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Sample records for v-cr-ti type alloys

  1. Welding development for V-Cr-Ti alloys

    SciTech Connect

    Goodwin, G.M.; King, J.F.

    1994-09-01

    Welds have been produced and characterized using the gas-tungsten arc (GTA) and electron beam (EB) welding processes. Thin sheet (0.75 mm) welds were made with three levels of interstitial contamination, and hardness and tensile properties were found to be strongly affected by oxygen pickup. Thick-section (6 mm) welds have been produced using both processes, and no embrittlement is experienced when high purity atmosphere is maintained. Metallographic examination shows a narrow, but coarse grained, heat affected zone for the GTA welds. Transition joint welding development between vanadium alloy and stainless steel has shown encouraging results.

  2. Performance of V-Cr-Ti alloys in a hydrogen environment

    SciTech Connect

    Natesan, K.; Soppet, W. K.

    2000-04-03

    A systematic study is underway at Argonne National Laboratory to evaluate the mechanical properties of several V-Cr-Ti alloys after exposure to environments containing hydrogen at various partial pressures. The goal is to correlate the chemistry of the exposure environment with hydrogen uptake by the samples and with the resulting influence on microstructures and tensile properties of the alloys. Other variables examined are specimen cooling rate and synergistic effects, if any, of oxygen and hydrogen on tensile behavior of the alloys. Experiments were conducted to evaluate the effect of pH{sub 2} in the range of 3 x 10{sup {minus}6} and 1 torr on tensile properties of two V-Cr-Ti alloys. Up to pH{sub 2} of 0.05 torr, negligible effect of H was observed on either maximum engineering stress or uniform and total elongation. However, uniform and total elongation decreased substantially when the alloys were exposed at 500 C to 1.0 torr of H{sub 2} pressure. Preliminary data from sequential exposures of the materials to low-pO{sub 2} and several low-pH{sub 2} environments did not reveal adverse effects on the maximum engineering stress or on uniform and total elongation when the alloy contained {approx} 2,000 wppm O and 16 wppm H. Furthermore, tests in H{sub 2}-exposed specimens, initially annealed at various temperatures, showed that grain-size variation by a factor of {approx} 2 had little or no effect on tensile properties. Also, specimen cooling rate had a small effect, if any, on the tensile properties of the alloy.

  3. Subtask 12B1: Welding development for V-Cr-Ti alloys

    SciTech Connect

    King, J.F.; Goodwin, G.M.; Grossbeck, M.L.; Alexander, D.J.

    1995-03-01

    Development of the metallurgical and technological basis for the welding of thick sections of V-Cr-Ti alloys. The weldability and weldment properties of the V-5Cr-5Ti alloy have been evaluated. Results for the Sigmajig test of the vanadium alloy were similar to the cracking resistance of stainless steels, and indicates hot-cracking is unlikely to be a problem. Subsize Charpy test results for GTA weld metal in the as-welded condition have shown a significant reduction in toughness compared to the base metal. The weld metal toughness properties were restored to approximately that of the base metal after exposure to a PWHT 950{degrees}C. The subsize Charpy toughness results for the EB weld metal from this same heat of vanadium alloy has shown significant improvement in properties compared to the GTA weld metal and the base metal. Further testing and analysis will be conducted to more fully characterize the properties of weld metal for each welding process and develop a basic understanding of the cause of the toughness decrease in the GTA welds. 5 figs., 1 tab.

  4. Impurity effects on gas tungsten arc welds in V?Cr?Ti alloys

    NASA Astrophysics Data System (ADS)

    Grossbeck, M. L.; King, J. F.; Hoelzer, D. T.

    2000-12-01

    Plates 6.4 mm thick of V-Cr-Ti alloys, mostly V-4Cr-4Ti, were welded in a glove box argon atmosphere. A hot titanium getter led to excessive hydrogen concentrations. A cold zirconium-aluminum getter was used to reduce both oxygen and hydrogen. It was observed that a major source of hydrogen was dissociation of water vapor by the electric arc of the welding torch. Careful monitoring of atmospheric impurities and successive pumping and backfilling cycles permitted welds of higher quality than previously achieved. Welds were evaluated primarily by the Charpy impact test. A ductile-to-brittle transition temperature (DBTT) of -28°C was achieved in V-4Cr-4Ti. Previous GTA welds in the same material seldom had a DBTT below room temperature. Electron beam welding can achieve a DBTT of below -90°C in the V-4Cr-4Ti alloy, indicating a lower limit to the DBTT by impurity control.

  5. Feasibility of correlating V-Cr-Ti alloy weld strength with weld chemistry. CRADA final report

    SciTech Connect

    Grossbeck, M.L.; Odom, R.W.

    1998-06-01

    The mechanical properties of refractory metals such as vanadium are determined to a large extent by the interstitial impurities in the alloy. In the case of welding, interstitial impurities are introduced in the welding process from the atmosphere and by dissolution of existing precipitates in the alloy itself. Because of the necessity of having an ultra-pure atmosphere, a vacuum chamber or a glove box is necessary. In the V-Cr-Ti system, the titanium serves as a getter to control the concentration of oxygen and nitrogen in solid solution in the alloy. In this project the secondary ion mass spectrometry (SIMS) technique was used to detect, measure, and map the spacial distribution of impurity elements in welds in the alloy V-4Cr-4Ti. An attempt was then made to correlate the concentrations and distributions of the impurities with mechanical properties of the welds. Mechanical integrity of the welds was determined by Charpy V-notch testing. Welds were prepared by the gas-tungsten-arc (GTA) method. Charpy testing established a correlation between weld impurity concentration and the ductile to brittle transition temperature (DBTT). Higher concentrations of oxygen resulted in a higher DBTT. An exception was noted in the case of a low-oxygen weld which had a high hydrogen concentration resulting in a brittle weld. The concentrations and distributions of the impurities determined by SIMS could not be correlated with the mechanical properties of the welds. This research supports efforts to develop fusion reactor first wall and blanket structural materials.

  6. Effects of oxygen and hydrogen at low pressure on the mechanical properties of V?Cr?Ti alloys*1

    NASA Astrophysics Data System (ADS)

    DiStefano, J. R.; Pint, B. A.; DeVan, J. H.; Rhrig, H. D.; Chitwood, L. D.

    2000-12-01

    Exposure of V-Cr-Ti alloys to low oxygen partial pressures at high temperature results in oxygen absorption and internal oxidation. Characterization of a V-4Cr-4Ti alloy after oxidation at 500C revealed a microstructure with ultrafine oxide precipitates in the matrix and along grain boundaries. Heat treatment at 950C following oxidation resulted in large TiO x precipitates in the matrix and grain boundaries. Tensile ductility was reduced by exposure to low-pressure oxygen under the temperature and pressure conditions. However, heat treatment at 950C following oxidation was generally effective in recovering ductility irrespective of initial annealing treatment or grain size. Without increases in oxygen, >500 wppm hydrogen was required to cause significant decreases in tensile elongation. When oxygen was added either during or prior to hydrogen exposure, significant embrittlement occurred with 100 wppm hydrogen. Because of this synergism with hydrogen, oxygen pick-up remains a major concern for V-Cr-Ti alloys in fusion reactor applications.

  7. Fatigue and crack growth behavior of V?Cr?Ti alloys

    NASA Astrophysics Data System (ADS)

    Gieseke, B. G.; Stevens, C. O.; Grossbeck, M. L.

    1996-10-01

    The results of in-vacuum low cycle fatigue tests are presented for unirradiated V?5Cr?5Ti tested at 25, 250, and 400C. A pronounced environmental degradation of the fatigue properties is observed in this alloy at 25C. Fatigue life was reduced by as much as 84% when testing was completed in a rough vacuum. Cyclic stress range data and SEM observations suggest that this reduction is due to a combination of increases in rates of crack initiation and subsequent growth. In high vacuum, the fatigue results also show a trend of increasing cyclic life with increasing temperature between 25 and 400C. At 250C, life averages 1.7 times that at 25C, and at 400C, life averages 3.2 times that at 25C. A comparison of low cycle fatigue results for V?5Cr?5Ti was made to 20% cold-worked 316 stainless steel and several vanadium-base alloys. The results suggest that V?5Cr?5Ti has better resistance to fatigue than 316-SS in the temperature range of 25 to 400C. At 400C, the data also show that V?5Cr?5Ti out performs Vanstar alloys 7 and 8 over the entire range of strains investigated. Furthermore, the fatigue properties of the V?5Cr?5Ti alloy compare favorably to V?15Cr?5Ti (at 25C) and Vanstar 9 (at 400C) at strains greater than 1%. At lower strains, the lower fatigue resistance of V?5Cr?5Ti is attributed to the higher strengths of the V?15Cr?5Ti and Vanstar 9 alloys.

  8. Hardness recovery of 85% cold-worked V-Ti and V-Cr-Ti alloys upon annealing at 180{degrees}C to 1200{degrees}C

    SciTech Connect

    Loomis, B.A.; Nowicki, L.J.; Smith, D.L.

    1995-04-01

    The objective of this research is to determine the effect of heat treatment of cold-worked V-Ti and V-Cr-Ti alloys on their resulting microstructures and to correlate the results with the physical and mechanical properties of these alloys. Annealing of 85% cold-worked unalloyed V and V-(1-18)Ti alloys for 1 hr at 180 to 1200{degree}C results in hardness maxima at 180-250{degree}C, 420-600{degree}C, and 1050-1200{degree}C and in hardness minima at 280-360{degree}C and, depending on Ti concentration in the alloy, at 840-1050{degree}C. Annealing of 85% cold-worked V-(4-15)Cr-(3-6)Ti alloys for 1 hr at 180{degree}C to 1200{degree}C results in harness maxima at 180-250{degree}C, 420-800{degree}C, and 1050-1200{degree}C, and in hardness minima at 280-360{degree}C and 920-1050{degree}C.

  9. Revision of the tensile database for V-Ti and V-Cr-Ti alloys tested at ANL.

    SciTech Connect

    Billone, M. C.

    1998-01-13

    The published database for the tensile properties of unirradiated and irradiated vanadium-based alloys tested at Argonne National Laboratory (ANL) has been reviewed. The alloys tested are in the ranges of V-(0-18)wt.%Ti and V-(4-15)wt.%Cr-(3-15)wt.%Ti. A consistent methodology, based on ASTM terminology and standards, has been used to re-analyze the unpublished load vs. displacement curves for 162 unirradiated samples and 91 irradiated samples to determine revised values for yield strength (YS), ultimate tensile strength (UTS), uniform elongation (UE) and total elongation (TE). The revised data set contains lower values for UE ({minus}5{+-}2% strain) and TE ({minus}4{+-}2% strain) than previously reported. Revised values for YS and UTS are consistent with the previously-published values in that they are within the scatter usually associated with these properties.

  10. Effect of Low Temperature Irradiation in ATR On The Mechanical Properties of Ternary V-Cr-Ti Alloys

    SciTech Connect

    Hamilton, Margaret L.; Toloczko, Mychailo B.; Oliver, Brian M.; Garner, Francis A.

    2000-09-01

    Tensile tests and shear punch teats were performed on a variety of vanadium alloys that were irradiated in the Advanced Test Reactor (ATR) at temperatures between 200 and 300 degrees C to doses between 3 and 5 dpa. Tests were performed at room temperature and the irradiation temperature. The results of both the tensile tests and the shear punch tests show that following low temperature irradiation, the yield strength increased by a factor of 3-4 while the ultimate strength increased by a factor of approximately 3.

  11. CaO insulator coatings and self-healing of defects on V-Cr-Ti alloys in liquid lithium system

    SciTech Connect

    Park, J.H.; Kassner, T.F.

    1995-09-01

    Electrically insulating and corrosion-resistant coatings are required at the liquid metal/structural interface in fusion first-wall/blanket applications. Electrical resistance of CaO coatings that were produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li containing 0.5-85 wt.% dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. The solute element, Ca in liquid Li, reacted with the alloy substrate at 400-420{degrees}C to produce a CaO coating. Resistance of the coating layer measured in-situ in liquid Li was {approx}10{sup 6} {Omega} at 400{degrees}C. Thermal cycling between 300 and 700{degrees}C changed the coating layer resistance, which followed insulator behavior. These results suggest that thin homogeneous coatings can be produced on variously shaped surfaces by controlling the exposure time, temperature, and composition of the liquid metal. The technique can be applied to various shapes (e.g., inside/outside of tubes, complex geometrical shapes) because the coating is formed by liquid-phase reaction. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at {>=}360{degrees}C.

  12. Research and development on vanadium alloys for fusion applications

    SciTech Connect

    Zinkle, S.J.; Rowcliffe, A.F.; Matsui, H.; Abe, K.; Smith, D.L.; Osch, E. van; Kazakov, V.A.

    1998-03-01

    The current status of research and development on unirradiated and irradiated V-Cr-Ti alloys intended for fusion reactor structural applications is reviewed, with particular emphasis on the flow and fracture behavior of neutron-irradiated vanadium alloys. Recent progress on fabrication, joining, oxidation behavior, and the development of insulator coatings is also summarized. Fabrication of large (>500 kg) heats of V-4Cr-4Ti with properties similar to previous small laboratory heats has now been demonstrated. Impressive advances in the joining of thick sections of vanadium alloys using GTA and electron beam welds have been achieved in the past two years, although further improvements are still needed.

  13. Gas tungsten arc welding of vanadium alloys with impurity control

    NASA Astrophysics Data System (ADS)

    Grossbeck, M. L.; King, J. F.; Nagasaka, T.; David, S. A.

    2002-12-01

    Gas tungsten arc welding in vanadium alloys is controlled by interstitial impurities. Techniques have been developed to weld V-4Cr-4Ti in a high-purity argon atmosphere resulting in a DBTT of -20 °C. The atmosphere was controlled by a Zr-Al getter which is activated at high temperature to obtain a clean surface then cooled and allowed to absorb hydrogen and oxygen impurities. Through the use of low-oxygen base metal and high-purity weld filler wire, a DBTT of -145 °C was obtained. Experiments using electron beam welding have shown that grain size also has an important effect on weld ductility. Introduction of nitrogen and yttrium has been used to study their effect on grain size. Using a combination of atmosphere control, alloy purity control, and grain size control, it is anticipated that V-Cr-Ti alloys will be weldable in field conditions.

  14. Reference vanadium alloy V-4Cr-4Ti for fusion application

    SciTech Connect

    Smith, D.L.; Chung, H.M.; Loomis, B.A.; Tsai, H.C.

    1995-09-01

    Vanadium alloys exhibit important advantages as a candidate structural material for fusion first-wall/blanket applications. These advantages include high temperature and high wall load capability, favorable safety and environmental features, resistance to irradiation damage, and alloys of interest are readily fabricable. A substantial data base has been developed on laboratory-scale heats of V-Ti, V-Cr-Ti and V-Ti-Si alloys before and after irradiation. Investigations in recent years have focused primarily on compositions of V-(0--15)Cr-(0--20)Ti (0--1)Si. Results from these investigations have provided a basis for identifying a V-4Cr-4Ti alloy as the US reference vanadium alloy for further development. Major results obtained on one production-scale heat and three laboratory heats with compositions of V-(4--5)Cr-(4--5)Ti are presented in this paper. Properties measured were input properties, tensile properties, creep, and radiation effects.

  15. Effects of oxygen, hydrogen and neutron irradiation on the mechanical properties of several vanadium alloys

    NASA Astrophysics Data System (ADS)

    Chen, Jiming; Qiu, Shaoyu; Yang, Lin; Xu, Zengyu; Deng, Ying; Xu, Ying

    2002-04-01

    Several V-Cr-Ti-Al-Si alloys were studied or reviewed of their mechanical properties after their exposure to oxygen, hydrogen and neutron irradiation environments. The results showed that the oxidation kinetic of V4Cr4Ti alloy exhibited parabolic behavior in a flowing argon gas with low partial pressure oxygen over the temperatures from 450 to 600 C. Most of the alloys showed ductility losses with the increasing oxygen concentration with an exception of V4Ti3Al. Strong sensitivity to hydrogen embrittlement was found for the alloys with the combination of high oxygen concentration and high mechanical strength. It was found that the effect of hydrogen and neutron irradiation on the uniform deformation capability caused by their hardening are equivalent with that of the strain hardening. Fine grain was recommended for the alloys to improve their properties against hydrogen embrittlement and neutron irradiation induced ductility loss.

  16. Magnetoelastic Properties, of Hitperm-Type Alloys, from Torque Moment

    NASA Astrophysics Data System (ADS)

    Salach, J.; Bie?kowski, A.; Szewczyk, R.

    2008-01-01

    The following paper presents the results of the investigation on the influence of the torque on the magnetic characteristics of the Hitperm-type Fe41.5 Co41.5Cu1Nb3B13 alloy, in as-quenched and nanocrystalline state. The methodology of application of the torque to the ring-shaped core is also described. This methodology gives a possibility of achieving uniform shearing stresses in the core. The results indicate that shearing stress sensitivity of Hitperm-type alloys depends on the annealing and nanocrystallization process. This effect should be considered during the development of magnetoelastic torque sensors.

  17. Electrode characteristics of nanostructured Mg{sub 2}Ni-type alloys prepared by mechanical alloying

    SciTech Connect

    Woo, J.H.; Lee, K.S.

    1999-03-01

    A mechanical alloying process is introduced to produce nanocrystalline Mg{sub 2}Ni-type metal hydride. The mechanical alloying process has recently emerged as a novel technique for producing alloy powders whose structures are nanocrystalline. Mg{sub 2}Ni alloys were prepared using planetary ball mill starting from mixtures of elemental powders. Nanocrystalline Mg{sub 2}Ni-type alloys were obtained by both the long-term ballmilling (mechanical alloying) and heat-treatment of the ballmilled powders. In comparison with the polycrystalline material, nanocrystalline Mg{sub 2}Ni showed a lower temperature for hydrogenation and a higher discharge capacity at 30 C. The partial substitution of Cu for Ni increased hydrogen absorption and desorption at 200 C and greatly improved the discharge capacity of the nanostructured Mg{sub 2}Ni electrode at 30 C. The discharge capacity of the 120 h milled Mg{sub 2}(Ni{sub 0.9}Cu{sub 0.1}) electrode was 350 mAh/g.

  18. Electrochemical behavior of Alloy 22 and friction type rock bolt

    NASA Astrophysics Data System (ADS)

    Rahman, Md Sazzadur

    Alloy 22 (Ni-22Cr-13Mo-3Fe-3W) is a candidate alloy for the outer shell of spent nuclear materials storage containers in the Yucca Mountain High Level Nuclear Waste Repository because of its excellent corrosion resistance. The nuclear waste container is cylindrical in shape and the end caps are welded. Typically, Alloy 22 retains the high temperature single phase cubic structure near room temperature, but topologically close packed (TCP) phases such as mu, P, sigma etc. and Cr rich carbides can form during thermal aging and welding. Rock bolts that are used for reinforcing subsurface tunnels are generally made of carbon or low alloy steels; these are being used in the nuclear repository tunnel. The corrosion behavior of these rock bolts have not been systematically evaluated under the environmental conditions of the repository. The ground waters at the Yucca Mountain (YM) repository permeate through the pores of the rock mass, and have propensity to corrode the rock bolts and waste package container. The environmental (aerated and deaerated) conditions influence the rate of corrosion in these material; these have not been systematically evaluated yet under the repository environment. In this study, the corrosion behavior of Alloy 22 and a friction type rock bolts was investigated as a function of temperature and concentration in complex multi-ionic electrolytes. Simulated electrolyte of YM ground water found in the repository environment was made in different concentrations (1X, 10X, and 100X). The interaction of simulated electrolytes in aerated and deaerated condition with Alloy 22 and low alloy steel of friction type rock bolt (split tapered cylinder type commercial design) has been investigated. Polarization resistance method was used to measure the corrosion rates. We found that the corrosion rate of Alloy 22 was higher in the deaerated electrolyte as compared to the aerated. The presence of oxygen in the electrolyte during aeration is conducive to formation of passive films that inhibits the corrosion process. The temperature dependency of the corrosion rate was affected by aeration and deaeration of the electrolytes. Another study related to corrosion behavior of weld Alloy 22 was undertaken to understand electrochemical behavior of welded structures. Corrosion studies were carried out in more aggressive electrolyte (0.1M HCl at 66C) after solution annealing at 1121C for 1 hr. In the as-welded structure a dendritic microstructure was observed in the weld region. However, after solution annealing these dendrites are not observed; suggesting homogenization of the grains. Three different specimens were made out from a welded Alloy 22 plates with large welded surface; weld interface, half weld and base metal away from the weld and heat affected zone, and corrosion rates of all these samples were measured. The results showed that the corrosion resistance of the solution annealed was higher in all three specimens than those of as-welded specimens. Corrosion rates of friction type set rock bolts (split set) were measured at 25C, 45C, 65C and 90C using 1X, 10X and 100X concentration of electrolyte both in aerated and deaerated conditions. The corrosion rates of rock bolts in 1X and 10X electrolyte showed ranged from 30 to 200mum/yr for deaerated and 150 to 1600 mum/yr for aerated. In summary, we have investigated the electrochemical behavior of the Alloy 22 and steels that have significance to the YM nuclear repository. The effects of temperature, type of electrolyte, condition of the alloys on the corrosion rates are reported.

  19. Development and testing ov danadium alloys for fusion applications

    SciTech Connect

    Chung, H.M.; Loomis, B.A.; Smith, D.L.

    1996-10-01

    V base alloys have advantages for fusion reactor first-wall and blanket structure. To screen candidate alloys and optimize a V-base alloy, physical and mechanical properties of V-Ti, V-Cr-Ti, and V-Ti- Si alloys were studied before and after irradiation in Li environment in fast fission reactors. V-4Cr-4Ti containing 500-1000 wppM Si and <1000 wppM O+N+C was investigated as the most promising alloy, and more testing is being done. Major results of the work are presented in this paper. The reference V-4Cr-4Ti had the most attractive combination of the mechanical and physical properties that are prerequisite for first-wall and blanket structures: good thermal creep, good tensile strength/ductility, high impact energy, excellent resistance to swelling, and very low ductile-brittle transition temperature before and after irradiation. The alloy was highly resistant to irradiation-induced embrittlement in Li at 420-600 C, and the effects of dynamically charged He on swelling and mechanical properties were insignificant. However, several important issues remain unresolved: welding, low-temperature irradiation, He effect at high dose and high He concentration, irradiation creep, and irradiation performance in air or He. Initial results of investigation of some of these issues are also given.

  20. The effect of cobalt content in U-700 type alloys on degradation of aluminide coatings

    NASA Technical Reports Server (NTRS)

    Zaplatynsky, I.

    1985-01-01

    The influence of cobalt content in U-700 type alloys on the behavior of aluminide coatings is studied in burner rig cyclic oxidation tests at 1100C. It is determined that aluminide coatings on alloys with higher cobalt offer better oxidation protection than the same coatings on alloys containing less cobalt.

  1. The fabrication of vanadium base alloys as candidate fusion reactor materials*1

    NASA Astrophysics Data System (ADS)

    Thresh, H. R.; Hins, A. G.; Smith, D. L.

    1988-07-01

    An alloy fabrication program has been initiated at Argonne National Laboratory to provide suitable materials for the evaluation of vanadium base alloys in the United States Fusion Power Program. The initial phase of the work has focused on the V?Cr?Ti ternary system. Emphasis has been placed on minimizing impurity levels in the alloy feedstock constituents and on controlling these levels during subsequent processing operations. The effort includes evaluation of the effects of processing variables on the properties of the alloys. Consideration is given to processing techniques that are applicable to larger scale production. Fabrication of 6.8 kg of V?15Cr?5Ti alloy was carried out by dc arc casting of a number of 350-g ingots. This material was processed by consumable arc melting to yield a 5.9-cm-diameter ingot of the alloy. Further consumable arc melting produced a 9.7-cm-diameter ingot that was used at the start of hot working. This cast ingot was extruded at 1125C, with stainless steel cladding, to give a 6.6 cm 3.3 cm 114.3 cm bar. By scaling down this operation, a 3.5 kg heat of V?10Cr?5Ti alloy was processed from a cast ingot that was 5.9 cm in diameter. Material from both alloys has been processed further by hot and cold rolling.

  2. alloys

    NASA Astrophysics Data System (ADS)

    Pan, Z. B.; Liu, J. J.; Wang, R.; Liu, X. Y.; Wang, J.; Sun, N. K.; Si, P. Z.

    2014-06-01

    Structural, magnetic and magnetostrictive properties of Tb0.4Nd0.6(Fe0.8Co0.2) x (1.50 ? x ? 1.90) alloys have been investigated by means of X-ray diffraction (XRD), a vibrating sample magnetometer and a standard strain technique. XRD analysis shows the presence of single Laves phase with a cubic MgCu2-type structure for the high Nd content alloy around the composition of x = 1.80, which tends to be formed by curing at relatively low annealing temperature. The easy direction of magnetization at room temperature is observed toward <111> axis, accompanied by a rhombohedral distortion with a large spontaneous magnetostriction ?111. An optimized effect on the linear anisotropic magnetostriction, 360 ppm at 3 kOe, was observed for the high Nd content Tb0.4Nd0.6(Fe0.8Co0.2)1.80 alloy, which can be attributed to its single Laves phase, the large ?111 (~1,520 ppm) of the MgCu2-type (Tb,Nd)(Fe,Co)2 phase and the good soft magnetic behaviors.

  3. NDE detectability of fatigue type cracks in high strength alloys

    NASA Technical Reports Server (NTRS)

    Christner, B. K.; Rummel, W. D.

    1983-01-01

    Specimens suitable for investigating the reliability of production nondestructive evaluation (NDE) to detect tightly closed fatigue cracks in high strength alloys representative of those materials used in spacecraft engine/booster construction were produced. Inconel 718 was selected as representative of nickel base alloys and Haynes 188 was selected as representative of cobalt base alloys used in this application. Cleaning procedures were developed to insure the reusability of the test specimens and a flaw detection reliability assessment of the fluorescent penetrant inspection method was performed using the test specimens produced to characterize their use for future reliability assessments and to provide additional NDE flaw detection reliability data for high strength alloys. The statistical analysis of the fluorescent penetrant inspection data was performed to determine the detection reliabilities for each inspection at a 90% probability/95% confidence level.

  4. Design and fabrication of a metastable ?-type titanium alloy with ultralow elastic modulus and high strength

    NASA Astrophysics Data System (ADS)

    Guo, Shun; Meng, Qingkun; Zhao, Xinqing; Wei, Qiuming; Xu, Huibin

    2015-10-01

    Titanium and its alloys have become the most attractive implant materials due to their high corrosion resistance, excellent biocompatibility and relatively low elastic modulus. However, the current Ti materials used for implant applications exhibit much higher Youngs modulus (50?~?120?GPa) than human bone (~30?GPa). This large mismatch in the elastic modulus between implant and human bone can lead to so-called stress shielding effect and eventual implant failure. Therefore, the development of ?-type Ti alloys with modulus comparable to that of human bone has become an ever more pressing subject in the area of advanced biomedical materials. In this study, an attempt was made to produce a bone-compatible metastable ?-type Ti alloy. By alloying and thermo-mechanical treatment, a metastable ?-type Ti-33Nb-4Sn (wt. %) alloy with ultralow Youngs modulus (36?GPa, versus ~30?GPa for human bone) and high ultimate strength (853?MPa) was fabricated. We believe that this method can be applied to developing advanced metastable ?-type titanium alloys for implant applications. Also, this approach can shed light on design and development of novel ?-type titanium alloys with large elastic limit due to their high strength and low elastic modulus.

  5. Design and fabrication of a metastable ?-type titanium alloy with ultralow elastic modulus and high strength.

    PubMed

    Guo, Shun; Meng, Qingkun; Zhao, Xinqing; Wei, Qiuming; Xu, Huibin

    2015-01-01

    Titanium and its alloys have become the most attractive implant materials due to their high corrosion resistance, excellent biocompatibility and relatively low elastic modulus. However, the current Ti materials used for implant applications exhibit much higher Young's modulus (50 ~ 120 GPa) than human bone (~30 GPa). This large mismatch in the elastic modulus between implant and human bone can lead to so-called "stress shielding effect" and eventual implant failure. Therefore, the development of ?-type Ti alloys with modulus comparable to that of human bone has become an ever more pressing subject in the area of advanced biomedical materials. In this study, an attempt was made to produce a bone-compatible metastable ?-type Ti alloy. By alloying and thermo-mechanical treatment, a metastable ?-type Ti-33Nb-4Sn (wt. %) alloy with ultralow Young's modulus (36 GPa, versus ~30 GPa for human bone) and high ultimate strength (853 MPa) was fabricated. We believe that this method can be applied to developing advanced metastable ?-type titanium alloys for implant applications. Also, this approach can shed light on design and development of novel ?-type titanium alloys with large elastic limit due to their high strength and low elastic modulus. PMID:26434766

  6. Thermal evolution of vacancy-type defects in quenched FeCrNi alloys

    NASA Astrophysics Data System (ADS)

    Zhang, C. X.; Cao, X. Z.; Li, Y. H.; Jin, S. X.; Lu, E. Y.; Tian, H. W.; Zhang, P.; Wang, B. Y.

    2015-06-01

    The effect of isochronal annealing on vacancy-type defects in quenched FeCrNi alloys and SUS316 was investigated via positron annihilation technique. Vacancy-type defects clustered and grew with increasing annealing temperatures of up to 523 K and, in FeCrNi alloys, were gradually annihilated with increasing temperature. The annihilation temperature was relatively insensitive to the addition of Mo and nonmetal elements, and after annealing at 673 K, the vacancy-type defects were annihilated and dislocation-type defects were formed in all of the alloys. In addition, due to the formation of Mo-vacancy complexes, the density of defects in the Mo-diluted FeCrNi model alloy was lower than that in the FeCrNi model alloy. The long lifetime of vacancy-type defects in commercial stainless steel SUS316 was smaller than that in the FeCrNi model alloys due to the nonmetal-element-induced change in mobility of the defects. Moreover, the vacancy-type and dislocation-type defects contributed to the S and W parameters of positron annihilation during the entire annealing treatment.

  7. Effect of irradiation damage and helium on the swelling and structure of vanadium-base alloys

    SciTech Connect

    Chung, H.M.; Loomis, B.A.; Smith, D.L.

    1993-12-01

    Swelling behavior and microstructural evolution of V-Ti, V-Cr-Ti, and V-Ti-Si alloys were investigated after irradiation at 420--600C up to 114 dpa. The alloys exhibited swelling maxima between 30 and 80 dpa and swelling decreased on irradiation to higher dpa. This is in contrast to the monotonically increasing swelling of binary alloys that contain Fe, Ni, Cr, Mo, W, and Si. Precipitation of dense Ti{sub 5}Si{sub 3} promotes good resistance to swelling of the Ti-containing alloys and it was concluded that Ti of >3 wt.% and 400--1000 wppm Si are necessary to effectively suppress swelling. Swelling was minimal in V-4Cr-4Ti, identified as the most promising alloy based on good mechanical properties and superior resistance to irradiation embrittlement. V-20Ti doped with B exhibited somewhat higher swelling because of He generation. Lithium atoms, generated from transmutation of {sup 10}B, formed {gamma}-LiV{sub 2}O{sub 5} precipitates and did not seem to produce undesirable effects on mechanical properties.

  8. Grain size control and superplasticity in 6013-type aluminum alloys

    NASA Astrophysics Data System (ADS)

    Troeger, Lillianne Plaster Whitelock

    Aluminum alloys have been the material of choice for aircraft construction since the 1930's. Currently, the automotive industry is also showing an increasing interest in aluminum alloys as structural materials. 6xxx aluminum alloys possess a combination of strength and formability which makes them attractive to both industries. In addition, 6xxx alloys are highly weldable, corrosion resistant, and low in cost as compared with the 2xxx and 7xxx aluminum alloys. Superplastic forming (SPF) is a manufacturing process which exploits the phenomenon of superplasticity in which gas pressure is used to form complex-shaped parts in a single forming operation. This reduces part counts and the need for fasteners and connectors, resulting in reduced product weight. Reduced product/vehicle weight improves fuel economy. Most alloys must be specially processed for superplasticity. Much research effort has been directed at the development of thermomechanical processes for the grain refinement of aluminum alloys by static or dynamic recrystallization. to induce superplasticity. While large numbers of studies have been conducted on 2xxx, 5xxx, 7xxx, and 8xxx aluminum alloys, very few studies have been focused on the grain refinement of 6xxx aluminum alloys for superplasticity. The current research describes a new thermomechanical process for application to 6xxx aluminum alloys for grain refinement and superplasticity. The process is shown to successfully refine and induce superplasticity in an Al-Mg-Si-Cu alloy which falls within the compositional limits of both 6013 and 6111. The grain refinement is by particle-stimulated nucleation of recrystallization. The microstructural evolution during the thermomechanical processing is characterized in terms of precipitate size, shape, distribution and composition; texture; recrystallization; and grain size, shape, and thermal stability. The new process produces a statically-stable, weakly-textured, equiaxed grain structure with an average grain diameter of 10 mum. The refined microstructure exhibits superplasticity above 500C, where the strain rate sensitivity reaches a maximum of 0.5 (at 540C for strain rates between 2 x 10-4 s-1 and 5 x 10-4 s-1). The maximum uniaxial elongation (375%) occurred in the regime of the maximum strain rate sensitivity. The corresponding flow stress was 680 psi (4.7 Mpa). Biaxial cone tests were performed in order to better evaluate the high-temperature forming characteristics of the material. During tests with back pressure, cone height-to-radius ratios near 1.2 were obtained with maximum strain approaching 2.0 for strain rates near 1 x 10-3 s-1 . The effect of superplastic deformation on the microstructure is described in terms of the effect of strain on grain size and porosity for a cone sample. The ultimate goal of the project is to advance the fundamental understanding of the complex interrelationships between processing, microstructure, and superplastic performance.

  9. Invar-type effect induced by cold-rolling deformation in shape memory alloys

    NASA Astrophysics Data System (ADS)

    Kainuma, R.; Wang, J. J.; Omori, T.; Sutou, Y.; Ishida, K.

    2002-06-01

    Since the discovery of Fe-Ni alloys showing low thermal expansion (LTE) in 1896, many Invar alloys have been developed based on magnetovolume effect where negative thermal expansion is induced by magnetic transformation. Herein, we show that the control of stress-induced martensitic transformation due to cold working of the Cu-Zn-Al polycrystalline alloy results in the LTE. This type of LTE material is easily fabricated by conventional cold rolling, and the coefficient of thermal expansion in the range from about 0 to 32 x10-6 K-1 can be obtained by controlling the reduction ratio. The LTE effect due to the present method can also be obtained for other shape memory (SM) alloys such as Ni-Ti, Cu-Mn-Al and Ni-Al base alloys, which have high potential for various practical applications.

  10. Strain glass transition in a multifunctional ?-type Ti alloy

    NASA Astrophysics Data System (ADS)

    Wang, Yu; Gao, Jinghui; Wu, Haijun; Yang, Sen; Ding, Xiangdong; Wang, Dong; Ren, Xiaobing; Wang, Yunzhi; Song, Xiaoping; Gao, Jianrong

    2014-02-01

    Recently, a class of multifunctional Ti alloys called GUM metals attracts tremendous attentions for their superior mechanical behaviors (high strength, high ductility and superelasticity) and novel physical properties (Invar effect, Elinvar effect and low modulus). The Invar and Elinvar effects are known to originate from structural or magnetic transitions, but none of these transitions were found in the GUM metals. This challenges our fundamental understanding of their physical properties. In this study, we show that the typical GUM metal Ti-23Nb-0.7Ta-2Zr-1.2O (at%) alloy undergoes a strain glass transition, where martensitic nano-domains are frozen gradually over a broad temperature range by random point defects. These nano-domains develop strong texture after cold rolling, which causes the lattice elongation in the rolling direction associated with the transition upon cooling and leads to its Invar effect. Moreover, its Elinvar effect and low modulus can also be explained by the nano-domain structure of strain glass.

  11. Strain glass transition in a multifunctional ?-type Ti alloy.

    PubMed

    Wang, Yu; Gao, Jinghui; Wu, Haijun; Yang, Sen; Ding, Xiangdong; Wang, Dong; Ren, Xiaobing; Wang, Yunzhi; Song, Xiaoping; Gao, Jianrong

    2014-01-01

    Recently, a class of multifunctional Ti alloys called GUM metals attracts tremendous attentions for their superior mechanical behaviors (high strength, high ductility and superelasticity) and novel physical properties (Invar effect, Elinvar effect and low modulus). The Invar and Elinvar effects are known to originate from structural or magnetic transitions, but none of these transitions were found in the GUM metals. This challenges our fundamental understanding of their physical properties. In this study, we show that the typical GUM metal Ti-23Nb-0.7Ta-2Zr-1.2O (at%) alloy undergoes a strain glass transition, where martensitic nano-domains are frozen gradually over a broad temperature range by random point defects. These nano-domains develop strong texture after cold rolling, which causes the lattice elongation in the rolling direction associated with the transition upon cooling and leads to its Invar effect. Moreover, its Elinvar effect and low modulus can also be explained by the nano-domain structure of strain glass. PMID:24500779

  12. Strain glass transition in a multifunctional ?-type Ti alloy

    PubMed Central

    Wang, Yu; Gao, Jinghui; Wu, Haijun; Yang, Sen; Ding, Xiangdong; Wang, Dong; Ren, Xiaobing; Wang, Yunzhi; Song, Xiaoping; Gao, Jianrong

    2014-01-01

    Recently, a class of multifunctional Ti alloys called GUM metals attracts tremendous attentions for their superior mechanical behaviors (high strength, high ductility and superelasticity) and novel physical properties (Invar effect, Elinvar effect and low modulus). The Invar and Elinvar effects are known to originate from structural or magnetic transitions, but none of these transitions were found in the GUM metals. This challenges our fundamental understanding of their physical properties. In this study, we show that the typical GUM metal Ti-23Nb-0.7Ta-2Zr-1.2O (at%) alloy undergoes a strain glass transition, where martensitic nano-domains are frozen gradually over a broad temperature range by random point defects. These nano-domains develop strong texture after cold rolling, which causes the lattice elongation in the rolling direction associated with the transition upon cooling and leads to its Invar effect. Moreover, its Elinvar effect and low modulus can also be explained by the nano-domain structure of strain glass. PMID:24500779

  13. Titanium bearing MCrAlY type alloy and composite articles

    SciTech Connect

    Wilson, L.

    1980-07-22

    A coated article having hot corrosion resistance comprising: (A) a substrate selected from the group consisting of iron, nickel and cobalt based alloys; and (B) an mcraly type overlay alloy coating on said substrate, said coating consisting of by weight about 3-6 percent titanium, about 10-40 percent chromium, about 9-25 percent aluminum and about 0.01-5.0 percent reactive metal selected from the group consisting of yttrium, scandium, thorium and other rare earth elements, balance selected from the group consisting of nickel, cobalt and iron, said coated article having improved resistance to hot corrosion by virtue of the presence of titanium in the coating.

  14. Tensile impact properties of vanadium-base alloys irradiated at <430{degree}C.

    SciTech Connect

    Chung, H. M.

    1998-05-18

    Tensile and impact properties were investigated at <430 C on V-Cr-Ti, V-Ti-Si, and V-Ti alloys after irradiation to {approx}2-46 dpa at 205-430 C in lithium or helium in the Fast Flux Test Facility (FFTF), High Flux Isotope Reactor (HFIR), Experimental Breeder Reactor II (EBR-II), and Advanced Test Reactor (ATR). A 500-kg heat of V-4Cr-4Ti exhibited high ductile-brittle transition temperature and minimal uniform elongation as a result of irradiation-induced loss of work-hardening capability. Work-hardening capabilities of 30- and 100-kg heats of V-4Cr-4Ti varied significantly with irradiation conditions, although the 30-kg heat exhibited excellent impact properties after irradiation at {approx}390-430 C. The origin of the significant variations in the work-hardening capability of V-4Cr-4Ti is not understood, although fabrication variables, annealing history, and contamination from the irradiation environment are believed to play important roles. A 15-kg heat of V-3Ti-1Si exhibited good work-hardening capability and excellent impact properties after irradiation at {approx}390-430 C. Helium atoms, either charged dynamically or produced via transmutation of boron in the alloys, promote work-hardening capability in V-4Cr-4Ti and V-3Ti-1Si.

  15. Vapor Growth of Alloy-Type Semiconductor Crystals

    NASA Technical Reports Server (NTRS)

    Wiedemeier, H.

    1985-01-01

    The present effort is part of a continuing research program directed towards the investigation of basic vapor transport phenomena and of crystal growth properties of electronic materials. The primary purpose of ground-based studies is the development and definition of optimum experimental parameters for flight experiments. The ground-based effort includes the investigation of gravity-driven convection effects on mass transport rates and on crystal morphology for different orientations of the density gradient with respect to the gravity vector, and as a function of pressure and of temperature. In addition to the experimental tasks, theoretical efforts involve the quantitative thermodynamic analysis of the systems under investigation, the computation of fluid dynamic parameters, and the consideration of other possible effects on fluid flow under vertical, stabilizing and microgravity conditions. The specific experiments to be performed in a microgravity environment include the investigation of vapor transport and crystal growth phenomena of the GeSe-Xenon system and of the mass flux and growth of bulk and layer-type crystals of Hg sub (1-x) Cd sub x Te using HgI as a transport agent.

  16. Alloy

    NASA Astrophysics Data System (ADS)

    Cabeza, Sandra; Garcés, Gerardo; Pérez, Pablo; Adeva, Paloma

    2014-07-01

    The Mg98.5Gd1Zn0.5 alloy produced by a powder metallurgy route was studied and compared with the same alloy produced by extrusion of ingots. Atomized powders were cold compacted and extruded at 623 K and 673 K (350 °C and 400 °C). The microstructure of extruded materials was characterized by α-Mg grains, and Mg3Gd and 14H-LPSO particles located at grain boundaries. Grain size decreased from 6.8 μm in the extruded ingot, down to 1.6 μm for powders extruded at 623 K (350 °C). Grain refinement resulted in an increase in mechanical properties at room and high temperatures. Moreover, at high temperatures the PM alloy showed superplasticity at high strain rates, with elongations to failure up to 700 pct.

  17. Surface treatment for inhibition of corrosion and hydrogen penetration of type 718 alloy

    SciTech Connect

    Popov, B.N.; Zheng, G.; White, R.E. . Dept. of Chemical Engineering)

    1994-08-01

    Polarization and permeation experiments showed that a monolayer coverage of lead (Pb) effectively inhibited the hydrogen (H) evolution reaction and H penetration through type 718 (UNS N07718) alloy. Observed inhibition effects were a result of the kinetic limitations of the H discharge reaction and suppression of H absorption on the deposited monolayer. H evolution reaction and H permeation rates were reduced by [approximately]67% and 70%, respectively.

  18. Mechanical properties of L1{sub 2} type Zn{sub 3}Ti-based alloy

    SciTech Connect

    Hosoda, Hideki; Hanada, Shuji

    1999-07-01

    An alloy composed of L1{sub 2}-type Zn{sub 3}Ti was investigated in terms of phase stability and mechanical properties. Zn and Ti powders were mixed at a composition of Zn-25mol%Ti using a ball mill in Ar, and an ingot was made by melting the powders. Optical microscopy, X-ray diffraction analysis and thermogravimetry--differential thermal analysis were carried out. Mechanical properties were investigated by Vickers hardness tests at room temperature (RT) and compression tests from RT to 703K in Ar. It is found that (1) the alloy is mainly composed of L1{sub 2}Zn{sub 3}Ti, (2) the alloy has weak positive temperature dependence of strength, and (3) normalized strength by melting point is comparable to that of L1{sub 2}Al{sub 3}Ti-Cr alloys. L1{sub 2}Zn{sub 3}Ti has HV178 and is brittle at RT. Reaction temperatures of Zn-rich portion of the Zn-Ti phase diagram were also reinvestigated and a peritectic-reaction temperature between Zn{sub 3}Ti and liquid + Zn{sub 2}Ti is determined to be at 880K.

  19. Site preference of Mg acceptors and improvement of p-type doping efficiency in nitride alloys

    NASA Astrophysics Data System (ADS)

    Park, Ji-Sang; Chang, K. J.

    2013-06-01

    We perform first-principles density functional calculations to investigate the effect of Al and In on the formation energy and acceptor level of Mg in group-III nitride alloys. Our calculations reveal a tendency for the Mg dopants to prefer to occupy the lattice sites surrounded with Al atoms, whereas hole carriers are generated in In- or Ga-rich sites. The separation of the Mg dopants and hole carriers is energetically more favourable than a random distribution of dopants, being attributed to the local bonding effect of weak In and strong Al potentials in alloys. As a consequence, the Mg acceptor level, which represents the activation energy of Mg, tends to decrease with increasing numbers of Al next-nearest neighbours, whereas it increases as the number of In next-nearest neighbours increases. Based on the results, we suggest that the incorporation of higher Al and lower In compositions will improve the p-type doping efficiency in quaternary alloys, in comparison with GaN or AlGaN ternary alloys with similar band gaps.

  20. Effect of Off-Stoichiometry on the Thermoelectric Properties of Heusler-Type Fe2VAl Sintered Alloys

    NASA Astrophysics Data System (ADS)

    Mikami, M.; Inukai, M.; Miyazaki, H.; Nishino, Y.

    2016-03-01

    Heusler-type Fe2V1- x Al1+ x sintered alloys with micrometer-sized grains were fabricated by the powder metallurgical process using mechanical alloying and pulse-current sintering. Both positive (˜90 μV/K) and negative (˜-140 μV/K) Seebeck coefficients were obtained for the composition ranges of x > 0 and x < 0, respectively, resulting from a Fermi level shift caused by the change in the valence electron concentration. The electrical resistivity was reduced by the carrier doping effect, especially at lower temperatures, resulting in an increased thermoelectric power factor of 2.8 mW/m-K2 for the p-type alloy with x = 0.06 and 5.0 mW/m-K2 for the n-type alloy with x = -0.06. In addition, the lattice thermal conductivity decreased with | x| because of phonon scattering at crystal lattice defects induced by the off-stoichiometry. Consequently, the thermoelectric figure of merit, ZT, was enhanced and reached 0.07 for p-type alloys with 0.06 < x < 0.15 and 0.18 for n-type alloys with -0.15 < x < -0.10 around 500 K. The ZT value was especially enhanced at higher temperatures by the off-stoichiometric composition control, which could extend the range of heat source temperatures for thermoelectric power generation applications using this alloy.

  1. Effect of Off-Stoichiometry on the Thermoelectric Properties of Heusler-Type Fe2VAl Sintered Alloys

    NASA Astrophysics Data System (ADS)

    Mikami, M.; Inukai, M.; Miyazaki, H.; Nishino, Y.

    2015-08-01

    Heusler-type Fe2V1-x Al1+x sintered alloys with micrometer-sized grains were fabricated by the powder metallurgical process using mechanical alloying and pulse-current sintering. Both positive (90 ?V/K) and negative (-140 ?V/K) Seebeck coefficients were obtained for the composition ranges of x > 0 and x < 0, respectively, resulting from a Fermi level shift caused by the change in the valence electron concentration. The electrical resistivity was reduced by the carrier doping effect, especially at lower temperatures, resulting in an increased thermoelectric power factor of 2.8 mW/m-K2 for the p-type alloy with x = 0.06 and 5.0 mW/m-K2 for the n-type alloy with x = -0.06. In addition, the lattice thermal conductivity decreased with |x| because of phonon scattering at crystal lattice defects induced by the off-stoichiometry. Consequently, the thermoelectric figure of merit, ZT, was enhanced and reached 0.07 for p-type alloys with 0.06 < x < 0.15 and 0.18 for n-type alloys with -0.15 < x < -0.10 around 500 K. The ZT value was especially enhanced at higher temperatures by the off-stoichiometric composition control, which could extend the range of heat source temperatures for thermoelectric power generation applications using this alloy.

  2. Design and fabrication of a metastable β-type titanium alloy with ultralow elastic modulus and high strength

    PubMed Central

    Guo, Shun; Meng, Qingkun; Zhao, Xinqing; Wei, Qiuming; Xu, Huibin

    2015-01-01

    Titanium and its alloys have become the most attractive implant materials due to their high corrosion resistance, excellent biocompatibility and relatively low elastic modulus. However, the current Ti materials used for implant applications exhibit much higher Young’s modulus (50 ~ 120 GPa) than human bone (~30 GPa). This large mismatch in the elastic modulus between implant and human bone can lead to so-called “stress shielding effect” and eventual implant failure. Therefore, the development of β-type Ti alloys with modulus comparable to that of human bone has become an ever more pressing subject in the area of advanced biomedical materials. In this study, an attempt was made to produce a bone-compatible metastable β-type Ti alloy. By alloying and thermo-mechanical treatment, a metastable β-type Ti-33Nb-4Sn (wt. %) alloy with ultralow Young’s modulus (36 GPa, versus ~30 GPa for human bone) and high ultimate strength (853 MPa) was fabricated. We believe that this method can be applied to developing advanced metastable β-type titanium alloys for implant applications. Also, this approach can shed light on design and development of novel β-type titanium alloys with large elastic limit due to their high strength and low elastic modulus. PMID:26434766

  3. Elastic softening of ?-type Ti-Nb alloys by indium (In) additions.

    PubMed

    Calin, Mariana; Helth, Arne; Gutierrez Moreno, Julio J; Bnisch, Matthias; Brackmann, Varvara; Giebeler, Lars; Gemming, Thomas; Lekka, Christina E; Gebert, Annett; Schnettler, Reinhard; Eckert, Jrgen

    2014-11-01

    Recent developments showed that ?-type Ti-Nb alloys are good candidates for hard tissue replacement and repair. However, their elastic moduli are still to be further reduced to match Young?s modulus values of human bone, in order to avoid stress shielding. In the present study, the effect of indium (In) additions on the structural characteristics and elastic modulus of Ti-40 Nb was investigated by experimental and theoretical (ab initio) methods. Several ?-type (Ti-40 Nb)-xIn alloys (with x ? 5.2 wt%) were produced by cold-crucible casting and subsequent heat treatments (solid solutioning in the ?-field followed by water quenching). All studied alloys completely retain the ?-phase in the quenched condition. Room temperature mechanical tests revealed ultimate compressive strengths exceeding 770 MPa, large plastic strains (>20%) and a remarkable strain hardening. The addition of up to 5.2 wt% indium leads to a noticeable decrease of the elastic modulus from 69 GPa to 49 GPa, which is closer to that of cortical bone (<30 GPa). Young's modulus is closely related to the bcc lattice stability and bonding characteristics. The presence of In atoms softens the parent bcc crystal lattice, as reflected by a lower elastic modulus and reduced yield strength. Ab initio and XRD data agree that upon In substitution the bcc unit cell volume increases almost linearly. The bonding characteristics of In were studied in detail, focusing on the energies that appeared from the EDOSs significant for possible hybridizations. It came out that minor In additions introduce low energy states with s character that present antibonding features with the Ti first neighboring atoms as well as with the Ti-Nb second neighboring atoms thus weakening the chemical bonds and leading to elastic softening. These results could be of use in the design of low rigidity ?-type Ti-alloys with non-toxic additions, suitable for orthopedic applications. PMID:25128870

  4. Thermoelectric properties of the Heusler-type Fe2VTaxAl1-x alloys

    NASA Astrophysics Data System (ADS)

    Renard, Krystel; Mori, Arinori; Yamada, Yuichiro; Tanaka, Suguru; Miyazaki, Hidetoshi; Nishino, Yoichi

    2014-01-01

    This study focuses on the thermoelectric properties of the Heusler-type Fe2VTaxAl1-x alloys (0?x?0.12). By means of Rietveld analyses on synchrotron X-ray diffraction patterns, it is shown that the Ta atoms enter sites occupied by V atoms in the stoichiometric Fe2VAl alloy, while the ejected V atoms are transferred to the vacant Al sites. This Ta substitution leads to an improvement of the n-type thermoelectric properties owing to two mechanisms. On the one hand, the atoms position in the structure leads to an off-stoichiometric effect such as already observed in V-rich Fe2V1+yAl1-y compounds: the Seebeck coefficient is increased towards negative absolute values and the electrical resistivity is decreased, with a large shift of their peak temperature towards higher temperature. The maximum power factor is 6.5 10-3 W/mK2 for x = 0.05 at 340 K. On the other hand, the heavy element Ta substitution combined with this off-stoichiometric effect leads to a large decrease of the thermal conductivity, owing to an increase of the scattering events. Consequently, the dimensionless figure of merit is seen to reach higher values than for the Fe2V1+yAl1-y alloys, i.e., 0.21-0.22 around 400-500 K for x = 0.05 and 500 K for x = 0.08.

  5. Electroplating of thin films of bismuth onto type 4340 steel and alloy 718 to prevent hydrogen embrittlement

    SciTech Connect

    Popov, B.N.; Zheng, G.; White, R.E.

    1995-06-01

    Polarization and permeation experiments showed that a thin layer of electroplated bismuth (1 {mu}m to 2 {mu}m) inhibited the evolution and penetration of hydrogen through nickel-chromium alloy 718 (UNS N07718) and type 4340 (UNS G43400) steel. Inhibition effects were due to the kinetic limitations of the hydrogen discharge reaction and to the suppression of hydrogen adsorption on the deposited layers. The hydrogen evolution reactions on alloy 718 and type 4340 steel were inhibited by 28% and 85%, respectively. The hydrogen permeation rates through these alloys were reduced by 76% and 65%, respectively.

  6. Structure, Magnetic, and Electrical Properties of Heusler-Type Fe3- x Co x Si Ferromagnetic Alloys

    NASA Astrophysics Data System (ADS)

    Raja, M. Manivel; Kamat, S. V.

    2015-10-01

    The effect of substitution of Co for Fe on structure, magnetic, and electrical resistivity of Heusler-type Fe3- x Co x Si (0 ? x ? 1) alloys was investigated using X-ray powder diffraction, 57Fe Mssbauer spectroscopy, magnetic, and electrical transport measurements. The results revealed that these alloys consist of ordered DO3 phase and some L21 phase up to x ? 0.5. However, for x > 0.5, the alloys consisted of L21 ordered phase and B2 disordered phase. The magnetization value was close to that predicted from Slater-Pauling rule for x ? 0.5 alloys. The Curie temperature increased from 832 K (559 C) for x = 0 (Fe3Si) alloy to 1016 K (743 C) for x = 1 (Fe2CoSi) alloy. Electrical transport studies revealed the presence of half-metallic behavior at low temperatures in x ? 0.5 alloys. No half-metallic behavior was observed for x = 0 and 0.25 alloys; however, a high resistivity with ferromagnetism was observed in these alloys, which is desirable for ferromagnetic metal/semiconductor spintronic devices.

  7. Deformation behavior of metastable ?-type Ti-25Nb-2Mo-4Sn alloy for biomedical applications.

    PubMed

    Guo, S; Meng, Q K; Cheng, X N; Zhao, X Q

    2014-10-01

    The deformation behavior of metastable ?-type Ti-25Nb-2Mo-4Sn (wt%) alloy subjected to different thermo-mechanical treatments was discussed by the combining results from transmission electron microscope, tensile test and in-situ synchrotron X-ray diffraction. Visible "double yielding" behavior, which is characterized by the presence of stress-plateau, was observed in the solution treated specimen. Upon a cold rolling treatment, the Ti-25Nb-2Mo-4Sn alloy performs nonlinear deformation because of the combined effects of elastic deformation and stress-induced ?? martensitic transformation. After the subsequent annealing, the ? phase is completely stabilized and no stress-induced martensitic transformation takes place on loading due to the inhibitory effect of grain boundaries and dislocations on martensitic transformation. As a result, the annealed specimen exhibits linear elastic deformation. PMID:25011015

  8. P-type InGaN across the entire alloy composition range

    SciTech Connect

    Wang, K.; Araki, T.; Katsuki, T.; Yu, K. M.; Mayer, M. A.; Ager, J. W. III; Walukiewicz, W.; Alarcon-Llado, E.; Ecole Polytechnique Federale de Lausanne, Lausanne ; Nanishi, Y.; WCU Hybrid Materials Program, Department of Materials Science and Engineering, Seoul National University, Seoul 151-744

    2013-03-11

    A systematic investigation on Mg doped and undoped InGaN epilayers grown by plasma-assisted molecular beam epitaxy has been conducted. Single phase InGaN alloys across the entire composition range were synthesized and Mg was doped into In{sub x}Ga{sub 1-x}N (0.1 {<=} x {<=} 0.88) epilayers up to {approx}10{sup 20}/cm{sup 3}. Hall effect, thermopower, and electrochemical capacitance voltage experimental results demonstrate the realization of p-type InGaN across the entire alloy composition range for properly Mg doped InGaN. Hole densities have been measured or estimated to be in the lower {approx}10{sup 18}/cm{sup 3} range when the net acceptor concentrations are in the lower {approx}10{sup 19}/cm{sup 3} range across the composition range.

  9. Predominant factor determining wear properties of ?-type and (?+?)-type titanium alloys in metal-to-metal contact for biomedical applications.

    PubMed

    Lee, Yoon-Seok; Niinomi, Mitsuo; Nakai, Masaaki; Narita, Kengo; Cho, Ken

    2015-01-01

    The predominant factor determining the wear properties of a new titanium alloy, Ti-29Nb-13Ta-4.6Zr (TNTZ) and a conventional titanium alloy, Ti-6Al-4V extra-low interstitial (Ti64) was investigated for TNTZ and Ti64 combinations in metal-to-metal contacting bio-implant applications. The worn surfaces, wear debris, and subsurface damages were analyzed using a scanning electron microscopy combined with energy-dispersive spectroscopy and electron-back scattered diffraction analysis. The volume loss of TNTZ is found to be larger than that of Ti64, regardless of the mating material. The wear track of TNTZ exhibits the galled regions and severe plastic deformation with large flake-like debris, indicative of delamination wear, which strongly suggests the occurrence of adhesive wear. Whereas, the wear track of Ti64 have a large number of regular grooves and microcuttings with cutting chip-like wear debris and microfragmentation of fine oxide debris, indicative of abrasive wear combined with oxidative wear. This difference in the wear type is caused by severe and mild subsurface deformations of TNTZ and Ti64, respectively. The lower resistance to plastic shearing for TNTZ compared to that of Ti64 induces delamination, resulting in a higher wear rate. PMID:25460417

  10. Annihilation momentum density of positrons trapped at vacancy-type defects in metals and alloys

    SciTech Connect

    Bansil, A.; Prasad, R.; Benedek, R.

    1988-01-01

    Positron annihilation, especially the angular correlation of annihilation radiation, is a powerful tool for investigating the electronic spectra of ordered as well as defected materials. The tendency of positrons to trap at vacancy-type defects should enable this technique to study the local environment of such defects. However, we need to develop a theoretical basis for calculating the two-photon annihilation momentum density rho/sub 2gamma/(p-vector). We have recently formulated and implemented a theory of rho/sub 2gamma/(p-vector) from vacancy-type defects in metals and alloys. This article gives an outline of our approach together with a few of our results. Section 2 summarizes the basic equations for evaluating rho/sub 2gamma/(p-vector). Our Green's function-based approach is nonperturbative and employs a realistic (one-particle) muffin-tin Hamiltonian for treating electrons and positrons. Section 3 presents and discusses rho/sub 2gamma/(p-vector) results for a mono-vacancy in Cu. We have neglected the effects of electron-positron correlations and of lattice distortion around the vacancy. Section 4 comments briefly on the question of treating defects such as divacancies and metal-impurity complexes in metals and alloys. Finally, in Section 5, we remark on the form of rho/sub 2gamma/(p-vector) for a mono-vacancy in jellium. 2 figs.

  11. Highly Conductive p-Type Silicon Carbon Alloys Deposited by Hot-Wire Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Tao Chen,; Deren Yang,; Reinhard Carius,; Friedhelm Finger,

    2010-04-01

    P-type microcrystalline silicon carbide (μc-SiC:H) alloys for application as a window layer in silicon based thin film solar cells were grown by hot-wire chemical vapor deposition using hydrogen diluted monomethylsilane and trimethylaluminum. Conductivities up to 0.1 S/cm were obtained for p-type material. The optical properties were studied by photothermal deflection spectroscopy. At photon energies below 1.25 eV, both free carrier and defect absorption lead to a high absorption coefficient. For photon energies >2.0 eV, the absorption coefficient is affected by the crystallinity and the structural composition. The structure of Al-doped μc-SiC:H thin films were investigated by infrared and Raman spectroscopy. It was found that increase of the deposition pressure can compensate for the loss of crystallinity caused by Al-doping. At high deposition pressure (>100 Pa), increasing contributions of hexagonal SiC alloys, and separated carbon phases are observed.

