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Sample records for high-temperature aerospace alloys

  1. 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.

  2. Metals Technology for Aerospace Applications in 2020: Development of High Temperature Aluminum Alloys For Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Dicus, Dennis (Technical Monitor); Starke, Edgar A., Jr.

    2003-01-01

    The role of trace additions on the nucleation and stability of the primary strengthening phase, omega, is of paramount importance for the enhancement of mechanical properties for moderate temperature application of Al-Cu-Mg-(Ag) alloys. In order to better understand the competition for solute, which governs the microstructural evolution of these alloys, a series of Al-Cu-Mg-Si quaternary alloys were prepared to investigate the role of trace Si additions on the nucleation of the omega phase. Si additions were found to quell omega nucleation in conjunction with the enhanced matrix precipitation of competing phases. These initial results indicate that it is necessary to overcome a critical Mg/Si ratio for omega precipitation, rather than a particular Si content.

  3. System integration and demonstration of adhesive bonded high temperature aluminum alloys for aerospace structure, phase 2

    NASA Technical Reports Server (NTRS)

    Falcone, Anthony; Laakso, John H.

    1993-01-01

    Adhesive bonding materials and processes were evaluated for assembly of future high-temperature aluminum alloy structural components such as may be used in high-speed civil transport aircraft and space launch vehicles. A number of candidate high-temperature adhesives were selected and screening tests were conducted using single lap shear specimens. The selected adhesives were then used to bond sandwich (titanium core) test specimens, adhesive toughness test specimens, and isothermally aged lap shear specimens. Moderate-to-high lap shear strengths were obtained from bonded high-temperature aluminum and silicon carbide particulate-reinforced (SiC(sub p)) aluminum specimens. Shear strengths typically exceeded 3500 to 4000 lb/in(sup 2) and flatwise tensile strengths exceeded 750 lb/in(sup 2) even at elevated temperatures (300 F) using a bismaleimide adhesive. All faceskin-to-core bonds displayed excellent tear strength. The existing production phosphoric acid anodize surface preparation process developed at Boeing was used, and gave good performance with all of the aluminum and silicon carbide particulate-reinforced aluminum alloys investigated. The results of this program support using bonded assemblies of high-temperature aluminum components in applications where bonding is often used (e.g., secondary structures and tear stoppers).

  4. Application of thermal life prediction model to high-temperature aerospace alloys B1900+Hf and Haynes 188

    NASA Technical Reports Server (NTRS)

    Halford, Gary R.; Saltsman, James F.; Verrilli, Michael J.; Arya, Vinod K.

    1990-01-01

    The results of the application of a newly proposed thermomechanical fatigue (TMF) life prediction method to a series of laboratory TMF results on two high-temperature aerospace engine alloys are presented. The method, referred to as TMF/TS-SRP, is based on three relatively recent developments: the total strain version of the method of Strainrange Partitioning (TS-SRP), the bithermal testing technique for characterizing TMF behavior, and advanced viscoplastic constitutive models. The high-temperature data reported in a companion publication are used to evaluate the constants in the model and to provide the TMF verification data to check its accuracy. Predicted lives are in agreement with the experimental lives to within a factor of approximately 2.

  5. Potential aerospace applications of high temperature superconductors

    NASA Astrophysics Data System (ADS)

    Selim, Raouf

    1994-12-01

    The recent discovery of High Temperature Superconductors (HTS) with superconducting transition temperature, T(sub c), above the boiling point of liquid nitrogen has opened the door for using these materials in new and practical applications. These materials have zero resistance to electric current, have the capability of carrying large currents and as such have the potential to be used in high magnetic field applications. One of the space applications that can use superconductors is electromagnetic launch of payloads to low-earth-orbit. An electromagnetic gun-type launcher can be used in small payload systems that are launched at very high velocity, while sled-type magnetically levitated launcher can be used to launch larger payloads at smaller velocities. Both types of launchers are being studied by NASA and the aerospace industry. The use of superconductors will be essential in any of these types of launchers in order to produce the large magnetic fields required to obtain large thrust forces. Low Temperature Superconductor (LTS) technology is mature enough and can be easily integrated in such systems. As for the HTS, many leading companies are currently producing HTS coils and magnets that potentially can be mass-produced for these launchers. It seems that designing and building a small-scale electromagnetic launcher is the next logical step toward seriously considering this method for launching payloads into low-earth-orbit. A second potential application is the use of HTS to build sensitive portable devices for the use in Non Destructive Evaluation (NDE). Superconducting Quantum Interference Devices (SQUID's) are the most sensitive instruments for measuring changes in magnetic flux. By using HTS in SQUID's, one will be able to design a portable unit that uses liquid nitrogen or a cryocooler pump to explore the use of gradiometers or magnetometers to detect deep cracks or corrosion in structures. A third use is the replacement of Infra-Red (IR) sensor leads on

  6. Potential aerospace applications of high temperature superconductors

    NASA Technical Reports Server (NTRS)

    Selim, Raouf

    1994-01-01

    The recent discovery of High Temperature Superconductors (HTS) with superconducting transition temperature, T(sub c), above the boiling point of liquid nitrogen has opened the door for using these materials in new and practical applications. These materials have zero resistance to electric current, have the capability of carrying large currents and as such have the potential to be used in high magnetic field applications. One of the space applications that can use superconductors is electromagnetic launch of payloads to low-earth-orbit. An electromagnetic gun-type launcher can be used in small payload systems that are launched at very high velocity, while sled-type magnetically levitated launcher can be used to launch larger payloads at smaller velocities. Both types of launchers are being studied by NASA and the aerospace industry. The use of superconductors will be essential in any of these types of launchers in order to produce the large magnetic fields required to obtain large thrust forces. Low Temperature Superconductor (LTS) technology is mature enough and can be easily integrated in such systems. As for the HTS, many leading companies are currently producing HTS coils and magnets that potentially can be mass-produced for these launchers. It seems that designing and building a small-scale electromagnetic launcher is the next logical step toward seriously considering this method for launching payloads into low-earth-orbit. A second potential application is the use of HTS to build sensitive portable devices for the use in Non Destructive Evaluation (NDE). Superconducting Quantum Interference Devices (SQUID's) are the most sensitive instruments for measuring changes in magnetic flux. By using HTS in SQUID's, one will be able to design a portable unit that uses liquid nitrogen or a cryocooler pump to explore the use of gradiometers or magnetometers to detect deep cracks or corrosion in structures. A third use is the replacement of Infra-Red (IR) sensor leads on

  7. Aerospace applications of high temperature superconductivity

    NASA Technical Reports Server (NTRS)

    Heinen, V. O.; Connolly, D. J.

    1991-01-01

    Space application of high temperature superconducting (HTS) materials may occur before most terrestrial applications because of the passive cooling possibilities in space and because of the economic feasibility of introducing an expensive new technology which has a significant system benefit in space. NASA Lewis Research Center has an ongoing program to develop space technology capitalizing on the potential benefit of HTS materials. The applications being pursued include space communications, power and propulsion systems, and magnetic bearings. In addition, NASA Lewis is pursuing materials research to improve the performance of HTS materials for space applications.

  8. Aerospace applications of high temperature superconductivity

    NASA Technical Reports Server (NTRS)

    Connolly, D. J.; Heinen, V. O.; Aron, P. R.; Lazar, J.; Romanofsky, Robert R.

    1990-01-01

    A review is presented of all the applications that are part of the NASA program to develop space technology capitalizing on the potential benefit of high temperature superconducting materials. The applications in three major areas are being pursued: sensors and cryogenic systems, space communications, and propulsion and power systems. This review places emphasis on space communications applications and the propulsion and power applications. It is concluded that the power and propulsion applications will eventually be limited by structural considerations rather than by the availability of suitable superconductors. A cursory examination of structural limitations implied by the virial theorem suggested that there is an upper limit to the size of high field magnetic systems that are feasible in space.

  9. High temperature arc-track resistant aerospace insulation

    NASA Technical Reports Server (NTRS)

    Dorogy, William

    1994-01-01

    The topics are presented in viewgraph form and include the following: high temperature aerospace insulation; Foster-Miller approach to develop a 300 C rated, arc-track resistant aerospace insulation; advantages and disadvantages of key structural features; summary goals and achievements of the phase 1 program; performance goals for selected materials; materials under evaluation; molecular structures of candidate polymers; candidate polymer properties; film properties; and a detailed program plan.

  10. Aerospace Applications Of High Temperature Superconductivity

    NASA Astrophysics Data System (ADS)

    Anderson, W. W.

    1988-05-01

    The existence of superconductors with TcOOK (which implies device operating temper-atures the order of Top ≍45K) opens up a variety of potential applications within the aerospace/defense industry. This is partly due to the existence of well developed cooler technologies to reach this temperature regime and partly due to the present operation of some specialized components at cryogenic temperatures. In particular, LWIR focal planes may operate at 10K with some of the signal processing electronics at an intermediate temperature of 40K. Addition of high Tc superconducting components in the latter system may be "free" in the sense of additional system complexity required. The established techniques for cooling in the 20K to 50K temperature regime are either open cycle, expendable material (stored gas with Joule-Thomson expansion, liquid cryogen or solid cryogen) or mechanical refrigerators (Stirling cycle, Brayton cycle or closed cycle Joule-Thomson). The high Tc materials may also contribute to the development of coolers through magnetically levitated bearings or providing the field for a stage of magnetic refrigeration. The discovery of materials with Tc, 90K has generated a veritable shopping list of applications. The superconductor properties which are of interest for applications are (1) zero resistance, (2) Meissner effect, (3) phase coherence and (4) existence of an energy gap. The zero resistance property is significant in the development of high field magnets requiring neglible power to maintain the field. In addition to the publicized applications to rail guns and electromagnetic launcher, we can think of space born magnets for charged particle shielding or whistler mode propagation through a plasma sheath. Conductor losses dominate attenuation and dispersion in microstrip transmission lines. While the surface impedance of a superconductor is non vanishing, significant improvements in signal transmission may be obtained. The Meissner effect may be utilized

  11. Development of an advanced high-temperature fastener system for advanced aerospace vehicle application

    NASA Technical Reports Server (NTRS)

    Kull, F. R.

    1975-01-01

    The results of a program to develop a lightweight high temperature reusable fastening system for aerospace vehicle thermal protection system applications are documented. This feasibility program resulted in several fastener innovations which will meet the specific needs of the heat shield application. Three systems were designed from Hayes 188 alloy and tested by environmental exposure and residual mechanical properties. The designs include a clinch stud with a collar retainer, a weld stud with a split ring retainer, and a caged stud with a collar retainer. The results indicated that a lightweight, reusable, high temperature fastening system can be developed for aerospace vehicle application.

  12. Computational technology for high-temperature aerospace structures

    NASA Technical Reports Server (NTRS)

    Noor, A. K.; Card, M. F.

    1992-01-01

    The status and some recent developments of computational technology for high-temperature aerospace structures are summarized. Discussion focuses on a number of aspects including: goals of computational technology for high-temperature structures; computational material modeling; life prediction methodology; computational modeling of high-temperature composites; error estimation and adaptive improvement strategies; strategies for solution of fluid flow/thermal/structural problems; and probabilistic methods and stochastic modeling approaches, integrated analysis and design. Recent trends in high-performance computing environment are described and the research areas which have high potential for meeting future technological needs are identified.

  13. Caldron For High-Temperature Alloys

    NASA Technical Reports Server (NTRS)

    Geringer, Henry J.

    1989-01-01

    Induction-heated caldron melts high-temperature alloys. Prevents sort of contamination of melts occurring during arc melting in ceramic crucibles. Liquefies 200 grams of solid metal components of alloy like niobium aluminum and makes alloy homogeneous in less than 3 minutes. Plugged sleeve constitutes main body of caldron. Coolant flows through sleeve to prevent it from melting. Mandrel-wound induction coils adjusted to tune source of power. Also serves as mold for casting alloys into such shapes as bars.

  14. Braze alloys for high temperature service

    NASA Technical Reports Server (NTRS)

    Lindberg, R. A.; Mckisson, R. L.; Erwin, G., Jr.

    1973-01-01

    Two groups of refractory metal compositions have been developed that are very useful as high temperature brazing alloys for sealing between ceramic and metal parts. Each group consists of various compositions of three selected refractory metals which, when combined, have characteristics required of good braze alloys.

  15. Optical Fiber Strain Instrumentation for High Temperature Aerospace Structural Monitoring

    NASA Technical Reports Server (NTRS)

    Wang, A.

    2002-01-01

    The objective of the program is the development and laboratory demonstration of sensors based on silica optical fibers for measurement of high temperature strain for aerospace materials evaluations. A complete fiber strain sensor system based on white-light interferometry was designed and implemented. An experiment set-up was constructed to permit testing of strain measurement up to 850 C. The strain is created by bending an alumina cantilever beam to which is the fiber sensor is attached. The strain calibration is provided by the application of known beam deflections. To ensure the high temperature operation capability of the sensor, gold-coated single-mode fiber is used. Moreover, a new method of sensor surface attachment which permits accurate sensor gage length determination is also developed. Excellent results were obtained at temperatures up to 800-850 C.

  16. High-Temperature Strain Sensing for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Piazza, Anthony; Richards, Lance W.; Hudson, Larry D.

    2008-01-01

    Thermal protection systems (TPS) and hot structures are utilizing advanced materials that operate at temperatures that exceed abilities to measure structural performance. Robust strain sensors that operate accurately and reliably beyond 1800 F are needed but do not exist. These shortcomings hinder the ability to validate analysis and modeling techniques and hinders the ability to optimize structural designs. This presentation examines high-temperature strain sensing for aerospace applications and, more specifically, seeks to provide strain data for validating finite element models and thermal-structural analyses. Efforts have been made to develop sensor attachment techniques for relevant structural materials at the small test specimen level and to perform laboratory tests to characterize sensor and generate corrections to apply to indicated strains. Areas highlighted in this presentation include sensors, sensor attachment techniques, laboratory evaluation/characterization of strain measurement, and sensor use in large-scale structures.

  17. The metallurgy of high temperature alloys

    NASA Technical Reports Server (NTRS)

    Tien, J. K.; Purushothaman, S.

    1976-01-01

    Nickel-base, cobalt-base, and high nickel and chromium iron-base alloys are dissected, and their microstructural and chemical components are assessed with respect to the various functions expected of high temperature structural materials. These functions include the maintenance of mechanical integrity over the strain-rate spectrum from creep resistance through fatigue crack growth resistance, and such alloy stability expectations as microstructural coarsening resistance, phase instability resistance and oxidation and corrosion resistance. Special attention will be given to the perennial conflict and trade-off between strength, ductility and corrosion and oxidation resistance. The newest developments in the constitution of high temperature alloys will also be discussed, including aspects relating to materials conservation.

  18. Precipitation Hardenable High Temperature Shape Memory Alloy

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald Dean (Inventor); Draper, Susan L. (Inventor); Nathal, Michael V. (Inventor); Crombie, Edwin A. (Inventor)

    2010-01-01

    A composition of the invention is a high temperature shape memory alloy having high work output, and is made from (Ni+Pt+Y),Ti(100-x) wherein x is present in a total amount of 49-55 atomic % Pt is present in a total amount of 10-30 atomic %, Y is one or more of Au, Pd. and Cu and is present in a total amount of 0 to 10 atomic %. The alloy has a matrix phase wherein the total concentration of Ni, Pt, and the one or more of Pd. Au, and Cu is greater than 50 atomic %.

  19. Thermal stability of high temperature structural alloys

    SciTech Connect

    Jordan, C.E.; Rasefske, R.K.; Castagna, A.

    1999-03-01

    High temperature structural alloys were evaluated for suitability for long term operation at elevated temperatures. The effect of elevated temperature exposure on the microstructure and mechanical properties of a number of alloys was characterized. Fe-based alloys (330 stainless steel, 800H, and mechanically alloyed MA 956), and Ni-based alloys (Hastelloy X, Haynes 230, Alloy 718, and mechanically alloyed MA 758) were evaluated for room temperature tensile and impact toughness properties after exposure at 750 C for 10,000 hours. Of the Fe-based alloys evaluated, 330 stainless steel and 800H showed secondary carbide (M{sub 23}C{sub 6}) precipitation and a corresponding reduction in ductility and toughness as compared to the as-received condition. Within the group of Ni-based alloys tested, Alloy 718 showed the most dramatic structure change as it formed delta phase during 10,000 hours of exposure at 750 C with significant reductions in strength, ductility, and toughness. Haynes 230 and Hastelloy X showed significant M{sub 23}C{sub 6} carbide precipitation and a resulting reduction in ductility and toughness. Haynes 230 was also evaluated after 10,000 hours of exposure at 850, 950, and 1050 C. For the 750--950 C exposures the M{sub 23}C{sub 6} carbides in Haynes 230 coarsened. This resulted in large reductions in impact strength and ductility for the 750, 850 and 950 C specimens. The 1050 C exposure specimens showed the resolution of M{sub 23}C{sub 6} secondary carbides, and mechanical properties similar to the as-received solution annealed condition.

  20. Simulated Single Tooth Bending of High Temperature Alloys

    NASA Technical Reports Server (NTRS)

    Handschuh, Robert, F.; Burke, Christopher

    2012-01-01

    Future unmanned space missions will require mechanisms to operate at extreme conditions in order to be successful. In some of these mechanisms, very high gear reductions will be needed to permit very small motors to drive other components at low rotational speed with high output torque. Therefore gearing components are required that can meet the mission requirements. In mechanisms such as this, bending fatigue strength capacity of the gears is very important. The bending fatigue capacity of a high temperature, nickel-based alloy, typically used for turbine disks in gas turbine engines and two tool steel materials with high vanadium content, were compared to that of a typical aerospace alloy-AISI 9310. Test specimens were fabricated by electro-discharge machining without post machining processing. Tests were run at 24 and at 490 C. As test temperature increased from 24 to 490 C the bending fatigue strength was reduced by a factor of five.

  1. Precipitate Phases in Several High Temperature Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Yang, Fan

    Initiated by the aerospace industry, there has been a great interest to develop high temperature shape memory alloys (HTSMAs) for actuator type of application at elevated temperatures. Several NiTi based ternary systems have been shown to be potential candidates for HTSMAs and this work focuses on one or more alloys in the TiNiPt, TiNiPd, NiTiHf, NiPdTiHf systems. The sheer scope of alloys of varying compositions across all four systems suggests that the questions raised and addressed in this work are just the tip of the iceberg. This work focuses on materials characterization and aims to investigate microstructural evolution of these alloys as a function of heat treatment. The information gained through the study can serve as guidance for future alloy processing. The emphasis of this work is to describe novel precipitate phases that are formed under aging in the ternary systems and one quaternary system. Employing conventional transmission electron microscopy (TEM), high resolution high angle annular dark field (HAADF) scanning transmission electron microscopy (STEM), 3D atom probe tomography (3D APT), as well as ab initio calculations, the complete description of the unit cell for the new precipitates was determined. The methodology is summarized in the appendix to help elucidate some basics of such a process.

  2. High temperature erosion of nickel alloys

    SciTech Connect

    Zhou, J.

    1995-12-31

    High temperature erosion behavior was studied on three commercial nickel alloys, Inconel 718, Inconel 601 and Inconel X-750, using a vertical sand-blast type of erosion test rig. Effect of temperature on erosion was investigated by varying test temperature in six steps from ambient up to 800 C. Other erosion variables investigated included impingement angle, changed from 10{degree} to 90{degree}, and impingement velocity, covered a range of 40 to 90 m/s. Extensive studies on erosion surface morphological features were done on eroded or eroded-corroded specimen surfaces using scanning electron microscopy. Thermogravimetric analysis and scratch test revealed corrosion rate, characteristics of oxide scale formed at high temperature, and some effects of corrosion on erosion. It was found that variation of erosion rate with temperature was directly related to temperature-dependent mechanical property changes of the materials. The mechanisms of the high-temperature erosion were analyzed based on test results. It was observed that erosion was dominant in temperature range up to 800 C, while corrosion played increased roles in upper portion of the temperature range tested.

  3. Bolting alloy fills high-temperature gap

    SciTech Connect

    Buzolits, S.R.; Kline, L.A.

    1995-02-01

    A high-strength, high-temperature fastener alloy has been developed by SPS Technologies to meet the requirements of today`s advanced turbine engines. Designated Aerex 350, it is based on the multiphase materials cobalt, nickel, and molybdenum to take advantage of their low notch sensitivity, high strength, and excellent resistance to creep and corrosion. In choosing the chemical composition of Aerex 350 Alloy (25Co, 17Cr, 3Mo, 2Ti, 1Al, 1Nb, 4Ta, 2W, balance Ni), researchers sought to produce physical properties equivalent to those of conventional nickel-base superalloys such as Waspaloy. As a result, thermal expansion coefficient, thermal conductivity, electrical resistivity, specific heat, enthalpy, modulus, Poisson`s ratio, and density are all in the ranges common to that class. Perhaps the most important of these is its coefficient of thermal expansion, which ranges from 13.5 {mu}m/m{degree}C at 425 C to 14.8 {mu}m/m{degree}C at 700 C. A bolt with a higher coefficient of expansion than the joint material would be detrimental because clamp load can be reduced significantly as the assembly heats up. Therefore, the expansion characteristics of Aerex 350 Alloy ensure joint integrity up to the highest operating temperatures.

  4. Laser Brazing of High Temperature Braze Alloy

    NASA Technical Reports Server (NTRS)

    Gao, Y. P.; Seaman, R. F.; McQuillan, T. J.; Martiens, R. F.

    2000-01-01

    The Space Shuttle Main Engine (SSME) consists of 1080 conical tubes, which are furnace brazed themselves, manifolds, and surrounding structural jacket making almost four miles of braze joints. Subsequent furnace braze cycles are performed due to localized braze voids between the coolant tubes. SSME nozzle experiences extremely high heat flux (180 mW/sq m) during hot fire. Braze voids between coolant tubes may result in hot combustion gas escape causing jacket bulges. The nozzle can be disqualified for flight or result in mission failure if the braze voids exceed the limits. Localized braze processes were considered to eliminate braze voids, however, damage to the parent materials often prohibited use of such process. Being the only manned flight reusable rocket engine, it has stringent requirement on the braze process. Poor braze quality or damage to the parent materials limits the nozzle service life. The objective of this study was to develop a laser brazing process to provide quality, localized braze joints without adverse affect on the parent materials. Gold (Au-Cu-Ni-Pd-Mn) based high temperature braze alloys were used in both powder and wire form. Thin section iron base superalloy A286 tube was used as substrate materials. Different Laser Systems including CO2 (10.6 micrometers, 1kW), ND:YAG (1.06 micrometers, 4kW). and direct diode laser (808nm. 150W) were investigated for brazing process. The laser process variables including wavelength. laser power, travel speed and angle of inclination were optimized according to bead geometry and braze alloy wetting at minimum heat input level, The properties of laser brazing were compared to that of furnace brazing. Microhardness profiles were used for braze joint property comparison between laser and furnace brazing. The cooling rate of laser brazing was compared to furnace brazing based on secondary dendritic arm spacing, Both optical and Scanning Electron Microscope (SEM) were used to evaluate the microstructures of

  5. Substitution of ceramics for high temperature alloys

    NASA Technical Reports Server (NTRS)

    Probst, H. B.

    1978-01-01

    Ceramics such as silicon nitride and silicon carbide are currently receiving a great deal of attention as potential materials for advanced gas turbine engines. The primary advantage offered by ceramics is their high temperature capability which can result in turbine engines of improved efficiency. Other advantages when compared to the nickel and cobalt alloys in current use are raw material availability, lower weight, erosion/corrosion resistance, and potentially lower cost. The use of ceramics in three different sizes of gas turbine engines is considered; these are the large utility turbines, advanced aircraft turbines, and small automotive turbines. The effects of material substitutions are reviewed in terms of engine performance, operating economy, and secondary effects.

  6. High-Temperature Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Biffi, C. A.; Tuissi, A.

    2014-10-01

    In this paper, an experimental study of laser micro-processing on a Cu-Zr-based shape memory alloy (SMA), which is suitable for high-temperature (HT) applications, is discussed. A first evaluation of the interaction between a laser beam and Zr50Cu28Ni7Co15 HT SMA is highlighted. Single laser pulses at various levels of power and pulse duration were applied to evaluate their effect on the sample surfaces. Blind and through microholes were produced with sizes on the order of a few hundreds of microns; the results were characterized from the morphological viewpoint using a scanning electron microscope. The high beam quality allows the holes to be created with good circularity and little melted material around the hole periphery. An analysis of the chemical composition was performed using energy dispersive spectroscopy, revealing that compositional changes were limited, while important oxidation occurred on the hole surfaces. Additionally, laser micro-cutting tests were also proposed to evaluate the cut edge morphology and dimensions. The main result of this paper concerned the good behavior of the material upon interaction with the laser beam, which suggests that microfeatures can be successfully produced in this alloy.

  7. Alloys based on NiAl for high temperature applications

    NASA Technical Reports Server (NTRS)

    Vedula, K. M.; Pathare, V.; Aslanidis, I.; Titran, R. H.

    1984-01-01

    The NiAl alloys for potential high temperature applications were studied. Alloys were prepared by powder metallurgy techniques. Flow stress values at slow strain rates and high temperatures were measured. Some ternary alloying additions (Hf, Ta and Nb) were identified. The mechanism of strengthening in alloys containing these additions appears to be a form of particle dislocation interaction. The effects of grain size and stoichiometry in binary alloys are also presented.

  8. Surface modification of high temperature iron alloys

    DOEpatents

    Park, Jong-Hee

    1995-01-01

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

  9. Surface modification of high temperature iron alloys

    DOEpatents

    Park, J.H.

    1995-06-06

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

  10. A polytetrafluorethylene insulated cable for high temperature oxygen aerospace applications

    NASA Technical Reports Server (NTRS)

    Sheppard, A. T.; Webber, R. G.

    1983-01-01

    For electrical cables to function and survive in the severe high temperature oxygen environment that will be experienced in the external tanks of the space shuttle, extreme cleanliness and material purity is required. A flexible light weight cable has been developed for use in pure oxygen at worst case temperatures of -190 to +260 degrees Centigrade and pressures as high as 44 pounds per square inch absolute. A comprehensive series of tests were performed on cables manufactured to the best commercial practices in order to establish the basic guidelines for control of build configuration as well as each material used in construction of the cable.

  11. High temperature cyclic oxidation data. Part 1: Turbine alloys

    NASA Technical Reports Server (NTRS)

    Barrett, Charles A.; Garlick, Ralph G.; Lowell, Carl E.

    1989-01-01

    Specific-weight-change-versus-time data and x ray diffraction results are presented derived from high temperature cyclic tests on high temperature, high strength nickel-base gamma/gamma prime and cobalt-base turbine alloys. Each page of data summarizes a complete test on a given alloy sample.

  12. High-temperature cyclic oxidation data. Part 2: Turbine alloys

    NASA Technical Reports Server (NTRS)

    Barrett, Charles A.; Garlick, Ralph G.

    1989-01-01

    Specific-weight-change-versus-time data and x ray diffraction results are presented derived from high temperature cyclic tests on high temperature, high strength nickel-base gamma/gamma prime and cobalt-base turbine alloys. Each page of data summarizes a complete test on a given alloy sample.

  13. Ductile aluminide alloys for high temperature applications

    SciTech Connect

    Liu, C.T.; Stiegler, J.O.

    1986-09-16

    An alloy is described consisting essentially of sufficient nickel and aluminum to form Ni/sub 3/A1, an amount of boron sufficient to promote ductility in the alloy and 0.3 to 1.5 atomic percent of an element selected from the group consisting of hafnium and zirconium. The alloy further including 6 to 12 atomic percent iron.

  14. CORROSION OF HIGH-TEMPERATURE ALLOYS

    SciTech Connect

    John P. Hurley; John P. Kay

    1999-10-01

    Five alloys were tested in the presence of water vapor and water vapor with HCl for 1000 hours using simulated combustion gas. Samples were removed at intervals during each test and measured for determination of corrosion rates. One sample of each alloy was examined with a SEM after the completion of each test. Cumulative corrosion depths were similar for the superstainless alloys. Corrosion for Alloy TP310 roughly doubled. Corrosion for the enhanced stainless alloys changed dramatically with the addition of chlorine. Corrosion for Alloy RA85H increased threefold, whereas Alloy TP347HFG showed an eightfold increase. SEM examination of the alloys revealed that water vapor alone allowed the formation of chromium oxide protective layers on the superstainless alloys. The enhanced stainless alloys underwent more corrosion due to greater attack of sulfur. Iron-rich oxide layers were more likely to form, which do not provide protection from further corrosion. The addition of chlorine further increased the corrosion because of its ability to diffuse through the oxide layers and react with iron. This resulted in a broken, discontinuous, and loose oxide layer that offered less protection. Niobium, although added to aid in creep strength, was found to be detrimental to corrosion resistance. The niobium tended to be concentrated in nodules and was easily attacked through sulfidation, providing conduits for further corrosion deep into the alloy. The alloys that displayed the best corrosion resistance were those which could produce chromium oxide protective layers. The predicted microstructure of all alloys except Alloy HR3C is the same and provided no further information relating to corrosion resistance. No correlation can be found relating corrosion resistance to the quantity of minor austenite-or ferrite-stabilizing elements. Also, there does not appear to be a correlation between corrosion resistance and the Cr:Ni ratio of the alloy. These alloys were tested for their

  15. Al-Fe-Zr alloys for high temperature applications produced by rapid quenching from the melt

    SciTech Connect

    Okazaki, K.; Skinner, D.J.

    1984-09-01

    The melt-spinning technique to produce microstructure for high temperature-high strength Al-Fe-Zr alloys, meeting aerospace structural requirements, is presented, including the investigations for the improvement of the thermal stability of iron aluminide dispersoids by addition of Zr. The alloys containing about 27 to 30 percent volume fraction of dispersoids would be the optimum to meet the requirements from the strength and ductility viewpoint. The thermal stability of the alloys was determined by measuring the microvickers hardness on the isochronally annealed ribbons. 9 references.

  16. Oxide dispersion hardened mechanically alloyed materials for high temperatures

    NASA Technical Reports Server (NTRS)

    Benjamin, J. S.; Strassburg, F. W.

    1982-01-01

    The procedure of mechanical alloying makes it possible to obtain, with the aid of powder-metallurgy techniques, alloys that consist of a metallic matrix in which very fine oxide particles are dispersed. Mechanically alloyed compound powders can be used for making either forged or hot-rolled semifinished products. For these products, dispersion strengthening and precipitation hardening has been combined. At high temperatures, the strength characteristics of the alloy are determined by both dispersion hardening and by precipitation hardening processes. The effect produced by each process is independent of that due to the other. Attention is given to the principle of mechanical alloying developed by Benjamin (1970, 1976), the strength characteristics of mechanically alloyed materials, the corrosion resistance of mechanically alloyed material at high temperatures, and the preparation and characteristics of the alloy MA 6000 E.

  17. High-temperature alloys: Single-crystal performance boost

    NASA Astrophysics Data System (ADS)

    Schütze, Michael

    2016-08-01

    Titanium aluminide alloys are lightweight and have attractive properties for high-temperature applications. A new growth method that enables single-crystal production now boosts their mechanical performance.

  18. 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.

  19. Cast Aluminum Alloy for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2003-01-01

    Originally developed by NASA as high performance piston alloys to meet U.S. automotive legislation requiring low exhaust emission, the novel NASA alloys now offer dramatic increase in tensile strength for many other applications at elevated temperatures from 450 F (232 C) to about 750 F (400 C). It is an ideal low cost material for cast automotive components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. It can be very economically produced from conventional permanent mold, sand casting or investment casting, with silicon content ranging from 6% to 18%. At high silicon levels, the alloy exhibits excellent dimensional stability, surface hardness and wear resistant properties.

  20. Improved high temperature creep resistant austenitic alloy

    DOEpatents

    Maziasz, P.J.; Swindeman, R.W.; Goodwin, G.M.

    1988-05-13

    An improved austenitic alloy having in wt% 19-21 Cr, 30-35 Ni, 1.5-2.5 Mn, 2-3 Mo, 0.1-0.4 Si, 0.3-0.5 Ti, 0.1-0.3 Nb, 0.1-0.5 V, 0.001-0.005 P, 0.08-0.12 C, 0.01-0.03 N, 0.005-0.01 B and the balance iron that is further improved by annealing for up to 1 hour at 1150-1200/degree/C and then cold deforming 5-15%. The alloy exhibits dramatically improved creep rupture resistance and ductility at 700/degree/C. 2 figs.

  1. High temperature creep resistant austenitic alloy

    DOEpatents

    Maziasz, Philip J.; Swindeman, Robert W.; Goodwin, Gene M.

    1989-01-01

    An improved austenitic alloy having in wt % 19-21 Cr, 30-35 Ni, 1.5-2.5 Mn, 2-3 Mo, 0.1-0.4 Si, 0.3-0.5 Ti, 0.1-0.3 Nb, 0.1-0.5 V, 0.001-0.005 P, 0.08-0.12 C, 0.01-0.03 N, 0.005-0.01 B and the balance iron that is further improved by annealing for up to 1 hour at 1150.degree.-1200.degree. C. and then cold deforming 5-15 %. The alloy exhibits dramatically improved creep rupture resistance and ductility at 700.degree. C.

  2. High Temperature Fracture Characteristics of a Nanostructured Ferritic Alloy (NFA)

    SciTech Connect

    Byun, Thak Sang; Kim, Jeoung H; Ji Hyun, Yoon; Hoelzer, David T

    2010-01-01

    High temperature fracture behavior has been investigated for the nanostructured ferritic alloy 14YWT (SM10). The fracture toughness of the alloy was above 140 MPa m at low temperatures, room temperature (RT) and 200 C, but decreased to a low fracture toughness range of 52 82 MPa m at higher temperatures up to 700 C. This behavior was explained by the fractography results indicating that the unique nanostructure of 14YWT alloy produced shallow plasticity layers at high temperatures and a low-ductility grain boundary debonding occurred at 700 C.

  3. Silver alloys for high-temperature superconducting wire

    NASA Astrophysics Data System (ADS)

    Hubert, B. N.; Zhou, R.; Holesinger, T. G.; Hults, W. L.; Lacerda, A.; Murray, A. S.; Ray, R. D.; Buford, Cm.; Phillips, L. G.; Kebede, A.; Smith, J. L.

    1995-12-01

    The silver cladding for high-temperature superconducting wire can be modified for various applications by alloying. For example, for powder-in-tube wire, stiffer cladding improves the smoothness of the interface. For large coils, higher strength is needed at low temperatures to hold them together. Power applications require more resistance in the cladding. We have made a survey of the properties of alloys to check their feasibility for various applications. Alloys with several elements added to silver have been prepared and evaluated for hardness, electrical properties, and compatibility with high-temperature superconductors during processing.

  4. Advanced lightweight alloys for aerospace applications

    NASA Astrophysics Data System (ADS)

    Frazier, William E.; Lee, Eui W.; Donnellan, Mary E.; Thompson, James J.

    1989-05-01

    The design requirements of the next generation of advanced aerospace vehicles and propulsion systems necessitate the development of structural materials with properties vastly superior to those which are currently achievable. Recognizing that each class of materials possesses its own unique set of advantages and disadvantages, the designers of tomorrow's aircraft must choose wisely from the plethora of available alloys.

  5. High-temperature corrosion: Issues in alloy selection

    NASA Astrophysics Data System (ADS)

    Lai, George Y.

    1991-11-01

    This article examines the modes of high-temperature corrosion that are often responsible for equipment failures in a variety of industries, including aerospace and gas turbines; heat treating; mineral and metallurgical processing; chemical processing; refining and petrochemical processing; ceramic, electronic, and glass manufacturing; automotive; pulp and paper; waste incineration; and power generation and energy conversion. Corrosion data related to each corrosion mode are reviewed to provide readers with a brief materials selection guide.

  6. Synthesis and characterization of a high-temperature, low-volatility phosphate additive for aerospace applications

    SciTech Connect

    Gschwender, L.J.; Snyder, C.E., Jr.; Fultz, G.W.; Chen, L.S. Dayton, University, OH )

    1991-11-01

    Tricresyl phosphate (TCP) is a widely used and effective antiwear additive for a variety of lubricants used in aerospace military applications. However, for a high-temperature gas turbine engine oil (GTO) application, volatility and thermo-oxidative stability limitations preclude the use of TCP. For this GTO application, high molecular weight, and thermally and thermo-oxidatively stable groups were incorporated into a phosphate-based additive. This paper describes the synthesis of this additive and its successful performance. 3 refs.

  7. Potential High-Temperature Shape-Memory Alloys Identified in the Ti(Ni,Pt) System

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald D.; Biles, Tiffany A.; Garg, Anita; Nathal, Michael V.

    2004-01-01

    "Shape memory" is a unique property of certain alloys that, when deformed (within certain strain limits) at low temperatures, will remember and recover to their original predeformed shape upon heating. It occurs when an alloy is deformed in the low-temperature martensitic phase and is then heated above its transformation temperature back to an austenitic state. As the material passes through this solid-state phase transformation on heating, it also recovers its original shape. This behavior is widely exploited, near room temperature, in commercially available NiTi alloys for connectors, couplings, valves, actuators, stents, and other medical and dental devices. In addition, there are limitless applications in the aerospace, automotive, chemical processing, and many other industries for materials that exhibit this type of shape-memory behavior at higher temperatures. But for high temperatures, there are currently no commercial shape-memory alloys. Although there are significant challenges to the development of high-temperature shape-memory alloys, at the NASA Glenn Research Center we have identified a series of alloy compositions in the Ti-Ni-Pt system that show great promise as potential high-temperature shape-memory materials.

  8. The use of β titanium alloys in the aerospace industry

    NASA Astrophysics Data System (ADS)

    Boyer, R. R.; Briggs, R. D.

    2005-12-01

    Beta titanium alloys have been available since the 1950s (Ti-13V-11Cr-3Mo or B120VCA), but significant applications of these alloys, beyond the SR-71 Blackbird, have been slow in coming. The next significant usage of a β alloy did not occur until the mid-1980s on the B-1B bomber. This aircraft used Ti-15V-3Cr-3Al-3Sn sheet due to its capability for strip rolling, improved formability, and higher strength than Ti-6Al-4V. The next major usage was on a commercial aircraft, the Boeing 777, which made extensive use of Ti-10V-2Fe-3Al high-strength forgings. Ti-15V-3Cr-3Al-3Sn environmental control system ducting, castings, and springs were also used, along with Ti-3Al-8V-6Cr-4Mo-4Zr (β-C) springs. Beta-21S was also introduced for high-temperature usage. More recent work at Boeing has focused on the development of Ti-5Al-5Mo-5V-3Cr, a high-strength alloy that can be used at higher strength than Ti-10V-2Fe-3Al and is much more robust; it has a much wider, or friendlier, processing window. This, along with additional studies at Boeing, and from within the aerospace industry in general will be discussed in detail, summarizing applications and the rationale for the selection of this alloy system for aerospace applications.

  9. High-temperature alloys for high-power thermionic systems

    SciTech Connect

    Shin, Kwang S.; Jacobson, D.L.; D'cruz, L.; Luo, Anhua; Chen, Bor-Ling.

    1990-08-01

    The need for structural materials with useful strength above 1600 k has stimulated interest in refractory-metal alloys. Tungsten possesses an extreme high modulus of elasticity as well as the highest melting temperature among metals, and hence is being considered as one of the most promising candidate materials for high temperature structural applications such as space nuclear power systems. This report is divided into three chapters covering the following: (1) the processing of tungsten base alloys; (2) the tensile properties of tungsten base alloys; and (3) creep behavior of tungsten base alloys. Separate abstracts were prepared for each chapter. (SC)

  10. High-entropy alloys as high-temperature thermoelectric materials

    SciTech Connect

    Shafeie, Samrand; Guo, Sheng; Hu, Qiang; Fahlquist, Henrik; Erhart, Paul; Palmqvist, Anders

    2015-11-14

    Thermoelectric (TE) generators that efficiently recycle a large portion of waste heat will be an important complementary energy technology in the future. While many efficient TE materials exist in the lower temperature region, few are efficient at high temperatures. Here, we present the high temperature properties of high-entropy alloys (HEAs), as a potential new class of high temperature TE materials. We show that their TE properties can be controlled significantly by changing the valence electron concentration (VEC) of the system with appropriate substitutional elements. Both the electrical and thermal transport properties in this system were found to decrease with a lower VEC number. Overall, the large microstructural complexity and lower average VEC in these types of alloys can potentially be used to lower both the total and the lattice thermal conductivity. These findings highlight the possibility to exploit HEAs as a new class of future high temperature TE materials.

  11. High-entropy alloys as high-temperature thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Shafeie, Samrand; Guo, Sheng; Hu, Qiang; Fahlquist, Henrik; Erhart, Paul; Palmqvist, Anders

    2015-11-01

    Thermoelectric (TE) generators that efficiently recycle a large portion of waste heat will be an important complementary energy technology in the future. While many efficient TE materials exist in the lower temperature region, few are efficient at high temperatures. Here, we present the high temperature properties of high-entropy alloys (HEAs), as a potential new class of high temperature TE materials. We show that their TE properties can be controlled significantly by changing the valence electron concentration (VEC) of the system with appropriate substitutional elements. Both the electrical and thermal transport properties in this system were found to decrease with a lower VEC number. Overall, the large microstructural complexity and lower average VEC in these types of alloys can potentially be used to lower both the total and the lattice thermal conductivity. These findings highlight the possibility to exploit HEAs as a new class of future high temperature TE materials.

  12. 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.

  13. Hot Workability of CuZr-Based Shape Memory Alloys for Potential High-Temperature Applications

    NASA Astrophysics Data System (ADS)

    Biffi, Carlo Alberto; Tuissi, Ausonio

    2014-07-01

    The research on high-temperature shape memory alloys has been growing because of the interest of several potential industrial fields, such as automotive, aerospace, mechanical, and control systems. One suitable candidate is given by the CuZr system, because of its relative low price in comparison with others, like the NiTi-based one. In this context, the goal of this work is the study of hot workability of some CuZr-based shape memory alloys. In particular, this study addresses on the effect of hot rolling process on the metallurgical and calorimetric properties of the CuZr system. The addition of some alloying elements (Cr, Co, Ni, and Ti) is taken into account and their effect is also put in comparison with each other. The alloys were produced by means of an arc melting furnace in inert atmosphere under the shape of cigars. Due to the high reactivity of these alloys at high temperature, the cigars were sealed in a stainless steel can before the processing and two different procedures of hot rolling were tested. The characterization of the rolled alloys is performed using discrete scanning calorimetry in terms of evolution of the martensitic transformation and scanning electron microscopy for the microstructural investigations. Additionally, preliminary tests of laser interaction has been also proposed on the alloy more interesting for potential applications, characterized by high transformation temperatures and its good thermal stability.

  14. High temperature corrosion performance of automotive coupling alloys

    SciTech Connect

    Smith, G.D.; Crum, J.R.; Flower, H.L.

    1998-12-31

    Key to the satisfactory performance of automotive exhaust couplings is adequate high temperature corrosion resistance. This is becoming especially critical as service life is being extended by government legislation and as service temperatures are increasing due to the need for increased fuel efficiency and faster catalyst light-off. Currently employed and candidate coupling alloys, including 409, 304, 316Ti and 321 stainless steels (SS) and alloys 600, 800, 864 and 625, are selectively evaluated for resistance to road salt spray corrosion, oxidation in air and engine exhaust gases and under cyclic burner rig conditions, These laboratory results are compared with alloy performance of couplings subjected to test track and field exposure.

  15. Alloy performance in high temperature oil refining environments

    SciTech Connect

    Sorell, G.; Humphries, M.J.; McLaughlin, J.E.

    1995-12-31

    The performance of steels and alloys in high temperature petroleum refining applications is strongly influenced by detrimental interactions with aggressive process environments. These are encountered in conventional refining processes and especially in processing schemes for fuels conversion and upgrading. Metal-environment interactions can shorten equipment life and cause impairment of mechanical properties, metallurgical stability and weldability. Corrosion and other high temperature attack modes discussed are sulfidation, hydrogen attack, carburization, and metal dusting. Sulfidation is characterized by bulky scales that are generally ineffective corrosion barriers. Metal loss is often accompanied by sub-surface sulfide penetration. Hydrogen attack and carburization proceed without metal loss and are detectable only by metallographic examination. In advanced stages, these deterioration modes cause severe impairment of mechanical properties. Harmful metal-environment interactions are characterized and illustrated with data drawn from test exposures and plant experience. Alloys employed for high temperature oil refining equipment are identified, including some promising newcomers.

  16. Fatigue crack propagation in aerospace aluminum alloys

    NASA Technical Reports Server (NTRS)

    Gangloff, R. P.; Piascik, R. S.; Dicus, D. L.; Newman, J. C., Jr.

    1990-01-01

    This paper reviews fracture mechanics based, damage tolerant characterizations and predictions of fatigue crack growth in aerospace aluminum alloys. The results of laboratory experimentation and modeling are summarized in the areas of: (1) fatigue crack closure, (2) the wide range crack growth rate response of conventional aluminum alloys, (3) the fatigue behavior of advanced monolithic aluminum alloys and metal matrix composites, (4) the short crack problem, (5) environmental fatigue, and (6) variable amplitude loading. Remaining uncertainties and necessary research are identified. This work provides a foundation for the development of fatigue resistant alloys and composites, next generation life prediction codes for new structural designs and extreme environments, and to counter the problem of aging components.

  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. Spectroscopic Challenges in the Modelling and Diagnostics of High Temperature Air Plasma Radiation for Aerospace Applications

    SciTech Connect

    Laux, Christophe O.

    2007-04-06

    State-of-the-art spectroscopic models of the radiative transitions of interest for Earth re-entry and ground-based diagnostic facilities for aerospace applications are reviewed. The spectral range considered extends from the vacuum ultraviolet to the mid-infrared range (80 nm to 5.5 {mu}m). The modeling results are compared with absolute intensity measurements of the ultraviolet-visible-infrared emission of a well-characterized high-temperature air plasma produced with a 50 kW inductively coupled radio-frequency plasma torch, and with high-resolution absorption spectra from the Center for Astrophysics in the vacuum ultraviolet. The Spectroscopic data required to better model the spectral features of interest for aerospace applications are discussed.

  19. NiAl alloys for high-temperature structural applications

    NASA Astrophysics Data System (ADS)

    Darolia, Ram

    1991-03-01

    If their properties can be improved, nickel aluminide alloys offer significant payoffs in gas turbine engine applications. For these materials, excellent progress has been made toward understanding their mechanical behavior as well as improving their low-temperature ductility and high-temperature strength. For example, recent work shows that room-temperature ductility can be improved dramatically by microalloying with iron, gallium or molybdenum. The next challenge is to develop an alloy which has the required balance of ductility, toughness and strength. Development of design and test methodologies for components made out of low-ductility, anisotropic materials will also be required. While significant challenges remain, the continuing developments suggest that the prognosis for using NiAl alloys as high-temperature structural materials is good.

  20. High Temperature Irradiation Effects in Selected Generation IV Structural Alloys

    SciTech Connect

    Nanstad, Randy K; McClintock, David A; Hoelzer, David T; Tan, Lizhen; Allen, Todd R.

    2009-01-01

    In the Generation IV Materials Program cross-cutting task, irradiation and testing were carried out to address the issue of high temperature irradiation effects with selected current and potential candidate metallic alloys. The materials tested were (1) a high-nickel iron-base alloy (Alloy 800H); (2) a nickel-base alloy (Alloy 617); (3) two advanced nano-structured ferritic alloys (designated 14YWT and 14WT); and (4) a commercial ferritic-martensitic steel (annealed 9Cr-1MoV). Small tensile specimens were irradiated in rabbit capsules in the High-Flux Isotope Reactor at temperatures from about 550 to 700 C and to irradiation doses in the range 1.2 to 1.6 dpa. The Alloy 800H and Alloy 617 exhibited significant hardening after irradiation at 580 C; some hardening occurred at 660 C as well, but the 800H showed extremely low tensile elongations when tested at 700 C. Notably, the grain boundary engineered 800H exhibited even greater hardening at 580 C and retained a high amount of ductility. Irradiation effects on the two nano-structured ferritic alloys and the annealed 9Cr-1MoV were relatively slight at this low dose.

  1. Computational and Experimental Development of Novel High Temperature Alloys

    SciTech Connect

    Kramer, M.J.; Ray, P.K.; and Akinc, M.

    2010-06-29

    The work done in this paper is based on our earlier work on developing an extended Miedema model and then using it to downselect potential alloy systems. Our approach is to closely couple the semi-empirical methodologies to more accurate ab initio methods to dentify the best candidates for ternary alloying additions. The architectural framework for our material's design is a refractory base metal with a high temperature intermetallic which provides both high temperature creep strength and a source of oxidatively stable elements. Potential refractory base metals are groups IIIA, IVA and VA. For Fossil applications, Ni-Al appears to be the best choice to provide the source of oxidatively stable elements but this system requires a 'boost' in melting temperatures to be a viable candidate in the ultra-high temperature regime (> 1200C). Some late transition metals and noble elements are known to increase the melting temperature of Ni-Al phases. Such an approach suggested that a Mo-Ni-Al system would be a good base alloy system that could be further improved upon by dding Platinum group metals (PGMs). In this paper, we demonstrate the variety of microstructures that can be synthesized for the base alloy system, its oxidation behavior as well as the oxidation behavior of the PGM substituted oxidation resistant B2 NiAl phase.

  2. Development of high temperature fasteners using directionally solidified eutectic alloys

    NASA Technical Reports Server (NTRS)

    George, F. D.

    1972-01-01

    The suitability of the eutectics for high temperature fasteners was investigated. Material properties were determined as a function of temperature, and included shear parallel and perpendicular to the growth direction and torsion parallel to it. Techniques for fabricating typical fastener shapes included grinding, creep forming, and direct casting. Both lamellar Ni3Al-Ni3Nb and fibrous (Co,Cr,Al)-(Cr,Co)7C3 alloys showed promise as candidate materials for high temperature fastener applications. A brief evaluation of the performance of the best fabricated fastener design was made.

  3. High temperature seal for joining ceramics and metal alloys

    DOEpatents

    Maiya, P. Subraya; Picciolo, John J.; Emerson, James E.; Dusek, Joseph T.; Balachandran, Uthamalingam

    1998-01-01

    For a combination of a membrane of SrFeCo.sub.0.5 O.sub.x and an Inconel alloy, a high-temperature seal is formed between the membrane and the alloy. The seal is interposed between the alloy and the membrane, and is a fritted compound of Sr oxide and boric oxide and a fritted compound of Sr, Fe and Co oxides. The fritted compound of SrFeCo.sub.0.50 O.sub.x is present in the range of from about 30 to 70 percent by weight of the total sealant material and the fritted compound of Sr oxide and boric oxide has a mole ratio of 2 moles of the Sr oxide for each mole of boric oxide. A method of sealing a ceramic to an Inconel metal alloy is also disclosed.

  4. High temperature seal for joining ceramics and metal alloys

    DOEpatents

    Maiya, P.S.; Picciolo, J.J.; Emerson, J.E.; Dusek, J.T.; Balachandran, U.

    1998-03-10

    For a combination of a membrane of SrFeCo{sub 0.5}O{sub x} and an Inconel alloy, a high-temperature seal is formed between the membrane and the alloy. The seal is interposed between the alloy and the membrane, and is a fritted compound of Sr oxide and boric oxide and a fritted compound of Sr, Fe and Co oxides. The fritted compound of SrFeCo{sub 0.50}O{sub x} is present in the range of from about 30 to 70 percent by weight of the total sealant material and the fritted compound of Sr oxide and boric oxide has a mole ratio of 2 moles of the Sr oxide for each mole of boric oxide. A method of sealing a ceramic to an Inconel metal alloy is also disclosed. 3 figs.

  5. Phase stability in processing of high temperature intermetallic alloys

    SciTech Connect

    Perepezko, J.H.; Nunes, C.A.; Yi, S.H.; Thoma, D.J.

    1997-12-31

    In the development of high temperature intermetallics involving various aluminides, silicides and Laves phases, it has become evident that it is essential to consider the strong influence of materials processing throughout all stages. The underlying basis for alloy synthesis, processing and the assessment of thermal stability is established by the relevant phase equilibria, the characteristic diffusivities and the possible solidification reaction pathways. In almost all cases the microstructures of the most useful metallic alloys are multiphase assemblies in which the relative phase fractions, compositions and morphologies play key roles in optimizing the performance under high temperature conditions. The microstructure designs are usually tailored for strength, toughness, creep resistance and environmental stability and involve a balance of features derived from mixtures of a ductile phase and intermetallic phases. There is a clear experience that the level of materials processing can only be as sophisticated as the level of knowledge of the phase equilibria and the underlying kinetics. In many of the contemporary intermetallic alloys the phase stability must be considered in terms of multicomponent equilibria and non-stoichiometric intermetallic compositions. Recent developments in several important intermetallic alloy classes illustrate the guidance into alloy design and processing options provided by systematic studies of phase stability. 58 refs., 7 figs.

  6. Silver Alloys for High-Temperature Superconducting Wire

    NASA Astrophysics Data System (ADS)

    Smith, J. L.; Zhou, R.; Holesinger, T. C.; Hults, W. L.; Peterson, E. J.

    1996-03-01

    Pure silver is commonly used for cladding or as substrates for making bismuth- and thallium-based high-temperature superconductor wires. Pure silver's softness, lack of mechanical strength, and high-electrical conductivity cause various problems with the final conductor. We have made many alloys of silver with small amounts of additions, studied their mechanical and electrical properties, and checked compatibility with the superconducting materials. The use of silver alloys improves the usefulness of the conductors and improves or does not change the critical currents of the final conductor. This work was performed under the auspices of the U.S.D.O.E.

  7. High temperature, oxidation resistant noble metal-Al alloy thermocouple

    NASA Technical Reports Server (NTRS)

    Smialek, James L. (Inventor); Gedwill, Michael G. (Inventor)

    1994-01-01

    A thermocouple is disclosed. The thermocouple is comprised of an electropositive leg formed of a noble metal-Al alloy and an electronegative leg electrically joined to form a thermocouple junction. The thermocouple provides for accurate and reproducible measurement of high temperatures (600 - 1300 C) in inert, oxidizing or reducing environments, gases, or vacuum. Furthermore, the thermocouple circumvents the need for expensive, strategic precious metals such as rhodium as a constituent component. Selective oxidation of rhodium is also thereby precluded.

  8. Oxidation of Palladium-Chromium Alloys for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Piltch, Nancy D.; Jih-Fen, Lei; Zeller, Mary V.

    1994-01-01

    An alloy consisting of Pd with 13 wt % Cr is a promising material for high temperature applications. High temperature performance is degraded by the oxidation of the material, which is more severe in the fine wires and thin films used for sensor applications than in the bulk. The present study was undertaken to improve our understanding of the physical and chemical changes occurring at these temperatures and to identify approaches to limit oxidation of the alloy. The alloy was studied in both ribbon and wire forms. Ribbon samples were chosen to examine the role of grain boundaries in the oxidation process because of the convenience of handling for the oxidation studies. Wire samples 25 microns in diameter which are used in resistance strain gages were studied to correlate chemical properties with observed electrical, physical, and structural properties. Overcoating the material with a metallic Cr film did prevent the segregation of Pd to the surface; however, it did not eliminate the oxidation of the alloy.

  9. Damping of High-temperature Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

    Duffy, Kirsten P.; Padula, Santo A., II; Scheiman, Daniel A.

    2008-01-01

    Researchers at NASA Glenn Research Center have been investigating high temperature shape memory alloys as potential damping materials for turbomachinery rotor blades. Analysis shows that a thin layer of SMA with a loss factor of 0.04 or more would be effective at reducing the resonant response of a titanium alloy beam. Two NiTiHf shape memory alloy compositions were tested to determine their loss factors at frequencies from 0.1 to 100 Hz, at temperatures from room temperature to 300 C, and at alternating strain levels of 34-35x10(exp -6). Elevated damping was demonstrated between the M(sub s) and M(sub f) phase transformation temperatures and between the A(sub s) and A(sub f) temperatures. The highest damping occurred at the lowest frequencies, with a loss factor of 0.2-0.26 at 0.1 Hz. However, the peak damping decreased with increasing frequency, and showed significant temperature hysteresis in heating and cooling. Keywords: High-temperature, shape memory alloy, damping, aircraft engine blades, NiTiHf

  10. Amorphous Alloy Membranes for High Temperature Hydrogen Separation

    SciTech Connect

    Coulter, K

    2013-09-30

    At the beginning of this project, thin film amorphous alloy membranes were considered a nascent but promising new technology for industrial-scale hydrogen gas separations from coal- derived syngas. This project used a combination of theoretical modeling, advanced physical vapor deposition fabricating, and laboratory and gasifier testing to develop amorphous alloy membranes that had the potential to meet Department of Energy (DOE) targets in the testing strategies outlined in the NETL Membrane Test Protocol. The project is complete with Southwest Research Institute® (SwRI®), Georgia Institute of Technology (GT), and Western Research Institute (WRI) having all operated independently and concurrently. GT studied the hydrogen transport properties of several amorphous alloys and found that ZrCu and ZrCuTi were the most promising candidates. GT also evaluated the hydrogen transport properties of V, Nb and Ta membranes coated with different transition-metal carbides (TMCs) (TM = Ti, Hf, Zr) catalytic layers by employing first-principles calculations together with statistical mechanics methods and determined that TiC was the most promising material to provide catalytic hydrogen dissociation. SwRI developed magnetron coating techniques to deposit a range of amorphous alloys onto both porous discs and tubular substrates. Unfortunately none of the amorphous alloys could be deposited without pinhole defects that undermined the selectivity of the membranes. WRI tested the thermal properties of the ZrCu and ZrNi alloys and found that under reducing environments the upper temperature limit of operation without recrystallization is ~250 °C. There were four publications generated from this project with two additional manuscripts in progress and six presentations were made at national and international technical conferences. The combination of the pinhole defects and the lack of high temperature stability make the theoretically identified most promising candidate amorphous alloys

  11. Aerospace applications of beta titanium alloys

    NASA Astrophysics Data System (ADS)

    Boyer, Rodney R.

    1994-07-01

    Beta alloys are beginning to play a significant role in both military and commercial aircraft. Ti-10V-2Fe-3Al forgings, for example, play major roles in the McDonnell Douglas C-17 and the Boeing 777. The attractive properties of Beta-C are increasing the use of titanium, rather than steel, in aircraft springs. Ti-15V-3Cr-3Al-3Sn is subject to increasing usage primarily because of its strip producibility and formability. Beta-21S is gaining importance for high-temperature applications. New alloys such as β-CEZ, SP-700, and Timetal® LCB could become important because of advantageous costs, processing, and/or properties. In the past, the use of beta alloys has largely been driven by their superior properties and weight-savings potential. In the future, cost will become more important. As a result, a greater emphasis will be placed on lower cost alloys and/or taking advantage of the improved processing capabilities of these alloys to minimize final component costs.

  12. 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.

  13. High Temperature Fatigue Crack Growth Behavior of Alloy 10

    NASA Technical Reports Server (NTRS)

    Gayda, John

    2001-01-01

    Methods to improve the high temperature, dwell crack growth resistance of Alloy 10, a high strength, nickel-base disk alloy, were studied. Two approaches, heat treat variations and composition modifications, were investigated. Under the heat treat approach, solution temperature, cooling rates, and stabilization, were studied. It was found that higher solution temperatures, which promote coarser grain sizes, coupled with a 1550 F stabilization treatment were found to significantly reduce dwell crack growth rates at 1300 F Changes in the niobium and tantalum content were found to have a much smaller impact on crack growth behavior. Lowering the niobium:tantalum ratio did improve crack growth resistance and this effect was most pronounced for coarse grain microstructures. Based on these findings, a coarse grain microstructure for Alloy 10 appears to be the best option for improving dwell crack growth resistance, especially in the rim of a disk where temperatures can reach or exceed 1300 T. Further, the use of advanced processing technologies, which can produce a coarse grain rim and fine grain bore, would be the preferred option for Alloy 10 to obtain the optimal balance between tensile, creep, and crack growth requirements for small gas turbine engines.

  14. INCOLOY alloy 803, a cost effective alloy for high temperature service

    SciTech Connect

    Ganesan, P.; Plyburn, J.A.; Tassen, C.S.

    1995-12-31

    INCOLOY alloy 800 was the first of the 800 series of alloys invented by Inco Alloys International in the 1940`s. Because of its excellent oxidation and carburization resistance as well as high temperature creep strength, alloy 800 found uses for many applications such as heat treating hardware, petrochemical processing, home appliances, food processing, industrial heating, super-heater and re-heater tubing and soon became the workhorse material for the chemical processing industries. Alloy 803 has superior resistance to oxidation and carburization without sacrificing mechanical properties. In this paper the history of alloy 800 with introductions of alloys 800H and 800HT and the differences in properties and chemical compositions among them will be described. The development of alloy 803 for petrochemical applications is also covered. The performance of alloy 803 in cyclic oxidation, carburization and sulfidation tests will be presented and compared with several alloys including alloy HPM. The mechanical properties of alloy 803 including room temperature and high temperature tensile data and stress rupture and creep strengths up to 1,093 C (2,000 F) will be presented. The choice of available filler metals and welding electrodes to join alloy 803, using gas metal arc welding and shielded metal arc welding processes, will also be presented.

