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Sample records for al fe ti

  1. Investigation of Phase Equilibria and Some Properties of Alloys of Ti-Al-Fe and Ti-Al-V Systems,

    DTIC Science & Technology

    Some data on the structure and properties of Ti-Al-Fe alloys are presented. The phase equilibria in alloys in the system Ti-Al-V were studies...However, the data available in the literature on phase equilibria in the systems Ti-Al-Fe and Ti-Al-V require refinement, as they are insufficiently

  2. Oxidation Resistant Ti-Al-Fe Diffusion Barrier for FeCrAlY Coatings on Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialke, James L. (Inventor); Brindley, William J. (Inventor)

    1996-01-01

    A diffusion barrier to help protect titanium aluminide alloys, including the coated alloys of the TiAl gamma + Ti3Al (alpha2) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C is disclosed. The coating may comprise FeCrAlX alloys. The diffusion barrier comprises titanium, aluminum, and iron in the following approximate atomic percent: Ti-(50-55)Al-(9-20)Fe. This alloy is also suitable as an oxidative or structural coating for such substrates.

  3. Decomposition of Al2.7Fe0.3Ti in heated Al-Al2.7Fe0.3Ti refiner fabricated by spark plasma sintering and its refining performance

    NASA Astrophysics Data System (ADS)

    Watanabe, Yoshimi; Hamada, Takayuki; Sato, Hisashi

    2017-01-01

    In our previous study, a novel Al-L12-type Al2.7Fe0.3Ti refiner was fabricated by spark plasma sintering (SPS) and its refining performance was studied. It was found that L12-type Al2.7Fe0.3Ti particles can be favorable heterogeneous nucleation sites for Al casts, since the lattice matching between Al2.7Fe0.3Ti and Al is good. It was also found that the thermal stability of heterogeneous nucleation sites affects the grain-refining performance. In this study, the decomposition phenomena of the Al2.7Fe0.3Ti phase in a refiner are studied by heating an Al-Al2.7Fe0.3Ti refiner fabricated by SPS. In addition, the refining performance of a heated Al-Al2.7Fe0.3Ti refiner is investigated.

  4. FeAl-TiC and FeAl-WC composites - melt infiltration processing, microstructure and mechanical properties

    SciTech Connect

    Subramanian, R.; Schneibel, J.H.

    1997-04-01

    TiC-based and WC-based cermets were processed with iron aluminide, an intermetallic, as a binder by pressureless melt infiltration to near full density (> 97 % theoretical density). Phase equilibria calculations in the quaternary Fe-Al-Ti-C and Fe-Al-W-C systems at 145{degrees}C were performed to determine the solubility of the carbide phases in liquid iron aluminide. This was done by using Thermocalc{trademark} and the results show that molten Fe-40 at.% Al in equilibrium with Ti{sub 0.512}C{sub 0.488} and graphite, dissolves 4.9 at% carbon and 64 atomic ppm titanium. In the Fe-Al-W-C system, liquid Fe-40 at.% Al in equilibrium with graphite dissolves about 5 at.% carbon and 1 at.% tungsten. Due to the low values for the solubility of the carbide phases in liquid iron aluminide, liquid phase sintering of mixed powders does not yield a dense, homogeneous microstructure for carbide volume fractions greater than 0.70. Melt infiltration of molten FeAl into TiC and WC preforms serves as a successful approach to process cermets with carbide contents ranging from 70 to 90 vol. %, to greater than 97% of theoretical density. Also, the microstructures of cermets prepared by melt infiltration were very homogeneous. Typical properties such as hardness, bend strength and fracture toughness are reported. SEM observations of fracture surfaces suggest the improved fracture toughness to result from the ductility of the intermetallic phase. Preliminary experiments for the evaluation of the oxidation resistance of iron aluminide bonded cermets indicate that they are more resistant than WC-Co cermets.

  5. Investigation on Tool Life and Surface Integrity when Drilling Ti-6Al-4V and Ti-5Al-4V-Mo/Fe

    NASA Astrophysics Data System (ADS)

    Rahim, Erween Abd.; Sharif, Safian

    Machinability study on the drilling of two alpha beta titanium alloy series, Ti-6Al-4V and Ti-5Al-4V-0.6Mo-0.4Fe were conducted using an uncoated carbide drill. The effect of cutting speed on tool life, tool failure mode, cutting force and surface integrity of the drilled surface were discussed. Results showed that Ti-6Al-4V exhibited a more superior machinability property when compared to the Ti-5Al-4V-Mo/Fe alloy system. The tool wear progression when drilling Ti-6Al-4V was lower than that of Ti-5Al-4V-Mo/Fe. The tool experienced similar failure mechanisms which were non uniform wear and chipping when drilling both alloys. At high cutting speed and after prolonged machining, excessive plastic deformation was observed on the subsurface layer of the drilled surface which resulted in increase in the hardness value.

  6. Electrochemical corrosion behavior and elasticity properties of Ti-6Al-xFe alloys for biomedical applications.

    PubMed

    Lu, Jinwen; Zhao, Yongqing; Niu, Hongzhi; Zhang, Yusheng; Du, Yuzhou; Zhang, Wei; Huo, Wangtu

    2016-05-01

    The present study is to investigate the microstructural characteristics, electrochemical corrosion behavior and elasticity properties of Ti-6Al-xFe alloys with Fe addition for biomedical application, and Ti-6Al-4V alloy with two-phase (α+β) microstructure is also studied as a comparison. Microstructural characterization reveals that the phase and crystal structure are sensitive to the Fe content. Ti-6Al alloy displays feather-like hexagonal α phase, and Ti-6Al-1Fe exhibits coarse lath structure of hexagonal α phase and a small amount of β phase. Ti-6Al-2Fe and Ti-6Al-4Fe alloys are dominated by elongated, equiaxed α phase and retained β phase, but the size of α phase particle in Ti-6Al-4Fe alloy is much smaller than that in Ti-6Al-2Fe alloy. The corrosion resistance of these alloys is determined in SBF solution at 37 °C. It is found that the alloys spontaneously form a passive oxide film on their surface after immersion for 500 s, and then they are stable for polarizations up to 0 VSCE. In comparison with Ti-6Al and Ti-6Al-4V alloys, Ti-6Al-xFe alloys exhibit better corrosion resistance with lower anodic current densities, larger polarization resistances and higher open-circuit potentials. The passive layers show stable characteristics, and the wide frequency ranges displaying capacitive characteristics occur for high iron contents. Elasticity experiments are performed to evaluate the elasticity property at room temperature. Ti-6Al-4Fe alloy has the lowest Young's modulus (112 GPa) and exhibits the highest strength/modulus ratios as large as 8.6, which is similar to that of c.p. Ti (8.5). These characteristics of Ti-6Al-xFe alloys form the basis of a great potential to be used as biomedical implantation materials.

  7. Mechanical Properties of In-Situ FeAl-TiB2 Intermetallic Matrix Composites

    NASA Astrophysics Data System (ADS)

    Kim, Jonghoon; Park, Bonggyu; Park, Yongho; Park, Ikmin; Lee, Heesoo

    Intermetallic matrix composites reinforced with ceramic particles have received a great deal of attention. Iron aluminide is known to be a good material for the matrix in such composites. Two processes were used to fabricate FeAl-TiB2 intermetallic matrix composites. One was liquid melt in-situ mixing, and the other was arc melting and suction casting processes. FeAl-TiB2 IMCs obtained by two different methods were investigated to elucidate the influence of TiB2 content. In both methods, the grain size in the FeAl alloy decreased with the presence of titanium diboride. The grain size of in-situ FeAl-TiB2 IMCs became smaller than that of arc FeAl-TiB2 IMCs. Significant increase in fracture stress and hardness was achieved in the composites. The in-situ process gives clean, contamination-free matrix/reinforcement interface which maintained good bonding causing high load bearing capability. This contributed to the increase in the mechanical properties of composites.

  8. Effects of TiFe Intermetallic Compounds on the Tensile Behavior of Ti-4Al-4Fe-0.25Si Alloy

    NASA Astrophysics Data System (ADS)

    Lee, Sang Won; Kim, Kyong Min; Park, Chan Hee; Hong, Jea Keun; Yeom, Jong-Taek; Shih, Donald S.

    2017-02-01

    The effect of the B2 (ordered BCC) intermetallic compound TiFe on the tensile behavior of the Ti-4Al-4Fe-0.25Si alloy was investigated. The nucleation mechanism of TiFe was dependent on the solution temperature, and the solution treatment and aging temperatures were also important to the final alloy. The presence of intra-granular TiFe, which nucleated at α' (HCP) sites during aging, resulted in alloy brittleness. Alternatively, the presence of inter-granular TiFe, which nucleated only at nano-sized α (HCP) sites during aging, resulted in an excellent combination of strength and ductility compared to the original microstructure.

  9. Enhanced Homogenization of Vanadium in Spark Plasma Sintering of Ti-10V-2Fe-3Al Alloy from Titanium and V-Fe-Al Master Alloy Powder Blends

    NASA Astrophysics Data System (ADS)

    Yang, Y. F.; Imai, H.; Kondoh, K.; Qian, M.

    2017-02-01

    Strong and ductile powder metallurgy (PM) Ti-10V-2Fe-3Al alloy has been fabricated by spark plasma sintering (SPS) of titanium and V-Fe-Al master alloy powder blends at 1100°C for 30 min under 30 MPa. The homogenization of vanadium, which dictates the realization of a uniform microstructure of the Ti-10V-2Fe-3Al alloy, was markedly accelerated by SPS. The mechanism is attributed to the intensive Joule heating effect produced by the direct current passing through the electric conducting powder blends, rather than through spark plasma discharge, because homogenization occurred mainly after near full identification had been achieved. The chemical and microstructural homogeneity ensured the achievement of excellent tensile properties of PM Ti-10V-2Fe-3Al in the as-sintered state, with tensile strength >1250 MPa and elongation >10%.

  10. Microstructures and Mechanical Properties of NiTiFeAlCu High-Entropy Alloys with Exceptional Nano-precipitates

    NASA Astrophysics Data System (ADS)

    Zhang, Yanqiu; Wang, Sibing; Jiang, Shuyong; Zhu, Xiaoming; Sun, Dong

    2017-01-01

    Three novel NiTiFeAlCu high-entropy alloys, which consist of nano-precipitates with face-centered cubic structure and matrix with body-centered cubic structure, were fabricated to investigate microstructures and mechanical properties. With the increase in Ni and Ti contents, the strength of NiTiFeAlCu alloy is enhanced, while the plasticity of NiTiFeAlCu alloy is lowered. Plenty of dislocations can be observed in the Ni32Ti32Fe12Al12Cu12 high-entropy alloy. The size of nano-precipitates decreases with the increase in Ni and Ti contents, while lattice distortion becomes more and more severe with the increase in Ni and Ti contents. The existence of nano-precipitates, dislocations and lattice distortion is responsible for the increase in the strength of NiTiFeAlCu alloy, but it has an adverse influence on the plasticity of NiTiFeAlCu alloy. Ni20Ti20Fe20Al20Cu20 alloy exhibits the substantial ability of plastic deformation and a characteristic of steady flow at 850 and 1000 °C. This phenomenon is attributed to a competition between the increase in the dislocation density induced by plastic strain and the decrease in the dislocation density due to the dynamic recrystallization.

  11. Microstructures and Mechanical Properties of NiTiFeAlCu High-Entropy Alloys with Exceptional Nano-precipitates

    NASA Astrophysics Data System (ADS)

    Zhang, Yanqiu; Wang, Sibing; Jiang, Shuyong; Zhu, Xiaoming; Sun, Dong

    2016-10-01

    Three novel NiTiFeAlCu high-entropy alloys, which consist of nano-precipitates with face-centered cubic structure and matrix with body-centered cubic structure, were fabricated to investigate microstructures and mechanical properties. With the increase in Ni and Ti contents, the strength of NiTiFeAlCu alloy is enhanced, while the plasticity of NiTiFeAlCu alloy is lowered. Plenty of dislocations can be observed in the Ni32Ti32Fe12Al12Cu12 high-entropy alloy. The size of nano-precipitates decreases with the increase in Ni and Ti contents, while lattice distortion becomes more and more severe with the increase in Ni and Ti contents. The existence of nano-precipitates, dislocations and lattice distortion is responsible for the increase in the strength of NiTiFeAlCu alloy, but it has an adverse influence on the plasticity of NiTiFeAlCu alloy. Ni20Ti20Fe20Al20Cu20 alloy exhibits the substantial ability of plastic deformation and a characteristic of steady flow at 850 and 1000 °C. This phenomenon is attributed to a competition between the increase in the dislocation density induced by plastic strain and the decrease in the dislocation density due to the dynamic recrystallization.

  12. Influence of Ti and V substitution for Al on the properties of Nd 60Fe 30Al 10 alloys

    NASA Astrophysics Data System (ADS)

    Chau, N.; Luong, N. H.; Huu, C. X.; Thep, N. T.; Anh, H. D.

    2003-06-01

    Systems with compositions Nd 60Fe 30Al 10- xTi x and Nd 60Fe 30Al 10- xV x ( x=2, 4, 6, 8, and 10) have been prepared by arc melting and copper mold suction-casting. The cast surface of the samples is partially crystalline. At increasing the Ti or V content, the crystalline fraction in the samples increases and for x=10, the alloys are fully crystalline. Melting temperatures also increase with increasing Ti or V content in the samples. All samples, some of them in a partly crystalline state, exhibit good hard magnetic properties at room temperature. With increasing Ti or V content, the magnetization continuously decreases, whereas both the coercivity and the Curie temperature increase. Thermomagnetic curves measured for all samples at low field exhibit an interesting shape. The temperature dependence of the coercivity of the samples has been determined.

  13. Development of Ti-6Al-4V and Ti-1Al-8V-5Fe Alloys Using Low-Cost TiH2 Powder Feedstock

    SciTech Connect

    Joshi, Vineet V.; Lavender, Curt; Moxon, Vladimir; Duz, Vlad; Nyberg, Eric; Weil, K. Scott

    2012-09-25

    Thermo-mechanical processing was performed on two titanium alloy billets, a beta-titanium alloy (Ti1Al8V5Fe) and an alpha-beta titanium alloy (Ti6Al4V), which had been produced using a novel low-cost powder metallurgy process that relies on the use of TiH2 powder as a feedstock material. The thermomechanical processing was performed in the beta region of the respective alloys to form 16-mm diameter bars. The hot working followed by the heat treatment processes not only eliminated the porosity within the materials but also developed the preferred microstructures. Tensile testing and rotating beam fatigue tests were conducted on the as-rolled and heat-treated materials to evaluate their mechanical properties. The mechanical properties of these alloys matched well with those produced by the conventional ingot processing route.

  14. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel by Atom Probe Tomography

    NASA Astrophysics Data System (ADS)

    Pereloma, E. V.; Stohr, R. A.; Miller, M. K.; Ringer, S. P.

    2009-12-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 °C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe)3Ti and (Ni,Fe)3(Al,Mn) precipitates eventually form after isothermal aging for ~60 seconds. The morphology of the (Ni,Fe)3Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe)3(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe)3Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  15. Observation of Precipitation Evolution in Fe-Ni-Mn-Ti-Al Maraging Steel using Atom Probe Tomography

    SciTech Connect

    Pereloma, E. V.; Stohr, R A; Miller, Michael K; Ringer, S. P.

    2009-01-01

    We describe the full decomposition sequence in an Fe-Ni-Mn-Ti-Al maraging steel during isothermal annealing at 550 C. Following significant pre-precipitation clustering reactions within the supersaturated martensitic solid solution, (Ni,Fe){sub 3}Ti and (Ni,Fe){sub 3}(Al,Mn) precipitates eventually form after isothermal aging for {approx}60 seconds. The morphology of the (Ni,Fe){sub 3}Ti particles changes gradually during aging from predominantly plate-like to rod-like, and, importantly, Mn and Al were observed to segregate to these precipitate/matrix interfaces. The (Ni,Fe){sub 3}(Al,Mn) precipitates occurred at two main locations: uniformly within the matrix and at the periphery of the (Ni,Fe){sub 3}Ti particles. We relate this latter mode of precipitation to the Mn-Al segregation.

  16. Fabrication of Fe-TiC-Al2O3 composites on the surface of steel using a TiO2-Al-C-Fe combustion reaction induced by gas tungsten arc cladding

    NASA Astrophysics Data System (ADS)

    Sharifitabar, Mahmood; Khaki, Jalil Vahdati; Sabzevar, Mohsen Haddad

    2016-02-01

    The aim of the present study was to fabricate Fe-TiC-Al2O3 composites on the surface of medium carbon steel. For this purpose, TiO2-3C and 3TiO2-4Al-3C- xFe (0 ≤ x ≤ 4.6 by mole) mixtures were pre-placed on the surface of a medium carbon steel plate. The mixtures and substrate were then melted using a gas tungsten arc cladding process. The results show that the martensite forms in the layer produced by the TiO2-3C mixture. However, ferrite-Fe3C-TiC phases are the main phases in the microstructure of the clad layer produced by the 3TiO2-4Al-3C mixture. The addition of Fe to the TiO2-4Al-3C reactants with the content from 0 to 20wt% increases the volume fraction of particles, and a composite containing approximately 9vol% TiC and Al2O3 particles forms. This composite substantially improves the substrate hardness. The mechanism by which Fe particles enhance the TiC + Al2O3 volume fraction in the composite is determined.

  17. Elastic moduli of nanocrystalline binary Al alloys with Fe, Co, Ti, Mg and Pb alloying elements

    NASA Astrophysics Data System (ADS)

    Babicheva, Rita I.; Bachurin, Dmitry V.; Dmitriev, Sergey V.; Zhang, Ying; Kok, Shaw Wei; Bai, Lichun; Zhou, Kun

    2016-05-01

    The paper studies the elastic moduli of nanocrystalline (NC) Al and NC binary Al-X alloys (X is Fe, Co, Ti, Mg or Pb) by using molecular dynamics simulations. X atoms in the alloys are either segregated to grain boundaries (GBs) or distributed randomly as in disordered solid solution. At 0 K, the rigidity of the alloys increases with decrease in atomic radii of the alloying elements. An addition of Fe, Co or Ti to the NC Al leads to increase in the Young's E and shear μ moduli, while an alloying with Pb decreases them. The elastic moduli of the alloys depend on a distribution of the alloying elements. The alloys with the random distribution of Fe or Ti demonstrate larger E and μ than those for the corresponding alloys with GB segregations, while the rigidity of the Al-Co alloy is higher for the case of the GB segregations. The moduli E and μ for polycrystalline aggregates of Al and Al-X alloys with randomly distributed X atoms are estimated based on the elastic constants of corresponding single-crystals according to the Voigt-Reuss-Hill approximation, which neglects the contribution of GBs to the rigidity. The results show that GBs in NC materials noticeably reduce their rigidity. Furthermore, the temperature dependence of μ for the NC Al-X alloys is analyzed. Only the Al-Co alloy with GB segregations shows the decrease in μ to the lowest extent in the temperature range of 0-600 K in comparison with the NC pure Al.

  18. Weldability of high toughness Fe-12% Ni alloys containing Ti, Al or Nb

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

    Three exceptionally high-toughness Fe-12%Ni alloys designed for cryogenic service were welded using the GTA welding process. Evaluation of weldability included equivalent energy (KIed) fracture toughness tests, transverse-weld tensile tests at -196 and 25 C and weld crack sensitivity tests. The Fe-12%Ni-0.25%Ti alloy proved extremely weldable for cryogenic applications, having weld and HAZ properties comparable with those of the wrought base alloy. The Fe-12%Ni-0.5%Al had good weld properties only after the weld joint was heat treated. The Fe-12%Ni-0.25%Nb alloy was not considered weldable for cryogenic use because of its poor weld joint properties at -196 C and its susceptibility to hot cracking.

  19. Processing, properties, and wear resistance of aluminides. [Fe[sub 3]Al; Al[sub 3]Ti

    SciTech Connect

    Wright, R.N.; Rabin, B.H.; Wright, J.K.

    1993-03-01

    Fully dense alloys based on Fe[sub 3]Al were produced by reaction synthesis from low cost elemental powders using hot pressing, hot isostatic pressing or Ceracon process. The reaction proceeds by outward spreading of a transient liquid phase from the initial aluminum particle site and precipitation of the compound phase from the liquid. Combustion synthesized material has a very fine grain size that is resistant to coarsening at high temperature because of a high density of fine oxides from the prior particle boundaries. The fine grain size results in approximately twice the yield strength in the reaction synthesized material compared to hot extruded pre-alloyed powder. Combustion synthesis has also been successfully applied to joining Fe[sub 3]Al and to forming coatings on carbon steel substrates. Combustion synthesis has been shown to be viable for fabricating trialuminides from elemental powder compacts. Al[sub 3]Ti, Al[sub 73]Ti[sub 24]Cr[sub 3] and Al[sub 67]Ti[sub 25]Cr[sub 8] were examined. Fully dense, homogeneous materials exhibiting an equiaxed grain structure were produced by conducting reaction and homogenization under pressure, or in a furnace at ambient pressure and subsequently densifying the porous preform by hot consolidation. The tetragonal DO[sub 22] structure was the primary reaction product for all compositions. Most of the Cr remained undissolved after reaction and a homogenization heat treatment at 1200C or above was used to put the Cr into solution and form the desired L1[sub 2] phase.

  20. Experimental determination of coexisting iron titanium oxides in the systems FeTiAlO, FeTiAlMgO, FeTiAlMnO, and FeTiAlMgMnO at 800 and 900°C, 1 4 kbar, and relatively high oxygen fugacity

    NASA Astrophysics Data System (ADS)

    Evans, Bernard W.; Scaillet, Bruno; Kuehner, Scott M.

    2006-08-01

    A synthetic, low-melting rhyolite composition containing TiO2 and iron oxide, with further separate additions of MgO, MnO, and MgO + MnO, was used in hydrothermal experiments to crystallize Ilm-Hem and Usp-Mt solid solutions at 800 and 900°C under redox conditions slightly below nickel nickel oxide (NNO) to ≈ 3 log_{10} f_{{{text{O}}2}} units above the NNO oxygen buffer. These experiments provide calibration of the FeTi-oxide thermometer + oxygen barometer at conditions of temperature and oxygen fugacity poorly covered by previous equilibrium experiments. Isotherms for our data in Roozeboom diagrams of projected %usp vs. %ilm show a change in slope at ≈ 60% ilm, consistent with the second-order transition from FeTi-ordered Ilm to FeTi-disordered Ilm-Hem. This feature of the system accounts for some, but not all, of the differences from earlier thermodynamic calibrations of the thermobarometer. In rhyolite containing 1.0 wt.% MgO, 0.8 wt.% MnO, or MgO + MnO, Usp-Mt crystallized with up to 14% of aluminate components, and Ilm-Hem crystallized with up to 13% geikielite component and 17% pyrophanite component. Relative to the FeTiAlO system, these components displace the ferrite components in Usp-Mt, and the hematite component in Ilm-Hem. As a result, projected contents of ulvöspinel and ilmenite are increased. These changes are attributed to increased non-ideality along joins from end-member hematite and magnetite to their respective Mg- and Mn-bearing titanate and aluminate end-members. The compositional shifts are most pronounced in Ilm-Hem in the range Ilm50 80, a solvus region where the chemical potentials of the hematite and ilmenite components are nearly independent of composition. The solvus gap widens with addition of Mg and even further with Mn. The Bacon Hirschmann correlation of Mg/Mn in Usp-Mt and coexisting Ilm-Hem is displaced toward increasing Mg/Mn in ilmenite with passage from ordered ilmenite to disordered hematite. Orthopyroxene and biotite

  1. Evolution of the electronic structure and physical properties of Fe2MeAl (Me = Ti, V, Cr) Heusler alloys

    NASA Astrophysics Data System (ADS)

    Shreder, E.; Streltsov, S. V.; Svyazhin, A.; Makhnev, A.; Marchenkov, V. V.; Lukoyanov, A.; Weber, H. W.

    2008-01-01

    We present the results of experiments on the optical, electrical and magnetic properties and electronic structure and optical spectrum calculations of the Heusler alloys Fe2TiAl, Fe2VAl and Fe2CrAl. We find that the drastic transformation of the band spectrum, especially near the Fermi level, when replacing the Me element (Me = Ti, V, Cr), is accompanied by a significant change in the electrical and optical properties. The electrical and optical properties of Fe2TiAl are typical for metals. The abnormal behavior of the electrical resistivity and the optical properties in the infrared range for Fe2VAl and Fe2CrAl are determined by electronic states at the Fermi level. Both the optical spectroscopic measurements and the theoretical calculations demonstrate the presence of low-energy gaps in the band spectrum of the Heusler alloys. In addition, we demonstrate that the formation of Fe clusters may be responsible for the large enhancement of the total magnetic moment in Fe2CrAl.

  2. Galvanomagnetic properties of Fe{sub 2}YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    SciTech Connect

    Kourov, N. I. Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-15

    The Hall effect and the magnetoresistance of Fe{sub 2}YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit (H > 10 kOe), the value and the sign of the normal (R{sub 0}) and anomalous (R{sub s}) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R{sub s} in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio (R{sub s} ∝ ρ{sub 0}{sup 3.1}), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  3. Galvanomagnetic properties of Fe2YZ (Y = Ti, V, Cr, Mn, Fe, Ni; Z = Al, Si) heusler alloys

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2015-11-01

    The Hall effect and the magnetoresistance of Fe2YZ Heusler alloys, where Y = Ti, V, Cr, Mn, Fe, and Ni, are the 3 d transition metals and Z = Al and Si are the s, p elements of the third period of the periodic table, are studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. It is shown that, in the high-field limit ( H > 10 kOe), the value and the sign of the normal ( R 0) and anomalous ( R s ) Hall coefficients change anomalously during transition from paramagnetic (Y = Ti, V) to ferromagnetic (Y = Cr, Mn, Fe, Ni) alloys. These coefficients have different signs for all alloys. Constant R s in the ferromagnetic alloys is positive, proportional to the residual resistivity ratio ( R s ∝ ρ 0 3.1 ), and inversely proportional to spontaneous magnetization. The magnetoresistance of the alloys is a few percent and has a negative sign. A positive addition to transverse magnetoresistance is only detected in high magnetic fields, H > 10 kOe.

  4. Fracture characteristics, microstructure, and tissue reaction of Ti-5Al-2.5Fe for orthopedic surgery

    NASA Astrophysics Data System (ADS)

    Niinomi, Mitsuo; Kobayashi, Toshiro; Toriyama, Osamu; Kawakami, Noriaki; Ishida, Yoshihito; Matsuyama, Yukihiro

    1996-12-01

    The microstructure of Ti-5Al-2.5Fe, which is expected to be used widely as an implant material not only for artificial hip joints but also for instrumentations of scoliosis surgery, was variously changed by heat treatments. The effect of the microstructure on mechanical properties, fracture toughness, and rotating-bending fatigue strength in the air and simulated body environment, that is, Ringer’s solution, was then investigated. Furthermore, the effect of the living body environment on mechanical properties and fracture toughness in Ti-5Al-2.5Fe were investigated on the specimens implanted into rabbit for about 11 months. The data of Ti-5Al-2.5Fe were compared with those of Ti-6Al-4V ELI, which has been used as an implant material mainly for artificial hip joints, and SUS 316L, which has been used as an implant material for many parts, including the instrumentation of scoliosis surgery. The equiaxed α structure, which is formed by annealing at a temperature below β transus, gives the best balance of strength and ductility in Ti-5Al-2.5Fe. The coarse Widmanstätten α structure, which is formed by solutionizing over β transus followed by air cooling and aging, gives the greatest fracture toughness in Ti-5Al-2.5Fe. This trend is similar to that reported in Ti-6Al-4V ELI. The rotating-bending fatigue strength is the greatest in the equiaxed α structure, which is formed by solutionizing below β transus followed by air cooling and aging in Ti-5Al-2.5Fe. Ti-5Al-2.5Fe exhibits much greater rotating-bending fatigue strength compared with SUS 316L, and equivalent rotating-bending fatigue strength to that of Ti-6Al-4V ELI in both the air and simulated body environments. The rotating-bending fatigue strength of SUS 316L is degraded in the simulated body environment. The corrosion fatigue, therefore, occurs in SUS 316L in the simulated body environment. Fatigue strength of Ti-5Al-2.5Fe in the simulated body environment is degraded by lowering oxygen content in the

  5. Mg, Al, Si, Ca, Ti, Fe, and Ni abundance for a sample of solar analogues

    NASA Astrophysics Data System (ADS)

    López-Valdivia, Ricardo; Bertone, Emanuele; Chávez, Miguel

    2017-01-01

    We report on the determination of chemical abundances of 38 solar analogues, including 11 objects previously identified as super metal-rich stars. We have measured the equivalent widths for 34 lines of 7 different chemical elements (Mg, Al, Si, Ca, Ti, Fe, and Ni) in high-resolution (R ˜ 80 000) spectroscopic images, obtained at the Observatorio Astrofísico Guillermo Haro (Sonora, Mexico), with the Cananea High-resolution Spectrograph. We derived chemical abundances using ATLAS12 model atmospheres and the Fortran code MOOG. We confirmed the super metallicity status of 6 solar analogues. Within our sample, BD+60 600 is the most metal-rich star ([Fe/H]=+0.35 dex), while for HD 166991 we obtained the lowest iron abundance ([Fe/H]=-0.53 dex). We also computed the so-called [Ref] index for 25 of our solar analogues, and we found, that BD+60 600 ([Ref]=+0.42) and BD+28 3198 ([Ref]=+0.34) are good targets for exoplanet search.

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

    NASA Astrophysics Data System (ADS)

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

    2014-11-01

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

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

    DOE PAGES

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

    2014-11-07

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

  8. New Fe-Co-Ni-Cu-Al-Ti Alloy for Single-Crystal Permanent Magnets

    NASA Astrophysics Data System (ADS)

    Belyaev, I. V.; Bazhenov, V. E.; Moiseev, A. V.; Kireev, A. V.

    2016-03-01

    A new alloy intended for single-crystal permanent magnets has been suggested. The new alloy has been designed based on the well-known Fe-Co-Ni-Cu-Al-Ti system and contains to 1 wt % Hf. The alloy demonstrates an enhanced potential ability for single-crystal forming in the course of unidirectional solidification of ingot. Single-crystal permanent magnets manufactured from this alloy are characterized by a high level of magnetic properties. When designing the new alloy, computer simulation of the phase composition and calculations of solidification parameters of complex metallic systems have been performed using the Thermo-Calc software and calculation and experimental procedures based on quantitative metallographic analysis of quenched structures. After the corresponding heat treatment, the content of high-magnetic phase in the alloy is 10% higher than that in available analogous alloys.

  9. Macrosegregation Behavior of Ti-10V-2Fe-3Al Alloy During Vacuum Consumable Arc Remelting Process

    NASA Astrophysics Data System (ADS)

    Yang, Zhijun; Kou, Hongchao; Li, Jinshan; Hu, Rui; Chang, Hui; Zhou, Lian

    2011-02-01

    The effects of melting current and magnetic field in vacuum consumable arc remelting (VAR) process on the macrosegregation of Ti-10V-2Fe-3Al ingot are investigated in this paper. The results show that Fe content increases gradually from the bottom to the top of ingots along axial direction and the degree of macrosegregation is greater in the radial direction in the middle of the ingot versus the top and bottom. The macrosegregation rate of Fe element is higher with melting current of 2.6 kA than that of 1.7 kA in Ti-10V-2Al-3Fe ingot. There are two forces, buoyancy and Lorentz forces which arise from the flow of current through the pool of VAR when without magnetic stirring, but a new Lorentz force arising from the presence of external inductors occurs with adding magnetic stirring which decreases the macrosegregation rate of Fe element in Ti-10V-2Fe-3Al.

  10. Spray Forming of Bulk Ultrafine-Grained Al-Fe-Cr-Ti

    NASA Astrophysics Data System (ADS)

    Banjongprasert, C.; Hogg, S. C.; Liotti, E.; Kirk, C. A.; Thompson, S. P.; Mi, J.; Grant, P. S.

    2010-12-01

    An Al-2.7Fe-1.9Cr-1.8Ti alloy has been spray formed in bulk and the microstructure and properties compared with those of similar alloys produced by casting, powder aomization (PA), and mechanical alloying (MA) routes. In PA and MA routes, a nanoscale metastable icosahedral phase is usually formed and is known to confer high tensile strength. Unlike previous studies of the spray forming of similar Al-based metastable phase containing alloys that were restricted to small billets with high porosity, standard spray forming conditions were used here to produce a ~98 pct dense 19-kg billet that was hot isostatically pressed (“HIPed”), forged, and/or extruded. The microstructure has been investigated at all stages of processing using scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and synchrotron X-ray diffraction (XRD) at the Diamond Light Source. Consistent with the relatively low cooling rate in spray forming under standard conditions, the microstructure showed no compelling evidence for the formation of metastable icosahedral phases. Nonetheless, after downstream processing, the spray-formed mechanical properties as a function of temperature were very similar to both PA rapid solidification (RS) materials and those made by MA. These aspects have been rationalized in terms of the typical phases, defects, and residual strains produced in each process route.

  11. Low-temperature heat capacity upon the transition from paramagnetic to ferromagnetic Heusler alloys Fe2 MeAl ( Me = Ti, V, Cr, Mn, Fe, Co, Ni)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Lukoyanov, A. V.

    2016-07-01

    The heat capacity of band magnets Fe2 MeAl ( Me = Ti, V, Cr, Mn, Fe, Co, Ni) ordered in crystal structure L21 has been measured in the range 2 K ≤ T ≤ 50 K. The dependences of the Debye temperature ΘD, the Sommerfeld coefficient γ, and the temperature-independent contribution to heat capacity C 0 on the number of valence electrons z in the alloys have been determined.

  12. High-field magnetization of heusler alloys Fe2 XY ( X = Ti, V, Cr, Mn, Fe, Co, Ni; Y = Al, Si)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Korolev, A. V.; Belozerova, K. A.; Weber, H. W.

    2015-10-01

    The magnetization curves of ferromagnetic Heusler alloys Fe2 XY (where X = Ti, V, Cr, Mn, Fe, Co, Ni are transition 3 d elements and Y = Al, Si are the s and p elements of the third period of the Periodic Table) have been measured at T = 4.2 K in the field range H ≤ 70 kOe. It has been shown that the high-field ( H ≥ 20 kOe) magnetization is described within the Stoner model.

  13. High-pressure synthesis of BiFeO3-BiAlO3 and BiFeO3-MnTiO3 solid solution

    NASA Astrophysics Data System (ADS)

    Shimura, Gen; Kusaba, Keiji; Miyawaki, Tetsuya; Niwa, Ken; Asano, Hidefumi; Hasegawa, Masashi

    2013-06-01

    There have been so many investigations for high-pressure synthesis of perovskite-type oxides in the material science field. Multiferroic material is particularly attracted in the field of electronic device materials. BiFeO3 (ferroelectric antiferromagnet) is known as the only Bi-contained perovskite which can be synthesized at ambient pressure. We investigated solid solution systems of BiFeO3-BiAlO3 and BiFeO3-MnTiO3 under high pressure and high temperature to synthesize a new multiferroic compound in the present study. Chemical reagents of simple oxides were mixed with a mortar as a starting material. The mixture was rapped with a gold foil, and it encased in a cubic pressure-medium with a graphite furnace. High pressure experiments were carried out using two DIA-type high pressure apparatuses installed in Nagoya University. X-ray powder diffraction patterns of all recovered specimens were collected using Cu-K α radiation and magnetic susceptibilities for some of the recovered specimens were measured using a vibrating sample magnetometer. In the system of BiFeO3-BiAlO3, the BiFeO3-type solid solution was only obtained in the both Fe- and Al-rich composition. While in the system of BiFeO3-MnTiO3, no solid solutions were observed.

  14. Processing of AlCoCrFeNiTi high entropy alloy by atmospheric plasma spraying

    NASA Astrophysics Data System (ADS)

    Löbel, M.; Lindner, T.; Kohrt, C.; Lampke, T.

    2017-03-01

    High Entropy Alloys (HEA) are gaining increasing interest due to their unique combination of properties. Especially the combination of high mechanical strength and hardness with distinct ductility makes them attractive for numerous applications. One interesting alloy system that exhibits excellent properties in bulk state is AlCoCrFeNiTi. A high strength, wear resistance and high-temperature resistance are the necessary requirements for the application in surface engineering. The suitability of blended, mechanically ball milled and inert gas atomized feedstock powders for the development of atmospheric plasma sprayed (APS) coatings is investigated in this study. The ball milled and inert gas atomized powders were characterized regarding their particle morphology, phase composition, chemical composition and powder size distribution. The microstructure and phase composition of the thermal spray coatings produced with different feedstock materials was investigated and compared with the feedstock material. Furthermore, the Vickers hardness (HV) was measured and the wear behavior under different tribological conditions was tested in ball-on-disk, oscillating wear and scratch tests. The results show that all produced feedstock materials and coatings exhibit a multiphase composition. The coatings produced with inert gas atomized feedstock material provide the best wear resistance and the highest degree of homogeneity.

  15. Ion Nitriding of Ti-10V-2Fe-3Al Alloy for Aerospace Applications

    NASA Astrophysics Data System (ADS)

    Qian, Jin

    In this study, a low-temperature ion nitriding treatment has been developed with the aim of improving the sliding behaviour of Ti-10V-2Fe-3Al, without adverse effects on its strength and ductility. The optimized nitriding treatment was carried out at a temperature of 600°C for 8 hours in a pressure dilute nitriding atmosphere of 67 Pa and 2.9 vol.% N2. The microstructural analysis indicated that the ion nitriding treatment led to the formation of a 0.5 mum thick compound layer. The microhardness measurements revealed the formation of an approximately 35 mum thick nitrogen diffusion zone beneath the compound layer. The tensile test results showed improvements in the tensile and yield strengths of the alloy with a minor decrease in the elongation. The load bearing capacity and friction properties of the nitrided surfaces under sliding were investigated by microscratch tests. It was found that the coefficient of friction values were reduced and the surfaces exhibited an excellent load bearing capacity.

  16. The ductile-brittle size transition of iron aluminide ligaments in an FeAl/TiC composite

    SciTech Connect

    Subramanian, R.; Schneibel, J.H.

    1998-08-10

    The fracture surfaces of FeAl/TiC composites containing 70 vol% TiC were investigated. Since thin iron aluminide ligaments in the composites fractured in a ductile manner, whereas thicker ones fractured by cleavage, a systematic correlation of the fracture mode to the ligament thickness was performed. The results clearly show that FeAl ligaments thicker than about 1--2 {micro}m fracture by cleavage and those smaller in size fracture predominantly in a ductile manner. The ductile failure mode is attributed to the limited dislocation pile-up distance available for very thin ligaments, which prevents high stresses from building up and eliminates cleavage fracture. It is also shown that the ductile-brittle transition size is controlled by alloying and/or heat treatment. No significant dependence of the fracture toughness on the fracture mode would be found.

  17. Isothermal Decomposition of β-Solid Solution in Titanium Alloy Ti - 10 V - 2Fe - 3Al

    NASA Astrophysics Data System (ADS)

    Illarionov, A. G.; Trubochkin, A. V.; Shalaev, A. M.; Illarionova, S. M.; Popov, A. A.

    2017-03-01

    Regular features of variation of structure, phase composition and hardness characteristics in a β-phase-based titanium alloy Ti - 10 V - 2Fe - 3Al subjected to isothermal treatment in a melt of lead and tin for 5 sec - 32 h at 250 - 800 °C after a hold at 860 °C are considered. The types of the phases precipitated in the process of isothermal decomposition of the high-temperature β-solid solution and the dependences of the lattice constant of the β-phase and of the hardness on the temperature-and-time mode of the treatment are determined. Adiagram of isothermal decomposition of the β-solid solution in alloy Ti - 10 V - 2Fe - 3Al is plotted.

  18. Sintering and heat treatment of Al15Ti5Co35Ni25Fe20 high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Górecki, K.; Zýka, J.; Malek, J.; Horvát, J.; Čapek, J.; Bała, P.

    2017-02-01

    The new Al15Ti5Co35Ni25Fe20 high entropy alloy was obtained by the powder metallurgy from the elemental powders (-325 mesh). The obtained alloy should be characterized by the dual BCC + FCC phase microstructure according to the valence electron concentration calculations (VEC=7.9). The main aim of the research was to determine the optimal conditions for sintering and heat treatment of Al15Ti5Co35Ni25Fe20 high entropy alloy. The alloy was sintered for 40 minutes at 600 °C for the preliminary consolidation of the powders and initial diffusion of the material. Then samples were annealed at various temperatures: 700, 800, 900, 1000 °C for 1 hour. Samples after annealing were characterized by the XRD and SEM. For the chosen temperature the annealing time was elongated to 2, 3, 5, 10 and 20 hours. The chemical homogeneity was determined.

  19. Superior Mechanical Properties of AlCoCrFeNiTi x High-Entropy Alloys upon Dynamic Loading

    NASA Astrophysics Data System (ADS)

    Jiao, Z. M.; Ma, S. G.; Chu, M. Y.; Yang, H. J.; Wang, Z. H.; Zhang, Y.; Qiao, J. W.

    2016-02-01

    High-entropy alloys with composition of AlCoCrFeNiTi x ( x: molar ratio; x = 0, 0.2, 0.4) under quasi-static and dynamic compression exhibit excellent mechanical properties. A positive strain-rate sensitivity of yield strength and the strong work-hardening behavior during plastic flows dominate upon dynamic loading in the present alloy system. The constitutive relationships are extracted to model flow behaviors by employing the Johnson-Cook constitutive model. Upon dynamic loading, the ultimate strength and fracture strain of AlCoCrFeNiTi x alloys are superior to most of bulk metallic glasses and in situ metallic glass matrix composites.

  20. Site preference of ternary alloying additions to NiTi: Fe, Pt, Pd, Au, Al, Cu, Zr and Hf

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Noebe, Ronald D.; Mosca, Hugo O.

    2004-01-01

    Atomistic modeling of the site substitution behavior of Pd in NiTi (J. Alloys and Comp. (2004), in press) has been extended to examine the behavior of several other alloying additions, namely, Fe, Pt, Au, Al, Cu, Zr and Hf in this important shape memory alloy. It was found that all elements, to a varying degree, displayed absolute preference for available sites in the deficient sublattice. How- ever, the energetics of the different substitutional schemes, coupled with large scale simulations indicate that the general trend in all cases is for the ternary addition to want to form stronger ordered structures with Ti.

  1. Processing and Properties of Mechanical Alloyed Al93Fe3Cr2Ti2 Alloys

    DTIC Science & Technology

    2004-10-01

    Nanomaterials, Aluminum Alloys ABSTRACT Nanostructured A193Fe3Ti2Cr2 alloys were prepared via mechanical alloying (MA) starting from elemental powders...2Cr2 . The aluminum powder had a purity of 99.5 wt% with a mean particle size of 70 ^rn, while the corresponding values for iron, chromium and...increases. 2) All aluminum reflections exhibit broadening even after only 2-hours of milling, indicating the grain size reduction and possibly the

  2. Impact of CrSiTi and NiSi on the Thermodynamics, Microstructure, and Properties of AlCoCuFe-Based High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-Rong; Wang, Zhao-Qin; Lin, Tie-Song; He, Peng; Sekulic, Dusan P.

    2016-05-01

    Aiming to solve the problem of spontaneous combustion on titanium via electrospark deposition (ESD), two AlCoCuFe-based high-entropy alloys (HEAs), AlCoCuFe- x ( x = CrSiTi, NiSi), were produced by vacuum arc melting as electrodes in ESD process. The thermodynamic analysis of AlCoCuFe-based HEAs were carried out using the concept of mixing enthalpy matrix and a powerful thermodynamic calculation toolbox (HEA-Thermo-Calcu). The microstructure and mechanical properties of the two alloys were investigated. The AlCoCuFeCrSiTi alloy contains a body-centered cubic (BCC) phase and a face-centered cubic (FCC) phase. The AlCoCuFeNiSi alloy is composed of two BCC phases and an FCC phase. Addition of CrSiTi and NiSi to AlCoCuFe-based alloys makes the enthalpy of mixing to be sizably more negative than for the other AlCoCuFe-based HEAs. Notwithstanding the fact that the thermodynamic parameters do not agree with Yang's proposition, the two alloys form simple solid solutions. The electronegativity difference (Δ χ) favors a formation of the solid solution when Δχ ≤ 14.2. The hardness of AlCoCuFe- x ( x = CrSiTi, NiSi) alloys reaches 935 HV and 688 HV, respectively. The yield strength, fracture strength, and ultimate strain of AlCoCuFeNiSi are larger, i.e., 29, 30, and 45%, respectively, than those of the AlCoCuFeCrSiTi alloy.

  3. Specific features of the electrical resistivity of half-metallic ferromagnets Fe2MeAl (Me = Ti, V, Cr, Mn, Fe, Ni)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Marchenkov, V. V.; Belozerova, K. A.; Weber, H. W.

    2014-03-01

    The transport properties of half-metallic ferromagnetic Heusler alloys Fe2MeAl (where Me = Ti, V, Cr, Mn, Fe, and Ni are 3 d transition elements) have been measured in the temperature range of 4-900 K. The specific features in the behavior of the electrical resistivity have been considered in terms of the two-current conduction model, which takes into account the presence of an energy gap in the electron spectrum of the alloys near the Fermi level.

  4. The influence of the X atoms and Al 3p occupied states in AlTiX2(X=Fe,Cu,Co,Ni) intermetallics

    NASA Astrophysics Data System (ADS)

    Fu, Hongzhi; Chen, Dong; Cheng, Xinlu; Gao, Tao; Yang, Xiangdong

    2007-01-01

    The electronic structures of the ternary (Heusler) L21-phase compounds AlTiX2(X=Fe,Cu,Co,Ni) are calculated by first-principles using full potential linearized augmented plane wave (FLAPW) method with the generalized gradient approximation (GGA). The ab initio results are analyzed with a simplified model for Al-based compounds containing transition metal (TM) atoms. The results show that the total density of state (DOS) depends strongly on the positions of TM atoms, and the TM d DOS not only connects with the pseudo-gap which is the indication of the stability of the intermetallic ternary Hume-Rothery (H-R) alloys, but also plays a crucial role in hybridization with other element valence electrons. However, the Al 3s states are repelled far away from the Fermi energy in all studied samples, and the Al 3d states are far more extended-like in the character than the d states. Furthermore, the total DOSs in all the studied samples are modulated by Al 3p states and the Al 3p states are more sensitive than d states to change in the electronic interactions. Then, the Al 3p is also responsible for the major part of the H-R stability of the intermetallic compounds which we have concerned with here. Indeed, the DOSs of the studied alloys show a pseudo-gap near the Fermi level, commonly attributed to the H-R phenomenon. Especially, the AlCu2Ti has more particular flat total DOS than the other AlTiX2 alloys (X=Fe,Co,Ni), which shows the so-called half-metallic behavior or poor metallic character.

  5. Columnar-to-equiaxed transition during the solidification of a Ti-10V-2Fe-3Al alloy

    NASA Astrophysics Data System (ADS)

    Leder, M. O.; Kondrashov, E. N.

    2016-12-01

    The columnar-to-equiaxed transition in the solidification of a Ti-10V-2Fe-3Al alloy is considered during vacuum arc remelting. A GV curve is plotted using a linear model of a multicomponent alloy along with modified Hunt (to determine temperature gradient G as a function of supercooling Δ T) and Ivantsov (to determine the concentrations at the dendrite tip versus liquidus isotherm velocity V) models. The unknown parameters of the models are determined by comparing the results of model calculations with experimental data, which are also obtained in this work. The plotted GV curve is compared with the GV curve of a VT3-1 alloy.

  6. Fe and Ti in Plagioclase From the Lac Saint-Jean Anorthosite: Significance of the Si4O8 and AlAl3SiO8 End-Members in Plagioclase

    NASA Astrophysics Data System (ADS)

    Murakami, H.; Lalonde, A. E.

    2004-05-01

    Plagioclase phenocrysts from the Proterozoic Lac Saint-Jean massif anorthosite have a distinctive black color that is attributed to myriads of oriented μ m-size Fe-Ti oxides. These inclusions have variable composition within the ilmenite-hematite solid solution and are responsible for the black color of the plagioclase. In some plagioclase specimens the fine inclusions have coarsened by Ostwald ripening to acicular grains of hematite ~10 μ m in length. In addition, coarser crystals or clusters of crystals of ilmenite or magnetite, ~1 mm in diameter, are observed and on occasion are rimmed by late amphibole that formed presumably by late deuteric hydration. Electron microprobe and X-ray fluorescence analyses of the plagioclase reveal significant contents of the Si4O8 (up to 2.2 mole %) and AlAl3SiO8 (up to 6.6 mole %) end members. A positive relationship is observed between the content of these two end members. Furthermore, the ratio of Si4O8 to AlAl3SiO8 is between 3 to 4. We believe that the high content of Si4O8 and AlAl3SiO8 in plagioclase, and the presence of minute Fe-Ti oxide inclusions are both products of a late postmagmatic oxidation via the following chemical reactions: 1) 4Ti2+Fe2+Si3O8 + 2O2 -> 4FeTiO3 + 3 Si4O8 2) 12Fe2+Fe2+Si3O8 + 4O2 -> 8Fe3O4 + 9 Si4O8 3) 8Fe2+Al2Si2O8 + 2O2 -> 4Fe2O3 + 3 Si4O8 + 4AlAl3SiO8 4) 4Ti2+Al2Si2O8 + 4Fe2+Al2Si2O8 + 2O2 -> 4FeTiO3 + 3 Si4O8 + 4AlAl3SiO8 These reactions indicate that significant amounts of Fe2+ and Ti2+ were originally present in the tetrahedral and cavity sites of the plagioclase. We conclude that plagioclase in the Lac Saint-Jean anorthosite crystallized under fairly reducing conditions and later underwent postmagmatic oxidation when the plutonic mass was uplifted and came into contact with crustally-derived oxygenated fluids.

  7. Effect of beta flecks on low-cycle fatigue properties of Ti-10V-2Fe-3Al

    SciTech Connect

    Weldong, Z.; Yigang, Z.; Hanquing, Y.

    2000-04-01

    The effect of beta flecks on low-cycle fatigue (LCF) properties was investigated at room temperature for a high-temperature ({alpha} + {beta})-processed and also a {beta}-processed Ti-10V-2Fe-3Al alloy. For both the ({alpha} + {beta})-processed and the {beta}-processed material, beta flecks had a significant influence on LCF and tensile properties. The materials with beta flecks showed a loss in LCF life and ductility. Larger beta flecks resulted in lower LCF life and ductility. It seemed that {beta}-forged material contained much smaller beta flecks but had a similar detrimental effect on LCF properties as the ({alpha} + {beta})-processed one. Based on the diffusion calculation, it could be concluded that chemical composition inhomogeneities could not be reduced by using beta forging in the 820 C {beta} region. Extensive light microscopy and scanning electron microscopy (SEM) observations showed that beta flecks were susceptible to crack nucleation and propagation.

  8. The Molar Volume of FeO-MgO-Fe2O3-Cr2O3-Al2O3-TiO2 Spinels

    NASA Astrophysics Data System (ADS)

    Hamecher, E. A.; Antoshechkina, P. M.; Ghiorso, M. S.; Asimow, P. D.

    2011-12-01

    A new model of molar volume has been calibrated in the spinel supersystem (Mg,Fe2+)(Al,Cr,Fe3+)2O4 - (Mg,Fe2+)2TiO4. A total of 832 X-ray and neutron diffraction experiments performed on spinels at ambient and in situ high-P, T conditions (from the American Mineralogist Crystal Structure Database (Downs and Hall-Wallace, 2003) and other sources) were used to calibrate end-member equations of state and an excess volume model for this system. The effect on molar volume of cation ordering over the octahedral and tetrahedral sites is captured with linear dependence on Mg2+, Al3+, and Fe3+ site occupancy terms. We allowed standard state volumes and coefficients of thermal expansion of the end members to vary within their uncertainties during extraction of the mixing properties, in order to achieve the best fit. Published equations of states of the various spinel end members were analyzed to obtain optimal values of the bulk modulus and its pressure derivative, for each explicit end member. For any spinel composition in the supersystem, the model molar volume is obtained by adding excess volume and cation order-dependent terms to a linear combination of the five end member volumes, estimated at pressure and temperature using the high-T Vinet equation of state. The model has a total of 31 parameters and fits nearly all experiments to within 0.02 J/bar/mol, or better than 0.5% in volume. The model is compared to the current MELTS (Ghiorso and Sack, 1995; Ghiorso et al., 2002) spinel model with a demonstration of the impact of the model difference on the estimated spinel-garnet lherzolite transition pressure. Our primary motivation in this work is the development of a comprehensive spinel molar volume model for use in calibration of activity-composition models of garnet and pyroxene solid solutions. The thermodynamic models, along with a new silicate liquid equation of state, will be incorporated into the next generation MELTS model, xMELTS. The new solid solution models

  9. Lunar highland rocks - Element partitioning among minerals. II - Electron microprobe analyses of Al, P, Ca, Ti, Cr, Mn and Fe in olivine

    NASA Technical Reports Server (NTRS)

    Smith, J. V.; Hansen, E. C.; Steele, I. M.

    1980-01-01

    Lunar olivines from anorthosites, granulitic impactites, and rocks in the Mg-rich plutonic trend were subjected to electron probe measurements for Al, P, Ca, Ti, Cr and Mn, which show that the FeO/MnO ratio for lunar olivines lies between 80 and 110 with little difference among the rock types. The low values of Ca in lunar olivines indicate slow cooling to subsolidus temperatures, with blocking temperatures of about 750 C for 67667 and 1000 C for 60255,73-alpha determined by the Finnerty and Boyd (1978) experiments. An important paradox is noted in the low Ti content of Fe-rich olivines from anorthosites, although both Ti and Fe tend to become enriched in liquid during fractional distillation. Except for Ca and Mn, olivine from anorthosites has lower minor element values than other rock types. Formation from a chemically distinct system is therefore implied.

  10. Gradient Distribution of Martensite Phase in Melt-Spun Ribbons of a Fe-Ni-Ti-Al Alloy.

    PubMed

    Bondar, Volodymyr; Danilchenko, Vitalij; Dzevin, Ievgenij

    2016-12-01

    Metallographic, X-ray diffraction and magnetometric analysis were used to study the regularities of martensitic transformation in melt-spun ribbons of a Fe - 28 wt. % Ni - 2.1 wt. % Ti - 2 wt. % Al - 0.05 wt. % C alloy. The substantial differences in volume fractions of the martensite phase in local regions of thin melt-spun ribbons of the alloy are related to the size effect of the transformation and structural inhomogeneity of the ribbons. The distribution of austenitic grain size in different local areas of melt-spun ribbons is significantly different. The principal factor for changing the completeness of the martensitic transformation is the size effect of transformation. Difference in the martensite volume fraction in local regions of a ribbon is mainly determined by the different volume fractions of ultrafine-grained (500-1000 nm) and nanosized (80-100 nm and less) initial austenite grains, in which the transformation was slowed down or completely suppressed. Other factors almost do not affect the completeness of the martensitic transformation. The strong stabilizing effect of the reverse α-γ transformation with respect to the subsequent direct γ-α transformation in the melt-spun ribbons is also related to the grain size effect.

  11. Gradient Distribution of Martensite Phase in Melt-Spun Ribbons of a Fe-Ni-Ti-Al Alloy

    NASA Astrophysics Data System (ADS)

    Bondar, Volodymyr; Danilchenko, Vitalij; Dzevin, Ievgenij

    2016-02-01

    Metallographic, X-ray diffraction and magnetometric analysis were used to study the regularities of martensitic transformation in melt-spun ribbons of a Fe - 28 wt. % Ni - 2.1 wt. % Ti - 2 wt. % Al - 0.05 wt. % C alloy. The substantial differences in volume fractions of the martensite phase in local regions of thin melt-spun ribbons of the alloy are related to the size effect of the transformation and structural inhomogeneity of the ribbons. The distribution of austenitic grain size in different local areas of melt-spun ribbons is significantly different. The principal factor for changing the completeness of the martensitic transformation is the size effect of transformation. Difference in the martensite volume fraction in local regions of a ribbon is mainly determined by the different volume fractions of ultrafine-grained (500-1000 nm) and nanosized (80-100 nm and less) initial austenite grains, in which the transformation was slowed down or completely suppressed. Other factors almost do not affect the completeness of the martensitic transformation. The strong stabilizing effect of the reverse α-γ transformation with respect to the subsequent direct γ-α transformation in the melt-spun ribbons is also related to the grain size effect.

  12. Dynamic and static strain aging effects in Fe-modified L1[sub 2] Al[sub 3]Ti

    SciTech Connect

    Wu, Z.L.; Pope, D.P.; Vitek, V. . Dept. of Materials Science and Engineering)

    1994-10-01

    Serrations have been observed in the stress-strain curves of Fe-modified L1[sub 2] Al[sub 3] Ti-based alloys at intermediate temperatures and related to dynamic interactions between mobile dislocations and solute atoms, i.e. dynamic strain aging effects. Serrations appear only at intermediate, not at high or low temperatures, because of the following reasons: at high temperatures the diffusivity of the solute atoms is high enough that the solute atoms and dislocations move together, thereby requiring no break-away of the dislocations. At low temperatures the diffusivity of the solute atoms is so low that no dynamic interaction can occur, but a static interaction is observed, instead. Thus the entire range of yielding phenomena can be consistently explained in terms of interactions between solute atoms and mobile dislocations and requires no assumptions about changes in the nature of dislocation cores. The solutes giving rise to this effect are likely of substitutional type but have not been identified.

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

    SciTech Connect

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

    2014-11-07

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

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

    SciTech Connect

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

    2014-11-07

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

  15. Enhanced photocatalytic degradation of humic acids using Al and Fe co-doped TiO2 nanotubes under UV/ozonation for drinking water purification.

    PubMed

    Yuan, Rongfang; Zhou, Beihai; Hua, Duo; Shi, Chunhong

    2013-11-15

    O3/UV/TiO2 was used to effectively decompose humic acids (HAs) in drinking water. To obtain a large specific surface area and low band gap energy, Al and Fe co-doped TiO2 nanotubes were successfully synthesized using the hydrothermal method. The effect of the optimal co-doped TiO2 nanotubes catalyst on the HAs removal efficiency through O3/UV/co-doped TiO2 process was investigated. The highest HAs removal efficiency (79.4%) that exhibited a pseudo-first-order rate constant of 0.172 min(-1) was achieved, in the presence of 550 °C calcined 1.0% co-doped TiO2 nanotubes with an Al:Fe ratio of 0.25:0.75. The effects of calcination temperature and doping concentration on anatase phase weight fractions, average crystallite sizes, Brunauer-Emmett-Teller surface area, catalyst band gap energy, and catalyst photocatalytic activity were also discussed. The inorganic anions also affected the catalyst photocatalytic ability. In a neutral solution, SO4(2-) slightly promoted HAs removal. However, HCO3(-) was found to significantly inhibit the catalyst activity, whereas Cl(-) had negligible effect on photocatalytic ability.

  16. Effect of Ti content on the microstructure and mechanical behavior of (Fe36Ni18Mn33Al13)100–xTix high entropy alloys

    DOE PAGES

    Wang, Zhangwei; Wu, Margaret; Cai, Zhonghou; ...

    2016-06-13

    The microstructure and mechanical properties studies of a series of two-phase f.c.c./B2 (ordered b.c.c.) lamellar-structured, high entropy alloys (HEA) Fe36Ni18Mn33Al13Tix with x up to 6 at. % Ti have been investigated. X-ray microanalysis in a TEM showed that the Ti resided mostly in the B2 phase. The lamellar spacing decreased significantly with increasing Ti content from 1.56 μm for the undoped alloy to 155 nm with an addition of 4 at. % Ti, leading to a sharp increase in room-temperature yield strength,σy, from 270 MPa to 953 MPa, but with a concomitant decrease in ductility from 22% elongation to 2.3%.more » Annealing at 1173 K for 20 h greatly increased the lamellar spacing of Fe36Ni18Mn33Al13Ti4 to 577 nm, producing a corresponding decrease in σy to 511 MPa. The yield strengths of all the doped alloys decreased significantly when tensile tested at 973 K with a concomitant increase in ductility due to softening of the B2 phase. The fracture mode changed from cleavage at room temperature to a ductile dimple-type rupture at 973 K. Lastly, the results are discussed in terms of the Hall-Petch-type relationship.« less

  17. The effects of Ni, Mo, Ti and Si on the mechanical properties of Cr free Mn steel (Fe-25Mn-5Al-2C)

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

    The FeMnAlC alloys may hold potential as Cr-free replacements for high strategic material iron base superalloys, but little is known about their intermediate temperature (650 C to 870 C) mechanical properties. The effects of alloying elements on the mechanical properties of model FeMnAlC alloys were studied. Results showed that modified FeMnAlC alloys had promising short term, intermediate temperature properties but had relatively poor stress rupture lives at 172 MPa and 788 C. Room temperature and 788 C tensile strength of FeMnAlC alloys were better than common cast stainless steels. Changes in room temperature tensile and 788 C tensile strength and ductility, and 788 C stress rupture life were correlated with changes in Ni, Mo, Ti, and Si levels due to alloying effects on interstitial carbon levels and carbide morphology. Fe-25Mn-5Al-2C had a very poor stress rupture life at 172 MPa and 788 C. Addition of carbide-forming elements improved the stress rupture life.

  18. Diffusion Research in BCC Ti-Al-Mo Ternary Alloys

    NASA Astrophysics Data System (ADS)

    Chen, Yi; Tang, Bin; Xu, Guanglong; Wang, Chuanyun; Kou, Hongchao; Li, Jinshan; Cui, Yuwen

    2014-04-01

    Interdiffusion in Ti-Al-Mo β solid solution was investigated at 1523 K (1250 °C) by analyzing diffusion couples. From the concentration profiles analytically represented by error function expansion (ERFEX), the ternary interdiffusion coefficients and impurity diffusivity were extracted by the Whittle-Green and generalized Hall methods. A comparison of the diffusion in five Ti-Al-X (Co, Cr, Fe, Mo, and V) ternaries reveals Ti-Al-Mo is comparably like Ti-Al-(Cr, V) while Ti-Al-(Co, Fe) are predominantly of interstitial nature.

  19. Quantitative Analysis of Dynamic Softening Behaviors Induced by Dynamic Recrystallization for Ti-10V-2Fe-2Al Alloy

    NASA Astrophysics Data System (ADS)

    Quan, Guozheng; Pu, Shiao; Wen, Hairong; Zou, Zhenyu; Zhou, Jie

    2015-10-01

    In order to investigate the effect of dynamic recrystallization (DRX) behavior on dynamic softening behavior of wrought Ti-10V-2Fe-3Al titanium alloy, a series of laboratory scale isothermal hot compression tests with a height reduction of 60% were performed in a temperature range of 948 K 1023 K in the (σ + β) phase field, and a strain rate range of 0.01 10 s-1 on a Gleeble-3500 thermo-mechanical simulator. The flow curves show a continuous softening at all strain rate after peak stress. The constitutive equation and the DRX kinetic mold were established to study the dynamic softening based on the flow curves. By the regression analysis for conventional hyperbolic sine equation, the activation energy was determined as Q = 479.4169 kJ·mol-1, According to the strain hardening rate curves (dσ/dɛ versus σ), two characteristic parameters including the critical strain for DRX initiation (ɛc) and the strain for peak stress (ɛp) were identified, and the linear dependence of the critical strain (ɛc) for DRX initiation on the strain for peak stress (ɛp) can be specified by the equation: ɛc = 0.5667ɛp. A modified Avrami type equation X_{DRX} = 1 - exp[-β_{d}(\\varepsilon - \\varepsilon_c over \\varepsilon_{0.5})k_d] was introduced to characterize the evolution of DRX volume fraction. The evolution of DRX volume was described as the following: for a fixed strain rate, the strain required for the same amount of DRX volume fraction increases with decreasing deformation temperature, in contrast, for a fixed temperature, it increases with increasing strain rate. Finally, the impact of dynamic recrystallized behavior on degree of dynamic softening became weaker and weaker with the increasing of temperature for the strain rate of 0.01 s-1, 0.1 s-1, 1 s-1 and 10 s-1, due to the volume of α phase decreased with the increasing of temperature.

  20. Corrosion of alumina-forming austenitic steel Fe-20Ni-14Cr-3Al-0.6Nb-0.1Ti in supercritical water

    NASA Astrophysics Data System (ADS)

    Nie, S. H.; Chen, Y.; Ren, X.; Sridharan, K.; Allen, T. R.

    2010-04-01

    The oxidation behavior of alumina-forming austenitic (AFA) steel Fe-20Ni-14Cr-3Al-0.6Nb-0.1Ti has been examined after exposure to supercritical water (SCW) at 500 °C and 25 MPa pressure and with a dissolved oxygen content of 25 wppb, for exposure periods of 1300 h, 1700 h and 3000 h. A double layer oxide structure developed on all samples, consisting specifically of a Fe-rich outer hematite layer and an inner layer of Al-Cr-Fe-rich oxide containing a small fraction of FCC Ni-rich metal. Additionally, a thin Ni-rich layer in the bulk alloy close to the oxide/metal interface was also observed. Based on weight gain measurements, the oxidation resistance of the AFA steel was superior to other austenitic alloys, 800H, D9, and 316 stainless steel, tested under similar conditions. The formation of the protective Al-Cr-Fe-rich oxide layer may provide good long-term protection against corrosion in SCW environment.

  1. Specific features of the electrical resistivity of half-metallic ferromagnets Co2 MeAl ( Me = Ti, V, Cr, Mn, Fe)

    NASA Astrophysics Data System (ADS)

    Kourov, N. I.; Perevozchikova, Yu. A.; Weber, H. W.; Marchenkov, V. V.

    2016-07-01

    The transport properties of half-metallic ferromagnetic Heusler alloys Co2 MeAl ( Me = Ti, V, Cr, Mn, Fe are transition 3 d metals) have been measured in the temperature range of 4-900 K. The specific features of the behavior of the resistivity have been considered in the framework of the two-current model of conductivity that takes into account the existence of the energy gap in the electronic spectra of the alloys near the Fermi level of one of electron subbands that differs in the spin direction.

  2. Liquid-solid equilibria involving spinel, ilmenite, and ferropseudobrookite in the system 'FeO'-Al2O3-TiO2 in contact with metallic iron

    NASA Technical Reports Server (NTRS)

    Schreifels, W. A.; Muan, A.

    1975-01-01

    Phase relations in the liquidus temperature region of the system 'FeO'-Al2O3-TiO2 in contact with metallic iron, at a total pressure below 1 atm, have been determined by the quenching technique. Four invariant points have been located, with phase assemblages and temperatures as follows; wuestite, ulvoespinel, nercynite and liquid, 1306 C; ulvoespinel, ilmenite, ferropseudobrookite and liquid, 1340 C; ulvoespinel, hercynite, ferropseudobrookite and liquid, 1367 C; hercynite, ferropseudobrookite, corundum and liquid, 1465 C. The data obtained confirm the presence of a miscibility gap between titanate and aluminate spinels, and provide quantitative data for the effect of Al2O3 on mutual stability relations among spinel, ilmenite, and ferropseudobrookite phases in the presence of liquid at high temperatures and strongly reducing conditions. It is shown that Al2O3 has a strong stabilizing effect on the phase assemblage ferropseudobrookite and spinel relative to ilmenite.

  3. Solid-state reactions during mechanical alloying of ternary Fe-Al-X (X=Ni, Mn, Cu, Ti, Cr, B, Si) systems: A review

    NASA Astrophysics Data System (ADS)

    Hadef, Fatma

    2016-12-01

    The last decade has witnessed an intensive research in the field of nanocrystalline materials due to their enhanced properties. A lot of processing techniques were developed in order to synthesis these novel materials, among them mechanical alloying or high-energy ball milling. In fact, mechanical alloying is one of the most common operations in the processing of solids. It can be used to quickly and easily synthesize a variety of technologically useful materials which are very difficult to manufacture by other techniques. One advantage of MA over many other techniques is that is a solid state technique and consequently problems associated with melting and solidification are bypassed. Special attention is being paid to the synthesis of alloys through reactions mainly occurring in solid state in many metallic ternary Fe-Al-X systems, in order to improve mainly Fe-Al structural and mechanical properties. The results show that nanocrystallization is the common result occurring in all systems during MA process. The aim of this work is to illustrate the uniqueness of MA process to induce phase transformation in metallic Fe-Al-X (X=Ni, Mn, Cu, Ti, Cr, B, Si) systems.

  4. The Relationships Between Microstructure, Tensile Properties and Fatigue Life in Ti-5Al-5V-5Mo-3Cr-0.4Fe (Ti-5553)

    NASA Astrophysics Data System (ADS)

    Foltz, John W., IV

    beta-titanium alloys are being increasingly used in airframes as a way to decrease the weight of the aircraft. As a result of this movement, Ti-5Al-5V-5Mo-3Cr-0.4Fe (Timetal 555), a high-strength beta titanium alloy, is being used on the current generation of landing gear. This alloy features good combinations of strength, ductility, toughness and fatigue life in alpha+beta processed conditions, but little is known about beta-processed conditions. Recent work by the Center for the Accelerated Maturation of Materials (CAMM) research group at The Ohio State University has improved the tensile property knowledge base for beta-processed conditions in this alloy, and this thesis augments the aforementioned development with description of how microstructure affects fatigue life. In this work, beta-processed microstructures have been produced in a Gleeble(TM) thermomechanical simulator and subsequently characterized with a combination of electron and optical microscopy techniques. Four-point bending fatigue tests have been carried out on the material to characterize fatigue life. All the microstructural conditions have been fatigue tested with the maximum test stress equal to 90% of the measured yield strength. The subsequent results from tensile tests, fatigue tests, and microstructural quantification have been analyzed using Bayesian neural networks in an attempt to predict fatigue life using microstructural and tensile inputs. Good correlation has been developed between lifetime predictions and experimental results using microstructure and tensile inputs. Trained Bayesian neural networks have also been used in a predictive fashion to explore functional dependencies between these inputs and fatigue life. In this work, one section discusses the thermal treatments that led to the observed microstructures, and the possible sequence of precipitation that led to these microstructures. The thesis then describes the implications of microstructure on fatigue life and

  5. Microstructure and Wear Behavior of Atmospheric Plasma-Sprayed AlCoCrFeNiTi High-Entropy Alloy Coating

    NASA Astrophysics Data System (ADS)

    Tian, Li-Hui; Xiong, Wei; Liu, Chuan; Lu, Sheng; Fu, Ming

    2016-12-01

    Due to the advantages such as high strength, high hardness and good wear resistance, high-entropy alloys (HEAs) attracted more and more attentions in recent decades. However, most reports on HEAs were limited to bulk materials. Although a few of studies on atmospheric plasma-sprayed (APS) HEA coatings were carried out, the wear behavior, especially the high-temperature wear behavior of those coatings has not been investigated till now. Therefore, in this study, APS was employed to deposit AlCoCrFeNiTi high-entropy alloy coating using mechanically alloyed AlCoCrFeNiTi powder as the feedstock. The phase structure of the initial powder, the feedstock powder and the as-sprayed coating was examined by an x-ray diffractometer. The surface morphology of the feedstock powder and the microstructure of the as-sprayed coating were analyzed by field emission scanning electron microscopy and energy-dispersive spectroscopy. The bonding strength and the microhardness of the as-sprayed coating were tested. The wear behavior of the coating at 25, 500, 700 and 900 °C was investigated by analysis of the wear surface morphology and measurements of the volume wear rate and the coefficient of friction.

