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Sample records for octonary alloys based

  1. 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.

  2. NICKEL-BASE ALLOY

    DOEpatents

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

    1960-01-19

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

  3. 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.

  4. Nickel base coating alloy

    NASA Technical Reports Server (NTRS)

    Barrett, C. A. (Inventor); Lowell, C. E. (Inventor)

    1986-01-01

    Zirconium is added to a Ni-30 Al (beta) intermetallic alloy in the range of 0.05 w/o to 0.25 w/o. This addition is made during melting or by using metal powders. The addition of zirconium improves the cyclic oxidation resistance of the alloys at temperatures above 1100 C.

  5. High strength forgeable tantalum base alloy

    NASA Technical Reports Server (NTRS)

    Buckman, R. W., Jr.

    1975-01-01

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

  6. Nickel-base alloys combat corrosion

    SciTech Connect

    Agarwal, D.C.; Herda, W.

    1995-06-01

    The modern chemical process industry must increase production efficiency to remain competitive. Manufacturers typically meet this challenge by utilizing higher temperatures and pressures, and more-corrosive catalysts. At the same time, the industry has to solve the technical and commercial problems resulting from rigid environmental regulations. To overcome these obstacles, new alloys having higher levels of corrosion resistance have been developed. These materials are based on increased understanding of the physical metallurgy of nickel-base alloys, especially the role of alloying elements. Results of many studies have led to innovations in nickel-chromium-molybdenum alloys containing both high and low amounts of nickel. Higher molybdenum and chromium contents, together with nitrogen additions, have opened up an entirely new class of alloys having unique properties. In addition, a new chromium-base, fully wrought super stainless steel shows excellent promise in solving many corrosion problems. These newer alloys have the ability to combat uniform corrosion, localized corrosion, and stress-corrosion cracking in the harsh halogenic environment of the chemical process industry. This article briefly lists some of the major highlights and corrosion data on recent nickel-chromium-molybdenum and nickel-molybdenum alloys, and the development of a chromium-base, wrought super-austenitic alloy known as Nicrofer 3033 (Alloy 33). Some comparisons with existing alloys are presented, along with a few commercial applications.

  7. Iron-based amorphous alloys and methods of synthesizing iron-based amorphous alloys

    DOEpatents

    Saw, Cheng Kiong; Bauer, William A.; Choi, Jor-Shan; Day, Dan; Farmer, Joseph C.

    2016-05-03

    A method according to one embodiment includes combining an amorphous iron-based alloy and at least one metal selected from a group consisting of molybdenum, chromium, tungsten, boron, gadolinium, nickel phosphorous, yttrium, and alloys thereof to form a mixture, wherein the at least one metal is present in the mixture from about 5 atomic percent (at %) to about 55 at %; and ball milling the mixture at least until an amorphous alloy of the iron-based alloy and the at least one metal is formed. Several amorphous iron-based metal alloys are also presented, including corrosion-resistant amorphous iron-based metal alloys and radiation-shielding amorphous iron-based metal alloys.

  8. Corrosion of nickel-base alloys

    SciTech Connect

    Scarberry, R.C.

    1985-01-01

    The volume consists of three tutorial lectures and 18 contributed papers. The three tutorial lectures provide state-of-the-art background on the physical metallurgy of nickel-base alloys as it relates to corrosion. Also featured are the mechanisms and applications of these alloys and an insight into the corrosion testing techniques. The three tutorial lecture papers will help acquaint newcomers to this family of alloys with a thorough overview. The contributed papers are categorized into four major topics: general corrosion, stress corrosion cracking, fatigue and localized corrosion. Each topic is key-noted by one invited lecture followed by several contributed papers. The papers in the general corrosion section are wide ranging and cover the aspects of material selection, development of galvanic series in corrosive environments, corrosion resistance characteristics, hydrogen permeation and hydrogen embrittlement of nickel and some nickel-base alloys.

  9. Transient oxidation of multiphase Ni-Cr base alloys

    SciTech Connect

    Baran, G.; Meraner, M.; Farrell, P.

    1988-06-01

    Four commercially available Ni-Cr-based alloys used with porcelain enamels were studied. Major alloying elements were Al, Be, Si, B, Nb, and Mo. All alloys were multiphase. During heat treatments simulating enameling conditions, phase changes occurred in most alloys and were detected using hardness testing, differential thermal analysis (DTA), and microscopy. Oxidation of these alloys at 1000/degrees/C for 10 min produced an oxide layer consisting principally of chromium oxide, but the oxide morphology varied with each alloy depending on the alloy microstructure. Controlling alloy microstructure while keeping the overall composition unchanged may be a means of preventing wrinkled poorly adherent scales from forming.

  10. Irradiation creep of vanadium-base alloys

    SciTech Connect

    Tsai, H.; Billone, M.C.; Strain, R.V.; Smith, D.L.; Matsui, H.

    1998-03-01

    A study of irradiation creep in vanadium-base alloys is underway with experiments in the Advanced Test Reactor (ATR) and the High Flux Isotope Reactor (HFIR) in the United States. Test specimens are thin-wall sealed tubes with internal pressure loading. The results from the initial ATR irradiation at low temperature (200--300 C) to a neutron damage level of 4.7 dpa show creep rates ranging from {approx}0 to 1.2 {times} 10{sup {minus}5}/dpa/MPa for a 500-kg heat of V-4Cr-4Ti alloy. These rates were generally lower than reported from a previous experiment in BR-10. Because both the attained neutron damage levels and the creep strains were low in the present study, however, these creep rates should be regarded as only preliminary. Substantially more testing is required before a data base on irradiation creep of vanadium alloys can be developed and used with confidence.

  11. Rapid solidification of Nb-base alloys

    NASA Technical Reports Server (NTRS)

    Gokhale, A. B.; Javed, K. R.; Abbaschian, G. J.; Lewis, R. E.

    1988-01-01

    New Nb-base alloys are of interest for aerospace structural applications at high temperatures, viz, 800 to 1650 C. Fundamental information regarding the effects of rapid solidification in achieving greatly refined microstructures, extended solid solubility, suppression of embrittling equilibrium phases, and formation of new phases is desired in a number of Nb-X alloys. The microstructures and selected properties of Nb-Si and other Nb-base alloys are presented for materials both rapidly quenched from the equilibrium liquidus and rapidly solidified following deep supercooling. Electromagnetic levitation was used to achieve melting and supercooling in a containerless inert gas environment. A variety of solidification conditions were employed including splatting or drop casting of supercooled samples. The morphology and composition of phases formed are discussed in terms of both solidification history and bulk composition.

  12. 21 CFR 872.3710 - Base metal alloy.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Base metal alloy. 872.3710 Section 872.3710 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3710 Base metal alloy. (a) Identification. A base metal alloy is a device composed primarily of base metals, such as nickel, chromium, or cobalt, that...

  13. 21 CFR 872.3710 - Base metal alloy.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Base metal alloy. 872.3710 Section 872.3710 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3710 Base metal alloy. (a) Identification. A base metal alloy is a device composed primarily of base metals, such as nickel, chromium, or cobalt, that...

  14. 21 CFR 872.3710 - Base metal alloy.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Base metal alloy. 872.3710 Section 872.3710 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3710 Base metal alloy. (a) Identification. A base metal alloy is a device composed primarily of base metals, such as nickel, chromium, or cobalt, that...

  15. 21 CFR 872.3710 - Base metal alloy.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Base metal alloy. 872.3710 Section 872.3710 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3710 Base metal alloy. (a) Identification. A base metal alloy is a device composed primarily of base metals, such as nickel, chromium, or cobalt, that...

  16. 21 CFR 872.3710 - Base metal alloy.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Base metal alloy. 872.3710 Section 872.3710 Food... DEVICES DENTAL DEVICES Prosthetic Devices § 872.3710 Base metal alloy. (a) Identification. A base metal alloy is a device composed primarily of base metals, such as nickel, chromium, or cobalt, that...

  17. 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.

  18. Vanadium-base alloys for fusion reactor applications

    SciTech Connect

    Smith, D.L.; Loomis, B.A.; Diercks, D.R.

    1984-10-01

    Vanadium-base alloys offer potentially significant advantages over other candidate alloys as a structural material for fusion reactor first wall/blanket applications. Although the data base is more limited than that for the other leading candidate structural materials, viz., austenitic and ferritic steels, vanadium-base alloys exhibit several properties that make them particularly attractive for the fusion reactor environment. This paper presents a review of the structural material requirements, a summary of the materials data base for selected vanadium-base alloys, and a comparison of projected performance characteristics compared to other candidate alloys. Also, critical research and development (R and D) needs are defined.

  19. Fabric cutting application of FeAl-based alloys

    SciTech Connect

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

    1998-11-01

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

  20. Metal dusting and carburization resistance of nickel-base alloys

    SciTech Connect

    Kloewer, J.; Grabke, H.J.; Mueller-Lorenz, E.M.; Agarwal, D.C.

    1997-08-01

    Severe material failures caused by so-called metal dusting have been reported during recent years. The reason for these failures were strongly carburizing CO-H{sub 2} gas mixtures such as encountered in chemical plants for the synthesis of hydrocarbons, methanol, ammonia etc. as well as in plants for the reduction of iron ores. The carburization behavior of nine commercial nickel-base alloys and four iron-nickel-chromium alloys was investigated at 650 C in a carburizing H{sub 2}-CO-H{sub 2}O-gas with a carbon activity of a{sub c} {much_gt} 1. The iron-nickel-chromium alloys suffered severe metal dusting after a very short test period. Nickel base alloys were generally less susceptible to metal dusting than iron-base alloys. However, their corrosion behavior was found to depend sensitively on the chromium concentration of the respective alloys. Alloys like alloy 600H, with a chromium concentration of only 16%, suffered wastage rates which were similar to those of the more resistant iron-base alloys. Nickel-base alloys with chromium concentrations of 25% and above, on the other hand, showed no significant evidence of metal dusting even after 10,000 hours of exposure. It was found that these alloys are protected against metal dusting by the formation of a dense, self-healing chromia scale, which prevents the penetration of carbon into the base metal.

  1. [Mechanical studies on casting titanium alloy denture base].

    PubMed

    Ito, M

    1990-03-01

    The mechanical properties of the Akers type clasp, bar and frame made by the newly developed Ti-20Cr-0.2Si alloy were studied in order to obtain the indices for designing the cast partial denture base. In the case of the clasp, the bending strength of the Ti-20Cr-0.2Si alloy and pure Ti was lower than that of the Co-Cr alloy. The Ti-20Cr-0.2Si alloy and pure Ti may have the same retentive force as the gold type IV alloy because its bending behavior was similar to that of the gold alloy. In the cyclic bending test, the permanent deflection of the Ti-20Cr-0.2Si alloy was lower than that of the pure Ti and Co-Cr alloy. It had almost the same value as that of the gold alloy. Considering the permanent deflection and fracture, it is preferable that the undercut of the abutment tooth for the Ti-20Cr-0.02Si alloy clasp is 0.50mm or less. The Ti-20Cr-0.2Si alloy bars and frame showed the same bending behavior and strain distribution as the gold alloy. In the case of the Ti-20Cr-0.2Si alloy bar thickened about 30%, the strain was decreased and close to that of the Co-Cr alloy. It was suggested that the Ti-20Cr-0.2Si alloy bar or frame should be designed like the gold alloy. PMID:2196313

  2. Grain Refinement of Permanent Mold Cast Copper Base Alloys

    SciTech Connect

    M.Sadayappan; J.P.Thomson; M.Elboujdaini; G.Ping Gu; M. Sahoo

    2005-04-01

    Grain refinement is a well established process for many cast and wrought alloys. The mechanical properties of various alloys could be enhanced by reducing the grain size. Refinement is also known to improve casting characteristics such as fluidity and hot tearing. Grain refinement of copper-base alloys is not widely used, especially in sand casting process. However, in permanent mold casting of copper alloys it is now common to use grain refinement to counteract the problem of severe hot tearing which also improves the pressure tightness of plumbing components. The mechanism of grain refinement in copper-base alloys is not well understood. The issues to be studied include the effect of minor alloy additions on the microstructure, their interaction with the grain refiner, effect of cooling rate, and loss of grain refinement (fading). In this investigation, efforts were made to explore and understand grain refinement of copper alloys, especially in permanent mold casting conditions.

  3. Cast Fe-base cylinder/regenerator housing alloy

    NASA Technical Reports Server (NTRS)

    Larson, F.; Kindlimann, L.

    1980-01-01

    The development of an iron-base alloy that can meet the requirements of automotive Stirling engine cylinders and regenerator housings is described. Alloy requirements are as follows: a cast alloy, stress for 5000-hr rupture life of 200 MPa (29 ksi) at 775 C (1427 F), oxidation/corrosion resistance comparable to that of N-155, compatibility with hydrogen, and an alloy cost less than or equal to that of 19-9DL. The preliminary screening and evaluation of ten alloys are described.

  4. Stress corrosion crack tip microstructure in nickel-based alloys

    SciTech Connect

    Shei, S.A.; Yang, W.J.

    1994-04-01

    Stress corrosion cracking behavior of several nickel-base alloys in high temperature caustic environments has been evaluated. The crack tip and fracture surfaces were examined using Auger/ESCA and Analytical Electron Microscopy (AEM) to determine the near crack tip microstructure and microchemistry. Results showed formation of chromium-rich oxides at or near the crack tip and nickel-rich de-alloying layers away from the crack tip. The stress corrosion resistance of different nickel-base alloys in caustic may be explained by the preferential oxidation and dissolution of different alloying elements at the crack tip. Alloy 600 (UNS N06600) shows good general corrosion and intergranular attack resistance in caustic because of its high nickel content. Thermally treated Alloy 690 (UNS N06690) and Alloy 600 provide good stress corrosion cracking resistance because of high chromium contents along grain boundaries. Alloy 625 (UNS N06625) does not show as good stress corrosion cracking resistance as Alloy 690 or Alloy 600 because of its high molybdenum content.

  5. Weldability of Fe3Al based iron aluminide alloys

    NASA Astrophysics Data System (ADS)

    Zacharia, T.; Maziasz, P. J.; David, S. A.; McKamey, C. G.

    An investigation was carried out to determine the weldability of Fe3Al type alloys. Sigmajig tests of a commercial heat of FA-129 alloy indicate that hot-cracking may not be a problem for this alloy. Additionally, several new Fe3Al based iron aluminides were evaluated for weldability. The preliminary results are encouraging and suggest that some of these alloys have comparable or better weldability than FA-129 based iron-aluminides. For the first time, successful welds, without hot or cold cracking, were made on 13 mm (0.5 in.) thick plates from a commercial heat of FA-129 using the proper choice of welding conditions and parameters.

  6. Cast iron-base alloy for cylinder/regenerator housing

    NASA Technical Reports Server (NTRS)

    Witter, Stewart L.; Simmons, Harold E.; Woulds, Michael J.

    1985-01-01

    NASACC-1 is a castable iron-base alloy designed to replace the costly and strategic cobalt-base X-40 alloy used in the automotive Stirling engine cylinder/generator housing. Over 40 alloy compositions were evaluated using investment cast test bars for stress-rupture testing. Also, hydrogen compatibility and oxygen corrosion resistance tests were used to determine the optimal alloy. NASACC-1 alloy was characterized using elevated and room temperature tensile, creep-rupture, low cycle fatigue, heat capacity, specific heat, and thermal expansion testing. Furthermore, phase analysis was performed on samples with several heat treated conditions. The properties are very encouraging. NASACC-1 alloy shows stress-rupture and low cycle fatigue properties equivalent to X-40. The oxidation resistance surpassed the program goal while maintaining acceptable resistance to hydrogen exposure. The welding, brazing, and casting characteristics are excellent. Finally, the cost of NASACC-1 is significantly lower than that of X-40.

  7. 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.

  8. On the cytocompatibility of biodegradable Fe-based alloys.

    PubMed

    Schinhammer, Michael; Gerber, Isabel; Hänzi, Anja C; Uggowitzer, Peter J

    2013-03-01

    Biodegradable iron-based alloys are potential candidates for application as temporary implant material. This study summarizes the design strategy applied in the development of biodegradable Fe-Mn-C-Pd alloys and describes the key factors which make them suitable for medical applications. The study's in vitro cytotoxicity tests using human umbilical vein endothelial cells revealed acceptable cytocompatibility based on the alloys' eluates. An analysis of the eluates revealed that Fe is predominantly bound in insoluble degradation products, whereas a considerable amount of Mn is in solution. The investigation's results are discussed using dose-response curves for the main alloying elements Fe and Mn. They show that it is mainly Mn which limits the cytocompatibility of the alloys. The study also supplies a summary of the alloying elements' influence on metabolic processes. The results and discussion presented are considered important and instructive for future alloy development. The Fe-based alloys developed show an advantageous combination of microstructural, mechanical and biological properties, which makes them interesting as degradable implant material.

  9. Surface modification of nickel based alloys for improved oxidation resistance

    SciTech Connect

    Jablonski, Paul D.; Alman, David E.

    2005-02-01

    The present research is aimed at the evaluation of a surface modification treatment to enhance the high temperature stability of nickel-base superalloys. A low Coefficient Thermal Expansion (CTE ~12.5x10-6/°C) alloy based on the composition (in weight %) of Ni-22Mo-12.5Cr was produced by Vacuum Induction Melting and Vacuum Arc Melting and reduced to sheet by conventional thermal-mechanical processing. A surface treatment was devised to enhance the oxidation resistance of the alloys at high temperature. Oxidation tests (in dry and wet air; treated and untreated) were conducted 800°C to evaluate the oxidation resistance of the alloys. The results were compared to the behavior of Haynes 230 (Ni-22Cr) in the treated and untreated conditions. The treatment was not very effective for Haynes 230, as this alloy had similar oxidation behavior in both the treated and untreated conditions. However, the treatment had a significant effect on the behavior of the low CTE alloy. At 800°C, the untreated Ni-12.5Cr alloy was 5 times less oxidation resistant than Haynes 230. However, in the treated condition, the Ni-12.5Cr alloy had comparable oxidation resistance to the Haynes 230 alloy.

  10. Cr{sub 2}Nb-based alloy development

    SciTech Connect

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A.

    1996-08-01

    Alloys of Cr-Cr{sub 2}Nb with exceptionally high strength at 1200{degrees}C have been developed. However, these compositions suffer from limited ductility and toughness at room temperature. Despite improvements from processing modifications, as-fabricated defects still limit room temperature mechanical behavior. In contrast, an alloy system with only a small mismatch of the coefficients of thermal expansion of the two phases, Cr-Cr{sub 2}Zr, showed good fabricability. However, these alloys are weaker than Cr-Cr{sub 2}Nb compositions at high temperatures and have poor oxidation resistance. Silicide coatings can provide high-temperature oxidation and sulfidation protection of these alloys. Improvements in room temperature mechanical properties of Laves-phase-strengthened alloys will rely on further development based on increasing the ductility of the matrix phase by impurity control and compositional modifications.

  11. Permeation characteristics of some iron and nickel based alloys

    SciTech Connect

    Mitchell, D.J.; Edge, E.M.

    1985-06-15

    The permeation characteristics of deuterium in several iron and nickel based alloys were measured by the gas phase breakthrough technique in the temperature range 100 to 500 /sup 0/C with applied pressures ranging from 10 Pa to 100 kPa. The restriction of the gas flux imposed by surface oxides was modeled in order to evaluate the effects of surface oxide retardation of the gas flux on the effective values of the deuterium permeabilities and diffusivities in the alloys. The most permeable alloys were 430 and 431 stainless steels. The next most permeable alloy was Monel K-500, which exceeded the permeability of pure Ni by more than a factor of five at room temperature. The alloys with permeabilities less than pure Ni were, in order of decreasing permeability: the Inconels 625, 718, and 750, the Fe-Ni-Co glass-sealing alloys Kovar and Ceramvar, and the 300-series stainless steels. Deuterium trapping within the alloys appeared to influence the values of bulk diffusivities, which were not correlated with either the permeabilities or the chemical compositions of the alloys.

  12. Surface segregations in platinum-based alloy nanoparticles

    NASA Astrophysics Data System (ADS)

    Yamakawa, Shunsuke; Asahi, Ryoji; Koyama, Toshiyuki

    2014-04-01

    A phase-field model that describes the radial distributions of the ordered-disordered phase and surface segregation in a single-alloy nanoparticle is introduced to clarify the overall behavior of surface segregation of various Pt-based alloy nanoparticles. One of the obstacles to apply a platinum-transition metal alloy as a cathode electro-catalyst of a polymer electrolyte fuel cell is the need to ensure the retention of the designed surface composition in an alloy nanoparticle against the alloy combinations, a particle size, and heat treatment. From the results of calculations for CrPt, FePt, CoPt, NiPt, CuPt, PdPt, IrPt, and AuPt binary nanoparticles with diameters below 10 nm at 973.15 K, the compositional variation within a single particle was found to depend on the balance between the atomic interaction within particles and the surface free energy. In addition, the obtained specific steady-state composition of the surface varied significantly with alloy combination and particle diameter. Based on the general tendencies of a binary system to exhibit segregation, attempts to control the amount of platinum segregation on the surface using a ternary-alloy system were examined.

  13. Microstructures and oxidation behavior of some Molybdenum based alloys

    SciTech Connect

    Ray, Pratik Kumar

    2011-01-01

    The advent of Ni based superalloys revolutionized the high temperature alloy industry. These materials are capable of operating in extremely harsh environments, comprising of temperatures around 1050 C, under oxidative conditions. Demands for increased fuel efficiency, however, has highlighted the need for materials that can be used under oxidative conditions at temperatures in excess of 1200 C. The Ni based superalloys are restricted to lower temperatures due to the presence of a number of low melting phases that melt in the 1250 - 1450 C, resulting in softening of the alloys above 1000 C. Therefore, recent research directions have been skewed towards exploring and developing newer alloy systems. This thesis comprises a part of such an effort. Techniques for rapid thermodynamic assessments were developed and applied to two different systems - Mo-Si alloys with transition metal substitutions (and this forms the first part of the thesis) and Ni-Al alloys with added components for providing high temperature strength and ductility. A hierarchical approach towards alloy design indicated the Mo-Ni-Al system as a prospective candidate for high temperature applications. Investigations on microstructures and oxidation behavior, under both isothermal and cyclic conditions, of these alloys constitute the second part of this thesis. It was seen that refractory metal systems show a marked microstructure dependence of oxidation.

  14. Permeability of hydrogen isotopes through nickel-based alloys

    SciTech Connect

    Edge, E.M.; Mitchell, D.J.

    1983-04-01

    Permeabilities and diffusivities of deuterium in several nickel-based alloys were measured in this investigation. Measurements were made by the gas-phase breakthrough technique in the temperature range 200 to 450/sup 0/C with applied pressures ranging from 1 to 100 kPa. The results were extrapolated to predict the permeabilities (K) of the alloys at room temperature. The alloy with the smallest deuterium permeability is Carpenter 49, for which K = 4.3 x 10/sup -18/ mol s/sup -1/ m/sup -1/ Pa/sup -//sup 1/2/ at 22/sup 0/C. The permeability of deuterium in Kovar or Ceramvar is about 80% greater than that for Carpenter 49. Premeabilities of Inconel 625, Inconel 718, Inconel 750 and Monel K-500 are all equal to about 5 x 10/sup -17/ mol m/sup -1/ s/sup -1/ Pa/sup -//sup 1/2/ at 22/sup 0/C. The validity (from a statistical standpoint) of the extrapolation of the permeabilities to room temperature is considered in detail. Published permeabilities of stainless steels and nickel-iron alloys are also reviewed. The greatest differences in permeabilities among the nickel-based alloys appear to be associated with the tendency for some alloys to form protective oxide layers. Permeabilities of deuterium through laminates containing copper are smaller than for any of the iron-nickel alloys.

  15. Cladding burst behavior of Fe-based alloys under LOCA

    DOE PAGES

    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

  16. Cladding burst behavior of Fe-based alloys under LOCA

    SciTech Connect

    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. The 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.

  17. METHOD FOR ANNEALING AND ROLLING ZIRCONIUM-BASE ALLOYS

    DOEpatents

    Picklesimer, M.L.

    1959-07-14

    A fabrication procedure is presented for alpha-stabilized zirconium-base alloys, and in particular Zircaloy-2. The alloy is initially worked at a temperature outside the alpha-plus-beta range (810 to 970 deg ), held at a temperature above 970 deg C for 30 minutes and cooled rapidly. The alloy is then cold-worked to reduce the size at least 20% and annealed at a temperature from 700 to 810 deg C. This procedure serves both to prevent the formation of stringers and to provide a randomly oriented crystal structure.

  18. Amorphous phase formation in mechanically alloyed iron-based systems

    NASA Astrophysics Data System (ADS)

    Sharma, Satyajeet

    Bulk metallic glasses have interesting combination of physical, chemical, mechanical, and magnetic properties which make them attractive for a variety of applications. Consequently there has been a lot of interest in understanding the structure and properties of these materials. More varied applications can be sought if one understands the reasons for glass formation and the methods to control them. The glass-forming ability (GFA) of alloys can be substantially increased by a proper selection of alloying elements and the chemical composition of the alloy. High GFA will enable in obtaining large section thickness of amorphous alloys. Ability to produce glassy alloys in larger section thicknesses enables exploitation of these advanced materials for a variety of different applications. The technique of mechanical alloying (MA) is a powerful non-equilibrium processing technique and is known to produce glassy (or amorphous) alloys in several alloy systems. Metallic amorphous alloys have been produced by MA starting from either blended elemental metal powders or pre-alloyed powders. Subsequently, these amorphous alloy powders could be consolidated to full density in the temperature range between the glass transition and crystallization temperatures, where the amorphous phase has a very low viscosity. This Dissertation focuses on identifying the various Fe-based multicomponent alloy systems that can be amorphized using the MA technique, studying the GFA of alloys with emphasis on improving it, and also on analyzing the effect of extended milling time on the constitution of the amorphous alloy powder produced at earlier times. The Dissertation contains seven chapters, where the lead chapter deals with the background, history and introduction to bulk metallic glasses. The following four chapters are the published/to be published work, where the criterion for predicting glass formation, effect of Niobium addition on glass-forming ability (GFA), lattice contraction on

  19. A Computationally Based Approach to Homogenizing Advanced Alloys

    SciTech Connect

    Jablonski, P D; Cowen, C J

    2011-02-27

    We have developed a computationally based approach to optimizing the homogenization heat treatment of complex alloys. The Scheil module within the Thermo-Calc software is used to predict the as-cast segregation present within alloys, and DICTRA (Diffusion Controlled TRAnsformations) is used to model the homogenization kinetics as a function of time, temperature and microstructural scale. We will discuss this approach as it is applied to both Ni based superalloys as well as the more complex (computationally) case of alloys that solidify with more than one matrix phase as a result of segregation. Such is the case typically observed in martensitic steels. With these alloys it is doubly important to homogenize them correctly, especially at the laboratory scale, since they are austenitic at high temperature and thus constituent elements will diffuse slowly. The computationally designed heat treatment and the subsequent verification real castings are presented.

  20. Directionally solidified iron-base eutectic alloys

    NASA Technical Reports Server (NTRS)

    Tewari, S. N.

    1976-01-01

    Pseudobinary eutectic alloys with nominal compositions of Fe-25Ta-22Ni-10Cr and Fe-15.5Nb-14.5Ni-6.0Cr were directionally solidified at 0.5 centimeter per hour. Their microstructure consisted of the fcc, iron solid-solution, matrix phase reinforced by about 41-volume-percent, hcp, faceted Fe2Ta fibers and 41-volume-percent, hcp, Fe2Nb lamellae for the tantalum- and niobium-containing alloys, respectively. The microstructural stability under thermal cycling and the temperature dependence of tensile properties were investigated. These alloys showed low elevated-temperature strength and were not considered suitable for application in aircraft-gas-turbine blades although they may have applicability as vane materials.

  1. Fe-based long range ordered alloys

    DOEpatents

    Liu, Chain T; Inouye, Henry; Schaffhauser, Anthony C.

    1980-01-01

    Malleable long range ordered alloys having high critical ordering temperatures exist in the V(Co,Fe).sub.3 and V(Co,Fe,Ni).sub.3 system having the composition comprising by weight 22-23% V, 35-50% Fe, 0-22% Co and 19-40% Ni with an electron density no greater than 8.00. Excellent high temperature properties occur in alloys having compositions comprising by weight 22-23% V, 35-45% Fe, 0-10% Co, 25-35% Ni; 22-23% V, 28-33% Ni and the remainder Fe; and 22-23% V, 19-22% Ni, 19-22% Co and the remainder Fe. The alloys are fabricable by casting, deforming and annealing for sufficient time to provide ordered structure.

  2. Fe-based long range ordered alloys

    DOEpatents

    Liu, C.T.

    Malleable long range ordered alloys with high critical ordering temperatures exist in the V(Co,Fe)/sub 3/ and V(Co,Fe,Ni)/sub 3/ system. The composition comprising by weight 22 to 23% V, 35 to 50% Fe, 0 to 22% Co and 19 to 40% Ni with an electron density no greater than 8.00. Excellent high temperature properties occur in alloys having compositions comprising by weight 22 to 23% V, 35 to 45% Fe, 0 to 10% Co, 25 to 35% Ni; 22 to 23% V, 28 to 33% Ni and the remainder Fe; and 22 to 23% V, 19 to 22% Co and the remainder Fe. The alloys are fabricable by casting, deforming and annealing for sufficient time to provide ordered structure.

  3. Damping capacity of TiNi-based shape memory alloys

    NASA Astrophysics Data System (ADS)

    Rong, L. J.; Jiang, H. C.; Liu, S. W.; Zhao, X. Q.

    2007-07-01

    Damping capacity is another primary characteristic of shape memory alloys (SMA) besides shape memory effect and superelasticity. Damping behavior of Ti-riched TiNi SMA, porous TiNi SMA and a novel TiNi/AlSi composite have been investigated using dynamic mechanical analyzer (DMA) in this investigation. All these alloys are in martensitic state at room temperature and thus possess the high potential application value. Ti 50.2Ni 49.8 SMA has better damping capacity in pure martensitic state and phase transformation region due to the motion of martensite twin interface. As a kind of promising material for effective dampers and shock absorbing devices, porous TiNi SMA can exhibit higher damping capacity than the dense one due to the existence of the three-dimensioned connecting pore structure. It is found that the internal friction of porous TiNi SMA mainly originates from microplastic deformation and mobility of martensite interface and increases with the increase of the porosity. A novel TiNi/AlSi composite has been developed successfully by infiltrating AlSi alloy into the open pores of porous TiNi alloy with 60% porosity through compression casting. It shows the same phase transformation characteristics as the porous TiNi alloy. The damping capacity of the composite has been increased and the compressive strength has been also promoted remarkably. Suggestions for developing higher damping alloys based on TiNi shape memory alloy are proposed in this paper.

  4. Fabrication of tungsten wire reinforced nickel-base alloy composites

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  5. Salt Fog Testing Iron-Based Amorphous Alloys

    SciTech Connect

    Rebak, Raul B.; Aprigliano, Louis F.; Day, S. Daniel; Farmer, Joseph C.

    2007-07-01

    Iron-based amorphous alloys are hard and highly corrosion resistant, which make them desirable for salt water and other applications. These alloys can be produced as powder and can be deposited as coatings on any surface that needs to be protected from the environment. It was of interest to examine the behavior of these amorphous alloys in the standard salt-fog testing ASTM B 117. Three different amorphous coating compositions were deposited on 316L SS coupons and exposed for many cycles of the salt fog test. Other common engineering alloys such as 1018 carbon steel, 316L SS and Hastelloy C-22 were also tested together with the amorphous coatings. Results show that amorphous coatings are resistant to rusting in salt fog. Partial devitrification may be responsible for isolated rust spots in one of the coatings. (authors)

  6. Metallurgical characterization of experimental Ag-based soldering alloys

    PubMed Central

    Ntasi, Argyro; Al Jabbari, Youssef S.; Silikas, Nick; Al Taweel, Sara M.; Zinelis, Spiros

    2014-01-01

    Aim To characterize microstructure, hardness and thermal properties of experimental Ag-based soldering alloys for dental applications. Materials and methods Ag12Ga (AgGa) and Ag10Ga5Sn (AgGaSn) were fabricated by induction melting. Six samples were prepared for each alloy and microstructure, hardness and their melting range were determined by, scanning electron microscopy, energy dispersive X-ray (EDX) microanalysis, X-ray diffraction (XRD), Vickers hardness testing and differential scanning calorimetry (DSC). Results Both alloys demonstrated a gross dendritic microstructure while according to XRD results both materials consisted predominately of a Ag-rich face centered cubic phase The hardness of AgGa (61 ± 2) was statistically lower than that of AgGaSn (84 ± 2) while the alloys tested showed similar melting range of 627–762 °C for AgGa and 631–756 °C for AgGaSn. Conclusion The experimental alloys tested demonstrated similar microstructures and melting ranges. Ga and Sn might be used as alternative to Cu and Zn to modify the selected properties of Ag based soldering alloys. PMID:25382945

  7. Stack linings in high-alloy stainless steels and nickel-base alloys

    SciTech Connect

    Herda, W.R.; Grossmann, G.K.

    1999-11-01

    In power stations as well as in waste incineration plants, the stack is the last component in which residues and condensates can separate from the treated flue gas. The process of condensate formation due to temperatures below dewpoint, and the extreme corrosiveness of specific condensates are discussed in detail. Stack lining, using an appropriately corrosion-resistant metallic material, has proven to be an effective means of corrosion protection. Selected high-alloy stainless steels and nickel-base alloys, particularly well suited to this application, are introduced. The various techniques available for fitting such highly corrosion resistant linings are described in selected case histories.

  8. Iron and iron-based alloys for temporary cardiovascular applications.

    PubMed

    Francis, A; Yang, Y; Virtanen, S; Boccaccini, A R

    2015-03-01

    In the last decade, biodegradable metals have emerged as a topic of interest for particular biomedical applications which require high strength to bulk ratio, including for cardiovascular stents. The advantages of biodegradable materials are related to the reduction of long term risks associated with the presence of permanent metal implants, e.g. chronic inflammation and in-stent restenosis. From a structural point of view, the analysis of the literature reveals that iron-based alloys used as temporary biodegradable stents have several advantages over Mg-based alloys in terms of ductility and strength. Efforts on the modification and tunability of iron-based alloys design and compositions have been mainly focused on controlling the degradation rate while retaining the mechanical integrity within a reasonable period. The early pre-clinical results of many iron-based alloys seem promising for future implants developments. This review discusses the available literature focusing mainly on: (i) Fe and Fe-based alloys design and fabrication techniques; (ii) in vitro and in vivo performance; (iii) cytotoxicity and cell viability tests.

  9. The resistance of selected high strength alloys to embrittlement by a hydrogen environment. [iron and cobalt base alloys

    NASA Technical Reports Server (NTRS)

    Benson, R. B., Jr.

    1974-01-01

    Selected high strength iron base and cobalt base alloys were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature. These alloys were strengthened initially by cold working which produced strain induced martensite and fcc mechanical twins in an fcc matrix. Heat treatment of the cobalt base alloy after cold working produced carbide precipitates with retention of an hcp epsilon phase which increased the yield strength level. High strength alloys can be produced which have some resistance to degradation of mechanical properties by a hydrogen environment under certain conditions.

  10. Cyclic and Linear Polarization of Yttrium-Containing Iron-Based Amorphous Alloys

    SciTech Connect

    Day, S D; Lian, T; Farmer, J C; Rebak, R B

    2007-08-10

    Iron-based amorphous alloys are produced by rapid solidification from the melt. These alloys may possess unique mechanical and corrosion resistant properties. The chemical composition of the alloy may influence the cooling rate that is necessary for the alloys to be completely vitreous. At the same time, the corrosion resistance of the amorphous alloys may also depend on their chemical composition. This paper examines the anodic behavior of iron-based amorphous alloys containing three different concentrations (1, 3 and 5 atomic %) of yttrium (Y) in several electrolyte solutions. Results from polarization resistance potentiodynamic polarization show that when the alloy contains 5% atomic Y, the corrosion resistance decreases.

  11. Durable pd-based alloy and hydrogen generation membrane thereof

    DOEpatents

    Benn, Raymond C.; Opalka, Susanne M.; Vanderspurt, Thomas Henry

    2010-02-02

    A durable Pd-based alloy is used for a H.sub.2-selective membrane in a hydrogen generator, as in the fuel processor of a fuel cell plant. The Pd-based alloy includes Cu as a binary element, and further includes "X", where "X" comprises at least one metal from group "M" that is BCC and acts to stabilize the .beta. BCC phase for stability during operating temperatures. The metal from group "M" is selected from the group consisting of Fe, Cr, Nb, Ta, V, Mo, and W, with Nb and Ta being most preferred. "X" may further comprise at least one metal from a group "N" that is non-BCC, preferably FCC, that enhances other properties of the membrane, such as ductility. The metal from group "N" is selected from the group consisting of Ag, Au, Re, Ru, Rh, Y, Ce, Ni, Ir, Pt, Co, La and In. The at. % of Pd in the binary Pd--Cu alloy ranges from about 35 at. % to about 55 at. %, and the at. % of "X" in the higher order alloy, based on said binary alloy, is in the range of about 1 at. % to about 15 at. %. The metals are selected according to a novel process.

  12. Recrystallization characteristics of oxide dispersion strengthened nickel-base alloys

    NASA Technical Reports Server (NTRS)

    Hotzler, R. K.; Glasgow, T. K.

    1980-01-01

    Electron microscopy was employed to study the process of recrystallization in two oxide dispersion strengthened (ODS) mechanically alloyed nickel-base alloys, MA 754 and MA 6000E. MA 754 contained both fine, uniformly dispersed particles and coarser oxides aligned along the working direction. Hot rolled MA 754 had a grain size of 0.5 microns and high dislocation densities. After partial primary recrystallization, the fine grains transformed to large elongated grains via secondary (or abnormal) grain growth. Extruded and rolled MA 6000E contained equiaxed grains of 0.2 micron diameter. Primary recrystallization occurring during working eliminated virtually all dislocations. Conversion from fine to coarse grains was triggered by gamma prime dissolution; this was also a process of secondary or abnormal grain growth. Comparisons were made to conventional and oxide dispersion strengthened nickel-base alloys.

  13. Melting and casting of FeAl-based cast alloy

    SciTech Connect

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

    1998-11-01

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

  14. Cr{sub 2}Nb-based alloy development

    SciTech Connect

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A.; Easton, D.S.; Heatherly, L.

    1996-06-01

    The objective of this work is to develop a new generation of structural materials based on intermetallic alloys for use at high temperatures in advanced fossil energy conversion systems. Target applications of such ultrahigh strength alloys include hot components (for example, air heat exchangers) in advanced energy conversion systems and heat engines. However, these materials may also find use as wear-resistant parts in coal handling systems (for example, nozzles), drill bits for oil/gas wells, and valve guides in diesel engines. One potential class of such alloys is that based on Cr-Cr{sub 2}Nb alloys. The intermetallic phase, Cr{sub 2}Nb, with a complex cubic structure (C-15) has been selected for initial development because of its high melting point (1770{degrees}C), relatively low material density (7.7 g/cm{sup 2}), and excellent high-temperature strength (at 1000 to 1250{degrees}C). This intermetallic phase, like many other Laves phases, has a wide range of compositional homogeneity suggesting the possibility of improving its mechanical and metallurgical properties by alloying additions.

  15. The effect of selected alloying element additions on properties of Mg-based alloy as bioimplants: A literature review

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Nan; Hou, Zeng-Tao; Ye, Xin; Xu, Zhao-Bin; Bai, Xue-Ling; Shang, Peng

    2013-09-01

    This review investigates the current application limitations of Mg and Mg alloys. The key issues hindering the application of biodegradable Mg alloys as implants are their fast degradation rate and biological consideration. We have discussed the effect of some selected alloying element additions on the properties of the Mg-based alloy, especially the nutrient elements in human (Zn, Mn, Ca, Sr). Different grain sizes, phase constituents and distributions consequently influence the mechanical properties of the Mg alloys. Solution strengthening and precipitation strengthening are enhanced by the addition of alloying elements, generally improving the mechanical properties. Besides, the hot working process can also improve the mechanical properties. Combination of different processing steps is suggested to be adopted in the fabrication of Mg-based alloys. Corrosion properties of these Mg-based alloys have been measured in vitro and in vivo. The degradation mechanism is also discussed in terms of corrosion types, rates, byproducts and response of the surrounding tissues. Moreover, the clinical response and requirements of degradable implants are presented, especially for the nutrient elements (Ca, Mn, Zn, Sr). This review provides information related to different Mg alloying elements and presents the promising candidates for an ideal implant.

  16. Microfluidic platforms for gallium-based liquid metal alloy

    NASA Astrophysics Data System (ADS)

    Kim, Daeyoung

    As an alternative to toxic mercury, non-toxic gallium-based liquid metal alloy has been gaining popularity due to its higher thermal and electrical conductivities, and low toxicity along with liquid property. However, it is difficult to handle as the alloy becomes readily oxidized in atmospheric air environment. This instant oxidation causes the gallium-based liquid metal alloy to wet almost any solid surface. Therefore, it has been primarily limited to applications which rely only on its deformability, not on its mobility. In this research, various approaches to mobilize gallium-based liquid metal alloy were investigated. Multi-scale surface patterned with polydimethylsiloxane (PDMS) micro pillar array showed super-lyophobic property against gallium-based liquid metal alloy by minimizing the contact area between the solid surface and the liquid metal, and it was expanded to a three-dimensional tunnel shaped microfluidic channel. Vertically-aligned carbon nanotube forest leads to another promising super-lyophobic surface due to its hierarchical micro/nano scale combined structures and chemical inertness. When the carbon nanotubes were transferred onto flexible PDMS by imprinting, the super-lyophobic property was still maintained even under the mechanical deformation such as stretching and bending. Alternatively, the gallium-based liquid metal can be manipulated by modifying the surface of liquid metal itself. With chemical reaction with HCl 'vapor', the oxidized surface (mainly Ga2O3/Ga2O) of gallium-based liquid metal was converted to GaCl3/InCl 3 resulting in the recovery of non-wetting characteristics. Paper which is intrinsically porous is attractive as a super-lyophobic surface and it was found that hydrochloric acid (HCl) impregnation enhanced the anti-wetting property by the chemical reaction. As another alternative method, by coating the viscoelastic oxidized surface of liquid metal with ferromagnetic materials (CoNiMnP or Fe), it showed non

  17. [Dimensional changes of silver and gallium-based alloy].

    PubMed

    Ballester, R Y; Markarian, R A; Loguercio, A D

    2001-01-01

    Gallium-based dental alloys were created with the aim of solving the problem of toxicity of mercury. The material shows mechanical properties similar to those of dental amalgam, but researches point out two unfavorable characteristics: great corrosion and excessive post-setting expansion, and the latter is capable of cracking dental structures. The aim of this study was to evaluate, during 7 days, the in vitro dimensional alteration of a gallium dental alloy (Galloy, SDI, Australia), in comparison with a dental amalgam containing zinc (F400, SDI, Australia), as a function of the contact with saline solution (0.9% NaCl) during the setting period. The storage experimental conditions were: storage in dry environment, immersion in saline solution and contamination during condensation. Additionally, the effects of contamination during the trituration of dental amalgam and the effects of protecting the surface of the gallium alloy with a fluid resin were studied. Specimens were stored at 37 degrees C +/- 1 degree C, and measuring was carried out, sequentially, every 24 h during 7 days. When the gallium alloy was either contaminated or immersed, an expansion significantly greater than that observed in the other experimental conditions was noticed after 7 days. The application of a fluid resin to protect the surface of the cylinders was able to avoid the increase in expansion caused by superficial moisture. The amalgam alloy did not show significant dimensional alterations, except when it was contaminated during trituration.

  18. Thermodynamic and structural properties of Bi-based liquid alloys

    NASA Astrophysics Data System (ADS)

    Yadav, S. K.; Jha, L. N.; Adhikari, D.

    2015-10-01

    Thermodynamic and microscopic structural properties of two Bi-based liquid alloys, such as In-Bi at 900 K and Tl-Bi at 750 K have been studied employing the regular associated solution model. We have estimated the mole fractions of the complexes and the free monomers assuming the existence of complexes In2 Bi in In-Bi melt and TlBi in Tl-Bi melt. The thermodynamic properties have been studied by computing the Gibbs free energy of mixing, enthalpy of mixing, entropy of mixing and activities of the monomers. The compositional contributions of the heat associated with the formation of complexes and the heat of mixing of the monomers to the net enthalpy change has also been studied. The structural properties of the liquid alloys have been studied by computing concentration fluctuation in the long-wavelength limit, chemical short-range order parameter and the ratio of mutual to intrinsic diffusion coefficients. For both of the alloy systems, the theoretical as well as the experimental values of SCC (0) are found to be lower than the corresponding ideal values over the whole composition range, indicating the hetero-coordinating nature of Bi-In and Bi-Tl alloy melts. All the interaction energy parameters are found to be negative and temperature dependent, and both the alloy systems are found to be weakly interacting.

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

    DOEpatents

    Flinn, John E.

    1998-01-01

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

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

    DOEpatents

    Flinn, J.E.

    1998-11-03

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

  1. Hot corrosion of S-57, 1 cobalt-base alloy

    NASA Technical Reports Server (NTRS)

    Santoro, G. J.

    1977-01-01

    A cobalt base alloy, S-57, was hot corrosion tested in Mach 0.3 burner rig combustion gases at maximum alloy temperatures of 900 and 1000 C. Various salt concentrations were injected into the burner: 0.5, 2, 5, and 10 ppm synthetic sea salt and 4 ppm sodium sulfate (Na2SO4). S-57 underwent accelerated corrosion only under the most severe test conditions, for example, 4 ppm Na2SO4 at 900 C. The process of the accelerated corrosion was primarily sulfidation.

  2. Improved Mg-based alloys for hydrogen storage

    SciTech Connect

    Sapru, K.; Ming, L.; Stetson, N.T.; Evans, J.

    1998-08-01

    The overall objective of this on-going work is to develop low temperature alloys capable of reversibly storing at least 3 wt.% hydrogen, allowing greater than for 2 wt.% at the system level which is required by most applications. Surface modification of Mg can be used to improve its H-sorption kinetics. The authors show here that the same Mg-transition metal-based multi-component alloy when prepared by melt-spinning results in a more homogeneous materials with a higher plateau pressure as compared to preparing the material by mechanical grinding. They have also shown that mechanically alloyed Mg{sub 50}Al{sub 45}Zn{sub 5} results in a sample having a higher plateau pressure.

  3. Enhanced Corrosion Resistance of Iron-Based Amorphous Alloys

    SciTech Connect

    Rebak, R B; Day, S D; Lian, T; Aprigliano, L F; Hailey, P D; Farmer, J C

    2007-02-18

    Iron-based amorphous alloys possess enhanced hardness and are highly resistant to corrosion, which make them desirable for wear applications in corrosive environments. It was of interest to examine the behavior of amorphous alloys during anodic polarization in concentrated salt solutions and in the salt-fog testing. Results from the testing of one amorphous material (SAM2X5) both in ribbon form and as an applied coating are reported here. Cyclic polarization tests were performed on SAM2X5 ribbon as well as on other nuclear engineering materials. SAM2X5 showed the highest resistance to localized corrosion in 5 M CaCl{sub 2} solution at 105 C. Salt fog tests of 316L SS and Alloy 22 coupons coated with amorphous SAM2X5 powder showed resistance to rusting. Partial devitrification may be responsible for isolated pinpoint rust spots in some coatings.

  4. Nickel base alloy. [for gas turbine engine stator vanes

    NASA Technical Reports Server (NTRS)

    Freche, J. C.; Waters, W. J. (Inventor)

    1977-01-01

    A nickel base superalloy for use at temperatures of 2000 F (1095 C) to 2200 F (1205 C) was developed for use as stator vane material in advanced gas turbine engines. The alloy has a nominal composition in weight percent of 16 tungsten, 7 aluminum, 1 molybdenum, 2 columbium, 0.3 zirconium, 0.2 carbon and the balance nickel.

  5. Bulk amorphous steels based on Fe alloys

    DOEpatents

    Lu, ZhaoPing; Liu, Chain T.

    2006-05-30

    A bulk amorphous alloy has the approximate composition: Fe.sub.(100-a-b-c-d-e)Y.sub.aMn.sub.bT.sub.cM.sub.dX.sub.e wherein: T includes at least one of the group consisting of: Ni, Cu, Cr and Co; M includes at least one of the group consisting of W, Mo, Nb, Ta, Al and Ti; X includes at least one of the group consisting of Co, Ni and Cr; a is an atomic percentage, and a<5; b is an atomic percentage, and b.ltoreq.25; c is an atomic percentage, and c.ltoreq.25; d is an atomic percentage, and d.ltoreq.25; and e is an atomic percentage, and 5.ltoreq.e.ltoreq.30.

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

    DOEpatents

    Mariani, Robert Dominick

    2014-09-09

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

  7. Electrochemical hydrogen storage alloys and batteries fabricated from Mg containing base alloys

    DOEpatents

    Ovshinsky, Stanford R.; Fetcenko, Michael A.

    1996-01-01

    An electrochemical hydrogen storage material comprising: (Base Alloy).sub.a M.sub.b where, Base Alloy is an alloy of Mg and Ni in a ratio of from about 1:2 to about 2:1, preferably 1:1; M represents at least one modifier element chosen from the group consisting of Co, Mn, Al, Fe, Cu, Mo, W, Cr, V, Ti, Zr, Sn, Th, Si, Zn, Li, Cd, Na, Pb, La, Mm, and Ca; b is greater than 0.5, preferably 2.5, atomic percent and less than 30 atomic percent; and a+b=100 atomic percent. Preferably, the at least one modifier is chosen from the group consisting of Co, Mn, Al, Fe, and Cu and the total mass of the at least one modifier element is less than 25 atomic percent of the final composition. Most preferably, the total mass of said at least one modifier element is less than 20 atomic percent of the final composition.

  8. Hydrogen uptake characteristics of mischmetal based alloy

    NASA Astrophysics Data System (ADS)

    Jain, Ankur; Jain, R. K.; Jain, I. P.

    Hydrogen storage properties of Mm 39.2Ni 42.1Mn 4.9Al 1.25Co 10.2Fe 2.35 alloy have been systematically studied in the present work. An attempt is made to relate the content of hydrogen with change in resistance. It is found that the resistance of material increases with the increase in value of H/ M due to hydrogen absorption. Pressure composition (P-C-T) isotherm using water displacement method has been investigated in the temperature and pressure ranges of 308 ≤ T ≤ 338 K and 0.5 ≤ P ≤ 10 bar, respectively. The P-C isotherms show the presence of two single α and β regions one mixed α + β phase. The maximum H (wt%) was found to be around 1.53 at 308 K and around 6 bar. Since enthalpy is an index of thermochemical stability of metal hydride the thermo dynamical parameters viz., the relative partial molar enthalpy (Δ H) and relative partial molar entropy (Δ S) of dissolved hydrogen have been calculated by plotting the Van't Hoff plot. The variation of Δ H and Δ S with the hydrogen concentration confirm the phase boundaries.

  9. Ni3Al-based alloys for die and tool application

    DOEpatents

    Liu, Chain T.; Bloom, Everett E.

    2001-01-01

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

  10. Studies of microstructural imperfections of powdered Zirconium-based alloys

    SciTech Connect

    Chowdhury, P.S.; Mukherjee, P.

    2010-11-15

    Different model based approaches of X-ray diffraction line profile analysis have been applied on the heavily deformed zirconium-based alloys in the powdered form to characterize the microstructural parameters like domain size, microstrain and dislocation density. In characterizing the microstructure of the material, these methods are complimentary to each other. Though the parameters obtained by different techniques are differently defined and thus not necessarily comparable, the values of domain size and microstrain obtained from the different techniques show similar trends.

  11. 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.

  12. 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.

  13. Elevated temperature tribology of cobalt and tantalum-based alloys

    DOE PAGES

    Scharf, T. W.; Prasad, S. V.; Kotula, P. G.; Michael, J. R.; Robino, C. V.

    2014-12-31

    This paper describes the friction and wear behavior of a Co–Cr alloy sliding on a Ta–W alloy. Measurements were performed in a pin-on-flat configuration with a hemispherically tipped Co-base alloy pin sliding on a Ta–W alloy flat from ambient to 430°C. Focused ion beam-scanning electron microscopy (FIB-SEM) and cross-sectional transmission electron microscopy (TEM) were used to identify the friction-induced changes to the chemistry and crystal structure in the subsurface regions of wear tracks. During sliding contact, transfer of material varied as a function of the test temperature, either from pin-to-flat, flat-to-pin, or both, resulting in either wear loss and/or volumemore » gain. Friction coefficients (μ) and wear rates also varied as a function of test temperature. The lowest friction coefficient (μ=0.25) and wear rate (1×10–4 mm3/N•m) were observed at 430°C in argon atmosphere. This was attributed to the formation of a Co-base metal oxide layer (glaze), predominantly (Co, Cr)O with Rocksalt crystal structure, on the pin surface. Part of this oxide film transferred to the wear track on Ta–W, providing a self-mated oxide-on-oxide contact. Once the oxide glaze is formed, it is able to provide friction reduction for the entire temperature range of this study, ambient to 430°C. Furthermore, the results of this study indicate that glazing the surfaces of Haynes alloys with continuous layers of cobalt chrome oxide prior to wear could protect the cladded surfaces from damage.« less

  14. Elevated temperature tribology of cobalt and tantalum-based alloys

    SciTech Connect

    Scharf, T. W.; Prasad, S. V.; Kotula, P. G.; Michael, J. R.; Robino, C. V.

    2014-12-31

    This paper describes the friction and wear behavior of a Co–Cr alloy sliding on a Ta–W alloy. Measurements were performed in a pin-on-flat configuration with a hemispherically tipped Co-base alloy pin sliding on a Ta–W alloy flat from ambient to 430°C. Focused ion beam-scanning electron microscopy (FIB-SEM) and cross-sectional transmission electron microscopy (TEM) were used to identify the friction-induced changes to the chemistry and crystal structure in the subsurface regions of wear tracks. During sliding contact, transfer of material varied as a function of the test temperature, either from pin-to-flat, flat-to-pin, or both, resulting in either wear loss and/or volume gain. Friction coefficients (μ) and wear rates also varied as a function of test temperature. The lowest friction coefficient (μ=0.25) and wear rate (1×10–4 mm3/N•m) were observed at 430°C in argon atmosphere. This was attributed to the formation of a Co-base metal oxide layer (glaze), predominantly (Co, Cr)O with Rocksalt crystal structure, on the pin surface. Part of this oxide film transferred to the wear track on Ta–W, providing a self-mated oxide-on-oxide contact. Once the oxide glaze is formed, it is able to provide friction reduction for the entire temperature range of this study, ambient to 430°C. Furthermore, the results of this study indicate that glazing the surfaces of Haynes alloys with continuous layers of cobalt chrome oxide prior to wear could protect the cladded surfaces from damage.

  15. Octonary resistance states in La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 multiferroic tunnel junctions

    DOE PAGES

    Yue -Wei Yin; Tao, Jing; Huang, Wei -Chuan; Liu, Yu -Kuai; Yang, Sheng -Wei; Dong, Si -Ning; Zhu, Yi -Mei; Li, Qi; Li, Xiao -Guang

    2015-10-06

    General drawbacks of current electronic/spintronic devices are high power consumption and low density storage. A multiferroic tunnel junction (MFTJ), employing a ferroelectric barrier layer sandwiched between two ferromagnetic layers, presents four resistance states in a single device and therefore provides an alternative way to achieve high density memories. Here, an MFTJ device with eight nonvolatile resistance states by further integrating the design of noncollinear magnetization alignments between the ferromagnetic layers is demonstrated. Through the angle-resolved tunneling magnetoresistance investigations on La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 junctions, it is found that, besides collinear parallel/antiparallel magnetic configurations, the MFTJ shows at least two other stable noncollinear (45°more » and 90°) magnetic configurations. As a result, combining the tunneling electroresistance effect caused by the ferroelectricity reversal of the BaTiO3 barrier, an octonary memory device is obtained, representing potential applications in high density nonvolatile storage in the future.« less

  16. Microstructure Evolution of Gas Atomized Iron Based ODS Alloys

    SciTech Connect

    Rieken, J.R.; Anderson, I.E.; Kramer, M.J.

    2011-08-09

    In a simplified process to produce precursor powders for oxide dispersion-strengthened (ODS) alloys, gas-atomization reaction synthesis (GARS) was used to induce a surface oxide layer on molten droplets of three differing erritic stainless steel alloys during break-up and rapid solidification. The chemistry of the surface oxide was identified using auger electron spectroscopy (AES) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The precursor iron-base powders were consolidated at 850 C and 1,300 C using hot isostatic pressing (HIPing). Consolidation at the lower temperature resulted in a fully dense microstructure, while preventing substantial prior particle-boundary-oxide dissociation. Microstructural analysis of the alloys consolidated at the higher temperature confirmed a significant reduction in prior-particle-boundary-oxide volume fraction, in comparison with the lower-temperature-consolidated sample. This provided evidence that a high-temperature internal oxygen-exchange reaction occurred between the metastable prior particle-boundary-oxide phase (chromium oxide) and the yttrium contained within each prior particle. This internal oxygen-exchange reaction is shown to result in the formation of yttrium-enriched oxide dispersoids throughout the alloy microstructure. The evolving microstructure was characterized using transmission electron microscopy (TEM) and high-energy X-ray diffraction (HE-XRD).

  17. Microstructure Evolution of Gas Atomized Iron Based ODS Alloys

    SciTech Connect

    Rieken, J.R.; Anderson, I.E.; Kramer, M.J.; Anderegg, J.W.; Shechtman, D.

    2009-12-01

    In a simplified process to produce precursor powders for oxide dispersion-strength- ened (ODS) alloys, gas-atomization reaction synthesis (GARS) was used to induce a surface oxide layer on molten droplets of three differing erritic stainless steel alloys during break-up and rapid solidification. The chemistry of the surface oxide was identified using auger electron spectroscopy (AES) and scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS). The precursor iron-base powders were consolidated at 850 C and 1,300 C using hot isostatic pressing (HIPing). Consolidation at the lower temperature resulted in a fully dense microstructure, while preventing substantial prior particle-boundary-oxide dissociation. Microstructural analysis of the alloys consolidated at the higher temperature confirmed a significant reduction in prior-particle-boundary-oxide volume fraction, in comparison with the lower-temperature-consolidated sample. This provided evidence that a high-temperature internal oxygen-exchange reaction occurred between the metastable prior particle-boundary-oxide phase (chromium oxide) and the yttrium contained within each prior particle. This internal oxygen-exchange reaction is shown to result in the formation of yttrium-enriched oxide dispersoids throughout the alloy microstructure. The evolving microstructure was characterized using transmission electron microscopy (TEM) and high-energy X-ray diffraction (HE-XRD).

  18. Tungsten wire-nickel base alloy composite development

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  19. Electronic Structure Calculations of delta-Pu Based Alloys

    SciTech Connect

    Landa, A; Soderlind, P; Ruban, A

    2003-11-13

    First-principles methods are employed to study the ground-state properties of {delta}-Pu-based alloys. The calculations show that an alloy component larger than {delta}-Pu has a stabilizing effect. Detailed calculations have been performed for the {delta}-Pu{sub 1-c}Am{sub c} system. Calculated density of Pu-Am alloys agrees well with the experimental data. The paramagnetic {yields} antiferromagnetic transition temperature (T{sub c}) of {delta}-Pu{sub 1-c}Am{sub c} alloys is calculated by a Monte-Carlo technique. By introducing Am into the system, one could lower T{sub c} from 548 K (pure Pu) to 372 K (Pu{sub 70}Am{sub 30}). We also found that, contrary to pure Pu where this transition destabilizes {delta}-phase, Pu{sub 3}Am compound remains stable in the antiferromagnetic phase that correlates with the recent discovery of a Curie-Weiss behavior of {delta}-Pu{sub 1-c}Am{sub c} at c {approx} 24 at. %.

  20. Dendritic growth and structure of undercooled nickel base alloys

    NASA Technical Reports Server (NTRS)

    Flemings, M. C.; Shiohara, Y.

    1988-01-01

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

  1. Synthesis and characterization of nanostructured palladium-based alloy electrocatalysts

    NASA Astrophysics Data System (ADS)

    Sarkar, Arindam

    Low temperature fuel cells like proton exchange membrane fuel cells (PEMFC) are expected to play a crucial role in the future hydrogen economy, especially for transportation applications. These electrochemical devices offer significantly higher efficiency compared to conventional heat engines. However, use of exotic and expensive platinum as the electrocatalyst poses serious problems for commercial viability. In this regard, there is an urgent need to develop low-platinum or non-platinum electrocatalysts with electrocatalytic activity for the oxygen reduction reaction (ORR) superior or comparable to that of platinum. This dissertation first investigates non-platinum, palladium-based alloy electrocatalysts for ORR. Particularly, Pd-M (M = Mo and W) alloys are synthesized by a novel thermal decomposition of organo-metallic precursors. The carbon-supported Pd-M (M = Mo, W) electrocatalyts are then heat treated up to 900°C in H2 atmosphere and investigated for their phase behavior. Cyclic voltammetry (CV) and rotating disk electrode (RDE) measurements reveal that the alloying of Pd with Mo or W significantly enhances the catalytic activity for ORR as well as the stability (durability) of the electrocatalysts. Additionally, both the alloy systems exhibit high tolerance to methanol, which is particularly advantageous for direct methanol fuel cells (DMFC). The dissertation then focuses on one-pot synthesis of carbon-supported multi-metallic Pt-Pd-Co nanoalloys by a rapid microwave-assisted solvothermal (MW-ST) method. The multi-metallic alloy compositions synthesized by the MW-ST method show much higher catalytic activity for ORR compared to their counterparts synthesized by the conventional borohydride reduction method. Additionally, a series of Pt encapsulated Pd-Co nanoparticle electrocatalysts are synthesized by the MW-ST method and characterized to understand their phase behavior, surface composition, and electrocatalytic activity for ORR. Finally, the dissertation

  2. Cr{sub 2}Nb-based alloy development

    SciTech Connect

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A.