  15. High-temperature Hydrogen Permeation in Nickel Alloys

    SciTech Connect

    P. Calderoni; M. Ebner; R. Pawelko

    2010-10-01

    In gas cooled Very High Temperature Reactor concepts, tritium is produced as a tertiary fission product and by activation of graphite core contaminants, such as lithium; of the helium isotope, He-3, that is naturally present in the He gas coolant; and the boron in the B4C burnable poison. Because of its high mobility at the reactor outlet temperatures, tritium poses a risk of permeating through the walls of the intermediate heat exchanger (IHX) or steam generator (SG) systems, potentially contaminating the environment and in particular the hydrogen product when the reactor heat is utilized in connection with a hydrogen generation plant. An experiment to measure tritium permeation in structural materials at temperatures up to 1000 C has been constructed at the Idaho National Laboratory Safety and Tritium Applied Research (STAR) facility within the Next Generation Nuclear Plant program. The design is based on two counter flowing helium loops to represent heat exchanger conditions and was optimized to allow control of the materials surface condition and the investigation of the effects of thermal fatigue. In the ongoing campaign three nickel alloys are being considered because of their high-temperature creep properties, alloy 617, 800H and 230. This paper introduces the general issues related to tritium in the on-going assessment of gas cooled VHTR systems fission product transport and outlines the planned research activities in this area; outlines the features and capabilities of the experimental facility being operated at INL; presents and discusses the initial results of hydrogen permeability measurements in two of the selected alloys and compares them with the available database from previous studies.

  16. Cyclic Oxidation of High-Temperature Alloy Wires in Air

    NASA Technical Reports Server (NTRS)

    Reigel, Marissa M.

    2004-01-01

    High-temperature alloy wires are proposed for use in seal applications for future re-useable space vehicles. These alloys offer the potential for improved wear resistance of the seals. The wires must withstand the high temperature environments the seals are subjected to as well as maintain their oxidation resistance during the heating and cooling cycles of vehicle re-entry. To model this, the wires were subjected to cyclic oxidation in stagnant air. of this layer formation is dependent on temperature. Slow growing oxides such as chromia and alumina are desirable. Once the oxide is formed it can prevent the metal from further reacting with its environment. Cyclic oxidation models the changes in temperature these wires will undergo in application. Cycling the temperature introduces thermal stresses which can cause the oxide layer to break off. Re-growth of the oxide layer consumes more metal and therefore reduces the properties and durability of the material. were used for cyclic oxidation testing. The baseline material, Haynes 188, has a Co base and is a chromia former while the other two alloys, Kanthal A1 and PM2000, both have a Fe base and are alumina formers. Haynes 188 and Kanthal A1 wires are 250 pm in diameter and PM2000 wires are 150 pm in diameter. The coiled wire has a total surface area of 3 to 5 sq cm. The wires were oxidized for 11 cycles at 1204 C, each cycle containing a 1 hour heating time and a minimum 20 minute cooling time. Weights were taken between cycles. After 11 cycles, one wire of each composition was removed for analysis. The other wire continued testing for 70 cycles. Post-test analysis includes X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Energy Dispersive Spectroscopy (EDS) for phase identification and morphology.

  17. The 1992 NASA Langley Measurement Technology Conference: Measurement Technology for Aerospace Applications in High-Temperature Environments

    NASA Technical Reports Server (NTRS)

    Singh, Jag J. (Editor); Antcliff, Richard R. (Editor)

    1992-01-01

    An intensive 2-day conference to discuss the current status of measurement technology in the areas of temperature/heat flux, stress/strain, pressure, and flowfield diagnostics for high temperature aerospace applications was held at Langley Research Center, Hampton, Virginia, on April 22 and 23, 1993. Complete texts of the papers presented at the Conference are included in these proceedings.

  18. Constitutive relationships for anisotropic high-temperature alloys

    NASA Technical Reports Server (NTRS)

    Robinson, D. N.

    1982-01-01

    A constitutive theory is presented for representing the anisotropic viscoplastic behavior of high temperature alloys that posses directional properties resulting from controlled grain growth or solidification. The theory is an extension of a viscoplastic model that was applied in structural analyses involving isotropic metals. Anisotropy is introduced through the definition of a vector field that identifies a preferential (solidification) direction at each material point. Following the development of a full multiaxial theory, application is made to homogeneously stressed elements in pure shear and to a uniaxially stressed rectangular block in plane stress with the stress direction oriented at an arbitrary angle with the material direction. It is shown that an additional material parameter introduced to characterize the degree of anisotropy can be determined on the basis of simple creep tests.

  19. Intergranular failures of Alloy 600 in high temperature caustic environments

    SciTech Connect

    Bandy, R.; Roberge, R.; van Rooyen, D.

    1984-01-01

    This paper describes the results of our investigation of two commonly observed modes of failure of Alloy 600 in high temperature caustic environment namely, intergranular stress corrosion cracking (IGSCC) and intergranular attack (IGA). Specimens are studied as C-rings under constant deflection, wires with and without any externally applied load, and as straining electrodes. The potential dependence of average crack propagation rate is established in a single test by using several C-rings held at different potentials, by using a modification of the static potential gradient method of Seys and Van Haute. SCC appears to be governed by a film rupture mechanism and its propagation rate is significantly influenced by the electrochemical potential and associated surface film formation. The maximum crack propagation rate for C-rings and constant load specimens is very similar but much smaller than that calculated for a straining electrode at the same potential. IGA occurs over a wide range of potential - starting from a few tens of millivolts cathodic to the corrosion potential up to the lower end of anodic potentials normally required for SCC. IGA seems to be rather independent of stress and is generally more pronounced in the crevice area under the nuts used in C-rings. Examination of several creviced coupons shows that outside the crevice, enrichment of iron and chromium occurs on the surface as the potential is raised anodically, whereas the Ni:Fe and Ni:Cr ratios remain relatively independent of potential within the crevice.

  20. Intergranular failures of alloy 600 in high temperature caustic environments

    SciTech Connect

    Bandy, R.; van Rooyen, D.; Roberge, R.

    1985-03-01

    This paper describes the results of an investigation of two commonly observed modes of failure of Alloy 600 in high temperature caustic environment, namely, intergranular stress corrosion cracking (IGSCC) and intergranular attack (IGA). Specimens are studied as C-rings under constant deflection, wires with and without any externally applied load, and as straining electrodes. The potential dependence of average crack propagation rate is established in a single test in which several C-rings are held at different potentials by using a modification of the static potential gradient method of Seys and Van Haute. SCC appears to be governed by a film rupture mechanism, and its propagation rate is significantly influenced by the electrochemical potential and associated surface film formation. The maximum crack propagation rate for C-rings and constant load specimens is very similar but much smaller than that calculated for a straining electrode at the same potential. IGA occurs over a wide range of potential, starting from a few multiples of ten millivolts cathodic to the corrosion potential up to the lower end of anodic potentials normally required for SCC. IGA seems to be rather independent of stress and is generally more pronounced in the crevice area under the nuts used in C-rings. Examination of several creviced coupons shows that outside the crevice, enrichment of iron and chromium occurs on the surface as the potential is raised anodically, whereas the Ni:Fe and Ni:Cr ratios remain relatively independent of potential within the crevice. It is believed that a better knowledge of the crevice chemistry and its mass transport characteristics will provide a clue to the origin and extent of IGA.

  1. Statistical Analysis of Strength Data for an Aerospace Aluminum Alloy

    NASA Technical Reports Server (NTRS)

    Neergaard, Lynn; Malone, Tina; Gentz, Steven J. (Technical Monitor)

    2000-01-01

    Aerospace vehicles are produced in limited quantities that do not always allow development of MIL-HDBK-5 A-basis design allowables. One method of examining production and composition variations is to perform 100% lot acceptance testing for aerospace Aluminum (Al) alloys. This paper discusses statistical trends seen in strength data for one Al alloy. A four-step approach reduced the data to residuals, visualized residuals as a function of time, grouped data with quantified scatter, and conducted analysis of variance (ANOVA).

  2. Statistical Analysis of Strength Data for an Aerospace Aluminum Alloy

    NASA Technical Reports Server (NTRS)

    Neergaard, L.; Malone, T.

    2001-01-01

    Aerospace vehicles are produced in limited quantities that do not always allow development of MIL-HDBK-5 A-basis design allowables. One method of examining production and composition variations is to perform 100% lot acceptance testing for aerospace Aluminum (Al) alloys. This paper discusses statistical trends seen in strength data for one Al alloy. A four-step approach reduced the data to residuals, visualized residuals as a function of time, grouped data with quantified scatter, and conducted analysis of variance (ANOVA).

  3. Ceramic Matrix Composites: High Temperature Effects. (Latest Citations from the Aerospace Database)

    NASA Technical Reports Server (NTRS)

    1997-01-01

    The bibliography contains citations concerning the development and testing of ceramic matrix composites for high temperature use. Tests examining effects of the high temperatures on bond strength, thermal degradation, oxidation, thermal stress, thermal fatigue, and thermal expansion properties are referenced. Applications of the composites include space structures, gas turbine and engine components, control surfaces for spacecraft and transatmospheric vehicles, heat shields, and heat exchangers.

  4. 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.

  5. Fabrication of intermetallic coatings for electrical insulation and corrosion resistance on high-temperature alloys

    SciTech Connect

    Park, J.-H.; Cho, W.D.

    1996-11-01

    Several intermetallic films were applied to high-temperature alloys (V alloys and 304, 316 stainless steels) to provide electrical insulation and corrosion resistance. Alloy grain growth at 1000 C for the V-5Cr-5Ti alloy was investigated to determine stability of the alloy substrate during coating formation by CVD or metallic vapor processes at 800-850 C. Film layers were examined by optical and scanning electron microscopy and by electron-energy-dispersive and XRD analysis; they were also tested for electrical resistivity and corrosion resistance. Results elucidated the nature of the coatings, which provided both electrical insulation and high-temperature corrosion protection.

  6. Burner rig alkali salt corrosion of several high temperature alloys

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    The hot corrosion of five alloys was studied in cyclic tests in a Mach 0.3 burner rig into whose combustion chamber various aqueous salt solutions were injected. Three nickel-based alloys, a cobalt-base alloy, and an iron-base alloy were studied at temperatures of 700, 800, 900, and 1000 C with various salt concentrations and compositions. The relative resistance of the alloys to hot corrosion attack was found to vary with temperature and both concentration and composition of the injected salt solution. Results indicate that the corrosion of these alloys is a function of both the presence of salt condensed as a liquid on the surface and of the composition of the gas phases present.

  7. High-Temperature Alloys for Automotive Stirling Engines

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.; Titran, R. H.

    1986-01-01

    Stirling engine is external-combustion engine that offers fuel economy, low emissions, low noise, and low vibrations. One of most critical areas in engine development concerns material selection for component parts. Alloys CG-27 and XF-818 identified capable of withstanding rigorous requirements of automotive Stirling engine. Alloys chosen for availability, performance, and manufacturability. Advanced iron-base alloys have potential for variety of applications, including stationary solar-power systems.

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

    SciTech Connect

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

    1992-11-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

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

  10. Evaluating the Hot Corrosion Behavior of High-Temperature Alloys for Gas Turbine Engine Components

    NASA Astrophysics Data System (ADS)

    Deodeshmukh, V. P.

    2015-11-01

    The hot corrosion behavior of high-temperature alloys is critically important for gas turbine engine components operating near the marine environments. The two test methods—Two-Zone and Burner-Rig—used to evaluate the hot corrosion performance of high-temperature alloys are illustrated by comparing the Type I hot corrosion behavior of selected high-temperature alloys. Although the ranking of the alloys is quite comparable, it is evident that the two-zone hot corrosion test is significantly more aggressive than the burner-rig test. The effect of long-term exposures and the factors that influence the hot corrosion performance of high-temperature alloys are briefly discussed.

  11. Correlation between Mechanical Behavior and Actuator-type Performance of Ni-Ti-Pd High-temperature Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

    High-temperature shape memory alloys in the NiTiPd system are being investigated as lower cost alternatives to NiTiPt alloys for use in compact solid-state actuators for the aerospace, automotive, and power generation industries. A range of ternary NiTiPd alloys containing 15 to 46 at.% Pd has been processed and actuator mimicking tests (thermal cycling under load) were used to measure transformation temperatures, work behavior, and dimensional stability. With increasing Pd content, the work output of the material decreased, while the amount of permanent strain resulting from each load-biased thermal cycle increased. Monotonic isothermal tension testing of the high-temperature austenite and low temperature martensite phases was used to partially explain these behaviors, where a mismatch in yield strength between the austenite and martensite phases was observed at high Pd levels. Moreover, to further understand the source of the permanent strain at lower Pd levels, strain recovery tests were conducted to determine the onset of plastic deformation in the martensite phase. Consequently, the work behavior and dimensional stability during thermal cycling under load of the various NiTiPd alloys is discussed in relation to the deformation behavior of the materials as revealed by the strain recovery and monotonic tension tests.

  12. Deformation and thermal fatigue in high temperature austenitic alloys

    SciTech Connect

    Ferro, P.D.; Yost, B.; Swindeman, R.W.; Li, Che-Yu . Dept. of Materials Science and Engineering)

    1991-03-01

    The flow properties of modified austenitic alloys are reviewed. The important strengthening mechanisms discussed include precipitation hardening produced by a combination of cold work and aging and by creep aging. Grain boundary sliding enhanced by reduced grain size is shown to reduce the flow strength of these alloys. 5 refs., 11 figs., 2 tabs.

  13. Optical investigation of oxide scales on high-temperature alloys

    NASA Astrophysics Data System (ADS)

    Uran, Serif

    all crystallographic phases with Zr doping. The oxide scales are also thinner on the Zr doped specimen. The effects of reactive element (i.e., Zr) doping on deformation and residual stresses which develop in the vicinity of edges in single crystal β-NiAl is investigated as it is thermally oxidized at temperatures in the range 1100-1450°C. Data for both the deformation and stress are presented for the following pair of orientations: (001) and (11¯0), (111), and (11¯0). The effect of surface roughness on the properties of the oxide scale that is formed on Fe-Cr-Al alloys during oxidation in air at high temperatures has been investigated. Large and systematic differences in scale thickness, in the composition of the oxides forming the scale, and in the residual stress levels are found.

  14. Constitutive Modeling of High-Temperature Flow Behavior of Al-0.62Mg-0.73Si Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Sun, Y.; Ye, W. H.; Hu, L. X.

    2016-04-01

    The high-temperature flow behavior of an aerospace structural material Al-0.62 Mg-0.73Si aluminum alloy was researched in this work. The isothermal compression tests were carried out in the temperature range of 683-783 K and strain rate range of 0.001-1 s-1. Based on the obtained true stress-true strain curves, the constitutive relationship of the alloy was revealed by establishing the Arrhenius-type constitutive model and a modified Johnson-Cook model. It was found that the flow characteristics were closely related to deformation temperature and strain rate. The activation energy of the studied material was calculated to be approximately 174 kJ mol-1. A comparative study has been conducted on the accuracy and reliability of the proposed models using statistics analysis method. It was proved by error analysis that the Arrhenius-type model had a better performance than the modified Johnson-Cook model.

  15. Directions for High-Temperature Shape Memory Alloys' Improvement: Straight Way to High-Entropy Materials?

    NASA Astrophysics Data System (ADS)

    Firstov, G. S.; Kosorukova, T. A.; Koval, Yu N.; Verhovlyuk, P. A.

    2015-10-01

    Nowadays, all thermo-mechanical effects, associated with the martensitic structural phase transitions, are still in the focus of scientists and engineers, especially once these phenomena are taking place at elevated temperatures. The list of the materials, undergoing high-temperature martensitic transformation, is constantly widening. Still, industrial application of these materials, called high-temperature shape memory alloys, is far enough due to the lack of understanding of the peculiarities of the high-temperature martensitic transformation and shape memory effect. The present work attempts to show how the development of the proper directions for high-temperature shape memory alloys' improvement might lead to the creation of essentially new functional materials.

  16. Computational Thermodynamics and Kinetics-Based ICME Framework for High-Temperature Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Arróyave, Raymundo; Talapatra, Anjana; Johnson, Luke; Singh, Navdeep; Ma, Ji; Karaman, Ibrahim

    2015-11-01

    Over the last decade, considerable interest in the development of High-Temperature Shape Memory Alloys (HTSMAs) for solid-state actuation has increased dramatically as key applications in the aerospace and automotive industry demand actuation temperatures well above those of conventional SMAs. Most of the research to date has focused on establishing the (forward) connections between chemistry, processing, (micro)structure, properties, and performance. Much less work has been dedicated to the development of frameworks capable of addressing the inverse problem of establishing necessary chemistry and processing schedules to achieve specific performance goals. Integrated Computational Materials Engineering (ICME) has emerged as a powerful framework to address this problem, although it has yet to be applied to the development of HTSMAs. In this paper, the contributions of computational thermodynamics and kinetics to ICME of HTSMAs are described. Some representative examples of the use of computational thermodynamics and kinetics to understand the phase stability and microstructural evolution in HTSMAs are discussed. Some very recent efforts at combining both to assist in the design of HTSMAs and limitations to the full implementation of ICME frameworks for HTSMA development are presented.

  17. Two-phase chromium-niobium alloys exhibiting improved mechanical properties at high temperatures

    DOEpatents

    Liu, C.T.; Takeyama, Masao.

    1994-02-01

    The specification discloses chromium-niobium alloys which exhibit improved mechanical properties at high temperatures in the range of 1250 C and improved room temperature ductility. The alloys contain a Cr[sub 2]Nb-rich intermetallic phase and a Cr-rich phase with an overall niobium concentration in the range of from about 5 to about 18 at. %. The high temperature strength is substantially greater than that of state of the art nickel-based superalloys for enhanced high temperature service. Further improvements in the properties of the compositions are obtained by alloying with rhenium and aluminum; and additional rare-earth and other elements. 14 figures.

  18. Two-phase chromium-niobium alloys exhibiting improved mechanical properties at high temperatures

    DOEpatents

    Liu, Chain T.; Takeyama, Masao

    1994-01-01

    The specification discloses chromium-niobium alloys which exhibit improved mechanical properties at high temperatures in the range of 1250.degree. C. and improved room temperature ductility. The alloys contain a Cr.sub.2 Nb-rich intermetallic phase and a Cr-rich phase with an overall niobium concentration in the range of from about 5 to about 18 at. %. The high temperature strength is substantially greater than that of state of the art nickel-based superalloys for enhanced high temperature service. Further improvements in the properties of the compositions are obtained by alloying with rhenium and aluminum; and additional rare-earth and other elements.

  19. Development and Processing Improvement of Aerospace Aluminum Alloys

    NASA Technical Reports Server (NTRS)

    Lisagor, W. Barry; Bales, Thomas T.

    2007-01-01

    This final report, in multiple presentation format, describes a comprehensive multi-tasked contract study to improve the overall property response of selected aerospace alloys, explore further a newly-developed and registered alloy, and correlate the processing, metallurgical structure, and subsequent properties achieved with particular emphasis on the crystallographic orientation texture developed. Modifications to plate processing, specifically hot rolling practices, were evaluated for Al-Li alloys 2195 and 2297, for the recently registered Al-Cu-Ag alloy, 2139, and for the Al-Zn-Mg-Cu alloy, 7050. For all of the alloys evaluated, the processing modifications resulted in significant improvements in mechanical properties. Analyses also resulted in an enhanced understanding of the correlation of processing, crystallographic texture, and mechanical properties.

  20. 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.

  1. High temperature static strain gage alloy development program

    NASA Technical Reports Server (NTRS)

    Hulse, C. O.; Bailey, R. S.; Lemkey, F. D.

    1985-01-01

    The literature, applicable theory and finally an experimental program were used to identify new candidate alloy systems for use as the electrical resistance elements in static strain gages up to 1250K. The program goals were 50 hours of use in the environment of a test stand gas turbine engine with measurement accuracies equal to or better than 10 percent of full scale for strains up to + or - 2000 microstrain. As part of this effort, a computerized electrical resistance measurement system was constructed for use at temperatures between 300K and 1250K and heating and cooling rates of 250K/min and 10K/min. The two best alloys were an iron-chromium-aluminum alloy and a palladium base alloy. Although significant progress was made, it was concluded that a considerable additional effort would be needed to fully optimize and evaluate these candidate systems.

  2. Iron aluminide alloys with improved properties for high temperature applications

    DOEpatents

    McKamey, C.G.; Liu, C.T.

    1990-10-09

    An improved iron aluminide alloy of the DO[sub 3] type is described that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy conversion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26--30 at. % aluminum, 0.5--10 at. % chromium, 0.02--0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron. 3 figs.

  3. Iron aluminide alloys with improved properties for high temperature applications

    DOEpatents

    McKamey, Claudette G.; Liu, Chain T.

    1990-01-01

    An improved iron aluminide alloy of the DO.sub.3 type that has increased room temperature ductility and improved high elevated temperature strength. The alloy system further is resistant to corrosive attack in the environments of advanced energy corrosion systems such as those using fossil fuels. The resultant alloy is relatively inexpensive as contrasted to nickel based and high nickel steels currently utilized for structural components. The alloy system consists essentially of 26-30 at. % aluminum, 0.5-10 at. % chromium, 0.02-0.3 at. % boron plus carbon, up to 2 at. % molybdenum, up to 1 at. % niobium, up to 0.5 at. % zirconium, up to 0.1 at. % yttrium, up to 0.5 at. % vanadium and the balance iron.

  4. Dynamic mechanical response and a constitutive model of Fe-based high temperature alloy at high temperatures and strain rates.

    PubMed

    Su, Xiang; Wang, Gang; Li, Jianfeng; Rong, Yiming

    2016-01-01

    The effects of strain rate and temperature on the dynamic behavior of Fe-based high temperature alloy was studied. The strain rates were 0.001-12,000 s(-1), at temperatures ranging from room temperature to 800 °C. A phenomenological constitutive model (Power-Law constitutive model) was proposed considering adiabatic temperature rise and accurate material thermal physical properties. During which, the effects of the specific heat capacity on the adiabatic temperature rise was studied. The constitutive model was verified to be accurate by comparison between predicted and experimental results. PMID:27186468

  5. Light-weight alloys for aerospace applications; Proceedings of the Symposium, Las Vegas, NV, Feb. 28-Mar. 2, 1989

    SciTech Connect

    Lee, E.W.; Chia, E.H.; Kim, N.J.

    1989-01-01

    Various papers on lightweight alloys for aerospace applications are presented. Individual topics addressed include: P/M-aluminum alloy for high-temperature application, elevated temperature behavior of RST Al-Ti-X alloys, microstructural characterization of rapidly solidified Al-Ze-V alloys, high-strength aluminum alloys for aerospace applications, oxidation behavior of some Mg-Li and Mg-Li-SI alloys, the effect of various environments on fatigue crack propagation in a 2090 Al-Li alloy, and surface-generated scratches and their effects on the fatigue life of Al-Li alloys. Consideration is given to the stretch formability of sheet Al-Li, hydrogen solution in Al-Li alloys, particle-reinforced aluminum-based composites, applications for discontinuously reinforced aluminum, age hardening of cast SiC-reinforced Mg-6Zn, superplasticity in high-strength aluminum alloys and in spray-deposited 7075 Al alloys, and superplastic behavior in an aluminum-lithium alloy.

  6. Computational simulation of probabilistic lifetime strength for aerospace materials subjected to high temperature, mechanical fatigue, creep, and thermal fatigue

    NASA Technical Reports Server (NTRS)

    Boyce, Lola; Bast, Callie C.; Trimble, Greg A.

    1992-01-01

    The results of a fourth year effort of a research program conducted for NASA-LeRC by The University of Texas at San Antonio (UTSA) are presented. The research included on-going development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subjected to a number of effects or primitive variables. These primitive variables may include high temperature, fatigue, or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation was randomized and is included in the computer program, PROMISC. Also included in the research is the development of methodology to calibrate the above-described constitutive equation using actual experimental materials data together with regression analysis of that data, thereby predicting values for the empirical material constants for each effect or primitive variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from industry and the open literature for materials typically for applications in aerospace propulsion system components. Material data for Inconel 718 was analyzed using the developed methodology.

  7. Computational simulation of probabilistic lifetime strength for aerospace materials subjected to high temperature, mechanical fatigue, creep and thermal fatigue

    NASA Technical Reports Server (NTRS)

    Boyce, Lola; Bast, Callie C.; Trimble, Greg A.

    1992-01-01

    This report presents the results of a fourth year effort of a research program, conducted for NASA-LeRC by the University of Texas at San Antonio (UTSA). The research included on-going development of methodology that provides probabilistic lifetime strength of aerospace materials via computational simulation. A probabilistic material strength degradation model, in the form of a randomized multifactor interaction equation, is postulated for strength degradation of structural components of aerospace propulsion systems subject to a number of effects or primitive variables. These primitive variables may include high temperature, fatigue or creep. In most cases, strength is reduced as a result of the action of a variable. This multifactor interaction strength degradation equation has been randomized and is included in the computer program, PROMISS. Also included in the research is the development of methodology to calibrate the above-described constitutive equation using actual experimental materials data together with regression analysis of that data, thereby predicting values for the empirical material constants for each effect or primitive variable. This regression methodology is included in the computer program, PROMISC. Actual experimental materials data were obtained from industry and the open literature for materials typically for applications in aerospace propulsion system components. Material data for Inconel 718 has been analyzed using the developed methodology.

  8. Applications of high-temperature powder metal aluminum alloys to small gas turbines

    NASA Technical Reports Server (NTRS)

    Millan, P. P., Jr.

    1982-01-01

    A program aimed at the development of advanced powder-metallurgy (PM) aluminum alloys for high-temperature applications up to 650 F using the concepts of rapid solidification and mechanical alloying is discussed. In particular, application of rapidly solidified PM aluminum alloys to centrifugal compressor impellers, currently used in auxiliary power units for both military and commercial aircraft and potentially for advanced automotive gas turbine engines, is examined. It is shown that substitution of high-temperature aluminum for titanium alloy impellers operating in the 360-650 F range provides significant savings in material and machining costs and results in reduced component weight, and consequently, reduced rotating group inertia requirements.

  9. 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.

  10. Iron-niobium-aluminum alloy having high-temperature corrosion resistance

    DOEpatents

    Hsu, Huey S.

    1988-04-14

    An alloy for use in high temperature sulfur and oxygen containing environments, having aluminum for oxygen resistance, niobium for sulfur resistance and the balance iron, is discussed. 4 figs., 2 tabs.

  11. High Work Output Ni-Ti-Pt High Temperature Shape Memory Alloys and Associated Processing Methods

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald D. (Inventor); Draper, Susan L. (Inventor); Nathal, Michael V. (Inventor); Garg, Anita (Inventor)

    2009-01-01

    According to the invention, compositions of Ni-Ti-Pt high temperature, high force, shape memory alloys are disclosed that have transition temperatures above 100 C.; have narrow hysteresis; and produce a high specific work output.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  13. Oxidation behaviors of porous Haynes 214 alloy at high temperatures

    SciTech Connect

    Wang, Yan; Liu, Yong; Tang, Huiping; Li, Weijie

    2015-09-15

    The oxidation behaviors of porous Haynes 214 alloy at temperatures from 850 to 1000 °C were investigated. The porous alloys before and after the oxidation were examined by optical microscopy, scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) analyses, and X-ray photoelectron spectroscopy (XPS). The oxidation kinetics of the porous alloy approximately follows a parabolic rate law and exhibits two stages controlled by different oxidation courses. Complex oxide scales composed of Cr{sub 2}O{sub 3}, NiCr{sub 2}O{sub 4} and Al{sub 2}O{sub 3} are formed on the oxidized porous alloys, and the formation of Cr{sub 2}O{sub 3} on its outer layer is promoted with the oxidation proceeding. The rough surface as well as the micropores in the microstructures of the porous alloy caused by the manufacturing process provides fast diffusion paths for oxygen so as to affect the formation of the oxide layers. Both the maximum pore size and the permeability of the porous alloys decrease with the increase of oxidation temperature and exposure time, which may limit its applications. - Highlights: • Two-stage oxidation kinetics controlled by different oxidation courses is showed. • Oxide scale mainly consists of Cr{sub 2}O{sub 3}, NiCr{sub 2}O{sub 4} and Al{sub 2}O{sub 3}. • Rough surface and micropores lead to the formation of uneven oxide structure. • Content of Cr{sub 2}O{sub 3} in the outer layer of the scale increases with time at 1000 °C. • Maximum pore size and permeability decrease with increasing temperature and time.

  14. Dynamic high-temperature characterization of an iridium alloy in compression at high strain rates.

    SciTech Connect

    Song, Bo; Nelson, Kevin; Lipinski, Ronald J.; Bignell, John L.; Ulrich, G. B.; George, E. P.

    2014-06-01

    Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-temperature high-strain-rate performance are needed for understanding high-speed impacts in severe elevated-temperature environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain-rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. Current high-temperature Kolsky compression bar techniques are not capable of obtaining satisfactory high-temperature high-strain-rate stress-strain response of thin iridium specimens investigated in this study. We analyzed the difficulties encountered in high-temperature Kolsky compression bar testing of thin iridium alloy specimens. Appropriate modifications were made to the current high-temperature Kolsky compression bar technique to obtain reliable compressive stress-strain response of an iridium alloy at high strain rates (300 10000 s-1) and temperatures (750ÀC and 1030ÀC). Uncertainties in such high-temperature high-strain-rate experiments on thin iridium specimens were also analyzed. The compressive stress-strain response of the iridium alloy showed significant sensitivity to strain rate and temperature.

  15. High-Temperature Workability of Thixocast A356 Aluminum Alloy

    NASA Astrophysics Data System (ADS)

    Singh, Shailesh Kumar; Chattopadhyay, K.; Dutta, Pradip

    2015-07-01

    The present work highlights the role of globular microstructure on the workability of A356 aluminum alloy at elevated temperature. The hot deformation behavior was studied by isothermal hot compression tests in the temperature range 573 K to 773 K (300 °C to 500 °C) and strain rate range of 0.001 to 10 s-1. The flow stress data obtained from the tests were used to estimate the strain rate sensitivity and strain rate hardening. Flow stress analysis of the alloy shows that the effect of temperature on strain hardening is more significant at lower strain levels and strain rate sensitivity is independent of strain. The results also reveal that the flowability of conventionally cast alloy increases after changing the dendritic microstructure into a globular structure through semisolid processing route. Thixocast alloy exhibits lower yield strength and higher elongation at elevated temperature in comparisons to conventionally cast values. This property has an important implication toward thixo-forming at an elevated temperature.

  16. Oxidation resistant iron and nickel alloys for high temperature use

    NASA Technical Reports Server (NTRS)

    Hill, V. L.; Misra, S. K.; Wheaton, H. L.

    1970-01-01

    Iron-base and nickel-base alloys exhibit good oxidation resistance and improved ductility with addition of small amounts of yttrium, tantalum /or hafnium/, and thorium. They can be used in applications above the operating temperatures of the superalloys, if high strength materials are not required.

  17. High-temperature nitridation of Ni-Cr alloys

    NASA Astrophysics Data System (ADS)

    Kodentsov, A. A.; Gülpen, J. H.; Cserháti, C.; Kivilahti, J. K.; van Loo, F. J. J.

    1996-01-01

    The nitriding behavior of nickel-chromium alloys was investigated at 1398 K over the range 1 to 6000 bar of external nitrogen pressure. The morphology of the nitrided zone depends on the concentration of chromium in the initial alloy and the N2 pressure (fugacity) applied upon the system. The transition from CrN to Cr2N precipitation was observed within the reaction zone after nitriding at 100 to 6000 bar of N2 when the chromium content in the initial alloys was 28.0 at. pct or higher. It is shown that the ternary phase π (Cr10Ni7N3) is formed in this system at 1273 K. through a peritectoid reaction between Cr2N and nickel solid solution and becomes unstable above 1373 K. The thermodynamic evaluation of the Ni-Cr-N system was performed and phase equilibria calculated. Evidence for “up hill” diffusion of nitrogen near the reaction front during the internal nitridation of Ni-Cr alloys at 1398 K was found. It was attributed to the relative instability of chromium nitrides and strong Cr-N interaction in the matrix of the Ni-based solid solution within the nitrided zone.

  18. Welding and performance of advanced high temperature alloys

    SciTech Connect

    Prager, M.; Masuyama, F.

    1995-12-31

    The last decade has witnessed the development of many new alloys for elevated temperature service and recognition of a large number of them in the form of allowable stresses by the ASME Boiler and Pressure Vessel Code. These alloys offer considerable advantages in terms of higher tensile and stress rupture strengths, lower thermal stresses, superior corrosion resistance and, in one case, weldability. The improvements are obtained through additions of tungsten, vanadium, columbium, copper, nitrogen and other elements which significantly affect microstructure and weldability. The paper will discuss where introduction of these advanced materials may be warranted, the properties to be expected in comparison to conventional alloys, PWHT requirements and concerns regarding weld failure modes. Higher performance in operation of power plants is achieved by use of tungsten alloyed advanced 9--12%Cr ferritic steels, NF616 (9Cr-0.5 Mo-1.8W-V-Nb) and HCM12A (12Cr-0.4Mo-2W-1 Cu-V-Nb), which exhibit over 30% higher creep strength than T91/P91 (Mod. 9Cr-1 Mo) at 600 C. Thick-walled and large-diameter pipes of NF616 and HCM12A were subjected to fabrication tests such as joint welding and induction bending, and it was shown that the properties of the fabricated parts were satisfactory for the practical application of those steels. HCM2S, a newly developed low alloy steel (0.06C-2.25Cr-1.6W-0.25V0.05Nb) is approximately 1.8 times stronger than conventional T22 (2.25Cr-1 Mo) at around 600 C. The weldability of this low carbon content steel is much improved, as it needs no pre-weld nor postweld heat treatment. HCM2S was installed in a large capacity utility boiler.

  19. Temperature and heat flux measurements: Challenges for high temperature aerospace application

    NASA Technical Reports Server (NTRS)

    Neumann, Richard D.

    1992-01-01

    The measurement of high temperatures and the influence of heat transfer data is not strictly a problem of either the high temperatures involved or the level of the heating rates to be measured at those high temperatures. It is a problem of duration during which measurements are made and the nature of the materials in which the measurements are made. Thermal measurement techniques for each application must respect and work with the unique features of that application. Six challenges in the development of measurement technology are discussed: (1) to capture the character and localized peak values within highly nonuniform heating regions; (2) to manage large volumes of thermal instrumentation in order to efficiently derive critical information; (3) to accommodate thermal sensors into practical flight structures; (4) to broaden the capabilities of thermal survey techniques to replace discrete gages in flight and on the ground; (5) to provide supporting instrumentation conduits which connect the measurement points to the thermally controlled data acquisition system; and (6) to develop a class of 'vehicle tending' thermal sensors to assure the integrity of flight vehicles in an efficient manner.

  20. Creep Testing of High-Temperature Cu-8 Cr-4 Nb Alloy Completed

    NASA Technical Reports Server (NTRS)

    1995-01-01

    A Cu-8 at.% Cr-4 at.% Nb (Cu-8 Cr-4 Nb) alloy is under development for high-temperature, high heatflux applications, such as actively cooled, hypersonic vehicle heat exchangers and rocket engine combustion chambers. Cu-8 Cr-4 Nb offers a superior combination of strength and conductivity. It has also shown exceptional low-cycle fatigue properties. Following preliminary testing to determine the best processing route, a more detailed testing program was initiated to determine the creep lives and creep rates of Cu-8 Cr-4 Nb alloy specimens produced by extrusion. Testing was conducted at the NASA Lewis Research Center with constant-load vacuum creep units. Considering expected operating temperatures and mission lives, we developed a test matrix to accurately determine the creep properties of Cu-8 Cr-4 Nb between 500 and 800 C. Six bars of Cu-8 Cr-4 Nb were extruded. From these bars, 54 creep samples were machined and tested. The figure on the left shows the steady-state, or second-stage, creep rates for the samples. Comparison data for NARloy-Z (Cu-3 wt % Ag-0.5 wt % Zr), the alloy currently used in combustion chamber liners, were not unavailable. Therefore the steady-state creep rates for Cu at similar temperatures are presented. As expected, in comparison to pure Cu, the creep rates for Cu-8 Cr-4 Nb are much lower. The lives of the samples are presented in the figure on the right. As shown, Cu-8 Cr-4 Nb at 800 C is comparable to NARloy-Z at 648 C. At equivalent temperatures, Cu-8 Cr-4 Nb enjoys a 20 to 50 percent advantage in stress for a given life and 1 to 3 orders of magnitude greater life at a given stress. The improved properties allow for design tradeoffs and improvements in new and existing heat exchangers such as the next generation of combustion chamber liners. Average creep rates for Cu-8 Cr-4 Nb and pure Cu are shown. Average creep lives for Cu-8 Cr- 4 Nb and NARloy-Z are also shown. Currently, two companies are interested in the commercial usage of the Cu

  1. Environmental protection of titanium alloys at high temperatures

    NASA Technical Reports Server (NTRS)

    Wright, I. G.; Wood, R. A.; Seltzer, M. S.

    1974-01-01

    Various concepts were evaluated for protecting titanium alloys from oxygen contamination at 922 K (1200 F) and from hot-salt stress-corrosion at 755 K (900 F). It is indicated that oxygen-contamination resistance can be provided by a number of systems, but for hot-salt stress-corrosion resistance, factors such as coating integrity become very important. Titanium aluminides resist oxygen ingress at 922 K through the formation of alumina (on TiAl3) or modified TiO2 (on Ti3Al, TiAl) scales. TiAl has some resistance to attack by hot salt, but has limited ductility. Ductile Ti-Ni and Ti-Nb-Cr-Al alloys provide limited resistance to oxygen ingress, but are not greatly susceptible to hot-salt stress-corrosion cracking.

  2. 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.

  3. High Strength Aluminum Alloy For High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A. (Inventor); Chen, Po-Shou (Inventor)

    2005-01-01

    A cast article from an aluminum alloy has improved mechanical properties at elevated temperatures. The cast article has the following composition in weight percent: Silicon 6.0-25.0, Copper 5.0-8.0, Iron 0.05-1.2, Magnesium 0.5-1.5, Nickel 0.05-0.9, Manganese 0.05-1.2, Titanium 0.05-1.2, Zirconium 0.05-1.2, Vanadium 0.05-1.2, Zinc 0.05-0.9, Strontium 0.001-0.1, Phosphorus 0.001-0.1, and the balance is Aluminum, wherein the silicon-to-magnesium ratio is 10-25, and the copper-to-magnesium ratio is 4-15. The aluminum alloy contains a simultaneous dispersion of three types of Al3X compound particles (X=Ti, V, Zr) having a LI2 crystal structure, and their lattice parameters are coherent to the aluminum matrix lattice. A process for producing this cast article is also disclosed, as well as a metal matrix composite, which includes the aluminum alloy serving as a matrix containing up to about 60% by volume of a secondary filler material.

  4. Copper modified austenitic stainless steel alloys with improved high temperature creep resistance

    DOEpatents

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

    1987-04-28

    An improved austenitic stainless steel that incorporates copper into a base Fe-Ni-Cr alloy having minor alloying substituents of Mo, Mn, Si, T, Nb, V, C, N, P, B which exhibits significant improvement in high temperature creep resistance over previous steels. 3 figs.

  5. Fretting fatigue of 2XXX series aerospace aluminum alloys

    NASA Astrophysics Data System (ADS)

    Giummarra, Cindie

    Fretting is a wear mechanism that occurs at the contact region between two materials subject to minute cyclic relative motion. Fretting causes the initiation of surface cracks within the first few thousand cycles, which in the presence of a fatigue stress, grow to cause material failure approximately 10 to 100 times earlier than expected under standard fatigue conditions. Examples of fretting fatigue have been seen in joints in aircraft, and the aerospace industry acknowledges the possibility of catastrophic failure from this mechanism. Improvements in a material's resistance to fretting would benefit aluminum alloys in aerospace applications. This research investigated the effect of microstructural properties on the fretting response in 2XXX series aerospace aluminum alloys. Fretting wear and fretting fatigue tests were conducted to determine the influence of slip characteristics, alloy purity, grain orientation and yield strength on fretting crack initiation and growth. Crack length measurements and micrographs of the fretting indicated there was no significant difference in the fretting response of these alloys based on their microstructural characteristics. Results showed that fretting initiated cracks in the first 1--8% of the life while standard fatigue initiation took around 90% of the life. This reduction in initiation resulted in a shorter life under fretting conditions. Additionally, fretting normalized the initiation time in all alloys which eliminated any intrinsic initiation resistance. The alloys with the highest stress-life (S-N) fatigue properties exhibiting a greater reduction in fatigue strength under fretting conditions. The fretting stresses appeared to influence the crack growth to a distance below the surface of approximately 17mum under fretting fatigue conditions, after which some cracks changed direction and propagated under the influence of the fatigue stress. Under fretting wear conditions, the cracks tended to arrest at a depth of 8

  6. Corrosion Testing of Ni Alloy HVOF Coatings in High Temperature Environments for Biomass Applications

    NASA Astrophysics Data System (ADS)

    Paul, S.; Harvey, M. D. F.

    2013-03-01

    This paper reports the corrosion behavior of Ni alloy coatings deposited by high velocity oxyfuel spraying, and representative boiler substrate alloys in simulated high temperature biomass combustion conditions. Four commercially available oxidation resistant Ni alloy coating materials were selected: NiCrBSiFe, alloy 718, alloy 625, and alloy C-276. These were sprayed onto P91 substrates using a JP5000 spray system. The corrosion performance of the coatings varied when tested at ~525, 625, and 725 °C in K2SO4-KCl mixture and gaseous HCl-H2O-O2 containing environments. Alloy 625, NiCrBSiFe, and alloy 718 coatings performed better than alloy C-276 coating at 725 °C, which had very little corrosion resistance resulting in degradation similar to uncoated P91. Alloy 625 coatings provided good protection from corrosion at 725 °C, with the performance being comparable to wrought alloy 625, with significantly less attack of the substrate than uncoated P91. Alloy 625 performs best of these coating materials, with an overall ranking at 725 °C as follows: alloy 625 > NiCrBSiFe > alloy 718 ≫ alloy C-276. Although alloy C-276 coatings performed poorly in the corrosion test environment at 725 °C, at lower temperatures (i.e., below the eutectic temperature of the salt mixture) it outperformed the other coating types studied.

  7. High temperature solder alloys for underhood applications. Progress report

    SciTech Connect

    Drewien, C.A.; Yost, F.G.; Sackinger, S.; Kern, J.; Weiser, M.W.

    1995-02-01

    Under a cooperative research and development agreement with General Motors Corporation, lead-free solder systems including the flux, metallization, and solder are being developed for high temperature, underhood applications. Six tin-rich solders, five silver-rich metallizations, and four fluxes were screened using an experimental matrix whereby every combination was used to make sessile drops via hot plate or Heller oven processing. The contact angle, sessile drop appearance, and in some instances the microstructure was evaluated to determine combinations that would yield contact angles of less than 30{degrees}, well-formed sessile drops, and fine, uniform microstructures. Four solders, one metallization, and one flux were selected and will be used for further aging and mechanical property studies.

  8. High-Temperature Oxidation Behavior of Iridium-Rhenium Alloys

    NASA Technical Reports Server (NTRS)

    Reed, Brian D.

    1995-01-01

    The life-limiting mechanism for radiation-cooled rockets made from iridium-coated rhenium (Ir/Re) is the diffusion of Re into the Ir layer and the subsequent oxidation of the resulting Ir-Re alloy from the inner surface. In a previous study, a life model for Ir/Re rockets was developed. It incorporated Ir-Re diffusion and oxidation data to predict chamber lifetimes as a function of temperature and oxygen partial pressure. Oxidation testing at 1540 deg C suggested that a 20-wt percent Re concentration at the inner wall surface should be established as the failure criterion. The present study was performed to better define Ir-oxidation behavior as a function of Re concentration and to supplement the data base for the life model. Samples ranging from pure Ir to Ir-40 wt percent Re (Ir-40Re) were tested at 1500 deg C, in two different oxygen environments. There were indications that the oxidation rate of the Ir-Re alloy increased significantly when it went from a single-phase solid solution to a two-phase mixture, as was suggested in previous work. However, because of testing anomalies in this study, there were not enough dependable oxidation data to definitively raise the Ir/Re rocket failure criterion from 20-wt percent Re to a Re concentration corresponding to entry into the two-phase region.

  9. Dynamic high-temperature characterization of an iridium alloy in tension

    SciTech Connect

    Song, Bo; Nelson, Kevin; Jin, Helena; Lipinski, Ronald J.; Bignell, John; Ulrich, G. B.; George, E. P.

    2015-09-01

    Iridium alloys have been utilized as structural materials for certain high-temperature applications, due to their superior strength and ductility at elevated temperatures. The mechanical properties, including failure response at high strain rates and elevated temperatures of the iridium alloys need to be characterized to better understand high-speed impacts at elevated temperatures. A DOP-26 iridium alloy has been dynamically characterized in compression at elevated temperatures with high-temperature Kolsky compression bar techniques. However, the dynamic high-temperature compression tests were not able to provide sufficient dynamic high-temperature failure information of the iridium alloy. In this study, we modified current room-temperature Kolsky tension bar techniques for obtaining dynamic tensile stress-strain curves of the DOP-26 iridium alloy at two different strain rates (~1000 and ~3000 s-1) and temperatures (~750°C and ~1030°C). The effects of strain rate and temperature on the tensile stress-strain response of the iridium alloy were determined. The DOP-26 iridium alloy exhibited high ductility in stress-strain response that strongly depended on both strain rate and temperature.

  10. 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.

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

    NASA Technical Reports Server (NTRS)

    Oldrieve, R. E.

    1975-01-01

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

  12. Isothermal oxidation behavior of ternary Zr-Nb-Y alloys at high temperature

    SciTech Connect

    Prajitno, Djoko Hadi; Soepriyanto, Syoni; Basuki, Eddy Agus; Wiryolukito, Slameto

    2014-03-24

    The effect of yttrium content on isothermal oxidation behavior of Zr-2,5%Nb-0,5%Y, Zr-2,5%Nb-1%Y Zr-2,5%Nb-1,5%Y alloy at high temperature has been studied. High temperature oxidation carried out at tube furnace in air at 600,700 and 800°C for 1 hour. Optical microscope is used for microstructure characterization of the alloy. Oxidized and un oxidized specimen was characterized by x-ray diffraction. In this study, kinetic oxidation of Zr-2,5%Nb with different Y content at high temperature has also been studied. Characterization by optical microscope showed that microstructure of Zr-Nb-Y alloys relatively unchanged and showed equiaxed microstructure. X-ray diffraction of the alloys depicted that the oxide scale formed during oxidation of zirconium alloys is monoclinic ZrO2 while unoxidised alloy showed two phase α and β phase. SEM-EDS examination shows that depletion of Zr composition took place under the oxide layer. Kinetic rate of oxidation of zirconium alloy showed that increasing oxidation temperature will increase oxidation rate but increasing yttrium content in the alloys will decrease oxidation rate.

  13. Strength of copper alloys in high temperature environment

    NASA Astrophysics Data System (ADS)

    Nomura, Y.; Suzuki, R.; Saito, M.

    2002-12-01

    The first wall of ITER is expected to be hot isostatic pressing (HIP) bonded structure of copper-alloy/SS316. Firstly, fracture toughness and crack propagation tests were performed on DS-Cu and DS-Cu/SS316 HIP joints at ambient temperature and 573 K T. Yamada, M. Uno, M. Saito, Fall Meeting of the Atomic Energy Society of Japan, vol. I, 1998, p. 187 (in Japanese). JIC values of DS-Cu and DS-Cu/SS316 decreased significantly at 573 K. In crack propagation test, DS-Cu lost its ductility at 573 K. Secondly, we performed fracture toughness tests on CuCrZr and CuCrZr/CuCrZr, CuCrZr/SS316 HIP joints at ambient and 573 K. CuCrZr base metal had higher JIC values than DS-Cu. Concerning CuCrZr/CuCrZr and CuCrZr/SS316 HIP joint, its JIC value decreased to less than that of CuCrZr base metal.

  14. Controlling remelting processes for superalloys and aerospace Ti alloys

    NASA Astrophysics Data System (ADS)

    Melgaard, D. K.; Williamson, R. L.; Beaman, J. J.

    1998-03-01

    Remelting is performed to facilitate the production of clean, fully dense, homogeneous castings of superalloys and aerospace titanium alloys and is crucial to the defect-free production of these important materials. Modern electroslag remelting and vacuum arc remelting control systems are closed-loop, single input-single output systems that oversimplify the physical properties of the processes; the ever-increasing demand for cleaner, more highly engineered, chemically tuned alloys has pushed these control methodologies to their limit. A new generation of these controllers is being developed by the Specialty Metals Process Consortium and Sandia National Laboratories to answer the challenges of remelting control for the next generation of alloys; these control systems will use multiple sensor inputs and apply material-specific system and process models.

  15. GRCop-84: A High-Temperature Copper Alloy for High-Heat-Flux Applications

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    2005-01-01

    GRCop-84 (Cu-8 at.% Cr-4 at.% Nb) is a new high-temperature copper-based alloy. It possesses excellent high-temperature strength, creep resistance and low-cycle fatigue up to 700 C (1292 F) along with low thermal expansion and good conductivity. GRCop-84 can be processed and joined by a variety of methods such as extrusion, rolling, bending, stamping, brazing, friction stir welding, and electron beam welding. Considerable mechanical property data has been generated for as-produced material and following simulated braze cycles. The data shows that the alloy is extremely stable during thermal exposures. This paper reviews the major GRCop-84 mechanical and thermophysical properties and compares them to literature values for a variety of other high-temperature copper-based alloys.

  16. Effect of Carbon Nanotube on High-Temperature Formability of AZ31 Magnesium Alloy

    NASA Astrophysics Data System (ADS)

    Hassan, S. Fida; Paramsothy, M.; Gasem, Z. M.; Patel, F.; Gupta, M.

    2014-08-01

    Room-temperature tensile properties of AZ31 alloy have significantly been improved when reinforced with carbon nanotube via ingot metallurgy process. However, high-temperature (up to 250 °C) elongation-to-failure tensile test of the developed nanocomposite revealed a considerable softening in the AZ31 alloy matrix accompanied by an incredible ductility increment (up to 132%). Microstructural characterization of the fractured samples revealed that the dynamic recrystallization process has induced a complete recrystallization in the AZ31 alloy at a lower temperature (150 °C) followed by substantial grain growth at a higher temperature used in this study. Fractography on the fractured surfaces revealed that the room-temperature mixed brittle-ductile modes of fracture behavior of AZ31 alloy have transformed into a complete ductile mode of fracture at high temperature.

  17. Fabrication of intermetallic coatings for electrical and corrosion resistance on high-temperature alloys

    SciTech Connect

    Park, J.H.; Cho, W.D.

    1994-10-01

    Several intermetallic films were fabricated to high-temperature alloys (V-alloys and 304 and 316 stainless steels) to provide electrical insulation and corrosion resistance. Alloy grain-growth behavior at 1000{degrees}C for the V-5Cr-5Ti was investigated to determine the stability of alloy substrate during coating formation by chemical vapor deposition (CVD) or metallic vapor processes at 800-850{degrees}C. Film layers were examined by optical and scanning electron microscopy and by electron-energy-dispersive and X-ray diffraction analysis and tested for electrical resistivity and corrosion resistance. The results elucidated the nature of the coatings, which provided both electrical insulation and high-temperature corrosion protection.

  18. Thermocouples of tantalum and rhenium alloys for more stable vacuum-high temperature performance

    NASA Technical Reports Server (NTRS)

    Morris, J. F. (Inventor)

    1977-01-01

    Thermocouples of the present invention provide stability and performance reliability in systems involving high temperatures and vacuums by employing a bimetallic thermocouple sensor wherein each metal of the sensor is selected from a group of metals comprising tantalum and rhenium and alloys containing only those two metals. The tantalum, rhenium thermocouple sensor alloys provide bare metal thermocouple sensors having advantageous vapor pressure compatibilities and performance characteristics. The compatibility and physical characteristics of the thermocouple sensor alloys of the present invention result in improved emf, temperature properties and thermocouple hot junction performance. The thermocouples formed of the tantalum, rhenium alloys exhibit reliability and performance stability in systems involving high temperatures and vacuums and are adaptable to space propulsion and power systems and nuclear environments.

  19. Ion Implanted Nanolayers in Alloys and Ceramic Coatings for Improved Resistance to High-Temperature Corrosion

    NASA Astrophysics Data System (ADS)

    Werner, Z.; Szymczyk, W.; Piekoszewski, J.

    Ion implantation effects on resistance of alloys and ceramic coatings to the high-temperature corrosion have been reviewed. The most significant results on implantation of reactive elements (Y, La, Ce and other rare earth elements) into alloys and aluminum, boron, silicon, tantalum, and titanium into ceramic coatings have been cited. Ion implantation affects not only the oxide growth rate, but also seems to modify the growth mechanism and the oxide structure.

  20. An oxide dispersion strengthened Ni-W-Al alloy with superior high temperature strength

    NASA Technical Reports Server (NTRS)

    Glasgow, T. K.

    1976-01-01

    An experimental oxide dispersion strengthened (ODS) alloy, WAZ-D, derived from the WAZ-20 composition was produced by the mechanical alloying process. Cast WAZ-20 is strengthened by both a high refractory metal content, and 70 volume percent of gamma prime. The ODS alloy WAZ-D was responsive to variables of alloy content, of attritor processing, of consolidation by extrusion, and of heat treatment. The best material produced had large highly elongated grains. It exhibited tensile strengths generally superior to a comparable cast alloy. The ODS alloy exhibited high temperature stress rupture life considerably superior to any known cast superalloy. Tensile and rupture ductility were low, as was intermediate temperature rupture life. Very low creep rates were noted and some specimens failed with essentially no third stage creep. Also the benefit derived from the oxide dispersion, far out-weighed that from the elongated microstructure alone.

  1. Twin solution calorimeter determines heats of formation of alloys at high temperatures

    NASA Technical Reports Server (NTRS)

    Darby, J. B., Jr.; Kleb, R.; Kleppa, O. J.

    1968-01-01

    Calvert-type, twin liquid metal solution calorimeter determines the heats of formation of transition metal alloys at high temperatures. The twin differential calorimeter measures the small heat effects generated over extended periods of time, has maximum operating temperature of 1073 degrees K and an automatic data recording system.

  2. Thermocouples of molybdenum and iridium alloys for more stable vacuum-high temperature performance

    NASA Technical Reports Server (NTRS)

    Morris, J. F. (Inventor)

    1978-01-01

    Thermocouples providing stability and performance reliability in systems involving high temperatures and vacuums by employing a bimetallic thermocouple sensor are described. Each metal of the sensor is selected from a group of metals comprising molybdenum and iridium and alloys containing only those two metals. The molybdenum, iridium thermocouple sensor alloys provide bare metal thermocouple sensors having advantageous vapor pressure compatibility and performance characteristics. The compatibility and physical characteristics of the thermocouple sensor alloys result in improved emf, temperature properties and thermocouple hot junction performance.

  3. Mechanisms Governing the Creep Behavior of High Temperature Alloys for Generation IV Nuclear Energy Systems

    SciTech Connect

    Vasudevan, Vijay; Carroll, Laura; Sham, Sam

    2015-04-06

    This research project, which includes collaborators from INL and ORNL, focuses on the study of alloy 617 and alloy 800H that are candidates for applications as intermediate heat exchangers in GEN IV nuclear reactors, with an emphasis on the effects of grain size, grain boundaries and second phases on the creep properties; the mechanisms of dislocation creep, diffusional creep and cavitation; the onset of tertiary creep; and theoretical modeling for long-term predictions of materials behavior and for high temperature alloy design.

  4. HIGH TEMPERATURE BRAZING ALLOY FOR JOINT Fe-Cr-Al MATERIALS AND AUSTENITIC AND FERRITIC STAINLESS STEELS

    DOEpatents

    Cost, R.C.

    1958-07-15

    A new high temperature brazing alloy is described that is particularly suitable for brazing iron-chromiumaluminum alloys. It consists of approximately 20% Cr, 6% Al, 10% Si, and from 1.5 to 5% phosphorus, the balance being iron.

  5. Summary of workshop on alloys for very high-temperature applications

    SciTech Connect

    1996-08-01

    In current fossil energy systems, the maximum operating temperatures experienced by critical metal structures do not exceed approximately 732{degrees}C and the major limitation on the use of the alloys typically is corrosion resistance. In systems intended for higher performance and higher efficiency, increasingly higher working fluid temperatures will be employed, which will require materials with higher-temperature capabilities, in particular, higher creep strength and greater environmental resistance. There have been significant developments in alloys in recent years, from modifications of currently-used wrought ferritic and austenitic alloys with the intent of improving their high-temperature capabilities, to oxide dispersion-strengthened alloys targeted at extremely high-temperature applications. The aim of this workshop was to examine the temperature capability of these alloys compared to current alloys, and compared to the needs of advanced fossil fuel combustion or conversion systems, with the goals of identifying where modified/new alloys would be expected to find application, their limitations, and the information/actions required or that are being taken to qualify them for such use.

  6. The effect of the existing state of Y on high temperature oxidation properties of magnesium alloys

    NASA Astrophysics Data System (ADS)

    Yu, Xiaowen; Shen, Shijun; Jiang, Bin; Jiang, Zhongtao; Yang, Hong; Pan, Fusheng

    2016-05-01

    This paper studies the effect of the existing state of Y element on the high temperature oxidation resistance of magnesium alloys. Different levels of Al element were added into Mg-2.5Y alloy to obtain different existing state of Y. The oxidation rate of Mg-2.5Y-2.5Al alloy is the highest among Mg-2.5Y, Mg-2.5Y-2.5Al and Mg-2.5Y-4.2Al alloys at 500 °C. An effective and protective Y2O3/MgO composite oxide film was formed on the surface of Mg-2.5Y alloy after oxidized at 500 °C for 360 min. The results show that the dissolved Y element in the matrix was beneficial to improve the oxidation resistance of magnesium alloys. Once Y element transformed to the high temperature stable Al2Y compound, its ability in preventing oxidation would disappear. The formation of Al2Y compound severely deteriorated the oxidation resistance of Mg-2.5Y alloy. In addition, the dissolved Al can also cause the rise of oxidation resistance at a certain extent.

  7. Considerations of Alloy N for Fluoride Salt-Cooled High-Temperature Reactor Applications

    SciTech Connect

    Ren, Weiju; Muralidharan, Govindarajan; Wilson, Dane F; Holcomb, David Eugene

    2011-01-01

    Fluoride Salt-Cooled High-Temperature Reactors (FHRs) are a promising new class of thermal-spectrum nuclear reactors. The reactor structural materials must possess high-temperature strength and chemical compatibility with the liquid fluoride salt as well as with a power cycle fluid such as supercritical water while remaining resistant to residual air within the containment. Alloy N was developed for use with liquid fluoride salts and it possesses adequate strength and chemical compatibility up to about 700 C. A distinctive property of FHRs is that their maximum allowable coolant temperature is restricted by their structural alloy maximum service temperature. As the reactor thermal efficiency directly increases with the maximum coolant temperature, higher temperature resistant alloys are strongly desired. This paper reviews the current status of Alloy N and its relevance to FHRs including its design principles, development history, high temperature strength, environmental resistance, metallurgical stability, component manufacturability, ASME codification status, and reactor service requirements. The review will identify issues and provide guidance for improving the alloy properties or implementing engineering solutions.

  8. High-precision Non-Contact Measurement of Creep of Ultra-High Temperature Materials for Aerospace

    NASA Technical Reports Server (NTRS)

    Rogers, Jan R.; Hyers, Robert

    2008-01-01

    For high-temperature applications (greater than 2,000 C) such as solid rocket motors, hypersonic aircraft, nuclear electric/thermal propulsion for spacecraft, and more efficient jet engines, creep becomes one of the most important design factors to be considered. Conventional creep-testing methods, where the specimen and test apparatus are in contact with each other, are limited to temperatures approximately 1,700 C. Development of alloys for higher-temperature applications is limited by the availability of testing methods at temperatures above 2000 C. Development of alloys for applications requiring a long service life at temperatures as low as 1500 C, such as the next generation of jet turbine superalloys, is limited by the difficulty of accelerated testing at temperatures above 1700 C. For these reasons, a new, non-contact creep-measurement technique is needed for higher temperature applications. A new non-contact method for creep measurements of ultra-high-temperature metals and ceramics has been developed and validated. Using the electrostatic levitation (ESL) facility at NASA Marshall Space Flight Center, a spherical sample is rotated quickly enough to cause creep deformation due to centrifugal acceleration. Very accurate measurement of the deformed shape through digital image analysis allows the stress exponent n to be determined very precisely from a single test, rather than from numerous conventional tests. Validation tests on single-crystal niobium spheres showed excellent agreement with conventional tests at 1985 C; however the non-contact method provides much greater precision while using only about 40 milligrams of material. This method is being applied to materials including metals and ceramics for non-eroding throats in solid rockets and next-generation superalloys for turbine engines. Recent advances in the method and the current state of these new measurements will be presented.

  9. High temperature properties of alloys being considered for design of a concentric canister launcher

    SciTech Connect

    Kassner, M E; Lowry, R W; Rosen, R S

    1998-06-01

    This report describes a study to determine the high temperature mechanical properties of several titanium alloys and to compare them with properties of AISI 316L stainless steel and ASTM A 387 structural steel. The steel materials are less costly to procure but exhibit good resistance to corrosion in seawater environments. Six titanium alloys were evaluated as candidate materials for use in a c Concentric Canister Launcher (CCL). Each titanium alloy was tested at three temperatures (68°, 2000°F, and 2400°F). Strain-rate changes tests were used to determine the strain rate sensitivity of the alloys at each test temperature. Optical metallography was performed on two of the alloys to determine the relationship between test temperature and microstructure (presence of second phase precipitates, grain size). Complete test results are includes, a long with figures and tables of test data.

  10. High Strength and Wear Resistant Aluminum Alloy for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.; Munafo, Paul M. (Technical Monitor)

    2002-01-01

    In this paper, a new high strength and wear resistant aluminum cast alloy invented by NASA-MSFC for high temperature applications will be presented. Developed to meet U.S. automotive legislation requiring low-exhaust emission, the novel NASA 398 aluminum-silicon alloy offers dramatic improvement in tensile and fatigue strengths at elevated temperatures (500 F-800 F), enabling new pistons to utilize less material, which can lead to reducing part weight and cost as well as improving performance. NASA 398 alloy also offers greater wear resistance, surface hardness, dimensional stability, and lower thermal expansion compared to conventional aluminum alloys for several commercial and automotive applications. The new alloy can be produced economically using permanent steel molds from conventional gravity casting or sand casting. The technology was developed to stimulate the development of commercial aluminum casting products from NASA-developed technology by offering companies the opportunity to license this technology.