  6. A Characterization of Hot Flow Behaviors Involving Different Softening Mechanisms by ANN for As-Forged Ti-10V-2Fe-3Al Alloy

    NASA Astrophysics Data System (ADS)

    Quan, Guo-zheng; Zou, Zhen-yu; Wen, Hai-rong; Pu, Shi-ao; Lv, Wen-quan

    2015-11-01

    The isothermal compressions of as-forged Ti-10V-2Fe-3Al alloy at the deformation temperature range of 948-1,123 K and the strain rates in the range of 0.001-10 s-1 with a height reduction of 60% were conducted on a Gleeble-3500 thermo-mechanical simulator. The flow behaviors show nonlinear sensitivity to strain, strain rate and temperature. Based on the experimental data, an artificial neural network (ANN) with back-propagation algorithm was developed to deal with the complex deformation behavior characteristics. In the present ANN model, strain, strain rate and temperature were taken as inputs, and flow stress as output. A comparative study on the constitutive relationships based on regression and ANN methods was conducted. According to the predicted and experimental results, the predictabilities of the two models have been evaluated in terms of correlation coefficient (R) and average absolute relative error (AARE). The R-value and the AARE-value at strain of 0.5 from the ANN model is 0.9998 and 0.572%, respectively, better than 0.9902 and 6.583% from the regression model. The predicted strain-stress curves outside of experimental conditions indicate similar characteristics with experimental curves. The results have sufficiently articulated that the well-trained ANN model with back-propagation algorithm has excellent capability to deal with the complex flow behaviors of as-forged Ti-10V-2Fe-3Al alloy.

  7. The Influence of Hydrogen on Shape Memory Effect and Superelasticity in [001]-Oriented FeNiCoAlTi Single Crystals

    NASA Astrophysics Data System (ADS)

    Chumlyakov, Yu. I.; Kireeva, I. V.; Platonova, Yu. N.

    2016-04-01

    Using [001]-oriented single crystals of an iron-based alloy (Fe - 28% Ni - 17% Co - 11.5% Al - 2.5% Ti at.%), which were aged at 973 K for 7 h, the influence of hydrogen on the axial-stress temperature response σ0.1(T), the values of shape-memory effect (SME) and superelasticity (SE) is investigated during thermoelastic γ-α'-martensitic transformation (MT) (γ-FCC - face centered lattice, α'-BCT - body centered tetragonal lattice) under tensile conditions. It is found that saturation of [001]-oriented single crystals of the Fe - 28% Ni - 17% Co - 11.5% Al - 2.5% Ti alloy with hydrogen within 2 h at T = 300 K and current density j = 50 mA/cm2 results in lower starting temperature, Ms, of a forward MT during cooling and Md temperature, increased strength properties of the high-temperature phase at Md temperature and wider temperature range of SE observation compared to hydrogen-free crystals. It is shown that hydrogen affects but only slightly the SME and SE values, the temperature and stress hysteresis under the above saturation mode. In [001]-oriented crystals aged at 973 K for 7 h, which are saturated with hydrogen and hydrogen-free, the SME and SE values are found to be equal to 7.8-8 and 6.5-6.9%, respectively.

  8. Ageing behaviour of an Fe-20Ni-1.8Mn-1.6Ti-0.59Al (wt%) maraging alloy: clustering, precipitation and hardening

    SciTech Connect

    Pereloma, E.V. . E-mail: elena.pereloma@spme.monash.edu.au; Shekhter, A.; Miller, M.K.; Ringer, S.P.

    2004-11-08

    Changes in the solute distribution as well as the evolution of precipitation, microstructure and mechanical properties have been studied in an experimental maraging Fe-20Ni-1.8Mn-1.5Ti-0.59Al (wt%) alloy during ageing at 550 deg C. An initial hardening reaction within 5 s is reported, which is remarkable in terms of extent and rapidity. This strengthening was caused by the formation of complex multi-component atomic co-clusters containing primarily Ni-Ti-Al as well as some Mn. This cluster strengthened condition produced the optimum toughness observed throughout the ageing sequence. After 60 s ageing, the appearance of discrete precipitation of needle-shaped {eta}-Ni{sub 3}Ti particles was associated with a second rise in hardness towards an eventual peak at 600 s. This precipitation hardening was accompanied by an increase in tensile strength and a decrease in ductility. A reverse transformation of martensite to austenite occurs progressively during ageing and this contributes to the initial and secondary softening.

  9. Characterisation of a natural quartz crystal as a reference material for microanalytical determination of Ti, Al, Li, Fe, Mn, Ga and Ge

    USGS Publications Warehouse

    Audetat, Andreas; Garbe-Schonberg, Dieter; Kronz, Andreas; Pettke, Thomas; Rusk, Brian G.; Donovan, John J.; Lowers, Heather

    2015-01-01

    A natural smoky quartz crystal from Shandong province, China, was characterised by laser ablation ICP-MS, electron probe microanalysis (EPMA) and solution ICP-MS to determine the concentration of twenty-four trace and ultra trace elements. Our main focus was on Ti quantification because of the increased use of this element for titanium-in-quartz (TitaniQ) thermobarometry. Pieces of a uniform growth zone of 9 mm thickness within the quartz crystal were analysed in four different LA-ICP-MS laboratories, three EPMA laboratories and one solution-ICP-MS laboratory. The results reveal reproducible concentrations of Ti (57 ± 4 μg g-1), Al (154 ± 15 μg g-1), Li (30 ± 2 μg g-1), Fe (2.2 ± 0.3 μg g-1), Mn (0.34 ± 0.04 μg g-1), Ge (1.7 ± 0.2 μg g-1) and Ga (0.020 ± 0.002 μg g-1) and detectable, but less reproducible, concentrations of Be, B, Na, Cu, Zr, Sn and Pb. Concentrations of K, Ca, Sr, Mo, Ag, Sb, Ba and Au were below the limits of detection of all three techniques. The uncertainties on the average concentration determinations by multiple techniques and laboratories for Ti, Al, Li, Fe, Mn, Ga and Ge are low; hence, this quartz can serve as a reference material or a secondary reference material for microanalytical applications involving the quantification of trace elements in quartz.

  10. The Influence of Cooling Rate During Crystallization on the Effective Partitioning Coefficient in High-Entropy Alloys from Al-Ti-Co-Ni-Fe System

    NASA Astrophysics Data System (ADS)

    Górecki, Kamil; Bala, Piotr; Cios, Grzegorz; Koziel, Tomasz; Stępień, Milena; Wieczerzak, Krzysztof

    2016-07-01

    An influence of two different cooling rates on the microstructure and dispersion of the components of high-entropy alloy from Al-Ti-Co-Ni-Fe system has been examined. For investigated alloys, the effective partitioning coefficient has been calculated. This factor indicates the degree of segregation of elements and allows for the specification of the differences between dendrites and interdendritic regions. The obtained results allow for the conclusion that the cooling rate substantially affect the growth of dendrites and the volume fraction of interdendritic regions as well as the partitioning of elements in the alloy. Furthermore, the obtained results made it possible to compare the influence of the cooling rate and the chemical composition on the dispersion of the alloying elements.

  11. Effects of Annealing on the Microstructure and Properties of 6FeNiCoCrAlTiSi High-Entropy Alloy Coating Prepared by Laser Cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Pan, Ye; He, Yizhu

    2011-09-01

    The content of each constituent element in the newly developed high-entropy alloys is always restricted in equimolar or near-equimolar ratios to avoid the formation of complex brittle phases during the solidification process. In this article, a high-entropy alloy coating of 6FeNiCoCrAlTiSi has been prepared by laser cladding and subsequently annealed at 500, 750, 1000, and 1150 °C for 5 h. Surprisingly, the coating has a simple BCC solid solution phase with high microhardness, good resistance to softening, and high electrical resistivity properties. After annealing <750 °C, the coating shows high thermal stability, the electrical resistivity decreases slightly and the microhardness almost remains unchanged. After annealing above 750 °C, the microhardness of the coating slowly decreases with the decomposition of the supersaturated BCC solid solution.

  12. On the effect of incremental forming on alpha phase precipitation and mechanical behavior of beta-Ti-10V-2Fe-3Al

    NASA Astrophysics Data System (ADS)

    Winter, S.; F-X Wagner, M.

    2016-03-01

    A combination of good ductility and fatigue resistance makes β-titanium alloys interesting for many current and potential future applications. The mechanical behavior is primarily determined by microstructural parameters like (beta phase) grain size, morphology and volume fraction of primary / secondary α-phase precipitates, and this allows changing and optimizing their mechanical properties across a wide range. In this study, we investigate the possibility to modify the microstructure of the high-strength beta titanium alloy Ti-10V-2Fe-3Al, with a special focus on shape and volume fraction of primary α-phase. In addition to the conventional strategy for precipitation of primary α, a special thermo-mechanical processing is performed; this processing route combines the conventional heat treatment with incremental forming during the primary α-phase annealing. After incremental forming, considerable variations in terms of microstructure and mechanical properties can be obtained for different thermo-mechanical processing routes. The microstructures of the deformed samples are characterized by globular as well as lamellar (bimodal) α precipitates, whereas conventional annealing only results in the formation of lamellar precipitates. Because of the smaller size, and the lower amount, of α-phase after incremental forming, tensile strength is not as high as after the conventional strategy. However, high amounts of grain boundary α and lamellar αp-phase in the undeformed samples lead to a significantly lower ductility in comparison to the matrix with bimodal structures obtained by thermo-mechanical processing. These results illustrate the potential of incremental forming during the annealing to modify the microstructure of the beta titanium Ti-10V-2Fe-3Al in a wide range of volume fractions and morphologies of the primary α phase, which in turn leads to considerably changes, and improved, mechanical properties.

  13. Structural and magnetic properties of Co{sub 2}Ti{sub 1−x}Fe{sub x}Al (0 ≤ x ≤ 0.5) alloys

    SciTech Connect

    Pal, Lakhan Gupta, Sachin Suresh, K. G.

    2014-04-24

    In this work we studied the effect of partial Fe substitution for Ti on the structural and magnetic properties of the Co{sub 2}TiAl. X-ray diffraction analysis indicates the presence of B2 type disorder for x > 0, (111) reflections are absent for x > 0 which is the characteristic of B2 type disorder. XRD analysis also shows presence of second phase. Magnetization measurements also confirm the presence of dual phase. Curie temperature of the alloys increases with increase in Fe concentration. Saturation magnetic moments agree very well with those calculated by Slater-Pauling rule.

  14. Preparation and radar-absorbing properties of Al2O3/TiO2/Fe2O3/Yb2O3 composite powder

    NASA Astrophysics Data System (ADS)

    Zhang, Yi-fan; Ji, Zhen; Chen, Ke; Jia, Cheng-chang; Yang, Shan-wu; Wang, Meng-ya

    2017-02-01

    Al2O3/TiO2/Fe2O3/Yb2O3 composite powder was synthesized via the sol-gel method. The structure, morphology, and radar-absorption properties of the composite powder were characterized by transmission electron microscopy, X-ray diffraction analysis and RF impedance analysis. The results show that two types of particles exist in the composite powder. One is irregular flakes (100-200 nm) and the other is spherical Al2O3 particles (smaller than 80 nm). Electromagnetic wave attenuation is mostly achieved by dielectric loss. The maximum value of the dissipation factor reaches 0.76 (at 15.68 GHz) in the frequency range of 2-18 GHz. The electromagnetic absorption of waves covers 2-18 GHz with the matching thicknesses of 1.5-4.5 mm. The absorption peak shifts to the lower-frequency area with increasing matching thickness. The effective absorption band covers the frequency range of 2.16-9.76 GHz, and the maximum absorption peak reaches -20.18 dB with a matching thickness of 3.5 mm at a frequency of 3.52 GHz.

  15. Electrochemical evidences for promoted interfacial reactions: the role of Fe(II) adsorbed onto gamma-Al2O3 and TiO2 in reductive transformation of 2-nitrophenol.

    PubMed

    Li, Fang-Bai; Tao, Liang; Feng, Chun-hua; Li, Xiang-Zhong; Sun, Ke-Wen

    2009-05-15

    This study was aimed at elucidating the role of adsorbed Fe(II) on minerals in the reductive transformation of 2-nitrophenol (2-NP) by using electrochemical methods. The studies of Fe(ll) adsorption and 2-NP reduction kinetics showed that the identity of minerals such as gamma-Al2O3 and TiO and the solution pH were crucial factors to determine the Fe(ll) adsorption behavior and to influence the rate constant (k) of 2-NP reduction. Furthermore, two electrochemical methods, cyclic voltammetry (CV) and electrochemical impedance spectrometry (EIS), were applied to characterize the Fe(II) reactivity with both the mineral-coated and mineral-free electrodes. The electrochemical evidence confirmed that the peak oxidation potential (Ep) of complex Fe(II) can be significantly affected by the solution pH;the enhanced reductive transformation of 2-NP can be related to the reduced Ep of surface-complex Fe(II) and the reduced charge transfer resistance (R(CT)) of the Fe(III)/Fe(II) couple. All these relationships were studied quantitatively. At pH 6.7, the measured Ep and R(CT) decreased in the order TiO2/GC < gamma-Al2O3/ GC < GC (Ep, 0.140 < 0.190 < 0.242 V; R(CT), 0.30 < 0.41 < 0.78 komega), while the 2-NP reduction on different minerals were in the order TiO2 > gamma-Al2O3 > nonmineral (k x 10-2, 7.91 > 0.64 > 0.077 min(-l)).

  16. Theoretical investigations of an influence of Ti on electronic structure and magnetic properties of half-metallic Fe2Mn1-xTixSi0.5Al0.5 alloys

    NASA Astrophysics Data System (ADS)

    Go, Anna

    2015-02-01

    Ab-initio electronic structure calculations are carried out for quinternary Fe2Mn1-xTixSi0.5Al0.5 alloys basing on the density functional theory. When x=0, the alloy is a half-metallic ferromagnet with magnetic moment following the Slater-Pauling rule. Main carrier of magnetism of the alloy is manganese with the magnetic moment of about 2.5 μB. Replacement of Mn by Ti, changes its electronic and magnetic structure. Half-metallicity is present up to Ti concentration x=0.375. However, the further increase of Ti content leads to a strong decrease of electronic spin polarization. When the concentration of Ti increases, total magnetic moment strongly decreases. Fe magnetic moment, in the presence of titanium, changes its orientation into antiparallel in respect to the total magnetic moment and its absolute value increases with increasing Ti content. However, absolute value of Fe magnetic moment does not exceed 0.17 μB. Ti exhibits very weak spin polarization with magnetic moment not higher than 0.05 μB.

  17. Microstructure and properties of 6FeNiCoSiCrAlTi high-entropy alloy coating prepared by laser cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Hui; Pan, Ye; He, Yizhu; Jiao, Huisheng

    2011-01-01

    The content of each constituent element in the newly developed high-entropy alloys (HEAs) is always restricted in equimolar or near-equimolar ratio in order to avoid the formation of complex brittle phases during the solidification process. In this study, a 6FeNiCoSiCrAlTi high-entropy alloy coating with simple BCC solid solution phase has been prepared by laser cladding on a low carbon steel substrate. The microstructure, hardness and magnetic properties have been investigated. The experimental results show that the tendency of component segregation in the conventional solidification microstructure of multi-component alloy is effectively relieved. The microstructure of the coating is mainly composed of equiaxed polygonal grains, discontinuous interdendritic segregation and nano-precipitates. EBSD observation confirms that the polygonal grains and interdendritic segregation have similar BCC structure with lots of low angle grain boundaries at the interface. The microhardness of the coating reaches 780 HV 0.5, which is much higher than most of the HEAs prepared by other methods. In addition, the coating shows excellent soft magnetic properties.

  18. Al-Co-Fe (030)

    NASA Astrophysics Data System (ADS)

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

    This document is part of Part 1 http://dx.doi.org/10.1007/9getType="URL"/> 'Systems from Ag-Al-Ca to Au-Pd-Si' of Subvolume B 'Physical Properties of Ternary Amorphous Alloys' of Volume 37 'Phase Diagrams and Physical Properties of Nonequilibrium Alloys' of Landolt-Börnstein - Group III 'Condensed Matter'. It contains the Chapter 'Al-Co-Fe (030)' with the content:

  19. Significance of Elevated Contents of Si4O8 and AlAl3SiO8 End Members in Black Clouded Plagioclase From Anorthosite: Evidence for Oxidation-Induced Postmagmatic Exsolution of Fe-Ti Oxide Inclusions From Plagioclase

    NASA Astrophysics Data System (ADS)

    Murakami, H.; Lalonde, A. E.

    2004-12-01

    Plagioclase phenocrysts from large Proterozoic massif anorthosites that have escaped metamorphic recrystallization commonly have a distinctive black color that is attributed to myriads of minute Fe-Ti oxide inclusions. These inclusions are responsible for the black color of the feldspar. The orientation of these inclusions along specific crystallographic directions in the plagioclase is strong evidence that these formed by exsolution from the plagioclase. Plagioclase from the Proterozoic Lac Saint-Jean anorthosite in Québec is a good example of such clouded feldspar. In this plagioclase we recognize four types of Fe-Ti oxide inclusions: 1) Myriads of fine, submicroscopic and unidentifiable dust-like inclusions, presumably Fe-Ti oxides, and responsible in great part for the black color. 2) Small ˜1 μ m sized crystals of hemo-ilmenite that occur in regions of the plagioclase that are free of type 1 dust, suggesting that these originated by Ostwald ripening from the dusty material. 3) Larger aligned and acicular crystals of hematite, ˜10 μ m in diameter and with good rhombohedral sections. These occur, like type 2 inclusions, in zones free of type 1 dust suggesting again that they result from Ostwald ripening. 4) Millimetric inclusions of ilmenite or magnetite of magmatic origin, often rimmed by amphibole or biotite, signs of late hydration. As part of our study, EPMA analyses of plagioclase from Lac Saint-Jean were done. In addition, a large single crystal, ˜30 cm in diameter was analyzed by bulk XRF. Our results show that plagioclase contains significant amounts of the Si4O8 (up to 6.6 mole %) and AlAl3SiO8 (up to 2.2 mole %) endmembers. A positive relationship is observed between the content of these two endmembers. Furthermore, the ratio of Si4O8 to AlAl3SiO8 is approximately 3:4. We believe that the high content of Si4O8 and AlAl3SiO8 in plagioclase, and the presence of minute Fe-Ti oxide inclusions are both products of a late postmagmatic oxidation via the

  20. A new insight into high-strength Ti62Nb12.2Fe13.6Co6.4Al5.8 alloys with bimodal microstructure fabricated by semi-solid sintering

    PubMed Central

    Liu, L. H.; Yang, C.; Kang, L. M.; Qu, S. G.; Li, X. Q.; Zhang, W. W.; Chen, W. P.; Li, Y. Y.; Li, P. J.; Zhang, L. C.

    2016-01-01

    It is well known that semi-solid forming could only obtain coarse-grained microstructure in a few alloy systems with a low melting point, such as aluminum and magnesium alloys. This work presents that semi-solid forming could also produce novel bimodal microstructure composed of nanostructured matrix and micro-sized (CoFe)Ti2 twins in a titanium alloy, Ti62Nb12.2Fe13.6Co6.4Al5.8. The semi-solid sintering induced by eutectic transformation to form a bimodal microstructure in Ti62Nb12.2Fe13.6Co6.4Al5.8 alloy is a fundamentally different approach from other known methods. The fabricated alloy exhibits high yield strength of 1790 MPa and plastic strain of 15.5%. The novel idea provides a new insight into obtaining nano-grain or bimodal microstructure in alloy systems with high melting point by semi-solid forming and into fabricating high-performance metallic alloys in structural applications. PMID:27029858

  1. A new insight into high-strength Ti62Nb12.2Fe13.6Co6.4Al5.8 alloys with bimodal microstructure fabricated by semi-solid sintering

    NASA Astrophysics Data System (ADS)

    Liu, L. H.; Yang, C.; Kang, L. M.; Qu, S. G.; Li, X. Q.; Zhang, W. W.; Chen, W. P.; Li, Y. Y.; Li, P. J.; Zhang, L. C.

    2016-03-01

    It is well known that semi-solid forming could only obtain coarse-grained microstructure in a few alloy systems with a low melting point, such as aluminum and magnesium alloys. This work presents that semi-solid forming could also produce novel bimodal microstructure composed of nanostructured matrix and micro-sized (CoFe)Ti2 twins in a titanium alloy, Ti62Nb12.2Fe13.6Co6.4Al5.8. The semi-solid sintering induced by eutectic transformation to form a bimodal microstructure in Ti62Nb12.2Fe13.6Co6.4Al5.8 alloy is a fundamentally different approach from other known methods. The fabricated alloy exhibits high yield strength of 1790 MPa and plastic strain of 15.5%. The novel idea provides a new insight into obtaining nano-grain or bimodal microstructure in alloy systems with high melting point by semi-solid forming and into fabricating high-performance metallic alloys in structural applications.

  2. Rapidly solidified NiAl and FeAl

    NASA Technical Reports Server (NTRS)

    Gaydosh, D. J.; Crimp, M. A.

    1984-01-01

    Melt spinning was used to produce rapidly solidified ribbons of the B2 intermetallics NiAl and FeAl. Both Fe-40Al and Fe-45Al possessed some bend ductility in the as spun condition. The bend ductility of Fe-40Al, Fe-45Al, and equiatomic NiAl increased with subsequent heat treatment. Heat treatment at approximately 0.85 T (sub m) resulted in significant grain growth in equiatomic FeAl and in all the NiAl compositions. Low bend ductility in both FeAl and NiAl generally coincided with intergranular failure, while increased bend ductility was characterized by increasing amounts of transgranular cleavage fracture.

  3. Ultrasonic Characterization of Microstructural Changes in Ti-10V-4.5Fe-1.5Al β-Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Viswanath, A.; Kumar, Anish; Jayakumar, T.; Purnachandra Rao, B.

    2015-08-01

    Ultrasonic measurements have been carried out in Ti-10V-4.5Fe-1.5Al β-titanium alloy specimens subjected to β annealing at 1173 K (900 °C) for 1 hour followed by heat treatment in the temperature range of 823 K to 1173 K (550 °C to 900 °C) at an interval of 50 K (50 °C) for 1 hour, followed by water quenching. Ultrasonic parameters such as ultrasonic longitudinal wave velocity, ultrasonic shear wave velocity, shear anisotropy parameter, ultrasonic attenuation, and normalized nonlinear ultrasonic parameter have been correlated with various microstructural changes to understand the interaction of the propagating ultrasonic wave with microstructural features in the alloy. Simulation studies using JMatPro® software and X-ray diffraction measurements have been carried out to estimate the α-phase volume fraction in the specimens heat treated below the β-transus temperature (BTT). It is found that the α-phase (HCP) volume fraction increases from 0 to 52 pct, with decrease in the temperature from 1073 K to 823 K (800 °C to 550 °C). Ultrasonic longitudinal and shear wave velocities are found to increase with decrease in the heat treatment temperature below the BTT, and they exhibited linear relationships with the α-phase volume fraction. Thickness-independent ultrasonic parameters, Poisson's ratio, and the shear anisotropy parameter exhibited the opposite behavior, i.e., decrease with increase in the α-phase consequent to decrease in the heat treatment temperature from 1073 K to 823 K (800 °C to 550 °C). Ultrasonic attenuation is found to decrease from 0.7 dB/mm for the β-annealed specimen to 0.23 dB/mm in the specimen heat treated at 823 K (550 °C) due to the combined effect of the decrease in the β-phase (BCC) with higher damping characteristics and the reduction in scattering due to randomization of β grains with the precipitation of α-phase. Normalized nonlinear ultrasonic parameter is found to increase with increase in the α-phase volume fraction

  4. Preparation and characterization of (Ba,Cs)(M,Ti) 8O 16 (M = Al 3+, Fe 3+, Ga 3+, Cr 3+, Sc 3+, Mg 2+) hollandite ceramics developed for radioactive cesium immobilization

    NASA Astrophysics Data System (ADS)

    Aubin-Chevaldonnet, V.; Caurant, D.; Dannoux, A.; Gourier, D.; Charpentier, T.; Mazerolles, L.; Advocat, T.

    2007-06-01

    Among the different matrices proposed for selective and durable immobilization of radioactive cesium, (Ba x,Cs y)(M,Ti) 8O 16 hollandite ceramics, with x + y < 2 and M = divalent or trivalent cation appeared as the best candidates. In this study, hollandite ceramics were prepared using oxide route from oxide, carbonate and nitrate powders with and without Cs for different cations M (Al 3+, Cr 3+, Ga 3+, Fe 3+, Mg 2+, Sc 3+) of increasing size, in order to evaluate the effect of composition on ceramics microstructure and structure and on cesium incorporation. To reduce the risks of Cs vaporization during synthesis, calcined powders were sintered in air at moderate temperature (1200 °C). This oxide route appeared as an alternative to the alkoxide route generally proposed to prepare hollandite waste form. For y = 0, single phase Ba x(M,Ti) 8O 16 was obtained only for M 3+ = Al 3+, Cr 3+ and Fe 3+. For y ≠ 0 and Fe 3+, all cesium was incorporated in hollandite and ceramic was well densified. For Cr 3+ and Ga 3+, only 46% and 63%, respectively, of Cs were retained in hollandite phase. For these samples, a high fraction of Cs was either evaporated and/or concentrated in a Cs-rich parasitic phase. Mixed hollandite samples with M 3+ = Ga 3+ + Al 3+ and M 3+ = Fe 3+ + Al 3+ were also synthesized and the best results regarding Cs immobilization and ceramic density were obtained with iron + aluminum but the sample porosity was higher than that of the sample containing only iron. All results were discussed by considering cations size and refractory character of oxides and hollandite ceramics.

  5. Durability Assessment of TiAl Alloys

    NASA Technical Reports Server (NTRS)

    Draper, Susan L.; Lerch, Bradley A.

    2008-01-01

    The durability of TiAl is a prime concern for the implementation of TiAl into aerospace engines. Two durability issues, the effect of high temperature exposure on mechanical properties and impact resistance, have been investigated and the results are summarized in this paper. Exposure to elevated temperatures has been shown to be detrimental to the room temperature ductility of gamma alloys with the most likely mechanisms being the ingress of interstitials from the surface. Fluorine ion implantation has been shown to improve the oxidation resistance of gamma alloys, and ideally it could also improve the environmental embrittlement of high Nb content TiAl alloys. The effect of F ion implantation on the surface oxidation and embrittlement of a third generation, high Nb content TiAl alloy (Ti-45Al-5Nb-B-C) were investigated. Additionally, the ballistic impact resistance of a variety of gamma alloys, including Ti-48Al-2Cr- 2Nb, Ti-47Al-2Cr-2Nb, ABB-2, ABB-23, NCG359E, 95A and Ti-45Al-5Nb-B-C was accessed. Differences in the ballistic impact properties of the various alloys will be discussed, particularly with respect to their manufacturing process, microstructure, and tensile properties.

  6. Processing and properties of FeAl-bonded composites

    SciTech Connect

    Schneibel, J.H.; Subramanian, R.; Alexander, K.B.; Becher, P.F.

    1996-12-31

    Iron aluminides are thermodynamically compatible with a wide range of ceramics such as carbides, borides, oxides, and nitrides, which makes them suitable as the matrix in composites or cermets containing fine ceramic particulates. For ceramic contents varying from 30 to 60 vol.%, composites of Fe-40 at. % Al with WC, TiC, TiB{sub 2}, and ZrB{sub 2} were fabricated by conventional liquid phase sintering of powder mixtures. For ceramic contents from 70 to 85 vol.%, pressureless melt infiltration was found to be a more suitable processing technique. In FeAl-60 vol.% WC, flexure strengths of up to 1.8 GPa were obtained, even though processing defects consisting of small oxide clusters were present. Room temperature fracture toughnesses were determined by flexure testing of chevron-notched specimens. FeAl/WC and FeAl/TiC composites containing 60 vol.% carbide particles exhibited K{sub Q} values around 20 MPa m{sup 1/2}. Slow crack growth measurements carried out in water and in dry oxygen suggest a relatively small influence of water-vapor embrittlement. It appears therefore that the mechanical properties of iron aluminides in the form of fine ligaments are quite different from their bulk properties. Measurements of the oxidation resistance, dry wear resistance, and thermal expansion of iron aluminide composites suggest many potential applications for these new materials.

  7. Preparation and Pore Structure Stability at High Temperature of Porous Fe-Al Intermetallics

    NASA Astrophysics Data System (ADS)

    Shen, P. Z.; Gao, H. Y.; Song, M.; He, Y. H.

    2013-12-01

    Porous Fe-Al intermetallics with different nominal compositions (from Fe-8 wt.% Al to Fe-50 wt.% Al) were fabricated by Fe and Al elemental powders through reaction synthesis. The effects of the Al content on the pore structure properties, and the comparison of pore structure stabilities at high-temperatures among the porous Fe-Al intermetallics and porous Ti, Ni, 316L stainless steel samples, were systematically studied. Results showed that the open porosity, maximum pore size, and permeability vary with the Al content. Porous Fe-(25-30 wt.%) Al intermetallics show good shape controllability and excellent pore structure stability at 1073 K in air, which suggests that these porous Fe-Al intermetallics could be used for filtration at high temperatures.

  8. Orientation relationship of eutectoid FeAl and FeAl2

    PubMed Central

    Scherf, A.; Kauffmann, A.; Kauffmann-Weiss, S.; Scherer, T.; Li, X.; Stein, F.; Heilmaier, M.

    2016-01-01

    Fe–Al alloys in the aluminium range of 55–65 at.% exhibit a lamellar microstructure of B2-ordered FeAl and triclinic FeAl2, which is caused by a eutectoid decomposition of the high-temperature Fe5Al8 phase, the so-called ∊ phase. The orientation relationship of FeAl and FeAl2 has previously been studied by Bastin et al. [J. Cryst. Growth (1978 ▸), 43, 745] and Hirata et al. [Philos. Mag. Lett. (2008 ▸), 88, 491]. Since both results are based on different crystallographic data regarding FeAl2, the data are re-evaluated with respect to a recent re-determination of the FeAl2 phase provided by Chumak et al. [Acta Cryst. (2010 ▸), C66, i87]. It is found that both orientation relationships match subsequent to a rotation operation of 180° about a 〈112〉 crystallographic axis of FeAl or by applying the inversion symmetry of the FeAl2 crystal structure as suggested by the Chumak data set. Experimental evidence for the validity of the previously determined orientation relationships was found in as-cast fully lamellar material (random texture) as well as directionally solidified material (∼〈110〉FeAl || solidification direction) by means of orientation imaging microscopy and global texture measurements. In addition, a preferential interface between FeAl and FeAl2 was identified by means of trace analyses using cross sectioning with a focused ion beam. On the basis of these habit planes the orientation relationship between the two phases can be described by (01)FeAl || (114) and [111]FeAl || [10]. There is no evidence for twinning within FeAl lamellae or alternating orientations of FeAl lamellae. Based on the determined orientation and interface data, an atomistic model of the structure relationship of Fe5Al8, FeAl and FeAl2 in the vicinity of the eutectoid decomposition is derived. This model is analysed with respect to the strain which has to be accommodated at the interface of FeAl and FeAl2. PMID:27047304

  9. Machinability Evaluation of Ti-5Nb- xFe Alloys for Dental Applications

    NASA Astrophysics Data System (ADS)

    Hsu, Hsueh-Chuan; Wu, Shih-Ching; Hsu, Shih-Kuang; Hsu, Kuan-Huang; Ho, Wen-Fu

    2015-03-01

    In this study, we evaluated the machinability of a series of Ti-5Nb- xFe alloys with an Fe content ranging from 1 to 5 mass% and compared the results to those of commercially pure titanium (c.p. Ti) and Ti-6Al-4V. The alloys were slotted using a milling machine and end mills under four cutting conditions. Machinability was evaluated using cutting force which was measured using a dynamometer. The experimental results indicate that the addition of Fe significantly affected the machinability of the Ti alloys in terms of cutting force under the present cutting conditions. Under certain conditions, the cutting force of Ti-5Nb-4Fe was lower than that of c.p. Ti and Ti-6Al-4V, a result which can be explained by a higher degree of hardness and greater amounts of ω phase. Ti-5Nb-4Fe also had a better surface finish: cutting marks were less apparent and metal chips did not adhere to the cut surfaces under cutting condition C (cutting speed: 1.83 m/s, feed rate: 0.0005 m/s, and depth of cut: 0.0002 m). Ti-5Nb-4Fe had the lowest average surface roughness ( R a) after machining (approximately 0.27 μm under cutting condition C).

  10. Influence of W, Mo and Ti trace elements on the phase separation in Al8Co17Cr17Cu8Fe17Ni33 based high entropy alloy.

    PubMed

    Manzoni, Anna M; Daoud, Haneen M; Voelkl, Rainer; Glatzel, Uwe; Wanderka, Nelia

    2015-12-01

    Compositionally complex alloys, also called high entropy alloys, have been investigated for over a decade in view of different applications, but so far only a small number of alloys can be considered as presenting good enough properties for industrial application. The most common family of elements is Al-Co-Cr-Cu-Fe-Ni. The equiatomic alloy having 5 phases and being too brittle, the composition has been modified in order to improve the mechanical properties. Different compositions have been tested and as a first result ductile Al8Co17Cr17Cu8Fe17Ni33 has been chosen for deeper investigation. It shows a dendritic segregation into Co-Cr-Fe rich cores and Al-Cu-Ni rich interdendritic sites. The as-cast state is characterized mainly by two phases, namely Al-Cu-Ni rich precipitates of L12 structure inside a solid solution matrix. After homogenization both alloys consists of a single solid solution phase. Results are compared to calculations by ThermoCalc. In order to further improve the properties of the alloy the Cr content has been decreased and replaced by trace elements W, Mo and Ti, which, according to ThermoCalc, increase the melting point and the phase transition temperature which leads to the formation of the L12 phase. As-cast and heat treated samples of the base and the modified alloy have been investigated by transmission electron microscopy and three dimensional atom probe. Results of the investigations will be discussed in terms of microstructure, hardness and coherence with Thermo Calc predictions.

  11. Influence of Ti and La Additions on the Formation of Intermetallic Compounds in the Al-Zn-Si Bath

    NASA Astrophysics Data System (ADS)

    Xu, Jin; Gu, Qin-Fen; Li, Qian; Lu, Hu-Sheng

    2016-12-01

    The effect of Ti and La additions on the formation of intermetallic compounds (IMCs) in the galvalume (55Al-Zn-1.6Si wt pct) bath was investigated experimentally and further studied with first-principles calculation. The studied baths contain: 1 wt pct Fe, with Ti content ranging from 0.05 to 0.15 wt pct and La content ranging from 0.05 to 0.30 wt pct. Combination of the experimental results with the thermodynamic analysis shows that the solubility of Fe in the alloy bath decreases with an increase of Ti content, which results in the formation of mass dross. Compared with the Ti-containing alloy, La promotes the formation of τ 5 phase (Fe2Al8Si). When both Ti and La are added, Fe4Al13, τ 5, τ 6 (β-Al4.5FeSi), TiAl3, and Ti2Al20La phases were observed. Since these IMCs would consume more Si in the bath, the decrease of Si content with Ti and La additions is more significant than that of the bath without these additions. Furthermore, the formation mechanism of Ti/TiAl3/Ti2La20La core-shell structure in the coating bath is proposed. This study has implications for strategic design of industry hot-dip production with exceptional mechanical properties of Al alloy coating.

  12. Two-Phase (TiAl+TiCrAl) Coating Alloys for Titanium Aluminides

    NASA Technical Reports Server (NTRS)

    Brady, Michael P. (Inventor); Smialek, James L. (Inventor); Brindley, William J. (Inventor)

    1998-01-01

    A coating for protecting titanium aluminide alloys, including the TiAl gamma + Ti3Al (alpha(sub 2)) class, from oxidative attack and interstitial embrittlement at temperatures up to at least 1000 C. is disclosed. This protective coating consists essentially of titanium, aluminum. and chromium in the following approximate atomic ratio: Ti(41.5-34.5)Al(49-53)Cr(9.5-12.5)

  13. Surface Properties of the IN SITU Formed Ceramics Reinforced Composite Coatings on TI-3AL-2V Alloys

    NASA Astrophysics Data System (ADS)

    Liu, Peng; Guo, Wei; Hu, Dakui; Luo, Hui; Zhang, Yuanbin

    2012-04-01

    The synthesis of hard composite coating on titanium alloy by laser cladding of Al/Fe/Ni+C/Si3N4 pre-placed powders has been investigated in detail. SEM result indicated that a composite coating with metallurgical joint to the substrate was formed. XRD result indicated that the composite coating mainly consisted of γ-(Fe, Ni), FeAl, Ti3Al, TiC, TiNi, TiC0.3N0.7, Ti2N, SiC, Ti5Si3 and TiNi. Compared with Ti-3Al-2V substrate, an improvement of the micro-hardness and the wear resistance was observed for this composite coating.

  14. Magnetoelectric effect in Fe-embedded BaTiO{sub 3} single crystal

    SciTech Connect

    Gupta, Arti; Chatterjee, Ratnamala

    2011-06-15

    In this work, we experimentally demonstrate the magnetoelectric effect in a multilayered structure of Fe-BaTiO{sub 3}-Fe, with 70 A BaTiO{sub 3} (BT) sandwiched between 2 layers of implanted Fe, which was further treated by swift heavy ion (Ag{sup +15}) induced ion beam mixing/annealing. Due to this specific experimental procedure, condition of atomic orbital overlap between the Fe and Ti atoms could be favored in Fe-implanted BT crystal, showing a magnetoelectric effect arising from interfacial bonding at Fe/BT interface, as proposed by Duan et al.[Phys. Rev. Lett. 97, 047201 (2006)]. Results are successfully interpreted in terms of magnetostriction behavior of polycrystalline Fe.

  15. Effect of Ti content on the microstructure and mechanical behavior of (Fe36Ni18Mn33Al13)100–xTix high entropy alloys

    SciTech Connect

    Wang, Zhangwei; Wu, Margaret; Cai, Zhonghou; Chen, Si; Baker, Ian

    2016-06-13

    The microstructure and mechanical properties studies of a series of two-phase f.c.c./B2 (ordered b.c.c.) lamellar-structured, high entropy alloys (HEA) Fe36Ni18Mn33Al13Tix with x up to 6 at. % Ti have been investigated. X-ray microanalysis in a TEM showed that the Ti resided mostly in the B2 phase. The lamellar spacing decreased significantly with increasing Ti content from 1.56 μm for the undoped alloy to 155 nm with an addition of 4 at. % Ti, leading to a sharp increase in room-temperature yield strength,σy, from 270 MPa to 953 MPa, but with a concomitant decrease in ductility from 22% elongation to 2.3%. Annealing at 1173 K for 20 h greatly increased the lamellar spacing of Fe36Ni18Mn33Al13Ti4 to 577 nm, producing a corresponding decrease in σy to 511 MPa. The yield strengths of all the doped alloys decreased significantly when tensile tested at 973 K with a concomitant increase in ductility due to softening of the B2 phase. The fracture mode changed from cleavage at room temperature to a ductile dimple-type rupture at 973 K. Lastly, the results are discussed in terms of the Hall-Petch-type relationship.

  16. Calculation of defect properties of NiTi and FeTi

    SciTech Connect

    Lutton, R.T.; Sabochick, M.J. . Dept. of Engineering Physics); Lam, N.Q. )

    1990-12-01

    The energies and configurations of interstitials and vacancies in the B2 ordered compounds NiTi and FeTi were calculated using atomistic simulation. The stable configuration of a vacancy after the removal of an Ni atom was a vacant Ni site; similarly, the removal of an Fe atom in FeTi resulted in a vacant Fe site. Removal of a Ti atom in both compounds, however, resulted in a vacant Ni or Fe site and an adjacent antisite defect. The effective vacancy formation energies in NiTi and FeTi were calculated to be 1.48 and 1.07 eV, respectively. Interstitials in NiTi formed split {l angle}111{r angle} configurations consisting of a Ni-Ni dumbbell oriented in the {l angle}111{r angle} direction with one or two adjacent antisite defects. The Fe interstitial in FeTi had a similar configuration, except the dumbbell contained Fe atoms. The Ti interstitial in FeTi formed an {l angle}110{r angle} Fe-Fe dumbbell. 8 refs., 2 tabs.

  17. Tetragonal magnetostriction and magnetoelastic coupling in Fe-Al, Fe-Ga, Fe-Ge, Fe-Si, Fe-Ga-Al, and Fe-Ga-Ge alloys

    NASA Astrophysics Data System (ADS)

    Restorff, J. B.; Wun-Fogle, M.; Hathaway, K. B.; Clark, A. E.; Lograsso, T. A.; Petculescu, G.

    2012-01-01

    This paper presents a comparative study on the tetragonal magnetostriction constant, λγ,2, [ = (3/2)λ100] and magnetoelastic coupling, b1, of binary Fe100-xZx (0 < x < 35, Z = Al, Ga, Ge, and Si) and ternary Fe-Ga-Al and Fe-Ga-Ge alloys. The quantities are corrected for magnetostrains due to sample geometry (the magnetostrictive form effect). Recently published elastic constant data along with magnetization measurements at both room temperature and 77 K make these corrections possible. The form effect correction lowers the magnetostriction by ˜10 ppm for high-modulus alloys and by as much as 30 ppm for low-modulus alloys. The elastic constants are also used to determine the values of the magnetoelastic coupling constant, b1. With the new magnetostriction data on the Fe-Al-Ga alloy, it is possible to show how the double peak magnetostriction feature of the binary Fe-Ga alloy flows into the single peak binary Fe-Al alloy. The corrected magnetostriction and magnetoelastic coupling data for the various alloys are also compared using the electron-per-atom ratio, e/a, as the common variable. The Hume-Rothery rules link the e/a ratio to the regions of phase stability, which appear to be intimately related to the magnetostriction versus the solute concentration curve in these alloys. Using e/a as the abscissa tends to align the peaks in the magnetostriction and magnetoelastic coupling for the Fe-Ga, Fe-Ge, Fe-Al, Fe-Ga-Al, and Fe-Ga-Ge alloys, but not for the Fe-Si alloys for which the larger atomic size difference may play a greater role in phase stabilization. Corrections for the form effect are also presented for the rhombohedral magnetostriction, λɛ,2, and the magnetoelastic coupling, b2, of Fe100-xGax (0 < x < 35) alloys.

  18. Interdiffusion between the L1(2) trialuminides Al66Ti25Mn9 and Al67Ti25Cr8

    NASA Technical Reports Server (NTRS)

    Kumar, K. S.; Whittenberger, J. D.

    1992-01-01

    Concentration-distance profiles obtained from Al66Ti25Mn9/Al67Ti25Cr8 diffusion couples are used to determine the interdiffusion coeffients in the temperature range 1373-1073 K. The couples are treated as pseudobinaries, and the diffusion coefficients are determined using the Matano approach. The results are then used to compute the activation energies for diffusion, and a comparison is made with some existing data for the activation energy for creep of Al22Ti8Fe3.

  19. Development of Fe-Mn-Al-X-C alloys

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

    Development of a low cost Cr-free, iron-base alloy for aerospace applications involves both element substitution and enhancement of microstructural strengthening. When Mn is substituted for Ni and Al or Si is substituted for Cr, large changes occur in the mechanical and thermal stability of austenite in FeMnAlC alloys. The in situ strength of MC or M2C (M = Ti, V, Hf, Ta, or Mo) in FeMnAlC alloys was determined. The high temperature tensile strength depends more on the distribution of carbides than the carbide composition. Precipitation of a high volume percent-ordered phase was achieved in Fe2OMnlONi6Al6Ti (lC) alloys. As case, these alloys have a homogeneous austenitic structure. After solutioning at 1100 C for 5 hr followed by aging at 600 C for 16 hr, gamma prime or a perovskite carbide is precipitated. Overaging occurs at 900 C where eta is precipitated.

  20. Structure and Electrochemistry of LiNi1/3Co1/3-yMyMn1/3O2 (M=Ti, Al, Fe) Positive Electrode Materials

    SciTech Connect

    Wilcox, James; Patoux, Sebastien; Doeff, Marca

    2009-01-14

    A series of materials based on the LiNi1/3Co1/3-yMyMn1/3O2 (M = Ti,Al,Fe) system has been synthesized and examined structurally and electrochemically. It is found that the changes in electrochemical performance depend highly on the nature of the substituting atom and its effect on the crystal structure. Substitution with small amounts of Ti4+ (y = 1/12) leads to the formation of a high-capacity and high-rate positive electrode material. Iron substituted materials suffer from an increased antisite defect concentration and exhibit lower capacities and poor rate capabilities. Single-phase materials are found for LiNi1/3Co1/3-yAlyMn1/3O2 when y<_ 1/4 and all exhibit decreased capacities when cycled to 4.3 V. However, an increase in rate performance and cycle stability upon aluminum substitution is correlated with an improved lamellar structure.

  1. K-italic-shell ionization cross sections for Al, Ti, V, Cr, Fe, Ni, Cu, and Ag by protons and oxygen ions in the energy range 0. 3--6. 4 MeV

    SciTech Connect

    Geretschlaeger, M.; Benka, O.

    1986-08-01

    Absolute K-italic-shell ionization cross sections have been measured for thin targets of Al, Ti, and Cu for protons in the energy range 0.3--2.0 MeV and for thin targets of Ti, V, Cr, Fe, Ni, Cu, and Ag for oxygen ions in the energy range 1.36--6.4 Mev. The experimental results are compared to the perturbed-stationary-state (PSS) approximation with energy-loss (E), Coulomb (C), and relativistic (R) corrections, i.e., the ECPSSR approximation (Brandt and Lapicki), to the semiclassical approximation (Laegsgaard, Andersen, and Lund), and to a theory for direct Coulomb ionization of the 1s-italicsigma molecular orbital (Montenegro and Sigaud (MS)). The proton results agree within 3% with empirical reference cross sections. Also, the ECPSSR provides best overall agreement for protons. For oxygen ions, ECPSSR and MS predict experimental results satisfactorily for scaled velocities xi> or =0.4. For lower scaled velocities, the experimental cross sections become considerably higher than theoretical predictions for Coulomb ionization. This deviation increases with increasing Z-italic/sub 1//Z/sub 2/; it cannot be explained by electron transfer to the projectile or by ionization due to target recoil atoms.

  2. Investigation on W/Fe diffusion bonding using Ti foil and Ti powder interlayer by SPS

    NASA Astrophysics Data System (ADS)

    Chen, Hong-Yu; Luo, Lai-Ma; Zhang, Jun; Zan, Xiang; Zhu, Xiao-Yong; Luo, Guang-Nan; Wu, Yu-Cheng

    2015-12-01

    W/steel composites are being developed for potential application in He gas-cooled divertors and plasma-facing components in fusion reactors. In this study, the dissimilar metal joints between W and Fe were fabricated at 950 °C via spark plasma sintering method with Ti foil (Ti-F) and Ti powder (Ti-P) as the interlayer under Ar atmosphere for 5 min at 57 MPa. Microscopic structures of the W/Fe diffusion joints with Ti-F and Ti-P were investigated and compared via field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy. Thermal cycling tests were employed to measure the thermal stability of different types of W/Ti/Fe samples. The hardness distribution across joining interfaces was also determined. After thermal cycling tests, a crack occurred along the W/Ti-P interface in the W/Ti-P/Fe samples, whereas the W/Ti-F/Fe samples were intact at the interfaces. Results revealed that Ti-F is more suitable as an interlayer than Ti-P, and the interfaces of the W/Ti-F/Fe samples have better thermal stability than those of the W/Ti-P/Fe ones.

  3. Theoretical analysis of compatibility of several reinforcement materials with NiAl and FeAl matrices

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1989-01-01

    Several potential reinforcement materials were assessed for their chemical, coefficient of thermal expansion (CTE), and mechanical compatibility with the intermetallic matrices based on NiAl and FeAl. Among the ceramic reinforcement materials, Al2O3, TiC, and TiB2, appear to be the optimum choices for NiAl and FeAl matrices. However, the problem of CTE mismatch with the matrix needs to be solved for these three reinforcement materials. Beryllium-rich intermetallic compounds can be considered as potential reinforcement materials provided suitable reaction barrier coatings can be developed for these. Based on preliminary thermodynamic calculations, Sc2O3 and TiC appear to be suitable as reaction barrier coatings for the beryllides. Several reaction barrier coatings are also suggested for the currently available SiC fibers.

  4. Oxidation of TiAl3 and L12 Coatings on Ti-45Al-5Nb Alloy at 1173K

    NASA Astrophysics Data System (ADS)

    Nishimoto, Takumi; Kitajima, Yuri; Hayashi, Shigenari; Narita, Toshio

    Oxidation behavior of TiAl3 and L12 coated Ti-45at%Al-5at%Nb alloys at 1173K in air was investigated using mass gain measurement, field emission scanning electron microscopy, transmission electron microscopy, electron-probe microanalysis, glow discharge optical electron spectroscopy, and glancing angle X-ray diffraction analysis. The TiAl3 formed meta-stable alumina θ-Al2O3, while the oxide scale on the L12 consisted of a duplex structure with an outer rutile TiO2 and an inner α-Al2O3. During the very initial stages of oxidation both Ti and Al in the L12 coating could be oxidized, and then the faster diffusing Ti goes out to form an outer, continuous Ti-rich oxide which covers the slow growing Al2O3. In case of the TiAl3 an outer, continuous TiO2 layer was not observed because of the smaller amount of Ti in the TiAl3. It could be concluded that the outer, Ti-rich oxide enhanced a phase transformation of Al2O3 from θ to α. To elucidate the Ti effect, Ti-vapor treated TiAl3 and Ni-50at%Al were oxidized at 1173K in air, and showed formation of an α-Al2O3, in contrast to θ-Al2O3 on their bare alloys.

  5. Fe(3+)-Doped TiO₂ Nanotube Arrays on Ti-Fe Alloys for Enhanced Photoelectrocatalytic Activity.

    PubMed

    Yu, Jiangdong; Wu, Zhi; Gong, Cheng; Xiao, Wang; Sun, Lan; Lin, Changjian

    2016-06-06

    Highly ordered, vertically oriented Fe(3+)-doped TiO₂ nanotube arrays (Fe-TNTs) were prepared on Ti-Fe alloy substrates with different Fe contents by the electrochemical anodization method. The as-prepared Fe-TNTs were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and related electrochemical techniques. XPS results demonstrated that Fe(3+) ions were successfully doped into TiO₂ nanotubes. The photoelectrochemical activity of Fe-TNTs was compared with that of pure TiO₂ nanotube arrays (TNTs). The results showed that Fe-TNTs grown on low concentration (0.5 wt %-1 wt % Fe) Ti-Fe alloys possessed higher photocurrent density than TNTs. The Fe-TNTs grown on Ti-Fe alloy containing 0.8 wt % Fe exhibited the highest photoelectrochemical activity and the photoelectrocatalytic degradation rate of methylene blue (MB) aqueous solution was significantly higher than that of TNTs.

  6. Fe3+-Doped TiO2 Nanotube Arrays on Ti-Fe Alloys for Enhanced Photoelectrocatalytic Activity

    PubMed Central

    Yu, Jiangdong; Wu, Zhi; Gong, Cheng; Xiao, Wang; Sun, Lan; Lin, Changjian

    2016-01-01

    Highly ordered, vertically oriented Fe3+-doped TiO2 nanotube arrays (Fe-TNTs) were prepared on Ti-Fe alloy substrates with different Fe contents by the electrochemical anodization method. The as-prepared Fe-TNTs were characterized by scanning electron microscope (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and related electrochemical techniques. XPS results demonstrated that Fe3+ ions were successfully doped into TiO2 nanotubes. The photoelectrochemical activity of Fe-TNTs was compared with that of pure TiO2 nanotube arrays (TNTs). The results showed that Fe-TNTs grown on low concentration (0.5 wt %–1 wt % Fe) Ti-Fe alloys possessed higher photocurrent density than TNTs. The Fe-TNTs grown on Ti-Fe alloy containing 0.8 wt % Fe exhibited the highest photoelectrochemical activity and the photoelectrocatalytic degradation rate of methylene blue (MB) aqueous solution was significantly higher than that of TNTs. PMID:28335234

  7. Doping of the quadruple perovskites of type Nd 2Ba 2Cu 2Ti 2- xO xO 11,  Mn, Fe, Co, Al and NdBa 3Cu 2Ti 1+ xNb 1- xNb 1- xO 11

    NASA Astrophysics Data System (ADS)

    Rentschler, Thomas

    1997-02-01

    The synthesis of new ceramic materials NdBa 3Cu 2Ti 1+ xNb 1- xO 11 and Nd 2Ba 2Cu 2Ti 2- xM xO 11, M  Mn, Fe, Co, Al with a quadruple perovskite structure was successfully performed. Rietveld refinements verified the oxygen deficient layered a p ∗ a p ∗ 4a p superstructure (space group P4/mmm). Heterovalent doping in these groups of materials was carried out in order to provide a hole carrier concentration in the CuO 2 layers structurally related to the high- Tc superconductors. However, superconductivity was not observed. The formation of oxygen defects is discussed.

  8. Mechanical properties and electronic structures of Fe-Al intermetallic

    NASA Astrophysics Data System (ADS)

    Liu, YaHui; Chong, XiaoYu; Jiang, YeHua; Zhou, Rong; Feng, Jing

    2017-02-01

    Using the first-principles calculations, the elastic properties, anisotropy properties, electronic structures, Debye temperature and stability of Fe-Al (Fe3Al, FeAl, FeAl2, Fe2Al5 and FeAl3) binary compounds were calculated. The formation enthalpy and cohesive energy of these Fe-Al compounds are negative, and show they are thermodynamically stable structures. Fe2Al5 has the lowest formation enthalpy, which shows the Fe2Al5 is the most stable of Fe-Al binary compounds. These Fe-Al compounds display disparate anisotropy due to the calculated different shape of the 3D curved surface of the Young's modulus and anisotropic index. Fe3Al has the biggest bulk modulus with the value 233.2 GPa. FeAl has the biggest Yong's modulus and shear modulus with the value 296.2 GPa and 119.8 GPa, respectively. The partial density of states, total density of states and electron density distribution maps of the binary Fe-Al binary compounds are analyzed. The bonding characteristics of these Fe-Al binary compounds are mainly combination by covalent bond and metallic bonds. Meanwhile, also exist anti-bond effect. Moreover, the Debye temperatures and sound velocity of these Fe-Al compounds are explored.

  9. An ab initio study on atomic and electronic structures of two-dimensional Al3Ti at Al/TiB2 interface

    NASA Astrophysics Data System (ADS)

    Men, H.

    2016-09-01

    The atomic and electronic structures of a two-dimentional (2D) Al3Ti layer at Al/TiB2 interface has been investigated using first-principle calculations. The result reveals the 2D-Al3Ti adopts the structure of bulk Al3Ti. There exists a strong Ti(3d)-Al(3p) hybridization between Ti and Al atoms of the 2D-Al3Ti, as well as between surface Ti atoms of TiB2 and Al atoms of 2D-Al3Ti. It leads to a stronger covalent Ti-Al bonding at the Al/2D-Al3Ti/TiB2 interface than at the Al/TiB2 interface, which is responsible for the stability of 2D-Al3Ti.

  10. Structural inheritance and difference between Ti2AlC, Ti3AlC2 and Ti5Al2C3 under pressure from first principles

    NASA Astrophysics Data System (ADS)

    Gao, Qing-He; Du, An; Yang, Ze-Jin

    2017-01-01

    The structural inheritance and difference between Ti2AlC, Ti3AlC2 and Ti5Al2C3 under pressure from first principles are studied. The results indicate that the lattice parameter a are almost the same within Ti2AlC, Ti3AlC2 and Ti5Al2C3, and the value of c in Ti5Al2C3 is the sum of Ti2AlC and Ti3AlC2 which is revealed by the covalently bonded chain in the electron density difference: Al-Ti-C-Ti-Al for Ti2AlC, Al-Ti2-C-Ti1-C-Ti2-Al for Ti3AlC2 and Al-Ti3-C2-Ti3-Al-Ti2-C1-Ti1-C1-Ti2-Al for Ti5Al2C3. The calculated axial compressibilities, volumetric shrinkage, elastic constant c11, c33/c11 ratio, bulk modulus, shear modulus, and Young’s modulus of Ti5Al2C3 are within the range of the end members (Ti2AlC and Ti3AlC2) in a wide pressure range of 0-100 GPa. Only Ti2AlC is isotropic crystal at about 50 GPa within the Ti-Al-C compounds. All of the Ti 3d density of states curves of the three compounds move from lower energy to higher energy level with pressure increasing. The similarities of respective bond length, bond overlap population (Ti-C, Ti-Al and Ti-Ti), atom Mulliken charges under pressure as well as the electron density difference for the three compounds are discovered. Among the Ti-Al-C ternary compounds, Ti-Ti bond behaves least compressibility, whereas the Ti-Al bond is softer than that of Ti-C bonds, which can also been confirmed by the density of states and electron density difference. Bond overlap populations of Ti-Ti, Ti-C and Ti-Al indicate that the ionicity interaction becomes more and more stronger in the three structures as the pressure increasing. Mulliken charges of Ti1, Ti2, Ti3, C and Al are 0.65, 0.42, 0.39, ‑0.73, ‑0.04 at 0 GPa, respectively, which are consistent with the Pauling scale.

  11. Modified smoothed particle hydrodynamics (MSPH) for the analysis of centrifugally assisted TiC-Fe-Al2O3 combustion synthesis

    PubMed Central

    Hassan, M. A.; Mahmoodian, Reza; Hamdi, M.

    2014-01-01

    A modified smoothed particle hydrodynamic (MSPH) computational technique was utilized to simulate molten particle motion and infiltration speed on multi-scale analysis levels. The radial velocity and velocity gradient of molten alumina, iron infiltration in the TiC product and solidification rate, were predicted during centrifugal self-propagating high-temperature synthesis (SHS) simulation, which assisted the coating process by MSPH. The effects of particle size and temperature on infiltration and solidification of iron and alumina were mainly investigated. The obtained results were validated with experimental microstructure evidence. The simulation model successfully describes the magnitude of iron and alumina diffusion in a centrifugal thermite SHS and Ti + C hybrid reaction under centrifugal acceleration. PMID:24430621

  12. High-pressure high-temperature phase relations in FeTiO3 up to 35 GPa and 1600 °C

    NASA Astrophysics Data System (ADS)

    Akaogi, M.; Abe, K.; Yusa, H.; Ishii, T.; Tajima, T.; Kojitani, H.; Mori, D.; Inaguma, Y.

    2017-01-01

    Phase relations in FeTiO3 were precisely determined at 25-35 GPa and 600-1600 °C using multianvil high-pressure experiments with tungsten carbide anvils. Pressure generation up to about 36 GPa at 1600 °C was evaluated using Al2O3 solubility in MgSiO3 perovskite (Pv) in the system MgSiO3-Al2O3. At about 28 GPa, FeTiO3 Pv dissociates into an assemblage of calcium titanate (CT)-type Fe2TiO4 + orthorhombic-I (OI)-type TiO2 below 1200 °C. However, above 1200 °C at 28 GPa, FeTiO3 Pv decomposes into a new, denser phase assemblage of CT-type Fe2TiO4 + a new compound of FeTi2O5. The new phase FeTi2O5 was recovered as an amorphous phase at 1 atm. In situ X-ray diffraction experiments at 35.1 GPa indicated that the new phase (N-p) FeTi2O5 has orthorhombic symmetry with cell parameters a = 8.567(2) Å, b = 5.753(1) Å and c = 5.257(1) Å. In addition, the assemblage of CT-type Fe2TiO4 + OI-type TiO2 changes to FeO wüstite (Wu) + OI-type TiO2 at about 33 GPa below 1000 °C. The phase assemblages in FeTiO3 are denser in the order: FeTiO3 (Pv) → 1/2Fe2TiO4 (CT) + 1/2TiO2 (OI) → 1/3Fe2TiO4 (CT) + 1/3FeTi2O5 (N-p) → FeO (Wu) + TiO2 (OI). Our results indicate that the upper stability limit of FeTiO3 Pv is about 28 GPa at 600-1600 °C. This puts a constraint on peak shock pressure for formation of naturally discovered lithium niobate-type FeTiO3 which was interpreted to be retrograde transition product of FeTiO3 Pv on release of shock pressure.

  13. Redistribution of Ti and Al in deuterium charged TiAl

    NASA Technical Reports Server (NTRS)

    Legzdina, D.; Robertson, I. M.; Birnbaum, H. K.

    1992-01-01

    The redistribution of titanium and aluminum in a single-phase TiAl alloy that has been exposed to a high pressure of deuterium gas at high temperature is studied. The microstructure in the as-received, uncharged condition consisted of single-phase gamma TiAl grains and a random distribution of precipitates. Precipitates were distributed throughout the matrix and along the grain boundaries. The chemistry of the precipitates varied considerably; some were rich in Al, while other were mostly Ti with some Si and Al. The dislocation density in most grains was low, although in a few grains a high dislocation density was observed. FCC deuterides with a lattice parameter of 0.45 nm form in a Ti-52.1Al-2.1Ta (at. pct) alloy after exposure to 1.38 MPa of deuterium gas at 650 C for 213 hr. The structure and lattice parameter are consistent with the formation of Ti(l)D2. The deuterides that form in this alloy are enriched in Ti and deficient in Al and Ta compared to the deuteride-free matrix. Regions of the matrix contiguous with the deuterides have a correspondingly enhanced aluminum and tantalum concentration.

  14. Piezostrain tuning non-volatile 90° magnetic easy axis rotation in Co2FeAl Heusler alloy film grown on Pb(Mg1/3Nb2/3)O3-PbTiO3 heterostructures

    NASA Astrophysics Data System (ADS)

    Zhou, Cai; Wang, Fenglong; Dunzhu, Gesang; Yao, Jinli; Jiang, Changjun

    2016-11-01

    Non-volatile electric field-based control of magnetic anisotropy in Co2FeAl/ Pb(Mg1/3Nb2/3)O3-PbTiO3 (CFA/PMN-PT) heterostructures is investigated at room temperature. The remnant magnetization response under different electric fields shows a asymmetric butterfly-like behavior; specifically, this behavior is consistent with the asymmetric butterfly-like piezostrain versus applied electric field curve. Thus electric field-induced non-volatile 90° magnetic easy axis rotation can be attributed to the piezostrain effect. Further, the result measured by rotating-angle ferromagnetic resonance demonstrates piezostrain-mediated non-volatile 90° magnetic easy axis rotation at the initial state and the two remnant polarization states after application of the poling fields of 10 and  -10 kV cm-1 turned off. The angular dependence of magnetic damping also indicates a 90° phase shift at the above mentioned three different states. Additionally, the piezostrain-mediated non-volatile stable magnetization reversal in the two directions of easy and hard magnetization axes are observed under positive and negative pulsed electric fields, which can be used to improve the performance of low-loss multiple-state memory devices.

  15. Heavy ion irradiations on synthetic hollandite-type materials: Ba1.0Cs0.3A2.3Ti5.7O16 (A=Cr, Fe, Al)

    NASA Astrophysics Data System (ADS)

    Tang, Ming; Tumurugoti, Priyatham; Clark, Braeden; Sundaram, S. K.; Amoroso, Jake; Marra, James; Sun, Cheng; Lu, Ping; Wang, Yongqiang; Jiang, Ying.-Bing.

    2016-07-01

    The hollandite supergroup of minerals has received considerable attention as a nuclear waste form for immobilization of Cs. The radiation stability of synthetic hollandite-type compounds described generally as Ba1.0Cs0.3A2.3Ti5.7O16 (A=Cr, Fe, Al) were evaluated by heavy ion (Kr) irradiations on polycrystalline single phase materials and multiphase materials incorporating the hollandite phases. Ion irradiation damage effects on these samples were examined using grazing incidence X-ray diffraction (GIXRD) and transmission electron microscopy (TEM). Single phase compounds possess tetragonal structure with space group I4/m. GIXRD and TEM observations revealed that 600 keV Kr irradiation-induced amorphization on single phase hollandites compounds occurred at a fluence between 2.5×1014 Kr/cm2 and 5×1014 Kr/cm2. The critical amorphization fluence of single phase hollandite compounds obtained by in situ 1 MeV Kr ion irradiation was around 3.25×1014 Kr/cm2. The hollandite phase exhibited similar amorphization susceptibility under Kr ion irradiation when incorporated into a multiphase system.

  16. Study of the {alpha}{double_prime} phase texture obtained by martensitic {beta}-{alpha}{double_prime} phase transformation induced by tensile test in a sheet of Ti5Al2Sn4Zr4Mo2Cr1Fe

    SciTech Connect

    Pionnier, D.; Humbert, M.; Philippe, M.J.; Combres, Y.

    1998-10-09

    The purpose was to investigate the texture development of the {alpha}{double_prime} orthorhombic martensite phase induced by stress within a commercial sheet of Ti5Al2Sn4Zr4Mo2Cr1Fe. First, the experimental textures of the initial b.c.c. phase, then of the b.c.c. phase and the {alpha}{double_prime} martensite phase after a uniaxial deformation were determined from pole figures. Comparison of the {alpha}{double_prime} experimental texture with a {alpha}{double_prime} texture, simulated with no variant selection from the b.c.c. texture of the initial {beta} matrix clearly shows that a strong variant selection was induced by stress. In order to better understand the formation of this {alpha}{double_prime} orthorhombic texture, texture transformations were simulated according to different variant selection assumptions. As a result, it was shown that the {alpha}{double_prime} orthorhombic texture is formed by the variants favorably oriented with respect to stresses induced during tensile test.

  17. Phase stability in binary Ti-Al

    NASA Technical Reports Server (NTRS)

    Anderson, C. D.; Hofmeister, W. H.; Bayuzick, R. J.

    1991-01-01

    Binary Ti-Al samples containing from 46 to 54 at. pct Al were solidified while undercooled by various amounts using electromagnetic levitation techniques. A detailed thermal history of these samples was obtained with sampling rates as high as 500 KHz during recalescence. This very high sampling rate was essential to resolve the thermal events. Primary alpha solidification was observed in samples containing from 51 to 54 at. pct Al that were undercooled less than about 100 K at solidification. Primary beta solidification was found for all undercoolings tested in samples containing less than 51 at. pct Al and for undercoolings greater than about 100 K in samples containing 51 to 54 at. pct Al.

  18. Magnetic properties of Al/57Fe/Cr multilayers

    NASA Astrophysics Data System (ADS)

    Jani, Snehal; Lakshmi, N.; Jain, Vishal; Reddy, V. R.; Gupta, Ajay; Venugopalan, K.

    2013-06-01

    Conversion Electron Mössbauer Spectroscopy (CEMS) and DC magnetization are used to compare magnetic properties of as-deposited multilayer (MLS) and Fe2CrAl thin film made from Al/57Fe/Cr MLS deposited by ion beam sputtering and then annealed in UHV. Interdiffusion of elements on annealing sample-1 at 500°C leads to formation of a single, disordered film of Fe2CrAl as evidenced by hyperfine field values obtained by CEMS in the film which compares well with that in bulk Fe2CrAl. CEMS also shows contributions from Fe, Fe/Cr and Fe/Al interfaces in the MLS. Saturation magnetization of as-deposited sample-1 is much less than pure Fe due to reduced Fe thickness because of interface formation and also reduction in Fe-Fe interaction due to intervening Al and Cr layers.

  19. Structure and ductility of TiAl

    SciTech Connect

    Imayev, R.; Salishchev, G.; Imayev, V.; Shagiev, M.; Kuznetzov, A.

    1995-12-31

    The effect of structural factors (grain size and grain boundary structure) and strain rate on the deformation mechanism and ductility of TiAl in the temperature range of brittle-to-ductile transition and at room temperature was systematically investigated. It has been established that it is possible to substantially affect the deformation mechanism and ductility of this intermetallic by controlling structural factors, particularly the grain size, and varying the strain rate.

  20. Thermodynamic analysis of chemical compatibility of several compounds with Fe-Cr-Al alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1993-01-01

    Chemical compatibility between Fe-19.8Cr-4.8Al (weight percent), which is the base composition for the commercial superalloy MA956, and several carbides, borides, nitrides, oxides, and silicides was analyzed from thermodynamic considerations. The effect of addition of minor alloying elements, such as Ti, Y, and Y2O3, to the Fe-Cr-Al alloy on chemical compatibility between the alloy and various compounds was also analyzed. Several chemically compatible compounds that can be potential reinforcement materials and/or interface coating materials for Fe-Cr-Al based composites were identified.

  1. Fabrication of Fe-Al nanoparticles by selective oxidation of Fe-Al thin films

    NASA Astrophysics Data System (ADS)

    Jang, Pyungwoo; Shin, Seungchan; Jung, Chip-Sup; Kim, Kwang-Ho; Seomoon, Kyu

    2013-04-01

    The possibility of a new technique for fabricating nanoparticles from thin films using selective oxidation in an atmosphere mixture of water vapor and hydrogen was investigated. Fe-5wt.%Al films were RF-sputtered and annealed in the atmosphere mixture at 900°C for up to 200 min, in order to oxidize aluminum selectively. Thermodynamics simulation showed that temperatures exceeding 800°C are necessary to prevent iron from being oxidized, as confirmed by the depth profile of XPS. As the annealing time increased, the morphology of the 200-nm Fe-Al films changed from the continuous to the discontinuous type; thus, particulate Fe-Al films formed after 100 min. The particulate 10- to 100-nm Fe-Al films showed super-paramagnetic behavior after the oxidation. Thus, a new technique for fabricating nanoparticles was successfully introduced using selective oxidation.

  2. Effect of Al on the Wetting Behavior Between TiC x and Molten Ti-Al Alloys

    NASA Astrophysics Data System (ADS)

    Liu, Xuyang; Lv, Xuewei; Dong, Hongbiao; Li, Chunxin; Bai, Chenguang

    2015-10-01

    The wetting behavior and the interfacial reactions between TiC x substrate and molten Ti-Al alloys with different Al contents were studied using the Sessile Drop method at 1758 K (1485 °C) in argon atmosphere. It is found that the wettability and interface reaction products depend on Al content in the molten alloy. The initial contact angles between the molten Ti-Al alloy and TiC0.78 surface reduces from 110 to 80 deg when Al content in the alloy changes from 40 to 80 wt pct. The reduction in the initial contact angle is due to the decrease of surface tension of the molten Ti-Al alloys with increasing Al contents. The segregation of Al atoms to the surface occurred at all bulk concentrations of Ti-Al alloys. Al with lower surface tension tends to segregate on the surface of liquid Ti-Al alloy. In the spreading stage, the interfacial reaction led to the decrease in the contact angle. The adhesion in Ti-Al/TiC x system can be interpreted in terms of strong chemical interactions, which is greatly affected by the diffusion of C. The equilibrium contact angle was measured less than 10 deg. Finally, the reaction sequence at the Ti-Al melt and TiC x substrate interface is proposed.

  3. Improvement of the Electrochemical Behavior of Steel Surfaces Using a [Ti-Al/Ti-Al-N] n Multilayer System

    NASA Astrophysics Data System (ADS)

    Ipaz, L.; Aperador, W.; Caicedo, J. C.; Esteve, J.; Zambrano, G.

    2013-05-01

    The aim of this work is to improve the corrosion resistance of AISI D3 steel surfaces using a [Ti-Al/Ti-Al-N] n multilayer system deposited with different periods (Λ) and bilayer numbers ( n), via magnetron co-sputtering pulsed d.c. procedure, from a metallic (Ti-Al) binary target. The multilayer coatings were characterized by cross-sectional scanning electron microscopy that showed the modulation and microstructure of the [Ti-Al/Ti-Al-N] n multilayer system. The composition of the single Ti-Al and Ti-Al-N layer films was studied via x-ray photoelectron spectroscopy, where typical signals for Ti2p1/2, Ti2p, N1s, and Al2p3/2 were detected. The electrochemical properties were evaluated by electrochemical impedance spectroscopy and Tafel polarization curves. The optimal electrochemical behavior was obtained for the [Ti-Al/Ti-Al-N] n multilayered period of Λ = 25 nm (100 bilayers). At these conditions, the maximum polarization resistance (1719.32 kΩ cm2) and corrosion rate (0.7 μmy) were 300 and 35 times higher than that of uncoated AISI D3 steel substrate (5.61 kΩ cm2 and 25 μmy, respectively). Finally, scanning electron microscopy was used to analyze the [Ti-Al/Ti-Al-N] n multilayered surface after the corrosive attack. The improvement effects in the electrochemical behavior of the AISI D3 coated with the [Ti-Al/Ti-Al-N] n multilayered coatings could be attributed to the number of interfaces that act as obstacles for the inward and outward diffusions of Cl- ions, generating an increment in the energy or potential required for translating the corrosive ions across the coating/substrate interface.

