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Sample records for nanophase fe alloys

  1. Nanophase Nickel-Zirconium Alloys for Fuel Cells

    NASA Technical Reports Server (NTRS)

    Narayanan, Sekharipuram; Whitacre, jay; Valdez, Thomas

    2008-01-01

    Nanophase nickel-zirconium alloys have been investigated for use as electrically conductive coatings and catalyst supports in fuel cells. Heretofore, noble metals have been used because they resist corrosion in the harsh, acidic fuel cell interior environments. However, the high cost of noble metals has prompted a search for less-costly substitutes. Nickel-zirconium alloys belong to a class of base metal alloys formed from transition elements of widely different d-electron configurations. These alloys generally exhibit unique physical, chemical, and metallurgical properties that can include corrosion resistance. Inasmuch as corrosion is accelerated by free-energy differences between bulk material and grain boundaries, it was conjectured that amorphous (glassy) and nanophase forms of these alloys could offer the desired corrosion resistance. For experiments to test the conjecture, thin alloy films containing various proportions of nickel and zirconium were deposited by magnetron and radiofrequency co-sputtering of nickel and zirconium. The results of x-ray diffraction studies of the deposited films suggested that the films had a nanophase and nearly amorphous character.

  2. Unique Properties of Lunar Impact Glass: Nanophase Metallic Fe Synthesis

    SciTech Connect

    Liu, Yang; Taylor, Lawrence A.; Thompson, James R; Schnare, Darren W.; Park, Jae-Sung

    2007-01-01

    Lunar regolith contains important materials that can be used for in-situ resource utilization (ISRU) on the Moon, thereby providing for substantial economic savings for development of a manned base. However, virtually all activities on the Moon will be affected by the deleterious effects of the adhering, abrasive, and pervasive nature of lunar dust (<20 {micro}m portion of regolith, which constitutes {approx}20 wt% of the soil). In addition, the major impact-produced glass in the lunar soil, especially agglutinitic glass (60-80 vol% of the dust), contains unique nanometer-sized metallic Fe (np-Fe{sup 0}), which may pose severe pulmonary problems for humans. The presence of the np-Fe0 imparts considerable magnetic susceptibility to the fine portion of the lunar soil, and dust mitigation techniques can be designed using these magnetic properties. The limited availability of Apollo lunar soils for ISRU research has made it necessary to produce materials that simulate this unique np-Fe{sup 0} property, for testing different dust mitigation methods using electromagnetic fields, and for toxicity studies of human respiratory and pulmonary systems, and for microwave treatment of lunar soil to produce paved roads, etc. A method for synthesizing np-Fe{sup 0} in an amorphous silica matrix is presented here. This type of specific simulant can be used as an additive to other existing lunar soil simulants.

  3. Nanophase stability in a granular FeRh-Cu system

    NASA Astrophysics Data System (ADS)

    Barua, Radhika; Jimenez-Villacorta, Felix; Shield, J. E.; Heiman, D.; Lewis, L. H.

    2013-05-01

    A granular system of FeRh-based nanoprecipitates (˜10-15 nm diameter) embedded in a rapidly solidified copper ribbon matrix was found to transit from a metastable tetragonal L10 (AuCu-1-type) structure to a stable B2 (CsCl-type) structure upon annealing-induced coarsening to ˜94 nm. The hysteretic magnetic transition observed at ˜100 K develops a gradual broadening that accompanies the L10 → B2 crystal structure transition. It is proposed that the Cu matrix influences the structural and magnetic properties of the FeRh-based nanoparticles through interfacial strain and chemical effects. These results emphasize the sensitivity of the magnetostructural response of FeRh to changes in the nanostructural scale, and provide pathways for tailoring the transition.

  4. Average widths of grain boundaries in nanophase alloys synthesized by mechanical attrition

    NASA Astrophysics Data System (ADS)

    Fultz, B.; Kuwano, H.; Ouyang, H.

    1995-04-01

    Many binary ferrous alloys were synthesized by mechanical attrition in a high-energy ball mill. X-ray diffractometry and transmission electron microscopy were used to measure grain sizes, which were as small as a few nanometers in several alloys. The nanocrystalline alloys showed new features in their Mössbauer spectra, which we associated with 57Fe atoms at and near grain boundaries. The experimental data on the fraction of 57Fe atoms at and near grain boundaries were correlated to the measured grain sizes to obtain an average width of the grain boundaries. The average grain-boundary widths of the fcc alloys Fe-Mn and Ni-Fe were approximately 0.5 nm, but the average widths of grain boundaries in the bcc alloys Cr-Fe, Mo-Fe, and Fe-Ti were somewhat larger than 1 nm.

  5. Nanophasic biodegradation enhances the durability and biocompatibility of magnesium alloys for the next-generation vascular stents

    NASA Astrophysics Data System (ADS)

    Mao, Lin; Shen, Li; Niu, Jialin; Zhang, Jian; Ding, Wenjiang; Wu, Yu; Fan, Rong; Yuan, Guangyin

    2013-09-01

    Biodegradable metal alloys emerge as a new class of biomaterials for tissue engineering and medical devices such as cardiovascular stents. Deploying biodegradable materials to fabricate stents not only obviates a second surgical intervention for implant removal but also circumvents the long-term foreign body effect of permanent implants. However, these materials for stents suffer from an un-controlled degradation rate, acute toxic responses, and rapid structural failure presumably due to a non-uniform, fast corrosion process. Here we report that highly uniform, nanophasic degradation is achieved in a new Mg alloy with unique interstitial alloying composition as the nominal formula Mg-2.5Nd-0.2Zn-0.4Zr (wt%, hereafter, denoted as JDBM). This material exhibits highly homogeneous nanophasic biodegradation patterns as compared to other biodegradable metal alloy materials. Consequently it has significantly reduced degradation rate determined by electrochemical characterization. The in vitro cytotoxicity test using human vascular endothelial cells indicates excellent biocompatibility and potentially minimal toxic effect on arterial vessel walls. Finally, we fabricated a cardiovascular stent using JDBM and performed in vivo long-term assessment via implantation of this stent in an animal model. The results confirmed the reduced degradation rate in vivo, excellent tissue compatibility and long-term structural and mechanical durability. Thus, this new Mg-alloy with highly uniform nanophasic biodegradation represents a major breakthrough in the field and a promising material for manufacturing the next generation biodegradable vascular stents.

  6. Location of nanophase Fe-oxides in palagonitic soils: Implication for Martian pigments

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Morris, R. V.; Ming, D. W.; Lauer, H. V., Jr.

    1992-01-01

    Palagonitic materials from Mauna Kea, Hawaii, were identified as Mars analogs based on their spectral and magnetic properties. These materials probably resulted from hydrothermal alteration during eruption of the volcano and/or from weathering under ambient conditions. The reflectance spectra of the Mars surface obtained by Earth-based telescopes and the reflectance spectra of analogs obtained in the laboratory show features due to electronic transitions of Fe(III) in oxide particles that range in size from nanometer (nanophase) to micrometer sized or larger. The presence of Fe(III) suggests oxidizing conditions during the alteration process in Mars that may have occurred in the past or during a slow ongoing process. Two naturally altered basaltic samples from Hawaii (HWMK12 and HWMK13) and a laboratory-altered (PH-13-DCGT2) basaltic glass similar in elemental composition to the above two samples was examined. All three samples exhibited spectral characteristics similar to martian bright-region spectra. Chemical and mineralogical changes occurring at the surface of these basalts were studied in order to understand the basis for their Mars-like properties. The spectral properties of the three samples were examined after the removal of Fe oxides by chemical extractants.

  7. Stabilisation of Fe2O3-rich Perovskite Nanophase in Epitaxial Rare-earth Doped BiFeO3 Films

    PubMed Central

    Zhang, Huairuo; Reaney, Ian M.; Marincel, Daniel M.; Trolier-McKinstry, Susan; Ramasse, Quentin M.; MacLaren, Ian; Findlay, Scott D.; Fraleigh, Robert D.; Ross, Ian M.; Hu, Shunbo; Ren, Wei; Mark Rainforth, W.

    2015-01-01

    Researchers have demonstrated that BiFeO3 exhibits ferroelectric hysteresis but none have shown a strong ferromagnetic response in either bulk or thin film without significant structural or compositional modification. When remanent magnetisations are observed in BiFeO3 based thin films, iron oxide second phases are often detected. Using aberration-corrected scanning transmission electron microscopy, atomic resolution electron energy loss spectrum-mapping and quantitative energy dispersive X-ray spectroscopy analysis, we reveal the existence of a new Fe2O3-rich perovskite nanophase, with an approximate formula (Fe0.6Bi0.25Nd0.15)3+ Fe3+O3, formed within epitaxial Ti and Nd doped BiFeO3 perovskite films grown by pulsed laser deposition. The incorporation of Nd and Bi ions on the A-site and coherent growth with the matrix stabilise the Fe2O3-rich perovskite phase and preliminary density functional theory calculations suggest that it should have a ferrimagnetic response. Perovskite-structured Fe2O3 has been reported previously but never conclusively proven when fabricated at high-pressure high-temperature. This work suggests the incorporation of large A-site species may help stabilise perovskite-structured Fe2O3. This finding is therefore significant not only to the thin film but also to the high-pressure community. PMID:26272264

  8. Stabilisation of Fe2O3-rich Perovskite Nanophase in Epitaxial Rare-earth Doped BiFeO3 Films.

    PubMed

    Zhang, Huairuo; Reaney, Ian M; Marincel, Daniel M; Trolier-McKinstry, Susan; Ramasse, Quentin M; MacLaren, Ian; Findlay, Scott D; Fraleigh, Robert D; Ross, Ian M; Hu, Shunbo; Ren, Wei; Rainforth, W Mark

    2015-08-14

    Researchers have demonstrated that BiFeO3 exhibits ferroelectric hysteresis but none have shown a strong ferromagnetic response in either bulk or thin film without significant structural or compositional modification. When remanent magnetisations are observed in BiFeO3 based thin films, iron oxide second phases are often detected. Using aberration-corrected scanning transmission electron microscopy, atomic resolution electron energy loss spectrum-mapping and quantitative energy dispersive X-ray spectroscopy analysis, we reveal the existence of a new Fe2O3-rich perovskite nanophase, with an approximate formula (Fe0.6Bi0.25Nd0.15)(3+) Fe(3+)O3, formed within epitaxial Ti and Nd doped BiFeO3 perovskite films grown by pulsed laser deposition. The incorporation of Nd and Bi ions on the A-site and coherent growth with the matrix stabilise the Fe2O3-rich perovskite phase and preliminary density functional theory calculations suggest that it should have a ferrimagnetic response. Perovskite-structured Fe2O3 has been reported previously but never conclusively proven when fabricated at high-pressure high-temperature. This work suggests the incorporation of large A-site species may help stabilise perovskite-structured Fe2O3. This finding is therefore significant not only to the thin film but also to the high-pressure community.

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

    NASA Astrophysics Data System (ADS)

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

    2013-07-01

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

  10. Epitaxial Stabilization of Ferromagnetism in the Nanophase of FeGe

    SciTech Connect

    Zeng, Changgan; Varela del Arco, Maria; Kent, P. R. C.; Eisenbach, Markus; Stocks, George Malcolm; Torija Juana, Maria Asuncion; Shen, Jian; Weitering, Harm H

    2006-01-01

    Epitaxial nanocrystals of FeGe have been stabilized on Ge(111). The nanocrystals assume a quasi-one-dimensional shape as they grow exclusively along the (110) direction of the Ge(111) substrate, culminating in a compressed monoclinic modification of FeGe. Whereas monoclinic FeGe is antiferromagnetic in the bulk, the nanowires are surprisingly strong ferromagnets below ~200 K with an average magnetic moment of 0.8?? per Fe atom. Density functional calculations indicate an unusual stabilization mechanism for the observed in the bulk while increased p-d hybridization suppresses the magnetic moments and stabilizes ferromagnetism.

  11. Fe-Zr-Nd-Y-B permanent magnet derived from crystallization of bulk amorphous alloy

    NASA Astrophysics Data System (ADS)

    Tan, Xiaohua; Xu, Hui; Bai, Qin; Dong, Yuanda

    2007-12-01

    The microstructure and magnetic properties of Nd2Fe14B/(Fe3B,α-Fe) nanocomposite magnet derived form crystallization of bulk amorphous Fe68Zr2Y4B21Nd5 alloy, which was prepared by copper mold casting, have been investigated. The obtaining maximum values of Ms, Mr, Hci, and (BH)max annealed at 963K for Fe68Zr2Nd5Y4B21 alloy are 86Am2/kg, 49Am2/kg, 380kA/m, and 43kJ/m3, respectively. δM plot, high resolution transmission electron microscopy observation, and three-dimensional atom probe technique clarified that the hard magnetic behavior is due to the exchange coupling between soft and hard magnetic nanophases.

  12. Epitaxial Stabilization of Ferromagnetism in the Nanophase of FeGe

    SciTech Connect

    Zeng, C.; Kent, P. R. C.; Varela del Arco, Maria; Eisenbach, Markus; Stocks, George Malcolm; Torija Juana, Maria Asuncion; Shen, Jian; Weitering, Harm H

    2006-01-01

    Epitaxial nanocrystals of FeGe have been stabilized on Ge(111). The nanocrystals assume a quasi-one-dimensional shape as they grow exclusively along the {l_brace}1{ovr 1}0{r_brace} direction of the Ge(111) substrate, culminating in a compressed monoclinic modification of FeGe. Whereas monoclinic FeGe is antiferromagnetic in the bulk, the nanowires are surprisingly strong ferromagnets below {approx}200 K with an average magnetic moment of 0.8{mu}{sub B} per Fe atom. Density functional calculations indicate an unusual stabilization mechanism for the observed ferromagnetism: lattice compression destabilizes the antiferromagnetic Peierls-like ground state observed in the bulk while increased p-d hybridization suppresses the magnetic moments and stabilizes ferromagnetism.

  13. Effect of processing temperature on the properties of nanophase Fe-substituted Hydroxyapatite

    NASA Astrophysics Data System (ADS)

    Kathriarachchi, Vindu Wathsala

    The effect of processing temperature on the crystal structure properties of the Fe-substituted Hydroxyapatite (Fe-HAp) was studied by using the Rietveld refinement method of powder x-ray (XRD) and neutron diffraction (NPD) patterns. Superconducting QUantum Interference Device (SQUID) magnetometry, transmission electron microscopy (TEM) and x-ray fluorescence spectroscopy (XRF) were used to study the magnetic properties, particle morphology and chemical composition of the prepared samples. Two sets of samples of chemical formula Ca5- xFex(PO4)3OH were prepared with x = 0, 0.05, 0.1, 0.2 and 0.3 by using processing temperatures of 37°C and 80°C, following a two-step co-precipitation method. A single phase HAp was identified in samples with x = 0 and 0.05. Processing temperature affects the type and percentage of secondary phases: hematite was detected in samples prepared at 37°C with x ≥ 0.1, hematite and maghemite were detected in samples prepared at 80°C with x = 0.2 and 0.3. Rietveld refinements of NPD and XRD patterns showed that the a lattice constants are greater in Fe-substituted samples prepared at 37°C, whereas the c lattice constants are greater in the 80°C samples for x ≥ 0.05. Fe preferentially substitutes at the Ca2 site in the 80°C samples, whereas Ca1 is the preferred substitution site in the 37°C samples. Fe substitution results to a decrease of the lattice constants at both preparation temperatures. The ratios Fe/(Fe + Ca) of the refined atomic fractions of the samples prepared at 80°C are greater than those of the 37°C samples. Further, more secondary phases form in samples prepared at 37°C compared to 80°C samples. The magnetic measurements reveal that pure HAp is diamagnetic, whereas samples with x = 0.05 and 0.1 are paramagnetic. Samples with x = 0.3 showed superparamagnetic behavior based on ZFC and FC measurements. Similar hysteresis loops in samples x = 0.2 and 0.3 indicate that the samples with x = 0.2 may show

  14. Micromagnetic simulation of ferrimagnetic TbFeCo films with exchange coupled nanophases

    NASA Astrophysics Data System (ADS)

    Ma, Chung T.; Li, Xiaopu; Poon, S. Joseph

    2016-11-01

    Amorphous ferrimagnetic TbFeCo thin films are found to exhibit exchange bias effect near the compensation temperature by magnetic hysteresis loop measurement. The observed exchange anisotropy is believed to originate from the exchange interaction between the two nanoscale amorphous phases distributed within the films. Here, we present a computational model of phase-separated TbFeCo using micromagnetic simulation. Two types of cells with different Tb concentration are distributed within the simulated space to obtain a heterogeneous structure consisting of two nanoscale amorphous phases. Each cell contains separated Tb and FeCo components, forming two antiferromagnetically coupled sublattices. Using this model, we are able to show the existence of exchange bias effect, and the shift in hysteresis loops is in agreement with experiment. The micromagnetic model developed herein for a heterogeneous magnetic material may also account for some recent measurements of exchange bias effect in crystalline films.

  15. Identification of ε-Fe2O3 nano-phase in borate glasses doped with Fe and Gd

    NASA Astrophysics Data System (ADS)

    Ivanova, O. S.; Ivantsov, R. D.; Edelman, I. S.; Petrakovskaja, E. A.; Velikanov, D. A.; Zubavichus, Y. V.; Zaikovskii, V. I.; Stepanov, S. A.

    2016-03-01

    A new type of magnetic nanoparticles was revealed in borate glasses co-doped with low contents of iron and gadolinium. Structure and magnetic properties of the particles differ essentially from that of the α-Fe2O3, γ-Fe2O3, or Fe3O4 nanoparticles which were detected earlier in similar glass matrices. Transmission electron microscopy including STEM-HAADF and EDX, synchrotron radiation-based XRD, static magnetic measurements, magnetic circular dichroism, and electron magnetic resonance studies allow referring the nanoparticles to the iron oxide phase-ε-Fe2O3. Analysis of the data set has shown that it is Gd atoms that govern the process of nanoparticles' nucleation and its incorporation into the particles in different proportions can be used to adjust their magnetic and magneto-optical characteristics.

  16. Fe-based long range ordered alloys

    DOEpatents

    Liu, C.T.

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

  17. Fe-based long range ordered alloys

    DOEpatents

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

    1980-01-01

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

  18. Magnetostriction in a Co-30%Fe alloy

    SciTech Connect

    Chen, L.H.; Mavoori, H.; Klemmer, T.; Jin, S.

    1999-09-01

    The authors have studied the magnetostriction and magnetic properties of a deformed and annealed Co-30%Fe alloy. The cold-rolled and annealed (at 820 C for 40 min) sample exhibits a substantial magnetostriction of {approximately}110 x 10{sup {minus}6} at a practical, low field of {approximately}100 Oe, while only {approximately}10 x 10{sup {minus}6} for the same applied field is obtained for the as-cold-rolled sample. The saturation magnetostriction of the annealed Co-30%Fe alloy was {approximately}140 x 10{sup {minus}6}, which is significantly affected by the cold-rolling and annealing processes. This drastic dependence of the magnetostriction behavior on the alloy processing is believed to be a result of the microstructure and residual stress changes brought about by the heat treatment processing.

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

    PubMed

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

    2006-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  1. Ferromagnetism of Fe3Sn and Alloys

    PubMed Central

    Sales, Brian C.; Saparov, Bayrammurad; McGuire, Michael A.; Singh, David J.; Parker, David S.

    2014-01-01

    Hexagonal Fe3Sn has many of the desirable properties for a new permanent magnet phase with a Curie temperature of 725 K, a saturation moment of 1.18 MA/m. and anisotropy energy, K1 of 1.8 MJ/m3. However, contrary to earlier experimental reports, we found both experimentally and theoretically that the easy magnetic axis lies in the hexagonal plane, which is undesirable for a permanent magnet material. One possibility for changing the easy axis direction is through alloying. We used first principles calculations to investigate the effect of elemental substitutions. The calculations showed that substitution on the Sn site has the potential to switch the easy axis direction. However, transition metal substitutions with Co or Mn do not have this effect. We attempted synthesis of a number of these alloys and found results in accord with the theoretical predictions for those that were formed. However, the alloys that could be readily made all showed an in-plane easy axis. The electronic structure of Fe3Sn is reported, as are some are magnetic and structural properties for the Fe3Sn2, and Fe5Sn3 compounds, which could be prepared as mm-sized single crystals. PMID:25387850

  2. Ferromagnetism of Fe3Sn and alloys

    DOE PAGES

    Sales, Brian C.; Saparov, Bayrammurad; McGuire, Michael A.; ...

    2014-11-12

    Hexagonal Fe3Sn has many of the desirable properties for a new permanent magnet phase with a Curie temperature of 725 K, a saturation moment of 1.18 MA/m. and anisotropy energy, K1 of 1.8 MJ/m3. However, contrary to earlier experimental reports, we found both experimentally and theoretically that the easy magnetic axis lies in the hexagonal plane, which is undesirable for a permanent magnet material. One possibility for changing the easy axis direction is through alloying. We used first principles calculations to investigate the effect of elemental substitutions. The calculations showed that substitution on the Sn site has the potential tomore » switch the easy axis direction. Transition metal substitutions with Co or Mn do not have this effect. We attempted synthesis of a number of these alloys and found results in accord with the theoretical predictions for those that were formed. However, the alloys that could be readily made all showed an in-plane easy axis. The electronic structure of Fe3Sn is reported, as are some are magnetic and structural properties for the Fe3Sn2, and Fe5Sn3 compounds, which could be prepared as mm-sized single crystals.« less

  3. Magnetic properties of metastable Fe Pd alloys by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Yabe, Hiromasa; O'Handley, Robert C.; Kuji, Toshiro

    2007-03-01

    Metastable Fe-Pd powder samples with various Pd content were synthesized by mechanical alloying. Their fundamental properties, i.e., structure, magnetization and coercive fore are discussed. The saturation magnetizations of the metastable Fe-Pd powders gradually decreases with increasing Pd content. The coercive forces observed in as-milled samples are all less than 40 Oe. However, some of the heat-treated samples, notably, Pd content around 55 at% with L1 0 structure, shows Hc up to 1589 Oe.

  4. Functionally Graded Nanophase Beryllium/Carbon Composites

    NASA Technical Reports Server (NTRS)

    Choi, Michael K.

    2003-01-01

    Beryllium, beryllium alloys, beryllium carbide, and carbon are the ingredients of a class of nanophase Be/Be2C/C composite materials that can be formulated and functionally graded to suit a variety of applications. In a typical case, such a composite consists of a first layer of either pure beryllium or a beryllium alloy, a second layer of B2C, and a third layer of nanophase sintered carbon derived from fullerenes and nanotubes. The three layers are interconnected through interpenetrating spongelike structures. These Be/Be2C/C composite materials are similar to Co/WC/diamond functionally graded composite materials, except that (1) W and Co are replaced by Be and alloys thereof and (2) diamond is replaced by sintered carbon derived from fullerenes and nanotubes. (Optionally, one could form a Be/Be2C/diamond composite.) Because Be is lighter than W and Co, the present Be/Be2C/C composites weigh less than do the corresponding Co/WC/diamond composites. The nanophase carbon is almost as hard as diamond. WC/Co is the toughest material. It is widely used for drilling, digging, and machining. However, the fact that W is a heavy element (that is, has high atomic mass and mass density) makes W unattractive for applications in which weight is a severe disadvantage. Be is the lightest tough element, but its toughness is less than that of WC/Co alloy. Be strengthened by nanophase carbon is much tougher than pure or alloy Be. The nanophase carbon has an unsurpassed strength-to-weight ratio. The Be/Be2C/C composite materials are especially attractive for terrestrial and aerospace applications in which there are requirements for light weight along with the high strength and toughness of the denser Co/WC/diamond materials. These materials could be incorporated into diverse components, including cutting tools, bearings, rocket nozzles, and shields. Moreover, because Be and C are effective as neutron moderators, Be/Be2C/C composites could be attractive for some nuclear applications.

  5. Characterization of Nanophase Materials

    NASA Astrophysics Data System (ADS)

    Wang, Zhong Lin

    2000-01-01

    Engineering of nanophase materials and devices is of vital interest in electronics, semiconductors and optics, catalysis, ceramics and magnetism. Research associated with nanoparticles has widely spread and diffused into every field of scientific research, forming a trend of nanocrystal engineered materials. The unique properties of nanophase materials are entirely determined by their atomic scale structures, particularly the structures of interfaces and surfaces. Development of nanotechnology involves several steps, of which characterization of nanoparticles is indespensable to understand the behavior and properties of nanoparticles, aiming at implementing nanotechnolgy, controlling their behavior and designing new nanomaterials systems with super performance. The book will focus on structural and property characterization of nanocrystals and their assemblies, with an emphasis on basic physical approach, detailed techniques, data interpretation and applications. Intended readers of this comprehensive reference work are advanced graduate students and researchers in the field, who are specialized in materials chemistry, materials physics and materials science.

  6. Alloying Solid Solution Strengthening of Fe-Ga Alloys: A First-Principle Study

    DTIC Science & Technology

    2006-01-01

    effect from alloying additions of Nb, Mo, V, Cr and Co in cubic solid solution of Fe-Ga alloys. Mayer bond order "BO" values were used to evaluate the...that transition metal Nb achieves the best strengthening effect in Fe-Ga alloys. The solid solution strengthening follows a trend from larger to

  7. Mechanochemical synthesis of nanocrystalline Fe and Fe-B magnetic alloys

    NASA Astrophysics Data System (ADS)

    Mohammadi, Majid; Ghasemi, Ali; Tavoosi, Majid

    2016-12-01

    Mechanochemical synthesis and magnetic characterization of nanocrystalline Fe and Fe-B magnetic alloys was the goal of this study. In this regard, different Fe2O3-B2O3 powder mixtures with sufficient amount of CaH2 were milled in a planetary ball mill in order to produce nanocrystalline Fe, Fe95B5 and Fe85B15 alloys. The produced samples were characterized using X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM). The results showed that, nanocrystalline Fe, Fe95B5 and Fe85B15 alloys can be successfully synthesized by the reduction reaction of Fe2O3 and B2O3 with CaH2 during mechanical alloying. The structure of produced Fe95B5 and Fe85B15 alloys was a combination of Fe and Fe2B phases with average crystallite sizes of about 15 and 10 nm, respectively. The produced nanocrystalline alloys exhibited soft magnetic properties with the coercivity and saturation of magnetization in the range of 170-240 Oe and 9-28 emu/g, respectively. Increasing the boron content has a destructive effect on soft magnetic properties of Fe-B alloys.

  8. Fabric cutting application of FeAl-based alloys

    SciTech Connect

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

    1998-11-01

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

  9. Nanostructurization of Fe-Ni Alloy

    NASA Astrophysics Data System (ADS)

    Danilhenko, Vitaliy E.

    2017-03-01

    Data about an effect of cyclic γ-α-γ martensitic transformations on the structure state of reverted austenite Fe-31.7 wt.% Ni-0.06 wt.% C alloy are presented. The effect of multiple direct γ-α and reverse α-γ martensitic transformations on fragmentation of austenitic grains has been investigated by electron microscopy and X-ray diffraction methods. An ultrafine structure has been formed by nanofragmentation inside the initial austenite grains due to the successive misorientation of their crystal lattice. Austenite was nanofragmented as a result of multiple γ-α-γ martensitic transformations. Slow heating of the nanofragmented alloy at a rate below 2 °C/s results in nanograin refinement of the structure by multiplication of the reverted γ-phase orientations. The conditions of structure refinement up to ultrafine and nanocrystalline levels as a result of both shear and diffusion mechanisms of reverse α-γ transformation are determined.

  10. Research on pulse electrodeposition of Fe-Ni alloy

    SciTech Connect

    Peng, Yongsen; Zhu, Zengwei Ren, Jianhua; Chen, Jiangbo; Han, Taojie

    2014-03-15

    Fe-Ni alloys were fabricated on steel substrates by means of pulse electrodeposition in sulfate solutions. The layers were electrodeposited using different peak current densities, duty cycles and frequencies. Fe contents, microhardnesses and crystalline phases were examined systematically. The Fe content in the deposit decreased and the microhardness increased with increasing duty cycle and peak current density. The pulse frequency had little effect on Fe content but led to a slight decrease in microhardness. X-ray diffraction patterns show that the crystalline phases vary with changes in peak current density and duty cycle but are barely influenced by frequency. When the peak current density or duty cycle is relatively low, crystalline Fe-Ni alloy and pure Fe phases coexist; the pure Fe phases disappear as the peak current density or duty cycle increases. At still larger peak current densities or duty cycles, crystalline Fe-Ni alloy and pure Ni phases coexist.

  11. Lunar dust simulant containing nanophase iron and method for making the same

    NASA Technical Reports Server (NTRS)

    Hung, Chin-cheh (Inventor); McNatt, Jeremiah (Inventor)

    2012-01-01

    A lunar dust simulant containing nanophase iron and a method for making the same. Process (1) comprises a mixture of ferric chloride, fluorinated carbon powder, and glass beads, treating the mixture to produce nanophase iron, wherein the resulting lunar dust simulant contains .alpha.-iron nanoparticles, Fe.sub.2O.sub.3, and Fe.sub.3O.sub.4. Process (2) comprises a mixture of a material of mixed-metal oxides that contain iron and carbon black, treating the mixture to produce nanophase iron, wherein the resulting lunar dust simulant contains .alpha.-iron nanoparticles and Fe.sub.3O.sub.4.

  12. Wear Behavior of Nanostructured Hypoeutectic Fe-B Alloy

    NASA Astrophysics Data System (ADS)

    Fu, Licai; Yang, Jun; Zhou, Lingping; Liu, Weimin

    The wear behavior of nanostructured hypoeutectic Fe94.3B5.7 alloy was investigated in comparison with coarse grained counterpart. The friction coefficient of the Fe94.3B5.7 alloy changed slightly with grain size. While the wear rate decreased as the grain size decreased to nano scale. Both Fe2O3 and Fe2SiO4 oxides were found on the worn surfaces in the nanostructured Fe94.3B5.7 alloy, but only a few oxide films were observed for the coarse grained counterpart. These results suggested that the nanostructured eutectic was conducive to forming oxide films on the worn surface of the Fe94.3B5.7 alloy, and improved the wear resistance.

  13. Ferromagnetism of Fe86Mn14-yCuy alloys

    NASA Astrophysics Data System (ADS)

    França, F.; Paduani, C.; Krause, J. C.; Ardisson, J. D.; Yoshida, M. I.; Schaf, J.

    2007-01-01

    The magnetic properties of disordered Fe86Mn14-yCuy alloys were investigated with several experimental techniques. The results of X-ray diffraction showed that these alloys are single phase with the A2 (BCC) structure. These are ferromagnetic alloys at room temperature, and the Curie temperature decreases with the increase of the Cu content. An abrupt loss of magnetization was observed below TC at a temperature which increases with the reduction of the Mn content in the alloys. The addition of manganese enhances the solubility of copper in iron matrix and retains the BCC structure in iron-rich alloys. The behavior of the magnetization with temperature and its composition dependence indicate that an antiferromagnetic coupling is expected between the Fe and Mn atoms. The magnetic moments of both Fe and Mn atoms are expected to vary strongly with composition in these alloys.

  14. Thermal expansion measurements in Fe-base invar alloys

    NASA Astrophysics Data System (ADS)

    Ono, F.; Kittaka, T.; Maeta, H.

    1983-04-01

    By using the X-ray Bond method, measurements of thermal expansion curves have been made in Fe-Ni and Fe-Pd Invar alloys in the temperature range between 4.2 K and room temperatures. A minimum in the thermal expansion curve was observed for each alloy. This anomaly could be explained by considering the magnetovolume coupling term caused by the longitudinal spin fluctuation and the contribution due to the anharmonic terms in the normal lattice vibration energy. In 34.2 at% Pd-Fe alloy an abnormal increase of the linewidth of the (400) X-ray peak was observed with decreasing temperature from room temperature down to 4.2 K, while in Fe-Ni and Fe-Pt Invar alloys no such increase in linewidth was observed.

  15. Bulk amorphous steels based on Fe alloys

    DOEpatents

    Lu, ZhaoPing; Liu, Chain T.

    2006-05-30

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

  16. Accelerated decarburization of Fe-C metal alloys

    DOEpatents

    Pal, Uday B.; Sadoway, Donald R.

    1997-01-01

    A process for improving the rate of metal production and FeO utilization in a steelmaking process or a process combining iron-making and steelmaking in a single reactor that uses or generates Fe-C metal alloy droplets submerged in an FeO-containing slag. The process involves discharging a charge build-up (electron accumulation) in the slag at the slag-metal alloy interface by means of an electron conductor connected between the metal alloy droplets and a gas at a gas-slag interface, said gas having an oxygen partial pressure of at least about 0.01 atmosphere.

  17. Accelerated decarburization of Fe-C metal alloys

    DOEpatents

    Pal, U.B.; Sadoway, D.R.

    1997-05-27

    A process is described for improving the rate of metal production and FeO utilization in a steelmaking process or a process combining iron-making and steelmaking in a single reactor that uses or generates Fe-C metal alloy droplets submerged in an FeO-containing slag. The process involves discharging a charge build-up (electron accumulation) in the slag at the slag-metal alloy interface by means of an electron conductor connected between the metal alloy droplets and a gas at a gas-slag interface, said gas having an oxygen partial pressure of at least about 0.01 atmosphere. 2 figs.

  18. Magnetic anisotropy of FeGa alloys

    NASA Astrophysics Data System (ADS)

    Rafique, Sadia; Cullen, James R.; Wuttig, Manfred; Cui, Jun

    2004-06-01

    Cubic magnetocrystalline anisotropy constants, K1 and K2, for Fe1-xGax alloys were measured using magnetization curves with x=0.05, 0.125, 0.14, 0.18, and 0.20. Thin circular (110) disks all with <100>, <110>, and <111> in the plane of the disk were used to measure K1 and K2. K1 was also measured with (100) circular disks. K1 for 5 at. % Ga content was found to be larger than that of pure Fe. (All compositions mentioned hereafter are atomic percents.) K1 and K2 both drop gradually up to 18 at. % Ga substitution. Then there is a sharp drop in the magnitude of both constants. K2 was found to be equal to -9K1/4 and the <110> and <111> directions were equally hard magnetically for all compositions considered in this study. Calculation of the anisotropy energy density verifies this result. K1 measured from both (110) and (100) disks was reasonably consistent.

  19. Thermodynamic and Properties of Nanophases

    SciTech Connect

    Wunderlich, Bernhard {nmn}

    2009-01-01

    A large volume of today s research deals with nanophases of various types. The materials engineer, chemist, or physicist, however, when dealing with applications of nanophases is often unaware of the effect of the small size on structure and properties. The smallest nanophases reach the limit of phase definitions by approaching atomic dimensions. There, the required homogeneity of a phase is lost and undue property fluctuations destroy the usefulness of thermodynamic functions. In fact, itwas not expected that a definite nanophasewould exist belowthe size of a microphase.Aneffort ismadein this reviewto identify macrophases, microphases, and nanophases. It is shown that nanophases should contain no bulk matter as defined by macrophases and also found in microphases. The structure and properties of nanophases, thus, must be different from macrophases and microphases. These changes may include different crystal and amorphous structures, and phase transitions of higher or of lower temperature. The phase properties are changing continuously when going from one surface to the opposite one. The discussion makes use of results from structure determination, calorimetry, molecular motion evaluations, and molecular dynamics simulations.

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

    SciTech Connect

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

    1997-12-01

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

  1. Microstructure and magnetic properties of mechanically alloyed FeSiBAlNi (Nb) high entropy alloys

    NASA Astrophysics Data System (ADS)

    Wang, Jian; Zheng, Zhou; Xu, Jing; Wang, Yan

    2014-04-01

    In this paper, the effects of milling duration and composition on the microstructure and magnetic properties of equi-atomic FeSiBAlNi and FeSiBAlNiNb high entropy alloys during mechanical alloying have been investigated using X-ray diffraction, differential scanning calorimetry, scanning electron microscopy, transmission electron microscopy and alternating gradient magnetometry. The amorphous high entropy alloys have been successfully fabricated using the mechanical alloying method. The results show that the Nb addition prolongs the milling time for the formation of the fully FeSiBAlNi amorphous phase and decreases the glass forming ability. However, FeSiBAlNiNb amorphous high entropy alloy has the higher thermal stability and heat resisting properties. Moreover, the as-milled FeSiBAlNi(Nb) powders are soft-magnetic materials indicated by their low coercivity. The saturation magnetization of the as-milled FeSiBAlNi(Nb) powders decreases with prolonging of the milling time and shows the lowest value when the amorphous high entropy alloys are formed. It suggests that the as-milled products with solid solution phases show the better soft-magnetic properties than those with fully amorphous phases. The Nb addition does not improve the soft-magnetic properties of the FeSiBAlNi high entropy alloys. Rather, both amorphous high entropy alloys have similar soft-magnetic properties after a long milling time.

  2. Insulating 'nanocables': Invar Fe Ni alloy nanorods inside BN nanotubes

    NASA Astrophysics Data System (ADS)

    Bando, Y.; Ogawa, K.; Golberg, D.

    2001-10-01

    Here we present the results on synthesis, structural and chemical analysis of insulating boron nitride (BN) nanotubes (NTs) which have been filled with conducting Invar Fe-Ni alloy (˜60 at.% Fe; ˜40 at.% Ni) nanorods. The result was accomplished by a two-step process: (i) carbon (C) NTs containing Invar alloy nanoparticles placed at the tube tips were synthesized by plasma-assisted chemical vapor deposition (CVD) on an Invar Fe-Ni alloy substrate; and (ii) the material was heated to the melting point of the alloy (1723 K) in a flow of B 2O 3 and N 2 gases and held for 30 min. During this second stage, simultaneous filling of NTs with the Fe-Ni melt through capillarity and chemical modification of C tubular shells to form BN tubules occurred.

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

    PubMed

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

    2013-03-01

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

  4. Large magnetostriction in directionally solidified FeGa and FeGaAl alloys

    NASA Astrophysics Data System (ADS)

    Srisukhumbowornchai, N.; Guruswamy, S.

    2001-12-01

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

  5. Alloy development and processing of FeAl: An overview

    SciTech Connect

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

    1997-03-01

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

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

    DOE PAGES

    Terrani, Kurt A.; Dryepondt, Sebastien N.; Pint, Bruce A.; ...

    2015-12-17

    Burst behavior of austenitic and ferritic Fe-based alloy tubes has been examined under a simulated large break loss of coolant accident. Specifically, type 304 stainless steel (304SS) and oxidation resistant FeCrAl tubes were studied alongside Zircaloy-2 and Zircaloy-4 that are considered reference fuel cladding materials. Following the burst test, characterization of the cladding materials was carried out to gain insights regarding the integral burst behavior. Given the widespread availability of a comprehensive set of thermo-mechanical data at elevated temperatures for 304SS, a modeling framework was implemented to simulate the various processes that affect burst behavior in this Fe-based alloy. Themore » most important conclusion is that cladding ballooning due to creep is negligible for Fe-based alloys. Thus, unlike Zr-based alloys, cladding cross-sectional area remains largely unchanged up to the point of burst. Furthermore, for a given rod internal pressure, the temperature onset of burst in Fe-based alloys appears to be simply a function of the alloy's ultimate tensile strength, particularly at high rod internal pressures.« less

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

    SciTech Connect

    Terrani, Kurt A.; Dryepondt, Sebastien N.; Pint, Bruce A.; Massey, Caleb P.

    2015-12-17

    Burst behavior of austenitic and ferritic Fe-based alloy tubes has been examined under a simulated large break loss of coolant accident. Specifically, type 304 stainless steel (304SS) and oxidation resistant FeCrAl tubes were studied alongside Zircaloy-2 and Zircaloy-4 that are considered reference fuel cladding materials. Following the burst test, characterization of the cladding materials was carried out to gain insights regarding the integral burst behavior. Given the widespread availability of a comprehensive set of thermo-mechanical data at elevated temperatures for 304SS, a modeling framework was implemented to simulate the various processes that affect burst behavior in this Fe-based alloy. The most important conclusion is that cladding ballooning due to creep is negligible for Fe-based alloys. Thus, unlike Zr-based alloys, cladding cross-sectional area remains largely unchanged up to the point of burst. Furthermore, for a given rod internal pressure, the temperature onset of burst in Fe-based alloys appears to be simply a function of the alloy's ultimate tensile strength, particularly at high rod internal pressures.

  8. Tough cryogenic alloys from the Fe-Mn and Fe-Mn-Cr systems

    NASA Technical Reports Server (NTRS)

    Schanfein, M. J.; Zackay, V. F.; Morris, J. W., Jr.

    1974-01-01

    By adjusting composition, metastable gamma (austenite) and epsilon (hexagonal) martensite may be retained in Fe-Mn and Fe-Mn-Cr alloys and used to impact toughness through the TRIP mechanism. The resulting alloys have excellent toughness at cryogenic temperatures. The best alloys obtained to date are: Fe-20Mn, with sigma (sub y) = 79ksi and K sub IC = 275ksi square root of (in) at 77 K, and Fc-16Mn-8Cr, with sigma sub y = 85ksi and K sub IC = 72ksi square root of (in) at 77 K.

  9. Mold filling and microhardness of 1% Fe titanium alloys.

    PubMed

    Sato, Hideki; Komatsu, Masashi; Miller, Barbara; Shimizu, Hiroshi; Fujii, Hideki; Okabe, Toru

    2004-06-01

    We examined the mold filling capacity and microhardness of two industrial 1% Fe titanium alloys: Super-TIX800 (Nippon Steel Corp.) (Fe: 0.910%, O: 0.370%, N: 0.005%) and Super-TIX800N (Nippon Steel Corp.) (Fe: 0.960%, O: 0.300%, N: 0.041%). Two wedge-shaped acrylic patterns (with 30 degrees or 15 degrees angles) were prepared. Each alloy was cast in a centrifugal casting machine. Mold filling was evaluated as the missing length between the tip of the casting and the theoretical tip. Vickers hardness of the edge of the castings was also determined. For both angles tested, there were no significant differences (p>0.05) in mold filling among these alloys and the control (CP Ti). The results of testing the microhardness near the cast surfaces indicated that the hardened reaction layers on these alloys were thinner at the edge compared to CP Ti.

  10. Overview of the development of FeAl intermetallic alloys

    SciTech Connect

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

    1995-09-01

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

  11. Ductile Fe83C17 Alloys of Ultrafine Networklike Microstructure

    NASA Astrophysics Data System (ADS)

    Ho, C. M.; Leung, C. C.; Yip, Y. L.; Mok, S. W.; Kui, H. W.

    2010-12-01

    Fe83C17 alloy melt can be cast readily into white cast iron. It is brittle, with a compressive strength of ~1300 MPa. By a fluxing technique, a Fe83C17 melt can be quenched into a crystalline solid of ultrafine networklike microstructure, with a hardness value of ~536 HV, a yield strength of ~2000 MPa, and a strain to failure of about 18 pct. In particular, a cube made of Fe83C17 network alloy can be compressed to a disk.

  12. Nuclear fuel elements made from nanophase materials

    DOEpatents

    Heubeck, Norman B.

    1998-01-01

    A nuclear reactor core fuel element is composed of nanophase high temperature materials. An array of the fuel elements in rod form are joined in an open geometry fuel cell that preferably also uses such nanophase materials for the cell structures. The particular high temperature nanophase fuel element material must have the appropriate mechanical characteristics to avoid strain related failure even at high temperatures, in the order of about 3000.degree. F. Preferably, the reactor type is a pressurized or boiling water reactor and the nanophase material is a high temperature ceramic or ceramic composite. Nanophase metals, or nanophase metals with nanophase ceramics in a composite mixture, also have desirable characteristics, although their temperature capability is not as great as with all-ceramic nanophase material. Combinations of conventional or nanophase metals and conventional or nanophase ceramics can be employed as long as there is at least one nanophase material in the composite. The nuclear reactor so constructed has a number of high strength fuel particles, a nanophase structural material for supporting a fuel rod at high temperature, a configuration to allow passive cooling in the event of a primary cooling system failure, an ability to retain a coolable geometry even at high temperatures, an ability to resist generation of hydrogen gas, and a configuration having good nuclear, corrosion, and mechanical characteristics.

  13. Nuclear fuel elements made from nanophase materials

    DOEpatents

    Heubeck, N.B.

    1998-09-08

    A nuclear reactor core fuel element is composed of nanophase high temperature materials. An array of the fuel elements in rod form are joined in an open geometry fuel cell that preferably also uses such nanophase materials for the cell structures. The particular high temperature nanophase fuel element material must have the appropriate mechanical characteristics to avoid strain related failure even at high temperatures, in the order of about 3000 F. Preferably, the reactor type is a pressurized or boiling water reactor and the nanophase material is a high temperature ceramic or ceramic composite. Nanophase metals, or nanophase metals with nanophase ceramics in a composite mixture, also have desirable characteristics, although their temperature capability is not as great as with all-ceramic nanophase material. Combinations of conventional or nanophase metals and conventional or nanophase ceramics can be employed as long as there is at least one nanophase material in the composite. The nuclear reactor so constructed has a number of high strength fuel particles, a nanophase structural material for supporting a fuel rod at high temperature, a configuration to allow passive cooling in the event of a primary cooling system failure, an ability to retain a coolable geometry even at high temperatures, an ability to resist generation of hydrogen gas, and a configuration having good nuclear, corrosion, and mechanical characteristics. 5 figs.

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

    SciTech Connect

    Natesan, K.; Johnson, R.N.

    1995-05-01

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

  15. Evaluation of hardening behaviors in ion-irradiated Fe-9Cr and Fe-20Cr alloys by nanoindentation technique

    NASA Astrophysics Data System (ADS)

    Li, Shilei; Wang, Yanli; Dai, Xianyuan; Liu, Fang; Li, Jinyu; Wang, Xitao

    2016-09-01

    The ion irradiation hardening behaviors of Fe-9 wt% Cr and Fe-20 wt% Cr model alloys were investigated by nanoindentation technique. The specimens were irradiated with 3 MeV Fe11+ ions at room temperature up to 1 and 5 dpa for Fe-9Cr alloy and 1 and 2.5 for Fe-20Cr alloy. The ratio of average hardness in the same depth of irradiated and unirradiated (Hirr. av/Hunirr. av) was used to determine the critical indentation depth hcrit to eliminate the softer substrate effect. The Nix-Gao model was used to explain the indentation size effect. Irradiation hardening is clearly observed in both Fe-9Cr alloy and Fe-20Cr alloy after ion irradiation. The differences of ISE and irradiation hardening behaviors between Fe-9Cr and Fe-20Cr alloys are considered to be due to their different microstructures and microstructural evolution under ion irradiation.

  16. Progress in ODS Alloys: A Synopsis of a 2010 Workshop on Fe- Based ODS Alloys

    SciTech Connect

    Kad, Bimal; Dryepondt, Sebastien N; Jones, Andy R.; Vito, Cedro III; Tatlock, Gordon J; Pint, Bruce A; Tortorelli, Peter F; Rawls, Patricia A.

    2012-01-01

    In Fall 2010, a workshop on the role and future of Fe-based Oxide Dispersion Strengthened (ODS) alloys gathered together ODS alloy suppliers, potential industrial end-users, and technical experts in relevant areas. Presentations and discussions focused on the current state of development of these alloys, their availability from commercial suppliers, past major evaluations of ODS alloy components in fossil and nuclear energy applications, and the technical and economic issues attendant to commercial use of ODS alloys. Significant progress has been achieved in joining ODS alloys, with creep resistant joints successfully made by inertia welding, friction stir welding and plasma-assisted pulse diffusion bonding, and in improving models for the prediction of lifetime components. New powder and alloy fabrication methods to lower cost or improve endproduct properties were also described. The final open discussion centered on challenges and pathways for further development and large-scale use of ODS alloys.

  17. Structural evolution in mechanically alloyed Al-Fe powders

    SciTech Connect

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

    1995-08-01

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

  18. Inhibited Aluminization of an ODS FeCr Alloy

    SciTech Connect

    Vande Put Ep Rouaix, Aurelie; Pint, Bruce A

    2012-01-01

    Aluminide coatings are of interest for fusion energy applications both for compatibility with liquid Pb-Li and to form an alumina layer that acts as a tritium permeation barrier. Oxide dispersion strengthened (ODS) ferritic steels are a structural material candidate for commercial reactor concepts expected to operate above 600 C. Aluminizing was conducted in a laboratory scale chemical vapor deposition reactor using accepted conditions for coating Fe- and Ni-base alloys. However, the measured mass gains on the current batch of ODS Fe-14Cr were extremely low compared to other conventional and ODS alloys. After aluminizing at two different Al activities at 900 C and at 1100 C, characterization showed that the ODS Fe-14Cr specimens formed a dense, primarily AlN layer that prevented Al uptake. This alloy batch contained a higher (> 5000 ppma) N content than the other alloys coated and this is the most likely reason for the inhibited aluminization. Other factors such as the high O content, small ({approx} 140 nm) grain size and Y-Ti oxide nano-clusters in ODS Fe-14Cr also could have contributed to the observed behavior. Examples of typical aluminide coatings formed on conventional and ODS Fe- and Ni-base alloys are shown for comparison.

  19. Processing and Properties of Mechanical Alloyed Al93Fe3Cr2Ti2 Alloys

    DTIC Science & Technology

    2004-10-01

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

  20. Compression of Fe-Si-H alloys to core pressures

    NASA Astrophysics Data System (ADS)

    Tagawa, Shoh; Ohta, Kenji; Hirose, Kei; Kato, Chie; Ohishi, Yasuo

    2016-04-01

    We examined the compression behavior of hexagonal-close-packed (hcp) (Fe0.88Si0.12)1H0.61 and (Fe0.88Si0.12)1H0.79 (in atomic ratio) alloys up to 138 GPa in a diamond anvil cell (DAC). While contradicting experimental results were previously reported on the compression curve of double-hcp (dhcp) FeHx (x ≈ 1), our data show that the compressibility of hcp Fe0.88Si0.12Hx alloys is very similar to those of hcp Fe and Fe0.88Si0.12, indicating that the incorporation of hydrogen into iron does not change its compression behavior remarkably. The present experiments suggest that the inner core may contain up to 0.47 wt % hydrogen (FeH0.26) if temperature is 5000 K. The calculated density profile of Fe0.88Si0.12H0.17 alloy containing 0.32 wt % hydrogen in addition to geochemically required 6.5 wt % silicon matches the seismological observations of the outer core, supporting that hydrogen is an important core light element.

  1. Magnetism, elasticity, and magnetostriction of FeCoGa alloys

    NASA Astrophysics Data System (ADS)

    Dai, Liyang; Cullen, James; Wuttig, Manfred; Lograsso, T.; Quandt, Eckhard

    2003-05-01

    It is known that the substitution of Co for Fe gives rise to increases in magnetization and Curie temperature, not only in the bcc metals, but also in intermetallic compounds and alloys as well. With the expectation that this is the case in Co-substituted FeGa, we measured magnetization, Curie temperature, magnetostriction and elastic constants of a series of polycrystalline FeCoGa ternary alloys with up to 17% Ga and up to 10% Co. The magnetostriction at saturation for Fe0.93-xCo.07Gax increases to 90 ppm for x=0.17. For larger percentages of Co, the rise in magnetostriction is not as sharp as it is in the 7% case. The shear elastic modulus decreases with Ga, again in keeping with the results for FeGa. The magnetostriction and the elastic constants are sensitive to sample preparation for the high-Ga material. We conclude that the substitution of small (<0.10) percentages of Co for Fe in bcc FeCoGa alloys enhances the magnetic and magnetostrictive properties of the parent FeGa material.

  2. Nanostructured FeZrCuB alloys prepared by mechanosynthesis

    SciTech Connect

    Pereira, R. D.; Passamani, E. C.; Larica, C.; Freitas, J. C. C.; Takeuchi, A. Y.

    2007-08-01

    Nanostructured Fe{sub 84}Zr{sub 9}B{sub 6}Cu{sub 1} alloys were prepared by the mechanosynthesis method, following two alternative routes. In the first procedure, the alloy was directly obtained from the milling of the powder mixture of all elemental components. The resulting alloy was partially nanocrystalline, with dispersion of nanograins in an amorphous matrix. In the second route, Cu and B elemental powders were progressively added to a previously milled Fe{sub 90}Zr{sub 10} alloy. A nearly single amorphous phase was consequently obtained. The dispersion of nanograins was easily recovered in this case, after annealing the milled alloy. The hyperfine magnetic properties of the amorphous phase prepared by milling were comparable to those found in similar melt-spun alloys. The crystallization temperatures and activation energies, associated with the first and second crystallization stages, were found to be lower for the milled alloy when compared with the corresponding melt-spun alloy, an effect associated with the larger number of defects induced by the mechanosynthesis process.

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

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  4. Short range ordering and magnetostriction in Fe-Ga and other Fe alloy single crystals

    NASA Astrophysics Data System (ADS)

    Guruswamy, Sivaraman; Jayaraman, Tanjore V.; Corson, Robert P.; Garside, Gavin; Thuanboon, Swieng

    2008-12-01

    The magnetostrictive behaviors of Fe-Ga, Fe-Mo, Fe-W, and other Fe alloys have been observed to be sensitive to their thermal history. In this work, the changes in the structure with thermal history and how they correlate with the observed magnetostriction values in Fe-Ga, Fe-W, and Fe-Mo single crystals are examined. Single crystals were grown using the vertical Bridgman crystal growth technique. The magnetostriction constant (3/2)λ100 measured in (i) as-grown and air-cooled (DG) and (ii) annealed and water quenched single crystal samples of Fe-Ga and Fe-W alloys clearly indicate that annealing in the α-phase region followed by rapid quenching improves the magnetostriction values. High-resolution x-ray diffraction (XRD) studies on [100]-oriented Fe-Ga as well as other Fe alloy single crystals show (i) a diffuse scattering peak indicative of short range ordering, the extent of which depends on composition and thermal history, and (ii) (200) peak splitting and broadening indicative of the presence of long range ordered coherent second phases and associated coherency strains. A detailed examination of the XRD patterns suggests that the changes in magnetostriction with composition and thermal history are related to the local strain modulations associated with the solutes, short range order, long range ordered coherent second phases, incoherent precipitates, and other structural defects.

  5. Elastic anharmonicity of bcc Fe and Fe-based random alloys from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Li, Xiaoqing; Schönecker, Stephan; Zhao, Jijun; Vitos, Levente; Johansson, Börje

    2017-01-01

    We systematically investigate elastic anharmonic behavior in ferromagnetic body-centered cubic (bcc) Fe and Fe1 -xMx (M =Al , V, Cr, Co, or Ni) random alloys by means of density-functional simulations. To benchmark computational accuracy, three ab initio codes are used to obtain the complete set of second- and third-order elastic constants (TOECs) for bcc Fe. The TOECs of Fe1 -xMx alloys are studied employing the first-principles alloy theory formulated within the exact muffin-tin orbital method in combination with the coherent-potential approximation. It is found that the alloying effects on C111,C112 , and C123, which are governed by normal strains only, are more pronounced than those on C144,C166 , and C456, which involve shear strains. Remarkably, the magnitudes of all TOECs but C123 decrease upon alloying with Al, V, Cr, Co, or Ni. Using the computed TOECs, we study compositional effects on the pressure derivatives of the effective elastic constants (d Bi j/d P ), bulk (d K /d P ), and shear moduli (d G /d P ) and derive longitudinal acoustic nonlinearity parameters (β ). Our predictions show that the pressure derivatives of K and G decrease with x for all solute elements and reveal a strong correlation between the compositional trends on d K /d P and d G /d P arising from the fact that alloying predominantly alters d B11/d P . The sensitivity of d B11/d P to composition is attributed to intrinsic alloying effects as opposed to lattice parameter changes accompanying solute addition. For Fe and the considered Fe-based alloys, β along high-symmetry directions orders as β [111 ]>β [100 ]>β [110 ] , and alloying increases the directional anisotropy of β but reduces its magnitude.

  6. Theoretical elastic moduli of ferromagnetic bcc Fe alloys.

    PubMed

    Zhang, Hualei; Punkkinen, Marko P J; Johansson, Börje; Vitos, Levente

    2010-07-14

    The polycrystalline elastic parameters of ferromagnetic Fe(1-x)M(x) (M = Al, Si, V, Cr, Mn, Co, Ni, Rh; 0 ≤ x ≤ 0.1) random alloys in the body centered cubic (bcc) crystallographic phase have been calculated using first-principles alloy theory in combination with statistical averaging methods. With a few exceptions, the agreement between the calculated and the available experimental data for the polycrystalline aggregates is satisfactory. All additions considered here decrease the bulk modulus (B) and Poisson's ratio (ν) of bcc Fe. The complex composition dependence of the C(44) single-crystal elastic constant is reflected in the polycrystalline shear modulus (G), Young's modulus (E), and Debye temperature (Θ). The polycrystalline anisotropy of bcc Fe is increased by all additions, and Al, Si, Ni, and Rh yield the largest alloying effects.

  7. Precipitation phase transformation in nanocrystalline Fe-Mo alloys.

    PubMed

    Sarkar, Subhajit; Bansal, Chandrahaas

    2004-01-01

    Precipitation phase transformation was studied in nanocrystalline Fe-rich Fe-Mo alloys with the use of X-ray diffraction and Mössbauer spectroscopy. Alloys up to 5 at% Mo in Fe were synthesized by mechanical alloying and formed in alpha phase bcc solid solutions with average grain sizes in the range of 10-13 nm. The precipitation transformation (alpha-->alpha + lambda) was found to proceed via a Mo clustering that was correlated with the size of the nanograins. This was understood in terms of the Gibbs Thomson effect with a concept of negative surface energy contribution to the Gibbs free energy of mixing in a nanocrystalline alloy with positive internal energy of mixing. This contribution increased the stability of the solid solution for nanosized grains, and the Mo precipitation started once the grains grew beyond a critical size. We argue that the Mo precipitation takes place in the grain boundary regions, and the Mo-rich lambda phase also precipitates directly in the grain boundary regions, in contrast to the microcrystalline alloys, where the Mo clusters formed within the grains and were first dissolved in the Fe matrix before the lambda phase was formed.

  8. The Bain path of paramagnetic Fe-Cr based alloys

    NASA Astrophysics Data System (ADS)

    Al-Zoubi, N.; Johansson, B.; Nilson, G.; Vitos, L.