  11. Commercialization of NASA's High Strength Cast Aluminum Alloy for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2003-01-01

    In this paper, the commercialization of a new high strength cast aluminum alloy, invented by NASA-Marshall Space Flight Center, for high temperature applications will be presented. Originally developed to meet U.S. automotive legislation requiring low- exhaust emission, the novel NASA aluminum alloy offers dramatic improvement in tensile and fatigue strengths at elevated temperatures (450 F-750 F), which can lead to reducing part weight and cost as well as improving performance for automotive engine applications. It is an ideal low cost material for cast components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. NASA alloy also offers greater wear resistance, dimensional stability, and lower thermal expansion compared to conventional aluminum alloys, and the new alloy can be produced economically from sand, permanent mold and investment casting. Since 2001, this technology was licensed to several companies for automotive and marine internal combustion engines applications.

  12. Alloying effects on the high-temperature oxidation resistance of Cr-Cr{sub 2}Nb

    SciTech Connect

    Tortorelli, P.F.; DeVan, J.H.

    1994-09-01

    Alloying effects on the high-temperature oxidation resistance of Cr-Cr{sub 2}Nb were examined on the basis of isothermal exposures to air at 950 C. Additions of either Re and Al or Fe, Ni, and Al had relatively little effect on weight gains relative to the Cr-6% Nb binary alloy. One alloying element that improved the mechanical behavior of Cr-Cr{sub 2}Nb alloys substantially increased the oxidation rates and spallation susceptibilities of Cr-6 and -12% Nb alloys. However, the addition of another element completely offset these deleterious effects. The presence of this latter element resulted in the best overall oxidation behavior (in terms of both weight gains and spallation tendencies) of all Cr-Cr{sub 2}Nb compositions. Its beneficial effect can be attributed to improvement in the oxidation resistance of the Cr-rich phase.

  13. Super-High Temperature Alloys and Composites from NbW-Cr Systems

    SciTech Connect

    Shailendra Varma

    2008-12-31

    Nickel base superalloys must be replaced if the demand for the materials continues to rise for applications beyond 1000{sup o}C which is the upper limit for such alloys at this time. There are non-metallic materials available for such high temperature applications but they all present processing difficulties because of the lack of ductility. Metallic systems can present a chance to find materials with adequate room temperature ductility. Obviously the system must contain elements with high melting points. Nb has been chosen by many investigators which has a potential of being considered as a candidate if alloyed properly. This research is exploring the Nb-W-Cr system for the possible choice of alloys to be used as a high temperature material.

  14. Materials Properties Database for Selection of High-Temperature Alloys and Concepts of Alloy Design for SOFC Applications

    SciTech Connect

    Yang, Z Gary; Paxton, Dean M.; Weil, K. Scott; Stevenson, Jeffry W.; Singh, Prabhakar

    2002-11-24

    To serve as an interconnect / gas separator in an SOFC stack, an alloy should demonstrate the ability to provide (i) bulk and surface stability against oxidation and corrosion during prolonged exposure to the fuel cell environment, (ii) thermal expansion compatibility with the other stack components, (iii) chemical compatibility with adjacent stack components, (iv) high electrical conductivity of the surface reaction products, (v) mechanical reliability and durability at cell exposure conditions, (vii) good manufacturability, processability and fabricability, and (viii) cost effectiveness. As the first step of this approach, a composition and property database was compiled for high temperature alloys in order to assist in determining which alloys offer the most promise for SOFC interconnect applications in terms of oxidation and corrosion resistance. The high temperature alloys of interest included Ni-, Fe-, Co-base superal

  15. SCC Initiation in Alloy 600 Heat Affected Zones Exposed to High Temperature Water

    SciTech Connect

    E Richey; DS Morton; RA Etien; GA Young; RB Bucinell

    2006-11-03

    Studies have shown that grain boundary chromium carbides improve the stress corrosion cracking (SCC) resistance of nickel based alloys exposed to high temperature, high purity water. However, thermal cycles from welding can significantly alter the microstructure of the base material near the fusion line. In particular, the heat of welding can solutionize grain boundary carbides and produce locally high residual stresses and strains, reducing the SCC resistance of the Alloy 600 type material in the heat affected zone (HAZ). Testing has shown that the SCC growth rate in Alloy 600 heat affected zone samples can be {approx}30x faster than observed in the Alloy 600 base material under identical testing conditions due to fewer intergranular chromium rich carbides and increased plastic strain in the HAZ [1, 2]. Stress corrosion crack initiation tests were conducted on Alloy 600 HAZ samples at 360 C in hydrogenated, deaerated water to determine if these microstructural differences significantly affect the SCC initiation resistance of Alloy 600 heat affected zones compared to the Alloy 600 base material. Alloy 600 to EN82H to Alloy 600 heat-affected-zone (HAZ) specimens where fabricated from an Alloy 600 to Alloy 600 narrow groove weld with EN82H filler metal. The approximate middle third of the specimen gauge region was EN82H such that each specimen had two HAZ regions. Tests were conducted with in-situ monitored smooth tensile specimens under a constant load, and a direct current electric potential drop was used for in-situ detection of SCC. Test results suggest that the SCC initiation resistance of Alloy 600 and its weld metal follows the following order: EN82H > Alloy 600 HAZ > Alloy 600. The high SCC initiation resistance observed to date in Alloy 600 heat affected zones compared to wrought Alloy 600 is unexpected based on the microstructure of HAZ versus wrought material and based on prior SCC growth rate studies. The observed behavior for the HAZ specimens is likely

  16. High-Temperature Compressive Properties of TiC-Added Mo-Si-B Alloys

    NASA Astrophysics Data System (ADS)

    Yoshimi, Kyosuke; Nakamura, Junya; Kanekon, Daiki; Yamamoto, Shiho; Maruyama, Kouichi; Katsui, Hirokazu; Goto, Takashi

    2014-09-01

    High-temperature compressive properties of two TiC-added Mo-Si-B alloys with nominal compositions of Mo-5Si-10B-7.5TiC (70Mo alloy) and Mo-6.7Si-13.3B-7.5TiC (65Mo alloy) (at.%) were investigated. The alloys were composed of four constituent phases: Mo solid solution (Moss), Mo5SiB2, (Mo,Ti)C, and (Mo,Ti)2C. The primary phases of the 70Mo and 65Mo alloys were Moss and T2, respectively. The compressive deformability of the 65Mo alloy was significantly limited even at 1600°C because of the elongated, coarse primary T2 phase, whereas the 70Mo alloy had good compressive deformability and a high strength in the test-temperature range of 1000-1600°C; the peak stresses were 1800 MPa at 1000°C, 1230 MPa at 1200°C, and 350 MPa at 1600°C. At and above 1200°C, the peak stress values were more than double those of Mo-6.7Si-7.9B, Ti-Zr-Mo, and Mo-Hf-C alloys. The plastic strain in the 70Mo alloy at temperatures lower than the ductile-brittle transition temperature of T2 was generated by plastic deformation of not only Moss but also of (Mo,Ti)C and (Mo,Ti)2C. This work indicates that (Mo,Ti)C and (Mo,Ti)2C play an important role in determining the high-temperature strength and deformation properties of TiC-added Mo-Si-B alloys.

  17. Examination of some high-strength, high-conductivity copper alloys for high-temperature applications

    SciTech Connect

    Dadras, M.M.; Morris, D.G.

    1997-12-22

    Copper alloys with high strength and high thermal and electrical conductivity have received a lot of attention over the last decades. Most of such efforts have concentrated on the development of alloys containing fine, dispersed particles, and using rapid solidification techniques to ensure a sufficient volume fraction and sufficient fineness of the dispersed phase. In a recent study, a Cu-8Cr-4Nb alloy was developed which shows relatively good strength up to 700 C, a result which was explained by the resistance to coarsening of the fine Cr{sub 2}Nb intermetallic particles in this materials. The amount of intermetallic Cr{sub 2}Nb second phase in this alloy was about 14vol% and it was claimed that the special compound-nature of the intermetallic phase was responsible for the good stability and retention of strength to high temperature. In order to examine the influence of the nature of the fine particles present and their stability against coarsening, as well as to examine the influence of volume fraction of second phase on tensile strength, three different alloys have been chosen for study: Cu-2Nb and Cu-4Cr for examining the role of second phase chemistry (Nb or Cr) on structural and property stability; and a Cu-14Cr alloy, for comparison with the Cu-4Cr alloy, to examine the role of volume fraction of the second phase. The stability of these alloys will then be compared with that reported for the Cu-8Cr-4Nb alloy.

  18. Materials corrosion of high temperature alloys immersed in 600C binary nitrate salt.

    SciTech Connect

    Kruizenga, Alan Michael; Gill, David Dennis; LaFord, Marianne Elizabeth

    2013-03-01

    Thirteen high temperature alloys were immersion tested in a 60/40 binary nitrate salt. Samples were interval tested up to 3000 hours at 600%C2%B0C with air as the ullage gas. Chemical analysis of the molten salt indicated lower nitrite concentrations present in the salt, as predicted by the equilibrium equation. Corrosion rates were generally low for all alloys. Corrosion products were identified using x-ray diffraction and electron microprobe analysis. Fe-Cr based alloys tended to form mixtures of sodium and iron oxides, while Fe-Ni/Cr alloys had similar corrosion products plus oxides of nickel and chromium. Nickel based alloys primarily formed NiO, with chromium oxides near the oxide/base alloy interface. In625 exhibited similar corrosion performance in relation to previous tests, lending confidence in comparisons between past and present experiments. HA230 exhibited internal oxidation that consisted of a nickel/chromium oxide. Alloys with significant aluminum alloying tended to exhibit superior performance, due formation of a thin alumina layer. Soluble corrosion products of chromium, molybdenum, and tungsten were also formed and are thought to be a significant factor in alloy performance.

  19. Improved Mo-Re VPS Alloys for High-Temperature Uses

    NASA Technical Reports Server (NTRS)

    Hickman, Robert; Martin, James; McKechnie, Timothy; O'Dell, John Scott

    2011-01-01

    Dispersion-strengthened molybdenum- rhenium alloys for vacuum plasma spraying (VPS) fabrication of high-temperature-resistant components are undergoing development. In comparison with otherwise equivalent non-dispersion-strengthened Mo-Re alloys, these alloys have improved high-temperature properties. Examples of VPS-fabricated high-temperature-resistant components for which these alloys are expected to be suitable include parts of aircraft and spacecraft engines, furnaces, and nuclear power plants; wear coatings; sputtering targets; x-ray targets; heat pipes in which liquid metals are used as working fluids; and heat exchangers in general. These alloys could also be useful as coating materials in some biomedical applications. The alloys consist of 60 weight percent Mo with 40 weight percent Re made from (1) blends of elemental Mo and Re powders or (2) Re-coated Mo particles that have been subjected to a proprietary powder-alloying-and-spheroidization process. For most of the dispersion- strengthening experiments performed thus far in this development effort, 0.4 volume percent of transition-metal ceramic dispersoids were mixed into the feedstock powders. For one experiment, the proportion of dispersoid was 1 volume percent. In each case, the dispersoid consisted of either ZrN particles having sizes <45 m, ZrO2 particles having sizes of about 1 m, HfO2 particles having sizes <45 m, or HfN particles having sizes <1 m. These materials were chosen for evaluation on the basis of previously published thermodynamic stability data. For comparison, Mo-Re feedstock powders without dispersoids were also prepared.

  20. Development and Characterization of Improved NiTiPd High-Temperature Shape-Memory Alloys by Solid-Solution Strengthening and Thermomechanical Processing

    NASA Technical Reports Server (NTRS)

    Bigelow, Glen; Noebe, Ronald; Padula, Santo, II; Garg, Anita; Olson, David

    2006-01-01

    The need for compact, solid-state actuation systems for use in the aerospace, automotive, and other transportation industries is currently motivating research in high-temperature shape-memory alloys (HTSMA) with transformation temperatures greater than 100 C. One of the basic high-temperature alloys investigated to fill this need is Ni(19.5)Ti(50.5)Pd30. Initial testing has indicated that this alloy, while having acceptable work characteristics, suffers from significant permanent deformation (or ratcheting) during thermal cycling under load. In an effort to overcome this deficiency, various solid-solution alloying and thermomechanical processing schemes were investigated. Solid-solution strengthening was achieved by substituting 5at% gold or platinum for palladium in Ni(19.5)Ti(50.5)Pd30, the so-called baseline alloy, to strengthen the martensite and austenite phases against slip processes and improve thermomechanical behavior. Tensile properties, work behavior, and dimensional stability during repeated thermal cycling under load for the ternary and quaternary alloys were compared. The relative difference in yield strength between the martensite and austenite phases and the dimensional stability of the alloy were improved by the quaternary additions, while work output was only minimally impacted. The three alloys were also thermomechanically processed by cycling repeatedly through the transformation range under a constant stress. This so-called training process dramatically improved the dimensional stability in these samples and also recovered the slight decrease in work output caused by quaternary alloying. An added benefit of the solid-solution strengthening was maintenance of enhanced dimensional stability of the trained material to higher temperatures compared to the baseline alloy, providing a greater measure of over-temperature capability.

  1. Atomistic modeling of high temperature uranium-zirconium alloy structure and thermodynamics

    NASA Astrophysics Data System (ADS)

    Moore, A. P.; Beeler, B.; Deo, C.; Baskes, M. I.; Okuniewski, M. A.

    2015-12-01

    A semi-empirical Modified Embedded Atom Method (MEAM) potential is developed for application to the high temperature body-centered-cubic uranium-zirconium alloy (γ-U-Zr) phase and employed with molecular dynamics (MD) simulations to investigate the high temperature thermo-physical properties of U-Zr alloys. Uranium-rich U-Zr alloys (e.g. U-10Zr) have been tested and qualified for use as metallic nuclear fuel in U.S. fast reactors such as the Integral Fast Reactor and the Experimental Breeder Reactors, and are a common sub-system of ternary metallic alloys like U-Pu-Zr and U-Zr-Nb. The potential was constructed to ensure that basic properties (e.g., elastic constants, bulk modulus, and formation energies) were in agreement with first principles calculations and experimental results. After which, slight adjustments were made to the potential to fit the known thermal properties and thermodynamics of the system. The potentials successfully reproduce the experimental melting point, enthalpy of fusion, volume change upon melting, thermal expansion, and the heat capacity of pure U and Zr. Simulations of the U-Zr system are found to be in good agreement with experimental thermal expansion values, Vegard's law for the lattice constants, and the experimental enthalpy of mixing. This is the first simulation to reproduce the experimental thermodynamics of the high temperature γ-U-Zr metallic alloy system. The MEAM potential is then used to explore thermodynamics properties of the high temperature U-Zr system including the constant volume heat capacity, isothermal compressibility, adiabatic index, and the Grüneisen parameters.

  2. High temperature corrosion of a nickel base alloy by helium impurities

    NASA Astrophysics Data System (ADS)

    Rouillard, F.; Cabet, C.; Wolski, K.; Terlain, A.; Tabarant, M.; Pijolat, M.; Valdivieso, F.

    2007-05-01

    High temperature corrosion properties of Haynes 230 were investigated in a purposely-designed facility under a typical very high temperature reactor (VHTR) impure helium medium. The study was focused on the surface oxide scale formation and its stability at about 1223 K. The alloy developed a Mn/Cr rich oxide layer on its surface under impure helium at 1173 K. Nevertheless, a deleterious reaction destructing the chromium oxide was evidenced above a critical temperature, TA. Reagents and products of this last reaction were investigated.

  3. Internal friction and dynamic modulus in Ru-50Nb ultra-high temperature shape memory alloys

    NASA Astrophysics Data System (ADS)

    Dirand, L.; Nó, M. L.; Chastaing, K.; Denquin, A.; San Juan, J.

    2012-10-01

    The martensitic transformations in ultra-high temperature Ru-50Nb shape memory alloys have been studied by internal friction and dynamic modulus measurements. Two successive transformations from the high temperature cubic β phase to a tetragonal β' martensite and then to another monoclinic β″ martensite have been found. Both transformations exhibit a sharp internal friction peak and a clear softening of the dynamic modulus, being a signature of the thermo-elastic martensitic transformations. In addition, a pseudo relaxation peak strongly dependent on time has been found and analyzed, concluding that it is linked to a pinning effect of martensite interfaces by point defects.

  4. Long-Term Cyclic Oxidation Behavior of Wrought Commercial Alloys at High Temperatures

    SciTech Connect

    Bingtao Li

    2003-08-05

    The oxidation resistance of a high-temperature alloy is dependent upon sustaining the formation of a protective scale, which is strongly related to the alloying composition and the oxidation condition. The protective oxide scale only provides a finite period of oxidation resistance owing to its eventual breakdown, which is especially accelerated under thermal cycling conditions. This current study focuses on the long-term cyclic oxidation behavior of a number of commercial wrought alloys. The alloys studied were Fe- and Ni-based, containing different levels of minor elements, such as Si, Al, Mn, and Ti. Oxidation testing was conducted at 1000 and 1100 C in still air under both isothermal and thermal cycling conditions (1-day and 7-days). The specific aspects studied were the oxidation behavior of chromia-forming alloys that are used extensively in industry. The current study analyzed the effects of alloying elements, especially the effect of minor element Si, on cyclic oxidation resistance. The behavior of oxide scale growth, scale spallation, subsurface changes, and chromium interdiffusion in the alloy were analyzed in detail. A novel model was developed in the current study to predict the life-time during cyclic oxidation by simulating oxidation kinetics and chromium interdiffusion in the subsurface of chromia-forming alloys.

  5. Long-term-high temperature stability of alloy 803 in the chemical process industry

    SciTech Connect

    Sizek, H.W.; Baker, B.A.; Smith, G.D.

    1999-11-01

    Alloy 803 is used in the chemical process industry for its high temperature strength and corrosion resistance. Knowledge of the microstructural characteristics as a function of time and temperature are essential for accurate rationalization of mechanical property performance under actual service conditions. This paper seeks to determine the microstructure of alloy 803 as a function of time and temperature for times up to 34,000 hours and temperatures ranging from 595 C to 1095 C. Post-exposure room temperature tensile data are also presented as an indication of the alloy`s tolerance to downtime strains. Intermediate temperature mechanical strength can be attributed primarily to gamma prime ({gamma}{prime}) and higher temperature strength to M{sub 23}C{sub 6} content.

  6. Pu-Zr alloy for high-temperature foil-type fuel

    DOEpatents

    McCuaig, Franklin D.

    1977-01-01

    A nuclear reactor fuel alloy consists essentially of from slightly greater than 7 to about 4 w/o zirconium, balance plutonium, and is characterized in that the alloy is castable and is rollable to thin foils. A preferred embodiment of about 7 w/o zirconium, balance plutonium, has a melting point substantially above the melting point of plutonium, is rollable to foils as thin as 0.0005 inch thick, and is compatible with cladding material when repeatedly cycled to temperatures above 650.degree. C. Neutron reflux densities across a reactor core can be determined with a high-temperature activation-measurement foil which consists of a fuel alloy foil core sandwiched and sealed between two cladding material jackets, the fuel alloy foil core being a 7 w/o zirconium, plutonium foil which is from 0.005 to 0.0005 inch thick.

  7. Effect of High Temperature Aging on the Corrosion Resistance of Iron Based Amorphous Alloys

    SciTech Connect

    Day, S D; Haslam, J J; Farmer, J C; Rebak, R B

    2007-08-10

    Iron-based amorphous alloys can be more resistant to corrosion than polycrystalline materials of similar compositions. However, when the amorphous alloys are exposed to high temperatures they may recrystallize (or devitrify) thus losing their resistance to corrosion. Four different types of amorphous alloys melt spun ribbon specimens were exposed to several temperatures for short periods of time. The resulting corrosion resistance was evaluated in seawater at 90 C and compared with the as-prepared ribbons. Results show that the amorphous alloys can be exposed to 600 C for 1-hr. without losing the corrosion resistance; however, when the ribbons were exposed at 800 C for 1-hr. their localized corrosion resistance decreased significantly.

  8. Pu-ZR Alloy high-temperature activation-measurement foil

    DOEpatents

    McCuaig, Franklin D.

    1977-08-02

    A nuclear reactor fuel alloy consists essentially of from slightly greater than 7 to about 4 w/o zirconium, balance plutonium, and is characterized in that the alloy is castable and is rollable to thin foils. A preferred embodiment of about 7 w/o zirconium, balance plutonium, has a melting point substantially above the melting point of plutonium, is rollable to foils as thin as 0.0005 inch thick, and is compatible with cladding material when repeatedly cycled to temperatures above 650.degree. C. Neutron flux densities across a reactor core can be determined with a high-temperature activation-measurement foil which consists of a fuel alloy foil core sandwiched and sealed between two cladding material jackets, the fuel alloy foil core being a 7 w/o zirconium, plutonium foil which is from 0.005 to 0.0005 inch thick.

  9. The variation of the yield stress of Ti alloys with strain rate at high temperatures

    SciTech Connect

    Rosen, R.S.; Paddon, S.P.; Kassner, M.E.

    1999-06-01

    This study extended investigation on the elevated-temperature yield-strength dependence of beta-phase titanium alloys on strain rate and temperature. Yield stresses were found to increase substantially with increasing strain rate at elevated temperatures due to the high strain-rate sensitivity of titanium at high temperatures. Above 1000 C, the strain-rate sensitivities were found to increase substantially with increasing temperature and/or decreasing strain rate. The six alloys examined were TIMETAL 21S, Ti-15-3-, Ti-6-4, Ti-13-11-3, Beta C, and Beta III. There was particular interest in determining the strain-rate sensitivity of these alloys through strain-rate change tests above 1000 C. The yield stresses of all the titanium alloys at temperatures above 1093 C were less than 1% of their ambient temperature values. strain hardening was negligible in the alloys tested at these high temperatures. Extended tensile ductilities of 100 to 200% were observed due to the pronounced strain-rare sensitivity. The rate controlling mechanism for plasticity, based on activation energy and the strain-rate sensitivity measurements, is discussed.

  10. Influence of cerium additions on high-temperature-impact ductility and fracture behavior of iridium alloys

    SciTech Connect

    Gubbi, A.N.; Zee, R.H.; George, E.P.; Ohriner, E.K.

    1997-10-01

    Radioisotope thermoelectric generators (RTGs), used for supplying electric power to interplanetary space missions, utilize the energy liberated due to decay of the radioisotope fuel. The material used for cladding the fuel pellets is an iridium-based alloy developed at Oak Ridge National Laboratory, which contains nominally 0.3 wt pct W, 60 wppm Th, and 50 wppm Al, generally known as DOP-26. High-temperature tensile impact testing was carried out on Ir + 0.3 wt pct W alloys doped with cerium and thorium individually, and with cerium and thorium together. Impact ductility was evaluated as a function of grain size and test temperature. Cerium by itself was not as effective as thorium in improving the grain boundary cohesion, even though it segregated more strongly than thorium to the grain boundaries. This lower grain boundary cohesion was responsible for lower impact ductility and higher brittle-to-ductile transition temperature of cerium-doped alloys compared to those of the thorium- or thorium plus cerium-doped alloys. Reduction in thorium content by a factor of 5 (from 50 to 10 appm) in the bulk did not result in any significant reduction in high-temperature impact ductility or an increase in the brittle-to-ductile transition temperature as long as sufficient cerium was added to provide grain refinement. Grain boundary strengths of thorium- and thorium plus cerium-doped alloys were almost identical.

  11. Thermogravimetric study of oxidation of a PdCr alloy used for high-temperature sensors

    NASA Technical Reports Server (NTRS)

    Boyd, Darwin L.; Zeller, Mary V.

    1994-01-01

    In this study, the oxidation of Pd-13 weight percent Cr, a candidate alloy for high-temperature strain gages, was investigated by thermogravimetry. Although the bulk alloy exhibits linear electrical resistivity versus temperature and stable resistivity at elevated temperatures, problems attributed to oxidation occur when this material is fabricated into strain gages. In this work, isothermal thermogravimetry (TG) was used to study the oxidation kinetics. Results indicate that the oxidation of Pd-13 weight percent Cr was approximately parabolic in time at 600 C but exhibited greater passivation from 700 to 900 C. At 1100 C, the oxidation rate again increased.

  12. Impurity effects on high-temperature tensile ductility of iridium alloys at high strain rate

    SciTech Connect

    McKamey, C.G.; George, E.P.; Lee, E.H.; Ohriner, E.K.; Heatherly, L.; Cohron, J.W.

    1999-12-17

    The current study was undertaken to determine what effects, if any, larger amounts of certain impurities (Al,Cr,Fe,Ni, and Si) might have on the physical metallurgy and mechanical properties of the DOP-26 iridium alloy. This report summarizes the effects of these impurities on grain growth behavior and high-temperature high-strain-rate tensile ductility. Comparisons are made to the grain growth behavior and high-strain-rate tensile properties of the DOP-26 alloy without intentional impurity additions.

  13. Niobium-aluminum base alloys having improved, high temperature oxidation resistance

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G. (Inventor); Stephens, Joseph R. (Inventor)

    1991-01-01

    A niobium-aluminum base alloy having improved oxidation resistance at high temperatures and consisting essentially of 48%-52% niobium, 36%-42% aluminum, 4%-10% chromium, 0%-2%, more preferably 1%-2%, silicon and/or tungsten with tungsten being preferred, and 0.1%-2.0% of a rare earth selected from the group consisting of yttrium, ytterbium and erbium. Parabolic oxidation rates, k.sub.p, at 1200.degree. C. range from about 0.006 to 0.032 (mg/cm.sup.2).sup.2 /hr. The new alloys also exhibit excellent cyclic oxidation resistance.

  14. High temperature creep behavior of single crystal gamma prime and gamma alloys

    NASA Technical Reports Server (NTRS)

    Nathal, M. V.; Diaz, J. O.; Miner, R. V.

    1989-01-01

    The creep behavior of single crystals of gamma-prime and gamma alloys were investigated and compared to the response of two-phase superalloys tested previously. High temperature deformation in the gamma alloys was characteristic of a climb-controlled mechanism, whereas the gamma-prime based materials exhibited glide-controlled creep behavior. The superalloys were much more creep resistant than their constituent phases, which indicates the importance of the gamma/gamma-prime interface as a barrier for dislocation motion during creep.

  15. High-temperature steam oxidation kinetics of the E110G cladding alloy

    NASA Astrophysics Data System (ADS)

    Király, Márton; Kulacsy, Katalin; Hózer, Zoltán; Perez-Feró, Erzsébet; Novotny, Tamás

    2016-07-01

    In the course of recent years, several experiments were performed at MTA EK (Centre for Energy Research, Hungarian Academy of Sciences) on the isothermal high-temperature oxidation of the improved Russian cladding alloy E110G in steam/argon atmosphere. Using these data and designing additional supporting experiments, the oxidation kinetics of the E110G alloy was investigated in a wide temperature range, between 600 °C and 1200 °C. For short durations (below 500 s) or high temperatures (above 1065 °C) the oxidation kinetics was found to follow a square-root-of-time dependence, while for longer durations and in the intermediate temperature range (800-1000 °C) it was found to approach a cube-root-of-time dependence rather than a square-root one. Based on the results a new best-estimate and a conservative oxidation kinetics model were created.

  16. Dynamic High-temperature Testing of an Iridium Alloy in Compression at High-strain Rates: Dynamic High-temperature Testing

    SciTech Connect

    Song, B.; Nelson, K.; Lipinski, R.; Bignell, J.; Ulrich, G.; George, E. P.

    2014-08-21

    Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-strain -rate performance are needed for understanding high-speed impacts in severe environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain -rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. In our study, we analyzed the difficulties encountered in high-temperature Kolsky bar testing of thin iridium alloy specimens in compression. We made appropriate modifications using the current high-temperature Kolsky bar technique in order to obtain reliable compressive stress–strain response of an iridium alloy at high-strain rates (300–10 000 s-1) and temperatures (750 and 1030°C). The compressive stress–strain response of the iridium alloy showed significant sensitivity to both strain rate and temperature.

  17. Dynamic High-temperature Testing of an Iridium Alloy in Compression at High-strain Rates: Dynamic High-temperature Testing

    DOE PAGESBeta

    Song, B.; Nelson, K.; Lipinski, R.; Bignell, J.; Ulrich, G.; George, E. P.

    2014-08-21

    Iridium alloys have superior strength and ductility at elevated temperatures, making them useful as structural materials for certain high-temperature applications. However, experimental data on their high-strain -rate performance are needed for understanding high-speed impacts in severe environments. Kolsky bars (also called split Hopkinson bars) have been extensively employed for high-strain -rate characterization of materials at room temperature, but it has been challenging to adapt them for the measurement of dynamic properties at high temperatures. In our study, we analyzed the difficulties encountered in high-temperature Kolsky bar testing of thin iridium alloy specimens in compression. We made appropriate modifications using themore » current high-temperature Kolsky bar technique in order to obtain reliable compressive stress–strain response of an iridium alloy at high-strain rates (300–10 000 s-1) and temperatures (750 and 1030°C). The compressive stress–strain response of the iridium alloy showed significant sensitivity to both strain rate and temperature.« less

  18. Post-formed properties of superplastic aluminum aerospace alloys

    SciTech Connect

    Moore, W.L.; Zelin, M.; Chaudhury, P.K.

    1995-12-31

    Post-formed properties of commercially available superplastic aluminum alloys for aerospace applications are reviewed, focusing on the effect of both process variables and microstructural characteristics during superplastic forming. The post-formed properties include mechanical properties such as yield strength (YS), ultimate tensile strength (UTS), ductility, fatigue and fracture toughness (K{sub 1c}), and stress corrosion cracking (SCC) resistance. The microstructural processes, such as cavitation, grain growth, precipitation and texture evolution, that govern these post forming properties are reviewed to discuss the effect of forming process variables such as strain rate, temperature, back pressure, etc. The influence of pre- and post-processing treatments on these microstructural phenomena, hence, the post-formed properties, are also reviewed.

  19. Characterization of Ternary NiTiPt High-Temperature Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

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

  20. High-temperature microstructural stability in iron- and nickel-base alloys from rapid solidification processing

    SciTech Connect

    Flinn, J.E. ); Bae, J.C.; Kelly, T.F. )

    1991-08-01

    The properties and performance of metallic alloys for heat resistant applications depend on the fineness, homogeneity, and stability of their microstructures, particularly after high temperature exposures. Potential advantages of rapid solidification processing (RSP) of alloys for such applications are the homogeneity in composition and fine microstructural features derived from the nature of the RSP process. The main RSP product form is powder, is which obtained by atomizing a narrow melt stream into fine molten droplets. Rapid cooling of the droplets is typically achieved through convective cooling with noble gases such as argon or helium. Consolidation of RSP powder, either using near-net-shape methods or into forms that can be converted to final product shapes, requires exposures to fairly high temperatures, usually 900 to 1200{degrees}C for iron- and nickel-base alloys. Full consolidation, i.e., complete densification with accompanying particle bonding, usually requires pressure or stress assistance. Consolidation, as well as any subsequent thermal-mechanical processing, may affect the chemical homogeneity and fine microstructures. A study has been performed on a series of RSP iron- and nickel-base alloys. The results of microstructure examinations and mechanical properties tests of the consolidated powders, and their correlation, will be covered in this paper. 14 refs., 10 figs., 1 tab.

  1. 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.

  2. 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.

  3. Oxidation of High-temperature Alloy Wires in Dry Oxygen and Water Vapor

    NASA Technical Reports Server (NTRS)

    Opila, Elizabeth J.; Lorincz, Jonathan A.; DeMange, Jeffrey J.

    2004-01-01

    Small diameter wires (150 to 250 microns) of the high temperature alloys Haynes 188, Haynes 230, Haynes 230, Haynes 214, Kanthal Al and PM2000 were oxidized at 1204 C in dry oxygen or 50% H2O /50% O2 for 70 Hours. The oxidation kinetics were monitored using a thermogravimetric technique. Oxide phase composition and morphology of the oxidized wires were determined by X-ray diffraction,field emission scanning electron microscopy, and energy dispersive spectroscopy. The alumina-forming alloys, Kanthal Al and PM2000, out-performed the chromia-forming alloys under this conditions. PM2000 was recommended as the most promising candidate for advanced hybrid seal applications for space reentry control surface seals or hypersonic propulsion system seals. This study also demonstrated that thermogravimetric analysis of small diameter wires is a powerful technique for the study of oxide volatility, oxide adherence, and breakaway oxidation.

  4. Vacuum thermal-mechanical fatigue testing of two iron base high temperature alloys

    NASA Technical Reports Server (NTRS)

    Sheffler, K. D.

    1974-01-01

    Ultrahigh vacuum elevated temperature low cycle fatigue and thermal fatigue tests of 304 stainless steel and A-286 alloy have shown significant effects of frequency and combined temperature-strain cycling on fatigue life. At constant temperature, the cyclic life of both alloys was lower at lower frequencies. Combined temperature-strain cycling reduced fatigue life with respect to isothermal life at the maximum temperature of the thermal cycle. Life reductions with in-phase thermal cycling (tension at high temperature, compression at low temperature) were attributed to grain boundary cavitation caused by unreversed tensile grain boundary sliding. The proposed mechanism for out-of-phase cavity generation involved accumulation of unreversed compressive grain boundary displacements which could not be geometrically accomodated by intragranular deformation in the low-ductility A-286 alloy.

  5. High-temperature thermodynamic activities of zirconium in platinum alloys determined by nitrogen-nitride equilibria

    SciTech Connect

    Goodman, D.A.

    1980-05-01

    A high-temperature nitrogen-nitride equilibrium apparatus is constructed for the study of alloy thermodynamics to 2300/sup 0/C. Zirconium-platinum alloys are studied by means of the reaction 9ZrN + 11Pt ..-->.. Zr/sub 9/Pt/sub 11/ + 9/2 N/sub 2/. Carful attention is paid to the problems of diffusion-limited reaction and ternary phase formation. The results of this study are and a/sub Zr//sup 1985/sup 0/C/ = 2.4 x 10/sup -4/ in Zr/sub 9/Pt/sub 11/ ..delta..G/sub f 1985/sup 0/C//sup 0/ Zr/sub 9/Pt/sub 11/ less than or equal to -16.6 kcal/g atom. These results are in full accord with the valence bond theory developed by Engel and Brewer; this confirms their prediction of an unusual interaction of these alloys.

  6. Assessment of the Oxidation Behavior of a Pt-Based Alloy for High Temperature Applications

    NASA Astrophysics Data System (ADS)

    Odusote, J. K.; Cornish, L. A.; Papo, J. M.

    2013-11-01

    Pt-based alloys are being developed as a possible future replacement for Ni-based superalloy components in the hottest section of turbine engines. The critical properties of these alloys are their ability to withstand higher thermal and mechanical stresses as well as to resist aggressive corrosive and oxidizing environments in applications. Oxidation properties of these alloys were investigated between 1150 and 1350 °C. The surface roughness of the as-polished samples was determined using atomic force microscopy, while the microstructures of both the as-polished and oxidized samples were examined using scanning electron microscopy. The alloy was found to be composed of a two-phase gamma/gamma prime microstructure, while the average surface roughness decreased from 5.78 nm after 1 μm diamond paste polishing to 4.13 nm with 0.25 μm diamond paste polishing. Microstructure examination of the oxidized alloy samples revealed the formation of compact and protective external oxide scale composed of α-alumina, as confirmed by the XRD and Raman spectroscopy. The results also showed that the oxide scale thickens with increased exposure time and temperatures according to parabolic kinetics. It was concluded from the results that the Pt-based alloys possess good oxidation resistance and thus will be suitable for high temperature applications, such as turbine engines.

  7. 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.

  8. Thermogravimetric Study of Oxidation-Resistant Alloys for High-Temperature Solar Receivers

    NASA Astrophysics Data System (ADS)

    Olivares, Rene I.; Stein, Wes; Marvig, Paul

    2013-12-01

    Three special alloys likely to be suitable for high-temperature solar receivers were studied for their resistance to oxidation up to a temperature of 1050°C in dry atmospheres of CO2 and air. The alloys were Haynes HR160, Hastelloy X, and Haynes 230, all nickel-based alloys with greater than 20% chromium content. The oxidation rate of specimens cut from sample master alloys was followed by thermogravimetry by continuously monitoring the weight change with a microbalance for a test duration of 10 h. The corrosion resistance was deduced from the total weight increase of the specimens and the morphology of the oxide scale. The surface oxide layer formed (scale) was characterized by scanning electron microscopy and energy dispersive x-ray spectroscopy and in all cases was found to be chromia. Oxidation was analyzed by means of parabolic rate law, albeit in some instances linear breakaway corrosion was also observed. For the temperature range investigated, all alloys corroded more in CO2 than in air due to the formation of a stronger and more protective oxide scale in the presence of air. At 1000°C, the most resistant alloy to corrosion in CO2 was Haynes 230. Alloy Haynes HR160 was the most oxidized alloy at 1000°C in both CO2 and air. Hastelloy X oxidized to a similar extent in CO2 at both 900°C and 1000°C, but in air, it resisted oxidation better at 1000°C than either at 900°C or 1000°C.

  9. Basic principles of creating a new generation of high- temperature brazing filler alloys

    NASA Astrophysics Data System (ADS)

    Kalin, B. A.; Suchkov, A. N.

    2016-04-01

    The development of new materials is based on the formation of a structural-phase state providing the desired properties by selecting the base and the complex of alloying elements. The development of amorphous filler alloys for a high-temperature brazing has its own features that are due to the limited life cycle and the production method of brazing filler alloys. The work presents a cycle of analytical and experimental materials science investigations including justification of the composition of a new amorphous filler alloy for brazing the products from zirconium alloys at the temperature of no more than 800 °C and at the unbrazing temperature of permanent joints of more than 1200 °C. The experimental alloys have been used for manufacture of amorphous ribbons by rapid quenching, of which the certification has been made by X-ray investigations and a differential-thermal analysis. These ribbons were used to obtain permanent joints from the spacer grid cells (made from the alloy Zr-1% Nb) of fuel assemblies of the thermal nuclear reactor VVER-440. The brazed samples in the form of a pair of cells have been exposed to corrosion tests in autoclaves in superheated water at a temperature of 350 °C, a pressure of 160 MPa and duration of up to 6,000 h. They have been also exposed to destructive tests using a tensile machine. The experimental results obtained have made it possible to propose and patent a brazing filler alloy of the following composition: Zr-5.5Fe-(2.5-3.5)Be-1Nb-(5-8)Cu-2Sn-0.4Cr-(0.5-1.0)Ge. Its melting point is 780 °C and the recommended brazing temperature is 800°C.

  10. Development of Austenitic ODS Strengthened Alloys for Very High Temperature Applications

    SciTech Connect

    Stubbins, James; Heuser, Brent; Robertson, Ian; Sehitoglu, Huseyin; Sofronis, Petros; Gewirth, Andrew

    2015-04-22

    This “Blue Sky” project was directed at exploring the opportunities that would be gained by developing Oxide Dispersion Strengthened (ODS) alloys based on the Fe-Cr-Ni austenitic alloy system. A great deal of research effort has been directed toward ferritic and ferritic/martensitic ODS alloys which has resulted in reasonable advances in alloy properties. Similar gains should be possible with austenitic alloy which would also take advantage of other superior properties of that alloy system. The research effort was aimed at the developing an in-depth understanding of the microstructural-level strengthening effects of ODS particles in austentic alloys. This was accomplished on a variety of alloy compositions with the main focus on 304SS and 316SS compositions. A further goal was to develop an understanding other the role of ODS particles on crack propagation and creep performance. Since these later two properties require bulk alloy material which was not available, this work was carried out on promising austentic alloy systems which could later be enhanced with ODS strengthening. The research relied on a large variety of micro-analytical techniques, many of which were available through various scientific user facilities. Access to these facilities throughout the course of this work was instrumental in gathering complimentary data from various analysis techniques to form a well-rounded picture of the processes which control austenitic ODS alloy performance. Micromechanical testing of the austenitic ODS alloys confirmed their highly superior mechanical properties at elevated temperature from the enhanced strengthening effects. The study analyzed the microstructural mechanisms that provide this enhanced high temperature performance. The findings confirm that the smallest size ODS particles provide the most potent strengthening component. Larger particles and other thermally- driven precipitate structures were less effective contributors and, in some cases, limited

  11. Thermomechanical behavior of NiTiPdPt high temperature shape memory alloy springs

    NASA Astrophysics Data System (ADS)

    Nicholson, D. E.; Padula, S. A., II; Noebe, R. D.; Benafan, O.; Vaidyanathan, R.

    2014-12-01

    Transformation strains in high temperature shape memory alloys (HTSMAs) are generally smaller than for conventional NiTi alloys and can be purposefully limited in cases where stability and repeatability at elevated temperatures are desired. Yet such alloys can still be used in actuator applications that require large strokes when used in the form of springs. Thus there is a need to understand the thermomechanical behavior of shape memory alloy spring actuators, particularly those consisting of alternative alloys. In this work, a modular test setup was assembled with the objective of acquiring stroke, stress, temperature, and moment data in real time during joule heating and forced convective cooling of Ni19.5Ti50.5Pd25Pt5 HTSMA springs. The spring actuators were subjected to both monotonic axial loading and thermomechanical cycling. The role of rotational constraints (i.e., by restricting rotation or allowing for free rotation at the ends of the springs) on stroke performance was also assessed. Finally, recognizing that evolution in the material microstructure can result in changes in HTSMA spring geometry, the effect of material microstructural evolution on spring performance was examined. This was done by taking into consideration the changes in geometry that occurred during thermomechanical cycling. This work thus provides insight into designing with HTSMA springs and predicting their thermomechanical performance.

  12. High temperature coarsening of Cr2Nb precipitates in Cu-8 Cr-4 Nb alloy

    NASA Technical Reports Server (NTRS)

    Anderson, Kenneth Reed

    1996-01-01

    A new high-temperature-strength, high-conductivity Cu-Cr-Nb alloy with a CrNb ratio of 2:1 was developed to achieve improved performance and durability. The Cu-8 Cr4 Nb alloy studied has demonstrated remarkable thermal and microstructural stability after long exposures at temperatures up to 0.98 T(sub m). This stability was mainly attributed to the slow coarsening kinetics of the Cr2Nb precipitates present in the alloy. At all temperatures, the microstructure consists of a bimodal and sometimes trimodal distribution of strengthening Cr2Nb precipitates, depending on precipitation condition, i.e. from liquid or solid solution, and cooling rates. These precipitates remain in the same size range, i.e. large precipitates of approximately I pm, and small precipitates less dm 300 nm, and effectively pin the grain boundaries thus retaining a fine grain size of 2.7 micro-m after 100 h at 1323 K. (A relatively small number of Cr-rich and Nb-rich particles were also present.) This grain boundary pinning and sluggish coarsening of Cr2Nb particles explain the retention of good mechanical properties after prolonged holding at very high temperatures, e.g., 75% of the original hardness after aging for 100 h at 1273 K. Application of LSW-based coarsening models indicated that the coarsening kinetics of the large precipitates are most likely governed by grain boundary diffsion and, to a lesser extent, volume diffusion mechanisms.

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

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

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

  14. High-temperature ordered intermetallic alloys II; Proceedings of the Second Symposium, Boston, MA, Dec. 2-4, 1986

    NASA Technical Reports Server (NTRS)

    Stoloff, N. S. (Editor); Koch, C. C. (Editor); Liu, C. T. (Editor); Izumi, O. (Editor)

    1987-01-01

    The papers presented in this volume provide on overview of recent theoretical and experimental research in the field of high-temperature ordered intermetallic alloys. The papers are gouped under the following headings: ordering behavior and theory, microstructures, mechanical behavior, alloy design and microstructural control, and metallurgical properties. Specific topics discussed include antiphase domains, disordered films and the ductility of ordered alloys based on Ni3Al; kinetics and mechanics of formation of Al-Ni intermetallics; deformability improvements of L1(2)-type intermetallic compounds; B2 aluminides for high-temperature applications; and rapidly solidified binary TiAl alloys.

  15. Phase transformation of oxide film in zirconium alloy in high temperature hydrogenated water

    SciTech Connect

    Kim, Taeho; Kim, Jongjin; Choi, Kyoung Joon; Yoo, Seung Chang; Kim, Seung Hyun; Kim, Ji Hyun

    2015-07-23

    The effect of the variation of the dissolved hydrogen concentration on the oxide phase transformation under high-temperature hydrogenated water conditions was investigated using in situ Raman spectroscopy. The Raman spectrum in 50 cm(3)/kg of dissolved hydrogen concentration indicated the formation of monoclinic and tetragonal zirconium oxide at the water-substrate interface. As the dissolved hydrogen concentration decreased to 30 cm(3)/kg, the Raman peaks corresponding to the zirconium oxide phase changed, indicating an oxide phase transformation. And, the results of SEM and TEM analyses were compared with those of in situ analyses obtained for the oxide structure formed on the zirconium alloy.

  16. High-temperature relaxation in a Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Zhou, Z. C.; Han, F. S.

    2003-09-01

    Two relaxational internal friction peaks were found in a (wt%)Fe-25Cr-5Al alloy. The low-temperature peak is related to Zener relaxation and the high-temperature one to grain-boundary relaxation. Their activation energy values are 2.55 (+/-0.14) eV for the Zener peak and 4.07(+/-0.15) eV for the grain-boundary relaxation peak, respectively. Grain-boundary relaxation strength remarkably increases with decreasing grain size, while the Zener peak is independent of the grain size. (

  17. On thermomechanical testing in support of constitutive equation development for high temperature alloys

    NASA Technical Reports Server (NTRS)

    Robinson, D. N.

    1985-01-01

    Three major categories of testing are identified that are necessary to provide support for the development of constitutive equations for high temperature alloys. These are exploratory, charactrization and verification tests. Each category is addressed and specific examples of each are given. An extensive, but not exhaustive, set of references is provided concerning pertinent experimental results and their relationships to theoretical development. This guide to formulating a meaningful testing effort in support of consitutive equation development can also aid in defining the necessary testing equipment and instrumentation for the establishment of a deformation and structures testing laboratory.

  18. Probabilistic material degradation model for aerospace materials subjected to high temperature, mechanical and thermal fatigue, and creep

    NASA Technical Reports Server (NTRS)

    Boyce, L.

    1992-01-01

    A probabilistic general material strength degradation model has been developed for structural components of aerospace propulsion systems subjected to diverse random effects. The model has been implemented in two FORTRAN programs, PROMISS (Probabilistic Material Strength Simulator) and PROMISC (Probabilistic Material Strength Calibrator). PROMISS calculates the random lifetime strength of an aerospace propulsion component due to as many as eighteen diverse random effects. Results are presented in the form of probability density functions and cumulative distribution functions of lifetime strength. PROMISC calibrates the model by calculating the values of empirical material constants.

  19. 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.

  20. High strain rate behavior of alloy 800H at high temperatures

    NASA Astrophysics Data System (ADS)

    Shafiei, E.

    2016-05-01

    In this paper, a new model using linear estimation of strain hardening rate vs. stress, has been developed to predict dynamic behavior of alloy 800H at high temperatures. In order to prove the accuracy and competency of the presented model, Johnson-Cook model pertaining modeling of flow stress curves was used. Evaluation of mean error of flow stress at deformation temperatures from 850 °C to 1050 °C and at strain rates of 5 S-1 to 20 S-1 indicates that the predicted results are in a good agreement with experimentally measured ones. This analysis has been done for the stress-strain curves under hot working condition for alloy 800H. However, this model is not dependent on the type of material and can be extended for any similar conditions.

  1. 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.

  2. On massive carbide precipitation during high temperature low cycle fatigue in alloy 800H

    SciTech Connect

    Bhanu Sankara Rao, K.; Halford, G.R. . Lewis Research Center); Schuster, H. . Inst. for Reactor Materials)

    1994-08-15

    Alloys engineered for high-temperature application are frequently put into use in a thermodynamically unstable condition. Subsequent exposure to service temperatures may promote many thermally-assisted reactions such as formation, coarsening, and/or coalescence of precipitates. Superposition of cyclic straining may accelerate the kinetics of these reactions but also may cause reaction products having specific features not observed under simple thermal exposure. The influence of cyclic strain-induced microstructural changes on the fatigue behavior has to be considered in terms of their effects on both cyclic strength and life. The occurrence of massive (cellular) precipitation of M[sub 23]C[sub 6] on grain boundaries during elevated temperature low cycle fatigue testing has been reported in Type 304 stainless steel, Type 316 stainless steel, and Inconel 617 superalloy, and its presence has already been linked with reduction in high temperature ductility, an important engineering property on which low cycle fatigue (LCF) life depends to a large extent. Massive precipitation may render the austenitic engineering alloys susceptible to corrosion, which would have important bearing on the performance of these alloys in the oxidizing environments. Furthermore, the long term stability of massive M[sub 23]C[sub 6] particles is particularly important since the transformation of such a large structure into a brittle intermetallic phase (such as sigma) could produce a detrimental effect on the mechanical properties. The conditions and the mechanisms responsible for the occurrence of massive precipitation during LCF have not yet been established. This investigation is specifically aimed at understanding the influence of strain rate on massive precipitation and the mechanism responsible for the occurrence of massive M[sub 23]C[sub 6] precipitation in Alloy 800H during elevated temperature LCF testing.

  3. Deployable aerospace PV array based on amorphous silicon alloys

    NASA Technical Reports Server (NTRS)

    Hanak, Joseph J.; Walter, Lee; Dobias, David; Flaisher, Harvey

    1989-01-01

    The development of the first commercial, ultralight, flexible, deployable, PV array for aerospace applications is discussed. It is based on thin-film, amorphous silicon alloy, multijunction, solar cells deposited on a thin metal or polymer by a proprietary, roll-to-roll process. The array generates over 200 W at AM0 and is made of 20 giant cells, each 54 cm x 29 cm (1566 sq cm in area). Each cell is protected with bypass diodes. Fully encapsulated array blanket and the deployment mechanism weigh about 800 and 500 g, respectively. These data yield power per area ratio of over 60 W/sq m specific power of over 250 W/kg (4 kg/kW) for the blanket and 154 W/kg (6.5 kg/kW) for the power system. When stowed, the array is rolled up to a diameter of 7 cm and a length of 1.11 m. It is deployed quickly to its full area of 2.92 m x 1.11 m, for instant power. Potential applications include power for lightweight space vehicles, high altitude balloons, remotely piloted and tethered vehicles. These developments signal the dawning of a new age of lightweight, deployable, low-cost space arrays in the range from tens to tens of thousands of watts for near-term applications and the feasibility of multi-100 kW to MW arrays for future needs.

  4. Challenges and Progress in the Development of High-Temperature Shape Memory Alloys Based on NiTiX Compositions for High-Force Actuator Applications

    NASA Technical Reports Server (NTRS)

    Padula, Santo, II; Bigelow, Glen; Noebe, Ronald; Gaydosh, Darrell; Garg, Anita

    2006-01-01

    Interest in high-temperature shape memory alloys (HTSMA) has been growing in the aerospace, automotive, process control, and energy industries. However, actual materials development has seriously lagged component design, with current commercial NiTi alloys severely limited in their temperature capability. Additions of Pd, Pt, Au, Hf, and Zr at levels greater than 10 at.% have been shown to increase the transformation temperature of NiTi alloys, but with few exceptions, the shape memory behavior (strain recovery) of these NiTiX systems has been determined only under stress free conditions. Given the limited amount of basic mechanical test data and general lack of information regarding the work attributes of these materials, a program to investigate the mechanical behavior of potential HTSMAs, with transformation temperatures between 100 and 500 C, was initiated. This paper summarizes the results of studies, focusing on both the practical temperature limitations for ternary TiNiPd and TiNiPt systems based on the work output of these alloys and the ability of these alloys to undergo repeated thermal cycling under load without significant permanent deformation or "walking". These issues are ultimately controlled by the detwinning stress of the martensite and resistance to dislocation slip of the individual martensite and austenite phases. Finally, general rules that govern the development of useful, high work output, next-generation HTSMA materials, based on the lessons learned in this work, will be provided

  5. High Temperature Heat Capacity of Alloy D9 Using Drop Calorimetry Based Enthalpy Increment Measurements

    NASA Astrophysics Data System (ADS)

    Banerjee, Aritra; Raju, S.; Divakar, R.; Mohandas, E.

    2007-02-01

    Alloy D9 is a void-swelling resistant nuclear grade austenitic stainless steel (SS) based on AISI type 316-SS in which titanium constitutes an added predetermined alloying composition. In the present study, the high-temperature enthalpy values of alloy D9 with three different titanium-to-carbon mass percent ratios, namely Ti/C = 4, 6, and 8, have been measured using inverse drop calorimetry in the temperature range from 295 to 1323 K. It is found that within the level of experimental uncertainty, the enthalpy values are independent of the Ti-C mass ratio. The temperature dependence of the isobaric specific heat C P is obtained by a linear regression of the measured enthalpy data. The measured C P data for alloy D9 may be represented by the following best-fit expression: C_P(J \\cdot kg^{-1}\\cdot K^{-1})= 431 + 17.7 × 10^{-2}T + 8.72 × 10^{-5}/T^2. It is found that the measured enthalpy and specific heat values exhibit good agreement with reported data on 316 and other related austenitic stainless steels.

  6. Low Cycle Fatigue and Creep-Fatigue Behavior of Alloy 617 at High Temperature

    SciTech Connect

    Cabet, Celine; Carroll, Laura; Wright, Richard

    2013-10-01

    Alloy 617 is the leading candidate material for an intermediate heat exchanger (IHX) application of the Very High Temperature Nuclear Reactor (VHTR), expected to have an outlet temperature as high as 950 degrees C. Acceptance of Alloy 617 in Section III of the ASME Code for nuclear construction requires a detailed understanding of the creep-fatigue behavior. Initial creep-fatigue work on Alloy 617 suggests a more dominant role of environment with increasing temperature and/or hold times evidenced through changes in creep-fatigue crack growth mechanism/s and failure life. Continuous cycle fatigue and creep-fatigue testing of Alloy 617 was conducted at 950 degrees C and 0.3% and 0.6% total strain in air to simulate damage modes expected in a VHTR application. Continuous cycle specimens exhibited transgranular cracking. Intergranular cracking was observed in the creep-fatigue specimens, although evidence of grain boundary cavitation was not observed. Despite the absence of grain boundary cavitation to accelerate crack propagation, the addition of a hold time at peak tensile strain was detrimental to cycle life. This suggests that creepfatigue interaction may occur by a different mechanism or that the environment may be partially responsible for accelerating failure.

  7. The high-temperature work function of sintered dilute solution tungsten-lridium alloys

    NASA Astrophysics Data System (ADS)

    D'Cruz, L. A.; Bosch, D. R.; Jacobson, D. L.

    1993-02-01

    The effect of transition element additives molybdenum, rhenium, iridium, and osmium on the effective work function of tungsten has been the focus of thermionics research for several years.[1- 5] In this study, iridium-added tungsten powder mixtures were cold compacted and sintered to produce a range of tungsteniridium electrodes. An electron emission study was subsequently carried out to evaluate the work function behavior of the consolidated alloys. The work function was obtained from measurements of the current emitted from the electrode surface under ultrahigh vacuum conditions in the temperature range of 1800 to 2500 K using a vacuum emission vehicle (VEV). The data show that the magnitude of the work function in these alloys varied with temperature. Microstructural evaluation of the alloys indicated that the tested surfaces displayed accentuated thermal etching of the grain boundaries together with the fact that the final grain sizes in the sintered alloys were three to five times smaller than those found in equivalent are-melted alloys that were studied in earlier work.[4,5] Scanning electron microscopy (SEM) micrographs of the tested surfaces of the sintered alloys containing the highest iridium levels (~2 wt % ) show a high level of structural distortion, particularly in the vicinity of grain boundaries and corners. The extent of these distortions was found to vary with the iridium content, i.e., the W-IR3M and W-IR2M. The samples with compositions lower than 0.5 wt % Ir were virtually devoid of distortions. It is proposed that, during homogenization carried out prior to testing, a net accumulation of iridium occurs near the surface, particularly in the vicinity of structural heterogeneities. Subsequent cooling leads to the precipitation of iridium-rich second phase sources, which when reheated to the testing temperatures supplies iridium to a surface monolayer. This mechanism is capable of explaining the observed work function trends during high

  8. MULTI-PHASE Cr-BASED ALLOYS FOR AGGRESSIVE HIGH TEMPERATURE ENVIRONMENTS

    SciTech Connect

    Brady, MP

    2001-08-24

    Attractive high-temperature mechanical properties and oxidation/hot corrosion resistance have been achieved in a new family of Cr{sub 2}Ta-reinforced Cr alloys. However, inadequate room-temperature toughness remains a key challenge, with the best Cr-Cr{sub 2}Ta alloys exhibiting only modest toughness in the range of 12-14 MPa m{sup 1/2}. The addition of MgO has been shown to significantly improve the room-temperature mechanical properties of unalloyed Cr and was investigated as a means for improving the room-temperature mechanical properties of the Cr-Cr{sub 2}Ta alloys. Microstructural analysis of a series of Cr and Cr-6MgO base alloys was used to investigate the proposed ductilization mechanism of nitrogen gettering by a MgCr{sub 2}O{sub 4} spinel phase, which forms during consolidation of Cr and MgO powders. Nitride and related impurity precipitates have been linked to reduced ductility in Cr at room-temperature. Surprisingly, nitride (and carbide) impurity precipitates were found i n hot-pressed Cr-6 MgO base alloys despite room-temperature tensile ductility of 5%. These precipitates were found adjacent to MgO/MgCr{sub 2}O{sub 4} particles and were somewhat more blunt than those observed in unalloyed Cr. The addition of TiO{sub 2} to unalloyed Cr resulted in similar morphological changes to the nitride and carbide impurity precipitates; however, the TiO{sub 2} dispersed alloy was brittle at room-temperature. Why MgO dispersions are effective in ductilizing Cr, but others such as TiO{sub 2} are not, is not clear and is the subject of ongoing study. Efforts to introduce the effect in Cr-Cr{sub 2}Ta-MgO alloys were not successful, and it was concluded that significant modification of the Cr matrix phase in the Cr-Cr{sub 2}Ta alloys by macroalloying is necessary to improve room-temperature mechanical properties. Preliminary attempts at macroalloying with Fe were quite successful and resulted in an increase in room-temperature toughness to 18-20 MPa m{sup 1/2} in Cr

  9. MULTI-PHASE HIGH TEMPERATURE ALLOYS: EXPLORATION OF LAVES-STRENGTHENED STEELS

    SciTech Connect

    Yamamoto, Yukinori; Brady, Michael P; Lu, Zhao Ping; Liu, Chain T

    2007-01-01

    Exploratory effort was initiated for the development of Fe-base alloys strengthened by intermetallic Laves phase combined with MC (M: metals) carbide for improved elevated-temperature strength in fossil energy system components such as super-heater tubes and industrial gas turbines. Work in FY 2006 was focused on strengthening of Fe-Cr-Ni base austenitic stainless alloys by Fe2Nb Laves-phase precipitates with/without MC carbides, in combination with the improvement of oxidation resistance via Al-modification to promote alumina scale formation. A series of Fe-Cr-Ni-Nb base austenitic alloys with additions of Mo, Al, Si, C, B, etc. were cast and thermomechanically processed, and then tensile creep-rupture tested at the conditions of 750-850oC/70-170 MPa. The Al-modified alloys strengthened by Laves + MC show superior creep strength to that of conventional type 347 stainless steels, and their creep life-limit reaches up to 500 h at 750 oC/100 MPa. These alloys also show an excellent oxidation resistance from 650-800oC in air and air + 10% water vapor environments due to formation of a protective Al2O3 scale. Microstructural analysis of alloys strengthened by only Laves phase revealed that the Laves phase was effective to pin dislocations when the particle size is less than 0.5 m, but the resultant creep rupture lives were relatively short. The Al-modification was also applied to an advanced carbide-strengthened austenitic stainless steel, and it yielded creep resistance comparable to state-of-the-art austenitic alloys such as NF709, together with protective alumina scale formation. Modification of this alloy composition for its creep strength and oxidation resistance will be pursued in FY2007. Preliminary results suggest that the developed alloys with Al-modification combined with MC carbide strengthening are promising as a new class of high-temperature austenitic stainless steels.

