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Sample records for alloyed powders hyperfine

  1. Evolution of structure, microstructure and hyperfine properties of nanocrystalline Fe{sub 50}Co{sub 50} powders prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Akkouche, K. [LMMC, M' hamed Bougara University, Boumerdes 35000 (Algeria); Guittoum, A., E-mail: guittoum@yahoo.fr [Nuclear Research Centre of Algiers, 2 Bd Frantz Fanon, BP399 Alger-Gare, Algiers (Algeria); Boukherroub, N. [LMMC, M' hamed Bougara University, Boumerdes 35000 (Algeria); Souami, N. [Nuclear Research Centre of Algiers, 2 Bd Frantz Fanon, BP399 Alger-Gare, Algiers (Algeria)

    2011-11-15

    Nanostructured Fe{sub 50}Co{sub 50} powders were prepared by mechanical alloying of Fe and Co elements in a vario-planetary high-energy ball mill. The structural properties, morphology changes and local iron environment variations were investigated as a function of milling time (in the 0-200 h range) by means of X-ray diffraction, scanning electron microscopy (SEM), energy dispersive X-ray analysis and {sup 57}Fe Moessbauer spectroscopy. The complete formation of bcc Fe{sub 50}Co{sub 50} solid solution is observed after 100 h milling. As the milling time increases from 0 to 200 h, the lattice parameter decreases from 0.28655 nm for pure Fe to 0.28523 nm, the grain size decreases from 150 to 14 nm, while the meal level of strain increases from 0.0069% to 1.36%. The powder particle morphology at different stages of formation was observed by SEM. The parameters derived from the Moessbauer spectra confirm the beginning of the formation of Fe{sub 50}Co{sub 50} phase at 43 h of milling. After 200 h of milling the average hyperfine magnetic field of 35 T suggests that a disordered bcc Fe-Co solid solution is formed. - Highlights: > Nanostructured Fe{sub 50}Co{sub 50} powders were successfully prepared by mechanical alloying process. > Final average grain size value achieved after 200 h of milling was 14 nm. > For the longest milling time the majority of particle grains observed by SEM exhibits a round shape with small diameter.

  2. The hyperfine properties of iron-gallium alloys

    Science.gov (United States)

    Elzain, M.; Gismelseed, A.; Al-Rawas, A.; Yousif, A.; Widatallah, H.; Al-Azri, Maya; Al-Barwani, M.

    2016-12-01

    The hyperfine properties at Fe site in iron-gallium alloy are calculated using the full-potential linear-augmented-plane-waves method. We have calculated the Fermi contact field (Bhf) and isomer shift ( δ) at the Fe site versus the number of neighbouring Ga atoms. We found that Bhf decrease whereas δ increases with increasing number of neighbouring G atom. In addition we have calculated the hyperfine properties of FeGa system with DO3 structure, where various distributions of 4 the Ga atoms in the conventional unit cell are considered (including the regular DO3 structure). We found that the DO3 structure has the lowest energy as compared to the other configurations. The two distinct A and D sites of the ordered DO3 conventional unit cell have two distinct values for Bhf and δ. On changing the atomic arrangement of the Ga atoms within the conventional unit cell, the configuration of the A site is maintained whereas that of the D site becomes imperfect. The contact magnetic hyperfine fields of the D-like sites in the imperfect structures are lower than that of the DO3D site.

  3. Muonium hyperfine parameters in Si{sub 1-} {sub x} Ge {sub x} alloys

    Energy Technology Data Exchange (ETDEWEB)

    King, Philip [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX (United Kingdom)]. E-mail: p.j.c.king@rl.ac.uk; Lichti, Roger [Physics Department, Texas Tech University, Lubbock, TX 79409-1051 (United States); Cottrell, Stephen [ISIS Facility, Rutherford Appleton Laboratory, Chilton, Oxfordshire OX11 0QX (United Kingdom); Yonenaga, Ichiro [Institute for Materials Research, Tohoku University (Japan)

    2006-03-31

    We present studies of muonium behaviour in bulk, Czochralski-grown Si{sub 1-} {sub x} Ge {sub x} alloy material, focusing in particular on the hyperfine parameter of the tetrahedral muonium species. In contrast to the bond-centred species, the hyperfine parameter of the tetrahedral-site muonium centre (Mu{sub T}) appears to vary non-linearly with alloy composition. The temperature dependence of the Mu{sub T} hyperfine parameter observed in low-Ge alloy material is compared with that seen in pure Si, and previous models of the Mu{sub T} behaviour in Si are discussed in the light of results from Si{sub 1-} {sub x} Ge {sub x} alloys.

  4. Advanced powder metallurgy aluminum alloys and composites

    Science.gov (United States)

    Lisagor, W. B.; Stein, B. A.

    1982-01-01

    The differences between powder and ingot metallurgy processing of aluminum alloys are outlined. The potential payoff in the use of advanced powder metallurgy (PM) aluminum alloys in future transport aircraft is indicated. The national program to bring this technology to commercial fruition and the NASA Langley Research Center role in this program are briefly outlined. Some initial results of research in 2000-series PM alloys and composites that highlight the property improvements possible are given.

  5. Hyperfine field distributions in disordered Mn2CoSn and Mn2NiSn Heusler alloys

    Indian Academy of Sciences (India)

    N Lakshmi; Anil Pandey; K Venugopalan

    2002-08-01

    Heusler alloys, Mn2CoSn and Mn2NiSn, were prepared and characterized by X-ray studies. Mössbauer studies using Sn-119 were carried out to investigate the hyperfine fields present at the Sn site in these alloys. The hyperfine field distribution in these alloys as well as X-ray studies point to the chemical disorder present in both alloys. Co-existence of a paramagnetic portion along with the magnetic hyperfine part was observed in Mn2CoSn even at low temperatures, while this was not found in Mn2NiSn spectra. Hyperfine fields at Sn site were calculated using Blandin and Campbell model and compared with the experimental results.

  6. Hyperfine fields in Fe-Ni-X alloys and their application to a study of tempering of 9Ni steel

    Energy Technology Data Exchange (ETDEWEB)

    Fultz, B.; Morris, J.W. Jr.

    1984-12-01

    Hyperfine interactions due to solutes in Fe-Ni-X alloys were systematized, and interpreted with a model of linear response of hyperfine magnetic fields to magnetic moments. The effects of solutes on the /sup 57/Fe hmf were used for chemical analysis of the austenite formed in 9Ni steel during tempering. Diffusion kinetics of the Ni and X solutes were found to play an important role in the formation of the austenite particles.

  7. Powder metallurgy of turbine disc alloys

    Energy Technology Data Exchange (ETDEWEB)

    Ingesten, N.G. (Dep. of Engineering Metals)

    1981-03-01

    The first part embraced a study of carbide precipitated in IN 100 and astrology powders. The powder was heat treated at temperatures between 950/sup 0/C and 1150/sup 0/C. After aging at 950-1100/sup 0/C the MC-carbides formed during atomization were replaced by M/sub 23/C/sub 6/-carbides. After 1150/sup 0/C treatments the MC carbides were present again. Precipitation comparable with that obtained in HIP:ed specimens was not observed at free particle surfaces. However, powder particles which had agglomerated during atomization often exhibited considerable precipitation at contiguous surfaces. Obviously, contact between the particles must occur if coarse precipitation at particle surfaces is to develop. Reduced PPB-precipitation was obtained by pre-heat- treatment of powder before compaction. It is suggested that the carbon otherwise available for PPB-precipitation forms carbides in the interior of the powder particles. The aim of the second part was to ..gamma..-strengthen a Co-based super-alloy (Co-15Cr-3Mo-5Ti). Here the Ti-addition gives a coherent and ordered ..gamma..-phase Co/sub 3/Ti. However, upon ageing the alloy is unstable in order to increase the stability modifications of the alloy were prepared by: leaving out the Mo-content, adding 10 % Ni and by decreasing the Ti-content to 4.2 %. In addition, the effect of enhanced grain size and of deformation was investigated. Significant reduction of the transformation rate was only obtained by decresing the Ti-content while deformation of the alloy greatly increased the transformation rate.(author).

  8. Sintering of titanium alloy by powder metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Cosme, C.R.M. [Universidade de Brasilia (UnB), DF (Brazil); Henriques, V.A.R.; Cairo, C.A.A.; Taddei, E.B. [Centro Tecnico Aeroespacial (CTA), Sao Jose dos Campos, SP (Brazil)

    2009-07-01

    Full text: Titanium alloys are suitable for biomaterial applications, considering its biocompatibility and low elastic modulus compared to steel. Bone resorption in this case can be reduced by load sharing between the implant and natural bone.Starting powders were obtained by hydride method, carried out under positive hydrogen pressure at 500 deg C for titanium and 800 deg C for Nb, Zr and Ta powders. After reaching the nominal temperature, the material was held for 3h, with subsequent cooling to room temperature and milling of the friable hydride. Samples were produce by mixing of initial metallic powders followed by and cold isostatic pressing. Subsequent densification by sintering was performed at temperature range between 900 and 1700 deg C. Characterization was carried out with scanning electron microscopy, X-ray diffractometry and microhardness measurements. Microstructural examinations revealed higher amount of &⧣946;-phase for higher sintering temperature and dissolution of Ta and NB particles. In vitro tests revealed low cytotoxicity of sintered samples. (author)

  9. Advanced powder metallurgy aluminum alloys via rapid solidification technology

    Science.gov (United States)

    Ray, R.

    1984-01-01

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

  10. Electrochemical deposition and characterization of Ni-Mo alloy powders

    Directory of Open Access Journals (Sweden)

    M.G. Pavlović

    2007-12-01

    Full Text Available Electrodeposition of Ni-Mo alloy powders from ammonium sulfate and ammonium chloride containing electrolytes of different Ni/Mo ions concentration ratios was investigated by polarization measurements. The morphology, chemical composition and phase composition of electrodeposited Ni-Mo alloy powders were investigated using DSC, TGA, SEM, EDS and XRD analysis. EDS results showed that powder composition depends on Ni/Mo ions concentration ratio, as well as on the position where the EDS analysis was performed. As-deposited alloy powders were nanocrystalline showing no XRD peaks with undefined morphology (SEM. After recrystallization for 2 h in N2 atmosphere at 600°C the presence of NiMoO4 phase was identified in the powder electrodeposited from chloride electrolyte at the Ni/Mo ions concentration ratio 1/3, with well defined crystalline powder particles.

  11. Microstructure and Aging of Powder-Metallurgy Al Alloys

    Science.gov (United States)

    Blackburn, L. B.

    1987-01-01

    Report describes experimental study of thermal responses and aging behaviors of three new aluminum alloys. Alloys produced from rapidly solidified powders and contain 3.20 to 5.15 percent copper, 0.24 to 1.73 percent magnesium, 0.08 to 0.92 percent iron, and smaller amounts of manganese, nickel, titanium, silicon, and zinc. Peak hardness achieved at lower aging temperatures than with standard ingot-metallurgy alloys. Alloys of interest for automobile, aircraft, and aerospace applications.

  12. TEM microstructure of mechanically alloyed Ti-12Mg powders

    Institute of Scientific and Technical Information of China (English)

    T. S. KIM; B. T. LEE; J. P. AHN; J. K. PARK; J. C. BAE

    2006-01-01

    The microstructures of mechanical alloyed(MA) Ti-12%Mg alloy powders were examined using a high resolution TEM (HRTEM). The effect of MA atmospheres such as argon gas and liquid isopropyl alcohol on the resultant microstructure was investigated. Both the MA powders form a homogeneous Ti-Mg solid solution, but the oxidation behavior is distinguished. The phase change was studied as a function of milling conditions and annealing temperatures.

  13. Powder Processing of Amorphous Tungsten-bearing Alloys and Composites

    Science.gov (United States)

    2015-03-01

    8725 John J. Kingman Road, MS-6201 Fort Belvoir, VA 22060-6201 T E C H N IC A L R E P O R T DTRA-TR-14-73 Powder Processing of Amorphous Tungsten ...Technology, Boise State University, Army Research Laboratory Project Title: Powder Processing of Amorphous Tungsten -bearing Alloys and Composites...strength, we made them better suited to study the mechanical alloying of tungsten -transition metal couples in which interdiffusion during mechanical

  14. TEM study of mechanically alloyed ODS steel powder

    Energy Technology Data Exchange (ETDEWEB)

    Hoffmann, Jan, E-mail: j.hoffmann@kit.edu [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM-AWP), Karlsruhe (Germany); Klimenkov, Michael; Lindau, Rainer; Rieth, Michael [Karlsruhe Institute of Technology (KIT), Institute for Applied Materials (IAM-AWP), Karlsruhe (Germany)

    2012-09-15

    Compared to present reactors, modern nuclear power plant concepts are based on materials which can be operated at higher temperatures and up to higher neutron doses. Oxide dispersion strengthened (ODS) steels - produced by mechanical alloying - with chromium contents of 9 and 14 wt.% (or even more) are typical candidate materials. As the preparation of TEM samples from milled powders is usually very difficult, a new approach has been successfully adopted coming from the TEM sample preparation of biological tissues. Here, the alloyed powder is first embedded and then cut into thin films of 60-90 nm thickness using a microtom. The focal point is to gain a better knowledge of the solution mechanism of Y{sub 2}O{sub 3} in the steel powder during mechanical alloying. Investigations on mechanically alloyed powders containing 13% Cr and Y{sub 2}O{sub 3} were made using a Tecnai Scanning Transmission Electron Microscope (STEM) with EDX detector. Detailed elemental mappings of the powder particles show the presence of Y{sub 2}O{sub 3} particles after different milling times. The non-dissolved Y{sub 2}O{sub 3} phase was detected on the surface of the mechanically alloyed powder particles in the specimen alloyed at times down to 24 h. After mechanically alloying of 80 h, no Y{sub 2}O{sub 3} phase has been detected. Inside the mechanically alloyed powder, no particles were detected. All further results of the elemental mappings after different milling times are analyzed, compared, and discussed in this paper.

  15. Hyperfine and Structural Properties of the Mechanically Alloyed (FeMn){sub 30}Cu{sub 70} System

    Energy Technology Data Exchange (ETDEWEB)

    Restrepo, J., E-mail: jrestre@fisica.udea.edu.co [Universidad de Antioquia, A.A, Grupo de Estado Solido, Instituto de Fisica (Colombia); Greneche, J. M. [Universite du Maine, Laboratoire de Physique de l' Etat Condense, UMR CNRS 6087 (France)

    2004-12-15

    Nanostructured Fe{sub 15}Mn{sub 15}Cu{sub 70} alloys were prepared by high-energy ball milling. The alloying process spans grinding times from 15 minutes to 114 hours. The Moessbauer isomer shifts are analyzed at 77 K and 4.2 K as a function of the average lattice parameter determined from Rietveld analysis of the X-ray diffraction data. Evidence of two different iron sites at 77 K to account for the asymmetry of the Moessbauer spectra is discussed by correlating hyperfine and structural parameters. This leads to conclude the occurrence of a low-spin to high-spin partial transition of iron at a critical volume of around 50 A{sup 3} at 77 K, supporting theoretical predictions.

  16. The Fatigue of Powder Metallurgy Alloys.

    Science.gov (United States)

    2014-09-26

    v1o -2- MATERIALS AND TESTS Table 1 provides a complete listing of the alloys studied in this program together with their chemical compositions ...use can minimize material waste and minimize machining costs. In addition there is the potential for the development of more fine-grained and...out under fully reversed loading conditions in the high cycle range with smooth specimens. X7090 and X7091 are P/M alloys, 7075 is an ingot alloy

  17. Mechanical alloying of Al-3 at. % Mo powders

    Energy Technology Data Exchange (ETDEWEB)

    Zdujic, M. (Srpska Akademija Nauka i Umetnosti, Belgrade (Yugoslavia). Dept. of Technical Science); Kobayashi, K.F. (Osaka Univ., Suita (Japan). Dept. of Welding and Production Engineering); Shingu, P.H. (Kyoto Univ. (Japan). Dept. of Metal Science and Technology)

    1990-05-01

    Mechanical alloying of elemental powders of aluminum and molybdenum (Al-3 at.% Mo) has been carried out in a conventional horizontal ball mill up to 1000 h of milling time. Mechanically alloyed powders were investigated by scanning electron microscopy, X-ray diffraction analysis and differential scanning calorimetry. After prolonged milling time molybdenum was finely dispersed in aluminum matrix. The dispersoid sizes were less than about 100 nm, with average size considerably smaller. By the heat treatment of the mechanically alloyed powders, the intermetallic compound Al{sub 12}Mo was formed. The reaction temperature for the formation of Al{sub 12}Mo decreased with increasing milling time. The Johnson-Mehl-Avrami exponent of n=2.8{plus minus}0.3 for the formation of Al{sub 12}Mo was obtained with the apparent activation energy of 165{plus minus}12 kJ/mol (1.7{plus minus}0.1 eV). (orig.).

  18. Mechanical alloying nanotechnology, materials science and powder metallurgy

    CERN Document Server

    El-Eskandarany, M Sherif

    2015-01-01

    This book is a detailed introduction to mechanical alloying, offering guidelines on the necessary equipment and facilities needed to carry out the process and giving a fundamental background to the reactions taking place. El-Eskandarany, a leading authority on mechanical alloying, discusses the mechanism of powder consolidations using different powder compaction processes. A new chapter will also be included on thermal, mechanically-induced and electrical discharge-assisted mechanical milling. Fully updated to cover recent developments in the field, this second edition also introduces new a

  19. Characteristics and Microstructure of a Hypereutectic Al-Si Alloy Powder by Ultrasonic Gas Atomization Process

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    A hypereutectic Al-Si alloy powder was prepared by ultrasonic gas atomization process. The morphologies, microstructure and phase constituent of the alloy powder were studied. The results showed that powder of the alloy was very fine and its rnicrostructure was mainly consisted of Si crystals plus intermetallic compound Al9FeSi3, which were. very fine and uniformly distributed.

  20. Reduction Expansion Synthesis for Magnetic Alloy Powders

    Science.gov (United States)

    2015-12-01

    with which the product is manufactured, are inversely proportional to grain size of the powder used in the manufacturing process. Thus, as particle size...additional form of agglomeration occurs due to the magnetic characteristics of the particles. This agglomeration results from the magnetic poles of

  1. Microstructure and properties of hot compacted powders of aluminium alloys.

    Science.gov (United States)

    Lityńska-Dobrzyńska, L; Dutkiewicz, J; Maziarz, W; Kanciruk, A

    2009-11-01

    Atomized 6061 aluminium alloy powders with and without the addition of 2 wt% Zr were milled for 80 h in a planetary ball mill and hot pressed in vacuum. The milled powders showed microhardness of about 170 HV, which increased after hot pressing up to 260 HV and up to 280 HV for powders without and with the Zr additions, respectively. Compression tests showed the high yield stress of 300 MPa obtained for the hot-pressed sample produced from the initial powders compared with ultimate compression strength of above 800 MPa for that of the milled sample and slightly higher for that with Zr additions. The effect of hot pressing on the structure of powders was investigated using a conventional analytical and high-resolution electron microscopy and high angle annular dark-field scanning transmission electron microscopy combined with energy dispersive X-ray microanalysis. The samples of initial powders hot pressed in vacuum showed a cell structure with particles of the Mg(2)Si and AlFeSi phases in intercell areas. In the milled and hot-pressed sample, the homogeneous structure of small grains of size below 200 nm was observed. The AlFeSi and Mg(2)Si particles with size 20-100 nm were uniformly distributed as well as the Zr rich particles in the Zr containing alloy. The Zr-rich particles containing up to 80 at% Zr were identified as a metastable fcc cubic phase with lattice parameter a= 0.48 nm.

  2. Laser surface treatment of magnesium alloys with aluminium oxide powder

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2009-11-01

    Full Text Available Purpose: The aim of this paper was to improve the magnesium cast alloys surface layer by laser surface treatment and to determine the laser treatment parameters.Design/methodology/approach: The laser treatment of magnesium alloys with alloying Al2O3 powder of the particle about 80μm was carried out using a high power diode laser (HPDL. The resulting microstructure in the modified surface layer was examined using scanning electron microscopy. Phase composition was determined by the X-ray diffraction method using the XPert device. The measurements of microhardness of the modified surface layer were also studied.Findings: The alloyed region has a fine microstructure with hard carbide particles. Microhardness of laser surface alloyed layer was significantly improved as compared to an alloy without laser treatment.Research limitations/implications: The investigations were conducted for cast magnesium alloys MCMgAl12Zn1, MCMgAl9Zn1, MCMgAl6Zn1, MCMgAl3Zn1 and Al2O3 powder of the particle size about 80 μm. One has used laser power in the range from 1.2to 2.0 kW.Practical implications: The results obtained in this investigation were promising comparing with the other conventional processes. High Power Diode Laser can be used as an economical substitute of Nd: YAG and CO2 to improve the surface magnesium alloy by feeding the carbide particles.Originality/value: The value of this paper is to define the influence of laser treatment parameters on quality, microstructure and microhardness of magnesium cast alloys surface layer.

  3. New alloying systems for ferrous powder metallurgy precision parts

    Directory of Open Access Journals (Sweden)

    Danninger H.

    2008-01-01

    Full Text Available Traditionally, the common alloy elements for sintered steels have been Cu and Ni. With increasing requirements towards mechanical properties, and also as a consequence of soaring prices especially for these two metals, other alloy elements have also become more and more attractive for sintered steels, which make the steels however more tricky to process through PM. Here, the chances and risks of using in particular Cr and Mn alloy steels are discussed, considering the different alloying techniques viable in powder metallurgy, and it is shown that there are specific requirements in particular for sintering process. The critical importance of chemical reactions between the metal and the atmosphere is described, and it is shown that not only O2 and H2O but also H2 and even N2 can critically affect sintering and microstructural homogenization.

  4. Powder metallurgical processing of a SiC particle reinforced Al-6wt.%Fe alloy

    OpenAIRE

    Staniek, G.; Lehnert, F.; Peters, M; Bunk, W.; Kaysser, W.

    1993-01-01

    Discontinuously reinforced aluminum alloys for elevated temperatures with a matrix hardened by intermetallic phases generally have to be produced by powder metallurgy because of their high content of alloying elements. The objective of this investigation was the evaluation of powder metallurgical processing for an A16Fe powder alloy containing various fractions and volume contents of SiC particles. During processing, the effect of powder mixing on SiC particle distribution in the extruded pro...

  5. Ferrous Alloy Powder for Laser Cladding

    Institute of Scientific and Technical Information of China (English)

    WEN Jialing; NIU Quanfeng; XU Yanmin

    2005-01-01

    This investigation aimed at how to improve the hardness and wear resistance by B, Si and Cr, and how to improve the synthesis property by Re (rare-earth element). Based on the experiment of Fe-based alloys of Fe-Cr-Ni-B-Si-Re, through experiments and a serious of synthesis analysis, including surface quality, spectrum composite, micro-hardness, scanning electron microscopy, as well as the synthesis evaluation,etc, prescriptions were optimized. As a result, a Fe-Cr-Ni-B-Si-Re cladding material with a high property was obtained.

  6. Structural and magnetic properties of nanocrystalline Fe–Co–Si alloy powders produced by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Shyni, P.C.; Perumal, Alagarsamy, E-mail: perumal@iitg.ernet.in

    2015-11-05

    We report the structural and magnetic properties of nanocrystalline Fe{sub 100−x−y}Co{sub y}Si{sub x} (x = 10, 15, y = 0–20) alloy powders prepared by mechanical alloying process in a planetary ball mill. All the as-milled powders exhibit non-equilibrium α-Fe(Co,Si) solid solution with average crystallite size of 7–11 nm. The lattice constant increases initially up to 10 at.% Co and then decreases with further increase in Co content due to delay in dissolution of Co into Fe lattice by the introduction of more Si. The variations of structural parameters such as average crystallite size, dislocation density and fraction of grain boundary as a function of Co content show good correlations among them. The substitution of Co in Fe{sub 100−x−y}Co{sub y}Si{sub x} alloy powder increases both saturation magnetization and coercivity due to atomic ordering which induce additional magnetic anisotropy. Thermomagnetization studies reveal that Curie temperature (T{sub C}) increases at a rate of 4 K per at.% Co for Co content up to 10 at.% and the rate of increase in T{sub C} reduces to 1.4 K per at.% Co for higher Co addition. The variation of structural and magnetic parameters reveals a strong dependence on the composition of Fe–Co–Si alloy. The observed results show the improvement in soft magnetic properties of nanocrystalline Fe–Co–Si alloy powders by proper substitution of Co and Si for Fe. - Graphical abstract: Structural and magnetic properties of nanocrystalline Fe{sub 100−x−y}Co{sub y}Si{sub x} alloy powders prepared by mechanical alloying process in a planetary ball mill are reported. The non-equilibrium solid solution with nanosized crystallites could be obtained for all the alloy powders. The substitution of Co in Fe{sub 100−x−y}Co{sub y}Si{sub x} alloy powder increases both saturation magnetization and coercivity. The Curie temperature also increases with increasing Co content. The observed results show the improvement in soft magnetic

  7. Interstitial control in titanium alloys produced by powder metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Henriques, V.A.R.; Petroni, S.L.G.; Cairo, C.A.A. [Instituto de Aeronautica e Espaco (AMR/CTA/IAE), Sao Jose dos Campos, SP (Brazil). Centro Tecnico Aeroespacial. Divisao de Materiais; Paula, M.S.M.; Galvani, E.T., E-mail: vinicius@iae.cta.br, E-mail: slpetroni@iae.cta.br, E-mail: Matheus@gmx.com, E-mail: ccairo@iae.cta.br, E-mail: eduardotgalvani@yahoo.com.br [Instituto Tecnologico de Aeronautica (ITA/CTA), Sao Jose dos Campos, SP (Brazil). Centro Tecnico Aeroespacial

    2009-07-01

    The titanium alloys are used for applications that demand high performance, including surgical implants and aerospace applications. Powder metallurgy is an advantageous alternative for titanium parts production with complex geometries at a relative low cost. Despite that, it is verified that the introduction of interstitial elements (oxygen, nitrogen and carbon) wile processing these alloys, though can increase hardness and mechanical resistance, which is frequently related to the reduction of ductility and fragility increase. The objective of this work is to investigate the influence of the interstitial elements in commercially pure Ti and Ti-{sup 13}Nb-{sup 13}Zr alloy produced by powder metallurgy (P/M). Samples were produced by the mixing of hydride metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering at 1400 °C, in vacuum. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. The interstitial content was analysed by Leco equipment. It was shown that the samples were sintered to high densities with a Widmanstatten microstructure. The oxygen and nitrogen contents are above the ELI (Extra Low Interstitial) and the critical issues were identified in the original blended elemental route. (author)

  8. Effect of heat treatment on Fe-B-Si-Nb alloy powder prepared by mechanical alloying

    Directory of Open Access Journals (Sweden)

    Rodrigo Estevam Coelho

    2005-06-01

    Full Text Available The effect of heat treatment on crystallization behavior of Fe73.5B15Si10Nb1.5 alloy powder prepared by mechanical alloying was studied. The powder samples were prepared by mechanical alloying (MA and for different milling times (1, 5, 25, 70 and 100 hours. Crystalline powders of iron, boron, silicon and niobium were sealed with tungsten carbide balls in a cylindrical vial under nitrogen atmosphere. The ball-to-powder weight ratio was 20 to 1. A Fritsch Pulverizette 5 planetary ball mill was used for MA the powders at room temperature and at 250 rpm. To study the microstructural evolution, a small amount of powder was collected after different milling times and examined by X-ray diffraction, using CuKalpha radiation (lambda = 0.15418 nm. The crystallization behavior was studied by differential thermal analysis, from 25 up to 1000 °C at a heating rate of 25 °C min-1.

  9. Mechanical behaviour of pressed and sintered titanium alloys obtained from master alloy addition powders.

    Science.gov (United States)

    Bolzoni, L; Esteban, P G; Ruiz-Navas, E M; Gordo, E

    2012-11-01

    The fabrication of the workhorse Ti-6Al-4V alloy and of the Ti-3Al-2.5V alloy was studied considering the master alloy addition variant of the blending elemental approach conventionally used for titanium powder metallurgy. The powders were characterised by means thermal analysis and X-ray diffraction and shaped by means of uniaxial pressing. The microstructural evolution with the sintering temperature (900-1400 °C) was evaluated by SEM and EDS was used to study the composition. XRD patterns as well as the density by Archimedes method were also obtained. The results indicate that master alloy addition is a suitable way to fabricate well developed titanium alloy but also to produce alloy with the desired composition, not available commercially. Density of 4.3 g/cm³ can be obtained where a temperature higher than 1200 °C is needed for the complete diffusion of the alloying elements. Flexural properties comparable to those specified for wrought Ti-6Al-4V medical devices are, generally, obtained.

  10. Microstructure and Properties of W-Cu Alloys Prepared with Mechanically Activated Powder

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    W-15% Cu (mass fraction) alloys were sintered with mechanically activated powder in order to develop new preparing processes and improve properties of alloys. The microstructures of the activated powder and the sintered alloy were observed. Properties such as density were measured. The results show that through mechanical activation, the particle size of the powder becomes finer to sub-micron or nanometer level, some copper was soluble in tungsten, and high density W-Cu alloys can be obtained by mechanically activated powder for its action to the activation sintering.

  11. Research on Semisolid Microstructural Evolution of 2024 Aluminum Alloy Prepared by Powder Thixoforming

    OpenAIRE

    Pubo Li; Tijun Chen; Suqing Zhang; Renguo Guan

    2015-01-01

    A novel method, powder thixoforming, for net-shape forming of the particle-reinforced Aluminum matrix composites in semi-solid state has been proposed based on powder metallurgy combining with thixoforming technology. The microstructural evolution and phase transformations have been investigated during partial remelting of the 2024 bulk alloy, prepared by cold pressing of atomized alloy powders to clarify the mechanisms of how the consolidated powders evolve into small and spheroidal primary...

  12. Studing Tungsten-containing Electroerosion Powders and Alloys Synthesized from Them

    Directory of Open Access Journals (Sweden)

    E.V. Ageev

    2014-07-01

    Full Text Available The results of the X-ray spectral microanalysis of the powder obtained using electroerosion dispersion of tungsten-containing wastes in distilled water, and the alloy powder synthesized from this powder are presented in the article. It is shown that the basic elements both in the powder obtained using electroerosion dispersion of tungsten-containing wastes in distilled water and in the synthesized alloy are tungsten, molybdenum, iron, oxygen and carbon.

  13. Heat-Resistance of the Powder Cobalt Alloys Reinforced by Niobium or Titanium Carbide

    Directory of Open Access Journals (Sweden)

    Cherepova, T.S.

    2016-01-01

    Full Text Available The characteristics of heat-resistance of powder cobalt alloys at 1100 °C were investigated. These alloys were developed for the protection of workers banding shelves GTE blades from wear. The alloys were prepared by hot pressing powders of cobalt, chromium, aluminum, iron and niobium or titanium carbides. The values of heat resistance alloys containing carbides between 30 and 70% (vol. depend on the type made of carbide alloys: alloys with titanium carbide superior in heat-resistant alloy of niobium carbide. The most significant factor affecting on the heat-resistant alloys, is porosity: with its increase the parameters decline regardless of the type and content of carbide. The optimum composition of powder heat resisting alloys of titanium carbide with a melting point above 1300 °C were determined for use in the aircraft engine.

  14. Powder injection molding of Fe-Ni soft magnetic alloys

    Institute of Scientific and Technical Information of China (English)

    DUAN Bohua; QU Xuanhui; QIN Mingli; GUO Shibo

    2006-01-01

    With miniaturization and complication of the shape of electronic devices in recent years, powder injection molding (PIM) seems to be a suitable process for fabricating the higher performance soft magnetic components. In this paper, high quality Fe-50Ni soft magnetic alloy was fabricated by PIM with carbonyl iron and nickel, and the effect of sintering process on its microstructure and magnetic properties were investigated. The mechanical and magnetic properties can be obviously improved by increasing the sintering temperature or using the hydrogen atmosphere instead of high vacuum, which causes by the increase of grain size and the densification. At the optimum sintering conditions, the PIM Fe-50Ni soft magnetic alloy with high properties are obtained, whose relative density, tensile strength, Bm, Hc,μm are 97%, 465MPa,1.52T, 16.62 A·m-1 , 42.5 mH·m-1 , respectively.

  15. Recycling high density tungsten alloy powder by oxidization-reduction process

    Institute of Scientific and Technical Information of China (English)

    张兆森; 陈立宝; 贺跃辉; 黄伯云

    2002-01-01

    The processes of directly recycling high density tungsten alloy by oxidation-reduction technique were investigated. The particle size of recycled powder is fine, and the shape of powder particle is regular when the final reduction temperature is 850℃, in which the average size of the tungsten alloy particles reduced is about 1.5μm. The average size of the alloy particles increase to 6μm and 9μm when increasing the reduction temperature to 900℃ and 950℃, respectively. However, if the reduction temperature is higher than 900℃, the surface feature of powder is complicated. Increasing reduction temperature from 900℃ to 950℃, the content of oxygen of recycled powder decreases from 0.2314% to 0.1700%, and powder particles grow slightly. It has been also found that the chemical composition of the recycled alloy powder is the same as the initial powder.

  16. Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition

    Science.gov (United States)

    2014-11-01

    Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition by Tiffany Ngo ARL-TN-0643...November 2014 Characterization of Nanocrystalline Aluminum Alloy 5083 Powders Produced by Cryogenic Attrition Tiffany Ngo Weapons and... Materials Research Directorate, ARL Approved for public release; distribution is unlimited

  17. Synthesis of amorphous Ti-Al alloys by mechanical alloying of elemental powders

    Institute of Scientific and Technical Information of China (English)

    张俊红; 黄伯云; 贺跃辉; 周科朝; 刘咏

    2002-01-01

    Blended elemental powders with the nominal compositions (mole fraction, %) of Ti54Al46, Ti52Al48 and Ti50Al50 were mechanically alloyed in a planetary ball milling system for up to 100h.The structure evolution in these powders was characterized by scanning electron microscope, X-ray diffraction and differential thermal a nalysis techniques. It was found that elemental powders were progressively trans formed into nanocrystalline Ti(Al) supersaturated solid solution, then into amor phous phase. With increasing Al content, the formation of a fully Ti(Al) supersa turated solid solution and amorphous phase were accelerated, which are attributed to the fine grain size. And the grain size condition for formation of amorpho us phase in this system is ≤16 nm.

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

    Science.gov (United States)

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

    1990-01-01

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

  19. Powder metallurgy processing of high strength turbine disk alloys

    Science.gov (United States)

    Evans, D. J.

    1976-01-01

    Using vacuum-atomized AF2-1DA and Mar-M432 powders, full-scale gas turbine engine disks were fabricated by hot isostatically pressing (HIP) billets which were then isothermally forged using the Pratt & Whitney Aircraft GATORIZING forging process. While a sound forging was produced in the AF2-1DA, a container leak had occurred in the Mar-M432 billet during HIP. This resulted in billet cracking during forging. In-process control procedures were developed to identify such leaks. The AF2-1DA forging was heat treated and metallographic and mechanical property evaluation was performed. Mechanical properties exceeded those of Astroloy, one of the highest temperature capability turbine disk alloys presently used.

  20. Reducing metal alloy powder costs for use in powder bed fusion additive manufacturing: Improving the economics for production

    Science.gov (United States)

    Medina, Fransisco

    Titanium and its associated alloys have been used in industry for over 50 years and have become more popular in the recent decades. Titanium has been most successful in areas where the high strength to weight ratio provides an advantage over aluminum and steels. Other advantages of titanium include biocompatibility and corrosion resistance. Electron Beam Melting (EBM) is an additive manufacturing (AM) technology that has been successfully applied in the manufacturing of titanium components for the aerospace and medical industry with equivalent or better mechanical properties as parts fabricated via more traditional casting and machining methods. As the demand for titanium powder continues to increase, the price also increases. Titanium spheroidized powder from different vendors has a price range from 260/kg-450/kg, other spheroidized alloys such as Niobium can cost as high as $1,200/kg. Alternative titanium powders produced from methods such as the Titanium Hydride-Dehydride (HDH) process and the Armstrong Commercially Pure Titanium (CPTi) process can be fabricated at a fraction of the cost of powders fabricated via gas atomization. The alternative powders can be spheroidized and blended. Current sectors in additive manufacturing such as the medical industry are concerned that there will not be enough spherical powder for production and are seeking other powder options. It is believed the EBM technology can use a blend of spherical and angular powder to build fully dense parts with equal mechanical properties to those produced using traditional powders. Some of the challenges with angular and irregular powders are overcoming the poor flow characteristics and the attainment of the same or better packing densities as spherical powders. The goal of this research is to demonstrate the feasibility of utilizing alternative and lower cost powders in the EBM process. As a result, reducing the cost of the raw material to reduce the overall cost of the product produced with

  1. Development of Al-TiC Alloys Using Powder Metallurgy as Grain Refiners for Aluminium and Its Alloys

    Directory of Open Access Journals (Sweden)

    Abdel-Nasser .M. Omran

    2014-07-01

    Full Text Available Al-Ti-C master alloys have been widely investigated for many years as grain refiner for aluminium and its alloys. In this work, the Al-Ti-C master alloys are synthesized using powder metallurgy technique through the mixing of aluminium and TiC powders with different TiC contents 3.75 (3, 5(4, 6.25(5 and 7.5(6 Wt% TiC(Wt% Ti. The mixing powders with different contents of TiC were pressed in cylinder shape. The pressed specimens were sintered from 450 oC in a tube furnace under argon atmosphere for 2 hrs. The produced alloys before and after sintering are examined using SEM, EDX and XRD. The results indicate that, the Al-TiC alloy containing fine TiC particles dispersed in all matrix was successfully prepared. The prepared Al-TiC alloys with different contents of TiC were evaluated using the KBI test mold as grain refiner for pure aluminum and its alloys. The results indicate that the prepared Al-TiC master alloy is high grain refining efficiency for pure aluminum and its alloys.

  2. Synthesis and Characterization of Nanocrystalline Al-20 at. % Cu Powders Produced by Mechanical Alloying

    Directory of Open Access Journals (Sweden)

    Molka Ben Makhlouf

    2016-06-01

    Full Text Available Mechanical alloying is a powder processing technique used to process materials farther from equilibrium state. This technique is mainly used to process difficult-to-alloy materials in which the solid solubility is limited and to process materials where nonequilibrium phases cannot be produced at room temperature through conventional processing techniques. This work deals with the microstructural properties of the Al-20 at. % Cu alloy prepared by high-energy ball milling of elemental aluminum and copper powders. The ball milling of powders was carried out in a planetary mill in order to obtain a nanostructured Al-20 at. % Cu alloy. The obtained powders were characterized using scanning electron microscopy (SEM, differential scanning calorimetry (DSC and X-ray diffraction (XRD. The structural modifications at different stages of the ball milling are investigated with X-ray diffraction. Several microstructure parameters such as the crystallite sizes, microstrains and lattice parameters are determined.

  3. Laser rapid forming of low cost hydride-dehydride titanium alloy powder

    Institute of Scientific and Technical Information of China (English)

    CHEN Jing; ZHANG Feng-ying; LIN Xin; TAN Hua; HUANG Wei-dong

    2006-01-01

    Low cost hydride-dehydride (HDH) Ti-6Al-4V (Ti-64) alloy powder was employed to investigate the metallurgical quality and mechanical properties of laser formed samples. With appropriate control of the laser forming processing parameters and the loose density of HDH powder, two kinds of defect, i.e. porosity and ill-bonding, can be avoided. Rare earth Nd powder was added to HDH Ti-64 powder to purify laser formed alloy. The results show that with a few additive of Nd, the microstructure of laser formed alloy changes from Widmanst-tten morphology to a basket weave microstructure. Accordingly an appropriate addition of Nd is effective to improve both the strength and ductility of laser formed HDH Ti-64 alloy. The values of tensile test meet the wrought specification with the content of Nd ranging from 0.1%-0.2%(mass fraction).

  4. Numerical simulation of tungsten alloy in powder injection molding process

    Institute of Scientific and Technical Information of China (English)

    ZHENG Zhen-xing; XIA Wei; ZHOU Zhao-yao; ZHU Quan-li

    2008-01-01

    The flow behavior of feedstock for the tungsten alloy powder in the mold cavity was approximately described using Hele-Shaw flow model. The math model consisting of momentum equation, consecutive equation and thermo-conduction equation for describing the injection process was established. The equations are solved by the finite element/finite difference hybrid method that means dispersing the feedstock model with finite element method, resolving the model along the depth with finite difference methpd, and tracking the movable boundary with control volume method, then the pressure equation and energy equation can be resolved in turn. The numerical simulation of the injection process and the identification of the process parameters were realized by the Moldflow software. The results indicate that there is low temperature gradient in the cavity while the pressure and shear rate gradient are high at high flow rate. The selection of the flow rate is affected by the structure of the gate. The shear rate and the pressure near the gate can be decreased by properly widening the dimension of the gate. There is a good agreement between the process parameters obtained by the numerical simulation and the actual ones.

  5. Corrosion of Mechanically Alloyed Nanostructured FeAl Intermetallic Powders

    Directory of Open Access Journals (Sweden)

    A. Torres-Islas

    2012-01-01

    Full Text Available The corrosion behavior of the Fe40Al60 nanostructured intermetallic composition was studied using electrochemical impedance spectroscopy (EIS and linear polarization resistance (LPR techniques with an innovative electrochemical cell arrangement. The Fe40Al60 (% at intermetallic composition was obtained by mechanical alloying using elemental powders of Fe (99.99% and Al (99.99%. All electrochemical testing was carried out in Fe40Al60 particles that were in water with different pH values. Temperature and test time were also varied. The experimental data was analyzed as an indicator of the monitoring of the particle corrosion current density icorr. Different oxide types that were formed at surface particle were found. These oxides promote two types of surface corrosion mechanisms: (i diffusion and (ii charge transfer mechanisms, which are a function of icorr behavior of the solution, pH, temperature, and test time. The intermetallic was characterized before and after each test by transmission electron microscopy. Furthermore, the results show that at the surface particles uniform corrosion takes place. These results confirm that it is possible to sense the nanoparticle corrosion behavior by EIS and LPR conventional electrochemical techniques.

  6. MECHANICAL ALLOYING SYNTHESIS OF FORSTERITE-DIOPSIDE NANOCOMPOSITE POWDER FOR USING IN TISSUE ENGINEERING

    Directory of Open Access Journals (Sweden)

    Sorour Sadeghzade

    2015-03-01

    Full Text Available In present study the pure forsterite-diopside nanocomposite powder was successfully synthesized by the economical method of mechanical alloying and subsequence sintering, for the first time. The starting economical materials were talc (Mg3Si4H2O12, magnesium carbonate (MgCO3 and calcium carbonate (CaCO3 powders. The prepared powder was characterized by thermo gravimetric analysis (TGA, X-ray diffraction (XRD, and scanning electron microscopy (SEM. The results showed preparation of forsterite- diopside nanocomposite powder after 10 h mechanical alloying and sintering at 1200oC for 1 h. The powder crystallite sizes and agglomerated particle sizes were measured about 73 +/- 4 nm and 0.3 - 4 μm, respectively. Absence of enstatite that causes a reduction in mechanical and bioactivity properties of forsterite ceramic, is an important feature of produced powder.

  7. Microstructures of Sintered Mo-Cu Alloys with Mechanically Activated Powder

    Institute of Scientific and Technical Information of China (English)

    蒋凯; 张秀英; 郭崇峰

    2001-01-01

    Mechanical activation and liquid phase sintering were used to manufacture high performance Mo-Cu alloy and develop new processes. The microstructures and properties of the alloy were investigated. The experimental results showed that: (1) the ball milled Mo/Cu powder has lamellar structure, (2) the microstructures of the sintered Mo-Cu alloy were homogenous compound structures of adhesive phase Cu linking Mo grains, (3) Mo grains frequently strung or ga thered in Cu phase, and (4) the full densities of Mo-Cu alloy was achieved through sintering and special densification process. As a result, the properties of the alloy are good enough to satisfy various requirements.

  8. Hard Alloy Synthesis from Tungsten-containing Electroerosion Powders of Micro- and Nanometric Fractions

    Directory of Open Access Journals (Sweden)

    E.V. Ageev

    2014-07-01

    Full Text Available The article presents the results of the studies of the composition, structure and properties of the hard alloy produced using hot-pressing technique with the high current passage from the powder produced using electroerosion dispersion of sintered hard alloys wastes in lamp kerosene and distilled water.

  9. Reaction mechanism in high Nb containing TiAl alloy by elemental powder metallurgy

    Institute of Scientific and Technical Information of China (English)

    WANG Yan-hang; LIN Jun-pin; HE Yue-hui; WANG Yan-li; LIN Zhi; CHEN Guo-liang

    2006-01-01

    High Nb containing TiAl alloy was fabricated in argon atmosphere by reactive hot pressing process. Reaction mechanism was investigated by means of microstructural analyses and thermodynamic calculations. The results show that it is feasible to prepare high Nb containing TiAl alloy with fine lamellar colonies by reactive hot pressing process. The reaction between Ti and Al powders is dominant in Ti-Al-Nb system. Nb powders dissolve into the Ti-Al matrix by diffusion. Pore nests are formed in situ after Nb powders diffusion. The hot pressing atmosphere is optimized by thermodynamic calculations. Vacuum or argon protective atmosphere should be adopted.

  10. A TECHNIQUE FOR IMPROVING THE TOUGHNESS OF Al-Li POWDER METALLURGY ALLOYS

    OpenAIRE

    1987-01-01

    A technique has been developed for increasing the toughness of Al-Li products made by powder metallurgy. The technique which involves the addition of unalloyed aluminum powder to Al-Li powder before compaction was evaluated with Al-Li-Cu-Mg-Zr alloys (Al 8090), and Al-Li-Zn-Cu-Mg-Zr and Al-Li-Mg-Si-Cr alloys . The addition of 15% aluminum to Al 8090 aged at 422K for 40 h produced an increase in impact toughness of 215% at the expense of a drop in yield strength of 11%. The Al-Li-Mg-Si-Cr allo...

  11. Characterization of Cu-Zn Alloy Nanocrystalline Powders Prepared by Wire Electrical Explosion

    Institute of Scientific and Technical Information of China (English)

    WANG Qun; YANG Hai-Bin; GUO Wei-Li; ZOU Guang-Tian

    2000-01-01

    Nanocrystalline powders of Cu-Zn alloy in size ranging from 10 to 140nm was prepared from α-Cu-Zn alloy wire containing 39.8at.% Zn by an electrical explosion method. The particles are identified from x-ray diffraction as a mixture of the α,β,γ, and ε phases of Cu-Zn alloy. Most of the particles are hexagonal in shape, with only a small part being spherical and cubic. The composition of Zn in the explosion products varied from 6.9 to 45.2 at.% in different particles as determined by energy dispersive x-ray spectrometer. A possible mechanism for the formation of the alloy nanocrystalline powders is proposed, in which a redistribution process occurred caused by strong collision and diffusion between the two kinds of atoms during the powder formation.

  12. Influence of Milling Media on the Mechanical Alloyed W-0.5 wt.% Ti Powder Alloy

    Directory of Open Access Journals (Sweden)

    Hadi Jahangiri

    2016-01-01

    Full Text Available The effects of milling atmosphere and mechanical alloying (MA duration on the effective lattice parameter, crystallite size, lattice strain, and amorphization rate of the W-0.5 wt.% Ti powders were investigated. W-0.5 wt.% Ti powders were mechanically alloyed (MA’d for 10 h and 20 h in a high energy ball mill. Moreover, morphology of the powders for various MA was analyzed using SEM microscopy. Their powder density was also measured by helium pycnometer. The dry milled agglomerated powders have spherical particle, while wet milled powders have layered morphology. Milling media and increasing of milling time significantly reduce the crystallite size. The smallest crystallite size is 4.93 nm which belonged to the dry milled powders measured by Lorentzian method after 20 hours’ MA. However, after 20 hours, MA’d powders show the biggest crystallite size, as big as 57.07 nm, measured with the same method in ethanol.

  13. Method of making quasicrystal alloy powder, protective coatings and articles

    Science.gov (United States)

    Shield, J.E.; Goldman, A.I.; Anderson, I.E.; Ellis, T.W.; McCallum, R.W.; Sordelet, D.J.

    1995-07-18

    A method of making quasicrystalline alloy particulates is disclosed wherein an alloy is superheated and the melt is atomized to form generally spherical alloy particulates free of mechanical fracture and exhibiting a predominantly quasicrystalline in the atomized condition structure. The particulates can be plasma sprayed to form a coating or consolidated to form an article of manufacture. 3 figs.

  14. Effect of carbon on mechanical properties of powder-processed Fe–0.35%P alloys

    Indian Academy of Sciences (India)

    Shefali Trivedi; Yashwant Mehta; K Chandra; P S Mishra

    2010-10-01

    The present paper records the results of mechanical tests on iron-phosphorus powder alloys which were made using a hot powder forging technique. In this process mild steel encapsulated powders were hot forged into slabs, hot rolled and annealed to relieve the residual stresses. These alloys were characterized in terms of microstructure, porosity content/densification, hardness and tensile properties. Densification as high as 98.9% of theoretical density, has been realized. Microstructures of these alloys consist of single-phase ferrite only. Alloys containing 0.35 wt% P, such as Fe–0.35P–2Cu–2Ni–1Si–0.5Mo and Fe–0.35P–2Cu–2Ni–1Si–0.5Mo–0.15C show very high strength. It was observed in this present investigation that, the alloying additions, such as Si, Mo, Ni, and C to Fe–P based alloys caused increase in strength along with reduction in ductility. Cu reduces porosity of Fe–P alloys. Alloys developed in the present investigation were capable of hot working to very thin gauge of sheets and wires.

  15. Dispersoid reinforced alloy powder and method of making

    Science.gov (United States)

    Anderson, Iver E.; Terpstra, Robert L.

    2010-04-20

    A method of making dispersion-strengthened alloy particles involves melting an alloy having a corrosion and/or oxidation resistance-imparting alloying element, a dispersoid-forming element, and a matrix metal wherein the dispersoid-forming element exhibits a greater tendency to react with a reactive species acquired from an atomizing gas than does the alloying element. The melted alloy is atomized with the atomizing gas including the reactive species to form atomized particles so that the reactive species is (a) dissolved in solid solution to a depth below the surface of atomized particles and/or (b) reacted with the dispersoid-forming element to form dispersoids in the atomized particles to a depth below the surface of said atomized particles. The atomized alloy particles are solidified as solidified alloy particles or as a solidified deposit of alloy particles. Bodies made from the dispersion strengthened alloy particles, deposit thereof, exhibit enhanced fatigue and creep resistance and reduced wear as well as enhanced corrosion and/or oxidation resistance at high temperatures by virtue of the presence of the corrosion and/or oxidation resistance imparting alloying element in solid solution in the particle alloy matrix.

  16. Properties of WZ21 (%wt) alloy processed by a powder metallurgy route.

    Science.gov (United States)

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

    2015-06-01

    Microstructure, mechanical properties and corrosion behaviour of WZ21 (%wt) alloy prepared by a powder metallurgy route from rapidly solidified powders have been studied. Results were compared to those of the same alloy prepared through a conventional route of casting and extrusion. The microstructure of the extruded ingot consisted of α-Mg grains and Mg3Zn3Y2 (W-phase) and LPSO-phase particles located at grain boundaries. Moreover, stacking faults were also observed within α-Mg grains. The alloy processed by the powder metallurgy route exhibited a more homogeneous and finer microstructure, with a grain size of 2 μm. In this case W-phase and Mg24Y5 phase were identified, but not the LPSO-phase. The microstructural refinement induced by the use of rapidly solidified powders strengthened the alloy at room temperature and promoted superplasticity at higher strain rates. Corrosion behaviour in PBS medium evidenced certain physical barrier effect of the almost continuous arrangements of second phases aligned along the extrusion direction in conventionally processed WZ21 alloy, with a stable tendency around 7 mm/year. On the other hand, powder metallurgy processing promoted significant pitting corrosion, inducing accelerated corrosion rate during prolonged immersion times.

  17. Moessbauer and X-ray diffraction studies of nanostructured Fe{sub 70}Al{sub 30} powders elaborated by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Kezrane, M., E-mail: mohamedkezrane@yahoo.fr [LMP2M Laboratory, University of Medea, (26000) (Algeria); Guittoum, A. [Nuclear Research Centre of Algiers, 2 Bd Frantz Fanon, BP 399, Algiers (Algeria); Boukherroub, N.; Lamrani, S. [LMMC, M' hamed Bougara University, Boumerdes, 35000 (Algeria); Sahraoui, T. [Laboratory of Materials and Surface Treatments, LTSM, University of Saad Dahleb Blida, BP. 270 route de Soumaa, Blida (09000) (Algeria)

    2012-09-25

    Highlights: Black-Right-Pointing-Pointer Nanocrystalline Fe{sub 70}Al{sub 30} powders were successfully elaborated by mechanical alloying. Black-Right-Pointing-Pointer The Moessbauer spectra show that from 4 h of milling, a disordered ferromagnetic. Black-Right-Pointing-Pointer Fe{sub 70}Al{sub 30} starts to form and dominates after 36 h. - Abstract: We have studied the effect of milling time on the structural and hyperfine properties of Fe{sub 70}Al{sub 30} compound elaborated by mechanical alloying. The elaboration was performed with a vario-planetary ball mill P4 at different milling times. The milled powders were characterized by X-ray diffraction (XRD) and Moessbauer spectroscopy. From XRD diffraction spectra, we show that the bcc Fe(Al) solid solution was completely formed after 27 h of milling time. When the milling time increases, the lattice parameter increases, whereas the grain size decreases and the mean level of microstrains increases. The analysis of Moessbauer spectra shows that from 4 h of milling, a disordered ferromagnetic Fe{sub 70}Al{sub 30} starts to form and dominates after 36 h.

  18. Synthesis of TiB2 nanocrystalline powder by mechanical alloying

    Institute of Scientific and Technical Information of China (English)

    TANG Wen-ming; ZHENG Zhi-xiang; WU Yu-cheng; WANG Jian-min; L(U) Jun; LIU Jun-wu

    2006-01-01

    TiB2 nanocrystalline powder was synthesized by mechanical alloying of Ti-67B elemental powder. X-ray diffraction(XRD)and transmission electron microscopy(TEM) were used to study the structural evolution of the powder during ball milling. The effects of heat treatment on the structural evolution and thermal stability of the mechanically alloyed(MAed) Ti-67B powder were also discussed. During ball milling the Ti-67B powder, a solid solution of B in Ti, Ti(B) is firstly formed. When the powder is milled for 10 h, the amorphous transition of Ti(B) from the crystalline to the amorphous phase occurs. When the powder is milled for 20 h,nanocrystalline TiB2 is formed from the amorphous Ti(B). When the powder is milled for 60 h, only TiB2 is detected with grain size of 10 nm. The formation of TiB2 nanocrystalline is controlled by the gradual diffusion reaction mechanism. During heat-treatment of the MAed Ti-67B powder, the structural changes of TiB2, including grain growth and lattice ordering degree increasing may occur.

  19. TEM and HRTEM studies of ball milled 6061 aluminium alloy powder with Zr addition.

    Science.gov (United States)

    Lityńska-Dobrzyńska, L; Dutkiewicz, J; Maziarz, W; Rogal, Ł

    2010-03-01

    The effect of mechanical alloying on the microstructure of atomized 6061 aluminium alloy powder and 6061 powder with a zirconium addition was studied in the work. The atomized 6061 aluminium alloy powder and 6061 powder with addition of 2 wt.% Zr were milled in a planetary ball mill and investigated using X-ray diffraction measurements, conventional and high-resolution electron microscopy (TEM/HRTEM) and high-angle annular dark field scanning transmission electron microscopy combined with energy dispersive X-ray microanalysis. An increase of stresses was observed in milled powders after the refinement of crystallites beyond 100 nm. In the powder with zirconium addition, some part of the Zr atoms diffused in aluminium forming a solid solution containing up to 0.5 wt.% Zr. The remaining was found to form Zr-rich particles containing up to 88 wt.% Zr and were identified as face centred cubic (fcc) phase with lattice constant a= 0.48 nm. That fcc phase partially transformed into the L1(2) ordered phase. Eighty-hour milling brought an increase of microhardness (measured with Vickers method) from about 50 HV (168 MPa) for the initial 6061 powder to about 170 HV (552 MPa). The addition of zirconium had no influence on the microhardness.

  20. Morphology and microstructure of rapidly solidified tin-lead alloy powders

    Institute of Scientific and Technical Information of China (English)

    Xiang Qingchun; Zhang Wei; Qiu Keqiang; Qu Yingdong; Li Rongde

    2014-01-01

    Sn60Pb40 al oy powders were fabricated using the planar flow casting (PFC) atomization process. By using OM, SEM and EPMA, the characteristics of the morphologies and microstructures of the powders have been investigated. It is observed that the environment of ambient gas in the atomization box has great effects on the morphology of the al oy powders. The microstructures of Sn60Pb40 al oy powders produced by the PFC atomization process are completely composed of eutectic, which is made up of both oversaturated αsolid solution and β solid solution. The microstructures of smal size powders are extraordinarily undeveloped dendritic eutectic, in which the large majority of the α phase appears nearly spherical, evidently since the cooling rate is higher and the under-cooling is larger. As for the large size powders, since the cooling rate and undercooling are relatively low, lamel ar α phase apparently increases in the eutectic microstructures of these powders, and there is even typical lamellar eutectic structure clearly observed in some micro-areas. After remelting tests by DTA, the microstructures of smal size powders are transformed, which become composed of large crumby α phase and eutectic (α+β), while those of large size powders change into classical tin-lead structures of primary α phase plus lamellar eutectic (α+β). By studying the microstructures of tin-lead alloy powders, a model has been proposed to predict the microstructure formation of Sn60Pb40 al oy powders.

  1. Structural Characterization and Ordering Transformation of Mechanically Alloyed Nanocrystalline Fe-28Al Powder

    Directory of Open Access Journals (Sweden)

    Lima Amiri Talischi

    2016-12-01

    Full Text Available The synthesis of nanocrystalline Fe3Al powder by mechanical alloying as well as the structural ordering of the synthesized Fe3Al particles during the subsequent thermal analysis were investigated. Mechanical alloying was performed up to 100 hours using a planetary ball mill apparatus with rotational speed of 300 rpm under argon atmosphere at ambient temperature. The synthesized powders were characterized using X-ray diffraction, SEM observations and differential scanning calorimetry (DSC. The results show that the A2-type Fe3Al with disordered bcc structure is only formed after 70 hours milling. The corresponding lattice strain, mean crystallite and particle sizes for the 70 hours milled Fe3Al powder were determined as 2.5%, 10 and 500 nm, respectively. The subsequent heating during DSC causes a DO3-type Fe3Al ordering in 70 and 100 hours milled powders, however in 40 hours milled powder it only assists for the formation of disordered solid solution. Longer milling time induces a large amount of lattice strain in Fe3Al powder particles and consequently facilitates the atomic diffusion thus decreases the activation energy of ordering. The activation energy for ordering transformation of 100 hours Fe3Al milled powder was calculated as 152.1 kJ/mole which is about 4 kJ/mole lower than that for 70 hours milled powder.

  2. Microstructures and mechanical properties of hot isostatically pressed powder metallurgy Alloy APK-1

    Science.gov (United States)

    Prakash, T. L.; Chari, Y. N.; Rao, E. S. Bhagiradha; Thamburaj, R.

    1983-03-01

    The influence of Hot Isostatic Pressing (HIP) and heat treatment parameters on the microstructure and mechanical properties of powder metallurgy alloy APK-1 (a low carbon modification of Astroloy) has been investigated. Poor mechanical properties result if carbide networks are present along the prior particle boundaries (PPBs). These networks which form during powder consolidation can be avoided by manipulating HIP parameters. Heat treatments which produce a large volume fraction of fine γ’ make this alloy susceptible to environment-assisted tensile embrittlement around 760 °C.

  3. Structural evolutions of the mechanically alloyed Al70Cu20Fe10 powders

    Indian Academy of Sciences (India)

    Musa Göğebakan; Bariş Avar

    2011-10-01

    Elemental mixtures of Al, Cu, Fe powders with the nominal composition of Al70Cu20Fe10 were mechanically alloyed in a planetary ball mill for 80 h. Subsequent annealing of the as-milled powders were performed at 600–800°C temperature range for 4 h. Structural characteristics of the mechanically alloyed Al70Cu20Fe10 powders with the milling time and the heat treatment were investigated by X-ray diffraction (XRD), differential scanning calorimeter (DSC) and differential thermal analysis (DTA). Mechanical alloying of the Al70Cu20Fe10 did not result in the formation of icosahedral quasicrystalline phase (i-phase) and a long time milling resulted in the formation of -Al(Cu,Fe) solid solution phase (-phase). The i-phase was observed only for short-time milled powders after heat treatment above 600°C. The -phase was one of the major phases in the Al70Cu20Fe10 alloy. The w-Al7Cu2Fe1 phase (w-phase) was obtained only after heat treatment of the short-time milled and unmilled samples. The present investigation indicated that a suitable technique to obtain a large amount of quasicrystalline powders is to use a combination of short-time milling and subsequent annealing.

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

    Science.gov (United States)

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

    2011-05-01

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

  5. Influence of Ti Powder Characteristics on Combustion Synthesis of Porous NiTi Alloy

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    Porous NiTi shape memory alloy (SMA) is a novel biomedical material used for human hard tissue implant. The influence of elemental titanium powder characteristics such as powder morphology, particle size and specific surface area (SSA) on the minimal ignition temperature, combustion temperature and final product of porous NiTi SMA fabricated by combustion synthesis method was investigated in this paper by scanning electron microscopy (SEM)and laser diffraction. The preliminary data indicated that the titanium powder characteristics had a strong effect on combustion synthesis of porous NiTi SMA.

  6. Dual-Alloy Disks are Formed by Powder Metallurgy

    Science.gov (United States)

    Harf, F. H.; Miner, R. V.; Kortovich, C. S.; Marder, J. M.

    1982-01-01

    High-performance disks have widely varying properties from hub to rim. Dual property disk is fabricated using two nickel-base alloys, AF-115 for rim and Rene 95 for hub. Dual-alloy fabrication may find applications in automobiles, earth-moving equipment, and energy conversion systems as well as aircraft powerplants. There is potential for such applications as shafts, gears, and blades.

  7. Low cycle fatigue improvement of powder metallurgy titanium alloy through thermomechanical treatment

    Institute of Scientific and Technical Information of China (English)

    LIU Bin; LIU Yong; HE Xiao-yu; TANG Hui-ping; CHEN Li-fang

    2008-01-01

    A low-cost β type Ti-1.5Fe-6.8Mo-4.8Al-1.2Nd (mass fraction, %)(T12LCC) alloy was produced by blended elemental powder metallurgy(P/M) method and subsequent thermomechanical treatment. Low cycle fatigue(LCF) behavior of P/M T12LCC alloy before and after thermomechanical treatment was studied. The results show that the LCF resistance of P/M titanium alloy is significantly enhanced through the thermomechanical treatment. The mechanisms for the improvement of LCF behavior are attributed to the elimination of residual pores, the microstructure refining and homogenization.

  8. The structure-property relationships of powder processed Fe-Al-Si alloys

    Energy Technology Data Exchange (ETDEWEB)

    Prichard, Paul D. [Iowa State Univ., Ames, IA (United States)

    1998-02-23

    Iron-aluminum alloys have been extensively evaluated as semi-continuous product such as sheet and bar, but have not been evaluated by net shape P/M processing techniques such as metal injection molding. The alloy compositions of iron-aluminum alloys have been optimized for room temperature ductility, but have limited high temperature strength. Hot extruded powder alloys in the Fe-Al-Si system have developed impressive mechanical properties, but the effects of sintering on mechanical properties have not been explored. This investigation evaluated three powder processed Fe-Al-Si alloys: Fe-15Al, Fe-15Al-2.8Si, Fe-15Al-5Si (atomic %). The powder alloys were produced with a high pressure gas atomization (HPGA) process to obtain a high fraction of metal injection molding (MIM) quality powder (D84 < 32 μm). The powders were consolidated either by P/M hot extrusion or by vacuum sintering. The extruded materials were near full density with grain sizes ranging from 30 to 50 μm. The vacuum sintering conditions produced samples with density ranging from 87% to 99% of theoretical density, with an average grain size ranging from 26 μm to 104 μm. Mechanical property testing was conducted on both extruded and sintered material using a small punch test. Tensile tests were conducted on extruded bar for comparison with the punch test data. Punch tests were conducted from 25 to 550 C to determine the yield strength, and fracture energy for each alloy as a function of processing condition. The ductile to brittle transition temperature (DBTT) was observed to increase with an increasing silicon content. The Fe-15Al-2.8Si alloy was selected for more extensive testing due to the combination of high temperature strength and low temperature toughness due to the two phase α + DO3 structure. This investigation provided a framework for understanding the effects of silicon in powder processing and mechanical property behavior of Fe-Al-Si alloys.

  9. Nano-particle precipitation in mechanically alloyed and annealed precursor powders of legacy PM2000 ODS alloy

    Energy Technology Data Exchange (ETDEWEB)

    Dawson, Karl, E-mail: k.dawson@liverpool.ac.uk [Centre for Materials and Structures, School of Engineering, University of Liverpool, L69 3GH (United Kingdom); Haigh, Sarah J. [School of Materials, Materials Science Centre, University of Manchester, M13 9PL (United Kingdom); Tatlock, Gordon J.; Jones, Andy R. [Centre for Materials and Structures, School of Engineering, University of Liverpool, L69 3GH (United Kingdom)

    2015-09-15

    Highlights: • Nano-particle formation identified in Plansee PM2000 ODS alloy powders. • Y–Al–O nano-particles observed after annealing at 923 K for 5 h. • Particle diameter ≈2 nm and N{sub V} > 10{sup 23} m{sup −3} over annealing range 1123–1223 K. • Particles dissolved at, and reprecipitated behind, recrystallisation fronts. - Abstract: The early stages of nano-particulate formation in mechanically alloyed and annealed, precursor powders used to manufacture the legacy commercial oxide dispersion strengthened alloy PM2000, formerly produced by Plansee GmbH, have been investigated. Powders were analysed in both the as-mechanically-alloyed condition and after annealing over the temperature range 923–1423 K. The nucleation and growth of coherent nano-particles in the partially recovered, fine grained, ferritic matrix of powders annealed at temperatures as low as 923 K has been confirmed. Powders annealed for 1 h at temperatures of 1123 K and 1223 K were partially recrystallised and contained high number densities (N{sub V} > 10{sup 23} m{sup −3}) of coherent 2 nm yttrium–aluminium–oxygen rich nano-particles. The identification of particle free zones in recrystallised grains, adjacent to recrystallising interfaces, plus the identical orientation relationships between nano-particles and the matrices in both unrecrystallised and recrystallised grains, indicates that the Y–Al–O nano-particles, first formed in fine grained regions, are dissolved during recrystallisation and re-precipitated subsequently in recrystallised grains.

  10. Research on Semisolid Microstructural Evolution of 2024 Aluminum Alloy Prepared by Powder Thixoforming

    Directory of Open Access Journals (Sweden)

    Pubo Li

    2015-04-01

    Full Text Available A novel method, powder thixoforming, for net-shape forming of the particle-reinforced Aluminum matrix composites in semi-solid state has been proposed based on powder metallurgy combining with thixoforming technology. The microstructural evolution and phase transformations have been investigated during partial remelting of the 2024 bulk alloy, prepared by cold pressing of atomized alloy powders to clarify the mechanisms of how the consolidated powders evolve into small and spheroidal primary particles available for thixoforming. The effect of heating temperature on the resulting semisolid microstructure has also been discussed. The results indicate that the microstructural evolution includes three stages—the initial rapid coarsening of the fine grains within the powders, the formation of continuous liquid layer on the primary particle surface (the original powder, and the final coarsening—that result from the phase transformations of θ→α, α→L, and α→L and L→α, respectively. The coarsening rate of the primary particles is low, and one original powder always evolves into one spheroidal particle with a continuous liquid layer surface. Properly raising the heating temperature is beneficial for obtaining an ideal semisolid microstructure.

  11. Structure and hardness of a hard metal alloy prepared with a WC powder synthesized at low temperature

    Energy Technology Data Exchange (ETDEWEB)

    Costa, F.A. da [Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil)], E-mail: francineac@yahoo.com; Medeiros, F.F.P. de [Programa de Pos-Graduacao em Ciencia e Engenharia de Materiais, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil); Silva, A.G.P. da [Laboratorio de Materiais Avancados, UENF, 28015-620 Campos de Goytacazes, RJ (Brazil); Gomes, U.U. [Departamento de Fisica Teorica e Experimental, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil); Filgueira, M. [Laboratorio de Materiais Avancados, UENF, 28015-620 Campos de Goytacazes, RJ (Brazil); Souza, C.P. de [Laboratorio de Termodinamica e Reatores, UFRN, Campus Universitario, 59072-970 Natal, RN (Brazil)

    2008-06-25

    The structure and hardness of a WC-10 wt% Co alloy prepared with an experimental WC powder are compared with those of another alloy of the same composition produced under the same conditions and prepared with a commercial WC powder. The experimental WC powder was synthesized by a gas-solid reaction between APT and methane at low temperature and the commercial WC powder was conventionally produced by a solid-solid reaction between tungsten and carbon black. WC-10 wt% Co alloys with the two powders were prepared under the same conditions of milling and sintering. The structure of the sample prepared with the experimental WC powder is homogeneous and coarse grained. The structure of the sample prepared with the commercial powder is heterogeneous. Furthermore the size and shape of the WC grains are significantly different.

  12. Microstructural and electrical investigation of Cu-Ni-Cr alloys obtained by powder metallurgy method

    Energy Technology Data Exchange (ETDEWEB)

    Carrio, Juan A.G.; Carvalhal, M.A.; Ayabe, L.M.; Monteiro, W.A., E-mail: jgcarrio@mackenzie.br [Universidade Presbiteriana Mackenzie (UPM/CCH), Sao Paulo, SP (Brazil). Centro de Ciencias e Humanidades. Dept. de Fisica; Silva, L.C.E. da; Silva Junior, R.V., E-mail: fisica.cch@mackenzie.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2009-07-01

    The aim of this work, using the powder metallurgy process, is to synthesize metallic alloys with high mechanical strength and high electric conductivity, after melting optimizing and thermal treatments. The Cu-Ni-Cr (wt%) alloys are characterized in their mechanical and electrical properties as well as the obtained microstructure. Through the process of powder metallurgy, contacts and structural parts can be obtained. The alloys elements are added to copper with the intention to improve their strength, ductility and thermal stability, without causing considerable damages in their form, electrical and thermal conductivity, and corrosion resistance. The metallic powders were mixed for a suitable time and then they were pressed in a cold uniaxial pressing (1000 kPa). Afterwards, the specimens were sintered in temperatures varying from 700 up to 800 deg C under vacuum. At last, the samples were homogenized at 550 deg C under vacuum, for special times. The comparative analysis is based on the sintered density, densification parameter, hardness, macrostructures and microstructures of the samples. The alloys were characterized by optical microscopy, X-rays powder diffraction, electrical conductivity and Vickers hardness. (author)

  13. The Densification of Molybdenum and Molybdenum Alloy Powders Using Hot Isostatic Pressing.

    Science.gov (United States)

    1985-08-01

    TECHNICAL REPORT ARLCB-TR-85025 00 THE DENSIFICATION OF MOLYBDENUM (n AND MOLYBDENUM ALLOY POWDERS USING HOT ISOSTATIC PRESSING J. BARRANCO I. AHMAD S...ISOSTATIC PRESSING Final 6. PERFORMING ORG. REPORT NUMBER 7. AUTHOR(o) . CONTRACT OR GRANT NUMBER(e) J. Barranco , I. Ahmad, S. Isserow, and R. Warenchak

  14. Mechanical behaviour of pressed and sintered titanium alloys obtained from prealloyed and blended elemental powders.

    Science.gov (United States)

    Bolzoni, L; Esteban, P G; Ruiz-Navas, E M; Gordo, E

    2012-10-01

    The applicability of irregular prealloyed Ti-6Al-4V powder for the fabrication of titanium products by pressing and sintering and its employment as a master alloy to obtain the Ti-3Al-2.5V alloy was studied. To this end, the starting powders were characterised by dilatometry, differential thermal analysis and XRD. Green samples were obtained by cold uniaxial pressing, and the evolution of the microstructure over the sintering temperature range 900-1400°C was studied. The variation of the final density and mechanical properties with the sintering temperature was considered. Based on the study carried out, it can be stated that more reliable powders are needed to open the titanium market to new applications. A relative density of 95% and diverse microstructural features and mechanical properties equivalent to those of biomedical devices can be obtained by the pressing and sintering route.