    1995-06-01

    The objective of this task is to develop a new generation of structural materials based on intermetallic alloys for use as critical hot components in advanced fossil energy conversion systems. The intermetallic phase, Cr{sub 2}Nb, with a complex cubic structure (C-15) has been selected for this development because of its high melting point (1770{degrees}C), relatively low material density (7.7 g/cm{sup 2}), excellent high-temperature strength (at 1000 to 1250{degrees}C), and potential resistance to oxidation and corrosion. This intermetallic phase, like many other Laves phases, has a wide range of compositional homogeneity suggesting the possibility of improving its mechanical and metallurgical properties by alloying additions. The major engineering concern with Cr{sub 2}Nb and other A{sub 2}B Laves phases is their poor fracture toughness and fracture resistance at ambient temperatures. The single-phase Cr{sub 2}Nb is very hard ({approximately}800 DPH) and brittle at room temperature. Because of this brittleness, the development effort has concentrated on two-phase structures containing the hard intermetallic phase Cr{sub 2}Nb and the softer Cr-rich solid solution phase. Potential applications of Cr-Cr{sub 2}Nb alloys include hot components (for example, air heat exchangers and turbine blades) in advanced energy conversion systems and heat engines, wear-resistant parts in coal handling systems (e.g., nozzles), drill bits for oil/gas wells, and valve guides in diesel engines. Current studies are focuses on enhancement of fracture resistance in tension at ambient temperatures and oxidation resistance above 1000{degrees}C. This report summarizes recent progress on controlling microstructure and improving the mechanical and metallurgical properties and the high-temperature corrosion behavior of Cr-Cr{sub 2}Nb alloys through alloying conditions, material processing, and heat treatment.

  3. Attack polish for nickel-base alloys and stainless steels

    DOEpatents

    Steeves, Arthur F.; Buono, Donald P.

    1983-01-01

    A chemical attack polish and polishing procedure for use on metal surfaces such as nickel base alloys and stainless steels. The chemical attack polish comprises Fe(NO.sub.3).sub.3, concentrated CH.sub.3 COOH, concentrated H.sub.2 SO.sub.4 and H.sub.2 O. The polishing procedure includes saturating a polishing cloth with the chemical attack polish and submicron abrasive particles and buffing the metal surface.

  4. Attack polish for nickel-base alloys and stainless steels

    DOEpatents

    Not Available

    1980-05-28

    A chemical attack polish and polishing procedure for use on metal surfaces such as nickel base alloys and stainless steels is described. The chemical attack polich comprises FeNO/sub 3/, concentrated CH/sub 3/COOH, concentrated H/sub 2/SO/sub 4/ and H/sub 2/O. The polishing procedure includes saturating a polishing cloth with the chemical attack polish and submicron abrasive particles and buffing the metal surface.

  5. Method of polishing nickel-base alloys and stainless steels

    DOEpatents

    Steeves, Arthur F.; Buono, Donald P.

    1981-01-01

    A chemical attack polish and polishing procedure for use on metal surfaces such as nickel base alloys and stainless steels. The chemical attack polish comprises Fe(NO.sub.3).sub.3, concentrated CH.sub.3 COOH, concentrated H.sub.2 SO.sub.4 and H.sub.2 O. The polishing procedure includes saturating a polishing cloth with the chemical attack polish and submicron abrasive particles and buffing the metal surface.

  6. Perspectives on radiation effects in nickel-base alloys for applications in advanced reactors

    NASA Astrophysics Data System (ADS)

    Rowcliffe, A. F.; Mansur, L. K.; Hoelzer, D. T.; Nanstad, R. K.

    2009-07-01

    Because of their superior high temperature strength and corrosion properties, a set of Ni-base alloys has been proposed for various in-core applications in Gen IV reactor systems. However, irradiation-performance data for these alloys is either limited or non-existent. A review is presented of the irradiation-performance of a group of Ni-base alloys based upon data from fast breeder reactor programs conducted in the 1975-1985 timeframe with emphasis on the mechanisms involved in the loss of high temperature ductility and the breakdown in swelling resistance with increasing neutron dose. The implications of these data for the performance of the Gen IV Ni-base alloys are discussed and possible pathways to mitigate the effects of irradiation on alloy performance are outlined. A radical approach to designing radiation damage-resistant Ni alloys based upon recent advances in mechanical alloying is also described.

  7. An investigation of the initiation stage of hot corrosion in Ni-base alloys

    NASA Technical Reports Server (NTRS)

    Huang, T. T.; Meier, G. H.

    1979-01-01

    The commercial nickel base alloy, IN-738, and high purity laboratory alloys were prepared to simulate the effects of the major elements in IN-738. Results indicate that the initiation of hot corrosion attack of IN-738 and other similar alloys is the result of local penetration of molten salt through the protective oxide scale.

  8. Iron-based alloys with corrosion resistance to oxygen-sulfur mixed gases

    DOEpatents

    Natesan, Krishnamurti

    1992-01-01

    An iron-based alloy with improved performance with exposure to oxygen-sulfur mixed gases with the alloy containing about 9-30 wt. % Cr and a small amount of Nb and/or Zr implanted on the surface of the alloy to diffuse a depth into the surface portion, with the alloy exhibiting corrosion resistance to the corrosive gases without bulk addition of Nb and/or Zr and without heat treatment at temperatures of 1000.degree.-1100.degree. C.

  9. Iron-based alloys with corrosion resistance to oxygen-sulfur mixed gases

    DOEpatents

    Natesan, K.

    1992-11-17

    An iron-based alloy with improved performance with exposure to oxygen-sulfur mixed gases with the alloy containing about 9--30 wt. % Cr and a small amount of Nb and/or Zr implanted on the surface of the alloy to diffuse a depth into the surface portion, with the alloy exhibiting corrosion resistance to the corrosive gases without bulk addition of Nb and/or Zr and without heat treatment at temperatures of 1000--1100 C. 7 figs.

  10. Resistance of a directionally solidified gamma/gamma prime-delta eutectic alloy to recrystallization. [Ni-base alloy

    NASA Technical Reports Server (NTRS)

    Tewari, S. N.; Scheuermann, C. M.; Andrews, C. W.

    1976-01-01

    A lamellar nickel-base directionally-solidified eutectic gamma/gamma prime-delta alloy has potential as an advanced gas turbine blade material. The microstructural stability of this alloy was investigated. Specimens were plastically deformed by uniform compression or Brinell indentation, then annealed between 750 and 1120 C. Microstructural changes observed after annealing included gamma prime coarsening, pinch-off and spheroidization of delta lamellae, and appearance of an unidentified blocky phase in surface layers. All but the first of these was localized in severely deformed regions, suggesting that microstructural instability may not be a serious problem in the use of this alloy.

  11. Cast iron-base alloy for cylinder/regenerator housing: Final report

    SciTech Connect

    Witter, S.L.; Simmons, H.E.; Woulds, M.J.

    1985-08-01

    The objective is to develop an Fe-base alloy that can meet the requirements of the automotive Stirling engine cylinders and regenerator housings. The scope of work was to test various alloys and select the one best demonstrating the following characteristics: It must be a cast alloy, using nonstrategic metals. It must withstand stresses for a 2500-hr rupture life at 200 MPa/775/degree/C. Oxidation/corrosion resistance must be comparable to that of N-155. It must be compatible with hydrogen. Fatigue properties must be superior to alloy XF 818. Cost must be less than or equal to that of 19-9DL. Major tests were designed to include the following: Selection, processing, and evaluation of candidate alloys within each alloy group system. Determination of casting parameters. Selection of a candidate alloy and establishment of a data base for this alloy. In the initial phase of the program designated as Round 1, a series of alloys representing each alloy system was cast and tested. In all there were 5 alloys of the nickel-manganese Group 1, 13 alloys of the nickel Group 2, and 3 alloys of the manganese Group 3. The aim was to maintain the chemistry of the major element(s) shown and vary the percentage of other elements to study their influence. Evaluation of results obtained from this series of tests enabled us to closely define the chemistry range for our candidate alloy, designated NASACC-1. A master heat was made to this composition. The heat was melted and poured under controlled casting conditions previously established and poured into investment shell molds. All castings and test bars were heat treated before actual testing. NASACC-1 proved to be an excellent alloy for casting. It could be melted in air and had good fluidity and fill characteristics. The alloy met or exceeded all program goals. 28 refs., 47 figs., 44 tabs.

  12. Role of alloying elements in adhesive transfer and friction of copper-base alloys

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1978-01-01

    Sliding friction experiments were conducted in a vacuum with binary-copper alloy riders sliding against a conventional bearing-steel surface with normal residual oxides present. The binary alloys contained 1 atomic percent of various alloying elements. Auger spectroscopy analysis was used to monitor the adhesive transfer of the copper alloys to the bearing-steel surface. A relation was found to exist between adhesive transfer and the reaction potential and free energy of formation of the alloying element in the copper. The more chemically active the element and the more stable its oxide, the greater was the adhesive transfer and wear of the copper alloy. Transfer occurred in all the alloys except copper-gold after relatively few (25) passes across the steel surface.

  13. Alloys based on NiAl for high temperature applications

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  14. Characterization of cold-sprayed nanostructured Fe-based alloy

    NASA Astrophysics Data System (ADS)

    Li, Wen-Ya; Li, Chang-Jiu

    2010-01-01

    The ball-milled Fe-Si alloy was used as feedstock for deposition of nanocrystalline Fe-Si by cold spraying process. The microstructure of the as-sprayed nanostructured Fe-Si was characterized by using optical microscopy, scanning electron microscopy and transmission electron microscopy. The grain sizes of the feedstock and as-sprayed deposit were estimated based on X-ray diffraction analysis. The microhardness and coercivity of the deposited Fe-Si alloy were characterized. The results showed that the as-sprayed deposit presented a dense microstructure. The mean grain size of the as-deposited Fe-Si was several tens nanometers and comparable to that of the corresponding milled feedstock. The temperature of driving gas presented little effect on the microstructure of cold-sprayed nanostructured Fe-Si deposit. The mechanical alloying induced oxygen contents up to 8 wt% in the feedstocks and subsequent deposits. The microhardness of the deposit reached about 400 Hv. The deposit achieved a high coercivity up to 190 kA/m indicating the potential possibility for applications to recording materials.

  15. Aqueous electrochemistry of precipitation-hardened nickel base alloys

    SciTech Connect

    Hosoya, K.; Ballinger, R.; Prybylowski, J.; Hwang, I.S. )

    1990-11-01

    An investigation has been conducted to explore the importance of local crack tip electrochemical processes in precipitation-hardened Ni-Cr-Fe alloys driven by galvanic couples between grain boundary precipitates and the local matrix. The electrochemical behavior of {gamma}{prime} (Ni{sub 3}(Al,Ti)) has been determined as a function of titanium concentration, temperature, and solution pH. The electrochemical behavior of Ni-Cr-Fe solid solution alloys has been investigated as a function of chromium content for a series of 10 Fe-variable Cr (6--18%)-balance Ni alloys, temperature, and pH. The investigation was conducted in neutral and pH3 solutions over the temperature range 25--300{degree}C. The results of the investigation show that the electrochemical behavior of these systems is a strong function of temperature and composition. This is especially true for the {gamma}{prime} (Ni{sub 3}(Al,Ti)) system where a transition from active/passive behavior to purely active behavior and back again occurs over a narrow temperature range near 100{degree}C. Behavior of this system was also found to be a strong function of titanium concentration. In all cases, the Ni{sub 3}(Al,Ti) phase was active with respect to the matrix. The peak in activity near 100{degree}C correlates well with accelerated crack growth in this temperature range, observed in nickel-base alloy X-750 heat treated to precipitate {gamma}{prime} on the grain boundaries. 20 refs., 23 figs., 3 tabs.

  16. Localized corrosion resistance of corrosion-resistant Ni based alloys in hot concentrated seawater

    SciTech Connect

    Sugahara, Katsuo; Takizawa, Yoshio

    1998-12-31

    Localized corrosion resistance of stainless steel (Type 316L), a titanium-based alloy (Ti-0.15Pd) and corrosion-resistant nickel-based alloys (a new alloy MAT-21 (Alloy T) and Alloy C-276) was evaluated in four simulated seawater solutions containing 1.8 to 22.0 wt% of chloride ions concentrated by evaporation. Stress corrosion cracking was observed on the 316L stainless steel but not on Alloy T and Alloy C-276 in the solutions. Pitting attack occurred on the surface of the 316L stainless steel base metal in all the solutions. Alloy C-276 suffered pitting attack on the surface including the welded section only in the solutions containing 18.9 and 22.0 wt% of chloride ions, respectively. No pitting attack occurred over any part of the surface including the welded section of Alloy T in any of the solutions. No crevice corrosion was observed in an immersion test of Alloy T and the Ti-0.15 5Pd alloy using test pieces with crevices although crevice corrosion was seen the creviced test pieces of Alloy C-276 and the 316L stainless steel. It was found that both Alloy T and the Ti-0.15Pd alloy, which exhibit high repassivation potentials for crevice corrosion (E{sub r,CREV})corresponding to crevice corrosion potentials, have excellent crevice corrosion resistance, while these alloys which exhibit corrosion potentials greater than E{sub r,CREV}in a solution with a high chloride ion concentration and a high dissolved oxygen concentration in open air may be corroding in the crevices.

  17. Chemical Compatibility of Barium-Calcium-Aluminosilicate Based Sealing Glasses with Heat Resistant Alloys

    SciTech Connect

    Yang, Z Gary; Weil, K. Scott; Meinhardt, Kerry D.; Stevenson, Jeffry W.; Paxton, Dean M.; Xia, Gordon; Kim, Dong-Sang

    2003-09-15

    Over the past several years, advances in the design and fabrication of planar SOFCs have led to a steady reduction in the temperatures necessary for their operation. Consequently, it appears more realistic now to use low cost heat resistant alloys for interconnect sub-components in the SOFC stack. Considering these materials requirements, heat resistant alloys, which overall demonstrate oxidation resistance at elevated temperatures, could be potential candidates. Overall, the heat resistant alloys of interest may include superalloys and the stainless steels. Depending whether a chromia or alumina scale forms on the alloy surface for protection, these heat resistant alloys can be also classified into chromia or alumina formers, repetitively. To help screening alloys and understanding the interface of sealing glass, a couple of alloy compositions have been carefully chosen as a reprehensive of different groups of alloys for the study on their chemical compatibility with a barium-aluminosilicate base glass. These alloys selected are AL 29-4, Nicrofer 6025, and Fecralloy, representing chromia forming stainless steels, superalloys and alumina formers, respectively. Results of chemical and microstructural analyses on sealing glass interfaces with different alloys will be presented, and accordingly, the applicability of alloys in terms of sealing glass chemical compatibility will be discussed. Possible means of modification on alloys for an improved applicability will be elaborated as well.

  18. Compressive creep behavior of alloys based on B2 FeAl

    NASA Technical Reports Server (NTRS)

    Mantravadi, N.; Vedula, K.; Gaydosh, D.; Titran, R. H.

    1986-01-01

    Alloys based on FeAl are attractive alternate materials for environmental resistance at intermediate temperatures. Addition of small amounts of Nb, Hf, Ta, Mo, Zr, and B were shown to improve the compressive creep of this alloy at 1100 K. Boron, in particular, was found to have a synergistic effect along with Zr in providing properties substantially better than the binary alloy. This improvement seems to be related to the higher activation energy found for this alloy, suggesting a modification in the diffusion behavior due to the alloying additions.

  19. Compressive creep behavior of alloys based on B2 FeAl

    NASA Technical Reports Server (NTRS)

    Mantravadi, N.; Vedula, K.; Gaydosh, D.; Titran, R. H.

    1987-01-01

    Alloys based on FeAl are attractive alternative materials for environmental resistance at intermediate temperatures. Addition of small amounts of Nb, Hf, Ta, Mo, Zr, and B were shown to improve the compressive creep of this alloy at 1100 K. Boron, in particular, was found to have a synergistic effect along with Zr in providing properties substantially better than the binary alloy. This improvement seems to be related to the higher activation energy found for this alloy, suggesting a modification in the diffusion behavior due to the alloying additions.

  20. Thermogravimetric study of reduction of oxides present in oxidized nickel-base alloy powders

    NASA Technical Reports Server (NTRS)

    Herbell, T. P.

    1976-01-01

    Carbon, hydrogen, and hydrogen plus carbon reduction of three oxidized nickel-base alloy powders (a solid solution strengthened alloy both with and without the gamma prime formers aluminum and titanium and the solid solution strengthened alloy NiCrAlY) were evaluated by thermogravimetry. Hydrogen and hydrogen plus carbon were completely effective in reducing an alloy containing chromium, columbium, tantalum, molybdenum, and tungsten. However, with aluminum and titanium present the reduction was limited to a weight loss of about 81 percent. Carbon alone was not effective in reducing any of the alloys, and none of the reducing conditions were effective for use with NiCrAlY.

  1. On the corrosion behavior and biocompatibility of palladium-based dental alloys

    NASA Astrophysics Data System (ADS)

    Sun, Desheng

    Palladium-based alloys have been used as dental restorative materials for about two decades with good clinical history. But there have been clinical case reports showing possible allergy effects from these alloys. The aim of this study was to characterize the corrosion behavior and mechanisms of several palladium-based dental alloys by potentiodynamic polarization methods, electrochemical impedance spectroscopy (EIS), and scanning Kelvin probe force microscopy/atomic force microscopy (SKPFM/AFM), and to evaluate their biocompatibility by a cell culture technique and an animal model. Using SKPFM/AFM and scanning electron microscopy, the Ru-enriched phase from the use of ruthenium as a grain-refining element was identified as being slightly more noble than the palladium solid solution matrix in a high-palladium alloy. Other secondary precipitates that exist in the microstructures of these high-palladium alloys have minimal differences in Volta potential compared to the matrix. For high-palladium alloys, corrosion is generally uniform due to the predominant palladium content in the different phases. Potentiodynamic polarization and EIS have shown that representative palladium-silver alloys have low corrosion tendency and high corrosion resistance, which are equivalent to a well-known high-noble gold-palladium alloy in simulated body fluid and oral environments. The palladium-silver alloys tested are resistant to chloride ion corrosion. Passivation and dealloying have been identified for all of the tested palladium-silver alloys. The great similarity in corrosion behavior among the palladium-silver alloys is attributed to their similar chemical compositions. The variation in microstructures of palladium-silver alloys tested does not cause significant difference in corrosion behavior. The corrosion resistance of these palladium-silver alloys at elevated potentials relevant to oral environment is still satisfactory. The release of elements from representative dental

  2. DENSITY-FUNCTIONAL STUDY OF Zr-BASED ACTINIDE ALLOYS

    SciTech Connect

    Landa, A; Soderlind, P; Turchi, P; Vitos, L; Ruban, A

    2008-06-26

    Density-functional formalism is applied to study the phase equilibria in the U-Zr system. The obtained ground-state properties of the {gamma} (bcc) and {delta} (C32) phases are in good agreement with experimental data. The decomposition curve for the {gamma}-based U-Zr solutions is calculated. We argue that stabilization of the {delta}-UZr{sub 2} phase relative to the {alpha}-Zr (hcp) structure is due to an increase of the Zr d-band occupancy that occurs when U is alloyed with Zr.

  3. Solidification study of some Ni- and Co-base alloys

    NASA Technical Reports Server (NTRS)

    Jeanfils, C. L.

    1984-01-01

    An ongoing research program aims to characterize the solidification of several Ni- and Co-based commercial wrought type alloys. The techniques used and the data items sought are: (1) thermal analysis, liquidus, nonequilibrium solidus as a function of cooling rate, secondary reactions temperatures, incipient melting, progress of solidification as a function of temperature; (2) optical metallography, characteristic structures and secondary dendrite arm spacing as a function of cooling rate; (3) X-ray diffraction, identification of precipitates; and (4) SEM/EDAX, measure of microsegregation.

  4. Investigation on corrosion and wear behaviors of nanoparticles reinforced Ni-based composite alloying layer

    NASA Astrophysics Data System (ADS)

    Xu, Jiang; Tao, Jie; Jiang, Shuyun; Xu, Zhong

    2008-04-01

    In order to investigate the role of amorphous SiO 2 particles in corrosion and wear resistance of Ni-based metal matrix composite alloying layer, the amorphous nano-SiO 2 particles reinforced Ni-based composite alloying layer has been prepared by double glow plasma alloying on AISI 316L stainless steel surface, where Ni/amorphous nano-SiO 2 was firstly predeposited by brush plating. The composition and microstructure of the nano-SiO 2 particles reinforced Ni-based composite alloying layer were analyzed by using SEM, TEM and XRD. The results indicated that the composite alloying layer consisted of γ-phase and amorphous nano-SiO 2 particles, and under alloying temperature (1000 °C) condition, the nano-SiO 2 particles were uniformly distributed in the alloying layer and still kept the amorphous structure. The corrosion resistance of composite alloying layer was investigated by an electrochemical method in 3.5%NaCl solution. Compared with single alloying layer, the amorphous nano-SiO 2 particles slightly decreased the corrosion resistance of the Ni-Cr-Mo-Cu alloying layer. X-ray photoelectron spectroscopy (XPS) revealed that the passive films formed on the composite alloying consisted of Cr 2O 3, MoO 3, SiO 2 and metallic Ni and Mo. The dry wear test results showed that the composite alloying layer had excellent friction-reduced property, and the wear weight loss of composite alloying layer was less than 60% of that of Ni-Cr-Mo-Cu alloying layer.

  5. Defect Interaction in Iron and Iron-based Alloys

    NASA Astrophysics Data System (ADS)

    Xu, Haixuan; Stocks, G. Malcolm; Stoller, Roger

    2014-03-01

    Magnetism has a profound influence on the defect properties in iron and iron-based alloys. For instance, it has been shown from first principles calculations that the helium interstitial occupies the tetrahedral site instead of octahedral site in contrast to all previous work that neglected the magnetic effects. In this study, we explore the effects of magnetism on the defect interaction, primarily interstitial-type defects, in bcc iron and Fe-Cr systems. The magnetic moment change during the interaction of two 1/2 <111>interstitial loops in bcc iron was calculated using the ab initio locally self-consistent multiple-scattering (LSMS) method and a significant fluctuation was observed. Adding Cr significantly modifies the magnetic structure of the defects and defect interactions. In addition, the effects of magnetism on the defect energetics are evaluated. This study provides useful insights on whether magnetism can be used as a effective means to manipulate the defect evolution in iron-based structural alloys. This material is based upon work supported as part of the Center for Defect Physics, an Energy Frontier Research Center funded by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences.

  6. HIP clad nickel base Alloy 625 for deep sour wells

    SciTech Connect

    Uhl, W.K.; Pendley, M.R.

    1984-05-01

    The hot isostatic pressing (HIP) process was used to clad nickel base Alloy 625 to AISI 4130 low alloy steel. The performance of the HIP clad material in the corrosive environment characteristic of deep, sour oil and gas wells was evaluated in laboratory tests. Included in the test program were NACE TM-01-77 sulfide stress cracking tests, chloride stress corrosion cracking tests in boiling MgCl /SUB 2'/ , and pitting and crevice corrosion tests. The HIP clad 625 performed excellently, displaying essentially the same corrosion resistance as wrought 625. Specifically the HIP clad 625 resisted sulfide stress cracking at applied stresses as high as 120% of yield strength and resisted chloride stress corrosion cracking at stresses exceeding 100% of yield. The HIP clad 625 also displayed immunity to pitting and crevice corrosion, with corrosion rates of <0.025 mm/y (1 mil/y). The 4130 base metal, however, was attacked severly in all tests. SEM/EDX analysis of the 625/4130 interface demonstrated that dilution of the cladding by the base metal was essentially eliminated.

  7. Weld induced base metal microfissuring in high temperature alloys

    SciTech Connect

    Lingenfelter, A.C.; Shoemaker, L.E.

    1984-06-22

    Three variables control the weld-induced, base-metal microfissuring sensitivity of Ni-Cr and Ni-Cr-Fe: thermal/mechanical history of the base material, chemical analysis of the base material, and the welding process used. Elements which tend to segregate to the grain boundaries such as B, C, and Zr, and to a lesser extent P, Si, S and Mg, increase the sensitivity. Welding processes listed from most to least severe in their tendency to produce microfissures are: gas metal arc - spray transfer, electron beam, gas metal arc - pulsed transfer, gas metal arc - short circuiting transfer, gas tungsten arc, submerged arc, and shielded metal arc. Microfissuring is always intergranular in nature. Coarse-grain size, whether arrived at by hot-working procedures or pre-weld annealing treatment, increases the sensitivity to microfissuring. Literature data and data for alloy 617 developed at Huntington Alloys suggest that microfissures, at least to 0.030 in. in length, do not affect the fatigue life, room-temperature tensile, and stress-rupture properties of a weldment.

  8. Thermodynamic properties of uranium in gallium-aluminium based alloys

    NASA Astrophysics Data System (ADS)

    Volkovich, V. A.; Maltsev, D. S.; Yamshchikov, L. F.; Chukin, A. V.; Smolenski, V. V.; Novoselova, A. V.; Osipenko, A. G.

    2015-10-01

    Activity, activity coefficients and solubility of uranium was determined in gallium-aluminium alloys containing 1.6 (eutectic), 5 and 20 wt.% aluminium. Additionally, activity of uranium was determined in aluminium and Ga-Al alloys containing 0.014-20 wt.% Al. Experiments were performed up to 1073 K. Intermetallic compounds formed in the alloys were characterized by X-ray diffraction. Partial and excess thermodynamic functions of U in the studied alloys were calculated.

  9. Method for improve x-ray diffraction determinations of residual stress in nickel-base alloys

    DOEpatents

    Berman, Robert M.; Cohen, Isadore

    1990-01-01

    A process for improving the technique of measuring residual stress by x-ray diffraction in pieces of nickel-base alloys which comprises covering part of a predetermined area of the surface of a nickel-base alloy with a dispersion, exposing the covered and uncovered portions of the surface of the alloy to x-rays by way of an x-ray diffractometry apparatus, making x-ray diffraction determinations of the exposed surface, and measuring the residual stress in the alloy based on these determinations. The dispersion is opaque to x-rays and serves a dual purpose since it masks off unsatisfactory signals such that only a small portion of the surface is measured, and it supplies an internal standard by providing diffractogram peaks comparable to the peaks of the nickel alloy so that the alloy peaks can be very accurately located regardless of any sources of error external to the sample.

  10. Method for improving x-ray diffraction determinations of residual stress in nickel-base alloys

    DOEpatents

    Berman, R.M.; Cohen, I.

    1988-04-26

    A process for improving the technique of measuring residual stress by x-ray diffraction in pieces of nickel-base alloys is discussed. Part of a predetermined area of the surface of a nickel-base alloy is covered with a dispersion. This exposes the covered and uncovered portions of the surface of the alloy to x-rays by way of an x-ray diffractometry apparatus, making x-ray diffraction determinations of the exposed surface, and measuring the residual stress in the alloy based on these determinations. The dispersion is opaque to x-rays and serves a dual purpose, since it masks off unsatisfactory signals such that only a small portion of the surface is measured, and it supplies an internal standard by providing diffractogram peaks comparable to the peaks of the nickel alloy so that the alloy peaks can be very accurately located regardless of any sources of error external to the sample. 2 figs.

  11. MODELING OF NI-CR-MO BASED ALLOYS: PART II - KINETICS

    SciTech Connect

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

    2006-07-07

    The CALPHAD approach is applied to kinetic studies of phase transformations and aging of prototypes of Ni-Cr-Mo-based alloys selected for waste disposal canisters in the Yucca Mountain Project (YMP). Based on a previous study on alloy stability for several candidate alloys, the thermodynamic driving forces together with a newly developed mobility database have been used to analyze diffusion-controlled transformations in these Ni-based alloys. Results on precipitation of the Ni{sub 2}Cr-ordered phase in Ni-Cr and Ni-Cr-Mo alloys, and of the complex P- and {delta}-phases in a surrogate of Alloy 22 are presented, and the output from the modeling are compared with experimental data on aging.

  12. Effect of Alloy 625 Buffer Layer on Hardfacing of Modified 9Cr-1Mo Steel Using Nickel Base Hardfacing Alloy

    NASA Astrophysics Data System (ADS)

    Chakraborty, Gopa; Das, C. R.; Albert, S. K.; Bhaduri, A. K.; Murugesan, S.; Dasgupta, Arup

    2016-04-01

    Dashpot piston, made up of modified 9Cr-1Mo steel, is a part of diverse safety rod used for safe shutdown of a nuclear reactor. This component was hardfaced using nickel base AWS ER NiCr-B alloy and extensive cracking was experienced during direct deposition of this alloy on dashpot piston. Cracking reduced considerably and the component was successfully hardfaced by application of Inconel 625 as buffer layer prior to hardface deposition. Hence, a separate study was undertaken to investigate the role of buffer layer in reducing the cracking and on the microstructure of the hardfaced deposit. Results indicate that in the direct deposition of hardfacing alloy on modified 9Cr-1Mo steel, both heat-affected zone (HAZ) formed and the deposit layer are hard making the thickness of the hard layer formed equal to combined thickness of both HAZ and deposit. This hard layer is unable to absorb thermal stresses resulting in the cracking of the deposit. By providing a buffer layer of Alloy 625 followed by a post-weld heat treatment, HAZ formed in the modified 9Cr-1Mo steel is effectively tempered, and HAZ formed during the subsequent deposition of the hardfacing alloy over the Alloy 625 buffer layer is almost completely confined to Alloy 625, which does not harden. This reduces the cracking susceptibility of the deposit. Further, unlike in the case of direct deposition on modified 9Cr-1Mo steel, dilution of the deposit by Ni-base buffer layer does not alter the hardness of the deposit and desired hardness on the deposit surface could be achieved even with lower thickness of the deposit. This gives an option for reducing the recommended thickness of the deposit, which can also reduce the risk of cracking.

  13. Wear-resistant coatings for cobalt-base alloys

    SciTech Connect

    Cockeram, B.V.

    2000-04-01

    High interfacial stresses and coating failure are expected when a hard coating protects a more-compliant substrate in applications involving high-stress wear contact. Assuming that small differences in stiffness (or modulus) between the coating and substrate are required for a wear-resistant coating in such applications, four approaches have been taken to develop such coatings for cobalt-base alloys. Hardness, scratch adhesion, and nano-indentation testing identified the most promising candidates for cobalt-base alloys: A thin coating with hard Cr{sub 2}N and less-stiff Cr-N(ss) layers; a thick, four-layered coating with a 4{mu}m inner layer of Cr-N(ss)/ 1 {mu}m layer of Cr{sub 2}N/4 {micro}m layer of Cr-N(ss)/1 {micro} outer layer of Cr{sub 2}N; a duplex approach of ion nitriding to harden the subsurface,followed by application of a dual-layered Cr{sub 2}N/Cr-N(ss) coating; and ion nitriding alone. The low scratch adhesion values and high modulus/hardness values indicate that ZrN, TiN, and plasma carburized coatings represent less beneficial approaches. Two different cobalt-base alloys were studied in this work: Haynes 25 and Stellite 3 (Stoody Deloro Stellite). Based on weight change, profilometry measurements, and metallographic and SEM examinations after four-ball wear testing, the thin Cr{sub 2}N/CrN(ss) coated coupons exhibited a significantly lower wear rate than the uncoated Haynes 25 coupons. Of greater importance, the thin Cr{sub 2}N/Cr-N(ss) coatings were adherent on the Stellite 3 intermediate balls and Haynes 25 cups, and prevented the wear of the cobalt-base substrate. based on these results, the thin Cr{sub 2}N/Cr-N(ss) coating was the best coating candidate, and this coating could result in a reduced wear rate and less cobalt wear debris. The ion nitrided coupons exhibited slightly higher wear than the thin Cr{sub 2}N/Cr-N(ss) coated coupons, while the wear of the thin duplex coated coupons was the highest. However, the nitride layer was adherent

  14. Tarnish evaluation of gold-based dental alloys.

    PubMed

    Corso, P P; German, R M; Simmons, H D

    1985-05-01

    Three commercial gold dental alloys and three ternary (Au-Ag-Cu) alloys of constant nobility were subjected to a standardized test battery for tarnish. The tests included sodium sulfide and artificial saliva solutions, both at 37 degrees C, in sealed containers. Quantitative measurements of tarnish were made from the alloy color change during a three-day exposure. Alloy nobility is a relatively important factor in determining tarnish resistance; however, microstructure can have a negative effect on tarnish resistance. Alloys with a two-phase microstructure produce microgalvanic conditions which lead to either silver chloride or silver sulfide tarnish products. A solution heat treatment improves tarnish resistance by eliminating microstructural inhomogeneities.

  15. Near-Threshold Fatigue Crack Growth Behavior of Fine-Grain Nickel-Based Alloys

    NASA Technical Reports Server (NTRS)

    Newman, John A.; Piascik, Robert S.

    2003-01-01

    Constant-Kmax fatigue crack growth tests were performed on two finegrain nickel-base alloys Inconel 718 (DA) and Ren 95 to determine if these alloys exhibit near-threshold time-dependent crack growth behavior observed for fine-grain aluminum alloys in room-temperature laboratory air. Test results showed that increases in K(sub max) values resulted in increased crack growth rates, but no evidence of time-dependent crack growth was observed for either nickel-base alloy at room temperature.

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

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

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

  17. Adhesion and friction of iron-base binary alloys in contact with silicon carbide in vacuum

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1980-01-01

    Single pass sliding friction experiments were conducted with various iron base binary alloys (alloying elements were Ti, Cr, Mn, Ni, Rh, and W) in contact with a single crystal silicon carbide /0001/ surface in vacuum. Results indicate that atomic size and concentration of alloying elements play an important role in controlling adhesion and friction properties of iron base binary alloys. The coefficient of friction generally increases with an increase in solute concentration. The coefficient of friction increases linearly as the solute to iron atomic radius ratio increases or decreases from unity. The chemical activity of the alloying elements was also an important parameter in controlling adhesion and friction of alloys, as these latter properties are highly dependent upon the d bond character of the elements.

  18. Combinatorial density functional theory-based screening of surface alloys for the oxygen reduction reaction.

    SciTech Connect

    Greeley, J.; Norskov, J.; Center for Nanoscale Materials; Technical Univ. of Denmark

    2009-03-26

    A density functional theory (DFT) -based, combinatorial search for improved oxygen reduction reaction (ORR) catalysts is presented. A descriptor-based approach to estimate the ORR activity of binary surface alloys, wherein alloying occurs only in the surface layer, is described, and rigorous, potential-dependent computational tests of the stability of these alloys in aqueous, acidic environments are presented. These activity and stability criteria are applied to a database of DFT calculations on nearly 750 binary transition metal surface alloys; of these, many are predicted to be active for the ORR but, with few exceptions, they are found to be thermodynamically unstable in the acidic environments typical of low-temperature fuel cells. The results suggest that, absent other thermodynamic or kinetic mechanisms to stabilize the alloys, surface alloys are unlikely to serve as useful ORR catalysts over extended periods of operation.

  19. Ellipsometric characterization of surface freezing in Ga-based alloys

    NASA Astrophysics Data System (ADS)

    Bartel, K.; Nattland, D.; Kumar, A.; Dogel, S.; Freyland, W.

    2006-04-01

    We present results on surface freezing of Ga-based alloys, GaBi, GaPb and GaTl, above the liquidus line between the Ga-rich eutectic and the monotectic point. Spectroscopic ellipsometry (0.8 eV <=hν<=4.2 eV) and kinetic single wavelength ellipsometry (2.75 eV) have been employed to probe the changes of the interfacial electronic structures on surface freezing. To minimize thermal gradients across the sample a heatable cap that covers the sample and crucible was developed. The surface freezing temperature, TSF, for the spontaneous formation of a solid-like film on top of the Ga-rich liquid on cooling the sample from the homogeneous phase region was found to be independent of the temperature difference between the upper and lower furnace (ΔT: +10 to -10 K) and only weakly dependent on the cooling rate (\\partial T/\\partial t : 2.5-20 K h-1). In the case of GaPb the solid film consists of solid Pb with a thickness h>=400 Å. Comparing with GaBi we draw analogous conclusions for GaPb and GaTl and suggest that the surface freezing transition precedes the bulk phase transition along the liquidus line as the alloy is cooled.

  20. Oxidation/vaporization of silicide coated columbium base alloys

    NASA Technical Reports Server (NTRS)

    Kohl, F. J.; Stearns, C. A.

    1971-01-01

    Mass spectrometric and target collection experiments were made at 1600 K to elucidate the mode of oxidative vaporization of two columbium alloys, fused-slurry-coated with a complex silicide former (Si-20Cr-Fe). At oxygen pressures up to 0.0005 torr the major vapor component detected by mass spectrometry for oxidized samples was gaseous silicon monoxide. Analysis of condensates collected at oxygen pressures of 0.1, 1.0 and 10 torr revealed that chromium-, silicon-, iron- and tungsten- containing species were the major products of vaporization. Equilibrium thermochemical diagrams were constructed for the metal-oxygen system corresponding to each constituent metal in both the coating and base alloy. The major vaporizing species are expected to be the gaseous oxides of chromium, silicon, iron and tungsten. Plots of vapor phase composition and maximum vaporization rate versus oxygen pressure were calculated for each coating constituent. The major contribution to weight loss by vaporization at oxygen pressures above 1 torr was shown to be the chromium-containing species.

  1. A Shape Memory Alloy Based Cryogenic Thermal Conduction Switch

    NASA Astrophysics Data System (ADS)

    Krishnan, V. B.; Singh, J. D.; Woodruff, T. R.; Notardonato, W. U.; Vaidyanathan, R.

    2004-06-01

    Shape memory alloys (SMAs) can produce large strains when deformed (e.g., up to 8%). Heating results in a phase transformation and associated recovery of all the accumulated strain. This strain recovery can occur against large forces, resulting in their use as actuators. Thus an SMA element can integrate both sensory and actuation functions, by inherently sensing a change in temperature and actuating by undergoing a shape change as a result of a temperature-induced phase transformation. Two aspects of our work on cryogenic SMAs are addressed here. First — a shape memory alloy based cryogenic thermal conduction switch for operation between dewars of liquid methane and liquid oxygen in a common bulkhead arrangement is discussed. Such a switch integrates the sensor element and the actuator element and can be used to create a variable thermal sink to other cryogenic tanks for liquefaction, densification, and zero boil-off systems for advanced spaceport applications. Second — fabrication via arc-melting and subsequent materials testing of SMAs with cryogenic transformation temperatures for use in the aforementioned switch is discussed.

  2. A Shape Memory Alloy Based Cryogenic Thermal Conduction Switch

    SciTech Connect

    Krishnan, V.B.; Singh, J.D.; Woodruff, T.R.; Vaidyanathan, R.; Notardonato, W.U.

    2004-06-28

    Shape memory alloys (SMAs) can produce large strains when deformed (e.g., up to 8%). Heating results in a phase transformation and associated recovery of all the accumulated strain. This strain recovery can occur against large forces, resulting in their use as actuators. Thus an SMA element can integrate both sensory and actuation functions, by inherently sensing a change in temperature and actuating by undergoing a shape change as a result of a temperature-induced phase transformation. Two aspects of our work on cryogenic SMAs are addressed here. First - a shape memory alloy based cryogenic thermal conduction switch for operation between dewars of liquid methane and liquid oxygen in a common bulkhead arrangement is discussed. Such a switch integrates the sensor element and the actuator element and can be used to create a variable thermal sink to other cryogenic tanks for liquefaction, densification, and zero boil-off systems for advanced spaceport applications. Second - fabrication via arc-melting and subsequent materials testing of SMAs with cryogenic transformation temperatures for use in the aforementioned switch is discussed.

  3. A Shape Memory Alloy Based Cryogenic Thermal Conduction Switch

    NASA Technical Reports Server (NTRS)

    Notardonato, W. U.; Krishnan, V. B.; Singh, J. D.; Woodruff, T. R.; Vaidyanathan, R.

    2005-01-01

    Shape memory alloys (SMAs) can produce large strains when deformed (e.g., up to 8%). Heating results in a phase transformation and associated recovery of all the accumulated strain. This strain recovery can occur against large forces, resulting in their use as actuators. Thus an SMA element can integrate both sensory and actuation functions, by inherently sensing a change in temperature and actuating by undergoing a shape change as a result of a temperature-induced phase transformation. Two aspects of our work on cryogenic SMAs are addressed here. First - a shape memory alloy based cryogenic thermal conduction switch for operation between dewars of liquid methane and liquid oxygen in a common bulkhead arrangement is discussed. Such a switch integrates the sensor element and the actuator element and can be used to create a variable thermal sink to other cryogenic tanks for liquefaction, densification, and zero boil-off systems for advanced spaceport applications. Second - fabrication via arc-melting and subsequent materials testing of SMAs with cryogenic transformation temperatures for use in the aforementioned switch is discussed.

  4. Alloy 2100 GT: A new Ta-fortified Ni-Cr-Al-alloy for land based gas turbines

    SciTech Connect

    Brill, U.; Agarwal, D.C.

    1999-11-01

    Alloy 2100 GT has been developed for use in the combustors of gas turbines. The improved high-temperature properties of the alloy should allow the metal temperature of the combustion chamber to be increased, which would provide the opportunity of increasing the efficiency, lowering emissions, and decreasing fuel consumption. This alloy is a cobalt, tungsten, and molybdenum-free Ni-base superalloy. It contains as major alloying elements 25 wt.% chromium, 8 wt.% tantalum, 3 wt.% aluminium, 0.3 wt.% carbon and 0.1 wt.% yttrium. High-temperature strength is achieved by solid solution strengthening by tantalum, carbide hardening due to the formation of primary precipitated tantalum carbides and {gamma}{prime}-precipitation hardening by aluminium and tantalum. In spite of the small grain size creep rupture strength and stress to produce 0.1 % creep is significantly increased in comparison to superalloys being in use today. Superior oxidation resistance up to 1200 C and corrosion behavior under deposits of sulfates up to 850 C is given by the formation of a very thin and tightly adherent alumina scale due to an aluminium content of approximately 3.0 wt.%, which is remarkably high for a wrought alloy, and additions of yttrium to improve spallation resistance under cycling conditions. Welding can easily be accomplished. The matching filler metal is recommended because it provides mechanical strength and oxidation resistance similar to the parent metal.

  5. Effects of neutron irradiation on deformation behavior of nickel-base fastener alloys

    SciTech Connect

    Bajaj, R.; Mills, W.J.; Kammenzind, B.F.; Burke, M.G.

    1999-07-01

    This paper presents the effects of neutron irradiation on the fracture behavior and deformation microstructure of high-strength nickel-base alloy fastener materials, Alloy X-750 and Alloy 625. Alloy X-750 in the HTH condition, and Alloy 625 in the direct aged condition were irradiated to a fluence of 2.4x10{sup 20} n/cm{sup 2} at 264 C in the Advanced Test Reactor. Deformation structures at low strains were examined. It was previously shown that Alloy X-750 undergoes hardening, a significant degradation in ductility and an increase in intergranular fracture. In contrast, Alloy 625 had shown softening with a concomitant increase in ductility and transgranular failure after irradiation. The deformation microstructures of the two alloys were also different. Alloy X-750 deformed by a planar slip mechanism with fine microcracks forming at the intersections of slip bands with grain boundaries. Alloy 625 showed much more homogeneous deformation with fine, closely spaced slip bands and an absence of microcracks. The mechanism(s) of irradiation assisted stress corrosion cracking (IASCC) are discussed.

  6. Dual Microstructure Heat Treatment of a Nickel-Base Disk Alloy

    NASA Technical Reports Server (NTRS)

    Gayda, John

    2001-01-01

    Existing Dual Microstructure Heat Treat (DMHT) technology was successfully applied to Alloy 10, a high strength, nickel-base disk alloy, to produce a disk with a fine grain bore and coarse grain rim. Specimens were extracted from the DMHT disk and tested in tension, creep, fatigue, and crack growth using conditions pertinent to disk applications. These data were then compared with data from "traditional" subsolvus and supersolvus heat treatments for Alloy 10. The results showed the DMHT disk to have a high strength, fatigue resistant bore comparable to that of subsolvus Alloy 10. Further, creep resistance of the DMHT rim was comparable to that of supersolvus Alloy 10. Crack growth resistance in the DMHT rim, while better than that for subsolvus, was inferior to that of supersolvus Alloy 10. The slow cool at the end of the DMHT conversion and/or the subsolvus resolution step are thought to be responsible for degrading rim DMHT crack growth resistance.

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

    SciTech Connect

    Purdy, I.M.

    1996-04-01

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

  8. Assessment of special stainless steels and nickel-base alloys for use under offshore conditions

    SciTech Connect

    Jasner, M.R.; Herda, W.R.

    1994-12-31

    Major offshore installations are designed for a 25-years` life span and more. To predict the corrosion behavior of various alloys for such a long period results from accelerated laboratory tests have to be verified by suitable field tests. The results from laboratory tests and exposure to natural seawater show that nickel-based alloys such as alloy 59 (UNS N06059) and alloy 31 (UNS N08031) can be employed to most severe conditions. For general applications 6Mo stainless steels with 25% Ni such as alloy 926 (UNS N08926) may be used. If higher strength is required alloy 24 (18 Ni-24.5 Cr-6.2 Mn-4.3 Mo-0.6 Cu-0.45 Mn) is the preferred material.

  9. Influence of alloying elements on the chlorination behavior of nickel- and iron-based alloys

    SciTech Connect

    Brill, U.; Kloewer, J.; Agarwal, D.C.

    1996-11-01

    A wide range of commercial heat-resistant alloys has been tested in a H{sub 2} + 10% HCl environment at 550 C, 650 C, 680 C, 750 C and 850 C. The tests were carried out using a 24 h cycle with a total test time of up to 1,056 H. Weight change was determined, and the average value for three specimens per alloy and temperature plotted versus time, followed by a metallographic examination of the depth of corrosion. By a statistical evaluation of the data generated, it was possible to describe the weight change and penetration depth of all the alloys under examination as a function of the concentration of their main alloying elements and test temperature. According to these results, alloying elements nickel and molybdenum have a beneficial influence on chlorination resistance, whereas silicon and titanium are detrimental. Increased temperature always resulted in enhance corrosion. Only Ni, Ni-Mo, and Ni-Cr-Mo alloys show acceptable resistance for temperatures up to 850 C.

  10. Thermodynamic properties of gadolinium in Ga-Sn and Ga-Zn eutectic based alloys

    NASA Astrophysics Data System (ADS)

    Maltsev, Dmitry S.; Volkovich, Vladimir A.; Yamshchikov, Leonid F.; Chukin, Andrey V.

    2016-09-01

    Thermodynamic properties of gadolinium in Ga-Sn and Ga-Zn eutectic based alloys were studied. Temperature dependences of gadolinium activity in the studied alloys were determined at 573-1073 K employing the EMF method. Solubility of gadolinium in the Ga-Sn and Ga-Zn alloys was measured at 462-1073 K using IMCs sedimentation method. Activity coefficients as well as partial and excess thermodynamic functions of gadolinium in the studied alloys were calculated on the basis of the obtained experimental data.

  11. Elevated temperature fretting fatigue of nickel based alloys

    NASA Astrophysics Data System (ADS)

    Gean, Matthew C.

    This document details the high temperature fretting fatigue of high temperature nickel based alloys common to turbine disk and blade applications. The research consists of three area of focus: Experiments are conducted to determine quantitatively the fretting fatigue lives of advanced nickel based alloys; Analytical tools are developed and used to investigate the fretting fatigue response of the material; Fractographic analysis of the experimental results is used to improve the analytical models employed in the analysis of the experiments. Sixty three fretting fatigue experiments were conducted at 649 °C using a polycrystalline Nickel specimen in contact with directionally solidified and single crystal Nickel pads. Various influences on the fretting fatigue life are investigated. Shot peened Rene' 95 had better fretting fatigue life compared to shot peened Rene' 88. Shot peening produced a 2x increase in life for Rene' 95, but only a marginal improvement in the fretting fatigue life for Rene' 88. Minor cycles in variable amplitude loading produces significant damage to the specimen. Addition of occasional overpeaks in load produces improvements in fretting fatigue life. Contact tractions and stresses are obtained through a variety of available tools. The contact tractions can be efficiently obtained for limited geometries, while FEM can provide the contact tractions for a broader class of problems, but with the cost of increased CPU requirements. Similarly, the subsurface contact stresses can be obtained using the contact tractions as a boundary condition with either a semi-analytical FFT method or FEM. It is found that to calculate contact stresses the FFT was only marginally faster than FEM. The experimental results are combined with the analysis to produce tools that are used to design against fretting fatigue. Fractographic analysis of the fracture surface indicates the nature of the fretting fatigue crack behavior. Interrupted tests were performed to analyze

  12. Corrosion resistance and electrochemical potentiokinetic reactivation testing of some iron-base hardfacing alloys

    SciTech Connect

    Cockeram, B.V.

    1999-11-01

    Hardfacing alloys are weld deposited on a base material to provide a wear resistant surface. Commercially available iron-base hardfacing alloys are being evaluated for replacement of cobalt-base alloys to reduce nuclear plant activation levels. Corrosion testing was used to evaluate the corrosion resistance of several iron-base hardfacing alloys in highly oxygenated environments. The corrosion test results indicate that iron-base hardfacing alloys in the as-deposited condition have acceptable corrosion resistance when the chromium to carbon ratio is greater than 4. Tristelle 5183, with a high niobium (stabilizer) content, did not follow this trend due to precipitation of niobium-rich carbides instead of chromium-rich carbides. This result indicates that iron-base hardfacing alloys containing high stabilizer contents may possess good corrosion resistance with Cr:C < 4. NOREM 02, NOREM 01, and NoCo-M2 hardfacing alloys had acceptable corrosion resistance in the as-deposited and 885 C/4 hour heat treated condition, but rusting from sensitization was observed in the 621 C/6 hour heat treated condition. The feasibility of using an Electrochemical Potentiokinetic Reactivation (EPR) test method, such as used for stainless steel, to detect sensitization in iron-base hardfacing alloys was evaluated. A single loop-EPR method was found to provide a more consistent measurement of sensitization than a double loop-EPR method. The high carbon content that is needed for a wear resistant hardfacing alloy produces a high volume fraction of chromium-rich carbides that are attacked during EPR testing. This results in inherently lower sensitivity for detection of a sensitized iron-base hardfacing alloy than stainless steel using conventional EPR test methods.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

    The paper reports on the study where we analyzed the surface structure and strength properties of coated Al alloys modified by electron-ion plasma treatment. The Al alloys were deposited with a thin (≈0.5 μm) TiCu film coating (TiCu-Al system) and with a hard TiCuN coating (TiCuN-AlSi system) on a TRIO vacuum setup in the plasma of low-pressure arc discharges. The temperature fields and phase transformations in the film-substrate system were estimated by numerical simulation in a wide range of electron energy densities (5-30 J/cm2) and pulse durations (50-200 μs). The calculations allowed us to determine the threshold energy density and pulse duration at which the surface structure of the irradiated Al-based systems is transformed in a single-phase state (solid or liquid) and in a two-phase state (solid plus liquid). The elemental composition, defect structure, phase state, and lattice state in the modified surface layers were examined by optical, scanning, and transmission electron microscopy, and by X-ray diffraction analysis. The mechanical characteristics of the modified layers were studied by measuring the hardness and Young's modulus. The tribological properties of the modified layers were analyzed by measuring the wear resistance and friction coefficient. It is shown that melting and subsequent high-rate crystallization of the TiCu-Al system makes possible a multiphase Al-based surface structure with the following characteristics: crystallite size ranging within micrometer, microhardness of more than 3 times that in the specimen bulk, and wear resistance ≈1.8 times higher compared to the initial material. Electron beam irradiation of the TiCuN-AlSi system allows fusion of the coating into the substrate, thus increasing the wear resistance of the material ≈2.2 times at a surface hardness of ˜14 GPa.

  14. Processing of New Materials by Additive Manufacturing: Iron-Based Alloys Containing Silver for Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Niendorf, Thomas; Brenne, Florian; Hoyer, Peter; Schwarze, Dieter; Schaper, Mirko; Grothe, Richard; Wiesener, Markus; Grundmeier, Guido; Maier, Hans Jürgen

    2015-07-01

    In the biomedical sector, production of bioresorbable implants remains challenging due to improper dissolution rates or deficient strength of many candidate alloys. Promising materials for overcoming the prevalent drawbacks are iron-based alloys containing silver. However, due to immiscibility of iron and silver these alloys cannot be manufactured based on conventional processing routes. In this study, iron-manganese-silver alloys were for the first time synthesized by means of additive manufacturing. Based on combined mechanical, microscopic, and electrochemical studies, it is shown that silver particles well distributed in the matrix can be obtained, leading to cathodic sites in the composite material. Eventually, this results in an increased dissolution rate of the alloy. Stress-strain curves showed that the incorporation of silver barely affects the mechanical properties.

  15. Friction and wear of iron-base binary alloys in sliding contact with silicon carbide in vacuum

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1980-01-01

    Multipass sliding friction experiments were conducted with various iron base binary alloys in contact with a single crystal silicon carbide surface in vacuum. Results indicate that the atomic size and concentration of alloy elements play important roles in controlling the transfer and friction properties of iron base binary alloys. Alloys having high solute concentration produce more transfer than do alloys having low solute concentration. The coefficient of friction during multipass sliding generally increases with an increase in the concentration of alloying element. The change of friction with succeeding passes after the initial pass also increases as the solute to iron, atomic radius ratio increases or decreases from unity.

  16. Influence of S. mutans on base-metal dental casting alloy toxicity.

    PubMed

    McGinley, E L; Dowling, A H; Moran, G P; Fleming, G J P

    2013-01-01

    We have highlighted that exposure of base-metal dental casting alloys to the acidogenic bacterium Streptococcus mutans significantly increases cellular toxicity following exposure to immortalized human TR146 oral keratinocytes. With Inductively Coupled Plasma-Mass Spectrometry (ICP-MS), S. mutans-treated nickel-based (Ni-based) and cobalt-chromium-based (Co-Cr-based) dental casting alloys were shown to leach elevated levels of metal ions compared with untreated dental casting alloys. We targeted several biological parameters: cell morphology, viable cell counts, cell metabolic activity, cell toxicity, and inflammatory cytokine expression. S. mutans-treated dental casting alloys disrupted cell morphology, elicited significantly decreased viable cell counts (p < 0.0001) and cell metabolic activity (p < 0.0001), and significantly increased cell toxicity (p < 0.0001) and inflammatory cytokine expression (p < 0.0001). S. mutans-treated Ni-based dental casting alloys induced elevated levels of cellular toxicity compared with S. mutans-treated Co-Cr-based dental casting alloys. While our findings indicated that the exacerbated release of metal ions from S. mutans-treated base-metal dental casting alloys was the likely result of the pH reduction during S. mutans growth, the exact nature of mechanisms leading to accelerated dissolution of alloy-discs is not yet fully understood. Given the predominance of S. mutans oral carriage and the exacerbated cytotoxicity observed in TR146 cells following exposure to S. mutans-treated base-metal dental casting alloys, the implications for the long-term stability of base-metal dental restorations in the oral cavity are a cause for concern.

  17. Infection free titanium alloys by stabile thiol based nanocoating.

    PubMed

    Cökeliler, Dilek; Göktaş, Hilal; Tosun, Pinar Deniz; Mutlu, Selma

    2010-04-01

    As biomedical materials, titanium and titanium alloys (Ti-6Al-4V) are superior to many materials in terms of mechanical properties and biocompatibility. However, they are still not sufficient for prolonged clinical use because the biocompatibility of these materials must be improved. In this study, the prevention of the attachment of test microorganism on the Ti alloy surfaces by thiol (-SH) and hydroxyl (-OH) functional group containing monomer in plasma based electron beam generator was reported in order to prepare anti-fouling surfaces. The precursor, 11-mercaptoundecanoic acid is used as plasma source to create nano-film with 30-60 nm approximately. The surface chemistry and topology of uncoated and coated samples are characterized by Fourier Transform Infrared Spectroscopy (FTIR) and Atomic Force Microscopy (AFM). Static contact angle measurements are performed to state the change of surface hydrophilicity. All coated samples are tested in-vitro environment with Staphylococcus epidermidis that is chosen as the test bacteria strain in view of its significance for the pathogenesis of medical-device-related infections. This test is repeated after certain period of times and samples are waited in dynamic fluid media in order to investigate the stability of nano-coating. Plasma polymerized 11-mercaptoundecanoic acid film (PP MUA) with 42 +/- 4 nm is found alternative, stabile and simple method to create bacterial anti-fouling surfaces. The static contact angle of the coated surface is 34 +/- 80 whereas the uncoated surface is 57 +/- 50. For the coated surface, the presence of C-OH and C==O groups in infrared spectra defining the PP MUA is achieved by the plasma polymerization. The attachment of the model microorganism on the biomaterial surface prepared by PP MUA is reduced 85.3% if compared to unmodified control surface.

  18. NEUTRON REACTOR FUEL ELEMENT UTILIZING ZIRCONIUM-BASE ALLOYS

    DOEpatents

    Saller, H.A.; Keeler, J.R.; Szumachowski, E.R.

    1957-11-12

    This patent relates to clad fuel elements for use in neutronic reactors and is drawn to such a fuel element which consists of a core of fissionable material, comprised of an alloy of zirconium and U/sup 235/ enriched uranium, encased in a jacket of a binary zirconium-tin alloy in which the tin content ranges between 1 and 15% by weight.

  19. Performance of Alumina-Forming Austenitic Steels, Fe-base and Ni-base alloys exposed to metal dusting environments

    SciTech Connect

    Vande Put Ep Rouaix, Aurelie; Unocic, Kinga A; Pint, Bruce A; Brady, Michael P

    2011-01-01

    A series of conventional Fe- and Ni- base, chromia- and alumina- forming alloys, and a newly developed creep-resistant, alumina-forming austenitic steel were developed and its performance relative to conventional Fe- and Ni-based chromia-forming alloys was evaluated in metal dusting environments with a range of water vapor contents. Five 500h experiments have been performed at 650 C with different water vapor contents and total pressures. Without water vapor, the Ni-base alloys showed greater resistance to metal dusting than the Fe-base alloys, including AFA. However, with 10-28% water vapor, more protective behavior was observed with the higher-alloyed materials and only small mass changes were observed. Longer exposure times are in progress to further differentiate performance.

  20. Cr{sub 2}Nb-based alloy development

    SciTech Connect

    Liu, C.T.; Horton, J.A.; Carmichael, C.A.

    1996-05-01

    This paper summarizes recent progress in developing Cr{sub 2}Nb/Cr(Nb) alloys for structural use in advanced fossil energy conversion systems. Alloy additions were added to control the microstructure and mechanical properties. Two beneficial elements have been identified among all alloying additions added to the alloys. One element is effective in refining the coarse eutectic structure and thus substantially improves the compressive strength and ductility of the alloys. The other element enhances oxidation resistance without sacrificing the ductility. The tensile properties are sensitive to cast defects, which can not be effectively reduced by HIPping at 1450-1580{degrees}C and/or directionally solidifying via a floating zone remelting method.

  1. 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.

  2. Development and study of chemical vapor deposited tantalum base alloys

    NASA Technical Reports Server (NTRS)

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

    1976-01-01

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

  3. Corrosion of austenitic stainless steels and nickel-base alloys in supercritical water and novel control methods

    SciTech Connect

    Tan, Lizhen; Allen, Todd R.; Yang, Ying

    2012-01-01

    This chapter contains sections titled: (1) Introduction; (2) Thermodynamics of Alloy Oxidation; (3) Corrosion of Austenitic Stainless Steels and Ni-Base Alloys in SCW; (4) Novel Corrosion Control Methods; (5) Factors Influencing Corrosion; (6) Summary; and (7) References.

  4. Perpendicular Magnetic Anisotropy in Co-Based Full Heusler Alloy Thin Films

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Xu, X. G.; Miao, J.; Jiang, Y.

    2015-12-01

    Half-metallic Co-based full Heusler alloys have been qualified as promising functional materials in spintronic devices due to their high spin polarization. The lack of perpendicular magnetic anisotropy (PMA) is one of the biggest obstacles restricting their application in next generation ultrahigh density storage such as magnetic random access memory (MARM). How to induce the PMA in Co-based full Heusler alloy thin films has attracted much research interest of scientists. This paper presents an overview of recent progress in this research area. We hope that this paper would provide some guidance and ideas to develop highly spin-polarized Co-based Heusler alloy thin films with PMA.

  5. Ductile-phase toughening and fatigue crack growth in Nb{sub 3}Al base alloys

    SciTech Connect

    Gnanamoorthy, R.; Hanada, S.; Kamata, K.