  10. A Promising New Class of High-Temperature Alloys: Eutectic High-Entropy Alloys

    PubMed Central

    Lu, Yiping; Dong, Yong; Guo, Sheng; Jiang, Li; Kang, Huijun; Wang, Tongmin; Wen, Bin; Wang, Zhijun; Jie, Jinchuan; Cao, Zhiqiang; Ruan, Haihui; Li, Tingju

    2014-01-01

    High-entropy alloys (HEAs) can have either high strength or high ductility, and a simultaneous achievement of both still constitutes a tough challenge. The inferior castability and compositional segregation of HEAs are also obstacles for their technological applications. To tackle these problems, here we proposed a novel strategy to design HEAs using the eutectic alloy concept, i.e. to achieve a microstructure composed of alternating soft fcc and hard bcc phases. As a manifestation of this concept, an AlCoCrFeNi2.1 (atomic portion) eutectic high-entropy alloy (EHEA) was designed. The as-cast EHEA possessed a fine lamellar fcc/B2 microstructure, and showed an unprecedented combination of high tensile ductility and high fracture strength at room temperature. The excellent mechanical properties could be kept up to 700°C. This new alloy design strategy can be readily adapted to large-scale industrial production of HEAs with simultaneous high fracture strength and high ductility. PMID:25160691

  11. Creep Behavior of High Temperature Alloys for Generation IV Nuclear Energy Systems

    NASA Astrophysics Data System (ADS)

    Wen, Xingshuo

    The Very High Temperature Reactor (VHTR) is one of the leading concepts of the Generation IV nuclear reactor development, which is the core component of Next Generation Nuclear Plant (NGNP). The major challenge in the research and development of NGNP is the performance and reliability of structure materials at high temperature. Alloy 617, with an exceptional combination of high temperature strength and oxidation resistance, has been selected as a primary candidate material for structural use, particularly in Intermediate Heat Exchanger (IHX) which has an outlet temperature in the range of 850 to 950°C and an inner pressure from 5 to 20MPa. In order to qualify the material to be used at the operation condition for a designed service life of 60 years, a comprehensive scientific understanding of creep behavior at high temperature and low stress regime is necessary. In addition, the creep mechanism and the impact factors such as precipitates, grain size, and grain boundary characters need to be evaluated for the purpose of alloy design and development. In this study, thermomechanically processed specimens of alloy 617 with different grain sizes were fabricated, and creep tests with a systematic test matrix covering the temperatures of 850 to 1050°C and stress levels from 5 to 100MPa were conducted. Creep data was analyzed, and the creep curves were found to be unconventional without a well-defined steady-state creep. Very good linear relationships were determined for minimum creep rate versus stress levels with the stress exponents determined around 3-5 depending on the grain size and test condition. Activation energies were also calculated for different stress levels, and the values are close to 400kJ/mol, which is higher than that for self-diffusion in nickel. Power law dislocation climb-glide mechanism was proposed as the dominant creep mechanism in the test condition regime. Dynamic recrystallization happening at high strain range enhanced dislocation climb and

  12. Transformation-induced plasticity in high-temperature shape memory alloys: a one-dimensional continuum model

    NASA Astrophysics Data System (ADS)

    Sakhaei, Amir Hosein; Lim, Kian-Meng

    2016-07-01

    A constitutive model based on isotropic plasticity consideration is presented in this work to model the thermo-mechanical behavior of high-temperature shape memory alloys. In high-temperature shape memory alloys (HTSMAs), both martensitic transformation and rate-dependent plasticity (creep) occur simultaneously at high temperatures. Furthermore, transformation-induced plasticity is another deformation mechanism during martensitic transformation. All these phenomena are considered as dissipative processes to model the mechanical behavior of HTSMAs in this study. The constitutive model was implemented for one-dimensional cases, and the results have been compared with experimental data from thermal cycling test for actuator applications.

  13. Ways of improving the high-temperature work service of vanadium and some alloys used in reactors

    NASA Astrophysics Data System (ADS)

    Shyrokov, V. V.; Vasyliv, Ch. B.; Shyrokov, O. V.

    2009-10-01

    We present new evidence for the high-temperature strength of vanadium and low-alloyed (up to 15 at.%) vanadium-based alloys under conditions of prolonged (up to 5000 h) high-temperature (973-1173 K) exposure to vacuum, helium, lithium and sodium melts, modeling reactor heat-transport media (10 Pa). The kinetics of phase transformations in alloys of the systems V-Zr-C, V-Nb-Zr-C, V-Mo-Zr-C, and V-Ti-O in the process of prolonged aging under stress is analyzed. It is established that the process of pre-decay of a solid solution has many stages and is intensified by the action of stresses. The corresponding isothermal diagrams of the decay of VTsU (V-Zr-C) alloy are constructed. We give recommendations as to the choice of alloying elements with the aim of enhancing the high-temperature strength of vanadium and vanadium alloys used for reactors. New alloys developed on the basis of the systems V-Ti-O, V-Nb-Zr, V-Ta-Hf, V-Cr-Sc, and V-Cr-Nd and a new method of strengthening thermochemical treatment of vanadium-titanium alloys with the use of oxygen from air have found application in pilot-engineering developments for high-temperature nuclear power plants.

  14. The 100,000-hour cyclic oxidation behavior at 815C (1500 F) of 33 high-temperature alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.

    1977-01-01

    Commercial high-temperature Fe-, Ni-, and Co-base alloys were oxidized in air at 815 deg C for ten 1000-hour cycles. Specific weight change versus time curves were derived and the 10,000-hour surface oxides were analyzed by X-ray diffraction. The alloys were ranked by a combination of appearance and metal loss estimates derived from gravimetric data.

  15. 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.

  16. The Effects of Water Vapor and Hydrogen on the High-Temperature Oxidation of Alloys

    SciTech Connect

    Mu, N; Jung, K; Yanar, N M; Pettit, F S; Holcomb, G R; Howard, B H; Meier, G H

    2013-06-01

    Essentially all alloys and coatings that are resistant to corrosion at high temperature require the formation of a protective (slowly-growing and adherent) oxide layer by a process known as selective oxidation. The fundamental understanding of this process has been developed over the years for exposure in pure oxygen or air. However, the atmospheres in most applications contain significant amounts of water vapor which can greatly modify the behavior of protective oxides. The development of oxy-fuel combustion systems in which fossil fuels are burned in a mixture of recirculated flue gas and oxygen, rather than in air, has caused renewed interest in the effects of water vapor and steam on alloy oxidation. The focus of this paper is on the ways the presence of water vapor can directly alter the selective oxidation process. The paper begins with a brief review of the fundamentals of selective oxidation followed by a description of recent experimental results regarding the effect of water vapor on the oxidation of a variety of chromia-forming alloys (Fe- and Ni-base) in the temperature range 600 to 700 °C. The atmospheres include air, air-H{sub 2}O, Ar-H{sub 2}O and Ar-H{sub 2}O-O{sub 2}. Then the behavior of alumina-forming alloys in H{sub 2}O-containing atmospheres is briefly described. As hydrogen is produced during oxidation of alloys in H{sub 2}O, it can be released back into the gas phase or injected into the metal (where it can diffuse through to the other side). Experiments in which hydrogen concentrations have been measured on both sides of thin specimens during oxidation by H{sub 2}O on only one side are described. Finally, it is attempted to catalogue the various experimental observations under a few general principles.

  17. Solidification processing and phase transformations in ordered high temperature alloys. Final report, 30 March 1990-30 September 1992

    SciTech Connect

    Boettinger, W.J.; Bendersky, L.A.; Kattner, U.R.

    1993-01-20

    Useful high temperature alloys generally have microstructures consisting of more than one phase. Multiphase microstructures are necessary to develop acceptable toughness and creep strength in high temperature intermetallic alloy matrices. The optimum microstructures must be developed by a careful selection of processing path that includes both solidification and solid state heat treatment. Research has been conducted on the rapid solidification of selected intermetallic alloys and on the phase transformation paths that occur during cooling, primarily in the Ti-Al-Nb system. This report describes research performed in the Metallurgy Division at NIST under DARPA order 7469 between 1/1/89 and 12/31/92. Various research tasks were completed and the results have been published or have been submitted for publication.... Intermetallics, Ti-Al-Nb Alloys, Phase Diagrams, Phase Transformations, Ti-Al-Ta Alloys, MoSi2 Alloys.

  18. GRCop-84: A High Temperature Copper-based Alloy For High Heat Flux Applications

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    2005-01-01

    While designed for rocket engine main combustion chamber liners, GRCop-84 (Cu-8 at.% Cr-4 at.% Nb) offers potential for high heat flux applications in industrial applications requiring a temperature capability up to approximately 700 C (1292 F). GRCop-84 is a copper-based alloy with excellent elevated temperature strength, good creep resistance, long LCF lives and enhanced oxidation resistance. It also has a lower thermal expansion than copper and many other low alloy copper-based alloys. GRCop-84 can be manufactured into a variety of shapes such as tubing, bar, plate and sheet using standard production techniques and requires no special production techniques. GRCop-84 forms well, so conventional fabrication methods including stamping and bending can be used. GRCop-84 has demonstrated an ability to be friction stir welded, brazed, inertia welded, diffusion bonded and electron beam welded for joining to itself and other materials. Potential applications include plastic injection molds, resistance welding electrodes and holders, permanent metal casting molds, vacuum plasma spray nozzles and high temperature heat exchanger applications.

  19. Structural Evolution and Mechanical Properties of a VT22 Titanium Alloy Under High-Temperature Deformation

    NASA Astrophysics Data System (ADS)

    Ratochka, I. V.; Mishin, I. P.; Lykova, O. N.; Naydenkin, E. V.; Varlamova, N. V.

    2016-07-01

    The special features inherent in the development of high-temperature deformation and structural evolution in materials are investigated, using a VT22 titanium alloy of the transition class (Ti - 4.74 mass% Al - 5.57 mass% Mo - 5.04 mass% V) subjected to helical rolling + aging as an example. This treatment is found to give rise to an intragrain fine acicular martensite structure with fine inclusions of α-phase particles of size ~1 μm. It is shown that in the alloy undergoing plastic deformation at temperatures approaching the polymorphic transformation temperature, the elongation to failure is in excess of 300%. The high plasticity of the alloy in the conditions considered is likely to be due to vigorous development of phase transformations and intensification of diffusion-controlled processes, including the effects of the evolution of the dislocation structure, growth of subgrains, and formation of new grains in the bulk of the pre-existing ones during plastic deformation.

  20. Oxidation Kinetics of a NiPtTi High Temperature Shape Memory Alloy

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Humphrey, Donald L.; Noebe, Ronald D.

    2007-01-01

    A high temperature shape memory alloy (HTSMA), Ni30Pt50Ti, with an M(sub s) near 600 C, was isothermally oxidized in air for 100 hr over the temperature range of 500 to 900 C. Parabolic kinetics were confirmed by log-log and parabolic plots and showed no indication of fast transient oxidation. The overall behavior could be best described by the Arrhenius relationship: k(sub p) = 1.64 x 10(exp 12)[(-250 kJ/mole)/RT] mg(sup 2)/cm(sup 4)hr. This is about a factor of 4 reduction compared to values measured here for a binary Ni47Ti commercial SMA. The activation energy agreed with most literature values for TiO2 scale growth measured for elemental Ti and other NiTi alloys. Assuming uniform alloy depletion of a 20 mil (0.5 mm) dia. HTSMA wire, approx. 1 percent Ti reduction is predicted after 20,000 hr oxidation at 500 C, but becomes much more serious at higher temperatures.

  1. Solid State Joining of High Temperature Alloy Tubes for USC and Heat-Exchanger Systems

    SciTech Connect

    Bimal Kad

    2011-12-31

    The principal objective of this project was to develop materials enabling joining technologies for use in forward looking heat-exchanger fabrication in Brayton cycle HIPPS, IGCC, FutureGen concepts capable of operating at temperatures in excess of 1000{degree}C as well as conventional technology upgrades via Ultra Super-Critical (USC) Rankine-cycle boilers capable of operating at 760{degree}C (1400F)/38.5MPa (5500psi) steam, while still using coal as the principal fossil fuel. The underlying mission in Rankine, Brayton or Brayton-Rankine, or IGCC combined cycle heat engine is a steady quest to improving operating efficiency while mitigating global environmental concerns. There has been a progressive move to higher overall cycle efficiencies, and in the case of fossil fuels this has accelerated recently in part because of concerns about greenhouse gas emissions, notably CO{sub 2}. For a heat engine, the overall efficiency is closely related to the difference between the highest temperature in the cycle and the lowest temperature. In most cases, efficiency gains are prompted by an increase in the high temperature, and this in turn has led to increasing demands on the materials of construction used in the high temperature end of the systems. Our migration to new advanced Ni-base and Oxide Dispersion Strengthened (ODS) alloys poses significant fabrication challenges, as these materials are not readily weldable or the weld performs poorly in the high temperature creep regime. Thus the joining challenge is two-fold to a) devise appropriate joining methodologies for similar/dissimilar Ni-base and ODS alloys while b) preserving the near baseline creep performance in the welded region. Our program focus is on solid state joining of similar and dissimilar metals/alloys for heat exchanger components currently under consideration for the USC, HIPPS and IGCC power systems. The emphasis is to manipulate the joining methods and variables available to optimize joint creep

  2. High temperature oxidation of copper and copper aluminium alloys: Impact on furnace side wall cooling systems

    NASA Astrophysics Data System (ADS)

    Plascencia Barrera, Gabriel

    The high temperature oxidation behaviours of copper and dilute Cu-Al alloys were investigated. Experiments were carried out by: (i) Oxidizing under various oxygen potentials at different temperatures using a combined TG-DTA apparatus. (ii) Oxidizing in a muffle furnace (in air) at different temperatures for extended periods of time. The oxidation mechanisms were evaluated based upon the kinetic data obtained as well as by X-ray diffraction and microscopical (SEM and optical) analyses. It was found that oxidation of copper strongly depends on the temperature. Two distinct mechanisms were encountered. Between 300 and 500°C, the oxidation rate is controlled by lateral growth of the oxide on the metal surface, whereas between 600 and 1000°C oxidation is controlled by lattice diffusion of copper ions through the oxide scale. On the other hand, the partial pressure of oxygen only has a small effect on the oxidation of copper. Alloy oxidation is also dependent on the temperature. As temperature increases, more aluminium is required to protect copper from being oxidized. It was shown that if the amount of oxygen that dissolves in the alloy exceeds the solubility limit of oxygen in copper, an internal oxidation layer will develop, leading to the formation of a tarnishing scale. On the other hand if the oxygen content in the alloy lies below the solubility limit of oxygen in copper, no oxidation products will form since a tight protective alumina layer will form on the alloy surface. Surface phenomena may affect the oxidation behaviour of dilute Cu-Al alloys. Immersion tests in molten copper matte and copper converting slag, using laboratory scale cooling elements with various copper based materials, were conducted. Results from these tests showed that alloying copper with 3 to 4 wt% Al decreases the oxidation rate of pure copper by 4 orders of magnitude; however due to a significant drop in thermal conductivity, the ability to extract heat is compromised, leading to

  3. 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.

  4. Corrosion behaviour of Alloy 800 in high temperature aqueous solutions: long term autoclave studies

    NASA Astrophysics Data System (ADS)

    Alvarez, M. G.; Olmedo, A. M.; Villegas, M.

    1996-04-01

    Generalized corrosion of Alloy 800 under primary coolant conditions was investigated by measuring the average thickness of oxide layers grown after long isothermal exposures in the autoclaves located out of core in the Embalse Nuclear Power Plant and shorter exposures in laboratory static autoclaves. The films exhibited the familiar double layer structure but after long exposures the inner layer was found to be hidden by the formation of overlayers and/or by the deposition of species inevitably present in high temperature coolant. The samples exposed to the primary coolant showed greater average oxide thickness than those in the static autoclave studies, indicating the deposition of corrosion products from the coolant. Analysis of the films grown in static autoclaves showed the presence of hydrated species at the oxide/solution interface and spinel structures inside the film. Oxidized nickel was found only within few nanometers in the outermost layer of the films whereas elementary nickel predominated in the rest of the oxide.

  5. THE DEVELOPMENT OF MICROSTRUCTURAL DAMAGE DURING HIGH TEMPERATURE CREEP-FATIGUE OF A NICKEL ALLOY

    SciTech Connect

    L.J. Carroll; M.C. Carroll; C. Cabet; R.N. Wright

    2013-02-01

    Alloy 617 is the leading candidate material for an Intermediate Heat Exchanger (IHX) of the Very High Temperature Reactor (VHTR). To evaluate the behavior of this material in the expected service conditions, strain-controlled cyclic tests that include hold times up to 9000 s at maximum tensile strain were conducted at 950 degrees C. The fatigue resistance decreased when a hold time was added at peak tensile strain, owing to the mechanisms resulting in a change in fracture mode from transgranular in pure fatigue to intergranular in creep–fatigue. Increases in the tensile hold duration beyond an initial value were not detrimental to the creep–fatigue resistance. An analysis of the evolving failure modes was facilitated by interrupting tests during cycling for ex situ microstructural investigation.

  6. High temperature seals between ceramic separation membranes and super-alloy housing

    NASA Technical Reports Server (NTRS)

    Honea, G.; Sridhar, K. R.

    1991-01-01

    One of the concepts for oxygen production from Martian atmospheric carbon dioxide involves the use of tubular electrochemical membranes for oxygen separation. The tubular configuration offers the advantage of being able to separate the oxygen at pressures of up to 500 psi, thereby eliminating the need for a pre-liquefaction oxygen compressor. A key technology that has to be developed in order for the electrochemical separator to combine as a compressor is a high temperature static seal between the ceramic separation cell and the nickel-based super-alloy tube. Equipment was designed and fabricated to test the seals. Efforts are under way to develop a finite element model to study the thermal stresses at the joints and on the seal, and the optimal shape of the seal. The choice of seal materials and the technique to be used to fabricate the seals are also being investigated.

  7. Design of High Temperature Ti-Pd-Cr Shape Memory Alloys with Small Thermal Hysteresis

    PubMed Central

    Xue, Deqing; Yuan, Ruihao; Zhou, Yumei; Xue, Dezhen; Lookman, Turab; Zhang, Guojun; Ding, Xiangdong; Sun, Jun

    2016-01-01

    The large thermal hysteresis (ΔT) during the temperature induced martensitic transformation is a major obstacle to the functional stability of shape memory alloys (SMAs), especially for high temperature applications. We propose a design strategy for finding SMAs with small thermal hysteresis. That is, a small ΔT can be achieved in the compositional crossover region between two different martensitic transformations with opposite positive and negative changes in electrical resistance at the transformation temperature. We demonstrate this for a high temperature ternary Ti-Pd-Cr SMA by achieving both a small ΔT and high transformation temperature. We propose two possible underlying physics governing the reduction in ΔT. One is that the interfacial strain is accommodated at the austenite/martensite interface via coexistence of B19 and 9R martensites. The other is that one of transformation eigenvalues equal to 1, i.e., λ2 = 1, indicating a perfect coherent interface between austenite and martensite. Our results are not limited to Ti-Pd-Cr SMAs but potentially provide a strategy for searching for SMAs with small thermal hysteresis. PMID:27328764

  8. Design of High Temperature Ti-Pd-Cr Shape Memory Alloys with Small Thermal Hysteresis.

    PubMed

    Xue, Deqing; Yuan, Ruihao; Zhou, Yumei; Xue, Dezhen; Lookman, Turab; Zhang, Guojun; Ding, Xiangdong; Sun, Jun

    2016-01-01

    The large thermal hysteresis (ΔT) during the temperature induced martensitic transformation is a major obstacle to the functional stability of shape memory alloys (SMAs), especially for high temperature applications. We propose a design strategy for finding SMAs with small thermal hysteresis. That is, a small ΔT can be achieved in the compositional crossover region between two different martensitic transformations with opposite positive and negative changes in electrical resistance at the transformation temperature. We demonstrate this for a high temperature ternary Ti-Pd-Cr SMA by achieving both a small ΔT and high transformation temperature. We propose two possible underlying physics governing the reduction in ΔT. One is that the interfacial strain is accommodated at the austenite/martensite interface via coexistence of B19 and 9R martensites. The other is that one of transformation eigenvalues equal to 1, i.e., λ2 = 1, indicating a perfect coherent interface between austenite and martensite. Our results are not limited to Ti-Pd-Cr SMAs but potentially provide a strategy for searching for SMAs with small thermal hysteresis. PMID:27328764

  9. 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.

  10. Development of a Numerical Model for High-Temperature Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

    DeCastro, Jonathan A.; Melcher, Kevin J.; Noebe, Ronald D.; Gaydosh, Darrell J.

    2006-01-01

    A thermomechanical hysteresis model for a high-temperature shape memory alloy (HTSMA) actuator material is presented. The model is capable of predicting strain output of a tensile-loaded HTSMA when excited by arbitrary temperature-stress inputs for the purpose of actuator and controls design. Common quasi-static generalized Preisach hysteresis models available in the literature require large sets of experimental data for model identification at a particular operating point, and substantially more data for multiple operating points. The novel algorithm introduced here proposes an alternate approach to Preisach methods that is better suited for research-stage alloys, such as recently-developed HTSMAs, for which a complete database is not yet available. A detailed description of the minor loop hysteresis model is presented in this paper, as well as a methodology for determination of model parameters. The model is then qualitatively evaluated with respect to well-established Preisach properties and against a set of low-temperature cycled loading data using a modified form of the one-dimensional Brinson constitutive equation. The computationally efficient algorithm demonstrates adherence to Preisach properties and excellent agreement to the validation data set.

  11. Creep and Environmental Effects on High Temperature Creep-Fatigue Behavior of Alloy 617

    SciTech Connect

    L. J. Carroll; C. Cabet; R. Madland; R. Wright

    2011-06-01

    Alloy 617 is the leading candidate material for Intermediate Heat Exchanger (IHX) of a Very High Temperature Reactor (VHTR), expected to have an outlet temperature as high as 950 C. System start-ups and shut-downs as well as power transients will produce low cycle fatigue (LCF) loadings of components. Acceptance of Alloy 617 in Section III of the ASME Code for nuclear construction requires a detailed understanding of the creep-fatigue behavior in both air and impure helium, representative of the VHTR primary coolant. Strain controlled LCF tests including hold times at maximum tensile strain were conducted at total strain range of 0.3% in air at 950 C. Creep-fatigue testing was also performed in a simulated VHTR impure helium coolant for selected experimental conditions. The fatigue resistance decreased when a hold time was added at peak tensile stress, consistent with the observed change in fracture mode from transgranular to intergranular with introduction of a tensile hold. Increases in the tensile hold time, beyond 180 sec, was not detrimental to the creep-fatigue resistance. Grain boundary damage in the form of grain boundary cracking was present in the bulk of the creep-fatigue specimens. This bulk cracking was quantified and found to be similar for hold times of up to 1800 sec consistent with the saturation in failure lives and rapid stress relaxation observed during the creep portion of the creep-fatigue cycle.

  12. Static rock splitters based on high temperature shape memory alloys for planetary explorations

    NASA Astrophysics Data System (ADS)

    Benafan, O.; Noebe, R. D.; Halsmer, T. J.

    2016-01-01

    A static rock splitter device based on high-force, high-temperature shape memory alloys (HTSMAs) was developed for space related applications requiring controlled geologic excavation in planetary bodies such as the moon, Mars, and near-Earth asteroids. The device, hereafter referred to as the shape memory alloy rock splitter (SMARS), consisted of active (expanding) elements made of Ni50.3Ti29.7Hf20 (at%) that generate extremely large forces in response to thermal input. The pre-shaping (training) of these elements was accomplished using isothermal, isobaric and cyclic training methods, which resulted in active components capable of generating stresses in excess of 1.5 GPa. The corresponding strains (or displacements) were also evaluated and were found to be 2-3%, essential to rock fracturing and/or splitting when placed in a borehole. SMARS performance was evaluated using a testbed consisting of a temperature controller, custom heaters and heater holders, and an enclosure for rock placement and breakage. The SMARS system was evaluated using various rock types including igneous rocks (e.g., basalt, quartz, granite) and sedimentary rocks (e.g., sandstone, limestone).

  13. Permeation of hydrogen in hastelloy C-276 alloy at high temperature

    SciTech Connect

    Zhang, D.; Liu, W.; Qian, Y.; Que, J.

    2015-03-15

    Tritium is generated by the interaction of neutrons with the lithium and beryllium in the molten salt reactors (MSRs), which use FLiBe as one of solvents of fluoride fuel. Tritium as by-product in the MSRs is an important safety issue because it could easily diffuse into environment through high temperature heat exchangers. The experimental technique of gas driven permeation has been used to investigate the transport parameter of hydrogen in Hastelloy C-276 which is considered as one of the candidate for structure materials. The measurements were carried out at the temperature range of 400-800 Celsius degrees with hydrogen loading pressures ranging from 5*10{sup 3} to 4*10{sup 4} Pa. The H diffusive transport parameters for Hastelloy C-276 follow an Arrhenius law in this temperature range. Regarding diffusivity and Sieverts' constant, Hastelloy C-276 has lower values compared with Ni201 alloy. The possible reason may be the trapping effects, which were formed by the alloying elements of Mo and Cr in the matrix. At the same time, the thin oxidation layer formed by the high Cr content could lead to a slower dissociation process of H{sub 2} at the surface. (authors)

  14. High-temperature corrosion behavior of coatings and ODS alloys based on Fe{sub 3}Al

    SciTech Connect

    Tortorelli, P.F.; Pint, B.A.; Wright, I.G.

    1996-06-01

    Iron aluminides containing greater than about 20-25 @ % Al have oxidation/sulfidation resistance at temperatures well above those at which these alloys have adequate mechanical strength. In addition to alloying modifications for improved creep resistance of wrought material, this strength limitation is being addressed by development of oxide-dispersion- strengthened (ODS) iron aluminides and by evaluation of Fe{sub 3}Al alloy compositions as coatings or claddings on higher-strength, less corrosion-resistant materials. As part of these efforts, the high-temperature corrosion behavior of iron-aluminide weld overlays and ODS alloys is being characterized and compared to previous results for ingot-processed material.

  15. Processing of Ni30Pt20Ti50 High-Temperature Shape-Memory Alloy Into Thin Rod Demonstrated

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald D.; Draper, Susan L.; Biles, Tiffany A.; Leonhardt, Todd

    2005-01-01

    High-temperature shape-memory alloys (HTSMAs) based on nickel-titanium (NiTi) with significant ternary additions of palladium (Pd), platinum (Pt), gold (Au), or hafnium (Hf) have been identified as potential high-temperature actuator materials for use up to 500 C. These materials provide an enabling technology for the development of "smart structures" used to control the noise, emissions, or efficiency of gas turbine engines. The demand for these high-temperature versions of conventional shape-memory alloys also has been growing in the automotive, process control, and energy industries. However these materials, including the NiPtTi alloys being developed at the NASA Glenn Research Center, will never find widespread acceptance unless they can be readily processed into useable forms.

  16. Low temperature magnetic transition and high temperature oxidation in INCONEL alloy 718

    SciTech Connect

    Seehra, M.S.; Babu, V.S.

    1996-05-01

    X-ray diffraction and temperature dependent (5 K{endash}380 K) magnetic measurements have been carried out in INCONEL 718 superalloy before and after high temperature aging treatments (INCONEL is a trademark of the INCO family of companies). The nominal composition of this alloy is Ni (52.5{percent}), Cr (19.0{percent}), Fe (18.5{percent}), Nb (5.1{percent}), Mo (3.0{percent}), Ti (0.9{percent}), Al (0.5{percent}), Cu (0.15{percent}) and C (0.08{percent}) and it yields an x-ray diffraction pattern consisting of a fcc phase with {ital a}=3.5987 (3) A and an orthorhombic phase associated with {delta}{minus}Ni{sub 3}Nb. It is concluded that the fcc pattern is due to both the {gamma} austenitic phase and {gamma}{prime} Ni{sub 3}(Al,Ti) phase of alloy 718. The standard annealing and aging treatment carried out in air at temperatures between 621 and 982{degree}C produces surface oxides (Cr,Fe){sub 2}O{sub 3} and FeNbO{sub 4} (which are easily removed by etching and polishing) and contracts the lattice. Magnetic measurements show a distinct phase transition at {ital T}{sub {ital c}}=14 K, which has been attributed to the {gamma}{prime}{minus}Ni{sub 3}(Al,Ti) phase by the process of elimination and by observing that it has most of the characteristics of the weak itinerant ferromagnet Ni{sub 74.5}Al{sub 25.5}. This transition may have some effects on the cryogenic applications of this alloy. {copyright} {ital 1996 Materials Research Society.}

  17. Structural properties and high-temperature reactions of the metastable Ω phase in Zr Nb alloys

    NASA Astrophysics Data System (ADS)

    Aurelio, Gabriela; Fernández Guillermet, Armando; Cuello, Gabriel J.; Campo, Javier

    2005-05-01

    This article presents an experimental study and a systematic phenomenological analysis of the structural properties and the high-temperature reactions of the Ω phase formed by quenching ('q') bcc (β) Zr-Nb alloys. In the first part of the work an extensive database with lattice parameters (LPs) for the Ω q and the untransformed β q phase is developed on the basis of neutron diffraction measurements. Various striking features of the LP vs. composition relations are detected, and a new method of analysis is applied which involves the concept of a 'reference behavior' (RB) describing the probable properties of each individual phase if it were unaffected by the other structures in the heterogeneous alloys. In this way, a detailed evaluation is performed of the effects of Ω q/β q coherence strains upon the LPs of these two phases. In the second part of the work, neutron thermodiffraction studies are reported of the structural properties of the Ω q + β q two-phase alloys at 300 K ⩽ T ⩽ 650 K. Extensive LP vs. time results are discussed. On this basis, the structural properties of the Ω a phase formed isothermally upon aging ('a') are established, and compared with those of the Ω q phase. In addition, new information is discussed on the evolution of the Ω a + β a system toward thermodynamic equilibrium. Moreover, it is shown how the present method of analysis may also be used to obtain indirect information of both theoretical and practical interest. In particular, considerable evidence is presented indicating that the Nb content of the Ω a phase decreases upon aging whereas that of β a increases. Finally, it is shown how these composition changes might be used to reconcile much of the long-standing conflicting reports concerning the structural properties of the Ω q and Ω a metastable phases.

  18. Candidate alloys for cost-effective, high-efficiency, high-temperature compact/foil heat-exchangers

    SciTech Connect

    Evans, Neal D; Maziasz, Philip J; Shingledecker, John P; Pint, Bruce A; Yamamoto, Yukinori

    2007-01-01

    Solid oxide fuel cell (SOFC) and molten carbonate fuel cell (MCFC) systems operate at high temperatures (up to 1000 C and 650 C, respectively), which makes them especially attractive sources for combined heat and power (CHP) cogeneration. However, improvements in the efficiency of heat exchange in these fuel cells require both development and careful processing of advanced cost-effective alloys for use in such high-temperature service conditions. The high-temperature properties of both sheet and foil forms of several alloys being considered for use in compact heat-exchangers (recuperators) have been characterized. Mechanical and creep-rupture testing, oxidation studies, and microstructural studies have been performed on commercially available sheet and foil forms of alloy 347, alloys 625, HR230, HR120, and the new AL20-25+Nb. These studies have led to a mechanistic understanding of the responses of these alloys to anticipated service conditions, and suggest that these alloys developed for gas- and micro-turbine recuperator applications are also suitable for use in fuel cell heat-exchangers. Additional work is still required to achieve foil forms with creep life comparable to thicker-section wrought product forms of the same alloys.

  19. Substitution of ceramics for high temperature alloys. [advantages of using silicon carbides and silicon nitrides in gas turbine engines

    NASA Technical Reports Server (NTRS)

    Probst, H. B.

    1978-01-01

    The high temperature capability of ceramics such as silicon nitride and silicon carbide can result in turbine engines of improved efficiency. Other advantages when compared to the nickel and cobalt alloys in current use are raw material availability, lower weight, erosion/corrosion resistance, and potentially lower cost. The use of ceramics in three different sizes of gas turbine is considered; these are the large utility turbines, advanced aircraft turbines, and small automotive turbines. Special consideration, unique to each of these applications, arise when one considers substituting ceramics for high temperature alloys. The effects of material substitutions are reviewed in terms of engine performance, operating economy, and secondary effects.

  20. Corrosion behavior of Ni and Ni-based alloys in concentrated NaOH solutions at high temperatures

    SciTech Connect

    Yasuda, M.; Fukumoto, K.; Ogata, Y.; Hine, F.

    1988-12-01

    Corrosion behavior of SUS 310S austenitic stainless steel, Alloy 600, Monel 400, and Ni 200 and NaOH solutions in the concentration range 30-60% at high temperatures up to 166/sup 0/C was studied. In solutions containing dissolved oxygen or under oxidizing conditions, all the specimens examined were corroded seriously due to oxygen diffusion through the porous oxide layer consisting of ..beta..-Ni(OH)/sub 2/. In hydrogen-saturated solutions, on the other hand, these Ni alloys were corrosion resistant because nickel in the alloys was active to oxidation of hydrogen. The specimens were corroded by deaerated solution at high temperatures in which hydrogen evolution took place as the counterreaction. The corrosion rate controlled by the hydrogen formation reaction increased exponentially with the decrease of the Ni content in the alloy.

  1. Application of neutron diffraction in characterization of texture evolution during high-temperature creep in magnesium alloys

    SciTech Connect

    Vogel, Sven C; Sediako, Dimitry; Shook, S; Sediako, A

    2010-01-01

    A good combination of room-temperature and elevated temperature strength and ductility, good salt-spray corrosion resistance and exceUent diecastability are frequently among the main considerations in development of a new alloy. Unfortunately, there has been much lesser effort in development of wrought-stock alloys for high temperature applications. Extrudability and high temperature performance of wrought material becomes an important factor in an effort to develop new wrought alloys and processing technologies. This paper shows some results received in creep testing and studies of in-creep texture evolution for several wrought magnesium alloys developed for use in elevated-temperature applications. These studies were performed using E3 neutron spectrometer of the Canadian Neutron Beam Centre in Chalk River, ON, and HIPPO time-of-flight (TOF) spectrometer at Los Alamos Neutron Science Center, NM.

  2. 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.

  3. Aerospace Patented High-Strength Aluminum Alloy Used in Commercial Industries

    NASA Technical Reports Server (NTRS)

    2004-01-01

    NASA structural materials engineer, Jonathan Lee, displays blocks and pistons as examples of some of the uses for NASA's patented high-strength aluminum alloy originally developed at Marshall Space Flight Center in Huntsville, Alabama. NASA desired an alloy for aerospace applications with higher strength and wear-resistance at elevated temperatures. The alloy is a solution to reduce costs of aluminum engine pistons and lower engine emissions for the automobile industry. The Boats and Outboard Engines Division at Bombardier Recreational Products of Sturtevant, Wisconsin is using the alloy for pistons in its Evinrude E-Tec outboard engine line.

  4. Evaluation of Sc-Bearing Aluminum Alloy C557 for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Domack, Marcia S.; Dicus, Dennis L.

    2002-01-01

    The performance of the Al-Mg-Sc alloy C557 was evaluated to assess its potential for a broad range of aerospace applications, including airframe and launch vehicle structures. Of specific interest were mechanical properties at anticipated service temperatures and thermal stability of the alloy. Performance was compared with conventional airframe aluminum alloys and with other emerging aluminum alloys developed for specific service environments. Mechanical properties and metallurgical structure were evaluated for commercially rolled sheet in the as-received H116 condition and after thermal exposures at 107 C. Metallurgical analyses were performed to de.ne grain morphology and texture, strengthening precipitates, and to assess the effect of thermal exposure.

  5. 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.

  6. Effect of multiaxial stresses on the high-temperature behavior and rupture of advanced alloys

    NASA Astrophysics Data System (ADS)

    Johnson, Nancy Louise

    1998-05-01

    The evolution and effect of multiaxial stress states on the high temperature deformation and rupture behavior of materials with non-uniform microstructures has been investigated. Through a detailed description of the role that multiaxial stresses play on damage evolution and rupture, the abundant existing data for uniaxial rupture can be used to more successfully design for the life of high temperature components. Three dimensional finite element calculations of primary creep deformation were performed for particulate reinforced metal matrix composites under a variety of multiaxial loading conditions. A quasi-steady state stress distribution develops during primary creep for each of the conditions considered. The results indicate that higher stresses exist in regions above and below the particles and accommodate the development of creep damage. The nature of the stress state within these regions is not significantly altered by the presence of the particles. The strain fields show a distribution similar to the stress fields. Despite significantly large regions of enhanced stress, the overall creep strain rates for all models are decreased by the presence of the particles. The applied effective stress does not have a unique relationship with overall effective strain rate for particulate reinforced composites under different applied stress states. The failure of sections of turbine rotor disks formed from the superalloy V-57 which operate under highly multiaxial stresses has been investigated. Optical microscopy of a turbine rotor disk removed from service after 30,000 hrs showed an intergranular crack that initiated at the root of a fir-tree turbine rotor blade attachment. Transmission electron microscopy studies showed heavy grain boundary oxidation that could account for the cracking and failure of the rotor disks. Heat treatments of a TiAl alloy have been established for producing a microstructure suitable for high temperature multiaxial rupture testing. The

  7. Flow and failure of an aluminium alloy from low to high temperature and strain rate

    NASA Astrophysics Data System (ADS)

    Sancho, Rafael; Cendón, David; Gálvez, Francisco

    2015-09-01

    The mechanical behaviour of an aluminium alloy is presented in this paper. The study has been carried out to analyse the flow and failure of the aluminium alloy 7075-T73. An experimental study has been planned performing tests of un-notched and notched tensile specimens at low strain rates using a servo-hydraulic machine. High strain rate tests have been carried out using the same geometry in a Hopkinson Split Tensile Bar. The dynamic experiments at low temperature were performed using a cryogenic chamber, and the high temperature ones with a furnace, both incorporated to the Hopkinson bar. Testing temperatures ranged from - 50 ∘C to 100 ∘C and the strain rates from 10-4 s-1 to 600 s-1. The material behaviour was modelled using the Modified Johnson-Cook model and simulated using LS-DYNA. The results show that the Voce type of strain hardening is the most accurate for this material, while the traditional Johnson-Cook is not enough accurate to reproduce the necking of un-notched specimens. The failure criterion was obtained by means of the numerical simulations using the analysis of the stress triaxiality versus the strain to failure. The diameters at the failure time were measured using the images taken with an image camera, and the strain to failure was computed for un-notched and notched specimens. The numerical simulations show that the analysis of the evolution of the stress triaxiality is crucial to achieve accurate results. A material model using the Modified Johnson-Cook for flow and failure is proposed.

  8. Effects of Cryogenic Treatment on the Residual Stress and Mechanical Properties of an Aerospace Aluminum Alloy

    NASA Technical Reports Server (NTRS)

    Chen, Po; Malone, Tina; Bod, Robert; Torres, Pablo

    2000-01-01

    Investigators at Marshall Space Flight Center (MSFC) are studying the potential benefits of cryogenic treatment for aerospace Aluminum (Al) alloys. This paper reports the effects of cryogenic treatment on residual stress, tensile strength, hardness, fatigue life, and stress corrosion cracking (SCC) resistance.

  9. Effects of Cryogenic Treatment on the Residual Stress and Mechanical Properties of an Aerospace Aluminum Alloy

    NASA Technical Reports Server (NTRS)

    Chen, P.; Malone, T.; Bond, R.; Torres, P.

    2001-01-01

    Investigators at Marshall Space Flight Center (MSFC) are studying the potential benefits of cryogenic treatment for aerospace Aluminum (Al) alloys. This paper reports the effects of cryogenic treatment on residual stress, tensile strength, hardness, fatigue life, and stress corrosion cracking (SCC) resistance.

  10. Structure and high temperature oxidation of mechanical alloyed Fe-Al coating

    NASA Astrophysics Data System (ADS)

    Aryanto, Didik; Sudiro, Toto; Wismogroho, Agus S.

    2016-04-01

    The structure and high temperature oxidation resistance of Fe-Al coating on low carbon steel were investigated. The Fe-Al coating was deposited on the surface of low carbon steel using a mechanical alloying method. The coating was then annealed at 600°C for 2 hour in a vacuum of 5 Pa. The cyclic-oxidation tests of low carbon steel, Fe-Al coatings with and without annealing were performed at 600°C for up to 60h in air. The structure of oxidized samples was studied by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy X-ray spectroscopy (EDS). The results show that the Fe-Al coatings exhibit high oxidation resistance compared to the uncoated steel. After 60 h exposure, the uncoated steel formed mainly Fe3O4 and Fe2O3 layers with the total thickness of around 75.93 µm. Fe-Al coating without annealing formed a thin oxide layer, probably (Fe,Al)2O3. Meanwhile, for annealed sample, EDX analysis observed the formation of two Fe-Al layers with difference in elements concentration. The obtained results suggest that the deposition of Fe-Al coating on low carbon steel can improve the oxidation resistance of low carbon steel.

  11. The nano-particle dispersion strengthening of V-4Cr-4Ti alloys for high temperature application in fusion reactors

    NASA Astrophysics Data System (ADS)

    Zheng, Pengfei; Chen, Jiming; Xu, Zengyu; Duan, Xuru

    2013-10-01

    V-4Cr-4Ti was identified as an attractive structural material for Li blanket in fusion reactors. However, both high temperature and irradiation induced degradation are great challenges for this material. It was thought that the nano-particles with high thermal stability can efficiently strengthen the alloy at elevated temperatures, and accommodate the irradiation induced defects at the boundaries. This study is a starting work aiming at improving the creep resistance and reducing the irradiation induced degradation for V-4Cr-4Ti alloy. Currently, we focus on the preparation of some comparative nano-particle dispersion strengthened V-4Cr-4Ti alloys. A mechanical alloying (MA) route is used to fabricate yttrium and carbides added V-4Cr-4Ti alloys. Nano-scale yttria, carbides and other possible particles have a combined dispersion-strengthening effect on the matrices of these MA-fabricated V-4Cr-4Ti alloys. High-temperature annealing is carried out to stabilize the optimized nano-particles. Mechanical properties are tested. Microstructures of the MA-fabricated V-4Cr-4Ti alloys with yttrium and carbide additions are characterized. Based on these results, the thermal stability of different nano-particle agents are classified. ITER related China domestic project 2011GB108007.

  12. 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.

  13. High Temperature - Thin Film Strain Gages Based on Alloys of Indium Tin Oxide

    NASA Technical Reports Server (NTRS)

    Gregory, Otto J.; Cooke, James D.; Bienkiewicz, Joseph M.

    1998-01-01

    A stable, high temperature strain gage based on reactively sputtered indium tin oxide (ITO) was demonstrated at temperatures up to 1050 C. These strain sensors exhibited relatively large, negative gage factors at room temperature and their piezoresistive response was both linear and reproducible when strained up to 700 micro-in/in. When cycled between compression and tension, these sensors also showed very little hysteresis, indicating excellent mechanical stability. Thin film strain gages based on selected ITO alloys withstood more than 50,000 strain cycles of +/- 500 micro-in/in during 180 hours of testing in air at 1000 C, with minimal drift at temperature. Drift rates as low as 0.0009%/hr at 1000 C were observed for ITO films that were annealed in nitrogen at 700 C prior to strain testing. These results compare favorably with state of the art 10 micro-m thick PdCr films deposited by NASA, where drift rates of 0.047%/hr at 1050 C were observed. Nitrogen annealing not only produced the lowest drift rates to date, but also produce the largest dynamic gage factors (G = 23.5). These wide bandgap, semiconductor strain sensors also exhibited moderately low temperature coefficients of resistance (TCR) at temperatures up to 1100 C, when tested in a nitrogen ambient. A TCR of +230 ppm/C over the temperature range 200 C < T < 500 C and a TCR of -469 ppm/C over the temperature range 600 C < T < 1100 C was observed for the films tested in nitrogen. However, the resistivity behavior changed considerably when the same films were tested in oxygen ambients. A TCR of -1560 ppm/C was obtained over the temperature range of 200 C < T < 1100 C. When similar films were protected with an overcoat or when ITO films were prepared with higher oxygen contents in the plasma, two distinct TCR's were observed. At T < 800 C, a linear TCR of -210 ppm/C was observed and at T > 800 C, a linear TCR of -2170 DDm/C was observed. The combination of a moderately low TCR and a relatively large gage

  14. MHD technologies for electroslag welding and melting of titanium alloys for aerospace industry

    NASA Astrophysics Data System (ADS)

    Shcherbinin, E.; Kompan, Ya.

    2006-09-01

    The basic tendency in improving titanium alloys is the need to increase the specific strength of structures of the aerospace engineering. Owing to the strength of advanced alloys Ti­10­2­3 (the USA) and VT22 (Russia), reaching 1300­1400 MPA, titanium is used widely in the load­carrying airframes and most loaded parts of engines of the modern airplanes "Boeing", "Airbus", "Antonov", "Ilyushin ", and others. At present, the problem is to develop alloys with a tensile strength of 1600 MPa and higher. Figs 2, Refs 6.

  15. Thermal conductivity, electrical resistivity, and thermopower of aerospace alloys from 4 to 300 K.

    NASA Technical Reports Server (NTRS)

    Hust, J. G.; Weitzel, D. H.; Powell, R. L.

    1971-01-01

    Measurement of thermal conductivity, electrical resistivity, and thermopower for several aerospace alloys: titanium alloy A110-AT, aluminum alloy 7039, Inconel 718, and Hastelloy X. Tables and graphs of the measured properties and Lorenz ratio are presented over the range from 4 to 300 K. Comparisons to other measurements and theoretical analysis of the data are included. The uncertainties of the property data are estimated as 0.7 to 2.5% for thermal conductivity, 0.25% in electrical resistivity, and about 0.1 microvolt/K in thermopower.

  16. High-temperature corrosion and wear properties of HVOF coatings of cobalt-based (CoCr) surfacing alloys

    SciTech Connect

    Raghu, D.; Lee, D.A.; Singh, P.M.

    1999-07-01

    High Velocity Oxy-Fuel (HVOF) thermal spraying is extensively used in industry to produce high-density, low porosity functional coatings to resist severe wear and corrosion. Increasingly there is a need to provide high-quality coatings that resist both wear and corrosion at high temperatures at the same time. Very few engineering data exist on such coatings. In this paper, a study of HVOF coatings of Co-Cr-Mo alloys, that relies on Laves phases or on carbides for wear and corrosion resistance is reported. The paper covers the basic metallurgy of the alloys, their design and microstructure. The oxidation and sulfidation resistances of the coatings are evaluated at 600 C. The high-temperature hardness and the room-temperature abrasion resistance, hardness and bond strengths are compared to assess their utility in high-temperature corrosion and wear-resistant applications. The test results indicate that these alloys are strong candidate materials for providing protection in the form of HVOF coatings, in high-temperature wear and corrosion environments.

  17. Interaction of a near-{alpha} type titanium alloy with NiCrAlY protective coating at high temperatures

    SciTech Connect

    Liu, H.; Hao, S.; Wang, X.; Feng, Z.

    1998-10-13

    MCrAlY coatings possess the properties of not only excellent oxidation and hot corrosion resistance but also sufficient toughness. This is why they have been commercially used on superalloys for several decades. Nevertheless, investigations revealed that there might be violent interactions between this kind of coating and titanium based alloys at high temperatures. This chemical incompatibility may promote the growth of brittle phases along the substrate/coating interface and thus deteriorates the mechanical properties. An effective barrier layer was desired to be sandwiched between the MCrAlY coating and Ti substrate to weaken the interdiffusion and chemical reactions. Ti60 is a near {alpha} type alloy intended to be used at 600 C. The interaction between this alloy and a NiCrAlY coating has never been investigated. Actually, in addition to the service at high temperature, another high temperature process, i.e., the post heat treatment in vacuum, is generally needed for the MCrAlY coating to eliminate possible defects within the received PVD coatings. Hence, the investigation on the interfacial stability of a Ti60/MCrAlY system at high temperatures is of importance in both theoretical and practical meanings. This paper is aimed at observing the interfacial reactions of this system at various temperatures in excess of 600 C. The obtained data may be useful in further work on optimizing the post treatment parameters and developing new coating systems with barrier interlayer.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    1994-03-01

    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.

  20. 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.

  1. A high-temperature shape memory alloy sensor for combustion monitoring and control

    NASA Astrophysics Data System (ADS)

    Shaw, Greg S.; Snyder, Joseph T.; Prince, Troy S.; Willett, Michael C.

    2005-05-01

    Innovations in the use of thin film SMA materials have enabled the development of a harsh environment pressure sensor useful for combustion monitoring and control. Development of such active combustion control has been driven by rising fuel costs and environmental pressures. Active combustion control, whether in diesel, spark ignited or turbine engines requires feedback to the engine control system in order to adjust the quantity, timing, and placement of fuel charges. To be fully effective, sensors must be integrated into each engine in a manner that will allow continuous combustion monitoring (turbine engines) or monitoring of each discrete combustion event (diesel and SI engines). To date, the sensors available for detection of combustion events and processes have suffered from one or more of three problems: 1) Low sensitivity: The sensors are unable to provide and adequate signal-to-noise ratio in the high temperature and electrically noisy environment of the engine compartment. Attempts to overcome this difficulty have focused on heat removal and/or temperature compensation or more challenging high temperature electronics. 2) Low reliability: Sensors and/or sensor packages have been unable to withstand the engine environment for extended periods of time. Issues have included gross degradation and more subtle issues such as migration of dopants in semiconductor sensor materials. 3) High cost: The materials that have been used, the package concepts employed, and the required support electronics have all contributed to the high cost of the few sensor systems available. Prices have remained high due to the limited demand associated with the poor reliability and the high price itself. Ternary titanium nickel alloys, with platinum group metal substitution for the nickel, are deposited as thin films on MEMS-based diaphragms and patterned to form strain gages of a standard metal film configuration. The strain induced phase transformation of the SMA is used as a

  2. High-temperature electronics

    NASA Technical Reports Server (NTRS)

    Matus, Lawrence G.; Seng, Gary T.

    1990-01-01

    To meet the needs of the aerospace propulsion and space power communities, the high temperature electronics program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. This program supports a major element of the Center's mission - to perform basic and developmental research aimed at improving aerospace propulsion systems. Research is focused on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of SiC devices.

  3. High-temperature electronics

    NASA Astrophysics Data System (ADS)

    Matus, Lawrence G.; Seng, Gary T.

    1990-02-01

    To meet the needs of the aerospace propulsion and space power communities, the high temperature electronics program at the Lewis Research Center is developing silicon carbide (SiC) as a high temperature semiconductor material. This program supports a major element of the Center's mission - to perform basic and developmental research aimed at improving aerospace propulsion systems. Research is focused on developing the crystal growth, characterization, and device fabrication technologies necessary to produce a family of SiC devices.

  4. High temperature mechanical properties of a zirconium-modified, precipitation- strengthened nickel, 30 percent copper alloy

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1974-01-01

    A precipitation-strengthened Monel-type alloy has been developed through minor alloying additions of zirconium to a base Ni-30Cu alloy. The results of this exploratory study indicate that thermomechanical processing of a solution-treated Ni-30Cu-0.2Zr alloy produced a dispersion of precipitates. The precipitates have been tentatively identified as a Ni5Zr compound. A comparison of the mechanical properties, as determined by testing in air, of the zirconium-modified alloy to those of a Ni-30Cu alloy reveals that the precipitation-strengthened alloy has improved tensile properties to 1200 K and improved stress-rupture properties to 1100 K. The oxidation characteristics of the modified alloy appeared to be equivalent to those of the base Ni-30Cu alloy.

  5. Influence of Crucible Materials on High-temperature Properties of Vacuum-melted Nickel-chromium-cobalt Alloy

    NASA Technical Reports Server (NTRS)

    Decker, R F; Rowe, John P; Freeman, J W

    1957-01-01

    A study of the effect of induction-vacuum-melting procedure on the high-temperature properties of a titanium-and-aluminum-hardened nickel-base alloy revealed that a major variable was the type of ceramic used as a crucible. Reactions between the melt and magnesia or zirconia crucibles apparently increased high-temperature properties by introducing small amounts of boron or zirconium into the melts. Heats melted in alumina crucibles had relatively low rupture life and ductility at 1,600 F and cracked during hot-working as a result of deriving no boron or zirconium from the crucible.

  6. Possibility of enhancement of the high-temperature strength and the heat resistance of a nickel aluminide-based structural intermetallic alloy

    NASA Astrophysics Data System (ADS)

    Bazyleva, O. A.; Shestakov, A. V.; Arginbaeva, E. G.; Turenko, E. Yu.

    2016-01-01

    The assimilation of a number of rare-earth metals (REM = praseodymium, neodymium, erbium) in a cast high-temperature nickel aluminide-based intermetallic alloy and the effect of REM alloying of the alloy on the critical temperatures, the high-temperature strength, and the heat resistance (time to failure) of the structural alloy are studied. It is shown that the heat resistance and the time to failure of the alloy at 1200°C can be increased by microalloying of the intermetallic alloy with REM.

  7. Thermal oxidation induced degradation of carbon fiber reinforced composites and carbon nanotube sheet enhanced fiber/matrix interface for high temperature aerospace structural applications

    NASA Astrophysics Data System (ADS)

    Haque, Mohammad Hamidul

    Recent increase in the use of carbon fiber reinforced polymer matrix composite, especially for high temperature applications in aerospace primary and secondary structures along with wind energy and automotive industries, have generated new challenges to predict its failure mechanisms and service life. This dissertation reports the experimental study of a unidirectional carbon fiber reinforced bismaleimide (BMI) composites (CFRC), an excellent candidate for high temperature aerospace components, undergoing thermal oxidation at 260 °C in air for over 3000 hours. The key focus of the work is to investigate the mechanical properties of the carbon fiber BMI composite subjected to thermal aging in three key aspects - first, studying its bulk flexural properties (in macro scale), second, characterizing the crack propagation along the fiber direction, representing the interfacial bonding strength between fiber and matrix (in micro scale), and third, introducing nano-structured materials to modify the interface (in nano scale) between the carbon fiber and BMI resin and mechanical characterization to study its influence on mitigating the aging effect. Under the first category, weight loss and flexural properties have been monitored as the oxidation propagates through the fiber/matrix interface. Dynamic mechanical analysis and micro-computed tomography analysis have been performed to analyze the aging effects. In the second category, the long-term effects of thermal oxidation on the delamination (between the composite plies) and debonding (between fiber and matrix) type fracture toughness have been characterized by preparing two distinct types of double cantilever beam specimens. Digital image correlation has been used to determine the deformation field and strain distribution around the crack propagation path. Finally the resin system and the fiber/matrix interface have been modified using nanomaterials to mitigate the degradations caused by oxidation. Nanoclay modified

  8. Corrosion of high temperature alloys in solar salt at 400, 500, and 680%C2%B0C.

    SciTech Connect

    Kruizenga, Alan Michael; Gill, David Dennis; LaFord, Marianne Elizabeth

    2013-09-01

    Corrosion tests at 400, 500, and 680%C2%B0C were performed using four high temperature alloys; 347SS, 321SS In625, and HA230. Molten salt chemistry was monitored over time through analysis of nitrite, carbonate, and dissolved metals. Metallography was performed on alloys at 500 and 680%C2%B0C, due to the relatively thin oxide scale observed at 400%C2%B0C. At 500%C2%B0C, corrosion of iron based alloys took the form of chromium depletion and iron oxides, while nickel based alloys also had chromium depletion and formation of NiO. Chromium was detected in relatively low concentrations at this temperature. At 680%C2%B0C, significant surface corrosion occurred with metal losses greater than 450microns/year after 1025hours of exposure. Iron based alloys formed complex iron, sodium, and chromium oxides. Some data suggests grain boundary chromium depletion of 321SS. Nickel alloys formed NiO and metallic nickel corrosion morphologies, with HA230 displaying significant internal oxidation in the form of chromia. Nickel alloys both exhibited worse corrosion than iron based alloys likely due to preferential dissolution of chromium, molybdenum, and tungsten.

  9. Fatigue strength of high-temperature alloys under conditions of cyclic temperature variation. Communication 1: Experimental procedure and results

    NASA Astrophysics Data System (ADS)

    Troshchenko, V. T.; Gryaznov, B. A.; Yamshanov, Yu. B.

    1994-03-01

    Determination of the serviceability of the material of gas-turbine engine blades, one of the most loaded elements of the engine, critical for the reliability of the turbine, is discussed. The NUM-3 setup, intended for studying fatigue strength of high-temperature alloys under conditions simulating service ones, is briefly described. The results of the investigation into the fatigue of alloys EP962 and EI698 under isothermal conditions and complex thermal-mechanical loading are presented. The analysis of the findings revealed a number of regularities in the effect of thermal cycling and resulting varying thermal stresses on the fatigue strength of the materials studied.

  10. Microstructure and High Temperature Oxidation Behavior of Cr-W Alloys

    SciTech Connect

    Dogan, O.N.

    2007-02-01

    Cr alloys containing 0-30%W by weight were investigated for use in elevated temperature applications. The alloys were melted in a water-cooled, copper-hearth arc furnace. Microstructure of the alloys was characterized using x-ray diffraction, scanning electron microscopy, and light microscopy. A pseudocyclic oxidation test was employed to study scale formation at 1000ºC in dry air. The scale was predominantly chromia and spalled upon cooling. Alloying with aluminum up to 8 weight percent reduced the spalling drastically. Furthermore, aluminizing the surface of the Cr-W alloys completely stopped the spalling.

  11. Effect of carbon content on high temperature tensile properties of Fe{sub 3}Al based intermetallic alloys

    SciTech Connect

    Baligidad, R.G.; Prakash, U.; Radhakrishna, A.; Rao, V.R.; Rao, P.K.; Ballal, N.B.

    1997-01-01

    Ordered intermetallic alloys based on the iron aluminide Fe{sub 3}Al are being considered for high temperature structural applications. Though these alloys exhibit poor room temperature ductility and low fracture toughness, significant improvement in these respects can be achieved by alloying addition and process control. Most of the reported literature is on compositions with very low (<0.01 wt.%) carbon contents because carbon is known to embrittle these alloys causing significant reduction in ductility. However, no reasons have been ascribed to this loss in ductility. Recently the authors have reported that addition of carbon in the range of 0.14 to 0.50 wt.% significantly increases the room temperature strength of Fe-16 wt.% (28 at.%)Al alloys. These alloys also exhibited good room temperature by the interstitial carbon, as well as precipitation hardening due to the presence of Fe{sub 3}AlC precipitates. Here, the authors report elevated temperature tensile properties of these alloys.

  12. The microstructure and hydriding characteristics of high temperature aged U-13 at.%Nb alloy

    NASA Astrophysics Data System (ADS)

    Ji, Hefei; Shi, Peng; Li, Ruiwen; Jiang, Chunli; Yang, Jiangrong; Hu, Guichao

    2015-09-01

    Niobium as alloying element significantly improves physical and chemical properties of metallic uranium, exhibiting great application potential in uranium alloy materials. The corrosion resistance performance as well as the internal alloy phase structure of uranium-niobium alloy is closely related to aging processes. Microstructure and hydriding characteristics of the 400 °C/9 h + 500 °C/2 h aged uranium-13 at.% niobium alloys (U-13 at.%Nb) were investigated from the point of view of relationship between the microstructure and growth of the hydriding areas. The microstructure, morphology and composition of the alloy phases before and after the hydriding were well characterized by the laser scanning confocal microscopy (LSCM), scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Experimental results indicated that the hydrogen preferentially reacted with the Nb-depleted phase α-like-U to form monolithic β-UH3Nbx, and the alloy microstructure played an important role in hydride growth.

  13. Phase Transformation and Creep Behavior in Ti50Pd30Ni20 High Temperature Shape Memory Alloy in Compression

    NASA Technical Reports Server (NTRS)

    Kumar, Parikshith K.; Desai, Uri; Monroe, James; Lagoudas, Dimitris C.; Karaman, Ibrahim; Noebe, Ron; Bigelow, Glenn

    2010-01-01

    The creep behavior and the phase transformation of Ti50Pd30Ni20 High Temperature Shape Memory Alloy (HTSMA) is investigated by standard creep tests and thermomechanical tests. Ingots of the alloy are induction melted, extruded at high temperature, from which cylindrical specimens are cut and surface polished. A custom high temperature test setup is assembled to conduct the thermomechanical tests. Following preliminary monotonic tests, standard creep tests and thermally induced phase transformation tests are conducted on the specimen. The creep test results suggest that over the operating temperatures and stresses of this alloy, the microstructural mechanisms responsible for creep change. At lower stresses and temperatures, the primary creep mechanism is a mixture of dislocation glide and dislocation creep. As the stress and temperature increase, the mechanism shifts to predominantly dislocation creep. If the operational stress or temperature is raised even further, the mechanism shifts to diffusion creep. The thermally induced phase transformation tests show that actuator performance can be affected by rate independent irrecoverable strain (transformation induced plasticity + retained martensite) as well as creep. The rate of heating and cooling can adversely impact the actuators performance. While the rate independent irrecoverable strain is readily apparent early in the actuators life, viscoplastic strain continues to accumulate over the lifespan of the HTSMA. Thus, in order to get full actuation out of the HTSMA, the heating and cooling rates must be sufficiently high enough to avoid creep.

  14. Experimental process development and aerospace alloy formability studies for hydroforming

    NASA Astrophysics Data System (ADS)

    Mojarad Farimani, Saeed

    In tube hydroforming process, a pressurized liquid is used to expand a thin walled tube inside a closed die in order to fill the die cavity. Tube hydroforming has many advantages that make it interesting for different industries such as automotive and aerospace, but due to the effects of different factors, such as formability of the material, load path (end feeding force and internal pressure during the process), tool geometry and friction, it is a quite complex manufacturing process. Therefore, finite element simulation along with optimization methods can significantly reduce the cost of trial and error approach used in conventional manufacturing methods. In this work, to investigate the effects of different process parameters such as friction condition, tube thickness and end feeding on the final product, tube hydroforming experiments were performed using a round to square-shape die. Experiments were performed on stainless steel 321 tubes with 50.8 mm (2 in) diameter and two different thicknesses; 0.9 mm and 1.2 mm. Experimental load paths were obtained via the data acquisition system of the hydroforming press, which is fully instrumented. An automated deformation measurement system, Argus, was used to measure the strains on the hydroformed tubes. Data collected from the initial experiments were used to simulate and then optimize the process. The process was simulated and optimized using Ls-Dyna and Ls-Opt software, respectively. Strains and thickness variations measured from experiments were compared to FE simulation results at critical sections. The comparison of the results from FE simulations and experiments were in good agreement, indicating that the approach can be used for predicting the final shape and thickness variations of the hydroformed parts for aerospace applications.

  15. Eutectic alloys. Citations from the International Aerospace Abstracts data base

    NASA Technical Reports Server (NTRS)

    Moore, P.

    1980-01-01

    These 250 abstracts from the international literature provide summaries of the preparation, treatments, composition and structure, and properties of eutectic alloys. Techniques for directional solidification and treatments including glazing, coating, and fiber reinforcement are discussed. In addition to the mechanical and thermal properties, the superconducting, corrosion, resistance, and thermionic emission and adsorption properties are described.

  16. Neutron diffraction studies of welds of aerospace aluminum alloys

    SciTech Connect

    Martukanitz, R.P.; Howell, P.R.; Payzant, E.A.; Spooner, S.; Hubbard, C.R.