  4. Constant stress of XD trademark TiAl containing nitrogen

    SciTech Connect

    Robertson, E.; Martin, P.L.

    1990-01-01

    Ti-47at%Al+7vol%(TiN+TiB{sub 2}) alloys, produced by the Martin Marietta XD{trademark} process, were subjected to tensile constant stress creep deformation in the range 760--850{degree}C temperature and 138--276 MPa (20--40 ksi) stress. These alloys have a matrix of TiAl and Ti{sub 3}Al initially containing 1 to 10 {mu}m diameter equiaxed particles of TiB{sub 2} and Ti{sub 2}AlN. Microstructures were examined using optical, SEM and TEM methods in an attempt to correlate the substructures with the property data. In particular, fine coherent particles have been observed to decorate dislocations and the interior of TiAl grains. The presence of these particles is thought to explain the creep resistance of this alloy. 14 refs., 5 figs.

  5. Forging of FeAl intermetallic compounds

    SciTech Connect

    Flores, O.; Juarez, J.; Campillo, B.; Martinez, L.; Schneibel, J.H.

    1994-09-01

    Much activity has been concentrated on the development of intermetallic compounds with the aim of improving tensile ductility, fracture toughness and high notch sensitivity in order to develop an attractive combination of properties for high and low temperature applications. This paper reports experience in processing and forging of FeAl intermetallic of B2 type. During the experiments two different temperatures were employed, and the specimens were forged after annealing in air, 10{sup {minus}2} torr vacuum and argon. From the results it was learned that annealing FeAl in argon atmosphere prior to forging resulted in better deformation behavior than for the other two environments. For the higher forging temperature used in the experiments (700C), the as-cast microstructure becomes partially recrystallized.

  6. Microstructure and Creep Properties of TiAl-Ti3Al In-Situ Composites

    SciTech Connect

    Hodge, A M; Hsiung, L L

    2004-02-18

    Objectives: {lg_bullet} Exploit thermomechanical-processing techniques to fabricate TiAl/Ti3Al in-situ laminate composites with the size of lamella width down to submicron or nanometer length-scales. {lg_bullet} Characterize microstructure and elevated-temperature creep resistance of the in-situ composites. {lg_bullet} Investigate the fundamental interrelationships among microstructures, alloying additions, and mechanical properties of the in-situ composites so as to achieve the desired properties of the in-situ composites for high-temperature structural applications.

  7. Brazing of zirconia to Ti and Ti6Al4V

    SciTech Connect

    Agathopoulos, S.; Moretto, P.; Peteves, S.D.

    1997-11-01

    The interface microstructure of tetragonal zirconia (Y{sub 2}O{sub 3}-stab.), (TZP), brazed to itself, Ti and Ti6Al4V with a commercial Ag35Cu1.65Ti filler alloy at 900{degrees}C in vacuum was investigated. TiO formed in the reaction zone in TZP/TZP joints irrespectively the brazing time. In TZP/Ti joints, a complex interface microstructure comprising Ti{sub 2}O, Cu{sub 2}Ti{sub 4}O and Cu-Ti-intermetallics was time dependent. High joint strengths of over 400 MPa were obtained for short brazing times. In TZP/Ti6Al4V joints, the evolution of the microstructure with brazing time depends on diffusion of Ti, Al and V to the interface forming Cu{sub 2}(Ti,A1,V){sub 4}O.

  8. Wear behavior of Al-Al{sub 3}Ti composite manufactured by a centrifugal method

    SciTech Connect

    Watanabe, Yoshimi; Yamanaka, Noboru; Fukui, Yasuyoshi

    1999-12-01

    The purpose of the present study was to develop a wear-resistant, light Al-Al{sub 3}Ti composite material. An Al-Al{sub 3}Ti composite specimen was machined from a thick-walled tube of Al-Al{sub 3}Ti functionally graded material (FGM) manufactured by the centrifugal method from a commercial ingot of Al-5 mass% Ti master alloy. The alloy was heated to a temperature where solid Al{sub 3}Ti particles resided in a liquid Al matrix, and then the centrifugal method was carried out. Al{sub 3}Ti particles in a commercial alloy ingot exist as platelets, and this shape was maintained through the casting. Three kinds of wear specimens were prepared, taking into account the morphology of the Al{sub 3}Ti particles in the thick-walled FGM tube; the Al{sub 3}Ti particles were arranged with their platelet planes nearly normal to the radial direction as a result of the applied centrifugal force. The wear resistance of the Al-Al{sub 3}Ti composite was significantly higher than that of pure Al. Wear-resistance anisotropy and dissolution of the Al{sub 3}Ti into the Al matrix at the near-surface region, around 100 {micro}m in depth, were also observed. The mechanism of the supersaturated-layer formation and the origin of the anisotropic wear resistance are discussed.

  9. Frustration of Negative Capacitance in Al2O3/BaTiO3 Bilayer Structure

    NASA Astrophysics Data System (ADS)

    Kim, Yu Jin; Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Jeon, Woojin; Moon, Taehwan; Do Kim, Keum; Jeong, Doo Seok; Yamada, Hiroyuki; Hwang, Cheol Seong

    2016-01-01

    Enhancement of capacitance by negative capacitance (NC) effect in a dielectric/ferroelectric (DE/FE) stacked film is gaining a greater interest. While the previous theory on NC effect was based on the Landau-Ginzburg-Devonshire theory, this work adopted a modified formalism to incorporate the depolarization effect to describe the energy of the general DE/FE system. The model predicted that the SrTiO3/BaTiO3 system will show a capacitance boost effect. It was also predicted that the 5 nm-thick Al2O3/150 nm-thick BaTiO3 system shows the capacitance boost effect with no FE-like hysteresis behavior, which was inconsistent with the experimental results; the amorphous-Al2O3/epitaxial-BaTiO3 system showed a typical FE-like hysteresis loop in the polarization – voltage test. This was due to the involvement of the trapped charges at the DE/FE interface, originating from the very high field across the thin Al2O3 layer when the BaTiO3 layer played a role as the NC layer. Therefore, the NC effect in the Al2O3/BaTiO3 system was frustrated by the involvement of reversible interface charge; the highly stored charge by the NC effect of the BaTiO3 during the charging period could not be retrieved during the discharging process because integral part of the polarization charge was retained within the system as a remanent polarization.

  10. Frustration of Negative Capacitance in Al2O3/BaTiO3 Bilayer Structure.

    PubMed

    Kim, Yu Jin; Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Jeon, Woojin; Moon, Taehwan; Kim, Keum Do; Jeong, Doo Seok; Yamada, Hiroyuki; Hwang, Cheol Seong

    2016-01-08

    Enhancement of capacitance by negative capacitance (NC) effect in a dielectric/ferroelectric (DE/FE) stacked film is gaining a greater interest. While the previous theory on NC effect was based on the Landau-Ginzburg-Devonshire theory, this work adopted a modified formalism to incorporate the depolarization effect to describe the energy of the general DE/FE system. The model predicted that the SrTiO3/BaTiO3 system will show a capacitance boost effect. It was also predicted that the 5 nm-thick Al2O3/150 nm-thick BaTiO3 system shows the capacitance boost effect with no FE-like hysteresis behavior, which was inconsistent with the experimental results; the amorphous-Al2O3/epitaxial-BaTiO3 system showed a typical FE-like hysteresis loop in the polarization - voltage test. This was due to the involvement of the trapped charges at the DE/FE interface, originating from the very high field across the thin Al2O3 layer when the BaTiO3 layer played a role as the NC layer. Therefore, the NC effect in the Al2O3/BaTiO3 system was frustrated by the involvement of reversible interface charge; the highly stored charge by the NC effect of the BaTiO3 during the charging period could not be retrieved during the discharging process because integral part of the polarization charge was retained within the system as a remanent polarization.

  11. Effects of boron on the mechanical properties of the TiAl-Ti3Al alloy: A first-principles investigation

    NASA Astrophysics Data System (ADS)

    Li, Zhong-Zhu; Wei, Ye; Zhou, Hong-Bo; Lu, Guang-Hong

    2017-01-01

    Employing a first-principles method in combination with the empirical criterions, we have investigated the site preference of boron (B) and its effect on the mechanical properties of the binary-phase TiAl-Ti3Al alloy. It is found that B energetically prefers to occupy the Ti-rich octahedral interstitial site, because B is more favorable to bond with Ti in comparison with Al. The occupancy tendency of B in the TiAl-Ti3Al alloy is the TiAl/Ti3Al interface > Ti3Al > TiAl, thus B tends to segregate into the binary-phase interface in the TiAl-Ti3Al alloy. The charge density difference shows that B at the TiAl-Ti3Al interface will form strong B-Ti bonds and weak B-Al bonds, leading to the significant increasing of the cleavage energy (γcl) and the unstable stacking fault energy (γus). This indicates that the presence of B will strengthen the TiAl/Ti3Al interface, but block its mobility. Further, the ratio of γcl/γus of the B-doped system is 4.63%, 8.19% lower than that of the clean system. Based on the empirical criterions, B will have a negative effect on the ductility of the TiAl-Ti3Al alloy.

  12. Synchrotron diffraction studies of TiC/FeTi cermets obtained by SHS

    SciTech Connect

    Contreras, L.; Turrillas, X.; Mas-Guindal, M.J.; Vaughan, G.B.M.; Kvick, A.; Rodriguez, M.A. . E-mail: mar@icv.csic.es

    2005-05-15

    TiC/FeTi composites have been obtained in situ by Self-propagating High-temperature Synthesis (SHS) of an intimate mixture of compacted powders of elemental carbon, titanium and iron. The reaction has been followed in real time by X-ray diffraction at the ESRF. The mechanism of the reaction is discussed in terms of the formation of a liquid phase corresponding to the eutectic of the Fe/Ti system prior to the TiC synthesis. Temperatures of reaction have been estimated by correlating thermal expansion coefficients with diffraction peaks shifts. The microstructures obtained by this method, suitable for cutting tools and wear resistant applications, are presented.

  13. Cost-Effective TiAl based Materials

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

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

  14. Analysis of Microstructural Evolution and Fracture Mechanisms in Ti-5Al-5V-5Mo-3Cr-0.4Fe in Response to Electron Beam Welding and Post Weld Heat Treatments

    NASA Astrophysics Data System (ADS)

    Sabol, Joseph C.

    Within the last half-century, advances in Ti and Ti alloys have increased their popularity in the aerospace industry as well as in commercial products. Some Ti alloys have even replaced steels and Ni-base alloys due to their high strength and superior corrosion resistance. Of the various Ti alloys, near-beta and metastable beta alloys have become more common since their first large-scale use in the SR-71 Blackbird. In particular, TIMET's Ti-5Al-5V-5Mo-3Cr (Timetal Ti555, Ti-5553) gained high attainable strengths, excellent forging characteristics, and increased sensitivity to heat treatments compared to other beta-Ti alloys. Ti-5553 has become widely known for its desirable attributes and has since become the baseline for the next generation of metastable beta and near-beta Ti alloys. However, as well known as Ti-5553 is in the aerospace and Ti industry, its responses to welding have, for the most part, gone uncharacterized. The work presented in this dissertation investigates the influence of electron beam welding and post weld heat treatments on the microstructural, mechanical, and fracture responses of Ti-5553. In this study, Ti-5553 was electron beam welded and heat-treated in accordance to three predetermined heat treatments: 700°C for 4 hours followed by air cooling to room temperature, 804°C for 1 hour followed by air cooling to room temperature, and 804°C for 1 hour followed by air cooling to room temperature then aging at 600°C for 4 hours followed by air cooling to room temperature. Subsequently, the mechanical properties, microstructure, solute partitioning, precipitate identities, and fracture characteristics were evaluated. With the use of traditional techniques and new technology it was shown that electron beam welded Ti-5553 in the as-welded condition and three post weld heat treatment conditions exhibited varying properties, distinctive to each of the corresponding microstructures. It was also found that the o-phase played a large role in the

  15. Development of ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

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

    2015-09-18

    FeCrAl alloys are prime candidates for accident-tolerant fuel cladding due to their excellent oxidation resistance up to 1400 C and good mechanical properties at intermediate temperature. Former commercial oxide dispersion strengthened (ODS) FeCrAl alloys such as PM2000 exhibit significantly better tensile strength than wrought FeCrAl alloys, which would alloy for the fabrication of a very thin (~250 m) ODS FeCrAl cladding and limit the neutronic penalty from the replacement of Zr-based alloys by Fe-based alloys. Several Fe-12-Cr-5Al ODS alloys where therefore fabricated by ball milling FeCrAl powders with Y2O3 and additional oxides such as TiO2 or ZrO2. The new Fe-12Cr-5Al ODS alloys showed excellent tensile strength up to 800 C but limited ductility. Good oxidation resistance in steam at 1200 and 1400 C was observed except for one ODS FeCrAl alloy containing Ti. Rolling trials were conducted at 300, 600 C and 800 C to simulate the fabrication of thin tube cladding and a plate thickness of ~0.6mm was reached before the formation of multiple edge cracks. Hardness measurements at different stages of the rolling process, before and after annealing for 1h at 1000 C, showed that a thinner plate thickness could likely be achieved by using a multi-step approach combining warm rolling and high temperature annealing. Finally, new Fe-10-12Cr-5.5-6Al-Z gas atomized powders have been purchased to fabricate the second generation of low-Cr ODS FeCrAl alloys. The main goals are to assess the effect of O, C, N and Zr contents on the ODS FeCrAl microstructure and mechanical properties, and to optimize the fabrication process to improve the ductility of the 2nd gen ODS FeCrAl while maintaining good mechanical strength and oxidation resistance.

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

    NASA Astrophysics Data System (ADS)

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

    2010-07-01

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

  17. Crystal structure of the mineral (Na,Ca,K){sub 2}(Ca,Na){sub 4}(Mg,Fe){sub 5}(Mg,Fe,Ti){sub 5}[Si{sub 12}Al{sub 4}O{sub 44}](F,O){sub 4}: a triclinic representative of the amphibole family

    SciTech Connect

    Rastsvetaeva, R. K. Aksenov, S. M.

    2012-05-15

    A mineral belonging to the amphibole family found at the Rothenberg paleovolcano (Eifel, Germany) was studied by single-crystal X-ray diffraction. The triclinic pseudomonoclinic unit-cell parameters are a = 5.3113(1) Angstrom-Sign , b = 18.0457(3) Angstrom-Sign ; c = 9.8684(2) Angstrom-Sign , {alpha} = 90.016(2) Degree-Sign , {beta} = 105.543(4) Degree-Sign , {gamma} = 89.985(2) Degree-Sign . The structure was solved by direct methods in sp. gr. P1 and refined to the R factor of 2.7% based on 6432 reflections with |F| > 3{sigma}(F) taking into account twinning. The mineral with the idealized formula (Na,Ca,K){sub 2}(Ca,Na){sub 4}(Mg,Fe){sub 5}(Mg,Fe,Ti){sub 5}[Si{sub 12}Al{sub 4}O{sub 44}](F,O){sub 4} has some symmetry and structural features that distinguish it from other minerals of this family.

  18. Thermoelastic Martensitic Transformations in Single Crystals of FeNiCoAlX(B) Alloys

    NASA Astrophysics Data System (ADS)

    Chumlyakov, Yu. I.; Kireeva, I. V.; Kuts, O. A.; Platonova, Yu. N.; Poklonov, V. V.; Kukshauzen, I. V.; Kukshauzen, D. A.; Panchenko, M. Yu.; Reunova, K. A.

    2016-03-01

    Using single crystals of Fe-based disordered alloys (Fe - 28% Ni - 17% Co - 11.5% Al - 2.5% X (0.05% B) (at.%) (X = Ti, Nb(B), (Ti + Nb)B), undergoing thermoelastic γ-α '-martensitic transformations (MTs), it is shown that precipitation of particles of the ordered γ'-phase in the course of aging at T = 973 K for 5 h results in the development of shape memory (SME) and superelasticity (SE) effects. It is experimentally found that variation in chemical composition and size of disperse particles of the γ'-phase allows controlling both mechanical and functional properties - SME and SE.

  19. Study of preparation of TiB{sub 2} by TiC in Al melts

    SciTech Connect

    Ding Haimin; Liu Xiangfa; Nie Jinfeng

    2012-01-15

    TiB{sub 2} particles are prepared by TiC in Al melts and the characteristics of them are studied. It is found that TiC particles are unstable when boron exists in Al melts with high temperature and will transform to TiB{sub 2} and Al{sub 4}C{sub 3}. Most of the synthesized TiB{sub 2} particles are regular hexagonal prisms with submicron size. The diameter of the undersurfaces of these prisms is ranging from 200 nm to 1 {mu}m and the height is ranging from 100 nm to 300 nm. It is considered that controlling the transformation from TiC to TiB{sub 2} is an effective method to prepare small and uniform TiB{sub 2} particles. - Highlights: Black-Right-Pointing-Pointer TiC can easily transform into TiB{sub 2} in Al melts. Black-Right-Pointing-Pointer TiB{sub 2} formed by TiC will grow into regular hexagonal prisms with submicron size. Black-Right-Pointing-Pointer Controlling the transformation from TiC to TiB{sub 2} is an effective method to prepare small and uniform TiB{sub 2} particles.

  20. Overview of the development of FeAl intermetallic alloys

    SciTech Connect

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

    1995-09-01

    B2-phase FeAl ordered intermetallic alloys based on an Fe-36 at.% Al composition are being developed to optimize a combination of properties that includes high-temperature strength, room-temperature ductility, and weldability. Microalloying with boron and proper processing are very important for FeAl properties optimization. These alloys also have the good to outstanding resistance to oxidation, sulfidation, and corrosion in molten salts or chlorides at elevated temperatures, characteristic of FeAl with 30--40 at.% Al. Ingot- and powder-metallurgy (IM and PM, respectively) processing both produce good properties, including strength above 400 MPa up to about 750 C. Technology development to produce FeAl components for industry testing is in progress. In parallel, weld-overlay cladding and powder coating technologies are also being developed to take immediate advantage of the high-temperature corrosion/oxidation and erosion/wear resistance of FeAl.

  1. Phase equilibria and structural investigations in the system Al-Fe-Si.

    PubMed

    Marker, Martin C J; Skolyszewska-Kühberger, Barbara; Effenberger, Herta S; Schmetterer, Clemens; Richter, Klaus W

    2011-12-01

    The Al-Fe-Si system was studied for an isothermal section at 800 °C in the Al-rich part and at 900 °C in the Fe-rich part, and for half a dozen vertical sections at 27, 35, 40, 50 and 60 at.% Fe and 5 at.% Al. Optical microscopy and powder X-ray diffraction (XRD) was used for initial sample characterization, and Electron Probe Microanalysis (EPMA) and Scanning Electron Microscopy (SEM) of the annealed samples was used to determine the exact phase compositions. Thermal reactions were studied by Differential Thermal Analysis (DTA). Our experimental results are generally in good agreement with the most recent phase diagram versions of the system Al-Fe-Si. A new ternary high-temperature phase τ12 (cF96, NiTi2-type) with the composition Al48Fe36Si16 was discovered and was structurally characterized by means of single-crystal and powder XRD. The variation of the lattice parameters of the triclinic phase τ1 with the composition Al2+x Fe3Si3-x (-0.3 < x < 1.3) was studied in detail. For the binary phase FeSi2 only small solubility of Al was found in the low-temperature modification LT-FeSi2 (ζβ ) but significant solubility in the high-temperature modification HT-FeSi2 (ζα ) (8.5 at.% Al). It was found that the high-temperature modification of FeSi2 is stabilized down to much lower temperature in the ternary, confirming earlier literature suggestions on this issue. DTA results in four selected vertical sections were compared with calculated sections based on a recent CALPHAD assessment. The deviations of liquidus values are significant suggesting the need for improvement of the thermodynamic models.

  2. Solute partitioning in TiAl/Ti{sub 3}Al alloys

    SciTech Connect

    Munroe, P.R.; Baker, I.

    1999-11-19

    Over the last few years there have been intense research and development efforts on two-phase alloys based on ({gamma}) TiAl + ({alpha}{sub 2}) Ti{sub 3}Al; the goal being to develop alloys for aerospace and, possibly, automotive applications. Two-phase alloys have been studied which contain numerous elemental additions, the more common ones of which are W, Mo, Nb, Cr, W, V, Si, Mn, Ta, C and B. These have been studied both for their phase stability and to determine their monotonic and cycling loading response both at low and high temperature. Although the mechanical properties and physical behavior of these alloys have been studied in detail, there is surprisingly little published information on the distribution of these alloying additions between the two phases. Here the authors report a short study on two recently developed alloys concerning how some of these elemental additions partition between the two phases.

  3. Energetics of point defects in {gamma}-TiAl

    SciTech Connect

    Raju, S.; Mohandas, E.; Raghunathan, V.S.

    1996-02-15

    {gamma}TiAl has been receiving a great deal of attention in recent times owing to its industrial importance. This structural intermetallic is a candidate material for high temperature aerospace applications. Therefore, a study of point defect properties is useful in elucidating its physical metallurgy. In this brief communication, the authors discuss the vacancy and antisite defect properties of {gamma}-TiAl.

  4. Ultrasound assisted combustion synthesis of TiC in Al-Ti-C system.

    PubMed

    Liu, Zhiwei; Rakita, Milan; Xu, Wilson; Wang, Xiaoming; Han, Qingyou

    2015-11-01

    This research investigated the effects of high-intensity ultrasound on the combustion synthesis of TiC particles in Al-Ti-C system. The process involved that high-intensity ultrasound was applied on the surface of a compacted Al-Ti-C pellet directly through a Nb probe during the thermal explosion reaction. By comparing with the sample without ultrasonic treatment, it was found that the thermal explosion reaction for synthesizing TiC phase could take place thoroughly in the ultrasonically treated sample. During the process of synthesizing TiC phase, the dissolution of solid graphite particles into the Al-Ti melt, as well as the nucleation and growth of TiC particles could be promoted effectively due to the effects of ultrasound, leading to an enhancement of the formation of TiC particles. Ultrasound assisted combustion synthesis as a simple and effective approach was proposed for synthesizing materials in this research.

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

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

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

  6. Machinability of Intermetallic Compound Fe3Al from the Viewpoint of Tool Wear

    NASA Astrophysics Data System (ADS)

    Sasaki, Tomohiro; Yakou, Takao

    The intermetallic compound Fe3Al was processed by a reactive sintering process, and its machinability from the viewpoint of tool wear was investigated using dry turning. In cutting Fe3Al with a cemented carbide tool, the tool life was approximately one tenth that of cutting carbon tool steel SK3 because of intense flank wear. The tool life for cutting Fe3Al using the cemented carbide P20(WC-TiC-TaC-Co) tool was longer than for cemented carbide K10(WC-Co). In addition, a cermet tool reached its tool life limit by chipping for the whole cutting speed range measured. The roughness of the machined surface of Fe3Al cut using a cemented carbide tool was much smaller than for SK3. However, for cutting using the cermet tool, the roughness showed a sharp rise due to chipping. It was found that the wear rate of the WC particles in the tool material is larger than TiC particles. The results of the study suggest that the cemented carbide P20 is suitable for cutting Fe3Al.

  7. Influence of impact speed on water droplet erosion of TiAl compared with Ti6Al4V.

    PubMed

    Mahdipoor, M S; Kirols, H S; Kevorkov, D; Jedrzejowski, P; Medraj, M

    2015-09-22

    Water Droplet Erosion (WDE) as a material degradation phenomenon has been a concern in power generation industries for decades. Steam turbine blades and the compressor blades of gas turbines that use water injection usually suffer from WDE. The present work focuses on studying erosion resistance of TiAl as a potential alloy for turbine blades compared to Ti6Al4V, a frequently used blade alloy. Their erosion behaviour is investigated at different droplet impact speeds to determine the relation between erosion performance and impact speed. It is found that the relationship is governed by a power law equation, ER ~ V(n), where the speed exponent is 7-9 for Ti6Al4V and 11-13 for TiAl. There is a contrast between the observed speed exponent in this work and the ones reported in the literature for Ti6Al4V. It is attributed to the different erosion setups and impingement conditions such as different droplet sizes. To verify this, the erosion experiments were performed at two different droplet sizes, 464 and 603 μm. TiAl showed superior erosion resistance in all erosion conditions; however, its erosion performance exhibits higher sensitivity to the impact speed compared to Ti6Al4V. It means that aggressive erosion conditions decrease the WDE resistance superiority of TiAl.

  8. Influence of impact speed on water droplet erosion of TiAl compared with Ti6Al4V

    NASA Astrophysics Data System (ADS)

    Mahdipoor, M. S.; Kirols, H. S.; Kevorkov, D.; Jedrzejowski, P.; Medraj, M.

    2015-09-01

    Water Droplet Erosion (WDE) as a material degradation phenomenon has been a concern in power generation industries for decades. Steam turbine blades and the compressor blades of gas turbines that use water injection usually suffer from WDE. The present work focuses on studying erosion resistance of TiAl as a potential alloy for turbine blades compared to Ti6Al4V, a frequently used blade alloy. Their erosion behaviour is investigated at different droplet impact speeds to determine the relation between erosion performance and impact speed. It is found that the relationship is governed by a power law equation, ER ~ Vn, where the speed exponent is 7-9 for Ti6Al4V and 11-13 for TiAl. There is a contrast between the observed speed exponent in this work and the ones reported in the literature for Ti6Al4V. It is attributed to the different erosion setups and impingement conditions such as different droplet sizes. To verify this, the erosion experiments were performed at two different droplet sizes, 464 and 603 μm. TiAl showed superior erosion resistance in all erosion conditions; however, its erosion performance exhibits higher sensitivity to the impact speed compared to Ti6Al4V. It means that aggressive erosion conditions decrease the WDE resistance superiority of TiAl.

  9. Influence of impact speed on water droplet erosion of TiAl compared with Ti6Al4V

    PubMed Central

    Mahdipoor, M.S.; Kirols, H.S.; Kevorkov, D.; Jedrzejowski, P.; Medraj, M.

    2015-01-01

    Water Droplet Erosion (WDE) as a material degradation phenomenon has been a concern in power generation industries for decades. Steam turbine blades and the compressor blades of gas turbines that use water injection usually suffer from WDE. The present work focuses on studying erosion resistance of TiAl as a potential alloy for turbine blades compared to Ti6Al4V, a frequently used blade alloy. Their erosion behaviour is investigated at different droplet impact speeds to determine the relation between erosion performance and impact speed. It is found that the relationship is governed by a power law equation, ER ~ Vn, where the speed exponent is 7–9 for Ti6Al4V and 11–13 for TiAl. There is a contrast between the observed speed exponent in this work and the ones reported in the literature for Ti6Al4V. It is attributed to the different erosion setups and impingement conditions such as different droplet sizes. To verify this, the erosion experiments were performed at two different droplet sizes, 464 and 603 μm. TiAl showed superior erosion resistance in all erosion conditions; however, its erosion performance exhibits higher sensitivity to the impact speed compared to Ti6Al4V. It means that aggressive erosion conditions decrease the WDE resistance superiority of TiAl. PMID:26391370

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

    NASA Astrophysics Data System (ADS)

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

    2012-05-01

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

  11. Comparison study of Cu-Fe-Ti and Co-Fe-Ti oxide catalysts for selective catalytic reduction of NO with NH3 at low temperature.

    PubMed

    Zhu, Lin; Zhong, Zhaoping; Yang, Han; Wang, Chunhua

    2016-09-15

    In this paper, a series of Cu-Fe-Ti and Co-Fe-Ti oxide catalysts were prepared by sol gel method. Cu-Fe-Ti and Co-Fe-Ti oxide catalysts showed the moderate catalytic activity for selective catalytic reduction (SCR) of NO with NH3 at low temperature. The catalysts with the molar ratio as 4:1:10 (M:Fe:Ti) were selected as the representatives for comparison of reaction properties and H2O resistance, which were denoted as Cu-Fe/TiO2 and Co-Fe/TiO2 respectively. The characterization results manifested Co-Fe/TiO2 owned more adsorption capacity of the reactants and Cu-Fe/TiO2 had better redox ability. The in situ DRIFTS experiments indicated that adsorbed NH3 species and nitrate species both exhibited reaction activity for Co-Fe/TiO2, while nitric oxide was only be reduced by adsorbed NH3 species through Eley-Rideal mechanism for Cu-Fe/TiO2 at 150°C. Co-Fe/TiO2 exhibited the better resistance to H2O and its temperature window shifted towards the higher temperature in presence of 10vol% H2O, while the SCR activity of Cu-Fe/TiO2 was inhibited significantly in the whole temperature range investigated. The suppression of adsorption and activation for NH3 and NOx might be the reasons for the reversible inactivation, which was confirmed by the inhibitation of catalytic activities for separation NH3 and NO oxidation under the wet condition. We speculated that different thermal stability of adsorbed species and redox capacity of catalysts leaded to the different SCR behavior in absence and presence of H2O.

  12. Microscopic Properties of Long-Period Ordering in Al-Rich TiAl Alloys

    NASA Astrophysics Data System (ADS)

    Hata, S.; Nakano, T.; Kuwano, N.; Itakura, M.; Matsumura, S.; Umakoshi, Y.

    2008-07-01

    The ordering mechanism of long-period superstructures (LPSs) in Al-rich TiAl alloys has been investigated by high-resolution transmission electron microscopy (HRTEM). The LPSs are classified in terms of arrangements of base clusters with different shapes and compositions formed in Ti-rich (002) layers of L10-TiAl matrix: square Ti4Al, fat rhombus Ti3Al, and lean rhombus Ti2Al type clusters. The HRTEM observations revealed that antiphase boundaries of long-range-ordered LPS domains and short-range-ordered microdomains are constructed by various space-filling arrangements of the base clusters. Such a microscopic property characterized by the base clusters and their arrangements is markedly analogous to that of the {left< {{text{1,1/2,0}}} rightrangle } * special-point ordering alloys such as Ni-Mo.

  13. Influence of Fe and Ti addition on properties of Na+-β/β″-alumina solid electrolytes

    NASA Astrophysics Data System (ADS)

    Lee, Sung-Tae; Lee, Dae-Han; Kim, Jin-Sik; Lim, Sung-Ki

    2017-02-01

    Transition metal (Fe, Ti)-doped Na+-β/β″-alumina samples were synthesized via a solid-state reaction, and the sintered specimens were characterized using X-ray diffraction, scanning electron microscopy, densitometry, and impedance analysis. The results indicated that both the sintered density and β″-alumina fraction were effectively improved by doping with Fe and Ti because of the increased concentration of Al3+ ion vacancies in the Na+-β/β″-alumina. These vacancies promoted stabilization of the β″-alumina phase and densification by providing a diffusion path for Al3+ ions. The presence of Fe and Ti in the alumina increased the grain boundary diffusivity, thereby improving the mass transport. Thus, anisotropic grain growth occurred with increasing dopant content. However, excessive liquid-phase formation during sintering occurred when the amount of Ti was greater than 2.0 mol%, and the lowered sintered density decreased the ionic conductivity of the Na+-β/β″-alumina because the ionic conductivity behavior has a closer relationship to the trend of sintered density. The highest ionic conductivities of the Fe- and Ti-doped sintered specimens were 1.4 × 10-1 S/cm (10.0 mol% Fe-doped) and 1.6 × 10-1 S/cm (1.5 mol% Ti-doped) at 350 °C.

  14. Influence of Fe and Ti addition on properties of Na+-β/β″-alumina solid electrolytes

    NASA Astrophysics Data System (ADS)

    Lee, Sung-Tae; Lee, Dae-Han; Kim, Jin-Sik; Lim, Sung-Ki

    2017-03-01

    Transition metal (Fe, Ti)-doped Na+-β/β″-alumina samples were synthesized via a solid-state reaction, and the sintered specimens were characterized using X-ray diffraction, scanning electron microscopy, densitometry, and impedance analysis. The results indicated that both the sintered density and β"-alumina fraction were effectively improved by doping with Fe and Ti because of the increased concentration of Al3+ ion vacancies in the Na+-β/β″-alumina. These vacancies promoted stabilization of the β″-alumina phase and densification by providing a diffusion path for Al3+ ions. The presence of Fe and Ti in the alumina increased the grain boundary diffusivity, thereby improving the mass transport. Thus, anisotropic grain growth occurred with increasing dopant content. However, excessive liquid-phase formation during sintering occurred when the amount of Ti was greater than 2.0 mol%, and the lowered sintered density decreased the ionic conductivity of the Na+-β/β″-alumina because the ionic conductivity behavior has a closer relationship to the trend of sintered density. The highest ionic conductivities of the Fe- and Ti-doped sintered specimens were 1.4 × 10-1 S/cm (10.0 mol% Fe-doped) and 1.6 × 10-1 S/cm (1.5 mol% Ti-doped) at 350 °C.

  15. Stabilization of itinerant (band) magnetism in FeAl by Ga substitution for Al

    NASA Astrophysics Data System (ADS)

    Papaconstantopoulos, D. A.; Mazin, I. I.; Hathaway, K. B.

    2001-06-01

    Band structure calculations of FeGa1-xAlx have been performed, to further investigate the stability of ferromagnetism in FeAl. The Stoner parameter increases by about 20% at the FeGa end. This is also confirmed by our spin-polarized calculations. We conclude that Ga substitution for Al is likely to stabilize the elusive (or illusive) ferromagnetic state in FeAl.

  16. Structure of Al-Ti-C master alloys

    NASA Astrophysics Data System (ADS)

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

    2011-06-01

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

  17. Newly developed Ti-Nb-Zr-Ta-Si-Fe biomedical beta titanium alloys with increased strength and enhanced biocompatibility.

    PubMed

    Kopova, Ivana; Stráský, Josef; Harcuba, Petr; Landa, Michal; Janeček, Miloš; Bačákova, Lucie

    2016-03-01

    Beta titanium alloys are promising materials for load-bearing orthopaedic implants due to their excellent corrosion resistance and biocompatibility, low elastic modulus and moderate strength. Metastable beta-Ti alloys can be hardened via precipitation of the alpha phase; however, this has an adverse effect on the elastic modulus. Small amounts of Fe (0-2 wt.%) and Si (0-1 wt.%) were added to Ti-35Nb-7Zr-6Ta (TNZT) biocompatible alloy to increase its strength in beta solution treated condition. Fe and Si additions were shown to cause a significant increase in tensile strength and also in the elastic modulus (from 65 GPa to 85 GPa). However, the elastic modulus of TNZT alloy with Fe and Si additions is still much lower than that of widely used Ti-6Al-4V alloy (115 GPa), and thus closer to that of the bone (10-30 GPa). Si decreases the elongation to failure, whereas Fe increases the uniform elongation thanks to increased work hardening. Primary human osteoblasts cultivated for 21 days on TNZT with 0.5Si+2Fe (wt.%) reached a significantly higher cell population density and significantly higher collagen I production than cells cultured on the standard Ti-6Al-4V alloy. In conclusion, the Ti-35Nb-7Zr-6Ta-2Fe-0.5Si alloy proves to be the best combination of elastic modulus, strength and also biological properties, which makes it a viable candidate for use in load-bearing implants.

  18. Centerless grinding of TiAl using conventional grinding wheels

    SciTech Connect

    Jones, P.E.; Smits, D.; Eylon, D.; Smits, C.

    1995-12-31

    Ordered gamma titanium aluminide (TiAl) based alloys are now under consideration for automotive valves because of their light weight and high strength at temperatures up to 850 C. Finishing comprises as much as 70% of the cost of an automotive valve, therefore the grindability of TiAl valves will influence their commercial viability. This study compared the grindability of the TiAl alloy Ti-47Al-2Nb-1.75Cr (at%) to standard valve steels, nickel base superalloys, and conventional titanium alloys using the centerless grinding process. Three grinding conditions simulating stem grinding were selected. The power requirements, grinding time, and grinding wheel consumption were used to estimate the cost to grind TiAl on conventional centerless grinding equipment using vitrified bonded silicon carbide wheels. The metallurgical effects of rough and finish stem grinding cycles on the surface were determined. The grindability factor of TiAl, a measure of grinding cost, was slightly inferior to conventional valve steels, but much better than conventional titanium alloys. The high work hardening rate of the TiAl resulted in much better surface finish at high metal removal rates than that achieved in steels. No grinding cracks were observed, even under the rough grinding conditions. Microhardness profiles indicated significant work hardening of the surface under all three grinding conditions.

  19. Ab initio studies on the adsorption and implantation of Al and Fe to nitride materials

    SciTech Connect

    Riedl, H.; Zálešák, J.; Arndt, M.; Polcik, P.; Holec, D.; Mayrhofer, P. H.

    2015-09-28

    The formation of transfer material products on coated cutting and forming tools is a major failure mechanism leading to various sorts of wear. To describe the atomistic processes behind the formation of transfer materials, we use ab initio to study the adsorption energy as well as the implantation barrier of Al and Fe atoms for (001)-oriented surfaces of TiN, Ti{sub 0.50}Al{sub 0.50}N, Ti{sub 0.90}Si{sub 0.10}N, CrN, and Cr{sub 0.90}Si{sub 0.10}N. The interactions between additional atoms and nitride-surfaces are described for pure adhesion, considering no additional stresses, and for the implantation barrier. The latter, we simplified to the stress required to implant Al and Fe into sub-surface regions of the nitride material. The adsorption energies exhibit pronounced extrema at high-symmetry positions and are generally highest at nitrogen sites. Here, the binary nitrides are comparable to their ternary counterparts and the average adhesive energy is higher (more negative) on CrN than TiN based systems. Contrary, the implantation barrier for Al and Fe atoms is higher for the ternary systems Ti{sub 0.50}Al{sub 0.50}N, Ti{sub 0.90}Si{sub 0.10}N, and Cr{sub 0.90}Si{sub 0.10}N than for their binary counterparts TiN and CrN. Based on our results, we can conclude that TiN based systems outperform CrN based systems with respect to pure adhesion, while the Si-containing ternaries exhibit higher implantation barriers for Al and Fe atoms. The data obtained are important to understand the atomistic interaction of metal atoms with nitride-based materials, which is valid not just for machining operations but also for any combination such as interfaces between coatings and substrates or multilayer and phase arrangements themselves.

  20. Ferroelectric transition of Aurivillius compounds Bi5Ti3FeO15 and Bi6Ti3Fe2O18

    NASA Astrophysics Data System (ADS)

    Li, J.-B.; Huang, Y. P.; Rao, G. H.; Liu, G. Y.; Luo, J.; Chen, J. R.; Liang, J. K.

    2010-05-01

    Single-phase Bi5Ti3FeO15 and Bi6Ti3Fe2O18 ceramics have been synthesized by solid state reaction. The ferroelectric transition of the compounds was studied by differential scanning calorimetry, high-temperature x-ray diffraction, and temperature-dependent dielectric measurements. Two solid-state structural transitions were observed in both compounds, one is the orthorhombic↔tetragonal transition (ferroelectric transition) at 1021 K for Bi5Ti3FeO15 and 973 K for Bi6Ti3Fe2O18, and the other is accompanied by an abrupt lattice expansion of the tetragonal phase at about 1110 K for Bi5Ti3FeO15 and about 1090 K for Bi6Ti3Fe2O18.

  1. Differentiation of nelsonitic magmas in the formation of the ~1.74 Ga Damiao Fe-Ti-P ore deposit, North China

    NASA Astrophysics Data System (ADS)

    Chen, Wei Terry; Zhou, Mei-Fu; Zhao, Tai-Ping

    2013-06-01

    The ~1.74 Ga Damiao anorthosite complex, North China, is composed of anorthosite and leuconorite with subordinate melanorite, mangerite, oxide-apatite gabbronorite, perthite noritic (i.e., jotunitic) and ferrodioritic dykes. The complex hosts abundant vein-, pod- and lens-like Fe-Ti-P ores containing variable amounts of apatite (10-60 modal%) and Fe-Ti oxides. In addition to Fe-Ti-P ores, there are also abundant Fe-Ti ores which are closely associated with Fe-Ti-P ores in the deposit. Most of Fe-Ti-P ores are dominated by Fe-Ti oxides and apatite, devoid of silicate minerals, mineralogically similar to the common nelsonites elsewhere. In contrast, Fe-Ti ores are dominated by Fe-Ti oxides with minor apatite (<5 modal %). The parental magma of these ores, estimated from olivine and apatite compositions using mineral-melt partition coefficients, has composition similar to the ferrodioritic dykes. Fe-Ti-P ores have variable Fe-Ti oxides and apatite proportions, indicating that they are cumulates. Their simple assemblage of Fe-Ti oxides and apatite and local net-texture suggest that the Fe-Ti-P ores in Damiao have formed from nelsonitic melts immiscibly separated from the ferrodioritic magma during late-stage differentiation. Fe-Ti ores are also cumulates and have mineral compositions similar to Fe-Ti-P ores. The close association between Fe-Ti and Fe-Ti-P ores indicates that the Fe-Ti ores may have also formed from the nelsonitic melts. We proposed that differentiation of nelsonitic melts accompanied by gravity settling is responsible for the formation of Fe-Ti and Fe-Ti-P ores. Such a differentiation process in nelsonitic melts is well supported by variations of Sr, Y, Th, U, REE and Eu/Eu* of apatite in Fe-Ti-P ores. Using oxides/apatite ratio of 2:1 and compositions of apatite and calculated primary oxides, we estimate the composition of the nelsonitic melt as ~52.0 wt% Fe2O3t, ~18.5 wt% CaO, ~14.2 wt% P2O5, ~8.7 wt% TiO2, ~4.0 wt% Al2O3 and ~1.1 wt% MgO with minor

  2. Strengthening mechanisms in Ti-Nb-Zr-Ta and Ti-Mo-Zr-Fe orthopaedic alloys.

    PubMed

    Banerjee, Rajarshi; Nag, Soumya; Stechschulte, John; Fraser, Hamish L

    2004-08-01

    The microstructural evolution and attendant strengthening mechanisms in two novel orthopaedic alloy systems, Ti-Nb-Zr-Ta and Ti-Mo-Zr-Fe, have been compared and contrasted in this paper. Specifically, the alloy compositions considered are Ti-34Nb-9Zr-8Ta and Ti-13Mo-7Zr-3Fe. In the homogenized condition, both alloys exhibited a microstructure consisting primarily of a beta matrix with grain boundary alpha precipitates and a low-volume fraction of intra-granular alpha precipitates. On ageing the homogenized alloys at 600 degrees C for 4 hr, both alloys exhibited the precipitation of refined scale secondary alpha precipitates homogeneously in the beta matrix. However, while the hardness of the Ti-Mo-Zr-Fe alloy marginally increased, that of the Ti-Nb-Zr-Ta alloy decreased substantially as a result of the ageing treatment. In order to understand this difference in the mechanical properties after ageing, TEM studies have been carried out on both alloys prior to and post the ageing treatment. The results indicate the existence of a metastable B2 ordering in the Ti-Nb-Zr-Ta alloy in the homogenized condition which is destroyed by the ageing treatment, consequently leading to a decrease in the hardness.

  3. Hydriding of TiZrNiFe nanocompounds

    NASA Astrophysics Data System (ADS)

    Żywczak, A.; Shinya, Daigo; Gondek, Ł.; Takasaki, Akito; Figiel, H.

    2010-01-01

    Ti-based quasicrystals belong to the second largest group of the stable quasicrystals, showing attractive properties as hydrogen storage materials. The Ti 45Zr 38Ni 17 intermetallic compound forms an icosahedral ( i-phase) structure, in which Ti and Zr atoms possess very good chemical affinity for hydrogen absorption. We modified the Ti 45Zr 38Ni 17 compounds by substituting 3d metals (iron) for Ni to obtain amorphous phase. The samples were produced by mechanical alloying. The 3d metal atoms are located in the same positions as nickel. The structural characterization was made by means of XRD measurements. Thermodynamic properties were studied by differential scanning calorimetry (DSC) and thermal desorption spectroscopy (TDS). The obtained amorphous phases Ti 45Zr 38Ni (9,13)Fe (8,4) transform to the i-phase at the similar temperature range as Ti 45Zr 38Ni 17. The final concentration of absorbed hydrogen depends on the amount of Fe. When increasing the amount of iron, the hydrogen release temperature becomes lower. After hydriding, the samples decompose into simple metal hydrides.

  4. Mechanical Response of Titanium Aluminide (TiAl3)

    DTIC Science & Technology

    2010-06-01

    Mechanical Response of Titanium Aluminide (TiAl3) by Ajmer Dwivedi and Jermaine Bradley ARL-CR-0669 June 2010 prepared by...Mechanical Response Of Titanium Aluminide (TiAl3) 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER...SUPPLEMENTARY NOTES 14. ABSTRACT Compression tests have been performed on TiAl3 at strain rates from 0.00003?500/s. All tests were done at room temperature

  5. Microstructural Evolution in Novel Suction Cast Multicomponent Ti-Fe-Co Alloys

    NASA Astrophysics Data System (ADS)

    Samal, Sumanta; Agarwal, Swapnil; Gautam, Priya; Biswas, Krishanu

    2015-02-01

    The present work is aimed at understanding the solidification pathways of the Ti-rich Ti-Fe-Co in situ composites consisting of ultrafine eutectic with micron-scale dendrites. The effect of addition of Co in the Ti-rich binary Ti-Fe alloys has been systematically investigated. The series of Ti-Fe-Co ternary alloys i.e., Ti75Fe25- x Co x ( x = 0, 5, 10, 12.5, 15, 20), (Ti70.5Fe29.5)100- x Co x ( x = 0, 2, 4, 6, 8, and 10), Ti70Fe30- x Co x ( x = 0, 5, 10, 15, 20, 25), Ti65Fe35- x Co x ( x = 0, 10, 15, 17.5, 20, 25), and Ti60Fe40- x Co x ( x = 0, 16, 18, 20, 22, 24) are synthesized by arc melting cum suction casting technique under high purity Ar atmosphere to obtain alloy cylinders having diameter ( ϕ) of 3 mm. Detailed X-ray diffraction and electron microscopic (SEM and TEM) study are carried out to identify the phases as well as to monitor the sequence of phase evolution in the ternary alloys. The present study conclusively proves that the Ti65Fe10Co25, Ti70Fe30- x Co x ( x = 10, 20, 25), and Ti75Fe15Co10 alloys show the ternary quasi-peritectic reaction of L + Ti(Co,Fe) → ( β-Ti)ss + Ti2(Co,Fe) at invariant point P (=Ti75.5±0.8Fe6.3±2.1Co18.2±2.7) which is cooperated by means of eutectic reaction of L → ( β-Ti)ss + Ti2(Co,Fe) below P and peritectic reaction L + Ti(Co,Fe) → Ti2(Co,Fe) for Ti65Fe10Co25,Ti70Fe10Co20, and Ti70Fe5Co25 alloys or eutectic reaction L → ( β-Ti)ss +Ti(Co,Fe) for Ti70Fe20Co10, and Ti75Fe15Co10 alloys above the point P. In addition, the peritectic reaction L + Ti(Co,Fe) → Ti2(Co,Fe) plays a significant role in the phase evolution. The microstructural evolution, phase equilibria and solidification pathways have been explained by generating liquidus projection of the investigated alloys. Interestingly, the Co addition leads to the formation of complex Ti2Co phase and significantly affects the compositional stability of TiFe phase. This is found to have significant influence on the microstructural development during suction

  6. Effect of ball-milling and Fe-/Al-doping on the structural aspect and visible light photocatalytic activity of TiO2 towards Escherichia coli bacteria abatement.

    PubMed

    Schlur, Laurent; Begin-Colin, Sylvie; Gilliot, Pierre; Gallart, Mathieu; Carré, Gaëlle; Zafeiratos, Spiros; Keller, Nicolas; Keller, Valérie; André, Philippe; Greneche, Jean-Marc; Hezard, Bernard; Desmonts, Marie-Hélène; Pourroy, Geneviève

    2014-05-01

    Escherichia coli abatement was studied in liquid phase under visible light in the presence of two commercial titania photocatalysts, and of Fe- and Al-doped titania samples prepared by high energy ball-milling. The two commercial titania photocatalysts, Aeroxide P25 (Evonik industries) exhibiting both rutile and anatase structures and MPT625 (Ishihara Sangyo Kaisha), a Fe-, Al-, P- and S-doped titania exhibiting only the rutile phase, are active suggesting that neither the structure nor the doping is the driving parameter. Although the MPT625 UV-visible spectrum is shifted towards the visible domain with respect to the P25 one, the effect on bacteria is not increased. On the other hand, the ball milled iron-doped P25 samples exhibit low activities in bacteria abatement under visible light due to charge recombinations unfavorable to catalysis as shown by photoluminescence measurements. While doping elements are in interstitial positions within the rutile structure in MPT625 sample, they are located at the surface in ball milled samples and in isolated octahedral units according to (57)Fe Mössbauer spectrometry. The location of doping elements at the surface is suggested to be responsible for the sample cytotoxicity observed in the dark.

  7. Phase diagram of Fe-based superconductor Sr2 FeAs(Mg,Ti)O3

    NASA Astrophysics Data System (ADS)

    Ogino, Hiraku; Singh, Shiv Jee; Yamamoto, Akiyasu; Kishio, Kohji; Shimoyama, Jun-Ichi

    2014-03-01

    In iron-based superconductors, many compounds having perovskite-type blocking layers such as Sr2FeAs(Mg,Ti)O3 and Ca4Fe2As2(Mg,Ti)3O8 were discovered. There compounds have chemical and structural varieties, and have much thicker blocking layers compared to other phases. Generally superconducting transitions appear without intentional carrier doping, and Tc reaches as high as 47 K. On the other hand, electronic state and electronic phase diagram of these compounds are much less studied compared to other phases, and there are no clear observation of antiferromagnetic ordering in these compounds. In this study, we have systematically investigated phase diagram of Sr2FeAs(Mg,Ti)O3 phase by controlling carriers through oxygen composition and post-annealing. Relationship between crystal structure, chemical compositions and physical properties will be discussed.

  8. Fusion of 48Ti+58Fe and 58Ni+54Fe below the Coulomb barrier

    NASA Astrophysics Data System (ADS)

    Stefanini, A. M.; Montagnoli, G.; Corradi, L.; Courtin, S.; Bourgin, D.; Fioretto, E.; Goasduff, A.; Grebosz, J.; Haas, F.; Mazzocco, M.; Mijatović, T.; Montanari, D.; Pagliaroli, M.; Parascandolo, C.; Scarlassara, F.; Strano, E.; Szilner, S.; Toniolo, N.; Torresi, D.

    2015-12-01

    Background: No data on the fusion excitation function of 48Ti+58Fe in the energy region near the Coulomb barrier existed prior to the present work, while fusion of 58Ni+54Fe was investigated in detail some years ago, down to very low energies, and clear evidence of fusion hindrance was noticed at relatively high cross sections. 48Ti and 58Fe are soft and have a low-lying quadrupole excitation lying at ≈800 -900 keV only. Instead, 58Ni and 54Fe have a closed shell (protons and neutrons, respectively) and are rather rigid. Purpose: We aim to investigate (1) the possible influence of the different structures of the involved nuclei on the fusion excitation functions far below the barrier and, in particular, (2) whether hindrance is observed in 48Ti+58Fe , and to compare the results with current coupled-channels models. Methods: 48Ti beams from the XTU Tandem accelerator of INFN-Laboratori Nazionali di Legnaro were used. The experimental setup was based on an electrostatic beam separator, and fusion-evaporation residues (ERs) were detected at very forward angles. Angular distributions of ERs were measured. Results: Fusion cross sections of 48Ti+58Fe have been obtained in a range of nearly six orders of magnitude around the Coulomb barrier, down to σ ≃2 μ b . The sub-barrier cross sections of 48Ti+58Fe are much larger than those of 58Ni+54Fe . Significant differences are also observed in the logarithmic derivatives and astrophysical S factors. No evidence of hindrance is observed, because coupled-channels calculations using a standard Woods-Saxon potential are able to reproduce the data in the whole measured energy range. Analogous calculations for 58Ni+54Fe predict clearly too large cross sections at low energies. The two fusion barrier distributions are wide and display a complex structure that is only qualitatively fit by calculations. Conclusions: It is pointed out that all these different trends originate from the dissimilar low-energy nuclear structures of

  9. Structural evolution in mechanically alloyed Al-Fe powders

    SciTech Connect

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

    1995-08-01

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

  10. In situ synthesis of Fe-based alloy clad coatings containing TiB2-TiN-(h-BN)

    NASA Astrophysics Data System (ADS)

    Jiang, Shao-qun; Wang, Gang; Ren, Qing-wen; Yang, Chuan-duo; Wang, Ze-hua; Zhou, Ze-hua

    2015-06-01

    Fe-based alloy coatings containing TiB2-TiN-(h-BN) were synthesized in situ on Q235 steel substrates by a plasma cladding process using the powders of Fe901 alloy, Ti, and h-BN as raw materials. The effects of Ti/h-BN mass ratio on interfacial bonds between the coating and substrate along with the microstructures and microhardnesses of the coatings were investigated. The results show that the Ti/h-BN mass ratio is a vital factor in the formation of the coatings. Free h-BN can be introduced into the coatings by adding an excess amount of h-BN into the precursor. Decreases in the Ti/h-BN mass ratio improve the microstructural uniformity and compactness and enhance the interfacial bonds of the coatings. At a Ti/h-BN mass ratio of 10/20, the coating is free of cracks and micropores, and mainly consists of Fe-Cr, Fe3B, TiB2, TiN, Ti2N, TiB, FeN, FeB, Fe2B, and h-BN phases. Its average microhardness in the zone between 0.1-2.8 mm from the coating surface is about Hv0.2 551.5.

  11. Light Sensitive Lattice Defects In BaTiO3 Containing Fe

    NASA Astrophysics Data System (ADS)

    Possenriede, Ewald; Schirmer, Ortwin F.; Godefroy, Genevieve; Maillard, Alain

    1989-01-01

    Electron spin resonance spectra, which can consistently be explained by the models Fe4+ - Vo and Fe5+ - vBa, have been observed with BaTiO3 containing Fe. Also Fe3+ and - Fe3+ - Vo have been identified. All these centers as well as several unidentified ones are observed to change their charge states under illumination. They thus are possibly in involved in photorefractive processes in BaTiO3 containing Fe.

  12. The stability of armalcolite - Experimental studies in the system MgO-Fe-Ti-O. [in lunar rocks

    NASA Technical Reports Server (NTRS)

    Lindsley, D. H.; Kesson, S. E.; Hartzman, M. J.; Cushman, M. K.

    1974-01-01

    The stability of armalcolite at low pressures is considered, taking into account experiments which confirm the low-temperature breakdown of the mineral. Effects of Al2O3, Cr2O3, and Ti2O3 components on armalcolite stability are discussed with the stability of armalcolite at high pressure. Attention is also given to several reactions involving Fe-Mg-Ti oxides in Apollo 11 and 17 basalts.

  13. Investigation of the mechanical properties of Ti-Fe-Sn ultrafine eutectic composites by dendrite phase selection

    NASA Astrophysics Data System (ADS)

    Lee, C. H.; Kim, J. T.; Hong, S. H.; Song, G. A.; Jo, J. H.; Moon, S. C.; Kim, K. B.

    2014-05-01

    Microstructural investigation of Ti-Fe-Sn ultrafine eutectic composites reveals that β-Ti primary dendrite in eutectic matrix consists of TiFe and β-Ti for Ti72Fe22Sn6 alloy. Similarly, the Ti64Fe32Sn4 alloy and Ti68Fe23Sn9 alloy consists of TiFe and Ti3Sn micron-scale primary dendrites uniformly embedded in the TiFe and β-Ti eutectic structure. The β-Ti dendrite was formed in Ti72Fe22Sn6 alloy, the large number of shear bands propagation and makes multiple steps on the fracture surface. The Ti3Sn dendrite in Ti68Fe23Sn9 ultrafine eutectic alloy leads slip bands which induce the work hardening that have important role in plasticity during deformation. On the other hand, TiFe dendrite in Ti64Fe32Sn4 alloy was presented shear bands bypass and extinction while the propagation of shear bands. These microstructural changes lead to different deformation behavior in primary dendrite. Therefore, it is believed that the mechanical properties of Ti-Fe-Sn alloys could improve due to a different deformation behavior through the minute compositional tuning of Ti-Fe-Sn alloys.

  14. Superconductivity in new iron pnictide oxide Fe2As2Sr4(Mg,Ti)2O6

    NASA Astrophysics Data System (ADS)

    Sato, Shinya; Ogino, Hiraku; Kishio, Kohji; Shimoyama, Jun-Ichi

    2010-03-01

    A new iron arsenide oxide Fe2As2Sr4MgTiO6, which is isostructural with the iron-based superconductor Fe2Pn2Sr4M2O6^[1,2], has been successfully synthesized by the solid-state reaction in quartz ampoules. Fe2As2Sr4MgTiO6 has antifluorite-type iron arsenide layer and K2NiF4-type oxide layer, while the M-site is composed of a combination of divalent (Mg^2+) and tetravalent (Ti^4+) cations as in the case of a double perovskite La(Mg,Ti)O3. This fact indicates chemical flexibility of the perovskite-related layer in this system. This compound showed bulk superconductivity with Tc of ˜20 K by partial substitution of Co for Fe. Moreover, high Tc above 35 K was recorded by samples starting from Co-free and Ti-rich compositions, Fe2As2Sr4(Mg1-xTix)2O6 (x =0.7˜0.8). [1] H. Ogino et al., Supercond. Sci. Technol. 22 (2009) 075008. [2] X. Zhu et al., Phys. Rev. B 79 (2009) 220512(R).

  15. Thermophysical Properties of Liquid AlTi-Based Alloys

    NASA Astrophysics Data System (ADS)

    Egry, I.; Holland-Moritz, D.; Novakovic, R.; Ricci, E.; Wunderlich, R.; Sobczak, N.

    2010-05-01

    The surface tension and density of three liquid AlTi-based alloys (AlTiV, AlTiNb, and AlTiTa) have been measured using electromagnetic levitation as a tool for containerless processing. Surface tension has been determined by the oscillating-drop method, while the density was measured using a shadowgraph technique. Both quantities were determined over a wide temperature range, including the undercooled regime. In addition, sessile-drop and pendant-drop experiments to determine the surface tension were performed in a recently built high-temperature furnace. The measured data were compared to thermodynamic calculations using phenomenological models and the Butler equation. Generally, good agreement was found.

  16. TI--CR--AL--O thin film resistors

    DOEpatents

    Jankowski, Alan F.; Schmid, Anthony P.

    2000-01-01

    Thin films of Ti--Cr--Al--O are used as a resistor material. The films are rf sputter deposited from ceramic targets using a reactive working gas mixture of Ar and O.sub.2. Resistivity values from 10.sup.4 to 10.sup.10 Ohm-cm have been measured for Ti--Cr--Al--O film <1 .mu.m thick. The film resistivity can be discretely selected through control of the target composition and the deposition parameters. The application of Ti--Cr--Al--O as a thin film resistor has been found to be thermodynamically stable, unlike other metal-oxide films. The Ti--Cr--Al--O film can be used as a vertical or lateral resistor, for example, as a layer beneath a field emission cathode in a flat panel display; or used to control surface emissivity, for example, as a coating on an insulating material such as vertical wall supports in flat panel displays.

  17. Graphite Reinforced Fe-Al-X Composites for Slide Bearing Applications

    NASA Astrophysics Data System (ADS)

    Ko, Se-Hyun; Lee, Wonsik; Jang, Jin Man; Kim, Il-Ho; Shin, Seong-Gun

    The Fe-Al-X(Cu, Ni, Ti) composites reinforced with graphite particles were fabricated employing the powder metallurgy process for slide bearing applications. In all samples, graphite particles of 6 wt.% were added. Elemental powders were mixed to specific compositions with a powder lubricant, and then the mixed powders were compacted at 500 MPa. The green compacts were heated to 450°C to remove the lubricant and sintered at 1200°C for 1 h. The sintering was conducted in vacuum. The sintering of binary Fe-Al-graphite system showed low density and growth in dimension. Complex addition of Cu, Ni and Ti improved the sinterability of green compacts due to occurrence of partial liquid phases. Hardness of sintered samples strongly depended on dimensional change during sintering. The samples of high hardness showed better wear resistance properties.

  18. Dynamic recrystallization and superplasticity in TiAl

    SciTech Connect

    Salishchev, G.; Imayev, R.; Imayev, V.; Shagiev, M.

    1995-12-31

    The effect of structural factors (grain size, grain boundary structure and fraction of the second phase) on dynamic recrystallization and superplasticity in the TiAl intermetallic alloy was studied. The possibilities of the formation of submicrocrystalline structure and the abrupt decrease of the superplastic temperature were shown. It was established that the occurrence of dynamic recrystallization and superplastic flow led to the formation of homogeneous microstructure and the improvement of low-temperature ductility in TiAl.

  19. Thermoelectric properties of Fe and Al co-added Ge

    NASA Astrophysics Data System (ADS)

    Sasaki, Takayuki; Kurosaki, Ken; Yusufu, Aikebaier; Ohishi, Yuji; Muta, Hiroaki; Yamanaka, Shinsuke

    2017-04-01

    The polycrystalline bulk samples of Fe and Al co-added Ge were synthesized by melt-spinning followed by spark plasma sintering and the thermoelectric properties were examined. Here, Al acts as a p-type dopant, while Fe is expected to form FeGe2 as precipitates. Since the lattice mismatch between Ge and FeGe2 is small (<4%), they would coherently connect with each other, reducing the thermal conductivity without affecting the electrical transport. In this study, a reduction in thermal conductivity was achieved by dispersing the FeGe2 precipitates in the Al-doped Ge matrix, while they had little influences on both the carrier mobility and the Seebeck coefficient. As the results, the maximum ZT value of 0.13 was obtained at 773 K, which is three times higher than that of single-crystal Ge reported by the authors’ group [Y. Ohishi et al., Jpn. J. Appl. Phys. 55, 051301 (2016)].

  20. Fretting Wear of Ti-48Al-2Cr-2Nb

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.

    2001-01-01

    An investigation was conducted to examine the wear behavior of gamma titanium aluminide (Ti-48Al-2Cr-2Nb in atomic percent) in contact with a typical nickel-base superalloy under repeated microscopic vibratory motion in air at temperatures from 296-823 K. The surface damage observed on the interacting surfaces of both Ti-48Al-2Cr-2Nb and superalloy consisted of fracture pits, oxides, metallic debris, scratches, craters, plastic deformation, and cracks. The Ti-48Al-2Cr-2Nb transferred to the superalloy at all fretting conditions and caused scuffing or galling. The increasing rate of oxidation at elevated temperatures led to a drop in Ti-48Al-2Cr-2Nb wear at 473 K. Mild oxidative wear was observed at 473 K. However, fretting wear increased as the temperature was increased from 473-823 K. At 723 and 823 K, oxide disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Ti-48Al-2Cr-2Nb wear generally decreased with increasing fretting frequency. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals. Keywords

  1. Granular nanostructures and magnetic characteristics of FePt-TiO{sub 2}/FePt-C stacked granular films

    SciTech Connect

    Ono, Takuya Moriya, Tomohiro; Hatayama, Masatoshi; Kikuchi, Nobuaki; Okamoto, Satoshi; Kitakami, Osamu; Shimatsu, Takehito

    2014-05-07

    To realize a granular film composed of L1{sub 0}-FePt grains with high uniaxial magnetic anisotropy energy, K{sub u}, and segregants for heat-assisted magnetic recording, the FePt-TiO{sub 2}/FePt-C stacked film was investigated. The FePt-TiO{sub 2}/FePt-C stacked film has well-isolated granular structure with average grain size of 6.7 nm because the FePt-TiO{sub 2} film follows the FePt-C template film in microstructural growth. However, the K{sub u} value is quite low for total thickness of 9 nm: 5 × 10{sup 6} erg/cm{sup 3}. Exploration of the thickness dependence of L1{sub 0}-FePt(001) peaks in XRD spectra and cross-sectional TEM images suggest that degradation of the L1{sub 0} ordering appears near the middle of the FePt-TiO{sub 2} layer. The EDX-STEM mapping reveals that Ti atoms exist within the FePt grains in addition to the grain boundary. This indicates the possibility that TiO{sub 2} tends to be incorporated into the FePt grains and that it prevents L1{sub 0}-ordering of the FePt grains along the normal-to-plane direction.

  2. Strength anomaly in B2 FeAl single crystals

    SciTech Connect

    Yoshimi, K.; Hanada, S.; Yoo, M.H.; Matsumoto, N.

    1994-12-31

    Strength and deformation microstructure of B2 Fe-39 and 48%Al single crystals (composition given in atomic percent), which were fully annealed to remove frozen-in vacancies, have been investigated at temperatures between room temperature and 1073K. The hardness of as-homogenized Fe-48Al is higher than that of as-homogenized Fe-39Al while after additional annealing at 698K the hardness of Fe-48Al becomes lower than that of Fe-39Al. Fe-39Al single crystals slowly cooled after homogenizing at a high temperature were deformed in compression as a function of temperature and crystal orientation. A peak of yield strength appears around 0.5T{sub m} (T{sub m} = melting temperature). The orientation dependence of the critical resolved shear stress does not obey Schmid`s law even at room temperature and is quite different from that of b.c.c. metals and B2 intermetallics at low temperatures. At the peak temperature slip transition from <111>-type to <001>-type is found to occur macroscopically and microscopically, while it is observed in TEM that some of the [111] dislocations decompose into [101] and [010] on the (1096I) plane below the peak temperature. The physical sources for the positive temperature dependence of yield stress of B2 FeAl are discussed based on the obtained results.

  3. Creep behavior of alloys based on TiAl containing TiB sub 2 and TiN particulates

    SciTech Connect

    Martin, P.L.; Carter, D.H.; Aikin, R.M. Sr. ); Aikin, R.M. Jr.; Christodoulou, L. )

    1990-01-01

    Ordered alloys based on the L1{sub 0} crystal structure compound TiAl were tested in constant stress creep. The alloys ranged from 45 to 47 at. % Al with and without V substitutions. The ingot processing, utilizing the XD{trademark} technique, incorporated 1 to 5 {mu}m diameter particles of boride or nitride compounds. Emphasis was placed on characterizing the initial stages of creep using digital data acquisition and analysis in the range 70 to 280 MPa stress and 760 to 850{degrees}C temperature. When TiN (converting to Ti{sub 2}AlN in processing) and TiB{sub 2} are both added to the matrix, the creep properties are significantly improved. Fine particles were observed to decorate dislocations and to have nucleated homogeneously within the TiAl grains. 16 refs., 7 figs., 3 tabs.

  4. Properties of the thermally stable Al{sub 95}Cr{sub 3.1}Fe{sub 1.1}Ti{sub 0.8} alloy prepared by cold-compression at ultra-high pressure and by hot-extrusion

    SciTech Connect

    Vojtech, D.; Michalcova, A.; Prusa, F.; Dam, K.; Seda, P.

    2012-04-15

    An Al{sub 95}Cr{sub 3.1}Fe{sub 1.1}Ti{sub 0.8} (in at.%) alloy was made into rapidly solidified powder by melt atomization. The powder was compacted by two processes: 1) uni-axial cold compression at an ultra-high pressure of 6 GPa and 2) hot extrusion at 480 Degree-Sign C. The structures, mechanical properties and thermal stability of both materials were compared with the commercial AlSi{sub 12}Cu{sub 1}Mg{sub 1}Ni{sub 1} (in wt.%) casting alloy, which is generally considered to be thermally stable. It was found that cold compression at ultra-high pressure created a compact and porosity-free material, which was similar to the material that was prepared with the commonly used hot extrusion method. The Vickers hardness, compressive strength and compressive yield strength of the cold-compressed alloy were 161 HV, 680 MPa and 547 MPa, respectively, which were higher than the values obtained for the hot-extruded and casting alloys. The thermal stability of the hot-extruded Al{sub 95}Cr{sub 3.1}Fe{sub 1.1}Ti{sub 0.8} alloy was excellent because its mechanical properties did not change significantly, even after 100 h of annealing at 500 Degree-Sign C. The mechanical properties and thermal stability of the investigated materials were discussed in relation to their structures and diffusivities of the alloying elements. - Highlights: Black-Right-Pointing-Pointer The Al{sub 95}Cr{sub 3.1}Fe{sub 1.1}Ti{sub 0.8} alloy was prepared by compression at an ultra-high pressure of 6 GPa. Black-Right-Pointing-Pointer The resulting material was dense and porosity-free. Black-Right-Pointing-Pointer The material had high hardness of 161 HV and a compressive strength of 680 MPa. Black-Right-Pointing-Pointer The material had excellent thermal stability at 500 Degree-Sign C.

  5. 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.

  6. Magnetic anisotropy and order structure of L1{sub 0}-FePt(001) single-crystal films grown epitaxially on (001) planes of MgO, SrTiO{sub 3}, and MgAl{sub 2}O{sub 4} substrates

    SciTech Connect

    Hotta, A. Hatayama, M.; Tsumura, K.; Ono, T.; Kikuchi, N.; Okamoto, S.; Kitakami, O.; Shimatsu, T.

    2014-05-07

    L1{sub 0}–FePt(001) single-crystal films were grown epitaxially on SrTiO{sub 3}(001), MgAl{sub 2}O{sub 4}(001), and MgO(001) substrates. Their uniaxial magnetic anisotropy K{sub u} and the order structure were examined for the film thickness t range of 2–14 nm. All series of films show large K{sub u} of 4 × 10{sup 7} erg/cm{sup 3} in the thickness range higher than 10 nm, with order parameter S of 0.8 and saturation magnetization M{sub s} of 1120 emu/cm{sup 3}. K{sub u} decreased gradually as t decreased. The K{sub u} reduction was considerable when t decreased from 4 nm to 2 nm. No marked difference in the thickness dependence of K{sub u} was found in any series of films, although the lattice mismatch between FePt and the substrates was markedly different. K{sub u} reduction showed good agreement with the reduction of S for the films on MgAl{sub 2}O{sub 4} and MgO. The K{sub u} ∼ S{sup 2} plot showed an almost linear relation, which is in good agreement with theoretical predictions. Transmission electron microscopy images for a FePt film on MgO substrate revealed that the lattice mismatch between FePt(001) and MgO(001) was relaxed in the initial 1 or 2 layers of FePt(001) lattices, which is likely to be true also for two other series of films.

  7. Oxidation behavior of FeAl+Hf,Zr,B

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Doychak, Joseph

    1988-01-01

    The oxidation behavior of Fe-40Al-1Hf, Fe-40Al-1Hf-0.4B, and Fe-40Al-0.1Zr-0.4B (at. percent) alloys was characterized after 900, 1000, and 100 C exposures. Isothermal tests revealed parabolic kinetics after a period of transitional theta-alumina scale growth. The parabolic growth rates for the subsequent alpha-alumina scales were about five times higher than those for NiAl+0.1Zr alloys. The isothermally grown scales showed a propensity toward massive scale spallation due to both extensive rumpling from growth stresses and to an inner layer of HfO2. Cyclic oxidation for 200 1-hr cycles produced little degradation at 900 or 1000 C, but caused significant spallation at 1100 C in the form of small segments of the outer scale. The major difference in the cyclic oxidation of the three FeAl alloys was increased initial spallation for FeAl+Zr,B. Although these FeAl alloys showed many similarities to NiAl alloys, they were generally less oxidation resistant. It is believed that this resulted from nonoptimal levels of dopants and larger thermal expansion mismatch stresses.

  8. Morphological characteristics of mechanochemically synthesized Fe/Ti composites

    NASA Astrophysics Data System (ADS)

    Grigor'eva, T. F.; Kovaleva, S. A.; Kiseleva, T. Yu.; Vosmerikov, S. V.; Devyatkina, E. T.; Pastukhov, E. A.; Lyakhov, N. Z.

