtures. Additionally, the crack growth behavior across an abrupt change from one alloy to the other shows no discontinuity and the crack smoothly transitions from one crack growth regime into another.

  9. 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.

  10. Manufacture and engine test of advanced oxide dispersion strengthened alloy turbine vanes. [for space shuttle thermal protection

    NASA Technical Reports Server (NTRS)

    Bailey, P. G.

    1977-01-01

    Oxide-Dispersion-strengthened (ODS) Ni-Cr-Al alloy systems were exploited for turbine engine vanes which would be used for the space shuttle thermal protection system. Available commercial and developmental advanced ODS alloys were evaluated, and three were selected based on established vane property goals and manufacturing criteria. The selected alloys were evaluated in an engine test. Candidate alloys were screened by strength, thermal fatigue resistance, oxidation and sulfidation resistance. The Ni-16Cr (3 to 5)Al-ThO2 system was identified as having attractive high temperature oxidation resistance. Subsequent work also indicated exceptional sulfidation resistance for these alloys.

  11. Investigation of Advanced Processed Single-Crystal Turbine Blade Alloys

    NASA Technical Reports Server (NTRS)

    Peters, B. J.; Biondo, C. M.; DeLuca, D. P.

    1995-01-01

    This investigation studied the influence of thermal processing and microstructure on the mechanical properties of the single-crystal, nickel-based superalloys PWA 1482 and PWA 1484. The objective of the program was to develop an improved single-crystal turbine blade alloy that is specifically tailored for use in hydrogen fueled rocket engine turbopumps. High-gradient casting, hot isostatic pressing (HIP), and alternate heat treatment (HT) processing parameters were developed to produce pore-free, eutectic-free microstructures with different (gamma)' precipitate morphologies. Test materials were cast in high thermal gradient solidification (greater than 30 C/cm (137 F/in.)) casting furnaces for reduced dendrite arm spacing, improved chemical homogeneity, and reduced interdendritic pore size. The HIP processing was conducted in 40 cm (15.7 in.) diameter production furnaces using a set of parameters selected from a trial matrix study. Metallography was conducted on test samples taken from each respective trial run to characterize the as-HIP microstructure. Post-HIP alternate HT processes were developed for each of the two alloys. The goal of the alternate HT processing was to fully solution the eutectic gamma/(gamma)' phase islands and to develop a series of modified (gamma)' morphologies for subsequent characterization testing. This was accomplished by slow cooling through the (gamma)' solvus at controlled rates to precipitate volume fractions of large (gamma)'. Post-solution alternate HT parameters were established for each alloy providing additional volume fractions of finer precipitates. Screening tests included tensile, high-cycle fatigue (HCF), smooth and notched low-cycle fatigue (LCF), creep, and fatigue crack growth evaluations performed in air and high pressure (34.5 MPa (5 ksi)) hydrogen at room and elevated temperature. Under the most severe embrittling conditions (HCF and smooth and notched LCF in 34.5 MPa (5 ksi) hydrogen at 20 C (68 F), screening test

  12. Characterization of the Temperature Capabilities of Advanced Disk Alloy ME3

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Telesman, Jack; Kantzos, Peter T.; OConnor, Kenneth

    2002-01-01

    The successful development of an advanced powder metallurgy disk alloy, ME3, was initiated in the NASA High Speed Research/Enabling Propulsion Materials (HSR/EPM) Compressor/Turbine Disk program in cooperation with General Electric Engine Company and Pratt & Whitney Aircraft Engines. This alloy was designed using statistical screening and optimization of composition and processing variables to have extended durability at 1200 F in large disks. Disks of this alloy were produced at the conclusion of the program using a realistic scaled-up disk shape and processing to enable demonstration of these properties. The objective of the Ultra-Efficient Engine Technologies disk program was to assess the mechanical properties of these ME3 disks as functions of temperature in order to estimate the maximum temperature capabilities of this advanced alloy. These disks were sectioned, machined into specimens, and extensively tested. Additional sub-scale disks and blanks were processed and selectively tested to explore the effects of several processing variations on mechanical properties. Results indicate the baseline ME3 alloy and process can produce 1300 to 1350 F temperature capabilities, dependent on detailed disk and engine design property requirements.

  13. Characteristics of aluminum alloy microplastic deformation in different structural states

    SciTech Connect

    Seregin, G.V.; Efimenko, L.L.; Leonov, M.V.

    1995-07-01

    The solution to the problem of improving the mechanical properties (including cyclic strength) of structural materials is largely dependent on our knowledge of the laws governing the development of microplastic deformations in them. The effect of heat and mechanical treatment on the elastoplastic properties and fatigue resistance of the commercial aluminum alloys AK4-1 and D16 is analyzed.

  14. Hydrogen embrittlement of structural alloys. A technology survey

    NASA Technical Reports Server (NTRS)

    Carpenter, J. L., Jr.; Stuhrke, W. F.

    1976-01-01

    Technical abstracts for about 90 significant documents relating to hydrogen embrittlement of structural metals and alloys are reviewed. Particular note was taken of documents regarding hydrogen effects in rocket propulsion, aircraft propulsion and hydrogen energy systems, including storage and transfer systems.

  15. Deployable truss structure advanced technology

    NASA Technical Reports Server (NTRS)

    Dyer, J. E.; Dudeck, M. P.

    1986-01-01

    The 5-meter technology antenna program demonstrated the overall feasibility of integrating a mesh reflector surface with a deployable truss structure to achieve a precision surface contour compatible with future, high-performance antenna requirements. Specifically, the program demonstrated: the feasibility of fabricating a precision, edge-mounted, deployable, tetrahedral truss structure; the feasibility of adjusting a truss-supported mesh reflector contour to a surface error less than 10 mils rms; and good RF test performance, which correlated well with analytical predictions. Further analysis and testing (including flight testing) programs are needed to fully verify all the technology issues, including structural dynamics, thermodynamics, control, and on-orbit RF performance, which are associated with large, deployable, truss antenna structures.

  16. B2 structure of high-entropy alloys with addition of Al

    NASA Astrophysics Data System (ADS)

    Li, C.; Zhao, M.; Li, J. C.; Jiang, Q.

    2008-12-01

    A series of AlCrCoNiFe based alloys with equal percentage of principal components (high-entropy alloys or HE alloys) is fabricated. The related crystalline structures of the alloys are measured and calculated. Results show that the formed bcc phase is a compound based B2 structure where there is partial ionic bonding between Al and other transition metals. Thus, the bcc structure of the alloys should be a B2 instead of an A2 due to the large difference in electronegativities among the components consisting of the HE alloys.

  17. The history of development of molybdenum alloys for structural applications

    SciTech Connect

    Wadsworth, J.; Wittenauer, J.P.

    1993-02-01

    Molybdenum was first isolated as an element in 1893 and found initial commercial application as a filament support for incandescent lamps in 1910. The advent of arc melting practice in the 1940s led to an increase in availability of Mo sheet, bar, and plate products. Alloy development programs were heavily supported starting in the 1950s and several key alloys emerged over the next twenty years that remain in use to the present time such as Mo-TZM, unalloyed Mo, and Mo-Re. In recent years, improved understanding of the role of oxygen and carbide distributions at grain boundaries have led to increased reliability and use of Mo in aerospace products. Current developmental programs in areas of propulsion and energy conversion will ensure the prominent position of Mo as a high-temperature structural material. This paper highlights some of these key developments in the evolution of Mo alloys.

  18. Structural Acoustic Response of Shape Memory Alloy Hybrid Composite Panels

    NASA Technical Reports Server (NTRS)

    Turner, Travis L.

    1996-01-01

    A method has been developed to predict the structural acoustic response of shape memory alloy hybrid composite panels subjected to acoustic excitation. The panel is modeled by a finite element analysis and the radiated field is predicted using Rayleigh's integral. Transmission loss predictions for the case of an aluminum panel excited by a harmonic acoustic pressure are shown to compare very well with a classical analysis. Predictions of the normal velocity response and transmitted acoustic pressure for a clamped aluminum panel show excellent agreement with experimental measurements. Predicted transmission loss performance for a composite panel with and without shape memory alloy reinforcement are also presented. The preliminary results demonstrate that the transmission loss can be significantly increased with shape memory alloy reinforcement.

  19. Structure and recalescence behavior of undercooled nickel-tin alloys

    NASA Technical Reports Server (NTRS)

    Wu, Yanzhong; Piccone, Thomas J.; Shiohara, Yuh; Flemings, Merton C.

    1984-01-01

    The effects of undercooling on the thermal behavior and structure of Ni-Sn alloys are investigated. Hypoeutectic (Ni-25 wt pct Sn) and eutectic (Ni-32.5 wt pct Sn) compositions of the Ni-Sn alloy were undercooled using a levitation melting with glass encasement technique, and the recalescence of these alloys was measured using a high speed temperature sensing device and a digital oscilloscope. It is observed that in both samples the total solidification and recalescence times decrease with increasing undercooling; the volume fraction of normal lamellar eutectic decreases with increasing undercooling; and in the hypoeutectic sample, the morphology of the primary phase changes from dendritic to spherical with increasing undercooling.

  20. Structural and Thermoelectric Properties of Ternary Full-Heusler Alloys

    NASA Astrophysics Data System (ADS)

    Hayashi, K.; Eguchi, M.; Miyazaki, Y.

    2016-09-01

    The thermoelectric properties of ternary full-Heusler alloys, Co2 YZ, which are in a ferromagnetic state up to high temperature above 300 K, were measured and are discussed in terms of the crystal structure and electronic states. Among the full-Heusler alloys studied, the Co2MnSi sample exhibited the highest absolute value of Seebeck coefficient and also the highest electrical conductivity in the temperature range from 300 K to 1023 K. The highest power factor of 2.9 × 10-3 W/m-K2 was obtained for the Co2MnSi sample at 550 K, demonstrating the potential of half-metallic full-Heusler alloys as thermoelectric materials.

  1. Highly mismatched GaN1-x Sb x alloys: synthesis, structure and electronic properties

    NASA Astrophysics Data System (ADS)

    Yu, K. M.; Sarney, W. L.; Novikov, S. V.; Segercrantz, N.; Ting, M.; Shaw, M.; Svensson, S. P.; Martin, R. W.; Walukiewicz, W.; Foxon, C. T.

    2016-08-01

    Highly mismatched alloys (HMAs) is a class of semiconductor alloys whose constituents are distinctly different in terms of size, ionicity and/or electronegativity. Electronic properties of the alloys deviate significantly from an interpolation scheme based on small deviations from the virtual crystal approximation. Most of the HMAs were only studied in a dilute composition limit. Recent advances in understanding of the semiconductor synthesis processes allowed growth of thin films of HMAs under non-equilibrium conditions. Thus reducing the growth temperature allowed synthesis of group III-N-V HMAs over almost the entire composition range. This paper focuses on the GaN x Sb1-x HMA which has been suggested as a potential material for solar water dissociation devices. Here we review our recent work on the synthesis, structural and optical characterization of GaN1-x Sb x HMA. Theoretical modeling studies on its electronic structure based on the band anticrossing (BAC) model are also reviewed. In particular we discuss the effects of growth temperature, Ga flux and Sb flux on the incorporation of Sb, film microstructure and optical properties of the alloys. Results obtained from two separate MBE growths are directly compared. Our work demonstrates that a large range of direct bandgap energies from 3.4 eV to below 1.0 eV can be achieved for this alloy grown at low temperature. We show that the electronic band structure of GaN1-x Sb x HMA over the entire composition range is well described by a modified BAC model which includes the dependence of the host matrix band edges as well as the BAC model coupling parameters on composition. We emphasize that the modified BAC model of the electronic band structure developed for the full composition of GaN x Sb1-x is general and is applicable to any HMA.

  2. Aluminum alloy material structure impact localization by using FBG sensors

    NASA Astrophysics Data System (ADS)

    Zhu, Xiubin

    2014-12-01

    The aluminum alloy structure impact localization system by using fiber Bragg grating (FBG) sensors and impact localization algorithm was investigated. A four-FBG sensing network was established. And the power intensity demodulation method was initialized employing the narrow-band tunable laser. The wavelet transform was used to weaken the impact signal noise. And the impact signal time difference was extracted to build the time difference localization algorithm. At last, a fiber Bragg grating impact localization system was established and experimentally verified. The experimental results showed that in the aluminum alloy plate with the 500 mm*500 mm*2 mm test area, the maximum and average impact abscissa localization errors were 11 mm and 6.25 mm, and the maximum and average impact ordinate localization errors were 9 mm and 4.25 mm, respectively. The fiber Bragg grating sensors and demodulation system are feasible to realize the aviation aluminum alloy material structure impact localization. The research results provide a reliable method for the aluminum alloy material structure impact localization.

  3. Efficient determination of alloy ground-state structures

    NASA Astrophysics Data System (ADS)

    Seko, Atsuto; Shitara, Kazuki; Tanaka, Isao

    2014-11-01

    We propose an efficient approach to accurately finding the ground-state structures in alloys based on the cluster expansion method. In this approach, a small number of candidate ground-state structures are obtained without any information regarding the energy. To generate the candidates, we employ the convex hull constructed from the correlation functions of all possible structures by using an efficient algorithm. This approach is applicable to not only simple lattices, but also complex lattices. First, we evaluate the convex hulls for binary alloys with four types of simple lattice. Then we discuss the structures on the vertices. To examine the accuracy of this approach, we perform a set of density functional theory calculations and the cluster expansion for the Ag-Au alloy and compare the formation energies of the vertex structures with those of all possible structures. As applications, the ground-state structures of the intermetallic compounds CuAu, CuAg, CuPd, AuAg, AuPd, AgPd, MoTa, MoW, and TaW are similarly evaluated. Finally, the energy distribution is obtained for different cation arrangements in the MgAl2O4 spinel, for which long-range interactions are essential for the accurate description of its energetics.

  4. Advanced High Temperature Structural Seals

    NASA Technical Reports Server (NTRS)

    Newquist, Charles W.; Verzemnieks, Juris; Keller, Peter C.; Rorabaugh, Michael; Shorey, Mark

    2002-01-01

    This program addresses the development of high temperature structural seals for control surfaces for a new generation of small reusable launch vehicles. Successful development will contribute significantly to the mission goal of reducing launch cost for small, 200 to 300 pound payloads. Development of high temperature seals is mission enabling. For instance, ineffective control surface seals can result in high temperature (3100 F) flows in the elevon area exceeding structural material limits. Longer sealing life will allow use for many missions before replacement, contributing to the reduction of hardware, operation and launch costs.

  5. NASA-UVA Light Aerospace Alloy and Structures Technology Program: LA(2)ST

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

    The NASA-UVA Light Aerospace Alloy and Structures Technology (LA(2)ST) Program continues a high level of activity, with projects being conducted by graduate students and faculty advisors in the Departments of Materials Science and Engineering, Civil Engineering and Applied Mechanics, and Mechanical and Aerospace Engineering at the University of Virginia. This work is funded by the NASA-Langley Research Center under Grant NAG-1-745. We report on progress achieved between July 1 and December 31, 1992. The objective of the LA(2)ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light weight aerospace alloys, composites and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. We generally aim to produce relevant data and basic understanding of material mechanical response, corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement advances; and critically, a pool of educated graduate students for aerospace technologies.

  6. NASA-UVA light aerospace alloy and structures technology program (LA2ST)

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

    The NASA-UVA Light Aerospace Alloy and Structures Technology (LA2ST) Program was initiated in 1986, and continues a high level of activity, with projects being conducted by graduate students and faculty advisors in the Departments of Materials Science and Engineering, and Mechanical and Aerospace Engineering at the University of Virginia. This work is funded by the NASA-Langley Research Center under Grant NAG-1-745. Here, we report on progress achieved between July 1 and December 31, 1993. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light weight aerospace alloys, composites and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. We generally aim to produce relevant data and basic understanding of material mechanical response, environmental/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement and modeling advances; and critically, a pool of educated graduate students for aerospace technologies.

  7. NASA-UVA light aerospace alloy and structures technology program (LA2ST)

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

    The NASA-UVa Light Aerospace Alloy and Structures Technology (LA2ST) Program was initiated in 1986 and continues with a high level of activity. Projects are being conducted by graduate students and faculty advisors in the Department of Materials Science and Engineering, as well as in the Department of Civil Engineering and Applied Mechanics, at the University of Virginia. Here, we report on progress achieved between July 1 and December 31, 1994. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, light-weight aerospace alloys, composites and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. We generally aim to produce relevant data and basic understanding of material mechanical response, environmental/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement and modeling advances; and a pool of educated graduate students for aerospace technologies.

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

    NASA Technical Reports Server (NTRS)

    Gangloff, Richard P.

    1994-01-01

    The NASA-UVA Light Aerospace Alloy and Structures Technology (LA2ST) Program was initiated in 1986 and continues with a high level of activity. Projects are being conducted by graduate students and faculty advisors in the Department of Materials Science and Engineering, as well as in the Department of Civil Engineering and Applied Mechanics, at the University of Virginia. This work is funded by the NASA-Langley Research Center under Grant NAG-1-745. Here, we report on progress achieved between January 1 and June 30, 1994. These results were presented at the Fifth Annual NASA LA2ST Grant Review Meeting held at the Langley Research Center in July of 1994. The objective of the LA2ST Program is to conduct interdisciplinary graduate student research on the performance of next generation, lightweight aerospace alloys, composites, and thermal gradient structures in collaboration with NASA-Langley researchers. Specific technical objectives are presented for each research project. We generally aim to produce relevant data and basic understanding of material mechanical response, environmental/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; new solid and fluid mechanics analyses; measurement and modeling advances; and a pool of educated graduate students for aerospace technologies.

  9. Alloys for advanced steam turbines--Oxidation behavior

    SciTech Connect

    Holcomb, G.R.

    2007-10-01

    Advanced or ultra supercritical (USC) steam power plants offer the promise of higher efficiencies and lower emissions. Current goals of the U.S. Department of Energy (DOE) include power generation from coal at 60% efficiency, which would require steam temperatures of up to 760°C. Current research on the oxidation of candidate materials for advanced steam turbines is presented with a focus on a methodology for estimating chromium evaporation rates from protective chromia scales. The high velocities and pressures of advanced steam turbines lead to evaporation predictions as high as 5 × 10-8 kg m-2s-1 of CrO2(OH)2(g) at 760°C and 34.5 MPa. This is equivalent to 0.077 mm per year of solid Cr loss.

  10. New structures in Pd-rich ordered alloys

    NASA Astrophysics Data System (ADS)

    Corbitt, Jacqueline; Gilmartin, Erin; Hart, Gus

    2009-03-01

    An intriguing intermetallic structure with 8:1 stoichiometry was discovered in the 1950s in the Pt-Ti system. Since then a handful of other Pt/Pd/Ni binary systems have been observed to exhibit this curious structure (Pt8Zr, Pd8Mo, Ni8Nb, etc). This ordered structure can significantly increase the hardness of an alloy. For jewelry applications involving Pt and Pd, international hallmarking standards require that the alloys be at least 95% pure by weight. However, Pt- and Pd-rich alloys are often soft when purity is high if the minority atoms are disordered. Because the 8:1 structure maintains a high weight percentage of Pt/Pd, it can satisfy purity standards while increasing performance. Recent calculations and experiments suggest that the 8:1 structure may form in about 20 previously unsuspected Pt/Pd binary systems. Using first-principles calculations and cluster expansion modeling, we have performed a ground state search to find the stable structures in Pd-Nb and Pd-Cu. In collaboration with Candace Lang's group at University of Capetown South Africa, we are working to experimentally validate the predicted ground states.

  11. New structures in Pd-rich ordered alloys

    NASA Astrophysics Data System (ADS)

    Corbitt, Jacqueline; Gilmartin, Erin; Hart, Gus

    2010-03-01

    An intriguing intermetallic structure with 8:1 stoichiometry was discovered in 1959 in the Pt-Ti system. Since then a handful of other Pt/Pd/Ni binary systems have been observed to exhibit this structure (Pt8Zr, Pd8Mo, Ni8Nb, etc). Precipitates of this ordered structure can significantly increase the hardness of an alloy. For jewelry applications involving Pt and Pd, international hallmarking standards require that the alloys be at least 95% pure by weight. However, Pt- and Pd-rich alloys are often too soft for jewelry applications when purity is high and the minority atoms are disordered. Because the 8:1 structure maintains a high weight percentage of Pt/Pd, it can satisfy hallmarking while increasing performance. Recent calculations and experiments suggest that the 8:1 structure may form in about 20 previously unsuspected Pt/Pd binary systems. Using first-principles calculations and cluster expansion modeling, we have performed a ground state search to find the stable structures in Pd-Nb and Pd-Cu. In collaboration with Candace Lang's group at University of Capetown South Africa, we are working to experimentally validate the predicted ground states.

  12. New structures in Pd-rich ordered alloys

    NASA Astrophysics Data System (ADS)

    Corbitt, Jacqueline; Gilmartin, Erin; Hart, Gus

    2010-10-01

    An intriguing intermetallic structure with 8:1 stoichiometry was discovered in the 1950s in the Pt-Ti system. Since then a handful of other Pt/Pd/Ni binary systems have been observed to exhibit this curious structure (Pt8Zr, Pd8Mo, Ni8Nb, etc). This ordered structure can significantly increase the hardness of an alloy. For jewelry applications involving Pt and Pd, international hallmarking standards require that the alloys be at least 95% pure by weight. However, Pt- and Pd-rich alloys are often soft when purity is high if the minority atoms are disordered. Because the 8:1 structure maintains a high weight percentage of Pt/Pd, it can satisfy purity standards while increasing performance. Recent calculations and experiments suggest that the 8:1 structure may form in about 20 previously unsuspected Pt/Pd binary systems. Using first-principles calculations and cluster expansion modeling, we have performed a ground state search to find the stable structures in Pd-Nb and Pd-Cu. In collaboration with Candace Lang's group at University of Capetown South Africa, we are working to experimentally validate the predicted ground states.

  13. Code qualification of structural materials for AFCI advanced recycling reactors.

    SciTech Connect

    Natesan, K.; Li, M.; Majumdar, S.; Nanstad, R.K.; Sham, T.-L.

    2012-05-31

    This report summarizes the further findings from the assessments of current status and future needs in code qualification and licensing of reference structural materials and new advanced alloys for advanced recycling reactors (ARRs) in support of Advanced Fuel Cycle Initiative (AFCI). The work is a combined effort between Argonne National Laboratory (ANL) and Oak Ridge National Laboratory (ORNL) with ANL as the technical lead, as part of Advanced Structural Materials Program for AFCI Reactor Campaign. The report is the second deliverable in FY08 (M505011401) under the work package 'Advanced Materials Code Qualification'. The overall objective of the Advanced Materials Code Qualification project is to evaluate key requirements for the ASME Code qualification and the Nuclear Regulatory Commission (NRC) approval of structural materials in support of the design and licensing of the ARR. Advanced materials are a critical element in the development of sodium reactor technologies. Enhanced materials performance not only improves safety margins and provides design flexibility, but also is essential for the economics of future advanced sodium reactors. Code qualification and licensing of advanced materials are prominent needs for developing and implementing advanced sodium reactor technologies. Nuclear structural component design in the U.S. must comply with the ASME Boiler and Pressure Vessel Code Section III (Rules for Construction of Nuclear Facility Components) and the NRC grants the operational license. As the ARR will operate at higher temperatures than the current light water reactors (LWRs), the design of elevated-temperature components must comply with ASME Subsection NH (Class 1 Components in Elevated Temperature Service). However, the NRC has not approved the use of Subsection NH for reactor components, and this puts additional burdens on materials qualification of the ARR. In the past licensing review for the Clinch River Breeder Reactor Project (CRBRP) and the

  14. Microscopic study of the structure of the Steel Ni-based Alloy: Hastelloy G35 Alloy

    NASA Astrophysics Data System (ADS)

    Sabir, F.; Ben Lenda, O.; Saissi, S.; Marbouh, K.; Tyouke, B.; Zerrouk, L.; Ibnlfassi, A.; Ouzaouit, K.; Elmadani, S.

    2017-03-01

    The study of the influence of heat treatment on changes of mechanical and structural properties of Steel Ni-based Alloy is a highly interdisciplinary topic at the interface of the physical chemistry of metallic materials, which also helps in environmental and economic protection.After heat treatment, the structural and micro-structural studies for the different transformation temperature led to identify phases formed and the morphology. This work has been carried out using different techniques: X-ray diffraction, optical microscopy and scanning electron microscopy.

  15. 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.

  16. Influence of alloying elements Nb, Zr, Sn, and oxygen on structural stability and elastic properties of the Ti2448 alloy

    NASA Astrophysics Data System (ADS)

    Dai, J. H.; Song, Y.; Li, W.; Yang, R.; Vitos, L.

    2014-01-01

    The mechanisms of how alloying elements and oxygen influence the stability and elastic properties of binary Ti-X (X = Nb, Zr, or Sn) and Ti2448 (Ti-24Nb-4Zr-8Sn in wt.%) alloys are studied via first principles calculations. In addition to the fully disordered solid solution phase, we consider 44 quasirandom configurations to search for the possible distributions of the alloying elements in Ti2448. Our results show that all alloying elements considered here are good β-stabilizers for Ti, and the formation energies are greatly affected by their distributions. The site preference of oxygen and its concentration dependence in binary Ti alloys and in Ti2448 are also investigated. Oxygen prefers to occupy the octahedral site regardless of the concentrations of the alloys and strongly interacts with Ti and Nb in Ti-Nb. The elastic properties of Ti2448 alloy and the influence of oxygen on the elastic parameters are evaluated. The calculated polycrystalline Young's modulus of the Ti2448 alloy is very close to that of the human bone (10-40 GPa). We find that oxygen has a weak effect on the elastic moduli of Ti2448. The electronic structures are analyzed to reveal how the alloying elements and oxygen influence the stability of binary Ti-X and Ti2448 alloys.

  17. Structural properties of bismuth-bearing semiconductor alloys

    NASA Technical Reports Server (NTRS)

    Berding, M. A.; Sher, A.; Chen, A. B.

    1986-01-01

    The structural properties of bismuth-bearing III-V semiconductor alloys are addressed. Because the Bi compounds are not known to form zincblende structures, only the anion-substituted alloys InPBi, InAsBi, and InSbBi are considered candidates as narrow-gap semiconductors. Miscibility calculations indicate that InSbBi will be the most miscible, and InPBi, with the large lattice mismatch of the constituents, will be the most difficult to mix. Calculations of the hardness of the Bi compounds indicate that, once formed, the InPBi alloy will be harder than the other Bi alloys, and substantially harder than the currently favored narrow-gap semiconductor HgCdTe. Thus, although InSbBi may be an easier material to prepare, InPBi promises to be a harder material. Growth of the Bi compounds will require high effective growth temperatures, probably attainable only through the use of nonequilibrium energy-assisted epitaxial growth techniques.

  18. Structural and magnetic properties of Co 2CrAl Heusler alloys prepared by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Hakimi, M.; Kameli, P.; Salamati, H.

    2010-11-01

    Mechanical alloying has been used to produce nanocrystalline samples of Co 2CrAl Heusler alloys. The samples were characterized by using different methods. The results indicate that, it is possible to produce L2 1-Co 2CrAl powders after 15 h of ball-milling. The grain size of 15 h ball milled L2 1-Co 2CrAl Heusler phase, calculated by analyzing the XRD peak broadening using Williamson and Hall approach was 14 nm. The estimated magnetic moment per formula unit is ˜2 μ B. The obtained magnetic moment is significantly smaller than the theoretical value of 2.96 μ B for L2 1 structure. It seems that an atomic disorder from the crystalline L2 1-type ordered state and two-phase separation depresses the ferromagnetic ordering in alloy. Also, the effect of annealing on the structural and magnetic properties of ball milled powders was investigated. Two structures were identified for annealed sample, namely L2 1 and B2. The obtained value for magnetic moment of annealed sample is smaller than the as-milled sample due to the presence of disordered B2 phase and improvement of phase separation.

  19. Analysis of the Defect Structure of B2 Feal Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John; Noebe, Ronald D.; Amador, Carlos

    1995-01-01

    The Bozzolo, Ferrante and Smith (BFS) method for alloys is applied to the study of the defect structure of B2 FeAI alloys. First-principles Linear Muffin Tin Orbital calculations are used to determine the input parameters to the BFS method used in this work. The calculations successfully determine the phase field of the B2 structure, as well as the dependence with composition of the lattice parameter. Finally, the method is used to perform 'static' simulations where instead of determining the ground state configuration of the alloy with a certain concentration of vacancies, a large number of candidate ordered structures are studied and compared, in order to determine not only the lowest energy configurations but other possible metastable states as well. The results provide a description of the defect structure consistent with available experimental data. The simplicity of the BFS method also allows for a simple explanation of some of the essential features found in the concentration dependence of the heat of formation, lattice parameter and the defect structure.

  20. Structural Uses for Ductile Ordered Alloys. Report of the Committee on Application Potential for Ductile Ordered Alloys

    DTIC Science & Technology

    1984-08-31

    Ordered Alloys: Structural Applications and Physical Metallurgy, Proceedings of the 3rd Bolton Landing Conference, Lake George , N.Y., September 1969...ordering reactions. In Order-Disorder Transformations in Alloys, p. 494, Ed. by H. Warlimont. New York: Springer-Verlag. Williams, A. R., J. Kubler

  1. Advanced TEM characterization of oxide nanoparticles in ODS Fe–12Cr–5Al alloys

    SciTech Connect

    Unocic, Kinga A; Hoelzer, David T; Pint, Bruce A

    2016-01-01

    For oxide nanoparticles present in three oxide-dispersion-strengthened (ODS) Fe–12Cr–5Al alloys containing additions of (1) Y2O3 (125Y), (2) Y2O3 + ZrO2 (125YZ), and (3) Y2O3 + HfO2 (125YH), were investigated using transmission and scanning transmission electron microscopy. Furthermore, in all three alloys nano-sized (<3.5 nm) oxide particles distributed uniformly throughout the microstructure were characterized using advanced electron microscopy techniques. In the 125Y alloy, mainly Al2O3 and yttrium–aluminum garnet (YAG) phases (Y3Al5O12) were present, while in the 125YZ alloy, additional Zr(C,N) precipitates were identified. The 125YH alloy had the most complex precipitation sequence whereby in addition to the YAG and Al2O3 phases, Hf(C,N), Y2Hf2O7, and HfO2 precipitates were also found. The presence of HfO2 was mainly due to the incomplete incorporation of HfO2 powder during mechanical alloying of the 125YH alloy. The alloy having the highest total number density of the oxides, the smallest grain size, and the highest Vickers hardness was the 125YZ alloy indicating, that Y2O3 + ZrO2 additions had the strongest effect on grain size and tensile properties. Finally, high-temperature mechanical testing will be addressed in the near future, while irradiation studies are underway to investigate the irradiation resistance of these new ODS FeCrAl alloys.

  2. Structural and magnetic properties of samarium iron and related alloys

    NASA Astrophysics Data System (ADS)

    Meacham, Brian Eugene

    There were three research objectives. The first objective was to determine what controls the structural scale of the microstructure in Sm-Fe alloys. The second objective was to study the morphological development of antiphase domains. The last objective was to determine the effect of the microstructural state on the coercivity and magnetization reversal of Sm2Fe 17Nx. The as-solidified alloys had large grains with irregular shape but the metal carbide modified alloys had a refinement of the microstructural scale and improved homogeneous grain shape. The magnitude of the scale reduction depended on the additives. It was determined that an important factor for the refinement was the glass forming ability of the alloy composition. The evidence points to solute segregation at the solidification boundary as the dominant mechanism that controls the grain size. The as-solidified binary alloy had significant strain. As annealing occurs the development of antiphase domains causes the reduction of strain, which reduces the defect density. A similar morphology occurs in the TiC modified alloy. It was discovered that order pattern in the antiphase domains has a twin symmetry. This is a new structural feature that has not been seen in antiphase domains before and is called rebel ordering. The recoil data showed that nucleation of reversed domains causes a peak in the remanent susceptibility curve. However, when domain wall pinning occurs there are fluctuations. It was discovered that as the loop shape improves, the separation between the coercivity and the peak center decreases linearly with either the squareness ratio or the fullness factor. The nitrided binary alloy coercivity decreases with increasing ordering. However, there is a narrow order parameter region where the antiphase structure effectively pins domain walls resulting in an enhancement of the coercivity. The microstructural scale affects the coercivity. The single domain limit was determined to be about 300 nm

  3. Use of Shape Memory Alloys in the Robust Control of Smart Structures

    DTIC Science & Technology

    1993-08-01

    o.W w’,. Xi) 18 2.3.4 Phase Transformation and Shape Recovery In-TI alloys in a certain composition range have a FCC structure as a parent phase and...Alloy Films Alloys in the composition range of 15-30 at% thallium are known to have a face centered cubic( FCC ) structure as a parent phase which...24 Structure of as-deposited alloys In-TI alloys in a certain composition range have a face centered cubic( FCC ) structure as a parent phase and

  4. Advanced Gear Alloys for Ultra High Strength Applications

    NASA Technical Reports Server (NTRS)

    Shen, Tony; Krantz, Timothy; Sebastian, Jason

    2011-01-01

    Single tooth bending fatigue (STBF) test data of UHS Ferrium C61 and C64 alloys are presented in comparison with historical test data of conventional gear steels (9310 and Pyrowear 53) with comparable statistical analysis methods. Pitting and scoring tests of C61 and C64 are works in progress. Boeing statistical analysis of STBF test data for the four gear steels (C61, C64, 9310 and Pyrowear 53) indicates that the UHS grades exhibit increases in fatigue strength in the low cycle fatigue (LCF) regime. In the high cycle fatigue (HCF) regime, the UHS steels exhibit better mean fatigue strength endurance limit behavior (particularly as compared to Pyrowear 53). However, due to considerable scatter in the UHS test data, the anticipated overall benefits of the UHS grades in bending fatigue have not been fully demonstrated. Based on all the test data and on Boeing s analysis, C61 has been selected by Boeing as the gear steel for the final ERDS demonstrator test gearboxes. In terms of potential follow-up work, detailed physics-based, micromechanical analysis and modeling of the fatigue data would allow for a better understanding of the causes of the experimental scatter, and of the transition from high-stress LCF (surface-dominated) to low-stress HCF (subsurface-dominated) fatigue failure. Additional STBF test data and failure analysis work, particularly in the HCF regime and around the endurance limit stress, could allow for better statistical confidence and could reduce the observed effects of experimental test scatter. Finally, the need for further optimization of the residual compressive stress profiles of the UHS steels (resulting from carburization and peening) is noted, particularly for the case of the higher hardness C64 material.

  5. Properties of Graphite Intercalates and of Aircraft Structural Metals and Alloys. A Comprehensive Data Survey.

    DTIC Science & Technology

    1974-05-01

    Thermal Conductivity of Pure and Alloyed Aluminum . L Solid Aluminum as a Reference Material," From Advances in Thermophysical properties at Extreme...Willey, L.A., Smith, D.W., and Edwards, J.D., "The Properties of High-Purity Aluminum , "Metals and Alloys , 7(8), 189-92, 1938. 4 52254 Irmonn, R...Termal expansion-Specific beat-Beat of fusion-Graphite compound---Composite-Carbides--Aluonun-- Aluminum alloy -Titanium--Titanium alloy -agnesium alloy

  6. 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.

  7. RESEARCH ON THE BASIC NATURE OF STRESS CORROSION FOR VARIOUS STRUCTURAL ALLOYS AT ROOM AND ELEVATED TEMPERATURE,

    DTIC Science & Technology

    LIFE), GRAIN STRUCTURES(METALLURGY), FRACTURE(MECHANICS), TENSILE PROPERTIES , HEAT TREATMENT, TEMPERATURE, SEA WATER, CHLORIDES, SHEETS, STEEL, MOLYBDENUM ALLOYS, VANADIUM ALLOYS, ENVIRONMENTAL TESTS, MICROSTRUCTURE.

  8. Concentration dependent structural parameters of liquid Al-Fe alloys

    NASA Astrophysics Data System (ADS)

    Lalnuntluanga, C.; Mishra, Raj Kumar

    2016-10-01

    Square well potential is perturbed over Lebowtiz solution of hard sphere mixtures to determine direct correlation function,C(0) ij(r) in repulsive and attractive regions under Mean Spherical Model Approximation [1]. Obtained direct correlation functions were employed to derive partial structure factors and then total structure factor, S(k) in liquid Al-Fe alloy at different atomic percent of Al. Fourier transform of partial and total structure factors gives partial and total radial distribution functions, g(r) from which partial and total coordination numbers and the partial nearest-neighbor distances were computed.

  9. Advances and trends in computational structural mechanics

    NASA Technical Reports Server (NTRS)

    Noor, Ahmed K.; Atluri, Satya N.

    1987-01-01

    The development status and applicational range of techniques in computational structural mechanics (CSM) are evaluated with a view to advances in computational models for material behavior, discrete-element technology, quality assessment, the control of numerical simulations of structural response, hybrid analysis techniques, techniques for large-scale optimization, and the impact of new computing systems on CSM. Primary pacers of CSM development encompass prediction and analysis of novel materials for structural components, computational strategies for large-scale structural calculations, and the assessment of response prediction reliability together with its adaptive improvement.

  10. Effect of Silicon Alloying on the Structure of Exoplanetary Cores

    NASA Astrophysics Data System (ADS)

    Wicks, J. K.; Smith, R.; Coppari, F.; Kraus, R. G.; Newman, M.; Duffy, T. S.

    2015-12-01

    The composition of cores of terrestrial planets are expected to be broadly similar to that of Earth in that they are comprised of a Fe-Ni alloy with variable amounts of light elements such as O, Si, C, S, and H. With the increasing number of discoveries of Super-Earths (rocky planets many times the mass of our own), the properties of terrestrial phases at ultrahigh pressures are required to understand and interpret the variability of large-scale exoplanet observations. The properties of the cores of these bodies are important for understanding the bulk chemistry, thermal evolution, magnetic fields, and, ultimately, habitability of a planet. Recent diamond anvil cell studies interrogating the structure of iron generally agree that Fe should be hcp at core pressures and temperatures, although other structures have been proposed. At higher pressures and with the addition of light elements, the structure is less understood. The addition of large amounts of Si, for example, stabilizes the cubic B2 structure with respect to hcp at outer core pressures. Our goal in this study is to explore the effect of Si-alloying at inner core and exoplanetary-core pressures. Dynamic compression experiments were carried out at the Omega Laser at the Laboratory for Laser Energetics, University of Rochester. High pressures were achieved by focusing laser drives onto target packages containing Fe-Si alloys. Pressures within the sample were determined by monitoring the velocity history at the sample/window interface. Quasi-monochromatic X-rays, timed with maximum compression of the Fe-alloy sample, were generated via laser irradiation of iron or germanium foils arranged in a backlighter configuration and collected on image plates lining the inner walls of a box attached to the target package. In this presentation we will report on the effect of Si-alloying on the structure and density of Fe over the pressure range 100-1000 GPa. We find that while Fe with 7 wt.% Si remains in the hcp

  11. FAA/NASA International Symposium on Advanced Structural Integrity Methods for Airframe Durability and Damage Tolerance

    NASA Technical Reports Server (NTRS)

    Harris, Charles E. (Editor)

    1994-01-01

    International technical experts in durability and damage tolerance of metallic airframe structures were assembled to present and discuss recent research findings and the development of advanced design and analysis methods, structural concepts, and advanced materials. The symposium focused on the dissemination of new knowledge and the peer-review of progress on the development of advanced methodologies. Papers were presented on: structural concepts for enhanced durability, damage tolerance, and maintainability; new metallic alloys and processing technology; fatigue crack initiation and small crack effects; fatigue crack growth models; fracture mechanics failure, criteria for ductile materials; structural mechanics methodology for residual strength and life prediction; development of flight load spectra for design and testing; and advanced approaches to resist corrosion and environmentally assisted fatigue.

  12. Fatigue-crack propagation in advanced aerospace materials: Aluminum-lithium alloys

    SciTech Connect

    Venkateswara Rao, K.T.; Ritchie, R.O.

    1988-10-01

    Characteristics of fatigue-crack propagation behavior are reviewed for recently developed commercial aluminum-lithium alloys, with emphasis on the underlying micromechanisms associated with crack advance and their implications to damage-tolerant design. Specifically, crack-growth kinetics in Alcoa 2090-T8E41, Alcan 8090 and 8091, and Pechiney 2091 alloys, and in certain powder-metallurgy alloys, are examined as a function of microstructure, plate orientation, temperature, crack size, load ratio and loading sequence. In general, it is found that growth rates for long (> 10 mm) cracks are nearly 2--3 orders of magnitude slower than in traditional 2000 and 7000 series alloys at comparable stress-intensity levels. In additions, Al-Li alloys shown enhanced crack-growth retardations following the application of tensile overloads and retain superior fatigue properties even after prolonged exposure at overaging temperatures; however, they are less impressive in the presence of compression overloads and further show accelerated crack-growth behavior for microstructurally-small (2--1000 {mu}m) cracks (some three orders of magnitude faster than long cracks). These contrasting observations are attributed to a very prominent role of crack-tip shielding during fatigue-crack growth in Al-Li alloys, promoted largely by the tortuous and zig-zag nature of the crack-path morphologies. Such crack paths result in locally reduced crack-tip stress intensities, due to crack deflection and consequent crack wedging from fracture-surface asperities (roughness-induced crack closure); however, such mechanisms are far less potent in the presence of compressive loads, which act to crush the asperities, and for small cracks, where the limited crack wake severely restricts the shielding effect. 50 refs., 21 figs.

  13. Lightweight Multifunctional Linear Cellular Alloy Ballistic Structures

    DTIC Science & Technology

    2006-04-26

    for densification. For this program, square cell LCA honeycomb with both maraging steel and super invar compositions were fabricated using SAI’s...provide high levels of energy absorption; 5 to 7 times that of that of conventional materials. Maraging steel honeycomb structure having a density of 2.1 g...cm3 and yield strength ~650 MPa, has been shown to absorb ~180 MJ/m3. Figure 2 shows stress train curves for maraging steel under quasistatic and

  14. Investigation of high-energy external influences on structural heredity of the Ti-Nb alloy

    NASA Astrophysics Data System (ADS)

    Khimich, M. A.; Parilov, E. A.; Kovalevskaya, Zh G.; Sharkeev, Yu P.

    2015-10-01

    The effects of high-energy external influences on structural heredity of Ti-Nb alloy is investigated in this paper. By the methods of XRD, SEM, EDX and optical microscopy it was founded that thermal treatment and severe plastic deformation lead to the phase transformations in the alloy, the dendritic segregation occurs and retains in the alloy under external influences.

  15. Dendritic growth and structure of undercooled nickel base alloys

    NASA Technical Reports Server (NTRS)

    Flemings, M. C.; Shiohara, Y.

    1988-01-01

    The principal objectives of this overall investigation are to: study means for obtaining high undercooling in levitation melted droplets, and study structures produced upon the solidification of these undercooled specimens. Thermal measurements are made of the undercooling, and of the rapid recalescence, to develop an understanding of the solidification mechanism. Comparison of results is made with the modeling studies. Characterization and metallographic work is done to gain an understanding of the relationship between rapid solidification variables and the structures so produced. In ground based work to date, solidification of undercooled Ni-25 wt percent Sn alloy was observed by high-speed cinematography and the results compared with optical temperature measurements. Also in ground based work, high-speed optical temperature measurements were made of the solidification behavior of levitated metal samples within a transparent glass medium. Two undercooled Ni-Sn alloys were examined. Measurements were carried out on samples at undercoolings up to 330 K. Microstructures of samples produced in ground based work were determined by optical metallography and by SEM, and microsegregation by electron microprobe measurements. A series of flight tests were planned to conduct experiments similar to the ground based experiments. The Space Shuttle Columbia carried an alloy undercooled experiment in the STS 61-C mission in January 1986. A sample of Ni-32.5 wt percent Sn eutectic was melted and solidified under microgravity conditions.

  16. Fault structures in rapidly quenched Ni-Mo binary alloys

    NASA Technical Reports Server (NTRS)

    Jayaraman, N.; Tewari, S. N.

    1986-01-01

    Fault structures in two Ni-Mo alloy ribbons (Ni-28 at. pct Mo and Ni-35 at. pct Mo) cast by a free jet chill block melt spinning process were studied. Thin foils for TEM studies were made by electrochemical thinning using an alcohol/butyl cellosolve/perchloric acid mixture in a twin jet electropolishing device. The samples displayed typical grains containing linear faulted regions on the wheelside of the two alloy ribbons. However, an anomalous diffraction behavior was observed upon continuous tilting of the sample: the network of diffraction spots from a single grain appeared to expand or contract and rotate. This anomalous diffraction behavior was explained by assuming extended spike formation at reciprocal lattice points, resulting in a network of continuous rel rods. The validity of the model was confirmed by observations of a cross section of the reciprocal lattice parallel to the rel rods.

  17. QuikForm: Intelligent deformation processing of structural alloys

    SciTech Connect

    Bourcier, R.J.; Wellman, G.W.

    1994-09-01

    There currently exists a critical need for tools to enhance the industrial competitiveness and agility of US industries involved in deformation processing of structural alloys. In response to this need, Sandia National Laboratories has embarked upon the QuikForm Initiative. The goal of this program is the development of computer-based tools to facilitate the design of deformation processing operations. The authors are currently focusing their efforts on the definition/development of a comprehensive system for the design of sheet metal stamping operations. The overall structure of the proposed QuikForm system is presented, and the focus of their thrust in each technical area is discussed.

  18. Investigation of austenitic alloys for advanced heat recovery and hot gas cleanup systems

    SciTech Connect

    Swindeman, R.W.; Ren, W.

    1996-06-01

    The objective of the research is to provide databases and design criteria to assist in the selection of optimum alloys for construction of components needed to contain process streams in advanced heat recovery and hot-gas cleanup systems. Typical components include: steam line piping and superheater tubing for low emission boilers (600 to 700{degrees}C), heat exchanger tubing for advanced steam cycles and topping cycle systems (650 to 800{degrees}C), foil materials for recuperators, on advanced turbine systems (700 to 750{degrees}C), and tubesheets for barrier filters, liners for piping, cyclones, and blowback system tubing for hot-gas cleanup systems (850 to 1000{degrees}C). The materials being examined fall into several classes, depending on which of the advanced heat recovery concepts is of concern. These classes include martensitic steels for service to 650{degrees}C, lean stainless steels and modified 25Cr-30Ni steels for service to 700{degrees}C, modified 25Cr-20Ni steels for service to 900{degrees}C, and high Ni-Cr-Fe or Ni-Cr-Co-Fe alloys for service to 1000{degrees}C.

  19. Quality Assurance Protocol for AFCI Advanced Structural Materials Testing

    SciTech Connect

    Busby, Jeremy T

    2009-05-01

    The objective of this letter is to inform you of recent progress on the development of advanced structural materials in support of advanced fast reactors and AFCI. As you know, the alloy development effort has been initiated in recent months with the procurement of adequate quantities of the NF616 and HT-UPS alloys. As the test alloys become available in the coming days, mechanical testing, evaluation of optimizing treatments, and screening of environmental effects will be possible at a larger scale. It is therefore important to establish proper quality assurance protocols for this testing effort in a timely manner to ensure high technical quality throughout testing. A properly implemented quality assurance effort will also enable preliminary data taken in this effort to be qualified as NQA-1 during any subsequent licensing discussions for an advanced design or actual prototype. The objective of this report is to describe the quality assurance protocols that will be used for this effort. An essential first step in evaluating quality protocols is assessing the end use of the data. Currently, the advanced structural materials effort is part of a long-range, basic research and development effort and not, as yet, involved in licensing discussions for a specific reactor design. After consultation with Mark Vance (an ORNL QA expert) and based on the recently-issued AFCI QA requirements, the application of NQA-1 quality requirements will follow the guidance provided in Part IV, Subpart 4.2 of the NQA-1 standard (Guidance on Graded Application of QA for Nuclear-Related Research and Development). This guidance mandates the application of sound scientific methodology and a robust peer review process in all phases, allowing for the data to be qualified for use even if the programmatic mission changes to include licensing discussions of a specific design or prototype. ORNL has previously implemented a QA program dedicated to GNEP activities and based on an appropriately graded

  20. Thermal and Mechanical Property Characterization of the Advanced Disk Alloy LSHR

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Gayda, John; Telesman, Jack; Kantzos, Peter T.