    1996-10-01

    Neutron diffraction and electron microscopy were done on residual stress in various regions comprising variable polarity plasma arc welds of alloys 2219 (Al-6.3Cu) and 2195 (Al-4.0Cu-1.0Li-0.5Mg-0.5Ag). Results indicate that lattice parameter changes in the various weld regions may be attributed to residual stresses generated during welding, as well as local changes in microstructure. Distribution of longitudinal and transverse stress of welded panels shows peaks of tension and compression, respectively, within the HAZ and corroborate earlier theoretical results. Position of these peaks are related to position of minimum strength within the HAZ, and the magnitude of these peaks are a fraction of the local yield strength in this region. Weldments of alloy 2195-T8 exhibited higher peak residual stress than alloy 2219-T87. Comparison of neutron diffraction and microstructural analysis indicate decreased lattice parameters associated with the solid solution of the near HAZ; this results in decreased apparent tensile residual stress within this region and may significantly alter interpretation of residual stress measurements of these alloys. Considerable relaxation of residual stress occurs during removal of specimens from welded panels and was used to aid in differentiating changes in lattice parameters attributed to residual stress from welding and modifications in microstructure.

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

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2000-01-01

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

  18. Development of powder metallurgy Al alloys for high temperature aircraft structural applications, phase 2

    NASA Technical Reports Server (NTRS)

    Chellman, D. J.

    1982-01-01

    In this continuing study, the development of mechanically alloyed heat resistant aluminum alloys for aircraft were studied to develop higher strength targets and higher service temperatures. The use of higher alloy additions to MA Al-Fe-Co alloys, employment of prealloyed starting materials, and higher extrusion temperatures were investigated. While the MA Al-Fe-Co alloys exhibited good retention of strength and ductility properties at elevated temperatures and excellent stability of properties after 1000 hour exposure at elevated temperatures, a sensitivity of this system to low extrusion strain rates adversely affected the level of strength achieved. MA alloys in the Al-Li family showed excellent notched toughness and property stability after long time exposures at elevated temperatures. A loss of Li during processing and the higher extrusion temperature 482 K (900 F) resulted in low mechanical strengths. Subsequent hot and cold working of the MA Al-Li had only a mild influence on properties.

  19. 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.

  20. 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.

  1. Constitutive Modeling of High Temperature Uniaxial Creep-Fatigue and Creep-Ratcheting Responses of Alloy 617

    SciTech Connect

    P.G. Pritchard; L.J. Carroll; T. Hassan

    2013-07-01

    Inconel Alloy 617 is a high temperature creep and corrosion resistant alloy and is a leading candidate for use in Intermediate Heat Exchangers (IHX) of the Next Generation Nuclear Plants (NGNP). The IHX of the NGNP is expected to experience operating temperatures in the range of 800 degrees - 950 degrees C, which is in the creep regime of Alloy 617. A broad set of uniaxial, low-cycle fatigue, fatigue-creep, ratcheting, and ratcheting-creep experiments are conducted in order to study the fatigue and ratcheting responses, and their interactions with the creep response at high temperatures. A unified constitutive model developed at North Carolina State University is used to simulate these experimental responses. The model is developed based on the Chaboche viscoplastic model framework. It includes cyclic hardening/softening, strain rate dependence, strain range dependence, static and dynamic recovery modeling features. For simulation of the alloy 617 responses, new techniques of model parameter determination are developed for optimized simulations. This paper compares the experimental responses and model simulations for demonstrating the strengths and shortcomings of the model.

  2. Radiation-induced strengthening in EB welds of Mo-Re alloys during high temperature neutron irradiation

    NASA Astrophysics Data System (ADS)

    Morito, F.; Chakin, V. P.; Danylenko, M. I.; Krajnikov, A. V.

    2011-10-01

    Mo-Re alloys have been known as excellent construction materials with good thermal stability and resistivity for chemical corrosion. These alloys may be fabricated into equipments for various chemical plants and new energy facilities such as fusion reactor. Accordingly it is interesting to elucidate the weldability and radiation performance of Mo-Re alloys in the actual constructions. In this study Mo-Re welds with 16-50% Re exhibited a large radiation-induced strengthening and embrittlement by irradiation at ˜1073 K to ˜5 × 10 21 cm -2 ( E > 0.1 MeV). High temperature neutron irradiation leads to intensive homogeneous nucleation of Re-rich σ-phases in all studied Mo-Re alloys that equalizes the difference in mechanical properties between melting zone, heat-affected zone and base metal. As a result, all parts of as-irradiated welds displayed approximately same level of strength. Therefore, the application of EB welding in Mo-Re constructions operating under high temperature neutron irradiation does not limit lifetime of such constructions.

  3. Aerospace Patented High-Strength Aluminum Alloy Used in Commercial Industries

    NASA Technical Reports Server (NTRS)

    2004-01-01

    NASA structural materials engineers at Marshall Space Flight Center (MSFC) in Huntsville, Alabama developed a high-strength aluminum alloy for aerospace applications with higher strength and wear-resistance at elevated temperatures. The alloy is a solution to reduce costs of aluminum engine pistons and lower engine emissions for the automobile industry. The Boats and Outboard Engines Division at Bombardier Recreational Products of Sturtevant, Wisconsin is using the alloy for pistons in its Evinrude E-Tec outboard, 40-90 horsepower, engine line. The alloy pistons make the outboard motor quieter and cleaner, while improving fuel mileage and increasing engine durability. The engines comply with California Air resources Board emissions standards, some of the most stringent in the United States. (photo credit: Bombardiier Recreational Products)

  4. High temperature embrittlement caused by traces of calcium or strontium in an Al-5.5 mol% Mg alloy

    SciTech Connect

    Horikawa, Keitaro; Kuramoto, Shigeru; Kanno, Motohiro

    1998-09-04

    Al-5--10mol%Mg alloys are now being developed for automotive parts since they have good formability. However, an alloy containing magnesium of more than 5mol% has poor hot rolling characteristics. It has been reported that an Al-5.5mol%Mg alloy shows high temperature embrittlement (HTE) based on intergranular fracture at around 300 C depending on strain rate. This embrittlement is considered to be closely related to the unfavorable hot rolling characteristics of the Al-Mg alloy. One of the present authors reported recently that this embrittlement is caused by a trace amount of sodium of only of only 0.6mass ppm (0.7mol ppm) in a coarse-grained Al-5.5mol%Mg alloy produced using high purity ingots. Although numerous studies have been made on the effect of sodium, little is known about the effect of alkali and alkaline-earth elements other than sodium. However, unusual impurities may inevitably creep in the recycling process in future. For example, it is reported that the Al-Mg alloy is contaminated by calcium through the ceramic tube filter using during melting and casting, and strontium is used commercially as an additional element in Al-Si alloys. Hence, aluminum alloys made using recycled stock may be contaminated at least by calcium and strontium. The purpose of this study is to determine the effect of traces of calcium or strontium on hot ductility of an Al-5.5mol%Mg alloy.

  5. High Temperature Oxidation of Silicon Carbide and Advanced Iron-Based Alloys in Steam-Hydrogen Environments

    SciTech Connect

    Terrani, Kurt A; Keiser, James R; Brady, Michael P; Cheng, Ting; Silva, G W Chinthaka M; Pint, Bruce A; Snead, Lance Lewis

    2012-01-01

    A side by side comparison of the oxidation behavior of zirconium alloys with SiC materials and advanced iron-based alloys is provided. Oxidation tests were conducted in steam and steam-hydrogen environments at 800-1350 C and 0.34-2MPa for durations up to 48 hours. Monolithic SiC specimens as well as SiC/SiC composites were examined during the study where the material recession mechanism appeared to be governed by silica layer volatilization at the surface for CVD SiC. A wide set of austenitic and ferritic steels were also examined where a critical Cr content (>20 wt.%) was shown to be necessary to achieve oxidation resistance at high temperatures. SiC materials and alumina-forming ferritic steels exhibited slowest oxidation kinetics; roughly two orders of magnitude lower than zirconium alloys.

  6. A Finemet-type alloy as a low-cost candidate for high-temperature magnetic refrigeration

    NASA Astrophysics Data System (ADS)

    Franco, V.; Blázquez, J. S.; Conde, C. F.; Conde, A.

    2006-01-01

    The refrigerant capacity (RC) of Fe68.5Mo5Si13.5B9Cu1Nb3 alloy is studied. For the amorphous sample, RC =63Jkg-1 for an optimal reversible cycle with cold and hot ends at 328K and 520K, respectively, for a maximum applied field H =15kOe. Nanocrystallization diminishes both the peak entropy change and RC of the material. Although the measured RC is smaller than for Gd5Ge1.9Si2Fe0.1 (240Jkg-1 for H =50kOe), the Mo-Finemet alloy is more than 20 times cheaper, the applied field employed is smaller, and the temperature span of the optimal cycle is increased. This makes this alloy a promising material for high-temperature refrigeration.

  7. Auger electron spectroscopy study of oxidation of a PdCr alloy used for high-temperature sensors

    NASA Technical Reports Server (NTRS)

    Boyd, Darwin L.; Zeller, Mary V.; Vargas-Aburto, Carlos

    1993-01-01

    A Pd-13 wt. percent Cr solid solution is a promising high-temperature strain gage alloy. In bulk form it has a number of properties that are desirable in a resistance strain gage material, such as a linear electrical resistance versus temperature curve to 1000 C and stable electrical resistance in air at 1000 C. However, unprotected fine wire gages fabricated from this alloy perform well only to 600 C. At higher temperatures severe oxidation degrades their electrical performance. In this work Auger electron spectroscopy was used to study the oxidation chemistry of the alloy wires and ribbons. Results indicate that the oxidation is caused by a complex mechanism that is not yet fully understood. As expected, during oxidation, a layer of chromium oxide is formed. This layer, however, forms beneath a layer of metallic palladium. The results of this study have increased the understanding of the oxidation mechanism of Pd-13 wt. percent Cr.

  8. Development of high-emittance scales on thoriated nickel-chromium-aluminum-base alloys. [produced by high temperature oxidation

    NASA Technical Reports Server (NTRS)

    Seltzer, M. S.; Wright, I. G.; Wilcox, B. A.

    1973-01-01

    The surface regions of a DSNiCrAl alloy have been doped, by a pack diffusion process, with small amounts of Mn, Fe, or Co, and the effect of these dopants on the total normal emissivity of the scales produced by subsequent high temperature oxidation has been measured. While all three elements lead to a modest increase in emissivity, (up to 23% greater than the undoped alloy) only the change caused by manganese is thermally stable. However, this increased emissivity is within 85 percent of that of TDNiCr oxidized to form a chromia scale. The maganese-doped alloy is some 50 percent weaker than undoped DSNiCrAl after the doping treatment, and approximately 30 percent weaker after oxidation.

  9. Development of platinum-modified gamma-nickel+gamma-nickel-aluminum-based alloys for high-temperature applications

    NASA Astrophysics Data System (ADS)

    Heidloff, Andrew James

    Nickel-base superalloys have been used extensively in high-temperature applications where strength and structural stability are required, most notably in aero gas turbine engines. To increase the efficiency of such engines, a continuous increase in superalloy operating temperatures has been observed. As temperatures continue to increase, multiple aspects of alloy stability become increasingly important. In that regard, the high-temperature performance of superalloys can be generally discussed from two important standpoints, surface stability and structural stability. Historically, structural stability has been the primary concern to alloy designers, such that superalloys that may be exposed to high-temperature applications exceeding 1100°C typically utilize a coating for environmental protection. However, the use of coatings introduces potential deficiencies. For instance, aluminide coatings can lead to extensive instabilities when in contact with newer generation superalloys. Also, a few niche applications exist where the use of a coating is impractical. In such cases, the alloys require both environmental resistance and high-temperature strength. The primary goal of this study was to develop novel heat-treatable gamma-Ni+gamma'-Ni 3Al-based alloys having excellent resistance to both high-temperature oxidation and creep. The alloys were developed in a systematic manner using multiple alloying additions, including Pt and Ir, i.e., platinum group metals (PGMs). The microstructures and environmental and thermal stabilities of the alloys studied were fully characterized through a series of experiments, including: oxidation (both isothermal and cyclic); hot corrosion (both Type I and Type II); microstructure analysis (including lattice misfit); and phase equilibria calculations with partitioning coefficient analysis. Pt modification was found to significantly affect the lattice misfit of an alloy by expanding the gamma' lattice parameter through its Ni sublattice site

  10. Static and dynamic cyclic oxidation of 12 nickel-, cobalt-, and iron-base high-temperature alloys

    NASA Technical Reports Server (NTRS)

    Barrett, C. A.; Johnston, J. R.; Sanders, W. A.

    1978-01-01

    Twelve typical high-temperature nickel-, cobalt-, and iron-base alloys were tested by 1 hr cyclic exposures at 1038, 1093, and 1149 C and 0.05 hr exposures at 1093 C. The alloys were tested in both a dynamic burner rig at Mach 0.3 gas flow and in static air furnace for times up to 100 hr. The alloys were evaluated in terms of specific weight loss as a function of time, and X-ray diffraction analysis and metallographic examination of the posttest specimens. A method previously developed was used to estimate specific metal weight loss from the specific weight change of the sample. The alloys were then ranked on this basis. The burner-rig test was more severe than a comparable furnace test and resulted in an increased tendency for oxide spalling due to volatility of Cr in the protective scale and the more drastic cooling due to the air-blast quench of the samples. Increased cycle frequency also increased the tendency to spall for a given test exposure. The behavior of the alloys in both types of tests was related to their composition and their tendency to form scales. The alloys with the best overall behavior formed alpha-Al2O3 aluminate spinels.

  11. High-Temperature Creep and Oxidation Behavior of Mo-Si-B Alloys with High Ti Contents

    NASA Astrophysics Data System (ADS)

    Schliephake, Daniel; Azim, Maria; von Klinski-Wetzel, Katharina; Gorr, Bronislava; Christ, Hans-Jürgen; Bei, Hongbin; George, Easo P.; Heilmaier, Martin

    2013-08-01

    Multiphase alloys in the Mo-Si-B system are potential high-temperature structural materials due to their good oxidation and creep resistance. Since they suffer from relatively high densities, the current study focuses on the influence of density-reducing Ti additions on creep and oxidation behavior at temperatures above 1273 K (1000 °C). Two alloys with compositions of Mo-12.5Si-8.5B-27.5Ti and Mo-9Si-8B-29Ti (in at. pct) were synthesized by arc melting and then homogenized by annealing in vacuum for 150 hours at 1873 K (1600 °C). Both alloys show similar creep behavior at stresses of 100 to 300 MPa and temperatures of 1473 K and 1573 K (1200 °C and 1300 °C), although they possess different intermetallic volume fractions. They exhibit superior creep resistance and lower density than a state-of-the-art Ni-base superalloy (single-crystalline CMSX-4) as well as other Mo-Si-B alloys. Solid solution strengthening due to Ti was confirmed by Vickers hardness measurements and is believed to be the reason for the significant increase in creep resistance compared to Mo-Si-B alloys without Ti, but with comparable microstructural length scales. The addition of Ti degrades oxidation resistance relative to a Mo-9Si-8B reference alloy due to the formation of a relatively porous duplex layer with titania matrix enabling easy inward diffusion of oxygen.

  12. Development of Cast Alumina-forming Austenitic Stainless Steel Alloys for use in High Temperature Process Environments

    SciTech Connect

    Muralidharan, Govindarajan; Yamamoto, Yukinori; Brady, Michael P; Pint, Bruce A; Pankiw, Roman; Voke, Don

    2015-01-01

    There is significant interest in the development of alumina-forming, creep resistant alloys for use in various industrial process environments. It is expected that these alloys can be fabricated into components for use in these environments through centrifugal casting and welding. Based on the successful earlier studies on the development of wrought versions of Alumina-Forming Austenitic (AFA) alloys, new alloy compositions have been developed for cast products. These alloys achieve good high-temperature oxidation resistance due to the formation of protective Al2O3 scales while multiple second-phase precipitation strengthening contributes to excellent creep resistance. This work will summarize the results on the development and properties of a centrifugally cast AFA alloy. This paper highlights the strength, oxidation resistance in air and water vapor containing environments, and creep properties in the as-cast condition over the temperature range of 750°C to 900°C in a centrifugally cast heat. Preliminary results for a laboratory cast AFA composition with good oxidation resistance at 1100°C are also presented.

  13. High-temperature compatibility study of iridium (DOP-26 alloy) with graphite and plutonia

    SciTech Connect

    Axler, K.M.; Eash, D.T.

    1987-12-01

    This report outlines the materials compatibility tests conducted on DOP-26 iridium alloy and carbon. The carbon used was in the form of woven graphite as present in the impact shell used to encase plutonia in nuclear heat sources. In addition, compatibility tests of the DOP-26 alloy with plutonia are described. The reactivity observed in both systems is discussed. 4 refs., 6 figs.

  14. High-temperature corrosion of metallic alloys in an oxidizing atmosphere containing NaCl

    SciTech Connect

    Federer, J.I.

    1989-02-01

    A particular heat-exchanger application involved metallic alloys exposed to flue gases of an aluminum remelt furnace. Because the flue gases might contain NaCl and other halides, the corrosion behavior of the alloys was to be investigated. Planned direct exposure of candidate alloys to the flue gases, however, was not conducted because of premature termination of the project. Complementary laboratory testing was conducted on seven commercially available alloys and two nickel aluminides. These materials were exposed to an oxidizing atmosphere containing 0.06 wt % NaCl for 1100 h at 1000/degree/C. Most of the alloy exhibited grain-boundary attack, which resulted in complete oxidation of enveloped grains. The alloys Incoloy MA-956, Incoloy 800, Inconel 625, Inconel 601, Hastelloy X, Haynes 188, and nickel aluminide IC-50 were substantially more corroded than Alloy 214 and nickel aluminide IC-221. The latter two alloys, therefore, would probably be superior to the others in application involving flue gases containing NaCl. Strength fabricability, and weldability, which are briefly discussed, would also affect selection of materials. 8 refs., 12 figs., 5 tabs.

  15. High-Temperature Oxidation Behavior of Fe-Si-Ce Alloys

    NASA Astrophysics Data System (ADS)

    Su, Yong; Zhang, Shunke; Fu, Guangyan; Liu, Qun; Tang, Yuanze

    2016-02-01

    The oxidation behavior of Fe-Si-Ce alloys with different Ce content at 1,173 and 1,273 K has been studied by means of optical microscope (OM), thermogravimetric analysis (TGA), X-ray diffraction (XRD) and scanning electron microscope (SEM). Results show that the Ce addition refines the grain size of Fe-Si alloys, and correspondingly the grain size of the oxides decreases, which increases the grain boundary concentration and promotes the short-path diffusion of the alloying elements and oxygen. During oxidation, the positive effect of the grain refinement on the oxidation behavior of the alloy is more obvious than negative effect, so the Ce addition improves the oxidation resistances of the Fe-3Si alloys. Compared to Fe-3Si-0.5Ce alloy, Fe-3Si-5.0Ce alloy has the larger mass gain for the preferential oxidation of the excessive content of Ce exceeding its beneficial effects. The rare earth Ce changes the oxidation mechanism of Fe-Si alloys. Oxygen penetrates the oxide scales and reacts preferentially with Ce-rich phases, which results in the pinning effect and improves the adhesion of the oxide scales.

  16. High-temperature oxidation of a rapidly solidified amorphous Ta-Ir alloy

    NASA Technical Reports Server (NTRS)

    Cotell, Catherine M.; Yurek, Gregory J.

    1986-01-01

    The oxidation products formed at 500 and 700 C on an amorphous Ta-44.5 at. pct Ir alloy in an Ar-0.1 percent O2 gas mixture were characterized using SEM, XRD, EPMA, TEM, STEM, AES, and XPS. Initially, a thin (3-4 nm) layer of Ta2O5 formed at the surface of the alloy. Continued growth of the Ta2O5, which occurred very rapidly, involved diffusion of oxygen anions from the Ta2O5/gas interface to the alloy/Ta2O5 interface, where tantalum was selectively oxidized. Because the oxide grew more quickly than iridium could diffuse back into the alloy, the iridium coalesced into platelets of crystalline iridium-rich alloy that were oriented approximately parallel to the oxide/alloy interface, and which became embedded in a matrix of Ta2O5. The unoxidized core remained in the glassy state. The oxidation process and/or the dissolution of oxygen into the unoxidized alloy caused the alloy to become embrittled.

  17. Precipitation-Strengthened, High-Temperature, High-Force Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald D.; Draper, Susan L.; Nathal, Michael V.; Crombie, Edwin A.

    2008-01-01

    Shape memory alloys (SMAs) are an enabling component in the development of compact, lightweight, durable, high-force actuation systems particularly for use where hydraulics or electrical motors are not practical. However, commercial shape memory alloys based on NiTi are only suitable for applications near room temperature, due to their relatively low transformation temperatures, while many potential applications require higher temperature capability. Consequently, a family of (Ni,Pt)(sub 1-x)Ti(sub x) shape memory alloys with Ti concentrations ranging from about 15 to 25 at.% have been developed for applications in which there are requirements for SMA actuators to exert high forces at operating temperatures higher than those of conventional binary NiTi SMAs. These alloys can be heat treated in the range of 500 C to produce a series of fine precipitate phases that increase the strength of alloy while maintaining a high transformation temperature, even in Ti-lean compositions.

  18. High-temperature corrosion-resistant iron-aluminide (FeAl) alloys exhibiting improved weldability

    DOEpatents

    Maziasz, P.J.; Goodwin, G.M.; Liu, C.T.

    1996-08-13

    This invention relates to improved corrosion-resistant iron-aluminide intermetallic alloys. The alloys of this invention comprise, in atomic percent, from about 30% to about 40% aluminum alloyed with from about 0.1% to about 0.5% carbon, no more than about 0.04% boron such that the atomic weight ratio of boron to carbon in the alloy is in the range of from about 0.01:1 to about 0.08:1, from about 0.01 to about 3.5% of one or more transition metals selected from Group IVB, VB, and VIB elements and the balance iron wherein the alloy exhibits improved resistance to hot cracking during welding. 13 figs.

  19. High-temperature corrosion-resistant iron-aluminide (FeAl) alloys exhibiting improved weldability

    DOEpatents

    Maziasz, Philip J.; Goodwin, Gene M.; Liu, Chain T.

    1996-01-01

    This invention relates to improved corrosion-resistant iron-aluminide intermetallic alloys. The alloys of this invention comprise, in atomic percent, from about 30% to about 40% aluminum alloyed with from about 0.1% to about 0.5% carbon, no more than about 0.04% boron such that the atomic weight ratio of boron to carbon in the alloy is in the range of from about 0.01:1 to about 0.08:1, from about 0.01 to about 3.5% of one or more transition metals selected from Group IVB, VB, and VIB elements and the balance iron wherein the alloy exhibits improved resistance to hot cracking during welding.

  20. Monolithic Cu-Cr-Nb Alloys for High Temperature, High Heat Flux Applications

    NASA Technical Reports Server (NTRS)

    Ellis, David L.; Locci, Ivan E.; Michal, Gary M.; Humphrey, Derek M.

    1999-01-01

    Work during the prior four years of this grant has resulted in significant advances in the development of Cu-8 Cr4 Nb and related Cu-Cr-Nb alloys. The alloys are nearing commercial use in the Reusable Launch Vehicle (RLV) where they are candidate materials for the thrust cell liners of the aerospike engines being developed by Rocketdyne. During the fifth and final year of the grant, it is proposed to complete development of the design level database of mechanical and thermophysical properties and transfer it to NASA Glenn Research Center and Rocketdyne. The database development work will be divided into three main areas: Thermophysical Database Augmentation, Mechanical Testing and Metallography and Fractography. In addition to the database development, work will continue that is focussed on the production of alternatives to the powder metallurgy alloys currently used. Exploration of alternative alloys will be aimed at both the development of lower cost materials and higher performance materials. A key element of this effort will be the use of Thermo-Calc software to survey the solubility behavior of a wide range of alloying elements in a copper matrix. The ultimate goals would be to define suitable alloy compositions and processing routes to produce thin sheets of the material at either a lower cost, or, with improved mechanical and thermal properties compared to the current Cu-Cr-Nb powder metallurgy alloys.

  1. Properties and Potential of Two (ni,pt)ti Alloys for Use as High-temperature Actuator Materials

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald; Gaydosh, Darrell; Padula, Santo, II.; Garg, Anita; Biles, Tiffany; Nathal, Michael

    2005-01-01

    The microstructure, transformation temperatures, basic tensile properties, shape memory behavior, and work output for two (Ni,Ti)Pt high-temperature shape memory alloys have been characterized. One was a Ni30Pt20Ti50 alloy (referred to as 20Pt) with transformation temperatures above 230 C and the other was a Ni20Pt30Ti50 alloy (30Pt) with transformation temperatures about 530 C. Both materials displayed shape memory behavior and were capable of 100% (no-load) strain recovery for strain levels up to their fracture limit (3-4%) when deformed at room temperature. For the 20Pt alloy, the tensile strength, modulus, and ductility dramatically increased when the material was tested just about the austenite finish (A(sub f)) temperature. For the 30Pt alloy, a similar change in yield behavior at temperatures above the A(sub f) was not observed. In this case the strength of the austentite phase was at best comparable and generally much weaker than the martensite phase. A ductility minimum was also observed just below the A(sub s) temperature in this alloy. As a result of these differences in tensile behavior, the two alloys performed completely different when thermally cycled under constant load. The 20Pt alloy behaved similar to conventional binary NiTi alloys with work output due to the martensite-to-austenite transformation initially increasing with applied stress. The maximum work output measured in the 20Pt alloy was nearly 9 J/cu cm and was limited by the tensile ductility of the material. In contrast, the martensite-to-austenite transformation in the 30Pt alloy was not capable of performing work against any bias load. The reason for this behavior was traced back to its basic mechanical properties, where the yield strength of the austenite phase was similar to or lower than that of the martensite phase, depending on temperature. Hence, the recovery or transformation strain for the 30Pt alloy under load was essentially zero, resulting in zero work output.

  2. Radiation-induced softening of Fe-Mo alloy under high- temperature electron irradiation

    NASA Astrophysics Data System (ADS)

    Tsepelev, A.

    2016-04-01

    Effect of radiation-induced change of mechanical properties of Fe-5 wt.% Mo alloy irradiated with electrons (2 MeV) at room temperature and 400°C has been investigated. Mechanical properties were estimated by Miniaturized Disk Bend Test technique. Effect of radiation softening of the alloy is ascertained the value of which was increased with temperature rise. With the purpose of separation of thermal and radiation contributions into the effects, the tests were carried out for specimens annealed in the same thermal conditions (temperature and duration of annealing) just as during irradiation. Thermal annealing and electron irradiation at 400°C is found to bring to multidirectional effects of the alloy strengthening and softening respectively. It is concluded that irradiation suppresses the effect of thermal-induced strengthening and stimulates a softening of the alloy due to more significant changes in the structure and phase composition of it.

  3. A new lead alloy for automotive batteries operating under high-temperature conditions

    NASA Astrophysics Data System (ADS)

    Albert, L.; Goguelin, A.; Jullian, E.

    The operating conditions of automotive and some industrial batteries are involving increasingly higher temperatures and heavier duty cycles. These place stress on the positive-grid materials which are presently not sufficiently resistant to corrosion and to creep. Conventional lead-calcium-tin-aluminium alloys can usually be optimized by a proper choice of calcium and tin contents for each specific manufacturing technology. With the new requirements of customers and the typical behaviour of these conventional alloys, however, there is no more room for improvement without searching for additional alloying elements. The work reported here shows how the doping of conventional lead-calcium-tin-aluminium alloys with barium improves mechanical properties (tensile strength and creep resistance) and increases corrosion resistance at temperatures between 50 and 75°C. Grid materials prepared by two manufacturing technologies (gravity cast; continuous cast followed by expansion) are investigated. Both the mechanical properties and the corrosion behaviour of the resulting grids are evaluated.

  4. Solid state thin film battery having a high temperature lithium alloy anode

    DOEpatents

    Hobson, David O.

    1998-01-01

    An improved rechargeable thin-film lithium battery involves the provision of a higher melting temperature lithium anode. Lithium is alloyed with a suitable solute element to elevate the melting point of the anode to withstand moderately elevated temperatures.

  5. High-temperature oxidation behavior of two-phase iron-manganese-aluminum alloys

    SciTech Connect

    Liu, S.Y.; Lee, C.L.; Kao, C.H.; Perng, T.P.

    2000-04-01

    Oxidation behavior of two series of two-phase Fe-Mn-Al alloys in air up to 800 C was investigated. For the first series of alloys with various ratios of ferrite-austenite, the oxidation resistance of these alloys increased as the ferrite content increased. Two layers of oxide were formed mainly on the austenite grains, and oxidation in the ferrite phase was much less severe. The other layer of the scale on austenite was enriched with Mn and Fe, while Al was concentrated in the inner layer. For the second series of alloys with nearly the same contents of ferrite and C but various contents of Cr, the addition of Cr changed the oxidation characteristics and increased the oxidation resistance. Cr assisted the formation of a dense film of alumina (Al{sub 2}O{sub 3}) to prevent further oxidation.

  6. A new Cu-8 Cr-4 Nb alloy for high temperature applications

    NASA Technical Reports Server (NTRS)

    Ellis, D. L.; Michal, G. M.; Dreshfield, R. L.

    1995-01-01

    Various applications exist where a high conductivity alloy with good strength and creep resistance are required. NASA LeRC has developed a Cu-8 at. percent Cr-4 at. percent Nb (Cu-8 Cr-4 Nb) alloy for these applications. The alloy is designed for use up to 700 C and shows exceptional strength, low cycle fatigue (LCF) resistance, and creep resistance. Cu-8 Cr-4 Nb also has a thermal conductivity of at least 72 percent that of pure Cu. Furthermore, the microstructure and mechanical properties of the alloy are very stable. In addition to the original application in combustion chambers, Cu-8 Cr-4 Nb shows promise for welding electrodes, brazing fixtures, and other applications requiring high conductivity and strength at elevated temperatures.

  7. Grain growth behavior and high-temperature high-strain-rate tensile ductility of iridium alloy DOP-26

    SciTech Connect

    McKamey, C.G.; Gubbi, A.N.; Lin, Y.; Cohron, J.W.; Lee, E.H.; George, E.P.

    1998-04-01

    This report summarizes results of studies conducted to date under the Iridium Alloy Characterization and Development subtask of the Radioisotope Power System Materials Production and Technology Program to characterize the properties of the new-process iridium-based DOP-26 alloy used for the Cassini space mission. This alloy was developed at Oak Ridge National Laboratory (ORNL) in the early 1980`s and is currently used by NASA for cladding and post-impact containment of the radioactive fuel in radioisotope thermoelectric generator (RTG) heat sources which provide electric power for interplanetary spacecraft. Included within this report are data generated on grain growth in vacuum or low-pressure oxygen environments; a comparison of grain growth in vacuum of the clad vent set cup material with sheet material; effect of grain size, test temperature, and oxygen exposure on high-temperature high-strain-rate tensile ductility; and grain growth in vacuum and high-temperature high-strain-rate tensile ductility of welded DOP-26. The data for the new-process material is compared to available old-process data.

  8. High Temperature Strength and Stress Relaxation Behavior of Dilute Binary Mg Alloys

    NASA Astrophysics Data System (ADS)

    Abaspour, Saeideh; Cáceres, Carlos H.

    2016-03-01

    Monotonic compression and stress relaxation tests were carried out on specimens of 6 cast binary alloys with (at. pct) 2.5 Al, 0.6 Sn, 2.2 Zn, 0.9 Nd, 0.8 Gd and 1.3 Y, and of a similarly cast AZ91D alloy for reference. The solute concentration of the binary alloys was kept deliberately low to limit precipitation hardening effects during the testing, done in the solution heat treated and quenched condition. Compression testing was carried out at 298 K, 373 K and 453 K (25 °C, 100 °C and 180 °C) for all of the alloys and at 493 K and 523 K (220 °C and 250 °C) for the Nd-, Gd- and Y- containing ones. Stress relaxation was done at 453 K (180 °C) at either a predetermined strain (0.05) or stress (150 MPa). The Mg-Al and the AZ91 alloys softened considerably above 373 K (100 °C). The rest of the alloys exhibited increasing linear strain hardening in compression and reduced stress relaxation, in the order Sn, Zn, Nd, Gd and Y, an indication of a progressively stable dislocation substructure, hence of an increasingly extended athermal regime in the strength-temperature relationship. The overall strain hardening behavior matches that of commercial alloys involving the same solutes at comparable or higher concentrations, and can be accounted for through the respective tendency of the solute atoms to develop short range order. This tendency is lowest for the near-random solid solution introduced by Al, and highest for Nd, Gd and Y, in agreement with their respective phase diagrams. The implications for creep resistant alloy selection and design are discussed.

  9. Corrosion of V and V-base alloys in high-temperature water

    SciTech Connect

    Purdy, I.M.; Toben, P.T.; Kassner, T.F.

    1996-04-01

    Corrosion of nonalloyed V, V-5Cr-5Ti, and V-15Cr-5Ti were conducted in high-purity deoxygenated water at 230{degrees}C for up to {approx}4500h. The effects of Cr concentration in the alloy and temperature on the corrosion behavior were determined from weight-change measurements and microstructural observations. An expression was obtained for the kinetics of corrosion as a function of Cr content of the alloy and temperature.

  10. The high-temperature work function of sintered dilute solution tungsten-iridium alloys

    SciTech Connect

    D'Cruz, L.A.; Bosch, D.R.; Jacobsen, D.L. )

    1993-02-01

    The effect of transition element additives molybdenum, rhenium, iridium, and osmium on the effective work function of tungsten has been the focus of thermionics research for several years. In this study, iridium-added tungsten powder mixtures were cold compacted and sintered to produce a range of tungsten-iridium electrodes. An electron emission study was subsequently carried out to evaluate the work function behavior of the consolidated alloys. The work function was obtained from measurements of the current emitted from the electrode surface under ultrahigh vacuum conditions in the temperature range of 1,800 to 2,500 K using a vacuum emission vehicle (VEV). The data show that the magnitude of the work function in these alloys varied with temperature. Microstructural evaluation of the alloys indicated that the tested surfaces displayed accentuated thermal etching of the grain boundaries together with the fact that the final grain sizes in the sintered alloys were three to five times smaller than those found in equivalent arc-melted alloys that were studied in earlier work. Scanning electron microscopy (SEM) micrographs of the tested surfaces of the sintered alloys containing the highest iridium levels ([approximately]2 wt%) show a high level of structural distortion, particularly in the vicinity of grain boundaries and corners. The extent of these distortions was found to vary with the iridium content, i.e., the W-IR3M and W-IR2M. The samples with compositions lower than 0.5 wt% Ir were virtually devoid of distortions.

  11. Corrosion reduction of aluminum alloys in flowing high-temperature water

    NASA Technical Reports Server (NTRS)

    Draley, J. E.; Ruther, W. E.

    1969-01-01

    Report describes a technique for reducing the corrosion rate of aluminum by adding colloidal substances in a closed-loop system. Experimental work shows that the addition of graphite and colloidal hydrated aluminum oxide significantly reduces the corrosion rate in flowing high-temperature water.

  12. NASA-UVA Light Aerospace Alloy and Structures Technology Program (LA2ST). Progress Report, 1 Jan. - 30 Jun. 1991

    SciTech Connect

    Not Available

    1991-06-01

    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.

  13. Phase Equilibria, Microstructure, and High-Temperature Strength of TiC-Added Mo-Si-B Alloys

    NASA Astrophysics Data System (ADS)

    Miyamoto, Shimpei; Yoshimi, Kyosuke; Ha, Seong-Ho; Kaneko, Takahiro; Nakamura, Junya; Sato, Tetsuya; Maruyama, Kouichi; Tu, Rong; Goto, Takashi

    2013-05-01

    TiC was added to Mo-Si-B alloys using a conventional Ar arc-melting technique, and the phase equilibria, microstructure evolution, and high-temperature strength at 1673 K (1400 °C) were investigated. The primary phase changed to Mo solid solution (Moss), Mo5SiB2 (T2), or TiC depending on the composition. Following the primary phase solidification, a Moss + TiC, Moss + T2, or Moss + T2 + TiC + Mo2C eutectic reaction took place as the secondary solidification step. In some alloys, Moss + T2 + TiC and Moss + T2 + Mo2C eutectic reactions were present as higher-order solidification steps. After annealing at 2073 K (1800 °C) for 24 hours, Moss, T2, TiC, and Mo2C coexisted stably with microstructural coarsening. The coarsening rate was much faster in an alloy with no TiC dispersion, suggesting that TiC has a strong pinning effect on the grain boundary and interface migration. Compression tests conducted at 1673 K (1400 °C) revealed strength properties of almost all the alloys that were better than those of the Mo-Hf-C alloy (MHC). Alloy densities were 9 g/cm3 or less, which is lighter than pure Mo and MHC (≥10 g/cm3) and competitive with Ni-base superalloys. TiC-added Mo-Si-B alloys are promising candidates for ultrahigh-temperature materials beyond Ni-base superalloys.

  14. The influence of FeTi and NiTi intermetallide additions on high-temperature oxidation of permalloy alloy

    SciTech Connect

    Klimenko, V.N.; Lavrenko, V.A.; Panasyuk, O.A.; Blasova, O.V.; Protsenko, T.G.

    1995-11-01

    As a rule powder metallurgy Permalloy alloys are used in production of parts for electronic instruments. For the purpose of controlling the magnetic and electrical properties and also the wear (in the case of production of magnetic heads) and corrosion resistance appropriate additions of metals or such compounds as carbides and oxides are added to the alloy. In this work use of FeTi and NiTi intermetallides produced by reaction sintering of powders of pure metals in a protective atmosphere as alloying additions to Permalloy is recommended. The size of the original powders is less than 100 {mu}m. For reaction sintering at temperature 50{degrees}C above the eutectic temperature in the Ti-TiFe and TiNi-Ni systems was selected. The contents of titanium, iron, and oxygen in the FeTi alloy is 51.9, 45.7, and 2.4 wt.%, respectively, and of titanium, nickel, and oxygen in the NiTi alloy 59.6, 31.9, and 4.6 wt.%. High-temperature oxidation in air up to 1300{degrees}C with a rate of change in temperature of 15{degrees}C of type 78N Permalloy with additions of FeTi and NiTi alloys was investigated with use of methods of differential thermal and differential thermogravimetric analyses on an OD-103 derivatograph under nonisothermal conditions. The reaction products were studied by x-ray diffraction phase analysis on a DRON-3 instrument in CoK{sub {alpha}}-radiation. Pure 78N alloy powder with a composition of 78.1% Ni + 19.3% Fe (specimen 1) and also with additions of 1% FeTi (specimen 2) and 1% NiTi (specimen 3) were subjected to oxidation.

  15. The corrosion behavior of Alloy 52 weld metal in cyclic hydrogenated and oxygenated water chemistry in high temperature aqueous environment

    NASA Astrophysics Data System (ADS)

    Xu, Jian; Shoji, Tetsuo

    2015-06-01

    The corrosion behavior of Alloy 52 weld metal in cyclic hydrogenated and oxygenated water chemistry in high temperature water is studied by in situ monitoring corrosion potential (Ecorr), contact electric resistance (CER) and electrochemical impedance measurements (EIS), and ex situ scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analysis. The Ecorr and film resistance show large change when the environment is changed from hydrogenated water to oxygenated water and changeable with changing environment while the morphology and composition only show obvious distinction in the first cycle. The main factor controlling the electric/electrochemical properties of the oxide film is Ecorr.

  16. Lead induced stress corrosion cracking of Alloy 690 in high temperature water

    SciTech Connect

    Chung, K.K.; Lim, J.K.; Moriya, Shinichi; Watanabe, Yutaka; Shoji, Tetsuo

    1995-12-31

    Recent investigations of cracked steam generator tubes at nuclear power plants concluded that lead significantly contributed to cracking the Alloy 600 materials. In order to investigate the stress corrosion cracking (SCC) behavior of Alloy 690, slow strain rate tests (SSRT) and anodic polarization measurements were performed. The SSRTs were conducted in a lead-chloride solution (PbCl{sub 2}) and in a chloride but lead free solution (NaCl) at pH of 3 and 4.5 at 288 C. The anodic polarization measurements were carried out at 30 C using the same solutions as in SSRT. The SSRT results showed that Alloy 690 was susceptible to SCC in both solutions. In the lead chloride solution, cracking had slight dependence on lead concentration and pH. Cracking tend to increase with a higher lead concentration and a lower pH and was mainly intergranular and was to be a few tens to hundreds micrometers in length. In the chloride only solution, cracking was similar to the lead induced SCC. The results of anodic polarization measurement and electron probe micro analysis (EPMA) helped to understand lead induced SCC. Lead was a stronger active corrosive element but had a minor affect on cracking susceptibility of the alloy. While, chloride was quite different from lead effect to SCC. A possible mechanism of lead induced SCC of Alloy 690 was also discussed based on the test results.

  17. Thermal Decoating of Aerospace Aluminum Alloys for Aircraft Recycling

    NASA Astrophysics Data System (ADS)

    Muñiz Lerma, Jose Alberto; Jung, In-Ho; Brochu, Mathieu

    2016-03-01

    Recycling of aircraft aluminum alloys can be complex due to the presence of their corrosion protection coating that includes inorganic compounds containing Cr(VI). In this study, the characterization and thermal degradation behavior of the coating on aluminum substrates coming from an aircraft destined for recycling are presented. Elements such as Sr, Cr, Si, Ba, Ti, S, C, and O were found in three different layers by EDS elemental mapping corresponding to SrCrO4, Rutile-TiO2, SiO2, and BaSO4 with an overall particle size D 50 = 1.96 µm. The thermal degradation profile analyzed by TGA showed four different stages. The temperature of complete degradation at the fourth stage occurred at 753.15 K (480 °C) at lower heating rates. At higher heating rates and holding an isotherm at the same temperature, the residence time to fully decompose the aircraft coating has been estimated as 4.0 ± 0.2 minutes. The activation energy calculated by the Flynn-Wall-Ozawa and the modified Coats-Redfern methods for multiple fraction of decomposition showed a non-constant behavior indicating the complexity of the reaction. Finally, the concentration of Cr(VI) released to the environment during thermal decoating was obtained by UV-Vis spectroscopy. It was found that 2.6 ± 0.1 µg of Cr(VI)/mm2 of aluminum substrate could be released unless adequate particle controls are used.

  18. Thermal Decoating of Aerospace Aluminum Alloys for Aircraft Recycling

    NASA Astrophysics Data System (ADS)

    Muñiz Lerma, Jose Alberto; Jung, In-Ho; Brochu, Mathieu

    2016-06-01

    Recycling of aircraft aluminum alloys can be complex due to the presence of their corrosion protection coating that includes inorganic compounds containing Cr(VI). In this study, the characterization and thermal degradation behavior of the coating on aluminum substrates coming from an aircraft destined for recycling are presented. Elements such as Sr, Cr, Si, Ba, Ti, S, C, and O were found in three different layers by EDS elemental mapping corresponding to SrCrO4, Rutile-TiO2, SiO2, and BaSO4 with an overall particle size D 50 = 1.96 µm. The thermal degradation profile analyzed by TGA showed four different stages. The temperature of complete degradation at the fourth stage occurred at 753.15 K (480 °C) at lower heating rates. At higher heating rates and holding an isotherm at the same temperature, the residence time to fully decompose the aircraft coating has been estimated as 4.0 ± 0.2 minutes. The activation energy calculated by the Flynn-Wall-Ozawa and the modified Coats-Redfern methods for multiple fraction of decomposition showed a non-constant behavior indicating the complexity of the reaction. Finally, the concentration of Cr(VI) released to the environment during thermal decoating was obtained by UV-Vis spectroscopy. It was found that 2.6 ± 0.1 µg of Cr(VI)/mm2 of aluminum substrate could be released unless adequate particle controls are used.

  19. Structure and thermoelastic martensitic transformations in ternary Ni-Ti-Hf alloys with a high-temperature shape memory effect

    NASA Astrophysics Data System (ADS)

    Pushin, V. G.; Kuranova, N. N.; Pushin, A. V.; Uksusnikov, A. N.; Kourov, N. I.

    2016-07-01

    The effect of alloying by 12-20 at % Hf on the structure, the phase composition, and the thermoelastic martensitic transformations in ternary alloys of the quasi-binary NiTi-NiHf section is studied by transmission electron microscopy, scanning electron microscopy, electron diffraction, and X-ray diffraction. The electrical resistivity is measured at various temperatures to determine the critical transformation temperatures. The data on phase composition are used to plot a full diagram for the high-temperature thermoelastic B2 ↔ B19' martensitic transformations, which occur in the temperature range 320-600 K when the hafnium content increases from 12 to 20 at %. The lattice parameters of the B2 and B19' phases are measured, and the microstructure of the B19' martensite is analyzed.

  20. Effects of high temperature aging in an impure helium environment on low temperature embrittlement of Alloy 617 and Haynes 230

    NASA Astrophysics Data System (ADS)

    Kim, Daejong; Sah, Injin; Jang, Changheui

    2010-10-01

    The effects of high temperature environmental damage on low temperature embrittlement of wrought nickel-base superalloys, Alloy 617 and Haynes 230 were evaluated. They were aged in an impure helium environment at 1000 °C for up to 500 h before tensile tested at room temperature. The tensile test results showed that the loss of ductility was associated with the increase in the inter-granular fracture with aging time. For Alloy 617, inter-granular oxidation and coarsening of grain boundary carbides contributed to the embrittlement. The significant loss of ductility in Haynes 230 was only observed after 500 h of aging when the globular intermetallic precipitates were extensively formed and brittle inter-granular cracking began to occur.

  1. In-situ electrochemical study of Zr1nb alloy corrosion in high temperature Li+ containing water

    NASA Astrophysics Data System (ADS)

    Krausová, Aneta; Macák, Jan; Sajdl, Petr; Novotný, Radek; Renčiuková, Veronika; Vrtílková, Věra

    2015-12-01

    Long-term in-situ corrosion tests were performed in order to evaluate the influence of lithium ions on the corrosion of zirconium alloy. Experiments were carried out in a high-pressure high-temperature loop (280 °C, 8 MPa) in a high concentration water solution of LiOH (70 and 200 ppm Li+) and in a simulated WWER primary coolant environment. The kinetic parameters characterising the oxidation process have been explored using in-situ electrochemical impedance spectroscopy and slow potentiodynamic polarization. Also, a suitable equivalent circuit was suggested, which would approximate the impedance characteristics of the corrosion of Zr-1Nb alloy. The Mott-Schottky approach was used to determine the semiconducting character of the passive film.

  2. Potential High-Temperature Shape-Memory-Alloy Actuator Material Identified

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald D.; Gaydosh, Darrell J.; Biles, Tiffany A.; Garg, Anita

    2005-01-01

    Shape-memory alloys are unique "smart materials" that can be used in a wide variety of adaptive or "intelligent" components. Because of a martensitic solid-state phase transformation in these materials, they can display rather unusual mechanical properties including shape-memory behavior. This phenomenon occurs when the material is deformed at low temperatures (below the martensite finish temperature, Mf) and then heated through the martensite-to-austenite phase transformation. As the material is heated to the austenite finish temperature Af, it is able to recover its predeformed shape. If a bias is applied to the material as it tries to recover its original shape, work can be extracted from the shape-memory alloy as it transforms. Therefore, shape-memory alloys are being considered for compact solid-state actuation devices to replace hydraulic, pneumatic, or motor-driven systems.

  3. High Strength and Wear Resistant Aluminum Alloy for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.; Chen, Po Shou

    2003-01-01

    Originally developed by NASA as high performance piston alloys to meet U.S. automotive legislation requiring low exhaust emission, the novel NASA alloys now offer dramatic increase in tensile strength for many other applications at elevated temperatures from 450 F (232 C) to about 750 F (400 C). It is an ideal low cost material for cast automotive components such as pistons, cylinder heads, cylinder liners, connecting rods, turbo chargers, impellers, actuators, brake calipers and rotors. It can be very economically produced from conventional permanent mold, sand casting or investment casting, with silicon content ranging from 6% to 18%. At high silicon levels, the alloy exhibits excellent thermal growth stability, surface hardness and wear resistant properties.

  4. Development of nanostructured CoFe-based alloys for high temperature magnetic applications.

    PubMed

    Panda, A K; Mohanta, O; Ghosh, M; Mitra, A

    2009-09-01

    The effect of substituting Fe by Co on the crystallization, structural and magnetic behaviour of Fe(72-x)Co(x)Si4B20Nb4 (X = 10, 20, 36, 50 at%) and Co36Fe36Si(4-Y)Al(y)B20Nb4 (Y = 0, 1 at%) alloys prepared in the form of melt spun ribbons has been discussed. Alloys containing optimum content of cobalt = 36 at% showed consistent coercivity at elevated temperatures. This soft magnetic property was further improved with aluminium incorporation. Transmission electron microscopy (TEM) indicated that such enhancement in the properties was due to finer dispersions of (CoFe)SiAl nanoparticles in amorphous matrix. Nanocrystallisation also raised the Curie temperature of the aluminium contained alloy. PMID:19928272

  5. High Temperature Analysis of Aluminum-Lithium 2195 Alloy to Aid in the Design of Improved Welding Techniques

    NASA Technical Reports Server (NTRS)

    Talia, George E.; Widener, Christian

    1996-01-01

    Aluminum-lithium alloys have extraordinary properties. The addition of lithium to an aluminum alloy decreases its density, while making large increases in its strength and hardness. The down side is that they are unstable at higher temperatures, and are subsequently difficult to weld or even manufacture. Martin Marietta, though, developed an aluminum-lithium alloy 2195 that was reported to have exceptional properties and good weldability. Thus, it was chosen as the alloy for the space shuttles super light external tank. Unfortunately, welding 2195 has turned out to be much more of a challenge than anticipated. Thus, research has been undergone in order to understand the mechanisms that are causing the welding problems. Gas reactions have been observed to be detrimental to weld strength. Water vapor has often been identified as having a significant role in these reactions. Nitrogen, however, has also been shown to have a direct correlation to porosity. These reactions were suspected as being complex and responsible for the two main problems of welding 2195. One, the initial welds of 2195 are much weaker than the parent metal. Second, each subsequent welding pass increases the size and number of cracks and porosity, yielding significant reductions in strength. Consequently, the objective of this research was to characterize the high-temperature reactions of 2195 in order to understand the mechanisms for crack growth and the formation of porosity in welds. In order to accomplish that goal, an optical hot-stage microscope, HSM, was used to observe those reactions as they occurred. Surface reactions of 2195 were observed in a variety of environments, such as air, vacuum, nitrogen and helium. For comparison, some samples of Al-2219 were also observed. Some of the reacted surfaces were then analyzed on a scanning electron microscope, SEM. Additionally, a gas chromatograph was used to analyze the gaseous products of the high temperature reactions.

  6. Nanostructured Hypoeutectic Fe-B Alloy Prepared by a Self-propagating High Temperature Synthesis Combining a Rapid Cooling Technique

    PubMed Central

    2009-01-01

    We have successfully synthesized bulk nanostructured Fe94.3B5.7 alloy using the one-step approach of a self-propagating high temperature synthesis (SHS) combining a rapid cooling technique. This method is convenient, low in cost, and capable of being scaled up for processing the bulk nanostructured materials. The solidification microstructure is composed of a relatively coarse, uniformly distributed dendriteto a nanostructured eutectic matrix with α-Fe(B) and t-Fe2B phases. The fine eutectic structure is disorganized, and the precipitation Fe2B is found in the α-Fe(B) phase of the eutectic. The dendrite phase has the t-Fe2B structure rather than α-Fe(B) in the Fe94.3B5.7 alloy, because the growth velocity of t-Fe2B is faster than that of the α-Fe with the deeply super-cooling degree. The coercivity (Hc) and saturation magnetization (Ms) values of the Fe94.3B5.7 alloy are 11 A/m and 1.74T, respectively. Moreover, the Fe94.3B5.7 alloy yields at 1430 MPa and fractures at 1710 MPa with a large ductility of 19.8% at compressive test. PMID:20596402

  7. A View of Compatible Heat-Resistant Alloy and Coating Systems at High-Temperatures

    SciTech Connect

    Narita, Toshio

    2009-09-14

    Conventional and advanced coatings were reviewed, and it was pointed out that the coated Ni-base superalloys decreased their creep rupture life significantly at higher temperatures, and the advanced high strength superalloy became more remarkably. Concept of diffusion barrier coating system (DBC system) and their formation process was introduced, and the results obtained for several heat-resistant alloys, stainless steel (SUS310S), Ni-Mo base alloy (Hastelloy-X), and 4{sup th} generation single crystal superalloy (TMS-138) were given. It was noted that creep-rupture life of the SUS310S and Hastelloy-X with the DBC system became longer than those of the bare alloys with or without conventional {beta}-NiAl coatings. This is due to slow creep-deformation of the Re-base alloy layer as the diffusion barrier. A novel concept based on combination of superalloys and coatings was proposed, by taking both the materials science and corrosion science into consideration.

  8. RAPID COMMUNICATION: Thermal conductivity of silver alloy stabilizers for high temperature superconductor current leads

    NASA Astrophysics Data System (ADS)

    Putti, M.; Bellingeri, E.; Ferdeghini, C.; Goldacker, W.; Vase, P.

    2001-02-01

    In this rapid communication, we present thermal and electrical conductivity measurements of several Ag alloy sheaths for Bi-2223 tapes suitable for current lead applications. The main result is that sheaths based on AgAu alloys with a small addition of Mg and, mainly, AgMg tapes used as dispersion hardened sheaths for mechanical reinforcement show an unexpected low thermal conductivity. SEM analysis of these samples emphasizes a small grain size due to a partial oxidation of Mg, which causes a strong reduction of the phonon mean free path. Moreover, resistivity measurements show that the Mg atoms dispersed in the Ag matrix provide a significant reduction of the electron mean free path. Anyway, the AgAu alloy is preferable in order to preserve the performances of the superconducting filaments, therefore a compromise can be obtained by developing composite Bi-2223 tapes with the AgAu alloy around the superconducting filaments and an outer layer containing Mg around the filament bundle.

  9. Corrosion of alloy 625 in high-temperature, high-pressure sulfate solutions

    SciTech Connect

    Kritzer, P.; Boukis, N.; Dinjus, E.

    1998-09-01

    Corrosion phenomena of alloy 625 (UNS NO6625) were investigated in oxygenated aqueous solutions containing sulfuric acid (H{sub 2}SO{sub 4}), sodium hydrogen sulfate (NaHSO{sub 4}), or sodium sulfate (Na{sub 2}SO{sub 4}) and in deaerated H{sub 2}SO{sub 4} solution. Tests were conducted at temperatures and pressures up to 500 C and 38 MPa, respectively. Corrosion in the oxygenated acidic solution started {approximately}150 C with intergranular attack (IGA). Above 250 C, the whole surface of the alloy was attacked, and shallow pits and deep IGA appeared. This behavior was explained by transpassive dissolution of the protecting Cr(III) oxide layer. Severe material loss occurred between 300 C and 390 C. At higher temperatures, only weak corrosion was detected probably because of the lower density of the solution. Corrosion phenomena in oxygenated NaHSO{sub 4} solution were comparable but less severe than in H{sub 2}SO{sub 4}. In oxygenated Na{sub 2}SO{sub 4} solutions, no corrosion was observed up to the maximum test temperature of 350 C. In oxygen-free solutions, severe material loss occurred between 135 C and 220 C. The cathodic reaction was the reduction of sulfate, and the resulting potential was in the active region of the alloy. Above 230 C, the alloy passivated, and corrosion rates were low.

  10. Solid state thin film battery having a high temperature lithium alloy anode

    DOEpatents

    Hobson, D.O.

    1998-01-06

    An improved rechargeable thin-film lithium battery involves the provision of a higher melting temperature lithium anode. Lithium is alloyed with a suitable solute element to elevate the melting point of the anode to withstand moderately elevated temperatures. 2 figs.

  11. Further investigations on high temperature magnetic after-effect in iron alloys containing oxygen

    NASA Astrophysics Data System (ADS)

    Földeáki, M.; Stefán, M.; Köszegi, L.; Kisdi-Koszó, É.

    1980-04-01

    Magnetic after-effect and disaccommodation measurements were performed on iron alloys containing oxygen. A new effect was found. Time dependence, activation energy and ageing properties were determined and interpreted as the relaxation of dislocations with mobile oxygen Cottrell clouds and as the relaxation of interstitial clusters around the precipitates.

  12. 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) .

  13. Characteristics of lead induced stress corrosion cracking of alloy 690 in high temperature

    SciTech Connect

    Chung, K.K.; Lim, J.K.; Watanabe, Yutaka; Shoji, Tetsuo

    1996-10-01

    Slow strain rate tests (SSRT) were conducted on alloy 690 in various lead chloride solutions and metal lead added to 100 ppm chloride solution at 288 C. The corrosion potential (rest potential) for the alloy was measured with SSRT tests. The cracking was observed by metallographic examination and electron probe micro analyzer. Also, the corrosion behavior of the alloy was evaluated by anodic polarized measurement at 30 C. Resulting from the tests, cracking was characterized by cracking behavior, crack length and crack growth rate, and lead effects on cracking. The cracking was mainly intergranular in mode, approximately from 60 um to 450 um in crack length, and approximately 10{sup {minus}6} to 10{sup {minus}7} mmS-1 in crack velocity. The cracking was evaluated through the variation the corrosion potential in potential-time and lead behavior during SSRTs. The lead effect in corrosion was evaluated through active to passive transition behavior in anodic polarized curves. The corrosion reactions in the cracking region were confirmed by electron probe microanalysis. Alloy 690 is used for steam generation tubes in pressurized water reactors.

  14. Vibrational entropy changes the solid solubility of a random alloy at high temperatures

    NASA Astrophysics Data System (ADS)

    Shulumba, Nina; Hellman, Olle; Raza, Zamaan; Barrirero, Jenifer; Mücklich, Frank; Abrikosov, Igor A.; Odén, Magnus

    2015-03-01

    We have developed a method to accurately and efficiently determine vibrational entropy as a function of temperature and volume for substitutional alloys from first principles. Using Ti1-xAlxN metal alloy as a model system we calculate the isostructural phase diagram by minimization of the free energy, solving the original Gibbs problem of finding its global minimum corresponding to the true equilibrium state of the system. We demonstrate that the vibrational contribution to the free energy has a decisive impact on the calculated phase diagram of Ti1-xAlxN alloy, lowering the maximum temperature for the miscibility gap from 9000 K to 2400 K. The solubility limit of the predicted phase diagram is experimentally verified by local chemical composition measurements of thermally aged Ti50Al50N alloys. DocMASE, SECO Tools AB, SSF RMA 08-0069 and SRL 10-002, VR 2012-4401 and 637-2013-7296, Vinnova M-ERA.net, MC2, (KAW) (Isotopic Control for Ultimate Material Properties).

  15. A View of Compatible Heat-Resistant Alloy and Coating Systems at High-Temperatures

    NASA Astrophysics Data System (ADS)

    Narita, Toshio

    2009-09-01

    Conventional and advanced coatings were reviewed, and it was pointed out that the coated Ni-base superalloys decreased their creep rupture life significantly at higher temperatures, and the advanced high strength superalloy became more remarkably. Concept of diffusion barrier coating system (DBC system) and their formation process was introduced, and the results obtained for several heat-resistant alloys, stainless steel (SUS310S), Ni-Mo base alloy (Hastelloy-X), and 4th generation single crystal superalloy (TMS-138) were given. It was noted that creep-rupture life of the SUS310S and Hastelloy-X with the DBC system became longer than those of the bare alloys with or without conventional β-NiAl coatings. This is due to slow creep-deformation of the Re-base alloy layer as the diffusion barrier. A novel concept based on combination of superalloys and coatings was proposed, by taking both the materials science and corrosion science into consideration.

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

    NASA Technical Reports Server (NTRS)

    Chellman, D. J.

    1984-01-01

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

  17. High temperature fiber optic laser-induced breakdown spectroscopy sensor for analysis of molten alloy constituents

    NASA Astrophysics Data System (ADS)

    Rai, Awadhesh K.; Yueh, Fang Y.; Singh, Jagdish P.; Zhang, Hansheng

    2002-10-01

    A fiber optic (FO) laser-induced breakdown spectroscopy (LIBS) sensor that measures the on-line, in situ elemental composition of a molten alloy inside the melt in a furnace is described. This sensor has applications as a process monitor and control tool for glass, aluminum, and steel melters. The sensor is based on the transmission of laser energy through a multimode optical fiber. The laser radiation from the fiber is collimated and finally focused inside the aluminum melt in the furnace by a specially designed stainless steel holder that holds the collimating and focusing lens. Atomic emission from sparks from the laser plasma is collected by the same stainless steel lens holder and transmitted back through the optical fiber and finally fed into the entrance slit of the spectrograph. The present design of the stainless steel holder is useful for obtaining a collimated LIBS signal over a long distance (the distance between the focusing and collimated lenses is more than 200 cm). Parametric studies such as sample-to-lens distance and the effect of the angle of incidence of the laser beam on the sample surface were performed. Calibration curves for minor elements were obtained for solid Al alloys as well as for a molten Al alloy in the laboratory furnace by inserting the FO LIBS probe inside the molten material. The performance of the probe was also tested by inserting the stainless steel holder into the melt at a 45° angle, which is necessary for collecting LIBS data in an industrial furnace. LIBS spectra in different spectral regions were recorded in the pilot furnace during different tests where known amounts of minor elements were added to the melt. The results obtained from this sensor for different Al alloys demonstrate the usefulness of this sensor to monitor the concentration of different constituents of the molten Al alloy in an industrial furnace.