  15. Microstructure and microanalysis studies of copper-nickel-tin alloys obtained by conventional powder metallurgy processing

    Energy Technology Data Exchange (ETDEWEB)

    Monteiro, Waldemar A.; Carrio, Juan A.G.; Masson, T.J.; Vitor, E.; Abreu, C.D.; Marques, I.M., E-mail: fisica.cch@mackenzie.br [Universidade Presbiteriana Mackenzie (CCH), Sao Paulo, SP (Brazil). Centro de Ciencias e Humanidades; Silva, L.C.E. da, E-mail: jgcarrio@mackenzie.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2009-07-01

    The aim of this paper was to analyze the microstructural development in samples of Cu-Ni-Sn alloys (weight %) obtained by powder metallurgy (P/M). The powders were mixed for 1/2 hour. After this, they were pressed, in a cold uniaxial pressing (1000 kPa). In the next step the specimens were sintered at temperatures varying from 650 up to 780 deg C under vacuum. Secondly, the samples were homogenized at 500 deg C for several special times. The alloys were characterized by optical microscopy, electrical conductivity and Vickers hardness. X-rays powder diffraction data were collected for the sintered samples in order to a structural and microstructural analysis. The comparative analysis is based on the sintered density, densification parameter, hardness, macrostructures and microstructures of the samples. (author)

  16. Structural and electrical properties of copper-nickel-aluminum alloys obtained by conventional powder metallurgy method

    Energy Technology Data Exchange (ETDEWEB)

    Monteiro, Waldemar A.; Carrio, Juan A.G.; Silveira, C.R. da; Pertile, H.K.S., E-mail: fisica.cch@mackenzie.br [Universidade Presbiteriana Mackenzie (UPM/CCH), Sao Paulo, SP (Brazil). Centro de Ciencias e Humanidades. Dept. de Fisica; Silva, L.C.E. da; Buso, S.J., E-mail: jgcarrio@mackenzie.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil)

    2009-07-01

    This work looked for to search out systematically, in scale of laboratory, copper-nickel-aluminum alloys (Cu-Ni-Al) with conventional powder metallurgy processing, in view of the maintenance of the electric and mechanical properties with the intention of getting electric connectors of high performance or high mechanical damping. After cold uniaxial pressing (1000 kPa), sintering (780 deg C) and convenient homogenization treatments (500 deg C for different times) under vacuum (powder metallurgy), the obtained Cu-Ni-Al alloys were characterized by optical microscopy, electrical conductivity, Vickers hardness. X rays powder diffraction data were collected for the sintered samples in order to a structural and microstructural analysis. The comparative analysis is based on the sintered density, hardness, macrostructures and microstructures of the samples. (author)

  17. Structure evolution of Cu-based shape memory powder during mechanical alloying

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    The microstructures of shape memory powders of Cu-Al-Ni prepared from pure powders of Cu, Al and Ni using the mechanical alloying(MA) technique were studied by means of hardness measurement, metallograph observation, XRD and SEM.The hardness reaches the peak as the increase in hardness due to plastic deformation and the decrease in hardness due to kinetic annealing reach a balance. The process of MA leads to the formation of a laminated structure, and the layer becomes thinner with an increase in milling time. The pre-alloyed shape memory powder can be formed by milling at 300 r/min for 50 h using a planetary ball mill.

  18. Mechanical alloying of Mo-Si-Fe powders

    Institute of Scientific and Technical Information of China (English)

    曹昱; 易丹青; 张松

    2002-01-01

    Mechanical milling behavior of Mo-Si-Fe powders was investigated u sing XRD, SEM and TEM techniques. The mixtures of elemental molybdenum (>99%), s ilicon (>99%) and iron (>98%) powders with a stoichiometry of Mo5-xFe xSi3 (x=0.5, 1, 2) were milled in a planetary mill for up to 195 h. For all three powder mixt ures, high-energy milling of 60h led to formation of the Mo(Fe, Si) supers aturated solid solution (Moss); and to a remarkable expansion of the solub ility of Fe, Si in molybdenum. The transformation of Moss to an amorphous phase was identified after longer time milling. In the milling process, the grain size of Mo (Fe, Si) decreased gradually and the internal stress increased linearly. After 40 h milling, the grain size was reduced to about 11 nm. SEM analysis of milled powders showed that the particle size increased initially with milling time. After 195 h milling, particles exhibited a spherical morphology and the particle size were reduced to about 100 nm.

  19. Laser surface treatment of magnesium alloy with WC and TiC powders using HPDL

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2008-06-01

    Full Text Available Purpose: The aim of this work was to improve the surface layer cast magnesium alloy EN-MCMgAl6Zn1 by laser surface treatment. The purpose of this work was also to determine the laser treatment parameter.Design/methodology/approach: The laser treatment of an EN-MCMgAl6Zn1 magnesium alloy with alloying WC and also TiC powders was carried out using a high power diode laser (HPDL. The resulting microstructure in the modified surface layer was examinated using scanning electron microscopy. Phase composition was determined by the X-ray diffraction method using the XPert device. The measurements of microhardness of the modified surface layer was also studied.Findings: The alloyed region has a fine microstructure with hard carbide particles. Microhardness of laser surface alloyed layer with both TiC and WC particles was significantly improved as compared to alloy without laser treatment.Research limitations/implications: In this research two powders (WC and TiC were used with the particle size over 5µm This investigation presents different speed rates feed by one process laser power.Practical implications: The results obtained in this investigation were promising to compared other conventional processes. High Power Diode Laser can be used as an economical substitute of Nd:YAG and CO2 to improve the surface magnesium alloy by feeding the carbide particles.Originality/value: The originality of this work is applying of High Power Diode Laser for alloying of magnesium alloy using hard particles like tungsten carbide and titanium carbide.

  20. Microstructure and Mechanical Behavior of Hot Pressed Cu-Sn Powder Alloys

    Directory of Open Access Journals (Sweden)

    Ahmed Nassef

    2016-01-01

    Full Text Available Cu-Sn based alloy powders with additives of elemental Pb or C were densified by hot pressing technique. The influence of densifying on the properties of the hot pressed materials was investigated. The properties, such as the hardness, compressive strength, and wear resistance of these materials, were determined. The hot pressed Cu-Sn specimens included intermetallic/phases, which were homogeneously distributed. The presence of graphite improved the wear resistance of Cu-Sn alloys three times. Similarly, the presence of lead improved the densification parameter of Cu-Sn alloys three times. There was no significant difference in the mechanical behavior associated with the addition of Pb to the Cu-Sn alloys, although Cu-Pb alloys showed considerably higher ultimate strength and higher elongation. The Cu-Sn-C alloys had lower strength compared with those of Cu-Sn alloys. Evidence of severe melting spots was noticed in the higher magnifications of the compression fracture surface of 85% Cu-10% Sn-5% C and 80% Cu-10% Sn-10% Pb alloys. This was explained by the release of load at the final event of the fracture limited area.

  1. Evaluation of Sintering Behavior of Premix Al-Zn-Mg-Cu Alloy Powder

    Directory of Open Access Journals (Sweden)

    Haris Rudianto

    2015-01-01

    Full Text Available Sintering of light aluminium alloys powder has been investigated as a way to substitute steels in automotive and aerospace industries. Premix Al-5.5Zn-2.5Mg-0.5Cu composite powder called Alumix 431D was analyzed in this research. Sintering was carried out under ultra high purity nitrogen gas and before reaching sintering temperature, green samples were delubricated at 400°C for 30 min. The powder possesses high sinterability by reaching 96% relative density at 580°C sintering temperature. Formation of liquid phase seems to support achieving high sintering density. Optimum mechanical properties also were obtained under those conditions. T6 heat treatment was done to improve the mechanical properties by formation of precipitation strengthening, and MgZn2 appears to be dominant strengthening precipitate. X-ray diffraction, optical microscopy, and SEM-EDS were used to characterize powder, and sintered and heat treated samples.

  2. Effect of Mg as sintering additive on the consolidation of mechanically alloyed Al powder

    Energy Technology Data Exchange (ETDEWEB)

    Fuentes, J.J. [UNET, Dept. de Ingenieria Mecanica, San Cristobal (Venezuela); Rodriguez, J.A.; Herrera, E.J. [Grupo de Metalurgia e Ingenieria de los Materiales, Escuela Superior de Ingenieros, Univ. de Sevilla, Camino de los Descubrimientos, Sevilla (Spain)

    2003-07-01

    Mechanically alloyed aluminium, MA Al, powder particles are hard and covered by surface oxide layers. This gives problems in consolidation processing. Consolidation is often carried out by hot extrusion, as the main processing step. An alternative consolidation method consisting in a press-and-sinter process has been developed at the University of Seville. MA Al powder was prepared by attrition milling. To improve the sinterability of MA Al powder, small amounts of magnesium, ranging from 0.0 to 1.2 wt% Mg, were added after milling. The mixed powder was consolidated by cold pressing (1120 MPa) and vacuum sintering (650 C, 1 h). Different mechanical and structural studies have been carried out. It has been observed that the addition of magnesium improves the mechanical properties of sintered MA Al. This is attributed to the reducing action of Mg on the Al sesquioxide layer and to the formation of liquid phases during sintering. (orig.)

  3. Microstructure and Mechanical Properties of Ti-Mo-Zr-Cr Biomedical Alloys by Powder Metallurgy

    Science.gov (United States)

    Elshalakany, Abou Bakr; Ali, Shady; Amigó Mata, A.; Eessaa, Ashraf K.; Mohan, P.; Osman, T. A.; Amigó Borrás, V.

    2017-03-01

    Titanium and its alloys have been widely used as biometals due to their excellent biocompatibility, corrosion resistance and moderate mechanical properties. Ti-15Mo-6Zr-based alloys and a series of Ti-15Mo-6Zr-xCr ( x = 1, 2, 3, 4 wt.%) alloys were designed and fabricated by powder metallurgy for the first time to develop novel biomedical materials. The microstructure, internal porosity and mechanical properties of the sintered Ti-15Mo-6Zr and Ti-15Mo-6Zr-xCr alloys were investigated using scanning electronic microscopy (SEM) and bending and compression tests. The experimental results indicated that the microstructure and mechanical properties of these alloys changed as different Cr levels were added. The addition of small Cr levels further increased the β-phase stability, improving the properties of the Ti-15Mo-6Zr-xCr alloy. However, all of the alloys had good ductility, and the Ti-15Mo-6Zr-2Cr alloy had lower bending and compression moduli (31 and 23 GPa, respectively) than the Ti-15Mo-6Zr-based alloys (40 and 36 GPa, respectively). Moreover, the Ti-15Mo-6Zr-2Cr alloys exhibited higher bending and compression strength/modulus ratios, which were as large as 48.4 and 52.2, respectively; these were higher than those of the Ti-15Mo-6Zr-based alloy (41.3 and 33.6, respectively). In the search for a better implant material, β phase Ti-15Mo-6Zr-2Cr, with its low modulus, ductile properties and reasonably high strength, is a promising candidate.

  4. Cost-effective blended elemental powder metallurgy of titanium alloys for transportation application

    Energy Technology Data Exchange (ETDEWEB)

    Ivasishin, O.M.; Demidik, A.N.; Savvakin, D.G. [AN Ukrainskoj SSR, Kiev (Ukraine). Inst. Fiziki Metallov; Anokhin, V.M. [State Research and Design Titanium Inst., Zaporozhie (Ukraine)

    2000-07-01

    Transportation industry is one of the perspective areas of application for lightweight advanced materials, including titanium alloys. However, despite the excellent mechanical properties and corrosion resistance of titanium alloys, automobile and other transportation industries cannot afford titanium unless its cost is significantly reduced. Near-net-shape processings, amongst which are powder metallurgy (PM) techniques, look the most appealing ways of cost reduction. Economic potentiality of titanium PM processes depends on the availability of low-cost powder and particular consolidation technology used. In this paper the blended elemental technology by a simple press-and-sinter method has been investigated using various titanium powders, in order to find if this technology can be applied to production of parts from titanium alloys for transportation industry. Main part of work was done on Ti-6Al-4V (wt.%) composition although some other compositions were tried. Chemical and dimensional characteristics of initial powders, cold-compaction pressure, temperature and time of sintering were main variables of the study. It was shown that at proper choice of elemental constituents and consolidation parameters high density of the final product (98% of theoretical) could be obtained. For this case, microstructural investigations showed a phase and structural homogeneity of the synthesized material. This can give rise to the mechanical properties to be comparable with those of cast and wrought material. (orig.)

  5. Hyperfine interactions on iron nuclei in the BCC and fractally decomposed BCC/FCC mixed phase iron-gold alloys

    Energy Technology Data Exchange (ETDEWEB)

    Blachowski, A. [Moessbauer Spectroscopy Division, Institute of Physics, Pedagogical University, PL-30-084 Krakow, ul. Podchorazych 2 (Poland); Ruebenbauer, K. [Moessbauer Spectroscopy Division, Institute of Physics, Pedagogical University, PL-30-084 Krakow, ul. Podchorazych 2 (Poland)], E-mail: sfrueben@cyf-kr.edu.pl; Przewoznik, J.; Zukrowski, J. [Solid State Physics Department, Faculty of Physics and Applied Computer Science, AGH University of Science and Technology, PL-30-059 Krakow, Al. Mickiewicza 30 (Poland)

    2008-06-30

    Iron-gold alloys for the gold concentration ranging from 1 at.% till 70 at.% were investigated by means of the {sup 57}Fe-14.4 keV Moessbauer spectroscopy, X-ray diffraction and scanning electron microscopy. Samples were prepared by arc melting of the elements, and investigated as cast and after annealing. A single BCC phase is obtained for the gold concentration up to about 3 at.%, while for the higher gold concentration one obtains mixed phase samples containing BCC and FCC phases both. The BCC phase is ferromagnetically ordered at room temperature. Contributions to the charge and spin density on iron atoms in the BCC phase due to the gold impurities were determined up to the second neighbors. The FCC phase is either magnetically ordered at room temperature or it is paramagnetic at the above temperature depending upon iron concentration, as the magnetic transition temperature is increasing with the increasing iron concentration. BCC/FCC mixed phase samples are characterized by very small crystallites (nanoparticles) of both phases. These nanoparticles form hierarchical fractal structures on the scale ranging from more than 1 mm till less than 30 nm.

  6. Annealing temperature effect on microstructure, magnetic and microwave properties of Fe-based amorphous alloy powders

    Energy Technology Data Exchange (ETDEWEB)

    He Jinghua; Wang Wei; Wang Aimin [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China); Guan Jianguo, E-mail: guanjg@whut.edu.cn [State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070 (China)

    2012-09-15

    Fe{sub 74}Ni{sub 3}Si{sub 13}Cr{sub 6}W{sub 4} amorphous alloy powders were annealed at different temperature (T) for 1.5 h to fabricate the corresponding amorphous and nanocrystalline powders. The influences of T on the crystalline structure, morphology, magnetic and microwave electromagnetic properties of the resultant samples were investigated via X-ray diffraction, scanning electron microscopy, vibrating sample magnetometer and vector network analyzer. The results show that the powder samples obtained at T of 650 Degree-Sign C or more are composed of lots of ultra-fine {alpha}-Fe(Si) grains embedded in an amorphous matrix. When T increases from 350 to 750 Degree-Sign C, the saturated magnetization and coercivity of the as-annealed powder samples both increase monotonously whereas the relative real permittivity shows a minimal value and the relative real permeability shows a maximal value at T of 650 Degree-Sign C. Thus the powder samples annealed at 650 Degree-Sign C show optimal reflection loss under -10 dB in the whole C-band. These results here suggest that the annealing heat treatment of Fe-based amorphous alloy is an effective approach to fabricate high performance microwave absorber with reasonable permittivity and large permeability simultaneously via adjusting T. - Highlights: Black-Right-Pointing-Pointer The annealing temperature effect of Fe-based amorphous alloy was studied. Black-Right-Pointing-Pointer Fe-based amorphous and nanocrystalline alloy has a good absorbing property in C-band. Black-Right-Pointing-Pointer There exists a correspondence between microwave properties and microstructure.

  7. Microstructural evolution and mechanical properties of powder metallurgy Ti–6Al–4V alloy based on heat response

    Energy Technology Data Exchange (ETDEWEB)

    Guo, Ruipeng [School of Materials and Metallurgy, Northeastern University, Shenyang 110819 (China); Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Xu, Lei, E-mail: lxu@imr.ac.cn [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Wu, Jie; Yang, Rui [Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016 (China); Zong, Bernie Y. [Key Laboratory for Anisotropy and Texture of Materials, Ministry of Education, Northeastern University, Shenyang 110819 (China)

    2015-07-15

    In present work, powder metallurgy (PM) Ti–6Al–4V alloy was produced by hot isostatic pressing (HIPing) from gas atomized powder. Various HIPing conditions and heat treatments were used to investigate the heat response of PM Ti–6Al–4V alloy. The results show that the optimization of HIPing parameters is temperature from 920 to 940 °C, pressure over 120 MPa and holding for 3 h. The microstructure of powder compact changes significantly after different heat treatments, while there was no obvious difference in tensile properties. Temperature induced porosity (TIP) in powder compact occurred after annealing at 930 °C for 1 h plus aging. The TIP has no obvious effects on tensile, impact, and fracture toughness properties of powder compact, but the TIP has an adverse effect on fatigue property, especially at shorter fatigue lives. In order to eliminate the TIP in powder compact, several probable solutions were suggested for the application of titanium powder components.

  8. Formation mechanism of Ti5Si3 powder by mechanical alloying

    Institute of Scientific and Technical Information of China (English)

    Pengchao Kang; Zhongda Yin; Yue Jiang; Mingwei Li

    2004-01-01

    The formation mechanism of stoichiometry Ti5Si3 by mechanical alloying (MA) from elemental powders has been investigated. The results of XRD and SEM analyses of the powder show that Ti5Si3 can be synthesized by MA in a planetary mill with two different formation mechanisms. Ti5Si3 was formed gradually with the mechanical collusion reaction (MCR) mechanism under a lower impact energy, and the Ti5Si3 was formed abruptly with the self-propagating high-temperature synthesis (SHS) formation mechanism under a higher impact energy.

  9. Microstructure and properties of liquid-phase sintered tungsten heavy alloys by using ultra-fine tungsten powders

    Institute of Scientific and Technical Information of China (English)

    于洋; 王尔德

    2004-01-01

    The microstructure and properties of liquid-phase sintered 93W-4.9Ni-2.1Fe tungsten heavy alloys using ultra-fine tungsten powders (medium particle size of 700 nm) and original tungsten powders (medium particle size of 3 μm) were investigated respectively. Commercial tungsten powders (original tungsten powders) were mechanically milled in a high-energy attritor mill for 35 h. Ultra-fine tungsten powders and commercial Ni, Fe powders were consolidated into green compacts by using CIP method and liquid-phase sintering at 1 465 ℃ for 30 min in the dissociated ammonia atmosphere. Liquid-phase sintered tungsten heavy alloys using ultra-fine tungsten powders exhibit full densification (above 99% in relative density) and higher strength and elongation compared with conventional liquidphase sintered alloys using original tungsten powders due to lower sintering temperature at 1 465 ℃ and short sintering time. The mechanical properties of sintered tungsten heavy alloy are found to be mainly dependent on the particles size of raw tungsten powders and liquid-phase sintering temperature.

  10. Surface chemical state of Ti powders and its alloys: Effect of storage conditions and alloy composition

    Science.gov (United States)

    Hryha, Eduard; Shvab, Ruslan; Bram, Martin; Bitzer, Martin; Nyborg, Lars

    2016-12-01

    High affinity of titanium to oxygen in combination with the high surface area of the powder results in tremendous powder reactivity and almost inevitable presence of passivation oxide film on the powder surface. Oxide film is formed during the short exposure of the powder to the environment at even a trace amount of oxygen. Hence, surface state of the powder determines its usefulness for powder metallurgy processing. Present study is focused on the evaluation of the surface oxide state of the Ti, NiTi and Ti6Al4V powders in as-atomized state and after storage under air or Ar for up to eight years. Powder surface oxide state was studied by X-ray photoelectron spectroscopy (XPS) and high resolution scanning electron microscopy (HR SEM). Results indicate that powder in as-atomized state is covered by homogeneous Ti-oxide layer with the thickness of ∼2.9 nm for Ti, ∼3.2 nm and ∼4.2 nm in case of Ti6Al4V and NiTi powders, respectively. Exposure to the air results in oxide growth of about 30% in case of Ti and only about 10% in case of NiTi and Ti6Al4V. After the storage under the dry air for two years oxide growth of only about 3-4% was detected in case of both, Ti and NiTi powders. NiTi powder, stored under the dry air for eight years, indicates oxide thickness of about 5.3 nm, which is about 30% thicker in comparison with the as-atomized powder. Oxide thickness increase of only ∼15% during the storage for eight years in comparison with the powder, shortly exposed to the air after manufacturing, was detected. Results indicate a high passivation of the Ti, Ti6Al4V and NiTi powder surface by homogeneous layer of Ti-oxide formed even during short exposure of the powder to the air.

  11. Preparation of Permanent Mold Coating Using Magnesia Powder for Magnesium Alloys

    Science.gov (United States)

    Guo, Guangsi; Wang, Guangtai; Yu, Haifeng; Ye, Sheng

    A kind of permanent mold coating for magnesium alloy was developed using magnesia powder and diatomite as refractory aggregate. The properties of the coating were tested and analyzed by various ingredients. The final ingredient was determined through the tests which are to find out the optimal proportion of two kinds of aggregate and the influences to coating properties by changing the proportion of binder and suspending agents. The experimental results shown that the permanent mold coating performed good properties on magnesium alloys when the optimized ratio of magnesia powder and diatomite was 6: 4, and the integrated property is very excellent when the coating was prepared with 2 percent of sodium bentonite, 0.4 percent of CMC, 7 percent of sodium hexametaphosphate, and 7 percent of sodium silicate. The excellent performance has also been proved by actual casting test.

  12. Microstructure and mechanical properties of a Mg–Zn–Y alloy produced by a powder metallurgy route

    Energy Technology Data Exchange (ETDEWEB)

    Asgharzadeh, H. [Department of Materials Engineering, Faculty of Mechanical Engineering, University of Tabriz, P.O. Box 51666-16471, Tabriz (Iran, Islamic Republic of); Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Yoon, E.Y. [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Chae, H.J.; Kim, T.S. [Korea Institute for Rare Metals, Korea Institute of Industrial Technology, Incheon 406-840 (Korea, Republic of); Lee, J.W. [Korea Institute of Materials Science (KIMS), Changwon 641-831 (Korea, Republic of); Kim, H.S., E-mail: hskim@postech.ac.kr [Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of)

    2014-02-15

    In this paper, a bulk Mg–Zn–Y alloy reinforced by quasicrystalline particles was produced by hot extrusion of rapidly-solidified powders. MgZn{sub 4.3}Y{sub 0.7} powders with different particle sizes were prepared by an inert gas atomizer and then extruded at 380 °C with extrusion ratios of 10:1, 15:1, and 20:1. Microstructural studies were performed using an optical microscope, scanning electron microscope, transmission electron microscope, and X-ray diffraction. The mechanical strength and hardness of the extruded materials were enhanced by employing finer Mg alloy powders. More uniform deformation of powders in extruded billets with good tensile properties was achieved at higher extrusion ratios, especially for finer powders. The high strength of the MgZn{sub 4.3}Y{sub 0.7} alloy was preserved at elevated temperatures due to the presence of icosahedral phase nanoparticles.

  13. Fabrication of Ni-Nb-Sn metallic glassy alloy powder and its microwave-induced sintering behavior.

    Science.gov (United States)

    Xie, Guoqiang; Li, Song; Louzguine-Luzgin, D V; Cao, Ziping; Yoshikawa, Noboru; Sato, Motoyasu; Inoue, Akihisa

    2009-01-01

    In the present study, we prepared Ni59.35Nb34.45Sn6.2 metallic glassy alloy powder by an argon gas atomization process. Microwave (MW)-induced heating and sintering was carried out by a single-mode 2.45 GHz MW applicator in the separated magnetic field or electric field using the obtained glassy powders. The structure and thermal stability of the sintered glassy alloy specimens were investigated.

  14. Particle size evolution in non-adhered ductile powders during mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Guerrero-Paz, J. [Centro de Investigaciones en Materiales y Metalurgica, UAEH (Mexico); Robles-Hernandez, F.C.; Hernandez-Silva, D.; Jaramillo-Vigueras, D. [Dept. de Ingenieria Metalurgica, ESIQIE - Inst. Politecnico Nacional, Mexico D.F. (Mexico); Martinez-Sanchez, R. [Centro de Investigacion en Materiales Avanzados, Chihuahua (Mexico)

    2001-07-01

    The interaction among events as deformation, cold-welding and fracture, occurring during the mechanical milling of powders is unclear and controversial. We believe that the understanding of such interaction can be deduced from particle size evolution studies. It is well known that the elemental ductile powders adhere to the milling media. However when some of these powders are combined to form an alloy by milling, the adherence phenomenon is not observed. Systems which include ductile powders, such as, Cu-15at.%Al, Co-68at.%Al and Ni-25at.%Al were processed with not adherence to the milling media, thus allowing to follow up the particle size evolution during the complete milling process. The particle size was measured by the sedimentation-photometry technique. Those results were supported by scanning and transmission electron microscopy. The results showed a high proportion near 95% in number of particles of submicrometric size at early milling times for the three systems. However its particle size evolution for each system was different. Such findings can be important to understand some mechanisms as the grain size refinement, the alloy formation and the microstructural evolution. In the studied systems, the particle size measurements are presented based on volume or mass, area, line and number of the particles. The particle size results based on volume and line or number of the particles can give an idea of the evolution of the biggest particles and the finest ones respectively during the milling. Also the behavior of the complete particle system can be deduced from the results based in the area of the particles. Results of particle size as well as observations by microscopy helped to suggest the particle size and shape evolution of the studied systems. Such findings were employed to previously propose a grain size refinement mechanism for ductile powder systems non-adherent to the milling media during the mechanical alloying. (orig.)

  15. Production of a low young modulus titanium alloy by powder metallurgy

    Directory of Open Access Journals (Sweden)

    Dalcy Roberto dos Santos

    2005-12-01

    Full Text Available Titanium alloys have several advantages over ferrous and non-ferrous metallic materials, such as high strengthto-weight ratio and excellent corrosion resistance. A blended elemental titanium powder metallurgy process has been developed to offer low cost commercial products. The process employs hydride-dehydride (HDH powders as raw material. In this work, results of the Ti-35Nb alloy sintering are presented. This alloy due to its lower modulus of elasticity and high biocompatibility is a promising candidate for aerospace and medical use. Samples were produced by mixing of initial metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by isochronal sintering between 900 up to 1600 °C, in vacuum. Sintering behavior was studied by means of microscopy and density. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. Samples sintered at high temperatures display a fine plate-like alpha structure and intergranular beta. A few remaining pores are still found and density above 90% for specimens sintered in temperatures over 1500 °C is reached.

  16. The substitution of nickel for cobalt in hot isostatically pressed powder metallurgy UDIMET 700 alloys

    Science.gov (United States)

    Harf, F. H.

    1985-01-01

    Nickel was substituted in various proportions for cobalt in a series of five hot-isostatically-pressed powder metallurgy alloys based on the UDIMET 700 composition. These alloys were given 5-step heat treatments appropriate for use in turbine engine disks. The resultant microstructures displayed three distinct sizes of gamma-prime particles in a gamma matrix. The higher cobalt-content alloys contained larger amounts of the finest gamma-prime particles, and had the lowest gamma-gamma-prime lattice mismatch. While all alloys had approximately the same tensile properties at 25 and 650 gamma C, the rupture lives at 650 and 760 C peaked in the alloys with cobalt contents between 12.7 and 4.3 pct. Minimum creep rates increased as cobalt contents were lowered, suggesting their correlation with the gamma-prime particle size distribution and the gamma-gamma-prime mismatch. It was also found that, on overaging at temperatures higher than suitable for turbine disk use, the high cobalt-content alloys were prone to sigma phase formation.

  17. Investigation of powdering ductile gamma U-10 wt%Mo alloy for dispersion fuels

    Science.gov (United States)

    Leal Neto, R. M.; Rocha, C. J.; Urano de Carvalho, E.; Riella, H. G.; Durazzo, M.

    2014-02-01

    This work forms part of the studies presently ongoing at Nuclear and Energy Research Institute - IPEN/CNEN-SP investigating the feasibility of powdering ductile U-10 wt%Mo alloy by hydriding-milling-dehydriding of the gamma phase (HMD). Hydriding was conducted at room temperature in a Sievert apparatus following heat treatment activation. Hydrided pieces were fragile enough to be hand milled to the desired particle size range. Hydrogen was removed by heating the samples under high vacuum. X-ray diffraction analysis of the hydrided material showed an amorphous-like pattern that is completely reversed following dehydriding. The hydrogen content of the hydrided samples corresponds to a trihydride, i.e. (U,Mo)H3. SEM analysis of HMD powder particles revealed equiaxial powder particles together with some plate-like particles. A hypothesis for the amorphous hydride phase formation is suggested.

  18. Feasibility study of the production of biomedical Ti-6Al-4V alloy by powder metallurgy.

    Science.gov (United States)

    Bolzoni, L; Ruiz-Navas, E M; Gordo, E

    2015-04-01

    Titanium and its alloys are characterized by an exceptional combination of properties like high strength, good corrosion resistance and biocompatibility which makes them suitable materials for biomedical prosthesis and devices. The wrought Ti-6Al-4V alloy is generally favored in comparison to other metallic biomaterials due to its relatively low elastic modulus and it has been long used to obtain products for biomedical applications. In this work an alternative route to fabricate biomedical implants made out of the Ti-6Al-4V alloy is investigated. Specifically, the feasibility of the conventional powder metallurgy route of cold uniaxial pressing and sintering is addressed by considering two types of powders (i.e. blended elemental and prealloyed). The characterization of physical properties, chemical analysis, mechanical behavior and microstructural analysis is carried out in-depth and the properties are correlated among them. On the base of the results found, the produced alloys are promising materials for biomedical applications as well as cheaper surgical devices and tools.

  19. High entropy alloy thin films deposited by magnetron sputtering of powder targets

    Energy Technology Data Exchange (ETDEWEB)

    Braeckman, B.R., E-mail: BertR.Braeckman@Ugent.be [Department of Solid State Sciences, Ghent University, Krijgslaan 281 (S1), 9000 Gent (Belgium); Boydens, F. [Department of Solid State Sciences, Ghent University, Krijgslaan 281 (S1), 9000 Gent (Belgium); Hidalgo, H.; Dutheil, P. [GREMI, UMR7344 CNRS, Université d' Orléans, BP6744, 45067 Orléans Cedex 2 (France); Jullien, M. [Institut Jean Lamour, Université de Lorraine, UMR CNRS, 7198 Vandoeuvre-lès-Nancy (France); Thomann, A.-L. [GREMI, UMR7344 CNRS, Université d' Orléans, BP6744, 45067 Orléans Cedex 2 (France); Depla, D. [Department of Solid State Sciences, Ghent University, Krijgslaan 281 (S1), 9000 Gent (Belgium)

    2015-04-01

    High entropy alloys (HEA) contain at least five principal elements in equimolar or near-equimolar ratios. These materials crystallize typically as a face-centered cubic (FCC), body-centered cubic (BCC) solid solution or as a mixture of these two crystal structures. AlCoCrCuFeNi thin films were deposited by magnetron sputtering of homemade pressed powder targets. Four targets with different compositions were sputtered under various conditions to modify the alloy composition. Scanning electron microscopy and energy-dispersive X-ray spectroscopy were used to study the surface morphology and composition whereas X-ray diffraction and X-ray reflectivity provided information regarding the phase formation and density of the films. It is suggested that, when taking into account the atomic radii of the constituent elements, the sputter deposited alloy thin films can be topologically regarded as binary alloys of the form Al-(CoCrCuFeNi). If the concentration of the largest atom (Al) increases, a transition from FCC to BCC is noticed. This structure transition could be attributed to a critical lattice distortion. - Highlights: • AlCoCrCuFeNi thin films were deposited by sputtering pressed power targets. • Sputter deposition of powder targets allows good control over the film composition. • With increasing Al fraction, a crystallographic structure transition was noticed. • The transition was made semi-quantitative with Egami's atomic-level stress theory.

  20. Morphology and microstructure characterization of 95W-3.5Ni-1.5Fe powder prepared by mechanical alloying

    Institute of Scientific and Technical Information of China (English)

    Islam S. Humail; Xuanhui Qu; Chengchang Jia; Mingli Qin; Xinbo He

    2006-01-01

    The mechanism of mechanical solid-state reactions for formation of tungsten heavy alloy powder was discussed. A highenergy ball mill operating at room temperature was used for preparing tungsten heavy alloy powders, starting from elemental tungsten (W), nickel (Ni), and iron (Fe) powders. X-ray diffraction (XRD), particle size analyzer, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to follow the progress of the mechanical solid-state reaction of W, Ni, and Fe powders. These morphological studies revealed three stages in the milling process. In the first stage, the particle deformation changes the irregular structure of the as-received powder particles to flattened morphology, and the average particle size increases. In the second stage, the powder is sufficiently deformed and the tendency to fracture predominates over welding, and the particle size decreases. With continuous milling, the system reaches steady state, and relatively small and uniform particle size distribution is obtained after 20 h of milling.

  1. Preparation of oxide powder by continuous oxidation process from recycled Fe-77Ni alloy scrap

    Science.gov (United States)

    Yun, J. Y.; Park, D. H.; Jung, G. J.; Wang, J. P.

    2015-12-01

    The oxidation behavior of Fe-77Ni alloy scrap was studied under a 0.2 atm oxygen partial pressure at the temperature range of 400°C to 900°C. The oxidation rate was found to be increased with an increase of temperature and followed the parabolic rate law with linearly proportional to temperature. Microstructure and cross-sectional area of the oxide layer were examined by SEM, EDX, and XRD. It could be speculated that rate-limiting step was controlled by diffusion through either the spinel structure or the NiO layer, both of which were present in this alloy during oxidation at elevated temperatures. In the long run, oxide powder less than 10 μm from Fe-77Ni alloy scrap was obtained using ball-milling and sieving processes and recovery ratio approached up to 97% for 15 hours.

  2. Effects of (Cr,Fe){sub 2}B borides on hardness in powder-injection-molded product fabricated with Fe-based alloy powders

    Energy Technology Data Exchange (ETDEWEB)

    Do, Jeonghyeon; Jeon, Changwoo; Paul Kim, Choongnyun; Lee, Byeong-Joo [Center for Advanced Aerospace Material, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Lee, Sunghak, E-mail: shlee@postech.ac.kr [Center for Advanced Aerospace Material, Pohang University of Science and Technology, Pohang 790-784 (Korea, Republic of); Lee, Eon-Sik [Advanced Metallic Materials Research Department, Research Institute of Industrial Science and Technology, Pohang 790-330 (Korea, Republic of); Shik Yoon, Tae [Bestner Co., 146-8 Sangdaewon-dong, Sungnam 462-121 (Korea, Republic of); Su Shin, Yang [New Growth Technology Strategy Department, POSCO, Seoul 135-777 (Korea, Republic of)

    2012-10-30

    In the present study, a powder injection molding (PIM) product containing (Cr,Fe){sub 2}B borides was fabricated with Fe-based alloy powders, and its microstructure and hardness were investigated in relation with volume fraction of (Cr,Fe){sub 2}B. In the Fe-based alloys designed by the thermodynamic calculation, the volume fractions of (Cr,Fe){sub 2}B increased with increasing (X{sub Cr}+X{sub B}) value, and were well matched with those obtained from the thermodynamic calculation. The hardness of the Fe-based alloys linearly increased with increasing volume fraction of (Cr,Fe){sub 2}B. When Fe-based alloy powders were injection-molded and sintered at 1165 Degree-Sign C, a densified microstructure with almost no pores was obtained. In the sintered microstructure, 56 vol% of (Cr,Fe){sub 2}B borides, together with a few pores (porosity; 0.5%), were relatively homogeneously distributed in the tempered martensite matrix, which resulted in the very high hardness over 600 VHN. Such a high hardness suggested that the present Fe-based alloy powders could be readily adopted for fabricating PIM products or for replacing conventional stainless steel PIM products.

  3. Structural changes during synthesizing of nanostructured W-20 wt% Cu composite powder by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Maneshian, M.H. [Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of); Simchi, A. [Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of) and Institute for Nanoscience and Nanotechnology, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of)]. E-mail: simchi@sharif.edu; Hesabi, Z. Razavi [Department of Materials Science and Engineering, Sharif University of Technology, P.O. Box 11365-9466, Azadi Avenue, 14588 Tehran (Iran, Islamic Republic of)

    2007-02-15

    Nanostructured W-20 wt% Cu composite powder was synthesized by mechanical alloying (MA) in an Attritor ball mill. The morphological changes and structural evolution of the composite powder during MA was studied by employing scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray (EDX), laser particle size analyzer (LPS), inductively coupled plasma (ICP) spectrometry, atomic absorption spectrophotometery (AAS), and the bulk powder density measurement. The results were compared with those obtained from attrition milling of monolithic W and Cu powders processed at the same condition. Whereas the milling mechanism of the monolithic powders follow the ductile (for Cu) and semi-brittle (for W) systems, the W/Cu powder mixture exhibits different behavior. At the early stage of milling, the copper particles are fragmented and incorporated into the W matrix, resulting in the formation of W/Cu composite with laminar structure. With increasing milling time and due to continuous fracturing, the laminar structure is refined and a homogenous distribution of fine Cu particles (0.3-0.6 {mu}m) in the W matrix is formed. The analysis of XRD patterns indicated that the composite powder composes of nanostructured grains with the size of 49 nm for Cu and 23 nm for W. A faster grain refinement in the composite powder compared to the monolithic particles was noticed. The XRD peak intensity also revealed that partial mutual solubility of the constituent elements ({approx}4-7 at% for Cu in W and {approx}2-3 at% for W in Cu) was induced by prolonged mechanical milling.

  4. Application of powder metallurgy to an advanced-temperature nickel-base alloy, NASA-TRW 6-A

    Science.gov (United States)

    Freche, J. C.; Ashbrook, R. L.; Waters, W. J.

    1971-01-01

    Bar stock of the NASA-TRW 6-A alloy was made by prealloyed powder techniques and its properties evaluated over a range of temperatures. Room temperature ultimate tensile strength was 1894 MN/sq m (274 500 psi). The as-extruded powder product showed substantial improvements in strength over the cast alloy up to 649 C (1200 F) and superplasticity at 1093 C (2000 F). Both conventional and autoclave heat treatments were applied to the extruded powder product. The conventional heat treatment was effective in increasing rupture life at 649 and 704 C (1200 and 1300 F); the autoclave heat treatment, at 760 and 816 C (1400 and 1500 F).

  5. Influence of Powder Metallurgical Processing Routes on Phase Formations in a Multicomponent NbSi-Alloy

    Science.gov (United States)

    Seemüller, C.; Hartwig, T.; Mulser, M.; Adkins, N.; Wickins, M.; Heilmaier, M.

    2014-09-01

    Refractory metal silicide composites on the basis of Nbss-Nb5Si3 have been investigated as potential alternatives for nickel-base superalloys for years because of their low densities and good high-temperature strengths. NbSi-based composites are typically produced by arc-melting or casting. Samples in this study, however, were produced by powder metallurgy because of the potential for near net-shape component fabrication with very homogeneous microstructures. Either gas atomized powder or high-energy mechanically alloyed elemental powders were compacted by powder injection molding or hot isostatic pressing. Heat treatments were applied for phase stability evaluation. Slight compositional changes (oxygen, nitrogen, or iron) introduced by the processing route, i.e., powder production and consolidation, can affect phase formations and phase transitions during the process. Special focus is put on the distinction between different silicides (Nb5Si3 and Nb3Si) and silicide modifications (α-, β-, and γ-Nb5Si3), respectively. These were evaluated by x-ray diffraction and energy-dispersive spectroscopy measurements with the additional inclusion of thermodynamic calculations using the calculated phase diagram method.

  6. Size-dependent structure and magnetocaloric properties of Fe-based glass-forming alloy powders

    Directory of Open Access Journals (Sweden)

    Qiang Luo

    2016-04-01

    Full Text Available We investigated the influence of particle size on the microstructure and magnetocaloric effect of Fe-based alloy powders (11 μm to 100 μm in diameter. The degree of structure order varies with the powder size. The 11 μm to 18 μm powders show the largest peak magnetic entropy change (MEC. Increasing the degree of structure order tends to decrease the maximum MEC. Nevertheless, enhancement of refrigerant capacity and MEC (above 70 K is achieved when the crystalline phase content is ∼50% (above 75 μm in the 75 μm to 100 μm powders. Exponent n of the field dependence of MEC increases with the decrease in powder size above 22.5 K. The size dependence of the structure and properties is associated with the fact that a larger particle has a slower cooling rate and takes a longer time to form medium-to-long range ordered structures.

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

    Science.gov (United States)

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

    2015-01-01

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

  8. Copper alloys with improved properties: standard ingot metallurgy vs. powder metallurgy

    Directory of Open Access Journals (Sweden)

    Milan T. Jovanović

    2014-09-01

    Full Text Available Three copper-based alloys: two composites reinforced with Al2O3 particles and processed through powder metallurgy (P/M route, i.e. by internal oxidation (Cu-2.5Al composite and by mechanical alloying (Cu-4.7Al2O3 and Cu-0.4Cr-0.08Zr alloy produced by ingot metallurgy (vacuum melting and casting were the object of this investigation. Light microscope and scanning electron microscope (SEM equipped with electron X-ray spectrometer (EDS were used for microstructural characterization. Microhardness and electrical conductivity were also measured. Compared to composite materials, Cu-0.4Cr-0.08Zr alloy possesses highest electrical conductivity in the range from 20 to 800 ℃, whereas the lowest conductivity shows composite Cu-2.5Al processed by internal oxidation. In spite to somewhat lower electrical conductivity (probably due to inadequate density, Cu-2.5Al composite exhibits thermal stability enabling its application at much higher temperatures than materials processed by mechanical alloying or by vacuum melting and casting.

  9. Effects of porosity on corrosion resistance of Mg alloy foam produced by powder metallurgy technology

    Energy Technology Data Exchange (ETDEWEB)

    Aghion, E., E-mail: egyon@bgu.ac.il; Perez, Y.

    2014-10-15

    Magnesium alloy foams have the potential to serve as structural material for regular light-weight applications as well as for biodegradable scaffold implants. However, their main disadvantage relates to the high reactivity of magnesium and consequently their natural tendency to corrode in regular service conditions and in physiological environments. The present study aims at evaluating the effect of porosity on the corrosion resistance of MRI 201S magnesium alloy foams in 0.9% NaCl solution and in phosphate buffer saline solution as a simulated physiological electrolyte. The magnesium foams were produced by powder metallurgy technology using space-holding particles to control the porosity content. Machined chips were used as raw material for the production of Mg alloy powder by milling process. The microstructure of the foams was examined using optical and scanning electron microscopy, X-ray diffraction, and X-ray photoelectron spectroscopy analysis. The corrosion behavior was evaluated by immersion test and potentiodynamic polarization analysis. The results obtained clearly demonstrate that the porosity has a significant effect on the corrosion resistance of the tested foams. Foams with 14–19% porosity have a corrosion rate of 4–10 mcd and 7–15 mcd in NaCl and phosphate buffer saline solution, respectively, compared to only 0.10 mcd for the same alloy in as cast conditions. This increased corrosion degradation of the Mg foams by more than one order of magnitude compared to the cast alloy may limit their potential application in regular and physiological environments. - Highlights: • Porosity has a detrimental effect on corrosion resistance of MRI 201S Mg foams. • 14–19% porosity increases the corrosion rate by more than one order of magnitude. • Accelerated corrosion limits the use of foams in regular/physiological environments.

  10. Mechanical alloying: A method to obtain metallic powders and composite materials; Aleacion mecanica: Metodo de obtencion de polvos metalicos y materiales compuestos

    Energy Technology Data Exchange (ETDEWEB)

    Ruiz-Navas, E. M.; Velasco Lopez, F.; Torralba Castello, J. M. [Universidad Carlos III. Madrid (Spain); Edil da Costa, C. [Universidad do Estado de Santa Catarina. Brasil (Brazil)

    2000-07-01

    This work deals with the mechanical alloying process as a method for powder production. The main aspects involved are as well as the fundaments and their particular application to the metal powder production. (Author) 75 refs.

  11. The effect of transverse magnetic field treatment on wave-absorbing properties of FeNi alloy powders

    Science.gov (United States)

    Zhao, Hui; Zhu, Zhenghou; Xiong, Chao; Xu, Xing; Lin, Qianying

    2017-01-01

    The Fe50Ni50 alloy powders were successfully synthesized with the liquid phase reduction method and then treated with the transverse magnetic field of 200 kA/m. The influences of transverse magnetic field treatment on microstructures and radar absorbing properties of the powders were mainly investigated. Whether the powders were treated with the transverse magnetic field or not, the main phases of Fe50Ni50 alloy powders were FeNi3 and a small amount of Fe2O3. Results showed that the real part of complex permeability μʹ; of the Fe50Ni50 alloy powders in 1-5 GHz increased significantly, especially at the frequency of 1 GHz, the μʹ; increased from 2.2 to 2.8 after transverse magnetic field treatment. The magnetic loss tanδm of the Fe50Ni50 alloy powders after transverse magnetic field treatment was ≥0.3 in the frequency range of 1-13 GHz and 0.7-1.05 in the frequency range of 3.5-9.0 GHz. Compared with those of the untreated powders, the wave-absorbing properties of the powders after transverse magnetic field treatment were significantly improved. The Fe50Ni50 alloy powders coatings with thickness of 1.5 mm exhibited excellent wave-absorbing properties after transverse magnetic field treatment, and the qualified absorption band width reached nearly 3 GHz when the reflectivity |R| was ≥10 dB.

  12. Selective Laser Melting of Magnesium and Magnesium Alloy Powders: A Review

    Directory of Open Access Journals (Sweden)

    Vyasaraj Manakari

    2016-12-01

    Full Text Available Magnesium-based materials are used primarily in developing lightweight structures owing to their lower density. Further, being biocompatible they offer potential for use as bioresorbable materials for degradable bone replacement implants. The design and manufacture of complex shaped components made of magnesium with good quality are in high demand in the automotive, aerospace, and biomedical areas. Selective laser melting (SLM is becoming a powerful additive manufacturing technology, enabling the manufacture of customized, complex metallic designs. This article reviews the recent progress in the SLM of magnesium based materials. Effects of SLM process parameters and powder properties on the processing and densification of the magnesium alloys are discussed in detail. The microstructure and metallurgical defects encountered in the SLM processed parts are described. Applications of SLM for potential biomedical applications in magnesium alloys are also addressed. Finally, the paper summarizes the findings from this review together with some proposed future challenges for advancing the knowledge in the SLM processing of magnesium alloy powders.

  13. Neutron powder thermo-diffraction in mechanically alloyed Fe{sub 64}Ni{sub 36} invar alloy

    Energy Technology Data Exchange (ETDEWEB)

    Gorria, Pedro, E-mail: pgorria@uniovi.e [Departamento de Fisica, Universidad de Oviedo, Avda. Calvo Sotelo s/n, Oviedo 33007, Asturias (Spain); Martinez-Blanco, David [Unidad de Magnetometria, SCT' s, Universidad de Oviedo, Julian Claveria 8, 33006 Oviedo (Spain); Blanco, Jesus A. [Departamento de Fisica, Universidad de Oviedo, Avda. Calvo Sotelo s/n, Oviedo 33007, Asturias (Spain); Smith, Ronald I. [ISIS Facility, RAL, Chilton, Didcot, Oxon OX11 0QX (United Kingdom)

    2010-04-16

    Nanostructured Fe{sub 64}Ni{sub 36} alloy has been obtained using high-energy ball milling for 35 h of milling time, Fe{sub 64}Ni{sub 36} MA-35 h. The initial as-milled Fe{sub 64}Ni{sub 36} MA-35 h powders are inhomogeneous, showing a majority phase with a face-centred cubic (fcc) crystal structure [88(2)%] and a minority phase with body-centred cubic (bcc) crystal structure [7(2)%]. The evolution of the microstructure with temperature between 300 K and 1100 K has been followed by means of in situ neutron powder thermo-diffraction experiments. The room temperature values for the mean crystalline size and the mechanical-induced microstrain of the fcc phase in the as-milled sample are {approx}10 nm and {approx}0.7%, respectively. Moreover, after heating the Fe{sub 64}Ni{sub 36} MA-35 h powders up to 1100 K, an increase of around 65 K in the Curie temperature respect to that of the commercial coarse-grained alloy of the same composition is observed. The latter together with the observed temperature dependence of the lattice parameter suggests that the Fe{sub 64}Ni{sub 36} MA-35 h sample subjected to the heating process exhibits invar behaviour. On heating up to 1100 K thermal relaxation of the microstructure occurs giving rise to grain growth above 100 nm, nearly vanishing values for the maximum strain, and the transformation of the bcc phase into the fcc one above 800 K, being the latter stable in subsequent heating-cooling processes.

  14. Effect of nanostructured composite powders on the structure and strength properties of the high-temperature inconel 718 alloy

    Science.gov (United States)

    Cherepanov, A. N.; Ovcharenko, V. E.

    2015-12-01

    The experimental results of the effect of powder nanomodifiers of refractory compounds on the strength properties, the macro- and microstructure of the high-temperature Inconel 718 alloy have been presented. It has been shown that the introduction of powder modifiers into the melt leads to a decrease in the average grain size by a factor of 1.5-2 in the alloy. The long-term tensile strength of the alloy at 650°C increases 1.5-2 times, and the number of cycles at 482°C before fracture grows by more than three times. The effect of nanoparticles on the grain structure and strength properties of the alloy is due to an increase in the number of generated crystallization centers and the formation of nanoparticle clusters of refractory compounds at boundaries and junctions in the formed grain structure, which hinder the development of recrystallization processes in the alloy.

  15. Development of Low Cost Gas Atomization of Precursor Powders for Simplified ODS Alloy Production

    Energy Technology Data Exchange (ETDEWEB)

    Anderson, Iver [Ames Lab., Ames, IA (United States)

    2014-08-05

    A novel gas atomization reaction synthesis (GARS) method was developed in this project to enable production (at our partner’s facility) a precursor Ni-Cr-Y-Ti powder with a surface oxide and an internal rare earth (RE) containing intermetallic compound (IMC) phase. Consolidation and heat-treatment experiments were performed at Ames Lab to promote the exchange of oxygen from the surface oxide to the RE intermetallic to form nano-metric oxide dispersoids. Alloy selection was aided by an internal oxidation and serial grinding experiments at Ames Lab and found that Hf-containing alloys may form more stable dispersoids than Ti-containing alloy, i.e., the Hf-containing system exhibited five different oxide phases and two different intermetallics compared to the two oxide phases and one intermetallic in the Ti-containing alloys. Since the simpler Ti-containing system was less complex to characterize, and make observations on the effects of processing parameters, the Ti-containing system was selected by Ames Lab for experimental atomization trials at our partner. An internal oxidation model was developed at Ames Lab and used to predict the heat treatment times necessary for dispersoid formation as a function of powder size and temperature. A new high-pressure gas atomization (HPGA) nozzle was developed at Ames Lab with the aim of promoting fine powder production at scales similar to that of the high gas-flow and melt-flow of industrial atomizers. The atomization nozzle was characterized using schlieren imaging and aspiration pressure testing at Ames Lab to determine the optimum melt delivery tip geometry and atomization pressure to promote enhanced secondary atomization mechanisms. Six atomization trials were performed at our partner to investigate the effects of: gas atomization pressure and reactive gas concentration on the particle size distribution (PSD) and the oxygen content of the resulting powder. Also, the effect on the rapidly solidified microstructure (as a

  16. Gas atomized precursor alloy powder for oxide dispersion strengthened ferritic stainless steel

    Energy Technology Data Exchange (ETDEWEB)

    Rieken, Joel [Iowa State Univ., Ames, IA (United States)

    2011-12-13

    Gas atomization reaction synthesis (GARS) was employed as a simplified method for producing precursor powders for oxide dispersion strengthened (ODS) ferritic stainless steels (e.g., Fe-Cr-Y-(Ti,Hf)-O), departing from the conventional mechanical alloying (MA) process. During GARS processing a reactive atomization gas (i.e., Ar-O2) was used to oxidize the powder surfaces during primary break-up and rapid solidification of the molten alloy. This resulted in envelopment of the powders by an ultra-thin (t < 150 nm) metastable Cr-enriched oxide layer that was used as a vehicle for solid-state transport of O into the consolidated microstructure. In an attempt to better understand the kinetics of this GARS reaction, theoretical cooling curves for the atomized droplets were calculated and used to establish an oxidation model for this process. Subsequent elevated temperature heat treatments, which were derived from Rhines pack measurements using an internal oxidation model, were used to promote thermodynamically driven O exchange reactions between trapped films of the initial Cr-enriched surface oxide and internal Y-enriched intermetallic precipitates. This novel microstructural evolution process resulted in the successful formation of nano-metric Y-enriched dispersoids, as confirmed using high energy X-ray diffraction and transmission electron microscopy (TEM), equivalent to conventional ODS alloys from MA powders. The thermal stability of these Y-enriched dispersoids was evaluated using high temperature (1200°C) annealing treatments ranging from 2.5 to 1,000 hrs of exposure. In a further departure from current ODS practice, replacing Ti with additions of Hf appeared to improve the Y-enriched dispersoid thermal stability by means of crystal structure modification. Additionally, the spatial distribution of the dispersoids was found to depend strongly on the original rapidly solidified microstructure. To exploit this, ODS microstructures were engineered from

  17. Influence of electronic structure on Compton scattering through comparing Cu-Ni alloys with Cu-Ni powder mixtures

    Institute of Scientific and Technical Information of China (English)

    Guang LUO; Xianquan HU; Guangyu XIAO; Chunyang KONG

    2012-01-01

    The application fields of Compton scattering have been further broadened through the studies of theories and experiments as well as the electronic structure of the scatters.The relationship between the contents of binary alloys (also binary powder mixtures) and the number of Compton scattered photons has been thoroughly examined.The linear expression of the relationship has been obtained approximately according to the Compton scattering theory.And the relationship has been validated well through the Compton scattering experiments with the scatters of Cu-Ni binary alloys or Cu-Ni binary powder mixtures.Furthermore,it is found that the slope of Cu-Ni powder mixture series is steeper than that of Cu-Ni alloy series,and through the pseudopotential plane wave theory of DFT the microscopic principles of Compton scattering of Cu-Ni alloy and Cu-Ni powder mixture series have been discussed and compared with each other.The results show that the electronic structure is the main reason for the difference of the linear slopes,and the line slope of Cu-Ni powder mixtures series is steeper than that of Cu-Ni alloy series.

  18. Structural evolution and magnetic properties of nanocrystalline 50 Permalloy powders prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Gheisari, Kh., E-mail: khgheisari@scu.ac.ir [Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University, Ahvaz (Iran, Islamic Republic of); Shahriari, Sh. [Department of Materials Science and Engineering, Islamic Azad University of Ahvaz, Ahvaz (Iran, Islamic Republic of); Javadpour, S. [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of)

    2013-10-15

    Highlights: •Nanocrystalline 50 Permalloy powders were prepared by mechanical alloying. •In addition to the nonuniform lattice strain, a uniform lattice strain was observed. •A good combination of M{sub s} (∼150 emu/g) and H{sub c} (∼0.13 Oe) was obtained after 60 h of milling. •Curie temperature was estimated to be ∼600 °C. -- Abstract: FeNi-based alloys commonly called Permalloys are interesting in their applications as soft magnetic materials with low coercivity and high permeability. In this study, nanocrystalline Fe–50 wt.% Ni alloy powders were prepared using a planetary ball mill at different milling times. The evolution of the microstructure and magnetic properties during the milling process were studied by the X-ray diffraction technique, the scanning electron microscope, the transmission electron microscope and the vibrating sample magnetometer. The results indicate that in the course of ball milling the Fe and Ni mixture, nanocrystalline FCC γ-(Fe, Ni) phase with the average crystallite size of 15 nm, particle size of 39 μm, nonuniform lattice strain of 0.45% and lattice parameter of 0.36062 nm formed after 24 h milling time. Although the crystallite size of the as-synthesized Permalloy powder is smaller than the magnetic exchange length, a low coercivity as expected from Herzer’s random anisotropy model is not observed. Among the different reasons, residual stress, γ-(Fe, Ni) phase formation and contamination are suggested as possible causes, which affect both coercivity and saturation magnetization.

  19. Advancements in Ti Alloy Powder Production by Close-Coupled Gas Atomization

    Energy Technology Data Exchange (ETDEWEB)

    Heidloff, Andy; Rieken, Joel; Anderson, Iver; Byrd, David

    2011-04-01

    As the technology for titanium metal injection molding (Ti-MIM) becomes more readily available, efficient Ti alloy fine powder production methods are required. An update on a novel close-coupled gas atomization system has been given. Unique features of the melting apparatus are shown to have measurable effects on the efficiency and ability to fully melt within the induction skull melting system (ISM). The means to initiate the melt flow were also found to be dependent on melt apparatus. Starting oxygen contents of atomization feedstock are suggested based on oxygen pick up during the atomization and MIM processes and compared to a new ASTM specification. Forming of titanium by metal injection molding (Ti-MIM) has been extensively studied with regards to binders, particle shape, and size distribution and suitable de-binding methods have been discovered. As a result, the visibility of Ti-MIM has steadily increased as reviews of technology, acceptability, and availability have been released. In addition, new ASTM specification ASTM F2885-11 for Ti-MIM for biomedical implants was released in early 2011. As the general acceptance of Ti-MIM as a viable fabrication route increases, demand for economical production of high quality Ti alloy powder for the preparation of Ti-MIM feedstock correspondingly increases. The production of spherical powders from the liquid state has required extensive pre-processing into different shapes thereby increasing costs. This has prompted examination of Ti-MIM with non-spherical particle shape. These particles are produced by the hydride/de-hydride process and are equi-axed but fragmented and angular which is less than ideal. Current prices for MIM quality titanium powder range from $40-$220/kg. While it is ideal for the MIM process to utilize spherical powders within the size range of 0.5-20 {mu}m, titanium's high affinity for oxygen to date has prohibited the use of this powder size range. In order to meet oxygen requirements the top

  20. Sintered Fe-Ni-Cu-Sn-C Alloys Made of Ball-Milled Powders

    Directory of Open Access Journals (Sweden)

    Romański A.

    2014-10-01

    Full Text Available The main objective of this paper was to perform sinterability studies of ball-milled Fe-12%Ni-6.4%Cu-1.6%Sn-0.6%C powders. A mixture of precisely weighed amounts of elemental iron, nickel and graphite, and pre-alloyed 80/20 bronze powders was ball-milled for 8, 30 and 120 hours. After cold-pressing at 400 MPa the specimens were sintered at 900oC for 30 minutes in a reducing atmosphere and subsequently tested for density and hardness as well as subjected to structural studies using scanning electron microscopy (SEM and X-ray diffraction (XRD analysis.

  1. CHARACTERISTICS OF FATIGUE SURFACE MICROCRACK GROWTH IN VICINAL INCLUSION FOR POWDER METALLURGY ALLOYS

    Institute of Scientific and Technical Information of China (English)

    WangXishu; LiYongqiang

    2003-01-01

    Inclusion flaw is one of the worst flaws of powder metallurgy. The inclusion flaw plays an important role in the failure of high temperature turbine materials in aircraft components and automotive parts, especially fatigue failure. In this paper, an experimental investigation of fatigue microcrack propagation in the vicinal inclusion were carried out by the servo-hydraulic fatigue test system with scanning electron microscope (SEM). It has been found from the SEM images that the fatigue surface microcrack occurs in the matrix and inclusion. According to the SEM images, the characteristics of fatigue crack initiation and growth in vicinal inclusion for powder metallurgy alloys are analyzed in detail. The effect of the geometrical shape and material type of surface inclusions on the cracking is also discussed with the finite element method (FEM).

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

    Science.gov (United States)

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

    2001-02-01

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

  3. Martensitic transformation of Ti50Ni30Cu20 alloy prepared by powder metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Valeanu, M., E-mail: valeanu@infim.ro [National Institute of Materials Physics, 077125 Bucharest (Romania); Lucaci, M. [National Institute for Electrical Engineering ICPE-CA, 030138 Bucharest (Romania); Crisan, A.D.; Sofronie, M. [National Institute of Materials Physics, 077125 Bucharest (Romania); Leonat, L. [National Institute for Electrical Engineering ICPE-CA, 030138 Bucharest (Romania); Kuncser, V. [National Institute of Materials Physics, 077125 Bucharest (Romania)

    2011-03-31

    Research highlights: > Martensitic transformation sequence in Ti50Ni30Cu20 prepared high - energy milling. > Two transformations (B2-B19, B2-B19') are evidenced after 10 hours of milling. > B2-B19 transformation is not more observed after 20 hours of milling. > A longer milling process promotes the formation of the secondary Ti{sub 2}(NiCu) phase. - Abstract: Phase transformation behavior of Ti50Ni30Cu20 shape memory alloys prepared by powder metallurgy is analyzed with respect to the duration of mechanical alloying. The processed blends were studied by differential scanning calorimetry and room temperature X-ray diffraction. The martensitic transformations evidenced by thermal scans are discussed in correlation with the relative phase content obtained from the refinement of the X-ray diffraction patterns.

  4. Structural evolution of Ni-20Cr alloy during ball milling of elemental powders

    Energy Technology Data Exchange (ETDEWEB)

    Lopez B, I.; Trapaga M, L. G. [IPN, Centro de Investigacion y de Estudios Avanzados, Unidad Queretaro, Libramiento Norponiente No. 2000, Juriquilla, 76230 Queretaro (Mexico); Martinez F, E. [Centro de Investigacion e Innovacion Tecnologica, Cerrada de Cecati s/n, Col. Santa Catarina Azcapotzalco, 02250 Mexico D. F. (Mexico); Zoz, H., E-mail: israelbaez@gmail.co [Zoz GmbH, D-57482, Wenden (Germany)

    2011-07-01

    The ball milling (B M) of blended Ni and Cr elemental powders was carried out in a Simoloyer performing on high-energy scale mode at maximum production to obtain a nano structured Ni-20Cr alloy. The phase transformations and structural changes occurring during mechanical alloying were investigated by X-ray diffraction (XRD) and optical microscopy (Om). A gradual solid solubility of Cr and the subsequent formation of crystalline metastable solid solutions described in terms of the Avrami-Ero fe ev kinetics model were calculated. The XRD analysis of the structure indicates that cumulative lattice strain contributes to the driving force for solid solution between Ni and Cr during B M. Microstructure evolution has shown, additionally to the lamellar length refinement commonly observed, the folding of lamellae in the final processing stage. Om observations revealed that the lamellar spacing of Ni rich zones reaches a steady value near 500 nm and almost disappears after 30 h of milling. (Author)

  5. Laser cladding of Al + Ir powders on ZM5 magnesium base alloy

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Laser cladding of preplaced Al + Ir powders on a ZM5 magnesium alloy was performed to enhance the corrosion resistance of the ZM5 magnesium alloy. A metallurgical bond was obtained at the coating/substrate interface. The corrosion potential (Ecorr) of the laser cladded sample was 169 mV positive to that of the untreated ZM5 substrate, while the corrosion current (Icorr) was some one order of magnitude lower. The laser cladded sample, unlike the untreated ZM5 substrate,showed a passive region in the polarization plot. Immersion tests confirmed that the corrosion resistance of the laser cladded ZM5 sample was significantly enhanced in 3.5 wt.% NaCl solution. The Al-rich phases of AlIr, Mg17Al12, and Al formed in the cladding layer and the rapid solid characteristics were contributed to the improved corrosion behavior of the coating.

  6. The properties of high-energy milled pre-alloyed copper powders containing 1 wt. % Al

    Directory of Open Access Journals (Sweden)

    VISESLAVA RAJKOVIC

    2007-01-01

    Full Text Available The microstructural and morphological changes of inert gas atomized pre-alloyed Cu-1 wt. % Al powders subjected to hith-energy milling were studied. The microhardness of hot-pressed compacts was measured as a function of milling time. The thermal stability during exposure at 800 °C and the electrical conductivity of compacts were also examined. During the high-energy milling, severe deformation led to refinement of the powder particle grain size (from 550 nm to about 55 nm and a decrease in the lattice parameter (0.10 %, indicating precipitation of aluminium from the copper matrix. The microhardness of compacts obtained from 5 h-milled powders was 2160 MPa. After exposure at 800 °C for 5 h, these compacts still exhibited a high microhardness value (1325 MPa, indicating good thermal stability. The increase of microhardness and good thermal stability is attributed to the small grain size (270 and 390 nm before and after high temperature exposure, respectively. The room temperature electrical conductivity of compacts processed from 5 h-milled powder was 79 % IACS.

  7. Morphology and microstructure of annealed Ni-Co alloy powders electrodeposited on copper substrates

    Directory of Open Access Journals (Sweden)

    Rafailović L.D.

    2009-01-01

    Full Text Available Nickel and cobalt alloy powders from two different electrolyte compositions were obtained by electrodeposition from an ammonium sulfate solution. The structure of Ni-Co deposits formed by electrodeposition at a galvanostatic regime and the influence of current density and the bath composition were studied by SEM, DSC and X-ray diffraction methods. It was shown that the microstructure and morphology of the powders depended on the deposition current density as well as bath composition. Both, bath composition and current density affect strongly the deposit growth mechanism and the deposit composition, microstructure, grain size and surface morphology. It was found that the overpotential significantly affects the structure of the formed deposits. When electrodeposition was performed far from equilibrium conditions face-centered cubic (FCC cobalt was deposited while at low overpotential hexagonal close packed (HCP Co was formed with a lower rate of hydrogen evolution. The increase of HCP phase in the nanocrystalline deposits was caused by increase of the Co content in the powder as well by decrease of the deposition current density. It was shown that the powders change their structure in the temperature interval from 300°C to 600°C. In Co rich samples, structural changes during heating were attributed to the phase transformation of HCP to FCC.

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

    Science.gov (United States)

    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%.

  9. Effect of Graphite Content and Granularity on Mechanical and Tribological Properties of Bronze Alloyed Powder Composite

    Institute of Scientific and Technical Information of China (English)

    DENG Chen-hong; CHEN Guang-zhi; GE Qi-lu

    2005-01-01

    The bronze alloyed powder composite containing nanoparticles was developed by hot pressing. The effects of the content and granularity of graphite on hardness, machinability, bending strength, compression strength, and friction and wear behavior of the composites were studied. The microstructures of the specimens were analyzed by SEM. The results showed that the graphites are distributed in net when nanographites are added, resulting in the decrease of mechanical properties and abrasive resistance. When the content of nanographite is 10%, the composite is brittle. The graphite is distributed in the form of block when micrographite is added, improving the mechanical properties and abrasive resistance. Wear track was studied by SEM.

  10. Mechanical Properties and Friction/Wear Behavior of Copper Alloyed Powder Composites

    Institute of Scientific and Technical Information of China (English)

    DENG Chen-hong; CHEN Guang-zhi; GE Qi-lu

    2005-01-01

    Copper alloyed powder composites containing nanoparticles were developed by hot pressing. Effects of nanoscale activated sintering aid and fine ceramic particles Al2O3 on hardness, working quality, and behaviors of friction and wear of the composites have been studied, compared with the composites including microscale activated sintering aid and microscale ceramic particles. The microstructures of the samples were analyzed by SEM. The results show that the materials with nanoscale sintering aid and fine ceramic particles have better mechanical properties and abrasive resistance than the materials with microscale activated sintering aid and microceramic particles. Moreover, element mutual transfer occurs between samples (strip) and abrasive wheel (ring).

  11. Accelerated Near-Threshold Fatigue Crack Growth Behavior of an Aluminum Powder Metallurgy Alloy

    Science.gov (United States)

    Piascik, Robert S.; Newman, John A.

    2002-01-01

    Fatigue crack growth (FCG) research conducted in the near threshold regime has identified a room temperature creep crack growth damage mechanism for a fine grain powder metallurgy (PM) aluminum alloy (8009). At very low DK, an abrupt acceleration in room temperature FCG rate occurs at high stress ratio (R = Kmin/Kmax). The near threshold accelerated FCG rates are exacerbated by increased levels of Kmax (Kmax less than 0.4 KIC). Detailed fractographic analysis correlates accelerated FCG with the formation of crack-tip process zone micro-void damage. Experimental results show that the near threshold and Kmax influenced accelerated crack growth is time and temperature dependent.

  12. Sinter-hardening of Ni-Mo pre-alloyed powders with tungsten addition

    Directory of Open Access Journals (Sweden)

    L.A. Dobrzański

    2007-01-01

    Full Text Available Purpose: Purpose of this paper was to present the benefits of powder metallurgy technology and development ofsinter-hardening process. The mechanical properties, focusing in particular on hardness and wear resistance, oftwo different carbon levels pre-alloyed steel powders processed with sinter-hardening method, were described.Microstructure characteristic of produced sinter-hardened Ni-Mo steels with increasing amount of tungsten(from 0 to 0.3% wt. was taken under consideration.Design/methodology/approach: Different compositions have been tested in order to investigate the influenceof various tungsten additions into low (0.4% and high (0.6% carbon content of pre-alloyed steel powders.Powders, with addition of 0.7% lubricant, were pressed in a 2000kN hydraulic press. De-waxing process at550ºC for 60 minutes in a fully nitrogen atmosphere was performed before the sintering. Sintering was carriedout in vacuum furnace with argon backfilling. The furnace was equipped with a cooling zone to provideaccelerated cooling from the sintering temperature. Green compacts were sintered at the temperature 1120ºC for1 hour and rapidly cooled with a rate 2.5ºC/s.Findings: The applied sinter-hardening process resulted with achievement of material characterized by goodwear resistance. The investigation of Ni-Mo and Ni-Mo-W sinter-hardened steels with low and high carboncontent proved that applied process of sintering under vacuum and rapid cooling brought expected outcome.Research limitations/implications: Considering the achieved outcome, it was revealed that chemical compositionand applied process of steels preparation, sinter-hardening with the cooling rate 2.5ºC/s, results in achieving materialswith relatively high hardness and significant resistance to abrasion. Anyhow, further research should be performed.Originality/value: Sinter-hardening of Ni-Mo pre-alloyed powders with the addition of different additions oftungsten, especially in terms of

  13. Effect of electrodeposition current density on the microstructure and magnetic properties of nickel-cobalt-molybdenum alloy powders

    Directory of Open Access Journals (Sweden)

    Pešić O.