    2005-01-01

    A low solvus, high refractory (LSHR) powder metallurgy disk alloy was recently designed using experimental screening and statistical modeling of composition and processing variables on sub-scale disks to have versatile processing-property capabilities for advanced disk applications. The objective of the present study was to produce a scaled-up disk and apply varied heat treat processes to enable full-scale demonstration of LSHR properties. Scaled-up disks were produced, heat treated, sectioned, and then machined into specimens for mechanical testing. Results indicate the LSHR alloy can be processed to produce fine and coarse grain microstructures with differing combinations of strength and time-dependent mechanical properties, for application at temperatures exceeding 1300 F.

  1. Development of advanced high strength tantalum base alloys. Part 2: Scale-up investigation

    NASA Technical Reports Server (NTRS)

    Ammon, R. L.; Buckman, R. W., Jr.

    1970-01-01

    Three experimental tantalum alloy compositions containing 14-16% W, 1% Re, 0.7% Hf, 0.025% C or 0.015% C and 0.015% N were prepared as two inch diameter ingots by consumable electrode vacuum arc melting. The as-cast ingots were processed by extrusion and swaging to one inch and 0.4 inch diameter rod and evaluated. Excellent high temperature forging behavior was exhibited by all three compositions. Creep strength at 2000 F to 2400 F was enhanced by higher tungsten additions as well as substitution of nitrogen for carbon. Weldability of all three compositions was determined to be adequate. Room temperature ductility was retained in the advanced tantalum alloy compositions as well as a notched/unnotched strength ratio of 1.4 for a notched bar having a K sub t = 2.9.

  2. Superplastic forming of Al-Li alloys for lightweight, low-cost structures

    NASA Technical Reports Server (NTRS)

    Hales, Stephen J.; Wagner, John A.

    1991-01-01

    Superplastic forming of advanced aluminum alloys is being evaluated as an approach for fabricating low-cost, light-weight, cryogenic propellant tanks. Built-up structure concepts (with inherent reduced scrap rate) are under investigation to offset the additional raw material expenses incurred by using aluminum lithium alloys. This approach to fabrication offers the potential for significant improvements in both structural efficiency and overall manufacturing costs. Superplasticity is the ability of specially processed material to sustain very large forming strains without failure at elevated temperatures under controlled deformation conditions. It was demonstrated that superplastic forming technology can be used to fabricate complex structural components in a single operation and increase structural efficiency by as much as 60 percent compared to conventional configurations in skin-stiffened structures. Details involved in the application of this technology to commercial grade superplastic aluminum lithium material are presented. Included are identification of optimum forming parameters, development of forming procedures, and assessment of final part quality in terms of cavitation volume and thickness variation.

  3. The design of repairable advanced composite structures

    NASA Technical Reports Server (NTRS)

    Hart-Smith, L. J.

    1985-01-01

    This paper addresses the repair of advanced composite structures by mechanical fasteners or by adhesive bonding. It is shown that many of today's composite designs are unreasonably difficult to repair. Conversely, the knowledge to design repairable structures is already available, if only it is applied during the initial design stage. Bolted or riveted repairs require only the avoidance of extremely orthotropic composite fiber patterns; those near the quasi-isotropic layup are the most suitable. Mildly orthotropic fiber patterns are appropriate for structures in which there is a dominant load direction. Thick composite structures are shown to require bolted or riveted repairs while thin structures favor adhesively bonded permanent repairs, although provisions can be easily made for temporary mechanical repairs. The reasons why integrally stiffened cocured composite designs are usually impractical to repair are explained and alternative repairable design concepts are presented.

  4. High Temperature, Slow Strain Rate Forging of Advanced Disk Alloy ME3

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; OConnor, Kenneth

    2001-01-01

    The advanced disk alloy ME3 was designed in the HSR/EPM disk program to have extended durability at 1150 to 1250 F in large disks. This was achieved by designing a disk alloy and process producing balanced monotonic, cyclic, and time-dependent mechanical properties. combined with robust processing and manufacturing characteristics. The resulting baseline alloy, processing, and supersolvus heat treatment produces a uniform, relatively fine mean grain size of about ASTM 7, with as-large-as (ALA) grain size of about ASTM 3. There is a long term need for disks with higher rim temperature capabilities than 1250 F. This would allow higher compressor exit (T3) temperatures and allow the full utilization of advanced combustor and airfoil concepts under development. Several approaches are being studied that modify the processing and chemistry of ME3, to possibly improve high temperature properties. Promising approaches would be applied to subscale material, for screening the resulting mechanical properties at these high temperatures. n obvious path traditionally employed to improve the high temperature and time-dependent capabilities of disk alloys is to coarsen the grain size. A coarser grain size than ASTM 7 could potentially be achieved by varying the forging conditions and supersolvus heat treatment. The objective of this study was to perform forging and heat treatment experiments ("thermomechanical processing experiments") on small compression test specimens of the baseline ME3 composition, to identify a viable forging process allowing significantly coarser grain size targeted at ASTM 3-5, than that of the baseline, ASTM 7.

  5. Cryogenic Fracture Toughness Evaluation of an Investment Cast Al-Be Alloy for Structural Applications

    NASA Technical Reports Server (NTRS)

    Gamwell, W. R.; McGill, P. B.

    2006-01-01

    Aluminum-Beryllium metal matrix composite materials are useful due to their desirable performance characteristics for aerospace applications. Desirable characteristics of this material includes light-weight, dimensional stability, stiffness, good vibration damping characteristics, low coefficient of thermal expansion, and workability, This material is 3.5 times stiffer and 22% lighter than conventional aluminum alloys. electro-optical systems, advanced sensor and guidance components for flight and satellite systems, components for light-weight high-performance aircraft engines, and structural components for helicopters. Aluminum-beryllium materials are now available in the form of near net shape investment castings. In this materials properties characterization study, the cryogenic tensile and fracture properties of an investment casting alloy, Beralcast 363, were determined. Tensile testing was performed at 21 C (70 F), -73.3 C (-100 F), -195.5 C (-320 F) and -252.8 C (-423 F), and fracture (K(sub lc) and da/dN) testing was performed at -73.3 C (-100 F), -195.5 C (-320 F) and -252.8 C (-423 F). Their use is attractive for weight critical structural applications such as advanced

  6. Structural evolution in mechanically alloyed Al-Fe powders

    SciTech Connect

    Mukhopadhyay, D.K.; Suryanarayana, C.; Froes, F.H.

    1995-08-01

    The structural evolution in mechanically alloyed binary aluminum-iron powder mixtures containing 1, 4, 7.3, 10.7, and 25 at pct Fe was investigated using X-ray diffraction (XRD) and electron microscopic techniques. The constitution (number and identity of phases present), microstructure (crystal size, particle size), and transformation behavior of the powders on annealing were studied. The solid solubility of Fe in Al has been extended up to at least 4.5 at. pct, which is close to that observed using rapid solidification (RS) (4.4 at. pct), compared with the equilibrium value of 0.025 at. pct Fe at room temperature. Nanometer-sized grains were observed in as-milled crystalline powders in all compositions. Increasing the ball-to-powder weight ratio (BPR) resulted in a faster rate of decrease of crystal size. A fully amorphous phase was obtained in the Al-25 at. pct Fe composition, and a mixed amorphous phase plus solid solution of Fe in Al was developed in the Al-10.7 at. pct Fe alloy, agreeing well with the predictions made using the semiempirical Miedema model. Heat treatment of the mechanically alloyed powders containing the supersaturated solid solution or the amorphous phase resulted in the formation of the Al{sub 3}Fe intermetallic in all but the Al-25 at. pct Fe powders. In the Al-25 at. pct Fe powder, formation of nanocrystalline Al{sub 5}Fe{sub 2} was observed directly by milling. Electron microscope studies of the shock-consolidated mechanically alloyed Al-10.7 and 25 at. pct Fe powders indicated that nanometer-sized grains were retained after compaction.

  7. Complex nanoprecipitate structures induced by irradiation in immiscible alloy systems

    NASA Astrophysics Data System (ADS)

    Shu, Shipeng; Bellon, P.; Averback, R. S.

    2013-04-01

    We investigate the fundamentals of compositional patterning induced by energetic particle irradiation in model A-B substitutional binary alloys using kinetic Monte Carlo simulations. The study focuses on a type of nanostructure that was recently observed in dilute Cu-Fe and Cu-V alloys, where precipitates form within precipitates, a morphology that we term “cherry-pit” structures. The simulations show that the domain of stability of these cherry-pit structures depends on the thermodynamic and kinetic asymmetry between the A and B elements. In particular, both lower solubilities and diffusivities of A in B compared to those of B in A favor the stabilization of these cherry-pit structures for A-rich average compositions. The simulation results are rationalized by extending the analytic model introduced by Frost and Russell for irradiation-induced compositional patterning so as to include the possible formation of pits within precipitates. The simulations indicate also that the pits are dynamical structures that undergo nearly periodic cycles of nucleation, growth, and absorption by the matrix.

  8. Near net shape forming of advanced structural ceramic devices

    NASA Astrophysics Data System (ADS)

    Liu, Hao-Chih

    This research applied a combination of rapid prototyping techniques and ceramic gelcasting processes in the design and manufacturing of advanced structural ceramic components that cannot be fabricated by other shape-forming processes. An Assembly Mold SDM process, a derivative process of Shape Deposition Manufacturing, was adopted along with modified gelcasting with great success. The fabricated gas turbine rotors, inlet nozzles, and mesoscale burner arrays have demonstrated superior shape accuracy, mechanical strength, and surface smoothness with a feature size of 200 mum. The design concepts and functionalities of the ceramic devices were verified with performance tests. The shape complexity and surface quality of ceramic parts have been further improved by the use of a mold assembly made of a low melting temperature metal alloy. The introduction of metal alloy required modifications in the mold design, machining procedure, and ceramic processing. A complete shape forming process (from slurry to final parts) was developed for the low melting temperature metal alloy. In addition, the choice of ceramic material now includes SiC, which is critical to the development of micro heat exchangers. Forty-channel, high-aspect-ratio structured SiC heat exchangers were fabricated, and the thermal conductivity value of SiC was found to be comparable to that of steel. The catalyst deposition and ceramic precursor impregnation processes were proposed to enable use of the SiC heat exchangers as micro reactors. Micro-electro-mechanical-systems (MEMS)-related techniques such as SU-8 deep photolithography and polydimethylsiloxane (PDMS) soft lithography were combined with gelcasting to make micro patterns on structural ceramics. A feature size of 125 mum and aspect ratio of 8 have been achieved in the preliminary experiments. Based on the fabricated ceramic devices, a graphical method to characterize the shape attributes of complex-shaped components was proposed and used to compare

  9. Corrosion performance of advanced structural materials in sodium.

    SciTech Connect

    Natesan, K.; Momozaki, Y.; Li, M.; Rink, D.L.

    2012-05-16

    This report gives a description of the activities in design, fabrication, construction, and assembling of a pumped sodium loop for the sodium compatibility studies on advanced structural materials. The work is the Argonne National Laboratory (ANL) portion of the effort on the work project entitled, 'Sodium Compatibility of Advanced Fast Reactor Materials,' and is a part of Advanced Materials Development within the Reactor Campaign. The objective of this project is to develop information on sodium corrosion compatibility of advanced materials being considered for sodium reactor applications. This report gives the status of the sodium pumped loop at Argonne National Laboratory, the specimen details, and the technical approach to evaluate the sodium compatibility of advanced structural alloys. This report is a deliverable from ANL in FY2010 (M2GAN10SF050302) under the work package G-AN10SF0503 'Sodium Compatibility of Advanced Fast Reactor Materials.' Two reports were issued in 2009 (Natesan and Meimei Li 2009, Natesan et al. 2009) which examined the thermodynamic and kinetic factors involved in the purity of liquid sodium coolant for sodium reactor applications as well as the design specifications for the ANL pumped loop for testing advanced structural materials. Available information was presented on solubility of several metallic and nonmetallic elements along with a discussion of the possible mechanisms for the accumulation of impurities in sodium. That report concluded that the solubility of many metals in sodium is low (<1 part per million) in the temperature range of interest in sodium reactors and such trace amounts would not impact the mechanical integrity of structural materials and components. The earlier report also analyzed the solubility and transport mechanisms of nonmetallic elements such as oxygen, nitrogen, carbon, and hydrogen in laboratory sodium loops and in reactor systems such as Experimental Breeder Reactor-II, Fast Flux Test Facility, and

  10. Advanced design concepts for shuttle airframe structure

    NASA Technical Reports Server (NTRS)

    Card, M. F.; Davis, J. G., Jr.; Shideler, J. L.

    1972-01-01

    The development of weight-saving advanced design concepts for shuttle airframe structure is presented. Design concepts under investigation employ selective composite reinforcement and/or efficient geometric arrangements. An effort to develop metallic panel designs which exploit the relaxation of smooth external-surface requirements for skin structure is reviewed. Available highlights from research and development studies which investigate the application of composite reinforcement to the design of two types of fuselage panels, a shear web, a large fuselage frame, and a landing-gear-door assembly are presented. Preliminary results from these studies suggest weight savings of 25 percent can be obtained.

  11. Electronic structure of disordered α-FeMn alloys

    NASA Astrophysics Data System (ADS)

    Paduani, C.; da Silva, E. G.

    1996-08-01

    Cluster calculations were performed with the first-principles discrete variational method, in the LSD approximation and spin-polarized case, to investigate the electronic structure of the ferromagnetic disordered α-FeMn alloys. We investigated the effect on the local magnetic properties at iron sites of the introduction of Mn atoms in their first and second neighborhoods. The calculated magnetic moment and hyperfine magnetic field ( Hc) for an isolated Mn atom in a bcc iron host were obtained as -3.15 μB and -230 kG, respectively, in good agreement with experimental results.

  12. Mechanical alloying of Co and P: Structural and photoacoustic studies

    NASA Astrophysics Data System (ADS)

    Souza, S. M.; Trichês, D. M.; de Lima, J. C.; Grandi, T. A.; Campos, C. E. M.

    2007-09-01

    A mixture of elemental Co and P powders with nominal CoP3 composition was investigated by the mechanical alloying technique. For milling times greater than 26h, the measured x-ray diffraction (XRD) patterns revealed the coexistence of the skutterudite CoP3, the orthorhombic CoP, and Co2P phases. The structural and photoacoustic properties of as-milled powders were studied by the XRD and photoacoustic spectroscopy (PAS) techniques. The thermal diffusivity parameter of the as-milled sample was measured from fitting the PAS signal phase. The thermoelastic bending process is the main contribution to the PAS signal amplitude.

  13. Advances in Structures for Large Space Systems

    NASA Technical Reports Server (NTRS)

    Belvin, W. Keith

    2004-01-01

    The development of structural systems for scientific remote sensing and space exploration has been underway for four decades. The seminal work from 1960 to 1980 provided the basis for many of the design principles of modern space systems. From 1980- 2000 advances in active materials and structures and the maturing of composites technology led to high precision active systems such those used in the Space Interferometry Mission. Recently, thin-film membrane or gossamer structures are being investigated for use in large area space systems because of their low mass and high packaging efficiency. Various classes of Large Space Systems (LSS) are defined in order to describe the goals and system challenges in structures and materials technologies. With an appreciation of both past and current technology developments, future technology challenges are used to develop a list of technology investments that can have significant impacts on LSS development.

  14. Advances of Ag, Cu, and Ag-Cu alloy nanoparticles synthesized via chemical reduction route

    NASA Astrophysics Data System (ADS)

    Tan, Kim Seah; Cheong, Kuan Yew

    2013-04-01

    Silver (Ag) and copper (Cu) nanoparticles have shown great potential in variety applications due to their excellent electrical and thermal properties resulting high demand in the market. Decreasing in size to nanometer scale has shown distinct improvement in these inherent properties due to larger surface-to-volume ratio. Ag and Cu nanoparticles are also shown higher surface reactivity, and therefore being used to improve interfacial and catalytic process. Their melting points have also dramatically decreased compared with bulk and thus can be processed at relatively low temperature. Besides, regularly alloying Ag into Cu to create Ag-Cu alloy nanoparticles could be used to improve fast oxidizing property of Cu nanoparticles. There are varieties methods have been reported on the synthesis of Ag, Cu, and Ag-Cu alloy nanoparticles. This review aims to cover chemical reduction means for synthesis of those nanoparticles. Advances of this technique utilizing different reagents namely metal salt precursors, reducing agents, and stabilizers, as well as their effects on respective nanoparticles have been systematically reviewed. Other parameters such as pH and temperature that have been considered as an important factor influencing the quality of those nanoparticles have also been reviewed thoroughly.

  15. Process Optimization of Dual-Laser Beam Welding of Advanced Al-Li Alloys Through Hot Cracking Susceptibility Modeling

    NASA Astrophysics Data System (ADS)

    Tian, Yingtao; Robson, Joseph D.; Riekehr, Stefan; Kashaev, Nikolai; Wang, Li; Lowe, Tristan; Karanika, Alexandra

    2016-07-01

    Laser welding of advanced Al-Li alloys has been developed to meet the increasing demand for light-weight and high-strength aerospace structures. However, welding of high-strength Al-Li alloys can be problematic due to the tendency for hot cracking. Finding suitable welding parameters and filler material for this combination currently requires extensive and costly trial and error experimentation. The present work describes a novel coupled model to predict hot crack susceptibility (HCS) in Al-Li welds. Such a model can be used to shortcut the weld development process. The coupled model combines finite element process simulation with a two-level HCS model. The finite element process model predicts thermal field data for the subsequent HCS hot cracking prediction. The model can be used to predict the influences of filler wire composition and welding parameters on HCS. The modeling results have been validated by comparing predictions with results from fully instrumented laser welds performed under a range of process parameters and analyzed using high-resolution X-ray tomography to identify weld defects. It is shown that the model is capable of accurately predicting the thermal field around the weld and the trend of HCS as a function of process parameters.

  16. Advanced fabrication techniques for cooled engine structures

    NASA Technical Reports Server (NTRS)

    Buchmann, O. A.

    1978-01-01

    An improved design for regeneratively cooled engine structures was identified. This design uses photochemically machined (PCM) coolant passages. It permits the braze joint to be placed in a relatively cool area, remote from the critical hot face sheet. The geometry of the passages at the face sheet also minimizes stress concentration and, therefore, enhances the low cycle fatigue performance. The two most promising alloys identified for this application are Inconel 617 and Nickel 201. Inconel 617 was selected because it has excellent creep rupture properties, while Nickel 201 was selected because of its predicted good performance under low cycle fatigue loading. The fabrication of the PCM coolant passages in both Inconel 617 and Nickel 201 was successfully developed. During fabrication of Inconel 617, undesirable characteristics were observed in the braze joints. A development program to resolve this condition was undertaken and led to definition of an isothermal solidification process for joining Inconel 617 panels. This process produced joints which approach parent metal strength and homogeneity.

  17. Understanding the electronic band structure of Pt-alloys for surface reactivity

    NASA Astrophysics Data System (ADS)

    Jung, Jongkeun; Kim, Beomyoung; Hong, Ji Sook; Jin, Tae Won; Shim, Ji Hoon; Nemsak, Slavomir; Denlinger, Jonathan D.; Masashi, Arita; Kenya, Shimada; Kim, Changyoung; Mun, Bongjin Simon

    In polymer exchange membrane fuel cell (PEMFC), the oxygen reduction reaction (ORR) at cathode side has been continuously investigated due to its critical importance in performance of fuel cell. So far, even with best industrial catalyst made with Pt, the performance of ORR is too far below from the commercial purpose. In 2007, Stamenkovic et al. showed that Pt alloys with 3- dtransition metal exhibited significantly improved ORR performance and pointed out the altered electronic structure of surface as the major contributing factor for enhanced ORR. Since 1990, with the advance of DFT calculation, the trend of surface chemical reactivity is explained with the analysis of d-band structures, known as d-band model. While d-band provides valid insight on surface chemical reactivity based on the valence band DOS, the relation between surface work function and DOS has not been well understood. The element-specific local electronic band structure of Pt alloys are identified by ARPES measurement, and the correlation between surface work function and local charge density is investigated.

  18. Advanced Technology Composite Fuselage-Structural Performance

    NASA Technical Reports Server (NTRS)

    Walker, T. H.; Minguet, P. J.; Flynn, B. W.; Carbery, D. J.; Swanson, G. D.; Ilcewicz, L. B.

    1997-01-01

    Boeing is studying the technologies associated with the application of composite materials to commercial transport fuselage structure under the NASA-sponsored contracts for Advanced Technology Composite Aircraft Structures (ATCAS) and Materials Development Omnibus Contract (MDOC). This report addresses the program activities related to structural performance of the selected concepts, including both the design development and subsequent detailed evaluation. Design criteria were developed to ensure compliance with regulatory requirements and typical company objectives. Accurate analysis methods were selected and/or developed where practical, and conservative approaches were used where significant approximations were necessary. Design sizing activities supported subsequent development by providing representative design configurations for structural evaluation and by identifying the critical performance issues. Significant program efforts were directed towards assessing structural performance predictive capability. The structural database collected to perform this assessment was intimately linked to the manufacturing scale-up activities to ensure inclusion of manufacturing-induced performance traits. Mechanical tests were conducted to support the development and critical evaluation of analysis methods addressing internal loads, stability, ultimate strength, attachment and splice strength, and damage tolerance. Unresolved aspects of these performance issues were identified as part of the assessments, providing direction for future development.

  19. Structural evolution of NiAg heterogeneous alloys upon annealing

    NASA Astrophysics Data System (ADS)

    Proux, O.; Mimault, J.; Revenant-Brizard, C.; Regnard, J. R.; Mevel, B.

    1999-01-01

    NiAg heterogeneous alloys were studied by x-ray diffraction and x-ray absorption spectroscopy at the Ni K-edge using a total electron yield detection. In the as-deposited 0953-8984/11/1/013/img8 alloys of 0.10 and 0.15 Ni atomic fraction, most of the Ni atoms are in substitutional sites in the Ag matrix. At higher Ni concentration, the Ni atoms outside the Ag-rich phase become numerous enough to group together in small clusters. An important disorder in the neighbourhood of Ni atoms is demonstrated. At low annealing temperature (up to 0953-8984/11/1/013/img9C), in 0953-8984/11/1/013/img10 and 0953-8984/11/1/013/img11, some Ni atoms are still present in substitutional sites in the Ag matrix and the small Ni particles are under strain. A very short-range order exists in this state. After a 0953-8984/11/1/013/img9C annealing, the Ni particles grow, and the Ag-rich phase remains in a steady structural state. After a higher annealing (0953-8984/11/1/013/img13C), the local Ni atomic environment becomes well ordered and typical of the pure Ni FCC phase. The Ag-rich crystallites are impoverished in Ni atoms and grow with elimination of defects. Ni grains are generally smaller than 1 nm for as-deposited alloys and reach several nanometres after a 0953-8984/11/1/013/img13C annealing for 10 min.

  20. High-Entropy Alloys in Hexagonal Close-Packed Structure

    NASA Astrophysics Data System (ADS)

    Gao, M. C.; Zhang, B.; Guo, S. M.; Qiao, J. W.; Hawk, J. A.

    2016-07-01

    The microstructures and properties of high-entropy alloys (HEAs) based on the face-centered cubic and body-centered cubic structures have been studied extensively in the literature, but reports on HEAs in the hexagonal close-packed (HCP) structure are very limited. Using an efficient strategy in combining phase diagram inspection, CALPHAD modeling, and ab initio molecular dynamics simulations, a variety of new compositions are suggested that may hold great potentials in forming single-phase HCP HEAs that comprise rare earth elements and transition metals, respectively. Experimental verification was carried out on CoFeReRu and CoReRuV using X-ray diffraction, scanning electron microscopy, and energy dispersion spectroscopy.

  1. High-entropy alloys in hexagonal close-packed structure

    DOE PAGES

    Gao, Michael C.; Zhang, B.; Guo, S. M.; ...

    2015-08-28

    The microstructures and properties of high-entropy alloys (HEAs) based on the face-centered cubic and body-centered cubic structures have been studied extensively in the literature, but reports on HEAs in the hexagonal close-packed (HCP) structure are very limited. Using an efficient strategy in combining phase diagram inspection, CALPHAD modeling, and ab initio molecular dynamics simulations, a variety of new compositions are suggested that may hold great potentials in forming single-phase HCP HEAs that comprise rare earth elements and transition metals, respectively. Lastly, experimental verification was carried out on CoFeReRu and CoReRuV using X-ray diffraction, scanning electron microscopy, and energy dispersion spectroscopy.

  2. High-entropy alloys in hexagonal close-packed structure

    SciTech Connect

    Gao, Michael C.; Zhang, B.; Guo, S. M.; Qiao, J. W.; Hawk, J. A.

    2015-08-28

    The microstructures and properties of high-entropy alloys (HEAs) based on the face-centered cubic and body-centered cubic structures have been studied extensively in the literature, but reports on HEAs in the hexagonal close-packed (HCP) structure are very limited. Using an efficient strategy in combining phase diagram inspection, CALPHAD modeling, and ab initio molecular dynamics simulations, a variety of new compositions are suggested that may hold great potentials in forming single-phase HCP HEAs that comprise rare earth elements and transition metals, respectively. Lastly, experimental verification was carried out on CoFeReRu and CoReRuV using X-ray diffraction, scanning electron microscopy, and energy dispersion spectroscopy.

  3. Structure and properties of Ti-7.5Mo-xFe alloys.

    PubMed

    Lin, D J; Lin, J H Chern; Ju, C P

    2002-04-01

    The present work is a study of a series of Ti-7.5Mo-xFe alloys, with the focus on the effect of iron addition on the structure and mechanical properties of the alloys. Experimental results indicate that alpha" phase-dominated binary Ti-7.5Mo alloy exhibited a fine, acicular martensitic structure. When 1 wt% or more iron was added, the entire alloy became equi-axed beta phase structure with a grain size decreasing with increasing iron content. A thermal omega phase was formed in the alloys containing iron of roughly between 0.5 and 3 wt%. The largest quantity of omega phase and highest microhardness were found in Ti-7.5Mo-1Fe alloy. The binary Ti 7.5Mo alloy had a lower microhardness, bending strength and modulus than all iron-containing alloys. The largest bending strength was found in Ti-7.5Mo-2Fe alloy. The present alloys with iron contents of about 2-5 wt% seem to have a great potential for use as an implant material.

  4. Advances in Hot-Structure Development

    NASA Technical Reports Server (NTRS)

    Rivers, H. Kevin; Glass, David E.

    2006-01-01

    The National Aeronautics and Space Administration has actively participated in the development of hot structures technology for application to hypersonic flight systems. Hot structures have been developed for vehicles including the X-43A, X-37, and the Space Shuttle. These trans-atmospheric and atmospheric entry flight systems that incorporate hot-structures technology are lighter weight and require less maintenance than those that incorporate parasitic, thermal-protection materials that attach to warm or cool substructure. The development of hot structures requires a thorough understanding of material performance in an extreme environment, boundary conditions and load interactions, structural joint performance, and thermal and mechanical performance of integrated structural systems that operate at temperatures ranging from 1500 C to 3000 C, depending on the application. This paper will present recent advances in the development of hot structures, including development of environmentally durable, high temperature leading edges and control surfaces, integrated thermal protection systems, and repair technologies. The X-43A Mach-10 vehicle utilized carbon/carbon (C/C) leading edges on the nose, horizontal control surface, and vertical tail. The nose and vertical and horizontal tail leading edges were fabricated out of a 3:1 biased, high thermal conductivity C/C. The leading edges were coated with a three-layer coating comprised of a SiC conversion of the C/C, followed by a CVD layer of SiC, followed by a thin CVD layer of HfC. Work has also been performed on the development of an integrated structure and was focused on both hot and warm (insulated) structures and integrated fuselage/tank/TPS systems. The objective was to develop integrated multifunctional airframe structures that eliminate fragile external thermal-protection systems and incorporate the insulating function within the structure. The approach taken to achieve this goal was to develop candidate hypersonic

  5. Structure and ductility of eutectic type iron-carbon alloys

    NASA Astrophysics Data System (ADS)

    Nizhnikovskaya, P. F.

    1984-09-01

    The ductility of iron-carbon alloys of the eutectic type is governed by the structure of eutectic carbides and it may be increased by two methods. The first envisages formation during prior heat treatment of dislocations in eutectic carbides and creation of subgrain boundaries along which during deformation there is carbide fragmentation. This method, as a result of the specific effect of the metal base on formation of dislocations in carbides and prevention of carbide failure under the action of compressive stresses from the surrounding solid solution, may only be used for alloys in which the carbide phase reinforces a metal matrix. The second method involves a marked increase in carbide ductility as a result of transformation occurring in them under the action of deformation [10]. This method may be used to increase the ductility of cast irons around the eutectic composition with eutectics whose matrix phase is carbide. In this way forming may be accomplished by rolling in the range of rates used in metallurgical production practice.

  6. Advancements in vibroacoustic evaluation of satellite structures

    NASA Astrophysics Data System (ADS)

    Stavrinidis, C.; Witting, M.; Ikoss, S. I.; Klein, M.

    2001-02-01

    The importance of the launcher vibroacoustic environment is increasing with respect to satellite loads due to the increase in size and decrease in surface mass of lightweight appendages like antennas and solar arrays. The loads generated by the vibroacoustic environment need to be covered adequately to ensure satellite structural integrity. This is of particular importance in the low-frequency range where the low frequencies of light appendages and equipment couple with the acoustic environment. In order to cope with the increasing demand for prediction of structural loads due to the acoustic environment, various methods have been developed in the frame of ESA research and development activities. These range from simplified approaches with partial fluid-structure coupling, e.g. the POSTAR package provided by INTESPACE (France) to more sophisticated approaches with full fluid-structure coupling. In the frequency domain this includes pure finite element modelling techniques, where specific tools have been developed by FFA (Sweden) using the ASKA package, as well as coupled finite element—boundary element approaches that have been developed in cooperation with DASA-Dornier (Germany), STRACO (France) and FFA using the commercial packages ASKA and RAYON. For fully coupled fluid structure analysis in the time domain the ASTRYD code from METRAVIB (France) is employed where advancements have been supported by CNES. Applications of these tools range from simple benchmarks such as simply supported plates, cavity enclosures or generic satellite-fairing models to complex satellite structure configurations. Evaluations of antenna reflector structures (Artemis communication antenna) and satellite equipment panels (polar platform) are presented. The paper covers also the investigation of payload/fairing effects (influence of fairing helium purging on the coupled-system response) together with DASA-Dornier, FFA and STRACO, as well as the vibroacoustic analysis of solar array

  7. The structural stability and superconductivity of TiMo alloys under pressure. I - Structural stability

    NASA Astrophysics Data System (ADS)

    Leibovitch, C.; Gartstein, E.; Rabinkin, A. G.

    1980-07-01

    A study is presented of changes in the crystal structure induced by high-pressure soaking (hps) up to 9.2 GPa in Ti with 3 to 35 at.% Mo alloys which were in the as-quenched metastable state. The retained structure was analyzed by X-ray diffractography and transmission electron microscopy. It is observed that after application of critical pressure, the omega phase increases in all crystal structures that are observed usually in Ti-base alloys and consisting of alpha', alpha' + beta + omega, beta + omega or beta phases. In addition, strong diffuse scattering patterns created by short range order in displacement of atomic rows were observed. Finally, analysis of the relative stability of all different structures with regard to hps was performed using detailed data on Debye temperature, density of electronic states at Fermi level and other parameters.

  8. A manufacturing database of advanced materials used in spacecraft structures

    NASA Technical Reports Server (NTRS)

    Bao, Han P.

    1994-01-01

    Cost savings opportunities over the life cycle of a product are highest in the early exploratory phase when different design alternatives are evaluated not only for their performance characteristics but also their methods of fabrication which really control the ultimate manufacturing costs of the product. In the past, Design-To-Cost methodologies for spacecraft design concentrated on the sizing and weight issues more than anything else at the early so-called 'Vehicle Level' (Ref: DOD/NASA Advanced Composites Design Guide). Given the impact of manufacturing cost, the objective of this study is to identify the principal cost drivers for each materials technology and propose a quantitative approach to incorporating these cost drivers into the family of optimization tools used by the Vehicle Analysis Branch of NASA LaRC to assess various conceptual vehicle designs. The advanced materials being considered include aluminum-lithium alloys, thermoplastic graphite-polyether etherketone composites, graphite-bismaleimide composites, graphite- polyimide composites, and carbon-carbon composites. Two conventional materials are added to the study to serve as baseline materials against which the other materials are compared. These two conventional materials are aircraft aluminum alloys series 2000 and series 7000, and graphite-epoxy composites T-300/934. The following information is available in the database. For each material type, the mechanical, physical, thermal, and environmental properties are first listed. Next the principal manufacturing processes are described. Whenever possible, guidelines for optimum processing conditions for specific applications are provided. Finally, six categories of cost drivers are discussed. They include, design features affecting processing, tooling, materials, fabrication, joining/assembly, and quality assurance issues. It should be emphasized that this database is not an exhaustive database. Its primary use is to make the vehicle designer

  9. Supercooling and structure of levitation melted Fe-Ni alloys

    NASA Technical Reports Server (NTRS)

    Abbaschian, G. J.; Flemings, M. C.

    1983-01-01

    A study has been made of the effect of supercooling, quenching rate, growth inhibitors, and grain refiners on the structure of levitation-melted Fe- 25 pct Ni alloys. A combination of three morphologies, dendritic, spherical, and mixed dendritic and spherical, is observed in samples superheated or supercooled by less than 175 K. At larger supercooling, however, only the spherical morphology is observed. The grain size and the grain boundary shape are found to be strongly dependent on the subgrain morphology but not on the quenching temperature. Considerable grain growth is evident in samples with spherical and mixed morphologies but not in the dendriitic samples. The average cooling rates during solidification and the heat transfer coefficients at the metal-quenching medium boundary are calculated. For samples solidified in water, molten lead, and ceramic molds, the heat transfer coefficients are 0.41, 0.52, and 0.15 w/sq cm, respectively.

  10. Structural properties and relative stability of (meta)stable ordered, partially ordered, and disordered Al-Li alloy phases

    NASA Astrophysics Data System (ADS)

    Alam, Aftab; Johnson, D. D.

    2012-04-01

    We resolve issues that have plagued reliable prediction of relative phase stability for solid solutions and compounds. Due to its commercially important phase diagram, we showcase the Al-Li system because historically density-functional theory (DFT) results show large scatter and limited success in predicting the structural properties and stability of solid solutions relative to ordered compounds. Using recent advances in an optimal basis-set representation of the topology of electronic charge density (and, hence, atomic size), we present DFT results that agree reasonably well with all known experimental data for the structural properties and formation energies of ordered, off-stoichiometric partially ordered, and disordered alloys, opening the way for reliable study in complex alloys.

  11. Robust biomimetic-structural superhydrophobic surface on aluminum alloy.

    PubMed

    Li, Lingjie; Huang, Tao; Lei, Jinglei; He, Jianxin; Qu, Linfeng; Huang, Peiling; Zhou, Wei; Li, Nianbing; Pan, Fusheng

    2015-01-28

    The following facile approach has been developed to prepare a biomimetic-structural superhydrophobic surface with high stabilities and strong resistances on 2024 Al alloy that are robust to harsh environments. First, a simple hydrothermal treatment in a La(NO3)3 aqueous solution was used to fabricate ginkgo-leaf like nanostructures, resulting in a superhydrophilic surface on 2024 Al. Then a low-surface-energy compound, dodecafluoroheptyl-propyl-trimethoxylsilane (Actyflon-G502), was used to modify the superhydrophilic 2024 Al, changing the surface character from superhydrophilicity to superhydrophobicity. The water contact angle (WCA) of such a superhydrophobic surface reaches up to 160°, demonstrating excellent superhydrophobicity. Moreover, the as-prepared superhydrophobic surface shows high stabilities in air-storage, chemical and thermal environments, and has strong resistances to UV irradiation, corrosion, and abrasion. The WCAs of such a surface almost remain unchanged (160°) after storage in air for 80 days, exposure in 250 °C atmosphere for 24 h, and being exposed under UV irradiation for 24 h, are more than 144° whether in acidic or alkali medium, and are more than 150° after 48 h corrosion and after abrasion under 0.98 kPa for 1000 mm length. The remarkable durability of the as-prepared superhydrophobic surface can be attributed to its stable structure and composition, which are due to the existence of lanthanum (hydr)oxides in surface layer. The robustness of the as-prepared superhydrophobic surface to harsh environments will open their much wider applications. The fabricating approach for such robust superhydrophobic surface can be easily extended to other metals and alloys.

  12. Processing of Advanced Cast Alloys for A-USC Steam Turbine Applications

    NASA Astrophysics Data System (ADS)

    Jablonski, Paul D.; Hawk, Jeffery A.; Cowen, Christopher J.; Maziasz, Philip J.

    2012-02-01

    The high-temperature components within conventional supercritical coal-fired power plants are manufactured from ferritic/martensitic steels. To reduce greenhouse-gas emissions, the efficiency of pulverized coal steam power plants must be increased to as high a temperature and pressure as feasible. The proposed steam temperature in the DOE/NETL Advanced Ultra Supercritical power plant is high enough (760°C) that ferritic/martensitic steels will not work for the majority of high-temperature components in the turbine or for pipes and tubes in the boiler due to temperature limitations of this class of materials. Thus, Ni-based superalloys are being considered for many of these components. Off-the-shelf forged nickel alloys have shown good promise at these temperatures, but further improvements can be made through experimentation within the nominal chemistry range as well as through thermomechanical processing and subsequent heat treatment. However, cast nickel-based superalloys, which possess high strength, creep resistance, and weldability, are typically not available, particularly those with good ductility and toughness that are weldable in thick sections. To address those issues related to thick casting for turbine casings, for example, cast analogs of selected wrought nickel-based superalloys such as alloy 263, Haynes 282, and Nimonic 105 have been produced. Alloy design criteria, melt processing experiences, and heat treatment are discussed with respect to the as-processed and heat-treated microstructures and selected mechanical properties. The discussion concludes with the prospects for full-scale development of a thick section casting for a steam turbine valve chest or rotor casing.

  13. On the effects of geometry, defects, and material asymmetry on the mechanical response of shape memory alloy cellular lattice structures

    NASA Astrophysics Data System (ADS)

    Karamooz Ravari, M. R.; Nasr Esfahani, S.; Taheri Andani, M.; Kadkhodaei, M.; Ghaei, A.; Karaca, H.; Elahinia, M.

    2016-02-01

    Shape memory alloy (such as NiTi) cellular lattice structures are a new class of advanced materials with many potential applications. The cost of fabrication of these structures however is high. It is therefore necessary to develop modeling methods to predict the functional behavior of these alloys before fabrication. The main aim of the present study is to assess the effects of geometry, microstructural imperfections and material asymmetric response of dense shape memory alloys on the mechanical response of cellular structures. To this end, several cellular and dense NiTi samples are fabricated using a selective laser melting process. Both cellular and dense specimens were tested in compression in order to obtain their stress-strain response. For modeling purposes, a three -dimensional (3D) constitutive model based on microplane theory which is able to describe the material asymmetry was employed. Five finite element models based on unit cell and multi-cell methods were generated to predict the mechanical response of cellular lattices. The results show the considerable effects of the microstructural imperfections on the mechanical response of the cellular lattice structures. The asymmetric material response of the bulk material also affects the mechanical response of the corresponding cellular structure.

  14. Ultrafine-grained structure formation in Ti-6Al-4V alloy via warm swaging

    NASA Astrophysics Data System (ADS)

    Klimova, M.; Boeva, M.; Zherebtsov, S.; Salishchev, G.

    2014-08-01

    The influence of warm swaging on the structure and properties of Ti-6Al-4V alloy was studied. Warm swaging of the alloy in the interval 680-500°C with the total strain of ɛ=2.66 was found to be resulted in the formation of a homogeneous globular microstructure with a grain size of 0.4 μm in both longitudinal and transversal sections. Room temperature tensile strength and tensile elongation of the swaged alloy was 1315MPa and 10.5%, respectively. Ultrafine-grained Ti-6Al-4V alloy produced by swaging exhibited good workability at 600-700 °C.

  15. Evaluation of Nb-base alloys for the divertor structure in fusion reactors

    SciTech Connect

    Purdy, I.M.

    1996-04-01

    Niobium-base alloys are candidate materials for the divertor structure in fusion reactors. For this application, an alloy should resist aqueous corrosion, hydrogen embrittlement, and radiation damage and should have high thermal conductivity and low thermal expansion. Results of corrosion and embrittlement screening tests of several binary and ternary Nb alloys in high-temperature water indicated the Mb-1Zr, Nb-5MO-1Zr, and Nb-5V-1Z4 (wt %) showed sufficient promise for further investigation. These alloys, together with pure Nb and Zircaloy-4 have been exposed to high purity water containing a low concentration of dissolved oxygen (<12 ppb) at 170, 230, and 300{degrees}C for up to {approx}3200 h. Weight-change data, microstructural observations, and qualitative mechanical-property evaluation reveal that Nb-5V-1Zr is the most promising alloy at higher temperatures. Below {approx}200{degrees}C, the alloys exhibit similiar corrosion behavior.

  16. Feasibility of conducting a dynamic helium charging experiment for vanadium alloys in the advanced test reactor

    SciTech Connect

    Tsai, H.; Gomes, I.; Strain, R.V.; Smith, D.L.; Matsui, H.

    1996-10-01

    The feasibility of conducting a dynamic helium charging experiment (DHCE) for vanadium alloys in the water-cooled Advanced Test Reactor (ATR) is being investigated as part of the U.S./Monbusho collaboration. Preliminary findings suggest that such an experiment is feasible, with certain constraints. Creating a suitable irradiation position in the ATR, designing an effective thermal neutron filter, incorporating thermocouples for limited specimen temperature monitoring, and handling of tritium during various phases of the assembly and reactor operation all appear to be feasible. An issue that would require special attention, however, is tritium permeation loss through the capsule wall at the higher design temperatures (>{approx}600{degrees}C). If permeation is excessive, the reduced amount of tritium entering the test specimens would limit the helium generation rates in them. At the lower design temperatures (<{approx}425{degrees}C), sodium, instead of lithium, may have to be used as the bond material to overcome the tritium solubility limitation.

  17. High Strength, Nano-Structured Mg-Al-Zn Alloy

    DTIC Science & Technology

    2011-01-01

    nanocrystalline (nc) Mg AZ80 alloy, synthesized via a cryomilling and spark plasma sintering (SPS) approach are reported and discussed. The effects of...nanocrystalline (nc) Mg AZ80 alloy, synthesized via a cryomilling and spark plasma sintering (SPS) approach are reported and discussed. The effects of...forging capability [23,24]. Therefore, the Mg AZ80 alloy system was selected and processed using a cryomilling and spark plasma sintering (SPS

  18. Aging Optimization of Aluminum-Lithium Alloy C458 for Application to Cryotank Structures

    NASA Technical Reports Server (NTRS)

    Sova, B. J.; Sankaran, K. K.; Babel, H. W.; Farahmand, B.; Rioja, R.

    2003-01-01

    This viewgraph report presents an examination of the fracture toughness of aluminum-lithium alloy C458 for use in cryotank structures. Topics cover include: cryogenics, alloy composition, strengthing precipitates in C458, cryogenic fracture toughness improvements, design of experiments for measuring aging optimization of C458 plate and effects of aging of properties of C458 plate.

  19. Mechanical properties and the electronic structure of transition of metal alloys

    NASA Technical Reports Server (NTRS)

    Arsenault, R. J.; Drew, H. D.

    1977-01-01

    This interdiscipline research program was undertaken in an effort to investigate the relationship between the mechanical strength of Mo based alloys with their electronic structure. Electronic properties of these alloys were examined through optical studies, and the classical solid solution strengthening mechanisms were considered, based on size and molecular differences to determine if these mechanisms could explain the hardness data.

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

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

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

  1. JPRS Report, Science & Technology, Japan, Structure, Properties of Al Amorphous Alloys

    DTIC Science & Technology

    2007-11-02

    JPRS-JST-90-054 4 DECEMBER 1990 FOREIGN BROADCAST INFORMATION SERVICE JPRS Report-- Science & Technology Japan STRUCTURE , PROPERTIES OF AL...JPRS-JST-90-054 4 DECEMBER 1990 SCIENCE & TECHNOLOGY JAPAN STRUCTURE . PROPERTIES OF AL AMORPHOUS ALLOYS 906C7531 Tokyo AL KEI AMORUFASU GOKIN NO KOZO...TO TOKUSEI in Japanese 6 Feb 90 pp 1-40 [Papers presented at the Symposium for Structure and Properties of Al Amorphous Alloys, held 6 Feb 90 in

  2. Thermal stability of the cellular structure of an austenitic alloy after selective laser melting

    NASA Astrophysics Data System (ADS)

    Bazaleeva, K. O.; Tsvetkova, E. V.; Balakirev, E. V.; Yadroitsev, I. A.; Smurov, I. Yu.

    2016-05-01

    The thermal stability of the cellular structure of an austenitic Fe-17% Cr-12% Ni-2% Mo-1% Mn-0.7% Si-0.02% C alloy produced by selective laser melting in the temperature range 20-1200°C is investigated. Metallographic analysis, transmission electron microscopy, and scanning electron microscopy show that structural changes in the alloy begin at 600-700°C and are fully completed at ~1150°C. Differential scanning calorimetry of the alloy with a cellular structure reveals three exothermic processes occurring upon annealing within the temperature ranges 450-650, 800-1000, and 1050-1200°C.

  3. Advanced composite combustor structural concepts program

    NASA Technical Reports Server (NTRS)

    Sattar, M. A.; Lohmann, R. P.

    1984-01-01

    An analytical study was conducted to assess the feasibility of and benefits derived from the use of high temperature composite materials in aircraft turbine engine combustor liners. The study included a survey and screening of the properties of three candidate composite materials including tungsten reinforced superalloys, carbon-carbon and silicon carbide (SiC) fibers reinforcing a ceramic matrix of lithium aluminosilicate (LAS). The SiC-LAS material was selected as offering the greatest near term potential primarily on the basis of high temperature capability. A limited experimental investigation was conducted to quantify some of the more critical mechanical properties of the SiC-LAS composite having a multidirection 0/45/-45/90 deg fiber orientation favored for the combustor linear application. Rigorous cyclic thermal tests demonstrated that SiC-LAS was extremely resistant to the thermal fatigue mechanisms that usually limit the life of metallic combustor liners. A thermal design study led to the definition of a composite liner concept that incorporated film cooled SiC-LAS shingles mounted on a Hastelloy X shell. With coolant fluxes consistent with the most advanced metallic liner technology, the calculated hot surface temperatures of the shingles were within the apparent near term capability of the material. Structural analyses indicated that the stresses in the composite panels were low, primarily because of the low coefficient of expansion of the material and it was concluded that the dominant failure mode of the liner would be an as yet unidentified deterioration of the composite from prolonged exposure to high temperature. An economic study, based on a medium thrust size commercial aircraft engine, indicated that the SiC-LAS combustor liner would weigh 22.8N (11.27 lb) less and cost less to manufacture than advanced metallic liner concepts intended for use in the late 1980's.

  4. Advances and Achievements in In Situ Analysis of Corrosion and Structure–Property Relationship in Mg Alloys

    SciTech Connect

    Orlov, D.; Joshi, V.

    2016-11-03

    Every year, TMS Magnesium Committee carefully selects a special topic in magnesium (Mg) related research and development not only having the hottest subject from both academic and industrial perspectives but also demonstrating major achievements within this subject. Following last year’s topic on Mg microallying [1], this year’s focus is on in-situ methods and associated techniques in their broad definition spanning from laboratory- to large- scale facilities to process monitoring. The applications of in-situ techniques have a wide spectrum from the analysis of melts and liquid-solid transitions to solid-state phenomena during thermo-mechanical processing and heat treatments to surface interactions with various environments. Therefore, such works are of significant interest to scientists working in the area of Mg alloy development as well as to a much broader audience from both academia and industry. This interest is primarily caused by challenges in the analysis of structure-property relationship in Mg alloys, and even cursory glance of literature reveals sharp increase of publications relevant to this topic recently. For instance, very high reactivity of Mg as well as its well-known propensity to substantially alter structure upon unloading in mechanical testing makes it difficult to understand and thus to simulate correlation between microstructures observed in post-mortem analysis and physical processes during testing or fabrication. However, recent advances in in-situ analysis based on large-scale research facilities such as neutron scattering and synchrotron radiation sources as well as microscopy-based, acoustic emission, and other more traditional techniques allowed significant achievements. Apart from apparent development of relevant experimental techniques, a significant part of this success should also be attributed to increasing accessibility of the facilities and simplification of their use from a user perspective. The selection of articles in this

  5. Structural characteristics and elevated temperature mechanical properties of AJ62 Mg alloy

    SciTech Connect

    Kubásek, J. Vojtěch, D.; Martínek, M.