    2011-07-01

    Employing the first-principles exact muffin-tin orbital method in combination with the coherent potential approximation, we calculated the total energy and local magnetic moments of paramagnetic Fe-Cr-M (M = Cr, Mn, Fe, Co, Ni) alloys along the tetragonal distortion (Bain) path connecting the body centered cubic (bcc) and the face centered cubic (fcc) structures. The paramagnetic phase is modeled by the disordered local magnetic moment scheme. For all alloys, the local magnetic moments on Fe atoms decrease from the maximum value corresponding to the bcc phase toward the minimum value realized for the fcc phase. Cobalt atoms have non-vanishing local magnetic moments only for tetragonal lattices with c/a < 1.30, whereas the local magnetic moments of Mn show weak crystal structure dependence. We find that Cr stabilizes the bcc lattice and increases the energy barrier as going from the bcc toward the fcc phase. Both Co and Ni favor the fcc lattice and decrease the energy barrier relative to the bcc phase. On the other hand, the tetragonal distortion around the fcc phase is facilitated by Cr and to a somewhat lesser extent also by Ni, but strongly impeded by Co. Manganese has negligible effect on the structural energy difference as well as on the energy barrier along the Bain path. Our findings on the alloying induced softening or hardening of Fe-Cr based alloys against tetragonal distortions are important for understanding the interstitial driven martensitic transformations in alloy steels.

  9. Origin of large magnetostriction in FeGa alloys

    NASA Astrophysics Data System (ADS)

    Wu, Ruqian

    2002-05-01

    Using the highly precise full potential linearized augmented plane wave method, the phase stability, magnetism, and magnetostriction of Fe3Ga alloys were investigated. The magnetostrictive coefficients strongly depend on the atomic arrangement. The B2-like structure, although it is unstable in the small unit cell chosen here, appears to play a crucial rule for the large positive magnetostriction in the FeGa alloys as observed recently. Electronic origin of enhancement in magnetostriction is discussed in terms of density of states and band structures.

  10. Nano-sized Superlattice Clusters Created by Oxygen Ordering in Mechanically Alloyed Fe Alloys

    PubMed Central

    Hu, Yong-Jie; Li, Jing; Darling, Kristopher A.; Wang, William Y.; VanLeeuwen, Brian K.; Liu, Xuan L.; Kecskes, Laszlo J.; Dickey, Elizabeth C.; Liu, Zi-Kui

    2015-01-01

    Creating and maintaining precipitates coherent with the host matrix, under service conditions is one of the most effective approaches for successful development of alloys for high temperature applications; prominent examples include Ni- and Co-based superalloys and Al alloys. While ferritic alloys are among the most important structural engineering alloys in our society, no reliable coherent precipitates stable at high temperatures have been found for these alloys. Here we report discovery of a new, nano-sized superlattice (NSS) phase in ball-milled Fe alloys, which maintains coherency with the BCC matrix up to at least 913 °C. Different from other precipitates in ferritic alloys, this NSS phase is created by oxygen-ordering in the BCC Fe matrix. It is proposed that this phase has a chemistry of Fe3O and a D03 crystal structure and becomes more stable with the addition of Zr. These nano-sized coherent precipitates effectively double the strength of the BCC matrix above that provided by grain size reduction alone. This discovery provides a new opportunity for developing high-strength ferritic alloys for high temperature applications. PMID:26134420

  11. Oxidation sulfidation resistance of Fe-Cr-Ni alloys

    DOEpatents

    Natesan, Ken; Baxter, David J.

    1984-01-01

    High temperature resistance of Fe-Cr-Ni alloy compositions to oxidative and/or sulfidative conditions is provided by the incorporation of about 1-8 wt. % of Zr or Nb and results in a two-phase composition having an alloy matrix as the first phase and a fine grained intermetallic composition as the second phase. The presence and location of the intermetallic composition between grains of the matrix provides mechanical strength, enhanced surface scale adhesion, and resistance to corrosive attack between grains of the alloy matrix at temperatures of 500.degree.-1000.degree. C.

  12. Improved oxidation sulfidation resistance of Fe-Cr-Ni alloys

    DOEpatents

    Natesan, K.; Baxter, D.J.

    1983-07-26

    High temperature resistance of Fe-Cr-Ni alloy compositions to oxidative and/or sulfidative conditions is provided by the incorporation of about 1 to 8 wt % of Zr or Nb and results in a two-phase composition having an alloy matrix as the first phase and a fine grained intermetallic composition as the second phase. The presence and location of the intermetallic composition between grains of the matrix provides mechanical strength, enhanced surface scale adhesion, and resistance to corrosive attack between grains of the alloy matrix at temperatures of 500 to 1000/sup 0/C.

  13. Pressure induced phase transition in FeGa alloys

    NASA Astrophysics Data System (ADS)

    Devreugd, Christopher; Ahart, Muhtar; Gehring, Peter; Viehland, Dwight; Hemley, Russell

    2011-03-01

    Giant magnetostriction in Fe-- x Ga alloys (15 -- x - 27) offers potential for future generations of sensors and actuators. A maximum in the magnetostrictive strain is found at Ga content of about 19 percent, which is ten times higher than that of pure alpha-Fe. To investigate the behavior of FeGa alloys under pressure, we chose a slow cooled alloy of FeGa-19 as our sample and performed x-ray diffraction experiments in a diamond anvil cell up to 45 GPa. Diffraction pattern shows powder rings associated with (110), (200), and (211) Bragg reflections from expected bcc structure of iron below 24 GPa. We also observed the intensity increases along the powder rings associated with the crystal structure of Galfenol. Considering the (110) Bragg peak splits into three peaks above 24 GPa, our results indicate that FeGa alloy undergoes a bcc cubic to a hexagonal transition around 24 GPa. When the pressure is decreased, the hcp phase transforms back to the bcc phase. The transition mechanism can be understood by using the analogy to the bcc-hcp phase transition in pure iron under pressure. The transition in iron is a martensitic or displacive one. The hcp structure can be derived from the bcc structure through a relatively minor distortion of the bcc structure.

  14. Formability Analysis of Magnesium Alloy Sheet Bulging Using FE Simulation

    SciTech Connect

    Mac Donald, B. J.; Hunt, D.; Yoshihara, S.; Manabe, K.

    2007-05-17

    There is currently much focus on the application of magnesium alloys to automotive structural components. This has arisen due to the positive environmental aspects associated with use of magnesium alloys such as weight reduction and recycling potential. In recent years many researchers have focused on the application of various forming processes to magnesium alloys. Magnesium alloys would seem highly suitable for sheet forming due to high N and r values, however, in application their formability has been inferior to, for example, aluminium alloys. It has thus been concluded that, when dealing with magnesium alloys, it is difficult to predict formability based on material properties. In order to improve formability and forming accuracy when using Mg alloys it is necessary to build a database and inference system which could decide the optimal forming parameters for complex automotive components. Currently not enough data is available to build such a database due to the limited number of studies available in literature. In this study an experimental analysis of hemispherical bulge forming at elevated temperature was undertaken in order to evaluate formability and hence build a database for forming process design. A finite element model based on the experiment has been built and validated against the experimental results. A ductile failure criterion has been integrated with the FE model and is used to predict the onset of failure. This paper discusses the development and validation of the finite element model with the ductile failure criterion and presents results from the experimental tests and FE simulations.

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

    NASA Technical Reports Server (NTRS)

    Schuon, S. R.

    1982-01-01

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

  16. Melting and casting of FeAl-based cast alloy

    SciTech Connect

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

    1998-11-01

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

  17. Phase relations of Fe-Si alloy in Earth's core

    SciTech Connect

    Lin, J -F; Scott, H P; Fischer, R A; Chang, Y -Y; Kantor, I; Prakapenka, V B

    2009-04-01

    Phase relations of an Fe0.85Si0.15 alloy were investigated up to 240 GPa and 3000 K using in situ X-ray diffraction in a laser-heated diamond anvil cell. An alloy of this composition as starting material is found to result in a stabilized mixture of Si-rich bcc and Si-poor hcp Fe-Si phases up to at least 150 GPa and 3000 K, whereas only hcp-Fe0.85Si0.15 is found to be stable between approximately 170 GPa and 240 GPa at high temperatures. Our extended results indicate that Fe0.85Si0.15 alloy is likely to have the hcp structure in the inner core, instead of the previously proposed mixture of hcp and bcc phases. Due to the volumetric dominance of the hcp phase in the hcp + bcc coexistence region close to the outer-core conditions, the dense closest-packed Fe-Si liquid is more relevant to understanding the properties of the outer core.

  18. Secondary particles precipitates in Be-Fe alloys

    NASA Astrophysics Data System (ADS)

    Filippov, V. P.; Petrov, V. I.; Martynenko, S. S.; Salomasov, V. A.

    2016-12-01

    Mössbauer spectra of monocrystalline Be-Fe alloy (0.85 % Fe) were obtained with the use of resonant detector after isothermal annealing at 600 °C for total duration of 2659 hours, and Mössbauer spectra of coarse-grained Be-Fe alloys (0,09-0,80 % Fe) samples were obtained after annealing at 500-600 °C for different durations. The alloys were prepared from the beryllium of different purity. Spectra of phases were fitted by a convolution equation of the three Lorentz lines. The coherent analysis of the solid solution decomposition process by means of the kinetic law classification and the secondary particles precipitate growth processes based on the diffusion models has been implemented. Nucleation on the numerous dislocation clusters and diffusion growth of the FeBe 11 nano-particles are the dominant processes in the analyzed materials. The phase distribution, the incubation period and the diffusion path were obtained. The dependence between the impurity concentration and Mössbauer parameters of the phases is discussed.

  19. Magnetic Domains in Magnetostrictive Fe-Ga Alloys

    SciTech Connect

    Q. Xing; T.A. Lograsso

    2008-11-03

    Lorentz microscopy was applied to the observation of magnetic domains in iron-gallium (Fe-Ga) alloys. Results did not show any link between the magnetic domains and the magnetostriction enhancement by Ga addition, but did reveal that the drastic decrease in magnetostriction for Fe-31.2 at. % Ga was due to the presence of large scale precipitates. Magnetic domain features did not change in the alloys of A2, D0{sub 3}, A2+D0{sub 3}, A2+B2+D0{sub 3}, and A2+fine scale precipitates. Large scale precipitates within the slow-cooled Fe-31.2 at. % Ga affected both the distribution and wall motion of magnetic domains.

  20. The nanophase iron mineral(s) in Mars soil

    NASA Technical Reports Server (NTRS)

    Banin, A.; Ben-Shlomo, T.; Margulies, L.; Blake, D. F.; Mancinelli, R. L.; Gehring, A. U.

    1993-01-01

    A series of surface-modified clays containing nanophase (np) iron oxide/oxyhydroxides of extremely small particle sizes, with total iron contents as high as found in Mars soil, were prepared by iron deposition on the clay surface from ferrous chloride solution. Comprehensive studies of the iron mineralogy in these "Mars-soil analogs" were conducted using chemical extractions, solubility analyses, pH and redox, x ray and electron diffractometry, electron microscopic imaging, specific surface area and particle size determinations, differential thermal analyses, magnetic properties characterization, spectral reflectance, and Viking biology simulation experiments. The clay matrix and the procedure used for synthesis produced nanophase iron oxides containing a certain proportion of divalent iron, which slowly converts to more stable, fully oxidized iron minerals. The clay acted as an effective matrix, both chemically and sterically, preventing the major part of the synthesized iron oxides from ripening, i.e., growing and developing larger crystals. The precipitated iron oxides appear as isodiametric or slightly elongated particles in the size range 1-10 nm, having large specific surface area. The noncrystalline nature of the iron compounds precipitated on the surface of the clay was verified by their complete extractability in oxalate. Lepidocrocite (gamma-FeOOH) was detected by selected area electron diffraction. It is formed from a double iron Fe(II)/Fe(III) hydroxy mineral such as "green rust," or ferrosic hydroxide. Magnetic measurements suggested that lepidocrocite converted to the more stable maghemite (gamma-Fe2O3) by mild heat treatment and then to nanophase hematite (alpha-Fe2O3) by extensive heat treatment. After mild heating, the iron-enriched clay became slightly magnetic, to the extent that it adheres to a hand-held magnet, as was observed with Mars soil. The chemical reactivity of the iron-enriched clays strongly resembles, and offers a plausible mechanism

  1. Magnetic properties of Fe-Cu alloys prepared by pulsed electrodeposition

    NASA Astrophysics Data System (ADS)

    Noce, R. D.; Gomes, O. D. M.; de Magalhães, S. D.; Wolf, W.; Guimarães, R. B.; de Castro, A. C.; Pires, M. J. M.; Macedo, W. A. A.; Givord, D.; Barthem, V. M. T. S.

    2009-11-01

    FexCu100-x metastable alloys were prepared by pulsed electrodeposition for 5Fe-rich alloys crystallize in the bcc structure of α-Fe and the Fe-poor ones in the fcc structure of Cu. The magnetic properties of the ferromagnetic Fe-rich alloys (x>50) are reminiscent of those observed in Fe-Cu alloys prepared by other methods. The Curie temperature decreases regularly with decreasing x. In the Fe-poor alloys (x≤30), the observed properties indicate that Fe-rich clusters form within a Cu-rich matrix. In the x=10 alloy, the Fe clusters are found to be superparamagnetic at room temperature, but a superferromagnetic order develops below a critical temperature of about 120 K. It is suggested that the intercluster coupling is mediated by Ruderman-Kittel-Kasuya-Yosida interactions which are predominantly positive due to the very short intercluster distances.

  2. Moessbauer Analysis of Fe94-xNb6Bx (x = 9, 14, 20) Alloys Developed by Mechanical Alloying

    SciTech Connect

    Bruna, P.

    2005-04-26

    The alloys were prepared by milling elemental powders in a planetary ball mill. XRD analysis of the powders indicate that a nanocrystalline heterogeneous bcc alloy was obtained. DSC study of the thermal stability of the powders obtained indicate that some grain growth and reordering of the structure was obtained at temperatures as low as 350 deg. C up to 600 deg. C. Room temperature Transmission Moessbauer spectroscopy from the as milled alloys as well as from the annealed alloys was performed to determine the structure, homogeneity and how the structure changed after annealing at 600 deg. C. The results indicate that the as milled alloys are mainly a crystalline bcc alloy containing most of the Fe, Nb and B. A small amount of a disordered/amorphous phase is also formed for the three alloys. Annealing of the to B richer alloys results in the diffusion of most of the B outside the alloy structure and the crystallization of Fe2B and {alpha}-Fe. Annealing the heterogeneous as-milled powders enhances the separation of Fe rich ({alpha}-Fe ), B rich (Fe2B) and Nb rich regions in the two richer in B alloys studied. On the contrary, the alloy x=9 does not change significantly during annealing.

  3. Mössbauer study of Fe-Re alloys prepared by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Konieczny, R.; Idczak, R.

    2016-12-01

    The room temperature Mössbauer spectra of 57Fe were measured for nanocrystalline iron-based solid solutions Fe 1- x Re x , prepared by mechanical alloying with x in the range 0.01 ≤ x ≤ 0.04. The obtained data were analysed in terms of the binding energy E b between two rhenium atoms in the Fe-Re system. The extrapolated value of E b for x = 0 was used for computation of enthalpy of solution of rhenium in iron. The result was compared with that resulting from the cellular atomic model of alloys by Miedema as well as with value, derived from proper data for Fe-Re solid solutions obtained by melting in an arc furnace. From the comparison it follows that our findings are in agreement with the Miedema's model predictions and previous Mössbauer studies.

  4. Study of intergranular embrittlement in Fe-12Mn alloys

    SciTech Connect

    Lee, H.J.

    1982-06-01

    A high resolution scanning Auger microscopic study has been performed on the intergranular fracture surfaces of Fe-12Mn steels in the as-austenitized condition. Fracture mode below the ductile-brittle transition temperature was intergranular whenever the alloy was quenched from the austenite field. The intergranular fracture surface failed to reveal any consistent segregation of P, S, As, O, or N. The occasional appearance of S or O on the fracture surface was found to be due to a low density precipitation of MnS and MnO/sub 2/ along the prior austenite boundaries. An AES study with Ar/sup +/ ion-sputtering showed no evidence of manganese enrichment along the prior austenite boundaries, but a slight segregation of carbon which does not appear to be implicated in the tendency toward intergranular fracture. Addition of 0.002% B with a 1000/sup 0/C/1h/WQ treatment yielded a high Charpy impact energy at liquid nitrogen temperature, preventing the intergranular fracture. High resolution AES studies showed that 3 at. % B on the prior austenite grain boundaries is most effective in increasing the grain boundary cohesive strength in an Fe-12Mn alloy. Trace additions of Mg, Zr, or V had negligible effects on the intergranular embrittlement. A 450/sup 0/C temper of the boron-modified alloys was found to cause tempered martensite embrittlement, leading to intergranular fracture. The embrittling treatment of the Fe-12Mn alloys with and without boron additions raised the ductile-brittle transition by 150/sup 0/C. This tempered martensite embrittlement was found to be due to the Mn enrichment of the fracture surface to 32 at. % Mn in the boron-modified alloy and 38 at. % Mn in the unmodified alloy. The Mn-enriched region along the prior austenite grain boundaries upon further tempering is believed to cause nucleation of austenite and to change the chemistry of the intergranular fracture surfaces. 61 figures.

  5. In vitro corrosion properties and cytocompatibility of Fe-Ga alloys as potential biodegradable metallic materials.

    PubMed

    Wang, Henan; Zheng, Yang; Liu, Jinghua; Jiang, Chengbao; Li, Yan

    2017-02-01

    The in vitro biodegradable properties and cytocompatibility of Fe-Ga alloys including Fe81Ga19, (Fe81Ga19)98B2 and (Fe81Ga19)99.5(TaC)0.5, and pure Fe were investigated for biomedical applications. The microstructure of the alloys was characterized using X-ray diffraction spectroscopy and optical microscopy. The results showed that A2 and D03 phases were detected for the three types of Fe-Ga alloys, and additional Fe2B and TaC phases were found in the (Fe81Ga19)98B2 and (Fe81Ga19)99.5(TaC)0.5 alloys, respectively. The corrosion rates of the Fe-Ga alloys were higher than that of pure Fe, as demonstrated by both potentiodynamic polarization measurements and immersion tests in simulated body fluid. The alloying element Ga lowered the corrosion potential of the Fe matrix and made it more susceptible to corrosion. Severe pitting corrosion developed on the surface of the Fe81Ga19 alloy after the addition of ternary B or TaC due to the multi-phase microstructures. The MC3T3-E1 cells exhibited good adhesion and proliferation behavior on the surfaces of the Fe-Ga alloys after culture for 4h and 24h.

  6. Role of lead in electrochemical reaction of alloy 600, alloy 690, Ni, Cr, and Fe in water

    NASA Astrophysics Data System (ADS)

    Hwang, Seong Sik; Kim, Joung Soo; Kim, Ju Yup

    2003-08-01

    It has been reported that lead causes stress corrosion cracking (SCC) in the secondary side of steam generators (SG) in pressurized water reactors (PWR). The materials of SG tubings are alloy 600, alloy 690, or alloy 800, among which the main alloying elements are Ni, Cr, and Fe. The effect of lead on the electrochemical behaviors of alloy 600 and alloy 690 using an anodic polarization technique was evaluated. We also obtained polarization curves of pure Ni, Cr, and Fe in water containing lead. As the amount of lead in the solution increased, critical current densities and passive current densities of alloy 600 and alloy 690 increased, while the breakdown potential of the alloys decreased. Lead increased critical current density and the passive current of Cr in pH 4 and pH 10. The instability of passive film of steam generator tubings in water containing lead might arise from the instability of Cr passivity.

  7. Nanostructured Fe-Cr Alloys for Advanced Nuclear Energy Applications

    SciTech Connect

    Scattergood, Ronald O.

    2016-04-26

    We have completed research on the grain-size stabilization of model nanostructured Fe14Cr base alloys at high temperatures by the addition of non-equilibrium solutes. Fe14Cr base alloys are representative for nuclear reactor applications. The neutron flux in a nuclear reactor will generate He atoms that coalesce to form He bubbles. These can lead to premature failure of the reactor components, limiting their lifetime and increasing the cost and capacity for power generation. In order to mitigate such failures, Fe14Cr base alloys have been processed to contain very small nano-size oxide particles (less than 10 nm in size) that trap He atoms and reduce bubble formation. Theoretical and experimental results indicate that the grain boundaries can also be very effective traps for He atoms and bubble formation. An optimum grain size will be less than 100 nm, ie., nanocrystalline alloys must be used. Powder metallurgy methods based on high-energy ball milling can produce Fe-Cr base nanocrystalline alloys that are suitable for nuclear energy applications. The problem with nanocrystalline alloys is that excess grain-boundary energy will cause grains to grow at higher temperatures and their propensity for He trapping will be lost. The nano-size oxide particles in current generation nuclear alloys provide some grain size stabilization by reducing grain-boundary mobility (Zener pinning – a kinetic effect). However the current mitigation strategy minimizing bubble formation is based primarily on He trapping by nano-size oxide particles. An alternate approach to nanoscale grain size stabilization has been proposed. This is based on the addition of small amounts of atoms that are large compared to the base alloy. At higher temperatures these will diffuse to the grain boundaries and will produce an equilibrium state for the grain size at higher temperatures (thermodynamic stabilization – an equilibrium effect). This would be preferred compared to a kinetic effect, which is not

  8. Ab initio calculations of elastic properties of bcc Fe-Mg and Fe-Cr random alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Hualei; Johansson, Börje; Vitos, Levente

    2009-06-01

    Using the ab initio exact muffin-tin orbitals method in combination with the coherent-potential approximation, we have calculated the elastic parameters of ferromagnetic Fe1-mMgm (0≤m≤0.1) and Fe1-cCrc (0≤c≤0.2) random alloys in the body-centered cubic (bcc) crystallographic phase. Results obtained for Fe1-cCrc demonstrate that the employed theoretical approach accurately describes the experimentally observed composition dependence of the polycrystalline elastic moduli of Fe-rich alloys encompassing maximum ˜10% Cr. The elastic parameters of Fe-Cr alloys are found to exhibit anomalous composition dependence around 5% Cr. The immiscibility between Fe and Mg at ambient conditions is well reproduced by the present theory. The calculated lattice parameter for the Fe-Mg regular solid solution increases by ˜1.95% when 10% Mg is introduced in Fe, which corresponds approximately to 11% decrease in the average alloy density, in perfect agreement with the experimental finding. At the same time, we find that all of the elastic parameters of bcc Fe-Mg alloys decrease almost linearly with increasing Mg content. The present results show a much stronger alloying effect for Mg on the elastic properties of α-Fe than that for Cr. Our results call for further experimental studies on the mechanical properties of the Fe-Mg system.

  9. Comparative study using MS and XRD of Fe80Al20 alloy produced by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Hadef, F.; Otmani, A.; Grenèche, J. M.

    2013-08-01

    An X-ray diffraction and 57Fe Mössbauer effect study of mechanically alloyed Fe80Al20 is presented. X-ray measurements indicate that the disordered bcc α-Fe(Al) solid solution was formed after 2 h of milling, while the analysis of Mössbauer spectra suggested that total dissolution of aluminium is achieved after 10 h of milling. These differences can be attributed to: (i) rapid nanocrystallization of aluminium and/or (ii) small particles with small amounts of aluminium cannot be detected by the X-ray diffraction technique.

  10. Saturation and forced volume magnetostrictions of Fe-rich FeZr and FeNiZr amorphous alloys

    NASA Astrophysics Data System (ADS)

    Tange, H.; Kamimori, T.; Goto, M.; Fukamichi, K.

    1990-12-01

    The saturation and forced volume magnetostrictions, ac susceptibility have been investigated for Fe 90Zr 10 and Fe 90-xNi xZr 10 amorphous alloys. The linear magnetostriction in the re-entrant spin glass state exhibits a hysteresis due to a remarkable magnetic after effect. The temperature dependence of the forced volume magnetostriction shows a peak at the spin freezing temperature.

  11. Structural and magnetic properties of nanocrystalline Fe-Co-Ni alloy processed by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Raanaei, Hossein; Eskandari, Hossein; Mohammad-Hosseini, Vahid

    2016-01-01

    In this present work, a nanostructured iron-cobalt-nickel alloy with Fe50Co30Ni20 composition has been processed by mechanical alloying. The structural and magnetic properties have been investigated by X-ray diffraction, scanning electron microscopy, energy dispersive X-ray spectroscopy and vibrating sample magnetometer. It is shown that the crystallize size reaches to about 18.7 nm after 32 h milling time. A remarkable decrease in coercivity after 16 h milling time and also a continuous increase in remanent magnetization during the mechanical alloying process are observed. Heat treatment of the samples milled at 32 and 48 h demonstrates the crystalline constituent elements and also Fe3O4 crystalline phase.

  12. Point Defect Concentrations in Metastable Fe-C Alloys

    SciTech Connect

    Foerst, Clemens J.; Yip, Sidney; Slycke, Jan; Vliet, Krystyn J. van

    2006-05-05

    Point defect species and concentrations in metastable Fe-C alloys are determined using density functional theory and a constrained free-energy functional. Carbon interstitials dominate unless iron vacancies are in significant excess, whereas excess carbon causes greatly enhanced vacancy concentration. Our predictions are amenable to experimental verification; they provide a baseline for rationalizing complex microstructures known in hardened and tempered steels, and by extension other technological materials created by or subjected to extreme environments.

  13. Joint properties of cast Fe-Pt magnetic alloy laser-welded to Co-Cr alloy.

    PubMed

    Baba, Naoki; Watanabe, Ikuya; Tanaka, Yasuhiro; Hisatsune, Kunihiro; Atsuta, Mitsuru

    2005-12-01

    This study investigated the joint properties of Fe-Pt alloy laser-welded to Co-Cr alloy. Cast plates (0.5 x 3.0 x 10 mm) were prepared with Fe-Pt and Co-Cr alloys. Fe-Pt plates were butted against Co-Cr plates and laser-welded using Nd:YAG laser. Control and homogeneously welded specimens were also prepared. Laser welding was performed with and without argon shielding. Tensile testing was conducted, and both fracture force (Ff: N) and elongation (El: %) were recorded. There were no differences in the Ff value between the specimens with and without argon shielding for the welded Fe-Pt/Co-Cr. Lower Ff value of the welded specimen was obtained in the order of Fe-Pt alloy < Fe-Pt/Co-Cr < Co-Cr alloy. The results indicated that Fe-Pt welded to Co-Cr had Ff values between the values of homogeneously welded Fe-Pt and Co-Cr alloys. Argon shielding, on the other hand, had no effect on the weld strength between Fe-Pt and Co-Cr alloys.

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

    SciTech Connect

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

    2011-01-17

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

  15. A new hard magnetic phase in binary Nd-Fe and Pr-Fe alloys

    NASA Astrophysics Data System (ADS)

    Hadjipanayis, G. C.; Tsoukatos, A.; Strzeszewski, J.; Long, Gary J.; Pringle, O. A.

    1989-01-01

    A new magnetic phase has been observed in as-cast and melt-spun Nd-Fe and Pr-Fe alloys with a Curie temperature around 265°C. SEM studies show the presence of this phase in the form of spherical and elongated particles 5 μ m in size with a composition having a ratio of Fe/Nd=4:1. This phase is believed to be a ternary Nd-Fe-O phase stabilized with oxygen. The phase appears to have a high anisotropy leading to coercivities of about 6 kOe in as-cast samples at room temperature. The Mössbauer spectra of this phase can be fitted to four Fe sites with magnetic moments ranging from 1.7 to 2.54μ B.

  16. Crystallization kinetics of Fe based amorphous alloy

    NASA Astrophysics Data System (ADS)

    Shanker Rao, T.; Lilly Shanker Rao, T.

    2015-02-01

    Differential Scanning Calorimetry(DSC) experimental data under non-isothermal conditions for Fe based Metglas 2605SA1 (wt% Fe=85-95, Si=5-10, B=1-5) metallic glass ribbons are reported and discussed. The DSC Scans performed at different heating rates showed two step crystallization processes and are interpreted in terms of different models like Kissinger, Ozawa, Boswell, Augis & Bennett and Gao & Wang. From the heating rate dependence of the onset temperature (To) and the crystallization peak temperature (Tp), the kinetic triplet, activation energy of crystallization (E), Avrami exponent (n) and the frequency factor (A) are determined. The determined E for peak I is 354.5 ± 2.5 kJ/mol and for the peak II is 348.2 ± 2.2 kJ/mol, respectively. The frequency factor for peak I is 1.1 × 1023sec-1 and for peak II is 6.1 × 1020sec-1.

  17. Heat treatment of NiCrFe alloy to optimize resistance to intergrannular stress corrosion

    DOEpatents

    Steeves, Arthur F.; Bibb, Albert E.

    1984-01-01

    A process of producing a NiCrFe alloy having a high resistance to stress corrosion cracking comprising heating a NiCrFe alloy to a temperature sufficient to enable the carbon present in the alloy body in the form of carbide deposits to enter into solution, rapidly cool the alloy body, and heat the cooled body to a temperature between 1100.degree. to 1500.degree. F. for about 1 to 30 hours.

  18. Heat treatment of NiCrFe alloy 600 to optimize resistance to intergranular stress corrosion

    DOEpatents

    Steeves, A.F.; Bibb, A.E.

    A process of producing a NiCrFe alloy having a high resistance to stress corrosion cracking comprises heating a NiCrFe alloy to a temperature sufficient to enable the carbon present in the alloy body in the form of carbide deposits to enter into solution, rapidly cooling the alloy body, and heating the cooled body to a temperature between 1100 to 1500/sup 0/F for about 1 to 30 hours.

  19. Oxidation resistance of aluminum-coated Fe-20Cr alloys containing rare earths or yttrium

    SciTech Connect

    Sigler, D.R. )

    1993-10-01

    Aluminum-coated Fe-20Cr (rare earth or yttrium) alloy foils were developed with oxidation resistance equivalent or superior to Fe-20Cr-5Al (rare earth or yttrium) alloy foils. The coated foils were made by dipping Fe-20Cr sheet into a salt-covered aluminum bath and then rolling the sheet to foil. Oxidation resistance of the coated foil was enhanced by adding rare earths or yttrium to the Fe-20Cr substrate alloys to insure oxide adherence. Test results indicate that only sufficient addition to tie up sulfur as a stable sulfide is needed in the Fe-20Cr alloy. Aluminum-coated foils show lower oxide growth rates than similar Fe-Cr-Al alloys, most likely the result of fewer impurities (particularly Fe) is the coated foils' growing oxide scale. 31 refs., 18 figs., 2 tabs.

  20. Thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys

    SciTech Connect

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-06-12

    Understanding the stability of precipitate phases in the Fe-rich Fe-Cr-Ni-Mo alloys is critical to the alloy design and application of Mo-containing Austenitic steels. Coupled with thermodynamic modeling, stability of the chi and Laves phases in two Fe-Cr-Ni-Mo alloys were investigated at 1000, 850 and 700 °C for different annealing time. The morphologies, compositions and crystal structures of the matrix and precipitate phases were carefully examined by Scanning Electron Microscopy, Electron Probe Microanalysis, X-ray diffraction and Transmission Electron Microscopy. The two key findings resulted from this work. One is that the chi phase is stable at high temperature and transformed into the Laves phase at low temperature. The other is that both the chi and Laves phases have large solubilites of Cr, Mo and Ni, among which the Mo solubility has a major role on the relative stability of the precipitate phases. The developed thermodynamic models were then applied to evaluating the Mo effect on the stability of precipitate phases in AISI 316 and NF709 alloys.

  1. Thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys

    DOE PAGES

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-06-12

    Understanding the stability of precipitate phases in the Fe-rich Fe-Cr-Ni-Mo alloys is critical to the alloy design and application of Mo-containing Austenitic steels. Coupled with thermodynamic modeling, stability of the chi and Laves phases in two Fe-Cr-Ni-Mo alloys were investigated at 1000, 850 and 700 °C for different annealing time. The morphologies, compositions and crystal structures of the matrix and precipitate phases were carefully examined by Scanning Electron Microscopy, Electron Probe Microanalysis, X-ray diffraction and Transmission Electron Microscopy. The two key findings resulted from this work. One is that the chi phase is stable at high temperature and transformed intomore » the Laves phase at low temperature. The other is that both the chi and Laves phases have large solubilites of Cr, Mo and Ni, among which the Mo solubility has a major role on the relative stability of the precipitate phases. The developed thermodynamic models were then applied to evaluating the Mo effect on the stability of precipitate phases in AISI 316 and NF709 alloys.« less

  2. Fe-based nanocrystalline FeBCCu soft magnetic alloys with high magnetic flux density

    NASA Astrophysics Data System (ADS)

    Fan, Xingdu; Ma, Aibin; Men, He; Xie, Guoqiang; Shen, Baolong; Makino, Akihiro; Inoue, Akihisa

    2011-04-01

    In this study, the magnetic properties and crystalline behavior of Fe84-xB10C6Cux (x = 0-1.3) alloys prepared by annealing the melt-spun ribbon have been investigated. A Cu element was added to this system with the aim of decreasing the coercivity because the addition of Cu clusters prior to the crystallization stimulates the nucleation of α-Fe primary crystals, which greatly influences the final microstructure. It is found that in the Fe84-xB10C6Cux alloy system, the coercivity decreases with increasing x and exhibits a minimum at around x = 1.0. When x = 1.0, the alloy exhibits excellent magnetic properties after the appropriate heat treatment with a high Bs of 1.78 T, low Hc of 5.1 A/m, and low core loss less than 4.3 W/kg at 1.0 T and 400 Hz that is about 55% of that of oriented Si-steel. These results indicate that the application of this alloy to power transformers will produce very large energy savings.

  3. Amorphous phase formation in Fe-6.0wt%Si alloy by mechanical alloying

    SciTech Connect

    Filho, A.F.; Bolfarini, C.; Xu, Y.; Kiminami, C.S.

    1999-12-31

    Mechanical alloying, MA, is a high-energy ball milling technique, in which elemental blends are milled to achieve alloying at atomic level. This communication describes the results of an investigation on the phase transformation of a mixture of Fe and Si powders with 6wt%Si during MA processing. Besides the verification of the effect of milling time on the structure and on the compositional homogeneity, this study was undertaken in order to confirm, by using TEM technique, the possibility of amorphous phase formation for Si content lower than 17.7wt%.

  4. Compression behavior of Fe-Si-H alloys

    NASA Astrophysics Data System (ADS)

    Tagawa, S.; Ohta, K.; Hirose, K.; Ohishi, Y.

    2015-12-01

    Although the light elements in the Earth's core are still enigmatic, hydrogen has recently been receiving much attention. Planetary formation theory suggested that a large amount of water, much more than is in the oceans, could have been brought to the Earth during its accretion. Hydrogen is a strong siderophile element and could be incorporated into the core as a consequence of a reaction between water and molten iron in a magma ocean [Okuchi, 1997 Science]. Nevertheless, the effect of hydrogen on the property of iron is not well known so far. Here, we have experimentally examined the compression behavior of hcp Fe0.88Si0.12Hx (6.5 wt.% Si) at two different hydrogen concentrations (x = 0.7 and 0.9). Fe0.88Si0.12 foil was loaded into a diamond-anvil cell, and then liquid hydrogen was introduced to a sample chamber below 20 K. Hydrogenation occurred upon thermal annealing below 1500 K at 25-62 GPa, and hcp Fe0.88Si0.12Hx was obtained as a single phase. Unlike the Fe-H alloy, hydrogen did not fully occupy the octahedral sites even under hydrogen-saturated conditions. Two compression curves, one from 25 to 136 GPa, and the other from 62 to 128 GPa, were obtained at room temperature. While the effect of hydrogen on the compressibility of iron has been controversial in earlier experimental studies [Hirao et al., 2004 GRL; Pépin et al., 2014 PRL], our data indicate that the compressibility of Fe0.88Si0.12Hx alloy does not change with changing hydrogen content from x = 0 to 0.9. Such compression behavior observed is consistent with the recent ab initio calculations for hcp Fe-H alloys by Caracas[2015 GRL]. The extrapolation of present data to the outer core pressure and temperature range, assuming thermal expansivity is the same as that for iron and there is no density difference between solid and liquid, shows that the density of Fe0.88Si0.12H0.3 matches the PREM in the whole outer core within 1%.

  5. Oxidation of Fe-W Alloy Electrodeposits for Application to Anodes as Lithium Ion Batteries

    NASA Astrophysics Data System (ADS)

    Su, Changwei; Ye, Mengchao; Zhon, Linxing; Hou, Jianping; Li, Junmin; Guo, Junming

    2016-12-01

    A citrate-ammonia bath was selected to electrodeposit Fe-W alloys, which exhibit a crystalline structure even if the content of W in the Fe-W alloy is up to 37.8wt%. Those alloys could be oxidized partly at 700∘C. Resultant oxides were composed of Fe2O3, Fe3O4 and amorphous products. The composite oxides presented better electrochemical properties than those of the Fe2O3 and Fe3O4 composite formed by oxidation of Fe deposits. For instance, such an electrode demonstrates the reversible capacity of up to 2438.3mAhg-1 (in terms of incremental oxygen) after 100 charge-discharge cycles, while the electrodes of Fe2O3 and Fe3O4 composites formed by oxidation of Fe deposits were of only 667.5mAhg-1.

  6. Nanophase materials assembled from clusters

    SciTech Connect

    Siegel, R.W.

    1992-02-01

    The preparation of metal and ceramic atom clusters by means of the gas-condensation method, followed by their in situ collection and consolidation under high-vacuum conditions, has recently led to the synthesis of a new class of ultrafine-grained materials. These nanophase materials, with typical average grain sizes of 5 to 50 nm and, hence, a large fraction of their atoms in interfaces, exhibit properties that are often considerably improved relative to those of conventional materials. Furthermore, their synthesis and processing characteristics should enable the design of new materials with unique properties. Some examples are ductile ceramics that can be formed and sintered to full density at low temperatures without the need for binding or sintering aids, and metals with dramatically increased strength. The synthesis of these materials is briefly described along with what is presently known of their structure and properties. Their future impact on materials science and technology is also considered.

  7. Reversibility and coercivity of Fe-alloy/Fe:SiO2 multilayers

    NASA Astrophysics Data System (ADS)

    Zhang, Rui; Skomski, Ralph; Yin, Xiaolu; Liou, Sy-Hwang; Sellmyer, D. J.

    2010-05-01

    Soft bilayer alloys were produced by depositing granular Fe:SiO2 onto transition-metal thin films. We have prepared series of samples using different soft-magnetic materials including permalloy (Ni80Fe20), hcp Co90Fe10, and amorphous Co60Fe20B20, all covered by a layer of superparamagnetic Fe particles in a silicon-oxide matrix. The thickness of transition-metal layer was fixed and the magnetic properties of the bilayer system were studied by varying the Fe:SiO2 layers thicknesses from 0 to 70 nm. The bilayer yields a moderate improvement of the soft-magnetic performance. The hysteresis loops show a pronounced twofold anisotropy in the film plane for permalloy and amorphous CoFeB, which is consistent with the presence of external magnetic field during processing. This indicates that the coercivity is controlled by the pinning of 180° domain walls and that the effect of the Fe particles on the hysteresis is mediated by the interaction with the domain-wall stray fields.

  8. Fine structure of Fe-Co-Ga and Fe-Cr-Ga alloys with low Ga content

    SciTech Connect

    Kleinerman, Nadezhda M. Serikov, Vadim V. Vershinin, Aleksandr V. Mushnikov, Nikolai V. Stashkova, Liudmila A.

    2014-10-27

    Investigation of Ga influence on the structure of Fe-Cr and Fe-Co alloys was performed with the use of {sup 57}Fe Mössbauer spectroscopy and X-ray diffraction methods. In the alloys of the Fe-Cr system, doping with Ga handicaps the decomposition of solid solutions, observed in the binary alloys, and increases its stability. In the alloys with Co, Ga also favors the uniformity of solid solutions. The analysis of Mössbauer experiments gives some grounds to conclude that if, owing to liquation, clusterization, or initial stages of phase separation, there exist regions enriched in iron, some amount of Ga atoms prefer to enter the nearest surroundings of iron atoms, thus forming binary Fe-Ga regions (or phases)

  9. Mechanism and Kinetics of Mechanical Alloying in an Immiscible Fe-Mg System

    NASA Astrophysics Data System (ADS)

    Yelsukov, E. P.; Dorofeev, G. A.; Ulyanov, A. L.

    2005-07-01

    Mössbauer spectroscopy, X-ray diffraction, Auger spectroscopy, secondary ion mass-spectrometry and chemical analysis were used to study mechanical alloying of Fe and Mg powder mixture with the atomic ratio of 93:7. It has been shown that the process of mechanical alloying involves the formation of nanostructure in α-Fe particles, penetration and segregation of Mg atoms along the α-Fe grain boundaries, formation of the α-Fe(Mg) supersaturated solid solution.

  10. Irradiation-induced patterning in dilute Cu-Fe alloys

    NASA Astrophysics Data System (ADS)

    Stumphy, B.; Chee, S. W.; Vo, N. Q.; Averback, R. S.; Bellon, P.; Ghafari, M.

    2014-10-01

    Compositional patterning in dilute Cu1-xFex (x ≈ 12%) induced by 1.8 MeV Kr+ irradiation was studied as a function of temperature using atom probe tomography. Irradiation near room temperature led to homogenization of the sample, whereas irradiation at 300 °C and above led to precipitation and macroscopic coarsening. Between these two temperatures the irradiated alloys formed steady state patterns of composition where precipitates grew to a fixed size. The size in this regime increased somewhat with temperature. It was also observed that the steady state concentrations of Fe in Cu matrix and Cu in the Fe precipitates both greatly exceeded their equilibrium solubilities, with the degree of supersaturation in each phase decreasing with increasing temperature. In the macroscopic coarsening regime, the Fe-rich precipitates showed indications of a “cherry-pit” structure, with Cu precipitates forming within the Fe precipitates. In the patterning regime, interfaces between Fe-rich precipitates and the Cu-rich matrix were irregular and diffuse.

  11. Determination of the deformation mechanism of Fe-Mn alloys

    NASA Astrophysics Data System (ADS)

    Jo, Minho; Koo, Yang Mo; Kwon, Se Kyun

    2015-03-01

    The energy parameters of planar defects are decisive for understanding the deformation mechanisms of metals. The stacking fault energy has been regarded as a key parameter to determine the activation of the deformation mechanisms of the face-centered cubic metals and alloys. However, it is still under a long debate why the stacking fault energy can be treated to be such an exclusive parameter among the general planar fault energies. We have employed molecular dynamics method to examine the effects of Mn alloying on the deformation behavior of austenitic Fe-Mn systems. The energies of stable and unstable states are calculated by sliding the (111) plane and are analyzed in two different schemes, stacking fault energy and energy barriers, which leads to a contradiction between them. We show that a linear relationship can be identified among the energy barriers. This finding is used to identify the activated deformation mechanism. A new parameter is also suggested to characterize the material deformation.

  12. Oxidation behavior of Fe-20Cr steels alloyed with titanium at 1073 K

    NASA Astrophysics Data System (ADS)

    Setiawan, Asep Ridwan; Artono, Tri Juni

    2016-02-01

    In this work, the oxidation behavior of Fe-20 wt%Cr steels alloyed with different titanium contents: 0, 0.5, and 1 wt% are studied as a function of time in air atmosphere. The samples were isothermally oxidized at 1073 K for 86.4, 172.8, and 345.6 ks in a muffle furnace. The mass of specimen were recorded before and after oxidation. After the oxidation, phases in the oxide were identified by X-ray diffraction (XRD). Optical microscopy observation on the chromium base alloys show that the microstructure consist only ferritic phases. The addition of titanium in the Fe-20Cr alloys does not alter the microstructure significantly. The oxidation behavior of Fe-20Cr, Fe-20Cr-0.5Ti and Fe-20Cr-1Ti were followed the classical parabolic relationship with time. XRD analysis indicated that the oxide scales developed on the Fe-20Cr alloys surface during oxidation tests consisted mainly of Cr2O3. On the other hand, the oxide scales developed on the surface of Fe-20Cr-0.5Ti and Fe-20Cr-1Ti alloys comprised of Cr2O3 and TiO2 oxide. The formation of TiO2 oxide in the Ti-containing alloys consequently increases the mass gain of the alloys during oxidation compared to that of Fe-20Cr alloys.

  13. Magnetic properties of ball milled Fe-40Al at.% alloys

    SciTech Connect

    Amils, X.; Nogues, J.; Surinach, S.; Baro, M.D.; Munoz, J.S.

    1998-07-01

    A direct correlation between the lattice parameter and the saturation magnetization, during the disordering (ball milling) and posterior reordering (annealing) processes, has been found in Fe-40Al At.% compounds. These results indicate that the paramagnetic-ferromagnetic-paramagnetic transitions induced by ball milling and subsequent annealing could be related to the changes in volume, and not only to nearest neighbors effects as is commonly assumed. Moreover, these alloys have been found to become spin glass at low temperatures, independently of their structural state (ordered or disordered).

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

    NASA Astrophysics Data System (ADS)

    Lalnuntluanga, C.; Mishra, Raj Kumar

    2016-10-01

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

  15. Electronic structure of disordered α-FeMn alloys

    NASA Astrophysics Data System (ADS)

    Paduani, C.; da Silva, E. G.

    1996-08-01

    Cluster calculations were performed with the first-principles discrete variational method, in the LSD approximation and spin-polarized case, to investigate the electronic structure of the ferromagnetic disordered α-FeMn alloys. We investigated the effect on the local magnetic properties at iron sites of the introduction of Mn atoms in their first and second neighborhoods. The calculated magnetic moment and hyperfine magnetic field ( Hc) for an isolated Mn atom in a bcc iron host were obtained as -3.15 μB and -230 kG, respectively, in good agreement with experimental results.

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

    PubMed

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

    2016-06-06

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

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

    PubMed Central

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

    2016-01-01

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

  18. X-Ray Absorption Fine Structure Study for Fe60Ni40 Alloy

    SciTech Connect

    Yang, Dong-Seok; Oh, Kyuseung; Na, Wonkyung; Kim, Nayoung; Yoo, Yong-Goo; Min, Seung-Gi; Yu, Seong-Cho

    2007-02-02

    Fe60Ni40 alloys were fabricated by the mechanical alloying process with process periods of 1, 2, 4, 6, 12 and 24 hours, respectively. The formation of alloy and the structural evolution of the alloy were examined by X-ray diffraction and extended X-ray absorption fine structure methods. With increase of alloying time the BCC phase of iron was changed significantly during the mechanical alloying process. The alloying was activated in about 6 hours and completed in about 24 hours.

  19. Thermal Stability of Intermetallic Phases in Fe-rich Fe-Cr-Ni-Mo Alloys

    NASA Astrophysics Data System (ADS)

    Yang, Ying; Tan, Lizhen; Busby, Jeremy T.

    2015-09-01

    Understanding the thermal stability of intermetallic phases in Fe-rich Fe-Cr-Ni-Mo alloys is critical to alloy design and application of Mo-containing austenitic steels. Coupled with thermodynamic modeling, the thermal stability of intermetallic Chi and Laves phases in two Fe-Cr-Ni-Mo alloys was investigated at 1273 K, 1123 K, and 973 K (1000 °C, 850 °C, and 700 °C) for different annealing times. The morphologies, compositions, and crystal structures of the precipitates of the intermetallic phases were carefully examined by scanning electron microscopy, electron probe microanalysis, X-ray diffraction, and transmission electron microscopy. Two key findings resulted from this study. First, the Chi phase is stable at high temperature, and with the decreasing temperature it transforms into the Laves phase that is stable at low temperature. Secondly, Cr, Mo, and Ni are soluble in both the Chi and Laves phases, with the solubility of Mo playing a major role in the relative stability of the intermetallic phases. The thermodynamic models that were developed were then applied to evaluating the effect of Mo on the thermal stability of intermetallic phases in type 316 and NF709 stainless steels.

  20. Local magnetic effects of interface alloying in Fe/Co superlattices.

    PubMed

    Kamali-M, S; Bergman, A; Andersson, G; Stanciu, V; Häggström, L

    2006-07-05

    Effects of interface alloying and the thickness dependence of magnetic properties of Fe/Co(001) multilayers have been investigated. The thicknesses of the Fe layers have been varied between two and 14 monolayers while the Co layers have been held constant at 7 ML. From conversion electron Mössbauer spectroscopy (CEMS) measurements and electronic structure calculations it is found that the magnitude of the Fe magnetic hyperfine field is larger close to the interface and smaller in the middle of thick (≥9 ML) Fe layers. For a thinner Fe layer (≤5 ML) the largest field is found in the centre of the Fe layer. By modelling the effects of interface alloying from earlier data for bulk Fe-Co alloys, and comparing with the experimental results, the degree of interface alloying is estimated to be 2-3 ML at each interface.

  1. Effect of Thermomechanical Processing on the Microstructure and Properties of a Cu-Fe-P Alloy

    NASA Astrophysics Data System (ADS)

    Dong, Qiyi; Shen, Leinuo; Cao, Feng; Jia, Yanlin; Liao, Kaiju; Wang, Mingpu

    2015-04-01

    A Cu-0.7Fe-0.15P (wt.%) alloy was designed, and its comprehensive properties, especially electrical conductivity and temper-softening resistance of the designed alloy, were higher than those of traditional Cu-Fe-P alloys. The microstructure of this alloy was investigated with optical microscopy, scanning electron microscopy, and transmission electron microscopy. The particle of secondary phase was confirmed to be Fe2P with x-ray spectroscopy and digital diffractogram. By virtue of precipitation hardening and work hardening, the tensile strength and electrical conductivity of Cu-0.7Fe-0.15P alloy were 498 MPa and 62% IACS, respectively. The electrical conductivity of this alloy can be up to 92% IACS due to the complete precipitation of Fe2P. After repeating the cold rolling and aging process for three times, the tensile strength, elongation, and conductivity of this alloy were 467 MPa, 22%, and 78% IACS, respectively. Due to the low driving force of recrystallization and the pinning effect of fine dispersed Fe2P, the alloy with low deformation rate showed excellent softening resistance. The designed alloy can be used as a high-strength, high-electrical-conductivity lead-frame alloy.

  2. Effects of Be and Fe content on plane strain fracture toughness in A357 alloys

    SciTech Connect

    Tan, Y.H.; Lee, S.L.; Lin, Y.L.

    1995-11-01

    The effect of Be and Fe content on the plane strain fracture toughness K{sub IC} of aluminum-based A357 alloys is investigated. The fracture behavior of A357 alloys has been evaluated as a function of both the magnitude and morphology of iron-bearing compounds and silicon particles. Addition of Be is beneficial for tensile properties and fracture toughness in the case of alloys containing intermediate (0.07 pct) and higher (0.15 pct) Fe levels. On the other hand, Be added to alloys containing the lower Fe (0.01 pct) level appears detrimental to tensile strength, but the quality index, notch-yield ratio (NYR), and plane strain fracture toughness were improved. Fractographic analysis reveals that crack extension of A357 alloys occurs mainly in an intergranular fracture mode. The fracture processes are initiated by void nucleation at iron-bearing compounds or irregularly shaped eutectic silicon particles as a result of their cracking and decohesion from the matrix. Then, void growth and coalescence result in growth of the main crack by shear-linkage-induced breakdown of submicron-strengthening particles. The effect of Be on increasing K{sub IC} is more apparent in the higher Fe alloys than in the lower Fe alloys. Superior toughness obtained by microstructural control has also been achieved in the intermediate and higher Fe levels of Be-containing alloys, with values equal to those obtained in alloys of lower Fe content.

  3. Effects of be and fe content on plane strain fracture toughness in A357 alloys

    NASA Astrophysics Data System (ADS)

    Tan, Yen-Hung; Lee, Sheng-Long; Lin, Yu-Lom

    1995-11-01

    The effect of Be and Fe content on the plane strain fracture toughness K IC of aluminum-based A357 alloys is investigated. The fracture behavior of A357 alloys has been evaluated as a function of both the magnitude and morphology of iron-bearing compounds and silicon particles. Addition of Be is beneficial for tensile properties and fracture toughness in the case of alloys containing intermediate (0.07 pct) and higher (0.15 pct) Fe levels. On the other hand, Be added to alloys containing the lower Fe (0.01 pct) level appears detrimental to tensile strength, but the quality index, notch-yield ratio (NYR), and plane strain fracture toughness were improved. Fractographic analysis reveals that crack extension of A357 alloys occurs mainly in an intergranular fracture mode. The fracture processes are initiated by void nucleation at iron-bearing compounds or irregularly shaped eutectic silicon particles as a result of their cracking and decohesion from the matrix. Then, void growth and coalescence result in growth of the main crack by shear-linkage-induced breakdown of submicronstrengthening particles. The effect of Be on increasing K IC is more apparent in the higher Fe alloys than in the lower Fe alloys. Superior toughness obtained by microstructural control has also been achieved in the intermediate and higher Fe levels of Be-containing alloys, with values equal to those obtained in alloys of lower Fe content.

  4. New Fe-Ni based metal-metalloid glassy alloys prepared by mechanical alloying and rapid solidification

    SciTech Connect

    Sunol, J.J.; Clavaguera-Mora, M.T.; Clavaguera, N.; Pradell, T.

    1997-12-31

    Mechanical alloying and rapid solidification are two important routes to obtain glassy alloys. New Fe-Ni based metal-metalloid (P-Si) alloys prepared by these two different processing routes were studied by differential scanning calorimetry and transmission Moessbauer spectroscopy. Mechanical alloyed samples were prepared with elemental precursors, and different nominal compositions. Rapidly solidified alloys were obtained by melt-spinning. The structural analyses show that, independent of the composition, the materials obtained by mechanical alloying are not completely disordered whereas fully amorphous alloys were obtained by rapid solidification. Consequently, the thermal stability of mechanically alloyed samples is lower than that of the analogous material prepared by rapid solidification. The P/Si ratio controls the magnetic interaction of the glassy ribbons obtained by rapid solidification. The experimental results are discussed in terms of the degree of amorphization and crystallization versus processing route and P/Si ratio content.

  5. Biskyrmion bubble lattice in Fe/Gd alloy thin films

    NASA Astrophysics Data System (ADS)

    Lee, James; Shi, Xiaowen; Chess, Jordan; Montoya, Sergio; Mishra, Shrawan; Sakharov, Lev; Parks, Daniel; McMorran, Ben; Kevan, Steven; Fullerton, Eric; Roy, Sujoy

    2015-03-01

    Magnetic bubbles with topologically non-trivial twists, called ``skyrmion bubbles,'' exhibit particle-like properties and novel magnetic interactions with each other. They are seen in non-centrosymmetric crystals, such as MnSi, and monolayers of Fe on Ir(111) substrates. Our study considers whether skyrmion bubbles can also form in soft ferrimagnetic alloys with perpendicular anisotropy. Using resonant x-ray scattering at the Fe L3 and Gd M5 transition edges, we show that triangular lattices of skyrmion bubbles form in Fe/Gd thin films in a limited temperature and magnetic field range. Uniaxial anisotropy in the resonant scattering pattern indicates the lattice unit cell contains two skyrmions. Lorentz TEM images reveal that the repeating unit is a bound pair of bubbles called biskyrmions. Adjusting the composition of the films can shift the temperature range of the biskyrmion lattice by 100 K, allowing the lattice to form at room temperature. Fe/Gd thin films may prove a promising material for spintronics.

  6. A systematic ALCHEMI study of Fe-doped NiAl alloys

    SciTech Connect

    Anderson, I.M.; Bentley, J.; Duncan, A.J.

    1995-06-01

    ALCHEMI site-occupation studies of alloying additions to ordered aluminide intermetallic alloys have been performed with varying degrees of success, depending on the ionization delocalization correction. This study examines the variation in the site-occupancy of Fe in B2-ordered NiAl vs solute concentration and alloy stoichiometry. The fraction of Fe on the `Ni` site is plotted vs Fe concentration. The good separation among the data from alloys of the three stoichiometries shows that the site occupancy of iron depends on the relative concentrations of the Ni and Al host elements; however a preference for the `Ni` site is clearly indicated.

  7. A comparative study of short range order in Fe-Cr and Fe-V alloys around equiatomic composition

    SciTech Connect

    Turchi, P.E.A.; Sluiter, M. ); Stocks, G.M. )

    1990-12-04

    Configurational energies have been calculated for equiatomic Fe-Cr and Fe-V alloys possessing the high temperature bcc crystalline structure, within a first principles electronic band structure approach. In agreement with experimental facts, a tendency towards order, with a B2 ordered structure of CsCl type, is found for FeV whereas phase separation characterized FeCr. These results suggest that the nature of short range order in the high temperature bcc solid solution is not the primary driving force for describing the structural transformation from bcc to sigma which takes place in both alloys upon decreasing temperature. 15 refs., 9 figs., 1 tab.

  8. Spin glass transition in canonical AuFe alloys: A numerical study

    NASA Astrophysics Data System (ADS)

    Zhang, Kai-Cheng; Li, Yong-Feng; Liu, Gui-Bin; Zhu, Yan

    2012-05-01

    Although spin glass transitions have long been observed in diluted magnetic alloys, e.g. AuFe and CuMn alloys, previous numerical studies are not completely consistent with the experiment results. The abnormal critical exponents of the alloys remain still puzzling. By employing parallel tempering algorithm with finite-size scaling analysis, we investigated the phase transitions in canonical AuFe alloys. Our results strongly support that spin glass transitions occur at finite temperatures in the alloys. The calculated critical exponents agree well with those obtained from experiments.

  9. Elastic Modulus Measurement of ORNL ATF FeCrAl Alloys

    SciTech Connect

    Thompson, Zachary T.; Terrani, Kurt A.; Yamamoto, Yukinori

    2015-10-01

    Elastic modulus and Poisson’s ratio for a number of wrought FeCrAl alloys, intended for accident tolerant fuel cladding application, are determined via resonant ultrasonic spectroscopy. The results are reported as a function of temperature from room temperature to 850°C. The wrought alloys were in the fully annealed and unirradiated state. The elastic modulus for the wrought FeCrAl alloys is at least twice that of Zr-based alloys over the temperature range of this study. The Poisson’s ratio of the alloys was 0.28 on average and increased very slightly with increasing temperature.

  10. Application of damping mechanism model and stacking fault probability in Fe-Mn alloy

    SciTech Connect

    Huang, S.K.; Wen, Y.H.; Li, N. Teng, J.; Ding, S.; Xu, Y.G.