    2014-01-01

    Full Text Available Nanostructured nickel-cobalt-molybdenum alloy powders were electrodeposited from an ammonium sulfate bath. The powders mostly consist of an amorphous phase and a very small amount of nanocrystals with an mean size of less than 3 nm. An increase in deposition current density increases the amorphous phase percentage, the density of chaotically distributed dislocations and internal microstrains in the powders, while decreasing the mean nanocrystal size. The temperature range over which the structural relaxation of the powders deposited at higher current densities occurs is shifted towards lower temperatures. A change in relative magnetic permeability during structural relaxation is higher in powders deposited at higher current densities. Powder crystallization takes place at temperatures above 700ºC. The formation of the stable crystal structure causes a decrease in relative magnetic permeability. [Projekat Ministarstva nauke Republike Srbije, br. 172057

  14. Powder Metallurgy of Uranium Alloy Fuels for TRU-Burning Reactors Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    McDeavitt, Sean M

    2011-04-29

    Overview Fast reactors were evaluated to enable the transmutation of transuranic isotopes generated by nuclear energy systems. The motivation for this was that TRU isotopes have high radiotoxicity and relatively long half-lives, making them unattractive for disposal in a long-term geologic repository. Fast reactors provide an efficient means to utilize the energy content of the TRUs while destroying them. An enabling technology that requires research and development is the fabrication metallic fuel containing TRU isotopes using powder metallurgy methods. This project focused upon developing a powder metallurgical fabrication method to produce U-Zr-transuranic (TRU) alloys at relatively low processing temperatures (500ºC to 600ºC) using either hot extrusion or alpha-phase sintering for charecterization. Researchers quantified the fundamental aspects of both processing methods using surrogate metals to simulate the TRU elements. The process produced novel solutions to some of the issues relating to metallic fuels, such as fuel-cladding chemical interactions, fuel swelling, volatility losses during casting, and casting mold material losses. Workscope There were two primary tasks associated with this project: 1. Hot working fabrication using mechanical alloying and extrusion • Design, fabricate, and assemble extrusion equipment • Extrusion database on DU metal • Extrusion database on U-10Zr alloys • Extrusion database on U-20xx-10Zr alloys • Evaluation and testing of tube sheath metals 2. Low-temperature sintering of U alloys • Design, fabricate, and assemble equipment • Sintering database on DU metal • Sintering database on U-10Zr alloys • Liquid assisted phase sintering on U-20xx-10Zr alloys Appendices Outline Appendix A contains a Fuel Cycle Research & Development (FCR&D) poster and contact presentation where TAMU made primary contributions. Appendix B contains MSNE theses and final defense presentations by David Garnetti and Grant Helmreich

  15. Powder Metallurgy of Uranium Alloy Fuels for TRU-Burning Reactors Final Technical Report

    Energy Technology Data Exchange (ETDEWEB)

    McDeavitt, Sean M

    2011-04-29

    Overview Fast reactors were evaluated to enable the transmutation of transuranic isotopes generated by nuclear energy systems. The motivation for this was that TRU isotopes have high radiotoxicity and relatively long half-lives, making them unattractive for disposal in a long-term geologic repository. Fast reactors provide an efficient means to utilize the energy content of the TRUs while destroying them. An enabling technology that requires research and development is the fabrication metallic fuel containing TRU isotopes using powder metallurgy methods. This project focused upon developing a powder metallurgical fabrication method to produce U-Zr-transuranic (TRU) alloys at relatively low processing temperatures (500ºC to 600ºC) using either hot extrusion or alpha-phase sintering for charecterization. Researchers quantified the fundamental aspects of both processing methods using surrogate metals to simulate the TRU elements. The process produced novel solutions to some of the issues relating to metallic fuels, such as fuel-cladding chemical interactions, fuel swelling, volatility losses during casting, and casting mold material losses. Workscope There were two primary tasks associated with this project: 1. Hot working fabrication using mechanical alloying and extrusion • Design, fabricate, and assemble extrusion equipment • Extrusion database on DU metal • Extrusion database on U-10Zr alloys • Extrusion database on U-20xx-10Zr alloys • Evaluation and testing of tube sheath metals 2. Low-temperature sintering of U alloys • Design, fabricate, and assemble equipment • Sintering database on DU metal • Sintering database on U-10Zr alloys • Liquid assisted phase sintering on U-20xx-10Zr alloys Appendices Outline Appendix A contains a Fuel Cycle Research & Development (FCR&D) poster and contact presentation where TAMU made primary contributions. Appendix B contains MSNE theses and final defense presentations by David Garnetti and Grant Helmreich

  16. Hyperfine interaction in Co{sub 2}SiO{sub 4} investigated by high resolution neutron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Chatterji, Tapan, E-mail: chatterji@ill.f [JCNS, Forschungszentrum Juelich Outstation at Institut Laue-Langevin, B.P. 156, 38042 Grenoble Cedex 9 (France); Wuttke, J. [JCNS, Forschungszentrum Juelich Outstation at FRMII, Lichtenbergstrasse 1, 85747 Garching (Germany); Sazonov, A.P. [FRMII, Technische Universitaet Muenchen, Lichtenbergstrasse 1, 85747 Garching (Germany)

    2010-10-15

    We have investigated the hyperfine interaction in Co{sub 2}SiO{sub 4} by inelastic neutron scattering with a high resolution back-scattering neutron spectrometer. The energy spectrum measured from a Co{sub 2}SiO{sub 4} powder sample revealed inelastic peaks at E=1.387{+-}0.006{mu}eV at T=3.5 K on both energy gain and energy loss sides. The inelastic peaks move gradually towards lower energy with increasing temperature and finally merge with the elastic peak at the electronic magnetic ordering temperature T{sub N{approx}}50K. The inelastic peaks have been interpreted to be due to the transition between hyperfine-split nuclear level of the {sup 59}Co isotopes with spin I=7/2 . The temperature dependence of the energy of the inelastic peak in Co{sub 2}SiO{sub 4} showed that this energy can be considered to be the order parameter of the antiferromagnetic phase transition. The determined hyperfine splitting in Co{sub 2}SiO{sub 4} deviates from the linear relationship between the ordered electronic magnetic moment and the hyperfine splitting in Co, Co-P amorphous alloys and CoO presumably due to the presence of unquenched orbital moment. These results are very similar to those of CoF{sub 2} recently reported by Chatterji and Schneider.

  17. The effect of heat treatment on the structure and magnetic properties of mechanically alloyed Fe-45%Ni nanostructured powders

    Energy Technology Data Exchange (ETDEWEB)

    Gheisari, Kh., E-mail: khgheisari@scu.ac.ir [Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University, Ahvaz (Iran, Islamic Republic of); Oh, J.T. [School of Materials Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Javadpour, S. [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz 7134851154 (Iran, Islamic Republic of)

    2011-01-21

    Research highlights: > In this study, nanocrystalline Fe-45%Ni alloy powders were prepared by mechanical alloying process using a planetary high-energy ball mill under argon atmosphere. The synthesized powders were heat treated at different temperatures using a vacuum furnace. The results showed that lattice strain decreases and crystallite size increases with annealing temperature. We also found that the variation of coercivity is dominated by the removal of residual stress at low annealing temperature whereas the value of coercivity depends on the crystallite size at higher annealing temperature. - Abstract: Magnetic iron-nickel alloys generally called permalloys are of great interest due to their magnetic properties. Fe-45%Ni alloy is one of the major iron-nickel compositions, well-known for high flux density, low coercivity and their responsiveness to the magnetic annealing. In this study, nanocrystalline Fe-45%Ni alloy powders were prepared by mechanical alloying process using a planetary high-energy ball mill under an argon atmosphere. The synthesized powders were heat treated at different temperatures using a vacuum furnace. The structural properties of the as-milled and the post-heat treated powders were studied by means of X-ray diffraction (XRD) technique and transmission electron microscopy (TEM). The magnetic measurements on the powders were carried out using a vibrating sample magnetometer (VSM). The results showed that the lattice strain decreases and the crystallite size increases with annealing temperature. It was also found that the variation of coercivity is dominated by the removal of residual stress at low annealing temperatures, whereas the value of coercivity depends on the crystallite size at higher annealing temperatures.

  18. Effect of reduced cobalt contents on hot isostatically pressed powder metallurgy U-700 alloys

    Science.gov (United States)

    Harf, F. H.

    1982-01-01

    The effect of reducing the cobalt content of prealloyed powders of UDIMET 700 (U-700) alloys to 12.7, 8.6, 4.3, and 0% was examined. The powders were hot isostatically pressed into billets, which were given heat treatments appropriate for turbine disks, namely partial solutioning at temperatures below the gamma prime solvus and four step aging treatments. Chemical analyses, metallographic examinations, and X-ray diffraction measurements were performed on the materials. Minor effects on gamma prime content and on room temperature and 650 C tensile properties were observed. Creep rupture lives at 650 C reached a maximum at the 8.4% concentration, while at 760 C a maximum in life was reached at the 4.3% cobalt level. Minimum creep rates increased with decreasing cobalt content at both test temperatures. Extended exposures at 760 and 815 C resulted in decreased tensile strengths and rupture lives for all alloys. Evidence of sigma phase formation was also found.

  19. Phase transformations of mechanically alloyed Fe-Cr-P-C powders

    Energy Technology Data Exchange (ETDEWEB)

    Bensebaa, N. [Laboratoire de Magnetisme et de Spectroscopie des Solides, Departement de Physique, Faculte des Sciences, Universite de Annaba, B.P. 12, 23000 Annaba, Algerie (Algeria); Alleg, S. [Laboratoire de Magnetisme et de Spectroscopie des Solides, Departement de Physique, Faculte des Sciences, Universite de Annaba, B.P. 12, 23000 Annaba, Algerie (Algeria); Greneche, J.M. [Laboratoire de Physique de l' Etat Condense - UMR 6087, Universite du Maine, Faculte des Sciences 72085, Le Mans Cedex 9 (France)]. E-mail: greneche@univ-lemans.fr

    2005-05-03

    Fe{sub 77}Cr{sub 4}P{sub 8}C{sub 11} alloy was prepared by mechanical alloying (MA) of elemental Fe, Cr, P and C (graphite) powders in a planetary ball mill type Fritsch P7 under argon atmosphere. Morphological changes, microstructural and structural evolutions during ball milling were followed by scanning electron microscopy (SEM), X-ray diffraction (XRD) and {sup 57}Fe Moessbauer spectrometry (MS) as a function of the milling time. The crystallite size refinement against the milling time is accompanied by an increase of the atomic level strain. After 6 h of milling, the dissolution of phosphorous into the {alpha}-Fe matrix is evidenced by the formation of a small amount ({approx}4%) of the paramagnetic Fe{sub 2}P phase as revealed by Moessbauer spectrometry. The complete mixing of all the elemental powders at the atomic level is achieved at 12 h of milling and results, after 24 h, in an amorphous matrix where nanocrystalline phosphides and carbides with nearly equal crystallite sizes are embedded. Further milling time up to 190 h gives rise to the formation of both the orthorhombic and the hexagonal (FeCr){sub 7}C{sub 3} carbide as well as the superparamagnetic {epsilon}'-Fe{sub 2.2}C carbide through the recrystallisation of the amorphous phase.

  20. Electrical conductivity and microstructure by Rietveld refinement of doped Cu-Ni powder alloys

    Energy Technology Data Exchange (ETDEWEB)

    Fambrini, A.S.; Monteiro, W.A.; Orrego, R.M.M.; Marques, I.M.; Carrio, Juan A.G., E-mail: jgcarrio@mackenzie.br, E-mail: iara_m_@hotmail.com [Universidade Presbiteriana Mackenzie (UPM/CCH), Sao Paulo, SP (Brazil). Centro de Ciencias e Humanidades. Dept. de Fisica

    2009-07-01

    This work presents a comparative study of microstructural and electrical properties of polycrystalline material from two different Cu-Ni alloys: Cu-Ni-Pt and Cu-Ni-Al. The first one of them was produced in electric furnace with voltaic arc and the other was produced by powder metallurgy. The microstructure of the samples was studied by optical microscopy, Vickers micro hardness and x rays powder diffraction. Their electrical conductivity was measured with a milliohmmeter Agilent (HP) 4338B. Refinements of the crystalline structure of the samples were performed by the Rietveld method, using the refinement program GSAS. The refinement results and Fourier differences calculations indicate that the copper matrix structure presents not significant distortions by the used amounts of the other metal atoms. In both cases a sequence of thermo mechanical treatments was developed with the intention of increasing the hardness maintaining the electrical conductivity of the alloys. The refinements also allowed a study of the dependence of the micro-structure and the thermo mechanical treatments of the samples. (author)

  1. Characterization of U-2 wt% Mo and U-10 wt% Mo alloy powders prepared by centrifugal atomization

    Science.gov (United States)

    Kim, Ki Hwan; Lee, Don Bac; Kim, Chang Kyu; Hofman, Gerard E.; Paik, Kyung Wook

    1997-06-01

    The characteristics of high density UMo alloy powder solidified rapidly by the centrifugal atomization process have been examined. The results indicate that most of the atomized UMo alloy particles have a smooth surface and near-perfect spherical shape. The atomized powder, irrespective of particle size, is found to be single phase γ-U alloy with isotropic structure and non-dendritic grain. The continuous cooling DSC trace of U-2 wt% Mo alloy shows a small, broad endothermic peak originated from the formation of α-U phase and U 2Mo phase, whereas that of U-10 wt% Mo alloy shows no peak over all temperature ranges associated with the decomposition of γ-U phase. The γ-U phase of U-2 wt% Mo powder is decomposed as the α-U phase and the U 2Mo phase after an annealing treatment at 400°C for 100 h. But the γ-U phase of atomized U-10 wt% Mo powder remains as it was.

  2. Alloy

    Science.gov (United States)

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

    2014-07-01

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

  3. Stress relaxation study of water atomized Cu-Cr-Zr powder alloys consolidated by inverse warm extrusion

    Energy Technology Data Exchange (ETDEWEB)

    Poblano-Salas, C.A., E-mail: carlos.poblano@ciateq.m [CIATEQ A.C., Centro de Tecnologia Avanzada, Av. Manantiales 23 A, Parque Industrial Bernardo Quintana, El Marques, Queretaro, C.P. 76246 (Mexico); Barceinas-Sanchez, J.D.O., E-mail: obarceinas@ipn.m [CICATA-IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Cerro Blanco 141, Colinas del Cimatario, Santiago de Queretaro, Queretaro, C.P. 76090 (Mexico)

    2009-10-19

    Stress relaxation testing in compression at high temperature was performed on Cu-Cr-Zr alloys produced by consolidation of water atomized powders. Precipitation and recrystallization were monitored during stress relaxation experiments carried out at an ageing temperature of 723 K. Pre-straining imposed to the Cu-Cr-Zr samples prior to stress relaxation testing resulted in reduced hardness compared to that reported for conventionally-aged alloys; it also resulted in shorter times for achieving maximum strengthening on ageing.

  4. Assessment of Low Cycle Fatigue Behavior of Powder Metallurgy Alloy U720

    Science.gov (United States)

    Gabb, Tomothy P.; Bonacuse, Peter J.; Ghosn, Louis J.; Sweeney, Joseph W.; Chatterjee, Amit; Green, Kenneth A.

    2000-01-01

    The fatigue lives of modem powder metallurgy disk alloys are influenced by variabilities in alloy microstructure and mechanical properties. These properties can vary as functions of variables the different steps of materials/component processing: powder atomization, consolidation, extrusion, forging, heat treating, and machining. It is important to understand the relationship between the statistical variations in life and these variables, as well as the change in life distribution due to changes in fatigue loading conditions. The objective of this study was to investigate these relationships in a nickel-base disk superalloy, U720, produced using powder metallurgy processing. Multiple strain-controlled fatigue tests were performed at 538 C (1000 F) at limited sets of test conditions. Analyses were performed to: (1) assess variations of microstructure, mechanical properties, and LCF failure initiation sites as functions of disk processing and loading conditions; and (2) compare mean and minimum fatigue life predictions using different approaches for modeling the data from assorted test conditions. Significant variations in life were observed as functions of the disk processing variables evaluated. However, the lives of all specimens could still be combined and modeled together. The failure initiation sites for tests performed at a strain ratio R(sub epsilon) = epsilon(sub min)/epsilon(sub max) of 0 were different from those in tests at a strain ratio of -1. An approach could still be applied to account for the differences in mean and maximum stresses and strains. This allowed the data in tests of various conditions to be combined for more robust statistical estimates of mean and minimum lives.

  5. Toughness enhancement of powder metallurgy zirconium containing aluminum-lithium alloys through degassing

    Energy Technology Data Exchange (ETDEWEB)

    LaSalle, J.C.; Raybould, D.; Das, S.K.; Limoncelli, E.V.

    1993-07-06

    In a method for producing a consolidated article from a rapidly solidified, zirconium containing aluminum lithium alloy powder, the improvement is described comprising the step of: degassing said powder in a vacuum at a temperature of at least about 450 C, said powder consisting essentially of the formula Al[sub bal]Li[sub a]Cu[sub b]Mg[sub c]Zr[sub d], where a' ranges from about 2.4 to 2.8 wt%, b' ranges from about 0.5 to 2.0 wt%, c' ranges from 0.2 to 2.0 wt% and d' ranges from greater than about 0.8 to 1.0 wt%, the balance being aluminum and said article having an ultimate tensile strength ranging from 75 to 80 ksi, a tensile elongation ranging from about 5 to 8% and a T-L notched impact toughness ranging from about 100 to 150 in-lb/in[sup 2].

  6. Manufacturing of self-passivating tungsten based alloys by different powder metallurgical routes

    Science.gov (United States)

    Calvo, A.; Ordás, N.; Iturriza, I.; Pastor, J. Y.; Tejado, E.; Palacios, T.; García-Rosales, C.

    2016-02-01

    Self-passivating tungsten based alloys will provide a major safety advantage compared to pure tungsten when used as first wall armor of future fusion reactors, due to the formation of a protective oxide layer which prevents the formation of volatile and radioactive WO3 in case of a loss of coolant accident with simultaneous air ingress. Bulk WCr10Ti2 alloys were manufactured by two different powder metallurgical routes: (1) mechanical alloying (MA) followed by hot isostatic pressing (HIP) of metallic capsules, and (2) MA, compaction, pressureless sintering in H2 and subsequent HIPing without encapsulation. Both routes resulted in fully dense materials with homogeneous microstructure and grain sizes of 300 nm and 1 μm, respectively. The content of impurities remained unchanged after HIP, but it increased after sintering due to binder residue. It was not possible to produce large samples by route (2) due to difficulties in the uniaxial compaction stage. Flexural strength and fracture toughness measured on samples produced by route (1) revealed a ductile-to-brittle-transition temperature (DBTT) of about 950 °C. The strength increased from room temperature to 800 °C, decreasing significantly in the plastic region. An increase of fracture toughness is observed around the DBTT.

  7. Preparation of Mg55Ni35Si10 Amorphous Powders by Mechanical Alloying and Consolidation by Vacuum Hot Pressing

    Institute of Scientific and Technical Information of China (English)

    YANG Deng-Ke; WEN Cui-E; HAN Fu-Sheng; WANG Qing-Zhou; LI Hai-Jin

    2006-01-01

    @@ Amorphous Mg55Ni35Si10 powders are fabricated by using a mechanical alloying technique. The amorphous powders are found to exhibit a relatively high crystallization temperature of 380℃. The as-milled amorphous Mg55Ni35Si10 powders are consolidated successfully into bulk body by vacuum hot pressing technique. Limited nanocrystallization is noticed. The Vickers microhardness range of the Mg55Ni35Si10 bulk sample is 7834 to 8048 Mpa. Its bending strength and compressive strength are 529 Mpa and 1466 Mpa, respectively.

  8. Formation of Structure in Hard-Alloy Coatings from Powders Under Passage of a Powerful Pulse of Electric Current

    Science.gov (United States)

    Novikov, S. V.; Peretyagin, P. Yu.; Dolzhikova, E. Yu.; Torrecillas, R.

    2016-01-01

    A method of ultrafast deposition of hard-alloy coatings from powders upon passage of a powerful pulse of electric current is considered. The structure of the coatings obtained by the electric-pulse and standard processes is studied by metallographic, electron microscope and x-ray diffraction analyses. The physical, mechanical and cutting properties of the hard-alloy coatings are determined. The endurance of the cutting tools with hard-alloy coatings is estimated under the conditions of large-scale and pilot productions. The possibility of creation of tools with enhanced operating characteristics is demonstrated.

  9. The influence of structural changes on electrical and magnetic characteristics of amorphous powder of the nixmoy alloy

    Directory of Open Access Journals (Sweden)

    Ribić-Zelenović Lenka

    2006-01-01

    Full Text Available Nickel and molybdenum alloy powder was electrodeposited on a titanium cathode from a NiSO4⋅7H2O and (NH46 Mo7O24⋅4H2O ammonium solution. The desired chemical composition, structure, size and shape of particles in the powder samples were achieved by an appropriate choice of electrolysis parameters (current density, composition and temperature of the solution, cathode material and electrolysis duration. Metal coatings form in the current density range 15 mA cm-2powders form. The chemical composition of powder samples depends on the current density of electrodeposition. The molybdenum content in the powder increases with the increase of current density (in the low current density range, while in the higher current density range the molybdenum content in the alloy decreases with the increase of the current density of deposition. Smaller sized particles form at higher current density. X-ray analysis, differential scanning calorimetric and measurements of the temperature dependence of electric resistance and magnetic permeability of the powder samples were all used to establish a predominantly amorphous structure of the powder samples formed at the current density of j≥70mA cm-2. The crystalline particle content in the powder samples increases with the decrease of the current density of deposition. Powder heating causes structural changes. The process of thermal stabilization of nickel and molybdenum amorphous powders takes place in the temperature interval from 463K to 573K and causes a decrease in electrical resistance and increase in magnetic permeability. The crystallization temperature depends on the value of current density of powder electrodeposition. Powder formed at j=180 mA cm-2 begins to crystallize at 573K, while the powder deposited at j=50 mA cm-2 begins to crystallize at 673K. Crystallization of the powder causes a decrease in electric resistivity and magnetic

  10. Near-Net Shape Fabrication Using Low-Cost Titanium Alloy Powders

    Energy Technology Data Exchange (ETDEWEB)

    Dr. David M. Bowden; Dr. William H. Peter

    2012-03-31

    The use of titanium in commercial aircraft production has risen steadily over the last half century. The aerospace industry currently accounts for 58% of the domestic titanium market. The Kroll process, which has been used for over 50 years to produce titanium metal from its mineral form, consumes large quantities of energy. And, methods used to convert the titanium sponge output of the Kroll process into useful mill products also require significant energy resources. These traditional approaches result in product forms that are very expensive, have long lead times of up to a year or more, and require costly operations to fabricate finished parts. Given the increasing role of titanium in commercial aircraft, new titanium technologies are needed to create a more sustainable manufacturing strategy that consumes less energy, requires less material, and significantly reduces material and fabrication costs. A number of emerging processes are under development which could lead to a breakthrough in extraction technology. Several of these processes produce titanium alloy powder as a product. The availability of low-cost titanium powders may in turn enable a more efficient approach to the manufacture of titanium components using powder metallurgical processing. The objective of this project was to define energy-efficient strategies for manufacturing large-scale titanium structures using these low-cost powders as the starting material. Strategies include approaches to powder consolidation to achieve fully dense mill products, and joining technologies such as friction and laser welding to combine those mill products into near net shape (NNS) preforms for machining. The near net shape approach reduces material and machining requirements providing for improved affordability of titanium structures. Energy and cost modeling was used to define those approaches that offer the largest energy savings together with the economic benefits needed to drive implementation. Technical

  11. Hydrogen Generation from Ammonia Borane and Water Through the Combustion Reactions with Mechanically Alloyed Al/Mg Powder

    Science.gov (United States)

    2014-08-11

    synthesis of ammonia -A ‘‘never ending story? " Angewandte...34 # && , (/ -%(/ &$’$) ) ! -( ( !( &" # ( %’ !&% # ’)( (% (" %’% (" ( & *%" # ’)( *! % + 3 HYDROGEN GENERATION FROM AMMONIA BORANE AND WATER THROUGH THE...FROM AMMONIA BORANE AND WATER THROUGH THE COMBUSTION REACTIONS WITH MECHANICALLY ALLOYED AL/MG POWDER by DANIEL RODRIGUEZ THESIS Presented to

  12. Study on the formation of cubic texture in Ni-7 at.% W alloy substrates by powder metallurgy routes

    DEFF Research Database (Denmark)

    Zhao, Yue; Suo, HongLi; Zhu, YongHua;

    2009-01-01

    One of the main challenges for coated conductor applications is to produce sharp cubic textured alloy substrates with high strength and low magnetism. In this work, the cubic textured Ni–7 at.% W substrates were prepared from different powder metallurgy ingots by rolling-assisted biaxially textur...

  13. Effect of carbon on the mechanical properties of powder-processed Fe–0·45 wt% P alloys

    Indian Academy of Sciences (India)

    Shefali Trivedi; Yashwant Mehta; K Chandra; P S Mishra

    2010-08-01

    The present paper records the results of mechanical tests on iron–phosphorus powder alloys which were made using a hot powder forging technique. In this process mild steel encapsulated powders were hot forged into slabs. Then the slabs were hot rolled and annealed to relieve the residual stresses. These alloys were characterized in terms of microstructure, porosity content/densification, hardness and tensile properties. Densification as high as 98·9% of theoretical density; has been realized. Microstructures of these alloys consist of single-phase ferrite only. Alloys containing 0·45 wt% P; such as Fe–0·45P–2Cu–2Ni–1Si–0·5Mo and Fe–0·45P–2Cu–2Ni–1Si–0·5Mo–0·15C show very high strength. Alloys developed in the present investigation were capable of being hot enough to be worked to very thin sheets and fine wires.

  14. Neutron diffraction analyses of U-(6-10 wt.%)Mo alloy powders fabricated by centrifugal atomization

    Energy Technology Data Exchange (ETDEWEB)

    Park, Jong Man [Advanced Fuel Technology Development Division, Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Ryu, Ho Jin, E-mail: hjryu@kaeri.re.k [Advanced Fuel Technology Development Division, Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Kim, Ki Hwan; Lee, Don Bae; Lee, Yoon Sang [Advanced Fuel Technology Development Division, Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Lee, Jeong Soo; Seong, Baek Seok [Neutron Science Division, Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Kim, Chang Kyu [Advanced Fuel Technology Development Division, Korea Atomic Energy Research Institute, 150 Deokjin-dong, Yuseong, Daejeon 305-353 (Korea, Republic of); Cornen, Marilyne [INSA de Rennes, UMR CNRS 6226 Sciences Chimiques de Rennes/Chimie-Metallurgie, 20 Avenue des Buttes de Coesmes, 35043 Rennes Cedex (France)

    2010-02-15

    Lattice parameters of U-(6-10 wt.%)Mo alloy powders fabricated by a centrifugal atomization technique were measured by neutron diffraction analyses. A micro-segregation of Mo at cell boundaries was observed in the centrifugally atomized U-Mo alloy powders with varying Mo content. Lattice parameters of gamma phases decrease linearly with the increasing Mo content. By separating the overlapped diffraction peaks from cell boundaries and cell interior, lattice parameters and Mo contents of each region were calculated. The Mo content at cell boundaries is about 2-5 at.% lower than that in the cell interior and the lattice parameters for the cell boundaries are higher than those for the cell interior of the atomized U-Mo powder.

  15. Neutron diffraction analyses of U-(6-10 wt.%)Mo alloy powders fabricated by centrifugal atomization

    Science.gov (United States)

    Park, Jong Man; Ryu, Ho Jin; Kim, Ki Hwan; Lee, Don Bae; Lee, Yoon Sang; Lee, Jeong Soo; Seong, Baek Seok; Kim, Chang Kyu; Cornen, Marilyne

    2010-02-01

    Lattice parameters of U-(6-10 wt.%)Mo alloy powders fabricated by a centrifugal atomization technique were measured by neutron diffraction analyses. A micro-segregation of Mo at cell boundaries was observed in the centrifugally atomized U-Mo alloy powders with varying Mo content. Lattice parameters of gamma phases decrease linearly with the increasing Mo content. By separating the overlapped diffraction peaks from cell boundaries and cell interior, lattice parameters and Mo contents of each region were calculated. The Mo content at cell boundaries is about 2-5 at.% lower than that in the cell interior and the lattice parameters for the cell boundaries are higher than those for the cell interior of the atomized U-Mo powder.

  16. Accelerated Threshold Fatigue Crack Growth Effect-Powder Metallurgy Aluminum Alloy

    Science.gov (United States)

    Piascik, R. S.; Newman, J. A.

    2002-01-01

    Fatigue crack growth (FCG) research conducted in the near threshold regime has identified a room temperature creep crack growth damage mechanism for a fine grain powder metallurgy (PM) aluminum alloy (8009). At very low (Delta) K, an abrupt acceleration in room temperature FCG rate occurs at high stress ratio (R = K(sub min)/K(sub max)). The near threshold accelerated FCG rates are exacerbated by increased levels of K(sub max) (K(sub max) = 0.4 K(sub IC)). Detailed fractographic analysis correlates accelerated FCG with the formation of crack-tip process zone micro-void damage. Experimental results show that the near threshold and K(sub max) influenced accelerated crack growth is time and temperature dependent.

  17. Investigation of the Wear and Hardness Behaviour of Aluminium Alloy Coated Using the Powder Flame Spraying Method

    Directory of Open Access Journals (Sweden)

    Nurullah KIRATLI

    2009-03-01

    Full Text Available In this study, the wear behavior of aluminum alloy AL 5754 ( Etial 53 coated with powders of 10Al-Cu alloy (RotoTec® 19850 and 15Cr7Fe-Ni alloy (RotoTec® 19985 using powder flame spraying method has been investigated. To avoid thermal expansions between substrate and coating materials, Ni-Al RotoTec® 51000 was used as binding material. The wear test was performed on a pin-on-disc test apparatus. As an abrasive material, a SiC, 800 sandpaper was used. The wear tests of coated materials were carried out at room temperature and at 1.0m/s sliding speed with 0.35 and 0.70MPa pressures. To characterize coated specimens, they have been examined with optical microscope. As a result, it is found that the both coating materials have improved wear resistance.

  18. Laser surface cladding of ZM5 Mg-base alloy with Al+Y powder

    Institute of Scientific and Technical Information of China (English)

    陈长军; 王东生; 王茂才

    2004-01-01

    The surface properties of ZM5 Mg-base alloy were modified by laser cladding with Al+ Y powder. Laser cladding was carried out with a 5 kW continuous wave CO2 laser by melting the preplaced powder mixture of Al and Y. Following laser cladding, the cladding zone was characterized by a detailed microstructural observation and phase analysis. Moreover, the microhardness and element distribution were evaluated in detail. The surface modified layer consists of Mg17 Al12 and Al4 MgY phases, while a-Mg and Mg17 Al12 in the substrate. The microhardness of the cladding zone was significantly enhanced as high as HV122 - 180 as compared to HV60 - 80 of the substrate region. The maximal hardness about HV224 is in the interface due to the formation of intermetallic Mg17 Al12 phase. The microstructure is refined and Mg diffuses into the cladding material which leads to the formation of Mg17 Al12.

  19. Enhanced Sintering Kinetics in Aluminum Alloy Powder Consolidated Using DC Electric Fields

    Science.gov (United States)

    McWilliams, Brandon; Yu, Jian; Kellogg, Frank; Kilczewski, Steven

    2017-02-01

    Direct current (DC) electric currents were applied during sintering of aluminum alloy (AA5083) green powder compacts and it was found that the kinetics of sintering were greatly enhanced compared to samples processed without a field. In situ sintering kinetics during pressure-less sintering employing electric field strengths and amperages ranging from 0 to 56 V/cm and 0 to 3 A were quantified using digital image correlation. It was found that the application of a DC field during sintering results in a discontinuous change in volume at a critical temperature along with a transition in electrical properties of the compact from insulating to conductive. This effect is similar to the phenomena observed in the flash sintering process currently being actively researched for ceramic powder processing. The temperature at which the flash event occurs was found to be field strength dependent and doubling the field strength was found to decrease the flash temperature by 25 pct. Joule heating of the specimen was measured using thermal imaging and it was found to not contribute enough additional thermal energy to account for the substantially increased sintering rates observed in specimens processed using electric fields.

  20. Rapidly solidified Fe-6.5%Si alloy powders for high frequency use (abstract)

    Science.gov (United States)

    Duk Choi, Seung; Jin Yang, Choong

    1996-04-01

    Fe-(3˜6.5%) Si alloy powders having a high magnetic induction (Bs) and a low core loss value for high frequency use were obtained by an extractive melt spinning as well as a centrifugal atomization technique. Sintered core rings made by the rapidly solidified Fe-6.5% Si powders exhibited the high frequency electromagnetic properties: saturated induction (B8) of 1.23 T, coercivity (Hc) of 9.5 A/m, relative permeability (μa) of 6321, and core loss (W10/50) of 1.27 W/kg from the rings of 1.1 mm thick. The saturated induction values were found to be almost identical to those of nonoriented Fe-3% Si steel sheet and 6.5% Si sheet prepared by the CVD technique. The high frequency core loss values were measured not to be changed much up to 10 kHz (W1/10k=55 W/kg) in applied ac frequency.

  1. Titanium nitride deposition in titanium implant alloys produced by powder metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Henriques, V.A.R.; Cairo, C.A.A.; Faria, J., E-mail: vinicius@iae.cta.br, E-mail: ccairo@iae.cta.br, E-mail: juliacfaria@gmail.com [Instituto de Aeronautica e Espaco (AMR/CTA/IAE), Sao Jose dos Campos, SP (Brazil). Centro Tecnico Aeroespacial. Divisao de Materiais; Lemos, T.G., E-mail: tgorla@hotmail.com [Universidade de Sao Paulo (DEMAR/EEL/USP), Lorena, SP (Brazil). Escola de Engenharia; Galvani, E.T., E-mail: eduardotgalvani@yahoo.com.br [Instituto Tecnologico de Aeronautica (CTA/ITA), Sao Jose dos Campos, SP (Brazil). Centro Tecnico Aeroespacial

    2009-07-01

    Titanium nitride (TiN) is an extremely hard material, often used as a coating on titanium alloy, steel, carbide, and aluminum components to improve wear resistance. Electron Beam Physical Vapor Deposition (EB-PVD) is a form of deposition in which a target anode is bombarded with an electron beam given off by a charged tungsten filament under high vacuum, producing a thin film in a substrate. In this work are presented results of TiN deposition in targets and substrates of Ti (C.P.) and Ti-{sup 13}Nb-{sup 13}Zr obtained by powder metallurgy. Samples were produced by mixing of hydride metallic powders followed by uniaxial and cold isostatic pressing with subsequent densification by sintering between 900°C up to 1400 °C, in vacuum. The deposition was carried out under nitrogen atmosphere. Sintered samples were characterized for phase composition, microstructure and microhardness by X-ray diffraction, scanning electron microscopy and Vickers indentation, respectively. It was shown that the samples were sintered to high densities and presented homogeneous microstructure, with ideal characteristics for an adequate deposition and adherence. The film layer presented a continuous structure with 15μm. (author)

  2. Enhanced Sintering Kinetics in Aluminum Alloy Powder Consolidated Using DC Electric Fields

    Science.gov (United States)

    McWilliams, Brandon; Yu, Jian; Kellogg, Frank; Kilczewski, Steven

    2016-11-01

    Direct current (DC) electric currents were applied during sintering of aluminum alloy (AA5083) green powder compacts and it was found that the kinetics of sintering were greatly enhanced compared to samples processed without a field. In situ sintering kinetics during pressure-less sintering employing electric field strengths and amperages ranging from 0 to 56 V/cm and 0 to 3 A were quantified using digital image correlation. It was found that the application of a DC field during sintering results in a discontinuous change in volume at a critical temperature along with a transition in electrical properties of the compact from insulating to conductive. This effect is similar to the phenomena observed in the flash sintering process currently being actively researched for ceramic powder processing. The temperature at which the flash event occurs was found to be field strength dependent and doubling the field strength was found to decrease the flash temperature by 25 pct. Joule heating of the specimen was measured using thermal imaging and it was found to not contribute enough additional thermal energy to account for the substantially increased sintering rates observed in specimens processed using electric fields.

  3. Mechanisms of fatigue crack retardation following single tensile overloads in powder metallurgy aluminum alloys

    Science.gov (United States)

    Bray, G. H.; Reynolds, A. P.; Starke, E. A., Jr.

    1992-01-01

    In ingot metallurgy (IM) alloys, the number of delay cycles following a single tensile overload typically increases from a minimum at an intermediate baseline stress intensity range, Delta-K(B), with decreasing Delta-K(B) approaching threshold and increasing Delta-K(B) approaching unstable fracture to produce a characteristic 'U' shaped curve. Two models have been proposed to explain this behavior. One model is based on the interaction between roughness and plasticity-induced closure, while the other model only utilizes plasticity-induced closure. This article examines these models, using experimental results from constant amplitude and single overload fatigue tests performed on two powder metallurgy (PM) aluminum alloys, AL-905XL and AA 8009. The results indicate that the 'U'-shaped curve is primarily due to plasticity-induced closure, and that the plasticity-induced retardation effect is through-thickness in nature, occurring in both the surface and interior regions. However, the retardation effect is greater at the surface, because the increase in plastic strain at the crack tip and overload plastic zone size are larger in the plane-stress surface regions than in the plane-strain interior regions. These results are not entirely consistent with either of the proposed models.

  4. Microstructure, cytotoxicity and corrosion of powder-metallurgical iron alloys for biodegradable bone replacement materials

    Energy Technology Data Exchange (ETDEWEB)

    Wegener, Bernd; Sievers, Birte; Utzschneider, Sandra; Mueller, Peter; Jansson, Volkmar [Department of Orthopedic Surgery, Ludwig-Maximilians-University of Munich, Marchioninistrasse 15, 81377 Muenchen (Germany); Roessler, Sophie; Nies, Berthold [InnoTERE GmbH, Tatzberg 47, 01307 Dresden (Germany); Stephani, Guenter; Kieback, Bernd [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Dresden Branch Lab, Winterbergstrasse 28, 01277 Dresden (Germany); Quadbeck, Peter, E-mail: peter.quadbeck@ifam-dd.fraunhofer.de [Fraunhofer Institute for Manufacturing Technology and Advanced Materials (IFAM), Dresden Branch Lab, Winterbergstrasse 28, 01277 Dresden (Germany)

    2011-12-15

    Up to now biodegradable bone implants with the ability of bearing high loads for the temporary replacement of bones or as osteosynthesis material are not available. Iron and iron based alloys have been identified as appropriate materials, since they combine high strength at medium corrosion rates. Thus, the aim of the present study is the development of a degradable iron based alloy with the perspective of using them as matrix material of cellular structures with biomechanical tailored properties. A powder metallurgical approach has been used to manufacture Fe-C, Fe-0.6P, Fe-1.6P, Fe-B and Fe-Ag samples, which have been tested with respect to their microstructure, their cytotoxicity, and their degradation rate. In order to determine the cytotoxicity of the material a monolayer culture of fibroblast and a perfusion chamber system has been chosen, which was recommended by the ISO 10993-5:1999 for biological testing of medical devices. It has been found, that in particular phosphorus features beneficial properties, since density and thus the strength of the material are increased. No corrosion inhibiting effects of phosphorus on the degradation rate have been found.

  5. Fabrication and characterization of nanocrystalline Al/Al12(Fe,V)3Si alloys by consolidation of mechanically alloyed powders

    Institute of Scientific and Technical Information of China (English)

    Hamid Ashrafi; Rahmatollah Emadi; Mohammad Hosein Enayati

    2014-01-01

    The aim of this study was to produce bulk nanocrystalline Al/Al12(Fe,V)3Si alloys by mechanical alloying (MA) and subsequent hot pressing (HP) of elemental powders. A nanostructured Al-based solid solution was formed by MA of elemental powders for 60 h. After HP of the as-milled powders at 550°C for 20 min, the Al12(Fe,V)3Si phase was precipitated in a nanocrystalline Al matrix. Scanning electron microscopy (SEM) images of the bulk samples represented a homogeneous and uniform microstructure that was superior to those previously obtained by rapid solidification–powder metallurgy (RS–PM). Nanostructured Al−8.5Fe−1.3V−1.7Si and Al−11.6Fe−1.3V−2.3Si alloys ex-hibited high HV hardness values of~205 and~254, respectively, which are significantly higher than those reported for the RS–PM counter-parts.

  6. Structural and Phase State of Ti-Nb Alloy at Selective Laser Melting of the Composite Powder

    Science.gov (United States)

    Sharkeev, Yu. P.; Eroshenko, A. Yu.; Kovalevskaya, Zh. G.; Saprykin, A. A.; Ibragimov, E. A.; Glukhov, I. A.; Khimich, M. A.; Uvarkin, P. V.; Babakova, E. V.

    2016-07-01

    Phase composition and microstructure of Ti-Nb alloy produced from the composite titanium and niobium powder by selective laser melting (SLM) method were studied in the present research. Ti-Nb alloy produced by SLM is a monolayer and has zones of fine-grained and medium-grained structure with homogenous elemental composition within the range of 36-38 wt.% Nb. Phase state of the alloy corresponds to the main phase of β- solid solution (grain size of 5-7 μm) and non-equilibrium martensite α″-phase (grain size of 0.1-0.7 μm). Grains of the α″-phase are localized along the boundaries of β-phase grains and have a reduced content of niobium. Microhardness of the alloy varies within the range of 4200-5500 MPa.

  7. Microstructure evolution of laser solid forming of Ti-A1-V ternary system alloys from blended elemental powders

    Institute of Scientific and Technical Information of China (English)

    Hua Tan; Fengying Zhang; Jing Chen; Xin Lin; Weidong Huang

    2011-01-01

    @@ Morphology evolution of prior β grains of laser solid forming (LSF) Ti-xAl-yV (x ≤ 11,y ≤ 20) alloys from blended elemental powders is investigated.The formation mechanism of grain morphology is revealed by incorporating columnar to equiaxed transition (CET) mechanism during solidification.%Morphology evolution of prior β grains of laser solid forming (LSF) Ti-xAl-yV (x ≤ 11,y ≤ 20) alloys from blended elemental powders is investigated. The formation mechanism of grain morphology is revealed by incorporating columnar to equiaxed transition (CET) mechanism during solidification. The morphology of prior β grains of LSF Ti-6Al-yV changes from columnar to equiaxed grains with increasing element V content from 4 to 20 wt.-%. This agrees well with CET theoretical prediction. Likewise, the grain morphology of LSF Ti-xA1-2V from blended elemental powders changes from large columnar to small equiaxed with increasing A1 content from 2 to 11 wt.-%. The macro-morphologies of LSF Ti-8A1-2V and Ti-11A1-2V from blended elemental powders do not agree with CET predictions. This is caused by the increased disturbance effects of mixing enthalpy with increasing A1 content, generated in the alloying process of Ti, Al, and V in the molten pool.

  8. Development of heat resistant Pb-free joints by TLPS process of Ag and Sn-Bi-Ag alloy powders

    Directory of Open Access Journals (Sweden)

    Ohnuma I.

    2012-01-01

    Full Text Available TLPS (Transient Liquid Phase Sintering process is a candidate method of heat-resistant bonding, which makes use of the reaction between low-melting temperature powder of Sn-Bi base alloys and reactive powder of Ag. During heat treatment above the melting temperature of a Sn-Bi base alloy, the molten Sn-Bi reacts rapidly with solid Ag particles, which results in the formation of heat-resistant intermetallic compound (IMC. In this study, the TLPS properties between Sn-17Bi-1Ag (at.% powder with its liquidus temperature of 200°C and pure Ag powder were investigated. During differential scanning calorimetry (DSC measurement, an exothermic reaction and an endothermic reaction occurred, which correspond to the formation of the e-Ag3Sn IMC phase and the melting of the Sn-17Bi-1Ag alloy, respectively. After the overall measurement, the obtained reactant consists of the Ag3Sn-IMC and Bi-rich phases, both of which start melting above 250°C, with a small amount of the residual Sn-Bi eutectic phase. These results suggest that the TLPS process can be applied for Pb-free heatresistant bonding.

  9. Friction stir surfacing of cast A356 aluminium–silicon alloy with boron carbide and molybdenum disulphide powders

    Directory of Open Access Journals (Sweden)

    R. Srinivasu

    2015-06-01

    Full Text Available Good castability and high strength properties of Al–Si alloys are useful in defence applications like torpedoes, manufacture of Missile bodies, and parts of automobile such as engine cylinders and pistons. Poor wear resistance of the alloys is major limitation for their use. Friction stir processing (FSP is a recognized surfacing technique as it overcomes the problems of fusion route surface modification methods. Keeping in view of the requirement of improving wear resistance of cast aluminium–silicon alloy, friction stir processing was attempted for surface modification with boron carbide (B4C and molybdenum disulfide (MoS2 powders. Metallography, micro compositional analysis, hardness and pin-on-disc wear testing were used for characterizing the surface composite coating. Microscopic study revealed breaking of coarse silicon needles and uniformly distributed carbides in the A356 alloy matrix after FSP. Improvement and uniformity in hardness was obtained in surface composite layer. Higher wear resistance was achieved in friction stir processed coating with carbide powders. Addition of solid lubricant MoS2 powder was found to improve wear resistance of the base metal significantly.

  10. Modelling of laser cladding of magnesium alloys with pre-placed powders

    Science.gov (United States)

    Guo, Li-Feng

    As a surface engineering technique, high-power laser cladding, has shown great potential for improving the corrosion resistance of magnesium alloys. Its main advantage over other processes, is its ability to form relatively thick protective coatings on selected areas where improved properties are desired. It is also a 'clean' process. However, previous research studies have found that in laser cladding of magnesium alloys, the problem of a high degree of dilution cannot be easily overcome. Moreover, in-depth studies using analytical or numerical modelling can rarely be found in the literature for addressing laser cladding with pre-placed powders with the aim of predicting the level of dilution. In the first phase of this study, a simplified thermal model based on the finite element method (FEM) was developed to study the phenomenon of dilution in laser cladding of a magnesium alloy. In the model, the powder bed was treated as a continuum, and a high power continuous wave (CW) laser was employed. The results of the simulations of the FEM model together with those of the statistical analyses showed that although, under normal cladding conditions, a process window can be established for achieving good interfacial bonding between the substrate and the clad coating, a low dilution level was extremely difficult to achieve. This was primarily attributed to the low melting point and the high thermal diffusivity of magnesium as well as the relatively long laser-material interaction time. To overcome the dilution problem, the double-layer cladding technique was explored, and was found to be able to produce low dilution clads with improved corrosion resistance. In considering the improvement of corrosion resistance that can be caused by laser surface modification to magnesium alloys, a comparison was made between the techniques of laser surface melting and laser cladding. The results of the potentiodynamic polarisation tests showed that the improvement obtained from laser

  11. Similarities and Differences in Mechanical Alloying Processes of V-Si-B and Mo-Si-B Powders

    Directory of Open Access Journals (Sweden)

    Manja Krüger

    2016-10-01

    Full Text Available V-Si-B and Mo-Si-B alloys are currently the focus of materials research due to their excellent high temperature capabilities. To optimize the mechanical alloying (MA process for these materials, we compare microstructures, morphology and particles size as well as hardness evolution during the milling process for the model alloys V-9Si-13B and Mo-9Si-8B. A variation of the rotational speed of the planetary ball mill and the type of grinding materials is therefore investigated. These modifications result in different impact energies during ball-powder-wall collisions, which are quantitatively described in this comparative study. Processing with tungsten carbide vials and balls provides slightly improved impact energies compared to vials and balls made of steel. However, contamination of the mechanically alloyed powders with flaked particles of tungsten carbide is unavoidable. In the case of using steel grinding materials, Fe contaminations are also detectable, which are solved in the V and Mo solid solution phases, respectively. Typical mechanisms that occur during the MA process such as fracturing and comminution are analyzed using the comminution rate KP. In both alloys, the welding processes are more pronounced compared to the fracturing processes.

  12. Electron microscopy study of microtexture in Cu-Al-Ni shape memory alloys processed by powder metallurgy

    Science.gov (United States)

    Rodriguez, P. P.; San Jean, J.; Iza-Mendia, A.; Recarte, V.; Pérez-Landazabal, J. J.; No, M. L.

    2003-10-01

    Cu-AI-Ni shape memory alloys processed by powder metallurgy show very good thermomechanical properties, being the mechanical behavior similar to the one observed in single crystals. In this paper we present the microstructural characterization of a sample elaborated by powder metallurgy in two different stages of the process: after being compacted by Hot Isostatic Pressing (HIP) and after compaction and hot rolling, in order to find the microscopic mechanisms responsible of their mechanical behavior. The characterization has been carried out by means of Scanning Electron Microscopy using Backscattered Electron Imaging (SEM-BSE) and Electron BackScattered Diffraction (EBSD), as well as Transmission Electron Microscopy (TEM).

  13. Effect of Fe base alloy content in Ti-C-Fe base alloy powder mixtures on the SHS products structure

    Science.gov (United States)

    Pribytkov, Gennadii A.; Krinitcyn, Maxim G.; Korzhova, Victoria V.; Baranovskii, Anton V.; Korosteleva, Elena N.

    2016-11-01

    The paper investigates the morphology, phase composition, and internal structure of "TiC-high chromium cast iron binder" and "TiC-high speed steel binder" composite powders. The powders were produced by self-propagating high temperature synthesis of Ti-C-Me powder mixtures in the layer by layer burning mode. X-ray diffractometry, optical and scanning electron microscopy methods were used for the powders characterization.

  14. Additive manufacturing of metal alloy for aerospace by means of Powder Laser Cladding: station tuning and clad characterization

    OpenAIRE

    Fierro, Ilaria

    2016-01-01

    2014 - 2015 This thesis investigates the application of continuous coaxial laser cladding by powder injection as repair and cover process. The investigation aimed to check the possibility of repairing a V-groove geometry on a substrate of AA2024 and A357 aluminum alloy. Chapter one is an introduction to the laser cladding. This presents a general overview of the laser cladding methods and some applications for the processes. In the second chapter, the laser cladding process is analys...

  15. Comparison of surface laser alloying of chosen tool steel using Al2O3 and ZrO2 powder

    Directory of Open Access Journals (Sweden)

    K. Labisz

    2010-03-01

    Full Text Available Purpose: In this work there are presented the investigation results of mechanical properties and microstructure of the hot work tool steel 32CrMoV12-28 alloyed with oxide powders like aluminium oxide and zirconium oxide. The purpose of this work was also to determine the laser treatment conditions for surface hardening of the investigation alloys with appliance of transmission electron microscopy.Design/methodology/approach: The investigations were performed using optical microscopy for the microstructure determination. By mind of the transmission electron microscopy the high resolution and phase determination was possible to obtain. The morphology of the ceramic powder particles was studied as well the lattice parameters for the Fe matrix and phase identification using diffraction methods was applied.Findings: After the laser alloying of the hot work tool steel with the selected oxide powders the structure of the samples changes in a way, that there are zones detected like the remelting zone the heat influence zone where the grains are larger and not so uniform as in the metal matrix. The used oxide powders are not present after the laser treatment in the steel matrix.Research limitations/implications: The investigated steel samples were examined metallographically using optical microscope with different image techniques, SEM, TEM and analyzed using a Rockwell hardness tester, also EDS microanalysis and electron diffraction with Fourier transform was made.Practical implications: As an implication for the practice a new technology can be possible to develop, based no diode laser usage. Some other investigation should be performed in the future, but the knowledge found in this research shows an interesting investigation direction.Originality/value: The combination of TEM investigation for laser alloying of hot work tool steels makes the investigation very attractive for automotive and other heavy industries.

  16. Precipitation in cold-rolled Al-Sc-Zr and Al-Mn-Sc-Zr alloys prepared by powder metallurgy

    KAUST Repository

    Vlach, Martin

    2013-12-01

    The effects of cold-rolling on thermal, mechanical and electrical properties, microstructure and recrystallization behaviour of the AlScZr and AlMnScZr alloys prepared by powder metallurgy were studied. The powder was produced by atomising in argon with 1% oxygen and then consolidated by hot extrusion at 350 C. The electrical resistometry and microhardness together with differential scanning calorimetry measurements were compared with microstructure development observed by transmission and scanning electron microscopy, X-ray diffraction and electron backscatter diffraction. Fine (sub)grain structure developed and fine coherent Al3Sc and/or Al3(Sc,Zr) particles precipitated during extrusion at 350 C in the alloys studied. Additional precipitation of the Al3Sc and/or Al3(Sc,Zr) particles and/or their coarsening was slightly facilitated by the previous cold rolling. The presence of Sc,Zr-containing particles has a significant antirecrystallization effect that prevents recrystallization at temperatures minimally up to 420 C. The precipitation of the Al6Mn- and/or Al 6(Mn,Fe) particles of a size ~ 1.0 μm at subgrain boundaries has also an essential antirecrystallization effect and totally suppresses recrystallization during 32 h long annealing at 550 C. The texture development of the alloys seems to be affected by high solid solution strengthening by Mn. The precipitation of the Mn-containing alloy is highly enhanced by a cold rolling. The apparent activation energy of the Al3Sc particles formation and/or coarsening and that of the Al6Mn and/or Al 6(Mn,Fe) particle precipitation in the powder and in the compacted alloys were determined. The cold deformation has no effect on the apparent activation energy values of the Al3Sc-phase and the Al 6Mn-phase precipitation. © 2013 Elsevier Inc.

  17. Metal release from stainless steel powders and massive sheets--comparison and implication for risk assessment of alloys.

    Science.gov (United States)

    Hedberg, Yolanda; Mazinanian, Neda; Odnevall Wallinder, Inger

    2013-02-01

    Industries that place metal and alloy products on the market are required to demonstrate that they are safe for all intended uses, and that any risks to humans, animals or the environment are adequately controlled. This requires reliable and robust in vitro test procedures. The aim of this study is to compare the release of alloy constituents from stainless steel powders of different grades (focus on AISI 316L) and production routes into synthetic body fluids with the release of the same metals from massive sheets in relation to material and surface characteristics. The comparison is justified by the fact that the difference between massive surfaces and powders from a metal release/dissolution and surface perspective is not clearly elucidated within current legislations. Powders and abraded and aged (24 h) massive sheets were exposed to synthetic solutions of relevance for biological settings and human exposure routes, for periods of up to one week. Concentrations of released iron, chromium, nickel, and manganese in solution were measured, and the effect of solution pH, acidity, complexation capacity, and proteins elucidated in relation to surface oxide composition and its properties. Implications for risk assessments based on in vitro metal release data from alloys are elucidated.

  18. Effect of carbon on corrosion resistance of powder-processed Fe–0.35%P alloys

    Indian Academy of Sciences (India)

    Yashwant Mehta; Shefali Trivedi; K Chandra; P S Mishra

    2010-08-01

    The corrosion behaviour of phosphoric irons containing 0.35 wt % P, 2% copper, 2% nickel, 1% silicon, 0.5% molybdenum, with/without 0.15% carbon prepared by powder forging route were studied in different environments. The various environments chosen were acidic (0.25 M H2SO4 solution of pH 0.6), neutral/marine (3.5% NaCl solution of pH 6.8) and alkaline (0.5 M Na2CO3 + 1.0 M NaHCO3 solution of pH 9.4). The corrosion studies were conducted using Tafel extrapolation and linear polarization methods. The studies also compare Armco iron with phosphoric irons. It was observed that the addition of carbon improved the corrosion resistance of a Fe–0.35%P–2%Ni–2%Cu–1%Si–0.5%Mo alloy in all the environments. Corrosion rates were highest in acid medium, minimal in alkaline medium and low in neutral solution. SEM/EDAX was used to characterize the compositions.

  19. Dwell Notch Low Cycle Fatigue Behavior of a Powder Metallurgy Nickel Disk Alloy

    Science.gov (United States)

    Telesman, J.; Gabb, T. P.; Yamada, Y.; Ghosn, L. J.; Jayaraman, N.

    2012-01-01

    A study was conducted to determine the processes which govern dwell notch low cycle fatigue (NLCF) behavior of a powder metallurgy (P/M) ME3 disk superalloy. The emphasis was placed on the environmentally driven mechanisms which may embrittle the highly stressed notch surface regions and reduce NLCF life. In conjunction with the environmentally driven notch surface degradation processes, the visco-plastic driven mechanisms which can significantly change the notch root stresses were also considered. Dwell notch low cycle fatigue testing was performed in air and vacuum on a ME3 P/M disk alloy specimens heat treated using either a fast or a slow cooling rate from the solutioning treatment. It was shown that dwells at the minimum stress typically produced a greater life debit than the dwells applied at the maximum stress, especially for the slow cooled heat treatment. Two different environmentally driven failure mechanisms were identified as the root cause of early crack initiation in the min dwell tests. Both of these failure mechanisms produced mostly a transgranular crack initiation failure mode and yet still resulted in low NLCF fatigue lives. The lack of stress relaxation during the min dwell tests produced higher notch root stresses which caused early crack initiation and premature failure when combined with the environmentally driven surface degradation mechanisms. The importance of environmental degradation mechanisms was further highlighted by vacuum dwell NLCF tests which resulted in considerably longer NLCF lives, especially for the min dwell tests.

  20. Phase evolution in Fe-Cr-Mn-Mo powders processed by mechanical alloying in N{sub 2} atmosphere

    Energy Technology Data Exchange (ETDEWEB)

    Mancha, H.; Mendoza, G.; Belmares, S.; Escalante, J.I.; Mendez, M. [Cinvestav-Saltillo, Mex. (Mexico); Cisneros, M.M. [Inst. Tecnologico de Saltillo (Mexico); Lopez, H. [Univ. of Wisconsin, Milwaukee, Dept. of Materials Engineering, WI (United States)

    2001-07-01

    Nanostructured Fe-18Cr-11Mo-xN alloys were prepared by attrition milling of elemental powders under N{sub 2} atmosphere for different times. It was found that the amount of nitrogen present in the powder mixture increased up to 1.6 wt% after 192 h. As-milled powders were encapsulated in quartz tubes and heat treated at 1173 and 1473 K to promote austenisation. Different phases were identified posterior to crystallization namely, ferrite, austenite and Cr{sub 2}N, which occurred in different amounts depending on the nitrogen content and the heat-treatment temperature. No nitrogen desorption was perceptible after the crystallization annealing treatment. The results showed that it is feasible to obtain a fully austenitic structure by controlling the processing parameters. (orig.)

  1. Shape memory characteristics and mechanical properties of powder metallurgy processed Ti50Ni40Cu10 alloy.

    Science.gov (United States)

    Kim, Yeon-Wook

    2014-10-01

    Ti-Ni-Cu alloy powders were prepared by gas atomization and porous bulk specimens were fabricated by spark plasma sintering (SPS). The microstructure of as-solidified powders exhibited a cellular structure and they contained a high density of nano-sized porosities which were located in the intercellular regions. XRD analysis showed that one-step martensitic transformation of B2-B19 occurred in all alloy powders and SPS specimens. When the martensitic transformation start temperature (M(s)) and austenite transformation finish temperature (A(f)) were determined in order to analyze the dependence of powder size on transformation temperatures, the M(s) increased slightly from -17.5 degrees C to - 14.6 degrees C as increasing the powder size ranging from between 25 and 50 μm to ranging between 100 and 150 μm. However, the M(s) and A(f) of the as-atomized powders is much smaller than those of SPS specimens and the M(s) of porous specimen was about 10.9 degrees C. Loading-unloading compressive tests were carried out to investigate the mechanical properties of porous Ti-Ni-Cu specimen. The specimen was compressed to the strain of 6% at a temperature higher than A,. After unloading, the residual strain was 2.1%. After the compressed specimen was heated to 60 degrees C and held for 30 minutes and then cooled to room temperature, the changes in the length of the specimens were measured. Then it was found that the recovered strain ascribed to shape memory effect was 1.5%.

  2. Mechanical properties of Mo-Si-B alloys fabricated by using core-shell powder with dispersion of yttria nanoparticles

    Science.gov (United States)

    Byun, Jong Min; Bang, Su-Ryong; Choi, Won June; Kim, Min Sang; Noh, Goo Won; Kim, Young Do

    2017-01-01

    In recent years, refractory materials with excellent high-temperature properties have been in the spotlight as a next generation's high-temperature materials. Among these, Mo-Si-B alloys composed of two intermetallic compound phases (Mo5SiB2 and Mo3Si) and a ductile α-Mo phase have shown an outstanding thermal properties. However, due to the brittleness of the intermetallic compound phases, Mo-Si-B alloys were restricted to apply for the structural materials. So, to enhance the mechanical properties of Mo-Si-B alloys, many efforts to add rare-earth oxide particles in the Mo-Si-B alloy were performed to induce the improvement of strength and fracture toughness. In this study, to investigate the effect of adding nano-sized Y2O3 particles in Mo-Si-B alloy, a core-shell powder consisting of intermetallic compound phases as the core and nano-sized α-Mo and Y2O3 particles surrounding the core was fabricated. Then pressureless sintering was carried out at 1400 °C for 3 h, and the mechanical properties of sintered bodies with different amounts of Y2O3 particles were evaluated by Vickers hardness and 3-point bending test. Vickers hardness was improved by dispersed Y2O3 particles in the Mo-Si-B alloy. Especially, Mo-3Si-1B-1.5Y2O3 alloy had the highest value, 589 Hv. The fracture toughness was measured using Mo-3Si-1B-1.5Y2O3 alloy and the value indicated as 13.5 MPa·√m.

  3. Effect Of DyMn Alloy-Powder Addition On Microstructure And Magnetic Properties Of NdFeB Sintered Magnets

    Directory of Open Access Journals (Sweden)

    Lee M.-W.

    2015-06-01

    Full Text Available Micostructural change and corresponding effect on coercivity of a NdFeB sintered magnet mixed with small amount of DyMn powder was investigated. In the sintered magnet mixed with the DyMn alloy-powder Dy-rich shell was formed at outer layer of the main grains, while Mn was mostly concentrated at Nd-rich triple junction phase (TJP, lowering melting temperature of the Nd-rich phase that eventually improved the microstructural characteristics of the gain boundary phase. The coercivity of a magnet increased more than 3.5 kOe by the mixing of the DyMn alloy-powder.

  4. Electro-explosive alloying of VT6 alloy surface by boron carbide powder with the subsequent electron-beam treatment

    Science.gov (United States)

    Romanov, D. A.; Raykov, S. V.; Gromov, V. E.; Ivanov, Yu F.

    2015-11-01

    The formation of electro-explosive alloying zone with the thickness up to 50 μm has been revealed. It has been shown that it has a gradient structure, characterized by the decrease of carbon and boron concentration with the increase of the distance up to the treatment surface. The subsequent electron-beam treatment of alloying zone leads to flattening of alloying surface relief and is accompanied by the formation of a multilevel structure at the depth up to 30 μm, characterized by the interchange of some layers with a different level of alloying, having structure of a submicro- and nanoscale level.

  5. Effect of the milling conditions on the formation of nanostructured Fe-Co powders

    Energy Technology Data Exchange (ETDEWEB)

    Alleg, Safia; Bentayeb, Fatima Z.; Bensalem, Rachid; Djebbari, Chafia [Laboratoire de Magnetisme et de Spectroscopie des Solides, Departement de Physique, Faculte des Sciences, Universite de Annaba (Algeria); Bessais, Lotfi [CNRS-Laboratoire de Chimie Metallurgique des Terres Rares-Groupe des Laboratoires de Thiais (France); Greneche, Jean M. [Laboratoire de Physique de l' Etat Condense, UMR CNRS, Universite du Maine, Le Mans cedex (France)

    2008-07-15

    Nanostructured Fe-12Co (wt%) powders were prepared by mechanical alloying in a planetary ball mill. The milling process was carried out at different milling conditions. The obtained powders were characterized by X-ray diffraction, {sup 57}Fe Moessbauer spectrometry and magnetic measurements. The low and high speed ball-milling conditions lead to the formation of a single and two-bcc Fe(Co) structure, respectively, having different crystallite sizes, microstrains hyperfine parameters and magnetic properties. The average hyperfine magnetic field values: left angle B right angle {sub 1}=34.8 T and left angle B right angle {sub 2} =28.2 T of the two-bcc Fe(Co) structure could be attributed to the nanocrystalline grains and to the grain boundaries, respectively. (copyright 2008 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. Modeling molecular hyperfine line emission

    CERN Document Server

    Keto, Eric

    2010-01-01

    In this paper we discuss two approximate methods previously suggested for modeling hyperfine spectral line emission for molecules whose collisional transitions rates between hyperfine levels are unknown. Hyperfine structure is seen in the rotational spectra of many commonly observed molecules such as HCN, HNC, NH3, N2H+, and C17O. The intensities of these spectral lines can be modeled by numerical techniques such as Lambda-iteration that alternately solve the equations of statistical equilibrium and the equation of radiative transfer. However, these calculations require knowledge of both the radiative and collisional rates for all transitions. For most commonly observed radio frequency spectral lines, only the net collisional rates between rotational levels are known. For such cases, two approximate methods have been suggested. The first method, hyperfine statistical equilibrium (HSE), distributes the hyperfine level populations according to their statistical weight, but allows the population of the rotationa...

  7. A study of the method of making dental prosthetic appliances by sintered titanium alloys: effect of copper powder content on properties of sintered titanium alloy.

    Science.gov (United States)

    Oda, Y; Nakanishi, K; Sumii, T

    1990-02-01

    The effects of added copper powder to the properties of the sintered titanium alloys were investigated by measuring the compressive strength and densities of the green and sintered compacts, the thermal expansion curves and dimensional changes in the sintered compacts, and the accuracy of the crown-type restorations. The compressive strengths of green compacts ranged from 55 to 75 MPa. The expansion of green compacts increased with increased copper content. The sintered density was lower than the green density. The compressive yield strength of sintered compacts ranged from 260 MPa to 410 MPa. The sintered compacts expanded from 0.35% to 1.03% and the expansion increased with increased copper content. The dimensional accuracy of crown-type restorations showed the same dimensional change tendencies as did the sintered compacts. These results showed that the fit and the strength of sintered titanium alloy restorations could be improved.

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

    Science.gov (United States)

    Ray, Ranjan; Jha, Sunil C.

    1987-01-01

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

  9. Influence of dysprosium substitution on magnetic and mechanical properties of high intrinsic coercivity Nd-Fe-B magnets prepared by double-alloy powder mixed method

    Institute of Scientific and Technical Information of China (English)

    胡志华; 瞿海锦; 马冬威; 罗成; 王会杰

    2016-01-01

    The double-alloy powder mixed method is very proper for developing new small-mass products by changing the composi-tion of sintered Nd-Fe-B magnets, and there is little research on this aspect. The variation on magnetic and mechanical properties of high intrinsic coercivity Nd-Fe-B magnets prepared by double-alloy powder mixed method was discussed, which is a method blend-ing two-type main phase alloy powders with different components. The results showed that the intrinsic coercivity and density of sin-tered Nd-Fe-B magnets increased gradually with the increase in Dy content, and the double-alloy powder mixed method could obtain high intrinsic coercivity Nd-Fe-B magnets with good crystallographic alignment and microstructure. The bending strength of sintered Nd-Fe-B magnets declined, and the Rockwell hardness of sintered Nd-Fe-B magnets first declined, and then increased with the in-crease in Dy content. The microstructure showed that there existed the phenomenon that the Dy element diffused into main phase dur-ing sintering process, and the distribution of Dy content in main phase had some variation in homogeneity as a result of incomplete reaction between the double-alloy powder types.

  10. Laser cladding of a Mg based Mg-Gd-Y-Zr alloy with Al-Si powders

    Science.gov (United States)

    Chen, Erlei; Zhang, Kemin; Zou, Jianxin

    2016-03-01

    In the present work, a Mg based Mg-Gd-Y-Zr alloy was subjected to laser cladding with Al-Si powders at different laser scanning speeds in order to improve its surface properties. It is observed that the laser clad layer mainly contains Mg2Si, Mg17Al12 and Al2(Gd,Y) phases distributed in the Mg matrix. The depth of the laser clad layer increases with decreasing the scanning speed. The clad layer has graded microstructures and compositions. Both the volume fraction and size of Mg2Si, Mg17Al12 and Al2(Gd,Y) phases decreases with the increasing depth. Due to the formation of these hardening phases, the hardness of clad layer reached a maximum value of HV440 when the laser scanning speed is 2 mm/s, more than 5 times of the substrate (HV75). Besides, the corrosion properties of the untreated and laser treated samples were all measured in a NaCl (3.5 wt.%) aqueous solution. The corrosion potential was increased from -1.77 V for the untreated alloy to -1.13 V for the laser clad alloy with scanning rate of 2 mm/s, while the corrosion current density was reduced from 2.10 × 10-5 A cm-2 to 1.64 × 10-6 A cm-2. The results show that laser cladding is an efficient method to improve surface properties of Mg-Rare earth alloys.

  11. A new titanium based alloy Ti-27Nb-13Zr produced by powder metallurgy with biomimetic coating for use as a biomaterial.

    Science.gov (United States)

    Mendes, Marcio W D; Ágreda, Carola G; Bressiani, Ana H A; Bressiani, José C

    2016-06-01

    Titanium alloys are widely used in biomedical applications due to their excellent properties such as high strength, good corrosion resistance and biocompatibility. Titanium alloys with alloying elements such as Nb and Zr are biocompatible and have Young's modulus close to that of human bone. To increase the bioactivity of titanium alloy surfaces is used chemical treatment with NaOH followed by immersion in simulated body fluid (SBF). The purpose of this study was to produce the alloy Ti-27Nb-13Zr with low Young's modulus by powder metallurgy using powders produced by the HDH process. The formation of biomimetic coatings on samples immersed in SBF for 3, 7, 11 and 15 days was evaluated. Characterization of the coating was performed by diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and scanning electron microscope. The microstructure and composition of the alloy were determined using SEM and XRD, while the mechanical properties were evaluated by determining the elastic modulus and the Vickers microhardness. The sintered alloys were composed of α and β phases, equiaxed grains and with density around 97.8% of its theoretical density. The Vickers microhardness and elasticity modulus of the alloy were determined and their values indicate that this alloy can be used as a biomaterial. Analysis of the coating revealed the presence of calcium phosphate layers on samples immersed for >3 days in the SBF solution.

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

    Science.gov (United States)

    Chellman, D. J.

    1982-01-01

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

  13. Mechanical Properties of Refractory High Entropy Alloys Fabricated by Powder Processing

    Energy Technology Data Exchange (ETDEWEB)

    Kuk, Seoung Woo; Kim, Ki Hwan [Korea Atomic Energy Research Institute, Yuseong, Daejeon (Korea, Republic of); Lim, Woo Jin; Kang, Byung Chul; Hong, Soon Hyung; Ryu, Ho Jin [KAIST, Daejeon (Korea, Republic of)

    2015-10-15

    The effects of high configurational entropy, lattice distortion and sluggish diffusion are attributed to the distinguishable behavior of high entropy alloys. The structural applications of high entropy alloys are also promising in advanced nuclear energy systems for nuclear fission and fusion applications. Because of the randomly occupied lattice points by atoms with different atomic radius, lattice distortions and local atomic level strain were developed. The local lattice distortions influence the mechanical properties of high entropy alloys. The strengthening of high entropy alloys is attributed to the lattice distortions and local atomic level strain that increase the resistance to the dislocation motion. Some high entropy alloys exhibit remarkable irradiation resistance. Nagase et al. reported that the Conference alloy was irradiation resistant up to 40 dpa. Ega mi proposed that the irradiation defects can be self-healed because the recrystallization happens more easily in high entropy alloys. The mechanically alloyed and sintered samples have a much smaller grain size than that in cast high entropy alloys.

  14. Preparation of Zr50Al15−Ni10Cu25Y amorphous powders by mechanical alloying and thermodynamic calculation

    Indian Academy of Sciences (India)

    Woyun Long; Anxian Lu; Jing Li

    2013-12-01

    Amorphous Zr50Al15−Ni10Cu25Y powders were fabricated by mechanical alloying at a low rotation speed from commercial pure element powders. The beneficial effect of Al partially substituted by Y in Zr50Al15Ni10Cu25 on glass-forming ability was investigated. The as-milled powders were characterized by X-ray diffraction and transmission electron microscopy. The results show that partial substitution of Al by Y can improve the glass-forming ability of Zr50Al15Ni10Cu25 alloy. Thermodynamic calculation of equivalent free energy shows that Zr50Al13.8Ni10Cu25Y1.2 alloy has the highest glass-forming ability, which is in good agreement with the report of orthogonal experiments.

  15. The use of amorphous boron powder enhances mechanical alloying in soft magnetic FeNbB alloy: A magnetic study

    Energy Technology Data Exchange (ETDEWEB)

    Ipus, J. J.; Blazquez, J. S.; Franco, V.; Conde, A. [Dpto. Fisica de la Materia Condensada, ICMSE-CSIC, Universidad de Sevilla, P.O. Box 1065, 41080 Sevilla (Spain)

    2013-05-07

    Saturation magnetization and magnetic anisotropy have been studied during mechanical alloying of Fe{sub 75}Nb{sub 10}B{sub 15} alloys prepared using crystalline and commercial amorphous boron. The evolution of saturation magnetization indicates a more efficient dissolution of boron into the matrix using amorphous boron, particularly for short milling times. The magnetization of the crystalline phase increases as boron is incorporated into this phase. Two milling time regimes can be used to describe the evolution of magnetic anisotropy: a first regime governed by microstrains and a second one mainly governed by crystal size and amorphous fraction.

  16. Structural, microstructural and Mössbauer studies of nanocrystalline Fe100-x Alx powders elaborated by mechanical alloying

    Directory of Open Access Journals (Sweden)

    Akkouche K.