    2013-12-15

    Structure and mechanical properties of the novel casting AJ62 (Mg–6Al–2Sr) alloy developed for elevated temperature applications were studied. The AJ62 alloy was compared to commercial casting AZ91 (Mg–9Al–1Zn) and WE43 (Mg–4Y–3RE) alloys. The structure was examined by scanning electron microscopy, x-ray diffraction and energy dispersive spectrometry. Mechanical properties were characterized by Viskers hardness measurements in the as-cast state and after a long-term heat treatment at 250 °C/150 hours. Compressive mechanical tests were also carried out both at room and elevated temperatures. Compressive creep tests were conducted at a temperature of 250 °C and compressive stresses of 60, 100 and 140 MPa. The structure of the AJ62 alloy consisted of primary α-Mg dendrites and interdendritic nework of the Al{sub 4}Sr and massive Al{sub 3}Mg{sub 13}Sr phases. By increasing the cooling rate during solidification from 10 and 120 K/s the average dendrite arm thickness decreased from 18 to 5 μm and the total volume fraction of the interdendritic phases from 20% to 30%. Both factors slightly increased hardness and compressive strength. The room temperature compressive strength and hardness of the alloy solidified at 30 K/s were 298 MPa and 50 HV 5, i.e. similar to those of the as-cast WE43 alloy and lower than those of the AZ91 alloy. At 250 °C the compressive strength of the AJ62 alloy decreased by 50 MPa, whereas those of the AZ91 and WE43 alloys by 100 and 20 MPa, respectively. The creep rate of the AJ62 alloy was higher than that of the WE43 alloy, but significantly lower in comparison with the AZ91 alloy. Different thermal stabilities of the alloys were discussed and related to structural changes during elevated temperature expositions. - Highlights: • Small effect of cooling rate on the compressive strength and hardness of AJ 62 • A bit lower compressive strength of AJ 62 compared to AZ91 at room temperature • Higher resistance of the AJ 62

  6. High-temperature, low-cycle fatigue of advanced copper-base alloys for rocket nozzles. Part 2: NASA 1.1, Glidcop, and sputtered copper alloys

    NASA Technical Reports Server (NTRS)

    Conway, J. B.; Stentz, R. H.; Berling, J. T.

    1974-01-01

    Short-term tensile and low-cycle fatigue data are reported for five advance copper-base alloys: Sputtered Zr-Cu as received, sputtered Zr-Cu heat-treated, Glidcop AL-10, and NASA alloys 1-1A and 1-1B. Tensile tests were performed in argon at 538 C using an axial strain rate of 0.002/sec. Yield strength and ultimate tensile strength data are reported along with reduction in area values. Axial strain controlled low-cycle fatigue tests were performed in argon at 538C using an axial strain rate of 0.002/sec to define the fatigue life over the range from 100 to 3000 cycles for the five materials studied. It was found that the fatigue characteristics of the NASA 1-1A and NASA 1-1B compositions are identical and represent fatique life values which are much greater than those for the other materials tested. The effect of temperature on NASA 1-1B alloy at a strain rate of 0.002/sec was evaluated along with the effect of strain rates of 0.0004 and 0.01/sec at 538 C. Hold-time data are reported for the NASA 1-1B alloy at 538 C using 5 minute hold periods in tension only and compression only at two different strain range values. Hold periods in tension were much more detrimental than hold periods in compression.

  7. Structural transformation studies on the rare earth containing Heusler alloys Pd 2RESn

    NASA Astrophysics Data System (ADS)

    Umarji, A. M.; Malik, S. K.; Shenoy, G. K.

    1985-03-01

    The Heusler alloys Pd 2RESn form for rare-earths (RE) from Tb to Lu and for Sc and Y. Of these, the alloys containing Yb, Tm, Lu, Sc and Y are superconducting. We have carried out structural studies on all these alloys by studying the temperature dependence of the X-ray patterns in the temperature range 5 to 300 K. Some nonstoichiometric compositions were also investigated. Structural transformation is observed only in Tb and Dy containing alloys while none of the superconducting alloys show a transformation. The transformation temperature is lowered by about 50 K in going from stoichiometric Pd 2TbSn to nonstoichiometric Pd 2Tb 0.95Sn while it is completely suppressed in Pd 2Dy 0.95Sn. Magnetic and Mössbauer studies on Dy compound are also reported.

  8. Development of Damped Metal Matrix Composites for Advanced Structural Applications

    DTIC Science & Technology

    1990-04-01

    DTIP FiLE COPY Applied Research Laboratory (Dto 00 CD Technical Report NO DEVELOPMENT OF DAMPED METAL MATRIX COMPOSITES FOR ADVANCED STRUCTURAL...DEVELOPMENT OF DAMPED METAL MATRIX COMPOSITES FOR ADVANCED STRUCTURAL APPLICATIONS by Clark A. Updike Ram B. Bhagat Technical Report No. TR 90-004 April 1990... Metal Matrix Composites for Advanced Structural Applications 12 PERSONAL AUTHOR(S) C.A. Updike, R. Bhagat 1 3a TYPE OF REPORT 13b TIME COVERED 14. DATE

  9. Compound semiconductor alloys: From atomic-scale structure to bandgap bowing

    NASA Astrophysics Data System (ADS)

    Schnohr, C. S.

    2015-09-01

    Compound semiconductor alloys such as InxGa1-xAs, GaAsxP1-x, or CuInxGa1-xSe2 are increasingly employed in numerous electronic, optoelectronic, and photonic devices due to the possibility of tuning their properties over a wide parameter range simply by adjusting the alloy composition. Interestingly, the material properties are also determined by the atomic-scale structure of the alloys on the subnanometer scale. These local atomic arrangements exhibit a striking deviation from the average crystallographic structure featuring different element-specific bond lengths, pronounced bond angle relaxation and severe atomic displacements. The latter, in particular, have a strong influence on the bandgap energy and give rise to a significant contribution to the experimentally observed bandgap bowing. This article therefore reviews experimental and theoretical studies of the atomic-scale structure of III-V and II-VI zincblende alloys and I-III-VI2 chalcopyrite alloys and explains the characteristic findings in terms of bond length and bond angle relaxation. Different approaches to describe and predict the bandgap bowing are presented and the correlation with local structural parameters is discussed in detail. The article further highlights both similarities and differences between the cubic zincblende alloys and the more complex chalcopyrite alloys and demonstrates that similar effects can also be expected for other tetrahedrally coordinated semiconductors of the adamantine structural family.

  10. Development of Advanced Corrosion-Resistant Fe-Cr-Ni Austenitic Stainless Steel Alloy with Improved High-Temperature Strength and Creep-Resistance

    SciTech Connect

    Maziasz, P.J.; Swindeman, R.W.

    2001-06-15

    In February of 1999, a Cooperative Research and Development Agreement (CRADA) was undertaken between Oak Ridge National Laboratory (ORNL) and Special Metals Corporation - Huntington Alloys (formerly INCO Alloys International, Inc.) to develop a modified wrought austenitic stainless alloy with considerably more strength and corrosion resistance than alloy 800H or 800HT, but with otherwise similar engineering and application characteristics. Alloy 800H and related alloys have extensive use in coal flue gas environments, as well as for tubing or structural components in chemical and petrochemical applications. The main concept of the project was make small, deliberate elemental microalloying additions to this Fe-based alloy to produce, with proper processing, fine stable carbide dispersions for enhanced high temperature creep-strength and rupture resistance, with similar or better oxidation/corrosion resistance. The project began with alloy 803, a Fe-25Cr-35NiTi,Nb alloy recently developed by INCO, as the base alloy for modification. Smaller commercial developmental alloy heats were produced by Special Metal. At the end of the project, three rounds of alloy development had produced a modified 803 alloy with significantly better creep resistance above 815 C (1500 C) than standard alloy 803 in the solution-annealed (SA) condition. The new upgraded 803 alloy also had the potential for a processing boost in that creep resistance for certain kinds of manufactured components that was not found in the standard alloy. The upgraded 803 alloy showed similar or slightly better oxidation and corrosion resistance relative to standard 803. Creep strength and oxidation/corrosion resistance of the upgraded 803 alloy were significantly better than found in alloy 800 H, as originally intended. The CRADA was terminated in February 2003. A contributing factor was Special Metals Corporation being in Chapter 11 Bankruptcy. Additional testing, further commercial scale-up, and any potential

  11. Effect of Crystal Structure Fineness for Charge Alloy AK6M2 on Its Flux Treatment Efficiency

    NASA Astrophysics Data System (ADS)

    Nikitin, K. V.; Nikitin, V. I.; Timoshkin, I. Yu.; Chikova, O. A.

    2016-09-01

    The effect of charge billet structure and form of fluxes on structure, density, and gas content of alloy AK6M2 (Al - Si - Cu system) is studied. Alloys prepared from finely crystalline charge billet have smaller phase component sizes, lower gas content, and increased solid state density, and use of coarsely crystalline charge billets for alloy preparation necessitates an increase in flux preparation consumption in the stage of alloy preparation for casting.

  12. Cryogenic Fracture Toughness Evaluation of an Investment Cast Aluminum-Beryllium Alloy for Structural Applications

    NASA Technical Reports Server (NTRS)

    Gamwell, Wayne; McGill, Preston

    2006-01-01

    This document is a viewgraph presentation that details the fracture toughness of Aluminum-Beryllium Alloy for use in structures at cryogenic temperatures. Graphs and charts are presented in the presentation

  13. Study to determine peening stress profile of rod peened aluminum structural alloys versus shot peened material

    NASA Technical Reports Server (NTRS)

    Rosas, R. E.; Calfin, B. G.

    1976-01-01

    The objective of this program was to determine the peening stress profiles of rod peened aluminum structural alloys versus shot peened material to define the effective depth of the compressed surface layer.

  14. Advancement of Al - Li alloys and of multistage modes of their heat treatment

    NASA Astrophysics Data System (ADS)

    Antipov, V. V.; Kolobnev, N. I.; Khokhlatova, L. B.

    2014-01-01

    Third-generation aluminum alloys 1441, 1424 and V-1461, V-1469 of medium and high strength, respectively, which have been developed as an alternative to the base aluminum alloys 1163 and V95 widely used in the aircraft industry, are studied. The advantages of the suggested alloys with respect to the strength, life characteristics, weldability and corrosion resistance are shown.

  15. Nickel aluminide alloy for high temperature structural use

    DOEpatents

    Liu, Chain T.; Sikka, Vinod K.

    1991-01-01

    The specification discloses nickel aluminide alloys including nickel, aluminum, chromium, zirconium and boron wherein the concentration of zirconium is maintained in the range of from about 0.05 to about 0.35 atomic percent to improve the ductility, strength and fabricability of the alloys at 1200.degree. C. Titanium may be added in an amount equal to about 0.2 to about 0.5 atomic percent to improve the mechanical properties of the alloys and the addition of a small amount of carbon further improves hot fabricability.

  16. Characterization of Tubing from Advanced ODS alloy (FCRD-NFA1)

    SciTech Connect

    Maloy, Stuart Andrew; Aydogan, Eda; Anderoglu, Osman; Lavender, Curt; Anderson, Iver; Rieken, Joel; Lewandowski, John; Hoelzer, Dave; Odette, George R.

    2016-09-20

    Fabrication methods are being developed and tested for producing fuel clad tubing of the advanced ODS 14YWT and FCRD-NFA1 ferritic alloys. Three fabrication methods were based on plastically deforming a machined thick-wall tube sample of the ODS alloys by pilgering, hydrostatic extrusion or drawing to decrease the outer diameter and wall thickness and increase the length of the final tube. The fourth fabrication method consisted of the additive manufacturing approach involving solid-state spray deposition (SSSD) of ball milled and annealed powder of 14YWT for producing thin-wall tubes. Of the four fabrication methods, two methods were successful at producing tubing for further characterization: production of tubing by high-velocity oxy-fuel spray forming and production of tubing using high-temperature hydrostatic extrusion. The characterization described shows through neutron diffraction the texture produced during extrusion while maintaining the beneficial oxide dispersion. In this research, the parameters for innovative thermal spray deposition and hot extrusion processing methods have been developed to produce the final nanostructured ferritic alloy (NFA) tubes having approximately 0.5 mm wall thickness. Effect of different processing routes on texture and grain boundary characteristics has been investigated. It was found that hydrostatic extrusion results in combination of plane strain and shear deformations which generate rolling textures of α- and γ-fibers on {001}<110> and {111}<110> together with a shear texture of ζ-fiber on {011}<211> and {011}<011>. On the other hand, multi-step plane strain deformation in cross directions leads to a strong rolling textures of θ- and ε-fiber on {001}<110> together with weak γ-fiber on {111}<112>. Even though the amount of the equivalent strain is similar, shear deformation leads to much lower texture indexes compared to the plane strain deformations. Moreover, while 50% of hot rolling brings about a large number of

  17. Crystallization of germanium-carbon alloys -- Structure and electronic transport

    SciTech Connect

    John, T.M.; Blaesing, J.; Veit, P.; Druesedau, T.

    1997-07-01

    Amorphous Ge{sub 1{minus}x}C{sub x} alloys were deposited by rf-magnetron sputtering from a germanium target in methane-argon atmosphere. Structural investigations were performed by means of wide and small angle X-ray scattering, X-ray reflectometry and cross-sectional transmission electron microscopy. The electronic transport properties were characterized using Hall-measurements and temperature depended conductivity. The results of X-ray techniques together with the electron microscopy clearly prove the existence of a segregation of the electronic conductivity in the as-prepared films follows the Mott' T{sup {minus}1/4} law, indicating transport by a hopping process. After annealing at 870 K, samples with x {le} 0.4 show crystallization of the Ge-clusters with a crystallite size being a function of x. After Ge-crystallization, the conductivity increases by 4 to 5 orders of magnitude. Above room temperature, electronic transport is determined by a thermally activated process. For lower temperatures, the {sigma}(T) curves show a behavior which is determined by the crystallite size and the free carrier concentration, both depending on the carbon content.

  18. 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.

  19. Energy harvesting from structural vibrations of magnetic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Farsangi, Mohammad Amin Askari; Cottone, Francesco; Sayyaadi, Hassan; Zakerzadeh, Mohammad Reza; Orfei, Francesco; Gammaitoni, Luca

    2017-03-01

    This letter presents the idea of scavenging energy from vibrating structures through magnetic shape memory alloy (MSMA). To this end, a MSMA specimen made of Ni50Mn28Ga22 is coupled to a cantilever beam through a step. Two permanent magnets installed at the top and bottom of the beam create a bias field perpendicular to the magnetization axis of the specimen. When vibrating the device, a longitudinal axial load applies on the MSMA, which in turn changes the magnetization, due to the martensitic variant reorientation mechanism. A pick-up coil wounded around the MSMA converts this variation into voltage according to the Faraday's law. Experimental test confirms the possibility of generating voltage in a vibrating MSMA. In particular, 15 μW power is harvested for acceleration of 0.3 g RMS at a frequency of 19.1 Hz, which is comparable with piezoelectric energy harvesters. It is also found that the optimum bias magnetic field for maximum voltage is lower than the starting field of pseudo elastic behavior.

  20. Fracture characteristics of structural aerospace alloys containing deep surface flaws. [aluminum-titanium alloys

    NASA Technical Reports Server (NTRS)

    Masters, J. N.; Bixler, W. D.; Finger, R. W.

    1973-01-01

    Conditions controlling the growth and fracture of deep surface flaws in aerospace alloys were investigated. Static fracture tests were performed on 7075-T651 and 2219-T87 aluminum, and 6Ai-4V STA titanium . Cyclic flaw growth tests were performed on the two latter alloys, and sustain load tests were performed on the titanium alloy. Both the cyclic and the sustain load tests were performed with and without a prior proof overload cycle to investigate possible growth retardation effects. Variables included in all test series were thickness, flaw depth-to-thickness ratio, and flaw shape. Results were analyzed and compared with previously developed data to determine the limits of applicability of available modified linear elastic fracture solutions.

  1. Advanced powder metallurgy aluminum alloys via rapid solidification technology, phase 2

    NASA Technical Reports Server (NTRS)

    Ray, Ranjan; Jha, Sunil C.

    1987-01-01

    Marko's rapid solidification technology was applied to processing high strength aluminum alloys. Four classes of alloys, namely, Al-Li based (class 1), 2124 type (class 2), high temperature Al-Fe-Mo (class 3), and PM X7091 type (class 4) alloy, were produced as melt-spun ribbons. The ribbons were pulverized, cold compacted, hot-degassed, and consolidated through single or double stage extrusion. The mechanical properties of all four classes of alloys were measured at room and elevated temperatures and their microstructures were investigated optically and through electron microscopy. The microstructure of class 1 Al-Li-Mg alloy was predominantly unrecrystallized due to Zr addition. Yield strengths to the order of 50 Ksi were obtained, but tensile elongation in most cases remained below 2 percent. The class 2 alloys were modified composition of 2124 aluminum alloy, through addition of 0.6 weight percent Zr and 1 weight percent Ni. Nickel addition gave rise to a fine dispersion of intermetallic particles resisting coarsening during elevated temperature exposure. The class 2 alloy showed good combination of tensile strength and ductility and retained high strength after 1000 hour exposure at 177 C. The class 3 Al-Fe-Mo alloy showed high strength and good ductility both at room and high temperatures. The yield and tensile strength of class 4 alloy exceeded those of the commercial 7075 aluminum alloy.

  2. Recent advances on the development of magnesium alloys for biodegradable implants.

    PubMed

    Chen, Yongjun; Xu, Zhigang; Smith, Christopher; Sankar, Jag

    2014-11-01

    In recent years, much progress has been made on the development of biodegradable magnesium alloys as "smart" implants in cardiovascular and orthopedic applications. Mg-based alloys as biodegradable implants have outstanding advantages over Fe-based and Zn-based ones. However, the extensive applications of Mg-based alloys are still inhibited mainly by their high degradation rates and consequent loss in mechanical integrity. Consequently, extensive studies have been conducted to develop Mg-based alloys with superior mechanical and corrosion performance. This review focuses on the following topics: (i) the design criteria of biodegradable materials; (ii) alloy development strategy; (iii) in vitro performances of currently developed Mg-based alloys; and (iv) in vivo performances of currently developed Mg-based implants, especially Mg-based alloys under clinical trials.

  3. Nonequilibrium Phase Chemistry in High Temperature Structure Alloys

    NASA Technical Reports Server (NTRS)

    Wang, R.

    1991-01-01

    Titanium and nickel aluminides of nonequilibrium microstructures and in thin gauge thickness were identified, characterized and produced for potential high temperature applications. A high rate sputter deposition technique for rapid surveillance of the microstructures and nonequilibrium phase is demonstrated. Alloys with specific compositions were synthesized with extended solid solutions, stable dispersoids, and specific phase boundaries associated with different heat treatments. Phase stability and mechanical behavior of these nonequilibrium alloys were investigated and compared.

  4. Advanced methods of structural and trajectory analysis for transport aircraft

    NASA Technical Reports Server (NTRS)

    Ardema, Mark D.

    1995-01-01

    This report summarizes the efforts in two areas: (1) development of advanced methods of structural weight estimation, and (2) development of advanced methods of trajectory optimization. The majority of the effort was spent in the structural weight area. A draft of 'Analytical Fuselage and Wing Weight Estimation of Transport Aircraft', resulting from this research, is included as an appendix.

  5. High-throughput study of crystal structures and stability of strengthening precipitates in Mg alloys

    NASA Astrophysics Data System (ADS)

    Wang, Dongshu; Amsler, Maxmilian; Hegde, Vinay; Saal, James; Issa, Ahmed; Zeng, Xiaoqin; Wolverton, Christopher

    Age hardening, in which precipitates form and impede the movement of dislocations, can be applied to magnesium alloys in order to increase their limited strengthening behavior. To help clarify the energetics of precipitation hardening of Mg alloys, we employed first principles density functional theory calculations to elucidate both crystal structures and energetics of a very large set of precipitates in Mg alloys. We find the enthalpy changes of (stable and metastable) observed precipitates during the age hardening process are consistent with the experimental sequence of formation for many Mg binary alloys (Mg- {Nd, Gd, Y, Sn, Al, Zn}). For cases where the metastable precipitate crystal structure is unavailable, we search over several prototypes and predict structures/stoichiometries for several ternary precipitates. In addition, high-throughput calculations are performed to construct hcp-based based convex hulls, which assist the identification of coherent GP zones and new metastable phases in age-hardened hcp systems.

  6. Synthesis of Ti-Ta alloys with dual structure by incomplete diffusion between elemental powders.

    PubMed

    Liu, Yong; Li, Kaiyang; Wu, Hong; Song, Min; Wang, Wen; Li, Nianfeng; Tang, Huiping

    2015-11-01

    In this work, powder metallurgical (PM) Ti-Ta alloys were sintered using blended elemental powders. A dual structure, consisting of Ti-rich and Ta-rich zones, was formed due to the insufficient diffusion between Ti and Ta powders. The microstructure, mechanical properties and in vitro biological properties of the alloys were studied. Results indicated that the alloys have inhomogenous microstructures and compositions, but the grain structures were continuous from the Ti-rich zone to the Ta-rich zone. The Ta-rich zone exhibited a much finer grain size than the Ti-rich zone. The alloys had a high relative density in the range of 95-98%, with the porosity increasing with the content of Ta due to the increased difficulty in sintering and the formation of Kirkendall pores. The alloys had a good combination of low elastic modulus and high tensile strength. The strength of alloys was almost doubled compared to that of the ingot metallurgy alloys with the same compositions. The low elastic modulus was due to the residual pores and the alloying effect of Ta, while the high tensile strength resulted from the strengthening effects of solid solution, fine grain size and α phase. The alloys had a high biocompatibility due to the addition of Ta, and were suitable for the attachment of cells due to the surface porosity. It was also indicated that PM Ti-(20-30)Ta alloys are promising for biomedical applications after the evaluations of both the mechanical and the biological properties.

  7. Advances in processing of NiAl intermetallic alloys and composites for high temperature aerospace applications

    NASA Astrophysics Data System (ADS)

    Bochenek, Kamil; Basista, Michal

    2015-11-01

    Over the last few decades intermetallic compounds such as NiAl have been considered as potential high temperature structural materials for aerospace industry. A large number of investigations have been reported describing complex fabrication routes, introducing various reinforcing/alloying elements along with theoretical analyses. These research works were mainly focused on the overcoming of main disadvantage of nickel aluminides that still restricts their application range, i.e. brittleness at room temperature. In this paper we present an overview of research on NiAl processing and indicate methods that are promising in solving the low fracture toughness issue at room temperature. Other material properties relevant for high temperature applications are also addressed. The analysis is primarily done from the perspective of NiAl application in aero engines in temperature regimes from room up to the operating temperature (over 1150 °C) of turbine blades.

  8. A review of modeling techniques for advanced effects in shape memory alloy behavior

    NASA Astrophysics Data System (ADS)

    Cisse, Cheikh; Zaki, Wael; Ben Zineb, Tarak

    2016-10-01

    micro, micro-macro and macro scales focusing pseudoelastic and shape memory effects. The paper reviews and discusses various techniques used in the literature for modeling complex behaviors observed in shape memory alloys (SMAs) that go beyond the core pseudoelastic and shape memory effects. These behaviors, which will be collectively referred to herein as ‘secondary effects’, include mismatch between austenite and martensite moduli, martensite reorientation under nonproportional multiaxial loading, slip and transformation-induced plasticity and their influence on martensite transformation, strong thermomechanical coupling and the influence of loading rate, tensile-compressive asymmetry, and the formation of internal loops due to incomplete phase transformation. In addition, because of their importance for practical design considerations, the paper discusses functional and structural fatigue, and fracture mechanics of SMAs.

  9. Advances in experimental mechanics for advanced aircraft structures

    NASA Astrophysics Data System (ADS)

    O'Brien, Eddie W.

    1997-03-01

    The industrial requirement for higher efficiency, lean performance, airframe structures to form the basis of more cost effective Commercial Aircraft has encouraged developments in all aspects of aeronautical design and manufacture. Until recently the main emphasis has been in the area of computer and numerical analysis, however new developments in experimental mechanics are emerging as very powerful tools for use in the validation of numerical analyses and for primary stress analysis data. The developments described have been forced by economic drivers that address more efficient analysis techniques with respect to cost, specific weight and expended time for analysis.

  10. Fabrication and evaluation of advanced titanium structural panels for supersonic cruise aircraft

    NASA Technical Reports Server (NTRS)

    Payne, L.

    1977-01-01

    Flightworthy primary structural panels were designed, fabricated, and tested to investigate two advanced fabrication methods for titanium alloys. Skin-stringer panels fabricated using the weldbraze process, and honeycomb-core sandwich panels fabricated using a diffusion bonding process, were designed to replace an existing integrally stiffened shear panel on the upper wing surface of the NASA YF-12 research aircraft. The investigation included ground testing and Mach 3 flight testing of full-scale panels, and laboratory testing of representative structural element specimens. Test results obtained on full-scale panels and structural element specimens indicate that both of the fabrication methods investigated are suitable for primary structural applications on future civil and military supersonic cruise aircraft.

  11. 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.

  12. Development of Low Density Titanium Alloys for Structural Applications

    NASA Technical Reports Server (NTRS)

    Froes, F. H.; Suryanarayana, C.; Powell, C.; Ward-Close, C. Malcolm; Wilkes, D. M. J.

    1996-01-01

    In this report the results of a program designed to reduce the density of titanium by adding magnesium are presented. Because these two elements are immiscible under conventional ingot metallurgy techniques, two specialized powder metallurgy methods namely, mechanical alloying (MA) and physical vapor deposition (PVD) were implemented. The mechanical alloying experiments were done both at the University of Idaho and at the Defense Research Agency in UK. Since titanium is reactive with interstitial elements, a secondary goal of this research was to correlate solubility extensions with interstitial contamination content, especially oxygen and nitrogen. MA was carried out in SPEX 8000 shaker mils and different milling containers were utilized to control the level of contamination. Results showed that solubilities of Mg in Ti were obtained up to 28 at.% (16.4 wt. %) Mg in Ti for Ti-39.6 at. % (25 wt. %) Mg alloys, which greatly exceed those obtained under equilibrium conditions. This reflects a density reduction of approximately 26 %. Contamination of oxygen and nitrogen seemed to increase the solubility of magnesium in titanium in some cases; however, we were not able to make a clear correlation between contamination levels with solubilities. Work at the DRA has emphasized optimization of present PVD equipment, specifically composition and temperature control. Preliminary PVD data has shown Ti-Mg deposits have successfully been made up to 2 mm thick and that solubility extensions were achieved. The potential for density reduction of titanium by alloying with magnesium has been demonstrated; however, this work has only scratched the surface of the development of such low density alloys. Much research is needed before such alloys could be implemented into industry. Further funding is required in order to optimize the MA/PVD processes including contamination control, determination of optimal alloy compositions, microstructure development, and mechanical property

  13. Structure and thermomechanical behavior of NiTiPt shape memory alloy wires.

    PubMed

    Lin, Brian; Gall, Ken; Maier, Hans J; Waldron, Robbie

    2009-01-01

    The objective of this work is to understand the structure-property relationships in polycrystalline NiTiPt (Ti 42.7 at.% Ni 7.5 at %Pt) with a composition showing pseudoelasticity at ambient temperatures. Structural characterization of the alloy includes grain size determination and texture analysis while the thermomechanical properties are explored using tensile testing. Variation in heat treatment is used as a vehicle to modify microstructure. The results are compared to experiments on Ni-rich NiTi alloy wires (Ti-51.0 at.% Ni), which are in commercial use in various biomedical applications. With regards to microstructure, both alloys exhibit a <111> fiber texture along the wire drawing axis; however, the NiTiPt alloy grain size is smaller than that of the Ni-rich NiTi wires, while the latter materials contain second-phase precipitates. Given the nanometer-scale grain size in NiTiPt and the dispersed, nanometer-scale precipitate size in NiTi, the overall strength and ductility of the alloys are essentially identical when given appropriate heat treatments. Property differences include a much smaller stress hysteresis and smaller temperature dependence of the transformation stress for NiTiPt alloys compared to NiTi alloys. Potential benefits and implications for use in vascular stent applications are discussed.

  14. Advanced image analysis of the surface pattern emerging in Ni3Al intermetallic alloys on anodization

    NASA Astrophysics Data System (ADS)

    Salerno, Marco; Stępniowski, Wojciech; Cieślak, Grzegorz; Norek, Małgorzata; Michalska-Domańska, Marta; Karczewski, Krzysztof; Chilimoniuk, Paulina; Polkowski, Wojciech; Jóźwik, Paweł; Bojar, Zbigniew

    2016-07-01

    Anodization of Ni3Al alloy is of interest in the field of industrial manufacturing, thanks to the formation of protective oxide layer on the materials working in corrosive environments and high temperatures. However, homogeneous surface treatment is paramount for technological applications of this material. The anodization conditions have to be set outside the ranges of corrosion and “burning”, which is the electric field enhanced anodic dissolution of the metal. In order to check against occurrence of these events, proper quantitative means for assessing the surface quality have to be developed and established. We approached this task by advanced analysis of scanning electron microscope images of anodized Ni3Al plates. The anodization was carried out in 0.3 M citric acid at two temperatures of 0 and 30°C and at voltages in the range of 2 12 V. Different figures can be used to characterize the quality of the surface, in terms of uniformity. Here, the concept of regularity ratio spread is used for the first time on surfaces of technological interest. Additionally, the Minkowski parameters have been calculated and their meaning is discussed.

  15. Influence of sp-d hybridization on the electronic structure of Al-Mn alloys

    SciTech Connect

    Shukla, A. K.; Biswas, C.; Dhaka, R. S.; Das, S. C.; Barman, S. R.; Krueger, P.

    2008-05-15

    The influence of sp-d hybridization on the electronic structure of different Al-Mn alloys has been studied by photoelectron spectroscopy. Experimental evidence of a pseudogap in a crystalline binary Hume-Rothery alloy is provided. The pseudogap varies systematically with Mn concentration. The sp-d hybridization alone, even in the absence of Hume-Rothery mechanism, can produce the pseudogap. Existence of the pseudogap, suppression of the Mn 2p satellite, and decrease in the Doniach-Sunjic asymmetry parameter are the consequences of the sp-d hybridization. An in situ method of preparing these alloys by annealing a Mn adlayer on Al(111) is presented.

  16. Structural and magnetic transformations in Ni51 - x Mn36 + x Sn13 alloys

    NASA Astrophysics Data System (ADS)

    Kaletina, Yu. V.; Gerasimov, E. G.; Schastlivtsev, V. M.; Gaviko, V. S.; Terentev, P. B.

    2015-02-01

    The structural and magnetic phase transitions in Ni-Mn-Sn-based alloys have been studied. The temperature dependences of the martensitic and magnetic phase transformations in Ni51 - x Mn36 + x Sn13 alloys (0 ≤ x ≤ 4) have been determined in the case where manganese atoms substitute for nickel atoms. For the studied alloys, the concentration phase diagram has been constructed and the temperature regions of the existence of the high-temperature austenite phase L21 and the low-temperature martensite phase in different magnetic states have been determined.

  17. Influence of sp-d hybridization on the electronic structure of Al-Mn alloys

    NASA Astrophysics Data System (ADS)

    Shukla, A. K.; Biswas, C.; Dhaka, R. S.; Das, S. C.; Krüger, P.; Barman, S. R.

    2008-05-01

    The influence of sp-d hybridization on the electronic structure of different Al-Mn alloys has been studied by photoelectron spectroscopy. Experimental evidence of a pseudogap in a crystalline binary Hume-Rothery alloy is provided. The pseudogap varies systematically with Mn concentration. The sp-d hybridization alone, even in the absence of Hume-Rothery mechanism, can produce the pseudogap. Existence of the pseudogap, suppression of the Mn2p satellite, and decrease in the Doniach-Šunjić asymmetry parameter are the consequences of the sp-d hybridization. An in situ method of preparing these alloys by annealing a Mn adlayer on Al(111) is presented.

  18. Effect of silicon and yttrium on the structure and properties of diffusion coatings on nickel alloys

    NASA Astrophysics Data System (ADS)

    Abraimov, N. V.; Romashov, A. S.; Lukina, V. V.; Kotel'nikov, G. I.; Zubarev, K. A.

    2016-12-01

    The processes occurring during the formation of combined aluminide coatings on nickel alloys using gas and plasma vacuum technology are considered. It is shown that the external surface of the coating has the structure of a secondary β-NiAl solid solution after the application of a diffusion coating from an Al‒Si-Y alloy directly on the surface of alloys or on samples preliminary aluminized or chromoaluminized at 1000°C. The results of heat-resistance tests at temperatures of 1000 and 1050°C are presented.

  19. Natural ageing responses of duplex structured Mg-Li based alloys.

    PubMed

    Li, C Q; Xu, D K; Wang, B J; Sheng, L Y; Qiao, Y X; Han, E H

    2017-01-05

    Natural ageing responses of duplex structured Mg-6%Li and Mg-6%Li-6%Zn-1.2%Y alloys have been investigated. Microstructural analyses revealed that the precipitation and coarsening process of α-Mg particles could occur in β-Li phases of both two alloys during ageing process. Since a certain amount of Mg atoms in β-Li phases were consumed for the precipitation of abundant tiny MgLiZn particles, the size of α-Mg precipitates in Mg-6%Li-6%Zn-1.2%Y alloy was relatively smaller than that in Mg-6%Li alloy. Micro hardness measurements demonstrated that with the ageing time increasing, the α-Mg phases in Mg-6%Li alloy could have a constant hardness value of 41 HV, but the contained β-Li phases exhibited a slight age-softening response. Compared with the Mg-6%Li alloy, the age-softening response of β-Li phases in Mg-6%Li-6%Zn-1.2%Y alloy was much more profound. Meanwhile, a normal age-hardening response of α-Mg phases was maintained. Tensile results indicated that obvious ageing-softening phenomenon in terms of macro tensile strength occurred in both two alloys. Failure analysis demonstrated that for the Mg-6%Li alloy, cracks were preferentially initiated at α-Mg/β-Li interfaces. For the Mg-6%Li-6%Zn-1.2%Y alloy, cracks occurred at both α-Mg/β-Li interfaces and slip bands in α-Mg and β-Li phases.

  20. Natural ageing responses of duplex structured Mg-Li based alloys

    PubMed Central

    Li, C. Q.; Xu, D. K.; Wang, B. J.; Sheng, L. Y.; Qiao, Y. X.; Han, E. H.

    2017-01-01

    Natural ageing responses of duplex structured Mg-6%Li and Mg-6%Li-6%Zn-1.2%Y alloys have been investigated. Microstructural analyses revealed that the precipitation and coarsening process of α-Mg particles could occur in β-Li phases of both two alloys during ageing process. Since a certain amount of Mg atoms in β-Li phases were consumed for the precipitation of abundant tiny MgLiZn particles, the size of α-Mg precipitates in Mg-6%Li-6%Zn-1.2%Y alloy was relatively smaller than that in Mg-6%Li alloy. Micro hardness measurements demonstrated that with the ageing time increasing, the α-Mg phases in Mg-6%Li alloy could have a constant hardness value of 41 HV, but the contained β-Li phases exhibited a slight age-softening response. Compared with the Mg-6%Li alloy, the age-softening response of β-Li phases in Mg-6%Li-6%Zn-1.2%Y alloy was much more profound. Meanwhile, a normal age-hardening response of α-Mg phases was maintained. Tensile results indicated that obvious ageing-softening phenomenon in terms of macro tensile strength occurred in both two alloys. Failure analysis demonstrated that for the Mg-6%Li alloy, cracks were preferentially initiated at α-Mg/β-Li interfaces. For the Mg-6%Li-6%Zn-1.2%Y alloy, cracks occurred at both α-Mg/β-Li interfaces and slip bands in α-Mg and β-Li phases. PMID:28053318

  1. Natural ageing responses of duplex structured Mg-Li based alloys

    NASA Astrophysics Data System (ADS)

    Li, C. Q.; Xu, D. K.; Wang, B. J.; Sheng, L. Y.; Qiao, Y. X.; Han, E. H.

    2017-01-01

    Natural ageing responses of duplex structured Mg-6%Li and Mg-6%Li-6%Zn-1.2%Y alloys have been investigated. Microstructural analyses revealed that the precipitation and coarsening process of α-Mg particles could occur in β-Li phases of both two alloys during ageing process. Since a certain amount of Mg atoms in β-Li phases were consumed for the precipitation of abundant tiny MgLiZn particles, the size of α-Mg precipitates in Mg-6%Li-6%Zn-1.2%Y alloy was relatively smaller than that in Mg-6%Li alloy. Micro hardness measurements demonstrated that with the ageing time increasing, the α-Mg phases in Mg-6%Li alloy could have a constant hardness value of 41 HV, but the contained β-Li phases exhibited a slight age-softening response. Compared with the Mg-6%Li alloy, the age-softening response of β-Li phases in Mg-6%Li-6%Zn-1.2%Y alloy was much more profound. Meanwhile, a normal age-hardening response of α-Mg phases was maintained. Tensile results indicated that obvious ageing-softening phenomenon in terms of macro tensile strength occurred in both two alloys. Failure analysis demonstrated that for the Mg-6%Li alloy, cracks were preferentially initiated at α-Mg/β-Li interfaces. For the Mg-6%Li-6%Zn-1.2%Y alloy, cracks occurred at both α-Mg/β-Li interfaces and slip bands in α-Mg and β-Li phases.

  2. Advanced Testing Techniques to Measure the PWSCC Resistance of Alloy 690 and its Weld Metals

    SciTech Connect

    P.Andreson

    2004-10-01

    Wrought Alloy 600 and its weld metals (Alloy 182 and Alloy 82) were originally used in pressurized water reactors (PWRs) due to the material's inherent resistance to general corrosion in a number of aggressive environments and because of a coefficient of thermal expansion that is very close to that of low alloy and carbon steel. Over the last thirty years, stress corrosion cracking in PWR primary water (PWSCC) has been observed in numerous Alloy 600 component items and associated welds, sometimes after relatively long incubation times. The occurrence of PWSCC has been responsible for significant downtime and replacement power costs. As part of an ongoing, comprehensive program involving utilities, reactor vendors and engineering/research organizations, this report will help to ensure that corrosion degradation of nickel-base alloys does not limit service life and that full benefit can be obtained from improved designs for both replacement components and new reactors.

  3. [Casting faults and structural studies on bonded alloys comparing centrifugal castings and vacuum pressure castings].

    PubMed

    Fuchs, P; Küfmann, W

    1978-07-01

    The casting processes in use today such as centrifugal casting and vacuum pressure casting were compared with one another. An effort was made to answer the question whether the occurrence of shrink cavities and the mean diameter of the grain of the alloy is dependent on the method of casting. 80 crowns were made by both processes from the baked alloys Degudent Universal, Degudent N and the trial alloy 4437 of the firm Degusa. Slice sections were examined for macro and micro-porosity and the structural appearance was evaluated by linear analysis. Statistical analysis showed that casting faults and casting structure is independent of the method used and their causes must be found in the conditions of casting and the composition of the alloy.

  4. Construction of layered structures on valve metal alloys by microplasma oxidation

    NASA Astrophysics Data System (ADS)

    Baranova, T. A.; Chubenko, A. K.; Mamaev, A. I.; Mamaeva, V. A.; Kovalskaya, Ya B.

    2016-11-01

    Process of layered structure materials creation based on aluminum alloys is presented. Microplasma texturing method, microplasma oxidation method and chemical metallization method were used to create these structures. Non-conductive nonmetallic inorganic coatings were produced by microplasma oxidation method. Obtained structures showed high durability under thermal stress loads due to substrate metal - non-conductive nonmetallic inorganic coating phase boundary texturing.

  5. NASA-UVA Light Aerospace Alloy and Structures Technology Program (LA2ST). Research on Materials for the High Speed Civil Transport

    NASA Technical Reports Server (NTRS)

    Gangloff, Richard P.; Starke, Edgar A., Jr.; Kelly, Robert G.; Scully, John R.; Stoner, Glenn E.; Wert, John A.

    1997-01-01

    Since 1986, the NASA-Langley Research Center has sponsored the NASA-UVa Light Alloy and Structures Technology (LA2ST) Program at the University of Virginia (UVa). The fundamental objective of the LA2ST program is to conduct interdisciplinary graduate student research on the performance of next generation, light-weight aerospace alloys, composites and thermal gradient structures. The LA2ST program has aimed to product relevant data and basic understanding of material mechanical response, environmental/corrosion behavior, and microstructure; new monolithic and composite alloys; advanced processing methods; measurement and modeling advances; and a pool of educated graduate students for aerospace technologies. The scope of the LA2ST Program is broad. Research areas include: (1) Mechanical and Environmental Degradation Mechanisms in Advanced Light Metals and Composites, (2) Aerospace Materials Science, (3) Mechanics of materials for Aerospace Structures, and (4) Thermal Gradient Structures. A substantial series of semi-annual progress reports issued since 1987 documents the technical objectives, experimental or analytical procedures, and detailed results of graduate student research in these topical areas.

  6. FAA/NASA International Symposium on Advanced Structural Integrity Methods for Airframe Durability and Damage Tolerance, part 2

    NASA Technical Reports Server (NTRS)

    Harris, Charles E. (Editor)

    1994-01-01

    The international technical experts in the areas of durability and damage tolerance of metallic airframe structures were assembled to present and discuss recent research findings and the development of advanced design and analysis methods, structural concepts, and advanced materials. The principal focus of the symposium was on the dissemination of new knowledge and the peer-review of progress on the development of advanced methodologies. Papers were presented on the following topics: structural concepts for enhanced durability, damage tolerance, and maintainability; new metallic alloys and processing technology; fatigue crack initiation and small crack effects; fatigue crack growth models; fracture mechanics failure criteria for ductile materials; structural mechanics methodology for residual strength and life prediction; development of flight load spectra for design and testing; and corrosion resistance.

  7. Advanced methods for preparation and characterization of infrared detector materials. [mercury cadmium telluride alloys

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

    Differential thermal analysis data were obtained on mercury cadmium telluride alloys in order to establish the liquidus temperatures for the various alloy compositions. Preliminary theoretical analyses was performed to establish the ternary phase equilibrium parameters for the metal rich region of the phase diagram. Liquid-solid equilibrium parameters were determined for the pseudobinary alloy system. Phase equilibrium was calculated and Hg(l-x) Cd(x) Te alloys were directionally solidified from pseudobinary melts. Electrical resistivity and Hall coefficient measurements were obtained.

  8. Production of Gas-Solid Structures in Aluminum and Nickel Alloys by Gasar Processing

    SciTech Connect

    Apprill, J.M.; Baldwin, M.D.; Maguire, M.C.; Miszkiel, M.E.; Shapovalov, V.I.

    1999-01-06

    Experimental data on directional and bulk solidification of hydrogen-charged samples of aluminum alloy A356 and nickel alloy Inconel 718 are discussed. The solidification structure of the porous zone is shown to be dependent on many process variables. Of these variables, hydrogen content in the melt prior to solidification, and furnace atmospheric pressure during solidification play the decisive role. Also important are the furnace atmosphere composition, the solidification velocity, and the temperature distribution of the liquid metal inside the mold.

  9. Raising the Structural Strength of Systematically Alloyed Fe - Cr - Ni - Mo-Base Maraging Steels

    NASA Astrophysics Data System (ADS)

    Gladkovskii, S. V.; Ishina, E. A.; Kuteneva, S. V.

    2016-03-01

    The effect of systematical Mo, Ti, Al and Ca alloying of corrosion-resistant maraging steels of type Kh11N10M2T and of the modes of their heat treatment on the phase composition, combination of properties and resistance to brittle fracture is studied. It is shown that the structural strength of the steels can be raised by additional alloying with copper and formation of a regulated content of metastable retained austenite.

  10. The Crystal Structure at Room Temperature of Six Cast Heat-Resisting Alloys

    NASA Technical Reports Server (NTRS)

    Rosenbaum, Burt M.

    1947-01-01

    The crystal structures of alloys 61, X-40,X-50, 422-19, 6059, and Vitallium, derived from x-ray diffraction, are discussed. The alloys have been, or are being considered for use in gas turbine applications. The predominant phase was a solid solution of the face centered cubic type of the principal constituent elements.The lattice parameters were found to be between 3.5525 and 3.5662.

  11. Predicting Career Advancement with Structural Equation Modelling

    ERIC Educational Resources Information Center

    Heimler, Ronald; Rosenberg, Stuart; Morote, Elsa-Sofia

    2012-01-01

    Purpose: The purpose of this paper is to use the authors' prior findings concerning basic employability skills in order to determine which skills best predict career advancement potential. Design/methodology/approach: Utilizing survey responses of human resource managers, the employability skills showing the largest relationships to career…

  12. Radiation behavior of high-entropy alloys for advanced reactors. Final report

    SciTech Connect

    Liaw, Peter K.; Egami, Takeshi; Zhang, Chuan; Zhang, Fan; Zhang, Yanwen

    2015-04-30

    In the first task, we have demonstrated the radiation damage and the recrystallization behaviors in multicomponent alloys through molecular-dynamics simulations. It is found that by alloying with atoms of different sizes, the atomic-level strain increases, and the propensity of the radiation-induced crystalline to amorphous transition increases as the defects cluster in the cascade body. Recrystallization of the radiation induced supercooled or glass regions show that by tuning the composition and the equilibrium temperature, the multicomponent alloys can be healed. The crystalline-amorphous-crystalline transitions predict the potential high radiation resistance in multicomponent alloys. In the second task, three types of high-entropy alloys (HEAs) were fabricated from AlCoCrFeNi and AlCuCrFeNi quinary alloys. Hardness and reduced contact modulus were measured using nanoindentation tests. Heavy ion irradiation were performed using 10 MeV gold and 5 MeV nickel to study radiation effects. Al0.5CrCuFeNi2 shows phase separation upon the presence of copper. Both hardness and contact modulus exhibit the same trend as increasing the applied load, and it indicates that excessive free volume may alter the growth rate of the plastic zone. The as-cast Al0.1CoCrFeNi specimen undergone the hot isostatic pressing (HIP) process and steady cooling rate which mitigate the quenching effect. The swelling behavior was characterized by the atomic force microscopy (AFM), and the swelling rate is approximately 0.02% dpa. Selected area diffraction (SAD) patters show irradiation-induced amorphization throughout the ion projected range. Within the peak damage region, an amorpous ring is observed, and a mixture of amorphous/ crystalline structure at deeper depth is found. The Al0.3CoCrFeNi HEAs shows good radiation resistance up to 60 peak dpa. No voids or dislocations are observed. The crystal structures remain face-centered-cubic (FCC) before and

  13. Superplasticity of nickel-based alloys with micro- and sub-microcrystalline structures

    SciTech Connect

    Valitov, V.A.; Bewlay, B.P.; Mukhtarov, S.K.; Kaibyshev, O.A.; Gigliotti, M.F.X.

    2000-07-01

    This paper describes the generation of micro- and sub-microcrystalline structures in two Ni-based alloys that are typically strengthened by phases, such as {gamma}{prime} and {gamma}{double_prime}+{delta}. The relationship between the superplastic behavior and microstructure is discussed. High strain deformation processing in the temperature range of 0.9T{sub m} to 0.6T{sub m} results in reduction of the initial coarse-grained structure (> 100 {micro}m) to a range of structures including microcrystalline (MC) (grain size < 10 {micro}m) and sub-microcrystalline (SMC) (grain size < 1 {micro}m) with increasing deformation. The influence of alloy chemistry and constituent phases on dynamic and static recrystallization is considered, and their effect on grain refinement is described. Low-temperature and high strain rate superplasticity can be observed in dispersion-strengthened alloys with SMC structures. it was established that in dispersion-hardened Ni alloys with SMC structures, superplasticity can be observed at temperatures 200--250 C lower than in alloys with MC structure.