    1996-03-15

    Niobium aluminide (Nb{sub 3}Al) base intermetallic compounds exhibit good high-temperature strength and creep properties and potential for applications above 1,200 C provided their inadequately low room-temperature ductility, fracture toughness and fatigue crack growth behavior are improved. Addition of tantalum to Nb{sub 3}Al base materials improves the high-temperature strength significantly and seems to be a potential alloying element. In the present study, room temperature fracture toughness and fatigue crack growth behavior of tantalum alloyed Nb{sub 3}Al base alloy prepared by ingot metallurgy are investigated.

  6. Solidification Behavior in Newly Designed Ni-Rich Ni-Ti-Based Alloys

    NASA Astrophysics Data System (ADS)

    Samal, Sumanta; Biswas, Krishanu; Phanikumar, Gandham

    2016-10-01

    The present investigation reports phase and microstructure evolution during solidification of novel Ni-rich Ni-Ti-based alloys, Ni60Ti40, Ni50Cu10Ti40, Ni48Cu10Co2Ti40, and Ni48Cu10Co2Ti38Ta2 during suction casting. The design philosophy of the multicomponent alloys involves judicious selection of alloying elements such as Cu, Co, and Ta in the near Ni60Ti40 eutectic alloy by replacing both Ni and Ti so that phase mixture in the microstructure remains the same from the binary to quinary alloy. The basic objective is to study the effect of addition of Cu, Co, and Ta on the phase evolution and transformation in the Ni-rich Ni-Ti-based alloys. The detailed electron microscopic studies on these suction cast alloys reveal the presence of ultrafine eutectic lamellae between NiTi and Ni3Ti phases along with dendritic NiTi and Ti2Ni phases. It has also been observed that in the binary (Ni60Ti40) alloy, the ordered NiTi (B2) phase transforms to trigonal (R) phase followed by NiTi martensitic phase (M-phase), i.e., B2 → R-phase → M-phase during solid-state cooling. However, the addition of alloying elements such as Cu, Co to the binary (Ni60Ti40) alloy suppresses the martensitic transformation of the ordered NiTi (B2) dendrite. Thus, in the ternary and quaternary alloys, the ordered NiTi (B2) phase is transformed to only trigonal (R) phase, i.e., B2 → R-phase. The secondary precipitate of Ti2Ni has been observed in all of the studied alloys. Interestingly, Ni48Cu10Co2Ti38Ta2 quinary alloy shows the disordered nature of NiTi dendrites. The experimentally observed solidification path is in good agreement with Gulliver-Scheil simulated path for binary alloy, whereas simulated solidification path deviates from the experimental results in case of ternary, quaternary, and quinary alloys.

  7. Melting, Processing, and Properties of Disordered Fe-Al and Fe-Al-C Based Alloys

    NASA Astrophysics Data System (ADS)

    Satya Prasad, V. V.; Khaple, Shivkumar; Baligidad, R. G.

    2014-09-01

    This article presents a part of the research work conducted in our laboratory to develop lightweight steels based on Fe-Al alloys containing 7 wt.% and 9 wt.% aluminum for construction of advanced lightweight ground transportation systems, such as automotive vehicles and heavy-haul truck, and for civil engineering construction, such as bridges, tunnels, and buildings. The melting and casting of sound, porosity-free ingots of Fe-Al-based alloys was accomplished by a newly developed cost-effective technique. The technique consists of using a special flux cover and proprietary charging schedule during air induction melting. These alloys were also produced using a vacuum induction melting (VIM) process for comparison purposes. The effect of aluminum (7 wt.% and 9 wt.%) on melting, processing, and properties of disordered solid solution Fe-Al alloys has been studied in detail. Fe-7 wt.% Al alloy could be produced using air induction melting with a flux cover with the properties comparable to the alloy produced through the VIM route. This material could be further processed through hot and cold working to produce sheets and thin foils. The cold-rolled and annealed sheet exhibited excellent room-temperature ductility. The role of carbon in Fe-7 wt.% Al alloys has also been examined. The results indicate that Fe-Al and Fe-Al-C alloys containing about 7 wt.% Al are potential lightweight steels.

  8. Imprecise knowledge based design and development of titanium alloys for prosthetic applications.

    PubMed

    Datta, S; Mahfouf, M; Zhang, Q; Chattopadhyay, P P; Sultana, N

    2016-01-01

    Imprecise knowledge on the composition-processing-microstructure-property correlation of titanium alloys combined with experimental data are used for developing rule based models for predicting the strength and elastic modulus of titanium alloys. The developed models are used for designing alloys suitable for orthopedic and dental applications. Reduced Space Searching Algorithm is employed for the multi-objective optimization to find composition, processing and microstructure of titanium alloys suitable for orthopedic applications. The conflicting requirements attributes of the alloys for this particular purpose are high strength with low elastic modulus, along with adequate biocompatibility and low costs. The 'Pareto' solutions developed through multi-objective optimization show that the preferred compositions for the fulfilling the above objectives lead to β or near β-alloys. The concept of decision making employed on the solutions leads to some compositions, which should provide better combination of the required attributes. The experimental development of some of the alloys has been carried out as guided by the model-based design methodology presented in this research. Primary characterizations of the alloys show encouraging results in terms of the mechanical properties.

  9. MECHANICAL BEHAVIOR OF MOLYBDENUM DISILICIDE-BASED ALLOYS

    SciTech Connect

    A. MISRA; A. SHARIF; ET AL

    2000-12-01

    We have investigated the mechanical behavior of the following single-phase polycrystalline alloys with the MoSi{sub 2} body-center tetragonal structure: MoSi{sub 2} alloyed with {approximately}2.5 at.% Re, MoSi{sub 2} alloyed with 2 at.% Al, MoSi{sub 2} alloyed with 1 at.% Nb, and MoSi{sub 2} alloyed with 1 at.% Re and 2 at.% Al. Several anomalies in the mechanical behavior of alloyed materials were observed. For example, (1) addition of only {approximately}2.5 at. % Re results in an order of magnitude increase in compressive strength at 1600 C, (2) additions of Nb and Al cause solution softening at near-ambient temperatures, and (3) quaternary MoSi{sub 2}-Re-Al alloys show strengthening at elevated temperatures and reduction in flow stress with enhanced plasticity at near-ambient temperatures in compression. The mechanisms of anomalous solution hardening and softening are discussed.

  10. Cr{sub 2}Nb-based alloy development

    SciTech Connect

    Liu, C.T.; Tortorelli, P.F.; Horton, J.A.; Easton, D.S.; Schneibel, J.H.; Heatherly, L.; Carmichael, C.A.; Howell, M.; Wright, J.L.

    1995-07-01

    Two-phase Cr-Cr{sub 2}Nb alloys (designated as CN alloys) were prepared by arc melting, followed by directional solidification, HIPping, or hot extrusion at 1450 to 1500C. The microstructure of CN alloys containing 6 to 12 at.% Nb depended strongly on alloying additions, heat treatment, and material processing. Tensile properties were sensitive to defects. Hot extrusion at 1480C was most effective in reducing as-cast defects and refining the cast Cr-Cr{sub 2}Nb eutectic structure and thus improving ductility. Beneficial alloying elements that modified the eutectic microstructure, improved oxidation resistance, or increased high-temperature strength were identified. One particular composition had a room-temperature fracture strength of 548 MPa and an ultimate tensile strength of 388 MPa, and 23% elongation at 1200C. Another CN alloy showed a fracture toughness of 7.6 MPa{radical}m at room temperature and 24.4 MPa{radical}m at 1100C. Silicide coatings applied by a pack cementation process substantially improved the oxidation resistance of the Cr-Cr{sub 2}Nb alloys at 950 and 1100C.

  11. Effect of exposure in steam or argon on the creep properties of Ni-based alloys: Creep properties of Ni-based alloys

    SciTech Connect

    Dryepondt, S.; Unocic, K. A.; Pint, B. A.

    2012-09-17

    Although expensive, Ni-based superalloys are of interest for the ultrasupercritical steam program because of their good creep and oxidation resistance at temperature above 700 C. However, the effect of steam oxidation on the alloy mechanical properties is unknown, and creep specimens of alloy CCA617, 740 and 230 were pre-oxidized for 2000 and 4000h in steam at 800 C before testing in air at the same temperature. Exposure in steam decreased the creep properties of alloy CCA617 compared with as fabricated material, had less of an effect on alloy 740, and did not affect alloy 230. Testing of a specimen repolished after steam exposure as well as microstructure observation indicate that the oxidation affected zone at the specimen surface is not responsible for the properties degradation. Surprisingly, a similar time anneal in an inert environment resulted in a drastic decrease of creep rupture life and an increase in the creep rate and elongation at rupture. TEM analysis revealed that the mechanical properties decrease for alloy CCA617 is related to the absence of precipitates in the grain.

  12. Internal nitridation of nickel-base alloys. Part 2: Behavior of quaternary Ni-Cr-Al-Ti alloys and computer-based description

    SciTech Connect

    Krupp, U.; Christ, H.J.

    1999-10-01

    Whereas in Part 1 of this study the process of internal nitridation was described for binary and ternary alloys within the Ni-Cr-Al-Ti system, this part focuses on quaternary Ni-Cr-Al-Ti alloys, which are similar to commercial Ni-base alloys used in high-temperature applications regarding their chemical compositions. These alloys can simultaneously form two different nitride-precipitation zones consisting of TiN and AlN. In order to quantify the nitridation process, thermogravimetric measurements in an oxygen-free nitrogen atmosphere in the temperature range 800--1100 C were carried out and supplemented by extensive microstructural studies. While single-nitride internal nitridation can easily be described by Wagner`s theory of internal oxidation, modeling of the more complex internal-precipitation reactions that involves more than one nitride requires a numerical treatment of both the diffusion and the thermochemical processes in the alloy. For this purpose, a computer simulation was developed in which the commercial thermodynamic software ChemApp is combined with a finite-difference diffusion calculation. It was shown that this calculation technique can be applied successfully to quantitatively describe the internal-nitridation process of the Ni-Cr-Al-Ti model alloys used in this study.

  13. Shape memory alloy-based active chiral composite cells

    NASA Astrophysics Data System (ADS)

    Prajapati, Maulik; Roy Mahapatra, D.

    2014-04-01

    Wing morphing is one of the emerging methodology towards improving aerodynamic efficiency of flight vehicle structures. In this paper a morphing structural element is designed and studied which has its origin in the well known chiral structures. The new aspect of design and functionality explored in this paper is that the chiral cell is actuated using thermal Shape Memory Alloy (SMA) actuator wires to provide directional motion. Such structure utilizes the potential of different actuations concepts based on actuator embedded in the chiral structure skin. This paper describes a new class of chiral cell structure with integrated SMA wire for actuation. Chiral topological constructs are obtained by considering passive and active load path decoupling and sub-optimal shape changes. Single cell of chiral honeycomb with actuators are analyzed using finite element simulation results and experiments. To this end, a multi-cell plan-form is characterized showing interesting possibilities in structural morphing applications. The applicability of the developed chiral cell to flexible wing skin, variable stiffness based design and controlling longitudinal-to-transverse stiffness ratio are discussed.

  14. Evaluation of Surface Roughness and Tensile Strength of Base Metal Alloys Used for Crown and Bridge on Recasting (Recycling)

    PubMed Central

    Hashmi, Syed W.; Rao, Yogesh; Garg, Akanksha

    2015-01-01

    Background Dental casting alloys play a prominent role in the restoration of the partial dentition. Casting alloys have to survive long term in the mouth and also have the combination of structure, molecules, wear resistance and biologic compatibility. According to ADA system casting alloys were divided into three groups (wt%); high noble, Noble and predominantly base metal alloys. Aim To evaluate the mechanical properties such as tensile strength and surface roughness of the new and recast base metal (nickel-chromium) alloys. Materials and Methods Recasting of the base metal alloys derived from sprue and button, to make it reusable has been done. A total of 200 test specimens were fabricated using specially fabricated jig of metal and divided into two groups- 100 specimens of new alloy and 100 specimens of recast alloys, which were tested for tensile strength on universal testing machine and surface roughness on surface roughness tester. Results Tensile strength of new alloy showed no statistically significant difference (p-value>0.05) from recast alloy whereas new alloy had statistically significant surface roughness (Maximum and Average surface roughness) difference (p-value<0.01) as compared to recast alloy. Conclusion Within the limitations of the study it is concluded that the tensile strength will not be affected by recasting of nickel-chromium alloy whereas surface roughness increases markedly. PMID:26393194

  15. Ignition characteristics of the nickel-based alloy UNS N07718 in pressurized oxygen

    NASA Technical Reports Server (NTRS)

    Bransford, James W.; Billiard, Phillip A.; Hurley, James A.; Mcdermott, Kathleen M.; Vazquez, Isaura

    1989-01-01

    The development of ignition and combustion in pressurized oxygen atmospheres was studied for the nickel based alloy UNS N07718. Ignition of the alloy was achieved by heating the top. It was found that the alloy would autoheat to destruction from temperatures below the solidus temperature. In addition, endothermic events occurred as the alloy was heated, many at reproducible temperatures. Many endothermic events occurred prior to abrupt increases in surface temperature and appeared to accelerate the rate of increase in specimen temperature. It appeared that the source of some endotherms may increase the oxidation rate of the alloy. Ignition parameters are defined and the temperatures at which these parameters occur are given for the oxygen pressure range of 1.72 to 13.8 MPa (250 to 2000 psia).

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

    SciTech Connect

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

    1995-08-01

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

  17. Chemical Interactions of Barium-Calcium-Aluminosilicate Based Sealing Glasses with Oxidation Resistant Alloys

    SciTech Connect

    Yang, Z Gary ); Stevenson, Jeffry W. ); Meinhardt, Kerry D. )

    2003-04-04

    In most planar SOFC stack designs, the interconnect, which is typically made from an oxidation resistant alloy, potentially including austenitic chromia-forming, ferritic chromia-forming, and alumina-forming alloys, has to be hermitically sealed to its adjacent components, usually by a sealing glass. To maintain the structural stability and minimize the degradation of stack performance, the sealing glass must be chemically compatible with the alloy used for the interconnect. In this work, Nicrofer6025, AISI446 and a Fecralloy were selected as examples of austenitic chromia-forming, ferritic chromia-forming, and alumina-forming alloys, respectively. Their chemical compatibility with a barium-calcium-aluminosilicate (BCAS) based glass, specifically developed as a sealant in SOFC stacks, was evaluated. It was found that the BCAS sealing glass interacted chemically with both the chromia-forming alloys and the alumina-forming alloys. The extent and nature of the interactions and their final products depended on the matrix alloy compositions, the exposure conditions and/or proximity of the glass/alloy interface to the ambient air. These interactions and their mechanisms will be discussed with the assistance of thermodynamic modeling.

  18. Advanced oxidation-resistant iron-based alloys for LWR fuel cladding

    NASA Astrophysics Data System (ADS)

    Terrani, K. A.; Zinkle, S. J.; Snead, L. L.

    2014-05-01

    Application of advanced oxidation-resistant iron alloys as light water reactor fuel cladding is proposed. The motivations are based on specific limitations associated with zirconium alloys, currently used as fuel cladding, under design-basis and beyond-design-basis accident scenarios. Using a simplified methodology, gains in safety margins under severe accidents upon transition to advanced oxidation-resistant iron alloys as fuel cladding are showcased. Oxidation behavior, mechanical properties, and irradiation effects of advanced iron alloys are briefly reviewed and compared to zirconium alloys as well as historic austenitic stainless steel cladding materials. Neutronic characteristics of iron-alloy-clad fuel bundles are determined and fed into a simple economic model to estimate the impact on nuclear electricity production cost. Prior experience with steel cladding is combined with the current understanding of the mechanical properties and irradiation behavior of advanced iron alloys to identify a combination of cladding thickness reduction and fuel enrichment increase (∼0.5%) as an efficient route to offset any penalties in cycle length, due to higher neutron absorption in the iron alloy cladding, with modest impact on the economics.

  19. Atomic-scale properties of Ni-based FCC ternary, and quaternary alloys

    SciTech Connect

    Tamm, Artur; Aabloo, Alvo; Klintenberg, Mattias; Stocks, Malcolm; Caro, Alfredo

    2015-08-26

    The aim of our study is to characterize some atomic-scale properties of Ni-based FCC multicomponent alloys. For this purpose, we use Monte Carlo method combined with density functional theory calculations to study short-range order (SRO), atomic displacements, electronic density of states, and magnetic moments in equimolar ternary NiCrCo, and quaternary NiCrCoFe alloys. The salient features for the ternary alloy are a negative SRO parameter between Ni Cr and a positive between Cr Cr pairs as well as a weakly magnetic state. For the quaternary alloy we predict negative SRO parameter for Ni Cr and Ni Fe pairs and positive for Cr Cr and Fe Fe pairs. Atomic displacements for both ternary and quaternary alloys are negligible. In contrast to the ternary, the quaternary alloy shows a complex magnetic structure. The electronic structure of the ternary and quaternary alloys shows differences near the Fermi energy between a random solid solution and the predicted structure with SRO. Despite that, the calculated EXAFS spectra does not show enough contrast to discriminate between random and ordered structures. Finally, the predicted SRO has an impact on point-defect energetics, electron phonon coupling and thermodynamic functions and thus, SRO should not be neglected when studying properties of these two alloys.

  20. Atomic-scale properties of Ni-based FCC ternary, and quaternary alloys

    DOE PAGES

    Tamm, Artur; Aabloo, Alvo; Klintenberg, Mattias; Stocks, Malcolm; Caro, Alfredo

    2015-08-26

    The aim of our study is to characterize some atomic-scale properties of Ni-based FCC multicomponent alloys. For this purpose, we use Monte Carlo method combined with density functional theory calculations to study short-range order (SRO), atomic displacements, electronic density of states, and magnetic moments in equimolar ternary NiCrCo, and quaternary NiCrCoFe alloys. The salient features for the ternary alloy are a negative SRO parameter between Ni Cr and a positive between Cr Cr pairs as well as a weakly magnetic state. For the quaternary alloy we predict negative SRO parameter for Ni Cr and Ni Fe pairs and positive formore » Cr Cr and Fe Fe pairs. Atomic displacements for both ternary and quaternary alloys are negligible. In contrast to the ternary, the quaternary alloy shows a complex magnetic structure. The electronic structure of the ternary and quaternary alloys shows differences near the Fermi energy between a random solid solution and the predicted structure with SRO. Despite that, the calculated EXAFS spectra does not show enough contrast to discriminate between random and ordered structures. Finally, the predicted SRO has an impact on point-defect energetics, electron phonon coupling and thermodynamic functions and thus, SRO should not be neglected when studying properties of these two alloys.« less

  1. Thermodynamic Prediction of Compositional Phases Confirmed by Transmission Electron Microscopy on Tantalum-Based Alloy Weldments

    SciTech Connect

    Moddeman, William E.; Birkbeck, Janine C.; Barklay, Chadwick D.; Kramer, Daniel P.; Miller, Roger G.; Allard, Lawrence F.

    2007-01-30

    Tantalum alloys have been used by the U.S. Department of Energy as structural alloys for radioisotope based thermal to electrical power systems since the 1960s. Tantalum alloys are attractive for high temperature structural applications due to their high melting point, excellent formability, good thermal conductivity, good ductility (even at low temperatures), corrosion resistance, and weldability. Tantalum alloys have demonstrated sufficient high-temperature toughness to survive prolonged exposure to the radioisotope power-system working environment. Typically, the fabrication of power systems requires the welding of various components including the structural members made of tantalum alloys. Issues such as thermodynamics, lattice structure, weld pool dynamics, material purity and contamination, and welding atmosphere purity all potentially confound the understanding of the differences between the weldment properties of the different tantalum-based alloys. The objective of this paper is to outline the thermodynamically favorable material phases in tantalum alloys, with and without small amounts of hafnium, during and following solidification, based on the results derived from the FactSage(c) Integrated Thermodynamic Databank. In addition, Transition Electron Microscopy (TEM) data will show for the first time, the changes occurring in the HfC before and after welding, and the data will elucidate the role HfC plays in pinning grain boundaries.

  2. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOEpatents

    Brager, Howard R.; Garner, Francis A.

    1987-09-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  3. Mn-Fe base and Mn-Cr-Fe base austenitic alloys

    DOEpatents

    Brager, Howard R.; Garner, Francis A.

    1987-01-01

    Manganese-iron base and manganese-chromium-iron base austenitic alloys designed to have resistance to neutron irradiation induced swelling and low activation have the following compositions (in weight percent): 20 to 40 Mn; up to about 15 Cr; about 0.4 to about 3.0 Si; an austenite stabilizing element selected from C and N, alone or in combination with each other, and in an amount effective to substantially stabilize the austenite phase, but less than about 0.7 C, and less than about 0.3 N; up to about 2.5 V; up to about 0.1 P; up to about 0.01 B; up to about 3.0 Al; up to about 0.5 Ni; up to about 2.0 W; up to about 1.0 Ti; up to about 1.0 Ta; and with the remainder of the alloy being essentially iron.

  4. Shape Memory Alloy (SMA)-Based Launch Lock

    NASA Technical Reports Server (NTRS)

    Badescu, Mircea; Bao, Xiaoqi; Bar-Cohen, Yoseph

    2014-01-01

    Most NASA missions require the use of a launch lock for securing moving components during the launch or securing the payload before release. A launch lock is a device used to prevent unwanted motion and secure the controlled components. The current launch locks are based on pyrotechnic, electro mechanically or NiTi driven pin pullers and they are mostly one time use mechanisms that are usually bulky and involve a relatively high mass. Generally, the use of piezoelectric actuation provides high precession nanometer accuracy but it relies on friction to generate displacement. During launch, the generated vibrations can release the normal force between the actuator components allowing shaft's free motion which could result in damage to the actuated structures or instruments. This problem is common to other linear actuators that consist of a ball screw mechanism. The authors are exploring the development of a novel launch lock mechanism that is activated by a shape memory alloy (SMA) material ring, a rigid element and an SMA ring holding flexure. The proposed design and analytical model will be described and discussed in this paper.

  5. The HIP-nitriding of steels and titanium based alloys

    SciTech Connect

    Jacobs, M.H.; Ashworth, M.A.; Marshall, A.J.

    1996-12-31

    The paper discusses the HIP processing of nitriding steels (S106 and EN41B), austenitic stainless steel and titanium based alloys (cp Ti, Ti-6Al-4V and Ti-48Al-2Mn-2Nb), using ammonia and nitrogen gases as the pressurizing media to produce a nitrided surface. The paper compares the HIP-nitrided material with conventionally nitrided samples in terms of microstructure, case depths (in particular the ability to nitride uniformly down blind holes) and mechanical properties. The effect of HIP process parameters (time, temperature and pressure) on the resultant nitrided surface will also be discussed. Results obtained using NH{sub 3} will be compared with those obtained on samples HIPed in a pure N{sub 2} atmosphere with particular reference to the nitriding steels and the formation of a white layer. The use of NH{sub 3}/N{sub 2} gas mixtures on the nitriding of steels is investigated to determine the effect of NH{sub 3} concentration on process kinetics.

  6. Coarsening in high volume fraction nickel-base alloys

    NASA Technical Reports Server (NTRS)

    Mackay, R. A.; Nathal, M. V.

    1990-01-01

    The coarsening behavior of the gamma-prime precipitate has been examined in high volume fraction nickel-base alloys aged at elevated temperatures for times of up to 5000 h. Although the cube rate law was observed during coarsening, none of the presently available coarsening theories showed complete agreement with the experimental particle size distributions (PSDs). These discrepancies were thought to be due to elastic coherency strains which were not considered by the available models. Increasing the Mo content significantly influenced the PSDs and decreased the coarsening rate of the gamma-prime cubes, as a result of increasing the magnitude of the lattice mismatch. After extended aging times, the gamma-prime cubes underwent massive coalescence into plates at a rate which was much faster than the cuboidal coarsening rate. Once the gamma-prime plates were formed, further coarsening was not observed, and this stabilization of the microstructure was attributed to the development of dislocation networks at the gamma-gamma-prime interfaces.

  7. Nanocrystalline films of soft magnetic iron-based alloys

    NASA Astrophysics Data System (ADS)

    Sheftel', E. N.; Bannykh, O. A.

    2006-10-01

    The physicochemical and structural aspects of designing soft magnetic alloys Fe- MX (where M is a Group III V metal of the periodic table and X = C, N, O) in the form of nanocrystalline films precipitation-hardened by refractory interstitial phases are discussed and developed. The results of studying the structure and magnetic properties of Fe78Zr10N12 films are reported. The films in the amorphous state are produced by reactive magnetron sputtering. Upon annealing at 300 600°C, the amorphous films crystallize to form mainly a bcc α-Fe-based phase and the fcc ZrN phase. The grain size of the bcc phase is shown to increase from ˜3 nm to ˜30 nm as the annealing temperature increases; the grain size of the fcc phase does not exceed 2 3 nm. Films annealed at 400°C exhibit a record level of magnetic properties: H c = 5 6 A/m and B s = 1.7 1.8 T. The experimental results obtained confirm the validity of our scientific approach.

  8. Shape-Memory-Alloy-Based Deicing System Developed

    NASA Technical Reports Server (NTRS)

    1996-01-01

    Ice buildup on aircraft leading edge surfaces has historically been a problem. Most conventional deicing systems rely either on surface heating to melt the accreted ice or pneumatic surface inflation to mechanically debond the ice. Deicers that rely solely on surface heating require large amounts of power. Pneumatic deicers usually cannot remove thin layers of ice and lack durability. Thus, there is a need for an advanced, low-power ice protection system. As part of the NASA Small Business and Innovation Research (SBIR) program, Innovative Dynamics, Inc., developed an aircraft deicing system that utilizes the properties of Shape Memory Alloys (SMA). The SMA-based system has achieved promising improvements in energy efficiency and durability over more conventional deicers. When they are thermally activated, SMA materials change shape; this is analogous to a conventional thermal expansion. The thermal input is currently applied via conventional technology, but there are plans to implement a passive thermal input that is supplied from the energy transfer due to the formation of the ice itself. The actively powered deicer was tested in the NASA Lewis Icing Research Tunnel on a powered rotating rig in early 1995. The system showed promise, deicing both rime and glaze ice shapes as thin as 1/8 in. The first prototype SMA deicer reduced power usage by 45 percent over existing electrothermal systems. This prototype system was targeted for rotorcraft system development. However, there are current plans underway to develop a fixed-wing version of the deicer.

  9. Shape Memory Alloy (SMA)-based launch lock

    NASA Astrophysics Data System (ADS)

    Badescu, Mircea; Bao, Xiaoqi; Bar-Cohen, Yoseph

    2014-04-01

    Most NASA missions require the use of a launch lock for securing moving components during the launch or securing the payload before release. A launch lock is a device used to prevent unwanted motion and secure the controlled components. The current launch locks are based on pyrotechnic, electro mechanically or NiTi driven pin pullers and they are mostly one time use mechanisms that are usually bulky and involve a relatively high mass. Generally, the use of piezoelectric actuation provides high precession nanometer accuracy but it relies on friction to generate displacement. During launch, the generated vibrations can release the normal force between the actuator components allowing free motion of the shaft, which could result in damage to the actuated structures or instruments. This problem is common to other linear actuators that consist of a ball screw mechanism. The authors are exploring the development of a novel launch lock mechanism that is activated by a shape memory alloy (SMA) material ring, a rigid element and an SMA ring holding flexure. The proposed design and analytical model will be described and discussed in this paper.

  10. Corrosion behavior of experimental and commercial nickel-base alloys in HCl and HCl containing Fe3+

    SciTech Connect

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

    2006-03-01

    The effects of ferric ions on the corrosion resistance and electrochemical behavior of a series of Ni-based alloys in 20% HCl at 30ºC were investigated. The alloys studied were those prepared by the Albany Research Center (ARC), alloys J5, J12, J13, and those sold commercially, alloys 22, 242, 276, and 2000. Tests included mass loss, potentiodynamic polarization, and linear polarization.

  11. Application of STEM characterization for investigating radiation effects in BCC Fe-based alloys

    DOE PAGES

    Parish, Chad M.; Field, Kevin G.; Certain, Alicia G.; Wharry, Janelle P.

    2015-04-20

    This paper provides a general overview of advanced scanning transmission electron microscopy (STEM) techniques used for characterization of irradiated BCC Fe-based alloys. Advanced STEM methods provide the high-resolution imaging and chemical analysis necessary to understand the irradiation response of BCC Fe-based alloys. The use of STEM with energy dispersive x-ray spectroscopy (EDX) for measurement of radiation-induced segregation (RIS) is described, with an illustrated example of RIS in proton- and self-ion irradiated T91. Aberration-corrected STEM-EDX for nanocluster/nanoparticle imaging and chemical analysis is also discussed, and examples are provided from ion-irradiated oxide dispersion strengthened (ODS) alloys. In conclusion, STEM techniques for void,more » cavity, and dislocation loop imaging are described, with examples from various BCC Fe-based alloys.« less

  12. Application of STEM characterization for investigating radiation effects in BCC Fe-based alloys

    SciTech Connect

    Parish, Chad M.; Field, Kevin G.; Certain, Alicia G.; Wharry, Janelle P.

    2015-04-20

    This paper provides a general overview of advanced scanning transmission electron microscopy (STEM) techniques used for characterization of irradiated BCC Fe-based alloys. Advanced STEM methods provide the high-resolution imaging and chemical analysis necessary to understand the irradiation response of BCC Fe-based alloys. The use of STEM with energy dispersive x-ray spectroscopy (EDX) for measurement of radiation-induced segregation (RIS) is described, with an illustrated example of RIS in proton- and self-ion irradiated T91. Aberration-corrected STEM-EDX for nanocluster/nanoparticle imaging and chemical analysis is also discussed, and examples are provided from ion-irradiated oxide dispersion strengthened (ODS) alloys. In conclusion, STEM techniques for void, cavity, and dislocation loop imaging are described, with examples from various BCC Fe-based alloys.

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

    NASA Astrophysics Data System (ADS)

    Biffi, Carlo Alberto; Tuissi, Ausonio

    2014-07-01

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

  14. Development of tough, strong, iron-base alloy for cryogenic applications

    NASA Technical Reports Server (NTRS)

    Stephens, J. R.

    1983-01-01

    The development of an iron-base alloy that combines the normally divergent properties of high toughness and high strength at cryogenic temperatures is discussed. Specifically, alloy properties were sought which at -196 C would exhibit a fracture toughness of 220 MPa-m(1/2) with a corresponding yield strength of 1.4 GPa (200 ksi). Early work showed that high toughness could be achieved in Fe-12Ni alloys containing reactive metal additions such as Al, Nb, Ti, and V. Further research emphasized strengthening of these tough alloys by thermomechanical processing and the addition of Cu. Results showed that high strength and high toughness could be achieved in a single alloy at temperatures as low as -196 C. An alloy with composition Fe-12Ni-9.5Al-2Cu exhibited a yield strength of 1.65 GPa with a corresponding fracture toughness of 220 MPa-m(1/2) at -196 C. Strengthening due to Cu additions to the Fe-12Ni base alloys results primarily from precipitation of Cu-rich epsilon particles approximately 20 nm in diameter. Strengthening mechanisms are discussed in terms of an elastic modulus hardening model and are supported by transimission electron microscopy examinations of selected test specimens.

  15. Corrosion Performance Based on the Microstructural Array of Al-Based Monotectic Alloys in a NaCl Solution

    NASA Astrophysics Data System (ADS)

    Osório, Wislei R.; Freitas, Emmanuelle S.; Garcia, Amauri

    2014-01-01

    The aim of this study is to compare the electrochemical behavior of three monotectic Al-based alloys (Al-Pb, Al-Bi, and Al-In) in a 0.5 M NaCl solution at room temperature. Two distinct microstructure arrays were experimentally obtained for each Al monotectic alloy by using a water-cooled unidirectional solidification system. Results of electrochemical impedance spectroscopy (EIS) plots, potentiodynamic polarization curves, and impedance parameters obtained by an equivalent circuit analysis are discussed. It was found that the Al-Pb alloy has lower corrosion current density, higher polarization resistance, lower relative weight, and cost than the corresponding values of Al-Bi and Al-In alloys. It is also shown that the electrochemical behavior of the three alloys examined are intimately correlated with the scale of the corresponding microstructure, with smaller droplets and spacings (i.e., cell and interphase spacings) being associated with a decrease in the corrosion resistance.

  16. Interstitial-phase precipitation in iron-base alloys: a comparative study

    SciTech Connect

    Pelton, A.R.

    1982-06-01

    Recent developments have elucidated the atomistic mechanisms of precipitation of interstitial elements in simple alloy systems. However, in the more technologically important iron base alloys, interstitial phase precipitation is generally not well understood. The present experimental study was therefore designed to test the applicability of these concepts to more complex ferrous alloys. Hence, a comparative study was made of interstitial phase precipitation in ferritic Fe-Si-C and in austenitic phosphorus-containing Fe-Cr-Ni steels. These systems were subjected to a variety of quench-age thermal treatments, and the microstructural development was subsequently characterized by transmission electron microscopy.

  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.

  18. Antiferromagnetic FeMn alloys electrodeposited from chloride-based electrolytes.

    PubMed

    Ruiz-Gómez, Sandra; Ranchal, Rocío; Abuín, Manuel; Aragón, Ana María; Velasco, Víctor; Marín, Pilar; Mascaraque, Arantzazu; Pérez, Lucas

    2016-03-21

    The capability of synthesizing Fe-based antiferromagnetic metal alloys would fuel the use of electrodeposition in the design of new magnetic devices such as high-aspect-ratio spin valves or new nanostructured hard magnetic composites. Here we report the synthesis of high quality antiferromagnetic FeMn alloys electrodeposited from chloride-based electrolytes. We have found that in order to grow homogeneous FeMn films it is necessary to incorporate a large concentration of NH4Cl as an additive in the electrolyte. The study of the structure and magnetic properties shows that films with composition close to Fe50Mn50 are homogeneous antiferromagnetic alloys. We have established a parameter window for the synthesis of FeMn alloys that show antiferromagnetism at room temperature.

  19. Iron-based alloy and nitridation treatment for PEM fuel cell bipolar plates

    DOEpatents

    Brady, Michael P [Oak Ridge, TN; Yang, Bing [Oak Ridge, TN; Maziasz, Philip J [Oak Ridge, TN

    2010-11-09

    A corrosion resistant electrically conductive component that can be used as a bipolar plate in a PEM fuel cell application is composed of an alloy substrate which has 10-30 wt. % Cr, 0.5 to 7 wt. % V, and base metal being Fe, and a continuous surface layer of chromium nitride and vanadium nitride essentially free of base metal. A oxide layer of chromium vanadium oxide can be disposed between the alloy substrate and the continuous surface nitride layer. A method to prepare the corrosion resistant electrically conductive component involves a two-step nitridization sequence by exposing the alloy to a oxygen containing gas at an elevated temperature, and subsequently exposing the alloy to an oxygen free nitrogen containing gas at an elevated temperature to yield a component where a continuous chromium nitride layer free of iron has formed at the surface.

  20. Tailoring Fe-Base Alloys for Intermediate Temperature SOFC Interconnect Application

    SciTech Connect

    J.H. Zhu; M.P. Brady; H.U. Anderson

    2007-12-31

    This report summarized the research efforts and major conclusions for our SECA Phase I and II project focused on Cr-free or low Cr Fe-Ni based alloy development for intermediate temperature solid oxide fuel cell (SOFC) interconnect application. Electrical conductivity measurement on bulk (Fe,Ni){sub 3}O{sub 4} coupons indicated that this spinel phase possessed a higher electrical conductivity than Cr{sub 1.5}Mn{sub 1.5}O{sub 4} spinel and Cr{sub 2}O{sub 3}, which was consistent with the low area specific resistance (ASR) of the oxide scale formed on these Fe-Ni based alloys. For Cr-free Fe-Ni binary alloys, although the increase in Ni content in the alloys improved the oxidation resistance, and the Fe-Ni binary alloys exhibited adequate CTE and oxide scale ASR, their oxidation resistance needs to be further improved. Systematic alloy design efforts have led to the identification of one low-Cr (6wt.%) Fe-Ni-Co based alloy which formed a protective, electrically-conductive Cr{sub 2}O{sub 3} inner layer underneath a Cr-free, highly conductive spinel outer layer. This low-Cr, Fe-Ni-Co alloy has demonstrated a good CTE match with other cell components; high oxidation resistance comparable to that of Crofer; low oxide scale ASR with the formation of electrically-insulating phases in the oxide scale; no scale spallation during thermal cycling; adequate compatibility with cathode materials; and comparable mechanical properties with Crofer. The existence of the Cr-free (Fe,Co,Ni){sub 3}O{sub 4} outer layer effectively reduced the Cr evaporation and in transpiration testing resulted in a 6-fold decrease in Cr evaporation as compared to a state-of-the-art ferritic interconnect alloy. In-cell testing using an anode supported cell with a configuration of Alloy/Pt/LSM/YSZ/Ni+YSZ indicates that the formation of the Cr-free spinel layer via thermal oxidation was effective in blocking the Cr migration and thus improving the cell performance stability. Electroplating of the Fe

  1. Control of metal dusting corrosion in Ni-base alloys.

    SciTech Connect

    Zeng, Z.; Natesan, K.; Energy Technology

    2007-11-01

    Metal dusting is a major issue in plants used in the production of hydrogen-and methanol-reformer systems, and syngas (H{sub 2}/CO mixtures) systems that are pertinent to the chemical and petrochemical industries. Usually, metal dusting corrosion has two stages: incubation and growth resulting in propagation of metal dusting pits. The two stages were studied by scanning electron microscopy and profile mapping to evaluate the scale of the surface oxide in the initiation and propagation of metal dusting attack. The initiation occurs because of the presence of defects, and the propagation is determined by the diffusion of carbon into the alloy. The carbon diffusion pathways can be blocked by periodically oxidizing alloy surface at moderate temperatures in controlled atmospheres. It was concluded that metal dusting degradation can be mitigated by selecting an alloy with a long incubation time and subjecting it to intermediate oxidation.

  2. Burner Rig Hot Corrosion of Five Ni-Base Alloys Including Mar-M247

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Helmink, R.; Harris, K.; Erickson, G.

    2000-01-01

    The hot corrosion resistance of four new Ni-base superalloys was compared to that of Mar-M247 by testing in a Mach 0.3 burner rig at 900 C for 300 1-hr cycles. While the Al content was held the same as in the Mar-M247, the Cr and Co levels in the four new alloys were decreased while other strengthening elements (Re, Ta) were increased. Surprisingly, despite their lower Cr and Co contents, the hot corrosion behavior of all four new alloys was superior to that of the Mar-M247 alloy. The Mar-M247 alloy began to lose weight almost immediately whereas the other four alloys appeared to undergo an incubation period of 50-150 1-hr cycles. Examination of the cross-sectional microstructures showed regions of rampant corrosion attack (propagation stage) in all five alloys after 300 1-hr cycles . This rampant corrosion morphology was similar for each of the alloys with Ni and Cr sulfides located in an inner subscale region. The morphology of the attack suggests a classic "Type I", or high temperature, hot corrosion attack.

  3. Interfacial shear bond strength between different base metal alloys and five low fusing feldspathic ceramic systems.

    PubMed

    Sipahi, Cumhur; Ozcan, Mutlu

    2012-01-01

    This study compared the bond strength between metal alloys and 5 ceramic systems. Ceramic systems (Vita VMK68, Ivoclar IPSd. SIGN, Ceramco II, Matchmaker and Finesse) were fired onto either Ni-Cr or Co-Cr base metal alloy. Metal-ceramic interfaces were subjected to shear loading until failure. The ceramic type significantly affected the bond strength results (p<0.05). For Ni-Cr alloy, the results ranged between 15.4-25.3 MPa and for Co-Cr alloy between 13.3-19.0 MPa. The highest mean bond strength value was obtained with the combination of Ni-Cr alloy-Ceramco II (25.3 MPa), the lowest bond strength was received from the combination of Co-Cr alloy-Ivoclar IPS d.SIGN ceramic (13.3 MPa). Adhesive failures between metal and ceramic were significantly more frequent with Ni-Cr alloy (31 out of 50) than with Co-Cr (20 out of 50) (p<0.05). Ceramco II presented the highest bond strength with both Ni-Cr and Co-Cr being significantly different from one another.

  4. Chromium boron surfaced nickel-iron base alloys

    NASA Technical Reports Server (NTRS)

    Rashid, James M. (Inventor); Friedrich, Leonard A. (Inventor); Freling, Melvin (Inventor)

    1984-01-01

    Chromium boron diffusion coatings on nickel iron alloys uniquely provide them with improvement in high cycle fatigue strength (up to 30%) and erosion resistance (up to 15 times), compared to uncoated alloy. The diffused chromium layer extends in two essential concentration zones to a total depth of about 40.times.10.sup.-6 m, while the succeeding boron layer is limited to 50-90% of the depth of the richest Cr layer nearest the surface. Both coatings are applied using conventional pack diffusion processes.

  5. Creep behavior of uranium carbide-based alloys

    NASA Technical Reports Server (NTRS)

    Seltzer, M. S.; Wright, T. R.; Moak, D. P.

    1975-01-01

    The present work gives the results of experiments on the influence of zirconium carbide and tungsten on the creep properties of uranium carbide. The creep behavior of high-density UC samples follows the classical time-dependence pattern of (1) an instantaneous deformation, (2) a primary creep region, and (3) a period of steady-state creep. Creep rates for unalloyed UC-1.01 and UC-1.05 are several orders of magnitude greater than those measured for carbide alloys containing a Zr-C and/or W dispersoid. The difference in creep strength between alloyed and unalloyed materials varies with temperature and applied stress.

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  7. Micromagnetic analysis of Heusler alloy-based perpendicular double barrier synthetic antiferromagnetic free layer MTJs

    NASA Astrophysics Data System (ADS)

    Ghosh, Bahniman; Dwivedi, Kshitij

    2015-07-01

    We investigate spin transfer torque switching in a perpendicular double barrier synthetic antiferromagnetic free layer MTJ stack using micromagnetic simulations. For the material used in free layers, we use two different Cobalt-based Heusler alloys and compare their performance on the basis of switching speed, thermal stability and Tunnel magnetoresistance. We show that for Heusler alloys switching from one state to other is significantly faster but they suffer from the drawback of low thermal stability.

  8. Subtask 12D5: Thermal creep properties of vanadium-base alloys

    SciTech Connect

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

    1995-03-01

    The objective of this work is to provide baseline data on the thermal creep properties of candidate vanadium base alloys. Vanadium-base alloys are promising candidate materials for application in fusion reactor structural components because of several important advantages. V-4Cr-4Ti has been identified as one of the most promising candidate alloys and was selected for comprehensive tests and examination. In the present investigation, thermal creep rates and stress-rupture life of V-4Cr-4Ti and V-10Cr-5Ti alloys were determined at 600{degrees}C. The impurity composition and microstructural characteristics of creep-tested specimens were analyzed and correlated with the measured creep properties. The results of these tests show that V-4Cr-4Ti, which contains impurity compositions typical of a commercially fabricated vanadium-based alloy, exhibits creep strength substantially superior to that of V-20Ti, HT-9, or Type 316 stainless steel. The V-10Cr-5Ti alloy exhibits creep strength somewhat higher than that of V-4Cr-4Ti. 9 refs., 7 figs., 2 tabs.

  9. Bond Strength of Resin Cements to Noble and Base Metal Alloys with Different Surface Treatments

    PubMed Central

    Raeisosadat, Farkhondeh; Ghavam, Maryam; Hasani Tabatabaei, Masoomeh; Arami, Sakineh; Sedaghati, Maedeh

    2014-01-01

    Objectives: The bond strength of resin cements to metal alloys depends on the type of the metal, conditioning methods and the adhesive resins used. The purpose of this study was to evaluate the bond strength of resin cements to base and noble metal alloys after sand blasting or application of silano-pen. Materials and Method: Cylinders of light cured Z 250 composite were cemented to “Degubond 4” (Au Pd) and “Verabond” (Ni Cr) alloys by either RelyX Unicem or Panavia F2, after sandblasting or treating the alloys with Silano-Pen. The shear bond strengths were evaluated. Data were analyzed by three-way ANOVA and t tests at a significance level of P<0.05. Results: When the alloys were treated by Silano-Pen, RelyX Unicem showed a higher bond strength for Degubond 4 (P=0.021) and Verabond (P< 0.001). No significant difference was observed in the bond strength of Panavia F2 to the alloys after either of surface treatments, Degubond 4 (P=0.291) and Verabond (P=0.899). Panavia F2 showed a higher bond strength to sandblasted Verabond compared to RelyX Unicem (P=0.003). The bond strength of RelyX Unicem was significantly higher to Silano-Pen treated Verabond (P=0.011). The bond strength of the cements to sandblasted Degubond 4 showed no significant difference (P=0.59). RelyX Unicem had a higher bond strength to Silano-Pen treated Degubond 4 (P=0.035). Conclusion: The bond strength of resin cements to Verabond alloy was significantly higher than Degubond 4. RelyX Unicem had a higher bond strength to Silano-Pen treated alloys. Surface treatments of the alloys did not affect the bond strength of Panavia F2. PMID:25628687

  10. Progress with alloy 33 (UNS R20033), a new corrosion resistant chromium-based austenitic material

    SciTech Connect

    Koehler, M.; Heubner, U.; Eichenhofer, K.W.; Renner, M.

    1996-11-01

    Alloy 33 (UNS R20033), a new chromium-based corrosion resistant austenitic material with nominally (wt. %) 33 Cr, 32 Fe, 31 Ni, 1.6 Mo, 0.6 Cu, 0.4 N has been introduced to the market in 1995. This paper provides new data on this alloy with respect to mechanical properties, formability, weldability, sensitization characteristics and corrosion behavior. Mechanical properties of weldments including ductility have been established, and match well with those of wrought plate material, without any degradation of ISO V-notch impact toughness in the heat affected zone. When aged up to 8 hours between 600 C and 1,000 C the alloy is not sensitized when tested in boiling azeotropic nitric acid (Huey test). Under field test conditions alloy 33 shows excellent resistance to corrosion in flowing 96--98.5% H{sub 2}SO{sub 4} at 135 C--140 C and flowing 99.1% H{sub 2}SO{sub 4} at 150 C. Alloy 33 has also been tested with some success in 96% H{sub 2}SO{sub 4} with nitrosyl additions at 240 C. In nitric acid alloy 33 is corrosion resistant up to 85% HNO{sub 3} and 75 C or even more. Alloy 33 is also corrosion resistant in 1 mol. HCl at 40 C and in NaOH/NaOCl-solutions. In artificial seawater the pitting potential remains unchanged up to 75 C and is still well above the seawater`s redox potential at 95 C. Alloy 33 can be easily manufactured into all product forms required. The new data provided support the multipurpose character of alloy 33 to cope successfully with many requirements of the Chemical Process Industry, the Oil and Gas Industry and the Refinery Industry.

  11. Fracture behavior of nickel-based alloys in water

    SciTech Connect

    Mills, W.J.; Brown, C.M.

    1999-08-01

    The cracking resistance of Alloy 600, Alloy 690 and their welds, EN82H and EN52, was characterized by conducting J{sub IC} tests in air and hydrogenated water. All test materials displayed excellent toughness in air and high temperature water, but Alloy 690 and the two welds were severely embrittled in low temperature water. In 54 C water with 150 cc H{sub 2}/kg H{sub 2}O, J{sub IC} values were typically 70% to 95% lower than their air counterparts. The toughness degradation was associated with a fracture mechanism transition from microvoid coalescence to intergranular fracture. Comparison of the cracking response in water with that for hydrogen-precharged specimens tested in air demonstrated that susceptibility to low temperature cracking is due to hydrogen embrittlement of grain boundaries. The effects of water temperature, hydrogen content and loading rate on low temperature crack propagation were studied. In addition, testing of specimens containing natural weld defects and as-machined notches was performed to determine if low temperature cracking can initiate at these features. Unlike the other materials, Alloy 600 is not susceptible to low temperature cracking as the toughness in 54 C water remained high and a microvoid coalescence mechanism was operative in both air and water.

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

    NASA Technical Reports Server (NTRS)

    Moore, P.

    1980-01-01

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

  13. Application of Laser Design of Amorphous Feco-Based Alloys for the Formation of Amorphous-Crystalline Composites

    NASA Astrophysics Data System (ADS)

    Permyakova, I. E.; Glezer, A. M.; Ivanov, A. A.; Shelyakov, A. V.

    2016-01-01

    Morphological and fractographic features of change of FeCo-based amorphous alloy surfaces after laser treatment are studied in detail. Regimes of laser treatment that allow various degrees of crystallization of the examined alloys to be obtained, including thin (<1 •m) crystal layers on amorphous alloy surfaces, amorphous-crystalline composites, and completely crystalline alloys are adjusted. The Vickers hardness is estimated in zones of selective laser irradiation. The structure of the examined alloys attendant to the change of their mechanical properties is analyzed.

  14. Structure-property correlation of Zr-base alloys

    NASA Astrophysics Data System (ADS)

    Wadekar, S. L.; Raman, V. V.; Banerjee, S.; Asundi, M. K.

    1988-01-01

    Zirconium alloys, because of their unique combination of high strength, good corrosion resistance in water and low capture cross-section for thermal neutrons, have become attractive for use as structural materials in the nuclear industry. Presently, Zircaloy-2 and Zircaloy-4 find wide application as fuel and pressure tube materials for water cooled power reactors. In order to understand how the various alloying elements of Zircaloy, namely Sn, Fe, Cr and Ni, affect the mechanical properties, a programme has been initiated to evolve a correlation between chemistry, microstructure and mechanical properties of Zr-alloy containing various amounts of Sn, Fe and Cr. In the present investigation, mechanical properties of Zr-alloys with various addition of Sn, Fe and Cr have been determined at 300 K and 573 K in various metallurgical conditions such as recrystallised annealed, β-quenched, tempered and α-annealed conditions. The study revealed that the reduced tin content dit not affect the mechanical properties as the reduced tin leads to formation of fine precipitates. The mechanical properties were also not altered drastically with the low level of iron and chromium concentrations studied. Cold work and α-annealing after β-quenching resulted in the growth and redistribution of second phase particles. Metallographie studies showed that particle distribution was not uniform. A TEM investigation of the alloys has also been undertaken to study the details of microstructure developed during various heat-treated conditions. It has been found that the β-quenched samples exhibit the most uniform microstructure consisting of acicular alpha phase with lath boundary enriched by solute element and fine intermetallic particle formation. The observed microstructural features together with the mechanical properties data have been compared with the available mechanical properties cum microstructure of Zircaloy.

  15. Ductility enhancement in NiAl (B2)-base alloys by microstructural control

    NASA Astrophysics Data System (ADS)

    Ishida, K.; Kainuma, R.; Ueno, N.; Nishizawa, T.

    1991-02-01

    An attempt to improve ductility of NiAl (B2)-base alloys has been made by the addition of alloying elements and the control of microstructure. It has been found that a small amount of fcc γ phase formed by the addition of Fe, Co, and Cr has a drastic effect not only on the hot workability but also on the tensile ductility at room temperature. The enhancement in ductility is mainly due to the modification of Β-phase grains by the coexistence of γ phase. The effect of alloying elements on the hot forming ability is strongly related to the phase equilibria and partition behavior among γ, γ' (L12 structure), and Β phases in the Ni-Al-X alloy systems. The ductility-enhancement method shows promise for expanding the practical application of nickel aluminide.

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

    SciTech Connect

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

    2007-08-10

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

  17. Combating high temperature environmental degradation by existing and new nickel and iron base alloys

    SciTech Connect

    Agarwal, D.C.; Brill, U.

    1994-12-31

    The need for high temperature materials is encountered in a wide variety of modem industries such as in metallurgical, chemical, petrochemical, glass manufacture, heat treatment, waste incinerators, heat recovery, advanced energy conversion systems and others. Depending on the condition of chemical make-up and temperatures, a variety of aggressive corrosive environments are produced, which could be either sulfidizing, carburizing, halogenizing, nitriding, reducing and oxidizing in nature or a combination thereof All high temperature alloys have certain limitations and the optimum choice is often a compromise between the mechanical property requirement constraints at maximum temperature of operation and environmental degradation constraints imposed due to the corrosive species present. This paper addresses the various deterioration mechanisms in metallic alloys system due to the above modes of attack and the role of various alloying elements in minimizing the environmental degradation. Some laboratory and field data on two new nickel base alloys are also presented.

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

    SciTech Connect

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

    1993-06-01

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

  19. Pack cementation diffusion coatings for Fe-base and refractory alloys. Final report

    SciTech Connect

    Rapp, R.A.

    1998-03-10

    With the aid of computer-assisted calculations of the equilibrium vapor pressures in halide-activated cementation packs, processing conditions have been identified and experimentally verified for the codeposition of two or more alloying elements in a diffusion coating on a variety of steels and refractory metal alloys. A new comprehensive theory to treat the multi-component thermodynamic equilibria in the gas phase for several coexisting solid phases was developed and used. Many different processes to deposit various types of coatings on several types of steels were developed: Cr-Si codeposition for low- or medium-carbon steels, Cr-Al codeposition on low-carbon steels to yield either a Kanthal-type composition (Fe-25Cr-4Al in wt.%) or else a (Fe, Cr){sub 3}Al surface composition. An Fe{sub 3}Al substrate was aluminized to achieve an FeAl surface composition, and boron was also added to ductilize the coating. The developmental Cr-lean ORNL alloys with exceptional creep resistance were Cr-Al coated to achieve excellent oxidation resistance. Alloy wires of Ni-base were aluminized to provide an average composition of Ni{sub 3}Al for use as welding rods. Several different refractory metal alloys based on Cr-Cr{sub 2}Nb have been silicided, also with germanium additions, to provide excellent oxidation resistance. A couple of developmental Cr-Zr alloys were similarly coated and tested.

  20. Subtask 12F1: Effect of neutron irradiation on swelling of vanadium-base alloys

    SciTech Connect

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

    1995-03-01

    The objective of this work is to determine the effects of neutron irradiation on the density change, void distribution, and microstructural evolution of vanadium-base alloys. Swelling behavior and microstructural evolution of V-Ti, V-Cr-Ti, and V-Ti-Si alloys were investigated after irradiation at 420-600{degrees}C 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. 18 refs., 6 figs., 1 tab.

  1. Subtask 12F3: Effects of neutron irradiation on tensile properties of vanadium-base alloys

    SciTech Connect

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

    1995-03-01

    The objective of this work is to determine the effects of neutron irradiation on the tensile properties of candidate vanadium-base alloys. Vanadium-base alloys of the V-Cr-Ti system are attractive candidates for use as structural materials in fusion reactors. The current focus of the U.S. program of research on these alloys is on the V-(4-6)Cr-(3-6)Ti-(0.05-0.1)Si (in wt.%) alloys. In this paper, we present experimental results on the effects of neutron irradiation on tensile properties of selected candidate alloys after irradiation at 400{degrees}C-600{degrees}C in lithium in fast fission reactors to displacement damages of up to {approx}120 displacement per atom (dpa). Effects of irradiation temperature and dose on yield and ultimate tensile strengths and uniform and total elongations are given for tensile test temperatures of 25{degrees}C, 420{degrees}C, 500{degrees}, and 600{degrees}C. Effects of neutron damage on tensile properties of the U.S. reference alloy V-4Cr-4Ti are examined in detail. 7 refs., 10 figs., 1 tab.

  2. Corrosion Performance of Fe-Based Alloys in Simulated Oxy-Fuel Environment

    NASA Astrophysics Data System (ADS)

    Zeng, Zuotao; Natesan, Ken; Cai, Zhonghou; Rink, David L.

    2016-09-01

    The long-term corrosion of Fe-based alloys in simulated oxy-fuel environment at 1023 K (750 °C) was studied. Detailed results are presented on weight change, scale thickness, internal penetration, microstructural characteristics of the corrosion products, and the cracking of scales for the alloys after exposure at 1023 K (750 °C) for up to 3600 hours. An incubation period during which the corrosion rate was low was observed for the alloys. After the incubation period, the corrosion accelerated, and the corrosion process followed linear kinetics. Effects of alloy, CaO-containing ash, and gas composition on the corrosion rate were also studied. In addition, synchrotron nanobeam X-ray analysis was employed to determine the phase and chemical composition of the oxide layers on the alloy surface. Results from these studies are being used to address the long-term corrosion performance of Fe-based alloys in various coal-ash combustion environments and to develop methods to mitigate high-temperature ash corrosion.

  3. Physical Simulation of Friction Stir Welding and Processing of Nickel-Base Alloys Using Hot Torsion

    NASA Astrophysics Data System (ADS)

    Rule, James R.; Lippold, John C.

    2013-08-01

    The Gleeble hot torsion test was utilized in an attempt to simulate the friction stir-processed microstructure of three Ni-base alloys: Hastelloy X, Alloy 625, and Alloy 718. The simulation temperatures were based on actual thermal cycles measured by embedded thermocouples during friction stir processing of these alloys. Peak process temperatures were determined to be approximately 1423 K (1150 °C) for Hastelloy X and Alloy 625 K and 1373 K (352 °C and 1100 °C) for Alloy 718. The peak temperature and cooling rates were programed into the Gleeble™ 3800 thermo-mechanical simulator to reproduce the stir zone and thermo-mechanically affected zone (TMAZ) microstructures. The TMAZ was successfully simulated using this technique, but the stir zone microstructure could not be accurately reproduced, with hot torsion samples exhibiting larger grain size than actual friction stir processing trials. Shear stress and strain rates as a function of temperature were determined for each material using hot torsion simulation.

  4. Effect of alloying elements on passivity and breakdown of passivity of Fe- and Ni-based alloys mechanistics aspects

    SciTech Connect

    Szklarska-Amialowska, Z.

    1992-06-01

    On the basis of the literature data and the current results, the mechanism of pitting corrosion of Al-alloys is proposed. An assumption is made that the transport of Cl- ions through defects in the passive film of aluminum an aluminum alloys is not a rate determining step in pitting. The pit development is controlled by the solubility of the oxidized alloying elements in acid solutions. A very good correlation was found between the pitting potential and the oxidized alloying elements for metastable Al-Cr, Al-Zr, Al-W, and Al-Zn alloys. We expect that the effect of oxidized alloying elements in other passive alloys will be the same as in Al-alloys. To verify this hypothesis, susceptibility to pitting in the function of alloying elements in the binary alloys and the composition of the oxide film has to be measured. We propose studying Fe- and Ni-alloys produced by a sputtering deposition method. Using this method one-phaseous alloy can be obtained, even when the two metals are immiscible using conventional methods. Another advantage to studying sputtered alloys is to find new materials with superior resistance to localized corrosion.

  5. Computer-Aided Design of Manufacturing Chain Based on Closed Die Forging for Hardly Deformable Cu-Based Alloys

    NASA Astrophysics Data System (ADS)

    Pietrzyk, Maciej; Kuziak, Roman; Pidvysots'kyy, Valeriy; Nowak, Jarosław; Węglarczyk, Stanisław; Drozdowski, Krzysztof

    2013-07-01

    Two copper-based alloys were considered, Cu-1 pct Cr and Cu-0.7 pct Cr-1 pct Si-2 pct Ni. The thermal, electrical, and mechanical properties of these alloys are given in the paper and compared to pure copper and steel. The role of aging and precipitation kinetics in hardening of the alloys is discussed based upon the developed model. Results of plastometric tests performed at various temperatures and various strain rates are presented. The effect of the initial microstructure on the flow stress was investigated. Rheologic models for the alloys were developed. A finite element (FE) model based on the Norton-Hoff visco-plastic flow rule was applied to the simulation of forging of the alloys. Analysis of the die wear for various processes of hot and cold forging is presented as well. A microstructure evolution model was implemented into the FE code, and the microstructure and mechanical properties of final products were predicted. Various variants of the manufacturing cycles were considered. These include different preheating schedules, hot forging, cold forging, and aging. All variants were simulated using the FE method and loads, die filling, tool wear, and mechanical properties of products were predicted. Three variants giving the best combination of forging parameters were selected and industrial trials were performed. The best manufacturing technology for the copper-based alloys is proposed.

  6. Wear Behavior Characterization for the Screening of Magnesium-based Alloys

    NASA Astrophysics Data System (ADS)

    McGhee, Paul R.

    This research is focused on the development of a systematic approach to evaluate the selection of materials for Mg-based alloys under wear conditions for biomedical applications. A pilot study was carried out in order to establish an accurate and reliable wear testing technique for magnesium and its alloys. This pilot study was conducted on aluminum (Al) and pure Mg, and showed that aluminum has a lower wear rate compared to Mg. The technique displayed good repeatability and high precision. For the main study, an ERC Mg-based alloy was to be compared with pure Mg. The same technique, when applied to pure Mg from a different vendor, produced up to 90% scatter in the data. Microstructure was studied to see if it had any correlation with the scatter. It was discovered that Mg ingot from the second vendor had outsized grains that contributed to the disproportional scatter in the wear data. Increasing the stroke length during wear testing was required so that the wear data would be averaged over multiple grains and reduces the variation in computed wear rates. In the main study, wear behavior and friction properties were analyzed using microtribometery, mechanical stylus profilometry, and microindentation. Surface morphology and microstructure were characterized using optical microscopy, scanning electron microscopy, and optical profilometry. For the main study, pure Mg and the ERC alloy as-cast and extruded conditions were compared. Pure Mg and MZCR alloys were extruded at 350°C and 400°C, respectively. Mg and MZCR alloy were cast at 350°C and heat treated at 510°C. The extruded specimens were divided into two sections, cross-section and longitudinal section. Wear tests were carried out under the applied normal load 0.5 N - 2.5 N in 0.5 N increments sliding at a rate of 0.2 Hz for 240 passes. The results show that the alloying and extrusion processes increase the hardness of the MZCR alloy significantly up to 80%. The as-cast MZCR has a lower resistance to wear

  7. Challenges in Developing Oxidation-Resistant Chromium-Based Alloys for Applications Above 900°C

    NASA Astrophysics Data System (ADS)

    Dorcheh, Ali S.; Galetz, Mathias C.