  12. Highly Conductive p-Type Silicon Carbon Alloys Deposited by Hot-Wire Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Chen, Tao; Yang, Deren; Carius, Reinhard; Finger, Friedhelm

    2010-04-01

    P-type microcrystalline silicon carbide (µc-SiC:H) alloys for application as a window layer in silicon based thin film solar cells were grown by hot-wire chemical vapor deposition using hydrogen diluted monomethylsilane and trimethylaluminum. Conductivities up to 0.1 S/cm were obtained for p-type material. The optical properties were studied by photothermal deflection spectroscopy. At photon energies below 1.25 eV, both free carrier and defect absorption lead to a high absorption coefficient. For photon energies >2.0 eV, the absorption coefficient is affected by the crystallinity and the structural composition. The structure of Al-doped µc-SiC:H thin films were investigated by infrared and Raman spectroscopy. It was found that increase of the deposition pressure can compensate for the loss of crystallinity caused by Al-doping. At high deposition pressure (>100 Pa), increasing contributions of hexagonal SiC alloys, and separated carbon phases are observed.

  13. Elasto-Plasticity Behavior of Type 5000 and 6000 Aluminum Alloy Sheets and Its Constitutive Modeling

    SciTech Connect

    Tamura, Shohei; Sumikawa, Satoshi; Hamasaki, Hiroshi; Yoshida, Fusahito; Uemori, Takeshi

    2010-06-15

    To examine the deformation characteristic of type 5000 and 6000 aluminum alloy sheets, uniaxial tension, biaxial stretching and in-plane cyclic tension-compression experiments were performed, and from these, r-values (r{sub 0}, r{sub 45} and r{sub 90}), yield loci and cyclic stress-strain responses were obtained. For the accurate description of anisotropies of the materials, high-ordered anisotropic yield functions, such as Gotoh's biquadratic yield function and Barlat's Yld2000-2d, are necessary. Furthermore, for the simulation of cyclic behavior, an advanced kinematic hardening model, such as Yoshida-Uemori model (Y-U model), should be employed. The effect of the selection of material models on the accuracy of the springback prediction was discussed by performing hat bending FE simulation using several yield functions and two types of hardening laws (the isotropic hardening model and Y-U model).

  14. Elasto-Plasticity Behavior of Type 5000 and 6000 Aluminum Alloy Sheets and Its Constitutive Modeling

    NASA Astrophysics Data System (ADS)

    Tamura, Shohei; Sumikawa, Satoshi; Hamasaki, Hiroshi; Uemori, Takeshi; Yoshida, Fusahito

    2010-06-01

    To examine the deformation characteristic of type 5000 and 6000 aluminum alloy sheets, uniaxial tension, biaxial stretching and in-plane cyclic tension-compression experiments were performed, and from these, r-values (r0, r45 and r90), yield loci and cyclic stress-strain responses were obtained. For the accurate description of anisotropies of the materials, high-ordered anisotropic yield functions, such as Gotoh's biquadratic yield function and Barlat's Yld2000-2d, are necessary. Furthermore, for the simulation of cyclic behavior, an advanced kinematic hardening model, such as Yoshida-Uemori model (Y-U model), should be employed. The effect of the selection of material models on the accuracy of the springback prediction was discussed by performing hat bending FE simulation using several yield functions and two types of hardening laws (the isotropic hardening model and Y-U model).

  15. Thermoelectric properties of Heusler-type off-stoichiometric Fe2V1+xAl1-x alloys

    NASA Astrophysics Data System (ADS)

    Miyazaki, Hidetoshi; Tanaka, Suguru; Ide, Naoki; Soda, Kazuo; Nishino, Yoichi

    2014-03-01

    We report the thermoelectric properties of Heusler-type off-stoichiometric Fe2V1+xAl1-x alloys. Due to the off-stoichiometric effect, which is the substitution of V/Al atoms with Al/V atoms, semiconductor-like electric resistivity behavior in Fe2VAl is changed to metallic behavior in Fe2V1+xAl1-x alloys and both positive and negative absolute Seebeck coefficients are drastically increased. The maximum thermoelectric power factor of Fe2V1+xAl1-x alloys is 4.3 10-3 (x = -0.03: p-type) and 6.8 10-3 W mK-2 (x = 0.05: n-type) with a peak temperature in the range 300-600 K, exceeding the values of previously reported Fe-based Heusler alloys as well as those of available thermoelectric materials such as Bi-Te semiconductors. Based on x-ray diffraction and photoemission spectroscopy results, it is thought that the maintenance of the Heusler-type (L21) crystal structure and the modification of the electronic structure due to the off-stoichiometry could explain the large thermoelectric power factor and high peak temperature in Fe2V1+xAl1-x alloys.

  16. Retrogression and reaging and the role of dislocations in the stress corrosion of 7000-type aluminum alloys

    NASA Astrophysics Data System (ADS)

    Talianker, M.; Cina, B.

    1989-10-01

    The 7000-type aluminum alloys in the T6 temper are known to be highly susceptible to stress-corrosion cracking (SCC). Some years ago, a heat treatment known as retrogression and reaging (RR) was developed by one of the authors (B.C.), providing for enhanced stress-corrosion resistance without any sacrifice of yield or tensile strength in 7075 aluminum alloy. The idea behind the process was based on the suggestion that dislocations developed during quenching from the solution treatment were responsible for susceptibility to stress corrosion. In spite of considerable practical development of the RR process, the above basic hypothesis as to the role of dislocations has never been investigated. In the present work, the effect of the RR treatments on the dislocation structure of 7000-type aluminum alloys was studied using transmission electron microscopy (TEM). A clear relationship has been found between the presence of dislocations adjacent to grain boundaries and the susceptibility to stress corrosion of 7000-type aluminum alloys. The beneficial effect of the RR treatment on the SCC of 7000-type aluminum alloys in the T6 temper is believed to be due to the disappearance of the above dislocations as a result of RR treatment.

  17. Microstructure and mechanical properties of thermoelectric nanostructured n-type silicon-germanium alloys synthesized employing spark plasma sintering

    SciTech Connect

    Bathula, Sivaiah; Gahtori, Bhasker; Tripathy, S. K.; Tyagi, Kriti; Srivastava, A. K.; Dhar, Ajay; Jayasimhadri, M.

    2014-08-11

    Owing to their high thermoelectric (TE) figure-of-merit, nanostructured Si{sub 80}Ge{sub 20} alloys are evolving as a potential replacement for their bulk counterparts in designing efficient radio-isotope TE generators. However, as the mechanical properties of these alloys are equally important in order to avoid in-service catastrophic failure of their TE modules, we report the strength, hardness, fracture toughness, and thermal shock resistance of nanostructured n-type Si{sub 80}Ge{sub 20} alloys synthesized employing spark plasma sintering of mechanically alloyed nanopowders of its constituent elements. These mechanical properties show a significant enhancement, which has been correlated with the microstructural features at nano-scale, delineated by transmission electron microscopy.

  18. Effects of the types of overlap on the mechanical properties of FSSW welded AZ series magnesium alloy joints

    NASA Astrophysics Data System (ADS)

    Wang, Dan; Shen, Jun; Wang, Lin-Zhi

    2012-03-01

    The effects of the types of overlap on the mechanical properties of the friction stir spot welding (FSSW) welded AZ series magnesium alloy joints were investigated by microstructural observations, microhardness tests, and tensile tests. The results show that the microstructure of the stir zone adjacent to the periphery of the rotating pin is mainly composed of the upper sheet. The average distance D between the longitudinal segment of the curved interface and the keyhole periphery, the tensile shear force, and the microhardness of the stir zone of the FSSW welded AZ61 alloy joint are the highest in all samples. During FSSW of AZ31 and AZ61 dissimilar magnesium alloys, the irregular deformation of the longitudinal segment of the curved interface appears, while the microhardness of the stir zone is higher when AZ61 alloy is the upper sheet. Moreover, the microhardness of the stir zone increases initially and then decreases sharply in the longitudinal test position.

  19. Adhesive strength of medical polymer on anodic oxide nanostructures fabricated on biomedical ?-type titanium alloy.

    PubMed

    Hieda, Junko; Niinomi, Mitsuo; Nakai, Masaaki; Cho, Ken; Mohri, Tomoyoshi; Hanawa, Takao

    2014-03-01

    Anodic oxide nanostructures (nanopores and nanotubes) were fabricated on a biomedical ?-type titanium alloy, Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), by anodization in order to improve the adhesive strength of a medical polymer, segmented polyurethane (SPU), to TNTZ. TNTZ was anodized in 1.0M H3PO4 solution with 0.5 mass% NaF using a direct-current power supply at a voltage of 20V. A nanoporous structure is formed on TNTZ in the first stage of anodization, and the formation of a nanotube structure occurs subsequently beneath the nanoporous structure. The nanostructures formed on TNTZ by anodization for less than 3,600s exhibit higher adhesive strengths than those formed at longer anodization times. The adhesive strength of the SPU coating on the nanoporous structure formed on top of TNTZ by anodization for 1,200s improves by 144% compared to that of the SPU coating on as-polished TNTZ with a mirror surface. The adhesive strength of the SPU coating on the nanotube structure formed on TNTZ by anodization for 3,600s increases by 50%. These improvements in the adhesive strength of SPU are the result of an anchor effect introduced by the nanostructures formed by anodization. Fracture occurs at the interface of the nanoporous structure and the SPU coating layer. In contrast, in the case that SPU coating has been performed on the nanotube structure, fracture occurs inside the nanotubes. PMID:24433910

  20. Origin of thickness dependent spin reorientation transition of B2 type FeCo alloy films

    SciTech Connect

    Kim, Dongyoo; Hong, Jisang

    2013-12-07

    We have investigated the origin of thickness dependent spin reorientation transition (SRT) of B2 type FeCo alloy using the full potential linearized augmented plane wave method. It has been reported that FeCo alloy films on various substrates show a SRT from perpendicular to in-plane magnetization at an approximate thickness of 15 monolayers (MLs). The enhanced perpendicular magnetic anisotropy in bulk FeCo is attributed to a tetragonal distortion. However, we have found that the tetragonal distortion tends to suppress the magnetocrystalline anisotropy (MCA) energy at increasing film thickness in two-dimensional structure. In contrast, the magnitude of the shape anisotropy energy increases at increasing FeCo film thickness. Interestingly, the shape anisotropy overcomes the MCA and the SRT, from perpendicular anisotropy to in-plane magnetization, which occurs at a thickness of 15 ML. Consequently, we are able to clearly understand the physical mechanism of the thickness dependent SRT in terms of the competing reactions of these two counteracting contributions.

  1. Tritium release behavior from molten lithium-lead alloy by permeation through stainless steel type 304

    NASA Astrophysics Data System (ADS)

    Terai, Takayuki; Uozumi, Kouichi; Takahashi, Yoichi

    1992-09-01

    Tritium release behavior through stainless steel type 304 as a structural material in the presence of molten lithium-lead alloy (Li 17Pb 83) was studied at 600°C under neutron irradiation, The tritium permeation ratio to the secondary purge gas line was affected by the existence of H 2 in the purge gas. The tritium permeation rate changed with elapsed time, and decreased by 70% after 20 days since the start of an experimental series. This is attributed to the formation of an oxide layer on the SUS304 surface that is stable in H 2 atmosphere. An analytical model was applied to the experimental data on tritium release to obtain the mass transfer coefficient of tritium through the SUS304 tube.

  2. Distribution of distances between dislocations in different types of dislocation substructures in deformed Cu-Al alloys

    NASA Astrophysics Data System (ADS)

    Trishkina, L.; Cherkasova, T.; Zboykova, N.; Koneva, N.; Kozlov, E.

    2016-01-01

    The aim of the investigation was the determination of the statistic description of dislocation distribution in each dislocation substructures component forming after different deformation degrees in the Cu-Al alloys. The dislocation structures were investigated by the transmission diffraction electron microscopy method. In the work the statistic description of distance distribution between the dislocations, dislocation barriers and dislocation tangles in the deformed Cu-Al alloys with different concentration of Al and test temperature at the grain size of 100 m was carried out. It was established that the above parameters influence the dislocation distribution in different types of the dislocation substructures (DSS): dislocation chaos, dislocation networks without disorientation, nondisoriented and disoriented cells, in the walls and inside the cells. The distributions of the distances between dislocations in the investigated alloys for each DSS type formed at certain deformation degrees and various test temperatures were plotted.

  3. [Mechanical analysis on a new type of biodegradable magnesium-alloy stent].

    PubMed

    Wang, Xiaoping; Cui, Fuzhai; Li, Jianguo; Zhao, Xingshan

    2009-04-01

    Biodegradable magnesium-alloy stents have been employed in animal experiments and clinical researches in recent years. Magnesium-alloy stents have been reported to be biocompatible, and degradable due to corrosion after being implanted into blood vessel. However, magnesium alloy is brittle compared with stainless steel. This may cause strut break under large deformation. In this paper, a finite element model of magnesium-alloy stent was set up, with reference to pictures from Biotronik Corporation, to simulate the expanding and bending processes. The results of analysis show that the maximum strain during expanding reaches 20%, being greater than the elongation limit of the commercially available magnesium alloys. Therefore, to avoid strut breakage during expanding, the magnesium alloys should be custom-made. The plasticity of the material should be improved by grain refinement processes before practicable magnesium-alloy stents could be developed. PMID:19499798

  4. Ni{sub x}Cd{sub 1−x}O: Semiconducting alloys with extreme type III band offsets

    SciTech Connect

    Francis, Christopher A.; Detert, Douglas M.; Dubon, Oscar D.; Chen, Guibin; Yu, Kin M.; Walukiewicz, Wladek

    2015-01-12

    We have synthesized alloys of NiO and CdO that exhibit an extreme type III band offset and have studied the structural, electrical, and optical properties of Ni{sub x}Cd{sub 1−x}O over the entire composition range. The alloys are rocksalt structured and exhibit a monotonic shift of the (220) diffraction peak to higher 2θ angles with increasing Ni concentration. The electron mobility and electron concentration decrease with increasing x, and samples become insulating for Ni content x > 0.44. This decrease in n-type conductivity is consistent with the movement of the conduction band minimum from below to above the Fermi stabilization energy with increasing Ni content. The optical absorption edge of the alloys can be tuned continuously from CdO to NiO. The intrinsic gap of the alloys was calculated with the electrical and optical measurements and accounting for Burstein-Moss carrier filling and carrier-induced bandgap renormalization effects. We observe an uncommon composition dependence of the intrinsic bandgap on the alloy composition. The effect is tentatively attributed to an interaction between extended states of the conduction band and localized d-states of Ni.

  5. Reduced thermal conductivity due to scattering centers in p-type SiGe alloys

    NASA Technical Reports Server (NTRS)

    Beaty, John S.; Rolfe, Jonathon L.; Vandersande, Jan; Fleurial, Jean-Pierre

    1992-01-01

    Spark erosion was used to produce ultra-fine particles of SiGe thermoelectric material and boron nitride, an inert phonon-scattering material. A homogeneous powder was made by mixing the two powders. The mixture was hot pressed to produce a thermoelectric material with uniformity dispersed, ultra-fine, inert, phonon-scattering centers. It is shown that, in samples with inert boron nitride or silicon nitride, thermal conductivity of a SiGe alloy can be reduced by about 25 percent while maintaining the electrical properties of the samples. Annealing of all the samples at 1525 K caused grain growth to over a micron, eliminating the detrimental effect attributable to small grains. Only in the sample with boron nitride the thermal conductivity did remain well below that for standard p-type SiGe (about 25 percent), while the electrical resistivity and Seebeck coefficient were very close to the values for standard p-type 80/20 SiGe.

  6. Synthesis of Zr-based perovskite-type alloy phosphors by polymerized complex method

    NASA Astrophysics Data System (ADS)

    Komagata, Hiroki; Kato, Riku; Kato, Ariyuki

    2014-02-01

    To demonstrate the fabrication of inorganic electroluminescent (EL) devices using perovskite-type oxide phosphors by electrophoretic deposition (EPD), AZrO3:RE (A = Ca, Sr, Ba; RE = Eu, Tb) were synthesized by the polymerized complex method. AZrO3:Eu showed orange or red emissions and AZrO3:Tb showed blue-green or green emissions depending on their crystal structures. The emission intensity was found to be enhanced by introducing strains to the host matrices by Mg codoping or alloying. Inorganic EL devices prepared by EPD using BaZrO3:Eu and SrZrO3:Eu as the phosphor layers showed orange and blue emissions that were observable under room light, respectively, which is the first observation of EL emission from the devices prepared by EPD to the best of our knowledge. The combination of perovskite-type oxide phosphors and EPD was found to be a promising way to fabricate inorganic EL devices.

  7. Valence Band Structure of Highly Efficient p-type Thermoelectric PbTe-PbS Alloys

    SciTech Connect

    Jaworski, C. M.; Nielsen, Mechele; Wang, Hsin; Girard, Steven N.; Cai, Wei; Porter, Wallace D; Kanatzidis, Mercouri G.; Heremans, J. P.

    2013-01-01

    New experimental evidence is given relevant to the temperature-dependence of valence band structure of PbTe and PbTe1-xSx alloys (0.04 x 0.12), and its effect on the thermoelectric figure of merit zT. The x = 0.08 sample has zT ~ 1.55 at 773K. The magnetic field dependence of the high-temperature Hall resistivity of heavily p-type (> 1019 cm-3) Na-doped PbTe1-xSx reveals the presence of high-mobility electrons. This put in question prior analyses of the Hall coefficient and the conclusion that PbTe would be an indirect gap semiconductor at temperatures where its zT is optimal. Possible origins for these electrons are discussed: they can be induced by photoconductivity, or by the topology of the Fermi surface when the L and -bands merge. Negative values for the low-temperature thermopower are also observed. Our data show that PbTe continues to be a direct gap semiconductor at temperatures where the zT and S2 of p-type PbTe are optimal e.g. 700-900K. The previously suggested temperature induced rapid rise in energy of the heavy hole LVB relative to the light hole UVB is not supported by the experimental data.

  8. Short-range-order types in binary alloys: a reflection of coherent phase stability

    NASA Astrophysics Data System (ADS)

    Wolverton, C.; Ozolins, V.; Zunger, Alex

    2000-03-01

    The short-range order (SRO) present in disordered solid solutions is classified according to three characteristic system-dependent energies: (1) formation enthalpies of ordered compounds, (2) enthalpies of mixing of disordered alloys, and (3) the energy of coherent phase separation (the composition-weighted energy of the constituents each constrained to maintain a common lattice constant along an A/B interface). These energies are all compared against a common reference, the energy of incoherent phase separation (the composition-weighted energy of the constituents each at their own equilibrium volumes). Unlike long-range order (LRO), short-range order is determined by energetic competition between phases at a fixed composition , and hence only coherent phase-separated states are of relevance for SRO. We find five distinct SRO types, and give examples showing each of these five types, including Cu-Au, Al-Mg, GaP-InP, Ni-Au, and Cu-Ag. The SRO is calculated from first principles using the mixed-space cluster expansion approach combined with Monte Carlo simulations. Additionally, we examine the effect of inclusion of coherency strain in the calculation of SRO, and specifically examine the appropriate functional form for accurate SRO calculations.

  9. Dot arrays of L11 type Co-Pt ordered alloy perpendicular films

    NASA Astrophysics Data System (ADS)

    Shimatsu, T.; Sato, H.; Mitsuzuka, K.; Kataoka, H.; Aoi, H.; Okamoto, S.; Kitakami, O.

    2009-04-01

    Magnetic properties of dot arrays of L11 type Co-Pt ordered alloy perpendicular films were studied. L11-Co-Pt films with a large uniaxial magnetic anisotropy Ku of the order of 107 erg/cm3 were fabricated at a substrate temperature of 360 °C using ultrahigh vacuum sputter film deposition. Dot patterns with dot diameters of 70-200 nm were made using high resolution e-beam lithography and reactive ion etching (RIE). The values of Ku were measured by the GST method using the Anomalous Hall Effect; we observed the averaged signals of 6000 dots. The values of Ku for dot arrays of 10-nm-thick L11-Co50Pt50 films deposited on MgO(111) substrates (single crystal films) and glass disks (polycrystalline films) were nearly the same as those of the original films independent of D, indicating no significant etching damage by the RIE process. Magnetic force microscopy images revealed that all dots were single domains in the present D region. The coercivity Hc of the dot arrays was 25.0 kOe [MgO(111) substrate, D =70 nm] and 14.3 kOe (glass disks, D =80 nm). The switching field distribution σ /Hc was relatively small, σ /Hc=0.15, even for dot arrays fabricated on glass disks, indicating the homogeneous formation of a L11 type ordered structure in the Co50Pt50 layers.

  10. Use of titanium alloy swarf for the production of TK type hard metals

    SciTech Connect

    Kiparison, S.S.; Deulina, I.P.; Levinskii, Yu. V.; Petrov, A.P.

    1986-02-01

    Titanium alloy swarf has considerable potential as a raw material for the production of powders of titanium and its refractory compounds. This paper employs a trial batch (200 kg) of titanium carbide of nonstoichiometric composition made under industrial conditions for the production of TK grade hard metals. The compositions of VT-3-1 titanium alloy swarf and of titanium carbide, complex carbide and T5K10 alloy produced from it are presented. The results of metallographic analyses of the experimental batches of T5K10 alloy specimens are shown.

  11. Study on Effective Thermal Conductivity of Hydrogen Absorbing Alloys Bed for Passive Type Hydrogen Absorption and Desorption Systems

    NASA Astrophysics Data System (ADS)

    Shirato, Hiroyasu; Hamada, Yasuhiro; Suda, Takanori; Oka, Yoshiaki; Nagano, Katsunori

    This paper indicates the effective thermal conductivity of the hydrogen absorbing alloys bed of the passive type hydrogen storing systems for residential energy systems or stand-alone power supplies by experimental measurement. The effective thermal conductivity of the alloys bed depended on the cylinder pressure and the H/M composition of the alloys. Moreover, the conductivity was linear to the H/M composition at Plateau area. The introduction of 15 mass% Cu wires to the bed for improving the heat transfer was effective to raise the effective thermal conductivity of the bed. 50% of void fraction of the bed was also useful. The use of MmNi5 resulted in raising the effective thermal conductivity compared to the use of MmNi4.50Co0.10Al0.15Mn0.25 at the same H/M composition and the void fraction.

  12. Production and Precipitation Hardening of Beta-Type Ti-35Nb-10Cu Alloy Foam for Implant Applications

    NASA Astrophysics Data System (ADS)

    Mutlu, Ilven; Yeniyol, Sinem; Oktay, Enver

    2016-03-01

    In this study, beta-type Ti-35Nb-10Cu alloy foams were produced by powder metallurgy method for dental implant applications. 35% Nb was added to stabilize the beta-Ti phase with low Young's modulus. Cu addition enhanced sinterability and gave precipitation hardening capacity to the alloy. Sintered specimens were precipitation hardened in order to enhance the mechanical properties. Electrochemical corrosion behavior of the specimens was examined by electrochemical impedance spectroscopy in artificial saliva. Electrochemical impedance spectroscopy results indicated that the oxide film on the surface of foam is a bi-layer structure consisting of outer porous layer and inner barrier layer. Impedance values of barrier layer were higher than porous layer. Corrosion resistance of specimens decreased at high fluoride concentrations and at low pH of artificial saliva. Corrosion resistance of alloys was slightly decreased with aging. Mechanical properties, microstructure, and surface roughness of the specimens were also examined.

  13. Preferential orientation and thermoelectric properties of n-type Bi2Te2.85Se0.15 alloys by mechanical alloying and equal channel angular extrusion

    NASA Astrophysics Data System (ADS)

    Fan, X. A.; Yang, J. Y.; Zhu, W.; Bao, S. Q.; Duan, X. K.; Xiao, C. J.; Li, K.

    2007-09-01

    Starting from elemental bismuth, tellurium and selenium powders, n-type Bi2Te2.85Se0.15 solid solution with a fine microstructure was prepared by mechanical alloying and equal channel angular extrusion (ECAE) in the present work. The effect of extrusion temperature on the microstructure and thermoelectric properties of the as-ECAEed samples was investigated. A preferentially oriented microstructure with the basal planes (0 0 l) in the parallel direction to extrusion was formed, and the orientation factors F of the (0 0 l) planes of the 703 K and 753 K ECAEed Bi2Te2.85Se0.15 alloys were 0.26 and 0.28, respectively. The electrical resistivity and the Seebeck coefficient decreased, and the thermal conductivity increased with increasing extrusion temperature. The electrical and thermal transmission performances were strongly affected by the preferentially oriented microstructure and the preferential orientation improved the thermoelectric properties of the ECAEed Bi2Te2.85Se0.15 alloys in the parallel direction to extrusion. The maximum dimensionless figure of merit was obtained when extruded at 753 K at a testing temperature of 343 K, ZT = 0.66.

  14. Antiphase boundaries, inversion, and ferroelastic domains in the striped-type superstructure of ?-brass Cu-Al alloys

    NASA Astrophysics Data System (ADS)

    Koyama, Y.; Hatano, M.; Tanimura, M.

    1996-05-01

    Features of the striped-type superstructure in ?-brass Cu-Al alloys have been investigated mainly by transmission electron microscopy in order to understand the role of a rhombohedral distortion in its stability. From dark field images taken from alloys exhibiting the superstructure, it was found that there exist two types of ferroelastic rhombohedral domains, which are in a twin relation. In other words, the superstructure is characterized by a periodic array of the ferroelastic domains as well as inversion antiphase boundaries. Because charge density waves should be responsible for the formation of the superstructure, as suggested in our previous paper [Phys. Rev. B 40, 5378 (1989)], the rhombohedral distortion must play a crucial role in their appearance. Presumably the distortion enlarges parallel portions of the Fermi surface. On the basis of the present experimental data, the interplay between the striped-type superstructure and the rhombohedral ?-brass structure is also discussed.

  15. Relationship between Magnetocrystalline Anisotropy and Orbital Magnetic Moment in L10-Type Ordered and Disordered Alloys

    NASA Astrophysics Data System (ADS)

    Kota, Yohei; Sakuma, Akimasa

    2012-08-01

    The magnetocrystalline anisotropy energy and orbital magnetic moment in L10-type transition metal alloys such as FePt, FePd, FeNi, CoPt, CoPd, and MnAl are evaluated while continuously varying the degree of order. The electronic structure with spin--orbit interaction is calculated by employing the tight-binding linear muffin-tin orbital method based on the local spin-density approximation. To control the degree of order, we consider a substitutional disorder and then adopt the coherent potential approximation. The magnetocrystalline anisotropy energy ? E is roughly proportional to the power of the long-range order parameter S, i.e., ? E \\propto Sn (n 1.6{--}2.4). We also discuss the relationship between the magnetocrystalline anisotropy energy and the orbital magnetic moment. In the same compositional system with different degrees of order, the difference between the orbital magnetic moment in the magnetic easy axis and that in the hard one is proportional to ? E. However, the coefficient corresponding to the effective spin--orbit coupling is inconsistent with the intrinsic one in some cases.

  16. Influence of substrate metal alloy type on the properties of hydroxyapatite coatings deposited using a novel ambient temperature deposition technique.

    PubMed

    Barry, J N; Cowley, A; McNally, P J; Dowling, D P

    2014-03-01

    Hydroxyapatite (HA) coatings are applied widely to enhance the level of osteointegration onto orthopedic implants. Atmospheric plasma spray (APS) is typically used for the deposition of these coatings; however, HA crystalline changes regularly occur during this high-thermal process. This article reports on the evaluation of a novel low-temperature (<47°C) HA deposition technique, called CoBlast, for the application of crystalline HA coatings. To-date, reports on the CoBlast technique have been limited to titanium alloy substrates. This study addresses the suitability of the CoBlast technique for the deposition of HA coatings on a number of alternative metal alloys utilized in the fabrication of orthopedic devices. In addition to titanium grade 5, both cobalt chromium and stainless steel 316 were investigated. In this study, HA coatings were deposited using both the CoBlast and the plasma sprayed techniques, and the resultant HA coating and substrate properties were evaluated and compared. The CoBlast-deposited HA coatings were found to present similar surface morphologies, interfacial properties, and composition irrespective of the substrate alloy type. Coating thickness however displayed some variation with the substrate alloy, ranging from 2.0 to 3.0 μm. This perhaps is associated with the electronegativity of the metal alloys. The APS-treated samples exhibited evidence of both coating, and significantly, substrate phase alterations for two metal alloys; titanium grade 5 and cobalt chrome. Conversely, the CoBlast-processed samples exhibited no phase changes in the substrates after depositions. The APS alterations were attributed to the brief, but high-intensity temperatures experienced during processing. PMID:23589437

  17. Dot arrays of L1{sub 1} type Co-Pt ordered alloy perpendicular films

    SciTech Connect

    Shimatsu, T.; Mitsuzuka, K.; Aoi, H.; Sato, H.; Kataoka, H.; Okamoto, S.; Kitakami, O.

    2009-04-01

    Magnetic properties of dot arrays of L1{sub 1} type Co-Pt ordered alloy perpendicular films were studied. L1{sub 1}-Co-Pt films with a large uniaxial magnetic anisotropy K{sub u} of the order of 10{sup 7} erg/cm{sup 3} were fabricated at a substrate temperature of 360 deg. C using ultrahigh vacuum sputter film deposition. Dot patterns with dot diameters of 70-200 nm were made using high resolution e-beam lithography and reactive ion etching (RIE). The values of K{sub u} were measured by the GST method using the Anomalous Hall Effect; we observed the averaged signals of 6000 dots. The values of K{sub u} for dot arrays of 10-nm-thick L1{sub 1}-Co{sub 50}Pt{sub 50} films deposited on MgO(111) substrates (single crystal films) and glass disks (polycrystalline films) were nearly the same as those of the original films independent of D, indicating no significant etching damage by the RIE process. Magnetic force microscopy images revealed that all dots were single domains in the present D region. The coercivity H{sub c} of the dot arrays was 25.0 kOe [MgO(111) substrate, D=70 nm] and 14.3 kOe (glass disks, D=80 nm). The switching field distribution {sigma}/H{sub c} was relatively small, {sigma}/H{sub c}=0.15, even for dot arrays fabricated on glass disks, indicating the homogeneous formation of a L1{sub 1} type ordered structure in the Co{sub 50}Pt{sub 50} layers.

  18. Two different types of age-hardening behaviors in commercial dental gold alloys.

    PubMed

    Hisatsune, Kunihiro; Shiraishi, Takanobu; Takuma, Yasuko; Tanaka, Yasuhiro; Luciano, Rhodora H

    2007-04-01

    Age-hardening behavior during continuous heating in commercial dental casting gold alloys was investigated by means of electrical resistivity measurements, hardness tests and X-ray diffraction. Two distinguishable behaviors were detected. It is considered that the difference was attributed to the amount of platinum, and the atomic ratio of gold and copper in each alloy. The phase transformations during continuous heating progressed into two steps (stages I and II). Increase of the platinum addition in gold-based alloys retards the rate of the reaction and decreases remarkably the amount of stage I. PMID:17546416

  19. 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.

  20. Fatigue strength of titanium alloys with a VK-type detonation coating

    SciTech Connect

    Fedorenko, V.K.; Sergeev, V.V.; Shkanov, I.N.

    1995-07-01

    The influence of the structural, phase, and size factors, and the bonding of hard tungsten alloys to titanium alloy bases on the mechanism by which the system fails under alternating loads is studied. The failure mechanism of materials with detonation coatings applied by different methods is discussed in regard to the classical sequence of fatigue phenomena, i.e., hardening-softening and crack nucleation and growth.

  1. [New type titan alloy with shape memory for use in dental implantology].

    PubMed

    Grigor'ian, A S; Filonov, M R; Arkhipov, A V; Selezneva, I I; Zhukova, Iu S

    2013-01-01

    The paper summarizes the results of in vitro and in vivo studies that have proved biocompatibility and medical safety of Ta and Ti-Nb-Ta-bases alloys. According to some in vitro data Ti-Nb-Ta-based alloy possesses certain advantages when comparing to Ta-based. In particular, it contributes to elevation of viability of cellular elements and to definite increase of their adhesive potential. PMID:23528392

  2. Atomic structure of cascades of atomic displacements in metals and alloys after different types of radiation

    NASA Astrophysics Data System (ADS)

    Ivchenko, V. A.

    2016-02-01

    Using the methods of field ion microscopy, we studied radiation induced defects on an atomically clean surface and within a subsurface volume of platinum initiated by the interaction of neutron (E > 0.1MeV) and Ar+ beams (E = 30 keV). It is shown that the interaction of fast neutrons (E > 0.1 MeV) F = 6.7-1021 m-2, F = 3.5-1022 m-2 with matter leads to the formation in the amount of platinum such as radiation damage which occur after ion irradiation by beams of charged Ar+ ions with E = 30 keV, F = 1020 ion/m2. They are observed at a depth of about 1.5-2 nm irradiated under the surface of Pt by ions Ar+. Thus, we have carried out modeling of neutron impact with matter when replacing the neutron beam by an ion beam that causes the same radiation damage in the bulk of the material. Experimental results on atomic-spatial investigation of radiative defect formation in surface layers of materials, initiated by neutron bombardment (of Pt, E > 0.1 MeV) and ion implantation (in Cu3Au: E = 40 keV, F = 1020 ion/m2, j = 10-3 A/cm2), are considered. Quantitative estimates obtained for the size, shape, and volume fraction of cascades of atomic displacements formed under various types of irradiation in the surface layers of the materials. It is showing that the average size of radiation clusters after irradiation of platinum to a fast neutron fluence of 6.7-1022 m-2 (E > 0.1 MeV) is about 3.2 nm. The experimentally established average size of a radiation cluster (disordered zone) in the alloy after ion bombardment is 4×4×1.5 nm.

  3. Invar behavior of NANOPERM-type amorphous Fe-(Pt)-Zr-Nb-Cu-B alloys

    NASA Astrophysics Data System (ADS)

    Gondro, J.; ?wierczek, J.; Rz?cki, J.; Ciurzy?ska, W.; Olszewski, J.; Zbroszczyk, J.; B?och, K.; Osyra, M.; ?ukiewska, A.

    2013-09-01

    Transmission Mssbauer spectra of amorphous Fe86Zr7Nb1Cu1B5, Fe81Zr7Nb1Cu1B10 and Fe81Pt5Zr7Nb1Cu1B5 alloys in the as-quenched state and subjected to the accumulative annealing for 15 min in the temperature range from 573 K up to 750 K are presented. After these heat treatments the alloys remain in the amorphous state. The accumulative annealing for 15 min at 573 K and then 600 K of the Fe86Zr7Nb1Cu1B5 and Fe81Zr7Nb1Cu1B10 alloys causes the narrowing of the transmission Mssbauer spectra as compared to the as-quenched state and the decrease of the average hyperfine field induction which is connected with the invar effect. For similar behavior in Fe81Pt5Zr7Nb1Cu1B5 alloy the accumulative annealing up to 700 K is needed. With further increase of the annealing temperature up to 750 K the broadening of the Mssbauer spectra and the increase of the average hyperfine field induction occur. The lowest value of the average hyperfine field induction of amorphous samples is accompanied by the lowest value of the Curie temperature. The investigated amorphous alloys do not reach the magnetic saturation up to the magnetizing field of 2 T and the coefficient in Holstein-Primakoff term is about one order in magnitude larger than in other classical FeCo-based amorphous alloys due to the non-collinear magnetic structure. The Mssbauer spectra and hysteresis loops of the amorphous Fe86Zr7Nb1Cu1B5 alloy in the as-quenched state and after the accumulative annealing at 573+620 K for 15 min are sensitive to the tensile stresses subjected to the sample. Such behavior is ascribed to the invar anomalies.

  4. Formation Mechanism of Spinel-Type Inclusions in High-Alloyed Stainless Steel Melts

    NASA Astrophysics Data System (ADS)

    Park, Joo Hyun

    2007-08-01

    Fundamental thermodynamics of the relationship between high-alloyed stainless steel melts (Fe-20 mass pct Cr-13 mass pct Ni-3 mass pct Si) and the inclusions were investigated. The formation mechanism of the inclusions containing the spinel crystals was developed based on the experimental results and from the compositions of the inclusions in the steel samples taken during plant operations. The molar content of alumina in the inclusions was found to be linearly proportional to the increase of aluminum content, indicating that the inclusions could contain alumina even with less than about 200 ppm aluminum in the steel melt, e.g., steel melts that were mainly deoxidized by silicon. Furthermore, the composition of the inclusions is shown to be a function of the activity of the deoxidizers such as aluminum and silicon in the steel melt. From the analysis of the plant samples, it was found that the contents of MgO and Al2O3 in the calcium silicate type inclusions increased continuously as the steel melt transfers from the argon oxygen decarburization (AOD) converter to the tundish. This composition change in the inclusions originated from the reduction of MgO and Al2O3 in the slags or refractories by silicon in the steel melt. Increases of MgO and Al2O3 contents were prominent in tundish samples, and thus, the spinel phase could be crystallized in the calcium silicate inclusion matrix in the tundish; and finally the spinel crystals grew during cooling of the steel melt through the continuous casting (CC) mold and in the slabs. On the other hand, manganese silicate type inclusions containing chromium oxide were observed after tapping of the molten steel to the ladle. The MnO and Cr2O3 in these inclusions was initially reduced by silicon in the steel melt in the ladle treatment (LT) process, followed by further reduction by aluminum through the LT to the CC mold. The fractions of inclusions containing spinel crystals in cast slabs were negligible at the alumina content of less than about 20 mass pct, while they critically increased at alumina contents greater than about 20 mass pct.

  5. Effect of indium (In) on corrosion and passivity of a beta-type Ti-Nb alloy in Ringer's solution

    NASA Astrophysics Data System (ADS)

    Gebert, Annett; Oswald, Steffen; Helth, Arne; Voss, Andrea; Gostin, Petre Flaviu; Rohnke, Marcus; Janek, Jürgen; Calin, Mariana; Eckert, Jürgen

    2015-04-01

    Beta-phase Ti-Nb-based alloys are considered as new generation of biomaterials with improved mechanical compatibility for load-bearing implant applications. Small homogeneously dissolved In additions have a positive impact on the elastic properties of beta-type Ti-40Nb. For (Ti-40Nb)-4In the best match between low Young's modulus, high elastic energy and appropriate strength was achieved. In the present study the effect of In addition to Ti-40Nb on the corrosion and passivation behavior in Ringer's solution is assessed by means of potentiodynamic polarization, ICP-OES metal release analysis, XPS and ToF-SIMS for passive film characterization. Like Ti-40Nb, (Ti-40Nb)-4In exhibits very low corrosion rates (icorr = 0.1-0.2 μA/cm2) and stable anodic passivity (ipass = 3-4 μA/cm2). Small In additions do not have a detectable effect on the anodic response of the alloy. For both beta-phase alloys metal release rates are below the quantification limits of ICP-OES. Their strong passivating nature is governed by the formation of thin barrier-type Ti- and Nb-oxide films. Passive films on (Ti-40Nb)-4In surfaces which were formed during OCP exposure or anodic polarization comprise oxidized In species (In2O3, In(OH3)). From the viewpoint of corrosion stability (Ti-40Nb)-4In appears to be suitable for implant applications.

  6. The role of nanoscale defect features in enhancing the thermoelectric performance of p-type nanostructured SiGe alloys.

    PubMed

    Bathula, Sivaiah; Jayasimhadri, M; Gahtori, Bhasker; Singh, Niraj Kumar; Tyagi, Kriti; Srivastava, A K; Dhar, Ajay

    2015-08-01

    Despite SiGe being one of the most widely studied thermoelectric materials owing to its application in radioisotope thermoelectric generators (RTG), the thermoelectric figure-of merit (ZT) of p-type SiGe is still quite low, resulting in poor device efficiencies. In the present study, we report a substantial enhancement in ZT∼ 1.2 at 900 °C for p-type nanostructured Si80Ge20 alloys by creating several types of defect features within the Si80Ge20 nanostructured matrix in a spectrum of nano to meso-scale dimensions during its nanostructuring, by employing mechanical alloying followed by spark plasma sintering. This enhancement in ZT, which is ∼25% over the existing state-of-the-art value for a p-type nanostructured Si80Ge20 alloy, is primarily due to its ultralow thermal conductivity of ∼2.04 W m(-1) K(-1) at 900 °C, resulting from the scattering of low-to-high wavelength heat-carrying phonons by different types of defect features in a range of nano to meso-scale dimensions in the Si80Ge20 nanostructured matrix. These include point defects, dislocations, isolated amorphous regions, nano-scale grain boundaries and more importantly, the nano to meso-scale residual porosity distributed throughout the Si80Ge20 matrix. These nanoscale multi-dimensional defect features have been characterized by employing scanning and transmission electron microscopy and correlated with the electrical and thermal transport properties, based on which the enhancement of ZT has been discussed. PMID:26138852

  7. Microstructural variations induced by gravity level during directional solidification of near-eutectic iron-carbon type alloys

    NASA Technical Reports Server (NTRS)

    Stefanescu, Doru M.; Fiske, Michael R.; Curreri, Peter A.

    1986-01-01

    The effects of gravity on the microstructure of directionally solidified near-eutectic cast irons are studied, using a Bridgman-type automatic directional solidification furnace aboard a NASA KC-135 aircraft which flies parabolic arcs and generates alternating periods of low-g (0.01 to 0.001 g, 30 seconds long) and high-g (1.8 g, 1.5 minutes long). Results show a refinement of the interlamellar spacing of the eutectic during low-g processing of metastable Fe-C eutectic alloys. Low-g processing of stable Fe-C-Si eutectic alloys (lamellar or spheroidal graphic) results in a coarsening of the eutectic grain structure. Secondary dendrite arm spacing of austenite increases in low-g and decreases in high-g. The effectiveness of low-gravity in the removal of buoyancy-driven graphite phase segregation is demonstrated.

  8. Antiferromagnetic half-metals, gapless half-metals, and spin gapless semiconductors: The D0{sub 3}-type Heusler alloys

    SciTech Connect

    Gao, G. Y. Yao, Kai-Lun

    2013-12-02

    High-spin-polarization materials are desired for the realization of high-performance spintronic devices. We combine recent experimental and theoretical findings to theoretically design several high-spin-polarization materials in binary D0{sub 3}-type Heusler alloys: gapless (zero-gap) half-metallic ferrimagnets of V{sub 3}Si and V{sub 3}Ge, half-metallic antiferromagnets of Mn{sub 3}Al and Mn{sub 3}Ga, half-metallic ferrimagnets of Mn{sub 3}Si and Mn{sub 3}Ge, and a spin gapless semiconductor of Cr{sub 3}Al. The high spin polarization, zero net magnetic moment, zero energy gap, and slight disorder compared to the ternary and quaternary Heusler alloys make these binary materials promising candidates for spintronic applications. All results are obtained by the electronic structure calculations from first-principles.

  9. Age Hardening Kinetics in 7xxx Type (Al-Mg-Zn) Alloys

    SciTech Connect

    Vevecka-Priftaj, A.; Lamani, E.; Fjerdingen, J.; Langsrud, Y.; Gjoennes, J.; Hansen, V.

    2007-04-23

    Age hardening in industrial 7xxx alloys at the temperature 100 deg. and 150 deg. C up to 144 hrs, after solid solution treatments at 450 deg. and 550 deg. C, has been followed by measurements of Vickers hardness, scanning and transmission electron microscopy. The influence of silicon on phase and kinetic of age hardening zones and precipitates has been studied. High iron and silicon content increase the number of primary particle in the alloy. Size distribution of {eta}'-precipitates has been determined.

  10. Mechanical properties of modified low cobalt powder metallurgy Udimet 700 type alloys

    NASA Technical Reports Server (NTRS)

    Harf, Fredric H.

    1989-01-01

    Eight superalloys derived from Udimet 700 were prepared by powder metallurgy, hot isostatically pressed, heat treated and their tensile and creep rupture properties determined. Several of these alloys displayed properties superior to those of Udimet 700 similarly prepared, in one case exceeding the creep rupture life tenfold. Filter clogging by extracted gamma prime, its measurement and significance are discussed in an appendix.

  11. Magsimal-59, an AlMgMnSi-type squeeze-casting alloy designed for temper F

    SciTech Connect

    Hielscher, U.; Sternau, H.; Koch, H.; Franke, A.J.

    1996-10-01

    To get high mechanical properties using standard squeeze casting alloys (for example A356) it is indispensable to make a heat treatment. That means solution heat treatment and quenching and artificially aging. For this reason, the authors were challenged to develop an alloy that provides sophisticated mechanical properties without any heat treatment. Compared to A 356 T6 values in brackets, the new alloy has yield strength > 21 ksi (> 32 ksi) tensile strengths > 42 ksi (43 ksi) and elongation > 15% (10%) in temper F. fatigue strength (r = {minus}1, high frequency pulsation test) is > {+-} 16 ksi (13.5). To meet these properties, a casting process with high solidification velocity like squeeze casting or high pressure die-casting is necessary. Magsimal-59 is of the AlMgMnSi-type. The microstructure consists of {alpha}-Al and a very fine dispersed ternary eutectic. The microstructure and the influence of cooling rate on the mechanical properties will be discussed including some examples of castings.

  12. Effect of specimen type and size on fracture resistance curve determination for CuCrZr alloy

    NASA Astrophysics Data System (ADS)

    Karjalainen-Roikonen, Pivi; Pyykknen, Mika; Thtinen, Seppo

    1998-10-01

    The precipitation hardened copper alloy CuCrZr is one of the candidate materials for the first wall and divertor components of ITER. In order to validate the applicability of copper alloys in the structural components of ITER, the effect of neutron irradiation on the fracture toughness behaviour has to be studied. Fracture toughness testing of irradiated materials requires the use of miniaturised specimens and the verification of specimen size effects on fracture toughness test results. In the present study the effects of specimen type, size as well as temperature on the ductile tearing fracture resistance behaviour of CuCrZr alloy will be shown. The applicability of miniaturised specimens for fracture resistance curve determination is considered by studying the allowable crack extension with which the miniaturised specimens still have similar fracture resistance curves as full-size specimens. The crack length and J-integral values will be compared to ASTM standard requirements for the maximum allowable crack extension and J-integral values in the fracture resistance test.

  13. Investigation of a new type of Al{sub 3}Ti-based L1{sub 2} alloy with second phase precipitation

    SciTech Connect

    Hu, G.; Sun, J.; Weng, X.; Li, T.; Chen, S.

    1995-07-01

    Since the L1{sub 2} structured Al{sub 3}Ti alloy exists only in a narrow compositional range, further alloying of the single phase L1{sub 2} alloy to improve its property seems hardly successful. Developing two-phase or multiphase Al{sub 3}Ti alloys may be an effective approach for strengthening and toughening. In this article, a new type of Al{sub 3}Ti-based alloy which has a L1{sub 2} matrix with precipitates of a second phase is reported. The quaternary alloys based on Al{sub 67}Mn{sub 8}Ti{sub 25}, and modified with Nb additions, consist of an L1{sub 2} matrix and DO{sub 22} second phase particles in the annealed state, but the second phase can be dissolved by solution treatment and precipitated during high temperature aging. Remarkable strengthening and promising compressive ductility were exhibited by the experimental alloy. The influence of composition on the microstructure and properties of the alloys are reported also.

  14. Direct synthesis of BiCuChO-type oxychalcogenides by mechanical alloying

    SciTech Connect

    Pele, Vincent; Barreteau, Celine; Berardan, David; Zhao, Lidong; Dragoe, Nita

    2013-07-15

    We report on the direct synthesis of BiCuChO based materials by mechanical alloying (Ch=Se, Te). We show that contrary to the synthesis paths used in the previous reports dealing with this family of materials, which use costly annealings in closed silica tubes under controlled atmosphere, this new synthesis route enables the synthesis of pure phase materials at room temperature under air, with reasonable milling time. This synthesis procedure is easily scalable for large scale applications. - Highlights: • Phase pure BiCuSeO doped and undoped prepared by mechanical alloying. • Synthesis performed under air at room temperature. • Electrical properties similar to that of samples synthesized by a classical path.

  15. Invar and Elinvar type amorphous Fe-Cr-B alloys with high corrosion resistance

    NASA Technical Reports Server (NTRS)

    Kikuci, M.; Fukamichi, K.; Masumoto, T.

    1987-01-01

    Amorphous (Fe(1-x)Cr(x))85B15 alloys (x = 0 to 0.15) were prepared from the melts by rapid quenching using a single roller techinque, and their Invar and Elinvar characteristics and corrosion resistance were investigated. With an increase in chromium content the Curie temperature and the saturation magnetic moment per iron atom decreased monotonically, while the crystallization temperature incresed gradually. The thermal expansion coefficient alpha around room temperature became slightly larger with increasing chromium content. Nevertheless, these amorphous alloys exhibited excellent Invar characteristics below the Curie temperature. The value of Young's modulus increased remarkably in a relatively low magnetic field and then saturated at a field of about 80 kA/m, showing a large delta E effect. Its value as well as a longitudinal linear magnetostriction became smaller with an increase in chromium content. The temperature coefficient of Young's modulus changed from postive to negative, and the temperature range showing the Elinvar characteristics became narrower with chromium content. The temperature coefficient of delay time determined from the values of alpha and e was very small. The corrosion resistance of these alloys was extremely improved by chromium addition.

  16. Crevice Repassivation Potential of Alloy 22 in High-Nitrate Dust Deliquescence Type Environments

    SciTech Connect

    Lian, T; Gdowski, G E; Hailey, P D; Rebak, R B

    2007-02-08

    The nitrate ion (NO{sub 3}{sup -}) is an inhibitor for crevice corrosion of Alloy 22 (N06022) in chloride (Cl{sup -}) aqueous solutions. Naturally formed electrolytes may contain both chloride and nitrate ions. The higher the ratio R = [NO{sub 3}{sup -}]/[Cl{sup -}] in the solution the stronger the inhibition of crevice corrosion. Atmospheric desert dust contains both chloride and nitrate salts, generally based on sodium (Na{sup +}) and potassium (K{sup +}). Some of these salts may deliquescence at relatively low humidity at temperatures on the order of 150 C and higher. The resulting deliquescent brines are highly concentrated and especially rich in nitrate. Electrochemical tests have been performed to explore the anodic behavior of Alloy 22 in high chloride high nitrate electrolytes at temperatures as high as 150 C at ambient atmospheres. Naturally formed brines at temperatures higher than 120 C do not induce crevice corrosion in Alloy 22 because they contain high levels of nitrate. The inhibitive effect of nitrate on crevice corrosion is still active for temperatures higher than 100 C.

  17. Influence of alloy components on electromagnetic characteristics of core/shell-type Fe-Ni nanoparticles

    NASA Astrophysics Data System (ADS)

    Lu, Bo; Huang, Hao; Dong, Xing Long; Zhang, Xue Feng; Lei, Jun Peng; Sun, Jian Peng; Dong, Chuang

    2008-12-01

    Fe-Ni alloy nanoparticles with various alloy components were fabricated by a direct current arc-discharge method. By dispersing the nanoparticles homogeneously into a paraffin matrix, the complex permittivity (?r=?r'+i?r?) and permeability (?r=?r'+i?r?) of the nanoparticles have been investigated in the frequency range of 2-18 GHz and the effects of alloy components on the electromagnetic parameters were discussed. It is found that the permittivities of the nanoparticles are lower than those of the microscale counterparts and almost independent of frequency. The magnetic loss is attributed to natural resonance and the resonance peak shifts to high frequency range with the increase in Fe content. Better microwave absorption performances can be obtained by adjusting the composition and tailoring the core/shell structures to balance the electromagnetic parameters. The calculated results indicate that the Fe-Ni nanoparticles with 49 wt % Ni exhibit excellent electromagnetic wave (EMW) absorption properties (reflection loss <-20 dB) over the range of 7.6-16.0 GHz in the thickness of 1.02-1.70 mm. The mechanism of effective EMW introduction and attenuation is discussed on the basis of the experimental results.

  18. Effect of Sn Doping on the Thermoelectric Properties of n-type Bi2(Te,Se)3 Alloys

    NASA Astrophysics Data System (ADS)

    Lee, Jae-Uk; Lee, Deuk-Hee; Kwon, Beomjin; Hyun, Dow-Bin; Nahm, Sahn; Baek, Seung-Hyub; Kim, Jin-Sang

    2015-06-01

    In the present work, 0.01-0.05wt.% Sn-doped Bi2(Te0.9Se0.1)3 alloys were prepared by mechanical deformation followed by hot pressing, and their thermoelectric properties were studied. We observed that the Sn element is a very effective dopant as an acceptor to control the carrier concentration in the n-type Bi2(Te0.9Se0.1)3 alloys to optimize their thermoelectric property. The n-type carrier concentration can be controlled from 4.2 1019/cm3 to 2.4 1019/cm3 by 0.05wt.% Sn-doping. While the Seebeck coefficient and the electrical resistivity are both increased with doping, the power factor remains the same. Therefore, we found that the thermoelectric figure-of-merit becomes maximized at 0.75 when the thermal conductivity has a minimum value for the 0.03wt.% Sn-doped sample.

  19. Microstructure, elastic deformation behavior and mechanical properties of biomedical ?-type titanium alloy thin-tube used for stents.

    PubMed

    Tian, Yuxing; Yu, Zhentao; Ong, Chun Yee Aaron; Kent, Damon; Wang, Gui

    2015-05-01

    Cold-deformability and mechanical compatibility of the biomedical ?-type titanium alloy are the foremost considerations for their application in stents, because the lower ductility restricts the cold-forming of thin-tube and unsatisfactory mechanical performance causes a failed tissue repair. In this paper, ?-type titanium alloy (Ti-25Nb-3Zr-3Mo-2Sn, wt%) thin-tube fabricated by routine cold rolling is reported for the first time, and its elastic behavior and mechanical properties are discussed for the various microstructures. The as cold-rolled tube exhibits nonlinear elastic behavior with large recoverable strain of 2.3%. After annealing and aging, a nonlinear elasticity, considered as the intermediate stage between "double yielding" and normal linear elasticity, is attributable to a moderate precipitation of ? phase. Quantitive relationships are established between volume fraction of ? phase (V?) and elastic modulus, strength as well as maximal recoverable strain (?max-R), where the ?max-R of above 2.0% corresponds to the V? range of 3-10%. It is considered that the "mechanical" stabilization of the (?+?) microstructure is a possible elastic mechanism for explaining the nonlinear elastic behavior. PMID:25706668

  20. Nanocomposite Nd-rich Nd-Fe-B alloys: Approaching ideal Stoner-Wohlfarth type behavior

    NASA Astrophysics Data System (ADS)

    Girt, Er.; Krishnan, Kannan M.; Thomas, G.; Altounian, Z.

    2000-03-01

    Starting from rapidly quenched NdδFe13.1B(2.05⩽δ⩽147.6) alloys and by appropriate annealing, the microstructure was tailored from strongly interacting Nd2Fe14B grains to magnetically isolated single domain Nd2Fe14B grains embedded in a nonmagnetic Nd-rich matrix (α-Nd and γ-Nd). This change in microstructure was found to have a large effect on coercivity, i.e., coercivity, μ0Hc, increases with an increase of the Nd concentration from 1.25 T in Nd2.05Fe13.1B to 2.75 T in Nd147.6Fe13.1B at 290 K. Using transmission electron microscopy, the Nd2Fe14B grains in Nd147.6Fe13.1B were confirmed to be randomly oriented platelets with the c axis normal to the plate and an average size of 100×40×25 nm. For these randomly oriented, noninteracting, single domain Nd2Fe14B grains, the coercivity was calculated using a Stoner-Wohlfarth model which included the shape anisotropy of the grains. The observed coercivity of Nd2Fe14B in such nanocomposite Nd147.6Fe13.1B alloys is ˜83% of its theoretical value.

  1. Two types of the first cycle effects in copper based shape memory alloys

    SciTech Connect

    Hornbogen, E.; Mertinger, V.; Spielfeld, J.

    1999-05-21

    The effects of thermo mechanical treatments on transformation temperatures and hysteresis are important for many shape memory applications. Depending on the field of application either a large or small hysteresis is required. A high hysteresis for the first cycle is especially important for one way applications, when the material has to be stored in the transformable martensitic condition. For this reason the material is deformed slightly in the martensitic state (T{sub MF}alloy. Treppman et al., Spielfeld et al. and also Zhang et al. found that the defects formed in martensite domain boundaries are able to induce a shift of austenite temperatures to significantly higher values and thus increase the transformation hysteresis of the first cycle. In this work it will be shown that a different first cycle effect occurs after ausforming of the Copper based shape memory alloy. For the first cycle the A{sub s} temperature is lowered. For the following DSC cycles it is increased nearly to its original value after betatising.

  2. SEM, EDS, EPMA-WDS and EBSD characterization of carbides in HP type heat resistant alloys

    SciTech Connect

    Laigo, J.; Christien, F.; Le Gall, R.; Tancret, F. Furtado, J.

    2008-11-15

    The microstructure of centrifugally cast heat resistant alloys of the HP-series (Fe-35Ni-25Cr-0.4C, wt.%) contains several minor phases, like carbides (M{sub 7}C{sub 3}, M{sub 23}C{sub 6} and MC). Several alloys are characterized by means of scanning electron microscopy in back-scattered electron imaging and energy dispersive spectroscopy, of electron probe micro-analysis by X-ray wavelength dispersive spectroscopy, and of electron back-scattered diffraction. On the one hand, scanning electron microscopy imaging in the back-scattered mode, associated with energy dispersive spectroscopy analysis and electron back-scattered diffraction, can lead to the identification of all phases, but with a lack of accuracy in certain cases. On the other hand, electron probe micro-analysis by X-ray wavelength dispersive spectroscopy alone can always provide a strict identification of all phases, with additional precise information on phase composition, including for light elements, which is important in the case of carbides.

  3. Thermoelectric properties of fine-grained FeVSb half-Heusler alloys tuned to p-type by substituting vanadium with titanium

    NASA Astrophysics Data System (ADS)

    Zou, Minmin; Li, Jing-Feng; Kita, Takuji

    2013-02-01

    Fine-grained Ti-doped FeVSb half-Heusler alloys were synthesized by combining mechanical alloying and spark plasma sintering and their thermoelectric properties were investigated with an emphasis on the influences of Ti doping and phase purity. It was found that substituting V with Ti can change the electrical transport behavior from n-type to p-type due to one less valence electron of Ti than V, and the sample with nominal composition FeV0.8Ti0.4Sb exhibits the largest Seebeck coefficient and the maximum power factor. By optimizing the sintering temperature and applying annealing treatment, the power factor is significantly improved and the thermal conductivity is reduced simultaneously, resulting in a ZT value of 0.43 at 500 °C, which is relatively high as for p-type half-Heusler alloys containing earth-abundant elements.

  4. Electrochemical corrosion and modeling studies of types 7075 and 2219 aluminum alloys in a nitric acid + ferric sulfate deoxidizer solution

    NASA Astrophysics Data System (ADS)

    Savas, Terence P.

    The corrosion behavior of types 7075-T73 and 2219-T852 high strength aluminum alloys have been investigated in a HNO3 + Fe2(SO 4)3 solution. The materials are characterized in the time domain using the electrochemical noise resistance parameter (Rn) and in the frequency-domain using the spectral noise impedance parameter ( Rsn). The Rsn parameter is derived from an equivalent electrical circuit model that represents the corrosion test cell schematic used in the present study. These calculated parameters are correlated to each other, and to corresponding scanning electron microscopy (SEM) examinations of the corroded surfaces. In addition, energy dispersive spectroscopy (EDS) spectra are used in conjunction with SEM exams for particle mapping and identification. These constituent particles are characterized with respect to their size and composition and their effect on the localized corrosion mechanisms taking place. Pitting mechanisms are identified as 'circumferential' where the particles appeared noble with respect to the aluminum matrix and by 'selective dissolution' where they are anodic to the aluminum matrix. The electrochemical data are found to be in good agreement with the surface examinations. Specifically, the electrochemical parameters Rn and Rsn were consistent in predicting the corrosion resistance of 7075-T73 to be lower than for the 2219-T852 alloy. Other characteristic features used in understanding the corrosion mechanisms include the open circuit potential (OCP) and coupling-current time records.