  14. Development of Advanced Corrosion-Resistant Fe-Cr-Ni Austenitic Stainless Steel Alloy with Improved High Temperature Strenth and Creep-Resistance

    SciTech Connect

    Maziasz, PJ

    2004-09-30

    In February of 1999, a Cooperative Research and Development Agreement (CRADA) was undertaken between Oak Ridge National Laboratory (ORNL) and Special Metals Corporation-Huntington Alloys (formerly INCO Alloys International, Inc.) to develop a modified wrought austenitic stainless alloy with considerably more strength and corrosion resistance than alloy 800H or 800HT, but with otherwise similar engineering and application characteristics. Alloy 800H and related alloys have extensive use in coal flue gas environments, as well as for tubing or structural components in chemical and petrochemical applications. The main concept of the project was make small, deliberate elemental microalloying additions to this Fe-based alloy to produce, with proper processing, fine stable carbide dispersions for enhanced high temperature creep-strength and rupture resistance, with similar or better oxidation/corrosion resistance. The project began with alloy 803, a Fe-25Cr-35NiTi,Nb alloy recently developed by INCO, as the base alloy for modification. Smaller commercial developmental alloy heats were produced by Special Metals. At the end of the project, three rounds of alloy development had produced a modified 803 alloy with significantly better creep resistance above 815EC (1500EC) than standard alloy 803 in the solution-annealed (SA) condition. The new upgraded 803 alloy also had the potential for a processing boost in that creep resistance for certain kinds of manufactured components that was not found in the standard alloy. The upgraded 803 alloy showed similar or slightly better oxidation and corrosion resistance relative to standard 803. Creep strength and oxidation/corrosion resistance of the upgraded 803 alloy were significantly better than found in alloy 800H, as originally intended. The CRADA was terminated in February 2003. A contributing factor was Special Metals Corporation being in Chapter 11 Bankruptcy. Additional testing, further commercial scale-up, and any potential

  15. 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.

  16. Functionally graded Co-Cr-Mo coating on Ti-6Al-4V alloy structures.

    PubMed

    Vamsi Krishna, B; Xue, Weichang; Bose, Susmita; Bandyopadhyay, Amit

    2008-05-01

    Functionally graded, hard and wear-resistant Co-Cr-Mo alloy was coated on Ti-6Al-4V alloy with a metallurgically sound interface using Laser Engineering Net Shaping (LENS). The addition of the Co-Cr-Mo alloy onto the surface of Ti-6Al-4V alloy significantly increased the surface hardness without any intermetallic phases in the transition region. A 100% Co-Cr-Mo transition from Ti-6Al-4V was difficult to produce due to cracking. However, using optimized LENS processing parameters, crack-free coatings containing up to 86% Co-Cr-Mo were deposited on Ti-6Al-4V alloy with excellent reproducibility. Human osteoblast cells were cultured to test in vitro biocompatibility of the coatings. Based on in vitro biocompatibility, increasing the Co-Cr-Mo concentration in the coating reduced the live cell numbers after 14 days of culture on the coating compared with base Ti-6Al-4V alloy. However, coated samples always showed better bone cell proliferation than 100% Co-Cr-Mo alloy. Producing near net shape components with graded compositions using LENS could potentially be a viable route for manufacturing unitized structures for metal-on-metal prosthetic devices to minimize the wear-induced osteolysis and aseptic loosening that are significant problems in current implant design.

  17. Advanced Materials and Multifunctional Structures for Aerospace Vehicles

    DTIC Science & Technology

    2006-10-01

    through covalent integration of functional nanotubes ”, Advanced Functional Materials, 14(7) (2004) 643-648. 185 R.Z. Ma, J. Wu, B.Q. Wei, J. Liang, and...on Advanced Materials for Multi Functional Structures in Aerospace Vehicles. The advanced synthesis, processing and the characterization techniques...when more than one primary function is performed either simultaneously or sequentially in time. These systems are based on metallic, ceramic and

  18. Advanced Standing and Bridge Courses: Structures and Issues

    ERIC Educational Resources Information Center

    GlenMaye, Linnea F.; Lause, Timothy W.; Bolin, Brien L.

    2010-01-01

    This study explores the issue of advanced standing in MSW programs in light of the new Educational Policy and Accreditation Standards (EPAS). Advanced standing structures of MSW programs were studied using a purposive sample consisting of 203 MSW program directors with a response rate of 28% (N=58). The results indicate that slightly more than 15%…

  19. Toughness testing and high-temperature oxidation evaluations of advanced alloys for core internals

    SciTech Connect

    Tan, Lizhen; Pint, Bruce A.; Chen, Xiang

    2016-09-16

    Alloy X-750 was procured from Carpenter Technology and Bodycote in this year. An appropriate TMT was developed on Alloy 439 to obtain materials with refined grain size for property screening tests. Charpy V-notch impact tests were completed for the three ferritic steels Grade 92, Alloy 439, and 14YWT. Fracture toughness tests at elevated temperatures were completed for 14YWT. The tests will be completed for the other alloys in next fiscal year. Steam oxidation tests of the three ferritic steels, 316L, and Zr–2.5Nb have been completed. The steam tests of the Ni-based superalloys and the other austenitic stainless steels will be continued and finished in next fiscal year. Performance ranking in terms of steam oxidation resistance and impact/fracture toughness of the alloys will be deduced.

  20. Local structure of disordered Au-Cu and Au-Ag alloys

    NASA Astrophysics Data System (ADS)

    Frenkel, A. I.; Machavariani, V. Sh.; Rubshtein, A.; Rosenberg, Yu.; Voronel, A.; Stern, E. A.

    2000-10-01

    X-ray-absorption fine structure (XAFS) and x-ray-diffraction (XRD) measurements of disordered alloys AuxCu1-x and Au0.5Ag0.5 prepared by melt spinning were performed. In the Au0.5Ag0.5 alloy, no significant local deviations of the atoms from the average fcc lattice were detected while in AuxCu1-x alloys, significant deviations of atoms from the average fcc lattice were found. Mean-square vibrations of the Cu-Cu distances revealed by the XAFS in AuxCu1-x alloys indicate the weakening of contact between Cu atoms in the dilute limit. Our computer simulation for AuxCu1-x clusters of 105 atoms reproduces the main features of both the XAFS and XRD data.

  1. Phase and structural transformations in the alloy on the basis of the orthorhombic titanium aluminide

    NASA Astrophysics Data System (ADS)

    Popov, A. A.; Illarionov, A. G.; Grib, S. V.; Demakov, S. L.; Karabanalov, M. S.; Elkina, O. A.

    2008-10-01

    Phase and structural transformations in the Ti-24.3 Al-24.8 Nb-1.0 Zr-1.4 V-0.6 Mo-0.3 Si (at %) alloy that take place during heating in the temperature range of 700 1050°C have been investigated. The temperature ranges of existence of the O + β, O + β + α2, β + α2, and β phase fields have been established. A scheme of the relationships between the volume fractions of the O, β, and α2 phases depending on the temperature of heating of the alloy have been investigated. The formation of an ordered incommensurate ω ( V ω) phase has been revealed in the alloy during quenching from 900°C. The existence of a correlation between the hardness properties and changes in the phase composition and morphology of particles precipitating in the alloy has been shown.

  2. Advanced Data Structure and Geographic Information Systems

    NASA Technical Reports Server (NTRS)

    Peuquet, D. (Principal Investigator)

    1984-01-01

    The current state of the art in specified areas of Geographic Information Systems GIS technology is examined. Study of the question of very large, efficient, heterogeneous spatial databases is required in order to explore the potential application of remotely sensed data for studying the long term habitability of the Earth. Research includes a review of spatial data structures and storage, development of operations required by GIS, and preparation of a testbed system to compare Vaster data structure with NASA's Topological Raster Structure.

  3. Theory of the electronic structure of substitutional semiconductor alloys: Analytical approaches

    SciTech Connect

    Zakharov, A. Yu.

    2015-07-15

    Methods of predicting the electronic structure of disordered semiconductor alloys involving mainly isoelectronic substitution are reviewed. Special emphasis is placed on analytical methods of studying currently available models of alloys. An approximate equation for the localization threshold of electronic states in the Lifshitz model is considered, and the inaccuracy of this equation is estimated. The contributions of the perturbation potential of an individual impurity and of crystal-lattice distortions in the vicinity of the impurity center are analyzed on the basis of the Faddeev equations. The contributions of intrinsic impurity potentials and volume effects to the formation of the electronic structure of semiconductor alloys are esti- mated. Methods of calculating matrix elements of the perturbation potentials of isoelectronic impurities in alloys with consideration for deformation effects are considered. The procedure of calculating the compositional dependence of the band gap of multicomponent alloys is described. A comparative analysis of various methods for predicting the formation of electronic states bound at individual isoelectronic impurities in semiconductors is conducted. The theory of the energy spectrum of charged impurities in isoelectronic alloys is presented.

  4. Predicting RNA structure: advances and limitations.

    PubMed

    Hofacker, Ivo L; Lorenz, Ronny

    2014-01-01

    RNA secondary structures can be predicted using efficient algorithms. A widely used software package implementing a large number of computational methods is the ViennaRNA Package. This chapter describes how to use programs from the ViennaRNA Package to perform common tasks such as prediction of minimum free-energy structures, suboptimal structures, or base pairing probabilities, and generating secondary structure plots with reliability annotation. Moreover, we present recent methods to assess the folding kinetics of an RNA via 2D projections of the energy landscape, identification of local minima and energy barriers, or simulation of RNA folding as a Markov process.

  5. Advances in Solid State Joining of Haynes 230 High Temperature Alloy

    NASA Technical Reports Server (NTRS)

    Ding, Jeff; Schneider, Judy; Walker, Bryant

    2010-01-01

    The J-2X engine is being designed for NASA s new class of crew and launch vehicles, the Ares I and Ares V. The J-2X is a LOX/Hydrogen upper stage engine with 294,000 lbs of thrust and a minimum Isp of 448 seconds. As part of the design criteria to meet the performance requirements a large film-cooled nozzle extension is being designed to further expand the hot gases and increases the specific impulse. The nozzle extension is designed using Haynes 230, a nickel-chromium-tungsten-molybdenum superalloy. The alloy was selected for its high strength at elevated temperatures and resistance to hydrogen embrittlement. The nozzle extension is manufactured from Haynes 230 plate spun-forged to form the contour and chemically-milled pockets for weight reduction. Currently fusion welding is being evaluated for joining the panels which are then mechanically etched and thinned to required dimensions for the nozzle extension blank. This blank is then spun formed into the parabolic geometry required for the nozzle. After forming the nozzle extension, weight reduction pockets are chemically milled into the nozzle. Fusion welding of Haynes results in columnar grains which are prone to hot cracking during forming processes. This restricts the ability to use spin forging to produce the nozzle contour. Solid state joining processes are being pursued as an alternative process to produce a structure more amenable to spin forming. Solid state processes have been shown to produce a refined grain structure within the joint regions as illustrated in Figure 1. Solid state joining processes include friction stir welding (FSW) and a patented modification termed thermal stir welding (TSW). The configuration of TSWing utilizes an induction coil to preheat the material minimizing the burden on the weld tool extending its life. This provides the ability to precisely select and control the temperature. The work presented in this presentation investigates the feasibility of joining the Haynes 230

  6. Hydrogen absorption in uranium-based alloys with cubic γ -U structure

    NASA Astrophysics Data System (ADS)

    Havela, L.; Kim-Ngan, N.-T. H.

    2017-03-01

    UH3-type hydrides were formed by hydrogenation of splat-cooled U-based alloys upon applying high H2 pressures (>2.5 bar). Hydrogenation of U1‑x Mo x alloys (with x  ⩾  0.12 (12 at.% Mo) containing the cubic γ-U phase leads to a formation of nanocrystalline β-UH3, why those of U1‑x Zr x alloys (with x  ⩾15 at.% Zr) implies a pure α-UH3. The Curie temperature of hydride (UH3)0.85Mo0.15 reaches 200 K it may be the first U-based ferromagnet with such high T C. The results reflect the dominant U–H interaction. Invited talk at 8th International Workshop on Advanced Materials Science and Nanotechnology (IWAMSN2016), 8–12 November 2016, Ha Long City, Vietnam.

  7. Establishing a Scientific Basis for Optimizing Compositions, Process Paths and Fabrication Methods for Nanostructured Ferritic Alloys for Use in Advanced Fission Energy Systems

    SciTech Connect

    Odette, G Robert; Cunningham, Nicholas J., Wu, Yuan; Etienne, Auriane; Stergar, Erich; Yamamoto, Takuya

    2012-02-21

    O3 concentration of 0.2 wt.%. An APT characterization of MA957 joined by friction stir welding (FSW) showed that this solid sate joining procedure had only a modest effect on the NF number density (N) and average diameter () compared to an as extruded sample. FSW appears to rearrange the NFs, which become highly aligned with sub-boundary and dislocation structures to an extent that are not observed in the as extruded case. The aligned NF structures are less apparent, but seem to persist after post weld annealing at 1150ºC for 3 h following which reduces N, consistent with a significant reduction in hardness. Lastly, several NFA materials, including MA957 and various 14YWT alloys, have been included in irradiation experiments performed at the Advanced Test Reactor, the JOYO sodium cooled fast reactor, the High Flux Isotope Reactor, and the SINQ spallation neut

  8. Advanced Structural and Inflatable Hybrid Spacecraft Module

    NASA Technical Reports Server (NTRS)

    Schneider, William C. (Inventor); delaFuente, Horacio M. (Inventor); Edeen, Gregg A. (Inventor); Kennedy, Kriss J. (Inventor); Lester, James D. (Inventor); Gupta, Shalini (Inventor); Hess, Linda F. (Inventor); Lin, Chin H. (Inventor); Malecki, Richard H. (Inventor); Raboin, Jasen L. (Inventor)

    2001-01-01

    An inflatable module comprising a structural core and an inflatable shell, wherein the inflatable shell is sealingly attached to the structural core. In its launch configuration, the wall thickness of the inflatable shell is collapsed by vacuum. Also in this configuration, the inflatable shell is collapsed and efficiently folded around the structural core. Upon deployment, the wall thickness of the inflatable shell is inflated; whereby the inflatable shell itself, is thereby inflated around the structural core, defining therein a large enclosed volume. A plurality of removable shelves are arranged interior to the structural core in the launch configuration. The structural core also includes at least one longeron that, in conjunction with the shelves, primarily constitute the rigid, strong, and lightweight load-bearing structure of the module during launch. The removable shelves are detachable from their arrangement in the launch configuration so that, when the module is in its deployed configuration and launch loads no longer exist, the shelves can be rearranged to provide a module interior arrangement suitable for human habitation and work. In the preferred embodiment, to provide efficiency in structural load paths and attachments, the shape of the inflatable shell is a cylinder with semi-toroidal ends.

  9. Advances in structure-based vaccine design

    PubMed Central

    Kulp, Daniel W; Schief, William R

    2014-01-01

    Despite the tremendous successes of current vaccines, infectious diseases still take a heavy toll on the global population, and that provides strong rationale for broadening our vaccine development repertoire. Structural vaccinology, in which protein structure information is utilized to design immunogens, has promise to provide new vaccines against traditionally difficult targets. Crystal structures of antigens containing one or more protection epitopes, especially when in complex with a protective antibody, are the launching point for immunogen design. Integrating structure and sequence information for families of broadly neutralizing antibodies (bNAbs) has recently enabled the creation of germline-targeting immunogens that bind and activate germline B-cells in order to initiate the elicitation of such antibodies. The contacts between antigen and neutralizing antibody define a structural epitope, and methods have been developed to transplant epitopes to scaffold proteins for structural stabilization, and to design minimized antigens that retain one or more key epitopes while eliminating other potentially distracting or unnecessary features. To develop vaccines that protect against antigenically variable pathogens, pioneering structure-based work demonstrated that multiple strain-specific epitopes could be engineered onto a single immunogen. We review these recent structural vaccinology efforts to engineer germline-targeting, epitope-specific, and/or broad coverage immunogens. PMID:23806515

  10. 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

  11. Study of atomic structure of liquid Hg-In alloys using ab-initio molecular dynamics

    SciTech Connect

    Sharma, Nalini; Ahluwalia, P. K.; Thakur, Anil

    2015-05-15

    Ab-initio molecular dynamics simulations are performed to study the structural properties of liquid Hg-In alloys. The interatomic interactions are described by ab-initio pseudopotentials given by Troullier and Martins. Five liquid Hg-In mixtures (Hg{sub 10}In{sub 90}, Hg{sub 30}In{sub 70}, Hg{sub 50}In{sub 50}, Hg{sub 70}In{sub 30} and Hg{sub 90}In{sub 10}) at 299K are considered. The radial distribution function g(r) and structure factor S(q) of considered alloys are compared with respective experimental results for liquid Hg (l-Hg) and (l-In). The radial distribution function g(r) shows the presence of short range order in the systems considered. Smooth curves of Bhatia-Thornton partial structure factors factor shows the presence of liquid state in the considered alloys.

  12. Atomic structure and magnetic properties of Cu 80Co 20 nanocrystalline compound produced by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Ivchenko, V. A.; Uimin, M. A.; Yermakov, A. Ye; Korobeinikov, A. Yu

    1999-10-01

    Direct observation of the atomic structure of the mechanically alloyed Cu 80Co 20 compounds has been made using the field ion microscope (FIM). Phase composition, defect structure and morphology of material on the atomic scale have been determined. It has been established that the studied material is chemically inhomogeneous, presenting a mixture of two main phases: heterogeneous solid solution of cobalt in copper, and pure cobalt. Phase volume ratios, particle and cluster sizes have been estimated. An evaluation of Co content in CuCo solid solution has been made. The width of interfaces in this mechanically alloyed material was revealed to be at least twice the width of phase boundaries in metals and alloys. Superparamagnetism of the compound studied at elevated temperatures and saturation magnetization deficit at low temperatures are discussed on the basis of the above-mentioned structural data.

  13. Study of atomic structure of liquid Hg-In alloys using ab-initio molecular dynamics

    NASA Astrophysics Data System (ADS)

    Sharma, Nalini; Thakur, Anil; Ahluwalia, P. K.

    2015-05-01

    Ab-initio molecular dynamics simulations are performed to study the structural properties of liquid Hg-In alloys. The interatomic interactions are described by ab-initio pseudopotentials given by Troullier and Martins. Five liquid Hg-In mixtures (Hg10In90, Hg30In70, Hg50In50, Hg70In30 and Hg90In10) at 299K are considered. The radial distribution function g(r) and structure factor S(q) of considered alloys are compared with respective experimental results for liquid Hg (l-Hg) and (l-In). The radial distribution function g(r) shows the presence of short range order in the systems considered. Smooth curves of Bhatia-Thornton partial structure factors factor shows the presence of liquid state in the considered alloys.

  14. Evaluation of an advanced directionally solidified gamma/gamma'-alpha Mo eutectic alloy

    NASA Technical Reports Server (NTRS)

    Henry, M. F.; Jackson, M. R.; Gigliotti, M. F. X.; Nelson, P. B.

    1979-01-01

    An attempt was made to improve on the properties of the candidate jet engine turbine blade material AG-60, a gamma/gamma prime-alpha Mo eutectic composite. Alloy 38 (AG-170) was evaluated in the greatest detail. This alloy, Ni-5.88 A1-29.74 Mo-1.65 V-1.2C Re (weight percent), represents an improvement beyond AG-60, based on mechanical testing of the transverse and/or longitudinal orientations over a range of temperatures in tension, shear, rupture, and rupture after thermal exposure. It is likely that other alloys in the study represent a similar improvement.

  15. The Hume-Rothery Rules for Structurally Complex Alloy Phases

    NASA Astrophysics Data System (ADS)

    Mizutani, Uichiro

    The underlying physics behind the Hume-Rothery rules, which have earned great reputations over the past century in the field of materials science in designing new alloys, is reviewed. The discussion is developed following several key themes: (a) what is the critical depth and width of the pseudo-gap to stabilize a complex metallic alloy?, (b) what does the Hume-Rothery stabilization mechanism mean?, (c) the existence of FsBz-induced and orbital hybridization-induced pseudo-gaps, (d) the need of distinguishing two different electron concentrations e/a and VEC, (e) are most quasicrystals really scaled in terms of e/a and stabilized via the FsBz-induced pseudo-gap mechanism? The answer is "no".

  16. Solidification behavior and structure of Al-Cu alloy welds

    SciTech Connect

    Brooks, J.A.; Li, M.; Yang, N.C.Y.

    1997-09-01

    The microsegregation behavior of electron beam (EB) and gas tungsten arc (GTA) welds of Al-Cu alloys covering a range from 0.19 to 7.74 wt% Cu were characterized for dendrite core concentrations and fraction eutectic solidification. Although a single weld speed of 12.7 mm/sec was used, some differences were observed in the segregation behavior of the two weld types. The microsegregation behavior was also modeled using a finite differences technique considering dendrite tip and eutectic undercooling and solid state diffusion. Fairly good agreement was observed between measured and calculated segregation behavior although differences between the two weld types could not be completely accounted for. The concept of dendrite tip undercooling was used to explain the formation of a single through thickness centerline grain in the higher alloy content GTA welds.

  17. Aerospace Structural Metals Handbook. Volume 5. Supplement XI. Nonferrous Alloys

    DTIC Science & Technology

    1978-12-01

    355, C355 Mar 77 3105 A1-7Si- 0 .3Mg...Ix INTRODUCTION I GENERAL DISCUSSION OF HANDBOOK CONTENTS 3 0 . INTRODUCTION 1. GENERAL 2. PHYSICAL AND CHEMICAL PROPERTIES 3. MECHANICAL PROPERTIES 4...FABRICATION CODE DESIGNATION REVISED CARBON AND LOW ALLOY STEELS (FeC) 1103 Fe-(T.15C)-0.9?M,-O.8801-O.50Cr- 0 . 4 6ro-0.3?Cu-0.265 1 0 -1 Dec 72 ULTRA

  18. Structure and mechanical properties of as-cast Ti-5Nb-xFe alloys

    SciTech Connect

    Hsu, Hsueh-Chuan; Hsu, Shih-Kuang; Wu, Shih-Ching; Lee, Chih-Jhan; Ho, Wen-Fu

    2010-09-15

    In this study, as-cast Ti-5Nb and a series of Ti-5Nb-xFe alloys were investigated and compared with commercially pure titanium (c.p. Ti) in order to determine their structure and mechanical properties. The series of Ti-5Nb-xFe alloys contained an iron content ranging from 1 to 5 mass% and were prepared by using a commercial arc-melting vacuum-pressure casting system. Additionally, X-ray diffraction (XRD) for phase analysis was conducted with a diffractometer, and three-point bending tests were performed to evaluate the mechanical properties of all specimens. The fractured surfaces were observed by using scanning electron microscopy (SEM). The experimental results indicated that these alloys possessed a range of different structures and mechanical properties dependent upon the various additions of Fe. With an addition of 1 mass% Fe, retention of the metastable {beta} phase began. However, when 4 mass% Fe or greater was added, the {beta} phase was entirely retained with a bcc crystal structure. Moreover, the {omega} phase was only detected in the Ti-5Nb-2Fe, Ti-5Nb-3Fe and Ti-5Nb-4Fe alloys. The largest quantity of {omega} phase and the highest bending modulus were found in the Ti-5Nb-3Fe alloy. The Ti-5Nb-2Fe alloy had the lowest bending modulus, which was lower than that of c.p. Ti by 20%. This alloy exhibited the highest bending strength/modulus ratio of 26.7, which was higher than that of c.p. Ti by 214%, and of the Ti-5Nb alloy (14.4 ) by 85%. Additionally, the elastically recoverable angles of the ductile Ti-5Nb-1Fe (19.9{sup o}) and Ti-5Nb-5Fe (29.5{sup o}) alloys were greater than that of c.p. Ti (2.7{sup o}) by as much as 637% and 993%, respectively. Furthermore, the preliminary cell culturing results revealed that the Ti-5Nb-xFe alloys were not only biocompatible, but also supported cell attachment.

  19. Advanced textile structural composites -- status and outlook

    SciTech Connect

    Arendts, F.J.; Drechsler, K.; Brandt, J.

    1993-12-31

    Composites with 3D woven, braided or knitted fiber reinforcement offer a high potential for the cost-effective manufacturing of structures featuring an interesting mechanical performance, for example with regard to damage tolerance or energy absorption capability. In this paper, the properties of various textile structural composites with regard to stiffness, strength, damage tolerance, energy absorption capability as well as the respective manufacturing processes (RTM or thermoplastic hybrid-yarn technique) are presented in comparison to conventional ud tape based composites. The influence of the fiber architecture on the mechanical performance (tensile stiffness and strength, compression strength, interlaminar shear strength, compression strength after impact, fracture mechanical properties, through-penetration resistance) of monolithic and composite sandwich structures has been evaluated in an experimental study. It has been shown that composites involving new 3D weavings with minimum fiber crimp can compete with tape-based laminates as far as stiffness and strength are concerned. Using knittings makes it possible to manufacture composites having superior through-penetration resistance. The specific feature of the 3D braiding process is the ability to produce complex shaped structures having a high degree of freedom with regard to fiber geometry. Finally, the application of various textile structural composites will be presented on the basis of three demonstrator components (automotive engine mount, aircraft leading edge and motor cycle helmet), and the potential for further developments will be discussed.

  20. Evaluation of low activation vanadium alloys for structural material in a fusion reactor

    SciTech Connect

    Loomis, B.A.; Hull, A.B.; Smith, D.L.

    1989-10-23

    The V-7.2Cr-14.5Ti, V-9.2Cr-4.9Ti, V-9.9Cr-9.2Ti, V-13.5Cr-5.2Ti, V-4.1Cr-4.3Ti, Vanstar-7, V-4.6Ti, V-17.7Ti, and V-3.1Ti-(0.5-1.0)Si alloys were evaluated for use as structural material in a fusion reactor. The alloys were evaluated on the basis of their yield strength, swelling resistance, resistance to hydrogen and irradiation embrittlement, and compatibility with a lithium reactor coolant. On the basis of these evaluations, the V-7.2Cr-14.5Ti, V-9.2Cr-4.9Ti, V-9.9Cr-9.2Ti, V-13.5Cr-5.2Ti, Vanstar-7, and V-3.1Ti-(0.5-1.0)Si alloys are considered unacceptable for structural material in a fusion reactor, whereas the V-4.1Cr-4.3Ti, V-4.6Ti, and V-17.7Ti alloys are recommended for more intensive evaluation. The V-7Cr-5Ti alloy may have the optimum combination of strength, DBTT, swelling rate, and lithium dissolution rate for a structural material in a fusion reactor. 4 refs., 6 figs., 4 tabs.

  1. Structural and magnetic properties of mechanically alloyed Co 20Cu 80 solid solution

    NASA Astrophysics Data System (ADS)

    Yoo, Y. G.; Yang, D. S.; Yu, S. C.; Kim, W. T.; M. Lee, J.

    1999-08-01

    Microstructural change during the mechanical alloying of Co 20Cu 80 has been studied by X-ray diffractometry (XRD) and extended X-ray absorption fine structure (EXAFS) techniques. EXAFS analysis shows clearly the formation of supersaturated Co 20Cu 80 solid solution with FCC crystal structure during mechanical alloying, which is in good agreement with XRD analysis. Magnetic properties also have been studied by SQUID magnetometer from 4 to 290 K. The supersaturated Co 20Cu 80 solid solution shows wide distribution in Co cluster size due to the continuous blocking of Co cluster as a function of temperature.

  2. Local Atomic Structure of Semiconductor Alloys Using Pair Distribution Function Analysis

    SciTech Connect

    Billinge, S.J.L.; Thorpe, M.F.

    2002-06-24

    We have been taking advantage of recent experimental developments, which involve utilizing diffraction data from x-rays or neutrons out to very large wave-vectors, to obtain a detailed structural characterization of semiconductor alloys. This approach allows an accurate Pair Distribution Function (PDF) to be obtained to 20A and beyond and reveals the local structure of the alloy directly. These data can be modeled explicitly to learn about local correlations and short-range order in materials. We are combining theory, modeling and experiments to study a range of materials from semiconductors to thermoelectrics and proton conductors.

  3. Formation of Structure, Phase Composition and Properties in Refractory Titanium Alloy Under Quenching

    NASA Astrophysics Data System (ADS)

    Gadeev, D. V.; Illarionov, A. G.; Demakov, S. L.

    2015-11-01

    The evolution of structure and phase composition in titanium alloy VT18U under cooling from 900 - 1035°C is studied by the methods of light and electron microscopy, x-ray imaging, hardness measurement and measurement of the modulus of elasticity. The critical temperature of heating for quenching and the dependence of the volume fraction of the phases on this temperature are determined. The effect of the structural and phase state of the alloy quenched from different temperatures on the combination of its physical and mechanical properties (modulus of elasticity, hardness) is analyzed.

  4. 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

  5. Pumped lithium loop test to evaluate advanced refractory metal alloys and simulated nuclear fuel elements

    NASA Technical Reports Server (NTRS)

    Brandenburf, G. P.; Hoffman, E. E.; Smith, J. P.

    1974-01-01

    The performance was determined of refractory metal alloys and uranium nitride fuel element specimens in flowing 1900F (1083C) lithium. The results demonstrate the suitability of the selected materials to perform satisfactorily from a chemical compatibility standpoint.

  6. Blanch Resistant and Thermal Barrier NiAl Coating Systems for Advanced Copper Alloys

    NASA Technical Reports Server (NTRS)

    Raj, Sai V. (Inventor)

    2005-01-01

    A method of forming an environmental resistant thermal barrier coating on a copper alloy is disclosed. The steps include cleansing a surface of a copper alloy, depositing a bond coat on the cleansed surface of the copper alloy, depositing a NiAl top coat on the bond coat and consolidating the bond coat and the NiAl top coat to form the thermal barrier coating. The bond coat may be a nickel layer or a layer composed of at least one of copper and chromium-copper alloy and either the bond coat or the NiAl top coat or both may be deposited using a low pressure or vacuum plasma spray.

  7. Concentration-dependent crystal structure, elastic constants and electronic structure of Zr x Ti1- x alloys under high pressure

    NASA Astrophysics Data System (ADS)

    Yuan, Xiao-Li; Xue, Mi-An; Chen, Wen; An, Tian-Qing

    2014-04-01

    The physical properties of Zr x Ti1- x ( x = 0.0, 0.33, 0.5, 0.67, 0.75 and 1.00) alloys were simulated by virtual crystal approximation (VCA) methods which is generally used for disordered solid solutions modeling. The elastic constant, electronic structure and thermal Equation of state (EOS) of disordered Zr x Ti1- x alloys under pressure are investigated by plane-wave pseudo-potential method. Our simulations reveal increasement of variations of the calculated equilibrium volumes and decreasement of Bulk modulus as a function of the alloy compositions. Lattice parameters a and c of alloys with different Zr concentrations decrease linearly with pressure increasing, but the c/avalues are increasing as pressure increases, indicating no phase transitions under pressure from 0 GPa to 100 GPa. The elastic constants and the Bulk modulus to the Shear modulus ratios ( B/G) indicate good ductility of Zr, Zr0.33Ti0.67, Zr0.5Ti0.5, Zr0.75Ti0.25 and Ti, but the Zr0.67Ti0.33 alloy is brittle under 0 K and 0 GPa. The metallic behavior of these alloys was also proved by analyzing partial and total DOS.

  8. Computer Aided Design of Advanced Turbine Airfoil Alloys for Industrial Gas Turbines in Coal Fired Environments

    SciTech Connect

    G.E. Fuchs

    2007-12-31

    Recent initiatives for fuel flexibility, increased efficiency and decreased emissions in power generating industrial gas turbines (IGT's), have highlighted the need for the development of techniques to produce large single crystal or columnar grained, directionally solidified Ni-base superalloy turbine blades and vanes. In order to address the technical difficulties of producing large single crystal components, a program has been initiated to, using computational materials science, better understand how alloy composition in potential IGT alloys and solidification conditions during processing, effect castability, defect formation and environmental resistance. This program will help to identify potential routes for the development of high strength, corrosion resistant airfoil/vane alloys, which would be a benefit to all IGT's, including small IGT's and even aerospace gas turbines. During the first year, collaboration with Siemens Power Corporation (SPC), Rolls-Royce, Howmet and Solar Turbines has identified and evaluated about 50 alloy compositions that are of interest for this potential application. In addition, alloy modifications to an existing alloy (CMSX-4) were also evaluated. Collaborating with SPC and using computational software at SPC to evaluate about 50 alloy compositions identified 5 candidate alloys for experimental evaluation. The results obtained from the experimentally determined phase transformation temperatures did not compare well to the calculated values in many cases. The effects of small additions of boundary strengtheners (i.e., C, B and N) to CMSX-4 were also examined. The calculated phase transformation temperatures were somewhat closer to the experimentally determined values than for the 5 candidate alloys, discussed above. The calculated partitioning coefficients were similar for all of the CMSX-4 alloys, similar to the experimentally determined segregation behavior. In general, it appears that computational materials science has become a

  9. Advanced control evaluation for structures (ACES) programs

    NASA Technical Reports Server (NTRS)

    Pearson, Jerome; Waites, Henry

    1988-01-01

    The ACES programs are a series of past, present, and future activities at the Marshall Space Flight Center (MSFC) Ground facility for Large Space Structure Control Verification (GF/LSSCV). The main objectives of the ACES programs are to implement control techniques on a series of complex dynamical systems, to determine the control/structure interaction for the control techniques, and to provide a national facility in which dynamics and control verification can be effected. The focus is on these objectives and how they are implemented under various engineering and economic constraints. Future plans that will be effected in upcoming ACES programs are considered.

  10. Corrosion Protection of Al Alloys for Aircraft by Coatings With Advanced Properties and Enhanced Performance

    DTIC Science & Technology

    2007-12-20

    Sim6es, D. E. Tallman, G. P. Bierwagen, "Electrochemical Behaviour of a Mg-Rich Primer in the Protection of Al Alloys ," Corrosion Science 48 (2006...December 20, 200 Final Report July 1, 2004-June 30, 2007 4. TITLE AND SUBTITLE Sa. CONTRACT NUMBER Corrosion Protection of Al Alloys for Aircraft by...Prof. Dennis E. Tallman: A) New Scanning Probe Studies of Novel Cr-free Active Coatings B) Examination of the Influence of Surface Preparation of Al

  11. Magnetic and structural characteristics of PrCo13-xSiO alloys and their nitrides

    SciTech Connect

    Huang, M.Q.; Wallace, W.E.; Obermyer, R.T.; Simizu, S.; Sankar, S.G.

    1996-01-31

    PrCo13-xSix alloys with 0 <= x <= 4.5 have been synthesized and studied at temperatures from 10 to 1273 K and in fields up to 17 kOe. The structure and magnetic properties of the alloys vary significantly with changes in Si content x. In the alloys with x = 0, TMA and XRD studies show the phases present to be Pr2Co17 and Co. For x = 1.5 or 2.0, the alloys are essentially single-phase fcc materials (NaZn13 structure type). At larger values of x the ternary alloy formed in a bet structure (Ce2Ni17Si0 structure type). Replacement of Co by Si in PrCo13 results in a drop in T{sub c} from 1318 K (for LaCo13) to approx. 900 K for fcc Pr(Co.Si)13 alloy and to approx. 20 K for bct Pr(Co.Si)sub 13 alloys. There is also a large drop in magnetization from 104.6 emu/g for the alloy with x = 1.5 to 19.2 emu/g for the alloys with x = 4.0. A bct alloy (x = 3.5) showed negligible magnetic anisotropy. Si doping sharply reduces the Co moment. Si doping also reduces tbe Pr moment to 1.5 micrometer sub s (fcc alloys) and to 1.8 micrometers sub s (bct alloys). Nitrogenation fails to improve Pr(Co.Si)13 alloys as permanent magnet materials.

  12. Aging Optimization of Aluminum-Lithium Alloy C458 for Application to Cryotank Structures

    NASA Technical Reports Server (NTRS)

    Sova, B. J.; Sankaran, K. K.; Babel, H.; Farahmand, B.; Rioja, R.

    2003-01-01

    Compared with aluminum alloys such as 2219, which is widely used in space vehicle for cryogenic tanks and unpressurized structures, aluminum-lithium alloys possess attractive combinations of lower density and higher modulus along with comparable mechanical properties. These characteristics have resulted in the successful use of the aluminum-lithium alloy 2195 (Al-1.0 Li-4.0 Cu-0.4 Mg-0.4 Ag-0.12 Zr) for the Space Shuttle External Tank, and the consideration of newer U.S. aluminum-lithium alloys such as L277 and C458 for future space vehicles. These newer alloys generally have lithium content less than 2 wt. % and their composition and processing have been carefully tailored to increase the toughness and reduce the mechanical property anisotropy of the earlier generation alloys such 2090 and 8090. Alloy processing, particularly the aging treatment, has a significant influence on the strength-toughness combinations and their dependence on service environments for aluminum-lithium alloys. Work at NASA Marshall Space Flight Center on alloy 2195 has shown that the cryogenic toughness can be improved by employing a two-step aging process. This is accomplished by aging at a lower temperature in the first step to suppress nucleation of the strengthening precipitate at sub-grain boundaries while promoting nucleation in the interior of the grains. Second step aging at the normal aging temperature results in precipitate growth to the optimum size. A design of experiments aging study was conducted for plate. To achieve the T8 temper, Alloy C458 (Al-1.8 Li-2.7 Cu-0.3 Mg- 0.08 Zr-0.3 Mn-0.6 Zn) is typically aged at 300 F for 24 hours. In this study, a two-step aging treatment was developed through a comprehensive 24 full factorial design of experiments study and the typical one-step aging used as a reference. Based on the higher lithium content of C458 compared with 2195, the first step aging temperature was varied between 175 F and 250 F. The second step aging temperatures was

  13. Effect of heat treatment on the fracture and structure of tin-indium solder alloy

    NASA Astrophysics Data System (ADS)

    Shalaby, R. M.; El-Sayed, M.

    2005-01-01

    The effect of heat treatment on the structure, hardness, and electrical resistivity of the crystalline Sn100-x In-x (x=10 wt.%) solder alloy is studied. The structures of as-casted and heat-treated alloys have been investigated by means of a X-ray diffraction technique. Using X-ray analysis a crystalline beta-Sn and an In phase are detected. The amount of the crystalline phases increases upon increasing the annealing temperature. It is found that the fracture is delayed from 8.6 kg/mm(2) at 50 s and 100 g at room temperature to 4 kg/mm(2) at 90 s and 100 g at 423 K. Differential thermal analysis was used to investigate the melting characteristics of the alloy (m.p. similar to 214 degrees C). The resistivity is also determined for samples thermally and non-thermally treated.

  14. Phase structure and magnetic properties of Mn{sub 3}Ga{sub 2} alloy

    SciTech Connect

    Lu, Q. M. Yu, F.; Yue, M.; Zhang, H. G.; Li, Y. Q.; Liu, Y. Q.; Zhang, J. X.; Yan, X. L.

    2014-05-07

    In this paper, Mn{sub 3}Ga{sub 2} alloys with high saturation magnetization and high Curie temperatures were prepared by levitation melting high pure Mn and Ga elements followed by annealing. The effect of annealing temperature on phase structure and magnetic properties was investigated by means of x-ray diffraction and a vibrating sample magnetometer. A single phase alloy Mn{sub 3}Ga{sub 2}, which has tetragonal P4/mmm structure, was obtained with an annealing temperature of 773 K and annealing time of 24 h. The hysteresis curve of its easy axis for this single phase alloy shows that the room temperature coercivity and saturation magnetization are 4.18 kOe and 50.81 emu/g, respectively. The thermomagnetic curves indicate that the Curie temperature is about 650 K and a phase transformation occurs above 823 K.

  15. Optimization of the random multilayer structure to break the random-alloy limit of thermal conductivity

    SciTech Connect

    Wang, Yan; Gu, Chongjie; Ruan, Xiulin

    2015-02-16

    A low lattice thermal conductivity (κ) is desired for thermoelectrics, and a highly anisotropic κ is essential for applications such as magnetic layers for heat-assisted magnetic recording, where a high cross-plane (perpendicular to layer) κ is needed to ensure fast writing while a low in-plane κ is required to avoid interaction between adjacent bits of data. In this work, we conduct molecular dynamics simulations to investigate the κ of superlattice (SL), random multilayer (RML) and alloy, and reveal that RML can have 1–2 orders of magnitude higher anisotropy in κ than SL and alloy. We systematically explore how the κ of SL, RML, and alloy changes relative to each other for different bond strength, interface roughness, atomic mass, and structure size, which provides guidance for choosing materials and structural parameters to build RMLs with optimal performance for specific applications.

  16. Fractal structures and their computer simulation in rapidly quenched Ai-Mn alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Meng; Hong, Chunyong; Dai, Hong; Yang, Pinsheng; Tan, Yuxi

    1999-02-01

    The microstructure of rapidly quenched A1-Mn alloys were studied by TEM and SEM. The icosahedral phase in AI-Mn alloys was observed to show various types of fractal morphologies, which may be classified into four kinds: 1) dendritic shape, 2) flower-like shape, 3) granular shape and 4) grain-oscillation shape. After being digitized by a computer, the fractal dimensions (D) of these morphologies were calculated. Based on the traditional diffusion limited aggregation (DLA) model computer simulations were made with two-seeded and many-seeded clusters, which reflect the growing mechanism of some fractal structures in A1-Mn alloys. It is suggested that these fractal structures are formed by many icosahedral particles about 20 nm in size aggregating during the rapid quenching process.

  17. Pressure-induced structural transition of CdxZn1-xO alloys

    NASA Astrophysics Data System (ADS)

    Chen, Yabin; Zhang, Shuai; Gao, Weiwei; Ke, Feng; Yan, Jinyuan; Saha, Bivas; Ko, Changhyun; Suh, Joonki; Chen, Bin; Ager, Joel W.; Walukiewicz, Wladek; Jeanloz, Raymond; Wu, Junqiao

    2016-04-01

    CdxZn1-xO alloys, as a transparent conducting oxide, have recently attracted much attention for potential optoelectronic applications. In this letter, we report a hydrostatic pressure-induced phase transition of CdxZn1-xO alloys from the wurtzite to the rocksalt structure and its phase diagram probed using a diamond anvil cell. It is found that the transition pressure, determined by changes in optical and structural properties, depends sensitively on the composition. As the Cd content increases, the critical pressure decreases, until at x = 0.67 where the alloy is intrinsically stable in the rocksalt phase even at ambient pressure. The wurtzite phase is light emitting with a direct bandgap that slightly widens with increasing pressure, while the rocksalt phase has a much wider bandgap that is indirect. The pressure-sensitive light emission and phase transition may find potential applications in fields such as stress sensing and energy storage.

  18. Microstructural Evolution and Creep-Rupture Behavior of Fusion Welds Involving Alloys for Advanced Ultrasupercritical Power Generation

    NASA Astrophysics Data System (ADS)

    Bechetti, Daniel H., Jr.

    Projections for large increases in the global demand for electric power produced by the burning of fossil fuels, in combination with growing environmental concerns surrounding these fuel sources, have sparked initiatives in the United States, Europe, and Asia aimed at developing a new generation of coal fired power plant, termed Advanced Ultrasupercritical (A-USC). These plants are slated to operate at higher steam temperatures and pressures than current generation plants, and in so doing will offer increased process cycle efficiency and reduced greenhouse gas emissions. Several gamma' precipitation strengthened Ni-based superalloys have been identified as candidates for the hottest sections of these plants, but the microstructural instability and poor creep behavior (compared to wrought products) of fusion welds involving these alloys present significant hurdles to their implementation and a gap in knowledge that must be addressed. In this work, creep testing and in-depth microstructural characterization have been used to provide insight into the long-term performance of these alloys. First, an investigation of the weld metal microstructural evolution as it relates to creep strength reductions in A-USC alloys INCONELRTM 740, NIMONICRTM 263 (INCONEL and NIMONIC are registered trademarks of Special Metals Corporation), and HaynesRTM 282RTM (Haynes and 282 are registered trademarks of Haynes International) was performed. gamma'-precipitate free zones were identified in two of these three alloys, and their development was linked to the evolution of phases that precipitate at the expense of gamma'. Alloy 282 was shown to avoid precipitate free zone formation because the precipitates that form during long term aging in this alloy are poor in the gamma'-forming elements. Next, the microstructural evolution of INCONELRTM 740H (a compositional variant of alloy 740) during creep was investigated. Gleeble-based interrupted creep and creep-rupture testing was used to

  19. Laser-induced surface alloying in nanosized Ni/Ti multilayer structures

    NASA Astrophysics Data System (ADS)

    Petrović, Suzana; Radak, B.; Peruško, D.; Pelicon, P.; Kovač, J.; Mitrić, M.; Gaković, B.; Trtica, M.

    2013-01-01

    Laser-induced alloying effects on the composition and structure of different Ni/Ti multilayer structures were studied. Thin films composed of one, five, and ten (Ni/Ti) bilayers were deposited by DC ion sputtering on (1 0 0) Si wafers. Laser irradiations were performed by 150 ps pulses of a Nd:YAG laser operating at 1064 nm. The samples were characterized by Rutherford backscattering spectrometry (RBS), Auger electron spectroscopy (AES), X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM). At a laser fluence of 0.9 J cm-2, interaction between Ni and Ti layers was initiated, and NiTi alloy formed in 5- and 10-bilayered samples. Progressed alloying was achieved at a laser fluence of 1.2 J cm-2. The alloy was formed mostly within the heat affected zone (HAZ) of the sample. Surface segregation of titanium was followed by formation of a 25 nm thin TiO2 film on the surface of the multilayered structures. In addition, parallel periodic surface structures on the surfaces of the 5- and 10-bilayered samples were clearly recorded. Their period in the case of the 5-bilayered system (0.77 μm) agrees very well with the predictions of the common theory, whereas, in the case of the 10-bilayered system, two periods of such structures are observed (1.43 μm and 0.4 μm), and none of them coincides with the prediction.

  20. Microscopic structural change in a liquid Fe-C alloy of ~5 GPa

    DOE PAGES

    Shibazaki, Yuki; Kono, Yoshio; Fei, Yingwei

    2015-07-04

    The structure of a liquid Fe-3.5 wt% C alloy is examined for up to 7.2 GPa via multiangle energy-dispersive X-ray diffraction using a Paris-Edinburgh type large-volume press. X-ray diffraction data show clear changes in the pressure-dependent peak positions of structure factor and reduced pair distribution function at 5GPa. These results suggest that the liquid Fe-3.5wt%C alloys change structurally at approximately 5GPa. This finding serves as a microscopic explanation for the alloy’s previously observed density change at the same pressure. The pressure dependencies of the nearest and second neighbor distances of the liquid Fe-3.5 wt% C alloy are similar to thosemore » of liquid Fe which exhibits a structural change near the bcc-fcc-liquid triple point (5.2GPa and 1991 K). Here, similarities between Fe-3.5wt% C and Fe suggest that a density change also occurs in liquid Fe and that this structural change extends to other Fe-light element alloys.« less

  1. Microscopic structural change in a liquid Fe-C alloy of ~5 GPa

    SciTech Connect

    Shibazaki, Yuki; Kono, Yoshio; Fei, Yingwei

    2015-07-04

    The structure of a liquid Fe-3.5 wt% C alloy is examined for up to 7.2 GPa via multiangle energy-dispersive X-ray diffraction using a Paris-Edinburgh type large-volume press. X-ray diffraction data show clear changes in the pressure-dependent peak positions of structure factor and reduced pair distribution function at 5GPa. These results suggest that the liquid Fe-3.5wt%C alloys change structurally at approximately 5GPa. This finding serves as a microscopic explanation for the alloy’s previously observed density change at the same pressure. The pressure dependencies of the nearest and second neighbor distances of the liquid Fe-3.5 wt% C alloy are similar to those of liquid Fe which exhibits a structural change near the bcc-fcc-liquid triple point (5.2GPa and 1991 K). Here, similarities between Fe-3.5wt% C and Fe suggest that a density change also occurs in liquid Fe and that this structural change extends to other Fe-light element alloys.

  2. Modifying structure and properties of nickel alloys by nanostructured composite powders

    NASA Astrophysics Data System (ADS)

    Cherepanov, A. N.; Ovcharenko, V. E.; Liu, G.; Cao, L.

    2015-01-01

    The article presents the results of an experimental study of the influence of powder nanomodifiers of refractory compounds on the mechanical properties, macro- and microstructure of heat-resistant alloys ZhS-6K and Inconel 718. It is shown that the introduction of nanomodifiers into the melt leads to the refinement of the alloy structure: the average grain size decreases 1.5-2 times, and their morphology becomes similar to equiaxial at significant reduction of the particle size in the carbide phase. The service life of ZhS-6K alloy under cyclic loading at 600°C increases 2.7 times, and at 975 °C by 40 %, and relative elongation increases more than twice. The mechanical properties of Inconel 718 significantly increase: long-term strength at 650 °C increases 1.5-2 times, and the number of cycles before the collapse at 482 °C grows more than three times. It has been found out that addition of nanomodifiers to the melt, in alloys, forms clusters of particles of refractory compounds at borders and joints of the formed grain structure that may help slowing down the processes of recrystallization (prevents the increase in the size of the contacting grains by their associations) and stabilizes the strength properties of the alloys at higher temperatures.