    2016-08-01

    Chromium-based alloys are potential candidates for high-temperature structural applications. This article reviews the challenges of chromium and Cr-alloys used at temperatures higher than 900°C with the focus on their oxidation behavior. First, latest findings on the key environmental factors affecting the oxidation resistance such as volatilization and the impact of nitrogen in air are summarized. Oxidation resistance is addressed with regards to the effects of major alloying elements and reactive elements as well as its correlation with microstructure in multi-phase alloys. Secondly, the existing challenges to develop chromium alloys with enhanced high-temperature oxidation resistance are discussed. It is shown that volatilization and nitridation, the two major obstacles for the use of chromium alloys in air, can be significantly improved by alloy design.

  8. PROCESS OF COATING METALS WITH BISMUTH OR BISMUTH-BASE ALLOYS

    DOEpatents

    Beach, J.G.

    1958-01-28

    A method is described for producing coatings of bismuth or bismuth alloys on a metal base. This is accomplished by electrodepositing the bismuth from an aqueous solution of BiCl/sub 3/, and by making the metal base alternately the cathode and the anode, the cathode periods being twice as long as the anode periods. In one embodiment a nickel coating is first electrodeposited in a known way, and this nickel plated piece is tae base upon which tae bismuth is deposited by the process of this patent. The coated piece is then heat treated to produce a homogeneous Ni--Bi alloy by diffusion.

  9. Dilatometer study of rapidly solidified aluminium-silicon based alloys

    NASA Astrophysics Data System (ADS)

    Varga, B.; Fazakas, E.; Hargitai, H.; Varga, L. K.

    2009-01-01

    Aluminum-Silicon alloys are sought in a large number of automotive and aerospace applications due to their low coefficient of thermal expansion and high wear resistance. The present study focused on structural transformations as a function of the temperature of rapidly solidified hypereutectic Al100-xSix (x = 12, 22 and 40) alloys. Different structures out of equilibrium have been obtained after casting in sand, graphite and copper moulds and by melt spinning. The retained Si content in supersaturated alpha Al and the precipitation of Si is discussed in the light of the dilatometer studies [1, 2, 3] complemented by metallographic microscopy, XRD and DSC [4] measurements. A Kissinger analysis was used to determine the activation energy for the precipitation of supersaturated Si content.

  10. Microstructure Evaluation of Fe-BASED Amorphous Alloys Investigated by Doppler Broadening Positron Annihilation Technique

    NASA Astrophysics Data System (ADS)

    Lu, Wei; Huang, Ping; Wang, Yuxin; Yan, Biao

    2013-07-01

    Microstructure of Fe-based amorphous and nanocrystalline soft magnetic alloy has been investigated by X-ray diffraction (XRD), transmission electronic microscopy (TEM) and Doppler broadening positron annihilation technique (PAT). Doppler broadening measurement reveals that amorphous alloys (Finemet, Type I) which can form a nanocrystalline phase have more defects (free volume) than alloys (Metglas, Type II) which cannot form this microstructure. XRD and TEM characterization indicates that the nanocrystallization of amorphous Finemet alloy occurs at 460°C, where nanocrystallites of α-Fe with an average grain size of a few nanometers are formed in an amorphous matrix. With increasing annealing temperature up to 500°C, the average grain size increases up to around 12 nm. During the annealing of Finemet alloy, it has been demonstrated that positron annihilates in quenched-in defect, crystalline nanophase and amorphous-nanocrystalline interfaces. The change of line shape parameter S with annealing temperature in Finemet alloy is mainly due to the structural relaxation, the pre-nucleation of Cu nucleus and the nanocrystallization of α-Fe(Si) phase during annealing. This study throws new insights into positron behavior in the nanocrystallization of metallic glasses, especially in the presence of single or multiple nanophases embedded in the amorphous matrix.

  11. Nanostructure Characterization of Bismuth Telluride-Based Powders and Extruded Alloys by Various Experimental Methods

    NASA Astrophysics Data System (ADS)

    Vasilevskiy, D.; Bourbia, O.; Gosselin, S.; Turenne, S.; Masut, R. A.

    2011-05-01

    High-resolution transmission electron microscopy (HRTEM) observations of mechanically alloyed powders and bulk extruded alloys give experimental evidence of nanosized grains in bismuth telluride-based materials. In this study we combine HRTEM observations and x-ray diffraction (XRD) measurements, of both mechanically alloyed powders and extruded samples, with mechanical spectroscopy (MS) of extruded rods. Both HRTEM and XRD show that nanostructures with an average grain size near 25 nm can be achieved within 2 h of mechanical alloying from pure elements in an attritor-type milling machine. Residual strain orthogonal to the c-axis of powder nanoparticles has been evaluated at about 1.2% by XRD peak broadening. In contrast, XRD has been found unreliable for evaluation of grain size in highly textured extruded materials for which diffraction conditions are similar to those of single crystals, while MS appears promising for study of bulk extruded samples. Nanostructured extruded alloys at room temperature exhibit an internal friction (IF) background that is one order of magnitude higher than that of conventional zone-melted material with a grain size of several millimeters. IF as a function of sample temperature gives activation energies that are also different between bulk materials having nano- and millimeter-size grains, a result that is attributed to different creep mechanisms. Nanograin size, as well as orientation and volumetric proportion, provide valuable information for optimization of technological parameters of thermoelectric alloys and should be carefully cross-examined by various independent methods.

  12. Tensile properties of vanadium-base alloys with a tungsten/inert-gas weld zone

    SciTech Connect

    Loomis, B.A.; Konicek, C.F.; Nowicki, L.J.; Smith, D.L.

    1992-12-31

    The tensile properties of V-(0-20)Ti and V-(O-15)Cr-5Ti alloys after butt-joining by tungsten/inert-gas (TIG) welding were determined from tests at 25{degrees}C. Tensile tests were conducted on both annealed and cold-worked materials with a TIG weld zone. The tensile properties of these materials were strongly influenced by the microstructure in the heat-affected zone adjacent to the weld zone and by the intrinsic fracture toughness of the alloys. TIG weld zones in these vanadium-base alloys had tensile properties comparable to those of recrystallized alloys without a weld zone. Least affected by the TIG welding were tensile properties of the V-5Ti and V-5Cr-5Ti alloys. Although the tensile properties of the V-5Ti and V- 5Cr-5Ti alloys with a TIG weld zone were acceptable for structural material, these properties would be improved by optimization of the welding parameters for minimum grain size in the heat-affected zone.

  13. Hot Corrosion of Nickel-Base Alloys in Biomass-Derived Fuel Simulated Atmosphere

    SciTech Connect

    Leyens, C.; Pint, B.A.; Wright, I.G.

    1999-02-28

    Biomass fuels are considered to be a promising renewable source of energy. However, impurities present in the fuel may cause corrosion problems with the materials used in the hot sections of gas turbines and only limited data are available so far. As part of the Advanced Turbine Systems Program initiated by the U.S. Department of Energy, the present study provides initial data on the hot corrosion resistance of different nickel-base alloys against sodium sulfate-induced corrosion as a baseline, and against salt compositions simulating biomass-derived fuel deposits. Single crystal nickel-superalloy Rene N5, a cast NiCrAlY alloy, a NiCoCrAlY alloy representing industrially used overlay compositions, and a model {beta}NiAl+Hf alloy were tested in 1h thermal cycles at 950 C with different salt coatings deposited onto the surfaces. Whereas the NiCoCrAlY alloy exhibited reasonable resistance against pure sodium sulfate deposits, the NiCrAiY alloy and Rene N5 were attacked severely. Although considered to be an ideal alumina former in air and oxygen at higher temperatures, {beta}NiAl+Hf also suffered from rapid corrosion attack at 950 C when coated with sodium sulfate. The higher level of potassium present in biomass fuels compared with conventional fuels was addressed by testing a NiCoCrAlY alloy coated with salts of different K/Na atomic ratios. Starting at zero Na, the corrosion rate increased considerably when sodium was added to potassium sulfate. In an intermediate region the corrosion rate was initially insensitive to the K/Na ratio but accelerated when very Na-rich compositions were deposited. The key driver for corrosion of the NiCoCrAlY alloy was sodium sulfate rather than potassium sulfate, and no simple additive or synergistic effect of combining sodium and potassium was found.

  14. Degradation mode survey of titanium-base alloys

    SciTech Connect

    Gdowski, G.E.; Ahluwalia, H.S.

    1995-01-30

    Of the materials reviewed, commercially pure titanium, Ti Gr 2, is the most susceptible to crevice corrosion. Ti Gr 7, 12, and 16 are likely to be resistant to crevice corrosion under the current expected Yucca Mountain repository conditions. Although Grade 7 has the greatest resistance to crevice corrosion it is also the most expensive. Although the possibility of sustained loads cracking exists, it has not yet been observed in a Ti alloys. For hydride precipitation to occur 100{degrees}C, the hydrogen concentration would need to be relatively high, much higher than the maximum amount of hydrogen allowed during the manufacture of ({alpha} Ti alloys (0.0 15 wt%). A large amount of (SCC) stress corrosion cracking data accumulated at SNL and BNL for the WIPP program and by the Canadian Waste Management Program on titanium grades 2 and 12 indicates that there is no SCC at naturally occurring potentials in various brines. Hydride-induced cracking of titanium is a possibility and therefore, further investigation of this phenomenon under credible repository conditions is warranted. One disadvantage of titanium and its alloys is that their strengths decrease rather rapidly with temperature. This is due to the strong temperature dependence of interstitial solute strengthening mechanisms. Ti Gr 12 and 16 are recommended for further consideration as candidate materials for high level nuclear waste containers.

  15. Room temperature synthesis of Ni-based alloy nanoparticles by radiolysis.

    SciTech Connect

    Nenoff, Tina Maria; Berry, Donald T.; Lu, Ping; Leung, Kevin; Provencio, Paula Polyak; Stumpf, Roland Rudolph; Huang, Jian Yu; Zhang, Zhenyuan

    2009-09-01

    Room temperature radiolysis, density functional theory, and various nanoscale characterization methods were used to synthesize and fully describe Ni-based alloy nanoparticles (NPs) that were synthesized at room temperature. These complementary methods provide a strong basis in understanding and describing metastable phase regimes of alloy NPs whose reaction formation is determined by kinetic rather than thermodynamic reaction processes. Four series of NPs, (Ag-Ni, Pd-Ni, Co-Ni, and W-Ni) were analyzed and characterized by a variety of methods, including UV-vis, TEM/HRTEM, HAADF-STEM and EFTEM mapping. In the first focus of research, AgNi and PdNi were studied. Different ratios of Ag{sub x}- Ni{sub 1-x} alloy NPs and Pd{sub 0.5}- Ni{sub 0.5} alloy NP were prepared using a high dose rate from gamma irradiation. Images from high-angle annular dark-field (HAADF) show that the Ag-Ni NPs are not core-shell structure but are homogeneous alloys in composition. Energy filtered transmission electron microscopy (EFTEM) maps show the homogeneity of the metals in each alloy NP. Of particular interest are the normally immiscible Ag-Ni NPs. All evidence confirmed that homogeneous Ag-Ni and Pd-Ni alloy NPs presented here were successfully synthesized by high dose rate radiolytic methodology. A mechanism is provided to explain the homogeneous formation of the alloy NPs. Furthermore, studies of Pd-Ni NPs by in situ TEM (with heated stage) shows the ability to sinter these NPs at temperatures below 800 C. In the second set of work, CoNi and WNi superalloy NPs were attempted at 50/50 concentration ratios using high dose rates from gamma irradiation. Preliminary results on synthesis and characterization have been completed and are presented. As with the earlier alloy NPs, no evidence of core-shell NP formation occurs. Microscopy results seem to indicate alloying occurred with the CoNi alloys. However, there appears to be incomplete reduction of the Na{sub 2}WO{sub 4} to form the W

  16. Alloy B-10, a new nickel-based alloy for strong chloride-containing, highly acidic and oxygen-deficient environments

    SciTech Connect

    Kohler, M.; Kirchheiner, R.; Stenner, F.

    1998-12-31

    Alloy B-10 is a Ni-Mo-Cr alloy, recently developed for highly acidic but oxygen-deficient environments in the chemical process and environmental protection industries. The new nickel-based alloy with nominally (wt. %) 62 Ni, 24 MO, 8 Cr and 6 Fe, exhibits excellent corrosion resistance in intermediate concentrations of sulfuric acid, as well as in hydrochloric acid, even with additions of small amounts of oxidizing agents. In a simulated Flue Gas Desulfurization (FGD) environment of sulfuric acid of pH 1 with additions of 7% chloride and 0.01% fluoride, and also containing 15% gypsum the new alloy demonstrated high crevice corrosion resistance at 100 C, whereas a common Ni-Cr-Mo alloy of the C-type suffers crevice corrosion under the same conditions. This new alloy can easily be welded without filler or using matching filler. Good practical experience has been gained with Alloy B-10 in a district heating power station as a tube sheet and bottom wall liner for a glass tube heat exchanger working at 130 C with condensing 70% sulfuric acid.

  17. Joint effect of scandium and zirconium on the structure and the strength properties of Al-Mg2Si-Based alloys

    NASA Astrophysics Data System (ADS)

    Rokhlin, L. L.; Bochvar, N. R.; Tarytina, I. E.

    2015-09-01

    The joint effect of scandium and zirconium on the strength properties and the electrical resistivity of industrial Al-Mg2Si-based alloys has been studied. The additional alloying of Al-Mg2Si alloys with transition metals leads to substantial grain refinement of the aluminum solid-solution and, therefore, an increase in the strength properties of the industrial alloys.

  18. Tetragonal Heusler-Like Mn-Ga Alloys Based Perpendicular Magnetic Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Ma, Qinli; Sugihara, Atsushi; Suzuki, Kazuya; Zhang, Xianmin; Miyazaki, Terunobu; Mizukami, Shigemi

    2014-10-01

    Films of the Mn-based tetragonal Heusler-like alloys, such as Mn-Ga, exhibit a large perpendicular magnetic anisotropy (PMA), small damping constant, small saturation magnetization and large spin polarizations. These properties are attractive for the application to the next generation high density spin-transfer-torque (STT) magnetic random access memory (STT-MRAM). We reviewed the structure, magnetic properties and Gilbert damping of the alloy films with large PMA, and the current status of research on tunnel magnetoresistance (TMR) in perpendicular magnetic tunnel junctions (p-MTJs) based on Mn-based tetragonal Heusler-like alloy electrode, and also discuss the issues for the application of those to STT-MRAM.

  19. Quantitative tool for FGD alloy selection based on pH and chloride

    SciTech Connect

    Ellis, P.F. II

    1998-12-31

    The pitting resistance equivalent (PRE) parameter is a widely recognized tool for ranking the relative pitting and crevice corrosion resistance of austenitic stainless steels and chromium-containing nickel-base alloys. However, it has not previously been correlated to alloy performance under specific flue gas desulfurization (FGD) conditions of temperature, chloride, and pH. Quantitative correlations have now been developed between the extended PRE parameter--which includes the effects of nitrogen and tungsten as well as chromium and molybdenum--and predicted alloy performance under FGD conditions based on previously published Schillmoller-Kijhlert pH-Chloride diagrams. The resulting equations allow estimation of the threshold chloride level for significant localized corrosion in mechanical crevices or under deposits on fouled surfaces based on alloy composition and solution pH. While developed for lime/limestone FGD slurry, the correlations are valid for other aerated aqueous solutions with pH between 4 and 8 and temperatures between 49 and 66 C (120--150 F). Results for 35 FGD construction alloys are presented for three cases: the nominal chloride thresholds, the conservative chloride thresholds, and the critical, or ultraconservative, chloride thresholds.

  20. The strengthening mechanism of a nickel-based alloy after laser shock processing at high temperatures

    NASA Astrophysics Data System (ADS)

    Li, Yinghong; Zhou, Liucheng; He, Weifeng; He, Guangyu; Wang, Xuede; Nie, Xiangfan; Wang, Bo; Luo, Sihai; Li, Yuqin

    2013-10-01

    We investigated the strengthening mechanism of laser shock processing (LSP) at high temperatures in the K417 nickel-based alloy. Using a laser-induced shock wave, residual compressive stresses and nanocrystals with a length of 30-200 nm and a thickness of 1 μm are produced on the surface of the nickel-based alloy K417. When the K417 alloy is subjected to heat treatment at 900 °C after LSP, most of the residual compressive stress relaxes while the microhardness retains good thermal stability; the nanocrystalline surface has not obviously grown after the 900 °C per 10 h heat treatment, which shows a comparatively good thermal stability. There are several reasons for the good thermal stability of the nanocrystalline surface, such as the low value of cold hardening of LSP, extreme high-density defects and the grain boundary pinning of an impure element. The results of the vibration fatigue experiments show that the fatigue strength of K417 alloy is enhanced and improved from 110 to 285 MPa after LSP. After the 900 °C per 10 h heat treatment, the fatigue strength is 225 MPa the heat treatment has not significantly reduced the reinforcement effect. The feature of the LSP strengthening mechanism of nickel-based alloy at a high temperature is the co-working effect of the nanocrystalline surface and the residual compressive stress after thermal relaxation.

  1. Novel Zn-based alloys for biodegradable stent applications: Design, development and in vitro degradation.

    PubMed

    Mostaed, E; Sikora-Jasinska, M; Mostaed, A; Loffredo, S; Demir, A G; Previtali, B; Mantovani, D; Beanland, R; Vedani, M

    2016-07-01

    The search for a degradable metal simultaneously showing mechanical properties equal or higher to that of stainless steel and uniform degradation is still an open challenge. Several magnesium-based alloys have been studied, but their degradation rate has proved to be too fast and rarely homogeneous. Fe-based alloys show appropriate mechanical properties but very low degradation rate. In the present work, four novel Zn-Mg and two Zn-Al binary alloys were investigated as potential biodegradable materials for stent applications. The alloys were developed by casting process and homogenized at 350°C for 48h followed by hot extrusion at 250°C. Tube extrusion was performed at 300°C to produce tubes with outer/inner diameter of 4/1.5mm as precursors for biodegradable stents. Corrosion tests were performed using Hanks׳ modified solution. Extruded alloys exhibited slightly superior corrosion resistance and slower degradation rate than those of their cast counterparts, but all had corrosion rates roughly half that of a standard purity Mg control. Hot extrusion of Zn-Mg alloys shifted the corrosion regime from localized pitting to more uniform erosion, mainly due to the refinement of second phase particles. Zn-0.5Mg is the most promising material for stent applications with a good combination of strength, ductility, strain hardening exponent and an appropriate rate of loss of mechanical integrity during degradation. An EBSD analysis in the vicinity of the laser cut Zn-0.5Mg tube found no grain coarsening or texture modification confirming that, after laser cutting, the grain size and texture orientation of the final stent remains unchanged. This work shows the potential for Zn alloys to be considered for stent applications. PMID:27062241

  2. Novel Zn-based alloys for biodegradable stent applications: Design, development and in vitro degradation.

    PubMed

    Mostaed, E; Sikora-Jasinska, M; Mostaed, A; Loffredo, S; Demir, A G; Previtali, B; Mantovani, D; Beanland, R; Vedani, M

    2016-07-01

    The search for a degradable metal simultaneously showing mechanical properties equal or higher to that of stainless steel and uniform degradation is still an open challenge. Several magnesium-based alloys have been studied, but their degradation rate has proved to be too fast and rarely homogeneous. Fe-based alloys show appropriate mechanical properties but very low degradation rate. In the present work, four novel Zn-Mg and two Zn-Al binary alloys were investigated as potential biodegradable materials for stent applications. The alloys were developed by casting process and homogenized at 350°C for 48h followed by hot extrusion at 250°C. Tube extrusion was performed at 300°C to produce tubes with outer/inner diameter of 4/1.5mm as precursors for biodegradable stents. Corrosion tests were performed using Hanks׳ modified solution. Extruded alloys exhibited slightly superior corrosion resistance and slower degradation rate than those of their cast counterparts, but all had corrosion rates roughly half that of a standard purity Mg control. Hot extrusion of Zn-Mg alloys shifted the corrosion regime from localized pitting to more uniform erosion, mainly due to the refinement of second phase particles. Zn-0.5Mg is the most promising material for stent applications with a good combination of strength, ductility, strain hardening exponent and an appropriate rate of loss of mechanical integrity during degradation. An EBSD analysis in the vicinity of the laser cut Zn-0.5Mg tube found no grain coarsening or texture modification confirming that, after laser cutting, the grain size and texture orientation of the final stent remains unchanged. This work shows the potential for Zn alloys to be considered for stent applications.

  3. VANADIUM ALLOYS

    DOEpatents

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

    1959-05-12

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

  4. Base metal alloys with self-healing native conductive oxides for electrical contact materials

    NASA Astrophysics Data System (ADS)

    Aindow, M.; Alpay, S. P.; Liu, Y.; Mantese, J. V.; Senturk, B. S.

    2010-10-01

    Base metals for electrical contacts exhibit high bulk conductivities but form low-conductivity native oxide scales in air, leading to unacceptably high contact resistances. Here we show that alloying base metals can lead to higher conductivity native scales by: doping to enhance carrier concentration; inducing mixed oxidation states to give electron/polaron hopping; and/or phase separation for conducting pathways. Data from Cu-La, Fe-V, and Ni-Ru alloys demonstrate the viability of these approaches, yielding contact resistances up to 106 times lower than that for oxidized Cu.

  5. Irradiation effects in oxide dispersion strengthened (ODS) Ni-base alloys for Gen. IV nuclear reactors

    NASA Astrophysics Data System (ADS)

    Oono, Naoko; Ukai, Shigeharu; Kondo, Sosuke; Hashitomi, Okinobu; Kimura, Akihiko

    2015-10-01

    Oxide particle dispersion strengthened (ODS) Ni-base alloys are irradiated by using simulation technique (Fe/He dual-ion irradiation) to investigate the reliability to Gen. IV high-temperature reactors. The fine oxide particles with less than 10 nm in average size and approximately 8.0 × 1022 m-3 in number density remained after 101 dpa irradiation. The tiny helium bubbles were inside grains, not at grain-boundaries; it is advantageous effect of oxide particles which trap the helium atoms at the particle-matrix interface. Ni-base ODS alloys demonstrated their great ability to overcome He embrittlement.

  6. Effect of rhenium on short term oxidation of niobium based alloys for high temperature applications

    NASA Astrophysics Data System (ADS)

    Sierra, Ruth M.

    The effect of adding Re to Nb-based alloys and is intended to analyze in depth the microstructures of Nb based alloys with Re, Si and Cr additions, in atomic percentages. The binary alloys (Nb-5Re, Nb-5Si and Nb-5Cr) reveal the formation of a single phase, NbSS, NbSS + Nb3Si and NbSS+NbCr2 respectively. The formation of the single phase was confirmed by TEM studies for the Nb-5Re alloy. Addition of Re to form ternary alloys, has helped in the formation of Nb5Si 3 and (Nb, Re) Cr2, in Nb-5Re- 5Si and Nb-5Re-5Cr respectively. Quaternary alloy Nb-5Re-5Si-5Cr has Nb5Si3, NbCr2 and NbSS. The oxidation behavior has been studied and the formation of the oxides has been characterized using XRD, SEM, EDS. Nb-Re-Si-Cr-X (Al, B, W) alloy system has been examined at temperatures between 700 and 1400°C in air. The continued work was to develop and discover a new materials system capable of replacing nickel based super alloys. Additions of aluminum were found to provide limited oxidation resistance. A discontinuous layer of Al2O3 and SiO2 was observed to form at all temperatures adapted for this study. Alloy containing aluminum additions were observed to suffer from pest oxidation at intermediate temperatures due to the development of Nb2O5. Poor oxidation resistance at intermediate temperatures for alloys with aluminum additions was attributed to a transformation in the structure of Nb2O5 formed. Pesting was observed at 900°C, consuming the metal completely. Additions of chromium were observed to increase oxidation resistance through the development of a layered oxide structure containing SiO2 and CrNbO4. Internal oxidation layer was observed to develop oxides in the midst of the phases formed. Boron addition has helped in the formation of the 3, 5 silicides, NbSS, and Laves phase. The combination of oxides of Nb2O5, CrNbO4 and SiO2 has helped improve the oxidation resistance of the alloy. Rhenium in this alloy has been a major element in terms of forming Re-oxides which has

  7. Microstructural Characterization of Base Metal Alloys with Conductive Native Oxides for Electrical Contact Applications

    NASA Astrophysics Data System (ADS)

    Senturk, Bilge Seda

    Metallic contacts are a ubiquitous method of connecting electrical and electronic components/systems. These contacts are usually fabricated from base metals because they are inexpensive, have high bulk electrical conductivities and exhibit excellent formability. Unfortunately, such base metals oxidize in air under ambient conditions, and the characteristics of the native oxide scales leads to contact resistances orders of magnitude higher than those for mating bare metal surface. This is a critical technological issue since the development of unacceptably high contact resistances over time is now by far the most common cause of failure in electrical/electronic devices and systems. To overcome these problems, several distinct approaches are developed for alloying base metals to promote the formation of self-healing inherently conductive native oxide scales. The objective of this dissertation study is to demonstrate the viability of these approaches through analyzing the data from Cu-9La (at%) and Fe-V binary alloy systems. The Cu-9 La alloy structure consists of eutectic colonies tens of microns in diameter wherein a rod-like Cu phase lies within a Cu6La matrix phase. The thin oxide scale formed on the Cu phase was found to be Cu2O as expected while the thicker oxide scale formed on the Cu6La phase was found to be a polycrystalline La-rich Cu2O. The enhanced electrical conductivity in the native oxide scale of the Cu-9La alloy arises from heavy n-type doping of the Cu2O lattice by La3+. The Fe-V alloy structures consist of a mixture of large elongated and equiaxed grains. A thin polycrystalline Fe3O4 oxide scale formed on all of the Fe-V alloys. The electrical conductivities of the oxide scales formed on the Fe-V alloys are higher than that formed on pure Fe. It is inferred that this enhanced conductivity arises from doping of the magnetite with V+4 which promotes electron-polaron hopping. Thus, it has been demonstrated that even in simple binary alloy systems one

  8. Theoretical study of surface plasmon resonance sensors based on 2D bimetallic alloy grating

    NASA Astrophysics Data System (ADS)

    Dhibi, Abdelhak; Khemiri, Mehdi; Oumezzine, Mohamed

    2016-11-01

    A surface plasmon resonance (SPR) sensor based on 2D alloy grating with a high performance is proposed. The grating consists of homogeneous alloys of formula MxAg1-x, where M is gold, copper, platinum and palladium. Compared to the SPR sensors based a pure metal, the sensor based on angular interrogation with silver exhibits a sharper (i.e. larger depth-to-width ratio) reflectivity dip, which provides a big detection accuracy, whereas the sensor based on gold exhibits the broadest dips and the highest sensitivity. The detection accuracy of SPR sensor based a metal alloy is enhanced by the increase of silver composition. In addition, the composition of silver which is around 0.8 improves the sensitivity and the quality of SPR sensor of pure metal. Numerical simulations based on rigorous coupled wave analysis (RCWA) show that the sensor based on a metal alloy not only has a high sensitivity and a high detection accuracy, but also exhibits a good linearity and a good quality.

  9. Hydrogen gas sensor based on palladium and yttrium alloy ultrathin film.

    PubMed

    Yi, Liu; You-Ping, Chen; Han, Song; Gang, Zhang

    2012-12-01

    Compared with the other hydrogen sensors, optical fiber hydrogen sensors based on thin films exhibits inherent safety, small volume, immunity to electromagnetic interference, and distributed remote sensing capability, but slower response characteristics. To improve response and recovery rate of the sensors, a novel reflection-type optical fiber hydrogen gas sensor with a 10 nm palladium and yttrium alloy thin film is fabricated. The alloy thin film shows a good hydrogen sensing property for hydrogen-containing atmosphere and a complete restorability for dry air at room temperature. The variation in response value of the sensor linearly increases with increased natural logarithm of hydrogen concentration (ln[H(2)]). The shortest response time and recovery response time to 4% hydrogen are 6 and 8 s, respectively. The hydrogen sensors based on Pd(0.91)Y(0.09) alloy ultrathin film have potential applications in hydrogen detection and measurement.

  10. Hydrogen gas sensor based on palladium and yttrium alloy ultrathin film

    NASA Astrophysics Data System (ADS)

    Yi, Liu; You-ping, Chen; Han, Song; Gang, Zhang

    2012-12-01

    Compared with the other hydrogen sensors, optical fiber hydrogen sensors based on thin films exhibits inherent safety, small volume, immunity to electromagnetic interference, and distributed remote sensing capability, but slower response characteristics. To improve response and recovery rate of the sensors, a novel reflection-type optical fiber hydrogen gas sensor with a 10 nm palladium and yttrium alloy thin film is fabricated. The alloy thin film shows a good hydrogen sensing property for hydrogen-containing atmosphere and a complete restorability for dry air at room temperature. The variation in response value of the sensor linearly increases with increased natural logarithm of hydrogen concentration (ln[H2]). The shortest response time and recovery response time to 4% hydrogen are 6 and 8 s, respectively. The hydrogen sensors based on Pd0.91Y0.09 alloy ultrathin film have potential applications in hydrogen detection and measurement.

  11. Binary alloy of virus capsids and gold nanoparticles as a Mie-resonance-based optical metamaterial

    NASA Astrophysics Data System (ADS)

    Yannopapas, Vassilios

    2015-02-01

    We present a metamaterial design based on a binary alloy of gold nanoparticles and virus capsids (protein nanoparticles) which possesses metamaterial functionalities in the optical regime. Such binary alloys have already been realized in the laboratory by means of DNA-programmed crystallization of metallic nanoparticles and virus capsids with suitable DNA linkers. The resulting binary alloy has a NaTl-lattice symmetry and operates as Mie resonance-based metamaterial thanks to the extremely high values of the electric permittivity of the virus capsids. By employing an effective-medium theory and rigorous electrodynamic calculations we identify regions of photo-induced magnetic activity stemming from the Mie resonances of the virus capsids. The magnetic activity of the virus particles accompanied by the ordinary electric activity of the gold nanoparticles results in spectral regions of negative refractive index which can be tuned to a desired spectral window by varying the concentration of the RNA within the virus capsids.

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

    SciTech Connect

    Fuchs, G.E.

    1995-02-01

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

  13. Modeling of self-controlling hyperthermia based on nickel alloy ferrofluids: Proposition of new nanoparticles

    NASA Astrophysics Data System (ADS)

    Delavari H., Hamid; Madaah Hosseini, Hamid R.; Wolff, Max

    2013-06-01

    In order to provide sufficient heat without overheating healthy tissue in magnetic fluid hyperthermia (MFH), a careful design of the magnetic properties of nanoparticles is essential. We perform a systematic calculation of magnetic properties of Ni-alloy nanoparticles. Stoner-Wohlfarth model based theories (SWMBTs) are considered and the linear response theory (LRT) is used to extract the hysteresis loop of nickel alloy nanoparticles in alternating magnetic fields. It is demonstrated that in the safe range of magnetic field intensity and frequency the LRT cannot be used for the calculation of the area in the hysteresis for magnetic fields relevant for hyperthermia. The best composition and particle size for self-controlling hyperthermia with nickel alloys is determined based on SWMBTs. It is concluded that Ni-V and Ni-Zn are good candidates for self-controlling hyperthermia.

  14. Fabrication methods and applications of microstructured gallium based liquid metal alloys

    NASA Astrophysics Data System (ADS)

    Khondoker, M. A. H.; Sameoto, D.

    2016-09-01

    This review contains a comparative study of reported fabrication techniques of gallium based liquid metal alloys embedded in elastomers such as polydimethylsiloxane or other rubbers as well as the primary challenges associated with their use. The eutectic gallium–indium binary alloy (EGaIn) and gallium–indium–tin ternary alloy (galinstan) are the most common non-toxic liquid metals in use today. Due to their deformability, non-toxicity and superior electrical conductivity, these alloys have become very popular among researchers for flexible and reconfigurable electronics applications. All the available manufacturing techniques have been grouped into four major classes. Among them, casting by needle injection is the most widely used technique as it is capable of producing features as small as 150 nm width by high-pressure infiltration. One particular fabrication challenge with gallium based liquid metals is that an oxide skin is rapidly formed on the entire exposed surface. This oxide skin increases wettability on many surfaces, which is excellent for keeping patterned metal in position, but is a drawback in applications like reconfigurable circuits, where the position of liquid metal needs to be altered and controlled accurately. The major challenges involved in many applications of liquid metal alloys have also been discussed thoroughly in this article.

  15. Neutronics Evaluation of Lithium-Based Ternary Alloys in IFE Blankets

    SciTech Connect

    Jolodosky, A.; Fratoni, M.

    2014-11-20

    Pre-conceptual fusion blanket designs require research and development to reflect important proposed changes in the design of essential systems, and the new challenges they impose on related fuel cycle systems. One attractive feature of using liquid lithium as the breeder and coolant is that it has very high tritium solubility and results in very low levels of tritium permeation throughout the facility infrastructure. However, lithium metal vigorously reacts with air and water and presents plant safety concerns. If the chemical reactivity of lithium could be overcome, the result would have a profound impact on fusion energy and associated safety basis. The overriding goal of this project is to develop a lithium-based alloy that maintains beneficial properties of lithium (e.g. high tritium breeding and solubility) while reducing overall flammability concerns. To minimize the number of alloy combinations that must be explored, only those alloys that meet certain nuclear performance metrics will be considered for subsequent thermodynamic study. The specific scope of this study is to evaluate the neutronics performance of lithium-based alloys in the blanket of an inertial confinement fusion (ICF) engine. The results of this study will inform the development of lithium alloys that would guarantee acceptable neutronics performance while mitigating the chemical reactivity issues of pure lithium.

  16. Evaluation of Ni-Cr-base alloys for SOFC interconnect applications

    NASA Astrophysics Data System (ADS)

    Yang, Zhenguo; Xia, Guan-Guang; Stevenson, Jeffry W.

    To further understand the suitability of Ni-Cr-base alloys for solid oxide fuel cell (SOFC) interconnect applications, three commercial Ni-Cr-base alloys, Haynes 230, Hastelloy S and Haynes 242 were selected and evaluated for oxidation behavior under different exposure conditions, scale conductivity and thermal expansion. Haynes 230 and Hastelloy S, which have a relatively high Cr content, formed a thin scale mainly comprised of Cr 2O 3 and (Mn,Cr,Ni) 3O 4 spinels under SOFC operating conditions, demonstrating excellent oxidation resistance and a high scale electrical conductivity. In contrast, a thick double-layer scale with a NiO outer layer above a chromia-rich substrate was grown on Haynes 242 in moist air or at the air side of dual exposure samples, indicating limited oxidation resistance for the interconnect application. With a face-centered-cubic (FCC) substrate, all three alloys possess a coefficient of thermal expansion (CTE) that is higher than that of candidate ferritic stainless steels, e.g. Crofer22 APU. Among the three alloys, Haynes 242, which is heavily alloyed with W and Mo and contains a low Cr content, demonstrated the lowest average CTE at 13.1 × 10 -6 K -1 from room temperature to 800 °C, but it was also observed that the CTE behavior of Haynes 242 was very non-linear.

  17. The Estimation of Localized Corrosion Behavior of Ni-Based Dental Alloys Using Electrochemical Techniques

    NASA Astrophysics Data System (ADS)

    Mareci, Daniel; Chelariu, Romeu; Iacoban, Sorin; Munteanu, Corneliu; Bolat, Georgiana; Sutiman, Daniel

    2012-07-01

    The aim of this study is to investigate the electrochemical behavior of the five non-precious Ni-based dental casting alloys in acidified artificial saliva. For comparison, nickel was also investigated. In order to study the localized corrosion resistance, the cyclic potentiodynamic polarization (CCP) and electrochemical impedance spectroscopy were performed. Scanning electron microscopy (SEM) observations were made after the CCP tests. The Ni-Cr alloys with chromium (14-18%) contents were susceptible to localized corrosion. The Ni-Cr-Mo alloy with contents of chromium (≈13%) and molybdenum (9%) presents a dangerous breakdown, but have a zero corrosion potential so that the difference between them is around 650 mV. The Ni-Cr-Mo alloys with higher chromium (22-25%) and molybdenum (9-11%) contents had a much larger passive range in the polarization curve and were immune to pitting corrosion. Pitting resistance equivalent (PRE) of about ≈54 could provide the Ni-based alloy with a good pitting corrosion resistance.

  18. Electron–phonon coupling in Ni-based binary alloys with application to displacement cascade modeling

    NASA Astrophysics Data System (ADS)

    Samolyuk, G. D.; Béland, L. K.; Stocks, G. M.; Stoller, R. E.

    2016-05-01

    Energy transfer between lattice atoms and electrons is an important channel of energy dissipation during displacement cascade evolution in irradiated materials. On the assumption of small atomic displacements, the intensity of this transfer is controlled by the strength of electron–phonon (el–ph) coupling. The el–ph coupling in concentrated Ni-based alloys was calculated using electronic structure results obtained within the coherent potential approximation. It was found that Ni0.5Fe0.5, Ni0.5Co0.5 and Ni0.5Pd0.5 are ordered ferromagnetically, whereas Ni0.5Cr0.5 is nonmagnetic. Since the magnetism in these alloys has a Stoner-type origin, the magnetic ordering is accompanied by a decrease of electronic density of states at the Fermi level, which in turn reduces the el–ph coupling. Thus, the el–ph coupling values for all alloys are approximately 50% smaller in the magnetic state than for the same alloy in a nonmagnetic state. As the temperature increases, the calculated coupling initially increases. After passing the Curie temperature, the coupling decreases. The rate of decrease is controlled by the shape of the density of states above the Fermi level. Introducing a two-temperature model based on these parameters in 10 keV molecular dynamics cascade simulation increases defect production by 10–20% in the alloys under consideration.

  19. Cerium-based, intermetallic-strengthened aluminum casting alloy: High-volume co-product development

    DOE PAGES

    Sims, Zachary C.; Weiss, D.; McCall, S. K.; McGuire, M. A.; Ott, R. T.; Geer, Tom; Rios, Orlando; Turchi, P. A. E.

    2016-05-23

    Here, several rare earth elements are considered by-products to rare earth mining efforts. By using one of these by-product elements in a high-volume application such as aluminum casting alloys, the supply of more valuable rare earths can be globally stabilized. Stabilizing the global rare earth market will decrease the long-term criticality of other rare earth elements. The low demand for Ce, the most abundant rare earth, contributes to the instability of rare earth extraction. In this article, we discuss a series of intermetallic-strengthened Al alloys that exhibit the potential for new high-volume use of Ce. The castability, structure, and mechanicalmore » properties of binary, ternary, and quaternary Al-Ce based alloys are discussed. We have determined Al-Ce based alloys to be highly castable across a broad range of compositions. Nanoscale intermetallics dominate the microstructure and are the theorized source of the high ductility. In addition, room-temperature physical properties appear to be competitive with existing aluminum alloys with extended high-temperature stability of the nanostructured intermetallic.« less

  20. Electron phonon coupling in Ni-based binary alloys with application to displacement cascade modeling

    DOE PAGES

    Samolyuk, German D.; Stocks, George Malcolm; Stoller, Roger E.

    2016-04-01

    Energy transfer between lattice atoms and electrons is an important channel of energy dissipation during displacement cascade evolution in irradiated materials. On the assumption of small atomic displacements, the intensity of this transfer is controlled by the strength of electron–phonon (el–ph) coupling. The el–ph coupling in concentrated Ni-based alloys was calculated using electronic structure results obtained within the coherent potential approximation. It was found that Ni0.5Fe0.5, Ni0.5Co0.5 and Ni0.5Pd0.5 are ordered ferromagnetically, whereas Ni0.5Cr0.5 is nonmagnetic. Since the magnetism in these alloys has a Stoner-type origin, the magnetic ordering is accompanied by a decrease of electronic density of states atmore » the Fermi level, which in turn reduces the el–ph coupling. Thus, the el–ph coupling values for all alloys are approximately 50% smaller in the magnetic state than for the same alloy in a nonmagnetic state. As the temperature increases, the calculated coupling initially increases. After passing the Curie temperature, the coupling decreases. The rate of decrease is controlled by the shape of the density of states above the Fermi level. Introducing a two-temperature model based on these parameters in 10 keV molecular dynamics cascade simulation increases defect production by 10–20% in the alloys under consideration.« less

  1. Fabrication methods and applications of microstructured gallium based liquid metal alloys

    NASA Astrophysics Data System (ADS)

    Khondoker, M. A. H.; Sameoto, D.

    2016-09-01

    This review contains a comparative study of reported fabrication techniques of gallium based liquid metal alloys embedded in elastomers such as polydimethylsiloxane or other rubbers as well as the primary challenges associated with their use. The eutectic gallium-indium binary alloy (EGaIn) and gallium-indium-tin ternary alloy (galinstan) are the most common non-toxic liquid metals in use today. Due to their deformability, non-toxicity and superior electrical conductivity, these alloys have become very popular among researchers for flexible and reconfigurable electronics applications. All the available manufacturing techniques have been grouped into four major classes. Among them, casting by needle injection is the most widely used technique as it is capable of producing features as small as 150 nm width by high-pressure infiltration. One particular fabrication challenge with gallium based liquid metals is that an oxide skin is rapidly formed on the entire exposed surface. This oxide skin increases wettability on many surfaces, which is excellent for keeping patterned metal in position, but is a drawback in applications like reconfigurable circuits, where the position of liquid metal needs to be altered and controlled accurately. The major challenges involved in many applications of liquid metal alloys have also been discussed thoroughly in this article.

  2. Potentiality of the "Gum Metal" titanium-based alloy for biomedical applications.

    PubMed

    Gordin, D M; Ion, R; Vasilescu, C; Drob, S I; Cimpean, A; Gloriant, T

    2014-11-01

    In this study, the "Gum Metal" titanium-based alloy (Ti-23Nb-0.7Ta-2Zr-1.2O) was synthesized by melting and then characterized in order to evaluate its potential for biomedical applications. Thus, the mechanical properties, the corrosion resistance in simulated body fluid and the in vitro cell response were investigated. It was shown that this alloy presents a very high strength, a low Young's modulus and a high recoverable strain by comparison with the titanium alloys currently used in medicine. On the other hand, all electrochemical and corrosion parameters exhibited more favorable values showing a nobler behavior and negligible toxicity in comparison with the commercially pure Ti taken as reference. Furthermore, the biocompatibility tests showed that this alloy induced an excellent response of MC3T3-E1 pre-osteoblasts in terms of attachment, spreading, viability, proliferation and differentiation. Consequently, the "Gum Metal" titanium-based alloy processes useful characteristics for the manufacturing of highly biocompatible medical devices.

  3. Electron-phonon coupling in Ni-based binary alloys with application to displacement cascade modeling

    NASA Astrophysics Data System (ADS)

    Samolyuk, G. D.; Béland, L. K.; Stocks, G. M.; Stoller, R. E.

    2016-05-01

    Energy transfer between lattice atoms and electrons is an important channel of energy dissipation during displacement cascade evolution in irradiated materials. On the assumption of small atomic displacements, the intensity of this transfer is controlled by the strength of electron-phonon (el-ph) coupling. The el-ph coupling in concentrated Ni-based alloys was calculated using electronic structure results obtained within the coherent potential approximation. It was found that Ni0.5Fe0.5, Ni0.5Co0.5 and Ni0.5Pd0.5 are ordered ferromagnetically, whereas Ni0.5Cr0.5 is nonmagnetic. Since the magnetism in these alloys has a Stoner-type origin, the magnetic ordering is accompanied by a decrease of electronic density of states at the Fermi level, which in turn reduces the el-ph coupling. Thus, the el-ph coupling values for all alloys are approximately 50% smaller in the magnetic state than for the same alloy in a nonmagnetic state. As the temperature increases, the calculated coupling initially increases. After passing the Curie temperature, the coupling decreases. The rate of decrease is controlled by the shape of the density of states above the Fermi level. Introducing a two-temperature model based on these parameters in 10 keV molecular dynamics cascade simulation increases defect production by 10-20% in the alloys under consideration.

  4. Cerium-Based, Intermetallic-Strengthened Aluminum Casting Alloy: High-Volume Co-product Development

    NASA Astrophysics Data System (ADS)

    Sims, Zachary C.; Weiss, D.; McCall, S. K.; McGuire, M. A.; Ott, R. T.; Geer, Tom; Rios, Orlando; Turchi, P. A. E.

    2016-07-01

    Several rare earth elements are considered by-products to rare earth mining efforts. By using one of these by-product elements in a high-volume application such as aluminum casting alloys, the supply of more valuable rare earths can be globally stabilized. Stabilizing the global rare earth market will decrease the long-term criticality of other rare earth elements. The low demand for Ce, the most abundant rare earth, contributes to the instability of rare earth extraction. In this article, we discuss a series of intermetallic-strengthened Al alloys that exhibit the potential for new high-volume use of Ce. The castability, structure, and mechanical properties of binary, ternary, and quaternary Al-Ce based alloys are discussed. We have determined Al-Ce based alloys to be highly castable across a broad range of compositions. Nanoscale intermetallics dominate the microstructure and are the theorized source of the high ductility. In addition, room-temperature physical properties appear to be competitive with existing aluminum alloys with extended high-temperature stability of the nanostructured intermetallic.

  5. Indoor environmental corrosion of Ag-based alloys in the Egyptian Museum (Cairo, Egypt)

    NASA Astrophysics Data System (ADS)

    Ingo, G. M.; Angelini, E.; Riccucci, C.; de Caro, T.; Mezzi, A.; Faraldi, F.; Caschera, D.; Giuliani, C.; Di Carlo, G.

    2015-01-01

    In this study, we have investigated the indoor environmental corrosion of Ag-based alloys after long-term exposure in a showcase of an exhibition room and in the open atmosphere at the Egyptian Museum of Cairo (Egypt). In order to simulate the corrosion processes that occur at the surface of archaeological artefacts, Ag-based alloys with chemical composition, metallurgical features and micro-chemical structure similar to those of ancient alloys have been purposely produced as sacrificial reference samples. Our findings show that corrosion phenomena on alloy surface are mainly caused by environmental sulphur and chlorine containing species that react in different ways depending on the exhibition conditions and on the alloy composition. This approach allows to identify the degradation agents and mechanisms that really take place at the surface of objects similar to ancient artefacts without the necessity of sampling them. Moreover, it is possible to get useful indications for the safe storage or exhibition of silver archaeological artefacts, their cleaning and conservation.

  6. Evaluation of Ni-Cr-Base Alloys for SOFC Interconnect Applications

    SciTech Connect

    Yang, Z Gary; Xia, Gordon; Stevenson, Jeffry W.

    2006-10-06

    To further understand the suitability of Ni-Cr-base alloys for solid oxide fuel cell (SOFC) interconnect applications, three commercial Ni-Cr-base alloys, Haynes 230, Hastelloy S and Haynes 242 were selected and evaluated for oxidation behavior under different exposure conditions, scale conductivity and thermal expansion. Haynes 230 and Hastelloy S, which have a relatively high Cr content, formed a thin scale mainly comprised of Cr2O3 and (Mn,Cr,Ni)3O4 spinels under SOFC operating conditions, demonstrating excellent oxidation resistance and a high scale electrical conductivity. In contrast, a thick double-layer scale with a NiO outer layer above a chromia-rich substrate was grown on Haynes 242 in moist air or at the air side of dual exposure samples, indicating limited oxidation resistance for the interconnect application. With a face-centered-cubic (FCC) substrate, all three alloys possess a coefficient of thermal expansion (CTE) that is higher than that of candidate ferritic stainless steels, e.g. Crofer22 APU. Among the three alloys, Haynes 242, which is heavily alloyed with W and Mo and contains a low Cr content, demonstrated the lowest average CTE at 13.1x10-6 K-1 from room temperature to 800oC, but it was also observed that the CTE behavior of Haynes 242 was very nonlinear.

  7. Effect of chromium and phosphorus on the physical properties of iron and titanium-based amorphous metallic alloy films

    NASA Technical Reports Server (NTRS)

    Distefano, S.; Rameshan, R.; Fitzgerald, D. J.

    1991-01-01

    Amorphous iron and titanium-based alloys containing various amounts of chromium, phosphorus, and boron exhibit high corrosion resistance. Some physical properties of Fe and Ti-based metallic alloy films deposited on a glass substrate by a dc-magnetron sputtering technique are reported. The films were characterized using differential scanning calorimetry, stress analysis, SEM, XRD, SIMS, electron microprobe, and potentiodynamic polarization techniques.

  8. Synthesis and characterization of mechanically alloyed aluminum-based compounds as high energy density materials

    NASA Astrophysics Data System (ADS)

    Zhu, Xiaoying

    2006-12-01

    A new type of metastable reactive powders for potential use as high energy density materials in propellants, explosives, and pyrotechnics was developed. These powders are intended to replace aluminum typically added to energetic formulations to increase reaction enthalpy and temperature. The new materials are metastable aluminum-based alloys, which enable achievement of substantially reduced ignition temperatures and accelerated bulk burn rates compared to aluminum. Titanium and lithium were used as alloying components. The materials properties and characteristics leading to their enhanced combustion performance were investigated. The powders were prepared using mechanical alloying and characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive X-ray spectrometer (SEM/EDX), and thermal analysis. Detailed ignition measurements were performed to identify the processes affecting ignition for the prepared metastable powders. Al-Ti alloys were prepared with compositions ranging from Al0.95 Ti0.05 to Al0.75Ti0.25. Mechanically alloyed powders comprised solid solution of Ti and Al. Upon their heating, a number of subsolidus exothermic transitions were detected and assigned to formation of different modifications of Al3Ti. Three distinguishable oxidation steps were observed for the prepared alloys. The products formed at different oxidation stages were quantitatively analyzed by XRD. Ignition of mechanically alloyed Al-Ti powders was investigated experimentally for heating rates ranging from 3·103 to 2·10 4 K/s. It was shown that ignition was triggered by the exothermic formation of a metastable L12 phase of Al3Ti. Al-Li alloys were synthesized with a fixed bulk composition of Al 0.7Li0.3. At short milling times, an intermetallic LiAl delta-phase was readily produced. At longer milling times, the LiAl phase disappears and a solid solution of Li in Al (alpha-phase) formed with as much as 10 at % of dissolved Li. Continuing milling

  9. A new approach to the hazard classification of alloys based on transformation/dissolution.

    PubMed

    Skeaff, James M; Hardy, David J; King, Pierrette

    2008-01-01

    . For the other alloys, we developed a new critical surface area-toxic units (CSA-TU) approach to derive their GHS classification proposals. The CSA-TU approach can be readily applied to other multicomponent alloy systems, without the need to arbitrarily select a particular component among several as the determinant of toxicity. This paper shows how regulatory obligations, such as those mandated by REACH, can be met with a laboratory-based CSA-TU method for deriving hazard classification proposals for alloys, linking to attendant environmental protection management decisions. Drawing on T/D data derived from laboratory testing of the alloy itself, the CSA-TU approach can be applied to establish scientifically defensible decisions on hazard classification proposals for an alloy of interest. The resulting decisions can then be incorporated into environmental management measures in such jurisdictions as the European Union. Based on an approach developed specifically for alloys, the hazard classification decisions can be regarded as relevant, credible, and protective of the environment. Since alloys are usually more resistant to chemical attack than their components, this approach is a considerable improvement over the possibility provided for in the GHS of calculating a hazard classification level for an alloy from the classification levels of its components. PMID:17944545

  10. Tensile and stress-rupture behavior of hafnium carbide dispersed molybdenum and tungsten base alloy wires

    NASA Technical Reports Server (NTRS)

    Yun, Hee Mann; Titran, Robert H.

    1993-01-01

    The tensile strain rate sensitivity and the stress-rupture strength of Mo-base and W-base alloy wires, 380 microns in diameter, were determined over the temperature range from 1200 K to 1600 K. Three molybdenum alloy wires; Mo + 1.1w/o hafnium carbide (MoHfC), Mo + 25w/o W + 1.1w/o hafnium carbide (MoHfC+25W) and Mo + 45w/o W + 1.1w/o hafnium carbide (MoHfC+45W), and a W + 0.4w/o hafnium carbide (WHfC) tungsten alloy wire were evaluated. The tensile strength of all wires studied was found to have a positive strain rate sensitivity. The strain rate dependency increased with increasing temperature and is associated with grain broadening of the initial fibrous structures. The hafnium carbide dispersed W-base and Mo-base alloys have superior tensile and stress-rupture properties than those without HfC. On a density compensated basis the MoHfC wires exhibit superior tensile and stress-rupture strengths to the WHfC wires up to approximately 1400 K. Addition of tungsten in the Mo-alloy wires was found to increase the long-term stress rupture strength at temperatures above 1400 K. Theoretical calculations indicate that the strength and ductility advantage of the HfC dispersed alloy wires is due to the resistance to recrystallization imparted by the dispersoid.

  11. Creep rupture testing of alloy 617 and A508/533 base metals and weldments.

    SciTech Connect

    Natesan, K.; Li, M.; Soppet, W.K.; Rink, D.L.

    2012-01-17

    The NGNP, which is an advanced HTGR concept with emphasis on both electricity and hydrogen production, involves helium as the coolant and a closed-cycle gas turbine for power generation with a core outlet/gas turbine inlet temperature of 750-1000 C. Alloy 617 is a prime candidate for VHTR structural components such as reactor internals, piping, and heat exchangers in view of its resistance to oxidation and elevated temperature strength. However, lack of adequate data on the performance of the alloy in welded condition prompted to initiate a creep test program at Argonne National Laboratory. In addition, Testing has been initiated to evaluate the creep rupture properties of the pressure vessel steel A508/533 in air and in helium environments. The program, which began in December 2009, was certified for quality assurance NQA-1 requirements during January and February 2010. Specimens were designed and fabricated during March and the tests were initiated in April 2010. During the past year, several creep tests were conducted in air on Alloy 617 base metal and weldment specimens at temperatures of 750, 850, and 950 C. Idaho National Laboratory, using gas tungsten arc welding method with Alloy 617 weld wire, fabricated the weldment specimens. Eight tests were conducted on Alloy 617 base metal specimens and nine were on Alloy 617 weldments. The creep rupture times for the base alloy and weldment tests were up to {approx}3900 and {approx}4500 h, respectively. The results showed that the creep rupture lives of weld specimens are much longer than those for the base alloy, when tested under identical test conditions. The test results also showed that the creep strain at fracture is in the range of 7-18% for weldment samples and were much lower than those for the base alloy, under similar test conditions. In general, the weldment specimens showed more of a flat or constant creep rate region than the base metal specimens. The base alloy and the weldment exhibited tertiary creep

  12. Thermodynamics-Based Selection and Design of Creep-Resistant Cast Mg Alloys

    NASA Astrophysics Data System (ADS)

    Abaspour, Saeideh; Cáceres, Carlos H.

    2015-12-01

    Atomic level thermodynamics arguments that account for the generally weak age hardening response while suggesting that extending the athermal regime through short-range order (SRO) is a most feasible path to increasing the creep strength of many current alloys are presented. The tendency, or otherwise, of many solutes to develop SRO in dilute solid solutions rationalizes a number of observations in current multicomponent Mg alloys, and in particular the retention of linear strain hardening at high temperatures, while it disputes the viability of several micromechanisms often considered active, such as pinning of edge dislocations by mobile solute clouds, dynamic precipitation of thermally stable precipitates, or atomic size effects on the diffusivity. Potential solutes are sorted out and ranked based on the sign and value of the enthalpy of mixing of binary solid solutions using the Miedema phenomenological scheme. Due to their large negative energy of mixing and reasonable solubility (>1 at. pct) at ~473 K (~200 °C), Y and Gd appear as the best candidates to increase the creep strength through SRO, followed by Nd and Ca, in close agreement with data reported in the literature. The feasibility of enhancing the age hardening response through homogeneously nucleated, coherent precipitates, in some cases despite the negative energy of mixing of the alloy, or via internally ordered precipitates mimicking those present in Mg-Th alloys is considered by making parallels with the Al-Zn and the Al-Cu alloy systems. The possible optimization of the strengthening of high pressure die cast alloys combining SRO and intergranular eutectics or of heat-treatable cast alloys through internally ordered precipitates and SRO is discussed.

  13. Grain refinement of permanent mold cast copper base alloys. Final report

    SciTech Connect

    Sadayappan, M.; Thomson, J. P.; Elboujdaini, M.; Gu, G. Ping; Sahoo, M.

    2004-04-29

    control tool was proved in two foundries. The method can also correctly predict the onset of fading. The corrosion resistance of the grain refined alloys was measured in two solutions having different hydrogen activities, pH 6 and pH8, and compared with the base alloys. Potentiodynamic polarization and long term weight loss experiments were conducted to evaluate the corrosion resistance. Cu-Zn alloys were evaluated for dezincification. In general, the grain refined alloys performed marginally better than the base alloys.

  14. Gilbert damping and anisotropic magnetoresistance in iron-based alloys

    NASA Astrophysics Data System (ADS)

    Berger, L.

    2016-07-01

    We use the two-current model of Campbell and Fert to understand the compositional dependence of the Gilbert damping parameter in certain iron alloys. In that model, spin-up and spin-down carriers have different resistivities ρ↑ and ρ↓. We emphasize the part of the Gilbert parameter, called Gsf, generated by spin-flip interband processes. Both Gsf and the anisotropic magnetoresistance Δρ are proportional to the square of the spin-orbit parameter, and also proportional to ρ↑. In bcc alloys of iron with V, Cr, Mo, etc. solutes on the left of iron in the periodic table, ρ↑ is increased by a scattering resonance (Gomes and Campbell, 1966, 1968). Then ρ↑, Δρ, and Gsf all exhibit a peak at the same moderate concentration of the solute. We find the best fit between this theory and existing experimental data of Gilbert damping for Fe-V epitaxial films at room temperature (Cheng, 2006; Scheck et al., 2007). At room temperature, the predicted Gsf peak is masked by a background arising from non-flip intraband processes. At elevated temperatures, the peak is expected to become more prominent, and less hidden in the background.

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

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  16. Dual Microstructure Heat Treatment of a Nickel-Base Disk Alloy Assessed

    NASA Technical Reports Server (NTRS)

    Gayda, John

    2002-01-01

    Gas turbine engines for future subsonic aircraft will require nickel-base disk alloys that can be used at temperatures in excess of 1300 F. Smaller turbine engines, with higher rotational speeds, also require disk alloys with high strength. To address these challenges, NASA funded a series of disk programs in the 1990's. Under these initiatives, Honeywell and Allison focused their attention on Alloy 10, a high-strength, nickel-base disk alloy developed by Honeywell for application in the small turbine engines used in regional jet aircraft. Since tensile, creep, and fatigue properties are strongly influenced by alloy grain size, the effect of heat treatment on grain size and the attendant properties were studied in detail. It was observed that a fine grain microstructure offered the best tensile and fatigue properties, whereas a coarse grain microstructure offered the best creep resistance at high temperatures. Therefore, a disk with a dual microstructure, consisting of a fine-grained bore and a coarse-grained rim, should have a high potential for optimal performance. Under NASA's Ultra-Safe Propulsion Project and Ultra-Efficient Engine Technology (UEET) Program, a disk program was initiated at the NASA Glenn Research Center to assess the feasibility of using Alloy 10 to produce a dual-microstructure disk. The objectives of this program were twofold. First, existing dual-microstructure heat treatment (DMHT) technology would be applied and refined as necessary for Alloy 10 to yield the desired grain structure in full-scale forgings appropriate for use in regional gas turbine engines. Second, key mechanical properties from the bore and rim of a DMHT Alloy 10 disk would be measured and compared with conventional heat treatments to assess the benefits of DMHT technology. At Wyman Gordon and Honeywell, an active-cooling DMHT process was used to convert four full-scale Alloy 10 disks to a dual-grain microstructure. The resulting microstructures are illustrated in the

  17. Magnetostriction and texture development in binary and ternary iron-gallium-based alloys

    NASA Astrophysics Data System (ADS)

    Mungsantisuk, Pinai

    2005-07-01

    The rare earth-free bcc FeGa-based alloys have an excellent combination of large low-field magnetostriction at room temperature, good mechanical properties, low hysteresis, and relatively low cost. These alloys are attractive for use in numerous sensor and actuator devices. The first part of this dissertation examines the influence of partial substitutions of Ga with Al, Be, Si, Ge, and Sn and partial substitutions of Fe with Co and Ni. The work involved directional growth of [001] textured rods of these ternary alloys using a Vertical Bridgman process, X-ray diffraction analysis, magnetic property measurements using vibrating sample magnetometry, and magnetostriction measurements. It is shown that substitution of Ga with Al can be made in FeGa alloys in certain composition ranges without a reduction in magnetostriction, and the additions of Si, Ge, and Sn results in a sharp decrease of magnetostriction. The addition or substitute of Be, due to its smaller size than Fe, resulted in only a slight decrease of magnetostriction. Substitution of Fe with Ni and Co results in a significant decrease of the magnetostriction. The work also evaluated the elastic properties of Fe-x at. % Ga and Fe-(20-y) at. % Ga-y at. % Al polycrystalline alloys using resonant ultrasound spectroscopy. Young's modulus obtained for FeGa and FeGaAl alloys were in the range of 110 to 170 GPa which are several times that for Terfenol-D alloys. Thus, large-force delivery is possible from FeGa alloy based actuators even though saturation strain values are smaller than that of Terfenol-D. The second part of this work examined the development of an inexpensive thermomechanical processing method to obtain [001] textured polycrystalline Fe-15 at. % Ga alloys. The processing involved a sequence of controlled hot rolling, two-stage warm rolling with intermediate anneal, and texture anneal. Roll forces measured and the extent of reductions feasible indicated an excellent processability. Texture evolution

  18. Structure and hot hardness of RuAl-based alloys produced by reactive sintering using hot isostatic pressing

    NASA Astrophysics Data System (ADS)

    Povarova, K. B.; Morozov, A. E.; Padalko, A. G.; Drozdov, A. A.