    2008-06-15

    In this paper, the damping mechanism model of Fe-Mn alloy was analyzed using dislocation theory. Moreover, as an important parameter in Fe-Mn based alloy, the effect of stacking fault probability on the damping capacity of Fe-19.35Mn alloy after deep-cooling or tensile deformation was also studied. The damping capacity was measured using reversal torsion pendulum. The stacking fault probability of {gamma}-austenite and {epsilon}-martensite was determined by means of X-ray diffraction (XRD) profile analysis. The microstructure was observed using scanning electronic microscope (SEM). The results indicated that with the strain amplitude increasing above a critical value, the damping capacity of Fe-19.35Mn alloy increased rapidly which could be explained using the breakaway model of Shockley partial dislocations. Deep-cooling and suitable tensile deformation could improve the damping capacity owning to the increasing of stacking fault probability of Fe-19.35Mn alloy.

  11. Chemically synthesized magnetic Co-Fe-Ga alloy nanoparticles

    NASA Astrophysics Data System (ADS)

    Imai, Takatomo; Shima, Mutsuhiro

    2017-01-01

    Magnetic properties of Co2Fe x Ga y alloy nanoparticles in the L21 ordered phase produced by chemical synthesis and post annealing have been investigated. Structural analyses of the Co2Fe x Ga y samples by X-ray diffraction show that both ordered B2 and L21 phases are formed when Ga composition is in the range 0.66 ≤ y ≤ 1.42. With increasing y from 0.58 to 1.4 at x = 1.0, the coercivity increases from 7.1 to 23 mT, while the saturation magnetization decreases from 970 to 410 kA/m. Microstructural analyses using TEM reveal that the alloy particles annealed at 973 K are agglomerated by sintering. When Al(NO3)3 was added during the synthesis, the average particle size significantly decreases from 84 to 12 nm, presumably due to the formation of aluminum oxides, resulting in the decrease in coercivity from 29 to 5.1 mT.

  12. Synthesis, characterization, and microwave absorption properties of Fe-40 wt%Ni alloy prepared by mechanical alloying and annealing

    NASA Astrophysics Data System (ADS)

    Liu, Jun; Feng, Yongbao; Qiu, Tai

    2011-12-01

    Fe-40 wt%Ni alloys with granular shape and flake shape were prepared by a mechanical alloying (MA) and annealing method. The phase composition and morphology of the FeNi alloys, electromagnetic parameters, and microwave absorbing properties of the silicone rubber composite absorbers filled with the as-prepared FeNi alloy particles were characterized using X-ray diffraction (XRD), scanning electron microscope (SEM) and vector network analyzer. The XRD results indicate that the crystalline structures of the Fe-40 wt%Ni alloys prepared by both one-step and two-step MA processes are face-centered cubic (fcc) Ni (Fe) solid solutions, and the structures can be retained after annealing at 600 °C for 2 h. SEM images show that the FeNi alloy powders for one-step process have a granular shape; however the particles turned into flake form when they were sequentially milled with absolute ethyl alcohol. With the increase in thickness of composite absorber, the reflection loss (RL) decreases, and the peak for minimum reflection loss shifts towards the lower frequency range. Compared to the absorbers filled with the granular FeNi alloy, the absorbers filled with flaky FeNi alloys possess higher complex permittivities and permeabilities and have a lower RL and peak frequency under the same thickness. Microwave absorbing materials with a low reflection loss peak in the range of 1-4 GHz are obtained, and their microwave absorbing properties can be adjustable by changing their thicknesses.

  13. Phase separation in equiatomic AlCoCrFeNi high-entropy alloy.

    PubMed

    Manzoni, A; Daoud, H; Völkl, R; Glatzel, U; Wanderka, N

    2013-09-01

    The microstructure of the as-cast AlCoCrFeNi high entropy alloy has been investigated by transmission electron microscopy and atom probe tomography. The alloy shows a very pronounced microstructure with clearly distinguishable dendrites and interdendrites. In both regions a separation into an Al-Ni rich matrix and Cr-Fe-rich precipitates can be observed. Moreover, fluctuations of single elements within the Cr-Fe rich phase have been singled out by three dimensional atom probe measurements. The results of investigations are discussed in terms of spinodal decomposition of the alloying elements inside the Cr-Fe-rich precipitates.

  14. Ordering, magnetostriction, and elastic properties in Fe-27.5 at. % Ga alloy single crystals

    SciTech Connect

    Jayaraman, Tanjore V.; Corson, Robert P.; Guruswamy, Sivaraman

    2007-09-01

    Fe-Ga alloys, with composition around 27.5 at. % Ga, can be heat treated to obtain {alpha} (A2, bcc), {alpha}{sup ''} (D0{sub 3}-like, ordered bcc), {beta}-Fe{sub 3}Ga (D0{sub 19}, ordered hexagonal), and {alpha}-Fe{sub 3}Ga (L1{sub 2} ordered fcc) phases. In this work, the influence of {alpha}{sup ''} ordering on the magnetostriction coefficient (3/2) {lambda}{sub 100}, elastic constants (C{sub 11}, C{sub 12}, and C{sub 44}), and the magnetomechanical coefficients (B{sub 1}) of the single crystals of {alpha}-Fe-27.5 at.% Ga and {alpha}{sup ''}-Fe-27.5 at. % Ga alloy is examined. Single crystals of Fe-27.5 at. % Ga were grown using the vertical Bridgman technique. Magnetostriction measurements were performed using [100]-oriented single crystals. Elastic constants were estimated using resonant ultrasound spectroscopy and analysis technique. It is shown that the {alpha}{sup ''} ordering in Fe-27.5 at. % Ga alloy decreases the (3/2) {lambda}{sub 100} value from that of {alpha} phase. This is consistent with our previous work on polycrystalline Fe-27.5 at. % Ga alloys. The {alpha}-Fe-27.5 at.% Ga alloy single crystal was found to have a higher magnetoelastic coupling constant than the {alpha}{sup ''}-Fe-27.5 at. % Ga alloy single crystal.

  15. Ordering, magnetostriction, and elastic properties in Fe-27.5 at. % Ga alloy single crystals

    NASA Astrophysics Data System (ADS)

    Jayaraman, Tanjore V.; Corson, Robert P.; Guruswamy, Sivaraman

    2007-09-01

    Fe-Ga alloys, with composition around 27.5at.% Ga, can be heat treated to obtain α (A2, bcc), α″ (D03-like, ordered bcc), β-Fe3Ga (D019, ordered hexagonal), and α-Fe3Ga (L12 ordered fcc) phases. In this work, the influence of α″ ordering on the magnetostriction coefficient (3/2) λ100, elastic constants (C11, C12, and C44), and the magnetomechanical coefficients (B1) of the single crystals of α-Fe-27.5at. % Ga and α″-Fe-27.5at.% Ga alloy is examined. Single crystals of Fe-27.5at.% Ga were grown using the vertical Bridgman technique. Magnetostriction measurements were performed using [100]-oriented single crystals. Elastic constants were estimated using resonant ultrasound spectroscopy and analysis technique. It is shown that the α″ ordering in Fe-27.5at.% Ga alloy decreases the (3/2) λ100 value from that of α phase. This is consistent with our previous work on polycrystalline Fe-27.5at.% Ga alloys. The α-Fe-27.5at. % Ga alloy single crystal was found to have a higher magnetoelastic coupling constant than the α″-Fe-27.5at.% Ga alloy single crystal.

  16. Seismic parameters of hcp-Fe alloyed with Ni and Si in the Earth's inner core

    NASA Astrophysics Data System (ADS)

    Liu, Jin; Lin, Jung-Fu; Alatas, Ahmet; Hu, Michael Y.; Zhao, Jiyong; Dubrovinsky, Leonid

    2016-02-01

    Iron alloyed with Ni and Si has been suggested to be a major component of the Earth's inner core. High-pressure results on the combined alloying effects of Ni and Si on seismic parameters of iron are thus essential for establishing satisfactory geophysical and geochemical models of the region. Here we have investigated the compressional (VP) and shear (Vs) wave velocity-density (ρ) relations, Poisson's ratio (ν), and seismic heterogeneity ratios (dlnρ/dlnVP, dlnρ/dlnVS, and dlnVP/dlnVS) of hcp-Fe and hcp-Fe86.8Ni8.6Si4.6 alloy up to 206 GPa and 136 GPa, respectively, using multiple complementary techniques. Compared with the literature velocity values for hcp-Fe and Fe-Ni-Si alloys, our results show that the combined addition of 9.0 wt % Ni and 2.3 wt % Si slightly increases the VP but significantly decreases the VS of hcp-Fe at a given density relevant to the inner core. Such distinct alloying effects on velocities of hcp-Fe produce a high ν of about 0.40 for the alloy at inner core densities, which is approximately 20% higher than that for hcp-Fe. Analysis of the literature high P-T results on VP and VS of Fe alloyed with light elements shows that high temperature can further enhance the ν of hcp-Fe alloyed with Ni and Si. Most significantly, the derived seismic heterogeneity ratios of this hcp alloy present a better match with global seismic observations. Our results provide a multifactored geophysical constraint on the compositional model of the inner core which is consistent with silicon being a major light element alloyed with Fe and 5 wt % Ni.

  17. Time evolution of morphology in mechanically alloyed Fe-Cu.

    PubMed

    Wille, Catharina G; Al-Kassab, Tala'at; Kirchheim, Reiner

    2011-05-01

    Being widely accessible as well as already utilised in many applications, Fe-Cu acts as an ideal binary model alloy to elaborate the enforced nonequilibrium enhanced solubility in such a solution system that shows a limited regime of miscibility and characterised by a large positive heat of mixing. In addition to the detailed analysis of ball milled Fe-Cu powders by means of Atom Probe Tomography (APT), site specific structural analysis has been performed in this study using Transmission Electron Microscopy (TEM). In this contribution results on powders with low Cu concentrations (2.5-10 at%) are presented. Combining a ductile element (Cu, fcc) and a brittle one (Fe, bcc), striking differences in morphology were expected and found on all length-scales, depending on the mixing ratio of the two elements. However, not only could the atomic mixing of Fe and Cu be evaluated, but also the distribution of impurities, mostly stemming from the fabrication procedure. The combination of APT and TEM enables a correlation between the structural evolution and the chemical mixing during the milling process. For the first time, a clear distinction can be drawn between the morphological evolution at the surface and in the interior of the powder particles. This became possible owing to the site specific sample preparation of TEM lamellae by Focussed Ion Beam (FIB). Surprisingly, the texture arising from the ball milling process can directly be related to the classical rolling texture of cold rolled Fe. In addition, full homogeneity can be achieved even on the nano-scale for this material as shown by APT, resulting in an extended miscibility region in comparison to the equilibrium phase diagram. Grain sizes were determined by means of XRD and TEM. The strain corrected XRD results are in very good agreement with the values derived by TEM, both confirming a truly nanocrystalline structure.

  18. Production of Fe from Fe2O3 using a dry Mechanical Alloying Process

    SciTech Connect

    Waanders, F.B.; Mulaba-Bafubiandi, A.F.

    2005-04-26

    Mechanical alloying has been, and is still being employed extensively to synthesize a variety of alloy phases. The primary interest is to produce materials for scientific research and technological applications for magnetic recording media and permanent magnetic field devices. In the present investigation however the aim was not to produce a special alloy phases but to prove the viability of the production of iron from naturally occurring hematite, using mechanical alloying. Discard fines from the biggest hematite producer, Kumba Resources, Sishen, South Africa, were obtained and mixed with aluminum powder in the ratio of 25 at.% Al, balance hematite. About 50 g of the hematite-Al mixture, to be mechanically milled, was dry milled in a planetary ball milling equipment. The milling times varied between 30 min. and 30 hours and samples for Moessbauer spectroscopy, SEM analyses and Malvern sizing were obtained for each milling interval. Milling of the fine hematite with the much coarser Al resulted in a mixture with a particle size distribution of d0.5 = 54{mu}m to be extracted from the mill after 30 min. The Moessbauer spectra yielded 93% Fe2O3 and a 7% intermetallic Fe-Al component for this milling period. A final particle size of d0.5 = 20{mu}m for the milled product was obtained after milling for up to 30 h. However, within an hour all the hematite was completely converted to iron ({approx_equal} 86%) and two intermetallic Fe-Al compounds of combined intensity {approx_equal} 14%. The intensity ratio of the two intermetallic Fe-Al alloys that were observed as two doublets, changed after 3 h milling time and the averaged Moessbauer parameters for the two doublets are reported as: D1 = ({delta} = 0.50 {+-} 0.03 mm.s-1 and {delta} = 0.24 {+-} 0.03 mm.s-1) and D2 = ({delta} = 2.07 {+-} 0.03 mm.s-1 and {delta} = 0.98 {+-} 0.03 mm.s-1) respectively.

  19. Evaluation of Magnetostrictive Shunt Damper Performance Using Iron (Fe)-Gallium (Ga) Alloy

    DTIC Science & Technology

    2013-09-01

    Evaluation of Magnetostrictive Shunt Damper Performance Using Iron (Fe)-Gallium (Ga) Alloy by Andrew James Murray and Dr. JinHyeong Yoo...Aberdeen Proving Ground, MD 21005 ARL-TN-0566 September 2013 Evaluation of Magnetostrictive Shunt Damper Performance Using Iron (Fe... Magnetostrictive Shunt Damper Performance Using Iron (Fe)- Gallium (Ga) Alloy 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6

  20. Modified embedded-atom method interatomic potential for the Fe-Cu alloy system and cascade simulations on pure Fe and Fe-Cu alloys

    NASA Astrophysics Data System (ADS)

    Lee, Byeong-Joo; Wirth, Brian D.; Shim, Jae-Hyeok; Kwon, Junhyun; Kwon, Sang Chul; Hong, Jun-Hwa

    2005-05-01

    A modified embedded-atom method (MEAM) interatomic potential for the Fe-Cu binary system has been developed using previously developed MEAM potentials of Fe and Cu. The Fe-Cu potential was determined by fitting to data on the mixing enthalpy and the composition dependencies of the lattice parameters in terminal solid solutions. The potential gives a value of 0.65eV for the dilute heat of solution and reproduces the increase of lattice parameter of Fe with addition of Cu in good agreement with experiments. The potential was used to investigate the primary irradiation defect formation in pure Fe and Fe-0.5at.%Cu alloy by a molecular dynamics cascade simulation study with a PKA energy of 2keV at 573K . A tendency for self-interstitial atom-Cu binding, the formation of mixed (Fe-Cu) dumbbells and even Cu-Cu dumbbells was observed. Given a positive binding energy between Cu atoms and self-interstitials, Cu transport by an interstitial diffusion mechanism could be proposed to contribute to the formation of Cu-rich precipitates and irradiation-induced embrittlement in nuclear structural steels.

  1. Ferromagnetic interactions and martensitic transformation in Fe doped Ni-Mn-In shape memory alloys

    SciTech Connect

    Lobo, D. N.; Priolkar, K. R.; Emura, S.; Nigam, A. K.

    2014-11-14

    The structure, magnetic, and martensitic properties of Fe doped Ni-Mn-In magnetic shape memory alloys have been studied by differential scanning calorimetry, magnetization, resistivity, X-ray diffraction (XRD), and EXAFS. While Ni{sub 2}MnIn{sub 1−x}Fe{sub x} (0 ≤ x ≤ 0.6) alloys are ferromagnetic and non martensitic, the martensitic transformation temperature in Ni{sub 2}Mn{sub 1.5}In{sub 1−y}Fe{sub y} and Ni{sub 2}Mn{sub 1.6}In{sub 1−y}Fe{sub y} increases for lower Fe concentrations (y ≤ 0.05) before decreasing sharply for higher Fe concentrations. XRD analysis reveals presence of cubic and tetragonal structural phases in Ni{sub 2}MnIn{sub 1−x}Fe{sub x} at room temperature with tetragonal phase content increasing with Fe doping. Even though the local structure around Mn and Ni in these Fe doped alloys is similar to martensitic Mn rich Ni-Mn-In alloys, presence of ferromagnetic interactions and structural disorder induced by Fe affect Mn-Ni-Mn antiferromagnetic interactions resulting in suppression of martensitic transformation in these Fe doped alloys.

  2. Binder-jetting 3D printing and alloy development of new biodegradable Fe-Mn-Ca/Mg alloys.

    PubMed

    Hong, Daeho; Chou, Da-Tren; Velikokhatnyi, Oleg I; Roy, Abhijit; Lee, Boeun; Swink, Isaac; Issaev, Ilona; Kuhn, Howard A; Kumta, Prashant N

    2016-11-01

    3D printing of various biomaterials including titanium and stainless steel has been studied for treating patients with cranio-maxillofacial bone defect. The potential long term complications with use of inert biometals have opened the opportunities for use of biodegradable metals in the clinical arena. The authors previously reported that binder-jet 3D printing technique enhanced the degradation rates of biodegradable Fe-Mn alloy by creating engineered micropores rendering the system attractive as biodegradable implantable devices. In the present study, the authors employed CALPHAD modeling to systematically study and modify the Fe-Mn alloy composition to achieve enhanced degradation rates. Accordingly, Ca and Mg addition to Fe-35wt% Mn solid solution predicted increase in degradation rates. In order to validate the CALPHAD results, Fe - (35-y)wt% Mn - ywt% X (X=Ca, Mg, and y=0, 1, 2) were synthesized by using high energy mechanical alloying (HEMA). Sintered pellets of Fe-Mn-Ca and Fe-Mn-Mg were then subjected to potentiodynamic polarization (PDP) and live/dead cell viability tests. Sintered pellets of Fe-Mn, Fe-Mn-Ca, and Fe-Mn-Mg also exhibited MC3T3 murine pre-osteoblast cells viability in the live/dead assay results. Fe-Mn and Fe-Mn-1Ca were thus accordingly selected for 3D printing and the results further confirmed enhanced degradation of Ca addition to 3D printed constructs validating the theoretical and alloy development studies. Live/dead and MTT cell viability results also confirmed good cytocompatibility of the 3D-printed Fe-Mn and Fe-Mn-1Ca constructs.

  3. Magnetic and magnetotransport properties of nanocrystalline Ag 0.85Fe 0.15 and Ag 0.70Fe 0.30 alloys prepared by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Gómez, J. A.; Xia, S. K.; Passamani, E. C.; Giordanengo, B.; Baggio-Saitovitch, E. M.

    2001-01-01

    The magnetic and magnetotransport properties of nanocrystalline Ag 0.85Fe 0.15 and Ag 0.70Fe 0.30 alloys have been studied by Mössbauer spectroscopy, magnetization and resistivity measurements. The samples were prepared by mechanical alloying of Fe and Ag powders in a high-energy ball mill. Mössbauer spectroscopy and magnetic measurements of the final milled samples indicate the presence of single-domain 'Fe' particles. The magnetoresistance values, at 4.2 K and for a magnetic field of 8 T, are 2.5% and 5.7% for samples Ag 0.85Fe 0.15 and Ag 0.70Fe 0.30, respectively. The magnetoresistance behavior indicates the cluster-glass-like features in both the final milled samples.

  4. Effect of niobium on the HDDR behaviour of near-stoichiometric NdFeB alloys

    NASA Astrophysics Data System (ADS)

    Ahmed, F. M.; Ataie, A.; Williams, A. J.; Harris, I. R.

    1996-05-01

    The HDDR behaviours of Nd11.8Fe81.3Nb1B5.9, Nd11.8Fe80.3Nb2B5.9 (at%) alloys were studied using a high resolution scanning electron microscope (HRSEM) in order to relate the initial, intermediate and final microstructures, to that of NdFeB-type alloys without additions. The disproportionation of the Nd2Fe14B (φ) matrix phase starts at the grain boundary and at the interface of the Nb26Fe32B42/φ phases, resulting in the formation of a submicron structure consisting of Fe, Fe2B and Nd-hydride. The HDDR process proved to be a very rapid and efficient method of homogenising the as-cast alloys. Promising magnetic properties have been obtained for bonded magnets using the HDDR powder.

  5. oxide and FeNi alloy: product dependence on the reduction ability

    NASA Astrophysics Data System (ADS)

    Cao, Jungang; Qin, Yuyang; Li, Minglun; Zhao, Shuyuan; Li, Jianjun

    2014-12-01

    Based on the sol-gel combustion method, stoichiometric Fe3+, Mn2+, Ni2+ ions and citric acid were chosen as the initial reactants for the preparation of magnetic particles. Due to the different reduction ability of metal ions, completely different magnetic products (MnFe2O4 oxide and FeNi alloy) were obtained by heating the flakes at 600 °C under nitrogen atmosphere. MnFe2O4 particles exhibit superparamagnetic behavior at room temperature, and martensitic phase transformation is observed magnetically at 125 K for FeNi alloy particles.

  6. Comparative Study by MS and XRD of Fe50Al50 Alloys Produced by Mechanical Alloying, Using Different Ball Mills

    NASA Astrophysics Data System (ADS)

    Rojas Martínez, Y.; Pérez Alcázar, G. A.; Bustos Rodríguez, H.; Oyola Lozano, D.

    2005-02-01

    In this work we report a comparative study of the magnetic and structural properties of Fe50Al50 alloys produced by mechanical alloying using two different planetary ball mills with the same ball mass to powder mass relation. The Fe50Al50 sample milled during 48 h using the Fritsch planetary ball mill pulverisette 5 and balls of 20 mm, presents only a bcc alloy phase with a majority of paramagnetic sites, whereas that sample milled during the same time using the Fritsch planetary ball mill pulverisette 7 with balls of 15 mm, presents a bcc alloy phase with paramagnetic site (doublet) and a majority of ferromagnetic sites which include pure Fe. However for 72 h of milling this sample presents a bcc paramagnetic phase, very similar to that prepared with the first system during 48 h. These results show that the conditions used in the first ball mill equipment make more efficient the milling process.

  7. An APFIM/AEM Study of Phase Decompositions in Fe-Ni Alloys at Low Temperatures

    NASA Technical Reports Server (NTRS)

    Zhang, J.; Miller, M. K.; Williams, D. B.; Goldstein, J. I.

    1992-01-01

    A combined atom probe field ion microscopy and analytical electron microscopy characterization has been performed on laboratory aged martensitic and austenitic specimens of FeNi and FeNiP alloys. These techniques revealed that the martensitic 24.1 and 28.6 at.% Ni alloys decomposed during aging for 1 year at 300 C to form face centered cubic precipitates of approx. 56 at.% Ni in a body centered cubic matrix containing approx. 20 at.% Ni. Some thin platelets were observed in the field ion micrographs of the austenitic Fe-42.9 at. % Ni alloy and the Fe-43.2 at.% Ni-0.44 at.% P alloy after aging at 400 and 350 C. Atom probe analysis revealed phosphorus clustering in the ternary alloy aged at 300 C.

  8. The effect of heat treatment on amorphous Fe74Zr19Ta7 and Fe90Y10 alloys

    NASA Astrophysics Data System (ADS)

    Prater, J. T.; Merz, M. D.

    1981-03-01

    Magnetic measurements are reported for two iron-based amorphous alloys: Fe90Y10 and Fe74Zr19Ta7. Each is prepared by sputter deposition. X-tay diffraction is used to established the amorphous structure and X-ray fluorescence analysis to confirm the composition. Fe74Zr19Ta7 has a Curie temperature of 195 K and a crystallization temperature of 733 K (460 °C). Annealing studies on Fe74Zr19Ta7 indicate that this alloy does not show the dramatic increases in Curie temperature that are commonly observed in amorphous alloys that contain metalloid elements. Rather, this alloy exhibits small irreversible decreases in the Curie temperature following heat treatments up to 733 K (460 °C), the crystallization temperature. The amorphous Fe90Y10 alloy shows only short range order and has a large anisotropy field that prevents the saturation of the magnetic moment in a 10 kOe field at 78 K. The anisotropy decreases upon crystallization to a bcc iron structure, but ferromagnetism is observed only after annealing the alloy at elevated temperatures.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  10. Thermodynamic analysis of binary Fe85B15 to quinary Fe85Si2B8P4Cu1 alloys for primary crystallizations of α-Fe in nanocrystalline soft magnetic alloys

    NASA Astrophysics Data System (ADS)

    Takeuchi, A.; Zhang, Y.; Takenaka, K.; Makino, A.

    2015-05-01

    Fe-based Fe85B15, Fe84B15Cu1, Fe82Si2B15Cu1, Fe85Si2B12Cu1, and Fe85Si2B8P4Cu1 (NANOMET®) alloys were experimental and computational analyzed to clarify the features of NANOMET that exhibits high saturation magnetic flux density (Bs) nearly 1.9 T and low core loss than conventional nanocrystalline soft magnetic alloys. The X-ray diffraction analysis for ribbon specimens produced experimentally by melt spinning from melts revealed that the samples were almost formed into an amorphous single phase. Then, the as-quenched samples were analyzed with differential scanning calorimeter (DSC) experimentally for exothermic enthalpies of the primary and secondary crystallizations (ΔHx1 and ΔHx2) and their crystallization temperatures (Tx1 and Tx2), respectively. The ratio ΔHx1/ΔHx2 measured by DSC experimentally tended to be extremely high for the Fe85Si2B8P4Cu1 alloy, and this tendency was reproduced by the analysis with commercial software, Thermo-Calc, with database for Fe-based alloys, TCFE7 for Gibbs free energy (G) assessments. The calculations exhibit that a volume fraction (Vf) of α-Fe tends to increase from 0.56 for the Fe85B15 to 0.75 for the Fe85Si2B8P4Cu1 alloy. The computational analysis of the alloys for G of α-Fe and amorphous phases (Gα-Fe and Gamor) shows that a relationship Gα-Fe ˜ Gamor holds for the Fe85Si2B12Cu1, whereas Gα-Fe < Gamor for the Fe85Si2B8P4Cu1 alloy at Tx1 and that an extremely high Vf = 0.75 was achieved for the Fe85Si2B8P4Cu1 alloy by including 2.8 at. % Si and 4.5 at. % P into α-Fe. These computational results indicate that the Fe85Si2B8P4Cu1 alloy barely forms amorphous phase, which, in turn, leads to high Vf and resultant high Bs.

  11. Effect of Fe on Microstructure and Properties of 8xxx Aluminum Conductor Alloys

    NASA Astrophysics Data System (ADS)

    Pan, Lei; Liu, Kun; Breton, Francis; -Grant Chen, X.

    2016-12-01

    The effect of Fe contents (0.3-0.7 wt.%) on the microstructure, electrical conductivity, mechanical and creep properties of 8xxx aluminum conductor alloys was investigated. Results revealed that the as-cast microstructure of 8xxx alloys was consisted of equiaxed α-Al grains and secondary Fe-rich intermetallics distributed in the interdendritic region. The extruded microstructure showed partially recrystallized structure for 0.3% Fe alloy but only dynamically recovered structures for 0.5 and 0.7% Fe alloys. With increasing Fe contents, the ultimate tensile strength and yield strength were remarkably improved, while the electrical conductivity was slightly decreased. Moreover, the creep resistance was greatly improved, which is attributed to the larger volume fraction of fine intermetallic particles and smaller subgrain size in the higher Fe-containing alloys. The creep threshold stress was found to increase from 24.6 to 33.9 MPa with increasing Fe contents from 0.3 to 0.7%, respectively. The true stress exponent values were close to 3 for all three experimental alloys, indicating that the creep mechanism of 8xxx alloys was controlled by dislocation glide.

  12. Cluster formula of Fe-containing Monel alloys with high corrosion-resistance

    SciTech Connect

    Li Baozeng; Gu Junjie; Wang Qing; Ji Chunjun; Wang Yingmin; Qiang Jianbing; Dong Chuang

    2012-06-15

    The cluster-plus-glue-atom model is applied in the composition interpretation of Monel alloys. This model considers ideal atomic nearest neighbor configurations among the constituent elements and has been used in understanding compositions of complex alloys like quasicrystals, amorphous alloys, and cupronickels. According to this model, any structure can be expressed by cluster formula [cluster](glue atom){sub x}, x denoting the number of glue atoms matching one cluster. According to this model, two groups of experimental composition series [Fe{sub 1}Ni{sub 12}]Cu{sub x} and [Fe{sub y}Ni{sub 12}]Cu{sub 5} were designed which fell close to conventional Fe-containing Monel alloys. The designed alloys after solution treatment plus water quenching, are monolithic FCC Ni-based solid solutions. Among them, the [Fe{sub 1}Ni{sub 12}]Cu{sub 5} alloy has the highest corrosion resistance in simulated sea water, and its performance is superior to that of industrial Monel 400 alloy. - Highlights: Black-Right-Pointing-Pointer A stable solid solution model is proposed using our 'cluster-plus-glue-atom model'. Black-Right-Pointing-Pointer This model is used to develop Monel corrosion resistant alloys. Black-Right-Pointing-Pointer Single FCC structure is easily retained. Black-Right-Pointing-Pointer The alloys show good corrosion properties. Black-Right-Pointing-Pointer This work contributes to the general understanding of engineering alloys.

  13. Microstructure and mechanical properties of ultrafine-grained Fe-14Cr and ODS Fe-14Cr model alloys

    NASA Astrophysics Data System (ADS)

    Auger, M. A.; Leguey, T.; Muñoz, A.; Monge, M. A.; de Castro, V.; Fernández, P.; Garcés, G.; Pareja, R.

    2011-10-01

    Reduced activation ferritic Fe-14 wt%Cr and Fe-14 wt%Cr-0.3 wt%Y 2O 3 alloys were produced by mechanical alloying and hot isostatic pressing followed by forging and heat treating. The alloy containing Y 2O 3 developed a submicron-grained structure with homogeneous dispersion of oxide nanoparticles that enhanced the tensile properties in comparison to the Y 2O 3 free alloy. Strengthening induced by the Y 2O 3 dispersion appears to be effective up to 873 K, at least. A uniform distribution of Cr-rich precipitates, stable upon a heat treatment at 1123 K for 2 h, was also found in both alloys.

  14. Saturation and forced volume magnetostriction of Fe-rich FeZr amorphous alloys

    NASA Astrophysics Data System (ADS)

    Tange, H.; Tanaka, Y.; Goto, M.; Fukamichi, K.

    1989-10-01

    AC susceptibility, saturation and forced volume magnetostriction were studied on iron-rich zirconium amorphous alloys a-Fe 100- xZr x (8 at% ≤ x ≤ 12 at%). The experimental results are discussed in relation to the re-entrant spin glass state. It is found that the transverse magnetostriction accompanies a remarkable magnetic aftereffect in the spin glass phase, and that the forced volume magnetostriction shows an apparent peak at the ferromagnet to spin glass transition where the ac susceptibility has a cusp.

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

    PubMed

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

    2016-03-21

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

  16. Influence of Be and Al on the magnetostrictive behavior of FeGa alloys

    SciTech Connect

    Mungsantisuk, Pinai; Corson, Robert P.; Guruswamy, Sivaraman

    2005-12-15

    The rare-earth-free body-centered-cubic FeGa-based alloys have an attractive combination of large low-field magnetostriction at room temperature, good mechanical properties, low hysteresis, and relatively low cost for use in sensor and actuator devices. This paper examines the influence of partially substituting Ga in FeGa alloys with Be and Al on their magnetostrictive behavior. Magnetic and magnetostrictive properties of the various ternary FeGaAl and FeGaBe alloys prepared by directional growth process are presented. It is shown that substitution of Ga with Al and Be can be made in FeGa alloys in certain composition ranges without a significant reduction in magnetostriction. Minimal reductions in magnetostriction when Ga is partially substituted by smaller Be or larger Al atoms in certain composition ranges indicate that local electronic environments are more important and that the effects of Ga and Be are additive.

  17. Influence of Be and Al on the magnetostrictive behavior of FeGa alloys

    NASA Astrophysics Data System (ADS)

    Mungsantisuk, Pinai; Corson, Robert P.; Guruswamy, Sivaraman

    2005-12-01

    The rare-earth-free body-centered-cubic FeGa-based alloys have an attractive combination of large low-field magnetostriction at room temperature, good mechanical properties, low hysteresis, and relatively low cost for use in sensor and actuator devices. This paper examines the influence of partially substituting Ga in FeGa alloys with Be and Al on their magnetostrictive behavior. Magnetic and magnetostrictive properties of the various ternary FeGaAl and FeGaBe alloys prepared by directional growth process are presented. It is shown that substitution of Ga with Al and Be can be made in FeGa alloys in certain composition ranges without a significant reduction in magnetostriction. Minimal reductions in magnetostriction when Ga is partially substituted by smaller Be or larger Al atoms in certain composition ranges indicate that local electronic environments are more important and that the effects of Ga and Be are additive.

  18. NEUTRON-INDUCED SWELLING OF Fe-Cr BINARY ALLOYS IN FFTF AT ~400 DEGREES C

    SciTech Connect

    Garner, Francis A.; Greenwood, Lawrence R.; Okita, Taira; Sekimura, Naoto; Wolfer, W. G.

    2002-12-31

    The purpose of this effort is to determine the influence of dpa rate, He/dpa ratio and composition on the void swelling of simple binary Fe-Cr alloys. Contrary to the behavior of swelling of model fcc Fe-Cr-Ni alloys irradiated in the same FFTF-MOTA experiment, model bcc Fe-Cr alloys do not exhibit a dependence of swelling on dpa rate at approximately 400 degrees C. This is surprising in that an apparent flux-sensitivity was observed in an earlier comparative irradiation of Fe-Cr binaries conducted in EBR-II and FFTF. The difference in behavior is ascribed to the higher helium generation rates of Fe-Cr alloys in EBR-II compared to that of FFTF, and also the fact that lower dpa rates in FFTF are accompanied by progressively lower helium generation rates.

  19. Theory of the Invar Effect in FeNi Alloy

    NASA Astrophysics Data System (ADS)

    Kakehashi, Yoshiro

    1981-07-01

    Anomalous thermal expansion of FeNi alloy is calculated on the basis of Liberman-Pettifor’s virial theorem and the full single site approximation in the functional integral method. Results explain well the Invar effect. In general, the electronic contribution to the thermal expansion consists of three terms, i.e. the positive term proportional to the specific heat, the local moment term caused by the temperature variation of the amplitudes of the local moments and the term due to the s-d charge transfer. It is verified that the large negative thermal expansion of the electron system is caused by the local moment term. The lattice parameter, the bulk modulus at T{=}0 K and other magnetic quantities are also calculated, which are consistent with the experimental results.

  20. Supercooling and structure of levitation melted Fe-Ni alloys

    NASA Technical Reports Server (NTRS)

    Abbaschian, G. J.; Flemings, M. C.

    1983-01-01

    A study has been made of the effect of supercooling, quenching rate, growth inhibitors, and grain refiners on the structure of levitation-melted Fe- 25 pct Ni alloys. A combination of three morphologies, dendritic, spherical, and mixed dendritic and spherical, is observed in samples superheated or supercooled by less than 175 K. At larger supercooling, however, only the spherical morphology is observed. The grain size and the grain boundary shape are found to be strongly dependent on the subgrain morphology but not on the quenching temperature. Considerable grain growth is evident in samples with spherical and mixed morphologies but not in the dendriitic samples. The average cooling rates during solidification and the heat transfer coefficients at the metal-quenching medium boundary are calculated. For samples solidified in water, molten lead, and ceramic molds, the heat transfer coefficients are 0.41, 0.52, and 0.15 w/sq cm, respectively.

  1. Cu precipitation dynamics in Fe-Cu alloy

    NASA Astrophysics Data System (ADS)

    Ren, H.-P.; Wang, H.-Y.; Liu, Z.-C.

    2008-02-01

    The precipitation of copper during aging at 600°C in high-purity Fe-Cu alloy was examined by means of transmission electron microscopy, Nano-scale copper-rich clusters with B2-like structure were observed during either solution treatment or aging, which should play important role on precipitation strengthening. In addition, the precipitation process has been analyzed in terms of the evolution of microstructure by Monte Carlo method. An description of the coherent precipitation of copper in iron, based on vacancy diffusion mechanism, thermally activated jump frequencies and cohesive energy was discussed to deal with simultaneous precipitation of metastable and stable phases of Cu-containing steel during aging, which gives an estimation of the precipitation dynamics, as well as the evolution of Cu precipitates in a wide range of temperature.

  2. Electronic properties of excess Cr at Fe site in FeCr{sub 0.02}Se alloy

    SciTech Connect

    Kumar, Sandeep Singh, Prabhakar P.

    2015-06-24

    We have studied the effect of substitution of transition-metal chromium (Cr) in excess on Fe sub-lattice in the electronic structure of iron-selenide alloys, FeCr{sub 0.02}Se. In our calculations, we used Korringa-Kohn-Rostoker coherent potential approximation method in the atomic sphere approximation (KKR-ASA-CPA). We obtained different band structure of this alloy with respect to the parent FeSe and this may be reason of changing their superconducting properties. We did unpolarized calculations for FeCr{sub 0.02}Se alloy in terms of density of states (DOS) and Fermi surfaces. The local density approximation (LDA) is used in terms of exchange correlation potential.

  3. Nanophase change for data storage applications.

    PubMed

    Shi, L P; Chong, T C

    2007-01-01

    Phase change materials are widely used for date storage. The most widespread and important applications are rewritable optical disc and Phase Change Random Access Memory (PCRAM), which utilizes the light and electric induced phase change respectively. For decades, miniaturization has been the major driving force to increase the density. Now the working unit area of the current data storage media is in the order of nano-scale. On the nano-scale, extreme dimensional and nano-structural constraints and the large proportion of interfaces will cause the deviation of the phase change behavior from that of bulk. Hence an in-depth understanding of nanophase change and the related issues has become more and more important. Nanophase change can be defined as: phase change at the scale within nano range of 100 nm, which is size-dependent, interface-dominated and surrounding materials related. Nanophase change can be classified into two groups, thin film related and structure related. Film thickness and clapping materials are key factors for thin film type, while structure shape, size and surrounding materials are critical parameters for structure type. In this paper, the recent development of nanophase change is reviewed, including crystallization of small element at nano size, thickness dependence of crystallization, effect of clapping layer on the phase change of phase change thin film and so on. The applications of nanophase change technology on data storage is introduced, including optical recording such as super lattice like optical disc, initialization free disc, near field, super-RENS, dual layer, multi level, probe storage, and PCRAM including, superlattice-like structure, side edge structure, and line type structure. Future key research issues of nanophase change are also discussed.

  4. Behavior of Fe-ODS Alloys After Thermal Aging Treatments

    NASA Astrophysics Data System (ADS)

    Serrano Garcia, Marta; Hernández-Mayoral, Mercedes; Esparraguera, Elvira Oñorbe

    2016-06-01

    Oxide dispersion alloys are one of the candidates as cladding materials for Gen IV fast reactors, due to their high strength at high temperature, good creep properties, and swelling resistance. This good performance is mainly due to a fine dispersion of nano-oxide particles on the microstructure and to non-grained structure. The microstructural stability and the mechanical properties of a Fe-ODS alloy are studied after different thermal aging experiments at 973 K (700 °C), 5000 hours; 973 K (700 °C), 10,000 hours; and 1123 K (850 °C), 10,000 hours. SEM/EBSD and TEM together with tensile and impact tests on the as-received and thermally aged material have been carried out. In general, for all the tested conditions, a slight softening effect is observed attributed to the changes in the grain structure as well as to the changes in the amount and size of nano-oxide particles. In addition, the aged material shows a lower impact USE value while the DBTT is maintained.

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

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1993-01-01

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

  6. Thermodynamic analysis of compatibility of several reinforcement materials with FeAl alloys

    NASA Technical Reports Server (NTRS)

    Misra, Ajay K.

    1988-01-01

    Chemical compatibility of several reinforcement materials with FeAl alloys within the concentration range 40 to 50 at pct Al have been analyzed from thermodynamic considerations at 1173 and 1273 K. The reinforcement materials considered in this study include carbides, borides, oxides, nitrides, and silicides. Although several chemically compatible reinforcement materials are identified, the coefficients of thermal expansion for none of these materials match closely with that of FeAl alloys and this might pose serious problems in the design of composite systems based on FeAl alloys.

  7. The Effect of H and He on Irradiation Performance of Fe and Ferritic Alloys

    SciTech Connect

    James F. Stubbins

    2010-01-22

    This research program was designed to look at basic radiation damage and effects and mechanical properties in Fe and ferritic alloys. The program scope included a number of materials ranging from pure single crystal Fe to more complex Fe-Cr-C alloys. The range of materials was designed to examine materials response and performance on ideal/model systems and gradually move to more complex systems. The experimental program was coordinated with a modeling effort. The use of pure and model alloys also facilitated the ability to develop and employ atomistic-scale modeling techniques to understand the inherent physics underlying materials performance

  8. Phase stability of ternary fcc and bcc Fe-Cr-Ni alloys

    NASA Astrophysics Data System (ADS)

    Wróbel, Jan S.; Nguyen-Manh, Duc; Lavrentiev, Mikhail Yu.; Muzyk, Marek; Dudarev, Sergei L.

    2015-01-01

    The phase stability of fcc and bcc magnetic binary Fe-Cr, Fe-Ni, and Cr-Ni alloys, and ternary Fe-Cr-Ni alloys is investigated using a combination of density functional theory (DFT), cluster expansion (CE), and magnetic cluster expansion (MCE) approaches. Energies, magnetic moments, and volumes of more than 500 alloy structures have been evaluated using DFT, and the predicted most stable configurations are compared with experimental observations. Deviations from the Vegard law in fcc Fe-Cr-Ni alloys, resulting from the nonlinear variation of atomic magnetic moments as functions of alloy composition, are observed. The accuracy of the CE model is assessed against the DFT data, where for ternary Fe-Cr-Ni alloys the cross-validation error is found to be less than 12 meV/atom. A set of cluster interaction parameters is defined for each alloy, where it is used for predicting new ordered alloy structures. The fcc Fe2CrNi phase with Cu2NiZn -like crystal structure is predicted to be the global ground state of ternary Fe-Cr-Ni alloys, with the lowest chemical ordering temperature of 650 K. DFT-based Monte Carlo (MC) simulations are applied to the investigation of order-disorder transitions in Fe-Cr-Ni alloys. The enthalpies of formation of ternary alloys predicted by MC simulations at 1600 K, combined with magnetic correction derived from MCE, are in excellent agreement with experimental values measured at 1565 K. The relative stability of fcc and bcc phases is assessed by comparing the free energies of alloy formation. The evaluation of the free energies involved the application of a dedicated algorithm for computing the configurational entropies of the alloys. Chemical order is analyzed, as a function of temperature and composition, in terms of the Warren-Cowley short-range order (SRO) parameters and effective chemical pairwise interactions. In addition to compositions close to binary intermetallic phases CrNi2, FeNi, FeNi3, and FeNi8, pronounced chemical order is found

  9. The effect of Fe-Rh alloying on CO hydrogenation to C2+ oxygenates

    DOE PAGES

    Palomino, Robert; Magee, Joseph W.; Llorca, Jordi; ...

    2015-05-20

    A combination of reactivity and structural studies using X-ray diffraction (XRD), pair distribution function (PDF), and transmission electron microscopy (TEM) was used to identify the active phases of Fe-modified Rh/TiO2 catalysts for the synthesis of ethanol and other C2+ oxygenates from CO hydrogenation. XRD and TEM confirm the existence of Fe–Rh alloys for catalyst with 1–7 wt% Fe and ~2 wt% Rh. Rietveld refinements show that FeRh alloy content increases with Fe loading up to ~4 wt%, beyond which segregation to metallic Fe becomes favored over alloy formation. Catalysts that contain Fe metal after reduction exhibit some carburization as evidencedmore » by the formation of small amounts of Fe3C during CO hydrogenation. Analysis of the total Fe content of the catalysts also suggests the presence of FeOx also increased under reaction conditions. Reactivity studies show that enhancement of ethanol selectivity with Fe loading is accompanied by a significant drop in CO conversion. Comparison of the XRD phase analyses with selectivity suggests that higher ethanol selectivity is correlated with the presence of Fe–Rh alloy phases. As a result, the interface between Fe and Rh serves to enhance the selectivity of ethanol, but suppresses the activity of the catalyst which is attributed to the blocking or modifying of Rh active sites.« less

  10. Magnetic properties of carbon-encapsulated Fe-Co alloy nanoparticles.

    PubMed

    Wu, Aibing; Yang, Xuwei; Yang, Hua

    2013-04-14

    Carbon-encapsulated Fe-Co alloy nanoparticles (Fe-Co(C)) have been fabricated with different Co/Fe ratios by an efficient solid-state route using melamine as carbon source. The structure and morphology of Fe-Co(C) nanoparticles were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). The XRD characterization results reveal that all products are alloys with no carbide impurity. The TEM and HRTEM observations show that the alloy nanoparticles are encapsulated in carbon shells. Additionally, the reactions involved in the syntheses are postulated. The variation of magnetic properties of Fe-Co(C) with Co/Fe has been discussed according to the room temperature VSM measurement results.

  11. Magnetic x-ray linear dichroism of ultrathin Fe-Ni alloy films

    SciTech Connect

    Schumann, F.O.; Willis, R.F.; Goodman, K.W.

    1997-04-01

    The authors have studied the magnetic structure of ultrathin Fe-Ni alloy films as a function of Fe concentration by measuring the linear dichroism of the 3p-core levels in angle-resolved photoemission spectroscopy. The alloy films, grown by molecular-beam epitaxy on Cu(001) surfaces, were fcc and approximately four monolayers thick. The intensity of the Fe dichroism varied with Fe concentration, with larger dichroisms at lower Fe concentrations. The implication of these results to an ultrathin film analogue of the bulk Invar effect in Fe-Ni alloys will be discussed. These measurements were performed at the Spectromicroscopy Facility (Beamline 7.0.1) of the Advanced Light Source.

  12. Abnormal magnetization behaviors in Sm-Ni-Fe-Cu alloys

    NASA Astrophysics Data System (ADS)

    Yang, W. Y.; Zhang, Y. F.; Zhao, H.; Chen, G. F.; Zhang, Y.; Du, H. L.; Liu, S. Q.; Wang, C. S.; Han, J. Z.; Yang, Y. C.; Yang, J. B.

    2016-06-01

    The magnetization behaviors in Sm-Ni-Fe-Cu alloys at low temperatures have been investigated. It was found that the hysteresis loops show wasp-waisted character at low temperatures, which has been proved to be related to the existence of multi-phases, the Fe/Ni soft magnetic phases and the CaCu5-type hard magnetic phase. A smooth-jump behavior of the magnetization is observed at T>5 K, whereas a step-like magnetization process appears at T<5 K. The CaCu5-type phase is responsible for such abnormal magnetization behavior. The magnetic moment reversal model with thermal activation is used to explain the relation of the critical magnetic field (Hcm) to the temperature (T>5 K). The reversal of the moment direction has to cross over an energy barrier of about 6.6×10-15 erg. The step-like jumps of the magnetization below 5 K is proposed to be resulted from a sharp increase of the sample temperature under the heat released by the irreversible domain wall motion.

  13. Effect of Al substitution for Ga on the mechanical properties of directional solidified Fe-Ga alloys

    NASA Astrophysics Data System (ADS)

    Liu, Yangyang; Li, Jiheng; Gao, Xuexu

    2017-02-01

    Alloys of Fe82Ga18-xAlx (x=0, 4.5, 6, 9, 12, 13.5) were prepared by directional solidification technique and exhibited a <001> preferred orientation along the axis of alloy rods. The saturation magnetostriction value of the Fe82Ga13.5Al4.5 alloy was 247 ppm under no pre-stress. The tensile properties of alloys of Fe82Ga18-xAlx at room temperature were investigated. The results showed that tensile ductility of binary Fe-Ga alloy was significantly improved with Al addition. The fracture elongation of the Fe82Ga18 alloy was only 1.3%, while that of the Fe82Ga9Al9 alloy increased up to 16.5%. Addition of Al increased the strength of grain boundary and cleavage, resulting in the enhancement of tensile ductility of the Fe-Ga-Al alloys. Analysis of deformation microstructure showed that a great number of deformation twins formed in the Fe-Ga-Al alloys, which were thought to be the source of serrated yielding in the stress-strain curves. The effect of Al content in the Fe-Ga-Al alloys on tensile ductility was also studied by the analysis of deformation twins. It indicated that the joint effect of slip and twinning was beneficial to obtain the best ductility in the Fe82Ga9Al9 alloy.

  14. High Resolution Transmission Electron Microscopy (HRTEM) of nanophase ferric oxides

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Morris, R. V.; Ming, D. W.; Lauer, H. V., Jr.

    1994-01-01

    Iron oxide minerals are the prime candidates for Fe(III) signatures in remotely sensed Martian surface spectra. Magnetic, Mossbauer, and reflectance spectroscopy have been carried out in the laboratory in order to understand the mineralogical nature of Martian analog ferric oxide minerals of submicron or nanometer size range. Out of the iron oxide minerals studied, nanometer sized ferric oxides are promising candidates for possible Martian spectral analogs. 'Nanophase ferric oxide (np-Ox)' is a generic term for ferric oxide/oxihydroxide particles having nanoscale (less than 10 nm) particle dimensions. Ferrihydrite, superparamagnetic particles of hematite, maghemite and goethite, and nanometer sized particles of inherently paramagnetic lepidocrocite are all examples of nanophase ferric oxides. np-Ox particles in general do not give X-ray diffraction (XRD) patterns with well defined peaks and would often be classified as X-ray amorphous. Therefore, different np-Oxs preparations should be characterized using a more sensitive technique e.g., high resolution transmission electron microscopy (HRTEM). The purpose of this study is to report the particle size, morphology and crystalline order, of five np-Ox samples by HRTEM imaging and electron diffraction (ED).

  15. Tribological Properties of the Fe-Al-Cr Alloyed Layer by Double Glow Plasma Surface Metallurgy

    NASA Astrophysics Data System (ADS)

    Luo, Xixi; Yao, Zhengjun; Zhang, Pingze; Zhou, Keyin; Wang, Zhangzhong

    2016-09-01

    A Fe-Al-Cr alloyed layer was deposited onto the surface of Q235 low-carbon steel via double glow plasma surface metallurgy (DGPSM) to improve the steel's wear resistance. After the DGPSM treatment, the Fe-Al-Cr alloyed layer grown on the Q235 low-carbon steel was homogeneous and compact and had a thickness of 25 µm. The layer was found to be metallurgically adhered to the substrate. The frictional coefficient and specific wear rate of the sample with a Fe-Al-Cr alloyed layer (treated sample) were both lower than those of the bare substrate (untreated sample) at the measured temperatures (25, 250 and 450 °C). The results indicated that the substrate and the alloyed layer suffered oxidative wear and abrasive wear, respectively, and that the treated samples exhibited much better tribological properties than did the substrate. The formation of Fe2AlCr, Fe3Al(Cr), FeAl(Cr), Fe(Cr) sosoloid and Cr23C6 phases in the alloyed layer dramatically enhanced the wear resistance of the treated sample. In addition, the alloyed layer's oxidation film exhibited a self-healing capacity with lubrication action that also contributed to the improvement of the wear resistance at high temperature. In particular, at 450 °C, the specific wear rate of treated sample was 2.524 × 10-4 mm3/N m, which was only 45.2% of the untreated sample.

  16. Compressive creep behavior of alloys based on B2 FeAl

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  17. Compressive creep behavior of alloys based on B2 FeAl

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  18. Weldability of a high entropy CrMnFeCoNi alloy

    SciTech Connect

    Wu, Zhenggang; David, Stan A.; Feng, Zhili; Bei, Hongbin

    2016-07-19

    We present the high-entropy alloys are unique alloys in which five or more elements are all in high concentrations. In order to determine its potential as a structural alloy, a model face-centered-cubic CrMnFeCoNi alloy was selected to investigate its weldability. Welds produced by electron beam welding show no cracking. The grain structures within the fusion zone (FZ) are controlled by the solidification behavior of the weld pool. The weldment possesses mechanical properties comparable to those of the base metal (BM) at both room and cryogenic temperatures. Finally, compared with the BM, deformation twinning was more pronounced in the FZ of the tested alloy.

  19. Structure and properties of Ti-7.5Mo-xFe alloys.

    PubMed

    Lin, D J; Lin, J H Chern; Ju, C P

    2002-04-01

    The present work is a study of a series of Ti-7.5Mo-xFe alloys, with the focus on the effect of iron addition on the structure and mechanical properties of the alloys. Experimental results indicate that alpha" phase-dominated binary Ti-7.5Mo alloy exhibited a fine, acicular martensitic structure. When 1 wt% or more iron was added, the entire alloy became equi-axed beta phase structure with a grain size decreasing with increasing iron content. A thermal omega phase was formed in the alloys containing iron of roughly between 0.5 and 3 wt%. The largest quantity of omega phase and highest microhardness were found in Ti-7.5Mo-1Fe alloy. The binary Ti 7.5Mo alloy had a lower microhardness, bending strength and modulus than all iron-containing alloys. The largest bending strength was found in Ti-7.5Mo-2Fe alloy. The present alloys with iron contents of about 2-5 wt% seem to have a great potential for use as an implant material.

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

    SciTech Connect

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

    2015-09-18

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

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

    SciTech Connect

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

    2010-09-15

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

  2. Positron Annihilation Studies in Search of Fine Precipitates in Fe-9Cr alloys

    SciTech Connect

    Babu, S. Hari; Rajaraman, R.; Govindaraj, R.; Amarendra, G.; Sundar, C. S.

    2011-07-15

    Positron annihilation lifetime studies were carried out on cold worked pure Fe and Fe-9Cr alloy subjected to isochronal annealing in the temperature range from 300 to 1323 K. The measured lifetimes of Fe-9Cr alloy showed three distinct annealing stages as compared to pure Fe viz., initial annealing of defects, a plateau between 623 K and 873 K and noticeable increase beyond 1123 K. The second annealing stage is likely due to the formation of chromium rich nanoclusters. Third annealing stage beyond 1123 K is attributed to highly defected martensitic phase formation during cooling from y-phase.

  3. Phonon densities of states of face-centered-cubic Ni-Fe alloys

    SciTech Connect

    Lucas, Matthew; Mauger, L; Munoz, Jorge A.; Halevy, I; Horwath, J; Semiatin, S L; Leontsev, S. O.; Stone, Matthew B; Abernathy, Douglas L; Xiao, Yuming; Chow, P; Fultz, B.

    2013-01-01

    Inelastic neutron scattering and nuclear resonant inelastic x-ray scattering were used to determine the phonon densities of states of face-centered-cubic Ni-Fe alloys. Increasing Fe concentration results in an average softening of the phonon modes. Chemical ordering of the Ni0.72Fe0.28 alloy results in a reduction of the partial vibrational entropy of the Fe atoms but does not significantly change the partial vibrational entropy of the Ni atoms. Changes in the phonon densities of states with composition and chemical ordering are discussed and analyzed with a cluster expansion method.

  4. Single magnetic domain precipitates of Fe/Co and Fe and Co in Cu matrix produced from (Fe-Co)/Cu metastable alloys

    NASA Astrophysics Data System (ADS)

    Nascimento, V. P.; Passamani, E. C.; Takeuchi, A. Y.; Larica, C.; Nunes, E.

    2001-01-01

    Structural and magnetic properties of nanocrystalline Fe2Co and (Fe2Co)0.30 Cu0.70 alloys prepared by high energy ball milling have been studied basically by x-ray, Mössbauer spectroscopy and magnetization measurements. For the Fe2Co alloy case, the Mössbauer measurements indicate that the sample with 160 hours of milling has two magnetic components with the same average hyperfine parameters: one magnetic crystalline component associated with the bcc Fe2Co phase and another component attributed to the small particles of the same bcc Fe2Co phase (SP-Fe2Co). (Fe2Co)0.30Cu0.70 alloys have been prepared by milling in two different ways: (1) starting from the mixture of Fe2Co milled alloy and pure Cu powders (sample I) and (2) milling of the elemental powder mixture of Fe, Co and Cu (sample II). The x-ray diffraction and bulk magnetization results of samples I and II indicate the formation of a (Fe2Co)0.30Cu0.70 supersaturated solid solution, with features of a ferromagnetic material and Tc at about (420+/-1) K. High temperature magnetization measurements of the (Fe/Co)Cu milled materials show particle precipitation effects. Heat treatment at 675 and 875 K of the final milled materials leads to different results: in the sample I case to the precipitation of single magnetic Fe/Co particles into the Cu matrix, and in the case of sample II the precipitation of single magnetic particles of Fe and of Co into the Cu matrix.

  5. An Experimental Investigation of Fe-Si Alloy Corrosion in the Solar Nebula

    NASA Technical Reports Server (NTRS)

    Zega, Thomas J.; Lauretta, Dante S.; Buseck, Peter R.

    2001-01-01

    We have performed an experimental study of Fe-Si alloy corrosion under dust-rich nebular conditions. The reaction products are silica and fayalite. Additional information is contained in the original extended abstract.

  6. On the Anomalous Thermal Expansion of FeNi Invar Alloy

    NASA Astrophysics Data System (ADS)

    Kakehashi, Yoshiro

    1980-12-01

    The thermal expansion of FeNi invar alloy is calculated by using Liberman-Pettifor’s virial theorem and CPA-static approximation in the functional integral method. The results explain well the invar anomaly.

  7. Thermal stability comparison of nanocrystalline Fe-based binary alloy pairs

    DOE PAGES

    Clark, Blythe G.; Hattar, Khalid Mikhiel; Marshall, Michael Thomas; ...

    2016-03-24

    Here, the widely recognized property improvements of nanocrystalline (NC) materials have generated significant interest, yet have been difficult to realize in engineering applications due to the propensity for grain growth in these interface-dense systems. While traditional pathways to thermal stabilization can slow the mobility of grain boundaries, recent theories suggest that solute segregation in NC alloy can reduce the grain boundary energy such that thermodynamic stabilization is achieved. Following the predictions of Murdock et al., here we compare for the first time the thermal stability of a predicted NC stable alloy (Fe-10at.% Mg) with a predicted non-NC stable alloy (Fe-10at.%more » Cu) using the same processing and characterization methodologies. Results indicate improved thermal stability of the Fe-Mg alloy in comparison to the Fe-Cu, and observed microstructures are consistent with those predicted by Monte Carlo simulations.« less

  8. Thermal stability comparison of nanocrystalline Fe-based binary alloy pairs

    SciTech Connect

    Clark, Blythe G.; Hattar, Khalid Mikhiel; Marshall, Michael Thomas; Chookajorn, Tonghai; Boyce, Brad L.; Schuh, Christopher A.

    2016-03-24

    Here, the widely recognized property improvements of nanocrystalline (NC) materials have generated significant interest, yet have been difficult to realize in engineering applications due to the propensity for grain growth in these interface-dense systems. While traditional pathways to thermal stabilization can slow the mobility of grain boundaries, recent theories suggest that solute segregation in NC alloy can reduce the grain boundary energy such that thermodynamic stabilization is achieved. Following the predictions of Murdock et al., here we compare for the first time the thermal stability of a predicted NC stable alloy (Fe-10at.% Mg) with a predicted non-NC stable alloy (Fe-10at.% Cu) using the same processing and characterization methodologies. Results indicate improved thermal stability of the Fe-Mg alloy in comparison to the Fe-Cu, and observed microstructures are consistent with those predicted by Monte Carlo simulations.