    2012-06-01

    Full Text Available Nanocrystalline Fe100-xAlx powders (x= 25, 30, 34 and 40 at % were prepared by the mechanical alloying process using a vario-planetary high-energy ball mill for a milling time of 35 h. The formation and physical properties of the alloys were investigated as a function of Al content by means of X-ray diffraction, scanning electron microscopy (SEM, energy dispersive X-ray and Mössbauer spectroscopy. For all Fe100-xAlx samples, the complete formation of bcc phase was observed after 35 h of milling. As Al content increases, the lattice parameter increases, whereas the grain size decreases from 106 to 12 nm. The powder particle morphology for different compositions was observed by SEM. The Mössbauer spectra were adjusted with a singlet line and a sextet containing two components. The singlet was attributed to the formation of paramagnetic A2 disordered structure rich with Al. About the sextet, the first component indicated the formation of Fe clusters/ Fe-rich phases; however, the second component is characteristic of disordered ferromagnetic phase.

  17. The effect of structural changes during sintering on the electric and magnetic traits of the Ni96.7Mo3.3 alloy nanostructured powder

    Directory of Open Access Journals (Sweden)

    Ribić-Zelenović L.

    2009-01-01

    Full Text Available Ni96.7Mo3.3 powder was electrochemically obtained. An X-ray diffraction analysis determined that the powder consisted of a 20% amorphous and 80% crystalline phase. The crystalline phase consisted of a nanocrystalline solid nickel and molybdenum solution with a face-centred cubic (FCC lattice with a high density of chaotically distributed dislocations and high microstrain value. The scanning electronic microscopy (SEM showed that two particle structures were formed: larger cauliflower-like particles and smaller dendriteshaped ones. The thermal stability of the alloy was examined by differential scanning calorimetry (DSC and by measuring the temperature dependence of the electrical resistivity and magnetic permeability. Structural powder relaxation was carried out in the temperature range of 450 K to 560 K causing considerable changes in the electrical resistivity and magnetic permeability. Upon structural relaxation, the magnetic permeability of the cooled alloy was about 80% higher than the magnetic permeability of the fresh powder. The crystallisation of the amorphous portion of the powder and crystalline grain increase occurred in the 630 K to 900 K temperature interval. Upon crystallisation of the amorphous phase and crystalline grain increase, the powder had about 50% lower magnetic permeability than the fresh powder and 3.6 times lower permeability than the powder where only structural relaxation took place.

  18. From Powders to Dense Metal Parts: Characterization of a Commercial AlSiMg Alloy Processed through Direct Metal Laser Sintering

    Directory of Open Access Journals (Sweden)

    Eleonora Atzeni

    2013-03-01

    Full Text Available In this paper, a characterization of an AlSiMg alloy processed by direct metal laser sintering (DMLS is presented, from the analysis of the starting powders, in terms of size, morphology and chemical composition, through to the evaluation of mechanical and microstructural properties of specimens built along different orientations parallel and perpendicular to the powder deposition plane. With respect to a similar aluminum alloy as-fabricated, a higher yield strength of about 40% due to the very fine microstructure, closely related to the mechanisms involved in this additive process is observed.

  19. Effect of process control agent on the porous structure and mechanical properties of a biomedical Ti-Sn-Nb alloy produced by powder metallurgy.

    Science.gov (United States)

    Nouri, A; Hodgson, P D; Wen, C E

    2010-04-01

    The influence of different amounts and types of process control agent (PCA), i.e., stearic acid and ethylene bis-stearamide, on the porous structure and mechanical properties of a biomedical Ti-16Sn-4Nb (wt.%) alloy was investigated. Alloy synthesis was performed on elemental metal powders using high-energy ball milling for 5h. Results indicated that varying the PCA content during ball milling led to a drastic change in morphology and particle-size distribution of the ball-milled powders. Porous titanium alloy samples sintered from the powders ball milled with the addition of various amounts of PCA also revealed different pore morphology and porosity. The Vickers hardness of the sintered titanium alloy samples exhibited a considerable increase with increasing PCA content. Moreover, the addition of larger amounts of PCA in the powder mixture resulted in a significant increase in the elastic modulus and peak stress for the sintered porous titanium alloy samples under compression. It should also be mentioned that the addition of PCA introduced contamination (mainly carbon and oxygen) into the sintered porous product.

  20. Effect of milling duration on the evolution of shape memory properties in a powder processed Cu-Al-Ni-Ti alloy

    Energy Technology Data Exchange (ETDEWEB)

    Sharma, Mohit; Gupta, Gaurav K.; Shafeeq, Muhamed M.; Modi, Om P.; Prasad, Braj K. [CSIR - Advanced Materials and Processes Research Institute, Bhopal (India)

    2013-09-15

    The present work describes the effect of milling duration on the properties of a powder metallurgy processed Cu-Al-Ni-Ti shape memory alloy employing mechanical alloying. Powder mixtures milled for different durations were sintered in order to investigate the formation of solid solution and evolution of martensitic structure. The idea was to optimize the duration of milling (mechanical alloying) to obtain chemical homogeneity as well as shape memory properties in the processed material without undergoing extensive post homogenization treatment. The martensitic structure was noted to evolve in the powder mix milled for at least 16 hrs, whereas complete transformation to martensite occurred after milling for 40 hrs. Interestingly, the dissolution of alloying elements (to form the {beta} phase prior to the formation of martensite) was noted to complete partially only during mechanical alloying for 40 hrs and remaining during subsequent sintering for 1 hr. The hot pressed compacts of the powders milled for 40 hrs were chemically homogeneous and consisted of fully martensite phase, which is essential for the realization of shape memory properties. They also revealed almost 100% shape recovery at the applied pre-strain levels of 1 and 2%. (orig.)

  1. The phase structure and morphology of electrodeposited nickel-cobalt alloy powders

    Directory of Open Access Journals (Sweden)

    Spasojević M.

    2011-01-01

    Full Text Available Cobalt and nickel powders of three different compositions: Ni0.8Co0.2, Ni0.55Co0.45 and Ni0.2Co0.8 were obtained by electrodeposition from an ammonium chloride-sulphate solution. It was shown that the microstructure and morphology of the powders depended on the deposition current density as well as on the bath composition. Amorphous powder of Ni0.8Co0.2 was obtained at the current density higher than 200 mA cm-2, but nanocrystalline powders having the same composition were obtained at current densities lower than 200 mAcm-2. The nanocrystalline powders with lower Ni contents (0.55 and 0.2 obtained at a current density ranging from 40 mA cm-2 to 450 mA cm-2 were solid solutions of two phases, FCC (β-Ni and HCP (α-Co ones. The increase of the HCP phase in the powder was a result of both the Co content increase in the powder and decrease of the deposition current density.

  2. Preparation of Nb3Al superconductor by powder metallurgy and effect of mechanical alloying on the phase formation

    Institute of Scientific and Technical Information of China (English)

    Zhao Liu; Yongliang Chen; Lupeng Du; Pingyuan Li; Yajing Cui; Xifeng Pan; Guo Yan

    2014-01-01

    Adoption of powder-in-tube method to fabri-cate superconducting wire can realize a large application of Nb3Al prepared by powder metallurgy. Powder metallurgy was used to synthesize Nb3Al under various heat-treatment conditions, annealing temperature was varied from 700 to 1,000 ?C and heating time was varied from 10 to 50 h. X-ray diffraction patterns reveal that a reaction between Nb and Al took place and formed NbAl3 phase. Under current heat-treatment conditions (annealing temperature was varied from 700 to 1,000 ?C and heating time was varied from 10 to 50 h), NbAl3 was so stable that it did not further react with the unreacted Nb and was not sensitive to the heat-treatment condition. By mechanical alloying, adoption of high-energy ball milling significantly decreases particle size and enhances surface free energy, which promotes the formation of Nb3Al phase. X-ray diffraction patterns indicate that relatively pure Nb3Al phase was obtained under the same heat-treatment condition. Energy-disper-sive X-ray analysis measurement demonstrates that the obtained samples were close to the right stoichiometry of A15 structure Nb3Al.

  3. Preparation of Al-Mg Alloy Electrodes by Using Powder Metallurgy and Their Application for Hydrogen Production

    Directory of Open Access Journals (Sweden)

    Wen-Nong Hsu

    2014-01-01

    Full Text Available The choice of an electrode is the most critical parameter for water electrolysis. In this study, powder metallurgy is used to prepare aluminum-magnesium (Al-Mg alloy electrodes. In addition to pure Mg and Al electrodes, five Al-Mg alloy electrodes composed of Al-Mg (10 wt%, Al-Mg (25 wt%, Al-Mg (50 wt%, and Al-Mg (75 wt% were prepared. In water electrolysis experiments, the pure Al electrode exhibited optimal electrolytic efficiency. However, the Al-Mg (25 wt% alloy was the most efficient when the anticorrosion effect and materials costs were considered. In this study, an ultrasonic field was applied to the electrolysis cell to improve its efficiency. The results revealed that the current increased by approximately 23.1% when placed in a 30 wt% KOH solution under the ultrasonic field. Electrochemical polarization impedance spectroscopy (EIS was employed to evaluate the effect of the ultrasonic field on the reduction of polarization resistance. The results showed that the concentration impedance in the 30 wt% KOH electrolyte decreased markedly by 44%–51% Ω.

  4. Tribological Analysis of Mg2Si Particulates Reinforced Powder Metallurgy Magnesium Alloy Composites under Oil Lubrication Condition

    Directory of Open Access Journals (Sweden)

    Katsuyoshi Kondoh

    2009-01-01

    Full Text Available For the evaluation of wear behavior of Mg composites under oil lubrication conditions, powder metallurgy Mg97Y2Zn1 alloy reinforced with additive Mg2Si particles were fabricated by the repeated plastic working (RPW and hot extrusion. The RPW process was effective in refining both Mg2Si reinforcements and α-Mg grains causing the matrix hardening. When increasing the repetition number of RPW process from 200 to 600 cycles, the particle size of Mg2Si additives changed from 8 μm to 1~2 μm, and α-Mg grain size was 1 μm or less. With regard to the defensive and offensive properties of Mg alloys reinforced with Mg2Si dispersoids, the composite had superior adhesive wear resistance compared with the conventional Mg alloys because of its extremely high microhardness of 95~180 Hv by RPW process. The uniform distribution of refined Mg2Si particles was useful for improving both defensive and offensive properties against AZ31B counter disk specimens. The Mg2Si prominent dispersoids in the matrix were also effective in forming the oil grooves around them, and caused the low and stable friction coefficient. On the other hand, in the case of the composite containing coarse Mg2Si particles, severely deep scratches were given on the counter face of the AZ31B disk, and resulted in an unstable and high friction coefficient.

  5. Nitrogen alloying of steel powder using ammonia gas in the fluidised bed

    Energy Technology Data Exchange (ETDEWEB)

    Virta, J.; Hannula, S.-P. [VTT Manuf. Technol. (Finland)

    1999-07-01

    Powder nitriding method utilising ammonia gas and fluidised bed technique was developed. The expected advantages of this method are the short processing time, low processing temperature and homogeneous nitrogen content of the powder charge. The nitrogen content of 0.4 wt.-% was achieved in 10 minutes at the temperature of 570 C for AISI 316 L powder. The nitrogen content increased linearly with the nitriding time being 6.8 wt.-% after two hours. For the control of the nitrogen content the heating-up and cooling of the powder must occur in an inert atmosphere. Because of the low processing temperatures nitrogen gas could be used. The short processing times, low processing temperatures and the use of inexpensive processing gases makes the method economically very attractive. (orig.)

  6. Synthesis and characteristics of W-Ni-Fe nano-composite powders prepared by mechanical alloying

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The mixture of 90W-7Ni-3Fe(mass fraction, %) powders was milled in a planetary ball mill. Its structurechanged during milling, the surface characteristics and thermal stability of the milled powders were studied with X-raydiffraction(XRD), Brunaure-Emmett-Teller (BET) nitrogen adsorption technique and differential thermal analysis(DTA). The results show that high-energy ball milling leads to the formation of composite powders with amorphousbinder phase and supersaturated W(Ni, Fe) nano-crystalline grains in which great lattice distortion exists. The crystallization temperature of the amorphous binder phase during heating decreases with milling time. The specific surface area andthe pore size of the powder mixtures decreases with milling time due to agglomeration and welding hetween particles

  7. Structure and magnetic properties of hot pressed powder Co77Si11.5B11.5 alloy

    Directory of Open Access Journals (Sweden)

    J. Konieczny

    2008-12-01

    Full Text Available Purpose: The aim of the work is to investigate the structure and magnetic properties of the cobalt based hot pressed Co77Si11.5B11.5 powder obtained in high-energy ball milling process.Design/methodology/approach: The nanocrystalline ferromagnetic powders were manufactured by high-energy ball milling (SPEX 8000 mill of metallic glasses ribbons in as state. The hot pressing process was made on machine “Degussa”. Observations of the structure of die stampings were made on the OPTON DSM-940 and ZEISS SUPRA 35 scanning electron microscope. Tests of magnetic properties were carried out by the use of Lake Shore’s Vibrating Sample Magnetometer VSM model 7307.Findings: The analysis of the results enabled determination of the hot pressing parameters on magnetic properties and structure of obtained stampings.Research limitations/implications: For the metallic Co-based amorphous ribbons, further mechanical and structure examinations are planed.Practical implications: Structure and magnetic properties analysis of die stampings of powdered amorphous metallic ribbons is helpful to prepare this material by laboratory methods. Feature an alternative to commercial alloys and composite materials are the amorphous and nanocrystalline metal amorphous ribbons obtained by melt spinning technique and make it possible to obtain the new composite materials with best magnetic properties, which dimensions and shape can be freely formed.Originality/value: The paper presents influence of hot pressing parameters process of metallic powdered ribbons Co77Si11.5B11.5 on structure and magnetic properties of obtained die stampings.

  8. The design of cobalt-free, nickel-based alloy powder (Ni-3) used for sealing surfaces of nuclear power valves and its structure of laser cladding coating

    Energy Technology Data Exchange (ETDEWEB)

    Fu Geyan, E-mail: fugeyan@suda.edu.c [School of Mechanical and Electric Engineering, Soochow University, Suzhou 215021 (China); Liu Shuang [School of Mechanical and Electric Engineering, Soochow University, Suzhou 215021 (China); Fan Jiwei [School of Materials Science and Chemical Engineering, Zhongyuan University of Technology, Zhengzhou 450007 (China)

    2011-05-15

    Research highlights: The Ni-3 Co-free alloy coating prepared by laser welding. Ni-3 alloy has excellent combination with stainless steel base. Ni-3 alloy containing those strengthening phases could have excellent wear resistance and anti-oxidation ability at high temperature. - Abstract: To meet the demand of cobalt-free for the cladding coating materials used on sealing surface of nuclear power valves, a new Co-free, Ni-Cr based alloy powder (Ni-3) has been developed. It has been successfully coated on the surface of stainless steel as the strengthening layer. The XRD result reveals that the primary phase of cladding coating is Ni-based solid solution, and the carbides M{sub 7}C{sub 3} and M{sub 23}C{sub 6} as well as several A{sub 3}B types of {gamma}' strengthening phases. It indicates that the alloy possesses the high wear resistance, good corrosion resistance and high temperature tolerance. The test results suggest that the micro-hardness of Ni-3 corresponds to that of alloy Stellite 6 which containing cobalt and currently used as material for nuclear power valves. Hence, the developed Ni-3 alloy powder can be the hopeful candidate material for Co-free cladding material used on the surface of nuclear power valves; it can reduce the nuclear pollution and save the expensive metals.

  9. Studies on in situ magnetic alignment of bonded anisotropic Nd-Fe-B alloy powders

    Science.gov (United States)

    Nlebedim, I. C.; Ucar, Huseyin; Hatter, Christine B.; McCallum, R. W.; McCall, Scott K.; Kramer, M. J.; Paranthaman, M. Parans

    2017-01-01

    Considerations for achieving high degree of alignment in polymer bonded permanent magnets are presented via the results of a study on in situ magnetic alignment of anisotropic Nd-Fe-B magnet powders. Contributions from effect of the alignment temperature, alignment magnetic field and the properties of the polymer on the hard magnetic properties of the bonded magnet were considered. The thermo-rheological properties of the polymer and the response of the magnet powders to the applied magnetic field indicate that hard magnetic properties were optimized at an alignment temperature just above the melting temperature of the EVA co-polymer. This agrees with an observed correlation between the change in magnetization due to improved magnetic alignment of the anisotropic powders and the change in viscosity of the binder. Manufacturing cost can be minimized by identifying optimum alignment temperatures and magnetic field strengths.

  10. Characteristics Of The Porous Body Sintered By Nano-Sized Fe-Cr-Al Alloy Powder

    Directory of Open Access Journals (Sweden)

    Lee Su-In

    2015-06-01

    Full Text Available Porous metal with uniform honeycomb structure was successfully produced by sintering using Fe-Cr-Al nano powder, which was prepared by the pulsed wire evaporation (PWE in ethanol. Its process consisted of the several steps; 1 coating on the surface of polyurethane sponge with the liquid droplets generated from the ethanol-based slurry where the Fe-Cr-Al nano powders were uniformly dispersed, 2 heat treatment of debinding to remove the polyurethane sponge and 3 sintering of the porous green body formed by Fe-Cr-Al nano powders. The strut thickness of porous Fe-Cr-Al was increased by the increase of spraying times in ESP step. Also, The shrinkages and the oxidation resistance of the sintered porous body was increased with increase of sintering temperature. The optimal sintering temperature was shown to 1450°C in views to maximize the oxidation resistance and sinterability.

  11. Producing Fe-W-Co-Cr-C Alloy Cutting Tool Material Through Powder Metallurgy Route

    Science.gov (United States)

    Datta Banik, Bibhas; Dutta, Debasish; Ray, Siddhartha

    2016-06-01

    High speed steel tools can withstand high impact forces as they are tough in nature. But they cannot retain their hardness at elevated temperature i.e. their hot hardness is low. Therefore permissible cutting speed is low and tools wear out easily. Use of lubricants is essential for HSS cutting tools. On the other hand cemented carbide tools can withstand greater compressive force, but due to lower toughness the tool can break easily. Moreover the cost of the tool is comparatively high. To achieve a better machining economy, Fe-W-Co-Cr-C alloys are being used nowadays. Their toughness is as good as HSS tools and hardness is very near to carbide tools. Even, at moderate cutting speeds they can be safely used in old machines having vibration. Moreover it is much cheaper than carbide tools. This paper highlights the Manufacturing Technology of the alloy and studies the comparative tribological properties of the alloy and tungsten mono carbide.

  12. Moessbauer comparative study of Fe-Si (3.5 wt%) alloys produced by melting and by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Sanchez Sthepa, H.; Fajardo, M.; Perez Alcazar, G.A. [Universidad del Valle, A.A, Departamento de Materiales (Colombia)

    1999-11-15

    Moessbauer spectroscopy and X-ray diffraction measurements were done on Fe-Si (3.5 wt%) alloys produced by melting and by mechanical alloying during 15, 30, 50 and 75 milling hours from over 99% purity powders. The Moessbauer spectra were fitted using hyperfine field distribution and it was obtained for all the samples in three ferromagnetic sites with fields of 27, 30 and 33 T for the mechanical alloyed samples and 26.8, 30.13 and 32.83 T for the commercial sample. These three sites are attributed to the pure Fe, Fe with one Si in the next near neighbor (nnn) and Fe with two Si in the nnn. As the milling time increases, the mean field increases too. X-ray diffraction measurement shows that all the samples are BCC, with a lattice parameter that increases with the milling time. These lattice parameters are bigger than that of the commercial alloy.

  13. Production of copper-niobium carbide nanocomposite powders via mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Marques, M.T. [INETI-DMTP, Estrada do Paco do Lumiar, 22, 1649-038 Lisbon (Portugal)]. E-mail: tmarques@ineti.pt; Livramento, V. [INETI-DMTP, Estrada do Paco do Lumiar, 22, 1649-038 Lisbon (Portugal); Correia, J.B. [INETI-DMTP, Estrada do Paco do Lumiar, 22, 1649-038 Lisbon (Portugal); Almeida, A. [IST-Dep. Eng. de Materiais, Av. Rovisco Pais, 1049-001 Lisbon (Portugal); Vilar, R. [IST-Dep. Eng. de Materiais, Av. Rovisco Pais, 1049-001 Lisbon (Portugal)

    2005-06-15

    Nanocrystalline niobium carbide was synthesed in situ in a copper matrix during high-energy milling of elemental powders. Three powder batches were produced with nominal compositions of 5, 10 and 20 vol.% NbC. Characterisation by X-ray diffraction and scanning electron microscopy indicates that early during the milling process a carbide dispersion is formed within a nanostructured copper matrix. After annealing at 873 K, the carbide structure and particle size are maintained, reflecting the ability of the microstructure to resist to coarsening. The hardness levels attained are more than twice those of nanostructured copper.

  14. The structure and phase composition of hard alloys of the Cr3C2-Ti system produced by explosive compacting of powders

    Science.gov (United States)

    Kharlamov, V. O.; Krokhalev, A. V.; Tupitsin, M. A.; Kuz’min, S. V.; Lysak, V. I.

    2017-02-01

    The work presents the findings of theoretical and experimental studies by scanning electron microscopy and energy-dispersive electron microprobe analysis of the phase composition of hard alloys produced by explosive compacting of the powders of chromium carbide Cr3C2 with titanium. It was found that when the powder mixture is heated in shock waves to 660 °C, the phase composition of hard alloys corresponds to that of the initial components of the powder mixture. With the increasing intensity of the explosive compacting, formation of secondary carbides is observed on the border of the initial components. A further increase in temperature results in a local melting and formation of new fine phases. With the subsequent temperature rise in the shock waves, a transition to the calculated equilibrium composition is observed.

  15. Optimization of the processing parameters during internal oxidation of Cu-Al alloy powders using an artificial neural network

    Energy Technology Data Exchange (ETDEWEB)

    Song Kexing; Xing Jiandong; Dong Qiming; Liu Ping; Tian Baohong; Cao Xianjie

    2005-06-15

    Internal oxidation is a commercial method for producing oxide dispersion strengthened copper (ODS Cu). In this paper, the dilute Cu-Al alloy powders containing 0.26 wt% of Al have been internally oxidized at temperatures (T) from 700 to 1000 deg. C, for holding times (t) up to 10 h. The alumina particle size has been observed and determined by electron microscopy using the two-stage preshadowed carbon replica method. By the use of backpropagation network, the non-linear relationship between internal oxidation process parameters (T,t) and alumina particle size has been established on the base of dealing with the experimental data. The results show that the well-trained backpropagation neural network can predict the alumina particle size during internal oxidation precisely and the prediction values have sufficiently mined the basic domain knowledge of internal oxidation process. Therefore, a new way of optimizing process parameters has been provided by the authors.

  16. Role of Disclinations and Nanocrystalline State in the Formation of Quasicrystalline Phases on Mechanical Alloying of Cu-Fe Powders

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    @@Elemental powders of Cu and Fe were ball milled for various time durations up to 100 h. The various stages of forced alloying by ball milling, leading to instability of elemental crystalline phases and formation of quasicrystalline phases were monitored using X-ray diffraction. Diffusion of Fe into the Cu matrix is proposed as the cause which triggers the instability of crystalline phases and leads to the formation of quasicrystalline phases after 10 h of milling. Milling for 100 h resulted in two different quasicrystalline phases with different lattice constants. Role of the nanocrystalline microstructure as an important criterion for the destabilisation of crystalline phases is explained. It is suggested that the formation of nanocrystalline microstructure and their subsequent transformation into quasicrystalline phases may be associated with a continuous increase in the disclination content of the system, which had formed as a result of continued milling and mechanical deformation.

  17. Effect of chromium on the corrosion behaviour of powder-processed Fe–0·45 wt% P alloys

    Indian Academy of Sciences (India)

    Yashwant Mehta; Shefali Trivedi; K Chandra; P S Mishra

    2010-08-01

    The corrosion behaviour of Fe–0·45P with/without addition of chromium, prepared by powder forging route was studied in different environments. The corrosion studies in acidic (0·25 M H2SO4 solution of pH 0·6) and neutral/marine (3·5% NaCl solution of pH 6·8) solutions were conducted using Tafel Extrapolation method. The rate of corrosion in alkaline medium (0·5 M Na2CO3 + 1·0 M NaHCO3 solution of pH 9·4) was measured using linear polarization technique. The studies compare electrolytic Armco iron with Fe–P alloys. It was observed that, chromium improved the resistance to corrosion in acidic and marine environments. The corrosion rates were minimal in alkaline medium and low in neutral solution.

  18. Dental amalgam - the effect of the technology of alloy powder preparation on the corrosion behaviour and the release of mercury

    Energy Technology Data Exchange (ETDEWEB)

    Joska, L.; Bystriansky, J.; Novak, P. [Institute of Chemical Technology, Prague, Institute of Metals and Corrosion Engineering, Technicka 5, 166 28 Prague 6 (Czech Republic)

    2003-03-01

    Dental amalgams are based on a broad spectrum of materials differing in their chemical composition, metallurgical treatment, and in the way the initial alloys powders are prepared. In addition to their chemical composition, amalgams based on various powders differ in both their microstructure and the amount of mercury needed for preparation. All these facts may affect electrochemical processes occurring during their interaction with oral fluids, and also mercury release. While verifying the effect of the technology used for the preparation of the high-copper ternary alloy powder on the properties of resulting amalgams, this study aimed at the mechanism of their interaction with a model saliva solution as well as mercury release was included. Measurements were done in a model saliva solution using standard electrochemical methods and exposition measurements. The interaction of individual types of amalgams with artificial saliva did not reveal any significant differences. The free corrosion potential of all these amalgams in an aerated solution settled in the range of values in which tin oxidation, resulting in a layer of insoluble corrosion products, turned out to be the dominant anodic process. The rate of mercury release was the lowest for amalgams based on a gas-atomized alloy. The highest rate of mercury release, and also its dependence on time, was exhibited by lathe-cut powder based amalgam. In addition to different volume fraction of the Ag-Hg phase and the level of its tin alloying, this different behaviour may be explained by differences in the rate at which a layer of tin corrosion products acting as a barrier to mercury release is formed. (Abstract Copyright [2003], Wiley Periodicals, Inc.) [German] Dentalamalgame basieren auf einem breitem Spektrum von Werkstoffen, die sich in ihrer chemischen Zusammensetzung, der metallurgischen Behandlung und der Art, wie die Ausgangslegierungspulver hergestellt werden, unterscheiden. Zusaetzlich zu ihrer chemischen

  19. Powder metallurgy and mechanical alloying effects on the formation of thermally induced martensite in an FeMnSiCrNi SMA

    Directory of Open Access Journals (Sweden)

    Pricop Bogdan

    2015-01-01

    Full Text Available By ingot metallurgy (IM, melting, alloying and casting, powder metallurgy (PM, using as-blended elemental powders and mechanical alloying (MA of 50 % of particle volume, three types of FeMnSiCrNi shape memory alloy (SMA specimens were fabricated, respectively. After specimen thickness reduction by hot rolling, solution treatments were applied, at 973 and 1273 K, to thermally induce martensite. The resulting specimens were analysed by X-ray diffraction (XRD and scanning electron microscopy (SEM, in order to reveal the presence of ε (hexagonal close-packed, hcp and α’ (body centred cubic, bcc thermally induced martensites. The reversion of thermally induced martensites, to γ (face centred cubic, fcc austenite, during heating, was confirmed by dynamic mechanical analysis (DMA, which emphasized marked increases of storage modulus and obvious internal friction maxima on DMA thermograms. The results proved that the increase of porosity degree, after PM processing, increased internal friction, while MA enhanced crystallinity degree.

  20. Laser engineered surfaces from glass forming alloy powder precursors : Microstructure and wear

    NARCIS (Netherlands)

    Matthews, D. T. A.; Ocelik, V.; Branagan, D.; de Hosson, J. Th. M.

    2009-01-01

    Fe-based metallic glass forming powders have been deposited on mild steel substrates using high power laser cladding. Coatings microstructures have been analysed by scanning- and transmission-electron microscopy and at varying substrate dilutions, have been found to comprise a 100 to 500 nm interden

  1. Demonstration of Shear Localization in Ultrafine Grained Tungsten Alloys via Powder Metallurgy Processing Route

    Science.gov (United States)

    2012-09-01

    Hardness Vickers microhardness tests were performed to determine the hardness of the material. Indents were analyzed to determine basic information...shear banding observed in depleted uranium. Microhardness testing indicated that the boron containing sample had a higher propensity to shear...18 cm3) tungsten based alloy tested in the as-sintered state. 15. SUBJECT TERMS tungsten, shear localization, kinetic energy penetrator, depleted

  2. Histomorphologic evaluation of Ti-13Nb-13Zr alloys processed via powder metallurgy. A study in rabbits

    Energy Technology Data Exchange (ETDEWEB)

    Bottino, M.C. [Department of Materials Science and Engineering, University of Alabama at Birmingham, BEC 254 1530 3rd Avenue South, Birmingham, AL, 35294 (United States); Coelho, P.G. [Department of Biomaterials and Biomimetics, New York University, College of Dentistry, 345 East 24th Street, Room 804S, New York, NY, 10100 (United States)], E-mail: pgcoelho@nyu.edu; Yoshimoto, M. [Materials Science and Technology Center, Institute for Energy and Nuclear Research, Av. Prof. Lineu Prestes, 2242, Sao Paulo, SP, 05508-000 (Brazil); Koenig, B. [Department of Anatomy, Institute of Biomedical Sciences, University of Sao Paulo (ICB-USP) Av. Prof. Lineu Prestes, 2415, Sao Paulo, SP, 05508-900 (Brazil); Henriques, V.A.R. [Materials Division (AMR/IAE), CTA Brazilian Aerospace Technical Center, Sao Jose dos Campos, SP, 12228-904 (Brazil); Bressiani, A.H.A.; Bressiani, J.C. [Materials Science and Technology Center, Institute for Energy and Nuclear Research, Av. Prof. Lineu Prestes, 2242, Sao Paulo, SP, 05508-000 (Brazil)

    2008-03-10

    This study presents the in-vivo evaluation of Ti-13Nb-13Zr alloy implants obtained by the hydride route via powder metallurgy. The cylindrical implants were processed at different sintering and holding times. The implants' were characterized for density, microstructure (SEM), crystalline phases (XRD), and bulk (EDS) and surface composition (XPS). The implants were then sterilized and surgically placed in the central region of the rabbit's tibiae. Two double fluorescent markers were applied at 2 and 3 weeks, and 6 and 7 weeks after implantation. After an 8-week healing period, the implants were retrieved, non-decalcified section processed, and evaluated by electron, UV light (fluorescent labeling), and light microscopy (toluidine blue). BSE-SEM showed close contact between bone and implants. Fluorescent labeling assessment showed high bone activity levels at regions close to the implant surface. Toluidine blue staining revealed regions comprising osteoblasts at regions of newly forming/formed bone close to the implant surface. The results obtained in this study support biocompatible and osseoconductive properties of Ti-13Nb-13Zr processed through the hydride powder route.

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

    Science.gov (United States)

    Chellman, D. J.

    1984-01-01

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

  4. Bulk amorphous Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} alloys fabricated by consolidation of mechanically alloyed amorphous powders

    Energy Technology Data Exchange (ETDEWEB)

    Zhu, Bo; Wang, Xinfu; Li, Xianyu; Wang, Dan; Qin, Yong; Han, Fusheng, E-mail: fshan@issp.ac.cn

    2014-02-15

    Highlights: • Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} (x = 0, 6.25, and 12.5 at%) amorphous powders were synthesized by MA. • Bulk Al{sub 75}V{sub 12.5}Fe{sub 12.5} amorphous alloy is obtained by means of hydraulic pressing. • The Vickers microhardness of bulk sample is in the range of 821-927 HV. -- Abstract: Hydraulic press was used to produce bulk amorphous Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} (x = 0, 6.25, and 12.5) (at.%) alloy by consolidation of mechanically alloyed amorphous powder. The as-milled powders and bulk alloy were examined by X-ray diffraction, transmission electron microscopy and differential scanning calorimetry. The glass-forming ability was evaluated in accordance with the milling time. The results show that the glass-forming ability of the mechanical-alloyed Al{sub 75}V{sub 12.5}Fe{sub 12.5−x}Cu{sub x} powders decreases with the increase of x. The onset crystallization temperatures (T{sub x}{sup onset}) of the three powders are 749 K, 771 K and 712 K, respectively. The results also indicate that the quality of consolidation is very good and the product’s Vickers microhardness is relatively high (821–927 HV)

  5. XRD and TEM characterizations of the mechanically alloyed CuIn{sub 0.5}Ga{sub 0.5}Se{sub 2} powders

    Energy Technology Data Exchange (ETDEWEB)

    Benslim, N. [Laboratoire d' Etude de Surfaces et Interfaces de la Matiere Solide (LESIMS), Departement de Physique, Faculte des Sciences, Universite Badji Mokhtar, Annaba (Algeria); Mehdaoui, S., E-mail: fac782004@yahoo.f [Laboratoire d' Etude de Surfaces et Interfaces de la Matiere Solide (LESIMS), Departement de Physique, Faculte des Sciences, Universite Badji Mokhtar, Annaba (Algeria); Aissaoui, O.; Benabdeslem, M.; Bouasla, A.; Bechiri, L. [Laboratoire d' Etude de Surfaces et Interfaces de la Matiere Solide (LESIMS), Departement de Physique, Faculte des Sciences, Universite Badji Mokhtar, Annaba (Algeria); Otmani, A. [Laboratoire de Recherche en Physico-Chimie des Surfaces et Interfaces (LRPCSI), Faculte des Sciences, Universite de Skikda, BP26 route El-Hadaek 21000, Skikda (Algeria); Portier, X. [Cimap-ENSICAEN, Universite, 6 Boulevard du Marechal Juin, 14050 Caen (France)

    2010-01-21

    The CuIn{sub 0.5}Ga{sub 0.5}Se{sub 2} (CIGS) nanocrystalline powders were prepared by mechanical alloying method. Effect of various milling times and higher milling speed on the structure of CIGS nanoparticles was investigated by X-ray diffraction measurements. The Rietveld method was used to refine the XRD data using the MAUD program. Refinement process reveals that the main phase of the CIGS powders milled for different milling times is of chalcopyrite structure. Milling time dependence of the unit-cell parameters and crystallite size has also been reported. The TEM observations demonstrated that the size of agglomerated CIGS powder is about 140 nm. The EDAX analysis of various grains of the milled powder shows that the compositions vary from one grain to another. However, the global composition was found slightly copper rich.

  6. Effect of Sintering Atmosphere and Solution Treatment on Density, Microstructure and Tensile Properties of Duplex Stainless Steels Developed from Pre-alloyed Powders

    Science.gov (United States)

    Murali, Arun Prasad; Mahendran, Sudhahar; Ramajayam, Mariappan; Ganesan, Dharmalingam; Chinnaraj, Raj Kumar

    2017-01-01

    In this research, Powder Metallurgy (P/M) of Duplex Stainless Steels (DSS) of different compositions were prepared through pre-alloyed powders and elemental powders with and without addition of copper. The powder mix was developed by pot mill for 12 h to obtain the homogeneous mixture of pre-alloyed powder with elemental compositions. Cylindrical green compacts with the dimensions of 30 mm diameter and 12 mm height were compacted through universal testing machine at a pressure level of 560 ± 10 MPa. These green compacts were sintered at 1350 °C for 2 h in hydrogen and argon atmospheres. Some of the sintered stainless steel preforms were solution treated at 1050 °C followed by water quenching. The sintered as well as solution treated samples were analysed by metallography examination, Scanning Electron Microscopy and evaluation of mechanical properties. Ferrite content of sintered and solution treated DSS were measured by Fischer Ferritoscope. It is inferred that the hydrogen sintered DSS depicted better density (94% theoretical density) and tensile strength (695 MPa) than the argon sintered steels. Similarly the microstructure of solution treated DSS revealed existence of more volume of ferrite grains than its sintered condition. Solution treated hydrogen sintered DSS A (50 wt% 316L + 50 wt% 430L) exhibited higher tensile strength of 716 MPa and elongation of 17%, which are 10-13% increment than the sintered stainless steels.

  7. The characterization of magnetic and photo-catalytic properties of nanocrystalline Ni-doped TiO{sub 2} powder synthesized by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Uhm, Young Rang [Nuclear Nano Materials Developmen Lab., Korea Atomic Energy Research Institute, KAERI, Daejeon 305-600 (Korea, Republic of); Woo, Seung Hee [Nuclear Nano Materials Developmen Lab., Korea Atomic Energy Research Institute, KAERI, Daejeon 305-600 (Korea, Republic of); Kim, Whung Whoe [Nuclear Nano Materials Developmen Lab., Korea Atomic Energy Research Institute, KAERI, Daejeon 305-600 (Korea, Republic of); Kim, Sun Jae [Department of Advanced Materials Engineering, Sejong University, Seoul 143-747 (Korea, Republic of); Rhee, Chang Kyu [Nuclear Nano Materials Developmen Lab., Korea Atomic Energy Research Institute, KAERI, Daejeon 305-600 (Korea, Republic of)]. E-mail: ckrhee@kaeri.re.kr

    2006-09-15

    Nanocrystalline Ni-doped TiO{sub 2} powders were prepared by mechanical alloying. The X-ray patterns for samples showed three phases of TiO{sub 2} such as rutile, anatase and brookhite. Transmission electron microscopy analyses were carried out to clarify morphologies and position of Ni within the mechanically alloyed powders. The Ni-doped powder consisted of spherical particles and average grain size was less than 10 nm. For the Ni-doped TiO{sub 2}, the colour of powders changes from white to bright yellow with increasing concentration of Ni. The UV-vis absorption showed that the UV absorption for the Ni-doped powder shifted to a longer wavelength (red shift) and the photo-efficiency was enhanced. The absorption threshold depends on the concentration of nano-sized Ni dopant. Ferromagnetic behaviour such as the magnetic hysteresis loops was observed at room temperature. The coercivity (H {sub c}) changed from 40 to 60 Oe with increasing Ni concentration. Based on the UV absorption and magnetization, the dopant level is localized to the valence band of TiO{sub 2}.

  8. Phase evolution during early stages of mechanical alloying of Cu–13 wt.% Al powder mixtures in a high-energy ball mill

    Energy Technology Data Exchange (ETDEWEB)

    Dudina, Dina V.; Lomovsky, Oleg I. [Institute of Solid State Chemistry and Mechanochemistry SB RAS, Kutateladze str. 18, Novosibirsk 630128 (Russian Federation); Valeev, Konstantin R.; Tikhov, Serguey F.; Boldyreva, Natalya N. [Boreskov Institute of Catalysis SB RAS, pr. Lavrentieva 5, Novosibirsk 630090 (Russian Federation); Salanov, Aleksey N.; Cherepanova, Svetlana V.; Zaikovskii, Vladimir I. [Boreskov Institute of Catalysis SB RAS, pr. Lavrentieva 5, Novosibirsk 630090 (Russian Federation); Novosibirsk State University (NSU), Pirogova str. 2, Novosibirsk 630090 (Russian Federation); Andreev, Andrey S. [Boreskov Institute of Catalysis SB RAS, pr. Lavrentieva 5, Novosibirsk 630090 (Russian Federation); Novosibirsk State University (NSU), Pirogova str. 2, Novosibirsk 630090 (Russian Federation); Soft Matter Sciences and Engineering Laboratory, UMR 7615 CNRS UPMC, ESPCI ParisTech, 10 rue Vauquelin, Paris 75005 (France); Lapina, Olga B.; Sadykov, Vladislav A. [Boreskov Institute of Catalysis SB RAS, pr. Lavrentieva 5, Novosibirsk 630090 (Russian Federation); Novosibirsk State University (NSU), Pirogova str. 2, Novosibirsk 630090 (Russian Federation)

    2015-04-25

    Highlights: • Phase formation during early stages of Cu–Al mechanical alloying was studied. • The products of mechanical alloying are of highly non-equilibrium character. • X-ray amorphous phases are present in the products of mechanical alloying. • An Al-rich X-ray amorphous phase is distributed between the crystallites. - Abstract: We report the phase and microstructure evolution of the Cu–13 wt.% Al mixture during treatment in a high-energy planetary ball mill with a particular focus on the early stages of mechanical alloying. Several characterization techniques, including X-ray diffraction phase analysis, nuclear magnetic resonance spectroscopy, differential dissolution, thermal analysis, and electron microscopy/elemental analysis, have been combined to study the evolution of the phase composition of the mechanically alloyed powders and describe the microstructure of the multi-phase products of mechanical alloying at different length scales. The following reaction sequence has been confirmed: Cu + Al → CuAl{sub 2}(+Cu) → Cu{sub 9}Al{sub 4} + (Cu) → Cu(Al). The phase evolution was accompanied by the microstructure changes, the layered structure of the powder agglomerates disappearing with milling time. This scheme is further complicated by the processes of copper oxidation, reduction of copper oxides by metallic aluminum, and by variation of the stoichiometry of Cu(Al) solid solutions with milling time. Substantial amounts of X-ray amorphous phases were detected as well. Differential dissolution technique has revealed that a high content of aluminum in the Cu(Al) solid solution-based powders is due to the presence of Al-rich phases distributed between the Cu(Al) crystallites.

  9. Microstructural evolution and final properties of a cold-swaged multifunctional Ti–Nb–Ta–Zr–O alloy produced by a powder metallurgy route

    Energy Technology Data Exchange (ETDEWEB)

    Guo, W., E-mail: wei.guo@unsw.edu.au [School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Australian Research Council Centre of Excellence for Design in Light Metals (Australia); Quadir, M.Z., E-mail: mzquadir@unsw.edu.au [School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Australian Research Council Centre of Excellence for Design in Light Metals (Australia); Electron Microscope Unit, University of New South Wales, NSW 2052 (Australia); Moricca, S., E-mail: sam.moricca@ansto.gov.au [Institute of Materials Engineering, Australian Nuclear Science and Technology Organization (ANSTO), NSW 2232 (Australia); Eddows, T., E-mail: tex@ansto.gov.au [Institute of Materials Engineering, Australian Nuclear Science and Technology Organization (ANSTO), NSW 2232 (Australia); Ferry, M., E-mail: m.ferry@unsw.edu.au [School of Materials Science and Engineering, University of New South Wales, Sydney, NSW 2052 (Australia); Australian Research Council Centre of Excellence for Design in Light Metals (Australia)

    2013-07-15

    Body centred cubic (BCC) β-phase multifunctional titanium alloys have been developed with a very unique combination of thermal and mechanical properties. In this investigation, a very low porosity Ti–36.8–Nb–2.7Zr–2.0Ta–0.44O (wt%) alloy was produced by powder sintering, hot forging, solution treatment and cold swaging. X-ray diffraction and transmission electron microscopy (TEM) of the solution treated alloy revealed the presence of a small amount of ω-phase in a predominantly BCC β-phase matrix. Electron backscatter diffraction (EBSD) of the swaged alloy revealed a highly elongated and fragmented microstructure, and a strong 〈110〉 fibre texture. TEM also revealed the existence of stress-induced twin lamella, dislocations and ω-phase. Consistent with previous studies on these types of alloys, the swaged alloy exhibited non-linear elasticity during tensile straining, low elastic modulus (45.4 GPa), high elastic limit (2.3%), high elongation to failure (8.1%), and a high yield strength (880 MPa) and tensile strength (940 MPa). The coefficient of thermal expansion was also low (∼5×10{sup −6} K{sup −1} between 50 and 300 °C) in this alloy.

  10. Numerical Simulation for Heat and Mass Transfer During Selective Laser Melting of Titanium alloys Powder

    Science.gov (United States)

    Li, Cheng-Jui; Tsai, Tsung-Wen; Tseng, Chien-Chou

    The purpose of this research is to analyse the complex phase change and the heat transfer behavior of the Ti-6Al-4 V powder particle during the Selective Laser Melting (SLM) process. In this study, the rapid melting and solidification process is presented by Computational Fluid Dynamics (CFD) approach under the framework of the volume-of-fluid (VOF) method. The interaction between the laser velocity and power to the solidification shape and defects of the metal components will be studied numerically as a guideline to improve quality and reduce costs.

  11. Using Alloys of Cr-Ni-Co system as metallic bond in powder metallurgy products

    Directory of Open Access Journals (Sweden)

    A. M. Gazaliyev

    2015-10-01

    Full Text Available There is studied the possibility of using alloys of the Cr-Ni-Cо system as a metallic bond in producing ceramet. As the basic material there was used titanium carbide. There were measured such mechanical properties as bending strength, tensile strength, impact viscosity. There is considered a possibility of using ceramet with a metallic bond of the Cr-Ni-Co system as a refractory material. As a heat resistance indicator there was estimated the limit of long durability. It is established that in the studied range of temperatures the material properties are the function of the bond content.

  12. STRUCTURE, PHASE COMPOSITION AND PROPERTIES OF GAS-THERMAL COVERINGS OF MECHANICALLY ALLOYED THERMOREACTING COMPOSITE POWDERS OF NICKEL-ALUMINIUM SYSTEM

    Directory of Open Access Journals (Sweden)

    F. G. Lovshenko

    2015-01-01

    Full Text Available The presented results show that coverings from mechanically alloyed thermoreacting powders of system «nickel–aluminum» are nonequilibrium multiphase systems which basis represents solid solution of aluminum in nickel. It has the microcrystalline type of structure which is characterized by an advanced surface of borders of the grains and subgrains stabilized by nanodimensional inclusions of oxides and alyuminid. These coverings surpass by 1,2–1,6 times analogs in durability, hardness and wear resistance.

  13. Preparation of fine-grained tungsten heavy alloys by spark plasma sintered W–7Ni–3Fe composite powders with different ball milling time

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, D.P., E-mail: dpxiang@hainu.edu.cn [Key Laboratory of Advanced Materials of Tropical Island Resources, Ministry of Education, Hainan University, Haikou 570228 (China); School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China); Ding, L. [Key Laboratory of Advanced Materials of Tropical Island Resources, Ministry of Education, Hainan University, Haikou 570228 (China); Li, Y.Y.; Chen, G.B. [School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China); Zhao, Y.W. [Key Laboratory of Advanced Materials of Tropical Island Resources, Ministry of Education, Hainan University, Haikou 570228 (China)

    2013-06-15

    Highlights: ► We fabricate fine-grained W–7Ni–3Fe alloys using HEBM assisted SPS method. ► The γ-(Ni, Fe, W) phase is not observed in HEBM raw powders. ► The density of the WHAs gradually decreased with increasing HEBM time. ► The hardness and bending strength of the WHAs show different trends of variation. ► The intergranular fracture was the main bending fracture mode of the WHAs. -- Abstract: The fine-grained tungsten heavy alloys (WHAs) with grain size of about 1–3 μm were successfully prepared by spark plasma sintered W–7Ni–3Fe composite powders with different high-energy ball milling (HEBM) time. This study analyzes the effects of HEBM time not only on the composite powders but on the microstructure and mechanical properties of WHAs. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) were used to investigate the microstructure and phase evolution rules of powders and alloys, respectively. The γ-(Ni, Fe, W) is not observed in XRD patterns of the ball milled powders. With prolonging HEBM time, the W phase diffraction peak becomes increasingly wider, and its intensity continues to decline. However, the completely amorphous structures are not formed even after HEBM 40 h. The relative density of the WHAs prepared by HEBM assisted SPS technique decreases gradually with increasing the ball milling time. For the WHAs sintered in 1150 °C for 8 min, the W grains grow finer and the content of the γ-(Ni, Fe, W) binding phase greatly increases with prolonging the HEBM time. Meanwhile, over 5 h of HEBM time, the bending strength continuously decreases and the hardness slightly increases. The intergranular fracture of the W grains is the main bending fracture mode in all the WHAs. The microporous of different sizes are distributed on the bending fracture and progressively increased with prolonging the ball milling time.

  14. Identification of Optimum Magnetic Behavior of NanoCrystalline CmFeAl Type Heusler Alloy Powders Using Response Surface Methodology

    Science.gov (United States)

    Srivastava, Y.; Srivastava, S.; Boriwal, L.

    2016-09-01

    Mechanical alloying is a novelistic solid state process that has received considerable attention due to many advantages over other conventional processes. In the present work, Co2FeAl healer alloy powder, prepared successfully from premix basic powders of Cobalt (Co), Iron (Fe) and Aluminum (Al) in stoichiometric of 60Co-26Fe-14Al (weight %) by novelistic mechano-chemical route. Magnetic properties of mechanically alloyed powders were characterized by vibrating sample magnetometer (VSM). 2 factor 5 level design matrix was applied to experiment process. Experimental results were used for response surface methodology. Interaction between the input process parameters and the response has been established with the help of regression analysis. Further analysis of variance technique was applied to check the adequacy of developed model and significance of process parameters. Test case study was performed with those parameters, which was not selected for main experimentation but range was same. Response surface methodology, the process parameters must be optimized to obtain improved magnetic properties. Further optimum process parameters were identified using numerical and graphical optimization techniques.

  15. Effect of Al2O3 Micro-powder Additives on the Properties of Micro-arc Oxidation Coatings Formed on 6061 Aluminum Alloy

    Science.gov (United States)

    Wang, Ping; Wu, Ting; Xiao, You Tao; Pu, Jun; Guo, Xiao Yang; Huang, Jun; Xiang, Chun Lang

    2016-09-01

    Al2O3 micro-powder was suspended in the basis electrolyte to form micro-arc oxidation (MAO) coatings on 6061 aluminum alloy by MAO. During the stage of micro-arc oxidation, Al2O3 micro-powder with negative surface charge was melted by the micro-arc around the anode and incorporated into the MAO coatings. With the continuous addition of Al2O3 micro-powder, the oxidation voltages rose up firstly and then decreased. The surface and cross-sectional morphologies showed that the size of micropores decreased and the MAO coatings surface got loosened following the variation in Al2O3 micro-powder concentration. As a consequence of the changing coating structure, the corrosion resistance of the coatings decreased apparently. The micro-hardness of the coatings increased firstly and then decreased, opposite to the trend of the average friction coefficient. It revealed the minimum average friction coefficient of MAO coatings and maximum adhesion between the coatings and substrate when 2.0 g/L Al2O3 micro-powder was added into electrolyte. There were visible cracks and peelings on the coating surface merely at 4.0 g/L after thermal shock tests. The x-ray diffraction results indicated that the addition of Al2O3 micro-powder had less effect on the phase composition of MAO coatings.

  16. Biaxially textured articles formed by powder metallurgy

    Science.gov (United States)

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2003-07-29

    A biaxially textured alloy article having a magnetism less than pure Ni includes a rolled and annealed compacted and sintered powder-metallurgy preform article, the preform article having been formed from a powder mixture selected from the group of mixtures consisting of: at least 60 at % Ni powder and at least one of Cr powder, W powder, V powder, Mo powder, Cu powder, Al powder, Ce powder, YSZ powder, Y powder, Mg powder, and RE powder; the article having a fine and homogeneous grain structure; and having a dominant cube oriented {100} orientation texture; and further having a Curie temperature less than that of pure Ni.

  17. Potential applications of cold sprayed Cu50Ti20Ni30 metallic glassy alloy powders for antibacterial protective coating in medical and food sectors.

    Science.gov (United States)

    El-Eskandrany, M Sherif; Al-Azmi, Ahmed

    2016-03-01

    Mechanical alloying was utilized for synthesizing of metallic glassy Cu50Ti20Ni30 alloy powders, using a low energy ball milling technique. The metallic glassy powders obtained after 100 h of ball milling had an average particle size of 1.7 mm in diameter and possessed excellent thermal stability, indexed by a relatively high glass transition temperature (358.3 °C) with a wide supercooled liquid region (61 °C). This amorphous phase crystallized into Ti2Cu and CuTiNi2 ordered phases through two overlapped crystallization temperatures at 419.3 °C and 447.5 °C, respectively. The total enthalpy change of crystallization was -4.8 kJ/mol. The glassy powders were employed as feedstock materials to double-face coating the surface of SUS 304 substrate, using cold spraying process under helium gas pressure at 400 °C. This coating material had an extraordinary high nanohardness value of 3.1 GPa. Moreover, it showed a high resistance to wear with a low value of the coefficient of friction ranging from 0.45 to 0.45. Biofilms were grown on 20-mm(2) SUS304 sheets coated coupons inoculated with 1.5 × 10(8) CFU ml(-1)E. coli. Significant biofilm inhibition (p The inhibition of biofilm formation by nanocrystalline powders of Cu-based provides a practical approach to achieve the inhibition of biofilms formation.

  18. The effect of ageing on microstructure and mechanical properties of powder Ti–5Al–5Mo–5V–1Cr–1Fe alloy

    Energy Technology Data Exchange (ETDEWEB)

    Ahmed, Mansur, E-mail: ma960@uowmail.edu.au [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2522 (Australia); Savvakin, Dmytro G.; Ivasishin, Orest M. [Institute for Metal Physics, National Academy of Sciences of Ukraine, UA-03142 Kiev (Ukraine); Pereloma, Elena V. [School of Mechanical, Materials and Mechatronic Engineering, University of Wollongong, NSW 2522 (Australia); Electron Microscopy Centre, University of Wollongong, NSW 2519 (Australia)

    2014-05-01

    The thermo-mechanically processed powder Ti–5Al–5V–5Mo–1Cr–1Fe alloy was aged at 923 K for 1–8 h in order to investigate the effect of ageing time on the microstructure–mechanical properties relationships. The microstructures of the alloy after ageing consist of the both primary and secondary α phases with retained β matrix phase. The shift of β peaks in X-ray pattern with ageing time indicates an increase in lattice parameter distortion due to diffusion into the retained β phase of more β stabilisers with smaller atomic radius compared to the elemental Ti. The tensile test results indicate that the sample aged for 1 h has achieved the best combination of mechanical properties with ultimate tensile strength of 1194 MPa and total elongation of 14.1% among all the experimented conditions. The modified Crussard–Jaoul method is applied to characterise the work hardening behaviour of the alloy.

  19. Fatigue-crack-initiation numerical modelling of a Ni-base powder metallurgy alloy

    Institute of Scientific and Technical Information of China (English)

    2012-01-01

    A simplified three-dimensional numerical model was presented to simulate the micro-crack nucleation and growth to some predefined dimension(approximately 0.38 mm) on the throat surface of a Ni-base powder metallurgy(PM) specimen.The numerical simulation of micro-crack initiation was based on the Tanaka-Mura micro-crack initiation models,where individual grains of the mesoscopic model were simulated using the Voronoi tessellation.Four improvements were made in the model.(1) Considering crack initiation along with 12 principal slip systems on octahedral slip planes of face centered cubic(FCC) crystal in three-dimensional(3-D) models.(2) Considering the effect of secondary phase precipitate due to impinging slip and dislocation pileup.(3) The Tanaka-Mura theory of fatigue-crack-initiation from notches was applied to simulate the crack initiation from another crack tip.(4) The coalescence of random initiated micro-cracks was simulated once they intersected with each other and a macro-crack was finally formed.The calculated results were in good agreement with the experimental data which verified the rationality of the simulation model.The applicability of the proposed model for treating fatigue-crack-initiation life in engineering structures was preliminarily achieved.%A simplified three-dimensional numerical model was presented to simulate the micro-crack nucleation and growth to some predefined dimension(approximately 0.38 mm) on the throat surface of a Ni-base powder metallurgy(PM) specimen.The numerical simulation of micro-crack initiation was based on the Tanaka-Mura micro-crack initiation models,where individual grains of the mesoscopic model were simulated using the Voronoi tessellation.Four improvements were made in the model.(1) Considering crack initiation along with 12 principal slip systems on octahedral slip planes of face centered cubic(FCC) crystal in three-dimensional(3-D) models.(2) Considering the effect of secondary phase

  20. Microstructural characterization and amorphous phase formation in Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} powders produced by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Taghvaei, Amir Hossein, E-mail: amirtaghvaei@gmail.com [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of); Stoica, Mihai [IFW Dresden, Institute for Complex Materials, Helmholtzstr. 20, D-01069 Dresden (Germany); Vaughan, Gavin [ESRF, F-38042 Grenoble (France); Ghaffari, Mohammad [School of Electrical and Electronic Engineering, Nanyang Technological University, Nanyang Avenue, Singapore 639798 (Singapore); Maleksaeedi, Saeed [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, Singapore 638075 (Singapore); Janghorban, Kamal [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz (Iran, Islamic Republic of)

    2012-01-25

    Highlights: Black-Right-Pointing-Pointer Mechanical alloying developed the amorphous phase in Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} alloy. Black-Right-Pointing-Pointer The powders had 96 wt% amorphous phase after 200 h milling. Black-Right-Pointing-Pointer The 200 h milled powders showed the huge relaxation hump in the DSC plot. Black-Right-Pointing-Pointer The mean volume lattice strain was calculated based on the Miracle's model. - Abstract: In this work, microstructural evolution and amorphous phase formation in Co{sub 40}Fe{sub 22}Ta{sub 8}B{sub 30} alloy produced by mechanical alloying (MA) of the elemental powder mixture under argon gas atmosphere was investigated. Milling time had a profound effect on the phase transformation, microstructure, morphological evolution and thermal behavior of the powders. These effects were studied by the X-ray powder diffraction (XRD) in reflection mode using Cu K{alpha} and in transmission configuration using synchrotron radiation, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and differential scanning calorimetry (DSC). The results showed that at the early stage of the milling, microstructure consisted of nanocrystalline bcc-(Fe, Co) phases and unreacted tantalum. Further milling, produced an amorphous phase, which became a dominant phase with a fraction of 96 wt% after 200 h milling. The DSC profile of 200 h milled powders demonstrated a huge and broad exothermic hump due to the structural relaxation, followed by a single exothermic peak, indicating the crystallization of the amorphous phase. Further XRD studies in transmission mode by synchrotron radiation revealed that the crystalline products were (Co, Fe){sub 20.82}Ta{sub 2.18}B{sub 6}, (Co, Fe){sub 21} Ta{sub 2} B{sub 6}, and (Co, Fe){sub 3}B{sub 2}. The amorphization mechanisms were discussed in terms of severe grain refinement, atomic size effect, the concept of local topological instability and the heat of mixing of the reactants.

  1. Application of ultrasound irradiation on sol-gel technique for corrosion protection of Al65Cu20Fe15 alloy powder

    Science.gov (United States)

    Liang, Bo; Zhang, Baoyan; Wang, Guodong; Li, Di; Zhang, Xiaoming

    2013-11-01

    Al65Cu20Fe15 alloy powder was firstly encapsulated by the conventional sol-gel technique utilizing tetraethoxysilane (TEOS) as the precursor in order to improve its corrosion resistance. The optimization was based on nine well-planned orthogonal experiments (L9 (34)). Four main factors in the encapsulation process (i.e. reaction temperature, ethylenediamine concentration, TEOS concentration and feeding method) were investigated. According to the visual analyses of the result, the optimum condition was obtained. Based on the optimal condition in the conventional sol-gel technique, the encapsulation process was then conducted under ultrasonic irradiation. The effects of ultrasound amplitude and irradiation time on the encapsulation process were also studied. FTIR, XRD, SEM, DLS and EDS were also used to characterize the resulting sample. Finally, the corrosion inhibition efficiency of encapsulated powder attained 99.3% in the acidic condition of pH 1, and the average grain size (d50) of the encapsulated powder was just 4.8% larger than that of the raw powder, implying that there was a thin silica film on the surface of powder.

  2. Phase composition, microstructure, and mechanical properties of porous Ti-Nb-Zr alloys prepared by a two-step foaming powder metallurgy method.

    Science.gov (United States)

    Rao, X; Chu, C L; Zheng, Y Y

    2014-06-01

    Porous Ti-Nb-Zr alloys with different porosities from 6.06 to 62.8% are prepared by a two-step foaming powder metallurgy method using TiH2, Nb, and Zr powders together with 0 to 50wt% of NH4HCO3. The effects of the amounts of Nb and Zr as well as the sintering temperature (1473 to 1673K) on their phase composition, porosity, morphology, and mechanical characteristics are investigated. By controlling the porosity, Nb and Zr concentrations as well as the sintering temperature, porous Ti-Nb-Zr alloys with different mechanical properties can be obtained, for example, the hardness between 290 and 63HV, the compressive strength between 1530.5 and 73.4MPa, and the elastic modulus between 10.8 and 1.2GPa. The mechanical properties of the sintered porous Ti-Nb-Zr alloys can be tailored to match different requirements for the human bones and are thus potentially useful in the hard tissue implants.

  3. In situ elaboration of a binary Ti–26Nb alloy by selective laser melting of elemental titanium and niobium mixed powders

    Energy Technology Data Exchange (ETDEWEB)

    Fischer, M. [Laboratoire d' Etude des Microstructures et de Mécanique des Matériaux LEM3 (UMR CNRS 7239), Université de Lorraine, Ile de Saulcy, F-57045 Metz (France); Joguet, D. [Laboratoire d' Etudes et de Recherches sur les Matériaux, les Procédés et les Surfaces LERMPS, Université de Technologie de Belfort Montbéliard, Sevenans, 90010 Belfort (France); Robin, G. [Laboratoire d' Etude des Microstructures et de Mécanique des Matériaux LEM3 (UMR CNRS 7239), Université de Lorraine, Ile de Saulcy, F-57045 Metz (France); Peltier, L. [Laboratoire d' Etude des Microstructures et de Mécanique des Matériaux LEM3 (UMR CNRS 7239), Ecole Nationale Supérieure d' Arts et Métiers, F-57078 Metz (France); Laheurte, P. [Laboratoire d' Etude des Microstructures et de Mécanique des Matériaux LEM3 (UMR CNRS 7239), Université de Lorraine, Ile de Saulcy, F-57045 Metz (France)

    2016-05-01

    Ti–Nb alloys are excellent candidates for biomedical applications such as implantology and joint replacement because of their very low elastic modulus, their excellent biocompatibility and their high strength. A low elastic modulus, close to that of the cortical bone minimizes the stress shielding effect that appears subsequent to the insertion of an implant. The objective of this study is to investigate the microstructural and mechanical properties of a Ti–Nb alloy elaborated by selective laser melting on powder bed of a mixture of Ti and Nb elemental powders (26 at.%). The influence of operating parameters on porosity of manufactured samples and on efficacy of dissolving Nb particles in Ti was studied. The results obtained by optical microscopy, SEM analysis and X-ray microtomography show that the laser energy has a significant effect on the compactness and homogeneity of the manufactured parts. Homogeneous and compact samples were obtained for high energy levels. Microstructure of these samples has been further characterized. Their mechanical properties were assessed by ultrasonic measures and the Young's modulus found is close to that of classically elaborated Ti–26Nb ingot. - Highlights: • Biomimetic implants can be provided from additive manufacturing with Ti–Nb. • We made parts in a Ti–Nb alloy elaborated in situ from a mixture of elemental powders. • Process parameters have a significant impact on homogeneity and compactness. • Non-columnar elongated beta-grains are stacked with an orientation {001}<100 >. • Low Young's modulus is achieved by this texture.

  4. Data on the densification during sintering of binder jet printed samples made from water- and gas-atomized alloy 625 powders

    Directory of Open Access Journals (Sweden)

    Amir Mostafaei

    2017-02-01

    Full Text Available Binder jet printing (BJP is a metal additive manufacturing method that manufactures parts with complex geometry by depositing powder layer-by-layer, selectively joining particles in each layer with a polymeric binder and finally curing the binder. After the printing process, the parts still in the powder bed must be sintered to achieve full densification (A. Mostafaei, Y. Behnamian, Y.L. Krimer, E.L. Stevens, J.L. Luo, M. Chmielus, 2016; A. Mostafaei, E. Stevens, E. Hughes, S. Biery, C. Hilla, M. Chmielus, 2016; A. Mostafaei, Y. Behnamian, Y.L. Krimer, E.L. Stevens, J.L. Luo, M. Chmielus, 2016 [1–3]. The collected data presents the characterization of the as-received gas- and water-atomized alloy 625 powders, BJP processing parameters and density of the sintered samples. The effect of sintering temperatures on the microstructure and the relative density of binder jet printed parts made from differently atomized nickel-based superalloy 625 powders are briefly compared in this paper. Detailed data can be found in the original published papers by authors in (A. Mostafaei, J. Toman, E.L. Stevens, E.T. Hughes, Y.L. Krimer, M. Chmielus, 2017 [4].

  5. Effect of Copper and Bronze Addition on Corrosion Resistance of Alloyed 316L Stainless Steel Cladded on Plain Carbon Steel by Powder Metallurgy

    Institute of Scientific and Technical Information of China (English)

    Wenjue CHEN; Yueying WU; Jianian SHEN

    2004-01-01

    A sandwich structure with cladding alloyed 316L stainless steel on plain carbon steel was prepared by means of powder metallurgy (PM) processing. Electrolytic Cu and prealloyed bronze (95Cu wt pct, 5Sn wt pct) were added in different contents up to 15% into the surface cladded 316L layers and the effect of alloying concentrations on the corrosion resistance of the 316L cladding layers was studied. The corrosion performances of the cladding samples were studied by immersion tests and potentio-dynamic anodic polarization tests in H2SO4 and FeCl3 solutions. Both 316L and alloyed 316L surface layers with 1.0 mm depth produced by PM cladding had an effect to improve corrosion resistance in H2SO4 and FeCl3 solutions. Small Cu and bronze addition (4%) had a positive effect in H2SO4 and FeCl3 solutions. 4% Cu alloyed 316L surface layer produced by PM cladding showed similar anodic polarization behaviour to the 316L cladding layer in H2SO4 and FeCl3 solutions.

  6. Standard Specification for Pressure Consolidated Powder Metallurgy Iron-Nickel-Chromium-Molybdenum (UNS N08367), Nickel-Chromium-Molybdenum-Columbium (Nb) (UNS N06625), Nickel-Chromium-Iron Alloys (UNS N06600 and N06690), and Nickel-Chromium-Iron-Columbium-Molybdenum (UNS N07718) Alloy Pipe Flanges, Fittings, Valves, and Parts

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2015-01-01

    Standard Specification for Pressure Consolidated Powder Metallurgy Iron-Nickel-Chromium-Molybdenum (UNS N08367), Nickel-Chromium-Molybdenum-Columbium (Nb) (UNS N06625), Nickel-Chromium-Iron Alloys (UNS N06600 and N06690), and Nickel-Chromium-Iron-Columbium-Molybdenum (UNS N07718) Alloy Pipe Flanges, Fittings, Valves, and Parts

  7. Effect of Elemental Powder Size on Foaming Behavior of NiTi Alloy Made by Combustion Synthesis

    Directory of Open Access Journals (Sweden)

    Naoyuki Kanetake

    2012-07-01

    Full Text Available Nickel titanium (NiTi foams were made by combustion synthesis of powders with the help of ZrH2 as foaming agent and TiB2 as endothermic agent. In this paper, we investigated the effect of elemental powder size on the foaming. The powder size of Ni and Ti affected the ignition temperature of the combustion reaction, cell morphology and microstructure of the foams. The cell morphology of the foams was also modified by the powder size of TiB2.

  8. 2S Hyperfine splitting of muonic hydrogen

    CERN Document Server

    Martynenko, A P

    2004-01-01

    Corrections of orders alpha^5, alpha^6 are calculated in the hyperfine splitting of the 2S state in the muonic hydrogen. The nuclear structure effects are taken into account in the one- and two-loop Feynman amplitudes by means of the proton electromagnetic form factors. Total numerical value of the 2S state hyperfine splitting 22.8148 meV in the (\\mu p) can be considered as reliable estimation for the corresponding experiment with the accuracy 10^{-5}. The value of the Sternheim's hyperfine splitting interval [8\\Delta E^{HFS}(2S)-\\Delta E^{HFS}(1S)] is obtained with the accuracy 10^{-6}.

  9. Investigation of mechanosynthesized Fe{sub 50}Ni{sub 40}Al{sub 10} powders

    Energy Technology Data Exchange (ETDEWEB)

    Hadef, F., E-mail: hadef77@yahoo.fr [Laboratoire de Recherche sur la Physico-Chimie des Surfaces et Interfaces, LRPCSI, Université 20 Août 1955, BP 26, Route d’El-Hadaiek, Skikda 21000 (Algeria); Otmani, A. [Laboratoire de Recherche sur la Physico-Chimie des Surfaces et Interfaces, LRPCSI, Université 20 Août 1955, BP 26, Route d’El-Hadaiek, Skikda 21000 (Algeria); Djekoun, A. [Laboratoire de Magnétisme et Spectroscopie des Solides, LM2S, Université Badji Mokhtar, BP 12, Annaba 23000 (Algeria); Grenèche, J.M. [LUNAM, Université du Maine, Institut des Molécules et Matériaux du Mans, UMR CNRS 6283, 72085 Le Mans (France)

    2013-10-15

    The synthesis of Fe{sub 50}Ni{sub 40}Al{sub 10} powder mixture has been performed in a high-energy planetary ball mill. The phase transformations and structural changes occurring during mechanical alloying were investigated by X-ray diffraction (XRD) and Mössbauer spectroscopy. XRD analysis and Rietveld method revealed the formation of a single nanocrystalline fcc γ-Ni(Fe,Al) solid solution with a lattice parameter close to a{sub γ-Ni(Fe,Al)}=0.3612 nm, after 4 h of milling. The final powder is characterized by an average crystallite size of 14 nm accompanied by the introduction of a lattice strain of order of 1.37%. These values are markedly higher than those reported for mechanically alloyed Fe{sub 50}Ni{sub 50} powders. It was found that the formation of the bcc phase, which coexisted with the fcc structure in the Fe–Ni phase diagram, was inhibited. However, mechanical alloying process gives rise to the Ni{sub 3}Al intermetallic phase, at the early stages of milling. Mössbauer spectroscopy showed that all powders exhibited a ferromagnetic behavior and no paramagnetic phase was detected. The addition of low aluminium content caused more broadening of hyperfine field distributions and lower magnetic field due to the diffusion of Al atoms into γ-FeNi lattice. - Highlights: • A nanocrystalline fcc γ-Ni(Fe,Al) solid solution is formed from Fe, Ni and Al powders. • Al addition engenders an increase in a, L and 〈σ{sup 2}〉{sup 1/2} of MA Fe–Ni based alloys. • Al addition causes more broadening of P(B{sub hf}) and lower B{sub hf}.

  10. Production of titanium-tin alloy powder by ball milling: Formation of titanium-tin oxynitride composite powder produced by annealing in air

    Energy Technology Data Exchange (ETDEWEB)

    Bolokang, A.S., E-mail: Sylvester.Bolokang@transnet.net [Department of Physics, University of the Western Cape, Private Bag x 17, Bellville 7535 (South Africa); DST/CSIR National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria 0001 (South Africa); Transnet Engineering, Product Development, Private Bag X 528, Kilnerpark, Pretoria 0127 (South Africa); Motaung, D.E., E-mail: dmotaung@csir.co.za [DST/CSIR National Centre for Nano-Structured Materials, Council for Scientific and Industrial Research, Pretoria 0001 (South Africa); Arendse, C.J.; Muller, T.F.G. [Department of Physics, University of the Western Cape, Private Bag x 17, Bellville 7535 (South Africa)

    2015-02-15

    Highlights: • HCP solid solution of Ti{sub 75}-Sn{sub 25} powder was synthesized by ball milling. • Formation of Ti-Sn to intermetallic Ti{sub 3}Sn was realized after annealing in Ar. • Thermal analysis of milled Ti-Sn in air yielded HCP with a = 4.985 Å; c = 2.962 Å. • Thermal analysis of milled Ti{sub 3}Sn in air yielded HCP with a = 4.582 Å; c = 2.953 Å. • Raman analysis has confirmed structural change upon annealing. - Abstract: Phase transformation was induced by ball milling and annealing of Ti{sub 75}-Sn{sub 25} powder. HCP solid solution was induced by Ball milling and yielded a compressed lattice parameters a = 2.929 Å; c = 4.780 Å and c/a = 1.63. Upon annealing in Ar at 700 °C, Ti{sub 3}Sn intermetallic with lattice parameters a = 5.916 Å; c = 4.764 Å with (c/a = 0.80) was detected. Subsequent TGA analysis of HCP milled Ti-Sn and Ti{sub 3}Sn intermetallic in air have resulted in tetragonal oxynitride powders with lattice parameters a = 4.985 Å; c = 2.962 Å, c/a = 0.594 for the former and a = 4.582 Å; c = 2.953 Å and c/a = 0.644 for the latter, respectively. The powder morphology was monitored by the high-resolution transmission electron microscopy while the roughness of the milled was analysed by the atomic force microscopy. Phase transformation was monitored by the X-ray diffraction and complemented by the Raman spectroscopy.