    2008-04-01

    The structure and hot hardness (at temperatures up to 1100°C) of RuAl-based powder alloys with 1 3 at % Ni, Mo, Re, or Ru are studied. The alloys are produced by the reactive sintering of cold-compacted bars and subsequent threefold isostatic pressing with intermediate annealing at 1500°C performed after the first hot isostatic pressing. The samples have a residual pore content of 1 2.5 vol % and are characterized by a micrononuniform distribution of base and alloying elements. The alloys with refractory metals, such as Re, Mo, or Ru, are found to have the maximum hardness at all temperatures under study. At low temperatures, the effect is more substantial; the hardness of the Re-containing alloys exceeds that of the other alloys by a factor of 1.3 3.6. The increase in the hardness related to solid-solution alloying becomes more substantial owing to the microinhomogeneity of the sintered powder alloys and weakens because of microporosity. Recommendations that allow the uniformity of the distribution of the base and alloying elements to be increased are given.

  19. Boundary Engineering for the Thermoelectric Performance of Bulk Alloys Based on Bismuth Telluride.

    PubMed

    Mun, Hyeona; Choi, Soon-Mok; Lee, Kyu Hyoung; Kim, Sung Wng

    2015-07-20

    Thermoelectrics, which transports heat for refrigeration or converts heat into electricity directly, is a key technology for renewable energy harvesting and solid-state refrigeration. Despite its importance, the widespread use of thermoelectric devices is constrained because of the low efficiency of thermoelectric bulk alloys. However, boundary engineering has been demonstrated as one of the most effective ways to enhance the thermoelectric performance of conventional thermoelectric materials such as Bi2 Te3 , PbTe, and SiGe alloys because their thermal and electronic transport properties can be manipulated separately by this approach. We review our recent progress on the enhancement of the thermoelectric figure of merit through boundary engineering together with the processing technologies for boundary engineering developed most recently using Bi2 Te3 -based bulk alloys. A brief discussion of the principles and current status of boundary-engineered bulk alloys for the enhancement of the thermoelectric figure of merit is presented. We focus mainly on (1) the reduction of the thermal conductivity by grain boundary engineering and (2) the reduction of thermal conductivity without deterioration of the electrical conductivity by phase boundary engineering. We also discuss the next potential approach using two boundary engineering strategies for a breakthrough in the area of bulk thermoelectric alloys.

  20. The observations of faulted dipoles in deformed TiAl-based alloys

    SciTech Connect

    Gao, Y.; Zhu, J.; Cai, Q.G.

    1995-08-01

    The deformation structure of polycrystalline TiAl-based alloys after uniaxial compression at temperature range from 77K to 1073K has been examined using transmission electron microscopy. It was observed that a large number of faulted dipoles are commonly present in deformation structure of the alloys compressed at low temperature 77K and room temperature. The nature of the faulted dipoles has been determined to be intrinsic stacking fault lying on {l_brace}111{r_brace} plane, bounded by 1/6 {l_brace}112] partial dislocations. A possible mechanism for the formation of the faulted dipoles was suggested. The results of the statistic observation shows that faulted dipoles in deformed Ti-48Al and Ti-(47-48)Al-X (X = V, Cr, Mn) alloys are less than those in single phase Ti-52Al alloy, and the number of the faulted dipoles decreases with increasing deformation temperature. The effect of the faulted dipoles on plastic deformation of the alloy was discussed.

  1. Ignition characteristics of the iron-based alloy UNS S66286 in pressurized oxygen

    NASA Technical Reports Server (NTRS)

    Bransford, James W.; Billard, Phillip A.; Hurley, James A.; Mcdermott, Kathleen M.; Vazquez, Isaura

    1988-01-01

    The development of ignition and combustion in pressurized oxygen atmospheres was studied for the iron based alloy UNS S66286. Ignition of the alloy was achieved by heating the top surface of a cylindrical specimen with a continuous-wave CO2 laser. Two heating procedures were used. In the first, laser power was adjusted to maintain an approximately linear increase in surface temperature. In the second, laser power was periodically increased until autoheating (self-heating) was established. It was found that the alloy would autoheat to destruction from temperatures below the solidus temperature. In addition endothermic events occurred as the alloy was heated, many at reproducible temperatures. Many endothermic events occurred prior to abrupt increases in surface temperature and appeared to accelerate the rate of increase in specimen temperature to rates greater than what would be expected from increased temperature alone. It is suggested that the source of these endotherms may increase the oxidation rate of the alloy. Ignition parameters are defined and the temperatures at which these parameters occur are given for the oxygen pressure range of 1.72 to 13.8 MPa (25 to 2000 psia).

  2. Mechanical behavior and phase stability of NiAl-based shape memory alloys

    SciTech Connect

    George, E.P.; Liu, C.T.; Horton, J.A.; Kunsmann, H.; King, T.; Kao, M.

    1993-12-31

    NiAl-based shape memory alloys (SMAs) can be made ductile by alloying with 100--300 wppm B and 14--20 at.% Fe. The addition of Fe has the undesirable effect that it lowers the temperature (A{sub p}) of the martensite {yields} austenite phase transformation. Fortunately, however, A can be raised by lowering the ``equivalent`` amount of Al in the alloy. In this way a high A{sub p} temperature of {approximately}190 C has been obtained without sacrificing ductility. Furthermore, a recoverable strain of 0.7% has been obtained in a Ni-Al-Fe alloy with A{sub p} temperature of {approximately}140 C. Iron additions do not suppress the aging-induced embrittlement that occurs in NiAl alloys at 300--500 C as a result of Ni{sub 5}Al{sub 3} precipitation. Manganese additions (up to 10 at.%) have the effect of lowering A{sub p}, degrading hot workability, and decreasing room-temperature ductility.

  3. Strengthening of Mg based alloy through grain refinement for orthopaedic application.

    PubMed

    Nayak, Soumyaranjan; Bhushan, Bharat; Jayaganthan, R; Gopinath, P; Agarwal, R D; Lahiri, Debrupa

    2016-06-01

    Magnesium is presently attracting a lot of interest as a replacement to clinically used orthopaedic implant materials, due to its ability to solve the stress shielding problems, biodegradability and osteocompatibility. However, the strength of Mg is still lower than the requirement and it becomes worse after it starts degrading fast, while being exposed in living body environment. This research explores the effectiveness of 'grain refinement through deformation', as a tool to modify the strength (while keeping elastic modulus unaffected) of Mg based alloys in orthopaedic application. Hot rolled Mg-3wt% Zn alloy (MZ3) has been investigated for its potential in orthopaedic implant. Microstructure, mechanical properties, bio-corrosion properties and biocompatibility of the rolled samples are probed into. Grain size gets refined significantly with increasing amount of deformation. The alloy experiences a marked improvement in hardness, yield strength, ultimate tensile strength, strain and toughness with finer grain size. An increment in accelerated corrosion rate is noted with decreasing grain size, which is correlated to the increased grain boundary area and mechano-chemical dissolution. However, immersion test in simulated body fluid (SBF) reveals reduction in corrosion rate after third day of immersion. This was possible owing to precipitation of protective hydroxyapatite (HA) layer, formed out of the interaction of SBF and the alloy. More nucleation sites at the grain boundary for fine grained samples help in forming more HA and thus reduce the corrosion rate. Human osteosarcoma cells show less viability and adhesion on grain refined alloy. PMID:26745721

  4. Boundary Engineering for the Thermoelectric Performance of Bulk Alloys Based on Bismuth Telluride.

    PubMed

    Mun, Hyeona; Choi, Soon-Mok; Lee, Kyu Hyoung; Kim, Sung Wng

    2015-07-20

    Thermoelectrics, which transports heat for refrigeration or converts heat into electricity directly, is a key technology for renewable energy harvesting and solid-state refrigeration. Despite its importance, the widespread use of thermoelectric devices is constrained because of the low efficiency of thermoelectric bulk alloys. However, boundary engineering has been demonstrated as one of the most effective ways to enhance the thermoelectric performance of conventional thermoelectric materials such as Bi2 Te3 , PbTe, and SiGe alloys because their thermal and electronic transport properties can be manipulated separately by this approach. We review our recent progress on the enhancement of the thermoelectric figure of merit through boundary engineering together with the processing technologies for boundary engineering developed most recently using Bi2 Te3 -based bulk alloys. A brief discussion of the principles and current status of boundary-engineered bulk alloys for the enhancement of the thermoelectric figure of merit is presented. We focus mainly on (1) the reduction of the thermal conductivity by grain boundary engineering and (2) the reduction of thermal conductivity without deterioration of the electrical conductivity by phase boundary engineering. We also discuss the next potential approach using two boundary engineering strategies for a breakthrough in the area of bulk thermoelectric alloys. PMID:25782971

  5. Intergranular tellurium cracking of nickel-based alloys in molten Li, Be, Th, U/F salt mixture

    NASA Astrophysics Data System (ADS)

    Ignatiev, Victor; Surenkov, Alexander; Gnidoy, Ivan; Kulakov, Alexander; Uglov, Vadim; Vasiliev, Alexander; Presniakov, Mikhail

    2013-09-01

    In Russia, R&D on Molten Salt Reactor (MSR) are concentrated now on fast/intermediate spectrum concepts which were recognized as long term alternative to solid fueled fast reactors due to their attractive features: strong negative feedback coefficients, easy in-service inspection, and simplified fuel cycle. For high-temperature MSR corrosion of the metallic container alloy in primary circuit is the primary concern. Key problem receiving current attention include surface fissures in Ni-based alloys probably arising from fission product tellurium attack. This paper summarizes results of corrosion tests conducted recently to study effect of oxidation state in selected fuel salt on tellurium attack and to develop means of controlling tellurium cracking in the special Ni-based alloys recently developed for molten salt actinide recycler and tranforming (MOSART) system. Tellurium corrosion of Ni-based alloys was tested at temperatures up to 750 °C in stressed and unloaded conditions in molten LiF-BeF2 salt mixture fueled by about 20 mol% of ThF4 and 2 mol% of UF4 at different [U(IV)]/[U(III)] ratios: 0.7, 4, 20, 100 and 500. Following Ni-based alloys (in mass%): HN80М-VI (Mo—12, Cr—7.6, Nb—1.5), HN80МТY (Mo—13, Cr—6.8, Al—1.1, Ti—0.9), HN80МТW (Mo—9.4, Cr—7.0, Ti—1.7, W—5.5) and ЕМ-721 (W—25.2, Cr—5.7, Ti—0.17) were used for the study in the corrosion facility. If the redox state the fuel salt is characterized by uranium ratio [U(IV)]/[U(III)] < 1 the alloys' specimens get a more negative stationary electrode potential than equilibrium electrode potentials of some uranium intermetallic compounds and alloys with nickel and molybdenum. This leads to spontaneous behavior of alloy formation processes on the specimens' surface and further diffusion of uranium deep into the metallic phase. As consequence of this films of intermetallic compounds and alloys of nickel, molybdenum, tungsten with uranium are formed on the alloys specimens' surface

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  7. Integrated Design and Rapid Development of Refractory Metal Based Alloys for Fossil Energy Applications

    SciTech Connect

    Dogan, O.N.; King, P.E.; Gao, M.C.

    2008-07-01

    One common barrier in the development of new technologies for future energy generating systems is insufficiency of existing materials at high temperatures (>1150oC) and aggressive atmospheres (e.g., steam, oxygen, CO2). To overcome this barrier, integrated design methodology will be applied to the development of refractory metal based alloys. The integrated design utilizes the multi-scale computational methods to design materials for requirements of processing and performance. This report summarizes the integrated design approach to the alloy development and project accomplishments in FY 2008.

  8. Chemical durability and degradation mechanisms of HT9 based alloy waste forms with variable Zr content

    SciTech Connect

    Olson, L. N.

    2015-10-30

    In Corrosion studies were undertaken on alloy waste forms that can result from advanced electrometallurgical processing techniques to better classify their durability and degradation mechanisms. The waste forms were based on the RAW3-(URe) composition, consisting primarily of HT9 steel and other elemental additions to simulate nuclear fuel reprocessing byproducts. The solution conditions of the corrosion studies were taken from an electrochemical testing protocol, and meant to simulate conditions in a repository. The alloys durability was examined in alkaline and acidic brines.

  9. Evolution of precipitate in nickel-base alloy 718 irradiated with argon ions at elevated temperature

    NASA Astrophysics Data System (ADS)

    Jin, Shuoxue; Luo, Fengfeng; Ma, Shuli; Chen, Jihong; Li, Tiecheng; Tang, Rui; Guo, Liping

    2013-07-01

    Alloy 718 is a nickel-base superalloy whose strength derives from γ'(Ni3(Al,Ti)) and γ″(Ni3Nb) precipitates. The evolution of the precipitates in alloy 718 irradiated with argon ions at elevated temperature were examined via transmission electron microscopy. Selected-area electron diffraction indicated superlattice spots disappeared after argon ion irradiation, which showing that the ordered structure of the γ' and γ″ precipitates became disordered. The size of the precipitates became smaller with the irradiation dose increasing at 290 °C.

  10. The corrosion performance of nickel-based alloys in a reverse osmosis plant utilizing seawater

    SciTech Connect

    Al-Hashem, A.; Carew, J.; Al-Odwani, A.

    1998-12-31

    Four nickel-based alloys, UNS N06625, UNS N08825, UNS N10276, and UNS N05500, were evaluated in terms of their corrosion performance in a seawater reverse osmosis plant using the electrochemical impedance spectroscopy (EIS), open circuit potential (OCP) and linear polarization resistance (LPR) measurements. Slight changes in the EIS spectra were observed for UNS N06625, UNSN10276 and UNS N05500 at low frequencies. However, UNS N08825 EIS spectra exhibited more changes than the other alloys at low frequencies. The OCP of UNS N10276 was more noble than the other alloys under the same conditions. The LPR measurements indicated that UNS N10276 and UNS N05500 exhibited lower corrosion rates than UNS NO6625 and UNS N08825.

  11. Microstructures and Mechanical Properties of Two-Phase Alloys Based on NbCr(2)

    SciTech Connect

    Cady, C.M.; Chen, K.C.; Kotula, P.G.; Mauro, M.E.; Thoma, D.J.

    1998-12-07

    A two-phase, Nb-Cr-Ti alloy (bee+ C15 Laves phase) has been developed using several alloy design methodologies. In effort to understand processing-microstructure-property relationships, diffment processing routes were employed. The resulting microstructure and mechanical properties are discussed and compared. Plasma arc-melted samples served to establish baseline, . . . as-cast properties. In addition, a novel processing technique, involving decomposition of a supersaturated and metastable precursor phase during hot isostatic pressing (HIP), was used to produce a refined, equilibrium two-phase microstructure. Quasi-static compression tests as a ~ function of temperature were performed on both alloy types. Different deformation mechanisms were encountered based upon temperature and microstructure.

  12. The Degradation Interface of Magnesium Based Alloys in Direct Contact with Human Primary Osteoblast Cells

    PubMed Central

    Willumeit-Römer, Regine; Laipple, Daniel; Luthringer, Bérengère; Feyerabend, Frank

    2016-01-01

    Magnesium alloys have been identified as a new generation material of orthopaedic implants. In vitro setups mimicking physiological conditions are promising for material / degradation analysis prior to in vivo studies however the direct influence of cell on the degradation mechanism has never been investigated. For the first time, the direct, active, influence of human primary osteoblasts on magnesium-based materials (pure magnesium, Mg-2Ag and Mg-10Gd alloys) is studied for up to 14 days. Several parameters such as composition of the degradation interface (directly beneath the cells) are analysed with a scanning electron microscope equipped with energy dispersive X-ray and focused ion beam. Furthermore, influence of the materials on cell metabolism is examined via different parameters like active mineralisation process. The results are highlighting the influences of the selected alloying element on the initial cells metabolic activity. PMID:27327435

  13. Creep-rupture behavior of a developmental cast-iron-base alloy for use up to 800 deg C

    NASA Technical Reports Server (NTRS)

    Titran, Robert H.; Scheuermann, Coulson M.

    1987-01-01

    A promising iron-base cast alloy is being developed as part of the DOE/NASA Stirling Engine Systems Project under contract DEN 3-282 with the United Technologies Research Center. This report presents the results of a study at the Lewis Research Center of the alloy's creep-rupture properties. The alloy was tested under a variety of conditions and was found to exhibit the normal 3-stage creep response. The alloy compared favorably with others being used or under consideration for the automotive Stirling engine cylinder/regenerator housing.

  14. Improved Warm-Working Process For An Iron-Base Alloy

    NASA Technical Reports Server (NTRS)

    Cone, Fred P.; Cryns, Brendan J.; Miller, John A.; Zanoni, Robert

    1992-01-01

    Warm-working process produces predominantly unrecrystallized grain structure in forgings of iron-base alloy A286 (PWA 1052 composition). Yield strength and ultimate strength increased, and elongation and reduction of area at break decreased. Improved process used on forgings up to 10 in. thick and weighing up to 900 lb.

  15. Simulation of deep drawing of aluminium alloy sheets using convex texture based plastic potentials

    NASA Astrophysics Data System (ADS)

    He, S.; Van Bael, A.; Van Houtte, P.

    2004-06-01

    In the present study, texture based convex plastic potentials are used to derive the yield locus for the anisotropic materials. Finite element analysis is performed on cup drawing process of aluminium alloy sheets. The predicted results are compared to the experimental data.

  16. Alloy 600 corrosion monitor based on fiber optic strain gage

    SciTech Connect

    Berthold, J.W.; Passell, T.O.

    1996-10-01

    There is a real need to measure strain at high temperatures in many applications. For example, in nuclear steam generators that contain Alloy 600 tubing, intergranular attack (IGA) and stress corrosion cracking (SCC) are significant problems. Measuring strain in this tubing might provide an early warning of the onset of IGA/SCC and the rate of SCC progression. This report describes a method to measure the onset of IGA and the progression of SCC that occurs at a crevice on the inside surface of a tube. The measurement is accomplished by monitoring strain on the outside surface of the tube using welded, fiber-optic strain gages. In an actual application of this approach in a power plant, the strain gages must survive temperatures above 600 F for extended periods (months or years) and must provide repeatable measurements.

  17. Large anisotropic magnetoresistance of ruthenium-based Heusler alloys

    NASA Astrophysics Data System (ADS)

    Mizusaki, S.; Ohnishi, T.; Douzono, A.; Nagata, Y.; Ozawa, T. C.; Samata, H.; Noro, Y.

    2009-04-01

    Anomalous magnetic behavior was found in the polycrystalline Heusler alloy system Ru2Mn1-xFexGe. Samples of x =0 and 1.0 show no magnetoresistance (MR); however, the anisotropic MR effect is observed for x =0.5 (MR ratios of -4% and +2% are observed under parallel and perpendicular configurations of applied field and applied current, respectively). Moreover, magnetic measurement revealed that the sample of x =0 is antiferromagnetic, whereas the samples of x =0.5 and 1.0 are ferromagnetic with Curie temperatures of 270 and 490 K, respectively. The saturation magnetization and coercivity at 5 K are 3.1μB/f.u. and negligibly small for x =1.0 and 1.8μB/f.u. and 0.1 T for x =0.5, respectively. The MR effect is explained by a model in which antiferromagnetic and ferromagnetic domains coexist.

  18. Characterization of hydrogen barrier coatings for titanium-base alloys

    NASA Astrophysics Data System (ADS)

    Leguey, T.; Baluc, N.; Jansen, F.; Victoria, M.

    2002-12-01

    The purpose of this study was to investigate the barrier efficiency of a thick thermal spray deposit on the α-titanium alloy, Ti-5Al-2.4Sn against hydrogen penetration. Therefore, a duplex coating has been applied by plasma spraying using a Sulzer Metco F4 gun. The selected duplex coating system consisted of a 0.1-0.2 mm thick tantalum bond layer and a chromium oxide top layer doped with 3 wt% titanium oxide. The achieved thickness of the top layer was about 0.6 mm. The coated specimens have been characterized with regard to bond strength, hardness and microstructure. Hydrogen charging experiments were performed in a Sievert's apparatus.

  19. Comparison of methanol and ethylene glycol oxidation by alloy and Core-Shell platinum based catalysts

    NASA Astrophysics Data System (ADS)

    Kaplan, D.; Burstein, L.; Rosenberg, Yu.; Peled, E.

    2011-10-01

    Two Core-Shell, RuCore-PtShell and IrNiCore-PtRuShell, XC72-supported catalyst were synthesized in a two-step deposition process with NaBH4 as reducing agent. The structure and composition of the Core-Shell catalysts were determined by EDS, XPS and XRD. Electrochemical characterization was performed with the use of cyclic voltammetry. Methanol and ethylene glycol oxidation activities of the Core-Shell catalysts (in terms of surface and mass activities) were studied at 80 °C and compared to those of a commercial Pt-Ru alloy catalyst. The surface activity of the alloy based catalyst, in the case of methanol oxidation, was found to be superior as a result of optimized surface Pt:Ru composition. However, the mass activity of the PtRu/IrNi/XC72 was higher than that of the alloy based catalyst by ∼50%. Regarding ethylene glycol oxidation, while the surface activity of the alloy based catalyst was slightly higher than that of the Pt/Ru/XC72 catalyst, the latter showed ∼66% higher activities in terms of A g-1 of Pt. These results show the potential of Core-Shell catalysts for reducing the cost of catalysts for DMFC and DEGFC.

  20. Octonary resistance states in La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 multiferroic tunnel junctions

    SciTech Connect

    Yue -Wei Yin; Tao, Jing; Huang, Wei -Chuan; Liu, Yu -Kuai; Yang, Sheng -Wei; Dong, Si -Ning; Zhu, Yi -Mei; Li, Qi; Li, Xiao -Guang

    2015-10-06

    General drawbacks of current electronic/spintronic devices are high power consumption and low density storage. A multiferroic tunnel junction (MFTJ), employing a ferroelectric barrier layer sandwiched between two ferromagnetic layers, presents four resistance states in a single device and therefore provides an alternative way to achieve high density memories. Here, an MFTJ device with eight nonvolatile resistance states by further integrating the design of noncollinear magnetization alignments between the ferromagnetic layers is demonstrated. Through the angle-resolved tunneling magnetoresistance investigations on La0.7Sr0.3MnO3/BaTiO3/La0.7Sr0.3MnO3 junctions, it is found that, besides collinear parallel/antiparallel magnetic configurations, the MFTJ shows at least two other stable noncollinear (45° and 90°) magnetic configurations. As a result, combining the tunneling electroresistance effect caused by the ferroelectricity reversal of the BaTiO3 barrier, an octonary memory device is obtained, representing potential applications in high density nonvolatile storage in the future.

  1. Breaking through the strength-ductility trade-off dilemma in an Al-Si-based casting alloy

    PubMed Central

    Dang, B.; Zhang, X.; Chen, Y. Z.; Chen, C. X.; Wang, H. T.; Liu, F.

    2016-01-01

    Al-Si-based casting alloys have a great potential in various industrial applications. Common strengthening strategies on these alloys are accompanied inevitably by sacrifice of ductility, known as strength-ductility trade-off dilemma. Here, we report a simple route by combining rapid solidification (RS) with a post-solidification heat treatment (PHT), i.e. a RS + PHT route, to break through this dilemma using a commercial Al-Si-based casting alloy (A356 alloy) as an example. It is shown that yield strength and elongation to failure of the RS + PHT processed alloy are elevated simultaneously by increasing the cooling rate upon RS, which are not influenced by subsequent T6 heat treatment. Breaking through the dilemma is attributed to the hierarchical microstructure formed by the RS + PHT route, i.e. highly dispersed nanoscale Si particles in Al dendrites and nanoscale Al particles decorated in eutectic Si. Simplicity of the RS + PHT route makes it being suitable for industrial scaling production. The strategy of engineering microstructures offers a general pathway in tailoring mechanical properties of other Al-Si-based alloys. Moreover, the remarkably enhanced ductility of A356 alloy not only permits strengthening further the material by work hardening but also enables possibly conventional solid-state forming of the material, thus extending the applications of such an alloy. PMID:27502444

  2. Breaking through the strength-ductility trade-off dilemma in an Al-Si-based casting alloy

    NASA Astrophysics Data System (ADS)

    Dang, B.; Zhang, X.; Chen, Y. Z.; Chen, C. X.; Wang, H. T.; Liu, F.

    2016-08-01

    Al-Si-based casting alloys have a great potential in various industrial applications. Common strengthening strategies on these alloys are accompanied inevitably by sacrifice of ductility, known as strength-ductility trade-off dilemma. Here, we report a simple route by combining rapid solidification (RS) with a post-solidification heat treatment (PHT), i.e. a RS + PHT route, to break through this dilemma using a commercial Al-Si-based casting alloy (A356 alloy) as an example. It is shown that yield strength and elongation to failure of the RS + PHT processed alloy are elevated simultaneously by increasing the cooling rate upon RS, which are not influenced by subsequent T6 heat treatment. Breaking through the dilemma is attributed to the hierarchical microstructure formed by the RS + PHT route, i.e. highly dispersed nanoscale Si particles in Al dendrites and nanoscale Al particles decorated in eutectic Si. Simplicity of the RS + PHT route makes it being suitable for industrial scaling production. The strategy of engineering microstructures offers a general pathway in tailoring mechanical properties of other Al-Si-based alloys. Moreover, the remarkably enhanced ductility of A356 alloy not only permits strengthening further the material by work hardening but also enables possibly conventional solid-state forming of the material, thus extending the applications of such an alloy.

  3. Breaking through the strength-ductility trade-off dilemma in an Al-Si-based casting alloy.

    PubMed

    Dang, B; Zhang, X; Chen, Y Z; Chen, C X; Wang, H T; Liu, F

    2016-01-01

    Al-Si-based casting alloys have a great potential in various industrial applications. Common strengthening strategies on these alloys are accompanied inevitably by sacrifice of ductility, known as strength-ductility trade-off dilemma. Here, we report a simple route by combining rapid solidification (RS) with a post-solidification heat treatment (PHT), i.e. a RS + PHT route, to break through this dilemma using a commercial Al-Si-based casting alloy (A356 alloy) as an example. It is shown that yield strength and elongation to failure of the RS + PHT processed alloy are elevated simultaneously by increasing the cooling rate upon RS, which are not influenced by subsequent T6 heat treatment. Breaking through the dilemma is attributed to the hierarchical microstructure formed by the RS + PHT route, i.e. highly dispersed nanoscale Si particles in Al dendrites and nanoscale Al particles decorated in eutectic Si. Simplicity of the RS + PHT route makes it being suitable for industrial scaling production. The strategy of engineering microstructures offers a general pathway in tailoring mechanical properties of other Al-Si-based alloys. Moreover, the remarkably enhanced ductility of A356 alloy not only permits strengthening further the material by work hardening but also enables possibly conventional solid-state forming of the material, thus extending the applications of such an alloy. PMID:27502444

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

    SciTech Connect

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

    1991-08-01

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

  5. Biocorrosion behavior and cell viability of adhesive polymer coated magnesium based alloys for medical implants

    NASA Astrophysics Data System (ADS)

    Abdal-hay, Abdalla; Dewidar, Montasser; Lim, Jae Kyoo

    2012-11-01

    The present study was ultimately aimed to design novel adhesive biodegradable polymer, poly(vinyl acetate) (PVAc), coatings onto Mg based alloys by the dip-coating technique in order to control the degradation rate and enhance the biocompatibility of magnesium alloys. The influence of various solvents on PVAc surface topography and their protection of Mg alloys were dramatically studied in vitro. Electrochemical polarization, degradation, and PVAc film cytocompatibility were also tested. Our results showed that the solvent had a significant effect on coating quality. PVAc/dichloromethane solution showed a porous structure and solution concentration could control the porous size. The coatings prepared using tetrahydrofuran and dimethylformamide solvents are exceptional in their ability to generate porous morphology even at low polymer concentration. In general, the corrosion performance appears to be different on different PVAc-solvent system. Immersion tests illustrated that the porous morphology on PVAc stabilized corrosion rates. A uniform corrosion attack in artificial simulation body fluid was also exhibited. The cytocompatibility of osteoblast cells (MC3T3) revealed high adherence, proliferation, and survival on the porous structure of PVAc coated Mg alloy, which was not observed for the uncoated samples. This novel PVAc coating is a promising candidate for biodegradable implant materials, which might widen the use of Mg based implants.

  6. Industrial Environmental Testing of Coupons and Prototype Cylinders Coated With Iron-Based Amorphous Alloys

    SciTech Connect

    Rebak, R B; Aprigliano, L F; Day, S D; Lian, T; Farmer, J C

    2007-03-06

    Iron-based amorphous alloys are desirable for many industrial applications due to their dual capacity to resist corrosion and wear. These alloys may also contain a significant amount of boron which makes them candidates for criticality control, for example, in high-level nuclear waste disposition applications. The Fe-based amorphous alloys can be produced in powder form and then deposited using a HVOF thermal spray process on any surface that needs to be protected. For the current testing coupons of 316L stainless steels were coated with the amorphous alloy SAM2X5 and then tested for corrosion resistance in the salt-fog chamber and in other industrial environments. Prototype cylinders were also prepared and environmentally tested. One cylinder was 30-inch diameter, 88-inch long, and 3/8-inch thick. The coating thickness was 0.015 to 0.019-inch thick. The cylinder was in good condition after the test. Along the body of the cylinder only two pinpoint spot sized signs of rust were seen. Test results will be compared with the behavior of witness materials under the same tested conditions.

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  8. Thermal cooling effects in the microstructure and properties of cast cobalt-base biomedical alloys

    NASA Astrophysics Data System (ADS)

    Vega Valer, Vladimir

    Joint replacement prosthesis is widely used in the biomedical field to provide a solution for dysfunctional human body joints. The demand for orthopedic knee and hip implants motivate scientists and manufacturers to develop novel materials or to increase the life of service and efficiency of current materials. Cobalt-base alloys have been investigated by various researchers for biomedical implantations. When these alloys contain Chromium, Molybdenum, and Carbon, they exhibit good tribological and mechanical properties, as well as excellent biocompatibility and corrosion resistance. In this study, the microstructure of cast Co-Cr-Mo-C alloy is purposely modified by inducing rapid solidification through fusion welding processes and solution annealing heat treatment (quenched in water at room temperature. In particular the effect of high cooling rates on the athermal phase transformation FCC(gamma)↔HCP(epsilon) on the alloy hardness and corrosion resistance is investigated. The Co-alloy microstructures were characterized using metallography and microscopy techniques. It was found that the as cast sample typically dendritic with dendritic grain sizes of approximately 150 microm and containing Cr-rich coarse carbide precipitates along the interdendritic boundaries. Solution annealing gives rise to a refined microstructure with grain size of 30 microm, common among Co-Cr-Mo alloys after heat treating. Alternatively, an ultrafine grain structure (between 2 and 10 microm) was developed in the fusion zone for specimens melted using Laser and TIG welding methods. When laser surface modification treatments were implemented, the developed solidification microstructure shifted from dendritic to a fine cellular morphology, with possible nanoscale carbide precipitates along the cellular boundaries. In turn, the solidified regions exhibited high hardness values (461.5HV), which exceeds by almost 110 points from the alloy in the as-cast condition. The amount of developed athermal

  9. Application of sintered titanium alloys to metal denture bases: a study of titanium powder sheets for complete denture base.

    PubMed

    Doi, H; Harrori, M; Hasegawa, K; Yoshinari, M; Kawada, E; Oda, Y

    2001-02-01

    The purpose of this study was the fabrication of titanium powder sheets to enable the application of sintered titanium alloys as metal denture bases. The effects of titanium particle shape and size, binder content, and plasticizer content on the surface smoothness, tensile strength and elongation of titanium powder sheets was investigated. To select a suitable ratio of powdered metal contents for application as a metal denture base, the effects of aluminum content in Ti sheets and various other powder metal contents in Ti-Al sheets on the density, sintering shrinkage, and bending strength were evaluated. Based on the results of the above experiments, we developed a mixed powder sheet composed of 83Ti-7Al-10Cr with TA45 titanium powder (atomized, -45 microm), and 8 mass% binder content. This titanium alloy sheet had good formability and ductility. Its sintered titanium alloy had a density of 3.2 g/cm3, sintering shrinkage of 3.8%, and bending strength of 403 MPa. The titanium alloy sheet is clinically acceptable for fabricating denture bases. PMID:11484793

  10. Application of sintered titanium alloys to metal denture bases: a study of titanium powder sheets for complete denture base.

    PubMed

    Doi, H; Harrori, M; Hasegawa, K; Yoshinari, M; Kawada, E; Oda, Y

    2001-02-01

    The purpose of this study was the fabrication of titanium powder sheets to enable the application of sintered titanium alloys as metal denture bases. The effects of titanium particle shape and size, binder content, and plasticizer content on the surface smoothness, tensile strength and elongation of titanium powder sheets was investigated. To select a suitable ratio of powdered metal contents for application as a metal denture base, the effects of aluminum content in Ti sheets and various other powder metal contents in Ti-Al sheets on the density, sintering shrinkage, and bending strength were evaluated. Based on the results of the above experiments, we developed a mixed powder sheet composed of 83Ti-7Al-10Cr with TA45 titanium powder (atomized, -45 microm), and 8 mass% binder content. This titanium alloy sheet had good formability and ductility. Its sintered titanium alloy had a density of 3.2 g/cm3, sintering shrinkage of 3.8%, and bending strength of 403 MPa. The titanium alloy sheet is clinically acceptable for fabricating denture bases.

  11. The resistance to embrittlement by a hydrogen environment of selected high strength iron-manganese base alloys

    NASA Technical Reports Server (NTRS)

    Benson, R. B., Jr.; Kim, D. K.; Atteridge, D.; Gerberich, W. W.

    1974-01-01

    Fe-16Mn and Fe-25Mn base alloys, which had been cold worked to yield strength levels of 201 and 178 KSI, were resistant to degradation of mechanical properties in a one atmosphere hydrogen environment at ambient temperature under the loading conditions employed in this investigation. Transmission electron microscopy established that bands of epsilon phase martensite and fcc mechanical twins were formed throughout the fcc matrix when these alloys were cold worked. In the cold worked alloys a high density of crystal defects were observed associated with both types of strain induced structures, which should contribute significantly to the strengthening of these alloys. High strength iron base alloys can be produced which appear to have some resistance to degradation of mechanical properties in a hydrogen environment under certain conditions.

  12. Axial and torsional fatigue behavior of a cobalt-base alloy

    NASA Technical Reports Server (NTRS)

    Bonacuse, Peter J.; Kalluri, Sreeramesh

    1991-01-01

    In order to develop elevated temperature multiaxial fatigue life prediction models for the wrought cobalt-base alloy, Haynes 188, a multiaxial fatigue data base is required. To satisfy this need, an elevated temperature experimental program on Haynes 188 consisting of axial, torsional, inphase and out of phase axial-torsional fatigue experiments was designed. Elevated temperature axial and torsional fatigue experiments were conducted under strain control on thin wall tubular specimens of Haynes 188 in air. Test results are given.

  13. Thermodynamic Considerations of Contamination by Alloying Elements of Remelted End-of-Life Nickel- and Cobalt-Based Superalloys

    NASA Astrophysics Data System (ADS)

    Lu, Xin; Matsubae, Kazuyo; Nakajima, Kenichi; Nakamura, Shinichiro; Nagasaka, Tetsuya

    2016-06-01

    Cobalt and nickel are high-value commodity metals and are mostly used in the form of highly alloyed materials. The alloying elements used may cause contamination problems during recycling. To ensure maximum resource efficiency, an understanding of the removability of these alloying elements and the controllability of some of the primary alloying elements is essential with respect to the recycling of end-of-life (EoL) nickel- and cobalt-based superalloys by remelting. In this study, the distribution behaviors of approximately 30 elements that are usually present in EoL nickel- and cobalt-based superalloys in the solvent metal (nickel, cobalt, or nickel-cobalt alloy), oxide slag, and gas phases during the remelting were quantitatively evaluated using a thermodynamic approach. The results showed that most of the alloying elements can be removed either in the slag phase or into the gas phase. However, the removal of copper, tin, arsenic, and antimony by remelting is difficult, and they remain as tramp elements during the recycling. On the other hand, the distribution tendencies of iron, molybdenum, and tungsten can be controlled by changing the remelting conditions. To increase the resource efficiency of recycling, preventing contamination by the tramp elements and identifying the alloying compositions of EoL superalloys are significantly essential, which will require the development of efficient prior alloy-sorting systems and advanced separation technologies.

  14. Comparison of Crevice Corrosion of Fe-Based Amorphous Metal and Crystalline Ni-Cr-Mo Alloy

    SciTech Connect

    Shan, X; Ha, H; Payer, J H

    2008-07-24

    The crevice corrosion behaviors of an Fe-based bulk metallic glass alloy (SAM1651) and a Ni-Cr-Mo crystalline alloy (C-22) were studied in 4M NaCl at 100 C with cyclic potentiodynamic polarization and constant potential tests. The corrosion damage morphologies, corrosion products and the compositions of corroded surfaces of these two alloys were studied with optical 3D reconstruction, Scanning Electron Microscopy (SEM), Energy Dispersive Spectroscopy (EDS) and Auger Electron Spectroscopy (AES). It was found that the Fe-based bulk metallic glass (amorphous alloy) SAM1651 had a more positive breakdown potential and repassivation potential than crystalline alloy C-22 in cyclic potentiodynamic polarization tests and required a more positive oxidizing potential to initiate crevice corrosion in constant potential test. Once crevice corrosion initiated, the corrosion propagation of C-22 was more localized near the crevice border compared to SAM1651, and SAM1651 repassivated more readily than C-22. The EDS results indicated that the corrosion products of both alloys contained high amount of O and were enriched in Mo and Cr. The AES results indicated that a Cr-rich oxide passive film was formed on the surfaces of both alloys, and both alloys were corroded congruently.

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

    NASA Technical Reports Server (NTRS)

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

    2004-01-01

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

  16. Effect of hydrogen storage alloy on combustion properties of ammonium perchlorate /glycidylazide polymer -based propellant

    NASA Astrophysics Data System (ADS)

    Li, G. P.; Dou, Y. M.; Chai, C. P.; Luo, Y. J.

    2015-12-01

    Hydrogen storage alloys can serve as good potential fuels for propellant design, by improving the energy and combustion properties. The influence of hydrogen storage alloy (A30) on the combustion properties of ammonium perchlorate/glycidylazide polymer (AP/GAP)-based on propellant were studied. The results showed that A30 could increase the burning rate of propellants by 29.75% and 74.78%, compared with B30 and Al. The combustion model of AP/GAP-based propellant containing different fuel was built. Firstly, A30 reduced the high decomposition temperature and promote condensed phase reaction heat of AP. Secondly, A30 deduced the burning surface temperature. Thirdly, A30 might prove the explosive heat of propellant. Therefore, A30 could greatly improve combustion properties of AP/GAP-based propellant.

  17. Microstructural characterization of a new mechanically alloyed Ni-base ODS superalloy powder

    SciTech Connect

    Seyyed Aghamiri, S.M.; Shahverdi, H.R.; Ukai, S.; Oono, N.; Taya, K.; Miura, S.; Hayashi, S.; Okuda, T.

    2015-02-15

    The microstructure of a new Ni-base oxide dispersion strengthened superalloy powder was studied for high temperature gas turbine applications after the mechanical alloying process. In this study, an atomized powder with a composition similar to the CMSX-10 superalloy was mechanically alloyed with yttria and Hf powders. The mechanically alloyed powder included only the supersaturated solid solution γ phase without γ′ and yttria provided by severe plastic deformation, while after the 3-step aging, the γ′ phase was precipitated due to the partitioning of Al and Ta to the γ′ and Co, Cr, Re, W, and Mo to the γ phase. Mechanical alloying modified the morphology of γ′ to the new coherent γ–γ′ nanoscale lamellar structure to minimize the elastic strain energy of the precipitation, which yielded a low lattice misfit of 0.16% at high temperature. The γ′ lamellae aligned preferentially along the elastically soft [100] direction. Also, the precipitated oxide particles were refined in the γ phase by adding Hf from large incoherent YAlO{sub 3} to fine semi-coherent Y{sub 2}Hf{sub 2}O{sub 7} oxide particles with the average size of 7 nm and low interparticle spacing of 76 nm. - Highlights: • A new Ni-base ODS superalloy powder was produced by mechanical alloying. • The nanoscale γ–γ′ lamellar structure was precipitated after the aging treatment. • Fine semi-coherent Y{sub 2}Hf{sub 2}O{sub 7} oxide particles were precipitated by addition of Hf.

  18. Development of silicide coating over molybdenum based refractory alloy and its characterization

    NASA Astrophysics Data System (ADS)

    Chakraborty, S. P.; Banerjee, S.; Sharma, I. G.; Suri, A. K.

    2010-08-01

    Molybdenum based refractory alloys are potential candidate materials for structural applications in high temperature compact nuclear reactors and fusion reactors. However, these alloys being highly susceptible to oxidation in air or oxygen at elevated temperature, undergoes severe losses from highly volatile molybdenum trioxide species. Present investigation, therefore, examines the feasibility of development of silicide type of coating over molybdenum base TZM alloy shape (Mo > 99 wt.%) using pack cementation coating technique. TZM alloy was synthesized in this laboratory from oxide intermediates of MoO 2, TiO 2 and ZrO 2 in presence of requisite amount of carbon, by alumino-thermic reduction smelting technique. The arc melted and homogenized samples of TZM alloy substrate was then embedded in the chosen and intimately mixed pack composition consisting of inert matrix (Al 2O 3), coating powder (Si) and activator (NH 4Cl) taken in the judicious proportion. The sealed charge packs contained in an alumina crucible were heated at temperatures of 1000 °C for 8-16 h heating cycle to develop the coating. The coating phase was confirmed to be of made of MoSi 2 by XRD analysis. The morphology of the coating was studied by SEM characterization. It had revealed that the coating was diffusion bonded where Si from coating diffused inward and Mo from TZM substrate diffused outward to form the coating. The coating was found to be resistant to oxidation when tested in air up to 1200 °C. A maximum 100 μm of coating thickness was achieved on each side of the substrate.

  19. Influence of the pulsed plasma treatment on the corrosion resistance of the low-alloy steel plated by Ni-based alloy

    NASA Astrophysics Data System (ADS)

    Dzhumaev, P.; Yakushin, V.; Kalin, B.; Polsky, V.; Yurlova, M.

    2016-04-01

    This paper presents investigation results of the influence of high temperature pulsed plasma flows (HTPPF) treatment on the corrosion resistance of low-alloy steel 0.2C-Cr-Mn- Ni-Mo cladded by the rapidly quenched nickel-based alloy. A technique that allows obtaining a defect-free clad layer with a good adhesion to the substrate was developed. It is shown that the preliminary treatment of steel samples by nitrogen plasma flows significantly increases their corrosion resistance in the conditions of intergranular corrosion test in a water solution of sulfuric acid. A change of the corrosion mechanism of the clad layer from intergranular to uniform corrosion was observed as a result of sub-microcrystalline structure formation and homogeneous distribution of alloying elements in the plasma treated surface layer thus leading to the significant increase of the corrosion resistance.

  20. Urinary levels of nickel and chromium associated with dental restoration by nickel–chromium based alloys

    PubMed Central

    Chen, Bo; Xia, Gang; Cao, Xin-Ming; Wang, Jue; Xu, Bi-Yao; Huang, Pu; Chen, Yue; Jiang, Qing-Wu

    2013-01-01

    This paper aims to investigate if the dental restoration of nickel–chromium based alloy (Ni–Cr) leads to the enhanced excretions of Ni and Cr in urine. Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni–Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination. Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry. Compared to the control group, the urinary level of Ni was significantly higher in the patient group of <1 month of the restoration duration, among which higher Ni excretions were found in those with either a higher number of teeth replaced by dental alloys or a higher index of metal crown not covered with the porcelain. Urinary levels of Cr were significantly higher in the three patient groups of <1, 1 to <3 and 3 to <6 months, especially in those with a higher metal crown exposure index. Linear curve estimations showed better relationships between urinary Ni and Cr in patients within 6-month groups. Our data suggested significant increased excretions of urinary Ni and Cr after dental restoration. Potential short- and long-term effects of Ni–Cr alloy restoration need to be investigated. PMID:23579466

  1. Airfoil-based piezoelectric energy harvesting by exploiting the pseudoelastic hysteresis of shape memory alloy springs

    NASA Astrophysics Data System (ADS)

    de Sousa, Vagner Candido; De Marqui Junior, Carlos

    2015-12-01

    The modeling and analysis of an electromechanically coupled typical aeroelastic section with shape memory alloy springs for wind energy harvesting is addressed in this paper. An airfoil with two-degrees-of-freedom, namely pitch and plunge, is considered and piezoelectric coupling is added to the plunge degree-of-freedom. A load resistance is assumed in the electrical domain of the problem in order to estimate the electrical power output. Shape memory alloy coil springs are modeled in the pitch degree-of-freedom of the typical section. A nickel-titanium alloy that exhibits pseudoelasticity at room temperature is assumed. The constitutive model for the shape memory alloy is based on classical phenomenological models. The unsteady aerodynamic loads are obtained by Jones’ approximation to Wagner’s indicial function. The resulting nonlinear electroaeroelastic model is cast into a state-space representation and solved with a Runge-Kutta method. The effects of preload values of the shape memory springs and resistive power generation on the aeroelastic behavior of the wind energy harvester are investigated at the flutter boundary and in a post-flutter regime. The nonlinear kinetics of the austenite-to-martensite phase transformation changes the typical linear flutter behavior to stable limit-cycle oscillations over a range of airflow speeds. Such nonlinear aeroelastic behavior introduced by the hysteretic behavior of the SMA springs provides an important source of persistent electrical power.

  2. Ignition characteristics of the nickel-based alloy UNS N07001 in pressurized oxygen

    NASA Technical Reports Server (NTRS)

    Bransford, J. W.; Billiard, P. A.

    1990-01-01

    The development of ignition and combustion in pressurized oxygen atmospheres was studied for the nickel-based alloy UNS N07001. Ignition of the alloy was achieved by heating the top surface of a cylindrical specimen with a continuous-wave CO2 laser. Two heating procedures were used. In the first, laser power was adjusted to maintain an approximately linear increase in surface temperature. In the second, laser power was periodically increased until autoheating (self-heating) was established. It was found that the alloy would autoheat to combustion from temperatures below the solidus temperature. In addition, the alloy had a tendency to develop combustion zones (hot spots) at high oxygen pressures when the incremental (step) heating test mode was used. Unique points on the temperature-time curves that describe certain events are defined and the temperatures at which these events occur are given for the oxygen pressure range of 1.72 to 13.8 MPa (250 to 2000 psia).

  3. Tunable elastic modulus in Mn-based antiferromagnetic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Cui, S. S.; Shi, S.; Zhao, Z. M.; Cui, Y. G.; Liu, C.; Yuan, F.; Hou, J. W.; Wan, J. F.; Zhang, J. H.; Rong, Y. H.

    2016-07-01

    Compared with the normal relation between temperature (T) and elastic modulus (E) in most materials, martensitic transformation (MT) and magnetic transition could result in the softening of elastic modulus (dE/dT > 0) within a narrow range of T (<100 °C). It becomes possible in MnFeCu alloys to tune this range and broaden it to about 200 °C through combining MT and paramagnetic-antiferromagnetic (P-A) transition. The alloying elements and their contents play a key role in making MT separate from P-A transition, in which first-order MT made a greater contribution to this maximum value than second-order P-A transition. The intrinsic mechanism is that MT can continue causing the modulus to soften even after the P-A transition ends. This wide range keeps stable under different cooling/heating rates. An expression for dE/dT is deduced based on the proposed free energy model and the corresponding theoretical curve (dE/dT-T) gives a reasonable explanation on the experimental results in MnFeCu alloys. A modulus–temperature–composition phase diagram is obtained to describe such critical behaviors and it is found that there exists a specific triangle zone in which dE/dT > 0. The present results may enrich approaches to designing new functional materials, e.g. the elastic and Elinvar alloys.

  4. A Constitutive Model of 6111-T4 Aluminum Alloy Sheet Based on the Warm Tensile Test

    NASA Astrophysics Data System (ADS)

    Hua, Lin; Meng, Fanzhi; Song, Yanli; Liu, Jianing; Qin, Xunpeng; Suo, Lianbing

    2014-03-01

    As main light-weight material, aluminum alloy sheets have been widely applied to produce auto body panels. In order to predict the formability and springback of aluminum alloy sheets, a precise constitutive model is a necessity. In this article, a series of warm tensile tests were conducted on Gleeble-1500D thermal mechanical simulator for 6111-T4 aluminum alloy sheets. The corresponding strain rate ranged from 0.015 to 1.5 s-1, and the temperature ranged from 25 to 350 °C. The relationship between the temperature, the strain rate, and the flow stress were discussed. A constitutive model based on the updated Fields-Backofen equation was established to describe the flow behavior of 6111-T4 aluminum alloy during the warm tensile tests. Subsequently, the average absolute relative error (AARE) was introduced to verify the predictability of the constitutive model. The value of AARE at the uniform plastic deformation stage was calculated to be 1.677%, which demonstrates that the predicted flow stress values were in accordance with the experimental ones. The constitutive model was validated by the fact that the simulated results of the warm tensile tests coincided with the experimental ones.

  5. Urinary levels of nickel and chromium associated with dental restoration by nickel-chromium based alloys.

    PubMed

    Chen, Bo; Xia, Gang; Cao, Xin-Ming; Wang, Jue; Xu, Bi-Yao; Huang, Pu; Chen, Yue; Jiang, Qing-Wu

    2013-03-01

    This paper aims to investigate if the dental restoration of nickel-chromium based alloy (Ni-Cr) leads to the enhanced excretions of Ni and Cr in urine. Seven hundred and ninety-five patients in a dental hospital had single or multiple Ni-Cr alloy restoration recently and 198 controls were recruited to collect information on dental restoration by questionnaire and clinical examination. Urinary concentrations of Ni and Cr from each subject were measure by graphite furnace atomic absorption spectrometry. Compared to the control group, the urinary level of Ni was significantly higher in the patient group of <1 month of the restoration duration, among which higher Ni excretions were found in those with either a higher number of teeth replaced by dental alloys or a higher index of metal crown not covered with the porcelain. Urinary levels of Cr were significantly higher in the three patient groups of <1, 1 to <3 and 3 to <6 months, especially in those with a higher metal crown exposure index. Linear curve estimations showed better relationships between urinary Ni and Cr in patients within 6-month groups. Our data suggested significant increased excretions of urinary Ni and Cr after dental restoration. Potential short- and long-term effects of Ni-Cr alloy restoration need to be investigated.

  6. Growth Stresses in Thermally Grown Oxides on Nickel-Based Single-Crystal Alloys

    NASA Astrophysics Data System (ADS)

    Rettberg, Luke H.; Laux, Britta; He, Ming Y.; Hovis, David; Heuer, Arthur H.; Pollock, Tresa M.

    2016-03-01

    Growth stresses that develop in α-Al2O3 scale that form during isothermal oxidation of three Ni-based single crystal alloys have been studied to elucidate their role in coating and substrate degradation at elevated temperatures. Piezospectroscopy measurements at room temperature indicate large room temperature compressive stresses in the oxides formed at 1255 K or 1366 K (982 °C or 1093 °C) on the alloys, ranging from a high of 4.8 GPa for René N4 at 1366 K (1093 °C) to a low of 3.8 GPa for René N5 at 1255 K (982 °C). Finite element modeling of each of these systems to account for differences in coefficients of thermal expansion of the oxide and substrate indicates growth strains in the range from 0.21 to 0.44 pct at the oxidation temperature, which is an order of magnitude higher than the growth strains measured in the oxides on intermetallic coatings that are typically applied to these superalloys. The magnitudes of the growth strains do not scale with the parabolic oxidation rate constants measured for the alloys. Significant spatial inhomogeneities in the growth stresses were observed, due to (i) the presence of dendritic segregation and (ii) large carbides in the material that locally disrupts the structure of the oxide scale. The implications of these observations for failure during cyclic oxidation, fatigue cycling, and alloy design are considered.

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

    NASA Astrophysics Data System (ADS)

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

    2007-02-01

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

  8. Failure analysis of AZ31 magnesium alloy sheets based on the extended GTN damage model

    NASA Astrophysics Data System (ADS)

    Wang, Rui-ze; Chen, Zhang-hua; Li, Yu-jie; Dong, Chao-fang

    2013-12-01

    Based on the Gurson-Tvergaard-Needleman (GTN) model and Hill's quadratic anisotropic yield criterion, a combined experimental-numerical study on fracture initiation in the process of thermal stamping of Mg alloy AZ31 sheets was carried out. The aim is to predict the formability of thermal stamping of the Mg alloy sheets at different temperatures. The presented theoretical framework was implemented into a VUMAT subroutine for ABAQUS/EXPLICIT. Internal damage evolution due to void growth and coalescence developed at different temperatures in the Mg alloy sheets was observed by scanning electron microscopy (SEM). Moreover, the thermal effects on the void growth, coalescence, and fracture behavior of the Mg alloy sheets were analyzed by the extended GTN model and forming limit diagrams (FLD). Parameters employed in the GTN model were determined from tensile tests and numerical iterative computation. The distribution of major and minor principal strains in the specimens was determined from the numerical results. Therefore, the corresponding forming limit diagrams at different stress levels and temperatures were drawn. The comparison between the predicted forming limits and the experimental data shows a good agreement.

  9. Tunable elastic modulus in Mn-based antiferromagnetic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Cui, S. S.; Shi, S.; Zhao, Z. M.; Cui, Y. G.; Liu, C.; Yuan, F.; Hou, J. W.; Wan, J. F.; Zhang, J. H.; Rong, Y. H.

    2016-07-01

    Compared with the normal relation between temperature (T) and elastic modulus (E) in most materials, martensitic transformation (MT) and magnetic transition could result in the softening of elastic modulus (dE/dT > 0) within a narrow range of T (<100 °C). It becomes possible in MnFeCu alloys to tune this range and broaden it to about 200 °C through combining MT and paramagnetic-antiferromagnetic (P-A) transition. The alloying elements and their contents play a key role in making MT separate from P-A transition, in which first-order MT made a greater contribution to this maximum value than second-order P-A transition. The intrinsic mechanism is that MT can continue causing the modulus to soften even after the P-A transition ends. This wide range keeps stable under different cooling/heating rates. An expression for dE/dT is deduced based on the proposed free energy model and the corresponding theoretical curve (dE/dT-T) gives a reasonable explanation on the experimental results in MnFeCu alloys. A modulus-temperature-composition phase diagram is obtained to describe such critical behaviors and it is found that there exists a specific triangle zone in which dE/dT > 0. The present results may enrich approaches to designing new functional materials, e.g. the elastic and Elinvar alloys.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  11. Atom probe tomography of Ni-base superalloys Allvac 718Plus and Alloy 718.

    PubMed

    Viskari, L; Stiller, K

    2011-05-01

    Atom probe tomography (APT) allows near atomic scale compositional- and morphological studies of, e.g. matrix, precipitates and interfaces in a wide range of materials. In this work two Ni-base superalloys with similar compositions, Alloy 718 and its derivative Allvac 718Plus, are subject for investigation with special emphasis on the latter alloy. The structural and chemical nuances of these alloys are important for their properties. Of special interest are grain boundaries as their structure and chemistry are important for the materials' ability to resist rapid environmentally induced crack propagation. APT has proved to be suitable for analyses of these types of alloys using voltage pulsed APT. However, for investigations of specimens containing grain boundaries and other interfaces the risk for early specimen fracture is high. Analyses using laser pulsing impose lower electrical field on the specimen thereby significantly increasing the success rate of investigations. Here, the effect of laser pulsing was studied and the derived appropriate acquisition parameters were then applied for microstructural studies, from which initial results are shown. Furthermore, the influence of the higher evaporation field experienced by the hardening γ' Ni(3)(Al,Nb) precipitates on the obtained results is discussed.

  12. Neutronics and activation analysis of lithium-based ternary alloys in IFE blankets

    DOE PAGES

    Jolodosky, Alejandra; Kramer, Kevin; Meier, Wayne; DeMuth, James; Reyes, Susana; Fratoni, Massimiliano

    2016-04-09

    Here we report that an attractive feature of using liquid lithium as the breeder and coolant in fusion blankets is that it has very high tritium solubility and results in very low levels of tritium permeation throughout the facility infrastructure. However, lithium metal vigorously reacts with air and water and presents plant safety concerns. The Lawrence Livermore National Laboratory is carrying an effort to develop a lithium-based alloy that maintains the beneficial properties of lithium (e.g. high tritium breeding and solubility) and at the same time reduces overall flammability concerns. This study evaluates the neutronics performance of lithium-based alloys inmore » the blanket of an inertial fusion energy chamber in order to inform such development. 3-D Monte Carlo calculations were performed to evaluate two main neutronics performance parameters for the blanket: tritium breeding ratio (TBR), and the fusion energy multiplication factor (EMF). It was found that elements that exhibit low absorption cross sections and higher q-values such as lead, tin, and strontium, perform well with those that have high neutron multiplication such as lead and bismuth. These elements meet TBR constrains ranging from 1.02 to 1.1. However, most alloys do not reach EMFs greater than 1.15. Additionally, it was found that enriching lithium significantly increases the TBR and decreases the minimum lithium concentration by more than 60%. The amount of enrichment depends on how much total lithium is in the alloy to begin with. Alloys that performed well in the TBR and EMF calculations were considered for activation analysis. Activation simulations were executed with 50 years of irradiation and 300 years of cooling. It was discovered that bismuth is a poor choice due to achieving the highest decay heat, contact dose rates, and accident doses. In addition, it does not meet the waste disposal ratings (WDR). Some of the activation results for alloys with tin, zinc, and gallium were in

  13. Corrosion of ferritic-martensitic steels and nickel-based alloys in supercritical water

    NASA Astrophysics Data System (ADS)

    Ren, Xiaowei

    The corrosion behavior of ferritic/martensitic (F/M) steels and Ni-based alloys in supercritical water (SCW) has been studied due to their potential applications in future nuclear reactor systems, fossil fuel power plants and waste treatment processes. 9˜12% chromium ferritic/martensitic steels exhibit good radiation resistance and stress corrosion cracking resistance. Ni-based alloys with an austenitic face-centered cubic (FCC) structure are designed to retain good mechanical strength and corrosion/oxidation resistance at elevated temperatures. Corrosion tests were carried out at three temperatures, 360°C, 500°C and 600°C, with two dissolved oxygen contents, 25 ppb and 2 ppm for up to 3000 hours. Alloys modified by grain refinement and reactive element addition were also investigated to determine their ability to improve the corrosion resistance in SCW. A duplex oxide structure was observed in the F/M steels after exposure to 25 ppb oxygen SCW, including an outer oxide layer with columnar magnetite grains and an inner oxide layer constituted of a mixture of spinel and ferrite phases in an equiaxed grain structure. An additional outermost hematite layer formed in the SCW-exposed samples when the oxygen content was increased to 2 ppm. Weight gain in the F/M steels increased with exposure temperatures and times, and followed parabolic growth kinetics in most of the samples. In Ni-based alloys after exposure to SCW, general corrosion and pitting corrosion were observed, and intergranular corrosion was found when exposed at 600°C due to formation of a local healing layer. The general oxide structure on the Ni-based alloys was characterized as NiO/Spinel/(CrxFe 1-x)2O3/(Fe,Ni). No change in oxidation mechanism was observed in crossing the critical point despite the large change in water properties. Corrosion resistance of the F/M steels was significantly improved by plasma-based yttrium surface treatment because of restrained outward diffusion of iron by the

  14. NASA-UVa light aerospace alloy and structures technology program supplement: Aluminum-based materials for high speed aircraft

    NASA Technical Reports Server (NTRS)

    Starke, E. A., Jr. (Editor)

    1995-01-01

    This report on the NASA-UVa light aerospace alloy and structure technology program supplement: Aluminum-Based Materials for High Speed Aircraft covers the period from July 1, 1992. The objective of the research is to develop aluminum alloys and aluminum matrix composites for the airframe which can efficiently perform in the HSCT environment for periods as long as 60,000 hours (certification for 120,000 hours) and, at the same time, meet the cost and weight requirements for an economically viable aircraft. Current industry baselines focus on flight at Mach 2.4. The research covers four major materials systems: (1) Ingot metallurgy 2XXX, 6XXX, and 8XXX alloys, (2) Powder metallurgy 2XXX alloys, (3) Rapidly solidified, dispersion strengthened Al-Fe-X alloys, and (4) Discontinuously reinforced metal matrix composites. There are ten major tasks in the program which also include evaluation and trade-off studies by Boeing and Douglas aircraft companies.