  9. Thermal Stability Comparison of Nanocrystalline Fe-Based Binary Alloy Pairs

    NASA Astrophysics Data System (ADS)

    Clark, B. G.; Hattar, K.; Marshall, M. T.; Chookajorn, T.; Boyce, B. L.; Schuh, C. A.

    2016-06-01

    The widely recognized property improvements of nanocrystalline (NC) materials have generated significant interest; yet, they have been difficult to realize in engineering applications due to the propensity for grain growth in these interface-dominated systems. Although traditional pathways to thermal stabilization can slow the mobility of grain boundaries, recent theories suggest that solute segregation in NC alloys can reduce the grain boundary energy such that thermodynamic stabilization is achieved. Following the predictions of Murdoch et al., here we compare for the first time the thermal stability of a predicted NC stable alloy (Fe-10 at.% Mg) with a predicted non-NC stable alloy (Fe-10 at.% Cu) using the same processing and characterization methodologies. Results show improved thermal stability of the Fe-Mg alloy in comparison with the Fe-Cu, and thermally-evolved microstructures that are consistent with those predicted by Monte Carlo simulations.

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

    NASA Technical Reports Server (NTRS)

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

    1977-01-01

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

  11. Adhesion of Pseudomonas fluorescens onto nanophase materials

    NASA Astrophysics Data System (ADS)

    Webster, Thomas J.; Tong, Zonghua; Liu, Jin; Banks, M. Katherine

    2005-07-01

    Nanobiotechnology is a growing area of research, primarily due to the potentially numerous applications of new synthetic nanomaterials in engineering/science. Although various definitions have been given for the word 'nanomaterials' by many different experts, the commonly accepted one refers to nanomaterials as those materials which possess grains, particles, fibres, or other constituent components that have one dimension specifically less than 100 nm. In biological applications, most of the research to date has focused on the interactions between mammalian cells and synthetic nanophase surfaces for the creation of better tissue engineering materials. Although mammalian cells have shown a definite positive response to nanophase materials, information on bacterial interactions with nanophase materials remains elusive. For this reason, this study was designed to assess the adhesion of Pseudomonas fluorescens on nanophase compared to conventional grain size alumina substrates. Results provide the first evidence of increased adhesion of Pseudomonas fluorescens on alumina with nanometre compared to conventional grain sizes. To understand more about the process, polymer (specifically, poly-lactic-co-glycolic acid or PLGA) casts were made of the conventional and nanostructured alumina surfaces. Results showed similar increased Pseudomonas fluorescens capture on PLGA casts of nanostructured compared to conventional alumina as on the alumina itself. For these reasons, a key material property shown to enhance bacterial adhesion was elucidated in this study for both polymers and ceramics: nanostructured surface features.

  12. The Center for Nanophase Materials Sciences

    ScienceCinema

    Christen, Hans; Ovchinnikova, Olga; Jesse, Stephen; Mazumder, Baishakhi; Norred, Liz; Idrobo, Juan Carlos; Berlijn, Tom

    2016-07-12

    The Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory (ORNL) integrates nanoscale science with neutron science; synthesis science; and theory, modeling, and simulation. Operating as a national user facility, the CNMS supports a multidisciplinary environment for research to understand nanoscale materials and phenomena.

  13. The Center for Nanophase Materials Sciences

    SciTech Connect

    Christen, Hans; Ovchinnikova, Olga; Jesse, Stephen; Mazumder, Baishakhi; Norred, Liz; Idrobo, Juan Carlos; Berlijn, Tom

    2016-03-11

    The Center for Nanophase Materials Sciences (CNMS) at Oak Ridge National Laboratory (ORNL) integrates nanoscale science with neutron science; synthesis science; and theory, modeling, and simulation. Operating as a national user facility, the CNMS supports a multidisciplinary environment for research to understand nanoscale materials and phenomena.

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

    SciTech Connect

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

    2007-12-31

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

  15. Microstructural and magnetic characterization of iron precipitation in Ni-Fe-Al alloys

    SciTech Connect

    Duman, Nagehan; Mekhrabov, Amdulla O.; Akdeniz, M. Vedat

    2011-06-15

    The influence of annealing on the microstructural evolution and magnetic properties of Ni{sub 50}Fe{sub x}Al{sub 50-x} alloys for x = 20, 25, and 30 has been investigated. Solidification microstructures of as-cast alloys reveal coarse grains of a single B2 type {beta}-phase and typical off eutectic microstructure consisting of proeutectic B2 type {beta} dendrites and interdendritic eutectic for x = 20 and x > 20 at.% Fe respectively. However, annealing at 1073 K results in the formation of FCC {gamma}-phase particles along the grain boundaries as well as grain interior in x = 20 at.% Fe alloy. The volume fraction of interdentritic eutectic regions tend to decrease and their morphologies start to degenerate by forming FCC {gamma}-phase for x > 20 at.% Fe alloys with increasing annealing temperatures. Increasing Fe content of alloys induce an enhancement in magnetization and a rise in the Curie transition temperature (T{sub C}). Temperature scan magnetic measurements and transmission electron microscopy reveal that a transient rise in the magnetization at temperatures well above the T{sub C} of the alloys would be attributed to the precipitation of a nano-scale ferromagnetic BCC {alpha}-Fe phase. Retained magnetization above the Curie transition temperature of alloy matrix, together with enhanced room temperature saturation magnetization of alloys annealed at favorable temperatures support the presence of ferromagnetic precipitates. These nano-scale precipitates are shown to induce significant precipitation hardening of the {beta}-phase in conjunction with enhanced room temperature saturation magnetization in particular when an annealing temperature of 673 K is used. - Research Highlights: {yields} Evolution of microstructure and magnetic properties with varying Fe content. {yields} Transient rise in magnetization via the formation of ferromagnetic phase. {yields} Enhancements in saturation magnetization owing to precipitated ferromagnetic phase. {yields} Nanoscale

  16. Magnetic and microstructural properties of nanocrystalline Fe-25 at% Al and Fe-25 at% Al +0.2 at%B alloys prepared by mechanical alloying process

    NASA Astrophysics Data System (ADS)

    Ibn Gharsallah, H.; Makhlouf, T.; Escoda, L.; Suñol, J. J.; Khitouni, M.

    2016-04-01

    In the present work, structural and magnetic properties of nanocrystalline Fe-25at%Al and Fe-25at%Al+0.02at%B alloys produced by mechanical alloying were studied. Their microstructural properties were investigated by X-ray diffraction, scanning electron microscopy and vibrating sample magnetometer. A BCC-nanostructured Fe(Al,B) solid solution with an average crystallite size of about 18nm has been produced by milling for 4h. Whereas in Fe-25at%Al the alloying process has been accomplished after 16h of milling. It is found that B speeds up the formation of a bcc phase with finer microstructure (around 5nm) after 40h of milling. When increasing the milling time, the crystallite size decreases for all powders. An increase in microstrain was observed with increasing the milling time and also with addition of boron. Coercivity and the saturation magnetization of alloyed powders were measured at room temperature by a vibration sample magnetization. The magnetic measurements show a contrasting saturation magnetization and coercivity ( Hc) in both alloys. These variations are explained by crystallite size and strain variations in the samples during milling.

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

    NASA Astrophysics Data System (ADS)

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

    2015-02-01

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

  18. Evaporative segregation in 80% Ni-20% Cr and 60% Fe-40% Ni alloys

    NASA Technical Reports Server (NTRS)

    Gupta, K. P.; Mukherjee, J. L.; Li, C. H.

    1974-01-01

    An analytical approach is outlined to calculate the evaporative segregation behavior in metallic alloys. The theoretical predictions are based on a 'normal' evaporation model and have been examined for Fe-Ni and Ni-Cr alloys. A fairly good agreement has been found between the predicted values and the experimental results found in the literature.

  19. A Study of Phase Composition and Structure of Alloys of the Al - Mg - Si - Fe System

    NASA Astrophysics Data System (ADS)

    Mailybaeva, A. D.; Zolotorevskii, V. S.; Smagulov, D. U.; Islamkulov, K. M.

    2017-03-01

    The Thermo-Calc software is used to compute the phase transformations occurring during cooling of alloys. Polythermal and isothermal sections of the phase diagram of the Al - Mg - Si - Fe system are plotted. The phase composition and the structure of aluminum alloys in cast condition and after a heat treatment are studied experimentally.

  20. Recent progress in high Bs Fe-based nanocrystalline soft magnetic alloys

    NASA Astrophysics Data System (ADS)

    Ohta, M.; Yoshizawa, Y.

    2011-02-01

    High saturation magnetic flux density (high-Bs) alloy has been developed in an Fe-based nanocrystalline alloy system. A nanocrystalline phase with an average grain size of about 20 nm is obtained by annealing Cu-substituted and/or Cu-and-Si-complex-substituted Fe-B amorphous alloys. The alloy exhibits low coercivity of less than 7 A m-1 and a high Bs of more than 1.8 T. The iron loss at 50 Hz and 1.6 T for a toroidal core made of Fe80.5Cu1.5Si4B14 nanocrystalline alloy is 0.46 W kg-1, which is about 2/3 of that of grain-oriented Si steel. Moreover, the iron loss at 10 kHz and 0.2 T for a wound core made of this alloy is 7.5 W kg-1, which is about 25% of that of non-grain-oriented Si steel and about 60% of that of an Fe-based amorphous alloy. In addition, the cut cores made of the alloy show good superimposed dc-current characteristics and appear promising in applications such as power choke coils (at the high-frequency region).

  1. Thermally Induced Structural Transformations of Fe40Ni40P14B6 Amorphous Alloy

    NASA Astrophysics Data System (ADS)

    Vasić, Milica M.; Roupcová, Pavla; Pizúrová, Naděžda; Stevanović, Sanja; Blagojević, Vladimir A.; Žák, Tomáš; Minić, Dragica M.

    2016-01-01

    Thermal stability and thermally induced structural transformations of Fe40Ni40P14B6 amorphous alloy were examined under non-isothermal and isothermal conditions. Formation of metastable α-(Fe,Ni), and stable γ-(Fe,Ni) and (Fe,Ni)3(P,B) crystalline phases as the main crystallization products was observed, while the presence of small amounts of other crystalline phases like Fe23B6 and Fe2NiB was indicated by electron diffraction in HRTEM. Thermomagnetic curve indicated that Fe content in different crystalline phases is very different, resulting in markedly different Curie temperatures after crystallization. Transmission electron microscopy and atomic force microscopy study suggested multiple-layered platelet-shaped morphology, both on the surface and in the bulk of the crystallized alloy sample. The thermal treatment heating rate and maximum temperature affected surface roughness and grain size inhomogeneity.

  2. Contribution of di-SIA to mass transport in Fe-Cr alloys

    NASA Astrophysics Data System (ADS)

    Ryabov, V. A.; Pechenkin, V. A.; Molodtsov, V. L.; Terentyev, D.

    2016-04-01

    Molecular dynamics simulations have been performed to study the diffusion characteristics of di-self interstitial atom (di-SIA) in BCC Fe-Cr alloys and corresponding mass transport of Fe and Cratoms in the temperature range 600-1000 K in the alloys with Cr content 5-25 at%, which is relevant for ferritic/martensitic steels. An original treatment is proposed in this work to account for a mixed migration mode composed of the diffusion of the cluster itself and break-up into a pair of independent SIAs. The ratio of self-diffusion coefficients of Cr and Fe is found to exceed unity in Fe-5Cr and Fe-10Cr alloys, which implies that under cascade-producing damage, 3D-migrating small SIA clusters will effectively contribute to the segregation of Cr to neutral and SIA-preferential sinks, eventually causing radiation induced segregation.

  3. Cr precipitation in neutron irradiated industrial purity Fe-Cr model alloys

    NASA Astrophysics Data System (ADS)

    Kuksenko, V.; Pareige, C.; Pareige, P.

    2013-01-01

    The microstructure of four neutron irradiated Fe-Cr model alloys of industrial purity (Fe-2.5%Cr, Fe-5%Cr, Fe-9%Cr and Fe-12%Cr) has been characterized by atom probe tomography (APT). Irradiation has been performed at 300 °C up to 0.6 dpa in MTR reactor. APT investigations confirmed the enhanced precipitation of α' clusters as these clusters have only been observed in supersaturated model alloys. In addition a nonexpected family of clusters has been revealed due to irradiation induced segregation of impurities: NiSiPCr-enriched clusters. They might be associated to defect clusters invisible by transmission electron microscopy (TEM). A quantitative description of these objects is presented in this paper and results are compared with TEM and SANS data of the literature obtained on the same model alloy.

  4. Solidification Behavior and Cooling Curves for Hypereutectic Fe-21 At. Pct B Alloy

    NASA Astrophysics Data System (ADS)

    Xu, Junfeng; Jian, Zengyun; Dang, Bo; Zhang, Di; Liu, Feng

    2017-04-01

    The cooling curves for Fe-21 at. pct B hypereutectic alloy were measured, which are correlated with the solidification behaviors. At small undercoolings, the cooling curve has two recalescences, corresponding to L → Fe2B and L → Fe2B + Fe, respectively. At moderate undercoolings, also two recalescences can be observed from the cooling curve, corresponding to L → Fe3B and L + Fe3B → Fe2B + Fe. At large undercoolings, the cooling curve has only one recalescence, corresponding to L → Fe3B + Fe. From TEM analysis, the matrix phase is α-Fe in cases of solidification at small and moderate undercoolings, but is Fe3B in case of large undercooling. HRTEM analysis shows that α-Fe stores deformation energy by irregular atom region, but intermetallic phase (Fe2B or Fe3B) stores deformation energy by increasing grain boundaries and stacking faults, which can explain why α-Fe has good deformation ability and small hardness, but the Fe2B or Fe3B phase on the contrary.

  5. Solidification Behavior and Cooling Curves for Hypereutectic Fe-21 At. Pct B Alloy

    NASA Astrophysics Data System (ADS)

    Xu, Junfeng; Jian, Zengyun; Dang, Bo; Zhang, Di; Liu, Feng

    2017-01-01

    The cooling curves for Fe-21 at. pct B hypereutectic alloy were measured, which are correlated with the solidification behaviors. At small undercoolings, the cooling curve has two recalescences, corresponding to L → Fe2B and L → Fe2B + Fe, respectively. At moderate undercoolings, also two recalescences can be observed from the cooling curve, corresponding to L → Fe3B and L + Fe3B → Fe2B + Fe. At large undercoolings, the cooling curve has only one recalescence, corresponding to L → Fe3B + Fe. From TEM analysis, the matrix phase is α-Fe in cases of solidification at small and moderate undercoolings, but is Fe3B in case of large undercooling. HRTEM analysis shows that α-Fe stores deformation energy by irregular atom region, but intermetallic phase (Fe2B or Fe3B) stores deformation energy by increasing grain boundaries and stacking faults, which can explain why α-Fe has good deformation ability and small hardness, but the Fe2B or Fe3B phase on the contrary.

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

    PubMed

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

    2004-08-01

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

  7. Advanced ODS FeCrAl alloys for accident-tolerant fuel cladding

    SciTech Connect

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

    2014-09-01

    ODS FeCrAl alloys are being developed with optimum composition and properties for accident tolerant fuel cladding. Two oxide dispersion strengthened (ODS) Fe-15Cr-5Al+Y2O3 alloys were fabricated by ball milling and extrusion of gas atomized metallic powder mixed with Y2O3 powder. To assess the impact of Mo on the alloy mechanical properties, one alloy contained 1%Mo. The hardness and tensile properties of the two alloys were close and higher than the values reported for fine grain PM2000 alloy. This is likely due to the combination of a very fine grain structure and the presence of nano oxide precipitates. The nano oxide dispersion was however not sufficient to prevent grain boundary sliding at 800 C and the creep properties of the alloys were similar or only slightly superior to fine grain PM2000 alloy. Both alloys formed a protective alumina scale at 1200 C in air and steam and the mass gain curves were similar to curves generated with 12Cr-5Al+Y2O3 (+Hf or Zr) ODS alloys fabricated for a different project. To estimate the maximum temperature limit of use for the two alloys in steam, ramp tests at a rate of 5 C/min were carried out in steam. Like other ODS alloys, the two alloys showed a significant increase of the mas gains at T~ 1380 C compared with ~1480 C for wrought alloys of similar composition. The beneficial effect of Yttrium for wrought FeCrAl does not seem effective for most ODS FeCrAl alloys. Characterization of the hardness of annealed specimens revealed that the microstructure of the two alloys was not stable above 1000 C. Concurrent radiation results suggested that Cr levels <15wt% are desirable and the creep and oxidation results from the 12Cr ODS alloys indicate that a lower Cr, high strength ODS alloy with a higher maximum use temperature could be achieved.

  8. Development of weldable, corrosion-resistant iron-aluminide (FeAl) alloys

    SciTech Connect

    Maziasz, P.J.; Goodwin, G.M.; Wang, X.L.; Alexander, D.J.

    1997-04-01

    A boron-microalloyed FeAl alloy (Fe-36Al-0.2Mo-0.05Zr-0.13C, at.%, with 100-400 appm B) with improved weldability and mechanical properties was developed in FY 1994. A new scale-up and industry technology development phase for this work began in FY 1995, pursuing two parallel paths. One path was developing monolithic FeAl component and application technology, and the other was developing coating/cladding technology for alloy steels, stainless steels and other Fe-Cr-Ni alloys. In FY 1995, it was found that cast FeAl alloys had good strength at 700-750{degrees}C, and some (2.5%) ductility in air at room-temperature. Hot-extruded FeAl with refined grain size was found to have ductility and to also have good impact-toughness at room-temperature. Further, it was discovered that powder-metallurgy (P/M) FeAl, consolidated by direct hot-extrusion at 950-1000{degrees}C to have an ultra fine-grained microstructure, had the highest ductility, strength and impact-toughness ever seen in such intermetallic alloys.

  9. Nanophase Magnetite and Pyrrhotite in ALH84001 Martian Meteorite: Evidence for an Abiotic Origin

    NASA Technical Reports Server (NTRS)

    Golden, D. C.; Lauer, H. V., Jr. III; Ming, D. W.; Morris, R. V.

    2006-01-01

    The nanophase magnetite crystals in the black rims of pancake-shaped carbonate globules of the Martian meteorite ALH84001 have been studied extensively because of the claim by McKay et al.that they are biogenic in origin. A subpopulation of these magnetite crystals are reported to conform to a unique elongated shape called "truncated hexa-octahedral" or "THO" by Thomas-Keprta et al. They claim these THO magnetite crystals can only be produced by living bacteria thus forming a biomarker in the meteorite. In contrast, thermal decomposition of Fe-rich carbonate has been suggested as an alternate hypothesis for the elongated magnetite formation in ALH84001 carbonates. The experimental and observational evidence for the inorganic formation of nanophase magnetite and pyrrhotite in ALH84001 by decomposition of Fe-rich carbonate in the presence of pyrite are provided.

  10. Hyperfine and X-ray investigations of amorphous Fe2Er and Fe2Ce alloys and the effect of hydrogenation on short-range order

    NASA Astrophysics Data System (ADS)

    Ghafari, M.; Keune, W.; Matsuura, M.; Schletz, K. P.

    1990-07-01

    The effect of hydrogenation on the short-range order of amorphous Fe2Er and Fe2Ce alloys has been investigated by Mössbauer, X-ray and magnetization measurements. The hydrogenation leads to drastic changes in the short-range order. The results of Mössbauer measurements show two different distributions of magnetic hyperfine fields for amorphous Fe2CeH4 alloys (a-Fe2CeH4). For a-Fe2ErH3 alloys we found drastic changes in magnetic structure, which is different from the well-known magnetic structures.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  12. Crystallization in Fe- and Co-Based Amorphous Alloys Studied by In-Situ X-Ray Diffraction

    NASA Astrophysics Data System (ADS)

    Zhang, L. J.; Yu, P. F.; Cheng, H.; Zhang, M. D.; Liu, D. J.; Zhou, Z.; Jin, Q.; Liaw, P. K.; Li, G.; Liu, R. P.

    2016-12-01

    The amorphous alloys, Fe80Si20, Fe78Si9B13, and Fe4Co67Mo1.5Si16.5B11, were prepared by the spinning method in pure argon. The crystallization behaviors of the three amorphous alloys were researched by in-situ X-ray diffraction (XRD), and the crystallization activation energy was calculated, based on the results of differential scanning calorimetry. The crystallization mechanism of the Fe- and Co-based alloys was analyzed, based on the experimental data. The transformation kinetics was described in terms of Johnson-Mehl-Avrami kinetics, except that the Avrami exponent of the Fe78Si9B13 amorphous alloy annealed at 753 K (480 °C) was 4.12; the obtained values for the overall Avrami exponents of the other three amorphous alloys were below 1, as usually found for the Fe-Si amorphous alloys.

  13. Modeling of radiation-induced segregation in austenitic Fe-Cr-Ni alloys

    NASA Astrophysics Data System (ADS)

    Allen, Todd Randall

    Radiation-induced segregation (RIS) was studied in Fe-Cr-Ni alloys irradiated with protons to better understand the mechanisms causing changes in grain boundary chemistry and to improve the ability to predict RIS in austenitic Fe-Cr-Ni alloys. Ni-18Cr, Ni-18Cr-9Fe, Ni-18Cr-0.08P, and Fe-20Cr-9Fe were irradiated with 3.2MeV protons at temperatures from 200sp°C to 500sp°C and to doses from 0.1 to 3 dpa. Grain boundary chemistry was measured using both Auger electron spectroscopy (AES) and scanning transmission electron microscopy with energy dispersive x-ray spectroscopy (STEM/EDS). The significant driving mechanism far segregation in Fe-Cr-Ni alloys is shown to be the inverse Kirkendall (IK) mechanism, specifically the coupling between alloying elements and the vacancy flux. The inclusion of interstitial binding effects to RIS models results in poor agreement between model predictions and segregation measurements, severely overpredicting the measured Ni enrichment and Fe depletion. Grain boundary segregation is unique for each bulk alloy composition in that the amount and the rate of segregation differs for alloys irradiated under the same conditions. Kinetic parameters must be known for each alloy to accurately predict segregation, but the kinetic parameters in Fe-Cr-Ni alloys at low temperature are not well studied. Additionally, short range ordering interactions are important in determining the segregation in all Fe-Cr-Ni alloys. Ordering enthalpies must be included in RIS models to correctly describe the segregation process. Therefore, to develop a predictive RIS model, a method for calculating diffusivities from the bulk composition that includes ordering enthalpies was developed. The Perks (IK) model has been modified to account for composition dependent segregation kinetics by calculating the migration energy using pair interaction potentials, ordering enthalpies, and the local concentration. Based on segregation measurements from seven different alloys

  14. Microscopic structural change in a liquid Fe-C alloy of ~5 GPa

    DOE PAGES

    Shibazaki, Yuki; Kono, Yoshio; Fei, Yingwei

    2015-07-04

    The structure of a liquid Fe-3.5 wt% C alloy is examined for up to 7.2 GPa via multiangle energy-dispersive X-ray diffraction using a Paris-Edinburgh type large-volume press. X-ray diffraction data show clear changes in the pressure-dependent peak positions of structure factor and reduced pair distribution function at 5GPa. These results suggest that the liquid Fe-3.5wt%C alloys change structurally at approximately 5GPa. This finding serves as a microscopic explanation for the alloy’s previously observed density change at the same pressure. The pressure dependencies of the nearest and second neighbor distances of the liquid Fe-3.5 wt% C alloy are similar to thosemore » of liquid Fe which exhibits a structural change near the bcc-fcc-liquid triple point (5.2GPa and 1991 K). Here, similarities between Fe-3.5wt% C and Fe suggest that a density change also occurs in liquid Fe and that this structural change extends to other Fe-light element alloys.« less

  15. Microscopic structural change in a liquid Fe-C alloy of ~5 GPa

    SciTech Connect

    Shibazaki, Yuki; Kono, Yoshio; Fei, Yingwei

    2015-07-04

    The structure of a liquid Fe-3.5 wt% C alloy is examined for up to 7.2 GPa via multiangle energy-dispersive X-ray diffraction using a Paris-Edinburgh type large-volume press. X-ray diffraction data show clear changes in the pressure-dependent peak positions of structure factor and reduced pair distribution function at 5GPa. These results suggest that the liquid Fe-3.5wt%C alloys change structurally at approximately 5GPa. This finding serves as a microscopic explanation for the alloy’s previously observed density change at the same pressure. The pressure dependencies of the nearest and second neighbor distances of the liquid Fe-3.5 wt% C alloy are similar to those of liquid Fe which exhibits a structural change near the bcc-fcc-liquid triple point (5.2GPa and 1991 K). Here, similarities between Fe-3.5wt% C and Fe suggest that a density change also occurs in liquid Fe and that this structural change extends to other Fe-light element alloys.

  16. Observation of inverse spin Hall effect in ferromagnetic FePt alloys using spin Seebeck effect

    SciTech Connect

    Seki, Takeshi Takanashi, Koki; Uchida, Ken-ichi; Kikkawa, Takashi; Qiu, Zhiyong; Saitoh, Eiji

    2015-08-31

    We experimentally observed the inverse spin Hall effect (ISHE) of ferromagnetic FePt alloys. Spin Seebeck effect due to the temperature gradient generated the spin current (J{sub s}) in the FePt|Y{sub 3}Fe{sub 5}O{sub 12} (YIG) structure, and J{sub s} was injected from YIG to FePt and converted to the charge current through ISHE of FePt. The significant difference in magnetization switching fields for FePt and YIG led to the clear separation of the voltage of ISHE from that of anomalous Nernst effect in FePt. We also investigated the effect of ordering of FePt crystal structure on the magnitude of ISHE voltage in FePt.

  17. Observation of inverse spin Hall effect in ferromagnetic FePt alloys using spin Seebeck effect

    NASA Astrophysics Data System (ADS)

    Seki, Takeshi; Uchida, Ken-ichi; Kikkawa, Takashi; Qiu, Zhiyong; Saitoh, Eiji; Takanashi, Koki

    2015-08-01

    We experimentally observed the inverse spin Hall effect (ISHE) of ferromagnetic FePt alloys. Spin Seebeck effect due to the temperature gradient generated the spin current (Js) in the FePt|Y3Fe5O12 (YIG) structure, and Js was injected from YIG to FePt and converted to the charge current through ISHE of FePt. The significant difference in magnetization switching fields for FePt and YIG led to the clear separation of the voltage of ISHE from that of anomalous Nernst effect in FePt. We also investigated the effect of ordering of FePt crystal structure on the magnitude of ISHE voltage in FePt.

  18. Magnetic and thermodynamic properties of face-centered cubic Fe-Ni alloys.

    PubMed

    Lavrentiev, M Yu; Wróbel, J S; Nguyen-Manh, D; Dudarev, S L

    2014-08-14

    A model lattice ab initio parameterized Heisenberg-Landau magnetic cluster expansion Hamiltonian spanning a broad range of alloy compositions and a large variety of chemical and magnetic configurations has been developed for face-centered cubic Fe-Ni alloys. The thermodynamic and magnetic properties of the alloys are explored using configuration and magnetic Monte Carlo simulations over a temperature range extending well over 1000 K. The predicted face-centered cubic-body-centered cubic coexistence curve, the phase stability of ordered Fe3Ni, FeNi, and FeNi3 intermetallic compounds, and the predicted temperatures of magnetic transitions simulated as functions of alloy composition agree well with experimental observations. Simulations show that magnetic interactions stabilize the face-centered cubic phase of Fe-Ni alloys. Both the model Hamiltonian simulations and ab initio data exhibit a particularly large number of magnetic configurations in a relatively narrow range of alloy compositions corresponding to the occurrence of the Invar effect.

  19. Exceptionally high glass-forming ability of an FeCoCrMoCBY alloy

    NASA Astrophysics Data System (ADS)

    Shen, Jun; Chen, Qingjun; Sun, Jianfei; Fan, Hongbo; Wang, Gang

    2005-04-01

    It has been well documented that the maximum thickness of as-cast glassy samples attainable through conventional metallurgical routes is the decisive criteria for measuring the glass-forming ability (GFA) of bulk metallic glasses (BMGs). Here we report the exceptionally high GFA of an FeCoCrMoCBY alloy which can be fabricated in the form of glassy rods with a maximum sample thickness of at least 16mm. It is demonstrated that, by substituting Fe with a proper amount of Co in a previously reported Fe-based BMG alloy, the glass formation of the resultant new alloy can be extensively favored both thermodynamically and kinetically. The new ferrous BMG alloy also exhibits a high fracture strength of 3500MPa and Vickers hardness of 1253kgmm-2.

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

    DOE PAGES

    Parish, Chad M.; Field, Kevin G.; Certain, Alicia G.; ...

    2015-04-20

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

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

    SciTech Connect

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

    2015-04-20

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

  2. Fabrication and Spark Plasma Sintering of Magnetic alpha-Fe/MgO Nanocomposite by Mechanical Alloying.

    PubMed

    Lee, Chung-Hyo

    2016-02-01

    Solid-state reduction has occurred during mechanical alloying of a mixture of Fe2O3 and Mg powders at room temperature. It is found that magnetic nanocomposite in which MgO is dispersed in alpha-Fe matrix with nano-sized grains is obtained by mechanical alloying of Fe2O3 with Mg for 30 min. Consolidation of the ball-milled powders was performed in a spark plasma sintering (SPS) machine up to 800-1000 degrees C. X-ray diffraction result shows that the average grain size of alpha-Fe in a-Fe/MgO nanocomposite sintered at 800 degrees C is in the range of 110 nm. It can be also seen that the coercivity of SPS sample sintered at 800 degrees C is still high value of 88 Oe, suggesting that the grain growth of magnetic alpha-Fe phase during SPS process tends to be suppressed.

  3. Tailoring the magnetic properties of CoFeNi alloys with variations in copper contents

    NASA Astrophysics Data System (ADS)

    Lee, Jeong Oh; Kim, Hyun Kyung; Kim, Gyeung Ho; Jeung, Won Young

    2006-04-01

    CoFeNi alloys are some of the most studied soft magnetic materials because of their superior properties over FeNi alloys as write head core materials in hard disk drives. Pulsed electrodeposition was shown to be an interesting approach to vary the crystalline structure of the fcc-bcc mixed phase CoFeNi and CoFeNiCu films without changing the composition and the grain size by using a single bath. The permeability μ of CoFeNiCu films plated from bath composition exceeded 4.6×106. Coercivity Hc was 20-73 A/m. The high saturation magnetic flux Bs was 1.8 T. The soft magnetic CoFeNiCu film prepared satisfies all the requirements needed for the preparation of magnetic recording heads, as all magnetic properties were improved in this direction.

  4. No alloying in Fe deposited on Pd(001) at room temperature

    SciTech Connect

    Meyerheim, H. L.; Popescu, R.; Kirschner, J.

    2006-06-15

    Using surface x-ray diffraction we have investigated growth and structure of Fe deposited on Pd(001) at room temperature. Up to about 4.2 ML, the maximum film thickness studied, Fe grows in layer-by-layer mode without sizable intermixing with Pd. Up to 1.5 ML coverage the Fe film adopts a fct-structure followed by a transition to a bct-structure at higher film thickness. The top Pd interlayer spacing, which in the case of uncovered Pd(001) is expanded by up to 6.5{+-}2.0% relative to the bulk due to adsorbed hydrogen relaxes to 0{+-}2% upon adsorption of 0.6 ML Fe, possibly due to displacement into subsurface sites. Mild annealing (400 K) of a 1 ML Fe/Pd(001) sample induces surface alloying leading to a disordered two layer thick fct-Fe{sub 50}Pd{sub 50}-alloy.

  5. Magnetic Properties of Liquid Gd-TM (TM = Mn, Fe, Co, Ni) Alloys

    NASA Astrophysics Data System (ADS)

    Ohno, Satoru; Shimakura, Hironori; Tahara, Shuta; Okada, Tatsuya

    2016-12-01

    Liquid Gd-TM (TM = Mn, Fe, Ni) alloys on the TM-rich side have relatively small and negative temperature coefficients of the magnetic susceptibility χ, which become large and negative with increasing Gd content. The large and negative temperature coefficient of χ for liquid Co gradually weakens at up to 70 at. % Co with the addition of Gd. Liquid Gd and GdcCo1-c alloys with c ≥ 0.5 also have a relatively large and negative temperature coefficient of χ. Liquid Gd-TM alloys on the Gd-rich side obey the Curie law. The magnetic susceptibilities of liquid Gd-Fe and Gd-Co alloys exhibit Curie-Weiss behavior on the TM-rich side. The dependence of χ on the composition for liquid Gd-TM (TM = Mn, Fe, Ni) alloys gradually increases with the Gd content, and that for liquid Gd-Co alloys has a minimum at the composition of 20 at. % Gd. The dependences of χ3d and χ4f on the composition due to the 3d- and 4f-electrons were analyzed by subtracting the corresponding data for liquid La-TM alloys from χ for the liquid Gd-TM alloys.

  6. Chemical, electronic, and magnetic structure of LaFeCoSi alloy: Surface and bulk properties

    SciTech Connect

    Lollobrigida, V.; Basso, V.; Kuepferling, M.; Coïsson, M.; Olivetti, E. S.; Celegato, F.; Borgatti, F.; Torelli, P.; Panaccione, G.; Tortora, L.; Stefani, G.; Offi, F.

    2014-05-28

    We investigate the chemical, electronic, and magnetic structure of the magnetocaloric LaFeCoSi compound with bulk and surface sensitive techniques. We put in evidence that the surface retains a soft ferromagnetic behavior at temperatures higher than the Curie temperature of the bulk due to the presence of Fe clusters at the surface only. This peculiar magnetic surface effect is attributed to the exchange interaction between the ferromagnetic Fe clusters located at the surface and the bulk magnetocaloric alloy, and it is used here to monitor the magnetic properties of the alloy itself.

  7. Influence of recrystallization on phase separation kinetics of oxide dispersion strengthened Fe Cr Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Pimentel, G.; Chao, J.

    2012-01-01

    The effect of different starting microstructures on the kinetics of Fe-rich ({alpha}) and Cr-rich ({alpha}') phase separation during aging of Fe-Cr-Al oxide dispersion strengthened (ODS) alloys has been analyzed with a combination of atom probe tomography and thermoelectric power measurements. The results revealed that the high recrystallization temperature necessary to produce a coarse grained microstructure in Fe-base ODS alloys affects the randomness of Cr-atom distributions and defect density, which consequently affect the phase separation kinetics at low annealing temperatures.

  8. Cyclic voltammetric study of Co-Ni-Fe alloys electrodeposition in sulfate medium

    SciTech Connect

    Hanafi, I.; Daud, A. R.; Radiman, S.

    2013-11-27

    Electrochemical technique has been used to study the electrodeposition of cobalt, nickel, iron and Co-Ni-Fe alloy on indium tin oxide (ITO) coated glass substrate. To obtain the nucleation mechanism, cyclic voltammetry is used to characterize the Co-Ni-Fe system. The scanning rate effect on the deposition process was investigated. Deposition of single metal occurs at potential values more positive than that estimated stability potential. Based on the cyclic voltammetry results, the electrodeposition of cobalt, nickel, iron and Co-Ni-Fe alloy clearly show that the process of diffusion occurs is controlled by the typical nucleation mechanism.

  9. Characteristics of Fe-Ni-Sm alloys in the as-cast state

    NASA Astrophysics Data System (ADS)

    Koval', Yu. M.; Ponomarova, S. O.; Odnosum, V. V.; Ponomarov, O. P.; Efimova, T. V.; Shimko, Yu. M.

    2015-04-01

    The effect of samarium on the microstructure and the parameters of martensitic and magnetic transformations in Fe-Ni alloys is studied, and the alloys with 0.5-2 u. % Sm are found to exhibit a martensitic transformation in the as-cast state. The temperatures of the onset of the direct and reverse martensitic transformations increase with the samarium content as compared to the corresponding binary alloys. Moreover, samarium substantially increases the Curie temperature and significantly decreases the grain size in the alloys.

  10. Ab initio theory of phase stability and structural selectivity in Fe-Pd alloys

    NASA Astrophysics Data System (ADS)

    Chepulskii, Roman V.; Barabash, Sergey V.; Zunger, Alex

    2012-04-01

    In Fe-Pd alloys, the competing geometric (fcc versus bcc) and magnetic tendencies result in rich phase stability and ordering physics. Here, we study these alloys via a first principles mixed-basis cluster expansion (CE) approach. Highly accurate fcc and bcc CEs are iteratively and self-consistently constructed using a genetic algorithm, based on the first principles results for ˜100 ordered structures. The structural and magnetic “filters” are introduced to determine whether a fully relaxed structure is of fcc/bcc and high-/low-spin types. All structures satisfying the Lifshitz condition for stability in extended phase diagram regions are included as inputs to our CEs. We find that in a wide composition range (with more than 1/3 atomic content of Fe), an fcc-constrained alloy has a single stable ordered compound, L10 FePd. However, L10 is higher in energy than the phase-separated mixture of bcc Fe and fcc-FePd2 (β2 structure) at low temperatures. In the Pd-rich composition range, we find several fcc β2-like ground states: FePd2 (β2), Fe3Pd9, Fe2Pd7, FePd5, Fe2Pd13, and FePd8, yet we do not find FePd3 with the the experimentally observed L12 structure. Fcc Monte Carlo simulations show a transformation from any of the attempted β2-like ground states directly into a disordered alloy. We suggest that the phonon and/or spin excitation contributions to the free energy are responsible for the observed stability of L12 at higher temperatures, and likely lead to a β2↔L12 transition. Finally, we present here a complete characterization of all the fcc and bcc Lifshitz structures, i.e., the structures with ordering vectors exclusively at high-symmetry k points.

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

    SciTech Connect

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

    2015-11-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  13. Photoemission Electron Microscopy Study of Ultrathin FeNi Alloy Films on Cu(111)

    NASA Astrophysics Data System (ADS)

    Sato, Yu; Johnson, Tracey; Giacomo, Jason; Chiang, Shirley; Zhu, Xiangdong; Land, Donald; Nolting, Frithjof; Scholl, Andreas

    2002-03-01

    We are studying the system of FeNi/Cu(111) to understand and control the surface/interface magnetism relevant to the application of the giant magnetoresistive effect to magnetic recording heads. We used the Photoemission Electron Microscope (PEEM2) at the Advanced Light Source to observe the domain structures of the alloy films. PEEM has the unique capability of imaging the film's magnetic structure with high spatial resolution and elemental specificity. At two different thicknesses, we have made sixteen samples and studied the dependence of magnetic structure on varying Fe concentration and substrate quality. Samples with higher Fe content were non-magnetic at room temperature. We speculate this is a structure-driven effect related to the "Invar effect" in the bulk alloy. The PEEM images clearly show that Fe and Ni form a good alloy and have the same domain structures with their magnetization aligned. Further, we find a strong thickness and concentration dependence of the magnetic domain structures.

  14. Specific heat capacity and dendritic growth kinetics of liquid peritectic Fe-Cu alloys

    NASA Astrophysics Data System (ADS)

    Xia, Z. C.; Wang, W. L.; Luo, S. B.; Wei, B.

    2016-08-01

    The specific heat and dendritic growth of highly undercooled peritectic Fe-Cu alloys were investigated by electromagnetic levitation technique. The specific heat values of liquid peritectic Fe92.8Cu7.2 and hyperperitectic Fe88.5Cu11.5 alloys were determined to be 40.4 and 39.58 J·mol-1·K-1 over wide temperature ranges. The measured growth velocities rose rapidly with increasing undercooling, which reached 69 and 68 m·s-1 at the maximum undercoolings of 401 K (0.23 TL) and 468 K (0.27 TL). The microstructures of peritectic Fe-Cu alloys were refined significantly with enhanced undercooling. Theoretical analyses showed that almost segregationless solidification was realized if undercooling was sufficiently large.

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

    NASA Astrophysics Data System (ADS)

    Leibowitz, Joshua; Allcorn, Eric; Manthiram, Arumugam

    2015-11-01

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

  16. Superelasticity, corrosion resistance and biocompatibility of the Ti-19Zr-10Nb-1Fe alloy.

    PubMed

    Xue, Pengfei; Li, Yan; Li, Kangming; Zhang, Deyuan; Zhou, Chungen

    2015-05-01

    Microstructure, mechanical properties, superelasticity and biocompatibility of a Ti-19Zr-10Nb-1Fe alloy are investigated. X-ray diffraction spectroscopy and transmission electron microscopy observations show that the as-cast Ti-19Zr-10Nb-1Fe alloy is composed of α' and β phases, but only the β phase exists in the as-rolled and as-quenched alloys. The tensile stress-strain tests indicate that the as-quenched alloy exhibits a good combination of mechanical properties with a large elongation of 25%, a low Young's modulus of 59 GPa and a high ultimate tensile stress of 723 MPa. Superelastic recovery behavior is found in the as-quenched alloy during tensile tests, and the corresponding maximum of superelastic strain is 4.7% at the pre-strain of 6%. A superelastic recovery of 4% with high stability is achieved after 10 cyclic loading-unloading training processes. Potentiodynamic polarization and ion release measurements indicate that the as-quenched alloy shows a lower corrosion rate in Hank's solution and a much less ion release rate in 0.9% NaCl solution than those of the NiTi alloys. Cell culture results indicate that the osteoblasts' adhesion and proliferation are similar on both the Ti-19Zr-10Nb-1Fe and NiTi alloys. A better hemocompatibility is confirmed for the as-quenched Ti-19Zr-10Nb-1Fe alloy, attributed to more stable platelet adhesion and small activation degree, and a much lower hemolysis rate compared with the NiTi alloy.

  17. Formation Mechanisms of Alloying Element Nitrides in Recrystallized and Deformed Ferritic Fe-Cr-Al Alloy

    NASA Astrophysics Data System (ADS)

    Akhlaghi, Maryam; Meka, Sai Ramudu; Jägle, Eric A.; Kurz, Silke J. B.; Bischoff, Ewald; Mittemeijer, Eric J.

    2016-09-01

    The effect of the initial microstructure (recrystallized or cold-rolled) on the nitride precipitation process upon gaseous nitriding of ternary Fe-4.3 at. pct Cr-8.1 at. pct Al alloy was investigated at 723 K (450 °C) employing X-ray diffraction (XRD) analyses, transmission electron microscopy (TEM), atom probe tomography (APT), and electron probe microanalysis (EPMA). In recrystallized Fe-Cr-Al specimens, one type of nitride develops: ternary, cubic, NaCl-type mixed Cr1- x Al x N. In cold-rolled Fe-Cr-Al specimens, precipitation of two types of nitrides occurs: ternary, cubic, NaCl-type mixed Cr1- x Al x N and binary, cubic, NaCl-type AlN. By theoretical analysis, it was shown that for the recrystallized specimens an energy barrier for the nucleation of mixed Cr1- x Al x N exists, whereas in the cold-rolled specimens no such energy barriers for the development of mixed Cr1- x Al x N and of binary, cubic AlN occur. The additional development of the cubic AlN in the cold-rolled microstructure could be ascribed to the preferred heterogeneous nucleation of cubic AlN on dislocations. The nitrogen concentration-depth profile of the cold-rolled specimen shows a stepped nature upon prolonged nitriding as a consequence of instantaneous nucleation of nitride upon arrival of nitrogen and nitride growth rate-limited by nitrogen transport through the thickening nitrided zone.

  18. Cast Fe-base cylinder/regenerator housing alloy

    NASA Technical Reports Server (NTRS)

    Larson, F.; Kindlimann, L.

    1980-01-01

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

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

    PubMed

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

    2016-05-01

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

  20. Investigation of FeNiCrWMn - a new high entropy alloy

    NASA Astrophysics Data System (ADS)

    Buluc, G.; Florea, I.; Bălţătescu, O.; Florea, R. M.; Carcea, I.

    2015-11-01

    The term of high entropy alloys started from the analysis of multicomponent alloys, which were produced at an experimental level since 1995 by developing a new concept related to the development of metallic materials. Recent developments in the field of high-entropy alloys have revealed that they have versatile properties like: ductility, toughness, hardness and corrosion resistance [1]. Up until now, it has been demonstrated that the explored this alloys are feasible to be synthesized, processed and analyzed contrary to the misunderstanding based on traditional experiences. Moreover, there are many opportunities in this field for academic studies and industrial applications [1, 2]. As the combinations of composition and process for producing high entropy alloys are numerous and each high entropy alloy has its own microstructure and properties to be identified and understood, the research work is truly limitless. The novelty of these alloys consists of chemical composition. These alloys have been named high entropy alloys due to the atomic scale mixing entropies higher than traditional alloys. In this paper, I will present the microscopy and the mechanical properties of high entropy alloy FeNiCrWMn.

  1. Studies on microstructural changes and phase transition during preparation of FeGeNi ternary alloy by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Lin, Fangting; Shi, Wangzhou; Jiang, Dongmei; Ma, Xueming; Shen, Gang

    2006-01-01

    FeGeNi ternary alloy has been prepared by mechanical alloying followed by thermal treatment. Microstructure of the as-milled and annealed samples as well as thermally induced phase transition and variations in degree of order were investigated through a combination of X-ray diffraction and Mössbauer spectroscopy. The results show that alloying in the (Fe 0.81Ni 0.19) 3.94Ge 2 ternary system initiates during ball milling, with the appearance of partially D0 3-ordered A2 solid solution phase and paramagnetic B8 2 FeGeNi ternary phase. A subsequent thermal treatment of 2 h at 800 K produces a remarkable increase in the degree of the D0 3 order, whilst ferromagnetic phase with amorphous character in the as-milled sample is transformed into paramagnetic B8 2 FeGeNi ternary phase where almost all Ni atoms occupy the vacant 2d site. Therefore in the annealed system coexist two phases, namely the D0 3 phase and paramagnetic B8 2 FeGeNi ternary phase.

  2. Effects of composition and heat treatments on the strength and ductility of Fe-Cr-Co alloys

    SciTech Connect

    Kubarych, K.G.

    1980-06-01

    The relationship between the microstructure and mechanical properties of spinodally decomposed Fe-Cr-Co ductile permanent magnet alloys was investigated using transmission electron microscopy, electron diffraction, tensile testing, and Charpy impact testing. Isothermal aging and step aging of four alloys (Fe-28 wt % Cr-15 wt % Co, Fe-23 wt % Cr-15-wt % Co-5 wt % V, Fe-23 wt % Cr-15 wt % Co-3 wt % V-2 wt % Ti, and Fe-31 wt % Cr-23 % Co) resulted in decomposition into two phases, an Fe-Co rich (..cap alpha../sub 1/) phase and a Cr rich (..cap alpha../sub 2/) phase. The microstructural features of the decomposition products were consistent with those expected from a spinodal reaction and agree with the reported work on the Fe-Cr-Co system. An Fe-23 wt % Cr-15 wt % Co-5 wt % V alloy was found to have, among the four alloys, the best combinations of strength and ductility.

  3. Solid State Reactions in the Mo/O--Fe System under Mechanical Alloying

    SciTech Connect

    Elsukov, E. P.; Protasov, A. V.; Povstugar, I. V.

    2010-07-13

    Two types of solid state reactions that occur during mechanical alloying of Mo/O --20 at. % Fe system with various oxygen concentrations were studied by Moessbauer spectroscopy and X-ray diffraction. The first type of solid state reaction, Mo/O+Fe{yields}bcc Mo(O)-Fe, was observed for Mo samples with 8 at. % of oxygen. The second type of solid state reaction proceeds as Mo/O+Fe{yields}bcc Mo(O)-Fe+hcp Mo(O)-Fe{yields}bcc Mo(O)-Fe+Am Mo(O)-Fe for Mo samples with 14 at. % of oxygen and 1.6 at. % of MoO{sub 3} phase. The assumption about correlation between the second component dissolution rate and mixture components yield point ratio is confirmed.

  4. Magnetic properties and atomic ordering of BCC Heusler alloy Fe2MnGa ribbons

    NASA Astrophysics Data System (ADS)

    Xin, Yuepeng; Ma, Yuexing; Luo, Hongzhi; Meng, Fanbin; Liu, Heyan

    2016-05-01

    The electronic structure, atomic disorder and magnetic properties of the Heusler alloy Fe2MnGa have been investigated experimentally and theoretically. BCC Fe2MnGa ribbon samples were prepared. Experimentally, a saturation magnetic moment (3.68 μB at 5 K) much larger than the theoretical value (2.04 μB) has been reported. First-principles calculations indicate that the difference is related to the Fe-Mn disorder between A, B sites, as can also be deduced from the XRD pattern. L21 type Fe2MnGa is a ferrimagnet with antiparallel Fe and Mn spin moments. However, when Fe-Mn disorder occurs, part of Mn moments will be parallel to Fe moments, and the Fe moments also clearly increase simultaneously. All this results in a total moment of 3.74 μB, close to the experimental value.

  5. Effect of diffusion and alloying on the magnetic and transport properties of Fe/V/Fe trilayers

    NASA Astrophysics Data System (ADS)

    Iuşan, Diana; Alouani, M.; Bengone, O.; Eriksson, O.

    2007-01-01

    The magnetic and transport properties of the Fe/V/Fe(001) trilayers were studied using the self-consistent Green’s function technique based on the tight-binding linear muffin-tin orbital method in the atomic-sphere approximation. The coherent potential approximation was used to describe the effects of interdiffusion and alloying at the interfaces on the properties of the semi-infinite bcc Fe(001)/mFe/nV/mFe/Fe(001) trilayers. The electric conductance was calculated using the Kubo-Landauer formalism, in the current-perpendicular-to-plane geometry. It is shown that a dipole moment is created at the Fe/V interface due to the charge transfer from vanadium to iron, and a small induced magnetic moment is present in the first vanadium layer and is antiparallel to that of iron. The interlayer exchange coupling shows rapid oscillations for small spacer thicknesses, and the interdiffusion and alloying at the interface stabilize the ferromagnetic coupling. Moreover, the interdiffusion reduces the vanadium-induced magnetic moment and increases the iron magnetic moment at the interface. The giant magnetoresistance (GMR) ratio presents damped oscillations as a function of the vanadium spacer thickness. The interdiffusion and the presence of Mn impurities at the interface reduce considerably the GMR ratio and produce results that are in agreement with experimental data.

  6. Structural ordering tendencies in the new ferromagnetic Ni-Co-Fe-Ga-Zn Heusler alloys

    NASA Astrophysics Data System (ADS)

    Dannenberg, Antje; Siewert, Mario; Gruner, Markus E.; Wuttig, Manfred; Entel, Peter

    In search for new ferromagnetic shape memory alloys (FSMA) we have calculated structural energy differences, magnetic exchange interaction constants and mixing energies of quaternary (X1X2)YZ Heusler alloys with X1,X2,Y =Ni,Co,Fe and Z=Ga, Zn using density functional theory. The comparison of the energy profiles of (NiCo)FeZ, (FeNi)CoZ, and (FeCo)NiZ with Z=Ga and Zn as a function of the tetragonal distortion c / a reveals that the energetically preferred ordering type is (NiCo)FeGa and (NiCo)FeZn which shows that Fe prefers to occupy the same cubic sublattice as Ga or Zn what implies that Fe favors Co and Ni as nearest neighbors, respectively. The Curie temperatures of (NiCo)FeGa and (NiCo)FeZn are high of the order of 600 K. (NiCo)FeGa, which has the same valence electron concentration (e/a=7.5) as Ni2MnGa and also possesses a high martensitic transformation temperature (>500 K), is of interest for future magnetic shape memory devices.

  7. The oxidation of Fe-2 and 5 at.% Y alloys at 600--800 C in air

    SciTech Connect

    Zeng, C.L. |; Rizzo, F.C.; Monteiro, M.J.; Wu, W.T.

    1999-06-01

    The oxidation of Fe-Y alloys containing 2 and 5 at.% Y and pure iron has been studied at 600--800 C in air. The oxidation of pure iron follows the parabolic rate law at all temperatures. The oxidation of Fe-Y alloys at 600 C approximately follows the parabolic rate law, but not at 700 and 800 C, where the oxidation goes through several stages with quite different rates. The oxide scales on Fe-2Y and Fe-5Y at 700 and 800 C are composed of external pure Fe oxides containing Fe{sub 2}O{sub 3}, Fe{sub 3}O{sub 4}, and FeO, with FeO being the main oxide and an inner mixture of FeO and YFeO{sub 3}. The scales on Fe-2Y and Fe-5Y at 600 C consist of Fe{sub 2}O{sub 3}, Fe{sub 3}O{sub 4}, and Y{sub 2}O{sub 3}, with a minor amount of FeO. Significant internal oxidation in both Fe-Y alloys occurred at all temperatures. The Y-containing oxides follow the distribution of the original intermetallic compound phase in the alloys. The effects of Y on the oxidation of pure Fe are discussed.

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

    SciTech Connect

    Rapp, R.A.

    1998-03-10

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

  9. Microstructural, mechanical, corrosion and cytotoxicity characterization of the hot forged FeMn30(wt.%) alloy.

    PubMed

    Čapek, Jaroslav; Kubásek, Jiří; Vojtěch, Dalibor; Jablonská, Eva; Lipov, Jan; Ruml, Tomáš

    2016-01-01

    An interest in biodegradable metallic materials has been increasing in the last two decades. Besides magnesium based materials, iron-manganese alloys have been considered as possible candidates for fabrication of biodegradable stents and orthopedic implants. In this study, we prepared a hot forged FeMn30 (wt.%) alloy and investigated its microstructural, mechanical and corrosion characteristics as well as cytotoxicity towards mouse L 929 fibroblasts. The obtained results were compared with those of iron. The FeMn30 alloy was composed of antiferromagnetic γ-austenite and ε-martensite phases and possessed better mechanical properties than iron and even that of 316 L steel. The potentiodynamic measurements in simulated body fluids showed that alloying with manganese lowered the free corrosion potential and enhanced the corrosion rate, compared to iron. On the other hand, the corrosion rate of FeMn30 obtained by a semi-static immersion test was significantly lower than that of iron, most likely due to a higher degree of alkalization in sample surrounding. The presence of manganese in the alloy slightly enhanced toxicity towards the L 929 cells; however, the toxicity did not exceed the allowed limit and FeMn30 alloy fulfilled the requirements of the ISO 10993-5 standard.

  10. Database on Performance of Neutron Irradiated FeCrAl Alloys

    SciTech Connect

    Field, Kevin G.; Briggs, Samuel A.; Littrell, Ken; Parish, Chad M.; Yamamoto, Yukinori

    2016-08-01

    The present report summarizes and discusses the database on radiation tolerance for Generation I, Generation II, and commercial FeCrAl alloys. This database has been built upon mechanical testing and microstructural characterization on selected alloys irradiated within the High Flux Isotope Reactor (HFIR) at Oak Ridge National Laboratory (ORNL) up to doses of 13.8 dpa at temperatures ranging from 200°C to 550°C. The structure and performance of these irradiated alloys were characterized using advanced microstructural characterization techniques and mechanical testing. The primary objective of developing this database is to enhance the rapid development of a mechanistic understanding on the radiation tolerance of FeCrAl alloys, thereby enabling informed decisions on the optimization of composition and microstructure of FeCrAl alloys for application as an accident tolerant fuel (ATF) cladding. This report is structured to provide a brief summary of critical results related to the database on radiation tolerance of FeCrAl alloys.

  11. In situ observation of defect annihilation in Kr ion-irradiated bulk Fe/amorphous-Fe 2 Zr nanocomposite alloy

    DOE PAGES

    Yu, K. Y.; Fan, Z.; Chen, Y.; ...

    2014-08-26

    Enhanced irradiation tolerance in crystalline multilayers has received significant attention lately. However, little is known on the irradiation response of crystal/amorphous nanolayers. We report on in situ Kr ion irradiation studies of a bulk Fe96Zr4 nanocomposite alloy. Irradiation resulted in amorphization of Fe2Zr and formed crystal/amorphous nanolayers. α-Fe layers exhibited drastically lower defect density and size than those in large α-Fe grains. In situ video revealed that mobile dislocation loops in α-Fe layers were confined by the crystal/amorphous interfaces and kept migrating to annihilate other defects. This study provides new insights on the design of irradiation-tolerant crystal/amorphous nanocomposites.

  12. Magnetic susceptibilities of liquid Cr-Au, Mn-Au and Fe-Au alloys

    SciTech Connect

    Ohno, S.; Shimakura, H.; Tahara, S.; Okada, T.

    2015-08-17

    The magnetic susceptibility of liquid Cr-Au, Mn-Au, Fe-Au and Cu-Au alloys was investigated as a function of temperature and composition. Liquid Cr{sub 1-c}Au{sub c} with 0.5 ≤ c and Mn{sub 1-c}Au{sub c} with 0.3≤c obeyed the Curie-Weiss law with regard to their dependence of χ on temperature. The magnetic susceptibilities of liquid Fe-Au alloys also exhibited Curie-Weiss behavior with a reasonable value for the effective number of Bohr magneton. On the Au-rich side, the composition dependence of χ for liquid TM-Au (TM=Cr, Mn, Fe) alloys increased rapidly with increasing TM content, respectively. Additionally, the composition dependences of χ for liquid Cr-Au, Mn-Au, and Fe-Au alloys had maxima at compositions of 50 at% Cr, 70 at% Mn, and 85 at% Fe, respectively. We compared the composition dependences of χ{sub 3d} due to 3d electrons for liquid binary TM-M (M=Au, Al, Si, Sb), and investigated the relationship between χ{sub 3d} and E{sub F} in liquid binary TM-M alloys at a composition of 50 at% TM.

  13. Effect of Boron and Cerium on Corrosion Resistance of Cu -Fe -P Alloy

    NASA Astrophysics Data System (ADS)

    Zou, Jin; Lu, Lei; Lu, De-ping; Liu, Ke-Ming; Chen, Zhi-bao; Zhai, Qi-jie

    2016-03-01

    The effects of B and Ce on the corrosion resistance of Cu-0.22Fe-0.06P alloy were investigated by salt spray and electrochemical tests. The corrosion morphology was studied by scanning electron microscopy. The corrosion products were characterized by energy-dispersive x-ray spectroscopy and x-ray diffraction analysis. The impurity content was determined by inductively coupled plasma mass spectrometry. The conductivity was measured using an eddy current conductivity meter. The grains of Cu-0.22Fe-0.06P alloy were refined by the addition of B and Ce. The electrochemical corrosion process of alloy is retarded due to purification effect of B and Ce. After the addition of a trace amount of B, the corrosion resistance of the alloy decreased. The corrosion resistance of Cu-0.22Fe-0.06P-0.025B-0.05Ce was better than that of Cu-0.22Fe-0.06P-0.025B due to the fact that the purification effect of Ce is better than that of B. The main corrosion products of the Cu-Fe-P alloys in a NaCl solution are Cu2Cl(OH)3 and Cu2O. The addition of trace amounts of B and Ce did not change the components of the corrosion product.