  11. Development and characterization of Powder Metallurgy (PM) 2XXX series Al alloy products and Metal Matrix Composite (MMC) 2XXX Al/SiC materials for high temperature aircraft structural applications

    Science.gov (United States)

    Chellman, D. J.; Gurganus, T. B.; Walker, J. A.

    1992-01-01

    The results of a series of material studies performed by the Lockheed Aeronautical Systems Company over the time period from 1980 to 1991 are discussed. The technical objective of these evaluations was to develop and characterize advanced aluminum alloy materials with temperature capabilities extending to 350 F. An overview is given of the first five alloy development efforts under this contract. Prior work conducted during the first five modifications of the alloy development program are listed. Recent developments based on the addition of high Zr levels to an optimum Al-Cu-Mg alloy composition by powder metallurgy processing are discussed. Both reinforced and SiC or B4C ceramic reinforced alloys were explored to achieve specific target goals for high temperature aluminum alloy applications.

  12. Causal Factors of Weld Porosity in Gas Tungsten Arc Welding of Powder-Metallurgy-Produced Titanium Alloys

    Science.gov (United States)

    Muth, T. R.; Yamamoto, Y.; Frederick, D. A.; Contescu, C. I.; Chen, W.; Lim, Y. C.; Peter, W. H.; Feng, Z.

    2013-05-01

    An investigation was undertaken using gas tungsten arc (GTA) welding on consolidated powder metallurgy (PM) titanium (Ti) plate to identify the causal factors behind observed porosity in fusion welding. Tramp element compounds of sodium and magnesium, residual from the metallothermic reduction of titanium chloride used to produce the titanium, were remnant in the starting powder and were identified as gas-forming species. PM-titanium made from revert scrap, where sodium and magnesium were absent, showed fusion weld porosity, although to a lesser degree. We show that porosity was attributable to hydrogen from adsorbed water on the surface of the powders prior to consolidation. The removal and minimization of both adsorbed water on the surface of titanium powder and the residues from the reduction process prior to consolidation of titanium powders are critical for achieving equivalent fusion welding success similar to that seen in wrought titanium produced via the Kroll process.

  13. Cold Spray Coating Technique with FeCrAl Alloy Powder for Developing Accident Tolerant Fuel Cladding

    Energy Technology Data Exchange (ETDEWEB)

    Park, Dong Jun; Kim, Hyun Gil; Park, Jeong Yong; Jung, Yang Il; Park, Jung Hwan; Koo, Yang Hyun [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2015-05-15

    Various approaches to enhance safety have been suggested, replacing current Zr-based alloys for fuel cladding with advanced materials exhibiting lower oxidation rates can be a basic solution. Many advanced materials such as FeCrAl alloys; Mn+1AXn, (MAX) phases, where n = 1 to 3, M is an early transition metal, A is an A-group (mostly IIIA and IVA, or groups 13 and 14) element and X is either carbon or nitrogen; Mo; and SiC are being considered as possible candidates. Among the proposed fuel cladding substitutes, Fe-based alloys are one of the most promising candidates owing to their excellent formability, high strength, and oxidation resistance at high temperature. In this work, the ATF technology concept of Fe-based alloy coating on the existing Zr-alloy cladding was considered and results on the optimization study for fabrication of coated tube samples were described. Result obtained from high temperature oxidation test under steam environment at 1200 .deg. C indicates that FeCrAl alloy coated Zr metal matrix may maintain its integrity during LOCA. This means that accident tolerance of FeCrAl alloy coated Zr cladding sample had been greatly improved compared to that of existing Zr-based alloy fuel cladding.

  14. APPLICATION OF MODIFYING ALLOYING ALLOY CONTAINING NANOSIZED POWDERS OF ACTIVE ELEMENTS IN PRODUCTION OF HIGH-STRENGTH CAST IRON WITH GLOBULAR GRAPHITE

    Directory of Open Access Journals (Sweden)

    A. S. Kalinichenko

    2015-01-01

    Full Text Available Scientific and practical interest is the application of alloying alloy-modifiers for secondary treatment of high-strength cast iron to stabilize the process of spheroidization graphite and achieving higher physical-mechanical properties of castings. The peculiarity of the high-strength cast irons manufacturing technology is their tendency to supercooling during solidification in the mold. This leads to the formation of shrinkage defects and structurally free cementite, especially in thin-walled sections of the finished castings. To minimize these effects in foundry practice during production of ductile iron the secondary inoculation is widely used. In this regard, the question of the choice of the additives with effective impact not only on the graphitization process but also on the formation of the metallic base of ductile iron is relevant. The aim of the present work is to study the peculiarities of structure formation in cast iron with nodular graphite when alloying alloy-modifier based on tin with additions of nanoparticles of titanium carbide, yttrium oxide and graphite nano-pipes is used for secondary treatment. Melting of iron in laboratory conditions was performed in crucible induction furnace IST-006 with an acid lining held. Spheroidizing treatment of melt was realized with magnesium containing alloying alloy FeSiMg7 by means of ladle method. Secondary treatment of high strength cast iron was carried out by addition of alloying alloy-modifier in an amount of 0.1% to the bottom of the pouring ladle. Cast samples for chemical composition analysis, study of microstructure, technological and mechanical properties of the resultant alloy were made. Studies have shown that the secondary treatment of high strength cast iron with developed modifier-alloying alloy results in formation of the perlite metallic base due to the tin impact and nodular graphite with regular shape under the influence of titanium carbide, yttrium oxide and graphite nano

  15. In situ elaboration of a binary Ti-26Nb alloy by selective laser melting of elemental titanium and niobium mixed powders.

    Science.gov (United States)

    Fischer, M; Joguet, D; Robin, G; Peltier, L; Laheurte, P

    2016-05-01

    Ti-Nb alloys are excellent candidates for biomedical applications such as implantology and joint replacement because of their very low elastic modulus, their excellent biocompatibility and their high strength. A low elastic modulus, close to that of the cortical bone minimizes the stress shielding effect that appears subsequent to the insertion of an implant. The objective of this study is to investigate the microstructural and mechanical properties of a Ti-Nb alloy elaborated by selective laser melting on powder bed of a mixture of Ti and Nb elemental powders (26 at.%). The influence of operating parameters on porosity of manufactured samples and on efficacy of dissolving Nb particles in Ti was studied. The results obtained by optical microscopy, SEM analysis and X-ray microtomography show that the laser energy has a significant effect on the compactness and homogeneity of the manufactured parts. Homogeneous and compact samples were obtained for high energy levels. Microstructure of these samples has been further characterized. Their mechanical properties were assessed by ultrasonic measures and the Young's modulus found is close to that of classically elaborated Ti-26 Nbingot.

  16. The hyperfine Paschen-Back Faraday effect

    OpenAIRE

    Zentile, Mark A.; Andrews, Rebecca; Weller, Lee; Knappe, Svenja; Adams, Charles S.; Hughes, Ifan G

    2014-01-01

    We investigate experimentally and theoretically the Faraday effect in an atomic medium in the hyperfine Paschen-Back regime, where the Zeeman interaction is larger than the hyperfine splitting. We use a small permanent magnet and a micro-fabricated vapour cell, giving magnetic fields of the order of a Tesla. We show that for low absorption and small rotation angles, the refractive index is well approximated by the Faraday rotation signal, giving a simple way to measure the atomic refractive i...

  17. Friction Stir Processing of Al with Mechanically Alloyed Al-TiO2-Graphite Powder: Microstructure and Mechanical Properties

    Science.gov (United States)

    Beygi, R.; Mehrizi, M. Zarezadeh; Eisaabadi B, G.

    2017-02-01

    Commercial pure aluminum was friction stir processed with Al-TiO2-graphite mixture pre-placed into a groove in Al. Two kinds of powders were used as starting particles for friction stir processing; as-mixed powder and 60-h ball-milled powder. Characterization by XRD, SEM and EDS analysis showed that with as-mixed powder an Al composite reinforced with Al3Ti and Al2O3 was produced. Graphite particles were remained in the matrix unchanged. Using 60-h ball-milled powder as starting particle in friction stir processing, resulted in an Al composite reinforced with TiC-Al2O3 nanoparticles dispersed uniformly into the matrix having the size of 100 nm on average. In this state, the microhardness values obtained in the stir zone were higher than those ones obtained using as-mixed powders. The mechanism of phases formation during friction stir processing with two different kinds of powders are elaborated and discussed in this study. Also the mechanical properties of samples were investigated.

  18. Effect of pressing temperature on the wear resistance of a Co-based Cr-Mo powder alloy produced by hot pressing

    Energy Technology Data Exchange (ETDEWEB)

    Somunkiran, Ilyas [Firat Univ., Elazig (Turkey). Metallurgical and Materials Engineering Dept.; Balin, Ahmet [Siirt Univ. (Turkey). Dept. of Vocational High School

    2016-02-01

    In this study, Co-based Cr-Mo powder alloy was produced at different pressing temperatures by using hot pressing technique and abrasive wear behaviors of the produced specimens were examined. Produced specimens were exposed to abrasive wear experiment using block on disc wear test device by applying a load of 50 N with 100-mesh SiC abrasive paper. Each specimen was investigated at 25, 50, 75 and 100 m. At the end of the experiment, abrasive wear results of the specimens were determined by calculating their mass losses. Microstructural properties of the specimens which were produced at different pressing temperatures were investigated by optical and SEM examinations and their wear resistances were examined by abrasive wear experiments. Consequently, it was observed that in Co-based Cr-Mo powder alloy produced by hot pressing technique; as sintering temperature increased, size of neck formations between the powder grains increased, porosity decreased and abrasive wear resistance increased. [German] In diesem Beitrag zugrunde liegenden Studie wurde eine Co-basierte Cr-Mo-Legierung mittels Heisspressens hergestellt und der Abrasivverschleisswiderstand dieser Proben untersucht. Die hergestellten Proben wurden dem Abrasivverschleissversuch durch einen Block-Scheibe-Versuchsaufbau unterzogen, wobei eine Kraft von 50 N mit einem SiC-Papier (100 mesh) verwendet wurde. Jede Probe wurde ueber eine Distanz von 25, 50, 75 und 100 m untersucht. Am Ende der jeweiligen Experimente wurden die Abrasivverschleissergebnisse ermittelt, indem die Massenverluste berechnet wurden. Die mikrostrukturellen Eigenschaften der Proben, die bei verschiedenen Presstemperaturen hergestellt wurden, wurden mittels optischer und Rasterelektronenmikroskopie bestimmt und ihr Verschleisswiderstand anhand der Verschleissversuche ermittelt. Schliesslich wurde beobachtet, dass bei steigender Sintertemperatur der heissgespressten Co-basierten Cr-Mo-Pulverlegierung die Groesse der Einschnuerungen zwischen den

  19. 熔盐电解法制备钨铜合金粉%Preparation of W-Cu Alloy Powder with Molten Salt Electrolysis Process

    Institute of Scientific and Technical Information of China (English)

    肖志华; 廖春发; 王旭

    2013-01-01

    在NaCl-KCl-Na2WO4-CuO体系中采用熔盐电解法直接制取钨铜合金粉,并对产物进行了XRD、SEM及EDS分析.结果表明,在780~800℃电解、阴极电流密度106~133mA/cm2、电解时间3~4 h、电压2.2~3.2 V的条件下,可以得到纯度99%以上、平均粒度0.91 μm的钨铜合金粉末,各项指标基本达到了工业上烧结钨铜合金的要求.%Tungsten copper alloy powder was directly prepared in NaCl-KCl-Na2 WO4-CuO system with molten salt electrolysis.The cathode electrolysis products were analyzed by XRD, SEM and EDS.The results show that copper tungsten alloy powder with purity of above 99% and average particle size of 0.91 μm is obtained under the reaction conditions including electrolytic temperature of 740~820℃, cathode current density of 106~133 mA/cm2, electrolysis time of 1.5~3.5 h, cell voltage of 2.2~3.2 V.The product reaches the manufacture requirement of sintering tungsten copper alloy in industry.

  20. Tungsten and tungsten alloy powder metallurgy. (Latest citations from the EI Compendex*plus database). Published Search

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    1998-03-01

    The bibliography contains citations concerning tungsten powder preparation and processing. Studies include sintering, densification, shrinkage, phase analysis, and heat treatment. The physical and mechanical properties of tungsten powder metal products are included. The effects of additives and particle size on the sintering and sintered articles are also described. (Contains 50-250 citations and includes a subject term index and title list.) (Copyright NERAC, Inc. 1995)

  1. A study of Al-Mo powder processing as a possible way to corrosion resistent aluminum-alloys

    Directory of Open Access Journals (Sweden)

    Wilson Corrêa Rodrigues

    2009-06-01

    Full Text Available Elementary Al and Mo powder mixtures have been processed by high energy ball milling up to milling times of 100 hours. The shift of the pitting potential and the X ray analysis of green milled samples showed that part of the Mo has formed a supersaturated solid solution of Mo in Al. Elementary Mo powder, however, was still present after 100 hours of milling. Sintering led to the formation of the intermetallic Al12Mo phase.

  2. INVESTIGATION OF POWDER-GAS EMISSIONS, FONNED AT MELTING AND REFINING OF ALUMINIUM ALLOYS IN REVERBERATING FURNACES

    Directory of Open Access Journals (Sweden)

    S. P. Zadrutskij

    2009-01-01

    Full Text Available As a result of carried out analysis of processes of aluminium alloys casting and refining in reverberating  furnaces it is determined that searching source of harmful emissions are the refining processes.

  3. Adsorption properties of ultradispersed powders of aluminum alloys with rare-earth metals, before and after water treatment

    Science.gov (United States)

    Ryabina, A. V.; Shevchenko, V. G.; Eselevich, D. A.

    2014-10-01

    Adsorption of nitrogen on Al-3% La, Al-1.5% Sc, and Al-3% Ce powders before and after processing with water in the relative pressure range p/p s = 10˜3 to 0.999 is experimentally studied at a temperature of 78 K. It is shown that the interaction between ultradispersed powder and water depends on the properties of the original powder, including the original content and composition of the oxide-hydroxide phases in the surface layers of metal particles, and the length and conditions of storage. Results confirming that processing powders containing rare-earth metals with water at room temperature leads to the formation of new phases and affects their morphology are presented. It is shown that the nanopores formed between crystallites on the surface of the particles during oxidation with water and subsequent thermal dehydration play an important role in the properties of powders processed with water. The specific surface and the porosity of powders are calculated.

  4. Aluminum powder metallurgy processing

    Energy Technology Data Exchange (ETDEWEB)

    Flumerfelt, J.F.

    1999-02-12

    The objective of this dissertation is to explore the hypothesis that there is a strong linkage between gas atomization processing conditions, as-atomized aluminum powder characteristics, and the consolidation methodology required to make components from aluminum powder. The hypothesis was tested with pure aluminum powders produced by commercial air atomization, commercial inert gas atomization, and gas atomization reaction synthesis (GARS). A comparison of the GARS aluminum powders with the commercial aluminum powders showed the former to exhibit superior powder characteristics. The powders were compared in terms of size and shape, bulk chemistry, surface oxide chemistry and structure, and oxide film thickness. Minimum explosive concentration measurements assessed the dependence of explosibility hazard on surface area, oxide film thickness, and gas atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization processing conditions. The GARS aluminum powders were exposed to different relative humidity levels, demonstrating the effect of atmospheric conditions on post-atomization oxidation of aluminum powder. An Al-Ti-Y GARS alloy exposed in ambient air at different temperatures revealed the effect of reactive alloy elements on post-atomization powder oxidation. The pure aluminum powders were consolidated by two different routes, a conventional consolidation process for fabricating aerospace components with aluminum powder and a proposed alternative. The consolidation procedures were compared by evaluating the consolidated microstructures and the corresponding mechanical properties. A low temperature solid state sintering experiment demonstrated that tap densified GARS aluminum powders can form sintering necks between contacting powder particles, unlike the total resistance to sintering of commercial air atomization aluminum powder.

  5. Friction stir surfacing of cast A356 aluminium–silicon alloy with boron carbide and molybdenum disulphide powders

    OpenAIRE

    R. Srinivasu; A.Sambasiva Rao; Madhusudhan Reddy, G.; Srinivasa Rao, K.

    2015-01-01

    Good castability and high strength properties of Al–Si alloys are useful in defence applications like torpedoes, manufacture of Missile bodies, and parts of automobile such as engine cylinders and pistons. Poor wear resistance of the alloys is major limitation for their use. Friction stir processing (FSP) is a recognized surfacing technique as it overcomes the problems of fusion route surface modification methods. Keeping in view of the requirement of improving wear resistance of cast alumini...

  6. Structural, microstructural and magnetic properties of amorphous/nanocrystalline Ni{sub 63}Fe{sub 13}Mo{sub 4}Nb{sub 20} powders prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Karimi, L., E-mail: leilakarimi@iauahvaz.ac.ir [Materials Science and Engineering Department, Islamic Azad University of Ahvaz, Ahvaz (Iran, Islamic Republic of); Shokrollahi, H. [Materials Science and Engineering Department, Shiraz University of Technology, 71555-313, Shiraz (Iran, Islamic Republic of)

    2011-06-09

    Highlights: > The amorphous/nanocrystalline Ni{sub 63}Fe{sub 13}Mo{sub 4}Nb{sub 20} magnetic powders were prepared by mechanical alloying. > The saturation magnetization decreases and the coercivity increases as a result of the electronic interactions and the grain size reduction. > The use of amorphous alloy is due to the lower magnetic losses and higher electrical resistivity compared with other magnetic material - Abstract: This paper focuses on the magnetic, structural and microstructural studies of amorphous/nanocrystalline Ni{sub 63}Fe{sub 13}Mo{sub 4}Nb{sub 20} powders prepared by mechanical alloying. The ball-milling of Ni, Fe, Mo and Nb powders leads to alloying the element powders, the nanocrystalline and an amorphization matrix with Mo element up to 120 h followed by the strain and thermal-induced nucleation of a single nanocrystalline Ni-based phase from the amorphous matrix at 190 h. The results showed that the saturation magnetization decreases as a result of the electronic interactions between magnetic and non-magnetic elements and finally increases by the partial crystallization of the amorphous matrix. The coercive force increases as the milling time increases and finally decreases due to sub-grains formation.

  7. Effect of dielectric fluid with surfactant and graphite powder on Electrical Discharge Machining of titanium alloy using Taguchi method

    Directory of Open Access Journals (Sweden)

    Murahari Kolli

    2015-12-01

    Full Text Available In this paper, Taguchi method was employed to optimize the surfactant and graphite powder concentration in dielectric fluid for the machining of Ti-6Al-4V using Electrical Discharge Machining (EDM. The process parameters such as discharge current, surfactant concentration and powder concentration were changed to explore their effects on Material Removal Rate (MRR, Surface Roughness (SR, Tool wear rate (TWR and Recast Layer Thickness (RLT. Detailed analysis of structural features of machined surface was carried out using Scanning Electron Microscope (SEM to observe the influence of surfactant and graphite powder on the machining process. It was observed from the experimental results that the graphite powder and surfactant added dielectric fluid significantly improved the MRR, reduces the SR, TWR and RLT at various conditions. Analysis of Variance (ANOVA and F-test of experimental data values related to the important process parameters of EDM revealed that discharge current and surfactant concentration has more percentage of contribution on the MRR and TWR whereas the SR, and RLT were found to be affected greatly by the discharge current and graphite powder concentration.

  8. Hyperfine interaction and some thermomagnetic properties of amorphous and partially crystallized Fe70−xMxMo5Cr4Nb6B15 (M = Co or Ni, x = 0 or 10 alloys

    Directory of Open Access Journals (Sweden)

    Rzącki Jakub

    2015-03-01

    Full Text Available As revealed by Mössbauer spectroscopy, replacement of 10 at.% of iron in the amorphous Fe70Mo5Cr4Nb6B15 alloy by cobalt or nickel has no effect on the magnetic structure in the vicinity of room temperature, although the Curie point moves from 190 K towards ambient one. In the early stages of crystallization, the paramagnetic crystalline Cr12Fe36Mo10 phase appears before α-Fe or α-FeCo are formed, as is confirmed by X-ray diffractometry and transmission electron microscopy. Creation of the crystalline Cr12Fe36Mo10 phase is accompanied by the amorphous ferromagnetic phase formation at the expense of amorphous paramagnetic one.

  9. Microstructure and Magnetic Properties of Fe-Ni Alloy Fabricated by Selective Laser Melting Fe/Ni Mixed Powders

    Institute of Scientific and Technical Information of China (English)

    Baicheng Zhang; Nour-Eddine Fenineche; Hanlin Liao; Christian Coddet

    2013-01-01

    Fe-Ni alloy,as a widely applied ferromagnetic material,is synthesized using selective laser melting (SLM).The chemical compositions and microstructure of the SLM Fe-Ni alloy are characterized by X-ray diffraction (XRD),energy dispersive X-ray spectroscopy and scanning electron microscopy.It was found that the samples exhibited fine grains with homogenous distribution when a low laser scanning velocity was used.Moreover,the magnetic properties of the samples with different laser parameters are also measured.It shows that the SLM Fe-30%Ni alloy possesses a low coercivity and high saturation magnetization.It also can be obtained that SLM is an alternative faster method to prepare soft magnetic material with complex shapes.Moreover,the magnetic properties can be influenced by the laser parameters.

  10. Evidence of magnetic dipolar interaction in micrometric powders of the Fe{sub 50}Mn{sub 10}Al{sub 40} system: Melted alloys

    Energy Technology Data Exchange (ETDEWEB)

    Perez Alcazar, G.A., E-mail: gpgeperez@gmail.com [Departamento de Fisica, Universidad del Valle, A. A. 25360, Cali (Colombia); Unidad Asociada ICMM-IMA, Apdo. 155, 28230 Las Rozas, Madrid (Spain); Zamora, L.E. [Departamento de Fisica, Universidad del Valle, A. A. 25360, Cali (Colombia); Unidad Asociada ICMM-IMA, Apdo. 155, 28230 Las Rozas, Madrid (Spain); Tabares, J.A.; Piamba, J.F. [Departamento de Fisica, Universidad del Valle, A. A. 25360, Cali (Colombia); Gonzalez, J.M. [Unidad Asociada ICMM-IMA, Apdo. 155, 28230 Las Rozas, Madrid (Spain); Greneche, J.M. [LUNAM, Universite du Maine, Institut des Molecules et Materiaux du Mans, UMR CNRS 6283, 72085 Le Mans Cedex 9 (France); Martinez, A. [Instituto de Magnetismo Aplicado, P.O. Box 155, 28230 Las Rozas (Spain); Romero, J.J. [Instituto de Ceramica y Vidrio, CSIC, C/Kelsen 5, 28049, Madrid (Spain); Marco, J.F. [Instituto de Quimica Fisica Rocasolano, CSIC, C/Serrano 119, 28006 Madrid (Spain)

    2013-02-15

    Powders of melted disordered Fe{sub 50}Mn{sub 10}Al{sub 40} alloy were separated at different mean particle sizes as well as magnetically and structurally characterized. All the samples are BCC and show the same nanostructure. Particles larger than 250 {mu}m showed a lamellar shape compared to smaller particles, which exhibited a more regular form. All the samples are ferromagnetic at room temperature and showed reentrant spin-glass (RSG) and superparamagnetic (SP)-like behaviors between 30 and 60 K and 265 and > 280 K, respectively, as a function of frequency and particle size. The freezing temperature increases with increasing particle size while the blocking one decreases with particle size. The origin of these magnetic phenomena relies in the internal disordered character of samples and the competitive interaction of Fe and Mn atoms. The increase of their critical freezing temperature with increasing mean particle size is due to the increase of the magnetic dipolar interaction between the magnetic moment of each particle with the field produced by the other magnetic moments of their surrounding particles. - Highlights: Black-Right-Pointing-Pointer The effect of particle size in microsized powders of Fe{sub 50}Mn{sub 10}Al{sub 40} melted disordered alloy is studied. Black-Right-Pointing-Pointer Dipolar magnetic interaction between particles exists and this changes with the particle size. Black-Right-Pointing-Pointer For all the particle sizes the reentrant spin- glass and the superparamagnetic-like phases exist. Black-Right-Pointing-Pointer RSG and SP critical temperatures increase with increasing the dipolar magnetic interaction (the mean particle size).

  11. 低温真空扩散反应制备高性能TiAl合金粉%Preparation of TiAl Alloy Powders by Diffusion Reaction at Low Temperature and in High Vacuum

    Institute of Scientific and Technical Information of China (English)

    王军; 邵慧萍; 郭志猛

    2013-01-01

    TiAl alloy powder was prepared by high-energy ball milling and heat preservation under the condition of low temperature and high vacuum with titanium powder of 43 μm and aluminium powder of 9~12 μm as starting materials.After heat treated for different time and at different temperatures,the alloying of blended powder of titanium and aluminium was investigated.The results show that the alloy powder with the main intermetallic compounds of TiAl and a small quantity of Ti3Al can be obtained through 1 h high-energy ball milling and heat preservation at 500 ℃ for 2 h,and 600 ℃ for 3 h in high vacuum.The particle size of the prepared alloy powder is about 20 μm.%通过高能球磨均匀混合以及低温真空预烧工艺制备TiAl合金粉,原料为粒度43 μm Ti粉和9~12 μmAl粉,研究不同温度下不同保温时间后Ti、Al混合粉的合金化程度.结果表明:高能球磨1h的Ti、Al混合粉在500℃保温2h,再在600℃保温3h能制得主要为TiAl相和少量Ti3Al相的合金粉,制备合金粉的平均粒径为20μm左右.

  12. The role of silicon on the microstructure and magnetic behaviour of nanostructured (Fe0.7Co0.3)100-xSix powders

    Science.gov (United States)

    Hocine, M.; Guittoum, A.; Hemmous, M.; Martínez-Blanco, D.; Gorria, P.; Rahal, B.; Blanco, J. A.; Sunol, J. J.; Laggoun, A.

    2017-01-01

    Single-phase(Fe0.7Co0.3)100-xSix nanostructured powders (x=0,5, 10, 15 and 20) have been elaborated by mechanical alloying in order to investigate the effect of silicon on the microstructure and magnetic properties of these alloys. A disordered Fe(Co, Si) solid solution with body centred cubic (bcc) crystal structure is formed after 72 h of milling for all the compositions. The addition of Si gives rise to a progressive decrease of the lattice parameter, from about 2.865 Å for the binary Fe70Co30 compound down to 2.841 Å for the powder with x=20. The sample with the uppermost Si content exhibits the lowest value for the mean grain size (≈10 nm) as well as the largest microstrain (above 1.1%). All the samples are ferromagnetic at room temperature, although the saturation magnetization value reduces almost linearly by adding Si to the composition. A similar trend is observed for the hyperfine magnetic field obtained from the analysis of the room temperature Mössbauer spectra. The hyperfine field distributions show a broad double-peak shape for x>0, which can be ascribed to multiple local environments for the Fe atoms inside a disordered solid solution.

  13. Hyperfine splitting in lithium-like bismuth

    Energy Technology Data Exchange (ETDEWEB)

    Lochmann, Matthias; Froemmgen, Nadja; Hammen, Michael; Will, Elisa [Universitaet Mainz (Germany); Andelkovic, Zoran; Kuehl, Thomas; Litvinov, Yuri; Winters, Danyal; Sanchez, Rodolfo [GSI Helmholtzzentrum, Darmstadt (Germany); Botermann, Benjamin; Noertershaeuser, Wilfried [Technische Universitaet Darmstadt (Germany); Bussmann, Michael [Helmholtzzentrum Dresden-Rossendorf (Germany); Dax, Andreas [CERN, Genf (Switzerland); Hannen, Volker; Joehren, Raphael; Vollbrecht, Jonas; Weinheimer, Christian [Universitaet Muenster (Germany); Geppert, Christopher [Universitaet Mainz (Germany); GSI Helmholtzzentrum, Darmstadt (Germany); Stoehlker, Thomas [GSI Helmholtzzentrum, Darmstadt (Germany); Universitaet Heidelberg (Germany); Thompson, Richard [Imperial College, London (United Kingdom); Volotka, Andrey [Technische Universitaet Dresden (Germany); Wen, Weiqiang [IMP Lanzhou (China)

    2013-07-01

    High-precision measurements of the hyperfine splitting values on Li- and H-like bismuth ions, combined with precise atomic structure calculations allow us to test QED-effects in the regime of the strongest magnetic fields that are available in the laboratory. Performing laser spectroscopy at the experimental storage ring (ESR) at GSI Darmstadt, we have now succeeded in measuring the hyperfine splitting in Li-like bismuth. Probing this transition has not been easy because of its extremely low fluorescence rate. Details about this challenging experiment will be given and the achieved experimental accuracy are presented.

  14. Hyperfine splitting in hydrogen with form factors

    CERN Document Server

    Daza, F Garcia; Nowakowski, M

    2010-01-01

    Proton structure corrections to the hyperfine splittings in hydrogen are evaluated using the Breit potential with electromagnetic form factors. In contrast to other methods, several new features emerge: the Breit potential with $q^2$-dependent form factors is just an extension of the standard Breit equation which gives the hyperfine Hamiltonian. Order $\\alpha^5$ corrections are obtained from a one-photon exchange amplitude and time-independent perturbation theory. Structure corrections to $D_{21} = 8 E^{2S}_{hfs} - E^{1S}_{hfs}$ start at order $\\alpha^6$. QED corrections are comparable to structure corrections which must be evaluated ab initio.

  15. Spin relaxation in nanowires by hyperfine coupling

    Energy Technology Data Exchange (ETDEWEB)

    Echeverria-Arrondo, C. [Department of Physical Chemistry, Universidad del Pais Vasco UPV/EHU, 48080 Bilbao (Spain); Sherman, E.Ya. [Department of Physical Chemistry, Universidad del Pais Vasco UPV/EHU, 48080 Bilbao (Spain); IKERBASQUE Basque Foundation for Science, 48011 Bilbao, Bizkaia (Spain)

    2012-08-15

    Hyperfine interactions establish limits on spin dynamics and relaxation rates in ensembles of semiconductor quantum dots. It is the confinement of electrons which determines nonzero hyperfine coupling and leads to the spin relaxation. As a result, in nanowires one would expect the vanishing of this effect due to extended electron states. However, even for relatively clean wires, disorder plays a crucial role and makes electron localization sufficient to cause spin relaxation on the time scale of the order of 10 ns. (copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  16. Dust Explosion Characteristics of Aluminum, Titanium, Zinc, and Iron-Based Alloy Powders Used in Cold Spray Processing

    Science.gov (United States)

    Sakata, K.; Tagomori, K.; Sugiyama, N.; Sasaki, S.; Shinya, Y.; Nanbu, T.; Kawashita, Y.; Narita, I.; Kuwatori, K.; Ikeda, T.; Hara, R.; Miyahara, H.

    2014-01-01

    Compared to conventional thermal spray coating, cold spray processing typically employs finer, smaller-diameter metal powders. Furthermore, cold-sprayed particles exhibit fewer surface oxides than thermally sprayed particles due to the absence of particle melting during spraying. For these reasons, it is important to consider the potential for dust explosions or fires during cold spray processing, for both industrial and R&D applications. This work examined the dust explosion characteristics of metal powders typically used in cold spray coating, for the purpose of preventing dust explosions and fires and thus protecting the health and safety of workers and guarding against property damage. In order to safely make use of the new cold spray technology in industrial settings, it is necessary to manage the risks based on an appropriate assessment of the hazards. However, there have been few research reports focused on such risk management. Therefore, in this study, the dust explosion characteristics of aluminum, titanium, zinc, carbonyl iron, and eutectoid steel containing chromium at 4 wt.% (4 wt.% Cr-eutectoid steel) powders were evaluated according to the standard protocols JIS Z 8818, IEC61241-2-3(1994-09) section 3, and JIS Z 8817. This paper reports our results concerning the dust explosion properties of the above-mentioned metal powders.

  17. POWDER-GAS DISCHARGE, FORMED AT MELTING OF ALUMINIUM CASTING ALLOYS IN INDUCTION CRUCIBLE FURNACE IAT- 6

    Directory of Open Access Journals (Sweden)

    G. A. Rumjantseva

    2009-01-01

    Full Text Available The carried out analysis of powder-gas discharge shows that volumes and composition of the forming dust are determined by composition of recycled material, type of lubrication for machines under high pressure, quality of recycled material preparation and technology of refining processing.

  18. Hyperfine and magnetic properties of Fe-Cu clusters and Fe precipitates embedded in a Cu matrix

    Energy Technology Data Exchange (ETDEWEB)

    Klautau, A B [Faculdade de Fisica, Universidade Federal do Para, 66075-110, Belem, PA (Brazil); Socolovsky, L M [Laboratorio de Solidos Amorfos, INTECIN, Facultad de Ingenieria, Universidad de Buenos Aires, C1063ACV, Buenos Aires (Argentina); Nogueira, R N [Faculdade Taboao da Serra, 06768-000, Taboao da Serra, SP (Brazil); Petrilli, H M, E-mail: aklautau@ufpa.b [Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05315-970 Sao Paulo, SP (Brazil)

    2009-12-16

    Using the first-principles real-space linear muffin-tin orbital method within the atomic sphere approximation (RS-LMTO-ASA) we study hyperfine and local magnetic properties of substituted pure Fe and Fe-Cu clusters in an fcc Cu matrix. Spin and orbital contributions to magnetic moments, hyperfine fields and the Moessbauer isomer shifts at the Fe sites in Fe precipitates and Fe-Cu alloy clusters of sizes up to 60 Fe atoms embedded in the Cu matrix are calculated and the influence of the local environment on these properties is discussed.

  19. Low temperature study of micrometric powder of melted Fe{sub 50}Mn{sub 10}Al{sub 40} alloy

    Energy Technology Data Exchange (ETDEWEB)

    Zamora, Ligia E. [Departamento de Fisica, Universidad del Valle, A. A. 25360 Cali (Colombia); Perez Alcazar, G.A., E-mail: gpgeperez@gmail.com [Departamento de Fisica, Universidad del Valle, A. A. 25360 Cali (Colombia); Tabares, J.A. [Departamento de Fisica, Universidad del Valle, A. A. 25360 Cali (Colombia); Romero, J.J. [Instituto de Ceramica y Vidrio, CSIC, C/Kelsen 5, 28049 Madrid (Spain); Martinez, A. [Instituto de Magnetismo Aplicado, P.O. Box 155, Las Rozas, 28230 Madrid (Spain); Gonzalez, J.M. [Unidad Asociada ICMM-IMA, c/Sor Juana Ines de la Cruz 3, 28049 Madrid (Spain); Palomares, F.J. [Instituto de Ciencia de Materiales de Madrid, CSIC, C/Sor Juana Ines de la Cruz, 28049 Cantoblanco, Madrid (Spain); Marco, J.F. [Instituto de Quimica-Fisica Rocasolano, CSIC, c/Serrano 119, 28006 Madrid (Spain)

    2012-06-15

    Melted Fe{sub 50}Mn{sub 10}Al{sub 40} alloy powder with particle size less than 40 {mu}m was characterized at room temperature by XRD, SEM and XPS; and at low temperatures by Moessbauer spectrometry, ac susceptibility, and magnetization analysis. The results show that the sample is BCC ferromagnetic but with a big contribution of paramagnetic sites, and presents super-paramagnetic and re-entrant spin-glass phases with critical temperatures of 265 and 35 K, respectively. The presence of the different phases detected is due to the disordered character of the sample and the competitive magnetic interactions. The obtained values of the saturation magnetization and the coercive field as a function of temperature present a behavior which indicates a ferromagnetic phase. However, the behavior of the FC curve and that of the coercive field as a function of temperature suggest that the dipolar magnetic interaction between particles contributes to the internal magnetic field in the same way as was reported for nanoparticulate powders.

  20. Preparation of Functionally Graded Materials (FGMs) Using Coal Fly Ash and NiCr-Based Alloy Powder by Spark Plasma Sintering (SPS)

    Science.gov (United States)

    Kaneko, Gen-yo; Kitagawa, Hiroyuki; Hasezaki, Kazuhiro; Ito, Yuji; Kakuda, Hideaki

    2008-02-01

    Functionally Graded Materials (FGMs) were prepared by spark plasma sintering (SPS) using coal fly ash and NiCr alloy powder. The coal fly ash was produced by the Misumi Coal Thermal Power Station (Chugoku Electric Power Co., Inc.), with 80 wt% nickel and 20 wt% chromium (Fukuda Metal Foil & Powder Co., Ltd.) used as source materials. The sintering temperature in the graphite die was 1000 °C. X-ray diffraction patterns of the sintered coal fly ash materials indicated that mullite (3Al2O3ṡ2SiO2) and silica (SiO2) phases were predominant. Direct joining of coal fly ash and NiCr causes fracture at the interface. This is due to the mismatch in the thermal expansion coefficients (CTE). A crack in the FGM was observed between the two layers with a CTE difference of over 4.86×10-6 K-1, while a crack in the FGM was difficult to detect when the CTE difference was less than 2.77×10-6 K-1.

  1. Selective Laser Sintering And Melting Of Pristine Titanium And Titanium Ti6Al4V Alloy Powders And Selection Of Chemical Environment For Etching Of Such Materials

    Directory of Open Access Journals (Sweden)

    Dobrzański L.A.

    2015-09-01

    Full Text Available The aim of the investigations described in this article is to present a selective laser sintering and melting technology to fabricate metallic scaffolds made of pristine titanium and titanium Ti6Al4V alloy powders. Titanium scaffolds with different properties and structure were manufactured with this technique using appropriate conditions, notably laser power and laser beam size. The purpose of such elements is to replace the missing pieces of bones, mainly cranial and facial bones in the implantation treatment process. All the samples for the investigations were designed in CAD/CAM (3D MARCARM ENGINEERING AutoFab (Software for Manufacturing Applications software suitably integrated with an SLS/SLM system. Cube-shaped test samples dimensioned 10×10×10 mm were designed for the investigations using a hexagon-shaped base cell. The so designed 3D models were transferred to the machine software and the actual rapid manufacturing process was commenced. The samples produced according to the laser sintering technology were subjected to chemical processing consisting of etching the scaffolds’ surface in different chemical mediums. Etching was carried out to remove the loosely bound powder from the surface of scaffolds, which might detach from their surface during implantation treatment and travel elsewhere in an organism. The scaffolds created were subjected to micro- and spectroscopic examinations

  2. Structural Characteristics and Properties of Precious Metal Powders and Copper Powder Prepared by High-speed Centrifugal Atomization Technique

    Institute of Scientific and Technical Information of China (English)

    XIE Ming; YANG You-cai; LI Yu-shen; ZHANG Jian-kan; FU Shi-ji; SHI Qing-nan

    2007-01-01

    The principle and characteristics of the rapidly solidified centrifugal atomization technique are studied in present paper. It has been widely used to make fine, rapidly solidified precious metal powders for application as the electrical engineering materials, conductive coatings for electromagnetic shielding and brazing alloys. The silver powder, copper powder and some precious metal alloys powders are prepared by the new method. A comparative analysis is carried out with the conventional electrolytic silver powder and chemical deposition silver powder. The results show that rapidly solidified powders are fine and have higher solid solubility of the alloying elements, and their alloys have excellent properties in various aspects.

  3. Fluctuating hyperfine interactions: an updated computational implementation

    Science.gov (United States)

    Zacate, M. O.; Evenson, W. E.

    2015-04-01

    The stochastic hyperfine interactions modeling library (SHIML) is a set of routines written in the C programming language designed to assist in the analysis of stochastic models of hyperfine interactions. The routines read a text-file description of the model, set up the Blume matrix, upon which the evolution operator of the quantum mechanical system depends, and calculate the eigenvalues and eigenvectors of the Blume matrix, from which theoretical spectra of experimental techniques can be calculated. The original version of SHIML constructs Blume matrices applicable for methods that measure hyperfine interactions with only a single nuclear spin state. In this paper, we report an extension of the library to provide support for methods such as Mössbauer spectroscopy and nuclear resonant scattering of synchrotron radiation, which are sensitive to interactions with two nuclear spin states. Examples will be presented that illustrate the use of this extension of SHIML to generate Mössbauer spectra for polycrystalline samples under a number of fluctuating hyperfine field models.

  4. Fluctuating hyperfine interactions: an updated computational implementation

    Energy Technology Data Exchange (ETDEWEB)

    Zacate, M. O., E-mail: zacatem1@nku.edu [Northern Kentucky University, Department of Physics and Geology (United States); Evenson, W. E. [Utah Valley University, Department of Physics (United States)

    2015-04-15

    The stochastic hyperfine interactions modeling library (SHIML) is a set of routines written in the C programming language designed to assist in the analysis of stochastic models of hyperfine interactions. The routines read a text-file description of the model, set up the Blume matrix, upon which the evolution operator of the quantum mechanical system depends, and calculate the eigenvalues and eigenvectors of the Blume matrix, from which theoretical spectra of experimental techniques can be calculated. The original version of SHIML constructs Blume matrices applicable for methods that measure hyperfine interactions with only a single nuclear spin state. In this paper, we report an extension of the library to provide support for methods such as Mössbauer spectroscopy and nuclear resonant scattering of synchrotron radiation, which are sensitive to interactions with two nuclear spin states. Examples will be presented that illustrate the use of this extension of SHIML to generate Mössbauer spectra for polycrystalline samples under a number of fluctuating hyperfine field models.

  5. Hyperfine interactions, the key to multiquark physics

    Energy Technology Data Exchange (ETDEWEB)

    Likpink, H.J.

    1988-08-08

    Clues in the search for a fundamental description of hadron physics based on QCD may be obtained from a phenomenological constituent quark model in which the color-electric force binds quarks into saturated color-singlet hadrons, and finer details of the spectrum and multiquark physics are dominated by the color-magnetic hyperfine interaction. 47 refs.

  6. 钛和沥青机械合金化合成纳米级碳化钛%Synthesis of TiC Powder by Mechanical Alloying of Titanium and Asphalt

    Institute of Scientific and Technical Information of China (English)

    李渤; 崔立山; 郑雁军; 徐春明

    2007-01-01

    TiC powder was synthesized by mechanical alloying of titanium and asphalt in this paper. Deoiled asphalt as a carbon source not only provided element C in the fabrication of TiC but also cracked itself by the mechanical alloying process. The results of X-ray diffraction demonstrated the synthesis of cubic TiC. Gas phase chromatography showed that the discharged gas was composed of low molecular weight hydrocarbons, including H2, CH4 and C2H6. The formation mechanism of titanium carbide by mechanical alloying, and the thermodynamic and kinetics were discussed. These results showed that mechanical alloying is a promising method to prepare TiC and to crack asphalt with some light fraction byproducts.

  7. Structure and magnetic properties of nanostructured Ni{sub 0.77}Fe{sub 0.16}Cu{sub 0.05}Cr{sub 0.02} (Mumetal) powders prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Choo, K.S. [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue S639798 (Singapore); Gheisari, Kh. [Department of Materials Science and Engineering, Faculty of Engineering, Shahid Chamran University, Ahvaz (Iran, Islamic Republic of)], E-mail: ahledel227@yahoo.com; Oh, J.T. [School of Materials Science and Engineering, Nanyang Technological University, Nanyang Avenue S639798 (Singapore); Javadpour, S. [Department of Materials Science and Engineering, School of Engineering, Shiraz University, Shiraz, 7134851154 (Iran, Islamic Republic of)

    2009-02-15

    Ni-Fe based alloy powders are interesting materials for their application as soft magnetic material with low coercivity and high permeability. In this study, nanocrystalline Ni{sub 0.77}Fe{sub 0.16}Cu{sub 0.05}Cr{sub 0.02} (Mumetal) alloy powders were synthesized by mechanical alloying process using planetary high-energy ball mill under argon atmosphere. The alloy formation and different physical properties were studied as a function of milling time (h), ranging from 0 h to 96 h, using X-ray diffraction (XRD) technique, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and the vibrating sample magnetometer (VSM). The complete phase formation of {gamma}-(Fe, Ni, Cu, Cr) is observed after 12 h milling time. Powder morphology at different stages was examined by SEM and different particle shape was observed. Saturation magnetization and coercivity derived from the hysteresis curves are discussed as a function of milling time and showed that saturation magnetization increases and coercivity decreases with milling time. Increase in milling time, led to reduction in crystallite size and increase in lattice parameter , thus inducing a higher magnetization and lower coercitivity.

  8. 21 CFR 73.1646 - Bronze powder.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 1 2010-04-01 2010-04-01 false Bronze powder. 73.1646 Section 73.1646 Food and... ADDITIVES EXEMPT FROM CERTIFICATION Drugs § 73.1646 Bronze powder. (a) Identity. (1) The color additive bronze powder is a very fine metallic powder prepared from alloys consisting principally of...

  9. Deformation twinning characteristic of mechanically alloyed Cu-Nb alloy powders%机械合金化法制备Cu-Nb合金过程中的形变孪生特性

    Institute of Scientific and Technical Information of China (English)

    雷若姗; 汪明朴; 郭明星; 李周; 魏海根

    2011-01-01

    The microstructure evolution and deformation twinning characteristics of nanocrystalline Cu-10%Nb alloy during mechanical alloying (MA) were investigated by microhardness measurements, transmission electron microscopy (TEM) and high resolution TEM (HRTEM) observation. A local stress concentration model was proposed to explain the deformation twin nucleation mechanism of Cu-Nb alloy. The results show that the Vickers microhardness of the powders increases gradually with the increase of milling time, and reaches 4.8 GPa after 120 h milling. The main structure of the powders is the dislocation cells in the initial milling. After 50 h milling, the average Cu grain size decreases to about 50 nm, and nano-deformation twins begin to form in some regions. With the continued increase of the milling time, the number of twin increases, and the twin boundary strengthening enhances accordingly. Due to the deformation twinning will contribute to further refine the nano-grains, after 120 h milling, the nano-crystalline size decreases to below 20 nm.%采用机械合金化法制备纳米Cu-10%Nb合金,通过显微硬度测量以及高分辨透射电镜观察,对该合金粉末在室温球磨过程中的微观结构演变和形变孪生特性进行研究;利用局部应力集中模型分析形变孪晶的形核机制.结果表明:随着球磨时间的增加,该合金硬度(HV)不断升高,球磨120 h后可达4.8 GPa;该合金在球磨初期以位错胞结构为主;球磨50 h后,Cu平均晶粒尺寸减小至约50 nm,部分区域出现纳米形变孪晶;继续增加球磨时间,孪晶数量增加,孪晶界强化效果显著;由于孪生将促进纳米晶粒的进一步细化,球磨120 h后,纳米晶尺寸减小到20nm以下.

  10. Radiative transfer of HCN: interpreting observations of hyperfine anomalies

    Science.gov (United States)

    Mullins, A. M.; Loughnane, R. M.; Redman, M. P.; Wiles, B.; Guegan, N.; Barrett, J.; Keto, E. R.

    2016-07-01

    Molecules with hyperfine splitting of their rotational line spectra are useful probes of optical depth, via the relative line strengths of their hyperfine components. The hyperfine splitting is particularly advantageous in interpreting the physical conditions of the emitting gas because with a second rotational transition, both gas density and temperature can be derived. For HCN however, the relative strengths of the hyperfine lines are anomalous. They appear in ratios which can vary significantly from source to source, and are inconsistent with local thermodynamic equilibrium (LTE). This is the HCN hyperfine anomaly, and it prevents the use of simple LTE models of HCN emission to derive reliable optical depths. In this paper, we demonstrate how to model HCN hyperfine line emission, and derive accurate line ratios, spectral line shapes and optical depths. We show that by carrying out radiative transfer calculations over each hyperfine level individually, as opposed to summing them over each rotational level, the anomalous hyperfine emission emerges naturally. To do this requires not only accurate radiative rates between hyperfine states, but also accurate collisional rates. We investigate the effects of different sets of hyperfine collisional rates, derived via the proportional method and through direct recoupling calculations. Through an extensive parameter sweep over typical low-mass star-forming conditions, we show the HCN line ratios to be highly variable to optical depth. We also reproduce an observed effect whereby the red-blue asymmetry of the hyperfine lines (an infall signature) switches sense within a single rotational transition.

  11. Structural, Optical, and Magnetic Properties of Co Doped CdTe Alloy Powders Prepared by Solid-State Reaction Method

    Directory of Open Access Journals (Sweden)

    M. Rigana Begam

    2013-01-01

    Full Text Available Co doped CdTe powder samples were prepared by solid-state reaction method. In the present work effect of Co doping on structural, optical, and magnetic properties has been studied. X-ray diffraction studies confirm zinc blend structure for all the samples. The lattice parameter showed linear increase with the increase in Co content. The elemental constituents were characterized by EDAX. Optical studies showed the increase in band gap with increase in Co level. The samples were diluted magnetic semiconductors and exhibited clear hysteresis loop showing room temperature ferromagnetism as confirmed by vibrating sample magnetometer.

  12. Radiative Transfer of HCN: Interpreting observations of hyperfine anomalies

    CERN Document Server

    Mullins, A M; Redman, M P; Wiles, B; Guegan, N; Barrett, J; Keto, E R

    2016-01-01

    Molecules with hyperfine splitting of their rotational line spectra are useful probes of optical depth, via the relative line strengths of their hyperfine components.The hyperfine splitting is particularly advantageous in interpreting the physical conditions of the emitting gas because with a second rotational transition, both gas density and temperature can be derived. For HCN however, the relative strengths of the hyperfine lines are anomalous. They appear in ratios which can vary significantly from source to source, and are inconsistent with local thermodynamic equilibrium. This is the HCN hyperfine anomaly, and it prevents the use of simple LTE models of HCN emission to derive reliable optical depths. In this paper we demonstrate how to model HCN hyperfine line emission, and derive accurate line ratios, spectral line shapes and optical depths. We show that by carrying out radiative transfer calculations over each hyperfine level individually, as opposed to summing them over each rotational level, the anom...

  13. Calculation of hyperfine interaction in spherical quantum dot

    Science.gov (United States)

    Yakar, Yusuf; Çakır, Bekir; Özmen, Ayhan

    2015-10-01

    In this study, we have calculated the unperturbed wavefunctions and energy eigenvalues of the ground and excited states of a spherical quantum dot, GaAs/AlxGa1-xAs, by using quantum genetic algorithm and Hartree-Fock Roothaan method. Hyperfine coupling constant and hyperfine energy of 1s, 2p, 3d and 4f levels are carried out as a function of dot radius. The results show that the hyperfine constant and hyperfine energy varies rapidly in the strong and medium confining regions as dot radius decreases. It is worth pointing out that dot radius, impurity charge and angular momentum have a strong influence on the hyperfine energy. It is also found that hyperfine energy and hyperfine splitting vary with aluminium concentration ratio x.

  14. Study of Oxidation Behaviour of Bond Coating Nanocomposites Ni-20Cr-6Al Powder Synthesized by Mechanical Alloying

    Directory of Open Access Journals (Sweden)

    Akbar Salarvand

    2011-08-01

    Full Text Available In this study, nano crystalline Ni-20Cr-6Al composite powder was produced using a high energy planetary ball milling and a two-stage process. Then the oxidation behavior of coating of that superalloy at different temperatures considered. Nanostructured Ni-20Cr-6Al coating was deposited by cold spray for application as a bond coat to thermal barrier coating on industrial gas turbine components. The paper samples synthesized were characterized by scanning electron microscopy (SEM and transmission microscope (TEM. The crystallite size was found to be less than 18 nm. XRD pattern of the nanostructured Ni-20Cr-6Al milled powder consisted of two phases (Ni,Cr rich and (Ni3Al and so pure metals of Ni,Cr and Al that transferred into the coating. XRD pattern of the oxidized coating revealed that α-Al2O3 oxide was the main phase of the oxide and so Ni(Cr,Al 2O4 spinel phases despite the formation of α- Al2O3 oxide.

  15. Comparisons of particles thermal behavior between Fe-base alloy and boron carbide during plasma transferred-arc powder surfacing

    Institute of Scientific and Technical Information of China (English)

    王惜宝

    2003-01-01

    Comparisons of particle's thermal behavior between Fe-base alloy and boron carbide in plasma transferred-arc (PTA) space was made based on theoretical evaluation results in this article. It was found that most of the Fe base particles would be fully melted while they transporting through the central plasma field with 200 A surfacing currents. And the particles with a diameter less than 0.5×10-4 m might be fully evaporated. However, for the boron carbide (B4C) particles, only the one with a diameter less than 0.5×10-4 m could be melted in the same PTA space. Most of B4C particles are only preheated at its solid state when they were fed through the central field of PTA plasma when the surfacing current is equal to or less than 200 A. When the arc current was smaller than100 A, only the particles smaller than 0.5×10-4 m could be melted in the PTA space for the Fe-base alloy. Almost none of the discussed B4C particles could be melted in the 100 A PTA space.

  16. Mechanical Properties and Microstructures of As Printed and Heat Treated Samples of Selective Laser Melted IN625 Alloy Powder

    Directory of Open Access Journals (Sweden)

    Srinivasan Raghavan

    2015-01-01

    Full Text Available The current study focusses in evaluating the mechanical properties (yield strength, ultimate tensile strength and elongation % and microstructures of as printed and heat treated tensile samples produced by Selective Laser Melting (SLM which is an Additive Manufacturing (AM technique. The as printed IN625 alloy exhibited good mechanical properties as compared to cast and wrought alloy, owing to fast cooling rates that give very fine dendritic/cellular structures during the SLM process. Standard solutionizing and precipitation hardening treatment was given to the SLM as printed samples. The as printed sample’s ductility increased from 30% elongation to 47% elongation with small drop in tensile strength from 878MPa to 836MPa. The increase of ductility after heat treatment was evident in the change of fracture morphology from long straight striations with dimple shape ductile like features in the as printed sample to mainly dimple shaped ductile-like fracture surface in the heat treated sample as observed in the FESEM.

  17. Quantitative phase analysis from powder diffraction using de Rietveld method in hydrogen storage alloys based on TiCr

    Science.gov (United States)

    Martinez, A.; Bellon, D.; Reina, L.

    2016-08-01

    Hydrogen storage is one of the important steps in the implementation of the hydrogen economy; metal hydrides are a promising way to achieve this goal. We present in this work the use of Rietveld analysis to characterize structurally TiCr-based alloys that are able to store hydrogen. TiCruV09, TiCrL1V0.45Nb0.45, TiCr1.1V0.2 Nb0.8, TiCr1.1Nb0.9 alloys were synthesized in an arc furnace under argon atmosphere. The analysis of phases was developed by X-Ray Diffraction (XRD) for further refinement of both the two lattice parameters and the percentage of the phases. Our results confirmed that a structure bcc, mostly combined with a small percentage of Laves phases, leads to obtain important properties in this area. Rietveld analysis was performed by the Fullprof program and this program allows us to obtain the different structural parameters.

  18. The hyperfine Paschen-Back Faraday effect

    CERN Document Server

    Zentile, Mark A; Weller, Lee; Knappe, Svenja; Adams, Charles S; Hughes, Ifan G

    2014-01-01

    We investigate experimentally and theoretically the Faraday effect in an atomic medium in the hyperfine Paschen-Back regime, where the Zeeman interaction is larger than the hyperfine splitting. We use a small permanent magnet and a micro-fabricated vapour cell, giving magnetic fields of the order of a Tesla. We show that for low absorption and small rotation angles, the refractive index is well approximated by the Faraday rotation signal, giving a simple way to measure the atomic refractive index. Fitting to the atomic spectra, we achieve magnetic field sensitivity at the $10^{-4}$ level. Finally we note that the Faraday signal shows zero crossings which can be used as temperature insensitive error signals for laser frequency stabilisation at large detuning. The theoretical sensitivity for $^{87}$Rb is found to be $\\sim 40$ kHz/$^\\circ$C.

  19. The hyperfine Paschen-Back Faraday effect

    Science.gov (United States)

    Zentile, Mark A.; Andrews, Rebecca; Weller, Lee; Knappe, Svenja; Adams, Charles S.; Hughes, Ifan G.

    2014-04-01

    We investigate experimentally and theoretically the Faraday effect in an atomic medium in the hyperfine Paschen-Back regime, where the Zeeman interaction is larger than the hyperfine splitting. We use a small permanent magnet and a micro-fabricated vapour cell, giving magnetic fields of the order of a tesla. We show that for low absorption and small rotation angles, the refractive index is well approximated by the Faraday rotation signal, giving a simple way to measure the atomic refractive index. Fitting to the atomic spectra, we achieve magnetic field sensitivity at the 10-4 level. Finally we note that the Faraday signal shows zero crossings which can be used as temperature insensitive error signals for laser frequency stabilization at large detuning. The theoretical sensitivity for 87Rb is found to be ˜40 kHz °C-1.

  20. HfS, Hyperfine Structure Fitting Tool

    CERN Document Server

    Estalella, Robert

    2016-01-01

    HfS is a tool to fit the hyperfine structure of spectral lines, with multiple velocity components. The HfS_nh3 procedures included in HfS fit simultaneously the hyperfine structure of the NH$_3$ (J,K)= (1,1) and (2,2) transitions, and perform a standard analysis to derive $T_\\mathrm{ex}$, NH$_3$ column density, $T_\\mathrm{rot}$, and $T_\\mathrm{k}$. HfS uses a Monte Carlo approach for fitting the line parameters. Especial attention is paid to the derivation of the parameter uncertainties. HfS includes procedures that make use of parallel computing for fitting spectra from a data cube.

  1. Temperature dependence of the hyperfine interaction at

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Garcia, Alberto; de la Presa, Patricia; Ayala, Alejandro

    2001-06-01

    The temperature dependence of the quadrupole hyperfine parameters covering the temperature range from 293 to 1173 K was measured at {sup 181}Ta probes in SrHfO{sub 3} by perturbed angular correlation spectroscopy. A fluctuating distribution of quadrupole interactions model was applied to interpret the data. At low temperatures above {approximately}300 K a static, asymmetric, and distributed electric quadrupole interaction was detected. At intermediate temperatures ({approx}600 K) a different quadrupole interaction appears, characterized by a fluctuating distribution of axially symmetric electric field gradient tensors. Above 873 K, the unique presence of a nuclear spin relaxation mechanism shows a second change in the perturbation acting on probes. These changes in the hyperfine interaction are consistent with the structural phase transitions detected by diffraction techniques. The probe effects were also analyzed, comparing {sup 181}Ta with {sup 111}Cd experiments.

  2. Interlaboratory Study for Nickel Alloy 625 Made by Laser Powder Bed Fusion to Quantify Mechanical Property Variability

    Science.gov (United States)

    Brown, Christopher U.; Jacob, Gregor; Stoudt, Mark; Moylan, Shawn; Slotwinski, John; Donmez, Alkan

    2016-08-01

    Six different organizations participated in this interlaboratory study to quantify the variability in the tensile properties of Inconel 625 specimens manufactured using laser powder bed fusion-additive manufacturing machines. The tensile specimens were heat treated and tensile tests were conducted until failure. The properties measured were yield strength, ultimate tensile strength, elastic modulus, and elongation. Statistical analysis revealed that between-participant variability for yield strength, ultimate tensile strength, and elastic modulus values were significantly higher (up to four times) than typical within-participant variations. Only between-participant and within-participant variability were both similar for elongation. A scanning electron microscope was used to examine one tensile specimen for fractography. The fracture surface does not have many secondary cracks or other features that would reduce the mechanical properties. In fact, the features largely consist of microvoid coalescence and are entirely consistent with ductile failure.

  3. Hyperfine and Optical Barium Ion Qubits

    CERN Document Server

    Dietrich, M R; Noel, T; Shu, G; Blinov, B B

    2010-01-01

    State preparation, qubit rotation, and high fidelity readout are demonstrated for two separate \\baseven qubit types. First, an optical qubit on the narrow 6S$_{1/2}$ to 5D$_{5/2}$ transition at 1.76 $\\mu$m is implemented. Then, leveraging the techniques developed there for readout, a ground state hyperfine qubit using the magnetically insensitive transition at 8 GHz is accomplished.

  4. Cavity QED with Multiple Hyperfine Levels

    CERN Document Server

    Birnbaum, K M; Kimble, H J

    2006-01-01

    We calculate the weak-driving transmission of a linearly polarized cavity mode strongly coupled to the D2 transition of a single Cesium atom. Results are relevant to future experiments with microtoroid cavities, where the single-photon Rabi frequency g exceeds the excited-state hyperfine splittings, and photonic bandgap resonators, where g is greater than both the excited- and ground-state splitting.

  5. Hyperfine coupling constant for {sup 59}Co estimated from a high-field susceptibility and high-field NMR shift in ferromagnetic Co{sub 2}TiGa and Co{sub 2}VGa

    Energy Technology Data Exchange (ETDEWEB)

    Nishihara, H; Furutani, Y; Wada, T [Faculty of Science and Technology, Ryukoku University, Otsu 520-2194 (Japan); Kanomata, T [Faculty of Engineering, Tohoku Gakuin University, Tagajo 985-8537 (Japan); Kobayashi, K; Ishida, K [Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Kainuma, R [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, Sendai 980-8577 (Japan); Koyama, K; Watanabe, K, E-mail: nishihara@rins.ryukoku.ac.j [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan)

    2010-01-01

    The hyperfine coupling constant for {sup 59}Co in the ferromagnetic state of a Heusler alloy Co{sub 2}TiGa in the high-field range has been estimated to be 170 kOe per 1 {mu}{sub B} of the moment of cobalt atom from the high-field magnetic susceptibility of 2.3 x 10{sup -6} emu/gOe measured at 5 K in a field range from 20 to 70 kOe and a reported positive high-field NMR shift of +0.83 percent. The value of the hyperfine coupling constant has been found to be even larger in the case of Co{sub 2}VGa. These features suggest that the positive hyperfine field at Co nucleus in the Co-based Heusler alloys is due to conduction electron polarization rather than a transferred hyperfine field.

  6. Liquid phase surface melting of AA8011 aluminum alloy by addition of Al/Al{sub 2}O{sub 3} nano-composite powders synthesized by high-energy milling

    Energy Technology Data Exchange (ETDEWEB)

    Sohi, M. Heydarzadeh [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of); Hojjatzadeh, S.M.H., E-mail: Hojatzadeh@yahoo.com [Department of Welding, Science and Research Branch, Azad University, Tehran (Iran, Islamic Republic of); Moosavifar, Sh. S.; Heshmati-Manesh, S. [School of Metallurgy and Materials Engineering, College of Engineering, University of Tehran, Tehran (Iran, Islamic Republic of)

    2014-09-15

    Highlights: • Aluminum matrix composite layers reinforced with alumina particles were fabricated. • Non milled powders caused porosity in the microstructures because of poor wettability. • The ball milling of powders was significantly improved the wettability of nano ceramic particles. • The micro hardness of the layers was approximately 3 times greater than that of the base metal. - Abstract: Poor wettability of particles is an obstacle in formation of sound composite layer via surface melting. Pre-coating of particles with metallic material by different techniques, such as ball milling may enhance the wettability of the particles with molten metal. In this study, composite surface layers containing Al{sub 2}O{sub 3} particles were fabricated on the surface of AA8011 aluminum substrates by tungsten inert gas (TIG) surface melting using preplaced layers of Al/Al{sub 2}O{sub 3} powder mixtures in two different forms: (1) a mixture of 40 wt% Al and 60 wt% of 50 nm Al{sub 2}O{sub 3} powders and (2) a mixture obtained by mechanical alloying of 40 wt% Al and 60 wt% of 60 μm Al{sub 2}O{sub 3} powders. Morphology evolution of powders during ball milling and the microstructure of the fabricated composite layers were studied through conventional characterization techniques, such as optical microscopy, scanning electron microscopy (SEM), and X-ray diffraction (XRD). Microhardness measurements were also performed across the alloyed zone. The results indicated that the layer fabricated by the second route showed a defect free structure with a more uniform distribution of Al{sub 2}O{sub 3} particles in comparison with the layer obtained by the first route. It was also noticed that the uniform dispersion of Al{sub 2}O{sub 3} particles in the fabricated layer increased the hardness to 133 HV which was over 3 times of that of the base metal.

  7. Mechanical alloying and subsequent heat treatment of Ag-Zn powders%Ag-Zn粉末的机械合金化和随后的热处理

    Institute of Scientific and Technical Information of China (English)

    Danny GUZMN; Oscar RIVERA; Claudio AGUILAR; Stella ORDOEZ; Carola MARTNEZ; Daniel SERAFINI; Paula ROJAS

    2013-01-01

    Microstructural evolution during mechanical alloying of Ag and Zn, and subsequent heat treatments were investigated. The mechanical alloying was carried out in a SPEX 8000D miller. The microstructural characterization was obtained by X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The thermal behavior was studied using differential scanning calorimetry (DSC). Based on the results obtained, it can be concluded that at the early stages of milling was possible to detect theε,β,β′,αsolid solutions and remaining Zn. Later, theε,β,β′and Zn phases disappeared while the Zn concentration of theαsolid solution was strongly increased. After 7.2 ks of milling, the mechanical alloying process reached a steady state. During this period, both the composition and crystallite size of theαsolid solution remained practically unchanged. On the other hand, subsequent heat treatments of milled powders showed that the α solid solution could also be obtained by the combination of mechanical alloying and heat treatment. Finally, the evolution of the microstructure during milling and annealing was combined to propose an optimal processing route in order to obtain aαsolid solution.%  研究了在机械合金化过程中Ag 和 Zn以及随后的热处理中的显微组织演变。机械合金化在SPEX 8000D铣床中进行。采用X射线衍射(XRD)﹑透射电子显微镜(TEM)和扫描电子显微镜(SEM)观察样品的显微组织。使用差示扫描量热计(DSC)研究样品的热性能。结果表明,在合金化初期的碾磨过程中能观察到ε,β,β′,α固溶体和剩余的Zn。随后,ε,β,β′和 Zn相消失,α固溶体中的Zn浓度剧烈升高。在碾磨7.2 ks后,机械合金化过程达到稳定状态。在此期间,α固溶体的组分和晶粒尺寸保持不变。后续热处理表明α固溶体也能够通过机械合金化结合热处理得到。最后,为了得到α固

  8. Mössbauer study of alloy Fe{sub 67.5}Ni{sub 32.5}, prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Benitez Rodríguez, Edson Daniel, E-mail: edbenitezr@ut.edu.co; Bustos Rodríguez, Humberto; Oyola Lozano, Dagoberto; Rojas Martínez, Yebrail Antonio [University of Tolima, Department of Physics (Colombia); Pérez Alcázar, German Antonio [University of Valle, Department of Physics (Colombia)

    2015-06-15

    We present the study of effect of the particle size on the structural and magnetic properties of the Fe{sub 67.5}Ni{sub 32.5} alloy, prepared by mechanical alloying (MA). After milling the powders during 10 hours they were separated by sieving using different meshes. The refinement of the X-ray patterns showed the coexistence of the BCC (Body Centered Cubic) and the FCC (Face Centered Cubic) phases in all samples with lattice parameters and crystallite sizes independent of the mean particle size. However, big particles presented bigger volumetric fraction of BCC grains. The Mossbauer spectra were fitted with a broad sextet corresponding to the ferromagnetic BCC phase, a hyperfine magnetic field distribution and a broad singlet which correspond to the ferromagnetic and paramagnetic sites of the FCC phase, respectively. Hysteresis loops showed a magnetically, soft behavior for all the samples, however, the saturation magnetization values are smaller for the original powder and for the powders with small, mean, particle size due to the dipolar magnetic interaction and the smaller mean magnetic moment, respectively. These effects were proved by Henkel plots that were made to the samples.

  9. Nagaoka's atomic model and hyperfine interactions.

    Science.gov (United States)

    Inamura, Takashi T

    2016-01-01

    The prevailing view of Nagaoka's "Saturnian" atom is so misleading that today many people have an erroneous picture of Nagaoka's vision. They believe it to be a system involving a 'giant core' with electrons circulating just outside. Actually, though, in view of the Coulomb potential related to the atomic nucleus, Nagaoka's model is exactly the same as Rutherford's. This is true of the Bohr atom, too. To give proper credit, Nagaoka should be remembered together with Rutherford and Bohr in the history of the atomic model. It is also pointed out that Nagaoka was a pioneer of understanding hyperfine interactions in order to study nuclear structure.

  10. Laboratory Powder Metallurgy Makes Tough Aluminum Sheet

    Science.gov (United States)

    Royster, D. M.; Thomas, J. R.; Singleton, O. R.

    1993-01-01

    Aluminum alloy sheet exhibits high tensile and Kahn tear strengths. Rapid solidification of aluminum alloys in powder form and subsequent consolidation and fabrication processes used to tailor parts made of these alloys to satisfy such specific aerospace design requirements as high strength and toughness.

  11. Influence of milling time on the structural, microstructural and magnetic properties of mechanically alloyed Ni{sub 58}Fe{sub 12}Zr{sub 10}Hf{sub 10}B{sub 10} nanostructured/amorphous powders

    Energy Technology Data Exchange (ETDEWEB)

    Besmel, R., E-mail: r.besmel@iauahvaz.ac.ir [Materials Science and Engineering Department, Islamic Azad University Ahvaz Branch, Ahvaz (Iran, Islamic Republic of); Ghaffari, M. [School of Electrical and Electronic Engineering, Sensor and Actuator Laboratory II, BLK S2.1, B6-02, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798 (Singapore); Shokrollahi, H., E-mail: shokrollahi@sutech.ac.ir [Electroceramics Group, Materials Science and Engineering Department, Shiraz University of Technology, 71555-313, Shiraz (Iran, Islamic Republic of); Chitsazan, B.; Karimi, L. [Materials Science and Engineering Department, Islamic Azad University Ahvaz Branch, Ahvaz (Iran, Islamic Republic of)

    2011-11-15

    This paper investigates structural, microstructural and magnetic properties of amorphous/nanocrystalline Ni{sub 58}Fe{sub 12}Zr{sub 10}Hf{sub 10}B{sub 10} powders prepared by high energy milling. Ball milling of Ni, Fe, Zr, Hf and B leads to alloying of the element powders at 120 h. The results show that at 190 h the amorphous content is at the highest level and the grain size is about 2 nm. The magnetic measurements reveal that the coercivity and the saturation magnetization reach about 20 Oe and 30 emu/g at 190 h and become approximately 5 Oe and 40 emu/g after a suitable heat treatment, respectively. - Highlights: > We investigated the influence of milling time on the structural and magnetic properties of mechanically alloyed Ni{sub 58}Fe{sub 12}Zr{sub 10}Hf{sub 10}B{sub 10} nanostructured/amorphous powders. > Results showed that at 190 h the amorphous content is at the highest level and the grain size is about 2 nm. > By obtaining the amorphous structure and applying a suitable heat treatment the magnetic properties were improved.

  12. Particle size effect on microwave absorbing of La0.67Ba0.33Mn0.94Ti0.06O3 powders prepared by mechanical alloying with the assistance of ultrasonic irradiation

    Science.gov (United States)

    Saptari, Sitti Ahmiatri; Manaf, Azwar; Kurniawan, Budhy

    2016-03-01

    Doped manganites have attracted substantial interest due to their unique chemical and physics properties, which makes it possible to be used for microwave absorbing materials. In this paper we report synthesizes and characterization of La0.67Ba0.33Mn0.94Ti0.06O3 powders prepared by mechanical alloying with the assistance of a high power ultrasonic treatment. After solid state reaction, the presence of single phase was confirmed by X-ray Diffraction (XRD). Refinement results showed that samples are single phase with monoclinic structure. It was found that powder materials derived from mechanical alloying results in large variation in the particle size. A significant improvement was obtained upon subjecting the mechanically milled powder materials to an ultrasonication treatment for a relatively short period of time. As determined by particle size analyzer (PSA), the mean particle size gradually decreased from the original size of 5.02 µm to 0.36 µm. Magnetic properties were characterized by VSM, and hysteresis loops results showed that samples are soft magnetic. It was found that when the mean particle size decreases, saturation was increases and coersitivity was decreases. Microwave absorption properties were investigated in the frequency range of 8-12 GHz using vector network analyzer. An optimal reflection loss of 24.44 dB is reached at 11.4 GHz.