  15. Influence of creep damage on the low cycle thermal-mechanical fatigue behavior of two tantalum base alloys

    NASA Technical Reports Server (NTRS)

    Sheffler, K. D.; Doble, G. S.

    1972-01-01

    Low cycle fatigue tests have been performed on the tantalum base alloys T-111 and ASTAR 811C with synchronized, independently programmed temperature and strain cycling. The thermal-mechanical cycles applied fell into three basic categories: these were isothermal cycling, in-phase thermal cycling, and out-of-phase thermal cycling. In-phase cycling was defined as tensile deformation associated with high temperature and compressive deformation with low temperature, while out-of-phase thermal cycling was defined as the reverse case. The in-phase thermal cycling had a pronounced detrimental influence on the fatigue life of both alloys, with the life reduction being greater in the solid solution strengthened T-111 alloy than in the carbide strengthened ASTAR 811C alloy. The out-of-phase tests also showed pronounced effects on the fatigue life of both alloys, although not as dramatic.

  16. Mechanism by which porous structure is formed on the surface of gold alloy containing only Cu as base metal.

    PubMed

    Ohno, Hiroki; Endo, Kazuhiko; Haneda, Katsumi; Tamura, Makoto; Hikita, Kazuhiro

    2005-12-01

    Gold alloys with Cu contents of 10 mass%, 20%, and 30% were used for morphological observation of porous surface structures after heating at 800 degrees C in air followed by pickling with acid solution. With increasing Cu content in the gold alloy, the internal oxidation zone became well-developed in the alloy matrix. The mechanism by which a porous structure was formed on the surface of a gold alloy containing only Cu as a base metal was thought to be as follows: Cu2O which formed along the grain boundaries acted as a diffusion path, permitting the penetration of O2- into the inner alloy matrix, and thereby resulting in internal oxidation occurring predominantly along the grain boundaries. PMID:16445010

  17. Brushing-Induced Surface Roughness of Two Nickel Based Alloys and a Titanium Based Alloy: A Comparative Study - In Vitro Study

    PubMed Central

    Acharya, B L Guruprasanna; Nadiger, Ramesh; Shetty, Bharathraj; Gururaj, G; Kumar, K Naveen; Darshan, D D

    2014-01-01

    be given to the selection of the toothbrushes and toothpastes with the medium abrasives in patients with these restorations. How to cite the article: Acharya BL, Nadiger R, Shetty B, Gururaj G, Kumar KN, Darshan DD. Brushing induced surface roughness of two nickel based alloys and a titanium based alloy: A comparative study - In vitro study. J Int Oral Health 2014;6(3):36-49. PMID:25083031

  18. Multi-scale Modelling of bcc-Fe Based Alloys for Nuclear Applications

    SciTech Connect

    Malerba, Lorenzo

    2008-07-01

    , advanced techniques to fit interatomic potentials consistent with thermodynamics are proposed and the results of their application to the mentioned alloys are presented. Next, the development of advanced methods, based on the use of artificial intelligence, to improve both the physical reliability and the computational efficiency of kinetic Monte Carlo codes for the study of point-defect clustering and phase changes beyond the scale of MD, is reported. These recent progresses bear the promise of being able, in the near future, of producing reliable tools for the description of the microstructure evolution of realistic model alloys under irradiation. (author)

  19. AB INITIO Modeling of Thermomechanical Properties of Mo-Based Alloys for Fossil Energy Conversion

    SciTech Connect

    Ching, Wai-Yim

    2013-12-31

    In this final scientific/technical report covering the period of 3.5 years started on July 1, 2011, we report the accomplishments on the study of thermo-mechanical properties of Mo-based intermetallic compounds under NETL support. These include computational method development, physical properties investigation of Mo-based compounds and alloys. The main focus is on the mechanical and thermo mechanical properties at high temperature since these are the most crucial properties for their potential applications. In particular, recent development of applying ab initio molecular dynamic (AIMD) simulations to the T1 (Mo{sub 5}Si{sub 3}) and T2 (Mo{sub 5}SiB{sub 2}) phases are highlighted for alloy design in further improving their properties.

  20. A simple spectrophotometric method for determination of zirconium or hafnium in selected molybdenum-base alloys

    NASA Technical Reports Server (NTRS)

    Dupraw, W. A.

    1972-01-01

    A simple analytical procedure is described for accurately and precisely determining the zirconium or hafnium content of molybdenum-base alloys. The procedure is based on the reaction of the reagent Arsenazo III with zirconium or hafnium in strong hydrochloric acid solution. The colored complexes of zirconium or hafnium are formed in the presence of molybdenum. Titanium or rhenium in the alloy have no adverse effect on the zirconium or hafnium complex at the following levels in the selected aliquot: Mo, 10 mg; Re, 10 mg; Ti, 1 mg. The spectrophotometric measurement of the zirconium or hafnium complex is accomplished without prior separation with a relative standard deviation of 1.3 to 2.7 percent.

  1. Mechanical Properties of Aluminum-Based Dissimilar Alloy Joints by Power Beams, Arc and FSW Processes

    NASA Astrophysics Data System (ADS)

    Okubo, Michinori; Kon, Tomokuni; Abe, Nobuyuki

    Dissimilar smart joints are useful. In this research, welded quality of dissimilar aluminum alloys of 3 mm thickness by various welding processes and process parameters have been investigated by hardness and tensile tests, and observation of imperfection and microstructure. Base metals used in this study are A1050-H24, A2017-T3, A5083-O, A6061-T6 and A7075-T651. Welding processes used are YAG laser beam, electron beam, metal inert gas arc, tungsten inert gas arc and friction stir welding. The properties of weld zones are affected by welding processes, welding parameters and combination of base metals. Properties of high strength aluminum alloy joints are improved by friction stir welding.

  2. Effects of Counterpart Materials on Wear Behavior of Thermally Sprayed Ni-BASED Self-Flux Alloy Coatings

    NASA Astrophysics Data System (ADS)

    Kim, Kyun Tak; Kim, Yeong Sik

    This study aims at investigating the wear behavior of thermally sprayed Ni-based self-flux alloy coatings against different counterparts. Ni-based self-flux alloy powders were flame-sprayed onto a carbon steel substrate and then heat-treated at temperature of 1000 °C. Dry sliding wear tests were performed using the sliding speeds of 0.2 and 0.8 m/s and the applied loads of 5 and 20 N. AISI 52100, Al2O3, Si3N4 and ZrO2 balls were used as counterpart materials. Wear behavior of Ni-based self-flux alloy coatings against different counterparts were studied using a scanning electron microscope(SEM) and energy dispersive X-ray spectroscopy (EDX). It was revealed that wear behavior of Ni-based self-flux alloy coatings were much influenced by counterpart materials.

  3. Corrosion behavior of iron and nickel base alloys under solid oxide fuel cell exposure conditions

    SciTech Connect

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

    2006-03-01

    Topography and phase composition of the scales formed on commercial ferritic stainless steels and experimental low CTE nickel-based alloys were studied in atmospheres simulating solid oxide fuel cell (SOFC) environments. The materials were studied under dual environment conditions with air on one side of the sample and carbon monoxide on the other side at 750°C. Surface characterization techniques, such as scanning electron microscopy and X-ray diffraction analysis were used in this study.

  4. Interdiffusion behavior of Pt-modified γ-Ni + γ'-Ni3Al alloys coupled to Ni-Al-based alloys

    NASA Astrophysics Data System (ADS)

    Hayashi, Shigenari; Wang, Wen; Sordelet, Daniel J.; Gleeson, Brian

    2005-07-01

    The effect of platinum addition on the interdiffusion behavior of γ-Ni + γ'-Ni3Al alloys was studied by using diffusion couples comprised of a Ni-Al-Pt alloy mated to a Ni-Al, Ni-Al-Cr, or Ni-based commercial alloy. The commercial alloys studied were CMSX-4 and CMSX-10. Diffusion annealing was at 1150 °C for up to 100 hours. An Al-enriched γ'-layer often formed in the interdiffusion zone of a given couple during diffusion annealing due to the uphill diffusion of Al. This uphill diffusion was ascribed to Pt addition decreasing the chemical activity of aluminum in the γ + γ' alloys. For a given diffusion couple end member, the thickening kinetics of the γ' layer that formed increased with increasing Pt content in the Ni-Al-Pt γ + γ' alloy. The γ'-layer thickening kinetics in diffusion couples with Cr showed less of a dependence on Pt concentration. Inference of a negative effect of Pt and positive effect of Cr on the Al diffusion in this system enabled explanation of the observed interdiffusion behaviors. There was no or minimal formation of detrimental topologically close-packed (TCP) phases in the interdiffusion zone of the couples with CMSX-4 or CMSX-10. An overlay Pt-modified γ + γ' coating on CMSX-4 showed excellent oxidation resistance when exposed to air for 1000 hours at 1150 °C. Moreover, the Al content in the coating was maintained at a relatively high level due to Al replenishment from the CMSX-4 substrate.

  5. Spin-transfer magnetization switching in ordered alloy-based nanopillar devices

    NASA Astrophysics Data System (ADS)

    Mitani, S.

    2011-09-01

    This paper reviews spin-transfer magnetization switching in ordered alloy-based nanopillar devices. L10-ordered FePt was used for one of the earliest demonstrations of spin-transfer switching in perpendicularly magnetized systems. The behaviour of magnetization switching deviates from the predictions based on a macro-spin model, suggesting incoherent magnetization switching in the system with a large perpendicular magnetic anisotropy. The effect of a 90° spin injector on spin-transfer switching was also examined using L10-ordered FePt. Full-Heusler alloys are in another fascinating material class for spin-transfer switching because of their high-spin polarization of conduction electrons and possible small magnetization damping. A B2-ordered Co2FeAl0.5Si0.5-based device showed a low intrinsic critical current density of 9.3 × 106 A cm-2 for spin-transfer switching as well as a relatively large current-perpendicular-to-plane giant-magnetoresistance (CPP-GMR) up to ~9%. The specific physical properties of ordered alloys may be useful for fundamental studies and applications in spin-transfer switching.

  6. Development of wear-resistant coatings for cobalt-base alloys

    SciTech Connect

    Cockeram, B.V.

    1999-03-01

    The costs and hazards resulting from nuclear plant radiation exposure with activated cobalt wear debris could potentially be reduced by covering the cobalt-base materials with a wear resistant coating. However, the hardnesses of many cobalt-base wear alloys are significantly lower than conventional PVD hard coatings, and mechanical support of the hard coating is a concern. Four approaches have been taken to minimize the hardness differences between the substrate and PVD hard coating: (1) use a thin Cr-nitride hard coating with layers that are graded with respect to hardness, (2) use a thicker, multilayered coating (Cr-nitride or Zr-nitride) with graded layers, (3) use nitriding to harden the alloy subsurface followed by application of a multilayered coating of Cr-nitride, and (4) use of nitriding alone. Since little work has been done on application of PVD hard coatings to cobalt-base alloys, some details on process development and characterization of the coatings is presented. Scratch testing was used to evaluate the adhesion of the different coatings. A bench-top rolling contact test was used to evaluate the wear resistance of the coatings. The test results are discussed, and the more desirable coating approaches are identified.

  7. Spin Transfer Torque Switching and Perpendicular Magnetic Anisotropy in Full Heusler Alloy Co2FeAl-BASED Tunnel Junctions

    NASA Astrophysics Data System (ADS)

    Sukegawa, H.; Wen, Z. C.; Kasai, S.; Inomata, K.; Mitani, S.

    2014-12-01

    Some of Co-based full Heusler alloys have remarkable properties in spintronics, that is, high spin polarization of conduction electrons and low magnetic damping. Owing to these properties, magnetic tunnel junctions (MTJs) using Co-based full Heusler alloys are potentially of particular importance for spintronic application such as magnetoresistive random access memories (MRAMs). Recently, we have first demonstrated spin transfer torque (STT) switching and perpendicular magnetic anisotropy (PMA), which are required for developing high-density MRAMs, in full-Heusler Co2FeAl alloy-based MTJs. In this review, the main results of the experimental demonstrations are shown with referring to related issues, and the prospect of MTJs using Heusler alloys is also discussed.

  8. An investigation of the initiation stage of hot corrosion in Ni-base alloys

    NASA Technical Reports Server (NTRS)

    Huang, T. T.; Meier, G. H.

    1979-01-01

    The mechanisms which lead to the destruction of a normally protective scale during the initial stages of hot corrosion of 14 nickel-base alloys contaminated with Na2SO4 and other condensed deposits were investigated. A continuous reading microbalance was used to record weight changes at temperatures between 900 C and 1000 C at 1 atmosphere pressure of slowly flowing oxygen. The reaction was initiated by raising a preheated furnace around the quartz tube in which the specimen was supported with oxygen flowing. The furnace was raised in a time period of seconds. At 900 C, the system and specimen came to thermal equilibrium in less than one minute. Oxidized specimens were studied using optical and scanning electron metallography and X-ray diffraction techniques. Transmission electron microscopy and electron diffraction spectroscopy were also used to identify the structure of carbides in some of the commercial alloys.

  9. Development of strength and conductivity in deformation processed copper base alloys

    SciTech Connect

    Insoo, M.

    1992-07-20

    Deformation processed copper based composite alloys have been recently investigated. In these composite alloys, copper, a matrix material, contributes to a high thermal and electrical conductivity, and a second phase material such as Fe, Nb, Cr, Mo, Ta and W acts as a reinforcement of the strength of the composites. Tungsten was chosen as the bcc phase in the first experiment because W has a high melting temperature which is expected to reduce the decrease in high temperature strength resulting from coarsening of fibers. However, brittleness of tungsten may bring crack problems. Because the matrix is ductile but the second phase is hard enough to resist the external forces, cracks may occur at the interfaces between deformed matrix and undeformed second phase. The purpose of the first experiment is to investigate the possibility of deformation of Cu-W compacts.

  10. Observation of Pseudopartial Grain Boundary Wetting in the NdFeB-Based Alloy

    NASA Astrophysics Data System (ADS)

    Straumal, B. B.; Mazilkin, A. A.; Protasova, S. G.; Schütz, G.; Straumal, A. B.; Baretzky, B.

    2016-03-01

    The NdFeB-based alloys were invented in 1980s and remain the best-known hard magnetic alloys. In order to reach the optimum magnetic properties, the grains of hard magnetic Nd2Fe14B phase have to be isolated from one another by the (possibly thin) layers of a non-ferromagnetic Nd-rich phase. In this work, we observe that the few-nanometer-thin layers of the Nd-rich phase appear between Nd2Fe14B grains due to the pseudopartial grain boundary (GB) wetting. Namely, some Nd2Fe14B/Nd2Fe14B GBs are not completely wetted by the Nd-rich melt and have the high contact angle with the liquid phase and, nevertheless, contain the 2-4-nm-thin uniform Nd-rich layer.

  11. Identification of epsilon martensite in a Fe-based shape memory alloy by means of EBSD.

    PubMed

    Verbeken, K; Van Caenegem, N; Raabe, D

    2009-01-01

    Ferrous shape memory alloys (SMAs) are often thought to become a new, important group of SMAs. The shape memory effect in these alloys is based on the reversible, stress-induced martensitic transformation of austenite to epsilon martensite. The identification and quantification of epsilon martensite is crucial when evaluating the shape memory behaviour of this material. Previous work displayed that promising results were obtained when studying the evolution of the amount of epsilon martensite after different processing steps with Electron BackScatter Diffraction (EBSD). The present work will discuss in detail, on the one hand, the challenges and opportunities arising during the identification of epsilon martensite by means of EBSD and, on the other hand, the possible interpretations that might be given to these findings. It will be illustrated that although the specific nature of the austenite to epsilon martensite transformation can still cause some points of discussion, EBSD has a high potential for identifying epsilon martensite.

  12. Fractal properties of worn surface of Fe-based alloy coatings during rolling contact process

    NASA Astrophysics Data System (ADS)

    Chen, Shu-ying; Wang, Hai-dou; Ma, Guo-zheng; Kang, Jia-jie; Xu, Bin-shi

    2016-02-01

    The rolling contact fatigue (RCF) failure procedure of Fe-based alloy coating, fabricated by high efficient plasma spray (PS) technology, was investigated by a double-roller test machine with oil lubrication under pure rolling contact condition. The fractal dimension (FD) was utilized to quantitatively characterize the profile of the worn surface at different experiment stage and the failure mechanism of the coating was discussed. The results indicated that the nonlinear morphologies of the worn surface of Fe-Cr alloy coating possessed excellent fractal properties. The failure procedure could be divided into four stages according to the value and change rule of FD, i.e. (1) running-in stage, (2) stable abrade stage, (3) accelerated damage stage, (4) unstable removal stage.

  13. A structural investigation of a plasma sprayed Ni--Cr based alloy coating

    SciTech Connect

    Sampath, S.; Neiser, R.A.; Herman, H. ); Kirkland, J.P.; Elam, W.T. )

    1993-01-01

    A Ni--Cr based hardfacing alloy has been plasma sprayed in ambient and low pressure atmospheres onto mild steel substrates. These coatings exhibit excellent wear and corrosion resistance; however, the significance of microstructure on properties has not been reported. This study relates the structure of the sprayed coatings to the processing conditions. X-ray diffraction results indicate phase separation in air plasma sprayed deposits, while low pressure plasma sprayed deposits exhibit a single supersaturated solid solution. Annealing of the air plasma sprayed coating shows dissolution of the bcc chromium phase, confirming its metastable nature. These results were confirmed using Extended X-ray Absorption Fine Structure (EXAFS) analysis, which further suggests a highly disordered structure, with partial oxidation of selected alloying elements, such as chromium. Transmission electron microscopy indicates a wide variety of microstructures in the air plasma sprayed deposit. In the case of low pressure sprayed deposit, the microstructures are homogeneous and uniform.

  14. Comparison of joining processes for Haynes 230 nickel based super alloy

    NASA Astrophysics Data System (ADS)

    Williston, David Hugh

    Haynes 230 is a nickel based, solid-solution strengthened alloy that is used for high-temperature applications in the aero-engine and power generation industries. The alloy composition is balanced to avoid precipitation of undesirable topologically closed-packed (TCP) intermetallic phases, such as Sigma, Mu, or Laves-type, that are detrimental to mechanical and corrosion properties. This material is currently being used for the NASA's J2X upper stage rocket nozzle extension. Current fabrication procedures use fusion welding processes to join blanks that are subsequently formed. Cracks have been noted to occur in the fusion welded region during the forming operations. Use of solid state joining processes, such as friction stir welding are being proposed to eliminate the fusion weld cracks. Of interest is a modified friction stir welding process called thermal stir welding. Three welding process: Gas Metal Arc Welding (GMAW), Electron Beam Welding (EBW), and Thermal Stir Welding (TSWing) are compared in this study.

  15. Thermodynamic properties and atomic structure of Ca-based liquid alloys

    NASA Astrophysics Data System (ADS)

    Poizeau, Sophie

    To identify the most promising positive electrodes for Ca-based liquid metal batteries, the thermodynamic properties of diverse Ca-based liquid alloys were investigated. The thermodynamic properties of Ca-Sb alloys were determined by emf measurements. It was found that Sb as positive electrode would provide the highest voltage for Ca-based liquid metal batteries (1 V). The price of such a battery would be competitive for the grid-scale energy storage market. The impact of Pb, a natural impurity of Sb, was predicted successfully and confirmed via electrochemical measurements. It was shown that the impact on the open circuit voltage would be minor. Indeed, the interaction between Ca and Sb was demonstrated to be much stronger than between Ca and Pb using thermodynamic modeling, which explains why the partial thermodynamic properties of Ca would not vary much with the addition of Pb to Sb. However, the usage of the positive electrode would be reduced, which would limit the interest of a Pb-Sb positive electrode. Throughout this work, the molecular interaction volume model (MIVM) was used for the first time for alloys with thermodynamic properties showing strong negative deviation from ideality. This model showed that systems such as Ca-Sb have strong short-range order: Ca is most stable when its first nearest neighbors are Sb. This is consistent with what the more traditional thermodynamic model, the regular association model, would predict. The advantages of the MIVM are the absence of assumption regarding the composition of an associate, and the reduced number of fitting parameters (2 instead of 5). Based on the parameters derived from the thermodynamic modeling using the MIVM, a new potential of mixing for liquid alloys was defined to compare the strength of interaction in different Ca-based alloys. Comparing this trend with the strength of interaction in the solid state of these systems (assessed by the energy of formation of the intermetallics), the systems with

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

    NASA Technical Reports Server (NTRS)

    Ellis, David L.

    2005-01-01

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

  17. Rapid solidification processing of iron-base alloys for structural applications

    SciTech Connect

    Flinn, J.E.

    1991-09-01

    The response of iron-base alloys to rapid solidification is reviewed with an emphasis on the effects of processing on the microstructure and mechanical property behavior. The processing topics addressed are powder atomization, powder consolidation, joining, and thermal-mechanical exposure. The value of rapid solidification processing (RSP) lies in the ability to promote compositional homogeneity and retention of fine and stable (to high temperatures) microstructures. Achieving the maximum benefit from RSP requires proper application of the basic principles of composition control and rapid crystallization. This investigation has disclosed two very important facets of the RSP approach that can be applied using current technologies. Dissociated oxygen appears to play a significant role in stabilizing microstructural features. In conjunction with oxygen, vacancies trapped during crystallization provide a very stable matrix dispersion for enhanced strengthening. With a fundamental understanding of the response of iron-base alloys to RSP, alloys can be designed that will have substantially better properties and performance than their conventionally processed counterparts. 77 refs., 94 figs., 14 tabs.

  18. COATED ALLOYS

    DOEpatents

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

    1958-07-15

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

  19. Structural aspects of the manufacture of semiproducts made from titanium nickelide-based alloys

    NASA Astrophysics Data System (ADS)

    Kollerov, M. Yu.; Ilyin, A. A.; Pol'Kin, I. S.; Fainbron, A. S.; Gusev, D. E.; Khachin, S. V.

    2007-10-01

    The effects of the charge composition, casting method, and metal forming method on the structure and shape-memory-effect (SME) and superelasticity characteristics of titanium nickelide-based alloys are studied. The shape recovery temperatures of semiproducts are shown to depend substantially on the volume fraction of the Ti2Ni intermetallic phase, whose formation is stimulated by the oxygen present in a charge or absorbed during casting. An increase in the volume fraction of Ti2Ni in an alloy leads to nickel enrichment of the B2 phase and a decrease in the shape recovery temperatures. Subsequent metal forming at the stage of semiproduct manufacture only weakly affects the volume fraction of Ti2Ni and favors the formation of its equiaxed shape and a more uniform Ti2Ni distribution in the B2 matrix. In alloys where the B2 phase contains more than 56.5 wt % Ni, quenching from temperatures above 600°C and aging in the temperature range 400 500°C result in the dissolution and precipitation, respectively, of the nickel-rich Ti3Ni4 and Ti2Ni3 intermetallics. Therefore, the shape recovery temperatures of semiproducts and finished products can be controlled. Moreover, as the aging temperature changes, the volume fraction and size of nickel-rich intermetallic particles, the slip stresses, and the SME force characteristics change. For example, to increase the compression forces for osteosynthesis fixation devices, one has to use a titanium nickelide-based alloy with a high nickel content in the B2 phase and to perform aging at low temperatures (400 450°C).

  20. Influence of base alloy composition on processing time during transient liquid phase bonding of nickel-base superalloys

    NASA Astrophysics Data System (ADS)

    Hunedy, Juhaina Farouk

    An experimental investigation to study the influence of base metal composition on the time required to achieve complete isothermal solidification (t f) during TLP bonding of three Ni-base superalloys was performed. Alloys IN 738, DS Rene80 and DS IC 6 show similar behaviour when bonded at 1100 °C, with comparable tf. However, at higher temperatures, IN 738 requires extended period of time (as compared to DS Rene80 and DS IC 6) to achieve complete isothermal solidification. The prolonged tf in IN 738 appears to be caused by a more pronounced reduction in concentration gradient of the diffusing solute within the material during bonding. In contrast, the shorter complete isothermal solidification time experienced by alloy DS IC6 is attributable to its capability to better accommodate the diffusing solute, through the formation of densely packed second-phase precipitates in the diffusion affected zone (DAZ).

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

    NASA Technical Reports Server (NTRS)

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

    1974-01-01

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

  2. Effect of Y2O3 content on the oxidation behavior of Fe-Cr-Al-based ODS alloys

    NASA Astrophysics Data System (ADS)

    Ul-Hamid, Anwar

    2003-02-01

    A study was conducted to investigate the cyclic oxidation behavior of two oxide dispersion strengthened (ODS) Fe-Cr-Al based alloys containing 0.17 wt.% and 0.7 wt.% Y2O3. The alloys were oxidized in air for 100 h at 1200°C based on a 24 h cycle period. X-ray diffraction (XRD) and analytical transmission electron microscopy (TEM) were used to characterize the structure, morphology, and composition of the oxide scales. Both alloys formed highly adherent and continuous layers of α-Al2O3 exhibiting a morphology indicative of inward scale growth. The role of Y2O3 was to promote adherence by segregating to the grain boundaries within the oxide. Concurrently, Y2O3 generated micro-porosity resulting in a scale of comparatively higher thickness in the alloy with 0.7 wt.% Y2O3.

  3. Investigation on corrosion behavior of Ni-based alloys in molten fluoride salt using synchrotron radiation techniques

    NASA Astrophysics Data System (ADS)

    Liu, Min; Zheng, Junyi; Lu, Yanling; Li, Zhijun; Zou, Yang; Yu, Xiaohan; Zhou, Xingtai

    2013-09-01

    Ni-based alloys have been selected as the structural materials in molten-salt reactors due to their high corrosion resistance and excellent mechanical properties. In this paper, the corrosion behavior of some Ni-based superalloys including Inconel 600, Hastelloy X and Hastelloy C-276 were investigated in molten fluoride salts at 750 °C. Morphology and microstructure of corroded samples were analyzed using scanning electron microscope (SEM), synchrotron radiation X-ray microbeam fluorescence (μ-XRF) and synchrotron radiation X-ray diffraction (SR-XRD) techniques. Results from μ-XRF and SR-XRD show that the main depleted alloying element of Ni-based alloys in molten fluoride salt is Cr. In addition, the results indicate that Mo can enhance the corrosion resistance in molten FLiNaK salts. Among the above three Ni-based alloys, Hastelloy C-276 exhibits the best corrosion resistance in molten fluoride salts 750 °C. Higher-content Mo and lower-content Cr in Hastelloy C-276 alloy were responsible for the better anti-corrosive performance, compared to the other two alloys.

  4. Zirconium, calcium, and strontium contents in magnesium based biodegradable alloys modulate the efficiency of implant-induced osseointegration

    PubMed Central

    Mushahary, Dolly; Sravanthi, Ragamouni; Li, Yuncang; Kumar, Mahesh J; Harishankar, Nemani; Hodgson, Peter D; Wen, Cuie; Pande, Gopal

    2013-01-01

    Development of new biodegradable implants and devices is necessary to meet the increasing needs of regenerative orthopedic procedures. An important consideration while formulating new implant materials is that they should physicochemically and biologically mimic bone-like properties. In earlier studies, we have developed and characterized magnesium based biodegradable alloys, in particular magnesium-zirconium (Mg-Zr) alloys. Here we have reported the biological properties of four Mg-Zr alloys containing different quantities of strontium or calcium. The alloys were implanted in small cavities made in femur bones of New Zealand White rabbits, and the quantitative and qualitative assessments of newly induced bone tissue were carried out. A total of 30 experimental animals, three for each implant type, were studied, and bone induction was assessed by histological, immunohistochemical and radiological methods; cavities in the femurs with no implants and observed for the same period of time were kept as controls. Our results showed that Mg-Zr alloys containing appropriate quantities of strontium were more efficient in inducing good quality mineralized bone than other alloys. Our results have been discussed in the context of physicochemical and biological properties of the alloys, and they could be very useful in determining the nature of future generations of biodegradable orthopedic implants. PMID:23976848

  5. Zirconium, calcium, and strontium contents in magnesium based biodegradable alloys modulate the efficiency of implant-induced osseointegration.

    PubMed

    Mushahary, Dolly; Sravanthi, Ragamouni; Li, Yuncang; Kumar, Mahesh J; Harishankar, Nemani; Hodgson, Peter D; Wen, Cuie; Pande, Gopal

    2013-01-01

    Development of new biodegradable implants and devices is necessary to meet the increasing needs of regenerative orthopedic procedures. An important consideration while formulating new implant materials is that they should physicochemically and biologically mimic bone-like properties. In earlier studies, we have developed and characterized magnesium based biodegradable alloys, in particular magnesium-zirconium (Mg-Zr) alloys. Here we have reported the biological properties of four Mg-Zr alloys containing different quantities of strontium or calcium. The alloys were implanted in small cavities made in femur bones of New Zealand White rabbits, and the quantitative and qualitative assessments of newly induced bone tissue were carried out. A total of 30 experimental animals, three for each implant type, were studied, and bone induction was assessed by histological, immunohistochemical and radiological methods; cavities in the femurs with no implants and observed for the same period of time were kept as controls. Our results showed that Mg-Zr alloys containing appropriate quantities of strontium were more efficient in inducing good quality mineralized bone than other alloys. Our results have been discussed in the context of physicochemical and biological properties of the alloys, and they could be very useful in determining the nature of future generations of biodegradable orthopedic implants.

  6. Alloying Element Nitride Development in Ferritic Fe-Based Materials Upon Nitriding: A Review

    NASA Astrophysics Data System (ADS)

    Steiner, T.; Mittemeijer, E. J.

    2016-06-01

    With the aim of achieving a better understanding of the nitriding process of iron-based components (steels), as applied in engineering practice, the theoretical background and experimental observations currently available on the crystallographic, morphological, and compositional properties of the nitride precipitates in nitrided model binary and ternary, ferritic Fe-based alloys are summarily presented. Thermodynamic and kinetic considerations are employed in order to highlight their importance for the nitriding reaction and the resulting properties of the nitrided zone, thereby providing a more fundamental understanding of the nitriding process.

  7. Impact properties of vanadium-base alloys irradiated at < 430 C

    SciTech Connect

    Chung, H.M.; Smith, D.L.

    1998-03-01

    Recent attention to vanadium-base alloys has focused on the effect of low-temperature (<430 C) neutron irradiation on the mechanical properties, especially the phenomena of loss of work-hardening capability under tensile loading and loss of dynamic toughness manifested by low impact energy and high ductile-brittle-transition temperature (DBTT). This paper summarizes results of an investigation of the low-temperature impact properties of V-5Ti, V-4Cr-4Ti, and V-3Ti-Si that were irradiated in several fission reactor experiments, i.e., FFTF-MOTA, EBR-II X-530, and ATR-A1. Irradiation performance of one production-scale and one laboratory heat of V-4C-4Ti and one laboratory heat of V-3Ti-Si was the focus of the investigation. Even among the same lass of alloy, strong heat-to-heat variation was observed in low-temperature impact properties. A laboratory heat of V-4Cr-4Ti and V-3Ti-1Si exhibited good impact properties whereas a 500-kg heat of V-4Cr-4Ti exhibited unacceptably high DBTT. The strong heat-to-heat variation in impact properties of V-4Cr-4Ti indicates that fabrication procedures and minor impurities play important roles in the low-temperature irradiation performance of the alloys.

  8. Infrared repair brazing of 403 stainless steel with a nickel-based braze alloy

    NASA Astrophysics Data System (ADS)

    Shiue, R. K.; Wu, S. K.; Hung, C. M.

    2002-06-01

    Martensitic stainless steel (403SS) is extensively used for intermediate and low-pressure steam turbine blades in fossil-fuel power plants. The purpose of this investigation is to study the repair of shallow cracks on the surface of 403SS steam turbine blades by infrared repair brazing using rapid thermal cycles. A nickel-based braze alloy (NICROBRAZ LM) is used as filler metal. The braze alloy after brazing is primarily comprised of borides and an FeNi3 matrix with different amounts of alloying elements, especially B and Si. As the brazing temperature increases, more Fe atoms are dissolved into the molten braze. Some boron atoms diffuse into the 403SS substrate primarily via grain boundary diffusion and form B-Cr-Fe intermetallic precipitates along the grain boundaries. The LM filler metal demonstrates better performance than 403SS in both microhardness and wear tests. It is also noted that specimens brazed in a vacuum have less porosity than those brazed in an Ar atmosphere. The shear strength of the joint is around 300 MPa except for specimens brazed in short time periods, e.g., 5 seconds in Ar flow and 30 seconds in vacuum. The fractographs mainly consist of brittle fractures and no ductile dimple fractures observed in the scanning electron microscope (SEM) examination.

  9. Resistance to sulfur poisoning of Ni-based alloy with coinage (IB) metals

    NASA Astrophysics Data System (ADS)

    Xu, Xiaopei; Zhang, Yanxing; Yang, Zongxian

    2015-12-01

    The poisoning effects of S atom on the (1 0 0), (1 1 0) and (1 1 1) metal surfaces of pure Ni and Ni-based alloy with IB (coinage) metals (Cu, Ag, Au) are systematically studied. The effects of IB metal dopants on the S poisoning features are analyzed combining the density functional theory (DFT) results with thermodynamics data using the ab initio atomistic thermodynamic method. It is found that introducing IB doping metals into Ni surface can shift the d-band center downward from the Fermi level and weaken the adsorption of S on the (1 0 0) and (1 1 0) surfaces, and the S tolerance ability increases in the order of Ni, Cu/Ni, Ag/Ni and Au/Ni. Nevertheless, on the (1 1 1) surface, the S tolerance ability increases in the order of Ag/Ni (or Cu/Ni), Ni, and Au/Ni. When we increase the coverage of the IB metal dopants, we found that not only Au, but Cu and Ag can increase its S tolerance. We therefore propose that alloying can increase its S tolerance and alloying with Au would be a better way to increase the resistance to sulfur poisoning of the Ni anode as compared with the pure Ni and the Ag- or, Cu-doped Ni materials.

  10. Preliminary Study of Fabricating Bulk Fe-Based Amorphous Alloy by Cold Gas Dynamic Spraying

    NASA Astrophysics Data System (ADS)

    Guan, Leding; Yan, Biao; Long, Ling; Yang, Sha

    Cold gas dynamic spraying (CGDS) technique makes use of high-speed gas current to spray diversified metal, alloy and composite materials under room temperature or with a little heated. It is one kind of novel surface engineering technologies, aimed at eliminating such negative influences as oxidation, gasification, melt, crystallization and gas decomposition and so on existing in hot spraying technologies. Due to its peculiar characteristics such as low spraying temperature, non-oxidation, low stress among coating layers, compactification, and high utilization rate of raw materials, as well as effective applications in the domain of fabricating coatings, the CGDS technique has attracted great attention. As it has the advantages aforementioned, especially avoiding the changes of material properties resulted from high spraying temperature, CGDS provides a kind of revolutionary means for fabricating such heat-sensitive materials as amorphous alloys. The paper reviews the current situation and application development of the CGDS technique, and presents our preliminary exploration of fabricating bulk Fe-based amorphous alloy via CGDS together with mechanical milling process.

  11. Enhanced ferroelectric polarization and possible morphotrophic phase boundary in PZT-based alloys

    DOE PAGES

    Parker, David S.; Singh, David; McGuire, Michael A.; Herklotz, Andreas; Ward, Thomas Zac

    2016-05-16

    We present a combined theoretical and experimental study of alloys of the high performance piezoelectric PZT (PbZr0.5Ti0.5O3) with BZnT (BiZn0.5Ti0.5O3) and BZnZr (BiZn0.5Zr0.5O3), focusing on atomic displacements, ferroelectric polarization, and elastic stability. From theory we find that the 75-25 PZT-BZnT alloy has substantially larger cation displacements, and hence ferroelectric polarization than the PZT base material, on the tetragonal side of the phase diagram. We also find a possible morphotrophic phase boundary in this system by comparing displacement patterns and optimized c/a ratios. Elastic stability calculations find the structures to be essentially stable. Lastly, experiments indicate the feasibility of sample synthesismore » within this alloy system, although measurements do not find significant polarization, probably due to a large coercive field.« less

  12. Manufacturing of self-passivating tungsten based alloys by different powder metallurgical routes

    NASA Astrophysics Data System (ADS)

    Calvo, A.; Ordás, N.; Iturriza, I.; Pastor, J. Y.; Tejado, E.; Palacios, T.; García-Rosales, C.

    2016-02-01

    Self-passivating tungsten based alloys will provide a major safety advantage compared to pure tungsten when used as first wall armor of future fusion reactors, due to the formation of a protective oxide layer which prevents the formation of volatile and radioactive WO3 in case of a loss of coolant accident with simultaneous air ingress. Bulk WCr10Ti2 alloys were manufactured by two different powder metallurgical routes: (1) mechanical alloying (MA) followed by hot isostatic pressing (HIP) of metallic capsules, and (2) MA, compaction, pressureless sintering in H2 and subsequent HIPing without encapsulation. Both routes resulted in fully dense materials with homogeneous microstructure and grain sizes of 300 nm and 1 μm, respectively. The content of impurities remained unchanged after HIP, but it increased after sintering due to binder residue. It was not possible to produce large samples by route (2) due to difficulties in the uniaxial compaction stage. Flexural strength and fracture toughness measured on samples produced by route (1) revealed a ductile-to-brittle-transition temperature (DBTT) of about 950 °C. The strength increased from room temperature to 800 °C, decreasing significantly in the plastic region. An increase of fracture toughness is observed around the DBTT.

  13. Preparation of tantalum-based alloys by a unique CVD process

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    The paper describes a sequential pulsing technique for deposition of refractory alloys and evaluates the technique for the deposition of the tantalum-base alloys Ta-10W (Ta-10 st% W) and T-111 (Ta-8 wt% W-2 wt% Hf). The deposition cycle for Ta-10W was chosen as alternate injections of TaCl5 plus hydrogen and WCl6 plus hydrogen. The cycle for T-111 was chosen as injections of TaCl5 plus hydrogen interspersed with injections of WCl6 plus hydrogen. A temperature range of 900-1300 C was chosen for both alloys. The ability of the pulse process to blanket a uniformly heated section of substrate with a mixture of gases, whose composition varies not with position on the substrate but instead with time of residence in the reactor, allows metal of uniform thickness to be deposited. It is shown that Ta and W can be deposited at high temperature with the formation of a dense columnar grain structure, so that the feasibility of preparing uniformly thick deposits of these elements by a 'pulsing' modification of CVD is demonstrated. A similar attempt to deposit T-111 was unsuccessful due to the difficulty in reducing HfCl4.

  14. Fatigue properties of alloy 718 overlay-coated with a Co-based X40 alloy by the Micro Spark Coating

    NASA Astrophysics Data System (ADS)

    Kamma, Ryohta; Sakaguchi, Motoki; Okazaki, Masakazu; Shimoda, Yukihiro; Uchiyama, Takehiko; Ochiai, Hiroyuki; Watanabe, Mitsutoshi

    Micro Spark Coating (MSC) has been developed as a new functional coating process for Ni-based superalloys used in advanced gas turbines. In this study, some metallurgical and mechanical properties of a MSC layer made of a Co-based wear resisting alloy (X40), and its influence on the high temperature fatigue properties of Ni-based superalloy, Alloy718, were investigated. Prior evaluation of the metallurgical and mechanical properties of the MSC layer that the cavity fraction of MSC layer significantly decreased during the thermal exposure period at 650°C associating with the generation of an oxide phase, progressive sintering and the subsequent increase in hardness and elastic modulus of MSC layer. However, at 480°C these changes were not significant even after 1000hrs exposure. It was found from the high temperature fatigue tests at 480°C and 650°C that the fatigue life of the specimen with MSC layer was almost comparable to that of bare Alloy718 specimen at 480°C, while at 650°C the life of the former was slightly longer than that of the latter. These results suggested that the MSC would have a potential to add a new function to Ni-based superalloy without a reduction in fatigue properties at elevated temperature.

  15. Coercivity and nanostructure of melt-spun Ti-Fe-Co-B-based alloys

    NASA Astrophysics Data System (ADS)

    Zhang, W. Y.; Skomski, R.; Kashyap, A.; Valloppilly, S.; Li, X. Z.; Shield, J. E.; Sellmyer, D. J.

    2016-05-01

    Nanocrystalline Ti-Fe-Co-B-based alloys, prepared by melt spinning and subsequent annealing, have been characterized structurally and magnetically. X-ray diffraction and thermomagnetic measurements show that the ribbons consist of tetragonal Ti3(Fe,Co)5B2, FeCo-rich bcc, and NiAl-rich L21 phases; Ti3(Fe,Co)5B2, is a new substitutional alloy series whose end members Ti3Co5B2 and Ti3Fe5B2 have never been investigated magnetically and may not even exist, respectively. Two compositions are considered, namely Ti11+xFe37.5-0.5xCo37.5-0.5xB14 (x = 0, 4) and alnico-like Ti11Fe26Co26Ni10Al11Cu2B14, the latter also containing an L21-type alloy. The volume fraction of the Ti3(Fe,Co)5B2 phase increases with x, which leads to a coercivity increase from 221 Oe for x = 0 to 452 Oe for x = 4. Since the grains are nearly equiaxed, there is little or no shape anisotropy, and the coercivity is largely due to the magnetocrystalline anisotropy of the tetragonal Ti3(Fe,Co)5B2 phase. The alloy containing Ni, Al, and Cu exhibits a magnetization of 10.6 kG and a remanence ratio of 0.59. Our results indicate that magnetocrystalline anisotropy can be introduced in alnico-like magnets, adding to shape anisotropy that may be induced by field annealing.

  16. Nickel-based Gadolinium Alloy for Neutron Adsorption Application in Ram Packages

    SciTech Connect

    Gregg Wachs; James Sterbentz; William Hurt; P. E. McConnell; C. V. Robino; F. Tovesson; T. S. Hill

    2007-10-01

    Neutron transmission experiments were performed on samples of an advanced nickel-chromium-molybdenum-gadolinium (Ni-Cr-Mo-Gd) neutron absorber alloy and chromium-nickel (Cr-Ni) stainless steel, modified by the addition of boron. The primary purpose of the experiments was to demonstrate the thermal neutron absorbing capability of the materials at specific gadolinium and boron dopant levels. The Ni-Cr-Mo-Gd alloy is envisioned to be deployed for criticality control of highly enriched U.S. Department of Energy (DOE)-owned spent nuclear fuel (SNF). For these transmission experiments, test samples were fabricated with 0.0, 1.58 and 2.1 wt% natural gadolinium dispersed in a Ni-Cr-Mo base alloy and 1.16 wt% boron in stainless steel. The transmission experiments were successfully carried out at the Los Alamos Neutron Science Center (LANSCE). Measured data from the neutron transmission experiments were compared to calculated results derived from a simple exponential transmission formula using total neutron cross sections. Excellent agreement between the measured and calculated results demonstrated the expected strong thermal absorption capability of the gadolinium and boron elements and in addition, verified the measured elemental composition of the Ni-Cr-Mo-Gd alloy and borated stainless steel test samples. The good agreement also indirectly confirmed that the size and distribution of the gadolinium in both the hot-top (as-cast) and Ni-Cr-Mo-Gd converted to plate was not a discriminator related to neutron absorption. Moreover, the Evaluated Nuclear Data File (ENDF VII) total neutron cross section data were accurate.

  17. Corrosion behavior of stainless steel and nickel-base alloys in molten carbonate

    SciTech Connect

    Vossen, J.P.T.; Plomp, L.; Rietveld, G.; Wit, J.H.W. de

    1995-10-01

    The corrosion behavior of five commercially available alloys (AISI 316L, AISI 310S, Inconel 601, Thermax 4762, and Kanthal A1) in molten carbonate under reducing gas atmospheres was investigated with cyclic voltammetry and quasi-stationary polarization curve measurements. The reactions that proceed on these materials at distinct potentials could be deduced by comparison of the cyclic voltammograms and polarization curves with those of pure metals and model alloys. The shape of the polarization curves of all materials strongly depends on the preceding electrochemical treatment. A polarization curve recorded immediately after immersion of a sample resulted in a high anodic current. This implies that the passivation of the materials is poor. When a specimen was conditioned at {minus}1,060 mV for 10 h before recording the polarization curve, the anodic current diminished, which indicates passivation. This occurred for all materials except AISI 316L. A ranking of the corrosion properties was determined from polarization curves of samples that had been conditioned assuming the current densities to be representative. The resistance against corrosion of the alloys increases in the order: AISI 316Lbase alloys.

  18. Surface modification of high temperature iron alloys

    DOEpatents

    Park, Jong-Hee

    1995-01-01

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

  19. 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.

  20. Improved High-Temperature Microstructural Stability and Creep Property of Novel Co-Base Single-Crystal Alloys Containing Ta and Ti

    NASA Astrophysics Data System (ADS)

    Xue, F.; Zhou, H. J.; Feng, Q.

    2014-12-01

    The influence of Ta and Ti additions on microstructural stability and creep behavior in novel Co-Al-W base single-crystal alloys has been investigated. Compared to the ternary alloy, the γ' solvus temperature and γ' volume fraction were raised by individual additions of Ta and Ti, and increased further in the quinary alloy containing both alloying additions. In contrast to ternary and quaternary alloys, an improved microstructural stability with the stable γ- γ' two-phase microstructure and more than 60% γ' volume fraction existed in the quinary alloy after prolonged aging treatment at 1050°C for 1000 h. The creep behavior at 900°C revealed lower creep rates and longer rupture lives in the quaternary alloys compared to the ternary alloy, whereas the quinary alloy exhibited even better creep resistance. When the creep temperature was elevated to about 1000°C, the creep resistance of the quinary alloy exceeded the previously reported Co-Al-W-base alloys and first-generation Ni-base single-crystal superalloys. The improved creep resistance at approximately 1000°C was considered to be associated with high γ' volume fraction, γ' directional coarsening, and dislocation substructure, which included γ- γ' interfacial dislocation networks and the sheared γ' precipitates containing stacking faults and anti-phase boundaries.

  1. The effect of interface properties on nickel base alloy composites

    NASA Technical Reports Server (NTRS)

    Groves, M.; Grossman, T.; Senemeier, M.; Wright, K.

    1995-01-01

    This program was performed to assess the extent to which mechanical behavior models can predict the properties of sapphire fiber/nickel aluminide matrix composites and help guide their development by defining improved combinations of matrix and interface coating. The program consisted of four tasks: 1) selection of the matrices and interface coating constituents using a modeling-based approach; 2) fabrication of the selected materials; 3) testing and evaluation of the materials; and 4) evaluation of the behavior models to develop recommendations. Ni-50Al and Ni-20AI-30Fe (a/o) matrices were selected which gave brittle and ductile behavior, respectively, and an interface coating of PVD YSZ was selected which provided strong bonding to the sapphire fiber. Significant fiber damage and strength loss was observed in the composites which made straightforward comparison of properties with models difficult. Nevertheless, the models selected generally provided property predictions which agreed well with results when fiber degradation was incorporated. The presence of a strong interface bond was felt to be detrimental in the NiAI MMC system where low toughness and low strength were observed.

  2. Influence of oxide microstructure on corrosion behavior of zirconium-based model alloys

    NASA Astrophysics Data System (ADS)

    Silva, Marcelo Jose Gomes Da

    The extensive utilization of zirconium-based alloys in fuel cladding and other reactor internal components in the nuclear power industry has led to the continuous improvement of these alloys. At the present moment, demands for better performing nuclear fuel cladding materials are increasing. Also, new reactor designs have been proposed that would require the materials to withstand even more rigorous conditions. One of the factors that limit s fuel cladding utilization in nuclear reactors is uniform corrosion and the consequent hydriding of the fuel. In an attempt to develop mechanistic understanding of the role of alloying elements in the growth of a stable protective oxide, a series of model zirconium-based alloys was prepared (Zr-xFe-yCr, Zr-xCu-yMo, Zr-xNb-ySn, for various x and y, pure Zr and Zircaloy-4) and examined with advanced characterization techniques. The alloys were corrosion tested in autoclaves under three different conditions: 360°C water, 500°C steam and 500°C supercritical water in excess of 400 days. These autoclave testing conditions simulate nuclear reactor environment for both current designs (360°C water) and the new supercritical water reactor (500°C steam and 500°C supercritical water) proposed by the generation-IV initiative. The oxide films formed were systematically examined at the Advanced Photon Source using microbeam synchrotron radiation diffraction and fluorescence of cross-sectional samples to determine the oxide phases present and their crystallographic texture as a function of distance from the metal/oxide interface. Also, the overall texture of the oxide layers was investigated using synchrotron radiation diffraction in frontal geometry. The corrosion kinetics is a function of the alloy system and showed a wide range of behaviors, from immediately unstable oxide growth to stable behavior. The corrosion weight gains from testing at high temperature are a factor of five higher than those measured at 360°C but the

  3. High gas velocity oxidation and hot corrosion testing of oxide dispersion-strengthened nickel-base alloys

    NASA Technical Reports Server (NTRS)

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

    1975-01-01

    Several oxide dispersion strengthened (ODS) nickel-base alloys were tested in high velocity gases for cyclic oxidation resistance at temperatures to 1200 C and times to 500 hours and for hot corrosion resistance at 900 C for 200 hours. Nickel-chromium-aluminum ODS alloys were found to have superior resistance to oxidation and hot corrosion when compared to bare and coated nickel-chromium ODS alloys. The best of the alloys tested had compositions of nickel - 15.5 to 16 weight percent chromium with aluminum weight percents between 4.5 and 5.0. All of the nickel-chromium-aluminum ODS materials experienced small weight losses (less than 16 mg/sq cm).

  4. Plastic Behavior of a Nickel-Based Alloy under Monotonic-Tension and Low-Cycle-Fatigue Loading

    SciTech Connect

    Huang, E-Wen; Barabash, Rozaliya; Wang, Yandong; Clausen, Bjorn; Li, Li; Liaw, Peter K; Ice, Gene E; Yang, Dr Ren; Choo, Hahn; Pike, Lee M; Klarstrom, Dwaine L

    2008-01-01

    The plasticity behavior of the annealed HASTELLOY C-22HSTM alloy, a face-centered cubic (FCC), nickel-based superalloy, was examined by the in-situ neutron-diffraction experiments at room temperature. Monotonic-tension and low-cycle-fatigue experiments were conducted to observe the plastic behavior of the alloy. The tension straining and cyclic-loading deformation were studied as a function of the stress. The plastic behaviors during the deformation are discussed in the light of the relationship between the stress and dislocation-density evolutions. The calculated dislocation-density evolutions within the alloys reflect the strain hardening and cyclic hardening/softening. Experimental lattice strains are compared to verify the hardening mechanism at the selected stress levels for tension and cyclic loadings. Combining with the calculations of the dislocation densities, the neutron-diffraction experiments give an evidence of the strain and cyclic hardening of the alloy.

  5. A positron study on the microstructural evolution of Al-Li based alloys in the early stages of plastic deformation

    SciTech Connect

    Diego, N. de; Rio, J. del; Romero, R.; Somoza, A. |

    1997-11-01

    The formation of voids by coalescence of microvoids initiated at precipitates has been proposed to explain the fracture mechanisms in alloys containing a large number of second phase particles whereas in binary Al-Li alloys with shearable particles the brittleness could be linked with the grain boundary fracture. Most of the microstructure studies of Al-Li alloys have been performed by deforming to fracture; however, little is known about the processes and mechanisms involved in the early stages of plastic deformation. Butler et al. have studied a quaternary Al-Li alloy and have found that there is a critical effective strain to cause voiding, which is about 0.06 and 0.1% for the aged and for the solution treated material respectively. It is very well established that positrons are very sensitive to vacancy-like defects. With the aim of clarifying the behavior of Al-Li based alloys in the very early stages of deformation, and detecting the eventual formation of microvoids, the authors have studied the response of the positron lifetime parameters to the degrees of deformation in age-hardenable Al-Li based alloys plastically deformed under tensile stress.

  6. Phase Stability of L21 Phase in Co-BASED Heusler Alloys

    NASA Astrophysics Data System (ADS)

    Umetsu, Rie Y.; Okubo, Akinari; Nagasako, Makoto; Ohtsuka, Makoto; Kainuma, Ryosuke; Ishida, Kiyohito

    2014-10-01

    Order-disorder phase transition temperature from L21 to B2 phase, TtL21/B2, in Co-based Heusler alloys was systematically investigated based on the Braggs-Williams-Gorsky (BWG) approximation. Because height of TtL21/B2 closely correlates to phase stability of the L21 phase, confirmation of TtL21/B2 would be a key to obtain a highly ordered L21 phase. From modification with the BWG approximation it was shown that the degree of order indicated temperature dependence, namely, the degree of order decreased above around 0.6 TtL21/B2 and reached zero at TtL21/B2. Therefore, it should be better to select the Co-based Heusler alloys with a higher value of TtL21/B2 if the higher degree of order in the L21 phase is desired by thermal annealing at as low temperature as possible. From powder neutron diffraction (ND) studies of Co2YGa (Y = Ti, V, Cr, Mn and Fe) alloys it was actually confirmed that materials with higher value of TtL21/B2 indicated higher degree of order even in the same annealing temperature. Studies for the phase state in Co-Ti-Fe-Ga films also showed that a height of TtL21/B2 concretely correlated to the phase stability of the L21 phases, that is, the specimen with higher value of TtL21/B2 was easy to obtain with a higher degree of order.

  7. Degradation of the shape memory effect in copper-base alloys

    SciTech Connect

    Stalmans, R.; Van Humbeeck, J.; Delaey, L. . Dept. of Metallurgy and Materials Science)

    1994-12-01

    The reversible transformation of the parent phase (austenite) to the product phase (martensite) is the basis of several shape memory properties in specific Cu-base alloys. In this respect, the two-way memory effect (TWME) refers the reversible, spontaneous shape change from a hot austenitic shape to a cold martensitic shape during cooling and heating without the application of external stresses. It is known that the magnitude of the TWME decrease during thermal or thermomechanical cycling, in particular in Cu-base shape memory alloys. It is however important to remark that this decrease, indicated as degradation of the TWME, can be caused as well by a decrease of the spontaneous martensitic strain, i.e. a degradation of the cold shape, as by an increase of the residual austenitic strain, i.e. a degradation of the hot shape, or by a combination of both. The degradation of the TWME, and of the hot and cold shape is influenced by a number of factors including the alloy composition, the processing, the heat treatment, the training procedure and the parameters of the thermal or thermomechanical cycling. The knowledge of the degradation phenomena is still limited. In a subsequent study of the relationships between training and the two-way memory behavior, the authors have shown that the degradation of the hot shape already starts during training. It was found that the residual austenitic strain [gamma][sub a] increases gradually during training cycling; [gamma][sub a] is also in the case of training composed of a recoverable residual strain [gamma][sub ar] and a non-recoverable residual strain [gamma][sub anr]. The present paper reports the results of the specific experiments which were designed based upon the results described above. The evolutions during thermal cycling of the TWME, of the martensitic strain and austenitic strain, and of the recoverable and non-recoverable austenitic strain are presented and discussed.

  8. Ion irradiation induced disappearance of dislocations in a nickel-based alloy

    NASA Astrophysics Data System (ADS)

    Chen, H. C.; Li, D. H.; Lui, R. D.; Huang, H. F.; Li, J. J.; Lei, G. H.; Huang, Q.; Bao, L. M.; Yan, L.; Zhou, X. T.; Zhu, Z. Y.

    2016-06-01

    Under Xe ion irradiation, the microstructural evolution of a nickel based alloy, Hastelloy N (US N10003), was studied. The intrinsic dislocations are decorated with irradiation induced interstitial loops and/or clusters. Moreover, the intrinsic dislocations density reduces as the irradiation damage increases. The disappearance of the intrinsic dislocations is ascribed to the dislocations climb to the free surface by the absorption of interstitials under the ion irradiation. Moreover, the in situ annealing experiment reveals that the small interstitial loops and/or clusters induced by the ion irradiation are stable below 600 °C.

  9. Laser-Aided Direct Writing of Nickel-Based Single-Crystal Super Alloy (N5)

    NASA Astrophysics Data System (ADS)

    Wang, Yichen; Choi, Jeongyoung; Mazumder, Jyoti

    2016-09-01

    This communication reports direct writing of René N5 nickel-based Super alloy. N5 powder was deposited on (100) single-crystal substrate of René N5, for epitaxial growth, using laser and induction heating with a specially designed closed-loop thermal control system. A thin wall (1 mm width) of René N5 single crystal of 22.1 mm (including 3 mm SX substrate) in height was successfully deposited within 100 layers. SEM and EBSD characterized the single-crystal nature of the deposit.

  10. Interface reaction between nickel-base self-fluxing alloy coating and steel substrate

    NASA Astrophysics Data System (ADS)

    Otsubo, F.; Era, H.; Kishitake, K.

    2000-06-01

    The interface reaction between a nickel-base, self-fluxing alloy coating and a steel substrate has been investigated to examine the formation of “pores,” which are observed along the interface of used boiler tubes. It was found that lumpy precipitates form along the interface instead of pores after heating at high temperatures and that the precipitates are of Fe2B boride. The adhesion strength of the coating is not decreased by the formation of Fe2B precipitates along the interface because of the increase of the adhesion due to interdiffusion.

  11. Thermal and mechanical treatments for nickel and some nickel-base alloys: Effects on mechanical properties

    NASA Technical Reports Server (NTRS)

    Hall, A. M.; Beuhring, V. F.

    1972-01-01

    This report deals with heat treating and working nickel and nickel-base alloys, and with the effects of these operations on the mechanical properties of the materials. The subjects covered are annealing, solution treating, stress relieving, stress equalizing, age hardening, hot working, cold working, combinations of working and heat treating (often referred to as thermomechanical treating), and properties of the materials at various temperatures. The equipment and procedures used in working the materials are discussed, along with the common problems that may be encountered and the precautions and corrective measures that are available.

  12. Design of a suture anchor based on the superelasticity of the Ni-Ti alloy.

    PubMed

    Puértolas, J A; Pérez-García, J M; Juan, E; Ríos, R

    2002-01-01

    We have designed and manufacture a prototype of a new anchoring system for soft bone tissue fixation, based on the superelasticity of the Ni-Ti alloy. The anchoring capability has been observed in femoral hips by radiographs. The performance of this new anchor have been measured by tensile experiments and contrasted with finite element model. The results point out that keeping the fixation capacity, the new configuration presents advantages concerning to a minor damaged volume bone, a reduction of the manufacture cost and a simpler insertion. PMID:12446943

  13. Grain boundary chemistry effects on environment-induced crack growth of iron-based alloys

    SciTech Connect

    Jones, R.H.

    1992-11-01

    Relation between grain boundary chemistry and environment-induced crack growth of Fe-based alloys is reviewed. The importance of the cleanliness of steels is clearly demonstrated by direct relations between grain boundary chemistry and crack growth behavior for both H and anodic dissolution-induced crack growth. Relationships between strain to failure, work of fracture, K{sub ISCC}, crack velocity and fracture mode and grain boundary chemistry are presented. Only results in which the grain boundary chemistry has been measured directly by Auger electron spectroscopy (AES) on intergranular surfaces exposed by in situ fracture have been considered in this review.

  14. Grain boundary chemistry effects on environment-induced crack growth of iron-based alloys

    SciTech Connect

    Jones, R.H.

    1992-11-01

    Relation between grain boundary chemistry and environment-induced crack growth of Fe-based alloys is reviewed. The importance of the cleanliness of steels is clearly demonstrated by direct relations between grain boundary chemistry and crack growth behavior for both H and anodic dissolution-induced crack growth. Relationships between strain to failure, work of fracture, K[sub ISCC], crack velocity and fracture mode and grain boundary chemistry are presented. Only results in which the grain boundary chemistry has been measured directly by Auger electron spectroscopy (AES) on intergranular surfaces exposed by in situ fracture have been considered in this review.

  15. Highly Fluorescent Gene Carrier Based on Ag-Au Alloy Nanoclusters.

    PubMed

    Wang, Ping; Lin, Lin; Guo, Zhaopei; Chen, Jie; Tian, Huayu; Chen, Xuesi; Yang, Hua

    2016-01-01

    For systemic delivery of gene, gold nanoparticles (GNPs) have been exploited as novel gene carriers because of the excellent characteristics for "visible" in intracellular trafficking. Herein, a highly fluorescent gene carrier was prepared by conjugating polyethylenimines on Ag-Au alloy nanoclusters. This carrier exhibited remarkable high gene transfection efficiencies and relatively low cytotoxicity toward B16F10, HeLa, and CHO cells. More interestingly, the high fluorescent Ag-Au-PEI conjugates showed high quantum yield of 14.56%, which is much higher than most of the reported gold nanocluster-based quantum dots and Ag-Au-PEI possessed bioimaging capacity both in vitro and in vivo.

  16. Evaluation of commercially available coating techniques for application of thermographic phosphor to nickel-based alloys

    SciTech Connect

    Beshears, D.L.; Bridges, M.J.; Harris, L.A.

    1986-04-01

    Remote temperature measurements using laser-induced fluorescence of phosphors has been established for temperatures ranging from room temperature to 1200/sup 0/C. This remote surface thermometry requires that the phosphors be firmly bonded to the surface of interest. The intent of this paper is to take a quick look at several bonding techniques used to bond the thermographic phosphor yttrium oxide doped with europium (Y/sub 2/O/sub 3/:Eu) to nickel-based alloy. The evaluation of the samples were performed after the samples had been subjected to extreme heat and, in some cases, mechanically deformed.