    2016-08-01

    The joint mechanical activation of chemically interacting iron and titanium has been studied by X-ray diffraction and atomic force microscopy. It is shown that chemically interacting metals Fe and Ti do not form any intermetallic compounds or solid solutions upon intense mechanical activation in a high-energy planetary mill. The products of mechanical activation are Fe/Ti mechanocomposites, in which titanium is distributed over the iron grain surface. An increase in the mechanical activation time leads to the agglomeration of powders and the formation of particles with a wide size range (5-25 μm). The iron crystallite sizes and the level of microstresses are reduced, indicating a decrease in the particle strength.

  9. Atomistic Simulations of Ti Additions to NiAl

    NASA Technical Reports Server (NTRS)

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

    1997-01-01

    The development of more efficient engines and power plants for future supersonic transports depends on the advancement of new high-temperature materials with temperature capabilities exceeding those of Ni-based superalloys. Having theoretical modelling techniques to aid in the design of these alloys would greatly facilitate this development. The present paper discusses a successful attempt to correlate theoretical predictions of alloy properties with experimental confirmation for ternary NiAl-Ti alloys. The B.F.S. (Bozzolo-Ferrante-Smith) method for alloys is used to predict the solubility limit and site preference energies for Ti additions of 1 to 25 at.% to NiAl. The results show the solubility limit to be around 5% Ti, above which the formation of Heusler precipitates is favored. These results were confirmed by transmission electron microscopy performed on a series of NiAl-Ti alloys.

  10. Visible light catalysis of rhodamine B using nanostructured Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) thin films.

    PubMed

    Mahadik, M A; Shinde, S S; Mohite, V S; Kumbhar, S S; Moholkar, A V; Rajpure, K Y; Ganesan, V; Nayak, J; Barman, S R; Bhosale, C H

    2014-04-05

    The Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) composite films are deposited using spray pyrolysis method onto glass and FTO coated substrates. The structural, morphological, optical and photocatalytic properties of Fe(2)O(3), TiO(2) and TiO(2)/Fe(2)O(3) thin films are studied. XRD analysis confirms that films are polycrystalline with rhombohedral and tetragonal crystal structures for Fe2O3 and TiO(2) respectively. The photocatalytic activity was tested for the degradation of Rhrodamine B (Rh B) in aqueous medium. The rate constant (-k) was evaluated as a function of the initial concentration of species. Substantial reduction in concentrations of organic species was observed from COD and TOC analysis. Photocatalytic degradation effect is relatively higher in case of the TiO(2)/Fe(2)O(3) than TiO(2) and Fe(2)O(3) thin film photoelectrodes in the degradation of Rh B and 98% removal efficiency of Rh B is obtained after 20min. The photocatalytic experimental results indicate that TiO(2)/α-Fe(2)O(3) photoelectrode is promising material for removing of water pollutants.

  11. The corrosion behaviour of Ti-6Al-4V, Ti-6Al-7Nb and Ti-13Nb-13Zr in protein solutions.

    PubMed

    Khan, M A; Williams, R L; Williams, D F

    1999-04-01

    Ti alloys are used in orthopaedic applications owing to their appropriate mechanical properties and their excellent corrosion resistance. The release of titanium and the other alloying elements into the surrounding tissue has been reported due either to passive corrosion or accelerating processes such as wear. Since the passive layer can be broken down in certain circumstances by wear it is important to study the ability of these alloys to repassivate in biological environments, in particular in the presence of proteins, and evaluate how the repassivated surface may vary from the original surface. In this study we investigated the ability of Ti-6Al-4V, Ti-6Al-7Nb and Ti-13Nb-13Zr to repassivate in phosphate buffered saline (PBS), bovine albumin solutions in PBS and 10% foetal calf serum in PBS at different pH values and at different albumin concentrations. It was found that an increase in pH had a greater effect on the corrosion behaviour of Ti-6Al-4V and Ti-6Al-7Nb than on Ti-13Nb-13Zr in PBS and that the addition of protein to the PBS reduced the influence of pH on the corrosion behaviour of all the alloys. The effect of the corrosion and repassivation was investigated by measuring changes in the surface hardness of the alloys and it was found that corrosion reduced the hardness of the surface oxides of all the alloys. In PBS the reduction was smallest for Ti-6Al-4V and largest for Ti-13Nb- 3Zr and that corrosion in protein solutions further reduced the hardness of the surface oxides. This effect was greater for Ti-6Al-4V and Ti-6Al-7Nb than for Ti-13Nb-13Zr. In conclusion, proteins in the environment appear to interact with the repassivation process at the surface of these alloys and influence the resulting surface properties.

  12. Sodium hydroxide anodization of Ti-Al-4V adherends

    NASA Technical Reports Server (NTRS)

    Filbey, Jennifer A.; Wightman, J. P.; Progar, D. J.

    1987-01-01

    The use of sodium hydroxide anodization (SHA) for Ti-6Al-4V adherends is examined. The SHA surface is evaluated using SEM, X-ray photoelectron spectroscopy, and Auger electron spectroscopy. The SHA procedures of Kennedy et al. (1983) were employed in this experiment. The photomicrographs of the SHA (sandblasted) and PSHA (sandblasted and pickled) oxide surface reveal that the two surfaces differ. The PSHA is patchy and similar to a chromic acid anodization surface and the porosity of the PSHA is more uniform than the SHA surface. The compositions of the surfaces are studied. It is noted that SHA is an effective pretreatment for Ti-6Al-4V adherends.

  13. Structure Formation Mechanisms during Solid Ti with Molten Al Interaction

    NASA Astrophysics Data System (ADS)

    Gurevich, L.; Pronichev, D.; Trunov, M.

    2016-02-01

    The study discuses advantages and disadvantages of previously proposed mechanisms of the formation of structure between solid Ti and molten Al and presents a new mechanism based on the reviewed and experimental data. The previously proposed mechanisms were classified into three groups: mechanisms of precipitation, mechanisms of destruction and mechanisms of chemical interaction between intermetallics and melt. The reviewed mechanisms did not explain the formation of heterogeneous interlayer with globular aluminide particles and thin layers of pure Al, while the present study reveals variation in the solid Ti/molten Al reaction kinetics during various phases of laminated metal-intermetallic composite formation. The proposed mechanism considers formed during composite fabrication thin oxide interlayers between Ti and Al evolution and its impact on the intermetallic compound formation and explains the initial slow rate of intermetallic interlayer formation and its subsequent acceleration when the oxide foils are ruptured.

  14. Corrosion behavior and biocompatibility of nanostructured TiO2 film on Ti6Al4V.

    PubMed

    Karpagavalli, Ramji; Zhou, Anhong; Chellamuthu, Prithiviraj; Nguyen, Kytai

    2007-12-15

    The corrosion behavior and cell adhesion property of nanostructured TiO2 films deposited electrolytically on Ti6Al4V were examined in the present in vitro study. The nanostructured TiO2 film deposition on Ti6Al4V was achieved via peroxoprecursors. SEM micrographs exhibit the formation of amorphous and crystallite TiO2 nanoparticles on Ti6Al4V before and after being annealed at 500 degrees C. Corrosion behavior of TiO2-deposited and uncoated Ti6Al4V was evaluated in freely aerated Hank's solution at 37 degrees C by the measurement and analysis of open-circuit potential variation with time, Tafel plots, and electrochemical impedance spectroscopy. The electrochemical results indicated that nano-TiO2 coated Ti6Al4V showed a better corrosion resistance in simulated biofluid than uncoated Ti6Al4V. Rat bone cells and human aortic smooth muscle cells were grown on these substrates to study the cellular responses in vitro. The SEM images revealed enhanced cell adhesion, cell spreading, and proliferation on nano-TiO2 coated Ti6Al4V compared to those grown on uncoated substrates for both cell lines. These results suggested that nanotopography produced by deposition of nanostructured TiO2 onto Ti alloy surfaces might enhance corrosion resistance, biocompatibility, and cell integration for implants made of Ti alloys.

  15. Observations of Al, Fe and Ca(+) in Mercury's Exosphere

    NASA Technical Reports Server (NTRS)

    Bida, Thomas A.; Killen, Rosemary M.

    2011-01-01

    We report 5-(sigma) tangent column detections of Al and Fe, and strict 3-(sigma) tangent column upper limits for Ca(+) in Mercury's exosphere obtained using the HIRES spectrometer on the Keck I telescope. These are the first direct detections of Al and Fe in Mercury's exosphere. Our Ca(-) observation is consistent with that reported by The Mercury Atmospheric and Surface Composition Spectrometer (MASCS) on the MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft.

  16. Asymmetry of radiation damage properties in Al-Ti nanolayers

    SciTech Connect

    Setyawan, Wahyu; Gerboth, Matthew D.; Yao, Bo; Henager, Charles H.; Devaraj, Arun; Vemuri, Venkata Rama Ses; Thevuthasan, Suntharampillai; Shutthanandan, V.

    2014-02-01

    Molecular dynamics (MD) simulations were employed with empirical potentials to study the effects of multilayer interfaces and interface spacing in Al-Ti nanolayers. Several model interfaces derived from stacking of close-packed layers or face-centered cubic \\{100\\} layers were investigated. The simulations reveal significant and important asymmetries in defect production with $\\sim$60\\% of vacancies created in Al layers compared to Ti layers within the Al-Ti multilayer system. The asymmetry in the creation of interstitials is even more pronounced. The asymmetries cause an imbalance in the ratio of vacancies and interstitials in films of dissimilar materials leading to $>$90\\% of the surviving interstitials located in the Al layers. While in the close-packed nanolayers the interstitials migrate to the atomic layers adjacent to the interface of the Al layers, in the \\{100\\} nanolayers the interstitials migrate to the center of the Al layers and away from the interfaces. The degree of asymmetry and defect ratio imbalance increases as the layer spacing decreases in the multilayer films. Underlying physical processes are discussed including the interfacial strain fields and the individual elemental layer stopping power in nanolayered systems. In addition, experimental work was performed on low-dose (10$^{16}$ atoms/cm$^2$) helium (He) irradiation on Al/Ti nanolayers (5 nm per film), resulting in He bubble formation $\\sim$1 nm in diameter in the Ti film near the interface. The correlation between the preferential flux of displaced atoms from Ti films to Al films during the defect production that is revealed in the simulations and the morphology and location of He bubbles from the experiments is discussed.

  17. Improving the osteointegration of Ti6Al4V by zeolite MFI coating

    SciTech Connect

    Li, Yong; Jiao, Yilai; Li, Xiaokang; Guo, Zheng

    2015-05-01

    Osteointegration is crucial for success in orthopedic implantation. In recent decades, there have been numerous studies aiming to modify titanium alloys, which are the most widely used materials in orthopedics. Zeolites are solid aluminosilicates whose application in the biomedical field has recently been explored. To this end, MFI zeolites have been developed as titanium alloy coatings and tested in vitro. Nevertheless, the effect of the MFI coating of biomaterials in vivo has not yet been addressed. The aim of the present work is to evaluate the effects of MFI-coated Ti6Al4V implants in vitro and in vivo. After surface modification, the surface was investigated using field emission scanning electron microscopy (FE-SEM) and energy dispersive spectroscopy (EDS). No difference was observed regarding the proliferation of MC3T3-E1 cells on the Ti6Al4V (Ti) and MFI-coated Ti6Al4V (M−Ti) (p > 0.05). However, the attachment of MC3T3-E1 cells was found to be better in the M−Ti group. Additionally, ALP staining and activity assays and quantitative real-time RT-PCR indicated that MC3T3-E1 cells grown on the M−Ti displayed high levels of osteogenic differentiation markers. Moreover, Van-Gieson staining of histological sections demonstrated that the MFI coating on Ti6Al4V scaffolds significantly enhanced osteointegration and promoted bone regeneration after implantation in rabbit femoral condylar defects at 4 and 12 weeks. Therefore, this study provides a method for modifying Ti6Al4V to achieve improved osteointegration and osteogenesis. - Highlights: • Osteointegration is a crucial factor for orthopedic implants. • We coated MFI zeolite on Ti6Al4V substrates and investigated the effects in vitro and in vivo. • The MFI coating displayed good biocompatibility and promoted osteogenic differentiation in vitro. • The MFI coating promoted osteointegration and osteogenesis peri-implant in vivo.

  18. Metastable Phases of Rapidly Solidified Al-Rich Al-Fe Alloys

    DTIC Science & Technology

    1984-01-01

    same contrast. 20 FIGURE 9. Convergent beam diffraction pattern taken from a single crystal globular "S" phase. 21 FIGURE 10. The flower -like phase. 21...FIGURE 11. Convergent beam diffraction pattern obtained from the flower -like phase. 21 iii "- "’., % i ’ % " PAGE FIGURE 12. At-i wt.% Fe. Cellular...any of the previously reported aluminum-rich phases (Al3Fe, AlxFe, AI6Fe, A19Fe2, or AlmFe) [2,3]. An additional flower - shaped phase was detected in

  19. Laser Processed TiN Reinforced Ti6Al4V Composite Coatings

    PubMed Central

    Balla, Vamsi Krishna; Bhat, Abhimanyu; Bose, Susmita; Bandyopadhyay, Amit

    2011-01-01

    The purpose of this first generation investigation is to evaluate fabrication, in vitro cytotoxicity, cell-materials interactions and tribological performance of TiN particle reinforced Ti6Al4V composite coatings for potential wear resistant load bearing implant applications. The microstructural analysis of the composites was performed using scanning electron microscope and phase analysis was done with X-ray diffraction. In vitro cell-materials interactions, using human fetal osteoblast cell line, have been assessed on these composite coatings and compared with Ti6Al4V alloy control samples. The tribological performance of the coatings were evaluated, in simulated body fluids, up to 1000 m sliding distance under 10N normal load. The results show that the composite coatings contain distinct TiN particles embedded in α + β phase matrix. The average top surface hardness of Ti6Al4V alloy increased from 394 ± 8 HV to 1138 ± 61 HV with 40 wt.% TiN reinforcement. Among the composite coatings, the coatings reinforced with 40 wt. % TiN exhibited the highest wear resistance of 3.74 × 10-6 mm3/Nm, which is lower than the wear rate, 1.04 × 10-5 mm3/Nm, of laser processed CoCrMo alloy tested under identical experimental conditions. In vitro biocompatibility study showed that these composite coatings were non-toxic and provides superior cell-material interactions compared to Ti6Al4V control, as a result of their high surface energy. In summary, excellent in vitro wear resistance and biocompatibility of present laser processed TiN reinforced Ti6Al4V alloy composite coatings clearly show their potential as wear resistant contact surfaces for load bearing implant applications. PMID:22301169

  20. Oxidation Kinetics of Cast TiAl3

    NASA Technical Reports Server (NTRS)

    Smialek, J. L.; Humphrey, D. L.

    1992-01-01

    The isothermal oxidation kinetics of the TiAl3 compound over a wide temperature range is documented, and these rates are related to exclusive alpha-Al2O3 scale growth. The specific weight change vs time curves are shown. Two abnormalities are immediately apparent. One is that a rapid initial uptake of oxygen occurs at times less than 5 h, followed by a lower oxidation rate at longer times, for tests at 900 C and below. The other is that the final weight changes for the 700, 800, and 900 C tests are not in the sequence expected with respect to temperature. Isothermal oxidation of drop cast TiAl above 1000 C was found to exhibit parabolic oxidation controlled by protective alpha-Al2O3 scale formation. TiAl is the only phase in the binary Ti-Al system that forms exclusive scales of alpha-Al2O3 in isothermal oxidation. High anomalous rates at short times and at temperatures below 1000 C resulted from the internal oxidation of a second phase of aluminum.

  1. Alloy development and processing of FeAl: An overview

    SciTech Connect

    Maziasz, P.J.; Goodwin, G.M.; Alexander, D.J.; Viswanathan, S.

    1997-03-01

    In the last few years, considerable progress has been made in developing B2-phase FeAl alloys with improved weldability, room-temperature ductility, and high-temperature strength. Controlling the processing-induced microstructure is also important, particularly for minimizing trade-offs in various properties. FeAl alloys have outstanding resistance to high-temperature oxidation, sulfidation, and corrosion in various kinds of molten salts due to formation of protective Al{sub 2}O{sub 3} scales. Recent work shows that FeAl alloys are carburization-resistant as well. Alloys with 36 to 40 at. % Al have the best combination of corrosion resistance and mechanical properties. Minor alloying additions of Mo, Zr, and C, together with microalloying additions of B, produce the best combination of weldability and mechanical behavior. Cast FeAl alloys, with 200 to 400 {mu}m grain size and finely dispersed ZrC, have 2 to 5% tensile ductility in air at room-temperature, and a yield strength > 400 MPa up to about 700 to 750{degrees}C. Extruded ingot metallurgy (I/M) and powder metallurgy (P/M) materials with refined grain sizes ranging from 2 to 50 {mu}m, can have 10 to 15% ductility in air and be much stronger, and can even be quite tough, with Charpy impact energies ranging from 25 to 105 J at room-temperature. This paper highlights progress made in refining the alloy composition and exploring processing effects on FeAl for monolithic applications. It also includes recent progress on developing FeAl weld-overlay technology, and new results on welding of FeAl alloys. It summarizes some of the current industrial testing and interest for applications.

  2. Ti/Al Design/Cost Trade-Off Analysis

    DTIC Science & Technology

    1978-10-01

    4099 5705 41 6388 9304 (44/Rev) 46 8258 9761 Speed - 13, 533 rpm (100% N) 31 10,000 2T I42/Rev Material Clamped atI a goo - Rene ’ 80 DovetailI 0TiAl...as the F1O1 Stage 4 Blade Materiel. 41 9. Maximum Blade and Dovetail Stresses for Ti-36-5Nb F1O0 Fourth-Stage Compressor Blade. 42 10. Strain Range of...Tensile Properties. 92 A-4. Ti-36A1-5Nb rreep and Stress Rupture Results. 93 A-5. Ti-36AI-5Nb Strain Control LCF Results. 93 A-6. HCF Results on Ti

  3. High performance magnetoimpedance in FeNi/Ti nanostructured multilayers with opened magnetic flux.

    PubMed

    Fernández, E; Svalov, A V; García-Arribas, A; Feuchtwanger, J; Barandiaran, J M; Kurlyandskaya, G V

    2012-09-01

    Magnetic [FeNi (170 nm)/Ti (6 nm)]3/Cu (L(cu) = 250 or 500 nm)/[Ti (6 nm)/FeNi (170 nm)]3 multilayers were designed with focus on high frequency applications. They were deposited onto glass or a microfluidic system compatible flexible Ciclo Olefin Copolymer substrate and comparatively tested. A maximum sensitivity for the total impedance of 110%/Oe was obtained for a driving current frequency of 30 MHz for [FeNi/Ti]3/Cu (L(cu) = 500 nm)/[Ti/FeNi]3 multilayers deposited onto a glass substrate and 45%/Oe for a driving current frequency of 65 MHz for the same multilayers deposited onto the flexible polymer substrate, a very promising result for applications. The possibility of using flexible substrate/[FeNi/Ti],/Cu/[Ti/FeNi]3 multilayers as MI pressure-sensitive elements was also demonstrated.

  4. TiC/Ti-Al composite fabricated by SHS/dynamic pseudo isostatic compaction through sand medium

    SciTech Connect

    Ohyanagi, M.; Fukushima, M.; Koizumi, M.

    1996-12-31

    TiC/Ti-Al composite was fabricated by pseudo isostatic compaction (DPIC) just after self-propagating high temperature synthesis (SHS). The pressing of 100 MPa was performed through a sand medium. The process enables to simultaneously synthesize and densify the TiC/Ti-Al composite from Ti/C/Al powders. The sample could be taken out from a reaction vessel within a couple of minutes after ignition. The adiabatic combustion temperatures were also calculated as a function of the mixing ratio of the elemental powders in the reaction system. X-ray diffraction patterns of TiC/Ti-Al produced revealed that the Ti-Al portion consisted of TiAl, Ti{sub 3}Al, TiAl{sub 3} and a slight Ti{sub 4}Al{sub 2}C{sub 2} alloys. The time delay between SHS and DPIC was affected greatly on the product density. The influence of the reactant mixing time on the phase component of the product was also studied. The density and Vickers hardness of the composite were highest in a mixing mole ratio of Ti/C/Al = 2/1/1, 4.2 g/cm{sup 3} and 13 GPa. The Young`s modulus and bending strength were approximately 300 GPa and 500 MPa, respectively.

  5. Effect of Cr, Ti, V, and Zr Micro-additions on Microstructure and Mechanical Properties of the Al-Si-Cu-Mg Cast Alloy

    NASA Astrophysics Data System (ADS)

    Shaha, S. K.; Czerwinski, F.; Kasprzak, W.; Friedman, J.; Chen, D. L.

    2016-05-01

    Uniaxial static and cyclic tests were used to assess the role of Cr, Ti, V, and Zr additions on properties of the Al-7Si-1Cu-0.5Mg (wt pct) alloy in as-cast and T6 heat-treated conditions. The microstructure of the as-cast alloy consisted of α-Al, eutectic Si, and Cu-, Mg-, and Fe-rich phases Al2.1Cu, Al8.5Si2.4Cu, Al5.2CuMg4Si5.1, and Al14Si7.1FeMg3.3. In addition, the micro-sized Cr/Zr/Ti/V-rich phases Al10.7SiTi3.6, Al6.7Si1.2TiZr1.8, Al21.4Si3.4Ti4.7VZr1.8, Al18.5Si7.3Cr2.6V, Al7.9Si8.5Cr6.8V4.1Ti, Al6.3Si23.2FeCr9.2V1.6Ti1.3, Al92.2Si16.7Fe7.6Cr8.3V1.8, and Al8.2Si30.1Fe1.6Cr18.8V3.3Ti2.9Zr were present. During solution treatment, Cu-rich phases were completely dissolved, while the eutectic silicon, Fe-, and Cr/Zr/Ti/V-rich intermetallics experienced only partial dissolution. Micro-additions of Cr, Zr, Ti, and V positively affected the alloy strength. The modified alloy in the T6 temper during uniaxial tensile tests exhibited yield strength of 289 MPa and ultimate tensile strength of 342 MPa, being significantly higher than that for the Al-Si-Cu-Mg base. Besides, the cyclic yield stress of the modified alloy in the T6 state increased by 23 pct over that of the base alloy. The fatigue life of the modified alloy was substantially longer than that of the base alloy tested using the same parameters. The role of Cr, Ti, V, and Zr containing phases in controlling the alloy fracture during static and cyclic loading is discussed.

  6. Solid-State Reaction Between Fe-Al-Ca Alloy and Al2O3-CaO-FeO Oxide During Heat Treatment at 1473 K (1200 °C)

    NASA Astrophysics Data System (ADS)

    Liu, Chengsong; Yang, Shufeng; Li, Jingshe; Ni, Hongwei; Zhang, Xueliang

    2016-12-01

    The aim of this study was to control the physicochemical characteristics of inclusions in steel through appropriate heat treatment. Using a confocal scanning laser microscope (CSLM) and pipe furnace, the solid-state reactions between Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide during heat treatment at 1473 K (1200 °C) and the influence of these reactions on the compositions of and phases in the alloy and oxide were investigated by the diffusion couple method. Suitable pretreatment of the oxide using a CSLM and production of the diffusion couple of Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide gave good contact between the alloy and oxide. The diffusion couple was then sealed in a quartz tube with a piece of Ti foil to lower oxygen partial pressure and a block of Fe-Al-Ca alloy was introduced to conduct heat treatment experiments. Solid-state reactions between the alloy and oxide during heat treatment at 1473 K (1200 °C) were analyzed and discussed. A dynamic model to calculate the width of the particle precipitation zone based on the Wagner model of internal oxidation of metal was proposed. This model was helpful to understand the solid-state reaction mechanism between Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide.

  7. Solid-State Reaction Between Fe-Al-Ca Alloy and Al2O3-CaO-FeO Oxide During Heat Treatment at 1473 K (1200 °C)

    NASA Astrophysics Data System (ADS)

    Liu, Chengsong; Yang, Shufeng; Li, Jingshe; Ni, Hongwei; Zhang, Xueliang

    2017-04-01

    The aim of this study was to control the physicochemical characteristics of inclusions in steel through appropriate heat treatment. Using a confocal scanning laser microscope (CSLM) and pipe furnace, the solid-state reactions between Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide during heat treatment at 1473 K (1200 °C) and the influence of these reactions on the compositions of and phases in the alloy and oxide were investigated by the diffusion couple method. Suitable pretreatment of the oxide using a CSLM and production of the diffusion couple of Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide gave good contact between the alloy and oxide. The diffusion couple was then sealed in a quartz tube with a piece of Ti foil to lower oxygen partial pressure and a block of Fe-Al-Ca alloy was introduced to conduct heat treatment experiments. Solid-state reactions between the alloy and oxide during heat treatment at 1473 K (1200 °C) were analyzed and discussed. A dynamic model to calculate the width of the particle precipitation zone based on the Wagner model of internal oxidation of metal was proposed. This model was helpful to understand the solid-state reaction mechanism between Fe-Al-Ca alloy and Al2O3-CaO-FeO oxide.

  8. Fe Segregation Effects on Grain Boundary Migration in Al

    NASA Astrophysics Data System (ADS)

    Mendelev, Mikhail; Srolovitz, David; Ackland, Graeme; Han, Seungwu

    2004-03-01

    We investigate the effect of Fe impurities on grain boundary migration in Al. We fit a new interatomic potential to experimental data and our first principles results. This potential is validated by comparing simulated and experimental liquid Al-Fe alloy structure factors. This potential was used to simulate boundary migration in pure Al. The boundary velocity vs. driving force data at several temperatures were used to extract the boundary mobility and the activation energy for boundary migration. The activation energy was found to be at least an order of magnitude smaller than that obtained from experiment. This discrepancy is presumably associated with impurities in the Al samples. Therefore, we examined the effect of Fe on boundary migration in Al by determining the heat of segregation and the Fe diffusivity in Al as input to the Cahn-Lücke-Stüwe analytical impurity drag model. This analysis showed that even extremely small quantities of Fe (less than 1 ppm) in Al can reduce the grain boundary mobility by two orders of magnitude at T=723 K and even more at lower T, consistent with the extant experimental data.

  9. An Assessment of the Al- Fe- N System

    NASA Astrophysics Data System (ADS)

    Hillert, Mats; Jonsson, Stefan

    1992-11-01

    The thermodynamic properties of the Al-Fe-N system are assessed, taking various types of information into account. For solid AIN, a description very similar to that given by JANAF is found to yield reasonable predictions for the solubility of A1N in face-centered cubic (fcc) Fe and in liquid Fe. An ionic two-sublattice model is applied to the liquid phase, containing two N species, N-3 and N0 The melting point of A1N is taken as 3068 K, and a required gas pressure of 9.75 bar is predicted. A sublimation point of 2690 K at 1 bar is also predicted. A plot of the liquidus surfaces in the Fe-rich end of the Al-Fe-N system is presented.

  10. Infrared spectral studies of pre- and post-irradiated Li{sub 0.5(1+x)}Ti{sub x}Al{sub 0.1}Fe{sub 2.4-1.5x}O{sub 4} system

    SciTech Connect

    Chhantbar, M. C.; Joshi, H. H.

    2015-06-24

    The consequences of 50 MeV Li{sup 3+} ions irradiation on the structural behaviour of polycrystalline samples of spinel ferrite system Li{sub 0.5(1+x)}Ti{sub x}Al{sub 0.1}Fe{sub 2.4-1.5x}O{sub 4} are investigated by using infrared absorption spectroscopy. The IR spectrum showed two main absorption bands ν{sub 1} and ν{sub 2} in the range 400-700 cm{sup −1} arising from tetrahedral and octahedral interstitial sites in the spinel lattice. The shifting and splitting observed in IR frequency bands ν{sub 1} and ν{sub 2} for tetrahedral and octahedral sites under irradiation effect are ascribed to redistribution of cations.

  11. Influence of Nb on the β→α″ martensitic phase transformation and properties of the newly designed Ti-Fe-Nb alloys.

    PubMed

    Ehtemam-Haghighi, Shima; Liu, Yujing; Cao, Guanghui; Zhang, Lai-Chang

    2016-03-01

    A series of Ti-7Fe-xNb (x=0, 1, 4, 6, 9, 11 wt.%) alloys was designed and cast to investigate the β→α″ martensitic phase transformation, β phase stability, the resulting microstructure and mechanical properties. Phase analysis revealed that only Ti-7Fe-11Nb alloy shows a single body-centred cubic β phase microstructure while the others are comprised of β and orthorhombic α″ phases. Moreover, Nb addition up to 11 wt.% enhances the stability and volume fraction of β phase in the microstructure, hence reducing the propensity of the alloy system to form α″ phase during quenching. Compressive yield strength and hardness of the alloys are (985-1847) MPa and (325-520) Hv respectively. Additionally, Ti-7Fe-11Nb possesses the lowest Young's modulus (84 GPa) and the highest deformability (42% strain) among the designed alloys due to the single β phase microstructure. This high deformability is also corroborated by the large plastic deformation zone underneath the Vickers indenter. In contrast, the fractured surfaces of Ti-7Fe and Ti-7Fe-1Nb alloys after compressive tests mostly contain shallow dimples, verifying their low ductility. The good combination of mechanical properties obtained for Ti-7Fe-11Nb renders it more desirable than commonly used CP-Ti and Ti-6Al-4V materials and makes it a promising candidate for biomedical application.

  12. Fabrication of Al/Al3Ti Functionally Graded Materials by Reaction Centrifugal Mixed-Powder Method

    NASA Astrophysics Data System (ADS)

    El-Hadad, Shimaa; Sato, Hisashi; Miura-Fujiwara, Eri; Watanabe, Yoshimi

    2011-01-01

    Formation of compositional gradient in Al/Al3Ti Functionally graded materials (FGMs) fabricated by the centrifugal method (CM) depends mainly on the centrifugal force and the processing temperature. In this study, a novel centrifugal method, reaction centrifugal mixed-powder method (RCMPM), was proposed to fabricate Al/Al3Ti FGMs under fixed centrifugal force (G=80). The effects of RCMPM processing temperature on the formation of Al3Ti intermetallics, its morphology and its distribution in the fabricated Al/Al3Ti FGMs have been investigated. Fine granular Al3Ti were observed at relatively lower processing temperature while the known coarse platelet-like particles of Al3Ti could be achieved at higher casting temperatures. Moreover, Ti3Al intermetallics compound and unreacted Ti phases are also observed along with Al3Ti particles. In addition, distribution of Al3Ti intermetallics size and their volume fraction showed a significant change when the Al/Al3Ti FGMs processed at different temperatures relative to the liquidus temperature of the master alloy.

  13. Substitutional and Interstitial Diffusion in alpha2-Ti3Al(O)

    NASA Technical Reports Server (NTRS)

    Copland, Evan; Young, David J.; Gleeson, Brian; Jacobson, Nathan

    2007-01-01

    The reaction between Al2O3 and alpha2-Ti3Al was studied with a series of Al2O3/alpha2-Ti3Al multiphase diffusion couples annealed at 900, 1000 and 1100 C. The diffusion-paths were found to strongly depend on alpha2- Ti3Al(O) composition. For alloys with low oxygen concentrations the reaction involved the reduction of Al2O3, the formation of a gamma-TiAl reaction-layer and diffusion of Al and O into the alpha2-Ti3Al substrate. Measured concentration profiles across the interaction-zone showed "up-hill" diffusion of O in alpha2-Ti3Al(O) indicating a significant thermodynamic interaction between O and Al, Ti or both. Diffusion coefficients for the interstitial O in alpha2-Ti3Al(O) were determined independently from the interdiffusion of Ti and Al on the substitutional lattice. Diffusion coefficients are reported for alpha2-Ti3Al(O) as well as gamma-TiAl. Interpretation of the results were aided with the subsequent measurement of the activities of Al, Ti and O in alpha 2-Ti3Al(O) by Knudsen effusion-cell mass spectrometry.

  14. Thermally unstable hydrides of titanium aluminide Ti3Al

    NASA Astrophysics Data System (ADS)

    Kazantseva, N. V.; Popov, A. G.; Mushnikov, N. V.; Skripov, A. V.; Soloninin, A. V.; Aleksashin, B. A.; Novozhenov, V. I.; Sazonova, V. A.; Kharisova, A. G.

    2011-04-01

    The hydrogen capacity of (Ti, Nb)3Al titanium aluminides subjected to mechanical activation in a hydrogen atmosphere has been studied. It has been shown that the application of this procedure allows one to prepare thermally unstable titanium aluminide (Ti3Al) hydrides with a high hydrogen content (to 2.6 wt %) at room temperature and normal pressure; in this case, no special requirements for the hydrogen purity are placed. The thermally unstable nanostructured Ti3Al hydrides were found to exhibit a higher hydrogen mobility as compared to that of the microcrystalline hydrides. Low niobium additions (to 2.1 at %) have been found to decrease the hydrogen capacity. Experiments on the preparation of bulk samples from the hydride powders obtained were performed.

  15. Compton Profile Study of Intermetallic Ti{sub 3}Al

    SciTech Connect

    Vyas, V.; Sharma, G.; Mishra, M. C.; Sharma, B. K.; Joshi, K. B.

    2011-10-20

    The Compton scattering measurement on intermetallic alloy Ti{sub 3}Al is reported in this work. The measurement is made using 59.54 keV gamma-rays from Am{sup 241} source. Theoretical calculation of Compton profile is also performed employing CRYSTAL code within the framework of density functional theory to compare with the measurement. The theoretical profile of the alloy is also synthesized following the superposition model taking the published Compton profiles of elemental solids from the APW method. The experimental study of charge transfer in the alloys has also been done by performing the experimental Compton profile measurements on Ti and Al following the superposition model and charge transfer from Al to Ti is clearly seen on the alloy formation.

  16. Plasma torch production of Ti/Al nanoparticles

    SciTech Connect

    Phillips, Jonathan; Zea, Hugo; Cheng, Lily; Luhrs, Claudia; Courtney, Matthew

    2009-01-01

    Using the Aerosol-through-Plasma (A-T-P) technique high surface area bi-cationic (Ti-Al) oxide particles of a range of stoichiometries were produced that showed remarkable resistance to sintering. Specifically, we found that homogeneous nanoparticles with surface areas greater than 150 m{sup 2}/gm were produced at all stoichiometries. In particular, for particles with a Ti:Al ratio of 1:3 a surface area of just over 200 m{sup 2}/gm was measured using the BET method. The most significant characteristic of these particles was that their sinter resistance was far superior to that of TiAl particles produced using any other method. For example, A-T-P generated particles retained >70% of their surface area even after sintering at 1000 C for five hours. In contrast, particles made using all other methods lost virtually all of their surface area after an 800 C treatment.

  17. AC conductivity studies of Fe doped TiO2 nanotubes

    NASA Astrophysics Data System (ADS)

    Vijayan, P. P.; Thomas, M.; George, K. C.

    2015-02-01

    Fe-doped TiO2 nanotubes are prepared by the combination of sol-gel process with hydrothermal treatment. The morphology and crystalline structure of TiO2 nanotubes are characterized by transmission electron microscopy (TEM), X-ray diffraction respectively (XRD). Fe doping induces a structural transformation from anatase to rutile. The temperature dependence of the ac electrical conductivity is investigated in the temperature range 303-413 K. Positive temperature coefficient of resistance is observed in the Fe doped TiO2 nanotubes. PL spectrum shows the presence of oxygen vacancies and self trapped excitons in Fe doped TiO2 nanotubes and undoped samples.

  18. Electronic structure and magnetic properties of LiMn{sub 1.5}M{sub 0.5}O{sub 4} (M=Al, Mg, Ni, Fe) and LiMn{sub 2}O{sub 4}/TiO{sub 2} nanocrystalline electrode materials

    SciTech Connect

    Talik, E.; Lipińska, L.; Zajdel, P.; Załóg, A.; Michalska, M.; Guzik, A.

    2013-10-15

    The process of sol–gel synthesis was applied to obtain LiMn{sub 1.5}M{sub 0.5}O{sub 4} (M=Al, Mg, Ni, Fe) and LiMn{sub 2}O{sub 4}/TiO{sub 2} nanopowders. The samples were characterized by following methods: X-ray diffraction (XRD), scanning electron microscopy (SEM/EDX), X-ray photoelectron spectroscopy (XPS) and SQUID magnetometry. XPS was used to examine the chemical composition and oxidation state of manganese, in particular the Mn{sup 3+}/Mn{sup 4+} ratio from the deconvolution of the complex Mn3p lines. The size of the grains and crystallites were independently obtained from SEM images and XRD patterns, respectively. In all the cases a critical interplay of electronic (Mn{sup 3+}/Mn{sup 4+} ratio), structural (unit cell volume) and magnetic properties was observed depending on the synthesis process. - Graphical abstract: SEM image of Li{sub 0.79}Ni{sub 0.41}Mn{sub 1.35}O{sub 4.45} sample. Display Omitted - Highlights: • LiMn{sub 1.5}M{sub 0.5}O{sub 4} (M=Al, Mg, Ni, Fe) and LiMn{sub 2}O{sub 4}/TiO{sub 2} obtained by sol–gel method. • XRD method was used to determine the crystal structure. • SEM/EDX imaging have been done. • XPS electronic structure was examined and discussed. • Experimental effective magnetic moment and the calculated one were compared.

  19. Pulsed Nd-YAG laser deposition of TiN and TiAlN coating

    NASA Astrophysics Data System (ADS)

    Kathuria, Y. P.; Uchida, Yoshiyuki

    This paper demonstrates the feasibility of generating a thin clad coating of TiN and TiAlN on SS304 base material by using the pulsed Nd-YAG laser. In the experiment TiN based coating was created with and without the addition of Al-powder. In the post processing, a precision grinder was employed to smoothen the top surface. SEM, XRD and EDS analysis were employed to study the surface topography etc. Microhardness mapping was performed at various points across the surface. The results show the average microhardness of the coating deposited with TiN is lower (1035 HV) than that of using Al-mixed powder (1264 HV).

  20. Large magnetostriction in directionally solidified FeGa and FeGaAl alloys

    NASA Astrophysics Data System (ADS)

    Srisukhumbowornchai, N.; Guruswamy, S.

    2001-12-01

    The magnetostriction of Fe-x at. % Ga (x=15, 20, and 27.5) was measured, for alloys processed under different directional solidification conditions, and the effect of partial substitution of Ga with Al on the magnetostriction of the alloys was examined. Magnetostriction measurements were carried out at different prestress levels varying from 0 to 55 MPa. Ga additions in the range of 15-27.5 at. % Ga in Fe were found to improve the magnetostriction of the disordered bcc phase of Fe by as much as 1 order of magnitude. The applied fields for saturation magnetostriction and the hysteresis observed were small. Magnetostriction values as high as 271×10-6 were obtained in polycrystalline Fe-27.5 at. % Ga rods prepared using a directional growth (DG) process at a growth rate of 22.5 mm/h. This process, which is essentially a seedless vertical Bridgman technique, resulted in near [001] textured polycrystalline Fe-Ga alloys. The preferred [001] crystallographic orientation of the DG alloys was approximately 14° away from the rod direction. For Ga contents between 15 and 27.5 at. % in Fe, the Ga atoms increase the Fe-Fe spacing in the disordered bcc (A2) phase and reduce the magnetic moment of Fe. Substitution of Ga with Al has a significant effect on the magnetostriction of the Fe-Ga alloys. Small substitution of 5 at. % Al for Ga in the Fe-20 at. % Ga alloy increases the magnetostriction in Fe, and the value is slightly larger than that of the Fe-20 at. % Ga alloy. A higher substitution amount of Al tends to decrease the magnetostriction.

  1. Segregation-Induced Subsurface Restructuring of FeAl(100)

    NASA Astrophysics Data System (ADS)

    Kottche, M.; Graupner, H.; Hammer, L.; Heinz, K.; Zehner, D. M.

    1996-03-01

    For FeAl, the stacking sequence in the [100] direction of the bulk crystal (CsCl structure) consists of alternating, single element planes. After sputtering, the selvedge region is depleted in Al. Following annealing to 350 ^circC, Al segregates to the surface region and a c(2 x 2) structure develops.(H. Graupner, L. Hammer, K. Müller, and D. M. Zehner, Surf. Sci. 322 (1995) 103. Research is sponsored by the *University of Erlangen-Nürnberg, Germany and DAAD, and the **Division of Materials Sciences, U.S. Department of Energy, under contract DE-AC05-84OR21400 with Lockheed Martin Energy Systems, Inc.) We have used low-energy electron diffraction (LEED) and Auger electron spectroscopy to investigate the structure and composition of this surface. From a detailed LEED I-V analysis, it has been determined that the subsurface region of the (100) surface orders with annealing, to form a stable Fe_3Al slab which is capped by an Al top layer and acts as an interface to the bulk FeAl. Within the limits of error, the interfacial Fe_3Al is similar to the bulk phase with some slight geometric rippling of the layers containing both elements. Annealing to higher temperatures leads to additional Al diffusion and eliminates the restructuring, resulting in a (1 x 1) phase.

  2. CONDENSED MATTER: ELECTRONIC STRUCTURE, ELECTRICAL, MAGNETIC, AND OPTICAL PROPERTIES: Electronic Structure and Elastic Properties of Ti3AlC from First-Principles Calculations

    NASA Astrophysics Data System (ADS)

    Du, Yu-Lei

    2009-11-01

    We perform a first-principles study on the electronic structure and elastic properties of Ti3AlC with an antiperovskite structure. The absence of band gap at the Fermi level and the finite value of the density of states at the Fermi energy reveal the metallic behavior of this compound. The elastic constants of Ti3AlC are derived yielding c11 = 356 GPa, c11 = 55 GPa, c44 = 157 GPa. The bulk modulus B, shear modulus G and Young's modulus E are determined to be 156, 151 and 342 GPa, respectively. These properties are compared with those of Ti3AlC2 and Ti2AlC with a layered structure in the Ti-Al-C system and Fe3AlC with the same antiperovskite structure.

  3. Reverse-Ballistic Impact Study of Shear Plug Formation and Displacement in Ti6Al4V Alloy

    DTIC Science & Technology

    1992-06-01

    temperatures at least as high as the 1660*C melting temperature for Ti6AI4V. 19 This melting observation is further supported by energy-dispersive...vicinity, an observed temperature would be lower but sufficiently high for melting to occur. Calculations by Bryant, et al., 20 on Ti 10V2Fe3A1 alloy...Ti6A14V alloy was selected for this work because it is known experimentally to be very prone to adiabatic shear band formation in response to high strain

  4. Spin-glass behaviors in carrier polarity controlled Fe{sub 3−x}Ti{sub x}O{sub 4} semiconductor thin films

    SciTech Connect

    Yamahara, H.; Seki, M.; Adachi, M.; Takahashi, M.; Nasu, H.; Tabata, H.; Horiba, K.; Kumigashira, H.

    2015-08-14

    Carrier-type control of spin-glass (cluster spin-glass) is studied in order to engineer basic magnetic semiconductor elements using the memory functions of spin-glass. A key of carrier-polarity control in magnetite is the valence engineering between Fe(II) and Fe(III) that is achieved by Ti(IV) substitution. Single phases of (001)-oriented Fe{sub 3−x}Ti{sub x}O{sub 4} thin films have been obtained on spinel MgAl{sub 2}O{sub 4} substrates by pulsed laser deposition. Thermoelectric power measurements reveal that Ti-rich films (x = 0.8) show p-type conduction, while Ti-poor films (x = 0.6–0.75) show n-type conduction. The systematic Fe(III) reduction to Fe(II) followed by Ti(IV) substitution in the octahedral sublattice is confirmed by the X-ray absorption spectra. All of the Fe{sub 3−x}Ti{sub x}O{sub 4} films (x = 0.6–0.8) exhibit ferrimagnetism above room temperature. Next, the spin-glass behaviors of Ti-rich Fe{sub 2.2}Ti{sub 0.8}O{sub 4} film are studied, since this magnetically diluted system is expected to exhibit the spin-glass behaviors. The DC magnetization and AC susceptibility measurements for the Ti-rich Fe{sub 2.2}Ti{sub 0.8}O{sub 4} film reveal the presence of the spin glass phase. Thermal- and magnetic-field-history memory effects are observed and are attributed to the long time-decay nature of remanent magnetization. The detailed analysis of the time-dependent thermoremanent magnetization reveals the presence of the cluster spin glass state.

  5. Influence of high-strain rate and temperature on the mechanical behavior of Nl-, Fe-, and Ti- based aluminides

    SciTech Connect

    Gray, G.T. III

    1996-09-01

    The majority of the strength characterization studies on ordered intermetallics have concentrated on the assessment of strength and work-hardening at conventional strain rates. Although the influence of strain rate on the structure/property relationships of pure nickel, iron, and titanium and a variety of their alloys have been extensively studied, the effect of strain rate on the stress-strain response of Ni-, Fe-, and Ti-based aluminides remains poorly understood. Dynamic constitutive behavior is however relevant to high speed impact performance of these materials such as during foreign object damage in aerospace applications, high-rate forging, and localized deformation behavior during machining. The influence of strain rate, varied between 0.001 and 10{sup 4} s{sup -1}, and temperatures, between 77 & 800K, on the compressive mechanical behavior of Ni{sub 3}A1, NiAl, Fe{sub 3}Al, Fe-40Al-0.1B, Ti-24Al-11Nb, and Ti-48Al-2Cr-2Nb will be presented. In this paper the influence of strain rate on the anomalous temperature dependency of the flow stresses in these aluminides will be reviewed and compared between aluminides. The rate sensitivity and work hardening of each aluminide will be discussed as a function of strain rate and temperature and contrasted to each other and to the values typical for their respective disordered base metals. 66 refs., 16 figs., 2 tabs.

  6. Effect of ion irradiation on the interdiffusion growth of aluminide phases in Ti Al diffusion couple

    NASA Astrophysics Data System (ADS)

    Romankov, S. E.; Mamaeva, A.; Vdovichenko, E.; Ermakov, E.

    2005-08-01

    During annealing on the Ti surface coated by the Al film, different aluminide phases were formed as the result of reactions between Ti and Al. Preliminary irradiation of the Al film with the thickness of 7 μm by Ti + ions had a strong effect on the interdiffusion growth of aluminide phases on the Ti substrate. Preliminary ion irradiation resulted in the development of more homogeneous and fine-grain microstructure during subsequent annealing. During ion irradiation of the two-phase (TiAl + Ti 3Al) overlayer the decomposition of the TiAl compound and the formation of Ti 3Al happened. In the processing of subsequent annealing, diffusion cementation of the overlayer occurred faster on the surface of the irradiated samples. After irradiation by different ions (Ti + and Al +), and during subsequent annealing the kinetics of structural formation developed in a different way.

  7. Ti-O-N/Ti composite coating on Ti-6Al-4V: surface characteristics, corrosion properties and cellular responses.

    PubMed

    Cao, Xiao-Lin; Sun, Tao; Yu, Yonghao

    2015-03-01

    To enhance the corrosion resistance of Ti-6Al-4V and extend its lifetime in medical applications, Ti-O-N/Ti composite coating was synthesized on the surface via plasma immersion ion implantation and deposition (PIIID). Surface morphology and cross sectional morphology of the composite coating were characterized using atomic force microscopy and scanning electron microscopy, respectively. Although X-ray photoelectron spectroscopic analysis revealed that the Ti-O-N/Ti composite coating was composed of non-stoichiometric titanium oxide, titanium nitride and titanium oxynitride, no obvious characteristic peak corresponding to the crystalline phases of them was detected in the X-ray diffraction pattern. In accordance with Owens-Wendt equation, surface free energy of the uncoated and coated samples was calculated and compared. Moreover, the corrosion behavior of uncoated and coated samples was evaluated by means of electrochemical impedance spectroscopy measurement, and an equivalent circuit deriving from Randles model was used to fit Bode plots and describe the electrochemical processes occurring at the sample/electrolyte interface. On the basis of the equivalent circuit model, the resistance of the composite coating was 4.7 times higher than that of the passive layer on uncoated samples, indicating the enhanced corrosion resistance after PIIID treatment. Compared to uncoated Ti-6Al-V, Ti-O-N/Ti-coated samples facilitated ostoblast proliferation within 7 days of cell culture, while there was no statistically significant difference in alkaline phosphate activity between uncoated and coated samples during 21 days of cell culture.

  8. Effect of Al Doping on Optical Band Gap Energy of Al-TiO2 Thin Films.

    PubMed

    Song, Yo-Seung; Kim, Bae-Yeon; Cho, Nam-Ihn; Lee, Deuk Yong

    2015-07-01

    Al-TiO2 thin films were prepared using a sol-gel derived spin coating by varying the Al/Ti molar ratio from 0 to 0.73 to investigate the effect of Al doping on the optical band gap energy (Eg) of the films. GAXRD results indicated that Al-TiO2 is composed of anatase and FTO phases when the Al/Ti molar ratio was less than 0.18. Above 0.38, no other peaks except FTO were found and transparency of the films was severely deteriorated. Eg of Al-TiO2 decreased from 3.20 eV to 2.07 eV when the Al/Ti ratio was raised from 0 to 0.38. Eg of 2.59 eV was found for the anatase Al-TiO2 films having the Al/Ti ratio of 0.18. The absorption band of Al-TiO2 coatings shifted dramatically from the UV region to the visible region with increasing the amount of Al dopant. The Al doping was mainly attributed to the optical band gap energy of Al-TiO2.

  9. Monte Carlo simulation of antiphase boundaries and growth of antiphase domains in Al5Ti3 phase in Al-rich γ-TiAl intermetallics

    NASA Astrophysics Data System (ADS)

    Kulkarni, U. D.; Hata, S.; Nakano, T.; Mitsuhara, M.; Ikeda, K.; Nakashima, H.

    2011-08-01

    Predominantly two kinds of antiphase boundaries (APBs) form in Al5Ti3, which is an Al-rich ordered derivative of the γ-TiAl (L10) phase. This phase can be viewed as a periodic arrangement of lean rhombs and squares on the Ti-rich (002) planes of the tetragonal L10. Energies of the two types of APBs were varied in a Monte Carlo simulation by suitably changing the pair interaction parameters. APBs of both types form boundaries of Al5Ti3 antiphase domains (APDs), which coarsen with time. An important observation in this regard is that mostly facetted APBs form at lower ageing temperatures, whereas curved APBs appear to form at relatively higher ageing temperatures. The findings of this work suggest that there exists a critical temperature, akin to the roughening transition temperature for crystals, that marks the transition from facetted to curved APBs.

  10. Influence of Melt Superheat, Sr Modifier, and Al-5Ti-1B Grain Refiner on Microstructural Evolution of Secondary Al-Si-Cu Alloys

    NASA Astrophysics Data System (ADS)

    Rakhmonov, Jovid; Timelli, Giulio; Bonollo, Franco

    2016-11-01

    The role of impurity elements and melt superheat on the efficiency of Sr modification, grain refinement with Al-Ti-B and the precipitation behavior of intermetallic phases in a secondary Al-7Si-3Cu-0.3Mg alloy were investigated. Metallographic and thermal analysis techniques were used to quantitatively examine the macro- and microstructural changes occurring with modifier and grain refiner additions at various pouring temperatures. The results indicate how the Sr modification and grain refinement with Al-Ti-B can be effective enough despite the presence of impurity elements in the material and the variation of pouring temperature. A slight poisonous effect of impurities, in particular, Zr and V, in the grain refinement efficiency can be eventually induced due to their action in promoting the formation of primary AlSiTi compounds. Moreover, grain refiner addition exerted a pronounced influence on the precipitation sequence of Fe-rich phases. The TiB2 particles appeared to promote the formation of Al5FeSi during solidification by acting as a favorable nucleation site.

  11. Plume dynamics from UV pulsed ablation of Al and Ti

    NASA Astrophysics Data System (ADS)

    Bauer, William; Perram, Glen; Haugan, Timothy

    2016-12-01

    Pulsed laser ablation of Al and Ti with a < 3.3 J/cm2 KrF laser and Ar background pressure of up to 1 Torr was performed to study the ablated plume. Mass loss experiments revealed the number of ablated atoms per pulse increases by 30% for Ti and 20% for Al as pressure decreases from 1 Torr to vacuum. Optical emission imaging performed using a gated ICCD revealed a strong dependence of shock front parameters, defined by the Sedov-Taylor blast and classical drag models, on background pressure. Spatially resolved optical emission spectroscopy from Al I, Al II, Ti I, and Ti II revealed ion temperatures of 104 K that decreased away from the target surface along the surface normal and neutral temperatures of 103 K independent of target distance. Comparison between kinetic energy in the shock and internal excitation energy reveals that nearly 100% of the energy is partitioned into shock front kinetic energy and 1% into internal excitation.

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

    SciTech Connect

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

    1995-11-01

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

  13. Hafnium influence on the microstructure of FeCrAl alloys

    NASA Astrophysics Data System (ADS)

    Geanta, V.; Voiculescu, I.; Stanciu, E.-M.

    2016-06-01

    Due to their special properties at high temperatures, FeCrAl alloys micro-alloyed with Zr can be regarded as potential materials for use at nuclear power plants, generation 4R. These materials are resistant to oxidation at high temperatures, to corrosion, erosion and to the penetrating radiations in liquid metal environments. Also, these are able to form continuously, by the self-generation process of an oxide coating with high adhesive strength. The protective oxide layers must be textured and regenerable, with a good mechanical strength, so that crack and peeling can not appear. To improve the mechanical and chemical characteristics of the oxide layer, we introduced limited quantities of Zr, Ti, Y, Hf, Ce in the range of 1-3%wt in the FeCrAl alloy. These elements, with very high affinity to the oxygen, are capable to stabilize the alumina structure and to improve the oxide adherence to the metallic substrate. FeCrAl alloys microalloyed with Hf were prepared using VAR (Vacuum Arc Remelting) unit, under high argon purity atmosphere. Three different experimental alloys have been prepared using the same metallic matrix of Fe-14Cr-5Al, by adding of 0.5%wt Hf, 1.0%wt Hf and respectively 1.5%wt Hf. The microhardness values for the experimental alloys have been in the range 154 ... 157 HV0.2. EDAX analyses have been performed to determine chemical composition on the oxide layer and in the bulk of sample and SEM analyze has been done to determine the microstructural features. The results have shown the capacity of FeCrAl alloy to form oxide layers, with different texture and rich in elements such as Al and Hf.

  14. Layered Composite of TiC-TiB2 to Ti-6Al-4V in Graded Composition by Combustion Synthesis in High-gravity Field

    NASA Astrophysics Data System (ADS)

    Huang, Xuegang; Zhao, Zhongmin; Zhang, Long

    2013-03-01

    By taking combustion synthesis to prepare solidified TiB2 matrix ceramic in high-gravity field, the layered composite of TiC-TiB2 ceramic to Ti-6Al-4V substrate in graded composition was achieved. XRD, FESEM and EDS results showed that the bulk full-density solidified TiC-TiB2 composite was composed of fine TiB2 platelets, TiC irregular grains, a few of α-Al2O3 inclusions and Cr alloy phases, and α'-Ti phases alternating with Ti-enriched carbides constituted the matrix of the joint in which fine TiB platelets were embedded, whereas some C, B atoms were also detected at the heat-affected zone of Ti-6A1-4V substrate. The layered composite of the solidified ceramic to Ti-6Al-4V substrate in graded composition with continuous microstructure was considered a result of fused joint and inter-diffusion between liquid ceramic and surface-molten Ti alloy, followed by TiB2-Ti peritectic reaction and subsequent eutectic reaction in TiC-TiB-Ti ternary system.

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

    SciTech Connect

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

    2010-09-15

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

  16. The Kinetics of TiAl3 Formation in Explosively Welded Ti-Al Multilayers During Heat Treatment

    NASA Astrophysics Data System (ADS)

    Foadian, Farzad; Soltanieh, Mansour; Adeli, Mandana; Etminanbakhsh, Majid

    2016-10-01

    Metallic-intermetallic laminate (MIL) composites, including Ti/TiAl3 composite, are promising materials for many applications, namely, in the aerospace industry. One method to produce Ti/TiAl3 laminate composite is to provide close attachment between desired number of titanium and aluminum plates, so that by applying heat and/or pressure, the formation of intermetallic phases between the layers becomes possible. In this work, explosive welding was used to make a strong bond between six alternative Ti and Al layers. The welded samples were annealed at three different temperatures: 903 K, 873 K, and 843 K (630 °C, 600 °C, and 570 °C) in ambient atmosphere, and the variation of the intermetallic layer thickness was used to study the growth kinetics. Microstructural investigations were carried out on the welded and annealed samples using optical microscopy and scanning electron microscopy equipped with energy-dispersive X-ray spectrometer (EDS). X-ray diffraction (XRD) technique was used to identify the formed intermetallic phases. It was found that at each temperature, two different mechanisms govern the process: reaction controlled and diffusion controlled. The calculated values of activation energies for reaction-controlled and diffusion-controlled mechanisms are 232.1 and 17.4 kJ, respectively.

  17. Comparison of microstructural evolution in Ti-Mo-Zr-Fe and Ti-15Mo biocompatible alloys.

    PubMed

    Nag, S; Banerjee, R; Stechschulte, J; Fraser, H L

    2005-07-01

    The microstructural evolution and attendant strengthening mechanisms in two biocompatible alloy systems, the binary Ti-15Mo and the quaternary Ti-13Mo-7Zr-3Fe (TMZF), have been compared and contrasted in this paper. In the homogenized condition, while the Ti-15Mo alloy exhibited a single phase microstructure consisting of large beta grains, the TMZF alloy exhibited a microstructure consisting primarily of a beta matrix with grain boundary alpha precipitates and a low volume fraction of intra-granular alpha precipitates. On ageing the homogenized alloys at 600 degrees C for 4 h, both alloys exhibited the precipitation of refined scale secondary alpha precipitates homogeneously in the beta matrix. However, while the hardness of the TMZF alloy marginally increased, that of the Ti-15Mo alloy decreased substantially as a result of the ageing treatment. In order to understand this difference in the mechanical properties after ageing, TEM studies have been carried out on both alloys in the homogenized and homogenized plus aged conditions. The results indicate that the omega precipitates dissolve on ageing in case of the Ti-15Mo alloy, consequently leading to a substantial decrease in the hardness. In contrast, the omega precipitates do not dissolve on ageing in the TMZF alloy and the precipitation of the fine scale secondary alpha leads to increased hardness.

  18. In vitro evaluation of human osteoblast adhesion to a thermally oxidized gamma-TiAl intermetallic alloy of composition Ti-48Al-2Cr-2Nb (at.%).

    PubMed

    Bello, Samir A; de Jesús-Maldonado, Idaris; Rosim-Fachini, Esteban; Sundaram, Paul A; Diffoot-Carlo, Nanette

    2010-05-01

    Ti-48Al-2Cr-2Nb (at.%) (gamma-TiAl), a gamma titanium aluminide alloy originally designed for aerospace applications, appears to have excellent potential as implant material. Thermal treatment of gamma-TiAl renders this alloy extremely corrosion resistant in vitro, which could improve its biocompatibility. In this study, the surface oxides produced by thermal oxidation (at 500 degrees C, and at 800 degrees C for 1 h in air) on gamma-TiAl were characterized by X-ray photoelectron spectroscopy (XPS). hFOB 1.19 cell adhesion on thermally oxidized gamma-TiAl was examined in vitro by a hexosaminidase assay, scanning electron microscopy (SEM) and confocal laser scanning microscopy (CLSM) after 1, 7 and 14 days. Ti-6Al-4V surfaces were used for comparison. Hexosaminidase assay data and CLSM analysis of focal contacts and cytoskeleton organization showed no differences in cell attachment on autoclaved and both heat-treated gamma-TiAl surfaces at the different time points. SEM images showed well organized multi-layers of differentiated cells adhered on thermally oxidized gamma-TiAl surfaces at day 14. Unexpectedly, thermally oxidized Ti-6Al-4V surfaces oxidized at 800 degrees C exhibited cytotoxic effects on hFOB 1.19 cells. Our results indicate that thermal oxidation of gamma-TiAl seems to be a promising method to generate highly corrosion resistant and biocompatible surfaces for implant applications.

  19. Wear resistance of TiAlSiN thin coatings.

    PubMed

    Silva, F J G; Martinho, R P; Alexandre, R J D; Baptista, A P M

    2012-12-01

    In the last decades TiAIN coatings deposited by PVD techniques have been extensively investigated but, nowadays, their potential development for tribological applications is relatively low. However, new coatings are emerging based on them, trying to improve wear behavior. TiAlSiN thin coatings are now investigated, analyzing if Si introduction increases the wear resistance of PVD films. Attending to the application, several wear test configurations has been recently used by some researchers. In this work, TiAISiN thin coatings were produced by PVD Unbalanced Magnetron Sputtering technique and they were conveniently characterized using Scanning Electron Microscopy (SEM) provided with Energy Dispersive Spectroscopy (EDS), Atomic Force Microscopy (AFM), Electron Probe Micro-Analyzer (EPMA), Micro Hardness (MH) and Scratch Test Analysis. Properties as morphology, thickness, roughness, chemical composition and structure, hardness and film adhesion to the substrate were investigated. Concerning to wear characterization, two very different ways were chosen: micro-abrasion with ball-on-flat configuration and industrial non-standardized tests based on samples inserted in a feed channel of a selected plastic injection mould working with 30% (wt.) glass fiber reinforced polypropylene. TiAISiN coatings with a small amount of about 5% (wt.) Si showed a similar wear behavior when compared with TiAIN reported performances, denoting that Si addition does not improve the wear performance of the TiAIN coatings in these wear test conditions.

  20. FeSn2-TiC nanocomposite alloy anodes for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Leibowitz, Joshua; Allcorn, Eric; Manthiram, Arumugam

    2015-11-01

    FeSn2-TiC nanocomposite alloy anodes for lithium-ion batteries have been synthesized by a mechanochemical process involving high-energy mechanical milling of Fe/Ti, Ti/Sn, and carbon black. Characterization of the nanocomposites formed with x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) reveals that this alloy is composed of crystalline nanoparticles of FeSn2 dispersed in a matrix of TiC. The FeSn2-TiC alloy shows an initial gravimetric capacity of 511 mAh g-1 (1073 mAh cm-3) with a first-cycle coulombic efficiency of 77% and a tap density of 2.1 g cm-3. The TiC buffer matrix in the nanocomposite anode accommodates the large volume change occurring during the charge-discharge process and leads to good cyclability compared to similar Sn-based anodes.

  1. Comparison of Fe-AlPILC and Fe-ZSM-5 catalysts used for degradation of methomyl

    NASA Astrophysics Data System (ADS)

    Lázár, Károly; Tomašević, Andjelka; Bošković, Goran; Kiss, Ernő

    2009-07-01

    Catalytic performances of Fe-AlPILC (14 wt.% Fe) and Fe-ZSM-5 (5 wt.% Fe) catalysts are compared in the wet oxidative degradation of methomyl. Fe-ZSM-5 exhibits outstanding whereas Fe-AlPILC shows only mediocre activity. Positions of iron are analysed in the two catalysts by Mössbauer spectroscopy. Iron is in highly dispersed state in Fe-AlPILC whereas in the other case a hematite/ZSM-5 composite is formed. The catalytic activity is attributed to iron located and stabilized in ionic dispersion.

  2. Application of the Ti-in-quartz thermobarometer to rutile-free systems. Reply to: a comment on: `TitaniQ under pressure: the effect of pressure and temperature on the solubility of Ti in quartz' by Thomas et al.

    NASA Astrophysics Data System (ADS)

    Thomas, Jay B.; Bruce Watson, E.

    2012-08-01

    The premise of the Wilson et al. comment is that the Ti-in-quartz solubility calibration (Thomas et al. in Contrib Mineral Petrol 160:743-759, 2010) is fundamentally flawed. They reach this conclusion because P- T estimates using the Ti-in-quartz calibration differ from their previous interpretations for crystallization conditions of the Bishop and Oruanui rhyolites. If correct, this assertion has far-reaching implications, so a careful assessment of the Wilson et al. reasoning is warranted. Application of the Ti-in-quartz calibration as a thermobarometer in rutile-free rocks requires an estimation of TiO2 activity in the liquid ( a_{{{{TiO}}_{ 2} }} (liquid-rutile); referenced to rutile saturation) and an independent constraint on either P or T to obtain the crystallization temperature or pressure, respectively. The foundation of Wilson et al.'s argument is that temperature estimates obtained from Fe-Ti oxide thermometry accurately reflect crystallization conditions of quartz in the two rhyolites discussed. We maintain that our experimental approach is sound, the thermodynamic basis of the Ti-in-quartz calibration is fundamentally correct, and our experimental results are robust and reproducible. We suggest that the reason Wilson et al. obtain implausible pressure estimates is because estimates for T and a_{{{{TiO}}_{ 2} }} they used as input values for the Ti-in-quartz calibration are demonstrably too high. Numerous studies show that Fe-Ti oxide temperature estimates of some rhyolites are substantially higher than those predicted by well-constrained phase equilibria. In this reply, we show that when reasonable input values for T and a_{{{{TiO}}_{ 2} }} (liquid-rutile) are used, pressure estimates obtained from the Ti-in-quartz calibration are well aligned with phase equilibria and essentially identical to melt inclusion volatile saturation pressures.

  3. Thermodynamic Modeling and Experimental Study of Phase Transformations in Alloys Based on γ-TiAl

    NASA Astrophysics Data System (ADS)

    Kuznetsov, A. V.; Sokolovskii, V. S.; Salishchev, G. A.; Belov, N. A.; Nochovnaya, N. A.

    2016-09-01

    Thermo-Calc software is used to model the composition diagram for alloys based on γ-TiAl of the systems Ti - Al - Mo - (4 - 10) at.% Nb and Ti - Al - Nb - X ( X is Cr, Mo, V). The effect of alloying on critical points and sequence of phase transformations is established. Changes in phase composition in relation to alloy TNM-B1 temperature are analyzed using a polythermal section of the Ti - Al - Nb - Mo system.

  4. High-temperature phase equilibria in the Al-rich corner of the Al-Ti-C system

    SciTech Connect

    Frage, N.; Frumin, N.; Levin, L.; Polak, M.; Dariel, M.P.

    1998-04-01

    A thermodynamic analysis of the Al-rich corner in the ternary Al-Ti-C diagram, providing phase relations and regions of phase stability, is presented. An invariant four-phase equilibrium between Al, Al{sub 4}C{sub 3}, Al{sub 3}Ti, and TiC{sub x} takes place at 0.53 at. pct Ti, 7.10{sup {minus}6} at. pct C, and TiC{sub 0.883} at 966 K. The carbon content of the TiC{sub x} phase, which extends from x = 0.48 to 0.98, exerts a significant effect on phase relationships in this ternary system. In particular, it is shown that stoichiometric TiC is not stable in the presence of liquid Al. For example, at 1,300 K, a two-phase equilibrium between Al{sub L} and TiC{sub x} exists only in the 0.91 < x < 0.82 range. Thus, the interaction of Al{sub L} with stoichiometric TiC leads to the formation of the Al{sub 4}C{sub 3} aluminum carbide phase, whereas for x < 0.82, only the intermetallic compound Al{sub 3}Ti can form at this temperature. The results of this analysis were confirmed by X-ray diffraction (XRD) measurements of relevant composites.

  5. Study on improved tribological properties by alloying copper to CP-Ti and Ti-6Al-4V alloy.

    PubMed

    Wang, Song; Ma, Zheng; Liao, Zhenhua; Song, Jian; Yang, Ke; Liu, Weiqiang

    2015-12-01

    Copper alloying to titanium and its alloys is believed to show an antibacterial performance. However, the tribological properties of Cu alloyed titanium alloys were seldom studied. Ti-5Cu and Ti-6Al-4V-5Cu alloys were fabricated in the present study in order to further study the friction and wear properties of titanium alloys with Cu additive. The microstructure, composition and hardness were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscope (TEM) and hardness tester. The tribological behaviors were tested with ZrO2 counterface in 25% bovine serum using a ball-on-disc tribo-tester. The results revealed that precipitations of Ti2Cu intermetallic compounds appeared in both Ti-5Cu and Ti-6Al-4V-5Cu alloys. The tribological results showed an improvement in friction and wear resistance for both Ti-5Cu and Ti-6Al-4V-5Cu alloys due to the precipitation of Ti2Cu. The results also indicated that both CP-Ti and Ti-5Cu behaved better wear resistance than Ti-6Al-4V and Ti-6Al-4V-5Cu due to different wear mechanisms when articulated with hard zirconia. Both CP-Ti and Ti-5Cu revealed dominant adhesive wear with secondary abrasive wear mechanism while both Ti-6Al-4V and Ti-6Al-4V-5Cu showed severe abrasive wear and cracks with secondary adhesive wear mechanism due to different surface hardness integrated by their microstructures and material types.

  6. Oxidation of Sulfonamides in Aqueous Solution by UV-TiO2-Fe(VI).

    PubMed

    Ma, Yan; Zhang, Kejia; Li, Cong; Zhang, Tuqiao; Gao, Naiyun

    2015-01-01

    The photocatalytic degradation of sulfonamides in aqueous TiO2 suspension under UV irradiation has been investigated using potassium ferrate as electron acceptors. The results showed that the stability of Fe(VI) is dependent on pH significantly, and the stability reduces obviously in the presence of UV-TiO2. The experiments indicated that Fe(VI) could effectively scavenge the conduction band electrons from the surface of TiO2. The photocatalytic oxidation of sulfonamides with Fe(VI) was found to be much faster than that without Fe(VI). The SD, SM, and SMX concentration was greatly reduced by 89.2%, 83.4%, and 82.0%, respectively, after 10 min with UV-TiO2-Fe(VI), comparing to 65.2%, 66.0%, and 71.9%, respectively, with Fe(VI) only in the dark and 71.3%, 72.7%, and 76.0%, respectively, with UV-TiO2. The pH value of solution significantly influenced the sulfonamides degradation in UV-TiO2-Fe(VI) system. The degradation amount of sulfonamides after 10 min was a maximum at pH 7. The intermediate products of sulfonamides oxidation by UV-TiO2-Fe(VI) were analysed by LC-HESI-MS-MS and the results suggested that a majority of sulfonamides turned into large-molecule products without complete mineralization.

  7. Anisotropic swelling and microcracking of neutron irradiated Ti3AlC2-Ti5Al2C3 materials

    DOE PAGES

    Ang, Caen K.; Silva, Chinthaka M.; Shih, Chunghao Phillip; ...

    2015-12-17

    Mn + 1AXn (MAX) phase materials based on Ti–Al–C have been irradiated at 400 °C (673 K) with fission neutrons to a fluence of 2 × 1025 n/m2 (E > 0.1 MeV), corresponding to ~ 2 displacements per atom (dpa). We report preliminary results of microcracking in the Al-containing MAX phase, which contained the phases Ti3AlC2 and Ti5Al2C3. Equibiaxial ring-on-ring tests of irradiated coupons showed that samples retained 10% of pre-irradiated strength. Volumetric swelling of up to 4% was observed. Phase analysis and microscopy suggest that anisotropic lattice parameter swelling caused microcracking. Lastly, variants of titanium aluminum carbide may bemore » unsuitable materials for irradiation at light water reactor-relevant temperatures.« less

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

    SciTech Connect

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

    2000-09-15

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

  9. Development of ODS-Fe{sub 3}Al alloys

    SciTech Connect

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

    1997-12-01

    The overall goal of this program is to develop an oxide dispersion-strengthened (ODS) version of Fe{sub 3}Al that has sufficient creep strength and resistance to oxidation at temperatures in the range 1000 to 1200 C to be suitable for application as heat exchanger tubing in advanced power generation cycles. The main areas being addressed are: (a) alloy processing to achieve the desired alloy grain size and shape, and (b) optimization of the oxidation behavior to provide increased service life compared to semi-commercial ODS-FeCrAl alloys intended for the same applications. The recent studies have focused on mechanically-alloyed powder from a commercial alloy vendor. These starting alloy powders were very clean in terms of oxygen content compared to ORNL-produced powders, but contained similar levels of carbon picked up during the milling process. The specific environment used in milling the powder appears to exert a considerable influence on the post-consolidation recrystallization behavior of the alloy. A milling environment which produced powder particles having a high surface carbon content resulted in a consolidated alloy which readily recrystallized, whereas powder with a low surface carbon level after milling resulted in no recrystallization even at 1380 C. A feature of these alloys was the appearance of voids or porosity after the recrystallization anneal, as had been found with ORNL-produced alloys. Adjustment of the recrystallization parameters did not reveal any range of conditions where recrystallization could be accomplished without the formation of voids. Initial creep tests of specimens of the recrystallized alloys indicated a significant increase in creep strength compared to cast or wrought Fe{sub 3}Al, but the specimens failed prematurely by a mechanism that involved brittle fracture of one of the two grains in the test cross section, followed by ductile fracture of the remaining grain. The reasons for this behavior are not yet understood. The

  10. Aluminum matrix texture in Al-Al3Ti functionally graded materials analyzed by electron back-scattering diffraction

    NASA Astrophysics Data System (ADS)

    Watanabe, Yoshimi; Sequeira, Paulo D.; Sato, Hisashi; Inamura, Tomonari; Hosoda, Hideki

    2016-01-01

    Al matrix functionally graded materials (FGMs) with oriented Al3Ti platelets were fabricated by a centrifugal solid-particle method. The applied centrifugal forces were 30, 60, and 120G (units of gravity). The orientation and volume fraction gradients of the Al3Ti platelets within the samples were measured. Since a good lattice correspondence was reported for the close-packed directions and the close-packed planes between Al and Al3Ti, the Al matrix in the Al-Al3Ti FGMs fabricated by the centrifugal solid-particle method should have some texture. Al matrix texture was, therefore, analyzed by electron back-scattering diffraction (EBSD). Analysis of the resulting pole figures indicates a preferred orientation along the (200) plane for the Al matrix crystals. Furthermore, increasing the applied centrifugal force enhances the orientation effect. A correlation appears to exist between platelet orientation and the preferred texture of the Al matrix.