  5. High-velocity-oxidation performance of metal-chromium-aluminum (MCrAl), cermet, and modified aluminide coatings on IN-100 and type VIA alloys at 1093 C

    NASA Technical Reports Server (NTRS)

    Deadmore, D. L.

    1974-01-01

    Cermet, MCrAl, and modified aluminide types of coatings applied to IN-100 and NASA-TRW-VIA alloy specimens were cyclically oxidation tested in a high velocity (Mach 1) gas flame at 1093 C. Several coating compositions of each type were evaluated for oxidation resistance. The modified aluminide coating, Pt-Al, applied to alloy 6A proved to be the best, providing oxidation protection to approximately 750 hours based on weight change measurements. The second best, a CoCrAlY coating applied to 6A, provided protection to 450 hours. The third best was a cermet + aluminide coating on 6A with a protection time to 385 hours.

  6. The characterization of shape memory effect for low elastic modulus biomedical {beta}-type titanium alloy

    SciTech Connect

    Wang Liqiang; Lu Weijie; Qin Jining; Zhang Fan; Zhang Di

    2010-05-15

    This work investigates the textures of biomedical TiNbTaZr alloy rolled by 99% cold reduction ratios in thickness. The relationship between textures and superelasticity of the specimens treated at 873 K and 1223 K for 1.2 ks is studied. The microstructure of tensile specimen is investigated by transmission electron microscopy. Textures of cold-rolled and heat-treated specimens are studied. During unloading, the anisotropy of superelastic strain and pure elastic strain in the heat-treated specimens is observed. Superelastic strain along rolling direction and transverse direction is larger than those along 45 deg. from rolling direction while pure elastic strain shows the highest value along 45 deg. from rolling direction in the specimen treated at 873 K. For the specimen treated at 1223 K, higher pure elastic strain is obtained along rolling direction. The maximum recovered strain around 2.11% is obtained along rolling direction.

  7. Enhanced cycling stability and high rate dischargeability of (La,Mg)2Ni7-type hydrogen storage alloys with (La,Mg)5Ni19 minor phase

    NASA Astrophysics Data System (ADS)

    Liu, Jingjing; Han, Shumin; Han, Da; Li, Yuan; Yang, Shuqin; Zhang, Lu; Zhao, Yumeng

    2015-08-01

    The A2B7-type lanthanum (La)-magnesium (Mg)-nickel (Ni)-based alloy with single (La,Mg)2Ni7 phase and different amounts of (La,Mg)5Ni19 minor phase was obtained by step-wise sintering. The impact of (La,Mg)5Ni19 phase on the alloy's microstructure and electrochemical performance was subsequently studied. It was found that the average subunit volume in (La,Mg)5Ni19 phase is smaller than that in (La,Mg)2Ni7 phase, resulting in increases of strains inside the alloys and decreases of cell volumes. During battery charge/discharge, the (La,Mg)5Ni19 phase network scattered in the alloys relieves internal stress, alleviates pulverization and oxidation of the alloys, stabilizes the stacking structures against amorphization, and finally improves the cycling stability of the alloys. Furthermore, (La,Mg)5Ni19 phase with higher Ni content desorbs hydrogen ahead of (La,Mg)2Ni7 phase. The reduced hydrogen pressure in (La,Mg)5Ni19 phase can subsequently lead to the fast discharge of (La,Mg)2Ni7 phase, thus making a remarkable improvement in high rate dischargeability at 1500 mA g-1 from 46.2% to 58.9% with increasing (La,Mg)5Ni19 phase abundance from 0 to 37.4 wt.%. Therefore, it is believed that A2B7-type La-Mg-Ni-based alloys with A5B19-type minor phase are promising prototypes for high-power and long-lifetime nickel/metal hydride battery electrode materials.

  8. Atomic interaction of the MEAM type for the study of intermetallics in the Al-U alloy

    NASA Astrophysics Data System (ADS)

    Pascuet, M. I.; Fernndez, J. R.

    2015-12-01

    Interaction for both pure Al and Al-U alloys of the MEAM type are developed. The obtained Al interatomic potential assures its compatibility with the details of the framework presently adopted. The Al-U interaction fits various properties of the Al2U, Al3U and Al4U intermetallics. The potential verifies the stability of the intermetallic structures in a temperature range compatible with that observed in the phase diagram, and also takes into account the greater stability of these structures relative to others that are competitive in energy. The intermetallics are characterized by calculating elastic and thermal properties and point defect parameters. Molecular dynamics simulations show a growth of the Al3U intermetallic in the Al/U interface in agreement with experimental evidence.

  9. Mechanical alloying synthesis of K{sub 2}Bi{sub 8}Se{sub 13}-type solid solutions.

    SciTech Connect

    Toumpas, N.; Kyratsi, T.; Hatzikraniotis, E.; Tsiappos, A.; Pavlidou, E.; Paraskevopoulos, K. M.; Chung, D. Y.; Kanatzidis, M. G.; Materials Science Division; Univ. of Cyprus; Aristotle Univ. Thessaloniki; Northwestern Univ.

    2008-01-01

    Solid solutions of K{sub 2}Bi{sub 8-x}Sb{sub x}Se{sub 13} are an interesting series of materials for thermoelectric investigations due to their very low thermal conductivity and highly anisotropic electrical properties. In this work, we aimed to synthesize solid solutions of O-K{sub 2}Bi{sub 8-x}Sb{sub x}Se{sub 13} type materials using powder techniques. The synthesis was based on mechanical alloying as well as sintering procedures. The products were studied in terms of structural features, composition and purity with powder x-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy. Preliminary results on thermoelectric properties as well as IR reflectivity measurements are presented.

  10. Corrosion resistance of AA6063-Type Al-Mg-Si alloy by silicon carbide in sodium chloride solution for marine application

    NASA Astrophysics Data System (ADS)

    Fayomi, Ojo Sunday Isaac; Abdulwahab, Malik; Popoola, Abimbola Patricia Idowu; Asuke, Ferdinand

    2015-12-01

    The present work focused on corrosion inhibition of AA6063 type (Al-Mg-Si) alloy in sodium chloride (NaCl) solution with a silicon carbide inhibitor, using the potentiodynamic electrochemical method. The aluminium alloy surface morphology was examined, in the as-received and as-corroded in the un-inhibited state, with scanning electron microscopy equipped with energy dispersive spectroscopy (SEM-EDS). The results obtained via linear polarization indicated a high corrosion potential for the unprotected as-received alloy. Equally, inhibition efficiency as high as 98.82% at 10.0 g/v silicon carbide addition was obtained with increased polarization resistance ( R p), while the current density reduced significantly for inhibited samples compared to the un-inhibited aluminium alloy. The adsorption mechanism of the inhibitor aluminium alloy follows the Langmuir adsorption isotherm. This shows that the corrosion rate of aluminium alloy with silicon carbide in NaCl environment decreased significantly with addition of the inhibitor.

  11. NDE detectability of fatigue-type cracks in high-strength alloys: NDI reliability assessments

    NASA Technical Reports Server (NTRS)

    Christner, Brent K.; Long, Donald L.; Rummel, Ward D.

    1988-01-01

    This program was conducted to generate quantitative flaw detection capability data for the nondestructive evaluation (NDE) techniques typically practiced by aerospace contractors. Inconel 718 and Haynes 188 alloy test specimens containing fatigue flaws with a wide distribution of sizes were used to assess the flaw detection capabilities at a number of contractor and government facilities. During this program 85 inspection sequences were completed presenting a total of 20,994 fatigue cracks to 53 different inspectors. The inspection sequences completed included 78 liquid penetrant, 4 eddy current, and 3 ultrasonic evaluations. The results of the assessment inspections are presented and discussed. In generating the flaw detection capability data base, procedures for data collection, data analysis, and specimen care and maintenance were developed, demonstrated, and validated. The data collection procedures and methods that evolved during this program for the measurement of flaw detection capabilities and the effects of inspection variables on performance are discussed. The Inconel 718 and Haynes 188 test specimens that were used in conducting this program and the NDE assessment procedures that were demonstrated, provide NASA with the capability to accurately assess the flaw detection capabilities of specific inspection procedures being applied or proposed for use on current and future fracture control hardware program.

  12. Quantification of zinc atoms in a surface alloy on copper in an industrial-type methanol synthesis catalyst.

    PubMed

    Kuld, Sebastian; Conradsen, Christian; Moses, Poul Georg; Chorkendorff, Ib; Sehested, Jens

    2014-06-01

    Methanol has recently attracted renewed interest because of its potential importance as a solar fuel. Methanol is also an important bulk chemical that is most efficiently formed over the industrial Cu/ZnO/Al2O3 catalyst. The identity of the active site and, in particular, the role of ZnO as a promoter for this type of catalyst is still under intense debate. Structural changes that are strongly dependent on the pretreatment method have now been observed for an industrial-type methanol synthesis catalyst. A combination of chemisorption, reaction, and spectroscopic techniques provides a consistent picture of surface alloying between copper and zinc. This analysis enables a reinterpretation of the methods that have been used for the determination of the Cu surface area and provides an opportunity to independently quantify the specific Cu and Zn areas. This method may also be applied to other systems where metal-support interactions are important, and this work generally addresses the role of the carrier and the nature of the interactions between carrier and metal in heterogeneous catalysts. PMID:24764288

  13. Comparison of different pressing techniques for the preparation of n-type silicon-germanium thermoelectric alloys

    SciTech Connect

    Harringa, J.L.; Cook, B.A.

    1996-06-01

    Improvements to state-of-the-art Si{sub 80}Ge{sub 20} thermoelectric alloys have been observed in laboratory-scale samples by the powder metallurgy techniques of mechanical alloying and hot pressing. Incorporating these improvements in large scale compacts for the production of thermoelectric generator elements is the next step in achieving higher efficiency RTGs. This paper discusses consolidation of large quantities of mechanically alloyed powders into production size compacts. Differences in thermoelectric properties are noted between the compacts prepared by the standard technique of hot uniaxial pressing and hot isostatic pressing. Most significant is the difference in carrier concentration between the alloys prepared by the two consolidation techniques.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  15. Low-cycle fatigue of Type 347 stainless steel and Hastelloy alloy X in hydrogen gas and in air at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Jaske, C. E.; Rice, R. C.; Buchheit, R. D.; Roach, D. B.; Porfilio, T. L.

    1976-01-01

    An investigation was conducted to assess the low-cycle fatigue resistance of two alloys, Type 347 stainless steel and Hastelloy Alloy X, that were under consideration for use in nuclear-powered rocket vehicles. Constant-amplitude, strain-controlled fatigue tests were conducted under compressive strain cycling at a constant strain rate of 0.001/sec and at total axial strain ranges of 1.5, 3.0, and 5.0 %, in both laboratory-air and low-pressure hydrogen-gas environments at temperatures from 538 to 871 C. Specimens were obtained from three heats of Type 347 stainless steel bar and two heats of Hastelloy Alloy X. The tensile properties of each heat were determined at 21, 538, 649, and 760 C. The continuous cycling fatigue resistance was determined for each heat at temperatures of 538, 760, and 871 C. The Type 347 stainless steel exhibited equal or superior fatigue resistance to the Hastelloy Alloy X at all conditions of this study.

  16. Determination of thermal conductivities of Sn-Zn lead-free solder alloys with radial heat flow and Bridgman-type apparatus

    NASA Astrophysics Data System (ADS)

    Meydaneri, Fatma; Saati, Buket; Gndz, Mehmet; zdemir, Mehmet

    2013-11-01

    The variations of thermal conductivities of solid phases versus temperature for pure Sn, pure Zn and Sn-9 wt.% Zn, Sn-14 wt.% Zn, Sn-50 wt.% Zn, Sn-80 wt.% Zn binary alloys were measured with a radial heat flow apparatus. The thermal conductivity ratios of liquid phase to solid phase for the pure Sn, pure Zn and eutectic Sn-9 wt.% Zn alloy at their melting temperature are found with a Bridgman-type directional solidification apparatus. Thus, the thermal conductivities of liquid phases for pure Sn, pure Zn and eutectic Sn-9 wt.% Zn binary alloy at their melting temperature were evaluated by using the values of solid phase thermal conductivities and the thermal conductivity ratios of liquid phase to solid phase.

  17. Mg acceptor energy levels in AlxInyGa1-x-yN quaternary alloys: An approach to overcome the p -type doping bottleneck in nitrides

    NASA Astrophysics Data System (ADS)

    Wang, Fei; Li, Jingbo; Li, Shu-Shen; Xia, Jian-Bai; Wei, Su-Huai

    2008-03-01

    The MgGa acceptor energy levels in GaN and random Al8In4Ga20N32 quaternary alloys are calculated using the first-principles band-structure method. We show that due to wave function localization, the MgGa acceptor energy level in the alloy is significantly lower than that of GaN, although the two materials have nearly identical band gaps. Our study demonstrates that forming AlxInyGa1-x-yN quaternary alloys can be a useful approach to lower acceptor ionization energy in the nitrides and thus provides an approach to overcome the p -type doping difficulty in the nitride system.

  18. Surface alloying of Mg alloys after surface nanocrystallization.

    PubMed

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

    2008-05-01

    Surface nanocrystallization using a surface mechanical attrition treatment effectively activates the surface of magnesium alloys due to the increase in grain boundary diffusion channels. As a result, the temperature of subsequent surface alloying treatment of pure Mg and AZ91 alloy can be reduced from 430 degrees C to 380 degrees C. Thus, it is possible to combine the surface alloying process with the solution treatment for this type of alloy. After surface alloying, the hardness of the alloyed layer is 3 to 4 times higher than that of the substrate and this may significantly improve the wear resistance of magnesium alloys. PMID:18572716

  19. N-type Doped PbTe and PbSe Alloys for Thermoelectric Applications

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey (Inventor); LaLonde, Aaron (Inventor); Pei, Yanzhong (Inventor); Wang, Heng (Inventor)

    2014-01-01

    The present invention demonstrates that weak scattering of carriers leads to a high mobility and therefore helps achieve low electric resistivity with high Seebeck coefficient for a thermoelectric material. The inventors demonstrate this effect by obtaining a thermoelectric figure of merit, zT, higher than 1.3 at high temperatures in n-type PbSe, because of the weak scattering of carriers in the conduction band as compared with that in the valence band. The invention further demonstrates favorable thermoelectric transport properties of n-type PbTe.sub.1-xI.sub.x with carrier concentrations ranging from 5.8.times.10.sup.18-1.4.times.10.sup.20 cm.sup.-3.

  20. The Correlations Between Heat Treatment, Microstructure and Magnetic Properties in a 2:17 Type Samarium:. Transition Metal Magnetic Alloy

    NASA Astrophysics Data System (ADS)

    Kianvash, A.

    2000-09-01

    In this work the correlations between heat treatment (HT), metallographic structures and magnetic properties in a 2:17-type Sm(Co0.67 Cu0.08 Fe0.22 Zr0.03)8.92 magnetic alloy have been investigated. It was found that for a fixed solution treatment (ST) time of 4 h, magnetic properties were critically dependent on the ST temperature prior to a standard step aging treatment (SAT). When the ST temperature was too low (T ? 1140 C) then the inhomogeneity of the "as- cast" condition was not completely removed and this gave rise to a very uneven distribution of precipitates on subsequent SAT. When the ST temperature was too high (T ? 1180 C) then incipient melting was observed at grain boundaries and phase interfaces which again led to a very uneven distribution of precipitates on SAT. An optimum ST temperature (T 1170 C) was established which resulted in an even distribution of precipitates on SAT and hence the best magnetic properties.

  1. Atomic states, potential energies, volumes, stability and brittleness of ordered FCC TiAl 2 type alloys

    NASA Astrophysics Data System (ADS)

    Xie, Y. Q.; Tao, H. J.; Peng, H. J.; Li, X. B.; Liu, X. B.; Peng, K.

    2005-09-01

    In this paper, the framework of the systematic science of alloys (SSA) is presented. It has been proved that according to the basic information of sequences of characteristic crystals in the FCC Ti-Al system, not only the states, potential energies and volumes of atoms at various lattice points, and average atomic states, average atomic potential energies, average atomic volumes and lattice constants of the cells, as well as cohesive energies, heats of formation, bulk moduli and Debye temperatures for h- and ?-TiAl 2 compounds can be calculated, but also the compositional variations of the atomic states, atomic potential energies, atomic volumes, lattice constants, cohesive energies, heat of formation, bulk moduli and Debye temperatures of the ordered FCC TiAl 2 type alloys and their Ti- and Al-components can be calculated by the SSA framework. The average atomic states of h- and ?-TiAl 2 compounds are, respectively, ?(h-TiAl)=1/6?10,1Ti+1/6?10,2Ti+1/2?8,4Al+1/6?6,6Al and ?(?-TiAl)=1/3?10,1Ti+1/3?8,6Al+1/3?6,6Al. At low temperature, the h-TiAl 2 compound with lower potential energy and smaller volume is more stable than the ?-TiAl 2 compound, because the ?10,2Ti and the ?8,4Al atoms have lower potential energies and smaller volumes than the corresponding ?10,1Ti and ?8,6Al atoms. But at high temperature, the ?-TiAl 2 compound with larger vibrational entropy and larger mixing entropy due to containing ?8,6Al- and more the same state ?10,1Ti-atoms with higher potential energy may be more stable than h-TiAl 2 compound. The calculated lattice constants of ?-TiAl 2 compounds are in good agreement with experimental ones. The relationships of brittleness with atomic states and potential energy wave planes for FCC TiAl 2 compounds have been analysed.

  2. Influence of the temperature, the interaction time, and the type of ore on the transition of boron to an alloy during reduction

    NASA Astrophysics Data System (ADS)

    Zhuchkov, V. I.; Sychev, A. V.; Babenko, A. A.

    2015-07-01

    The melting of an FSB high-silicon boron-containing ferroalloy using FS65 ferrosilicon and borate ore (colemanite) as a reducing agent is studied. The reduction of boron is estimated as a function of the temperature, the interaction time, and the type of boron-containing raw material. On the basis of the obtained results, the main parameters of making of a complex Fe-Si-B alloy have been determined.

  3. Effect of Fe substitution for Co on structure, electrical resistivity, and magnetic properties of Heusler type Co2-xFe1+xSi alloys

    NASA Astrophysics Data System (ADS)

    Srinivas, K.; Prasanna Kumari, T.; Manivel Raja, M.; Kamat, S. V.

    2013-07-01

    The effect of substitution of Fe for Co on structure, electrical resistivity, and magnetic properties of full Heusler type Co2-xFe1+xSi (0 ? x ? 1) alloys was investigated. The order-disorder transitions were studied by X-ray diffraction measurements followed by Rietveld refinement analysis as well as by 57Fe Mssbauer spectroscopy. The results revealed that these alloys consist of mostly L21 ordered phase and some B2 disordered phase up to x < 0.25. However, for x ? 0.25, the alloys consisted of L21 ordered phase and DO3 disordered phase. The electrical resistivity behaviour with temperature showed two distinct regions. In region I, the resistivity exhibited two-magnon scattering mechanism (T9/2 dependence) showing a signature of half-metallic ferromagnetism. However, in region II, the resistivity behaviour was governed by Tn power law and n value was found to vary from 2.98 to 1.38 with increasing Fe content. The room temperature magnetization studies confirmed the enhancement of the magnetic moment with increasing Fe substitution up to x = 0.5 in Co2-xFe1+xSi alloys. However, upon further increasing Fe content, the magnetic moment was found to decrease and this was explained in terms of localization effects originating mainly in the Co anti-site disorder.

  4. Microstructural characterization of a Zr-Ti-Ni-Mn-V-Cr based AB{sub 2}-type battery alloy

    SciTech Connect

    Shi, Zhan

    1999-01-01

    Transmission Electron Microscopy (TEM), combined with X-ray Diffraction (XRD) and Scanning Electron Microscopy (SEM) was employed to investigate a proprietary and multicomponent AB{sub 2} type Nickel-Metal Hydride (Ni-MH) battery alloy. This material was prepared by High Pressure Gas Atomization (HPGA) and examined in both the as-atomized and heat treated condition. TEM examination showed a heavily faulted dendritic growth structure in as-atomized powder. Selected Area Diffraction (SAD) showed that this region consisted of both a cubic C15 structure with lattice constant a=7.03 and a hexagonal C14 structure with lattice parameter a=4.97 {angstrom}, c=8.11 {angstrom}. The Orientation Relationship (OR) between the C14 and C15 structures was determined to be (111)[1{bar 1}0]{sub C15}//(0001)[11{bar 2}0]{sub C14}. An interdendritic phase possessing the C14 structure was also seen. There was also a very fine grain region consisting of the C14 structure. Upon heat treatment, the faulted structure became more defined and appeared as intercalation layers within the grains. Spherical particles rich in Zr and Ni appeared scattered at the grain boundaries instead of the C14 interdendritic phase. The polycrystalline region also changed to a mixture of C14 and C15 structures. These results as well as phase stability of the C15 and C14 structures based on a consideration of atomic size factor and the average electron concentration are discussed.

  5. Atomic states, potential energies, volumes, stability and brittleness of ordered FCC Ti 3Al-type alloys

    NASA Astrophysics Data System (ADS)

    Xie, Y. Q.; Peng, H. J.; Liu, X. B.; Peng, K.

    2005-05-01

    According to the basic information of sequences of characteristic atoms in the FCC Ti-Al system, the compositional variations of the atomic states, atomic potential energies, atomic volumes, lattice constants and cohesive energies of the ordered FCC Ti 3Al-type alloys have been calculated. Without considering the influence of the second nearest neighbouring atoms, the D0 22- and L1 2-Ti 3Al compounds have the same atomic state, same atomic volume, same lattice constant and same cohesive energy. Their average atomic state is 0.75[Ar](3d n) 0.229(3d c) 2.5669(4s c) 0.5448(4s f) 0.6593 +0.25[Ne](3s c) 1.772(3p c) 1.008(3s f) 0.22. Considering the influence of second neighbouring atoms, the calculated atomic potential energies, formation energies and lattice constants of the D0 22- and L1 2-Ti 3Al compounds are, respectively, ?a=-4.8158 eV/atom, ? H=-0.3378 eV/atom, a=0.39131 nm, c=0.44108 nm, c/a=1.1272; and ? a=-4.7952 eV/atom, ? H=-0.3172 eV/atom, a=0.41091 nm. The D0 22-Ti 3Al compound is slightly more stable than the L1 2- Ti 3Al compound. The correctness of these results has been proved indirectly by the calculated results of the D0 22- and L1 2-TiAl 3 as well as HfGa 2- and ZrGa 2-type TiAl 2 compounds with the same basic information and the same method. Between 0 and 40 at.%Al, the HCP lattice is more stable than the FCC lattice, for which the atomic state factor may play determining action. The brittleness order of these compounds is L1 2-Ti 3Al

  6. Optical anisotropy and domain structure of multiferroic Ni-Mn-Ga and Co-Ni-Ga Heusler-type alloys

    NASA Astrophysics Data System (ADS)

    Ivanova, A. I.; Gasanov, O. V.; Kaplunova, E. I.; Kalimullina, E. T.; Zalyotov, A. B.; Grechishkin, R. M.

    2015-03-01

    A study is made of the reflectance anisotropy of martensitic and magnetic domains in ferromagnetic shape memory alloys (FSMA) Ni-Mn-Ga and Co-Ni-Ga. The reflectance of metallographic sections of these alloys was measured in the visible with the aid of standard inverted polarized light microscope with a 360° rotatable specimen stage. Calculations are presented for the estimation of image contrast values between neighboring martensite twins. Qualitative and quantitative observations and angular measurements in reflected polarized light proved to be useful for the analysis of specific features of the martensite microstructure of multiferroic materials.

  7. Random-type scanning patterns in laser shock peening without absorbing coating in 2024-T351 Al alloy: A solution to reduce residual stress anisotropy

    NASA Astrophysics Data System (ADS)

    Correa, C.; Peral, D.; Porro, J. A.; Díaz, M.; Ruiz de Lara, L.; García-Beltrán, A.; Ocaña, J. L.

    2015-10-01

    Laser Shock Peening (LSP) is considered as an alternative technology to shot peening (SP) for the induction of compressive residual stresses in metallic alloys in order to improve their fatigue, corrosion and wear resistance. Since laser pulses generated by high-intensity laser systems cover only a small area, laser pulses are generally overlapped and scanned in a zigzag-type pattern to cover completely the surface to be treated. However, zigzag-type scanning patterns induce residual stress anisotropy as collateral effect. The purpose of this paper is to describe and explain, for the first time and with the aid of the numerical model developed by the authors, the influence of the scanning pattern directionality on the residual stress tensor. As an effective solution, the authors propose the application of random-type scanning patterns instead of zigzag-type in order to reduce the mentioned residual stress anisotropy.

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

    PubMed

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

    2006-01-01

    This study investigated the joint properties of a cast Fe-Pt magnetic alloy (Fe-36 at % Pt) laser welded to three gold alloys. The gold alloys used were ADA Type II and Type IV gold alloys, and an Ag-based (Ag-Au) gold alloy. Cast plates (0.5 x 3.0 x 10 mm) were prepared for each alloy. After the cast Fe-Pt plates were heat treated, they were butted against each of the three alloys and then laser welded with Nd:YAG laser at 200 V. Homogeneously welded specimens were also prepared for each alloy. Tensile testing was conducted at a crosshead speed of 1 mm/min. Failure load (N) and elongation (%) were recorded. After tensile testing, the fractured surfaces were examined with the use of SEM. The failure-load values of the group of alloys welded homogeneously were ranked in the order of: Ag-Au alloy > Type IV alloy > Type II alloy > Fe-Pt alloy. The Type IV alloy welded to Fe-Pt alloy had the highest failure-load value among the three alloys tested. The elongation results tended to follow a similar pattern. The results of this study indicated that Type IV gold alloy is a suitable alloy for metal frameworks to which cast Fe-Pt magnetic alloy is laser welded. PMID:16044421

  9. A comparative study on improved Arrhenius-type and artificial neural network models to predict high-temperature flow behaviors in 20MnNiMo alloy.

    PubMed

    Quan, Guo-zheng; Yu, Chun-tang; Liu, Ying-ying; Xia, Yu-feng

    2014-01-01

    The stress-strain data of 20MnNiMo alloy were collected from a series of hot compressions on Gleeble-1500 thermal-mechanical simulator in the temperature range of 1173 ? 1473 K and strain rate range of 0.01 ? 10 s(-1). Based on the experimental data, the improved Arrhenius-type constitutive model and the artificial neural network (ANN) model were established to predict the high temperature flow stress of as-cast 20MnNiMo alloy. The accuracy and reliability of the improved Arrhenius-type model and the trained ANN model were further evaluated in terms of the correlation coefficient (R), the average absolute relative error (AARE), and the relative error (?). For the former, R and AARE were found to be 0.9954 and 5.26%, respectively, while, for the latter, 0.9997 and 1.02%, respectively. The relative errors (?) of the improved Arrhenius-type model and the ANN model were, respectively, in the range of -39.99% ? 35.05% and -3.77% ? 16.74%. As for the former, only 16.3% of the test data set possesses ?-values within 1%, while, as for the latter, more than 79% possesses. The results indicate that the ANN model presents a higher predictable ability than the improved Arrhenius-type constitutive model. PMID:24688358

  10. A Comparative Study on Improved Arrhenius-Type and Artificial Neural Network Models to Predict High-Temperature Flow Behaviors in 20MnNiMo Alloy

    PubMed Central

    Yu, Chun-tang; Liu, Ying-ying; Xia, Yu-feng

    2014-01-01

    The stress-strain data of 20MnNiMo alloy were collected from a series of hot compressions on Gleeble-1500 thermal-mechanical simulator in the temperature range of 1173∼1473 K and strain rate range of 0.01∼10 s−1. Based on the experimental data, the improved Arrhenius-type constitutive model and the artificial neural network (ANN) model were established to predict the high temperature flow stress of as-cast 20MnNiMo alloy. The accuracy and reliability of the improved Arrhenius-type model and the trained ANN model were further evaluated in terms of the correlation coefficient (R), the average absolute relative error (AARE), and the relative error (η). For the former, R and AARE were found to be 0.9954 and 5.26%, respectively, while, for the latter, 0.9997 and 1.02%, respectively. The relative errors (η) of the improved Arrhenius-type model and the ANN model were, respectively, in the range of −39.99%∼35.05% and −3.77%∼16.74%. As for the former, only 16.3% of the test data set possesses η-values within ±1%, while, as for the latter, more than 79% possesses. The results indicate that the ANN model presents a higher predictable ability than the improved Arrhenius-type constitutive model. PMID:24688358

  11. Subband Structure and Effective Mass in the Inversion Layer of a Strain Si-Based Alloy P-Type MOSFET.

    PubMed

    Chen, Kuan-Ting; Fan, Jun Wei; Chang, Shu-Tong; Lin, Chung-Yi

    2015-03-01

    In this paper, the subband structure and effective mass of an Si-based alloy inversion layer in a PMOSFET are studied theoretically. The strain condition considered in our calculations is the intrinsic strain resulting from growth of the silicon-carbon alloy on a (001) Si substrate and mechanical uniaxial stress. The quantum confinement effect resulting from the vertically effective electric field was incorporated into the k p calculation. The distinct effective mass, such as the quantization effective mass and the density-of-states (DOS) effective mass, as well as the subband structure of the silicon-carbon alloy inversion layer for a PMOSFET under substrate strain and various effective electric field strengths, were all investigated. Ore results show that subband structure of relaxed silicon-carbon alloys with low carbon content are almost the same as silicon. We find that an external stress applied parallel to the channel direction can efficiently reduce the effective mass along the channel direction, thus producing hole mobility enhancement. PMID:26413635

  12. 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.

  13. Development and validation of capabilities to measure thermal properties of layered monolithic U-Mo alloy plate-type fuel

    SciTech Connect

    Burkes, Douglas; Casella, Andrew M.; Buck, Edgar C.; Casella, Amanda J.; Edwards, Matthew K.; MacFarlan, Paul J.; Pool, Karl N.; Smith, Frances N.; Steen, Franciska H.

    2014-07-19

    The uranium-molybdenum (U-Mo) alloy in a monolithic form has been proposed as one fuel design capable of converting some of the world’s highest power research reactors from the use of high enriched uranium (HEU) to low enriched uranium (LEU). One aspect of the fuel development and qualification process is to demonstrate appropriate understanding of thermal conductivity behavior of the fuel system as a function of temperature and expected irradiation conditions. The purpose of this paper is to verify and validate the functionality of equipment methods installed in hot cells for eventual measurements on irradiated uranium-molybdenum (U-Mo) monolithic fuel specimens, procedures to operate the equipment, and models to extract the desired thermal properties. The results presented here demonstrate the adequacy of the equipment, procedures and models that have been developed for this purpose based on measurements conducted on surrogate depleted uranium-molybdenum (DU-Mo) alloy samples containing a zirconium diffusion barrier and clad in aluminum alloy 6061 (AA6061). The results are in excellent agreement with thermal property data reported in the literature for similar U-Mo alloys as a function of temperature.

  14. Half-metallicity in Heusler-type Fe2Cr1‑x Co x Si alloys

    NASA Astrophysics Data System (ADS)

    Ramudu, M.; Inamdar, Swaleha; Arout Chelvane, J.; Manivel Raja, M.; Kamat, S. V.

    2016-02-01

    The effects of the substitution of Cr with Co on microstructure, phase composition, structure, magnetic, and electrical properties in \\text{F}{{\\text{e}}2}\\text{C}{{\\text{r}}1-x}\\text{C}{{\\text{o}}x}\\text{Si} (0  ⩽  x  ⩽  1) alloys was investigated to identify the compositions with the potential to exhibit half-metallicity. The microstructural and structural studies revealed that only \\text{F}{{\\text{e}}2}\\text{C}{{\\text{r}}1-x}\\text{C}{{\\text{o}}x}\\text{Si} alloys with x  ⩾  0.5 exhibited the desired single phase L21 full Heusler alloy structure. Both the saturation magnetization (M s) and Curie temperature (T C) were found to increase with the increase in Co concentration. The experimentally measured M s values are in good agreement with the Slater–Pauling rule. The electrical resistivity measurements in the temperature range 10–300 K gives indirect evidence of half-metallic behaviour in these alloys at low temperatures. The temperature range in which the half-metallic behaviour was observed also increased with an increase in Co concentration.

  15. Development and Validation of Capabilities to Measure Thermal Properties of Layered Monolithic U-Mo Alloy Plate-Type Fuel

    NASA Astrophysics Data System (ADS)

    Burkes, Douglas E.; Casella, Andrew M.; Buck, Edgar C.; Casella, Amanda J.; Edwards, Matthew K.; MacFarlan, Paul J.; Pool, Karl N.; Smith, Frances N.; Steen, Franciska H.

    2014-07-01

    The uranium-molybdenum (U-Mo) alloy in a monolithic form has been proposed as one fuel design capable of converting some of the world's highest power research reactors from the use of high enriched uranium to low enriched uranium. One aspect of the fuel development and qualification process is to demonstrate appropriate understanding of the thermal-conductivity behavior of the fuel system as a function of temperature and expected irradiation conditions. The purpose of this paper is to verify functionality of equipment installed in hot cells for eventual measurements on irradiated uranium-molybdenum (U-Mo) monolithic fuel specimens, refine procedures to operate the equipment, and validate models to extract the desired thermal properties. The results presented here demonstrate the adequacy of the equipment, procedures, and models that have been developed for this purpose based on measurements conducted on surrogate depleted uranium-molybdenum (DU-Mo) alloy samples containing a Zr diffusion barrier and clad in aluminum alloy 6061 (AA6061). The results are in excellent agreement with thermal property data reported in the literature for similar U-Mo alloys as a function of temperature.

  16. Effect of texture of polishing particle on the surface roughness of a cobalt-chromium alloy using a centrifugal shooting type polishing machine.

    PubMed

    Ono, Takahiro; Ishikawa, Kaori; Yamaba, Osamu; Nokubi, Takashi

    2005-12-01

    In a previous report, we investigated the influence of the shooting angle of polishing particle on the surface roughness of a cobalt-chromium (Co-Cr) alloy using a centrifugal shooting type polishing machine. In the present work, we examined the effects of the texture of polishing particle and polishing time on the surface roughness of Co-Cr alloy cast specimens. Nine different textures of polishing particle were investigated with respect to core material and particle abrasiveness: three different elastic body cores (core A, hard chloroprene rubber; core B, soft chloroprene rubber; core C, natural rubber) and three different green carborundum powders as abrasives (#800, #3000, and #6000). Polishing was performed under a fixed shooting angle of 30 degrees for six different polishing times (1, 2, 3, 5, 7, and 10 minutes). Surface roughness (Ra, Sm) and cutting depth on the polished surface were measured after each polishing stage. Surface roughness was significantly improved within three minutes, particularly using a polishing particle with rough carborundum powder (#800 or #3000) and a heavy core (core A or core B). Cutting depth increased in proportion to polishing time and roughness of carborundum powder, and was least with core C. These results suggested that a polishing particle composed of core B and #3000 carborundum paste was superior for the intermediate polishing of a Co-Cr alloy, and that polishing time should be limited to within three minutes. PMID:16445008

  17. Effects of micro- and nano-scale wave-like structures on fatigue strength of a beta-type titanium alloy developed as a biomaterial.

    PubMed

    Narita, Kengo; Niinomi, Mitsuo; Nakai, Masaaki

    2014-01-01

    Some newly developed ?-type titanium alloys for biomedical applications exhibit distinctive heterogeneous structures. The formation mechanisms for these structures have not been completely revealed; however, understanding these mechanisms could lead to improving their properties. In this study, the heterogeneous structures of a Ti-29Nb-13Ta-4.6Zr alloy (TNTZ), which is a candidate for next-generation metallic biomaterials, were analyzed. Furthermore, the effects of such heterogeneous structures on the mechanical strength of this alloy, including fatigue strength, were revealed by comparing its strength to that of homogenous TNTZ. The heterogeneous structures were characterized micro-, submicro- and nano-scale wave-like structures. The formation mechanisms of these wave-like structures are found to be different from each other even though their morphologies are similar. It is revealed that the micro-, submicro- and nano-scale wave-like structures are caused by elemental segregation, crystal distortion related to kink band and phase separation into ? and ?', respectively. However, these structures have no significant effect on both tensile properties and fatigue strength comparison with homogeneous structure in this study. PMID:24184863

  18. Amorphous metal alloy

    DOEpatents

    Wang, R.; Merz, M.D.

    1980-04-09

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  19. The structural, electronic and dynamic properties of the L1{sub 2}- type Co{sub 3}Ti alloy

    SciTech Connect

    Arikan, Nihat; Özduran, Mustafa

    2014-10-06

    The structural, electronic and dynamic properties of the cubic Co{sub 3}Ti alloy in L1{sub 2} structure have been investigated using a pseudopotential plane wave (PP-PW) method within the generalized gradient approximation proposed by Perdew–Burke–Ernzerhof (GGA-PBE). The structural properties, including the lattice constant, the bulk modulus and its pressure derivative agree reasonably with the previous results. The density of state (DOS), projected density of state (PDOS) and electronic band structure are also reported. The DOS shows that Co{sub 3}Ti alloy has a metallic character since the energy bands cross the Fermi level. The density of states at Fermi level mainly comes from the Co-3d states. Phonon dispersion curves and their corresponding total densities of states were obtained using a linear response in the framework of the density functional perturbation theory. All computed phonon frequencies are no imaginer and thus, Co{sub 3}Ti alloy is dynamically stable. The zone center phonon modes have been founded to be 9.307, 9.626 and 13.891 THz for Co{sub 3}Ti.

  20. Thermoelectric properties of the Heusler-type Fe{sub 2}VTa{sub x}Al{sub 1?x} alloys

    SciTech Connect

    Renard, Krystel Mori, Arinori; Yamada, Yuichiro; Tanaka, Suguru; Nishino, Yoichi; Miyazaki, Hidetoshi

    2014-01-21

    This study focuses on the thermoelectric properties of the Heusler-type Fe{sub 2}VTa{sub x}Al{sub 1?x} alloys (0?x?0.12). By means of Rietveld analyses on synchrotron X-ray diffraction patterns, it is shown that the Ta atoms enter sites occupied by V atoms in the stoichiometric Fe{sub 2}VAl alloy, while the ejected V atoms are transferred to the vacant Al sites. This Ta substitution leads to an improvement of the n-type thermoelectric properties owing to two mechanisms. On the one hand, the atoms position in the structure leads to an off-stoichiometric effect such as already observed in V-rich Fe{sub 2}V{sub 1+y}Al{sub 1?y} compounds: the Seebeck coefficient is increased towards negative absolute values and the electrical resistivity is decreased, with a large shift of their peak temperature towards higher temperature. The maximum power factor is 6.5??10{sup ?3} W/mK{sup 2} for x?=?0.05 at 340?K. On the other hand, the heavy element Ta substitution combined with this off-stoichiometric effect leads to a large decrease of the thermal conductivity, owing to an increase of the scattering events. Consequently, the dimensionless figure of merit is seen to reach higher values than for the Fe{sub 2}V{sub 1+y}Al{sub 1?y} alloys, i.e., 0.210.22 around 400500?K for x?=?0.05 and 500?K for x?=?0.08.

  1. In vivo corrosion, tumor outcome, and microarray gene expression for two types of muscle-implanted tungsten alloys.

    PubMed

    Schuster, B E; Roszell, L E; Murr, L E; Ramirez, D A; Demaree, J D; Klotz, B R; Rosencrance, A B; Dennis, W E; Bao, W; Perkins, E J; Dillman, J F; Bannon, D I

    2012-11-15

    Tungsten alloys are composed of tungsten microparticles embedded in a solid matrix of transition metals such as nickel, cobalt, or iron. To understand the toxicology of these alloys, male F344 rats were intramuscularly implanted with pellets of tungsten/nickel/cobalt, tungsten/nickel/iron, or pure tungsten, with tantalum pellets as a negative control. Between 6 and 12 months, aggressive rhabdomyosarcomas formed around tungsten/nickel/cobalt pellets, while those of tungsten/nickel/iron or pure tungsten did not cause cancers. Electron microscopy showed a progressive corrosion of the matrix phase of tungsten/nickel/cobalt pellets over 6 months, accompanied by high urinary concentrations of nickel and cobalt. In contrast, non-carcinogenic tungsten/nickel/iron pellets were minimally corroded and urinary metals were low; these pellets having developed a surface oxide layer in vivo that may have restricted the mobilization of carcinogenic nickel. Microarray analysis of tumors revealed large changes in gene expression compared with normal muscle, with biological processes involving the cell cycle significantly up-regulated and those involved with muscle development and differentiation significantly down-regulated. Top KEGG pathways disrupted were adherens junction, p53 signaling, and the cell cycle. Chromosomal enrichment analysis of genes showed a highly significant impact at cytoband 7q22 (chromosome 7) which included mouse double minute (MDM2) and cyclin-dependant kinase (CDK4) as well as other genes associated with human sarcomas. In conclusion, the tumorigenic potential of implanted tungsten alloys is related to mobilization of carcinogenic metals nickel and cobalt from corroding pellets, while gene expression changes in the consequent tumors are similar to radiation induced animal sarcomas as well as sporadic human sarcomas. PMID:22982072

  2. Alloying of aluminum-beryllium alloys

    NASA Astrophysics Data System (ADS)

    Molchanova, L. V.; Ilyushin, V. N.

    2013-01-01

    The existing phase diagrams of Al-Be- X alloys, where X is an alloying element, are analyzed. Element X is noted to poorly dissolve in both aluminum and beryllium. It is shown that the absence of intermetallic compounds in the Al-Be system affects the phase equilibria in an Al-Be- X system. Possible phase equilibria involving phases based on aluminum, beryllium, and intermetallic compounds are proposed, and the types of strengthening of Al-Be alloys by an addition of a third element are classified.

  3. Irradiation Performance of U-Mo Alloy Based ‘Monolithic’ Plate-Type Fuel – Design Selection

    SciTech Connect

    A. B. Robinson; G. S. Chang; D. D. Keiser, Jr.; D. M. Wachs; D. L. Porter

    2009-08-01

    A down-selection process has been applied to the U-Mo fuel alloy based monolithic plate fuel design, supported by irradiation testing of small fuel plates containing various design parameters. The irradiation testing provided data on fuel performance issues such as swelling, fuel-cladding interaction (interdiffusion), blister formation at elevated temperatures, and fuel/cladding bond quality and effectiveness. U-10Mo (wt%) was selected as the fuel alloy of choice, accepting a somewhat lower uranium density for the benefits of phase stability. U-7Mo could be used, with a barrier, where the trade-off for uranium density is critical to nuclear performance. A zirconium foil barrier between fuel and cladding was chosen to provide a predictable, well-bonded, fuel-cladding interface, allowing little or no fuel-cladding interaction. The fuel plate testing conducted to inform this selection was based on the use of U-10Mo foils fabricated by hot co-rolling with a Zr foil. The foils were subsequently bonded to Al-6061 cladding by hot isostatic pressing or friction stir bonding.

  4. Enhanced thermoelectric figure-of-merit in p-type nanostructured bismuth antimony tellurium alloys made from elemental chunks.

    PubMed

    Ma, Yi; Hao, Qing; Poudel, Bed; Lan, Yucheng; Yu, Bo; Wang, Dezhi; Chen, Gang; Ren, Zhifeng

    2008-08-01

    By ball milling alloyed bulk crystalline ingots into nanopowders and hot pressing them, we had demonstrated high figure-of-merit in nanostructured bulk bismuth antimony telluride. In this study, we use the same ball milling and hot press technique, but start with elemental chunks of bismuth, antimony, and tellurium to avoid the ingot formation step. We show that a peak ZT of about 1.3 in the temperature range of 75 and 100 degrees C has been achieved. This process is more economical and environmentally friendly than starting from alloyed bulk crystalline ingots. The ZT improvement is caused mostly by the lower thermal conductivity, similar as the case using ingot. Transmission electron microscopy observations of the microstructures suggest that the lower thermal conductivity is mainly due to the increased phonon scattering from the increased grain boundaries of the nanograins, precipitates, nanodots, and defects. Our material also exhibits a ZT of 0.7 at 250 degrees C, similar to the value obtained when ingot was used. This study demonstrates that high ZT values can be achieved in nanostructured bulk materials with ball milling elemental chunks, suggesting that the approach can be applied to other materials that are hard to be made into ingot, in addition to its advantage of lower manufacturing cost. PMID:18624384

  5. Impact of yttria stabilized zirconia nanoinclusions on the thermal conductivity of n-type Si80Ge20 alloys prepared by spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Lahwal, Ali; Bhattacharya, S.; He, Jian; Wu, Di; Peterson, A.; Poon, S. J.; Williams, L.; Dehkordi, A. Mehdizadeh; Tritt, T. M.

    2015-04-01

    Nanocomposites have become a new paradigm for thermoelectric research in recent years and have resulted in the reduction of thermal conductivity via the nano-inclusion and grain boundary scattering. In this work, we report the preparation and thermoelectric study of SiGe-yttria stabilized zirconia (YSZ) nanocomposites prepared by Spark Plasma Sintering (SPS). We experimentally investigated the reduction of lattice thermal conductivity (?L) in the temperature range (30-800 K) of n-type Si80Ge20P2 alloys with the incorporation of YSZ nanoparticles (20-40 nm diameter) into the Si-Ge matrix. These samples synthesized by using the SPS technique were found to have densities > 95% of the theoretical density. The thermal conductivity, at both low and high temperatures, was measured by steady state and laser flash techniques, respectively. At room temperature, we observed approximately a 50% reduction in the lattice thermal conductivity as result of adding 10% YSZ by volume to the Si80Ge20P2 host matrix. A phenomenological model developed by Callaway was used to corroborate both the temperature dependence and reduction of ? L over the measured temperature range (30-800 K) of both Si80Ge20P2 and Si80Ge20P2 + YSZ samples. The observed ?L is discussed and interpreted in terms of various phonon scattering mechanisms such as alloy disorder, the Umklapp phonon scattering, and boundary scattering. In addition, a contribution from the phonon scattering by YSZ nanoparticles was further included to account for the ?L of Si80Ge20P2 + YSZ sample. The theoretical calculations are in reasonably good agreement with the experimental results for both the Si80Ge20P2 and Si80Ge20P2 + YSZ alloys.

  6. THE INFLUENCE OF SCREW TYPE, ALLOY AND CYLINDER POSITION ON THE MARGINAL FIT OF IMPLANT FRAMEWORKS BEFORE AND AFTER LASER WELDING

    PubMed Central

    Castilio, Daniela; Pedreira, Ana Paula Ribeiro do Vale; Rossetti, Paulo Henrique Orlato; Rossetti, Leylha Maria Nunes; Bonachela, Wellington Cardoso

    2006-01-01

    Misfit at the abutment-prosthetic cylinder interface can cause loss of preload, leading to loosening or fracture of gold and titanium screws. Objectives: To evaluate the influence of screw type, alloy, and cylinder position on marginal fit of implant frameworks before and after laser welding. Methods: After Estheticone-like abutments were screwed to the implants, thirty plastic prosthetic cylinders were mounted and waxed-up to fifteen cylindrical bars. Each specimen had three interconnected prosthetic components. Five specimens were one-piece cast in titanium and five in cobalt-chromium alloy. On each specimen, tests were conducted with hexagonal titanium and slotted gold screws separately, performing a total of thirty tested screws. Measurements at the interfaces were performed using an optical microscope with 5 μm accuracy. After sectioning, specimens were laser welded and new measurements were obtained. Data were submitted to a four-way ANOVA and Tukey's multiple comparisons test (α =0.05). Results: Slotted and hexagonal screws did not present significant differences regarding to the fit of cylinders cast in titanium, either in one-piece casting framework or after laser welding. When slotted and hexagonal screws were tested on the cobalt-chromium specimens, statistically significant differences were found for the one-piece casting condition, with the slotted screws presenting better fit (24.13μm) than the hexagonal screws (27.93 μm). Besides, no statistically significant differences were found after laser welding. Conclusions: 1) The use of different metal alloys do exert influence on the marginal fit, 2) The slotted and hexagonal screws play the exclusive role of fixing the prosthesis, and did not improve the fit of cylinders, and 3) cylinder position did not affect marginal fit values. PMID:19089035

  7. Electronic structures and magnetism in the Li2AgSb-type Heusler alloys, Zr2CoZ (Z=Al, Ga, In, Si, Ge, Sn, Pb, Sb): A first-principles study

    NASA Astrophysics Data System (ADS)

    Wang, X. T.; Cui, Y. T.; Liu, X. F.; Liu, G. D.

    2015-11-01

    The electronic and magnetic properties of Zr2CoZ (Z=Al, Ga, In, Si, Ge, Sn, Pb, and Sb) alloys with a Li2AgSb-type structure were investigated systematically using the first-principle calculations. Zr2CoZ (Z=Al, Ga, In, Si, Ge, Sn, and Pb) alloys are predicted to be half-metallic ferromagnets at their equilibrium lattice constants. The Zr2Co-based alloys have Mt (the total magnetic moment per unit cell) and Zt (the valence concentration) values following Slater-Pauling rule of Mt=Zt-18. The effects of lattice constants on the electronic and the magnetic properties are discussed in detail. Moreover, all the alloys investigated in this paper have a negative formation energy, which implies that they are thermodynamically stable.

  8. Effect of solid-solution concentration on the type and parameters of the dislocation structure formed in the process of deformation of the alloys Cu-Mn and Cu-Al

    NASA Astrophysics Data System (ADS)

    Kozlov, . V.; Trishkina, L. I.; Daneliya, G. V.; Tsypin, M. I.; Koneva, N. A.

    1991-10-01

    A comparative study of the evolution of dislocation structure accompanying deformation in the alloys Cu-Mn and Cu-Al for concentrations 0 19 at.% Mn and 0.5 14 at.% Al was performed by the method of transmission diffraction electron microscopy. It was determined that the concentration of the solid solution affects the character of the evolution and the parameters of the substructure. It was found that the type of observed substructures are virtually identical for the alloys of both systems, but in contrast to the alloys Cu-Al twinning does not occur in Cu-Mn. In the solid solution Cu-Mn the substructures are observed to change at higher concentrations than in the alloys Cu-Al. It was established that a decrease in the packing-defect energy affects the change in the substructure in the same direction as does an increase in solid solution hardening.

  9. In vivo corrosion, tumor outcome, and microarray gene expression for two types of muscle-implanted tungsten alloys

    SciTech Connect

    Schuster, B.E.; Roszell, L.E.; Murr, L.E.; Ramirez, D.A.; Demaree, J.D.; Klotz, B.R.; Rosencrance, A.B.; Dennis, W.E.; Bao, W.; Perkins, E.J.; Dillman, J.F.; Bannon, D.I.

    2012-11-15

    Tungsten alloys are composed of tungsten microparticles embedded in a solid matrix of transition metals such as nickel, cobalt, or iron. To understand the toxicology of these alloys, male F344 rats were intramuscularly implanted with pellets of tungsten/nickel/cobalt, tungsten/nickel/iron, or pure tungsten, with tantalum pellets as a negative control. Between 6 and 12 months, aggressive rhabdomyosarcomas formed around tungsten/nickel/cobalt pellets, while those of tungsten/nickel/iron or pure tungsten did not cause cancers. Electron microscopy showed a progressive corrosion of the matrix phase of tungsten/nickel/cobalt pellets over 6 months, accompanied by high urinary concentrations of nickel and cobalt. In contrast, non-carcinogenic tungsten/nickel/iron pellets were minimally corroded and urinary metals were low; these pellets having developed a surface oxide layer in vivo that may have restricted the mobilization of carcinogenic nickel. Microarray analysis of tumors revealed large changes in gene expression compared with normal muscle, with biological processes involving the cell cycle significantly up‐regulated and those involved with muscle development and differentiation significantly down‐regulated. Top KEGG pathways disrupted were adherens junction, p53 signaling, and the cell cycle. Chromosomal enrichment analysis of genes showed a highly significant impact at cytoband 7q22 (chromosome 7) which included mouse double minute (MDM2) and cyclin‐dependant kinase (CDK4) as well as other genes associated with human sarcomas. In conclusion, the tumorigenic potential of implanted tungsten alloys is related to mobilization of carcinogenic metals nickel and cobalt from corroding pellets, while gene expression changes in the consequent tumors are similar to radiation induced animal sarcomas as well as sporadic human sarcomas. -- Highlights: ► Tungsten/nickel/cobalt, tungsten/nickel/iron, and pure tungsten were studied. ► Male Fischer rats implanted with pellets in gastrocnemius muscle of each hind leg. ► Aggressive rhabdomyosarcomas developed from tungsten/nickel/cobalt pellets only. ► Microarray gene expression analysis was carried out on selected tumors. ► Pellet degradation, urinary metal concentration, and sarcoma were correlated.

  10. Investigation of early cell-surface interactions of human mesenchymal stem cells on nanopatterned β-type titanium-niobium alloy surfaces.

    PubMed

    Medda, Rebecca; Helth, Arne; Herre, Patrick; Pohl, Darius; Rellinghaus, Bernd; Perschmann, Nadine; Neubauer, Stefanie; Kessler, Horst; Oswald, Steffen; Eckert, Jürgen; Spatz, Joachim P; Gebert, Annett; Cavalcanti-Adam, Elisabetta A

    2014-02-01

    Multi-potent adult mesenchymal stem cells (MSCs) derived from bone marrow have therapeutic potential for bone diseases and regenerative medicine. However, an intrinsic heterogeneity in their phenotype, which in turn results in various differentiation potentials, makes it difficult to predict the response of these cells. The aim of this study is to investigate initial cell-surface interactions of human MSCs on modified titanium alloys. Gold nanoparticles deposited on β-type Ti-40Nb alloys by block copolymer micelle nanolithography served as nanotopographical cues as well as specific binding sites for the immobilization of thiolated peptides present in several extracellular matrix proteins. MSC heterogeneity persists on polished and nanopatterned Ti-40Nb samples. However, cell heterogeneity and donor variability decreased upon functionalization of the gold nanoparticles with cyclic RGD peptides. In particular, the number of large cells significantly decreased after 24 h owing to the arrangement of cell anchorage sites, rather than peptide specificity. However, the size and number of integrin-mediated adhesion clusters increased in the presence of the integrin-binding peptide (cRGDfK) compared with the control peptide (cRADfK). These results suggest that the use of integrin ligands in defined patterns could improve MSC-material interactions, not only by regulating cell adhesion locally, but also by reducing population heterogeneity. PMID:24501674

  11. Investigation of early cell–surface interactions of human mesenchymal stem cells on nanopatterned β-type titanium–niobium alloy surfaces

    PubMed Central

    Medda, Rebecca; Helth, Arne; Herre, Patrick; Pohl, Darius; Rellinghaus, Bernd; Perschmann, Nadine; Neubauer, Stefanie; Kessler, Horst; Oswald, Steffen; Eckert, Jürgen; Spatz, Joachim P.; Gebert, Annett; Cavalcanti-Adam, Elisabetta A.

    2014-01-01

    Multi-potent adult mesenchymal stem cells (MSCs) derived from bone marrow have therapeutic potential for bone diseases and regenerative medicine. However, an intrinsic heterogeneity in their phenotype, which in turn results in various differentiation potentials, makes it difficult to predict the response of these cells. The aim of this study is to investigate initial cell–surface interactions of human MSCs on modified titanium alloys. Gold nanoparticles deposited on β-type Ti–40Nb alloys by block copolymer micelle nanolithography served as nanotopographical cues as well as specific binding sites for the immobilization of thiolated peptides present in several extracellular matrix proteins. MSC heterogeneity persists on polished and nanopatterned Ti–40Nb samples. However, cell heterogeneity and donor variability decreased upon functionalization of the gold nanoparticles with cyclic RGD peptides. In particular, the number of large cells significantly decreased after 24 h owing to the arrangement of cell anchorage sites, rather than peptide specificity. However, the size and number of integrin-mediated adhesion clusters increased in the presence of the integrin-binding peptide (cRGDfK) compared with the control peptide (cRADfK). These results suggest that the use of integrin ligands in defined patterns could improve MSC-material interactions, not only by regulating cell adhesion locally, but also by reducing population heterogeneity. PMID:24501674

  12. Extrusion die geometry effects on the energy absorbing properties and deformation response of 6063-type Al-Mg-Si aluminum alloy

    NASA Astrophysics Data System (ADS)

    Gbenebor, O. P.; Fayomi, O. S. I.; Popoola, A. P. I.; Inegbenebor, A. O.; Oyawale, F.

    The response of 6063-type Al-Mg-Si alloy to deformation via extrusion was studied using tool steel dies with 15, 30, 45, 60 and 75 entry angles. Compressive loads were subjected to each sample using the AVERY DENISON machine, adapted to supply a compressive load on the punch. The ability of the extrudate to absorb energy before fracture was calculated by integrating numerically the polynomial relationship between the compressive stress and sample strains. Strain rate was calculated for each specimen and the deformation zone length was mathematically derived from the die geometry to decipher its influence on both lateral and axial deformations. Results showed that extruding with a 15 die was the fastest as a result of the low flow stress encountered. Outstanding compressive strength, plastic deformation, strain rate and energy absorbing capacity were observed for the alloy extruded with a 75 die angle. Increase in die angles led to a decrease in deformation zone length and samples deformed more in the axial direction than in the lateral except for the 45o die which showed the opposite; the sample also showed the least ductility.

  13. New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy.

    PubMed

    He, Zhanbing; Ma, Haikun; Li, Hua; Li, Xingzhong; Ma, Xiuliang

    2016-01-01

    A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23?nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91?nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description. PMID:26928759

  14. New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy

    PubMed Central

    He, Zhanbing; Ma, Haikun; Li, Hua; Li, Xingzhong; Ma, Xiuliang

    2016-01-01

    A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23 nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91 nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description. PMID:26928759

  15. New type of Al-based decagonal quasicrystal in Al60Cr20Fe10Si10 alloy

    NASA Astrophysics Data System (ADS)

    He, Zhanbing; Ma, Haikun; Li, Hua; Li, Xingzhong; Ma, Xiuliang

    2016-03-01

    A new kind of decagonal quasicrystal (DQC) with a periodicity of 1.23 nm was observed in the as-cast quaternary Al60Cr20Fe10Si10 alloy. The intensity distribution of some spots in the selected-area electron diffraction pattern along the tenfold zone axis was found to be different from other Al-based DQCs. High-angle annular dark-field scanning transmission electron microscopy was adopted to reveal the structural features at an atomic level. Both the tenfold symmetry and symmetry-broken decagonal (D) clusters of 1.91 nm in diameter were found, but with structural characteristics different from the corresponding D clusters in the other Al-based DQCs. The neighboring D clusters are connected by sharing one edge rather than covering, suggesting the tiling model is better than the covering model for structural description.

  16. Microstructural studies on Alloy 693

    NASA Astrophysics Data System (ADS)

    Halder, R.; Dutta, R. S.; Sengupta, P.; Samajdar, I.; Dey, G. K.

    2014-10-01

    Superalloy 693, is a newly identified high-temperature corrosion resistant alloy. Present study focuses on microstructure and mechanical properties of the alloy prepared by double vacuum melting route. In general, the alloy contains ordered Ni3Al precipitates distributed within austenitic matrix. M6C primary carbide, M23C6 type secondary carbide and NbC particles are also found to be present. Heat treatment of the alloy at 1373 K for 30 min followed by water quenching (WQ) brings about a microstructure that is free from secondary carbides and Ni3Al type precipitates but contains primary carbides. Tensile property of Alloy 693 materials was measured with as received and solution annealed (1323 K, 60 min, WQ) and (1373 K, 30 min, WQ) conditions. Yield strength, ultimate tensile strength (UTS) and hardness of the alloy are found to drop with annealing. It is noted that in annealed condition, considerable cold working of the alloy can be performed.

  17. Influence of shooting angle of polishing particle on surface roughness of a cobalt-chromium alloy using a centrifugal shooting type polishing machine.