  17. High-cycle Fatigue Properties of Alloy718 Base Metal and Electron Beam Welded Joint

    NASA Astrophysics Data System (ADS)

    Ono, Yoshinori; Yuri, Tetsumi; Nagashima, Nobuo; Sumiyoshi, Hideshi; Ogata, Toshio; Nagao, Naoki

    High-cycle fatigue properties of Alloy 718 plate and its electron beam (EB) welded joint were investigated at 293 K and 77 K under uniaxial loading. At 293 K, the high-cycle fatigue strength of the EB welded joint with the post heat treatment exhibited somewhat lower values than that of the base metal. The fatigue strengths of both samples basically increased at 77 K. However, in longer life region, the EB welded joint fractured from a blow hole formed in the welded zone, resulting in almost the same fatigue strength at 107 cycles as that at 293 K.

  18. Finger vein recognition based on local directional code.

    PubMed

    Meng, Xianjing; Yang, Gongping; Yin, Yilong; Xiao, Rongyang

    2012-01-01

    Finger vein patterns are considered as one of the most promising biometric authentication methods for its security and convenience. Most of the current available finger vein recognition methods utilize features from a segmented blood vessel network. As an improperly segmented network may degrade the recognition accuracy, binary pattern based methods are proposed, such as Local Binary Pattern (LBP), Local Derivative Pattern (LDP) and Local Line Binary Pattern (LLBP). However, the rich directional information hidden in the finger vein pattern has not been fully exploited by the existing local patterns. Inspired by the Webber Local Descriptor (WLD), this paper represents a new direction based local descriptor called Local Directional Code (LDC) and applies it to finger vein recognition. In LDC, the local gradient orientation information is coded as an octonary decimal number. Experimental results show that the proposed method using LDC achieves better performance than methods using LLBP. PMID:23202194

  19. Transient liquid phase bonding of titanium-, iron- and nickel-based alloys

    NASA Astrophysics Data System (ADS)

    Rahman, A. H. M. Esfakur

    The operating temperature of land-based gas turbines and jet engines are ever-increasing to increase the efficiency, decrease the emissions and minimize the cost. Within the engines, complex-shaped parts experience extreme temperature, fatigue and corrosion conditions. Ti-based, Ni-based and Fe-based alloys are commonly used in gas turbines and jet engines depending on the temperatures of different sections. Although those alloys have superior mechanical, high temperature and corrosion properties, severe operating conditions cause fast degradation and failure of the components. Repair of these components could reduce lifecycle costs. Unfortunately, conventional fusion welding is not very attractive, because Ti reacts very easily with oxygen and nitrogen at high temperatures, Ni-based superalloys show heat affected zone (HAZ) cracking, and stainless steels show intergranular corrosion and knife-line attack. On the other hand, transient liquid phase (TLP) bonding method has been considered as preferred joining method for those types of alloys. During the initial phase of the current work commercially pure Ti, Fe and Ni were diffusion bonded using commercially available interlayer materials. Commercially pure Ti (Ti-grade 2) has been diffusion bonded using silver and copper interlayers and without any interlayer. With a silver (Ag) interlayer, different intermetallics (AgTi, AgTi2) appeared in the joint centerline microstructure. While with a Cu interlayer eutectic mixtures and Ti-Cu solid solutions appeared in the joint centerline. The maximum tensile strengths achieved were 160 MPa, 502 MPa, and 382 MPa when Ag, Cu and no interlayers were used, respectively. Commercially pure Fe (cp-Fe) was diffusion bonded using Cu (25 m) and Au-12Ge eutectic interlayer (100 microm). Cu diffused predominantly along austenite grain boundaries in all bonding conditions. Residual interlayers appeared at lower bonding temperature and time, however, voids were observed in the joint

  20. Friction and wear with a single-crystal abrasive grit of silicon carbide in contact with iron base binary alloys in oil: Effects of alloying element and its content

    NASA Technical Reports Server (NTRS)

    Miyoshi, K.; Buckley, D. H.

    1979-01-01

    Sliding friction experiments were conducted with various iron-base binary alloys (alloying elements were Ti, Cr, Mn, Ni, Rh, and W) in contact with a rider of 0.025-millimeter-radius, single-crystal silicon carbide in mineral oil. Results indicate that atomic size and content of alloying element play a dominant role in controlling the abrasive-wear and -friction properties of iron-base binary alloys. The coefficient of friction and groove height (wear volume) general alloy decrease, and the contact pressure increases in solute content. There appears to be very good correlation of the solute to iron atomic radius ratio with the decreasing rate of coefficient of friction, the decreasing rate of groove height (wear volume), and the increasing rate of contact pressure with increasing solute content C. Those rates increase as the solute to iron atomic radius ratio increases from unity.

  1. PLUTONIUM-THORIUM ALLOYS

    DOEpatents

    Schonfeld, F.W.

    1959-09-15

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

  2. A Comparison between Shear Bond Strength of VMK Master Porcelain with Three Base-metal Alloys (Ni-cr-T3, VeraBond, Super Cast) and One Noble Alloy (X-33) in Metal-ceramic Restorations

    PubMed Central

    Ahmadzadeh, A; Neshati, A; Mousavi, N; Epakchi, S; Dabaghi Tabriz, F; Sarbazi, AH

    2013-01-01

    Statement of Problem: The increase in the use of metal-ceramic restorations and a high prevalence of porcelain chipping entails introducing an alloy which is more compatible with porcelain and causes a stronger bond between the two. This study is to compare shear bond strength of three base-metal alloys and one noble alloy with the commonly used VMK Master Porcelain. Materials and Method: Three different groups of base-metal alloys (Ni-cr-T3, Super Cast, and VeraBond) and one group of noble alloy (X-33) were selected. Each group consisted of 15 alloy samples. All groups went through the casting process and change from wax pattern into metal disks. The VMK Master Porcelain was then fired on each group. All the specimens were put in the UTM; a shear force was loaded until a fracture occurred and the fracture force was consequently recorded. The data were analyzed by SPSS Version 16 and One-Way ANOVA was run to compare the shear strength between the groups. Furthermore, the groups were compared two-by-two by adopting Tukey test. Results: The findings of this study revealed shear bond strength of Ni-Cr-T3 alloy was higher than the three other alloys (94 MPa or 330 N). Super Cast alloy had the second greatest shear bond strength (80. 87Mpa or 283.87 N). Both VeraBond (69.66 MPa or 245 N) and x-33 alloys (66.53 MPa or 234 N) took the third place. Conclusion: Ni-Cr-T3 with VMK Master Porcelain has the greatest shear bond strength. Therefore, employment of this low-cost alloy is recommended in metal-ceramic restorations. PMID:24724144

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

    DOE PAGES

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

    2016-02-19

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

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

    PubMed

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

    2016-02-19

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

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

  6. Characterization of fabricated cobalt-based alloy/nano bioactive glass composites.

    PubMed

    Bafandeh, Mohammad Reza; Gharahkhani, Raziyeh; Fathi, Mohammad Hossein

    2016-12-01

    In this work, cobalt-based alloy/nano bioactive glass (NBG) composites with 10, 15 and 20wt% NBG were prepared and their bioactivity after immersion in simulated body fluid (SBF) for 1 to 4weeks was studied. Scanning electron microscopy images of two- step sintered composites revealed relatively dense microstructure. The results showed that density of composite samples decreased with increase in NBG amount. The microstructure analysis as well as energy dispersive X-ray analysis (EDX) revealed that small amount of calcium phosphate phases precipitates on the surface of composite samples after 1week immersion in SBF. After 2weeks immersion, considerable amounts of cauliflower-like shaped precipitations were seen on the surface of the composites. Based on EDX analysis, these precipitations were composed mainly from Ca, P and Si. The observed bands in the Fourier transform infrared spectroscopy of immersed composites samples for 4weeks in SBF, were characteristic bands of hydroxyapatite. Therefore it is possible to form hydroxyapatite layer on the surface of composite samples during immersion in SBF. The results indicated that prepared composites unlike cobalt-based alloy are bioactive, promising their possibility for implant applications. PMID:27612763

  7. Characterization of fabricated cobalt-based alloy/nano bioactive glass composites.

    PubMed

    Bafandeh, Mohammad Reza; Gharahkhani, Raziyeh; Fathi, Mohammad Hossein

    2016-12-01

    In this work, cobalt-based alloy/nano bioactive glass (NBG) composites with 10, 15 and 20wt% NBG were prepared and their bioactivity after immersion in simulated body fluid (SBF) for 1 to 4weeks was studied. Scanning electron microscopy images of two- step sintered composites revealed relatively dense microstructure. The results showed that density of composite samples decreased with increase in NBG amount. The microstructure analysis as well as energy dispersive X-ray analysis (EDX) revealed that small amount of calcium phosphate phases precipitates on the surface of composite samples after 1week immersion in SBF. After 2weeks immersion, considerable amounts of cauliflower-like shaped precipitations were seen on the surface of the composites. Based on EDX analysis, these precipitations were composed mainly from Ca, P and Si. The observed bands in the Fourier transform infrared spectroscopy of immersed composites samples for 4weeks in SBF, were characteristic bands of hydroxyapatite. Therefore it is possible to form hydroxyapatite layer on the surface of composite samples during immersion in SBF. The results indicated that prepared composites unlike cobalt-based alloy are bioactive, promising their possibility for implant applications.

  8. Laser rapid manufacturing of special pattern Inco 718 nickel-based alloy component

    NASA Astrophysics Data System (ADS)

    Zhong, Minlin; Yang, Lin; Liu, Wenjin; Huang, Ting; He, Jingjiang

    2005-01-01

    Laser rapid manufacturing based on laser cladding is a novel layer additive manufacturing technology, which can be well used for producing specific material, geometry and properties components normally unavailable or very costly by conventional methods. This paper presents a project research work on laser rapid manufacturing of special pattern Inco 718 nickel based alloy component with special pattern for aeronautical application. The required pattern Inco 718 nickel based alloy component was manufactured directly by laser deposition with optimized parameters: laser power: 800W, laser beam diameter: 0.8 mm, scanning speed: 0.5 m/min, powder feeding rate: 3g/min; The basic microstructure of laser deposited sample is directionally solidified columnar structure, with metallurgical bound to the substrate. Laser deposited component has good metallurgical and compositional and hardness homogeneity. The average hardness is about Hv0.2 440. The tensile strength of the laser deposited Inco 718 sample is respectively 121 and 116 kgf/mm2 at room temperature and at 650°C, which are a little bit less than the data of forged Inco 718 plate 142 and 127 kgf/mm2 due to its directional solidified columnar structure perpendicular to the tensile test force.

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

    PubMed Central

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

    2016-01-01

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

  10. In vitro cytotoxicity of Ag-Pd-Cu-based casting alloys.

    PubMed

    Niemi, L; Hensten-Pettersen, A

    1985-01-01

    The cytotoxicity and its correlation to alloy composition, structure, corrosion, as well as galvanic coupling was studied with 12 Ag-Pd-Cu-type alloys, one conventional type III gold alloy and pure Ag, Cu, and Pd. The agar overlay cell culture technique was used. Single phase binary CuPd alloys were only slightly cytotoxic below a Cu content of 30 wt%. The tested multiphase alloys were all toxic, but no correlation between toxicity and Cu content could be observed. Solid solution annealing increased the cytotoxicity of a multiphase alloy. Exposure of a single phase alloy to an artificial saliva for 1 week prior to the test decreased its cytotoxicity significantly. Galvanic coupling of the alloys through an outer copper wire decreased their cytotoxicity.

  11. [Experimental base for construction alloy choice for implant-retained restorations].

    PubMed

    Savashinskaia, N S; Shashmurina, V R; Latyshev, A V; Kirillov, S K

    2013-01-01

    The paper contains the results of experimental studies on galvanic features of "implant-construction alloy" contact pair. These results may be used as criteria for implant-retained restorations alloy choice.

  12. Corrosion characteristics of nickel alloys. Citations from the International Aerospace Abstracts data base

    NASA Technical Reports Server (NTRS)

    Zollars, G. F.

    1979-01-01

    This bibliography cites 118 articles from the international literature concerning corrosion characteristics of nickel alloys. Articles dealing with corrosion resistance, corrosion tests, intergranular corrosion, oxidation resistance, and stress corrosion cracking of nickel alloys are included.

  13. Tailoring the physical properties of Ni-based single-phase equiatomic alloys by modifying the chemical complexity

    DOE PAGES

    Jin, Ke; Sales, Brian C.; Stocks, George Malcolm; Samolyuk, German D.; Daene, Markus; Weber, William J.; Zhang, Yanwen; Bei, Hongbin

    2016-02-01

    We discovered that equiatomic alloys (e.g. high entropy alloys) have recently attracted considerable interest due to their exceptional properties, which might be closely related to their extreme disorder induced by the chemical complexity. To understand the effects of chemical complexity on their fundamental physical properties, a family of (eight) Ni-based, face-center-cubic (FCC), equiatomic alloys, extending from elemental Ni to quinary high entropy alloys, has been synthesized, and their electrical, thermal, and magnetic properties are systematically investigated in the range of 4–300 K by combining experiments with ab initio Korring-Kohn-Rostoker coherent-potential-approximation (KKR-CPA) calculations. The scattering of electrons is significantly increased duemore » to the chemical (especially magnetic) disorder. It has weak correlation with the number of elements but strongly depends on the type of elements. Thermal conductivities of the alloys are largely lower than pure metals, primarily because the high electrical resistivity suppresses the electronic thermal conductivity. Moreover, the temperature dependence of the electrical and thermal transport properties is further discussed, and the magnetization of five alloys containing three or more elements is measured in magnetic fields up to 4 T.« less

  14. Tailoring the physical properties of Ni-based single-phase equiatomic alloys by modifying the chemical complexity

    PubMed Central

    Jin, K.; Sales, B. C.; Stocks, G. M.; Samolyuk, G. D.; Daene, M.; Weber, W. J.; Zhang, Y.; Bei, H.

    2016-01-01

    Equiatomic alloys (e.g. high entropy alloys) have recently attracted considerable interest due to their exceptional properties, which might be closely related to their extreme disorder induced by the chemical complexity. In order to understand the effects of chemical complexity on their fundamental physical properties, a family of (eight) Ni-based, face-center-cubic (FCC), equiatomic alloys, extending from elemental Ni to quinary high entropy alloys, has been synthesized, and their electrical, thermal, and magnetic properties are systematically investigated in the range of 4–300 K by combining experiments with ab initio Korring-Kohn-Rostoker coherent-potential-approximation (KKR-CPA) calculations. The scattering of electrons is significantly increased due to the chemical (especially magnetic) disorder. It has weak correlation with the number of elements but strongly depends on the type of elements. Thermal conductivities of the alloys are largely lower than pure metals, primarily because the high electrical resistivity suppresses the electronic thermal conductivity. The temperature dependence of the electrical and thermal transport properties is further discussed, and the magnetization of five alloys containing three or more elements is measured in magnetic fields up to 4 T. PMID:26832223

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

    NASA Technical Reports Server (NTRS)

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

    1978-01-01

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

  16. Production of Al-Co-Ni Ternary Alloys by the SHS Method for Use in Nickel Based Superalloys Manufacturing

    NASA Astrophysics Data System (ADS)

    Alkan, Murat; Sonmez, M. Seref; Derin, Bora; Yücel, Onuralp; Andreev, Dmitrii E.; Sanin, Vladimir N.; Yukhvid, Vladimir I.

    2015-05-01

    In this study, Al-Co-Ni ternary alloys were synthesized, in order to obtain low-cost starting material for Ni-based superalloy production, by a self-propagating high temperature synthesis (SHS) both under normal gravity conditions (a = 9.81 m/s2) and under high gravity conditions (up to 1000 g-force) by using a centrifugal machine. The mixture of Co3O4-NiO powder were reduced by Al powder for the production of SHS alloys with the estimated compositions of 5-10 mass% Al, 20-65 mass% Co, 25-75 mass% Ni. The effect of green mixture compositions and centrifugal overload on combustion temperature, alloy/slag separations, chemical composition and microstructure of final alloys were investigated. The chemical analysis results showed that production of SHS alloys were achieved by having up to 86.12% of Co and 92.32% of Ni recoveries. The highest metal recovery value was obtained in SHS alloy with the estimated composition of 10%Al-65%Co-25%Ni by the addition of 20% Al2O3 into the green mixture. The metal/slag separation efficiency increased by increasing the centrifugal overload.

  17. Effects of Shot Peening on Fatigue Properties of Zr-based Amorphous Alloys Containing Ductile Crystalline Particles

    NASA Astrophysics Data System (ADS)

    Jeon, Changwoo; Son, Chang Young; Kim, Choongyun Paul; Lee, Sunghak

    2012-02-01

    In this study, the fatigue properties of a shot-peened Zr-based amorphous alloy containing ductile crystalline particles were investigated, and fatigue processes were analyzed and compared with those of a non-shot-peened (as-cast) alloy. The microstructural analysis results of the shot-peened alloy surface indicated that the flexion and microstructural deformation were observed as the hot-peening time or pressure increased. However, the compressive residual stress formed on the shot-peened surface was approximately half of the ultimate tensile strength and was not varied much with shot-peening time or pressure. The fatigue limit and fatigue ratio of the shot-peened alloy were 368 MPa and 0.24, respectively, which were considerably higher than those of the as-cast alloy. This was because the compressive residual stress formed by the shot peening induced the initiation of fatigue cracks at the specimen interior instead of the specimen surface and, thus, enhanced the overall fatigue limit and fatigue life. These findings suggested that the shot peening was useful for improving fatigue properties in amorphous alloys.

  18. Sprue design alterations and its effect on the properties of base metal alloy castings: An in vitro study

    PubMed Central

    Geetha Prabhu, K. R.; Prabhu, R.; Maheswari, H.; Eswaran, M. A.; Phanikrishna, G.; Deepthi, B.

    2015-01-01

    Introduction: To study the effect of various sprue designs on the properties of base metal alloy castings. The base metal alloys are extensively used for their excellent properties such as an increase in hardness, high melting range, high elastic modulus, its compatibility with ceramic material and low cost. However, to improve the properties of the base metal alloys is an ongoing research leading to various modifications in their fabrication procedure – which include sprue designs and their mode of attachment to the wax pattern. Aims and Objectives: Study compared the effect of three sprue designs viz. conical sprue, cylindrical sprue and bottleneck sprue on the properties of mass and microhardness of base metal alloy castings. Materials and Methods: A prefabricated wax mesh pattern was selected for the fabrication of the alloy test samples in the study. The cylindrical sprue design was connected to the mesh pattern with a straight attachment. The bottleneck sprue design was connected to the mesh pattern with a constricted attachment. The conical sprue design was connected to the mesh pattern with a flared attachment. In this manner, ten samples for each of the three different sprue designs were prepared. Results: The obtained value for mass and microhardness were subjected to statistical analysis. ANOVA test was performed to determine the difference between the sprue designs. Conclusion: The bottleneck sprue, conical sprue, and cylindrical sprue designs did not exert any apparent influence on the mass and microhardness. PMID:26538911

  19. Hot corrosion behavior of platinum-modified nickel- and cobalt-based alloys and coatings

    NASA Astrophysics Data System (ADS)

    Deodeshmukh, Vinay Prakash

    High temperature degradation by hot corrosion (650-1000°C) and/or oxidation (>1000°C) can severely reduce the longevity of advanced gas turbine engine components. The protection of high-temperature components against hot corrosion or oxidation is typically conferred by the application of either a diffusion or overlay metallic coating that is able to form a continuous, adherent, and slow-growing oxide scale. There are currently no coatings that provide adequate protection to both hot corrosion and oxidation. Indeed, there is a particular need for such protective coatings because many advanced aero, marine, and industrial gas-turbines operate in both hot corrosion and oxidation regimes in their duty cycle. Recent work at Iowa State University (ISU) has showed that a wide range Pt+Hf-modified gamma'-Ni3Al + gamma-Ni alloy compositions form a very adherent and slow-growing Al 2O3 scale. In fact, the results reported suggest that Pt+Hf-modified gamma' + gamma coatings offer a viable superior alternative to beta-NiAl(Pt)-based coatings. The main thrust of this study was to assess and establish optimum target gamma' + gamma coating compositions for extending the service life of high-temperature gas turbine components exposed to hot corrosion and oxidation conditions. Both high temperature hot-corrosion (HTHC-900°C) and low temperature hot-corrosion (LTHC-705°C) behaviors of the Pt+Hf-modified gamma' + gamma alloys were assessed. The salt used to bring about hot corrosion was Na 2SO4. Quite interestingly, it was found that the HTHC resistance of gamma' + gamma alloys improved with up to about 10 at.% Pt addition, but then decreased significantly with increasing Pt content up to 30 at.% (the maximum level studied); however, under LTHC conditions the resistance of gamma' + gamma alloys improved with increasing Pt content up to 30 at.%. To further improve hot corrosion resistance of Pt+Hf-modified gamma' + gamma alloys, the effects of systematic additions of Cr, Si, and

  20. Creep and tensile properties of several oxide dispersion strengthened nickel base alloys

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. D.

    1977-01-01

    The creep properties at 1365 K of several oxide dispersion strengthened (ODS) alloys were studied, where the creep exposures involved low strains, on the order of 1% or less, after nominally 100 hours of testing. It was found that ODS alloys possess threshold stresses for creep. Creep in polycrystalline ODS alloys is an inhomogeneous process. The threshold stresses in large grain size ODS Ni-20Cr and Ni-16Cr-4/5Al type alloys are dependent on the grain aspect ratio.

  1. Microstructure, oxidation behavior and mechanical behavior of lens deposited niobium-titanium-silicon and niobium-titanium-silicon based alloys

    NASA Astrophysics Data System (ADS)

    Dehoff, Ryan Richard

    With current high temperature structural materials such as nickel based superalloys being pushed to the limits of suitable operating conditions, there comes a need for replacement materials with even higher temperature capabilities. Niobium silicon based systems have been shown to have superior density normalized strength at elevated temperatures when compared to currently used alloys. The drawbacks associated with the niobium silicon system are due to catastrophic oxidation behavior at elevated temperatures. Alloying addition have been shown to increase the oxidation resistance near suitable levels, but also decrease the high temperature strength and increases creep rates when compared to the binary alloy system. The microstructure of the material is similar to metal matrix composites in which high melting temperature silicides are dispersed in a niobium based matrix phase. The silicides produce high temperature strength while the niobium based matrix increases the room temperature properties such as fracture toughness. The bulk of the research has been conducted on directionally solidified material which has a coarse microstructure due to the slow cooling rates associated with the processing condition. The current research uses a powder metallurgy process termed Laser Engineered Net Shaping, or LENS, to produce material with a significantly refined microstructure due to fast cooling rates associated with the laser process. Several compositions of alloys were examined and the ideal processing parameters were determined for each alloy. The resulting microstructures show a refinement of the microstructure as expected with a fine scale distribution of Nb5Si3 and Nb3Si dispersed in a niobium based matrix phase. The high temperature oxidation behavior of the LENS deposited alloys was comparable to alloys produced using other techniques. A non protective oxide scale formed on samples exposed for only 0.5 hours but was not protective and showed large amounts of

  2. Development of improved low-strain creep strength in Cabot alloy R-41 sheet. [nickel base sheet alloy for reentry shielding

    NASA Technical Reports Server (NTRS)

    Rothman, M. F.

    1984-01-01

    The feasibility of improving the low-strain creep properties of a thin gauge nickel base sheet alloy through modified heat treatment or through development of a preferred crystal-lographic texture was investigated. The basic approach taken to improve the creep strength of the material by heat treatment was to increase grain size by raising the solution treatment temperature for the alloy to the range of 1420 K to 1475 K (2100 F to 2200 F). The key technical issue involved was maintenance of adequate tensile ductility following the solutioning of M6C primary carbides during the higher temperature solution treatment. The approach to improve creep properties by developing a sheet texture involved varying both annealing temperatures and the amount of prior cold work. Results identified a heat treatment for alloy R-14 sheet which yields a substantial creep-life advantage at temperatures above 1090 K (1500 F) when compared with material given the standard heat treatment. At the same time, this treatment provides reasonable tensile ductility over the entire temperature range of interest. The mechanical properties of the material given the new heat treatment are compared with those for material given the standard heat treatment. Attempts to improve creep strength by developing a sheet texture were unsuccessful.

  3. Shape memory alloys for astronomical instrumentation: space and ground-based applications

    NASA Astrophysics Data System (ADS)

    Riva, M.; Rigamonti, D.; Zanetti, F.; Passaretti, F.; Villa, E.; Zerbi, F. M.

    2012-09-01

    This paper wants to illustrate possible applications of Shape Memory Alloy (SMA) as functional devices for space and ground based application in Instrumentations for Astronomy. Thermal activated Shape Memory Alloys are materials able to recover their original shape, after an external deformation, if heated above a characteristic temperature. If the recovery of the shape is completely or partially prevented by the presence of constraints, the material can generate recovery stress. Thanks to this feature, these materials can be positively exploited in Smart Structures if properly embedded into host materials. Some technological processes developed for an ecient use of SMA-based actuators embedded in smart structures tailored to astronomical instrumentation will be presented here. Some possible modeling approaches of the actuators behavior will be addressed taking into account trade- offs between detailed analysis and overall performance prediction as a function of the computational time. The Material characterization procedure adopted for the constitutive laws implementation will be described as well. Deformable composite mirrors,1 opto-mechanical mounting with superelastic kinematic behavior and damping of launch loads onto optical element2 are feasible applications that will be deeply investigated in this paper.

  4. Analysis of wear properties of aluminium based journal bearing alloys with and without lubrication.

    NASA Astrophysics Data System (ADS)

    Mathavan, J. Joy; Patnaik, Amar

    2016-09-01

    Apart from classical bearing materials, Aluminium alloys are used as bearing materials these days because of their superior quality. In this analysis, new Aluminium based bearing materials, with filler metals Si, Ni, and Cr are prepared by metal mould casting in burnout furnace machine, and tribological properties of these alloys with and without lubrication were tested. The experiments for wear with lubrication are conducted on multiple specimen tester and experiments without lubrication is conducted on Pin on disk tribometer. The disc material used was SAE 1050 steel. Wear tests were conducted at a sliding speed of 0.785 m/s and at a normal load of 20 N. Coefficient of friction values, temperature changes and wear of the specimens were plotted on graph according to the above mentioned working conditions. Hardness and weight losses of the specimens were calculated. The obtained results demonstrate how the friction and wear properties of these samples have changed with the % addition of Silicon, Chromium and Nickel to the base metal aluminium.

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

    SciTech Connect

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

    1996-02-01

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

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

    SciTech Connect

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

    1995-05-01

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

  7. Formation of Aluminide Coatings on Fe-Based Alloys by Chemical Vapor Deposition

    SciTech Connect

    Zhang, Ying; Pint, Bruce A; Cooley, Kevin M; Haynes, James A

    2008-01-01

    Aluminide and Al-containing coatings were synthesized on commercial ferritic (P91) and austenitic (304L) alloys via a laboratory chemical vapor deposition (CVD) procedure for rigorous control over coating composition, purity and microstructure. The effect of the CVD aluminizing parameters such as temperature, Al activity, and post-aluminizing anneal on coating growth was investigated. Two procedures involving different Al activities were employed with and without including Cr-Al pellets in the CVD reactor to produce coatings with suitable thickness and composition for coating performance evaluation. The phase constitution of the as-synthesized coatings was assessed with the aid of a combination of X-ray diffraction, electron probe microanalysis, and existing phase diagrams. The mechanisms of formation of these CVD coatings on the Fe-based alloys are discussed, and compared with nickel aluminide coatings on Ni-base superalloys. In addition, Cr-Al pellets were replaced with Fe-Al metals in some aluminizing process runs and similar coatings were achieved.

  8. NASA-UVA Light Aerospace Alloy and Structure Technology Program Supplement: Aluminum-Based Materials for High Speed Aircraft

    NASA Technical Reports Server (NTRS)

    Starke, E. A., Jr.

    1997-01-01

    This is the final report of the study "Aluminum-Based Materials for High Speed Aircraft" which had the objectives (1) to identify the most promising aluminum-based materials with respect to major structural use on the HSCT and to further develop those materials and (2) to assess the materials through detailed trade and evaluation studies with respect to their structural efficiency on the HSCT. The research team consisted of ALCOA, Allied-Signal, Boeing, McDonnell Douglas, Reynolds Metals and the University of Virginia. Four classes of aluminum alloys were investigated: (1) I/M 2XXX containing Li and I/M 2XXX without Li, (2) I/M 6XXX, (3) two P/M 2XXX alloys, and (4) two different aluminum-based metal matrix composites (MMC). The I/M alloys were targeted for a Mach 2.0 aircraft and the P/M and MMC alloys were targeted for a Mach 2.4 aircraft. Design studies were conducted using several different concepts including skin/stiffener (baseline), honeycomb sandwich, integrally stiffened and hybrid adaptations (conventionally stiffened thin-sandwich skins). Alloy development included fundamental studies of coarsening behavior, the effect of stress on nucleation and growth of precipitates, and fracture toughness as a function of temperature were an integral part of this program. The details of all phases of the research are described in this final report.

  9. In vivo evaluation of a Ti-based bulk metallic glass alloy bar.

    PubMed

    Kokubun, Ryo; Wang, Wei; Zhu, Shengli; Xie, Guoqiang; Ichinose, Shizuko; Itoh, Soichiro; Takakuda, Kazuo

    2015-01-01

    Ti-based bulk metallic glasses are reported with high strength, low Young modulus and high corrosion resistance, suggesting their potentials in biomedical applications. However a thorough in vivo evaluation of its biocompatibilities has not been conducted yet. In this study, we implanted bars of Ti-based bulk metallic glass in the femoral bone of rats, followed up local tissue reaction as well as its component ions' diffusion in local area and whole body. The Ti-based BMG (Ti40Zr10Cu34Pd14Sn2) alloy exhibited favorable features of both high strength and high elasticity. In vivo implant evaluation showed that it has a good tissue compatibility, equivalent bone integration and bonding ability with Ti sample. No component ion diffusion was detected up to 3 months post implantation. The possibility and efficacy of its use for bone implant is confirmed. Thus further long term implant study is recommended.

  10. Surface Engineering of Mo-Base Alloys for Elevated-Temperature Environmental Resistance

    NASA Astrophysics Data System (ADS)

    Perepezko, J. H.

    2015-07-01

    The synthesis of robust coatings that provide protection against environmental attack at ultrahigh temperatures is a difficult challenge. To achieve this goal for Mo-base alloys, the fundamental concepts of reactive diffusion pathway analysis and kinetic biasing are used to design a multilayer Mo-Si-B-base coating with a phase sequencing that allows for structural and thermodynamic compatibility and an underlying diffusion barrier to maintain coating integrity. The coating design concepts have a general applicability. The coating structure evolution during high-temperature exposure facilitates a prolonged lifetime as well as self-healing capability. The borosilicide coatings that can be synthesized by a pack cementation process yield superior environmental resistance for Mo-base systems at temperatures up to at least 1,700°C and can be adapted to apply to other refractory metal and ceramic systems.

  11. Effects of alloying element and temperature on the stacking fault energies of dilute Ni-base superalloys.

    PubMed

    Shang, S L; Zacherl, C L; Fang, H Z; Wang, Y; Du, Y; Liu, Z K

    2012-12-19

    A systematic study of stacking fault energy (γ(SF)) resulting from induced alias shear deformation has been performed by means of first-principles calculations for dilute Ni-base superalloys (Ni(23)X and Ni(71)X) for various alloying elements (X) as a function of temperature. Twenty-six alloying elements are considered, i.e., Al, Co, Cr, Cu, Fe, Hf, Ir, Mn, Mo, Nb, Os, Pd, Pt, Re, Rh, Ru, Sc, Si, Ta, Tc, Ti, V, W, Y, Zn, and Zr. The temperature dependence of γ(SF) is computed using the proposed quasistatic approach based on a predicted γ(SF)-volume-temperature relationship. Besides γ(SF), equilibrium volume and the normalized stacking fault energy (Γ(SF) = γ(SF)/Gb, with G the shear modulus and b the Burgers vector) are also studied as a function of temperature for the 26 alloying elements. The following conclusions are obtained: all alloying elements X studied herein decrease the γ(SF) of fcc Ni, approximately the further the alloying element X is from Ni on the periodic table, the larger the decrease of γ(SF) for the dilute Ni-X alloy, and roughly the γ(SF) of Ni-X decreases with increasing equilibrium volume. In addition, the values of γ(SF) for all Ni-X systems decrease with increasing temperature (except for Ni-Cr at higher Cr content), and the largest decrease is observed for pure Ni. Similar to the case of the shear modulus, the variation of γ(SF) for Ni-X systems due to various alloying elements is traceable from the distribution of (magnetization) charge density: the spherical distribution of charge density around a Ni atom, especially a smaller sphere, results in a lower value of γ(SF) due to the facility of redistribution of charges. Computed stacking fault energies and the related properties are in favorable accord with available experimental and theoretical data.

  12. Effects of alloying element and temperature on the stacking fault energies of dilute Ni-base superalloys

    NASA Astrophysics Data System (ADS)

    Shang, S. L.; Zacherl, C. L.; Fang, H. Z.; Wang, Y.; Du, Y.; Liu, Z. K.

    2012-12-01

    A systematic study of stacking fault energy (γSF) resulting from induced alias shear deformation has been performed by means of first-principles calculations for dilute Ni-base superalloys (Ni23X and Ni71X) for various alloying elements (X) as a function of temperature. Twenty-six alloying elements are considered, i.e., Al, Co, Cr, Cu, Fe, Hf, Ir, Mn, Mo, Nb, Os, Pd, Pt, Re, Rh, Ru, Sc, Si, Ta, Tc, Ti, V, W, Y, Zn, and Zr. The temperature dependence of γSF is computed using the proposed quasistatic approach based on a predicted γSF-volume-temperature relationship. Besides γSF, equilibrium volume and the normalized stacking fault energy (ΓSF = γSF/Gb, with G the shear modulus and b the Burgers vector) are also studied as a function of temperature for the 26 alloying elements. The following conclusions are obtained: all alloying elements X studied herein decrease the γSF of fcc Ni, approximately the further the alloying element X is from Ni on the periodic table, the larger the decrease of γSF for the dilute Ni-X alloy, and roughly the γSF of Ni-X decreases with increasing equilibrium volume. In addition, the values of γSF for all Ni-X systems decrease with increasing temperature (except for Ni-Cr at higher Cr content), and the largest decrease is observed for pure Ni. Similar to the case of the shear modulus, the variation of γSF for Ni-X systems due to various alloying elements is traceable from the distribution of (magnetization) charge density: the spherical distribution of charge density around a Ni atom, especially a smaller sphere, results in a lower value of γSF due to the facility of redistribution of charges. Computed stacking fault energies and the related properties are in favorable accord with available experimental and theoretical data.

  13. Microstructure Based Modeling of β Phase Influence on Mechanical Response of Cast AM Series Mg Alloys

    SciTech Connect

    Barker, Erin I.; Choi, Kyoo Sil; Sun, Xin; Deda, Erin; Allison, John; Li, Mei; Forsmark, Joy; Zindel, Jacob; Godlewski, Larry

    2014-09-30

    Magnesium alloys have become popular alternatives to aluminums and steels for the purpose of vehicle light-weighting. However, Mg alloys are hindered from wider application due to limited ductility as well as poor creep and corrosion performance. Understanding the impact of microstructural features on bulk response is key to improving Mg alloys for more widespread use and for moving towards truly predicting modeling capabilities. This study focuses on modeling the intrinsic features, particularly volume fraction and morphology of beta phase present, of cast Mg alloy microstructure and quantifying their impact on bulk performance. Computational results are compared to experimental measurements of cast plates of Mg alloy with varying aluminum content.

  14. A first-principles study of the phase stability of fcc-based Ti-Al alloys

    SciTech Connect

    Asta, M.; de Fontaine, D. |; van Schilfgaarde, M.; Sluiter, M.; Methfessel, M.

    1992-04-01

    In this paper we present results of a first-principles phase stability study of fcc-based Ti-Al alloys. In particular the full-potential linear muffin tin orbital method has been used to determine heats of format on and other zero-temperature properties of 9 fcc ordered superstructures as well as fcc and hcp Ti, and fcc Al. From these results a set of effective cluster interactions are determined which are used in a cluster variation method calculation of the thermodynamic properties and the composition-temperature phase diagram of fcc-based alloys.

  15. [Study on grinding of base metal alloys. 4. Constant pressure grinding of a Ni-Cr alloy with vitrified wheels].

    PubMed

    Miyakawa, O; Watanabe, K; Okawa, S; Nakano, S; Shiokawa, N; Kobayashi, M; Tamura, H

    1989-09-01

    The grinding techniques and the constituent element of vitrified wheels suitable for a 13% Cr-Ni dental casting alloy were determined. The lever-type grinding test machine used in the previous study was modified so that a work might be ground under a constant pressure as it moved reciprocally within a short stroke along the tangential direction of a rotating wheel. The grinding performance of two marketed wheels and eleven experimental wheels with different constituent elements was tested. Abrasive grains on the working surface of alumina wheel wore extremely due to abrasive attrition. Carborundum wheels proved to be more suitable for grinding of the comparatively soft Ni-Cr alloy. Not only depressing a wheel against a work but also moving the wheel over it with heavier pressure should be desired for the maximal grinding efficiency. The experimental carborundum wheels exhibited much the same performance as the marketed carborundum wheel under a less grinding pressure that 100 gf. Only the wheel of grain size #150 bonded with 19% binder wore obviously under the pressure of 150 or 200 gf and provided about two times the performance of the marketed wheel.

  16. Observations on the oxidation of Mn-modified Ni-base Haynes 230 alloy under SOFC exposure conditions

    SciTech Connect

    Yang, Z Gary; Xia, Gordon; Stevenson, Jeffry W.; Singh, Prabhakar

    2005-07-01

    The commercial Ni-base Haynes 230 alloy (Ni-Cr-Mo-W-Mn) was modified with two increased levels of Mn (1 and 2 wt per cent) and evaluated for its oxidation resistance under simulated SOFC interconnect exposure conditions. Oxidation rate, oxide morphology, oxide conductivity and thermal expansion were measured and compared with commercial Haynes 230. It was observed that additions of higher levels of Mn to the bulk alloy facilitated the formation of a bi-layered oxide scale that was comprised of an outer M3O4 (M=Mn, Cr, Ni) spinel-rich layer at the oxide – gas interface over a Cr2O3-rich sub-layer at the metal – oxide interface. The modified alloys showed higher oxidation rates and the formation of thicker oxide scales compared to the base alloy. The formation of a spinel-rich top layer improved the scale conductivity, especially during the early stages of the oxidation, but the higher scale growth rate resulted in an increase in the area-specific electrical resistance over time. Due to their face-centered cubic crystal structure, both commercial and modified alloys demonstrated a coefficient of thermal expansion that was higher than that of typical anode-supported and electrolyte-supported SOFCs.

  17. Initial assessment of Ni-base alloy performance in 0.1 MPa and supercritical CO2

    DOE PAGES

    Pint, B. A.; Keiser, J. R.

    2015-09-25

    There is considerable interest in increasing the working temperature of both open and closed supercritical CO2 (sCO2) cycles to ≥700 °C. At these temperatures, it is unlikely that any Fe-base alloys have suitable strength and therefore the focus is on Ni-base alloys for this application. To begin addressing the lack of compatibility data under these conditions, initial work exposed a wide range of candidate alloys in 500-h exposures at 20 MPa (200 bar) CO2 at 650 -750 °C in high purity CO2. In general, the reaction products were thin and protective in these exposures. A smaller group of alloy couponsmore » focusing on chromia- and alumina-forming alloys was exposed for 500h in 0.1 MPa (1bar) air, CO2, CO2+O2 and CO2+H2O for comparison. Thus, the thin surface oxides formed were very similar to those formed at high pressure and no clear detrimental effect of CO2 oxidation or O2 or H2O impurities could be observed in these exposures.« less

  18. On the performance of low pressure die-cast Al-Cu based automotive alloys: Role of additives

    NASA Astrophysics Data System (ADS)

    Zaki, Gergis Adel

    The present study focuses on the effect of alloying elements, namely, strontium (Sr), titanium (Ti), zirconium (Zr), scandium (Sc) and silver(Ag) individually or in combination, on the performance of a newly developed Al-2%Cu based alloy. A total of thirteen alloy compositions were used in the study. Tensile test bar castings were prepared employing the low pressure die casting (LPDC) technique. The test bars were solution heat treated at 495°C for 8 hours, followed by quenching in warm water, and then subjected to different isochronal aging treatments using an aging time of 5 hours and aging temperatures of 155°C, 180°C, 200°C, 240°C and 300°C. Tensile testing of as-cast and heat-treated test bars was carried out at room temperature using a strain rate of 4 x 10-4s-1. Five test bars were used per alloy composition/condition. Hardness measurements were also carried out on these alloys using a Brinell hardness tester. The microstructures of selected samples were examined using optical microscopy and electron probe microanalysis (EPMA). The results showed that adding Ti in the amount of 0.15 wt% in the form of Al-5%Ti-1%B master alloy is sufficient to refine the grains in the cast structure in the presence of 200 ppm Sr (0.02 wt%). Addition of Zr and Sc did not contribute further to the grain refining effect. The main role of addition of these two elements appeared in the formation of complex compounds with Al and Ti. Their presence resulted in extending the aging temperature range before the onset of softening. Mathematical analysis of the hardness and tensile data was carried out using the Minitab statistical software program. It was determined that the alloy containing (0.5wt% Zr + 0.15wt% Ti) is the most effective in maximizing the alloy tensile strength over the range of aging temperatures, from 155°C to 300°C. Addition of Ag is beneficial at high aging temperatures, in the range of 240°C-300°C. However, it is less effective compared to the (Zr + Ti

  19. Shakedown based model for high-cycle fatigue of shape memory alloys

    NASA Astrophysics Data System (ADS)

    Gu, Xiaojun; Moumni, Ziad; Zaki, Wael; Zhang, Weihong

    2016-11-01

    The paper presents a high-cycle fatigue criterion for shape memory alloys (SMAs) based on shakedown analysis. The analysis accounts for phase transformation as well as reorientation of martensite variants as possible sources of fatigue damage. In the case of high-cycle fatigue, once the structure has reached an asymptotic state, damage is assumed to become confined at the mesoscopic scale, or the scale of the grain, with no discernable inelasticity at the macroscopic scale. Using a multiscale approach, a high-cycle fatigue criterion analogous to the Dang Van model (Dang Van 1973) for elastoplastic metals is derived for SMAs obeying the Zaki–Moumni model for SMAs (Zaki and Moumni 2007a). For these alloys, a safe domain is established in stress deviator space, consisting of a hypercylinder with axis parallel to the direction of martensite orientation at the mesoscopic scale. Safety with regard to high-cycle fatigue, upon elastic shakedown, is conditioned by the persistence of the macroscopic stress path at every material point within the hypercylinder, whose size depends on the volume fraction of martensite. The proposed criterion computes a fatigue factor at each material point, indicating its degree of safeness with respect to high cycle fatigue.

  20. On the Challenges of Reducing Contact Resistances in Thermoelectric Generators Based on Half-Heusler Alloys

    NASA Astrophysics Data System (ADS)

    Ngan, Pham Hoang; Van Nong, Ngo; Hung, Le Thanh; Balke, Benjamin; Han, Li; Hedegaard, Ellen Marie Jensen; Linderoth, Søren; Pryds, Nini

    2016-01-01

    A method using fast hot pressing to join half-Heusler (HH) thermoelectric materials directly to an electrical current collector (Ag electrode) without using a third filler material is introduced. The compositions of the HH alloys used are Hf0.5Zr0.5CoSn0.2Sb0.8 and Ti0.6Hf0.4NiSn for p- and n-type, respectively. Using this method, the quality of the HH-electrode contacts is improved due to their low electrical contact resistance and less reaction-diffusion layer. The microstructure and chemical composition of the joints were examined using a scanning electron microscope equipped with energy-dispersive x-ray analysis. The electrical characteristics of the interfaces at the contacts were studied based on electrical contact resistance and Seebeck scanning microprobe measurements. In this paper, we show that joining the HH to a Ag electrode directly using fast hot pressing resulted in lower contact resistance and better performance compared with the method of using active brazing filler alloy.

  1. Synthesis and thermal behavior of tin-based alloy (Sn-Ag-Cu) nanoparticles.

    PubMed

    Roshanghias, Ali; Yakymovych, Andriy; Bernardi, Johannes; Ipser, Herbert

    2015-03-19

    The prominent melting point depression of nanoparticles has been the subject of a considerable amount of research. For their promising applications in electronics, tin-based nano-alloys such as near-eutectic Sn-Ag-Cu (SAC) alloys have been synthesized via various techniques. However, due to issues such as particle aggregation and oxidation or introduced impurities, the application of these nano-size particles has been confined or aborted. For instance, thermal investigations by DTA/DSC in a large number of studies revealed exothermic peaks in the range of 240-500 °C, i.e. above the melting point of SAC nanoparticles, with different and quite controversial explanations for this unclear phenomenon. This represents a considerable drawback for the application of nanoparticles. Correspondingly, in the current study, the thermal stability of SAC nanoparticles has been investigated via electron microscopy, XRD, FTIR, and DSC/TG analysis. It was found that the nanoparticles consist mainly of a metallic β-Sn core and an amorphous tin hydroxide shell structure. The SnO crystalline phase formation from this amorphous shell has been associated with the exothermic peaks on the first heating cycle of the nanoparticles, followed by a disproportionation reaction into metallic Sn and SnO₂.The results also revealed that the surfactant and reducing agent cannot only affect the size and size distribution of the nanoparticles, they might also alter the ratio between the amorphous shell and the crystalline core in the structure of particles. PMID:25757694

  2. Sample-Size Effects on the Compression Behavior of a Ni-BASED Amorphous Alloy

    NASA Astrophysics Data System (ADS)

    Liang, Weizhong; Zhao, Guogang; Wu, Linzhi; Yu, Hongjun; Li, Ming; Zhang, Lin

    Ni42Cu5Ti20Zr21.5Al8Si3.5 bulk metallic glasses rods with diameters of 1 mm and 3 mm, were prepared by arc melting of composing elements in a Ti-gettered argon atmosphere. The compressive deformation and fracture behavior of the amorphous alloy samples with different size were investigated by testing machine and scanning electron microscope. The compressive stress-strain curves of 1 mm and 3 mm samples exhibited 4.5% and 0% plastic strain, while the compressive fracture strength for 1 mm and 3 mm rod is 4691 MPa and 2631 MPa, respectively. The compressive fracture surface of different size sample consisted of shear zone and non-shear one. Typical vein patterns with some melting drops can be seen on the shear region of 1 mm rod, while fish-bone shape patterns can be observed on 3 mm specimen surface. Some interesting different spacing periodic ripples existed on the non-shear zone of 1 and 3 mm rods. On the side surface of 1 mm sample, high density of shear bands was observed. The skip of shear bands can be seen on 1 mm sample surface. The mechanisms of the effect of sample size on fracture strength and plasticity of the Ni-based amorphous alloy are discussed.

  3. Critical Stresses for Twinning, Slip, and Transformation in Ti-Based Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Ojha, A.; Sehitoglu, H.

    2016-06-01

    We investigate the effect of Nb and Ta contents on the (i) critical resolved shear stress (CRSS) for the β - α″ transformation, (ii) the CRSS for austenite slip, and (iii) the CRSS for twin nucleation in martensite ( α″ phase) that govern shape memory and superelasticity in Ti-based alloys. The critical stresses for slip and twinning are achieved with a modified Peierls Nabarro formalism utilizing generalized stacking fault energy and the generalized planar fault energy (GPFE), respectively, obtained from first-principles density functional theory (DFT) calculations. During the calculation of the twinning stress, we show the importance of the shuffling process in stabilizing and lowering the GPFE curve. Similarly, the transformation stress is obtained with heterogeneous martensite nucleation mechanism incorporating the energy barriers associated with the transformation process. Here, we point to the role of dislocations in the shuffling process during the early stage of transformation. We show that the increase of Ta content raises the CRSS more effectively for the case of slip compared to twinning or transformation. The slip stress and twin stress magnitudes increase with an increase in the unstable fault energy ( {γ_{{us}} } ) and unstable twinning fault energy ( {γ_{{ut}} } ), respectively. In summary, as the Ta composition increases, the difference between martensite/austenite slip resistance and the transformation/twinning stress widens showing the efficacy of Ta alloying additions.

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

    NASA Astrophysics Data System (ADS)

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

    2016-01-01

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

  5. Positioning devices based on submicro-textured magnetostrictive alloys (Fe85Ga15)

    NASA Astrophysics Data System (ADS)

    Dannangoda, Gamage; Martirosyan, Karen

    2011-10-01

    Magnetostrictive materials can convert magnetic energy into kinetic energy. Under the influence of an external magnetic field, the rotation of small magnetic domains causes a change in a magnetostrictive materials shape in the direction of the magnetic field. Applying stronger magnetic field will tend to rotate more domains and makes the material to stretch even more until it reaches its saturation. This property has been used in many applications such as micro acoustic sensors, generators, marine sonar, devices, linear motors, robust actuators, automotive accessories, positioning devices etc. There is increasing interest in magnetostrictive applications after discovering the giant magnetostrictive alloys such as Galfenol and Terfenol-D which is capable of generating strains 100 times greater than traditional magnetostrictive materials at high temperatures. Even though Galfenol doesn't produce as much as magnetostriction as Terfenol-D, it can be constructed mechanically strong with tensile strengths up to 500 MPa and can be rolled, extruded, and welded. The magnetostrictive positioning devices based on submicro-textured magnetostrictive alloys (Fe85Ga15) and their advantages will be discussed.

  6. HfCo7-Based Rare-Earth-Free Permanent-Magnet Alloys

    SciTech Connect

    Das, B; Balamurugan, B; Kumar, P; Skomski, R; Shah, VR; Shield, JE; Kashyap, A; Sellmyer, DJ

    2013-07-01

    This study presents the structural and magnetic properties of melt-spun HfCo7, HfCo7-xFex (0.25 <= x <=), and HfCo7Six (0.2 <= x <= 1.2) alloys. Appreciable permanent-magnet properties with a magnetocrystalline anisotropy of about 9.6-16.5, Mergs/cm(3), a magnetic polarization J(s) approximate to 7.2-10.6 kG, and coercivities H-c = 0.5-3.0 kOe were obtained by varying the composition of these alloys. Structural analysis reveals that the positions of x-ray diffraction peaks of HfCo7 show good agreement with those corresponding to an orthorhombic structure having lattice parameters of about a = 4.719 angstrom, b = 4.278 angstrom, and c = 8.070 angstrom. Based on these results, a model crystal structure for HfCo7 is developed and used to estimate the magnetic properties of HfCo7 using density-functional calculations, which agree with the experimental results.

  7. Tensile and creep rupture behavior of P/M processed Nb-base alloy, WC-3009

    NASA Technical Reports Server (NTRS)

    Hebsur, Mohan G.; Titran, Robert H.

    1988-01-01

    Due to its high strength at temperatures up to 1600 K, fabrication of niobium base alloy WC-3009 (Nb30Hf9W) by traditional methods is difficult. Powder metallurgy (P/M) processing offers an attractive fabrication alternative for this high strength alloy. Spherical powders of WC-3009 produced by electron beam atomizing (EBA) process were successfully consolidated into a one inch diameter rod by vacuum hot pressing and swaging techniques. Tensile strength of the fully dense P/M material at 300-1590 K were similar to the arc-melted material. Creep rupture tests in vacuum indicated that WC-3009 exhibits a class 1 solid solution (glide controlled) creep behavior in the 1480 to 1590 K temperature range and stress range of 14 to 70 MPa. The creep behavior was correlated with temperature and stress using a power law relationship. The calculated stress exponent n, was about 3.2 and the apparent activation energy, Q, was about 270 kJ/mol. The large creep ductility exhibited by WC-3009 was attributed to its high strain rate sensitivity.

  8. Modelling of hydrogen assisted cracking of nickel-base Alloy X-750 in water

    SciTech Connect

    Oka, T.; Ballinger, R.G.; Hwang, I.S.

    1992-12-31

    A closed-form, semi-empirical, electrochemical model has been developed to rationalize the intergranular corrosion fatigue behavior of alloy X-750 in aqueous electrolytes. The model is based on the assumption that, in the electrolytes investigated and for the microstructures studied, that hydrogen assisted crack growth is the dominant mechanism. Further, it is assumed that the rate of hydrogen reduction is a controlling factor in the magnitude of the environmental component of crack growth. Electrolyte conductivity, dissolution and passivation kinetics of precipitates, grain boundary coverage of precipitates are identified as important environmental and microstructural variables governing the hydrogen reduction rate at the crack tip. The model is compared with experimental data for fatigue crack growth where hydrogen is supplied by external charging and with data where galvanically-generated local hydrogen is responsible for enhanced crack growth. It is shown that predicted results characterize the observed effects of frequency, microstructure, electrolyte conductivity, and stress intensity factor. The agreement between the hydrogen reduction model and measured crack growth rate is believed to support the proposed galvanic corrosion mechanism for the intergranular cracking of alloy X-750 in low temperature water.

  9. Impurity-driven nanocrystallization of Zr-based bulk amorphous alloys.

    PubMed

    Akdeniz, M Vedat; Mekhrabov, Amdulla O

    2008-02-01

    The effect of oxygen content and Ti addition on the glass forming ability (GFA) and crystallization kinetic of Zr-based bulk glass forming alloys have been studied by means of thermal analysis and X-ray diffraction techniques. Presence of oxygen triggers the formation of a nanocrystalline metastable f.c.c. Zr2 Ni-type phase which can act as heterogenous nucleation sites for the formation of dendrites during solidification. An increase in oxygen content changes the crystallization behaviour from a single- to a double-step process and triggers the crystallization of stable Zr2(Cu,Al) besides metastable Zr2 Ni-type phase. Oxygen-triggered nucleation of a nanocrystalline metastable Zr2 Ni-type phase is found to be the initial step of crystallization. The important parameters of GFA such as glass transition temperatures, Tg, the crystallization temperatures, Tx, and crystallization enthalpies, deltaH, were determined by using DSC. It was observed that the presence of oxygen, even in a very small amount, and Ti addition cause a drastic reduction of the supercooled liquid region, deltaTx, accompanied by a change of the crystallization kinetic. This leads to the decrease in stability of the supercooled liquid, consequently results in a deterioration of the glass forming ability of the alloy.

  10. Effect of alloying elements on passivity and breakdown of passivity of Fe- and Ni-based alloys mechanistics aspects. Annual report, August 1, 1991--July 31, 1992

    SciTech Connect

    Szklarska-Amialowska, Z.

    1992-06-01

    On the basis of the literature data and the current results, the mechanism of pitting corrosion of Al-alloys is proposed. An assumption is made that the transport of Cl- ions through defects in the passive film of aluminum an aluminum alloys is not a rate determining step in pitting. The pit development is controlled by the solubility of the oxidized alloying elements in acid solutions. A very good correlation was found between the pitting potential and the oxidized alloying elements for metastable Al-Cr, Al-Zr, Al-W, and Al-Zn alloys. We expect that the effect of oxidized alloying elements in other passive alloys will be the same as in Al-alloys. To verify this hypothesis, susceptibility to pitting in the function of alloying elements in the binary alloys and the composition of the oxide film has to be measured. We propose studying Fe- and Ni-alloys produced by a sputtering deposition method. Using this method one-phaseous alloy can be obtained, even when the two metals are immiscible using conventional methods. Another advantage to studying sputtered alloys is to find new materials with superior resistance to localized corrosion.

  11. Transient liquid phase bonding of titanium-, iron- and nickel-based alloys

    NASA Astrophysics Data System (ADS)

    Rahman, A. H. M. Esfakur

    The operating temperature of land-based gas turbines and jet engines are ever-increasing to increase the efficiency, decrease the emissions and minimize the cost. Within the engines, complex-shaped parts experience extreme temperature, fatigue and corrosion conditions. Ti-based, Ni-based and Fe-based alloys are commonly used in gas turbines and jet engines depending on the temperatures of different sections. Although those alloys have superior mechanical, high temperature and corrosion properties, severe operating conditions cause fast degradation and failure of the components. Repair of these components could reduce lifecycle costs. Unfortunately, conventional fusion welding is not very attractive, because Ti reacts very easily with oxygen and nitrogen at high temperatures, Ni-based superalloys show heat affected zone (HAZ) cracking, and stainless steels show intergranular corrosion and knife-line attack. On the other hand, transient liquid phase (TLP) bonding method has been considered as preferred joining method for those types of alloys. During the initial phase of the current work commercially pure Ti, Fe and Ni were diffusion bonded using commercially available interlayer materials. Commercially pure Ti (Ti-grade 2) has been diffusion bonded using silver and copper interlayers and without any interlayer. With a silver (Ag) interlayer, different intermetallics (AgTi, AgTi2) appeared in the joint centerline microstructure. While with a Cu interlayer eutectic mixtures and Ti-Cu solid solutions appeared in the joint centerline. The maximum tensile strengths achieved were 160 MPa, 502 MPa, and 382 MPa when Ag, Cu and no interlayers were used, respectively. Commercially pure Fe (cp-Fe) was diffusion bonded using Cu (25 m) and Au-12Ge eutectic interlayer (100 microm). Cu diffused predominantly along austenite grain boundaries in all bonding conditions. Residual interlayers appeared at lower bonding temperature and time, however, voids were observed in the joint

  12. NASA-UVa light aerospace alloy and structure technology program supplement: Aluminum-based materials for high speed aircraft

    NASA Technical Reports Server (NTRS)

    Starke, E. A., Jr.

    1993-01-01

    This report on the NASA-UVa Light Aerospace Alloy and Structure Technology Program Supplement: Aluminum-Based Materials for High Speed Aircraft covers the period from January 1, 1992 to June 30, 1992. The objective of the research is to develop aluminum alloys and aluminum matrix composites for the airframe which can efficiently perform in the HSCT environment for periods as long as 60,000 hours (certification for 120,000 hours) and, at the same time, meet the cost and weight requirements for an economically viable aircraft. Current industry baselines focus on flight at Mach 2.4. The research covers four major materials systems: (1) ingot metallurgy 2XXX, 6XXX, and 8XXX alloys, (2) powder metallurgy 2XXX alloys, (3) rapidly solidified, dispersion strengthened Al-Fe-X alloys, and (4) discontinuously reinforced metal matrix composites. There are ten major tasks in the program which also include evaluation and trade-off studies by Boeing and Douglas aircraft companies.

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

    SciTech Connect

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

    1997-05-01

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

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

    SciTech Connect

    Kad, B.K.

    1999-07-01

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

  15. Titanium and zirconium based alloys modified by intensive plastic deformation and nitrogen ion implantation for biocompatible implants.

    PubMed

    Byeli, A V; Kukareko, V A; Kononov, A G

    2012-02-01

    Titanium and zirconium alloys are considered to be promising materials for orthopaedics because of their biocompatibility with tissues. Their main drawbacks for application as implants have generally been considered to be insufficient levels of mechanical and tribological properties. In this research the influence of equal channel angular pressing and nitrogen ion implantation on the structure and properties of Ti and Zr alloys has been investigated to ensure the optimum combination of the bulk material and surface layer properties. The data obtained showed that equal channel angular pressing and nitrogen ion implantation can be efficiently used to improve bulk and surface properties of Ti and Zr based implants.

  16. CORROSION OF AMORPHOUS AND NANOCRYSTALLINE Fe-BASED ALLOYS IN NaCl AND H2SO4 SOLUTIONS

    NASA Astrophysics Data System (ADS)

    Li, Xiang; Lu, Wei; Wang, Yuxin; Yan, Biao; Pan, Deng

    2013-07-01

    Corrosion resistance of nanocrystalline Fe73.5Si13.5B9Nb3Cu1 alloy was investigated and compared to its amorphous counterpart. Low-temperature crystallization occurred during the annealing of amorphous tapes was used to obtain a nanocrystalline structure. The influence of annealing condition on the structure and corrosion resistance of the alloy in NaCl and H2SO4 solutions was investigated. Based on the testing results, it was found that nanocrystalline tapes have higher corrosion resistance than amorphous counterpart and H2SO4 can promote the occurrence of corrosion compared with NaCl.

  17. Formation of the thermodeformational properties of Mn-Cu-based alloys having the two-way shape memory effect

    NASA Astrophysics Data System (ADS)

    Nosova, G. I.

    2008-08-01

    The specific features of the thermodeformational behavior of Mn-Cu-based alloys with the two-way shape memory effect are revealed, and their connection with the diffusionless fcc → fct phase transition and the forming structure is discussed. The mechanism of the reversible thermal deformation caused by directed internal stresses is considered. The factors that affect the temperature interval of the highest thermal sensitivity and the value of reversible and specific thermal deformation are found, and the possibilities of their change by additional alloying and heat treatment are studied.

  18. Microstructural study of the nickel-base alloy WAZ-20 using qualitative and quantitative electron optical techniques

    NASA Technical Reports Server (NTRS)

    Young, S. G.

    1973-01-01

    The NASA nickel-base alloy WAZ-20 was analyzed by advanced metallographic techniques to qualitatively and quantitatively characterize its phases and stability. The as-cast alloy contained primary gamma-prime, a coarse gamma-gamma prime eutectic, a gamma-fine gamma prime matrix, and MC carbides. A specimen aged at 870 C for 1000 hours contained these same constituents and a few widely scattered high W particles. No detrimental phases (such as sigma or mu) were observed. Scanning electron microscope, light metallography, and replica electron microscope methods are compared. The value of quantitative electron microprobe techniques such as spot and area analysis is demonstrated.