  3. THE STRUCTURAL AND ELECTRONIC PROPERTIES OF BNxAs1-x ALLOYS

    NASA Astrophysics Data System (ADS)

    Mohammad, Rezek; Katircioğlu, Şenay

    2012-10-01

    The structural and electronic properties of BNxAs1-x alloys have been investigated in the total range of nitrogen by the FP-LAPW method based on DFT within the EV-PW-GGA scheme. The equilibrium lattice constants, bulk moduli, first-order pressure derivatives of the bulk moduli, and cohesive energies have been obtained by total energy calculations of the alloys after both volume and geometry optimizations. The large bowing parameters found for the lattice constants and bulk moduli have demonstrated that the validity of Vegard's linear rule in the definitions of these structural features of the BNxAs1-x alloys is broken. The energy bands and the effective masses of the alloys have been calculated as a function of nitrogen concentration. The large bowing displayed by the variation of the energy gaps has indicated the band gap engineering capacity of the BNxAs1-x alloys and again in deviations from Vegard's linear rule. The effective electron masses calculated either at the edges of the conduction bands or along the directions approaching the edges of the conduction bands are all found to be small with respect to the effective electron masses in the BAs and BN compounds calculated at the Δmin and X points, respectively.

  4. Zener Pinning of Grain Boundaries and Structural Stability of Immiscible Alloys

    NASA Astrophysics Data System (ADS)

    Koju, R. K.; Darling, K. A.; Kecskes, L. J.; Mishin, Y.

    2016-06-01

    Immiscible Cu-Ta alloys produced by mechanical alloying are currently the subject of intensive research due to their mechanical strength combined with extraordinary structural stability at high temperatures. Previous experimental and simulation studies suggested that grain boundaries (GBs) in Cu-Ta alloys are stabilized by Ta nano-clusters coherent with the Cu matrix. To better understand the stabilization effect of Ta, we performed atomistic computer simulations of GB-cluster interactions in Cu-Ta alloys with various compositions and GB velocities. The study focuses on a single plane GB driven by an applied shear stress due to the shear-coupling effect. The results of the simulations are in close quantitative agreement with the Zener model of GB pinning. This agreement and the large magnitude of the unpinning stress confirm that the structural stability of these alloys is due to the drastically decreased GB mobility rather than a reduction in GB energy. For comparison, we simulated GB motion in a random solid solution. While the latter also reduces the GB mobility, the effect is not as strong as in the presence of Ta clusters. GB motion in the random solution itself induces precipitation of Ta clusters due to short-circuit diffusion of Ta in GBs, suggesting a possible mechanism of cluster formation inside the grains.

  5. Advances in Computational Stability Analysis of Composite Aerospace Structures

    SciTech Connect

    Degenhardt, R.; Araujo, F. C. de

    2010-09-30

    European aircraft industry demands for reduced development and operating costs. Structural weight reduction by exploitation of structural reserves in composite aerospace structures contributes to this aim, however, it requires accurate and experimentally validated stability analysis of real structures under realistic loading conditions. This paper presents different advances from the area of computational stability analysis of composite aerospace structures which contribute to that field. For stringer stiffened panels main results of the finished EU project COCOMAT are given. It investigated the exploitation of reserves in primary fibre composite fuselage structures through an accurate and reliable simulation of postbuckling and collapse. For unstiffened cylindrical composite shells a proposal for a new design method is presented.

  6. Advanced organic composite materials for aircraft structures: Future program

    NASA Technical Reports Server (NTRS)

    1987-01-01

    Revolutionary advances in structural materials have been responsible for revolutionary changes in all fields of engineering. These advances have had and are still having a significant impact on aircraft design and performance. Composites are engineered materials. Their properties are tailored through the use of a mix or blend of different constituents to maximize selected properties of strength and/or stiffness at reduced weights. More than 20 years have passed since the potentials of filamentary composite materials were identified. During the 1970s much lower cost carbon filaments became a reality and gradually designers turned from boron to carbon composites. Despite progress in this field, filamentary composites still have significant unfulfilled potential for increasing aircraft productivity; the rendering of advanced organic composite materials into production aircraft structures was disappointingly slow. Why this is and research and technology development actions that will assist in accelerating the application of advanced organic composites to production aircraft is discussed.

  7. Advanced reliability methods for structural evaluation

    NASA Technical Reports Server (NTRS)

    Wirsching, P. H.; Wu, Y.-T.

    1985-01-01

    Fast probability integration (FPI) methods, which can yield approximate solutions to such general structural reliability problems as the computation of the probabilities of complicated functions of random variables, are known to require one-tenth the computer time of Monte Carlo methods for a probability level of 0.001; lower probabilities yield even more dramatic differences. A strategy is presented in which a computer routine is run k times with selected perturbed values of the variables to obtain k solutions for a response variable Y. An approximating polynomial is fit to the k 'data' sets, and FPI methods are employed for this explicit form.

  8. The use of slow strain rate technique for studying stress corrosion cracking of an advanced silver-bearing aluminum-lithium alloy

    SciTech Connect

    Frefer, Abdulbaset Ali; Raddad, Bashir S.

    2013-12-16

    In the present study, stress corrosion cracking (SCC) behavior of naturally aged advanced silver-bearing Al-Li alloy in NaCl solution was investigated using slow strain rate test (SSRT) method. The SSRT’s were conducted at different strain rates and applied potentials at room temperature. The results were discussed based on percent reductions in tensile elongation in a SCC-causing environment over those in air tended to express the SCC susceptbility of the alloy under study at T3. The SCC behavior of the alloy was also discussed based on the microstructural and fractographic examinations.

  9. Identification of salt-alloy combinations for thermal energy storage applications in advanced solar dynamic power systems

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.; Misra, A. K.

    1987-01-01

    Thermodynamic calculations based on the available data for flouride salt systems reveal that a number of congruently melting compositions and eutectics exist which have the potential to meet the lightweight, high energy storage requirements imposed for advanced solar dynamic systems operating between about 1000 and 1400 K. Compatibility studies to determine suitable containment alloys to be used with NaF-22CaF2-13MgF2, NaF-32CaF2, and NaF-23MgF2 have been conducted at the eutectic temperature + 25 K for each system. For these three NaF-based eutectics, none of the common, commercially available high temperature alloys appear to offer adequate corrosion resistance for a long lifetime; however mild steel, pure nickel and Nb-1Zr could prove useful. These latter materials suggest the possibility that a strong, corrosion resistant, nonrefractory, elevated temperature alloy based on the Ni-Ni3Nb system could be developed.

  10. Advances in hadronic structure from Lattice QCD

    NASA Astrophysics Data System (ADS)

    Constantinou, Martha

    2017-01-01

    Understanding nucleon structure is considered a milestone of hadronic physics and new facilities are planned devoted to its study. A future Electron-Ion-Collider proposed by the scientific community will greatly deepen our knowledge on the fundamental constituents of the visible world. To achieve this goal, a synergy between the experimental and theoretical sectors is imperative, and Lattice QCD is in a unique position to provide input from first principle calculations. In this talk we will discuss recent progress in nucleon structure from Lattice QCD, focusing on the evaluation of matrix elements using state-of-the-art simulations with pion masses at their physical value. The axial form factors, electromagnetic radii, the quark momentum fraction and the spin content of the nucleon will be discussed. We will also highlight quantities that may guide New Physics searches, such as the scalar and tensor charges. Finally, we will give updates on a new direct approach to compute quark parton distributions functions on the lattice.

  11. Core-shell structured titanium-nitrogen alloys with high strength, high thermal stability and good plasticity.

    PubMed

    Zhang, Y S; Zhao, Y H; Zhang, W; Lu, J W; Hu, J J; Huo, W T; Zhang, P X

    2017-01-06

    Multifunctional materials with more than two good properties are widely required in modern industries. However, some properties are often trade-off with each other by single microstructural designation. For example, nanostructured materials have high strength, but low ductility and thermal stability. Here by means of spark plasma sintering (SPS) of nitrided Ti particles, we synthesized bulk core-shell structured Ti alloys with isolated soft coarse-grained Ti cores and hard Ti-N solid solution shells. The core-shell Ti alloys exhibit a high yield strength (~1.4 GPa) comparable to that of nanostructured states and high thermal stability (over 1100 °C, 0.71 of melting temperature), contributed by the hard Ti-N shells, as well as a good plasticity (fracture plasticity of 12%) due to the soft Ti cores. Our results demonstrate that this core-shell structure offers a design pathway towards an advanced material with enhancing strength-plasticity-thermal stability synergy.

  12. Core-shell structured titanium-nitrogen alloys with high strength, high thermal stability and good plasticity

    NASA Astrophysics Data System (ADS)

    Zhang, Y. S.; Zhao, Y. H.; Zhang, W.; Lu, J. W.; Hu, J. J.; Huo, W. T.; Zhang, P. X.

    2017-01-01

    Multifunctional materials with more than two good properties are widely required in modern industries. However, some properties are often trade-off with each other by single microstructural designation. For example, nanostructured materials have high strength, but low ductility and thermal stability. Here by means of spark plasma sintering (SPS) of nitrided Ti particles, we synthesized bulk core-shell structured Ti alloys with isolated soft coarse-grained Ti cores and hard Ti-N solid solution shells. The core-shell Ti alloys exhibit a high yield strength (~1.4 GPa) comparable to that of nanostructured states and high thermal stability (over 1100 °C, 0.71 of melting temperature), contributed by the hard Ti-N shells, as well as a good plasticity (fracture plasticity of 12%) due to the soft Ti cores. Our results demonstrate that this core-shell structure offers a design pathway towards an advanced material with enhancing strength-plasticity-thermal stability synergy.

  13. Core-shell structured titanium-nitrogen alloys with high strength, high thermal stability and good plasticity

    PubMed Central

    Zhang, Y. S.; Zhao, Y. H.; Zhang, W.; Lu, J. W.; Hu, J. J.; Huo, W. T.; Zhang, P. X.

    2017-01-01

    Multifunctional materials with more than two good properties are widely required in modern industries. However, some properties are often trade-off with each other by single microstructural designation. For example, nanostructured materials have high strength, but low ductility and thermal stability. Here by means of spark plasma sintering (SPS) of nitrided Ti particles, we synthesized bulk core-shell structured Ti alloys with isolated soft coarse-grained Ti cores and hard Ti-N solid solution shells. The core-shell Ti alloys exhibit a high yield strength (~1.4 GPa) comparable to that of nanostructured states and high thermal stability (over 1100 °C, 0.71 of melting temperature), contributed by the hard Ti-N shells, as well as a good plasticity (fracture plasticity of 12%) due to the soft Ti cores. Our results demonstrate that this core-shell structure offers a design pathway towards an advanced material with enhancing strength-plasticity-thermal stability synergy. PMID:28059150

  14. Half-metallic alloys: electronic structure, magnetism and spin polarization.

    PubMed

    Dederichs, P H; Galanakis, I; Mavropoulos, Ph

    2005-01-01

    Using the state-of-the-art screened Korringa-Kohn-Rostoker Green function method we study the electronic and magnetic properties of NiMnSb and similar Heusler alloys. We show that all these compounds are half-metals, e.g. the minority-spin band is semiconducting and the Fermi level falls within this gap resulting in 100% spin polarization at the Fermi level. The total spin moment M(t) shows the so-called Slater-Pauling behaviour and scales with the total valence charge Z(t) following the rule M(t) = Z(t) - 18 for half and M(t) = Z(t) - 24 for full Heusler alloys. These rules are connected to the origin of the gap. Finally we show that the inclusion of the spin-orbit interaction in our calculations kills the half-metallic gap but the spin-polarization at the Fermi level can be still very high, approximately 99% for NiMnSb, but much lower for a half-metallic compound like zinc-blende MnBi (77%).

  15. Recent advancement in optical fiber sensing for aerospace composite structures

    NASA Astrophysics Data System (ADS)

    Minakuchi, Shu; Takeda, Nobuo

    2013-12-01

    Optical fiber sensors have attracted considerable attention in health monitoring of aerospace composite structures. This paper briefly reviews our recent advancement mainly in Brillouin-based distributed sensing. Damage detection, life cycle monitoring and shape reconstruction systems applicable to large-scale composite structures are presented, and new technical concepts, "smart crack arrester" and "hierarchical sensing system", are described as well, highlighting the great potential of optical fiber sensors for the structural health monitoring (SHM) field.

  16. XANES (X-ray Absorption Near Edge Structure) investigation of cerium as an inhibitor for Al alloys

    SciTech Connect

    Davenport, A.J.; Isaacs, H.S. ); Kendig, M.W. . Science Center)

    1991-01-01

    Cerium ions are under investigation as possible replacements for toxic chromates. The use of cerium ions as corrosion inhibitors for aluminum alloys is investigated using XANES (x-ray absorption near edge structure). On immersion in a dilute solution of cerium ions, cerium is incorporated into the oxide films on aluminum alloys in either the 3- or 4-valent state depending upon the alloy and on the surface preparation. 7 refs., 2 figs.

  17. First-principles study of structural, elastic, and thermodynamic properties of ZrHf alloy

    NASA Astrophysics Data System (ADS)

    Wei, Zhao; Zhai, Dong; Shao, Xiao-Hong; Lu, Yong; Zhang, Ping

    2015-04-01

    Structural parameters, elastic constants, and thermodynamic properties of ordered and disordered solid solutions of ZrHf alloys are investigated through first-principles calculations based on density-functional theory (DFT). The special quasi-random structure (SQS) method is used to model the disordered phase as a single unit cell, and two lamella structures are generated to model the ordered alloys. Small strains are applied to the unit cells to measure the elastic behavior and mechanical stability of ZrHf alloys and to obtain the independent elastic constants by the stress-strain relationship. Phonon dispersions and phonon density of states are presented to verify the thermodynamic stability of the considered phases. Our results show that both the ordered and disordered phases of ZrHf alloys are structurally stable. Based on the obtained phonon frequencies, thermodynamic properties, including Gibbs free energy, entropy, and heat capacity, are predicted within the quasi-harmonic approximation. It is verified that there are no obvious differences in energy between ordered and disordered phases over a wide temperature range. Project supported by the National Natural Science Foundation of China (Grant No. 51102009) and the Long-Term Subsidy Mechanism from the Ministry of Finance and the Ministry of Education of China.

  18. Deformation and Damage Studies for Advanced Structural Materials

    NASA Technical Reports Server (NTRS)

    2005-01-01

    Advancements made in understanding deformation and damage of advanced structural materials have enabled the development of new technologies including the attainment of a nationally significant NASA Level 1 Milestone and the provision of expertise to the Shuttle Return to Flight effort. During this collaborative agreement multiple theoretical and experimental research programs, facilitating safe durable high temperature structures using advanced materials, have been conceived, planned, executed. Over 26 publications, independent assessments of structures and materials in hostile environments, were published within this agreement. This attainment has been recognized by 2002 Space Flight Awareness Team Award, 2004 NASA Group Achievement Award and 2003 and 2004 OAI Service Awards. Accomplishments in the individual research efforts are described as follows.

  19. Morphology, deformation, and defect structures of TiCr{sub 2} in Ti-Cr alloys

    SciTech Connect

    Chen, K.C.; Allen, S.M.; Livingston, J.D.

    1992-12-31

    The morphologies and defect structures of TiCr{sub 2} in several Ti-Cr alloys have been examined by optical metallography, x-ray diffraction, and transmission electron microscopy (TEM), in order to explore the room-temperature deformability of the Laves phase TiCr{sub 2}. The morphology of the Laves phase was found to be dependent upon alloy composition and annealing temperature. Samples deformed by compression have also been studied using TEM. Comparisons of microstructures before and after deformation suggest an increase in twin, stacking fault, and dislocation density within the Laves phase, indicating some but not extensive room-temperature deformability.

  20. Fabrication of structural components from commercial aluminum alloys using superplastic forming

    NASA Technical Reports Server (NTRS)

    Hales, S. J.; Bales, T. T.; Shinn, J. M.; James, W. F.

    1990-01-01

    SPF technology was used to fabricate structural components from the 7475 Al and 8090 Al-Li commercial alloys. Gas-pressurization cycles were established for SPF three-hat stiffener configurations on the basis of uniaxial data and component-geometry considerations. It is established that higher forming rates than the optimum strain rates selected from the uniaxial data for each alloy could be used in the later stages of forming without reducing SPF components' dimensional conformity. Cavitation was precluded through the use of back pressure during forming.

  1. Chemical, electronic, and magnetic structure of LaFeCoSi alloy: Surface and bulk properties

    SciTech Connect

    Lollobrigida, V.; Basso, V.; Kuepferling, M.; Coïsson, M.; Olivetti, E. S.; Celegato, F.; Borgatti, F.; Torelli, P.; Panaccione, G.; Tortora, L.; Stefani, G.; Offi, F.

    2014-05-28

    We investigate the chemical, electronic, and magnetic structure of the magnetocaloric LaFeCoSi compound with bulk and surface sensitive techniques. We put in evidence that the surface retains a soft ferromagnetic behavior at temperatures higher than the Curie temperature of the bulk due to the presence of Fe clusters at the surface only. This peculiar magnetic surface effect is attributed to the exchange interaction between the ferromagnetic Fe clusters located at the surface and the bulk magnetocaloric alloy, and it is used here to monitor the magnetic properties of the alloy itself.

  2. Inelastic deformation and dislocation structure of a nickel alloy - Effects of deformation and thermal histories

    NASA Technical Reports Server (NTRS)

    Chan, K. S.; Page, R. A.

    1988-01-01

    Inelastic deformation behavior of the cast Ni-base alloy, B1900 + Hf, was investigated using data from step-temperature tensile tests and thermomechanical cyclic tests in the temperature ranges 538-760 C and 760-982 C. The deformation results were correlated with the dislocation structures of deformed specimens, identified by TEM. It was found that, in the 760-982 C temperature range, there are no thermal history effects in the inelastic deformation behavior of B1900 + Hf. In the 538-760 range, anomalous cyclic hardening and, possibly, thermal history effects were observed in thermomechanically deformed alloy, caused by sessile (010) dislocations in the gamma-prime phase.

  3. Effect of rhenium on the structure and properties of the weld metal of a molybdenum alloy

    NASA Technical Reports Server (NTRS)

    Dyachenko, V. V.; Morozov, B. P.; Tylkina, M. A.; Savitskiy, Y. M.; Nikishanov, V. V.

    1984-01-01

    The structure and properties of welds made in molybdenum alloy VM-1 as a function of rhenium concentrations in the weld metal were studied. Rhenium was introduced into the weld using rhenium wire and tape or wires of Mo-47Re and Mo-52Re alloys. The properties of the weld metal were studied by means of metallographic techniques, electron microscopy, X-ray analysis, and autoradiography. The plasticity of the weld metal sharply was found to increase with increasing concentration of rhenium up to 50%. During welding, a decarburization process was observed which was more pronounced at higher concentrations of rhenium.

  4. The role of strain in the surface structures of III-V alloyed semiconductor films

    NASA Astrophysics Data System (ADS)

    Bickel, Jessica E.

    As length scales continue to decrease, it is vital to understand the fundamental physical parameters governing surfaces and surface interactions. In semiconductors particularly, surface reconstructions are known to impact film growth, bulk atomic ordering and the development of interfacial structure, all of which can drastically impact device growth. While the parameters that determine surface reconstructions in homoepitaxially grown films are well known and understood, those that impact alloy film growth are less studied. This work examines the impact of strain on alloy surface reconstructions, using the III-V semiconductors as a model system for any covalently bonded crystal structure. The presence of surface reconstruction coexistence in both mixed cation and mixed anion systems suggests that localized strain fields on alloy surfaces stabilize elastic relaxation at boundaries, resulting in more complex surface structures than those seen on binary, unstrained films. Atomic size mismatch strain is shown to induce an ordering in alloyed surface reconstructions that is not seen in the non-alloyed constituent surfaces. Lattice mismatch strain is shown to both stabilize new reconstructions not common to the homoepitaxial system and to induce surface reconstruction coexistence on alloy surfaces. The supplied flux of material is shown to affect the kinetics of transformation between the two coexisting surface reconstructions and an incorporation model for material on the alloy surface is developed. The effects of strained surface reconstructions on subsequent film growth is explored and it is shown that identical films grown on two different surfaces have very different strain relaxation profiles, surface topographies and defect structures. The strain fields of surface reconstructions and defects are also shown to interact which may have an impact on the insertion of dislocations in these films. Combined together, this deep understanding of the role that alloy induced

  5. Photonic crystal alloys: a new twist in controlling photonic band structure properties.

    PubMed

    Kim, Hee Jin; Kim, Dong-Uk; Roh, Young-Geun; Yu, Jaejun; Jeon, Heonsu; Park, Q-Han

    2008-04-28

    We identified new photonic structures and phenomenon that are analogous to alloy crystals and the associated electronic bandgap engineering. From a set of diamond-lattice microwave photonic crystals of randomly mixed silica and alumina spheres but with a well defined mixing composition, we observed that both bandedges of the L-point bandgap monotonically shifted with very little bowing as the composition was varied. The observed results were in excellent agreement with the virtual crystal approximation theory originally developed for electronic properties of alloy crystals. This result signifies the similarity and correspondence between photonics and electronics.

  6. Effects of the Al content on pore structures of porous TieAl alloys

    SciTech Connect

    Jaing, Y; He, Y H; Xu, N P; Zou, J; Huang, B; Lui, C T

    2008-01-01

    Porous TieAl alloys with different nominal compositions were fabricated through a reactive synthesis of Ti and Al elemental powders. It has been found that the pore parameters vary with the Al contents, indicating that the nature of the pores can be manipulated through changing the Al contents. In addition, detailed structural characterizations showed that the fabricated porous TieAl alloys can have three crystalline phases (i.e., a2-Ti3Al, g-TiAl, and TiAl3) when using different compositions. The fundamental reasons behind these phenomena have been explored.

  7. Fine precipitation scenarios of AlZnMg(Cu) alloys revealed by advanced atomic-resolution electron microscopy study Part II: Fine precipitation scenarios in AlZnMg(Cu) alloys

    SciTech Connect

    Liu, J.Z.; Chen, J.H.; Liu, Z.R.; Wu, C.L.

    2015-01-15

    Although they are among the most important precipitation-hardened materials for industry applications, the high-strength AlZnMg(Cu) alloys have thus far not yet been understood adequately about their underlying precipitation scenarios in relation with the properties. This is partly due to the fact that the structures of a number of different precipitates involved in the alloys are unknown, and partly due to the complexity that the precipitation behaviors of the alloys may be closely related to the alloy's composition. In Part I of the present study, we have determined all the unknown precipitate structures in the alloys. Here in Part II, using atomic-resolution electron microscopy in association with the first principles energy calculations, we further studied and correlated the phase/structure transformation/evolution among these hardening precipitates in relation with the alloy's composition. It is shown that there are actually two coexisting classes of hardening precipitates in these alloys: the first class includes the η′-precipitates and their early-stage Guinier–Preston (GP-η′) zones; the second class includes the precursors of the equilibrium η-phase (referred to η{sub p}, or η-precursor) and their early-stage Guinier–Preston (GP-η{sub p}) zones. The two coexisting classes of precipitates correspond to two precipitation scenarios. - Highlights: • We determine and verify all the key precipitate structures in AlMgZn(Cu) alloys. • We employ aberration-corrected scanning transmission electron microscopy (STEM). • We use aberration-corrected high-resolution TEM (HRTEM) for the investigations. • We obtain atomic-resolution images of the precipitates and model their structures. • We refine all precipitate structures with quantitative image simulation analysis. • The hardening precipitates in AlZnMg alloys shall be classified into two groups. • Two precipitation scenarios coexist in the alloys. • The precipitation behavior of such an

  8. Automated S/TEM metrology on advanced semiconductor gate structures

    NASA Astrophysics Data System (ADS)

    Strauss, M.; Arjavac, J.; Horspool, D. N.; Nakahara, K.; Deeb, C.; Hobbs, C.

    2012-03-01

    Alternate techniques for obatining metrology data from advanced semiconductor device structures may be required. Automated STEM-based dimensional metrology (CD-STEM) was developed for complex 3D geometries in read/write head metrology in teh hard disk drive industry. It has been widely adopted, and is the process of record for metrology. Fully automated S/TEM metrology on advanced semiconductor gate structures is viable, with good repeatability and robustness. Consistent automated throughput of 10 samples per hour was achieved. Automated sample preparation was developed with sufficient throughput and quality to support the automated CD-STEM.

  9. ITER structural design criteria and their extension to advanced fusion reactor blankets.

    SciTech Connect

    Kalnin, G.; Majumdar, S.

    1999-09-03

    Application of the new low-temperature-design rules of the ITER Structural Design Criteria (ISDC) is illustrated by considering copper alloys that, according to recent data, are particularly prone to irradiation embrittlement at relatively low fluences at certain temperatures, Allowable stresses are derived and the impact of the embrittlement on allowable surface heat flux of a simple first-wall/limiter design is demonstrated. High-temperature-design rules of ISDC are applied to EVOLVE (Evaporation Of Lithium and Vapor Extraction), a blanket design concept currently being investigated under the U.S. APEX (Advanced Power Extraction) program. One version of this concept envisions the use of a series of parallel tungsten tubes (first-wall) that are cooled internally by lithium vapor, typically. at 1200 C. A single tungsten first-wall tube is considered for thermal and stress analyses by finite-element method.

  10. Structural and corrosion protection properties of electrochemically deposited nano-sized Zn-Ni alloy coatings

    NASA Astrophysics Data System (ADS)

    Tozar, A.; Karahan, İ. H.

    2014-11-01

    Zn-Ni alloy coatings were fabricated galvanostatically by applying varied current densities from 10 to 30 mA cm-2. Surface morphology of the coatings was examined with SEM. Crystal structure of the coatings was studied with X-ray diffraction spectroscopy (XRD). Compositions of the coatings were determined by atomic absorption spectroscopy (AAS). Corrosion protection properties studied using open circuit potential (OCP) measurements, potentiodynamic polarization measurements (Tafel), electrochemical impedance spectroscopy (EIS). Deposited alloy coatings were compact and nano-sized. Crystallite sizes of the coatings were varying from 26 nm to 36 nm. Nickel content of the samples were increased by increasing current densities and varied from 6.7 to 18.9 wt.%. Best corrosion protection performance was seen on the sample obtained at 30 mA cm-2. Our results are considerably encouraging for protection of mild steel against corrosion by obtained Zn-Ni alloys.

  11. Improvement of Structural and Mechanical Properties of Al-1100 Alloy via Friction Stir Processing

    NASA Astrophysics Data System (ADS)

    Mosallaee, M.; Dehghan, M.

    2014-10-01

    In the present study, the relationship between structural and mechanical properties of friction stir processed Al-1100 alloy and process parameters (tool rotation rate: ω and traverse speed: ν) was studied to get an better understanding and optimizing the friction stir processing (FSP) condition of this alloy. Microstructural studies revealed that increasing of ω up to 720 rpm resulted in grain refinement in the stirred zone (SZ), but higher increasing of ω caused grain growth in this zone. These variations of SZ grain size illustrated that the prevailing factor that determined the SZ grain size was plastic deformation at first and thereafter, peak temperature in the SZ. Mechanical properties investigations were in accordance with microstructural findings and illustrated that optimized FSP condition for Al-1100 alloy was 720 rpm and 20 mm/min. Optimized FSP condition resulted in a significant improvement of tensile strength and elongation up to 22 and 8% of those of base metal, respectively.

  12. Reactive wetting of amorphous silica by molten Al-Mg alloys and their interfacial structures

    NASA Astrophysics Data System (ADS)

    Shi, Laixin; Shen, Ping; Zhang, Dan; Jiang, Qichuan

    2016-07-01

    The reactive wetting of amorphous silica substrates by molten Al-Mg alloys over a wide composition range was studied using a dispensed sessile drop method in a flowing Ar atmosphere. The effects of the nominal Mg concentration and temperature on the wetting and interfacial microstructures were discussed. The initial contact angle for pure Al on the SiO2 surface was 115° while that for pure Mg was 35° at 1073 K. For the Al-Mg alloy drop, it decreased with increasing nominal Mg concentration. The reaction zone was characterized by layered structures, whose formation was primarily controlled by the variation in the alloy concentration due to the evaporation of Mg and the interfacial reaction from the viewpoint of thermodynamics as well as by the penetration or diffusion of Mg, Al and Si from the viewpoint of kinetics. In addition, the effects of the reaction and the evaporation of Mg on the movement of the triple line were examined. The spreading of the Al-Mg alloy on the SiO2 surface was mainly attributed to the formation of Mg2Si at the interface and the recession of the triple line to the diminishing Mg concentration in the alloy.

  13. Ultra-Fine Grain Structures Of Model Al-Mg-Si Alloys Produced By Hydrostatic Extrusion

    NASA Astrophysics Data System (ADS)

    Adamczyk-Cieślak, Bogusława; Mizera, Jarosław

    2011-01-01

    Microstructure and mechanical properties were studied in model Al-Mg-Si alloys (Al-1 % Mg-0.8% Si and Al-0.5% Mg-0.3% Si-wt %) deformed by hydrostatic extrusion (HE) to strains of 1.4 and 3.8. In these alloys the different percentage of two hardening second-phase precipitates (Mg2Si and Si) were observed. The microstructure was characterized by transmission electron microscopy and optical microscopy. The microstructure of the alloys in the initial state was built of coarse grains of an average diameter of ˜30 rim. The refined microstructure was examined qualitatively and quantitatively using the stereological method and a computer image analysis. The deformation-processed structures evolved very rapidly, forming ultrafine grained (UFG) materials with grains of about 0.4 μm. In addition, the grain refinement in the HE-treated materials has a substantial effect on their properties, such as the mechanical strength and micro-hardness which increase significantly. It has been found that, after ɛ = 3.8 in the Al-1% Mg-0.8% Si alloy, the micro-hardness increases approximately twofold. The yield stress is more than four times higher in the UFG alloys, in comparison to the initial state. Similar results were identified in the Al-0.5% Mg-0.3% Si. This is due to the very rapid refinement of the microstructure during the deformation and presence of second-phase particles.

  14. Aging Optimization of Aluminum-Lithium Alloy L277 for Application to Cryotank Structures

    NASA Technical Reports Server (NTRS)

    Sova, B. J.; Sankaran, K. K.; Babel, H.; Farahmand, B.; Cho, A.

    2003-01-01

    Compared with aluminum alloys such as 2219, which is widely used in space vehicle for cryogenic tanks and unpressurized structures, aluminum-lithium alloys possess attractive combinations of lower density and higher modulus along with comparable mechanical properties and improved damage tolerance. These characteristics have resulted in the successful use of the aluminum-lithium alloy 2195 for the Space Shuttle External Tank, and the consideration of newer U.S. aluminum-lithium alloys such as L277 and C458 for future space vehicles. A design of experiments aging study was conducted for plate and a limited study on extrusions. To achieve the T8 temper, Alloy L277 is typically aged at 290 F for 40 hours. In the study for plate, a two-step aging treatment was developed through a design of experiments study and the one step aging used as a control. Based on the earlier NASA studies on 2195, the first step aging temperature was varied between 220 F and 260 F. The second step aging temperatures was varied between 290 F and 310 F, which is in the range of the single-step aging temperature. For extrusions, two, single-step, and one two-step aging condition were evaluated. The results of the design of experiments used for the T8 temper as well as a smaller set of experiments for the T6 temper for plate and the results for extrusions will be presented.

  15. Ultra-Fine Grain Structures Of Model Al-Mg-Si Alloys Produced By Hydrostatic Extrusion

    SciTech Connect

    Adamczyk-Cieslak, Boguslawa; Mizera, Jaroslaw

    2011-01-17

    Microstructure and mechanical properties were studied in model Al-Mg-Si alloys (Al-1 % Mg-0.8% Si and Al-0.5% Mg-0.3% Si-wt %) deformed by hydrostatic extrusion (HE) to strains of 1.4 and 3.8. In these alloys the different percentage of two hardening second-phase precipitates (Mg{sub 2}Si and Si) were observed. The microstructure was characterized by transmission electron microscopy and optical microscopy. The microstructure of the alloys in the initial state was built of coarse grains of an average diameter of {approx}30 rim. The refined microstructure was examined qualitatively and quantitatively using the stereological method and a computer image analysis. The deformation-processed structures evolved very rapidly, forming ultrafine grained (UFG) materials with grains of about 0.4 {mu}m. In addition, the grain refinement in the HE-treated materials has a substantial effect on their properties, such as the mechanical strength and micro-hardness which increase significantly. It has been found that, after {epsilon} = 3.8 in the Al-1% Mg-0.8% Si alloy, the micro-hardness increases approximately twofold. The yield stress is more than four times higher in the UFG alloys, in comparison to the initial state. Similar results were identified in the Al-0.5% Mg-0.3% Si. This is due to the very rapid refinement of the microstructure during the deformation and presence of second-phase particles.

  16. The influence of simple and complex loading on structure changes in two-phase titanium alloy

    SciTech Connect

    Bylja, O.I.; Vasin, R.A.; Muravlev, A.V.; Chistjakov, P.V.; Ermachenko, A.G.; Karavaeva, M.V.

    1997-04-15

    Titanium alloys are widely used in modern engineering. The ensuring of property of articles and designs during their service is one of the most important problems. It is known that mechanical properties of metals and alloys are determined by their microstructure, formed in a process of thermomechanical treatment according to a history of strain and conditions of a thermal effect. The processing of the required properties of an alloy is an important and difficult task. Its decision assumes comprehensive study of the alloy strain history and determination of an effect of a complex loading that takes place almost in any real technological process. However, as a rule, investigations devoted to this question consider only results of uniaxial loading. This paper presents the results of experimental studies of the influence of a deformation path on changes in globular and lamellar structures of the two-phase titanium alloy Ti-6.5Al-3.5Mo-1.6Zr-0.27Si.

  17. Effect of cryogenic irradiation on NERVA structural alloys

    NASA Technical Reports Server (NTRS)

    Dixon, C. E.; Davidson, M. J.; Funk, C. W.

    1972-01-01

    Several alloys (Hastelloy X, AISI 347, A-286 bolts, Inconel 718, Al 7039-T63 and Ti-5Al-2.5Sn ELI) were irradiated in liquid nitrogen (140 R) to neutron fluences between 10 to the 17th power and 10 to the 19th power nvt (E greater than 1.0 Mev). After irradiation, tensile properties were obtained in liquid nitrogen without permitting any warmup except for some specimens which were annealed at 540 R. The usual trend of radiation damage typical for materials irradiated at and above room temperature was observed, such as an increase in strength and decrease in ductility. However, the damage at 140 R was greater because this temperature prevented the annealing of radiation-induced defects which occurs above 140 R.

  18. Cladding and Structural Materials for Advanced Nuclear Energy Systems

    SciTech Connect

    Was, G S; Allen, T R; Ila, D; C,; Levi,; Morgan, D; Motta, A; Wang, L; Wirth, B

    2011-06-30

    The goal of this consortium is to address key materials issues in the most promising advanced reactor concepts that have yet to be resolved or that are beyond the existing experience base of dose or burnup. The research program consists of three major thrusts: 1) high-dose radiation stability of advanced fast reactor fuel cladding alloys, 2) irradiation creep at high temperature, and 3) innovative cladding concepts embodying functionally-graded barrier materials. This NERI-Consortium final report represents the collective efforts of a large number of individuals over a period of three and a half years and included 9 PIs, 4 scientists, 3 post-docs and 12 students from the seven participating institutions and 8 partners from 5 national laboratories and 3 industrial institutions (see table). University participants met semi-annually and participants and partners met annually for meetings lasting 2-3 days and designed to disseminate and discuss results, update partners, address outstanding issues and maintain focus and direction toward achieving the objectives of the program. The participants felt that this was a highly successful program to address broader issues that can only be done by the assembly of a range of talent and capabilities at a more substantial funding level than the traditional NERI or NEUP grant. As evidence of the success, this group, collectively, has published 20 articles in archival journals and made 57 presentations at international conferences on the results of this consortium.

  19. Ab-initio calculations of electronic structure and optical properties of TiAl alloy

    NASA Astrophysics Data System (ADS)

    Hussain, Altaf; Sikandar Hayat, Sardar; Choudhry, M. A.

    2011-05-01

    The electronic structures and optical properties of TiAl intermetallic alloy system are studied by the first-principle orthogonalized linear combination of atomic orbitals method. Results on the band structure, total and partial density of states, localization index, effective atomic charges, and optical conductivity are presented and discussed in detail. Total density of states spectra reveal that (near the Fermi level) the majority of the contribution is from Ti-3d states. The effective charge calculations show an average charge transfer of 0.52 electrons from Ti to Al in primitive cell calculations of TiAl alloy. On the other hand, calculations using supercell approach reveal an average charge transfer of 0.48 electrons from Ti to Al. The localization index calculations, of primitive cell as well as of supercell, show the presence of relatively localized states even above the Fermi level for this alloy. The calculated optical conductivity spectra of TiAl alloy are rich in structures, showing the highest peak at 5.73 eV for supercell calculations. Calculations of the imaginary part of the linear dielectric function show a prominent peak at 5.71 eV and a plateau in the range 1.1-3.5 eV.

  20. Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer

    DOEpatents

    Spahn, Olga B.; Lear, Kevin L.

    1998-01-01

    A semiconductor structure. The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g. Al.sub.2 O.sub.3), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3-1.6 .mu.m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation.

  1. Structure relaxation and crystallization of the CoW-CoNiW-NiW electrodeposited alloys

    PubMed Central

    2014-01-01

    The structure of electrolytically deposited nanocrystalline alloys of the CoW-CoNiW-NiW systems under low-temperature heating was investigated by means of high-resolution transmission electron microscopy (HRTEM), high-angle annular dark-field scanning transmission electron microscopy (HAADF STEM), and analytical methods such as energy dispersive x-ray spectroscopy (EDS) and electron energy loss spectroscopy (EELS). Structural relaxation and crystallization were investigated at temperatures of 200°C to 300°C. The structural and compositional inhomogeneities were found in the CoW-CoNiW-NiW alloys, while the local changes in composition were found to reach 18 at.%. Nanocrystals in the alloys grew most intensely in the presence of a free surface, and we found their nuclei density to range from 2 × 1023 /m3 to 3 × 1023 /m3. It was determined that the local diffusion coefficient ranged from 0.9 to 1.7 10−18 m2/s, which could be explained by the prevalence of surface diffusion. The data gathered in these investigations can be used to predict the thermal stability of CoW-CoNiW-NiW alloys. PMID:24506913

  2. Microscopic models of PdZn alloy catalysts: structure and reactivity in methanol decomposition.

    PubMed

    Neyman, Konstantin M; Lim, Kok Hwa; Chen, Zhao-Xu; Moskaleva, Lyudmila V; Bayer, Andreas; Reindl, Armin; Borgmann, Dieter; Denecke, Reinhard; Steinrück, Hans-Peter; Rösch, Notker

    2007-07-21

    We review systematic experimental and theoretical efforts that explored formation, structure and reactivity of PdZn catalysts for methanol steam reforming, a material recently proposed to be superior to the industrially used Cu based catalysts. Experimentally, ordered surface alloys with a Pd : Zn ratio of approximately 1 : 1 were prepared by deposition of thin Zn layers on a Pd(111) surface and characterized by photoelectron spectroscopy and low-energy electron diffraction. The valence band spectrum of the PdZn alloy resembles closely the spectrum of Cu(111), in good agreement with the calculated density of states for a PdZn alloy of 1 : 1 stoichiometry. Among the issues studied with the help of density functional calculations are surface structure and stability of PdZn alloys and effects of Zn segregation in them, and the nature of the most likely water-related surface species present under the conditions of methanol steam reforming. Furthermore, a series of elementary reactions starting with the decomposition of methoxide, CH(3)O, along both C-H and C-O bond scission channels, on various surfaces of the 1 : 1 PdZn alloy [planar (111), (100) and stepped (221)] were quantified in detail thermodynamically and kinetically in comparison with the corresponding reactions on the surfaces Pd(111) and Cu(111). The overall surface reactivity of PdZn alloy was found to be similar to that of metallic Cu. Reactive methanol adsorption was also investigated by in situ X-ray photoelectron spectroscopy for pressures between 3 x 10(-8) and 0.3 mbar.

  3. Investigation of mechanical properties for open cellular structure CoCrMo alloy fabricated by selective laser melting process

    NASA Astrophysics Data System (ADS)

    Azidin, A.; Taib, Z. A. M.; Harun, W. S. W.; Che Ghani, S. A.; Faisae, M. F.; Omar, M. A.; Ramli, H.

    2015-12-01

    Orthodontic implants have been a major focus through mechanical and biological performance in advance to fabricate shape of complex anatomical. Designing the part with a complex mechanism is one of the challenging process and addition to achieve the balance and desired mechanical performance brought to the right manufacture technique to fabricate. Metal additive manufacturing (MAM) is brought forward to the newest fabrication technology in this field. In this study, selective laser melting (SLM) process was utilized on a medical grade cobalt-chrome molybdenum (CoCrMo) alloy. The work has focused on mechanical properties of the CoCrMo open cellular structures samples with 60%, 70%, and 80% designed volume porosity that could potentially emulate the properties of human bone. It was observed that hardness values decreased as the soaking time increases except for bottom face. For compression test, 60% designed volume porosity demonstrated highest ultimate compressive strength compared to 70% and 80%.

  4. Structural Configuration Systems Analysis for Advanced Aircraft Fuselage Concepts

    NASA Technical Reports Server (NTRS)

    Mukhopadhyay, Vivek; Welstead, Jason R.; Quinlan, Jesse R.; Guynn, Mark D.

    2016-01-01

    Structural configuration analysis of an advanced aircraft fuselage concept is investigated. This concept is characterized by a double-bubble section fuselage with rear mounted engines. Based on lessons learned from structural systems analysis of unconventional aircraft, high-fidelity finite-element models (FEM) are developed for evaluating structural performance of three double-bubble section configurations. Structural sizing and stress analysis are applied for design improvement and weight reduction. Among the three double-bubble configurations, the double-D cross-section fuselage design was found to have a relatively lower structural weight. The structural FEM weights of these three double-bubble fuselage section concepts are also compared with several cylindrical fuselage models. Since these fuselage concepts are different in size, shape and material, the fuselage structural FEM weights are normalized by the corresponding passenger floor area for a relative comparison. This structural systems analysis indicates that an advanced composite double-D section fuselage may have a relative structural weight ratio advantage over a conventional aluminum fuselage. Ten commercial and conceptual aircraft fuselage structural weight estimates, which are empirically derived from the corresponding maximum takeoff gross weight, are also presented and compared with the FEM- based estimates for possible correlation. A conceptual full vehicle FEM model with a double-D fuselage is also developed for preliminary structural analysis and weight estimation.

  5. Probabilistic Evaluation of Advanced Ceramic Matrix Composite Structures

    NASA Technical Reports Server (NTRS)

    Abumeri, Galib H.; Chamis, Christos C.

    2003-01-01

    The objective of this report is to summarize the deterministic and probabilistic structural evaluation results of two structures made with advanced ceramic composites (CMC): internally pressurized tube and uniformly loaded flange. The deterministic structural evaluation includes stress, displacement, and buckling analyses. It is carried out using the finite element code MHOST, developed for the 3-D inelastic analysis of structures that are made with advanced materials. The probabilistic evaluation is performed using the integrated probabilistic assessment of composite structures computer code IPACS. The affects of uncertainties in primitive variables related to the material, fabrication process, and loadings on the material property and structural response behavior are quantified. The primitive variables considered are: thermo-mechanical properties of fiber and matrix, fiber and void volume ratios, use temperature, and pressure. The probabilistic structural analysis and probabilistic strength results are used by IPACS to perform reliability and risk evaluation of the two structures. The results will show that the sensitivity information obtained for the two composite structures from the computational simulation can be used to alter the design process to meet desired service requirements. In addition to detailed probabilistic analysis of the two structures, the following were performed specifically on the CMC tube: (1) predicted the failure load and the buckling load, (2) performed coupled non-deterministic multi-disciplinary structural analysis, and (3) demonstrated that probabilistic sensitivities can be used to select a reduced set of design variables for optimization.

  6. Long-Length Semiproducts from Ni - Ti Alloys with Advanced Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Andreev, V. A.; Yusupov, V. S.; Perkas, M. M.; Prosvirnin, V. V.; Bondareva, S. A.

    2015-05-01

    The effect of cold deformation and heat treatment on the mechanical properties of hot-rolled long-length semiproducts from shape-memory Ni - Ti alloys is studied. It is shown that cold deformation to ɛtot = 30% with intermediate annealing operations promotes reversible changes in the shape. The effect may be associated with relaxation of oriented microstresses created during plastic deformation.

  7. Development of High-Temperature Ferritic Alloys and Performance Prediction Methods for Advanced Fission Energy Systems

    SciTech Connect

    G. RObert Odette; Takuya Yamamoto

    2009-08-14

    Reports the results of a comprehensive development and analysis of a database on irradiation hardening and embrittlement of tempered martensitic steels (TMS). Alloy specific quantitative semi-empirical models were derived for the dpa dose, irradiation temperature (ti) and test (Tt) temperature of yield stress hardening (or softening) .

  8. RNA Structure: Advances and Assessment of 3D Structure Prediction.

    PubMed

    Miao, Zhichao; Westhof, Eric

    2017-03-30

    Biological functions of RNA molecules are dependent upon sustained specific three-dimensional (3D) structures of RNA, with or without the help of proteins. Understanding of RNA structure is frequently based on 2D structures, which describe only the Watson-Crick (WC) base pairs. Here, we hierarchically review the structural elements of RNA and how they contribute to RNA 3D structure. We focus our analysis on the non-WC base pairs and on RNA modules. Several computer programs have now been designed to predict RNA modules. We describe the RNA-Puzzles initiative, which is a community-wide, blind assessment of RNA 3D structure prediction programs to determine the capabilities and bottlenecks of current predictions. The assessment metrics used in RNA-Puzzles are briefly described. The detection of RNA 3D modules from sequence data and their automatic implementation belong to the current challenges in RNA 3D structure prediction. Expected final online publication date for the Annual Review of Biophysics Volume 46 is May 20, 2017. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

  9. Structure of Ti-6Al-4V nanostructured titanium alloy joint obtained by resistance spot welding

    SciTech Connect

    Klimenov, V. A.; Kurgan, K. A.; Chumaevskii, A. V.; Gnyusov, S. F.

    2016-01-15

    The structure of weld joints of the titanium alloy Ti-6Al-4V in the initial ultrafine-grained state, obtained by resistance spot welding, is studied using the optical and scanning electron microscopy method and the X-ray structure analysis. The carried out studies show the relationship of the metal structure in the weld zone with main joint zones. The structure in the core zone and the heat affected zone is represented by finely dispersed grains of needle-shaped martensite, differently oriented in these zones. The change in the microhardness in the longitudinal section of the weld joint clearly correlates with structural changes during welding.

  10. Local structures of high-entropy alloys (HEAs) on atomic scales: An overview

    SciTech Connect

    Diao, Haoyan; Santodonato, Louis J.; Tang, Zhi; Egami, Takeshi; Liaw, Peter K.

    2015-01-01

    The high-entropy alloys, containing several elements mixed in equimolar or near-equimolar ratios, have shown exceptional engineering properties. Local structures on the atomic level are essential to understand the mechanical behaviors and related mechanisms. This article covers the local structure and stress on the atomic level are reviewed by the pair-distribution function of neutron-diffraction data, ab-initio molecular dynamics simulations, and the atomic probe microscopy.

  11. Ab initio theory of phase stability and structural selectivity in Fe-Pd alloys

    NASA Astrophysics Data System (ADS)

    Chepulskii, Roman V.; Barabash, Sergey V.; Zunger, Alex

    2012-04-01

    In Fe-Pd alloys, the competing geometric (fcc versus bcc) and magnetic tendencies result in rich phase stability and ordering physics. Here, we study these alloys via a first principles mixed-basis cluster expansion (CE) approach. Highly accurate fcc and bcc CEs are iteratively and self-consistently constructed using a genetic algorithm, based on the first principles results for ˜100 ordered structures. The structural and magnetic “filters” are introduced to determine whether a fully relaxed structure is of fcc/bcc and high-/low-spin types. All structures satisfying the Lifshitz condition for stability in extended phase diagram regions are included as inputs to our CEs. We find that in a wide composition range (with more than 1/3 atomic content of Fe), an fcc-constrained alloy has a single stable ordered compound, L10 FePd. However, L10 is higher in energy than the phase-separated mixture of bcc Fe and fcc-FePd2 (β2 structure) at low temperatures. In the Pd-rich composition range, we find several fcc β2-like ground states: FePd2 (β2), Fe3Pd9, Fe2Pd7, FePd5, Fe2Pd13, and FePd8, yet we do not find FePd3 with the the experimentally observed L12 structure. Fcc Monte Carlo simulations show a transformation from any of the attempted β2-like ground states directly into a disordered alloy. We suggest that the phonon and/or spin excitation contributions to the free energy are responsible for the observed stability of L12 at higher temperatures, and likely lead to a β2↔L12 transition. Finally, we present here a complete characterization of all the fcc and bcc Lifshitz structures, i.e., the structures with ordering vectors exclusively at high-symmetry k points.