  11. Morphological evolution and strengthening behavior of α-Al(Fe,Mn)Si in Al-6Si-2Fe-xMn alloys

    NASA Astrophysics Data System (ADS)

    Gao, Tong; Hu, Kaiqi; Wang, Longshuai; Zhang, Bangran; Liu, Xiangfa

    β-Al5FeSi is preferred to form in Al-Si-Fe alloys, normally exhibiting needlelike, which is harmful for the mechanical properties. In this paper, with the addition of 1%, 1.5% and 3% Mn into an Al-6Si-2Fe alloy, β-Al5FeSi phase was found to transform to skeleton, flower-like and coarse dendritic α-Al(Fe,Mn)Si, respectively. The novel flower-like α-Al(Fe,Mn)Si crystals contain developed branches with the average diameter of ∼200 nm, performing strengthening effect on the tensile property. Detailed morphologies of α-Al(Fe,Mn)Si phase and the formation mechanism were discussed.

  12. Hibonite, Ca2/Al, Ti/24O38, from the Leoville and Allende chondritic meteorites.

    NASA Technical Reports Server (NTRS)

    Keil, K.; Fuchs, L. H.

    1971-01-01

    Hibonite was discovered in light-colored, Ca-Al-Ti-rich and Si-Fe-poor, achondritic inclusions of the Leoville and Allende HL-group chondrites. Two varieties of hibonite occur: one emits a bright red-orange luminescence under electron bombardment and has high amounts of Al2O3 (87.7; 87.9) and low amounts of MgO (0.65; 0.8) and TiO2 (0.68; 0.8). The other emits a bright blue luminescence and is low in Al2O3 (78.7; 79.2) and high in MgO (3.3; 3.7) and TiO2 (6.5; 7.9) (in wt. %). The oxide CaO is about the same in both varieties. It is suggested that the change in the color of the visible luminescence results from changes in composition. The origin of hibonite which occurs in complex mineral assemblages together with anorthite, gelhenite, wollastonite, aluminous diopside, andradite, Ca-pyroxene, perovskite, spinel, taenite, chromite, and pentlandite, and in close proximity to nodules containing calcite, whewellite, forsterite and many of the aforementioned phases, is discussed. The proposition that hibonite and associated phases originated by contact metamorphism and metasomatism of calcite-dolomite bearing assemblages cannot, at this time, be completely ruled out.

  13. Oxidation characteristics of Ti-14Al-21Nb ingot alloy

    NASA Technical Reports Server (NTRS)

    Sankaran, Sankara N.; Clark, Ronald K.; Unnam, Jalaiah; Wiedemann, Karl E.

    1990-01-01

    Static oxidation kinetics of Ti14Al21Nb (wt pct) ingot alloy were studied in air over the temperature interval of 649 to 1093 C in a thermogravimetric apparatus. The oxidation products were characterized by x ray diffraction, electron microprobe analysis, energy dispersive x ray analysis, and Auger electron spectroscopy. Cross-sections of the oxidized samples were also examined using light and scanning electron microscopy. The oxidation rate was substantially lower than the conventional alloys of titanium, but the kinetics displayed a complex behavior involving two or more oxidation rates depending on the temperature and duration of exposure. The primary oxide formed was TiO2, but this oxide was doped with Nb. Small amounts of Al2O3 and TiN were also present in the scale. Diffusion of oxygen into the alloy was observed and the diffusivity seemed to be dependent on the microstructure of the metal. A model was presented to explain the oxidation behavior of the alloy in terms of the reduction in the oxygen diffusivity in the oxide caused by the modification of the defect structure of TiO2 by Nb ions.

  14. Composition and solidification microstructure selection in the interdendritic matrix between primary Al{sub 3}Fe dendrites in hypereutectic Al-Fe alloys

    SciTech Connect

    Liang, D.; Korgul, P.; Jones, H.

    1996-07-01

    The composition and constitution of matrix microstructure between plate-like Al{sub 3}Fe dendrites in Bridgman-grown hypereutectic Al-Fe alloys has been determined as a function of alloy concentration C{sub 0} and growth velocity V in the ranges 2.5 < C{sub 0} < 28.1 wt%Fe and 0.01 < V < 5.0 mm/s. The transition at V = 0.1 mm/s from a fully eutectic matrix at C{sub 0} = 3.5 wt%Fe to one containing {alpha}Al dendrites at C{sub 0} {ge} 4.7 wt%Fe is attributed to growth temperatures of {alpha}Al dendrites that are higher than those of eutectic in a matrix of lower iron-content, which results from these conditions. The matrix eutectic changes from irregular {alpha}-Al-Al{sub 3}Fe to regular {alpha}Al-Al{sub x}Fe with increasing V, the transition velocity increasing from 0.1 to 0.2 mm/s for C{sub 0} values of 9.5 and 14 wt%Fe up to 0.35--1.0 mm/s for C{sub 0} values of 18.7--28.1 wt%Fe. This increased transition velocity, compared with that for {alpha}-Al-Al{sub 3}Fe to {alpha}Al-Al{sub 6}Fe at lower concentration, is indicative of a lower formation temperature for the {alpha}Al-Al{sub x}Fe than the {alpha}Al-Al{sub 6}Fe eutectic.

  15. Au-free ohmic Ti/Al/TiN contacts to UID n-GaN fabricated by sputter deposition

    NASA Astrophysics Data System (ADS)

    Garbe, V.; Weise, J.; Motylenko, M.; Münchgesang, W.; Schmid, A.; Rafaja, D.; Abendroth, B.; Meyer, D. C.

    2017-02-01

    The fabrication and characterization of an Au-free Ti/Al/TiN (20/100/100 nm) contact stack to unintentionally doped n-GaN with TiN serving as the diffusion barrier is presented. Sputter deposition and lift-off in combination with post deposition annealing at 850 °C are used for contact formation. After annealing, contact shows ohmic behavior to n-GaN and a specific contact resistivity of 1.60 × 10-3 Ω cm2. To understand the contact formation on the microscopic scale, the contact was characterized by current-voltage measurements, linear transmission line method, X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. The results show the formation of Ti-N bonds at the GaN/Ti interface in the as-deposited stack. Annealing leads to diffusion of Ti, Al, Ga, and N, and the remaining metallic Ti is fully consumed by the formation of the intermetallic tetragonal Al3Ti phase. Native oxide from the GaN surface is trapped during annealing and accumulated in the Al interlayer. The TiN capping layer, however, was chemically stable during annealing. It prevented oxidation of the Ti/Al contact bilayer successfully and thus proved to be a well suitable diffusion barrier with ideal compatibility to the Ti/Al contact metallization.

  16. Gas nitriding and subsequent oxidation of Ti-6Al-4V alloys

    PubMed Central

    2012-01-01

    Ti-6Al-4V alloys consisting of α-Ti grains and intergranular β-Ti islands were nitrided at 850°C for 1 to 12 h under a nitrogen pressure of 1 Pa. With increasing nitriding time, the Ti-N compound layer became thicker, and the α-Ti diffusion zone containing dissolved nitrogen became wider. In the Ti-N compound layer, the initially formed Ti2N became TiN as the nitriding progressed. The nitride layers were oxidized to rutile-TiO2 after oxidation at 700°C for 10 h in air. PMID:22221679

  17. Dilute ferrimagnetism of ilmenites Mn3FeTiSbO9 and Mn4FeTi2SbO12

    NASA Astrophysics Data System (ADS)

    Bazuev, G. V.; Korolev, A. V.; Golovkin, B. G.

    2016-07-01

    Metastable solid solutions (SS) Mn3FeTiSbO9 and Mn4FeTi2SbO12 with the ilmenite structure (space group R bar 3) have been prepared by quenching at normal conditions. The compositions of the compounds have been justified using EDX spectroscopy and X-ray diffraction. The magnetic properties of SSs have been analyzed by comparison with ferrimagnetic ilmenite Mn2FeSbO6 ( T N = 269 K) as a natural mineral and ceramics obtained at high pressure and high temperature. The solid solutions have been characterized as dilute magnetic systems formed as a result of substitution of nonmagnetic cations Ti4+ for a part of Fe3+ and Sb5+ cations. Mn3FeTiSbO9 is considered as a ferromagnetic with T N = 171 K and Mn4FeTi2SbO12 as a magnetic with the concentration of magnetic clusters below the percolation threshold.

  18. An Innovative Method for Manufacturing Gamma-TiAl Foil

    NASA Technical Reports Server (NTRS)

    Hales, Stephen J.; Saqib, Mohammad; Alexa, Joel A.

    2003-01-01

    The manufacture and entrance into service of thin gage gamma-TiAl product has been hampered by the inherent low room temperature ductility of the material. In the present study a new approach was explored for the efficient manufacture of gamma-TiAl foil with improved ductility. The objective was to produce a very clean material (low interstitial content) with a highly refined, homogeneous microstructure placed in a fully lamellar condition. The processing route involved the use of RF plasma spray deposition of pre-alloyed powders, followed by consolidation via vacuum hot pressing and heat treatment. The approach took advantage of a deposition process which included no electrodes, no binders and high cooling rates. Results and discussion of the work performed to date are presented.

  19. Ferroquadrupolar ordering in PrTi2Al20

    NASA Astrophysics Data System (ADS)

    Sato, Taku J.; Ibuka, Soshi; Nambu, Yusuke; Yamazaki, Teruo; Hong, Tao; Sakai, Akito; Nakatsuji, Satoru

    2012-11-01

    The origin of the nonmagnetic phase transition in PrTi2Al20, reported earlier in a macroscopic study, has been asserted microscopically using elastic and inelastic neutron scattering techniques. It has been shown spectroscopically that the crystalline-electric-field ground state is a nonmagnetic Γ3 doublet, whereas the excited states are two triplets (Γ4 and Γ5) and a singlet (Γ1). The diffraction experiment under external magnetic field shows that the nonmagnetic transition is indeed ferroquadrupolar ordering, which takes place as a consequence of cooperative removal of the ground-state-doublet degeneracy. It is therefore concluded that PrTi2Al20 is another rare example of Pr compounds exhibiting nonmagnetic quadrupolar order.

  20. Laser Metal Deposition of the Intermetallic TiAl Alloy

    NASA Astrophysics Data System (ADS)

    Thomas, Marc; Malot, Thierry; Aubry, Pascal

    2017-03-01

    Laser metal deposition of the commercial intermetallic Ti-47Al-2Cr-2Nb alloy was investigated. A large number of experiments were conducted under controlled atmosphere by changing the processing parameters to manufacture a series of beads, thin walls, and massive blocks. Optimal process parameters were successfully found to prevent cracking which is generally observed in this brittle material due to built-up residual stresses during fast cooling. These non-equilibrium cooling conditions tend to generate ultra-fine and metastable structures exhibiting high microhardness values, thus requiring post-heat treatments. The latter were successfully used to restore homogeneous lamellar or duplex microstructures and to relieve residual stresses. Subsequent tensile tests enabled us to validate the soundness and homogeneity of the Intermetallic TiAl alloy. Finally, a higher mechanical performance was achieved for the LMD material with respect to cast+HIP and EBM counterparts.

  1. Thermally Driven Electronic Topological Transition in FeTi

    SciTech Connect

    Yang, F. C.; Muñoz, J. A.; Hellman, O.; Mauger, L.; Lucas, M. S.; Tracy, S. J.; Stone, M. B.; Abernathy, D. L.; Xiao, Yuming; Fultz, B.

    2016-08-08

    In this paper, ab initio molecular dynamics, supported by inelastic neutron scattering and nuclear resonant inelastic x-ray scattering, showed an anomalous thermal softening of the M5- phonon mode in B2-ordered FeTi that could not be explained by phonon-phonon interactions or electron-phonon interactions calculated at low temperatures. A computational investigation showed that the Fermi surface undergoes a novel thermally driven electronic topological transition, in which new features of the Fermi surface arise at elevated temperatures. Finally, the thermally induced electronic topological transition causes an increased electronic screening for the atom displacements in the M5- phonon mode and an adiabatic electron-phonon interaction with an unusual temperature dependence.

  2. Thermally Driven Electronic Topological Transition in FeTi

    DOE PAGES

    Yang, F. C.; Muñoz, J. A.; Hellman, O.; ...

    2016-08-08

    In this paper, ab initio molecular dynamics, supported by inelastic neutron scattering and nuclear resonant inelastic x-ray scattering, showed an anomalous thermal softening of the M5- phonon mode in B2-ordered FeTi that could not be explained by phonon-phonon interactions or electron-phonon interactions calculated at low temperatures. A computational investigation showed that the Fermi surface undergoes a novel thermally driven electronic topological transition, in which new features of the Fermi surface arise at elevated temperatures. Finally, the thermally induced electronic topological transition causes an increased electronic screening for the atom displacements in the M5- phonon mode and an adiabatic electron-phonon interactionmore » with an unusual temperature dependence.« less

  3. Synthesis of TiB2-TiC/Fe nano-composite coating by laser surface engineering

    NASA Astrophysics Data System (ADS)

    Du, Baoshuai; Paital, Sameer R.; Dahotre, Narendra B.

    2013-02-01

    The study explores the synthesis of TiB2 and TiC reinforced Fe-based nano-composite coating by laser surface engineering using Ti, B4C and Fe powder mixture as precursor. The effect of laser scanning speed on the size, morphology, and amount of nano-sized ceramic reinforcements were studied at laser fluence of 1111 J/cm2, 1667 J/cm2 and 3333 J/cm2 respectively. A bimodal microstructure with TiC and TiB2 particles dispersed in fine α-Fe matrix was evolved in the laser processed coatings. Besides, the nature of formation of nano-sized ceramic phase was examined. The laser synthesized nano-composite coating yielded 3-5 times increase in microhardness. It appears that the presence of nano-sized TiB2 and TiC particles coupled with the highly refined α-Fe matrix improves the hardness significantly. This coating offers the potential to increase the hardness and toughness simultaneously for developing wear-resistance coatings.

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

    SciTech Connect

    Natesan, K.; Johnson, R.N.

    1995-05-01

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

  5. Knudsen Cell Studies of Ti-Al Thermodynamics

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.; Copland, Evan H.; Mehrotra, Gopal M.; Auping, Judith; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    In this paper we describe the Knudsen cell technique for measurement of thermodynamic activities in alloys. Numerous experimental details must be adhered to in order to obtain useful experimental data. These include introduction of an in-situ standard, precise temperature measurement, elimination of thermal gradients, and precise cell positioning. Our first design is discussed and some sample data on Ti-Al alloys is presented. The second modification and associated improvements are also discussed.

  6. Conditions for CET in a gamma TiAl alloy

    NASA Astrophysics Data System (ADS)

    Mooney, R. P.; Lapin, J.; Klimová, A.; McFadden, S.

    2015-06-01

    The solidification of gamma TiAl alloys is of interest to the aerospace and automotive industries. A gamma TiAl multicomponent alloy: Ti-45.5Al-4.7Nb-0.2C-0.2B (at. %) has been the focus of a study to investigate the solidification conditions that led to a Columnar to Equiaxed Transition (CET) in a directional solidification experiment where traditional Bridgman solidification was combined in series with the power down method. In this paper, a numerical modelling result (a locus plot of columnar growth rate and temperature gradient) from this experiment is superimposed onto CET maps generated using an established analytical model for CET from the literature. A parametric study is carried out over suitable ranges of nucleation undercooling and nuclei density values. The predicted CET positions are compared with the experimentally measured CET position. Reasonable agreement is found at low levels of nuclei density. The paper concludes with estimates for the solidification conditions (nuclei density and nucleation undercooling) that led to the CET.

  7. Oxidation behavior of cubic phases formed by alloying Al3Ti with Cr and Mn

    NASA Technical Reports Server (NTRS)

    Parfitt, L. J.; Nic, J. P.; Mikkola, D. E.; Smialek, J. L.

    1991-01-01

    Gravimetric, SEM, and XRD data are presented which document the significant improvement obtainable in the oxidation resistance of Al3Ti-containing alloys through additions of Cr. The L1(2) Al(67)Cr(8)Ti25 alloy exhibited excellent cyclic oxidation resistance at 1473 K, with the primary oxide formed being the ideally protective alpha-Al2O3. The Al(67)Mn(8)Ti(25) alloy also tested for comparison exhibited poor cyclic oxidation resistance, with substantial occurrence of TiO2 in the protective scales. Catastrophic oxidation was also encountered in the quaternary alloy Al(67)Mn(8)Ti(22)V(3).

  8. Initial Oxidation Behavior in Air of TiAl-2Nb and TiAl-8Nb Alloys Produced by Electron Beam Melting

    NASA Astrophysics Data System (ADS)

    Terner, M.; Biamino, S.; Baudana, G.; Penna, A.; Fino, P.; Pavese, M.; Ugues, D.; Badini, C.

    2015-10-01

    Titanium aluminide alloys are good candidates for structural applications thanks to their low density and good balance of properties up to relatively high temperatures. However, their application is still limited by significant oxidation. Four γ-TiAl alloys with different content of aluminum and niobium were produced by electron beam melting: Ti-45Al-2Cr-2Nb, Ti-48Al-2Cr-2Nb, Ti-45Al-2Cr-8Nb, and Ti-46Al-2Cr-8Nb. The behavior of these alloys in response to oxidation in air during constant heating up to 1000 °C and isothermal oxidation for 10 h at 850 and 950 °C were studied by thermogravimetric analysis. The mass gain due to oxidation of the low Nb-containing alloys was always at least twice that of the high Nb-containing alloys. Both low and high Nb-containing alloys exhibited on their surface oxidation products of the same nature: oxides TiO2 and Al2O3, and nitrides TiN and Ti2AlN. Niobium addition up to 8 at.% did not suppress the growth of rutile and promote the formation of a protective alumina layer. However, it efficiently reduced the formation of rutile, mainly responsible for the mass gain due to oxidation of γ-TiAl alloys and with tendency to spallation.

  9. High temperature properties of equiatomic FeAl with ternary additions

    NASA Technical Reports Server (NTRS)

    Titran, R. H.; Vedula, K. M.; Anderson, G. G.

    1984-01-01

    The aluminide intermetallic compounds are considered potential structural materials for aerospace applications. The B2 binary aluminide FeAl has a melting point in excess of 1500 K, is of simple cubic structure, exits over a wide range of composition with solubility for third elements and is potentially self-protecting in extreme environments. The B2 FeAl compound has been alloyed with 1 to 5 at % ternary additions of Si, Ti, Zr, Hf, Cr, Ni, Co, Nb, Ta, Mo, W, and Re. The alloys were prepared by blending a third elemental powder with prealloyed binary FeAl powder. Consolidation was by hot extrusion at 1250 K. Annealing studies on the extruded rods showed that the third element addition can be classified into three categories based upon the amount of homogenization and the extent of solid solutioning. Constant strain rate compression tests were performed to determine the flow stress as a function of temperature and composition. The mechanical strength behavior was dependent upon the third element homogenization classification.

  10. High temperature properties of equiatomic FeAl with ternary additions

    NASA Technical Reports Server (NTRS)

    Titran, R. H.; Vedula, K. M.; Anderson, G. G.

    1985-01-01

    The aluminide intermetallic compounds are considered potential structural materials for aerospace applications. The B2 binary aluminide FeAl has a melting point in excess of 1500 K, is of simple cubic structure, exists over a wide range of composition with solubility for third elements and is potentially self-protecting in extreme environments. The B2 FeAl compound has been alloyed with 1 to 5 at. pct ternary additions of Si, Ti, Zr, Hf, Cr, Ni, Co, Nb, Ta, Mo, W, and Re. The alloys were prepared by blending a third elemental powder with pre-alloyed binary FeAl powder. Consolidation was by hot extrusion at 1250 K. Annealing studies on the extruded rods showed that the third element addition can be classified into three categories based upon the amount of homogenization and the extent of solid solutioning. Constant strain rate compression tests were performed to determine the flow stress as a function of temperature and composition. The mechanical strength behavior was dependent upon the third element homogenization classification.

  11. Development of ODS FeCrAl for compatibility in fusion and fission energy applications

    SciTech Connect

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

    2014-11-15

    In this paper, oxide dispersion strengthened (ODS) FeCrAl alloys with 12–15% Cr are being evaluated for improved compatibility with Pb-Li for a fusion energy application and with high temperature steam for a more accident-tolerant light water reactor fuel cladding application. A 12% Cr content alloy showed low mass losses in static Pb-Li at 700°C, where a LiAlO2 surface oxide formed and inhibited dissolution into the liquid metal. All the evaluated compositions formed a protective scale in steam at 1200°C, which is not possible with ODS FeCr alloys. However, most of the compositions were not protective at 1400°C, which is a general and somewhat surprising problem with ODS FeCrAl alloys that is still being studied. More work is needed to optimize the alloy composition, microstructure and oxide dispersion, but initial promising tensile and creep results have been obtained with mixed oxide additions, i.e. Y2O3 with ZrO2, HfO2 or TiO2.

  12. Development of ODS FeCrAl for compatibility in fusion and fission energy applications

    DOE PAGES

    Pint, Bruce A.; Dryepondt, Sebastien N.; Unocic, Kinga A.; ...

    2014-11-15

    In this paper, oxide dispersion strengthened (ODS) FeCrAl alloys with 12–15% Cr are being evaluated for improved compatibility with Pb-Li for a fusion energy application and with high temperature steam for a more accident-tolerant light water reactor fuel cladding application. A 12% Cr content alloy showed low mass losses in static Pb-Li at 700°C, where a LiAlO2 surface oxide formed and inhibited dissolution into the liquid metal. All the evaluated compositions formed a protective scale in steam at 1200°C, which is not possible with ODS FeCr alloys. However, most of the compositions were not protective at 1400°C, which is amore » general and somewhat surprising problem with ODS FeCrAl alloys that is still being studied. More work is needed to optimize the alloy composition, microstructure and oxide dispersion, but initial promising tensile and creep results have been obtained with mixed oxide additions, i.e. Y2O3 with ZrO2, HfO2 or TiO2.« less

  13. Effect of neutron irradiation on defect evolution in Ti3SiC2 and Ti2AlC

    DOE PAGES

    Tallman, Darin J.; He, Lingfeng; Garcia-Diaz, Brenda L.; ...

    2015-10-23

    Here, we report on the characterization of defects formed in polycrystalline Ti3SiC2 and Ti2AlC samples exposed to neutron irradiation – up to 0.1 displacements per atom (dpa) at 350 ± 40 °C or 695 ± 25 °C, and up to 0.4 dpa at 350 ± 40 °C. Black spots are observed in both Ti3SiC2 and Ti2AlC after irradiation to both 0.1 and 0.4 dpa at 350 °C. After irradiation to 0.1 dpa at 695 °C, small basal dislocation loops, with a Burgers vector of b = 1/2 [0001] are observed in both materials. At 9 ± 3 and 10 ±more » 5 nm, the loop diameters in the Ti3SiC2 and Ti2AlC samples, respectively, were comparable. At 1 × 1023 loops/m3, the dislocation loop density in Ti2AlC was ≈1.5 orders of magnitude greater than in Ti3SiC2, at 3 x 1021 loops/m3. After irradiation at 350 °C, extensive microcracking was observed in Ti2AlC, but not in Ti3SiC2. The room temperature electrical resistivities increased as a function of neutron dose for all samples tested, and appear to saturate in the case of Ti3SiC2. The MAX phases are unequivocally more neutron radiation tolerant than the impurity phases TiC and Al2O3. Based on these results, Ti3SiC2 appears to be a more promising MAX phase candidate for high temperature nuclear applications than Ti2AlC.« less

  14. Multilayer (TiN, TiAlN) ceramic coatings for nuclear fuel cladding

    NASA Astrophysics Data System (ADS)

    Alat, Ece; Motta, Arthur T.; Comstock, Robert J.; Partezana, Jonna M.; Wolfe, Douglas E.

    2016-09-01

    In an attempt to develop an accident-tolerant fuel (ATF) that can delay the deleterious consequences of loss-of-coolant-accidents (LOCA), multilayer coatings were deposited onto ZIRLO® coupon substrates by cathodic arc physical vapor deposition (CA-PVD). Coatings were composed of alternating TiN (top) and Ti1-xAlxN (2-layer, 4-layer, 8-layer and 16-layer) layers. The minimum TiN top coating thickness and coating architecture were optimized for good corrosion and oxidation resistance. Corrosion tests were performed in static pure water at 360 °C and 18.7 MPa for up to 90 days. The optimized coatings showed no spallation/delamination and had a maximum of 6 mg/dm2 weight gain, which is 6 times smaller than that of a control sample of uncoated ZIRLO® which showed a weight gain of 40.2 mg/dm2. The optimized architecture features a ∼1 μm TiN top layer to prevent boehmite phase formation during corrosion and a TiN/TiAlN 8-layer architecture which provides the best corrosion performance.

  15. Diffusion Bonding of Ti-6Al-4V Sheet with Ti-6Al-4V Foam for Biomedical Implant Applications

    NASA Astrophysics Data System (ADS)

    Hamilton, Brittany; Oppenheimer, Scott; Dunand, David C.; Lewis, Daniel

    2013-12-01

    Advanced metallic bone implants are designed to have a porous surface to improve osseointegration and reduce risks of loosening. An alternative approach to existing surface treatments to create a porous surface is to bond separately produced metallic foams onto the implant. To assess the feasibility of this approach, a Ti-6Al-4V foam was diffusion bonded onto bulk Ti-6Al-4V in an argon atmosphere at temperatures between 1173 K and 1223 K (900 °C and 950 °C) for times between 45 and 75 minutes. These specimens were tested in tension to determine bond quality: failures occurred in the foam, indicating a strong diffusion-bonded interface. The quality of the bond was confirmed by metallographic studies, indicating that this approach, which can also be applied to creating of sandwich with porous cores, is successful.

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

    SciTech Connect

    Howard, R.L.; Ball, A.

    1996-08-01

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

  17. Ferroelectric switching induced magnetic anisotropy in Fe/BaTiO3 bilayers

    NASA Astrophysics Data System (ADS)

    Duan, Chun-Gang; Jaswal, S. S.; Tsymbal, E. Y.

    2007-03-01

    Ferromagnetic/ferroelectric heterostructures have recently attracted significantly interest due to their potential applications in multifunctional electronic devices. We have recently predicted a magnetoelectric effect at the Fe/BaTiO3 interface induced by ferroelectric polarization reversal [1]. In this report, calculations are being carried out on the magnetic anisotropy of Fe/BaTiO3 films. Preliminary results show that the ferroelectric switching of the BaTiO3 has appreciable effect on the magnetic anisotropy of magnetic Fe films. This should be of interest in multiferroic device applications. [1] Chun-gang Duan, S. S. Jaswal, E. Y. Tsymbal, Phys. Rev. Lett. 97, 047201 (2006).

  18. Long-period ordered superstructures that appear in an (Al,Ga)-rich (Al,Ga)Ti system

    NASA Astrophysics Data System (ADS)

    Nakano, Takayoshi; Hagihara, Koji; Hata, Satoshi; Shigyo, Hajime; Nakashima, Hideharu; Umakoshi, Yukichi; Arya, Ashok; Kulkarni, Ulhas D.

    2013-01-01

    Long-period ordered superstructures in an (Al,Ga)-rich (Al,Ga)Ti system composed of (Al,Ga) x Ti100- x (x = 50-65 at. %) were investigated by using melt-spun ribbons, focusing on the ordering process of the superstructural phases. Compositional regions in which h-(Al,Ga)2Ti (Ga2Zr-type), (Al,Ga)5Ti3 and (Al,Ga)3Ti2 with threefold, fourfold and fivefold periodicity, respectively, appeared coherently in the L10 matrix were identified by electron diffraction patterns in two different temperature conditions of as-spun (a relatively high-temperature state) and heat-treatment at 700°C (a relatively low-temperature state). The (Al,Ga)5Ti3 superstructural phase always existed between the compositional region where h-(Al,Ga)2Ti and (Al,Ga)3Ti2 dominantly appear. Therefore, periodical ordering proceeds following the periodicity of the concentration wave of pure (Al,Ga) layers parallel to {310) in the Ti (002) layers from threefold to fivefold periodicity via fourfold periodicity. We found that the (Al,Ga)3Ti2 long-period superstructural phase preferentially appeared with increasing Ga concentration in the melt-spun ribbon annealed at 700°C. In other words, the h-(Al,Ga)2Ti superstructure with threefold periodicity preferentially appeared at the high temperature and a low Ga concentration. Thus, the (Al,Ga)3Ti2-type superstructure was never produced without the addition of Ga in the present study. The long-period ordered superstructures were composed of three pairs of primitive cells, (Al,Ga)Ti2, (Al,Ga)Ti3 and (Al,Ga)Ti4, with periodic atomic arrangements corresponding to lean rhombus, fat rhombus and square, respectively. We discuss the ordering process throughout the (Al,Ga)5 ? superstructure based on the periodic concentration wave and exchange of atoms. The effect of long-period ordered superstructures on hardness is also mentioned.

  19. Finite Element Modelling and Residual Stress Prediction in End Milling of Ti6Al4Valloy

    NASA Astrophysics Data System (ADS)

    Krishnakumar, P.; Sripathi, J.; Vijay, P.; Ramachandran, K. I.

    2016-09-01

    Titanium and its alloys are materials that exhibit unique combination of mechanical and physical properties that enable their usage in various fields. In spite of having a lot of advantages, their usage is limited because they are difficult to machine due to their inherent properties of high specific heat capacity, reactivity with tool and low thermal conductivity thereby causing excessive tool wear. To facilitate the process of machining, it becomes necessary to find out and relieve the residual stress caused during machining. Since experiments cannot be performed for each instance, creation of an FE model is desirable. In this paper a finite element analysis (FEA) of the machining of Ti6Al4V for different cutting speeds is presented. A 3D finite element model is developed with the Titanium alloy (Ti6Al4V) as the workpiece and a four flute carbide tip end mill cutter as the tool to predict the residual stress developed within the titanium alloy after machining. The finite element model utilises the Johnson-Cook model to depict the plasticity and the damage criteria and implements the Arbitrary Lagrangian Eulerian (ALE) formulation to increase the accuracy of the model. The FE model has been developed and the findings are presented. The results indicate that residual stresses are maximum at the surface and decrease linearly along the depth and increase as the cutting speed and depth of cut are increased.

  20. Preparation and characterization of Fe3+-doped TiO2 on fly ash cenospheres for photocatalytic application

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Li, Qin; Wang, Wei; Li, Ying; Zhai, Jianping

    2011-02-01

    Fe3+-doped TiO2 film deposited on fly ash cenosphere (Fe-TiO2/FAC) was successfully synthesized by the sol-gel method. These fresh photocatalysts were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and thermogravimetric analyses (TGA). The XRD results showed that Fe element can maintain metastable anatase phase of TiO2, and effect of temperature showed rutile phase appears in 650 °C for 0.01% Fe-TiO2/FAC. The SEM analysis revealed the Fe-TiO2 films on the surface of a fly ash cenosphere with a thickness of 2 μm. The absorption threshold of Fe-TiO2/FACs shifted to a longer wavelength compared to the photocatalyst without Fe3+-doping in the UV-vis absorption spectra. The photocatalytic activity and kinetics of Fe-TiO2/FAC with varying the iron content and the calcination temperatures were investigated by measuring the photodegradation of methyl blue (MB) during visible light irradiation. Compared with TiO2/FAC and Fe3+-doped TiO2 powder (Fe-TiO2), the degradation ratio using Fe-TiO2/FAC increased by 33% and 30%, respectively, and the best calcined temperature was 450 °C and the optimum doping of Fe/Ti molar ratio was 0.01%. The Fe-TiO2/FAC particles can float in water due to the low density of FAC in favor of phase separation to recover these photocatalyst after the reaction, and the recovery test shows that calcination contributes to regaining photocatalytic activity of Fe-TiO2/FAC photocatalyst.

  1. Distribution of Al{sub 12}Fe{sub 3}Si and (FeAl{sub 6})Si in a HIPed Al-10.71 wt. % Si casting

    SciTech Connect

    Chama, C.C.

    1996-10-01

    An investigation on microstructural development in a hot isostatically pressed (HIPed) Al-10.71 wt. % Si casting is described. The as-cast material contained 0.006 total volume fraction of Al{sub 12}Fe{sub 3}Si and (FeAl{sub 6})Si particles but HIPing at 550 C and 68.95 MPa produced a moderate increase in this fraction, to a maximum value of 0.061 when HIPed for 120 min. Dislocations appeared to be the dominant nucleation sites for the particles in both the as-cast and the HIPed materials.

  2. Compositions and morphologies of TiAlSi intermetallics in different diffusion couples

    SciTech Connect

    Gao, Tong; Liu, Guiliang; Liu, Xiangfa

    2014-09-15

    Two kinds of diffusion couples were designed to investigate the formation of ternary TiAlSi phases in Al–Si–Ti alloys. It was found that different diffusion processes result in various compositions and morphologies of TiAlSi intermetallics. The melted Al, Si and Ti atoms in the diffusion couple leads to the formation of flake-like TiAlSi phase through liquid–liquid reaction. Besides, unidirectional diffusion of Al and Si atoms into blocky TiAl{sub 3} particles or Ti powders via a liquid–solid diffusion process also results in the formation of TiAlSi, while keeping the block-like morphology. This kind of diffusion is a gradual process, driven by the concentration gradient. The reactions in the diffusion couples are helpful to understand the compositional and morphological evolutions of TiAlSi as reported in previous work. - Highlights: • Two diffusion couples were designed to investigate the formation of TiAlSi phases. • Compositions and morphologies of TiAlSi are influenced by the diffusion process. • Liquid–liquid and liquid–solid diffusions were detected. • The corresponding mechanisms were discussed.

  3. Thin-Layer Fe2TiO5 on Hematite for Efficient Solar Water Oxidation.

    PubMed

    Deng, Jiujun; Lv, Xiaoxin; Liu, Jinyin; Zhang, Hui; Nie, Kaiqi; Hong, Caihao; Wang, Jiaou; Sun, Xuhui; Zhong, Jun; Lee, Shuit-Tong

    2015-05-26

    A thin Fe2TiO5 layer was produced on hematite either by evaporating a TiCl4 solution on FeOOH or by a simple HF-assisted Ti treatment of FeOOH, both followed by annealing. The prepared Fe2TiO5-hematite heterostructure showed a significant enhancement in photocurrent density compared to that of the pristine hematite. For example, the sample after HF-assisted Ti treatment exhibited a significantly enhanced photocurrent of 2.0 mA/cm(2) at 1.23 V vs RHE. Moreover, the performance of the Fe2TiO5-hematite heterostructure can be further improved by coupling with Co-Pi catalysts, achieving a higher photocurrent of 2.6 mA/cm(2) at 1.23 V vs RHE. Synchrotron-based soft X-ray absorption spectroscopy analyses clearly revealed the existence of an Fe2TiO5 structure on hematite forming a heterojunction, which reduced the photogenerated hole accumulation and then improved the performance.

  4. Visible-light-induced photoelectrochemical behaviors of Fe-modified TiO2 nanotube arrays.

    PubMed

    Xu, Zhihua; Yu, Jiaguo

    2011-08-01

    Fe-modified TiO(2) nanotube arrays (TiO(2) NTs) were prepared by annealing amorphous TiO(2) NTs whose surface was covered with Fe(3+) by a dip-coating procedure, and characterized by scanning electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy and UV-visible reflectance spectroscopy. The photoelectrochemical properties were evaluated by the photocurrent response and photoelectrocatalytic (PEC) degradation of methylene orange (MO) and 4-chlorophenol in water under visible-light irradiation (λ > 420 nm). The results showed that a Fe-modified TiO(2) NTs electrode exhibited a larger photocurrent response and higher PEC activity for the degradation of organic pollutants than a pure TiO(2) NTs electrode. At a bias potential of 0.4 V, the photocurrent response of a 0.5 M Fe-modified TiO(2) NTs electrode exceeded that of a pure TiO(2) NTs electrode by a factor of about 10, and the PEC degradation rates of MO and 4-chlorophenol on a 0.5 M Fe-modified TiO(2) NTs electrode exceeded those on a pure TiO(2) NTs electrode by a factor of about 2.5. The larger photocurrent response and higher PEC activity of Fe-modified TiO(2) NTs could be attributed to the enhancement of separation of charge-carriers at the external electric field and the extension of the light response range of TiO(2) to the visible-light region with the narrowing of the band gap.

  5. Mechanical and Tribological Properties of Cold-Sprayed Ti Coatings on Ti-6Al-4V Substrates

    NASA Astrophysics Data System (ADS)

    Khun, N. W.; Tan, A. W. Y.; Liu, E.

    2016-04-01

    A cold spray process was used to deposit titanium (Ti) coatings of different thicknesses on commercial Ti-6Al-4V (Ti64) substrates. The hardness of the Ti coatings was measured using a Vickers micro-indenter. It was found that the thicker Ti coatings had higher hardness probably due to the better uniformity and higher density of the coatings. The tribological results showed that the friction and wear of the Ti coatings tested against a steel ball under dry condition became lower with higher thickness probably due to the higher wear resistance of the thicker coatings associated with their higher hardness. The specific wear rates of all the Ti coatings were significantly lower than that of the Ti64 substrate as a result of the higher wear resistance of the Ti coatings associated with their cold-worked microstructures and the formation of high wear resistant oxide layers on their wear tracks during the wear testing.

  6. Water droplet erosion mechanisms of Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Kamkar Zahmatkesh, Niloofar

    Water impingement erosion of materials can be a life-limiting phenomenon for the components in many erosive environments. For example, aircraft body exposed to rain, steam turbine blade, and recently in gas turbine coupled with inlet fogging system. The last is the focus of this study. Inlet fogging system is the most common method used to augment gas turbine output during hot days; high ambient temperature causes strong deterioration of the engine performance. Micro-scaled droplets introduced into the inlet airflow allow the cooling of entering air as well as intercooling the compressor (overspray) and thus optimizes the output power. However, erosion damage of the compressor blades in overspray stage is one of the major concerns associated with the inlet fogging system. The main objective of this research work (CRIAQ MANU419 project) is to understand the erosion induced by water droplets on Titanium alloy to eventually optimize the erosion resistance of the Ti-based compressor blade. Therefore, characterization of the water droplet erosion damage on Ti-6Al-4V receives the major importance. The influence of base material microstructure and impact parameters were considered in erosion evaluation in present study. This work covers the characterization of the erosion damage on Ti-6Al-4V alloy in two parts: - The water droplet erosion damage through a novel experimental approach. The collected data were processed both qualitatively and quantitatively for multi-aspects damage study. - The influence of impact velocity on erosion in an attempt to represent the in-service conditions.

  7. Nanogranular metallic Fe oxygen deficient TiO2-δ composite films: a room temperature, highly carrier polarized magnetic semiconductor

    NASA Astrophysics Data System (ADS)

    Yoon, S. D.; Widom, A.; Miller, K. E.; McHenry, M. E.; Vittoria, C.; Harris, V. G.

    2008-05-01

    Nanogranular metallic iron (Fe) and titanium dioxide (TiO2-δ) were sequentially deposited on (100) lanthanum aluminate (LaAlO3) substrates in a low oxygen chamber pressure using a pulsed laser ablation deposition (PLD) technique. By sequential deposition, ≈10 nm diameter metallic Fe spherical grains were suspended within a TiO2-δ matrix. The films show ferromagnetic behavior with a saturation magnetization of 3100 G at room temperature. Our estimate of the saturation magnetization based on the size and distribution of the Fe spheres agreed with the measured value. The film composite structure was characterized as a p-type magnetic semiconductor at 300 K with a carrier density of the order of ≈1022 cm-3. The hole carriers were excited at the interface between the nanogranular Fe and TiO2-δ matrix, similar to holes excited in the metal/n-type semiconductor interface commonly observed in metal-oxide-semiconductor (MOS) devices. From the large anomalous Hall effect measured in these films, we observed that the holes at the interface were strongly spin polarized. Structure and magnetotransport properties suggested that these PLD films have potential spintronics applications.

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

    NASA Astrophysics Data System (ADS)

    Lalnuntluanga, C.; Mishra, Raj Kumar

    2016-10-01

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

  9. The local structure and ferromagnetism in Fe-implanted SrTiO3 single crystals

    NASA Astrophysics Data System (ADS)

    Lobacheva, O.; Chavarha, M.; Yiu, Y. M.; Sham, T. K.; Goncharova, L. V.

    2014-07-01

    We report a connection between the local structure of low-level Fe impurities and vacancies as the cause of ferromagnetic behavior observed in strontium titanate single crystals (STO), which were implanted with Fe and Si ions at different doses then annealed in oxygen. The effects of Fe doping and post-implantation annealing of STO were studied by X-ray Absorption Near Edge Structure (XANES) spectroscopy and Superconducting Quantum Interference Device magnetometry. XANES spectra for Fe and Ti K- and L-edge reveal the changes in the local environment of Fe and Ti following the implantation and annealing steps. The annealing in oxygen atmosphere partially healed implantation damages and changed the oxidation state of the implanted iron from metallic Fe0 to Fe2+/Fe3+ oxide. The STO single crystals were weak ferromagnets prior to implantation. The maximum saturation moment was obtained after our highest implantation dose of 2 × 1016 Fe atom/cm2, which could be correlated with the metallic Fe0 phases in addition to the presence of O/Ti vacancies. After recrystallization annealing, the ferromagnetic response disappears. Iron oxide phases with Fe2+ and Fe3+ corresponding to this regime were identified and confirmed by calculations using Real Space Multiple Scattering program (FEFF9).

  10. Role of Fe and sign reversal of the Hall coefficient in quasicrystalline Al-Cu-Fe

    NASA Astrophysics Data System (ADS)

    Lindqvist, P.; Berger, C.; Klein, T.; Lanco, P.; Cyrot-Lackmann, F.; Calvayrac, Y.

    1993-07-01

    Electronic transport properties were measured for the stable icosahedral phase of Al-Cu-Fe for a large number of high-structural-quality samples of different compositions. At low temperature, the Hall coefficient RH and the conductivity σ are found to best correlate with the Fe content rather than with the electron per atom parameter which is usually used; RH changes sign at a concentration of 12.5 at. % Fe, where σ is at minimum. RH has a strong temperature dependence and can change sign with temperature. These features put the focus on the Fe d states and can be interpreted by a Hume-Rothery type of behavior including the sp-d hybridization effects.

  11. Effect of Al content on impact resistance behavior of Al-Ti-B4C composite fabricated under air atmosphere.

    PubMed

    Zhao, Qian; Liang, Yunhong; Zhang, Zhihui; Li, Xiujuan; Ren, Luquan

    2016-12-01

    Reaction behavior, mechanical property and impact resistance of TiC-TiB2/Al composite reacted from Al-Ti-B4C system with various Al content via combination method of combustion synthesis and hot pressed sintering under air was investigated. Al content was the key point to the variation of mechanical property and impact resistance. Increasing Al content could increase the density, strength and toughness of the composite. Due to exorbitant ceramic content, 10wt.% and 20wt.% Al-Ti-B4C composites exhibited poor molding ability and machinability. Flexural strength, fracture toughness, compressive strength and impact toughness of 30-50wt.% Al-Ti-B4C composite were higher than those of Al matrix. The intergranular fracture dispersed and defused impact load and restricted crack extension, enhancing the impact resistance of the composite. The composite with 50wt.% Al content owned highest mechanical properties and impact resistance. The results were useful for the application of TiC-TiB2/Al composite in impact resistance field of ceramic reinforced Al matrix composite.

  12. Towards a Superplastic Forming of Fe-Mn-Al Alloys

    SciTech Connect

    Guanabara, Paulo Jr.; Bueno, Levi de O.; Ferreira Batalha, Gilmar

    2011-01-17

    The aim is to study the characteristics of superplasticity, mostly on non qualified materials, such as austenitic steel of the Fe-Mn-Al alloy, which has some of the specific material parameters closely related to microstructural mechanisms. These parameters are used as indicators of material superplastic potentiality. The material was submitted to hot tensile testing, within a temperature range from 600 deg. C to 1000 deg. C and strain-rates varying from 10{sup -6} to 1 s{sup -1}. The strain rate sensitivity parameter (m) and observed maximum elongation until rupture ({epsilon}{sub r}) could be determined and also obtained from the hot tensile test. The experiments stated a possibility of superplastic behaviour in a Fe-Mn-Al alloy within a temperature range from 700 deg. C to 900 deg. C with grain size around 3 {mu}m (ASTM grain size 12) and average strain rate sensitivity of m {approx} 0.54, as well as a maximum elongation at rupture around 600%. The results are based on a more enhanced research from the authors; however, this paper has focused just on the hot tensile test, as further creep tests results are not available herein. There are rare examples of superplasticity study of an austenitic steel Fe-Mn-Al alloy, thus this work showed some possibility of exploring the potential use of such materials in this regime at temperatures {>=}700 deg. C.

  13. Yield stress anomaly in B2 FeAl

    SciTech Connect

    Yoshimi, K.; Hanada, S.; Yoo, M.H.

    1996-12-31

    The studies on yield stress anomaly of B2 FeAl single crystals are reviewed in this paper. A positive temperature dependence of yield stress, so-called yield stress anomaly, is observed in B2 FeAl in which excess vacancies are fully annealed out. Associated with the anomaly, characteristic asymmetry is found between tension and compression. While the strain-rate sensitivity is almost zero in the temperature range of the yield stress anomaly, the stress relaxation becomes significant with increasing temperature, indicating that a recovery process is thermally activated. It is ascertained by the two-surface trace analysis that slip transition from <111> direction at intermediate temperature to <100> at high temperature occurs around the peak temperature. Even at the peak temperature, in addition, operative slip vector for yielding is confirmed to be predominantly <111> by TEM. Also, it is observed that <111>-type superdislocations are frequently climb-dissociated in the temperature range of the anomaly. APB formation on {l_brace}111{r_brace} plane is energetically favorable, which is in agreement with the Flinn`s calculation for the B2 superlattice that APB energy on {l_brace}111{r_brace} plane is lower than that on {l_brace}110{r_brace} plane. Such an anisotropy of APB energy would offer specific driving force for the climb dissociation on <111> superdislocations. On the basis of the observed results, the anomalous strengthening behavior of B2 FeAl single crystals is discussed.

  14. 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.

  15. Microstructure and high-temperature oxidation resistance of TiN/Ti3Al intermetallic matrix composite coatings on Ti6Al4V alloy surface by laser cladding

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaowei; Liu, Hongxi; Wang, Chuanqi; Zeng, Weihua; Jiang, Yehua

    2010-11-01

    A high-temperature oxidation resistant TiN embedded in Ti3Al intermetallic matrix composite coating was fabricated on titanium alloy Ti6Al4V surface by 6kW transverse-flow CO2 laser apparatus. The composition, morphology and microstructure of the laser clad TiN/Ti3Al intermetallic matrix composite coating were characterized by optical microscopy (OM), scanning electron microscopy (SEM), X-ray diffraction (XRD) and energy dispersive spectrometer (EDS). In order to evaluate the high-temperature oxidation resistance of the composite coatings and the titanium alloy substrate, isothermal oxidation test was performed in a conventional high-temperature resistance furnace at 600°C and 800°C respectively. The result shows that the laser clad intermetallic composite coating has a rapidly solidified fine microstructure consisting of TiN primary phase (granular-like, flake-like, and dendrites), and uniformly distributed in the Ti3Al matrix. It indicates that a physical and chemical reaction between the Ti powder and AlN powder occurred completely under the laser irradiation. In addition, the microhardness of the TiN/Ti3Al intermetallic matrix composite coating is 844HV0.2, 3.4 times higher than that of the titanium alloy substrate. The high-temperature oxidation resistance test reveals that TiN/Ti3Al intermetallic matrix composite coating results in the better modification of high-temperature oxidation behavior than the titanium substrate. The excellent high-temperature oxidation resistance of the laser cladding layer is attributed to the formation of the reinforced phase TiN and Al2O3, TiO2 hybrid oxide. Therefore, the laser cladding TiN/Ti3Al intermetallic matrix composite coating is anticipated to be a promising oxidation resistance surface modification technique for Ti6Al4V alloy.

  16. Phase stability of U-Mo-Ti alloys and interdiffusion behaviors of U-Mo-Ti/Al-Si

    SciTech Connect

    Park, Jong Man; Ryu, Ho Jin; Park, Jae Soon; Oh, Seok Jin; Kim, Chang Kyu; Kim, Yeon Soo; Hofman, Gerard L.

    2008-07-15

    As a remedy for reducing reaction between U-Mo and Al in U-Mo/Al dispersion fuel, adding an alloying element such as Zr and Ti in U-Mo has been proposed at ANL. Although ANL's work showed the potential effectiveness of these elements based on thermodynamic and metallurgical analyses, the effect of a Ti addition in U-Mo remains unproven. The out-of-pile tests of U-Mo-Ti alloys, which focused on phase stability and interdiffusion behavior against Al, are meaningful to predict their efficacy during an irradiation. At the 2006 RERTR conference, we presented our work on the interdiffusion behaviors of U-Mo-Zr/Al-Si. In this paper, we will present the results for substituting U-Mo-Zr with U-Mo-Ti. Unlike U-Mo-Zr alloys, the gamma-heat-treated U-7Mo-xTi (x=1{approx}3 wt%) exhibited a metastable {gamma}-U phase, regardless of the Ti content. In these samples, however, a small amount of second-phase precipitates with a high Ti concentration was observed. The gamma phase stability of the U-Mo-Ti alloys at 500 deg C was similar to that of the U-Mo-Zr alloys. Interdiffusion test results between U-Mo-Ti alloys and Al-Si alloys will also be presented and a comparison with the previous results with U- Mo-Zr/Al-Si will also be included. (author)

  17. Analysis of structure and bonding strength of AlTiN coatings by cathodic ion plating

    NASA Astrophysics Data System (ADS)

    Dejun, Kong; Haoyuan, Guo

    2015-04-01

    AlTiN coating was prepared on the surface of YT14 hard alloy cutter by cathodic arc ion plating, and the surface-interface morphologies, line scans of the interface elements and valence state of chemical elements were analyzed with field emission scanning electron microscopy, energy dispersive spectrometer and X-ray photoelectron spectroscopy, respectively, and bonding strength of the coating was measured with scratching tester. The results show that the elements of Al and N mainly exist in the AlTiN coating with an AlN and AlTiN hard phase, and (the) Ti element mainly exists in the coating with a TiN hard phase, which improve wear resistance of AlTiN coating. The elements of Al, Ti and N are diffused at the coating interface, in which part of Ti atoms are replaced by Al atoms at the TiN lattice, still keep face-centered cubic structure of TiN coating to form metallurgical bonding, and bonding strength of the coating interface measured by scratching tester is 78.75 N, which is beneficial to improving service life of AlTiN coating prepared on the surface of carbide tool cutter.

  18. Electrochemical characterization of MC3T3-E1 cells cultured on γTiAl and Ti-6Al-4V alloys.

    PubMed

    Bueno-Vera, J A; Torres-Zapata, I; Sundaram, P A; Diffoot-Carlo, N; Vega-Olivencia, C A

    2015-12-01

    Electrochemical impedance spectroscopy (EIS) was used to study the behavior of MC3T3-E1 cells cultured in an αMEM+FBS solution on two Ti-based alloys (Ti-6Al-4V and γTiAl) for 4, 7 and 14 days. EIS measurements were carried out at an open-circuit potential in a 1 mHz to 100 kHz frequency range. Results indicate a general increase in impedance on the Ti alloy surfaces with cells as a function of time. Bode plots indicate changes corresponding to the passive oxide film, adsorption of proteins and cell tissue on surfaces with the passage of time. Normal cellular activity based on the polygonal morphology, with long and fine cytoplasmic prolongations of the cells on Ti-6Al-4V and γTiAl was observed from SEM images. Similarly, mineralization nodules corresponding to cell differentiation associated with the osseogenetic process were observed confirmed by Alizarin Red S staining. Immunofluorescence analysis to detect the presence of collagen Type I showed an increase in the segregation of collagen as a function of time. The impedance values obtained from EIS testing are indicative of the corrosion protection offered to the Ti alloy substrates by the cell layer. This study shows that γTiAl has better corrosion resistance than that of Ti-6Al-4V in the αMEM+FBS environment in the presence of MC3T3-E1 cells.

  19. ELECTROCHEMICAL CHARACTERIZATION OF MC3T3-E1 CELLS CULTURED ON γTiAl AND Ti-6Al-4V ALLOYS

    PubMed Central

    Bueno-Vera, J.A.; Torres-Zapata, I.; Sundaram, P.A.; Diffoot-Carlo, N.; Vega, C.A.

    2015-01-01

    Electrochemical Impedance Spectroscopy (EIS) was used to study the behavior of MC3T3-E1cells cultured in αMEM+FBS solution on two Ti-based alloys (Ti-6Al-4V and γTiAl) during 4, 7 and 14 days. EIS measurements were carried out at the open-circuit potential in the 1 mHz to 100 kHz frequency range. Results indicate a general increase in impedance on the Ti alloy surfaces with cells as a function of time. Bode plots indicate changes corresponding to the passive oxide film, adsorption of proteins and cell tissue on surfaces with the passage of time. Normal cellular activity based on the polygonal morphology, with long and fine cytoplasmic prolongations of the cells on Ti-6Al-4V and γTiAl was observed from SEM images. Similarly, mineralization nodules corresponding to cell differentiation associated with the osseogenetic process were observed confirmed by Alizarin Red S staining. Immunofluorescence analysis to detect the presence of collagen Type I showed an increase in the segregation of collagen as a function of time. The impedance values obtained from EIS testing are indicative of the corrosion protection offered to the Ti alloy substrates by the cell layer. This study shows that γTiAl has better corrosion resistance than Ti-6Al-4V in the αMEM+FBS environment in the presence of MC3T3-E1 cells. PMID:26145813

  20. Effect of conditions of pulsed electron-beam melting for Al (film)/Ti (substrate) systems on phase formation and properties of Ti-Al surface alloys

    NASA Astrophysics Data System (ADS)

    Rotshtein, V. P.; Kolubaeva, Yu. A.; Mei, X.; Markov, A. B.; Naiden, E. P.; Oskomov, K. V.; Pryadko, E. L.; Teresov, A. D.; Shulepov, I. A.; Shulov, V. A.

    2012-09-01

    Findings of comparative investigations are presented for phase formation, characteristics of hardening, tribological properties, and oxidation resistance of Ti-Al intermetallic surface alloys formed by multiple alternation of deposition of an Al film (0.1-1 μm) on a Ti substrate and pulsed liquid-phase mixing of Al and Ti by intense low-energy (˜15 keV) electron beams with microsecond (˜3 μs) and submillisecond (100 μs) duration. It is found that microsecond synthesis is effective for formation of γ(TiAl) oxidation-resistant surface alloys. In turn, submillisecond synthesis allows one to form Ti3Al surface alloys with enhanced wear resistance.

  1. Method of directly crystallizing a (Sm + Ti):Fe = 1:5 compound

    NASA Astrophysics Data System (ADS)

    Cadieu, F. J.

    1984-04-01

    The general object of this invention is to provide a method of directly crystallizing samples of the Sm-Fe system onto a substrate. A more particular object of the invention is to provide such a method of synthesizing a metastable phase at a composition corresponding to a (Sm + Ti) to Fe atomic ratio of 1:5. Metastable in this context means that the phase formed at a 1:5 atomic ratio is not present in the pure Sm-Fe system. It has now been found that the aforementioned objectives can be attained by synthesizing by selectively thermalizing sputtering onto heated substrates with the addition of Ti as a stabilizing agent. Room temperature intrinsic coercive forces of 6.2 kOe and static energy products of 5.5 MG-Oe have been obtained in this Ti stabilized (Sm + Ti):Fe 1:5 compound.

  2. Fabrication of TiN/AlN/TiN tunnel junctions

    NASA Astrophysics Data System (ADS)

    Nakayama, Takeru; Naruse, Masato; Myoren, Hiroaki; Taino, Tohru

    2016-11-01

    We have fabricated TiN/AlN/TiN tunnel junctions with an epitaxial layer. The critical temperature of TiN can be changed in the range from 0.5 to 5.0 K. Therefore, it is easy to set 5.0 K as the target critical temperature. When a Superconducting Tunnel Junction (STJ) is operated as a photon detector, it is necessary to cool it to within 0.1 K of the critical temperature in consideration of the noise of the thermally stimulated currents. Because 0.3 K was desirable, as for the manufacture of general purpose photon detectors, the critical temperature 5.0 K. TiN and AlN films were deposited by dc and rf magnetron sputtering in a load-lock sputtering system at ambient substrate temperatures. The junctions have a gap voltage of Vg = 1.1 mV, and critical current density of Jc = 0.24 A/cm2, and Rsg/Rn of 7.2, and low subgap leakage current (Isub@ 500 μV = 180 nA). We report our experiment system, the manufacture method and the junction properties in this paper.

  3. Fracture analysis of cast pure Ti and Ti-6Al-4V alloy for dental use.

    PubMed

    Kim, K H; Choi, M Y; Kishi, T

    1997-01-01

    The fracture behavior of cast two types of pure Ti and Ti-6Al-4V alloy was understood by acoustic emission (AE) analysis during a fracture toughness test. Specimens for test were cast by the lost wax method using a specially designed Ti casting machine of pressure-different method for dental use. A fatigue crack was inserted from the machined notch tip into the body of a specimen in the range of 0.45-0.55 a/W. Acoustic emission signals released during the fracture toughness test were detected by two sensors attached to both ends of the specimen. Then the signals were recorded and analysed by the PAC 3000/3104 system. From the early stage of the fracture toughness test, AE signals started to be released in all types of specimens tested. A reaction layer with the investment materials of about 50-100 microns was thought to be the result of the AE release from an early stage of the fracture toughness test. A microfracture behavior of the cast pure Ti and Ti alloys was proposed based on the results obtained from the AE releasing pattern and fracture surface findings.

  4. Physical properties modulation of Fe3O4/Pb(ZrTi)O3 heterostructure via Fe diffusion

    NASA Astrophysics Data System (ADS)

    Chichvarina, O.; Herng, T. S.; Ding, J.

    2016-03-01

    The manipulation of material properties in perovskite oxide heterojunctions has been increasingly studied, owing to their interacting lattice, charge, spin and orbital degrees of freedom. In this work, the switching, ferroelectricity and magneto-transport properties of epitaxially grown perovskite Pb(Zr0.52Ti0.48)O3 layers sandwiched between Fe3O4 (top electrode) and SrRuO3 (bottom electrode) are investigated. These films show a typical ferroelectric polarization of ˜50 μC/cm2. Once the Pb(Zr0.52Ti0.48)O3 films become thinner (˜30 nm), one can set (reset) the Fe3O4/Pb(Zr0.52Ti0.48)O3/SrRuO3 structures into a low (high) resistance state via formation (rupture) of an Fe-related filament in Pb(Zr0.52Ti0.48)O3 through manipulation of an electric field. Interestingly, at the low-resistance state, a prominent magnetoresistance signal of ˜3% was observed. There is no magnetoresistance signal detected in the virgin Pb(Zr0.52Ti0.48)O3 film (before switching), high-resistive state Pb(Zr0.52Ti0.48)O3 film and Au/Pb(Zr0.52Ti0.48)O3/SrRuO3. These phenomena are attributed to the diffusion of Fe-related ions into the Pb(Zr0.52Ti0.48)O3 film, turning a non-magnetic and insulating layer of perovskite Pb(Zr0.52Ti0.48)O3 into a magnetic and semiconducting-like Pb(Zr0.52Ti0.48)O3. The magneto-transport properties of Fe3O4/Pb(Zr0.52Ti0.48)O3/SrRuO3 have been studied extensively. Such resistance-ferroelectric-ferromagnetic coupling in a single compound paves the way to the realization of a non-volatile multiple-state Pb(ZrTi)O3 hybrid memory, as well as new computing approaches.

  5. Growth and Stress-induced Transformation of Zinc blende AlN Layers in Al-AlN-TiN Multilayers

    PubMed Central

    Li, Nan; Yadav, Satyesh K.; Wang, Jian; Liu, Xiang-Yang; Misra, Amit

    2015-01-01

    AlN nanolayers in sputter deposited {111}Al/AlN/TiN multilayers exhibit the metastable zinc-blende-structure (z-AlN). Based on density function theory calculations, the growth of the z-AlN is ascribed to the kinetically and energetically favored nitridation of the deposited aluminium layer. In situ nanoindentation of the as-deposited {111}Al/AlN/TiN multilayers in a high-resolution transmission electron microscope revealed the z-AlN to wurzite AlN phase transformation through collective glide of Shockley partial dislocations on every two {111} planes of the z-AlN. PMID:26681109

  6. Growth and stress-induced transformation of zinc blende AlN layers in Al-AlN-TiN multilayers

    DOE PAGES

    Li, Nan; Yadav, Satyesh K.; Wang, Jian; ...

    2015-12-18

    We report that AlN nanolayers in sputter deposited {111}Al/AlN/TiN multilayers exhibit the metastable zinc-blende-structure (z-AlN). Based on density function theory calculations, the growth of the z-AlN is ascribed to the kinetically and energetically favored nitridation of the deposited aluminium layer. In situ nanoindentation of the as-deposited {111}Al/AlN/TiN multilayers in a high-resolution transmission electron microscope revealed the z-AlN to wurzite AlN phase transformation through collective glide of Shockley partial dislocations on every two {111} planes of the z-AlN.

  7. Modified lattice parameter/Curie temperature diagrams for Titanomagnetite/titanomaghemite within the quadrilateral Fe3O4- Fe2TiO4-Fe2O3-Fe2TiO5

    NASA Astrophysics Data System (ADS)

    Xu, Weixin; Peacor, Donald R.; Van der Voo, Rob; Dollase, Wayne; Beaubouef, Rick

    Magnetic and mineralogical data were obtained on a sequence of titanomagnetite-titanomaghemite solid solutions from four basalt samples (0 to 70 Ma) dredged from four sites along a traverse normal to the mid-Atlantic Ridge. Data which characterized magnetic iron oxides with the spinel structure include Mössbauer, XRD (including Rietveld structure refinement), TEM/AEM, and magnetic data. The data indicate a sequence ranging from nearly unoxidized titanomagnetite to near end-member titanomaghemite. Compositions of samples with intermediate values of oxidation parameter, Z, varied significantly from those estimated using previously determined relations between lattice parameters and compositions. The data of this study, in conjunction with those of selected references, lead to more accurate contoured diagrams for Curie temperature and lattice parameter (as consistent with Vegard's law) for the quadrilateral Fe3O4-Fe2TiO4-Fe2O3-Fe2TiO5.

  8. Synergistic effects of F and Fe in co-doped TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhang, Yufei; Shen, Huiyuan; Liu, Yanhua

    2016-03-01

    TiO2 photocatalysts co-doped with F and Fe were synthesized by a sol-gel method. Synergistic effects of F and Fe in the co-doped TiO2 were verified by NH3 decomposition, X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS) and ultraviolet-visible (UV-Vis) absorption spectroscopy, and was analyzed by the simulation based on the density functional theory (DFT). The results from NH3 decomposition confirmed that the cooperation of F and Fe broadened the optical response of TiO2 to visible light region and also enhanced the photocatalytic activity of TiO2 under ultraviolet light. XRD patterns, SEM and HRTEM images showed that the co-doped samples were nanometric anatase with an average particle size of 25 nm. Co-doping with F and Fe inhibited the grain growth of TiO2 from anatase to rutile and resulted in a larger lattice defect. XPS analysis exhibited that the doped F and Fe atoms were into the TiO2 lattice. UV-Vis absorption spectra showed that its optical absorption edge was moved up to approximately 617 nm and its ultraviolet absorption was also enhanced. The DFT results indicated that the cooperation of Fe 3d and O 2p orbits narrowed the band gap of TiO2 and F 2p orbit widened the upper valence bands. The synergistic electron density around F and Fe in co-doped TiO2 was capable to enhance the photo-chemical stability of TiO2.

  9. Evolution of Fe Bearing Intermetallics During DC Casting and Homogenization of an Al-Mg-Si Al Alloy

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Grant, P. S.; O'Reilly, K. A. Q.

    2016-06-01

    The evolution of iron (Fe) bearing intermetallics (Fe-IMCs) during direct chill casting and homogenization of a grain-refined 6063 aluminum-magnesium-silicon (Al-Mg-Si) alloy has been studied. The as-cast and homogenized microstructure contained Fe-IMCs at the grain boundaries and within Al grains. The primary α-Al grain size, α-Al dendritic arm spacing, IMC particle size, and IMC three-dimensional (3D) inter-connectivity increased from the edge to the center of the as-cast billet; both α c-AlFeSi and β-AlFeSi Fe-IMCs were identified, and overall α c-AlFeSi was predominant. For the first time in industrial billets, the different Fe-rich IMCs have been characterized into types based on their 3D chemistry and morphology. Additionally, the role of β-AlFeSi in nucleating Mg2Si particles has been identified. After homogenization, α c-AlFeSi predominated across the entire billet cross section, with marked changes in the 3D morphology and strong reductions in inter-connectivity, both supporting a recovery in alloy ductility.

  10. 57Fe Mössbauer spectroscopy and magnetization of cation deficient Fe2TiO4 and FeCr2O4. Part II: Magnetization data

    NASA Astrophysics Data System (ADS)

    Schmidbauer, E.

    1987-12-01

    Magnetic properties are reported for synthetic cation deficient Fe2TiO4 and FeCr2O4 particles (<1 μm). Cation deficiency, achieved by oxidation, is characterized by the oxidation parameter z which represents the fraction of Fe2+ ions converted to Fe3+ in the spinel lattice (0≤ z≤1). Fe2TiO4 ( z=0.85) has a Curie temperature T c that can only approximately be given with a value in the range 400 700 K and it has a magnetic moment per formula unit M≈0.50 μB (μB=Bohr's magneton) at 4.2 K, for FeCr2O4 it is T c≥520 K and M (4.2 K) ≈0.16 μB. Magnetic hysteresis parameters at various temperatures show in part characteristic features due to relaxation phenomena. In the Ti-spinel, the latter are caused by a superposition of superparamagnetism and spin relaxation and in the Cr-spinel by superparamagnetism, in agreement with Mössbauer data (part I of this paper). The cation and vacancy distribution and magnetic coupling are discussed in both compositions with respect to magnetic moment data considering magnetic dilution by incorporated vacancies, and in the Ti-spinel also by non magnetic Ti4+.

  11. Microstructure and Wear Resistance of Composite Coating by Laser Cladding Al/TiN on the Ti-6Al-4V Substrate

    NASA Astrophysics Data System (ADS)

    Zhang, H. X.; Yu, H. J.; Chen, C. Z.

    2015-05-01

    The composite coatings were fabricated by laser cladding Al/TiN pre-placed powders on Ti-6Al-4V substrate for enhancing wear resistance and hardness of the substrate. The composite coatings were analyzed by means of X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectrometer (EDS). The sliding wear tests were performed by MM200 wear test machine. The hardness of the coatings was tested by HV-1000 hardness tester. After laser cladding, it was found that there was a good metallurgical bond between the coating and the substrate. The composite coatings were mainly composed of the matrix of β-Ti (Al) and the reinforcements of titanium nitride (TiN), Ti3Al, TiAl and Al3Ti. The hardness and wear resistance of the coatings on four samples were greatly improved, among which sample 4 exhibited the highest hardness and best wear resistance. The hardness of the coating on sample 4 was approximately 2.5 times of the Ti-6Al-4V substrate. And the wear resistance of sample 4 was four times of the substrate.

  12. Controllable two-scale network architecture and enhanced mechanical properties of (Ti5Si3+TiBw)/Ti6Al4V composites

    PubMed Central

    Jiao, Y.; Huang, L. J.; Duan, T. B.; Wei, S. L.; Kaveendran, B.; Geng, L.

    2016-01-01

    Novel Ti6Al4V alloy matrix composites with a controllable two-scale network architecture were successfully fabricated by reaction hot pressing (RHP). TiB whiskers (TiBw) were in-situ synthesized around the Ti6Al4V matrix particles, and formed the first-scale network structure (FSNS). Ti5Si3 needles (Ti5Si3) precipitated in the β phase around the equiaxed α phase, and formed the secondary-scale network structure (SSNS). This resulted in increased deformation compatibility accompanied with enhanced mechanical properties. Apart from the reinforcement distribution and the volume fraction, the ratio between Ti5Si3 and TiBw fraction were controlled. The prepared (Ti5Si3 + TiBw)/Ti6Al4V composites showed higher tensile strength and ductility than the composites with a one-scale microstructure, and superior wear resistance over the Ti6Al4V alloy under dry sliding wear conditions at room temperature. PMID:27622992

  13. Spall fracture in additive manufactured Ti-6Al-4V

    NASA Astrophysics Data System (ADS)

    Jones, D. R.; Fensin, S. J.; Dippo, O.; Beal, R. A.; Livescu, V.; Martinez, D. T.; Trujillo, C. P.; Florando, J. N.; Kumar, M.; Gray, G. T.

    2016-10-01

    We present a study on the spall strength of additive manufactured (AM) Ti-6Al-4V. Samples were obtained from two pieces of selective laser melted (SLM, a powder bed fusion technique) Ti-6Al-4V such that the response to dynamic tensile loading could be investigated as a function of the orientation between the build layers and the loading direction. A sample of wrought bar-stock Ti-6Al-4V was also tested to act as a baseline representing the traditionally manufactured material response. A single-stage light gas-gun was used to launch a thin flyer plate into the samples, generating a region of intense tensile stress on a plane normal to the impact direction. The rear free surface velocity time history of each sample was recorded with laser-based velocimetry to allow the spall strength to be calculated. The samples were also soft recovered to enable post-mortem characterization of the spall damage evolution. Results showed that when the tensile load was applied normal to the interfaces between the build layers caused by the SLM fabrication process the spall strength was drastically reduced, dropping to 60% of that of the wrought material. However, when loaded parallel to the AM build layer interfaces the spall strength was found to remain at 95% of the wrought control, suggesting that when loading normal to the AM layer interfaces, void nucleation is facilitated more readily due to weaknesses along these boundaries. Quasi-static testing of the same sample orientations revealed a much lower degree of anisotropy, demonstrating the importance of rate-dependent studies for damage evolution in AM materials.

  14. Spall fracture in additive manufactured Ti-6Al-4V

    DOE PAGES

    Jones, David Robert; Fensin, Saryu Jindal; Dippo, Olivia; ...