  13. Study of hyperfine parameters in Co-doped tin dioxide using PAC spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Ramos, Juliana M.; Carbonari, Artur W.; Martucci, Thiago; Costa, Messias S.; Saxena, Rajendra N. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Vianden, R.; Kessler, P.; Geruschke, T.; Steffens, M., E-mail: vianden@hiskp.uni-bonn.d [Rheinische Friedrich-Wilhelms-Universitaet Bonn (HISKP- Bonn) (Germany). Helmholtz - Institut fuer Strahlen- und Kernphysik

    2011-07-01

    PAC technique has been used to measure the hyperfine interactions in nano-structured powder samples of semiconducting SnO{sub 2} doped with Co. The aim of this work is to compare the results of PAC measurements using two different techniques of introducing the radioactive {sup 111}In probe nuclei in the sample of SnO{sub 2} doped with Co. The perturbed gamma-gamma angular correlation (PAC) spectroscopy is used for the measurements of the magnetic hyperfine field (MHF) and the electric field gradient (EFG) at {sup 111}Cd sites in SnO{sub 2} doped with 1% and 2% Co. The measurement of EFG is used to study the defects introduced in the semiconductor material and also for the identification of different phases formed within the compound. The techniques utilized for introducing the radioactive {sup 111}In in the sample are the ion-implantation using radioactive ion beam of {sup 111}In and the chemical process in which {sup 111}InCl{sub 3} solution is added during the preparation of SnO{sub 2} doped with Co using sol gel method. The ion-implantation of {sup 111}In in SnO{sub 2} doped with Co was carried out using the University of Bonn ion-implanter with beam energy of 160 keV. The PAC measurements were carried out with four BaF{sub 2} detector gamma spectrometer in the temperature range of 10-295 K. The results show no significant difference in the values of hyperfine parameters. Both techniques show practically the same electric quadrupole interaction for the substitutional site. The results were compared with previous PAC and Moessbauer measurements of SnO{sub 2} powder samples using {sup 111}In-{sup 111}Cd probe. (author)

  14. Proceedings of the 2nd KUR symposium on hyperfine interactions

    Science.gov (United States)

    Mekata, M.; Minamisono, T.; Kawase, Y.

    1991-10-01

    Hyperfine interactions between a nuclear spin and an electronic spin discovered from hyperfine splitting in atomic optical spectra have been utilized not only for the determination of nuclear parameters in nuclear physics but also for novel experimental techniques in many fields such as solid state physics, chemistry, biology, mineralogy, and for diagnostic methods in medical science. Experimental techniques based on hyperfine interactions yield information about microscopic states of matter so that they are important in material science. Probes for material research using hyperfine interactions have been nuclei in the ground state and radioactive isotopes prepared with nuclear reactors or particle accelerators. But the use of muons generated from accelerators is growing. Such wide spread application of hyperfine interaction techniques gives rise to some difficulty in collaboration among various research fields. This report summarizes the KUR symposium in the hope that this information will help to alleviate the problem.

  15. Microstructure and magnetic properties of nanostructured (Fe{sub 0.8}Al{sub 0.2}){sub 100–x}Si{sub x} alloy produced by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Boukherroub, N. [UR-MPE, M' hamed Bougara University, Boumerdes 35000 (Algeria); Guittoum, A., E-mail: aguittoum@gmail.com [Nuclear Research Centre of Algiers, 02 Bd Frantz Fanon, BP 399 Alger-Gare, Algiers (Algeria); Laggoun, A. [UR-MPE, M' hamed Bougara University, Boumerdes 35000 (Algeria); Hemmous, M. [Nuclear Research Centre of Algiers, 02 Bd Frantz Fanon, BP 399 Alger-Gare, Algiers (Algeria); Martínez-Blanco, D. [SCTs, University of Oviedo, EPM, 33600 Mieres (Spain); Blanco, J.A. [Department of Physics, University of Oviedo, Calvo Sotelo St., 33007 Oviedo (Spain); Souami, N. [Nuclear Research Centre of Algiers, 02 Bd Frantz Fanon, BP 399 Alger-Gare, Algiers (Algeria); Gorria, P. [Department of Physics and IUTA, EPI, University of Oviedo, 33203 Gijón (Spain); Bourzami, A. [Laboratoire d' Etudes des Surfaces et Interfaces des Matériaux Solides (LESIMS), Université Sétif1, 19000 Sétif (Algeria); Lenoble, O. [Institut Jean Lamour, CNRS-Université de Lorraine, Boulevard des aiguillettes, BP 70239, F-54506 Vandoeuvre lès Nancy (France)

    2015-07-01

    We report on how the microstructure and the silicon content of nanocrystalline ternary (Fe{sub 0.8}Al{sub 0.2}){sub 100–x}Si{sub x} powders (x=0, 5, 10, 15 and 20 at%) elaborated by high energy ball milling affect the magnetic properties of these alloys. The formation of a single-phase alloy with body centred cubic (bcc) crystal structure is completed after 72 h of milling time for all the compositions. This bcc phase is in fact a disordered Fe(Al,Si) solid solution with a lattice parameter that reduces its value almost linearly as the Si content is increased, from about 2.9 Å in the binary Fe{sub 80}Al{sub 20} alloy to 2.85 Å in the powder with x=20. The average nanocrystalline grain size also decreases linearly down to 10 nm for x=20, being roughly half of the value for the binary alloy, while the microstrain is somewhat enlarged. Mössbauer spectra show a sextet thus suggesting that the disordered Fe(Al,Si) solid solution is ferromagnetic at room temperature. However, the average hyperfine field diminishes from 27 T (x=0) to 16 T (x=20), and a paramagnetic doublet is observed for the powders with higher Si content. These results together with the evolution of both the saturation magnetization and the coercive field are discussed in terms of intrinsic and extrinsic properties. - Highlights: • Single-phase nanocrystalline (Fe{sub 0.8}Al{sub 0.2}){sub 100–x}Si{sub x} (x=0, 5, 10, 15 and 20 at%) powders were successfully fabricated by mechanical alloying for a milling time of 72 h. • The insertion of Si atoms leads to a unit-cell contraction and a decrease in the average crystallite size. • The hyperfine and magnetic properties of (Fe{sub 0.8}Al{sub 0.2}){sub 100–x}Si{sub x} were influenced by the Si content.

  16. Phase changes in Fe72-Al28Cr ( = 0; 2; 4; 6) alloys due to mechanical strain

    Indian Academy of Sciences (India)

    Brajesh Pandey; H C Verma

    2005-02-01

    Fe72-Al28Cr alloys ( = 0; 2; 4; 6) are made by arc melting a mixture of constituent elements in stoichiometric proportion, in argon atmosphere. The ingots so obtained are filed to make powder samples thereby giving them substantial mechanical deformation. It is observed that as-powdered samples show hyperfine field distribution typical of -phase, where the atoms are randomly distributed on the available sites. Annealing at 900°C for 60 h leads to preferential occupation of lattice sites by the atoms and this results in better defined groups of hyperfine magnetic field (HMF) which can be associated with specific configuration in the neighbourhood of probe iron atoms. The average HMF is found to decrease sharply with increasing Cr concentration even though the net chromium concentration remains low (≤ 6 at \\%). The results show that cold working on samples is very important in changing the atomic ordering and must be taken into account if properties of equilibrium phases are probed.

  17. Compaction of Titanium Powders

    Energy Technology Data Exchange (ETDEWEB)

    Gerdemann, Stephen,J; Jablonski, Paul, J

    2011-05-01

    Accurate modeling of powder densification has been an area of active research for more than 60 years. The earliest efforts were focused on linearization of the data because computers were not readily available to assist with curve-fitting methods. In this work, eight different titanium powders (three different sizes of sponge fines<150 {micro}m,<75 {micro}m, and<45 {micro}m; two different sizes of a hydride-dehydride [HDH]<75 {micro}m and<45 {micro}m; an atomized powder; a commercially pure [CP] Ti powder from International Titanium Powder [ITP]; and a Ti 6 4 alloy powder) were cold pressed in a single-acting die instrumented to collect stress and deformation data during compaction. From these data, the density of each compact was calculated and then plotted as a function of pressure. The results show that densification of all the powders, regardless of particle size, shape, or chemistry, can be modeled accurately as the sum of an initial density plus the sum of a rearrangement term and a work-hardening term. These last two terms are found to be a function of applied pressure and take the form of an exponential rise.

  18. Effects of Process Conditions on the Mechanical Behavior of Aluminium Wrought Alloy EN AW-2219 (AlCu6Mn Additively Manufactured by Laser Beam Melting in Powder Bed

    Directory of Open Access Journals (Sweden)

    Michael Cornelius Hermann Karg

    2017-01-01

    Full Text Available Additive manufacturing is especially suitable for complex-shaped 3D parts with integrated and optimized functionality realized by filigree geometries. Such designs benefit from low safety factors in mechanical layout. This demands ductile materials that reduce stress peaks by predictable plastic deformation instead of failure. Al–Cu wrought alloys are established materials meeting this requirement. Additionally, they provide high specific strengths. As the designation “Wrought Alloys” implies, they are intended for manufacturing by hot or cold working. When cast or welded, they are prone to solidification cracks. Al–Si fillers can alleviate this, but impair ductility. Being closely related to welding, Laser Beam Melting in Powder Bed (LBM of Al–Cu wrought alloys like EN AW-2219 can be considered challenging. In LBM of aluminium alloys, only easily-weldable Al–Si casting alloys have succeeded commercially today. This article discusses the influences of boundary conditions during LBM of EN AW-2219 on sample porosity and tensile test results, supported by metallographic microsections and fractography. Load direction was varied relative to LBM build-up direction. T6 heat treatment was applied to half of the samples. Pronounced anisotropy was observed. Remarkably, elongation at break of T6 specimens loaded along the build-up direction exceeded the values from literature for conventionally manufactured EN AW-2219 by a factor of two.

  19. 粉末冶金生物医用Ti合金的研究及应用现状%Research progress and application of biomedical titanium alloys prepared by powder metallurgy

    Institute of Scientific and Technical Information of China (English)

    赵腾飞; 路新; 曲选辉

    2012-01-01

    Ti及Ti合金具有低密度、高比强度、较低的弹性模量以及优异的耐腐蚀性能和生物相容性,因而成为生物医用材料的首选.本文简要介绍了粉末冶金技术制备Ti及其合金的主要特点及其优势,从粉末准备、成形、烧结、性能4个方面综述了粉末冶金医用Ti合金的研究进展,并总结了目前粉末冶金医用Ti合金的应用状况;针对目前存在的主要问题,分析了粉末冶金医用Ti合金的发展方向及其应用前景.%With low density, high specific strength, low elastic modulus, high melting temperature and favorable corrosion resistance and tissue compatibility, Ti and its alloys have been considered as a first choice for biomedical application. In this paper, the main characteristics and advantages of titanium alloys fabricated by powder metallurgy were briefly introduced. The recent research progresses and application of the P/M biomedical Ti-alloys were reviewed, especially in terms of powder preparation, forming, sintering and properties. The further development trend and application prospect of P/M Ti-alloys were analyzed in view of the existing problems of clinical application.

  20. Improved theory of the muonium hyperfine structure

    CERN Document Server

    Kinoshita, T

    1994-01-01

    Terms contributing to the hyperfine structure of the muonium ground state at the level of few tenths of keV have been evaluated. The $\\alpha^2 (Z\\alpha)$ radiative correction has been calculated numerically to the precision of 0.02 kHz. Leading $\\ln (Z\\alpha )$ terms of order $\\alpha^{4-n} (Z\\alpha)^n , n=1,2,3,$ and some relativistic corrections have been evaluated analytically. The theoretical uncertainty is now reduced to 0.17 keV. At present, however, it is not possible to test QED to this precision because of the 1.34 kHz uncertainty due to the muon mass.

  1. Effects of powder size segregation on tensile properties of Ti-5Al-2.5Sn ELI alloy powder%粉末粒度偏析对Ti-5Al-2.5Sn ELI粉末合金拉伸性能的影响

    Institute of Scientific and Technical Information of China (English)

    程文祥; 徐磊; 雷家峰; 刘羽寅; 杨锐

    2013-01-01

    Ti-5Al-2.5Sn ELI pre-alloyed powders were prepared by electrode induction melting gas atomization process, and Ti-5Al-2.5Sn ELI alloy was prepared through hot isostatic pressing route. Five different HIPed preforms of Ti-5Al-2.5Sn ELI alloy were prepared. Five HIPed performs were prepared by the same hot isostatic pressing, powder filling and taping parameters except various original powder size distribution ranges. Powder size segregation usually occurred during powder filling and long-time taping and its influence on alloy properties were both studied. The results show that, in the first group of HIPed preforms prepared by typical powder filling and taping parameters, the air contents of the five preforms are almost the same, while the largest grain size difference is about 10μm;no obvious difference is found on tensile properties of different samples. While in HIPed preforms prepared by long-time taping and powder filling process, cryogenic tensile properties of samples from the top of the capsule deteriorate significantly due to powder size segregation phenomenon.%  采用无坩埚感应熔炼超声气体雾化法制备洁净的Ti-5Al-2.5Sn ELI预合金粉末,用热等静压包套技术制备全致密的Ti-5Al-2.5Sn ELI粉末合金.采用常规工艺填充5种不同粒度分布的Ti-5Al-2.5Sn ELI粉末样品并进行热等静压处理,得到全致密的粉末合金;并采用长时间振实工艺填充一组粉末冶金样品.结果表明:以常规工艺填充的粉末样品制得的5组粉末合金压坯的气体含量处于同一水平,晶粒尺寸最大差异在10μm左右,合金的室温和低温拉伸性能无明显差异.长时间振实工艺填充粉末会引起大颗粒粉末聚集于包套上部、细小颗粒粉末则向下沉降的粒度偏析现象,该现象对粉末合金的室温性能无明显影响,但造成包套端部合金样品的低温塑性显著下降,下降幅度达50%.

  2. CHARACTERIZATION OF TiAl PRE-ALLOYED POWDER AND ITS DENSIFICATION MICROSTRUCTURE%TiAl预合金粉末的表征和后续致密化显微组织特点

    Institute of Scientific and Technical Information of China (English)

    王刚; 郑卓; 常立涛; 徐磊; 崔玉友; 杨锐

    2011-01-01

    采用感应熔炼气体雾化法制备了TiAl预合金粉末.粉末粒度主要分布在100-250 μm,呈正态分布,粉末平均粒度为120.7 μm.TiAl预合金粉末的相组成与粒度分布有关,γ相所占比例越高,预合金粉末粒度越大.小粒度的预合金粉末主要由α2相组成;预合金粉末在温度高于500℃时效处理,发生α2→γ转变.TiAl预合金粉末相组成不同会产生后续热等静压组织局部粗化现象.XPS结果表明TiAl预合金粉末颗粒表面形成Al2O3和TiO2薄膜.%TiAl pre-alloyed powder (nominal composition Ti-47Al-2Cr-2Nb-0.2W-0.15B, atomic fraction, %) was produced by electrode induction melting gas atomization (EIGA) technique. The average diameter is 120.7 μm, and the distribution of the powder diameter follows Gaussian distri-bution. The phase constitution is a function of particle diameter. The amount of the 7 phase increases with powder diameter increasing, the finest powder consists of predominantly α2 phase. The α2 phase in the powder was transformed into 7 phase after annealing at temperatures higher than 500 ℃. Local coarsening was observed in the microstructure of TiAl compact duo to the microsegregation of elements in the powder. The XPS result indicated that the outer layer of the TiAl pre-alloyed particle consists of a thin layer of AL2O3 and TiO2-

  3. Structural properties and hyperfine characterization of Sn-substituted goethites

    Energy Technology Data Exchange (ETDEWEB)

    Larralde, A.L. [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina); Ramos, C.P. [Departamento de Fisica de la Materia Condensada, GIyA - CAC - CNEA, Av. Gral. Paz 1499 (1650), San Martin, Bs. As. (Argentina); Arcondo, B. [Departamento de Fisica, Facultad de Ingenieria, Universidad de Buenos Aires, Av. Paseo Colon 850 (C1063ACV), Bs. As. (Argentina); Tufo, A.E. [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina); Saragovi, C. [Departamento de Fisica de la Materia Condensada, GIyA - CAC - CNEA, Av. Gral. Paz 1499 (1650), San Martin, Bs. As. (Argentina); Sileo, E.E., E-mail: sileo@qi.fcen.uba.ar [INQUIMAE, Departamento de Quimica Inorganica, Analitica y Quimica Fisica, Facultad de Ciencias Exactas y Naturales, Universidad de Buenos Aires (Argentina)

    2012-04-16

    Highlights: Black-Right-Pointing-Pointer Pure and tin-doped goethites were synthesized from Sn(II) solutions at ambient pressure and 70 Degree-Sign C. Black-Right-Pointing-Pointer The Rietveld refinement of PXRD data indicated that Sn partially substituted the Fe(III) ions. Black-Right-Pointing-Pointer The substitution provoked unit cell expansion, and a distortion of the coordination polyhedron. Black-Right-Pointing-Pointer {sup 119}Sn Moessbauer spectroscopy revealed that Sn(II) is incorporated as Sn(IV). Black-Right-Pointing-Pointer {sup 57}Fe Moessbauer spectroscopy showed a lower magnetic coupling as tin concentration increased. - Abstract: Tin-doped goethites obtained by a simple method at ambient pressure and 70 Degree-Sign C were characterized by inductively coupled plasma atomic emission spectrometry, scanning electron microscopy, Rietveld refinement of powder X-ray diffraction data, and {sup 57}Fe and {sup 119}Sn Moessbauer spectroscopy. The particles size and the length to width ratios decreased with tin-doping. Sn partially substituted the Fe(III) ions provoking unit cell expansion and increasing the crystallinity of the particles with enlarged domains that grow in the perpendicular and parallel directions to the anisotropic broadening (1 1 1) axis. Intermetallic E, E Prime and DC distances also change although the variations are not monotonous, indicating different variations in the coordination polyhedron. In general, the Sn-substituted samples present larger intermetallic distances than pure goethite, and the greatest change is shown in the E Prime distance which coincides with the c-parameter. {sup 119}Sn Moessbauer spectroscopy revealed that Sn(II) is incorporated as Sn(IV) in the samples. On the other hand, Fe(II) presence was not detected by {sup 57}Fe Moessbauer spectroscopy, suggesting the existence of vacancies in the Sn-doped samples. A lower magnetic coupling is also evidenced from the average magnetic hyperfine field values obtained as tin

  4. Electrical detection of hyperfine interactions in silicon

    Energy Technology Data Exchange (ETDEWEB)

    Hoehne, Felix

    2012-12-15

    The main focus of this work was the measurement of hyperfine interactions of defects in silicon using EDMR. We combined the high sensitivity of EDMR when compared to conventional ESR with the two most commonly used methods for the measurement of hyperfine interactions: ESEEM and ENDOR. We first demonstrated the electrical detection of ESEEM by measuring the hyperfine interactions of {sup 31}P donors in Si:P with {sup 29}Si nuclear spins. We then apply EDESEEM to P{sub b0} defects at the Si/SiO{sub 2} interface. In isotopically engineered, we observe an ESEEM modulation with a characteristic beating caused by {sup 29}Si nuclei at 4th and 5th nearest neighbor lattice sites. Then we combine pulsed ENDOR with the high sensitivity of EDMR (EDENDOR). First we demonstrate the measurement of {sup 31}P nuclear spin hyperfine transitions and the coherent manipulation and readout of the {sup 31}P nuclear spins under continuous illumination with above bandgap light. We further show that the EDENDOR method can be greatly improved by switching off the illumination during the microwave and rf pulses. This improves the signal-to-noise ratio by two orders of magnitude and removes the non-resonant background induced by the strong rf pulse allowing to measure ENDOR with a sensitivity <3000 nuclear spins. We apply EDENDOR to the {sup 31}P-P{sub b0} spin system and the {sup 31}P-SL1 spin system allowing us to compare the hyperfine interactions of bulk and interface-near donors. The pulsed illumination also makes spectroscopy of the {sup 31}P{sup +} nuclear spin possible, which due to its long coherence time of 18 ms compared to 280 {mu}s for the {sup 31}P{sub 0} nuclear spin, might be a candidate for a nuclear spin memory. In the last part, we devise a scheme for the hyperpolarization of {sup 31}P nuclei by combining pulsed optical excitation and pulsed ENDOR and demonstrate a {sup 31}P nuclear spin polarization of more than 50%. Crucial for these experiments was the development of a

  5. Cooling Rate Calculation of Non-Equilibrium Aluminum Alloy Powders Prepared by Gas Atomization%气雾化制备非平衡态铝合金粉末冷却速度的计算

    Institute of Scientific and Technical Information of China (English)

    何世文; 刘咏; 郭晟

    2009-01-01

    The cooling rate of aluminum alloy powders prepared by ultrasonic gas atomization process was calculated through the convection heat transfer principle.A simple and theoretical model is established,which can be expressed as |dTd/dt|=12/ρ·Cp·(Td-Tf)·kg/d2.The average cooling rates of Al-Ni-Ce-Fe-Cu alloy powders prepared by argon gas atomization and by helium gas atomization are about 104~107 K/s and 105~108 K/s,respectively.The critical cooling rate is calculated to be 3.74× 105 K/s for Al-Ni-Ce-Fe-Cu alloy amorphous powders prepared by argon gas atomization.The cooling rates of gas-atomized powder particles estimated from secondary dendrite arm spacing are in consistence to those predicted from the theoretical model.%依据对流换热原理,对超音速气体雾化非平衡态铝合金粉末的冷却速度进行了理论计算.获得了一个较简单的理论计算公式,其表达式为|dTd/dt|=12/p·Cp·(Td-Tf)·kg/d2.根据理论公式,氩气和氦气雾化制备铝合金粉的冷却速度分别为104~107和105~108K、s,其结果与前期科研者的计算结果相符,且计算公式更简化.对于氩气雾化制各Al-NiCe-Fe-Cu合金而言,获得非晶态粉末其临界冷却速度为3.74×109K/S.通过测定合金晶态粉末的二次枝晶臂间距,并利用冷却速度和枝晶臂间距之间的经验关系,验算了合金粉末的冷却速度.其结果与理论计算相吻合.

  6. Quantum Theory of Hyperfine Structure Transitions in Diatomic Molecules.

    Science.gov (United States)

    Klempt, E.; And Others

    1979-01-01

    Described is an advanced undergraduate laboratory experiment in which radio-frequency transitions between molecular hyperfine structure states may be observed. Aspects of the quantum theory applied to the analysis of this physical system, are discussed. (Authors/BT)

  7. Spin-torsion effects in the hyperfine structure of methanol

    Energy Technology Data Exchange (ETDEWEB)

    Coudert, L. H., E-mail: laurent.coudert@lisa.u-pec.fr; Gutlé, C. [Laboratoire Inter-Universitaire des Systèmes Atmosphériques, UMR 7583 CNRS-Universités Paris Est Créteil et Paris Diderot, 61 Avenue du Général de Gaulle, 94010 Créteil Cedex (France); Huet, T. R. [Laboratoire de Physique des Lasers, Atomes et Molécules, UMR 8523 CNRS-Université Lille 1, Bâtiment P5, 59655 Villeneuve d’Ascq Cedex (France); Grabow, J.-U. [Institut für Physikalische Chemie, Callinstrasse 3–3a, 30167 Hannover (Germany); Levshakov, S. A. [St. Petersburg Electrotechnical University “LETI,” 197376 St. Petersburg (Russian Federation)

    2015-07-28

    The magnetic hyperfine structure of the non-rigid methanol molecule is investigated experimentally and theoretically. 12 hyperfine patterns are recorded using molecular beam microwave spectrometers. These patterns, along with previously recorded ones, are analyzed in an attempt to evidence the effects of the magnetic spin-torsion coupling due to the large amplitude internal rotation of the methyl group [J. E. M. Heuvel and A. Dymanus, J. Mol. Spectrosc. 47, 363 (1973)]. The theoretical approach setup to analyze the observed data accounts for this spin-torsion in addition to the familiar magnetic spin-rotation and spin-spin interactions. The theoretical approach relies on symmetry considerations to build a hyperfine coupling Hamiltonian and spin-rotation-torsion wavefunctions compatible with the Pauli exclusion principle. Although all experimental hyperfine patterns are not fully resolved, the line position analysis yields values for several parameters including one describing the spin-torsion coupling.

  8. Hyperfine Interactions in Iron Meteorites: Comparative Study by Moessbauer Spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Oshtrakh, M. I., E-mail: oshtrakh@mail.utnet.ru [Ural State Technical University - UPI, Faculty of Physical Techniques and Devices for Quality Control (Russian Federation); Milder, O. B. [Ural State Technical University - UPI, Faculty of Experimental Physics (Russian Federation); Grokhovsky, V. I. [Ural State Technical University - UPI, Faculty of Physical Techniques and Devices for Quality Control (Russian Federation); Semionkin, V. A. [Ural State Technical University - UPI, Faculty of Experimental Physics (Russian Federation)

    2004-11-15

    The iron meteorites Sikhote-Alin, Bilibino, Chinga and Dronino with different Ni concentration and terrestrial age were studied by Moessbauer spectroscopy. Different Moessbauer hyperfine parameters were determined for studied meteorites and possible Fe-Ni phases were supposed.

  9. Hyperfine Coherence in the Presence of Spontaneous Photon Scattering

    CERN Document Server

    Ozeri, R; Jost, J D; De Marco, B L; Ben-Kish, A; Blakestad, B R; Britton, J L; Chiaverini, J; Itano, W M; Hume, D; Leibfried, D; Rosenband, T; Schmidt, P; Wineland, D J

    2005-01-01

    The coherence of a hyperfine-state superposition of a trapped $^{9}$Be$^+$ ion in the presence of off-resonant light is experimentally studied. It is shown that Rayleigh elastic scattering of photons that does not change state populations also does not affect coherence. Coherence times exceeding the average scattering time of 19 photons are observed. This result implies that, with sufficient control over its parameters, laser light can be used to manipulate hyperfine-state superpositions with very little decoherence.

  10. Thermal and nuclear hyperfine properties of Ho(OH)3

    Science.gov (United States)

    Karmakar, S.

    1985-05-01

    A reasonable explanation for the findings of Catanese and Meissner [Phys. Rev. B 8, 2071 (1973)] regarding the (hyperfine) heat capacity in the low-temperature region of Ho(OH)3 is given. The Schottky specific heat in the high-temperature region observed calorimetrically by Chirico et al. [J. Chem. Thermodyn. 13, 1092 (1981)] explained satisfactorily. Nuclear hyperfine constants for Ho3+ ions in Ho(OH)3 are determined.

  11. Hyperfine selectivity using multiquantum electron-nuclear-electron triple resonance

    Science.gov (United States)

    Christidis, T. C.; Mchaourab, Hassane S.; Hyde, James S.

    1996-06-01

    Hyperfine selectivity is demonstrated in a continuous wave electron-nuclear double resonance (ENDOR) experiment. A multiquantum electron-electron double resonance (ELDOR) signal is monitored as a function of the nuclear radio frequency. The signs and relative intensities of the ENDOR lines permit separating the case where both ELDOR and ENDOR frequencies match hyperfine couplings from the cases where this condition is not satisfied.

  12. Surface Powder Technology of Aluminium Alloy Based of Communication Filter Module%通信滤波器铝基模块表面喷粉工艺研究

    Institute of Scientific and Technical Information of China (English)

    王小青; 吴道琴

    2013-01-01

    In order to improve the corrosion resistance of the wrought aluminium alloy (6061) and die casting aluminium alloy (YL102 ) for the base of communication filter module, powder was sprayed on its surface. The effect of coating type, module structure, treatment process (module pre-processing, baking) on the film-forming corrosion resistance was studied. The results show that: the reasonable choice of different coating, proper rounding, narrow groove depth to width ratio and hole depth and the aperture ratio not greater than 3, special function of surface transition processing, reasonable arrangements for powder processing technology can improve corrosion resistance of powder sprayed film-forming.%为了提高以变形铝合金(6061)和压铸铝合金(YL102)为基材的通信滤波器模块的防腐蚀能力,在其表面进行喷粉处理,研究了涂料类型、模块结构、处理工艺(模块前处理、喷涂烘烤)对成膜耐蚀性能的影响.结果表明:针对不同基材选择涂料,适当的圆角过渡,窄槽的深宽比和孔深/孔径比不大于3,特殊的功能表面进行过渡处理,合理地安排喷粉处理工艺,均有利于提高喷粉层的防腐蚀能力.

  13. Influence of steam-based pre-treatment using acidic chemistries on the adhesion performance of powder coated aluminium alloy AA6060

    DEFF Research Database (Denmark)

    Din, Rameez Ud; Nikogeorgos, Nikolaos; Jellesen, Morten Stendahl

    2017-01-01

    In this study, the adhesion of a commercially applied powder coating on a steam treated AA6060 surface withpure steam and steam with citric and phosphoric acid chemistries has been investigated. Contact angle,roughness, and nanoscale pull off forces were determined as a function of the steam...... treatment prior toapplication of the powder coating. A focussed ion beam technique was used to examine the cross section of the powder coating, interface adhesion, and fracture morphology after the boiling test and interface indentation method. Transmission electron microscopy was used to study the fracture...

  14. Hyperfine interactions in nanocrystallized NANOPERM-type metallic glass containing Mo

    Science.gov (United States)

    Cesnek, M.; Kubániová, D.; Kohout, J.; Křišťan, P.; Štěpánková, H.; Závěta, K.; Lančok, A.; Štefánik, M.; Miglierini, M.

    2016-12-01

    NANOPERM-type alloy with chemical composition Fe76Mo8CuB15 was studied by combination of 57Fe Mössbauer spectroscopy and 57Fe(10B, 11B) nuclear magnetic resonance in order to determine distribution of hyperfine magnetic fields and evolution of relative concentration of Fe-containing crystalline phases within the surface layer and the volume of the nanocrystallized ribbons with annealing temperature. Differential scanning calorimetry revealed two crystallization stages at T x1 ˜ 510 ∘C and T x2 ˜ 640 ∘C, connected to precipitation of α-Fe and Fe(Mo,B) nanocrystals, respectively. The amorphous and partially crystalline state was obtained by annealing at several temperatures in the range 510-650 ∘C. The combination of conversion electron (CEMS) and transmission Mössbauer spectrometry (TMS) showed that annealing induces crystallization starting from both surfaces of the ribbons. For the as-quenched sample, scanning electron microscopy (SEM) and CEMS revealed significant differences in the "air" and "wheel" sides of the ribbons, crystallites were preferentially formed at the latter. While SEM micrographs of annealed samples showed various mean diameters of the crystals at opposite sides of the ribbons, the amounts of crystalline volume derived from the CEMS spectra approximately equaled. Mössbauer spectra of annealed samples contained narrow sextet ascribed to crystalline α-Fe phase, three sextets with distribution of hyperfine field assigned to the interface regions of the nanocrystals and the contribution of the amorphous phases. In-field TMS performed at 4.2 K with magnetic moments aligned by external magnetic field enabled to properly determine in particular the contribution of the amorphous phases in the samples. Resulting distributions of the hyperfine fields were compared with 57Fe(10B, 11B) nuclear magnetic resonance (NMR) spectra.

  15. Development of powder metallurgy 2XXX series Al alloy plate and sheet materials for high temperature aircraft structural applications, FY 1983/1984

    Science.gov (United States)

    Chellman, D. J.

    1985-01-01

    The objective of this investigation is to fabricate and evaluate PM 2124 Al alloy plate and sheet materials according to NASA program goals for damage tolerance and fatigue resistance. Previous research has indicated the outstanding strength-toughness relationship available with PM 2124 Al-Zr modified alloy compositions in extruded product forms. The range of processing conditions was explored in the fabrication of plate and sheet gage materials, as well as the resultant mechanical and metallurgical properties. The PM composition based on Al-3.70 Cu-1.85 Mg-0.20 Mn with 0.60 wt. pct. Zr was selected. Flat rolled material consisting of 0.250 in. thick plate was fabricated using selected thermal mechanical treatments (TMT). The schedule of TMT operations was designed to yield the extreme conditions of grain structure normally encountered in the fabrication of flat rolled products, specifically recrystallized and unrecrystallized. The PM Al alloy plate and sheet materials exhibited improved strength properties at thin gages compared to IM Al alloys, as a consequence of their enhanced ability to inhibit recrystallization and grain growth. In addition, the PM 2124 Al alloys offer much better combinations of strength and toughnessover equivalent IM Al. The alloy microstructures were examined by optical metallographic texture techniques in order to establish the metallurgical basis for these significant property improvements.

  16. Fabricating fine-grained tungsten heavy alloy by spark plasma sintering of low-energy ball-milled W–2Mo–7Ni–3Fe powders

    Energy Technology Data Exchange (ETDEWEB)

    Xiang, D.P., E-mail: dpxiang@hainu.edu.cn [Key Laboratory of Advanced Materials of Tropical Island Resources, Ministry of Education, Hainan University, Haikou 570228 (China); School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China); Ding, L. [Key Laboratory of Advanced Materials of Tropical Island Resources, Ministry of Education, Hainan University, Haikou 570228 (China); Li, Y.Y. [School of Mechanical and Automotive Engineering, South China University of Technology, Guangzhou 510640 (China); Chen, X.Y.; Zhang, T.M. [Key Laboratory of Advanced Materials of Tropical Island Resources, Ministry of Education, Hainan University, Haikou 570228 (China)

    2013-08-20

    Fine-grained W–2Mo–7Ni–3Fe heavy alloys were fabricated by low-energy ball milling (LEBM)-assisted spark plasma sintering at a temperature range of 1000–1250 °C. The effects of sintering temperature on the phase evolution, microstructural characteristics, and mechanical properties of the alloys were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), hardness testing, and universal testing. The XRD results show that small intermetallic compounds, such as NiW and Ni{sub 2}W{sub 4}C, form in the alloys. The W–2Mo–7Ni–3Fe alloys are characterized by white W grains, a gray W-rich microstructure that contains Mo, and a black γ–(Ni, Fe, W, Mo) binding phase. The X-ray energy dispersive analysis (EDS) shows that the Mo, Ni, and Fe that form a solid solution with W in the gray structure gradually decrease with increasing temperature. The hardness and bending strength of the alloys initially increase and then decrease with rising sintering temperature. Moreover, the alloys sintered at different temperatures exhibit dissimilar bending fracture modes.

  17. Powder-Metallurgy Process And Product

    Science.gov (United States)

    Paris, Henry G.

    1988-01-01

    Rapid-solidification processing yields alloys with improved properties. Study undertaken to extend favorable property combinations of I/M 2XXX alloys through recently developed technique of rapid-solidification processing using powder metallurgy(P/M). Rapid-solidification processing involves impingement of molten metal stream onto rapidly-spinning chill block or through gas medium using gas atomization technique.

  18. Computation of hyperfine energies of hydrogen, deuterium and tritium quantum dots

    Science.gov (United States)

    Çakır, Bekir; Özmen, Ayhan; Yakar, Yusuf

    2016-01-01

    The hyperfine energies and hyperfine constants of the ground and excited states of hydrogen, deuterium and tritium quantum dots(QDs) are calculated. Quantum genetic algorithm (QGA) and Hartree-Fock-Roothaan (HFR) methods are employed to calculate the unperturbed wave functions and energy eigenvalues. The results show that in the medium and strong confinement regions the hyperfine energy and hyperfine constant are strongly affected by dot radius, impurity charge, electron spin orientation, impurity spin and impurity magnetic moment. Besides, in all dot radii, the hyperfine splitting and hyperfine constant of the confined hydrogen and tritium atoms are approximately equivalent to each other and they are greater than the confined deuterium atom.

  19. Computation of hyperfine energies of hydrogen, deuterium and tritium quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Çakır, Bekir, E-mail: bcakir@selcuk.edu.tr [Physics Department, Faculty of Science, Selcuk University, Campus 42075, Konya (Turkey); Özmen, Ayhan [Physics Department, Faculty of Science, Selcuk University, Campus 42075, Konya (Turkey); Yakar, Yusuf, E-mail: yuyakar@yahoo.com [Physics Department, Faculty of Arts and Science, Aksaray University, Campus 68100, Aksaray (Turkey)

    2016-01-15

    The hyperfine energies and hyperfine constants of the ground and excited states of hydrogen, deuterium and tritium quantum dots(QDs) are calculated. Quantum genetic algorithm (QGA) and Hartree–Fock–Roothaan (HFR) methods are employed to calculate the unperturbed wave functions and energy eigenvalues. The results show that in the medium and strong confinement regions the hyperfine energy and hyperfine constant are strongly affected by dot radius, impurity charge, electron spin orientation, impurity spin and impurity magnetic moment. Besides, in all dot radii, the hyperfine splitting and hyperfine constant of the confined hydrogen and tritium atoms are approximately equivalent to each other and they are greater than the confined deuterium atom.

  20. Stochastic hyperfine interactions modeling library-Version 2

    Science.gov (United States)

    Zacate, Matthew O.; Evenson, William E.

    2016-02-01

    The stochastic hyperfine interactions modeling library (SHIML) provides a set of routines to assist in the development and application of stochastic models of hyperfine interactions. The library provides routines written in the C programming language that (1) read a text description of a model for fluctuating hyperfine fields, (2) set up the Blume matrix, upon which the evolution operator of the system depends, and (3) find the eigenvalues and eigenvectors of the Blume matrix so that theoretical spectra of experimental techniques that measure hyperfine interactions can be calculated. The optimized vector and matrix operations of the BLAS and LAPACK libraries are utilized. The original version of SHIML constructed and solved Blume matrices for methods that measure hyperfine interactions of nuclear probes in a single spin state. Version 2 provides additional support for methods that measure interactions on two different spin states such as Mössbauer spectroscopy and nuclear resonant scattering of synchrotron radiation. Example codes are provided to illustrate the use of SHIML to (1) generate perturbed angular correlation spectra for the special case of polycrystalline samples when anisotropy terms of higher order than A22 can be neglected and (2) generate Mössbauer spectra for polycrystalline samples for pure dipole or pure quadrupole transitions.

  1. Anomalous hyperfine coupling and nuclear magnetic relaxation in Weyl semimetals

    Science.gov (United States)

    Okvátovity, Zoltán; Simon, Ferenc; Dóra, Balázs

    2016-12-01

    The electron-nuclear hyperfine interaction shows up in a variety of phenomena including, e.g., NMR studies of correlated states and spin decoherence effects in quantum dots. Here we focus on the hyperfine coupling and the NMR spin relaxation time T1 in Weyl semimetals. Since the density of states in Weyl semimetals varies with the square of the energy around the Weyl point, a naive power counting predicts a 1 /T1T ˜E4 scaling, with E the maximum of temperature (T ) and chemical potential. By carefully investigating the hyperfine interaction between nuclear spins and Weyl fermions, we find that while its spin part behaves conventionally, its orbital part diverges unusually, with the inverse of the energy around the Weyl point. Consequently, the nuclear spin relaxation rate scales in a graphenelike manner as 1 /T1T ˜E2ln(E /ω0) , with ω0 the nuclear Larmor frequency. This allows us to identify an effective hyperfine coupling constant, which is tunable by gating or doping. This is relevant for the decoherence effect in spintronics devices and double quantum dots, where hyperfine coupling is the dominant source of spin-blockade lifting.

  2. Hyperfine structure of P-states in muonic deuterium

    CERN Document Server

    Faustov, R N; Martynenko, G A; Sorokin, V V

    2015-01-01

    On the basis of quasipotential approach to the bound state problem in quantum electrodynamics we calculate hyperfine structure intervals Delta E^{hfs}(2P_{1/2}) and Delta E^{hfs}(2P_{3/2}) for P-states in muonic deuterium. The tensor method of projection operators for the calculation of the hyperfine structure of P-states with definite quantum numbers of total atomic momentum F and total muon momentum j in muonic deuterium is formulated. We take into account vacuum polarization, relativistic, quadruple and structure corrections of orders alpha^4, alpha^5 and alpha^6. The obtained numerical values of hyperfine splittings are useful for the analysis of new experimental data of the CREMA collaboration regarding to muonic deuterium.

  3. In situ synchrotron X-ray diffraction experiments on Al-15%BN mechanically alloyed powder: Observation of AlN nanoparticles precipitation and enhanced thermal stability of nanostructured Al matrix

    Energy Technology Data Exchange (ETDEWEB)

    Lonardelli, I., E-mail: ivan.lonardelli@ing.unitn.i [Department of Materials Engineering and Industrial Technologies, University of Trento, Via Mesiano 77, Trento 38050 (Italy); Zadra, M.; Ischia, G. [Department of Materials Engineering and Industrial Technologies, University of Trento, Via Mesiano 77, Trento 38050 (Italy); Barreiro, J. Gomez [Earth and Planetary Sciences Dept., University of California at Berkeley, CA 94720 (United States); Department of Geochemistry and Petrology, University of Madrid, Madrid 28040 (Spain); Bortolotti, M.; Molinari, A. [Department of Materials Engineering and Industrial Technologies, University of Trento, Via Mesiano 77, Trento 38050 (Italy)

    2009-11-03

    Two different in situ experiments using high energy X-ray diffraction from synchrotron source were performed in order to understand carefully the phase transformation in nanostructured Al-15%BN mechanically alloyed powder. After milling at room temperature for 10 h, a solid solution of Al, B and N was achieved. During the heating, the formation and the evolution of the metastable trigonal Al{sub 2}B{sub 3} and a very fine precipitation of hexagonal AlN (d < 8 nm) within Al grains were detected quantitatively. We found a stabilization of Al{sub 2}B{sub 3} between 225 deg. C and 550 deg. C and, only around 600 deg. C the hexagonal AlB{sub 2} starts to form. A detectable decreasing of the Al crystallite size between 420 deg. C and 470 deg. C was attributed to the precipitation of AlN nanoparticles that reduce the Al volume fraction and, at the same time, hinder the grain boundary propagation. The powder loses the nanostructure above 600 deg. C exhibiting an exceptional thermal stability at temperatures close to 0.9T{sub m}.

  4. Low temperature study of mechanically alloyed Fe{sub 67.5}Ni{sub 32.5} Invar sample

    Energy Technology Data Exchange (ETDEWEB)

    Valenzuela, J.L. [Departamento de Física, Universidad del Valle, A. A. 25360, Cali (Colombia); Valderruten, J.F. [Departamento de Ingeniería, Universidad Cooperativa de Colombia, Bucaramanga (Colombia); Pérez Alcázar, G.A., E-mail: gpgeperez@gmail.com [Departamento de Física, Universidad del Valle, A. A. 25360, Cali (Colombia); Colorado, H.D. [Departamento de Física, Universidad del Valle, A. A. 25360, Cali (Colombia); Romero, J.J. [Instituto de Microelectrónica de Madrid, CNM, CSIC, C/Isaac Newton 8, Tres Cantos, 28760 Madrid (Spain); González, J.M. [Unidad Asociada ICMM-IMA, Apdo. 155, Las Rozas, 28230 Madrid (Spain); Greneche, J.M. [LUNAM, Université du Maine, Institut des Molécules et Matériaux du Mans, UMR CNRS 6283, 72085 Le Mans, Cedex 9 (France); Marco, J.F. [Instituto de Química-Física ' ' Rocasolano' ' , CSIC, C/Serrano 119, 28006 Madrid (Spain)

    2015-07-01

    The study at low temperatures of powder of the Invar alloy, Fe{sub 67.5}Ni{sub 32.5}, produced by mechanical alloying, shows that the sample presents two structural phases, the Fe–Ni BCC and the Fe–Ni FCC. The {sup 57}Fe Mössbauer spectra obtained in this sample at different temperatures were fitted considering two hyperfine magnetic field distributions. The first one having the larger mean field and only one peak (at ca. 35 T, varying with T), is associated with the BCC phase, and the second one, presenting several broad peaks (distributed between 10 and 35 T), is associated to the FCC phase. A singlet, which is associated to low spin Fe sites of the FCC phase, was also considered. The mean hyperfine magnetic field of the BCC phase increases monotonically as temperature decreases, while that of the FCC phase presents an anomaly near 75 K. The real part of the ac magnetic susceptibility temperature scans presents a peak whose position increases from 31 to 39 K, when the ac field frequency increases from 100 to 5000 Hz. These results permit to associate the detected anomaly to the occurrence of a reentrant spin glass transition. - Highlights: • XRD detect the BCC and FCC nanocrystalline phases in the Invar Fe{sub 67.5}Si{sub 32.5}. • Mössbauer spectra were fitted with two HMFDs and a singlet. • The MHMF and the isomer shift of the FCC structure present a kink near 61 K. • Magnetic susceptibility proved that this anomaly corresponds to a RSG- F transition. • The Invar composition of the MA Fe{sub 67.5}Si{sub 32.5} alloy presents the frustration phenomena.

  5. Ground state hyperfine splitting of high Z hydrogenlike ions

    CERN Document Server

    Shabaev, V M; Kühl, T; Artemiev, A N; Yerokhin, V A

    1997-01-01

    The ground state hyperfine splitting values of high Z hydrogenlike ions are calculated. The relativistic, nuclear and QED corrections are taken into account. The nuclear magnetization distribution correction (the Bohr-Weisskopf effect) is evaluated within the single particle model with the g_{S}-factor chosen to yield the observed nuclear moment. An additional contribution caused by the nuclear spin-orbit interaction is included in the calculation of the Bohr-Weisskopf effect. It is found that the theoretical value of the wavelength of the transition between the hyperfine splitting components in ^{165}Ho^{66+} is in good agreement with experiment.

  6. Research on Critical Powder Loading for Ti-6Al-4V Alloy Feedstocks%Ti-6Al-4V合金喂料临界粉末装载量的研究

    Institute of Scientific and Technical Information of China (English)

    王家惠; 史庆南; 席健

    2012-01-01

    Critical p owder loading of Ti-6A1-4V alloy feedstocks with four different wax-based binders were investigated and Theological measurements of feedstocks at critical powder loading were performed in a capillary rheometer. The results show that the critical powder loadings of 1# feedstock(100%PW), 2' feedstock(95%PW+5%SA), 3# feedstock (70%PW+25%PE+5%SA), 4# feedstock (70%PW+25%PE+5%SA) is 70vol%,71.53 vol%,72.24 vol%,73.02 vol%, respectively. Through Theological analysis, the feedstocks at critical powder loading are pseudo-plastic fluid, but flow index of feedstocks is lower than 0.2, not conducive to forming.%研究了4种不同蜡基粘结剂配方下钛合金喂料的临界固体粉末含量,并测试了临界固体粉末含量下喂料的流变学参数.实验结果表明:1#喂料(100%PW)、2#喂料(95%PW+5%SA)、3#喂料(70%PW+25%PE+5%SA)、4#喂料(60%PW+35%PE+5%SA)的临界粉末装载量(vo1.%)分别为:70%,71.53%,72.24%,73.02%;经流变学分析,临界粉末装载量下喂料仍呈假塑性流体,但其流动指数n值较小,在0.2以下,不利于成形.

  7. Site occupancy and magnetic moment of Fe in Ni{sub 2}Mn{sub 0.3}Fe{sub 0.7}Ga alloy by neutron powder diffraction study

    Energy Technology Data Exchange (ETDEWEB)

    Umetsu, R.Y., E-mail: rieume@imr.tohoku.ac.jp [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Japan Science and Technology Agency-Precursory Research for Embryonic Science and Technology (JST-PREST), Tokyo 102-0076 (Japan); Kikuchi, D. [Faculty of Engineering, Tohoku Gakuin. University, Tagajo 985-8537 (Japan); Koyama, K. [Faculty of Science, Kagoshima University, Kagoshima 890-0065 (Japan); Watanabe, K.; Yamaguchi, Y. [Institute for Materials Research, Tohoku University, Sendai 980-8577 (Japan); Kainuma, R. [Department of Material Science, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Kanomata, T. [Department of Material Science, Graduate School of Engineering, Tohoku University, Sendai 980-8579 (Japan); Research Institute for Engineering and Technology, Tohoku Gakuin University, Tagajo 985-8537 (Japan)

    2013-12-15

    Highlights: •Neutron powder diffraction measurements were carried out for Ni{sub 2}Mn{sub 0.3}Fe{sub 0.7}Ga shape memory alloy system. •It was clarified that the Mn and Fe atoms randomly occupied at 4a site in the L2{sub 1}-type structure. •Magnetic moment of Fe was estimated to be about 3.0 μ{sub B}, being significantly larger than that in pure bcc-Fe. -- Abstract: Neutron powder diffraction measurements were carried out in a wide temperature range from 14 to 500 K for Ni{sub 2}Mn{sub 0.3}Fe{sub 0.7}Ga alloy, which undergoes a martensitic transformation from L2{sub 1}-type austenite phase to four layered orthorhombic-type martensite phase at about 160 K during cooling. For the diffraction pattern measured at 500 K in the paramagnetic austenite phase, it was clarified that the Mn and Fe atoms randomly occupied 4a site in the L2{sub 1}-type structure. Magnetic moments of Ni, Mn and Fe in the ferromagnetic austenite phase at 200 K were decided to be 0.3 and 3.3 and 3.0 μ{sub B}, respectively. The magnetic moment of Fe is significantly larger than that in pure bcc-Fe of 2.2 μ{sub B}. Magnetic moments of Fe in two sites at 14 K in the martensite phase were obtained to be 2.3 and 2.6 μ{sub B}, respectively, suggesting that the comparatively large magnetic moments of Fe were kept even in the martensite phase. Total magnetic moment of the martensite phase at 14 K from the neutron powder diffractive analyses is 3.7 μ{sub B}/f.u., being in good agreement with the result of the magnetic measurement of 3.5 μ{sub B}/f.u. at 4.2 K.

  8. 机械球磨制备Ni2FeSb合金的烧结动力学%Sintering kinetics of Ni2FeSb powder alloys produced by mechanical milling

    Institute of Scientific and Technical Information of China (English)

    F ALVARADO-HERNNDEZ; O JIMNEZ; G GONZLEZ-CASTAEDA; V BALTAZAR-HERNNDEZ; J CABEZAS-VILLA; M ALBITER; H VERGARA-HERNNDEZ; L OLMOS

    2016-01-01

    A ternary Ni2FeSb shape memory alloy was fabricated by powder metallurgy route. Sintering kinetics was estimated from dilatometry tests;whereas the microstructure and morphology of the powder and consolidated bulk samples were evaluated by XRD and SEM, respectively. Microhardness tests were performed on the surface of sintered samples. The results indicated that milling time has an effect on the shape and particle size as well as the homogeneity of the crystalline structures of the powders. Samples with longer milling time presented higher relative densities, better distribution of the elements on the alloy as well as the L21 and martensite phases, which will give the shape memory effect. The estimated activation energy values ranged from 109 to 282 kJ/mol at temperatures between 750 and 1273 K, indicating that sintering is controlled mainly by volume diffusion. Microhardness was improved by increasing the milling time and the heating rate.%采用粉末冶金工艺制备Ni2FeSb三元形状记忆合金。利用膨胀实验研究合金的烧结动力学;采用XRD和SEM分别考察粉末样品和烧结样品的显微组织和形貌;测定烧结样品表面的显微硬度。结果表明:研磨时间对粉末样品的形状、晶粒尺寸和晶体结构的均匀性具有显著影响。经较长时间研磨的样品具有较高的相对密度和较均匀的元素分布,且为L21和马氏体相,这些性能使合金具有形状记忆功能。在温度为750~1273 K条件下,合金的激活能为109~283 kJ/mol,这表明烧结过程主要由体积扩散控制。增加研磨时间和加热速率,合金的显微硬度得到提高。

  9. The Influence of Extrusion Ratio on W-40 % Cu Alloy Produced by Powder Canning Hot Extrusion%挤压比对粉末包套热挤压致密W-40%Cu合金的影响

    Institute of Scientific and Technical Information of China (English)

    李达人; 蔡一湘; 刘祖岩; 王尔德

    2012-01-01

    采用不同挤压比对W-40%Cu混合粉末进行粉末包套热挤压,获得了W--40%Cu合金.研究了模具总挤压比λ对热挤压坯料致密化以及组织性能的影响.结果表明,随着挤压比的增加,热挤压坯料的相对密度也增加,同时电导率和硬度值也随之提高.由于含铜量比较高(质量分数为40%),即便在挤压比为25时,挤压坯内部W相也不发生变形,主要是铜相产生变形.进一步将模具总挤压比λ细分为不考虑体积变形的坯料总挤压比α,除去体积变形因素的坯料塑性挤压比β以及包套挤压比γ三种实际挤压比,分析了不同挤压比对热挤压致密化过程的影响.%W-40 wt.%Cu alloys with different extrusion ratio have been obtained by powder canning hot extrusion. The experimental results show that, the relative density, specific conductance and hardness of the billets increase with the adding extrusion ratio. There is no shape change of W phase after powder canning hot extrusion even if the extrusion ratio is up to 25 due to high content of Cu phase (40 wt.%). The deformation mainly occurs in Cu phase. The total extrusion ratio (λ) is divided into three kinds of actual extrusion ratio: the extrusion ratio of billet (α) without considering the volumetric deformation; the plastic extrusion ratio (β) excluding the influence of volumetric deformation; the extrusion ratio of can (γ). This article studies the influence of these three kinds of actual extrusion ratio on the densification of W-40 wt.% Cu alloy by powder canning hot extrusion.

  10. Calculation of the effect of alloy characteristics on the permanent expansion of cold compacted hypereutectic Al-Si-Fe-X powder after thermal treatment

    Energy Technology Data Exchange (ETDEWEB)

    Timmermans, G.; Froyen, L. [Katholieke Univ. Leuven (Belgium). Dept. Metaalkunde en Toegepaste Materiaalkunde

    1999-02-19

    For the atomized powder Al-17Si-5Fe-3.5Cu-1.1Mg-0.6Zr (wt%), investigated in this work, a permanent elongation of about 0.8% of a bar shape sample of a green product (cold compacted powder) is measured by Thermo Mechanical Analysis after a first thermal cycle up to 470 C, when a heating rate of 5 C/min or 1 C/min is applied. This 0.8% is the average of 10 measurements. In subsequent cycles, there is no extra permanent expansion anymore, indicating the mainly irreversible character. The irreversible part of the expansion mainly occurs between 200 and 300 C, where Si is precipitating, as detected by X-Ray Diffractometry (XRD) and Differential Scanning Calorimetry (DSC). This Si-precipitation from supersaturated Al solid solutions is observed by many researchers, using also XRD Al line shift analysis and microscopy techniques.

  11. Observation of Hyperfine Transitions in Trapped Ground-State Antihydrogen

    CERN Document Server

    Olin, Arthur

    2015-01-01

    This paper discusses the first observation of stimulated magnetic resonance transitions between the hyperfine levels of trapped ground state atomic antihydrogen, confirming its presence in the ALPHA apparatus. Our observations show that these transitions are consistent with the values in hydrogen to within 4~parts~in~$10^3$. Simulations of the trapped antiatoms in a microwave field are consistent with our measurements.

  12. The NH$_2$D hyperfine structure revealed by astrophysical observations

    CERN Document Server

    Daniel, F; Punanova, A; Harju, J; Faure, A; Roueff, E; Sipilä, O; Caselli, P; Güsten, R; Pon, A; Pineda, J E

    2016-01-01

    The 1$_{11}$-1$_{01}$ lines of ortho and para--NH$_2$D (o/p-NH$_2$D), respectively at 86 and 110 GHz, are commonly observed to provide constraints on the deuterium fractionation in the interstellar medium. In cold regions, the hyperfine structure due to the nitrogen ($^{14}$N) nucleus is resolved. To date, this splitting is the only one which is taken into account in the NH$_2$D column density estimates. We investigate how the inclusion of the hyperfine splitting caused by the deuterium (D) nucleus affects the analysis of the rotational lines of NH$_2$D. We present 30m IRAM observations of the above mentioned lines, as well as APEX o/p-NH$_2$D observations of the 1$_{01}$-0$_{00}$ lines at 333 GHz. The hyperfine spectra are first analyzed with a line list that only includes the hyperfine splitting due to the $^{14}$N nucleus. We find inconsistencies between the line widths of the 1$_{01}$-0$_{00}$ and 1$_{11}$-1$_{01}$ lines, the latter being larger by a factor of $\\sim$1.6$\\pm0.3$. Such a large difference is...

  13. Control of inhomogeneous atomic ensembles of hyperfine qudits

    DEFF Research Database (Denmark)

    Mischuck, Brian Edward; Merkel, Seth T.; Deutsch, Ivan H.

    2012-01-01

    We study the ability to control d-dimensional quantum systems (qudits) encoded in the hyperfine spin of alkali-metal atoms through the application of radio- and microwave-frequency magnetic fields in the presence of inhomogeneities in amplitude and detuning. Such a capability is essential...

  14. Kinetic models in spin chemistry. 1. The hyperfine interaction

    DEFF Research Database (Denmark)

    Mojaza, M.; Pedersen, J. B.

    2012-01-01

    Kinetic models for quantum systems are quite popular due to their simplicity, although they are difficult to justify. We show that the transformation from quantum to kinetic description can be done exactly for the hyperfine interaction of one nuclei with arbitrary spin; more spins are described w...

  15. Fabrication of Biomedical Titanium Alloys with High Strength and Low Modulus by Means of Powder Metallurgy%粉末冶金法合成高强低模超细晶医用钛合金

    Institute of Scientific and Technical Information of China (English)

    李元元; 邹黎明; 杨超

    2012-01-01

    为探寻有效的高强低模医用钛合金制备方法,采用机械合金化方法制备了不同Fe含量的(Ti69.7Nb23.7Zr4.9Ta1.7)100-xFex非晶/纳米晶合金粉末,随后采用放电等离子烧结-非晶晶化法得到了高强低模的超细晶钛基复合材料.结果表明:(1)机械合金化过程中,Fe含量对合金的非晶形成能力影响显著,文中实验条件下,只有当x增大至10时才能形成全非晶相的非晶粉末;(2)Fe含量也明显影响合成的块体钛合金的力学性能,合成的不同Fe含量合金中,只有(Ti69.7Nb23.7Zr4.9Ta1.7)94 Fe6合金具有高强度和显著塑性,其压缩屈服强度为2425 MPa,断裂强度为2650 MPa,断裂应变为0.0691,平均弹性模量仅为52 GPa,接近第三代生物医用钛合金的最低值.将所合成的超细晶钛合金与常用的两种生物钛合金(Ti-6Al-4V和Ti-13Nb-13Zr)进行抗摩擦磨损性能对比,发现所合成的钛合金具有最佳的耐磨性.%In order to explore an effective method to fabricate biomedical Ti alloy with high strength and low modulus, amorphous/nanocrystallized (Ti69.7Nb23.7Zr4.9Ta1.7) 100_x.Fe;c alloy powders with different Fe contents were synthesized via mechanical alloying, and, subsequently, ultrafine-grained Ti-based composites with high strength and low modulus were fabricated via the spark plasma sintering-amorphous crystallization. The results show that, during the performed mechanical alloying, Fe content significantly affects the glass-forming ability of the alloy system, concretely, fully amorphous structure forms only when x reaches 10; and that Fe content also has an obvious effect on the mechanical properties of the bulk composites, only the bulk composite at a x value of 6 possesses high strength and distinct plasticity, with the corresponding compressive yield stress, fracture stress and fracture strain respectively being 2425 MPa, 2650 MPa and 0. 069 1, and with an average elastic modulus of 52 GPa that is close to the minimum

  16. Effect of Process and Post-Process Conditions on the Mechanical Properties of an A357 Alloy Produced via Laser Powder Bed Fusion

    Directory of Open Access Journals (Sweden)

    Alberta Aversa

    2017-02-01

    Full Text Available A357 samples were realized by laser powder bed fusion (LPBF on building platforms heated up to different temperatures. The effect of the preheating temperature and of the post processing heat treatment on the microstructure and the mechanical properties of the samples was studied. It was demonstrated that building platform heating can act as an in situ ageing heat treatment following the fast cooling that arises during laser scanning. A 17% higher ultimate tensile strength was achieved by the selection of the optimum building platform temperature. Moreover, the possibility to further increase the mechanical properties by means of a direct ageing heat treatment was investigated.

  17. Magnetic properties of nanostructured Fe{sub 92}P{sub 8} powder mixture

    Energy Technology Data Exchange (ETDEWEB)

    Bensalem, R. [Laboratoire de Magnetisme et de Spectroscopie des Solides, Departement de Physique, Faculte des Sciences, Universite de Annaba, B.P. 12 (23000) Annaba (Algeria)], E-mail: rachid_bensalem06@yahoo.fr; Tebib, W.; Alleg, S. [Laboratoire de Magnetisme et de Spectroscopie des Solides, Departement de Physique, Faculte des Sciences, Universite de Annaba, B.P. 12 (23000) Annaba (Algeria); Sunol, J.J. [Dep. De fisica, Universitat de Girona, Campus de Montilivi, Girona 17017 (Spain); Bessais, L. [CNRS-Laboratoire de Chimie Metallurgique des Terres Rares-Groupe des Laboratoires de Thiais, 2-8 Rue Henri Durant, Thiais Cedex 94320 (France); Greneche, J.M. [Laboratoire de Physique de l' Etat Condense, UMR CNRS 6087, Universite du Maine, Le Mans Cedex 72085 (France)

    2009-03-05

    Structural and magnetic properties of nanostructured Fe{sub 92}P{sub 8} (wt.%) powder mixture prepared by mechanical alloying were investigated by X-ray diffraction (XRD), Moessbauer spectrometry and magnetic measurements. The crystallite sizes were found to decrease with milling time to the nanometer scale (6-14 nm). Milling for 21 h gives rise to a mixture of: (i) a two-bcc {alpha}-Fe structure with the same lattice parameter but different microstructural (crystallite size, microstrain) and hyperfine parameters (magnetic field, isomer shift), (ii) Fe{sub 3}P nanophase and (iii) a small amount of a paramagnetic FeP phosphide phase, not exceeding 2%. Furthermore, the temperature dependence of the magnetic susceptibility measurement reveals the presence of two magnetic phases with different Curie temperatures, Tc{sub 1} and Tc{sub 2}. One Curie temperature is nearly constant (Tc{sub 1} = 867 K) during the milling process, while the other one (Tc{sub 2}) is milling time dependent. Annealing at a temperature of 210 deg. C for half an hour leads to the formation of the FeP phosphide in addition to an {alpha}-Fe(P) solid solution and the Fe{sub 3}P nanophase.

  18. Evaluation of powder metallurgy superalloy disk materials

    Science.gov (United States)

    Evans, D. J.

    1975-01-01

    A program was conducted to develop nickel-base superalloy disk material using prealloyed powder metallurgy techniques. The program included fabrication of test specimens and subscale turbine disks from four different prealloyed powders (NASA-TRW-VIA, AF2-1DA, Mar-M-432 and MERL 80). Based on evaluation of these specimens and disks, two alloys (AF2-1DA and Mar-M-432) were selected for scale-up evaluation. Using fabricating experience gained in the subscale turbine disk effort, test specimens and full scale turbine disks were formed from the selected alloys. These specimens and disks were then subjected to a rigorous test program to evaluate their physical properties and determine their suitability for use in advanced performance turbine engines. A major objective of the program was to develop processes which would yield alloy properties that would be repeatable in producing jet engine disks from the same powder metallurgy alloys. The feasibility of manufacturing full scale gas turbine engine disks by thermomechanical processing of pre-alloyed metal powders was demonstrated. AF2-1DA was shown to possess tensile and creep-rupture properties in excess of those of Astroloy, one of the highest temperature capability disk alloys now in production. It was determined that metallographic evaluation after post-HIP elevated temperature exposure should be used to verify the effectiveness of consolidation of hot isostatically pressed billets.

  19. The shielding against radiation produced by powder metallurgy with tungsten copper alloy applied on transport equipment for radio-pharmaceutical products

    Energy Technology Data Exchange (ETDEWEB)

    Cione, Francisco C.; Sene, Frank F.; Souza, Armando C. de; Betini, Evandro G.; Rossi, Jesualdo L., E-mail: fceoni@hotmail.com, E-mail: ffsene@hotmail.com, E-mail: armandocirilo@yahoo.com, E-mail: evandrobetini@gmail.com, E-mail: jelrossi@ipen.br [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil); Rizzuto, Marcia A., E-mail: marizzutto@if.usp.br [Universidade de Sao Paulo (IF/USP), SP (Brazil). Instituto de Fisica

    2015-07-01

    Safety is mandatory on medicine radiopharmaceutical transportation and dependent on radiation shielding material. The focus of the present work is to minimize the use of harmful materials as lead and depleted uranium usually used in packages transportation. The tungsten-copper composite obtained by powder metallurgy (PM) is non-toxic. In powder metallurgy the density and the porosity of the compacted parts depends basically upon particle size distribution of each component, mixture, compacting pressure and sintering temperature cycle. The tungsten-copper composite, when used for shielding charged particles, X-rays, gamma photons or other photons of lower energy require proper interpretation of the radiation transport phenomena. The radioactive energy reduction varies according to the porosity and density of the materials used as shielding. The main factor for radiation attenuation is the cross section value for tungsten. The motivation research factor is an optimization of the tungsten and cooper composition in order to achieve the best linear absorption coefficient given by equation I{sub (x)} = I{sub 0}e{sup (-ux)}. Experiments were conducted to quantify the effective radiation shielding properties of tungsten-copper composite produced by PM, varying the cooper amount in the composite. The studied compositions were 15%, 20% and 25% copper in mass. The Compaction pressure was 270 MPa and the sintering atmosphere was in 1.1 atm in N{sub 2}+H{sub 2}. The sintering temperature was 980 deg C for 2 h. The linear absorption coefficient factor was similar either for the green and the sintered compacts, due the amount of porosity did not affect the radiation attenuation. Thus the sintered was meant for size reduction and mechanical properties enhancement. (author)

  20. A comparative study of different concentrations of pure Zn powder effects on synthesis, structure, magnetic and microwave-absorbing properties in mechanically-alloyed Ni-Zn ferrite

    Science.gov (United States)

    Hajalilou, Abdollah; Mazlan, Saiful Amri; Shameli, Kamyar

    2016-09-01

    In this study, a powder mixture of Zn, Fe2O3 and NiO was used to produce different compositions of Ni1-xZnxFe2O4 (x=0.36, 0.5 and 0.64) nanopowders. High-energy ball milling with a subsequent heat treatment method was carried out. The XRD results indicated that for the content of Zn, x=0.64 a single phase of Ni-Zn ferrite was produced after 30 h milling while for the contents of Zn, x=0.36 and 0.5, the desired ferrite was formed after sintering the 30 h-milled powders at 500 °C. The average crystallite size decreased with increase in the Zn content. A DC electrical resistivity of the Ni-Zn ferrite, however, decreased with increase in the Zn content, its value was much higher than those samples prepared by the conventional ceramic route by using ZnO instead of Zn. This is attributed to smaller grains size which were obtained by using Zn. The FT-IR results suggested two absorption bands for octahedral and tetrahedral sites in the range of 350-700 cm-1. The VSM results revealed that by increasing the Zn content from 0.36 to 0.5, a saturation magnetization reached its maximum value; afterwards, a decrease was observed for Zn with x=0.64. Finally, magnetic permeability and dielectric permittivity were studied by using vector network analyzer to explore microwave-absorbing properties in X-band frequency. The minimum reflection loss value obtained for Ni0.5Zn0.5Fe2O4 samples, about -34 dB at 9.7 GHz, making them the best candidates for high frequency applications.

  1. Laser cladding of titanium alloy coating on titanium aluminide alloy substrate

    Institute of Scientific and Technical Information of China (English)

    徐子文; 黄正; 阮中健

    2003-01-01

    A new diffusion bonding technique combined with laser cladding process was developed to join TiAl alloy to itself and Ti-alloys. In order to enhance the weldability of TiAl alloys, Ti-alloy coatings were fabricated by laser cladding on the TiAl alloy. Ti powder and shaped Ti-alloy were respectively used as laser cladding materials. The materials characterization was carried out by OM, SEM, EDS and XRD analysis. The results show that the laser cladding process with shaped Ti-alloy remedy the problems present in the conventional process with powder, such as impurities, cracks and pores. The diffusion bonding of TiAl alloy with Ti-alloy coating to itself and Ti-alloy was carried out with a Gleeble 1500 thermal simulator. The sound bonds of TiAl/TiAl, TiAl/Ti were obtained at a lower temperature and with shorter time.

  2. Chlorine Nuclear Quadrupole Hyperfine Structure in the Vinyl - Chloride Complex

    Science.gov (United States)

    Leung, Helen O.; Marshall, Mark D.; Messinger, Joseph P.

    2015-06-01

    The microwave spectrum of the vinyl chloride--hydrogen chloride complex, presented at last year's symposium, is greatly complicated by the presence of two chlorine nuclei as well as an observed, but not fully explained tunneling motion. Indeed, although it was possible at that time to demonstrate conclusively that the complex is nonplanar, the chlorine nuclear quadrupole hyperfine splitting in the rotational spectrum resisted analysis. With higher resolution, Balle-Flygare Fourier transform microwave spectra, the hyperfine structure has been more fully resolved, but appears to be perturbed for some rotational transitions. It appears that knowledge of the quadrupole coupling constants will provide essential information regarding the structure of the complex, specifically the location of the hydrogen atom in HCl. Our progress towards obtaining values for these constants will be presented.

  3. Hyperfine relaxation of an optically pumped cesium vapor

    Energy Technology Data Exchange (ETDEWEB)

    Tornos, J.; Amare, J.C.

    1986-07-01

    The relaxation of hyperfine orientation indirectly induced by optical pumping with a sigma-polarized D/sub 1/-light in a cesium vapor in the presence of Ar is experimentally studied. The detection technique ensures the absence of quadrupole relaxation contributions in the relaxation signals. The results from the dependences of the hyperfine relaxation rate on the temperature and argon pressure are: diffusion coefficient of Cs in Ar, D/sub 0/ = 0.101 +- 0.010 cm/sup 2/s/sup -1/ at 0/sup 0/C and 760 Torr; relaxation cross section by Cs-Ar collisions, sigma/sub c/ = (104 +- 5) x 10/sup -23/ cm/sup 2/; relaxation cross section by Cs-Cs (spin exchange) collisions, sigma/sub e//sub x/ = (1.63 +- 0.13) x 10/sup -14/ cm/sup 2/.

  4. Hyperfine meson splittings: chiral symmetry versus transverse gluon exchange

    CERN Document Server

    Llanes-Estrada, Felipe J; Swanson, Eric S; Szczepaniak, Adam P; Llanes-Estrada, Felipe J.; Cotanch, Stephen R.; Szczepaniak, Adam P.; Swanson, Eric S.

    2004-01-01

    Meson spin splittings are examined within an effective Coulomb gauge QCD Hamiltonian incorporating chiral symmetry and a transverse hyperfine interaction necessary for heavy quarks. For light and heavy quarkonium systems the pseudoscalar-vector meson spectrum is generated by approximate BCS-RPA diagonalizations. This relativistic formulation includes both $S$ and $D$ waves for the vector mesons which generates a set of coupled integral equations. A smooth transition from the heavy to the light quark regime is found with chiral symmetry dominating the $\\pi$-$\\rho$ mass difference. A good, consistent description of the observed meson spin splittings and chiral quantities, such as the quark condensate and the $\\pi$ mass, is obtained. Similar comparisons with TDA diagonalizations, which violate chiral symmetry, are deficient for light pseudoscalar mesons indicating the need to simultaneously include both chiral symmetry and a hyperfine interaction. The $\\eta_b$ mass is predicted to be around 9400 MeV consistent w...

  5. Tuning hyperfine fields in conjugated polymers for coherent organic spintronics.

    Science.gov (United States)

    Lee, Sang-Yun; Paik, Seo-Young; McCamey, Dane R; Yu, Justin; Burn, Paul L; Lupton, John M; Boehme, Christoph

    2011-02-23

    An appealing avenue for organic spintronics lies in direct coherent control of the spin population by means of pulsed electron spin resonance techniques. Whereas previous work has focused on the electrical detection of coherent spin dynamics, we demonstrate here the equivalence of an all-optical approach, allowing us to explore the influence of materials chemistry on the spin dynamics. We show that deuteration of the conjugated polymer side groups weakens the local hyperfine fields experienced by electron-hole pairs, thereby lowering the threshold for the resonant radiation intensity at which coherent coupling and spin beating occur. The technique is exquisitively sensitive to previously obscured material properties and offers a route to quantifying and tuning hyperfine fields in organic semiconductors.