    PubMed

    Ono, Takahiro; Ishikawa, Kaori; Yamaba, Osamu; Nokubi, Takashi

    2004-12-01

    The centrifugal shooting type polishing machine is a recently developed apparatus that seeks to improve the efficiency and environment of polishing removable prostheses. In an attempt to optimize the effectiveness of this apparatus, this study examined the influence of the shooting angle of polishing particle on the surface roughness of cobalt-chromium alloy casting specimens. Polishing was performed for three minutes under five shooting angle conditions: 90 degrees, 60 degrees, 45 degrees, 30 degrees, and 15 degrees. Surface roughness (Ra, Sm) was measured after each polishing stage. There were significant differences (p < 0.01) in Ra between shooting angle of 90 degrees (0.95 microm) and shooting angles of 45 degrees (0.62 microm) or less, and in Sm between 90 degrees (207 microm), 60 degrees (350 microm), and shooting angles of 45 degrees (868 microm) or less. These findings indicated that excellent surface texture was produced when shooting angle was 45 degrees or less. PMID:15688732

  18. High temperature low-cycle fatigue of friction welded joints - type 304-304 stainless steel and alloy 718-718 nickel base superalloy

    SciTech Connect

    Wakai, T. . Oarai Engineering Center); Sakane, M.; Ohnami, M. . Dept. of Mechanical Engineering); Okita, K. . Technical Center for Machinery and Metals); Fukuchi, Y. )

    1993-01-01

    This paper assesses the high-temperature low-cycle fatigue of the Type 304 stainless steel and Alloy 718 superalloy friction-welded joints. Strain controlled low-cycle fatigue tests for 304-304 and 718-718 friction-welded specimens were carried out at 923 K in air to obtain the fatigue strength of the joints. These materials were selected as the cyclic hardening and softening materials, respectively. The 304-304 welded specimens showed inferior fatigue strength in comparison with the base metal while the 718-718 specimens exhibited fatigue strength equivalent to that of the base metal. The difference in the fatigue strength between the two materials is discussed from the viewpoint of the cyclic deformation behavior and strain reduction at weld interface.

  19. Alloy materials

    DOEpatents

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

    2002-01-01

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

  20. Platinum-group minerals from placers related to the Nizhni Tagil (Middle Urals, Russia) Uralian-Alaskan-type ultramafic complex: ore-mineralogy and study of silicate inclusions in (Pt, Fe) alloys

    NASA Astrophysics Data System (ADS)

    Johan, Z.

    2006-05-01

    The study of platinum-group minerals (PGM) concentrates from the Nizhni Tagil placers related to the Soloviev Mountain (Gora Solovieva) Uralian-Alaskan-type intrusion revealed a predominance of (Pt, Fe) alloys over Ir-, and Os-bearing alloys. (Pt, Fe) alloys (“isoferroplatinum-type”) are interstitial with respect to chromite and show important variations in their chemical compositions, which are, however, falling within the experimentally determined stability field of isoferroplatinum. Tetraferroplatinum, enriched in Cu and Ni and tulameenite represent low-temperature mineral phases replacing (Pt, Fe) alloys. Alloys belonging to the Os-Ir-Ru ternary system have compositions corresponding to native osmium, iridium and ruthenium, respectively, and to rutheniridosmine. Osmium exsolutions appear in Ir-, and (Pt, Fe) alloys, and iridium exsolutions in (Pt, Fe) alloys. Laurite is a high-temperature phase included in native iridium and (Pt, Fe) alloys. Low-temperature PGM association comprises Ir-bearing sulpharsenides, including a phase (Ir, Os, Fe, Pt, Ru, Ni)3(As, Sb)0.85S, and a palladium antimonide Pd20Sb7. These two phases were previously unknown in nature. Furthermore, native palladium occurs in the studied concentrates. This low-temperature paragenesis indicates an interaction of Pt-, Os-, Ir- and Ru-bearing alloys with late fluids enriched in volatiles, As and Sb. The chromite composition is characterized by the predominance of Cr3+ → Fe3+ substitution like in other Uralian-Alaskan-type intrusions; that indicates a fO2 variation during the chromite precipitation. Monomineralic inclusions of euhedral clinopyroxene and chromite crystals in (Pt, Fe) alloys were observed. Furthermore, (Pt, Fe) alloys contain polyphase silicate inclusions, which occupy the alloy negative crystals. Two types of silicate inclusions were recognized: (1) Low-pressure inclusions composed of amphibole, biotite, Jd-poor clinopyroxene, magnetite, apatite and glass; (2) High-pressure inclusions include: omphacitic clinopyroxene (up to 56 mol.% Jd), tremolite, muscovite, apatite, titanite and glass. In this case, the clinopyroxene is strongly zoned, revealing a pressure drop from about 25 to 5 kbar. The chemical composition of glass is corundum-normative and its H2O content varies from about 12 to 15 wt.%. The composition of magmatic melts, from which the silicate inclusions have originated was estimated using EPMA and image analysis interpreted by stereology. Their compositions are close to those obtained experimentally by hydrous partial melting of upper mantle rocks. The interpretation of analytical data shows that magmatic melts entrapped by (Pt, Fe) alloys crystallized from about 1100 to 700 °C. The (Pt, Fe) alloys formed after the crystallization of chromite, clinopyroxene and albite. Consequently, the precipitation temperature of (Pt, Fe) alloys is estimated at about 900 °C. The significant pressure drop implies a decrease of volatile concentrations in the magmatic melt and the possible formation of a fluid phase, which might have generated, the precipitation of chromite and PGM.

  1. Thermodynamic Aspects of Homogeneous Nucleation Enhanced by Icosahedral Short Range Order in Liquid Fcc-Type Alloys

    NASA Astrophysics Data System (ADS)

    Rappaz, Michel; Kurtuldu, Güven

    2015-08-01

    We have recently shown that minute solute element additions to liquid metallic alloys can strongly influence the nucleation of the fcc phase and act as a grain refinement method. Electron back-scattered diffraction observations revealed a concomitant increase in the percentage of nearest neighbor (nn) grains that are in a twin relationship. Furthermore, multiple-twinned (MT) nn grain configurations with a fivefold symmetry around a common direction have been identified, an occurrence that can be explained when the symmetry of the icosahedron is accounted for. It was then conjectured that a new nucleation mechanism occurs in two steps: first, the formation of small icosahedral quasicrystals in the melt, followed by heteroepitaxy of the fcc phase on facets of these quasicrystals. In the present contribution, based on thermodynamics arguments, it is proposed that the first step occurs by spinodal decomposition of the liquid, in a manner similar to Guinier-Preston zones formation in solid state precipitation, while the second step is a transformation of these quasicrystal precursors into MT-fcc nanocrystals once the driving force for this transformation is sufficient to overcome the fcc-liquid interfacial energy and the elastic strains associated with MT-fcc nanoparticles. This explanation sets up guidelines for finding solute elements and composition ranges that favor this grain refinement mechanism.

  2. Alloys for crown and bridgework.

    PubMed

    Brockhurst, P J; Cannon, R W

    1981-10-01

    The requirements of alloys for metal-ceramic crowns and bridgework are examined. The functional requirements and manipulative behaviour and cost of cheaper alternatives to high gold alloys are discussed. All types use--high gold, reduced gold, silver palladium and base metal--appear to function satisfactorily in the mouth. Nickel and beryllium do not appear to be health hazards. Dental laboratory procedures and materials must be chosen to suit the type of alloy employed, although all alloy types appear suitable for crown and bridgework. The cost of alloy must be carefully examined in the context of total cost to the patient, and the use of alternatives to gold alloys in many cases may not warrant the required changes to laboratory procedures, but the saving is real, and can make permanent restorations available to greater proportion of the community. PMID:7036968

  3. Osmium isotope systematics of Os-rich alloys and Ru-Os sulfides from oceanic mantle: evidence from Proterozoic and Paleozoic ophiolite-type complexes

    NASA Astrophysics Data System (ADS)

    Badanina, Inna Yu.; Malitch, Kreshimir N.; Belousova, Elena A.; Lord, Richard A.; Meisel, Thomas C.; Murzin, Valery V.; Pearson, Norman J.

    2014-05-01

    This study presents a substantial data set of Os-isotope compositions of Os-rich alloys and Ru-Os sulfides from deep portions of ophiolite sections from oceanic mantle. These are represented by samples from different in age ophiolite-type massifs (i.e., Neoproterozoic Kunar in Northern Taimyr, Russia, and Hochgrossen in Eastern Alps, Austria, Paleozoic Verkh-Neivinsk in Middle Urals, Russia, and Shetland in northern Scotland). The investigation employed a number of analytical techniques, including electron microprobe analysis, ID ICP-MS after high pressure acid digestion, and laser ablation attached to multiple collector-inductively coupled plasma mass-spectrometry (LA MC-ICP-MS). Two distinct platinum-group mineral (PGM) assemblages have been recognized at the Shetland and Verkh-Neivinsk localities: a 'primary' euhedral PGM assemblage, which occur as inclusions in chromite, and a modified 'secondary' subeuhedral to anhedral PGM assemblage observed in cracks filled by chlorite or serpentine, interstitially to chromite grains [1]. A 'primary' PGM assemblage at Shetland is represented by solitary grains of laurite or iridian osmium and composite grains of laurite + osmian iridium iridian osmium that display well defined phase boundaries between two or three distinct PGMs. A 'primary' PGM assemblage at Verkh-Neivinsk is represented by Ru-Os-Ir alloy grains that frequently mantled by 'secondary' Ru-Os sulfide and/or Ru-Os sulfarsenide overgrowths. The osmium isotope results identify (1) a restricted range of 'unradiogenic' 187Os/188Os values for coexisting laurite and Os-rich alloy pairs that form 'primary' PGM assemblages at Hochgrossen and Shetland (0.11860-0.11866 and 0.12473-0.12488, respectively); (2) similar 'unradiogenic' 187Os/188Os values for both 'primary' and 'secondary' PGM assemblages at Shetland (with mean 187Os/188Os 0.12419 and 0.12464, respectively) and Verkh-Neivinsk (with distinct mean 187Os/188Os values), and (3) a wide scatter of subchondritic 187Os/188Os values for 'primary' PGM assemblages at Kunar (i.e., 187Os/188Os 0.11848-0.11239), Verkh-Neivinsk (0.11619-0.12565), and Hochgrossen (0.11860-0.12450). The whole-rock Os-isotope budget of chromitite at Shetland (0.12400.0006) is largely controlled by laurite-dominant assemblages. In this case, the 'secondary' PGM assemblage inherited the 'unradiogenic' Os-isotope signature of the 'primary' PGMs. No evidence for other source contributions during later thermal events has been observed here. However, the wide range of subchondritic 187Os/188Os values has been found in the 'primary' PGM assemblages (e.g., laurite and Os-rich alloys) from the ophiolite-type complexes worldwide [2 and references cited therein]. This wide range would be consistent with a model, in which a prolonged history of melting events of parent ultramafic source rocks took place in the mantle. This variability is in agreement with the conclusion that the Os-isotope system of PGMs records multiple events during the chemical differentiation history of the mantle [3] and could have been controlled by deep-geodynamic processes [4]. On the other hand, the observed Os-isotope heterogeneity may be also attributed to the presence of subcontinental lithospheric mantle (SCLM), characterized by highly unradiogenic 187Os/188Os values (i.e.,

  4. 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.

  5. Influence of Fluidized Bed Quenching on the Mechanical Properties and Quality Index of T6 Tempered B319.2-Type Aluminum Alloys

    NASA Astrophysics Data System (ADS)

    Ragab, Kh. A.; Samuel, A. M.; Al-Ahmari, A. M. A.; Samuel, F. H.; Doty, H. W.

    2013-11-01

    The current study aimed to investigate the effect of fluidized sand bed (FB) quenching on the mechanical performance of B319.2 aluminum cast alloys. Traditional water and conventional hot air (CF) quenching media were used to establish a relevant comparison with FB quenching. Quality charts were generated using two models of quality indices to support the selection of material conditions on the basis of the proposed quality indices. The use of an FB for the direct quenching-aging treatment of B319.2 casting alloys yields greater UTS and YS values compared to conventional furnace quenched alloys. The strength values of T6 tempered B319 alloys are greater when quenched in water compared with those quenched in an FB or CF. For the same aging conditions (170C/4h), the fluidized bed quenched-aged 319 alloys show nearly the same or better strength values than those quenched in water and then aged in a CF or an FB. Based on the quality charts developed for alloys subjected to different quenching media, higher quality index values are obtained by conventional furnace quenched-aged T6-tempered B319 alloys. The modification factor has the most significant effect on the quality results of the alloys investigated, for all heat treatment cycles, as compared to other metallurgical parameters. The results of alloys subjected to multi-temperature aging cycles reveal that the optimum strength properties of B319.2 alloys, however, is obtained by applying multi-temperature aging cycles such as, for example, 240 C/2 h followed by 170 C/8 h, rather than T6 aging treatments. The regression models indicate that the mean quality values of B319 alloys are highly quench sensitive due to the formation of a larger percent of clusters in Al-Si-Cu-Mg alloys. These clusters act as heterogeneous nucleation sites for precipitation and enhance the aging process.

  6. Load partitioning between the bcc-iron matrix and NiAl-type precipitates in a ferritic alloy on multiple length scales

    PubMed Central

    Sun, Zhiqian; Song, Gian; Sisneros, Thomas A.; Clausen, Bjørn; Pu, Chao; Li, Lin; Gao, Yanfei; Liaw, Peter K.

    2016-01-01

    An understanding of load sharing among constituent phases aids in designing mechanical properties of multiphase materials. Here we investigate load partitioning between the body-centered-cubic iron matrix and NiAl-type precipitates in a ferritic alloy during uniaxial tensile tests at 364 and 506 °C on multiple length scales by in situ neutron diffraction and crystal plasticity finite element modeling. Our findings show that the macroscopic load-transfer efficiency is not as high as that predicted by the Eshelby model; moreover, it depends on the matrix strain-hardening behavior. We explain the grain-level anisotropic load-partitioning behavior by considering the plastic anisotropy of the matrix and elastic anisotropy of precipitates. We further demonstrate that the partitioned load on NiAl-type precipitates relaxes at 506 °C, most likely through thermally-activated dislocation rearrangement on the microscopic scale. The study contributes to further understanding of load-partitioning characteristics in multiphase materials. PMID:26979660

  7. Load partitioning between the bcc-iron matrix and NiAl-type precipitates in a ferritic alloy on multiple length scales.

    PubMed

    Sun, Zhiqian; Song, Gian; Sisneros, Thomas A; Clausen, Bjørn; Pu, Chao; Li, Lin; Gao, Yanfei; Liaw, Peter K

    2016-01-01

    An understanding of load sharing among constituent phases aids in designing mechanical properties of multiphase materials. Here we investigate load partitioning between the body-centered-cubic iron matrix and NiAl-type precipitates in a ferritic alloy during uniaxial tensile tests at 364 and 506 °C on multiple length scales by in situ neutron diffraction and crystal plasticity finite element modeling. Our findings show that the macroscopic load-transfer efficiency is not as high as that predicted by the Eshelby model; moreover, it depends on the matrix strain-hardening behavior. We explain the grain-level anisotropic load-partitioning behavior by considering the plastic anisotropy of the matrix and elastic anisotropy of precipitates. We further demonstrate that the partitioned load on NiAl-type precipitates relaxes at 506 °C, most likely through thermally-activated dislocation rearrangement on the microscopic scale. The study contributes to further understanding of load-partitioning characteristics in multiphase materials. PMID:26979660

  8. Local structure and magnetism of L10-type FeNi alloy films with perpendicular magnetic anisotropy studied through 57Fe nuclear probes

    NASA Astrophysics Data System (ADS)

    Mibu, K.; Kojima, T.; Mizuguchi, M.; Takanashi, K.

    2015-05-01

    The local structure and magnetism of FeNi alloy films prepared by alternate deposition of Fe and Ni monatomic layers, where perpendicular magnetic anisotropy has been observed, were investigated through 57Fe nuclear probes using Mssbauer spectroscopy. It was confirmed that the films are composed of L10-type ordered FeNi phase and A1-type disordered FeNi phase. For the films grown at 40-70?C, which have no perpendicular anisotropy, the A1-disordered phase is dominant, whereas for the films grown at 100-190?C, which have a stronger perpendicular anisotropy, the relative amount of the L10-ordered phase reaches 40% or more. It was clearly shown that the magnetic anisotropy of these films is strongly correlated with the local environments of Fe in the films. The results imply that if a further increase in the ratio of the L10-ordered phase is successfully achieved, one would obtain films with a stronger magnetic anisotropy applicable to perpendicular magnetic recording.

  9. Enhanced Thermoelectric Performance of p-Type Bi-Sb-Te Alloys by Codoping with Ga and Ag

    NASA Astrophysics Data System (ADS)

    Lee, Kyu Hyoung; Choi, Soon-Mok; Roh, Jong Wook; Hwang, Sungwoo; Kim, Sang Il; Shin, Weon Ho; Park, Hee Jung; Lee, Jeong Hoon; Kim, Sung Wng; Yang, Dae Jin

    2015-06-01

    We report an enhancement of the thermoelectric performance in spark-plasma-sintered polycrystalline p-type Bi0.42Sb1.58Te3 by codoping with Ga and Ag at Bi/Sb-site. Through controlled doping of Ga ( n-type) and Ag ( p-type), electronic transport properties including the electrical conductivity (~988 S/cm at 300 K) and power factor (~3.91 mW m-1 K-2 at 300 K) could be maintained at values comparable to those of pristine Bi0.42Sb1.58Te3, while the lattice thermal conductivity was significantly reduced due to point-defect phonon scattering originating from the mass difference between the host atoms (Bi and Sb) and dopants (Ga and Ag). Through these synergetic effects, a peak ZT of 1.15 was obtained in Bi0.42Sb1.5535Ga0.025Ag0.0015Te3 at 360 K, and ZT could be engineered to be over 1.0 for a wide temperature range (300 K to 420 K).

  10. Amorphous metal alloy and composite

    DOEpatents

    Wang, Rong (Richland, WA); Merz, Martin D. (Richland, WA)

    1985-01-01

    Amorphous metal alloys of the iron-chromium and nickel-chromium type have excellent corrosion resistance and high temperature stability and are suitable for use as a protective coating on less corrosion resistant substrates. The alloys are stabilized in the amorphous state by one or more elements of titanium, zirconium, hafnium, niobium, tantalum, molybdenum, and tungsten. The alloy is preferably prepared by sputter deposition.

  11. Microtopographic Analysis of Part-Through Crack Growth in Alloy 304L Plate-type Tension Specimens

    SciTech Connect

    W. R. Lloyd; E. D. Steffler; J. H. Jackson

    2003-04-01

    The Idaho National Engineering and Environmental Laboratory (INEEL) used their microtopography analysis method to examine the fracture process in two Type 304 stainless steel, part-through crack, plate-type specimens. The two specimens had different initial defect geometries – one being nearly semicircular and moderately deep, the other being longer and shallower. The microtopographic analysis allowed determination of parameters such as: the crack tip opening displacement at initiation; the crack tip opening angle during ductile tearing; the crack mouth opening at through-thickness penetration; and, the incremental crack front profiles throughout the crack growth process. In essence, these data provide a nearly complete description of the entire ductile fracture process for the two cases examined. We describe the microtopographic analysis procedure as it was applied to these two specimens. Crack growth profiles predicted by the microtopography analysis are compared with those shown by heat tinting of the actual fracture subsurface, showing excellent agreement. Several areas of ductile crack growth theory relevant to the microtopographic method of analysis are discussed, including possible effects on the accuracy of the analyses. The accuracy of the resultant data is reviewed, and found acceptable or better. Areas for additional development of the microtopography method to improve accuracy in three-dimensional ductile fracture analysis are identified.

  12. Characterization of Newly Developed Semisolid Stir Joining Method for Cast Cu Base Alloy (Cu-Al-Si-Fe) and Effect of Stirrer Type on Uniformity of Microstructure

    NASA Astrophysics Data System (ADS)

    Ferasat, Keyvan; Aashuri, Hossein; Kokabi, Amir Hossein; Nikzad, Siamak; Shafizadeh, Mahdi

    2015-02-01

    In this research, the semisolid stir joining method was used to overcome the problem of hot cracking in welding aluminum and silicon bronzes. Moreover, the effects of grooved and cylindrical tools on the microstructure and mechanical properties of samples were examined. After welding specimens, mechanical tests were carried out to find differences between the cast and welded samples. Optical microscopy and scanning electron microscopy were used to study microstructure. X-ray diffraction was used to investigate compounds formed during casting and welding. The solidus and liquidus temperatures of the alloy were measured by differential scanning calorimetry. In this study, the temperature of the work pieces was raised to 1203 K (930 °C) that is in the semisolid region, and the weld seams were stirred by two different types of tools at the speed of 1600 rpm. Macro and micro-structural analyses show uniformity in the phase distribution for specimens welded by cylindrical tool. Desirable and uniform mechanical properties obtained when the cylindrical tool was used.

  13. Structural, magnetic and electronic state characterization of L1 0-type ordered FeNi alloy extracted from a natural meteorite.

    PubMed

    Kotsugi, M; Maruyama, H; Ishimatsu, N; Kawamura, N; Suzuki, M; Mizumaki, M; Osaka, K; Matsumoto, T; Ohkochi, T; Ohtsuki, T

    2014-02-12

    To understand the hard magnetism of L10-type ordered FeNi alloy, we extracted the L10-FeNi phase from a natural meteorite, and evaluated its fundamental solid-state properties: sample composition, magnetic hysteresis, crystal structure and electronic structure. We executed multidirectional analyses using scanning electron microscopy with an electron probe micro-analyzer (SEM-EPMA), a superconducting quantum interference device (SQUID), x-ray diffraction (XRD) and magnetic circular dichroism (MCD). As a result, we found that the composition was Fe: 50.47 ± 1.98 at.%, Ni: 49.60 ± 1.49 at.%, and an obvious superlattice peak is confirmed. The estimated degree of order was 0.608, with lattice constants a = b = 3.582 Å and c = 3.607 Å. The obtained coercivity was more than 500 Oe. MCD analysis using the K absorption edge suggests that the magnetic anisotropy could originate from the orbital magnetic moment of 3d electrons in Fe; this result is consistent with that in a previous report obtained with synthetic L10-FeNi. PMID:24469025

  14. Effect of small scattering centers on the thermoelectric properties of p-type SiGe alloys

    NASA Technical Reports Server (NTRS)

    Beaty, John S.; Rolfe, Jonathan L.; Vandersande, Jan W.

    1991-01-01

    Theory predicts that the addition of ultra-fine, inert, phonon-scattering centers to thermoelectric materials will reduce their thermal conductivity. To investigate this prediction, ultrafine particulates (20 to 120 A) of silicon nitride have been added to boron-doped, p-type, 80/20 SiGe. All of the SiGe samples produced from ultrafine powder have lower thermal conductivities than standard SiGe, but high-temperature heat treatment increases the thermal conductivity back to the value for standard SiGe. However, the SiGe samples with silicon nitride, inert, phonon-scattering centers retained the lower thermal conductivity after several heat treatments. A reduction of approximately 25 percent in thermal conductivity has been achieved in these samples. The magnitude of the reduction agrees with theoretical predictions.

  15. Enhanced thermoelectric performance in p-type BiSbTe bulk alloy with nanoinclusion of ZnAlO

    SciTech Connect

    Zhang Ting; Zhang Qiushi; Jiang Jun; Xiong Zhen; Chen Jianmin; Zhang Yulong; Li Wei; Xu Gaojie

    2011-01-10

    p-type BiSbTe/x wt % ZnAlO (x=0, 0.25, 0.5, 0.75, and 1.0) composites were prepared by zone melting method. A peak thermoelectric figure of merit (ZT) of 1.33 at 370 K was achieved for the sample with x=0.75, about 34% higher than that of BiSbTe at the same temperature, making these composites more attractive for commercial applications. This enhancement of ZT can be mainly ascribed to a remarkable increase of the electrical conductivity and a simultaneous decrease of the lattice thermal conductivity by the introduction of ZnAlO nanopowder.

  16. Grindability of dental magnetic alloys.

    PubMed

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

    2005-06-01

    In this study, the grindability of cast magnetic alloys (Fe-Pt-Nb magnetic alloy and magnetic stainless steel) was evaluated and compared with that of conventional dental casting alloys (Ag-Pd-Au alloy, Type 4 gold alloy, and cobalt-chromium alloy). Grindability was evaluated in terms of grinding rate (i.e., volume of metal removed per minute) and grinding ratio (i.e., volume ratio of metal removed compared to wheel material lost). Solution treated Fe-Pt-Nb magnetic alloy had a significantly higher grinding rate than the aged one at a grinding speed of 750-1500 m x min(-1). At 500 m x min(-1), there were no significant differences in grinding rate between solution treated and aged Fe-Pt-Nb magnetic alloys. At a lower speed of 500 m x min(-1) or 750 m x min(-1), it was found that the grinding rates of aged Fe-Pt-Nb magnetic alloy and stainless steel were higher than those of conventional casting alloys. PMID:16022434

  17. VANADIUM ALLOYS

    DOEpatents

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

    1959-05-12

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

  18. BRAZING ALLOYS

    DOEpatents

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

    1963-02-26

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

  19. Quantum evolution: The case of weak localization for a 3D alloy-type Anderson model and application to Hamiltonian based quantum computation

    NASA Astrophysics Data System (ADS)

    Cao, Zhenwei

    Over the years, people have found Quantum Mechanics to be extremely useful in explaining various physical phenomena from a microscopic point of view. Anderson localization, named after physicist P. W. Anderson, states that disorder in a crystal can cause non-spreading of wave packets, which is one possible mechanism (at single electron level) to explain metal-insulator transitions. The theory of quantum computation promises to bring greater computational power over classical computers by making use of some special features of Quantum Mechanics. The first part of this dissertation considers a 3D alloy-type model, where the Hamiltonian is the sum of the finite difference Laplacian corresponding to free motion of an electron and a random potential generated by a sign-indefinite single-site potential. The result shows that localization occurs in the weak disorder regime, i.e., when the coupling parameter lambda is very small, for energies E ? --Clambda 2. The second part of this dissertation considers adiabatic quantum computing (AQC) algorithms for the unstructured search problem to the case when the number of marked items is unknown. In an ideal situation, an explicit quantum algorithm together with a counting subroutine are given that achieve the optimal Grover speedup over classical algorithms, i.e., roughly speaking, reduce O(2n) to O(2n/2), where n is the size of the problem. However, if one considers more realistic settings, the result shows this quantum speedup is achievable only under a very rigid control precision requirement (e.g., exponentially small control error).

  20. Ferromagnetic bulk amorphous alloys

    SciTech Connect

    Inoue, Akihisa; Takeuchi, Akira; Zhang, T.

    1998-07-01

    This article reviews the authors recent results on the development of ferromagnetic bulk amorphous alloys prepared by casting processes. The multicomponent Fe-(Al,Ga)-(P,C,B,Si) alloys are amorphized in the bulk form with diameters up to 2 mm, and the temperature interval of the supercooled liquid region before crystallization is in the range of 50 to 67 K. These bulk amorphous alloys exhibit good soft magnetic properties, i.e., high B{sub s} of 1.1 to 1.2 T, low H{sub c} of 2 to 6 A/m, and high {mu}{sub e} of about 7,000 at 1 kHz. The Nd-Fe-Al and Pr-Fe-Al bulk amorphous alloys are also produced in the diameter range of up to 12 mm by the copper mold casting process and exhibit rather good hard magnetic properties, i.e., B{sub r} of about 0.1 T, high H{sub c} of 300 to 400 kA/m, and rather high (JH){sub max} of 13 to 20 kJ/m{sup 3}. The crystallization causes the disappearance of the hard magnetic properties. Furthermore, the melt-spun Nd-Fe-Al and Pr-Fe-Al alloy ribbons exhibit soft-type magnetic properties. Consequently, the hard magnetic properties are concluded to be obtained only for the bulk amorphous alloys. The Nd- and Pr-based bulk amorphous alloys can be regarded as a new type of clustered amorphous material, and the control of the clustered amorphous structure is expected to enable the appearance of novel functional properties which cannot be obtained for an ordinary amorphous structure.

  1. ZIRCONIUM ALLOY

    DOEpatents

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

    1959-02-01

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

  2. URANIUM ALLOYS

    DOEpatents

    Seybolt, A.U.

    1958-04-15

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

  3. The structure, anisotropy and coercivity of rapidly quenched TbCu7-type SmCo7-xZrx alloys and the effects of post-treatments

    NASA Astrophysics Data System (ADS)

    Feng, D. Y.; Liu, Z. W.; Zheng, Z. G.; Zeng, D. C.; Zhang, G. Q.

    2013-12-01

    The effects of wheel speed, Zr content, post-ball milling process and heat treatment on the structure, anisotropy, magnetic properties and phase transition of the melt-spun SmCo7-xZrx alloys were investigated. The crystallographic c-axis is parallel to the ribbon plane for the ribbons prepared at low speeds of 5 and 15 m/s, and this orientation is reduced at higher speeds. The out-of-plane coercivity of SmCo6.8Zr0.2 ribbon increases from 123 kA/m for 5 m/s to 1076 kA/m for 60 m/s. Zr doping improves the hard magnetic properties and the in-plane coercivity of SmCo7-xZrx alloys increases with the Zr content from 592 kA/m for x=0.1 to 1376 kA/m for x=0.4. The Rietveld refinements and theoretical analysis reveal that Zr atoms occupy the 2e site. The coercivity mechanisms are different for the alloys with various Zr contents. The ball milling process could enhance the coercivity and remanence of the ribbons due to the grain refinement and the precipitation of Co phase. Heat treatment can further modify the magnetic properties of the alloys. SmCo6.7Zr0.3 alloy heat treated at 400 °C has the high maximum energy product (BH)max of 64.5 kJ/m3, where the coercivity was enhanced to 1560 kA/m by 650 °C heat treatment. In addition, the SmCo7-xZrx alloys exhibit excellent hard magnetic properties at elevated temperatures.

  4. PLUTONIUM ALLOYS

    DOEpatents

    Chynoweth, W.

    1959-06-16

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

  5. Optimum composition of a Bi{sub 2}Te{sub 3-x}Se{sub x} alloy for the n-type leg of a thermoelectric generator

    SciTech Connect

    Prokofieva, L. V. Pshenay-Severin, D. A.; Konstantinov, P. P.; Shabaldin, A. A.

    2009-08-15

    The reliability of determination of model parameters for the Bi{sub 2}Te{sub 3-x}Se{sub x} alloys is improved by extending the concentration and temperature ranges in experimental studies and, correspondingly, in calculations of kinetic coefficients based on the two-band model of the electronic spectrum. The obtained results served as a motivation for a study of the thermoelectric figure of merit for the above-mentioned alloys with x = 0.3, 0.45, and 0.6 and with the electron concentration varied in the range (1-50) x 10{sup 18} cm{sup -3} at temperatures 300-550 K. Comparison of the results showed that the highest efficiency is exhibited by the Bi{sub 2}Te{sub 2.7}Se{sub 0.3} alloy with the absolute value of the thermoelectric power of about 165 {mu}VK{sup -1} at 300 K, and the dimensionless efficiency is equal to 1.2 at 410 K. An appreciable decrease in thermal conductivity in alloys with x = 0.6 at 410 K is related to a larger band gap and could beneficially affect the figure of merit. However, the magnitude of this effect is found to be too small to compensate a decrease in electrical conductivity due to a large fraction of heavy electrons in the concentration and to a high content of selenium.

  6. Effect of Mg and Sr additions on the formation of intermetallics in Al-6 wt pct Si-3.5 wt pct Cu-(0.45) to (0.8) wt pct Fe 319-type alloys

    SciTech Connect

    Samuel, F.H.; Ouellet, P.; Samuel, A.M.; Doty, H.W.

    1998-12-01

    Al-Si alloys are materials that have been developed over the years to meet the increasing demands of the automotive industry for smaller, lighter-weight, high-performance components. An important alloy in this respect is the 319 alloy, wherein silicon and copper are the main alloying elements, and magnesium is often added in automotive versions of the alloy for strengthening purposes. the mechanical properties are also ameliorated by modifying the eutectic silicon structure (strontium being commonly employed) and by reducing the harmful effect of the {beta}-Al{sub 5}FeSi iron intermetallic present in the cast structure. Magnesium is also found to refine the silicon structure. The present study was undertaken to investigate the individual and combined roles of Mg and Sr on the morphologies of Si, Mg{sub 2}Si, and the iron and copper intermetallics likely to form during the solidification of 319-type alloys at very slow (close to equilibrium) cooling rates. The results show that magnesium leads to the precipitation of Al{sub 8}Mg{sub 3}FeSi{sub 6}, Mg{sub 2}Si, and Al{sub 5}Mg{sub 8}Cu{sub 2}Si{sub 6} intermetallics. With a strontium addition, dissolution of a large proportion of the needle-like {beta}-Al{sub 5}FeSi intermetallic in the aluminum matrix takes place; no transformation of this phase into any other intermetallics (including the Al{sub 15}(Fe,Mn){sub 3}Si{sub 2} phase) is observed. When both Mg and Sr are added, the diminution of the {beta}-Al{sub 5}FeSi phase is enhanced, through both its dissolution in the aluminum matrix as well as its transformation into Al{sub 8}Mg{sub 3}FeSi{sub 6}. The reactions and phases obtained have been analyzed using thermal analysis, optical microscopy, image analysis, and electron microprobe analysis (EMPA) coupled with energy-dispersive X-ray (EDX) analysis.

  7. A theoretical investigation of mixing thermodynamics, age-hardening potential, and electronic structure of ternary M11–xM2xB2 alloys with AlB2 type structure

    PubMed Central

    Alling, B.; Högberg, H.; Armiento, R.; Rosen, J.; Hultman, L.

    2015-01-01

    Transition metal diborides are ceramic materials with potential applications as hard protective thin films and electrical contact materials. We investigate the possibility to obtain age hardening through isostructural clustering, including spinodal decomposition, or ordering-induced precipitation in ternary diboride alloys. By means of first-principles mixing thermodynamics calculations, 45 ternary M11–xM2xB2 alloys comprising MiB2 (Mi = Mg, Al, Sc, Y, Ti, Zr, Hf, V, Nb, Ta) with AlB2 type structure are studied. In particular Al1–xTixB2 is found to be of interest for coherent isostructural decomposition with a strong driving force for phase separation, while having almost concentration independent a and c lattice parameters. The results are explained by revealing the nature of the electronic structure in these alloys, and in particular, the origin of the pseudogap at EF in TiB2, ZrB2, and HfB2. PMID:25970763

  8. A theoretical investigation of mixing thermodynamics, age-hardening potential, and electronic structure of ternary M11-xM2xB2 alloys with AlB2 type structure

    NASA Astrophysics Data System (ADS)

    Alling, B.; Hgberg, H.; Armiento, R.; Rosen, J.; Hultman, L.

    2015-05-01

    Transition metal diborides are ceramic materials with potential applications as hard protective thin films and electrical contact materials. We investigate the possibility to obtain age hardening through isostructural clustering, including spinodal decomposition, or ordering-induced precipitation in ternary diboride alloys. By means of first-principles mixing thermodynamics calculations, 45 ternary M11-xM2xB2 alloys comprising MiB2 (Mi?=?Mg, Al, Sc, Y, Ti, Zr, Hf, V, Nb, Ta) with AlB2 type structure are studied. In particular Al1-xTixB2 is found to be of interest for coherent isostructural decomposition with a strong driving force for phase separation, while having almost concentration independent a and c lattice parameters. The results are explained by revealing the nature of the electronic structure in these alloys, and in particular, the origin of the pseudogap at EF in TiB2, ZrB2, and HfB2.

  9. BRAZING ALLOYS

    DOEpatents

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

    1962-02-20

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

  10. Fully epitaxial C1b-type NiMnSb half-Heusler alloy films for current-perpendicular-to-plane giant magnetoresistance devices with a Ag spacer

    PubMed Central

    Wen, Zhenchao; Kubota, Takahide; Yamamoto, Tatsuya; Takanashi, Koki

    2015-01-01

    Remarkable magnetic and spin-dependent transport properties arise from well-designed spintronic materials and heterostructures. Half-metallic Heusler alloys with high spin polarization exhibit properties that are particularly advantageous for the development of high-performance spintronic devices. Here, we report fully (001)-epitaxial growth of a high-quality half-metallic NiMnSb half-Heusler alloy films, and their application to current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with Ag spacer layers. Fully (001)-oriented NiMnSb epitaxial films with very flat surface and high magnetization were prepared on Cr/Ag-buffered MgO(001) single crystalline substrates by changing the substrate temperature. Epitaxial CPP-GMR devices using the NiMnSb films and a Ag spacer were fabricated, and room-temperature (RT) CPP-GMR ratios for the C1b-type half-Heusler alloy were determined for the first time. A CPP-GMR ratio of 8% (21%) at RT (4.2?K) was achieved in the fully epitaxial NiMnSb/Ag/NiMnSb structures. Furthermore, negative anisotropic magnetoresistance (AMR) ratio and small discrepancy of the AMR amplitudes between RT and 10?K were observed in a single epitaxial NiMnSb film, indicating robust bulk half metallicity against thermal fluctuation in the half-Heusler compound. The modest CPP-GMR ratios could be attributed to interface effects between NiMnSb and Ag. This work provides a pathway for engineering a new class of ordered alloy materials with particular emphasis on spintronics. PMID:26672482

  11. Fully epitaxial C1b-type NiMnSb half-Heusler alloy films for current-perpendicular-to-plane giant magnetoresistance devices with a Ag spacer

    NASA Astrophysics Data System (ADS)

    Wen, Zhenchao; Kubota, Takahide; Yamamoto, Tatsuya; Takanashi, Koki

    2015-12-01

    Remarkable magnetic and spin-dependent transport properties arise from well-designed spintronic materials and heterostructures. Half-metallic Heusler alloys with high spin polarization exhibit properties that are particularly advantageous for the development of high-performance spintronic devices. Here, we report fully (001)-epitaxial growth of a high-quality half-metallic NiMnSb half-Heusler alloy films, and their application to current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with Ag spacer layers. Fully (001)-oriented NiMnSb epitaxial films with very flat surface and high magnetization were prepared on Cr/Ag-buffered MgO(001) single crystalline substrates by changing the substrate temperature. Epitaxial CPP-GMR devices using the NiMnSb films and a Ag spacer were fabricated, and room-temperature (RT) CPP-GMR ratios for the C1b-type half-Heusler alloy were determined for the first time. A CPP-GMR ratio of 8% (21%) at RT (4.2?K) was achieved in the fully epitaxial NiMnSb/Ag/NiMnSb structures. Furthermore, negative anisotropic magnetoresistance (AMR) ratio and small discrepancy of the AMR amplitudes between RT and 10?K were observed in a single epitaxial NiMnSb film, indicating robust bulk half metallicity against thermal fluctuation in the half-Heusler compound. The modest CPP-GMR ratios could be attributed to interface effects between NiMnSb and Ag. This work provides a pathway for engineering a new class of ordered alloy materials with particular emphasis on spintronics.

  12. Fully epitaxial C1b-type NiMnSb half-Heusler alloy films for current-perpendicular-to-plane giant magnetoresistance devices with a Ag spacer.

    PubMed

    Wen, Zhenchao; Kubota, Takahide; Yamamoto, Tatsuya; Takanashi, Koki

    2015-01-01

    Remarkable magnetic and spin-dependent transport properties arise from well-designed spintronic materials and heterostructures. Half-metallic Heusler alloys with high spin polarization exhibit properties that are particularly advantageous for the development of high-performance spintronic devices. Here, we report fully (001)-epitaxial growth of a high-quality half-metallic NiMnSb half-Heusler alloy films, and their application to current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with Ag spacer layers. Fully (001)-oriented NiMnSb epitaxial films with very flat surface and high magnetization were prepared on Cr/Ag-buffered MgO(001) single crystalline substrates by changing the substrate temperature. Epitaxial CPP-GMR devices using the NiMnSb films and a Ag spacer were fabricated, and room-temperature (RT) CPP-GMR ratios for the C1b-type half-Heusler alloy were determined for the first time. A CPP-GMR ratio of 8% (21%) at RT (4.2?K) was achieved in the fully epitaxial NiMnSb/Ag/NiMnSb structures. Furthermore, negative anisotropic magnetoresistance (AMR) ratio and small discrepancy of the AMR amplitudes between RT and 10?K were observed in a single epitaxial NiMnSb film, indicating robust bulk half metallicity against thermal fluctuation in the half-Heusler compound. The modest CPP-GMR ratios could be attributed to interface effects between NiMnSb and Ag. This work provides a pathway for engineering a new class of ordered alloy materials with particular emphasis on spintronics. PMID:26672482

  13. Thermoelectric performance of nanostructured p-type Zr₀.₅Hf₀.₅Co₀.₄Rh₀.₆Sb1–xSnxhalf-Heusler alloys

    SciTech Connect

    Maji, Pramathesh; Makongo, Julien P.A.; Zhou, Xiaoyuan; Chi, Hang; Uher, Ctirad; Poudeu, Pierre F.P.

    2013-06-01

    Several compositions of the p-type half-Heusler alloys Zr₀.₅Hf₀.₅Co₀.₄Rh₀.₆Sb1–xSnx (0≤x≤0.4) were synthesized by mechanically alloying high purity elemental powders using hardened steel jars and balls on a high energy shaker mill. Powder X-ray diffraction (XRD) investigations of several aliquots taken after regularly spaced milling time suggested that single phase products with half-Heusler (HH) structure can be obtained after 10 h. However, XRD and transmission electron microscopy (TEM) studies of several specimens obtained from compacted polycrystalline powders of Z₀.₅Hf₀.₅Co₀.₄Rh₀.₆Sb1–xSnx alloys using a uniaxial hot press (HP) revealed the presence of CoSb inclusions with various sizes embedded inside the HH matrix. Hall effect, electrical conductivity, and thermopower data collected between 300 K and 775 K on several compositions suggested that electronic transport in the synthesized Zr₀.₅Hf₀.₅Co₀.₄Rh₀.₆Sb1–xSnx/CoSb composites strongly depends on the average size and/or mole fraction of the embedded CoSb inclusions rather than the fraction (x) of Sn substituting for Sb. Among the samples investigated, the nanocomposite with x=0.2, which contains nanometer-scale CoSb inclusions, showed the largest power factor (800 μW/K² m at 775 K) and the lowest lattice thermal conductivity (~2.2 W/m K at 775 K) leading to a six-fold enhancement in the figure of merit when compared to the Zr₀.₅Hf₀.₅Co₀.₄Rh₀.₆Sb₀.₉₉Sn₀.₀₁ bulk matrix. - Graphical abstract: CoSb nanoinclusions embedded into a p-type Zr₀.₅Hf₀.₅Co₀.₄Rh₀.₆Sb1–xSnx half-Heusler matrix simultaneously boost the thermopower and carrier mobility leading to a drastic enhancement of the power factor of the resulting bulk nanostructured materials. Highlights: • The phase composition of half-Heusler (HH) alloy is very sensitive to the synthesis method. • Mechanical alloying (MA) of elements results in bulk HH matrix with CoSb inclusions. • CoSb nanoinclusions simultaneously boost the thermopower and carrier mobility with the HH matrix. • The MA process reduces lattice thermal conductivity due to high density of grain boundaries.

  14. The fractography of casting alloys

    SciTech Connect

    Powell, G.W. )

    1994-10-01

    Several types of casting alloys were fractured using various loading modes (uniaxial tension, bending, impact, and torsion, and cyclic stressing), and the corresponding mechanical properties were determined. The unetched and etched fracture surfaces and the microstructures were examined using conventional techniques. The types of casting alloys that were the subjects f these investigations include gray iron, ductile iron, cast steel, and aluminum-base alloys (A380, A356, and 319). The fractographic studies have yielded these generalizations regarding the topography of the fracture surfaces. In the case of low-ductility alloys such as gray iron and the aluminum-base alloys, the tensile edge of a fracture surface produced by a stress system with a strong bending-moment component has a highly irregular contour, whereas the compressive edge of the fracture surface is quite straight and parallel to the bend axis. On the other hand, the periphery of a fracture surface produced by uniaxial tension has a completely irregular contour. The fracture surface produced by cyclic loading of a gray iron does not display any macroscopic evidence (such as a thumb nail) of the loading mode. However, the fracture surface of each of the other casting alloys displays clear, macroscopic evidence of failure induced by fatigue. The aluminum-base alloys fracture completely within the interdendritic region of the microstructure when subjected to monotonic loading by uniaxial tension or bending, whereas a fatigue crack propagates predominantly through the primary crystals of the microstructure.

  15. [Composition and morphology of oxides on porcelain fused to Ni-Cr alloys. Be containing alloys].

    PubMed

    Watanabe, T

    1989-06-01

    Bonding strength between porcelain and Ni-Cr alloy for the porcelain fused-to metal crown in which Be is contained in the alloy is known to be higher than those in which Be is not contained. Since, bonding between porcelain and alloy is the reaction of oxides and porcelain, the bonding is thought to be influenced by the quality the oxides film which forms on the alloy surface. The purpose of this study was to determine the composition and morphology of the oxides formed on both Be containing and non-Be contained Ni-Cr alloys. The oxides analysis was done using an EPMA and Auger analysis. Also, the Porcelain/Ni-Cr alloy interface was observed by a scanning electron microscope (SEM). The following results are indicated from this investigation: 1. The oxides from the alloys not containing Be are corundum type Cr2O3 and spinel type NiCr2O4. These oxide layers are uniform, thick and porous and the adhesion to alloy is poor. 2. The oxides from alloy containing Be is BeO only. The BeO is uniform, thin and condensed. The adhesion to the alloy is good. 3. The oxide layer formed when the porcelain is fused to alloy containing Be is thin (1 micron average) and has good adhesion to alloy. 4. Be is selectively oxidized and controlled the form of Cr2O3 and NiO. PMID:2700282

  16. Method of producing superplastic alloys and superplastic alloys produced by the method

    NASA Technical Reports Server (NTRS)

    Troeger, Lillianne P. (Inventor); Starke, Jr., Edgar A. (Inventor); Crooks, Roy (Inventor)

    2002-01-01

    A method for producing new superplastic alloys by inducing in an alloy the formation of precipitates having a sufficient size and homogeneous distribution that a sufficiently refined grain structure to produce superplasticity is obtained after subsequent PSN processing. An age-hardenable alloy having at least one dispersoid phase is selected for processing. The alloy is solution heat-treated and cooled to form a supersaturated solid solution. The alloy is plastically deformed sufficiently to form a high-energy defect structure useful for the subsequent heterogeneous nucleation of precipitates. The alloy is then aged, preferably by a multi-stage low and high temperature process, and precipitates are formed at the defect sites. The alloy then is subjected to a PSN process comprising plastically deforming the alloy to provide sufficient strain energy in the alloy to ensure recrystallization, and statically recrystallizing the alloy. A grain structure exhibiting new, fine, equiaxed and uniform grains is produced in the alloy. An exemplary 6xxx alloy of the type capable of being produced by the present invention, and which is useful for aerospace, automotive and other applications, is disclosed and claimed. The process is also suitable for processing any age-hardenable aluminum or other alloy.

  17. The crystal structure and electronic properties of a new metastable non-stoichiometric BaAl4-type compound crystallized from amorphous La6Ni34Ge60 alloy

    NASA Astrophysics Data System (ADS)

    Hasegawa, Masashi; Suzuki, Shoichiro; Ohsuna, Tetsu; Matsubara, Eiichiro; Endo, Satoshi; Inoue, Akihisa

    2004-11-01

    A new metastable La-Ge-Ni ternary BaAl4-type (ThCr2Si2-type) compound, of which the space group is I4/mmm is synthesized. It is obtained by a polymorphic transformation from an La6Ni34Ge60 amorphous alloy on crystallizing. The formula of the compound is (La0.3Ge0.7)(Ni0.85Ge0.15)2Ge2. This indicates that it is highly non-stoichiometric compared to the stoichiometric LaNi2Ge2. It is found that the c-axis lattice parameter of this compound is much longer than that of LaNi2Ge2. It should be noted that the longer c-axis unit cell parameter is attributable only to the longer interlayer distance between Ge site and Ni site layers. The temperature dependences of electrical resistivity and thermoelectric power of the (La0.3Ge0.7)(Ni0.85Ge0.15)2Ge2 compound and La6Ni34Ge60 amorphous alloy are also clarified. The comparison of these electronic properties between the two materials indicates that sp-electrons mainly contribute to the density of states around the Fermi level of this compound.

  18. Elevated temperature aluminum alloys

    NASA Technical Reports Server (NTRS)

    Meschter, Peter (Inventor); Lederich, Richard J. (Inventor); O'Neal, James E. (Inventor)

    1989-01-01

    Three aluminum-lithium alloys are provided for high performance aircraft structures and engines. All three alloys contain 3 wt % copper, 2 wt % lithium, 1 wt % magnesium, and 0.2 wt % zirconium. Alloy 1 has no further alloying elements. Alloy 2 has the addition of 1 wt % iron and 1 wt % nickel. Alloy 3 has the addition of 1.6 wt % chromium to the shared alloy composition of the three alloys. The balance of the three alloys, except for incidentql impurities, is aluminum. These alloys have low densities and improved strengths at temperatures up to 260.degree. C. for long periods of time.

  19. Investigation of Deformation Mechanisms in β-Type Ti-35Nb-2Ta-3Zr Alloy via FSP Leading to Surface Strengthening

    NASA Astrophysics Data System (ADS)

    Wang, Liqiang; Qu, Jiao; Chen, Liangyu; Meng, Qiang; Zhang, Lai-Chang; Qin, Jining; Zhang, Di; Lu, Weijie

    2015-11-01

    Friction-stir processing (FSP) is used to prepare Ti-35Nb-2Ta-3Zr alloys via different processing routes. Dislocation walls and tangles, deformation-induced α″ martensite, and deformation-induced ω phase are observed. The dominant deformation mechanisms are altered from deformation-induced α″ martensitic transformation and dislocation walls to twinning upon increasing the FSP passes. A reverse deformation-induced ω to β transformation and de-twinning process are observed together with grain refinement to the nanoscale. Meanwhile, compressive distortions along [0001] ω direction are favorable for the transformation from ω to β.

  20. Bond Strength of Gold Alloys Laser Welded to Cobalt-Chromium Alloy

    PubMed Central

    Watanabe, Ikuya; Wallace, Cameron

    2008-01-01

    The objective of this study was to investigate the joint properties between cast gold alloys and Co-Cr alloy laser-welded by Nd:YAG laser. Cast plates were fabricated from three types of gold alloys (Type IV, Type II and low-gold) and a Co-Cr alloy. Each gold alloy was laser-welded to Co-Cr using a dental laser-welding machine. Homogeneously-welded and non-welded control specimens were also prepared. Tensile testing was conducted and data were statistically analyzed using ANOVA. The homogeneously-welded groups showed inferior fracture load compared to corresponding control groups, except for Co-Cr. In the specimens welded heterogeneously to Co-Cr, Type IV was the greatest, followed by low-gold and Type II. There was no statistical difference (P<0.05) in fracture load between Type II control and that welded to Co-Cr. Higher elongations were obtained for Type II in all conditions, whereas the lowest elongation occurred for low-gold welded to Co-Cr. This study indicated that, of the three gold alloys tested, the Type IV gold alloy was the most suitable alloy for laser-welding to Co-Cr. PMID:19088892

  1. Bond strength of gold alloys laser welded to cobalt-chromium alloy.

    PubMed

    Watanabe, Ikuya; Wallace, Cameron

    2008-01-01

    The objective of this study was to investigate the joint properties between cast gold alloys and Co-Cr alloy laser-welded by Nd:YAG laser. Cast plates were fabricated from three types of gold alloys (Type IV, Type II and low-gold) and a Co-Cr alloy. Each gold alloy was laser-welded to Co-Cr using a dental laser-welding machine. Homogeneously-welded and non-welded control specimens were also prepared. Tensile testing was conducted and data were statistically analyzed using ANOVA. The homogeneously-welded groups showed inferior fracture load compared to corresponding control groups, except for Co-Cr. In the specimens welded heterogeneously to Co-Cr, Type IV was the greatest, followed by low-gold and Type II. There was no statistical difference (P<0.05) in fracture load between Type II control and that welded to Co-Cr. Higher elongations were obtained for Type II in all conditions, whereas the lowest elongation occurred for low-gold welded to Co-Cr. This study indicated that, of the three gold alloys tested, the Type IV gold alloy was the most suitable alloy for laser-welding to Co-Cr. PMID:19088892

  2. Comparison of Three Primary Surface Recuperator Alloys

    SciTech Connect

    Matthews, Wendy; More, Karren Leslie; Walker, Larry R

    2010-01-01

    Extensive work performed by Capstone Turbine Corporation, Oak Ridge National Laboratory, and various others has shown that the traditional primary surface recuperator alloy, type 347 stainless steel, is unsuitable for applications above 650 C ({approx}1200 F). Numerous studies have shown that the presence of water vapor greatly accelerates the oxidation rate of type 347 stainless steel at temperatures above 650 C ({approx}1200 F). Water vapor is present as a product of combustion in the microturbine exhaust, making it necessary to find replacement alloys for type 347 stainless steel that will meet the long life requirements of microturbine primary surface recuperators. It has been well established over the past few years that alloys with higher chromium and nickel contents than type 347 stainless steel have much greater oxidation resistance in the microturbine environment. One such alloy that has replaced type 347 stainless steel in primary surface recuperators is Haynes Alloy HR-120 (Haynes and HR-120 are trademarks of Haynes International, Inc.), a solid-solution-strengthened alloy with nominally 33 wt % Fe, 37 wt % Ni and 25 wt % Cr. Unfortunately, while HR-120 is significantly more oxidation resistant in the microturbine environment, it is also a much more expensive alloy. In the interest of cost reduction, other candidate primary surface recuperator alloys are being investigated as possible alternatives to type 347 stainless steel. An initial rainbow recuperator test has been performed at Capstone to compare the oxidation resistance of type 347 stainless steel, HR-120, and the Allegheny Ludlum austenitic alloy AL 20-25+Nb (AL 20-25+Nb is a trademark of ATI Properties, Inc. and is licensed to Allegheny Ludlum Corporation). Evaluation of surface oxide scale formation and associated alloy depletion and other compositional changes has been carried out at Oak Ridge National Laboratory. The results of this initial rainbow test will be presented and discussed in this paper.

  3. Tritium Production from Palladium Alloys

    SciTech Connect

    Claytor, T.N.; Schwab, M.J.; Thoma, D.J.; Teter, D.F.; Tuggle, D.G.

    1998-04-19

    A number of palladium alloys have been loaded with deuterium or hydrogen under low energy bombardment in a system that allows the continuous measurement of tritium. Long run times (up to 200 h) result in an integration of the tritium and this, coupled with the high intrinsic sensitivity of the system ({approximately}0.1 nCi/l), enables the significance of the tritium measurement to be many sigma (>10). We will show the difference in tritium generation rates between batches of palladium alloys (Rh, Co, Cu, Cr, Ni, Be, B, Li, Hf, Hg and Fe) of various concentrations to illustrate that tritium generation rate is dependent on alloy type as well as within a specific alloy, dependent on concentration.

  4. Thermoelectric performance of nanostructured p-type Zr0.5Hf0.5Co0.4Rh0.6Sb1-xSnx half-Heusler alloys

    NASA Astrophysics Data System (ADS)

    Maji, Pramathesh; Makongo, Julien P. A.; Zhou, Xiaoyuan; Chi, Hang; Uher, Ctirad; Poudeu, Pierre F. P.

    2013-06-01

    Several compositions of the p-type half-Heusler alloys Zr0.5Hf0.5Co0.4Rh0.6Sb1-xSnx (0?x?0.4) were synthesized by mechanically alloying high purity elemental powders using hardened steel jars and balls on a high energy shaker mill. Powder X-ray diffraction (XRD) investigations of several aliquots taken after regularly spaced milling time suggested that single phase products with half-Heusler (HH) structure can be obtained after 10 h. However, XRD and transmission electron microscopy (TEM) studies of several specimens obtained from compacted polycrystalline powders of Zr0.5Hf0.5Co0.4Rh0.6Sb1-xSnx alloys using a uniaxial hot press (HP) revealed the presence of CoSb inclusions with various sizes embedded inside the HH matrix. Hall effect, electrical conductivity, and thermopower data collected between 300 K and 775 K on several compositions suggested that electronic transport in the synthesized Zr0.5Hf0.5Co0.4Rh0.6Sb1-xSnx/CoSb composites strongly depends on the average size and/or mole fraction of the embedded CoSb inclusions rather than the fraction (x) of Sn substituting for Sb. Among the samples investigated, the nanocomposite with x=0.2, which contains nanometer-scale CoSb inclusions, showed the largest power factor (800 ?W/K2 m at 775 K) and the lowest lattice thermal conductivity (2.2 W/m K at 775 K) leading to a six-fold enhancement in the figure of merit when compared to the Zr0.5Hf0.5Co0.4Rh0.6Sb0.99Sn0.01 bulk matrix.

  5. Welding and brazing of nickel and nickel-base alloys

    NASA Technical Reports Server (NTRS)

    Mortland, J. E.; Evans, R. M.; Monroe, R. E.

    1972-01-01

    The joining of four types of nickel-base materials is described: (1) high-nickel, nonheat-treatable alloys, (2) solid-solution-hardening nickel-base alloys, (3) precipitation-hardening nickel-base alloys, and (4) dispersion-hardening nickel-base alloys. The high-nickel and solid-solution-hardening alloys are widely used in chemical containers and piping. These materials have excellent resistance to corrosion and oxidation, and retain useful strength at elevated temperatures. The precipitation-hardening alloys have good properties at elevated temperature. They are important in many aerospace applications. Dispersion-hardening nickel also is used for elevated-temperature service.

  6. Tantalum modified ferritic iron base alloys

    NASA Technical Reports Server (NTRS)

    Oldrieve, R. E.; Blankenship, C. P. (Inventor)

    1977-01-01

    Strong ferritic alloys of the Fe-CR-Al type containing 0.4% to 2% tantalum were developed. These alloys have improved fabricability without sacrificing high temperature strength and oxidation resistance in the 800 C (1475 F) to 1040 C (1900 F) range.

  7. Alloys of clathrate allotropes for rechargeable batteries

    DOEpatents

    Chan, Candace K; Miller, Michael A; Chan, Kwai S

    2014-12-09

    The present disclosure is directed at an electrode for a battery wherein the electrode comprises clathrate alloys of silicon, germanium or tin. In method form, the present disclosure is directed at methods of forming clathrate alloys of silicon, germanium or tin which methods lead to the formation of empty cage structures suitable for use as electrodes in rechargeable type batteries.

  8. Clinical evaluation of three amalgam alloys.

    PubMed

    Tyas, M J; Ewers, G J

    1993-06-01

    A total of 117 high-copper amalgams of three types (platinum-modified, palladium-modified and dispersed phase) was placed by two operators in 59 patients. Restorations were assessed for marginal fracture, tarnish, corrosion, and tooth staining on continuous linear photographic rating scales. After one year, the platinum- and palladium-modified alloys showed a significant amount of tarnish, and all three alloys had statistically significant marginal fracture. The only significant difference between alloys at one year was the greater tarnish of the platinum-modified alloy. There was no association between static creep and marginal fracture. PMID:8373297

  9. New alloys to conserve critical elements

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.

    1978-01-01

    Based on availability of domestic reserves, chromium is one of the most critical elements within the U.S. metal industry. New alloys having reduced chromium contents which offer potential as substitutes for higher chromium containing alloys currently in use are being investigated. This paper focuses primarily on modified Type 304 stainless steels having one-third less chromium, but maintaining comparable oxidation and corrosion properties to that of type 304 stainless steel, the largest single use of chromium. Substitutes for chromium in these modified Type 304 stainless steel alloys include silicon and aluminum plus molybdenum.

  10. The Development of the Low-Cost Titanium Alloy Containing Cr and Mn Alloying Elements

    NASA Astrophysics Data System (ADS)

    Zhu, Kailiang; Gui, Na; Jiang, Tao; Zhu, Ming; Lu, Xionggang; Zhang, Jieyu; Li, Chonghe

    2014-04-01

    The ? + ?-type Ti-4.5Al-6.9Cr-2.3Mn alloy has been theoretically designed on the basis of assessment of the Ti-Al-Cr-Mn thermodynamic system and the relationship between the molybdenum equivalent and mechanical properties of titanium alloys. The alloy is successfully prepared by the split water-cooled copper crucible, and its microstructures and mechanical properties at room temperature are investigated using the OM, SEM, and the universal testing machine. The results show that the Ti-4.5Al-6.9Cr-2.3Mn alloy is an ? + ?-type alloy which is consistent with the expectation, and its fracture strength, yield strength, and elongation reach 1191.3, 928.4 MPa, and 10.7 pct, respectively. Although there is no strong segregation of alloying elements under the condition of as-cast, the segregation of Cr and Mn is obvious at the grain boundary after thermomechanical treatment.