  14. Spectro-photometric determinations of Mn, Fe and Cu in aluminum master alloys

    NASA Astrophysics Data System (ADS)

    Rehan; Naveed, A.; Shan, A.; Afzal, M.; Saleem, J.; Noshad, M. A.

    2016-08-01

    Highly reliable, fast and cost effective Spectro-photometric methods have been developed for the determination of Mn, Fe & Cu in aluminum master alloys, based on the development of calibration curves being prepared via laboratory standards. The calibration curves are designed so as to induce maximum sensitivity and minimum instrumental error (Mn 1mg/100ml-2mg/100ml, Fe 0.01mg/100ml-0.2mg/100ml and Cu 2mg/100ml-10mg/ 100ml). The developed Spectro-photometric methods produce accurate results while analyzing Mn, Fe and Cu in certified reference materials. Particularly, these methods are suitable for all types of Al-Mn, Al-Fe and Al-Cu master alloys (5%, 10%, 50% etc. master alloys).Moreover, the sampling practices suggested herein include a reasonable amount of analytical sample, which truly represent the whole lot of a particular master alloy. Successive dilution technique was utilized to meet the calibration curve range. Furthermore, the workout methods were also found suitable for the analysis of said elements in ordinary aluminum alloys. However, it was observed that Cush owed a considerable interference with Fe, the later one may not be accurately measured in the presence of Cu greater than 0.01 %.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

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

  16. Structure and magnetic properties of surface alloyed Fe nanocapsules prepared by arc discharge

    NASA Astrophysics Data System (ADS)

    Si, P. Z.; Choi, C. J.; Brück, E.; Geng, D. Y.; Zhang, Z. D.

    2005-12-01

    C-Fe-Si alloy encapsulating Fe nanocapsules were fabricated by arc evaporating the mixture of Fe and SiC powders. The high temperature of the electric arc results in a surface reaction between SiC and Fe nanoparticles and therefore a uniform encapsulation of the Fe nanoparticles with its alloy. The size of the nanocapsules ranges from 10 to 60 nm while most shells are approximately 7 nm in thickness. Air oxidation to the as-prepared sample does not change the shell/core structure but the saturation magnetization and the coercivity are reduced. The characteristics of the nanocapsules were investigated systematically by using X-ray diffraction, transmission electron microscopy, energy dispersive spectra, X-ray photoelectron spectroscopy, and superconducting quantum interference device magnetometer.

  17. Synthesis of monosized magnetic-optical AuFe alloy nanoparticles

    NASA Astrophysics Data System (ADS)

    Liu, Hong Ling; Wu, Jun Hua; Min, Ji Hyun; Kim, Young Keun

    2008-04-01

    We report the preparation and characterization of multifunctional AuFe alloy nanoparticles of three compositions, Au0.25Fe0.75, Au0.5Fe0.5, and Au0.75Fe0.25, by a polyol process. It is found that the fusion of the two elements into one nanostructure entity retains the optical and magnetic properties of the individual components. The x-ray diffraction and transmission electron microscopy analyses confirm the formation of the alloy nanostructure with a narrow distribution of particle sizes and provides the detailed structural arrangements. The magnetic investigation shows the superparamagnetic or soft ferromagnetic behavior of the nanoparticles at room temperature, whereas the UV-visible measurements display the variation of the absorption bands at ˜560nm. The AuFe nanoparticles are rendered water soluble after thiolation.

  18. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    DOE PAGES

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; ...

    2015-03-19

    FeCrAl is an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In our study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. Also, the total tritium inventory insidemore » the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.« less

  19. Hydrogen permeation in FeCrAl alloys for LWR cladding application

    SciTech Connect

    Hu, Xunxiang; Terrani, Kurt A.; Wirth, Brian D.; Snead, Lance L.

    2015-03-19

    FeCrAl is an advanced oxidation-resistant iron-based alloy class, is a highly prevalent candidate as an accident-tolerant fuel cladding material. Compared with traditional zirconium alloy fuel cladding, increased tritium permeation through FeCrAl fuel cladding to the primary coolant is expected, raising potential safety concerns. In our study, the hydrogen permeability of several FeCrAl alloys was obtained using a static permeation test station, which was calibrated and validated using 304 stainless steel. The high hydrogen permeability of FeCrAl alloys leads to concerns with respect to potentially significant tritium release when used for fuel cladding in LWRs. Also, the total tritium inventory inside the primary coolant of a light water reactor was quantified by applying a 1-dimensional steady state tritium diffusion model to demonstrate the dependence of tritium inventory on fuel cladding type. Furthermore, potential mitigation strategies for tritium release from FeCrAl fuel cladding were discussed and indicate the potential for application of an alumina layer on the inner clad surface to serve as a tritium barrier. More effort is required to develop a robust, economical mitigation strategy for tritium permeation in reactors using FeCrAl clad fuel assemblies.

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

    PubMed

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

    2005-07-01

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

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

    SciTech Connect

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

    1995-08-01

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

  2. Galvanomagnetic properties of Heusler alloy Co2 YAl ( Y = Ti, V, Cr, Mn, Fe, and Ni)

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    The Hall effect and the magnetoresistance of ferromagnetic Heusler alloys Co2 YAl, where Y = Ti, V, Cr, Mn, Fe, and Ni have been studied at T = 4.2 K in magnetic fields H ≤ 100 kOe. Normal R 0 and anomalous R S Hall coefficients are shown to be maximal in magnitudes in the middle of the 3 d period of the periodic table of elements. Coefficient R 0 changes the negative sign to positive sign in going from weak ( Y = Ti, V) to strong ( Y = Cr, Mn, Fe, and Ni) ferromagnetic alloys. Constant R S is positive and proportional to ρ2.9 in all the alloys. The magnetoresistance of the alloys is not higher than several percent and its magnitude is changed fairly significantly in the dependence on the number of valence electrons z; the magnetoresistance signs vary arbitrarily.

  3. Microstructure properties and microhardness of rapidly solidified Al64Cu20Fe12Si4 quasicrystal alloy

    NASA Astrophysics Data System (ADS)

    Karaköse, Ercan; Keskin, Mustafa

    2012-04-01

    This paper presents differences in the microstructure and microhardness properties of conventional casting (ingot) and rapidly solidified Al64Cu20Fe12Si4 quasicrystal (QC) alloys. The phases present in the Al64Cu20Fe12Si4 ingot alloy were determined to be icosahedral quasicrystalline (IQC) Ψ-Al65Cu20Fe15, cubic β-AlFe, tetragonal θ-Al2Cu, and monoclinic λ-A13Fe4 phases, whereas only IQC Ψ-Al65Cu20Fe15 and cubic β-AlFe phases were identified in the rapidly solidified alloy. The microhardness value of the melt spun alloy was measured to be approximately 790 kg/mm2. Microhardness increases with increasing solidification rates.

  4. Phase stability and magnetic behavior of FeCrCoNiGe high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Huang, Shuo; Vida, Ádám; Molnár, Dávid; Kádas, Krisztina; Varga, Lajos Károly; Holmström, Erik; Vitos, Levente

    2015-12-01

    We report an alternative FeCrCoNiGe magnetic material based on FeCrCoNi high-entropy alloy with Curie point far below the room temperature. Investigations are done using first-principles calculations and key experimental measurements. Results show that the equimolar FeCrCoNiGe system is decomposed into a mixture of face-centered cubic and body-centered cubic solid solution phases. The increased stability of the ferromagnetic order in the as-cast FeCrCoNiGe composite, with measured Curie temperature of 640 K, is explained using the exchange interactions.

  5. Positron annihilation study of Fe-ion irradiated reactor pressure vessel model alloys

    NASA Astrophysics Data System (ADS)

    Chen, L.; Li, Z. C.; Schut, H.; Sekimura, N.

    2016-01-01

    The degradation of reactor pressure vessel steels under irradiation, which results from the hardening and embrittlement caused by a high number density of nanometer scale damage, is of increasingly crucial concern for safe nuclear power plant operation and possible reactor lifetime prolongation. In this paper, the radiation damage in model alloys with increasing chemical complexity (Fe, Fe-Cu, Fe-Cu-Si, Fe-Cu-Ni and Fe-Cu-Ni-Mn) has been studied by Positron Annihilation Doppler Broadening spectroscopy after 1.5 MeV Fe-ion implantation at room temperature or high temperature (290 oC). It is found that the room temperature irradiation generally leads to the formation of vacancy-type defects in the Fe matrix. The high temperature irradiation exhibits an additional annealing effect for the radiation damage. Besides the Cu-rich clusters observed by the positron probe, the results show formation of vacancy-Mn complexes for implantation at low temperatures.

  6. First-principles study on the ferrimagnetic half-metallic Mn2FeAs alloy

    NASA Astrophysics Data System (ADS)

    Qi, Santao; Zhang, Chuan-Hui; Chen, Bao; Shen, Jiang; Chen, Nanxian

    2015-05-01

    Mn-based full-Heusler alloys are kinds of promising candidates for new half-metallic materials. Basing on first principles, the electronic structures and magnetic properties of the Mn2FeAs full-Heusler alloy have been investigated in detail. The Hg2CuTi-type Mn2FeAs compound obeys the Slater-Pauling rule, while the anti-parallel alignment atomic magnetic moments of Mn locating at different sites indicate it a ferrimagnetic alloy. The calculated spin-down bands behave half-metallic character, exhibiting a direct gap of 0.46 eV with a 100% spin polarization at the Fermi level. More studies show the compound would maintain half-metallic nature in a large range of variational lattice constants. We expect that our calculated results may trigger Mn2FeAs applying in the future spintronics field.

  7. Monte Carlo simulations of copper clustering in Fe-Cu alloys under irradiation

    NASA Astrophysics Data System (ADS)

    Kwon, J.; Kwon, S. C.; Hong, J. H.

    2004-10-01

    We present the computational approach for studying the microstructures of Cu clusters in Fe-Cu alloys by combining the molecular dynamics (MD) simulation and Monte Carlo methods. The MD simulation is used to characterize the primary damage resulting from the displacement cascade in Fe. Then, using the Metropolis Monte Carlo methods, the microstructure of the Cu clusters is predicted under the assumption that the system will evolve towards the equilibrium state. The formation of the Cu clusters is apparent for Fe-Cu alloys of a higher Cu content (1.0 w/o), whereas the degree of Cu clustering is not significant for the lower Cu content (0.1 w/o) alloys. The atomic configuration of the Cu-vacancy complex under irradiation, produced by this simulation, is in a fair agreement with the experiments. The simulation is expected to provide important information on the Cu-cluster morphology, which is useful for experimental data analysis.

  8. Irradiation-enhanced α' precipitation in model FeCrAl alloys

    SciTech Connect

    Edmondson, Philip D.; Briggs, Samuel A.; Yamamoto, Yukinori; Howard, Richard H.; Sridharan, Kumar; Terrani, Kurt A.; Field, Kevin G.

    2016-02-17

    We have irradiated the model FeCrAl alloys with varying compositions (Fe(10–18)Cr(10–6)Al at.%) with a neutron at ~ 320 to damage levels of ~ 7 displacements per atom (dpa) to investigate the compositional influence on the formation of irradiation-induced Cr-rich α' precipitates using atom probe tomography. In all alloys, significant number densities of these precipitates were observed. Cluster compositions were investigated and it was found that the average cluster Cr content ranged between 51.1 and 62.5 at.% dependent on initial compositions. Furthermore, this is significantly lower than the Cr-content of α' in binary FeCr alloys. As a result, significant partitioning of the Al from the α' precipitates was also observed.

  9. Irradiation-enhanced α' precipitation in model FeCrAl alloys

    DOE PAGES

    Edmondson, Philip D.; Briggs, Samuel A.; Yamamoto, Yukinori; ...

    2016-02-17

    We have irradiated the model FeCrAl alloys with varying compositions (Fe(10–18)Cr(10–6)Al at.%) with a neutron at ~ 320 to damage levels of ~ 7 displacements per atom (dpa) to investigate the compositional influence on the formation of irradiation-induced Cr-rich α' precipitates using atom probe tomography. In all alloys, significant number densities of these precipitates were observed. Cluster compositions were investigated and it was found that the average cluster Cr content ranged between 51.1 and 62.5 at.% dependent on initial compositions. Furthermore, this is significantly lower than the Cr-content of α' in binary FeCr alloys. As a result, significant partitioning ofmore » the Al from the α' precipitates was also observed.« less

  10. Indentation creep in nanocrystalline Fe-TiN and Ni-TiN alloys prepared by mechanical alloying

    SciTech Connect

    Ogino, Yoshikiyo; Yamasaki, Tohru; Shen, B.L.

    1997-04-01

    Mechanical properties of nanocrystalline Fe-TiN and Ni-TiN alloys with various TiN contents between 17 and 64 vol pct, which are prepared by dynamically consolidating mechanically alloyed powders, have been investigated by means of hardness measurements and indentation creep tests at intermediate temperatures. The hardness increases with decreasing grain size to about 10 nm. The indentation creep curves conform well to an equation derived from a transient creep rate equation. The analysis of creep curves indicates that the deformation occurs by a dislocation mechanism controlled by grain boundary diffusion.

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

    SciTech Connect

    Ipus, J. J.; Blazquez, J. S.; Franco, V.; Conde, A.

    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.

  12. Hafnium influence on the microstructure of FeCrAl alloys

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  13. Assessment of Zr-Fe-V getter alloy for gas-gap heat switches

    NASA Technical Reports Server (NTRS)

    Prina, M.; Kulleck, J. G.; Bowman, R. C., Jr.

    2000-01-01

    A commercial Zr-V-Fe alloy (i.e., SAES Getters trade name alloy St-172) has been assessed as reversible hydrogen storage material for use in actuators of gas gap heat switches. Two prototype actuators containing the SAES St-172 material were built and operated for several thousand cycles to evaluate performance of the metal hydride system under conditions simulating heat switch operation.

  14. Modeling of the Site Preference in Ternary B2-Ordered Ni-Al-Fe Alloys

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo H.; Khalil, Joseph; Noebe, Ronald D.

    2002-01-01

    The underlying equilibrium structure, site substitution behavior, and lattice parameter of ternary Ni-Fe-Al alloys are determined via Monte Carlo-Metropolis computer simulations and analytical calculations using the BFS method for alloys for the energetics. As a result of the theoretical calculations presented, a simple approach based on the energetics of small atomic clusters is introduced to explain the observed site preference schemes.

  15. Effect of prior aging and flat rooling on the structure and magnetic properties of alloys of the Fe-Cr-Co-Cu system

    NASA Astrophysics Data System (ADS)

    Samarin, B. A.; Kolchin, A. E.; Kal'ner, Yu. V.

    1986-09-01

    In alloys based on Fe-33% Cr-12% Co-2% Cu alloyed with 1% Al (alloy 2) or 1.5% Nb (alloy 3) the temperature for quenching to α-solid solution is reduced from 1050 (alloy 1) to 1000 (alloy 2) or 950°C (alloy 3). The temperature for the start of α-solid solution decomposition for the alloys is 935-640°C.

  16. Microstructure, Mechanical Properties, and Electrochemical Behavior of Ti-Nb-Fe Alloys Applied as Biomaterials

    NASA Astrophysics Data System (ADS)

    Lopes, Éder Sócrates Najar; Salvador, Camilo Augusto Fernandes; Andrade, Denis Renato; Cremasco, Alessandra; Campo, Kaio Niitsu; Caram, Rubens

    2016-06-01

    New β metastable Ti alloys based on Ti-30Nb alloy with the addition of 1, 3, or 5 wt pct Fe have been developed using the bond order and the metal d-orbital energy level ( overline{{Bo}} {-} overline{{Md}} ) design theory. The samples were prepared by arc melting, hot working, and solution heat treatment above the β transus followed by water quenching (WQ) or furnace cooling (FC). The effect of the cooling rate on the microstructure of Ti-30Nb-3Fe wt pct was investigated in detail using a modified Jominy end quench test. The results show that Fe acts as a strong β-stabilizing alloying element. The addition of Fe also leads to a reduction in the ω and α phases volumetric fractions, although the ω phase was still detected in the WQ Ti-30Nb-5Fe samples, as shown by TEM, and α phase clusters were detected by SEM in the FC Ti-30Nb-3Fe samples. Among the WQ samples, the addition of 5 wt pct Fe improves the ultimate tensile strength (from 601 to 689 MPa), reduces the final elongation (from 28 to 16 pct), and impairs the electrochemical corrosion resistance, as evaluated by potentiodynamic polarization tests in Ringer's solution. The microstructural variation arising from the addition of Fe did not change the elastic modulus (approximately 80 GPa for all experimental WQ samples). This study shows that small Fe additions can tailor the microstructure of Ti-Nb alloys, modifying α and ω phase precipitation and improving mechanical strength.

  17. Structure and microwave absorption properties of (Pr,Dy)Ni4Fe alloy

    NASA Astrophysics Data System (ADS)

    Xiong, Jilei; Pan, Shunkang; Qiao, Ziqiang

    2017-03-01

    The DyxPr1-xNi4Fe (x=0.0, 0.1, 0.2, 0.3, 0.4) alloys were synthesized by arc-smelting and high energy ball milling method. The structure, morphology, particle size and electromagnetic parameters of the powder were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), laser diffraction-based particle size analyzer and vector network analyzer (VNA), respectively. The results reveal that the DyxPr1-xNi4Fe compounds are crystallized in PrNi4Fe structure. The minimum absorption peak frequency of DyxPr1-xNi4Fe shifts towards higher frequency region upon the Fe content. The minimum reflection loss of the DyxPr1-xNi4Fe alloys increases first and then decreases with increasing Dy substitution. The Dy0.3Pr0.7Ni4Fe alloy possess the best absorbing properties: the minimum reflection loss is -31.65 dB at 15.28 GHz with the best matching thickness d =1.0 mm and the reflection loss with the thickness ranging of 1.0-4.0 mm could reach -10 dB.

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

    DTIC Science & Technology

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

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

    SciTech Connect

    Prichard, Paul D.

    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.

  20. Grain boundary diffusion of {sup 181}W in Fe-Cr ferritic alloys

    SciTech Connect

    Cermak, J.; Ruzickova, J.; Pokorna, A.

    1995-07-15

    The grain boundary diffusivity s{delta}D{sub b} of {sup 181}W in binary Fe-Cr alloys with 8--12 wt.% Cr, in a ternary alloy Fe-8Cr-0.17C and in two commercial modifications of 8% Cr ferritic steels were measured by the serial sectioning method in the temperature range 773--1,123 K. A variation of the Cr concentration in the range 8--12 wt.% does not influence s{delta}D{sub b}. The addition of carbon and, probably also phosphorus, decreases s{delta}D{sub b} similarly as it was observed in a previous study on iron diffusion in austenitic alloys Fe-Ni-Cr-C and Fe-Ni-Cr-P. The binary alloys could be considered pure, i.e. free of carbon, above 883 K, whereas at lower temperatures, probably due to residual carbon segregation to grain boundaries, a considerable decrease in s{delta}D{sub b} was observed compared with the extrapolated values from the high temperature region. The tungsten grain boundary diffusivity was found to be insensitive to small changes in the concentration of other alloying or impurity elements.

  1. Ion irradiation testing and characterization of FeCrAl candidate alloys

    SciTech Connect

    Anderoglu, Osman; Aydogan, Eda; Maloy, Stuart Andrew; Wang, Yongqiang

    2014-10-29

    The Fuel Cycle Research and Development program’s Advanced Fuels Campaign has initiated a multifold effort aimed at facilitating development of accident tolerant fuels. This effort involves development of fuel cladding materials that will be resistant to oxidizing environments for extended period of time such as loss of coolant accident. Ferritic FeCrAl alloys are among the promising candidates due to formation of a stable Al₂O₃ oxide scale. In addition to being oxidation resistant, these promising alloys need to be radiation tolerant under LWR conditions (maximum dose of 10-15 dpa at 250 – 350°C). Thus, in addition to a number of commercially available alloys, nuclear grade FeCrAl alloys developed at ORNL were tested using high energy proton irradiations and subsequent characterization of irradiation hardening and damage microstructure. This report summarizes ion irradiation testing and characterization of three nuclear grade FeCrAl cladding materials developed at ORNL and four commercially available Kanthal series FeCrAl alloys in FY14 toward satisfying FCRD campaign goals.

  2. Magnetic properties of Fe-Cu alloys grown by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Grigorov, I. L.; Freeland, J. W.; Walker, J. C.

    1996-03-01

    Magnetic properties of Fe_xCu_1-x alloys are difficult to study due to the low mutual solid solubility of the components. These alloys can be formed by co-sputtering onto a cold substrate, however, they retain fcc phase only for x < 0.6footnote[1]C.L. Chien et. al. Phys.Rev. B 33, 3247 (1986). In this work Fe_xCu_1-x alloys were grown epitaxially by co-deposition onto the Cu(100) substrate. Using this technique we can stabilize the alloy in fcc phase across the entire Fe concentration range. During growth, the substrate was maintained at 0^0C to prevent clustering. Crystal structure was monitored by in-situ RHEED and ex-situ X-ray diffraction. The correlation between structural and magnetic properties of the alloys as well as their dependence on the film thickness were studied by SQUID magnetometry and Mössbauer spectroscopy. Initial results showed a non-zero quadrupole splitting of the room temperature Mössbauer absorption line indicating the random distribution of iron in the Cu matrix. Both low temperature Mössbauer and SQUID measurements on the alloys with low iron concentration showed significant reduction of the average magnetic moment and T_c.

  3. Solubility and magnetic properties enhancement in bi-phase nanostructure Cu-Fe-Mn alloy

    NASA Astrophysics Data System (ADS)

    Mondal, B. N.; Basumallick, A.; Nath, D. N.; Chattopadhyay, P. P.

    2013-09-01

    In order to improve solubility and magnetic properties, the ball milling technology was used for the production of 50Cu-40Fe-10Mn (wt%) alloy. The effect of Mn content on the microstructure and magnetic properties of Cu-Fe alloy was also investigated in detail. Microstructure and magnetic properties of the alloy were analyzed by X-ray diffraction, differential scanning calorimetry, high resolution transmission electron microscopy and superconducting quantum interface device magnetometry. The results showed that a complete solid solution of the alloy was produced after 30 h of milling. Quantitative phase analysis of X-ray diffraction data revealed that the milled alloy obtained after isothermal annealing at 550 °C for 1 h consisted of Cu (54.52 wt%), α-Fe (36.49 wt%) and MnO (8.99 wt%). The milled alloy obtained after annealing at 450 °C for 1 h leads to the maximum values of magnetic properties such as coercivity=438 Oe, remanent magnetization=14.3 emu/g, and saturation magnetization=51 emu/g.

  4. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    DOE PAGES

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; ...

    2015-07-14

    The Fe Cr Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe Cr Al alloys has not been fully established. In this study, a series of Fe Cr Al alloys with 10 18 wt % Cr and 2.9 4.9 wt % Al were neutron irradiated at 382 C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition.more » Dislocation loops with Burgers vector of a/2 111 and a 100 were detected and quantified. Results indicate precipitation of Cr-rich is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. Furthermore, a structure property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α' precipitates at sufficiently high chromium contents after irradiation.« less

  5. Radiation tolerance of neutron-irradiated model Fe-Cr-Al alloys

    SciTech Connect

    Field, Kevin G.; Hu, Xunxiang; Littrell, Kenneth C.; Yamamoto, Yukinori; Snead, Lance Lewis

    2015-07-14

    The Fe Cr Al alloy system has the potential to form an important class of enhanced accident-tolerant cladding materials in the nuclear power industry owing to the alloy system's higher oxidation resistance in high-temperature steam environments compared with traditional zirconium-based alloys. However, radiation tolerance of Fe Cr Al alloys has not been fully established. In this study, a series of Fe Cr Al alloys with 10 18 wt % Cr and 2.9 4.9 wt % Al were neutron irradiated at 382 C to 1.8 dpa to investigate the irradiation-induced microstructural and mechanical property evolution as a function of alloy composition. Dislocation loops with Burgers vector of a/2 111 and a 100 were detected and quantified. Results indicate precipitation of Cr-rich is primarily dependent on the bulk chromium composition. Mechanical testing of sub-size-irradiated tensile specimens indicates the hardening response seen after irradiation is dependent on the bulk chromium composition. Furthermore, a structure property relationship was developed; it indicated that the change in yield strength after irradiation is caused by the formation of these radiation-induced defects and is dominated by the large number density of Cr-rich α' precipitates at sufficiently high chromium contents after irradiation.

  6. Phase Structure and High-Temperature Mechanical Properties of Two-Phase Fe-25Al- xZr Alloys Compared to Three-Phase Fe-30Al- xZr Alloys

    NASA Astrophysics Data System (ADS)

    Kejzlar, Pavel; Kratochvíl, Petr; Král, Robert; Vodičková, Věra

    2014-01-01

    The structure and high-temperature mechanical properties of Fe-30 at. pct Al and Fe-25 at. pct Al alloys with various Zr contents are compared. The scanning electron microscope images in chemical contrast mode (R-BSE) as well as EDS, EBSD, and X-ray diffraction were used to determine the structure and phase composition. The as-cast alloys (both Fe-30Al and Fe-25Al) were observed to be two-phase DO3/B2 + Laves phase λ 1 (Fe,Al)2Zr alloys with typical fine lamellar eutectic areas. During the heat treatment of the Fe-25Al alloys, their structure transformed from a DO3/B2 matrix with fine lamellar eutectic into λ 1 globular particles situated in a DO3/B2 matrix. The same structure of Fe-30Al alloys decomposed into three phases: λ 1 and τ 1 Zr(Fe,Al)12 particles in a DO3/B2 matrix. The hardening in both groups of alloys (Fe-25Al and Fe-30Al) due to the presence of Zr-containing λ 1 and τ 1 phases is compared.

  7. On the existence of declared 9 R phase in Fe-Ni invar alloy

    NASA Astrophysics Data System (ADS)

    Kabanova, I. G.; Sagaradze, V. V.; Kataeva, N. V.

    2016-07-01

    An analysis of recently reported electron diffraction patterns suggests that metastable austenitic Fe-32Ni alloy subjected to α → γ transformation upon slow heating does not exhibit any signs of formation of the 9 R phase; the conventional nanocrystalline γ phase with an fcc lattice is formed instead. Extended lamellae with a layered structure, erroneously identified as a new phase of the (3 R + 9 R) type in Fe-32Ni alloy, are conventional twinning (midrib) regions of each initial α crystal, in which γ-phase twin nanolamellae are formed upon heating.

  8. K/Na-treated Fe-Cr-C hardfacing alloys with high-impact-abrasion resistance

    SciTech Connect

    Yang, J.H.; Wang, X.B.

    1995-03-01

    This paper deals with K/Na-containing additives in the coatings or cores of electrodes, transforming the martensitic matrix of Fe-Cr-C hardfacing alloy into an austenitic one. The austenitic matrix hardened by the fine dispersed (Cr, Fe){sub 7}C{sub 3}, together with the isolated lumpish eutectic carbide, enhance both the impact and abrasion resistance of this alloy. The authors also found that Na doubled the effectiveness of the additive, and 50% less is needed to get better results compared to the K addition.

  9. Martensitic transformation and shape memory effect in ferromagnetic Heusler alloy Ni2FeGa

    NASA Astrophysics Data System (ADS)

    Liu, Z. H.; Zhang, M.; Cui, Y. T.; Zhou, Y. Q.; Wang, W. H.; Wu, G. H.; Zhang, X. X.; Xiao, Gang

    2003-01-01

    We have synthesized ferromagnetic Heusler alloy Ni2FeGa using the melt-spinning technique. The Ni2FeGa ribbon, having a high chemical ordering L21 structure, exhibits a thermoelastic martensitic transformation from cubic to orthorhombic structure at 142 K and a premartensitic transformation. The alloy has a relatively high Curie temperature of 430 K, a magnetization of 73 Am2/kg, and a low saturated field of 0.6 T. The textured samples with preferentially oriented grains show a completely recoverable two-way shape memory effect with a strain of 0.3% upon the thermoelastic martensitic transformation.

  10. Effect of thermomechanical processing on mechanical properties of Fe-16 at. % Al alloy

    SciTech Connect

    Sikka, V.K.

    1994-12-31

    An iron-aluminum alloy containing 16 at. % Al, which is essentially free from environmental effect on its ductility, has been developed. This alloy has over 20% elongation at room temperature. This paper presents in detail the effect of vacuum versus air melting on the properties of Fe-16 at. % Al alloy. The comparative results have shown air-induction melting to produce lower room-temperature ductility for the identical processing steps. Additional processing steps required to improve the ductility of air-melted material are also identified.

  11. Magnetic properties of Co2Fe(Ga1-xSix) alloys

    NASA Astrophysics Data System (ADS)

    Deka, Bhargab; Chakraborty, Dibyashree; Srinivasan, Ananthakrishnan

    2014-09-01

    Magnetic and crystallographic properties of bulk Co2Fe(Ga1-xSix) alloys with 0≤x≤1 are reported in this work. The alloys with x=0.75 and 1.00 exhibit L21 structure whereas the alloys with x=0, 0.25 and 0.50 crystallized in the disordered A2 phase. Unit cell volume of this series of alloys decreased from 189.1 to 178.5 Å3 as x was increased from 0 to 1.00. All alloy compositions exhibit ferromagnetic behavior with a high Curie temperature (TC) which showed a systematic variation with x (1089 K, 1075 K, 1059 K, 1019 K and 1015 K for x=0, 0.25, 0.5, 0.75 and 1.00, respectively). The saturation magnetization moment Ms for the alloys with x=0, 0.25 and 0.50 are 5.05μB, 5.23μB, 5.49μB, respectively, in accordance with the Slater-Pauling rule, but alloys with x=0.75 and 1.00 deviated from this rule. The effective moment per magnetic atom (pc) of the alloys was estimated from the inverse DC magnetic susceptibility data above TC. A comparison of Ms with pc reveals the half-metallic character of the alloys.

  12. Weldability of a high entropy CrMnFeCoNi alloy

    DOE PAGES

    Wu, Zhenggang; David, Stan A.; Feng, Zhili; ...

    2016-07-19

    We present the high-entropy alloys are unique alloys in which five or more elements are all in high concentrations. In order to determine its potential as a structural alloy, a model face-centered-cubic CrMnFeCoNi alloy was selected to investigate its weldability. Welds produced by electron beam welding show no cracking. The grain structures within the fusion zone (FZ) are controlled by the solidification behavior of the weld pool. The weldment possesses mechanical properties comparable to those of the base metal (BM) at both room and cryogenic temperatures. Finally, compared with the BM, deformation twinning was more pronounced in the FZ ofmore » the tested alloy.« less

  13. Point defect properties of ternary fcc Fe-Cr-Ni alloys

    NASA Astrophysics Data System (ADS)

    Wróbel, J. S.; Nguyen-Manh, D.; Dudarev, S. L.; Kurzydłowski, K. J.

    2017-02-01

    The properties of point defects in Fe-Cr-Ni alloys are investigated, using density functional theory (DFT), for two alloy compositions, Fe50Cr25Ni25 and Fe55Cr15Ni30, assuming various degrees of short-range order. DFT-based Monte Carlo simulations are applied to explore short-range order parameters and generate representative structures of alloys. Chemical potentials for the relevant structures are estimated from the minimum of the substitutional energy at representative atoms sites. Vacancies and <1 0 0> dumbbells are introduced in the Fe2CrNi intermetallic phase as well as in two Fe55Cr15Ni30 alloy structures: the disordered and short range-ordered structures, generated using Monte Carlo simulations at 2000 K and 300 K, respectively. Formation energies and relaxation volumes of defects as well as changes of magnetic moments caused by the presence of defects are investigated as functions of the local environment of a defect.

  14. Microstructure of Fe-Cr-C hardfacing alloys with additions of Nb, Ti and, B

    SciTech Connect

    Berns, H.; Fischer, A.

    1987-11-01

    The abrasive wear of machine parts and tools used in the mining, earth moving, and transporting of mineral materials can be lowered by filler wire welding of hardfacing alloys. In this paper, the microstructures of Fe-Cr-C and Fe-Cr-C-Nb/Ti hardfacing alloys and deposits and those of newly developed Fe-Cr-C-B and Fe-Ti-Cr-C-B ones are described. They show up to 85 vol.% of primarily solidified coarse hard phases; i.e., Carbides of MC-, M/sub 7/C/sub 3/-, M/sub 3/C-type and Borides of MB/sub 2/-, M/sub 3/B/sub 2/-, M/sub 2/B-, M/sub 3/B-, M/sub 23/B/sub 6/-type, which are embedded in a hard eutectic. This itself consists of eutectic hard phases and a martensitic or austenitic metal matrix. The newly developed Fe-Cr-C-B alloys reach hardness values of up to 1200 HV and are harder than all purchased ones. The primary solidification of the MB/sub 2/-type phase of titanium requires such high amounts of titanium and boron that these alloys are not practical for manufacture as commercial filler wires.

  15. Martensitic transformation and magnetic properties of Heusler alloy Ni-Fe-Ga ribbon

    NASA Astrophysics Data System (ADS)

    Liu, Z. H.; Liu, H.; Zhang, X. X.; Zhang, M.; Dai, X. F.; Hu, H. N.; Chen, J. L.; Wu, G. H.

    2004-08-01

    The martensitic transformation and magnetic properties of ferromagnetic shape memory alloy Ni 50+ xFe 25- xGa 25 ( x=-1, 0, 1, 2, 3, 4) ribbons have been systematically studied. It has been found that with the increase of Ni concentration, the martensitic transformation temperature increases, but the Curie temperature decreases. Both the two-step thermally induced structural transformation and the one-step transition have been observed in NiFeGa alloys with different compositions. It is found that the two-step transition became the one-step transition after the ribbon being heat treated at 873 K or higher. X-ray diffraction patterns show that only L2→B2 transition occurs in the samples treated at 873 K, while the γ phase will form in the samples treated at higher temperature. Transmission electron microscopy (TEM) studies show that the alloys with martensitic transformation temperature above the room temperature are non-modulated martensite with the large domain size, being different from the stoichiometric Ni 2FeGa alloy that is a modulated martensite with small domain size. The influences of Fe substitution for Ni in Ni 2FeGa on the saturation magnetization and exchange interaction are also discussed.

  16. Laboratory Simulation of Space Weathering: ESR Measurements of Nanophase Metallic Iron in Laser-irradiated Olivine and Pyroxene Samples

    NASA Technical Reports Server (NTRS)

    Kurahashi, E.; Yamanaka, C.; Nakamura, K.; Sasaki, S.

    2003-01-01

    S-type asteroids are believed to be parent bodies of ordinary chondrites. Although both S-type asteroids and ordinary chondrites contain the same mineral assemblage, mainly olivine and pyroxene, the reflectance spectra of the asteroids exhibit more overall depletion (darkening) and reddening, and more weakening of absorption bands relative to the meteorites. This spectral mismatch is explained by space weathering process, where high-velocity dust particle impacts should change the optical properties of the uppermost regolith surface of asteroids. In order to simulate the space weathering, we irradiated nanosecond pulse laser beam onto pellet samples of olivine (8.97wt% FeO) and pyroxene (enstatite: 9.88wt% FeO, hypersthene: 16.70wt%). We got spectral changes in our samples similar to that by space weathering on asteroids and confirmed nanophase alpha-metallic iron particles, which were theoretically predicted, not only on olivine but also on pyroxene samples by Transmission Electron Microscopy (TEM). Nanophase metallic iron particles were widely scattered throughout the amorphous rims developed along the olivine grains, whereas they were embedded in aggregates of amorphous in enstatite samples. Recently, we also measured laser-irradiated samples by ESR (Electron Spin Resonance). Strong ESR signals, characteristic to nanophase iron particles, are observed on irradiated olivine samples. In this paper, we report the quantities of nanophase metallic iron particles in pyroxene samples by ESR observations in addition to olivine samples.

  17. Effect of Si addition on AC and DC magnetic properties of (Fe-P)-Si alloy

    NASA Astrophysics Data System (ADS)

    Gautam, Ravi; Prabhu, D.; Chandrasekaran, V.; Gopalan, R.; Sundararajan, G.

    2016-05-01

    We report a new (Fe-P)-Si based alloy with relatively high induction (1.8-1.9 T), low coercivity (< 80 A/m), high resistivity (˜38 μΩ cm) and low core loss (217 W/kg @ 1 T/1 kHz) comparable to the commercially available M530-50 A5 Si-steel. The attractive magnetic and electrical properties are attributed to i) the two phase microstructure of fine nano precipitates of Fe3P dispersed in α-Fe matrix achieved by a two-step heat-treatment process and ii) Si addition enhancing the resistivity of the α-Fe matrix phase. As the alloy processing is by conventional wrought metallurgy method, it has the potential for large scale production.

  18. Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

    SciTech Connect

    Zhang, Chuan; Zhang, Fan; Diao, Haoyan; Gao, Michael C.; Tang, Zhi; Poplawsky, Jonathan D.; Liaw, Peter K.

    2016-07-19

    The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result, the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.

  19. Physical and Mechanical Properties of LoVAR: A New Lightweight Particle-Reinforced Fe-36Ni Alloy

    NASA Technical Reports Server (NTRS)

    Stephenson, Timothy; Tricker, David; Tarrant, Andrew; Michel, Robert; Clune, Jason

    2015-01-01

    Fe-36Ni is an alloy of choice for low thermal expansion coefficient (CTE) for optical, instrument and electrical applications in particular where dimensional stability is critical. This paper outlines the development of a particle-reinforced Fe-36Ni alloy that offers reduced density and lower CTE compared to the matrix alloy. A summary of processing capability will be given relating the composition and microstructure to mechanical and physical properties.

  20. A study of thermodynamic properties of dilute Fe-Ru alloys by 57Fe Mössbauer spectroscopy

    NASA Astrophysics Data System (ADS)

    Idczak, R.; Konieczny, R.; Chojcan, J.

    2016-12-01

    The room temperature Mössbauer spectra of 57Fe were measured for Fe1- x Ru x solid solutions with x in the range 0.01 ≤ x ≤ 0.08. The obtained data were analysed in terms of short-range order parameter (SRO) and the binding energy E b between two ruthenium atoms in the studied materials using the extended Hrynkiewicz-Królas idea. The extrapolated value of E b for x = 0 was used to compute the enthalpy of solution H FeRu of Ru in Fe matrix. The result was compared with corresponding values given in the literature which were derived from experimental calorimetric data as well as with the value resulting from the cellular atomic model of alloys by Miedema. It was found that all the H FeRu values are negative or Ru atoms interact repulsively. At the same time, the Mössbauer data were used to determine values of the short-range order parameter α 1. For the as-obtained samples in which atoms are frozen-in high temperature state, close to the melting point, the negative α 1 values were found. The findings indicates ordering tendencies in such specimens. On the other hand, in the case of the annealed samples where the observed distributions of atoms should be frozen-in state corresponding to the temperature 700 K, the Fe1- x Ru x alloys with x ≥ 0.05 exhibit clustering tendencies (a predominance of Fe-Fe and Ru-Ru bonds), which manifest themselves by positive values of the calculated SRO parameter. The clustering process leads to a local increase in ruthenium concentration and nucleation of a new ruthenium-rich phase with the hcp structure.

  1. Weathering of PGE sulfides and Pt-Fe alloys in the Freetown Layered Complex, Sierra Leone

    NASA Astrophysics Data System (ADS)

    Bowles, John F. W.; Suárez, Saioa; Prichard, Hazel M.; Fisher, Peter C.

    2017-01-01

    Fresh and weathered rocks and saprolite from Horizon B of the Freetown Layered Complex contain platinum-group minerals (PGM). The PGM in the fresh rocks are 1-7 μm across, including cooperite (PtS), isoferroplatinum (Pt3Fe), minor tetraferroplatinum (PtFe), tulameenite (Pt2FeCu), Os-bearing laurite (RuS2), and other base metal-sulfide (BMS)-bearing PGM. The weathered rocks contain fewer of those PGM but a high proportion of disordered Cu-(±Pd)-bearing Pt-Fe alloys. The saprolite hosts scarce, smaller (1-3 μm) ordered PtFe and disordered PtFe3. The Pt-Fe alloys became increasingly Fe rich as weathering proceeded. Pt-Fe oxides appeared during weathering. Copper sulfides associated with the primary PGM and cooperite (with <3% Pd) were destroyed to provide the minor Cu and Pd found in some of the disordered Pt-Fe alloys. Platinum- and Pd-bearing saprolites have retained the original rock fabric and, to a depth of about 2 m, surround residual rocks that show progressive weathering (corestones). Ground water passing through the saprolite has transported Pt and Pd (and probably Au) in solution down slope into saprolite over unmineralized rocks. Transport is marked by changes in the Pt/Pd ratio indicating that the metals have moved independently. Palladium is present in marginally higher concentrations in the deeper saprolite than in the corestones suggesting some retention of Pd in the deeper saprolite. Platinum and Pd are less concentrated in the upper saprolite than the deeper saprolite indicating surface leaching. Alteration occurred over a long period in an organic and microbial rich environment that may have contributed to the leaching and transport of PGE.

  2. Improvement of microstructure and magnetic properties of Nd-Fe-B alloys by Nb and Co additions

    NASA Astrophysics Data System (ADS)

    Ahmed, F. M.; Harris, I. R.

    In order to establish the role of niobium on the hydrogenation, disproportionation, desorption and recombination (HDDR) behavior of near-stoichiometric alloys, two alloys: NdI3Fe8OB7 and Nd13Fe78Nb1Co1B7 (at%) were investigated before, during and after the HDDR process. The microstructure of the as-cast Nb-free alloy before employing the HDDR process was found to consist of three phases, the matrix Nd 2Fe 14B (φ) phase, Nd-rich phase and a significant amount of free iron; whereas, the microstructure of the Nb-containing alloy consisted of only the first two phases. The HDDR behavior of the above alloys was characterized using a high-resolution scanning electron microscope (HRSEM). The disproportionation of the Nd 2Fe 14B (φ) matrix phase starts at the Nd-rich/φ phase interface, resulting in the formation of a sub-micron structure consisting of Fe, Fe 2B and Nd-hydride. The disproportionated structures of the Nb-free alloy contained large arms of free iron dendrites, which were retained from the as-cast structures. In the niobium-containing alloy, the recombined grains appear finer and with more rounded shapes in comparison with those of the NdFeB alloy. Promising magnetic properties have been obtained for bonded magnets using the HDDR powder. The magnetic properties, especially the intrinsic coercivity, improved significantly by using ˜1% Nd in excess of the stoichiometric content.

  3. Effect of Mn on the Microstructure and Magnetic Properties in Cu-Fe-Co Alloys

    NASA Astrophysics Data System (ADS)

    Mondal, B. N.; Basu Mallick, A.; Nath, D. N.; Chattopadhyay, P. P.

    2011-02-01

    An attempt was made to study the effect of Mn addition on the formation of supersaturated solid solution of Co and Fe in Cu during ball milling and precipitation of the solute-rich phases during subsequent annealing of the ball-milled product. It is demonstrated that the addition of Mn in the ternary CuFeCo powder blend enhances the metastable solubility of Fe and Co in Cu and facilitates the formation of the nanocrystalline supersaturated single-phase solid solution. Field emission-scanning electron microscopy (FE-SEM) also revealed notable influence of Mn on the morphological evolution of the ball-milled and annealed alloy powders. X-ray diffraction (XRD) analysis revealed that the FeCo phase having the bcc Bravais lattice forms after annealing at and above 620 K (350 °C) in both alloys. Estimation of magnetic properties showed that Mn addition in the CuFeCo alloy improved the coercivity, remanence, and magnetic saturation.

  4. Pressure dependence on the remanent magnetization of Fe-Ni alloys and Ni metal

    NASA Astrophysics Data System (ADS)

    Wei, Qingguo; Gilder, Stuart Alan; Maier, Bernd

    2014-10-01

    We measured the acquisition of magnetic remanence of iron-nickel alloys (Fe64Ni36, Fe58Ni42, and Fe50Ni50) and pure Ni under pressures up to 23 GPa at room temperature. Magnetization decreases markedly for Fe64Ni36 between 5 and 7 GPa yet remains ferromagnetic until at least 16 GPa. Magnetization rises by a factor of 2-3 for the other compositions during compression to the highest applied pressures. Immediately upon decompression, magnetic remanence increases for all Fe-Ni alloys while magnetic coercivity remains fairly constant at relatively low values (5-20 mT). The amount of magnetization gained upon complete decompression correlates with the maximum pressure experienced by the sample. Martensitic effects best explain the increase in remanence rather than grain-size reduction, as the creation of single domain sized grains would raise the coercivity. The magnetic remanence of low Ni Invar alloys increases faster with pressure than for other body-centered-cubic compositions due to the higher magnetostriction of the low Ni Invar metals. Thermal demagnetization spectra of Fe64Ni36 measured after pressure release broaden as a function of peak pressure, with a systematic decrease in Curie temperature. Irreversible strain accumulation from the martensitic transition likely explains the broadening of the Curie temperature spectra, consistent with our x-ray diffraction analyses.

  5. Electronic structure and vibrational entropies of fcc Au-Fe alloys

    SciTech Connect

    Munoz, Jorge A.; Lucas, Matthew; Mauger, L; Halevy, I; Horwath, J; Semiatin, S L; Xiao, Yuming; Stone, Matthew B; Abernathy, Douglas L; Fultz, B.

    2013-01-01

    Phonon density of states (DOS) curves were measured on alloys of face-centered-cubic (fcc) Au-Fe using nuclear resonant inelastic x-ray scattering (NRIXS) and inelastic neutron scattering (INS). The NRIXS and INS results were combined to obtain the total phonon DOS and the partial phonon DOS curves of Au and Fe atoms. The 57Fe partial phonon DOS of the dilute alloy Au0.97 57Fe0.03 shows a localized mode centered 4.3% above the cutoff energy of the phonons in pure Au. The Mannheim model for impurity modes accurately reproduced this partial phonon DOS using the fcc Au phonon DOS with a ratio of host-host to impurity-host force constants of 1.55. First-principles calculations validated the assumption of first-nearest-neighbor forces in the Mannheim model and gave a similar ratio of force constants. The high energy local mode broadens with increasing Fe composition, but this has a small effect on the composition dependence of the vibrational entropy. The main effect on the vibrational entropy of alloying comes from a stiffening of the Au partial phonon DOS with Fe concentration. This stiffening is attributed to two main effects: 1) an increase in electron density in the free-electron-like states, and 2) stronger sd-hybridization. These two effects are comparable in magnitude.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  7. In-situ Density and Thermal Expansion Measurements of Fe and Fe-S Alloying Liquids Under Planetary Core Conditions

    NASA Astrophysics Data System (ADS)

    Jing, Z.; Chantel, J.; Yu, T.; Sakamaki, T.; Wang, Y.

    2015-12-01

    Liquid iron is likely the dominant constituent in the cores of terrestrial planets and icy satellites such as Earth, Mars, Mercury, the Moon, Ganymede, and Io. Suggested by geophysical and geochemical observations, light elements such as S, C, Si, etc., are likely present in planetary cores. These light elements can significantly reduce the density and melting temperature of the Fe cores, and hence their abundances are crucial to our understanding of the structure and thermal history of planetary cores, as well as the generation of intrinsic magnetic fields. Knowledge on the density of Fe-light element alloying liquids at high pressures is critical to place constraints on the composition of planetary cores. However, density data on liquid Fe-light element alloys at core pressures are very limited in pressure and composition and are sometimes controversial. In this study, we extend the density dataset for Fe-rich liquids by measuring the density of Fe, Fe-10wt%S, Fe-20wt%S, Fe-27wt%S, and FeS liquids using the X-ray absorption technique in a DIA-type multianvil apparatus up to 7 GPa and 2173 K. An ion chamber (1D-detector) and a CCD camera (2D-detector) were used to measure intensities of transmitted monochromatic X-rays through molten samples, with the photon energy optimized at 40 keV. The densities were then determined from the Beer-Lambert law using the mass absorption coefficients, calibrated by solid standards using X-ray diffraction. At each pressure, density measurements were conducted at a range of temperatures above the liquidus of the samples, enabling the determination of thermal expansion. Combined with our previous results on the sound velocity of Fe and Fe-S liquids at high pressures (Jing et al., 2014, Earth Planet. Sci. Lett. 396, 78-87), these data provide tight constraints on the equation of state and thermodynamic properties such as the adiabatic temperature gradient for Fe-S liquids. We will discuss these results with implications to planetary

  8. Fe-based bulk amorphous alloys with iron contents as high as 82 at%

    NASA Astrophysics Data System (ADS)

    Li, Jin-Feng; Liu, Xue; Zhao, Shao-Fan; Ding, Hong-Yu; Yao, Ke-Fu

    2015-07-01

    Fe-based bulk amorphous alloys (BAAs) with high Fe contents are advantageous due to their high saturation magnetization and low cost. However, preparing Fe-based BAAs with Fe contents higher than 80 at% is difficult due to their poor glass forming abilities (GFA). In this study, an Fe81P8.5C5.5B2Si3 BAA with a diameter of 1 mm and a saturation magnetization of 1.56 T was successfully prepared using the fluxing and copper mold casting methods. In addition, by introducing a small amount of elemental Mo to the alloy, an Fe82Mo1P6.5C5.5B2Si3 BAA rod with a diameter of 1 mm, a high saturation magnetization of 1.59 T, a high yield stress of 3265 MPa, and a clear plasticity of 1.3% was prepared in the same way. The cost effectiveness and good magnetic properties of these newly-developed Fe-based BAAs with Fe contents as high as 82 at% would be advantageous and promising for industrial applications.

  9. Thermal conductivity and Seebeck coefficient of Fe and Fe-Si alloys: Implications for variable Lorenz number

    NASA Astrophysics Data System (ADS)

    Secco, Richard A.

    2017-04-01

    The Wiedemann-Franz Law is often used to calculate the thermal conductivity of Fe from experimental measurements of the electrical conductivity. It is shown by measurements of the Seebeck coefficient (S) of solid and liquid Fe at pressures up to 6 GPa and temperatures up to 2100 K that the Sommerfeld value (L0 = 2.445 × 10-8 W Ω K-2) of the Lorenz number (L) represents more than 99% of the electronic component of the thermal conductivity of Fe. Using experimental values of electrical resistivity and thermal conductivity of Fe, L/L0 is shown to vary by as much as 1.22 in the solid state and 1.32 in the liquid state, signifying a non-negligible phonon component. An expression for the pressure dependence of L at the melting boundary up to 5 GPa is derived for electron-phonon scattering. For Fe-Si alloys, L/L0 varies more than for pure Fe and generally increases with increasing Si and state of disorder. New values for the conductive heat flow in a pure Fe core of Mercury are presented.

  10. Magnetism and electronic structure of CoFeCrX (X = Si, Ge) Heusler alloys

    NASA Astrophysics Data System (ADS)

    Jin, Y.; Kharel, P.; Lukashev, P.; Valloppilly, S.; Staten, B.; Herran, J.; Tutic, I.; Mitrakumar, M.; Bhusal, B.; O'Connell, A.; Yang, K.; Huh, Y.; Skomski, R.; Sellmyer, D. J.

    2016-08-01

    The structural, electronic, and magnetic properties of CoFeCrX (X = Si, Ge) Heusler alloys have been investigated. Experimentally, the alloys were synthesized in the cubic L21 structure with small disorder. The cubic phase of CoFeCrSi was found to be highly stable against heat treatment, but CoFeCrGe disintegrated into other new compounds when the temperature reached 402 °C (675 K). Although the first-principle calculation predicted the possibility of tetragonal phase in CoFeCrGe, the tetragonal phase could not be stabilized experimentally. Both CoFeCrSi and CoFeCrGe compounds showed ferrimagnetic spin order at room temperature and have Curie temperatures (TC) significantly above room temperature. The measured TC for CoFeCrSi is 790 K but that of CoFeCrGe could not be measured due to its dissociation into new compounds at 675 K. The saturation magnetizations of CoFeCrSi and CoFeCrGe are 2.82 μB/f.u. and 2.78 μB/f.u., respectively, which are close to the theoretically predicted value of 3 μB/f.u. for their half-metallic phases. The calculated band gaps for CoFeCrSi and CoFeCrGe are, respectively, 1 eV and 0.5 eV. These materials have potential for spintronic device applications, as they exhibit half-metallic electronic structures with large band gaps, and Curie temperatures significantly above room temperature.

  11. Effect of decomposition of the Cr-Fe-Co rich phase of AlCoCrCuFeNi high entropy alloy on magnetic properties.

    PubMed

    Singh, S; Wanderka, N; Kiefer, K; Siemensmeyer, K; Banhart, J

    2011-05-01

    Splat-quenched, as-cast and aged (2h at 600 °C after casting) AlCoCrCuFeNi high entropy alloys were investigated by means of transmission electron microscopy and three-dimensional atom probe (3D-AP). 3D-AP revealed anti-correlated fluctuations of the Cr and Fe-Co compositions in Cr-Fe-Co-rich regions of the as-cast alloy. The ferromagnetic behavior of AlCoCrCuFeNi high entropy alloy was correlated with the decomposition of the Cr-Fe-Co-rich regions into ferromagnetic Fe-Co-rich and antiferromagnetic Cr-rich domains, the size of which was determined by statistical analysis of 3D-AP data. The splat-quenched alloy showed a softer magnetic behavior as compared to the as-cast and aged alloys. The aged alloy possessed a higher saturation magnetization and coercivity as compared to the as-cast alloy.

  12. The Optical Properties of Nanophase Iron: Investigation of a Space Weathering Analog

    NASA Technical Reports Server (NTRS)

    Noble, S. K.; Pieters, C. M.; Keller, L. P.

    2003-01-01

    It is known that space weathering, in particular the nanophase iron (npFe(sup 0)) created via vapor and/or sputter deposition, has distinct and predictable effects on the optical properties of lunar soils. In addition to the attenuation of absorption bands, weathering introduces a characteristic continuum which is controlled by the amount of npFe(sup 0) present. The shape of this continuum may also be controlled by the size of the npFe(sup 0) grains. It is thought that small npFe(sup 0) grains result in reddening, while larger grains only darken the material. To investigate this phenomenon we have created a lunar weathering analog by impregnating silica gel powders with npFe(sup 0) following the methods presented.

  13. Nanophase Carbonates on Mars: Does Evolved Gas Analysis of Nanophase Carbonates Reveal a Large Organic Carbon Budget in Near-surface Martian Materials?

    NASA Astrophysics Data System (ADS)

    Archer, P. D., Jr.; Ming, D. W.; Sutter, B.; Niles, P. B.; Eigenbrode, J. L.

    2015-12-01

    Evolved Gas Analysis (EGA), which involves heating a sample and monitoring the gases released, has been performed on Mars by the Viking gas chromatography/mass spectrometry instruments, the Thermal and Evolved Gas Analyzer (TEGA) on the Phoenix lander, and the Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory. All of these instruments detected CO2 released during sample analysis at abundances of ~0.1 to 5 wt% assuming a carbonate source. The source of the CO2 can be constrained by evaluating the temperature of the gas release, a capability of both the TEGA and SAM instruments. The samples analyzed by SAM show that the majority of the CO2is released below 400 °C, much lower than traditional carbonate decomposition temperatures which can be as low as 400 °C for some siderites, with magnesites and calcites decomposing at even higher temperatures. In addition to mineralogy, decomposition temperature can depend on particle size (among other factors). If carbonates formed on Mars under low temperature and relative humidity conditions, the resulting small particle size (nanophase) carbonates could have low decomposition temperatures. We have found that calcite can be synthesized by exposing CaO to water vapor and CO2 and that the resulting mineral has an EGA peak of ~550 °C for CO2, which is about 200 °C lower than for other calcites. Work is ongoing to produce Fe and Mg-bearing carbonates using the same process. Current results suggest that nanophase calcium carbonates cannot explain the CO2 released from martian samples. If the decomposition temperatures of Mg and Fe-bearing nanophase carbonates are not significantly lower than 400 °C, other candidate sources include oxalates and carboxylated organic molecules. If present, the abundance of organic carbon in these samples could be > 0.1 wt % (1000s of ppm), a signficant departure from the paradigm of the organic-poor Mars based on Viking results.

  14. Nanophase Carbonates on Mars: Does Evolved Gas Analysis of Nanophase Carbonates Reveal a Large Organic Carbon Budget in Near-Surface Martian Materials?

    NASA Technical Reports Server (NTRS)

    Archer, P. Douglas, Jr.; Niles, Paul B.; Ming, Douglas W.; Sutter, Brad; Eigenbrode, Jen

    2015-01-01

    Evolved Gas Analysis (EGA), which involves heating a sample and monitoring the gases released, has been performed on Mars by the Viking gas chromatography/mass spectrometry instruments, the Thermal and Evolved Gas Analyzer (TEGA) on the Phoenix lander, and the Sample Analysis at Mars (SAM) instrument on the Mars Science Laboratory. All of these instruments detected CO2 released during sample analysis at abundances of approx. 0.1 to 5 wt% assuming a carbonate source. The source of the CO2 can be constrained by evaluating the temperature of the gas release, a capability of both the TEGA and SAM instruments. The samples analyzed by SAM show that the majority of the CO2 is released below 400C, much lower than traditional carbonate decomposition temperatures which can be as low as 400C for some siderites, with magnesites and calcites decomposing at even higher temperatures. In addition to mineralogy, decomposition temperature can depend on particle size (among other factors). If carbonates formed on Mars under low temperature and relative humidity conditions, the resulting small particle size (nanophase) carbonates could have low decomposition temperatures. We have found that calcite can be synthesized by exposing CaO to water vapor and CO2 and that the resulting mineral has an EGA peak of approx. 550C for CO2, which is about 200C lower than for other calcites. Work is ongoing to produce Fe and Mg-bearing carbonates using the same process. Current results suggest that nanophase calcium carbonates cannot explain the CO2 released from martian samples. If the decomposition temperatures of Mg and Fe-bearing nanophase carbonates are not significantly lower than 400C, other candidate sources include oxalates and carboxylated organic molecules. If present, the abundance of organic carbon in these samples could be greater than 0.1 wt % (1000s of ppm), a signficant departure from the paradigm of the organic-poor Mars based on Viking results.