  18. Effects of prior surface damage on high-temperature oxidation of Fe-, Ni-, and Co-based alloys

    SciTech Connect

    Blau, Peter Julian; Lowe, Tracie M; Pint, Bruce A

    2009-01-01

    Multi-component metallic alloys have been developed to withstand high-temperature service in corrosive environments. Some of these applications, like exhaust valve seats in internal combustion engines, must also resist sliding, impact, and abrasion. The conjoint effects of temperature, oxidation, and mechanical contact can result in accelerated wear and the formation of complex surface layers whose properties differ from those of the base metal and the oxide scale that forms in the absence of mechanical contact. The authors have investigated the effects of prior surface damage, produced by scratch tests, on the localized reformation of oxide layers. Three high-performance commercial alloys, based on iron, nickel, and cobalt, were used as model materials. Thermogravimetric analysis (TGA) was used to determine their static oxidation rates at elevated temperature (850o C). A micro-abrasion, ball-cratering technique was used to measure oxide layer thickness and to compare it with TGA results. By using taper-sectioning techniques and energy-dispersive elemental mapping, a comparison was made between oxide compositions grown on non-damaged surfaces and oxides that formed on grooves produced by a diamond stylus. Microindentation and scratch hardness data revealed the effects of high temperature exposure on both the substrate hardness and the nature of oxide scale disruption. There were significant differences in elemental distribution between statically-formed oxides and those that formed on scratched regions

  19. Influence of Si and W additions on high temperature oxidation of {gamma}-{alpha}{sub 2} Ti-Al alloys

    SciTech Connect

    Tomasi, A.; Noseda, C.; Nazmy, M.; Gialanella, S.

    1997-12-31

    Titanium aluminides have potential interest for high temperature applications because of their low density and high temperature strength. In this study the isothermal oxidation behavior in air and in the temperature range 700--850 C of {gamma}-{alpha}{sub 2}Ti-Al bulk alloys with different additions of W (0--9.5 wt.%) and Si (0--5.0 wt.%) was investigated. The samples were prepared by arc-melting starting from pure element powders (99.99%). After thermal treatments, for homogenization and phase stabilization, the samples were tested using a thermal analysis apparatus in order to evaluate their oxidation resistance. The oxidation rates show the beneficial effect of the W and Si additions. The growth and adherence to the protective scale on alloys have been investigated in conjunction with detailed oxide scale characterization using the techniques of scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results of the study are used for critical assessment of the oxidation mechanisms leading to the formation of surface layers of different compositions.

  20. Research of aluminium alloy aerospace structure aperture measurement based on 3D digital speckle correlation method

    NASA Astrophysics Data System (ADS)

    Bai, Lu; Wang, Hongbo; Zhou, Jiangfan; Yang, Rong; Zhang, Hui

    2014-11-01

    In this paper, the aperture change of the aluminium alloy aerospace structure under real load is researched. Static experiments are carried on which is simulated the load environment of flight course. Compared with the traditional methods, through experiments results, it's proved that 3D digital speckle correlation method has good adaptability and precision on testing aperture change, and it can satisfy measurement on non-contact,real-time 3D deformation or stress concentration. The test results of new method is compared with the traditional method.

  1. Corrosion and Creep of Candidate Alloys in High Temperature Helium and Steam Environments for the NGNP

    SciTech Connect

    Was, Gary; Jones, J. W.

    2013-06-21

    This project aims to understand the processes by which candidate materials degrade in He and supercritical water/steam environments characteristic of the current NGNP design. We will focus on understanding the roles of temperature, and carbon and oxygen potential in the 750-850 degree C range on both uniform oxidation and selective internal oxidation along grain boundaries in alloys 617 and 800H in supercritical water in the temperature range 500-600 degree C; and examining the application of static and cyclic stresses in combination with impure He environments in the temperature rang 750-850 degree C; and examining the application of static and cyclic stresses in combination with impure He environments in the temperature range 750-850 degree C over a range of oxygen and carbon potentials in helium. Combined, these studies wil elucidate the potential high damage rate processes in environments and alloys relevant to the NGNP.

  2. Constitutive Equation for 3104 Alloy at High Temperatures in Consideration of Strain

    NASA Astrophysics Data System (ADS)

    Zhen, Fuqiang; Sun, Jianlin; Li, Jian

    2016-06-01

    The flow behavior of 3104 aluminum alloy was investigated at temperatures ranging from 250°C to 500°C, and strain rates from 0.01 to 10 s-1 by isothermal compression tests. The true stress-strain curves were obtained from the measured load-stroke data and then modified by friction and temperature correction. The effects of temperature and strain rate on hot deformation behavior were represented by Zener-Hollomon parameter including Arrhenius term. Additionally, the influence of strain was incorporated considering the effect of strain on material constants. The derived constitution equation was applied to the finite element analysis of hot compression. The results show that the simulated force is consistent with the measured one. Consequently, the developed constitution equation is valid and feasible for numerical simulation in hot deformation process of 3104 alloy.

  3. On massive carbide precipitation during high temperature low cycle fatigue in alloy 800H

    NASA Technical Reports Server (NTRS)

    Sankararao, K. Bhanu; Schuster, H.; Halford, G. R.

    1994-01-01

    The effect of strain rate on massive precipitation and the mechanism for the occurrence of massive precipitation of M23C6 in alloy 800H is investigated during elevated temperature low cycle fatigue testing. It was observed that large M23C6 platelets were in the vicinity of grain and incoherent twin boundaries. The strain controlled fatigue testing at higher strain rates that promoted cyclic hardening enabled massive precipitation to occur more easily.

  4. High-temperature reverse-bend fatigue strength of Inconel Alloy 625

    SciTech Connect

    Purohit, A.; Greenfield, I.G.; Park, K.B.

    1983-06-01

    Inconel 625 has been selected as the clad material for Upgraded Transient Reactor Test Facility (TREAT Upgrade or TU) fuel assemblies. The range of temperatures investigated is 900 to 1100/sup 0/C. A reverse-bend fatigue test program was selected as the most-effective method of determining the fatigue characteristics of Inconel alloy 625 sheet metal. The paper describes the reverse bend fatigue experiments, the results obtained, and the analysis of data.

  5. Studies of the Crystallization Process of Aluminum-Silicon Alloys Using a High Temperature Microscope. Thesis

    NASA Technical Reports Server (NTRS)

    Justi, S.

    1985-01-01

    It is shown that primary silicon crystals grow polyhedral in super-eutectic AlSi melts and that phosphorus additives to the melt confirm the strong seeding capacity. Primary silicon exhibits strong dendritic seeding effects in eutectic silicon phases of various silicon alloys, whereas primary aluminum does not possess this capacity. Sodium addition also produces a dendritic silicon network growth in the interior of the sample that is attributed to the slower silicon diffusion velocity during cooling.

  6. An Integrated Study of a Novel Thermal Coating for Nb-Based High Temperature Alloy

    SciTech Connect

    Yang, Shizhong

    2015-01-31

    This report summarizes our recent works of ab initio density functional theory (DFT) method and molecular dynamics (MD) simulation on the interfaces between niobium substrate and coatings at atomic level. Potential oxidation barrier bond coat, Nb₂AlC and high entropy alloys, and top coat candidates were synthesized, characterized, and evaluated in our labs. The simulation methods, experimental validation techniques, achievements already reached, students and postdoc training, and future improvement are briefly introduced.

  7. Palladium/Copper Alloy Composite Membranes for High Temperature Hydrogen Separation

    SciTech Connect

    J. Douglas Way; Paul M. Thoen

    2005-08-31

    This report summarizes progress made during the second year of research funding from DOE Grant DE-FG26-03NT41792 at the Colorado School of Mines. The period of performance was September 1, 2004 through August of 2005. We have reformulated our Pd plating process to minimize the presence of carbon contamination in our membranes. This has improved durability and increased permeability. We have developed techniques for plating the outside diameter of ceramic and metal substrate tubes. This configuration has numerous advantages including a 40% increase in specific surface area, the ability to assay the alloy composition non-destructively, the ability to potentially repair defects in the plated surface, and the ability to visually examine the plated surfaces. These improvements have allowed us to already meet the 2007 DOE Fossil Energy pure H{sub 2} flux target of 100 SCFH/ft{sup 2} for a hydrogen partial pressure difference of 100 psi with several Pd-Cu alloy membranes on ceramic microfilter supports. Our highest pure H{sub 2} flux on inexpensive, porous alumina support tubes at the DOE target conditions is 215 SCFH/ft{sup 2}. Progress toward meeting the other DOE Fossil Energy performance targets is also summarized. Additionally, we have adapted our membrane fabrication procedure to apply Pd and Pd alloy films to commercially available porous stainless steel substrates. Stable performance of Pd-Cu films on stainless steel substrates was demonstrated over a three week period at 400 C. Finally, we have fabricated and tested Pd-Au alloy membranes. These membranes also exceed both the 2007 and 2010 DOE pure H{sub 2} flux targets and exhibit ideal H{sub 2}/N{sub 2} selectivities of over 1000 at partial pressure difference of 100 psi.

  8. High-temperature behavior of a Pd-Ag alloy for porcelain.

    PubMed

    Mackert, J R; Ringle, R D; Fairhurst, C W

    1983-12-01

    The mechanism of formation of nodular material on the surface of a Pd-Ag-based alloy for porcelain during pre-porcelainization heat treatment was investigated using scanning electron microscopy, x-ray diffraction, quantitative metallography, and Auger electron spectroscopy. The nodules were found to form by a Nabarro-Herring creep mechanism driven by the internal oxidation of tin and indium. Implications of this process with regard to porcelain bonding and discoloration are discussed. PMID:6581200

  9. Mechanical and functional behavior of high-temperature Ni-Ti-Pt shape memory alloys

    DOE PAGESBeta

    Buchheit, Thomas E.; Susan, Donald F.; Massad, Jordan E.; McElhanon, James R.; Noebe, Ronald D.

    2016-01-22

    A series of Ti-rich Ni-Ti-Pt ternary alloys with 13 to 18 at. pct Pt were processed by vacuum arc melting and characterized for their transformation behavior to identify shape memory alloys (SMA) that undergo transformation between 448 K and 498 K (175 °C and 225 °C) and achieve recoverable strain exceeding 2 pct. From this broader set of compositions, three alloys containing 15.5 to 16.5 at. pct Pt exhibited transformation temperatures in the vicinity of 473 K (200 °C), thus were targeted for more detailed characterization. Preliminary microstructural evaluation of these three compositions revealed a martensitic microstructure with small amountsmore » of Ti2(Ni,Pt) particles. Room temperature mechanical testing gave a response characteristic of martensitic de-twinning followed by a typical work-hardening behavior to failure. Elevated mechanical testing, performed while the materials were in the austenitic state, revealed yield stresses of approximately 500 MPa and 3.5 pct elongation to failure. Thermal strain recovery characteristics were more carefully investigated with unbiased incremental strain-temperature tests across the 1 to 5 pct strain range, as well as cyclic strain-temperature tests at 3 pct strain. As a result, the unbiased shape recovery results indicated a complicated strain recovery path, dependent on prestrain level, but overall acceptable SMA behavior within the targeted temperature and recoverable strain range.« less

  10. Mechanical and Functional Behavior of High-Temperature Ni-Ti-Pt Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Buchheit, Thomas E.; Susan, Donald F.; Massad, Jordan E.; McElhanon, James R.; Noebe, Ronald D.

    2016-04-01

    A series of Ti-rich Ni-Ti-Pt ternary alloys with 13 to 18 at. pct Pt were processed by vacuum arc melting and characterized for their transformation behavior to identify shape memory alloys (SMA) that undergo transformation between 448 K and 498 K (175 °C and 225 °C) and achieve recoverable strain exceeding 2 pct. From this broader set of compositions, three alloys containing 15.5 to 16.5 at. pct Pt exhibited transformation temperatures in the vicinity of 473 K (200 °C), thus were targeted for more detailed characterization. Preliminary microstructural evaluation of these three compositions revealed a martensitic microstructure with small amounts of Ti2(Ni,Pt) particles. Room temperature mechanical testing gave a response characteristic of martensitic de-twinning followed by a typical work-hardening behavior to failure. Elevated mechanical testing, performed while the materials were in the austenitic state, revealed yield stresses of approximately 500 MPa and 3.5 pct elongation to failure. Thermal strain recovery characteristics were more carefully investigated with unbiased incremental strain-temperature tests across the 1 to 5 pct strain range, as well as cyclic strain-temperature tests at 3 pct strain. The unbiased shape recovery results indicated a complicated strain recovery path, dependent on prestrain level, but overall acceptable SMA behavior within the targeted temperature and recoverable strain range.

  11. Influence of gaseous hydrogen on the mechanical properties of high temperature alloys

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Tensile tests of six nickel-base and one cobalt-base alloy were conducted in 34.5 MN/sq m helium and hydrogen environments at temperatures from 297 K to 1,088 K. Mechanical properties tests of the nickel-base alloy MAR M-246 (Hf modified), in two cast conditions, were conducted in gaseous environments at temperatures from 297 K to 1,144 K and pressures from one atmosphere to 34.5 MN/sq m. The objective of this program was to obtain the mechanical properties of the various alloys proposed for use in space propulsion systems in a pure hydrogen environment at different temperatures and to compare with the mechanical properties in helium at the same conditions. All testing was conducted on solid specimens exposed to external gaseous pressure. Smooth and notched tensile properties were determined using ASTM tensile testing techniques, and creep-rupture life was determined using ASTM creep-rupture techniques. Low-cycle fatigue life was established by constant total strain and constant stress testing using smooth specimens and a closed-loop test machine.

  12. High temperature oxidation behavior of Zr-1Nb cladding alloy E110.

    SciTech Connect

    Yan, Y.; Burtseva, T.; Billone, M. C.; Nuclear Engineering Division

    2009-09-15

    Oxidation experiments were conducted at 1000-1200 C in flowing steam with samples of as-received Zr-1Nb alloy E110 tubing and/or polished E110 tubing. The purpose was to determine the oxidation behavior of this alloy under postulated loss-of-coolant accident conditions in light water reactors. The as-received E110 tubing exhibited a high degree of susceptibility to nodular oxidation and breakaway oxidation at relatively low test times, as compared to other cladding alloys. The nodules grew much more rapidly at 1000 C than 1100 C, as did the associated hydrogen uptake. The oxidation behavior was strongly affected by the surface condition of the materials. Polishing to {approx}0.1 {micro}m roughness (the roughness of the as-received tubing was {approx}0.4 {micro}m) delayed breakaway oxidation. Polishing also removed surface impurities. For polished samples oxidized at 1100 C, no significant nodular oxidation appeared up to 1000 s. For polished samples oxidized at 1000 C, hydrogen uptake >100 wppm was delayed from {approx}300 s to >900 s. Weight-gain coefficients were determined for pre-breakaway oxidation of polished-only and machined-and-polished E110 tubing samples: 0.162 (mg/cm{sup 2})/s{sup 0.5} at 1000 C and 0.613 (mg/cm{sup 2})/s{sup 0.5} at 1100 C.

  13. PALLADIUM/COPPER ALLOY COMPOSITE MEMBRANES FOR HIGH TEMPERATURE HYDROGEN SEPARATION

    SciTech Connect

    J. Douglas Way

    2004-08-31

    This report summarizes progress made during the first year of research funding from DOE Grant No. DE-FG26-03NT41792 at the Colorado School of Mines. The period of performance was September 1, 2003 through August of 2004. Composite membranes, consisting of a thin Pd alloy film supported on a porous substrate have been investigated as a means of reducing the membrane cost and improving H{sub 2} flux. An electroless plating technique was utilized to deposit subsequent layers of palladium and copper over zirconia and alumina-based microfilters. The composite membranes thus made were annealed and tested at temperatures ranging from 250 to 500 C, under very high feed pressures (up to 450 psig) using pure gases and gaseous mixtures containing H{sub 2}, CO, CO{sub 2}, H{sub 2}O and H{sub 2}S, with the purpose of determining the effects these variables had on the H{sub 2} permeation rate, selectivity and percent recovery. The inhibition caused by CO/CO{sub 2} gases on a 7 {micro}m thick Pd-Cu composite membrane was less than 17% over a wide range of compositions at 350 C. H{sub 2}S caused a strong inhibition of the H{sub 2} flux of the same Pd-Cu composite membrane, which is accentuated at levels of 100 ppm or higher. The membrane was exposed to 50 ppm three times without permanent damage. At higher H{sub 2}S levels, above 100 ppm the membrane suffered some physical degradation and its performances was severely affected. The use of sweep gases improved the hydrogen flux and recovery of a Pd-Cu composite membrane. Recently, we have been able to dramatically reduce the thickness of these Pd alloy membranes to approximately one micron. This is significant because at this thickness, it is the cost of the porous support that controls the materials cost of a composite Pd alloy membrane, not the palladium inventory. Very recent results show that the productivity of our membranes is very high, essentially meeting the DOE pure hydrogen flux target value set by the DOE Hydrogen

  14. Design and development of NiTi-based precipitation-strengthened high-temperature shape memory alloys for actuator applications

    NASA Astrophysics Data System (ADS)

    Hsu, Derek Hsen Dai

    As a vital constituent in the field of smart materials and structures, shape memory alloys (SMAs) are becoming ever-more important due to their wide range of commercial and industrial applications such as aircraft couplings, orthodontic wires, and eyeglasses frames. However, two major obstacles preventing SMAs from fulfilling their potential as excellent actuator materials are: 1) the lack of commercially-viable SMAs that operate at elevated temperatures, and 2) the degradation of mechanical properties and shape memory behavior due to thermal cyclic fatigue. This research utilized a thermodynamically-driven systems design approach to optimize the desired properties by controlling the microstructure and processing of high-temperature SMAs (HTSMAs). To tackle the two aforementioned problems with HTSMAs, the introduction of Ni2TiAl coherent nanoprecipitates in a Ni-Ti-Zr/Hf HTSMA matrix is hypothesized to strengthen the martensite phase while simultaneously increasing the transformation temperature. Differential scanning calorimetry (DSC) was used to determine the transformation temperatures and thermal cyclic stability of each alloy. Also, microstructural characterization was performed using X-ray diffraction (XRD), optical microscopy (OM), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and atom probe tomography (APT). Lastly, compression testing was used to assess the mechanical behavior of the alloys. From the investigation of the first set of Ni48.5Ti31.5-X Zr20AlX (X = 0, 1, 2, 3) prototype alloys, Al addition was found to decrease the transformation temperatures, decrease the thermal cyclic stability, but also increase the strength due to the nucleation and growth of embrittling NiTi2 and NiTiZr Laves phases. However, the anticipated Heusler phase precipitation did not occur. The next study focused on Ni50Ti30-XHf20Al X (X = 0, 1, 2, 3, 4, 5) prototype alloys which replaced Zr with Hf to avoid the formation of brittle Laves phases

  15. Palladium/Copper Alloy Composite Membranes for High Temperature Hydrogen Separation

    SciTech Connect

    J. Douglas Way; Paul M. Thoen

    2006-08-31

    This report summarizes progress made during the a three year University Coal Research grant (DEFG26-03NT41792) at the Colorado School of Mines. The period of performance was September 1, 2003 through August of 2006. We made excellent progress toward our goal of contributing to the development of high productivity, sulfur tolerant composite metal membranes for hydrogen production and membrane reactors. Composite Pd and Pd alloy metal membranes with thin metal films (1-7 {micro}m) were prepared on porous stainless steel and ceramic supports that meet or exceed the DOE 2010 and 2015 pure hydrogen flux targets at differential pressure of only 20 psi. For example, a 2 {micro}m pure Pd membrane on a Pall AccuSep{reg_sign} substrate achieved an ideal H{sub 2}/N{sub 2} separation factor of over 6000, with a pure hydrogen flux of 210 SCFH/ft{sup 2} at only 20 psig feed pressure. Similar performance was achieved with a Pd{sub 80}Au{sub 20} composite membrane on a similar stainless steel substrate. Extrapolating the pure hydrogen flux of this PdAu membrane to the DOE Fossil Energy target conditions of 150 psia feed pressure and 50 psia permeate pressure gives a value of 508 SCFH/ft{sup 2}, exceeding the 2015 target. At these thicknesses, it is the support cost that will dominate the cost of a large scale module. In a direct comparison of FCC phase PdCu and PdAu alloys on identical supports, we showed that a Pd{sub 85}Au{sub 15} (mass %) alloy membrane is not inhibited by CO, CO{sub 2}, or steam present in a water-gas shift feed mixture at 400 C, has better resistance to sulfur than a Pd{sub 94}Cu{sub 6} membrane, and has over twice the hydrogen permeance.

  16. Continuous high temperature gradient solidification of in situ Cu-Nb alloys for large scale development

    SciTech Connect

    LeHuy, H.; Fihey, J.L.; Foner, S.; Roberge, R.

    1982-01-01

    Several research groups are evaluating various scale-up approaches for the in situ technique of preparing multiply-connected Nb/sub 3/Sn composite superconducting wire. Previously, the authors developed an arrangement for continuous high temperature gradient solidification, and now have upgraded the process to permit the solidification of larger diameter (9.5 mm) rods in virtually unlimited lengths. The preparation, the microstructure, and the characteristics (solidification rate, dendrite branching, and dendrite size) are given for three directionally solidified in situ materials with a nominal composition of Cu-30 wt% Nb. Micrographs of variously extracted Nb filaments and various-order dendrites are provided. The HTGS technique offers several advantages over other scale-up production methods, such as the control over the microstructure, form, and size of the Nb dendrites. A critical current density of 10 kA/cm/sup 2/ at roughly 16.5 T has been measured for the fine dendrite materials.

  17. Welding of dissimilar alloys for high temperature heat exchangers for SOFC

    SciTech Connect

    Wilson, R.D.; Hatem, J.; Dogan, O.N.; King, P.E.

    2006-10-01

    Reduction in the cost of balance of plant applications is one of the top priority focus areas for the successful implementation of solid oxide fuel cell technology. High temperature heat exchangers are employed to heat cathode air utilizing either hot gases coming from the anode side of the stack or other hot gases generated by external processes. In order to reduce the cost of heat exchangers, it may be necessary to apply several different materials, each in a different temperature zone, for the construction of the heat exchanger. This technique would require the joining of dissimilar materials in the construction. In this work, welding of commercial candidate dissimilar materials is explored. Filler materials were identified using equilibrium phase diagrams and thermodynamic simulation software. Autogenous welding was performed and the welding defects were characterized. Finally, experimental weld microstructures were compared to phases predicted by the simulations.

  18. Low-cycle fatigue of a VZh175 high-temperature alloy under elastoplastic deformation conditions

    NASA Astrophysics Data System (ADS)

    Belyaev, M. S.; Terent'ev, V. F.; Bakradze, M. M.; Gorbovets, M. A.; Gol'dberg, M. A.

    2015-04-01

    The low-cycle fatigue of a VZh175 nickel superalloy is studied under conditions of complete deformation per loading cycle at an initial cycle asymmetry R = 0, a deformation amplitude ɛa = 0.4-0.6%, and a temperature of 20 and 650°C. The specific features of cyclic hardening/softening of the alloy under these conditions are detected. The mechanisms of fatigue crack nucleation and growth are analyzed as functions of the deformation amplitude and the test temperature.

  19. Characterization of Ternary NiTiPd High-Temperature Shape-Memory Alloys under Load-Biased Thermal Cycling

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

    While NiTiPd alloys have been extensively studied for proposed use in high-temperature shape-memory applications, little is known about the shape-memory response of these materials under stress. Consequently, the isobaric thermal cyclic responses of five (Ni,Pd)49.5Ti50.5 alloys with constant stoichiometry and Pd contents ranging from 15 to 46 at. pct were investigated. From these tests, transformation temperatures, transformation strain (which is proportional to work output), and unrecovered strain per cycle (a measure of dimensional instability) were determined as a function of stress for each alloy. It was found that increasing the Pd content over this range resulted in a linear increase in transformation temperature, as expected. At a given stress level, work output decreased while the amount of unrecovered strain produced during each load-biased thermal cycle increased with increasing Pd content, during the initial thermal cycles. However, continued thermal cycling at constant stress resulted in a saturation of the work output and nearly eliminated further unrecovered strain under certain conditions, resulting in stable behavior amenable to many actuator applications.

  20. Effect of interstitial content on high- temperature fatigue crack propagation and low- cycle fatigue of alloy 720

    NASA Astrophysics Data System (ADS)

    Bashir, S.; Thomas, M. C.

    1993-08-01

    Alloy 720 is a high-strength cast and wrought turbine disc alloy currently in use for temperatures up to about 650 °C in Allison’s T800, T406, GMA 2100, and GMA 3007 engines. In the original composition in-tended for use as turbine blades, large carbide and boride stringers formed and acted as preferred crack initiators. Stringering was attributed to relatively higher boron and carbon levels. These interstitials are known to affect creep and ductility of superalloys, but the effects on low-cycle fatigue and fatigue crack propagation have not been studied. Recent emphasis on the total life approach in the design of turbine discs necessitates better understanding of the interactive fatigue crack propagation and low-cycle fatigue behavior at high temperatures. The objective of this study was to improve the damage tolerance of Alloy 720 by systematically modifying boron and carbon levels in the master melt, without altering the low-cy-cle fatigue and strength characteristics of the original composition. Improvement in strain-controlled low-cycle fatigue life was achieved by fragmenting the continuous stringers via composition modifica-tion. The fatigue crack propagation rate was reduced by a concurrent reduction of both carbon and bo-ron levels to optimally low levels at which the frequency of brittle second phases was minimal. The changes in composition have been incorporated for production disc forgings.

  1. Effect of interstitial content on high-temperature fatigue crack propagation and low-cycle fatigue of Alloy 720

    SciTech Connect

    Bashir, S. ); Thomas, M.C. . Allison Gas Turbine Div.)

    1993-08-01

    Alloy 720 is a high-strength cast and wrought turbine disc alloy currently in use for temperatures up to about 650 C in Allison's T800, T406, GMA 2100, and GMA 3007 engines. In the original composition intended for use as turbine blades, large carbide and borides stringers formed and acted as preferred crack initiators. Stringering was attributed to relatively higher boron and carbon levels. These interstitial are known to affect creep and ductility of superalloys, but the effects on low-cycle fatigue and fatigue crack propagation have not been studied. Recent emphasis on the total life approach in the design of turbine discs necessitates better understanding of the interactive fatigue crack propagation and low-cycle fatigue behavior at high temperatures. The objective of this study was to improve the damage tolerance of Alloy 720 by systematically modifying boron and carbon levels in the master melt, without altering the low-cycle fatigue and strength characteristics of the original composition. Improvement in strain-controlled low-cycle fatigue life was achieved by fragmenting the continuous stringers via composition modification. The fatigue crack propagation rate was reduced by a concurrent reduction of both carbon and boron levels to optimally low levels at which the frequency of brittle second phases was minimal. The changes in composition have been incorporated for production disc forgings.

  2. High temperature oxidation resistance of fluorine-treated TiAl alloys: Chemical vs. ion beam fluorination techniques

    NASA Astrophysics Data System (ADS)

    Neve, Sven; Masset, Patrick J.; Yankov, Rossen A.; Kolitsch, Andreas; Zschau, Hans-Eberhard; Schütze, Michael

    2010-11-01

    The modification of the alloy surface by halogens significantly improves their oxidation behaviour at high temperature. It corresponds to the preferential reaction of the aluminium with the applied fluorine at the oxide/alloy interface and it promotes the growth of an adherent and stable alumina layer. Well-defined fluorine profiles beneath the surface of the material can be achieved by either fluorine beam line ion implantation (BLI 2) or plasma immersion ion implantation (PI 3). As an alternative to the implantation-based approach, chemical fluorination techniques such as gas-phase treatment and dipping in F-based solutions were also investigated. The fluorine depth-profiles were measured before and after oxidation at 900 °C using non destructive ion beam analyses: Proton Induced Gamma-ray Emission (PIGE), Rutherford Backscattering Spectroscopy (RBS) as well as Elastic Recoil Detection Analysis (ERDA). It enables to control and to optimise the fluorination conditions of technical TiAl alloys for an industrial application.

  3. Vacuum-arc chromium-based coatings for protection of zirconium alloys from the high-temperature oxidation in air

    NASA Astrophysics Data System (ADS)

    Kuprin, A. S.; Belous, V. A.; Voyevodin, V. N.; Bryk, V. V.; Vasilenko, R. L.; Ovcharenko, V. D.; Reshetnyak, E. N.; Tolmachova, G. N.; V'yugov, P. N.

    2015-10-01

    Multilayer Cr-Zr/Cr/Cr-N coatings for protection of zirconium alloys from the high-temperature oxidation in air have been obtained by the vacuum-arc evaporation technique with application of filters for plasma cleaning from macroparticles. The effect of the coatings on the corrosion resistance of zirconium alloys at test temperatures between 660 and 1100 °C for 3600 s has been investigated. The thickness, structure, phase composition, mechanical properties of the coatings and oxide layers before and after oxidation tests were examined by scanning electron microscopy, X-ray diffraction analysis and nanoindentation technique. It is shown that the hard multilayer coating effectively protects zirconium from the oxidation in air for 1 h at test temperatures. As a result of the oxidation in the coating the CrO and Cr2O3 oxides are formed which reduce the oxygen penetration through the coating. At maximum test temperature of 1100 °C the oxide layer thickness in the coating is about 5 μm. The tube shape remains unchanged independent of alloy type. It has been found that uncoated zirconium oxidizes rapidly throughout the temperature range under study. At 1100 °C a porous monoclinic ZrO2 oxide layer of ≥120 μm is formed that leads to the deformation of the samples, cracking and spalling of the oxide layer.

  4. Creep-resistant, cobalt-free alloys for high temperature, liquid-salt heat exchanger systems

    DOEpatents

    Holcomb, David E; Muralidharan, Govindarajan; Wilson, Dane F.

    2016-09-06

    An essentially Fe- and Co-free alloy is composed essentially of, in terms of weight percent: 6.0 to 7.5 Cr, 0 to 0.15 Al, 0.5 to 0.85 Mn, 11 to 19.5 Mo, 0.03 to 4.5 Ta, 0.01 to 9 W, 0.03 to 0.08 C, 0 to 1 Re, 0 to 1 Ru, 0 to 0.001 B, 0.0005 to 0.005 N, balance Ni, the alloy being characterized by, at 850.degree. C., a yield strength of at least 25 Ksi, a tensile strength of at least 38 Ksi, a creep rupture life at 12 Ksi of at least 25 hours, and a corrosion rate, expressed in weight loss [g/(cm.sup.2 sec)]10.sup.-11 during a 1000 hour immersion in liquid FLiNaK at 850.degree. C., in the range of 3 to 10.

  5. High-temperature oxidation behavior of a wrought Ni-Cr-W-Mn-Si-La alloy

    SciTech Connect

    Tawancy, H.M.

    1996-04-01

    An investigation was carried out to study the kinetics and products of oxidation of a wrought Ni-Cr-W-Mn-Si-La alloy at temperatures in the range of 950 to 1150{degrees}C. Oxidation kinetics were evaluated from measurements of weight change, metal loss, and internal penetration. Analytical electron microscopy, scanning electron microscopy, electron probe microanalysis, and X-ray diffraction were used to characterize the scale microstructure. Initially, La was observed to segregate within a surface layer of about 5 {mu}m thick, which promoted selective oxidation of Cr and Mn. Oxidation kinetics were found to follow a parabolic-rate law with an activation energy of about 232 kJ/mol. During steady-state oxidation, the scale consisted of an inner adherent layer of {alpha}-Cr{sub 2}O{sub 3} modified by the presence of La and Si, and shielded by an outer layer of MnCr{sub 2}O{sub 4}. Most of the La was segregated to grain boundaries of the {alpha}-Cr{sub 2}O{sub 3} scale, however, Si was homogeneously distributed. It was concluded that the characteristic oxidation resistance of the alloy was related to the synergistic effects of Ni and Cr and to the effective minor additions of La, Si, and Mn; however, the useful life of the scale was limited by rupture and surface depletion in Cr, leading to accelerated internal oxidation.

  6. Slip Resistance of Ti-Based High-Temperature Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Ojha, A.; Sehitoglu, H.

    2016-03-01

    Titanium with Nb, Zr, and Ta alloying substitutions possesses high plastic slip resistance and high transformation strains upon bcc (β) to orthorhombic (α^'') transformation. In the current study, we determine the critical resolved shear stress (CRSS) for slip in Ti alloyed for a wide composition range of Nb, Ta, and Zr. The CRSS is obtained with a proposed Peierls-Nabarro formalism incorporating the generalized stacking fault energy barrier profile for slip obtained from the first-principles Density Functional Theory (DFT) calculations. The CRSS for slip of the orthorhombic martensite increases from 80 to 280 MPa linearly with increasing unstable fault energy. The addition of tantalum is most effective in raising the energy barriers. We also demonstrate the composition dependence of the lattice parameters of both β and α^'' crystal structures as a function of Nb, Ta, and Zr additions showing agreement with experiments. Using the lattice constants, the transformation strain is determined as high as 11 % in the [011] pole and its magnitude increases mainly with Zr addition.

  7. Alloying-Element Loss During High-Temperature Processing of a Nickel-Base Superalloy

    NASA Astrophysics Data System (ADS)

    Semiatin, S. L.; Shank, J. M.; Saurber, W. M.; Pilchak, A. L.; Ballard, D. L.; Zhang, F.; Gleeson, B.

    2014-02-01

    The effect of exposure at temperatures commonly used for wrought processing/heat treatment of nickel-base superalloys on the loss of alloying elements at the free surface has been determined. For this purpose, LSHR superalloy samples were exposed at 1408 K (1135 °C) for 0.25 to 4 hours in a vacuum or air furnace. Samples heat treated in the air furnace were either bare or enclosed in quartz capsules that had been evacuated or backfilled with argon. Following heat treatment, the alloy composition as a function of depth below the surface was determined by wavelength dispersive spectroscopy. Samples that had been heat treated in the vacuum furnace exhibited significant depletion of only chromium, a behavior explained on the basis of its high activity in nickel solid solution and corresponding rapid rate of evaporation. By contrast, samples heat treated in air exhibited an irregular scale at the surface and an underlying grain-coarsened, gamma-prime-depleted metal layer lean in aluminum, titanium, and chromium. A yet different behavior characterized primarily by aluminum loss at the surface was noted for samples that had been heat treated in evacuated or argon-backfilled capsules. These observations were interpreted in the context of a reaction between the quartz capsule and the aluminum evaporant.

  8. 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

  9. Processing, Microstructure and Creep Behavior of Mo-Si-B-Based Intermetallic Alloys for Very High Temperature Structural Applications

    SciTech Connect

    Vijay Vasudevan

    2008-03-31

    This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. In the first part of this project, the compression creep behavior of a Mo-8.9Si-7.71B (in at.%) alloy, at 1100 and 1200 C was studied, whereas in the second part of the project, the constant strain rate compression behavior at 1200, 1300 and 1400 C of a nominally Mo-20Si-10B (in at.%) alloy, processed such as to yield five different {alpha}-Mo volume fractions ranging from 5 to 46%, was studied. In order to determine the deformation and damage mechanisms and rationalize the creep/high temperature deformation data and parameters, the microstructure of both undeformed and deformed samples was characterized in detail using x-ray diffraction, scanning electron microscopy (SEM) with back scattered electron imaging (BSE) and energy dispersive x-ray spectroscopy (EDS), electron back scattered diffraction (EBSD)/orientation electron microscopy in the SEM and transmission electron microscopy (TEM). The microstructure of both alloys was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. The values of stress exponents and activation energies, and their dependence on microstructure were determined. The data suggested the operation of both dislocation as well as diffusional mechanisms, depending on alloy, test temperature, stress level and microstructure. Microstructural observations of post-crept/deformed samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. TEM observations revealed the presence of recrystallized {alpha}-Mo grains and sub-grain boundaries composed of dislocation arrays within the grains (in Mo-8.9Si-7.71B) or fine sub-grains with a high density of b = 1/2<111> dislocations (in Mo-20Si-10B), which

  10. The effect of alloying additions on the high temperature deformation characteristics of Ti-48Al (at%) alloys

    SciTech Connect

    Sabinash, C.M.; Sastry, S.M.L.; Jerina, K.L.

    1995-05-01

    Addition of ternary and quaternary alloying elements at levels between one and three atomic percent increase the room temperature ductility of Ti-48Al (at%) based titanium aluminides. In this investigation the deformation characteristics of Ti-48Al-2X (X = Cr, Mn) alloys at temperatures of 1,200 C to 1,300 C and strain rates of 10{sup {minus}3}s{sup {minus}1} to 10{sup {minus}1}s{sup {minus}1} were studied and compared with the deformation characteristics of Ti-48Al using the same conditions. Three titanium aluminide alloys with target compositions of Ti-48Al, Ti-48Al-2Cr, and Ti-48Al-2Mn (at%) were induction skull melted and cast into 69.85 mm. diameter ingots. The cast ingots were hot isostatically pressed (HIPed) at 103.5 MPa, 1,177 C for 4 hours to close casting porosity and homogenize the alloy microstructure and composition. Cylindrical test specimens 10 mm dia by 15 mm height were excised by EDM from the ingot and were subjected to isothermal compression testing in air at 1,200--1,300 C and the effective strain rates of 10{sup {minus}3}--10{sup {minus}1}s{sup {minus}1}.

  11. Zinc Treatment Effects on Corrosion Behavior of Alloy 600 in High Temperature, Hydrogenated Water

    SciTech Connect

    SE Ziemniak; ME Hanson

    2004-11-16

    Trace levels of soluble zinc(II) ions (30 ppb) maintained in mildly alkaline, hydrogenated water at 260 C were found to reduce the corrosion rate of Alloy 600 (UNS N06600) by about 40% relative to a non-zinc baseline test [2]. Characterizations of the corrosion oxide layer via SEM/TEM and grazing incidence X-ray diffraction confirmed the presence of a chromite-rich oxide phase and recrystallized nickel. The oxide crystals had an approximate surface density of 3500 {micro}m{sup -2} and an average size of 11 {+-} 5 nm. Application of X-ray photoelectron spectroscopy with argon ion milling, followed by target factor analyses, permitted speciated composition vs. depth profiles to be obtained. Numerical integration of the profiles revealed that: (1) alloy oxidation occurred non-selectively and (2) zinc(II) ions were incorporated into the chromite-rich spinel: (Zn{sub 0.55}Ni{sub 0.3}Fe{sub 0.15})(Fe{sub 0.25}Cr{sub 0.75}){sub 2}O{sub 4}. Spinel stoichiometry places the trivalent ion composition in the single phase oxide region, consistent with the absence of the usual outer, ferrite-rich solvus layer. By comparison with compositions of the chromite-rich spinel obtained in the non-zinc baseline test, it is hypothesized that zinc(II) ion incorporation was controlled by the equilibrium for 0.55 Zn{sup 2+}(aq) + (Ni{sub 0.7}Fe{sub 0.3})(Fe{sub 0.3}Cr{sub 0.7}){sub 2}O{sub 4}(s) {r_equilibrium} 0.40 Ni{sup 2+}(aq) + 0.15 Fe{sup 2+}(aq) + (Zn{sub 0.55}Ni{sub 0.3}Fe{sub 0.15})(Fe{sub 0.3}Cr{sub 0.7}){sub 2}O{sub 4}(s). It is estimated that only 8% of the Ni(II) ions generated during non-selective oxidation of the alloy were retained as Ni(II) in the corrosion layer; the remainder either recrystallized to Ni(0) (38%) or were released to the aqueous phase (54%).

  12. High-Temperature Stability and Grain Boundary Complexion Formation in a Nanocrystalline Cu-Zr Alloy

    NASA Astrophysics Data System (ADS)

    Khalajhedayati, Amirhossein; Rupert, Timothy J.

    2015-12-01

    Nanocrystalline Cu-3 at.% Zr powders with ~20 nm average grain size were created with mechanical alloying and their thermal stability was studied from 550-950°C. Annealing drove Zr segregation to the grain boundaries, which led to the formation of amorphous intergranular complexions at higher temperatures. Grain growth was retarded significantly, with 1 week of annealing at 950°C, or 98% of the solidus temperature, only leading to coarsening of the average grain size to 54 nm. The enhanced thermal stability can be connected to both a reduction in grain boundary energy with doping as well as the precipitation of ZrC particles. High mechanical strength is retained even after these aggressive heat treatments, showing that complexion engineering may be a viable path toward the fabrication of bulk nanostructured materials with excellent properties.

  13. [Dissertations 25 years after date 44. Behaviour at high temperatures of palladium based dental alloys].

    PubMed

    van der Zel, J M

    2016-02-01

    In the Netherlands in the 1980s palladium based dental alloys were often used in substructures of metal-ceramic restorations. However, after their introduction to the market some unexplained problems came to light: porosity on the metal-ceramic interface, frequent failure of solder joints, margin lift and distortion of bigger constructions. Later, palladium allergies could be added to the list. A 1989 dissertation investigated these problems and underlying causes and came up with answers and solutions. Recent problems like the breakage and chipping of porcelain on zirconia cores shows again that industry is sometimes unaware of adjustment problems at the moment that a new product is introduced to the market. PMID:26878716

  14. Passivity degradation of nuclear steam generator tubing alloy induced by Pb contamination at high temperature

    NASA Astrophysics Data System (ADS)

    Lu, B. T.; Luo, J. L.; Lu, Y. C.

    2012-10-01

    Effects of Pb contamination on the passivity of a Ni-based alloy (UNS N06690) in a simulated crevice chemistry of steam generator with near-neutral pH at 300 °C are elucidated using electrochemical measurements and surface analysis techniques. The experimental observations reveal that Pb impurity can enter anodic film, which results in substantial changes in the films structure via hindering the dehydration during the passivation and retarding the formation of spinel oxides. The presence of Pb-contamination can also increase hydrogen content in anodic film. Finally, the mechanism of passivity degradation induced by Pb contamination is described on the basis of the experimental data and established theory.

  15. NASA-UVA Light Aerospace Alloy and Structures Technology Program (LA2ST). Progress report, 1 January-30 June 1993

    SciTech Connect

    Gangloff, R.P.; Scully, J.R.; Stoner, G.E.; Thornton, E.A.; Wawner, F.E. Jr.; Wert, J.A.

    1993-07-01

    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.

  16. Surface Finishing—Chip Arrangement Relationship in the Dry Turning of Aerospace Titanium Alloys

    NASA Astrophysics Data System (ADS)

    Gerez, J. M.; Diaz-Vazquez, J. E.; Gonzalez, J. M.; Batista, M.; Huerta, M.; Marcos, M.

    2009-11-01

    Nowadays, one of the industrial sectors with greater implication in the technological development of Spain is the related one to the aerospace industry that, in some zones of the country, has gotten to become the industrial motor of the same ones, and to replace sectors that, by tradition and geographical strategy, had come occupying this place. Being located within this sector in height, the increasing application of titanium alloys is verified for the different constructions, that is to say, the use in light alloy rise. Along with the aluminium alloys, titanium alloys are widely used in the aeronautical industry. The good relationship hardness/weight and the high corrosion resistance turn them excellent candidates for high performance machining operations. Production requirements force a greater surface quality of the machined pieces. In this work a preliminary analysis of the evolution of the surface quality in the dry turning in of the Ti-6Al-4V is carried out, looking for a possible correlation with the geometry of the chips obtained in the tests. In order to evaluate the surface quality the arithmetical average roughness, Ra, has been used.

  17. Dynamic measurements of thermophysical properties of metals and alloys at high temperatures by subsecond pulse heating techniques

    NASA Technical Reports Server (NTRS)

    Cezairliyan, Ared

    1993-01-01

    Rapid (subsecond) heating techniques developed at the National Institute of Standards and Technology for the measurements of selected thermophysical and related properties of metals and alloys at high temperatures (above 1000 C) are described. The techniques are based on rapid resistive self-heating of the specimen from room temperature to the desired high temperature in short times and measuring the relevant experimental quantities, such as electrical current through the specimen, voltage across the specimen, specimen temperature, length, etc., with appropriate time resolution. The first technique, referred to as the millisecond-resolution technique, is for measurements on solid metals and alloys in the temperature range 1000 C to the melting temperature of the specimen. It utilizes a heavy battery bank for the energy source, and the total heating time of the specimen is typically in the range of 100-1000 ms. Data are recorded digitally every 0.5 ms with a full-scale resolution of about one part in 8000. The properties that can be measured with this system are as follows: specific heat, enthalpy, thermal expansion, electrical resistivity, normal spectral emissivity, hemispherical total emissivity, temperature and energy of solid-solid phase transformations, and melting temperature (solidus). The second technique, referred to as the microsecond-resolution technique, is for measurements on liquid metals and alloys in the temperature range 1200 to 6000 C. It utilizes a capacitor bank for the energy source, and the total heating time of the specimen is typically in the range 50-500 micro-s. Data are recorded digitally every 0.5 micro-s with a full-scale resolution of about one part in 4000. The properties that can be measured with this system are: melting temperature (solidus and liquidus), heat of fusion, specific heat, enthalpy, and electrical resistivity. The third technique is for measurements of the surface tension of liquid metals and alloys at their melting

  18. High temperature oxidation behavior of gamma-nickel+gamma'-nickel aluminum alloys and coatings modified with platinum and reactive elements

    NASA Astrophysics Data System (ADS)

    Mu, Nan

    Materials for high-pressure turbine blades must be able to operate in the high-temperature gases (above 1000°C) emerging from the combustion chamber. Accordingly, the development of nickel-based superalloys has been constantly motivated by the need to have improved engine efficiency, reliability and service lifetime under the harsh conditions imposed by the turbine environment. However, the melting point of nickel (1455°C) provides a natural ceiling for the temperature capability of nickel-based superalloys. Thus, surface-engineered turbine components with modified diffusion coatings and overlay coatings are used. Theses coatings are capable of forming a compact and adherent oxide scale, which greatly impedes the further transport of reactants between the high-temperature gases and the underlying metal and thus reducing attack by the atmosphere. Typically, these coatings contain beta-NiAl as a principal constituent phase in order to have sufficient aluminum content to form an Al2O3 scale at elevated temperatures. The drawbacks to the currently-used beta-based coatings, such as phase instabilities, associated stresses induced by such phase instabilities, and extensive coating/substrate interdiffusion, are major motivations in this study to seek next-generation coatings. The high-temperature oxidation resistance of novel Pt+Hf-modified gamma-Ni+gamma'-Ni 3Al-based alloys and coatings were investigated in this study. Both early-stage and 4-days isothermal oxidation behavior of single-phase gamma-Ni and gamma'-Ni3Al alloys were assessed by examining the weight changes, oxide-scale structures, and elemental concentration profiles through the scales and subsurface alloy regions. It was found that Pt promotes Al 2O3 formation by suppressing the NiO growth on both gamma-Ni and gamma'-Ni3Al single-phase alloys. This effect increases with increasing Pt content. Moreover, Pt exhibits this effect even at lower temperatures (˜970°C) in the very early stage of oxidation. It

  19. Mechanical properties of Inconel 718 and Nickel 201 alloys after thermal histories simulating brazing and high temperature service

    SciTech Connect

    James, W.F.

    1985-09-01

    An experimental investigation was made to evaluate two nickel base alloys (Nickel-201 and Inconel-718) in three heat treated conditions. These conditions were: (1) annealed; (2) after thermal exposure simulating a braze cycle; and (3) after a thermal exposure simulating a braze cycle plus one operational lifetime of high temperature service. For the Nickel-201, two different braze cycle temperatures were evaluated. A braze cycle utilizing a lower braze temperature resulted in less grain growth for Nickel-201 than the standard braze cycle used for joining Nickel-201 to Inconel-718. It was determined, however, that Nickel-201, was marginal for temperatures investigated due to large grain growth. After the thermal exposures described above, the mechanical properties of Nickel-201 were degraded, whereas similar exposure on Inconel-718 actually strengthened the material compared with the annealed condition. The investigation included tensile tests at both room temperature and elevated temperatures, stress-rupture tests, and metallographic examination.

  20. Structure Analysis of a Precipitate Phase in an Ni-Rich High Temperature NiTiHf Shape Memory Alloy

    SciTech Connect

    Yang, Fan; Coughlin, D. R.; Phillips, Patrick J.; Yang, L.; Devaraj, Arun; Kovarik, Libor; Noebe, Ronald D.; Mills, M. J.

    2013-03-22

    Thermal aging of the high temperature shape memory alloy 50.3Ni-29.7Ti-20Hf (at.%) introduces a novel precipitate phase, which plays an important role in improving shape memory properties. The precipitate phase was investigated by conventional electron diffraction, high resolution scanning transmission electron microscopy (STEM) and three dimensional atom probe tomography. An unrelaxed orthorhombic atomic structural model is proposed based on these observations. This model was subsequently relaxed by ab initio calculations. As a result of the relaxation, atom shuffle displacements occur, which in turn yields improved agreement with the STEM images. The relaxed structure, which is termed the “H-phase”, has also been verified to be thermodymanically stable at 0 K.

  1. Analytical electron microscopy study of the high temperature carbide formed in a V-5 Ti-C alloy

    SciTech Connect

    Bruemmer, S.M.; Fluhr, C.P.; Beggs, D.V.; Wert, C.A.; Fraser, H.L.

    1980-05-01

    A finely dispersed high temperature carbide that precipitates at 1000/sup 0/C in a V-5 pct Ti-C alloy has been studied using analytical electron microscopy. The crystal structure has been determined using electron diffraction as B1 (NaCl-type) with a lattice parameter of 4.29A. The carbide develops a habit plane parallel to (001) of the matrix. The orientation relationship between the carbide and the matrix is (010) carbide parallel to (010) matrix, (001) carbide parallel to (101) matrix. The elemental concentrations of the metal constituents of the carbide have been deduced using energy dispersive x-ray spectroscopy and electron energy loss spectroscopy, through examination of core electron excitations. The composition of the carbide is found to be V/sub 11/Ti/sub 39/C/sub 50/, assuming a stoichiometric carbide.

  2. A model for the high-temperature transport properties of heavily doped n-type silicon-germanium alloys

    NASA Technical Reports Server (NTRS)

    Vining, Cronin B.

    1991-01-01

    A model is presented for the high-temperature transport properties of large-grain-size, heavily doped n-type silicon-germanium alloys. Electron and phonon transport coefficients are calculated using standard Boltzmann equation expressions in the relaxation time approximation. Good agreement with experiment is found by considering acoustic phonon and ionized impurity scattering for electrons, and phonon-phonon, point defect, and electron-phonon scattering for phonons. The parameters describing electron transport in heavily doped and lightly doped materials are significantly different and suggest that most carriers in heavily doped materials are in a band formed largely from impurity states. The maximum dimensionless thermoelectric figure of merit for single-crystal, n-type Si(0.8)Ge(0.2) at 1300 K is estimated at ZT about 1.13 with an optimum carrier concentration of n about 2.9 x 10 to the 20th/cu cm.

  3. Mechanical properties of Inconel 718 and Nickel 201 alloys after thermal histories simulating brazing and high temperature service

    NASA Technical Reports Server (NTRS)

    James, W. F.

    1985-01-01

    An experimental investigation was made to evaluate two nickel base alloys (Nickel-201 and Inconel-718) in three heat treated conditions. These conditions were: (1) annealed; (2) after thermal exposure simulating a braze cycle; and (3) after a thermal exposure simulating a braze cycle plus one operational lifetime of high temperature service. For the Nickel-201, two different braze cycle temperatures were evaluated. A braze cycle utilizing a lower braze temperature resulted in less grain growth for Nickel-201 than the standard braze cycle used for joining Nickel-201 to Inconel-718. It was determined, however, that Nickel-201, was marginal for temperatures investigated due to large grain growth. After the thermal exposures described above, the mechanical properties of Nickel-201 were degraded, whereas similar exposure on Inconel-718 actually strengthened the material compared with the annealed condition. The investigation included tensile tests at both room temperature and elevated temperatures, stress-rupture tests, and metallographic examination.

  4. 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

  5. Influence of Hot-Working Conditions on High-Temperature Properties of a Heat-Resistant Alloy

    NASA Technical Reports Server (NTRS)

    Ewing, John F; Freeman, J W

    1957-01-01

    The relationships between conditions of hot-working and properties at high temperatures and the influence of the hot-working on response to heat treatment were investigated for an alloy containing nominally 20 percent molybdenum, 2 percent tungsten, and 1 percent columbium. Commercially produced bar stock was solution-treated at 2,200 degrees F. to minimize prior-history effects and then rolled at temperatures of 2,200 degrees, 2,100 degrees, 2,000 degrees, 1,800 degrees, and 1,600 degrees F. Working was carried out at constant temperature and with incremental decreases in temperature simulating a falling temperature during hot-working. In addition, a few special repeated cyclic conditions involving a small reduction at high temperature followed by a small reduction at a low temperature were used to study the possibility of inducing very low strengths by the extensive precipitation accompanying such properties. Most of the rolling was done in open passes with a few check tests being made with closed passes. Heat treatments at both 2,050 degrees and 2,200 degrees F. subsequent to working were used to study the influence on response to heat treatment.

  6. High-temperature Tensile Properties and Creep Life Assessment of 25Cr35NiNb Micro-alloyed Steel

    NASA Astrophysics Data System (ADS)

    Ghatak, Amitava; Robi, P. S.

    2016-05-01

    Reformer tubes in petrochemical industries are exposed to high temperatures and gas pressure for prolonged period. Exposure of these tubes at severe operating conditions results in change in the microstructure and degradation of mechanical properties which may lead to premature failure. The present work highlights the high-temperature tensile properties and remaining creep life prediction using Larson-Miller parametric technique of service exposed 25Cr35NiNb micro-alloyed reformer tube. Young's modulus, yield strength, and ultimate tensile strength of the steel are lower than the virgin material and decreases with the increase in temperature. Ductility continuously increases with the increase in temperature up to 1000 °C. Strain hardening exponent increases up to 600 °C, beyond which it starts decreasing. The tensile properties are discussed with reference to microstructure and fractographs. Based on Larson-Miller technique, a creep life of at least 8.3 years is predicted for the service exposed material at 800 °C and 5 MPa.

  7. Spin transport at high temperatures in epitaxial Heusler alloy/n-GaAs lateral spin valves

    NASA Astrophysics Data System (ADS)

    Peterson, Timothy A.; Christie, Kevin D.; Patel, Sahil J.; Crowell, Paul A.; Palmstrøm, Chris J.

    2015-03-01

    We report on electrical injection and detection of spin accumulation in ferromagnet/ n-GaAs lateral spin-valve devices, observed up to and above room temperature. The ferromagnet in these measurements is the Heusler alloy Co2FeSi, and the semiconductor channel is GaAs doped at 3 ×1016 cm-3. The spin signal is enhanced by operating the detection contact under forward bias. The enhancement originates from drift effects at low-temperatures and an increase of the detection efficiency at all temperatures. The detector bias dependence of the observed spin-valve signal is interpreted by taking into account the quantum well (QW) which forms in the degenerately doped region immediately behind the Schottky tunnel barrier. In particular, we believe the QW is responsible for the minority spin accumulation (majority spin current) under large forward bias. The spin diffusion length and lifetime are determined by measuring the separation dependence of the non-local spin valve signal in a family of devices patterned by electron beam lithography. A spin diffusion length of 700 nm and lifetime of 46 picoseconds are found at a temperature of 295 K. This work was supported by the NSF under DMR-1104951, the NSF MRSEC program and C-SPIN, a SRC STARNET center sponsored by MARCO and DARPA.

  8. Development of constitutive models for cyclic plasticity and creep behavior of super alloys at high temperature

    NASA Technical Reports Server (NTRS)

    Haisler, W. E.

    1983-01-01

    An uncoupled constitutive model for predicting the transient response of thermal and rate dependent, inelastic material behavior was developed. The uncoupled model assumes that there is a temperature below which the total strain consists essentially of elastic and rate insensitive inelastic strains only. Above this temperature, the rate dependent inelastic strain (creep) dominates. The rate insensitive inelastic strain component is modelled in an incremental form with a yield function, blow rule and hardening law. Revisions to the hardening rule permit the model to predict temperature-dependent kinematic-isotropic hardening behavior, cyclic saturation, asymmetric stress-strain response upon stress reversal, and variable Bauschinger effect. The rate dependent inelastic strain component is modelled using a rate equation in terms of back stress, drag stress and exponent n as functions of temperature and strain. A sequence of hysteresis loops and relaxation tests are utilized to define the rate dependent inelastic strain rate. Evaluation of the model has been performed by comparison with experiments involving various thermal and mechanical load histories on 5086 aluminum alloy, 304 stainless steel and Hastelloy X.

  9. 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

  10. Mechanisms of High-Temperature Fatigue Failure in Alloy 800H

    NASA Technical Reports Server (NTRS)

    BhanuSankaraRao, K.; Schuster, H.; Halford, G. R.

    1996-01-01

    The damage mechanisms influencing the axial strain-controlled Low-Cycle Fatigue (LCF) behavior of alloy 800H at 850 C have been evaluated under conditions of equal tension/compression ramp rates (Fast-Fast (F-F): 4 X 10(sup -3)/s and Slow-Slow (S-S): 4 X 10(sup -5)/s) and asymmetrical ramp rates (Fast-Slow (F-S): 4 x 10(sup -3)/s / 4 X 10(sup -5/s and Slow-Fast (S-F): 4 X 10(sup -5) / 4 X 10(sup -3)/s) in tension and compression. The fatigue life, cyclic stress response, and fracture modes were significantly influenced by the waveform shape. The fatigue lives displayed by different loading conditions were in the following order: F-F greater than S-S greater than F-S greater than S-F. The fracture mode was dictated by the ramp rate adopted in the tensile direction. The fast ramp rate in the tensile direction led to the occurrence of transgranular crack initiation and propagation, whereas the slow ramp rate caused intergranular initiation and propagation. The time-dependent processes and their synergistic interactions, which were at the basis of observed changes in cyclic stress response and fatigue life, were identified. Oxidation, creep damage, dynamic strain aging, massive carbide precipitation, time-dependent creep deformation, and deformation ratcheting were among the several factors influencing cyclic life. Irrespective of the loading condition, the largest effect on life was exerted by oxidation processes. Deformation ratcheting had its greatest influence on life under asymmetrical loading conditions. Creep damage accumulated the greatest amount during the slow tensile ramp under S-F conditions.

  11. Corrosion Behavior of NiCrFe Alloy 600 in High Temperature, Hydrogenated Water

    SciTech Connect

    SE Ziemniak; ME Hanson

    2004-11-02

    The corrosion behavior of Alloy 600 (UNS N06600) is investigated in hydrogenated water at 260 C. The corrosion kinetics are observed to be parabolic, the parabolic rate constant being determined by chemical descaling to be 0.055 mg dm{sup -2} hr{sup -1/2}. A combination of scanning and transmission electron microscopy, supplemented by energy dispersive X-ray spectroscopy and grazing incidence X-ray diffraction, are used to identify the oxide phases present (i.e., spinel) and to characterize their morphology and thickness. Two oxide layers are identified: an outer, ferrite-rich layer and an inner, chromite-rich layer. X-ray photoelectron spectroscopy with argon ion milling and target factor analysis is applied to determine spinel stoichiometry; the inner layer is (Ni{sub 0.7}Fe{sub 0.3})(Fe{sub 0.3}Cr{sub 0.7}){sub 2}O{sub 4}, while the outer layer is (Ni{sub 0.9}Fe{sub 0.1})(Fe{sub 0.85}Cr{sub 0.15}){sub 2}O{sub 4}. The distribution of trivalent iron and chromium cations in the inner and outer oxide layers is essentially the same as that found previously in stainless steel corrosion oxides, thus confirming their invariant nature as solvi in the immiscible spinel binary Fe{sub 3}O{sub 4}-FeCr{sub 2}O{sub 4} (or NiFe{sub 2}O{sub 4}-NiCr{sub 2}O{sub 4}). Although oxidation occurred non-selectively, excess quantities of nickel(II) oxide were not found. Instead, the excess nickel was accounted for as recrystallized nickel metal in the inner layer, as additional nickel ferrite in the outer layer, formed by pickup of iron ions from the aqueous phase, and by selective release to the aqueous phase.

  12. Composition, Compatibility, and the Functional Performances of Ternary NiTiX High-Temperature Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Bucsek, Ashley N.; Hudish, Grant A.; Bigelow, Glen S.; Noebe, Ronald D.; Stebner, Aaron P.

    2016-03-01

    A general procedure to optimize shape memory alloys (SMAs) for specific engineering performance metrics is outlined and demonstrated through a study of ternary, NiTiX high-temperature SMAs, where X = Pd, Hf, Zr. Transformation strains are calculated using the crystallographic theory of martensite and compared to the cofactor conditions, both requiring only lattice parameters as inputs. Measurements of transformation temperatures and hysteresis provide additional comparisons between microstructural-based and transformation properties. The relationships between microstructural-based properties and engineering performance metrics are then thoroughly explored. Use of this procedure demonstrates that SMAs can be tuned for specific applications using relatively simple, fast, and inexpensive measurements and theoretical calculations. The results also indicate an overall trade-off between compatibility and strains, suggesting that alloys may be optimized for either minimal hysteresis or large transformation strains and work output. However, further analysis of the effects of aging shows that better combinations of uncompromised properties are possible through solid solution strengthening.

  13. Deformation and Phase Transformation Processes in Polycrystalline NiTi and NiTiHf High Temperature Shape Memory Alloys

    NASA Technical Reports Server (NTRS)

    Benafan, Othmane

    2012-01-01

    The deformation and transformation mechanisms of polycrystalline Ni49.9Ti50.1 and Ni50.3Ti29.7Hf20 (in at.%) shape memory alloys were investigated by combined experimental and modeling efforts aided by an in situ neutron diffraction technique at stress and temperature. The thermomechanical response of the low temperature martensite, the high temperature austenite phases, and changes between these two states during thermomechanical cycling were probed and reported. In the cubic austenite phase, stress-induced martensite, deformation twinning and slip processes were observed which helped in constructing a deformation map that contained the limits over which each of the identified mechanisms was dominant. Deformation of the monoclinic martensitic phase was also investigated where the microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were compared to the bulk macroscopic response. When cycling between these two phases, the evolution of inelastic strains, along with the shape setting procedures were examined and used for the optimization of the transformation properties as a function of deformation levels and temperatures. Finally, this work was extended to the development of multiaxial capabilities at elevated temperatures for the in situ neutron diffraction measurements of shape memory alloys on the VULCAN Diffractometer at Oak Ridge National Laboratory.