  11. High-resolution electron microscopy analysis of structural defects in a (2/1, 5/3)-type approximant of a decagonal quasicrystal of an Al-Pd-Mn alloy

    SciTech Connect

    Yu, D.P.; Ren, G.; Zhang, Z.

    1996-10-01

    Structural defects were analyzed by means of high-resolution electron microscopy (HREM) in a crystalline (2/1, 5/3)-type Fibonacci approximant of an Al-Pd-Mn alloy system. A kind of stacking fault is observed with a projected displacement vector R parallel to the [{minus}3 0 29] direction; its amplitude {vert_bar}R{vert_bar} = 2a sin 18 deg = 1.19 nm, and its habit plane lies in the (1 0 1) plane. Two kinds of domain boundaries have been found and the domains are related by a 180 deg rotation around the c-axis plus a displacement along the [3 0 {minus}29] or the [{minus}3 0 {minus}29] direction in a plane perpendicular to the b-axis. The domain boundary planes are the {l_brace}1 0 1{r_brace} planes.

  12. Alloy softening in binary molybdenum alloys

    NASA Technical Reports Server (NTRS)

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

    1972-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Koster, Werner; Rauscher, Walter

    1951-01-01

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

  14. Electron mobility in n-type Hg(1-x)Cd(x)Te and Hg(1-x)Zn(x)Te alloys

    NASA Technical Reports Server (NTRS)

    Patterson, J. D.; Gobba, Wafaa A.; Lehoczky, S. L.

    1992-01-01

    Calculations of electron mobility in n-type mercury cadmium telluride (MCT), a candidate material for IR detectors, and n-type mercury zinc telluride (MZT) are compared. It is found that electron mobilities in MCT and MZT are nearly the same for equivalent energy gaps. The results are also found to compare will with experimental data. Directions of future research are briefly discussed.

  15. Effects of microstructure and alloy contents on the Lueders line formation in Al-Mg alloys

    SciTech Connect

    Choi, I.; Jin, S.; Kang, S.

    1998-02-13

    There have been several efforts to replace steel with aluminum for automobile weight reduction. Main efforts have been on the development of 5000 series Al alloys (Al-Mg alloys) because of their good formability. However, Al-Mg alloys suffer from the formation of various types of Lueders line. Particularly, type A Lueders lines formed under 1% elongation make a surface completely unacceptable for outer auto body panels. There are various nomenclatures of Lueders line according to researchers. Thompson`s classification will be used in this study because it classifies Lueders lines by surface appearance and shape of stress-strain curve. The effect of grain size and microstructure on the formation of type A Lueders lines in Al-Mg alloys has been investigated in this study. Additionally, the effect of Mg content on the mechanical properties and Lueders line formation in Al-Mg alloys has also been evaluated.

  16. Metal alloy identifier

    DOEpatents

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

    1987-01-01

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

  17. Effects of substitution, pressure, and temperature on the phonon mode in layered-rocksalt-type Li(1-x/2)Ga(1-x/2)ZnxO (x = 0.036-0.515) alloys

    NASA Astrophysics Data System (ADS)

    Tan, Lijie; Hu, Qiwei; Lei, Li; Jiang, Xiaodong; Gao, Shangpan; He, Duanwei

    2015-11-01

    ZnO-based semiconductor alloys, Li(1-x/2)Ga(1-x/2)ZnxO (x = 0.036-0.515) with a layered-rocksalt-type structure, have been prepared under high pressure. The composition, pressure, and temperature dependence of phonons have been studied by Raman spectroscopy. We observe two disorder-activated Raman (DAR) modes when the Zn composition x increases: a broad Raman peak at ca. 400 cm-1 and a left-shoulder peak at ca. 530 cm-1 on the low-frequency side of A1g mode at ca. 580 cm-1, which can be explained by reference to the phonon density of states for rocksalt-type ZnO. With the increase of the pressure and temperature, the left-shoulder DAR mode induced by substitution does not change at the same pace with the A1g mode at Brillouin-zone center. We find that ion substitution can be seen as a kind of chemical pressure, and the chemical pressure caused by internal substitution and the physical pressure caused by external compression have equivalent effects on the shortening of correlation length, the distortion of crystal lattice, and the change of atomic occupation.

  18. Improvements in the Superelasticity and Change in Deformation Mode of ?-Type TiNb24Zr2 Alloys Caused by Aging Treatments

    NASA Astrophysics Data System (ADS)

    Li, Qiang; Niinomi, Mitsuo; Nakai, Masaaki; Cui, Zhenduo; Zhu, Shengli; Yang, Xianjin

    2011-09-01

    The superelasticity and deformation behaviors of ?-type TiNb24Zr2 subjected to aging treatment were investigated in this study. As the aging time increased, the precipitation of isothermal ? phase was found to restrain the formations of twinning and stress-induced ?? martensite. The superelastic recovery of the sample first improves and then deteriorates with extended aging times. A maximum and stable superelastic recovery of 4.3 pct is obtained for an aging time of 7.2 ks.

  19. Structural alloys for high field superconducting magnets

    SciTech Connect

    Morris, J.W. Jr.

    1985-08-01

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

  20. Alloy 33 weld overlay extends boiler tube life and saves money

    SciTech Connect

    Paul, L.; Clark, G.; Ossenberg-Engels, A.

    2007-09-15

    Low-NOx burners installed in coal-fired utility boilers cause problems with boiler tube cracking. Materials with increased corrosion resistance such as the new Alloy 33 should be more resistant to this type of 'circumferential cracking'. Alloy 33 is cheaper and has lower nickel and molybdenum content than the traditional Alloy 622 and 625. The article describes extensive corrosion testing experiments carried out by ThyssenKrupp VDM on Alloy 33 and Alloy 622. In the lab, in environments representative of coal-fired boilers operating under low-NOx combustion conditions, Alloy 33 was found to be better than Alloy 622. Field tests compared Alloy 33 and Alloy 622 in two supercritical tangentially-fired boilers and one tangentially-fired high pressure drum boiler. After up to 23 months of exposure there was no evidence of cracks and only slight evidence of corrosion in Alloy 33. 1 fig., 2 tabs., 2 photos.

  1. Strain engineering of nanoscale Si P-type metal-oxide-semiconductor field-effect transistor devices with SiGe alloy integrated with contact-etch-stop layer stressors.

    PubMed

    Lee, Chang-Chun

    2012-07-01

    Strained-silicon (Si) has been incorporated into a leading nanoscale logic technology. By means of silicon-germanium (SiGe) alloy stressor embedded in source and drain (S/D) region, the performance of P-type metal-oxide-semiconductor field-effect transistors (PMOSFETs) is effectively enhanced. However, when a compressive contact-etch-stop layer (CESL) is combined, the stress interaction and relative impacts of SiGe stressor integrated with CESL on mobility enhancement has been little reported. Therefore, the research performs a three dimensional (3D) stress simulation evaluation based on finite element method (FEM) for PMOSFETs with S/D SiGe stressor and compressive CESL. The proposed simulation methodology is validated as compared with other technological literatures. In additions, the gate width dependency is systematically discussed to explore the stress effects on devices. The analysis results indicate that a -2.6 GPa CESL would continue boosting the stress magnitude on Si channel region except for a gate width smaller than 50 nm. The results are useful for nanoscale transistor while selecting a proper CESL in the manufacturing processes of advanced logic technologies. PMID:22966579

  2. Half-metallic and magnetic properties of full-Heusler alloys Zr2CrZ (Z=Ga, In) with Hg2CuTi-type structure: A first-principles study

    NASA Astrophysics Data System (ADS)

    Deng, Zun-Yi; Zhang, Jian-Min

    2016-01-01

    The half-metallic and magnetic properties of Heusler alloys Zr2 CrZ (Z=Ga, In) with Hg2 CuTi -type structure have been investigated by using the first-principles projector augmented wave (PAW) potential within the generalized gradient approximation (GGA). The equilibrium lattice constants are 6.635 and 6.875 for Zr2 CrGa and Zr2 CrIn, respectively. Under compression and expansion deformations within lattice constant ranges of 6.515-7.100 and 6.371-7.126 for Zr2 CrGa and Zr2 CrIn, respectively, the Zr2 CrZ (Z=Ga, In) maintain a half-metallic nature with a fixed total magnetic moment of -1 ?B / f.u ., following the Slater-Pauling rule ?t = Zt - 18, but the absolute values of the local magnetic moments on Zr and Cr atoms increase with increasing lattice constant.

  3. Nucleation mechanism of nano-sized NaZn13-type and ?-(Fe,Si) phases in La-Fe-Si alloys during rapid solidification.

    PubMed

    Hou, Xue-Ling; Xue, Yun; Liu, Chun-Yu; Xu, Hui; Han, Ning; Ma, Chun-Wei; Phan, Manh-Huong

    2015-01-01

    The nucleation mechanism involving rapid solidification of undercooled La-Fe-Si melts has been studied experimentally and theoretically. The classical nucleation theory-based simulations show a competitive nucleation process between the ?-(Fe,Si) phase (size approximately 10 to 30nm) and the cubic NaZn13-type phase (hereinafter 1:13 phase, size approximately 200 to 400nm) during rapid solidification, and that the undercooled temperature change ?T plays an important factor in this process. The simulated results about the nucleation rates of the ?-(Fe,Si) and 1:13 phases in La-Fe-Si ribbons fabricated by a melt-spinner using a copper wheel with a surface speed of 35m/s agree well with the XRD, SEM, and TEM studies of the phase structure and microstructure of the ribbons. Our study paves the way for designing novel La-Fe-Si materials for a wide range of technological applications. PMID:25852432

  4. Tellurium n-type doping of highly mismatched amorphous GaN1-xAsx alloys in plasma-assisted molecular beam epitaxy

    DOE PAGESBeta

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

    2014-10-01

    In this paper we report our study on n-type Te doping of amorphous GaN1-xAsx layers grown by plasma-assisted molecular beam epitaxy. We have used a low temperature PbTe source as a source of tellurium. Reproducible and uniform tellurium incorporation in amorphous GaN1-xAsx layers has been successfully achieved with a maximum Te concentration of 9×10²⁰ cm⁻³. Tellurium incorporation resulted in n-doping of GaN1-xAsx layers with Hall carrier concentrations up to 3×10¹⁹ cm⁻³ and mobilities of ~1 cm²/V s. The optimal growth temperature window for efficient Te doping of the amorphous GaN1-xAsx layers has been determined.

  5. Tellurium n-type doping of highly mismatched amorphous GaN1-xAsx alloys in plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    In this paper we report our study on n-type Te doping of amorphous GaN1-xAsx layers grown by plasma-assisted molecular beam epitaxy. We have used a low temperature PbTe source as a source of tellurium. Reproducible and uniform tellurium incorporation in amorphous GaN1-xAsx layers has been successfully achieved with a maximum Te concentration of 91020 cm-3. Tellurium incorporation resulted in n-doping of GaN1-xAsx layers with Hall carrier concentrations up to 31019 cm-3 and mobilities of ~1 cm2/V s. The optimal growth temperature window for efficient Te doping of the amorphous GaN1-xAsx layers has been determined.

  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. Binary Colloidal Alloy Test

    NASA Technical Reports Server (NTRS)

    2001-01-01

    Close-up view of the Binary Colloidal Alloy Test during an experiment run aboard the Russian Mir space station. BCAT is part of an extensive series of experiments plarned to investigate the fundamental properties of colloids so that scientists can make colloids more useful for technological applications. Some of the colloids studied in BCAT are made of two different sized particles (binary colloidal alloys) that are very tiny, uniform plastic spheres. Under the proper conditions, these colloids can arrange themselves in a pattern to form crystals, which may have many unique properties that may form the basis of new classes of light switches, displays, and optical devices that can fuel the evolution of the next generation of computer and communication technologies. This Slow Growth hardware consisted of a 35-mm camera aimed toward a module which contained 10 separate colloid samples. To begin the experiment, one of the astronauts would mix the samples to disperse the colloidal particles. Then the hardware operated autonomously, taking photos of the colloidal samples over a 90-day period. The investigation proved that gravity plays a central role in the formation and stability of these types of colloidal crystal structures. The investigation also helped identify the optimum conditions for the formation of colloidal crystals, which will be used for optimizing future microgravity experiments in the study of colloidal physics. Dr. David Weitz of the University of Pennsylvania and Dr. Peter Pusey of the University of Edinburgh, United Kingdom, are the principal investigators.

  8. Turbine Blade Alloy

    NASA Technical Reports Server (NTRS)

    MacKay, Rebecca

    2001-01-01

    The High Speed Research Airfoil Alloy Program developed a fourth-generation alloy with up to an +85 F increase in creep rupture capability over current production airfoil alloys. Since improved strength is typically obtained when the limits of microstructural stability are exceeded slightly, it is not surprising that this alloy has a tendency to exhibit microstructural instabilities after high temperature exposures. This presentation will discuss recent results obtained on coated fourth-generation alloys for subsonic turbine blade applications under the NASA Ultra-Efficient Engine Technology (UEET) Program. Progress made in reducing microstructural instabilities in these alloys will be presented. In addition, plans will be presented for advanced alloy development and for computational modeling, which will aid future alloy development efforts.

  9. Cobalt-base alloy

    NASA Technical Reports Server (NTRS)

    Dreshfield, R. L.; Sandrock, G. D.; Freche, J. C. (Inventor)

    1973-01-01

    A microstructurally stable, high strength cobalt based alloy for use at elevated temperatures to 2125 F was developed. The alloys are particularly directed for use in stators and other low stress components in advanced gas turbines.

  10. First-principles molecular spin dynamics study on the magnetic structure of Mn-based alloys with Cu3Au-type crystal structure

    NASA Astrophysics Data System (ADS)

    Uchida, T.; Kakehashi, Y.; Kimura, N.

    2016-02-01

    The magnetic and electronic structures of Mn3Pt and Mn3Rh, which are three-dimensional frustrated itinerant magnets with a Cu3Au-type crystal structure, have been investigated by means of the first-principles Molecular Spin Dynamics (MSD) method. The theory is based on the first-principles tight-binding linear muffin-tin orbital Hamiltonian combined with the functional integral method and the isothermal MSD technique, and allows us to determine automatically the magnetic structures of itinerant magnets at finite temperatures. The MSD calculations using a self-consistent site-dependent effective medium show that below the Nel temperature Mn3Pt with fixed crystal structure (Cu3Au structure) and volume exhibits a second-order transition from a triangular structure to another noncollinear phase with increasing temperature. Mn3Rh, on the other hand, shows no sign of a phase transition up to the Nel temperature. We found that the Mn-Eg DOS peak, which is responsible for the ferromagnetic couplings among the second nearest-neighbor Mn local moments, develops at the Fermi energy (EF) around 350 K for Mn3Pt, while the peak development for Mn3Rh occurs with increasing temperature slightly above EF.

  11. Investigation of crystallization of a mechanically alloyed Sm-Fe alloy

    SciTech Connect

    Lue, M.Q.; Wang, K.Y.; Miao, W.F.; Song, Q.H.; Sun, W.S.; Wei, W.D.; Wang, L.B. )

    1992-06-15

    The crystallization of a mechanically alloyed Sm-Fe alloy was investigated. The results show that the Sm-Fe alloy prepared by mechanical alloying consists of amorphous Sm-Fe phase and crystalline {alpha}-Fe phase. The composition of the alloy is inhomogeneous, i.e., the surface of the as-milled powder is relatively poor in iron. The crystallization process involves the long-range diffusion of iron atoms and solid state reaction. After proper crystallization, the as-milled powder transforms into a Sm{sub 2}Fe{sub 17} phase completely; no distinguishable crystalline {alpha}-Fe phase can be found. A metastable phase, which may be a Sm{sub 2}Fe{sub 17} phase with the structure of hexagonal Th{sub 2}Ni{sub 17} type, appears during the crystallization process.

  12. SUPERCONDUCTING VANADIUM BASE ALLOY

    DOEpatents

    Cleary, H.J.

    1958-10-21

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

  13. DELTA PHASE PLUTONIUM ALLOYS

    DOEpatents

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

    1960-03-22

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

  14. The influence of heat treatment and role of boron on sliding wear behaviour of ?-type Ti-35Nb-7.2Zr-5.7Ta alloy in dry condition and in simulated body fluids.

    PubMed

    Majumdar, P; Singh, S B; Chakraborty, M

    2011-04-01

    The wear behaviour of heat-treated Ti-35Nb-7.2Zr-5.7Ta (TNZT) and Ti-35Nb-7.2Zr-5.7Ta-0.5B (TNZTB) alloys (all compositions are in wt%) was investigated in dry condition and in simulated body fluids. It has been found that there is no straightforward relationship between the wear rate and the microstructure. The hardness has no appreciable effect on the wear behaviour of these alloys. The presence of boron in the TNZT alloy deteriorates its wear properties. The wear rate of TNZT and TNZTB alloys in various media increases in the following sequence: dry condition < Hank's solution < bovine serum. PMID:21316616

  15. High strength alloys

    SciTech Connect

    Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J; John, Randy Carl; Kim, Dong Sub

    2010-08-31

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tubular that is at least partially made from a material containing at least one of the metal alloys.

  16. High strength alloys

    SciTech Connect

    Maziasz, Phillip James; Shingledecker, John Paul; Santella, Michael Leonard; Schneibel, Joachim Hugo; Sikka, Vinod Kumar; Vinegar, Harold J.; John, Randy Carl; Kim, Dong Sub

    2012-06-05

    High strength metal alloys are described herein. At least one composition of a metal alloy includes chromium, nickel, copper, manganese, silicon, niobium, tungsten and iron. System, methods, and heaters that include the high strength metal alloys are described herein. At least one heater system may include a canister at least partially made from material containing at least one of the metal alloys. At least one system for heating a subterranean formation may include a tublar that is at least partially made from a material containing at least one of the metal alloys.

  17. Spark alloying of an AL9 alloy by hard alloys

    NASA Astrophysics Data System (ADS)

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

    2015-08-01

    The phase compositions of spark coatings of Kh12M steel with a VT1-0 (titanium) alloy and T15K6 and T30K4 hard alloys are studied. It is shown that the TiC titanium carbide forms in all cases and tungsten carbide decomposes with the formation of tungsten in a coating. These processes are intensified by increasing time, capacitance, and frequency. The surface hardness, the sample weight, and the white layer thickness increase monotonically.

  18. Hydrogen permeation characteristics of Incoloy 907 alloy

    SciTech Connect

    Xu, J.; Sun, X.K.; Liu, Q.Q.; Zhao, X.; Fan, C.G. )

    1993-05-15

    The problem of brittle fracture induced by hydrogen ingress from environment must be considered for some high-strength alloys, particularly for the superalloys strengthened by [gamma][prime] precipitation, used in fields such as aerospace and nuclear power. Therefore, a number of studies on hydrogen performance of superalloys have been recently carried out. The understanding of hydrogen transport characteristics in these alloys is important to clarify the hydrogen embrittlement mechanism. Although hydrogen permeabilities and diffusivities of some superalloys have been reported, the study of the hydrogen permeation and diffusion in Incoloy 907 alloy, a type of Fe-Ni-Co based superalloy, is still absent to date. In the present work, a gaseous permeation technique was employed to measure hydrogen permeability and diffusivity in this alloy, in order to understand the relationship between hydrogen permeation and microstructure.

  19. Environmental embrittlement in ordered intermetallic alloys

    SciTech Connect

    Liu, C.T.; Stoloff, N.S.

    1992-12-31

    Ordered intermetallics based on aluminides and silicides possess many promising properties for elevated-temperature applications; however, poor fracture resistance and limited fabricability restrict their use as engineering material. Recent studies have shown that environmental embrittlement is a major cause of low ductility and brittle fracture in many ordered intermetallic alloys. There are two types of environmental embrittlement observed in intermetallic alloys. One is hydrogen-induced embrittlement occurring at ambient temperatures in air. The other is oxygen-induced embrittlement in oxidizing atmospheres at elevated temperatures. In most cases, the embrittlements are due to a dynamic effect involving generation and penetration of embrittling agents (i.e., hydrogen or oxygen ) during testing. Diffusion of embrittling agents plays a dominant role in fracture of these intermetallic alloys. This chapter summarizes recent progress in understanding and reducing environmental embrittlement in these alloys.

  20. Creep Resistant Zinc Alloy

    SciTech Connect

    Frank E. Goodwin

    2002-12-31

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

  1. Weldability of High Alloys

    SciTech Connect

    Maroef, I

    2003-01-22

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

  2. The hydrogen storage properties of new Mg{sub 2}Ni alloy

    SciTech Connect

    Kohno, Tatsuoki; Tsuruta, Shinji; Kanda, Motoya

    1996-09-01

    The hydrogen storage properties of a novel Mg{sub 2}Ni alloy powder prepared with a mechanical grinding method were investigated. This alloy powder was transformed to an amorphous-like state by this treatment. As a result, an electrode of this alloy shows a large discharge capacity (750 mAh/g) which is 2.5 times higher than that of AB{sub 5}-type alloys. This significant improvement of hydrogen storage properties seems to be achieved by the increase in the crystal boundary and a heterogeneous strain in this alloy. The hydrogen equilibrium pressure of this alloy increased markedly.

  3. 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.

  4. Braze alloy spreading on steel

    NASA Technical Reports Server (NTRS)

    Siewert, T. A.; Heine, R. W.; Lagally, M. G.

    1978-01-01

    Scanning electron microscopy (SEM) and Auger electron microscopy (AEM) were employed to observe elemental surface decomposition resulting from the brazing of a copper-treated steel. Two types of steel were used for the study, stainless steel (treated with a eutectic silver-copper alloy), and low-carbon steel (treated with pure copper). Attention is given to oxygen partial pressure during the processes; a low enough pressure (8 x 10 to the -5th torr) was found to totally inhibit the spreading of the filler material at a fixed heating cycle. With both types of steel, copper treatment enhanced even spreading at a decreased temperature.

  5. Alloy 10: A 1300F Disk Alloy

    NASA Technical Reports Server (NTRS)

    Gayda, John

    2000-01-01

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

  6. Development of new metallic alloys for biomedical applications.

    PubMed

    Niinomi, Mitsuo; Nakai, Masaaki; Hieda, Junko

    2012-11-01

    New low modulus ?-type titanium alloys for biomedical applications are still currently being developed. Strong and enduring ?-type titanium alloy with a low Young's modulus are being investigated. A low modulus has been proved to be effective in inhibiting bone atrophy, leading to good bone remodeling in a bone fracture model in the rabbit tibia. Very recently ?-type titanium alloys with a self-tunable modulus have been proposed for the construction of removable implants. Nickel-free low modulus ?-type titanium alloys showing shape memory and super elastic behavior are also currently being developed. Nickel-free stainless steel and cobalt-chromium alloys for biomedical applications are receiving attention as well. Newly developed zirconium-based alloys for biomedical applications are proving very interesting. Magnesium-based or iron-based biodegradable biomaterials are under development. Further, tantalum, and niobium and its alloys are being investigated for biomedical applications. The development of new metallic alloys for biomedical applications is described in this paper. PMID:22765961

  7. Predicting the properties of the lead alloys from DFT calculations

    NASA Astrophysics Data System (ADS)

    Buimaga-Iarinca, L.; Calborean, A.

    2015-12-01

    We provide qualitative results for the physical properties of the lead alloys at atomic scale by using DFT calculations. Our approach is based on the two assumptions: (i) the geometric structure of lead atoms provides a matrix where the alloying elements can take their positions in the structure as substitutions and (ii) there is a small probability of a direct interaction between the alloying elements, thus the interactions of each alloying element may be approximated by the interactions to the lead matrix. DFT calculations are used to investigate the interaction between several types of impurities and the lead matrix for low concentrations of the alloying element. We report results such as the enthalpy of formation, charge transfer and mechanical stress induced by the impurities in the lead matrix; these results can be used as qualitative guide in tuning the physico-chemical properties of the lead alloys.

  8. Superplastic behavior in a commercial 5083 aluminum alloy

    SciTech Connect

    Vetrano, J.S.; Lavender, C.A.; Smith, M.T.; Bruemmer, S.M. ); Hamilton, C.H. . Dept. of Mechanical and Materials Engineering)

    1994-03-01

    When considering the forming and post-forming properties required of a superplastic material, attractive candidates are commercial Al-Mg-Mn weldable alloys such as AA5083. There have been several investigations of hot deformation of 5083-type alloys in the literature. Only two studies evaluated commercial-purity 5083 and they achieved tensile elongations of 150% and 200%. Alloy modification has produced improved behavior in three 5083-type alloys developed specifically for SPF. Two were deemed high-purity 5083 (low Fe and Si) and achieved elongations of 450% and 630%. Engineering strains up to 700% were measured by Watanabe et al. in a 5083-based alloy with the addition of 0.6% Cu as a grain refiner. These results suggest that alloy modifications such as reduced Fe and Si contents or Cu additions may be required to improve superplastic response. Unfortunately, specific SPF-grade 5083 alloys are substantially more expensive than the commercial grade, and the addition of Cu decreases the corrosion resistance of the base material. The purpose of this work is to examine the effect of prior degrees of cold work on the SPF behavior of a standard-grade 5083 alloy. Superplastic behavior of this material at 510[degree]C is assessed and compared to published results for the SPF-grade alloys.

  9. Analysis of thermoelectric properties of high-temperature complex alloys of nickel-base, iron-base and cobalt-base groups

    NASA Technical Reports Server (NTRS)

    Holanda, R.

    1984-01-01

    The thermoelectric properties alloys of the nickel-base, iron-base, and cobalt-base groups containing from 1% to 25% 106 chromium were compared and correlated with the following material characteristics: atomic percent of the principle alloy constituent; ratio of concentration of two constituents; alloy physical property (electrical resistivity); alloy phase structure (percent precipitate or percent hardener content); alloy electronic structure (electron concentration). For solid-solution-type alloys the most consistent correlation was obtained with electron concentration, for precipitation-hardenable alloys of the nickel-base superalloy group, the thermoelectric potential correlated with hardener content in the alloy structure. For solid-solution-type alloys, no problems were found with thermoelectric stability to 1000; for precipitation-hardenable alloys, thermoelectric stability was dependent on phase stability. The effects of the compositional range of alloy constituents on temperature measurement uncertainty are discussed.

  10. Ordered iron aluminide alloys having an improved room-temperature ductility and method thereof

    DOEpatents

    Sikka, Vinod K.

    1992-01-01

    A process is disclosed for improving the room temperature ductility and strength of iron aluminide intermetallic alloys. The process involves thermomechanically working an iron aluminide alloy by means which produce an elongated grain structure. The worked alloy is then heated at a temperature in the range of about 650.degree. C. to about 800.degree. C. to produce a B2-type crystal structure. The alloy is rapidly cooled in a moisture free atmosphere to retain the B2-type crystal structure at room temperature, thus providing an alloy having improved room temperature ductility and strength.

  11. Catalyst Alloys Processing

    NASA Astrophysics Data System (ADS)

    Tan, Xincai

    2014-10-01

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

  12. Mechanical, physical, and chemical characterization of Ti-35Nb-5Zr and Ti-35Nb-10Zr casting alloys.

    PubMed

    Ribeiro, Ana Lcia Roselino; Junior, Rubens Caram; Cardoso, Flvia Farias; Filho, Romeu Belon Fernandes; Vaz, Lus Geraldo

    2009-08-01

    Titanium is used due its excellent properties in medical and dentistry areas. With the objective of exploiting better mechanical properties, not altering its biocompatibility, it was intended to add niobium and zirconium to the titanium, being formulated two alloys Ti-35%Nb-5%Zr (alloy 1) and Ti-35%Nb-10%Zr (alloy 2) wt% produced by an arc melting method. The chemical analysis of the samples was accomplished by X-ray fluorescence, and the microstrutural evaluation by scanning electron microscopy and X-ray diffraction. The mechanical tests were: Vickers hardness, tensile strength, mechanical cycling, and fracture analysis. The results allowed characterizing the alloy 1 as alpha + beta type and the alloy 2 as beta type. It is found that the alloy 1 presented larger hardness and smaller tensile strength than the alloy 2. The fractures, after the tensile test, were of the ductile type and, after the mechanical cycling, they were of the mixed type for both alloys. PMID:19337820

  13. Photoelectron spectroscopic study on the electronic structures of the dental gold alloys and their interaction with L-cysteine

    SciTech Connect

    Ogawa, Koji; Takahashi, Kazutoshi; Azuma, Junpei; Kamada, Masao; Tsujibayashi, Toru; Ichimiya, Masayoshi; Fujimoto, Hitoshi; Sumimoto, Michinori

    2011-11-15

    The valence electronic structures of the dental gold alloys, type 1, type 3, and K14, and their interaction with L-cysteine have been studied by ultraviolet photoelectron spectroscopy with synchrotron radiation. It was found that the electronic structures of the type-1 and type-3 dental alloys are similar to that of polycrystalline Au, while that of the K14 dental alloy is much affected by Cu. The peak shift and the change in shape due to alloying are observed in all the dental alloys. It is suggested that the new peak observed around 2 eV for the L-cysteine thin films on all the dental alloys may be due to the bonding of S 3sp orbitals with the dental alloy surfaces, and the Cu-S bond, as well as the Au-S and Au-O bonds, may cause the change in the electronic structure of the L-cysteine on the alloys.

  14. PLUTONIUM-ZIRCONIUM ALLOYS

    DOEpatents

    Schonfeld, F.W.; Waber, J.T.

    1960-08-30

    A series of nuclear reactor fuel alloys consisting of from about 5 to about 50 at.% zirconium (or higher zirconium alloys such as Zircaloy), balance plutonium, and having the structural composition of a plutonium are described. Zirconium is a satisfactory diluent because it alloys readily with plutonium and has desirable nuclear properties. Additional advantages are corrosion resistance, excellent fabrication propenties, an isotropie structure, and initial softness.

  15. Low activation ferritic alloys

    DOEpatents

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

    1985-02-07

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

  16. Low activation ferritic alloys

    DOEpatents

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

    1986-01-01

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

  17. Magnesium Alloys as a Biomaterial for Degradable Craniofacial Screws

    PubMed Central

    Henderson, Sarah E.; Verdelis, Konstantinos; Maiti, Spandan; Pal, Siladitya; Chung, William L.; Chou, Da-Tren; Kumta, Prashant N.; Almarza, Alejandro J.

    2014-01-01

    Recently, magnesium (Mg) alloys have received significant attention as a potential biomaterial for degradable implants, and this study was directed at evaluating the suitability of Mg for craniofacial bone screws. The objective was to implant screws fabricated from commercially available Mg-alloys (pure Mg and AZ31) in-vivo in a rabbit mandible. First, Mg-alloy screws were compared to stainless steel screws in an in-vitro pull-out test and determined to have a similar holding strength (~40N). A finite element model of the screw was created using the pull-out test data, and the model can be used for future Mg-alloy screw design. Then, Mg-alloy screws were implanted for 4, 8, and 12 weeks, with two controls of an osteotomy site (hole) with no implant and a stainless steel screw implanted for 12 weeks. MicroCT (computed tomography) was used to assess bone remodeling and Mg-alloy degradation, both visually and qualitatively through volume fraction measurements for all time points. Histologic analysis was also completed for the Mg-alloys at 12 weeks. The results showed that craniofacial bone remodeling occurred around both Mg-alloy screw types. Pure Mg had a different degradation profile than AZ31, however bone growth occurred around both screw types. The degradation rate of both Mg-alloy screw types in the bone marrow space and the muscle were faster than in the cortical bone space at 12 weeks. Furthermore, it was shown that by alloying Mg, the degradation profile could be changed. These results indicate the promise of using Mg-alloys for craniofacial applications. PMID:24384125

  18. The Mg impurity in nitride alloys

    NASA Astrophysics Data System (ADS)

    Zvanut, M. E.; Willoughby, W. R.; Sunay, U. R.; Koleske, D. D.; Allerman, A. A.; Wang, Ke; Araki, Tsutomu; Nanishi, Yasushi

    2014-02-01

    Although several magnetic resonance studies address the Mg acceptor in GaN, there are few reports on Mg doping in the alloys, where hole production depends strongly on the Al or In content. Our electron paramagnetic resonance (EPR) measurements of the p-type alloys suggest that the Mg impurity retains the axial symmetry, characteristic of a p-type dopant in both alloys; however, In and Al produce additional, different characteristics of the acceptor. In InGaN, the behavior is consistent with a lowering of the acceptor level and increasing hole density as In concentration increases. For AlGaN, the amount of neutral Mg decreases with increasing Al content, which is attributed to different kinetics of hydrogen diffusion thought to occur in samples with higher Al mole fraction.

  19. The Mg impurity in nitride alloys

    SciTech Connect

    Zvanut, M. E.; Willoughby, W. R.; Sunay, U. R.; Koleske, D. D.; Allerman, A. A.; Wang, Ke; Araki, Tsutomu; Nanishi, Yasushi

    2014-02-21

    Although several magnetic resonance studies address the Mg acceptor in GaN, there are few reports on Mg doping in the alloys, where hole production depends strongly on the Al or In content. Our electron paramagnetic resonance (EPR) measurements of the p-type alloys suggest that the Mg impurity retains the axial symmetry, characteristic of a p-type dopant in both alloys; however, In and Al produce additional, different characteristics of the acceptor. In InGaN, the behavior is consistent with a lowering of the acceptor level and increasing hole density as In concentration increases. For AlGaN, the amount of neutral Mg decreases with increasing Al content, which is attributed to different kinetics of hydrogen diffusion thought to occur in samples with higher Al mole fraction.

  20. Machinability of Titanium Alloys

    NASA Astrophysics Data System (ADS)

    Rahman, Mustafizur; Wong, Yoke San; Zareena, A. Rahmath

    Titanium and its alloys find wide application in many industries because of their excellent and unique combination of high strength-to-weight ratio and high resistance to corrosion. The machinability of titanium and its alloys is impaired by its high chemical reactivity, low modulus of elasticity and low thermal conductivity. A number of literatures on machining of titanium alloys with conventional tools and advanced cutting tool materials is reviewed. The results obtained from the study on high speed machining of Ti-6Al-4V alloys with cubic boron nitride (CBN), binderless cubic boron nitride (BCBN) and polycrystalline diamond (PCD) are also summarized.

  1. Corrosion Embrittlement of Duralumin II Accelerated Corrosion Tests and the Behavior of High-Strength Aluminum Alloys of Different Compositions

    NASA Technical Reports Server (NTRS)

    Rawdon, Henry S

    1928-01-01

    The permanence, with respect to corrosion, of light aluminum alloy sheets of the duralumin type, that is, heat-treatable alloys containing Cu, Mg, Mn, and Si is discussed. Alloys of this type are subject to surface corrosion and corrosion of the interior by intercrystalline paths. Results are given of accelerated corrosion tests, tensile tests, the effect on corrosion of various alloying elements and heat treatments, electrical resistance measurements, and X-ray examinations.

  2. Laser surface alloying of coins for authenticity

    NASA Astrophysics Data System (ADS)

    Liu, Zhu; Watkins, Kenneth G.; Steen, William M.; Hatherley, P. G.

    1997-08-01

    This paper presents an exploratory investigation on verifying the feasibility of using a laser surface alloying technique to produce designs in the surface of coinage blanks. The specific aim of the work concerns the production of design features in coins that are difficult to produce by other techniques and which hence act as a barrier to forgery and features which permit automatic recognition in vending machines, particularly as a means of establishing the authenticity of the coins. Coins in many countries today are commonly manufactured from metal composites, where one substrate metal or alloy is coated with another by a process of electrodeposition or by mechanical bonding. The technique here described entails the use of a high power CO2 laser to bring about localized melting of the two layers. Visible distinction between alloyed and unalloyed regions or difference in other physical properties such as conductivity or magnetic properties can be obtained. The work also involved a fundamental study of the influence of the thermal properties of the materials on the CO2 laser alloying process. It was found that the thermal properties such as thermal conductivity of the substrate materials and the difference of the melting points between the coating layer and the substrate materials played an important role in the process. Laser control variables required for localized alloying for different substrate and coatings types were determined. The influence of both thermal properties and laser control variables on alloy type and alloy depth were investigated. Initial work on coin validation showed promising results of an automatic recognition of laser treated coins.

  3. High temperature magnetic permeability of Si-rich Finemet-type nanocrystalline (Fe1-xCox)74.5Nb2Si17.5B5Cu1 alloys

    NASA Astrophysics Data System (ADS)

    Wen, Li-xia; Wang, Zhi; Wang, Jia; Zhang, Hao

    2015-04-01

    Structure and magnetic properties of as-quenched and annealed (Fe0.9Co0.1)74.5Nb2Si17.5B5Cu1 alloy were mainly investigated by x-ray diffraction and by measuring the temperature dependence of initial permeability (?i-T curves) from room temperature up to 700 C. The as-quenched sample exhibits a lower onset primary crystallization temperature (TX 10 = 475 C) and a larger crystallized interval temperature (?TX = TX 20 - TX 10 = 201 C) for precipitating the single soft magnetic crystal phase. The Curie temperature of amorphous phase Tcam for as-quenched sample and the Curie temperature of crystalline phase Tccry for annealed sample were detected to be about 400 C and 670 C respectively, which are both higher than that of Fe74.5Nb2Si17.5B5Cu1 alloy. So promising high temperature soft magnetic properties are expected. Annealing temperature (Ta) exerts a significant effect on room- and high-temperature ?i. When Ta is at 600 C (optimum annealing condition), although, the room temperature permeability of nanocrystalline (Fe0.9Co0.1)74.5Nb2Si17.5B5Cu1 alloy was not as high as that of nanocrystalline Fe74.5Nb2Si17.5B5Cu1 alloy, an improved high temperature magnetic softness was observed. The values of ?i for the 600 C-annealed sample is larger than that of Fe74.5Nb2Si17.5B5Cu1 alloy when temperature increases from 520 C to 670 C. The origin for the evolution of initial permeability at elevated temperatures was also analyzed.

  4. Copper-tantalum alloy

    SciTech Connect

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

    1986-07-15

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

  5. Aluminum battery alloys

    DOEpatents

    Thompson, David S.; Scott, Darwin H.

    1985-01-01

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

  6. Aluminum battery alloys

    DOEpatents

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

    1984-09-28

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

  7. Shape memory alloys

    SciTech Connect

    Suzuki, K.

    1983-10-04

    A shape memory alloy is disclosed consisting essentially of, by weight ratio, 2 to 15% aluminium, 0.01 to 3% beryllium and the balance being substantially copper, with impurities being inevitably present in the process of preparation, and a shape memory alloy further including 0.05 to 15% zinc, both including composition ranges which allows cold work.

  8. Ductile transplutonium metal alloys

    DOEpatents

    Conner, W.V.

    1981-10-09

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

  9. Ductile transplutonium metal alloys

    DOEpatents

    Conner, William V.

    1983-01-01

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

  10. PLUTONIUM-CERIUM ALLOY

    DOEpatents

    Coffinberry, A.S.

    1959-01-01

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

  11. Cesium iodide alloys

    DOEpatents

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

    1992-12-15

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

  12. Alloy coated fuel cladding

    SciTech Connect

    Bryan, W.J.; Fuhrman, N.

    1989-11-14

    This patent describes an improvement in a fuel element for use in a nuclear reactor which includes a fissionable material contained within a zirconium-alloy cladding tube. The improvement comprises a coating on the inside of the zirconium-alloy cladding tube. The coating including a nickel-thallium -boron burnable poison compound.

  13. Neutron Absorbing Alloys

    DOEpatents

    Mizia, Ronald E. (Idaho Falls, ID); Shaber, Eric L. (Idaho Falls, ID); DuPont, John N. (Whitehall, PA); Robino, Charles V. (Albuquerque, NM); Williams, David B. (Bethlehem, PA)

    2004-05-04

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

  14. Thermoelectric properties of Ag-doped n-type (Bi{sub 2}Te{sub 3}){sub 0.9}-(Bi{sub 2-} {sub x} Ag {sub x} Se{sub 3}){sub 0.1} (x=0-0.4) alloys prepared by spark plasma sintering

    SciTech Connect

    Cui, J.L. Xiu, W.J.; Mao, L.D.; Ying, P.Z.; Jiang, L.; Qian, X.

    2007-03-15

    Ag-doped n-type (Bi{sub 2}Te{sub 3}){sub 0.9}-(Bi{sub 2-} {sub x} Ag {sub x} Se{sub 3}){sub 0.1} (x=0-0.4) alloys were prepared by spark plasma sintering and their physical properties evaluated. When at low Ag content (x=0.05), the temperature dependence of the lattice thermal conductivity follows the trend of (Bi{sub 2}Te{sub 3}){sub 0.9}-(Bi{sub 2}Se{sub 3}){sub 0.1}; while at higher Ag content, a relatively rapid reduction above 400 K can be observed due possibly to the enhancement of scattering of phonons by the increased defects. The Seebeck coefficient increases with Ag content, with some loss of electrical conductivity, but the maximum dimensionless figure of merit ZT can be obtained to be 0.86 for the alloy with x=0.4 at 505 K, about 0.2 higher than that of the alloy (Bi{sub 2}Te{sub 3}){sub 0.9}-(Bi{sub 2}Se{sub 3}){sub 0.1} without Ag-doping. - Graphical abstract: The temperature dependence of dimensionless thermoelectric figure of merit ZT for different (Bi{sub 2}Te{sub 3}){sub 0.9}-(Bi{sub 2-} {sub x} Ag {sub x} Se{sub 3}){sub 0.1} (x=0-0.4) alloys prepared by spark plasma sintering.

  15. Alloys in energy development

    SciTech Connect

    Frost, B.R.T.

    1984-02-01

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

  16. Plating on stainless steel alloys

    SciTech Connect

    Dini, J.W.; Johnson, H.R.

    1981-09-11

    Quantitative adhesion data are presented for a variety of electroplated stainless steel type alloys. Results show that excellent adhesion can be obtained by using a Wood's nickel strike or a sulfamate nickel strike prior to final plating. Specimens plated after Wood's nickel striking failed in the deposit rather than at the interface between the substrate and the coating. Flyer plate quantitative tests showed that use of anodic treatment in sulfuric acid prior to Wood's nickel striking even further improved adhesion. In contrast activation of stainless steels by immersion or cathodic treatment in hydrochloric acid resulted in very reduced bond strengths with failure always occurring at the interface between the coating and substrate.

  17. Electrodeposition of Bi-Te alloy films

    SciTech Connect

    Takahashi, Makoto; Oda, Youichi; Ogino, Takayuki; Furuta, Shinsaku . Dept. of Industrial Chemistry)

    1993-09-01

    Electrochemical deposition of Bi-Te alloy films from acidic solutions containing Bi(NO[sub 3])[sub 3] and TeO[sub 2] has been investigated. The thickness, compound, and composition of the Bi-Te alloy films have been examined using stylus-type surface profiling techniques, X-ray diffraction peak measurement, and inductively coupled plasma/Auger electron spectroscopy measurements. At potentials where limiting current was observed, the compositions of films were controlled by the mole ratio [Bi[sup 3+

  18. Fusion boundary microstructure evolution in aluminum alloys

    NASA Astrophysics Data System (ADS)

    Kostrivas, Anastasios Dimitrios

    2000-10-01

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

  19. The half-metallicity of LiMgPdSn-type quaternary Heusler alloys FeMnScZ (Z=Al, Ga, In): A first-principle study

    NASA Astrophysics Data System (ADS)

    Gao, Y. C.; Gao, X.

    2015-05-01

    Based on the first-principles calculations, quaternary Heusler alloys FeMnScZ (Z=Al, Ga, In) including its phase stability, band gap, the electronic structures and magnetic properties has been studied systematically. We have found that, in terms of the equilibrium lattice constants, FeMnScZ (Z=Al, Ga, In) are half-metallic ferrimagnets, which can sustain the high spin polarization under a very large amount of lattice distortions. The half-metallic band gap in FeMnScZ (Z=Al, Ga, In) alloys originates from the t1u-t2g splitting instead of the eu-t1u splitting. The total magnetic moments are 3?B per unit cell for FeMnScZ (Z=Al, Ga, In) alloys following the Slater-Pauling rule with the total number of valence electrons minus 18 rather than 24. According to the study, the conclusion can be drawn that all of these compounds which have a negative formation energy are possible to be synthesized experimentally.

  20. Dependence of melting, roughness and contact resistances on Ge and Ni content in alloyed AuGe/Ni/Au-type electrical contacts to GaAs/AlGaAs multilayer structures

    NASA Astrophysics Data System (ADS)

    Abhilash, T. S.; Kumar, Ch Ravi; Sreedhar, B.; Rajaram, G.

    2010-03-01

    Annealed AuGe/Ni/Au film structures on GaAs/AlGaAs multilayers have been examined for contact resistance, roughness, magnetization and melting as functions of anneal temperature, Ni-layer thickness and three AuGe compositions. Magnetization data indicate that a solid state, solubility-limited dissolution of Ni into AuGe takes place even for low-temperature anneals and that this dissolution is complete when alloying occurs at ~400 °C. An apparent melting temperature, detected in differential scanning calorimetry, increases with increasing Ni-layer thickness and decreasing Ge content in the AuGe alloy. Electrical contact formation and roughening of the surface occur in the range of melting temperatures of the structure. The eutectic alloy with a Ni-layer thickness of ~25-30 nm gives the optimum contact resistance. The contact resistance can be traded off for the reduction in roughness by either increasing the Ni-layer thickness or reducing the Ge content, with the latter being the better choice of the two. The temperature dependence (4-300 K) of the contact resistance shows indications of both thermionic and tunneling behaviors. The barrier height for the current conduction increases with the increase of the Ni-layer thickness and a decrease of the Ge content in the AuGe layer, relative to that of the structure with optimum contact resistance.

  1. Radiation-enhanced recrystallization in copper alloys

    NASA Astrophysics Data System (ADS)

    Zinkle, S. J.; Kulcinski, G. L.; Mansur, L. K.

    1986-11-01

    Two high-strength copper alloys, cold-worked and aged AMZIRC (Cu-Zr) and AMAX-MZC (Cu-Cr-Zr-Mg) were irradiated with 14-MeV Cu ions to a damage level of 10 dpa at temperatures of 100 to 500C. Cross-section examination of the irradiated foils using electron microscopy revealed signs of radiation-enhanced recrystallization for irradiation temperatures above 300C. The recrystallization temperature for both alloys is about 450C during thermal annealing for a time similar to the ion-irradiation time - 1.5 h. A simplified analysis of the results suggests that the accelerated recrystallization kinetics is due to radiation-enhanced diffusion (RED). This process may restrict the maximum operating temperature of fusion reactor components that incorporate these types of alloys to temperatures as low as 200C.

  2. Radiation-enhanced recrystallization in copper alloys

    SciTech Connect

    Zinkle, S.J.; Kulcinski, G.L.; Mansur, L.K.

    1986-01-01

    Two high-strength copper alloys, cold-worked-and-aged AMZIRC (Cu-Zr) and AMAX-MZC (Cu-Cr-Zr-Mg), were irradiated with 14-MeV Cu ions to a damage level of 10 dpa at temperatures of 100 to 500/sup 0/C. Cross-section examination of the irradiated foils using electron microscopy revealed signs of irradiation-enhanced recrystallization for irradiation temperatures above 300/sup 0/C. The recrystallization temperature for both alloys is about 450/sup 0/C during thermal annealing for a time similar to the ion-irradiation time -1.5 h. A simplified analysis of the results suggests that the accelerated recrystallization kinetics is due to radiation-enhanced diffusion (RED). This process may restrict the maximum operating temperature of fusion reactor components that incorporate these types of alloys to temperatures as low as 200/sup 0/C.

  3. THORIUM-SILICON-BERYLLIUM ALLOYS

    DOEpatents

    Foote, F.G.

    1959-02-10

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

  4. Alumina-forming Austenitic Alloys for Advanced Recuperators

    SciTech Connect

    Pint, Bruce A; Shingledecker, John P; Brady, Michael P; Maziasz, Philip J

    2007-01-01

    Materials selection for thin-walled recuperators has been extensively investigated over the past decade. In the latest generation of recuperated turbine engines, type 347 stainless steel has been replaced by higher alloyed steels and Ni-base chromia-forming alloys. However, high (linear) rates of chromia evaporation in exhaust gas fundamentally limits the oxidation lifetime of these chromia-forming alloys. One solution is to use alumina-forming alloys that are more resistant to this environment. The lower scale growth kinetics and resistance to evaporation in the presence of water vapor suggests an order of magnitude increase in lifetime for alumina-forming alloys. A significant problem with this strategy was the large drop in creep strength with the addition of sufficient Al to form an external alumina scale. However, new Fe-base austenitic compositions have been developed with sufficient strength for this application above 700 C.

  5. Technology status of tantalum alloys for space nuclear power applications

    NASA Technical Reports Server (NTRS)

    Hoffman, E. E.

    1985-01-01

    Tantalum alloys have a variety of properties which make them attractive candidates for application in nuclear power systems required to operate in space at elevated temperatures (1200 to 1600 K) for extended time periods. Most of the technology development on this class of alloys which is pertinent to space system application occurred during the 1960 to 1972 time period under NASA sponsorship. The most extensive data bases resulting from this earlier work were obtained on the alloys T-111 (Ta-8W-2Hf) and ASTAR 811C (Ta-8W-1Re-0.7Hf-0.025C). Emphasis in this paper is directed at the following technical factors: producibility, creep strength, weldability and compatibility. These factors are considered to be the most important elements in the selection of alloys for this application. Review of the available information indicates that alloys of this type are appropriate for application in many systems, particularly those utilizing alkali metals as the working fluid.

  6. DSC sample preparation for Al-based alloys

    SciTech Connect

    Starink, M.J.; Hobson, A.J.; Gregson, P.J.

    1996-06-01

    Differential Scanning Calorimetry (DSC) is a useful technique for the study of phase transformations and has been widely applied to study precipitation in aluminium alloys. In the present work the effect of sample preparation during DSC heating of a monolithic 8090 (Al-Cu-Mg-Li-Zr) alloy and an 8090 MMC is investigated. The 8090 alloy system seems especially suited for such a study since the main precipitation reactions which occur in this alloy (GPB-zone, {delta}{prime}(Al{sub 3}Li) and S{prime}(Al{sub 2}CuMg) formation) cover a wide range of different types of precipitation reactions. DSC experiments were performed with a Shimadzu DSC-50 employing a nitrogen gas flow using a heating rate of 10 C/min. DSC curves were corrected for the baseline of the DSC and for heat capacity of the alloys following a procedure outlined elsewhere. Hence, the presented DSC curves represent heat flows due to reactions only.

  7. TUNGSTEN BASE ALLOYS

    DOEpatents

    Schell, D.H.; Sheinberg, H.

    1959-12-15

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

  8. Alloy development of FeAl aluminide alloys for structural use in corrosive environments

    SciTech Connect

    Liu, C.T.; Sikka, V.K.; McKamey, C.G.

    1993-02-01

    Objectives include adequate ductilities ([ge]10%) at ambient temperature, high-temperature strength better than stainless steels (types 304 and 316), and fabricability and weldability by conventional techniques (gas tungsten arc). The alloys should be capable of being corrosion resistant in molten nitrate salts with rates lower than other iron-base structural alloys and coating materials (such as Fe-Cr-Al alloys). Such corrosion rates should be less than 0.3 mm per year. The FeAl aluminide containing 35.8 at. % Al was selected as base composition. Preliminary studies indicate that additions of B and Zr, increase the room-temperature ductility of FeAl. Further alloying with 0.2% Mo, and/or 5% Cr, improves the creep. Our preliminary alloying effort has led to identification of the following aluminide composition with promising properties: Fe - (35 [plus minus] 2)Al - (0.3 [plus minus] 0.2)Mo - (0.2 [plus minus] 0.15)Zr - (0.3 [plus minus] 0.2)B- up to 5Cr, at. %. However, this composition is likely to be modified in future work to improve the weldability of the alloy. The FeAl alloy FA-362 (Fe-35.8% Al-0.2% Mo-0.05% Zr-0.24% B) produced by hot extrusion at 900C showed a tensile ductility of more than 10% at room temperature and a creep rupture life longer than unalloyed FeAl by more than an order of magnitude at 593C at 138 MPa. Melting and processing of scaled-up heats of selected FeAl alloys are described. Forging, extruding, and hot-rolling processes for the scale-up heats are also described.

  9. Alloy development of FeAl aluminide alloys for structural use in corrosive environments

    SciTech Connect

    Liu, C.T.; Sikka, V.K.; McKamey, C.G.

    1993-02-01

    Objectives include adequate ductilities ({ge}10%) at ambient temperature, high-temperature strength better than stainless steels (types 304 and 316), and fabricability and weldability by conventional techniques (gas tungsten arc). The alloys should be capable of being corrosion resistant in molten nitrate salts with rates lower than other iron-base structural alloys and coating materials (such as Fe-Cr-Al alloys). Such corrosion rates should be less than 0.3 mm per year. The FeAl aluminide containing 35.8 at. % Al was selected as base composition. Preliminary studies indicate that additions of B and Zr, increase the room-temperature ductility of FeAl. Further alloying with 0.2% Mo, and/or 5% Cr, improves the creep. Our preliminary alloying effort has led to identification of the following aluminide composition with promising properties: Fe - (35 {plus_minus} 2)Al - (0.3 {plus_minus} 0.2)Mo - (0.2 {plus_minus} 0.15)Zr - (0.3 {plus_minus} 0.2)B- up to 5Cr, at. %. However, this composition is likely to be modified in future work to improve the weldability of the alloy. The FeAl alloy FA-362 (Fe-35.8% Al-0.2% Mo-0.05% Zr-0.24% B) produced by hot extrusion at 900C showed a tensile ductility of more than 10% at room temperature and a creep rupture life longer than unalloyed FeAl by more than an order of magnitude at 593C at 138 MPa. Melting and processing of scaled-up heats of selected FeAl alloys are described. Forging, extruding, and hot-rolling processes for the scale-up heats are also described.

  10. The time and temperature dependence of the thermoelectric properties of silicon-germanium alloy

    NASA Technical Reports Server (NTRS)

    Raag, V.

    1975-01-01

    Experimental data on the electrical resistivity and Seebeck coefficient of n-type and p-type silicon-germanium alloys are analyzed in terms of a solid-state dopant precipitation model proposed by Lifshitz and Slyozov (1961). Experimental findings on the time and temperature dependence of the thermal conductivity of these two types of alloy indicate that the thermal conductivity of silicon-germanium alloys changes with time, contrary to previous hypothesis. A preliminary model is presented which stipulates that the observed thermal conductivity decrease in silicon-germanium alloys is due partly to dopant precipitation underlying the electrical property changes and partly to enhanced alloying of the material. It is significant that all three properties asymptotically approach equilibrium values with time. Total characterization of these properties will enable the time change to be fully compensated in the design of a thermoelectric device employing silicon-germanium alloys.

  11. Pitting, galvanic, and long-term corrosion studies on candidate container alloys for the Tuff Repository

    SciTech Connect

    Beavers, J.A.; Thompson, N.G.; Durr, C.L. )

    1992-01-01

    Contest Columbus Technologies, Inc. (CC Technologies) investigated the long-term performance of container materials for high-level radioactive waste packages as part of the information needed by the Nuclear Regulatory Commission to assess the Department of Energy's application to construct a geologic repository for the high-level radioactive waste. The scope of work focused on the Tuff Repository and employed short-term techniques, such as electrochemical and mechanical techniques to examine a wide range of possible failure modes. Two classes of alloys were evaluated for use as container materials for the Tuff Repository; Fe-Cr-Ni alloys and copper-base alloys. The candidate Fe-Cr-Ni alloys were Type 304L Stainless Steel (Alloy 304L) and Incoloy Alloy 825 (Alloy 825). The candidate copper-base alloys were CDA 102 Copper (Alloy CDA 102) and CDA 715 Copper-3D Nickel (Alloy CDA 715). The corrosion testing was performed in a simulated J-13 well water and in solutions selected from an experimental matrix from Task 2 of the program. This report summarizes the results of Task 4 (Pitting Studies), Task 6 (Other Failure Modes) and Task 7 (Long-Term Exposures) of the program. Pit-initiation studies, performed in Task 4, focused on anomalous Cyclic Potentiodynamic Polarization (CPP) behavior of the copper-base alloys reported in Task 2 of the program. Pit propagation studies were performed on Alloy CDA 102 in Task A of the program. Two types of galvanic corrosion studies were performed in Task 6 of the program; thermogalvanic couples and borehole linear-container interactions. In the thermogalvanic couples tests, the effect of temperature variation on the surface of the container on acceleration of corrosion was evaluated for two alloys; Alloy CDA 102 and Alloy 304L. Long-term immersion tests were conducted in Task 7 of the program.

  12. Pitting, galvanic, and long-term corrosion studies on candidate container alloys for the Tuff Repository

    SciTech Connect

    Beavers, J.A.; Thompson, N.G.; Durr, C.L.

    1992-01-01

    Contest Columbus Technologies, Inc. (CC Technologies) investigated the long-term performance of container materials for high-level radioactive waste packages as part of the information needed by the Nuclear Regulatory Commission to assess the Department of Energy`s application to construct a geologic repository for the high-level radioactive waste. The scope of work focused on the Tuff Repository and employed short-term techniques, such as electrochemical and mechanical techniques to examine a wide range of possible failure modes. Two classes of alloys were evaluated for use as container materials for the Tuff Repository; Fe-Cr-Ni alloys and copper-base alloys. The candidate Fe-Cr-Ni alloys were Type 304L Stainless Steel (Alloy 304L) and Incoloy Alloy 825 (Alloy 825). The candidate copper-base alloys were CDA 102 Copper (Alloy CDA 102) and CDA 715 Copper-3D Nickel (Alloy CDA 715). The corrosion testing was performed in a simulated J-13 well water and in solutions selected from an experimental matrix from Task 2 of the program. This report summarizes the results of Task 4 (Pitting Studies), Task 6 (Other Failure Modes) and Task 7 (Long-Term Exposures) of the program. Pit-initiation studies, performed in Task 4, focused on anomalous Cyclic Potentiodynamic Polarization (CPP) behavior of the copper-base alloys reported in Task 2 of the program. Pit propagation studies were performed on Alloy CDA 102 in Task A of the program. Two types of galvanic corrosion studies were performed in Task 6 of the program; thermogalvanic couples and borehole linear-container interactions. In the thermogalvanic couples tests, the effect of temperature variation on the surface of the container on acceleration of corrosion was evaluated for two alloys; Alloy CDA 102 and Alloy 304L. Long-term immersion tests were conducted in Task 7 of the program.

  13. A comparative study on the bond strength of porcelain to the millingable Pd-Ag alloy

    PubMed Central

    Hong, Jun-Tae

    2014-01-01

    PURPOSE The porcelain fused to gold has been widely used as a restoration both with the natural esthetics of the porcelain and durability and marginal fit of metal casting. However, recently, due to the continuous rise in the price of gold, an interest towards materials to replace gold alloy is getting higher. This study compared the bond strength of porcelain to millingable palladium-silver (Pd-Ag) alloy, with that of 3 conventionally used metal-ceramic alloys. MATERIALS AND METHODS Four types of metal-ceramic alloys, castable nonprecious nickel-chrome alloy, castable precious metal alloys containing 83% and 32% of gold, and millingable Pd-Ag alloy were used to make metal specimens (n=40). And porcelain was applied on the center area of metal specimen. Three-point bending test was performed with universal testing machine. The bond strength data were analyzed with a one-way ANOVA and post hoc Scheffe's tests (?=.05). RESULTS The 3-point bending test showed the strongest (40.42 5.72 MPa) metal-ceramic bond in the nonprecious Ni-Cr alloy, followed by millingable Pd-Ag alloy (37.71 2.46 MPa), precious metal alloy containing 83% of gold (35.89 1.93 MPa), and precious metal alloy containing 32% of gold (34.59 2.63 MPa). Nonprecious Ni-Cr alloy and precious metal alloy containing 32% of gold showed significant difference (P<.05). CONCLUSION The type of metal-ceramic alloys affects the bond strength of porcelain. Every metal-ceramic alloy used in this study showed clinically applicable bond strength with porcelain (25 MPa). PMID:25352959

  14. Wear behavior of TiNi shape memory alloys

    SciTech Connect

    Li, D.Y.