  15. Oxidation of CoCrFeMnNi High Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Holcomb, Gordon R.; Tylczak, Joseph; Carney, Casey

    2015-06-01

    Eight model high entropy alloys (HEAs) in the CoCrFeMnNi family (including one alloy each in the CoCrFeNi and CoFeMnNi subfamilies) were made, prepared, and exposed to laboratory air for 1100 h at 650°C and 750°C. Two commercial alloys, nickel-base superalloy 230 (N06230) and austenitic stainless steel 304H (S30409), were simultaneously exposed for comparison. Mass change oxidation kinetics were measured and cross-sections of exposed samples were observed. Seven of these HEAs contained much more Mn (12-24 wt.%) than is found in commercial heat-resistant stainless steels and superalloys. The oxidation resistance of CoCrFeNi was excellent and comparable to 304H at 650°C and only slightly worse at 750°C. The thin oxide scale on CoCrFeNi was primarily Cr oxide (presumably Cr2O3) with some Mn oxide at the outer part of the scale. The CoCrFeMnNi HEAs all experienced more rapid oxidation than CoCrFeNi and, especially at 750°C, experienced oxide scale spallation. The addition of Y in the alloy to lower S improved the oxidation resistance of these HEAs. Alloy CoFeMnNi, without Cr, experienced much higher oxidation rates and scale spallation than the Cr-containing alloys. A linear regression analysis of the log of the parabolic rate constant, log(kp), as functions of wt.% Cr and Mn found a good correlation for the compositional dependence of the oxidation rate constant, especially at 650°C. Mn was found to be more detrimental increasing log(k p) than Cr was helpful reducing log(k p). If CoCrFeMnNi HEAs are to be used in high temperature oxidizing environments, then examining lower levels of Mn, while maintaining Cr levels, should be pursued.

  16. Section 2: Phase transformation studies in mechanically alloyed Fe-Nz and Fe-Zn-Si intermetallics

    SciTech Connect

    Jordan, A.; Uwakweh, O.N.C.; Maziasz, P.J.

    1997-04-01

    The initial stage of this study, which was completed in FY 1995, entailed an extensive analysis characterizing the structural evolution of the Fe-Zn intermetallic system. The primary interest in these Fe-Zn phases stems from the fact that they form an excellent coating for the corrosion protection of steel (i.e., automobile body panels). The Fe-Zn coating generally forms up to four intermetallic phases depending on the particular industrial application used, (i.e., galvanization, galvannealing, etc.). Since the different coating applications are non-equilibrium in nature, it becomes necessary to employ a non-equilibrium method for producing homogeneous alloys in the solid-state to reflect the structural changes occurring in a true coating. This was accomplished through the use of a high energy/non-equilibrium technique known as ball-milling which allowed the authors to monitor the evolution process of the alloys as they transformed from a metastable to stable equilibrium state. In FY 1996, this study was expanded to evaluate the presence of Si in the Fe-Zn system and its influence in the overall coating. The addition of silicon in steel gives rise to an increased coating. However, the mechanisms leading to the coating anomaly are still not fully understood. For this reason, mechanical alloying through ball-milling of pure elemental powders was used to study the structural changes occurring in the sandelin region (i.e., 0.12 wt % Si). Through the identification of invariant reactions (i.e., eutectic, etc.) the authors were able to explore the sandelin phenomenon and also determine the various fields or boundaries associated with the Fe-Zn-Si ternary system.

  17. On the stability of AuFe alloy nanoparticles.

    PubMed

    Velasco, V; Pohl, D; Surrey, A; Bonatto-Minella, A; Hernando, A; Crespo, P; Rellinghaus, B

    2014-05-30

    AuFe nanoparticles with mean diameters d p  = 13.2 nm have been prepared by inert-gas condensation. Conventional and high-resolution transmission electron microscopy and energy-dispersive x-ray spectroscopy investigations show that the particles are mostly icosahedra. Scanning transmission electron microscopy-energy-dispersive x-ray spectroscopy and scanning transmission electron microscopy-electron energy-loss spectroscopy show that the as-grown particles exhibit a core-shell structure. The shell is mainly composed of an amorphous FeO layer. Although Fe and Au are immiscible in the bulk, the particle cores are found to be homogeneously mixed at the atomic level with a local composition of around Au84Fe16 (at.%). AuFe nanoparticles exhibit a complex magnetic structure in which the core behaves as a spin glass with a freezing temperature of 35 K, whereas the amorphous FeO shell behaves as a ferro-ferrimagnetic system. On annealing above 300 °C, the AuFe icosahedra phases separate into their elemental constituents. Hence the as-grown AuFe icosahedra are metastable, thereby implying that the bulk phase diagram also applies for nanoscopic materials.

  18. Study of the effect of short ranged ordering on the magnetism in FeCr alloys

    NASA Astrophysics Data System (ADS)

    Jena, Ambika Prasad; Sanyal, Biplab; Mookerjee, Abhijit

    2014-01-01

    For the study of magnetism in systems where the local environment plays an important role, we propose a marriage between the Monte Carlo simulation and Zunger's special quasi-random structures. We apply this technique on disordered FeCr alloys and show that our estimates of the transition temperature is in good agreement with earlier experiments.

  19. Elevated Temperature Properties of a Dispersion Strengthened Al(Fe, V, Si) Alloy

    DTIC Science & Technology

    1991-12-01

    ASTM STP 890, M. E. Fine and E. A. Starke, Jr., Eds., American Society for Testing and Materials, pp. 211-236, 1986. 3. Raybould , D., "Forming of...and Materials Society, pp 181-197, 1988. 6. Skinner, D. J., Rye, D., Raybould , D., and Brown, A. M., "Dispersion Strengthened Al-Fe-V-Si Alloys

  20. The Formation of Crystal Defects in a Fe-Mn-Si Alloy Under Cyclic Martensitic Transformations.

    PubMed

    Bondar, Vladimir I; Danilchenko, Vitaliy E; Iakovlev, Viktor E

    2016-12-01

    Formation of crystalline defects due to cyclic martensitic transformations (CMT) in the iron-manganese Fe-18 wt.% Mn-2 wt.% Si alloy was investigated using X-ray diffractometry. Conditions for accumulation of fragment sub-boundaries with low-angle misorientations and chaotic stacking faults in crystal lattice of austenite and ε-martensite were analyzed.

  1. Gamma to alpha phase transformation in FeCoV alloys

    NASA Astrophysics Data System (ADS)

    Rezende, M. F. S.; Lacerda, A. M.; Pfannes, H.-D.; Mansur, R. A.; Ardisson, J. D.; Persiano, A. I. C.

    1994-12-01

    The effects of filing FeCoV alloys with equiatomic FeCo and up to 14 at% V is studied by Mössbauer spectroscopy and X-ray diffraction. We observed that filing eliminates the paramagnetic component observed in samples in the form of plates. The filed material also presents a linear increase of the lattice parameter and a linear decrease of the average hyperfine field of the alpha phase due to extra low-field satellites with increasing vanadium contents. This indicates that filing produces a gamma to alpha phase transformation, which increases the amount of vanadium in solid solution in the FeCo alpha phase.

  2. Dynamical interaction of helium bubbles with cascade damage in Fe-9Cr ferritic alloy.

    SciTech Connect

    Ono, K.; Miyamoto, M.; Arakawa, K.; Birtcher, R. C.; Materials Science Division; Shimane Univ.; Osaka Univ.

    2008-12-01

    Dynamic interaction of helium bubble with cascade damage in Fe-9Cr ferritic alloy has been studied using in situ irradiation and electron microscopy. During the irradiation of the alloy by 400 keV Fe{sup +} ions at temperatures where no thermal motion takes place, induced displacement of small helium bubbles was observed: the bubbles underwent sporadic and instant displacement. The displacement was of the order of a few nanometers. The experimentally determined displacement probability of helium bubbles is consistent with the calculated probability of their dynamic interaction with sub-cascades introduced by the irradiation. Furthermore, during the irradiation of the alloy at higher temperatures, both retarded and accelerated Brownian type motions were observed. These results are discussed on the basis of dynamic interaction of helium bubbles with point defects that survive through high-energy self-ion irradiation.

  3. Growth and surface alloying of Fe on Pt(9 9 7)

    NASA Astrophysics Data System (ADS)

    Lee, Tae-Yon; Sarbach, Samuel; Kuhnke, Klaus; Kern, Klaus

    2006-08-01

    The growth of ultra-thin layers of Fe on the vicinal Pt(9 9 7) surface is studied by thermal energy He atom scattering (TEAS) and Auger Electron Spectroscopy (AES) in the temperature range between 175 K and 800 K. We find three distinct regimes of qualitatively different growth type. Below 450 K the formation of a smooth first monolayer, at and above 600 K the onset of bulk alloy formation, and at intermediate temperature 500-550 K the formation of a surface alloy. Monatomic Fe rows are observed to decorate the substrate steps between 175 K and 500 K. The importance of the high step density is discussed with respect to the promotion of smooth layer growth and with respect to the alloying process and its kinetics.

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

    SciTech Connect

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

    1993-06-01

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

  5. SYNTHESIS AND PERFORMANCE OF FE-BASED AMORPHOUS ALLOYS FOR NUCLEAR WASTE REPOSITORY APPLICATIONS

    SciTech Connect

    Kaufman, L; Perepezko, J; Hildal, K

    2007-02-08

    In several Fe-based alloy systems it is possible to produce glasses with cooling rates as low as 100 K/s that exhibit outstanding corrosion resistance compared to typical crystalline alloys such as high-performance stainless steels and Ni-based C-22 alloy. Moreover, novel alloy compositions can be synthesized to maximize corrosion resistance (i.e. adding Cr and Mo) and to improve radiation compatibility (adding B) and still maintain glass forming ability. The applicability of Fe-based amorphous coatings in typical environments where corrosion resistance and thermal stability are critical issues has been examined in terms of amorphous phase stability and glass-forming ability through a coordinated computational analysis and experimental validation. Similarly, a novel computational thermodynamics approach has been developed to explore the compositional sensitivity of glass-forming ability and thermal stability. Also, the synthesis and characterization of alloys with increased cross-section for thermal neutron capture will be outlined to demonstrate that through careful design of alloy composition it is possible to tailor the material properties of the thermally spray-formed amorphous coating to accommodate the challenges anticipated in typical nuclear waste storage applications over tens of thousands of years in a variety of corrosive environments.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  7. Mössbauer study of oxide films of Fe-, Sn-, Cr- doped zirconium alloys during corrosion in autoclave

    NASA Astrophysics Data System (ADS)

    Filippov, V. P.; Bateev, A. B.; Lauer, Yu. A.

    2016-12-01

    Mössbauer investigations were used to compare iron atom states in oxide films of binary Zr-Fe, ternary Zr-Fe-Cu and quaternary Zr-Fe-Cr-Sn alloys. Oxide films are received in an autoclave at a temperature of 350-360 °C and at pressure of 16.8 MPa. The corrosion process decomposes the intermetallic precipitates in alloys and forms metallic iron with inclusions of chromium atoms α-Fe(Cr), α-Fe(Cu), α-Fe 2O3 and Fe 3O4 compounds. Some iron ions are formed in divalent and in trivalent paramagnetic states. The additional doping influences on corrosion kinetics and concentration of iron compounds and phases formed in oxide films. It was shown the correlation between concentration of iron in different chemical states and corrosion resistance of alloys.

  8. Ab initio studies of the effect of nanoclusters on magnetostriction of Fe1-xGax alloys

    NASA Astrophysics Data System (ADS)

    Wang, Hui; Zhang, Y. N.; Yang, Teng; Zhang, Z. D.; Sun, L. Z.; Wu, R. Q.

    2010-12-01

    Using the density functional calculations, we investigated the effect of nanoprecipitation on the magnetostriction of Fe1-xGax alloys. While the B2-like FeGa clusters undergo slight tetragonal distortion, D03-like FeGa clusters remain cubic in the Fe matrix. Moreover, we found that B2-like nanostructures produce negative magnetostriction, whereas D03-like nanostructures give small positive magnetostriction in the hypothetical inhomogeneous structures. Therefore, the formation of nanoscale precipitates cannot be the reason for the extraordinary enhancement of magnetostriction of Fe1-xGax alloys.

  9. Mechanical Properties and Microstructure of the CoCrFeMnNi High Entropy Alloy Under High Strain Rate Compression

    NASA Astrophysics Data System (ADS)

    Wang, Bingfeng; Fu, Ao; Huang, Xiaoxia; Liu, Bin; Liu, Yong; Li, Zezhou; Zan, Xiang

    2016-07-01

    The equiatomic CoCrFeMnNi high entropy alloy, which crystallizes in the face-centered cubic (FCC) crystal structure, was prepared by the spark plasma sintering technique. Dynamic compressive tests of the CoCrFeMnNi high entropy alloy were deformed at varying strain rates ranging from 1 × 103 to 3 × 103 s-1 using a split-Hopkinson pressure bar (SHPB) system. The dynamic yield strength of the CoCrFeMnNi high entropy alloy increases with increasing strain rate. The Zerilli-Armstrong (Z-A) plastic model was applied to model the dynamic flow behavior of the CoCrFeMnNi high entropy alloy, and the constitutive relationship was obtained. Serration behavior during plastic deformation was observed in the stress-strain curves. The mechanism for serration behavior of the alloy deformed at high strain rate is proposed.

  10. Atomic structure, alloying behavior, and magnetism in small Fe-Pt clusters

    NASA Astrophysics Data System (ADS)

    Chittari, Bheema Lingam; Kumar, Vijay

    2015-09-01

    We report results of the atomic structure, alloying behavior, and magnetism in F emP tn(m +n =2 -10 ) clusters using projector augmented wave (PAW) pseudopotential method and spin-polarized generalized gradient approximation (GGA) for the exchange-correlation energy. These results are compared with those obtained by using HCTH exchange-correlation functional and LANL2DZ basis set in the Gaussian program and the overall trends are found to be similar. As in bulk Fe-Pt alloys, clusters with equal composition of Fe and Pt have the largest binding energy and the largest heat of nanoalloy formation for a given number of atoms in the cluster. There are some deviations due to the different symmetries in clusters and in cases where the total number of atoms is odd. The lowest energy isomers tend to maximize bonds between unlike atoms with Fe (Pt) atoms occupying high (low) coordination sites in the core (surface) of the cluster. The binding energy, heat of formation, and the second order difference of the total energy show F e2P t2 , F e4P t4 , and F e4P t6 clusters to be the most stable ones among the different clusters we have studied. The magnetic moments on Fe atoms are high in Pt-rich clusters as well as in small Fe-rich clusters and decrease as the aggregation of Fe atoms and the cluster size increases. The maximum value of the magnetic moments on Fe atoms is ˜3.8 μB , whereas for Pt atoms it is 1 μB. These are quite high compared with the values for bulk Fe as well as bulk FePt and F e3Pt phases while bulk Pt is nonmagnetic. There is significant charge transfer from those Fe atoms that interact directly with Pt atoms. We discuss the hybridization between the electronic states of Pt and Fe atoms as well as the variation in the magnetic moments on Fe and Pt atoms. Our results provide insight into the understanding of the nanoalloy behavior of Fe-Pt and we hope that this would help to design Fe based nanoalloys and their assemblies with high magnetic moments for

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

    NASA Astrophysics Data System (ADS)

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

    2015-10-01

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

  12. Extended x-ray absorption fine structure studies of IBS Fe--Tb alloy films

    SciTech Connect

    Harris, V.G.; Aylesworth, K.D.; Kim, K.H.; Elam, W.T.; Koon, N.C. )

    1991-11-15

    We have employed extended x-ray absorption fine structure (EXAFS) analysis to study the compositional dependence of the atomic structure in Fe--Tb alloy films. Fourier transforms of EXAFS data, relative to both the Fe {ital K} and the Tb {ital L}{sub III} absorption edges, provide information about the local atomic environments relative to each atom. Results indicate the Fe EXAFS data to be dominated by Fe--Fe correlations, and consists of contributions from two Fe atomic shells at radial distances near 2.47 and 2.66 A and a Tb shell near 2.91 A. The coordination number of the Fe shells are measured to increase, while radial distances decrease, with increased Fe content. The Tb EXAFS data was found to have an atomic shells of Fe and Tb at 2.91 and 3.47 A, respectively. Analysis suggests that the Fe shell is very disordered and is comprised of approximately 9.5 atoms while the Tb shell has {approx}3 atoms.

  13. Effect of annealing on VmHn complexes in hydrogen ion irradiated Fe and Fe-0.3%Cu alloys

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Jin, Shuoxue; Lu, Eryang; Wang, Baoyi; Zheng, Yongnan; Yuan, Daqing; Cao, Xingzhong

    2015-04-01

    The effect of annealing on VmHn complexes and Cu precipitate behaviours in hydrogen ion irradiated Fe and Fe-0.3%Cu alloys was investigated by positron annihilation spectroscopy using a slow positron beam. The results of S parameters indicated that the room temperature irradiation was benefit for the formation of the VmHn complex compared to the elevated temperature irradiation. The S-W results confirmed the formation of Cu precipitates in Fe-0.3%Cu even at the irradiation dose of 0.1 dpa. The formation of the evident S value peaks in the damage region after annealing treatment suggested that the VmHn complexes were broken and a larger of hydrogen atoms were escaping. The residual vacancy defects would migrate towards both the surface region and the opposite direction with the increasing annealing temperature.

  14. Autonomous Repair Mechanism of Creep Damage in Fe-Au and Fe-Au-B-N Alloys

    NASA Astrophysics Data System (ADS)

    Zhang, S.; Kwakernaak, C.; Tichelaar, F. D.; Sloof, W. G.; Kuzmina, M.; Herbig, M.; Raabe, D.; Brück, E.; van der Zwaag, S.; van Dijk, N. H.

    2015-12-01

    The autonomous repair mechanism of creep cavitation during high-temperature deformation has been investigated in Fe-Au and Fe-Au-B-N alloys. Combined electron-microscopy techniques and atom probe tomography reveal how the improved creep properties result from Au precipitation within the creep cavities, preferentially formed on grain boundaries oriented perpendicular to the applied stress. The selective precipitation of Au atoms at the free creep cavity surface results in pore filling, and thereby, autonomous repair of the creep damage. The large difference in atomic size between the Au and Fe strongly hampers the nucleation of precipitates in the matrix. As a result, the matrix acts as a reservoir for the supersaturated solute until damage occurs. Grain boundaries and dislocations are found to act as fast transport routes for solute gold from the matrix to the creep cavities. The mechanism responsible for the self-healing can be characterized by a simple model for cavity growth and cavity filling.

  15. Phase relationships in Fe-Ni alloys at high pressures and temperatures

    NASA Technical Reports Server (NTRS)

    Huang, Eugene; Bassett, William A.; Weathers, Maura S.

    1988-01-01

    Diffusionless phase transformations in Fe-Ni alloys with up to 35 wt pct Ni were studied using resistance-heated diamond anvil cells and synchrotron radiation. At temperatures up to 600 C and pressures up to 25 GPa, Fe-35 percent Ni showed only the face-centered cubic (fcc) phase while Fe-25 percent Ni and Fe-10 percent Ni showed the body-centered cubic (bcc) and hexagonal close-packed (hcp) phases in addition to the fcc phase. The phase relationships of these solid phases are topologically similar to those of pure iron. The triple point becomes lower in temperature, and the slope (dT/dP) of the fcc/hcp boundary decreased as Ni-content increases in the alloys. From these results it is inferred that Fe-Ni alloys in the earth's inner core might exist as two phases, fcc and hcp. The existence of these two phases could have played an important role in the separation of the inner and outer core.

  16. Half-metallic properties of the new Ti2YPb(Y = Co, Fe) Heusler alloys

    NASA Astrophysics Data System (ADS)

    Hussain, Moaid K.; Gao, G. Y.; Yao, Kai-Lun

    2015-09-01

    The half-metallic properties of Ti2YPb(Y = Co, Fe) Heusler alloys with a CuHg2Ti-type structure were examined within the frame of the density functional theory and the Perdew-Burke-Ernzerh of generalized gradient approximation (GGA). Analysis of the electronic band structures and density of states for Ti2YPb(Y = Co, Fe) revealed that the spin-up bands are metallic, whereas the spin-down bands exhibit gaps of 0.73 and 0.70 eV, respectively. The magnetic moments calculated for the Ti2YPb(Y = Co, Fe) alloys were found to be equal to 3 μB/f.u. and 2 μB/f.u., values which both follows the Slater-Pauling rule of Mt = Zt - 18. The compounds’ negative enthalpy values should encourage their experimental realization in the future. The bandgap was elucidated to be mainly determined by the bonding and antibonding states created from the hybridizations of the d states between the Ti(1)-Ti(2) coupling and the Y = Co, Fe atom. The half-metallic properties of the Ti2YPb(Y = Co, Fe) compounds were found to be insensitive to lattice distortion, with full spin polarization achievable within a large range of lattice parameter values, making the alloys suitable for use in practical applications.

  17. Microstructural Investigation and Phase Relationships of Fe-Al-Hf Alloys

    NASA Astrophysics Data System (ADS)

    Yildirim, Mehmet; Akdeniz, M. Vedat; Mekhrabov, Amdulla O.

    2014-07-01

    The effect of Hf addition on microstructures, phase relationships, microhardness, and magnetic properties of Fe50Al50- n Hf n alloys for n = 1, 3, 5, 7, and 9 at. pct has been investigated. At all investigated compositions, the ternary intermetallic HfFe6Al6 τ 1 phase forms due to the limited solid solubility of Hf in FeAl phase and tends to develop a eutectic phase mixture with the Fe-Al-based phase. The Hf concentration of the eutectic composition is found to be 7 at. pct from the microstructural examinations and the eutectic phase transition temperature is determined as 1521 K (1248 °C) independent of Hf amount by differential scanning calorimetry measurements. Furthermore, the enthalpies and activation energies (based on Kissinger and Ozawa methods) of eutectic phase transitions are reported. The minimum activation energy is calculated for the fully eutectic composition. Moreover, variation of the microhardness of Fe-Al-based alloys as a function of the Hf content is investigated, and its dependence on the thermal history of the alloys is explained.

  18. Effects of Zn additions to highly magnetoelastic FeGa alloys

    SciTech Connect

    Lograsso, Thomas A.; Jones, Nicholas J.; Wun-Fogle, Marilyn; Restorff, James B.; Schlagel, Deborah L.; Petculescu, Gabriela; Clark, Arthur E.; Hathaway, Kristl B.

    2015-05-07

    Fe{sub 1−x}M{sub x} (M = Ga, Ge, Si, Al, Mo and x ∼ 0.18) alloys offer an extraordinary combination of magnetoelasticity and mechanical properties. They are rare-earth-free, can be processed using conventional deformation techniques, have high magnetic permeability, low hysteresis, and low magnetic saturation fields, making them attractive for device applications such as actuators and energy harvesters. Starting with Fe-Ga as a reference and using a rigid-band-filling argument, Zhang et al. predicted that lowering the Fermi level by reducing the total number of electrons could enhance magnetoelasticity. To provide a direct experimental validation for Zhang's hypothesis, elemental additions with lower-than-Ga valence are needed. Of the possible candidates, only Be and Zn have sufficient solubility. Single crystals of bcc Fe-Ga-Zn have been grown with up to 4.6 at. % Zn in a Bridgman furnace under elevated pressure (15 bars) in order to overcome the high vapor pressure of Zn and obtain homogeneous crystals. Single-crystal measurements of magnetostriction and elastic constants allow for the direct comparison of the magnetoelastic coupling constants of Fe-Ga-Zn with those of other magnetoelastic alloys in its class. The partial substitution of Ga with Zn yields values for the magnetoelastic coupling factor, −b{sub 1}, comparable to those of the binary Fe-Ga alloy.

  19. Configurational thermodynamics of Fe-Ni alloys at Earth's core conditions

    NASA Astrophysics Data System (ADS)

    Ekholm, M.; Mikhaylushkin, A. S.; Simak, S. I.; Johansson, B.; Abrikosov, I. A.

    2011-08-01

    By means of ab-initio calculations, we perform an analysis of the configurational thermodynamics, effects of disorder, and structural energy differences in Fe-Ni alloys at the pressure and temperature conditions of the Earth's core. We show from ab-initio calculations that the ordering energies of fcc and hcp-structured Fe-Ni solid solutions at these conditions depend sensitively on the alloy configuration, i.e., on the degree of chemical disorder, and are on a scale comparable with the structural energy differences. From configurational thermodynamic simulations we find that a distribution of Fe and Ni atoms in the solutions should be very close to completely disordered at these conditions. Using this model of the Fe-Ni system, we have calculated the fcc-hcp structural free energy difference in a wide pressure-temperature range of 120-360 GPa and 1000-6600 K. Our calculations show that alloying of Fe with Ni below 3000 K favours stabilisation of the fcc phase over the hcp, in agreement with experiments. However, above 3000 K the effect is reversed, and at conditions corresponding to those of the Earth's inner core, Ni acts as an agent to stabilise the hcp phase.

  20. Effects of Zn additions to highly magnetoelastic FeGa alloys

    NASA Astrophysics Data System (ADS)

    Lograsso, Thomas A.; Jones, Nicholas J.; Schlagel, Deborah L.; Petculescu, Gabriela; Wun-Fogle, Marilyn; Restorff, James B.; Clark, Arthur E.; Hathaway, Kristl B.

    2015-05-01

    Fe1-xMx (M = Ga, Ge, Si, Al, Mo and x ˜ 0.18) alloys offer an extraordinary combination of magnetoelasticity and mechanical properties. They are rare-earth-free, can be processed using conventional deformation techniques, have high magnetic permeability, low hysteresis, and low magnetic saturation fields, making them attractive for device applications such as actuators and energy harvesters. Starting with Fe-Ga as a reference and using a rigid-band-filling argument, Zhang et al. predicted that lowering the Fermi level by reducing the total number of electrons could enhance magnetoelasticity. To provide a direct experimental validation for Zhang's hypothesis, elemental additions with lower-than-Ga valence are needed. Of the possible candidates, only Be and Zn have sufficient solubility. Single crystals of bcc Fe-Ga-Zn have been grown with up to 4.6 at. % Zn in a Bridgman furnace under elevated pressure (15 bars) in order to overcome the high vapor pressure of Zn and obtain homogeneous crystals. Single-crystal measurements of magnetostriction and elastic constants allow for the direct comparison of the magnetoelastic coupling constants of Fe-Ga-Zn with those of other magnetoelastic alloys in its class. The partial substitution of Ga with Zn yields values for the magnetoelastic coupling factor, -b1, comparable to those of the binary Fe-Ga alloy.

  1. High strength bulk Fe-Co alloys produced by powder metallurgy

    SciTech Connect

    Turgut, Zafer; Huang Meiqing; Horwath, John C.; Fingers, Richard T.

    2008-04-01

    Fe-Co alloys are extensively used in lamination form, but there are certain power generation applications that require Fe-Co rotors in bulk form. Experiencing only a dc magnetic field, these rotors can be as large as 0.5 m in diameter, depending on the size of the generator. The forging of such large pieces of Fe-Co has proven to be difficult. The present study investigates powder metallurgy processing of a gas atomized FeCoNbV alloy through hot isostatic pressing (HIP) for manufacturing large size rotors with improved mechanical strength. Gas atomized FeCoNbV alloy powders with and without ball milling were hot isostatic pressed at temperatures between 675 and 850 deg. C at a fixed pressure of 193 MPa for up to 6 h. Ball milling prior to HIP improved the yield strength. A further improvement in yield strength and in ductility was obtained after a disordering heat treatment at 730 deg. C followed by a rapid quench to room temperature. The optimum HIP and annealing conditions resulted in samples with yield strengths of 870 MPa. The compacts exhibited average coercivity values of 6.4 Oe and maximum permeability values of 1100.

  2. Corrosion-wear behavior of nanocrystalline Fe88Si12 alloy in acid and alkaline solutions

    NASA Astrophysics Data System (ADS)

    Fu, Li-cai; Qin, Wen; Yang, Jun; Liu, Wei-min; Zhou, Ling-ping

    2017-01-01

    The corrosion-wear behavior of a nanocrystalline Fe88Si12 alloy disc coupled with a Si3N4 ball was investigated in acid (pH 3) and alkaline (pH 9) aqueous solutions. The dry wear was also measured for reference. The average friction coefficient of Fe88Si12 alloy in the pH 9 solution was approximately 0.2, which was lower than those observed for Fe88Si12 alloy in the pH 3 solution and in the case of dry wear. The fluctuation of the friction coefficient of samples subjected to the pH 9 solution also showed similar characteristics. The wear rate in the pH 9 solution slightly increased with increasing applied load. The wear rate was approximately one order of magnitude less than that in the pH 3 solution and was far lower than that in the case of dry wear, especially at high applied load. The wear traces of Fe88Si12 alloy under different wear conditions were examined and analyzed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The results indicated that the tribo-chemical reactions that involve oxidation of the worn surface and hydrolysis of the Si3N4 ball in the acid solution were restricted in the pH 9 aqueous solution. Thus, water lubrication can effectively improve the wear resistance of nanocrystalline Fe88Si12 alloy in the pH 9 aqueous solution.

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2016-10-01

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

  5. Low-cost Fe--Ni--Cr alloys for high temperature valve applications

    DOEpatents

    Muralidharan, Govindarajan

    2017-03-28

    An Fe--Ni--Cr alloy is composed essentially of, in terms of weight percent: 1 to 3.5 Al, up to 2 Co, 15 to 19.5 Cr, up to 2 Cu, 23 to 40 Fe, up to 0.3 Hf, up to 4 Mn, 0.15 to 2 Mo, up to 0.15 Si, up to 1.05 Ta, 2.8 to 4.3 Ti, up to 0.5 W, up to 0.06 Zr, 0.02 to 0.15 C, 0.0001 to 0.007 N, balance Ni, wherein, in terms of atomic percent: 6.5.ltoreq.Al+Ti+Zr+Hf+Ta.ltoreq.10, 0.33.ltoreq.Al/(Al+Ti+Zr+Hf+Ta).ltoreq.0.065, 4.ltoreq.(Fe+Cr)/(Al+Ti+Zr+Hf+Ta).ltoreq.10, the alloy being essentially free of Nb and V.

  6. Magnetic properties of Nd-Fe-Co(Cu)-Al-B amorphous alloys prepared by nonequilibrium techniques

    NASA Astrophysics Data System (ADS)

    Kumar, G.; Eckert, J.; Roth, S.; Löser, W.; Ram, S.; Schultz, L.

    2002-03-01

    The amorphous alloys Nd40Fe40Co5Al8B7, Nd57Fe20Co5Al10B8, and Nd57Fe20Cu5Al10B8 were prepared by copper mold casting, melt spinning, and mechanical alloying. Despite their similar x-ray diffraction patterns, samples display different magnetic and thermal behavior correlated with the method of preparation. The fully amorphous melt-spun ribbons exhibit relatively soft magnetic properties with coercivities ≈40 kA/m at room temperature and a Curie temperature (TC)≈474 K. Apparently only the mold-cast cylinders of 3 mm diameter show hard magnetic behavior with a coercivity in the range of 258-270 kA/m (depending on composition) and have approximately the same TC as that of the melt-spun ribbons. An additional magnetic transition at 585 K due to the presence of Nd2Fe14B phase in the case of Nd40Fe40Co5Al8B7 cast rod has been observed. Heat treatment above crystallization temperature in as-cast Nd57Fe20Co5Al10B8 and Nd57Fe20Cu5Al10B8 samples destroys the hard magnetic properties. In contrast, mechanically alloyed amorphous samples are soft magnetic with maximum coercivity up to 11 kA/m but show an entirely different TC≈680-740 K, which is rather characteristic of an Fe solid solution. The magnetic properties are discussed in terms of different local atomic environment and cluster sizes in amorphous samples prepared by different methods.

  7. Investigations of a nanostructured FeMnSi shape memory alloy produced via severe plastic deformation

    NASA Astrophysics Data System (ADS)

    Gurau, Gheorghe; Gurau, Carmela; Sampath, Vedamanickam; Bujoreanu, Leandru Gheorghe

    2016-11-01

    Low-cost iron-based shape memory alloys (SMAs) show great potential for engineering applications. The developments of new processing techniques have recently enabled the production of nanocrystalline materials with improved properties. These developments have opened avenues for newer applications for SMAs. The influence of severe plastic deformation induced by the high-speed high-pressure torsion (HSHPT) process on the microstructural evolution of an Fe-Mn-Si-Cr alloy was investigated. Transmission electron microscopic analysis of the alloy revealed the existence of nanoscale grains with an abundance of stacking faults. The high density of dislocations characteristic of severe plastic deformation was not observed in this alloy. X-ray diffraction studies revealed the presence of ɛ-martensite with an HCP crystal structure and γ-phase with an FCC structure.

  8. The effect of magnetic annealing on the magnetostriction for Sm-Dy-Fe rod alloys

    NASA Astrophysics Data System (ADS)

    Wang, Bowen; Wang, Zhihua; Weng, Ling; Huang, Wenmei; Sun, Ying; Cui, Baozhi

    2013-05-01

    The Sm0.86Dy0.14Fex (x = 1.85-2.05) magnetostrictive alloys have been prepared with arc-melting and then cast into a copper mold with a diameter of 8 mm. It is found that the magnetostriction (λ// - λ⊥) increases from -900 × 10-6 for untreated rod alloys to -1200 × 10-6 for magnetically annealed rod alloys at the magnetic field of 640 kA/m. In the magnetic annealing temperature range of 483-643 K, the magnetostriction value exhibits a peak at 543 K. The variation of magnetostriction and magnetization with magnetic fields has been determined and the mechanism of domains' movements has been discussed. This result is very important to improve the magnetostrictive property of Sm-Dy-Fe rod alloys.

  9. Microstructure and Properties of FeAlCrNiMo x High-Entropy Alloys

    NASA Astrophysics Data System (ADS)

    Li, X. C.; Dou, D.; Zheng, Z. Y.; Li, J. C.

    2016-06-01

    FeAlCrNiMo x high-entropy alloys were prepared. The effect of Mo content on the microstructure and the properties of the alloys were investigated. When the Mo content was 0.1, the alloys were composed of single BCC solid solution; when Mo content reaches 0.25, the alloys were composed of BCC solid solution and ordered B2 solid solution. When Mo content is more than 0.75, some σ phases emerged. The volume fraction of the second phase increases with the increasing Mo content, and the crystal grains became coarsening. The yield strength, fracture strength, and hardness increase with the increasing Mo content and reach 2252, 2612 MPa, and 1006 Hv, respectively. The magnetic transformation undergoes from the ferromagnetism to paramagnetism with the increasing Mo content. The saturation intensity and remnant magnetism are decreased with the increasing Mo content.

  10. Helium generation rates in isotopically tailored Fe-Cr-Ni alloys irradiated in FFTF/MOTA

    SciTech Connect

    Greenwood, L.R.; Garner, F.A.; Oliver, B.M.

    1991-11-01

    Three Fe-Cr-Ni alloys have been doped with 0.4% {sup 59}Ni for side-by-side irradiations of doped and undoped materials in order to determine the effects of fusion-relevant levels of helium production on microstructural development and mechanical properties. The alloys were irradiated in three successive cycles of the Materials Open Test Assembly (MOTA) located in the Fast Flux Test Facility (FFTF). Following irradiation, helium levels were measured by isotope dilution mass spectrometry. The highest level of helium achieved in doped alloys was 172 appm at 9.1 dpa for a helium(appm)-to-dpa ratio of 18.9. The overall pattern of predicted helium generation rates in doped and undoped alloys is in good agreement with the helium measurements.

  11. Thermal plasma synthesis of Fe{sub 1−x}Ni{sub x} alloy nanoparticles

    SciTech Connect

    Raut, Suyog A.; Kanhe, Nilesh S.; Bhoraskar, S. V.; Mathe, V. L.; Das, A. K.

    2014-04-24

    Fe-Ni alloy nanoparticles are of great interest because of diverse practical applications in the fields such as magnetic fluids, high density recording media, catalysis and medicine. We report the synthesis of Fe-Ni nanoparticles via thermal plasma route. Thermal plasma assisted synthesis is a high temperature process and gives high yields of production. Here, we have used direct arc thermal plasma plume of 6kw as a source of energy at operating pressure 500 Torr. The mixture of Fe-Ni powder in required proportion (Fe{sub 1−x}Ni{sub x}; x=0.30, 0.32, 0.34, 0.36, 0.38 and 0.40) was made to evaporate simultaneously from the graphite anode in thermal plasma reactor to form Fe-Ni bimetallic nanoparticles. The as synthesized particles were characterized by X-Ray Diffraction (XRD), Thermo-Gravimetric Analysis/Differential Scanning Calorimtry (TGA/DSC)

  12. Thermopower of LaFe13-xSix alloys

    NASA Astrophysics Data System (ADS)

    Hannemann, U.; Lyubina, J.; Ryan, M. P.; Alford, N. M.; Cohen, L. F.

    2012-12-01

    We measured the thermopower of LaFe11.6Si1.4 and its hydride LaFe11.6Si1.4Hy to investigate changes in the electronic structure induced by hydriding. Using a model based on a density-of-states (DOS) function we can accurately describe a non-linear temperature dependence of the thermopower over a wide temperature range. The fit of the model to experimental data yields a significantly broader maximum in the DOS function near the Fermi energy of the hydride as compared to LaFe11.6Si1.4. Additionally, a new scattering mechanism leading to a decreased thermopower is observed in LaFe11.6Si1.4Hy at low temperatures which is attributed to scattering of electrons on magnetic excitation.

  13. Ferritic Fe-Mn alloy for cryogenic applications

    DOEpatents

    Hwang, Sun-Keun; Morris, Jr., John W.

    1979-01-01

    A ferritic, nickel-free alloy steel composition, suitable for cryogenic applications, which consists essentially of about 10-13% manganese, 0.002-0.01% boron, 0.1-0.5% titanium, 0-0.05% aluminum, and the remainder iron and incidental impurities normally associated therewith.

  14. The influence of cooling rate and Fe/Cr content on the evolution of Fe-rich compounds in a secondary Al-Si-Cu diecasting alloy

    NASA Astrophysics Data System (ADS)

    Fabrizi, A.; Timelli, G.

    2016-03-01

    This study investigates the morphological evolution of primary α-Al(Fe,Mn,Cr)Si phase in a secondary Al-Si-Cu alloy with respect to the initial Fe and Cr contents as well as to the cooling rate. The solidification experiments have been designed in order to cover a wide range of cooling rates, and the Fe and Cr contents have been varied over two levels. Metallographic and image analysis techniques have been used to quantitatively examine the microstructural changes occurring at different experimental conditions. The morphological evolution of the α-Fe phase has been also analysed by observing deep etched samples. By changing the cooling rate, α-Al15(Fe,Mn,Cr)3Si2 dodecahedron crystals, as well as Chinese- script, branched structures and dendrites form, while primary coarse β-Al5(Fe,Mn)Si needles appear in the alloy with the highest Fe content at low cooling rates.

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

    NASA Astrophysics Data System (ADS)

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

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

  16. Influence of addition of Si in FeAl alloys: Theory

    NASA Astrophysics Data System (ADS)

    Apiñaniz, E.; Legarra, E.; Plazaola, F.; Garitaonandia, J. S.

    The magnetic behaviour of Fe-based magnetic systems has been studied theoretically and experimentally for many years [E.P. Wohlfath, K.H.J. Buschow, Handbook of Ferromagnetic Materials, vol. 4, North-Holland Elsevier Science Publishers, Amsterdam, New York, Oxford, Tokyo, 1988 (Chapter 1)]. Starting with Al dissolved in Fe, the first stable structure is the D03 cubic structure and it exists over the range 23-37 at% Al. In this range these alloys present interesting magnetic properties. The other stable compound existing over a wide range of composition is FeAl which is also cubic, with the B2 structure (CsCl), and it exists over the range 37-50 at% Al. On the other hand, the FeAlSi alloys show the D03 structure, but do not show the B2 structure. The effect of Si in these alloys is double; on the one hand, it contributes to the decrease of the lattice parameter which, as reported by Nogues et al. [Phys. Rev. B 74 (2006) 024407], has a major influence on the magnetism and, on the other hand, having one more p electron than the Al atom, it promotes the charge transfer from Si to Fe atoms, as reported by Legarra et al. [Hyperfine Interact. 169 (2006) 1217-1222]. In this work, we perform ab-initio electronic calculations by means of tight binding linear muffin-tin orbital (TBLMTO) and Vienna Ab-initio Simulation Package (VASP) in order to study the magnetic contribution of Si/Al substitution in the FeAl alloys.

  17. Stress Corrosion Cracking of Ni-Fe-Cr Alloys Relevant to Nuclear Power Plants

    NASA Astrophysics Data System (ADS)

    Persaud, Suraj

    Stress corrosion cracking (SCC) of Ni-Fe-Cr alloys and weld metals was investigated in simulated environments representative of high temperature water used in the primary and secondary circuits of nuclear power plants. The mechanism of primary water SCC (PWSCC) was studied in Alloys 600, 690, 800 and Alloy 82 dissimilar metal welds using the internal oxidation model as a guide. Initial experiments were carried out in a 480°C hydrogenated steam environment considered to simulate high temperature reducing primary water. Ni alloys underwent classical internal oxidation intragranularly resulting in the expulsion of the solvent metal, Ni, to the surface. Selective intergranular oxidation of Cr in Alloy 600 resulted in embrittlement, while other alloys were resistant owing to their increased Cr contents. Atom probe tomography was used to determine the short-circuit diffusion path used for Ni expulsion at a sub-nanometer scale, which was concluded to be oxide-metal interfaces. Further exposures of Alloys 600 and 800 were done in 315°C simulated primary water and intergranular oxidation tendency was comparable to 480°C hydrogenated steam. Secondary side work involved SCC experiments and electrochemical measurements, which were done at 315°C in acid sulfate solutions. Alloy 800 C-rings were found to undergo acid sulfate SCC (AcSCC) to a depth of up to 300 microm in 0.55 M sulfate solution at pH 4.3. A focused-ion beam was used to extract a crack tip from a C-ring and high resolution analytical electron microscopy revealed a duplex oxide structure and the presence of sulfur. Electrochemical measurements were taken on Ni alloys to complement crack tip analysis; sulfate was concluded to be the aggressive anion in mixed sulfate and chloride systems. Results from electrochemical measurements and crack tip analysis suggested a slip dissolution-type mechanism to explain AcSCC in Ni alloys.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  19. Experimental investigation of the efficiency of HTO reduction by Zr-Fe-Mn getter alloy

    SciTech Connect

    Ghezzi, F.; Shmayda, W.T.; Bonizzoni, G.

    1997-01-01

    Tritium gas handling involves the production of tritiated water, which is 10000 times more hazardous than tritium gas. If tritium emission to the environment must be minimized, the need to process tritiated water and recover the chemically bound tritium appears clear. Facilities for processing tritiated water produced in fission reactors are already available, while facilities for a deuterium-tritium fusion machine are under development. However, these facilities are intended for large-scale applications and are neither practical nor economical for small-scale applications. HTO vapor reduction to HT over a hot metal getter other than uranium offers a simple, safe, and economical solution. A high alloy capacity and conversion rate combined with a low tritium residual inventory in the exhausted alloy make this method attractive. An experimental investigation of the efficiency of reducing HTO by a Zr-Fe-Mn alloy is presented. The results, obtained by three independent diagnostics (stripper set, ionization chambers, and mass spectrometry), show that for gas residence times > 1 s and alloy temperature > 400{degree}C, a conversion efficiency exceeding 90% is achievable. Specific conversion rates > 0.1 {mu}mol/s.g{sup -1} are observed during te alloy usage, while a capacity of the alloy, measured as an oxygen-to-alloy mole ratio, > 2.6 has been measured. 50 refs., 21 figs., 5 tabs.

  20. Magnetocaloric Effect and Critical Behavior in Fe-Dy-Zr Rapidly Quenched Alloys

    NASA Astrophysics Data System (ADS)

    Dan, Nguyen Huy; Yen, Nguyen Hai; Thanh, Pham Thi

    2016-10-01

    In this paper, we present our study results for Fe90- x Dy x Zr10 ( x = 1-6) alloy ribbons with thickness of about 15 µm prepared by using a melt-spinning technique. Structure and magnetic properties of the ribbons were investigated by using x-ray diffraction analysis and magnetization measurements, respectively. The results show that the alloy is almost amorphous with x = 1, but partly crystalline with x ≥ 2, i.e. the glass forming ability (GFA) of the alloy is reduced with an increase of the Dy-concentration. Curie temperature, T C, of the alloy is considerably increased, from 273 K (for x = 1) to 305 K (for x = 3), by increasing the Dy-concentration. Maximum magnetic entropy change, |∆S m|max, of the alloys with x = 1 and 2 was respectively determined to be 0.84 and 0.93 J kg-1 K-1 with magnetic field change ΔH = 12 kOe. High refrigerant capacity (RC > 80 J kg-1) at room temperature region has been obtained for the alloy revealing its possibility for practical application in magnetic refrigeration. Critical analyses around the ferromagnetic-paramagnetic phase transitions, by using the Arrott-Noakes method, indicate long-range ferromagnetic orders in the alloys.

  1. Influence of boron on the magnetic and transport properties of FeZr amorphous and nanocrystalline alloys

    SciTech Connect

    Barandiaran, J.M.; Gorria, P. . Dept. de Electricidad y Electronica); Sal, J.C.G.; Brquin, L.F. ); Kaul, S.N. . School of Physics)

    1994-11-01

    The magnetic properties and electrical resistivity of amorphous and nanocrystalline FeZr and FeZrB(Cu) alloys are compared in a wide range of temperatures (4 to 1,000 K). The addition of boron increases the Curie temperature of the alloys and induces a broad minimum in the resistivity vs temperatures. A first step of crystallization occurs around 700 K in all the alloys, giving rise to [alpha]-Fe crystallites of very small size. Small amounts of boron greatly influence the exchange interactions, enhancing the ferromagnetic character of these compounds.

  2. Characteristics of Eutectic α(Cr,Fe)-(Cr,Fe)23C6 in the Eutectic Fe-Cr-C Hardfacing Alloy

    NASA Astrophysics Data System (ADS)

    Lai, Hsuan-Han; Hsieh, Chih-Chun; Lin, Chi-Ming; Wu, Weite

    2017-01-01

    A specific eutectic (Cr,Fe)-(Cr,Fe)23C6 structure had been previously reported in the research studies of Fe-Cr-C hardfacing alloys. In this study, a close observation and discussion of the eutectic (Cr,Fe)-(Cr,Fe)23C6 were conducted. The eutectic solidification occurred when the chromium content of the alloy exceeded 35 wt pct. The eutectic structure showed a triaxial radial fishbone structure which was the so called "complex regular structure." Lamellar costa plates showed local asymmetry at two sides of a spine. Individual costae were able to combine as one, and spines showed extra branches. Costae that were nearly parallel to the heat flow direction were longer than those that were vertical to the heat flow direction. The triaxial spines preferred to intersect at 120 deg, while the costae preferred to intersect the spine at 90 deg and 35.26 deg due to the lattice relationships. The solidified metal near the fusion boundary showed an irregular structure instead of a complex regular structure. The reason for the irregular morphology was the high growth rate near the fusion boundary.

  3. High temperature grain growth and oxidation of Fe-29Ni-17Co (Kovar (tm)) alloy leads

    NASA Astrophysics Data System (ADS)

    Stephens, J. J.; Greulich, F. A.; Beavis, L. C.

    One important application for the Fe-29Ni-17Co (Kovar(trademark)) alloy in wire form is in brazed feed through assemblies which are integral parts of vacuum electronic devices. Since Cu metal brazes are performed at process temperatures of about 1100 C, there is opportunity for significant grain growth to occur during the brazing operation. Additional high temperature exposure includes decarburization of the Fe-29Ni-17Co alloy wire in wet hydrogen for 30 min. at 1000 C prior to the Cu brazing operation. Two approaches were used to characterize grain growth in two lots of Fe-29Ni-17Co alloy: (1) a once-through processing study to study the effect of one-time-only device thermal processing on the resulting grain size, and (2) an isothermal grain growth study involving various times at 800-1100 C. The results of the once-through processing study indicate that acceptable grain sizes are obtained from both cold worked and mill-annealed wire lots following Cu brazing. The isothermal grain growth study indicates that the linear intercept distance for Fe-29Ni-17Co can be described with a power law function of time, and that thermal exposure must be controlled at temperatures in excess of 900 C in order to avoid excessive grain growth. A second study characterized the oxidation kinetics of Fe-29Ni-17Co alloy wire in air at temperatures ranging from 550-700 C. This study indicates the parabolic growth law applies for this material, and between 550 and 700 C, oxidation in this alloy occurs at an activation energy of 27.9 kcal/mole. Other oxidation studies at higher temperatures (greater than 750 C) indicate an activation energy of 52.2 kcal/mole for oxidation of Fe-29Ni-17Co alloy at temperatures greater than 790 C. Quantitative point analyses of the oxide scale formed at 600 C suggest that a significant fraction of the scale is close to the stoichiometry of the Fe2O3-type oxide.

  4. Nickel recovery from electronic waste II Electrodeposition of Ni and Ni–Fe alloys from diluted sulfate solutions

    SciTech Connect

    Robotin, B.; Ispas, A.; Coman, V.; Bund, A.; Ilea, P.

    2013-11-15

    Highlights: • Ni can be recovered from EG wastes as pure Ni or as Ni–Fe alloys. • The control of the experimental conditions gives a certain alloy composition. • Unusual deposits morphology shows different nucleation mechanisms for Ni vs Fe. • The nucleation mechanism was progressive for Ni and instantaneous for Fe and Ni–Fe. - Abstract: This study focuses on the electrodeposition of Ni and Ni–Fe alloys from synthetic solutions similar to those obtained by the dissolution of electron gun (an electrical component of cathode ray tubes) waste. The influence of various parameters (pH, electrolyte composition, Ni{sup 2+}/Fe{sup 2+} ratio, current density) on the electrodeposition process was investigated. Scanning electron microscopy (SEM) and X-ray fluorescence analysis (XRFA) were used to provide information about the obtained deposits’ thickness, morphology, and elemental composition. By controlling the experimental parameters, the composition of the Ni–Fe alloys can be tailored towards specific applications. Complementarily, the differences in the nucleation mechanisms for Ni, Fe and Ni–Fe deposition from sulfate solutions have been evaluated and discussed using cyclic voltammetry and potential step chronoamperometry. The obtained results suggest a progressive nucleation mechanism for Ni, while for Fe and Ni–Fe, the obtained data points are best fitted to an instantaneous nucleation model.

  5. The effect of Fe-Rh alloying on CO hydrogenation to C2+ oxygenates

    SciTech Connect

    Palomino, Robert; Magee, Joseph W.; Llorca, Jordi; Senanayake, Sanjaya D.; White, Michael G.

    2015-05-20

    A combination of reactivity and structural studies using X-ray diffraction (XRD), pair distribution function (PDF), and transmission electron microscopy (TEM) was used to identify the active phases of Fe-modified Rh/TiO2 catalysts for the synthesis of ethanol and other C2+ oxygenates from CO hydrogenation. XRD and TEM confirm the existence of Fe–Rh alloys for catalyst with 1–7 wt% Fe and ~2 wt% Rh. Rietveld refinements show that FeRh alloy content increases with Fe loading up to ~4 wt%, beyond which segregation to metallic Fe becomes favored over alloy formation. Catalysts that contain Fe metal after reduction exhibit some carburization as evidenced by the formation of small amounts of Fe3C during CO hydrogenation. Analysis of the total Fe content of the catalysts also suggests the presence of FeOx also increased under reaction conditions. Reactivity studies show that enhancement of ethanol selectivity with Fe loading is accompanied by a significant drop in CO conversion. Comparison of the XRD phase analyses with selectivity suggests that higher ethanol selectivity is correlated with the presence of Fe–Rh alloy phases. As a result, the interface between Fe and Rh serves to enhance the selectivity of ethanol, but suppresses the activity of the catalyst which is attributed to the blocking or modifying of Rh active sites.

  6. Carbonization of α-Fe upon mechanical alloying

    NASA Astrophysics Data System (ADS)

    Barinov, V. A.; Tsurin, V. A.; Kazantsev, V. A.; Surikov, V. T.

    2014-01-01

    Methods of thermomagnetic analysis (TMA) and Mössbauer spectrometry (57Fe) have been used to study the processes of the carburizing of α-Fe under the conditions of mechanical milling in a medium of liquid hydrocarbons. It has been established that, under the chosen conditions of the mechanical synthesis of carbides, the process of carbonization at T < 375 K occurs through the decomposition of the deformation-induced martensite, i.e., the supersaturated bct solid solution α″-Fe(C) with the formation of transitional hcp ɛ and ɛ' phases that precede the formation of cementite. The milling of the metallic iron in the toluene medium substantially enhances the catalytic capability of disperse powders of α-Fe in the process of conversion of cyclic structures of hydrocarbons into other chemical forms. The increase in the dispersity of the iron powder to a nanocrystalline state leads to an increase in the chemical activity of carbon and an increase in the rate of diffusion sufficient for the formation in the Fe-C mixture of both primary cementite (θ') with an anomalously low Curie temperature T C(θ')(first stage) and secondary cementite (θ″) at the second stage of mechanosynthesis. The parameters of hyperfine interactions have been calculated for a number of synthesized carbides. It has been shown that the change in the carbon concentration in iron carbides is determined by the following inequality: c C(θ') > c C(ɛ) > c C(ɛ'). The boundary of the temperature stability of cementite has been established. The effect of the decomposition of the θ phase (Fe3C) upon thermal cycling θ ⇔ γ in the temperature range of 300 < T < 1075 K has been revealed. Based on the results obtained, a scheme of the sequence of phase transformations that occur in the Fe-C system under the conditions of low-temperature mechanosynthesis has been derived.

  7. Transparent monolithic metal ion containing nanophase aerogels

    SciTech Connect

    Risen, W. M., Jr.; Hu, X.; Ji, S.; Littrell, K.

    1999-12-01

    The formation of monolithic and transparent transition metal containing aerogels has been achieved through cooperative interactions of high molecular weight functionalized carbohydrates and silica precursors, which strongly influence the kinetics of gelation. After initial gelation, subsequent modification of the ligating character of the system, coordination of the group VIII metal ions, and supercritical extraction afford the aerogels. The structures at the nanophase level have been probed by photon and electron transmission and neutron scattering techniques to help elucidate the basis for structural integrity together with the small entity sizes that permit transparency in the visible range. They also help with understanding the chemical reactivities of the metal-containing sites in these very high surface area materials. These results are discussed in connection with new reaction studies.

  8. Superhard nanophase materials for rock drilling applications

    SciTech Connect

    Sadangi, R.K.; Voronov, O.A.; Tompa, G.S.; Kear, B.H.

    1997-12-31

    Diamond Materials Incorporated is developing new class of superhard materials for rock drilling applications. In this paper, we will describe two types of superhard materials, (a) binderless polycrystalline diamond compacts (BPCD), and (b) functionally graded triphasic nanocomposite materials (FGTNC). BPCDs are true polycrystalline diamond ceramic with < 0.5 wt% binders and have demonstrated to maintain their wear properties in a granite-log test even after 700{degrees}C thermal treatment. FGTNCs are functionally-graded triphasic superhard material, comprising a nanophase WC/Co core and a diamond-enriched surface, that combine high strength and toughness with superior wear resistance, making FGTNC an attractive material for use as roller cone stud inserts.

  9. Low-cost Ce1-xSmx(Fe, Co, Ti)12 alloys for permanent magnets

    NASA Astrophysics Data System (ADS)

    Gabay, A. M.; Martín-Cid, A.; Barandiaran, J. M.; Salazar, D.; Hadjipanayis, G. C.

    2016-05-01

    Ce1-xSmxFe9Co2Ti alloys based on the ThMn12-type crystal structure have been synthesized via melt-spinning of prefabricated alloys and via mechanochemical processing of CeO2- Sm2O3- Fe2O3-TiO2- Co - Ca - CaO powder mixtures. Coercive fields up to 0.8 kOe and 2.1 kOe were obtained in annealed melt-spun alloys with x = 0 and x = 0.5, respectively. Submicron, partially anisotropic particles collected after the mechanochemical synthesis for x = 0.5 and x = 1 exhibited coercivity (energy product) of 1.8 kOe (5.4 MGOe) and 5.8 kOe (9.9 MGOe), respectively. The low magnetic anisotropy field of CeFe9Co2Ti alloy requires at least a partial Sm-substitution for Ce in order to develop a reasonably high coercivity.

  10. Growth, morphology, and structure of a monolayer thick GdFe2 surface alloy

    NASA Astrophysics Data System (ADS)

    Williams, R. P.; Alcock, S. G.; Howes, P. B.; Nicklin, C. L.

    2016-08-01

    The growth and structure of an ordered GdFe2 surface alloy deposited on Mo(110) has been studied using in situ surface x-ray diffraction. Growth curves and reflectivity scans of varying ratios of Gd to Fe show how the two species intermix prior to alloy formation. After annealing to form the ordered surface alloy, in-plane x-ray diffraction data indicate that the Fe atoms are laterally displaced along the [001] or [00 1 ¯] direction by 0.16 ±0.02 Å from the long bridge site positions. Out-of-plane crystal truncation rod analysis reveals that the Gd atoms lie 3.40 ±0.09 Å above the Mo(110) bridge site, an expansion of 22% relative to the expected hard sphere distance. This is significantly larger than observed in previous studies of the growth of pure Gd on Mo(110). Simple geometric changes are not able to account fully for this expansion and we propose that hydrogen incorporation during alloy formation may also contribute.

  11. Shape-Memory Effect and Pseudoelasticity in Fe-Mn-Based Alloys

    NASA Astrophysics Data System (ADS)

    La Roca, P.; Baruj, A.; Sade, M.

    2017-03-01

    Several Fe-based alloys are being considered as potential candidates for applications which require shape-memory behavior or superelastic properties. The possibility of using fabrication methods which are well known in the steel industry is very attractive and encourages a large amount of research in the field. In the present article, Fe-Mn-based alloys are mainly addressed. On the one hand, attention is paid to the shape-memory effect where the alloys contain (a) a maximum amount of Mn up to around 30 wt%, (b) several possible substitutional elements like Si, Cr, Ni, Co, and Nb and (c) some possible interstitial elements like C. On the other hand, superelastic alloys are analyzed, mainly the Fe-Mn-Al-Ni system discovered a few years ago. The most noticeable properties resulting from the martensitic transformations which are responsible for the mentioned properties, i.e., the fcc-hcp in the first case and the bcc-fcc in the latter are discussed. Selected potential applications are also analyzed.