  14. High-Temperature Deformation Characteristics of a β-Type Ti-29Nb-13Ta-4.6Zr Alloy

    NASA Astrophysics Data System (ADS)

    Ghanbari, E.; Zarei-Hanzaki, A.; Farghadany, E.; Abedi, H. R.; Khoddam, Sh.

    2016-04-01

    The hot deformation behavior of a biomedical β-type Ti-Nb-Ta-Zr alloy has been studied through applying hot compression tests over a wide range of temperatures and strain rates (600-900 °C and 0.003-0.3 s-1). The main microstructural feature of the specimens, which were deformed at 900 °C, is the pancaked primary grains decorated by the serrated boundaries. The latter may well imply to the occurrence of dynamic recovery. The dynamic recrystallization however is considered as the main restoration mechanism in the specimens, which were deformed at 800 °C under all strain rates. The sizes of the new recrystallized grains well follow the serration amplitude of the primary grain boundaries. At lower deformation temperatures (600 and 700 °C), the strain rate sensitivity is suddenly decreased and ended to the strain localization in the form of macro shear band. The higher accumulated energy within the shear band zones appears to stimulate the occurrence of dynamic recrystallization. To further clarify the high-temperature flow behavior of the experimental alloy, a quantitative approach has been also employed. The observed flow hardening and softening has been justified considering the evolved microstructural features.

  15. High temperature tensile and creep behaviour of low pressure plasma-sprayed Ni-Co-Cr-Al-Y coating alloy

    NASA Technical Reports Server (NTRS)

    Hebsur, M. G.; Miner, R. V.

    1986-01-01

    The high temperature tensile and creep behavior of low pressure plasma-sprayed plates of a typical Ni-Co-Cr-Al-Y alloy has been studied. From room temperature to 800 K, the Ni-Co-Cr-Al-Y alloy studied has nearly a constant low ductility and a high strength. At higher temperatures, it becomes weak and highly ductile. At and above 1123 K, the behavior is highly dependent on strain rate and exhibits classic superplastic characteristics with a high ductility at intermediate strain rates and a strain rate sensitivity of about 0.5. At either higher or lower strain rates, the ductility decreases and the strain rate sensitivities are about 0.2. In the superplastic deformation range, the activation energy for creep is 120 + or - 20 kJ/mol, suggesting a diffusion-aided grain boundary sliding mechanism. Outside the superplastic range, the activation energy for creep is calculated to be 290 + or - 20 kJ/mol.

  16. Reactive molecular dynamics study of Mo-based alloys under high-pressure, high-temperature conditions

    NASA Astrophysics Data System (ADS)

    Vasenkov, Alex; Newsome, David; Verners, Osvalds; Russo, Michael F.; Zaharieva, Roussislava; van Duin, Adri C. T.

    2012-07-01

    Structural metal alloys are of vital importance for a clean energy economy, but the current trial-and-error alloy development methodology is expensive and time consuming. In this study, we demonstrate the capability of the ReaxFF force field model to predict mechanical properties and provide a fully dynamic description of oxidation and sulfidation of Mo-based alloys under high-pressure, high-temperature conditions using molecular dynamics (MD) method. The advantage of the ReaxFF approach is in its ability to model the formation and breaking of chemical bonds within the quantum framework but several orders of magnitude faster than the traditional density functional theory models. ReaxFF-MD predictions were compared to the literature Mo shock compression measurements at 300 K and 1673 K in the pressure range of 0-350 Pa, and densities and Young's modulus in the temperature range of 300-1500 K. Analysis of oxidation of Mo and Ni clusters and surface slabs showed that Mo oxidation proceeded at a significantly higher rate than the Ni oxidation and involved oxygen transport inside the metal cluster coupled to large heat release that caused extensive surface melting. The oxidation simulations of Mo3Ni clusters showed high production of Mo oxides and a low concentration of Ni-oxides in the gas phase. This was attributed to the higher chemical stability of Mo-oxide gas phase species. Modeling of H2S interactions with Mo slab demonstrated that sulfur atoms increasingly agglomerated in the surfaces layers of the slab as the simulation proceeded, diffusing deeper into the slab in their atomic forms. A combined ReaxFF Mo/Ni/C/O/N/S/H parameter set enabled us to obtain a detailed atomistic analysis of complex physical and chemical events during the combustion of a complex fuel molecule on a reactor surface.

  17. In-situ X-ray diffraction analysis of zirconia layer formed on zirconium alloys oxidized at high temperature

    NASA Astrophysics Data System (ADS)

    Gosset, D.; Le Saux, M.

    2015-03-01

    In the case of a hypothetical loss of primary coolant accident (LOCA) in a light water reactor, the zirconium alloys fuel cladding would be oxidized in steam at high temperature, typically in the range 800-1200 °C. The monoclinic to tetragonal phase martensitic transition of zirconia occurs within this temperature range and complex phenomena possibly having an impact on the oxidation kinetics are then to be expected. In order to provide an accurate description of the structure and microstructure of the oxide layers, systematic X-ray diffraction analyses have been performed in-situ under oxidizing atmosphere at high temperature (between 800 and 1100 °C) on Zircaloy-4 and M5™ sheet samples. It was confirmed that the volume fraction of the tetragonal and monoclinic zirconia phases formed during oxide growth drastically depends on the oxidation temperature. For example, the few outer microns of the oxide are fully tetragonal above 1050 °C and contain only 20% of tetragonal phase at 800 °C. It was also shown that cooling after oxidation induces irreversible phase transitions within the oxide. As a consequence, both the structure and the microstructure of the growing oxide cannot be observed post-facto, neither at room temperature nor after reheating at the prior oxidation temperature. It has been deduced from microstructural analyses that the grain size of the tetragonal zirconia phase is nanometric, about 100 nm during oxidation at 1100 °C down to 20 nm after cooling down to room temperature. This small grain size allows the stabilization of the tetragonal phase. The lattice parameters of the monoclinic and tetragonal zirconia phases have been analyzed, during both high temperature oxidation and cooling. In both cases, it appears the 'a' and 'b' cell parameters of the monoclinic phase are strongly constrained by the tetragonal 'a' one. The structural characteristics of the oxide formed at high temperature on Zircaloy-4 and M5™ are quite similar. All those

  18. Materials for aerospace

    SciTech Connect

    Steinberg, M.A.

    1986-10-01

    Early last year the US Office of Science and Technology put forward an agenda for American aerospace activity in the coming decades. The plan established goals for subsonic, supersonic and transatmospheric hypersonic flight. Those goals, together with Reagan Administration's programs for a space station and the Strategic Defense Initiative, serve as a driving force for extensive improvements in the materials that enable airplanes and spacecraft to function efficiently. The development of materials, together with advances in the technology of fabricating parts, will play a key role in aerospace systems of the future. Among the materials developments projected for the year 2000 are new composites and alloys for structural members; superalloys, ceramics and glass composites for propulsion systems, and carbon-carbon composites (carbon fibers in a carbon matrix) for high-temperature applications in places where resistance to heat and ablation is critical. 5 figures.

  19. Metal-Coated Optical Fibers for High Temperature Applications

    NASA Technical Reports Server (NTRS)

    Zeakes, Jason; Murphy, Kent; Claus, Richard; Greene, Jonathan; Tran, Tuan

    1996-01-01

    This poster will highlight on-going research at the Virginia Tech Fiber & Electro-Optics Research Center (FEORC) in the area of thin films on optical fibers. Topics will include the sputter deposition of metals and metal; alloys onto optical fiber and fiber optic sensors for innovative applications. Specific information will be available on thin film fiber optic hydrogen sensors, corrosion sensors, and metal-coated optical fiber for high temperature aerospace applications.

  20. Cast Aluminum Alloys for High Temperature Applications Using Nanoparticles Al2O3 and Al3-X Compounds (X = Ti, V, Zr)

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2009-01-01

    In this paper, the effect of nanoparticles Al2O3 and Al3-X compounds (X = Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their low cost, chemical stability and low diffusions rates in aluminum at high temperatures. The strengthening mechanism at high temperature for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. For Al2O3 nanoparticles, the test samples were prepared from special Al2O3 preforms, which were produced using ceramic injection molding process and then pressure infiltrated by molten aluminum. In another method, Al2O3 nanoparticles can also be homogeneously mixed with fine aluminum powder and consolidated into test samples through hot pressing and sintering. With the Al3-X nanoparticles, the test samples are produced as precipitates from in-situ reactions with molten aluminum using conventional permanent mold or die casting techniques. It is found that cast aluminum alloy using nanoparticles Al3-X is the most cost effective method to produce high strength aluminum alloys for high temperature applications in comparison to nanoparticles Al2O3. Furthermore, significant mechanical properties retention in high temperature environment could be achieved with Al3-X nanoparticles, resulting in tensile strength of nearly 3 times higher than most 300- series conventional cast aluminum alloys tested at 600 F.

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

    NASA Technical Reports Server (NTRS)

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

    2007-01-01

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

  2. High-Temperature Tensile Strength of Al10Co25Cr8Fe15Ni36Ti6 Compositionally Complex Alloy (High-Entropy Alloy)

    NASA Astrophysics Data System (ADS)

    Daoud, H. M.; Manzoni, A. M.; Wanderka, N.; Glatzel, U.

    2015-06-01

    Homogenizing at 1220°C for 20 h and subsequent aging at 900°C for 5 h and 50 h of a novel Al10Co25Cr8Fe15Ni36Ti6 compositionally complex alloy (high-entropy alloy) produces a microstructure consisting of an L12 ordered γ' phase embedded in a face-centered cubic solid-solution γ matrix together with needle-like B2 precipitates (NiAl). The volume fraction of γ' phase is ~46% and of needle-like B2 precipitates <5%, which is in accordance with the prediction of calculation of phase diagram method (CALPHAD using Thermo-Calc software with TTNi7 database; Thermo-Calc Software, Stockholm, Sweden). The high-temperature tensile tests were carried out at room temperature, 600°C, 700°C, 800°C, and 1000°C. The tensile strength as well as the elongation to failure of both heat-treated specimens is very high at all tested temperatures. The values of tensile strength has been compared with literature data of well-known Alloy 800H and Inconel 617, and is discussed in terms of the observed microstructure.

  3. NASA-UVA light aerospace alloy and structures technology program (LA2ST). Progress report, 1 July-31 December 1993

    SciTech Connect

    Gangloff, R.P.; Scully, J.R.; Starke, E.A. Jr.; Stoner, G.E.; Thornton, E.A.; Wawner, F.E. Jr.; Wert, J.A.

    1994-03-01

    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, the authors 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. Projects 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.

  4. Developing Dislocation Subgrain Structures and Cyclic Softening During High-Temperature Creep-Fatigue of a Nickel Alloy

    NASA Astrophysics Data System (ADS)

    Carroll, M. C.; Carroll, L. J.

    2013-08-01

    The complex cyclic deformation response of Alloy 617 under creep-fatigue conditions is of practical interest both in terms of the observed detriment in failure life and the considerable cyclic softening that occurs. At the low strain ranges investigated, the inelastic strain is the sole predictor of the failure life without taking into consideration a potentially significant environmental influence. The tensile-hold creep-fatigue peak stress response can be directly correlated to the evolving dislocation substructure, which consists of a relatively homogenous distribution of subgrains. Progressive high-temperature cycling with a static hold allows for the rearrangement of loose tangles of dislocations into well-ordered hexagonal dislocation networks. The cyclic softening during tensile-hold creep-fatigue deformation is attributable to two factors: the rearrangement of dislocation substructures into lower-energy configurations, which includes a decreasing dislocation density in subgrain interiors through integration into the subgrain boundaries, and the formation of surface grain boundary cracks and cavity formation or separation at interior grain boundaries, which occurs perpendicular to the stress axis. Effects attributable to the tensile character of the hold cycle are further analyzed through variations in the creep-fatigue waveform and illuminate the effects of the hold-time character on the overall creep-fatigue behavior and evolution of the dislocation substructure.

  5. Experiment and Modeling of Simultaneous Creep, Plasticity and Transformation of High Temperature Shape Memory Alloys During Cyclic Actuation

    NASA Technical Reports Server (NTRS)

    Kumar, Parikshith K.; Desai, Uri; Chatzigeorgiou, George; Lagoudas, Dimitris C.; Monroe, James; Karaman, Ibrahim; Noebe, Ron; Bigelow, Glen

    2010-01-01

    The present work is focused on studying the cycling actuation behavior of HTSMAs undergoing simultaneous creep and transformation. For the thermomechanical testing, a high temperature test setup was assembled on a MTS frame with the capability to test up to temperatures of 600 C. Constant stress thermal cycling tests were conducted to establish the actuation characteristics and the phase diagram for the chosen HTSMA. Additionally, creep tests were conducted at constant stress levels at different test temperatures to characterize the creep behavior of the alloy over the operational range. A thermodynamic constitutive model is developed and extended to take into account a) the effect of multiple thermal cycling on the generation of plastic strains due to transformation (TRIP strains) and b) both primary and secondary creep effects. The model calibration is based on the test results. The creep tests and the uniaxial tests are used to identify the viscoplastic behavior of the material. The parameters for the SMA properties, regarding the transformation and transformation induced plastic strain evolutions, are obtained from the material phase diagram and the thermomechanical tests. The model is validated by predicting the material behavior at different thermomechanical test conditions.

  6. High temperature passive film on the surface of Co-Cr-Mo alloy and its tribological properties

    NASA Astrophysics Data System (ADS)

    Guo, Feifei; Dong, Guangneng; Dong, Lishe

    2014-09-01

    For the artificial hip joints, passive film formed on the Co-Cr-Mo alloy acted as a highly protective barrier in the body fluid. But its stability, composition and structure always influenced the protection. In this work, passive film was obtained by high temperature treatment. The effect of passivation environment on the properties of the passive film was investigated. The film's surface roughness, micro-hardness and structure were analyzed. In order to study the tribological behavior of the passive film, pin-on-disk tribotest was carried out under bovine serum albumin (BSA) and saline solution. Results indicated the sample passivated in vacuum had friction coefficient of 0.18 under BSA solution and 0.53 under saline solution; the sample passivated in air had friction coefficient of 0.14 under BSA solution and 0.56 under saline solution. In addition, the reference sample without passivation was tested under the same condition. It showed friction of 0.22 under BSA solution and 0.45 under solution. The lubricating mechanism was attributed to BSA tribo-film absorption on the surface and high hardness passive film.

  7. 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.

  8. Mechanical behaviour and functional properties of porous Ti-45 at. % Ni alloy produced by self-propagating high-temperature synthesis

    NASA Astrophysics Data System (ADS)

    Resnina, N.; Belyaev, S.; Voronkov, A.; Gracheva, A.

    2016-05-01

    The mechanical behaviour and shape memory effects were studied in the porous Ti-45.0 at. % Ni alloy produced by self-propagating high-temperature synthesis. It is shown that the porous Ti-45.0 at % Ni alloy is deformed by the same mechanisms as a cast Ti50Ni50 alloy. At low temperatures, the deformation of the porous alloy is realised via martensite reorientation at a low yield limit and by dislocation slip at a high yield limit. At high temperatures (in the austenite B2 phase) the porous Ti-45.0 at % Ni alloy is deformed by the stress-induced martensite at a low yield limit and by dislocation slip at a high yield limit. The pseudoelasticity effect is not found in this alloy, while the transformation plasticity and the shape memory effects are observed on cooling and heating under a constant load. The values of the transformation plasticity, and the shape memory effects, depend linearly on the stress acting on cooling and heating. The temperatures of the martensitic transformation increase linearly when the stress rises up to 80 MPa. The porous Ti-45.0 at % Ni alloy accumulates an irreversible strain on cooling and heating and demonstrates unstable functional behaviour during thermal cycling.

  9. High-temperature low-cycle fatigue and tensile properties of Hastelloy X and alloy 617 in air and HTGR-helium

    SciTech Connect

    Strizak, J.P.; Brinkman, C.R.; Rittenhouse, P.L.

    1981-01-01

    Results of strain controlled fatigue and tensile tests are presented for two nickel base solution hardened alloys which are reference structural alloys for use in several high temperature gas cooled reactor concepts. These alloys, Hastelloy X Inconel 617, were tested at temperatures ranging from room temperature to 871/sup 0/C in air and impure helium. Materials were tested in the solution annealed as well as in the pre-aged condition where aging consisted of isothermal exposure at one of several temperatures for periods of up to 20,000 h. Comparisons are also given between the strain controlled fatigue lives of these alloys and several other commonly used alloys all tested at 538/sup 0/C.

  10. The fabricability and corrosion resistance of several Al-Cu-Li aerospace alloys

    SciTech Connect

    Walsh, D.W.; Danford, M.; Sanders, J.

    1996-12-31

    Al-Li-Cu alloys are attractive to the aerospace industry. The high specific strength and stiffness of these alloys will improve lift efficiency, fuel economy, performance and increase payload capabilities. The objectives of this study were to measure the fabricability of Al 2195 (Al-4Cu-1Li) and to assess the effect of welding on corrosion behavior. Al 2219 samples were used in parallel tests to provide a baseline for the data generated. In this study samples were exposed to 3.5% NaCl and mild corrosive water solutions in both the as received and as welded conditions. Fabricability was assessed using Gleeble testing, Varestraint testing and differential scanning calorimetry (DSC). Results indicate that Alloy 2195 is much more susceptible to hot cracking than Al 2219, and that cracking sensitivity is a strong function of chemical composition within specification ranges for Al 2195. Furthermore, for base metal samples, corrosion in mild corrosive water was more severe than corrosion in salt water. In addition, welding increases the corrosion rate in Al 2195 and 2219, and causes severe localization in Al 2195. Furthermore, autogenously welded Al 2195 samples were more susceptible to attack than heterogeneously welded Al 2195 samples and autogenously welded Al2219 samples were less susceptible to corrosion than autogenously welded Al 2195 samples. Heterogeneously welded samples in both materials had high corrosion rates, but only the Al 2195 material was subject to localization of attack. The partially melted zones of Al 2195 samples were subject to severe, focused attack. In all cases, interdendritic constituents in welded areas and intergranular constituents in base material were cathodic to the Al rich matrix materials. Fabricability and corrosion resistance were correlated to material microstructure using optical microscopy, scanning electron microscopy, electron probe microanalysis, polarization resistance and environmental scanning electron microscopy.

  11. A Study on Formation and Thermal Stability of Nano-sized Oxide Clusters in Mechanically Alloyed Nickel Aluminum for High Temperature Applications

    NASA Astrophysics Data System (ADS)

    Kim, Yong-Deog

    The intermetallic compound, B2 NiAl, is a promising material for high temperature structural applications such as in aviation jet engines or gas turbines, provided that its high temperature mechanical properties can be improved. Although extensive efforts over the last several decades have been devoted toward enhancing ductility through alloying design and reducing impurities, as well as improving high temperature creep strength through precipitation and dispersion strengthening, these efforts have relied on traditional approaches, a combination of large grain size to limit diffusional creep and precipitation/dispersion (50 ˜ 100 nm size) strengthening to limit dislocation creep, for high temperature strengthening. While traditional approaches have shown a good improvement from a relatively high temperature strengthening point of view, the size and number density of dispersoids were not able to provide sufficient strength in the high temperature creep regime. Furthermore, details of the interaction mechanism between dislocations and dispersoids are not yet well understood. This study focuses on designing and developing advanced oxide dispersion strengthened (ODS) NiAl intermetallics with improved high temperature creep strength by incorporating a high number density (˜1024 m-3) of very thermally stable Y-Ti-O nano-clusters, akin to those recently observed to improve creep strength and radiation resistance in nano-structured ferritic alloys. Advanced ODS NiAl alloys have been produced by mechanical alloying of pre-alloyed Ni-50at%Al with Y2O3 and Ti elemental powders. The milled powders were subsequently consolidated by spark plasma sintering, with the objective of producing very high number densities of nano-sized Y-Ti-O precipitates, along with fine grain size. Advanced experimental characterization techniques, combined with microhardness strength measurement, were used to investigate the material microstructure and strength following processing and to evaluate

  12. Total hemispherical emissivity of very high temperature reactor (VHTR) candidate materials: Hastelloy X, Haynes 230, and Alloy 617

    NASA Astrophysics Data System (ADS)

    Maynard, Raymond K.

    An experimental system was constructed in accordance with the standard ASTM C835-06 to measure the total hemispherical emissivity of structural materials of interest in Very High Temperature Reactor (VHTR) systems. The system was tested with304 stainless steel as well as for oxidized and un-oxidized nickel, and good reproducibility and agreement with the literature data was found. Emissivity of Hastelloy X was measured under different conditions that included: (i) "as received" (original sample) from the supplier; (ii) with increased surface roughness; (iii) oxidized, and; (iv) graphite coated. Measurements were made over a wide range of temperatures. Hastelloy X, as received from the supplier, was cleaned before additional roughening of the surface and coating with graphite. The emissivity of the original samples (cleaned after received) varied from around 0.18 to 0.28 in the temperature range of 473 K to 1498 K. The apparent emissivity increased only slightly as the roughness of the surface increased (without corrections for the increased surface area due to the increased surface roughness). When Hastelloy X was coated with graphite or oxidized however, its emissivity was observed to increase substantially. With a deposited graphite layer on the Hastelloy, emissivity increased from 0.2 to 0.53 at 473 K and from 0.25 to 0.6 at 1473 K; a finding that has strong favorable safety implications in terms of decay heat removal in post-accident VHTR environments. Although initial oxidation of Hastelloy X increased the emissivity prolonged oxidation did not significantly increase emissivity. However as there is some oxidation of Hastelloy X used in the construction of VHTRs, this represents an essentially neutral finding in terms of the safety implications in post-accident VHTR environments. The total hemispherical emissivity of Haynes 230 alloy, which is regarded as a leading candidate material for heat exchangers in VHTR systems, was measured under various surface

  13. High-pressure and high-temperature phase diagram for Fe0.9Ni0.1-H alloy

    NASA Astrophysics Data System (ADS)

    Shibazaki, Yuki; Terasaki, Hidenori; Ohtani, Eiji; Tateyama, Ryuji; Nishida, Keisuke; Funakoshi, Ken-ichi; Higo, Yuji

    2014-03-01

    Planetary cores are considered to consist of an iron-nickel (Fe-Ni) alloy and light elements and hydrogen is one of plausible light elements in the core. Here we have performed in situ X-ray diffraction experiments on an Fe0.9Ni0.1-H system up to 15.1 GPa and 1673 K, and investigated the effect of Ni on phase relations of FeHx under high pressure and high temperature. The experimental system in the present work was oversaturated with hydrogen. We found a face-center-cubic (fcc) phase (with hydrogen concentration up to x∼1) and a body-center-cubic (bcc) phase (x < 0.1) as stable phases. The partial melting was observed below 6 GPa. We could not observe a double-hexagonal-close-packed (dhcp) phase because of limitations in pressure and temperature conditions. The stability field of each phase of Fe0.9Ni0.1Hx was almost same as that of FeHx. The solidus of Fe0.9Ni0.1Hx was 500-700 K lower than the melting curve of Fe and its liquidus was 400-600 K lower than that of Fe in the pressure range of this study. Both the solidus and liquidus of Fe0.9Ni0.1Hx were depressed at around 3.5 GPa, as was the solidus of FeHx. The hydrogen contents in fcc-Fe0.9Ni0.1Hx just below solidus were slightly lower than those of fcc-FeHx, which suggests that nickel is likely to prevent dissolution of hydrogen into iron. Due to the lower hydrogen solubilities in Fe0.9Ni0.1 compared to Fe, the solidus of Fe0.9Ni0.1Hx is about 100-150 K higher than that of FeHx.

  14. Formation behavior of basal texture under the high temperature plane strain compression deformation in AZ80 magnesium alloy

    NASA Astrophysics Data System (ADS)

    Kim, K.; Okayasu, K.; Fukutomi, H.

    2015-04-01

    The formation behavior of basal texture during high temperature deformation of AZ80 magnesium alloys in single phase was investigated by plane strain compression deformation. Three kinds of specimens with different initial textures were machined out from an extruded bar having a <101¯0> texture. Plane strain compression tests were conducted at temperatures of 623K and 723K and a strain rate of 5.0×10-2s-1, with a strain range of between - 0.4 and -1.0. After deformation, the specimens were immediately quenched in oil. Texture measurement was carried out on the compression planes by the Schulz reflection method using nickel filtered Cu Kα radiation. Electron backscatter diffraction (EBSD) measurements were also conducted in order to examine the spatial distribution of orientations. Three kinds of specimens named A, B and C were prepared from the same extruded bar. In the specimens A, B and C, {0001} was distributed preferentially parallel to ND, TD, and RD, respectively. After deformation, texture evaluation was conducted on the mid-plane section. At the plane strain compression deformation, peaks appeared in the true stress-true strain curves irrespective of the kinds of specimen used. It was found that the main components and the pole densities of the textures vary depending on deformation condition and initial texture. Six kinds of texture components were observed after deformation. The (0001)<101¯0> has formed regardless of the initial texture. There are two types of texture components; one exists before the deformation, and the other does not. Either types are considered to have stable orientations for plane strain compression. Also, the basal texture is composed of two crystal orientation components - (0001)<101¯0> and (0001)<112¯0>. When (0001) existed before deformation, an extremely sharp (0001) (compression plane) texture is formed.

  15. Development of a quantitative method for the characterization of hole quality during laser trepan drilling of high-temperature alloy

    NASA Astrophysics Data System (ADS)

    Zhang, Hongyu; Zhou, Ming; Wang, Yunlong; Zhang, Xiangchao; Yan, Yu; Wang, Rong

    2016-02-01

    Short-pulsed lasers are of significant industrial relevance in laser drilling, with an acceptable compromise between accuracy and efficiency. However, an intensive research with regard to qualitative and quantitative characterization of the hole quality has rarely been reported. In the present study, a series of through holes were fabricated on a high-temperature alloy workpiece with a thickness of 3 mm using a LASERTEC 80 PowerDrill manufacturing system, which incorporated a Nd:YAG millisecond laser into a five-axis positioning platform. The quality of the holes manufactured under different laser powers (80-140 W) and beam expanding ratios (1-6) was characterized by a scanning electron microscope associated with an energy-dispersive X-ray analysis, focusing mainly on the formation of micro-crack and recast layer. Additionally, the conicity and circularity of the holes were quantitatively evaluated by the apparent radius, root-mean-square deviation, and maximum deviation, which were calculated based on the extraction of hole edge through programming with MATLAB. The results showed that an amount of melting and spattering contents were presented at the entrance end and the exit end of the holes, and micro-cracks and recast layer (average thickness 15-30 µm) were detected along the side wall of the holes. The elemental composition of the melting and spattering contents and the recast layer was similar, with an obvious increase in the contents of O, Nb, and Cr and a great reduction in the contents of Fe and Ni in comparison with the bulk material. Furthermore, the conicity and circularity evaluation of the holes indicated that a laser power of 100 W and a beam expanding ratio of 4 or 5 represented the typical optimal drilling parameters in this specific experimental situation. It is anticipated that the quantitative method developed in the present study can be applied for the evaluation of hole quality in laser drilling and other drilling conditions.

  16. PALLADIUM/COPPER ALLOY COMPOSITE MEMBRANES FOR HIGH TEMPERATURE HYDROGEN SEPARATION FROM COAL-DERIVED GAS STREAMS

    SciTech Connect

    J. Douglas Way

    2001-07-31

    Recent advances have shown that Pd-Cu composite membranes are not susceptible to the mechanical, embrittlement, and poisoning problems that have prevented widespread industrial use of Pd for high temperature H2 separation. These membranes consist of a thin ({approx}1 mm) film of metal deposited on the inner surface of a porous metal or ceramic tube. Based on preliminary results, thin Pd{sub 60}Cu{sub 40} films are expected to exhibit hydrogen flux up to ten times larger than commercial polymer membranes for H2 separation, and resist poisoning by H{sub 2}S and other sulfur compounds typical of coal gas. Similar Pd-membranes have been operated at temperatures as high as 750 C. The overall objective of the proposed project is to demonstrate the feasibility of using sequential electroless plating to fabricate Pd{sub 60}Cu{sub 4}0 alloy membranes on porous supports for H{sub 2} separation. These following advantages of these membranes for processing of coal-derived gas will be demonstrated: High H{sub 2} flux; Sulfur tolerant, even at very high total sulfur levels (1000 ppm); Operation at temperatures well above 500 C; and Resistance to embrittlement and degradation by thermal cycling. The proposed research plan is designed to providing a fundamental understanding of: Factors important in membrane fabrication; Optimization of membrane structure and composition; Effect of temperature, pressure, and gas composition on H{sub 2} flux and membrane selectivity; and How this membrane technology can be integrated in coal gasification-fuel cell systems.

  17. NASA-UVA Light Aerospace Alloy and Structures Technology Program (LA2ST). Progress report, 1 January-30 June 1994

    SciTech Connect

    Gangloff, R.P.

    1994-07-01

    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, the authors 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. The authors 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.

  18. 10 000-hr Cyclic Oxidation Behavior of 68 High-Temperature Co-, Fe-, and Ni- Base Alloys Evaluated at 982 deg. C (1800 deg. F)

    NASA Technical Reports Server (NTRS)

    Barrett, Charles A.

    1999-01-01

    Power systems with operating temperatures in the range of 815 to 982 C (1500 to 1800 F) frequently require alloys that can operate for long times at these temperatures. A critical requirement is that these alloys have adequate oxidation resistance. The alloys used in these power systems require thousands of hours of operating life with intermittent shutdown to room temperature. Intermittent power plant shutdowns, however, offer the possibility that the protective scale will tend to spall (i.e., crack and flake off) upon cooling, increasing the rate of oxidative attack in subsequent heating cycles. Thus, it is critical that candidate alloys be evaluated for cyclic oxidation behavior. It was determined that exposing test alloys to ten 1000-hr cycles in static air at 982 10 000-hr Cyclic Oxidation Behavior of 68 High-Temperature Co-, Fe-, and Ni-Base Alloys Evaluated at 982 C (1800 F) could give a reasonable simulation of long-time power plant operation. Iron- (Fe-), nickel- (Ni-), and cobalt- (Co-) based high-temperature alloys with sufficient chromium (Cr) and/or aluminum (Al) content can exhibit excellent oxidation resistance. The protective oxides formed by these classes of alloys are typically Cr2O3 and/or Al2O3, and are usually influenced by their Cr, or Cr and Al, content. Sixty-eight Co-, Fe-, and Ni-base high-temperature alloys, typical of those used at this temperature or higher, were used in this study. At the NASA Lewis Research Center, the alloys were tested and compared on the basis of their weight change as a function of time, x-ray diffraction of the protective scale composition, and the physical appearance of the exposed samples. Although final appearance and x-ray diffraction of the final scale products were two factors used to evaluate the oxidation resistance of each alloy, the main criterion was the oxidation kinetics inferred from the specific weight change versus time data. These data indicated a range of oxidation behavior including parabolic

  19. High temperature pressure gauge

    DOEpatents

    Echtler, J. Paul; Scandrol, Roy O.

    1981-01-01

    A high temperature pressure gauge comprising a pressure gauge positioned in fluid communication with one end of a conduit which has a diaphragm mounted in its other end. The conduit is filled with a low melting metal alloy above the diaphragm for a portion of its length with a high temperature fluid being positioned in the remaining length of the conduit and in the pressure gauge.

  20. Improvement in the Shape Memory Response of Ti50.5Ni24.5Pd25 High-Temperature Shape Memory Alloy with Scandium Microalloying

    NASA Technical Reports Server (NTRS)

    Atli, K. C.; Karaman, I; Noebe, R. D.; Garg, A.; Chumlyakov, Y. I.; Kireeva, I. V.

    2010-01-01

    A Ti(50.5)Ni(24.5)Pd25 high-temperature shape memory alloy (HTSMA) is microalloyed with 0.5 at. pct scandium (Sc) to enhance its shape-memory characteristics, in particular, dimensional stability under repeated thermomechanical cycles. For both Ti(50.5)Ni(24.5)Pd25 and the Sc-alloyed material, differential scanning calorimetry is conducted for multiple cycles to characterize cyclic stability of the transformation temperatures. The microstructure is evaluated using electron microscopy, X-ray diffractometry, and wavelength dispersive spectroscopy. Isobaric thermal cycling experiments are used to determine transformation temperatures, dimensional stability, and work output as a function of stress. The Sc-doped alloy displays more stable shape memory response with smaller irrecoverable strain and narrower thermal hysteresis than the baseline ternary alloy. This improvement in performance is attributed to the solid solution hardening effect of Sc.

  1. 10,000-Hour Cyclic Oxidation Behavior at 982 C (1800 F) of 68 High-Temperature Co-, Fe-, and Ni-Base Alloys

    NASA Technical Reports Server (NTRS)

    Barrett, Charles A.

    1997-01-01

    Sixty-eight high temperature Co-, Fe-, and Ni-base alloys were tested for 10-one thousand hour cycles in static air at 982 C (1800 F). The oxidation behavior of the test samples was evaluated by specific weight change/time data, x-ray diffraction of the post-test samples, and their final appearance. The gravimetric and appearance data were combined into a single modified oxidation parameter, KB4 to rank the cyclic oxidation resistance from excellent to catastrophic. The alloys showing the 'best' resistance with no significant oxidation attack were the alumina/aluminate spinel forming Ni-base turbine alloys: U-700, NASA-VIA and B-1900; the Fe-base ferritic alloys with Al: TRW-Valve, HOS-875, NASA-18T, Thermenol and 18SR; and the Ni-base superalloy IN-702.

  2. Structure, Mechanical Properties, and Fracture Behavior of a Fe-Cr-V Alloy Doped with Nitrogen by High-Temperature Gas-Phase Nitriding

    NASA Astrophysics Data System (ADS)

    Nikulin, Sergey A.; Khatkevich, Vladimir M.; Rogachev, Stanislav O.; Denisenko, Kristina S.

    2015-12-01

    The microstructure, phase composition, and room-temperature mechanical properties of the corrosion-resistant Fe-20pctCr-5pctV alloy doped with nitrogen by high-temperature gas-phase nitriding under different conditions have been investigated. The nitriding of the Fe-20pctCr-5pctV alloy at T = 1223 K to 1373 K (950 °C to 1100 °C) and subsequent annealing at T = 973 K (700 °C) lead to the precipitation of large vanadium nitride and disperse chromium nitride particles in the ferrite matrix. Such a treatment increases the strength of the Fe-20pctCr-5pctV alloy at room temperature by 1.6 times, while maintaining the adequate relative elongation. The alloy in the initial state and after nitriding is highly resistant to corrosion.

  3. NASA-UVA Light Aerospace Alloy and Structures Technology program (LA2ST). Progress report, 1 January 1995-30 June 1995

    SciTech Connect

    Starke, E.A. Jr.; Gangloff, R.P.; Herakovich, C.T.; Scully, J.R.; Shiflet, G.J.; Stoner, G.E.; Wert, J.A.

    1995-07-01

    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.

  4. Standardization of shape memory alloy test methods toward certification of aerospace applications

    NASA Astrophysics Data System (ADS)

    Hartl, D. J.; Mabe, J. H.; Benafan, O.; Coda, A.; Conduit, B.; Padan, R.; Van Doren, B.

    2015-08-01

    The response of shape memory alloy (SMA) components employed as actuators has enabled a number of adaptable aero-structural solutions. However, there are currently no industry or government-accepted standardized test methods for SMA materials when used as actuators and their transition to commercialization and production has been hindered. This brief fast track communication introduces to the community a recently initiated collaborative and pre-competitive SMA specification and standardization effort that is expected to deliver the first ever regulatory agency-accepted material specification and test standards for SMA as employed as actuators for commercial and military aviation applications. In the first phase of this effort, described herein, the team is working to review past efforts and deliver a set of agreed-upon properties to be included in future material certification specifications as well as the associated experiments needed to obtain them in a consistent manner. Essential for the success of this project is the participation and input from a number of organizations and individuals, including engineers and designers working in materials and processing development, application design, SMA component fabrication, and testing at the material, component, and system level. Going forward, strong consensus among this diverse body of participants and the SMA research community at large is needed to advance standardization concepts for universal adoption by the greater aerospace community and especially regulatory bodies. It is expected that the development and release of public standards will be done in collaboration with an established standards development organization.

  5. Effect of Corrosion Film Composition and Structure on the Corrosion Kinetics of Ni-Cr-Fe Alloys in High Temperature Water

    SciTech Connect

    P.M. Rosecrans; N. Lewis; D.J. Duquette

    2002-02-27

    Nickel alloys such as Alloy 600 undergo Stress Corrosion Cracking (SCC) in pure water at temperatures between about 260 C and the critical point. Increasing the level of Cr in Ni-Fe-Cr alloys increases SCC resistance in aerated and deaerated water. The mechanism is not understood. The effect of Cr composition on oxide microstructure and corrosion kinetics of Ni-Fe-Cr alloys was determined experimentally, to evaluate whether the anodic dissolution model for SCC can account for the effect of Cr on SCC. The alloy corrosion rate and corrosion product oxide microstructure is strongly influenced by the Cr composition. Corrosion kinetics are parabolic and influenced by chromium concentration, with the parabolic constant first increasing then decreasing as Cr increases from 5 to 39%. Surface analyses using Analytical Electron microscopy (AEM) and Auger Electron Spectroscopy (AES) show that the corrosion product film that forms initially on all alloys exposed to high purity high temperature water is a nickel rich oxide. With time, the amount of chromium in the oxide film increases and corrosion proceeds toward the formation of the more thermodynamically stable spinel or hexagonal Cr-rich oxides, similar to high temperature gaseous oxidation. Due to the slower diffusion kinetics at the temperatures of water corrosion compared to those in high temperature gaseous oxidation, however, the films remain as a mixture of NiO, mixed Ni, Fe and Cr spinels, NiCrO{sub 3} and FeCrO{sub 3}. As the amount of Cr in the film increases and the nature of the film changes from NiO to spinel or hexagonal oxides, cation diffusion through the films slows, slowing the corrosion rate. These observations are qualitatively consistent with an anodic dissolution SCC mechanism. However, parametric modeling of the SCC growth process, applying available creep, oxide rupture strain and corrosion kinetics data, indicates that the anodic dissolution mechanism accounts for only a fraction of the effect of Cr

  6. Effect of temperature and type of stress state on the endurance of high-temperature cast alloy ZhS3DK

    SciTech Connect

    Pogrebnyak, A.D.; Palienko, E.Y.; Sinaiskii, B.N.; Yashchuk, N.V.

    1985-11-01

    In aviation gas-turbine practice there has been extensive use of high-temperature nickel-base alloy ZhS3DK as a material for gas-turbine blades. In view of the tendency towards increased operating tempertures with an increase in aircraft component life, an all-around study of its strength properties is undertaken, including resistance to cyclic loading over a wide temperature range. Results are presented for a study of the endurance of alloy ZhS3DK specimens over a wide temperature range (20-900 degrees C) with pure rotating bending and with tension-compression.

  7. Directly correlated transmission electron microscopy and atom probe tomography of grain boundary oxidation in a Ni-Al binary alloy exposed to high-temperature water

    SciTech Connect

    Schreiber, Daniel K.; Olszta, Matthew J.; Bruemmer, Stephen M.

    2013-06-14

    Intergranular oxidation of a Ni-4Al alloy exposed to hydrogenated, high-temperature water was characterized using directly correlated transmission electron microscopy and atom probe tomography. These combined analyses revealed that discrete, well-separated oxides (NiAl2O4) precipitated along grain boundaries in the metal. Aluminum was depleted from the grain boundary between oxides and also from one side of the boundary as a result of grain boundary migration. The discrete oxide morphology, disconnected from the continuous surface oxidation, suggests intergranular solid-state internal oxidation of Al. Keywords: oxidation; grain boundaries; nickel alloys; atom probe tomography; transmission electron microscopy (TEM)

  8. Cyclic degradation of titanium-tantalum high-temperature shape memory alloys — the role of dislocation activity and chemical decomposition

    NASA Astrophysics Data System (ADS)

    Niendorf, T.; Krooß, P.; Somsen, C.; Rynko, R.; Paulsen, A.; Batyrshina, E.; Frenzel, J.; Eggeler, G.; Maier, H. J.

    2015-05-01

    Titanium-tantalum shape memory alloys (SMAs) are promising candidates for actuator applications at elevated temperatures. They may even succeed in substituting ternary nickel-titanium high temperature SMAs, which are either extremely expensive or difficult to form. However, titanium-tantalum alloys show rapid functional and structural degradation under cyclic thermo-mechanical loading. The current work reveals that degradation is not only governed by the evolution of the ω-phase. Dislocation processes and chemical decomposition of the matrix at grain boundaries also play a major role.

  9. Diffraction-based study of fatigue crack initiation and propagation in aerospace aluminum alloys

    NASA Astrophysics Data System (ADS)

    Gupta, Vipul K.

    The crack initiation sites and microstructure-sensitive growth of small fatigue cracks are experimentally characterized in two precipitation-hardened aluminum alloys, 7075-T651 and 7050-T7451, stressed in ambient temperature moist-air (warm-humid) and -50°C dry N2 (cold-dry) environmental conditions. Backscattered electron imaging (BSE) and energy dispersive spectroscopy (EDS) of the fracture surfaces showed that Fe-Cu rich constituent particle clusters are the most common initiation sites within both alloys stressed in either environment. The crack growth within each alloy, on average, was observed to be slowed in the cold-dry environment than in the warm-humid environment, but only at longer crack lengths. Although no overwhelming effects of grain boundaries and grain orientations on small-crack growth were observed, crack growth data showed local fluctuations within individual grains. These observations are understood as crack propagation through the underlying substructure at the crack surface and frequent interaction with low/high-angle grain and subgrain boundaries, during cyclic loading, and, are further attributed to periodic changes in crack propagation path and multiple occurrences of crack-branching observed in the current study. SEM-based stereology in combination with electron backscattered diffraction (EBSD) established fatigue crack surface crystallography within the region from ˜1 to 50 mum of crack initiating particle clusters. Fatigue crack facets were parallel to a wide variety of crystallographic planes, with pole orientations distributed broadly across the irreducible stereographic triangle between the {001} and {101}-poles within both warm-humid and cold-dry environments. The results indicate environmentally affected fatigue cracking in both cases, given the similarity between the observed morphology and crystallography with that of a variety of aerospace aluminum alloys cracked in the presence of moist-air. There was no evidence of

  10. Modification of tribology and high-temperature behavior of Ti 48Al 2Cr 2Nb intermetallic alloy by laser cladding

    NASA Astrophysics Data System (ADS)

    Liu, Xiu-Bo; Wang, Hua-Ming

    2006-06-01

    In order to improve the tribology and high-temperature oxidation properties of the Ti-48Al-2Cr-2Nb intermetallic alloy simultaneously, mixed NiCr-Cr 3C 2 precursor powders had been investigated for laser cladding treatment to modify wear and high-temperature oxidation resistance of the material. The alloy samples were pre-placed with NiCr-80, 50 and 20%Cr 3C 2 (wt.%), respectively, and laser treated at the same parameters, i.e., laser output power 2.8 kW, beam scanning speed 2.0 mm/s, beam dimension 1 mm × 18 mm. The treated samples underwent tests of microhardness, wear and high-temperature oxidation. The results showed that laser cladding with different constitution of mixed precursor NiCr-Cr 3C 2 powders improved surface hardness in all cases. Laser cladding with NiCr-50%Cr 3C 2 resulted in the best modification of tribology and high-temperature oxidation behavior. X-ray diffraction (XRD), optical microscope (OM), scanning electron microscopy (SEM) and energy-dispersive spectrometer (EDS) analyses indicated that the formation of reinforced Cr 7C 3, TiC and both continuous and dense Al 2O 3, Cr 2O 3 oxide scales were supposed to be responsible for the modification of the relevant properties. As a result, the present work had laid beneficial surface engineering foundation for TiAl alloy applied as future light weight and high-temperature structural candidate materials.

  11. Investigation on Coating Uniformity of High-Temperature Alloy with SiC Thermal Barrier Coating Using Pulsed Infrared Thermographic Technique

    NASA Astrophysics Data System (ADS)

    Liu, J. Y.; Tang, Q. J.; Wang, Y.; Gong, J. L.; Qin, L.

    2015-06-01

    The SiC thermal barrier coating thickness uniformity of a high-temperature alloy was investigated using a pulsed infrared thermographic image. A thermal quadrupole method is used to solve a one-dimensional thermal conduction model. The temperature of the high-temperature alloy with SiC coating is directly affected by the pulse intensity of optical excitation; furthermore, the relation between the SiC thermal barrier coating thickness and temperature difference is obtained. Pulsed phase thermography and principal component analysis are applied to extract the characteristic information from thermal image sequences, and the signal-to-noise ratio of the thermal wave signal is clearly improved. The thermal contrast of the SiC thermal barrier coating thickness is related to the optical pulse intensity and infrared camera frame rate. Furthermore, a relatively simple quantitative method is developed to estimate the SiC thermal barrier coating thickness uniformity of the high-temperature alloy, and the coating thickness measurement using pulsed thermographic imaging is in very good agreement with the actual coating thickness value.

  12. An analytical electron microscopy study of the role of La and Y during high-temperature oxidation of selected Ni-base alloys

    SciTech Connect

    Tawancy, H.M.; Abbas, N.M. . Materials Characterization Lab.)

    1993-09-01

    Minor but critical additions of active elements such as Y to Al[sub 2]O[sub 3]-forming alloys and La to Cr[sub 2]O[sub 3]-forming alloys are known to have beneficial effects on their high-temperature oxidation resistance. Several mechanisms, sometimes opposing, particularly in the case of Al[sub 2]O[sub 3]-forming alloys have been proposed to explain the active element-effect. A number of extensive reviews have dealt with these mechanisms. In the case of Cr[sub 2]O[sub 3]-forming alloys, however, it is generally agreed that the role of active elements is to promote selective oxidation of Cr, reduce the scale growth rate, and improve its mechanical strength. For a better understanding of the active element-effect, it is essential to determine its atomic-scale distribution within the oxide scale. Using thin-foil analytical electron microscopy techniques, it has been shown that in some Al[sub 2]O[sub 3]-forming alloys and Cr[sub 2]O[sub 3]-forming alloys, Y tends to segregate at grain boundaries of the oxide scale resulting in modification of its transport properties and mechanical strength. Also, it has been suggested that other elements such as Ce and La may segregate to grain boundaries of oxide scale in Cr[sub 2]O[sub 3]-forming alloys. It was the objective of this study to determine the atomic-scale distribution of active elements in wrought Ni-base alloys of commercial grade using the techniques of analytical electron microscopy. Two alloys representing Al[sub 2]O[sub 3]-forming and Cr[sub 2]O[sub 3]-forming alloys were selected for the study. Haynes alloy no. 214 is a Y-containing alloy capable of developing Al[sub 2]O[sub 3] scale upon exposure at temperature exceeding 1,000C and Haynes alloy no. 230 is a La-containing alloy protected by Cr[sub 2]O[sub 3] scale.

  13. Effect of high-temperature aging on electrical properties of HipercoxAE 27, HipercoxAE 50, and HipercoxAE 50 HS alloys

    NASA Astrophysics Data System (ADS)

    Geist, B.; Peterson, T.; Horwath, J. C.; Turgut, Z.; Huang, M. Q.; Snyder, R. A.; Fingers, R. T.

    2003-05-01

    Some more electric aircraft concepts require soft magnetic FeCo materials to be stable at temperatures as high as 773 K for long periods of time. At this high operating temperature, aging related processes may occur that result in changes in material properties. The material supplier typically specifies only room-temperature properties, and only limited reports are available on properties at elevated temperatures. The change in properties as a function of time at 773 K will give information on the lifetime of the material to assist designers when selecting materials for high-temperature applications. We have conducted a study on the effects of long-term aging on the magnetic, mechanical, and electrical properties of Hiperco® 27, Hiperco® 50, and Hiperco® 50 HS FeCo soft magnetic alloys. Samples of each material were aged in argon for 100, 1000, 2000, and 5000 h at 773 K. Here, we report the changes in electrical resistivity after aging. Of the three alloys, high-temperature aging has the greatest effect on the resistivity of Hiperco® 50. The electrical resistivities for each sample are compared and conclusions are drawn on the relative thermal stability of each alloy. The changes in electrical resistivities for each alloy are also related to changes in other properties, such as total power loss and coercivity, that were observed during this study on aging.

  14. Effect of Mo on the High-Temperature Creep Resistance and Machinability of a Recycled Al-Alloy with High Iron Impurity

    NASA Astrophysics Data System (ADS)

    Ain, W. Q.; Faisal, M. K.; Talari, M. K.; Darham, W.; Ratnam, M. M.; Kwon, Y.; Kim, N. J.; Prasada Rao, A. K.

    2016-08-01

    Reported work focuses on the effect of morphology of the Fe-rich intermetallic phases on the machinability of Al-alloy containing >2wt.% Fe, obtained from automotive scrap. Effect of Mo addition on the microstructure, high-temperature impression creep and thereby the machinability of the Al-recycled alloy were studied. The machinability of the recycled alloy was estimated by investigating the built-up-edge (BUE) and surface roughness (R a). SEM-EDS and TEM-SADP studies have shown that the crystal structure (BCC) of the Al8Fe2Si phase remained unchanged; however, Mo replaced few Fe atoms with little effect on the lattice dimension. It has been found that the addition of Mo to the recycled alloy suppresses the formation of β-phase (Al5FeSi) by suppressing the peritectic transformation of α (Al8Fe2Si) phase. Such suppression is found to improve the high-temperature creep resistance and the machinability with the increase in the Mo addition level.

  15. Development of a nitride dispersion strengthened (NDS) metallic alloy for high-temperature recuperators. Final report, 1 October 1982-30 September 1984

    SciTech Connect

    Kindlimann, L.E.

    1985-06-01

    The objective of this program was to demonstrate the feasibility of using nitride dispersion-strengthened (NDS) stainless steel in fabricating a recuperator for advanced gas turbine engines. Test results showed an alloy--designated NDS 300--to have tensile properties comparable to those of Inconel 625 at temperatures up to 1650 F, and at higher temperatures the properties of the NDS alloy exceeded those of the Inconel 625. However, creep test results showed a three-fold improvement in strength of NDS 300 over Inconel 625 at temperatures above 1500 F. The NDS material demonstrated adequate formability and joinability by brazing with a filler metal of nominal composition Ni-19Cr-10Si (J8100). The same filler metal proved to be a good coating for high-temperature oxidation resistance. Tests on specimens prepared to a typical plate-fin recuperator configuration confirmed the strength of the brazing alloy and demonstrated the marked superiority of the NDS material over Inconel 625.

  16. Microstructural Response During Isothermal and Isobaric Loading of a Precipitation-Strengthened Ni-29.7Ti-20Hf High-Temperature Shape Memory Alloy

    NASA Astrophysics Data System (ADS)

    Benafan, O.; Noebe, R. D.; Padula, S. A.; Vaidyanathan, R.

    2012-12-01

    A stable Ni-rich Ni-29.7Ti-20Hf (at. pct) shape memory alloy, with relatively high transformation temperatures, was shown to exhibit promising properties at lower raw material cost when compared to typical NiTi-X (X = Pt, Pd, Au) high-temperature shape memory alloys (HTSMAs). The excellent dimensional stability and high work output for this alloy were attributed to a coherent, nanometer size precipitate phase observed using transmission electron microscopy. To establish an understanding of the role of these precipitates on the microstructure and ensuing stability of the NiTiHf alloy, a detailed study of the micromechanical and microstructural behaviors was performed. In-situ neutron diffraction at stress and temperature was used to obtain quantitative information on phase-specific internal strain, texture, and phase volume fractions during both isothermal and isobaric testing of the alloy. During isothermal testing, the alloy exhibited low isothermal strains due to limited detwinning, consistent with direct measurements of the bulk texture through neutron diffraction. This limited detwinning was attributed to the pinning of twin and variant boundaries by the dispersion of fine precipitates. During isobaric thermal cycling at 400 MPa, the high work output and near-perfect dimensional stability was attributed to the presence of the precipitates that act as homogeneous sources for the nucleation of martensite throughout the material, while providing resistance to irrecoverable processes such as plastic deformation.

  17. Microstructure of a complex Nb-Si-based alloy and its behavior during high-temperature oxidation

    NASA Astrophysics Data System (ADS)

    Leont'ev, L. I.; Udoeva, L. Yu.; Chumarev, V. M.; Gulyaeva, R. I.; Pankratov, A. A.; Sel'menskikh, N. I.; Zhidovinova, S. V.

    2016-01-01

    A in-situ composite Nb-Si-Ti-Hf-Cr-Mo-Al composite material alloyed with yttrium and zirconium is studied. The evolution of the structure-phase state of the alloy during oxidation under dynamic and isothermal conditions is considered on samples prepared by vacuum remelting and directional solidification. The phase composition and the microstructure of the alloy are examined by the methods of physico-chemical analysis, and the distribution of alloying elements in initial samples and the products of oxidation is estimated. Thermogravimetric experiments are performed on powders and compacted samples during continuous (in the range 25-1400°C) and isothermal (at 900 and 1100°C) heating in air. The directional solidification of an Nb-Si-Ti-Al-Hf-Cr-Mo-Zr-Y is found to cause the formation of an ultradispersed eutectic consisting of α-Nb ss and γ-Nb5Si3 ss cells. The as-cast sample prepared by vacuum remelting has a dendritic structure and contains Nb3Si apart from these phases. Oxidation leads to the formation of a double oxide layer and an inner oxidation zone, which retain the two-phase microstructure and the ratio of alloying elements that are characteristic of the initial alloy. Diffusion redistribution is only detected for molybdenum. The cyclicity of heating at the initial stage of oxidation weakly influences the oxidation resistance of the alloy.

  18. Corrosion potential behavior in high-temperature water of noble metal-doped alloy coatings deposited by underwater thermal spraying

    SciTech Connect

    Kim, Y.J.; Andresen, P.L.; Gray, D.M.; Lau, Y.C.; Offer, H.P.

    1996-06-01

    Intergranular stress corrosion cracking (IGSCC) of sensitized stainless steel (SS) components in boiling water reactors (BWR) is a major concern. The SCC susceptibility of structural materials in high-temperature water is affected by the electrochemical corrosion potential (ECP). The ECP of type 304 stainless steel coated under water by hyper-velocity oxy-fuel (HVOF) and plasma-spray (PS) techniques using noble metal-doped powders was measured to evaluate the catalytic behavior in high-temperature water under various water chemistry conditions. Thermal-spray coatings of noble metal-doped powders exhibited catalytic behavior for the recombination of oxygen and hydrogen in high-temperature water, which caused ECP to decrease well below a critical value of {minus}230 mV{sub SHE} for intergranular stress corrosion cracking protection in water. This was observed in water containing various amounts of oxygen and hydrogen peroxide when stoichiometric excess hydrogen was present.

  19. IGA of alloy 600 in high-temperature solutions of sodium hydroxide contaminated with carbonate. Final report. [PWR

    SciTech Connect

    Roberge, R.; Bandy, R.; van Rooyen, D.

    1983-05-01

    Alloy 600 was tested in sodium hydroxide contaminated with sodium carbonate at 300/sup 0/C and 315/sup 0/C to examine its resistance to intergranular attack (IGA) under controlled cathodic and anodic potentials. Specimens of alloy 600 were studied as C-rings under constant deflection, wires under constant load and wires without any applied tensile stress. The material was mainly used in its mill annealed condition, although some specimens were studied as solution annealed and solution annealed plus sensitized. Unlike the last two metallurgical states, the mill annealed alloy 600 material was rather sensitive to stress corrosion cracking (SCC) in a range of anodic potentials.

  20. High-Temperature Piezoelectric Sensing

    PubMed Central

    Jiang, Xiaoning; Kim, Kyungrim; Zhang, Shujun; Johnson, Joseph; Salazar, Giovanni

    2014-01-01

    Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented. PMID:24361928

  1. Microstructure and high-temperature wear properties of in situ TiC composite coatings by plasma transferred arc surface alloying on gray cast iron

    NASA Astrophysics Data System (ADS)

    Zhao, Hang; Li, Jian-jun; Zheng, Zhi-zhen; Wang, Ai-hua; Huang, Qi-wen; Zeng, Da-wen

    2015-12-01

    In this work, an in situ synthesized TiC-reinforced metal matrix composite (MMC) coating of approximately 350-400 µm thickness was fabricated on a gray cast iron (GCI) substrate by plasma transferred arc (PTA) surface alloying of Ti-Fe alloy powder. Microhardness tests showed that the surface hardness increased approximately four-fold after the alloying treatment. The microstructure of the MMC coating was mainly composed of residual austenite, acicular martensite, and eutectic ledeburite. Scanning electron microscopy (SEM) and X-ray diffraction analyzes revealed that the in situ TiC particles, which were formed by direct reaction of Ti with carbon originally contained in the GCI, was uniformly distributed at the boundary of residual austenite in the alloying zone. Pin-on-disc high-temperature wear tests were performed on samples both with and without the MMC coating at room temperature and at elevated temperatures (473 K and 623 K), and the wear behavior and mechanism were investigated. The results showed that, after the PTA alloying treatment, the wear resistance of the samples improved significantly. On the basis of our analysis of the composite coatings by optical microscopy, SEM with energy-dispersive X-ray spectroscopy, and microhardness measurements, we attributed this improvement of wear resistance to the transformation of the microstructure and to the presence of TiC particles.

  2. Investigation of Ni-B Alloys for Joining of TiB2 Ultra-High-Temperature Ceramic

    NASA Astrophysics Data System (ADS)

    Xi, L.; Kaban, I.; Nowak, R.; Bruzda, G.; Sobczak, N.; Stoica, M.; Eckert, J.

    2016-02-01

    Melting and wetting behavior of Ni83B17 and Ni50B50 alloys on TiB2 ceramic are investigated upon heating to 1105 and 1050 °C, respectively, using the sessile drop technique. Both alloys show a very good wetting on the TiB2 substrates immediately after incipient melting. Liquid Ni50B50 alloy is revealed not to dissolve TiB2, but penetrates along the grain boundaries into the ceramic. Upon heating and melting of the Ni83B17 alloy on TiB2, a small amount of ceramic is dissolved and the ternary Ni21Ti2B6 phase is formed. Whereas multiple microcracks are observed at the Ni83B17/TiB2 interface, the Ni50B50/TiB2 couple is well bonded and free of interfacial microcracks.

  3. The Influence of Ni and V Trace Elements on High-Temperature Tensile Properties and Aging of A356 Aluminum Foundry Alloy

    NASA Astrophysics Data System (ADS)

    di Giovanni, Maria Teresa; Cerri, Emanuela; Casari, Daniele; Merlin, Mattia; Arnberg, Lars; Garagnani, Gian Luca

    2016-05-01

    High-temperature tensile properties of unmodified A356 alloy with and without the addition of Ni or V in traces (600 and 1000 ppm of Ni and V, respectively) were investigated by analyzing samples obtained from sand and permanent mold castings in the as-cast and T6 heat-treated conditions. Tensile tests were performed at 508 K (235 °C) at a crosshead speed of 1 mm/min. In addition, samples were subjected to artificial aging at 508 K (235 °C) for different times, and corresponding hardness curves were plotted. Microstructures and fracture surfaces, analyzed by FEG-SEM equipped with energy dispersive X-ray spectroscopy, showed that neither Ni nor V addition had a detrimental effect on high-temperature tensile properties. Aging curves showed a strong loss of hardness affecting the T6 class between 30-min and 1-h exposure time. After 6-h aging, no evidence of aging treatment persisted on hardness of the tested material. Hardness values did not reveal any significant difference between the reference alloy and the Ni- and V-containing alloys in both casting conditions, in complete analogy with the tensile properties. Unmodified eutectic silicon particles provided inhomogeneity in the α-Al matrix and acted as the principal source of stress concentration leading to fracture.

  4. The solid-solution alloying effects of Ti on the high-temperature deformation behavior of NiAl single crystals

    SciTech Connect

    Kitabjian, P.H.; Nix, W.D.; Garg, A.; Noebe, R.

    1997-12-31

    The authors have investigated the high-temperature deformation behavior of the solid-solution strengthened alloy Ni-47.5Al-2.5Ti. Single crystals were deformed in compression in the hard <001> and soft <111> orientations, at temperatures between 900 C and 1,200 C. The results show that Ti has a very powerful solute strengthening effect in NiAl. The creep rates for the solid-solution alloy were observed to be three to four orders of magnitude lower than for the stoichiometric material. They discuss the efforts to understand this solid-solution strengthening effect. They have studied high-temperature deformation transients in an effort to determine whether solute drag effects contribute to the creep resistance of this solid solution. In addition, they have examined the solute size effect of Ti as it replaces Al on the Al sub-lattice. They discuss the probable mechanism of creep of this alloy in light of TEM observations of the dislocation structures in creep-deformed crystals.

  5. Application of indium tin oxide (ITO) thin film as a low emissivity film on Ni-based alloy at high temperature

    NASA Astrophysics Data System (ADS)

    Sun, Kewei; Zhou, Wancheng; Tang, Xiufeng; Luo, Fa

    2016-09-01

    Indium tin oxide (ITO) films as the low emissivity coatings of Ni-based alloy at high temperature were studies. ITO films were deposited on the polished surface of alloy K424 by direct current magnetron sputtering. These ITO-coated samples were heat-treated in air at 600-900 °C for 150 h to explore the effect of high temperature environment on the emissivity. The samples were analyzed by X-ray diffraction (XRD), SEM and EDS. The results show that the surface of sample is integrity after heat processing at 700 °C and below it. A small amount of fine crack is observed on the surface of sample heated at 800 °C and Ti oxide appears. There are lots of fine cracks on the sample annealed at 900 °C and a large number of various oxides are detected. The average infrared emissivities at 3-5 μm and 8-14 μm wavebands were tested by an infrared emissivity measurement instrument. The results show the emissivity of the sample after annealed at 600 and 700 °C is still kept at a low value as the sample before annealed. The ITO film can be used as a low emissivity coating of super alloy K424 up to 700 °C.