    1996-01-15

    TiNi alloy is a well-known shape memory alloy, which has demonstrated its great potential for a large variety of applications; this alloy is being actively applied to the development of new energy conversion systems, to the design for new robots and smart material systems, and to the development of medical implants and instruments. In addition to its shape memory effect, it has been observed that TiNi alloy also exhibits great resistance to wear. It is expected that the TiNi alloy, with its shape memory effect, vibration-damping feature, and high corrosion resistance, may become a new type of tribo-material and find new engineering applications. The high wear resistance of TiNi alloy may be attributed to its pseudoelastic behavior. This paper presents experimental results on wear behavior of TiNi alloy and its variation with microstructure. The pseudoelasticity of TiNi alloy was also studied, and its possible effect on wear resistance has been discussed in this paper.

  15. Tensile and impact properties of iron-aluminum alloys

    SciTech Connect

    Alexander, D.J.; Sikka, V.K.

    1993-12-31

    Tensile and impact tests have been conducted on specimens from a series of five heats of iron-aluminum alloys. These results have been compared to data for the iron aluminide alloy FA-129. The transition temperatures of all of the Fe{sub 3}Al-based alloys were similar, but the simple ternary alloy had a much higher upper-shelf energy. The reduced aluminum alloys [based on Fe-8Al (wt %)] had lower transition temperatures and higher upper-shelf energy levels than the Fe{sub 3}Al-type alloys. The reduced aluminum alloy with yttrium showed excellent tensile properties, with a room temperature total elongation of 40%, and a very high upper-shelf energy level. Despite the high tensile ductility at room temperature, the transition temperature of the yttrium-containing alloy was still about 150 C, compared to approximately 300 C for FA-129. In general, the microstructures were coarse and anisotropic. The fracture processes were dominated by second-phase particles.

  16. Electroplating on titanium alloy

    NASA Technical Reports Server (NTRS)

    Lowery, J. R.

    1971-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Ray, Ranjan; Jha, Sunil C.

    1987-01-01

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

  18. Mechanical and corrosion resistance of a new nanostructured Ti-Zr-Ta-Nb alloy.

    PubMed

    Raducanu, D; Vasilescu, E; Cojocaru, V D; Cinca, I; Drob, P; Vasilescu, C; Drob, S I

    2011-10-01

    In this work, a multi-elementary Ti-10Zr-5Nb-5Ta alloy, with non-toxic alloying elements, was used to develop an accumulative roll bonding, ARB-type procedure in order to improve its structural and mechanical properties. The alloy was obtained by cold crucible semi-levitation melting technique and then was ARB deformed following a special route. After three ARB cycles, the total deformation degree per layer is about 86%; the calculated medium layer thickness is about 13 ?m. The ARB processed alloy has a low Young's modulus of 46 GPa, a value very close to the value of the natural cortical bone (about 20 GPa). Data concerning ultimate tensile strength obtained for ARB processed alloy is rather high, suitable to be used as a material for bone substitute. Hardness of the ARB processed alloy is higher than that of the as-cast alloy, ensuring a better behaviour as a implant material. The tensile curve for the as-cast alloy shows an elastoplastic behaviour with a quite linear elastic behaviour and the tensile curve for the ARB processed alloy is quite similar with a strain-hardening elastoplastic body. Corrosion behaviour of the studied alloy revealed the improvement of the main electrochemical parameters, as a result of the positive influence of ARB processing. Lower corrosion and ion release rates for the ARB processed alloy than for the as-cast alloy, due to the favourable effect of ARB thermo-mechanical processing were obtained. PMID:21783152

  19. A new thermoelectric alloy for cooling applications

    NASA Astrophysics Data System (ADS)

    Ettenberg, Martin Harris

    In the last twenty years no improvements in bulk materials has been achieved for cooling in the thermoelectrics industry that has surpassed the cooling capabilities of the alloys developed at RCA by Yim and Rosi. In that work they achieved a DeltaT of 77.6K from room temperature. This work focuses on the development of a new n-type and improving the p-type alloy from the Bisb2Tesb3-Sbsb2Tesb3-Sbsb2Sesb3 pseudo-ternary alloy system. Improvements in the alloy have allowed the construction of a cooling device that achieves a DeltaT of 79.2K. In bulk material growth the highest figure of merit material, Z, for room temperature cooling applications is a p-type material (Bisb2Tesb3)sb{25}(Sbsb2Tesb3)sb{72}(Sbsb2Sesb3)sb3 that has a Z = 3.6 10sp{-3}/K and an n-type material (Bisb2Tesb3)sb{90}(Sbsb2Tesb3)sb5(Sbsb2Sesb3)sb5 with a Z = 3.2 10sp{-3}/K developed at the University of Virginia. The present work improves on these results by developing a new n-type material (Bisb2Tesb3)sb{70}(Sbsb2Tesb3)sb{25}(Sbsb2Sesb2)sb5 with a Z = 3.4 10sp{-3}/K. The improvement in this new alloy is due to a lower thermal conductivity with equivalent electrical properties to the old n-type alloy (Bisb2Tesb3)sb{90}(Sbsb2Tesb3)sb5(Sbsb2Sesb3)sb5. The temperature dependent properties from 250K-400K of the three alloys with various dopant concentrations was measured to study temperature effects on the thermoelectric properties. Studies were also conducted on ohmic contacts, including measuring the contact resistivity size and the resistivity of the solder. The contact resistivity is an effect that is critical to device performance in small modules. This work also found that the dopant material is relevant to the overall thermoelectric properties of the alloy. In the p-type material (Bisb2Tesb3)sb{25}(Sbsb2Tesb3)sb{72}(Sbsb2Sesb3)sb3 the figure of merit was lowered when SbIsb3 was used instead of Te as a compensator of excess holes. This effect was not apparent in the new n-type alloy (Bisb2Tesb3)sb{70}(Sbsb2Tesb3)sb{25}(Sbsb2Sesb3)sb5. Using the measured temperature dependent properties an improved finite difference model was constructed to evaluate the thermoelectric material. This model improved upon previous models by including the Thomson coefficient and resistance due to the contacts and the metal junctions. This model predicted the maximum cooling of the given thermoelectric material to within 3K of the actual device. Older models based on material parameters either overestimated the cooling by 5K or underestimated it by 3.5K.

  20. Reduction in Defect Content of ODS Alloys

    SciTech Connect

    Ritherdon, J

    2001-05-15

    The work detailed within this report is a continuation of earlier work carried out under contract number 1DX-SY382V. The earlier work comprises a literature review of the sources and types of defects found principally in Fe-based ODS alloys as well as experimental work designed to identify defects in the prototype ODS-Fe{sub 3}Al alloy, deduce their origins and to recommend methods of defect reduction. The present work is an extension of the experimental work already reported and concentrates on means of reduction of defects already identified rather than the search for new defect types. This report also includes results gathered during powder separation trials, conducted by the University of Groningen, Netherlands and coordinated by the University of Liverpool, involving the separation of different metallic powders in terms of their differing densities. The scope and objectives of the present work were laid out in the technical proposal ''Reduction in Defect Content in ODS Alloys-III''. All the work proposed in the ''Statement of Work'' section of the technical proposal has been carried out and all work extra to the ''Statement of Work'' falls within the context of an ODS-Fe{sub 3}Al alloy of improved overall quality and potential creep performance in the consolidated form. The outturn of the experimental work performed is reported in the following sections.

  1. Fabrication of a helical coil shape memory alloy actuator

    SciTech Connect

    O'Donnell, R.E.

    1992-02-01

    A fabrication process was developed to form, heat treat, and join NiTi shape memory alloy helical coils for use as mechanical actuators. Tooling and procedures were developed to wind both extension and compression-type coils on a manual lathe. Heat treating fixtures and techniques were used to set the memory'' of the NiTi alloy to the desired configuration. A swaging process was devised to fasten shape memory alloy extension coils to end fittings for use in actuator testing and for potential attachment to mechanical devices. The strength of this mechanical joint was evaluated.

  2. Fabrication of a helical coil shape memory alloy actuator

    SciTech Connect

    O`Donnell, R.E.

    1992-02-01

    A fabrication process was developed to form, heat treat, and join NiTi shape memory alloy helical coils for use as mechanical actuators. Tooling and procedures were developed to wind both extension and compression-type coils on a manual lathe. Heat treating fixtures and techniques were used to set the ``memory`` of the NiTi alloy to the desired configuration. A swaging process was devised to fasten shape memory alloy extension coils to end fittings for use in actuator testing and for potential attachment to mechanical devices. The strength of this mechanical joint was evaluated.

  3. Atomistic approach to alloy scattering in Si1-xGex

    NASA Astrophysics Data System (ADS)

    Mehrotra, Saumitra R.; Paul, Abhijeet; Klimeck, Gerhard

    2011-04-01

    SiGe alloy scattering is of significant importance with the introduction of strained layers and SiGe channels into complementary metal-oxide semiconductor technology. However, alloy scattering has till now been treated in an empirical fashion with a fitting parameter. We present a theoretical model within the atomistic tight-binding representation for treating alloy scattering in SiGe. This approach puts the scattering model on a solid atomistic footing with physical insights. The approach is shown to inherently capture the bulk alloy scattering potential parameters for both n-type and p-type carriers and matches experimental mobility data.

  4. Metallographic evaluation of the reactions between boronated graphite and Fe-Ni-Cr alloys

    SciTech Connect

    Tortorelli, P.F.; Mayotte, J.R.; Henson, T.J.; DeVan, J.H.

    1984-01-01

    The compatibility of boronated graphite with alloy 800H and type 316 stainless steel was evaluated metallographically after exposures at 700 and 810/sup 0/C for up to 10,000 h. At 700/sup 0/C, the principal reaction with both alloys was limited oxidation. At 810/sup 0/C, three types of reactions were observed: localized reactions at sites where the B/sub 4/C particles were in contact with the alloys' surfaces, intergranular penetration (much more prevalent for alloy 800H), and carburization.

  5. Effects Of B On Intergranular Hot Cracking In Ni Alloys

    NASA Technical Reports Server (NTRS)

    Thompson, Raymond G.

    1992-01-01

    Report describes experiments on role of boron on solidification of 718-type nickel/chromium/iron superalloys containing niobium and relative intergranular segregations of boron, sulfur, and phosphorus in alloys. Ten alloys studied by use of light and scanning electron microscopy (SEM), energy-dispersive x-ray analysis, transmission electron microscopy (TEM) with energy-dispersive analysis of thin-film specimens, mechanical tests for susceptibility to microfissuring, differential thermal analysis (DTA), scanning Auger microscopy, and Gleeble thermal analysis.

  6. Correlation between diffusion barriers and alloying energy in binary alloys.

    PubMed

    Vej-Hansen, Ulrik Grnbjerg; Rossmeisl, Jan; Stephens, Ifan E L; Schitz, Jakob

    2016-01-20

    In this paper, we explore the notion that a negative alloying energy may act as a descriptor for long term stability of Pt-alloys as cathode catalysts in low temperature fuel cells. Using density functional theory calculations, we show that there is a correlation between the alloying energy of an alloy, and the diffusion barriers of the minority component. Alloys with a negative alloying energy may show improved long term stability, despite the fact that there is typically a greater thermodynamic driving force towards dissolution of the solute metal over alloying. In addition to Pt, we find that this trend also appears to hold for alloys based on Al and Pd. PMID:26750475

  7. High copper alloys for dental amalgam.

    PubMed

    Beech, D R

    1982-09-01

    The nature, physical properties and clinical performance of amalgams made from alloys containing copper in excess of 6 per cent by weight are reviewed. There are two basic types of high copper alloy: (a) mixtures of 'spherical' silver/copper or silver/tin/copper particles with low copper low copper lathe-cut or 'spherical' and (b) single composition silver/tin/copper spherical or lathe-cut particles. Copper contents range from 8.5 per cent to 30 per cent. In amalgams made from high copper alloys the soft corrodible gamma 2 (Sn7Hg) phase is reduced or eliminated by preferential formation of the eta (Cu6Sn5) phase. Improved clinical performance (less marginal breakdown) has been related to low creep, little or no gamma 2 phase and the presence of zinc. The possible roles played by these factors in the mechanism of marginal breakdown are discussed. Physical properties are not a reliable guide to the clinical performance of amalgams. Although high copper amalgams as a group show 'superior' physical properties and clinical performance to low copper amalgams, a high copper content does not necessarily mean improved clinical performance. Indeed, certain well-manipulated low copper amalgams can show clinical results comparable with some high copper amalgams, but not as good as the best high copper amalgams. In most clinical studies the silver/copper plus lathe-cut (dispersed phase) alloys and some of the single composition high copper alloys show the greatest clinical durability. The most significant factor in clinical performance is the choice of alloy. PMID:6958652

  8. Vibrational entropies in metallic alloys

    NASA Astrophysics Data System (ADS)

    Ozolins, Vidvuds; Asta, Mark; Wolverton, Christopher

    2000-03-01

    Recently, it has been recognized that vibrational entropy can have significant effects on the phase stability of metallic alloys. Using density functional linear response calculations and molecular dynamics simulations we study three representative cases: (i) phase diagram of Al-rich Al-Sc alloys, (ii) stability of precipitate phases in CuAl_2, and (iii) phonon dynamics in bcc Zr. We find large vibrational entropy effects in all cases. In the Al-Sc system, vibrations increase the solid solubility of Sc in Al by decreasing the stability of the L12 (Al_3Sc) phase. This leads to a nearly ten-fold increase in the solid solubility of Sc in Al at T=800 K. In the Cu-Al system, our calculations predict that the tetragonal Laves phase of CuAl2 has 0.35 kB/atom higher vibrational entropy than the cubic CaF_2-type phase (the latter is predicted to be the T=0 K ground state of CuAl_2). This entropy difference causes a structural transformation in CuAl2 precipitates from the fluorite to the tetragonal Laves phase around T=500 K. Finally, we analyze the highly unusual dynamics of anharmonically stabilized bcc Zr, finding large diffuse-scattering intensity streaks between the bcc Bragg peaks.

  9. Quenching Alloys in Containerless Processing

    NASA Technical Reports Server (NTRS)

    Oran, W. A.

    1984-01-01

    Magnetic levitation and gas quenching combined in proposed method to melt and rapidly solidify alloys without contacting container walls. Method used to develop new carbides for drill bits, high-ductility structured steel and new high-strength superplastic alloys.

  10. Effects of Rh on the thermoelectric performance of the p-type Zr{sub 0.5}Hf{sub 0.5}Co{sub 1-x}Rh{sub x}Sb{sub 0.99}Sn{sub 0.01} half-Heusler alloys

    SciTech Connect

    Maji, Pramathesh; Takas, Nathan J.; Misra, Dinesh K.; Gabrisch, Heike; Stokes, Kevin; Poudeu, Pierre F.P.

    2010-05-15

    We show that Rh substitution at the Co site in Zr{sub 0.5}Hf{sub 0.5}Co{sub 1-x}Rh{sub x}Sb{sub 0.99}Sn{sub 0.01} (0<=x<=1) half-Heusler alloys strongly reduces the thermal conductivity with a simultaneous, significant improvement of the power factor of the materials. Thermoelectric properties of hot-pressed pellets of several compositions with various Rh concentrations were investigated in the temperature range from 300 to 775 K. The Rh 'free' composition shows n-type conduction, while Rh substitution at the Co site drives the system to p-type semiconducting behavior. The lattice thermal conductivity of Zr{sub 0.5}Hf{sub 0.5}Co{sub 1-x}Rh{sub x}Sb{sub 0.99}Sn{sub 0.01} alloys rapidly decreased with increasing Rh concentration and lattice thermal conductivity as low as 3.7 W/m*K was obtained at 300 K for Zr{sub 0.5}Hf{sub 0.5}RhSb{sub 0.99}Sn{sub 0.01}. The drastic reduction of the lattice thermal conductivity is attributed to mass fluctuation induced by the Rh substitution at the Co site, as well as enhanced phonon scattering at grain boundaries due to the small grain size of the synthesized materials. - Graphical abstract: Significant reduction of the lattice thermal conductivity with increasing Rh concentration in the p-type Zr{sub 0.5}Hf{sub 0.5}Co{sub 1-x}Rh{sub x}Sb{sub 0.99}Sn{sub 0.01} half-Heusler materials prepared by solid state reaction at 1173 K.

  11. Finding the Alloy Genome

    NASA Astrophysics Data System (ADS)

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

    2012-10-01

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

  12. Nickel-Titanium Alloys: Corrosion "Proof" Alloys for Space Bearing, Components and Mechanism Applications

    NASA Technical Reports Server (NTRS)

    DellaCorte, Christopher

    2010-01-01

    An intermetallic nickel-titanium alloy, 60NiTi (60wt%Ni, 40wt%Ti), is shown to be a promising candidate tribological material for space mechanisms. 60NiTi offers a broad combination of physical properties that make it unique among bearing materials. 60NiTi is hard, electrically conductive, highly corrosion resistant, readily machined prior to final heat treatment, and is non-magnetic. Despite its high titanium content, 60NiTi is non-galling even under dry sliding. No other bearing alloy, metallic or ceramic, encompasses all of these attributes. Since 60NiTi contains such a high proportion of titanium and possesses many metallic properties, it was expected to exhibit poor tribological performance typical of titanium alloys, namely galling type behavior and rapid lubricant degradation. In this poster-paper, the oil-lubricated behavior of 60NiTi is studied.

  13. Nickel-Titanium Alloys: Corrosion "Proof" Alloys for Space Bearing, Components and Mechanism Applications

    NASA Technical Reports Server (NTRS)

    DellaCorte, Christopher

    2010-01-01

    An intermetallic nickel-titanium alloy, 60NiTi (60 wt% Ni, 40 wt% Ti), is shown to be a promising candidate tribological material for space mechanisms. 60NiTi offers a broad combination of physical properties that make it unique among bearing materials. 60NiTi is hard, electrically conductive, highly corrosion resistant, readily machined prior to final heat treatment, and is non-magnetic. Despite its high Ti content, 60NiTi is non-galling even under dry sliding. No other bearing alloy, metallic or ceramic, encompasses all of these attributes. Since 60NiTi contains such a high proportion of Ti and possesses many metallic properties, it was expected to exhibit poor tribological performance typical of Ti alloys, namely galling type behavior and rapid lubricant degradation. In this poster-paper, the oil-lubricated behavior of 60NiTi is presented.

  14. Formation of single-walled bimetallic coinage alloy nanotubes in confined carbon nanotubes: molecular dynamics simulations.

    PubMed

    Han, Yang; Zhou, Jian; Dong, Jinming; Yoshiyuki, Kawazoe

    2013-10-28

    The growth of single-walled bimetallic Au-Ag, Au-Cu and Ag-Cu alloy nanotubes (NTs) and nanowires (NWs) in confined carbon nanotubes (CNTs) has been investigated by using the classical molecular dynamics (MD) method. It is found that three kinds of single-walled gold-silver, gold-copper and silver-copper alloy NTs could indeed be formed in confined CNTs at any alloy concentration, whose geometric structures are less sensitive to the alloy concentration. And an extra nearly pure Au (Cu) chain will exist at the center of Au-Ag (Au-Cu and Ag-Cu) NTs when the diameters of the outside CNTs are big enough, thus producing a new type of tube-like alloy NWs. The bonding energy differences between the mono- and hetero-elements of the coinage metal atoms and the quasi-one-dimensional confinement from the CNT play important roles in suppressing effectively the "self-purification" effects, leading to formation of these coinage alloy NTs. In addition, the fluid-solid phase transition temperatures of the bimetallic alloy NTs are found to locate between those of the corresponding pure metal tubes. Finally, the dependences of the radial breathing mode (RBM) frequencies and the tube diameters of the alloy NTs on the alloying concentration were obtained, which will be very helpful for identifying both the alloying concentration and the alloy tube diameters in future experiments. PMID:24013729

  15. Joints in fiber-reinforced aluminum alloys

    NASA Technical Reports Server (NTRS)

    Gerber, K.; Vanrensen, E.

    1988-01-01

    Problems of joining involving structural components made of aluminum alloys with boron-fiber reinforcements are discussed, giving attention to a diffusion-welding process. The tension characteristics and weight factors in the case of various types of welded joints are considered. Diffusion-welding equipment used in the experimental investigation is described. The strength characteristics obtained in various cases of weld and component design are examined, taking into account static and dynamic stresses.

  16. De-alloyed platinum nanoparticles

    DOEpatents

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

    2011-08-09

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

  17. PLUTONIUM-URANIUM-TITANIUM ALLOYS

    DOEpatents

    Coffinberry, A.S.

    1959-07-28

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

  18. Superplastic aluminum alloys containing scandium

    SciTech Connect

    Sawtell, R.R.; Bretz, P.E.; Jensen, C.L.

    1987-08-25

    This patent describes a method of superplastic forming wherein aluminum alloy stock is brought to superplastic forming temperature and superplastically formed into a shaped form at superplastic forming temperature. The improvement described here consists of providing the aluminum alloy stock as an alloy comprising more than 50% aluminum and including 0.05 to 10% scandium.

  19. Semiconductor alloys - Structural property engineering

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  20. Hydrogen in titanium alloys

    SciTech Connect

    Wille, G W; Davis, J W

    1981-04-01

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

  1. Magnesium and magnesium alloys

    SciTech Connect

    Avedesian, M.; Baker, H.

    1998-12-31

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

  2. Structural and Mssbauer spectroscopic study of Fe-Ni alloy nanoparticles

    SciTech Connect

    Kumar, Asheesh; Banerjee, S. Sudarsan, V.; Meena, S. S.

    2014-04-24

    Nano-crystalline Fe-Ni alloys have been synthesized in ethylene glycol medium. Based on XRD studies it is confirmed that, in these alloys Fe atoms are incorporated at Ni site to form Ni-Fe solid solutions. Mssbauer studies have established that for alloy particles having smaller size there is significant concentration of two different types of paramagnetic Fe species and their relative concentration decreased with increase in particle size.

  3. Utilization of Copper Alloys for Marine Applications

    NASA Astrophysics Data System (ADS)

    Drach, Andrew

    Utilization of copper alloy components in systems deployed in marine environment presents potential improvements by reducing maintenance costs, prolonging service life, and increasing reliability. However, integration of these materials faces technological challenges, which are discussed and addressed in this work, including characterization of material performance in seawater environment, hydrodynamics of copper alloy components, and design procedures for systems with copper alloys. To characterize the hydrodynamic behavior of copper alloy nets, mesh geometry of the major types of copper nets currently used in the marine aquaculture are analyzed and formulae for the solidity and strand length are proposed. Experimental studies of drag forces on copper alloy net panels are described. Based on these studies, empirical values for normal drag coefficients are proposed for various types of copper netting. These findings are compared to the previously published data on polymer nets. It is shown that copper nets exhibit significantly lower resistance to normal currents, which corresponds to lower values of normal drag coefficient. The seawater performance (corrosion and biofouling) of copper alloys is studied through the field trials of tensioned and untensioned specimens in a one-year deployment in the North Atlantic Ocean. The corrosion behavior is characterized by weight loss, optical microscopy, and SEM/EDX analyses. The biofouling performance is quantified in terms of the biomass accumulation. To estimate the effects of stray electrical currents on the seawater corrosion measurements, a low cost three-axis stray electric current monitoring device is designed and tested both in the lab and in the 30-day field deployment. The system consists of a remotely operated PC with a set of pseudo-electrodes and a digital compass. The collected data is processed to determine magnitudes of AC and DC components of electric field and dominant AC frequencies. Mechanical behavior of copper alloys is investigated through a series of uniaxial tension tests on virgin and weathered (after one-year deployment in the ocean) specimens. The changes in mechanical properties are quantified in terms of differences in Young's modulus, Poisson's ratio, ultimate strength, and ultimate strain. The obtained stress-strain data is used for numerical modeling of the mechanical behavior of chain-link nets. The simulations are compared with the experimental data on stiffness and strength of the nets. The available information on seawater performance of copper alloys (corrosion, biofouling, mechanics) and copper alloy nets (hydrodynamics) is used to develop engineering procedures for marine aquaculture fish cage systems with copper alloy netting. The design, analysis, and fabrication procedures are illustrated on a commercial size gravity-type offshore fish cage deployed in the Pacific Ocean near Isla Italia (Patagonia, Chile). The funding for this work was provided by the International Copper Association. This work was also supported through two UNH Fellowships: CEPS UNH Graduate Fellowship to Outstanding PhD Program Applicants and Dissertation Year Fellowship.

  4. Segregation phenomena at growing alumina/alloy interfaces

    SciTech Connect

    Hou, Peggy Y.

    2005-03-30

    The chemistry and structure at the scale/alloy interface are important factors governing scale adhesion. The chemical changes can occur from segregation of impurities in the alloy, such as sulphur and carbon, or alloying elements such as chromium, aluminium and reactive elements. This paper reviews studies of the changes of interfacial composition with oxidation time for Al{sub 2}O{sub 3} formed on several model alumina-forming alloys, and tries to relate that to the interfacial strength. Results show that sulphur segregation to oxide/metal interfaces can indeed occur, but the type and amount of segregants at the interface depend on the alloy composition and the interface structure. Co-segregation of impurities with alloying elements can also occur, resulting in multi-layer segregants at the interface. Sulphur-containing interfaces are indeed weaker, but the major role of sulphur is to enhance interfacial void formation. Reactive elements in the alloy not only gather sulfur but also exert an additional positive effect on scale adhesion.

  5. Solidification of an alloy 625 weld overlay

    NASA Astrophysics Data System (ADS)

    Dupont, J. N.

    1996-11-01

    The solidification behavior (microsegregation, secondary phase formation, and solidification temperature range) of an Alloy 625 weld overlay deposited on 2.25Cr - 1Mo steel by gas metal arc welding was investigated by light and electron optical microscopy, electron microprobe, and differential thermal analysis techniques. The overlay deposit was found to terminate solidification at ≈ 1216 °C by a γ/Laves eutectic-type reaction. The Laves phase was highly enriched in Nb, Mo, and Si. The solidification reaction and microsegregation potential of major alloying elements in the overlay deposit are compared to other Nb-bearing Ni base alloys and found to be very similar to those for Alloy 718. Solidification cracks observed in the overlay were attributed to the wide solidification temperature range (≈170 °C) and formation of interdendritic ( γ+Laves) constituent. Reasonable agreement is obtained between the calculated and measured volume percent ( γ+Laves) constituent with the Scheil equation by treating the overlay system as a simple γ-Nb “binary” and using an experimentally determined k Nb value from electron microprobe data.

  6. Solidification of an alloy 625 weld overlay

    SciTech Connect

    DuPont, J.N.

    1996-11-01

    The solidification behavior (microsegregation, secondary phase formation, and solidification temperature range) of an Alloy 625 weld overlay deposited on 2.25Cr-1Mo steel by gas metal arc welding was investigated by light and electron optical microscopy, electron microprobe, and differential thermal analysis techniques. The overlay deposit was found to terminate solidification at {approx}1,216 C by a {gamma}/Laves eutectic-type reaction. The Laves phase was highly enriched in Nb, Mo, and Si. The solidification reaction and microsegregation potential of major alloying elements in the overlay deposit are compared to other Nb-bearing Ni base alloys and found to be very similar to those for Alloy 718. Solidification cracks observed in the overlay were attributed to the wide solidification temperature range ({approx}170 C) and formation of interdendritic ({gamma} + Laves) constituent. Reasonable agreement is obtained between the calculated and measured volume percent ({gamma} + Laves) constituent with the Scheil equation by treating the overlay system as a simple {gamma}-Nb binary and using an experimentally determined k{sub Nb} value from electron microprobe data.

  7. Thermodynamically stable superstructures in binary alloys

    NASA Astrophysics Data System (ADS)

    Nelson, Lance

    2009-10-01

    Adding a second metal to another can induce the formation of ordered superstructures. These ordered phases have properties that are desireable in many industrial, manufacturing and technological applications. Our goal is to find which of the thousands of possible superstructures are thermodynamically stable through the use of computational tools. Owing to the many superstructures that are possible, as well as the complex nature of some of these, DFT calculations become impractical for searching for these superstructures. We employ a cluster expansion method, which uses energy information from a relatively small number of structures and fits that information to a set of interaction types. Because the resulting expansion provides a fast way to compute energies, we can use it to calculate the energies of the thousands of other superstructures. Specifically, I discuss the use of the cluster expansion on two binary alloys: AgPd and MgZn. Palladium alloys are of interest in the fabrication of jewelry, and a stable ordered phase at some concentrations would be a breakthrough for the jewelry manufacturers. Magnesium alloys are of interest because of their strength and light weight. They are being used increasingly in the manufacturing of things such as airplanes and automobiles. A cheap alloying agent that promotes the formation of an ordered structure would be a breakthrough.

  8. A study of surface tension driven segregation in monotectic alloy systems

    NASA Technical Reports Server (NTRS)

    Andrews, J. Barry; Andrews, Rosalia N.; Gowens, Terrell F.

    1988-01-01

    The compatibilities of various monotectic alloy systems with several different crucible materials were evaluated. The study was carried out using small candidate alloy samples of compositions that produced fifty volume percent of each liquid phase at the monotectic temperature. Compatibility was based on the evaluation of the wetting tendency of the two immiscible phases with the crucible material in a one-g solidified sample. Three types of wetting phenomena were observed during the evaluation. Type 1 indicates an alloy-crucible combination where the L2 phase preferentially wets the crucible material. Since L2 is usually the minority phase in desirable alloys, this material combination would be difficult to process and is therefore considered incompatible. Type 2 behavior indicates an alloy-crucible combination where the L1 phase preferentially wets the crucible material. This type of combination is considered compatible since surface tension effects should aid in processing the alloy to a useful form. Type 3 indicates any combination that leads to major reactions between the alloy and crucible material, gas entrapment, or separation of the metal from the crucible wall. Additional compatibility evaluations would have to be carried out on combinations of this category. The five alloy systems studied included aluminum-bismuth, copper-lead, aluminum-indium, aluminum-lead and cadmium-gallium. The systems were combined with crucibles of alumina, boron nitride, mullite, quartz, silicon carbide and zirconia.

  9. The bone tissue compatibility of a new Ti-Nb-Sn alloy with a low Young's modulus.

    PubMed

    Miura, Keiki; Yamada, Norikazu; Hanada, Shuji; Jung, Taek-Kyun; Itoi, Eiji

    2011-05-01

    A Ti-Nb-Sn alloy was developed as a new ?-type titanium alloy which had a low Young's modulus and high strength. The Young's modulus of the Ti-Nb-Sn alloy was reduced to about 45 GPa by cold rolling, much closer to human cortical bone (10-30 GPa) than that of Ti-6Al-4V alloy (110 GPa) and other ?-type titanium alloys developed for biomedical applications. The tensile strength of the Ti-Nb-Sn alloy was increased to a level greater than that of Ti-6Al-4V alloy by heat treatment after severe cold rolling. In this study the cytotoxicity of Ti-25Nb-11Sn alloy was evaluated in direct contact cell culture tests using metal disks and the bone tissue compatibility - examined using metal rods inserted into the medullary canal of rabbit femurs. The remarkable findings were that: (1) there were no significant differences in the relative growth ratio and relative absorbance ratio between cells grown with the Ti-Nb-Sn alloy, Ti-6Al-4V alloy and CP-Ti in direct contact cell culture tests; (2) there were no significant differences in the load at failure between the Ti-Nb-Sn alloy and Ti-6Al-4V alloy in pull-out metal rods tests; (3) there were no significant differences in new bone formation around metal rods between the Ti-Nb-Sn alloy and Ti-6Al-4V alloy in histological evaluations. The new Ti-Nb-Sn alloy with an elasticity closer to that of human bone is thus considered to be bioinert while also having a high degree of bone compatibility similar to that of Ti-6Al-4V alloy. PMID:21316491

  10. Gas-deposit-alloy corrosion interactions in simulated combustion environments

    NASA Astrophysics Data System (ADS)

    Luer, Kevin Raymond

    High temperature corrosion in aggressive coal combustion environments involves simultaneous corrosion reactions between combustion gases, ash deposits, and alloys. This research investigated the behavior of a ferritic steel (SA387-Gr11) and three weld claddings (309L SS, Alloy 72, and Alloy 622) in five combustion environments beneath solid deposits at 500°C for up to 1000 hours. The synthetic gases consisted of N2-CO-CO-H2-H2O-H 2S-SO2 mixtures that simulated a range of fuel-rich or fuel-lean combustion environments with a constant sulfur content. The synthetic deposits contained FeS2, FeS, Fe3O4 and/or carbon. Reaction kinetics was studied in individual gas-metal, gas deposit, and deposit-alloy systems. A test method was developed to investigate simultaneous gas-deposit-metal corrosion reactions. The results showed reaction kinetics varied widely, depending on the gas-alloy system and followed linear, parabolic, and logarithmic rate laws. Under reducing conditions, the alloys exhibited a range of corrosion mechanisms including carburization-sulfidation, sulfidation, and sulfidation-oxidation. Most alloys were not resistant to the highly reducing gases but offered moderate resistance to mixed oxidation-sulfidation by demonstrating parabolic or logarithmic behavior. Under oxidizing conditions, all of the alloys were resistant. Under oxidizing-sulfating conditions, alloys with high Fe or Cr contents sulfated whereas an alloy containing Mo and W was resistant. In the gas-deposit-metal tests, FeS2-bearing deposits were extremely corrosive to low alloy steel under both reducing and oxidizing conditions but they had little influence on the weld claddings. Accelerated corrosion was attributed to rapid decomposition or oxidation of FeS2 particles that generated sulfur-rich gases above the alloy surface. In contrast, FeS-type deposits had no influence under reducing conditions but they were aggressive to low alloy steel under oxidizing conditions. The extent of damage correlated with the initial sulfur content in the deposit. Fe3O4 in the deposit was beneficial because it acted as a sulfur getter or oxygen source. Carbon had a mixed effect. The reaction behavior was modeled using computational thermochemistry based on Gibbs free energy minimization. A calculation method was introduced to predict equilibrium corrosion microstructures and trace reaction paths in complex gas-deposit-metal environments. Kinetic factors were identified where equilibrium reaction products were not experimentally observed.

  11. Atomistic Method Applied to Computational Modeling of Surface Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo H.; Abel, Phillip B.

    2000-01-01

    The formation of surface alloys is a growing research field that, in terms of the surface structure of multicomponent systems, defines the frontier both for experimental and theoretical techniques. Because of the impact that the formation of surface alloys has on surface properties, researchers need reliable methods to predict new surface alloys and to help interpret unknown structures. The structure of surface alloys and when, and even if, they form are largely unpredictable from the known properties of the participating elements. No unified theory or model to date can infer surface alloy structures from the constituents properties or their bulk alloy characteristics. In spite of these severe limitations, a growing catalogue of such systems has been developed during the last decade, and only recently are global theories being advanced to fully understand the phenomenon. None of the methods used in other areas of surface science can properly model even the already known cases. Aware of these limitations, the Computational Materials Group at the NASA Glenn Research Center at Lewis Field has developed a useful, computationally economical, and physically sound methodology to enable the systematic study of surface alloy formation in metals. This tool has been tested successfully on several known systems for which hard experimental evidence exists and has been used to predict ternary surface alloy formation (results to be published: Garces, J.E.; Bozzolo, G.; and Mosca, H.: Atomistic Modeling of Pd/Cu(100) Surface Alloy Formation. Surf. Sci., 2000 (in press); Mosca, H.; Garces J.E.; and Bozzolo, G.: Surface Ternary Alloys of (Cu,Au)/Ni(110). (Accepted for publication in Surf. Sci., 2000.); and Garces, J.E.; Bozzolo, G.; Mosca, H.; and Abel, P.: A New Approach for Atomistic Modeling of Pd/Cu(110) Surface Alloy Formation. (Submitted to Appl. Surf. Sci.)). Ternary alloy formation is a field yet to be fully explored experimentally. The computational tool, which is based on the BFS (Bozzolo, Ferrante, and Smith) method for the calculation of the energetics, consists of a small number of simple PCbased computer codes that deal with the different aspects of surface alloy formation. Two analysis modes are available within this package. The first mode provides an atom-by-atom description of real and virtual stages 1. during the process of surface alloying, based on the construction of catalogues of configurations where each configuration describes one possible atomic distribution. BFS analysis of this catalogue provides information on accessible states, possible ordering patterns, and details of island formation or film growth. More importantly, it provides insight into the evolution of the system. Software developed by the Computational Materials Group allows for the study of an arbitrary number of elements forming surface alloys, including an arbitrary number of surface atomic layers. The second mode involves large-scale temperature-dependent computer 2. simulations that use the BFS method for the energetics and provide information on the dynamic processes during surface alloying. These simulations require the implementation of Monte-Carlo-based codes with high efficiency within current workstation environments. This methodology capitalizes on the advantages of the BFS method: there are no restrictions on the number or type of elements or on the type of crystallographic structure considered. This removes any restrictions in the definition of the configuration catalogues used in the analytical calculations, thus allowing for the study of arbitrary ordering patterns, ultimately leading to the actual surface alloy structure. Moreover, the Monte Carlo numerical technique used for the large-scale simulations allows for a detailed visualization of the simulated process, the main advantage of this type of analysis being the ability to understand the underlying features that drive these processes. Because of the simplicity of the BFS method for e energetics used in these calculations, a detailed atom-by-atom analysis can be performed at any

  12. 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.

  13. Surface modification of high temperature iron alloys

    DOEpatents

    Park, Jong-Hee (Clarendon Hills, IL)

    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.

  14. Alloyed coatings for dispersion strengthened alloys

    NASA Technical Reports Server (NTRS)

    Wermuth, F. R.; Stetson, A. R.

    1971-01-01

    Processing techniques were developed for applying several diffusion barriers to TD-Ni and TD-NiCr. Barrier coated specimens of both substrates were clad with Ni-Cr-Al and Fe-Cr-Al alloys and diffusion annealed in argon. Measurement of the aluminum distribution after annealing showed that, of the readily applicable diffusion barriers, a slurry applied tungsten barrier most effectively inhibited the diffusion of aluminum from the Ni-Cr-Al clad into the TD-alloy substrates. No barrier effectively limited interdiffusion of the Fe-Cr-Al clad with the substrates. A duplex process was then developed for applying Ni-Cr-Al coating compositions to the tungsten barrier coated substrates. A Ni-(16 to 32)Cr-3Si modifier was applied by slurry spraying and firing in vacuum, and was then aluminized by a fusion slurry process. Cyclic oxidation tests at 2300 F resulted in early coating failure due to inadequate edge coverage and areas of coating porosity. EMP analysis showed that oxidation had consumed 70 to 80 percent of the aluminum in the coating in less than 50 hours.

  15. Tensile and toughness assessment of the procured advanced alloys

    SciTech Connect

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

    2015-09-11

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

  16. 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.

  17. 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.

  18. Laser assisted high entropy alloy coating on aluminum: Microstructural evolution

    NASA Astrophysics Data System (ADS)

    Katakam, Shravana; Joshi, Sameehan S.; Mridha, Sanghita; Mukherjee, Sundeep; Dahotre, Narendra B.

    2014-09-01

    High entropy alloy (Al-Fe-Co-Cr-Ni) coatings were synthesized using laser surface engineering on aluminum substrate. Electron diffraction analysis confirmed the formation of solid solution of body centered cubic high entropy alloy phase along with phases with long range periodic structures within the coating. Evolution of such type of microstructure was a result of kinetics associated with laser process, which generates higher temperatures and rapid cooling resulting in retention of high entropy alloy phase followed by reheating and/or annealing in subsequent passes of the laser track giving rise to partial decomposition. The partial decomposition resulted in formation of precipitates having layered morphology with a mixture of high entropy alloy rich phases, compounds, and long range ordered phases.

  19. Laser assisted high entropy alloy coating on aluminum: Microstructural evolution

    SciTech Connect

    Katakam, Shravana; Joshi, Sameehan S.; Mridha, Sanghita; Mukherjee, Sundeep; Dahotre, Narendra B.

    2014-09-14

    High entropy alloy (Al-Fe-Co-Cr-Ni) coatings were synthesized using laser surface engineering on aluminum substrate. Electron diffraction analysis confirmed the formation of solid solution of body centered cubic high entropy alloy phase along with phases with long range periodic structures within the coating. Evolution of such type of microstructure was a result of kinetics associated with laser process, which generates higher temperatures and rapid cooling resulting in retention of high entropy alloy phase followed by reheating and/or annealing in subsequent passes of the laser track giving rise to partial decomposition. The partial decomposition resulted in formation of precipitates having layered morphology with a mixture of high entropy alloy rich phases, compounds, and long range ordered phases.

  20. Hydrogen pickup mechanism of zirconium alloys

    NASA Astrophysics Data System (ADS)

    Couet, Adrien

    Although the optimization of zirconium based alloys has led to significant improvements in hydrogen pickup and corrosion resistance, the mechanisms by which such alloy improvements occur are still not well understood. In an effort to understand such mechanisms, a systematic study of the alloy effect on hydrogen pickup is conducted, using advanced characterization techniques to rationalize precise measurements of hydrogen pickup. The hydrogen pick-up fraction is accurately measured for a specially designed set of commercial and model alloys to investigate the effects of alloying elements, microstructure and corrosion kinetics on hydrogen uptake. Two different techniques to measure hydrogen concentrations were used: a destructive technique, Vacuum Hot Extraction, and a non-destructive one, Cold Neutron Prompt Gamma Activation Analysis. The results indicate that hydrogen pickup varies not only from alloy to alloy but also during the corrosion process for a given alloy. For instance Zircaloy type alloys show high hydrogen pickup fraction and sub-parabolic oxidation kinetics whereas ZrNb alloys show lower hydrogen pickup fraction and close to parabolic oxidation kinetics. Hypothesis is made that hydrogen pickup result from the need to balance charge during the corrosion reaction, such that the pickup of hydrogen is directly related to (and indivisible of) the corrosion mechanism and decreases when the rate of electron transport or oxide electronic conductivity sigmao xe through the protective oxide increases. According to this hypothesis, alloying elements (either in solid solution or in precipitates) embedded in the oxide as well as space charge variations in the oxide would impact the hydrogen pick-up fraction by modifying sigmaox e, which drives oxidation and hydriding kinetics. Dedicated experiments and modelling were performed to assess and validate these hypotheses. In-situ electrochemical impedance spectroscopy (EIS) experiments were performed on Zircaloy-4 tubes to directly measure the evolution of sigma oxe as function of exposure time. The results show that sigmao xe decreases as function of exposure time and that its variations are directly correlated to the instantaneous hydrogen pickup fraction variations. The electron transport through the oxide layer is thus altered as the oxide grows, reasons for which are yet to be exactly determined. Preliminary results also show that sigma oxe of ZrNb alloys would be much higher compared with Zircaloy-4. Thus, it is confirmed that sigmaox e is a key parameter in the hydrogen and oxidation mechanism. Because the mechanism whereby alloying elements are incorporated into the oxide layer is critical to changing sigmao xe, the evolution of the oxidation state of two common alloying elements, Fe and Nb, when incorporated into the growing oxide layers is investigated using X-Ray Absorption Near-Edge Spectroscopy (XANES) using micro-beam synchrotron radiation on cross sectional oxide samples. The results show that the oxidation of both Fe and Nb is delayed in the oxide layer compared to that of Zr, and that this oxidation delay is related to the variations of the instantaneous hydrogen pick-up fraction with exposure time. The evolution of Nb oxidation as function of oxide depth is also compatible with space charge compensation in the oxide and with an increase in sigmaox e of ZrNb alloys compared to Zircaloys. Finally, various successively complex models from the well-known Wagner oxidation theory to the more complex effect of space charge on oxidation kinetics have been developed. The general purpose of the modeling effort is to provide a rationale for the sub-parabolic oxidation kinetics and demonstrate the correlation with hydrogen pickup fraction. It is directly demonstrated that parabolic oxidation kinetics is associated with high sigmao xe and low space charges in the oxide whereas sub-parabolic oxidation kinetics is associated with lower sigmaox e and higher space charge in the oxide. All these observations helped us to propose a general corrosion mechanism of zirconium alloys involving both oxidation and hydrogen pickup mechanism to better understand and predict the effect of alloying additions on the behavior of zirconium alloys.

  1. Modeling of Substitutional Site Preference in Ordered Intermetallic Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Honecy, Frank

    1998-01-01

    We investigate the site substitution scheme of specific alloying elements in ordered compounds and the dependence of site occupancy on compound stoichiometry, alloy concentration. This basic knowledge, and the interactions with other alloying additions are necessary in order to predict and understand the effect of various alloying schemes on the physical properties of a material, its response to various temperature treatments, and the resulting mechanical properties. Many theoretical methods can provide useful but limited insight in this area, since most techniques suffer from constraints in the type of elements and the crystallographic structures that can be modeled. With this in mind, the Bozzolo-Ferrante-Smith (BFS) method for alloys was designed to overcome these limitations, with the intent of providing an useful tool for the theoretical prediction of fundamental properties and structure of complex systems. After a brief description of the BFS method, its use for the determination of site substitution schemes for individual as well as collective alloying additions to intermetallic systems is described, including results for the concentration dependence of the lattice parameter. Focusing on B2 NiAl, FeAl and CoAl alloys, the energetics of Si, Ti, V, Cr, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Hf, Ta and W alloying additions are surveyed. The effect of single additions as well as the result of two simultaneous additions, discussing the interaction between additions and their influence on site preference schemes is considered. Finally, the BFS analysis is extended to ternary L1(sub 2) (Heusler phase) alloys. A comparison between experimental and theoretical results for the limited number of cases for which experimental data is available is also included.

  2. Superplasticity in aluminum alloys

    SciTech Connect

    Nieh, T. G.

    1997-12-01

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

  3. Shape Memory Alloy Actuator

    NASA Technical Reports Server (NTRS)

    Baumbick, Robert J. (Inventor)

    2002-01-01

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

  4. Shape Memory Alloy Actuator

    NASA Technical Reports Server (NTRS)

    Baumbick, Robert J. (Inventor)

    2000-01-01

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

  5. Annealing strained alloy 718

    NASA Technical Reports Server (NTRS)

    Morrison, T. J.

    1976-01-01

    Report shows that grain coarsening in Alloy 718 can result in greatly reduced resistance to weld-heat-produced zone fissuring, especially when final grain size is ASTM 2. Tensile tests and metallographic examination of bend test specimens provide necessary data.

  6. Quinary metallic glass alloys

    DOEpatents

    Lin, Xianghong; Johnson, William L.

    1998-01-01

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

  7. Ductile quasicrystalline alloys

    NASA Astrophysics Data System (ADS)

    Inoue, A.; Zhang, T.; Chen, M. W.; Sakurai, T.; Saida, J.; Matsushita, M.

    2000-02-01

    An icosahedral (I) quasicrystalline phase with a grain size below 40 nm was formed as a metastable phase in crystallization of the bulk glassy Zr65Al7.5Cu17.5-xNi10Mx (M=Ag, Pd, Au, or Pt; x=5 and 10 at %) alloys. The volume fraction (Vf) of the I phase is about 85% for the 5% M alloy and nearly 100% for the 10% M alloy. The I phase changes to Zr2Cu+Zr2Ni+Zr2Al3 in a fully annealed state. Compressive fracture strength (?c,f) and fracture elongation (?c,f) of the 10% Pd cylinder with a diameter of 2 mm are respectively 1640 MPa and 2.2% for the glassy phase and increase to 1830 MPa and 3.1% for the I phase. The increase in ?c,f is due to the suppression effect of the I particles against the shear deformation of the intergranular glassy phase, and the increase in ?c,f results from the localization effect of deformation into the glassy layer. The precipitation of the I phase implies that the glassy alloys include randomly oriented I configurations. The present work shows promise for the new class of high-strength nanoquasicrystalline materials.

  8. Quinary metallic glass alloys

    DOEpatents

    Lin, X.; Johnson, W.L.

    1998-04-07

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

  9. Weldable ductile molybdenum alloy development

    NASA Astrophysics Data System (ADS)

    Cockeram, B. V.; Ohriner, E. K.; Byun, T. S.; Miller, M. K.; Snead, L. L.

    2008-12-01

    Molybdenum and its alloys are attractive structural materials for high-temperature applications. However, various practical issues have limited its use. One concern relates to the loss of ductility occurring in the heat-affected weld zone caused by segregation of oxygen to grain boundaries. In this study, a series of arc melted molybdenum alloys have been produced containing controlled additions of B, C, Zr, and Al. These alloys were characterized with respect to their tensile properties, smooth bend properties, and impact energy for both the base metal and welds. These alloys were compared with a very high purity low carbon arc cast molybdenum reference. For discussion purposes the alloys produced are separated into two categories: Mo-Al-B alloys, and Mo-Zr-B alloys. The properties of Mo-Zr-B alloy welds containing higher carbon levels exhibited slight improvement over unalloyed molybdenum, though the base-metal properties for all Mo-Zr-B alloys were somewhat inconsistent with properties better, or worse, than unalloyed molybdenum. A Mo-Al-B alloy exhibited the best DBTT values for welds, and the base metal properties were comparable to or slightly better than unalloyed molybdenum. The Mo-Al-B alloy contained a low volume fraction of second-phase particles, with segregation of boron and carbon to grain boundaries believed to displace oxygen resulting in improved weld properties. The volume fractions of second-phase particles are higher for the Mo-Zr-B alloys, and these alloys were prone to brittle fracture. It is also noted that these Mo-Zr-B alloys exhibited segregation of zirconium, boron and carbon to the grain boundaries.

  10. Environmentally Assisted Cracking of Nickel Alloys

    SciTech Connect

    Rebak, R B

    2004-02-06

    Environmentally Assisted Cracking (EAC) is a general term that includes phenomena such as stress corrosion cracking (SCC), hydrogen embrittlement (HE), sulfide stress cracking (SSC), liquid metal embrittlement (LME), etc. EAC refers to a phenomenon by which a normally ductile metal looses its toughness (e.g. elongation to rupture) when it is subjected to mechanical stresses in presence of a specific corroding environment. For EAC to occur, three affecting factors must be present simultaneously. These include: (1) Mechanical tensile stresses, (2) A susceptible metal microstructure and (3) A specific aggressive environment. If any of these three factors is removed, EAC will not occur. That is, to mitigate the occurrence of EAC, engineers may for example eliminate residual stresses in a component or limit its application to certain chemicals (environment). The term environment not only includes chemical composition of the solution in contact with the component but also other variables such as temperature and applied potential. Nickel alloys are in general more resistant than stainless steels to EAC. For example, austenitic stainless steels (such as S30400) suffer SCC in presence of hot aqueous solutions containing chloride ions. Since chloride ions are ubiquitous in most industrial applications, the use of stressed stainless steels parts is seriously limited. On the other hand, nickel alloys (such as N10276) are practically immune to SCC in presence of hot chloride solutions and therefore an excellent alternative to replace the troubled stainless steels. Nonetheless, nickel alloys are not immune to other types of EAC. There are several environments (such as hot caustic and hot hydrofluoric acid) that may produce embrittlement in nickel alloys (Crum et al, 2000) (Table 1). The conditions where nickel alloys suffer EAC are highly specific and therefore avoidable by the proper design of the industrial components.

  11. Thermal coatings for titanium-aluminum alloys

    NASA Technical Reports Server (NTRS)

    Cunnington, George R.; Clark, Ronald K.; Robinson, John C.

    1993-01-01

    Titanium aluminides and titanium alloys are candidate materials for use in hot structure and heat-shield components of hypersonic vehicles because of their good strength-to-weight characteristics at elevated temperature. However, in order to utilize their maximum temperature capability, they must be coated to resist oxidation and to have a high total remittance. Also, surface catalysis for recombination of dissociated species in the aerodynamic boundary layer must be minimized. Very thin chemical vapor deposition (CVD) coatings are attractive candidates for this application because of durability and very light weight. To demonstrate this concept, coatings of boron-silicon and aluminum-boron-silicon compositions were applied to the titanium-aluminides alpha2 (Ti-14Al-21Nb), super-alpha2 (Ti-14Al-23-Nb-2V), and gamma (Ti-33Al-6Nb-1Ta) and to the titanium alloy beta-21S (Ti-15Mo-3Al-3Nb-0.2Si). Coated specimens of each alloy were subjected to a set of simulated hypersonic vehicle environmental tests to determine their properties of oxidation resistance, surface catalysis, radiative emittance, and thermal shock resistance. Surface catalysis results should be viewed as relative performance only of the several coating-alloy combinations tested under the specific environmental conditions of the LaRC Hypersonic Materials Environmental Test System (HYMETS) arc-plasma-heated hypersonic wind tunnel. Tests were also conducted to evaluate the hydrogen transport properties of the coatings and any effects of the coating processing itself on fatigue life of the base alloys. Results are presented for three types of coatings, which are as follows: (1) a single layer boron silicon coating, (2) a single layer aluminum-boron-silicon coating, and (3) a multilayer coating consisting of an aluminum-boron-silicon sublayer with a boron-silicon outer layer.

  12. Theoretical Studies of Hydrogen Storage Alloys.

    SciTech Connect

    Jonsson, Hannes

    2012-03-22

    Theoretical calculations were carried out to search for lightweight alloys that can be used to reversibly store hydrogen in mobile applications, such as automobiles. Our primary focus was on magnesium based alloys. While MgH{sub 2} is in many respects a promising hydrogen storage material, there are two serious problems which need to be solved in order to make it useful: (i) the binding energy of the hydrogen atoms in the hydride is too large, causing the release temperature to be too high, and (ii) the diffusion of hydrogen through the hydride is so slow that loading of hydrogen into the metal takes much too long. In the first year of the project, we found that the addition of ca. 15% of aluminum decreases the binding energy to the hydrogen to the target value of 0.25 eV which corresponds to release of 1 bar hydrogen gas at 100 degrees C. Also, the addition of ca. 15% of transition metal atoms, such as Ti or V, reduces the formation energy of interstitial H-atoms making the diffusion of H-atoms through the hydride more than ten orders of magnitude faster at room temperature. In the second year of the project, several calculations of alloys of magnesium with various other transition metals were carried out and systematic trends in stability, hydrogen binding energy and diffusivity established. Some calculations of ternary alloys and their hydrides were also carried out, for example of Mg{sub 6}AlTiH{sub 16}. It was found that the binding energy reduction due to the addition of aluminum and increased diffusivity due to the addition of a transition metal are both effective at the same time. This material would in principle work well for hydrogen storage but it is, unfortunately, unstable with respect to phase separation. A search was made for a ternary alloy of this type where both the alloy and the corresponding hydride are stable. Promising results were obtained by including Zn in the alloy.

  13. Rapid solidification of copper alloys with high strength and high conductivity

    SciTech Connect

    Lopez, F.; Reyes, J.; Campillo, B.; Aguilar-Sahagun, G.; Juarez-Islas, J.A.

    1997-10-01

    Rapid solidification has been employed to develop high-strength/high-conductivity copper alloys, because it offers advantages not achievable by conventional ingot metallurgy practice. The effect of rapid solidification on mechanical properties and electrical conductivity on copper alloys (with and without heat treatment) has been studied. Results indicated that alloys of the Cu-Cr-Zr type, rapidly solidified and aged, show a good combination of electrical conductivity [45.82 {times} 10{sup 6} (1/{Omega} {center_dot} m)] and microhardness Vickers (24.46 {times} 10{sup 6} Pa) values. These values are superior to those of optimally aged conventional copper alloys for resistance welding electrode applications.

  14. The shape memory capability and life of Cu-Al-Be-X alloys

    SciTech Connect

    Dong, Y.Y.; Dar, K.Z. ); Wang, T.M. ); Zin, S.J. )

    1994-09-01

    The shape memory capacity and the shape memory life of three alloys of the Cu-11.6Al-0.4Be-X type have been investigated using the strain angle restoration method and compared with the alloy Cu-25Zn-4Al. The alloys were subjected to various normalizing and normalizing plus aging treatments, and all were found to possess excellent shape memory properties. The alloy Cu-11.6Al-0.4Be-0.2Cr demonstrated the best shape memory capacity and life.

  15. Corrosion of high purity Fe-Cr-Ni alloys in 13 N boiling nitric acid

    SciTech Connect

    Ohta, Joji; Mayuzumi, Masami; Kusanagi, Hideo; Takaku, Hiroshi

    1998-12-31

    Corrosion in boiling nitric acid was investigated for high purity Fe-18%Cr-12%Ni alloys and type 304L stainless steels (SS). Owing to very low impurity concentration, the solution treated high purity alloys show almost no intergranular corrosion while the type 304L SS show severe intergranular corrosion. Both in the high purity alloys and type 304L SS, aging treatments ranging from 873 K to 1073 K for 1 h enhance intergranular corrosion. During the aging treatments, impurities should be segregated to the grain boundaries. The corrosion behaviors were discussed from a standpoint of impurity segregation to grain boundaries. This study is of importance for purex reprocessing of spent fuels.

  16. Mg sheet metal forming: Lessons learned from deep drawing Li and Y solid-solution alloys

    NASA Astrophysics Data System (ADS)

    Agnew, Sean R.; Senn, Jeremy W.; Horton, Joseph A.

    2006-05-01

    The sheet formability of current magnesium alloys at ambient temperatures is poor; however, the formability at moderately elevated temperatures can be excellent. Cylindrical cup drawing tests are used to compare the warm forming characteristics of conventional alloy AZ31B with alloys containing lithium oryttrium solid solutions. While both types of experimental alloy can have better room-temperature ductility (?f25-30%) than AZ31B, only the lithium alloy has comparable or better deep-drawing capacity. The results are discussed in terms of the sheet anisotropy. Particular attention is drawn to the fact that magnesium alloys exhibit poor bending ductility due to their anisotropy and mechanical twinning-induced tension-compression strength asymmetry.

  17. Prediction of novel, Earth abundant Cu2O based alloys for PV applications

    NASA Astrophysics Data System (ADS)

    Stevanovic, Vladan; Lany, Stephan

    2014-03-01

    Tuning the opto-electronic properties of semiconductors through alloying is essential for semiconductor industry. Currently, mostly isovalent and isostructural alloys are used (e.g. Si/Ge, GaN/InN or CdTe/ZnTe), but a vast and unexplored space of novel functional materials is conceivable when considering more complex alloys by mixing aliovalent and heterostructural constituents. The real challenge lies in the quantitative property prediction for such complex alloys to guide their experimental exploration. In our work we demonstrate how an Earth abundant p-type oxide Cu2O, can be engineered through alloying into a technologically useful absorber material. We use non-local external potentials (NLEP) fitted to GW calculations for correcting the DFT electronic structure and compute absorption coefficient of different alloy compositions and configurations. Work supported by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Next Generation Photovoltaics II (SunShot initiative).

  18. Characterization of amorphous Co-P alloy coatings electrodeposited with pulse current using gluconate bath

    NASA Astrophysics Data System (ADS)

    Bera, Parthasarathi; Seenivasan, H.; Rajam, K. S.; William Grips, V. K.

    2012-10-01

    Co-P alloy coatings were electrodeposited with pulse current using gluconate bath and characterized by XRD, FESEM, AFM, DSC and XPS. Co-P alloy coatings are amorphous in nature as demonstrated by XRD. FESEM exhibits the cauliflower type morphology that is distinctive of nanocrystalline metals and alloys. Co-P alloys are found to follow instantaneous growth mechanism as revealed by AFM studies. Two exothermic peaks at 320 and 340 C in DSC profiles of Co-P deposit correspond to the crystallization of the deposit. Detailed XPS studies of these alloy coatings have shown that as-deposited coatings consist of Co metal as well as oxidized Co species. P has mostly been present as bulk alloy on the surface as P?- form. Increase in the amounts of Co metal and P?- are observed upon intermittent sputtering. No appreciable increase in microhardness is observed with increase in the phosphorous content, but it increases with heat treatment significantly.

  19. Correlation of atomic packing with the boson peak in amorphous alloys

    SciTech Connect

    Yang, W. M.; Liu, H. S. E-mail: blshen@seu.edu.cn E-mail: jiangjz@zju.edu.cn; Zhao, Y. C.; Liu, X. J.; Chen, G. X.; Man, Q. K.; Chang, C. T.; Li, R. W. E-mail: blshen@seu.edu.cn E-mail: jiangjz@zju.edu.cn; Dun, C. C.; Shen, B. L. E-mail: blshen@seu.edu.cn E-mail: jiangjz@zju.edu.cn; Inoue, A.; and others

    2014-09-28

    Boson peaks (BP) have been observed from phonon specific heats in 10 studied amorphous alloys. Two Einstein-type vibration modes were proposed in this work and all data can be fitted well. By measuring and analyzing local atomic structures of studied amorphous alloys and 56 reported amorphous alloys, it is found that (a) the BP originates from local harmonic vibration modes associated with the lengths of short-range order (SRO) and medium-range order (MRO) in amorphous alloys, and (b) the atomic packing in amorphous alloys follows a universal scaling law, i.e., the ratios of SRO and MRO lengths to solvent atomic diameter are 3 and 7, respectively, which exact match with length ratios of BP vibration frequencies to Debye frequency for the studied amorphous alloys. This finding provides a new perspective for atomic packing in amorphous materials, and has significant implications for quantitative description of the local atomic orders and understanding the structure-property relationship.