  12. The structure-property relationships of powder processed Fe-Al-Si alloys

    SciTech Connect

    Prichard, Paul D.

    1998-02-23

    Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic %). The powder alloys were produced with a high pressure gas atomization (HPGA) process to obtain a high fraction of metal injection molding (MIM) quality powder (D84 < 32 μm). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 μm. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 μm to 104 μm. Mechanical property testing was conducted on both extruded and sintered material using a small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25 to 550 C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase α + DO3 structure. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.

  13. Mechanical and structural aspects of high-strain-rate deformation of NiTi alloy

    NASA Astrophysics Data System (ADS)

    Bragov, A. M.; Danilov, A. N.; Konstantinov, A. Yu.; Lomunov, A. K.; Motorin, A. S.; Razov, A. I.

    2015-04-01

    The mechanical behavior of the binary polycrystalline NiTi alloy with a quasi-equilibrium structure has been considered in the course of the high-strain-rate extension in a temperature range of 20-300°C. The quasi-equilibrium structure, which is necessary to ensure the long-term stability of special properties of the alloy, was achieved using aging, after which both the forward and reverse martensitic transformations exhibited a multistage character and the phase composition at room temperature was characterized by the presence of R and B19' martensites. To separate the contributions that come from the equilibrium structure and from the high rate of tension to the mechanical behavior of the alloy, a comparative analysis of the diagrams of high-strain-rate and quasi-static tension has been performed. It has been shown that the action of several mechanisms of reversible deformation is determined by the specific features of the equilibrium structure, and the level of stresses at which these mechanisms are developed is controlled by the rate of tension. The results of the X-ray diffraction study of the phase composition of the alloy samples after high-strain-rate tension, which make it possible to conclude that the mechanical behavior of martensite and austenite upon the dynamic tension of the alloy is determined by the development of stress-induced R → B19', B2 → R, and B2 → B19' transformations and by the processes of the detwinning and reorientation of crystals of B19' martensite, are given.

  14. Application of holographic interferometry for analysis of the dynamic and modal characteristics of an advanced exotic metal airfoil structure

    NASA Astrophysics Data System (ADS)

    Fein, Howard

    1999-03-01

    Holographic Interferometry has been successfully employed to characterize the materials and behavior of diverse types of structures under stress. Specialized variations of this technology have also been applied to define dynamic and vibration related structural behavior. Such applications of holographic technique offer some of the most effective methods of modal and dynamic analysis available. Real-time dynamic testing of the modal and mechanical behavior of aerodynamic control and airfoil structures for advanced aircraft has always required advanced instrumentation for data collection in either actual flight test or wind-tunnel simulations. Advanced optical holography techniques are alternate methods which result in actual full-field behavioral data on the ground in a noninvasive environment. These methods offer significant insight in both the development and subsequent operational test and modeling of advanced exotic metal control structures and their integration with total vehicle system dynamics. Structures and materials can be analyzed with very low amplitude excitation and the resultant data can be used to adjust the accuracy mathematically derived structural and behavioral models. Holographic Interferometry offers a powerful tool to aid in the developmental engineering of exotic metal structures for high stress applications. Advanced Titanium alloy is a significant example of these sorts of materials which has found continually increased use in advanced aerodynamic, undersea, and other highly mobil platforms. Aircraft applications in particular must consider environments where extremes in vibration and impulsive mechanical stress can affect both operation and structural stability. These considerations present ideal requisites for analysis using advanced holographic methods in the initial design and test of structures made with such advanced materials. Holographic techniques are nondestructive, real- time, and definitive in allowing the identification of

  15. Mg-Zn-Y alloys with long-period stacking ordered structure: in vitro assessments of biodegradation behavior.

    PubMed

    Zhao, Xu; Shi, Ling-ling; Xu, Jian

    2013-10-01

    Using Dulbecco's modified eagle medium (DMEM) with 10% fetal bovine serum (FBS) as simulated body fluid, degradation behavior of Mg100-3x(Zn1Y2)x (1≤x≤3) alloy series with long period stacking order (LPSO) structures was investigated. As indicated, with increasing the volume fraction of LPSO phase, degradation rate of the alloys is accelerated. Further refining the grain size by microalloying with zirconium and warm extrusion has a significant effect to mitigate the degradation rate of the Mg97Zn1Y2 alloy. Time-dependent behavior during degradation of the magnesium alloys can be described using an exponential decay function of WR=exp(a+bt+ct(2)), where WR is normalized residual mass/volume of the alloy. A parameter named as degradation half-life period (t0.5) is suggested to quantitatively assess the degradation rate. For the localized-corrosion controlled alloys, the t0.5 parameter physically scales with electrochemical response ΔE which is a range between corrosion potential (Ecorr) and pitting potential (Ept). In comparison with conventional engineering magnesium alloys such as the AZ31, WE43, ZK60 and ZX60 alloys, extruded Mg96.83Zn1Y2Zr0.17 alloy with LPSO structure exhibits a good combination of high mechanical strength, lower biodegradation rate and good biocompatibility.

  16. Advanced accelerating structures and their interaction with electron beams.

    SciTech Connect

    Gai, W.; High Energy Physics

    2008-01-01

    In this paper, we give a brief description of several advanced accelerating structures, such as dielectric loaded waveguides, photonic band gap, metamaterials and improved iris-loaded cavities. We describe wakefields generated by passing high current electron beams through these structures, and applications of wakefields to advanced accelerator schemes. One of the keys to success for high gradient wakefield acceleration is to develop high current drive beam sources. As an example, the high current RF photo injector at the Argonne Wakefield Accelerator, passed a {approx}80 nC electron beam through a high gradient dielectric loaded structure to achieve a 100 MV/m gradient. We will summarize recent related experiments on beam-structure interactions and also discuss high current electron beam generation and propagation and their applications to wakefield acceleration.

  17. Advanced Accelerating Structures and Their Interaction with Electron Beams

    SciTech Connect

    Gai Wei

    2009-01-22

    In this paper, we give a brief description of several advanced accelerating structures, such as dielectric loaded waveguides, photonic band gap, metamaterials and improved iris-loaded cavities. We describe wakefields generated by passing high current electron beams through these structures, and applications of wakefields to advanced accelerator schemes. One of the keys to success for high gradient wakefield acceleration is to develop high current drive beam sources. As an example, the high current RF photo injector at the Argonne Wakefield Accelerator, passed a {approx}80 nC electron beam through a high gradient dielectric loaded structure to achieve a 100 MV/m gradient. We will summarize recent related experiments on beam-structure interactions and also discuss high current electron beam generation and propagation and their applications to wakefield acceleration.

  18. Advanced accelerator and mm-wave structure research at LANL

    SciTech Connect

    Simakov, Evgenya Ivanovna

    2016-06-22

    This document outlines acceleration projects and mm-wave structure research performed at LANL. The motivation for PBG research is described first, with reference to couplers for superconducting accelerators and structures for room-temperature accelerators and W-band TWTs. These topics are then taken up in greater detail: PBG structures and the MIT PBG accelerator; SRF PBG cavities at LANL; X-band PBG cavities at LANL; and W-band PBG TWT at LANL. The presentation concludes by describing other advanced accelerator projects: beam shaping with an Emittance Exchanger, diamond field emitter array cathodes, and additive manufacturing of novel accelerator structures.

  19. Advanced Composite Structures At NASA Langley Research Center

    NASA Technical Reports Server (NTRS)

    Eldred, Lloyd B.

    2015-01-01

    Dr. Eldred's presentation will discuss several NASA efforts to improve and expand the use of composite structures within aerospace vehicles. Topics will include an overview of NASA's Advanced Composites Project (ACP), Space Launch System (SLS) applications, and Langley's ISAAC robotic composites research tool.

  20. Systems integration and demonstration of advanced reusable structure for ALS

    NASA Technical Reports Server (NTRS)

    Gibbins, Martin N.

    1991-01-01

    The objective was to investigate the potential of advanced material to achieve life cycle cost (LCC) benefits for reusable structure on the advanced launch system. Three structural elements were investigated - all components of an Advanced Launch System reusable propulsion/avionics module. Leading aeroshell configurations included sandwich structure using titanium, graphite/polyimide (Gr/PI), or high-temperature aluminum (HTA) face sheets. Thrust structure truss concepts used titanium, graphite/epoxy, or silicon carbide/aluminum struts. Leading aft bulkhead concepts employed graphite epoxy and aluminum. The technical effort focused on the aeroshell because the greatest benefits were expected there. Thermal analyses show the structural temperature profiles during operation. Finite element analyses show stresses during splash-down. Weight statements and manufacturing cost estimates were prepared for calculation of LCC for each design. The Gr/PI aeroshell showed the lowest potential LCC, but the HTA aeroshell was judged to be lower risk. A technology development plan was prepared to validate the applicable structural technology.

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

    NASA Astrophysics Data System (ADS)

    Adegoke, Oluwasesan; Park, Enoch Y.

    2016-06-01

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

  2. Formation, stability, and crystal structure of σ phase in Mo-Re-Si alloys

    SciTech Connect

    Bei, Hongbin; Yang, Ying; Viswanathan, G.; Rawn, Claudia J; George, Easo P; Tiley, Jaimie; Chang, Y. Austin

    2010-01-01

    The formation, stability and crystal structure of the {sigma} phase in Mo-Re-Si alloys were investigated. Guided by thermodynamic calculations, six critically selected alloys were arc melted and annealed at 1600 C for 150 h. Their as-cast and annealed microstructures, including phase fractions and distributions, the compositions of the constituent phases and the crystal structure of the {sigma} phase were analyzed by thermodynamic modeling coupled with experimental characterization by scanning electron microscopy, electron probe microanalysis, X-ray diffraction and transmission electron microscopy. Two key findings resulted from this work. One is the large homogeneity range of the {sigma} phase region, extending from binary Mo-Re to ternary Mo-Re-Si. The other is the formation of a {sigma} phase in Mo-rich alloys either through the peritectic reaction of liquid + Mo{sub ss} {yields} {sigma} or primary solidification. These findings are important in understanding the effects of Re on the microstructure and providing guidance on the design of Mo-Re-Si alloys.

  3. Semiconductor structures having electrically insulating and conducting portions formed from an AlSb-alloy layer

    DOEpatents

    Spahn, O.B.; Lear, K.L.

    1998-03-10

    The semiconductor structure comprises a plurality of semiconductor layers formed on a substrate including at least one layer of a III-V compound semiconductor alloy comprising aluminum (Al) and antimony (Sb), with at least a part of the AlSb-alloy layer being chemically converted by an oxidation process to form superposed electrically insulating and electrically conducting portions. The electrically insulating portion formed from the AlSb-alloy layer comprises an oxide of aluminum (e.g., Al{sub 2}O{sub 3}), while the electrically conducting portion comprises Sb. A lateral oxidation process allows formation of the superposed insulating and conducting portions below monocrystalline semiconductor layers for forming many different types of semiconductor structures having particular utility for optoelectronic devices such as light-emitting diodes, edge-emitting lasers, vertical-cavity surface-emitting lasers, photodetectors and optical modulators (waveguide and surface normal), and for electronic devices such as heterojunction bipolar transistors, field-effect transistors and quantum-effect devices. The invention is expected to be particularly useful for forming light-emitting devices for use in the 1.3--1.6 {mu}m wavelength range, with the AlSb-alloy layer acting to define an active region of the device and to effectively channel an electrical current therein for efficient light generation. 10 figs.

  4. Structural stability of NiCoFeCrAlx high-entropy alloy from ab initio theory

    NASA Astrophysics Data System (ADS)

    Tian, Fuyang; Delczeg, Lorand; Chen, Nanxian; Varga, Lajos Karoly; Shen, Jiang; Vitos, Levente

    2013-08-01

    First-principles alloy theory predicts that at room temperature the paramagnetic NiCoFeCrAlx high entropy alloys adopt the face centered cubic (fcc) structure for x≲0.60 and the body centered cubic (bcc) structure for x≳1.23, with an fcc-bcc duplex region in between the two pure phases. The calculated single- and polycrystal elastic parameters exhibit strong composition and crystal structure dependence. Based on the present theoretical findings, it is concluded that alloys around the equimolar NiCoFeCrAl composition have superior mechanical performance as compared to the single-phase regions.

  5. Acoustic emission location on aluminum alloy structure by using FBG sensors and PSO method

    NASA Astrophysics Data System (ADS)

    Lu, Shizeng; Jiang, Mingshun; Sui, Qingmei; Dong, Huijun; Sai, Yaozhang; Jia, Lei

    2016-04-01

    Acoustic emission location is important for finding the structural crack and ensuring the structural safety. In this paper, an acoustic emission location method by using fiber Bragg grating (FBG) sensors and particle swarm optimization (PSO) algorithm were investigated. Four FBG sensors were used to form a sensing network to detect the acoustic emission signals. According to the signals, the quadrilateral array location equations were established. By analyzing the acoustic emission signal propagation characteristics, the solution of location equations was converted to an optimization problem. Thus, acoustic emission location can be achieved by using an improved PSO algorithm, which was realized by using the information fusion of multiple standards PSO, to solve the optimization problem. Finally, acoustic emission location system was established and verified on an aluminum alloy plate. The experimental results showed that the average location error was 0.010 m. This paper provided a reliable method for aluminum alloy structural acoustic emission location.

  6. Electronic structure and magnetic properties of disordered Co{sub 2}FeAl Heusler alloy

    SciTech Connect

    Jain, Vishal Jain, Vivek Sudheesh, V. D. Lakshmi, N. Venugopalan, K.

    2014-04-24

    The effects of disorder on the magnetic properties of Co{sub 2}FeAl alloy are reported. X-ray diffraction exhibit A2-type disordered structure. Room temperature Mössbauer studies show the presence of two sextets with hyperfine field values of 31T and 30T along with a nonmagnetic singlet. The electronic structure of ordered and disordered Co{sub 2}FeAl alloys, investigated by means of the KKR Green's-function method shows that the magnetic moment of the ordered structure is 5.08μ{sub B} and is 5.10μ{sub B} when disordered. However, a much higher magnetic moment of 5.74μ{sub B} is observed experimentally.

  7. Transport, Structural and Mechanical Properties of Quaternary FeVTiAl Alloy

    NASA Astrophysics Data System (ADS)

    Bhat, Tahir Mohiuddin; Gupta, Dinesh C.

    2016-11-01

    The electronic, structural, magnetic and transport properties of FeVTiAl quaternary alloy have been investigated within the framework of density functional theory. The material is a completely spin-polarized half-metallic ferromagnet in its ground state with F-43m structure. The structural stability was further confirmed by elastic constants in the cubic phase with high Young's modulus and brittle nature. The present study predicts an energy band gap of 0.72 eV in a localized minority spin channel at equilibrium lattice parameter of 6.00 Å. The transport properties of the material are discussed based on the Seebeck coefficient, and electrical and thermal conductivity coefficients. The alloy presents large values of Seebeck coefficients, ~39 μV K-1 at room temperature (300 K), and has an excellent thermoelectric performance with ZT = ~0.8.

  8. A structural investigation of a plasma sprayed Ni--Cr based alloy coating

    SciTech Connect

    Sampath, S.; Neiser, R.A.; Herman, H. ); Kirkland, J.P.; Elam, W.T. )

    1993-01-01

    A Ni--Cr based hardfacing alloy has been plasma sprayed in ambient and low pressure atmospheres onto mild steel substrates. These coatings exhibit excellent wear and corrosion resistance; however, the significance of microstructure on properties has not been reported. This study relates the structure of the sprayed coatings to the processing conditions. X-ray diffraction results indicate phase separation in air plasma sprayed deposits, while low pressure plasma sprayed deposits exhibit a single supersaturated solid solution. Annealing of the air plasma sprayed coating shows dissolution of the bcc chromium phase, confirming its metastable nature. These results were confirmed using Extended X-ray Absorption Fine Structure (EXAFS) analysis, which further suggests a highly disordered structure, with partial oxidation of selected alloying elements, such as chromium. Transmission electron microscopy indicates a wide variety of microstructures in the air plasma sprayed deposit. In the case of low pressure sprayed deposit, the microstructures are homogeneous and uniform.

  9. Average Structure Evolution of δ-phase Pu-Ga Alloys

    SciTech Connect

    Smith, Alice Iulia; Page, Katharine L.; Gourdon, Olivier; Siewenie, Joan E.; Richmond, Scott; Saleh, Tarik A.; Ramos, Michael; Schwartz, Daniel S.

    2015-03-30

    [Full Text] Plutonium metal is a highly unusual element, exhibiting six allotropes at ambient pressure, from room temperature to its melting point. Many phases of plutonium metal are unstable with temperature, pressure, chemical additions, and time. This strongly affects structure and properties, and becomes of high importance, particularly when considering effects on structural integrity over long time periods. The fcc δ-phase deserves additional attention, not only in the context of understanding the electronic structure of Pu, but also as one of the few high-symmetry actinide phases that can be stabilized down to ambient pressure and room temperature by alloying it with trivalent elements. We will present results on recent work on aging of Pu-2at.%Ga and Pu-7at.%Ga alloys

  10. Structure and Hardness of 01570 Aluminum Alloy Friction Stir Welds Processed Under Different Conditions

    NASA Astrophysics Data System (ADS)

    Il'yasov, R. R.; Avtokratova, E. V.; Markushev, M. V.; Predko, P. Yu.; Konkevich, V. Yu.

    2015-10-01

    Structure and hardness of the 01570 aluminum alloy joints processed by friction stir welding at various speeds are investigated. It is shown that increasing the traverse tool speed lowers the probability of macrodefect formation in the nugget zone; however, this can lead to anomalous grain growth in the zone of contact with the tool shoulder. Typical "onion-like" structure of the weld consisting of rings that differ by optical contrast is formed for all examined welding regimes. It is demonstrated that this contrast is caused by the difference in the grain sizes in the rings rather than by their chemical or phase composition. Mechanisms of transformation of the alloy structure during friction stir welding are discussed.

  11. 4-d magnetism: Electronic structure and magnetism of some Mo-based alloys

    NASA Astrophysics Data System (ADS)

    Liu, Yong; Bose, S. K.; Kudrnovský, J.

    2017-02-01

    We report results of a first-principles density-functional study of alloys of the 4 d -element Mo with group IV elements Si, Ge and Sn in zinc blende (ZB) and rock salt (RS) structures. The study was motivated by a similar study of ours based on the 4 d -element Tc, which showed the presence of half-metallic states with integer magnetic moment (1μB) per formula unit in TcX (X=C, Si, Ge) alloys. The calculated Curie temperatures for the ferromagnetic (FM) phases were low, around or less than 300 K. Searching for the possibility of 4 d -based alloys with higher Curie temperatures we have carried out the study involving the elements Mo, Ru and Rh. Among these the most promising case appears to be that involving the element Mo. Among the MoX (X=Si, Ge, Sn) alloys in ZB and RS structures, both MoGe and MoSn in ZB structures are found to possess an integer magnetic moment of 2μB per formula unit. ZB MoSn can be classified as a marginal/weak half-metal or a spin gapless semiconductor, while ZB MoGe would be best described as a gapless magnetic semiconductor. The calculated Curie temperatures are in the range 300-700 K. Considering the theoretical uncertainty in the band gaps due not only to the treatment of exchange and correlation effects, but density functional theory itself, these classifications may change somewhat, but both merit investigation from the viewpoint of potential spintronic application. Based on their higher Curie temperatures, Mo-based alloys would serve such purpose better than the previously reported Tc-based ones.

  12. Structural Analysis, Electrochemical Behavior, and Biocompatibility of Novel Quaternary Titanium Alloy with near β Structure

    NASA Astrophysics Data System (ADS)

    Popa, Monica; Calderon Moreno, Jose Maria; Vasilescu, Cora; Drob, Silviu Iulian; Neacsu, Elena Ionela; Coer, Andrej; Hmeljak, Julija; Zerjav, Gregor; Milošev, Ingrid

    2014-06-01

    This article analyses the microstructure, electrochemical behavior, and biocompatibility of a novel Ti-20Nb-10Zr-5Ta alloy with low Young's modulus (59 GPa) much closer to that of bone, between 10 and 30 GPa, than Ti and other Ti alloys used as implant biomaterial. XRD and SEM measurements revealed a near β crystalline microstructure containing β phase matrix and secondary α phase, with a typical grain size of around 200 μm. The corrosion behavior in neutral Ringer solution evidenced: self-passivation behavior characterizing a very resistant passive film; an easy passivation as a result of favorable influence of the alloying elements Nb, Zr, and Ta that participate with their passive oxides to the formation of the alloy passive film; low corrosion and ion release rates corresponding with very low toxicity. In MEM solution, the novel alloy demonstrated very high corrosion resistance and no susceptibility to localized corrosion. Biocompatibility was evaluated on in vitro human osteoblast-like and human immortalized pulmonary fibroblast cell (Wi-38) lines and the new Ti-20Nb-10Zr-5Ta alloy exhibited no cytotoxicity. The new Ti-20Nb-10Zr5Ta alloy is a promising material for implants due to combined properties of low elastic modulus, very low corrosion rate, and good biocompatibility.

  13. Layer-structured hexagonal (BN)C semiconductor alloys with tunable optical and electrical properties

    SciTech Connect

    Uddin, M. R.; Majety, S.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2014-03-07

    Hexagonal boron nitride carbon, h(BN){sub 1-x}(C{sub 2}){sub x}, semiconductor alloys have been grown on sapphire substrates by metal-organic chemical vapor deposition. Bandgap tuning through compositional variation has been demonstrated via optical absorption measurements. Furthermore, an enhancement of approximately 10 orders of magnitude in the electrical conductivity has been attained by increasing the carbon concentration (x) from 0 to 0.21. Experimental results revealed evidences that the critical carbon concentration x{sub c} to form the homogenous h(BN){sub 1-x}(C{sub 2}){sub x} alloys, or the carbon solubility in hBN is about 3.2% at a growth temperature of 1300 °C before carbon clusters form. Based on the predicted phase diagram of cubic (BN){sub 1-x}(C{sub 2}){sub x} and the excellent matches in the structural and thermal properties of hBN and graphite, it is expected that homogenous h(BN){sub 1-x}(C{sub 2}){sub x} alloys with higher x can be achieved and the alloy miscibility gap can be reduced or completely removed by increasing the growth temperature. This is a huge advantage over the InGaN alloy system in which InN decomposes at high temperatures and high growth temperature cannot be utilized to close the miscibility gap. The results indicate that the h(BN){sub 1-x}(C{sub 2}){sub x} alloy system has the potential to tackle the challenging issues facing the emerging two-dimension materials beyond graphene, which include realizing the bandgap engineering, conductivity control, and large wafers of homogeneous films.

  14. Structure and optical properties of ternary alloy BeZnO and quaternary alloy BeMgZnO films growth by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Su, Longxing; Zhu, Yuan; Zhang, Quanlin; Chen, Mingming; Wu, Tianzhun; Gui, Xuchun; Pan, Bicai; Xiang, Rong; Tang, Zikang

    2013-06-01

    Ternary alloy BeZnO and quaternary alloy BeMgZnO films were prepared on sapphire (0 0 1) substrate by radio-frequency plasma-assisted molecular beam epitaxy (RF-PAMBE). Based on X-ray diffraction (XRD) analysis, no phase segregation is observed for all the alloys. However, BexZn1-xO alloys exhibit a constantly worse crystal quality than BexMgyZn1-x-yO alloys at the similar incorporation contents (i.e. x in BeZnO approximately equals to x + y in BeMgZnO). Optical transmittance spectra were recorded to determine the energy band gap of the films. BeMgZnO was revealed more effective in widening the band gap. Finally, BeZnO and BeMgZnO based MSM structure UV detectors were fabricated. BeMgZnO alloys with better crystal quality showed a favorable optical response and the cutoff wavelength shifted continuously to deep ultraviolet range, while BeZnO based detectors were found no response. This is the first report on BeMgZnO based UV detector, which is a meaningful step forward to the real application.

  15. Electronic Structure and Phase Equilibria in Ternary Substitutional Alloys: a Tight-Binding Approach

    NASA Astrophysics Data System (ADS)

    Traiber, Ariel Javier Sebastian

    1995-01-01

    The goal of this thesis is to develop and apply alloy theory methods to transition metals and alloys (particularly ternary systems) based on the tight-binding (TB) model of atomic cohesion in studies of stability and phase equilibria. At least two factors make this kind of formalism desirable: it can bring a clear understanding of the underlying physical mechanisms that many times get obscured in first-principles calculations, and it is easily adapted to complex problems and multicomponent solutions, at low computational cost. The original physical insight given by the TB method is demonstrated by the study of the relation between the atomic local environment and the relative stability of simple phases, through the calculation of the moments of the electronic density of states. We show that the relative stability of phases related to the Bain transformation is mainly controlled by the moment of order five, and we have identified the main contributions to this moment. We present a model for cohesive energy based on the assumption that it can be written as the sum of a band -structure contribution and a repulsive short-range contribution. We have calculated the band contribution using a TB Hamiltonian with d states and applied the linearized Green's function method based on the recursion technique. For the repulsive part of the energy we employ a Born-Mayer potential. The model was used to study total energies for Mo. We show that a six-moment approximation to the band energy is sufficient to reproduce more accurate results, using the standard recursion method, for the energetics of this transition metal. We describe a reliable and consistent scheme to study phase equilibria in ternary substitutional alloys based on the TB approximation. The TB electronic parameters are obtained from linear muffin-tin orbital calculations. The transfer integrals are scaled in distance with an orbital -dependent exponential decay parametrization, while the on-site energies are scaled

  16. Phase Structure and Cyclic Deformation in Eutectic Tin-Lead Alloy: A Numerical Analysis

    SciTech Connect

    FANG,HUEI ELIOT; Li,W; SHEN,Y.-L

    1999-09-09

    This study is devoted to providing a mechanistic rationale of coarsening induced failure in solder alloys during thermomechanical fatigue. Micromechanical modeling of cyclic deformation of eutectic tin-lead alloy was undertaken using the finite element method. The models consist of regularly arranged tin-rich and lead-rich phases, simulating the lamellar array and colony structure in a typical eutectic system. A fine structure and a coarse structure, bearing the same phase fraction but different in the aspect ratio of each lead-rich layer and in the number of lead-rich layers in each colony, are utilized for representing the microstructure before and after coarsening, respectively. Both phases are treated as elastic-plastic solids with their respective properties. For simplicity the creep effect is ignored without compromising the main objective of this study. Cyclic loading under pure shear and uniaxial conditions is modeled. It is found that both the fine and coarse structures exhibit essentially the same macroscopic stress-strain response. The coarse structure, however, shows a greater maximum effective plastic strain on a local scale throughout the deformation. The numerical result implies that, in a solder joint, a locally coarsened region may not be mechanically weaker than its surrounding, but it is subject to early damage initiation due to accumulated plasticity. Other implications regarding solder alloy failure and micromechanical modeling of two-phase materials are discussed.

  17. Effect of liquid-liquid structure transition on solidification of Sn57Bi43 alloy

    NASA Astrophysics Data System (ADS)

    Li, Mingyang; Zhang, Yongxing; Wu, Chen; Geng, Haoran

    2016-03-01

    In this paper, the effect of the liquid-liquid structure transition (L-LST) on the solidification behaviors and morphologies of Sn57Bi43 alloy was further studied. The liquid structure of Sn57Bi43 was studied with resistivity, thermal analysis and viscosity method. The obvious turning point is observed on resistivity-temperature, DSC and viscosity-temperature curves of Sn57Bi43 alloy. The resistivity increases linearly with increasing temperature before the turning point. These results indicate that temperature-induced liquid-liquid structure transition occurs at 943-1093 K and is reversible, which may be formed by large cooperative motions for molecular rearrangements. What is more, the results show that the undercooling of the eutectic phase increases and the microstructure becomes finer after solidifying from the melt experiencing L-LST. The spacing of eutectic phase decreases markedly. Based on these results explored the melt structure from different aspects, the nature of discontinuity of structural phase transition can be explored and the effect of L-LST on solidification of Sn57Bi43 alloy is studied.

  18. Development and Processing Improvement of Aerospace Aluminum Alloys-Development of AL-Cu-Mg-Ag Alloy (2139)

    NASA Technical Reports Server (NTRS)

    Cho, Alex; Lisagor, W. Barry; Bales, Thomas T.

    2007-01-01

    This final report supplement in presentation format describes a comprehensive multi-tasked contract study to continue the development of the silver bearing alloy now registered as aluminum alloy 2139 by the Aluminum Association. Two commercial scale ingots were processed into nominal plate gauges of two, four and six inches, and were extensively characterized in terms of metallurgical and crystallographic structure, and resulting mechanical properties. This report includes comparisons of the property combinations for this alloy and 2XXX and 7XXX alloys more widely used in high performance applications. Alloy 2139 shows dramatic improvement in all combinations of properties, moreover, the properties of this alloy are retained in all gauge thicknesses, contrary to typical reductions observed in thicker gauges of the other alloys in the comparison. The advancements achieved in this study are expected to result in rapid, widespread use of this alloy in a broad range of ground based, aircraft, and spacecraft applications.

  19. Critical evaluation on structural stiffness of porous cellular structure of cobalt chromium alloy

    NASA Astrophysics Data System (ADS)

    Abd Malek, N. M. S.; Mohamed, S. R.; Che Ghani, S. A.; Harun, W. S. Wan

    2015-12-01

    In order to improve the stiffness characteristics of orthopedic devices implants that mimic the mechanical behavior of bone need to be considered. With the capability of Additive layer manufacturing processes to produce orthopedic implants with tailored mechanical properties are needed. This paper discusses finite element (FE) analysis and mechanical characterization of porous medical grade cobalt chromium (CoCr) alloy in cubical structures with volume based porosity ranging between 60% to 80% produced using direct metal laser sintering (DMLS) process. ANSYS 14.0 FE modelling software was used to predict the effective elastic modulus of the samples and comparisons were made with the experimental data. The effective mechanical properties of porous samples that were determined by uniaxial compression testing show exponential decreasing trend with the increase in porosity. Finite element model shows good agreement with experimentally obtained stress-strain curve in the elastic regions. The models prove that numerical analysis of actual prosthesis implant can be computed particularly in load bearing condition

  20. Effect of nanostructured composite powders on the structure and strength properties of the high-temperature inconel 718 alloy

    NASA Astrophysics Data System (ADS)

    Cherepanov, A. N.; Ovcharenko, V. E.

    2015-12-01

    The experimental results of the effect of powder nanomodifiers of refractory compounds on the strength properties, the macro- and microstructure of the high-temperature Inconel 718 alloy have been presented. It has been shown that the introduction of powder modifiers into the melt leads to a decrease in the average grain size by a factor of 1.5-2 in the alloy. The long-term tensile strength of the alloy at 650°C increases 1.5-2 times, and the number of cycles at 482°C before fracture grows by more than three times. The effect of nanoparticles on the grain structure and strength properties of the alloy is due to an increase in the number of generated crystallization centers and the formation of nanoparticle clusters of refractory compounds at boundaries and junctions in the formed grain structure, which hinder the development of recrystallization processes in the alloy.

  1. Recent Advances In Optimization Of Aerospace Structures And Engines

    NASA Astrophysics Data System (ADS)

    Rao*, J. S.

    Optimization theories have been well advanced during the last few decades; however when it came to handle real life engineering structures it has been always time consuming and approximate when the structure geometry is highly complex. Design of Experiments has helped in understanding the influence of size and shape parameters on achieving a specified objective function with required constraints and a suitable analysis platform, but has its limitations in arriving at the final optimal solution. There are several commercial codes that addressed this need to handle large size structures subjected to dynamic loads. Most advanced tools in this category are Altair OptiStruct and Altair HyperStudy available in Altair HyperWorks suite. Application of these tools in achieving optimum solutions for linear advanced aircraft structures for minimization of weight are first explained. The application of these tools for globally elastic and locally plastic nonlinear structures to reduce local plastic strains and achieve higher life under dynamic loads will then be discussed.

  2. Adding structure to the transition process to advanced mathematical activity

    NASA Astrophysics Data System (ADS)

    Engelbrecht, Johann

    2010-03-01

    The transition process to advanced mathematical thinking is experienced as traumatic by many students. Experiences that students had of school mathematics differ greatly to what is expected from them at university. Success in school mathematics meant application of different methods to get an answer. Students are not familiar with logical deductive reasoning, required in advanced mathematics. It is necessary to assist students in this transition process, in moving from general to mathematical thinking. In this article some structure is suggested for this transition period. This essay is an argumentative exposition supported by personal experience and international literature. This makes this study theoretical rather than empirical.

  3. Structure, Magnetic, and Electrical Properties of Heusler-Type Fe3- x Co x Si Ferromagnetic Alloys

    NASA Astrophysics Data System (ADS)

    Raja, M. Manivel; Kamat, S. V.

    2015-10-01

    The effect of substitution of Co for Fe on structure, magnetic, and electrical resistivity of Heusler-type Fe3- x Co x Si (0 ≤ x ≤ 1) alloys was investigated using X-ray powder diffraction, 57Fe Mössbauer spectroscopy, magnetic, and electrical transport measurements. The results revealed that these alloys consist of ordered DO3 phase and some L21 phase up to x ≤ 0.5. However, for x > 0.5, the alloys consisted of L21 ordered phase and B2 disordered phase. The magnetization value was close to that predicted from Slater-Pauling rule for x ≥ 0.5 alloys. The Curie temperature increased from 832 K (559 °C) for x = 0 (Fe3Si) alloy to 1016 K (743 °C) for x = 1 (Fe2CoSi) alloy. Electrical transport studies revealed the presence of half-metallic behavior at low temperatures in x ≥ 0.5 alloys. No half-metallic behavior was observed for x = 0 and 0.25 alloys; however, a high resistivity with ferromagnetism was observed in these alloys, which is desirable for ferromagnetic metal/semiconductor spintronic devices.

  4. YF-12 Lockalloy ventral fin program, volume 1. [design analysis, fabrication, and manufacturing of aircraft structures using aluminum and beryllium alloys for the lockheed YF-12 aircraft

    NASA Technical Reports Server (NTRS)

    Duba, R. J.; Haramis, A. C.; Marks, R. F.; Payne, L.; Sessing, R. C.

    1976-01-01

    Results are presented of the YF-12 Lockalloy Ventral Fin Program which was carried out by Lockheed Aircraft Corporation - Advanced Development Projects for the joint NASA/USAF YF-12 Project. The primary purpose of the program was to redesign and fabricate the ventral fin of the YF-12 research airplane (to reduce flutter) using Lockalloy, and alloy of beryllium and aluminum, as a major structural material. A secondary purpose, was to make a material characterization study (thermodynamic properties, corrosion; fatigue tests, mechanical properties) of Lockalloy to validate the design of the ventral fin and expand the existing data base on this material. All significant information pertinent to the design and fabrication of the ventral fin is covered. Emphasis throughout is given to Lockalloy fabrication and machining techniques and attendant personnel safety precautions. Costs are also examined. Photographs of tested alloy specimens are shown along with the test equipment used.

  5. Biomimetic hydrophobic surface fabricated by chemical etching method from hierarchically structured magnesium alloy substrate

    NASA Astrophysics Data System (ADS)

    Liu, Yan; Yin, Xiaoming; Zhang, Jijia; Wang, Yaming; Han, Zhiwu; Ren, Luquan

    2013-09-01

    As one of the lightest metal materials, magnesium alloy plays an important role in industry such as automobile, airplane and electronic product. However, magnesium alloy is hindered due to its high chemical activity and easily corroded. Here, inspired by typical plant surfaces such as lotus leaves and petals of red rose with super-hydrophobic character, the new hydrophobic surface is fabricated on magnesium alloy to improve anti-corrosion by two-step methodology. The procedure is that the samples are processed by laser first and then immersed and etched in the aqueous AgNO3 solution concentrations of 0.1 mol/L, 0.3 mol/L and 0.5 mol/L for different times of 15 s, 40 s and 60 s, respectively, finally modified by DTS (CH3(CH2)11Si(OCH3)3). The microstructure, chemical composition, wettability and anti-corrosion are characterized by means of SEM, XPS, water contact angle measurement and electrochemical method. The hydrophobic surfaces with microscale crater-like and nanoscale flower-like binary structure are obtained. The low-energy material is contained in surface after DTS treatment. The contact angles could reach up to 138.4 ± 2°, which hydrophobic property is both related to the micro-nano binary structure and chemical composition. The results of electrochemical measurements show that anti-corrosion property of magnesium alloy is improved. Furthermore, our research is expected to create some ideas from natural enlightenment to improve anti-corrosion property of magnesium alloy while this method can be easily extended to other metal materials.

  6. Structural Order and Thermodynamic Stability of Disordered Cu2ZnSnS4 Alloys

    NASA Astrophysics Data System (ADS)

    Siah, Sin Cheng; Jaramillo, Rafael; Erslev, Pete; Teeter, Glenn; Buonassisi, Tonio

    2014-03-01

    Crystalline kesterite Cu2ZnSnS4 (c-CZTS) thin films, of interest for photovoltaics, has a narrow window of thermodynamic stability and complex point defect chemistry. Hence, c-CZTS solar cells are thought to suffer from the effects of secondary phase segregation and further improvements in device efficiency may hinge on using kinetic stabilization to inhibit decomposition. By growing films at room temperature (T), we achieve a disordered (CuZnSn)S4 alloy with an expanded solid solution window in the pseudo-ternary CuS-ZnS-SnS phase diagram that allows independent tuning of bandgap and carrier concentration. We use extended x-ray absorption fine structure to quantify short range order, and x-ray absorption near edge structure to quantify phase segregation of this new alloy. X-ray diffraction is used to elucidate the long range structural order. We study the structural evolution of the alloy as a function of annealing temperature and see continuous evolution towards c-CZTS phase that is nearly complete at 450°C. Our results inform the fabrication of conventional c-CZTS solar cells by establishing the temperature range over which thin films transform from a kinetically stabilized, metastable phase to a thermodynamically stabilized, crystalline phase. A NextGenPVII grant from U.S. Department of Energy and a fellowship (S.C.S) from Singapore NRF are acknowledged.

  7. The structural, electronic and dynamic properties of the L12- type Co3Ti alloy

    NASA Astrophysics Data System (ADS)

    Arikan, Nihat; Özduran, Mustafa

    2014-10-01

    The structural, electronic and dynamic properties of the cubic Co3Ti alloy in L12 structure have been investigated using a pseudopotential plane wave (PP-PW) method within the generalized gradient approximation proposed by Perdew-Burke-Ernzerhof (GGA-PBE). The structural properties, including the lattice constant, the bulk modulus and its pressure derivative agree reasonably with the previous results. The density of state (DOS), projected density of state (PDOS) and electronic band structure are also reported. The DOS shows that Co3Ti alloy has a metallic character since the energy bands cross the Fermi level. The density of states at Fermi level mainly comes from the Co-3d states. Phonon dispersion curves and their corresponding total densities of states were obtained using a linear response in the framework of the density functional perturbation theory. All computed phonon frequencies are no imaginer and thus, Co3Ti alloy is dynamically stable. The zone center phonon modes have been founded to be 9.307, 9.626 and 13.891 THz for Co3Ti.

  8. Features of structure and phase transitions in pure uranium and U-Mo alloys: atomistic simulation

    NASA Astrophysics Data System (ADS)

    Kolotova, L. N.; Kuksin, A. Yu; Smirnova, D. E.; Starikov, S. V.; Tseplyaev, V. I.

    2016-11-01

    We study structural properties of cubic and tetragonal phases of U-Mo alloys using atomistic simulations: molecular dynamics and density functional theory. For pure uranium and U-Mo alloys at low temperatures we observe body-centered tetragonal (bct) structure, which is similar to the metastable γ°-phase found in the experiments. At higher temperatures bct structure transforms to a quasi body-centered cubic (q-bcc) phase that exhibits cubic symmetry just on the scale of several interatomic spacings or when averaged over time. Instantaneous pair distribution function (PDF) differs from PDF for the time-averaged atomic coordinates corresponding to the bcc lattice. The local positions of uranium atoms in q-bcc lattice correspond to the bct structure, which is energetically favourable due to formation of short U-U bonds. Transition from bct to q-bcc could be considered as ferro-to paraelastic transition of order-disorder type. The temperature of transition depends on Mo concentration. For pure uranium it is equal to about 700 K, which is well below than the upper boundary of the stability region of the α-U phase. Due to this reason, bct phase is observed only in uranium alloys containing metals with low solubility in α-U.

  9. Recent advances in computational structural reliability analysis methods

    NASA Technical Reports Server (NTRS)

    Thacker, Ben H.; Wu, Y.-T.; Millwater, Harry R.; Torng, Tony Y.; Riha, David S.

    1993-01-01

    The goal of structural reliability analysis is to determine the probability that the structure will adequately perform its intended function when operating under the given environmental conditions. Thus, the notion of reliability admits the possibility of failure. Given the fact that many different modes of failure are usually possible, achievement of this goal is a formidable task, especially for large, complex structural systems. The traditional (deterministic) design methodology attempts to assure reliability by the application of safety factors and conservative assumptions. However, the safety factor approach lacks a quantitative basis in that the level of reliability is never known and usually results in overly conservative designs because of compounding conservatisms. Furthermore, problem parameters that control the reliability are not identified, nor their importance evaluated. A summary of recent advances in computational structural reliability assessment is presented. A significant level of activity in the research and development community was seen recently, much of which was directed towards the prediction of failure probabilities for single mode failures. The focus is to present some early results and demonstrations of advanced reliability methods applied to structural system problems. This includes structures that can fail as a result of multiple component failures (e.g., a redundant truss), or structural components that may fail due to multiple interacting failure modes (e.g., excessive deflection, resonate vibration, or creep rupture). From these results, some observations and recommendations are made with regard to future research needs.

  10. First-principles study of electronic structures and stability of body-centered cubic Ti–Mo alloys by special quasirandom structures

    PubMed Central

    Sahara, Ryoji; Emura, Satoshi; Ii, Seiichiro; Ueda, Shigenori; Tsuchiya, Koichi

    2014-01-01

    The electronic structures and structural properties of body-centered cubic Ti–Mo alloys were studied by first-principles calculations. The special quasirandom structures (SQS) model was adopted to emulate the solid solution state of the alloys. The valence band electronic structures of Ti–Mo and Ti–Mo–Fe alloys were measured by hard x-ray photoelectron spectroscopy. The structural parameters and valence band photoelectron spectra were calculated using first-principles calculations. The results obtained with the SQS models showed better agreement with the experimental results than those obtained using the conventional ordered structure models. This indicates that the SQS model is effective for predicting the various properties of solid solution alloys by means of first-principles calculations. PMID:27877690

  11. First-principles study of electronic structures and stability of body-centered cubic Ti-Mo alloys by special quasirandom structures.

    PubMed

    Sahara, Ryoji; Emura, Satoshi; Ii, Seiichiro; Ueda, Shigenori; Tsuchiya, Koichi

    2014-06-01

    The electronic structures and structural properties of body-centered cubic Ti-Mo alloys were studied by first-principles calculations. The special quasirandom structures (SQS) model was adopted to emulate the solid solution state of the alloys. The valence band electronic structures of Ti-Mo and Ti-Mo-Fe alloys were measured by hard x-ray photoelectron spectroscopy. The structural parameters and valence band photoelectron spectra were calculated using first-principles calculations. The results obtained with the SQS models showed better agreement with the experimental results than those obtained using the conventional ordered structure models. This indicates that the SQS model is effective for predicting the various properties of solid solution alloys by means of first-principles calculations.

  12. Structure and properties of cast and splat-quenched high-entropy Al-Cu-Fe-Ni-Si alloys

    NASA Astrophysics Data System (ADS)

    Bashev, V. F.; Kushnerov, O. I.

    2017-01-01

    The effect of the composition and cooling rate of the melt on the microhardness, phase composition, and fine-structure parameters of as-cast and splat-quenched (SQ) high-entropy (HE) Al-Cu-Fe-Ni-Si alloys was studied. The quenching was performed by conventional splat-cooling technique. The cooling rate was estimated to be 106 K/s. Components of the studied HE alloys were selected taking into account both criteria for designing and estimating their phase composition, which are available in the literature and based on the calculations of the entropy and enthalpy of mixing, and the difference between atomic radii of components as well. According to X-ray diffraction data, the majority of studied Al-Cu-Fe-Ni-Si compositions are two-phase HE alloys, the structure of which consists of disordered solid solutions with bcc and fcc structures. At the same time, the Al0.5CuFeNi alloy is single-phase in terms of X-ray diffraction and has an fcc structure. The studied alloys in the as-cast state have a dendritic structure, whereas, after splat quenching, the uniform small-grained structure is formed. It was found that, as the volume fraction of bcc solid solution in the studied HE alloys increases, the microhardness increases; the as-cast HE Al-Cu-Fe-Ni-Si alloys are characterized by higher microhardness compared to that of splat-quenched alloys. This is likely due to the more equilibrium multiphase state of as-cast alloys.

  13. Differently Structured Advance Organizers Lead to Different Initial Schemata and Learning Outcomes

    ERIC Educational Resources Information Center

    Gurlitt, Johannes; Dummel, Sebastian; Schuster, Silvia; Nuckles, Matthias

    2012-01-01

    Does the specific structure of advance organizers influence learning outcomes? In the first experiment, 48 psychology students were randomly assigned to three differently structured advance organizers: a well-structured, a well-structured and key-concept emphasizing, and a less structured advance organizer. These were followed by a sorting task, a…

  14. Growth, morphology, and structure of a monolayer thick GdFe2 surface alloy

    NASA Astrophysics Data System (ADS)

    Williams, R. P.; Alcock, S. G.; Howes, P. B.; Nicklin, C. L.

    2016-08-01

    The growth and structure of an ordered GdFe2 surface alloy deposited on Mo(110) has been studied using in situ surface x-ray diffraction. Growth curves and reflectivity scans of varying ratios of Gd to Fe show how the two species intermix prior to alloy formation. After annealing to form the ordered surface alloy, in-plane x-ray diffraction data indicate that the Fe atoms are laterally displaced along the [001] or [00 1 ¯] direction by 0.16 ±0.02 Å from the long bridge site positions. Out-of-plane crystal truncation rod analysis reveals that the Gd atoms lie 3.40 ±0.09 Å above the Mo(110) bridge site, an expansion of 22% relative to the expected hard sphere distance. This is significantly larger than observed in previous studies of the growth of pure Gd on Mo(110). Simple geometric changes are not able to account fully for this expansion and we propose that hydrogen incorporation during alloy formation may also contribute.

  15. Electrical and structural properties of In-implanted Si1–xGex alloys

    DOE PAGES

    Feng, Ruixing; Kremer, F.; Sprouster, D. J.; ...

    2016-01-14

    Here, we report on the effects of dopant concentration and substrate stoichiometry on the electrical and structural properties of In-implanted Si1–xGex alloys. Correlating the fraction of electrically active In atoms from Hall Effect measurements with the In atomic environment determined by X-ray absorption spectroscopy, we observed the transition from electrically active, substitutional In at low In concentration to electrically inactive metallic In at high In concentration. The In solid-solubility limit has been quantified and was dependent on the Si1–xGex alloy stoichiometry; the solid-solubility limit increased as the Ge fraction increased. This result was consistent with density functional theory calculations ofmore » two In atoms in a Si1–xGex supercell that demonstrated that In–In pairing was energetically favorable for x ≲ 0.7 and energetically unfavorable for x ≳ 0.7. Transmission electron microscopy imaging further complemented the results described earlier with the In concentration and Si1–xGex alloy stoichiometry dependencies readily visible. We have demonstrated that low resistivity values can be achieved with In implantation in Si1–xGex alloys, and this combination of dopant and substrate represents an effective doping protocol.« less

  16. Structure and phase stability of a Pu-0.32 wt% Ga alloy

    NASA Astrophysics Data System (ADS)

    Wheeler, D. W.; Ennaceur, S. M.; Matthews, M. B.; Roussel, P.; Bayer, P. D.