  12. Shape-Memory Effect and Pseudoelasticity in Fe-Mn-Based Alloys

    NASA Astrophysics Data System (ADS)

    La Roca, P.; Baruj, A.; Sade, M.

    2016-12-01

    Several Fe-based alloys are being considered as potential candidates for applications which require shape-memory behavior or superelastic properties. The possibility of using fabrication methods which are well known in the steel industry is very attractive and encourages a large amount of research in the field. In the present article, Fe-Mn-based alloys are mainly addressed. On the one hand, attention is paid to the shape-memory effect where the alloys contain (a) a maximum amount of Mn up to around 30 wt%, (b) several possible substitutional elements like Si, Cr, Ni, Co, and Nb and (c) some possible interstitial elements like C. On the other hand, superelastic alloys are analyzed, mainly the Fe-Mn-Al-Ni system discovered a few years ago. The most noticeable properties resulting from the martensitic transformations which are responsible for the mentioned properties, i.e., the fcc-hcp in the first case and the bcc-fcc in the latter are discussed. Selected potential applications are also analyzed.

  13. Zirconium hydrides and Fe redistribution in Zr-2.5%Nb alloy under ion irradiation

    NASA Astrophysics Data System (ADS)

    Idrees, Y.; Yao, Z.; Cui, J.; Shek, G. K.; Daymond, M. R.

    2016-11-01

    Zr-2.5%Nb alloy is used to fabricate the pressure tubes of the CANDU reactor. The pressure tube is the primary pressure boundary for coolant in the CANDU design and is susceptible to delayed hydride cracking, reduction in fracture toughness upon hydride precipitation and potentially hydride blister formation. The morphology and nature of hydrides in Zr-2.5%Nb with 100 wppm hydrogen has been investigated using transmission electron microscopy. The effect of hydrides on heavy ion irradiation induced decomposition of the β phase has been reported. STEM-EDX mapping was employed to investigate the distribution of alloying elements. The results show that hydrides are present in the form of stacks of different sizes, with length scales from nano- to micro-meters. Heavy ion irradiation experiments at 250 °C on as-received and hydrided Zr-2.5%Nb alloy, show interesting effects of hydrogen on the irradiation induced redistribution of Fe. It was found that Fe is widely redistributed from the β phase into the α phase in the as-received material, however, the loss of Fe from the β phase and subsequent precipitation is retarded in the hydrided material. This preliminary work will further the current understanding of microstructural evolution of Zr based alloys in the presence of hydrogen.

  14. The elastic properties and stability of fcc-Fe and fcc-FeNi alloys at inner-core conditions

    NASA Astrophysics Data System (ADS)

    Martorell, Benjamí; Brodholt, John; Wood, Ian G.; Vočadlo, Lidunka

    2015-07-01

    The agreement between shear wave velocities for the Earth's inner core observed from seismology with those derived from mineral physics is considerably worse than for any other region of the Earth. Furthermore, there is still debate as to the phase of iron present in the inner core, particularly when alloying with nickel and light elements is taken into account. To investigate the extent to which the mismatch between seismology and mineral physics is a function of either crystal structure and/or the amount of nickel present, we have used ab initio molecular dynamics simulations to calculate the elastic constants and seismic velocities (Vp and Vs) of face centred cubic (fcc) iron at Earth's inner core pressures (360 GPa) and at temperatures up to ˜7000 K. We find that Vp for fcc iron (fcc-Fe) is very similar to that for hexagonal close packed (hcp) iron at all temperatures. In contrast, Vs for fcc-Fe is significantly higher than in hcp-Fe, with the difference increasing with increasing temperature; the difference between Vs for the core (from seismology) and Vs for fcc-Fe exceeds 40 per cent. These results are consistent with previous work at lower temperatures. We have also investigated the effect of 6.5 and 13 atm% Ni in fcc-Fe. We find that Ni only slightly reduces Vp and Vs (e.g. by 2 per cent in Vs for 13 atm% Ni at 5500 K), and cannot account for the difference between the velocities observed in the core and those of pure fcc-Fe. We also tried to examine pre-melting behaviour in fcc-Fe, as reported in hcp-Fe by extending the study to very high temperatures (at which superheating may occur). However, we find that fcc-Fe spontaneously transforms to other hcp-like structures before melting; two hcp-like structures were found, both of hexagonal symmetry, which may most easily be regarded as being derived from an hcp crystal with stacking faults. That the structure did not transform to a true hcp phase is likely as a consequence of the limited size of the

  15. Tuning the Graphene on Ir(111) adsorption regime by Fe/Ir surface-alloying

    NASA Astrophysics Data System (ADS)

    Brede, Jens; Sławińska, Jagoda; Abadia, Mikel; Rogero, Celia; Ortega, J. Enrique; Piquero-Zulaica, Ignacio; Lobo-Checa, Jorge; Arnau, Andres; Iribas Cerdá, Jorge

    2017-03-01

    A combined scanning tunneling microscopy, x-ray photoelectron spectroscopy, angle-resolved photoemission spectroscopy, and density functional theory study of graphene on a Fe-Ir(111) alloy with variable Ir concentration is presented. Starting from an intercalated Fe layer between the graphene and Ir(111) surface we find that graphene-substrate interaction can be fine-tuned by Fe-Ir alloying at the interface. When a critical Ir-concentration close to 0.25 is reached in the Fe layer, the Dirac cone of graphene is largely restored and can thereafter be tuned across the Fermi level by further increasing the Ir content. Indeed, our study reveals an abrupt transition between a chemisorbed phase at small Ir concentrations and a physisorbed phase above the critical concentration. The latter phase is highly reminiscent of the graphene on the clean Ir(111) surface. Furthermore, the transition is accompanied by an inversion of the graphene’s induced magnetization due to the coupling with the Fe atoms from antiferromagnetic when chemisorbed to weakly ferromagnetic in the physisorption regime, with spin polarizations whose magnitude may be tuned with the amount of Fe content.

  16. First-principles study of alloy formation at Fe/GaAs interfaces

    NASA Astrophysics Data System (ADS)

    Zutic, Igor

    2005-03-01

    The combination of the high Curie temperature of Fe, high-quality epitaxial growth of Fe on GaAs, and demonstrated high-efficiency spin injection in GaAs, together make Fe/GaAs heterojunctions very attractive candidates for room-temperature spintronic applications. However, little is known about the structure of Fe/GaAs interfaces, and there is a range of conflicting experimental results describing them---including findings of magnetically dead layers [1], an intermediate FeGaAs phase [2], and bulk-like magnetic moments at the interface [3]. Motivated by these findings, we use density-functional theory to study the structural and magnetic properties of interfaces involving possible alloyed phases occurring between Fe and GaAs. From the calculation of interface formation energies we report results on the stability of various structural and magnetic configurations, and provide microscopic parameters which may be used in studies of spin transport to assess the device potential of these heterostructures. [1] J. J. Krebs, B. T. Jonker, and G. A. Prinz, J. Appl. Phys. 61, 2596 (1987). [2] J. Deputier, R. Guerin, B. Lepine, A. Guivarc'h, and G. Jezequel, J. Alloys Comp. 262, 416 (1997). [3] J. S. Claydon, Y. B. Hu, M. Tselepi, J. A. C. Bland, and G. van der Laan, Phys. Rev. Lett. 93, 037206 (2004).

  17. Simultaneous enhancement of magnetic and mechanical properties in Ni-Mn-Sn alloy by Fe doping

    PubMed Central

    Tan, Changlong; Tai, Zhipeng; Zhang, Kun; Tian, Xiaohua; Cai, Wei

    2017-01-01

    Both magnetic-field-induced reverse martensitic transformation (MFIRMT) and mechanical properties are crucial for application of Ni-Mn-Sn magnetic shape memory alloys. Here, we demonstrate that substitution of Fe for Ni can simultaneously enhance the MFIRMT and mechanical properties of Ni-Mn-Sn, which are advantageous for its applications. The austenite in Ni44Fe6Mn39Sn11 shows the typical ferromagnetic magnetization with the highest saturation magnetization of 69 emu/g at 223 K. The result shows that an appropriate amount of Fe substitution can really enhance the ferromagnetism of Ni50Mn39Sn11 alloy in austenite, which directly leads to the enhancement of MFIRMT. Meanwhile, the mechanical property significantly improves with Fe doping. When there is 4 at.% Fe added, the compressive and maximum strain reach the maximum value (approximately 725.4 MPa and 9.3%). Furthermore, using first-principles calculations, we clarify the origin of Fe doping on martensitic transformation and magnetic properties. PMID:28230152

  18. Flaky FeSiAl alloy-carbon nanotube composite with tunable electromagnetic properties for microwave absorption

    PubMed Central

    Huang, Lina; Liu, Xiaofang; Chuai, Dan; Chen, Yaxin; Yu, Ronghai

    2016-01-01

    Flaky FeSiAl alloy/multi-wall carbon nanotube (FeSiAl/MWCNT) composite was fabricated by facile and scalable ball milling method. The morphology and electromagnetic properties of the FeSiAl alloy can be well tuned by controlling the milling time. It is found that the magnetic loss of the FeSiAl alloy is improved by optimizing the milling time due to the increased anisotropy field. Meanwhile the addition of MWCNTs enhances the dielectric loss of the composite by increasing the interfacial polarizations, dipolar polarizations and conductive paths. Relative to conventional FeSiAl absorbers, the FeSiAl/MWCNT composite exhibits greatly improved microwave absorption performance with advantages of strong absorption and small thickness. The minimum reflection loss of the composite reaches −42.8 dB at 12.3 GHz at a very thin thickness of 1.9 mm. PMID:27762327

  19. Flaky FeSiAl alloy-carbon nanotube composite with tunable electromagnetic properties for microwave absorption.

    PubMed

    Huang, Lina; Liu, Xiaofang; Chuai, Dan; Chen, Yaxin; Yu, Ronghai

    2016-10-20

    Flaky FeSiAl alloy/multi-wall carbon nanotube (FeSiAl/MWCNT) composite was fabricated by facile and scalable ball milling method. The morphology and electromagnetic properties of the FeSiAl alloy can be well tuned by controlling the milling time. It is found that the magnetic loss of the FeSiAl alloy is improved by optimizing the milling time due to the increased anisotropy field. Meanwhile the addition of MWCNTs enhances the dielectric loss of the composite by increasing the interfacial polarizations, dipolar polarizations and conductive paths. Relative to conventional FeSiAl absorbers, the FeSiAl/MWCNT composite exhibits greatly improved microwave absorption performance with advantages of strong absorption and small thickness. The minimum reflection loss of the composite reaches -42.8 dB at 12.3 GHz at a very thin thickness of 1.9 mm.

  20. Flaky FeSiAl alloy-carbon nanotube composite with tunable electromagnetic properties for microwave absorption

    NASA Astrophysics Data System (ADS)

    Huang, Lina; Liu, Xiaofang; Chuai, Dan; Chen, Yaxin; Yu, Ronghai

    2016-10-01

    Flaky FeSiAl alloy/multi-wall carbon nanotube (FeSiAl/MWCNT) composite was fabricated by facile and scalable ball milling method. The morphology and electromagnetic properties of the FeSiAl alloy can be well tuned by controlling the milling time. It is found that the magnetic loss of the FeSiAl alloy is improved by optimizing the milling time due to the increased anisotropy field. Meanwhile the addition of MWCNTs enhances the dielectric loss of the composite by increasing the interfacial polarizations, dipolar polarizations and conductive paths. Relative to conventional FeSiAl absorbers, the FeSiAl/MWCNT composite exhibits greatly improved microwave absorption performance with advantages of strong absorption and small thickness. The minimum reflection loss of the composite reaches ‑42.8 dB at 12.3 GHz at a very thin thickness of 1.9 mm.

  1. A study of Fe2+xMn1-xAl alloys: Structural and magnetic properties

    NASA Astrophysics Data System (ADS)

    Paduani, C.; Migliavacca, A.; Pöttker, W. E.; Schaf, J.; Krause, J. C.; Ardisson, J. D.; Samudio Pérez, C. A.; Takeuchi, A. Y.; Yoshida, M. I.

    2007-08-01

    The Fe2+xMn1-xAl alloys were studied experimentally to assess the effect of variations of composition around stoichiometric on the structural and magnetic properties of this system. The results indicate that the ordered L21(X2YZ) structure of full Heusler alloys can be stabilized with small deviations of composition from the stoichiometric 2:1:1. The saturation magnetization is strongly composition dependent and decreases with the increase of the Mn concentration, in spite of the fact that the Mn atoms carry the largest moment in the ordered phase. The highest Curie temperature was observed for the Fe-richer alloy. Magnetic measurements suggest that atomic disorder and competition of the antiferromagnetic Fe-Mn and Mn-Mn interactions with the ferromagnetic Fe-Fe, Mn-Mn and Fe-Mn interactions lead to a frustrated couplings ending in a reentrant spin-glass behavior at low temperature.

  2. Disorder influenced magnetic phase transition in the Ce(Fe 0.9 Ru 0.1)2 alloy.

    PubMed

    Chattopadhyay, M K; Roy, S B

    2010-06-16

    We have studied a 10% Ru-doped CeFe(2) alloy, Ce(Fe(0.9)Ru(0.1))(2), through magnetization, magnetotransport, and heat capacity measurements. This study shows that, while this alloy is antiferromagnetic at low temperatures and paramagnetic at high temperatures, there exists evidence of ferromagnetic ordering in the intermediate temperature regime. We show here that with 10% Ru doping the first order magnetic transition observed in the Ce(Fe(1 - x)Ru(x))(2) alloys with x < 0.08 is reduced to a quasi-continuous phase transition. The characteristic thermomagnetic history effects associated with the ferromagnetic-antiferromagnetic phase transition in the Ce(Fe(1 - x)Ru(x))(2) alloys with x < 0.08 are not observed in the Ce(Fe(0.9)Ru(0.1))(2) alloy. This alloy continues to exhibit the large magnetoresistance and large magnetocaloric effect associated with this first order magnetic transition in the alloys with smaller Ru concentration, but it does not show any energy loss due to thermomagnetic hysteresis. The present work thus shows how the introduction of quenched disorder due to alloying effects may be used to tune the first order magnetic transition in a material for more efficient functional use.

  3. Fe-Mn alloys for metallic biodegradable stents: degradation and cell viability studies.

    PubMed

    Hermawan, Hendra; Purnama, Agung; Dube, Dominique; Couet, Jacques; Mantovani, Diego

    2010-05-01

    Biodegradable stents have shown their potential to be a valid alternative for the treatment of coronary artery occlusion. This new class of stents requires materials having excellent mechanical properties and controllable degradation behaviour without inducing toxicological problems. The properties of the currently considered gold standard material for stents, stainless steel 316L, were approached by new Fe-Mn alloys. The degradation characteristics of these Fe-Mn alloys were investigated including in vitro cell viability. A specific test bench was used to investigate the degradation in flow conditions simulating those of coronary artery. A water-soluble tetrazolium test method was used to study the effect of the alloy's degradation product to the viability of fibroblast cells. These tests have revealed the corrosion mechanism of the alloys. The degradation products consist of metal hydroxides and calcium/phosphorus layers. The alloys have shown low inhibition to fibroblast cells' metabolic activities. It is concluded that they demonstrate their potential to be developed as degradable metallic biomaterials.

  4. Ab initio lattice stability of fcc and hcp Fe-Mn random alloys.

    PubMed

    Gebhardt, T; Music, D; Hallstedt, B; Ekholm, M; Abrikosov, I A; Vitos, L; Schneider, J M

    2010-07-28

    We have studied the lattice stability of face centred cubic (fcc) versus hexagonal close packed (hcp) Fe-Mn random alloys using ab initio calculations. In the calculations we considered the antiferromagnetic order of local moments, which for fcc alloys models the magnetic configuration of this phase at room temperature (below its Néel temperature) as well as their complete disorder, corresponding to paramagnetic fcc and hcp alloys. For both cases, the results are consistent with our thermodynamic calculations, obtained within the Calphad approach. For the room temperature magnetic configuration, the cross-over of the total energies of the hcp phase and the fcc phase of Fe-Mn alloys is at the expected Mn content, whereas for the magnetic configuration above the fcc Néel temperature, the hcp lattice is more stable within the whole composition range studied. The increase of the total energy difference between hcp and antiferromagnetic fcc due to additions of Mn as well as the stabilizing effect of antiferromagnetic ordering on the fcc phase are well displayed. These results are of relevance for understanding the deformation mechanisms of these random alloys.

  5. Co-Fe-B-Si-Nb bulk glassy alloys with superhigh strength and extremely low magnetostriction

    SciTech Connect

    Chang Chuntao; Shen Baolong; Inoue, Akihisa

    2006-01-02

    Co-based bulk glassy alloys with diameters up to 4 mm were formed in a [(Co{sub 1-x}Fe{sub x}){sub 0.75}B{sub 0.2}Si{sub 0.05}]{sub 96}Nb{sub 4} system. The bulk glassy alloys exhibit a superhigh fracture strength of 3980-4170 MPa and Young's modulus of 190-210 GPa. The bulk glassy alloys also exhibit excellent soft-magnetic properties, i.e., high saturation magnetization of 0.71-0.97 T, low coercive force of 0.7-1.8 A/m, high permeability of 1.48-3.25x10{sup 4}, and extremely low saturation magnetostriction of 0.55-5.76x10{sup -6}. The first successful synthesis of the Co-Fe-B-Si-based bulk glassy alloys exhibiting superhigh fracture strength and excellent soft-magnetic properties with extremely low magnetostriction is encouraging for future development of Co-based bulk glassy alloys as new engineering and functional materials.

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

    PubMed

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

    2016-03-01

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

  7. Itenerant spin glass states and asperomagnetism of amorphous Fe and iron-rich Fe/Zr alloys

    NASA Astrophysics Data System (ADS)

    Krey, U.; Krauss, U.; Krompiewski, S.

    1992-01-01

    A realistic tight-binding approach for the self-consistent calculation of the itinerant spin configurations of disordered metallic systems has been developed and is used to study numerically the problem of the magnetic states at T = 0 K of iron-rich amorphous alloys of the type Fe 1- xZr xH y, and of fictitious amorphous Fe of different densities. In our approach, the local spin polarization is not restricted to the z-direction, i.e. the polarization magnitude as well as its direction can vary from site to site. The calculations show that the spin configurations depend strongly on the preparation, and that changes of the relative spin orientations can lead to drastic changes of the itinerant atomic moments. Metastable spin configurations with essentially isotropic distribution can be prepared by relaxing the system in gradually vanishing external fields with isotropically distributed randomness and zero spatial average, whereas with a non-vanishing average the so-called asperomagnetic configurations are obtained, i.e. ferromagnetic states with randomly frozen transverse components. For iron-rich Fe 1- xZr x alloys with x = 0.07, according to our calculation, the isotropic spin glass configuration would have slightly lower energy than the asperomagnetic state, by amounts corresponding to ≈ 0.003 eV per electron, while for the hydrogenated system Fe 1- xZr xH y with y ≈ 2 x, the asperomagnetic state would be favoured by ≈ 0.004 eV. For two computer models of (fictitious) amorphous Fe with densities of 7.39 and 9.19 g cm -3, the spin-glass and the asperomagnetic states have roughly the same energy, although for the low-density sample the magnitudes of the moments are quite different in both states.

  8. Application of the radioisotope excited X-ray fluorescence technique in charge optimization during thermite smelting of Fe-Ni, Fe-cr, and Fe-Ti alloys

    SciTech Connect

    Sharma, I.G.; Joseph, D.; Lal, M.; Bose, D.K.

    1995-10-01

    A wide range of ferroalloys are used to facilitate the addition of different alloying elements to molten steel. High-carbon ferroalloys are produced on a tonnage basis by carbothermic smelting in an electric furnace, and an aluminothermic route is generally adopted for small scale production of low-carbon varieties. The physicochemical principles of carbothermy and aluminothermy have been well documented in the literature. However, limited technical data are reported on the production of individual ferroalloys of low-carbon varieties from their selected resources. The authors demonstrate her the application of an energy dispersive X-ray fluorescence (EDXRF) technique in meeting the analytical requirements of a thermite smelting campaign, carried out with the aim of preparing low-carbon-low-nitrogen Fe-Ni, Fe-Cr, and Fe-Ti alloys from indigenously available nickel bearing spent catalyst, mineral chromite, and ilmenite/rutile, respectively. They have chosen the EDXRF technique to meet the analytical requirements because of its capability to analyze samples of ore, minerals, a metal, and alloys in different forms, such as powder, sponge, as-smelted, or as-cast, to obtain rapid multielement analyses with ease. Rapid analyses of thermite feed and product by this technique have aided in the appropriate alterations of the charge constitutents to obtain optimum charge consumption.

  9. Thermal and magnetic properties of the Co-Fe-B-Si-Ta alloy system for several Fe/Co ratios

    NASA Astrophysics Data System (ADS)

    Oh, Jiyun; Choi-Yim, Haein; Kang, Ki Hoon

    2016-12-01

    We studied the thermal and the magnetic properties of (Co1- x Fe x )72B19.2Si4.8Ta4 (0 ≤ x ≤ 1.0) alloy ribbons. These Co-based and Fe-based melt-spun ribbons were produced by using an arc-melting furnace and the melt-spinning technique. X-ray diffraction (XRD) peaks indicated that the ribbons had both an amorphous phase and a partial crystalline phase. The thermal properties, such as the crystallization temperatures (Tx), were determined by using differential scanning calorimetry (DSC). The magnetic properties, such as the saturation magnetization (Ms), were measured by using a vibration sample magnetometer (VSM). The Ms values increased to 1.39 T for Co43.2Fe28.8B19.2Si4.8Ta4 ( x = 0.4), decreased for Co36Fe36B19.2Si4.8Ta4 ( x = 0.5), and then increased again to 1.5 T for Fe72B19.2Si4.8Ta4 ( x = 1.0).

  10. Ferromagnetism of Fe3Sn and alloys

    SciTech Connect

    Sales, Brian C.; Saparov, Bayrammurad; McGuire, Michael A.; Singh, David J.; Parker, David S.

    2014-11-12

    Hexagonal Fe3Sn has many of the desirable properties for a new permanent magnet phase with a Curie temperature of 725 K, a saturation moment of 1.18 MA/m. and anisotropy energy, K1 of 1.8 MJ/m3. However, contrary to earlier experimental reports, we found both experimentally and theoretically that the easy magnetic axis lies in the hexagonal plane, which is undesirable for a permanent magnet material. One possibility for changing the easy axis direction is through alloying. We used first principles calculations to investigate the effect of elemental substitutions. The calculations showed that substitution on the Sn site has the potential to switch the easy axis direction. Transition metal substitutions with Co or Mn do not have this effect. We attempted synthesis of a number of these alloys and found results in accord with the theoretical predictions for those that were formed. However, the alloys that could be readily made all showed an in-plane easy axis. The electronic structure of Fe3Sn is reported, as are some are magnetic and structural properties for the Fe3Sn2, and Fe5Sn3 compounds, which could be prepared as mm-sized single crystals.

  11. Containerless electromagnetic levitation melting of Cu-Fe and Ag-Ni alloys

    NASA Technical Reports Server (NTRS)

    Abbaschian, G. J.; Ethridge, E. C.

    1983-01-01

    The feasibility of producing silver or copper alloys containing finely dispersed nickel or iron particles, respectively, by utilizing containerless electromagnetic levitation casting techniques was investigated. A levitation coil was designed to successfully levitate and melt a variety of alloys including Nb-Ge, Cu-Fe, Fe-C, and Ag-Ni. Samples of 70 Cu-30 Fe and 80 Ag-20 Ni (atomic %), prepared by mechanical pressing of the constituent powders, were levitated and heated either to the solid plus liquid range of the alloys or to the fully liquid region. The samples were then solidified by passing helium gas into the bell jar or they were dropped into a quenching oil. The structure of the samples which were heated to the solid plus liquid range consists of uniform distribution of Fe or Ni particle in their respective matrices. A considerable amount of entrapped gas bubbles were contained. Upon heating for longer periods or to higher temperatures, the bubbles coalesced and burst, causing the samples to become fragmented and usually fall out of the coil.

  12. Effects of Cr on the interdiffusion between Ce and Fe-Cr alloys

    NASA Astrophysics Data System (ADS)

    Lo, Wei-Yang; Silva, Nicolas; Wu, Yuedong; Winmann-Smith, Robert; Yang, Yong

    2015-03-01

    Fuel cladding chemical interaction (FCCI) has been a long-standing issue for the metallic fuel with a steel cladding in a sodium-cooled fast reactor, particularly for a high burnup fuel. Although the FCCI has been largely improved by alloying the fuels with Zr or Pd elements, applying a physical diffusion barrier between fuel and cladding, and employing advanced ferritic/martensitic (F/M) claddings, there is a scientific knowledge gap in understanding the behavior of chromium and its effects on the interdiffusion between lanthanides and advanced F/M steels that contain 9-12 wt.% Cr. In this paper, we systematically studied the interdiffusion between cerium and Fe-Cr model alloys with Cr contents of 6, 9 and 12 wt.%. Following the thermal annealing at 560 °C for up to 100 h, detailed microstructural characterizations were performed to determine the interdiffusion microstructures, compositional distributions, diffusion kinetics, and phase structures in the interdiffusion zone. This study unambiguously disclosed that, as the Ce diffuses into Fe-Cr model alloys, Cr segregates and precipitates into Cr-rich σ phase consisted of Fe and Cr instead of forming a ternary phase together with Fe and Ce. The precipitation of those nano-sized σ phase particles at the Ce diffusion front would effectively slow down the interdiffusion.

  13. Ductility and fracture in B2 FeAl alloys. Ph.D. Thesis Final Report

    NASA Technical Reports Server (NTRS)

    Crimp, Martin A.

    1987-01-01

    The mechanical behavior of B2FeAl alloys was studied. Stoichiometric Fe-50Al exhibits totally brittle behavior while iron-rich Fe-40Al yields and displays about 3% total strain. This change in behavior results from large decreases in the yield strength with iron-rich deviations from stoichiometry while the fracture stress remains essentially constant. Single crystal studies show that these yield strength decreases are directly related to decreases in the critical resolved shear stress for a group of zone axes /111/ set of (110) planes slip. This behavior is rationalized in terms of the decrease in antiphase boundary energy with decreasing aluminum content. The addition of boron results in improvements in the mechanical behavior of alloys on the iron-rich side of stoichiometry. These improvements are increased brittle fracture stresses of near-stoichiometric alloys, and enhanced ductility of up to 6% in Fe-40Al. These effects were attributed to increased grain boundary adhesion as reflected by changes in fracture mode from intergranular to transgranular failure. The increases in yield strength, which are observed in both polycrystals and single crystals, result from the quenching in of large numbers of thermal vacancies. Hall-Petch plots show that the cooling rate effects are a direct result of changes in the Hall-Petch intercept/lattice resistance flow.

  14. Reactions between U-Zr alloys and Fe at 1003 K

    NASA Astrophysics Data System (ADS)

    Ogata, Takanari; Nakamura, Kinya; Itoh, Akinori; Akabori, Mitsuo

    2013-10-01

    In metal fuel for fast reactors, liquefaction at the fuel-cladding interface may occur in off-normal events and enhance cladding wastage. To provide the basis for understanding this liquefaction phenomenon, reactions in diffusion couples of U-23 at.%Zr alloys and Fe at 1003 K have been examined. The selected temperature is 5 K higher than the eutectic point in the U-Fe binary system. The effect of lanthanide fission products on the liquefaction was evaluated by adding 1 at.%Ce to some of the U-Zr specimens. The test results indicated that a liquid phase formed in the reaction zone. The phases in the reaction zone were identified based on electron probe microanalysis results and the calculated U-Zr-Fe phase diagram. The reaction zone growth rate decreased with time. The thickness of the reaction zones at 1003 K in diffusion couples pre-annealed at 923 K was less than those in diffusion couples without the pre-anneal. Zirconium in the fuel alloy has little influence on the threshold temperature for the liquefaction onset, and the addition of 1 at.%Ce has little effect on the reaction of U-Zr alloy with Fe.

  15. Lattice dynamics and external magnetic-field effects in Ni-Fe-Ga alloys

    NASA Astrophysics Data System (ADS)

    Pérez-Landazábal, J. I.; Recarte, V.; Sánchez-Alarcos, V.; Rodríguez-Velamazán, J. A.; Jiménez-Ruiz, M.; Link, P.; Cesari, E.; Chumlyakov, Y. I.

    2009-10-01

    Precursor phenomena were investigated in a Ni-Fe-Ga alloy close to the stoichiometric Heusler composition Ni2FeGa . In particular, the phonon-dispersion curves, the diffuse scattering and the magnetic properties of a single crystalline Ni51.5Fe21.5Ga27 alloy were measured as a function of temperature. The TA2 branch along the [110] direction of the L21 phase shows a significant phonon softening around ξ=0.35 resulting in a marked dip which becomes more pronounced as the temperature decreases. Diffuse neutron-scattering measurements performed along [ξ¯ξ0] direction around Bragg reflections also reveal the presence of small satellite peaks at ξ=0.33 whose intensity increases on approaching the martensitic transformation temperature. Both elastic and inelastic-scattering anomalies confirm the occurrence of premartensitic phenomena in Ni-Fe-Ga alloys. The influence of an external magnetic field (6 T) on the anomalous phonon is shown to be negligible and just a small shift of the transformation temperature takes place because of the magnetic field.

  16. Development of FeSiBNbCu Nanocrystalline Soft Magnetic Alloys with High B s and Good Manufacturability

    NASA Astrophysics Data System (ADS)

    Wan, Fangpei; He, Aina; Zhang, Jianhua; Song, Jiancheng; Wang, Anding; Chang, Chuntao; Wang, Xinmin

    2016-10-01

    In order to develop Fe-based nanocrystalline soft magnetic alloys with high saturation magnetic flux density ( B s) and good manufacturability, the effect of the Nb content on the thermal stability, microstructural evolution and soft magnetic properties of Fe78- x Si13B8Nb x Cu1 ( x = 0, 1, 2 and 3) alloys were investigated. It is found that proper Nb addition is effective in widening the optimum annealing temperature range and refining the α-Fe grain in addition to enhancing the soft magnetic properties. For the representative Fe76 Si13B8Nb2Cu1 alloy, the effective annealing time can be over 60 min in the optimal temperature range of 500-600°C. FeSiBNbCu nanocrystalline soft magnetic alloys with desirable soft magnetic properties including high B s of 1.39 T, low coercivity ( H c) of 1.5 A/m and high effective permeability ( μ e) of 21,500 at 1 kHz have been developed. The enhanced soft magnetic performance and manufacturability of the FeSiBNbCu nanocrystalline alloys are attributed to the high activated energy for the precipitation of α-Fe(Si) and the second phase. These alloys with excellent performance have promising applications in electromagnetic fields like inductors.

  17. Evaluation of Pb-17Li compatibility of ODS Fe-12Cr-5Al alloys

    NASA Astrophysics Data System (ADS)

    Unocic, Kinga A.; Hoelzer, David T.

    2016-10-01

    The Dual Coolant Lead Lithium (DCLL: eutectic Pb-17Li and He) blanket concept requires improved Pb-17Li compatibility with ferritic steels in order to demonstrate acceptable performance in fusion reactors. As an initial step, static Pb-17at.%Li (Pb-17Li) capsule experiments were conducted on new oxide dispersion strengthened (ODS) FeCrAl alloys ((1) Y2O3 (125Y), (2) Y2O3 + ZrO2 (125YZ), (3) Y2O3 + HfO2 (125YH), and (4) Y2O3 + TiO2 (125YT)) produced at ORNL via mechanical alloying (MA). Tests were conducted in static Pb-17Li for 1000 h at 700 °C. Alloys showed promising compatibility with Pb-17Li with small mass change after testing for 125YZ, 125YH and 125YT, while the 125Y alloy experienced the highest mass loss associated with some oxide spallation and subsequent alloy dissolution. X-ray diffraction methods identified the surface reaction product as LiAlO2 on all four alloys. A small decrease (∼1 at.%) in Al content beneath the oxide scale was observed in all four ODS alloys, which extended 60 μm beneath the oxide/metal interface. This indicates improvements in alloy dissolution by decreasing the amount of Al loss from the alloy. Scales formed on 125YZ, 125YH and 125YT were examined via scanning transmission electron microscopy (S/TEM) and revealed incorporation of Zr-, Hf-, and Ti-rich precipitates within the LiAlO2 product, respectively. This indicates an inward scale growth mechanism. Future work in flowing Pb-17Li is needed to further evaluate the effectiveness of this strategy in a test blanket module.

  18. Evaluation of Pb-17Li compatibility of ODS Fe-12Cr-5Al alloys

    DOE PAGES

    Unocic, Kinga A.; Hoelzer, David T.

    2016-07-09

    The Dual Coolant Lead Lithium (DCLL: eutectic Pb–17Li and He) blanket concept requires improved Pb–17Li compatibility with ferritic steels in order to demonstrate acceptable performance in fusion reactors. As an initial step, static Pb-17at.%Li (Pb-17Li) capsule experiments were conducted on new oxide dispersion strengthened (ODS) FeCrAl alloys ((1) Y2O3 (125Y), (2) Y2O3+ZrO2 (125YZ), (3) Y2O3+HfO2 (125YH), and (4) Y2O3+TiO2 (125YT)) produced at ORNL via mechanical alloying (MA). Tests were conducted in static Pb–17Li for 1000 h at 700°C. Alloys showed promising compatibility with Pb–17Li with small mass change after testing for 125YZ, 125YH and 125YT, while the 125Y alloy experiencedmore » the highest mass loss associated with some oxide spallation and subsequent alloy dissolution. X-ray diffraction methods identified the surface reaction product as LiAlO2 on all four alloys. A small decrease (~1 at.%) in Al content beneath the oxide scale was observed in all 4 ODS alloys, which extended through 60 μm beneath the oxide/metal interface. This indicates improvements in alloy dissolution by decreasing the amount of Al loss from the alloy. Scales formed on 125YZ, 125YH and 125YT were examined via scanning transmission electron microscopy (S/TEM) and revealed incorporation of Zr-, Hf-, and Ti-rich precipitates within the LiAlO2 product, respectively. This indicates an inward scale growth mechanism. Future work in flowing Pb–17Li is needed to further evaluate the effectiveness of this strategy in a test blanket module.« less

  19. Evaluation of Pb-17Li compatibility of ODS Fe-12Cr-5Al alloys

    SciTech Connect

    Unocic, Kinga A.; Hoelzer, David T.

    2016-07-09

    The Dual Coolant Lead Lithium (DCLL: eutectic Pb–17Li and He) blanket concept requires improved Pb–17Li compatibility with ferritic steels in order to demonstrate acceptable performance in fusion reactors. As an initial step, static Pb-17at.%Li (Pb-17Li) capsule experiments were conducted on new oxide dispersion strengthened (ODS) FeCrAl alloys ((1) Y2O3 (125Y), (2) Y2O3+ZrO2 (125YZ), (3) Y2O3+HfO2 (125YH), and (4) Y2O3+TiO2 (125YT)) produced at ORNL via mechanical alloying (MA). Tests were conducted in static Pb–17Li for 1000 h at 700°C. Alloys showed promising compatibility with Pb–17Li with small mass change after testing for 125YZ, 125YH and 125YT, while the 125Y alloy experienced the highest mass loss associated with some oxide spallation and subsequent alloy dissolution. X-ray diffraction methods identified the surface reaction product as LiAlO2 on all four alloys. A small decrease (~1 at.%) in Al content beneath the oxide scale was observed in all 4 ODS alloys, which extended through 60 μm beneath the oxide/metal interface. This indicates improvements in alloy dissolution by decreasing the amount of Al loss from the alloy. Scales formed on 125YZ, 125YH and 125YT were examined via scanning transmission electron microscopy (S/TEM) and revealed incorporation of Zr-, Hf-, and Ti-rich precipitates within the LiAlO2 product, respectively. This indicates an inward scale growth mechanism. Future work in flowing Pb–17Li is needed to further evaluate the effectiveness of this strategy in a test blanket module.

  20. Polarization and resistivity measurements of post-crystallization changes in amorphous Fe-B-Si alloys

    SciTech Connect

    Chattoraj, I.; Bhattamishra, A.K. . CRP Div.); Mitra, A. . MTP Div.)

    1993-09-01

    The effects of grain growth and compositional changes on the electrochemical behavior and the resistivity of amorphous iron-boron-silicon (Fe[sub 77.5]B[sub 15]Si[sub 7.5]) alloys after crystallization were studied. Deterioration of the protective passive film was observed, along with increased annealing. Potentiodynamic polarization provided excellent information about microstructural and chemical changes. It was concluded that electrochemical measurements could be used in conjunction with resistivity measurements in direct studies of grain growth and chemical changes occurring in different phases of the devitrified alloy.

  1. Aspects of thermal martensite in a FeNiMnCo alloy.

    PubMed

    Güler, M; Güler, E; Kahveci, N

    2010-07-01

    Thermal martensite characteristics in Fe-29%Ni-2%Mn-2%Co alloy were investigated with scanning electron microscopy (SEM) and Mössbauer spectroscopy characterization techniques. SEM observations obviously revealed the lath martensite morphology in the prior austenite phase of examined alloy. As well, the martensitic transformation kinetics was found to be as athermal type. On the other hand, Mössbauer spectroscopy offered the paramagnetic austenite phase and ferromagnetic martensite phase with their volume fractions. Also, the internal magnetic field of the martensite was measured as 32.9T from the Mössbauer spectrometer.

  2. Magnetic, magnetocaloric properties and phenomenological model in amorphous Fe60Ru20B20 alloy

    NASA Astrophysics Data System (ADS)

    Boutahar, A.; Lassri, H.; Hlil, E. K.

    2015-11-01

    Magnetic, magnetocaloric properties and phenomenological model of amorphous Fe60Ru20B20 alloy are investigated in detail. The amorphous alloy has been synthesized using melt spinning method. The magnetic transition nature undergoes a second-order magnetic phase transition from ferromagnetic to paramagnetic states with a Curie temperature of 254 K. Basis on the thermodynamic Maxwell's relation, magnetic entropy change (-ΔSM) is calculated. Further, we also report a theoretical investigation of the magnetocaloric effect using a phenomenological model. The best model parameters and their variation with temperature and the magnetic field were determined. The theoretical predictions are found to agree closely with experimental measurements.

  3. Microstructure, hyperfine interaction and magnetic transition of Fe-25%Ni-5%Si-x%Co alloys

    NASA Astrophysics Data System (ADS)

    Gungunes, H.

    2016-12-01

    Morphological and magnetic properties in Fe-25%Ni-5%Si-x%Co (x = 0, 10, 15) alloys are investigated. Scanning electron microscopy (SEM), Mössbauer spectroscopy and AC magnetic susceptibility measurements are used to determine the physical properties of alloys. The martensite morphology changed depending on the Co content. The Mössbauer study shows that the volume fraction and hyperfine field of martensite increases while isomer shift values decrease with increasing Co content. On the other hand; AC susceptibility results showed that; Co is an effective element which can be used to control both the magnetic transition and martensitic transformation temperatures.

  4. Influence of nanophase titania topography on bacterial attachment and metabolism

    PubMed Central

    Park, Margaret R; Banks, Michelle K; Applegate, Bruce; Webster, Thomas J

    2008-01-01

    Surfaces with nanophase compared to conventional (or nanometer smooth) topographies are known to have different properties of area, charge, and reactivity. Previously published research indicates that the attachment of certain bacteria (such as Pseudomonas fluorescens 5RL) is higher on surfaces with nanophase compared to conventional topographies, however, their effect on bacterial metabolism is unclear. Results presented here show that the adhesion of Pseudomonas fluorescens 5RL and Pseudomonas putida TVA8 was higher on nanophase than conventional titania. Importantly, in terms of metabolism, bacteria attached to the nanophase surfaces had higher bioluminescence rates than on the conventional surfaces under all nutrient conditions. Thus, the results from this study show greater select bacterial metabolism on nanometer than conventional topographies, critical results with strong consequences for the design of improved biosensors for bacteria detection. PMID:19337418

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

    SciTech Connect

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

    2011-01-01

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

  6. Investigation of the mechanical properties of FeNiCrMnSi high entropy alloy wear resistant

    NASA Astrophysics Data System (ADS)

    Buluc, G.; Florea, I.; Chelariu, R.; Popescu, G.; Carcea, I.

    2016-06-01

    In this paper we investigated microstructure, hardness and wear resistance for FeNiCrMnAl, high entropy alloy. The FeNiCrMnSi, high entropy alloy was elaborated in a medium induction furnace, by choosing the silicon, as an alliance element within the equi- atomic high entropy alloy, we managed to obtain a dendritic structure, the formation of intermetallic compounds or separated silicon. The medium hardness value of the investigated alloy was 948.33 HV and the medium value of the friction coefficient was 0.6655 in the first 20 seconds and 0.5425 for 1667 seconds. The volume loss of the high entropy alloy FeNiCrMnSi was 0.0557 mm3.

  7. Swelling behavior of a simple ferritic alloy. [Fe-10% Cr

    SciTech Connect

    Horton, L.L.; Bentley, J.

    1983-01-01

    The swelling behavior which results from simulated fusion environment irradiation of Fe-10% Cr has been characterized with transmission electron microscopy. Specimens were bombarded at 850 K with: a triple-beam of He/sup +/, D/sup +//sub 2/, and 4 MeV Fe/sup + +/ ions to 0.3, 1, 3, 10, 30, and 100 dpa, a dual-beam of He/sup +/ and 4 MeV Fe/sup + +/ ions to 30 and 100 dpa; and a single-beam of 4 MeV Fe/sup + +/ ions to 30 dpa. The helium and hydrogen injection rates were approx. 10 appm He/dpa and approx. 40 appm D/dpa. Cavities were observed for damage levels of 3 dpa and greater. The swelling was <0.1% for damage levels <30 dpa, but at 100 dpa, there was an increase in the swelling to 2.5% for the triple-beam irradiation and 1.2% for the dual-beam irradiation. The swelling rates between 30 and 100 dpa correlate well with calculated values assuming a steady-state swelling-rate regime has been reached. Calculations show the rapid cavity growth associated with this swelling increase cannot be attributed to equilibrium bubble growth. For all of the bombardments, the cavities with a diameter greater than 10 nm had a truncated octahedral morphology with (111) facets and (100) truncations. Measurements indicate that the surface energy relationship was ..gamma../sub 111/approx. =0.8 ..gamma../sub 100/ for these cavities. At 30 dpa, the cavities in the specimen irradiated with the single-beam technique were larger and had a lower concentration than the specimens irradiated with specimens irradiated with the dual- and triple-ion beams suggests that deuterium has an effect on the damage microstructures in Fe-10% Cr.

  8. Evolution of Intermetallics, Dispersoids, and Elevated Temperature Properties at Various Fe Contents in Al-Mn-Mg 3004 Alloys

    NASA Astrophysics Data System (ADS)

    Liu, K.; Chen, X.-G.

    2016-12-01

    Nowadays, great interests are rising on aluminum alloys for the applications at elevated temperature, driven by the automotive and aerospace industries requiring high strength, light weight, and low-cost engineering materials. As one of the most promising candidates, Al-Mn-Mg 3004 alloys have been found to possess considerably high mechanical properties and creep resistance at elevated temperature resulted from the precipitation of a large number of thermally stable dispersoids during heat treatment. In present work, the effect of Fe contents on the evolution of microstructure as well as high-temperature properties of 3004 alloys has been investigated. Results show that the dominant intermetallic changes from α-Al(MnFe)Si at 0.1 wt pct Fe to Al6(MnFe) at both 0.3 and 0.6 wt pct Fe. In the Fe range of 0.1-0.6 wt pct studied, a significant improvement on mechanical properties at elevated temperature has been observed due to the precipitation of dispersoids, and the best combination of yield strength and creep resistance at 573 K (300 °C) is obtained in the 0.3 wt pct Fe alloy with the finest size and highest volume fraction of dispersoids. The superior properties obtained at 573 K (300 °C) make 3004 alloys more promising for high-temperature applications. The relationship between the Fe content and the dispersoid precipitation as well as the materials properties has been discussed.

  9. Effect of Wavelike Sloping Plate Rheocasting on Microstructures of Hypereutectic Al-18 pct Si-5 pct Fe Alloys

    NASA Astrophysics Data System (ADS)

    Guan, Ren-Guo; Zhao, Zhan-Yong; Lee, Chong Soo; Zhang, Qiu-Sheng; Liu, Chun-Ming

    2012-04-01

    To refine and spheroidize the microstructures of hypereutectic Al-Si-Fe alloys, a novel method of wavelike sloping plate (WSP) rheocasting was proposed, and the effect of the WSP rheocasting on the microstructures of hypereutectic Al-18 pct Si-5 pct Fe alloys was investigated. The results reveal that the morphologies of the primary Si crystal, the Al18Si10Fe5, and the Al8Si2Fe phases can be improved by the WSP rheocasting, and various phases tend to be refined and spheroidized with the decrease of the casting temperature. The alloy ingots with excellent microstructures can be obtained when the casting temperature is between 943 K and 953 K (670 °C and 680 °C). During the WSP rheocasting, the crystal nucleus multiplication, inhibited grain growth, and dendrite break-up take place simultaneously, which leads to grain refinement of the alloys.

  10. Effects of iron concentration on the microstructure of V-Fe alloys after low-dose neutron irradiation

    NASA Astrophysics Data System (ADS)

    Oono, Naoko; Nita, Nobuyasu; Abe, Yosuke; Satoh, Yuhki; Matsui, Hideki

    2011-11-01

    To examine the mechanism of huge swelling of V-Fe alloys, TEM observation was applied to V- x at.%Fe ( x = 0, 0.3, 1, 5, 7), after low-dose neutron irradiation of 0.1-1.17 dpa at 400-600 °C. Concentric Multi-Dislocation Loops (CMDLs) and rafts were observed in V-Fe alloys irradiated to 0.1 dpa. Voids were observed only within dislocation loops in both types of configurations. Ashby-Brown (AB) contrasts were always observed around voids, indicating that shell-like iron segregation with substantial elastic strain exists on the inner surface of the voids. For 1.17 dpa, swelling V-Fe alloys was always greater than those of un-alloyed vanadium, whatever the dislocation microstructures. Implication of a segregation shell in the swelling mechanism is discussed in addition to a model based on the dislocation bias.

  11. Electronic structures and optical properties of α-Fe2O3-xSex alloys for solar absorber

    NASA Astrophysics Data System (ADS)

    Xia, Congxin; Jia, Yu; Zhang, Qiming

    2015-05-01

    The band structures and optical properties of α-Fe2O3-xSex alloys are studied by means of first-principles methods, considering different Se contents x. Numerical results show that Se content has an obvious influence on band structures and optical properties of α-Fe2O3-xSex alloys. The band gap values of α-Fe2O3-xSex alloys decrease monotonically when Se concentrations increase, resulting in an obvious increase of the optical absorption edge in the visible range. In particular, our results show that α-Fe2O3-xSex alloys have the direct band gap properties with band gap values when Se content x ≈ 0.17, which is beneficial to solar cell applications.

  12. Morphology Control of FeCo Alloy Particles Synthesized by Polyol Process

    SciTech Connect

    Kodama, D.; Sato, Y.; Tohji, K.; Jeyadevan, B.; Shinoda, K.; Sato, K.

    2007-03-20

    FeCo alloy is a soft magnetic material that possesses the highest saturation magnetization of 2.4 T and crystallizes in bcc structure as in the case of {alpha}-Fe. However, the particles synthesized were highly agglomerated. Thus, in this paper, an attempt was made to control the morphology of the particles using different types and concentrations of surfactants such as oleic acid, oleyl amine, polyvinylpyrrolidone (PVP), etc., during the synthesis of the particles. Though all the surfactant experimented partially prevented the agglomeration, products had larger size distribution except for PVP, which provided nearly monodispersed particles. Furthermore, the FeCo particles synthesized in the presence of PVP were either cubic or nearly spherical depending on the concentration of Fe.

  13. Morphology Control of FeCo Alloy Particles Synthesized by Polyol Process

    NASA Astrophysics Data System (ADS)

    Kodama, D.; Shinoda, K.; Sato, K.; Sato, Y.; Tohji, K.; Jeyadevan, B.

    2007-03-01

    FeCo alloy is a soft magnetic material that possesses the highest saturation magnetization of 2.4 T and crystallizes in bcc structure as in the case of α-Fe. However, the particles synthesized were highly agglomerated. Thus, in this paper, an attempt was made to control the morphology of the particles using different types and concentrations of surfactants such as oleic acid, oleyl amine, polyvinylpyrrolidone (PVP), etc., during the synthesis of the particles. Though all the surfactant experimented partially prevented the agglomeration, products had larger size distribution except for PVP, which provided nearly monodispersed particles. Furthermore, the FeCo particles synthesized in the presence of PVP were either cubic or nearly spherical depending on the concentration of Fe.

  14. Microstructure and Mechanical Properties of Laves Phase-strengthened Fe-Cr-Zr Alloys

    SciTech Connect

    Tan, Lizhen; Yang, Ying

    2014-12-05

    Laves phase-reinforced alloys have shown some preliminary promising performance at room temperatures. This paper aims at evaluating mechanical properties of Laves phase-strengthened alloys at elevated temperatures. Three Fe-Cr-Zr alloys were designed to favor the formation of eutectic microstructures containing Laves and body-centered cubic phases with the aid of thermodynamic calculations. Microstructural characterization was carried out on the alloys in as-processed and aged states using optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The effect of thermal aging and alloy composition on microstructure has been discussed based on microstructural characterization results. Mechanical properties have been evaluated by means of Vickers microhardness measurements, tensile testing at temperatures up to 973.15 K (700.15 °C), and creep testing at 873.15 K (600.15 °C) and 260 MPa. Alloys close to the eutectic composition show significantly superior strength and creep resistance compared to P92. Finally, however, their low tensile ductility may limit their applications at relatively low temperatures.

  15. Microstructure and Mechanical Properties of Laves Phase-strengthened Fe-Cr-Zr Alloys

    DOE PAGES

    Tan, Lizhen; Yang, Ying

    2014-12-05

    Laves phase-reinforced alloys have shown some preliminary promising performance at room temperatures. This paper aims at evaluating mechanical properties of Laves phase-strengthened alloys at elevated temperatures. Three Fe-Cr-Zr alloys were designed to favor the formation of eutectic microstructures containing Laves and body-centered cubic phases with the aid of thermodynamic calculations. Microstructural characterization was carried out on the alloys in as-processed and aged states using optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The effect of thermal aging and alloy composition on microstructure has been discussed based on microstructural characterization results. Mechanical properties have been evaluated by meansmore » of Vickers microhardness measurements, tensile testing at temperatures up to 973.15 K (700.15 °C), and creep testing at 873.15 K (600.15 °C) and 260 MPa. Alloys close to the eutectic composition show significantly superior strength and creep resistance compared to P92. Finally, however, their low tensile ductility may limit their applications at relatively low temperatures.« less

  16. Effect of residual strain in Fe-based amorphous alloys on field induced magnetic anisotropy and domain structure

    NASA Astrophysics Data System (ADS)

    Azuma, Daichi; Hasegawa, Ryusuke; Saito, Shin; Takahashi, Migaku

    2013-05-01

    Field induced magnetic anisotropy in two Fe-based amorphous alloys with different saturation induction levels (1.56 T and 1.64 T) was investigated by varying magnetic field strength and annealing temperature and domain images were taken on these samples. Residual strain was evaluated by measuring coercivities of the materials after stress-relief annealing. These results are discussed, clarifying the difference between the two Fe-based amorphous alloys.

  17. A Mössbauer effect study of the Fe2+ x Mn1- x Al Heusler alloys

    NASA Astrophysics Data System (ADS)

    Paduani, C.; Samudio Pérez, C. A.; Schaf, J.; Ardisson, J. D.; Takeuchi, A. Y.; Yoshida, M. I.

    2010-01-01

    In this work the Mössbauer spectroscopy has been used to study the magnetic properties of Fe2 + x Mn1 - x Al alloys with small deviations of composition from the stoichiometric 2:1:1. The Mössbauer parameters obtained for the L21 phase indicate H hf fields of about 25 T and 30 T at 80 K for Fe atoms at X sites in the ordered X2YZ structure of the L21 full Heusler alloys.

  18. Degradation of Aluminide Coatings in Fe-Al-Cr Alloy on the Isothermal Oxidation

    NASA Astrophysics Data System (ADS)

    Juwita, L.; Prajitno, D. H.; Soedarsono, J. W.; Manaf, A.

    2008-03-01

    Fe base superalloy has a good mechanical strength to be used as component operating at high temperature with oxidative environment. Although, the oxidation rate can not be tolerated as it will be oxidized and form oxide scale of un-protective FeO. Coating is a proper solution that this alloy can be used at high temperature. In this research, pack aluminizing on sample was conducted with temperatures of 900 °C, 1000 °C and 1100 °C for 10 hours in inert (argon) environment and then an oxidation test was carried out at temperature of 650 °C by an isothermal method for 10 hours in air environment. It was carried out an analysis for characteristics of coating and oxide scale formed in Fe-Al-Cr super alloy resulted from pack aluminizing. From this experiment, it was indicated by XRD analysis that the coating formed on substrate was a layer of FeAl2 compound, other than coating it was found a diffused zone, where in this area it occurred movement of Fe and Cr atoms from substrate toward coating, while Al atoms moved from coating to substrate. The increase of temperature of pack aluminizing process will affect settling rate of Al and coating growth.

  19. The order parameter dependence of transition temperature in FeRhPd alloy films

    NASA Astrophysics Data System (ADS)

    Sato, Hideo; Yu, Jian; Mankey, Gary; Mryasov, Oleg; Leclair, Patrick

    2010-03-01

    FeRh alloys and FeRh-TM alloys have recently attracted great interest because well-ordered films exhibit a phase transition with antiferromagnetism observed at lower temperatures and ferromagnetism at higher temperatures. Here, the order parameter dependence of transition temperature in Fe47Rh47Pd6 films is reported. FeRhPd/Co films were fabricated such that different order parameters were obtained. A higher transition temperature was observed for a film with lower order parameter in sharp contrast to prior experiments with FeRh that show that the transition temperature monotonically increasing with order parameter [1]. The shift to lower transition temperature for the ordered film is accompanied by a sharpening of the phase transition. This is surprising, since disordered films are ferromagnetic throughout the temperature range of the measurements. These results, along with a possible explanation for the anomalous behavior including the effect of lattice constant on the transition temperature will be presented. Funded by the US DOE 1. Jiangwei Cao et al., J. Appl. Phys. 103, 07F501 (2008)

  20. Element Specific Spin and Orbital Moments in Fe1-x Vx Alloys

    SciTech Connect

    Guan, Y.; Scheck, C; Bailey, W

    2009-01-01

    We present transmission-mode X-ray magnetic circular dichroism (XMCD) measurements of element-specific magnetic moments for Fe and V at the L2,3 edges in polycrystalline Fe1-xVx ultrathin films. We find that the orbital-to-spin moment ratio of Fe does not change within experimental error. The V XMCD is not very informative, and a nearly pure-spin type V impurity moment ({approx}1.0 {mu}{sub B}/atom, antiparallel to the Fe host moment) is assumed to match known magnetization data. Data are further reduced to a two-sublattice model and found to be compatible with known spectroscopic splitting g-factor data in the alloy. The results confirm that the very low Gilbert damping, attained through the introduction of V into epitaxial Fe1-xVx films and found by ferromagnetic resonance (FMR), does not result from the reduction of orbital moment content in the alloy.

  1. Brazing characteristics of a Zr-Ti-Cu-Fe eutectic alloy filler metal for Zircaloy-4

    NASA Astrophysics Data System (ADS)

    Lee, Jung G.; Lim, C. H.; Kim, K. H.; Park, S. S.; Lee, M. K.; Rhee, C. K.

    2013-10-01

    A Zr-Ti-Cu-Fe quaternary eutectic alloy was employed as a new Be-free brazing filler metal for Zircaloy-4 to supersede physically vapor-deposited Be coatings used conventionally with several disadvantages. The quaternary eutectic composition of Zr58Ti16Cu10Fe16 (at.%) showing a low melting temperature range from 832 °C to 853 °C was designed by a partial substitution of Zr with Ti based on a Zr-Cu-Fe ternary eutectic system. By applying an alloy ribbon with the determined composition, a highly reliable joint was obtained with a homogeneous formation of predominantly grown α-Zr phases owing to a complete isothermal solidification, exhibiting strength higher than that of Zircaloy-4. The homogenization of the joint was rate-controlled by the diffusion of the filler elements (Ti, Cu, and Fe) into the Zircaloy-4 base metal, and the detrimental segregation of the Zr2Fe phase in the central zone was completely eliminated by an isothermal holding at a brazing temperature of 920 °C for 10 min.

  2. Hot Tear Susceptibility of Al-Mg-Si-Fe Alloys with Varying Iron Contents

    NASA Astrophysics Data System (ADS)

    Sweet, Lisa; Easton, Mark A.; Taylor, John A.; Grandfield, John F.; Davidson, Cameron J.; Lu, Liming; Couper, Malcolm J.; StJohn, David H.

    2013-12-01

    Hot tear susceptibility in cast Al-0.52Si-0.34Mg- xFe 6060 aluminum alloys was investigated using a hot tearing test apparatus to simulate hot tearing in DC casting. The test apparatus has two cast bars, one that is used to measure the load response and one which is fixed at both ends to restrain thermal contraction so that hot tearing can be observed and rated where it occurred. The iron (Fe) content, ranging from 0.02 to 0.5 wt pct, was seen to have a major influence on the load response during solidification and the tear rating of these alloys. The findings are discussed in terms of Rappaz-Drezet-Gremaud (RDG) model sensitivity analysis and related to the effect of Fe content on the morphology and prevalence of the β-Al5FeSi and α-AlFeSi intermetallic phases and their influence on the coherency and coalescence of the microstructure.

  3. Structure evolution of Fe-50%Al coating prepared by mechanical alloying

    NASA Astrophysics Data System (ADS)

    Aryanto, D.; Wismogroho, A. S.; Sudiro, T.