  19. Void structure and density change of vanadium-base alloys irradiated in the dynamic helium charging experiment

    SciTech Connect

    Chung, H.M.; Nowicki, L.; Gazda, J.

    1995-04-01

    The objective of this work is to determine void structure, distribution, and density changes of several promising vanadium-base alloys irradiated in the Dynamic Helium Charging Experiment (DHCE). Combined effects of dynamically charged helium and neutron damage on density change, void distribution, and microstructural evolution of V-4Cr-4Ti alloy have been determined after irradiation to 18-31 dpa at 425-600{degree}C in the DHCE, and the results compared with those from a non-DHCE in which helium generation was negligible.

  20. The effect of nanobioceramic reinforcement on mechanical and biological properties of Co-base alloy/hydroxyapatite nanocomposite.

    PubMed

    Bahrami, M; Fathi, M H; Ahmadian, M

    2015-03-01

    The goal of the present research was to fabricate, characterize, and evaluate mechanical and biological properties of Co-base alloy composites with different amounts of hydroxyapatite (HA) nanopowder reinforcement. The powder of Co-Cr-Mo alloy was mixed with different amounts of HA by ball milling and it was then cold pressed and sintered. X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques were used. Microhardness measurement and compressive tests were also carried out. Bioactivity behavior was evaluated in simulated body fluid (SBF). A significant decrease in modulus elasticity and an increase in microhardness of the sintered composites were observed. Apatite formation on the surface of the composites showed that it could successfully convert bioinert Co-Cr-Mo alloy to bioactive type by adding 10, 15, and 20wt.% HA which have lower modulus elasticity and higher microhardness.

  1. Development and Evaluation of Directionally-Solidified NiAl/(CR,MO)-Based Eutectic Alloys for Airfoil Applications

    NASA Technical Reports Server (NTRS)

    Raj, S. V.; Locci, I. E.; Whittenberger, J. D.

    2001-01-01

    The results of recent efforts to develop directionally-solidified alloys based on the Ni-33Al-31Cr-3Mo eutectic composition are discussed. These developmental efforts included studying the effects of macroalloying and growth rates on microstructure formation as well as the elevated temperature compressive and tensile properties of these alloys. These observations revealed that contrary to conventional opinion, the cellular microstructure was stronger and tougher than the planar eutectic microstructure due to a microstructural refinement of the cell size and interlamellar spacing. The high temperature strengths of these alloys are compared with those of commercial superalloys and advanced NiAl single crystals. The implications of this research on airfoil manufacturing and applications are discussed.

  2. 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).

  3. Development of Mo base alloys for conductive metal-alumina cermet applications

    SciTech Connect

    Stephens, J.J.; Damkroger, B.K.; Monroe, S.L.

    1996-12-31

    A study of thermal expansion for binary Mo-V and ternary Mo-V-Fe/Mo-V-Co alloys has been conducted, with the aim of finding a composition which matches the CTE of 94% alumina ceramic. The overall goal was to identify an alloy which can be used in conductive 27 vol.% metal/73 vol.% alumina cermets. Besides thermal expansion properties, two additional requirements exist for this alloy: (1) compatibility with a hydrogen sinter fire atmosphere and (2) a single phase BCC microstructure. They have identified a ternary alloy with a nominal composition of Mo-22wt.% V-3Fe for use in cermet fabrication efforts. This paper summarizes thermal expansion properties of the various alloys studied, and compares the results with previous CTE data for Mo-V binary alloys.

  4. Effect of alloying impurities and conditions of heat treatment of iron-based powder materials and their magnetic properties

    SciTech Connect

    Yago, G.I.; Vasil`ev, V.M.; Panasyuk, O.A.

    1994-07-01

    The structure of the initial iron powders, the type of alloying impurities, and the conditions of compaction and heat treatment of materials have been studied from the standpoint of their effect on the magnetic properties. Ways of enhancing the properties of magnetically-soft iron-based powder materials are recommended and methods of studying them are suggested.

  5. Vertical GaN based Light Emitting Diodes on Metal Alloy Substrate for Solid State Lighting Application

    NASA Astrophysics Data System (ADS)

    Doan, T.; Chu, C.; Chen, C.; Liu, W.; Chu, J.; Yeh, J.; Chen, H.; Fan, F.; Tran, C.

    2006-02-01

    Vertical GaN based Light Emitting Diodes on metal alloy substrate were realized and characterized for solid state lighting application. An efficiency of more than 70 lumens/watt was achieved. In addition, these LEDs exhibit many advantages over those on sapphire under extreme operation conditions for general lighting application.

  6. Understanding the solidification and microstructure evolution during CSC-MIG welding of Fe–Cr–B-based alloy

    SciTech Connect

    Sorour, A.A. Chromik, R.R. Gauvin, R. Jung, I.-H. Brochu, M.

    2013-12-15

    The present is a study of the solidification and microstructure of Fe–28.2%Cr–3.8%B–1.5%Si–1.5%Mn (wt.%) alloy deposited onto a 1020 plain carbon steel substrate using the controlled short-circuit metal inert gas welding process. The as-solidified alloy was a metal matrix composite with a hypereutectic microstructure. Thermodynamic calculation based on the Scheil–Gulliver model showed that a primary (Cr,Fe){sub 2}B phase formed first during solidification, followed by an eutectic formation of the (Cr,Fe){sub 2}B phase and a body-centered cubic Fe-based solid solution matrix, which contained Cr, Mn and Si. Microstructure analysis confirmed the formation of these phases and showed that the shape of the (Cr,Fe){sub 2}B phase was irregular plate. As the welding heat input increased, the weld dilution increased and thus the volume fraction of the (Cr,Fe){sub 2}B plates decreased while other microstructural characteristics were similar. - Highlights: • We deposit Fe–Cr–B-based alloy onto plain carbon steel using the CSC-MIG process. • We model the solidification behavior using thermodynamic calculation. • As deposited alloy consists of (Cr,Fe){sub 2}B plates embedded in Fe-based matrix. • We study the effect of the welding heat input on the microstructure.

  7. TEM characterization of Au-based alloys to join YSZ to steel for SOFC applications

    SciTech Connect

    Lin, Kun-Lin; Singh, Mrityunjay; Asthana, Rajiv

    2012-01-15

    The microstructures of two gold-based alloys with compositions (in wt.%) of 96.4Au-3Ni-0.6Ti and 97.5Au-0.75Ni-1.75V following oxidation at 850 Degree-Sign C for 200 min were characterized by analytical transmission electron microscopy with energy dispersive spectroscopy and by scanning electron microscopy. In the oxidized 96.4Au-3Ni-0.6Ti interlayer, a dense scale composed of nickel oxide (NiO) and nickel titanate (NiTiO{sub 3}) formed at the alloy surface. No evidence of titanium oxide was found because there was not enough Ti present to form titanium oxide. In the oxidized 97.5Au-0.75Ni-1.75V interlayer, loose vanadium oxide (V{sub 2}O{sub 5}) and nickel vanadate (Ni{sub 2}V{sub 2}O{sub 7}) formed and were distributed within the oxidized 97.5Au-0.75Ni-1.75V interlayer. Similarly, because of the low Ni content in the alloys, no NiO formed. The oxide products in the 96.4Au-3Ni-0.6Ti and 97.5Au-0.75Ni-1.75V interlayers after oxidation are consistent with the Pilling-Bedworth (PB) ratio considerations. - Highlights: Black-Right-Pointing-Pointer Two commercial Au-based reactive metallic interlayers were oxidized at 850 Degree-Sign C for 200 min. Black-Right-Pointing-Pointer The oxidized products at the surface were characterized by TEM/EDS and SEM. Black-Right-Pointing-Pointer NiO and NiTiO{sub 3} formed at the oxidized 96.4Au-3Ni-0.6Ti interlayer. Black-Right-Pointing-Pointer V{sub 2}O{sub 5} and Ni{sub 2}V{sub 2}O{sub 7} were found in the oxidized 97.5Au-0.75Ni-1.75V interlayer. Black-Right-Pointing-Pointer These oxide products are consistent with the Pilling-Bedworth (PB) ratio considerations.

  8. Effect of high temperature fatigue on the fracture toughness of a nickel-base alloy

    SciTech Connect

    Hwang, S.K.

    1981-01-01

    The purpose of the present work was to investigate the effect of cyclic loading at high temperature on the fracture toughness of a precipitate hardened alloy. A ..gamma..' precipitate hardened Inconcel X-750 alloy was chosen because of its importance in practical applications as well as its relatively well defined microstructure compared to other superalloys. This paper presents a study of the variation of the relative fracture toughness of this alloy during continuous and hold-time fatigue at 973/sup 0/K.

  9. DENSITY-FUNCTIONAL STUDY OF Zr-BASED ACTINIDE ALLOYS: 2. U-Pu-Zr SYSTEM

    SciTech Connect

    Landa, A; Soderlind, P; Turchi, P; Vitos, L; Ruban, A

    2009-02-09

    Density-functional theory, previously used to describe phase equilibria in the U-Zr alloys [1], is applied to study ground state properties of the bcc U-Pu-Zr solid solutions. Calculated heats of formation of the Pu-U and Pu-Zr alloys are in a good agreement with CALPHAD assessments. We found that account for spin-orbit coupling is important for successful description of Pu-containing alloys.

  10. Extractive spectrophotometric method for the determination of vanadium(V) in steels and titanium base alloy

    SciTech Connect

    Yerramilli, A.; Kavipurapu, C.S.; Manda, R.R.; Pillutla, C.M.

    1986-06-01

    Vanadium(V) forms anionic chelates with 4-(2-pyridylazo)-resorcinol (PAR) at pH 5.0-7.8, which can be quantitatively extracted into nitrobenzene as an ion pair with xylometazolonium cation (XMH). The ternary system has an absorption maximum at 540 nm and obeys Beer's law in the range 0-1.8 /sup +/g of vanadium/mL with a molar absorptivity 4.56 x 10/sup 4/ L mol/sup -1/ cm/sup -1/. The Job's method of continuous variations indicated a composition of 1:1:1 for vanadium: PAR:XMH for the extracting species. In the presence of 1,3-diaminocyclohexanetetraacetic acid as a masking agent, the extraction becomes highly selective, and this method can be applied for the determination of vanadium(V), in the presence of various metal ions in synthetic mixtures, in steels, and in titanium base alloy.

  11. Calibration and Finite Element Implementation of an Energy-Based Material Model for Shape Memory Alloys

    NASA Astrophysics Data System (ADS)

    Junker, Philipp; Hackl, Klaus

    2016-06-01

    Numerical simulations are a powerful tool to analyze the complex thermo-mechanically coupled material behavior of shape memory alloys during product engineering. The benefit of the simulations strongly depends on the quality of the underlying material model. In this contribution, we discuss a variational approach which is based solely on energetic considerations and demonstrate that unique calibration of such a model is sufficient to predict the material behavior at varying ambient temperature. In the beginning, we recall the necessary equations of the material model and explain the fundamental idea. Afterwards, we focus on the numerical implementation and provide all information that is needed for programing. Then, we show two different ways to calibrate the model and discuss the results. Furthermore, we show how this model is used during real-life industrial product engineering.

  12. Hall current sensor IC with integrated Co-based alloy thin film magnetic concentrator

    NASA Astrophysics Data System (ADS)

    Palumbo, V.; Marchesi, M.; Chiesi, V.; Paci, D.; Iuliano, P.; Toia, F.; Casoli, F.; Ranzieri, P.; Albertini, F.; Morelli, M.

    2013-01-01

    This work deals with a cobalt-based alloy thin film magnetic concentrator (MC) which is fully integrated on a Hall sensor integrated circuit (IC) developed in the 0.35 µm Bipolar CMOS DMOS (BCD) technology on 8" silicon wafer. An amorphous magnetic film with a thickness of 1µm, coercitive field Hc<10A/m and saturation magnetization (µ0MS) of 0.45T has been obtained with a sputtering process. The Hall sensor IC has shown sensitivity to magnetic field at room temperature of 240V/AT without concentrator and 2550V/AT with concentrator, gaining a factor of 10.5. A current sensor demonstrator has been realized showing linear response in the range -50 to 50A.

  13. Deterministic character of all-optical magnetization switching in GdFe-based ferrimagnetic alloys

    NASA Astrophysics Data System (ADS)

    Le Guyader, L.; El Moussaoui, S.; Buzzi, M.; Savoini, M.; Tsukamoto, A.; Itoh, A.; Kirilyuk, A.; Rasing, Th.; Nolting, F.; Kimel, A. V.

    2016-04-01

    Using photoemission electron microscopy with x-ray magnetic circular dichroism as a contrast mechanism, new insights into the all-optical magnetization switching (AOS) phenomenon in GdFe-based rare-earth transition-metal ferrimagnetic alloys are provided. From a sequence of static images taken after single linearly polarized laser pulse excitation, the repeatability of AOS can be quantified with a correlation coefficient. It is found that low coercivity enables thermally activated domain-wall motion, limiting in turn the repeatability of the switching. Time-resolved measurements of the magnetization dynamics reveal that while AOS occurs below and above the magnetization compensation temperature TM, it is not observed in GdFe samples where TM is absent. Finally, AOS is experimentally demonstrated against an applied magnetic field of up to 180 mT.

  14. [Dissertations 25 years after date 44. Behaviour at high temperatures of palladium based dental alloys].

    PubMed

    van der Zel, J M

    2016-02-01

    In the Netherlands in the 1980s palladium based dental alloys were often used in substructures of metal-ceramic restorations. However, after their introduction to the market some unexplained problems came to light: porosity on the metal-ceramic interface, frequent failure of solder joints, margin lift and distortion of bigger constructions. Later, palladium allergies could be added to the list. A 1989 dissertation investigated these problems and underlying causes and came up with answers and solutions. Recent problems like the breakage and chipping of porcelain on zirconia cores shows again that industry is sometimes unaware of adjustment problems at the moment that a new product is introduced to the market. PMID:26878716

  15. The preparation of the Ti-Al alloys based on intermetallic phases

    NASA Astrophysics Data System (ADS)

    Kosova, N.; Sachkov, V.; Kurzina, I.; Pichugina, A.; Vladimirov, A.; Kazantseva, L.; Sachkova, A.

    2016-01-01

    This article deals with a method of obtaining materials in the Ti-Al system. Research was carried out in accordance with the phase diagram of the system state. It was established, that both single-phase and multiphase systems, containing finely dispersed intermetallic compositions of phases Ti3Al, TiAl and TiAl3, are formed. Additionally, it was found that the pure finely dispersed (coherent-scattering region (CSR) up to 100 nm) intermetallic compound TiAl3 is formed at molar ratio of Ti:Al = 1:3. Experimentally proved the possibility of produce the complex composition of alloys and intermetallic compounds and products based on them.

  16. Development of shape memory alloy (SMA)-based actuator for remotely piloted vehicles (RPVs)

    NASA Astrophysics Data System (ADS)

    Prasad, M. Hari

    2003-10-01

    While the experimental use of shape memory alloys (SMAs) is widespread in aerospace integrated actuation systems, much of the practical value of SMA technology is realized in linear and rotary actuators. This report will introduce an attempt to develop a full-scaled SMA based actuator to replace electro-mechanical actuator for flap actuation of a Remotely Piloted Vehicle (RPV). At the heart of this actuator there is thermally sensitive wire that, when heated, contracts and provides useable mechanical energy. This linear actuation is converted into rotary, for the required actuation of flap. The actuator configurations were sized to fit inside the wing of the RPV where presently the electro-mechanical actuator is housed. The torque supplied to the flap is similarly calculated from full-scale requirements. Using common engineering principles, this design will demonstrate how to design a typical SMA actuator. Test of the actuator performance (stroke, force movement) is done on special test fixture.

  17. Highly Fluorescent Gene Carrier Based on Ag-Au Alloy Nanoclusters.

    PubMed

    Wang, Ping; Lin, Lin; Guo, Zhaopei; Chen, Jie; Tian, Huayu; Chen, Xuesi; Yang, Hua

    2016-01-01

    For systemic delivery of gene, gold nanoparticles (GNPs) have been exploited as novel gene carriers because of the excellent characteristics for "visible" in intracellular trafficking. Herein, a highly fluorescent gene carrier was prepared by conjugating polyethylenimines on Ag-Au alloy nanoclusters. This carrier exhibited remarkable high gene transfection efficiencies and relatively low cytotoxicity toward B16F10, HeLa, and CHO cells. More interestingly, the high fluorescent Ag-Au-PEI conjugates showed high quantum yield of 14.56%, which is much higher than most of the reported gold nanocluster-based quantum dots and Ag-Au-PEI possessed bioimaging capacity both in vitro and in vivo. PMID:26287567

  18. Aging processes in precipitation-hardening composite materials based on a D16 aluminum alloy

    NASA Astrophysics Data System (ADS)

    Chernyshova, T. A.; Kobeleva, L. I.

    2010-09-01

    Aging of composite materials (CMs) based on an aluminum D16 alloy and reinforced by Al3Ti intermetallic inclusions (0-10 vol %) having formed upon an in situ reaction and by SiC particles (0-30 vol %) ≤3 or 28 μm in size is studied. Oxide ceramic nanoparticles (0.1 wt %) are used to modify the structure of the CMs. The structures of the CMs before and after aging are analyzed by optical microscopy and scanning electron microscopy on a microscope equipped with an X-ray energy dispersive spectrometer. The hardness of the CMs is measured. The overall hardening of aged CMs is shown to result from a competition between the hardening effects induced by the formation of Guinier-Preston zones and the precipitation of the high-temperature θ and S phases. These effects are controlled by the dislocation density in the matrix.

  19. Energy-based fatigue model for shape memory alloys including thermomechanical coupling

    NASA Astrophysics Data System (ADS)

    Zhang, Yahui; Zhu, Jihong; Moumni, Ziad; Van Herpen, Alain; Zhang, Weihong

    2016-03-01

    This paper is aimed at developing a low cycle fatigue criterion for pseudoelastic shape memory alloys to take into account thermomechanical coupling. To this end, fatigue tests are carried out at different loading rates under strain control at room temperature using NiTi wires. Temperature distribution on the specimen is measured using a high speed thermal camera. Specimens are tested to failure and fatigue lifetimes of specimens are measured. Test results show that the fatigue lifetime is greatly influenced by the loading rate: as the strain rate increases, the fatigue lifetime decreases. Furthermore, it is shown that the fatigue cracks initiate when the stored energy inside the material reaches a critical value. An energy-based fatigue criterion is thus proposed as a function of the irreversible hysteresis energy of the stabilized cycle and the loading rate. Fatigue life is calculated using the proposed model. The experimental and computational results compare well.

  20. Fiber laser cladding of nickel-based alloy on cast iron

    NASA Astrophysics Data System (ADS)

    Arias-González, F.; del Val, J.; Comesaña, R.; Penide, J.; Lusquiños, F.; Quintero, F.; Riveiro, A.; Boutinguiza, M.; Pou, J.

    2016-06-01

    Gray cast iron is a ferrous alloy characterized by a carbon-rich phase in form of lamellar graphite in an iron matrix while ductile cast iron presents a carbon-rich phase in form of spheroidal graphite. Graphite presents a higher laser beam absorption than iron matrix and its morphology has also a strong influence on thermal conductivity of the material. The laser cladding process of cast iron is complicated by its heterogeneous microstructure which generates non-homogeneous thermal fields. In this research work, a comparison between different types of cast iron substrates (with different graphite morphology) has been carried out to analyze its impact on the process results. A fiber laser was used to generate a NiCrBSi coating over flat substrates of gray cast iron (EN-GJL-250) and nodular cast iron (EN-GJS-400-15). The relationship between processing parameters (laser irradiance and scanning speed) and geometry of a single laser track was examined. Moreover, microstructure and composition were studied by Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray Spectroscopy (EDS) and X-Ray Diffraction (XRD). The hardness and elastic modulus were analyzed by means of micro- and nanoindentation. A hardfacing coating was generated by fiber laser cladding. Suitable processing parameters to generate the Ni-based alloy coating were determined. For the same processing parameters, gray cast iron samples present higher dilution than cast iron samples. The elastic modulus is similar for the coating and the substrate, while the Ni-based coating obtained presents a significantly superior hardness than cast iron.

  1. Model-based melt rate control during vacuum arc remelting of alloy 718

    NASA Astrophysics Data System (ADS)

    Williamson, Rodney L.; Melgaard, David K.; Shelmidine, Gregory J.; Beaman, Joseph J.; Morrison, Robert

    2004-02-01

    Vacuum arc remelting (VAR) is used widely throughout the specialty metals industry to produce superalloy and titanium alloy cast ingots. Optimum VAR casting requires that the electrode melting rate be controlled at all times during the process. This is especially difficult when process conditions are such that the temperature distribution in the electrode has not achieved, or has been driven away from, steady state. This condition is encountered during the beginning and closing stages of the VAR process, and also during some process disturbances such as when the melt zone passes through a transverse crack. To address these transient melting situations, a new method of VAR melt rate control has been developed that incorporates an accurate, low-order melting model to continually estimate the temperature distribution in the electrode. This method of model-based control was tested at Carpenter Technology Corporation. In the first test, two 0.43-m-diameter alloy 718 electrodes were melted into 0.51-m-diameter ingots. Aggressive start-up and hot-top procedures were used to test the dynamic capabilities of the control technique. Additionally, a transverse cut was placed in each electrode with an abrasive saw to mimic an electrode crack. Accurate melt rate control was demonstrated throughout each melt. The second test used an electrode size and grade proprietary to the host company. Because it was not stress relieved after the primary casting process, the electrode was known to possess multiple cracks that make accurate melt rate control impossible using standard VAR controller technology. This electrode was also successfully melted with good melt rate control using the model-based controller.

  2. Elevated temperature creep-fatigue crack propagation in nickel-base alloys and 1 Cr-Mo-V steel

    NASA Astrophysics Data System (ADS)

    Nazmy, M.; Hoffelner, W.; Wüthrich, C.

    1988-04-01

    The crack growth behavior of several high temperature nickel-base alloys, under cyclic and static loading, is studied and reviewed. In the oxide dispersion strengthened (ODS) MA 6000 and MA 754 alloys, the high temperature crack propagation exhibited orientation dependence under cyclic as well as under static loading. The creep crack growth (CCG) behavior of cast nickel-base IN-738 and IN-939* superalloys at 850 °C could be characterized by the stress intensity factor, K 1. In the case of the alloy IN-901 at 500 °C and 600 °C, K 1 was found to be the relevant parameter to characterize the creep crack growth behavior. The energy rate line integral, C*, may be the appropriate loading parameter to describe the creep crack growth behavior of the nickel-iron base IN-800H alloy at 800 °C. The creep crack growth data of 1 Cr-Mo-V steel, with bainitic microstructure, at 550 °C could be correlated better by C * than by K 1.

  3. Design of a nitrogen-implanted titanium-based superelastic alloy with optimized properties for biomedical applications.

    PubMed

    Gordin, D M; Busardo, D; Cimpean, A; Vasilescu, C; Höche, D; Drob, S I; Mitran, V; Cornen, M; Gloriant, T

    2013-10-01

    In this study, a superelastic Ni-free Ti-based biomedical alloy was treated in surface by the implantation of nitrogen ions for the first time. The N-implanted surface was characterized by X-ray diffraction, X-ray photoelectron spectroscopy, and secondary ion mass spectroscopy, and the superficial mechanical properties were evaluated by nano-indentation and by ball-on-disk tribological tests. To investigate the biocompatibility, the corrosion resistance of the N-implanted Ti alloy was evaluated in simulated body fluids (SBF) complemented by in-vitro cytocompatibility tests on human fetal osteoblasts. After implantation, surface analysis methods revealed the formation of a titanium-based nitride on the substrate surface. Consequently, an increase in superficial hardness and a significant reduction of friction coefficient were observed compared to the non-implanted sample. Also, a better corrosion resistance and a significant decrease in ion release rates have been obtained. Cell culture experiments indicated that the cytocompatibility of the N-implanted Ti alloy was superior to that of the corresponding non-treated sample. Thus, this new functional N-implanted titanium-based superelastic alloy presents the optimized properties that are required for various medical devices: superelasticity, high superficial mechanical properties, high corrosion resistance and excellent cytocompatibility.

  4. Performance of chromia- and alumina-forming Fe- and Ni-base alloys exposed to metal dusting environments: The effect of water vapor and temperature

    DOE PAGES

    Rouaix-Vande Put, Aurelie; Unocic, Kinga A.; Brady, Michael P.; Pint, Bruce A.

    2015-11-18

    Fe- and Ni-base alloys including an alumina-forming austenitic alloy were exposed for 500 h under metal dusting environments with varying temperature, gas composition and total pressure. For one H2–CO–CO2–H2O environment, the increase in temperature from 550 to 750 °C generally decreased metal dusting. When H2O was added to a H2–CO–CO2 environment at 650 °C, the metal dusting attack was reduced. Even after 5000 h at a total pressure of 9.1 atm with 20%H2O, the higher alloyed specimens retained a thin protective oxide. Lastly, for gas mixtures containing little or no H2O, the Fe-base alloys were less resistant to metal dustingmore » than Ni-base alloys.« less

  5. 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.

  6. Neutronics Evaluation of Lithium-Based Ternary Alloys in IFE Blankets

    SciTech Connect

    Jolodosky, A.; Fratoni, M.

    2015-09-22

    , low electrical conductivity and therefore low MHD pressure drop, low chemical reactivity, and extremely low tritium inventory; the addition of sodium (FLiNaBe) has been considered because it retains the properties of FliBe but also lowers the melting point. Although many of these blanket concepts are promising, challenges still remain. The limited amount of beryllium available poses a problem for ceramic breeders such as the HCPB. FLiBe and FLiNaBe are highly viscous and have a low thermal conductivity. Lithium lead possesses a poor thermal conductivity which can cause problems in both DCLL and LiPb blankets. Additionally, the tritium permeation from these two blankets into plant components can be a problem and must be reduced. Consequently, Lawrence Livermore National Laboratory (LLNL) is attempting to develop a lithium-based alloy—most likely a ternary alloy—which maintains the beneficial properties of lithium (e.g. high tritium breeding and solubility) while reducing overall flammability concerns for use in the blanket of an inertial fusion energy (IFE) power plant. The LLNL concept employs inertial confinement fusion (ICF) through the use of lasers aimed at an indirect-driven target composed of deuterium-tritium fuel. The fusion driver/target design implements the same physics currently experimented at the National Ignition Facility (NIF). The plant uses lithium in both the primary coolant and blanket; therefore, lithium-related hazards are of primary concern. Although reducing chemical reactivity is the primary motivation for the development of new lithium alloys, the successful candidates will have to guarantee acceptable performance in all their functions. The scope of this study is to evaluate the neutronics performance of a large number of lithium-based alloys in the blanket of the IFE engine and assess their properties upon activation. This manuscript is organized as follows: Section 12 presents the models and methodologies used for the analysis; Section

  7. Synthesis and thermal behavior of tin-based alloy (Sn-Ag-Cu) nanoparticles

    NASA Astrophysics Data System (ADS)

    Roshanghias, Ali; Yakymovych, Andriy; Bernardi, Johannes; Ipser, Herbert

    2015-03-01

    The prominent melting point depression of nanoparticles has been the subject of a considerable amount of research. For their promising applications in electronics, tin-based nano-alloys such as near-eutectic Sn-Ag-Cu (SAC) alloys have been synthesized via various techniques. However, due to issues such as particle aggregation and oxidation or introduced impurities, the application of these nano-size particles has been confined or aborted. For instance, thermal investigations by DTA/DSC in a large number of studies revealed exothermic peaks in the range of 240-500 °C, i.e. above the melting point of SAC nanoparticles, with different and quite controversial explanations for this unclear phenomenon. This represents a considerable drawback for the application of nanoparticles. Correspondingly, in the current study, the thermal stability of SAC nanoparticles has been investigated via electron microscopy, XRD, FTIR, and DSC/TG analysis. It was found that the nanoparticles consist mainly of a metallic β-Sn core and an amorphous tin hydroxide shell structure. The SnO crystalline phase formation from this amorphous shell has been associated with the exothermic peaks on the first heating cycle of the nanoparticles, followed by a disproportionation reaction into metallic Sn and SnO2.The results also revealed that the surfactant and reducing agent cannot only affect the size and size distribution of the nanoparticles, they might also alter the ratio between the amorphous shell and the crystalline core in the structure of particles.The prominent melting point depression of nanoparticles has been the subject of a considerable amount of research. For their promising applications in electronics, tin-based nano-alloys such as near-eutectic Sn-Ag-Cu (SAC) alloys have been synthesized via various techniques. However, due to issues such as particle aggregation and oxidation or introduced impurities, the application of these nano-size particles has been confined or aborted. For

  8. Structure and properties of porous TiNi(Co, Mo)-based alloy produced by the reaction sintering

    NASA Astrophysics Data System (ADS)

    Artyukhova, Nadezda; Yasenchuk, Yuriy; Chekalkin, Timofey; Gunther, Victor; Kim, Ji-Soon; Kang, Ji-Hoon

    2016-10-01

    Modern medical technologies have developed many new devices that can be implanted into humans to repair, assist or take the place of diseased or defective bones, arteries and even organs. The materials, especially porous ones, used for these devices have evolved steadily over the past twenty years with TiNi-based alloys replacing stainless steels and titanium. The aim of the paper is to presents results for examination of porous TiNi(Co,Mo)-based alloys intended further to be used in clinical practice. The structure and properties of porous TiNi-based alloys obtained by reaction sintering of Ti and Ni powders with additions of Co and Mo have been studied. It has been shown that alloying additions both Co and Mo inhibit the compaction of nickel powders in the initial stage of sintering. The maximum irreversible strain of porous samples under loading in the austenitic state is fixed with the Co addition, and the minimum one is fixed with the Mo addition. The Co addition leads to the fact that the martensite transformation in the TiNi phase becomes close to a one-step, and the Mo addition leads to the fact that the martensite transformation becomes more uniform. Both Co and Mo lead to an increase in the maximum accumulated strain as a result of the formation of temperature martensite. The additional increase in the maximum accumulated strain of the Ti50Ni49Co1 alloy is caused by decreased resistance of the porous Ni γ -based mass during the load.

  9. Induced Anisotropy in FeCo-Based Nanocrystalline Ferromagnetic Alloys (HITPERM) by Very High Field Annealing

    NASA Technical Reports Server (NTRS)

    Johnson, F.; Garmestani, H.; Chu, S.-Y.; McHenry, M. E.; Laughlin, D. E.

    2004-01-01

    Very high magnetic field annealing is shown to affect the magnetic anisotropy in FeCo-base nanocrystalline soft ferromagnetic alloys. Alloys of composition Fe(44.5)Co(44.5)Zr(7)B(4) were prepared by melt spinning into amorphous ribbons, then wound to form toroidal bobbin cores. One set of cores was crystallized in a zero field at 600 deg. C for 1 h, then, field annealed at 17 tesla (T) at 480 deg. C for 1 h. Another set was crystallized in a 17-T field at 480 deg. C for 1 h. Field orientation was transverse to the magnetic path of the toroidal cores. An induced anisotropy is indicated by a sheared hysteresis loop. Sensitive torque magnetometry measurements with a Si cantilever sensor indicated a strong, uniaxial, longitudinal easy axis in the zero-field-crystallized sample. The source is most likely magnetoelastic anisotropy, caused by the residual stress from nanocrystallization and the nonzero magnetostriction coefficient for this material. The magnetostrictive coefficient lambda(5) is measured to be 36 ppm by a strain gage technique. Field annealing reduces the magnitude of the induced anisotropy. Core loss measurements were made in the zero-field-crystallized, zero-field-crystallized- than-field-annealed, and field-crystallized states. Core loss is reduced 30%-50% (depending on frequency) by field annealing. X-ray diffraction reveals no evidence of crystalline texture or orientation that would cause the induced anisotropy. Diffusional pair ordering is thought to be the cause of the induced anisotropy. However, reannealing the samples in the absence of a magnetic field at 480 deg. C does not completely remove the induced anisotropy.

  10. Parametric Study on the Tensile Properties of Ni-Based Alloy for a VHTR

    NASA Astrophysics Data System (ADS)

    Kim, Dong-Jin; Jung, Su Jin; Mun, Byung Hak; Kim, Sung Woo; Lim, Yun Soo

    2015-01-01

    A very high-temperature reactor (VHTR) has been studied among generation IV nuclear power plants owing to its many advantages such as high-electric efficiency and massive hydrogen production. The material used for the heat exchanger should sustain structural integrity for its life even though the material is exposed to a harsh environment at 1223 K (950 °C) in an impure helium coolant. Therefore, an enhancement of the material performance at high temperature gives a margin in determining the operating temperature and life time. This work is an effort to find an optimum combination of alloying elements and processing parameters to improve the material performance. The tensile property and microstructure for nickel-based alloys fabricated in a laboratory were evaluated as a function of the heat treatment, cold working, and grain boundary strengthener using a tension test at 1223 K (950 °C), scanning electron microscopy, and transmission electron microscopy. Elongation to rupture was increased by additional heat treatment and cold working, followed by additional heat treatment in the temperature range from 1293 K to 1383 K (1020 °C to 1110 °C) implying that the intergranular carbide contributes to grain boundary strengthening. The temperature at which the grain boundary is improved by carbide decoration was higher for a cold-worked specimen, which was described by the difference in carbide stability and carbide formation kinetics between no cold-worked and cold-worked specimens. Zr and Hf played a scavenging effect of harmful elements causing an increase in ductility.

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

    SciTech Connect

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

    1997-01-15

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

  12. Elastoplastic properties of a low-modulus titanium-based β alloy

    NASA Astrophysics Data System (ADS)

    Betekhtin, V. I.; Kolobov, Yu. R.; Golosova, O. A.; Kardashev, B. K.; Kadomtsev, A. G.; Narykova, M. V.; Ivanov, M. B.; Vershinina, T. N.

    2013-10-01

    The elastoplastic properties (elastic modulus, amplitude-independent damping ratio, microplastic flow stress) of a Ti-26Nb-7Mo-12Zr titanium β alloy are determined using an acoustic resonance method. The effect of the strain during thermomechanical treatment on the structural features of the micro-crystalline alloy and, hence, its elastoplastic properties is analyzed.

  13. Elasticity of the Sm1-xYxS alloy Based on Ultrasonic Measurements

    NASA Astrophysics Data System (ADS)

    Soboleva, EG; Igisheva, AL; Wojciechowski, KW

    2016-08-01

    The elastic moduli, sound velocities, Gruneisen parameter, Poisson's ratios and brittleness-plasticity criterion ratios are studied for the Sm1-xYxS alloys. Their dependence on the concentration of alloy components including a valence transition from semiconductors into the metal phase is presented. Auxeticity (negative Poisson's ratio) is found for some concentrations.

  14. Damage accumulation in ion-irradiated Ni-based concentrated solid-solution alloys

    DOE PAGES

    Ullah, Mohammad W.; Aidhy, Dilpuneet S.; Zhang, Yanwen; Weber, William J.

    2016-01-01

    We investigate Irradiation-induced damage accumulation in Ni0.8Fe0.2 and Ni0.8Cr0.2 alloys by using molecular dynamics simulations to assess possible enhanced radiation-resistance in these face-centered cubic (fcc), single-phase, concentrated solid-solution alloys, as compared with pure fcc Ni.

  15. 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.

  16. Microstructure and wear properties of Al2O3-CeO2/Ni-base alloy composite coatings on aluminum alloys by plasma spray

    NASA Astrophysics Data System (ADS)

    He, Long; Tan, Yefa; Wang, Xiaolong; Xu, Ting; Hong, Xiang

    2014-09-01

    Al2O3 and CeO2 particles reinforced Ni-base alloy composite coatings were prepared on aluminum alloy 7005 by plasma spray. The microstructure, microhardness, fracture toughness, critical bonding force and the wear behavior and mechanisms of the composite coatings were investigated. It is found that CeO2 particles can refine crystal grains, reduce porosity and unmelted Al2O3 particles in the composite coatings. The microhardness, fracture toughness, critical bonding force and wear resistance of the composite coatings are enhanced due to synergistic strengthening effects of Al2O3 and CeO2 particles. The friction coefficients and wear losses increase as loads increase. At the loads of 3-6 N, the composite coatings experience local plastic deformation and micro-cutting wear. At the loads in the range of 9-12 N, the calculated maximum contact stress and maximum tensile stress on friction surfaces increase leading to plastic deformation induced working hardening. The wear mechanisms change into micro-brittle fracture wear and slight oxidative wear.

  17. Mn in misch-metal based superlattice metal hydride alloy - Part 1 structural, hydrogen storage and electrochemical properties

    NASA Astrophysics Data System (ADS)

    Young, K.; Wong, D. F.; Wang, L.; Nei, J.; Ouchi, T.; Yasuoka, S.

    2015-03-01

    The structural, gaseous phase hydrogen storage, and electrochemical properties of a series of Mn-modified misch-metal based superlattice metal hydride alloys were investigated in part one of this two-part series of papers. X-ray diffraction analysis showed that these alloys are all multi-phased compositions with different abundances of AB2, AB3, A2B7, AB4, and AB5 phases. Substitution of Ni in the B-site by Mn promotes AB5 phase formation and decreases both gaseous phase and electrochemical capacities due to the reduction in the abundance of main hexagonal A2B7 phase. AC impedance and magnetic susceptibility measurement were employed to characterize the surface of Mn-free and Mn-modified alloys and show deterioration in surface catalytic ability as the Mn-content increases. Mn-modification adversely affected misch-metal based superlattice metal hydride alloy properties such as phase homogeneity, capacity, cycle stability, high-rate performance, and surface reaction.

  18. Assessing the Effects of Radiation Damage on Ni-base Alloys for the Prometheus Space Reactor System

    SciTech Connect

    T. Angeliu

    2006-01-19

    Ni-base alloys were considered for the Prometheus space reactor pressure vessel with operational parameters of {approx}900 K for 15 years and fluences up to 160 x 10{sup 20} n/cm{sup 2} (E > 0.1 MeV). This paper reviews the effects of irradiation on the behavior of Ni-base alloys and shows that radiation-induced swelling and creep are minor considerations compared to significant embrittlement with neutron ,exposure. While the mechanism responsible for radiation-induced embrittlement is not fully understood, it is likely a combination of helium embrittlement and solute segregation that can be highly dependent on the alloy composition and exposure conditions. Transmutation calculations show that detrimental helium levels would be expected at the end of life for the inner safety rod vessel (thimble) and possibly the outer pressure vessel, primarily from high energy (E > 1 MeV) n,{alpha} reactions with {sup 58}Ni. Helium from {sup 10}B is significant only for the outer vessel due to the proximity of the outer vessel to the Be0 control elements. Recommendations for further assessments of the material behavior and methods to minimize the effects of radiation damage through alloy design are provided.

  19. Assessing the Effects of Radiation Damage on Ni-base Alloys for the Prometheus Space Reactor System

    SciTech Connect

    T Angeliu; J Ward; J Witter

    2006-04-04

    Ni-base alloys were considered for the Prometheus space reactor pressure vessel with operational parameters of {approx}900 K for 15 years and fluences up to 160 x 10{sup 20} n/cm{sup 2} (E > 0.1 MeV). This paper reviews the effects of irradiation on the behavior of Ni-base alloys and shows that radiation-induced swelling and creep are minor considerations compared to significant embrittlement with neutron exposure. While the mechanism responsible for radiation-induced embrittlement is not fully understood, it is likely a combination of helium embrittlement and solute segregation that can be highly dependent on the alloy composition and exposure conditions. Transmutation calculations show that detrimental helium levels would be expected at the end of life for the inner safety rod vessel (thimble) and possibly the outer pressure vessel, primarily from high energy (E > 1 MeV) n,{alpha} reactions with {sup 58}Ni. Helium from {sup 10}B is significant only for the outer vessel due to the proximity of the outer vessel to the BeO control elements. Recommendations for further assessments of the material behavior and methods to minimize the effects of radiation damage through alloy design are provided.

  20. A nanoscale co-precipitation approach for property enhancement of Fe-base alloys

    PubMed Central

    Zhang, Zhongwu; Liu, Chain Tsuan; Miller, Michael K.; Wang, Xun-Li; Wen, Yuren; Fujita, Takeshi; Hirata, Akihiko; Chen, Mingwei; Chen, Guang; Chin, Bryan A.

    2013-01-01

    Precipitate size and number density are two key factors for tailoring the mechanical behavior of nanoscale precipitate-hardened alloys. However, during thermal aging, the precipitate size and number density change, leading to either poor strength or high strength but significantly reduced ductility. Here we demonstrate, by producing nanoscale co-precipitates in composition-optimized multicomponent precipitation-hardened alloys, a unique approach to improve the stability of the alloy against thermal aging and hence the mechanical properties. Our study provides compelling experimental evidence that these nanoscale co-precipitates consist of a Cu-enriched bcc core partially encased by a B2-ordered Ni(Mn, Al) phase. This co-precipitate provides a more complex obstacle for dislocation movement due to atomic ordering together with interphases, resulting in a high yield strength alloy without sacrificing alloy ductility. PMID:23429646

  1. Influence of Chromium and Molybdenum on the Corrosion of Nickel Based Alloys

    SciTech Connect

    Hayes, J R; Gray, J; Szmodis, A W; Orme, C A

    2005-08-02

    The addition of chromium and molybdenum to nickel creates alloys with exceptional corrosion resistance in a diverse range of environments. This study examines the complementary roles of Cr and Mo in Ni alloy passivation. Four nickel alloys with varying amounts of chromium and molybdenum were studied in 1 molar salt solutions over a broad pH range. The passive corrosion and breakdown behavior of the alloys suggests that chromium is the primary element influencing general corrosion resistance. The breakdown potential was nearly independent of molybdenum content, while the repassivation potential is strongly dependant on the molybdenum content. This indicates that chromium plays a strong role in maintaining the passivity of the alloy, while molybdenum acts to stabilize the passive film after a localized breakdown event.

  2. Fracture toughness of copper-base alloys for ITER applications: A preliminary report

    SciTech Connect

    Alexander, D.J.; Zinkle, S.J.; Rowcliffe, A.F.

    1997-04-01

    Oxide-dispersion strengthened copper alloys and a precipitation-hardened copper-nickel-beryllium alloy showed a significant reduction in toughness at elevated temperature (250{degrees}C). This decrease in toughness was much larger than would be expected from the relatively modest changes in the tensile properties over the same temperature range. However, a copper-chromium-zirconium alloy strengthened by precipitation showed only a small decrease in toughness at the higher temperatures. The embrittled alloys showed a transition in fracture mode, from transgranular microvoid coalescence at room temperature to intergranular with localized ductility at high temperatures. The Cu-Cr-Zr alloy maintained the ductile microvoid coalescence failure mode at all test temperatures.

  3. Probabilistic simulation of hydrogen gas porosity formation in A356 base hypoeutectic alloy castings

    NASA Astrophysics Data System (ADS)

    Asada, Jo

    Microporosity in cast aluminum alloy can be classified as gas porosity and/or shrinkage porosity. In prior research, two dimensional simulation programs employing a probabilistic modeling approach and cellular automaton method were developed to predict microporosity in cast aluminum alloys. In this research the 2D models were statistically compared with experimental data. Additionally, we investigated size and morphology distribution of grains and porosity in A356 alloy castings under variable hydrogen content and alloy treatment condition, i.e. eutectic phase modification and grain refinement. In order to improve the accuracy of the prediction method, new simulation models including a two and half dimensional analysis and a two phase evolution model were developed in the present body of work. The new models were statistically compared with experimental results changing silicon and hydrogen content and alloy treatment conditions. The new simulation technique exhibits improved agreement with experimental data tracking the morphology of gas porosities and the grain size distribution.

  4. Air Oxidation Behavior of Two Ti-Base Alloys Synthesized by HIP

    NASA Astrophysics Data System (ADS)

    Liu, S.; Guo, Q. Q.; Liu, L. L.; Xu, L.; Liu, Y. Y.

    2016-04-01

    The oxidation behavior of Ti-5Al-2.5Sn and Ti-6Al-4V produced by hot isostatic pressing (HIP) has been studied at 650-850°C in air for 24 h. The oxidation kinetics of both alloys followed the parabolic law with good approximation, except for Ti-5Al-2.5Sn oxidized at 850°C. Multi-layered scales formed on both alloys at 750°C and 850°C. Ternary additions of Sn and V accounted for the different morphology of the scales formed on these two alloys. In addition, the oxidation behavior of HIP alloys is compared with that of the corresponding cast alloys and the scaling mechanism is discussed.

  5. In vitro biocompatibility and corrosion resistance of a new implant titanium base alloy.

    PubMed

    Vasilescu, E; Drob, P; Raducanu, D; Cojocaru, V D; Cinca, I; Iordachescu, D; Ion, R; Popa, M; Vasilescu, C

    2010-06-01

    One objective of this work was to study the corrosion resistance of the new implant Ti-10Zr-5Ta-5Nb alloy in physiological fluids of different pH values, simulating the extreme functional conditions. Another objective was in vitro biocompatibility evaluation of the new alloy using human fetal osteoblast cell line hFOB 1.19. Cytocompatibility was assessed by determination of possible material cytotoxic effects, cell morphology and cell adhesion. The thermo-mechanical processing of the new implant alloy consisted in plastic deformation (almost 90%) performed by hot rolling accompanied by an initial and final heat treatment. The new Ti-10Zr-5Ta-5Nb alloy presented self-passivation, with a large passive potential range and low passive current densities, namely, a very good anticorrosive resistance in Ringer solution of acid, neutral and alkaline pH values. Cell viability was not affected by the alloy substrate presence and a very good compatibility was noticed.

  6. The Influence of Dynamic Strain Aging on Fatigue and Creep-Fatigue Characterization of Nickel-Base Solid Solution Strengthened Alloys

    SciTech Connect

    L.J. Carroll; W.R. Lloyd; J.A. Simpson; R.N. Wright

    2010-12-01

    The nickel-base solid solution alloys, Alloy 617 and Alloy 230, have been observed to exhibit serrated yielding or dynamic strain aging (DSA) in a temperature/strain rate regime of interest for intermediate heat exchangers (IHX) of high temperature nuclear reactors. At 800°C, these nickel-base alloys are prone to large serrated yielding events at relatively low strains. The presence of DSA introduces challenges in characterizing the creep-fatigue and low cycle fatigue behavior. These challenges include inability to control the target strains as a result of DSA induced strain excursions and distorted hysteresis loops. Methods to eliminate or reduce the influence of DSA on creep-fatigue testing have been investigated, including varying the strain rate, stepping to the target strain, and adjusting servo-hydraulic tuning parameters. It has not been possible to eliminate the impact of serrated flow in the temperature range of interest for these alloys without compromising the desired test protocols.

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

    SciTech Connect

    Kalay, Yunus Eren

    2009-01-01

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

  8. 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.

  9. Design, modelling and control of a micro-positioning actuator based on magnetic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Minorowicz, Bartosz; Leonetti, Giuseppe; Stefanski, Frederik; Binetti, Giulio; Naso, David

    2016-07-01

    This paper presents an actuator based on magnetic shape memory alloys (MSMAs) suitable for precise positioning in a wide range (up to 1 mm). The actuator is based on the spring returned operating mode and uses a Smalley wave spring to maintain the same operating parameters of a classical coil spring, while being characterized by a smaller dimension. The MSMA element inside the actuator provides a deformation when excited by an external magnetic field, but its behavior is characterized by an asymmetric and saturated hysteresis. Thus, two models are exploited in this work to represent such a non-linear behavior, i.e., the modified and generalized Prandtl–Ishlinskii models. These models are particularly suitable for control purposes due to the existence of their analytical inversion that can be easily exploited in real time control systems. To this aim, this paper investigates three closed-loop control strategies, namely a classical PID regulator, a PID regulator with direct hysteresis compensation, and a combined PID and feedforward compensation strategy. The effectiveness of both modelling and control strategies applied to the designed MSMA-based actuator is illustrated by means of experimental results.

  10. Design, modelling and control of a micro-positioning actuator based on magnetic shape memory alloys

    NASA Astrophysics Data System (ADS)

    Minorowicz, Bartosz; Leonetti, Giuseppe; Stefanski, Frederik; Binetti, Giulio; Naso, David

    2016-07-01

    This paper presents an actuator based on magnetic shape memory alloys (MSMAs) suitable for precise positioning in a wide range (up to 1 mm). The actuator is based on the spring returned operating mode and uses a Smalley wave spring to maintain the same operating parameters of a classical coil spring, while being characterized by a smaller dimension. The MSMA element inside the actuator provides a deformation when excited by an external magnetic field, but its behavior is characterized by an asymmetric and saturated hysteresis. Thus, two models are exploited in this work to represent such a non-linear behavior, i.e., the modified and generalized Prandtl-Ishlinskii models. These models are particularly suitable for control purposes due to the existence of their analytical inversion that can be easily exploited in real time control systems. To this aim, this paper investigates three closed-loop control strategies, namely a classical PID regulator, a PID regulator with direct hysteresis compensation, and a combined PID and feedforward compensation strategy. The effectiveness of both modelling and control strategies applied to the designed MSMA-based actuator is illustrated by means of experimental results.

  11. An innovative seismic bracing system based on a superelastic shape memory alloy ring

    NASA Astrophysics Data System (ADS)

    Gao, Nan; Jeon, Jong-Su; Hodgson, Darel E.; DesRoches, Reginald

    2016-05-01

    Shape memory alloys (SMAs) have great potential in seismic applications because of their remarkable superelasticity. Seismic bracing systems based on SMAs can mitigate the damage caused by earthquakes. The current study investigates a bracing system based on an SMA ring which is capable of both re-centering and energy dissipation. This lateral force resisting system is a cross-braced system consisting of an SMA ring and four tension-only cable assemblies, which can be applied to both new construction and seismic retrofit. The performance of this bracing system is examined through a quasi-static cyclic loading test and finite element (FE) analysis. This paper describes the experimental design in detail, discusses the experimental results, compares the performance with other bracing systems based on SMAs, and presents an Abaqus FE model calibrated on the basis of experimental results to simulate the superelastic behavior of the SMA ring. The experimental results indicate that the seismic performance of this system is promising in terms of damping and re-centering. The FE model can be used in the simulation of building structures using the proposed bracing system.

  12. Finite Element Analysis of a Copper Single Crystal Shape Memory Alloy-Based Endodontic Instruments

    NASA Astrophysics Data System (ADS)

    Vincent, Marin; Thiebaud, Frédéric; Bel Haj Khalifa, Saifeddine; Engels-Deutsch, Marc; Ben Zineb, Tarak

    2015-10-01

    The aim of the present paper is the development of endodontic Cu-based single crystal Shape Memory Alloy (SMA) instruments in order to eliminate the antimicrobial and mechanical deficiencies observed with the conventional Nickel-Titane (NiTi) SMA files. A thermomechanical constitutive law, already developed and implemented in a finite element code by our research group, is adopted for the simulation of the single crystal SMA behavior. The corresponding material parameters were identified starting from experimental results for a tensile test at room temperature. A computer-aided design geometry has been achieved and considered for a finite element structural analysis of the endodontic Cu-based single crystal SMA files. They are meshed with tetrahedral continuum elements to improve the computation time and the accuracy of results. The geometric parameters tested in this study are the length of the active blade, the rod length, the pitch, the taper, the tip diameter, and the rod diameter. For each set of adopted parameters, a finite element model is built and tested in a combined bending-torsion loading in accordance with ISO 3630-1 norm. The numerical analysis based on finite element procedure allowed purposing an optimal geometry suitable for Cu-based single crystal SMA endodontic files. The same analysis was carried out for the classical NiTi SMA files and a comparison was made between the two kinds of files. It showed that Cu-based single crystal SMA files are less stiff than the NiTi files. The Cu-based endodontic files could be used to improve the root canal treatments. However, the finite element analysis brought out the need for further investigation based on experiments.

  13. Characterization of low alloy ferritic steel–Ni base alloy dissimilar metal weld interface by SPM techniques, SEM/EDS, TEM/EDS and SVET

    SciTech Connect

    Wang, Siyan; Ding, Jie; Ming, Hongliang; Zhang, Zhiming; Wang, Jianqiu

    2015-02-15

    The interface region of welded A508–Alloy 52 M is characterized by scanning probe microscope (SPM) techniques, scanning electron microscopy (SEM)/energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM)/Energy Dispersive Spectroscopy (EDS) and scanning vibrate electrode technique (SVET). The regions along the welded A508–Alloy 52 M interface can be categorized into two types according to their different microstructures. In the type-I interface region, A508 and Alloy 52 M are separated by the fusion boundary, while in the type-II interface region, A508 and Alloy 52 M are separated by a martensite zone. A508, martensite zone and grain boundaries in Alloy 52 M are ferromagnetic while the Alloy 52 M matrix is paramagnetic. The Volta potentials measured by scanning Kelvin probe force microscopy (SKPFM) of A508, martensite zone and Alloy 52 M follow the order: V{sub 52} {sub M} > V{sub A508} > V{sub martensite}. The corrosion behavior of A508–Alloy 52 M interface region is galvanic corrosion, in which Alloy 52 M is cathode while A508 is anode. The martensite dissolves faster than Alloy 52 M, but slower than A508 in the test solution. - Highlights: • The A508–Alloy 52 M interface regions can be categorized into two types. • The chromium depleted region is observed along the Alloy 52 M grain boundary. • The Alloy 52 M grain boundaries which are close to the interface are ferromagnetic. • Martensite zone has lower Volta potential but higher corrosion resistance than A508.

  14. Effects of alloying elements and temperature on the elastic properties of dilute Ni-base superalloys from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Shang, S. L.; Kim, D. E.; Zacherl, C. L.; Wang, Y.; Du, Y.; Liu, Z. K.

    2012-09-01

    The variation of elastic properties, e.g., elastic constants, bulk modulus, and shear modulus of dilute Ni-base superalloys due to alloying elements (X's) and temperature, has been studied via first-principles calculations. Here, 26 alloying elements are considered: Al, Co, Cr, Cu, Fe, Hf, Ir, Mn, Mo, Nb, Os, Pd, Pt, Re, Rh, Ru, Sc, Si, Ta, Tc, Ti, V, W, Y, Zn, and Zr. It is found that (i) both the bulk and shear moduli of Ni-X decrease approximately linearly with increasing equilibrium volume, especially within each group of 3d, 4d, or 5d transition-metal alloying elements; (ii) all alloying elements considered herein increase the ratio of bulk to shear modulus (i.e., the ductility) and the elastic anisotropy of the Ni-X alloys; and (iii) the largest decrease of elastic properties of Ni is caused by alloying element Y. It is observed that the change of elastic properties of Ni due to various alloying elements is traceable from the distribution of (magnetization) charge density, for instance the spherical distribution of charge density facilitates shear deformation, resulting in a lower shear-related property. Using a proposed quasistatic approach based on the predicted elasticity-volume-temperature relationship, the isothermal and the isentropic elastic properties are predicted for the dilute Ni-X alloys at finite temperatures, displaying a decreasing trend with respect to temperature for each Ni-X system. Computed elastic properties are in favorable accord with available experimental data.

  15. Effect of molybdenum plus chromium on the corrosion of iron-, nickel-, and cobalt-base alloys in basaltic lava and simulated magmatic gas at 1150/sup 0/C

    SciTech Connect

    Ehrlich, S.A.; Douglass, D.L.

    1982-06-01

    The compatibility of several binary and ternary alloys in a magma environment was studied. Binary alloys containing molybdenum and ternary alloys containing chromium and molybdenum were exposed to basaltic lava at 1150/sup 0/C for periods of 24 and 96 hours. A cover gas was used to produce oxygen and sulfur fugacities corresponding to those of the gases dissolved in basaltic melts. Three base metals were used. These included iron, nickel, and cobalt. The primary reactions in binary alloys were found to be sulfidation. Oxide scales with a spinel layer formed on ternary alloys. The synergistic effect of molybdenum and chromium additions in ternary alloys exhibited superior corrosion resistance to binary alloys which formed base-metal sulfides down grain-boundaries. Extensive analyses of the reaction products by scanning electron microscopy, X-ray energy dispersive analysis, electron microprobe analysis, and metallography are presented for each alloys. The products formed are discussed with reference to thermodynamic stability diagrams, and the reaction path concept is used to explain some of the corrosion.

  16. Interpretation of Fracture Toughness and R-Curve Behavior by Direct Observation of Microfracture Process in Ti-Based Dendrite-Containing Amorphous Alloys

    NASA Astrophysics Data System (ADS)

    Jeon, Changwoo; Kim, Choongnyun Paul; Kim, Hyoung Seop; Lee, Sunghak

    2015-04-01

    Fracture properties of Ti-based amorphous alloys containing ductile β dendrites were explained by directly observing microfracture processes. Three Ti-based amorphous alloys were fabricated by adding Ti, Zr, V, Ni, Al, and Be into a Ti-6Al-4V alloy by a vacuum arc melting method. The effective sizes of dendrites varied from 63 to 104 μm, while their volume fractions were almost constant within the range from 74 to 76 pct. The observation of the microfracture of the alloy containing coarse dendrites revealed that a microcrack initiated at the amorphous matrix of the notch tip and propagated along the amorphous matrix. In the alloy containing fine dendrites, the crack propagation was frequently blocked by dendrites, and many deformation bands were formed near or in front of the propagating crack, thereby resulting in a zig-zag fracture path. Crack initiation toughness was almost the same at 35 to 36 MPa√m within error ranges in the three alloys because it was heavily affected by the stress applied to the specimen at the time of crack initiation at the crack tip as well as strength levels of the alloys. According to the R-curve behavior, however, the best overall fracture properties in the alloy containing fine dendrites were explained by mechanisms of blocking of the crack growth and crack blunting and deformation band formation at dendrites.

  17. Control of gigahertz permeability and permittivity dispersion by means of nanocrystallization in FeCo based nanocrystalline alloy

    NASA Astrophysics Data System (ADS)

    Han, Mangui; Lu, Haipeng; Deng, Longjiang

    2010-11-01

    An amorphous (FeCo) based alloy has been prepared by a rapid quench method. Subsequent annealing on the amorphous samples gives rise to the coexistence of two magnetic phases: amorphous matrix and nanocrystalline grains (α'-FeCo) with an average size of 9.8 nm. Permeability dispersion behaviors have been studied by Kittel theory [C. Kittel, J. Phys. Radium 12, 332 (1951)]. The results show that these two magnetic phases contribute to the permeability dispersion. The Cole-Cole dispersion law [K. S. Cole and R. H. Cole, J. Chem. Phys. 9, 341 (1941)] has been employed to explain the permittivity dispersion within microwave region based on the assumption that multiple dielectric relaxation processes existing. Our results indicate the possibility of tuning the high frequency permeability and permittivity values of (FeCo) based alloy by controlling the magnetic microstructure, which suggests an alternative method to develop smart electromagnetic materials.

  18. Effect of Creep and Oxidation on Reduced Creep-Fatigue life of Ni-based Alloy 617 at 850 C

    SciTech Connect

    Chen, Xiang; Yang, Zhiqing; Sokolov, Mikhail A; ERDMAN III, DONALD L; Mo, Kun; Stubbins, James

    2014-01-01

    Low cycle fatigue (LCF) and creep fatigue testing of Ni-based alloy 617 was carried out at 850 C. Compared with its LCF life, the material s creep fatigue life decreases to different extents depending on test conditions. To elucidate the microstructure-fatigue property relationship for alloy 617 and the effect of creep and oxidation on its fatigue life, systematic microstructural investigations were carried out using scanning electron microscopy, energy-dispersive X-ray spectroscopy, and electron backscatter diffraction (EBSD). In LCF tests, as the total strain range increased, deformations concentrated near high angle grain boundaries (HAGBs). The strain hold period in the creep fatigue tests introduced additional creep damage to the material, which revealed the detrimental effect of the strain hold time on the material fatigue life in two ways. First, the strain hold time enhanced the localized deformation near HAGBs, resulting in the promotion of intergranular cracking of alloy 617. Second, the strain hold time encouraged grain boundary sliding, which resulted in interior intergranular cracking of the material. Oxidation accelerated the initiation of intergranular cracking in alloy 617. In the crack propagation stage, if oxidation was promoted and the cyclic oxidation damage was greater than the fatigue damage, oxidation-assisted intergranular crack growth resulted in a significant reduction in the material s fatigue life.

  19. PROCESSING, MICROSTRUCTURE AND CREEP BEHAVIOR OF MO-SI-B-BASED INTERMETALLIC ALLOYS FOR VERY HIGH TEMPERATURE STRUCTURAL APPLICATIONS

    SciTech Connect

    Vijay K. Vasudevan

    2005-02-08

    This research project is concerned with developing a fundamental understanding of the effects of processing and microstructure on the creep behavior of refractory intermetallic alloys based on the Mo-Si-B system. During this year, the microstructure, bend strength and compressive creep behavior of a Mo-3Si-1B (in wt.%) alloy were studied. The microstructure of this alloy was three-phase, being composed of {alpha}-Mo, Mo{sub 3}Si and T2-Mo{sub 5}SiB{sub 2} phases. The elastic limit strength of the alloy remained quite high until 1200 C with a value of 800MPa, but dropped rapidly thereafter to a value of 220 MPa at 1400 C. Results of compressive creep tests at 1200 C showed that the creep rates were quite high and varied nearly linearly with stress between 250 and 500 MPa, which suggests that diffusional mechanisms dominate the creep process. Microstructural observations of post-crept samples indicated the presence of many voids in the {alpha}-Mo grains and few cracks in the intermetallic particles and along their interfaces with the {alpha}-Mo matrix. These results and presented and discussed.

  20. 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.