  20. Preparation of electrodeposited Zn–Ni–B alloy coatings

    NASA Astrophysics Data System (ADS)

    Sakai, Taro; Kamimoto, Yuki; Ichino, Ryoichi

    2016-01-01

    We prepared Zn–Ni–B alloys with high Zn content and high corrosion resistance. The composition of the alloys was controlled by potentiostatic electrolysis. In the electroplating bath, dimethylamineborane was used as the B source. The characterization of the alloys and corrosion resistance evaluation were carried out by X-ray diffraction (XRD) analysis, optical microscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), inductively coupled plasma–atomic emission spectrometry (ICP-AES), Tafel plots, and cyclic corrosion tests. All films were categorized into three groups on the basis of the results of XRD analysis, and it was found by TEM analysis that the Ni–B-type showed an amorphous structure. The Ni–B-type could contain up to 50.6 mol % Zn and showed similar or better anticorrosion properties than the amorphous Ni–B films. In the Ni–B-type, the higher the Zn content, the higher the corrosion resistance. The Zn–Ni–B alloys had almost the same electrochemical corrosion resistance and Zn content as the Zn–Ni–P alloys.

  1. Interfacial oxidations of pure titanium and titanium alloys with investments.

    PubMed

    Ban, S; Watanabe, T; Mizutani, N; Fukui, H; Hasegawa, J; Nakamura, H

    2000-12-01

    External oxides of a commercially pure titanium (cpTi), Ti6Al4V alloy, and an experimental beta-type titanium alloy (Ti 53.4 wt%, Nb 29 wt%, Ta 13 wt%, and Zr 4.6 wt%) were characterized after heating to 600, 900, 1150, and 1400 degrees C in contact with three types of investments (alumina cement, magnesia cement, and phosphate-bonded) in air. XRD studies demonstrated that MgO, Li2TiO3 and/or Li2Ti3O7 were formed through reactions with the metal and the constituents in the magnesia cement-investment after heating to 900, 1150, and 1400 degrees C. Except for these conditions, TiO2 (rutile) was only formed on cpTi. For titanium alloys, the other components apart from Ti also formed simple and complex oxides such as Al2O3 and Al2TiO5 on Ti6Al4V, and Zr0.25Ti0.75Nb2O7 on the beta-type titanium alloy. However, no oxides containing V or Ta were formed. These results suggest that the constituents of titanium alloys reacted with the investment oxides and atmospheric oxygen to form external oxides due to the free energy of oxide formation and the concentration of each element on the metal surface. PMID:11816365

  2. Environmental protection to 922K (1200 F) for titanium alloys

    NASA Technical Reports Server (NTRS)

    Groves, M. T.

    1973-01-01

    Evaluations are presented of potential coating systems for protection of titanium alloys from hot-salt stress-corrosion up to temperatures of 755 K (900 F) and from oxidation embrittlement up to temperature of 922 K (1200 F). Diffusion type coatings containing Si, Al, Cr, Ni or Fe as single coating elements or in various combinations were evaluated for oxidation protection, hot-salt stress-corrosion (HSSC) resistance, effects on tensile properties, fatigue properties, erosion resistance and ballistic impact resistance on an alpha and beta phase titanium alloy (Ti-6Al-2Sn-4Zr-2Mo). All of the coatings investigated demonstrated excellent oxidation protectiveness, but none of the coatings provided protection from hot-salt stress-corrosion. Experimental results indicated that both the aluminide and silicide types of coatings actually decreased the HSSC resistance of the substrate alloy. The types of coatings which have typically been used for oxidation protection of refractory metals and nickel base superalloys are not suitable for titanium alloys because they increase the susceptibility to hot-salt stress-corrosion, and that entirely new coating concepts must be developed for titanium alloy protection in advanced turbine engines.

  3. Corrosion performance of structural alloys.

    SciTech Connect

    Natesan, K.

    1999-07-15

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

  4. Reduction in Defect Content of ODS Alloys

    SciTech Connect

    Ritherdon, J

    2003-11-17

    The work detailed within this report is a continuation of earlier work carried out under contract number 1DX-SY382V. The earlier work comprises a literature review of the sources and types of defects found principally in Fe-based ODS alloys as well as experimental work designed to identify defects in the prototype ODS-Fe{sub 3}Al alloy, deduce their origins and to recommend methods of defect reduction. The present work is an extension of the experimental work already reported and concentrates on means of reduction of defects already identified rather than the search for new defect types. This report also includes work regarding the manipulation of grain structures via deformation processing and further results gathered during powder separation trials involving the separation of different metallic powders in terms of their differing densities. The scope and objectives of the present work were laid out in the technical proposal ''Reduction in Defect Content in ODS Alloys-IV''. All the work proposed in the ''Statement of Work'' section of the technical proposal has been carried out except for some of that dependent on the acquisition of materials from other sources. However, wherever omissions from the ''Plan of Action'' detailed in the ''Statement of Work'' have occurred due to lack of suitable materials, other related experimental work has been devised to fill the gaps where possible. All work extra to the ''Statement of Work'' falls within the context of an ODS-Fe{sub 3}Al alloy of improved overall quality and potential creep performance in the consolidated form. The outturn of the experimental work performed is reported in the following sections.

  5. Filler metal alloy for welding cast nickel aluminide alloys

    DOEpatents

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

    1998-03-10

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

  6. Filler metal alloy for welding cast nickel aluminide alloys

    DOEpatents

    Santella, Michael L.; Sikka, Vinod K.

    1998-01-01

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

  7. Mechanical behavior and properties of mechanically alloyed aluminum alloys

    SciTech Connect

    Last, H.R.; Garrett, R.K. Jr.

    1996-03-01

    The fracture and deformation behaviors of several product forms produced from mechanically alloyed (MA) aluminum alloys 9052 and 905XL were studied. The main operative strengthening mechanism is strengthening due to the submicron grain size. Ductility and toughness were found to be controlled by the morphology of the prior particle boundaries. The authors propose that the work-hardening behavior of these MA alloys is similar to the behavior exhibited by a deformed fcc alloy that (a) contains rigid barriers to dislocation motion, (b) deforms by wavy slip, and (c) forms a cell substructure upon deformation.

  8. Mechanical behavior and properties of mechanically alloyed aluminum alloys

    NASA Astrophysics Data System (ADS)

    Last, H. R.; Garrett, R. K.

    1996-03-01

    The fracture and deformation behaviors of several product forms produced from mechanically alloyed (MA) aluminum alloys 9052 and 905XL were studied. The main operative strengthening mechanism is strengthening due to the submicron grain size. Ductility and toughness were found to be controlled by the morphology of the prior particle boundaries. We propose that the work-hardening behavior of these MA alloys is similar to the behavior exhibited by a deformed fcc alloy that (a) contains rigid barriers to dislocation motion, (b) deforms by wavy slip, and (c) forms a cell substructure upon deformation.

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

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  10. Two phase titanium aluminide alloy

    DOEpatents

    Deevi, Seetharama C. (Midlothian, VA); Liu, C. T. (Oak Ridge, TN)

    2001-01-01

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

  11. Magnesium-lithium casting alloys

    NASA Technical Reports Server (NTRS)

    Latenko, V. P.; Silchenko, T. V.; Tikhonov, V. A.; Maltsev, V. P.; Korablin, V. P.

    1974-01-01

    The strength properties of magnesium-lithium alloys at room, low, and high temperatures are investigated. It is found that the alloys may have practical application at ambient temperatures up to 100 C, that negative temperatures have a favorable influence on the alloy strength, and that cyclic temperature variations have practically no effect on the strength characteristics. The influence of chemical coatings on corrosion resistance of the MgLi alloys is examined. Several facilities based on pressure casting machines, low-pressure casting machines, and magnetodynamic pumps were designed for producing MgLi alloy castings. Results were obtained for MgLi alloys reinforced with fibers having a volumetric content of 15%.

  12. TERNARY ALLOY-CONTAINING PLUTONIUM

    DOEpatents

    Waber, J.T.

    1960-02-23

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

  13. Alloy Interface Interdiffusion Modeled

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  14. Shape memory alloy actuator

    SciTech Connect

    Varma, Venugopal K.

    2001-01-01

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

  15. Nanocrystal dispersed amorphous alloys

    NASA Technical Reports Server (NTRS)

    Perepezko, John H. (Inventor); Allen, Donald R. (Inventor); Foley, James C. (Inventor)

    2001-01-01

    Compositions and methods for obtaining nanocrystal dispersed amorphous alloys are described. A composition includes an amorphous matrix forming element (e.g., Al or Fe); at least one transition metal element; and at least one crystallizing agent that is insoluble in the resulting amorphous matrix. During devitrification, the crystallizing agent causes the formation of a high density nanocrystal dispersion. The compositions and methods provide advantages in that materials with superior properties are provided.

  16. Duct and cladding alloy

    DOEpatents

    Korenko, Michael K.

    1983-01-01

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

  17. Materials data handbook, Inconel alloy 718

    NASA Technical Reports Server (NTRS)

    Sessler, J.; Weiss, V.

    1967-01-01

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

  18. Materials data handbook, aluminum alloy 7075

    NASA Technical Reports Server (NTRS)

    Sessler, J.; Weiss, V.

    1967-01-01

    Materials data handbook on aluminum alloy 7075 includes data on the properties of the alloy at cryogenic, ambient, and elevated temperatures, and other pertinent engineering information required for the design and fabrication of components and equipment utilizing this alloy.

  19. A Review on High-Speed Machining of Titanium Alloys

    NASA Astrophysics Data System (ADS)

    Rahman, Mustafizur; Wang, Zhi-Gang; Wong, Yoke-San

    Titanium alloys have been widely used in the aerospace, biomedical and automotive industries because of their good strength-to-weight ratio and superior corrosion resistance. However, it is very difficult to machine them due to their poor machinability. When machining titanium alloys with conventional tools, the tool wear rate progresses rapidly, and it is generally difficult to achieve a cutting speed of over 60m/min. Other types of tool materials, including ceramic, diamond, and cubic boron nitride (CBN), are highly reactive with titanium alloys at higher temperature. However, binder-less CBN (BCBN) tools, which do not have any binder, sintering agent or catalyst, have a remarkably longer tool life than conventional CBN inserts even at high cutting speeds. In order to get deeper understanding of high speed machining (HSM) of titanium alloys, the generation of mathematical models is essential. The models are also needed to predict the machining parameters for HSM. This paper aims to give an overview of recent developments in machining and HSM of titanium alloys, geometrical modeling of HSM, and cutting force models for HSM of titanium alloys.

  20. Magnetostrictive strains in polycrystalline FePdRh alloy

    NASA Astrophysics Data System (ADS)

    Jen, S. U.; Chen, Yuan-Tsung; Tsai, T. L.; Lin, Y. C.

    2008-04-01

    The conventional magnetostrictive property was studied in the polycrystalline Fe-30Pd-4Rh alloy. The alloy was solution treated at 950C for 1.5h and then water quenched. At room temperature, the alloy has a mixed adaptive (or intermediate) martensite structure with ao=3.784 and co=3.514. At a lower temperature (e.g., T =150K), the full martensitic transformation is finally completed, and an expansion of the c axis with ?c /co?6.8% was observed. The thermal expansion coefficient, (1/T)(?a/ao), is +3.8410-6K-1 between 300 and 150K. From the electrical resistance (R) measurement between 300 and 4K, we confirm that the second, or final, martensitic transformation temperature (TIM) is approximately 170K. In addition, at room temperature, the saturation magnetization Ms(300)=655G, while at T =5K, Ms(5)=808G. Because an external field (H) may rotate Ms in the sample plane of Fe-Pd-Rh alloy, we find that, at T =300K, its saturation magnetostriction ?s=62ppm, and at T =77K, ?s=115ppm. There are at least two advantages on using the Fe-Pd-Rh alloy as the material for a magnetic-type microactuator or spring: (1) the alloy is ductile, and (2) at room temperature, the magnetostrictive susceptibility (??)?s/(?H) is high, about 0.8ppm/Oe at low field (H=50Oe).

  1. New Theoretical Technique Developed for Predicting the Stability of Alloys

    NASA Technical Reports Server (NTRS)

    1996-01-01

    When alloys are being designed for aeronautical and other applications, a substantial experimental effort is necessary to make incremental changes in the desired alloy properties. A scheme to narrow the field to the most promising candidates would substantially reduce the high cost of this experimental screening. Such a method for determining alloy properties, called the BFS (Bozzolo, Ferrante, and Smith) method, has been developed at the NASA Lewis Research Center. This method was used to calculate the thermal stability and mechanical strength of 200 alloys of Ni3Al, with Cu and Au impurities forming ternary and quaternary compounds. With recent advances in the method, almost any metallic impurity and crystal structure can be addressed. In addition, thermal effects can be addressed with Monte Carlo techniques. At present, an experimental program is in progress to verify these results. The method identified a small number of the most promising candidates from the 200 alloys with the largest negative heat of formation and the highest bulk modulus. This calculation required only 5 min of CPU time on a VAX computer. It is clear that semi-empirical methods have achieved the level of development and reliability to warrant examining this new approach to the problem of alloy design. The present work was meant to demonstrate, perhaps in a rather simple way, this power. This type of application of atomistic simulation methods can narrow the gap and improve the feedback between theoretical predictions and laboratory experimentation.

  2. Cladding burst behavior of Fe-based alloys under LOCA

    DOE PAGESBeta

    Terrani, Kurt A.; Dryepondt, Sebastien N.; Pint, Bruce A.; Massey, Caleb P.

    2015-12-17

    Burst behavior of austenitic and ferritic Fe-based alloy tubes has been examined under a simulated large break loss of coolant accident. Specifically, type 304 stainless steel (304SS) and oxidation resistant FeCrAl tubes were studied alongside Zircaloy-2 and Zircaloy-4 that are considered reference fuel cladding materials. Following the burst test, characterization of the cladding materials was carried out to gain insights regarding the integral burst behavior. Given the widespread availability of a comprehensive set of thermo-mechanical data at elevated temperatures for 304SS, a modeling framework was implemented to simulate the various processes that affect burst behavior in this Fe-based alloy. Themore » most important conclusion is that cladding ballooning due to creep is negligible for Fe-based alloys. Thus, unlike Zr-based alloys, cladding cross-sectional area remains largely unchanged up to the point of burst. Furthermore, for a given rod internal pressure, the temperature onset of burst in Fe-based alloys appears to be simply a function of the alloy's ultimate tensile strength, particularly at high rod internal pressures.« less

  3. Surface Segregation in Ternary Alloys

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

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

  4. Hydrogen tolerance of a Ti3Al-based alloy

    NASA Technical Reports Server (NTRS)

    Chan, Kwai S.

    1993-01-01

    The Ti-24Al-11Nb (Ti-24-11) alloy heat-treated to the fine basketweave microstructure was shown previously to be hydrogen-tolerant. In order to assess its limit of hydrogen tolerance, the tensile, creep, fracture toughness, and sustained-load crack growth behaviors of this alloy were studied as a function of hydrogen content. The mechanical test results indicated that the fine basketweave microstructure was tolerant to hydride embrittlement for hydrogen contents up to about 1500 wppm. On the other hand, hydrogen charging experiments indicated that the Ti-24-11 alloy was severely cracked and pulverized under zero load when the hydrogen content exceeded 3000 wppm. X-ray diffraction results revealed that the dichotomous behaviors might be due to the formation of face-centered cubic (fcc) delta-type hydrides at higher hydrogen contents but face-centered tetragonal (fct) gamma-type hydrides at lower hydrogen contents.

  5. [Cast fractures of dental Ni-Cr alloys (author's transl)].

    PubMed

    Takahashi, J; Kaneda, S; Okazaki, M; Doi, Y; Moriwaki, Y; Kimura, H

    1981-10-01

    Cast fractures of Ni-Cr alloys were investigated by means of scanning electron microscopy, energy dispersive X-ray spectrometry, electron-probe microanalysis, density measurements, setting and thermal expansion measurements and compressive tests. Three-Ni-Cr alloys for crowns and bridges were cast in spiral configurations by an argon-arc pressured type or an induction argon-pressured type-casting machine. The amount of cast fracture increase with an increase in cast temperature, but not with an increase of holding time at cast temperature. Ni-Cr alloys have more cast fractures in a phosphate-bonded investment than in a gypsum-bonded cristobalite investment. Fracture surfaces have an exposed dendrite structure, indicating the presence of cast porosity. The trigger of cast crack can be a cast porosity and the propagation of crack to fracture may be mainly due to the strength of investments. PMID:7038000

  6. New hydrogenated amorphous silicon alloys

    NASA Astrophysics Data System (ADS)

    Lin, G. H.; Kapur, M.; Bockris, J. O'M.

    1990-07-01

    New alloys of hydogenated amorphous silicon with Al, Ga, S, and Se have been prepared by the rf glow discharge method. The energy gap of these materials can be varied in the 1-2 eV range, with the Al and Ga alloys being low band-gap semiconductors, and the S and Se alloys having higher energy gaps. The light to dark conductivity ratios of the various systems have been measured. The best photoresponse (102-103) was obtained with the Se and S alloys.

  7. Positron lifetime studies of decomposition in 2024 (Al-Cu-Mg) and 7010 (Al-Zn-Cu-Mg) alloys

    SciTech Connect

    Dlubek, G.; Lademann, P.; Krause, H.; Krause, S.; Unger, R.

    1998-09-04

    In the current paper, the decomposition behavior of the engineering alloys 2024 (Al-Cu-Mg) and 7010 (Al-Zn-Cu-Mg) is studied using positron lifetime measurements. Positrons probe open volume defects such as vacancies and dislocations. However, they may also be used to investigate coherent zones and incoherent precipitates. In order to understand the rather complicated precipitation sequences and the response of positrons to different type of precipitates occurring in 2024 and 7010 alloys, binary and ternary laboratory alloys were also investigated under the same experimental conditions as the engineering alloys. The interpretations of the results are based on experiences of the group from extensive positron studies of laboratory alloys such as Al-Zn, Al-Zn-Mg, Al-Cu, and further Al alloys (see also the review (4)). Their collected results are shown as lifetimes and curve-shape parameters S of the electron-positron momentum distribution curves characteristic for different precipitates in Al alloys.

  8. The effect of tensile stress on hydrogen diffusion in metal alloys

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1992-01-01

    The effect of tensile stress on hydrogen diffusion has been determined for Type 303 stainless steel, A286 CRES, and Waspaloy and IN100 nickel-base alloys. It was found that hydrogen diffusion coefficients are not significantly affected by stress, while the hydrogen permeabilities are greatly affected in Type 303 stainless steel and A286 CRES (iron-based alloys), but are affected little in Waspaloy (nickel-base) and not affected in all in IN100 (nickel base). These observations might be taken as an indication that hydrogen permeabilities are affected by stress in iron-based alloys, but only slightly affected in nickel-based alloys. However, it is too early to make such a generalization based on the study of only these four alloys.

  9. High-temperature deformation behavior of KCl-RbCl solid solution alloys

    SciTech Connect

    Duong, H.; McClelland, R.J.; Wolfenstine, J. ); Beeman, M. )

    1992-05-01

    It is well established that the creep behavior of metallic solid solution alloys can be divided into two types. The main criterion for this classification is based on the value of the stress exponent, n. When n {approximately} 5 the creep behavior of the metallic solid solution alloys is similar to that observed in pure metals, where the rate-controlling deformation mechanism is attributed to a dislocation climb process. This type of metallic alloy is designated as a class II solid solution ally after the original classification of Sherby and Burke and Cannon and Sherby. It is the purpose of this paper to present some preliminary results on the creep behavior of KCl-RbCl solid solution alloys and to compare these results with that observed in the KCl-NaCl system and metallic solid solution alloys. The variation of the stress exponent and dislocation substructure with composition will be reported.

  10. Corrosion behavior of cast and forged cobalt-based alloys for double-alloy joint endoprostheses.

    PubMed

    Sry, P; Semlitsch, M

    1978-09-01

    An ideal combination of mechanical and corrosion properties of long-term implants such as joint endoprostheses has yet to be found. Besides being resistant to pitting and crevice attack, which can lead to corrosion fatigue and stress corrosion cracking failures, the implant material must be highly resistant to wear and abrasion. Two cobalt-based alloys, wrought CoNiMoTi and air-cast CoCrMo, were subjected to a number of selected in vitro electrochemically and chemically accelerated corrosion tests in chloride-containing solutions with wrought AISI-316L used as a reference alloy. A limited number of immersion tests in FeCl3 and acidified FeCl3 solutions were also conducted. It is found that the mechanical properties of wrought CoNiCrMoTi alloy qualify it as a substitute for cast CoCrMo alloy and wrought AISI-316L in anchorage shaft production for all types of joint endoprostheses. Wrought CoNiCrMoTi has a higher resistance to fatigue cracking compared with cast CoCrMo and is as resistant to selective corrosion phenomena such as stress corrosion cracking. PMID:701305

  11. Alloy Design Data Generated for B2-Ordered Compounds

    NASA Technical Reports Server (NTRS)

    Noebe, Ronald D.; Bozzolo, Guillermo; Abel, Phillip B.

    2003-01-01

    Developing alloys based on ordered compounds is significantly more complicated than developing designs based on disordered materials. In ordered compounds, the major constituent elements reside on particular sublattices. Therefore, the addition of a ternary element to a binary-ordered compound is complicated by the manner in which the ternary addition is made (at the expense of which binary component). When ternary additions are substituted for the wrong constituent, the physical and mechanical properties usually degrade. In some cases the resulting degradation in properties can be quite severe. For example, adding alloying additions to NiAl in the wrong combination (i.e., alloying additions that prefer the Al sublattice but are added at the expense of Ni) will severely embrittle the alloy to the point that it can literally fall apart during processing on cooling from the molten state. Consequently, alloying additions that strongly prefer one sublattice over another should always be added at the expense of that component during alloy development. Elements that have a very weak preference for a sublattice can usually be safely added at the expense of either element and will accommodate any deviation from stoichiometry by filling in for the deficient component. Unfortunately, this type of information is not known beforehand for most ordered systems. Therefore, a computational survey study, using a recently developed quantum approximate method, was undertaken at the NASA Glenn Research Center to determine the preferred site occupancy of ternary alloying additions to 12 different B2-ordered compounds including NiAl, FeAl, CoAl, CoFe, CoHf, CoTi, FeTi, RuAl, RuSi, RuHf, RuTi, and RuZr. Some of these compounds are potential high temperature structural alloys; others are used in thin-film magnetic and other electronic applications. The results are summarized. The italicized elements represent the previous sum total alloying information known and verify the computational method used to establish the table. Details of the computational procedures used to determine the preferred site occupancy can be found in reference 2. As further substantiation of the validity of the technique, and its extension to even more complicated systems, it was applied to two simultaneous alloying additions in an ordered alloy.

  12. Study on improved tribological properties by alloying copper to CP-Ti and Ti-6Al-4V alloy.

    PubMed

    Wang, Song; Ma, Zheng; Liao, Zhenhua; Song, Jian; Yang, Ke; Liu, Weiqiang

    2015-12-01

    Copper alloying to titanium and its alloys is believed to show an antibacterial performance. However, the tribological properties of Cu alloyed titanium alloys were seldom studied. Ti-5Cu and Ti-6Al-4V-5Cu alloys were fabricated in the present study in order to further study the friction and wear properties of titanium alloys with Cu additive. The microstructure, composition and hardness were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and hardness tester. The tribological behaviors were tested with ZrO2 counterface in 25% bovine serum using a ball-on-disc tribo-tester. The results revealed that precipitations of Ti2Cu intermetallic compounds appeared in both Ti-5Cu and Ti-6Al-4V-5Cu alloys. The tribological results showed an improvement in friction and wear resistance for both Ti-5Cu and Ti-6Al-4V-5Cu alloys due to the precipitation of Ti2Cu. The results also indicated that both CP-Ti and Ti-5Cu behaved better wear resistance than Ti-6Al-4V and Ti-6Al-4V-5Cu due to different wear mechanisms when articulated with hard zirconia. Both CP-Ti and Ti-5Cu revealed dominant adhesive wear with secondary abrasive wear mechanism while both Ti-6Al-4V and Ti-6Al-4V-5Cu showed severe abrasive wear and cracks with secondary adhesive wear mechanism due to different surface hardness integrated by their microstructures and material types. PMID:26354247

  13. Using the method of positron annihilation for detecting defects in structural alloys caused by fatigue

    SciTech Connect

    Arefev, K.P.; Boev, O.V.; Chernitsyn, A.I.; Polukhin, Y.E.; Vordb'ev, S.A.

    1986-12-01

    This paper examines the possibilities of using the method ofpositron annihilation for detecting fatigue defects in structural alloys with various types of crystal structure. The parameter of the positron annihilation process most suitable for the inspection was determined.

  14. Fluoride technology of obtaining REM magnetic alloys and master alloys

    NASA Astrophysics Data System (ADS)

    Sophronov, V. L.; Zhiganov, A. N.; Makaseev, Yu N.; Rusakov, I. Yu; Verkhoturova, V. V.

    2016-02-01

    Rare earth permanent magnets (REPM) based on neodymium-Fe-boron system are the most promising, since they have the highest magnetic and satisfactory mechanical characteristics. The paper covers physical-chemical principles and shows the results of experimental studies of the process of obtaining REM alloys and master alloys using fundamentally new fluoride technology based on ladle calciothermal REM fluorides and Fe reduction.

  15. Evaluation of a hydrogen resistant titanium aluminide alloy

    NASA Technical Reports Server (NTRS)

    Chan, K. S.

    1991-01-01

    The Ti-24Al-11Nb (Ti-24-11) alloy heat treated to the fine basketweave microstructure was shown previously to be hydrogen tolerant. In order to assess its limit of hydrogen tolerance, the tensile, creep, fracture toughness, and sustained load crack growth behaviors of this alloy were studied as a function of hydrogen content. All test specimens were thermally charged with internal hydrogen and tested at 25 and 600 C. Coupon specimens were used for developing the hydrogen charging procedures and for studying compatibility of the alloy with high temperature, high pressure gaseous hydrogen. The mechanical test results indicated that the fine basketweave microstructure was tolerant to hydride embrittlement for hydrogen contents up to approximately 1500 wt. ppm, providing that the hydride formed was of the TiH2 type. On the other hand, hydrogen charging experiments indicated that the Ti-24-11 alloy was severely cracked and pulverized under zero load when the hydrogen content exceeded 3000 wt. ppm. X-ray diffraction results revealed that the dichotomous behaviors might be due to the formation of TiH(1.924) type hydrides at higher hydrogen contents. Thus, hydrogen embrittlement in the Ti-24-11 alloy with the fine basketweave microstructure depends on hydrogen content and the nature of the hydrides formed.

  16. Hydrogen tolerance of a Ti3AI-based alloy

    NASA Astrophysics Data System (ADS)

    Chan, Kwai S.

    1993-05-01

    The Ti-24Al-llNb (Ti-24-11) alloy heat-treated to the fine basketweave microstructure was shown previously to be hydrogen-tolerant. In order to assess its limit of hydrogen tolerance, the tensile, creep, fracture toughness, and sustained-load crack growth behaviors of this alloy were studied as a function of hydrogen content. All test specimens were charged thermally with internal hydrogen and tested at 25 C and 600 C. Coupon specimens were used for developing the hydrogen-charging procedures and for studying compatibility of the alloy with high-temperature, high-pressure gaseous hydrogen. The mechanical test results indicated that the fine basketweave microstructure was tolerant to hydride embrittlement for hydrogen contents up to ?1500 wppm. On the other hand, hydrogen charging experiments indicated that the Ti-24-11 alloy was severely cracked and pulverized under zero load when the hydrogen content exceeded 3000 wppm. X-ray diffraction (XRD) results revealed that the dichotomous behaviors might be due to the formation of face-centered cubic (fee) ?-type hydrides at higher hydrogen contents but face-centered tetragonal (fct) ?-type hydrides at lower hydrogen contents. Thus, hydrogen embrittlement in the Ti-24-11 alloy with the fine basketweave microstructure depends on hydrogen content and the nature of hydrides formed.

  17. Biocompatibility of new Ti-Nb-Ta base alloys.

    PubMed

    Hussein, Abdelrahman H; Gepreel, Mohamed A-H; Gouda, Mohamed K; Hefnawy, Ahmad M; Kandil, Sherif H

    2016-04-01

    β-type titanium alloys are promising materials in the field of medical implants. The effect of β-phase stability on the mechanical properties, corrosion resistance and cytotoxicity of a newly designed β-type (Ti77Nb17Ta6) biocompatible alloys are studied. The β-phase stability was controlled by the addition of small quantities of Fe and O. X-ray diffraction and microstructural analysis showed that the addition of O and Fe stabilized the β-phase in the treated solution condition. The strength and hardness have increased with the increase in β-phase stability while ductility and Young's modulus have decreased. The potentio-dynamic polarization tests showed that the corrosion resistance of the new alloys is better than Ti-6Al-4V alloy by at least ten times. Neutral red uptake assay cytotoxicity test showed cell viability of at least 95%. The new alloys are promising candidates for biomedical applications due to their high mechanical properties, corrosion resistance, and reduced cytotoxicity. PMID:26838885

  18. Radiation Effects in Refractory Alloys

    SciTech Connect

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

    2004-02-04

    In order to achieve the required low reactor mass per unit electrical power for space reactors, refractory alloys are essential due to their high operating temperature capability that in turn enables high thermal conversion efficiencies. One of the key issues associated with refractory alloys is their performance in a neutron irradiation environment. The available radiation effects data are reviewed for alloys based on Mo, W, Re, Nb and Ta. The largest database is associated with Mo alloys, whereas Re, W and Ta alloys have the least available information. Particular attention is focused on Nb-1Zr, which is a proposed cladding and structural material for the reactor in the Jupiter Icy Moons Orbiter (JIMO) project. All of the refractory alloys exhibit qualitatively similar temperature-dependent behavior. At low temperatures up to {approx}0.3TM, where TM is the melting temperature, the dominant effect of radiation is to produce pronounced radiation hardening and concomitant loss of ductility. The radiation hardening also causes a dramatic decrease in the fracture toughness of the refractory alloys. These low temperature radiation effects occur at relatively low damage levels of {approx}0.1 displacement per atom, dpa ({approx}2x1024 n/m2, E>0.1 MeV). As a consequence, operation at low temperatures in the presence of neutron irradiation must be avoided for all refractory alloys. At intermediate temperatures (0.3 to 0.6 TM), void swelling and irradiation creep are the dominant effects of irradiation. The amount of volumetric swelling associated with void formation in refractory alloys is generally within engineering design limits (<5%) even for high neutron exposures (>>10 dpa). Very little experimental data exist on irradiation creep of refractory alloys, but data for other body centered cubic alloys suggest that the irradiation creep will produce negligible deformation for near-term space reactor applications.

  19. Alloys by Microwave-Activated Hot Pressing

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Fan, Xi An; Rong, Zhen Zhou; Cai, Xin Zhi; Li, Guang Qiang

    2014-11-01

    The p-type Bi0.4Sb1.6Te3 alloys are prepared using a new method of mechanical alloying followed by microwave-activated hot pressing (MAHP). The effect of sintering temperature on the microstructure and thermoelectric properties of Bi0.4Sb1.6Te3 alloys is investigated. Compared with other sintering techniques, the MAHP process can be used to produce relatively compact bulk materials at lower sintering temperatures owing to its unique sintering mechanism. The grain size of the MAHP specimens increases gradually with the sintering temperature and a partially oriented lamellar structure can be formed in some regions of specimens obtained. The formation of the in situ-generated nano-phase is induced by the arcing effect of the MAHP process, which enhances the phonon scattering effect and decreases the lattice thermal conductivity. A minimum lattice thermal conductivity of 0.41 W/(mK) and a maximum figure of merit value of 1.04 are obtained at 100C for the MAHP specimen sintered at 325C. This technique may also be extended to other functional materials to obtain ultrafine microstructures at low sintering temperatures.

  20. Aluminum Alloy and Article Cast Therefrom

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    A cast article from an aluminum alloy, which has improved mechanical properties at elevated temperatures, has the following composition in weight percent: Silicon 14 - 25.0, Copper 5.5 - 8.0, Iron 0.05 - 1.2, Magnesium 0.5 - 1.5, Nickel 0.05 - 0.9, Manganese 0.05 - 1.0, Titanium 0.05 - 1.2, Zirconium 0.05 - 1.2, Vanadium 0.05 - 1.2, Zinc 0.05 - 0.9, 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 and containing up to about 60% by volume of a secondary filler material.

  1. Dislocation core structure in ordered intermetallic alloys

    NASA Astrophysics Data System (ADS)

    Pasianot, R.; Farkas, D.; Savino, E. J.

    1991-06-01

    The basic features of dislocation core structures in ordered intermetallic alloys are discussed, as revealed by atomistic computer simulation. The simulated dislocation core structures are for the most commonly observed slip systems in both L12 and B2 alloys. The simulations were carried out with embedded atom interatomic potentials. Screw and edge dislocations were studied, particularly investigating the planarity of the dislocations cores. The general trend of the results agrees with the results of previous investigators using pair potentials for model alloys. In all cases the core structure is spread in one or possibly more closed packed planes. Les caractristiques principales des structures de coeur des dislocations, simules par ordinateur, sont discutes. Les simulations sont effectues dans le cas des systmes de glissement les plus frquemment observs, dans les alliages de type L12 et B2. Elles sont obtenues l'aide de potentiels d'atomes entours. Les dislocations vis et coins ont t tudies, particulirement en ce qui concerne la planarit des coeurs de dislocations. La tendance gnrale des rsultats est en accord avec des rsultats antrieurs utilisant des potentiels de paire pour des alliages modles,. Dans tous les cas la structure de coeur est tale dans un ou ventuellement plusieurs plans compacts.

  2. Creep properties of phosphorus + boron-modified alloy 718

    SciTech Connect

    McKamey, C.G.; Carmichael, C.A.; Cao, W.D.; Kennedy, R.L.

    1998-01-06

    Creep-rupture testing of modified alloy 718 has confirmed the beneficial effect of optimum additions of P and B. Activation energies and creep exponent analyses suggest some type of pinning mechanism is involved in this strengthening. However, the exact mechanism of this improvement is still unclear.

  3. Loss of Alloy in Cast Restorations Fabricated by Dental Students.

    ERIC Educational Resources Information Center

    Soh, George

    1991-01-01

    A study investigated the quantity of alloy lost in the fabrication of three types of cast restoration by dental students, and identified the proportion of loss at each of the four principal stages of the fabrication process. Suggestions for reducing metal loss and related costs in dental schools are offered. (MSE)

  4. A comparison of tensile bond strengths of resin-retained prostheses made using five alloys.

    PubMed

    Rubo, J H; Pegoraro, L F; Ferreira, P M

    1996-01-01

    This in vitro study evaluated the bond strength of metal frameworks cast using Ni-Cr, Ni-Cr-Be, Cu-Al, type IV gold, and noble metal ceramic alloy with and without tin electroplating. The castings were luted to human teeth using Panavia Ex resin. It was found that tin electroplating had a negative effect for the Cu-Al and type IV gold alloys and a positive effect for gold for metal ceramic restorations. The best results were obtained using the Ni-Cr alloy. PMID:8957864

  5. Tensile and fatigue properties of two titanium alloys as candidate materials for fusion reactors

    NASA Astrophysics Data System (ADS)

    Marmy, P.; Leguey, T.; Belianov, I.; Victoria, M.

    2000-12-01

    Titanium alloys have been identified as candidate structural materials for the first wall, the blanket and the magnetic coil structures of fusion reactors. Titanium alloys are interesting materials because of their high specific strength and low elastic modulus, their low swelling tendency and their fast induced radioactivity decay. Other attractive properties are an excellent resistance to corrosion and good weldability, even in thick sections. Furthermore titanium alloys are suitable for components exposed to heat loads since they have a low thermal stress parameter. Titanium alloys with an ? structure are believed to have a good resistance against radiation embrittlement and ?+? alloys should possess the best tolerance to hydrogen embrittlement. Two classical industrially available alloys in the two families, the Ti5Al2.4Sn and the Ti6Al4V alloys have been used in this study. The tensile properties between room temperature and 450C are reported. A low cycle fatigue analysis has been performed under strain control at total strain ranges between 0.8% and 2% and at a temperature of 350C. The microstructure of both alloys was investigated before and after both types of deformation. Both alloys exhibit excellent mechanical properties comparable to or better than those of ferritic martensitic steels.

  6. Dendrite growth morphologies in aluminum alloys

    SciTech Connect

    Henry, S.; Minghetti, T.; Rappaz, M.

    1998-11-20

    Different aluminum alloys, in particular Al-Cu, Al-Mg and Al-Si, have been directionally solidified under well-controlled thermal and convection conditions. For relatively high solidification rates, particular growth morphologies were observed. The most common is linked with the formation of feathery grains: these are constituted by series of twinned lamellae, in which the dendrites have {l_angle}110{r_angle} trunks cut through by {l_brace}111{r_brace} twin planes. These grains undergo a selection mechanism which is similar to that occurring for regular {l_angle}100{r_angle} dendritic grains. The dendritic growth along {l_angle}110{r_angle} crystallographic directions is supposed to be due to a change in the anisotropy of certain properties of the alloy, such as the solid/liquid interfacial energy and/or the atom attachment kinetics. When solidification conditions become less favorable to {l_angle}110{r_angle} growth morphologies, a mixed dendritic form containing {l_angle}110{r_angle} trunks and {l_angle}100{r_angle} arms may be obtained. In the case of the 5182 Al-Mg type alloy, {l_angle}110{r_angle} columnar grains which were not twinned could be observed together with feathery crystals. The possibility of such changes in the growth direction of aluminum alloys was further demonstrated by the observation of dendrites of Al-Cu-Mg solidified in a Bridgman device. In this case, {l_angle}112{r_angle} dendrites grow and progressively change their growth direction, thus showing curved shapes.

  7. Welding Metallurgy of Alloy HR-160

    SciTech Connect

    DuPont, J.N.; Michael, J.R.; Newbury, B.D.

    1999-05-28

    The solidification behavior and resultant solidification cracking susceptibility of autogenous gas tungsten arc fusion welds in alloy HR-160 was investigated by Varestraint testing, differential thermal analysis, and various microstructural characterization techniques. The alloy exhibited a liquidus temperature of 1387 {deg}C and initiated solidification by a primary L - {gamma} reaction in which Ni, Si, and Ti segregated to the interdendritic liquid and Co segregated to the {gamma} dendrite cores. Chromium exhibited no preference for segregation to the solid or liquid phase during solidification. Solidification terminated at {approx} 1162 {deg}C by a eutectic-type L - [{gamma}+ (Ni,Co){sub 16}(Ti,Cr){sub 6}Si{sub 7}] reaction. The (Ni,Co){sub 16}(Ti,Cr){sub 6}Si{sub 7} phase is found to be analogous to the G phase which forms in the Ni-Ti-Si and Co-Ti-Si ternary systems, and similarities are found to exist between the solidification behavior of this commercial multicomponent alloy and the simple Ni-Si and Ni-Ti binary systems. Reasonable agreement is obtained between the calculated and measured volume percent of the [{gamma} +(Ni,Co){sub l6}(Ti,Cr){sub 6}Si{sub 7}] eutectic-typr constituent with the Scheil equation using experimentally determined k values for Si and Ti from electron microprobe data. The alloy exhibited a very high susceptibility to solidification cracking in the Varestraint test. This is attributed to a large solidification temperature range of 225 {deg}C and the presence of 2 to 5 vol% solute rich interdendritic liquid which preferentially wets the grain boundaries and interdendritic regions.

  8. Aluminum-Alloy-Matrix/Alumina-Reinforcement Composites

    NASA Technical Reports Server (NTRS)

    Kashalikar, Uday; Rozenoyer, Boris

    2004-01-01

    Isotropic composites of aluminum-alloy matrices reinforced with particulate alumina have been developed as lightweight, high-specific-strength, less-expensive alternatives to nickel-base and ferrous superalloys. These composites feature a specific gravity of about 3.45 grams per cubic centimeter and specific strengths of about 200 MPa/(grams per cubic centimeter). The room-temperature tensile strength is 100 ksi (689 MPa) and stiffness is 30 Msi (206 GPa). At 500 F (260 C), these composites have shown 80 percent retention in strength and 95 percent retention in stiffness. These materials also have excellent fatigue tolerance and tribological properties. They can be fabricated in net (or nearly net) sizes and shapes to make housings, pistons, valves, and ducts in turbomachinery, and to make structural components of such diverse systems as diesel engines, automotive brake systems, and power-generation, mining, and oil-drilling equipment. Separately, incorporation of these metal matrix composites within aluminum gravity castings for localized reinforcement has been demonstrated. A composite part of this type can be fabricated in a pressure infiltration casting process. The process begins with the placement of a mold with alumina particulate preform of net or nearly net size and shape in a crucible in a vacuum furnace. A charge of the alloy is placed in the crucible with the preform. The interior of the furnace is evacuated, then the furnace heaters are turned on to heat the alloy above its liquidus temperature. Next, the interior of the furnace is filled with argon gas at a pressure about 900 psi (approximately equal to 6.2 MPa) to force the molten alloy to infiltrate the preform. Once infiltrated, the entire contents of the crucible can be allowed to cool in place, and the composite part recovered from the mold.

  9. Welding of titanium alloy by Disk laser

    NASA Astrophysics Data System (ADS)

    Lisiecki, Aleksander

    2013-01-01

    The following article describes results of investigations on influence of laser welding parameters on the weld shape, quality and mechanical properties of 2.0 mm thick butt joints of titanium alloy Ti6Al4V (Grade 5 according to ASTM B265) welded with a new generation disk laser TRUMPF TRUDISK 3302, emitting at 1030 nm, with maximum output power 3300 W at circular laser beam spot, characterized by laser beam divergence 8.0 mm•mrad. The test butt joints of Ti6Al4V titanium alloy sheets were prepared as single square groove (I-type joint) and one-side laser welded without an additional material, at a flat position, using a specially designed system for shielding gas (purity 99.999%). The investigations at the initial stage were focused on detailed analysis of influence of the basic laser welding parameters such as laser power and welding speed on the shape and quality of single bead produced during bead-on-plate welding. Then the optimal parameters were chosen for laser welding of 2.0 mm thick butt joints of the titanium alloy Ti6Al4V. Edges of the titanium alloy sheets were melted in argon atmosphere by the laser beam focused on the top surface of butt joints. The test welded joints were investigated by visual inspection, metallographic examinations, hardness and micro-hardness measurements and mechanical tests such as tensile tests and bending tests. It was found that the welding mode is a keyhole welding and providing high quality of joints requires a special techniques and conditions of laser welding, as well as special gas shielding nozzles is required.

  10. Shape memory alloy thaw sensors

    SciTech Connect

    Shahinpoor, Mohsen; Martinez, David R.

    1998-01-01

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

  11. PLUTONIUM-CERIUM-COPPER ALLOYS

    DOEpatents

    Coffinberry, A.S.

    1959-05-12

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

  12. Palladium alloys for biomedical devices.

    PubMed

    Wataha, John C; Shor, Kavita

    2010-07-01

    In the biomedical field, palladium has primarily been used as a component of alloys for dental prostheses. However, recent research has shown the utility of palladium alloys for devices such as vascular stents that do not distort magnetic resonance images. Dental palladium alloys may contain minor or major percentages of palladium. As a minor constituent, palladium hardens, strengthens and increases the melting range of alloys. Alloys that contain palladium as the major component also contain copper, gallium and sometimes tin to produce strong alloys with high stiffness and relatively low corrosion rates. All current evidence suggests that palladium alloys are safe, despite fears about harmful effects of low-level corrosion products during biomedical use. Recent evidence suggests that palladium poses fewer biological risks than other elements, such as nickel or silver. Hypersensitivity to palladium alone is rare, but accompanies nickel hypersensitivity 90-100% of the time. The unstable price of palladium continues to influence the use of palladium alloys in biomedicine. PMID:20583886

  13. Aluminum and its light alloys

    NASA Technical Reports Server (NTRS)

    Merica, Paul D

    1920-01-01

    Report is a summary of research work which has been done here and abroad on the constitution and mechanical properties of the various alloy systems with aluminum. The mechanical properties and compositions of commercial light alloys for casting, forging, or rolling, obtainable in this country are described.

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

    NASA Astrophysics Data System (ADS)

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

    2009-04-01

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

  15. Role of replacement of Sb with Al in the phase transformation of Ni-Mn-Sb alloys

    NASA Astrophysics Data System (ADS)

    Agarwal, Sandeep; Mukhopadhyay, P. K.

    2013-06-01

    Ferromagnetic shape memory alloy with composition Ni50Mn34Sb8Al8 was prepared and its structural transformation temperatures were determined. The replacement of Sb with Al in this alloy led to increase in transition temperature but more interestingly, the low temperature magnetic behavior shows spin glass type nonergodic behavior, in contrast to simple ferromagnetic like other similar alloys. Resistivity measurements confirmed the structural transformation temperatures.

  16. Irradiation Resistance of Multicomponent Alloys

    NASA Astrophysics Data System (ADS)

    Egami, T.; Guo, W.; Rack, P. D.; Nagase, T.

    2014-01-01

    High-entropy alloys (HEAs) are characterized not only by high values of entropy but also by high atomic-level stresses originating from mixing of elements with different atomic sizes. Particle irradiation on solids produces atomic displacements and thermal spikes. The high atomic-level stresses in HEAs facilitate amorphization upon particle irradiation, followed by local melting and re-crystallization due to thermal spikes. We speculate that this process will leave much less defects in HEAs than in conventional alloys. For this reason, they may be excellent candidates as new nuclear materials. We discuss initial results of computer simulation on model binary alloys and an electron microscopy study on Zr-Hf-Nb alloys, which demonstrate extremely high irradiation resistance of these alloys against electron damage to support this speculation.

  17. Heat storage in alloy transformations

    NASA Technical Reports Server (NTRS)

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

    1981-01-01

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

  18. Equivalent crystal theory of alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John

    1991-01-01

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

  19. Wedlable nickel aluminide alloy

    DOEpatents

    Santella, Michael L. (Knoxville, TN); Sikka, Vinod K. (Oak Ridge, TN)

    2002-11-19

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

  20. ``Ideal'' Engineering Alloys

    NASA Astrophysics Data System (ADS)

    Li, Tianshu; Morris, J. W., Jr.; Nagasako, N.; Kuramoto, S.; Chrzan, D. C.

    2007-03-01

    A newly discovered group of alloys, called Gum Metals, approaches ideal strength in bulk form, exhibits significant plastic deformation prior to failure, and shows no indications of conventional-dislocation activity. Two conditions must be met for a material to exhibit this ideal behavior: (1) the stress required to trigger conventional-dislocation plasticity in the material must exceed its ideal strength, and (2) the material must be intrinsically ductile when stressed to ideal strength. Gum Metals satisfy both criteria, explaining their remarkable mechanical properties.

  1. New magnetic alloys.

    PubMed

    Chin, G Y

    1980-05-23

    Three notable new developments in magnetic alloys are highlighted. These include rare earth-cobalt permanent magnets with maximum energy products up to 240 kilojoules per cubic meter; chromium-cobalt-iron permanent magnets that have magnetic properties similar to those of the Alnicos, but contain only about half as much cobalt and are sufficiently ductile to be cold-formable; and high-induction grain-oriented silicon steels that exhibit 20 percent less core loss as transformer core materials than conventional oriented grades. PMID:17772813

  2. Thermomechanical treatment of alloys

    DOEpatents

    Bates, John F. (Ogden, UT); Brager, Howard R. (Richland, WA); Paxton, Michael M. (Gaithersburg, MD)

    1983-01-01

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

  3. Iron in relaxed Si1-xGex alloy: Band gap related levels, diffusion, and alloying effects

    NASA Astrophysics Data System (ADS)

    Mesli, A.; Vileno, B.; Eckert, C.; Slaoui, A.; Pedersen, C.; Larsen, A. Nylandsted; Abrosimov, N. V.

    2002-07-01

    The microscopic behavior of iron in relaxed Si1-xGex alloy is addressed in the present work where various new aspects are highlighted. In p-type materials two types of defects involving iron may coexist under equilibrium; the isolated form, Fei, and the iron-acceptor pair, Fei-As. The latter complex is favored over the former because it is thermodynamically more stable. In each case the iron atom stabilizes at the interstitial tetrahedral site. When boron is the acceptor impurity, both the isolated and the paired forms introduce donor-like levels, distant from each other by 0.28 eV. In the relaxed Si1-xGex bulk alloy, these levels are shown to remain separated by the same amount. However, they shift toward the valence band much faster than the shrinkage of the band gap when the Ge content is increased. The consequence is that the pair-related donor level merges with the valence band at a fairly low alloy composition (x>=7%) while the iron donor level is predicted to disappear from the gap for x>=25%. We also show that neither the entropy nor the enthalpy of migration of free iron, whose experimental determination requires one to take into account the above-mentioned shift, are affected by alloying. Therefore, the fast diffusing character, attributed to iron in silicon, still holds in the alloy. The origin of spectral broadening, related to the chemical disorder, is discussed. Finally, the major technological implication emerging from our new findings is addressed. In particular, we show that both the gettering by segregation, routinely used in silicon, and the field-induced outdiffusion, established in n-type silicon ten years ago, are totally inefficient in the Si1-xGex alloy.

  4. A theoretical investigation of the band alignment of type-I direct band gap dilute nitride phosphide alloy of GaNxAsyP1-x-y/GaP quantum wells on GaP substrates

    NASA Astrophysics Data System (ADS)

    , L. nsal; B, Gnl; M, Temiz

    2014-07-01

    The GaP-based dilute nitride direct band gap material Ga(NAsP) is gaining importance due to the monolithic integration of laser diodes on Si microprocessors. The major advantage of this newly proposed laser material system is the small lattice mismatch between GaP and Si. However, the large threshold current density of these promising laser diodes on Si substrates shows that the carrier leakage plays an important role in Ga(NAsP)/GaP QW lasers. Therefore, it is necessary to investigate the band alignment in this laser material system. In this paper, we present a theoretical investigation to optimize the band alignment of type-I direct band gap GaNxAsyP1-x-y/GaP QWs on GaP substrates. We examine the effect of nitrogen (N) concentration on the band offset ratios and band offset energies. We also provide a comparison of the band alignment of type-I direct band gap GaNxAsyP1-x-y/GaP QWs with that of the GaNxAsyP1-x-y/AlzGa1-zP QWs on GaP substrates. Our theoretical calculations indicate that the incorporations of N into the well and Al into the barrier improve the band alignment compared to that of the GaAsP/GaP QW laser heterostructures.

  5. Aluminum alloy and associated anode and battery

    SciTech Connect

    Tarcy, G.P.

    1990-08-21

    This patent describes an aluminum alloy. It comprises: eutectic amounts of at least two alloying elements selected from the group consisting of bismuth, cadmium, scandium, gallium, indium, lead, mercury, thallium, tin, and zinc with the balance being aluminum and the alloying elements being about 0.01 to 3.0 percent by weight of the alloy.

  6. Stable palladium alloys for diffusion of hydrogen

    NASA Technical Reports Server (NTRS)

    Patapoff, M.

    1973-01-01

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

  7. Stress Corrosion Cracking of Certain Aluminum Alloys

    NASA Technical Reports Server (NTRS)

    Hasse, K. R.; Dorward, R. C.

    1983-01-01

    SC resistance of new high-strength alloys tested. Research report describes progress in continuing investigation of stress corrosion (SC) cracking of some aluminum alloys. Objective of program is comparing SC behavior of newer high-strength alloys with established SC-resistant alloy.

  8. Interaction Of Hydrogen With Metal Alloys

    NASA Technical Reports Server (NTRS)

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

    1993-01-01

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

  9. B Alloy Melt

    NASA Astrophysics Data System (ADS)

    Liu, Feng; Xu, Junfeng; Zhang, Di; Jian, Zengyun

    2014-10-01

    The solidification of undercooled Ni-4.5 wt pct B alloy melt was investigated by using the glass fluxing technique. The alloy melt was undercooled up to ? T p ~ 245 K (245 C), where a mixture of ?-Ni dendrite, Ni3B dendrite, rod eutectic, and precipitates was obtained. If ? T p < 175 K 10 K (175 C 10 C), the solidification pathway was found as primary transformation and eutectic transformation (L ? Ni3B and L ? Ni/Ni3B); if ? T p ? 175 K 10 K (175 C 10 C), the pathway was found as metastable eutectic transformation, metastable phase decomposition, and residual liquid solidification (L ? Ni/Ni23B6, Ni23B6 ? Ni/Ni3B, and Lr ? Ni/Ni3B). A high-speed video system was adopted to observe the solidification front of each transformation. It showed that for residual liquid solidification, the solidification front velocity is the same magnitude as that for eutectic transformation, but is an order of magnitude larger than for metastable eutectic transformation, which confirms the reaction as Lr ? Ni/Ni3B; it also showed that this velocity decreases with increasing ? T r, which can be explained by reduction of the residual liquid fraction and decrease of Ni23B6 decomposition rate.

  10. The entropy of alloys.

    SciTech Connect

    Stan, M.

    2004-01-01

    A major problem in simulating thermodynamic properties of alloys is modeling the entropy. While configurational entropy is incorporated in most stability calculations, the other components, such as the vibrational and electronic entropy are often neglected or roughly estimated. In this work we propose a method of accounting for both configurational and vibrational entropy and discuss the electronic contribution for several actinide based alloys. The meaning of entropy in non-equilibrium thermodynamic processes is also discussed and illustrated for the case of phase transformations and diffusion. The influence of temperature on the enthalpy and free energy of delta-Pu-Ga phase, as resulted from Modified Embedded Atom Method (MEAM), and the influence of Ga content on the enthalpy and free energy of delta-Pu-Ga phase are discussed. The analysis of the thermodynamic properties of the fcc Pu-Ga phase, as calculated with MEAM shows that the vibrational entropy contribution to the free energy is ve ry important and non-linear with temperature. The free energy also changes with the Ga content.

  11. High performance alloy electroforming

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  12. Stop corrosion of carbon and low-alloy steels

    SciTech Connect

    Kirby, G.N.

    1995-06-01

    Steels corrode in a wide range of environments that induce both overall and localized corrosion. For any type of attack, the behavior of carbon steel may differ significantly from that of low-alloy steels. The paper discusses the different types of corrosion briefly, then discusses the following in more detail: corrosion in aqueous solutions, atmospheric corrosion, localized aqueous corrosion and SCC, pitting corrosion, hydrogen damage, hydrogen blistering, hydrogen embrittlement, decarburization, microbiologically-influenced corrosion, and organic corrosives.

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

    DOEpatents

    Dunning, John S.; Alman, David E.

    2002-11-05

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

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

    DOEpatents

    Dunning, John S. (Corvallis, OR); Alman, David E. (Salem, OR)

    2002-11-05

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

  15. The solidification metallurgy of Alloy 718 and other Nb-containing superalloys

    SciTech Connect

    Cieslak, M.J.; Knorovsky, G.A.; Headley, T.J.; Romig, A.D. Jr.

    1989-01-01

    The solidification behavior of Alloy 718 and other Nb-bearing austenitic superalloys has been examined using an integrated analytical approach. All alloys of this type begin solidification with the formation of Nb-lean austenitic dendrites. Interdendritic eutectic-type solidification constituents involving MC-type carbides and a Nb-rich Laves phase occur in these alloys. The ..gamma../Laves eutectic constituent terminates solidification in these alloys. Nb is the dominant element in the evolution of solidification microstructure with C and Si affecting the amounts of ..gamma../MC and ..gamma../Laves constituent observed. Simple solidification models predict reasonably well the amount of eutectic constituent observed. 11 refs., 9 figs., 2 tabs.

  16. Microstructures and mechanical properties of Ti-Mo alloys cold-rolled and heat treated

    SciTech Connect

    Zhou Yinglong; Luo Dongmei

    2011-10-15

    In this study, the microstructures and mechanical properties of Ti-10Mo and Ti-20Mo alloys (mass%) are investigated to assess the potential use in biomedical applications. The microstructures are examined by X-ray diffraction analysis (XRD) and scanning electron microscopy (SEM). The mechanical properties are determined from uniaxial tensile tests. The experimental results indicate that the microstructures and mechanical properties of Ti-Mo alloys are dependent upon the cold rolling, solution heat treatment, and Mo content. The Ti-10Mo alloy exhibits ({alpha}'' + {beta}) and ({beta} + {omega}) phases under the cold rolling (CR) and solution treatment (ST), respectively. By contrast, the Ti-20Mo alloy comprises only {beta} phase under such conditions. The quenched Ti-20Mo alloy has the lowest elastic modulus and CR Ti-20Mo alloy has the highest tensile strength. The quenched Ti-10Mo alloy exhibits the excellent ductility and two-stage yielding from stress-strain curves due to the stress-induced martensite transformation from {beta} to {alpha}'' during tensile deformation. These Ti-Mo alloys exhibit low yield strength and good ductility, and they are more suitable for biomedical applications than the conventional metallic biomaterials from the viewpoint of better mechanical compatibility. The quenched Ti-10Mo alloy has some advantages over the other {beta} binary Ti-Mo alloys for biomedical applications. {beta} type Ti-Mo-Sn alloys are expected to be promising candidates for novel metallic biomaterials. - Highlights: {yields} The microstructures and mechanical properties of Ti-Mo alloys are dependent upon the cold rolling, solution heat treatment, and Mo content. {yields} The quenched Ti-10Mo alloy exhibits the excellent ductility and two-stage yielding due to stress-induced martensite transformation from beta to alpha double prime during tensile deformation. {yields} The Ti-Mo alloys are more suitable for biomedical applications than the conventional metallic biomaterials from the viewpoint of better mechanical compatibility. {yields} The quenched Ti-10Mo alloy has more advantages over the other beta binary Ti-Mo alloys for biomedical applications.

  17. 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 not related to differences in the environment, differences in surface stress/strain between the various specimen regions (weld, HAZ, wrought), differences in surface residual stress, or differences in the microstructure of the various specimen regions (weld, HAZ, wrought). The behavior may be related to differences in the creep behavior of the various weld regions or differences in the surface area of the various materials (weld, HAZ, wrought) exposed to high temperature water.

  18. Fatigue of die cast zinc alloys

    SciTech Connect

    Schrems, K.K.; Dogan, O.N.; Goodwin, F.E.

    2006-04-01

    The rotating bending fatigue limit of die cast zinc alloy 2, alloy 3, alloy 5, AcuZinc 5, and ZA-8 were determined as a part of an on-going program by ILZRO into the mechanical properties of die cast zinc. The stress-life (S-N) curves of alloys 3, 5, AcuZinc 5, and ZA-8 were determined previously. This presentation reports the results of the S-N curve for Alloy 2 and the calculated fatigue limits for all five alloys. During the previous stress-life testing, the samples were stopped at 10 million cycles and the fatigue limit for alloy 3, alloy 5, and AcuZinc 5 appeared to be higher and the fatigue limit for ZA-8 appeared to be lower than the values reported in the literature. This was further investigated in alloy 5 and ZA-8 by testing continuous cast bulk alloy 5 and ZA-8.

  19. Fracturing behavior of aluminum alloys with welded joints

    NASA Astrophysics Data System (ADS)

    Polyakov, V. V.; Kolubaev, E. A.; Salita, D. S.; Dmitriev, A. A.; Lependin, A. A.

    2015-10-01

    In this paper, properties of aluminum-magnesium alloys with welded joints are investigated. The joints are produced by the friction stir welding under various conditions. This fact is used for studying the principles and patterns of defect structure development. Mechanical properties are evaluated by static tension tests. The impact of welding process conditions on loading curves and strength properties is analysed. Fracture surface structures for samples with and without welded joints are studied, and results are compared. It is revealed, that differences in deformation behavior and mechanical properties of aluminum-magnesium alloys produced under different welding process conditions are caused by developing of structure defects in a welded joints, mostly, nonuniformities/discontinuities of various types. The obtained results can be used for improvement and development of new welding process conditions for aluminum-magnesium alloys.