  6. Zirconium alloys produced by recycling zircaloy tunings

    Energy Technology Data Exchange (ETDEWEB)

    Gamba, N.S. [Instituto de Investigaciones en Catálisis y Petroquímica, INCAPE (FIQ, UNL–CONICET), Santiago del Estero 2829, 3000 Santa Fe (Argentina); Carbajal-Ramos, I.A. [Centro Atómico Bariloche, CNEA e Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400 Bariloche (Argentina); Ulla, M.A.; Pierini, B.T. [Instituto de Investigaciones en Catálisis y Petroquímica, INCAPE (FIQ, UNL–CONICET), Santiago del Estero 2829, 3000 Santa Fe (Argentina); Gennari, F.C., E-mail: gennari@cab.cnea.gov.ar [Centro Atómico Bariloche, CNEA e Instituto Balseiro, Universidad Nacional de Cuyo, Av. Bustillo 9500, 8400 Bariloche (Argentina)

    2013-11-25

    Highlights: •Zr–Ti alloys were successfully produced by two-step procedure. •Zircaloy tunings were used as a valuable source of Zr. •Zircaloy tunings and Ti powders was milled under hydrogen to produce hydride powders. •Hydride powders were decomposed by heating at 900 °C to synthesize the Zr-based alloy. •The procedure could be extended to the production of other Zr-based alloys. -- Abstract: Zircaloy chips were recycled to successfully produce Zr–Ti alloys with bcc structure and different compositions. The procedure developed involves two steps. First, the reactive mechanical alloying (RMA) of the zircaloy tunings and Ti powders was performed to produce metal hydride powders, with a high refinement of the microstructure and a Zr–Ti homogeneous composition. Second, the metal hydride powders were thermally decomposed by heating up to 900 °C to synthesize the Zr-based alloy with a selected composition. The change in the nature of the powders from ductile to brittle during milling avoids both cold working phenomena between the metals and the use of a control agent. A minimum milling time is necessary to produce the solid solution with the selected composition. The microstructure and structure of the final alloys obtained was studied. The present procedure could be extended to the production of Zr-based alloys with the addition of other metals different from Ti.

  7. Mg based alloys obtained by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Ordonez, S. [Univ. de Santiago de Chile (Chile). Fac. de Ingenieria; Garcia, G.; Serafini, D.; San Martin, A.

    1999-07-01

    In the present work, we studied the production of magnesium alloys, of stoichiometry 2Mg + Ni, by mechanical alloying (MA) and the behavior of the alloys under hydrogen in a Sievert`s type apparatus. The elemental powders were milled under argon atmosphere in a Spex 8000 high energy ball mill. The milled materials were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). Only minimum amounts of the Mg{sub 2}Ni intermetallic compound was obtained after 22 h of milling time. Most of the material was sticked to the inner surface of the container as well as to the milling balls. Powders milled only for 12 hours transforms to the intermetallic at around 433 K. Effects of the MA on the hydrogen absorption kinetics were also studied. (orig.) 10 refs.

  8. Hadronic deuteron polarizability contribution the hyperfine structure in muonic deuterium

    Directory of Open Access Journals (Sweden)

    Eskin A.V.

    2017-01-01

    Full Text Available The calculation of the contribution to the polarizability of the nucleus to hyperfine structure of muonic hydrogen is carried out within the unitary isobar model and on the basis of experimental data on the structure functions of deep inelastic lepton-proton and lepton-deuteron scattering. The calculation of virtual absorption cross sections of transversely and longitudinally polarized photons by nucleons in the resonance region is performed in the framework of the program MAID.

  9. Single pion contribution to the hyperfine splitting in muonic hydrogen

    CERN Document Server

    Huong, Nguyen Thu; Moussallam, Bachir

    2015-01-01

    We consider the simple one-pion exchange (Yukawa potential) contribution to the 2S hyperfine splitting in muonic hydrogen which had, until recently, been disregarded. We evaluate the relevant vertex amplitudes, in particular $\\pi^0\\mu^+\\mu^-$, combining low energy chiral expansions together with experimental data on $\\pi^0$ and $\\eta$ decays. The result for the 2S HFS is found to be small but not irrelevant.

  10. Plasma spheroidization of nickel powders in a plasma reactor

    Indian Academy of Sciences (India)

    G Shanmugavelayutham; V Selvarajan

    2004-10-01

    Thermal spray coatings of surfaces with metal, alloy and ceramic materials for protection against corrosion, erosion and wear is an intense field of research. The technique involves injection of the powder into a plasma flame, melting, acceleration of the powder particles, impact and bonding with the substrate. Feedstock powders of metals, alloys and ceramics for thermal spray applications have to meet several requirements. Particle shape, size and its distribution, powder flow characteristics and density are the important factors to be considered in order to ensure high spray efficiency and better coating properties. For smooth and uniform feeding of powders into plasma jet, the powder particles have to be spherical in shape. High temperatures and steep temperatures present in thermal plasma is exploited to spheroidize particles in the present investigation. Nickel powder particles in the size range from 40–100 m were spheroidized using plasma processing. SEM and optical micrographs showed spherical shape of processed particles.

  11. Fine- and hyperfine-structure effects in molecular photoionization: II. Resonance-enhanced multiphoton ionization and hyperfine-selective generation of molecular cations

    CERN Document Server

    Germann, Matthias

    2016-01-01

    Resonance-enhanced multiphoton ionization (REMPI) is a widely used technique for studying molecular photoionization and producing molecular cations for spectroscopy and dynamics studies. Here, we present a model for describing hyperfine-structure effects in the REMPI process and for predicting hyperfine populations in molecular ions produced by this method. This model is a generalization of our model for fine- and hyperfine- structure effects in one-photon ionization of molecules presented in the preceding companion article. This generalization is achieved by covering two main aspects: (1) treatment of the neutral bound-bound transition including hyperfine structure that makes up the first step of the REMPI process and (2) modification of our ionization model to account for anisotropic populations resulting from this first excitation step. Our findings may be used for analyzing results from experiments with molecular ions produced by REMPI and may serve as a theoretical background for hyperfine-selective ioni...

  12. Effect of process variables on the flexural behavior of alloys Ti - 3% at. X (X = Nb, Ta) obtained by powder metallurgy; Efecto de las variables de proceso sobre el comportamiento a flexion de aleaciones Ti - 3% at. X (X = Nb, Ta) obtenidas por pulvimetalurgia

    Energy Technology Data Exchange (ETDEWEB)

    Franconetti, P.; Candel, J. J.; Vicente, A.; Amigo, V.

    2013-07-01

    Niobium and tantalum are added to titanium alloys to form new beta alloys with higher biocompatibility for biomedical applications. Both elements have a high melting point, that is the reason for their limited solid state diffusion. In this work samples of titanium with 3% at. niobium and tantalum have been manufactured by powder metallurgy. The effect of the compacting pressure, temperature and the sintering time on the strength, elasticity and ductility in bending has been studied. The results show that both elements behave similarly: flexural strength increases between 20-25%, elasticity between 0-10% and ductility over 150%. Therefore, the addition of these elements is beneficial to mechanical properties. Statistical analysis shows that the effect of temperature and pressure are important, while the effect of time is insignificant and even harmful in these alloys. (Author)

  13. Porosity, mechanical properties, residual stresses of supersonic plasma-sprayed Ni-based alloy coatings prepared at different powder feed rates

    Science.gov (United States)

    Zhang, X. C.; Xu, B. S.; Wu, Y. X.; Xuan, F. Z.; Tu, S. T.

    2008-04-01

    The aim of this paper was to investigate the effect of powder feed rate (PFR) on the microstructure and mechanical properties of the supersonic plasma-sprayed Ni-Cr-B-Si-C coatings. The microstructure, porosity and mechanical properties of the coatings and the residual stresses at the coating surfaces were experimentally determined. Results showed that the variations of porosity, elastic moduli and micro-hardness of the coatings followed Weibull distribution. From the statistical trend, the porosity of the coating increased with increasing PFR. However, the elastic modulus and the micro-hardness of the coating decreased and reached local minima and then increased with increasing PFR. Elastic modulus could be generally considered to be an increasing function of micro-hardness. The mean value of the elastic modulus of the coating calculated from Weibull plot was almost proportional to the square root of the mean value of the micro-hardness of the coating. Moreover, with increasing PFR, the residual stress at the coating surface, which was mainly governed by the elastic modulus of the coating, decreased to a local minimum and then increased.

  14. High-pressure study of Ti{sub 50}Ni{sub 25}Fe{sub 25} powder produced by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Ferreira, A. S. [Departamento de Engenharia Mecânica, Universidade Federal de Santa Catarina, CP 476 Florianópolis, Santa Catarina 88040-900 (Brazil); Rovani, P. R. [Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul 91501-970 (Brazil); Lima, J. C. de, E-mail: joao.cardoso.lima@ufsc.br [Departamento de Física, Universidade Federal de Santa Catarina, CP 476 Florianópolis, 88040-900 Santa Catarina (Brazil); Pereira, A. S. [Instituto de Física, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul 91501-970 (Brazil); Departamento de Materiais, Escola de Engenharia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Rio Grande do Sul 91501-970 (Brazil)

    2015-02-21

    A nanostructured Ti{sub 50}Ni{sub 25}Fe{sub 25} phase (B2) was formed by mechanical alloying and its structural stability was studied as a function of pressure. The changes were followed by X-ray diffraction. The B2 phase was observed up to 7 GPa; for larger pressures, the B2 phase transformed into a trigonal/hexagonal phase (B19) that was observed up to the highest pressure used (18 GPa). Besides B2 and B19, elemental Ni or a SS-(Fe,Ni) and FeNi{sub 3} were observed. With decompression, the B2 phase was recovered. Using in situ angle-dispersive X-ray diffraction patterns, the single line method was applied to obtain the apparent crystallite size and the microstrain for both the B2 and the B19 phases as a function of the applied pressure. Values of the bulk modulus for the B2, B19, elemental Ni or SS-(Fe,Ni) and FeNi{sub 3} phases were obtained by fitting the pressure dependence of the volume to a Birch–Murnaghan equation of state (BMEOS)

  15. TUNGSTEN BASE ALLOYS

    Science.gov (United States)

    Schell, D.H.; Sheinberg, H.

    1959-12-15

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

  16. Study of the microstructural and mechanical properties of titanium-niobium-zirconium based alloys processed with hydrogen and powder metallurgy for use in dental implants; Estudo das propriedades mecanicas e microestruturais de ligas a base de titanio-niobiozirconio processados com hidrogenio e metalurgia do po para utilizacao em implantes dentarios

    Energy Technology Data Exchange (ETDEWEB)

    Duvaizem, Jose Helio

    2009-07-01

    Hydrogen has been used as pulverization agent in alloys based on rare earth and transition metals due to its extremely high diffusion rate even on low temperatures. Such materials are used on hydrogen storage dispositives, generation of electricity or magnetic fields, and are produced by a process which the first step is the transformation of the alloy in fine powder by miling. Besides those, hydrogenium is also being used to obtain alloys based on titanium - niobium - zirconium in the pulverization. Powder metallurgy is utilized on the production of these alloys, making it possible to obtain structures with porous surface as result, requirement for its application as biomaterials. Other advantages of powder metallurgy usage include better surface finish and better microstructural homogeneity. In this work samples were prepared in the Ti-13Nb-13Zr composition. The hydrogenation was performed at 700 degree C, 600 degree C, and 500 degree C for titanium, niobium and zirconium respectively. After hydrogenation, the milling stage was carried out on high energy planetary ball milling with 200rpm during 90 minutes, and also in conventional ball milling for 30 hours. Samples were pressed in uniaxial press, followed by isostatic cold press, and then sintered at 1150 degree C for 7-13 hours. Microstructural properties of the samples were characterized by scanning electron microscope (SEM), energy dispersive spectroscopy (EDS) and x-ray diffraction. Mechanical and structural properties determined were density, microhardness and moduli of elasticity. The sample sintered at 1150 degree C for 7h, hydrogenated using 10.000 mbar and produced by milling on high energy planetary ball milling presented the best mechanical properties and microstructural homogeneity. (author)

  17. A novel shape transformation of Fe MgO nanocomposites: microstructural, magnetic and hyperfine investigations

    Science.gov (United States)

    Mukherjee, S.; Kumar, S.; Das, D.

    2007-08-01

    Fe-MgO nanocomposites synthesized by the mechanical high-energy transfer technique were characterized by x-ray diffraction (XRD), transmission electron microscopy, Mössbauer spectroscopy and dc magnetization studies. By varying the duration of milling, powder with different grain sizes in the range 17-40 nm was produced. XRD and Mössbauer measurements could not detect the presence of any form of iron oxide in the nanocomposites. Transmission electron micrographs showed a shape transformation from spherical to acicular-like geometry in the samples ball milled for more than 36 h. Dc magnetization measurements show an increase in the coercive field with decrease in average grain size, with a sharp increase at the point of shape transformation. A marked decrease from the expected values of saturation magnetization and magnetic moment per formula unit was observed. This decrease was ascribed to the magnetic dead layer formed at the surface of the nanoparticles, which increased with the increase in milling time. The nanocomposites ball milled for more than 36 h exhibit a two-component Mössbauer spectra due to the presence of two phases: a crystalline phase and an additional phase corresponding to the atoms residing at the grain boundaries between the crystallites. The grain boundaries give rise to a distribution of hyperfine magnetic fields, typical of an amorphous-like compound.

  18. A novel shape transformation of Fe-MgO nanocomposites: microstructural, magnetic and hyperfine investigations

    Energy Technology Data Exchange (ETDEWEB)

    Mukherjee, S [UGC-DAE Consortium for Scientific Research, Kolkata Centre III/LB-8, Bidhannagar, Kolkata 700 098 (India); Kumar, S [Department of Physics, Jadavpur University, Kolkata 700 032 (India); Das, D [UGC-DAE Consortium for Scientific Research, Kolkata Centre III/LB-8, Bidhannagar, Kolkata 700 098 (India)

    2007-08-07

    Fe-MgO nanocomposites synthesized by the mechanical high-energy transfer technique were characterized by x-ray diffraction (XRD), transmission electron microscopy, Moessbauer spectroscopy and dc magnetization studies. By varying the duration of milling, powder with different grain sizes in the range 17-40 nm was produced. XRD and Moessbauer measurements could not detect the presence of any form of iron oxide in the nanocomposites. Transmission electron micrographs showed a shape transformation from spherical to acicular-like geometry in the samples ball milled for more than 36 h. Dc magnetization measurements show an increase in the coercive field with decrease in average grain size, with a sharp increase at the point of shape transformation. A marked decrease from the expected values of saturation magnetization and magnetic moment per formula unit was observed. This decrease was ascribed to the magnetic dead layer formed at the surface of the nanoparticles, which increased with the increase in milling time. The nanocomposites ball milled for more than 36 h exhibit a two-component Moessbauer spectra due to the presence of two phases: a crystalline phase and an additional phase corresponding to the atoms residing at the grain boundaries between the crystallites. The grain boundaries give rise to a distribution of hyperfine magnetic fields, typical of an amorphous-like compound.

  19. Microstructural and magnetic behavior of an equiatomic NiCoAlFe alloy prepared by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Gómez-Esparza, C.D.; Baldenebro-López, F.J.; Santillán-Rodríguez, C.R.; Estrada-Guel, I.; Matutes-Aquino, J.A.; Herrera-Ramírez, J.M., E-mail: martin.herrera@cimav.edu.mx; Martínez-Sánchez, R.

    2014-12-05

    Highlights: • Equiatomic NiCoAlFe powder alloys were synthesized by mechanical alloying. • The nanocrystalline alloys were characterized after milled and annealed conditions. • In alloyed and annealed powders, only BCC and FCC structure phases were observed. • Magnetic properties are strongly affected by the phases formed after annealing. - Abstract: Equiatomic NiCoAlFe powder alloys were synthesized by mechanical alloying. The microstructural evolution of the mechanically alloyed powders at different times was followed with X-ray diffraction and scanning electron microscopy. The as-mechanically alloyed powders were subjected to a rapid annealing treatment at 1273 K and 1473 K during 3 min in vacuum. X-ray diffraction studies show the structure of both, the as-mechanically alloyed and annealed powders, consisted in a mixture of nanocrystalline simple phases (FCC + BCC). Crystallite size, after annealing, still remained in nanoscale. Coercivity increased due to the decrease in crystallite size and because of the defects caused by mechanical alloying in the as-mechanically alloyed samples; then coercivity decreased due to the phenomenon of random magnetic anisotropy and tended to stabilize with longer alloying times. A similar behavior was observed in annealed samples at 1273 K. However, random magnetic anisotropy was not observed after annealing at 1473 K because crystals with larger sizes were produced, and a steady increase in coercivity was observed.

  20. Influence of alloy ingredients on mechanical properties of ternary boride hard alloy clad materials

    Institute of Scientific and Technical Information of China (English)

    LIU Fu-tian; SONG Shi-xue; YANG Jun-ru; HUANG Wei-ling; HUANG Chuan-zhen; CHENG Xin; LI Zhao-qian

    2004-01-01

    Using Mo, B-Fe alloy and Fe powders as raw materials, and adding C, Cr and Ni ingredients, respectively, or C, Cr and Ni mixed powders, ternary boride hard alloy clad materials was prepared on Q235 steel substrate by means of in-situ reaction and vacuum liquid phase sintering technology. The influence of alloy ingredients on the mechanical properties of ternary boride hard alloy clad materials was investigated. The results indicate that a mixture of 0.8% C, 5% Cr and 2% Ni ingredients gives a ternary boride hard alloy clad material with optimal mechanical properties, such as high transverse rupture strength, high hardness and good wear resistance.

  1. Formation of Silicide Coating layer on U-Mo Powder

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Ji Min; Kim, Sunghwan; Lee, Kyu Hong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    High-density U-Mo alloys are regarded as promising candidates for advanced research reactor fuel as they have shown stable irradiation performance when compared to other uranium alloys and compounds. However, interaction layer formation between the U-Mo alloys and Al matrix degrades the irradiation performance of U-Mo Dispersion fuel. Therefore, the addition of Ti in U-Mo alloys, the addition of Si in a Al matrix, and silicide or nitride coating on the surface of U-Mo particles have been proposed to inhibit the interaction layer growth. In this study, U-Mo alloy powder was produced using a centrifugal atomization method. In addition, silicide coating layers were fabricated by several mixing process changes on the surface of the U-Mo particles. The coated powders were characterized by using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDAX). Decreased annealing duration did not affect the forming of silicide coating layers on the surface of U-7wt%Mo powders. The variation in the mixing ratio between U-7wt%Mo and Si powders had an effect on the quality of silicide coating on the U-7wt%Mo powders. The weight of Si powders should be smaller than that of U-7wt%Mo powders for better silicide coating when it comes to the mixing ratio.

  2. Hyperfine interactions: the past, the present and the future

    Energy Technology Data Exchange (ETDEWEB)

    Langouche, Guido, E-mail: guido.langouche@kuleuven.be [Katholieke Universiteit Leuven, Physics Department, Institute of Nuclear and Radiation Physics (Belgium)

    2008-01-15

    Five major hyperfine interaction techniques, detected by nuclear radiation, originated in the short time span between 1950 and 1965. The coincidence with the demographic expansion, especially in Europe, of university education led to the creation of many new research laboratories applying these promising techniques in solid state physics, chemistry and biology. Since the turn of century many of the early pioneers are going into retirement, leading to a decline in activities in Europe, compensated in some degree by an increase in activities outside Europe. The organisation of the 2007 HI/NQI-conference was impeccable and took place in a superb setting. Thanks to all those involved in its organization.

  3. Hyperfine structure of singly ionized lanthanum and praseodymium

    Institute of Scientific and Technical Information of China (English)

    马洪良

    2002-01-01

    Hyperfine structure spectra of singly ionized lanthanum and praseodymium have been measured by collinearfast-ion-beam laser spectroscopy. All the spectral lines were resolved and the magnetic dipole and electric quadruplecoupling constants of the metastable levels and excited levels were determined. Our results are in agreement withthe published data within the experimental uncertainty. For praseodymium ions, the accuracy of the magnetic dipolecoupling constants are improved by one order of magnitude compared with other published data, and the electricquadruple coupling constants are reported for the first time.

  4. Modeling flux noise in SQUIDs due to hyperfine interactions.

    Science.gov (United States)

    Wu, Jiansheng; Yu, Clare C

    2012-06-15

    Recent experiments implicate spins on the surface of metals as the source of flux noise in superconducting quantum interference devices and indicate that these spins are able to relax without conserving total magnetization. We present a model of 1/f flux noise in which electron spins on the surface of metals can relax via hyperfine interactions. Our results indicate that flux noise would be significantly reduced in superconducting materials where the most abundant isotopes do not have nuclear moments, such as zinc and lead.

  5. Determination of hyperfine fields orientation in nuclear probe techniques

    Science.gov (United States)

    Szymański, K.; Olszewski, W.; Satuła, D.; Gawryluk, D. J.; Krzton-Maziopa, A.; Kalska-Szostko, B.

    2017-02-01

    One of the most popular nuclear probes, 57Fe is used for the investigation of orientations of hyperfine fields and also for the determination of other important properties. In particular, the orientation of iron magnetic moments can be unambiguously determined, including its signs. Experiments with polarized radiation are presented with regard to selected systems. Orientation of electric field gradient is used for acquiring information about the shape of the texture-free spectra. Applications on the analysis of iron-based superconductors are presented.

  6. Temperature field analysis in tungsten-copper alloy powder preparation by molten salt electrolysis%熔盐电解制备钨铜合金粉体槽内温场条件分析

    Institute of Scientific and Technical Information of China (English)

    王旭; 周才英; 廖春发

    2014-01-01

    在熔盐电解法由Na2WO4和CuO制取钨铜合金粉体的研究基础上,分析电解槽内的温度场分布,特别是电极区域的温度分布情况对电解行为的影响。通过位移法测量,采取比较法分析实验误差,结果表明:电解过程中2个主要的外部条件,即电解槽内温场分布与电场分布是联动的;温度条件影响着电极电位;同时,外部槽电压通过电流扰动槽内温场,使电极区域温场分布不均。%Based on the research of preparing tungsten copper alloy powder from Na 2WO4 and CuO by molten salt electrolysis method, the temperature field distribution of the electrolysis cell and the influence of the electrochemical behavior around temperature distribution nearby the electrode area are analyzed. Temperature is measured by the displacement method and the experimental error is analyzed. The results show that temperature field distribution and electric field distribution in the electrolytic cell interact with each other, and the electrode potential is affected by temperature conditions. In the meanwhile, the external electric field disturbs the temperature field in electrolysis cell to make the uneven distribution of temperature field around electrode area.

  7. Mo-Si alloy development

    Energy Technology Data Exchange (ETDEWEB)

    Liu, C.T.; Heatherly, L.; Wright, J.L. [Oak Ridge National Lab., TN (United States)

    1996-06-01

    The objective of this task is to develop new-generation corrosion-resistant Mo-Si intermetallic alloys as hot components in advanced fossil energy conversion and combustion systems. The initial effort is devoted to Mo{sub 5}-Si{sub 3}-base (MSB) alloys containing boron additions. Three MSB alloys based on Mo-10.5Si-1.1B (wt %), weighing 1500 g were prepared by hot pressing of elemental and alloy powders at temperatures to 1600{degrees}C in vacuum. Microporosities and glassy-phase (probably silicate phases) formations are identified as the major concerns for preparation of MSB alloys by powder metallurgy. Suggestions are made to alleviate the problems of material processing.

  8. Effects of Cobalt on the Sintering Behavior of Mechanically Activated Tungsten Powder

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Tungsten alloys were prepared with mechanically activated powder added microelement cobalt in order to improve the process and properties of alloys. Properties of alloys such as density, hardness and bending strength were measured. The results show that through mechanical activation, cobalt can accelerate the sintering process of these alloys. By the combination of mechanical activation and adding microelement cobalt, tungsten alloys with higher density and better properties can be obtained.

  9. Characterization of Ni{sub 5}3.5-Fe{sub 1}9.5-Ga{sub 2}7 Ni{sub 5}3.5 ferromagnetic shape memory alloy produced by powder metallurgy; Caracterizacion de la aleacion Ni{sub 5}3.5-Fe{sub 1}9.5-Ga{sub 2}7 con memoria de forma ferromagnetica producida por metalurgia de polvos

    Energy Technology Data Exchange (ETDEWEB)

    Olmos, L.; Alvarado-Hernandez, F.; Omar Jimenez, H.; Vergara-Hernandez, J.; Arroyo Albiter, M.; Ochoa-Gamboa, R. A.

    2015-07-01

    The main drawback of ferromagnetic shape memory alloys fabricated through casting methods are its brittleness. In order to overcome this disadvantage, powder metallurgy is an ideal technique for the consolidation of many engineering parts. This paper is focused on the study of the milling and sintering effects of metallic powders over the evolution of the crystalline phases responsibly for the shape memory effect of these materials. To achieve this objective, ferromagnetic shape memory alloy powders (Ni{sub 5}3.5-Fe{sub 1}9.5-Ga{sub 2}7) were prepared from a cast ingot by mechanical milling at two different times of 30 and 60 minutes. The evolution of the phases was investigated through high temperature X-ray diffraction (HTXRD), whereas sintering was analyzed with dilatometry tests. X-ray studies showed that four different phases can be present depending on the particle size and temperature at which the heat treatment was performed. Coarser powders showed a B2 structure along with a γ phase while the finer showed a L21 structure when treated below 1173 K. Furthermore, finer powders had a modulated M14 martensitic structure after sintering at temperatures above 1273 K. The sintering of powders was slow and a mass diffusion mechanism was not clearly observed. (Author)

  10. Study the Magnetic Properties of Invar Alloys by Using High Pressure Mössbaur Spectroscopy

    Directory of Open Access Journals (Sweden)

    N. A. Khalefa

    2015-12-01

    Full Text Available High pressure 57F MÖssbaur spectroscopy measurement ( up to 42 Gpa at room temperature have been carried out for investigation the magnetic properties of Ɣ(f.c.c Fe78Ni22 alloys using diamond anvil cell (DAC technique. The mÖssbaur spectrum at 0 Gpa shows a six line magnetic pattern with broad outer peaks and an average hyperfine field of ~32T characteristic of a disordered alloys. In the pressure rang (2alloys (25-35 at % Ni. Our data indicate a pressure induced invar effect for Fe78Ni22 alloy at ~7-12 Gpa. Above 20 Gpa the hyperfine field break down and the alloy becomes non-magnetic showing only a single line MÖsbauer spectrum.

  11. 稀土氧化物粒子对钼合金粉末冶金过程及力学性能的影响%EFFECTS OF RARE-EARTH PARTICLES ON MOLYBDENUM ALLOY POWDER METALLURGY PROCESSING AND MECHANICAL PROPERTIES

    Institute of Scientific and Technical Information of China (English)

    赵虎; 杨秦莉; 冯鹏发; 刘仁智; 付静波

    2013-01-01

    试验研究了掺杂LaO3、Y2 O3、CeO2稀土氧化物颗粒对钼合金的粉末物性、烧结进程、制品的烧结致密度及压力加工丝材的室温力学性能的影响规律.试验结果表明,掺杂稀土氧化物粒子细化了钼粉的粒度,降低了松装密度和粒度分布范围,同时导致粉末团聚现象增多;稀土氧化物粒子延迟了钼合金的烧结进程,降低了烧结制品的致密度,同时细化了烧结体晶粒尺寸.稀土氧化物粒子以弥散强化和细晶强化的形式,提高了钼合金丝的室温强度.CeO2显著提高了钼合金丝的室温韧性,La203、Y2O3则降低了钼合金丝的室温韧性.%The effects on the molybdenum alloy powder properties,sintering proceeding and sintering products density and mechanical properties of molybdenum alloy as-worked wire which was doped with rare-earth oxides particles such as La2O3 、Y2O3 、CeO2 were studied.The results showed that the particles size of the molybdenum alloy powder were refined,loose density and particle size distribution were reduced by doping rare-earth oxides particles,though at the same time molybdenum alloy powder aggregation were increased.Sintering proceeding was delayed,sintering products density was reduced and the grain size was refined by the rare-earth oxides particles during sintering process.The room temperature strength of the molybdenum alloy wire as-worked was increased by the grain refinement strengthening and dispersion strengthening of the doped rare-earth oxides particles.Room temperature toughness of molybdenum alloy wire as-worked was greatly improved as doped CeO2 particles but reduced as doped La2O3 and Y2O3 particles.

  12. Zeeman effects in the hyperfine structure of atomic iodine photodissociation laser emission.

    Science.gov (United States)

    Hwang, W. C.; Kasper, J. V. V.

    1972-01-01

    Observation of hyperfine structure in laser emission from CF3I and C2F5I photodissociation lasers. Constant magnetic fields affect the time behavior of the emission by changing the relative gains of the hyperfine transitions. Time-varying fields usually present in photodissociation lasers further complicate the emission.

  13. O(alpha(3) lnalpha) corrections to muonium and positronium hyperfine splitting.

    Science.gov (United States)

    Melnikov, K; Yelkhovsky, A

    2001-02-19

    We compute O(alpha(3)lnalpha) relative corrections to the ground-state hyperfine splitting of a QED two-body bound state with different masses of constituents. The general result is then applied to muonium and positronium. In particular, a new value of the muon-to-electron mass ratio is derived from the muonium ground-state hyperfine splitting.

  14. Synthesis of Al/Al sub 3 Ti two-phase alloys by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan, S.; Chen, S.R.; Schwarz, R.B.

    1991-01-01

    We have mechanically alloyed mixtures of elemental powders to prepare fine-grain two-phase A1/A1{sub 3}Ti powders at the compositions A1-20at% Ti and Al-10at% Ti. Hexane was used to prevent agglomeration of the powder during MA. Carbon from the decomposition of the hexane was incorporated in the powder. It reacted with Ti to form a fine dispersion of carbides in the final hot-pressed compact. We consolidated the mechanically alloyed powders by hot-pressing. Yield strength and ductility were measured in compression. At 25{degree}C, the compressive yield strengths were 1.25 and 0.6 GPa for the A1-20at% Ti and Al-10at% Ti alloys, respectively. The ductility of the A1-10at% Ti alloy exceeded 20% for 25 < T < 500{degree}C. 25 refs., 6 figs.

  15. Corrosion issues of powder coated AA6060 aluminium profiles

    DEFF Research Database (Denmark)

    Din, Rameez Ud; Valgarðsson, Smári; Jellesen, Morten Stendahl

    2015-01-01

    In this study detailed microstructural investigation of the reason for unexpected corrosion of powder coated aluminium alloy AA6060 windows profiles has been performed. The results from this study reveals that the failure of the window profiles was originated from the surface defects present...... on the extruded AA6060 aluminium profile after metallurgical process prior to powder coating. Surface defects are produced due to intermetallic particles in the alloy, which disturb the flow during the extrusion process. The corrosion mechanism leading to the failure of the powder coated AA6060 aluminium profiles...

  16. Resolution of hyperfine transitions in metastable 83Kr using Electromagnetically Induced Transparency

    CERN Document Server

    Kale, Y B; Tiwari, V B; Singh, S; Rawat, H S

    2015-01-01

    Narrow linewidth signals of Electromagnetically Induced Transparency (EIT) in the metastable 83Kr have been observed for the first time. Various hyperfine transitions in 4p55s[3/2]2 to 4p55p[5/2]3 manifolds of 83Kr have been identified through the experimentally observed EIT signals. Some unresolved or poorly resolved hyperfine transitions in saturated absorption spectroscopy (SAS) are clearly resolved in the present work. Using the spectral separation of these EIT identified hyperfine transitions, the magnetic hyperfine constant (A) and the electric quadrupole hyperfine constant (B) are determined with improved accuracy for 4p55s[3/2]2 and 4p55p[5/2]3 manifolds.

  17. Moessbauer study of Fe[sub 3-x]Cr[sub x]Si alloys with DO[sub 3]-type ordering. [Fe-Cr-Si

    Energy Technology Data Exchange (ETDEWEB)

    Satula, D.; Szymanski, K.; Dobrzynski, L.; Waliszewski, J. (Faculty of Physics, Warsaw Univ. Branch, Bialystok (Poland))

    1993-02-01

    The influence of chromium atoms substituting for iron in the Fe[sub 3-x]Cr[sub x]Si alloys with DO[sub 3]-type ordering is investigated by Moessbauer spectroscopy at room temperature. Using the correlation between local hyperfine magnetic field and magnetic moments observed for Fe[sub 3]Si it is inferred that the magnetic moment of iron in Fe[sub 3-x]Cr[sub x]Si decreases linearly with x for both (A,C) and B sites. A few models intended to describe an influence of Cr on local hyperfine fields are tested. It is found that the local hyperfine magnetic field depends primarily on the chemical composition of the nearest neighbour shell. The isomer shift and magnetic hyperfine field show no substantial dependence on the alloy composition. Chromium atoms occupy, unexpectedly, both B and (A, C) sites, although the B sites are preferentially occupied. (orig.).

  18. Relativistic extended coupled cluster method for magnetic hyperfine structure constant

    CERN Document Server

    Sasmal, Sudip; Nayak, Malaya K; Vaval, Nayana; Pal, Sourav

    2015-01-01

    This article deals with the general implementation of 4-component spinor relativistic extended coupled cluster (ECC) method to calculate first order property of atoms and molecules in their open-shell ground state configuration. The implemented relativistic ECC is employed to calculate hyperfine structure (HFS) constant of alkali metals (Li, Na, K, Rb and Cs), singly charged alkaline earth metal atoms (Be+, Mg+, Ca+ and Sr+) and molecules (BeH, MgF and CaH). We have compared our ECC results with the calculations based on restricted active space configuration interaction (RAS-CI) method. Our results are in better agreement with the available experimental values than those of the RAS-CI values.

  19. Control of inhomogeneous atomic ensembles of hyperfine qudits

    CERN Document Server

    Mischuck, Brian E; Deutsch, Ivan H

    2011-01-01

    We study the ability to control d-dimensional quantum systems (qudits) encoded in the hyperfine spin of alkali-metal atoms through the application of radio- and microwave-frequency magnetic fields in the presence of inhomogeneities in amplitude and detuning. Such a capability is essential to the design of robust pulses that mitigate the effects of experimental uncertainty and also for application to tomographic addressing of particular members of an extended ensemble. We study the problem of preparing an arbitrary state in the Hilbert space from an initial fiducial state. We prove that inhomogeneous control of qudit ensembles is possible based on a semi-analytic protocol that synthesizes the target through a sequence of alternating rf and microwave-driven SU(2) rotations in overlapping irreducible subspaces. Several examples of robust control are studied, and the semi-analytic protocol is compared to a brute force, full numerical search. For small inhomogeneities, < 1%, both approaches achieve average fide...

  20. Theoretical Investigation on Hyperfine Structures of Perfluoropolyether Radicals

    Institute of Scientific and Technical Information of China (English)

    DONG Su-li; LIU Ya-jun

    2011-01-01

    The geometries of CF3OCF2, CF3OCFCF3 and CF3OCF2CF2 radicals were investigated by density func tional theory(DFT) method. The calculated results indicate that all the three radicals have pyramidal shapes at their centers, and the aC is one top of the pyramids. Based on the DFT optimized geometries, the hyperfine coupling con stants(hfcc's) of the 19F atoms of the three radicals were calculated by B3LYP, MP2(full) and QCISD(full) methods.The calculated values agree with the experimental values, especially for the a values of Fa, the a values are 125.6× 10-4, 104.2× 10-4, and 83.2× 10-4 T of CF3OCF2, CF3OCFCF3 and CF3OCF2CF2, respectively. These results better explain the experimental observation.

  1. Exploration of hyperfine interaction between constituent quarks via eta productions

    CERN Document Server

    He, Jun; Xu, H S

    2011-01-01

    In this work, the different exchange freedom, one gluon, one pion or Goldstone boson, in constituent quark model is investigated, which is responsible to the hyperfine interaction between constituent quarks, via the combined analysis of the eta production processes, $\\pi^{-}p\\rightarrow\\eta n$ and $\\gamma p\\rightarrow\\eta p$. With the Goldstone-boson exchange, as well as the one-gluon or one-pion exchange, both the spectrum and observables, such as, the differential cross section and polarized beam asymmetry, are fitted to the suggested values of Particle Data Group and the experimental data. The first two types of exchange freedoms give acceptable description of the spectrum and observables while the one pion exchange can not describe the observables and spectrum simultaneously, so can be excluded. The experimental data for the two processes considered here strongly support the mixing angles for two lowest S11 sates and D13 states as about -30 and 6 degree respectively.

  2. Coulomb Artifacts and Bottomonium Hyperfine Splitting in Lattice NRQCD

    CERN Document Server

    Liu, Tao; Rayyan, Ahmed

    2016-01-01

    We study the role of the lattice artifacts associated with the Coulomb binding effects in the analysis of the heavy quarkonium within lattice NRQCD. We find that a "na\\"ive" perturbative matching generates spurious linear Coulomb artifacts, which result in a large systematic error in the lattice predictions for the heavy quarkonium spectrum. This effect is responsible, in particular, for the discrepancy between the recent determinations of the bottomonium hyperfine splitting in the radiatively improved lattice NRQCD [1, 2]. We show that the correct matching procedure which provides full control over discretization errors is based on the asymptotic expansion of the lattice theory about the continuum limit, which gives $M_{\\Upsilon(1S)}-M_{\\eta_b(1S)}=52.9\\pm 5.5~{\\rm MeV}$ [1].

  3. Measurement and modeling of hyperfine parameters in ferroic materials

    CERN Document Server

    Gonçalves, João Nuno; Correia, J G

    This thesis presents the results of perturbed angular correlation (PAC) experiments , an experimental technique which measures the hyperfine interaction at probes (radioactive ions implanted in the materials to study), from which one infers local information on an atomic scale. Furthermore, abinitio calculations using density functional theory electronic obtain results that directly complement the experiments, and are also used for theoretical research. These methods were applied in two families of materials. The manganites, with the possible existence of magnetic, charge, orbital and ferroelectric orders, are of fundamental and technological interest. The experimental results are obtained in the alkaline-earth manganites (Ca, Ba, Sr), with special interest due to the structural variety of possible polymorphs. With probes of Cd and In the stability of the probe and its location in a wide temperature range is established and a comparison with calculations allows the physical interpretation of the results. Cal...

  4. Dephasing and hyperfine interaction in carbon nanotubes double quantum dots

    DEFF Research Database (Denmark)

    Reynoso, Andres Alejandro; Flensberg, Karsten

    2012-01-01

    We study theoretically the return probability experiment, which is used to measure the dephasing time T-2*, in a double quantum dot (DQD) in semiconducting carbon nanotubes with spin-orbit coupling and disorder-induced valley mixing. Dephasing is due to hyperfine interaction with the spins of the C......-13 nuclei. Due to the valley and spin degrees of freedom, four bounded states exist for any given longitudinal mode in the quantum dot. At zero magnetic field, the spin-orbit coupling and the valley mixing split those four states into two Kramers doublets. The valley-mixing term for a given dot...... is determined by the intradot disorder; this leads to (i) states in the Kramers doublets belonging to different dots being different, and (ii) nonzero interdot tunneling amplitudes between states belonging to different doublets. We show that these amplitudes give rise to new avoided crossings, as a function...

  5. Hyperfine Structure and Isotope Shifts in Dy II

    Directory of Open Access Journals (Sweden)

    Dylan F. Del Papa

    2017-01-01

    Full Text Available Using fast-ion-beam laser-fluorescence spectroscopy (FIBLAS, we have measured the hyperfine structure (hfs of 14 levels and an additional four transitions in Dy II and the isotope shifts (IS of 12 transitions in the wavelength range of 422–460 nm. These are the first precision measurements of this kind in Dy II. Along with hfs and IS, new undocumented transitions were discovered within 3 GHz of the targeted transitions. These atomic data are essential for astrophysical studies of chemical abundances, allowing correction for saturation and the effects of blended lines. Lanthanide abundances are important in diffusion modeling of stellar interiors, and in the mechanisms and history of nucleosynthesis in the universe. Hfs and IS also play an important role in the classification of energy levels, and provide a benchmark for theoretical atomic structure calculations.

  6. Study on selective laser melting process and forming of AlSi10 Mg alloy powder%选择性激光熔化AlSi10 Mg合金粉末的成形工艺

    Institute of Scientific and Technical Information of China (English)

    刘锦辉; 史金光; 李亚

    2015-01-01

    This paper deals with the single-layer single-channel experiment and single-layer multi-channel experiment performed by using different process parameters to study the selective laser melting (SLM) forming process of AlSi10Mg alloy powder. This study consists of analyzing the effects of laser power, laser scanning speed, scanning interval on melting channel width and surface quality;testing the density of SLM AlSi10 Mg samples formed under different parameters and analyzing the relationship be-tween energy density and the sample density; and testing the microstructure and property, and micro-hardness. The results show that the optimal scanning track quality is governed the given process parame-ters:laser power between 240~280 W, scanning speed between 1 000~1 400 mm/s, scanning interval between 0 . 06~0 . 08 mm; SLM-produced AlSi10 Mg parts perform much better than conventionally cast AlSi10 Mg ones .%为了研究AlSi10 Mg合金粉末的选择性激光熔化成形,采用不同的工艺参数,进行了单层单道扫描实验和单层多道扫描实验。分析激光功率、激光扫描速度、扫描间距对激光扫描轨迹宽度和表面质量的影响。检测不同参数下选择性激光熔化成形的AlSi10 Mg合金块的致密度,分析成形件致密度与能量密度的关系,成形件的组织和性能,对成形件进行硬度测试。结果表明:激光功率在240~280 W,扫描速度在1000~1400 mm/s,扫描间距在0.06~0.08 mm时,扫描轨迹成形质量最佳。与传统铸造AlSi10Mg合金零件相比,SLM成形的零件具有更好的性能。

  7. HCN hyperfine ratio analysis of massive molecular clumps

    Science.gov (United States)

    Schap, W. J.; Barnes, P. J.; Ordoñez, A.; Ginsburg, A.; Yonekura, Y.; Fukui, Y.

    2017-03-01

    We report a new analysis protocol for HCN hyperfine data, based on the PYSPECKIT package, and results of using this new protocol to analyse a sample area of seven massive molecular clumps from the Census of High- and Medium-mass Protostars (CHaMP) survey, in order to derive maps of column density for this species. There is a strong correlation between the HCN integrated intensity, IHCN, and previously reported I_HCO+ in the clumps, but I_N_{2H+} is not well correlated with either of these other two 'dense gas tracers'. The four fitted parameters from PYSPECKIT in this region fall in the range of VLSR = 8-10 km s-1, σV = 1.2-2.2 km s-1, Tex = 4-15 K, and τ = 0.2-2.5. These parameters allow us to derive a column density map of these clouds, without limiting assumptions about the excitation or opacity. A more traditional (linear) method of converting IHCN to total mass column gives much lower clump masses than our results based on the hyperfine analysis. This is primarily due to areas in the sample region of low I, low Tex, and high τ. We conclude that there may be more dense gas in these massive clumps not engaged in massive star formation than previously recognized. If this result holds for other clouds in the CHaMP sample, it would have dramatic consequences for the calibration of the Kennicutt-Schmidt star formation laws, including a large increase in the gas depletion time-scale in such regions.

  8. Full hyperfine structure analysis of singly ionized molybdenum

    Science.gov (United States)

    Bouazza, Safa

    2017-03-01

    For a first time a parametric study of hyperfine structure of Mo II configuration levels is presented. The newly measured A and B hyperfine structure (hfs) constants values of Mo II 4d5, 4d45s and 4d35s2 configuration levels, for both 95 and 97 isotopes, using Fast-ion-beam laser-induced fluorescence spectroscopy [1] are gathered with other few data available in literature. A fitting procedure of an isolated set of these three lowest even-parity configuration levels has been performed by taking into account second-order of perturbation theory including the effects of closed shell-open shell excitations. Moreover the same study was done for Mo II odd-parity levels; for both parities two sets of fine structure parameters as well as the leading eigenvector percentages of levels and Landé-factor gJ, relevant for this paper are given. We present also predicted singlet, triplet and quintet positions of missing experimental levels up to 85000 cm-1. The single-electron hfs parameter values were extracted in their entirety for 97Mo II and for 95Mo II: for instance for 95Mo II, a4d01 =-133.37 MHz and a5p01 =-160.25 MHz for 4d45p; a4d01 =-140.84 MHz, a5p01 =-170.18 MHz and a5s10 =-2898 MHz for 4d35s5p; a5s10 =-2529 (2) MHz and a4d01 =-135.17 (0.44) MHz for the 4d45s. These parameter values were analysed and compared with diverse ab-initio calculations. We closed this work with giving predicted values of magnetic dipole and electric quadrupole hfs constants of all known levels, whose splitting are not yet measured.

  9. Multispectral plasmon-induced transparency in hyperfine terahertz meta-molecules

    Science.gov (United States)

    Yang, Shengyan; Xia, Xiaoxiang; Liu, Zhe; Yiwen, E.; Wang, Yujin; Tang, Chengchun; Li, Wuxia; Li, Junjie; Wang, Li; Gu, Changzhi

    2016-11-01

    We experimentally and theoretically demonstrated an approach to achieve multispectral plasmon-induced transparency (PIT) by utilizing meta-molecules that consist of hyperfine terahertz meta-atoms. The feature size of such hyperfine meta-atoms is 400 nm, which is one order smaller than that of normal terahertz metamaterials. The hyperfine meta-atoms with close eigenfrequencies and narrow resonant responses introduce different metastable energy levels, which makes the multispectral PIT possible. In the triple PIT system, the slow light effect is further confirmed as the effective group delay at three transmission windows can reach 7.3 ps, 7.4 ps and 4.5 ps, respectively. Precisely controllable manipulation of the PIT peaks in such hyperfine meta-molecules was also proven. The new hyperfine planar design is not only suitable for high-integration applications, but also exhibits significant slow light effect, which has great potential in advanced multichannel optical information processing. Moreover, it reveals the possibility to construct hyperfine N-level energy systems by artificial hyperfine plasmonic structures, which brings a significant prospect for applications on miniaturized plasmonic devices.

  10. Hyperfine Structure in Rotational Spectra of Deuterated Molecules: the Hds and ND_3 Case Studies

    Science.gov (United States)

    Cazzoli, Gabriele; Puzzarini, Cristina

    2016-06-01

    The determination of hyperfine parameters (quadrupole-coupling, spin-spin coupling, and spin-rotation constants) is one of the aims of high-resolution rotational spectroscopy. These parameters are relevant not only from a spectroscopic point of view, but also from a physical and/or chemical viewpoint, as they might provide detailed information on the chemical bond, structure, etc. In addition, the hyperfine structure of rotational spectra is so characteristic that its analysis may help in assigning the spectra of unknown species. In astronomical observations, hyperfine structures of rotational spectra would allow us to gain information on column densities and kinematics, and the omission of taking them into account can lead to a misinterpretation of the line width of the molecular emission lines. Nevertheless, the experimental determination of hyperfine constants can be a challenge not only for actual problems in resolving hyperfine structures themselves, but also due to the lack of reliable estimates or the complexity of the hyperfine structure itself. It is thus important to be able to rely on good predictions for such parameters, which can nowadays be provided by quantum-chemical calculations. In fact, the fruitful interplay of experiment and theory will be demonstrated by means of two study cases: the hypefine structure of the rotational spectra of HDS and ND_3. From an experimental point of view, the Lamb-dip technique has been employed to improve the resolving power in themillimeter- and submillimeterwave frequency range by at least one order of magnitude, thus making it possible to perform sub-Doppler measurements as well as to resolve narrow hyperfine structures. Concerning theory, it will be demonstrated that high-level calculations can provide quantitative estimates for hyperfine parameters (quadrupole coupling constants, spin-rotation tensors, spin-spin couplings, etc.) and shown how theoretical predictions are often essential for a detailed analysis of

  11. Adsorption interaction between Al-5% Pb alloy and water

    Science.gov (United States)

    Ryabina, A. V.; Shevchenko, V. G.

    2016-10-01

    The adsorption and structural features of Al-5% Pb alloy powder before and after reacting with water are analyzed. Results from studying the morphology and phase composition of the oxidation products are presented, and the specific surface area and porosity of the powders are calculated. It is shown experimentally that water treatment of Al-5% Pb alloy powder even at room temperature leads to the formation of new phases and affects the powder's morphology. It is established that a major role in the properties of the watertreated powders is played by nanopores that form between crystallites on a particle's surface during waterinduced oxidation and subsequent thermal dehydration.

  12. Measurement of the hyperfine splitting of the 6S$_{1/2}$ level in rubidium

    CERN Document Server

    Galvan, A Perez; Orozco, L A

    2008-01-01

    We present a measurement of the hyperfine splitting of the 6S$_{1/2}$ excited level of rubidium using two photon absorption spectroscopy in a glass cell. The values we obtain for the magnetic dipole constant A are 239.18(03) MHz and 807.66(08) MHz for $^{85}$Rb and $^{87}$Rb, respectively. The combination of the magnetic moments of the two isotopes and our measurements show a hyperfine anomaly in this atomic excited state. The observed hyperfine anomaly difference has a value of $_{87}\\delta_{85}=-0.0036(2)$ due to the finite distribution of nuclear magnetization, the Bohr-Weisskopf effect.

  13. Fine- and hyperfine-structure effects in molecular photoionization: I. General theory and direct photoionization

    CERN Document Server

    Germann, Matthias

    2016-01-01

    We develop a model for predicting fine- and hyperfine intensities in the direct photoionization of molecules based on the separability of electron and nuclear spin states from vibrational-electronic states. Using spherical tensor algebra, we derive highly symmetrized forms of the squared photoionization dipole matrix elements from which which we derive the salient selection and propensity rules for fine- and hyperfine resolved photoionizing transitions. Our theoretical results are validated by the analysis of the fine-structure resolved photoelectron spectrum of O$_2$ (reported by H. Palm and F. Merkt, Phys. Rev. Lett. 81, 1385 (1998)) and are used for predicting hyperfine populations of molecular ions produced by photoionization.

  14. Absorption of some powder materials to YAG laser

    Institute of Scientific and Technical Information of China (English)

    SHAOT.M.; LINX.C.; ZHOUM.

    2001-01-01

    Laser powder alloying is widely used for tribological applications. As one of the key pa-rameters , absorptivity of powder materials to laser plays an important role in the processing. Themeasurement of laser absorptivity is essential for absorptivity research. In present work, lumpedmethod based on heat transfer is established for laser absorptivity measurement. The absorptivityof some powder materials as Cu, Fe, Al, NiO, Al2O3, ZrO2, SiC, to YAG laser, are investigated.The results show that the absorptivity of powder materials to YAG laser is generally larger thanthat of bulk materials.

  15. 40Cr钢激光表面加Ni60B合金化及其磨蚀性能研究%LASER SURFACE ALLOYING OF 40Cr STEEL WITH Ni60B POWDER AND ITS RESISTANCE TO WEAR AND CORROSION

    Institute of Scientific and Technical Information of China (English)

    李刚; 邱玲; 邱星武

    2009-01-01

    对40Cr钢进行了表面加Ni60B粉末激光合金化处理.金相、扫描电镜、X射线衍射分析,硬度测试和磨损与盐雾腐蚀实验的结果表明:合金化层的结构为熔化区、过渡区及热影响区;熔化区显微组织为胞状-树枝状晶,热影响区为极细的隐晶马氏体;激光合金化处理后的试样产生了新相Cr_(23)C_6和Cr_3C_2,显微硬度Hk可达到8.6 GPa,比基体提高了近3倍;耐磨性与耐蚀性都比基体有明显提高.%The 40Cr steel has been laser surface alloyed with Ni60B powder.The alloyed layer is then char-acterized by SEM observation,XRD analysis and microhardeness tester.While its resistance to wear and cor-rosion is also examined.The results show that the alloyed layer consisted of a melted zone,a transition zone and a heat affected zone.The microstructure of melted zone is cellular-dendtrite crystallites.the heat affect-ed zone extremely small hidden martensite.Phases Cr_(23)C_6 and Cr_3C_2 are observaed.the microhardness of the alloyed layer can reach up to Hv 8.6 Gpa,which iS three times higher than that of the substrate.The wear and corrosion resistance of the alloyed layer is higher than that of the substrate as wall.

  16. Role of zero-point vibrational corrections to carbon hyperfine coupling constants in organic π radicals

    Science.gov (United States)

    Chen, X.; Rinkevicius, Z.; Ruud, K.; Ågren, H.

    2013-02-01

    By analyzing a set of organic π radicals, we demonstrate that zero-point vibrational corrections give significant contributions to carbon hyperfine coupling constants, in one case even inducing a sign reversal for the coupling constant. We discuss the implications of these findings for the computational analysis of electron paramagnetic spectra based on hyperfine coupling constants evaluated at the equilibrium geometry of radicals. In particular, we note that a dynamical description that involves the nuclear motion is in many cases necessary in order to achieve a semi-quantitatively predictive theory for carbon hyperfine coupling constants. In addition, we discuss the implications of the strong dependence of the carbon hyperfine coupling constants on the zero-point vibrational corrections for the selection of exchange-correlation functionals in density functional theory studies of these constants.

  17. Breakdown of Atomic Hyperfine Coupling in a Deep Optical-Dipole Trap

    CERN Document Server

    Neuzner, Andreas; Dürr, Stephan; Rempe, Gerhard; Ritter, Stephan

    2015-01-01

    We experimentally study the breakdown of hyperfine coupling for an atom in a deep optical-dipole trap. One-color laser spectroscopy is performed at the resonance lines of a single $^{87}$Rb atom for a trap wavelength of 1064 nm. Evidence of hyperfine breakdown comes from three observations, namely a nonlinear dependence of the transition frequencies on the trap intensity, a splitting of lines which are degenerate for small intensities, and the ability to drive transitions which would be forbidden by selection rules in the absence of hyperfine breakdown. From the data, we infer the hyperfine interval of the $5P_{1/2}$ state and the scalar and tensor polarizabilities for the $5P_{3/2}$ state.

  18. Model for the hyperfine structure of electronically-excited ${\\rm KCs}$ molecules

    CERN Document Server

    Orbán, A; Krieglsteiner, O; Nägerl, H -C; Dulieu, O; Crubellier, A; Bouloufa-Maafa, N

    2015-01-01

    A model for determining the hyperfine structure of the excited electronic states of diatomic bialkali heteronuclear molecules is formulated from the atomic hyperfine interactions, and is applied to the case of bosonic $^{39}$KCs and fermionic $^{40}$KCs molecules. The hyperfine structure of the potential energy curves of the states correlated to the K($4s\\,^2S_{1/2}$)+Cs($6p\\,^2P_{1/2,3/2}$) dissociation limits is described in terms of different coupling schemes depending on the internuclear distance $R$. These results provide the first step in the calculation of the hyperfine structure of rovibrational levels of these excited molecular states in the perspective of the identification of efficient paths for creating ultracold ground-state KCs molecules.

  19. Preparation and microstructure of Al-Ni-Y powder by rapid solidification

    Institute of Scientific and Technical Information of China (English)

    黄劲松; 刘咏; 陈仕奇; 刘祖铭

    2004-01-01

    The Al-Ni Y alloy powder was prepared by rapid solidification technology of inert gas atomization. The diameter of amorphous powder is less than 12 μm. The effects of atomization gas on cooling velocity, morphology,microstructure and microhardness of powder and fine powder ratio were investigated. The results show that the mor-phology, microstructure and microhardness of powder and fine powder ratio are affected by cooling velocity changed through atomization gas. The cooling velocity of inert gas atomization is more than 1 × 104 K/s. The larger the cool-ing velocity, the finer the powder, and the smoother the surface of powder; the smaller the diameter of powder, the larger the microhardness of powder.

  20. Mechanically Alloyed High Entropy Composite

    Science.gov (United States)

    Popescu, G.; Adrian, M. M.; Csaki, I.; Popescu, C. A.; Mitrică, D.; Vasile, S.; Carcea, I.

    2016-08-01

    In the last years high entropy alloys have been investigated due to their high hardness, high temperature stability and unusual properties that make these alloys to have significant interest. In comparison with traditional alloys that are based on two or three major elements, this new generation alloys consists at least of 5 principal elements, with the concentration between 5 and 35 at.%. The present paper reports synthesis of high entropy alloys (HEA) and high entropy composites (HEC) synthesized by mechanical alloying (MA). The equiatomic AlCrFeNiMn matrix was used for creating the HEA matrix, starting from elemental powders and as reinforcing material for composites was used pure graphite. The mechanical alloying process was carried out at different duration, in a high energy planetary ball mill, under argon atmosphere. The elemental powders alloying began after '5 hours of milling and was complete after 40 hours. The mechanical alloyed matrix and composite was pressed and heat treated under argon protection. The elemental powers were investigated for physical - technological properties, and by X-ray diffraction and scanning electron microscopy. Phase pressing operation was realized with a hydraulic press and the applied pressure was progressive. The sintering process was carried out at 850°C for 2 h. The X-ray diffraction revealed that the MA process resulted in solid solutions formation and also revealed body- centred cubic (BCC) and face-centred cubic (FCC) structures with average grain size around 40 nm. In addition, nanoscale particles were highlighted by scanning electron microscopy, as well as the homogeneity of the chemical composition of the matrix and composite that was confirmed by EDX microanalysis. It was noted that HEA matrix and HEA composites were processed with a high degree of compaction and with a quite large capacity of mixed powder densification (around 70%).

  1. Microstructural characterization of oxide dispersion strengthened (ODS) Fe-12Cr-0.5Y2O3 alloy

    Science.gov (United States)

    Shamsudin, Farha Mizana; Radiman, Shahidan; Abdullah, Yusof; Hamid, Nasri A.

    2016-11-01

    Oxide dispersion strengthened (ODS) ferritic alloy containing 12wt% Cr and 0.5wt% Y2O3 was prepared by mechanical alloying (MA) method and then compacted into bulk shape. Field emission scanning electron microscopy (FESEM) was performed to characterize the microstructure of milled alloy powder. The fragments and nanoclusters of Y2O3 were observed in this alloy powder. FESEM-EDS mapping on the milled alloy powder reveal the uniformity of the element distribution achieved by the alloy. The Y element is finely dispersed into the alloy matrix and the O element is observed indicating the presence of oxides throughout the alloy sample. The compacted alloy was then heat treated at 1050°C and analyzed by field emission scanning electron microscope (FESEM). The formations of nano-scale Y2O3 were observed after the heat treatment process of alloy indicating the dispersion and incorporation of Y2O3 nanoparticles into the alloy matrix.

  2. PREPARATION AND MAGNETIC-PROPERTIES OF AMORPHOUS FE1-XBX (15-LESS-THAN-OR-EQUAL-TO X LESS-THAN-40 ATMOSPHERIC PERCENT) ALLOY PARTICLES

    DEFF Research Database (Denmark)

    Linderoth, Søren; Mørup, S.

    1992-01-01

    Amorphous Fe1-xBx alloy particles have been prepared in aqueous solutions by reduction of Fe2+ ions to the metallic state by the use of NaBH4. It is demonstrated, that by changing the pH of the aqueous metal ion solution the amount of boron incorporated in the alloy particles can be varied between...... 15 and 28 at.%. Fe-57 Mossbauer spectra have been obtained at 10, 80 and 295 K. The hyperfine parameters for amorphous particles have been found to be similar to those found for ribbons and films prepared by the liquid-quench and sputtering techniques, respectively, though with a tendency...... for the magnetic hyperfine fields for the chemically prepared and sputter prepared alloys to deviate slightly from those for melt-spun samples. The magnetic hyperfine fields decrease linearly as a function of T3/2....

  3. Hyperfine interaction versus strong laser field-optical Back-Goudsmit (Paschen-Back) effect

    Science.gov (United States)

    Gawlik, Wojciech

    1991-08-01

    Strong laser perturbation of an atom with fine or hyperfine structure is analyzed in the context of a level-crossing experiment. The effect of sufficiently powerful, detuned, and/or spectrally broad light is to produce ``hyperfine uncoupling,'' which can be regarded as the optical Back-Goudsmit effect. It is easily understood in terms of an analogy between the level-crossing effect and double-slit experiment.

  4. Towards a test of QED in investigations of the hyperfine splitting in heavy ions.

    Science.gov (United States)

    Shabaev, V M; Artemyev, A N; Yerokhin, V A; Zherebtsov, O M; Soff, G

    2001-04-30

    A possibility for investigations of quantum electrodynamics (QED) in experiments on the hyperfine splitting in heavy ions is examined. It is found that QED effects can be probed on the level of a few percent in a specific difference of the hyperfine splitting values in hydrogenlike and lithiumlike bismuth. This could provide a test of QED in the strongest electric field available at present for experimental study.

  5. Hyperfine Magnetic Anomaly in the Atomic Spectra of the Rare-Earth Elements

    CERN Document Server

    Gangrsky, Yu P; Karaivanov, D V; Kolesnikov, N N; Marinova, K P; Markov, B N; Rostovsky, V S

    2001-01-01

    The constants of the hyperfine splitting in the atomic optical spectra of the rare-earth elements - Nd, Eu, Gd and Lu - were measured. The method of laser resonance fluorescence in the parallel atomic beam was used. The values of the hyperfine magnetic anomaly were determined from the comparison of magnetic dipole constant ratios of the neighbouring odd Z or N isotopes for the different atomic levels. The connection of these values and the parameters of atomic and nuclear structure is discussed.

  6. Hole spin dephasing time associated to hyperfine interaction in quantum dots

    OpenAIRE

    Testelin, C.; Bernardot, F.; Eble, B.; Chamarro, M.

    2009-01-01

    The spin interaction of a hole confined in a quantum dot with the surrounding nuclei is described in terms of an effective magnetic field. We show that, in contrast to the Fermi contact hyperfine interaction for conduction electrons, the dipole-dipole hyperfine interaction is anisotropic for a hole, for both pure or mixed hole states. We evaluate the coupling constants of the hole-nuclear interaction and demonstrate that they are only one order of magnitude smaller than the coupling constants...

  7. Sinterability and microstructure evolution during sintering of ferrous powder mixtures

    Directory of Open Access Journals (Sweden)

    Kétner Bendo Demétrio

    2013-01-01

    Full Text Available The present work is focused on ferrous powder metallurgy and presents some results of a development of a suitable masteralloy for use as an additive to iron powder for the production of sintered steels. The masteralloy was produced by melting a powder mixture containing approximately Fe + 20% Ni + 20% Mn + 20% Si + 1% C (wt%, in order to obtain a cast billet that was converted into fine powder by crushing and milling. It was observed presence of SiC in the masteralloy after melting that is undesirable in the alloy. Si element should be introduced by using ferrosilicon. Sintered alloys with distinct contents of alloying elements were prepared by mixing the masteralloy powder to plain iron powder. Samples were produced by die compaction of the powder mixtures and sintering at 1200 °C in a differential dilatometer in order to record their linear dimensional behaviour during heating up and isothermal sintering, aiming at studying the sinterability of the compacts. Microstructure development during sintering was studied by SEM, XRD and microprobe analyses.

  8. Synthesis and consolidation of γ-Ni-Fe nanoalloy powder

    Science.gov (United States)

    Lee, J. S.; Nam, J. G.; Knorr, P.

    1999-04-01

    The present work studies the synthesis and consolidation of γ-Ni-Fe nanoalloy powder by the mechano-chemical process comprising high-energy ball-milling of NiO-Fe2O3 powder and a subsequent hydrogen reduction process. To examine the formation mechanism of the nanoalloy powder, the effect of the oxide powder char-acteristics on the reduction process and alloying was investigated by varying the ball-milling time. The reduction process and the alloying of the γ-Ni-Fe phase proved to accelerate as the ball-milling time increased. However, prolonged milling (for 30 hours) retarded the reduction of Fe2O3 as well as the alloying process. The densification process of the Ni-Fe nanoalloy powder strongly depended on the degree of agglomeration which results in enhancing homogeneous sintering. The limited densification of the nanoalloy powder originates from the high degree of particle agglomeration. While intra-agglomerate porosity is easily eliminated in the course of sintering, it is found to resist densification. The limitation of the sintered density could be overcome by increasing the green density of the powder compacts. Full density was achieved by starting with a green density of 72% theoretical density.

  9. Fluxless Joining between Aluminium Alloy and Galvanized Steel by Fiber Laser Fusion Welding-Brazing with Filler Powder%铝/钢异种金属无钎剂激光填粉熔钎焊接

    Institute of Scientific and Technical Information of China (English)

    赵旭东; 肖荣诗

    2012-01-01

    The fluxless fusion welding-brazing result between 6061 aluminum alloy and galvanized steel with filler material is studied by using rectangular laser beam. The dependence of the mechanical properties on solidification behavior is established based on the joint formation and the weld microstructure. The results indicate that a fusion welding-brazing weld of AA6061 and galvanized steel without flux can be achieved using the welding with filler powder. By optimizing the welding parameters, the favorable weld without crack and porosity can be achieved. The weld width and the thickness of intermetallic compounds layer increase with laser energy input increasing. The intermetallic in the weld is composed of Al-Fe and Al-Fe-Si system phases. Specimens are fractured at the weld/steel interface with the brittle characteristic during tensile test. The weakness of the joint is the weld interface. The maximum intensity of 152. 5 N/mm is obtained. Al6Fe2Zn0.4 and α-Al are found in the fracture surface on the aluminum side. The intensity of joint is both determined by weld width and the thickness of intermetallic compound layer.%采用宽带激光光斑和填粉焊接技术,在不使用钎剂的情况下进行6061铝合金/镀锌钢板的熔钎焊接实验.分析测试了接头成形、焊缝组织和接头强度,并探讨了影响接头强度的因素.结果表明,采用此方法可实现6061铝合金/镀锌钢板的熔钎焊连接.选用优化的焊接工艺参数获得了成形饱满,无裂纹、气孔等缺陷的焊缝.焊缝熔宽和金属间化合物层厚度随焊接热输入量的增加而增大.熔钎焊缝中金属间化合物由AFFe和Al-Fe-Si系统化合物组成.拉伸试样均断裂在钎料/镀锌钢界面,接头最大机械抗力为152.5 N/mm,断口呈脆性断裂特征,钎料/镀锌钢界面为接头的薄弱环节.拉伸试样铝一侧断裂面由Al5 Fe2 Zno.4和α-Al组成.焊缝熔宽、金属间化合物层厚度共同决定了接头的机械抗力水平.

  10. New Precision Measurement of Hyperfine Splitting of Positronium

    CERN Document Server

    Ishida, A; Asai, S; Kobayashi, T; Saito, H; Yoshida, M; Tanaka, K; Yamamoto, A

    2014-01-01

    The ground state hyperfine splitting of positronium $\\Delta_{\\mathrm{HFS}}$ is sensitive to high order corrections of quantum electrodynamics (QED) in bound state. The theoretical prediction and the averaged experimental value for $\\Delta_{\\mathrm{HFS}}$ has a discrepancy of 15 ppm, which is equivalent to 3.9 standard deviations (s.d.). A new precision measurement which reduces the systematic uncertainty from the positronium thermalization effect was performed, in which the non-thermalization effect was measured to be as large as $10 \\pm 1\\,{\\mathrm{ppm}}$ in a timing window we used. When this effect is taken into account, our new result becomes $\\Delta_{\\mathrm{HFS}} = 203.394\\,1 \\pm 0.001\\,6 ({\\mathrm{stat., 8.0\\,ppm}}) \\pm 0.001\\,1 ({\\mathrm{sys., 5.4\\,ppm}})$\\,GHz, which favors the QED prediction within 1.2 s.d. and disfavors the previous experimental average by 2.7 s.d.

  11. Spin-dependent recombination and hyperfine interaction at deep defects

    Science.gov (United States)

    Ivchenko, E. L.; Bakaleinikov, L. A.; Kalevich, V. K.

    2015-05-01

    We present a theoretical study of optical electron-spin orientation and spin-dependent Shockley-Read-Hall recombination in the longitudinal magnetic field, taking into account the hyperfine coupling between the bound-electron spin and the nuclear spin of a deep paramagnetic center. The master rate equations for the coupled system are extended to describe the nuclear spin relaxation by using two distinct relaxation times, τn 1 and τn 2, respectively, for defect states with one and two (singlet) bound electrons. The general theory is developed for an arbitrary value of the nuclear spin I . The magnetic-field and excitation-power dependencies of the electron and nuclear spin polarizations are calculated for the value of I =1 /2 . In this particular case the nuclear effects can be taken into account by a simple replacement of the bound-electron spin relaxation time by an effective time dependent on free-electron and hole densities and free-electron spin polarization. The role of nuclear spin relaxation is visualized by isolines of the electron spin polarization on a two-dimensional graph with the axes log2(τn 1) and log2(τn 2) .

  12. Hyperfine coupling constants from internally contracted multireference perturbation theory

    CERN Document Server

    Shiozaki, Toru

    2016-01-01

    We present an accurate method for calculating hyperfine coupling constants (HFCCs) based on the complete active space second-order perturbation theory (CASPT2) with full internal contraction. The HFCCs are computed as a first-order property using the relaxed CASPT2 spin-density matrix that takes into account orbital and configurational relaxation due to dynamical electron correlation. The first-order unrelaxed spin-density matrix is calculated from one- and two-body spin-free counterparts that are readily available in the CASPT2 nuclear gradient program [M. K. MacLeod and T. Shiozaki, J. Chem. Phys. 142, 051103 (2015)], whereas the second-order part is computed directly using the newly extended automatic code generator. The relaxation contribution is then calculated from the so-called Z-vectors that are available in the CASPT2 nuclear gradient program. Numerical results are presented for the CN and AlO radicals, for which the CASPT2 values are comparable (or, even superior in some cases) to the ones computed ...

  13. Density functional theory predictions of isotropic hyperfine coupling constants.

    Science.gov (United States)

    Hermosilla, L; Calle, P; García de la Vega, J M; Sieiro, C

    2005-02-17

    The reliability of density functional theory (DFT) in the determination of the isotropic hyperfine coupling constants (hfccs) of the ground electronic states of organic and inorganic radicals is examined. Predictions using several DFT methods and 6-31G, TZVP, EPR-III and cc-pVQZ basis sets are made and compared to experimental values. The set of 75 radicals here studied was selected using a wide range of criteria. The systems studied are neutral, cationic, anionic; doublet, triplet, quartet; localized, and conjugated radicals, containing 1H, 9Be, 11B, 13C, 14N, 17O, 19F, 23Na, 25Mg, 27Al, 29Si, 31P, 33S, and 35Cl nuclei. The considered radicals provide 241 theoretical hfcc values, which are compared with 174 available experimental ones. The geometries of the studied systems are obtained by theoretical optimization using the same functional and basis set with which the hfccs were calculated. Regression analysis is used as a basic and appropriate methodology for this kind of comparative study. From this analysis, we conclude that DFT predictions of the hfccs are reliable for B3LYP/TZVP and B3LYP/EPR-III combinations. Both functional/basis set scheme are the more useful theoretical tools for predicting hfccs if compared to other much more expensive methods.

  14. Hyperfine Coupling Constants from Internally Contracted Multireference Perturbation Theory.

    Science.gov (United States)

    Shiozaki, Toru; Yanai, Takeshi

    2016-09-13

    We present an accurate method for calculating hyperfine coupling constants (HFCCs) based on the complete active space second-order perturbation theory (CASPT2) with full internal contraction. The HFCCs are computed as a first-order property using the relaxed CASPT2 spin-density matrix that takes into account orbital and configurational relaxation due to dynamical electron correlation. The first-order unrelaxed spin-density matrix is calculated from one- and two-body spin-free counterparts that are readily available in the CASPT2 nuclear gradient program [M. K. MacLeod and T. Shiozaki, J. Chem. Phys. 142, 051103 (2015)], whereas the second-order part is computed directly using the newly extended automatic code generator. The relaxation contribution is then calculated from the so-called Z-vectors that are available in the CASPT2 nuclear gradient program. Numerical results are presented for the CN and AlO radicals, for which the CASPT2 values are comparable (or, even superior in some cases) to the ones computed by the coupled-cluster and density matrix renormalization group methods. The HFCCs for the hexaaqua complexes with V(II), Cr(III), and Mn(II) are also presented to demonstrate the accuracy and efficiency of our code.