    2016-08-01

    In plutonium-gallium (Pu-Ga) alloys that have a Ga content of 0.3-0.4 wt%, their readiness to transform to α‧ renders them of particular interest in efforts to understand the tenuous nature of δ phase stability. The present study is a comprehensive examination of the structure and phase stability of a cast Pu-0.32 wt% Ga alloy, the Ga content being close to the minimum amount needed to retain the δ phase to ambient temperature. The alloy was characterised in both the as-cast condition as well as following a homogenising heat treatment. The 250-h heat treatment at 450 °C was shown to achieve an apparently stable δ-Pu phase. However, the stability of the δ-Pu phase was shown to be marginal: partial transformation to α‧-Pu was observed when the alloy was subjected to hydrostatic compression. Similar transformation was also apparent during metallographic preparation as well as during hardness indentation. The results provide new understanding of the nature of δ phase stability.

  17. Electronic Structure Evolution with Composition Alteration of RhxCuy Alloy Nanoparticles

    PubMed Central

    Palina, Natalia; Sakata, Osami; Kumara, L. S. R.; Song, Chulho; Sato, Katsutoshi; Nagaoka, Katsutoshi; Komatsu, Tokutaro; Kobayashi, Hirokazu; Kusada, Kohei; Kitagawa, Hiroshi

    2017-01-01

    The change in electronic structure of extremely small RhxCuy alloy nanoparticles (NPs) with composition variation was investigated by core-level (CL) and valence-band (VB) hard X-ray photoelectron spectroscopy. A combination of CL and VB spectra analyses confirmed that intermetallic charge transfer occurs between Rh and Cu. This is an important compensation mechanism that helps to explain the relationship between the catalytic activity and composition of RhxCuy alloy NPs. For monometallic Rh and Rh-rich alloy (Rh0.77Cu0.23) NPs, the formation of Rh surface oxide with a non-integer oxidation state (Rh(3−δ)+) resulted in high catalytic activity. Conversely, for alloy NPs with comparable Rh:Cu ratio (Rh0.53Cu0.47 and Rh0.50Cu0.50), the decreased fraction of catalytically active Rh(3−δ)+ oxide is compensated by charge transfer from Cu to Rh. As a result, ensuring negligible change in the catalytic activities of the NPs with comparable Rh:Cu ratio to those of Rh-rich and monometallic Rh NPs. PMID:28120907

  18. Electronic Structure Evolution with Composition Alteration of RhxCuy Alloy Nanoparticles

    NASA Astrophysics Data System (ADS)

    Palina, Natalia; Sakata, Osami; Kumara, L. S. R.; Song, Chulho; Sato, Katsutoshi; Nagaoka, Katsutoshi; Komatsu, Tokutaro; Kobayashi, Hirokazu; Kusada, Kohei; Kitagawa, Hiroshi

    2017-01-01

    The change in electronic structure of extremely small RhxCuy alloy nanoparticles (NPs) with composition variation was investigated by core-level (CL) and valence-band (VB) hard X-ray photoelectron spectroscopy. A combination of CL and VB spectra analyses confirmed that intermetallic charge transfer occurs between Rh and Cu. This is an important compensation mechanism that helps to explain the relationship between the catalytic activity and composition of RhxCuy alloy NPs. For monometallic Rh and Rh-rich alloy (Rh0.77Cu0.23) NPs, the formation of Rh surface oxide with a non-integer oxidation state (Rh(3‑δ)+) resulted in high catalytic activity. Conversely, for alloy NPs with comparable Rh:Cu ratio (Rh0.53Cu0.47 and Rh0.50Cu0.50), the decreased fraction of catalytically active Rh(3‑δ)+ oxide is compensated by charge transfer from Cu to Rh. As a result, ensuring negligible change in the catalytic activities of the NPs with comparable Rh:Cu ratio to those of Rh-rich and monometallic Rh NPs.

  19. Unexpected electronic structure of the alloyed and doped arsenene sheets: First-Principles calculations

    PubMed Central

    Liu, Ming-Yang; Huang, Yang; Chen, Qing-Yuan; Cao, Chao; He, Yao

    2016-01-01

    We study the equilibrium geometry and electronic structure of alloyed and doped arsenene sheets based on the density functional theory calculations. AsN, AsP and SbAs alloys possess indirect band gap and BiAs is direct band gap. Although AsP, SbAs and BiAs alloyed arsenene sheets maintain the semiconducting character of pure arsenene, they have indirect-direct and semiconducting-metallic transitions by applying biaxial strain. We find that B- and N-doped arsenene render p-type semiconducting character, while C- and O-doped arsenene are metallic character. Especially, the C-doped arsenene is spin-polarization asymmetric and can be tuned into the bipolar spin-gapless semiconductor by the external electric field. Moreover, the doping concentration can effectively affect the magnetism of the C-doped system. Finally, we briefly study the chemical molecule adsorbed arsenene. Our results may be valuable for alloyed and doped arsenene sheets applications in mechanical sensors and spintronic devices in the future. PMID:27373712

  20. Unexpected electronic structure of the alloyed and doped arsenene sheets: First-Principles calculations

    NASA Astrophysics Data System (ADS)

    Liu, Ming-Yang; Huang, Yang; Chen, Qing-Yuan; Cao, Chao; He, Yao

    2016-07-01

    We study the equilibrium geometry and electronic structure of alloyed and doped arsenene sheets based on the density functional theory calculations. AsN, AsP and SbAs alloys possess indirect band gap and BiAs is direct band gap. Although AsP, SbAs and BiAs alloyed arsenene sheets maintain the semiconducting character of pure arsenene, they have indirect-direct and semiconducting-metallic transitions by applying biaxial strain. We find that B- and N-doped arsenene render p-type semiconducting character, while C- and O-doped arsenene are metallic character. Especially, the C-doped arsenene is spin-polarization asymmetric and can be tuned into the bipolar spin-gapless semiconductor by the external electric field. Moreover, the doping concentration can effectively affect the magnetism of the C-doped system. Finally, we briefly study the chemical molecule adsorbed arsenene. Our results may be valuable for alloyed and doped arsenene sheets applications in mechanical sensors and spintronic devices in the future.

  1. Structure, mechanical properties, corrosion behavior and cytotoxicity of biodegradable Mg-X (X=Sn, Ga, In) alloys.

    PubMed

    Kubásek, J; Vojtěch, D; Lipov, J; Ruml, T

    2013-05-01

    As-cast Mg-Sn, Mg-Ga and Mg-In alloys containing 1-7 wt.% of alloying elements were studied in this work. Structural and chemical analysis of the alloys was performed by using light and scanning electron microscopy, energy dispersive spectrometry, x-ray diffraction, x-ray photoelectron spectroscopy and glow discharge spectrometry. Mechanical properties were determined by Vickers hardness measurements and tensile testing. Corrosion behavior in a simulated physiological solution (9 g/l NaCl) was studied by immersion tests and potentiodynamic measurements. The cytotoxicity effect of the alloys on human osteosarcoma cells (U-2 OS) was determined by an indirect contact assay. Structural investigation revealed the dendritic morphology of the as-cast alloys with the presence of secondary eutectic phases in the Mg-Sn and Mg-Ga alloys. All the alloying elements showed hardening and strengthening effects on magnesium. This effect was the most pronounced in the case of Ga. All the alloying elements at low concentrations of approximately 1 wt.% were also shown to positively affect the corrosion resistance of Mg. But at higher concentrations of Ga and Sn the corrosion resistance worsened due to galvanic effects of secondary phases. Cytotoxicity tests indicated that Ga had the lowest toxicity, followed by Sn. The most severe toxicity was observed in the case of In.

  2. An Assessment of the Residual Stresses in Low Pressure Plasma Sprayed Coatings on an Advanced Copper Alloy

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Ghosn, L. J.; Agarwal, A.; Lachtrupp, T. P.

    2002-01-01

    Modeling studies were conducted on low pressure plasma sprayed (LPPS) NiAl top coat applied to an advanced Cu-8(at.%)Cr-4%Nb alloy (GRCop-84) substrate using Ni as a bond coat. A thermal analysis suggested that the NiAl and Ni top and bond coats, respectively, would provide adequate thermal protection to the GRCop-84 substrate in a rocket engine operating under high heat flux conditions. Residual stress measurements were conducted at different depths from the free surface on coated and uncoated GRCop-84 specimens by x-ray diffraction. These data are compared with theoretically estimated values assessed by a finite element analysis simulating the development of these stresses as the coated substrate cools down from the plasma spraying temperature to room temperature.

  3. Advances in Fatigue and Fracture Mechanics Analyses for Aircraft Structures

    NASA Technical Reports Server (NTRS)

    Newman, J. C., Jr.

    1999-01-01

    This paper reviews some of the advances that have been made in stress analyses of cracked aircraft components, in the understanding of the fatigue and fatigue-crack growth process, and in the prediction of residual strength of complex aircraft structures with widespread fatigue damage. Finite-element analyses of cracked structures are now used to determine accurate stress-intensity factors for cracks at structural details. Observations of small-crack behavior at open and rivet-loaded holes and the development of small-crack theory has lead to the prediction of stress-life behavior for components with stress concentrations under aircraft spectrum loading. Fatigue-crack growth under simulated aircraft spectra can now be predicted with the crack-closure concept. Residual strength of cracked panels with severe out-of-plane deformations (buckling) in the presence of stiffeners and multiple-site damage can be predicted with advanced elastic-plastic finite-element analyses and the critical crack-tip-opening angle (CTOA) fracture criterion. These advances are helping to assure continued safety of aircraft structures.

  4. Computerized structural mechanics for 1990's: Advanced aircraft needs

    NASA Technical Reports Server (NTRS)

    Viswanathan, A. V.; Backman, B. F.

    1989-01-01

    The needs for computerized structural mechanics (CSM) as seen from the standpoint of the aircraft industry are discussed. These needs are projected into the 1990's with special focus on the new advanced materials. Preliminary design/analysis, research, and detail design/analysis are identified as major areas. The role of local/global analyses in these different areas is discussed. The lessons learned in the past are used as a basis for the design of a CSM framework that could modify and consolidate existing technology and include future developments in a rational and useful way. A philosophy is stated, and a set of analyses needs driven by the emerging advanced composites is enumerated. The roles of NASA, the universities, and the industry are identified. Finally, a set of rational research targets is recommended based on both the new types of computers and the increased complexity the industry faces. Computerized structural mechanics should be more than new methods in structural mechanics and numerical analyses. It should be a set of engineering applications software products that combines innovations in structural mechanics, numerical analysis, data processing, search and display features, and recent hardware advances and is organized in a framework that directly supports the design process.

  5. Design of Ternary Nanoalloy Catalysts: Effect of Nanoscale Alloying and Structural Perfection on Electrocatalytic Enhancement

    SciTech Connect

    Wanjala, Bridgid N.; Fang, Bin; Shan, Shiyao; Petkov, Valeri; Zhu, Pengyu; Loukrakpam, Rameshwori; Chen, Yongsheng; Luo, Jin; Yin, Jun; Yang, Lefu; Shao, Minhua; Zhong, Chuan-Jian

    2012-10-22

    The ability to tune the atomic-scale structural and chemical ordering in nanoalloy catalysts is essential for achieving the ultimate goal of high activity and stability of catalyst by design. This article shows this ability with a ternary nanoalloy of platinum with vanadium and cobalt for oxygen reduction reaction in fuel cells. The strategy is to enable nanoscale alloying and structural perfection through oxidative–reductive thermochemical treatments. The structural manipulation is shown to produce a significant enhancement in the electrocatalytic activity of the ternary nanoalloy catalysts for oxygen reduction reaction. Mass activities as high as 1 A/mg of Pt have been achieved by this strategy based on direct measurements of the kinetic currents from rotating disk electrode data. Using a synchrotron high-energy X-ray diffraction technique coupled with atomic pair function analysis and X-ray absorption fine structure spectroscopy as well as X-ray photoelectron spectroscopy, the atomic-scale structural and chemical ordering in nanoalloy catalysts prepared by the oxidative–reductive thermochemical treatments were examined. A phase transition has been observed, showing an fcc-type structure of the as-prepared and the lower-temperature-treated particles into an fct-type structure for the particles treated at the higher temperature. The results reveal a thermochemically driven evolution of the nanoalloys from a chemically disordered state into chemically ordered state with an enhanced degree of alloying. The increase in the chemical ordering and shrinking of interatomic distances as a result of thermochemical treatment at increased temperature is shown to increase the catalytic activity for oxygen reduction reaction, exhibiting an optimal activity at 600 °C. It is the alloying and structural perfection that allows the optimization of the catalytic performance in a controllable way, highlighting the significant role of atomic-scale structural and chemical ordering

  6. Design of Ternary Nanoalloy Catalysts: Effect of Nanoscale Alloying and Structural Perfection on Electrocatalytic Enhancement

    SciTech Connect

    Wanjala, Bridgid N.; Fang, Bin; Shan, Shiyao; Petkov, Valeri; Zhu, Pengyu; Loukrakpam, Rameshwori; Chen, Yongsheng; Luo, Jin; Yin, Jun; Yang, Lefu; Shao, Minhua; Zhong, Chuan-Jian

    2012-11-27

    The ability to tune the atomic-scale structural and chemical ordering in nanoalloy catalysts is essential for achieving the ultimate goal of high activity and stability of catalyst by design. This article demonstrates this ability with a ternary nanoalloy of platinum with vanadium and cobalt for oxygen reduction reaction in fuel cells. The strategy is to enable nanoscale alloying and structural perfection through oxidative–reductive thermochemical treatments. The structural manipulation is shown to produce a significant enhancement in the electrocatalytic activity of the ternary nanoalloy catalysts for oxygen reduction reaction. Mass activities as high as 1 A/mg of Pt have been achieved by this strategy based on direct measurements of the kinetic currents from rotating disk electrode data. Using a synchrotron high-energy X-ray diffraction technique coupled with atomic pair function analysis and X-ray absorption fine structure spectroscopy as well as X-ray photoelectron spectroscopy, the atomic-scale structural and chemical ordering in nanoalloy catalysts prepared by the oxidative–reductive thermochemical treatments were examined. A phase transition has been observed, showing an fcc-type structure of the as-prepared and the lower-temperature-treated particles into an fct-type structure for the particles treated at the higher temperature. The results reveal a thermochemically driven evolution of the nanoalloys from a chemically disordered state into chemically ordered state with an enhanced degree of alloying. The increase in the chemical ordering and shrinking of interatomic distances as a result of thermochemical treatment at increased temperature is shown to increase the catalytic activity for oxygen reduction reaction, exhibiting an optimal activity at 600 °C. It is the alloying and structural perfection that allows the optimization of the catalytic performance in a controllable way, highlighting the significant role of atomic-scale structural and chemical

  7. Finite Element Analysis and Die Design of Non-specific Engineering Structure of Aluminum Alloy during Extrusion

    SciTech Connect

    Chen, D.-C.; Lu, Y.-Y.

    2010-06-15

    Aluminum extension applies to industrial structure, light load, framework rolls and conveyer system platform. Many factors must be controlled in processing the non-specific engineering structure (hollow shape) of the aluminum alloy during extrusion, to obtain the required plastic strain and desired tolerance values. The major factors include the forming angle of the die and temperature of billet and various materials. This paper employs rigid-plastic finite element (FE) DEFORM 3D software to investigate the plastic deformation behavior of an aluminum alloy (A6061, A5052, A3003) workpiece during extrusion for the engineering structure of the aluminum alloy. This work analyzes effective strain, effective stress, damage and die radius load distribution of the billet under various conditions. The analytical results confirm the suitability of the current finite element software for the non-specific engineering structure of aluminum alloy extrusion.

  8. Structure of the c(2x2) Mn/Ni(001) surface alloy by quantitative photoelectron diffraction

    SciTech Connect

    Banerjee, S.; Denlinger, J.; Chen, X.

    1997-04-01

    Surface alloys are two-dimensional metallic systems that can have structures that are unique to the surface, and have no counterpart in the bulk binary phase diagram. A very unusual structure was reported for the Mn-Ni system, based on a quantitative LEED structure determination, which showed that the Mn atoms were displaced out of the surface by a substantial amount. This displacement was attributed to a large magnetic moment on the Mn atoms. The structure of the Mn-Ni surface alloy was proposed to be based on a bulk termination model. Magnetic measurements on the Mn-Ni surface alloys, however, showed conclusively that the magnetic structure of these surface alloys is completely different from the bulk alloy analogs. For example, bulk MnNi is an antiferromagnet, whereas the surface alloy is ferromagnetic. This suggests that the proposed structure based on bulk termination, may not be correct. X-ray Photoelectron Diffraction (XPD) techniques were used to investigate this structure, using both a comparison to multiple scattering calculations and photoelectron holography. In this article the authors present some of the results from the quantitative analysis of individual diffraction patterns by comparison to theory.

  9. Structural Change Can Be Detected in Advanced-Glaucoma Eyes

    PubMed Central

    Belghith, Akram; Medeiros, Felipe A.; Bowd, Christopher; Liebmann, Jeffrey M.; Girkin, Christopher A.; Weinreb, Robert N.; Zangwill, Linda M.

    2016-01-01

    Purpose To compare spectral-domain optical coherence tomography (SD-OCT) standard structural measures and a new three-dimensional (3D) volume optic nerve head (ONH) change detection method for detecting change over time in severely advanced-glaucoma (open-angle glaucoma [OAG]) patients. Methods Thirty-five eyes of 35 patients with very advanced glaucoma (defined as a visual field mean deviation < −21 dB) and 46 eyes of 30 healthy subjects to estimate aging changes were included. Circumpapillary retinal fiber layer thickness (cpRNFL), minimum rim width (MRW), and macular retinal ganglion cell–inner plexiform layer (GCIPL) thicknesses were measured using the San Diego Automated Layer Segmentation Algorithm (SALSA). Progression was defined as structural loss faster than 95th percentile of healthy eyes. Three-dimensional volume ONH change was estimated using the Bayesian-kernel detection scheme (BKDS), which does not require extensive retinal layer segmentation. Results The number of progressing glaucoma eyes identified was highest for 3D volume BKDS (13, 37%), followed by GCPIL (11, 31%), cpRNFL (4, 11%), and MRW (2, 6%). In advanced-OAG eyes, only the mean rate of GCIPL change reached statistical significance, −0.18 μm/y (P = 0.02); the mean rates of cpRNFL and MRW change were not statistically different from zero. In healthy eyes, the mean rates of cpRNFL, MRW, and GCIPL change were significantly different from zero. (all P < 0.001). Conclusions Ganglion cell–inner plexiform layer and 3D volume BKDS show promise for identifying change in severely advanced glaucoma. These results suggest that structural change can be detected in very advanced disease. Longer follow-up is needed to determine whether changes identified are false positives or true progression. PMID:27454660

  10. Effect of Microalloying, with Rem Inclusively, on the Structure, Phase Composition and Properties of (α + β)-Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Illarionov, A. G.; Popov, A. A.; Illarionova, S. M.

    2016-03-01

    The effect of microalloying with yttrium and zirconium in the amount of 0.06 and 0.07 wt.% respectively on the formation of structure, phase composition and measured hardness characteristics of a two-phase titanium alloy of the Ti - Al - Mo - V - Cr - Fe system is studied. The laws of variation of the phase composition and structure of the alloy with microadditives in the temperature range of 700 - 950°C and during subsequent cooling in water and air are determined. The diagram of variation of the phase composition of the alloy under water quenching is plotted.

  11. Non-Oxide Structural Ceramics - Alloy Design for Improved Sinterability and Mechanical Performance

    DTIC Science & Technology

    2007-11-02

    DATES COVERED Final Technical Report 1 Jan 95 to 31 Dec 97 4. TITLE AND SUBTITLE NON-OXIDE STRUCTURAL CERAMICS - ALLOY DESIGN FOR IMPROVED...SINTERABILITY AND MECHANICAL PERFORMANCE 6. AUTHOR(S) I-WEI CHEN TSENG-YING TIEN 5 . FUNDING NUMBERS F49620-95-1-0119 7. PERFORMING ORGANIZATION...Boiling AFB, DC 20332/ 8050 10. SPONSORING/MONITORING AGENCY REPORT NUMBER F49620-95-1-0119 11. SUPPLEMENTARY NOTES 12a. DISTRIBUTION AVAILABILITY

  12. Ball-Burnishing and Roller-Burnishing to Improve Fatigue Performance of Structural Alloys

    NASA Astrophysics Data System (ADS)

    Wagner, Lothar; Ludian, Tomasz; Wollmann, Manfred

    The HCF response to burnishing of a number of structural materials is compared and contrasted. It is shown that alloys which exhibit marked work-hardening during burnishing respond very beneficially with regard to HCF performance while others which show little work-hardening may even react with losses in HCF strength. Possible explanations for such behavior are outlined in terms of mean stress and environmental sensitivities of the fatigue strengths of the various materials and microstructures.

  13. Enhanced Magnetoelectric Coupling in Layered Structure of Piezoelectric Bimorph and Metallic Alloy

    NASA Astrophysics Data System (ADS)

    Petrov, V. M.; Bichurin, M. I.; Lavrentyeva, K. V.; Leontiev, V. S.

    2016-08-01

    We have investigated the enhanced magnetoelectric (ME) coupling in a layered structure of piezoelectric bimorph and magnetostrictive metallic alloy. The observed ME coefficient in the piezoelectric bimorph-based structure was found to be two times higher than in the traditional piezoelectric/magnetostrictive bilayer. The observed enhancement in ME coupling strength is related to equal signs of induced voltage in both lead zirconate titanate layers with opposite poling directions due to the flexural deformations. The piezoelectric bimorph-based structure has promising potential for sensor and technological applications.

  14. Comparative Structural Strength Research of Hardened Carbon Steel and Hot-Rolled Alloy Steel

    NASA Astrophysics Data System (ADS)

    Bogomolov, A. V.; Zhakupov, A. N.; Kanayev, A. T.; Sikach, I. A.; Tugumov, K. K.

    2016-08-01

    Experiments on quantitative evaluation of fatigue strength showed that St5ps and St5sp carbon steels with A400 strength class can be fully applied for erection of constructions and buildings having cyclical loads during operation. Study of corrosion resistance of hardened carbon steel in comparison with hot-rolled alloy steel consists in difference in structures and hence, difference in intensity of electric and chemical processes featuring presence of steel in concrete. Structure of St5sp steel with A400 strength class in surface area has significantly less corrosion rate than ferritic-perlitic structure of 35GS steel with A400 strength class.

  15. Evolution of grain boundary structure in submicrometer-grained Al-Mg alloy

    SciTech Connect

    Horita, Zenji; Nemoto, Minoru; Smith, D.J.; Furukawa, Minoru; Valiev, R.Z.; Langdon, T.G.

    1996-11-01

    This paper presents high-resolution electron microscopy studies of grain boundary structures in a submicrometer-grained Al-3%Mg solid solution alloy produced by an intense plastic straining technique. The studies include the effect of static annealing on the grain boundary structure. Many grain boundaries are in a high-energy nonequilibrium state in the as-strained sample. The nonequilibrium character is retained on some grain boundaries in samples annealed at temperatures below the onset of significant grain growth. The effect of electron irradiation on the grain boundary structure also is examined.

  16. Aging Optimization of Aluminum-Lithium Alloy C458 for Application to Cryotank Structures

    NASA Technical Reports Server (NTRS)

    Sova, B. J.; Sankaran, K. K.; Babel, H.; Farahmand, B.; Rioja, R.

    2003-01-01

    Compared with aluminum alloys such as 2219, which is widely used in space vehicle for cryogenic tanks and unpressurized structures, aluminum-lithium alloys possess attractive combinations of lower density and higher modulus along with comparable mechanical properties. These characteristics have resulted in the successful use of the aluminum-lithium alloy 2195 (Al-1.0 Li-4.0 Cu-0.4 Mg-0.4 Ag-0.12 Zr) for the Space Shuttle External Tank, and the consideration of newer U.S. aluminum-lithium alloys such as L277 and C458 for future space vehicles. These newer alloys generally have lithium content less than 2 wt. % and their composition and processing have been carefully tailored to increase the toughness and reduce the mechanical property anisotropy of the earlier generation alloys such 2090 and 8090. Alloy processing, particularly the aging treatment, has a significant influence on the strength-toughness combinations and their dependence on service environments for aluminum-lithium alloys. Work at NASA Marshall Space Flight Center on alloy 2195 has shown that the cryogenic toughness can be improved by employing a two-step aging process. This is accomplished by aging at a lower temperature in the first step to suppress nucleation of the strengthening precipitate at sub-grain boundaries while promoting nucleation in the interior of the grains. Second step aging at the normal aging temperature results in precipitate growth to the optimum size. A design of experiments aging study was conducted for plate. To achieve the T8 temper, Alloy C458 (Al-1.8 Li-2.7 Cu-0.3 Mg-0.08 Zr-0.3 Mn-0.6 Zn) is typically aged at 300F for 24hours. In this study, a two-step aging treatment was developed through a comprehensive 2(exp 4) full factorial design of experiments study and the typical one-step aging used as a reference. Based on the higher lithium content of C458 compared with 2195, the first step aging temperature was varied between 175F and 250F. The second step aging temperatures was

  17. Applications of Isotopes in Advancing Structural & Functional Heparanomics

    PubMed Central

    Tran, Vy M.; Nu Nguyen, Thao Kim; Raman, Karthik; Kuberan, Balagurunathan

    2011-01-01

    Heparanomics is the study of all the biologically active oligosaccharide domain structures in the entire heparanome and the nature of interactions among these domains and their protein ligands. Structural elucidation of heparan sulfate and heparin oligosaccharides is a major obstacle in advancing structure-function relationships and the study of heparanomics. There are several factors that exacerbate challenges involved in the structural elucidation of heparin and heparan sulfate. Therefore, there is a great interest in developing novel strategies and analytical tools to overcome the barriers in decoding the enigmatic heparanome. This review article focuses on the applications of isotopes, both radioisotopes and stable isotopes, in the structural elucidation of the complex heparanome at the disaccharide or oligosaccharide level using liquid chromatography, nuclear magnetic resonance spectroscopy and mass spectrometry. This review article also outlines the utility of isotopes in determining the substrate specificity of biosynthetic enzymes that eventually dictate the emergence of biologically active oligosaccharides. PMID:20838780

  18. Shake table tests and analytical simulations of a steel structure with shape memory alloy dampers

    NASA Astrophysics Data System (ADS)

    Parulekar, Y. M.; Kiran, A. Ravi; Reddy, G. R.; Singh, R. K.; Vaze, K. K.

    2014-12-01

    This study uses the pseudoelastic properties of Ni-Ti shape memory alloy wires for attenuation of the seismic response of a steel structure and evaluates its effectiveness and applicability in seismic response control. In this paper, shake table tests, carried out on a model of a steel structure with and without wire-based shape memory alloy dampers, are discussed in detail. Shake table tests, comprised of free vibration tests and spectrum compatible time history tests, were carried out. The former were used for the evaluation of the frequency and damping, and the later were used to prove the efficacy of the shape memory alloy dampers. Further analytical simulations are carried out using detailed time history analysis utilizing a thermomechanical model of an SMA and taking into account the residual martensite accumulation, which is irreversibly due to cyclic forward/reverse martensitic transformation. Moreover, a simple iterative response spectrum (IRS) method with equivalent damping and stiffness is also used to evaluate the response of the structure with SMA dampers, and it is proved that the method can be conservatively used by designers.

  19. Structural transformations in amorphous ↔ crystalline phase change of Ga-Sb alloys

    SciTech Connect

    Edwards, T. G.; Sen, S.; Hung, I.; Gan, Z.; Kalkan, B.; Raoux, S.

    2013-12-21

    Ga-Sb alloys with compositions ranging between ∼12 and 50 at. % Ga are promising materials for phase change random access memory applications. The short-range structures of two such alloys with compositions Ga{sub 14}Sb{sub 86} and Ga{sub 46}Sb{sub 54} are investigated, in their amorphous and crystalline states, using {sup 71}Ga and {sup 121}Sb nuclear magnetic resonance spectroscopy and synchrotron x-ray diffraction. The Ga and Sb atoms are fourfold coordinated in the as-deposited amorphous Ga{sub 46}Sb{sub 54} with nearly 40% of the constituent atoms being involved in Ga-Ga and Sb-Sb homopolar bonding. This necessitates extensive bond switching and elimination of homopolar bonds during crystallization. On the other hand, Ga and Sb atoms are all threefold coordinated in the as-deposited amorphous Ga{sub 14}Sb{sub 86}. Crystallization of this material involves phase separation of GaSb domains in Sb matrix and a concomitant increase in the Ga coordination number from 3 to 4. Results from crystallization kinetics experiments suggest that the melt-quenching results in the elimination of structural “defects” such as the homopolar bonds and threefold coordinated Ga atoms in the amorphous phases of these alloys, thereby rendering them structurally more similar to the corresponding crystalline states compared to the as-deposited amorphous phases.

  20. Mo-Si-B alloys for ultrahigh-temperature structural applications.

    PubMed

    Lemberg, J A; Ritchie, R O

    2012-07-10

    A continuing quest in science is the development of materials capable of operating structurally at ever-increasing temperatures. Indeed, the development of gas-turbine engines for aircraft/aerospace, which has had a seminal impact on our ability to travel, has been controlled by the availability of materials capable of withstanding the higher-temperature hostile environments encountered in these engines. Nickel-base superalloys, particularly as single crystals, represent a crowning achievement here as they can operate in the combustors at ~1100 °C, with hot spots of ~1200 °C. As this represents ~90% of their melting temperature, if higher-temperature engines are ever to be a reality, alternative materials must be utilized. One such class of materials is Mo-Si-B alloys; they have higher density but could operate several hundred degrees hotter. Here we describe the processing and structure versus mechanical properties of Mo-Si-B alloys and further document ways to optimize their nano/microstructures to achieve an appropriate balance of properties to realistically compete with Ni-alloys for elevated-temperature structural applications.

  1. Novel lubricated surface of titanium alloy based on porous structure and hydrophilic polymer brushes

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Xiong, Dangsheng; Niu, Yuxiang

    2014-10-01

    On the purpose of improving the tribological properties of titanium alloy through mimicking natural articular cartilage, porous structure was prepared on the surface of Ti6Al4V alloy by anodic oxidation method, and then hydrophilic polymer brushes were grafted onto its surface. Surface morphology of porous oxidized film was investigated by metalloscope and scanning electron microscope (SEM). The composition and structure of modified surface were characterized by Fourier-transform infrared spectroscopy with attenuated total reflection (FTIR/ATR), and the wettability was also evaluated. Friction and wear properties of modified alloys sliding against ultra-high molecular weight polyethylene (UHMWPE) were tested by a pin-on-disc tribometer in physiological saline. The results showed that, the optimum porous structure treated by anodic oxidation formed when the voltage reached as high as 100 V. Hydrophilic monomers [Acrylic acid (AA) and 3-dimethyl-(3-(N-methacrylamido) propyl) ammonium propane sulfonate (DMMPPS)] were successfully grafted onto porous Ti6Al4V surface to form polymer brushes by UV radiation. The change of contact angle showed that wettability of modified Ti6Al4V was improved significantly. The friction coefficient of modified Ti6Al4V was much lower and more stable than untreated ones. The lowest friction coefficient was obtained when the sample was anodized at 100 V and grafted with DMMPPS, and the value was 0.132. The wear of modified samples was also obviously improved.

  2. Development of an Advanced Carbide Cutting Tool for Nickel-based Alloy Machining

    DTIC Science & Technology

    2006-08-28

    Inconel 718 utilizing state-of-the-market and state-of-the-art methods. The goal of increasing machining productivity by 40% was achieved with the...project is turning of Inconel 718 alloy. 1.3 Funding The total NCDMM funding for the project was $150,000 ($120,000 for labor and $30,000 for workpiece...tasks Task 1: Review current Inconel machining practice Task 2: Establish the current state of the art in Inconel 718 turning  Establish baseline data

  3. Overview of an Advanced Hypersonic Structural Concept Test Program

    NASA Technical Reports Server (NTRS)

    Stephens, Craig A.; Hudson, Larry D.; Piazza, Anthony

    2007-01-01

    This viewgraph presentation provides an overview of hypersonics M&S advanced structural concepts development and experimental methods. The discussion on concepts development includes the background, task objectives, test plan, and current status of the C/SiC Ruddervator Subcomponent Test Article (RSTA). The discussion of experimental methods examines instrumentation needs, sensors of interest, and examples of ongoing efforts in the development of extreme environment sensors.

  4. Structural Tailoring of Advanced Turboprops (STAT) programmer's manual

    NASA Technical Reports Server (NTRS)

    Brown, K. W.; Harvey, P. R.

    1989-01-01

    The Structural Tailoring of Advanced Turboprops (STAT) computer program was developed to perform numerical optimizations on highly swept propfan blades. This manual describes the functionality of the STAT system from a programmer's viewpoint. It provides a top-down description of module intent and interaction. The purpose of this manual is to familiarize the programmer with the STAT system should he/she wish to enhance or verify the program's function.

  5. Advanced stress analysis methods applicable to turbine engine structures

    NASA Technical Reports Server (NTRS)

    Pian, T. H. H.

    1985-01-01

    Advanced stress analysis methods applicable to turbine engine structures are investigated. Constructions of special elements which containing traction-free circular boundaries are investigated. New versions of mixed variational principle and version of hybrid stress elements are formulated. A method is established for suppression of kinematic deformation modes. semiLoof plate and shell elements are constructed by assumed stress hybrid method. An elastic-plastic analysis is conducted by viscoplasticity theory using the mechanical subelement model.

  6. a Structural Investigation of the Passive Film on Iron and Iron/chromium Alloys.

    NASA Astrophysics Data System (ADS)

    Kerkar, Moussa

    Available from UMI in association with The British Library. Requires signed TDF. The Electrochemical Polarisation, Photocurrent Spectroscopy and Extended X-ray Absorption Fine Structure (EXAFS) techniques have been used to study the passive film on pure iron and iron alloy samples containing up to 25% chromium. The material used in this work was prepared both as bulk and thin films. The bulk samples were passivated electrochemically at various anodic potentials whereas the film ones were either fully converted into passive films by simple immersion in various solutions for one week or electrochemically at various anodic potentials. The Fe and Fe/Cr film samples used in the electrochemical passivation were deposited onto gold substrate and those passivated by immersion were deposited directly onto mylar. Polarisation curves for both the bulk and film materials were recorded. They suggest that the electrochemical behaviour of the two materials is similar. The wavelength and potential dependence of the photocurrent spectra were also recorded for the bulk and film samples of Fe and Fe/Cr alloys. The data were analysed to obtain the effective optical band gaps and flat band potentials of the passive films respectively. These results also show that the two materials are similar. Furthermore, the photocurrent data suggest that the passive film on Fe/Cr alloys consists of Fe(III) and Cr(III) phases. The fluorescence EXAFS above the Fe and Cr K-absorption edges of the passive film on Fe and Fe/Cr alloy films has been recorded both in-situ and ex-situ. The spectra obtained in these studies were analysed to obtain average Fe-O and Fe-Fe separations as well as Cr-O and Cr-Cr ones. These results together with a detailed examination of the XANES suggest that the passive film on iron in the absence of chromium is best described as a disordered gamma -FeOOH-like structure and that on Fe/Cr alloys as well as on pure Fe passivated in chromate solution contains two simultaneous

  7. Surface structure and properties of biomedical NiTi shape memory alloy after Fenton's oxidation.

    PubMed

    Chu, C L; Hu, T; Wu, S L; Dong, Y S; Yin, L H; Pu, Y P; Lin, P H; Chung, C Y; Yeung, K W K; Chu, Paul K

    2007-09-01

    Fenton's oxidation is traditionally used to remove inorganic and organic pollutants from water in waster water treatment. It is an advanced oxidation process in which H2O2 is catalytically decomposed by ferrous irons into hydroxyl radicals (*OH) which have a higher oxidation potential (2.8V) than H2O2. In the work reported here, we for the first time use Fenton's oxidation to modify the surface of biomedical NiTi shape memory alloy (SMA). The influences of Fenton's oxidation on the surface microstructure, blood compatibility, leaching of harmful Ni ions and corrosion resistance in simulated body fluids is assessed using scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma mass spectrometry, electrochemical tests, hemolysis analysis and the blood platelet adhesion test. The mechanical stability of the surface titania film produced by Fenton's oxidation as well as their effects on the shape memory behavior of the SMA are studied by bending tests. Our results show that Fenton's oxidation produces a novel nanostructured titania gel film with a graded structure on the NiTi substrate without an intermediate Ni-rich layer that is typical of high-temperature oxidation. Moreover, there is a clear Ni-free zone near the top surface of the titania film. The surface structural changes introduced by Fenton's oxidation improve the electrochemical corrosion resistance and mitigate Ni release. The latter effects are comparable to those observed after oxygen plasma immersion ion implantation reported previously and better than those of high-temperature oxidation. Aging in boiling water improves the crystallinity of the titania film and further reduces Ni leaching. Blood platelet adhesion is remarkably reduced after Fenton's oxidation, suggesting that the treated SMA has improved thrombo resistance. Enhancement of blood compatibility is believed to stem from the improved hemolysis resistance, the surface wettability and the

  8. NASA-UVa light aerospace alloy and structures technology program supplement: Aluminum-based materials for high speed aircraft

    NASA Technical Reports Server (NTRS)

    Starke, E. A., Jr. (Editor)

    1995-01-01

    This report on the NASA-UVa light aerospace alloy and structure technology program supplement: Aluminum-Based Materials for High Speed Aircraft covers the period from July 1, 1992. The objective of the research is to develop aluminum alloys and aluminum matrix composites for the airframe which can efficiently perform in the HSCT environment for periods as long as 60,000 hours (certification for 120,000 hours) and, at the same time, meet the cost and weight requirements for an economically viable aircraft. Current industry baselines focus on flight at Mach 2.4. The research covers four major materials systems: (1) Ingot metallurgy 2XXX, 6XXX, and 8XXX alloys, (2) Powder metallurgy 2XXX alloys, (3) Rapidly solidified, dispersion strengthened Al-Fe-X alloys, and (4) Discontinuously reinforced metal matrix composites. There are ten major tasks in the program which also include evaluation and trade-off studies by Boeing and Douglas aircraft companies.

  9. Assessment of Embrittlement of VHTR Structural Alloys in Impure Helium Environments

    SciTech Connect

    Crone, Wendy; Cao, Guoping; Sridhara, Kumar

    2013-05-31

    The helium coolant in high-temperature reactors inevitably contains low levels of impurities during steady-state operation, primarily consisting of small amounts of H{sub 2}, H{sub 2}O, CH{sub 4}, CO, CO{sub 2}, and N{sub 2} from a variety of sources in the reactor circuit. These impurities are problematic because they can cause significant long-term corrosion in the structural alloys used in the heat exchangers at elevated temperatures. Currently, the primary candidate materials for intermediate heat exchangers are Alloy 617, Haynes 230, Alloy 800H, and Hastelloy X. This project will evaluate the role of impurities in helium coolant on the stress-assisted grain boundary oxidation and creep crack growth in candidate alloys at elevated temperatures. The project team will: • Evaluate stress-assisted grain boundary oxidation and creep crack initiation and crack growth in the temperature range of 500-850°C in a prototypical helium environment. • Evaluate the effects of oxygen partial pressure on stress-assisted grain boundary oxidation and creep crack growth in impure helium at 500°C, 700°C, and 850°C respectively. • Characterize the microstructure of candidate alloys after long-term exposure to an impure helium environment in order to understand the correlation between stress-assisted grain boundary oxidation, creep crack growth, material composition, and impurities in the helium coolant. • Evaluate grain boundary engineering as a method to mitigate stress-assisted grain boundary oxidation and creep crack growth of candidate alloys in impure helium. The maximum primary helium coolant temperature in the high-temperature reactor is expected to be 850-1,000°C.Corrosion may involve oxidation, carburization, or decarburization mechanisms depending on the temperature, oxygen partial pressure, carbon activity, and alloy composition. These corrosion reactions can substantially affect long-term mechanical properties such as crack- growth rate and fracture

  10. ADVANCED SOLIDS NMR STUDIES OF COAL STRUCTURE AND CHEMISTRY

    SciTech Connect

    1997-09-01

    This report covers the progress made on the title project for the project period. The study of coal chemical structure is a vital component of research efforts to develop better chemical utilization of coals, and for furthering our basic understanding of coal geochemistry. In this grant we are addressing several structural questions pertaining to coals with advances in state of the art solids NMR methods. The main activity during this granting period was a completion of a detailed comparative analysis of the suite of spectral editing techniques developed in our laboratory for this purpose. The appended report is a manuscript being submitted to the Journal of Magnetic Resonance on this subject.

  11. Homogenizing Advanced Alloys: Thermodynamic and Kinetic Simulations Followed by Experimental Results

    NASA Astrophysics Data System (ADS)

    Jablonski, Paul D.; Hawk, Jeffrey A.

    2016-11-01

    Segregation of solute elements occurs in nearly all metal alloys during solidification. The resultant elemental partitioning can severely degrade as-cast material properties and lead to difficulties during post-processing (e.g., hot shorts and incipient melting). Many cast articles are subjected to a homogenization heat treatment in order to minimize segregation and improve their performance. Traditionally, homogenization heat treatments are based upon past practice or time-consuming trial and error experiments. Through the use of thermodynamic and kinetic modeling software, NETL has designed a systematic method to optimize homogenization heat treatments. Use of the method allows engineers and researchers to homogenize casting chemistries to levels appropriate for a given application. The method also allows for the adjustment of heat treatment schedules to fit limitations on in-house equipment (capability, reliability, etc.) while maintaining clear numeric targets for segregation reduction. In this approach, the Scheil module within Thermo-Calc is used to predict the as-cast segregation present within an alloy, and then diffusion controlled transformations is used to model homogenization kinetics as a function of time and temperature. Examples of computationally designed heat treatments and verification of their effects on segregation and properties of real castings are presented.

  12. Tungsten alloyed with rhenium as an advanced material for heat-resistant silicon ICs interconnects

    NASA Astrophysics Data System (ADS)

    Belov, A. N.; Chaplygin, Yu. A.; Golishnikov, A. A.; Kostyukov, D. A.; Putrya, M. G.; Safonov, S. O.; Shevyakov, V. I.

    2016-12-01

    This paper presents the results of comparative analysis of the electrical and mechanical characteristics of the tungsten and tungsten alloyed with rhenium films deposited on silicon, from the point of view of their use as interconnects in silicon ICs. W and W (Re-5%) alloyed with rhenium films were made by magnetron deposition. Sheet resistivity for W and W (Re- 5%) was 13 and 27 μOhm·cm respectively. Elemental composition the formed films was examined by Auger spectroscopy. To investigate the electromigration resistance of the conductors a methodology based on the accelerated electromigration testing at constant temperature was used. A comparative analysis of the mechanical stresses carried out in the W and W(Re - 5%) films. For this purpose was applied non-destructive method for optical laser scanning. At the same time, these films explored their ability of adhesion to silicon and silicon oxide. It is shown that the pull force of the W(Re - 5%) films was 1500 G/mm2, of the W films 700 G/mm2

  13. Identification of an advanced constitutive model of Magnesium alloy AZ31B

    SciTech Connect

    Liu, Z. G.; Massoni, E.

    2011-05-04

    The main aim of this paper is to study the flow behavior of the AZ31B magnesium alloy by means of tensile tests performed in extended ranges of temperature and strain rates. The flow stress-strain curves analyzed by power law type constitutive equation can only fit well with experimental curves at the work-hardening stage. A new mathematical model is studied to describe the softening behavior of material based on tensile experiments. The relative parameters are obtained by fitting the equation with the experimental data. The genetic algorithm has been used to obtain the global optimal fitting parameters. The comparison between the fitted and experimental data proves the effectiveness of the model. The results indicate that this model leads to a better simulation of the flow stress during the softening stage than that of the power law equation. Based on this model, the deep drawing process has been simulated with the commercial finite element code FORGE registered. The punch load and thickness distribution of AZ31 sheet have been studied. The study of the results is helpful to the application of the stamping technology for the magnesium alloy sheet.

  14. Homogenizing Advanced Alloys: Thermodynamic and Kinetic Simulations Followed by Experimental Results

    NASA Astrophysics Data System (ADS)

    Jablonski, Paul D.; Hawk, Jeffrey A.

    2017-01-01

    Segregation of solute elements occurs in nearly all metal alloys during solidification. The resultant elemental partitioning can severely degrade as-cast material properties and lead to difficulties during post-processing (e.g., hot shorts and incipient melting). Many cast articles are subjected to a homogenization heat treatment in order to minimize segregation and improve their performance. Traditionally, homogenization heat treatments are based upon past practice or time-consuming trial and error experiments. Through the use of thermodynamic and kinetic modeling software, NETL has designed a systematic method to optimize homogenization heat treatments. Use of the method allows engineers and researchers to homogenize casting chemistries to levels appropriate for a given application. The method also allows for the adjustment of heat treatment schedules to fit limitations on in-house equipment (capability, reliability, etc.) while maintaining clear numeric targets for segregation reduction. In this approach, the Scheil module within Thermo-Calc is used to predict the as-cast segregation present within an alloy, and then diffusion controlled transformations is used to model homogenization kinetics as a function of time and temperature. Examples of computationally designed heat treatments and verification of their effects on segregation and properties of real castings are presented.

  15. Cellular Model Simulations of Solidification Structures in Ternary Alloys

    NASA Astrophysics Data System (ADS)

    Alsoruji, Ghazi H.

    Solidification processes are an important part of many modem manufacturing processes. They can be found in different casting and welding processes. The solidification structure is very important for the quality of any product manufactured by such processes. This is so because the casting or weldment microstructure determines their mechanical properties. For welding processes, solidification theories can explain the evolution of the fusion zone microstructure and how this microstructure is influenced by the solidification parameters such as the temperature gradient and the solidification rate. In order to investigate the solidification parameters' effect on the microstructure, a numerical model based on Cellular Automaton combined with the finite difference method (CA-FD) is presented in this thesis. The simulation is conducted on a finite three dimensional control volume of the fusion zone. The model takes into account the solute-, curvature-, and kinetic undercooling. The temperatures are assumed to be distributed linearly within the control volume. The model predicts the morphology and density of the microstructure according to different values of the cooling rate and initial temperatures. It is demonstrated that the solidification structure has a columnar morphology at high temperature gradients and low cooling rates. The morphology changes to dendritic as the temperature gradient decreases and/or the cooling rate increases. It is also shown that an increase in the cooling rate results in the densification of the solidification structure. The results demonstrate that an increase in the initial substrate roughness can result in the increase in the density of the solidification structure. The simulation results show an agreement with the constitutional undercooling theory of solidification structures.

  16. Parametric Study of Amorphous High-Entropy Alloys formation from two New Perspectives: Atomic Radius Modification and Crystalline Structure of Alloying Elements.

    PubMed

    Hu, Q; Guo, S; Wang, J M; Yan, Y H; Chen, S S; Lu, D P; Liu, K M; Zou, J Z; Zeng, X R

    2017-01-04

    Chemical and topological parameters have been widely used for predicting the phase selection in high-entropy alloys (HEAs). Nevertheless, previous studies could be faulted due to the small number of available data points, the negligence of kinetic effects, and the insensitivity to small compositional changes. Here in this work, 92 TiZrHfM, TiZrHfMM, TiZrHfMMM (M = Fe, Cr, V, Nb, Al, Ag, Cu, Ni) HEAs were prepared by melt spinning, to build a reliable and sufficiently large material database to inspect the robustness of previously established parameters. Modification of atomic radii by considering the change of local electronic environment in alloys, was critically found out to be superior in distinguishing the formation of amorphous and crystalline alloys, when compared to using atomic radii of pure elements in topological parameters. Moreover, crystal structures of alloying element were found to play an important role in the amorphous phase formation, which was then attributed to how alloying hexagonal-close-packed elements and face-centered-cubic or body-centered-cubic elements can affect the mixing enthalpy. Findings from this work not only provide parametric studies for HEAs with new and important perspectives, but also reveal possibly a hidden connection among some important concepts in various fields.

  17. Parametric Study of Amorphous High-Entropy Alloys formation from two New Perspectives: Atomic Radius Modification and Crystalline Structure of Alloying Elements

    NASA Astrophysics Data System (ADS)

    Hu, Q.; Guo, S.; Wang, J. M.; Yan, Y. H.; Chen, S. S.; Lu, D. P.; Liu, K. M.; Zou, J. Z.; Zeng, X. R.