  6. NASA-UVa light aerospace alloy and structure technology program supplement: Aluminum-based materials for high speed aircraft

    NASA Technical Reports Server (NTRS)

    Starke, E. A., Jr.

    1993-01-01

    This report on the NASA-UVa Light Aerospace Alloy and Structure Technology Program Supplement: Aluminum-Based Materials for High Speed Aircraft covers the period from January 1, 1992 to June 30, 1992. The objective of the research is to develop aluminum alloys and aluminum matrix composites for the airframe which can efficiently perform in the HSCT environment for periods as long as 60,000 hours (certification for 120,000 hours) and, at the same time, meet the cost and weight requirements for an economically viable aircraft. Current industry baselines focus on flight at Mach 2.4. The research covers four major materials systems: (1) ingot metallurgy 2XXX, 6XXX, and 8XXX alloys, (2) powder metallurgy 2XXX alloys, (3) rapidly solidified, dispersion strengthened Al-Fe-X alloys, and (4) discontinuously reinforced metal matrix composites. There are ten major tasks in the program which also include evaluation and trade-off studies by Boeing and Douglas aircraft companies.

  7. Effects of proof loads and combined mode loadings on fracture and flaw growth characteristics of aerospace alloys

    NASA Technical Reports Server (NTRS)

    Shah, R. C.

    1974-01-01

    This experimental program was undertaken to determine the effects of (1) combined tensile and bending loadings, (2) combined tensile and shear loadings, and (3) proof overloads on fracture and flaw growth characteristics of aerospace alloys. Tests were performed on four alloys: 2219-T87 aluminum, 5Al-2.5Sn (ELl) titanium, 6Al-4V beta STA titanium and high strength 4340 steel. Tests were conducted in room air, gaseous nitrogen at -200F (144K), liquid nitrogen and liquid hydrogen. Flat center cracked and surface flawed specimens, cracked tube specimens, circumferentially notched round bar and surface flawed cylindrical specimens were tested. The three-dimensional photoelastic technique of stress freezing and slicing was used to determine stress intensity factors for surface flawed cylindrical specimens subjected to tension or torsion. Results showed that proof load/temperature histories used in the tests have a small beneficial effect or no effect on subsequent fracture strength and flaw growth rates.

  8. Resilient and Corrosion-Proof Rolling Element Bearings Made from Superelastic Ni-Ti Alloys for Aerospace

    NASA Technical Reports Server (NTRS)

    Dellacorte, Christopher

    2014-01-01

    Mechanical components (bearings, gears, mechanisms) typically utilize hardened construction materials to minimize wear and attain long life. In such components, loaded contact points (e.g., meshing gear teeth, bearing balls-raceway contacts) experience high contact stresses. The combination of high hardness and high elastic modulus often leads to damaging contact stress and denting, particularly during transient overload events such as shock impacts that occur during the launching of space vehicles or the landing of aircraft. In this webinar, Dr. DellaCorte will introduce the results of a research project that employs a superelastic alloy, Ni-Ti for rolling element bearing applications. Bearings and components made from such alloys can alleviate many problems encountered in advanced aerospace applications and may solve many terrestrial applications as well

  9. The effect of potential on the high-temperature fatigue crack growth response of low alloy steels: Part II, electrochemical results

    SciTech Connect

    Moshier, W.C.; James, L.A.

    1997-04-01

    Environmentally assisted cracking (EAC) in low alloy steels was found to be dependent on externally applied potential in low sulfur steels in high temperature water. EAC could be turned on when the specimen was polarized anodically above a critical potential. However, hydrogen (H) additions inhibited the ability of potential to affect EAC. The behavior was related to formation of H ions during H oxidation at the crack mouth. A mechanism based on formation of H sulfide at the crack tip and H ions at the crack mouth is presented to describe the process by which sulfides and H ions affect the critical sulfide concentration at the crack tip.

  10. Investigation of the oxidation behavior of dispersion stabilized alloys when exposed to a dynamic high temperature environment

    NASA Technical Reports Server (NTRS)

    Tenney, D. R.

    1974-01-01

    The oxidation behavior of TD-NiCr and TD-NiCrAlY alloys have been studied at 2000 and 2200 F in static and high speed flowing air environments. The TD-NiCrAlY alloys preoxidized to produce an Al2O3 scale on the surface showed good oxidation resistance in both types of environments. The TD-NiCr alloy which had a Cr2O3 oxide scale after preoxidation was found to oxidize more than an order of magnitude faster under the dynamic test conditions than at comparable static test conditions. Although Cr2O3 normally provides good oxidation protection, it was rapidly lost due to formation of volatile CrO3 when exposed to the high speed air stream. The preferred oxide arrangement for the dynamic test consisted of an external layer of NiO with a porous mushroom type morphology, an intermediate duplex layer of NiO and Cr2O3, and a continuous inner layer of Cr2O3 in contact with the alloy substrate. An oxidation model has been developed to explain the observed microstructure and overall oxidation behavior of all alloys.

  11. Deformation Behavior of Laser Welds in High Temperature Oxidation Resistant Fe-Cr-Al Alloys for Fuel Cladding Applications

    SciTech Connect

    Field, Kevin G; Gussev, Maxim N; Yamamoto, Yukinori; Snead, Lance Lewis

    2014-11-01

    Ferritic-structured Fe-Cr-Al alloys are being developed and show promise as oxidation resistant accident tolerant light water reactor fuel cladding. This study focuses on investigating the weldability of three model alloys in a range of Fe-(13-17.5)Cr-(3-4.4)Al in weight percent with a minor addition of yttrium using laser-welding techniques. A detailed study on the mechanical performance of bead-on-plate welds has been carried out to determine the performance of welds as a function of alloy composition. Laser welding resulted in a defect free weld devoid of cracking or inclusions for all alloys studied. Results indicated a reduction in the yield strength within the fusion zone compared to the base metal. Yield strength reduction was found to be primarily constrained to the fusion zone due to grain coarsening with a less severe reduction in the heat affected zone. No significant correlation was found between the deformation behavior/mechanical performance of welds and the level of Cr or Al in the alloy ranges studied.

  12. High-Temperature Interaction Between Molten AlSr10 Alloy and Glass-Like Carbon Substrate

    NASA Astrophysics Data System (ADS)

    Siewiorek, A.; Sobczak, N.; Sobczak, J.; Kudyba, A.; Kozera, R.; Boczkowska, A.

    2016-03-01

    Wettability of glass-like carbon substrate (Cglc) by molten Al-10 wt.% Sr alloy (AlSr10) has been examined by a sessile drop method at 700-800 °C for 120 min under vacuum. Non-contact heating to the test temperature combined with the removal of oxide film from the alloy drop was done using capillary purification procedure by squeezing the liquid alloy from a capillary. The influence of the type of capillary on wetting behavior of AlSr10/Cglc couples was noticed. Molten AlSr10 alloy does not wet Cglc at about 700 °C forming the contact angles of 111° with graphite capillary and 141° with alumina capillary. At 800 °C with alumina capillary, non-wetting-to-wetting transition takes place resulting in a final contact angle of 70°. After testing at 800 °C, the AlSr10/Cglc interface was revealed at the test temperature directly in the vacuum chamber by the drop suction procedure. Structural characterization of the interfaces by scanning and transmission electron microscopy combined with energy-dispersive x-ray spectroscopy and by scanning probe microscopy combined with Auger electron spectrometry did not show any new phases formed with Sr. It suggests that the dominant role in wettability improvement by alloying Al with 10 wt.% Sr was related with significant lowering of the surface tension of liquid metal and adsorption of Sr at the interface.

  13. Trichite growth during oxidation of titanium and TA6V4 alloy by water vapor at high temperatures

    NASA Technical Reports Server (NTRS)

    Coddet, C.; Motte, F.; Sarrazin, P.

    1982-01-01

    Analysis by electron scanning microscope detected the formation of rutile trichites on the surface of specimens of titanium and titanium alloy TA6V4 oxidized in water vapor in the temperature range 650 to 950 C and the water vapor pressure range from 0.5 to 18 torr. In all specimens, two sublayers of rutile were formed: an external layer of basalt-like appearance, and a microcrystalline inner layer. Morphology of the trichites depends on temperature and the material (whether metal or alloy), but not on vapor pressure.

  14. High Temperature Oxidation Behavior of gamma-Ni+gamma'-Ni3Al Alloys and Coatings Modified with Pt and Reactive Elements

    SciTech Connect

    Mu, Nan

    2007-12-01

    Materials for high-pressure turbine blades must be able to operate in the high-temperature gases (above 1000 C) emerging from the combustion chamber. Accordingly, the development of nickel-based superalloys has been constantly motivated by the need to have improved engine efficiency, reliability and service lifetime under the harsh conditions imposed by the turbine environment. However, the melting point of nickel (1455 C) provides a natural ceiling for the temperature capability of nickel-based superalloys. Thus, surface-engineered turbine components with modified diffusion coatings and overlay coatings are used. Theses coatings are capable of forming a compact and adherent oxide scale, which greatly impedes the further transport of reactants between the high-temperature gases and the underlying metal and thus reducing attack by the atmosphere. Typically, these coatings contain β-NiAl as a principal constituent phase in order to have sufficient aluminum content to form an Al2O3 scale at elevated temperatures. The drawbacks to the currently-used {beta}-based coatings, such as phase instabilities, associated stresses induced by such phase instabilities, and extensive coating/substrate interdiffusion, are major motivations in this study to seek next-generation coatings. The high-temperature oxidation resistance of novel Pt + Hf-modified γ-Ni + γ-Ni3Al-based alloys and coatings were investigated in this study. Both early-stage and 4-days isothermal oxidation behavior of single-phase γ-Ni and γ'-Ni3Al alloys were assessed by examining the weight changes, oxide-scale structures, and elemental concentration profiles through the scales and subsurface alloy regions. It was found that Pt promotes Al2O3 formation by suppressing the NiO growth on both γ-Ni and γ'Ni3Al single-phase alloys. This effect increases with increasing Pt content. Moreover, Pt exhibits this effect even at lower

  15. In situ Growth of NixCu1-x Alloy Nanocatalysts on Redox-reversible Rutile (Nb,Ti)O4 Towards High-Temperature Carbon Dioxide Electrolysis

    NASA Astrophysics Data System (ADS)

    Wei, Haoshan; Xie, Kui; Zhang, Jun; Zhang, Yong; Wang, Yan; Qin, Yongqiang; Cui, Jiewu; Yan, Jian; Wu, Yucheng

    2014-06-01

    In this paper, we report the in situ growth of NixCu1-x (x = 0, 0.25, 0.50, 0.75 and 1.0) alloy catalysts to anchor and decorate a redox-reversible Nb1.33Ti0.67O4 ceramic substrate with the aim of tailoring the electrocatalytic activity of the composite materials through direct exsolution of metal particles from the crystal lattice of a ceramic oxide in a reducing atmosphere at high temperatures. Combined analysis using XRD, SEM, EDS, TGA, TEM and XPS confirmed the completely reversible exsolution/dissolution of the NixCu1-x alloy particles during the redox cycling treatments. TEM results revealed that the alloy particles were exsolved to anchor onto the surface of highly electronically conducting Nb1.33Ti0.67O4 in the form of heterojunctions. The electrical properties of the nanosized NixCu1-x/Nb1.33Ti0.67O4 were systematically investigated and correlated to the electrochemical performance of the composite electrodes. A strong dependence of the improved electrode activity on the alloy compositions was observed in reducing atmospheres at high temperatures. Direct electrolysis of CO2 at the NixCu1-x/Nb1.33Ti0.67O4 composite cathodes was investigated in solid-oxide electrolysers. The CO2 splitting rates were observed to be positively correlated with the Ni composition; however, the Ni0.75Cu0.25 combined the advantages of metallic nickel and copper and therefore maximised the current efficiencies.

  16. In situ growth of Ni(x)Cu(1-x) alloy nanocatalysts on redox-reversible rutile (Nb,Ti)O₄ towards high-temperature carbon dioxide electrolysis.

    PubMed

    Wei, Haoshan; Xie, Kui; Zhang, Jun; Zhang, Yong; Wang, Yan; Qin, Yongqiang; Cui, Jiewu; Yan, Jian; Wu, Yucheng

    2014-01-01

    In this paper, we report the in situ growth of Ni(x)Cu(1-x) (x = 0, 0.25, 0.50, 0.75 and 1.0) alloy catalysts to anchor and decorate a redox-reversible Nb1.33Ti0.67O4 ceramic substrate with the aim of tailoring the electrocatalytic activity of the composite materials through direct exsolution of metal particles from the crystal lattice of a ceramic oxide in a reducing atmosphere at high temperatures. Combined analysis using XRD, SEM, EDS, TGA, TEM and XPS confirmed the completely reversible exsolution/dissolution of the Ni(x)Cu(1-x) alloy particles during the redox cycling treatments. TEM results revealed that the alloy particles were exsolved to anchor onto the surface of highly electronically conducting Nb1.33Ti0.67O4 in the form of heterojunctions. The electrical properties of the nanosized Ni(x)Cu(1-x)/Nb1.33Ti0.67O4 were systematically investigated and correlated to the electrochemical performance of the composite electrodes. A strong dependence of the improved electrode activity on the alloy compositions was observed in reducing atmospheres at high temperatures. Direct electrolysis of CO2 at the Ni(x)Cu(1-x)/Nb1.33Ti0.67O4 composite cathodes was investigated in solid-oxide electrolysers. The CO2 splitting rates were observed to be positively correlated with the Ni composition; however, the Ni0.75Cu0.25 combined the advantages of metallic nickel and copper and therefore maximised the current efficiencies. PMID:24889679

  17. In situ Growth of NixCu1-x Alloy Nanocatalysts on Redox-reversible Rutile (Nb,Ti)O4 Towards High-Temperature Carbon Dioxide Electrolysis

    PubMed Central

    Wei, Haoshan; Xie, Kui; Zhang, Jun; Zhang, Yong; Wang, Yan; Qin, Yongqiang; Cui, Jiewu; Yan, Jian; Wu, Yucheng

    2014-01-01

    In this paper, we report the in situ growth of NixCu1-x (x = 0, 0.25, 0.50, 0.75 and 1.0) alloy catalysts to anchor and decorate a redox-reversible Nb1.33Ti0.67O4 ceramic substrate with the aim of tailoring the electrocatalytic activity of the composite materials through direct exsolution of metal particles from the crystal lattice of a ceramic oxide in a reducing atmosphere at high temperatures. Combined analysis using XRD, SEM, EDS, TGA, TEM and XPS confirmed the completely reversible exsolution/dissolution of the NixCu1-x alloy particles during the redox cycling treatments. TEM results revealed that the alloy particles were exsolved to anchor onto the surface of highly electronically conducting Nb1.33Ti0.67O4 in the form of heterojunctions. The electrical properties of the nanosized NixCu1-x/Nb1.33Ti0.67O4 were systematically investigated and correlated to the electrochemical performance of the composite electrodes. A strong dependence of the improved electrode activity on the alloy compositions was observed in reducing atmospheres at high temperatures. Direct electrolysis of CO2 at the NixCu1-x/Nb1.33Ti0.67O4 composite cathodes was investigated in solid-oxide electrolysers. The CO2 splitting rates were observed to be positively correlated with the Ni composition; however, the Ni0.75Cu0.25 combined the advantages of metallic nickel and copper and therefore maximised the current efficiencies. PMID:24889679

  18. Strengthening Aluminum Alloys for High Temperature Applications Using Nanoparticles of Al203 and Al3-X Compounds (X= Ti, V, Zr)

    NASA Technical Reports Server (NTRS)

    Lee, Jonathan A.

    2007-01-01

    In this paper the effect of nanoparticles A12O3 and A13-X compounds (X= Ti, V, Zr) on the improvement of mechanical properties of aluminum alloys for elevated temperature applications is presented. These nanoparticles were selected based on their chemical stability and low diffusions rates in aluminum matrix at high temperatures. The strengthening mechanism for aluminum alloy is based on the mechanical blocking of dislocation movements by these nanoparticles. Samples were prepared from A12O3 nanoparticle preforms, which were produced using ceramic injection molding process and pressure infiltrated by molten aluminum. A12O3 nanoparticles can also be homogeneously mixed with aluminum powder and consolidated into samples through hot pressing and sintering. On the other hand, the Al3-X nanoparticles are produced as precipitates via in situ reactions with molten aluminum alloys using conventional casting techniques. The degree of alloy strengthening using nanoparticles will depend on the materials, particle size, shape, volume fraction, and mean inter-particle spacing.

  19. Atomic scale modelling of chromium diffusion and melting in α-iron and iron-chromium alloys using high-temperature molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Terentiev, Dmitri A.; Malerba, Lorenzo; Olsson, Par; Hou, Marc

    2004-04-01

    EAM interatomic potential to be used for radiation effect simulations in the Fe-Cr system has been recently proposed. In the present work, this potential is used to calculate by means of classical molecular dynamics (MD) the diffusivity of solute Cr atoms in Fe-12%Cr random alloy. Fe self-diffusivity is calculated as well, both in the alloy and in the pure metal, for comparison. In addition, the melting point for both the pure metal and the alloy, as predicted by the potential, has been determined and a comparison between the efficiency of vacancy and interstitial mechanisms for diffusion has been performed. This study allows the validity of the potential to be checked against experimental data outside its fitting range, while providing some insight into the description that this potential gives of irradiation effects. A correct prediction of the diffusivity of solute atoms at high temperature and the melting point are indeed an important pre-requisite for a correct prediction of ion mixing and point defect clustering within a displacement cascade during the thermal spike phase. The conclusion of the study is that the present potential is capable of reproducing with excellent accuracy both the diffusion coefficient and the melting point in Fe and in the Fe-Cr alloy. Atomic diffusion through interstitials is also seen to be a more efficient mechanism than through vacancies in the materials considered.

  20. Intergranular attack and stress corrosion cracking of Alloy 600 in high-temperature caustic solutions containing contaminants

    SciTech Connect

    Bandy, R.; Roberge, R.; van Rooyen, D.

    1985-06-01

    Concentrated caustic is a primary cause of stress corrosion cracking and intergranular attack of Alloy 600 tubing in PWRs. However, temperature, electrochemical potential, stress, and metallurgical state all play a role. This study provides the quantitative evidence needed to develop models of crack growth and to devise effective countermeasures.

  1. High-temperature corrosion behavior of coatings and ODS alloys based on Fe{sub 3}Al

    SciTech Connect

    Tortorelli, P.F.; Pint, B.A.; Wright, I.G.

    1996-08-01

    Iron-aluminide coatings were prepared by gas tungsten arc and gas metal arc weld-overlay techniques. All the weld overlays showed good oxidation/sulfidation behavior under isothermal conditions, including a gas metal arc deposit with only 21 at.% Al. A rapid degradation in corrosion resistance was observed under thermal cycling conditions when the initially grown scales spalled and the subsequent rate of reaction was not controlled by the formation of slowly growing aluminum oxides. Higher starting aluminum concentrations (>{approximately}25 at.%) are needed to assure adequate oxidation/sulfidation lifetimes of the weld overlays. A variety of stable oxides was added to a base Fe-28 at.% Al-2 % Cr alloy to assess the effect of these dopants on the oxidation behavior at 1200{degrees}C. A Y{sub 2}O{sub 3} dispersion improved the scale adhesion relative to a Zr alloy addition, but wasn`t as effective as it is in other alumina-forming alloys. Preliminary data for powder-processed Fe-28 at.% Al-2% Cr exposed to the H{sub 2}S-H{sub 2}-H{sub 2}O-Ar gas at 800{degrees}C showed that the oxidation/sulfidation rate was similar to that of many Fe{sub 3}Al alloys produced by ingot metallurgy routes.

  2. Standard specification for hot isostatically-pressed alloy steel flanges, fittings, valves, and parts for high temperature service. ASTM standard

    SciTech Connect

    1998-09-01

    This specification is under the jurisdiction of ASTM Committee A-1 on Steel, Stainless Steel, and Related Alloys and is the direct responsibility of Subcommittee A01.22 on Steel Forgings and Wrought Fittings for Piping Applications and Bolting Materials for Piping and Special Purpose Applications. Current edition approved Mar. 10, 1998 and published September 1998.

  3. Computer Simulation and Experimental Validation on the Oxidation and Sulfate Corrosion Resistance of Novel Chromium Based High Temperature Alloys

    SciTech Connect

    Yang, Shizhong

    2013-02-28

    This report summarizes our recent works of ab initio molecular dynamics inter-atomic potentials development on dilute rare earth element yttrium (Y) etc. doped chromium (Cr) alloy systems, its applications in oxidation and corrosion resistance simulation, and experiment validation on the candidate systems. The simulation methods, experimental validation techniques, achievements already reached, students training, and future improvement are briefly introduced.

  4. PROCESSING, MICROSTRUCTURE AND CREEP BEHAVIOR OF MO-SI-B-BASED INTERMETALLIC ALLOYS FOR VERY HIGH TEMPERATURE STRUCTURAL APPLICATIONS

    SciTech Connect

    Vijay K. Vasudevan

    2005-02-08

    This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. During this year, the microstructure, bend strength and compressive creep behavior of a Mo-3Si-1B (in wt.%) alloy were studied. The microstructure of this alloy was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. The elastic limit strength of the alloy remained quite high until 1200 C with a value of 800MPa, but dropped rapidly thereafter to a value of 220 MPa at 1400 C. Results of compressive creep tests at 1200 C showed that the creep rates were quite high and varied nearly linearly with stress between 250 and 500 MPa, which suggests that diffusional mechanisms dominate the creep process. Microstructural observations of post-crept samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. These results and presented and discussed.

  5. Deformation behavior of laser welds in high temperature oxidation resistant Fe-Cr-Al alloys for fuel cladding applications

    NASA Astrophysics Data System (ADS)

    Field, Kevin G.; Gussev, Maxim N.; Yamamoto, Yukinori; Snead, Lance L.

    2014-11-01

    Ferritic-structured Fe-Cr-Al alloys are being developed and show promise as oxidation resistant accident tolerant light water reactor fuel cladding. This study focuses on investigating the weldability and post-weld mechanical behavior of three model alloys in a range of Fe-(13-17.5)Cr-(3-4.4)Al (wt.%) with a minor addition of yttrium using modern laser-welding techniques. A detailed study on the mechanical performance of bead-on-plate welds using sub-sized, flat dog-bone tensile specimens and digital image correlation (DIC) has been carried out to determine the performance of welds as a function of alloy composition. Results indicated a reduction in the yield strength within the fusion zone compared to the base metal. Yield strength reduction was found to be primarily constrained to the fusion zone due to grain coarsening with a less severe reduction in the heat affected zone. For all proposed alloys, laser welding resulted in a defect free weld devoid of cracking or inclusions.

  6. 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.

  7. Corrosion characteristics of nickel alloys. Citations from the International Aerospace Abstracts data base

    NASA Technical Reports Server (NTRS)

    Zollars, G. F.

    1979-01-01

    This bibliography cites 118 articles from the international literature concerning corrosion characteristics of nickel alloys. Articles dealing with corrosion resistance, corrosion tests, intergranular corrosion, oxidation resistance, and stress corrosion cracking of nickel alloys are included.

  8. Effect of Thermal Treatments on Ni-Mn-Ga and Ni-Rich Ni-Ti-Hf/Zr High-Temperature Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Santamarta, Ruben; Evirgen, Alper; Perez-Sierra, Aquilina M.; Pons, Jaume; Cesari, Eduard; Karaman, Ibrahim; Noebe, Ron D.

    2015-11-01

    Among all the promising high-temperature shape memory alloys (HTSMAs), the Ni-Mn-Ga and the Ni-Ti-Hf/Zr systems exhibit interesting shape memory and superelastic properties that may place them in a good position for potential applications. The present work shows that thermal treatments play a crucial role in controlling the martensitic phase transformation characteristics of both systems, but in different ways. On one hand, the equilibrium phase diagram of the Ni-Mn-Ga family allows selecting compositions with high transformation temperatures and outstanding thermal stability at relatively high temperatures in air, showing no significant changes in the transformation behavior for continuous aging up to ˜5 years at 500 °C. Moreover, the excellent thermal stability correlates with a good thermal cyclic stability and an exceptional oxidation resistance of the parent phase. On the other hand, precipitation processes controlled by thermal treatments are needed to manipulate the transformation temperatures, mechanical properties, and thermal stability of Ni-rich Ni-Ti-Hf/Zr alloys to become HTSMAs. These changes in the functional properties are a consequence of the competition between the mechanical and compositional effects of the precipitates on the martensitic transformation.

  9. Effect of thermal exposure, forming, and welding on high-temperature, dispersion-strengthened aluminum alloy: Al-8Fe-1V-2Si

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    The feasibility of applying conventional hot forming and welding methods to high temperature aluminum alloy, Al-8Fe-1V-2Si (FVS812), for structural applications and the effect of thermal exposure on mechanical properties were determined. FVS812 (AA8009) sheet exhibited good hot forming and resistance welding characteristics. It was brake formed to 90 deg bends (0.5T bend radius) at temperatures greater than or equal to 390 C (730 F), indicating the feasibility of fabricating basic shapes, such as angles and zees. Hot forming of simple contoured-flanged parts was demonstrated. Resistance spot welds with good static and fatigue strength at room and elevated temperatures were readily produced. Extended vacuum degassing during billet fabrication reduced porosity in fusion and resistance welds. However, electron beam welding was not possible because of extreme degassing during welding, and gas-tungsten-arc welds were not acceptable because of severely degraded mechanical properties. The FVS812 alloy exhibited excellent high temperature strength stability after thermal exposures up to 315 C (600 F) for 1000 h. Extended billet degassing appeared to generally improve tensile ductility, fatigue strength, and notch toughness. But the effects of billet degassing and thermal exposure on properties need to be further clarified. The manufacture of zee-stiffened, riveted, and resistance-spot-welded compression panels was demonstrated.

  10. High frequency, high temperature specific core loss and dynamic B-H hysteresis loop characteristics of soft magnetic alloys

    SciTech Connect

    Wieserman, W.R.; Schwarze, G.E.; Niedra, J.M.

    1994-09-01

    Limited experimental data exists for the specific core loss and dynamic B-H loops for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglass 2605SC over the frequency range of 1-50 kHz and temperature range of 23-300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.

  11. Fundamental studies of stress distributions and stress relaxation in oxide scales on high temperature alloys. [Final progress report

    SciTech Connect

    Shores, D.A.; Stout, J.H.; Gerberich, W.W.

    1993-06-01

    This report summarizes a three-year study of stresses arising in the oxide scale and underlying metal during high temperature oxidation and of scale cracking. In-situ XRD was developed to measure strains during oxidation over 1000{degrees}C on pure metals. Acoustic emission was used to observe scale fracture during isothermal oxidation and cooling, and statistical analysis was used to infer mechanical aspects of cracking. A microscratch technique was used to measure the fracture toughness of scale/metal interface. A theoretical model was evaluated for the development and relaxation of stresses in scale and metal substrate during oxidation.

  12. High frequency, high temperature specific core loss and dynamic B-H hysteresis loop characteristics of soft magnetic alloys

    NASA Technical Reports Server (NTRS)

    Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

    1990-01-01

    Limited experimental data exists for the specific core loss and dynamic B-H loops for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1 to 50 kHz and temperature range of 23 to 300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.

  13. High frequency, high temperature specific core loss and dynamic B-H hysteresis loop characteristics of soft magnetic alloys

    NASA Technical Reports Server (NTRS)

    Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

    1990-01-01

    Limited experimental data exists for the specific core loss and dynamic B-H loop for soft magnetic materials for the combined conditions of high frequency and high temperature. This experimental study investigates the specific core loss and dynamic B-H loop characteristics of Supermalloy and Metglas 2605SC over the frequency range of 1 to 50 kHz and temperature range of 23 to 300 C under sinusoidal voltage excitation. The experimental setup used to conduct the investigation is described. The effects of the maximum magnetic flux density, frequency, and temperature on the specific core loss and on the size and shape of the B-H loops are examined.

  14. Rh-V alloy formation in Rh-VOx thin films after high-temperature reduction studied by electron microscopy.

    PubMed

    Penner, S; Jenewein, B; Wang, D; Schlögl, R; Hayek, K

    2006-03-14

    Rh nanoparticles (mean size 10 and 15 nm), prepared by epitaxial growth on NaCl surfaces, were covered with layers of crystalline vanadium oxide (mean thickness 1.5 and 25 nm) by reactive deposition in 10(-2) mbar O2. The 1.5 nm film was further stabilized with a coating layer of 25 nm amorphous alumina. The so-obtained Rh/vanadia films, containing vanadium in the V3+ and V2+ state, were treated in 1 bar O2 at 673 K for 1 h and thereafter reduced in 1 bar H2 at increased temperatures, particularly between 723 and 873 K. The structural and morphological changes were followed by (high-resolution) transmission electron microscopy and selected area diffraction. Oxidation at 673 K transforms the purely vanadia-supported samples into Rh/V2O5, while in the alumina-supported films containing only small amounts of VOx, the formation of topotactic V2O3 is observed. The formation of Rh-V alloys during the subsequent reduction is strongly determined by the intimate contact and the structural and orientational relationship between Rh particles and the surrounding VOx phase. Reduction above 473 K transforms the support into substoichiometric vanadium oxides of composition VO and V2O. Analysis of high-resolution images and diffraction patterns reveals the presence of different alloy phases after reduction with increasing T (from 573 up to 823 K). In the alumina-supported film (low V/Rh ratio) the epitaxial alignment between the Rh particles and the surrounding V2O3 phase apparently favours the primary formation of defined alloys of type V3Rh and VRh3, followed by VRh at higher temperature. On the contrary, mainly V3Rh5 is formed in the purely VOx-supported Rh/films, due to different epitaxial relations in the initial state. Possible pathways of alloy formation are discussed. PMID:16633603

  15. High temperature electronics

    NASA Astrophysics Data System (ADS)

    Seng, Gary T.

    1991-03-01

    In recent years, the aerospace propulsion and space power communities have acknowledged a growing need for electronic devices that are capable of sustained high-temperature operation. Aeropropulsion applications for high-temperature electronic devices include engine ground test instrumentation such as multiplexers, analog-to-digital converters, and telemetry systems capable of withstanding hot section engine temperatures in excess of 600 C. Uncooled operation of control and condition monitoring systems in advanced supersonic aircraft would subject the electronics to temperatures in excess of 300 C. Similarly, engine-mounted integrated electronic sensors could reach temperatures which exceed 500 C. In addition to aeronautics, there are many other areas that could benefit from the existence of high-temperature electronic devices. Space applications include power electronic devices for space platforms and satellites. Since power electronics require radiators to shed waste heat, electronic devices that operate at higher temperatures would allow a reduction in radiator size. Terrestrial applications include deep-well drilling instrumentation, high power electronics, and nuclear reactor instrumentation and control. To meet the needs of the applications mentioned previously, the high-temperature electronics (HTE) program at the Lewis Research Center is developing silicon carbide (SiC) as a high-temperature semiconductor material. Research is focused on developing the crystal growth, growth modeling, characterization, and device fabrication technologies necessary to produce a family of SiC devices. Interest in SiC has grown dramatically in recent years due to solid advances in the technology. Much research remains to be performed, but SiC appears ready to emerge as a useful semiconductor material.

  16. Transpassive dissolution of alloy 625, chromium, nickel, and molybdenum in high-temperature solutions containing hydrochloric acid and oxygen

    SciTech Connect

    Kritzer, P.; Boukis, N.; Dinjus, E.

    2000-03-01

    Coupons of nickel, molybdenum, chromium, and the nickel-based Alloy 625 (UNS 06625) were corroded in strongly oxidizing hydrochloric acid (HCl) solutions at 350 C and a pressure (p) of 24 MPa, with reaction times between 0.75 h and 50 h. For Alloy 625, the effect of surface roughness also was investigated. Nickel and molybdenum showed strong material loss after only 5 h of reaction as a result of the instability of the solid oxides formed under experimental conditions. The attack on chromium started at the grain boundaries. At longer reaction times, thick, spalling oxide layers formed on the surface. The attack on Alloy 625 also started at the grain boundaries and at inclusions leading to the formation of small pits. On polished surfaces, the growth of these pits occurred faster than on nonpolished surfaces, but fewer pits grew. Corrosion products formed at the surface consisted of oxygen and chromium. On isolated spots, nickel- and chlorine-containing products also were found.

  17. Arrhenius-Type Constitutive Model for High Temperature Flow Stress in a Nickel-Based Corrosion-Resistant Alloy

    NASA Astrophysics Data System (ADS)

    Wang, L.; Liu, F.; Cheng, J. J.; Zuo, Q.; Chen, C. F.

    2016-04-01

    Hot deformation behavior of Nickel-based corrosion-resistant alloy (N08028) was studied in compression tests conducted in the temperature range of 1050-1200 °C and the strain rate range of 0.001-1 s-1. The flow stress behavior and microstructural evolution were observed during the hot deformation process. The results show that the flow stress increases with deformation temperature decreasing and strain rate increasing, and that the deformation activation energy ( Q) is not a constant but increases with strain rate increasing at a given strain, which is closely related with dislocation movement. On this basis, a revised strain-dependent hyperbolic sine constitutive model was established, which considered that the "material constants" in the original model vary as functions of the strain and strain rate. The flow curves of N08028 alloy predicted by the proposed model are in good agreement with the experimental results, which indicates that the revised constitutive model can estimate precisely the flow curves of N08028 alloy.

  18. Influence of oxide layer morphology on hydrogen concentration in tin and niobium containing zirconium alloys after high temperature steam oxidation

    NASA Astrophysics Data System (ADS)

    Große, Mirco; Lehmann, Eberhard; Steinbrück, Martin; Kühne, Guido; Stuckert, Juri

    2009-03-01

    The influence of the oxide layer morphology on the hydrogen uptake during steam oxidation of (Zr,Sn) and Zr-Nb nuclear fuel rod cladding alloys was investigated in isothermal separate-effect tests and large-scale fuel rod bundle simulation experiments. From both it can be concluded that the concentration of hydrogen in the remaining metal strongly depends on the existence of tangential cracks in the oxide layers formed by the tetragonal - monoclinic phase transition in the oxide, known as breakaway effect. In these cracks hydrogen is strongly enriched. It results in very local high hydrogen partial pressure at the oxide/metal interface and in an increase of the hydrogen concentration in the metal at local regions where such cracks in the oxide layer exist. Due to this effect the hydrogen uptake of the remaining zirconium alloy does not depend monotonically on temperature. Differences between (Zr,Sn) and Zr-Nb alloys are caused by differences in the hydrogen production due to different oxidation kinetics and in the crack forming phase transformation in the oxides as well as in the mechanical stability of the oxides.

  19. Spectroscopic detection and analysis of atomic emissions during industrial pulsed laser-drilling of structural aerospace alloys

    NASA Astrophysics Data System (ADS)

    Bright, Robin Michael

    The ability to adequately cool internal gas-turbine engine components in next-generation commercial and military aircraft is of extreme importance to the aerospace industry as the demand for high-efficiency engines continues to push operating temperatures higher. Pulsed laser-drilling is rapidly becoming the preferred method of creating cooling holes in high temperature components due a variety of manufacturing advantages of laser-drilling over conventional hole-drilling techniques. As cooling requirements become more demanding, the impact of drilling conditions on material removal behavior and subsequent effects on hole quality becomes critical. In this work, the development of emission spectroscopy as a method to probe the laser-drilling process is presented and subsequently applied to the study of material behavior of various structural aerospace materials during drilling. Specifically, emitted photons associated with energy level transitions within excited neutral atoms in material ejected during drilling were detected and analyzed. Systematic spectroscopic studies indicated that electron energy level populations and calculated electron temperatures within ejected material are dependent on both laser pulse energy and duration. Local thermal conditions detected by the developed method were related to the characteristics of ejected material during drilling and to final hole quality. Finally, methods of utilizing the observed relationships for spectroscopic process monitoring and control were demonstrated.

  20. Isothermal nucleation and growth kinetics of Pd/Ag alloy phase via in-situ time-resolved high-temperature x-ray diffraction (HTXRD) analysis

    SciTech Connect

    Ayturk, Mahmut Engin; Payzant, E Andrew; Speakman, Scott A; Ma, Yi Hua

    2008-01-01

    Among several different approaches to form Pd/Ag alloys for hydrogen separation applications, ex-situ studies carried by conventional X-ray point scanning detectors might fail to reveal the key aspects of the phase transformation between Pd and Ag metals. In this respect, in-situ time-resolved high temperature X-ray diffraction (HTXRD) was employed to study the Pd/Ag alloy phase nucleation and growth kinetics. By the use of linear position sensitive detectors, advanced optics and profile fitting with the use of JADE-6.5 software, isothermal phase evolution of the Pd/Ag alloy at 500 C, 550 C and 600 C under hydrogen atmosphere were quantified to elucidate the mechanistic details of the Pd/Ag alloy phase nucleation and growth pattern. Analysis of the HTXRD data by the Avrami model indicated that the nucleation of the Pd/Ag alloy phase was instantaneous where the growth mechanism was through diffusion-controlled one-dimensional thickening of the Pd/Ag alloy layer. The value of the Avrami exponent, n, was found to increase with temperature with the values of 0.34, 0.39 and 0.67 at 500oC, 550oC and 600oC, respectively. In addition, parabolic rate law analysis suggested that the nucleation of the Pd/Ag alloy phase was through a heterogeneous nucleation mode, in which the nucleation sites were defined as the non-equilibrium defects. The cross-sectional SEI micrographs indicated that the Pd/Ag alloy phase growth was strongly dependent upon the deposition morphology of the as-synthesized Pd and Ag layers formed by the electroless plating. Based on the Avrami model and the parabolic rate law, the estimated activation energies for the phase transformation were 236.5 and 185.6 kJ/mol and in excellent agreement with the literature values (183-239.5 kJ/mol).

  1. Improving High-Temperature Tensile and Low-Cycle Fatigue Behavior of Al-Si-Cu-Mg Alloys Through Micro-additions of Ti, V, and Zr

    NASA Astrophysics Data System (ADS)

    Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

    2015-07-01

    High-temperature tensile and low-cycle fatigue tests were performed to assess the influence of micro-additions of Ti, V, and Zr on the improvement of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in the as-cast condition. Addition of transition metals led to modification of microstructure where in addition to conventional phases present in the Al-7Si-1Cu-0.5Mg base, new thermally stable micro-sized Zr-Ti-V-rich phases Al21.4Si4.1Ti3.5VZr3.9, Al6.7Si1.2TiZr1.8, Al2.8Si3.8V1.6Zr, and Al5.1Si35.4Ti1.6Zr5.7Fe were formed. The tensile tests showed that with increasing test temperature from 298 K to 673 K (25 °C to 400 °C), the yield stress and tensile strength of the present studied alloy decreased from 161 to 84 MPa and from 261 to 102 MPa, respectively. Also, the studied alloy exhibited 18, 12, and 5 pct higher tensile strength than the alloy A356, 354 and existing Al-Si-Cu-Mg alloy modified with additions of Zr, Ti, and Ni, respectively. The fatigue life of the studied alloy was substantially longer than those of the reference alloys A356 and the same Al-7Si-1Cu-0.5Mg base with minor additions of V, Zr, and Ti in the T6 condition. Fractographic analysis after tensile tests revealed that at the lower temperature up to 473 K (200 °C), the cleavage-type brittle fracture for the precipitates and ductile fracture for the matrix were dominant while at higher temperature fully ductile-type fracture with debonding and pull-out of cracked particles was identified. It is believed that the intermetallic precipitates containing Zr, Ti, and V improve the alloy performance at increased temperatures.

  2. High-Temperature Deformation Processing Map Approach for Obtaining the Desired Microstructure in a Multi-component (Ni-Ti-Cu-Fe) Alloy

    NASA Astrophysics Data System (ADS)

    Nayan, Niraj; Singh, Gaurav; Narayana Murty, S. V. S.; Jha, Abhay K.; Pant, Bhanu; George, Koshy M.

    2015-05-01

    An equiatomic NiTiCuFe multi-component alloy with simple body-centered cubic (bcc) and face-centered cubic solid-solution phases in the microstructure was processed by vacuum induction melting furnace under dynamic Ar atmosphere. High-temperature uniaxial compression experiments were conducted on it in the temperature range of 1073 K to 1303 K (800 °C to 1030 °C) and strain rate range of 10-3 to 10-1 s-1. The data generated were analyzed with the aid of the dynamic materials model through which power dissipation efficiency and instability maps were generated so as to identify the governing deformation mechanisms that are operative in different temperature-strain rate regimes with the aid of complementary microstructural analysis of the deformed specimens. Results indicate that the stable domain for the high temperature deformation of the multi-component alloy occurs in the temperature range of 1173 K to 1303 K (900 °C to 1030 °C) and range of 10-3 to 10-1.2 s-1, and the deformation is unstable at T = 1073 K to 1153 K (800 °C to 880 °C) and = 10-3 to 10-1.4 s-1 as well as T = 1223 K to 1293 K (950 °C to 1020 °C) and = 10-1.4 to 10-1 s-1, with adiabatic shear banding, localized plastic flow, or cracking being the unstable mechanisms. A constitutive equation that describes the flow stress of NiTiCuFe multi-component alloy as a function of strain rate and deformation temperature was also determined.

  3. Characterization of Ni19.5Ti50.5Pd25Pt5 High-Temperature Shape Memory Alloy Springs and their Potential Application in Aeronautics

    NASA Technical Reports Server (NTRS)

    Stebner, Aaron; Padula, Santo A.; Noebe, Ronald D.

    2008-01-01

    Shape memory alloys (SMAs) have been used as actuators in many different industries since the discovery of the shape memory effect, but the use of SMAs as actuation devices in aeronautics has been limited due to the temperature constraints of commercially available materials. Consequently, work is being done at NASA's Glenn Research Center to develop new SMAs capable of being used in high temperature environments. One of the more promising high-temperature shape memory alloys (HTSMAs) is Ni19.5Ti50.5Pd25Pt5. Recent work has shown that this material is capable of being used in operating environments of up to 250 C. This material has been shown to have very useful actuation capabilities, demonstrating repeatable strain recoveries up to 2.5% in the presence of an externally applied load. Based on these findings, further work has been initiated to explore potential applications and alternative forms of this alloy, such as springs. Thus, characterization of Ni19.5Ti50.5Pd25Pt5 springs, including their mechanical response and how variations in this response correlate to changes in geometric parameters, are discussed. The effects of loading history, or training, on spring behavior were also investigated. A comparison of the springs with wire actuators is made and the benefits of using one actuator form as opposed to the other discussed. These findings are used to discuss design considerations for a surge-control mechanism that could be used in the centrifugal compressor of a T-700 helicopter engine.

  4. Orientation dependence of high temperature creep strength and internal stress in Ni{sub 3}Al alloy single crystals

    SciTech Connect

    Miura, Seiji; Peng, Z.L.; Mishima, Yoshinao

    1997-12-31

    High temperature creep behavior of a nickel-rich Ni{sub 3}(Al,Ta) with the L1{sub 2} structure is investigated in order to clarify the influence of crystallographic orientation with respect to the stress axis. The single crystals with four different orientations are deformed in compressive creep at temperatures ranging from 1,123 to 1,273 K under a constant load, initial shear stress being 35 to 120 MPa for (111)[{bar 1}01] slip system. The results show a distinct orientation dependence of creep strength, although shape of creep curves, stress exponent and the activation energy seem to be independent of the orientation. It is shown, however, the internal stress, being measured by strain transient dip tests, is found to be orientation dependent and the creep behavior is independent on orientation if it is interpreted using the effective stress instead of the applied shear stress.

  5. A New Ductility Exhaustion Model for High Temperature Low Cycle Fatigue Life Prediction of Turbine Disk Alloys

    NASA Astrophysics Data System (ADS)

    Zhu, Shun-Peng; Huang, Hong-Zhong; Li, Haiqing; Sun, Rui; Zuo, Ming J.

    2011-06-01

    Based on ductility exhaustion theory and the generalized energy-based damage parameter, a new viscosity-based life prediction model is introduced to account for the mean strain/stress effects in the low cycle fatigue regime. The loading waveform parameters and cyclic hardening effects are also incorporated within this model. It is assumed that damage accrues by means of viscous flow and ductility consumption is only related to plastic strain and creep strain under high temperature low cycle fatigue conditions. In the developed model, dynamic viscosity is used to describe the flow behavior. This model provides a better prediction of Superalloy GH4133's fatigue behavior when compared to Goswami's ductility model and the generalized damage parameter. Under non-zero mean strain conditions, moreover, the proposed model provides more accurate predictions of Superalloy GH4133's fatigue behavior than that with zero mean strains.

  6. Cyclic Degradation of Co49Ni21Ga30 High-Temperature Shape Memory Alloy: On the Roles of Dislocation Activity and Chemical Order

    NASA Astrophysics Data System (ADS)

    Krooß, P.; Kadletz, P. M.; Somsen, C.; Gutmann, M. J.; Chumlyakov, Y. I.; Schmahl, W. W.; Maier, H. J.; Niendorf, T.

    2016-03-01

    Conventional shape memory alloys (SMAs), such as binary Ni-Ti, are typically limited to service temperatures below 100 °C. Recent studies on Co-Ni-Ga high-temperature SMAs revealed the potential that these alloys can be used up to temperatures of about 400 °C. Analysis of the cyclic functional properties showed that degradation in these alloys is mainly triggered by intensive dislocation motion. However, data on the cyclic stress-strain response and the mechanisms leading to functional degradation of Co-Ni-Ga above 300 °C were missing in open literature. Current results reveal that above 300 °C diffusion-controlled mechanisms, e.g., precipitation of secondary phases and changes in the chemical degree of order, seem to dictate cyclic instability. Detailed neutron and transmission electron microscopy analyses following superelastic cycling in a temperature range of 200-400 °C were employed to characterize the changes in degradation behavior above 300 °C.

  7. Ductility response of Ni{sub 3}Al-Zr-B base alloys with ternary elements to strain rate and high temperature

    SciTech Connect

    Wang, Y.; Lin, D.; Zhang, Y.

    1997-12-31

    The compressive ductilities of Ni{sub 3}Al-Zr-B base alloys with sole addition of magnesium (0.02--0.06wt.%) and combined addition of magnesium(0.02wt.%) and silicon(0.54{approximately}1.08wt.%) respectively responding to strain rate rising from 10{sup {minus}4}sec{sup {minus}1} have been studied in a high temperature range of 1,073--1,273 K. The results show that the compressive strains at rupture (CSR) of the alloys have been greatly improved by sole addition of magnesium and the alloys with combined addition of magnesium and silicon reveal even higher CSR values, furthermore, at temperatures of 1,073 K and 1,273 K, the strain rate dependence of CSR reveals to be anomalous, i.e., the CSR value increases as the strain rate rises, and then declines until it surpasses the peak value, which is corresponded to the strain rate of 10{sup {minus}3}sec{sup {minus}1} and 10{sup {minus}2}sec{sup {minus}1} respectively. The beneficial effect of magnesium and silicon exists in their competence of reducing strain rate sensitivity exponent values. The mechanisms of the anomalous ductilizing behavior in the Ni{sub 3}Al as affected by ternary elements are discussed.

  8. The Effect of Laves Phase (Fe,Al)2Zr on the High-Temperature Strength of Carbon-Alloyed Fe3Al Aluminide

    NASA Astrophysics Data System (ADS)

    Kratochvíl, Petr; Vodičková, Věra; Král, Robert; Švec, Martin

    2016-03-01

    The effects of carbon on the phase structure and on the yield stress σ 0.2 in the temperature range from 873 K to 1073 K (600 °C to 800 °C) of the Fe3Al type aluminides alloyed by Zr are analyzed. Four alloys with Zr and C in ranging from 1.0 to 5.0 at. pct of additives were used. The appearing of either Laves phase (Fe,Al)2Zr and/or carbides depend on the difference in concentrations, c Zr - c C. This parameter ( c Zr - c C) has been selected instead of the concentration ratio c Zr/ c C used in previous works since it exhibits a significantly better correlation with the Laves phase concentration which influences the high-temperature yield stress, σ 0.2, of the tested alloys. The presence of Laves phase or eutectic (matrix—Laves phase), respectively, enhances the value of the yield stress σ 0.2. The amount of Laves phase is decreased by the presence of C due to the affinity of carbon to Zr.

  9. High temperature barrier coatings for refractory metals

    NASA Technical Reports Server (NTRS)

    Malone, G. A.; Walech, T.

    1995-01-01

    Improvements in high temperature oxidation resistant metal coating technology will allow NASA and commercial entities to develop competitive civil space transport and communication systems. The success of investigations completed in this program will have a positive impact on broadening the technology base for high temperature materials. The work reported herein describes processes and procedures for successfully depositing coherent oxidation barrier coatings on refractory metals to prevent degradation under very severe operating environments. Application of the new technology developed is now being utilized in numerous Phase 3 applications through several prominent aerospace firms. Major achievements have included: (1) development of means to deposit thick platinum and rhodium coatings with lower stress and fewer microcracks than could be previously achieved; (2) development of processes to deposit thick adherent coatings of platinum group metals on refractory substrates that remain bonded through high temperature excursions and without need for intermediate coatings (bonding processes unique to specific refractory metals and alloys have been defined; (3) demonstration that useful alloys of refractory and platinum coatings can be made through thermal diffusion means; (4) demonstration that selected barrier coatings on refractory substrates can withstand severe oxidizing environments in the range of 1260 deg and 1760 deg C for long time periods essential to the life requirements of the hardware; and (5) successful application of the processes and procedures to prototype hardware. The results of these studies have been instrumental in improved thermal oxidation barrier coatings for the NASP propulsion system. Other Phase 3 applications currently being exploited include small uncooled thrusters for spacecraft and microsatellite maneuvering systems.

  10. PROCESSING, MICROSTRUCTURE AND CREEP BEHAVIOR OF Mo-Si-B-BASED INTERMETALLIC ALLOYS FOR VERY HIGH TEMPERATURE STRUCTURAL APPLICATIONS

    SciTech Connect

    Vijay K. Vasudevan

    2005-12-21

    This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. During this year, the compressive creep behavior of a Mo-3Si-1B (in wt.%) alloy at 1100 and 1200 C were studied and related to the deformation mechanisms through electron microscopy observations of microstructural changes and deformation structures. The microstructure of this alloy was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. Results of compressive creep tests at 1200 and 1100 C showed that the creep rates were quite high at stress levels between 250 and 500 MPa, Two minima in the creep strain rate versus strain data were noted, one at small strain values and the second at much larger strains. A stress exponent of 4.26 was obtained upon plotting the strain rate corresponding to the first minima versus stress, which suggests that dislocation climb and glide dominate the creep process in the early stages. On the other hand, the large strain, minimum creep rate versus stress data gave a stress exponent of {approx}1.18, which indicates diffusional mechanisms and recrystallization dominate the later stages of the creep process. At 1100 C, a stress exponent of 2.26 was obtained, which suggests that both diffusional and dislocation mechanisms contribute to the creep strain. Based on the minimum creep rate data at 1100 C and 1200 C, the activation energy for creep was determined to be 525 kJ/mole, which is somewhat higher than that reported for self diffusion in {alpha}-Mo. Microstructural observations of post-crept samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. In addition, TEM observations revealed the presence of recrystallized grains and sub-grain boundaries composed of dislocation arrays

  11. Effect of magnesium on the lead induced corrosion and SCC of alloy 800 in neutral crevice solution at high temperature

    NASA Astrophysics Data System (ADS)

    Palani, A.; Lu, B. T.; Tian, L. P.; Luo, J. L.; Lu, Y. C.

    2010-01-01

    Dissolved magnesium species in the feed water reduce the incidence of lead-induced stress corrosion cracking (PbSCC) of Alloy 800. The passivity of material was improved by replacing a part of chlorides in the lead-contaminated chemistry with magnesium chloride, as indicated by: (1) a higher pitting potential; (2) lower passive current densities; (3) a film structure with less defects and more spinel oxides. According to the constant extension rate tensile (CERT) tests conducted in the neutral crevice solutions at 300 °C, lead contamination would reduce the ultimate tensile strength (UTS) and elongation of material. The CERT test results were in agreement with the fracture morphology observations. Magnesium addition significantly reduced the detrimental effect of lead contamination.

  12. High-temperature, low-cycle fatigue of advanced copper-base alloys for rocket nozzles. Part 1: Narloy Z

    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 Narloy Z, a centrifugally cast, copper-base alloy. Tensile tests were performed at room temperature in air and in argon at 482, 538 and 593 C using an axial strain rate of .002/sec to the -1 power. In addition tensile tests were performed at 538 C in an evaluation of tensile properties at strain rates of .004 and .01/sec to the -1 power. Ultimate and yield strength values of about 315 and 200 MN/sq m respectively were recorded at room temperature and these decreased to about 120 and 105 respectively as the temperature was increased to 593 C. Reduction in area values were recorded in the range from 40 to 50% with some indication of a minimum ductility point at 538 C.

  13. High temperature structural silicides

    SciTech Connect

    Petrovic, J.J.

    1997-03-01

    Structural silicides have important high temperature applications in oxidizing and aggressive environments. Most prominent are MoSi{sub 2}-based materials, which are borderline ceramic-intermetallic compounds. MoSi{sub 2} single crystals exhibit macroscopic compressive ductility at temperatures below room temperature in some orientations. Polycrystalline MoSi{sub 2} possesses elevated temperature creep behavior which is highly sensitive to grain size. MoSi{sub 2}-Si{sub 3}N{sub 4} composites show an important combination of oxidation resistance, creep resistance, and low temperature fracture toughness. Current potential applications of MoSi{sub 2}-based materials include furnace heating elements, molten metal lances, industrial gas burners, aerospace turbine engine components, diesel engine glow plugs, and materials for glass processing.

  14. High temperature strain gages

    NASA Technical Reports Server (NTRS)

    Gregory, Otto J. (Inventor); You, Tao (Inventor)

    2011-01-01

    A ceramic strain gage based on reactively sputtered indium-tin-oxide (ITO) thin films is used to monitor the structural integrity of components employed in aerospace propulsion systems operating at temperatures in excess of 1500.degree. C. A scanning electron microscopy (SEM) of the thick ITO sensors reveals a partially sintered microstructure comprising a contiguous network of submicron ITO particles with well defined necks and isolated nanoporosity. Densification of the ITO particles was retarded during high temperature exposure with nitrogen thus stabilizing the nanoporosity. ITO strain sensors were prepared by reactive sputtering in various nitrogen/oxygen/argon partial pressures to incorporate more nitrogen into the films. Under these conditions, sintering and densification of the ITO particles containing these nitrogen rich grain boundaries was retarded and a contiguous network of nano-sized ITO particles was established.

  15. High-Resolution Characterization of Intergranular Attack and Stress Corrosion Cracking of Alloy 600 in High-Temperature Primary Water

    SciTech Connect

    Thomas, Larry E.; Bruemmer, Stephen M.

    2000-06-01

    Intergranular (IG) attack regions and stress-corrosion cracks in alloy 600 U-bend samples tested in 330C, pressurized-water-reactor water have been characterized by analytical transmission electron microscopy (ATEM). Observations of cross-sectional samples revealed short oxidized zones preceding crack tips and narrow (10-nm wide), deeply penetrated, oxidized zones along grain boundaries exposed along open cracks. High-resolution TEM imaging and fine-probe analysis were used to determine the local chemistries and structures in these corrosion-affected zones. Matrix areas surrounding the crack tips appeared highly strained, whereas the IG penetrations generally did not. The predominant oxide structure found along crack walls and just ahead of crack tips was NiO with metal-atom ratios similar to the alloy. The attacked grain boundaries off open cracks contained similar fine-grained NiO-structure oxide together with local areas of Cr-rich oxide and Ni-rich metal. In contrast, Cr-rich oxide identified as Cr2O3 predominated at the leading edges of the IG attack. Stereoscopic imaging of these tip structures revealed nm-scale porosity and tunnels within the oxide and pores along the grain-boundary plane ahead of the oxide. The general interpretation of these results is that IG attack and cracking follows local dissolution or oxidation and the formation of pores at grain boundaries. This degradation occurs at the nanometer scale and therefore requires high-resolution ATEM methods to reveal detailed characteristics. Experimental support for several possible IG degradation mechanisms is considered.

  16. Constitutive Modeling of High-Temperature Flow Behavior of an Nb Micro-alloyed Hot Stamping Steel

    NASA Astrophysics Data System (ADS)

    Zhang, Shiqi; Feng, Ding; Huang, Yunhua; Wei, Shizhong; Mohrbacher, Hardy; Zhang, Yue

    2016-03-01

    The thermal deformation behavior and constitutive models of an Nb micro-alloyed 22MnB5 steel were investigated by conducting isothermal uniaxial tensile tests at the temperature range of 873-1223 K with strain rates of 0.1-10 s-1. The results indicated that the investigated steel showed typical work hardening and dynamic recovery behavior during hot deformation, and the flow stress decreased with a decrease in strain rate and/or an increase in temperature. On the basis of the experimental data, the modified Johnson-Cook (modified JC), modified Norton-Hoff (modified NH), and Arrhenius-type (AT) constitutive models were established for the subject steel. However, the flow stress values predicted by these three models revealed some remarkable deviations from the experimental values for certain experimental conditions. Therefore, a new combined modified Norton-Hoff and Arrhenius-type constitutive model (combined modified NH-AT model), which accurately reflected both the work hardening and dynamic recovery behavior of the subject steel, was developed by introducing the modified parameter k ɛ. Furthermore, the accuracy of these constitutive models was assessed by the correlation coefficient, the average absolute relative error, and the root mean square error, which indicated that the flow stress values computed by the combined modified NH-AT model were highly consistent with the experimental values (R = 0.998, AARE = 1.63%, RMSE = 3.85 MPa). The result confirmed that the combined modified NH-AT model was suitable for the studied Nb micro-alloyed hot stamping steel. Additionally, the practicability of the new model was also verified using finite element simulations in ANSYS/LS-DYNA, and the results confirmed that the new model was practical and highly accurate.

  17. Comparison of high temperature, high frequency core loss and dynamic B-H loops of two 50 Ni-Fe crystalline alloys and an iron-based amorphous alloy

    SciTech Connect

    Wieserman, W.R.; Schwarze, G.E.; Niedra, J.M.

    1994-09-01

    The availability of experimental data that characterizes the performance of soft magnetic materials for the combined conditions of high temperature and high frequency is almost non-existent. An experimental investigation was conducted over the temperature range of 23 to 300 C and frequency range of 1 to 50 kHz to determine the effects of temperature and frequency on the core loss and dynamic B-H loops of three different soft magnetic materials; an oriented-grain 50Ni-50Fe alloy, a nonoriented-grain 50Ni-50Fe alloy, and an iron-based amorphous material (Metglas 2605SC). A comparison of these materials show that the nonoriented-grain 50Ni-50Fe alloy tends to have either the lowest or next lowest core loss for all temperatures and frequencies investigated.

  18. Comparison of high temperature, high frequency core loss and dynamic B-H loops of two 50 Ni-Fe crystalline alloys and an iron-based amorphous alloy

    NASA Technical Reports Server (NTRS)

    Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

    1991-01-01

    The availability of experimental data that characterizes the performance of soft magnetic materials for the combined conditions of high temperature and high frequency is almost nonexistent. An experimental investigation was conducted over the temperature range of 23 to 300 C and frequency range of 1 to 50 kHz to determine the effects of temperature and frequency on the core loss and dynamic B-H loops of three different soft magnetic materials; and oriented grain 50Ni-50Fe alloy, a nonoriented grain 50Ni-Fe alloy, and an iron based amorphous material (Metglas 2605SC). A comparison of these materials shows that the nonoriented grain 50Ni-50Fe alloy tends to have either the lowest or next lowest core loss for all temperatures and frequencies investigated.

  19. Comparison of high temperature, high frequency core loss and dynamic B-H loops of two 50 Ni-Fe crystalline alloys and an iron-based amorphous alloy

    NASA Technical Reports Server (NTRS)

    Wieserman, W. R.; Schwarze, G. E.; Niedra, J. M.

    1991-01-01

    The availability of experimental data that characterize the performance of soft magnetic materials for the combined conditions of high temperature and high frequency is almost nonexistent. An experimental investigation was conducted over the temperature range of 23 to 300 C and frequency range of 1 to 50 kHz to determine the effects of temperature and frequency on the core loss and dynamic B-H loops of three different soft magnetic materials: an oriented-grain 50Ni-50Fe alloy, a nonoriented-grain 50Ni-50Fe alloy, and an iron-based amorphous material (Metglas 2605SC). A comparison of these materials shows that the nonoriented-grain 50Ni-50Fe alloy tends to have either the lowest or the next lowest core loss for all temperatures and frequencies investigated.

  20. Influence of Al2O3/YSZ micro-laminated coatings on high temperature oxidation and spallation resistance of MCrAlY alloys

    NASA Astrophysics Data System (ADS)

    Yao, Junqi; He, Yedong; Wang, Deren

    2013-03-01

    Al2O3/YSZ micro-laminated coatings with different layers were prepared on MCrAlY alloys by magnetron sputtering and characterized by high-resolution field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). Results indicated that the laminated structures of Al2O3 and YSZ layers were observed with compact microstructure and the thickness at sub-micron level each layer. High-temperature cyclic oxidation test at 1000°C in air was performed to investigate the oxidation and spallation resistance of the coatings on MCrAlY substrates. Result shows that the coatings exhibit more excellent oxidation and spallation resistance with the increase of the layers, which can be attributed to the increase of stress tolerance and fracture toughness in the laminated coatings by the thinner layers and crack deflection toughening.