  15. New Precise Measurement of the Hyperfine Splitting of Positronium

    Energy Technology Data Exchange (ETDEWEB)

    Ishida, A., E-mail: ishida@icepp.s.u-tokyo.ac.jp [Department of Physics, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan)

    2015-09-15

    Positronium (Ps) is an ideal system for precision test of bound state quantum electrodynamics. The hyperfine splitting (HFS) of the ground state of Ps, which is one of the most precisely tested quantity, has a large discrepancy of 16 ppm (4.5 σ) between previous experiments and theoretical calculation up to O(α{sup 3}lnα{sup −1}) and part of O(α{sup 3}) corrections. A new experiment which reduces possible systematic uncertainties of Ps thermalization effect and nonuniformity of magnetic field was performed. It revealed that the Ps thermalization effect was as large as 10 ± 2 ppm. Treating the thermalization effect correctly, a new result of 203.3942 ± 0.0016(stat., 8.0 ppm) ± 0.0013(sys., 6.4 ppm) GHz was obtained. This result is consistent with theory within 1.1 σ, whereas it disfavors the previous experimental result by 2.6 σ. It shows that the Ps thermalization effect is crucial for precision measurement of HFS. Future prospects for improved precision are briefly discussed.

  16. Powder metallurgy bearings for advanced rocket engines

    Science.gov (United States)

    Fleck, J. N.; Killman, B. J.; Munson, H.E.

    1985-01-01

    Traditional ingot metallurgy was pushed to the limit for many demanding applications including antifriction bearings. New systems require corrosion resistance, better fatigue resistance, and higher toughness. With conventional processing, increasing the alloying level to achieve corrosion resistance results in a decrease in other properties such as toughness. Advanced powder metallurgy affords a viable solution to this problem. During powder manufacture, the individual particle solidifies very rapidly; as a consequence, the primary carbides are very small and uniformly distributed. When properly consolidated, this uniform structure is preserved while generating a fully dense product. Element tests including rolling contact fatigue, hot hardness, wear, fracture toughness, and corrosion resistance are underway on eleven candidate P/M bearing alloys and results are compared with those for wrought 440C steel, the current SSME bearing material. Several materials which offer the promise of a significant improvement in performance were identified.

  17. Moessbauer and XRD study of the Fe{sub 65}Si{sub 35} alloy obtained by mechanical alloying

    Energy Technology Data Exchange (ETDEWEB)

    Velez, G. Y., E-mail: giovelez29@gmail.com [Universidad del Valle, Departamento de Fisica (Colombia); Rodriguez, R. R. [Corporacion Universidad Autonoma de Occidente (Colombia); Melo, C. A.; Perez Alcazar, G. A.; Zamora, Ligia E.; Tabares, J. A. [Universidad del Valle, Departamento de Fisica (Colombia)

    2011-11-15

    A study was made on the alloy Fe{sub 65}Si{sub 35} using x-ray diffraction and Moessbauer spectrometry. The alloy was obtained by mechanical alloying in a high energy planetary mill, with milling times of 15, 30, 50, 75 and 100 h. The results show that in the alloys two structural phases are present, a Fe-Si BCC disordered phase and ferromagnetic, and a Fe-Si SC phase, whose nature is paramagnetic and which decreases with milling time. In the temporal evolution of the milling two stages are differentiated: one between 15 and 75 h of milling, in which silicon atoms diffuse into the bcc matrix of iron and its effect is to reduce the hyperfine magnetic field; the other, after 75 h of milling, where the alloy is consolidated, the effect of the milling is only to increase the disorder of the system, increasing the magnetic order.

  18. Powder-Metallurgical Bearings For Turbopumps

    Science.gov (United States)

    Bhat, B. N.; Humphries, T. S.; Thom, R. L.; Moxson, V.; Friedman, G. I.; Dolan, F. J.; Shipley, R. J.

    1993-01-01

    Bearings fabricated by powder metallurgy developed for use in machines subjected to extremes of temperature, rolling-contact cyclic stresses, and oxidizing or otherwise corrosive fluids. Bearings also extend operating lives of other machines in which bearings required to resist extreme thermal, mechanical, and chemical stresses. One alloy exhibiting outstanding properties was MRC-2001. Resistance to fatigue, stress corrosion cracking, and wear found superior to that of 440C stainless steel.

  19. Hyperfine Interactions, Magnetic Impurities and Ordering in Praseodymium

    DEFF Research Database (Denmark)

    Bjerrum Møller, Hans; Jensen, J. Z.; Wulff, M.;

    1982-01-01

    The antiferromagnetic ordering in Pr due to the coupling of the 4f electronic system to the nuclei and to magnetic Nd impurities has been studied by neutron diffraction. A pure monocrystal of Pr develops true long-range order at about 50-60 mK. The ordering in both this crystal and a PrNd alloy i...

  20. Cerium extraction by metallothermic reduction using cerium oxide powder injection

    Institute of Scientific and Technical Information of China (English)

    J.S. Luna A; A. Flores V; R. Mu(n)iz V; A.F. Fuentes; J. Torres; N. Rodríuez R; J.C. Ortiz; P.Orozco

    2011-01-01

    This work presented the feasibility of cerium recovery by Al-Mg alloy through the metallothermic reduction of CeO2 to obtain a master alloy Al-4%Ce. The master alloy obtained in this investigation was for the grain refinement and modification of Al-Si alloys. The reagent was incorporated into a molten alloy using the submerged powder injection technique, and metallic samples were obtained during injection. Chemical and microstructural analyses (by inductively coupled plasma (ICP) and scanning electron microscopy (SEM), respectively) confirmed the possibility of Ce uptake in the bath (0 to 4 wt.%), as CeO2 was reduced through metallothermic reactions in the molten alloys.Based on the characterization of reaction products, the sequence of the reaction was proposed.

  1. Method for forming biaxially textured articles by powder metallurgy

    Science.gov (United States)

    Goyal, Amit; Williams, Robert K.; Kroeger, Donald M.

    2002-01-01

    A method of preparing a biaxially textured alloy article comprises the steps of preparing a mixture comprising Ni powder and at least one powder selected from the group consisting of Cr, W, V, Mo, Cu, Al, Ce, YSZ, Y, Rare Earths, (RE), MgO, CeO.sub.2, and Y.sub.2 O.sub.3 ; compacting the mixture, followed by heat treating and rapidly recrystallizing to produce a biaxial texture on the article. In some embodiments the alloy article further comprises electromagnetic or electro-optical devices and possesses superconducting properties.

  2. Comparative study between melted and mechanically alloyed samples of the Fe{sub 50}Mn{sub 10}Al{sub 40} nanostructured system

    Energy Technology Data Exchange (ETDEWEB)

    Gonzalez, C. [Universidad Pontificia Bolivariana, Departamento de Ciencias Basicas (Colombia); Perez Alcazar, G. A., E-mail: gperezalcazar@yahoo.com; Zamora, L. E. [Universidad del Valle, Departamento de Fisica (Colombia); Greneche, J. M. [Universite du Maine, Laboratoire de Physique de l' Etat Condense, UMR CNRS 6087 (France); Romero, J. J.; Martin-Blanco, E. [Universidad Complutense de Madrid, Instituto de Magnetismo Aplicado (Spain); Gonzalez, J. M. [Unidad Asociada ICMM-IMA (Spain); Marco, J. F. [Instituto de Quimica Fisica Rocasolano, CSIC (Spain)

    2008-06-15

    Nanostructured powders of melted and 48 h-mechanically alloyed (MA) samples of the Fe{sub 50}Mn{sub 10}Al{sub 40} system were studied by XRD, SEM and Moessbauer spectroscopy (MS), and their properties were compared. The samples present BCC structure with similar mean lattice parameter (near 2.92 A) and grain size (around 22 nm). The MA sample presents additionally the {alpha}-Fe phase. Moessbauer spectra of the samples present a hyperfine field distribution (HFD), a broad paramagnetic (P) site and a sextet showing that the BCC ternary phase is disordered with Fe sites in environments rich in Fe (HFD) and rich in Al and Mn (P), respectively. The mean hyperfine magnetic field vs. temperature curve of melted sample presents two kinks, one at 28 K and other at 210 K and a Curie temperature at 340 K. A similar curve is observed for the milled sample but the kinks occur at 65 and 265K. Moessbauer spectra at different temperatures with and without applied field permit to conclude that the low temperature anomaly corresponds to the freezing temperature of a re-entrant spin-glass phase (RSG) and that of the second one corresponds to a blocking temperature of a superparamagnetic (SP) phase. These phases are possible in the samples due to their disordered character induced by the preparation conditions and the competitive interactions of the Fe and Mn atoms. The enhancement of the magnetic behaviour of the MA sample is due its larger disorder induced by the preparation method that can also explain the increase of the RSG and SP transition temperatures.

  3. Progress in Titanium Metal Powder Injection Molding

    Directory of Open Access Journals (Sweden)

    Randall M. German

    2013-08-01

    Full Text Available Metal powder injection molding is a shaping technology that has achieved solid scientific underpinnings. It is from this science base that recent progress has occurred in titanium powder injection molding. Much of the progress awaited development of the required particles with specific characteristics of particle size, particle shape, and purity. The production of titanium components by injection molding is stabilized by a good understanding of how each process variable impacts density and impurity level. As summarized here, recent research has isolated the four critical success factors in titanium metal powder injection molding (Ti-MIM that must be simultaneously satisfied—density, purity, alloying, and microstructure. The critical role of density and impurities, and the inability to remove impurities with sintering, compels attention to starting Ti-MIM with high quality alloy powders. This article addresses the four critical success factors to rationalize Ti-MIM processing conditions to the requirements for demanding applications in aerospace and medical fields. Based on extensive research, a baseline process is identified and reported here with attention to linking mechanical properties to the four critical success factors.

  4. Properties of duplex stainless steels made by powder metallurgy

    OpenAIRE

    Rosso, M.; M. Actis Grande; Z. Brytan; L.A. Dobrzański

    2007-01-01

    Purpose: of this paper was to examine the mechanical properties of duplex stainless steels.Design/methodology/approach: In presented study duplex stainless steels were obtained through powder metallurgy starting from austenitic, martensitic base powders by controlled addition of alloying elements, such as Cr, Ni, Mo and Cu. In the studies behind the preparation of mixes, Schaeffler’s diagram was taken into consideration. Prepared mixes have been sintered in a vacuu...

  5. Mossbauer analysis of the atomic and magnetic structure of alloys

    CERN Document Server

    Ovchinnikov, VV

    2007-01-01

    The monograph indicates the key problems that have to be solved for the further development of the Mössbauer methods for analysis of the nuclear and magnetic structure of alloys, and offer solution variants for some of these problems based on the generalised results of a wide range of theoretical and experimental investigations,including original work by the author of the book and his colleagues. Contents 1. Description of the nature of the Mössbauer effect 2. Interpretation of the ossbauer spectra of alloys 3.Electrical and magnetics hyperfine interactions of resonant nuclei in metals and

  6. Formación de la Aleación Zn-21.6%Al-2.0%Cu por Pulvimetalurgia: Efecto del Lubricante en las Briquetas Formation of Zn-21.6%Al-2.0%Cu Alloy by Powder Metallurgy: Effect of the Lubricant in Briquettes

    Directory of Open Access Journals (Sweden)

    José A Aragón

    2008-01-01

    Full Text Available En este trabajo se presenta la elaboración de la aleación Zn-21.6%Al-2.0%Cu (porcentajes en masa, por un método de metalurgia de polvos y se analiza el efecto de distintos lubricantes, usados en las briquetas. Se elaboraron mezclas de polvos de Zn, Al y Cu con acetona, cera y ácido esteárico como lubricantes, y se compactaron uniaxialmente a una presión de 77.4 MPa. Las briquetas se sinterizaron bajo un flujo de argón y en intervalos de 15 minutos a 357 °C. Los materiales fueron caracterizados estructuralmente con microscopio óptico, ensayos de microdureza Vickers, dureza Rockwell F y difracción de rayos X. El ácido esteárico y la cera funcionan similarmente como lubricantes y la acetona retarda la formación de la aleación, pero causa mayores durezas, luego del sinterizado. La aleación se forma totalmente cuando el lubricante es cera y se sinteriza más de 45 minutos. La rapidez de formación de la aleación depende del tipo de lubricante en las briquetas.In this work the elaboration of Zn-21.6%Al-2.0%Cu alloy (mass percentages, prepared by a method of powder metallurgy and the effect of different lubricants used in the briquettes were studied. Mixtures of powders of Zn, Al and Cu with acetone, wax and stearic acid as lubricants were prepared and compacted up to a pressure of 77.4 Mpa. The briquettes were sintered under argon flux and at intervals of 15 and 45 minutes at 357° C. The materials were structurally characterized by optical microscopy, micro-hardness Vickers, hardness Rockwell F tests and X-rays diffraction. The stearic acid and wax work similar to lubricants and acetone slows down the formation of the alloy, but it causes greater hardnesses after sintering. The alloy is completely formed when the lubricant is wax and the sintering time is more than 45 minutes. The velocity of formation of the alloy depends on the type of lubricant in the briquettes.

  7. Foaming behaviour of Al-Si-Cu-Mg alloys

    Energy Technology Data Exchange (ETDEWEB)

    Kim, A. [Kongju National University (Korea). Dept. of Mechanical Engineering; Cho, S.S. [Chungnam National University, Daejeon (Korea). School of Materials Engineering; Lee, H.J. [Hanbat National University, Daejeon (Korea). Dept. of Building Service Engineering

    2004-12-15

    The powder metallurgical route was utilised to obtain the Al-5Si-4Cu-4Mg (alloy 544) and Al-3Si-2Cu-2Mg (alloy 322) foams. Various steps such as centrifugal atomisation, mixing alloy powder and foaming agent (1 wt-%TiH{sub 2}), cold compaction of mixture, hot extrusion and foaming in a preheated furnace were performed. Foaming behaviour of the alloys was investigated by digital microscopy, image analysis, scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) mapping in this study. It was found that alloy 544 takes a shorter period of time to initiate pore nucleation than alloy 322. Alloy 544 had a higher pore growth rate than alloy 322 at the same pre-set furnace temperature. In both alloys, crack-like pore nucleation occurred between aluminium alloy powders elongated in a direction parallel to the extrusion direction. Both alloys showed the same foaming sequence of crack-like pore nucleation, spherical pore growth, coalescence of neighbouring pores and collapse of pores adjacent to the free surface of specimen. The time required to start pore nucleation decreased with the increase of foaming temperature. The cell walls of both alloys consisted of {alpha}-Al phase and eutectic phase. (author)

  8. Effect of composition of FeCoCu pre-alloyed powders on sintering characters used for diamond tools%金刚石工具用FeCoCu预合金粉组成对烧结特性的影响

    Institute of Scientific and Technical Information of China (English)

    谢德龙; 陈超; 肖乐银; 万隆; 宋冬冬; 王帅; 林峰; 吕智; 方啸虎; 潘晓毅; 秦海青

    2016-01-01

    The FeCoCu pre-alloyed powders were manufactured by co-precipitation method. The microstructure was characterized, the sintering experiments were carried out, the mechanical properties and wear loss were tested and the combination condition between diamond and the powders was analyzed. The results show that the mesophases, such as Co3Fe7, CoFe15.7 and FeCu4, are formulated in the three powders, and all the powders have irregular shapes, interconnected fine particles and large surface areas. Although the solid solutions are formed, the sintering, mechanical properties and mass loss of the three powders are based on the Fe-Cu ratios. With Fe content increasing, the ideal sintering temperatures, hardness and three point bend strength raise. The relative density decreases, the wear loss becomes better. Fe-Cu ratio has important influence on the powders microstructure. The mechanical retention is the main strength in the matrix and graphitization has occurred in the diamond surface after sintering with the FeCoCu pre-alloyed powders.%通过共沉淀法制备不同Fe-Cu配比的FeCoCu预合金粉,并对其微观结构进行表征与分析。同时,对3种粉体进行不同温度下的烧结实验和对烧结试样块进行力学性能及磨损质量损失进行测试,并对预合金粉与金刚石的界面结合情况进行探讨。结果表明:预合金粉中形成了Co3Fe7、CoFe15.7、FeCu4等中间相,在一定程度上实现合金化。3种预合金粉末的形状均为不规则状,粉末颗粒较细,且相互连接,表面疏松,有利于烧结。3种预合金粉中单质相仍占有较大比例,单质配比对烧结体性能有重要影响。Fe含量增加时,试样的理想烧结温度及烧结体力学性能均升高。Fe-Cu配比会对微观结构产生重要影响,胎体对金刚石以机械包镶为主,结合XRD及Raman光谱可知,与预合金粉烧结后的金刚石表面发生石墨化。

  9. Micro-Structures of Hard Coatings Deposited on Titanium Alloys by Laser Alloying Technique

    Science.gov (United States)

    Li, Wei; Yu, Huijun; Chen, Chuanzhong; Wang, Diangang; Weng, Fei

    2013-01-01

    This work is based on micro-structural performance of the Ti-B4C-C laser alloying coatings on Ti-6Al-4V titanium alloy. The test results indicated that laser alloying of the Ti-B4C-C pre-placed powders on the Ti-6Al-4V alloy substrate can form the ceramics reinforced hard alloying coatings, which increased the micro-hardness and wear resistance of substrate. The test result also indicated that the TiB phase was produced in alloying coating, which corresponded to its (101) crystal plane. In addition, yttria has a refining effect on micro-structures of the laser alloying coating, and its refinement mechanism was analyzed. This research provided essential experimental and theoretical basis to promote the applications of the laser alloying technique in manufacturing and repairing of the aerospace parts.

  10. Mossbauer studies of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy

    DEFF Research Database (Denmark)

    Jiang, Jianzhong

    1996-01-01

    This paper reports a Mossbauer study of amorphous Fe73.5Cu1Nb3Si13.5B9 alloy between 10 and 673 K. The Curie temperature Tc is found to be 620-+ 1 K. The temperature dependence of the reduced average hyperfine field can be explained on the basis of Handrich's model of amorphous ferromagnetism...

  11. Magnetic Properties of Amorphous Fe-Si-B Powder Cores Mixed with Pure Iron Powder

    Science.gov (United States)

    Kim, Hyeon-Jun; Nam, Seul Ki; Kim, Kyu-Sung; Yoon, Sung Chun; Sohn, Keun-Yong; Kim, Mi-Rae; Sul Song, Yong; Park, Won-Wook

    2012-10-01

    Amorphous Fe-Si-B alloy was prepared by melt-spinning, and then the ribbons were pulverized and ball-milled to make the amorphous powder of ˜25 µm in size. Subsequently those were mixed with pure iron powders with an average particle size of 3 µm, and 1.5 wt % water glass diluted by distilled water at the ratio of 1:2. The powder mixtures were cold compacted at 650 MPa in toroid die, and heat treated at 430-440 °C under a nitrogen atmosphere for 1 h and 30 min, respectively. The soft magnetic properties of powder core were investigated using a B-H analyzer and a flux meter at the frequency range of ˜100 kHz. The microstructure was observed using scanning electron microscope (SEM), and the density of the core was measured using the principle of Archimedes. Based on the experimental results, the amorphous powder mixed with pure iron powder showed the improved powder compactability, which resulted in the increased permeability and the reduced core loss.

  12. Influence of the control atmosphere and milling time on the morphology and microstructure of pure copper and copper-2.5 % lithium powders produced by mechanical alloying; Influencia de la atmosfera de control y tiempo de molienda sobre la morfologia y microestructura de polvos de cobre puro y cobre-2,5% litio producidos por aleado mecanio

    Energy Technology Data Exchange (ETDEWEB)

    Rojas, P. A.; Alvarez, M. P.; Penaloza, A.; Zuniga, A.; Ordonez, S.

    2009-07-01

    In the present work was investigated the effect of two milling parameters, atmosphere and milling time, on the morphology and microstructure of pure copper powder and a mixture of copper-2,5 wt. % lithium. The mechanical alloying was performed in a SPEX 8000D mill, using steel containers and balls. The two control atmospheres were argon and nitrogen and the milling time was varied from 3 up to 30 hours. The microstructural changes and the phases after milling were analyzed using scanning microscopy and X ray diffraction, whereas the amount of iron was measured by atomic absorption spectroscopy and the amount of oxygen by infrared spectroscopy. The results show the effect of the milling parameters studied on the microstructure as well as on the chemical composition of the samples. (Author) 22 refs.

  13. Modification of the titanium alloy surface in electroexplosive alloying with boron carbide and subsequent electron-beam treatment

    Science.gov (United States)

    Gromov, Victor E.; Budovskikh, Evgeniy A.; Ivanov, Yurii F.; Bashchenko, Lyudmila P.; Wang, Xinli; Kobzareva, Tatyana Yu.; Semin, Alexander P.

    2015-10-01

    The modification of the VT6 titanium alloy surface in electroexplosion alloying with plasma being formed in titanium foil with a weighed powder of boron carbide with subsequent irradiation by a pulsed electron beam has been carried out. An electroexplosive alloying zone of a thickness up to 50 μm with a gradient structure is found to form. The subsequent electron-beam treatment of the alloying zone results in smoothing of the alloying surface and is accompanied by the formation of the multilayer structure with alternating layers of various alloying degree at a depth of 30 μm.

  14. Modification of the titanium alloy surface in electroexplosive alloying with boron carbide and subsequent electron-beam treatment

    Energy Technology Data Exchange (ETDEWEB)

    Gromov, Victor E., E-mail: gromov@physics.sibsiu.ru; Budovskikh, Evgeniy A., E-mail: budovskikh-ea@physics.sibsiu.ru; Bashchenko, Lyudmila P., E-mail: gromov@physics.sibsiu.ru; Kobzareva, Tatyana Yu., E-mail: gromov@physics.sibsiu.ru; Semin, Alexander P., E-mail: gromov@physics.sibsiu.ru [Siberian State Industrial University, Novokuznetsk, 654007 (Russian Federation); Ivanov, Yurii F., E-mail: yufi55@mail.ru [Institute of High Current Electronics SB RAS, Tomsk, 634055 (Russian Federation); National Research Tomsk State University, Tomsk, 634050 (Russian Federation); Wang, Xinli, E-mail: wangxl520@hotmail.com [Northeastern University, Liaoning, Shenyang 110819 China (China)

    2015-10-27

    The modification of the VT6 titanium alloy surface in electroexplosion alloying with plasma being formed in titanium foil with a weighed powder of boron carbide with subsequent irradiation by a pulsed electron beam has been carried out. An electroexplosive alloying zone of a thickness up to 50 μm with a gradient structure is found to form. The subsequent electron-beam treatment of the alloying zone results in smoothing of the alloying surface and is accompanied by the formation of the multilayer structure with alternating layers of various alloying degree at a depth of 30 μm.

  15. Hyperfine structure of the hydroxyl free radical (OH) in electric and magnetic fields

    Science.gov (United States)

    Maeda, Kenji; Wall, Michael L.; Carr, Lincoln D.

    2015-05-01

    We investigate single-particle energy spectra of the hydroxyl free radical (OH) in the lowest electronic and rovibrational level under combined static electric and magnetic fields, as an example of heteronuclear polar diatomic molecules. In addition to the fine-structure interactions, the hyperfine interactions and centrifugal distortion effects are taken into account to yield the zero-field spectrum of the lowest 2Π3 / 2 manifold to an accuracy of less than 2kHz. We also examine level crossings and repulsions in the hyperfine structure induced by applied electric and magnetic fields. Compared to previous work, we found more than 10 percent reduction of the magnetic fields at level repulsions in the Zeeman spectrum subjected to a perpendicular electric field. In addition, we find new level repulsions, which we call Stark-induced hyperfine level repulsions, that require both an electric field and hyperfine structure. It is important to take into account hyperfine structure when we investigate physics of OH molecules at micro-Kelvin temperatures and below. This research was supported in part by AFOSR Grant No.FA9550-11-1-0224 and by the NSF under Grants PHY-1207881 and NSF PHY-1125915. We appreciate the Aspen Center for Physics, supported in part by the NSF Grant No.1066293, for hospitality.

  16. 铁基合金粉包覆改性及在雷达/红外兼容隐身中的应用%Surface Modification of Fe-based Alloy Powders and Application in Radar/Infrared Compatible Stealth Coatings

    Institute of Scientific and Technical Information of China (English)

    陈砚朋; 徐国跃; 陈慧敏; 郭腾超; 秦锐

    2011-01-01

    Fe-based pigment was modified with silane coupling agent(KH550), which was used as filler to prepare radar-infrared compatible stealth coatings. The influence of surface modification on microwave-absorbing properties and infrared emissivity was systematically investigated. The results indicate that Fe-based alloy powders were modified with silane coupling agent successfully. Compared to that of Fe-based alloy powders without modification, the low infrared emissivity of composite coatings treated with 2% coupling agent changes slightly. However, the value of permittivity decreases visibly, impedance matching is enhanced. The coatings with thickness of 2mm give microwave absorption -10dB with a band width of 2. 2GHz and the value of maximum absorption peak is improved.%用KH550硅烷偶联剂对铁基合金粉包覆改性,并以其为颜填料制备了雷达/红外兼容隐身单涂层,系统研究了包覆改性对涂层低红外发射率以及雷达吸波性能的影响.研究结果表明,偶联剂以化学键的形式吸附在铁基合金粉表面形成有机薄膜.2%偶联剂包覆对涂层的红外发射率影响较小,但显著降低铁基合金粉的介电常数,提高阻抗匹配度.涂层厚度为2mm时,-10dB的吸收带宽从包覆前1.5GHz增加至2.2GHz,吸收峰强度也有明显增加.

  17. Effect of mechanical alloying on FeCrC reinforced Ni alloys

    Energy Technology Data Exchange (ETDEWEB)

    Yilmaz, S. Osman [Univ. of Namik Kemal, Tekirdag (Turkey); Teker, Tanju [Adiyaman Univ. (Turkey). Dept. of Metallurgical and Materials Engineering; Demir, Fatih [Batman Univ. (Turkey)

    2016-05-01

    Mechanical alloying (MA) is a powder metallurgy processing technique involving cold welding, fracturing and rewelding of powder particles in a high-energy ball mill. In the present study, the intermetallic matrix composites (IMCs) of Ni-Al reinforced by M{sub 7}C{sub 3} were produced by powder metallurgical routes via solid state reaction of Ni, Al and M{sub 7}C{sub 3} particulates by mechanical alloying processes. Ni, Al and M{sub 7}C{sub 3} powders having 100 μm were mixed, mechanical alloyed and the compacts were combusted in a furnace. The mechanically alloyed (MAed) powders were investigated by X-ray diffraction (XRD), microhardness measurement, optic microscopy (OM), scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS). The presence of the carbides depressed the formation of unwanted NiAl intermetallic phases. The mechanical alloyed M{sub 7}C{sub 3} particles were unstable and decomposed partially within the matrix during alloying and sintering, and the morphology of the composites changed with the dissolution ratio of M{sub 7}C{sub 3} and sintering temperature.

  18. Structure of the Intermetallic Compound Ni3Al Synthesized under Compression of the Powder Mixture of Pure Elements Part II: Influence of Alloying by Boron on the Phase Composition and the Microstructure of Grains of the Main Phase

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    The Ni3B phase was formed when boron (0.5 at. pct B) was added to the intermetallic of stoichiometric and off-stoichiometric (Ni-24 at. pct Al) compounds. In the alloy of stoichiometric composition the particles of Ni3B phase has the size around 0.1μm and is located on the grain boundary of the main phase. The decreasing of concentrations of Al in the off-stoichiometric alloy leads to increase in the degree of the long-range order parameter, increasing the concentrations of boron in the solid solution and decreasing its localization on the grain boundary.Microalloying of boron leads to increasing in the fraction of grain monodomains with dislocations up to 0.7 in the alloy of the off-stoichiometric composition and up to 1 in the alloy of the stoichiometric composition. It was established the correlation between the degree of the concentration inhomogeneity, average density of the dislocations and the average long range-order parameter.

  19. Theoretical calculations of hyperfine coupling constants for muoniated butyl radicals.

    Science.gov (United States)

    Chen, Ya Kun; Fleming, Donald G; Wang, Yan Alexander

    2011-04-01

    The hyperfine coupling constants (HFCCs) of all the butyl radicals that can be produced by muonium (Mu) addition to butene isomers (1- and 2-butene and isobutene) have been calculated, to compare with the experimental results for the muon and proton HFFCs for these radicals reported in paper II (Fleming, D. G.; et al. J. Phys. Chem. A 2011, 10.1021/jp109676b) that follows. The equilibrium geometries and HFCCs of these muoniated butyl radicals as well as their unsubstituted isotopomers were treated at both the spin-unrestricted MP2/EPR-III and B3LYP/EPR-III levels of theory. Comparisons with calculations carried out for the EPR-II basis set have also been made. All calculations were carried out in vacuo at 0 K only. A C-Mu bond elongation scheme that lengthens the equilibrium C-H bond by a factor of 1.076, on the basis of recent quantum calculations of the muon HFCCs of the ethyl radical, has been exploited to determine the vibrationally corrected muon HFCCs. The sensitivity of the results to small variations around this scale factor was also investigated. The computational methodology employed was "benchmarked" in comparisons with the ethyl radical, both with higher level calculations and with experiment. For the β-HFCCs of interest, compared to B3LYP, the MP2 calculations agree better with higher level theories and with experiment in the case of the eclipsed C-Mu bond and are generally deemed to be more reliable in predicting the equilibrium conformations and muon HFCCs near 0 K, in the absence of environmental effects. In some cases though, the experimental results in paper II demonstrate that environmental effects enhance the muon HFCC in the solid phase, where much better agreement with the experimental muon HFCCs near 0 K is found from B3LYP than from MP2. This seemingly better level of agreement is probably fortuitous, due to error cancellations in the DFT calculations, which appear to mimic these environmental effects. For the staggered proton HFCCs of the

  20. Absolute frequency measurements and hyperfine structures of the molecular iodine transitions at 578 nm

    CERN Document Server

    Kobayashi, Takumi; Hosaka, Kazumoto; Inaba, Hajime; Okubo, Sho; Tanabe, Takehiko; Yasuda, Masami; Onae, Atsushi; Hong, Feng-Lei

    2016-01-01

    We report absolute frequency measurements of 81 hyperfine components of the rovibrational transitions of molecular iodine at 578 nm using the second harmonic generation of an 1156-nm external-cavity diode laser and a fiber-based optical frequency comb. The relative uncertainties of the measured absolute frequencies are typically $1.4\\times10^{-11}$. Accurate hyperfine constants of four rovibrational transitions are obtained by fitting the measured hyperfine splittings to a four-term effective Hamiltonian including the electric quadrupole, spin-rotation, tensor spin-spin, and scalar spin-spin interactions. The observed transitions can be good frequency references at 578 nm, and are especially useful for research using atomic ytterbium since the transitions are close to the $^{1}S_{0}-^{3}P_{0}$ clock transition of ytterbium.

  1. Paschen-Back effect involving atomic fine and hyperfine structure states

    Science.gov (United States)

    Sowmya, K.; Nagendra, K. N.; Sampoorna, M.; Stenflo, J. O.

    2015-10-01

    The linear polarization in spectral lines produced by coherent scattering is significantly modified by the quantum interference between the atomic states in the presence of a magnetic field. When magnetic fields produce a splitting which is of the order of or greater than the fine or hyperfine structure splittings, we enter the Paschen-Back effect (PBE) regime, in which the magnetic field dependence of the Zeeman splittings and transition amplitudes becomes non-linear. In general, PBE occurs for sufficiently strong fields when the fine structure states are involved and for weak fields in the case of hyperfine structure states. In this work, we apply the recently developed theory of PBE in the atomic fine and hyperfine structure states including the effects of partial frequency redistribution to the case of Li i 6708 Å doublet. We explore the signatures of PBE in a single scattering event and their applicability to the solar magnetic field diagnostics.

  2. Relativistic coupled cluster calculations on hyperfine structures and electromagnetic transition amplitudes of In III

    CERN Document Server

    Roy, Sourav; Majumder, Sonjoy

    2014-01-01

    Hyperfine constants and anomalies of ground as well as few low lying excited states of $^{113,115,117}$In III are studied with highly correlated relativistic coupled-cluster theory. The ground state hyperfine splitting of $^{115}$In III is estimated to be 106.8 GHz. A shift of almost 1.9 GHz of the above frequency has been calculated due to modified nuclear dipole moment. This splitting result shows its applicability as communication band and frequency standards at $10^{-11}$ sec. Correlations study of hyperfine constants indicates a few distinct features of many-body effects in the wave-functions in and near the nuclear region of this ion. Astrophysically important forbidden transition amplitudes are estimated for the first time in the literature to our knowledge. The calculated oscillator strengths of few allowed transitions are compared with recent experimental and theoretical results wherever available.

  3. Hyperfine electric parameters calculation in Si samples implanted with {sup 57}Mn→{sup 57}Fe

    Energy Technology Data Exchange (ETDEWEB)

    Abreu, Y., E-mail: yabreu@ceaden.edu.cu [Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Calle 30 No. 502 e/5ta y 7ma Ave., 11300 Miramar, Playa, La Habana (Cuba); Cruz, C.M.; Piñera, I.; Leyva, A.; Cabal, A.E. [Centro de Aplicaciones Tecnológicas y Desarrollo Nuclear (CEADEN), Calle 30 No. 502 e/5ta y 7ma Ave., 11300 Miramar, Playa, La Habana (Cuba); Van Espen, P. [Departement Chemie, Universiteit Antwerpen, Middelheimcampus, G.V.130, Groenenborgerlaan 171, 2020 Antwerpen (Belgium); Van Remortel, N. [Departement Fysica, Universiteit Antwerpen, Middelheimcampus, G.U.236, Groenenborgerlaan 171, 2020 Antwerpen (Belgium)

    2014-07-15

    Nowadays the electronic structure calculations allow the study of complex systems determining the hyperfine parameters measured at a probe atom, including the presence of crystalline defects. The hyperfine electric parameters have been measured by Mössbauer spectroscopy in silicon materials implanted with {sup 57}Mn→{sup 57}Fe ions, observing four main contributions to the spectra. Nevertheless, some ambiguities still remain in the {sup 57}Fe Mössbauer spectra interpretation in this case, regarding the damage configurations and its evolution with annealing. In the present work several implantation environments are evaluated and the {sup 57}Fe hyperfine parameters are calculated. The observed correlation among the studied local environments and the experimental observations is presented, and a tentative microscopic description of the behavior and thermal evolution of the characteristic defects local environments of the probe atoms concerning the location of vacancies and interstitial Si in the neighborhood of {sup 57}Fe ions in substitutional and interstitial sites is proposed.

  4. Combined effect of coherent Z exchange and the hyperfine interaction in atomic PNC

    CERN Document Server

    Johnson, W R; Safronova, U I

    2003-01-01

    The nuclear spin-dependent PNC interaction arising from a combination of the hyperfine interaction and the coherent, spin-independent, PNC interaction from Z exchange is evaluated using many-body perturbation theory. For the 6s-7s transition in 133Cs, we obtain a result that is about 60% smaller than that found previously by Bouchiat and Piketty [Phys. Lett. B 269, 195 (1991)]. Applying this result to 133Cs, leads to an increase in the experimental value of nuclear anapole moment and exacerbates differences between constraints on PNC meson coupling constants obtained from the Cs anapole moment and those obtained from other nuclear parity violating experiments. Nuclear spin-dependent PNC dipole matrix elements, including contributions from the combined weak-hyperfine interaction, are also given for the 7s-8s transition in 211Fr and for transitions between ground-state hyperfine levels in K, Rb, Cs, Ba+, Au, Tl, Fr, and Ra+.

  5. Lamb shifts and hyperfine structure in 6Li+ and 7Li+: Theory and experiment

    DEFF Research Database (Denmark)

    Riis, E.; Sinclair, A. G.; Poulsen, Ove;

    1994-01-01

    High-precision laser-resonance measurements accurate to +/-0.5 MHz, or better are reported for transitions among the 1s2s S-3(1)-1s2p P-3(J) hyperfine manifolds for each of J = 0, 1, and 2 in both Li-6(+) and Li-7(+). A detailed analysis of hyperfine structure is performed for both the S and P...... states, using newly calculated values for the magnetic dipole and electric quadrupole coupling constants, and the hyperfine shifts subtracted from the measurements. The resulting transition frequencies are then analysed on three different levels. First, the isotope shifts in the fine-structure splittings....... The accuracy of 11 parts per million is the best two-electron Lamb shift measurement in the literature, and is comparable to the accuracies achieved in hydrogen. Theoretical contributions to the two-electron Lamb shift are discussed, including terms of order (alpha Z)(4) recently obtained by Chen, Cheng...

  6. Hyperfine-frequency shifts of alkali-metal atoms during long-range collisions

    CERN Document Server

    McGuyer, B H

    2013-01-01

    Collisions with chemically inert atoms or molecules change the hyperfine coupling of an alkali-metal atom through the hyperfine-shift interaction. This interaction is responsible for the pressure shifts of the microwave resonances of alkali-metal atoms in buffer gases, is an important spin interaction in alkali-metal--noble-gas van der Waals molecules, and is anticipated to enable the magnetoassociation of ultracold molecules such as RbSr. An improved estimate is presented for the long-range asymptote of this interaction for Na, K, Rb, and Cs. To test the results, the change in hyperfine coupling due to a static electric field is estimated and reasonable agreement is found.

  7. Observation of hyperfine interaction in photoassociation spectra of ultracold RbYb

    Science.gov (United States)

    Bruni, C.; Görlitz, A.

    2016-08-01

    We report on the creation of ultracold heteronuclear and electronically excited Rb*Yb molecules in a hybrid conservative trap by photoassociation of ultracold 87Rb and 176Yb. The molecules are formed below the Rb5 p 1(1/2 2P)+Yb6 s 2(S10) dissociation limit and the resonances are detected using trap-loss spectroscopy. By addressing vibrational levels with binding energies down to EB=-h ×2.2 THz , we study the change in hyperfine coupling of the diatomic molecule as a function of internuclear separation. We observe a decreasing hyperfine splitting for more tightly bound excited molecular states where the hyperfine splitting is reduced by more than 30 % compared to the atomic value for 87Rb.

  8. Hyperfine-induced electric dipole contributions to the electric octupole and magnetic quadrupole atomic clock transitions

    CERN Document Server

    Dzuba, V A

    2016-01-01

    Hyperfine-induced electric dipole contributions may significantly increase probabilities of otherwise very weak electric octupole and magnetic quadrupole atomic clock transitions (e.g. transitions between $s$ and $f$ electron orbitals). These transitions can be used for exceptionally accurate atomic clocks, quantum information processing and search for dark matter. They are very sensitive to new physics beyond the Standard Model, such as temporal variation of the fine structure constant, the Lorentz invariance and Einstein equivalence principle violation. We formulate conditions under which the hyperfine-induced electric dipole contribution dominates. Due to the hyperfine quenching the electric octupole clock transition in $^{173}$Yb$^+$ is two orders of magnitude stronger than that in currently used $^{171}$Yb$^+$. Some enhancement is found in $^{143}$Nd$^{13+}$, $^{149}$Pm$^{14+}$, $^{147}$Sm$^{14+}$, and $^{147}$Sm$^{15+}$ ions.

  9. Shock-Wave Consolidation of Nanostructured Bismuth Telluride Powders

    Science.gov (United States)

    Beck, Jan; Alvarado, Manuel; Nemir, David; Nowell, Mathew; Murr, Lawrence; Prasad, Narasimha

    2012-06-01

    Nanostructured thermoelectric powders can be produced using a variety of techniques. However, it is very challenging to build a bulk material from these nanopowders without losing the nanostructure. In the present work, nanostructured powders of the bismuth telluride alloy system are obtained in kilogram quantities via a gas atomization process. These powders are characterized using a variety of methods including scanning electron microscopy, transition electron microscopy, and x-ray diffraction analysis. Then the powders are consolidated into a dense bulk material using a shock-wave consolidation technique whereby a nanopowder-containing tube is surrounded by explosives and then detonated. The resulting shock wave causes rapid fusing of the powders without the melt and subsequent grain growth of other techniques. We describe the test setup and consolidation results.

  10. Structural, microstructural and hyperfine properties of nanocrystalline iron particles

    Energy Technology Data Exchange (ETDEWEB)

    Guittoum, A., E-mail: guittoum@yahoo.f [Centre de Recherche Nucleaire d' Alger, 2 Bd Frantz Fanon, BP 399 Alger-Gare, Alger (Algeria); Layadi, A. [Departement de Physique, Faculte des Sciences, Universite Ferhat Abbas, Setif 19000 (Algeria); Tafat, H. [Faculte de Mecanique et Genie des Procedes, USTHB de Bab Ezzouar (Algeria); Souami, N. [Centre de Recherche Nucleaire d' Alger, 2 Bd Frantz Fanon, BP 399 Alger-Gare, Alger (Algeria)

    2010-03-15

    Nanocrystalline Fe particles were successfully prepared by the mechanical milling process using a high-energy planetary ball mill. The physical properties of the samples were investigated as a function of the milling time, t (in the 0-54 h range) by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) and Moessbauer spectroscopy. After 54 h of milling, the lattice parameter increases from 0.28620 (3) nm for the starting Fe powder to 0.28667 (3) nm, the grain size decreases from 110 to 13 nm, while the strain increases from 0.09% to 0.7%. The powder particle morphology was observed by SEM at different stages of milling. For t less than 24 h, the Moessbauer spectra are characterized by one sextet corresponding to the crystalline bcc Fe phase, while for t greater than 24 h, the iron particles exhibit a two-component Moessbauer spectrum due to the presence of two phases: the crystallites bcc Fe phase and the grain-boundary region. The appearance and the increase in intensity of the second sextet with t may indicate that the interfacial region effect increases with milling time due to the grain size reduction and a probable disordered state of the grain boundaries.

  11. Temperature-dependent hyperfine interactions at {sup 111}Cd-C complex in germanium

    Energy Technology Data Exchange (ETDEWEB)

    Mola, Genene Tessema [University of Kwazulu-Natal, School Chemistry and Physics, Pietermaritzburg Campus, Private Bag X01, Scottsville (South Africa)

    2013-09-15

    The temperature dependent nuclear hyperfine interaction of {sup 111}Cd-carbon complex in germanium has been studied using the perturbed {gamma}-{gamma} angular correlation (PAC) method. The parameters of the hyperfine interaction representing substitutional carbon-cadmium complex in germanium ({nu} {sub Q1}=207(1) MHz ({eta}=0.16)) shows dependence on temperature. The formation and thermal stability of the complex has been reported by the same author earlier. It was found in this study that the quadrupole coupling constant of the interaction increases at sample temperature below 293 K. The results are encouraging toward better understanding of the complex in the host matrix. (orig.)

  12. Study of coupled-cluster correlations on electromagnetic transitions and hyperfine structure constants of W VI

    CERN Document Server

    Bhowmik, Anal; Roy, Sourav; Majumder, Sonjoy

    2016-01-01

    This work presents precise calculations of important electromagnetic transition amplitudes along with detail of their many-body correlations using relativistic coupled cluster method. Studies of hyperfine interaction constants, useful for plasma diagnostic, with this correlation exhaustive many-body approach are another important area of this work. The calculated oscillator strengths of allowed transitions, amplitudes of forbidden transitions and lifetimes are compared with the other theoretical results wherever available and they show a good agreement. Hyperfine constants of ?different isotopes of W VI, presented in this paper will be helpful to get accurate picture of abundances of this element in different astronomical bodies.

  13. Absorption properties of a driven Doppler-broadened ladder system with hyperfine structure

    Institute of Scientific and Technical Information of China (English)

    吴金辉; 高锦岳

    2002-01-01

    We have studied the absorption spectrum of a Doppler-broadened ladder system, where the highest level is coupled into two middle hyperfine sublevels by a strong coherent field. We find that, when the system is considered as homoge- neous, either two or three spectral components are observed, depending on the detuning of the coherent field. But when the velocity distribution of atoms is considered, we can always observe one electromagnetically induced transparency (EIT) window with high dispersion. So the atomic hyperfine structure cannot be an impediment for obtaining EIT.

  14. Production of Nuclear Polarization of Na Isotopes at ISAC/TRIUMF and its Hyperfine Interaction

    Energy Technology Data Exchange (ETDEWEB)

    Minamisono, K., E-mail: minamiso@nscl.msu.edu [NSCL/MSU (United States); Matsuta, K.; Minamisono, T. [Osaka University, Department of Physics (Japan); Levy, C. D. P. [TRIUMF (Canada); Nagatomo, T.; Ogura, M. [Osaka University, Department of Physics (Japan); Sumikama, T. [RIKEN (Japan); Behr, J. A.; Jackson, K. P. [TRIUMF (Canada); Fujiwara, H.; Mihara, M.; Fukuda, M. [Osaka University, Department of Physics (Japan)

    2004-12-15

    Hyperfine interactions of Na isotopes in single crystals have been studied using highly nuclear polarized {sup 20,21,26,27,28}Na beams provided by ISAC/TRIUMF. The degree of polarization kept in the crystals, the spin-lattice relaxation times, the electric quadrupole coupling constants and the initial distribution of the populations were measured. Such knowledge is indispensable for the application of the hyperfine interactions in the study of precision measurements such as the nuclear structure through nuclear moments and the fundamental symmetries.

  15. Measurement of hyperfine structure in the $\\rm D_1$ line of $^{87}$Rb

    CERN Document Server

    Datar, Durgesh; Ananthamurthy, Sharath; Natarajan, Vasant

    2016-01-01

    This work reports a new measurement of the hyperfine structure constant of the $\\rm D_1 $ line in $ \\rm ^{87}Rb $ through precision laser spectroscopy. In a departure from methods that rely on locking the laser on the transitions of interest, the technique reported here relies on scanning around the transition. This is carried out so as to overcome potential frequency shifts caused by various noise sources including electronic noise and thermal fluctuations. The value of the hyperfine constant reported here is $ A = 408.29(25) $ MHz, which is in variance from an earlier value reported from our lab but is consistent with other recent measurements.

  16. Spin dynamics and hyperfine interaction in InAs semiconductor quantum dots

    Energy Technology Data Exchange (ETDEWEB)

    Eble, B.; Krebs, O.; Voisin, P.; Lemaitre, A.; Kudelski, A. [CNRS - Laboratoire de Photonique et Nanostructures, Route de Nozay, 91460 Marcoussis (France); Braun, P.F.; Lombez, L.; Marie, X.; Urbaszek, B.; Amand, T.; Lagarde, D.; Renucci, P. [Laboratoire de Nanophysique Magnetisme et Optoelectronique, INSA, 31077 Toulouse Cedex 4 (France); Kowalik, K. [CNRS - Laboratoire de Photonique et Nanostructures, Route de Nozay, 91460 Marcoussis (France); Institute of Experimental Physics, Warsaw University, Hoza 69, 00-681 Warsaw (Poland); Kalevich, V.K.; Kavokin, K.V. [Ioffe Institute, Politekhnicheskaya 26, St-Petersburg 194021 (Russian Federation)

    2006-08-15

    We present a detailed study of the hyperfine interaction between carrier and nuclear spins in InAs semiconductor quantum dots. Time resolved measurements on excitons in positively charged quantum dots show the electron spin relaxation due to random fluctuations of the spin orientation of the nuclei in the quantum dot. A complimentary aspect of the hyperfine interaction can be uncovered in single dot continuous wave photoluminescence experiments in a weak magnetic field, namely the Overhauser shift due to the dynamic polarisation of the nuclei following excitation with circularly polarised light. (copyright 2006 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  17. Hyperfine structure constants for singly ionized manganese (Mn II) using Fourier transform spectroscopy

    Science.gov (United States)

    Townley-Smith, Keeley; Nave, Gillian; Pickering, Juliet C.; Blackwell-Whitehead, Richard J.

    2016-09-01

    We expand on the comprehensive study of hyperfine structure (HFS) in Mn II conducted by Holt et al. (1999) by verifying hyperfine magnetic dipole constants (A) for 20 levels previously measured by Holt et al. (1999) and deriving A constants for 47 previously unstudied levels. The HFS patterns were measured in archival spectra from Fourier transform (FT) spectrometers at Imperial College London and the National Institute of Standards and Technology. Analysis of the FT spectra was carried out in XGREMLIN. Our A constant for the ground level has a lower uncertainty by a factor of 6 than that of Blackwell-Whitehead et al.

  18. Hyperfine spectroscopy of muonic hydrogen and the PSI Lamb shift experiment

    Energy Technology Data Exchange (ETDEWEB)

    Adamczak, Andrzej [Institute of Nuclear Physics, Polish Academy of Sciences, ul. Radzikowskiego 152, 31-342 Krakow (Poland); Bakalov, Dimitar, E-mail: dbakalov@inrne.bas.bg [Institute for Nuclear Research and Nuclear Energy, Bulgarian Academy of Sciences, Tsarigradsko chaussee 72, Sofia 1784 (Bulgaria); Stoychev, Lyubomir [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, Via A. Valerio 2, 34127 Trieste (Italy); The Abdus Salam International Centre for Theoretical Physics, Strada Costiera 11, 34014 Trieste (Italy); Vacchi, Andrea [Istituto Nazionale di Fisica Nucleare, Sezione di Trieste, Via A. Valerio 2, 34127 Trieste (Italy)

    2012-06-15

    The recent Lamb shift experiment at PSI and the discussions about the incompatibility of the proton radii extracted using different methods have revived the interest in the measurement of the hyperfine splitting of the ground state in muonic hydrogen. We summarize the existing experimental ideas for this measurement and analyze quantitatively the main methodological difficulties, expected to be related to the required power of the IR laser source, the signal-to-noise ratio and other systematic factors. An elaborate model is developed to estimate the statistical uncertainty of the experimental value of the hyperfine splitting.

  19. Hyperfine interactions in the itinerant system UFeGa{sub 5}

    Energy Technology Data Exchange (ETDEWEB)

    Kambe, S. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Shirakata-shirane-2-4, Ibaraki 319-1195 (Japan)], E-mail: kambe.shinsaku@jaea.go.jp; Sakai, H.; Tokunaga, Y.; Chudo, H.; Yasuoka, H.; Matsuda, T.D.; Haga, Y.; Ikeda, S.; Nakamura, A.; Yamamoto, E. [Advanced Science Research Center, Japan Atomic Energy Agency, Tokai-mura, Shirakata-shirane-2-4, Ibaraki 319-1195 (Japan); Aoki, D.; Homma, Y.; Shiokawa, Y. [Institute for Materials Research, Tohoku University, Oarai, Ibaraki 311-1313 (Japan); Onuki, Y. [Graduate School of Science, Osaka University, Toyonaka, Osaka 560-0043 (Japan)

    2009-03-15

    We report {sup 69}Ga NMR measurements on the itinerant compound UFeGa{sub 5} using a single crystal sample. Hyperfine coupling constants at both the Ga(1) and Ga(2) sites are determined for H-parallel a and c-axes based on Knight shift versus susceptibility plots. The T-dependence of the spin-lattice relaxation time (T{sub 1}) has been determined at both sites for H-parallel a and c-axes. From these quantities, the magnetic fluctuations are estimated for both axes. The complex nature of the hyperfine interactions is discussed.

  20. State selection of 2/sup 2/Ssub(1/2) hyperfine levels of hydrogen in zero magnetic field

    Energy Technology Data Exchange (ETDEWEB)

    Edwards, J.W.; Greene, G.L.; Hinds, E.A. (Yale Univ., New Haven, CT (USA). Gibbs Lab.)

    1982-06-15

    We describe a methd of hyperfine level selection using rf quenching of a metastable (2S) hydrogen beam in zero magnetic field. The method provides excellent suppression of unwanted states with acceptable transmission of desired states. The technique has been used to study a very weakly induced hyperfine transition.

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

    Energy Technology Data Exchange (ETDEWEB)

    Wright, I.G.; Pint, B.A.; Tortorelli, P.F.; McKamey, C.G. [Oak Ridge National Lab., TN (United States)

    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

  2. Powder metallurgy approaches to high temperature components for gas turbine engines

    Science.gov (United States)

    Probst, H. B.

    1974-01-01

    Research is reported for the tensile strength, ductility, and heat performance characterisitics of powder metallurgy (p/m) superalloys. Oxide dispersion strengthened alloys were also evaluated for their strength during thermal processing. The mechanical attributes evident in both p/m supperalloys and dispersion strengthened alloys are discussed in terms of research into their possible combination.

  3. PRODUCTION OF FeAl NANOSTRUCTURED ALLOY BY MECHANICAL ALLOYING AND ITS MICROSTRUCTURAL CHARACTERIZATION

    Directory of Open Access Journals (Sweden)

    Roberto. A. Rodríguez-Díaz

    2013-12-01

    Full Text Available In this work, a Fe40Al alloy was produced by the mechanical alloying technique, from a mixture of elemental powders constituted by Fe and Al, using different milling times. The evolution of size and morphology of powders depending on the milling time was characterized by scanning electron microscopy. The X-Ray Diffraction technique was utilized in order to characterize the crystalline structure evolution depending on the milling time. The Fe40Al alloy with a body centered cubic crystal structure was formed at 20 h of milling time. Besides, this alloy acquired a disordered crystal structure with a Nano metric grain size. The Nano metric grain size of disordered Fe40Al alloy was decreased at the same time as the milling time transcurred, while its lattice parameter was increased.

  4. Granulation of fine powder

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ching-Fong

    2016-08-09

    A mixture of fine powder including thorium oxide was converted to granulated powder by forming a first-green-body and heat treating the first-green-body at a high temperature to strengthen the first-green-body followed by granulation by crushing or milling the heat-treated first-green-body. The granulated powder was achieved by screening through a combination of sieves to achieve the desired granule size distribution. The granulated powder relies on the thermal bonding to maintain its shape and structure. The granulated powder contains no organic binder and can be stored in a radioactive or other extreme environment. The granulated powder was pressed and sintered to form a dense compact with a higher density and more uniform pore size distribution.

  5. Transition energy and lifetime for the ground state hyperfine splitting of high Z lithium-like ions

    CERN Document Server

    Shabaev, V M; Tupitsyn, I; Yerokhin, V A; Artemiev, A N; Kühl, T; Tomaselli, M; Zherebtsov, O M

    1998-01-01

    The ground state hyperfine splitting values and the transition probabilities between the hyperfine structure components of high Z lithiumlike ions are calculated in the range Z=49-83. The relativistic, nuclear, QED and interelectronic interaction corrections are taken into account. It is found that the Bohr-Weisskopf effect can be eliminated in a combination of the hyperfine splitting values of the hydrogenlike and lithiumlike ions of an isotope. This gives a good possibility for testing the QED effects in a combination of the strong electric and magnetic fields of the heavy nucleus. Using the experimental result for the 1s hyperfine splitting in ^{209}Bi^{82+}, the 2s hyperfine splitting in ^{209}Bi^{80+} is calculated to be \\Delta E=0.7981(2) eV while the contribution derived from QED constitutes 0.0007(1) eV.

  6. The effect of hyperfine interactions on ultracold molecular collisions: NH(^3Sigma^-) with Mg(^1S) in magnetic fields

    CERN Document Server

    González-Martínez, Maykel L

    2011-01-01

    We investigate the effect of hyperfine interactions on ultracold molecular collisions in magnetic fields, using ^{24}Mg(^1S) + ^{14}NH(^3Sigma^-) as a prototype system. We explore the energy and magnetic field dependence of the cross sections, comparing the results with previous calculations that neglected hyperfine interactions (Phys. Rev. Lett. 103, 183201 (2009)). The main effect of hyperfine interactions for spin relaxation cross sections is that the kinetic energy release of the dominant outgoing channels does not reduce to zero at low fields. This results in reduced centrifugal suppression on the cross sections and increased inelastic cross sections at low energy and low field. We also analyze state-to-state cross sections, for various initial states, and show that hyperfine interactions introduce additional mechanisms for spin relaxation. In particular, there are hyperfine-mediated collisions to outgoing channels that are not centrifugally suppressed. However, for Mg+NH these unsuppressed channels make...

  7. Production and Characterization of Atomized U-Mo Powder by the Rotating Electrode Process

    Energy Technology Data Exchange (ETDEWEB)

    C.R. Clark; B.R. Muntifering; J.F. Jue

    2007-09-01

    In order to produce feedstock fuel powder for irradiation testing, the Idaho National Laboratory has produced a rotating electrode type atomizer to fabricate uranium-molybdenum alloy fuel. Operating with the appropriate parameters, this laboratory-scale atomizer produces fuel in the desired size range for the RERTR dispersion experiments. Analysis of the powder shows a homogenous, rapidly solidified microstructure with fine equiaxed grains. This powder has been used to produce irradiation experiments to further test adjusted matrix U-Mo dispersion fuel.

  8. Influence of Fe{sub 2}O{sub 3} on alloying and magnetic properties of Fe–Al

    Energy Technology Data Exchange (ETDEWEB)

    Jiraskova, Y., E-mail: jirasko@ipm.cz [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno (Czech Republic); Bursik, J. [Institute of Physics of Materials, Academy of Sciences of the Czech Republic, Brno (Czech Republic); Zivotsky, O. [Department of Physics, VSB-Technical University of Ostrava, Ostrava (Czech Republic); Regional Material Science and Technological Centre, VSB-Technical University of Ostrava, Ostrava (Czech Republic); Cuda, J. [Regional Centre of Advanced Technologies, Palacky University in Olomouc, Olomouc (Czech Republic)

    2014-08-01

    Highlights: • The Fe–Al alloying in a presence of Fe{sub 2}O{sub 3} is detected after 2 h of milling. • The Fe–25 at.% Al substitutional solid solution is formed. • Next milling steps yield Al decrease in the alloy and hematite dissolution. • Dynamic process is reflected by changes in magnetic properties. • Intergrain exchange coupling yields dipolar interactions at low magnetic fields. - Abstract: The present study is devoted to changes of the magnetic properties during the high-energy ball milling of the Fe, Al and Fe{sub 2}O{sub 3} powders. The magnetic properties are supported by the structure morphology, phase composition, and changes in atomic ordering investigated using the structure sensitive scanning electron microscopy, X-ray diffraction and Mössbauer spectrometry. Intergrain exchange coupling results in negative values of δM(H) Henkel graphs yielding dipolar interactions among particles and only slightly depending on the milling time. The bcc-Fe–Al is detected after 2 h of milling coexisting with the α-(Fe,Al){sub 2}O{sub 3}, superparamagnetic oxides, and α-Fe. In the next milling steps the changes in the phase composition are seen. While a small amount of the superparamagnetic oxides and the bcc-Fe–Al phase are detected after 20 h, the α-(Fe,Al){sub 2}O{sub 3} has been dissolved. An increase in the hyperfine induction and saturation magnetization evidences a decrease in Al content in the bcc-Fe–Al estimated to be bellow 18 at.% Al.

  9. Use of the generalized spherical harmonic model for describing crystallographic texture in polycrystalline NiTi shape-memory alloy with time-of-flight neutron powder diffraction data

    CERN Document Server

    Sitepu, H; Dreele, R B V

    2002-01-01

    We present a feasibility study to extract quantitative texture and precise crystal structure information of polycrystalline monoclinic NiTi shape-memory alloys from a simultaneous refinement of 52 time-of-flight neutron-diffraction patterns taken in 13 orientations in the diffractometer. The multiple-data-set capabilities and the generalized spherical harmonic texture model of the GSAS program system were employed. (orig.)

  10. Effect of milling conditions on the properties of Cu-NbC alloys obtained by powder metallurgy; Efecto de las variables de molienda en las propiedades de aleaciones Cu-NbC obtenidas por pulvimetalurgia

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, M.; Jimenez, J. A.; Ruano, O.; Benavente, R.

    2006-07-01

    Copper-base composite materials were obtained by reinforcing with homogeneous dispersions of 0.5 and 1% vol. of very fine NbC particles, through mechanical milling process in a planetary mill during 8 and 24 h at two different rotational speeds. The consolidation of the alloyed reinforced particles was achieved through a hot uniaxial pressing at 923K under 90 MPa during 2 h under a protective argon atmosphere. Factors to the suitable combination of electrical conductivity and mechanical properties attained are the hardness and good thermal stability of the niobium carbide which affords furthers refinement in the size of copper particles and the reinforcement of the alloy. A lower embrittlement and higher electrical conductivity of this alloys was observed, as a consequence of the smaller amount of impurities (Fe, Cr, C and O) incorporated during the lower-energy milling. Scanning and transmission electron microscopy and X-ray diffraction show and additional strengthening of the grain substructure by precipitation of nanometer-size impurities. (Author) 18 refs.

  11. Titanium aluminides production by powder metallurgy

    Energy Technology Data Exchange (ETDEWEB)

    Henriques, V.A.R. [Centro Tecnico Aeroespacial (CTA), Sao Jose dos Campos, SP (Brazil); Silva, C.R.M. [Universidade de Brasilia (UnB), Brasilia, DF (Brazil); Goncalves, F.F.R. [Instituto Tecnologico de Aeronautica (ITA), Sao Jose dos Campos, SP (Brazil)

    2009-07-01

    Full text: The aim of this work is to analyze the gamma-titanium-aluminideo alloys obtained by powder metallurgy. Theses alloys have high temperature resistance (until 850 deg C) for a long time with utilization in aircraft with high speed and can be applied in automotive engines valves or turbocharger rotors. This paper shows the microstructures results of Ti-48Al-2Cr-2Nb obtained by pressureless sintering and hot uniaxial pressing. The powders were mixed for one hour and compacted using cold isostatic pressing (300 MPa). The specimens were processed by sintering in vacuum between 900-1300 deg C and by hot uniaxial pressing (20 MPa) in argon atmosphere between 900-1200 deg C, for 2h. The alloys were characterized by XRD (X-ray diffraction), SEM (Scanning Electron Microscopy), EDS (Energy Dispersive Spectroscopy) and Vickers microhardness measurements. The results evidence that hot uniaxial pressing route has the tendency to obtain gamma-TiAl and alpha 2-Ti3Al intermetallics ( in a lamellar distribution) than the pressureless sintering route, mainly because of the high niobium diffusion in the titanium matrix. (author)

  12. Influence of La2O3 on sintering performance of ultrafine W composite powders and micro-structure of W alloy%La2O3对超细钨复合粉末烧结性能与钨合金显微组织的影响

    Institute of Scientific and Technical Information of China (English)

    范景莲; 周强; 韩勇; 刘涛; 杨树忠

    2014-01-01

    Ultrafine/nano composite powders of W-La2O3 were prepared by Sol-spray drying-calcination-hydrogen reduction process, and sintered at 1 950 ℃ to form La2O3 dispersion strengthened tungsten materials and obtain high density after molding under the press of 275 MPa. The density and mechanical properties of the alloy were studied. Morphologies of superfine powder, microstructure and fracture morphology of the sintered materials were investigated by SEM. The results show, with increasing the amount of La2O3, particles size of the powder decreases. The BET particle size of W-0.7%La2O3 composite powder is 0.1μm. The highest relatively density can reach 99.1%after sintering due to high sintering activity of W-La2O3 ultrafine/nano composite powders. La2O3 uniformly disperses on the tungsten grain boundary and inside, which can restrain the grain growth process. As a result, the average grain size of W-0.7%La2O3 is 8.7μm. The property of La2O3 dispersion strengthened tungsten materials is greatly improved , the flexural strength of W-0.7%La2O3 is 548 MPa. The morphologies of fracture surface of W-La2O3 alloy show a mixed mode of transgranular and intergranular fracture.%采用溶胶喷雾干燥-煅烧还原方法制备超细/纳米W-La2O3复合粉末,将粉末压制成形后在1950℃烧结,制备 La2O3弥散强化钨合金,检测合金的密度与强度,并采用 SEM 对超细粉末形貌、合金的组织结构、断口形貌进行分析,结果表明:随La2O3加入量增加,粉末颗粒显著细化,W-0.7%La2O3复合粉末的粒径仅为0.1μm;制备的W-La2O3超细/纳米复合粉末具有很高的烧结活性,烧结后,合金最高相对密度达到99.1%;La2O3均匀弥散分布于钨晶界,抑制钨合金的晶粒长大,提高材料的强度,W-0.7%La2O3合金中钨平均晶粒尺寸仅为8.7μm,抗弯强度达到548 MPa;合金的断裂形式表现为穿晶-沿晶共有的复合断裂形式。

  13. Cow dung powder poisoning

    Directory of Open Access Journals (Sweden)

    Khaja Mohideen Sherfudeen

    2015-01-01

    Full Text Available Cow dung, which has germicidal property, was used in ancient days to clean living premises in South India. Nowadays, people are using commercially available synthetic cow dung powder. It is locally known as "saani powder" in Tamil Nadu. It is freely available in homes and is sometimes accidentally consumed by children. It is available in two colors - yellow and green. Cow dung powder poisoning is common in districts of Tamil Nadu such as Coimbatore, Tirupur, and Erode. We report two cases of yellow cow dung powder poisoning from our hospital.

  14. Surface passivity largely governs the bioaccessibility of nickel-based powder particles at human exposure conditions.

    Science.gov (United States)

    Hedberg, Yolanda S; Herting, Gunilla; Latvala, Siiri; Elihn, Karine; Karlsson, Hanna L; Odnevall Wallinder, Inger

    2016-11-01

    The European chemical framework REACH requires that hazards and risks posed by chemicals, including alloys and metals, are identified and proven safe for humans and the environment. Therefore, differences in bioaccessibility in terms of released metals in synthetic biological fluids (different pH (1.5-7.4) and composition) that are relevant for different human exposure routes (inhalation, ingestion, and dermal contact) have been assessed for powder particles of an alloy containing high levels of nickel (Inconel 718, 57 wt% nickel). This powder is compared with the bioaccessibility of two nickel-containing stainless steel powders (AISI 316L, 10-12% nickel) and with powders representing their main pure alloy constituents: two nickel metal powders (100% nickel), two iron metal powders and two chromium metal powders. X-ray photoelectron spectroscopy, microscopy, light scattering, and nitrogen absorption were employed for the particle and surface oxide characterization. Atomic absorption spectroscopy was used to quantify released amounts of metals in solution. Cytotoxicity (Alamar blue assay) and DNA damage (comet assay) of the Inconel powder were assessed following exposure of the human lung cell line A549, as well as its ability to generate reactive oxygen species (DCFH-DA assay). Despite its high nickel content, the Inconel alloy powder did not release any significant amounts of metals and did not induce any toxic response. It is concluded, that this is related to the high surface passivity of the Inconel powder governed by its chromium-rich surface oxide. Read-across from the pure metal constituents is hence not recommended either for this or any other passive alloy.

  15. 粉末冶金法制备多孔U-10%Mo合金及其微观组织结构分析%Preparation of Porous U-10%Mo Alloy by Powder Metallurgy and Its Microstructure Characterization

    Institute of Scientific and Technical Information of China (English)

    贾建平; 王志刚; 陈淼; 王锡胜; 张鹏程; 武胜

    2013-01-01

    U-Mo alloy is one of candidates of metallic fuel for advanced nuclear reactor due to its good irradiation behavior. Reasonably analysis suggests that the irradiation swell of U-Mo alloy can be decreased by introducing homogenously distributed voids, because they can accommodate gaseous fission products. The process of preparing low density U-Mo alloy by powder metallurgy was described, including preparing low density bulk materials by pressing and vacuum sintering. A serial of U-10% Mo alloys with different densities were obtained and the microstructure was analyzed by optical microscopy (OM) and scanning electron microscopy (SEM). It is proved that the density of sample increases with sinister time under 1 100 ℃. The void ratio can be controlled by adjusting sinister process conveniently.%U-Mo合金是近期广受关注的金属型核燃料材料之一,它具有良好的抗辐照肿胀能力.分析认为,若能在U-Mo合金中加入一定的孔隙,可起到容纳裂变气体以进一步提高其抗辐照肿胀性能的作用.本文利用冷等静压-真空固相烧结的粉末冶金方法制备低密度U-10%Mo合金材料,探索了烧结工艺对产品密度的影响规律.实验得到了一系列不同孔隙度的U-Mo合金材料,利用金相显微镜(OM)、扫描电子显微镜(SEM)对其微观结构进行了表征.结果证明,样品在1 100℃下烧结时密度随烧结时间的延长而提高,因此可通过改变烧结时间控制其孔隙率.

  16. Zeeman- and Paschen-Back-effect of the hyperfine structure of the sodium D 1-line

    Science.gov (United States)

    Windholz, L.

    1985-06-01

    Using high-resolution laser-atomic-beam spectroscopy, Zeeman- and Paschen-Back-effects of the hyperfine structure of the sodium resonance lines were studied in fields up to app. 280 G. The results derived for the D 1-line are given in graphical form and show clearly the change in the coupling of J and I of the upper level.

  17. Hyperfine field and magnetic structure in the B phase of CeCoIn5

    Energy Technology Data Exchange (ETDEWEB)

    Graf, Matthias J [Los Alamos National Laboratory; Curro, Nicholas J [UNIV OF CAL; Young, Ben - Li [NATIONAL CHIAO UNIV; Urbano, Ricardo R [FL STATE UNIV

    2009-01-01

    We re-analyze Nuclear Magnetic Resonance (NMR) spectra observed at low temperatures and high magnetic fields in the field-induced B-phase of CeCoIn{sub 5}. The NMR spectra are consistent with incommensurate antiferromagnetic order of the Ce magnetic moments. However, we find that the spectra of the In(2) sites depend critically on the direction of the ordered moments, the ordering wavevector and the symmetry of the hyperfine coupling to the Ce spins. Assuming isotropic hyperfine coupling, the NMR spectra observed for H {parallel} [100] are consistent with magnetic order with wavevector Q = {pi}(1+{delta}/a, 1/a, 1/c) and Ce moments ordered antiferromagnetically along the [100] direction in real space. If the hyperfine coupling has dipolar symmetry, then the NMR spectra require Ce moments along the [001] direction. The dipolar scenario is also consistent with recent neutron scattering measurements that find an ordered moment of 0.15{micro}{sub B} along [001] and Q{sub n} = {pi}(1+{delta}/a, 1+{delta}c, 1/c) with incommensuration {delta} = 0.12 for field H {parallel} [1{bar 1}0]. Using these parameters, we find that the hyperfine field is consistent with both experiments. We speculate that the B phase of CeCoIn{sub 5} represents an intrinsic phase of modulated superconductivity and antiferromagnetism that can only emerge in a highly clean system.

  18. First-principles calculations of Moessbauer hyperfine parameters for solids and large molecules

    Energy Technology Data Exchange (ETDEWEB)

    Guenzburger, Diana [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil); Ellis, D.E. [Northwestern Univ., Evanston, IL (United States). Dept. of Physics; Zeng, Z. [Academia Sinica, Hefei, AH (China). Inst. of Solid-State Physics

    1997-10-01

    Electronic structure calculations based on Density Functional theory were performed for solids and large molecules. The solids were represented by clusters of 60-100 atoms embedded in the potential of the external crystal. Magnetic moments and Moessbauer hyperfine parameters were derived. (author) 22 refs., 8 figs., 1 tab.

  19. Observation of HCN hyperfine line anomalies towards low- and high-mass star-forming cores

    CERN Document Server

    Loughnane, R M; Thompson, M A; Lo, N; O'Dwyer, B; Cunningham, M R; 10.1111/j.1365-2966.2011.20121.x

    2013-01-01

    HCN is becoming a popular choice of molecule for studying star formation in both low- and high-mass regions and for other astrophysical sources from comets to high-redshift galaxies. However, a major and often overlooked difficulty with HCN is that it can exhibit non-local thermodynamic equilibrium (non-LTE) behaviour in its hyperfine line structure. Individual hyperfine lines can be strongly boosted or suppressed. In low-mass star-forming cloud observations, this could possibly lead to large errors in the calculation of opacity and excitation temperature, while in massive star-forming clouds, where the hyperfine lines are blended due to turbulent broadening, errors will arise in infall measurements that are based on the separation of the peaks in a self-absorbed profile. The underlying line shape cannot be known for certain if hyperfine anomalies are present. We present a first observational investigation of these anomalies across a range of conditions and transitions by carrying out a survey of low-mass sta...

  20. Spectroscopy Apparatus for the Measurement of The Hyperfine Structure of Antihydrogen

    CERN Document Server

    Malbrunot, C; Diermaier, M; Dilaver, N; Friedreich, S; Kolbinger, B; Lehner, S; Lundmark, R; Massiczek, O; Radics, B; Sauerzopf, C; Simon, M; Widmann, E; Wolf, M; Wunschek, B; Zmeskal, J

    2014-01-01

    The ASACUSA CUSP collaboration at the Antiproton Decelerator (AD) of CERN is planning to measure the ground-state hyperfine splitting of antihydrogen using an atomic spectroscopy beamline. We describe here the latest developments on the spectroscopy apparatus developed to be coupled to the antihydrogen production setup (CUSP).