    2016-10-07

    Here, we present a study on the spall strength of additive manufactured (AM) Ti-6Al-4V. Samples were obtained from two pieces of selective laser melted (SLM, a powder bed fusion technique) Ti-6Al-4V such that the response to dynamic tensile loading could be investigated as a function of the orientation between the build layers and the loading direction. A sample of wrought bar-stock Ti-6Al-4V was also tested to act as a baseline representing the traditionally manufactured material response. A single-stage light gas-gun was used to launch a thin flyer plate into the samples, generating a region of intense tensile stress on amore » plane normal to the impact direction. The rear free surface velocity time history of each sample was recorded with laser-based velocimetry to allow the spall strength to be calculated. The samples were also soft recovered to enable post-mortem characterization of the spall damage evolution. Results showed that when the tensile load was applied normal to the interfaces between the build layers caused by the SLM fabrication process the spall strength was drastically reduced, dropping to 60% of that of the wrought material. However, when loaded parallel to the AM build layer interfaces the spall strength was found to remain at 95% of the wrought control, suggesting that when loading normal to the AM layer interfaces, void nucleation is facilitated more readily due to weaknesses along these boundaries. Quasi-static testing of the same sample orientations revealed a much lower degree of anisotropy, demonstrating the importance of rate-dependent studies for damage evolution in AM materials.« less

  15. Spall fracture in additive manufactured Ti-6Al-4V

    SciTech Connect

    Jones, David Robert; Fensin, Saryu Jindal; Dippo, Olivia; Beal, Roberta Ann; Livescu, Verpnica; Martinez, Daniel Tito; Trujillo, Carl Patrick; Florando, J. N.; Kumar, M.; Gray, III, George Thompson

    2016-10-07

    Here, we present a study on the spall strength of additive manufactured (AM) Ti-6Al-4V. Samples were obtained from two pieces of selective laser melted (SLM, a powder bed fusion technique) Ti-6Al-4V such that the response to dynamic tensile loading could be investigated as a function of the orientation between the build layers and the loading direction. A sample of wrought bar-stock Ti-6Al-4V was also tested to act as a baseline representing the traditionally manufactured material response. A single-stage light gas-gun was used to launch a thin flyer plate into the samples, generating a region of intense tensile stress on a plane normal to the impact direction. The rear free surface velocity time history of each sample was recorded with laser-based velocimetry to allow the spall strength to be calculated. The samples were also soft recovered to enable post-mortem characterization of the spall damage evolution. Results showed that when the tensile load was applied normal to the interfaces between the build layers caused by the SLM fabrication process the spall strength was drastically reduced, dropping to 60% of that of the wrought material. However, when loaded parallel to the AM build layer interfaces the spall strength was found to remain at 95% of the wrought control, suggesting that when loading normal to the AM layer interfaces, void nucleation is facilitated more readily due to weaknesses along these boundaries. Quasi-static testing of the same sample orientations revealed a much lower degree of anisotropy, demonstrating the importance of rate-dependent studies for damage evolution in AM materials.

  16. Half-metallic properties of the new Ti2YPb(Y = Co, Fe) Heusler alloys

    NASA Astrophysics Data System (ADS)

    Hussain, Moaid K.; Gao, G. Y.; Yao, Kai-Lun

    2015-09-01

    The half-metallic properties of Ti2YPb(Y = Co, Fe) Heusler alloys with a CuHg2Ti-type structure were examined within the frame of the density functional theory and the Perdew-Burke-Ernzerh of generalized gradient approximation (GGA). Analysis of the electronic band structures and density of states for Ti2YPb(Y = Co, Fe) revealed that the spin-up bands are metallic, whereas the spin-down bands exhibit gaps of 0.73 and 0.70 eV, respectively. The magnetic moments calculated for the Ti2YPb(Y = Co, Fe) alloys were found to be equal to 3 μB/f.u. and 2 μB/f.u., values which both follows the Slater-Pauling rule of Mt = Zt - 18. The compounds’ negative enthalpy values should encourage their experimental realization in the future. The bandgap was elucidated to be mainly determined by the bonding and antibonding states created from the hybridizations of the d states between the Ti(1)-Ti(2) coupling and the Y = Co, Fe atom. The half-metallic properties of the Ti2YPb(Y = Co, Fe) compounds were found to be insensitive to lattice distortion, with full spin polarization achievable within a large range of lattice parameter values, making the alloys suitable for use in practical applications.

  17. Elevated Temperature Deformation of Fe-39.8Al and Fe-15.6Mn-39.4Al

    NASA Technical Reports Server (NTRS)

    Whittenberger, J. Daniel

    2004-01-01

    The elevated temperature compressive properties of binary Fe-39.8 at % Al and Fe-15.6Mn-39.4Al have been measured between 1000 and 1300 K at strain rates between 10(exp 7) and 10(exp 3)/ s. Although the Mn addition to iron aluminide did not change the basic deformation characteristics, the Mn-modified alloy was slightly weaker. In the regime where deformation of FeAl occurs by a high stress exponent mechanism (n = 6), strength increases as the grain size decreases at least for diameters between approx. 200 and approx. 10 microns. Due to the limitation in the grain size-flow stress-temperature-strain rate database, the influence of further reductions of the grain size on strength is uncertain. Based on the appearance of subgrains in deformed iron aluminide, the comparison of grain diameters to expected subgrain sizes, and the grain size exponent and stress exponent calculated from deformation experiments, it is believed that grain size strengthening is the result of an artificial limitation on subgrain size as proposed by Sherby, Klundt and Miller.

  18. Effect of laser power on the microstructure and mechanical properties of TiN/Ti3Al composite coatings on Ti6Al4V

    NASA Astrophysics Data System (ADS)

    Liu, Zhengdao; Zhang, Xiancheng; Xuan, Fuzhen; Wang, Zhengdong; Tu, Shandong

    2013-07-01

    Laser nitriding is one of the effective techniques to improve the surface properties of titanium alloys and has potential application in the life extension of last-stage steam turbine blades. However, cracking of surface coating is a common problem due to heat concentration in laser nitriding process. Conventionally, the cracks can be avoided through heat treatment, which may have an important influence on the mechanical properties of coating. Crack-free TiN/Ti3Al IMC coatings on Ti6Al4V are prepared by plasma spraying and laser nitriding. The microstructures, phase constitutes and compositions of the coating are observed and analyzed with scanning electron microscopy(SEM), X-ray diffraction(XRD) and X-ray energy-dispersive spectroscopy(EDS). Microhardness, elastic modulus, fracture toughness of the coating are measured. The results show that the crack- and pore-free IMC coatings can be made through the proposed method; with increasing laser power, the amount and density of TiN phase in the coating first increased and then decreased, leading to the similar trend of microhardness and elastic modulus and the reverse trend of fracture toughness of the coating. Both the average microhardness and elastic modulus of the coating increase three times higher than those of the substrate. The volume fraction of the TiN reinforced phase in composite can be controlled by varying the laser power and the cracking problem in laser nitriding process is successfully solved.

  19. Wear Behavior of Low-Cost, Lightweight TiC/Ti-6Al-4V Composite Under Fretting: Effectiveness of Solid-Film Lubricant Counterparts

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Street, Kenneth W., Jr.; Sanders, Jeffrey H.; Hager, Carl H., Jr.; Zabinski, Jeffrey S.; VanderWal, Randall L.; Andrews, Rodney; Lerch, Bradley A.

    2007-01-01

    The wear behavior of low-cost, lightweight 10-wt% TiC-particulate-reinforced Ti-6Al-4V matrix composite (TiC/Ti- 6Al-4V) was examined under fretting at 296, 423, and 523 K in air. Bare 10-wt% TiC/Ti-6Al-4V hemispherical pins were used in contact with dispersed multiwalled carbon nanotubes (MWNTs), magnetron-sputtered diamondlike carbon/chromium (DLC/Cr), magnetron-sputtered graphite-like carbon/chromium (GLC/Cr), and magnetron-sputtered molybdenum disulphide/titanium (MoS2/Ti) deposited on Ti-6Al-4V, Ti-48Al-2Cr-2Nb, and nickel-based superalloy 718. When TiC/Ti-6Al-4V was brought into contact with bare Ti-6Al-4V, bare Ti-48Al-2Cr-2Nb, and bare nickel-based superalloy 718, strong adhesion, severe galling, and severe wear occurred. However, when TiC/Ti-6Al-4V was brought into contact with MWNT, DLC/Cr, GLC/Cr, and MoS2/Ti coatings, no galling occurred in the contact, and relatively minor wear was observed regardless of the coating. All the solid-film lubricants were effective from 296 to 523 K, but the effectiveness of the MWNT, DLC/Cr, GLC/Cr, and MoS2/Ti coatings decreased as temperature increased.

  20. Electronic structure and magnetic properties of the Fe16N2 doped with Ti

    NASA Astrophysics Data System (ADS)

    Benea, D.; Isnard, O.; Pop, V.

    2016-12-01

    Detailed theoretical investigations on the electronic and magnetic properties of the α″-Fe16N2 phase doped with Ti have been performed. The investigations done using the Korringa-Kohn-Rostoker (KKR) band structure method are based on the Local Spin Density (LSDA) and LSDA + U approximations, whilst the disorder in the systems has been accounted for by means of the Coherent Potential Approximation (CPA). We found that the Ti atoms substitute with preference on Fe crystal sites with N atoms as nearest neighbors (8 h) . In the spin resolved density of states (DOS) the covalent nature of the interatomic bands and the N-2p and Fe/Ti-3d hybridization can be observed. The change in the local environment by Ti substitution is evidenced in the distribution of local magnetic moments and hyperfine magnetic fields. The total magnetic moment of the α″-(Fe1-xTix) 16N2 compound increases by doping, due to the magneto-volume effect. The same increase is observed for the Fe magnetic moments on different crystal sites. The increase of the total magnetic moment by Ti doping cannot outpace the volume increase and, as consequence, the estimated volume magnetization decreases. As the Ti substitution is used in practice to increase the thermal stability of the α″-Fe16N2, our calculations may offer insights into the change of the magnetic properties by doping, which are very important for practical applications.

  1. Elemental Mercury Oxidation over Fe-Ti-Mn Spinel: Performance, Mechanism, and Reaction Kinetics.

    PubMed

    Xiong, Shangchao; Xiao, Xin; Huang, Nan; Dang, Hao; Liao, Yong; Zou, Sijie; Yang, Shijian

    2017-01-03

    The design of a high-performance catalyst for Hg(0) oxidation and predicting the extent of Hg(0) oxidation are both extremely limited due to the uncertainties of the reaction mechanism and the reaction kinetics. In this work, Fe-Ti-Mn spinel was developed as a high-performance catalyst for Hg(0) oxidation, and the reaction mechanism and the reaction kinetics of Hg(0) oxidation over Fe-Ti-Mn spinel were studied. The reaction orders of Hg(0) oxidation over Fe-Ti-Mn spinel with respect to gaseous Hg(0) concentration and gaseous HCl concentration were approximately 1 and 0, respectively. Therefore, Hg(0) oxidation over Fe-Ti-Mn spinel mainly followed the Eley-Rideal mechanism (i.e., the reaction of gaseous Hg(0) with adsorbed HCl), and the rate of Hg(0) oxidation mainly depended on Cl(•) concentration on the surface. As H2O, SO2, and NO not only inhibited Cl(•) formation on the surface but also interfered with the interface reaction between gaseous Hg(0) and Cl(•) on the surface, Hg(0) oxidation over Fe-Ti-Mn spinel was obviously inhibited in the presence of H2O, SO2, and NO. Furthermore, the extent of Hg(0) oxidation over Fe-Ti-Mn spinel can be predicted according to the kinetic parameter kE-R, and the predicted result was consistent with the experimental result.

  2. Creep of Nearly Lamellar TiAl Alloy Containing W

    SciTech Connect

    Hodge, A M; Hsiung, L M; Nieh, T

    2004-04-08

    Effects of W on the creep resistance of two nearly fully lamellar TiAl alloys with 1.0 and 2.0 at.%W have been investigated. In the low stress regime (LS) a nearly quadratic (1.5

  3. Development of Laser Fabricated Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    deGroh, Henry C., III

    2006-01-01

    Laser Engineered Net Shaping (LENS) depositions with Ti-6Al-4V gas-atomized powder were accomplished at five different temperatures, ranging from 30 to 400 C, imposed on the base plate. These base plate temperatures were employed in an effort to relieve stresses which develop during the deposition. Warpage of the base plate was monitored. Only a slight decline in warpage was observed as the base plate temperature was increased. Results indicate that substrate temperatures closer to the stress relief minimum of 480 C would relieve deposition stresses, though process parameters would likely need to be modified to compensate for the higher base plate temperature. The compositions of the as-received powder and the LENS deposited material were chemically analyzed. The oxygen content of the LENS material was 0.154 wt.% which is less than the maximum impurity limit of 0.2 percent for commercial Ti-6Al-4V alloys, but is over the limit allowed in ELI grade (0.13 percent). The level of oxygen in the commercial base plate used was only 0.0635 percent. Tensile specimens were machined from the LENS deposited material and tested in tension at room temperature. The ultimate and yield tensile stresses of the LENS material were about 1200 and 1150 MPa respectively, which is about 20 percent higher than the strengths of wrought Ti-6Al-4V. The higher strength of the LENS material was due to its fine structure and high oxygen content. The LENS deposits were not fully dense; voids were frequent at the interfaces between deposited layers. These dispersed sheets of voids were parallel to the longitudinal axis of the resulting tensile specimens. Apparently there was sufficient continuous, fully dense material longitudinally to enable the high strengths. Ductility was low in the LENS material. Percent elongation at failure in the LENS material was near 4 percent, which is less than half of what is usually expected from Ti-6Al-4V. The low ductility was caused by high oxygen levels, and the

  4. First principles investigation of Fe and Al bearing phase H

    NASA Astrophysics Data System (ADS)

    Tsuchiya, J.; Tsuchiya, T.

    2015-12-01

    The global circulation of water in the earth is important to investigate the evolution history and dynamics of the earth, since the physical properties (e.g. atomic diffusivity, melting temperature, electrical conductivity and seismic velocities) of the constituent minerals are considerably changed by the presence of water. It has been believed that water is carried into the deep Earth's interior by hydrous minerals such as the dense hydrous magnesium silicates (DHMSs) which are also known as alphabet phases (phase A, superhydrous phase B, and phase D etc.) in the descending cold plate. It has been thought that the relay of these hydrous phases was terminated at ~1200 km depth by the dehydration of phase D which was the highest pressure phase of DHMSs. Recently, we have theoretically predicted the high pressure phase of phase D and experimentally confirmed the existence of this new DHMS in lower mantle pressure conditions above ~45 GPa. This phase has MgSiO4H2chemical composition and named as phase H. At the lower mantle pressure conditions, Al and H-bearing SiO2, δ-AlOOH, ɛ-FeOOH and phase H may be the relevant hydrous phases in the subducting slabs. Interestingly, the crystal structure of these hydrous phases are almost same and have CaCl2type structure. This suggests that these hydrous phases may potentially be able to make the wide range of solid solution. Some experimental studies already reported that Al preferentially partitioned into phase H and the stability of phase H drastically increased by incorporation of Al (Nishi et al. 2014, Ohira et al. 2014). The density of subducted MORB is reported to be denser than that of pyrolite in the lower mantle (e.g. Kawai et al. 2009). Therefore, there is a possibility that phase H containing Al and Fe in subducted MORB survive down to the bottom of lower mantle and the melting of phase H at the core mantle boundary may contribute to the cause of ultra-low velocity zones. In this study, we further extends our

  5. Al-Ca and Al-Fe metal-metal composite strength, conductivity, and microstructure relationships

    SciTech Connect

    Kim, Hyong June

    2011-01-01

    Deformation processed metal-metal composites (DMMC’s) are composites formed by mechanical working (i.e., rolling, swaging, or wire drawing) of two-phase, ductile metal mixtures. Since both the matrix and reinforcing phase are ductile metals, the composites can be heavily deformed to reduce the thickness and spacing of the two phases. Recent studies have shown that heavily drawn DMMCs can achieve anomalously high strength and outstanding combinations of strength and conductivity. In this study, Al-Fe wire composite with 0.07, 0.1, and 0.2 volume fractions of Fe filaments and Al-Ca wire composite with 0.03, 0.06, and 0.09 volume fractions of Ca filaments were produced in situ, and their mechanical properties were measured as a function of deformation true strain. The Al-Fe composites displayed limited deformation of the Fe phase even at high true strains, resulting in little strengthening effect in those composites. Al-9vol%Ca wire was deformed to a deformation true strain of 13.76. The resulting Ca second-phase filaments were deformed to thicknesses on the order of one micrometer. The ultimate tensile strength increased exponentially with increasing deformation true strain, reaching a value of 197 MPa at a true strain of 13.76. This value is 2.5 times higher than the value predicted by the rule of mixtures. A quantitative relationship between UTS and deformation true strain was determined. X-ray diffraction data on transformation of Al + Ca microstructures to Al + various Al-Ca intermetallic compounds were obtained at the Advanced Photon Source at Argonne National Laboratory. Electrical conductivity was measured over a range of true strains and post-deformation heat treatment schedules.

  6. Constructing hierarchical interfaces: TiO2-supported PtFe-FeOx nanowires for room temperature CO oxidation

    DOE PAGES

    Zhu, Huiyuan; Wu, Zili; Dong, Su; ...

    2015-08-05

    This is a report of a facile approach to constructing catalytic active hierarchical interfaces in one-dimensional (1D) nanostructure, exemplified by the synthesis of TiO2-supported PtFe–FeOx nanowires (NWs). The hierarchical interface, constituting atomic level interactions between PtFe and FeOx within each NW and the interactions between NWs and support (TiO2), enables CO oxidation with 100% conversion at room temperature. We identify the role of the two interfaces by probing the CO oxidation reaction with isotopic labeling experiments. Both the oxygen atoms (Os) in FeOx and TiO2 participate in the initial CO oxidation, facilitating the reaction through a redox pathway. Moreover, themore » intact 1D structure leads to the high stability of the catalyst. After 30 h in the reaction stream, the PtFe–FeOx/TiO2 catalyst exhibits no activity decay. These results provide a general approach and new insights into the construction of hierarchical interfaces for advanced catalysis.« less

  7. Evaluation of Ti-48Al-2Cr-2Nb Under Fretting Conditions

    NASA Technical Reports Server (NTRS)

    Miyoshi, Kazuhisa; Lerch, Bradley A.; Draper, Susan L.; Raj, Sai V.

    2001-01-01

    The fretting behavior of Ti-48Al-2Cr-2Nb (y-TiAl) in contact with the nickel-base superalloy 718 was examined in air at temperatures from 296 to 823 K (23 to 550 C). The interfacial adhesive bonds between Ti-48Al-2Cr-2Nb and superalloy 718 were generally stronger than the cohesive bonds within Ti-48Al-2Cr-2Nb. The failed Ti-48Al-2Cr-2Nb debris subsequently transferred to the superalloy 718. In reference experiments conducted with Ti-6Al-4V against superalloy 718 under identical fretting conditions, the degree of transfer was greater for Ti-6A1-4V than for Ti-48Al-2Cr-2Nb. Wear of Ti-48Al-2Cr-2Nb generally decreased with increasing fretting frequency. The increasing rate of oxidation at elevated temperatures led to a drop in wear at 473 K. However, fretting wear increased as the temperature was increased from 473 to 823 K. At 723 and 823 K, oxide film disruption generated cracks, loose wear debris, and pits on the Ti-48Al-2Cr-2Nb wear surface. Both increasing slip amplitude and increasing load tended to produce more metallic wear debris, causing severe abrasive wear in the contacting metals.

  8. Theoretical Prediction of Transition Metal Alloying Effects on the Lightweight TiAl Intermetallic

    NASA Astrophysics Data System (ADS)

    Liu, Shuai; Tang, Chenghuang; Zhan, Yongzhong

    2016-03-01

    The structural, mechanical properties and Debye temperature of doped intermetallic Ti7Al8X (X = Sc, Ti, V, Cr, Y, Zr, Nb, Mo, Hf, Ta, W) have been investigated by employing the pseudo-potential plane-wave approach based on density functional theory, within the generalized gradient approximation (GGA) function. The calculated lattice constants of TiAl are found to be within 1 pct error, compared with the experimental values. The stability of calculated structures of Ti7Al8X at 0 GPa is measured by studying mechanical stability conditions and formation energy. All the single crystals are proved to be elastically anisotropic. The Young's modulus as a function of crystal orientations has been systematically investigated. Mechanical properties of polycrystals are computed from values of shear modulus ( G), bulk modulus ( B), Young's modulus ( E), Poisson's ratio ( υ), and microhardness parameter ( H) for Ti7Al8X. It is indicated that addition of alloying elements reduces the brittleness and microhardness of TiAl intermetallic. Debye temperature of TiAl calculated using elastic data of the present work is found to be influenced by the addition of alloying elements, which is further confirmed by the phonon dispersions of Ti8Al8, Ti7Al8Zr, and Ti7Al8Hf.

  9. Identification of an incommensurate FeAl{sub 2} overlayer on FeAl(110) using x-ray diffraction and reflectivity

    SciTech Connect

    Baddorf, A.P.; Chandavarkar, S.S.

    1995-06-30

    FeAl, like NiAl, crystallizes in the CsCl structure. Consequently the (110) planes contain equal amounts of Fe and Al distributed as interlocking rectangles. Unlike the NiAI(110) surface, which retains the (1{times}l) in-plane symmetry of the bulk, FeAl(l10) reconstructs to form an ordered, incommensurate overlayer. The reconstructed layer introduces x-ray diffraction rods at half-order positions along the [1{bar 1}0] direction, and displaced {plus_minus}0.2905 from integer positions along the [001] direction. Peak widths reveal excellent long range order. Specular reflectivity measurements above and below the Fe K{alpha} edge can be reproduced using a model containing a single reconstructed overlayer with an Fe:Al ratio of 1:2, consistent with FeA{sub I}2.

  10. Enhanced hardness in epitaxial TiAlScN alloy thin films and rocksalt TiN/(Al,Sc)N superlattices

    SciTech Connect

    Saha, Bivas; Lawrence, Samantha K.; Bahr, David F.; Schroeder, Jeremy L.; Birch, Jens; Sands, Timothy D.

    2014-10-13

    High hardness TiAlN alloys for wear-resistant coatings exhibit limited lifetimes at elevated temperatures due to a cubic-AlN to hexagonal-AlN phase transformation that leads to decreasing hardness. We enhance the hardness (up to 46 GPa) and maximum operating temperature (up to 1050 °C) of TiAlN-based coatings by alloying with scandium nitride to form both an epitaxial TiAlScN alloy film and epitaxial rocksalt TiN/(Al,Sc)N superlattices on MgO substrates. The superlattice hardness increases with decreasing period thickness, which is understood by the Orowan bowing mechanism of the confined layer slip model. These results make them worthy of additional research for industrial coating applications.

  11. Indentation creep in nanocrystalline Fe-TiN and Ni-TiN alloys prepared by mechanical alloying

    SciTech Connect

    Ogino, Yoshikiyo; Yamasaki, Tohru; Shen, B.L.

    1997-04-01

    Mechanical properties of nanocrystalline Fe-TiN and Ni-TiN alloys with various TiN contents between 17 and 64 vol pct, which are prepared by dynamically consolidating mechanically alloyed powders, have been investigated by means of hardness measurements and indentation creep tests at intermediate temperatures. The hardness increases with decreasing grain size to about 10 nm. The indentation creep curves conform well to an equation derived from a transient creep rate equation. The analysis of creep curves indicates that the deformation occurs by a dislocation mechanism controlled by grain boundary diffusion.

  12. The local structure and ferromagnetism in Fe-implanted SrTiO₃ single crystals

    SciTech Connect

    Lobacheva, O. Chavarha, M.; Yiu, Y. M.; Sham, T. K.; Goncharova, L. V.

    2014-07-07

    We report a connection between the local structure of low-level Fe impurities and vacancies as the cause of ferromagnetic behavior observed in strontium titanate single crystals (STO), which were implanted with Fe and Si ions at different doses then annealed in oxygen. The effects of Fe doping and post-implantation annealing of STO were studied by X-ray Absorption Near Edge Structure (XANES) spectroscopy and Superconducting Quantum Interference Device magnetometry. XANES spectra for Fe and Ti K- and L-edge reveal the changes in the local environment of Fe and Ti following the implantation and annealing steps. The annealing in oxygen atmosphere partially healed implantation damages and changed the oxidation state of the implanted iron from metallic Fe⁰ to Fe²⁺/Fe³⁺ oxide. The STO single crystals were weak ferromagnets prior to implantation. The maximum saturation moment was obtained after our highest implantation dose of 2×10¹⁶ Fe atom/cm², which could be correlated with the metallic Fe⁰ phases in addition to the presence of O/Ti vacancies. After recrystallization annealing, the ferromagnetic response disappears. Iron oxide phases with Fe²⁺ and Fe³⁺ corresponding to this regime were identified and confirmed by calculations using Real Space Multiple Scattering program (FEFF9).

  13. 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.

  14. Formation of Equiaxed Alpha and Titanium Nitride Precipitates in Spark Plasma Sintered TiB/Ti-6Al-4V Composites (Preprint)

    DTIC Science & Technology

    2012-08-01

    AFRL-RX-WP-TP-2012-0372 FORMATION OF EQUIAXED ALPHA AND TITANIUM NITRIDE PRECIPITATES IN SPARK PLASMA SINTERED TiB/Ti-6Al-4V COMPOSITES...ALPHA AND TITANIUM NITRIDE PRECIPITATES IN SPARK PLASMA SINTERED TiB/Ti-6Al-4V COMPOSITES (PREPRINT) 5a. CONTRACT NUMBER FA8650-08-C-5226 5b...distribution of TiN precipitates, as revealed by TEM studies. 15. SUBJECT TERMS Ti-6Al-4V; TiB; TiN; Spark Plasma Sintering ; Composite; α/β phase

  15. Crystallographic and magnetic properties of the hyperthermia material CoFe2O4@AlFe2O4

    NASA Astrophysics Data System (ADS)

    Choi, Hyunkyung; An, Mijeong; Eom, Wonyoung; Lim, Sae Wool; Shim, In-Bo; Kim, Chul Sung; Kim, Sam Jin

    2017-01-01

    Hard/soft CoFe2O4@AlFe2O4 core/shell nanoparticles were prepared by using a high temperature thermal decomposition method with seed-mediated growth. The structural, magnetic and thermal properties of the nanoparticles were investigated by using X-ray diffraction, vibrating sample magnetometer, MagneTherm, and Mössbauer spectroscopy. The crystal structure of nanoparticles was determined to be cubic spinel ferrite with space group Fd-3m. The CoFe2O4 nanoparticles were found to show high magnetization and coercivity while AlFe2O4 nanoparticles were found to show low magnetization and coercivity. The CoFe2O4@AlFe2O4 core/shell nanoparticles showed intermediate values of magnetization and the coercivity between those of CoFe2O4 and AlFe2O4. Also, the blocking temperature ( T B ) of the nanoparticles (NPs) was observed to be 280, 50, and 225 K for CoFe2O4, AlFe2O4 and CoFe2O4@AlFe2O4, respectively. The core/shell ferrite shows a T B near 225 K, associated with the harder CoFe2O4 NPs. Temperatures below 225 K, the zero-field-cooled curves show changes in their slopes at a temperature near 50 K, corresponding to the second blocking temperature associated with the softer AlFe2O4 NPs.

  16. Absence of ferromagnetism in Fe-doped TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Balcells, Ll.; Frontera, C.; Sandiumenge, F.; Roig, A.; Martínez, B.; Kouam, J.; Monty, C.

    2006-09-01

    The structural and magnetic properties of Ti1-xFexO2-ɛ (x≈0.13) nanoparticles prepared by vaporization-condensation method are analyzed. Samples, mainly of rutile phase, exhibit a pronounced mosaic structure and are free of secondary phases or impurities. Mössbauer spectroscopy evidences the absence of magnetic ordering and shows features indicative of the existence of two doublets assigned to two different structural arrangements of Fe3+ ions substituting for Ti4+ ions in the rutile structure. The application of the Goodenough-Kanamori rules clearly indicates that conventional FM ordering should not be expected in Fe-doped TiO2 with rutile structure.

  17. Synthesis, photoelectric properties and photocatalytic activity of the Fe2O3/TiO2 heterogeneous photocatalysts.

    PubMed

    Peng, Linlin; Xie, Tengfeng; Lu, Yongchun; Fan, Haimei; Wang, Dejun

    2010-07-28

    Fe(2)O(3)/TiO(2) heterogeneous photocatalysts with different mass ratios of Fe(2)O(3)vs. TiO(2) were synthesized by impregnation of Fe(3+) on the surface of TiO(2) microrods and calcination at 300 degrees C. Scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), photoluminescence spectra and X-ray diffraction (XRD) have been used to characterize the samples. The photocatalytic activities of Fe(2)O(3)/TiO(2) heterocomposites, pure Fe(2)O(3) and pure TiO(2) were evaluated by the photodegrading efficiency of Orange II under visible light (lambda > 420 nm). The experiments demonstrated that Orange II in aqueous solution was more efficiently photodegraded using Fe(2)O(3)/TiO(2) heterogeneous photocatalysts than either pure Fe(2)O(3) or TiO(2) under visible light irradiation. With an optimal mass ratio of 7:3 in Fe(2)O(3)/TiO(2) the highest rate of Orange II photodegradation was achieved under the experimental conditions. We have also compared the photoelectric properties of Fe(2)O(3)/TiO(2) heterogeneous photocatalysts with that of pure Fe(2)O(3) by surface photovoltage (SPV) and transient photovoltage (TPV) techniques. Based on the photovoltage responses, we discussed the influence of the hetero-interface between Fe(2)O(3) and TiO(2) on transfer characteristics of photogenerated charge carriers. We demonstrated that the formation of heterojunctions between Fe(2)O(3) and TiO(2) for Fe(2)O(3)/TiO(2) composites was pivotal for improving the separation and thus restraining the recombination of photogenerated electrons and holes, which accounts for the enhancement of photocatalytic activity.

  18. Microcrack propagation in Ti-6Al-4V alloys

    SciTech Connect

    Hines, J.A.; Peters, J.O.; Luetjering, G.

    1999-07-01

    In this study, microcrack propagation in Ti-6Al-4V was examined in regions just above and below the fatigue limit. Two different Ti-6Al-4V alloys with nominally similar chemical compositions were examined: the first alloy was thermo-mechanically treated in the laboratory to develop a bi-modal and a fully lamellar microstructure and the second alloy is from the High Cycle Fatigue MURI program (forging No. 197) containing a duplex microstructure. Microcracks were nucleated in smooth specimens of each microstructure in the LCF regime during tests conducted at R = {minus}1 (R = {sigma}{sub min}/{sigma}{sub max}) so that internal stresses could be minimized. These samples were then tested in the HCF regime to determine crack propagation rates for R values of {minus}1, 0.1, and 0.5. In addition, conventional fatigue crack propagation curves for macrocracks using CT-specimens were measured. Comparisons in microcrack growth behavior were evaluated and discussed for the bi-modal and fully lamellar microstructures, for bi-modal and forging No. 197 microstructures, and for forging No. 197 examining the influence of R = 0.1 and 0.5. Much of the observed behavior appeared to be explained by differences in crack front roughness.

  19. Drilling of intermetallic alloys gamma TiAl

    SciTech Connect

    Beranoagirre, A.; Olvera, D.; Lopez de Lacalle, L. N.; Urbicain, G.

    2011-01-17

    Due to their high strength/weight ratio and resistance to corrosion and wear, superalloys such as gamma TiAl or Inconel 718 appear as the best choice for the high mechanical/thermal demands in the vicinity of the combustion chamber of aircraft engines. There are assembled parts such as cases, disks or blisks; in the manufacturing of these components the last drilling operation could jeopardize the full work integrity adding new costs to the just very expensive parts. Therefore drilling is a high-added value step in the complete sequence. The present work is framed within the study of hole making in advanced materials used for lightweight applications in aerospace sector. Within this context, the paper presents the results from milling tests on three types of gamma TiAl alloys (extruded MoCuSi, ingot MoCuSi and TNB) to define an optimal set of cutting parameters, which will contribute to open the increase in use of these special alloys. Drilling tools made of integral hard metal were used, applying different feeds and cutting speeds. The influence of cutting speed and feed is discussed.

  20. Multilayered TiAlN films on Ti6Al4V alloy for biomedical applications by closed field unbalanced magnetron sputter ion plating process.

    PubMed

    Yi, Peiyun; Peng, Linfa; Huang, Jiaqiang

    2016-02-01

    Ti6Al4V alloy has been widely used as a suitable material for surgical implants such as artificial hip joints. In this study, a series of multilayered gradient TiAlN coatings were deposited on Ti6Al4V substrate using closed field unbalanced magnetron sputter ion plating (CFUBMSIP) process. Taguchi design of experiment approach was used to reveal the influence of depositing parameters to the film composition and performance of TiAlN coatings. The phase structure and chemical composition of the TiAlN films were characterized by X-ray diffractometry (XRD) and X-ray photoelectron spectroscopy (XPS). Mechanical properties, including hardness, Young's modulus, friction coefficient, wear rate and adhesion strength were systematically evaluated. Potentiodynamic tests were conducted to evaluate the corrosion resistance of the coated samples in Ringer's solution at 37°C to simulate human body environment. Comprehensive performance of TiAlN films was evaluated by assigning different weight according to the application environment. S8, deposited by Ti target current of 8A, Al target current of 6A, bias voltage of -60V and nitrogen content with OEM (optical emission monitor) value of 45%, was found to achieve best performance in orthogonal experiments. Depositing parameters of S8 might be practically applied for commercialization of surgical implants.

  1. Al-to-oxide and Ti-to-organic linkages in biogenic sediment: relationships to paleo-export production and bulk Al/Ti

    NASA Astrophysics Data System (ADS)

    Kryc, K. A.; Murray, R. W.; Murray, D. W.

    2003-06-01

    To increase our understanding of the mechanisms that control the distribution of Al and Ti within marine sediment, we performed sequential extractions targeting the chemical signatures of the loosely bound, exchangeable, carbonate, oxide, organic, opal, and residual fraction of sediment from a carbonate-dominated regime (equatorial Pacific) and from a mixed opal-terrigenous regime (West Antarctic Peninsula). We observe a systematic partitioning of Al and Ti between sediment phases that is related to bulk Al/Ti. We show that, where we can quantify an Al excess component, the dissolved Al is preferentially affiliated with the oxide fraction, resulting in Al/Ti molar ratios of 500-3000. This is interpreted as the result of surface complexation in the water column of dissolved Al onto oxyhydroxides. We also observe a previously undetected Ti excess with as much as 80% of the total Ti in the organic fraction, which is most likely a function of metal-organic colloidal removal from the water column. In samples where the excess metals are obscured by the detrital load, the Al and Ti are almost exclusively found in the residual phase. This argues for the paired removal of Al (preferentially by the oxide component) and Ti (preferentially by the organic component) from the water column by settling particulate matter. This research builds upon earlier work that shows changes in the bulk ratio of Al to Ti in carbonate sediment from the central-equatorial Pacific that coincide with changes in the sedimentary bulk accumulation rate (BAR). The ratios that are observed are as much as three times higher than typical shale values, and were interpreted as the result of scavenging of dissolved Al onto particles settling in the water column. Because this non-terrigenous Al excess accounts for up to 50% of the total sedimentary Al inventory and correlates best with BAR, the bulk Al/Ti may be a sensitive tracer of particle flux and, therefore, export production. Because we show that the

  2. Investigating the effects of phosphorus in a binary-phase TiAl-Ti3Al alloy by first-principles: from site preference, interfacial energetics to mechanical properties

    NASA Astrophysics Data System (ADS)

    Li, Zhong-Zhu; Wei, Ye; Zhou, Hong-Bo; Lu, Guang-Hong

    2016-12-01

    We investigate the site preference of phosphorus (P) and its effects on the mechanical properties of the binary phase TiAl-Ti3Al alloy using a first-principles method in combination with empirical criterions. We show that P is energetically sitting at the substitutional Al site in the Ti3Al layer of the TiAl/Ti3Al interface, which can be understood from the difference of electronegativity between P and Ti/Al. Both the cleavage energy ( γ cl ) and the unstable stacking fault energy ( γ us ) decrease with the presence of P, which indicates the strength of the TiAl/Ti3Al interface will be weaker and the mobility of the dislocation will be easier induced by P. Further, we demonstrate that the ratio of γ cl / γ us of TiAl/Ti3Al interface with P is 5.03, 0.19% lower than that of the clean TiAl/Ti3Al interface, suggesting that the P impurity will slightly reduce the ductility of the TiAl/Ti3Al interface.

  3. Microstructure, Mechanical Properties, and Electrochemical Behavior of Ti-Nb-Fe Alloys Applied as Biomaterials

    NASA Astrophysics Data System (ADS)

    Lopes, Éder Sócrates Najar; Salvador, Camilo Augusto Fernandes; Andrade, Denis Renato; Cremasco, Alessandra; Campo, Kaio Niitsu; Caram, Rubens

    2016-06-01

    New β metastable Ti alloys based on Ti-30Nb alloy with the addition of 1, 3, or 5 wt pct Fe have been developed using the bond order and the metal d-orbital energy level ( overline{{Bo}} {-} overline{{Md}} ) design theory. The samples were prepared by arc melting, hot working, and solution heat treatment above the β transus followed by water quenching (WQ) or furnace cooling (FC). The effect of the cooling rate on the microstructure of Ti-30Nb-3Fe wt pct was investigated in detail using a modified Jominy end quench test. The results show that Fe acts as a strong β-stabilizing alloying element. The addition of Fe also leads to a reduction in the ω and α phases volumetric fractions, although the ω phase was still detected in the WQ Ti-30Nb-5Fe samples, as shown by TEM, and α phase clusters were detected by SEM in the FC Ti-30Nb-3Fe samples. Among the WQ samples, the addition of 5 wt pct Fe improves the ultimate tensile strength (from 601 to 689 MPa), reduces the final elongation (from 28 to 16 pct), and impairs the electrochemical corrosion resistance, as evaluated by potentiodynamic polarization tests in Ringer's solution. The microstructural variation arising from the addition of Fe did not change the elastic modulus (approximately 80 GPa for all experimental WQ samples). This study shows that small Fe additions can tailor the microstructure of Ti-Nb alloys, modifying α and ω phase precipitation and improving mechanical strength.

  4. Chemical mixing at “Al on Fe” and “Fe on Al” interfaces

    SciTech Connect

    Süle, P.; Horváth, Z. E.; Kaptás, D.; Bujdosó, L.; Balogh, J.; Nakanishi, A.

    2015-10-07

    The chemical mixing at the “Al on Fe” and “Fe on Al” interfaces was studied by molecular dynamics simulations of the layer growth and by {sup 57}Fe Mössbauer spectroscopy. The concentration distribution along the layer growth direction was calculated for different crystallographic orientations, and atomically sharp “Al on Fe” interfaces were found when Al grows over (001) and (110) oriented Fe layers. The Al/Fe(111) interface is also narrow as compared to the intermixing found at the “Fe on Al” interfaces for any orientation. Conversion electron Mössbauer measurements of trilayers—Al/{sup 57}Fe/Al and Al/{sup 57}Fe/Ag grown simultaneously over Si(111) substrate by vacuum evaporation—support the results of the molecular dynamics calculations.

  5. Preparation, characterization and visible-light-driven photocatalytic activity of Fe-incorporated TiO2 microspheres photocatalysts

    NASA Astrophysics Data System (ADS)

    Li, Jun-Qi; Wang, De-Fang; Guo, Zhan-Yun; Zhu, Zhen-Feng

    2012-12-01

    Fe incorporated TiO2 microspheres (Fe-TiO2) were prepared by integrating the sol-gel method and impregnating-calcination method. Scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and UV-vis diffuse reflectance spectroscopy indicated that α-Fe2O3 nanoparticles were deposited onto the TiO2 microspheres, and in the mean time, some Fe3+ ions were doped into TiO2 lattice. The absorption of Fe-TiO2 microspheres in the visible light region increased with the increasing of Fe content. Photoluminescence (PL) analyses further confirmed that Fe-incorporation effectively promoted the separation and transfer of photogenerated charge carriers, which can improve the photocatalytic activity of the samples. The photocatalytic activity of Fe-TiO2 microspheres was evaluated by the degradation of methylene blue aqueous solution under visible light irradiation. The results demonstrated that the Fe-TiO2 microspheres exhibited significantly enhanced photocatalytic activity compared with pure TiO2 microspheres. What is more, the charge-transfer processes in Fe-TiO2 were also discussed.

  6. Synthesis and characterization of LaFeO3/TiO2 nanocomposites for visible light photocatalytic activity

    NASA Astrophysics Data System (ADS)

    Dhinesh Kumar, R.; Thangappan, R.; Jayavel, R.

    2017-02-01

    LaFeO3/TiO2 nanocomposites were successfully synthesized by hydrothermal method. The as-prepared nanoparticles were characterized by TGA, XRD, HRSEM, EDS, TEM, VSM and UV-Vis techniques. Thermal stability of the material was studied by thermal analysis. XRD studies confirm the orthorhombic and rutile phase for pure LaFeO3 and TiO2 nanoparticles. The LaFeO3/TiO2 composite shows the coexistence of LaFeO3 and TiO2 phases with no extra peaks. Morphological analysis shows the spherical nanoparticles and the average particle size of LaFeO3, TiO2 and LaFeO3/TiO2 was around 60 nm. The LaFeO3/TiO2 nanocomposites show a significant shift in the UV-vis absorption spectra in comparison with both TiO2 and LaFeO3 nanoparticles. The photocatalytic activity of the samples were tested for the degradation of methyl orange (MO) in aqueous solutions under visible light irradiations for 180 min. The LaFeO3/TiO2 composite exhibits enhanced visible light photocatalytic properties in comparison with that of LaFeO3 nanoparticles.

  7. Effect of Ti/Al ratio and Cr, Nb, and Hf additions on material factors and mechanical properties in TiAl

    NASA Astrophysics Data System (ADS)

    Kawabata, T.; Tamura, T.; Izumi, O.

    1993-01-01

    The effect of the Ti/Al ratio and Cr, Nb, and Hf additions on material factors, such as the grain size, second phase, la tice parameters and the axial ratio, and on mechanical properties in TiAl-base alloys has been studied. The grain size was decreased by the deviation from the stoichiometric composition o the Ti-rich side and the addition of the third elements. The Cr element was contained a little more in Ti3Al phase than in TiAl phase in two-phase Ti-rich alloys. The lattice parameters, a and c, and the axial ratio, c/a, of the binary alloys varied linearly with decreasing Al content even in the dual-phase region. The Cr addition decreased the a and c and also c/a. The Nb addition increased weakly the a and c and c/a. On the contrary, the Hf addition increased the a and c but decreased the c/a ratio. In the Cr added alloys, the decrease of volume of a unit cell, due to the substitution of Cr atoms for Ti and Al atoms, was larger than that expected from the difference of atom sizes. The Nb addition should decrease the volume of a unit cell, but it increased the volume. The Hf addition caused a larger increase of volume of a unit cell than that expected from the difference of atom sizes. We suggested that the Cr addition increases and the Nb and Hf additions decrease the bond strength in TiAl. The deviation from stoichiometry and the addition of third elements caused an increase of work-hardening rate. The alloys with Ti-rich composition have superior mechanical properties compared to those of alloys vith Al-rich composition. The Cr addition resulted in high solution hardening, and the Ti-47A1 3Cr (in atomic percent) alloys had the highest fracture strain of 2.7 pct in all alloys tested. The Nb addition resulted in poor ductility in both Ti- and Al-rich alloys. The Hf additions to the Ti-rich composition caused better mechanical properties than those of Al-rich alloys. Thi; trend was also similar to the Nb-added alloys. In the Hf-added alloys, the Ti-49Al-2Hf

  8. The electrochemical and mechanical behavior of passivated and TiN/AlN-coated CoCrMo and Ti6Al4V alloys.

    PubMed

    Goldberg, Jay R; Gilbert, Jeremy L

    2004-02-01

    The mechanical and electrochemical behavior of the surface oxides of CoCrMo and Ti6Al4V alloys during fracture and repassivation play an important role in the corrosion of the taper interfaces of modular hip implants. This behavior was investigated in one group of CoCrMo and Ti6Al4V alloy samples passivated with nitric acid and another group coated with a novel TiN/AlN coating. The effects of mechanical load and sample potential on peak currents and time constants resulting from fracture of the surface oxide or coating, and the effects of mechanical load on scratch depth were investigated to determine the mechanical and electrochemical properties of the oxides or coating. The polarization behavior of the samples after fracture of the oxide or coating was also investigated. CoCrMo had a stronger surface oxide and higher interfacial adhesion strength, making it more resistant to fracture than Ti6Al4V. If undisturbed, the oxide on the surface of Ti6Al4V significantly reduced dissolution currents at a wider range of potentials than CoCrMo, making Ti6Al4V more resistant to corrosion. The TiN/AlN coating had a higher hardness and modulus of elasticity than CoCrMo and Ti6Al4V. It was much less susceptible to fracture, had a higher interfacial adhesion strength, and was a better barrier to ionic diffusion than the surface oxides on CoCrMo and Ti6Al4V. The coating provided increased corrosion and fretting resistance to the substrate alloys.

  9. Photocatalytic activity of Fe-doped CaTiO₃ under UV-visible light.

    PubMed

    Yang, He; Han, Chong; Xue, Xiangxin

    2014-07-01

    The photocatalytic degradation of methylene blue (MB) over Fe-doped CaTiO₃ under UV-visible light was investigated. The as-prepared samples were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) equipped with an energy dispersive spectrometer (EDS) system, Fourier transform infrared spectra (FT-IR), and UV-visible diffuse reflectance spectroscopy (DRS). The results show that the doping with Fe significantly promoted the light absorption ability of CaTiO₃ in the visible light region. The Fe-doped CaTiO₃ exhibited higher photocatalytic activity than CaTiO₃ for the degradation of MB. However, the photocatalytic activity of the Fe-doped CaTiO₃ was greatly influenced by the calcination temperature during the preparation process. The Fe-doped CaTiO₃ prepared at 500°C exhibited the best photocatalytic activity, with degradation of almost 100% MB (10ppm) under UV-visible light for 180 min.

  10. ZnFe2O4-TiO2 Nanoparticles within Mesoporous MCM-41

    PubMed Central

    Tang, Aidong; Deng, Yuehua; Jin, Jiao; Yang, Huaming

    2012-01-01

    A novel nanocomposite ZnFe2O4-TiO2/MCM-41 (ZTM) was synthesized by a sol-gel method and characterized through X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), N2 adsorption-desorption, Raman spectroscopy, and ultraviolet visible (UV-vis) spectrophotometry. The results confirmed the incorporation of ZnFe2O4-TiO2 nanoparticles inside the pores of the mesoporous MCM-41 host without destroying its integrity. ZnFe2O4 nanoparticles can inhibit the transformation of anatase into rutile phase of TiO2. Incorporation of ZnFe2O4-TiO2 within MCM-41 avoided the agglomeration of nanoparticles and reduced the band gap energy of TiO2 to enhance its visible light photocatalytic activity. UV-vis absorption edges of ZTM nanocomposites redshifted with the increase of Zn/Ti molar ratio. The nanocomposite approach could be a potential choice for enhancing the photoactivity of TiO2, indicating an interesting application in the photodegradation and photoelectric fields. PMID:22919325

  11. Influence of manganese on sintering processes in the Ti-Fe system. 1. Volume changes in sintering of Ti-Fe-Mn compacts

    SciTech Connect

    Kivalo, L.I.; Skorokhod, V.V.

    1986-05-01

    An investigation was made of the influence of manganese on the sintering processes in the titanium-iron system in the area of temperatures of existence of the first ternary eutectic point. Powders of titanium obtained by hydride-calcium reduction, ferromanganese, and types PZh4M2 and V3 iron were used. A figure presents data on the character of the volume changes in sintering of compacts of mixtures of titanium and iron powders with and without manganese. The x-ray analysis was made on a DRON-0.5 instrument. The profiles of intensities of the x-ray lines of Ti(Fe, Mn) phase present in specimens of mixture II are shown. With an increase in sintering temperature the line, which is diffuse at 1050 degrees C, gradually narrows, and at 1250 degrees C a doublet appears. At the time, the lattice parameter changes from 0.2976 for unalloyed TiFe to 0.2991 nm for Ti(Fe, Mn) obtained at 1250 degrees C. To obtain Ti(Fe, Mn) compounds of the required composition, it is necessary to take into account the amount of evaporated manganese.

  12. Plasma preparation and low-temperature sintering of spherical TiC-Fe composite powder

    NASA Astrophysics Data System (ADS)

    Wang, Jian-jun; Hao, Jun-jie; Guo, Zhi-meng; Wang, Song

    2015-12-01

    A spherical Fe matrix composite powder containing a high volume fraction (82vol%) of fine TiC reinforcement was produced using a novel process combining in situ synthesis and plasma techniques. The composite powder exhibited good sphericity and a dense structure, and the fine sub-micron TiC particles were homogeneously distributed in the α-Fe matrix. A TiC-Fe cermet was prepared from the as-prepared spherical composite powder using powder metallurgy at a low sintering temperature; the product exhibited a hardness of HRA 88.5 and a flexural strength of 1360 MPa. The grain size of the fine-grained TiC and special surface structure of the spherical powder played the key roles in the fabrication process.

  13. Magnetic properties of ball milled Fe-40Al at.% alloys

    SciTech Connect

    Amils, X.; Nogues, J.; Surinach, S.; Baro, M.D.; Munoz, J.S.

    1998-07-01

    A direct correlation between the lattice parameter and the saturation magnetization, during the disordering (ball milling) and posterior reordering (annealing) processes, has been found in Fe-40Al At.% compounds. These results indicate that the paramagnetic-ferromagnetic-paramagnetic transitions induced by ball milling and subsequent annealing could be related to the changes in volume, and not only to nearest neighbors effects as is commonly assumed. Moreover, these alloys have been found to become spin glass at low temperatures, independently of their structural state (ordered or disordered).

  14. MOKE Study of Fe/Co/Al Multilayers

    SciTech Connect

    Jani, Snehal; Lakshmi, N.; Venugopalan, K.; Rajput, Parasmani; Zajaoc, M.; Rueffer, R.; Reddy, V. R.; Gupta, Ajay

    2011-07-15

    The multilayer system (MLS)-[{sup 57}Fe{sub 25}A/Co{sub 11}A/Al{sub 17}A]x20 has been deposited by Ion beam sputtering (IBS) technique. The MLS has been annealed at 700 deg. C for 1 h. Overall composition of as deposited and annealed MLS have been characterized by EDX and magnetic properties have been studied through angular dependent magneto optic Kerr effect (MOKE) hysteresis curves. The study shows that the as-deposited MLS has excellent soft magnetic properties coupled with perpendicular magnetic isotropy which is destroyed on annealing.

  15. Development of a high-performance TiAl exhaust valve

    SciTech Connect

    Maki, Kunio; Ehira, Atsushi; Sayashi, Mamoru; Sasaki, Toru; Noda, Toshiharu; Okabe, Michio; Isobe, Susumu

    1996-09-01

    A new high-performance and lightweight TiAl intermetallic compound exhaust valve has been developed. The TiAl valve can improve power output and fuel economy by contributing higher engine speeds and a reduction in valve train friction. It was achieved by developing A Ti-33.5Al-0.5Si-1Nb-0.5Cr (mass %) intermetallic compound, a precision casting method for TiAl that provides a low-cost, high-quality process, and a plasma carburizing technique for assuring good wear resistance on the valve stem end, stem and face.

  16. Comparative study of (N, Fe) doped TiO2 photocatalysts

    NASA Astrophysics Data System (ADS)

    Larumbe, S.; Monge, M.; Gómez-Polo, C.

    2015-02-01

    The effect of N and Fe doping on the structural, optical, photocatalytic and magnetic properties of TiO2 nanoparticles is analyzed. Undoped, N and Fe doped TiO2 nanoparticles were synthesized by sol-gel method. Titanium tetraisopropoxide (TTIP) was used as the alkoxyde precursor and iron (III) nitrate and urea were the employed precursors to obtain Fe and N doped TiO2 nanoparticles, respectively. Differential Scanning Calorimetry (DSC) and Thermogravimetrical Analysis (TGA) enabled the analysis of the thermal decomposition process and the final calcination temperature. X-Ray Diffraction patterns of the calcined nanoparticles displayed a monophasic anatase structure in all the samples with mean crystallite diameter around 4-6 nm. The introduction of Fe or N induced a red-shift in the absorption spectra. Such a red-shift is characterized by a decrease in the band-gap energy and the occurrence of an absorption (Urbach) tail in the visible region. Finally, the photocatalytic efficiency was evaluated under UV and Visible light, obtaining an improvement of the kinetic constants in the nitrogen doped TiO2 nanoparticles with respect to undoped and Fe doped TiO2. The differences in the photocatalytic response under Fe and N doping are also analyzed in terms of the magnetic response of the analyzed photocatalysts.

  17. Fe doped TiO2-graphene nanostructures: synthesis, DFT modeling and photocatalysis

    NASA Astrophysics Data System (ADS)

    Farhangi, Nasrin; Ayissi, Serge; Charpentier, Paul A.

    2014-08-01

    In this work, Fe-doped TiO2 nanoparticles ranging from a 0.2 to 1 weight % were grown from the surface of graphene sheet templates containing -COOH functionalities using sol-gel chemistry in a green solvent, a mixture of water/ethanol. The assemblies were characterized by a variety of analytical techniques, with the coordination mechanism examined theoretically using the density functional theory (DFT). Scanning electron microscopy and transmission electron microscopy images showed excellent decoration of the Fe-doped TiO2 nanoparticles on the surface of the graphene sheets >5 nm in diameter. The surface area and optical properties of the Fe-doped photocatalysts were measured by BET, UV and PL spectrometry and compared to non-graphene and pure TiO2 analogs, showing a plateau at 0.6% Fe. Interactions between graphene and Fe-doped anatase TiO2 were also studied theoretically using the Vienna ab initio Simulation Package based on DFT. Our first-principles theoretical investigations validated the experimental findings, showing the strength in the physical and chemical adsorption between the graphene and Fe-doped TiO2. The resulting assemblies were tested for photodegradation under visible light using 17β-estradiol (E2) as a model compound, with all investigated catalysts showing significant enhancements in photocatalytic activity in the degradation of E2.

  18. Al-TiC Composites Fabricated by a Thermally Activated Reaction Process in an Al Melt Using Al-Ti-C-CuO Powder Mixtures: Part II. Microstructure Control and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Cho, Young-Hee; Lee, Jung-Moo; Kim, Su-Hyeon

    2015-03-01

    Controlling the processing parameters is important to minimize such undesirable microstructural features in Al/TiC composites as unreacted C, incomplete reaction products of Al3Ti and TiC aggregates, which originate from the pellet microstructure upon the combustion reaction of an Al-Ti-C-CuO pellet in an Al melt. In particular, the mean particle size of elemental powders is a key factor linked to the formation of TiC aggregates, which is significantly suppressed with smaller initial particles of Ti and C by mixing them homogenously by ball milling. Al-Cu-Mg alloys reinforced with up to 12 vol pct TiC are fabricated by the developed process, followed by extrusion. The composites after heat treatment exhibit high elastic modulus and an ultimate tensile strength of 93 GPa and 461 MPa, respectively, with a low coefficient of thermal expansion of 17.11 ppm/K.

  19. Influence of the concentration in Fe-doped BaTiO 3 on magnetoelectric couping of layered composites BaTi 1-xFe xO 3-Tb 1-yDy yFe 2-z

    NASA Astrophysics Data System (ADS)

    Zhang, Ning; Wei, Jianjin

    Perovskites BaTi 1-xFe xO 3 has been synthesized with the concentration x ranging from 0.01 to 0.02. Their transformation point of ferroelectric to paraelectric and the corresponding latent heat of the phase transformation were observed to decrease with increasing the doping level of Fe 3+. Bonded layered composites BaTi 1-xFe xO 3-Tb 1-yDy yFe 2-z have been fabricated and their magnetoelectric effect has been investigated. The sample containing a layer of perovskite BaTi 0.985Fe 0.015O 3 was found to show the maximum transverse ME voltage coefficient, which is about 1422 mV Oe -1 cm -1 under a magnetic field of 1580 Oe, in these bilayers. Analysis shows that the Fe-doped BaTiO 3 with doping level at about 1.5% should have largest piezoelectric coefficient in these ceramics BaTi 1-xFe xO 3.

  20. Cyclic Oxidation of FeCrAlY/Al2O3 Composites

    NASA Technical Reports Server (NTRS)

    Nesbitt, James A.; Draper, Susan L.; Barrett, Charles A.

    1999-01-01

    Three-ply FeCrAlY/Al2O3 composites and FeCrAlY matrix-only samples were cyclically oxidized at 1000 C and 1100 C for up to 1000 1-hr cycles. Fiber ends were exposed at the ends of the composite samples. Following cyclic oxidation, cracks running parallel to and perpendicular to the fibers were observed on the large surface of the composite. In addition, there was evidence of increased scale damage and spallation around the exposed fiber ends, particularly around the middle ply fibers. This damage was more pronounced at the higher temperature. The exposed fiber ends showed cracking between fibers in the outer plies, occasionally with Fe and Cr-rich oxides growing out of the cracks. Large gaps developed at the fiber/matrix interface around many of the fibers, especially those in the outer plies. Oxygen penetrated many of these gaps resulting in significant oxide formation at the fiber/matrix interface far within the composite sample. Around several fibers, the matrix was also internally oxidized showing Al2O3 precipitates in a radial band around the fibers. The results show that these composites have poor cyclic oxidation resistance due to the CTE mismatch and inadequate fiber/matrix bond strength at temperatures of 1000 C and above.

  1. Preparation of iron aluminate (FeAl2O4) nanoparticles from FeAl2O4 hollow particles fabricated by using a spray pyrolysis process

    NASA Astrophysics Data System (ADS)

    Yun, Jaecheol; Kim, Yangdo; Park, Dahee; Yun, Jung-Yeul

    2015-05-01

    Iron aluminate (FeAl2O4) hollow particles with a spinel structure were synthesized by using a spray pyrolysis process. FeAl2O4 hollow particles were formed at a reaction temperature of 900 °C at a flow rate of 40 L/min as a result of the rapid solvent evaporation and decomposition gases from the droplets in the spray solution prepared from metal salts and organic reagents. FeAl2O4 hollow particles were fabricated at a reaction temperature of 900 °C with a flow rate of 40 L/min. The FeAl2O4 hollow particles were heat treated for 3 hours at 600 °C in a 5% H2/Ar atmosphere to form the crystal particles. Subsequently, FeAl2O4 nanoparticles were fabricated from the FeAl2O4 hollow particles by using the wet milling process. After milling for 60 minutes, transmission electron microscopy revealed the FeAl2O4 particles to have a mean size of approximately 50 nm. The FeAl2O4 nanoparticles were fabricated successfully by using a two-step process, spray pyrolysis and wet milling.

  2. The effect of Fe segregation on the photocatalytic growth of Ag nanoparticles on rutile TiO2(001)

    NASA Astrophysics Data System (ADS)

    Busiakiewicz, Adam; Kisielewska, Aneta; Piwoński, Ireneusz; Batory, Damian

    2017-04-01

    The photocatalytic growth of silver nanoparticles (AgNPs) on rutile TiO2(001) and Fe-modified rutile TiO2(001) monocrystals was investigated. Various amount of Fe was segregated in a controlled way from the doped TiO2 substrates in ultra-high vacuum conditions resulting in low- medium- and high- content of Fe on TiO2 substrates. AgNPs were grown on pristine TiO2 and substrates containing Fe by photoreduction of Ag+ ions under UV illumination. It was found that the size of AgNPs was larger on Fe/TiO2 than on TiO2 while the surface density exhibited the opposite behavior - a large number of AgNPs were present on the TiO2 surface but only a few AgNPs were visible on the Fe/TiO2 substrates. The reason for the differences in size and number of AgNPs on TiO2 and Fe/TiO2 is the limited access of Ag+ to the TiO2 surface caused by the large number of Fe grains segregated onto the TiO2 surface. Another possible reason for the various AgNPs morphologies is alteration in the mechanism of Ag+ photoreduction caused by iron present as Fe3+ ions and by newly formed AgNPs playing the role of electron traps. The surface elemental analysis of the investigated materials was performed with the use of X-ray photoelectron spectroscopy (XPS) and confirmed the composition of AgNPs/Fe/TiO2 systems. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) revealed sizes, morphology and distribution of the nanostructures.

  3. Evaluation of Pb-17Li compatibility of ODS Fe-12Cr-5Al alloys

    NASA Astrophysics Data System (ADS)

    Unocic, Kinga A.; Hoelzer, David T.

    2016-10-01

    The Dual Coolant Lead Lithium (DCLL: eutectic Pb-17Li and He) blanket concept requires improved Pb-17Li compatibility with ferritic steels in order to demonstrate acceptable performance in fusion reactors. As an initial step, static Pb-17at.%Li (Pb-17Li) capsule experiments were conducted on new oxide dispersion strengthened (ODS) FeCrAl alloys ((1) Y2O3 (125Y), (2) Y2O3 + ZrO2 (125YZ), (3) Y2O3 + HfO2 (125YH), and (4) Y2O3 + TiO2 (125YT)) produced at ORNL via mechanical alloying (MA). Tests were conducted in static Pb-17Li for 1000 h at 700 °C. Alloys showed promising compatibility with Pb-17Li with small mass change after testing for 125YZ, 125YH and 125YT, while the 125Y alloy experienced the highest mass loss associated with some oxide spallation and subsequent alloy dissolution. X-ray diffraction methods identified the surface reaction product as LiAlO2 on all four alloys. A small decrease (∼1 at.%) in Al content beneath the oxide scale was observed in all four ODS alloys, which extended 60 μm beneath the oxide/metal interface. This indicates improvements in alloy dissolution by decreasing the amount of Al loss from the alloy. Scales formed on 125YZ, 125YH and 125YT were examined via scanning transmission electron microscopy (S/TEM) and revealed incorporation of Zr-, Hf-, and Ti-rich precipitates within the LiAlO2 product, respectively. This indicates an inward scale growth mechanism. Future work in flowing Pb-17Li is needed to further evaluate the effectiveness of this strategy in a test blanket module.

  4. Evaluation of Pb-17Li compatibility of ODS Fe-12Cr-5Al alloys

    DOE PAGES

    Unocic, Kinga A.; Hoelzer, David T.

    2016-07-09

    The Dual Coolant Lead Lithium (DCLL: eutectic Pb–17Li and He) blanket concept requires improved Pb–17Li compatibility with ferritic steels in order to demonstrate acceptable performance in fusion reactors. As an initial step, static Pb-17at.%Li (Pb-17Li) capsule experiments were conducted on new oxide dispersion strengthened (ODS) FeCrAl alloys ((1) Y2O3 (125Y), (2) Y2O3+ZrO2 (125YZ), (3) Y2O3+HfO2 (125YH), and (4) Y2O3+TiO2 (125YT)) produced at ORNL via mechanical alloying (MA). Tests were conducted in static Pb–17Li for 1000 h at 700°C. Alloys showed promising compatibility with Pb–17Li with small mass change after testing for 125YZ, 125YH and 125YT, while the 125Y alloy experiencedmore » the highest mass loss associated with some oxide spallation and subsequent alloy dissolution. X-ray diffraction methods identified the surface reaction product as LiAlO2 on all four alloys. A small decrease (~1 at.%) in Al content beneath the oxide scale was observed in all 4 ODS alloys, which extended through 60 μm beneath the oxide/metal interface. This indicates improvements in alloy dissolution by decreasing the amount of Al loss from the alloy. Scales formed on 125YZ, 125YH and 125YT were examined via scanning transmission electron microscopy (S/TEM) and revealed incorporation of Zr-, Hf-, and Ti-rich precipitates within the LiAlO2 product, respectively. This indicates an inward scale growth mechanism. Future work in flowing Pb–17Li is needed to further evaluate the effectiveness of this strategy in a test blanket module.« less

  5. Evaluation of Pb-17Li compatibility of ODS Fe-12Cr-5Al alloys

    SciTech Connect

    Unocic, Kinga A.; Hoelzer, David T.

    2016-07-09

    The Dual Coolant Lead Lithium (DCLL: eutectic Pb–17Li and He) blanket concept requires improved Pb–17Li compatibility with ferritic steels in order to demonstrate acceptable performance in fusion reactors. As an initial step, static Pb-17at.%Li (Pb-17Li) capsule experiments were conducted on new oxide dispersion strengthened (ODS) FeCrAl alloys ((1) Y2O3 (125Y), (2) Y2O3+ZrO2 (125YZ), (3) Y2O3+HfO2 (125YH), and (4) Y2O3+TiO2 (125YT)) produced at ORNL via mechanical alloying (MA). Tests were conducted in static Pb–17Li for 1000 h at 700°C. Alloys showed promising compatibility with Pb–17Li with small mass change after testing for 125YZ, 125YH and 125YT, while the 125Y alloy experienced the highest mass loss associated with some oxide spallation and subsequent alloy dissolution. X-ray diffraction methods identified the surface reaction product as LiAlO2 on all four alloys. A small decrease (~1 at.%) in Al content beneath the oxide scale was observed in all 4 ODS alloys, which extended through 60 μm beneath the oxide/metal interface. This indicates improvements in alloy dissolution by decreasing the amount of Al loss from the alloy. Scales formed on 125YZ, 125YH and 125YT were examined via scanning transmission electron microscopy (S/TEM) and revealed incorporation of Zr-, Hf-, and Ti-rich precipitates within the LiAlO2 product, respectively. This indicates an inward scale growth mechanism. Future work in flowing Pb–17Li is needed to further evaluate the effectiveness of this strategy in a test blanket module.

  6. Cold Sprayability of Mixed Commercial Purity Ti Plus Ti6Al4V Metal Powders

    NASA Astrophysics Data System (ADS)

    Aydin, Huseyin; Alomair, Mashael; Wong, Wilson; Vo, Phuong; Yue, Stephen

    2017-02-01

    In the present work, metallic composite coatings of commercial purity Ti plus Ti6Al4V were produced by cold spraying to explore the effect of mixing on porosity and mechanical properties of the coatings. The coatings were deposited using N2 gas at 800 °C and 4 MPa pressure on 1020 steel substrate. Coating characteristics were studied by examining porosity percentages and Vickers's hardness. The microstructure was examined using optical and electron microscopy techniques. It was observed that mixing metal powders can lead to improvements in cold sprayability, specifically decreases in the porosity of the `matrix' powder. It is shown that a critical addition can significantly influence porosity, but above this critical level, there is a little change in porosity. Hardness differences between the two powders are considered to be the first-order influence, but differences in particle sizes and morphology may also be contributing factors.

  7. Uranium and minor-element partitioning in Fe-Ti oxides and zircon from partially melted granodiorite, Crater Lake, Oregon

    SciTech Connect

    La Tourrette, T.Z.; Burnett, D.S. ); Bacon C.R. )

    1991-02-01

    Crystal-liquid partitioning in Fe-Ti oxides and zircon was studied in partially melted granodiorite blocks ejected during the climactic eruption of Mt. Mazama (Crater Lake), Oregon. The blocks, which contain up to 33% rhyolite glass (75 wt% SiO{sub 2}), are interpreted to be portions of the magma chamber walls that were torn off during eruption. The glass is clear and well homogenized for all measured elements except Zr. Results for Fe-Ti oxides give D{sub U}{sup oxide/liq} {approx} 0.1. Partitioning of Mg, Mn, Al, Si, V, and Cr in Fe-Ti oxides indicates that grains surrounded by glass are modestly well equilibrated with the melt for many of the minor elements, while those that are inclusions in relict plagioclase are not. Uranium and ytterbium inhomogeneities in zircons indicate that the zircons have only partially equilibrated with the melt and that uranium appears to have been diffusing out of the zircons have only partially equilibrated with the melt and that uranium appears to have been diffusing out of the zircons faster that the zircons were dissolving. Based on the authors measurements and given their low abundances in most rocks, Fe-Ti oxides probably do not play a major role in U-Th fractional during partial melting. The partial melts were undersaturated with zircon and apatite, but both phases are present in the authors samples. This demonstrates an actual case of nonequilibrium source retention of accessory phases, which in general could be an important trace element fractionation mechanism. Their results do not support the hypothesis that liquid structure is the dominant factor controlling trace-element partitioning in high-silica rhyolites.

  8. Uranium and minor-element partitioning in Fe-Ti oxides and zircon from partially melted granodiorite, Crater Lake, Oregon

    USGS Publications Warehouse

    Tourrette, T.Z.L.; Burnett, D.S.; Bacon, C.R.

    1991-01-01

    Crystal-liquid partitioning in Fe-Ti oxides and zircon was studied in partially melted granodiorite blocks ejected during the climactic eruption of Mt. Mazama (Crater Lake), Oregon. The blocks, which contain up to 33% rhyolite glass (75 wt% SiO2), are interpreted to be portions of the magma chamber walls that were torn off during eruption. The glass is clear and well homogenized for all measured elements except Zr. Results for Fe-Ti oxides give DUoxide/liq ??? 0.1. Partitioning of Mg, Mn, Al, Si, V, and Cr in Fe-Ti oxides indicates that grains surrounded by glass are moderately well equilibrated with the melt for many of the minor elements, while those that are inclusions in relict plagioclase are not. Uranium and ytterbium inhomogeneities in zircons indicate that the zircons have only partially equilibrated with the melt and that uranium appears to have been diffusing out of the zircons faster than the zircons were dissolving. Minimum U, Y, and P concentrations in zircons give maximum DUzrc/liq = 13,DYzrc/liq = 23, and DPzrc/liq = 1, but these are considerably lower than reported by other workers for U and Y. Based on our measurements and given their low abundances in most rocks, Fe-Ti oxides probably do not play a major role in U-Th fractionation during partial melting. The partial melts were undersaturated with zircon and apatite, but both phases are present in our samples. This demonstrates an actual case of non-equilibrium source retention of accessory phases, which in general could be an important trace-element fractionation mechanism. Our results do not support the hypothesis that liquid structure is the dominant factor controlling trace-element partitioning in high-silica rhyolites. Rough calculations based on Zr gradients in the glass indicate that the samples could have been partially molten for 800 to 8000 years. ?? 1991.

  9. Mechanical Properties and High Temperature Oxidation Behavior of Ti-Al Coating Reinforced by Nitrides on Ti-6Al-4V Alloy

    NASA Astrophysics Data System (ADS)

    Dai, Jingjie; Yu, Huijun; Zhu, Jiyun; Weng, Fei; Chen, Chuanzhong

    2016-05-01

    Ti-Al alloyed coating reinforced by nitrides was fabricated by laser surface alloying technique to improve mechanical properties and high temperature oxidation resistance of Ti-6Al-4V titanium alloy. Microstructures, mechanical properties and high temperature oxidation behavior of the alloyed coating were analyzed. The results show that the alloyed coating consisted of Ti3Al, TiAl2, TiN and Ti2AlN phases. Nitrides with different morphologies were dispersed in the alloyed coating. The maximum microhardness of the alloyed coating was 906HV. The friction coefficients of the alloyed coating at room temperature and high temperature were both one-fourth of the substrate. Mass gain of the alloyed coating oxidized at 800∘C for 1000h in static air was 5.16×10-3mg/mm2, which was 1/35th of the substrate. No obvious spallation was observed for the alloyed coating after oxidation. The alloyed coating exhibited excellent mechanical properties and long-term high temperature oxidation resistance, which improved surface properties of Ti-6Al-4V titanium alloy significantly.