    2017-01-01

    Chemical and topological parameters have been widely used for predicting the phase selection in high-entropy alloys (HEAs). Nevertheless, previous studies could be faulted due to the small number of available data points, the negligence of kinetic effects, and the insensitivity to small compositional changes. Here in this work, 92 TiZrHfM, TiZrHfMM, TiZrHfMMM (M = Fe, Cr, V, Nb, Al, Ag, Cu, Ni) HEAs were prepared by melt spinning, to build a reliable and sufficiently large material database to inspect the robustness of previously established parameters. Modification of atomic radii by considering the change of local electronic environment in alloys, was critically found out to be superior in distinguishing the formation of amorphous and crystalline alloys, when compared to using atomic radii of pure elements in topological parameters. Moreover, crystal structures of alloying element were found to play an important role in the amorphous phase formation, which was then attributed to how alloying hexagonal-close-packed elements and face-centered-cubic or body-centered-cubic elements can affect the mixing enthalpy. Findings from this work not only provide parametric studies for HEAs with new and important perspectives, but also reveal possibly a hidden connection among some important concepts in various fields.

  18. Parametric Study of Amorphous High-Entropy Alloys formation from two New Perspectives: Atomic Radius Modification and Crystalline Structure of Alloying Elements

    PubMed Central

    Hu, Q.; Guo, S.; Wang, J.M.; Yan, Y.H.; Chen, S.S.; Lu, D.P.; Liu, K.M.; Zou, J.Z.; Zeng, X.R.

    2017-01-01

    Chemical and topological parameters have been widely used for predicting the phase selection in high-entropy alloys (HEAs). Nevertheless, previous studies could be faulted due to the small number of available data points, the negligence of kinetic effects, and the insensitivity to small compositional changes. Here in this work, 92 TiZrHfM, TiZrHfMM, TiZrHfMMM (M = Fe, Cr, V, Nb, Al, Ag, Cu, Ni) HEAs were prepared by melt spinning, to build a reliable and sufficiently large material database to inspect the robustness of previously established parameters. Modification of atomic radii by considering the change of local electronic environment in alloys, was critically found out to be superior in distinguishing the formation of amorphous and crystalline alloys, when compared to using atomic radii of pure elements in topological parameters. Moreover, crystal structures of alloying element were found to play an important role in the amorphous phase formation, which was then attributed to how alloying hexagonal-close-packed elements and face-centered-cubic or body-centered-cubic elements can affect the mixing enthalpy. Findings from this work not only provide parametric studies for HEAs with new and important perspectives, but also reveal possibly a hidden connection among some important concepts in various fields. PMID:28051186

  19. Effect of bimodal harmonic structure design on the deformation behaviour and mechanical properties of Co-Cr-Mo alloy.

    PubMed

    Vajpai, Sanjay Kumar; Sawangrat, Choncharoen; Yamaguchi, Osamu; Ciuca, Octav Paul; Ameyama, Kei

    2016-01-01

    In the present work, Co-Cr-Mo alloy compacts with a unique bimodal microstructural design, harmonic structure design, were successfully prepared via a powder metallurgy route consisting of controlled mechanical milling of pre-alloyed powders followed by spark plasma sintering. The harmonic structured Co-Cr-Mo alloy with bimodal grain size distribution exhibited relatively higher strength together with higher ductility as compared to the coarse-grained specimens. The harmonic Co-Cr-Mo alloy exhibited a very complex deformation behavior wherein it was found that the higher strength and the high retained ductility are derived from fine-grained shell and coarse-grained core regions, respectively. Finally, it was observed that the peculiar spatial/topological arrangement of stronger fine-grained and ductile coarse-grained regions in the harmonic structure promotes uniformity of strain distribution, leading to improved mechanical properties by suppressing the localized plastic deformation during straining.

  20. Composite Structure Modeling and Analysis of Advanced Aircraft Fuselage Concepts

    NASA Technical Reports Server (NTRS)

    Mukhopadhyay, Vivek; Sorokach, Michael R.

    2015-01-01

    NASA Environmentally Responsible Aviation (ERA) project and the Boeing Company are collabrating to advance the unitized damage arresting composite airframe technology with application to the Hybrid-Wing-Body (HWB) aircraft. The testing of a HWB fuselage section with Pultruded Rod Stitched Efficient Unitized Structure (PRSEUS) construction is presently being conducted at NASA Langley. Based on lessons learned from previous HWB structural design studies, improved finite-element models (FEM) of the HWB multi-bay and bulkhead assembly are developed to evaluate the performance of the PRSEUS construction. In order to assess the comparative weight reduction benefits of the PRSEUS technology, conventional cylindrical skin-stringer-frame models of a cylindrical and a double-bubble section fuselage concepts are developed. Stress analysis with design cabin-pressure load and scenario based case studies are conducted for design improvement in each case. Alternate analysis with stitched composite hat-stringers and C-frames are also presented, in addition to the foam-core sandwich frame and pultruded rod-stringer construction. The FEM structural stress, strain and weights are computed and compared for relative weight/strength benefit assessment. The structural analysis and specific weight comparison of these stitched composite advanced aircraft fuselage concepts demonstrated that the pressurized HWB fuselage section assembly can be structurally as efficient as the conventional cylindrical fuselage section with composite stringer-frame and PRSEUS construction, and significantly better than the conventional aluminum construction and the double-bubble section concept.

  1. Study of nanoscale structural biology using advanced particle beam microscopy

    NASA Astrophysics Data System (ADS)

    Boseman, Adam J.

    This work investigates developmental and structural biology at the nanoscale using current advancements in particle beam microscopy. Typically the examination of micro- and nanoscale features is performed using scanning electron microscopy (SEM), but in order to decrease surface charging, and increase resolution, an obscuring conductive layer is applied to the sample surface. As magnification increases, this layer begins to limit the ability to identify nanoscale surface structures. A new technology, Helium Ion Microscopy (HIM), is used to examine uncoated surface structures on the cuticle of wild type and mutant fruit flies. Corneal nanostructures observed with HIM are further investigated by FIB/SEM to provide detailed three dimensional information about internal events occurring during early structural development. These techniques are also used to reconstruct a mosquito germarium in order to characterize unknown events in early oogenesis. Findings from these studies, and many more like them, will soon unravel many of the mysteries surrounding the world of developmental biology.

  2. The electronic structure study of titanium-nickel alloys by x-ray photoelectron spectroscopy

    NASA Astrophysics Data System (ADS)

    Seabolt, Michael A.

    2002-01-01

    Purpose of the study. The purpose of the study was to investigate the electronic structure changes of titanium-nickel (Ti-Ni) alloys. The electronic structure was correlated with the physical property of shape memory effect demonstrated by 50% atomic nickel concentration Ti-Ni crystalline alloys. Methodology. The technique of x-ray photoelectron spectroscopy was used to collect spectra using an ESCA PHI 5100 system. The spectra were analyzed by measuring binding energies, Auger parameters, Shirley and Tougaard backgrounds, and electronegativity criteria. Changes in the density of state (DOS) at the Fermi level were modeled using binding energy shifts, Auger parameter changes, the intrinsic loss structure modeled from the Shirley and Tougaard background, and the electronegativity criteria. Results. Significant changes in binding energy (BE) were noted for alloys, but changes in BE could not be with electronegativity criteria. The Auger parameter demonstrated positive values for Ti and negative values for Ni with minimum values at the 50% atomic nickel concentration. This was interpreted as a transfer of charge from nickel to titanium. Wagner plots of the Auger parameter indicated Ti and Ni were in different chemical states in each of the alloys with a minimum for the 50% atomic concentration nickel, which correlates to the shape memory effect (SME). Chemical shifts indicated a shift in charge from Ni to Ti, correlating to the results yielded by the Auger parameter. Normalized background analysis (indicative of the intrinsic loss structure) obtained from Shirley and Tougaard methods correlated well with the Auger parameter and chemical shift results, indicating that background analysis is useful for studying changes in chemical state for these materials. Conclusions. This study demonstrated that BE shifts and electronegativity criteria can not be successfully used to model changes in chemical states for Ti-Ni alloys. The results from Auger parameter analysis

  3. Surface XPS characterization of NiTi shape memory alloy after advanced oxidation processes in UV/H 2O 2 photocatalytic system

    NASA Astrophysics Data System (ADS)

    Wang, R. M.; Chu, C. L.; Hu, T.; Dong, Y. S.; Guo, C.; Sheng, X. B.; Lin, P. H.; Chung, C. Y.; Chu, P. K.

    2007-08-01

    Surface structure of NiTi shape memory alloy (SMA) was modified by advanced oxidation processes (AOP) in an ultraviolet (UV)/H 2O 2 photocatalytic system, and then systematically characterized with x-ray photoelectron spectroscopy (XPS). It is found that the AOP in UV/H 2O 2 photocatalytic system leads to formation of titanium oxides film on NiTi substrate. Depth profiles of O, Ni and Ti show such a film possesses a graded interface structure to NiTi substrate and there is no intermediate Ni-rich layer like that produced in conventional high temperature oxidation. Except TiO 2 phase, some titanium suboxides (TiO, Ti 2O 3) may also exist in the titanium oxides film. Oxygen mainly presents in metal oxides and some chemisorbed water and OH - are found in titanium oxides film. Ni nearly reaches zero on the upper surface and relatively depleted in the whole titanium oxides film. The work indicates the AOP in UV/H 2O 2 photocatalytic system is a promising way to favor the widespread application of biomedical NiTi SMA by improving its biocompatibility.

  4. A novel active fire protection approach for structural steel members using NiTi shape memory alloy

    NASA Astrophysics Data System (ADS)

    Sadiq, H.; Wong, M. B.; Al-Mahaidi, R.; Zhao, X. L.

    2013-02-01

    A novel active fire protection approach, based on integrating a shape memory alloy, NiTi, with a steel structure, was proposed to satisfy the fire resistance requirements in structural design. To demonstrate the principles of this approach, a simple structure in the form of a simply supported steel beam was used. The internal action of the beam due to a transverse applied load was reduced by utilizing the shape memory effect in the NiTi alloy at rising temperatures. As a result, the net internal action from the load design was kept below the deteriorated load capacity of the beam during the fire scenario for period of time that was longer than that of the original beam without the NiTi alloy. By integrating the NiTi alloy into the beam system, the structure remained stable even though the steel temperature exceeded the critical temperature which may have caused the original beam structure to collapse. Prior to testing the composite NiTi-steel beam under simulated fire conditions, the NiTi alloy specimens were characterized at high temperatures. At 300 °C, the stiffness of the specimens increased by three times and its strength by four times over that at room temperature. The results obtained from the high-temperature characterization highlighted the great potential of the alloy being used in fire engineering applications.

  5. Structure and microwave absorption properties of (Pr,Dy)Ni4Fe alloy

    NASA Astrophysics Data System (ADS)

    Xiong, Jilei; Pan, Shunkang; Qiao, Ziqiang

    2017-03-01

    The DyxPr1-xNi4Fe (x=0.0, 0.1, 0.2, 0.3, 0.4) alloys were synthesized by arc-smelting and high energy ball milling method. The structure, morphology, particle size and electromagnetic parameters of the powder were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser diffraction-based particle size analyzer and vector network analyzer (VNA), respectively. The results reveal that the DyxPr1-xNi4Fe compounds are crystallized in PrNi4Fe structure. The minimum absorption peak frequency of DyxPr1-xNi4Fe shifts towards higher frequency region upon the Fe content. The minimum reflection loss of the DyxPr1-xNi4Fe alloys increases first and then decreases with increasing Dy substitution. The Dy0.3Pr0.7Ni4Fe alloy possess the best absorbing properties: the minimum reflection loss is -31.65 dB at 15.28 GHz with the best matching thickness d =1.0 mm and the reflection loss with the thickness ranging of 1.0-4.0 mm could reach -10 dB.

  6. Structure and mechanical characterization of Mg-Nd-Zn alloys prepared by different processes

    NASA Astrophysics Data System (ADS)

    Dvorský, D.; Kubásek, J.; Vojtěch, D.; Voňavková, I.; Veselý, M.; Čavojský, M.

    2017-02-01

    Magnesium alloys containing about 3 wt. % of Nd and 0.5 wt. % of Zn are considered as promising materials for application in transport and medical industry. Properly treated materials can reach ultimate tensile strength (UTS) higher than 300 MPa. Also the corrosion resistance of these alloys is superior to many other magnesium-based materials. Present work is focused on the preparation of Mg-3Nd-0.5Zn magnesium alloy by classical casting and subsequent thermal treatment. As-cast material was extruded at 400 °C, with extrusion ratio equal to 16 and velocity of 0.2 mm/s. The effect of thermal treatment and also strong plastic deformation during extrusion on final structure conditions and mechanical properties is specified. Present results confirm significant improvement of tensile yield strength (TYS) and UTS after extrusion process as a consequence of fine-grained structure combined with precipitation strengthening. Beside, texture strengthening in the direction parallel to the extrusion has been observed too.

  7. Study of structural changes and properties of some Sn-Ag lead-free solder alloys

    NASA Astrophysics Data System (ADS)

    Kamal, M.; Said Gouda, El

    2007-11-01

    Structure, wetting, mechanical and electrical transport properties of tin- (2.5, 3.5, 5 and 10) wt.% silver alloys have been investigated. The results showed that, addition of silver to pure tin causes more precipitations of the intermetallic compound Ag{3}Sn. A new intermetallic compound Ag{4}Sn has been formed with adding Ag more than 3.5 wt.%. This compound causes continuous increase in the Young's modulus and electrical resistivity. While for the wetting measurements, additions of silver to pure tin up to 5 wt.% reduces the contact angle. Above that, the contact angle increases due to more precipitations of Ag Sn compounds, which may tend to reduce the adhesive forces between molten alloys and the substrate.

  8. A promising structure for fabricating high strength and high electrical conductivity copper alloys

    PubMed Central

    Li, Rengeng; Kang, Huijun; Chen, Zongning; Fan, Guohua; Zou, Cunlei; Wang, Wei; Zhang, Shaojian; Lu, Yiping; Jie, Jinchuan; Cao, Zhiqiang; Li, Tingju; Wang, Tongmin

    2016-01-01

    To address the trade-off between strength and electrical conductivity, we propose a strategy: introducing precipitated particles into a structure composed of deformation twins. A Cu-0.3%Zr alloy was designed to verify our strategy. Zirconium was dissolved into a copper matrix by solution treatment prior to cryorolling and precipitated in the form of Cu5Zr from copper matrix via a subsequent aging treatment. The microstructure evolutions of the processed samples were investigated by transmission electron microscopy and X-ray diffraction analysis, and the mechanical and physical behaviours were evaluated through tensile and electrical conductivity tests. The results demonstrated that superior tensile strength (602.04 MPa) and electrical conductivity (81.4% IACS) was achieved. This strategy provides a new route for balancing the strength and electrical conductivity of copper alloys, which can be developed for large-scale industrial application. PMID:26856764

  9. A promising structure for fabricating high strength and high electrical conductivity copper alloys.

    PubMed

    Li, Rengeng; Kang, Huijun; Chen, Zongning; Fan, Guohua; Zou, Cunlei; Wang, Wei; Zhang, Shaojian; Lu, Yiping; Jie, Jinchuan; Cao, Zhiqiang; Li, Tingju; Wang, Tongmin

    2016-02-09

    To address the trade-off between strength and electrical conductivity, we propose a strategy: introducing precipitated particles into a structure composed of deformation twins. A Cu-0.3%Zr alloy was designed to verify our strategy. Zirconium was dissolved into a copper matrix by solution treatment prior to cryorolling and precipitated in the form of Cu5Zr from copper matrix via a subsequent aging treatment. The microstructure evolutions of the processed samples were investigated by transmission electron microscopy and X-ray diffraction analysis, and the mechanical and physical behaviours were evaluated through tensile and electrical conductivity tests. The results demonstrated that superior tensile strength (602.04 MPa) and electrical conductivity (81.4% IACS) was achieved. This strategy provides a new route for balancing the strength and electrical conductivity of copper alloys, which can be developed for large-scale industrial application.

  10. Alloying and Structure of Ultrathin Gallium Films on the (111) and (110) Surfaces of Palladium

    PubMed Central

    2013-01-01

    Growth, thermal stability, and structure of ultrathin gallium films on Pd(111) and Pd(110) are investigated by low-energy ion scattering and low-energy electron diffraction. Common to both surface orientations are growth of disordered Ga films at coverages of a few monolayers (T = 150 K), onset of alloy formation at low temperatures (T ≈ 200 K), and formation of a metastable, mostly disordered 1:1 surface alloy at temperatures around 400–500 K. At higher temperatures a Ga surface fraction of ∼0.3 is slightly stabilized on Pd(111), which we suggest to be related to the formation of Pd2Ga bulk-like films. While on Pd(110) only a Pd-up/Ga-down buckled surface was observed, an inversion of buckling was observed on Pd(111) upon heating. Similarities and differences to the related Zn/Pd system are discussed. PMID:24089625

  11. Structure and Magnetic Properties of Mechanical Alloyed Mn-15at.%Al

    NASA Astrophysics Data System (ADS)

    Hannora, Ahmed E.; Hanna, Faried F.; Marei, Lotfy K.

    2013-04-01

    Mechanical alloying (MA) method has been used to produce nanocrystallite Mn-15at.%Al alloy. X-ray diffraction (XRD) patterns for the as-milled elemental α-Mn and aluminum powder samples show a mixture of α + β-MnAl phases after 20 h of milling and changes to a dominant β-MnAl phase structure after 50 h. An average crystallite size of 40 nm was determined from Hall-Williamson method analysis after 5 h of milling. Moreover, the thermal analysis results using differential thermal analysis (DTA), suggested a possible phase transformation after 20 h of milling. Isothermal treatments are carried in the temperature range of 450°C to 1000°C. Room-temperature vibrating sample magnetometer (VSM) measurements of the hysteretic response revealed that the saturation magnetization Bs and coercivity Hc for 10 h ball milled sample are 2.1 emu/g and 92 Oe, respectively.

  12. Structure and magnetic properties of surface alloyed Fe nanocapsules prepared by arc discharge

    NASA Astrophysics Data System (ADS)

    Si, P. Z.; Choi, C. J.; Brück, E.; Geng, D. Y.; Zhang, Z. D.

    2005-12-01

    C-Fe-Si alloy encapsulating Fe nanocapsules were fabricated by arc evaporating the mixture of Fe and SiC powders. The high temperature of the electric arc results in a surface reaction between SiC and Fe nanoparticles and therefore a uniform encapsulation of the Fe nanoparticles with its alloy. The size of the nanocapsules ranges from 10 to 60 nm while most shells are approximately 7 nm in thickness. Air oxidation to the as-prepared sample does not change the shell/core structure but the saturation magnetization and the coercivity are reduced. The characteristics of the nanocapsules were investigated systematically by using X-ray diffraction, transmission electron microscopy, energy dispersive spectra, X-ray photoelectron spectroscopy, and superconducting quantum interference device magnetometer.

  13. Surface, dynamic and structural properties of liquid Al-Ti alloys

    NASA Astrophysics Data System (ADS)

    Novakovic, R.; Giuranno, D.; Ricci, E.; Tuissi, A.; Wunderlich, R.; Fecht, H.-J.; Egry, I.

    2012-01-01

    The systems containing highly reactive element such as Ti are the most difficult to be determined experimentally and therefore, it is often necessary to estimate the missing values by theoretical models. The thermodynamic data of the Al-Ti system are scarce, its phase diagram is still incomplete and there are very few data on the thermophysical properties of Al-Ti melts. The study on surface, dynamic and static structural properties of liquid Al-Ti alloys has been carried out within the framework of the Compound Formation Model. In spite of the experimental difficulties, the surface tension of liquid Al-2 at.%Ti alloy has been measured over a temperature range by the pinned drop method.

  14. Thermally Induced Structural Transformations of Fe40Ni40P14B6 Amorphous Alloy

    NASA Astrophysics Data System (ADS)

    Vasić, Milica M.; Roupcová, Pavla; Pizúrová, Naděžda; Stevanović, Sanja; Blagojević, Vladimir A.; Žák, Tomáš; Minić, Dragica M.

    2016-01-01

    Thermal stability and thermally induced structural transformations of Fe40Ni40P14B6 amorphous alloy were examined under non-isothermal and isothermal conditions. Formation of metastable α-(Fe,Ni), and stable γ-(Fe,Ni) and (Fe,Ni)3(P,B) crystalline phases as the main crystallization products was observed, while the presence of small amounts of other crystalline phases like Fe23B6 and Fe2NiB was indicated by electron diffraction in HRTEM. Thermomagnetic curve indicated that Fe content in different crystalline phases is very different, resulting in markedly different Curie temperatures after crystallization. Transmission electron microscopy and atomic force microscopy study suggested multiple-layered platelet-shaped morphology, both on the surface and in the bulk of the crystallized alloy sample. The thermal treatment heating rate and maximum temperature affected surface roughness and grain size inhomogeneity.

  15. Formation of the structure and properties of β-type titanium alloy upon thermomechanical treatment

    NASA Astrophysics Data System (ADS)

    Shaboldo, O. P.; Vitorskii, Ya. M.; Sagaradze, V. V.; Pecherkina, N. L.; Skotnikova, M. A.

    2017-01-01

    The rapid quenching of β-type titanium alloy from 800°C and cold deformation by drawing (ɛ = 24%) leads to the formation of a cellular-banded structure with a cell size of 200 × 400 nm and high density of dislocations ( 5 × 1014 m-2). During subsequent aging at 450°C, the decomposition of the β-phase occurs with a heterogeneous precipitation (at dislocations) of plates of the α phase with a thickness of 10-30 nm and length of 50-100 nm. The small size and high density of α crystals (5 × 1021 m-3) provide a substantial increase in the strength characteristics of the alloy.

  16. Structure-property relationships in oxide-dispersed iron-beryllia alloys

    NASA Technical Reports Server (NTRS)

    Wolf, S.; Grant, N. J.

    1977-01-01

    Two BeO dispersed iron alloys containing about 2.5 and 5.5 v/o dispersoid were produced by attritting, internally oxidizing, and extruding dilute, prealloyed Fe-Be powders. As-extruded alloys were given various thermomechanical treatments involving room temperature swaging and annealing above and below the allotropic transformation temperature. The elevated temperature rupture strengths were measured and correlated with changes in structure; strengthening trends were examined in the light of proposed models for such strengthening. The results obtained showed that the elevated temperature strength was determined by the oxide interparticle spacing (IPS) in recrystallized material and IPS as well as prior deformation in swaged specimens. In fact, a parametric correlation was found between rupture strength values in the longitudinal direction with prestrain during swaging. The overall pattern in strength and microstructural observations were more consistent with a strength-stored energy (substructure) dependence than a strength-grain shape (grain aspect ratio) relation.

  17. The Effect of Stabilization Heat Treatments on the Tensile and Creep Behavior of an Advanced Nickel-Based Disk Alloy

    NASA Technical Reports Server (NTRS)

    Gayda, John

    2003-01-01

    As part of NASA s Advanced Subsonic Technology Program, a study of stabilization heat treatment options for an advanced nickel-base disk alloy, ME 209, was performed. Using a simple, physically based approach, the effect of stabilization heat treatments on tensile and creep properties was analyzed in this paper. Solutions temperature, solution cooling rate, and stabilization temperature/time were found to have a significant impact on tensile and creep properties. These effects were readily quantified using the following methodology. First, the effect of solution cooling rate was assessed to determine its impact on a given property. The as-cooled property was then modified by using two multiplicative factors which assess the impact of solution temperature and stabilization parameters. Comparison of experimental data with predicted values showed this physically based analysis produced good results that rivaled the statistical analysis employed, which required numerous changes in the form of the regression equation depending on the property and temperature in question. As this physically based analysis uses the data for input, it should be noted that predictions which attempt to extrapolate beyond the bounds of the data must be viewed with skepticism. Future work aimed at expanding the range of the stabilization/aging parameters explored in this study would be highly desirable, especially at the higher solution cooling rates.

  18. Magnetic micromechanical structures based on CoNi electrodeposited alloys

    NASA Astrophysics Data System (ADS)

    Cojocaru, P.; Magagnin, L.; Gomez, E.; Vallés, E.; Liu, F.; Carraro, C.; Maboudian, R.

    2010-12-01

    Electrodeposited CoNi magnetic microstructures compatible with silicon microfabrication technology have been developed using a sulfamate acidic bath, as an alternative to a less environmentally friendly chloride bath. The galvanostatic electrodeposition in the formulated electrolyte allows the deposition of cobalt-rich CoNi films and microstructures defined by photoresist at high deposition rates. Microstructures are adherent to the substrate, with a good lateral definition and resistance to the wet etching for the release of the sacrificial layer. The released structures respond to applied magnetic fields and no breakage occurred during large deformation.

  19. Defect structures and structural relationships of the Z and T phases in an Al-Li-Cu-Mg alloy

    SciTech Connect

    Zhang, L.C. . Lab. of Atomic Imaging of Solids Univ. of Science and Technology, Beijing . State Key Lab. of Advanced Materials); He, A.Q.; Ye, H.Q. . State Key Lab. of Advanced materials)

    1994-01-01

    Al-Li alloys have stirred a lot of interest because of their high mechanical properties/density ratio for aerospace application. Recently, some intermetallic compounds in the vicinity of Al[sub 0.6] (Cu,Zn)[sub 0.1](Li[sub 9]Mg)[sub 0.3], namely the so-called R,Z,C and [tau] phases, have been detected and studied in detail, due to their intimate structural relationship to the T[sub 2] quasicrystal phase. These compounds (including of T phase) and T[sub 2] consist of similar structural units, such as blocks of icosahedra, dodecahedra and tricontahedral, that makes them often intergrow with each other Shiflet, Yang et al. interpreted six types of shear planes in the R phase, implying a structural link between R and T[sub 2] phases, due to transformation behavior from T[sub 2] to R phase. Zhou et al. observed a well defined crystallographic orientation relationship between the R and Z phases possessing the same basic building units in the Al-Li-Cu alloy. In spite of a large amount of work in Al-Li system, little study has gone to the structural defects of other phases and links among them. This paper present the defect structures of the hexagonal Z and the f.c.c. T phases, as well as two types of structural orientation relationships between them.

  20. THE STRUCTURE AND INTERDIFFUSIONAL DEGRADATION OF ALUMINIDE COATINGS ON OXIDE DISPERSION STRENGTHENED ALLOYS

    SciTech Connect

    Boone, D. H.; Crane, D. A.; Whittle, D. P.

    1981-04-01

    A study of the effects of oxide dispersion strengthened {ODS) superalloy composition and coating processing on the structure and diffusional stability of aluminide coatings was undertaken. Increasing substrate aluminum content results in the formation of a more typical nickel base superalloy aluminide coating structure that is more resistant to spallation during high temperature isothermal exposure. The coating application process also affected coating stability, a low aluminum, outward diffusion type resulting in greater apparent stability. A SEM deep etching and fractography examination technique was used in an attempt to establish the location and kinetics of void formation. Alurninide protective lifetimes are still found to be far short of the alloys rnechnital property capabilities.

  1. Improvement in performance of reinforced concrete structures using shape memory alloys

    NASA Astrophysics Data System (ADS)

    Bajoria, Kamal M.; Kaduskar, Shreya S.

    2015-04-01

    Shape memory alloys (SMA) are a unique class of materials which have ability to undergo large deformation and also regain its undeformed shape by removal of stress or by heating. This unique property could be effectively utilized to enhance the safety of a structure. This paper presents the pushover analysis performance of a Reinforced Concrete moment resistance frame with the traditional steel reinforcement replaced partially with Nickel-Titanium (Nitinol) SMA. The results are compared with the RC structure reinforced with conventional steel. Partial replacement of traditional steel reinforcement by SMA shows better performance.

  2. Column and Plate Compressive Strengths of Aircraft Structural Martials Extruded 0-1HTA Magnesium Alloy

    NASA Technical Reports Server (NTRS)

    Heimerl, George J; Niles, Donald E

    1947-01-01

    Column and plate compressive strengths of extruded 0-1HTA magnesium alloy were determined both within and beyond the elastic range from tests of flat end H-section columns and from local instability tests of H-, Z-, and channel section columns. These tests are part of an extensive research investigation to provide data on the structural strength of various aircraft materials. The results are presented in the form of curves and charts that are suitable for use in the design and analysis of aircraft structures.

  3. High-Temperature Thermomechanical Treatment of Alloyed Structural and Tool Steels

    NASA Astrophysics Data System (ADS)

    Smirnov, V. A.; Filatov, V. I.

    2015-01-01

    The effect of hot plastic deformation on decomposition of supercooled austenite in some structural and die steels with different contents of carbon and alloying elements is investigated. It is shown that high-temperature plastic deformation accelerates the transformation of supercooled austenite by the diffusion mechanism and decelerates the development of bainitic transformations by raising the hardenability of the steels. The general laws of formation of mechanical properties under high-temperature thermomechanical treatment of structural and die steels after low- and high-temperature tempering are studied.

  4. Effect of precipitate structure on hot deformation of Al-Mg-Mn alloys

    SciTech Connect

    Vetrano, J.S.; Lavender, C.A.; Smith, M.T.; Bruemmer, S.M.

    1993-10-01

    The size and nature of precipitates have strong effects on microstructural evolution from the cold-worked state through the course of deformation at high temperatures. Through selected heat treatments and minor alloying alterations the precipitate structure of AA5083 has been manipulated. Minor additions of Zr have been used to create fine (50 to 100 nm) precipitates. The number and size distribution of medium-sized (<1 {mu}m) Mn-rich precipitates were modified by increasing the Mn concentration in conjunction with several heat treatment paths. Effects of these precipitates on the dislocation structure, recrystallization behavior and grain growth during high-temperature deformation have been elucidated.

  5. Study of the Structure, Composition, and Stability of Yttrium-Ti-Oxygen nm-Scale Features in Nano-Structured Ferritic Alloys

    NASA Astrophysics Data System (ADS)

    Cunningham, Nicholas John

    This work advances the understanding of the Y-Ti-O nanofeatures (NFs) in nanostructured ferritic alloys (NFAs); a class of high temperature, oxide dispersion strengthened iron alloys with applications in both advanced fission and fusion reactors. NFAs exhibit high creep strength up to 800ºC and a remarkable radiation damage tolerance and He management. However, the NFs, which are responsible for these properties, are not fully understood. This work addresses key questions including: a) what is the NF structure and composition and how are they affected by alloy composition and processing; b) what is the NFA long-term thermal stability; c) and what alternative processing paths are available to reduce costs and produce more uniform NF distributions? A detailed study using small angle neutron scattering (SANS), transmission electron microscopy (TEM-group member Y. Wu), and atom probe tomography (APT) evaluated the NF average size (), number density (N), volume fraction (f), composition, and structure in two heats of the commercial NFA MA957. The and N were ≈2.6 nm and ≈5x1023 m-3 , respectively, for both heats, with TEM indicating the NF are Y 2Ti2O7. However, SANS indicates a mixture of NF compositions or atomic densities with a difference between the heats, while APT shows compositions with ≈ 10% Cr and a Y/Ti ratio < 1. However, microscope artifacts such as preferential undercounting of Y and O or trajectory aberrations that prevent resolving Ti segregation to the NF-matrix interface could account for the discrepancy. The microstructure and NFs in MA957 were stable for long times at temperatures up to 900ºC. Notably, Ti in the matrix and some from the NFs migrates to large, Ti-rich phases. Aging at higher temperatures up to 1000ºC for 19.5 kh produced modest coarsening for ≈ 3.8 nm and ≈30% increase in grain size for a corresponding 13% reduction in microhardness. A coarsening model shows no significant NF coarsening will occur at temperatures less than

  6. Microstructure-sensitive extreme value probabilities of fatigue in advanced engineering alloys

    NASA Astrophysics Data System (ADS)

    Przybyla, Craig P.

    A novel microstructure-sensitive extreme value probabilistic framework is introduced to evaluate material performance/variability for damage evolution processes (e.g., fatigue, fracture, creep). This framework employs newly developed extreme value marked correlation functions (EVMCF) to identify the coupled microstructure attributes (e.g., phase/grain size, grain orientation, grain misorientation) that have the greatest statistical relevance to the extreme value response variables (e.g., stress, elastic/plastic strain) that describe the damage evolution processes of interest. This is an improvement on previous approaches that account for distributed extreme value response variables that describe the damage evolution process of interest based only on the extreme value distributions of a single microstructure attribute; previous approaches have given no consideration of how coupled microstructure attributes affect the distributions of extreme value response. This framework also utilizes computational modeling techniques to identify correlations between microstructure attributes that significantly raise or lower the magnitudes of the damage response variables of interest through the simulation of multiple statistical volume elements (SVE). Each SVE for a given response is constructed to be a statistical sample of the entire microstructure ensemble (i.e., bulk material); therefore, the response of interest in each SVE is not expected to be the same. This is in contrast to computational simulation of a single representative volume element (RVE), which often is untenably large for response variables dependent on the extreme value microstructure attributes. This framework has been demonstrated in the context of characterizing microstructure-sensitive high cycle fatigue (HCF) variability due to the processes of fatigue crack formation (nucleation and microstructurally small crack growth) in polycrystalline metallic alloys. Specifically, the framework is exercised to

  7. Advancements in Ti Alloy Powder Production by Close-Coupled Gas Atomization

    SciTech Connect

    Heidloff, Andy; Rieken, Joel; Anderson, Iver; Byrd, David

    2011-04-01

    As the technology for titanium metal injection molding (Ti-MIM) becomes more readily available, efficient Ti alloy fine powder production methods are required. An update on a novel close-coupled gas atomization system has been given. Unique features of the melting apparatus are shown to have measurable effects on the efficiency and ability to fully melt within the induction skull melting system (ISM). The means to initiate the melt flow were also found to be dependent on melt apparatus. Starting oxygen contents of atomization feedstock are suggested based on oxygen pick up during the atomization and MIM processes and compared to a new ASTM specification. Forming of titanium by metal injection molding (Ti-MIM) has been extensively studied with regards to binders, particle shape, and size distribution and suitable de-binding methods have been discovered. As a result, the visibility of Ti-MIM has steadily increased as reviews of technology, acceptability, and availability have been released. In addition, new ASTM specification ASTM F2885-11 for Ti-MIM for biomedical implants was released in early 2011. As the general acceptance of Ti-MIM as a viable fabrication route increases, demand for economical production of high quality Ti alloy powder for the preparation of Ti-MIM feedstock correspondingly increases. The production of spherical powders from the liquid state has required extensive pre-processing into different shapes thereby increasing costs. This has prompted examination of Ti-MIM with non-spherical particle shape. These particles are produced by the hydride/de-hydride process and are equi-axed but fragmented and angular which is less than ideal. Current prices for MIM quality titanium powder range from $40-$220/kg. While it is ideal for the MIM process to utilize spherical powders within the size range of 0.5-20 {mu}m, titanium's high affinity for oxygen to date has prohibited the use of this powder size range. In order to meet oxygen requirements the top size

  8. Advanced tribological coatings for high-specific-strength alloys. Interim report No. 5

    SciTech Connect

    Vine, M.K.

    1989-09-29

    The objectives of this contract are to develop and test a surface treatment suitable for the hardening of a titanium alloy precision gear for use in a vacuum environment. Attention was primarily directed at surface hardening by the interstitial diffusion of the elements nitrogen, oxygen and carbon. Targets of a surface hardness of >500 HV and depth 50 microns, without the need of any post-heat-treatment operations were identified. The surface treatments under study were applied to specimens of IMI 318 (Ti6Al4V), cut from plate. The sample numbers and corresponding surface treatments carried out and tested to date are listed. SHT indicates that the plates sample was in a solution heat treated condition before surface treatment.H G indicates that the sample was in a hardened and ground condition before surface treatment.

  9. Effect of Pore Structure Regulation on the Properties of Porous TiNbZr Shape Memory Alloys for Biomedical Application

    NASA Astrophysics Data System (ADS)

    Lai, Ming; Gao, Yan; Yuan, Bin; Zhu, Min

    2015-01-01

    Recently, porous Ti-Nb-based shape memory alloys have been considered as promising implants for biomedical application, because of their non-toxic elements, low elastic modulus, and stable superelasticity. However, the inverse relationship between pore characteristics and superelasticity of porous SMAs will strongly affect their clinical application. Until now, there have been few works specifically focusing on the effect of pore structure on the mechanical properties and superelasticity of porous Ti-Nb-based SMAs. In this study, the pore structure, including porosity and pore size, of porous Ti-22Nb-6Zr alloys was successfully regulated by adjusting the amount and size of space-holder particles. XRD and SEM investigation showed that all these porous alloys had homogeneous composition. Compression tests indicated that porosity played an important role in the mechanical properties and superelasticity of these porous alloys. Those alloys with porosity in the range of 38.5%-49.7% exhibited mechanical properties approaching to cortical bones, with elastic modulus, compressive strength, and recoverable strain in the range of 7.2-11.4 GPa, 188-422 MPa, and 2.4%-2.6%, respectively. Under the same porosity, the alloys with larger pores exhibited lower elastic modulus, while the alloys with smaller pores presented higher compressive strength.

  10. Investigation of the structural, electronic, and magnetic properties of Ni-based Heusler alloys from first principles

    NASA Astrophysics Data System (ADS)

    Qawasmeh, Yasmeen; Hamad, Bothina

    2012-02-01

    Density functional theory (DFT) calculations are performed to investigate the structural, electronic, magnetic, and elastic properties of Ni2MnZ (Z = B, Al, Ga, In) and Ni2FeZ (Z = Al, Ga) full Heusler alloys. The alloys are found to be metallic ferromagnets with total magnetic moments of about 4μB/f.u. and 3μB/f.u for Ni2MnZ and Ni2FeZ alloys, respectively. The Ni2MnAl and Ni2MnIn alloys are found to be stable at L21 phase, while the other alloys are more stable in the tetragonal phase with c/a ratios of 1.38 and 1.27 for Ni2MnB and Ni2MnGa, respectively and 1.35 for both Ni2FeAl and Ni2FeGa. The Ni2MnB alloy exhibits the highest electron spin polarization in its tetragonal phase, which is about 88% greater than that of L21 structure. However, the Ni2MnGa, Ni2FeAl, and Ni2FeGa alloys exhibit lower spin polarizations in their tetragonal phase than those at the L21. The most contribution of the total magnetic moments comes from Mn or Fe atoms, whereas Ni atoms exhibit much smaller magnetic moments. However, Z atoms have small induced magnetic moments, which are coupled antiferromagnetically with Ni, Mn and Fe.

  11. Formation of Structure in Hard-Alloy Coatings from Powders Under Passage of a Powerful Pulse of Electric Current

    NASA Astrophysics Data System (ADS)

    Novikov, S. V.; Peretyagin, P. Yu.; Dolzhikova, E. Yu.; Torrecillas, R.

    2016-01-01

    A method of ultrafast deposition of hard-alloy coatings from powders upon passage of a powerful pulse of electric current is considered. The structure of the coatings obtained by the electric-pulse and standard processes is studied by metallographic, electron microscope and x-ray diffraction analyses. The physical, mechanical and cutting properties of the hard-alloy coatings are determined. The endurance of the cutting tools with hard-alloy coatings is estimated under the conditions of large-scale and pilot productions. The possibility of creation of tools with enhanced operating characteristics is demonstrated.

  12. Development of Nb-1%Zr-0.1%C alloy as structural components for high temperature reactors

    NASA Astrophysics Data System (ADS)

    Vishwanadh, B.; Vaibhav, K.; Jha, S. K.; Mirji, K. V.; Samajdar, I.; Srivastava, D.; Tewari, R.; Saibaba, N.; Dey, G. K.

    2012-08-01

    The Nb-1Zr-0.1C (wt.%) alloy is being considered for structural components in the proposed Compact High-Temperature-Reactors (HTR). The present work reports on the development of 30-50 kg ingots of the alloy in correct composition as well as technology for forming the material in various shapes. The work deals with the deformation behavior of as-cast material at different temperatures and strain rates, recrystallization behavior at different temperature and time and evolution of microstructures at different processing conditions (as-cast, deformed and recrystallized). The as-cast Nb alloys were deformed up to 35% at different temperatures. The deformation results showed that the flow stress of the as-cast Nb alloy increases with increasing temperature from 800 °C to 1000 °C. Beyond 1200 °C, substantial decrease in the strength of the alloy was noticed. To determine the optimum recrystallization temperature and time for the alloy, several heat treatments were conducted by systematically varying temperature and time. It was found that the deformed Nb alloy could be recrystallized by annealing at 1300 °C for 3 h. The microstructures of the as-cast, deformed and recrystallized samples of Nb-1%Zr-0.1%C alloy were systematically characterized by optical, electron back scattered diffraction (EBSD) and transmission electron microscopy techniques. The Nb-1Zr-0.1C alloy showed significant differences in the microstructure after different thermo-mechanical treatments. Microstructures of the Nb alloy showed two phases: the matrix (bcc) phase and the carbide phase. Electron Microscopy and energy dispersive spectroscopic analyses revealed that the carbide precipitation undergoes various phase transformations. The as-cast structure of Nb alloy had hexagonal Nb2C precipitates in the Nb matrix and after extrusion, the deformed microstructure had two types of carbide precipitates: needle and rectangular morphology precipitates. The needle shape precipitates were of (Nb, Zr)2C

  13. Fundamental studies of structure borne noise for advanced turboprop applications

    NASA Technical Reports Server (NTRS)

    Eversman, W.; Koval, L. R.

    1985-01-01

    The transmission of sound generated by wing-mounted, advanced turboprop engines into the cabin interior via structural paths is considered. The structural model employed is a beam representation of the wing box carried into the fuselage via a representative frame type of carry through structure. The structure for the cabin cavity is a stiffened shell of rectangular or cylindrical geometry. The structure is modelled using a finite element formulation and the acoustic cavity is modelled using an analytical representation appropriate for the geometry. The structural and acoustic models are coupled by the use of hard wall cavity modes for the interior and vacuum structural modes for the shell. The coupling is accomplished using a combination of analytical and finite element models. The advantage is the substantial reduction in dimensionality achieved by modelling the interior analytically. The mathematical model for the interior noise problem is demonstrated with a simple plate/cavity system which has all of the features of the fuselage interior noise problem.

  14. Structure, mechanical characteristics and in vitro degradation, cytotoxicity, genotoxicity and mutagenicity of novel biodegradable Zn-Mg alloys.

    PubMed

    Kubásek, J; Vojtěch, D; Jablonská, E; Pospíšilová, I; Lipov, J; Ruml, T

    2016-01-01

    Zn-(0-1.6)Mg (in wt.%) alloys were prepared by hot extrusion at 300 °C. The structure, mechanical properties and in vitro biocompatibility of the alloys were investigated. The hot-extruded magnesium-based WE43 alloy was used as a control. Mechanical properties were evaluated by hardness, compressive and tensile testing. The cytotoxicity, genotoxicity (comet assay) and mutagenicity (Ames test) of the alloy extracts and ZnCl2 solutions were evaluated with the use of murine fibroblasts L929 and human osteosarcoma cell line U-2 OS. The microstructure of the Zn alloys consisted of recrystallized Zn grains of 12 μm in size and fine Mg2Zn11 particles arranged parallel to the hot extrusion direction. Mechanical tests revealed that the hardness and strength increased with increasing Mg concentration. The Zn-0.8 Mg alloys showed the best combination of tensile mechanical properties (tensile yield strength of 203 MPa, ultimate tensile strength of 301 MPa and elongation of 15%). At higher Mg concentrations the plasticity of Zn-Mg alloys was deteriorated. Cytotoxicity tests with alloy extracts and ZnCl2 solutions proved the maximum safe Zn(2+) concentrations of 120 μM and 80 μM for the U-2 OS and L929 cell lines, respectively. Ames test with extracts of alloys indicated that the extracts were not mutagenic. The comet assay demonstrated that 1-day extracts of alloys were not genotoxic for U-2 OS and L929 cell lines after 1-day incubation.

  15. Fabrication of a smart air intake structure using shape memory alloy wire embedded composite

    NASA Astrophysics Data System (ADS)

    Jung, Beom-Seok; Kim, Min-Saeng; Kim, Ji-Soo; Kim, Yun-Mi; Lee, Woo-Yong; Ahn, Sung-Hoon

    2010-05-01

    Shape memory alloys (SMAs) have been actively studied in many fields utilizing their high energy density. Applying SMA wire-embedded composite to aerospace structures, such as air intake of jet engines and guided missiles, is attracting significant attention because it could generate a comparatively large actuating force. In this research, a scaled structure of SMA wire-embedded composite was fabricated for the air intake of aircraft. The structure was composed of several prestrained Nitinol (Ni-Ti) SMA wires embedded in ∩-shape glass fabric reinforced plastic (GFRP), and it was cured at room temperature for 72 h. The SMA wire-embedded GFRP could be actuated by applying electric current through the embedded SMA wires. The activation angle generated from the composite structure was large enough to make a smart air intake structure.

  16. 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.

  17. Alloy Cu₃Pt nanoframes through the structure evolution in Cu-Pt nanoparticles with a core-shell construction.

    PubMed

    Han, Lin; Liu, Hui; Cui, Penglei; Peng, Zhijian; Zhang, Suojiang; Yang, Jun

    2014-09-18

    Noble metal nanoparticles with hollow interiors and customizable shell compositions have immense potential for catalysis. Herein, we present an unique structure transformation phenomenon for the fabrication of alloy Cu₃Pt nanoframes with polyhedral morphology. This strategy starts with the preparation of polyhedral Cu-Pt nanoparticles with a core-shell construction upon the anisotropic growth of Pt on multiply twinned Cu seed particles, which are subsequently transformed into alloy Cu₃Pt nanoframes due to the Kirkendall effect between the Cu core and Pt shell. The as-prepared alloy Cu₃Pt nanoframes possess the rhombic dodecahedral morphology of their core-shell parents after the structural evolution. In particular, the resulting alloy Cu₃Pt nanoframes are more effective for oxygen reduction reaction but ineffective for methanol oxidation reaction in comparison with their original Cu-Pt core-shell precursors.

  18. Pressure-dependent structure of the null-scattering alloy Ti0.676 Zr0.324

    NASA Astrophysics Data System (ADS)

    Zeidler, Anita; Guthrie, Malcolm; Salmon, Philip S.

    2015-07-01

    The room temperature structure of the alloy ? was measured by X-ray diffraction under compression at pressures up to ?. This alloy is used as a construction material in high pressure neutron-scattering research and has a mean coherent neutron scattering length of zero, that is, it is a so-called null-scattering alloy. A broad phase transition was observed from a hexagonal close-packed α-phase to a hexagonal ω-phase, which started at a pressure of ? and was completed by ?. The data for the α-phase were fitted by using a third-order Birch-Murnaghan equation of state, giving an isothermal bulk modulus ? and pressure derivative ?. The results will help to ensure that accurate structural information can be gained from in situ high pressure neutron diffraction work on amorphous and liquid materials where the ? alloy is used as a gasket material.

  19. Electronic structures and optical properties of α-Fe2O3-xSex alloys for solar absorber

    NASA Astrophysics Data System (ADS)

    Xia, Congxin; Jia, Yu; Zhang, Qiming

    2015-05-01

    The band structures and optical properties of α-Fe2O3-xSex alloys are studied by means of first-principles methods, considering different Se contents x. Numerical results show that Se content has an obvious influence on band structures and optical properties of α-Fe2O3-xSex alloys. The band gap values of α-Fe2O3-xSex alloys decrease monotonically when Se concentrations increase, resulting in an obvious increase of the optical absorption edge in the visible range. In particular, our results show that α-Fe2O3-xSex alloys have the direct band gap properties with band gap values when Se content x ≈ 0.17, which is beneficial to solar cell applications.

  20. Advanced composite structural concepts and material technologies for primary aircraft structures

    NASA Technical Reports Server (NTRS)

    Jackson, Anthony

    1991-01-01

    Structural weight savings using advanced composites have been demonstrated for many years. Most military aircraft today use these materials extensively and Europe has taken the lead in their use in commercial aircraft primary structures. A major inhibiter to the use of advanced composites in the United States is cost. Material costs are high and will remain high relative to aluminum. The key therefore lies in the significant reduction in fabrication and assembly costs. The largest cost in most structures today is assembly. As part of the NASA Advanced Composite Technology Program, Lockheed Aeronautical Systems Company has a contract to explore and develop advanced structural and manufacturing concepts using advanced composites for transport aircraft. Wing and fuselage concepts and related trade studies are discussed. These concepts are intended to lower cost and weight through the use of innovative material forms, processes, structural configurations and minimization of parts. The approach to the trade studies and the downselect to the primary wing and fuselage concepts is detailed. The expectations for the development of these concepts is reviewed.