  20. Interactions of solid ceramic breeding materials with structural alloys

    NASA Astrophysics Data System (ADS)

    Chopra, O. K.; Smith, D. L.

    The reactivity of solid L1 2O, LiA10 2, and Li 2SiO 3w breeding materials with several commercial alloys has been investigated at 873 and 973 K. The results show that Li 2O is the most reactive and LiA10 2 is the least reactive of the three breeding materials. The alloy specimens in contact with LiA10 2 show a weak interaction and the reaction scales essentially consist of chromium and/or iron oxide. The surface scales on Type 316 stainless steel and HT-9 alloy exposed with Li 2O ceramic contain Li 5FeO 4 and LiCrO 2 compounds, whereas Li 2Ni 8O 10 and LiCrO 2 are observed on Inconel 625 specimens. The formation of Li 5FeO 4 compound may explain the greater interaction between the specimens and Li 2O material.

  1. Recrystallization behavior of cold-rolled Zr-1Nb alloy

    NASA Astrophysics Data System (ADS)

    Tian, Hang; Wang, Xitao; Gong, Weijia; Zhou, Jun; Zhang, Hailong

    2015-01-01

    The recrystallization behavior of cold-rolled Zr-1Nb alloy was investigated by measuring the micro-Vickers hardness of the specimens annealed for various times. Different deformation reductions and annealing temperatures were coupled to study the effects of deformation and temperature on the recrystallization behavior of Zr-1Nb alloy. The results show that both large deformation reduction and high annealing temperature accelerate the recrystallization process. The microstructural evolution during recrystallization was characterized by optical microscope (OM) and transmission electron microscope (TEM) to correlate with the variation of Vickers hardness. The TEM observation also revealed the distribution of different types of Nb-containing precipitates during recrystallization. The Vickers hardness data were fitted by using the Johnson-Mehl-Avrami-Kolmogorov (JMAK) equation to derive the activation energies for recrystallization, giving the corresponding recrystallization maps. This study provides useful guidelines for the processing of a broad family of zirconium alloys based on Zr-1Nb.

  2. Heat treatment in high Cr white cast iron Nb alloy

    NASA Astrophysics Data System (ADS)

    Farah, A. F.; Crnkovic, O. R.; Canale, L. C. F.

    2001-02-01

    Wear resistance of high Cr white cast irons can be improved by means of heat treatment. This type of cast iron alloy may present a microstructure with retained austenite. The amount of retained austenite changes with the applied heat treatment, which will have an influence on wear properties. The purpose of this work was to study the influence of several parameters such as quenching and tempering temperatures and subzero treatment in the wear performance of the high Cr white cast iron Nb alloy. In this way, the performance was evaluated using pin-on-disc abrasion test. The worn surface was examined by scanning electron microscopy, and the main wear mechanisms were identified. The microstructural characterization was also performed with carbide identification. This Fe alloy has proven to be good for applications in mining and alcohol-sugar industries.

  3. Heat storage in alloy transformations

    NASA Technical Reports Server (NTRS)

    Birchenall, C. E.

    1980-01-01

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

  4. Microstructural characterization of as-cast biocompatible Co-Cr-Mo alloys

    SciTech Connect

    Giacchi, J.V.; Morando, C.N.; Fornaro, O.; Palacio, H.A.

    2011-01-15

    The microstructure of a cobalt-base alloy (Co-Cr-Mo) obtained by the investment casting process was studied. This alloy complies with the ASTM F75 standard and is widely used in the manufacturing of orthopedic implants because of its high strength, good corrosion resistance and excellent biocompatibility properties. This work focuses on the resulting microstructures arising from samples poured under industrial environment conditions, of three different Co-Cr-Mo alloys. For this purpose, we used: 1) an alloy built up from commercial purity constituents, 2) a remelted alloy and 3) a certified alloy for comparison. The characterization of the samples was achieved by using optical microscopy (OM) with a colorant etchant to identify the present phases and scanning electron microscopy (SE-SEM) and energy dispersion spectrometry (EDS) techniques for a better identification. In general the as-cast microstructure is a Co-fcc dendritic matrix with the presence of a secondary phase, such as the M{sub 23}C{sub 6} carbides precipitated at grain boundaries and interdendritic zones. These precipitates are the main strengthening mechanism in this type of alloys. Other minority phases were also reported and their presence could be linked to the cooling rate and the manufacturing process variables and environment. - Research Highlights: {yields}The solidification microstructure of an ASTM-F75 type alloy were studied. {yields}The alloys were poured under an industrial environment. {yields}Carbides and sigma phase identified by color metallography and scanning microscopy (SEM and EDS). {yields}Two carbide morphologies were detected 'blocky type' and 'pearlite type'. {yields}Minority phases were also detected.

  5. Silicon Solar Cells with Front Hetero-Contact and Aluminum Alloy Back Junction: Preprint

    SciTech Connect

    Yuan, H.-C.; Page, M. R.; Iwaniczko, E.; Xu, Y.; Roybal, L.; Wang, Q.; Branz, H. M.; Meier, D. L.

    2008-05-01

    We prototype an alternative n-type monocrystalline silicon (c-Si) solar cell structure that utilizes an n/i-type hydrogenated amorphous silicon (a-Si:H) front hetero-contact and a back p-n junction formed by alloying aluminum (Al) with the n-type Si wafer.

  6. Industrial Experience on the Caustic Cracking of Stainless Steels and Nickel Alloys - A Review

    SciTech Connect

    Rebak, R B

    2005-10-09

    Caustic environments are present in several industries, from nuclear power generation to the fabrication of alkalis and alumina. The most common material of construction is carbon steel but its application is limited to a maximum temperature of approximately 80 C. The use of Nickel (Ni) alloys is recommended at higher temperatures. Commercially pure Ni is the most resistant material for caustic applications both from the general corrosion and the stress corrosion cracking (SCC) perspectives. Nickel rich alloys also offer a good performance. The most important alloying elements are Ni and chromium (Cr). Molybdenum (Mo) is not a beneficial alloying element and it dissolves preferentially from the alloy in presence of caustic environments. Austenitic stainless steels such as type 304 and 316 seem less resistant to caustic conditions than even plain carbon steel. Experimental evidence shows that the most likely mechanism for SCC is anodic dissolution.

  7. 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.

  8. Cryogenic mechanical behavior of 5000- and 6000-series aluminum alloys: Issues on application to offshore plants

    NASA Astrophysics Data System (ADS)

    Park, Doo-Hwan; Choi, Sung-Woong; Kim, Jeong-Hyeon; Lee, Jae-Myung

    2015-06-01

    The mechanical behavior of aluminum alloys was investigated in terms of four aspects: temperature, strain rate, material type, and fracture shape. The candidate materials were 5000- and 6000-series alloys. The material characteristics were investigated and summarized as a function of low temperature (110-293 K) and quasi-static strain rate (10-4 and 10-2 s-1). The results confirmed that the strength and ductility of aluminum alloys improved with a decrease in the temperature. The aluminum alloys showed a strain rate effect only in terms of the ductility of the 5000-series alloys. In addition, fractography analyses were performed on the fracture specimens to explain the material behavior at cryogenic temperatures.

  9. Superior magnetic softness at elevated temperature of Si-rich Fe-based nanocrystalline alloy

    NASA Astrophysics Data System (ADS)

    Shi, Rui-min; Wang, Zhi; Jia, Yun-yun; Wen, Zhuan-ping; Wang, Bo-wen; Zhang, Tao

    2012-10-01

    An excellent high-temperature magnetic softness was observed in a Si-rich nanocrystalline Fe74.5Cu1Nb2Si17.5B5 alloy. The Curie temperatures of amorphous and crystal phases, TCA* and TCcry, for this alloy were detected to be 365 C and 580 C, respectively. For the 480 C-annealed alloy, the initial permeability ?i drops to nearly zero just above TCA*; however, for the 540 C-annealed alloy, the ?i of about 10 000 at f = 10 kHz has no perceivable decline in this temperature range and can hold up to more than 400 C. Such a magnetic softness at elevated temperature is superior to that of Finemet-type Fe-based nanocrystalline alloys ever reported. The origin of the high temperature magnetic softness was interpreted by the enhancement effect of Curie temperature in residual amorphous matrix.

  10. Functionally Graded Al Alloy Matrix In-Situ Composites

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Subramaniya Sarma, V.; Murty, B. S.

    2010-01-01

    In the present work, functionally graded (FG) aluminum alloy matrix in-situ composites (FG-AMCs) with TiB2 and TiC reinforcements were synthesized using the horizontal centrifugal casting process. A commercial Al-Si alloy (A356) and an Al-Cu alloy were used as matrices in the present study. The material parameters (such as matrix and reinforcement type) and process parameters (such as mold temperature, mold speed, and melt stirring) were found to influence the gradient in the FG-AMCs. Detailed microstructural analysis of the composites in different processing conditions revealed that the gradients in the reinforcement modify the microstructure and hardness of the Al alloy. The segregated in-situ formed TiB2 and TiC particles change the morphology of Si particles during the solidification of Al-Si alloy. A maximum of 20 vol pct of reinforcement at the surface was achieved by this process in the Al-4Cu-TiB2 system. The stirring of the melt before pouring causes the reinforcement particles to segregate at the periphery of the casting, while in the absence of such stirring, the particles are segregated at the interior of the casting.

  11. Hydrogen permeation characteristics of some Fe-Cr-Al alloys

    NASA Astrophysics Data System (ADS)

    Van Deventer, E. H.; Maroni, V. A.

    1983-01-01

    Hydrogen permeation data are reported for two Fe-Cr-Al alloys, Type-405 SS (Cr 14-A1 0.2) and a member of the Fecralloy family of alloys (Cr 16-A1 5). The hydrogen permeability of each alloy (in a partially oxidized condition) was measured over a period of several weeks at randomly selected temperatures (between 150 and 850°C) and upstream H 2 pressures (between 2 and 1.5 × 10 4 Pa). The permeabilities showed considerable scatter with both time and temperature and were 10 2 to 10 3 times lower than those of pure iron, even in strongly reducing environments. The exponent, n, for the relationship between upstream H 2 pressure, P, and permeability, φ, ( φ ~ Pn) was closer to 0.7 than to the expected 0.5, indicating a process limited by surface effects (e.g., surface oxide films) as opposed to bulk material effects. Comparison of these results with prior permeation measurements on other Fe-Cr-Al alloys, on Fe-Cr alloys, and on pure iron shows that the presence of a few weight percent aluminum offers the best prospects for achieving low tritium permeabilities with martensitic and ferritic steels used in fusion-reactor first wall and blanket applications.

  12. Modelling the phase diagram of magnetic shape memory Heusler alloys

    NASA Astrophysics Data System (ADS)

    Entel, P.; Buchelnikov, V. D.; Khovailo, V. V.; Zayak, A. T.; Adeagbo, W. A.; Gruner, M. E.; Herper, H. C.; Wassermann, E. F.

    2006-03-01

    We have modelled the phase diagram of magnetic shape memory alloys of the Heusler type by using the phenomenological Ginzburg-Landau theory. When fixing the parameters by realistic values taken from experiment we are able to reproduce most details of, for example, the phase diagram of Ni2+xMn1-xGa in the (T, x) plane. We present the results of ab initio calculations of the electronic and phonon properties of several ferromagnetic Heusler alloys, which allow one to characterize the structural changes associated with the martensitic instability leading to the modulated and tetragonal phases. From the ab initio investigations emerges a complex pattern of the interplay of magic valence electron per atom numbers (Hume-Rothery rules for magnetic ternary alloys), Fermi surface nesting and phonon instability. As the main result, we find that the driving force for structural transformations is considerably enhanced by the extremely low lying optical modes of Ni in the Ni-based Heusler alloys, which interfere with the acoustical modes enhancing phonon softening of the TA2 mode. In contrast, the ferromagnetic Co-based Heusler alloys show no tendency for phonon softening.

  13. 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.

  14. Preparation of particle-dispersion alloys (M-6)

    NASA Technical Reports Server (NTRS)

    Muramatsu, Yuji

    1993-01-01

    A particle dispersion alloy is one type of metal-ceramic composite material, and is used as heat resistance material, wear resistance material, and electrical material. This material consists of a metal matrix and dispersed particles, and for its unique structure it has both tenacity as a metal and hardness as a ceramic. Its properties improve when the particles become finer and disperse more uniformly. Most of the particle dispersion alloys are produced by the powder metallurgical process. This process is favorable for uniform dispersion of particles, but it consists of complicated techniques such as mechanical alloying and hot extrusion, and has the following drawbacks: (1) it is difficult to fabricate large-sized products; (2) the amount of particles is limited to a few percent; and (3) the process is complicated and expensive. To overcome these drawbacks, recently special attention has been paid to conventional melting process. However, under terrestrial conditions, dispersions separate immediately due to the different specific gravities of the metal matrix and the particles and thermal convection effects. The microgravity environment is, therefore, considered to be an attractive place for fabricating the dispersion alloy. This space experiment is carried out to clarify the influence of microgravity on the properties of the particle dispersion alloy and to obtain a deeper understanding of the experiment under the microgravity environment.

  15. Modeling dissolution in aluminum alloys

    NASA Astrophysics Data System (ADS)

    Durbin, Tracie Lee

    2005-07-01

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

  16. Dissimilar friction welding of titanium alloys to alloy 718

    SciTech Connect

    Kuo, M.; Albright, C.E.; Baeslack, W.A. III

    1994-12-31

    The design of advanced, high-performance gas-turbine engines will require the utilization of elevated-temperature titanium-based materials, including conventional alloys, titanium aluminides, and titanium metal-matrix composites. The most efficient utilization of these materials in the engine compressor section would be achieved by directly joining these materials to existing nickel-base superalloys, such as Alloy 718. To date, the dissimilar welding of titanium alloys to nickel-based alloys has not been common practice because intermetallic compounds form in the weld and cause embrittlement. Special welding techniques must be developed to inhibit this compound formation and to provide high strength welds. In this investigation, a friction welding process was developed for joining titanium alloys (Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V) to nickel-based superalloy Alloy 718. An interlayer system comprised of copper and niobium sheet layers was employed as a diffusion barrier and weld deformation enhancer. A postweld heat treatment (PWHT, 700{degrees}C for 20 min in vacuum) under axial pressure (Ksi) was used to improve the joint strength consistency. The following conclusions can be drawn from this investigation: (1) A friction welding technique has been developed for joining titanium alloys (Ti-6Al-2Sn-4Zr-2Mo and Ti-6Al-4V) to Alloy 718 using an interlayer system of niobium and copper. Joint strengths averaging approximately 50 Ksi were achieved. (2) Deformation was concentrated in the interlayers, especially the copper interlayer, during friction welding. Increased reduction in length (RIL) during friction welding resulted in a decrease in the interlayer thicknesses. (3) The EDS results showed that the niobium and copper interlayers prevent interdiffusion between the two parent metals, producing formation of detrimental phases.

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

    PubMed

    Snchez-De Jess, F; Bolarn-Mir, A M; Torres-Villaseor, G; Corts-Escobedo, C A; Betancourt-Cantera, J A

    2010-07-01

    We report on an alternative route for the synthesis of crystalline Co-28Cr-6Mo alloy, which could be used for surgical implants. Co, Cr and Mo elemental powders, mixed in an adequate weight relation according to ISO Standard 58342-4 (ISO, 1996), were used for the mechanical alloying (MA) of nano-structured Co-alloy. The process was carried out at room temperature in a shaker mixer mill using hardened steel balls and vials as milling media, with a 1:8 ball:powder weight ratio. Crystalline structure characterization of milled powders was carried out by X-ray diffraction in order to analyze the phase transformations as a function of milling time. The aim of this work was to evaluate the alloying mechanism involved in the mechanical alloying of Co-28Cr-6Mo alloy. The evolution of the phase transformations with milling time is reported for each mixture. Results showed that the resultant alloy is a Co-alpha solid solution, successfully obtained by mechanical alloying after a total of 10 h of milling time: first Cr and Mo are mechanically prealloyed for 7 h, and then Co is mixed in for 3 h. In addition, different methods of premixing were studied. The particle size of the powders is reduced with increasing milling time, reaching about 5 mum at 10 h; a longer time promotes the formation of aggregates. The morphology and crystal structure of milled powders as a function of milling time were analyzed by scanning electron microscopy and XR diffraction. PMID:20364362

  18. 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.

  19. Rank correlation of laser-induced breakdown spectroscopic data for the identification of alloys used in jewelry manufacture

    NASA Astrophysics Data System (ADS)

    Jurado-Lpez, A.; Luque de Castro, M. D.

    2003-07-01

    The aim of the present study was the rapid identification of alloys used in the manufacture of jewelry pieces with the help of a spectral library. The laser-induced breakdown spectra of 32 alloys were stored, with 25 of them chosen as library standards; the remaining seven spectra were used as samples. The composition of the alloys was obtained by flame atomic absorption spectrometry. A rank correlation method was applied for comparison between spectra, providing good correlation coefficients for the alloys studied. The composition of the samples was also predicted by partial least-squares regression to demonstrate the capability of this technique for the rapid analysis of this type of material.

  20. Improved activation cross sections for vanadium and titanium

    SciTech Connect

    Muir, D.W.; Arthur, E.D.

    1983-01-01

    Vanadium alloys such as V-20Ti and V-Cr-Ti are attractive candidates for use as structural materials in fusion-reactor blankets. The virtual absence of long-lived activation products in these alloys suggest the possibility of reprocessing on an intermediate time scale. We have employed the modern Hauser-Feshbach nuclear-model code GNASH to calculate cross sections for neutron-activation reactions in /sup 50/V and /sup 51/V, to allow a more accurate assessment of induced radioactivity in vanadium alloys. In addition, cross sections are calculated for the reactions /sup 46/Ti(n,2n) and /sup 45/Ti(n,2n) in order to estimate the production of /sup 44/Ti, a 1.2-MeV gamma-ray source with a half-life of 47 years.

  1. Development of lead-free copper alloy graphite castings. Annual report, January--December 1995

    SciTech Connect

    Rohatgi, P.K.

    1996-10-01

    The distribution of graphite particles in graphite containing copper alloy was further improved very significantly using several procedures and technological modifications. The developed techniques attacked the graphite distribution problem in two ways. Realizing that clustering of very fine (5um) graphite particles is one of the two major problems, a pretreatment process has been developed using aluminum powders to deagglomerate graphite particles. Along with this, a two-stage stirring technique was used to first incorporate and then to distribute uniformly the deagglomerated particles in the melt. During this year, based on these developments, several components were cast to evaluate the castability of Cu alloy-graphite melts. In addition, machinability tests were done to clearly established that addition of graphite particles improve the machinability of copper MMC alloys over and above that of monolithic copper alloys. The results show that the machining chip sizes and cutting forces of Cu alloys containing graphite particles are smaller than these of the corresponding monolithic Cu alloys. This clearly establishes that the presence of graphite particles in copper alloy improves the machinability in a fashion similar to lead additions to copper alloys. Centrifugal casting of shapes of different sizes appear to be a very attractive method for casting graphite containing copper alloys, since all the graphite particles (regardless of their distribution in the melt) are forced to segregate to the inner periphery of the castings where they impart a very desirable solid lubrication property for bushing and bearing use. A very large number of cylindrical elements of lead bearing copper alloys are now used for similar bearing bushing applications and the manufacturers of these type of bearings are under safety and health hazard pressure to remove lead. This year several parameters for centrifugal casting of copper graphite alloys have been established.

  2. Alloyed steel wastes utilization

    SciTech Connect

    Sokol, I.V.

    1995-12-31

    Alloyed steel chips and swarf formed during metal processing are looked upon as additional raw materials in metallurgical production. This paper presents some new methods for steel waste chips and swarf cleaning. One of them is swarf and steel chips cleaning in tetrachloroethylene with ultrasonic assistance and solvent regeneration. Thermal cleaning of waste chips and swarf provides off gas products utilization. The catalyst influence of the metal surface on the thermal decomposition of liquid hydrocarbons during the cleaning process has been studied. It has been determined that the efficiency of this metal waste cleaning technique depends on the storage time of the swarf. The waste chips and swarf cleaning procedures have been proven to be economically advantageous and environmentally appropriate.

  3. Metallic alloy stability studies

    NASA Technical Reports Server (NTRS)

    Firth, G. C.

    1983-01-01

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

  4. Synthesis of WS2xSe2-2x Alloy Nanosheets with Composition-Tunable Electronic Properties.

    PubMed

    Duan, Xidong; Wang, Chen; Fan, Zheng; Hao, Guolin; Kou, Liangzhi; Halim, Udayabagya; Li, Honglai; Wu, Xueping; Wang, Yicheng; Jiang, Jianhui; Pan, Anlian; Huang, Yu; Yu, Ruqin; Duan, Xiangfeng

    2016-01-13

    Two-dimensional (2D) layered transition metal dichalcogenides (TMDs) have recently emerged as a new class of atomically thin semiconductors for diverse electronic, optoelectronic, and valleytronic applications. To explore the full potential of these 2D semiconductors requires a precise control of their band gap and electronic properties, which represents a significant challenge in 2D material systems. Here we demonstrate a systematic control of the electronic properties of 2D-TMDs by creating mixed alloys of the intrinsically p-type WSe2 and intrinsically n-type WS2 with variable alloy compositions. We show that a series of WS2xSe2-2x alloy nanosheets can be synthesized with fully tunable chemical compositions and optical properties. Electrical transport studies using back-gated field effect transistors demonstrate that charge carrier types and threshold voltages of the alloy nanosheet transistors can be systematically tuned by adjusting the alloy composition. A highly p-type behavior is observed in selenium-rich alloy, which gradually shifts to lightly p-type, and then switches to lightly n-type characteristics with the increasing sulfur atomic ratio, and eventually evolves into highly n-doped semiconductors in sulfur-rich alloys. The synthesis of WS2xSe2-2x nanosheets with tunable optical and electronic properties represents a critical step toward rational design of 2D electronics with tailored spectral responses and device characteristics. PMID:26633760

  5. Smart interfacial bonding alloys

    SciTech Connect

    R. Q. Hwang; J. C. Hamilton; J. E. Houston

    1999-04-01

    The goal of this LDRD was to explore the use of the newly discovered strain-stabilized 2-D interfacial alloys as smart interface bonding alloys (SIBA). These materials will be used as templates for the heteroepitaxial growth of metallic thin films. SIBA are formed by two metallic components which mix at an interface to relieve strain and prevent dislocations from forming in subsequent thin film growth. The composition of the SIBA is determined locally by the amount of strain, and therefore can react smartly to areas of the highest strain to relieve dislocations. In this way, SIBA can be used to tailor the dislocation structure of thin films. This project included growth, characterization and modeling of films grown using SIBA templates. Characterization will include atomic imaging of the dislocations structure, measurement of the mechanical properties of the film using interface force microscopy (IFM) and the nanoindenter, and measurement of the electronic structure of the SIBA with synchrotron photoemission. Resistance of films to sulfidation and oxidation will also be examined. The Paragon parallel processing computer will be used to calculate the structure of the SIBA and thin films in order to develop ability to predict and tailor SIBA and thin film behavior. This work will lead to the possible development of a new class of thin film materials with properties tailored by varying the composition of the SIBA, serving as a buffer layer to relieve the strain between the substrate and the thin film. Such films will have improved mechanical and corrosion resistance allowing application as protective barriers for weapons applications. They will also exhibit enhanced electrical conductivity and reduced electromigration making them particularly suitable for application as interconnects and other electronic needs.

  6. The effect of copper, chromium, and zirconium on the microstructure and mechanical properties of Al-Zn-Mg-Cu alloys

    NASA Technical Reports Server (NTRS)

    Wagner, John A.; Shenoy, R. N.

    1991-01-01

    The present study evaluates the effect of the systematic variation of copper, chromium, and zirconium contents on the microstructure and mechanical properties of a 7000-type aluminum alloy. Fracture toughness and tensile properties are evaluated for each alloy in both the peak aging, T8, and the overaging, T73, conditions. Results show that dimpled rupture essentially characterize the fracture process in these alloys. In the T8 condition, a significant loss of toughness is observed for alloys containing 2.5 pct Cu due to the increase in the quantity of Al-Cu-Mg-rich S-phase particles. An examination of T8 alloys at constant Cu levels shows that Zr-bearing alloys exhibit higher strength and toughness than the Cr-bearing alloys. In the T73 condition, Cr-bearing alloys are inherently tougher than Zr-bearing alloys. A void nucleation and growth mechanism accounts for the loss of toughness in these alloys with increasing copper content.

  7. Ignition of metals and alloys by high-velocity particles

    NASA Technical Reports Server (NTRS)

    Benz, F. J.; Williams, R. E.; Armstrong, D.

    1986-01-01

    The ignition of metals and alloys by impacting high-velocity particles in gaseous oxygen was investigated. A convergent/divergent nozzle was used to accelerate the flowing oxygen, which in turn accelerated the particles to velocities greater than 305 m/s (1000 ft/s). The test sample (target) was placed at the end of the chamber in the flow path. Aluminum 6061, type 316 stainless steel, type 304 stainless steel, and Inconel 718 were ignited with 1600-micron aluminum 2017 particles at elevated temperatures and pressures whereas Monel 400 could not be ignited. The ignition susceptibility of metals and alloys appeared to increase as the inlet pressure, sample temperature, and particle size were increased. Type 304 stainless steel particles required more extreme conditions for ignition of materials than similar sized aluminum particles. The results indicated that ignition and subsequent burning of the particles were required for ignition of the target materials with the possible exception of aluminum 6061.

  8. Microstructural characterization of low and high carbon CoCrMo alloy nanoparticles produced by mechanical milling

    NASA Astrophysics Data System (ADS)

    Simoes, T. A.; Goode, A. E.; Porter, A. E.; Ryan, M. P.; Milne, S. J.; Brown, A. P.; Brydson, R. M. D.

    2014-06-01

    CoCrMo alloys are utilised as the main material in hip prostheses. The link between this type of hip prosthesis and chronic pain remains unclear. Studies suggest that wear debris generated in-vivo may be related to post-operative complications such as inflammation. These alloys can contain different amounts of carbon, which improves the mechanical properties of the alloy. However, the formation of carbides could become sites that initiate corrosion, releasing ions and/or particles into the human body. This study analysed the mechanical milling of alloys containing both high and low carbon levels in relevant biological media, as an alternative route to generate wear debris. The results show that low carbon alloys produce significantly more nanoparticles than high carbon alloys. During the milling process, strain induces an fcc to hcp phase transformation. Evidence for cobalt and molybdenum dissolution in the presence of serum was confirmed by ICP-MS and TEM EDX techniques.

  9. Novel Ti-base superelastic alloys with large recovery strain and excellent biocompatibility.

    PubMed

    Fu, Jie; Yamamoto, Akiko; Kim, Hee Young; Hosoda, Hideki; Miyazaki, Shuichi

    2015-04-01

    In this study, a new Ti-Zr-Nb-Sn alloy system was developed as Ni-free biomedical superelastic alloys with a large recovery strain and excellent biocompatibility. Ti-18Zr-(9-16)Nb-(0-4)Sn alloys were prepared by an Ar arc melting method and the effect of composition on the crystal structure and superelastic properties was investigated. A large superelastic recovery strain of 6.0% was observed in Ti-18Zr-12.5Nb-2Sn, Ti-18Zr-11Nb-3Sn, and Ti-18Zr-9.5Nb-4Sn alloys subjected to cold-rolling and solution treatment. XRD results showed that the large recovery strain of Sn-added alloys is due to a combination effect of a large transformation strain and a strong recrystallization texture. The Ti-18Zr-11Nb-3Sn alloy exhibited excellent cyclic stability with an extremely narrow stress hysteresis about 20MPa. Cytocompatibility was also examined using three types of cell lines, murine fibroblast L929, human osteosarcoma SaOS-2, and human umbilical vein endothelial cell HUVEC and the results showed that the Ti-18Zr-11Nb-3Sn alloy exhibited larger cell covering ratios when compared with those of the Ti-50.5Ni alloy for all kinds of cells. PMID:25676584

  10. Mechanical Properties of Friction Stir Welded Aluminum Alloys 5083 and 5383

    NASA Astrophysics Data System (ADS)

    Paik, Jeoom Kee

    2009-09-01

    The use of high-strength aluminum alloys is increasing in shipbuilding industry, particularly for the design and construction of war ships, littoral surface craft and combat ships, and fast passenger ships. While various welding methods are used today to fabricate aluminum ship structures, namely gas metallic arc welding (GMAW), laser welding and friction stir welding (FSW), FSW technology has been recognized to have many advantages for the construction of aluminum structures, as it is a low-cost welding process. In the present study, mechanical properties of friction stir welded aluminum alloys are examined experimentally. Tensile testing is undertaken on dog-bone type test specimen for aluminum alloys 5083 and 5383. The test specimen includes friction stir welded material between identical alloys and also dissimilar alloys, as well as unwelded (base) alloys. Mechanical properties of fusion welded aluminum alloys are also tested and compared with those of friction stir welded alloys. The insights developed from the present study are documented together with details of the test database. Part of the present study was obtained from the Ship Structure Committee project SR-1454 (Paik, 2009), jointly funded by its member agencies

  11. Dynamic compressive behavior of Pr-Nd alloy at high strain rates and temperatures

    SciTech Connect

    Wang Huanran; Cai Canyuan; Chen Danian; Ma Dongfang

    2012-07-01

    Based on compressive tests, static on 810 material test system and dynamic on the first compressive loading in split Hopkinson pressure bar (SHPB) tests for Pr-Nd alloy cylinder specimens at high strain rates and temperatures, this study determined a J-C type [G. R. Johnson and W. H. Cook, in Proceedings of Seventh International Symposium on Ballistics (The Hague, The Netherlands, 1983), pp. 541-547] compressive constitutive equation of Pr-Nd alloy. It was recorded by a high speed camera that the Pr-Nd alloy cylinder specimens fractured during the first compressive loading in SHPB tests at high strain rates and temperatures. From high speed camera images, the critical strains of the dynamic shearing instability for Pr-Nd alloy in SHPB tests were determined, which were consistent with that estimated by using Batra and Wei's dynamic shearing instability criterion [R. C. Batra and Z. G. Wei, Int. J. Impact Eng. 34, 448 (2007)] and the determined compressive constitutive equation of Pr-Nd alloy. The transmitted and reflected pulses of SHPB tests for Pr-Nd alloy cylinder specimens computed with the determined compressive constitutive equation of Pr-Nd alloy and Batra and Wei's dynamic shearing instability criterion could be consistent with the experimental data. The fractured Pr-Nd alloy cylinder specimens of compressive tests were investigated by using 3D supper depth digital microscope and scanning electron microscope.

  12. Fatigue behavior of copper and selected copper alloys for high heat flux applications

    NASA Astrophysics Data System (ADS)

    Leedy, K. D.; Stubbins, J. F.; Singh, B. N.; Garner, F. A.

    1996-10-01

    The room temperature fatigue behavior of standard and subsize specimens was examined for five copper alloys: OFHC Cu, two CuNiBe alloys, a CuCrZr alloy, and a Cu?Al 2O 3 alloy. Fatigue tests were run in strain control to failure. In addition to establishing failure lives, the stress amplitudes were monitored as a function of numbers of accrued cycles. The results indicate that the alloys with high initial yield strengths provide the best fatigue response over the range of failure lives examined in the present study: Nf = 10 3 to 10 6. In fact, the fatigue performance of the best alloys is dominated by the elastic portion of the strain range, as would be expected from the correlation of performance with yield properties. The alumina strengthened alloy and the two CuNiBe alloys show the best overall performance of the group examined here. The fatigue response was found to be closely related to the uniformity of the material microstructure and particularly the distribution of the finely dispersed strengthening phases. The pre- and post-fatigue microstructures were examined to identify the types and distribution of secondary phases, and their role in fatigue response.

  13. Mechanical and Wear Properties of Sb- and Y-Added Mg-9Al-1Zn (AZ91) Alloy

    NASA Astrophysics Data System (ADS)

    Boby, Arun; Srinivasan, A.; Pillai, U. T. S.; Pai, B. C.

    2015-09-01

    This paper studies the effect of Sb and Y additions on the microstructure and mechanical properties of the AZ91 alloy. The results indicate that the Sb and Y additions lead to the formation of Mg3Sb2 and Al2Y phases. These phases modify the morphology of the ?-Mg17Al12 phase, and hence refine the microstructure. The effects of Sb and Y additions on the aging behavior have also been investigated. Aging of the AZ91 alloy results in the formation of continuous and discontinuous types of precipitates. Whereas Sb and Y additions to AZ91 alloy suppresses the formation of discontinuous precipitate. The paper also reports the mechanical properties of as-cast and aged Sb-added AZ91-xY alloys for room and high temperatures. The optimum tensile properties are obtained with the alloy having the combined addition of 0.5 wt pct Sb and 0.6 wt pct Y. The fracture surface of AZ91-0.5Sb-0.6Y alloy reveals more quasi-cleavage type of failure with a cleavage fracture than the base alloy. At HT, the AZ91-0.5Sb-0.6Y alloy displays more cleavage facets connected with tearing ridges and shallow dimples than AZ91 alloy. Furthermore, it observed the improvement in wear resistance through the addition of Y. The worn surface reveals abrasion, oxidation, delamination, and plastic deformation wear mechanisms.

  14. Manufacturing of High Entropy Alloys

    NASA Astrophysics Data System (ADS)

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

    2015-07-01

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

  15. Magnesium Alloys and their Applications

    NASA Astrophysics Data System (ADS)

    Kainer, Karl U.

    1999-04-01

    In the recent years there has been a dramatic increase in research activity and also applications of magnesium alloys. The driving force is the growing demand by the automobile industry resulting from the pressure to reduce weight and hence to reduce the fuel consumption. The U.S. car industry incorporates the largest amount of magnesium at the present time. In Europe, Volkswagen had a history of using magnesium in the VW Beetle. Volkswagen, in common with other major car producers has initiated a major research and development programme for advanced magnesium materials. The main emphasis of this book is in the field of general physical metallurgy and alloy development refelcting the need to provide a wider range of alloys both casting and wrought alloys to meet the increasing demands of industry. Other topics are nevertheless well represented such as casting, recycling, joining, corrosion, and surface treatment.

  16. Microbiological influence and electrochemical types of corrosion: Back to basics

    SciTech Connect

    Stoecker, J.G. II

    1994-12-31

    The topographic characteristics of electrochemically corroded metals and alloys are classified with respect to the various types of corrosion. Case histories are used to demonstrate that chemical environments can produce the same topographic characteristics as microbes with or without microbiological involvement. The cause(s) of this electrochemical and/or microbiological corrosion is examined from a thermodynamic energy exchange point of view. The types of corrosion reviewed are: general attack, intergranular, de-alloying, localized, galvanic, and cracking phenomena.

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

    NASA Astrophysics Data System (ADS)

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

    2011-11-01

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

  18. Superplastic forming of alloy 718

    SciTech Connect

    Smith, G.D.; Flower, H.L. )

    1994-04-01

    Inconel Alloy 718 (UNS N07718) is now available in a fine-grained, controlled composition modification that can be super-plastically formed. The new superplastic forming (SPF) capability allows the manufacture of large, complex, and detailed parts, which improves integrity by reducing the need for joining. Furthermore, it allows designers to fabricate components having higher strength, fatigue resistance, and temperature capability than parts made of aluminum or titanium alloys.

  19. Shape memory alloy thaw sensors

    DOEpatents

    Shahinpoor, M.; Martinez, D.R.

    1998-04-07

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

  20. Reducing Staphylococcus aureus growth on Ti alloy nanostructured surfaces through the addition of Sn.

    PubMed

    Verissimo, Nathlia C; Geilich, Benjamin M; Oliveira, Haroldo G; Caram, Rubens; Webster, Thomas J

    2015-12-01

    ?-type Ti alloys containing Nb are exciting materials for numerous orthopedic and dental applications due to their exceptional mechanical properties. To improve their cytocompatibility properties (such as increasing bone growth and decreasing infection), the surfaces of such materials can be optimized by adding elements and/or nanotexturing through anodization. Because of the increasing prevalence of orthopedic implant infections, the objective of this in vitro study was to add Sn and create unique nanoscale surface features on ?-type Ti alloys. Nanotubes and nanofeatures on Ti-35Nb and Ti-35Nb-4Sn alloys were created by anodization in a HF-based electrolyte and then heat treated in a furnace to promote amorphous structures and phases such as anatase, a mixture of anatase-rutile, and rutile. Samples were characterized by SEM, which indicated different morphologies dependent on the oxide content and method of modification. XPS experiments identified the oxide content which resulted in a phase transformation in the oxide layer formed onto Ti-35Nb and Ti-35Nb-4Sn alloys. Most importantly, regardless of the resulting nanostructures (nanotubes or nanofeatures) and crystalline phase, this study showed for the first time that adding Sn to ?-type Ti alloys strongly decreased the adhesion of Staphylococcus aureus (S. aureus; a bacteria which commonly infects orthopedic implants leading to their failure). Thus, this study demonstrated that ?-type Ti alloys with Nb and Sn have great promise to improve numerous orthopedic applications where infection may be a concern. PMID:26033413

  1. Casting Characteristics of Aluminum Die Casting Alloys

    SciTech Connect

    Makhlouf M. Makhlouf; Diran Apelian

    2002-02-05

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

  2. Corrosion Behavior of Alloys in Molten Fluoride Salts

    NASA Astrophysics Data System (ADS)

    Zheng, Guiqiu

    The molten fluoride salt-cooled high-temperature nuclear reactor (FHR) has been proposed as a candidate Generation IV nuclear reactor. This reactor combines the latest nuclear technology with the use of molten fluoride salt as coolant to significantly enhance safety and efficiency. However, an important challenge in FHR development is the corrosion of structural materials in high-temperature molten fluoride salt. The structural alloys' degradation, particularly in terms of chromium depletion, and the molten salt chemistry are key factors that impact the lifetime of nuclear reactors and the development of future FHR designs. In support of materials development for the FHR, the nickel base alloy of Hastelloy N and iron-chromium base alloy 316 stainless steel are being actively considered as critical structural alloys. Enriched 27LiF-BeF2 (named as FLiBe) is a promising coolant for the FHR because of its neutronic properties and heat transfer characteristics while operating at atmospheric pressure. In this study, the corrosion behavior of Ni-5Cr and Ni-20Cr binary model alloys, and Hastelloy N and 316 stainless steel in molten FLiBe with and without graphite were investigated through various microstructural analyses. Based on the understanding of the corrosion behavior and data of above four alloys in molten FLiBe, a long-term corrosion prediction model has been developed that is applicable specifically for these four materials in FLiBe at 700ºC. The model uses Cr concentration profile C(x, t) as a function of corrosion distance in the materials and duration fundamentally derived from the Fick's diffusion laws. This model was validated with reasonable accuracy for the four alloys by fitting the calculated profiles with experimental data and can be applied to evaluate corrosion attack depth over the long-term. The critical constant of the overall diffusion coefficient (Deff) in this model can be quickly calculated from the experimental measurement of alloys' weight loss due to Cr depletion. While many factors affect the Deff such as the grain boundary type, grain size, precipitates, initial Cr concentration as well as temperature, this model provides a methodology for estimating corrosion attack depth of alloys in molten fluoride salts obviating the need for difficult and challenging experiment.

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

    NASA Astrophysics Data System (ADS)

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

    2010-11-01

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

  4. Melting Behavior of Iron Alloys

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Lee, K. K. M.

    2014-12-01

    Earth's core consists of an iron-nickel alloy with approximately ten percent of other light elements (e.g., C, S, Si, O). Therefore, the behavior of iron alloys of similar composition at the temperatures and pressures that resemble the conditions of Earth's core is of fundamental importance to our understanding of the inner workings of our planet. The melting behavior of iron alloys is especially important as it sheds light on the conditions at the boundary between Earth's solid inner core and its liquid outer core, as well as puts constraints on the age of the inner core. Here, we report the melting curve of iron alloys based on laser-heated diamond anvil cell experiments. Four-color multi-wavelength imaging radiometry is used to determine the temperature profiles of the heated spot during melting and electron microscopy is used to map the compositional and textural changes of the iron alloys. An automated analysis of the texture, composition and temperature of the hot spots is conducted with an in-house developed image processing script, which identifies the melting point of the alloys and the preferred host phases of minor elements (e.g., Ni, Cr, Mn) at high-pressure/temperature conditions.

  5. In vitro degradation behavior and cytocompatibility of MgZnZr alloys

    PubMed Central

    Huan, Z. G.; Leeflang, M. A.; Fratila-Apachitei, L. E.; Duszczyk, J.

    2010-01-01

    Zinc and zirconium were selected as the alloying elements in biodegradable magnesium alloys, considering their strengthening effect and good biocompatibility. The degradation rate, hydrogen evolution, ion release, surface layer and in vitro cytotoxicity of two MgZnZr alloys, i.e. ZK30 and ZK60, and a WE-type alloy (MgYREZr) were investigated by means of long-term static immersion testing in Hanks solution, non-static immersion testing in Hanks solution and cell-material interaction analysis. It was found that, among these three magnesium alloys, ZK30 had the lowest degradation rate and the least hydrogen evolution. A magnesium calcium phosphate layer was formed on the surface of ZK30 sample during non-static immersion and its degradation caused minute changes in the ion concentrations and pH value of Hanks solution. In addition, the ZK30 alloy showed insignificant cytotoxicity against bone marrow stromal cells as compared with biocompatible hydroxyapatite (HA) and the WE-type alloy. After prolonged incubation for 7days, a stimulatory effect on cell proliferation was observed. The results of the present study suggested that ZK30 could be a promising material for biodegradable orthopedic implants and worth further investigation to evaluate its in vitro and in vivo degradation behavior. PMID:20532960

  6. Erosion of iron-chromium alloys by glass particles

    NASA Technical Reports Server (NTRS)

    Salik, J.; Buckley, D. H.

    1984-01-01

    The material loss upon erosion was measured for several iron-chromium alloys. Two types of erodent material were used: spherical glass beads and sharp particles of crushed glass. For erosion with glass beads the erosion resistance (defined as the reciprocal of material loss rate) was linearly dependent on hardness. This is in accordance with the erosion behavior of pure metals, but contrary to the erosion behavior of alloys of constant composition that were subjected to different heat treatments. For erosion with crushed glass, however, no correlation existed between hardness and erosion resistance. Instead, the erosion resistance depended on alloy composition rather than on hardness and increased with the chromium content of the alloy. The difference in erosion behavior for the two types of erodent particles suggested that two different material removal mechanisms were involved. This was confirmed by SEM micrographs of the eroded surfaces, which showed that for erosion with glass beads the mechanism of material removal was deformation-induced flaking of surface layers, or peening, whereas for erosion with crushed glass it was cutting or chopping.

  7. Oxide Film Aging on Alloy 22 in Halide Containing Solutions

    SciTech Connect

    Rodriguez, Martin A.; Carranza, Ricardo M.; Rebak, Raul B.

    2007-07-01

    Passive and corrosion behaviors of Alloy 22 in chloride and fluoride containing solutions, changing the heat treatment of the alloy, the halide concentration and the pH of the solutions at 90 deg. C, was investigated. The study was implemented using electrochemical techniques, which included open circuit potential monitoring over time, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements carried out at open circuit and at passivity potentials. Corrosion rates obtained by EIS measurements after 24 h immersion in naturally aerated solutions were below 0.5 {mu}m/year. The corrosion rates were practically independent of solution pH, alloy heat treatment and halide ion nature and concentration. EIS low frequency resistance values increased with applied potential in the passive domain and with polarization time in pH 6 - 1 M NaCl at 90 deg. C. This effect was attributed to an increase in the oxide film thickness and oxide film aging. High frequency capacitance measurements indicated that passive oxide on Alloy 22 presented a double n-type/p-type semiconductor behavior in the passive potential range. (authors)

  8. CREEP AND CREEP-FATIGUE OF ALLOY 617 WELDMENTS

    SciTech Connect

    Wright, Jill; Carroll, Laura; Wright, Richard

    2014-08-01

    The Very High Temperature Reactor (VHTR) Intermediate Heat Exchanger (IHX) may be joined to piping or other components by welding. Creep-fatigue deformation is expected to be a predominant failure mechanism of the IHX1 and thus weldments used in its fabrication will experience varying cyclic stresses interrupted by periods of elevated temperature deformation. These periods of elevated temperature deformation are greatly influenced by a materials’ creep behavior. The nickel-base solid solution strengthened alloy, Alloy 617, is the primary material candidate for a VHTR-type IHX, and it is expected that Alloy 617 filler metal will be used for welds. Alloy 617 is not yet been integrated into Section III of the Boiler and Pressure Vessel Code, however, nuclear component design with Alloy 617 requires ASME (American Society of Mechanical Engineers) Code qualification. The Code will dictate design for welded construction through significant performance reductions. Despite the similar compositions of the weldment and base material, significantly different microstructures and mechanical properties are inevitable. Experience of nickel alloy welds in structural applications suggests that most high temperature failures occur at the weldments or in the heat-affected zone. Reliably guarding against this type of failure is particularly challenging at high temperatures due to the variations in the inelastic response of the constituent parts of the weldment (i.e., weld metal, heat-affected zone, and base metal) [ref]. This work focuses on the creep-fatigue behavior of nickel-based weldments, a need noted during the development of the draft Alloy 617 ASME Code Case. An understanding of Alloy 617 weldments when subjected to this important deformation mode will enable determination of the appropriate design parameters associated with their use. Specifically, the three main areas emphasized are the performance reduction due to a weld discontinuity in terms of the reduced number of the cycles to failure and whether a saturation in reduced cycle life with increased hold times is observed, the microstructural stability over long cycle times, and finally, the location of the generated weldment data on a creep-fatigue damage diagram (D-diagram).

  9. A new amorphous alloy deposit with high corrosion resistance

    SciTech Connect

    Yao, S.; Zhao, S. Guo, H.; Kowaka, M.

    1996-03-01

    The corrosion behavior of electrodeposited Ni-P, Ni-W, Ni-W-P, and Fe-W alloys was tested, and the effects of the additive elements W and P on the corrosion resistance of amorphous deposits were studied. Corrosion rates of the alloys were compared to those of stainless steel. Results showed the W content in electrodeposited Ni-W-P amorphous alloy was as high as 55.2 wt%. The hardness (Vickers [HV]) of the alloy was from 700 HV to 800 HV and 1,300 HV to 1,400 HV after heat treatment at 550 C. The hardness, wear resistance, and corrosion resistance of the deposit were shown to be superior to those of Ni-P amorphous deposit. The corrosion potential was moved to noble by adding P to the deposit, and the passive current density dropped remarkably with the addition of W. Amorphous Ni-W, Ni-W-P, and Fe-W alloy deposits showed high corrosion resistance in acid solutions. Immersion tests in 1 mol/L hydrochloric acid solution t 30 C showed the corrosion rate of type 304 stainless steel was 10 times that of Ni-W-P amorphous deposit, 40 times that of Ni-W amorphous deposit, and 15 to 20 times that of Fe-W amorphous deposit. In 0.5 mol/L sulfuric acid solution at 30 C, the corrosion resistance of the amorphous deposit was poorer than that of type 304 SS, but at 60 C, the corrosion rate of type 304 SS increased dramatically, to 180 times that of Fe-W amorphous deposit and 100 to 700 times that of the Ni-based amorphous deposit.

  10. Overview of ODS Alloy Development

    SciTech Connect

    Wright, Ian G; Pint, Bruce A

    2005-01-01

    The overall goal of this effort is to address the materials-related barriers to expediting the use of oxide dispersion-strengthened (ODS) alloys in components required in the U.S. Department of Energy's (DOE's) Office of Fossil Energy's advanced coal combustion, gasification, and utilization processes to operate at temperatures higher than are possible with conventionally-strengthened alloys. The project is focused on the needs of the broad range of ferritic ODS-alloys, especially the FeCrAl-based alloys, with the purpose of developing a detailed understanding of the behavior of ODS alloys in all phases of their use, including fabrication, service performance, life prediction, mode of failure, repair, and refurbishment. The intended output of this project is a compilation of information that facilitates the assessment of the applicability of ODS alloys to the needs of high-temperature equipment required in DOE's advanced power plants. Particular emphasis has been placed on processing modifications to increase the hoop strength of ODS tubes, on joining, and on oxidation-limited life prediction. Approaches for modifying the alloy grain structure to increase the creep strength in the transverse/hoop direction (for tubes) have involved the examination of processes that modify the secondary recrystallization behavior of the alloy, with the intention of producing larger, more equiaxed grains, or a spiral grain structure that reduces the number of transverse grain boundaries. Processing using a commercial-scale pilgering/flow-forming/cross-rolling facility indicated the potential of this route, but also revealed some practical difficulties, especially since such processing of ODS alloys must be done at temperatures above approximately 600 C. Research to provide guidance for such processing has involved measurements using well-controlled, hot torsion testing, as well as trials with a small-scale cross-rolling mill. Progress has been made with joining approaches that involve inertia welding, and diffusion bonding, and the creep strength of butt joints made by some of the process variations approaches the transverse creep strength of the parent alloy. A particular feature of the ferritic ODS-FeCrAl alloys is that they exhibit relatively low oxidation rates up to 1200 C (2192 F), due to the formation of a protective Al2O3 film. In service, the mechanical load applied to these ODS alloys will be below the stress level at which significant creep occurs, so that it is likely that the effective service lifetime will be determined by the rate of environmental degradation. Operation at the very high temperatures possible with these alloys means that, should the ability to form a protective oxide scale be lost, the ensuing oxidation damage could be very rapid. However, since during protective oxidation there is very little loss in alloy section due to the thin alumina scales formed, it is doubtful that mechanical means for monitoring the rate consumption of the alloy would provide sufficient accuracy for assessment of remaining lifetime. Hence, there is a need for some form of lifetime model to provide reliable prediction of remaining lifetime in typical service environments. Efforts to develop a lifetime model are in progress for the condition where the life-limiting process is oxidation in air (or oxygen); some data also have been generated in reducing environments (where there is potential for sulfidation attack); and in steam. Comparison of predictions from the model with results from lifetime testing in air indicate that good progress is being made.

  11. Effect of Cu content on the defect evolution in Fe-Cu alloys investigated by PALS

    NASA Astrophysics Data System (ADS)

    Cao, X. Z.; Lai, X.; Cheng, G. D.; Jin, S. X.; Zhang, X.; Zhang, P.; Wang, B. Y.

    2016-01-01

    The effect of Cu content on the evolution of defects in Fe-x%Cu alloys (x= 0.15, 0.3, and 0.6) were investigated using Positron Annihilation Lifetime Spectroscopy (PALS). The vacancy-type and Cu-vacancy complexes defects were respectively produced by quenching from 1173 K and cold-rolled deformation followed by isochronal annealing. The PALS results with isochronal annealing showed that the temperature of defects recovery increased in deformed Fe-Cu alloys with Cu content. The increment of Cu content also restrained the migration of vacancies in as-quenched Fe-Cu alloys.

  12. Crystallization process and magnetic property of Fe81Zr3Nb6B10 alloy

    NASA Astrophysics Data System (ADS)

    Sun, Y. M.; Yu, W. Q.; Long, D.; Zhang, Y.; Hua, Z.

    2015-11-01

    Fe81Zr3Nb6B10 amorphous alloy was prepared by melt-spinning and annealed at various temperatures. The thermal property, microstructure and magnetic property were investigated by differential thermal analysis (DTA), X-ray diffraction (XRD) and vibrating sample magnetometer (VSM). The crystallization process of Fe81Zr3Nb6B10 alloy is as follow: Amorphous ? residual amorphous + ?-Fe + ?-Mntype ? ?-Fe solid solution. Coercivity (Hc) of Fe81Zr3Nb6B10 alloy changes complexly, which abruptly deteriorates at 843K and then softens with increasing annealing temperature (Ta).

  13. Response of solute and precipitation-strengthened copper alloys at high neutron exposure

    SciTech Connect

    Garner, F.A.; Hamilton, M.L. ); Shikama, T. ); Edwards, D.J.; Newkirk, J.W. )

    1991-11-01

    A variety of solute and precipitation strengthened copper base alloys have been irradiated to neutron-induced displacement levels of 34 to 150 dpa at 415{degrees}C and 32 dpa at 529{degrees}C in the Fast Flux Test Facility to assess their potential for high heat flux applications in fusion reactors. Several MZC-type alloys appear to offer the most promise for further study. For low fluence applications CuBeNi and spinodally strengthened CuNiTi alloys may also be suitable. Although Cu-2Be resists swelling, it is not recommended for fusion reactor applications because of its low conductivity.

  14. Thermodynamic modeling and experimental validation of the Fe-Al-Ni-Cr-Mo alloy system

    SciTech Connect

    Teng, Zhenke; Zhang, F; Miller, Michael K; Liu, Chain T; Huang, Shenyan; Chou, Y.T.; Tien, R; Chang, Y A; Liaw, Peter K

    2012-01-01

    NiAl-type precipitate-strengthened ferritic steels have been known as potential materials for the steam turbine applications. In this study, thermodynamic descriptions of the B2-NiAl type nano-scaled precipitates and body-centered-cubic (BCC) Fe matrix phase for four alloys based on the Fe-Al-Ni-Cr-Mo system were developed as a function of the alloy composition at the aging temperature. The calculated phase structure, composition, and volume fraction were validated by the experimental investigations using synchrotron X-ray diffraction and atom probe tomography. With the ability to accurately predict the key microstructural features related to the mechanical properties in a given alloy system, the established thermodynamic model in the current study may significantly accelerate the alloy design process of the NiAl-strengthened ferritic steels.

  15. Phase stability of laves intermetallics in stainless steel-zirconium alloys.

    SciTech Connect

    Abraham, D. P.

    1999-04-08

    Phase transformations occurring in a stainless steel-15 wt% zirconium (SS-15Zr) alloy were studied by in situ neutron diffraction. Neutron diffraction patterns as a function of time were obtained on alloys that were held at various elevated temperatures (1084-1275 C). As-cast SS-15Zr alloys contain ferrite, austenite, ZrFe{sub 2}-type Laves polytypes C36 and C15, and small amounts of a Fe{sub 23}Zr{sub 6}-type intermetallic. Annealing at high temperatures resulted in an increase of the Fe{sub 23}Zr{sub 6}, intermetallic content. The C15 Laves polytype is the equilibrium phase for T {le} 1230 C; C36 is the stable polytype at higher temperatures ({approximately}1275 C). Phase changes were slow for temperatures <1100 C.These findings have important implications for use of the SS-15Zr alloy as a nuclear waste form.

  16. Ni{sub 3}Al aluminide alloys

    SciTech Connect

    Liu, C.T.

    1993-10-01

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

  17. Choosing An Alloy For Automotive Stirling Engines

    NASA Technical Reports Server (NTRS)

    Stephens, Joseph R.

    1988-01-01

    Report describes study of chemical compositions and microstructures of alloys for automotive Stirling engines. Engines offer advantages of high efficiency, low pollution, low noise, and ability to use variety of fuels. Twenty alloys evaluated for resistance to corrosion permeation by hydrogen, and high temperature. Iron-based alloys considered primary candidates because of low cost. Nickel-based alloys second choice in case suitable iron-based alloy could not be found. Cobalt-based alloy included for comparison but not candidate, because it is expensive strategic material.

  18. Dendrite segregation in Ni3Al-based intermetallic single crystals alloyed with Cr, Mo, W, Ti, Co, and Re

    NASA Astrophysics Data System (ADS)

    Drozdov, A. A.; Povarova, K. B.; Morozov, A. E.; Antonova, A. V.; Bulakhtina, M. A.; Alad'ev, N. A.

    2015-07-01

    The character of dendrite segregation in Ni3Al-based intermetallic VKNA-type alloy single crystals with a dendritic-cellular structure is studied. Distribution coefficient k d of an alloying element (AE) in the alloy during solidification k d = c d.a.I/ c 0 ( c 0 is the AE content in the alloy (liquid phase composition), c d.a.I is the AE content in primary dendrite arms of the alloy (in the solid phase)) and segregation coefficient k s = c d.a.I/ c i.d ( c i.d is the AE content in the interdendritic space) have been found. A comparative study of the dendrite segregation parameters in VKNA-nype Ni3Al-based intermetallic alloys and the well-known ZhS36-type nickel superalloy shows that the intermetallic alloys satisfy to the rule deduced for two- and three-component nickel-based superalloys: if an introduced AE increases the melting temperature of the basic metal, we have k d > 1 (Co, W, Re); if it decreases the melting temperature, we have k d < 1 (Al, Ti, Cr, Mo). Dendrite segregation coefficients k s are dependent on the proportion of the AE contents in the alloys. In nickel superalloys, the dendrite segregation of aluminum, tungsten, and rhenium is higher than that in the intermetallic alloys. The dendrite segregation coefficients of tungsten and rhenium is higher by a factor of 1.5-2 than that in the VKNA-type intermetallic alloys with a low content of refractory metals. This can be due to the retardation of diffusion of refractory metals in the solid phase of a nickel superalloy highly alloyed with these elements.

  19. Effects of minor alloying additions on the formation of protective scales under sulfidizing conditions at 700 degree C

    SciTech Connect

    Wright, I.G.; Colwell, J.A. ); Baer, D.R.; Prater, J.T.; Schoenlein, L.H. )

    1990-10-30

    Effects of Al, Si, Mn, Y, and Hf on the formation of protective scales have been investigated in environments simulating substoichiometric combustion of high-S coal, and an oxidizing flue gas. Minor additions were made to three clean alloys bases: Fe-25Cr, Fe-25Cr-20Ni, and Fe-25Cr-6Al, by conventional alloying, and by powder metallurgical routes involving rapid solidification or high-energy milling. Scales formed at 700{degree}C were compared with those formed on the unalloyed base alloys, in terms of weight change, scale morphology and composition. Alumina scales on the Fe-25Cr-6Al-base alloys proved the most effective as a group, with excellent protection being provided for more than 6000 h in aggressively sulfidizing conditions. Chromia scales formed on Fe-25Cr-base alloys were markedly more effective than those on equivalent Fe-25Cr-20Ni-base alloys prepared by conventional casting. Observations of initial stages of corrosion of the base alloys indicated that a major difference was that the protective scales formed on the FeCr alloy were of the M{sub 2}O{sub 3}-type, whereas those that led to inferior protection on the FeCrNi alloy were of the M{sub 3}O{sub 4}-type, and led to the inclusion of higher levels of Fe in the nominally protective scale. It is postulated that alloy modifications that can promote the exclusive formation of M{sub 2}O{sub 3}-type scales alloys should also enhance their sulfidation resistance. 23 refs., 107 figs., 16 tabs.

  20. Improving p-type doping efficiency in Al{sub 0.83}Ga{sub 0.17}N alloy substituted by nanoscale (AlN){sub 5}/(GaN){sub 1} superlattice with Mg{sub Ga}-O{sub N} δ-codoping: Role of O-atom in GaN monolayer

    SciTech Connect

    Zhong, Hong-xia; Shi, Jun-jie Jiang, Xin-he; Huang, Pu; Ding, Yi-min; Zhang, Min

    2015-01-15

    We calculate Mg-acceptor activation energy E{sub A} and investigate the influence of O-atom, occupied the Mg nearest-neighbor, on E{sub A} in nanoscale (AlN){sub 5}/(GaN){sub 1} superlattice (SL), a substitution for Al{sub 0.83}Ga{sub 0.17}N disorder alloy, using first-principles calculations. We find that the N-atom bonded with Ga-atom is more easily substituted by O-atom and nMg{sub Ga}-O{sub N} (n = 1-3) complexes are favorable and stable in the SL. The O-atom plays a dominant role in reducing E{sub A}. The shorter the Mg-O bond is, the smaller the E{sub A} is. The Mg-acceptor activation energy can be reduced significantly by nMg{sub Ga}-O{sub N} δ-codoping. Our calculated E{sub A} for 2Mg{sub Ga}-O{sub N} is 0.21 eV, and can be further reduced to 0.13 eV for 3Mg{sub Ga}-O{sub N}, which results in a high hole concentration in the order of 10{sup 20} cm{sup −3} at room temperature in (AlN){sub 5}/(GaN){sub 1} SL. Our results prove that nMg{sub Ga}-O{sub N} (n = 2,3) δ-codoping in AlN/GaN SL with ultrathin GaN-layer is an effective way to improve p-type doping efficiency in Al-rich AlGaN.