  10. Applying the Fe(III) binding property of a chemical transferrin mimetic to Ti(IV) anticancer drug design.

    PubMed

    Parks, Timothy B; Cruz, Yahaira M; Tinoco, Arthur D

    2014-02-03

    As an endogenous serum protein binder of Ti(IV), transferrin (Tf) serves as an excellent vehicle to stabilize the hydrolysis prone metal ion and successfully transport it into cells. This transporting role is thought to be central to Ti(IV)'s anticancer function, but efforts to synthesize Ti(IV) compounds targeting transferrin have not produced a drug. Nonetheless, the Ti(IV) transferrin complex (Ti2Tf) greatly informs on a new Ti(IV)-based anticancer drug design strategy. Ti2Tf interferes with cellular uptake of Fe(III), which is particularly detrimental to cancer cells because of their higher requirement for iron. Ti(IV) compounds of chemical transferrin mimetic (cTfm) ligands were designed to facilitate Ti(IV) activity by attenuating Fe(III) intracellular levels. In having a higher affinity for Fe(III) than Ti(IV), these ligands feature the appropriate balance between stability and lability to effectively transport Ti(IV) into cancer cells, release Ti(IV) via displacement by Fe(III), and deplete the intracellular Fe(III) levels. The cTfm ligand N,N'-di(o-hydroxybenzyl)ethylenediamine-N,N'-diacetic acid (HBED) was selected to explore the feasibility of the design strategy. Kinetic studies on the Fe(III) displacement process revealed that Ti(IV) can be transported and released into cells by HBED on a physiologically relevant time scale. Cell viability studies using A549 cancerous and MRC5 normal human lung cells and testing the cytotoxicity of HBED and its Ti(IV), Fe(III), and Ga(III) compounds demonstrate the importance of Fe(III) depletion in the proposed drug design strategy and the specificity of the strategy for Ti(IV) activity. The readily derivatized cTfm ligands demonstrate great promise for improved Ti(IV) anticancer drugs.

  11. Microstructures and Properties of Ti-Coated SiCp Reinforced Al-Si Alloy Composites

    NASA Astrophysics Data System (ADS)

    Feng, Yan; Ren, Junpeng; Dong, Cuige; Wang, Richu

    2016-12-01

    A double-layer structure of Ti coating was plated on the surface of SiC particles using a diffusion method in a vacuum reactor, which is a new method to fabricate a Ti-coating layer on the SiC particles. The phase structure of Ti coating on the surface of SiC particles was composed inside of Ti5Si3 and outside of TiC investigated by x-ray diffraction. The Ti5Si3 and TiC double-layer structure realizes the tight chemical bonding between SiC particles and the Ti coating, and significantly promotes the wettability between the aluminum matrix and the Ti-coated SiC particles. The Ti-coated SiCp-reinforced Al-Si composites are prepared by a powder metallurgy method, and express excellent relative densities, desirable mechanical properties and frictional wear resistance.

  12. Interface behavior of Al2O3/Ti joints produced by liquid state bonding.

    PubMed

    Lemus-Ruiz, J; Guevara-Laureano, A O; Zarate-Medina, J; Arellano-Lara, A; Ceja-Cárdenas, L

    2015-04-01

    In this work we study brazing of Al2O3 to Ti with biocompatibility properties, using a Au-foil as joining element. Al2O3 was produced by sintering of powder at 1550°C. Al2O3 samples were coated with a 2 and 4μm thick of Mo layer and then stacked with Ti. Al2O3-Mo/Au/Ti combinations were joined at 1100°C in vacuum. Successful joining of Mo-Al2O3 to Ti was observed. Interface shows the formation of a homogeneous diffusion zone. Mo diffused inside Au forming a concentration line. Ti3Au and TiAu phases were observed.

  13. Phase Separation kinetics in an Fe-Cr-Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Chao, J.

    2012-01-01

    The {alpha}-{alpha}{prime} phase separation kinetics in a commercial Fe-20 wt.% Cr-6 wt.% Al oxide dispersion-strengthened PM 2000{trademark} steel have been characterized with the complementary techniques atom probe tomography and thermoelectric power measurements during isothermal aging at 673, 708, and 748 K for times up to 3600 h. A progressive decrease in the Al content of the Cr-rich {alpha}{prime} phase was observed at 708 and 748 K with increasing time, but no partitioning was observed at 673 K. The variation in the volume fraction of the {alpha}{prime} phase well inside the coarsening regime, along with the Avrami exponent 1.2 and activation energy 264 kJ mol{sup -1}, obtained after fitting the experimental results to an Austin-Rickett type equation, indicates that phase separation in PM 2000{trademark} is a transient coarsening process with overlapping nucleation, growth, and coarsening stages.

  14. Formation of layered Fe(II)-Al(III)-hydroxides during reaction of Fe(II) with aluminum oxide.

    PubMed

    Elzinga, Evert J

    2012-05-01

    The reactivity of aqueous Fe(II) with aluminum oxide in anoxic solutions was investigated with batch kinetic experiments combined with Fe K edge X-ray absorption spectroscopy measurements to characterize Fe(II) sorption products. Formation of Fe(II)-Al(III)-layered double hydroxides with an octahedral sheet structure similar to nikischerite (NaFe(II)(6) Al(3)(SO(4))(2)(OH)(18) (H(2)O)(12)) was observed within a few hours during sorption at pH 7.5 and aqueous Fe(II) concentrations of 1-3 mM. These Fe(II) phases are composed of brucite-like Fe(II)(OH)(2) sheets with partial substitution of Al(III) for Fe(II), charge balanced by anions coordinated along the basal planes. Their fast rate of formation suggests that these previously unrecognized Fe(II) phases, which are structurally and compositionally similar to green rust, may be an important sink of Fe(II) in suboxic and anoxic geochemical environments, and impact the fate of structurally compatible trace metals, such as Co(II), Ni(II), and Zn(II), as well as redox-reactive species including Cr(VI) and U(VI). Further studies are required to assess the thermodynamics, formation kinetics, and stability of these Fe(II) minerals under field conditions.

  15. Tribological and mechanical properties of Ti/TiAlN/TiAlCN nanoscale multilayer PVD coatings deposited on AISI H11 hot work tool steel

    NASA Astrophysics Data System (ADS)

    AL-Bukhaiti, M. A.; Al-hatab, K. A.; Tillmann, W.; Hoffmann, F.; Sprute, T.

    2014-11-01

    A new [Ti/TiAlN/TiAlCN]5 multilayer coatings were deposited onto polished substrate AISI H11 (DIN 1.2343) steel by an industrial magnetron sputtering device. The tribological performance of the coated system was investigated by a ball-on-disk tribometer against 100Cr6 steel and Al2O3 balls. The friction coefficients and specific wear rates were measured at various normal loads (2, 5, 8, and 10 N) and sliding velocities (0.2, 0.4, and 0.8 m/s) in ambient air and dry conditions. The phase structure, composition, wear tracks morphologies, hardness, and film/substrate adhesion of the coatings were characterized by light-microscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), 3D-surface analyzer, nanoindentation, and scratch tests. Results showed that the deposited coatings showed low wear rates in the scale of 10-15 m3/N m, low friction coefficients against 100Cr6 and Al2O3 balls in the range of 0.25-0.37, and good hardness in the range of 17-20 GPa. Results also revealed that the friction coefficients and disc wear rates decrease and increase, respectively with the increase in normal load and sliding velocity for both coating/Al2O3 and coating/100Cr6 sliding system. Compared with the uncoated-H11 substrate, the deposited coating exhibited superior tribological and mechanical properties. The dominant wear mechanism was abrasive wear for coating/Al2O3 pair, while for coating/100Cr6 pair, a combination of mild adhesive wear, severe adhesive wear, and abrasive wear (extensive plowing) were the dominant wear mechanisms at different applied normal loads.

  16. Importance of doping and frustration in itinerant Fe-doped Cr2Al

    DOE PAGES

    Susner, M. A.; Parker, D. S.; Sefat, A. S.

    2015-05-12

    We performed an experimental and theoretical study comparing the effects of Fe-doping of Cr2Al, an antiferromagnet with a N el temperature of 670 K, with known results on Fe-doping of antiferromagnetic bcc Cr. (Cr1-xFex)2Al materials are found to exhibit a rapid suppression of antiferromagnetic order with the presence of Fe, decreasing TN to 170 K for x=0.10. Antiferromagnetic behavior disappears entirely at x≈0.125 after which point increasing paramagnetic behavior is exhibited. Moreover, this is unlike the effects of Fe doping of bcc antiferromagnetic Cr, in which TN gradually decreases followed by the appearance of a ferromagnetic state. Theoretical calculations explainmore » that the Cr2Al-Fe suppression of magnetic order originates from two effects: the first is band narrowing caused by doping of additional electrons from Fe substitution that weakens itinerant magnetism; the second is magnetic frustration of the Cr itinerant moments in Fe-substituted Cr2Al. In pure-phase Cr2Al, the Cr moments have an antiparallel alignment; however, these are destroyed through Fe substitution and the preference of Fe for parallel alignment with Cr. This is unlike bulk Fe-doped Cr alloys in which the Fe anti-aligns with the Cr atoms, and speaks to the importance of the Al atoms in the magnetic structure of Cr2Al and Fe-doped Cr2Al.« less

  17. Enhanced Water Splitting by Fe2O3-TiO2-FTO Photoanode with Modified Energy Band Structure

    PubMed Central

    Noh, Eul; Noh, Kyung-Jong; Yun, Kang-Seop; Kim, Bo-Ra; Jeong, Hee-June; Oh, Hyo-Jin; Kang, Woo-Seung

    2013-01-01

    The effect of TiO2 layer applied to the conventional Fe2O3/FTO photoanode to improve the photoelectrochemical performance was assessed from the viewpoint of the microstructure and energy band structure. Regardless of the location of the TiO2 layer in the photoanodes, that is, Fe2O3/TiO2/FTO or TiO2/Fe2O3/FTO, high performance was obtained when α-Fe2O3 and H-TiNT/anatase-TiO2 phases existed in the constituent Fe2O3 and TiO2 layers after optimized heat treatments. The presence of the Fe2O3 nanoparticles with high uniformity in the each layer of the Fe2O3/TiO2/FTO photoanode achieved by a simple dipping process seemed to positively affect the performance improvement by modifying the energy band structure to a more favorable one for efficient electrons transfer. Our current study suggests that the application of the TiO2 interlayer, together with α-Fe2O3 nanoparticles present in the each constituent layers, could significantly contribute to the performance improvement of the conventional Fe2O3 photoanode. PMID:24501585

  18. Microstructure/Oxidation/Microhardness Correlations in Gamma-Based and Tau-Based Al-Ti-Cr Alloys

    NASA Technical Reports Server (NTRS)

    Brady, Michael P.; Smialek, J. L.; Humphrey, D. L.

    1994-01-01

    The relationships between alloy microstructure and air oxidation kinetics and alloy microstructure and microhardness in the Al-Ti-Cr system for exposures at 800 C and 1000 C were investigated. The relevant phases were identified as tau (Ll2), gamma (LIO), r-Al2Ti, TiCrAl (laves), and Cr2AI. Protective alumina formation was associated with tau, Al-rich TiCrAl, and gamma/TiCrAl mixtures. Brittleness was associated with the TiCrAl phase and tau decomposition to A12Ti + Cr2AI. It was concluded that two-phase gamma + TiCrAl alloys offer the greatest potential for oxidation resistance and room temperature ductility in the Al-Ti-Cr system.

  19. Sol-gel synthesis of mesoporous mixed Fe2O3/TiO2 photocatalyst: application for degradation of 4-chlorophenol.

    PubMed

    Palanisamy, B; Babu, C M; Sundaravel, B; Anandan, S; Murugesan, V

    2013-05-15

    Photosensitization of TiO2 with other transition metal oxides can extend its light absorption property in the visible region. Such materials could emerge as excellent catalysts for solar photocatalytic degradation. In the present study mesoporous Fe2O3/TiO2 (10, 30, 50, 70 and 90 wt% Fe2O3) photocatalysts were synthesized by sol-gel process and characterized using different techniques. The XRD patterns exhibited the presence of mesoporous structure and isomorphic substitution of Fe(3+) in TiO2 at low Fe(3+) loading and Ti(4+) in Fe2O3 at high Fe(3+) loading. The XPS results revealed the presence of Ti(4+) and Fe(3+) in Fe2O3/TiO2 materials. The DRS UV-vis spectra showed a shift in the band gap excitation of TiO2 to longer wavelength, thus illustrating incorporation of Fe(3+) in TiO2. In addition, free TiO2 and Fe2O3 particles were also present. Their photocatalytic activity was tested for the degradation of 4-chlorophenol in aqueous medium using sunlight. The activity of the catalysts followed the order: meso-30 wt% Fe2O3/TiO2>meso-10 wt% Fe2O3/TiO2>meso-50 wt% Fe2O3/TiO2>meso-70 Fe2O3/TiO2>meso-90 wt% Fe2O3/TiO2>meso-Fe2O3>meso-TiO2. This order concluded that mesoporous Fe2O3/TiO2 could be an active catalyst for pollutant degradation, as TiO2 with framework Fe(3+) and photosensitization with free Fe2O3 were involved in the activity.

  20. Weldability of Fe[sub 3]Al-type Aluminide

    SciTech Connect

    David, S.A.; Zacharia, T. )

    1993-05-01

    An investigation was carried out to determine the weldability of a series of Fe[sub 3]Al-type alloys. Autogenous welds were made on thin sheets of iron aluminide alloys using gas tungsten arc (GTA) and electron beam (EB) welding processes at different travel speeds and power levels. The results indicate that although these alloys can be successfully welded using the EB welding process, some compositions may hot crack during GTA welding. Boron and zirconium additions have been found to promote hot cracking in these alloys. Among the alloys investigated, Fe[sub 3]Al modified with chromium, niobium and carbon (FA-129) showed the most promise for good weldability. Hot-cracking severity of this alloy was further investigated using the Sigmajig test. The minimum threshold stress of 25 ksi measured is within the material range of other aluminides and some commercial stainless steels. Also, some of these alloys exhibited a tendency for cold cracking. This is related to severe hydrogen embrittlement associated with this class of alloys.

  1. Al, Ti, and Cr: Complex Zoning in Synthetic and Natural Nakhlite Pyroxenes

    NASA Technical Reports Server (NTRS)

    McKay, G.; Le, L.; Mikouchi, T.

    2007-01-01

    Nakhlites are olivine-bearing clinopyroxene cumulates. The cumulus pyroxenes have cores that are relatively homogeneous in Fe, Mg, and Ca, but show complex zoning of minor elements, especially Al, Ti, and Cr. Zoning patterns contain information about crystallization history parent magma compositions. But it has proven difficult to decipher this information and translate the zoning patterns into petrogenetic processes. This abstract reports results of high-precision Electron Probe MicroAnalysis (EPMA) analysis of synthetic nakhlite pyroxenes run at fO2 from IW to QFM. It compares these with concurrent analyses of natural nakhlite MIL03346 (MIL), and with standardprecision analyses of Y000593 (Y593) collected earlier. Results suggest that (1) different processes are responsible for the zoning of MIL and other more slowly-cooled nakhlites such as Y593, and (2) changes in oxidation conditions during MIL crystallization are not responsible for the unusual Cr zoning pattern

  2. Thickness dependent activity of nanostructured TiO 2/α-Fe 2O 3 photocatalyst thin films

    NASA Astrophysics Data System (ADS)

    Akhavan, O.

    2010-12-01

    The effect of thickness of TiO 2 coating on synergistic photocatalytic activity of TiO 2 (anatase)/α-Fe 2O 3/glass thin films as photocatalysts for degradation of Escherichia coli bacteria in a low-concentration H 2O 2 solution and under visible light irradiation was investigated. Nanograined α-Fe 2O 3 films with optical band-gap of 2.06 eV were fabricated by post-annealing of thermal evaporated iron oxide thin films at 400 °C in air. Increase in thickness of the Fe 2O 3 thin film (here, up to 200 nm) resulted in a slight reduction of the optical band-gap energy and an increase in the photoinactivation of the bacteria. Sol-gel TiO 2 coatings were deposited on the α-Fe 2O 3 (200 nm)/glass films, and then, they were annealed at 400 °C in air for crystallization of the TiO 2 and formation of TiO 2/Fe 2O 3 heterojunction. For the TiO 2 coatings with thicknesses ≤50 nm, the antibacterial activity of the TiO 2/α-Fe 2O 3 (200 nm) was found to be better than the activity of the bare α-Fe 2O 3 film. The optimum thickness of the TiO 2 coating was found to be 10 nm, resulting in about 70 and 250% improvement in visible light photo-induced antibacterial activity of the TiO 2/α-Fe 2O 3 thin film as compared to the corresponding activity of the bare α-Fe 2O 3 and TiO 2 thin films, respectively. The improvement in the photoinactivation of bacteria on surface of TiO 2/α-Fe 2O 3 was assigned to formation of Ti-O-Fe bond at the interface.

  3. Characteristics and Machining Performance of TiN and TiAlN Coatings on a Milling Cutter

    NASA Astrophysics Data System (ADS)

    Sarwar, Mohammed; Haider, Julfikar

    2011-01-01

    Titanium Nitride (TiN) coating deposited by Physical Vapour Deposition (PVD) or Chemical Vapour Deposition (CVD) techniques on cutting tools (single point or multipoint) has contributed towards the improvement of tool life, productivity and product quality [1]. Addition of Al in TiN coating (e.g., TiAlN or AlTiN) has further improved the coating properties required for machining applications [2, 3]. This work presents a comparative investigation on TiN and TiAlN coatings deposited on to a Powder Metallurgy High Speed Steel (PM HSS) milling cutter used for machining bimetal (M42+D6A) steel strips. PVD (Arc evaporation) technique was used to deposit the coatings after carefully preparing the cutting edges of the milling cutter. Microstructure, chemical composition, hardness and adhesion of the coatings have been characterised using different techniques. The incorporation of Al into TiN coating results in an improvement in hardness, wear resistance and cutting performance. Examination of the worn flank in the coated cutting edges revealed that abrasive and adhesive wear are the predominant failure mechanisms. Tool designers, coating suppliers and manufacturing engineers could benefit from the information provided.

  4. Osteoblastic behavior to zirconium coating on Ti-6Al-4V alloy

    PubMed Central

    Lee, Bo-Ah; Kim, Hae-Jin; Xuan, Yun-Ze; Park, Yeong-Joon; Chung, Hyun-Ju

    2014-01-01

    PURPOSE The purpose of this study was to assess the surface characteristics and the biocompatibility of zirconium (Zr) coating on Ti-6Al-4V alloy surface by radio frequency (RF) magnetron sputtering method. MATERIALS AND METHODS The zirconium films were developed on Ti-6Al-4V discs using RF magnetron sputtering method. Surface profile, surface composition, surface roughness and surface energy were evaluated. Electrochemical test was performed to evaluate the corrosion behavior. Cell proliferation, alkaline phosphatase (ALP) activity and gene expression of mineralized matrix markers were measured. RESULTS SEM and EDS analysis showed that zirconium deposition was performed successfully on Ti-6Al-4V alloy substrate. Ti-6Al-4V group and Zr-coating group showed no significant difference in surface roughness (P>.05). Surface energy was significantly higher in Zr-coating group than in Ti-6Al-4V group (P<.05). No difference in cell morphology was observed between Ti-6Al-4V group and Zr-coating group. Cell proliferation was higher in Zr-coating group than Ti-6Al-4V group at 1, 3 and 5 days (P<.05). Zr-coating group showed higher ALP activity level than Ti-6Al-4V group (P<.05). The mRNA expressions of bone sialoprotein (BSP) and osteocalcin (OCN) on Zr-coating group increased approximately 1.2-fold and 2.1-fold respectively, compared to that of Ti-6Al-4V group. CONCLUSION These results suggest that zirconium coating on Ti-6Al-4V alloy could enhance the early osteoblast responses. This property could make non-toxic metal coatings on Ti-6Al-4V alloy suitable for orthopedic and dental implants. PMID:25551012

  5. Optical and electrical properties of polycrystalline and amorphous Al-Ti thin films

    NASA Astrophysics Data System (ADS)

    Canulescu, S.; Borca, C. N.; Rechendorff, K.; Davidsdóttir, S.; Pagh Almtoft, K.; Nielsen, L. P.; Schou, J.

    2016-04-01

    The structural, optical, and transport properties of sputter-deposited Al-Ti thin films have been investigated as a function of Ti alloying with a concentration ranging from 2% to 46%. The optical reflectivity of Al-Ti films at visible and near-infrared wavelengths decreases with increasing Ti content. X-ray absorption fine structure measurements reveal that the atomic ordering around Ti atoms increases with increasing Ti content up to 20% and then decreases as a result of a transition from a polycrystalline to amorphous structure. The transport properties of the Al-Ti films are influenced by electron scattering at the grain boundaries in the case of polycrystalline films and static defects, such as anti-site effects and vacancies in the case of the amorphous alloys. The combination of Ti having a real refractive index (n) comparable with the extinction coefficient (k) and Al with n much smaller than k allows us to explore the parameter space for the free-electron behavior in transition metal-Al alloys. The free electron model, applied for the polycrystalline Al-Ti films with Ti content up to 20%, leads to an optical reflectance at near infrared wavelengths that scales linearly with the square root of the electrical resistivity.

  6. Substrate and band bending effects on monolayer FeSe on SrTiO3(001).

    PubMed

    Xu, Meiling; Song, Xianqi; Wang, Hui

    2017-03-15

    Motivated by the high superconducting transition temperature (TC) shown by monolayer FeSe on cubic perovskite SrTiO3(001) and SrTiO3(001)-2×1 reconstructed surfaces, in this study, we explore the atomic and electronic structures of monolayer FeSe on various SrTiO3(001)-2×1 surface reconstructions using the CALYPSO method and first-principles calculations. Our search reveals two new Ti2O2 and Ti2O reconstructed surface structures, besides the Ti2O3 and double TiO2 layer reconstructed surfaces, and the two new Ti2O2 and Ti2O reconstructed surface structures are more stable under Ti-rich conditions than under Ti-poor conditions. The Fermi-surface topology of an FeSe monolayer on Ti2O3- and Ti2O2-type reconstructed STO surfaces is different from that of an FeSe monolayer on a Ti2O-type STO reconstructed surface. The established structure of monolayer FeSe on a Ti2O-type STO(001) reconstructed surface can naturally explain the experimental observation of the electronic band structure on the monolayer FeSe superconductor and obtained electrons counting per Fe atom. Surface states in the mid-gap induced by various STO surface reconstructions will result in band bending. The surface-state-induced band bending is also responsible for the electron transfer from the STO substrate to the FeSe films.

  7. Photocatalytic performance of Fe-doped TiO2 nanoparticles under visible-light irradiation

    NASA Astrophysics Data System (ADS)

    Ali, T.; Tripathi, P.; Azam, Ameer; Raza, Waseem; Ahmed, Arham S.; Ahmed, Ateeq; Muneer, M.

    2017-01-01

    The present work focuses on the synthesis, characterization and photocatalytic activity of a nanosized Fe-doped TiO2 photocatalyst. The samples were synthesized by the sol–gel method and characterized by using techniques such as x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDS), UV–visible spectroscopy, photoluminescence (PL) spectroscopy, Raman spectroscopy and Fourier-transform infrared (FTIR). The powder XRD spectra revealed that the synthesized samples are pure and crystalline in nature and show a tetragonal anatase phase of TiO2. The Raman spectroscopy also confirmed the formation of an anatase phase structure in both pure and Fe-doped TiO2 nanoparticles (NPs). The UV–visible and PL spectra illustrated the red shift in Fe-doped TiO2 NPs. The FTIR spectra indicated the vibrational band of the Ti–O lattice. The photocatalytic experimental results demonstrate that Fe-doped TiO2 NPs effectively degrade MB under visible-light illumination. Interestingly, the prepared TiO2 NPs with a dopant concentration of 3.0 mole% showed the maximum photocatalytic activity under investigation.

  8. Investigation of Ti-6Al-4V alloy acoustic softening.

    PubMed

    Fartashvand, V; Abdullah, A; Sadough Vanini, S A

    2016-07-15

    High power ultrasonic vibration is widely used for improving manufacturing processes such as machining and metal forming. High frequency mechanical vibration affects material properties and friction forces in contacting surfaces. Flow stress reduction under superimposed ultrasonic vibration is called as acoustic softening. The amount of this parameter should be determined for ultrasonic assisted metal forming processes. For determination of this parameter for workhorse Ti-6Al-4V alloy, experimental setup was designed and fabricated. Then tensile test under longitudinal ultrasonic vibration was performed for different ultrasonic powers. Results show that ultrasonic vibration has considerable effect on plastic behavior of the alloy and decreases flow stress. Also, increasing ultrasonic power leads to higher acoustic softening. Yield stress reduction up to 9.52%, ultimate stress reduction up to 4.55% and elongation up to 13% were obtained at 340W ultrasonic power. After applying ultrasonic vibrations and its termination, hardness of specimens were measured in which increase up to 9% was observed.

  9. Evaluation of ARCAM Deposited Ti-6Al-4V

    NASA Technical Reports Server (NTRS)

    Slattery, Kevin; Slaughter, Blake; Speorl, Emily; Good, James; Gilley, Scott; McLemore, Carole

    2008-01-01

    A wide range of Metal Additive Manufacturing (MAM) technologies are becoming available. One of the challenges in using new technologies for aerospace systems is demonstrating that the process and system has the ability to manufacture components that meet the high quality requirements on a statistically significant basis. The widest-used system for small to medium sized components is the ARCAM system manufactured in Gothenburg, Sweden. This system features a 4kW electron-beam gun, and has a chamber volume of 250mm long x 250mm wide x 250mm to 400mm tall. This paper will describe the basis for the quality and consistency requirements, the experimental and evaluation procedures used for the evaluation, and an analysis of the results for Ti-6Al-4V.

  10. Synthesis and Characterization of Photocatalytic TiO 2 -ZnFe 2 O 4 Nanoparticles

    DOE PAGES

    Srinivasan, Sesha S.; Wade, Jeremy; Stefanakos, Elias K.

    2006-01-01

    A new coprecipimore » tation/hydrolysis synthesis route is used to create a TiO 2 -ZnFe 2 O 4 nanocomposite that is directed towards extending the photoresponse of TiO 2 from UV to visible wavelengths ( > 400   nm ). The effect of TiO 2 's accelerated anatase-rutile phase transformation due to the presence of the coupled ZnFe 2 O 4 narrow-bandgap semiconductor is evaluated. The transformation's dependence on pH, calcinations temperature, particle size, and ZnFe 2 O 4 concentration has been analyzed using XRD, SEM, and UV-visible spectrometry. The requirements for retaining the highly photoactive anatase phase present in a ZnFe 2 O 4 nanocomposite are outlined. The visible-light-activated photocatalytic activity of the TiO 2 -ZnFe 2 O 4 nanocomposites has been compared to an Aldrich TiO 2 reference catalyst, using a solar-simulated photoreactor for the degradation of phenol.« less

  11. Mechanical Properties of the TiAl IRIS Alloy

    NASA Astrophysics Data System (ADS)

    Voisin, Thomas; Monchoux, Jean-Philippe; Thomas, Marc; Deshayes, Christophe; Couret, Alain

    2016-12-01

    This paper presents a study of the mechanical properties at room and high temperature of the boron and tungsten containing IRIS alloy (Ti-48Al-2W-0.08B at. pct). This alloy was densified by Spark Plasma Sintering (SPS). The resultant microstructure consists of small lamellar colonies surrounded by γ regions containing B2 precipitates. Tensile tests are performed from room temperature to 1273 K (1000 °C). Creep properties are determined at 973 K (700 °C)/300 MPa, 1023 K (750 °C)/120 MPa, and 1023 K (750 °C)/200 MPa. The tensile strength and the creep resistance at high temperature are found to be very high compared to the data reported in the current literature while a plastic elongation of 1.6 pct is preserved at room temperature. A grain size dependence of both ductility and strength is highlighted at room temperature. The deformation mechanisms are studied by post-mortem analyses on deformed samples and by in situ straining experiments, both performed in a transmission electron microscope. In particular, a low mobility of non-screw segments of dislocations at room temperature and the activation of a mixed-climb mechanism during creep have been identified. The mechanical properties of this IRIS alloy processed by SPS are compared to those of other TiAl alloys developed for high-temperature structural applications as well as to those of similar tungsten containing alloys obtained by more conventional processing techniques. Finally, the relationships between mechanical properties and microstructural features together with the elementary deformation mechanisms are discussed.

  12. Interfacial reaction of intermetallic compounds of ultrasonic-assisted brazed joints between dissimilar alloys of Ti6Al4V and Al4Cu1Mg.

    PubMed

    Ma, Zhipeng; Zhao, Weiwei; Yan, Jiuchun; Li, Dacheng

    2011-09-01

    Ultrasonic-assisted brazing of Al4Cu1Mg and Ti6Al4V using Zn-based filler metal (without and with Si) has been investigated. Before brazing, the Ti6Al4V samples were pre-treated by hot-dip aluminizing and ultrasonic dipping in a molten filler metal bath in order to control the formation of intermetallic compounds between the Ti6Al4V samples and the filler metal. The results show that the TiAl(3) phase was formed in the interface between the Ti6Al4V substrate and the aluminized coating. For the Zn-based filler metal without Si, the Ti6Al4V interfacial area of the brazed joint did not change under the effect of the ultrasonic wave, and only consisted of the TiAl(3) phase. For the Zn-based filler metal with Si, the TiAl(3) phase disappeared and a Ti(7)Al(5)Si(12) phase was formed at the interfacial area of the brazed joints under the effect of the ultrasonic wave. Due to the TiAl(3) phase completely changing to a Ti(7)Al(5)Si(12) phase, the morphology of the intermetallic compounds changed from a block-like shape into a lamellar-like structure. The highest shear strength of 138MPa was obtained from the brazed joint free of the block-like TiAl(3) phase.

  13. Enhanced photocatalytic inactivation of bacteria on Fe-containing TiO2 nanoparticles under fluorescent light.

    PubMed

    Yadav, Hemraj M; Kolekar, Tanaji V; Pawar, Shivaji H; Kim, Jung-Sik

    2016-03-01

    In this paper, the photocatalytic activity of Fe-TiO2 nanoparticles (NPs) under fluorescent light was studied using Escherichia coli and Staphylococcus aureus. Fe-TiO2 NPs were synthesized using a sol-gel method and characterized with X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), UV-visible diffuse reflectance spectroscopy (UV-vis DRS) and transmission electron microscopy. The efficiency of photocatalytic inactivation towards E. coli was studied under different physicochemical parameters. The photocatalytic inactivation rate increased with increasing Fe content in TiO2 NPs and the highest inactivation was achieved for 3.0 mol% Fe-TiO2 NPs under fluorescent light. These results demonstrate that the presence of an optimum concentration of Fe in TiO2 matrix enhances the photocatalytic inactivation of TiO2 NPs under fluorescent light.

  14. Characterization of La/Fe/TiO2 and Its Photocatalytic Performance in Ammonia Nitrogen Wastewater

    PubMed Central

    Luo, Xianping; Chen, Chunfei; Yang, Jing; Wang, Junyu; Yan, Qun; Shi, Huquan; Wang, Chunying

    2015-01-01

    La/Fe/TiO2 composite photocatalysts were synthesized by Sol-Gel method and well characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen-physical adsorption, and UV-Vis diffuse reflectance spectra (UV-Vis DRS). It is interesting that the doped catalysts were in anatase phase while the pure TiO2 was in rutile phase. In addition, the composites possessed better physical chemical properties in photocatalytic activity than pure TiO2: stronger visible-light-response ability, larger specific surface area, and more regular shape in morphology. The photodegradation results of ammonia nitrogen indicate that: the La/Fe/TiO2 had higher catalytic activity to ammonia nitrogen waste water compared pure TiO2 and the other single metal-doped TiO2. pH 10 and 2 mmol/L H2O2 were all beneficial to the removal of ammonia nitrogen by La/Fe/TiO2. However, the common inorganic ions of Cl−, NO3−, SO42−, HCO3−/CO32−, Na+, K+, Ca2+ and Mg2+ in water all inhibited the degradation of ammonia nitrogen. By balance calculation, at least 20% of ammonia nitrogen was converted to N2 during the 64.6% removal efficiency of ammonia nitrogen. PMID:26593929

  15. Characterization of La/Fe/TiO₂ and Its Photocatalytic Performance in Ammonia Nitrogen Wastewater.

    PubMed

    Luo, Xianping; Chen, Chunfei; Yang, Jing; Wang, Junyu; Yan, Qun; Shi, Huquan; Wang, Chunying

    2015-11-17

    La/Fe/TiO₂ composite photocatalysts were synthesized by Sol-Gel method and well characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), nitrogen-physical adsorption, and UV-Vis diffuse reflectance spectra (UV-Vis DRS). It is interesting that the doped catalysts were in anatase phase while the pure TiO₂ was in rutile phase. In addition, the composites possessed better physical chemical properties in photocatalytic activity than pure TiO₂: stronger visible-light-response ability, larger specific surface area, and more regular shape in morphology. The photodegradation results of ammonia nitrogen indicate that: the La/Fe/TiO₂ had higher catalytic activity to ammonia nitrogen waste water compared pure TiO₂ and the other single metal-doped TiO₂. pH 10 and 2 mmol/L H₂O₂ were all beneficial to the removal of ammonia nitrogen by La/Fe/TiO₂. However, the common inorganic ions of Cl(-), NO₃(-), SO₄(2-), HCO₃(-)/CO₃²(-), Na⁺, K⁺, Ca(2+) and Mg(2+) in water all inhibited the degradation of ammonia nitrogen. By balance calculation, at least 20% of ammonia nitrogen was converted to N₂ during the 64.6% removal efficiency of ammonia nitrogen.

  16. Thermodynamically destabilized hydride formation in "bulk" Mg-AlTi multilayers for hydrogen storage.

    PubMed

    Kalisvaart, Peter; Shalchi-Amirkhiz, Babak; Zahiri, Ramin; Zahiri, Beniamin; Tan, XueHai; Danaie, Mohsen; Botton, Gianluigi; Mitlin, David

    2013-10-21

    Thermodynamic destabilization of MgH2 formation through interfacial interactions in free-standing Mg-AlTi multilayers of overall "bulk" (0.5 μm) dimensions with a hydrogen capacity of up to 5.5 wt% is demonstrated. The interfacial energies of Mg-AlTi and Mg-Ti (examined as a baseline) are calculated to be 0.81 and 0.44 J m(-2). The enhanced interfacial energy of AlTi opens the possibility of creating ultrathin alloy interlayers that provide further thermodynamic improvements in metal hydrides.

  17. Microstructural Observations in a Cast Al-Si-Cu/TiC Composite

    NASA Astrophysics Data System (ADS)

    Karantzalis, A. E.; Lekatou, A.; Georgatis, E.; Poulas, V.; Mavros, H.

    2010-06-01

    A 3-5 vol.% TiC particulate Al-Si-Cu composite was prepared by diluting Al/20 vol.% TiC composite in an Al-7Si-4Cu alloy matrix. TiC particle distribution consists of isolated and clustered particles which are both located at the primary-α grain boundaries and at the areas of the last solidified liquid. Particle pushing by the solidification front is responsible for the final particle location. The solidified microstructure consists of primary and intermetallic phases formed by a sequence of possible eutectic reactions. No evidence of TiC particle degradation was observed.

  18. Characterization and Formation of Rod-Shaped (Al,Si)3Ti Particles in an Al-7Si-0.35Mg-0.12Ti (Wt Pct) Alloy

    NASA Astrophysics Data System (ADS)

    Gao, Xiang; Zhu, Yuman; Easton, Mark A.; Rinderer, Barbara; Couper, Mal; Nie, Jian-Feng

    2015-08-01

    In this study, the rod-shaped particles in an Al-7Si-0.35Mg-0.12Ti (wt pct) casting alloy have been characterized using transmission electron microscopy. It is found that these particles invariably contain Ti, Al, and Si and that they have the structure of the equilibrium phase (Al,Si)3Ti. A near-rational orientation relationship is observed between the (Al,Si)3Ti particles and the α-Al matrix phase. For this orientation relationship, the long axes of the (Al,Si)3Ti rods are invariably parallel to the moiré planes defined by the intersection of closest-packed planes of the (Al,Si)3Ti and α-Al phases. In contrast to the (Al,Si)3Ti or Al3Ti particles form directly from the melt act as heterogeneous nucleation sites for aluminum grains and thus grain-refined Al-Si foundry alloys, the (Al,Si)3Ti particles are found to form during solution treatment at temperatures above 673 K (400 °C). Their formation occurs in the center of aluminum grains and/or dendrites which is Ti enriched due to partitioning during solidification. The low diffusivity of Ti in α-Al allows the particles to form in the Ti-enriched areas near the center of grains as the Ti concentration is not able to be homogenized during typical solution treatment times.

  19. Reduced toxicity and superior cellular response of preosteoblasts to Ti-6Al-7Nb alloy and comparison with Ti-6Al-4V.

    PubMed

    Challa, V S A; Mali, S; Misra, R D K

    2013-07-01

    There are serious concerns on the toxicity of vanadium in Ti-6Al-4V alloy. In this regard, we describe the biological footprint of Ti-6Al-4V and compare with a viable alternate Ti-6Al-7Nb alloy, in terms of novel experimentation pertaining to cellular activity that include qualitative and quantitative analysis of Feret's diameter of cells, area, and perimeter, and proteins-actin, vinculin, and fibronectin. Interestingly, Ti-6Al-7Nb was characterized by superior cell attachment, proliferation, viability, morphology, and spread, which were significantly different from Ti-6Al-4V alloy. Additionally, immunofluorescence studies demonstrated stronger vinculin signals associated with actin stress fibers in the outer regions of the cells and cellular extensions in Ti-6Al-7Nb alloy. These striking observations suggest enhanced cell-substrate interaction and activity on the surface of niobium-containing titanium alloy. The significant differences in the cellular response between the two alloys clearly point to the determining role of alloying element (Nb versus V) in a conclusive manner. Based on this study, next generation of titanium alloys is proposed to focus on niobium-containing alloy.

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

    SciTech Connect

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

    1997-02-01

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

  1. Brazing microstructure of Ti-6Al-6V-2Sn with Ti-Zr-Cu-Ni filler metal

    SciTech Connect

    Hsieh, K.C.; Kao, P.W.; Shu, M.F.

    1994-12-31

    Titanium and its alloys have been widely used in the aerospace industry since they have high specific strength and high corrosion resistance. The brazing of titanium is beneficial to join many contact areas simultaneously without severe distortion. The purpose of this study is to investigate the brazing microstructures under different brazing conditions with several Ti-Zr-Cu-Ni filler alloys. In our previous studies, the brazing microstructure of Ti-6Al-4V with Ti-Cu-Ni filler metal have been reported. Since Ti-6Al-6V-2Sn alloy has lower b-transus, the Ti-Cu-Ni filler alloy cannot successfully apply the brazing work. Several Ti-Zr-Cu-Ni alloys were prepared in powder form and pre-alloy form to perform the brazing of Ti-6Al-6V-2Sn at 870{degrees}C. The brazing microstructures are examined under optical metallograph, scanning electron microscopy (SEM), and X-ray analysis. The contents of this report include (1) DTA and phase analysis of Ti-Zr-Cu-Ni filler metals, (2) the brazing microstructure, and (3) the shear test result.

  2. The Effect of Ti on Microstructural Characteristics and Reaction Mechanism in Bonding of Al-Ceramic Composite

    NASA Astrophysics Data System (ADS)

    Juan, Li; Kehong, Wang; Deku, Zhang

    2016-09-01

    The effect of Ti on microstructural characteristics and reaction mechanism in bonding of Al-Ceramic composite was studied. Ti and Al-Ceramic composite were diffusion welded at 550, 600, 700, 800, and 900 °C in a vacuum furnace. The microstructures and compositions of the interface layers were analyzed, and the mechanical properties and fracture morphology of the joints were examined. The results indicated that there was a systematic switch from Ti/Ti7Al5Si12/composite at 600 °C and Ti/TiAl3/Ti7Al5Si12/composite at 700 °C to Ti/Ti7Al5Si12/TiAl3/Ti7Al5Si12/composite at 800 °C and Ti/Ti7Al5Si12/TiAl3/composite at 900 °C. The formation of TiAl3 at 700 and 800 °C depended on Al segregation, which was an uphill diffusion driven by chemical potential. The maximum shear strength was 40.9 MPa, found in the joint welded at 700 °C. Most joints fractured between Ti7Al5Si12 and Al-Ceramic composite. In any case, Ti7Al5Si12 was favorable for Al-Ceramic composite welding, which attached to Al-Ceramic composite, reducing the differences in physiochemical properties between SiC and metal, improving the mechanical properties of the joints and increasing the surface wettability of Al-Ceramic composite.

  3. Growth mechanism of atomic-layer-deposited TiAlC metal gate based on TiCl4 and TMA precursors

    NASA Astrophysics Data System (ADS)

    Jinjuan, Xiang; Yuqiang, Ding; Liyong, Du; Junfeng, Li; Wenwu, Wang; Chao, Zhao

    2016-03-01

    TiAlC metal gate for the metal-oxide-semiconductor field-effect-transistor (MOSFET) is grown by the atomic layer deposition method using TiCl4 and Al(CH3)3(TMA) as precursors. It is found that the major product of the TiCl4 and TMA reaction is TiAlC, and the components of C and Al are found to increase with higher growth temperature. The reaction mechanism is investigated by using x-ray photoemission spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscope (SEM). The reaction mechanism is as follows. Ti is generated through the reduction of TiCl4 by TMA. The reductive behavior of TMA involves the formation of ethane. The Ti from the reduction of TiCl4 by TMA reacts with ethane easily forming heterogenetic TiCH2, TiCH=CH2 and TiC fragments. In addition, TMA thermally decomposes, driving Al into the TiC film and leading to TiAlC formation. With the growth temperature increasing, TMA decomposes more severely, resulting in more C and Al in the TiAlC film. Thus, the film composition can be controlled by the growth temperature to a certain extent. Project supported by the Key Technology Study for 16/14 nm Program of the Ministry of Science and Technology of China (Grant No. 2013ZX02303).

  4. Magnetoelectric effect in laminate composites of Tb1-xDyxFe2-y and Fe-doped BaTiO3

    NASA Astrophysics Data System (ADS)

    Zhang, Ning; Fan, Junfeng; Rong, Xiaofang; Cao, Hongxia; Wei, Jianjun

    2007-03-01

    Fe-doped BaTiO3 has been synthesized with sol-gel technique. Its transformation point of ferroelectric to paraelectric and the latent heat of the transformation were observed at 103.27 °C and 169.9 J/mol, respectively. They are a little less than those for pure BaTiO3. Bonded layered composites Tb1-xDyxFe2-y/BaTi0.99Fe0.01O3 have been fabricated. Their magnetoelectric (ME) effect has been investigated. The transverse ME voltage coefficient for the bilayer Tb1-xDyxFe2-y-BaTi0.99Fe0.01O3 and the trilayer Tb1-xDyxFe2-y-BaTi0.99Fe0.01O3-Tb1-xDyxFe2-y can reach 578 (mv Oe-1 cm-1) and 2100 (mv Oe-1 cm-1), respectively, under a bias magnetic field of 350 Oe at room temperature. Those are about 50% larger than those for the bilayer and trilayer composed by pure BaTiO3. It suggests that the doped BaTiO3 can be a new choice of piezoelectrics to compose ME composites.

  5. Microstructure evolution during annealing of TiAl/NiCoCrAl multilayer composite prepared by EB-PVD

    SciTech Connect

    Zhang, Rubing; Zhang, Deming; Chen, Guiqing; Wang, Yuesheng

    2014-07-01

    TiAl/NiCoCrAl laminate composite sheet with a thickness of 0.4–0.6 mm as well as a dimension of 150 mm × 100 mm was fabricated successfully by using electron beam physical vapor deposition (EB-PVD) method. The annealing treatment was processed at 1123 and 1323 K for 3 h in a high vacuum atmosphere, respectively. The phase composition and microstructure of TiAl/NiCoCrAl microlaminated sheet have been analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Based on the sheet characterization and results of the microstructure evolution during annealing treatment process, the diffusion mechanism of interfacial reaction in TiAl/NiCoCrAl microlaminate was investigated and discussed.

  6. An Experimental Investigation of Effects of Fluxes (Na3AlF6 and K2TiF6), Element Alloys (Mg), and Composite Powders ((Al + TiC)CP and (Al + B4C)CP) on Distribution of Particles and Phases in Al-B4C and Al-TiC Composites

    NASA Astrophysics Data System (ADS)

    Mazaheri, Younes; Emadi, Rahmatollah; Meratian, Mahmood; Zarchi, Mehdi Karimi

    2017-04-01

    The wettability, incorporation, and gravity segregation of TiC and B4C particles into molten aluminum are important problems in the production of Al-TiC and Al-B4C composites by the casting techniques. In order to solve these problems, different methods consisting of adding the Na3AlF6 and K2TiF6 fluxes and Mg (as the alloying element) into the molten aluminum and injection of the (Al + TiC)CP and (Al + B4C)CP composite powders instead of B4C and TiC particles are evaluated. In this work, the conditions of sample preparation, such as particle addition temperature, stirring speed, and stirring time, are determined after many studies and tests. Microstructural characterizations of samples are investigated by scanning electron microscopy equipped with energy dispersive spectroscopy (EDS) and X-ray diffractometry. The results show better distribution and incorporation of TiCp and B4Cp in aluminum matrix when the fluxes are used, as well as EDS analysis of the interface between the matrix and reinforcement-strengthened formation of the different phases such as Al4C3 in the Al-TiC composites and Al3BC, TiB2 in the Al-B4C composites.

  7. An Experimental Investigation of Effects of Fluxes (Na3AlF6 and K2TiF6), Element Alloys (Mg), and Composite Powders ((Al + TiC)CP and (Al + B4C)CP) on Distribution of Particles and Phases in Al-B4C and Al-TiC Composites

    NASA Astrophysics Data System (ADS)

    Mazaheri, Younes; Emadi, Rahmatollah; Meratian, Mahmood; Zarchi, Mehdi Karimi

    2017-01-01

    The wettability, incorporation, and gravity segregation of TiC and B4C particles into molten aluminum are important problems in the production of Al-TiC and Al-B4C composites by the casting techniques. In order to solve these problems, different methods consisting of adding the Na3AlF6 and K2TiF6 fluxes and Mg (as the alloying element) into the molten aluminum and injection of the (Al + TiC)CP and (Al + B4C)CP composite powders instead of B4C and TiC particles are evaluated. In this work, the conditions of sample preparation, such as particle addition temperature, stirring speed, and stirring time, are determined after many studies and tests. Microstructural characterizations of samples are investigated by scanning electron microscopy equipped with energy dispersive spectroscopy (EDS) and X-ray diffractometry. The results show better distribution and incorporation of TiCp and B4Cp in aluminum matrix when the fluxes are used, as well as EDS analysis of the interface between the matrix and reinforcement-strengthened formation of the different phases such as Al4C3 in the Al-TiC composites and Al3BC, TiB2 in the Al-B4C composites.

  8. Synthesis and characterization of Fe-Ti-Sb intermetallic compounds: Discovery of a new Slater-Pauling phase

    NASA Astrophysics Data System (ADS)

    Naghibolashrafi, N.; Keshavarz, S.; Hegde, Vinay I.; Gupta, A.; Butler, W. H.; Romero, J.; Munira, K.; LeClair, P.; Mazumdar, D.; Ma, J.; Ghosh, A. W.; Wolverton, C.

    2016-03-01

    Compounds of Fe, Ti, and Sb were prepared using arc melting and vacuum annealing. Fe2TiSb , expected to be a full Heusler compound crystallizing in the L 21 structure, was shown by XRD and SEM analyses to be composed of weakly magnetic grains of nominal composition Fe1.5TiSb with iron-rich precipitates in the grain boundaries. FeTiSb, a composition consistent with the formation of a half-Heusler compound, also decomposed into Fe1.5TiSb grains with Ti-Sb rich precipitates and was weakly magnetic. The dominant Fe1.5TiSb phase appears to crystallize in a defective L 21 -like structure with iron vacancies. Based on this finding, a first-principles DFT-based binary cluster expansion of Fe and vacancies on the Fe sublattice of the L 21 structure was performed. Using the cluster expansion, we computationally scanned >103 configurations and predict a novel, stable, nonmagnetic semiconductor phase to be the zero-temperature ground state. This new structure is an ordered arrangement of Fe and vacancies, belonging to the space group R 3 m , with composition Fe1.5TiSb , i.e., between the full- and half-Heusler compositions. This phase can be visualized as alternate layers of L 21 phase Fe2TiSb and C 1b phase FeTiSb, with layering along the [111] direction of the original cubic phases. Our experimental results on annealed samples support this predicted ground-state composition, but further work is required to confirm that the R 3 m structure is the ground state.

  9. Microstructural characterization of the dispersed phases in Al-Ce-Fe system

    NASA Astrophysics Data System (ADS)

    Ayer, Raghavan; Angers, L. M.; Mueller, R. R.; Scanlon, J. C.; Klein, C. F.

    1988-07-01

    Analytical electron microscopy studies were conducted on a rapidly solidified Al-8.8Fe-3.7Ce alloy and arc melted buttons of aluminum rich Al-Fe-Ce alloys to determine the characteristics of the metastable and equilibrium phases. The rapidly solidified alloy consisted of binary and ternary metastable phases in the as-extruded condition. The binary metastable phase was identified to be Al6Fe, while the ternary metastable phases were identified to be Al10Fe2Ce and Al20Fe5Ce. The Al20Fe5Ce was a decagonal quasicrystal while the Al10Fe2Ce phase was determined to have an orthorhombic crystal structure belonging to space group Cmmm, Cmm2, or C222. Microscopy studies of RS alloy and cast buttons annealed at 700 K established the equilibrium phases to be Al13Fe4, Al4Ce, and an Al13Fe3Ce ternary phase which was first identified in the present study. The crystal structure of the equilibrium ternary phase was determined to be orthorhombic with a Cmcm or Cmc2 space group. The details of X-ray microanalysis and convergent beam electron diffraction analysis are described.

  10. Structural investigation of the (010) surface of the Al13 Fe4 catalyst.

    PubMed

    Ledieu, J; Gaudry, É; Loli, L N Serkovic; Villaseca, S Alarcón; de Weerd, M-C; Hahne, M; Gille, P; Grin, Y; Dubois, J-M; Fournée, V

    2013-02-15

    We have investigated the structure of the Al(13)Fe(4)(010) surface using both experimental and ab initio computational methods. The results indicate that the topmost surface layers correspond to incomplete puckered (P) planes present in the bulk crystal structure. The main building block of the corrugated termination consists of two adjacent pentagons of Al atoms, each centered by a protruding Fe atom. These motifs are interconnected via additional Al atoms referred to as "glue" atoms which partially desorb above 873 K. The surface structure of lower atomic density compared to the bulk P plane is explained by a strong Fe-Al-Fe covalent polar interaction that preserves intact clusters at the surface. The proposed surface model with identified Fe-containing atomic ensembles could explain the Al(13)Fe(4) catalytic properties recently reported in line with the site-isolation concept [M. Armbrüster et al., Nat. Mater. 11, 690 (2012)].

  11. From Tetrahedral to Octahedral Iron Coordination: Layer Compression in Topochemically Prepared FeLa2Ti3O10.

    PubMed

    Gustin, Léa; Hosaka, Yoshiteru; Tassel, Cédric; Aharen, Tomoko; Shimakawa, Yuichi; Kageyama, Hiroshi; Wiley, John B

    2016-11-07

    Synthesis, characterization, and thermal modification of the new layered perovskite FeLa2Ti3O10 have been studied. FeLa2Ti3O10 was prepared by ion exchange of the triple-layered Ruddlesden-Popper phase Li2La2Ti3O10 with FeCl2 at 350 °C under static vacuum. Rietveld refinement on synchrotron X-ray diffraction data indicates that the new phase is isostructural with CoLa2Ti3O10, where Fe(II) cations occupy slightly compressed/flattened interlayer tetrahedral sites. Magnetic measurements on FeLa2Ti3O10 display Curie-Weiss behavior at high temperatures and a spin-glass transition at lower temperatures (<30 K). Thermal treatment in oxygen shows that FeLa2Ti3O10 undergoes a significant cell contraction (Δc ≈ -2.7 Å) with a change in the oxidation state of iron (Fe(2+) to Fe(3+)); structural analysis and Mössbauer studies indicate that upon oxidation the local iron environment goes from tetrahedral to octahedral coordination with some deintercalation of iron as Fe2O3 to produce Fe0.67La2Ti3O10.

  12. Characteristics and anticorrosion performance of Fe-doped TiO2 films by liquid phase deposition method

    NASA Astrophysics Data System (ADS)

    Liu, Yu; Xu, Chao; Feng, ZuDe

    2014-09-01

    Fe-doped TiO2 thin films were fabricated by liquid phase deposition (LPD) method, using Fe(III) nitrate as both Fe element source and fluoride scavenger instead of commonly-used boric acid (H3BO3). Scanning electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis spectrum were employed to examine the effects of Fe element on morphology, structure and optical characteristics of TiO2 films. The as-prepared films were served as photoanode applied to photogenerated cathodic protection of SUS304 stainless steel (304SS). It was observed that the photoelectrochemical properties of the as-prepared films were enhanced with the addition of Fe element compared to the undoped TiO2 film. The highest photoactivity was achieved for Ti13Fe (Fe/Ti = 3 molar ratio) film prepared in precursor bath containing 0.02 M TiF4 + 0.06 M Fe(NO3)3 under white-light illumination. The effective anticorrosion behaviors can be attributed to the Fe element incorporation which decreases the probability of photogenerated charge-carrier recombination and extends the light response range of Fe-doped TiO2 films appeared to visible-light region.

  13. Effect of nitrogen upon structural and magnetic properties of FePt in FePt/AlN multilayer structures

    SciTech Connect

    Gao, Tenghua Zhang, Cong; Sannomiya, Takumi; Muraishi, Shinji; Nakamura, Yoshio; Shi, Ji

    2014-09-01

    This paper investigates the effect of the addition of nitrogen in FePt layers for ultrathin FePt/AlN multilayer structures. X-ray diffraction results reveal that a compressive stress relaxation occurs after annealing owing to the release of interstitial nitrogen atoms in the FePt layers. The introduction of nitrogen also induces a large in-plane compressive strain during grain growth not seen in FePt deposited without nitrogen. This strain is considered to decrease the driving force for (111) grain growth and FePt ordering.

  14. ADSORPTION AND DISSOCIATION OF O2 ON Ti3Al (0001) STUDIED BY FIRST-PRINCIPLES

    NASA Astrophysics Data System (ADS)

    Wei, Li-Jing; Guo, Jian-Xin; Dai, Xiu-Hong; Wang, Ying-Long; Liu, Bao-Ting

    2015-05-01

    The adsorption and dissociation of oxygen molecule on Ti3Al (0001) surface have been investigated by density functional theory (DFT) with the generalized gradient approximation (GGA). All possible adsorption sites including nine vertical and fifteen parallel sites of O2 are considered on Ti3Al (0001) surface. It is found that all oxygen molecules dissociate except for three vertical adsorption sites after structure optimization. This indicates that oxygen molecules prefer to dissociate on the junction site between Ti and Al atoms. Oxygen atoms coming from dissociation of oxygen molecule tend to occupy the most stable adsorption sites of the Ti3Al (0001) surface. The distance of O-O is related to the surface dissociation distance of Ti3Al (0001) surface. The valence electron localization function (ELF) and projected density of states (DOS) show that the bonds of O-O are breakaway at parallel adsorption end structures.

  15. Structural, electronic and magnetic properties of CoFeTiGa1-xSbx compounds

    NASA Astrophysics Data System (ADS)

    Zhang, Y. J.; Liu, Z. H.; Liu, G. D.; Ma, X. Q.

    2017-01-01

    Structural, electronic and magnetic properties of Heusler compounds CoFeTiGa1-xSbx have been studied. X-ray diffraction patterns show that CoFeTiGa1-xSbx (x=0.25, 0.5, 0.75, 1) crystallize into LiMgPdSn-type structure. First-principles calculations indicate that CoFeTiGa1-xSbx (x=0.25, 0.5, 0.75, 1) are half-metal with considerable minority band gaps. The substitution of Sb for Ga gives rise to the spin moments of the compounds, and makes them to be half-metallic ferrimagnets.

  16. Nanoscale spinel LiFeTiO4 for intercalation pseudocapacitive Li(+) storage.

    PubMed

    Chen, Ruiyong; Knapp, Michael; Yavuz, Murat; Ren, Shuhua; Witte, Ralf; Heinzmann, Ralf; Hahn, Horst; Ehrenberg, Helmut; Indris, Sylvio

    2015-01-14

    Intercalation pseudocapacitive Li(+) storage has been recognized recently in metal oxide materials, wherein Li(+) intercalation into the lattice is not solid-state diffusion-limited. This may bridge the performance gap between electrochemical capacitors and battery materials. To date, only a few materials with desired crystal structure and with well-defined nanoarchitectures have been found to exhibit such attractive behaviour. Herein, we report for the first time that nanoscale spinel LiFeTiO4 as a cathode material for Li-ion batteries exhibits intercalation pseudocapacitive Li(+) storage behaviour. Nanoscale LiFeTiO4 nanoparticles with native carbon coating were synthesized by a sol-gel route. A fast and large-amount of Li(+) storage (up to 1.6 Li(+) per formula unit over cycling) in the nanoscale LiFeTiO4 host has been achieved without compromising kinetics.

  17. Investigation of photocatalytic degradation of phenol by Fe(III)-doped TiO2 and TiO2 nanoparticles

    PubMed Central

    2014-01-01

    In this study Fe (III)-doped TiO2 nanoparticles were synthesized by sol–gel method at two atomic ratio of Fe/Ti, 0.006 and 0.034 percent. Then the photoactivity of them was investigated on degradation of phenol under UV (<380 nm) irradiation and visible light (>380 nm). Results showed that at appropriate atomic ratio of Fe to Ti (% 0.034) photoactivity of Fe(III)–doped TiO2 nanoparticles increased. In addition, the effects of various operational parameters on photocatalytic degradation, such as pH, initial concentration of phenol and amount of photocatalyst were examined and optimized. At all different initial concentration, highest degradation efficiency occurred at pH = 3 and 0.5 g/L Fe(III)–doped TiO2 dosage. With increase in initial concentration of phenol, photocatalytic degradation efficiency decreased. Photoactivity of Fe (III)-doped TiO2 under UV irradiation and visible light at optimal condition (pH = 3 and catalyst dosage = and 0.5 g/L) was compared with P25 TiO2 nanoparticles. Results showed that photoactivity of Fe(III)-doped TiO2 under visible light was more than P25 TiO2 photoactivity, but it was less than P25 TiO2 photoactivity under UV irradiation. Also efficiency of UV irradiation alone and amount of phenol adsorption on Fe(III)-doped TiO2 at dark condition was investigated. PMID:25105016

  18. Investigation of photocatalytic degradation of phenol by Fe(III)-doped TiO2 and TiO2 nanoparticles.

    PubMed

    Hemmati Borji, Saeedeh; Nasseri, Simin; Mahvi, Amir Hossein; Nabizadeh, Ramin; Javadi, Amir Hossein

    2014-01-01

    In this study Fe (III)-doped TiO2 nanoparticles were synthesized by sol-gel method at two atomic ratio of Fe/Ti, 0.006 and 0.034 percent. Then the photoactivity of them was investigated on degradation of phenol under UV (<380 nm) irradiation and visible light (>380 nm). Results showed that at appropriate atomic ratio of Fe to Ti (% 0.034) photoactivity of Fe(III)-doped TiO2 nanoparticles increased. In addition, the effects of various operational parameters on photocatalytic degradation, such as pH, initial concentration of phenol and amount of photocatalyst were examined and optimized. At all different initial concentration, highest degradation efficiency occurred at pH = 3 and 0.5 g/L Fe(III)-doped TiO2 dosage. With increase in initial concentration of phenol, photocatalytic degradation efficiency decreased. Photoactivity of Fe (III)-doped TiO2 under UV irradiation and visible light at optimal condition (pH = 3 and catalyst dosage = and 0.5 g/L) was compared with P25 TiO2 nanoparticles. Results showed that photoactivity of Fe(III)-doped TiO2 under visible light was more than P25 TiO2 photoactivity, but it was less than P25 TiO2 photoactivity under UV irradiation. Also efficiency of UV irradiation alone and amount of phenol adsorption on Fe(III)-doped TiO2 at dark condition was investigated.

  19. Magnetoimpedance effect in the FeNi/Ti-based multilayered structure: A pressure sensor prototype

    NASA Astrophysics Data System (ADS)

    Chlenova, A. A.; Melnikov, G. Yu.; Svalov, A. V.; Kurlyandskaya, G. V.

    2016-09-01

    Magnetically soft [Ti/FeNi]5/Ti/Cu/Ti/[FeNi/Ti]4 multilayered structures were obtained by magnetron sputtering. Based on them sensitive elements have been investigated with focus on the design of the giant magnetoimpedance (MI) pressure sensors. Magnetic properties and MI of fabricated sensitive elements were comparatively analyzed for both multilayers deposited both onto rigid and flexible polymer substrates. Structures on a rigid substrate had the highest MI ratio of 140 %. They showed the sensitivity of 0.70 %/Ba suitable for possible applications in pressure sensing. Structures deposited onto flexible Cyclo Olefin Copolymer substrates had slightly lower sensitivity of 0.55 %/Ba. That structures showing linear dependence of MI ratio in the pressure range of 0 to 360 Ba are promising for microfluidic and biosensor applications.

  20. Comparison study on photocatalytic oxidation of pharmaceuticals by TiO2-Fe and TiO2-reduced graphene oxide nanocomposites immobilized on optical fibers.

    PubMed

    Lin, Lu; Wang, Huiyao; Jiang, Wenbin; Mkaouar, Ahmed Radhi; Xu, Pei

    2017-03-08

    Incorporating reduced graphene oxide (rGO) or Fe(3+) ions in TiO2 photocatalyst could enhance photocatalytic degradation of organic contaminants in aqueous solutions. This study characterized the photocatalytic activities of TiO2-Fe and TiO2-rGO nanocomposites immobilized on optical fibers synthesized by polymer assisted hydrothermal deposition method. The photocatalysts presented a mixture phase of anatase and rutile in the TiO2-rGO and TiO2-Fe nanocomposites. Doping Fe into TiO2 particles (2.40eV) could reduce more band gap energy than incorporating rGO (2.85eV), thereby enhancing utilization efficiency of visible light. Incorporating Fe and rGO in TiO2 decreased significantly the intensity of TiO2 photoluminescence signals and enhanced the separation rate of photo-induced charge carriers. Photocatalytic performance of the synthesized nanocomposites was measured by the degradation of three pharmaceuticals under UV and visible light irradiation, including carbamazepine, ibuprofen, and sulfamethoxazole. TiO2-rGO exhibited higher photocatalytic activity for the degradation of pharmaceuticals under UV irradiation, while TiO2-Fe demonstrated more suitable for visible light oxidation. The results suggested that the enhanced photocatalytic performance of TiO2-rGO could be attributed to reduced recombination rate of photoexcited electrons-hole pairs, but for TiO2-Fe nanocomposite, narrower band gap would contribute to increased photocatalytic activity.

  1. Controlled synthesis and photocatalysis of sea urchin-like Fe3O4@TiO2@Ag nanocomposites

    NASA Astrophysics Data System (ADS)

    Zhao, Yilin; Tao, Chengran; Xiao, Gang; Wei, Guipeng; Li, Linghui; Liu, Changxia; Su, Haijia

    2016-02-01

    Based on the synergistic photocatalytic activities of nano-sized TiO2 and Ag, as well as the magnetic properties of Fe3O4, a sea urchin-like Fe3O4@TiO2@Ag nanocomposite (Fe3O4@TiO2@Ag NCs) is controllably synthesized with tunable cavity size, adjustable shell layer of TiO2 nanofiber, higher structural stability and larger specific surface area. Here, Fe3O4@TiO2@Ag NCs are obtained with Fe3O4 as the core and nanofiber TiO2/Fe3O4/Ag nanoheterojunctions as the shell; and Ag nanoparticles with diameter of approximately 4 nm are loaded both on TiO2 nanofibers and inside the cavities of sea urchin-like Fe3O4@TiO2 nanocomposites uniformly. Ag nanoparticles lead to the production of more photogenerated charges in the TiO2/Fe3O4/Ag heterojunction via LSPR absorption, and enhance the band-gap absorption of TiO2, while the Fe3O4 cocatalyst provides the active sites for oxygen reduction by the effective transfer of photogenerated electrons to oxygen. So the photocatalytic performance is improved due to the synergistic effect of TiO2/Fe3O4/Ag nanoheterojunctions. As photocatalysts under UV and visible irradiation, the as-synthesized nanocomposites display enhanced photocatalytic and recycling properties for the degradation of ampicillin. Moreover, they present better broad-spectrum antibiosis under visible irradiation. The enhanced photocatalytic activity and excellent chemical stability, in combination with the magnetic recyclability, makes this multifunctional nanostructure a promising candidate for antibiosis and remediation in aquatic environmental contamination in the future.Based on the synergistic photocatalytic activities of nano-sized TiO2 and Ag, as well as the magnetic properties of Fe3O4, a sea urchin-like Fe3O4@TiO2@Ag nanocomposite (Fe3O4@TiO2@Ag NCs) is controllably synthesized with tunable cavity size, adjustable shell layer of TiO2 nanofiber, higher structural stability and larger specific surface area. Here, Fe3O4@TiO2@Ag NCs are obtained with Fe3O4 as the

  2. Defect mechanisms of coloration in Fe-doped SrTiO3 from first principles

    NASA Astrophysics Data System (ADS)

    Baker, Jonathon N.; Bowes, Preston C.; Long, Daniel M.; Moballegh, Ali; Harris, Joshua S.; Dickey, Elizabeth C.; Irving, Douglas L.

    2017-03-01

    To understand the underlying defect mechanisms governing the coloration of Fe-doped SrTiO3 (Fe:STO), density functional theory calculations were used to determine defect formation energies and to interpret optical absorption spectra. A grand canonical defect equilibrium model was developed using the calculated formation energies, which enabled connection to annealing experiments. It was found that FeTi 0 is stable in oxidizing conditions and leads to the optical absorption signatures in oxidized Fe:STO, consistent with experiment. Fe:STO was found to transition from brown to transparent as P O2 was reduced during annealing. The defect equilibrium model reproduces a consistent P O2 of this coloration transition. Most critical to reproducing the P O2 of the coloration transition was inclusion of a Fe Ti - V O first nearest neighbor complex, which was found to be strongly interacting. The coloration transition P O2 was found to be insensitive to the presence of minority background impurities, slightly sensitive to Fe content, and more sensitive to annealing temperature.

  3. TiAl3-TiN Composite Nanoparticles Produced by Hydrogen Plasma-Metal Reaction: Synthesis, Passivation, and Characterization

    PubMed Central

    Li, Ju Ying; Mei, Qing Song

    2016-01-01

    TiAl3 and TiN composite nanoparticles were continuously synthesized from Ti–48Al master alloy by hydrogen plasma-metal reaction in a N2, H2 and Ar atmosphere. The phase, morphology, and size of the nanoparticles were studied by X-ray diffraction (XRD) and transmission electronic microscopy (TEM). X-ray photoelectron spectroscopy (XPS) and evolved gas analysis (EGA) were used to analyze the surface phase constitution and oxygen content of the nanoparticles. The as-synthesized nanopowders were mainly composed of nearly spherical TiAl3 and tetragonal TiN phases, with a mean diameter of ~42 nm and mass fractions of 49.1% and 24.3%, respectively. Passivation in the atmosphere of Ar and O2 for 24 h at room temperature led to the formation of amorphous Al2O3 shells on the TiAl3 particle surface, with a mean thickness of ~5.0 nm and a mass fraction of ~23.5%, as well as TiO2 with a mass fraction of ~3.2%. PMID:28335229

  4. In situ synthesized TiB-TiN reinforced Ti6Al4V alloy composite coatings: microstructure, tribological and in-vitro biocompatibility.

    PubMed

    Das, Mitun; Bhattacharya, Kaushik; Dittrick, Stanley A; Mandal, Chitra; Balla, Vamsi Krishna; Sampath Kumar, T S; Bandyopadhyay, Amit; Manna, Indranil

    2014-01-01

    Wear resistant TiB-TiN reinforced Ti6Al4V alloy composite coatings were deposited on Ti substrate using laser based additive manufacturing technology. Ti6Al4V alloy powder premixed with 5wt% and 15wt% of boron nitride (BN) powder was used to synthesize TiB-TiN reinforcements in situ during laser deposition. Influences of laser power, scanning speed and concentration of BN on the microstructure, mechanical, in vitro tribological and biological properties of the coatings were investigated. Microstructural analysis of the composite coatings showed that the high temperature generated due to laser interaction with Ti6Al4V alloy and BN results in situ formation of TiB and TiN phases. With increasing BN concentration, from 5wt% to 15wt%, the Young's modulus of the composite coatings, measured by nanoindentation, increased from 170±5GPa to 204±14GPa. In vitro tribological tests showed significant increase in the wear resistance with increasing BN concentration. Under identical test conditions TiB-TiN composite coatings with 15wt% BN exhibited an order of magnitude less wear rate than CoCrMo alloy-a common material for articulating surfaces of orthopedic implants. Average top surface hardness of the composite coatings increased from 543±21HV to 877±75HV with increase in the BN concentration. In vitro biocompatibility and flow cytometry study showed that these composite coatings were non-toxic, exhibit similar cell-materials interactions and biocompatibility as that of commercially pure titanium (CP-Ti) samples. In summary, excellent in vitro wear resistance, high stiffness and suitable biocompatibility make these composite coatings as a potential material for load-bearing articulating surfaces towards orthopaedic implants.

  5. Anomalous Dilatometric Response in Fe-Mn-Al-Si Steel

    NASA Astrophysics Data System (ADS)

    Ghosh, S. K.

    2012-04-01

    The present study deals with the transformation of an aggregate consisting of ferrite and pearlite into austenite in a Fe-0.36C-1.98Mn-1.97Al-0.30Si (wt%) steel. The transformation phenomenon has been studied using dilatometry which confirms that austenite starts to nucleate due to dissolution of ferrite and pearlite and subsequently it commences to grow when the appropriate elevated temperature is reached. The austenite formation has been accompanied with the formation of a hump in the dilatation curve which is different with respect to the results reported earlier. The non-conventional behaviour associated with the austenite formation has been explained using the X-ray diffraction data, microstructural investigation and also with MT-DATA theoretical calculations.

  6. Mechanical alloying Ti[sub 50]Al[sub 50] in nitrogen atmosphere

    SciTech Connect

    Wang, K.Y.; Chen, G.L.; Wang, J.G. )

    1994-07-01

    Titanium aluminides ([gamma]-TiAl or [alpha][sub 2]-Ti[sub 3]Al) are very useful structural materials for application in the aerospace industry owing to their low density, high specific strength and modulus, and good oxidation and corrosion resistance, at least up to 800 C. However, their use has been limited because of a poor ductility and fracture toughness at room temperature. To improve these properties, TiAl compound was recently made as a composite material containing a secondary phase such as boride, carbide, oxide or nitride or refinement of crystalline by inert gas condensation or mechanical alloying. Itsukaichi et al. reported the mechanical alloying of Al-Ti systems, where the amorphous phase was obtained for the Ti[sub 50]Al[sub 50] system after milling of 1,000h in Ar atmosphere. Suryanarayana et al. also reported that the amorphous phase could be obtained after milling for 25h of a Ti-50 at. % Al system and adding a surfactant such as hexane during mechanical alloying. Ogino et al. reported MA of Ti[sub 0.50]Al[sub 0.50] in N[sub 2] gas. The results obtained show that the diffraction peaks broadened at an intermediate stage of milling and thereafter the powder transformed into a cubic nitride (Ti[sub 0.50]Al[sub 0.50])N. But they have not confirmed the formation of an amorphous phase. In this paper, the authors prepared an amorphous Ti-Al phase through mechanical alloying in N[sub 2] gas; thermal behaviors of the amorphous phase were also investigated.

  7. Microstructural evolution and hardness of TiAl3 and TiAl2 phases on Ti-45Al-2Nb-2Mn-1B by plasma pack aluminizing

    NASA Astrophysics Data System (ADS)

    Rastkar, Ahmad Reza; Parseh, Pejman; Darvishnia, Naser; Hadavi, Seyed Mohammad Mehdi

    2013-07-01

    The surface of Ti-45Al-2Nb-2Mn-1B (at%) titanium aluminide was aluminized in a so called plasma pack aluminizing by packing the substrate in a mixture of aluminum copper alloy and application of an 18 kHz pulsed DC glow discharge plasma in argon gas. The plasma energy provided the necessary heat for melting and mutual diffusion of titanium and aluminum at the surface of titanium aluminide alloy in less than 1 h without any further heat treatment. The microstructure and hardness of different phases on the surface of Ti-45Al-2Nb-2Mn-1B alloy were characterized using optical and electron microscopy, X-ray diffraction (XRD), EDX analysis and Vickers microhardness tests. The thickness of the surface layers was up to 300 μm. The surface layers consisted mainly of TiAl3 and TiAl2 compounds. These compounds appeared in blocky and round shapes with different micrometer sizes in a matrix of aluminum alloy phase. The hardness of the surface layers was up to 600 HV0.1, which was higher than that of Ti-45Al-2Nb-2Mn-1B substrate (330 HV0.1).

  8. Synthesis and pyrolysis of novel polymeric precursors to TiC/Al[sub 2]O[sub 3], TiN/Al[sub 2]O[sub 3], and AlN/TiN nanocomposites

    SciTech Connect

    Jiang, Z.; Rhine, W.E. )

    1994-07-01

    The reaction between furfuryl alcohol (FuOH) and the products obtained by hydrolyzing a mixture of Ti(O-n-Bu)[sub 4] and Al(O-sec-Bu)[sub 3] resulted in the formation of soluble polymeric solids. Pyrolysis of these polymers in argon yielded TiC/Al[sub 2]O[sub 3] composites at 1250-1375[degrees]C; further heating the precursors to 1500[degrees]C in argon led to the formation of a new phase due to the reaction between C, Al[sub 2]O[sub 3], and TiC. When these polymers were pyrolyzed in ammonia or nitrogen, a TiN/Al[sub 2]O[sub 3] or TiN/AlN nanocomposite was formed, depending on the concentration of FuOH in the polymers. All these composites exhibited a fine-grained microstructure and excellent homogeneity. Furthermore, the structure and pyrolysis chemistry of these polymeric precursors, as well as the microstructure of the pyrolysis products, were studied by FTIR, TGA, GC, XRD, SEM, TEM, STEM, Auger electron spectroscopy (AES), and elemental analyses. 38 refs., 7 figs., 2 tabs.

  9. Effect of Helium ion irradiation on the structure, the phase stability, and the microhardness of TiN, TiAlN, and TiAlYN nanostructured coatings

    NASA Astrophysics Data System (ADS)

    Komarov, F. F.; Konstantinov, S. V.; Strel'nitskij, V. E.; Pilko, V. V.

    2016-05-01

    The radiation resistance of nanostructured TiN, TiAlN, and TiAlYN coatings is studied after 500-keV He+ ion irradiation in the fluence range 5 × 1016-3 × 1017 ions/cm2. The radiation-induced changes in the phase composition, the structure, the lattice parameters, the morphology, and the mechanical properties of coatings are investigated. Blistering is found to be absent, and the radiation fluence is shown to affect the strength properties of the thin coatings nonlinearly. A significant decrease in the grain sizes is detected upon ion irradiation, which causes an increase in the microhardness and the radiation resistance of the coatings. The TiN, TiAlN, and TiAlYN coatings are found to be radiation-resistant coatings, which do not undergo serious degradation during high-fluence ion irradiation.

  10. Thermodynamics, Solubility, and Diffusivity of Oxygen in Titanium and Ti-Al Alloys

    NASA Technical Reports Server (NTRS)

    Mehrotra, Gopal M.

    1992-01-01

    Titanium aluminides and titanium aluminide-based composites are attractive candidate materials for high-temperature structural applications. As these materials may be exposed to oxidizing environments durine their use at elevated temperatures, it is essential that they possess a good oxidation resistance. Previous studies have shown that the oxidation resistance of Al-rich alloys in the Ti-Al system is superior to that of the Ti-rich alloys. The scales formed on the surface of the Al-rich and Ti-rich alloys have been reported to be predominantly Al2O3 and TiO2, respectively. Since the relative stabilities of the oxides of Al and Ti at various temperatures and oxygen pressures can be assessed from their thermodynamic data, it is possible, With the help of thermodynamic calculations, to determine the compositions of the alloys which would form scales of Al2O3, TiO(x) or a ternary oxide such as TiAl2O5 during oxidation at a given temperature. The thermodynamic calculations require reliable activity data for the Ti-Al system. These data have not been determined for the entire composition and temperature range of interest. Using the data available in the literature, recently performed thermodynamic calculations and concluded that the stable oxide changed from TiO to Al2O3 in the existence region of the tial phase. In the case of titanium aluminide-based composites, another major concern is the mutual chemical compatibility of the matrix material with the reinforcement phase. Fibers of SiC, TiB2 and Al2O3 are currently being investigated for reinforcement of titanium aluminide matrices.

  11. Irradiation-induced disordering and amorphization of Al3Ti-based intermetallic compounds

    NASA Astrophysics Data System (ADS)

    Park, Jeong-Yong; Kim, Il-Hyun; Motta, Arthur T.; Ulmer, Christopher J.; Kirk, Marquis A.; Ryan, Edward A.; Baldo, Peter M.

    2015-12-01

    An in situ ion-irradiation study, simultaneously examined using transmission electron microscopy, was performed to investigate irradiation-induced disordering and amorphization of Al3Ti-based intermetallic compounds. Thin foil samples of two crystalline structures: D022-structured Al3Ti and L12-structured (Al,Cr)3Ti were irradiated using 1.0 MeV Kr ions at a temperature range from 40 K to 573 K to doses up to 4.06 × 1015 ions/cm2. The results showed that both the compounds underwent an order-disorder transformation under irradiation, where both Al3Ti and (Al,Cr)3Ti ordered structures were fully transformed to the disordered face-centered cubic (FCC) structure except at the highest irradiation temperature of 573 K. A slightly higher irradiation dose was required for order-disorder transformation in case of Al3Ti as compared to (Al,Cr)3Ti at a given temperature. However, their amorphization resistances were different: while the disordered FCC (Al,Cr)3Ti amorphized at the irradiation dose of 6.25 × 1014 ions/cm2 (0.92 dpa) at 40 K and 100 K, the Al3Ti compound with the same disordered FCC structure maintained crystallinity up to 4.06 × 1015 ions/cm2 (5.62 dpa) at 40 K. The critical temperature for amorphization of (Al,Cr)3Ti under Kr ion irradiation is likely between 100 K and room temperature and the critical temperature for disordering between room temperature and 573 K.

  12. [Joint prostheses components of warm-forged and surface treated Ti-6Al-7Nb alloy].

    PubMed

    Semlitsch, M; Weber, H; Streicher, R M; Schön, R

    1991-05-01

    In 1978 development of a TiAl alloy with the inert alloying element niobium was initiated. In 1984, the optimal composition was found to be Ti-6Al-7Nb (Protasul-100). This custom-made alloy for implants has the same alpha/beta micro-structure and equally good mechanical properties as Ti-6Al-4V. The corrosion resistance of Ti-6Al-7Nb is better than that of pure titanium and Ti-6Al-4V, due to the very dense and stable passive layer. Since 1985, highly stressed anchoring stems of various hip prosthesis designs have been manufactured from hot-forged Ti-6Al-7Nb/Protasul-100. Polished surfaces of hip, knee or wrist joints made of Ti-6Al-7Nb intended to articulate with polyethylene are surface-treated by the application of a very hard, 3-5 microns thick titanium nitride coating (Tribosul-TiN), or by oxygen diffusion hardening (Tribosul-ODH) to a depth of 30 microns.

  13. Commercially pure titanium (cp-Ti) versus titanium alloy (Ti6Al4V) materials as bone anchored implants - Is one truly better than the other?

    PubMed

    Shah, Furqan A; Trobos, Margarita; Thomsen, Peter; Palmquist, Anders

    2016-05-01

    Commercially pure titanium (cp-Ti) and titanium alloys (typically Ti6Al4V) display excellent corrosion resistance and biocompatibility. Although the chemical composition and topography are considered important, the mechanical properties of the material and the loading conditions in the host have, conventionally, influenced material selection for different clinical applications: predominantly Ti6Al4V in orthopaedics while cp-Ti in dentistry. This paper attempts to address three important questions: (i) To what extent do the surface properties differ when cp-Ti and Ti6Al4V materials are manufactured with the same processing technique?, (ii) Does bone tissue respond differently to the two materials, and (iii) Do bacteria responsible for causing biomaterial-associated infections respond differently to the two materials? It is concluded that: (i) Machined cp-Ti and Ti6Al4V exhibit similar surface morphology, topography, phase composition and chemistry, (ii) Under experimental conditions, cp-Ti and Ti6Al4V demonstrate similar osseointegration and biomechanical anchorage, and (iii) Experiments in vitro fail to disclose differences between cp-Ti and Ti6Al4V to harbour Staphylococcus epidermidis growth. No clinical comparative studies exist which could determine if long-term, clinical differences exist between the two types of bulk materials. It is debatable whether cp-Ti or Ti6Al4V exhibit superiority over the other, and further comparative studies, particularly in a clinical setting, are required.

  14. Combustion synthesis of metal-matrix composites. Part 2: The Ti-Ti{sub x}Al{sub y}-Al{sub 2}O{sub 3} system

    SciTech Connect

    Kunrath, A.O.; Strohaecker, T.R.; Moore, J.J.

    1996-01-15

    The production of high performance materials (ceramics, intermetallics and composites) by combustion synthesis is receiving considerable attention since the process offers certain advantages with respect to simplicity and a relatively low energy requirement. The methods by which combustion synthesis (or SHS) can be used to produce metal matrix composites were outlined in an earlier paper. The use of excess liquid metal in the combustion synthesis reaction has already been successfully employed to achieve low porosity products. This metallic phase may be generated by an in-situ reduction of a metal oxide or by adding an excess of some metal to the reactants. Coupling a simultaneous consolidation (pressing) process with the SHS reaction has been found to produce dense bodies. This work discussed in this paper is concerned with the synthesis of a metallic/intermetallic matrix composite reaction system which can be represented by equation. With this reaction, high volume fractions of metallic/intermetallic phases can be produced. The metal-matrix produced by this reaction is predominantly a mixture of Ti{sub 3}Al + Ti as indicated in the appropriate area of the Ti-Al phase diagram. Increasing x increases the volume fraction of Ti. TiAl was observed in only one of the four different stoichiometries studied, i.e., x = 1, as detected by XRD. Using this reaction, there is a constant amount of excess Al and a variable excess of Ti. These stoichiometries produce composites with varying Ti-Al ratios that allow the matrix composition of the composite to be varied along the concentration axis of the Ti-Al phase diagram.

  15. Controlled synthesis and photocatalysis of sea urchin-like Fe3O4@TiO2@Ag nanocomposites.

    PubMed

    Zhao, Yilin; Tao, Chengran; Xiao, Gang; Wei, Guipeng; Li, Linghui; Liu, Changxia; Su, Haijia

    2016-03-07

    Based on the synergistic photocatalytic activities of nano-sized TiO2 and Ag, as well as the magnetic properties of Fe3O4, a sea urchin-like Fe3O4@TiO2@Ag nanocomposite (Fe3O4@TiO2@Ag NCs) is controllably synthesized with tunable cavity size, adjustable shell layer of TiO2 nanofiber, higher structural stability and larger specific surface area. Here, Fe3O4@TiO2@Ag NCs are obtained with Fe3O4 as the core and nanofiber TiO2/Fe3O4/Ag nanoheterojunctions as the shell; and Ag nanoparticles with diameter of approximately 4 nm are loaded both on TiO2 nanofibers and inside the cavities of sea urchin-like Fe3O4@TiO2 nanocomposites uniformly. Ag nanoparticles lead to the production of more photogenerated charges in the TiO2/Fe3O4/Ag heterojunction via LSPR absorption, and enhance the band-gap absorption of TiO2, while the Fe3O4 cocatalyst provides the active sites for oxygen reduction by the effective transfer of photogenerated electrons to oxygen. So the photocatalytic performance is improved due to the synergistic effect of TiO2/Fe3O4/Ag nanoheterojunctions. As photocatalysts under UV and visible irradiation, the as-synthesized nanocomposites display enhanced photocatalytic and recycling properties for the degradation of ampicillin. Moreover, they present better broad-spectrum antibiosis under visible irradiation. The enhanced photocatalytic activity and excellent chemical stability, in combination with the magnetic recyclability, makes this multifunctional nanostructure a promising candidate for antibiosis and remediation in aquatic environmental contamination in the future.

  16. Electric control of magnetism at the Fe/BaTiO3 interface

    NASA Astrophysics Data System (ADS)

    Radaelli, G.; Petti, D.; Plekhanov, E.; Fina, I.; Torelli, P.; Salles, B. R.; Cantoni, M.; Rinaldi, C.; Gutiérrez, D.; Panaccione, G.; Varela, M.; Picozzi, S.; Fontcuberta, J.; Bertacco, R.

    2014-03-01

    Interfacial magnetoelectric coupling is a viable path to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO3 system, only tiny changes of the interfacial Fe magnetic moment upon reversal of the BaTiO3 dielectric polarization have been predicted so far. Here, by using X-ray magnetic circular dichroism in combination with high-resolution electron microscopy and first principles calculations, we report on an undisclosed physical mechanism for interfacial magnetoelectric coupling in the Fe/BaTiO3 system. At this interface, an ultrathin oxidized iron layer exists, whose magnetization can be electrically and reversibly switched on and off at room temperature by reversing the BaTiO3 polarization. The suppression/recovery of interfacial ferromagnetism results from the asymmetric effect that ionic displacements in BaTiO3 produces on the exchange coupling constants in the interfacial-oxidized Fe layer. The observed giant magnetoelectric response holds potential for optimizing interfacial magnetoelectric coupling in view of efficient, low-power spintronic devices.

  17. Electric control of magnetism at the Fe/BaTiO₃ interface.

    PubMed

    Radaelli, G; Petti, D; Plekhanov, E; Fina, I; Torelli, P; Salles, B R; Cantoni, M; Rinaldi, C; Gutiérrez, D; Panaccione, G; Varela, M; Picozzi, S; Fontcuberta, J; Bertacco, R

    2014-03-03

    Interfacial magnetoelectric coupling is a viable path to achieve electrical writing of magnetic information in spintronic devices. For the prototypical Fe/BaTiO₃ system, only tiny changes of the interfacial Fe magnetic moment upon reversal of the BaTiO₃ dielectric polarization have been predicted so far. Here, by using X-ray magnetic circular dichroism in combination with high-resolution electron microscopy and first principles calculations, we report on an undisclosed physical mechanism for interfacial magnetoelectric coupling in the Fe/BaTiO₃ system. At this interface, an ultrathin oxidized iron layer exists, whose magnetization can be electrically and reversibly switched on and off at room temperature by reversing the BaTiO₃ polarization. The suppression/recovery of interfacial ferromagnetism results from the asymmetric effect that ionic displacements in BaTiO₃ produces on the exchange coupling constants in the interfacial-oxidized Fe layer. The observed giant magnetoelectric response holds potential for optimizing interfacial magnetoelectric coupling in view of efficient, low-power spintronic devices.

  18. TiC-Fe-Based Composite Coating Prepared by Self-Propagating High-Temperature Synthesis

    NASA Astrophysics Data System (ADS)

    He, Shen; Fan, Xi'an; Chang, Qingming; Xiao, Lixiang

    2017-02-01

    TiC-Fe-based composite coatings were prepared in situ by self-propagating high-temperature synthesis combined with vacuum expendable pattern casting process. The band-like TiC phase embedded in a continuous Fe binder. There were no obvious defects and impurities at the interface between coatings and matrices. Fe presented consecutively in the coating zones and substrate zones without interruption and the microhardness in the cross-sectional area of the coating-matrix reduces continuously from the coating to the matrix area, indicating a good metallurgical bonding between the coatings and matrices. The effect of casting temperature on the microstructure and hardness of TiC-Fe-based composite coating was investigated in detail. The TiC particles formed at low casting temperature were nearly spherical in shape, and the size of TiC particles increased with increasing casting temperature due to more agglomeration. The hardness of the coatings increased first and then decreased with increasing casting temperature, and reached the highest value of 68 HRC when the casting temperature was 1773 K (1500 °C), which was twice more than that of the matrix.

  19. Nanostructure evolution in joining of Al and Fe nanoparticles with femtosecond laser irradiation

    SciTech Connect

    Jiao, Z.; Huang, H.; Zhou, Y. E-mail: nzhou@uwaterloo.ca; Liu, L.; Hu, A.; Duley, W.; He, P. E-mail: nzhou@uwaterloo.ca

    2014-04-07

    The joining of Al-Fe nanoparticles (NPs) by femtosecond (fs) laser irradiation is reported in this paper. Fe and Al NPs were deposited on a carbon film in vacuum via fs laser ablation. Particles were then exposed to multiple fs laser pulses at fluences between 0.5 and 1.3 mJ/cm{sup 2}. Transmission Electron Microscopy (TEM) and Electron Diffraction X-ray observations indicate that Al and Fe NPs bond to each other under these conditions. For comparison, bonding of Al to Al and Fe to Fe NPs was also investigated. The nanostructure, as observed using TEM, showed that individual Al NPs were monocrystalline while individual Fe NPs were polycrystalline prior to joining and that these structures are retained after the formation of Al-Al and Fe-Fe NPs. Al-Fe NPs produced by fs laser joining exhibited a mixed amorphous and crystalline phase at the interface. Bonding is suggested to originate from intermixing within a region of high field intensity between particles.

  20. Cyclic oxidation of aluminide coatings on Ti3Al+Nb

    NASA Technical Reports Server (NTRS)

    Smialek, James L.; Gedwill, Michael A.; Brindley, Pamela K.

    1990-01-01

    A number of pack aluminide coatings were produced on fiber-reinforced Ti3Al+Nb composites and were compared for their protection effect in cyclic oxidation at 982 C. It was found that pack aluminizing of Ti3Al+Nb can successfully produce an oxidation resistant TiAl3 coating which forms alpha-Al2O3 scales. These coatings offer a substantial improvement over the uncoated matrix material in 982 C cyclic oxidation. Coating cracks were found to contribute to degradation of thick coatings.

  1. First-principles investigation of hydrogen interaction with TiC precipitates in α -Fe

    NASA Astrophysics Data System (ADS)

    Di Stefano, Davide; Nazarov, Roman; Hickel, Tilmann; Neugebauer, Jörg; Mrovec, Matous; Elsässer, Christian

    2016-05-01

    A correct description of hydrogen diffusion and trapping is the prerequisite for an understanding of the phenomenon of hydrogen embrittlement. In this study, we carried out extensive first-principles calculations based on density functional theory to investigate the interaction of H with TiC precipitates that are assumed to be efficient trapping agents mitigating HE in advanced high-strength steels. We found that there exists a large variety of possible trapping sites for H associated with different types of interfaces between the TiC particle and the Fe matrix, with misfit dislocations and other defects at these interfaces, and with carbon vacancies in TiC. The most efficient trapping by more than 1 eV occurs at carbon vacancies in the interior of TiC particles. However, these traps are difficult to populate at ambient temperatures since the energy barrier for H entering the particles is high. H trapping at the semicoherent interfaces between the TiC particles and the Fe matrix is moderate, ranging from 0.3 to 0.5 eV. However, a sufficiently large concentration of the carbide particles can significantly reduce the amount of H segregated at dislocation cores in the Fe matrix. A systematic comparison of the obtained theoretical results with available experimental observations reveals a consistent picture of hydrogen trapping at the TiC particles that is expected to be qualitatively valid also for other carbide precipitates with the rock-salt crystal structure.

  2. Texture induced anisotropy in extruded Ti-6Al-4V-xB alloys

    SciTech Connect

    Chen, Wei; Boehlert, C. J.

    2011-01-01

    The tensile properties of extruded Ti 6Al 4V xB alloys (wt.%) were evaluated in an orientation perpendicular to the extrusion direction at room-temperature and 455 C. The extrusion process preferentially oriented the basal plane of -Ti perpendicular to the extrusion axis. This strong - phase texture resulted in tensile anisotropy. The tensile strength in the transverse orientation was lower than that in the longitudinal orientation, but it remained greater than that for the ascast Ti 6Al 4V. The TiB phasewas aligned in the extrusion direction and increased B content was found to weaken the -phase texture, causing a weakening of tensile anisotropy. Debonding was not observed during the tensile tests in the transverse orientation, indicating a strong interface bond exists between the TiB phase and the two-phase ( + ) Ti 6Al 4V matrix.

  3. Epitaxial Fe3Pt/FePt nanocomposites on MgO and SrTiO3

    NASA Astrophysics Data System (ADS)

    Casoli, F.; Lupo, P.; Nasi, L.; Cabassi, R.; Fabbrici, S.; Bolzoni, F.; Ranzieri, P.; Albertini, F.

    2015-02-01

    We have exploited the pseudomorphic growth of the magnetically soft Fe3Pt phase on top of L10-FePt to obtain fully epitaxial soft/hard nanocomposites on both MgO(100) and SrTiO3(100). The magnetic properties of this new nanocomposite system, driven by the soft/hard exchange-coupling, can be tailored by varying soft phase thickness, soft phase magnetic anisotropy and substrate. Coercivity is strongly reduced by the addition of the soft phase, a reduction which is definitely affected by the nominal composition of the soft phase and by the substrate choice; similarly is the magnetic phase diagram of the composite system. Coercive field decreases down to 21% of the hard layer value for Fe3Pt(5 nm)/FePt(3.55 nm) nanocomposites on SrTiO3; this maximum coercivity reduction was obtained with a nominal atomic content of Fe in the soft phase of 80%.

  4. Dependence of Reduction Behaviors on the Molar Ratio of Fe2TiO5 and MgTi2O5 in the Pseudobrookite-Karrooite

    NASA Astrophysics Data System (ADS)

    Zhang, Gengyu; Lei, Chao; Zhu, Qingshan; Zhang, Jianbo; Du, Zhan; Yang, Yafeng; Fan, Chuanlin

    2017-02-01

    The dependence of the reduction behaviors of the M3O5-type (Fe2TiO5) a (MgTi2O5) b on the ratio of Fe2TiO5 and MgTi2O5 was investigated in a CO-CO2 gas mixture at 1123 K (850 °C), and the phase transformation mechanism was revealed. The reduction process of (Fe2TiO5) a (MgTi2O5) b underwent the formation of the intermediate (FeTi2O5) e (MgTi2O5) f in the same M3O5-type, and subsequently this intermediate further decomposed into the M2O3 phase. The a/ b ratio had a marginal effect on its reduction of Fe3+→Fe2+ but largely influenced its phase transformation. To obtain a complete phase transformation into M2O3, a/ b ≥ 0.9 is required, below which a considerable amount of inadequately decomposed intermediate M3O5 phase remains. A principle of suitable acid leaching condition for titanium slags with different a/ b ratios was proposed accordingly, and an optimized plan for the upgrading process of low-grade titanium slags was recommended.

  5. Fe-Doped TiO2 Thin Films for CO Gas Sensing

    NASA Astrophysics Data System (ADS)

    Kumar, Mukesh; Kumar, Dinesh; Gupta, Anil Kumar

    2015-01-01

    Fe-doped TiO2 thin films were prepared by the sol-gel technique on silicon substrate. The thin films were evaluated for detection of carbon monoxide (CO) gas at room temperature. The TiO2 films were characterized by x-ray diffraction (XRD) analysis, field-emission scanning electron microscopy, and ultraviolet-visible (UV) spectroscopy. The characterization revealed that, as the doping concentration was increased, the grain size decreased. XRD patterns revealed the phase transition from rutile to anatase with addition of different percentages (weight/volume) of Fe. The bandgap determined from UV spectroscopy was found to decrease with increasing Fe doping concentration. Fe doping was observed to have a significant effect on the resistivity of the doped TiO2 thin films. The gas sensing behavior of the films was studied by exposure to different concentrations of CO gas with measurement of the electrical resistance. It was observed that Fe-doped (7% weight/volume) TiO2 exhibited high sensitivity and good response/recovery on exposure to CO gas in the concentration range from 100 ppm to 900 ppm in Ar.

  6. Brazing characteristics of a Zr-Ti-Cu-Fe eutectic alloy filler metal for Zircaloy-4

    NASA Astrophysics Data System (ADS)

    Lee, Jung G.; Lim, C. H.; Kim, K. H.; Park, S. S.; Lee, M. K.; Rhee, C. K.

    2013-10-01

    A Zr-Ti-Cu-Fe quaternary eutectic alloy was employed as a new Be-free brazing filler metal for Zircaloy-4 to supersede physically vapor-deposited Be coatings used conventionally with several disadvantages. The quaternary eutectic composition of Zr58Ti16Cu10Fe16 (at.%) showing a low melting temperature range from 832 °C to 853 °C was designed by a partial substitution of Zr with Ti based on a Zr-Cu-Fe ternary eutectic system. By applying an alloy ribbon with the determined composition, a highly reliable joint was obtained with a homogeneous formation of predominantly grown α-Zr phases owing to a complete isothermal solidification, exhibiting strength higher than that of Zircaloy-4. The homogenization of the joint was rate-controlled by the diffusion of the filler elements (Ti, Cu, and Fe) into the Zircaloy-4 base metal, and the detrimental segregation of the Zr2Fe phase in the central zone was completely eliminated by an isothermal holding at a brazing temperature of 920 °C for 10 min.

  7. Photoelectrolysis at Fe2O3/TiO2 heterojunction electrode

    NASA Astrophysics Data System (ADS)

    Liou, F.-T.; Yang, C. Y.; Levine, S. N.

    1982-02-01

    The fabrication of a heterojunction consisting of a thin film of n-type polycrystalline TiO2 deposited on n-type polycrystalline Fe2O3 to form an anode which can photodecompose water in the presence of light is reported. It has been found that under illumination, incident light passes through the TiO3 film and generates holes in the underlying Fe2O3 which, under an appropriate bias, contribute to the electrode reaction of the TiO2/electrolyte interface. The discontinuity at the conduction bands is estimated to be 0.38 eV and at the valence bands, 0.42 eV, which presents an energy barrier to the migration of holes from the Fe2O3. Tests involving CVD TiO2 films on Fe2O3 substrate were performed under 550 C to avoid formation of iron titanates. A photoresponse initiated at 560 nm indicated a hole contribution from the Fe2O3 substrate.

  8. Local structure and optical absorption characteristic investigation on Fe doped TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Zhao, Tian-Xing; Feng, Ya-Juan; Huang, Jun-Heng; He, Jin-Fu; Liu, Qing-Hua; Pan, Zhi-Yun; Wu, Zi-Yu

    2015-02-01

    The local structures and optical absorption characteristics of Fe doped TiO2 nanoparticles synthesized by the sol-gel method were characterized by X-ray diffraction (XRD), X-ray absorption fine structure spectroscopy (XAFS) and ultraviolet-visible absorption spectroscopy (UV-Vis). XRD patterns show that all Fe-doped TiO2 samples have the characteristic anatase structure. Accurate Fe and Ti K-edge EXAFS analysis further reveal that all Fe atoms replace Ti atoms in the anatase lattice. The analysis of UV-Vis data shows a red shift to the visible range. According to the above results, we claim that substitutional Fe atoms lead to the formation of structural defects and new intermediate energy levels appear, narrowing the band gap and extending the optical absorption edge towards the visible region. Supported by National Basic Research Program of China (2012CB825801), Science Fund for Creative Research Groups of NSFC (11321503), National Natural Science Foundation of China (11321503, 11179004) and Guangdong Natural Science Foundation (S2011040003985)

  9. Formation of a paramagnetic Al complex and extrusion of Fe during the reaction of (diiminepyridine)Fe with AlR3 (R = Me, Et).

    PubMed

    Scott, Jennifer; Gambarotta, Sandro; Korobkov, Ilia; Knijnenburg, Quinten; de Bruin, Bas; Budzelaar, Peter H M

    2005-12-14

    The reaction of the {2,6-[2,6-(iPr)2PhN=C(CH3)]2(C5H3N)}FeCl2 catalyst precursor with R3Al [R = Me, Et] afforded {2,6-[2,6-(iPr)2PhN=C(CH3)]2(C5H3N)}AlMe2 (1) and [eta4-LAl2Et3(mu-Cl)]Fe-(eta6-C7H8) (2), respectively. These paramagnetic species arises from both transmetalation, during which the strong terdentate ligand loses the Fe center, and reduction. The extent of reduction depends on the nature of the Al alkylating agent. The electrons necessary for the reduction are likely to be provided by cleavage of Fe-C bond of transient low-valent organo-Fe species.

  10. Defects in Thin-Film FeSe/SrTiO3: STM and DFT Investigations

    NASA Astrophysics Data System (ADS)

    Huang, Dennis; Webb, Tatiana A.; Song, Can-Li; Chang, Cui-Zu; Moodera, Jagadeesh S.; Kaxiras, Efthimios; Hoffman, Jennifer E.

    A single-layer of FeSe deposited on SrTiO3 exhibits an order-of-magnitude enhancement of its superconducting transition temperature compared to bulk FeSe. This dramatic effect is curiously absent in a second layer of FeSe deposited on the heterostructure, leading to many questions concerning the role of the interface structure, electron doping and phonon coupling. Here, we approach these questions by using STM to characterize and compare native defects that appear in multi-layer and single-layer FeSe/SrTiO3 grown by MBE under excess Se flux. We use DFT to explore candidate defect configurations, formation energies and diffusion barriers, in order to gain atomic-scale insights into the growth and structure of these film heterostructures. Work supported by NSF DMR-1231319 (STC CIQM) and Moore Foundation EPiQS GBMF4536. Computations run on Harvard RC Odyssey.

  11. Ti TiO2 Al normal metal insulator superconductor tunnel junctions fabricated in direct-write technology

    NASA Astrophysics Data System (ADS)

    Otto, Ernst; Tarasov, Mikhail; Kuzmin, Leonid

    2007-08-01

    We present a novel Ti-based direct-write technology for fabricating Ti TiO2 Al tunnel junctions for bolometer and thermometry applications. The goal of our research is to develop simple and efficient technology for fabricating SIS tunnel junctions between Ti and Al with TiO2 as an insulating barrier. The key point of this technology is the deposition of a Ti film as a base electrode and deposition of an Al electrode after oxidation of the Ti. This approach allows one to realize any geometry of the tunnel junctions and of the absorber with no limitation related to the area of the junctions or the thickness of the absorber. In particular, a very thin and completely flat absorber can be created with no bending parts, which is not possible using the shadow evaporation technique or standard trilayer technology. Besides, the proposed new approach does not require one-cycle evaporation for deposition of tunnel junctions which gives us more freedom in the geometry of the counter-electrodes. The junctions are to be used for bolometer applications, such as the fabrication of microwave receivers for sensitive measurements in new generation telescopes, e.g. CLOVER and BOOMERANG projects including polarization cosmic microwave background radiation measurements, and the OLIMPO balloon telescope project which is dedicated to measuring the Sunyaev Zeldovich effect in clusters of galaxies. As the first step, SIN tunnel junctions have been fabricated and characterized.

  12. Improving hot corrosion resistance of two phases intermetallic alloy α2-Ti3Al/γ-TiAl with enamel coating

    NASA Astrophysics Data System (ADS)

    Pambudi, Muhammad Jajar; Basuki, Eddy Agus; Prajitno, Djoko Hadi

    2017-01-01

    TiAl intermetallic alloys have attracted great interest among aerospace industry after successful utilization in low pressure turbine blades of aircraft engine which makes dramatic weight saving up to 40% weight saving. However, poor oxidation and corrosion resistance at temperatures above 800°C still become the drawbacks of this alloys, making the development of protective coatings to improve the resistance is important. This study investigates the hot corrosion behavior of two phases intermetallic alloy α2-Ti3Al/γ-TiAl with and without enamel coating using immersion test method in molten salt of 85%-wt Na2SO4 and 15%-wt NaCl at 850°C. The results show after 50 hours of hot corrosion test, bare alloy showed poor hot corrosion resistance due to the formation of non-protective Al2O3+TiO2 mixed scale at the surface of the alloy. Improvement of hot corrosion resistance was obtained in samples protected with enamel coating, indicated by significant decreasing in mass change (mg/cm2) by 98.20%. Enamel coating is expected to has the capability in suppressing the diffusion of oxygen and corrosive ions into the substrate layer, and consequently, it improves hot corrosion resistance of the alloy. The study showed that enamel coatings have strong adherent to the substrate and no spallation was observed after hot corrosion test. Nevertheless, the dissolution of oxides components of the enamel coating into the molten salts was observed that lead enamel coating degradation. This degradation is believed involving Cl- anion penetration into the substrate through voids in the coating that accelerates the corrosion of the two phases α2-Ti3Al/γ-TiAl alloy. Even though further observations are needed, it appears that enamel coating could be a promising protective coating to increase hot corrosion resistance of TiAl intermetallic alloys.

  13. High stability of magnetic parameters in Fe-Al nanocomposite powders

    NASA Astrophysics Data System (ADS)

    Jani, S.; Sebastian, V.; Sudheesh, V.; Nehra, J.; Lakshmi, N.; Venugopalan, K.

    2016-09-01

    The structural and magnetic properties of Fe75Al25 nanosystem prepared by high energy ball milling for 15 h milling time have been studied. Structural analysis shows the formation of distinct Fe-Al portions with Al at grain boundaries, indicating that Fe-Al nanocomposite formation is favored over alloying due to the formation of diffusion hindering Fe-Al phase at grain boundaries. The saturation magnetization (Ms) of the nanocomposite at 8 nm grain size is 117 emu/g (i.e. 55 % that of pure Fe). The Curie temperature (TC) 1053 K matches the value of pure bcc α-Fe. M-H curves recorded after M-T studies are the same as before indicating the extreme stability of this system against high temperatures. Low temperature M-T measurements and room temperature remanence measurements show that interparticle interactions are demagnetizing kind and dipolar in nature.

  14. Reaction pathways of dimethyl phthalate degradation in TiO2-UV-O2 and TiO2-UV-Fe(VI) systems.

    PubMed

    Yuan, Bao-ling; Li, Xiang-zhong; Graham, Nigel

    2008-05-01

    The photocatalytic degradation of dimethyl phthalate (DMP) in aqueous TiO2 suspension under UV illumination has been investigated using oxygen (O2) and ferrate (Fe(VI)) as electron acceptors. The experiments demonstrated that Fe(VI) was a more effective electron acceptor than O2 for scavenging the conduction band electrons from the surface of the catalyst. Some major intermediate products from DMP degradation were identified by HPLC and GC/MS analyses. The analytical results identified dimethyl 3-hydroxyphthalate and dimethyl 2-hydroxyphthalate as the two main intermediate products from the DMP degradation in the TiO2-UV-O2 system, while in contrast phthalic acid was found to be the main intermediate product in the TiO2-UV-Fe(VI) system. These findings indicate that DMP degradation in the TiO2-UV-O2 and TiO2-UV-Fe(VI) systems followed different reaction pathways. An electron spin resonance analysis confirmed that hydroxyl radicals existed in the TiO2-UV-O2 reaction system and an unknown radical species (most likely an iron-oxo species) is suspected to exist in the TiO2-UV-Fe(VI) reaction system. Two pathway schemes of DMP degradation in the TiO2-UV-O2 and TiO2-UV-Fe(VI) reaction systems are proposed. It is believed that the radicals formed in the TiO2-UV-O2 reaction system preferably attack the aromatic ring of the DMP, while in contrast the radicals formed in the TiO2-UV-Fe(VI) reaction systems attack the alkyl chain of DMP.

  15. Textural and geochemical studies of detrital Fe-Ti oxides and test of their validity in provenance determination, a case study from Central Iran

    NASA Astrophysics Data System (ADS)

    Amini, Abdolhossein; Anketell, Joseph Michael

    2015-03-01

    This paper aims to test the reliability of texture and composition of detrital Fe-Ti oxides in provenance determination, via a case study on the most important siliciclastic unit of Central Iran (Upper Red Formation). Significant exposures of the formation in its basin margins and abundance of detrital Fe-Ti oxides in its component facies nominate it for this study. Samples from representative sections of the formation are studied by SEM, equipped with X-ray analyzer, for textural and compositional properties of the Fe-Ti oxides. In terms of texture, ∼75% of the studied grains are found heterogeneous with ilmenite exsolution/intergrowth in the titanomagnetite host (∼60%), magnetite-hematite exsolution/intergrowth (∼12%) and magnetite-pseudobrookite (∼2%) and magnetite-hematite-rutile (∼1%) intergrowths. Remaining grains (∼25%) are homogenous with titanomagnetite (∼19%), ilmenite (∼5%) and rutile and chromite (∼1%) composition. Four major types of texture (trellis, sandwich, composite and no distinct pattern) are discriminated in the heterogeneous grains, which characteristics and proportion provide significant information on their provenance. In terms of composition, majority of studied grains fall into magnetite-ulvöspinel and ilmenite-hematite solid solution series in the TiO2-FeO-Fe2O3 system. The FeO, MnO, MgO, ZnO, TiO2, Fe2O3, Al2O3 and Cr2O3 contents of the grains are used for their provenance determination. On the basis of results from textural and geochemical properties of the studied grains, intermediate (andesitic to dacitic) to basic volcanic rocks (dissected arc) are determined as parent rocks of the studied grains. These findings are combined with paleocurrent patterns of the hosting facies to locate the transportation pathways of the grains and their source area. Texture and composition of Fe-Ti minerals from nominated parent rocks are studied in similar methods. Comparison of texture and composition of the detrital Fe-Ti oxides

  16. Surface, dynamic and structural properties of liquid Al-Ti alloys

    NASA Astrophysics Data System (ADS)

    Novakovic, R.; Giuranno, D.; Ricci, E.; Tuissi, A.; Wunderlich, R.; Fecht, H.-J.; Egry, I.

    2012-01-01

    The systems containing highly reactive element such as Ti are the most difficult to be determined experimentally and therefore, it is often necessary to estimate the missing values by theoretical models. The thermodynamic data of the Al-Ti system are scarce, its phase diagram is still incomplete and there are very few data on the thermophysical properties of Al-Ti melts. The study on surface, dynamic and static structural properties of liquid Al-Ti alloys has been carried out within the framework of the Compound Formation Model. In spite of the experimental difficulties, the surface tension of liquid Al-2 at.%Ti alloy has been measured over a temperature range by the pinned drop method.

  17. Brillouin light scattering study of Co2Cr0.6Fe0.4Al and Co2FeAl Heusler compounds

    NASA Astrophysics Data System (ADS)

    Gaier, O.; Hamrle, J.; Trudel, S.; Conca Parra, A.; Hillebrands, B.; Arbelo, E.; Herbort, C.; Jourdan, M.

    2009-04-01

    The thermal magnonic spectra of Co2Cr0.6Fe0.4Al (CCFA) and Co2FeAl were investigated using Brillouin light scattering (BLS) spectroscopy. For CCFA, the exchange constant A (exchange stiffness D) is found to be 0.48 ± 0.04 µerg cm-1 (203 ± 16 meV Å2), while for Co2FeAl the corresponding values of 1.55 ± 0.05 µerg cm-1 (370 ± 10 meV Å2) were found. The observed asymmetry in the BLS spectra between the Stokes and anti-Stokes frequencies was assigned to an interplay between the asymmetrical profiles of hybridized Damon-Esbach and perpendicular standing spin-wave modes, combined with the optical sensitivity of the BLS signal to the upper side of the CCFA or Co2FeAl film.

  18. Half-metallic properties of the Co 2Ti 1- xFe xGa Heusler alloys and Co 2Ti 0.5Fe 0.5Ga (0 0 1) surface

    NASA Astrophysics Data System (ADS)

    Ahmadian, F.; Boochani, A.

    2011-07-01

    Electronic and magnetic properties of the bulk Co 2Ti 1- xFe xGa Heusler alloys and Co 2Ti 0.5Fe 0.5Ga (0 0 1) surfaces are studied within the framework of density functional theory using the augmented plane wave plus local orbital (APW+lo) approach. It will be shown that all alloys have the spin polarization of the ideal 100% value except the Co 2FeGa alloy with spin polarization about 98%. Co 2Ti 0.5Fe 0.5Ga is an example that is stable against the effects destroying the half-metallicity due to the position of the Fermi energy ( EF) in the middle of the minority band gap. The phase diagram obtained by ab-initio atomistic thermodynamics shows that in the higher limit of μGa three surfaces of FeGa, TiGa and TiFeGa are accessible in the Co 2Ti 0.5Fe 0.5Ga alloy but on decreasing μGa, the accessible region gradually moves towards FeGa termination. It is discussed that, at the ideal surfaces, half-metallicity of the alloy is lost, although the TiGa surface keeps high spin polarization (about 95%).

  19. Ti/Al multilayer zone plate and Bragg-Fresnel lens.

    PubMed

    Koike, M; Suzuki, I H; Komiya, S; Amemiya, Y

    1998-05-01

    By using a helicon plasma sputtering technique, a one-dimensional Ti/Al multilayer zone plate with an outermost layer width of 76 nm has been successfully fabricated. A Bragg-Fresnel lens has been made by combining this zone plate with a Ge(422) crystal. Comparison of the Ti/Al multilayer zone plate with the Ag/Al zone plate is discussed in terms of focusing efficiency.

  20. Cracking and healing of oxide scales on Ti-Al alloys at 900 C

    SciTech Connect

    Schmitz-Niederau, M.

    1999-10-01

    This behavior of oxide scales on Ti-50Al and Ti-50Al-2Nb (at.%) was investigated in constant strain-rate tensile tests at 900 C in air. The strain rates ranged between 1 {times} 10{sup {minus}9} sec{sup {minus}1} and 3 {times} 10{sup {minus}4} sec{sup {minus}1}. The tests were accompanied by acoustic-emission measurements in order to detect scale-cracking processes during deformation. The critical strains to scale cracking amounted to 0.12-0.5% for the scales on TiAl and 0.17--0.58% for Ti-50Al-2Nb. These values were found to depend strongly on the size of the pores in the scales and, by using a fracture mechanics-based model, the results for the critical strains could be condensed into a narrow scatterband, which is independent of the applied strain rate. Healing of scale cracks was found for strain rates below 1.5 {times} 10{sup {minus}6} sec{sup {minus}1} (Ti-Al) and 1.9 {times} 10{sup {minus}4} sec{sup {minus}1} (Ti-Al-Nb), respectively. It turned out that the healing process is dominated by TiO{sub 2} growth. In a later healing stage, the original Al{sub 2}O{sub 3} barrier is, however, restored in the scale on Ti-50 Al. For Ti-50Al-2Nb, an Al{sub 2}O{sub 3} layer is found on the former scale-crack contours. The healing process is also described by a quantitative model. As a general conclusion from the investigations, it turned out that critical strains to oxide-scale cracking can be estimated from just simple oxidation experiments without sophisticated mechanical testing if the microstructural parameters of the scale are determined quantitatively as a function of oxidation time by metallographic means.

  1. Spherical nanoindentation stress-strain curves of commercially pure titanium and Ti-6Al-4V

    SciTech Connect

    Weaver, Jordan S.; Priddy, Matthew W.; McDowell, David L.; Kalidindi, Surya R.

    2016-07-27

    Spherical nanoindentation combined with electron back-scattered diffraction was employed to characterize the grain-scale elastic and plastic anisotropy of single crystal alpha-Ti for commercially pure (CP-Ti) and alloyed (Ti-64) titanium. In addition, alpha-beta Ti (single colony) grains were characterized. The data set includes the nanoindentation force, displacement, and contact stiffness, the nanoindentation stress-strain analysis, and the alpha-Ti crystal orientations. Details of the samples and experimental protocols can be found in Weaver et al. (2016) Acta Materialia doi:10.1016/j.actamat.2016.06.053.

  2. Superelasticity, corrosion resistance and biocompatibility of the Ti-19Zr-10Nb-1Fe alloy.

    PubMed

    Xue, Pengfei; Li, Yan; Li, Kangming; Zhang, Deyuan; Zhou, Chungen

    2015-05-01

    Microstructure, mechanical properties, superelasticity and biocompatibility of a Ti-19Zr-10Nb-1Fe alloy are investigated. X-ray diffraction spectroscopy and transmission electron microscopy observations show that the as-cast Ti-19Zr-10Nb-1Fe alloy is composed of α' and β phases, but only the β phase exists in the as-rolled and as-quenched alloys. The tensile stress-strain tests indicate that the as-quenched alloy exhibits a good combination of mechanical properties with a large elongation of 25%, a low Young's modulus of 59 GPa and a high ultimate tensile stress of 723 MPa. Superelastic recovery behavior is found in the as-quenched alloy during tensile tests, and the corresponding maximum of superelastic strain is 4.7% at the pre-strain of 6%. A superelastic recovery of 4% with high stability is achieved after 10 cyclic loading-unloading training processes. Potentiodynamic polarization and ion release measurements indicate that the as-quenched alloy shows a lower corrosion rate in Hank's solution and a much less ion release rate in 0.9% NaCl solution than those of the NiTi alloys. Cell culture results indicate that the osteoblasts' adhesion and proliferation are similar on both the Ti-19Zr-10Nb-1Fe and NiTi alloys. A better hemocompatibility is confirmed for the as-quenched Ti-19Zr-10Nb-1Fe alloy, attributed to more stable platelet adhesion and small activation degree, and a much lower hemolysis rate compared with the NiTi alloy.

  3. Microstructural evolution in joining of TiAl with a liquid Ti alloy

    SciTech Connect

    Blue, C.A.; Blue, R.A.; Lin, R.Y. . Dept. of Materials Science and Engineering)

    1995-01-01

    In this study, the reaction between titanium aluminide and a liquid titanium alloy, 70Ti-15Cu-15Ni in wt%, was investigated in order to reveal the behavior of TiAl during joining. The microstructural evolution of the reacted melt during solidification was also studied. Issues of concern in this study include: (1) the solidification process of the melt upon termination of heating, and (2) the diffusion of Cu and Ni into the substrate during processing. To accurately control the extent of reaction, an innovative infrared processing technique was used. Infrared processing can produce heating rates exceeding 100 C/s up to the processing temperature and cooling to below 500 C in a few seconds. Such rapid rates of processing decreases or eliminates the adverse effects associated with prolonged heating. In this study, experiments were conducted at various heating times in order to investigate the solidified zone microstructure, melt affected zone thickness, and base material microstructure. The system investigated in this study is directly related to joining of titanium aluminide with a titanium brazing alloy. Meanwhile, the evolution of the microstructure may be applied to other solid-liquid reactions of titanium alloys.

  4. Radiation effects in multilayer ohmic contacts Au-Ti-Al-Ti-n-GaN

    SciTech Connect

    Belyaev, A. E.; Boltovets, N. S.; Ivanov, V. N.; Kapitanchuk, L. M.; Konakova, R. V. Kudryk, Ya. Ya.; Lytvyn, O. S.; Milenin, V. V.; Sheremet, V. N.; Sveshnikov, Yu. N.

    2009-07-15

    Radiation effects in the Au-Ti-Al-Ti-n-GaN multilayer metallization subjected to irradiation with {sup 60}Co {gamma}-ray photons in the dose range 4 x 10{sup 6}-2 x 10{sup 7} Gy are considered, and the effect of radiation on the initial contact structures and the structures subjected to a rapid thermal annealing (RTA) at high-temperature in the nitrogen atmosphere is studied. Irradiation does not significantly affect the properties of structures that were not subjected to the heat treatment. An RTA at 700 deg. C brings about a deterioration of the contact-layer morphology. The morphological and structural transformations in the contact metallization due to the RTA are enhanced by irradiation with {gamma}-ray photons. The combined radiation-thermal treatment is conducive to the mass transfer between contacting layers. In addition, after {gamma}-ray irradiation with the dose of 2 x 10{sup 7} Gy, the oxygen-impurity atoms appear over the entire contact's structure and are observed in a large amount in the near-contact GaN region.

  5. An x-ray photoemission electron microscopy study of the formation of Ti-Al phases in 4 mol% TiCl3 catalyzed NaAlH4 during high energy ball milling

    NASA Astrophysics Data System (ADS)

    Dobbins, Tabbetha; Abrecht, Mike; Uprety, Youaraj; Moore, Kristan

    2009-05-01

    This study reports reaction pathways to form TiAlx metallic complexes during the high energy ball milling of 4 mol% TiCl3 with NaAlH4 powders determined using local structure analysis of Tix+ and Alx+ species. Using x-ray photoemission electron microscopy (XPEEM) and x-ray diffraction (XRD), the oxidation state of Alx+ and Tix+ and the crystalline compounds existing in equilibrium with NaAlH4 were tracked for samples milled for times of 0 (i.e. mixing), 5, and 25 min. XPEEM analysis of the Al K edge after 5 min of milling reveals that Al remains in the 3+ oxidation state (i.e. in NaAlH4) around Ti0-rich regions of the sample. After 25 min of high energy milling, Ti0 has reacted with Al3+ (in nearby NaAlH4) to form TiAlx complexes. This study reports the pathway for TiAlx complex formation during milling of 4 mol% TiCl3 catalyzed NaAlH4 to be as follows: (1) Ti3+ reduces to Ti0 (with Al3+ near Ti0 regions) and (2) Ti0 reacts with Al3+ in NaAlH4 to form TiAlx complexes.

  6. Infrared Brazing Fe3Al Using Ag-Based Filler Metals

    NASA Astrophysics Data System (ADS)

    Shiue, Ren-Kae; Li, Yao; Wu, Shyi-Kaan; Wu, Ling-Mei

    2010-11-01

    The microstructural evolution and bonding shear strength of infrared brazed Fe3Al using Ag and BAg-8 (72Ag-28Cu in wt pct) braze alloys have been studied. The Ag-rich phase alloyed with Al dominates the entire Ag brazed joints, and the shear strength is independent of the brazing time. The BAg-8 brazed joint contains Ag-Cu eutectic for all brazing conditions, and its shear strength increases slightly with increasing brazing time. The highest shear strength of 181 MPa is acquired from the joint infrared brazed at 1073 K (800 °C) for 600 seconds. A thin layer of Fe3Al is identified at the interface between the brazed zone and the substrate for both braze alloys. An Al depletion zone in the Fe3Al substrate next to the interfacial Fe3Al is identified as the α-Fe phase. The dissolution of Al from the Fe3Al substrate into the molten braze causes the formation of α-Fe in the Fe3Al substrate.

  7. Flux-assisted wetting and spreading of Al on TiC.

    PubMed

    López, V H; Kennedy, A R

    2006-06-01

    The effect of a K-Al-F-based flux on the spreading of Al on TiC, at temperatures up to 900 degrees C, in Ar and in air has been studied. Whilst obtuse contact angles were observed without flux, the flux facilitated rapid spreading to a perfect wetting condition, in both Ar and in air. The atmosphere was found to have a weak effect on the spreading kinetics as the liquid flux provides a locally protective atmosphere by spreading over the TiC surface and also on the solid surface of Al. The flux dissolves the aluminium oxide, covering Al, so that when Al melts, and the oxide layer has been removed or weakened, intimate contact occurs between liquid Al and the TiC substrate facilitating spontaneous spreading and instantaneous wetting of liquid Al on TiC. Since flux-assisted spreading is very rapid and occurs without the formation of a reaction layer at the Al/TiC interface, this process is very different to the reactive wetting behaviour previously reported in the Al-TiC system.

  8. Component Activity Measurements in the Ti-Al-O System by Knudsen Cell Mass Spectrometry

    NASA Technical Reports Server (NTRS)

    Copland, Evan; Jacobson, Nathan S.

    2003-01-01

    Titanium-aluminides (containing (alpha)2-Ti3Al and gamma-TiAl intermetallic phases) have received continued research focus due to their potential as low-density materials for structural applications at intermediate temperatures. However their application above about 850C is hindered by poor oxidation resistance, characterized by the formation of a non-protective TiO2+Al2O3 scale and an oxygen-enriched subsurface zone. Consistent with this are measured titanium and aluminum activities in "oxygen-free" titanium-aluminides, which indicate Al2O3 is only stable for aluminum concentrations greater then 54 atom percent at 1373 K. However, the inability to form a protective Al2O3 scale is in apparent conflict with phase diagram studies, as experimental isothermal sections of the Ti-Al-O system show gamma-TiAl + alpha2-Ti3Al structures are in equilibrium only with Al2O3. The apparent resolution to this conflict lies in the inclusion of oxygen effects in the thermodynamic measurements

  9. Strain and Cohesive Energy of TiN Deposit on Al(001) Surface: Density Functional Calculation

    NASA Astrophysics Data System (ADS)

    Ren, Yuan; Liu, Xuejie

    2016-07-01

    To apply the high hardness of TiN film to soft and hard multilayer composite sheets, we constructed a new type of composite structural material with ultra-high strength. The strain of crystal and cohesive energy between the atoms in the eight structures of N atom, Ti atom, 2N2Ti island and TiN rock salt deposited on the Al(001) surface were calculated with the first-principle ultra-soft pseudopotential approach of the plane wave based on the density functional theory. The calculations of the cohesive energy showed that N atoms could be deposited in the face-centered-cubic vacancy position of the Al(001) surface and results in a cubic structure AlN surface. The TiN film could be deposited on the interface of β-AlN. The calculations of the strains showed that the strain in the TiN film deposited on the Al(001) surface was less than that in the 2N2Ti island deposited on the Al(001) surface. The diffusion behavior of interface atom N was investigated by a nudged elastic band method. Diffusion energy calculation showed that the N atom hardly diffused to the substrate Al layer.

  10. Effect of Impact Damage on the Fatigue Response of TiAl Alloy-ABB-2

    NASA Technical Reports Server (NTRS)

    Draper, S. L.; Lerch, B. A.; Pereira, J. M.; Nathal, M. V.; Nazmy, M. Y.; Staubli, M.; Clemens, D. R.

    2001-01-01

    The ability of gamma-TiAl to withstand potential foreign or domestic object damage is a technical risk to the implementation of gamma-TiAl in low pressure turbine (LPT) blade applications. In the present study, the impact resistance of TiAl alloy ABB-2 was determined and compared to the impact resistance of Ti(48)Al(2)Nb(2)Cr. Specimens were impacted with four different impact conditions with impact energies ranging from 0.22 to 6.09 J. After impacting, the impact damage was characterized by crack lengths on both the front and backside of the impact. Due to the flat nature of gamma-TiAl's S-N (stress vs. cycles to failure) curve, step fatigue tests were used to determine the fatigue strength after impacting. Impact damage increased with increasing impact energy and led to a reduction in the fatigue strength of the alloy. For similar crack lengths, the fatigue strength of impacted ABB-2 was similar to the fatigue strength of impacted Ti(48)Al(2)Nb(2)Cr, even though the tensile properties of the two alloys are significantly different. Similar to Ti(48)Al(2)Nb(2)Cr, ABB-2 showed a classical mean stress dependence on fatigue strength. The fatigue strength of impacted ABB-2 could be accurately predicted using a threshold analysis.

  11. Synthesis of Nano-Crystalline Gamma-TiAl Materials

    NASA Technical Reports Server (NTRS)

    Hales, Stephen J.; Vasquez, Peter

    2003-01-01

    One of the principal problems with nano-crystalline materials is producing them in quantities and sizes large enough for valid mechanical property evaluation. The purpose of this study was to explore an innovative method for producing nano-crystalline gamma-TiAl bulk materials using high energy ball milling and brief secondary processes. Nano-crystalline powder feedstock was produced using a Fritsch P4(TM) vario-planetary ball mill recently installed at NASA-LaRC. The high energy ball milling process employed tungsten carbide tooling (vials and balls) and no process control agents to minimize contamination. In a collaborative effort, two approaches were investigated, namely mechanical alloying of elemental powders and attrition milling of pre-alloyed powders. The objective was to subsequently use RF plasma spray deposition and short cycle vacuum hot pressing in order to effect consolidation while retaining nano-crystalline structure in bulk material. Results and discussion of the work performed to date are presented.

  12. Development of Al-killed/Ti stabilized steels

    NASA Astrophysics Data System (ADS)

    Ramirez-Ledesma, A. L.; Aguilar-Mendez, M. A.; Rodriguez-Diaz, R. A.; >G Aramburo,

    2015-01-01

    Several Al-killed/Ti-stabilized low carbon steels were developed in a Mexican steel industry with the aim of obtaining an interstitial free steel for automotive applications. The steelmaking route involved the use of 100% sponge iron which was feed into an electric arc furnace, vacuum degassed, ladle treated and continuously casted. The resulting slabs were then hot rolled at 1100 °C and coiled at 650 °C. Then, the steel plates were cold rolled at room temperature and sheets annealed at 700 °C. As-cast micro structure showed the presence of α-ferrite with titanium nitrides in matrix and grain boundaries while in the ashot rolled condition, elongated grains showed the presence of titanium nitrides, titanium sulfides and titanium carbosulfides. The annealed sheets showed, additionally to the other precipitates, the presence of titanium carbides. Microstructure, texture, the Lankford ratio and mechanical properties of fully recrystallized coils fulfilled the target properties established by the automobile industry.

  13. Al-Ti Electrodes for Ferroelectric Thin Films

    NASA Astrophysics Data System (ADS)

    Blanco, Oscar; Heiras, Jesús

    2001-03-01

    We have prepared ferroelectric PZT thin films on silicon substrates with aluminum - titanium layers as bottom electrodes. This type of electrodes were used before and promising results were obtained. However, in order to optimize the ferroelectric properties of the deposited thin films a complete characterization of the electrodes has been undertaken. The Al and Ti layers were deposited by thermal evaporation over Si (111) and (100) substrates. Then the layer were annealed at seven different temperatures in the 300^oC to 600^oC range; the annealing was done in both open and vacuum furnaces. Structure and surface characteristics of the electrodes were determined by X-ray diffraction analysis (XRD), scanning electron microscopy (SEM) and Auger spectroscopy. The electrical properties of the electrodes were also studied. In addition, the structural and dielectric properties of the ferroelectric thin films deposited on these electrodes have been investigated. Thanks are given to I. Gradilla and E. Aparicio for their technical assistance. We gratefully acknowledge the financial support from CONACYT and DGAPA-UNAM.

  14. The Effect of Deposition Conditions on Adhesion Strength of Ti and Ti6Al4V Cold Spray Splats

    NASA Astrophysics Data System (ADS)

    Goldbaum, Dina; Shockley, J. Michael; Chromik, Richard R.; Rezaeian, Ahmad; Yue, Stephen; Legoux, Jean-Gabriel; Irissou, Eric

    2012-03-01

    Cold spray is a complex process where many parameters have to be considered in order to achieve optimized material deposition and properties. In the cold spray process, deposition velocity influences the degree of material deformation and material adhesion. While most materials can be easily deposited at relatively low deposition velocity (<700 m/s), this is not the case for high yield strength materials like Ti and its alloys. In the present study, we evaluate the effects of deposition velocity, powder size, particle position in the gas jet, gas temperature, and substrate temperature on the adhesion strength of cold spayed Ti and Ti6Al4V splats. A micromechanical test technique was used to shear individual splats of Ti or Ti6Al4V and measure their adhesion strength. The splats were deposited onto Ti or Ti6Al4V substrates over a range of deposition conditions with either nitrogen or helium as the propelling gas. The splat adhesion testing coupled with microstructural characterization was used to define the strength, the type and the continuity of the bonded interface between splat and substrate material. The results demonstrated that optimization of spray conditions makes it possible to obtain splats with continuous bonding along the splat/substrate interface and measured adhesion strengths approaching the shear strength of bulk material. The parameters shown to improve the splat adhesion included the increase of the splat deposition velocity well above the critical deposition velocity of the tested material, increase in the temperature of both powder and the substrate material, decrease in the powder size, and optimization of the flow dynamics for the cold spray gun nozzle. Through comparisons to the literature, the adhesion strength of Ti splats measured with the splat adhesion technique correlated well with the cohesion strength of Ti coatings deposited under similar conditions and measured with tubular coating tensile (TCT) test.

  15. Neutron Diffraction Study Oxygen Dissolution Alpha(sub 2)-Ti3Al

    NASA Technical Reports Server (NTRS)

    Jones, Camille Y.; Luecke, William E.; Copland, Evan

    2005-01-01

    Rietveld refinements of neutron powder diffraction data on alpha(sub 2)-Ti3Al have been performed to determine the crystal structure as a function of interstitial oxygen (O) concentration for three alloys with a Ti/Al ratio of approximately equal to 2.34 and O concentrations of 0.25%, 3.99% and 7.71%. The structures of the allows are hexagonal in space group P6(sub 3)/mmc where Ti and Al atoms populate unique sites with excess Al at the Ti site and O atoms occupy octahedral interstitial sites surrounded by six Ti sites. The length of the c-axis was found to increase linearly as the O occupancy of the interstitial sites increased; this lattice lengthening effect was much less pronounced along the alpha axis. Correspondingly, the increases in the lengths of Ti-Al and Ti-Ti bonds with a major component of their direction parallel to the c-axis were roughly an order of magnitude greater than the increases in the lengths of Ti-al and Ti-Ti bonds more closely aligned with the alpha-axis. Densities calculated form the lattice parameters and occupancy factors fall in the range (4.118 plus or minus 0.004) grams per cubic centimeter to (4.194 plus or minus 0.004) grams per cubic centimeter, and exhibit a nearly linear increase with oxygen concentration. Measured densities of (4.113 plus or minus 0.001) grams per cubic centimeter, (4.146 plus or minus 0.009) grams per cubic centimeter, and (4.191 plus or minus 0.002) grams per cubic centimeter for these alloys agree with the results of the refinements.

  16. Metal-organic framework templated synthesis of Fe2O3/TiO2 nanocomposite for hydrogen production.

    PubMed

    deKrafft, Kathryn E; Wang, Cheng; Lin, Wenbin

    2012-04-17

    A new metal-organic framework (MOF)-templated method has been developed for the synthesis of a metal oxide nanocomposite with interesting photophysical properties. Fe-containing nanoscale MOFs are coated with amorphous titania, then calcined to produce crystalline Fe(2)O(3)/TiO(2) composite nanoparticles. This material enables photocatalytic hydrogen production from water using visible light, which cannot be achieved by either Fe(2)O(3) or TiO(2) alone or a mixture of the two.

  17. Effects of Fe Doping on the Structural, Optical, and Magnetic Properties of TiO2 Nanoparticles

    NASA Astrophysics Data System (ADS)

    Thu, Dang Xuan; Trung, Vu Quoc; Nghia, Nguyen Manh; Khang, Nguyen Cao; Lam, Tran Dai

    2016-11-01

    Fe-doped TiO2 nanoparticles have been prepared by the hydrolysis method. The effects of Fe doping on the structural, optical, and magnetic properties of the Ti1- x Fe x O2 ( x = 0.00, 0.03, 0.06, 0.10, 0.13) materials were thoroughly investigated by a combination of various methods, including transmission electron microscopy (TEM), Brunauer-Emmett-Teller (BET) analysis, x-ray diffraction (XRD) analysis, ultraviolet-visible (UV-Vis) reflectance spectroscopy, Raman spectroscopy, and vibrating-sample magnetometry. Analysis of the TEM and XRD measurements showed that the resulting powders had nanoscale particle size. The Fe-doped samples were found to be paramagnetic at room temperature (by magnetization measurements), with Fe acting as substitutional impurity at Ti sites in the anatase TiO2 phase. Substitution of Fe at Ti sites was also confirmed by Raman spectra. The paramagnetic nature of the Ti1- x Fe x O2 samples was further investigated using density functional theory calculations of their electronic band structure and density of states. Finally, the photocatalytic activity of the Fe-doped TiO2 samples was studied by investigating their photocatalytic decomposition of methylene blue.

  18. Micro-arc oxidization fabrication and ethanol sensing performance of Fe-doped TiO2 thin films

    NASA Astrophysics Data System (ADS)

    Ren, Fu-jian; Yu, Xiao-bai; Ling, Yun-han; Feng, Jia-you

    2012-05-01

    In-situ pure TiO2 and Fe-doped TiO2 thin films were synthesized on Ti plates via the micro-arc oxidation (MAO) technique. The as-fabricated anatase TiO2 thin film-based conductometric sensors were employed to measure the gas sensitivity to ethanol. The results showed that Fe ions could be easily introduced into the MAO-TiO2 thin films by adding precursor K4(FeCN)6·3H2O into the Na3PO4 electrolyte. The amount of doped Fe ions increased almost linearly with the concentration of K4(FeCN)6·3H2O increasing, eventually affecting the ethanol sensing performances of TiO2 thin films. It was found that the enhanced sensor signals obtained had an optimal concentration of Fe dopant (1.28at%), by which the maximal gas sensor signal to 1000 ppm ethanol was estimated to be 7.91 at 275°C. The response time was generally reduced by doped Fe ions, which could be ascribed to the increase of oxygen vacancies caused by Fe3+ substituting for Ti4+.

  19. Combustion synthesis of ceramic-metal composite materials - The TiC-Al2O3-Al system

    NASA Technical Reports Server (NTRS)

    Feng, H. J.; Moore, John J.; Wirth, D. G.

    1992-01-01

    Combustion synthesis was applied for producing ceramic-metal composites with reduced levels of porosity, by allowing an excess amount of liquid metal, generated by the exothermic reaction during synthesis, to infiltrate the pores. It is shown that this method, when applied to TiC-Al2O3 system, led to a decreased level of porosity in the resulting TiC-Al2O3-Al product, as compared with that of TiC-Al2O3 system. This in situ procedure is more efficient than the two-stage conventional processes (i.e., sintering followed by liquid metal infiltration), although there are limitations with respect to total penetration of the liquid metal and maintaining a stable propagation of the combustion reaction.

  20. Use of pulsed high power ion beams to enhance tribological properties of stainless steel, Ti, and Al

    SciTech Connect

    Senft, D.C.; Renk, T.J.; Dugger, M.T.; Grabowski, K.S.; Thompson, M.O.

    1998-04-01

    Enhanced tribological properties have been observed after treatment with pulsed high power ion beams, which results in rapid melting and resolidification of the surface. The authors have treated and tested 440C martensitic stainless steel (Fe-17 Cr-1 C). Ti and Al samples were sputter coated and ion beam treated to produce surface alloying. The samples were treated at the RHEPP-I facility at Sandia National Laboratories (0.5 MV, 0.5--1 {micro}s at sample location, <10 J/cm{sup 2}, 1--5 {micro}m ion range). They have observed a reduction in size of second phase particles and other microstructural changes in 440C steel. The hardness of treated 440C increases with ion beam fluence and a maximum hardness increase of a factor of 5 is obtained. Low wear rates are observed in wear tested of treated 440C steel. Surface alloyed Ti-Pt layers show improvements in hardness up to a factor of 3 over untreated Ti, and surface alloys of Al-Si result in a hardness increase of a factor of two over untreated Al. Both surface alloys show increased durability in wear testing. Rutherford Backscattering (RBS) measurements show overlayer mixing to the depth of the melted layer. X-ray Diffraction (XRD) and TEM confirm the existence of metastable states within the treated layer. Treated layer depths have been measured from 1--10 {micro}m.

  1. Analysis of the interphase of a polyamide bonded to chromic acid anodized Ti-6AL-4V

    SciTech Connect

    Guinta, R.K.; Kander, R.G.

    2000-01-06

    Structural adhesive joints, when tested as made, typically fail cohesively through the centerline of the adhesive. However, in any study of adhesive joint durability, failure near the adhesive/substrate interface becomes an important consideration. In the current study, an interfacially debonding adhesive test, the notched coating adhesion (NCA) test, was applied to LaRC(trademark) PETI-5 adhesive bonded to chronic acid anodized (CAA) Ti-6Al-4V. Post-failure analysis of the interphase region included X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), field emission scanning electron microscopy (FE-SEM), and atomic force microscopy (AFM). Mechanical interlocking between an adhesive and a substrate occurs when the liquid adhesive flows into interstices of the substrate, solidifies, and becomes locked in place. Mechanical interlocking is believed to significantly contribute to the adhesion of substrates that exhibit microroughness, such as metal surfaces treated with chromic acid anodization or sodium hydroxide anodization. Filbey and Wightman found that an epoxy penetrated the pores of CAA Ti-6Al-4V, one of the limited number of pore penetration studies that have been reported. In the current study, the penetration of PETI-5 into the pores of CAA Ti-6Al-4V is investigated through analysis of adhesive/substrate failure surfaces.

  2. Wear behavior of the plasma and thermal oxidized Ti-15Mo and Ti-6Al-4V alloys

    NASA Astrophysics Data System (ADS)

    Hacisalioglu, I.; Yildiz, F.; Alsaran, A.; Purcek, G.

    2017-02-01

    Titanium and its alloys widely used in load bearing applications. Titanium alloys are capable of providing lower elastic modulus and better corrosion resistance with alloying processes. In spite of the modified mechanical properties, the surface degradation is still the main critical defect. Ti-15Mo alloy is one of the alpa+beta titanium alloys with acceptable mechanical and chemical superiority. Recent researches in literature show that the wear performance of base Ti-15Mo is relatively low as compared to Ti-6Al-4V, using in high performance applications. Plasma oxidized surfaces increase the tribological and chemical performance of titanium alloys. In this study the Ti-15Mo alloy and Ti-6Al-4V alloys were compared in terms of wear performance. To obtain alloys with similar microstructure they were solution treated at 800°C 1H and then air-cooled. The plasma and thermal oxidations were applied at 650°C for 1 hour. Wear performance of oxidized surfaces investigated in dry conditions. Oxidized surface characterized with XRD, SEM, 3D profilometer and hardness measurements. Wear volume calculated with 3D profilometer. Results show that oxidizing increased the surface roughness and improved the wear performance of Ti15Mo alloy. The plasma and thermal oxidized Ti-15Mo showed a remarkable increase in wear resistance.

  3. An innovative ultrasound, Fe(2+) and TiO(2) photoassisted process for bisphenol A mineralization.

    PubMed

    Torres-Palma, Ricardo A; Nieto, Jessica I; Combet, Evelyne; Pétrier, Christian; Pulgarin, Cesar

    2010-04-01

    This paper explores the degradation of a model pollutant, bisphenol A, by an advanced oxidation process that combines sonolysis, Fe(2+), and TiO(2) in a photoassisted process. Experiments were done under saturated oxygen conditions. The effect of different Fe(2+) (0.56 and 5.6 mg/L) and TiO(2) (10 and 50 mg/L) concentrations was investigated on both the elimination and mineralization of the pollutant. A pronounced synergistic effect that led to the complete and rapid elimination of dissolved organic carbon (DOC) was observed even at low catalyst loadings. In this system, almost a complete removal of DOC (93%) was observed after 4 h using 10 and 5.6 mg/L of TiO(2) and Fe(2+), respectively, whereas at the same time, only 5, 6, and 22% of DOC was removed by an individual process alone (TiO(2) photocatalysis, ultrasound, and photo-Fenton, respectively). In this system, ultrasound has the principal role of eliminating the initial substrate and providing hydrogen peroxide for the photocatalytic systems, while photo-Fenton and TiO(2) photocatalysis are mainly responsible for the transformation of the intermediates in CO(2) and H(2)O. The role of H(2)O(2) generated from the sonochemical process is also discussed.

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

    PubMed

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

    2002-04-01

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

  5. Crystallization Kinetics Study on Magnetron-Sputtered Amorphous TiAl Alloy Thin Films

    NASA Astrophysics Data System (ADS)

    Shui, Lu-Yu; Yan, Biao

    2014-04-01

    Crystallization kinetics of magnetron-sputtered amorphous TiAl alloy thin films is investigated by differential scanning calorimetry through isothermal analysis and non-isothermal analysis. In non-isothermal analysis, the Kissinger method and the Ozawa method are used to calculate the apparent activation energy and local activation energy, respectively, in the crystallization processes of amorphous TiAl thin films. Furthermore, the crystallization mechanism is discussed from the investigation of the Avrami exponent by isothermal analysis. In addition, x-ray diffraction is utilized to reveal the grain orientation and evolution during the crystallization of TiAl thin films.

  6. CEMS study of defect annealing in Fe implanted AlN

    NASA Astrophysics Data System (ADS)

    Bharuth-Ram, K.; Geburt, S.; Ronning, C.; Masenda, H.