    2016-08-01

    The deposition of Fe-50%Al coating (in at%) on low carbon steel was successfully prepared by using mechanical alloying (MA). The coating process was performed in a shaker mill with variation of milling times from 30 minute to 180 minutes. The deposited coating was then heat treated at 600°C for 2 hour in a vacuum furnace of 5.6 Pa. The structure evolution of mechanical alloyed samples before and after heat treatment was investigated by scanning electron microscopy (SEM) equipped with energy dispersive X-ray spectrometer (EDX) and X-ray diffractometer (XRD). The results revealed that before heat treatment, the deposited coating on low carbon steel is composed of Fe and Al. The Fe(Al) solid solution was mostly formed after 180 minutes of milling time. Metallographic observation indicated that the surface of Fe-Al coating was rough and the coating thickness was increased with increasing milling time. Meanwhile, the heat treatment process led to structural evolution by forming FeAl intermetallic phase on the surface of low carbon steel.

  4. Development of a new graded-porosity FeAl alloy by elemental reactive synthesis

    SciTech Connect

    Shen, P Z; He, Y H; Gao, H Y; Zou, J; Xu, N P; Jiang, Y; Huang, B; Lui, C T

    2009-01-01

    A new graded-porosity FeAl alloy can be fabricated through Fe and Al elemental reactive synthesis. FeAl alloy with large connecting open pores and permeability were used as porous supports. The coating was obtained by spraying slurries consisting of mixtures of Fe powder and Al powder with 3 5 m diameter onto porous FeAl support and then sintered at 1100 C. The performances of the coating were compared in terms of thickness, pore diameter and permeability. With an increase in the coating thickness up to 200 m, the changes of maximum pore size decreased from 23.6 m to 5.9 m and the permeability decreased from 184.2 m3m 2kPa 1h 1 to 76.2 m3m 2kPa 1h 1, respectively, for a sintering temperature equal to 1100 C. The composite membranes have potential application for excellent filters in severe environments.

  5. Deuterium absorption and material phase characteristics of SAES St 198 Zr-Fe Alloy. Revision 1

    SciTech Connect

    Nobile, A.; Mosley, W.C.; Holder, J.S.; Brooks, K.N.

    1994-01-01

    This document reports deuterium absorption and material phase characteristics of SAES St 198 Zr-Fe Alloy (76.5% Zr). Scanning electron microscope images of polished surfaces, electron probe microanalysis, and x-ray powder diffractometry indicated the presence of a primary Zr{sub 2}Fe phase with secondary phases of ZrFe{sub 2}, Zr{sub 5}FeSn, {alpha}-Zr, and Zr{sub 6}Fe{sub 3}O. A statistically designed experiment to determine the effects of temperature, time, and vacuum quality on activation of St 198 revealed that, when activated at low temperature (350C), deuterium absorption rate was slower when the vacuum quality was poor (2.5 Pa vs. 3 {times} 10{sup {minus}4} Pa). However, at higher activation temperature (500C), deuterium absorption rate was fast and was independent of vacuum quality. Deuterium pressure-composition-temperature (P-C-T) data are reported for St 198 in the temperature range 200 to 500C. The P-C-T data over the full range of deuterium loading and at temperatures of 350C and below is described an expression. At higher temperatures, one or more secondary reactions in the solid phase occur that slowly consume D{sub 2} from the gas phase. X-ray diffraction and other data suggest these reactions to be: 2 Zr{sub 2}FeD{sub x} {yields} xZrD{sub 2} + x/3 ZrFe{sub 2} + (2 {minus} 2/3x) Zr{sub 2}Fe and Zr{sub 2}FeD{sub x} + (2 {minus} 1/2x) D{sub 2} {yields} 2 ZrD{sub 2} + Fe, where 0 < x < 3. Reaction between gas-phase deuterium and Zr{sub 2}Fe formed in the first reaction accounts for the observed consumption of deuterium from the gas phase by this reaction.

  6. Metal elution from Ni- and Fe-based alloy reactors under hydrothermal conditions.

    PubMed

    Faisal, Muhammad; Quitain, Armando T; Urano, Shin-Ya; Daimon, Hiroyuki; Fujie, Koichi

    2004-05-20

    Elution of metals from Ni- and Fe-based alloy (i.e. Inconel 625 and SUS 316) under hydrothermal conditions was investigated. Results showed that metals could be eluted even in a short contact time. At subcritical conditions, a significant amount of Cr was extracted from SUS 316, while only traces of Ni, Fe, Mo, and Mn were eluted. In contrast, Ni was removed in significant amounts compared to Cr when Inconel 625 was tested. Several factors including temperature and contact time were found to affect elution behavior. The presence of air in the fluid even promoted elution under subcritical conditions.

  7. Structure fragmentation in Fe-based alloys by means of cyclic martensitic transformations of different types.

    PubMed

    Bondar, Volodimir I; Danilchenko, Vitalij Ie; Dzevin, Ievgenij M

    2014-02-24

    The effect of martensite transformations of different types on the misorientation of austenite crystalline lattice, which characterizes the degree of structure fragmentation, was investigated for Fe-Ni and Fe-Mn alloys. As a result of multiple face-centered cubic (f.c.c.)-body-centered cubic (b.c.c.)-f.c.c. transformations, an austenite single-crystalline specimen is transformed in a polycrystalline one due to progressive fragmentation. It was shown that the degree of fragmentation depends on the magnitude of volume change and the density of dislocations generated on martensitic transformations.

  8. Equation of State of an AlCoCrCuFeNi High-Entropy Alloy

    NASA Astrophysics Data System (ADS)

    Li, Gong; Xiao, Daihong; Yu, Pengfei; Zhang, Lijun; Liaw, Peter K.; Li, Yanchun; Liu, Riping

    2015-08-01

    The pressure-volume (P-V) relationship of the AlCoCrCuFeNi high-entropy alloy (HEA) at room temperature has been studied using in situ high-pressure energy-dispersive x-ray diffraction with synchrotron radiation at high pressures. The equation of state of the AlCoCrCuFeNi HEA is determined by the calculation of the radial distribution function. The experimental results indicate that the HEA keeps a stable face-centered-cubic + body-centered-cubic structure in the experimental pressure range from 0 GPa to 24 GPa.

  9. ALCHEMI of Fe-doped B2-ordered NiAl alloys with different doping levels

    SciTech Connect

    Anderson, I.M.; Bentley, J.; Duncan, A.J.

    1994-09-01

    The ALCHEMI technique yields exact expressions for best-fit parameters in terms of ionization localization constants and site distributions of 3 elements distributed over two sublattices. In this paper, a graphical plotting technique is applied to Fe-doped NiAl B2-ordered alloys Ni{sub 0.5-x}Fe{sub x}Al{sub 0.5}, with x=0.02 or 0.10. The thin foil samples were examined in an electron microscope with an x-ray spectrometer.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  11. Effects of phase transformation on the microstructures and magnetostriction of Fe-Ga and Fe-Ga-Zn ferromagnetic shape memory alloys

    SciTech Connect

    Lin, Yin-Chih Lin, Chien-Feng

    2015-05-07

    The phase transformation and magnetostriction of bulk Fe{sub 73}Ga{sub 27} and Fe{sub 73}Ga{sub 18}Zn{sub 9} (at. %) ferromagnetic shape memory alloys (FSMs) were investigated by transmission electron microscopy (TEM), x-ray diffraction (XRD), and a magnetostrictive-meter setup. For the Fe{sub 73}Ga{sub 27} FSM alloy solution treated at 1100 °C for 4 h and quenched in ice brine, the antiphase boundary segments of the D0{sub 3} domain were observed in the A2 (disordered) matrix, and the Fe{sub 73}Ga{sub 27} FSM alloy had an optimal magnetostriction (λ{sub ‖}{sup s }= 71 × 10{sup −6} and λ{sub ⊥}{sup s }= −31 × 10{sup −6}). In Fe{sub 73}Ga{sub 27} FSM alloy as-quenched, aged at 700 °C for 24 h, and furnace cooled, D0{sub 3} nanoclusters underwent phase transformation to an intermediate tetragonal phase (i.e., L1{sub 0}-like martensite) via Bain distortion, and finally L1{sub 2} (Fe{sub 3}Ga) structures precipitated, as observed by TEM and XRD. The L1{sub 0}-like martensite and L1{sub 2} phases in the aged Fe{sub 73}Ga{sub 27} FSM alloy drastically decreased the magnetostriction from positive to negative (λ{sub ‖}{sup s }= −20 × 10{sup −6} and λ{sub ⊥}{sup s }= −8 × 10{sup −6}). However, in Fe{sub 73}Ga{sub 18}Zn{sub 9} FSM alloy as-quenched and aged, the phase transformation of D0{sub 3} to an intermediate tetragonal martensite phase and precipitation of L1{sub 2} structures were not found. The results indicate that the aged Fe{sub 73}Ga{sub 18}Zn{sub 9} FSM alloy maintained stable magnetostriction (λ{sub ‖}{sup s }= 36 × 10{sup −6} and λ{sub ⊥}{sup s }= −31 × 10{sup −6}). Adding Zn can improve the ferromagnetic shape memory effect of aged Fe{sub 73}Ga{sub 18}Zn{sub 9} alloy, which may be useful in application of the alloy in high temperature environments.

  12. Segregation, precipitation, and α -α' phase separation in Fe-Cr alloys

    NASA Astrophysics Data System (ADS)

    Kuronen, A.; Granroth, S.; Heinonen, M. H.; Perälä, R. E.; Kilpi, T.; Laukkanen, P.; Lâng, J.; Dahl, J.; Punkkinen, M. P. J.; Kokko, K.; Ropo, M.; Johansson, B.; Vitos, L.

    2015-12-01

    Iron-chromium alloys, the base components of various stainless steel grades, have numerous technologically and scientifically interesting properties. However, these features are not yet sufficiently understood to allow their full exploitation in technological applications. In this work, we investigate segregation, precipitation, and phase separation in Fe-Cr systems analyzing the physical mechanisms behind the observed phenomena. To get a comprehensive picture of Fe-Cr alloys as a function of composition, temperature, and time the present investigation combines Monte Carlo simulations using semiempirical interatomic potential, first-principles total energy calculations, and experimental spectroscopy. In order to obtain a general picture of the relation of the atomic interactions and properties of Fe-Cr alloys in bulk, surface, and interface regions several complementary methods have to be used. Using the exact muffin-tin orbitals method with the coherent potential approximation (CPA-EMTO) the effective chemical potential as a function of Cr content (0-15 at. % Cr) is calculated for a surface, second atomic layer, and bulk. At ˜10 at. % Cr in the alloy the reversal of the driving force of a Cr atom to occupy either bulk or surface sites is obtained. The Cr-containing surfaces are expected when the Cr content exceeds ˜10 at. %. The second atomic layer forms about a 0.3 eV barrier for the migration of Cr atoms between the bulk and surface atomic layer. To get information on Fe-Cr in larger scales we use semiempirical methods. However, for Cr concentration regions less than 10 at. %, the ab initio (CPA-EMTO) result of the important role of the second atomic layer to the surface is not reproducible from the large-scale Monte Carlo molecular dynamics (MCMD) simulation. On the other hand, for the nominal concentration of Cr larger than 10 at. % the MCMD simulations show the precipitation of Cr into isolated pockets in bulk Fe-Cr and the existence of the upper limit of

  13. Effect of Zr Addition on the Magnetization Reversal Behavior for α-Fe/Pr2Fe14B Nanocomposite Alloys

    NASA Astrophysics Data System (ADS)

    Pan, Minxiang; Zhang, Pengyue; Ge, Hongliang; Hong, Zhanglian; Wu, Qiong; Jiao, Zhiwei; Yang, Hangfu

    2011-09-01

    The microstructure and magnetic properties of the Zr-doped α-Fe/Pr2Fe14B nanocomposite magnets prepared by melt-spinning method have been studied by X-ray diffraction (XRD), vibrating sample magnetometer (VSM) and superconducting quantum interference device (SQUID) measurements. The magnetization reversal behavior during the recoil processes of nanocomposite alloys has been investigated by analyzing the hysteresis curves and recoil loops of demagnetization curves. An enhanced magnetic properties has been obtained by the addition of 1 at. % Zr in α-Fe/Pr2Fe14B alloys, where the coercivity Hc increases from 470.7 to 793.2 kA/m, the maximum energy product (BH)max from 66.8 to 90.8 kJ/m3, the remanence ratio Mr/Ms from 0.74 to 0.77. The recoil loop results show that the maximum value of the integrated recoil loop area for 1 at. % Zr doped sample is quietly low of 1.87×10-3, only 1/2 for the Zr-free and 1/3 for 5 at. % Zr doped samples respectively. This result indicates that the 1 at. % Zr doped sample has a lower energy loss, resulting from a low recoverable portion of the magnetization remaining as long as the applied reversal field is below the coercivity Hc. This study provides a promising guideline for the future fabrication of low-energy-loss nanocomposite magnets for electric machines and generators.

  14. Strain rate sensitivity of nanoindentation creep in an AlCoCrFeNi high-entropy alloy

    NASA Astrophysics Data System (ADS)

    Jiao, Z. M.; Wang, Z. H.; Wu, R. F.; Qiao, J. W.

    2016-09-01

    Creep behaviors of an AlCoCrFeNi high-entropy alloy with the body-centered cubic structure were investigated by nanoindentation. The enhanced strain gradient induced by higher strain rate leads to decreased strain rate sensitivity during creep process. The present alloy exhibits excellent creep resistance, mainly due to its large entropy of mixing and highly distorted lattice structure.

  15. Effects of Be and Fe additions on the microstructure and mechanical properties of A357.0 alloys

    NASA Astrophysics Data System (ADS)

    Tan, Yen-Hung; Lee, Sheng-Long; Lin, Yu-Lom

    1995-05-01

    A357 hypoeutectic alloy is a heat-treatable Al-Si-Mg system with a nominal composition of Al-7 pct Si and about 0.6 pct Mg have widespreaded applications, especially in the aerospace and automotive industries. The purpose of this study was to determine the influences of Be and Fe content on the microstructure and mechanical properties of A357.0 alloys. Distinct morphologies were discerned between Be-containing and Be-free alloys. The Be-free alloys contain larger amount of iron-bearing phases with Mg than in Be-containing alloys. The addition of Be can change the plateletlike structure of iron-bearing phases to a comparatively harmless round nodular form. Also, the amounts of iron-rich phases are significantly lower and the silicon particles are smaller and more spherical in the Be-containing alloys. Small amounts of Be in A357.0 caused significant increases in the precipitation kinetics of Mg2Si. It was found that the addition of Be lowers the ternary and binary eutectic melting point. The amount of Mg available to form the major strengthening phase Mg2Si is increased promoting the tensile strength of A357.0 casting. The tensile properties were improved with decreasing Fe content and the addition of Be. The effect is more apparent in the higher Fe alloys than that in the lower Fe alloys.

  16. Densification behavior, nanocrystallization, and mechanical properties of spark plasma sintered Fe-based bulk amorphous alloys

    NASA Astrophysics Data System (ADS)

    Singh, Ashish Kumar

    Fe-based amorphous alloys are gaining increasing attention due to their exceptional wear and corrosion resistance for potential structural applications. Two major challenges that are hindering the commercialization of these amorphous alloys are difficulty in processing of bulk shapes (diameter > 10 mm) and lack of ductility. Spark plasma sintering (SPS) is evolving as a promising technique for processing bulk shapes of amorphous and nanocrystalline materials. The objective of this work is to investigate densification behavior, nanocrystallization, and mechanical properties of SPS sintered Fe-based amorphous alloys of composition Fe48Cr15Mo14Y2C15B6. SPS processing was performed in three distinct temperature ranges of amorphous alloys: (a) below glass transition temperature (Tg), (b) between Tg and crystallization temperature (Tx), and (c) above Tx. Punch displacement data obtained during SPS sintering was correlated with the SPS processing parameters such as temperature, pressure, and sintering time. Powder rearrangement, plastic deformation below T g, and viscous flow of the material between Tg and Tx were observed as the main densification stages during SPS sintering. Micro-scale temperature distributions at the point of contact and macro-scale temperature distribution throughout the sample during SPS of amorphous alloys were modeled. The bulk amorphous alloys are expected to undergo structural relaxation and nanocrystallization during SPS sintering. X-ray diffraction (XRD), small angle neutron scattering (SANS), and transmission electron microscopy (TEM) was performed to investigate the evolution of nanocrystallites in SPS sintered Fe-based bulk amorphous alloys. The SANS analysis showed significant scattering for the samples sintered in the supercooled region indicating local structural and compositional changes with the profuse nucleation of nano-clusters (~4 nm). Compression tests and microhardness were performed on the samples sintered at different

  17. Nucleation of Cr precipitates in Fe-Cr alloy under irradiation

    SciTech Connect

    Dai, Y. Y.; Ao, L.; Sun, Qing- Qiang; Yang, L.; Nie, JL; Peng, SM; Long, XG; Zhou, X. S.; Zu, Xiaotao; Liu, L.; Sun, Xin; Terentyev, Dimtry; Gao, Fei

    2015-04-01

    The nucleation of Cr precipitates induced by overlapping of displacement cascades in Fe-Cr alloys has been investigated using the combination of molecular dynamics (MD) and Metropolis Monte Carlo (MMC) simulations. The results reveal that the number of Frenkel pairs increases with the increasing of overlapped cascades. Overlapping cascades could promote the formation of Cr precipitates in Fe-Cr alloys, as analyzed using short range order (SRO) parameters to quantify the degree of ordering and clustering of Cr atoms. In addition, the simulations using MMC approach show that the presence of small Cr clusters and vacancy clusters formed within cascade overlapped region enhance the nucleation of Cr precipitates, leading to the formation of large Cr dilute precipitates.

  18. Tensile behavior of Fe-40Al alloys with B and Zr additions

    NASA Technical Reports Server (NTRS)

    Gaydosh, D. J.; Nathal, M. V.

    1986-01-01

    Both Fe-40Al and Fe-40Al-0.1Zr with and without B were produced by the hot extrusion of powdered metal. Tensile properties were determined from room temperature to 1100 K in air. All of the materials possessed some ductility at room temperature, and addition of B caused an increase in ductility and a change in fracture mode from intergranular to transgranular cleavage. At high temperatures, failure was caused primarily by the formation of grain boundary cavities in all of the alloys. The effect of Zr addition was unclear because of the complexity of the various microstructures. Comparison of air and vacuum testing at high temperatures revealed that an apparent oxidation assisted mechanism reduced high temperature ductility in these alloys, especially at 900 K.

  19. Electronic structure and magnetic properties of disordered Co{sub 2}FeAl Heusler alloy

    SciTech Connect

    Jain, Vishal Jain, Vivek Sudheesh, V. D. Lakshmi, N. Venugopalan, K.

    2014-04-24

    The effects of disorder on the magnetic properties of Co{sub 2}FeAl alloy are reported. X-ray diffraction exhibit A2-type disordered structure. Room temperature Mössbauer studies show the presence of two sextets with hyperfine field values of 31T and 30T along with a nonmagnetic singlet. The electronic structure of ordered and disordered Co{sub 2}FeAl alloys, investigated by means of the KKR Green's-function method shows that the magnetic moment of the ordered structure is 5.08μ{sub B} and is 5.10μ{sub B} when disordered. However, a much higher magnetic moment of 5.74μ{sub B} is observed experimentally.

  20. Premartensite transition in Ni{sub 2}FeGa Heusler alloy

    SciTech Connect

    Nath, Hrusikesh; Phanikumar, G.

    2015-04-15

    Martensitic phase transformation of Ni{sub 2}FeGa Heusler alloy was studied by differential scanning calorimetry. Atomic ordering induced in the austenite structure by quenching from high temperature plays a significant role on martensitic phase transformation. Higher magnetization and larger magneto-crystalline anisotropy of martensite phase than that of austenite phase are noticed. Tweed contrast regions observed in the transmission electron microscopy were correlated to premartensite phenomena. A shift in premartensitic transition temperature prior to martensitic transformation as measured by differential scanning calorimetry is being reported for the first time in this system. - Highlights: • Atomic ordering influences martensitic transformation in Ni{sub 2}FeGa Heusler alloy. • Observation of tweed contrast in TEM was correlated to premartensite phenomena. • For the first time the shift in premartensite peak was observed in DSC.

  1. Nickel recovery from electronic waste II electrodeposition of Ni and Ni-Fe alloys from diluted sulfate solutions.

    PubMed

    Robotin, B; Ispas, A; Coman, V; Bund, A; Ilea, P

    2013-11-01

    This study focuses on the electrodeposition of Ni and Ni-Fe alloys from synthetic solutions similar to those obtained by the dissolution of electron gun (an electrical component of cathode ray tubes) waste. The influence of various parameters (pH, electrolyte composition, Ni(2+)/Fe(2+) ratio, current density) on the electrodeposition process was investigated. Scanning electron microscopy (SEM) and X-ray fluorescence analysis (XRFA) were used to provide information about the obtained deposits' thickness, morphology, and elemental composition. By controlling the experimental parameters, the composition of the Ni-Fe alloys can be tailored towards specific applications. Complementarily, the differences in the nucleation mechanisms for Ni, Fe and Ni-Fe deposition from sulfate solutions have been evaluated and discussed using cyclic voltammetry and potential step chronoamperometry. The obtained results suggest a progressive nucleation mechanism for Ni, while for Fe and Ni-Fe, the obtained data points are best fitted to an instantaneous nucleation model.

  2. Temperature dependence of the magnetostriction in polycrystalline PrFe{sub 1.9} and TbFe{sub 2} alloys: Experiment and theory

    SciTech Connect

    Tang, Y. M.; Chen, L. Y.; Huang, H. F.; Xia, W. B.; Zhang, S. Y.; Wei, J.; Tang, S. L. Du, Y. W.; Zhang, L.

    2014-05-07

    A remarkable magnetostriction λ{sub 111} as large as 6700 ppm was found at 70 K in PrFe{sub 1.9} alloy. This value is even larger than the theoretical maximum of 5600 ppm estimated by the Steven's equivalent operator method. The temperature dependence of λ{sub 111} for PrFe{sub 1.9} and TbFe{sub 2} alloys follows well with the single-ion theory rule, which yields giant estimated λ{sub 111} values of about 8000 and 4200 ppm for PrFe{sub 1.9} and TbFe{sub 2} alloys, respectively, at 0 K. The easy magnetization direction of PrFe{sub 1.9} changes from [111] to [100] as temperature decreases, which leads to the abnormal decrease of the magnetostriction λ. The rare earth sublattice moment increases sharply in PrFe{sub 1.9} alloy with decreasing temperature, resulting in the remarkably largest estimated value of λ{sub 111} at 0 K according to the single-ion theory.

  3. Effect of annealing on structural and magnetic properties of Al substituted nanocrystalline Fe-Si-Co alloy powders

    NASA Astrophysics Data System (ADS)

    Shyni, P. C.; Alagarsamy, Perumal

    2016-11-01

    We report effects of annealing and substitution of Al on structural and magnetic properties of nanocrystalline Fe80-xAlxCo5Si15 (x=0-10) alloy powders prepared by mechanical alloying process using a planetary ball mill technique. All the as-milled powders exhibit non-equilibrium solid solution of α-Fe (Si,Co,Al). While the average size of crystals decreases, the lattice constant and dislocation density increase with increasing Al content. On the other hand, the annealing at elevated temperatures increases the size of the crystals and decreases the dislocation density. In addition, the substitution of Al in FeAlCoSi alloy powders controls growth of the crystals during annealing. As a result, coercivity (HC) of the annealed powders decreases considerably. However, the variation in HC is dominated by the dislocation density. Fe70Al10Co5Si15 powder annealed at 900 °C exhibits improved magnetic properties (HC~14 Oe and moderate magnetization of 160 emu/g) due to optimum nanocrystalline microstructure with fine nanocrystals (~18 nm) and reduced dislocation density. Systematic correlations observed between structural and magnetic properties for Fe80-xAlxCo5Si15 powders reveal a promising approach to control the growth of the crystals in the annealed nanocrystalline alloys and to improve the magnetic properties of mechanically alloyed Fe-Si based nanocrystalline alloys by adding suitable substituting elements.

  4. A combined APT and SANS investigation of α' phase precipitation in neutron-irradiated model FeCrAl alloys

    DOE PAGES

    Briggs, Samuel A.; Edmondson, Philip D.; Littrell, Kenneth C.; ...

    2017-03-01

    Here, FeCrAl alloys are currently under consideration for accident-tolerant fuel cladding applications in light water reactors owing to their superior high-temperature oxidation and corrosion resistance compared to the Zr-based alloys currently employed. However, their performance could be limited by precipitation of a Cr-rich α' phase that tends to embrittle high-Cr ferritic Fe-based alloys. In this study, four FeCrAl model alloys with 10–18 at.% Cr and 5.8–9.3 at.% Al were neutron-irradiated to nominal damage doses up to 7.0 displacements per atom at a target temperature of 320 °C. Small angle neutron scattering techniques were coupled with atom probe tomography to assessmore » the composition and morphology of the resulting α' precipitates. It was demonstrated that Al additions partially destabilize the α' phase, generally resulting in precipitates with lower Cr contents when compared with binary Fe-Cr systems. The precipitate morphology evolution with dose exhibited a transient coarsening regime akin to previously observed behavior in aged Fe-Cr alloys. Similar behavior to predictions of the LSW/UOKV models suggests that α' precipitation in irradiated FeCrAl is a diffusion-limited process with coarsening mechanisms similar to those in thermally aged high-Cr ferritic alloys.« less

  5. Investigating enhanced mechanical properties in dual-phase Fe-Ga-Tb alloys.

    PubMed

    Meng, Chongzheng; Wang, Hui; Wu, Yuye; Liu, Jinghua; Jiang, Chengbao

    2016-10-03

    Dual-phase (Fe83Ga17)100-xTbx alloys with 0 ≤ x ≤ 1 were synthesized by arc melting and homogenization treatment. The microstructures and the corresponding mechanical properties were systematically investigated. The chemical composition of the body centered cubic matrix is Fe83Ga17. The monoclinic second phase was composed of meltable precipitates with approximate composition Fe57Ga33Tb10. The nano-hardness of matrix and precipitates were 2.55 ± 0.17 GPa and 6.81 ± 1.03 GPa, respectively. Both the ultimate tensile strength (UTS) and fracture strain (ε) of the alloys were improved by the precipitates for x ≤ 0.2 alloys, but the strain decreases significantly at higher values of x. As potential structural-functional materials, the best mechanical properties obtained were a UTS of 595 ± 10 MPa and an ε of 3.5 ± 0.1%, four-fold and seven-fold improvements compared with the un-doped alloy. The mechanism for these anomalous changes of mechanical properties was attributed to the dispersed precipitates and semi-coherent interfaces, which serve as strong obstacles to dislocation motion and reduce the stress concentration at the grain boundaries. A sizeable improvement of magnetostriction induced by the precipitates in the range 0 ≤ x ≤ 0.2 was discovered and an optimal value of 150 ± 5 ppm is found, over three times higher than that of the un-doped alloy.

  6. Investigating enhanced mechanical properties in dual-phase Fe-Ga-Tb alloys

    PubMed Central

    Meng, Chongzheng; Wang, Hui; Wu, Yuye; Liu, Jinghua; Jiang, Chengbao

    2016-01-01

    Dual-phase (Fe83Ga17)100−xTbx alloys with 0 ≤ x ≤ 1 were synthesized by arc melting and homogenization treatment. The microstructures and the corresponding mechanical properties were systematically investigated. The chemical composition of the body centered cubic matrix is Fe83Ga17. The monoclinic second phase was composed of meltable precipitates with approximate composition Fe57Ga33Tb10. The nano-hardness of matrix and precipitates were 2.55 ± 0.17 GPa and 6.81 ± 1.03 GPa, respectively. Both the ultimate tensile strength (UTS) and fracture strain (ε) of the alloys were improved by the precipitates for x ≤ 0.2 alloys, but the strain decreases significantly at higher values of x. As potential structural-functional materials, the best mechanical properties obtained were a UTS of 595 ± 10 MPa and an ε of 3.5 ± 0.1%, four-fold and seven-fold improvements compared with the un-doped alloy. The mechanism for these anomalous changes of mechanical properties was attributed to the dispersed precipitates and semi-coherent interfaces, which serve as strong obstacles to dislocation motion and reduce the stress concentration at the grain boundaries. A sizeable improvement of magnetostriction induced by the precipitates in the range 0 ≤ x ≤ 0.2 was discovered and an optimal value of 150 ± 5 ppm is found, over three times higher than that of the un-doped alloy. PMID:27694839

  7. Investigating enhanced mechanical properties in dual-phase Fe-Ga-Tb alloys

    NASA Astrophysics Data System (ADS)

    Meng, Chongzheng; Wang, Hui; Wu, Yuye; Liu, Jinghua; Jiang, Chengbao

    2016-10-01

    Dual-phase (Fe83Ga17)100‑xTbx alloys with 0 ≤ x ≤ 1 were synthesized by arc melting and homogenization treatment. The microstructures and the corresponding mechanical properties were systematically investigated. The chemical composition of the body centered cubic matrix is Fe83Ga17. The monoclinic second phase was composed of meltable precipitates with approximate composition Fe57Ga33Tb10. The nano-hardness of matrix and precipitates were 2.55 ± 0.17 GPa and 6.81 ± 1.03 GPa, respectively. Both the ultimate tensile strength (UTS) and fracture strain (ε) of the alloys were improved by the precipitates for x ≤ 0.2 alloys, but the strain decreases significantly at higher values of x. As potential structural-functional materials, the best mechanical properties obtained were a UTS of 595 ± 10 MPa and an ε of 3.5 ± 0.1%, four-fold and seven-fold improvements compared with the un-doped alloy. The mechanism for these anomalous changes of mechanical properties was attributed to the dispersed precipitates and semi-coherent interfaces, which serve as strong obstacles to dislocation motion and reduce the stress concentration at the grain boundaries. A sizeable improvement of magnetostriction induced by the precipitates in the range 0 ≤ x ≤ 0.2 was discovered and an optimal value of 150 ± 5 ppm is found, over three times higher than that of the un-doped alloy.

  8. Ab initio studies of Co2FeAl1-xSix Heusler alloys

    NASA Astrophysics Data System (ADS)

    Szwacki, N. Gonzalez; Majewski, Jacek A.

    2016-07-01

    We present results of extensive theoretical studies of Co2FeAl1-xSix Heusler alloys, which have been performed in the framework of density functional theory employing the all-electron full-potential linearized augmented plane-wave scheme. It is shown that the Si-rich alloys are more resistive to structural disorder and as a consequence Si stabilizes the L21 structure. Si alloying changes position of the Fermi level, pushing it into the gap of the minority spin-band. It is also shown that the hyperfine field on Co nuclei increases with the Si concentration, and this increase originates mostly from the changes in the electronic density of the valence electrons.

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

    NASA Astrophysics Data System (ADS)

    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.

  10. Cryo-quenched Fe-Ni-Cr alloy single crystals: A new decorative steel

    SciTech Connect

    Boatner, Lynn A.; Kolopus, James A.; Lavrik, Nicolay V.; Phani, P. Sudharshan

    2016-08-31

    In this paper, a decorative steel is described that is formed by a process that is unlike that of the fabrication methods utilized in making the original Damascus steels over 2000 years ago. The decorative aspect of the steel arises from a three-dimensional surface pattern that results from cryogenically quenching polished austenitic alloy single crystals into the martensitic phase that is present below 190 K. No forging operations are involved – the mechanism is entirely based on the metallurgical phase properties of the ternary alloy. The symmetry of the decorative pattern is determined and controlled by the crystallographic orientation and symmetry of the 70%Fe,15%Ni,15%Cr alloy single crystals. Finally, in addition to using “cuts” made along principal crystallographic surface directions, an effectively infinite number of other random-orientation “cuts” can be utilized to produce decorative patterns where each pattern is unique after the austenitic-to-martensitic phase transformation.

  11. Mössbauer effect studies of disordered Fe-Ru alloys

    NASA Astrophysics Data System (ADS)

    Pöttker, W. E.; Paduani, C.; Ardisson, J. D.; Ioshida, M. I.

    2004-09-01

    The bcc and hcp phases of disordered Fe100-xRux alloys are investigated with several experimental techniques to study the composition dependence of the magnetic properties in these structures. With an appropriate annealing the prepared samples are single phase. The iron rich alloys are ferromagnetic at room temperature with the bcc structure. However, an antiferromagnetic coupling is introduced with the addition of ruthenium. Above 30 at% Ru a paramagnetic behavior is observed at 300 K and 77 K, where the alloys have the hcp structure. In the ferromagnetic phase the Curie temperature decreases steadly with the increase of the ruthenium concentration. In the paramagnetic hcp phase the mean volume per atom is al-most triplicated as compared to the bcc phase, which brings out the breakdown of the magnetization and the collapse of the hyperfine field at the iron sites simultaneously with the crystallographic phase transition.

  12. Evaluation of the Mechanical Properties of Electroslag Refined Fe-12Ni Alloys

    NASA Technical Reports Server (NTRS)

    Bhat, G. K.

    1978-01-01

    Three Fe-12Ni alloys, individually alloyed with small amounts of V, Ti, and Al, were manufactured through different melting techniques, with special emphasis on electroslag remelting, in order to achieve different levels of metal purity and associated costs. The relative effectiveness of these melting techniques was evaluated from tensile and slow bend fracture toughness behavior at 25 C and -196 C after tempering the test specimens at various temperatures. The best melting procedure was vacuum induction melting (VIM) with or without electroslag remelting (ESR). VIM+ESR is the recommended procedure since ESR provides increased yield of plate product, a reduction of overall manufacturing costs and, depending on the alloy composition, improved tensile and fracture toughness properties.

  13. Letter Report Documenting Progress of Second Generation ATF FeCrAl Alloy Fabrication

    SciTech Connect

    Yamamoto, Y.; Yang, Y.; Field, K. G.; Terrani, K.; Pint, B. A.; Snead, L. L.

    2014-06-10

    Development of the 2nd generation ATF FeCrAl alloy has been initiated, and a candidate alloy was selected for trial tube fabrication through hot-extrusion and gun-drilling processes. Four alloys based on Fe-13Cr-4.5Al-0.15Y in weight percent were newly cast with minor alloying additions of Mo, Si, Nb, and C to promote solid-solution and second-phase precipitate strengthening. The alloy compositions were selected with guidance from computational thermodynamic tools. The lab-scale heats of ~ 600g were arc-melted and drop-cast, homogenized, hot-forged and -rolled, and then annealed producing plate shape samples. An alloy with Mo and Nb additions (C35MN) processed at 800°C exhibits very fine sub-grain structure with the sub-grain size of 1-3μm which exhibited more than 25% better yield and tensile strengths together with decent ductility compared to the other FeCrAl alloys at room temperature. It was found that the Nb addition was key to improving thermal stability of the fine sub-grain structure. Optimally, grains of less than 30 microns are desired, with grains up to and order of magnitude in desired produced through Nb addition. Scale-up effort of the C35MN alloy was made in collaboration with a commercial cast company who has a capability of vacuum induction melting. A 39lb columnar ingot with ~81mm diameter and ~305mm height (with hot-top) was commercially cast, homogenized, hot-extruded, and annealed providing 10mm-diameter bar-shape samples with the fine sub-grain structure. This commercial heat proved consistent with materials produced at ORNL at the lab-scale. Tubes and end caps were machined from the bar sample and provided to another work package for the ATF-1 irradiation campaign in the milestone M3FT-14OR0202251.

  14. Effect of grain orientation on ductility in a nanocrystalline Ni-Fe alloy

    SciTech Connect

    Li, Hongqi; Misra, Amit; Liaw, Peter K; Choo, Hahn

    2008-01-01

    The influence of columnar grain geometry on mechanical property was studied in an electrodeposited nanocrystalline Ni-Fe alloy. The compressive results show that the strength is independent of grain orientation. However, the plastic strain increased remarkably when the loading axis is parallel to the direction of grain columns, which is due to the enhanced grain boundary and dislocation activities. The significance of the current study is that a new strategy was developed to improve the ductility of nanocrystalline materials.

  15. Mössbauer Diffraction Spectra in Partially Ordered Ni3Fe Alloy

    NASA Astrophysics Data System (ADS)

    Nakai, Yutaka; Ooi, Yoshiharu; Kunitomi, Nobuhiko

    1988-09-01

    The Bragg reflections due to nuclear resonant scattering (Mössbauer scattering) have been observed in a partially ordered Ni3Fe alloy. The system has a wide distribution of the resonant energy for Mössbauer γ-rays due to the variety of environmental conditions. The observed spectra are well reproduced by the simple theoretical formulae as a function of the Doppler velocity.

  16. Orientation magnetic phase transition induced by shock loading of the Fe-Cr-Co alloy

    NASA Astrophysics Data System (ADS)

    Sud'enkov, Yu. V.; Sarnatskii, V. M.; Smirnov, I. V.

    2017-02-01

    The strength characteristics of Fe-Cr-Co alloys have been investigated under high-strain-rate deformation of samples. It has been found that, under shock-wave loading, a significant remanent magnetization appears in the samples and their fragments due to the orientation magnetic phase transition. The threshold pressures of the magnetic phase transition have been determined, and the distribution of the remanent magnetization in the samples has been analyzed.

  17. Kinetics and mechanism of the oxidation process of two-component Fe-Al alloys

    NASA Technical Reports Server (NTRS)

    Przewlocka, H.; Siedlecka, J.

    1982-01-01

    The oxidation process of two-component Fe-Al alloys containing up to 7.2% Al and from 18 to 30% Al was studied. Kinetic measurements were conducted using the isothermal gravimetric method in the range of 1073-1223 K and 1073-1373 K for 50 hours. The methods used in studies of the mechanism of oxidation included: X-ray microanalysis, X-ray structural analysis, metallographic analysis and marker tests.

  18. Overview of the multifaceted activities towards development and deployment of nuclear-grade FeCrAl Alloys

    SciTech Connect

    Field, Kevin G; Yamamoto, Yukinori; Pint, Bruce A; Terrani, Kurt A

    2016-01-01

    A large effort is underway under the leadership of US DOE Fuel Cycle R&D program to develop advanced FeCrAl alloys as accident tolerant fuel (ATF) cladding to replace Zr-based alloys in light water reactors. The primary motivation is the excellent oxidation resistance of these alloys in high-temperature steam environments right up to their melting point (roughly three orders of magnitude slower oxidation kinetics than zirconium). A multifaceted effort is ongoing to rapidly advance FeCrAl alloys as a mature ATF concept. The activities span the broad spectrum of alloy development, environmental testing (high-temperature high-pressure water and elevated temperature steam), detailed mechanical characterization, material property database development, neutron irradiation, thin tube production, and multiple integral fuel test campaigns. Instead of off-the-shelf commercial alloys that might not prove optimal for the LWR fuel cladding application, a large amount of effort has been placed on the alloy development to identify the most optimum composition and microstructure for this application. The development program is targeting a cladding that offers performance comparable to or better than modern Zr-based alloys under normal operating and off-normal conditions. This paper provides a comprehensive overview of the systematic effort to advance nuclear-grade FeCrAl alloys as an ATF cladding in commercial LWRs.

  19. Study of Critical Behavior in Amorphous Fe85Sn5Zr10 Alloy Ribbon

    NASA Astrophysics Data System (ADS)

    Han, L. A.; Hua, X. H.; Zhu, H. Z.; Yang, J.; Yang, H. P.; Yan, Z. X.; Zhang, T.

    2017-02-01

    We have investigated the critical behavior in amorphous Fe85Sn5Zr10 alloy ribbon prepared using a single-roller melt-spinning method. This alloy shows a second-order magnetic transition from paramagnetic to ferromagnetic (FM) state at the Curie temperature T C (˜306 K). To obtain more information on the features of the magnetic transition, a detailed critical exponent study was carried out using isothermal magnetization M ( H, T) data in the vicinity of the T C. Modified Arrott plot, Kouvel-Fisher plot, Widom's scaling relation and critical isotherm analysis techniques were used to investigate the critical behavior of this alloy system around its phase transition point. The values of critical exponents determined using the above methods are self-consistent. The estimated critical exponents are fairly close to the theoretical prediction of the three-dimensional (3D) Heisenberg model, implying that short-range FM interactions dominate the critical behavior in amorphous Fe85Sn5Zr10 alloy ribbon.

  20. Chromium Extraction via Chemical Processing of Fe-Cr Alloys Fine Powder with High Carbon Content

    NASA Astrophysics Data System (ADS)

    Torres, D. M.; Navarro, R. C. S.; Souza, R. F. M.; Brocchi, E. A.

    2017-03-01

    Ferrous alloys are important raw materials for special steel production. In this context, alloys from the Fe-Cr system, with typical Cr weight fraction ranging from 0.45 to 0.95, are prominent, particularly for the stainless steel industry. During the process in which these alloys are obtained, there is considerable production of fine powder, which could be reused after suitable chemical treatment, for example, through coupling pyrometallurgical and hydrometallurgical processes. In the present study, the extraction of chromium from fine powder generated during the production of a Fe-Cr alloy with high C content was investigated. Roasting reactions were performed at 1073 K, 1173 K, and 1273 K (800 °C, 900 °C, and 1000 °C) with 300 pct (w/w) excess NaOH in an oxidizing atmosphere (air), followed by solubilization in deionized water, selective precipitation, and subsequent calcination at 1173 K (900 °C) in order to convert the obtained chromium hydroxide to Cr2O3. The maximum achieved Cr recovery was around 86 pct, suggesting that the proposed chemical route was satisfactory regarding the extraction of the chromium initially present. Moreover, after X-ray diffraction analysis, the final produced oxide has proven to be pure Cr2O3 with a mean crystallite size of 200 nm.

  1. Rapid Solidification Behavior of Fe-Cr-Mn-Mo-Si-C Alloys

    NASA Astrophysics Data System (ADS)

    Ranganathan, Sathees; Makaya, Advenit; Fredriksson, Hasse; Savage, Steven

    2007-12-01

    The rapid solidification behavior of alloys in the Fe-Cr-Mn-Mo-Si-C system was investigated for different compositions and cooling rates. The C content was varied and alloying additions of Mo and B were studied with respect to their effect on the microstructure. The alloys were cast as either melt-spun ribbons or as 1-mm-thick plates after levitation or as rods 2 to 4 mm in diameter by injection into copper molds. A homogeneous single-phase structure was obtained for the alloy of composition 72.8Fe-8Cr-6Mn-5Si-5Mo-3.2C (wt pct), for a sample diameter of 2.85 mm, at a cooling rate of ≈1100 K/s. The single-phase structure was identified as a metastable solid solution, exhibiting the characteristics of the ɛ phase. Upon reheating, decomposition of the single-phase structure into fine bainite plates and secondary carbides was observed between 600 °C and 700 °C. The annealed structure obtained showed high hardness values (>850 HV).

  2. Directional solidification of Al-8 wt. %Fe alloy under high magnetic field gradient

    NASA Astrophysics Data System (ADS)

    Wu, Mingxu; Liu, Tie; Dong, Meng; Sun, Jinmei; Dong, Shulin; Wang, Qiang

    2017-02-01

    We investigated applying a magnetic field (up to 6 T) during directional solidification of a hypereutectic Al-8 wt. %Fe alloy, finding that it dramatically affected the final microstructure. A eutectic area appeared at the top of the samples, and as the magnetic flux density increased, the eutectic area clearly enlarged. In addition, the Al3Fe phase was twisted and fractured, and some phases aggregated and distributed randomly in the samples. We also investigated the volume fraction distribution of the Al3Fe phase, revealing that applying the magnetic field during solidification caused dramatic disorder in the solute and phase distributions. The magnetic force induced by the interaction between the magnetic field gradient and the magnetic materials appeared to be the main reason not only for the occurrence and enlargement of the eutectic area but also for the movement of Fe-enriched zones during directional solidification. Otherwise, the deformation and fracture of the Al3Fe phase, the morphological instability in the interface between the eutectic area and the Al3Fe phase, and the random distribution of the aggregated Al3Fe phase appeared to come from the thermoelectric magnetic force/thermoelectric magnetic convection under the magnetic field.

  3. Precipitation behavior of AlxCoCrFeNi high entropy alloys under ion irradiation

    PubMed Central

    Yang, Tengfei; Xia, Songqin; Liu, Shi; Wang, Chenxu; Liu, Shaoshuai; Fang, Yuan; Zhang, Yong; Xue, Jianming; Yan, Sha; Wang, Yugang

    2016-01-01

    Materials performance is central to the satisfactory operation of current and future nuclear energy systems due to the severe irradiation environment in reactors. Searching for structural materials with excellent irradiation tolerance is crucial for developing the next generation nuclear reactors. Here, we report the irradiation responses of a novel multi-component alloy system, high entropy alloy (HEA) AlxCoCrFeNi (x = 0.1, 0.75 and 1.5), focusing on their precipitation behavior. It is found that the single phase system, Al0.1CoCrFeNi, exhibits a great phase stability against ion irradiation. No precipitate is observed even at the highest fluence. In contrast, numerous coherent precipitates are present in both multi-phase HEAs. Based on the irradiation-induced/enhanced precipitation theory, the excellent structural stability against precipitation of Al0.1CoCrFeNi is attributed to the high configurational entropy and low atomic diffusion, which reduces the thermodynamic driving force and kinetically restrains the formation of precipitate, respectively. For the multiphase HEAs, the phase separations and formation of ordered phases reduce the system configurational entropy, resulting in the similar precipitation behavior with corresponding binary or ternary conventional alloys. This study demonstrates the structural stability of single-phase HEAs under irradiation and provides important implications for searching for HEAs with higher irradiation tolerance. PMID:27562023

  4. Precipitation behavior of AlxCoCrFeNi high entropy alloys under ion irradiation.

    PubMed

    Yang, Tengfei; Xia, Songqin; Liu, Shi; Wang, Chenxu; Liu, Shaoshuai; Fang, Yuan; Zhang, Yong; Xue, Jianming; Yan, Sha; Wang, Yugang

    2016-08-26

    Materials performance is central to the satisfactory operation of current and future nuclear energy systems due to the severe irradiation environment in reactors. Searching for structural materials with excellent irradiation tolerance is crucial for developing the next generation nuclear reactors. Here, we report the irradiation responses of a novel multi-component alloy system, high entropy alloy (HEA) AlxCoCrFeNi (x = 0.1, 0.75 and 1.5), focusing on their precipitation behavior. It is found that the single phase system, Al0.1CoCrFeNi, exhibits a great phase stability against ion irradiation. No precipitate is observed even at the highest fluence. In contrast, numerous coherent precipitates are present in both multi-phase HEAs. Based on the irradiation-induced/enhanced precipitation theory, the excellent structural stability against precipitation of Al0.1CoCrFeNi is attributed to the high configurational entropy and low atomic diffusion, which reduces the thermodynamic driving force and kinetically restrains the formation of precipitate, respectively. For the multiphase HEAs, the phase separations and formation of ordered phases reduce the system configurational entropy, resulting in the similar precipitation behavior with corresponding binary or ternary conventional alloys. This study demonstrates the structural stability of single-phase HEAs under irradiation and provides important implications for searching for HEAs with higher irradiation tolerance.

  5. Precipitation behavior of AlxCoCrFeNi high entropy alloys under ion irradiation

    NASA Astrophysics Data System (ADS)

    Yang, Tengfei; Xia, Songqin; Liu, Shi; Wang, Chenxu; Liu, Shaoshuai; Fang, Yuan; Zhang, Yong; Xue, Jianming; Yan, Sha; Wang, Yugang

    2016-08-01

    Materials performance is central to the satisfactory operation of current and future nuclear energy systems due to the severe irradiation environment in reactors. Searching for structural materials with excellent irradiation tolerance is crucial for developing the next generation nuclear reactors. Here, we report the irradiation responses of a novel multi-component alloy system, high entropy alloy (HEA) AlxCoCrFeNi (x = 0.1, 0.75 and 1.5), focusing on their precipitation behavior. It is found that the single phase system, Al0.1CoCrFeNi, exhibits a great phase stability against ion irradiation. No precipitate is observed even at the highest fluence. In contrast, numerous coherent precipitates are present in both multi-phase HEAs. Based on the irradiation-induced/enhanced precipitation theory, the excellent structural stability against precipitation of Al0.1CoCrFeNi is attributed to the high configurational entropy and low atomic diffusion, which reduces the thermodynamic driving force and kinetically restrains the formation of precipitate, respectively. For the multiphase HEAs, the phase separations and formation of ordered phases reduce the system configurational entropy, resulting in the similar precipitation behavior with corresponding binary or ternary conventional alloys. This study demonstrates the structural stability of single-phase HEAs under irradiation and provides important implications for searching for HEAs with higher irradiation tolerance.

  6. Structure and microwave absorption properties of Pr-Fe-Ni alloys

    NASA Astrophysics Data System (ADS)

    Xiong, Jilei; Pan, Shunkang; Cheng, Lichun; Liu, Xing; Lin, Peihao

    2015-06-01

    The Pr2Fe17-xNix (X=0.0, 0.2, 0.6, 1.0) alloy powders were obtained by arc smelting and high energy ball milling method. The phase structure, morphology and particle size of the powders were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and laser diffraction-based particle size analyzer, respectively. The saturation magnetization and electromagnetic parameters were determined by vibrating sample magnetometer (VSM) and vector network analyzer (VNA), respectively. The results indicate that the lattice parameter and the saturation magnetization of Pr2Fe17-xNix alloys decrease with increasing Ni content. And the minimum absorption peak frequency shifts towards the higher region with increasing Ni content. Compared to the powders without heat treatment, the powders tempered at 100 °C for 2 h have better absorbing properties. The minimum reflectivity peak value of Pr2Fe16Ni alloy reaches about -23.6 dB at 2.72 GHz with the matching thickness of 3.5 mm.

  7. Microstructure and Mechanical Properties of n-irradiated Fe-Cr Model Alloys

    SciTech Connect

    Matijasevic, Milena; Al Mazouzi, Abderrahim

    2008-07-01

    High chromium ( 9-12 wt %) ferritic/martensitic steels are candidate structural materials for future fusion reactors and other advanced systems such as accelerator driven systems (ADS). Their use for these applications requires a careful assessment of their mechanical stability under high energy neutron irradiation and in aggressive environments. In particular, the Cr concentration has been shown to be a key parameter to be optimized in order to guarantee the best corrosion and swelling resistance, together with the least embrittlement. In this work, the characterization of the neutron irradiated Fe-Cr model alloys with different Cr % with respect to microstructure and mechanical tests will be presented. The behavior of Fe-Cr alloys have been studied using tensile tests at different temperature range ( from -160 deg. C to 300 deg. C). Irradiation-induced microstructure changes have been studied by TEM for two different irradiation doses at 300 deg. C. The density and the size distribution of the defects induced have been determined. The tensile test results indicate that Cr content affects the hardening behavior of Fe-Cr binary alloys. Hardening mechanisms are discussed in terms of Orowan type of approach by correlating TEM data to the measured irradiation hardening. (authors)

  8. Microstructural transitions during containerless processing of undercooled Fe-Ni alloys

    NASA Technical Reports Server (NTRS)

    Thoma, D. J.; Perepezko, J. H.

    1992-01-01

    In order to identify the possible hierarchy of microstructural pathways and transitions, a systematic evaluation of the microstructural evolution in undercooled Fe-Ni alloys was performed on uniformly processed samples covering seven orders of magnitude in volume. At appropriate undercooling levels, alternate solidification pathways become thermodynamically possible and metastable product structures can result from the operation of competitive solidification kinetics. For thermal history evaluation, a heat flow analysis was applied and tested with large Fe-Ni alloy particles (1 to 3 mm) to assess undercooling potential. Alloy powders (10 to 150 microns), with large liquid undercoolings, were studied under the same composition and processing conditions to evaluate the solidification kinetics and microstructural evolution, including fcc/bcc phase selection and the thermal stability of a retained metastable bcc phase. The identification of microstructural transitions with controlled variations in sample size and composition during containerless solidification processing was used to develop a microstructure map which delineates regimes of structural evolutions and provides a unified analysis of experimental observations in the Fe-Ni system.

  9. Industrialization of nanocrystalline Fe-Si-B-P-Cu alloys for high magnetic flux density cores

    NASA Astrophysics Data System (ADS)

    Takenaka, Kana; Setyawan, Albertus D.; Sharma, Parmanand; Nishiyama, Nobuyuki; Makino, Akihiro

    2016-03-01

    Nanocrystalline Fe-Si-B-P-Cu alloys exhibit high saturation magnetic flux density (Bs) and extremely low magnetic core loss (W), simultaneously. Low amorphous-forming ability of these alloys hinders their application potential in power transformers and motors. Here we report a solution to this problem. Minor addition of C is found to be effective in increasing the amorphous-forming ability of Fe-Si-B-P-Cu alloys. It allows fabrication of 120 mm wide ribbons (which was limited to less than 40 mm) without noticeable degradation in magnetic properties. The nanocrystalline (Fe85.7Si0.5B9.5P3.5Cu0.8)99C1 ribbons exhibit low coercivity (Hc)~4.5 A/m, high Bs~1.83 T and low W~0.27 W/kg (@ 1.5 T and 50 Hz). Success in fabrication of long (60-100 m) and wide (~120 mm) ribbons, which are made up of low cost elements is promising for mass production of energy efficient high power transformers and motors

  10. Effect of CeO{sub 2} addition on the properties of FeAl based alloy produced by mechanical alloying technique

    SciTech Connect

    Khaerudini, Deni S.; Muljadi,; Sardjono, P.; Tetuko, Anggito P.; Sebayang, P.; Ginting, M.

    2013-09-03

    Iron aluminides based on FeAl is notable for their low materials cost, ease of fabrication and good corrosion, suffixation and oxidation resistance. However, the application based on these unique properties still require the development of Fe-Al based alloy since it shows some drawbacks such as a lack of high temperature strength and low ductility. To improve the mechanical properties of FeAl based alloy, ceria (CeO{sub 2}) will be added to this compound. FeAl based alloy produced by the mechanical alloying (MA) technique. The developed specimens then assessed with respect to oxidation behaviour in high temperature, scale microstructure and hardness. The surface morphologies of the alloy evaluated and observed using scanning electron microscopy (SEM) with an energy dispersive X-ray spectroscopy (EDX). The phase structures of oxide scale formed on them were identified by X-ray diffraction (XRD). The results found that the FeAl intermetallic compound containing CeO{sub 2} 0.5 wt.% is less pores and CeO{sub 2} 1.0 wt.% is more homogen in powder and solid form, higher hardness and increase in their resistance to oxidation behaviour in high temperature compared with another percentage of CeO{sub 2}.

  11. The Effects of the Addition of Dy, Nb, and Ga on Microstructure and Magnetic Properties of Nd2Fe14B/α-Fe Nanocomposite Permanent Magnetic Alloys.

    PubMed

    Ren, Kezhi; Tan, Xiaohua; Li, Heyun; Xu, Hui; Han, Ke

    2017-03-20

    We study the effects of Dy, Nb, and Ga additions on the microstructure and magnetic properties of Nd2Fe14B/α-Fe nanocomposites. Dy, Nb, and Ga additions inhibit the growth of the soft magnetic α-Fe phase. Dy and Nb additions are able to refine the microstructure, whereas Ga addition plays only a minor role in prohibiting crystal growth. The magnetic properties are sensitive to Dy, Nb, and Ga additions. The Dy-containing alloy enhances the intrinsic coercivity of 872 kA/m because Dy partially replaces Nd, forming (Nd, Dy)2Fe14B. Nb addition refines the microstructure, and consequently increases the exchange coupling between magnetic grains. The Nd9.5Fe75.4Co5Zr3B6.5Ga0.6 alloy exhibits the highest remanence (0.92 T) due to Ga addition.

  12. Structural stability of NiCoFeCrAlx high-entropy alloy from ab initio theory

    NASA Astrophysics Data System (ADS)

    Tian, Fuyang; Delczeg, Lorand; Chen, Nanxian; Varga, Lajos Karoly; Shen, Jiang; Vitos, Levente

    2013-08-01

    First-principles alloy theory predicts that at room temperature the paramagnetic NiCoFeCrAlx high entropy alloys adopt the face centered cubic (fcc) structure for x≲0.60 and the body centered cubic (bcc) structure for x≳1.23, with an fcc-bcc duplex region in between the two pure phases. The calculated single- and polycrystal elastic parameters exhibit strong composition and crystal structure dependence. Based on the present theoretical findings, it is concluded that alloys around the equimolar NiCoFeCrAl composition have superior mechanical performance as compared to the single-phase regions.

  13. High field magnetic behavior in Boron doped Fe2VAl Heusler alloys

    NASA Astrophysics Data System (ADS)

    Venkatesh, Ch.; Vasundhara, M.; Srinivas, V.; Rao, V. V.

    2016-11-01

    We have investigated the magnetic behavior of Fe2VAl1-xBx (x=0, 0.03, 0.06 and 0.1) alloys under high temperature and high magnetic field conditions separately. Although, the low temperature DC magnetization data for the alloys above x>0 show clear magnetic transitions, the zero field cooled (ZFC) and field cooled (FC) curves indicate the presence of spin cluster like features. Further, critical exponent (γ) deduced from the initial susceptibility above the Tc, does not agree with standard models derived for 3 dimensional long range magnetic systems. The deviation in γ values are consistent with the short range magnetic nature of these alloys. We further extend the analysis of magnetic behavior by carrying the magnetization measurements at high temperatures and high magnetic fields distinctly. We mainly emphasize the following observations; (i) The magnetic hysteresis loops show sharp upturns at lower fields even at 900 K for all the alloys. (ii) High temperature inverse susceptibility do not overlap until T=900 K, indicating the persistent short range magnetic correlations even at high temperatures. (iii) The Arrott's plot of magnetization data shows spontaneous moment (MS) for the x=0 alloy at higher magnetic fields which is absent at lower fields (<50 kOe), while the Boron doped samples show feeble MS at lower fields. The origin of this short range correlation is due to presence of dilute magnetic heterogeneous phases which are not detected from the X-ray diffraction method.

  14. The Effect of Carbon Additions on the Creep Resistance of Fe-25Al-5Zr Alloy

    NASA Astrophysics Data System (ADS)

    Dobeš, Ferdinand; Vodičková, Věra; Veselý, Jozef; Kratochvíl, Petr

    2016-12-01

    Creep experiments were conducted on Fe-25 at. pct Al-5 at. pct Zr alloy with carbon additions at the temperatures of 973 K and 1173 K (700 °C and 900 °C). The alloys were tested in two different states: (i) cast and (ii) annealed at 1273 K (1000 °C) for 50 hours. Stress exponents and activation energies were estimated. The values of the stress exponent n could be explained by the dislocation motion controlled by climb. The increased values of n in the high-carbon alloy at the temperature of 1173 K (900 °C) can be described by means of the threshold stress concept. The creep resistance at 973 K (700 °C) decreased with the increasing content of carbon. This result is discussed in terms of the ratio of zirconium to carbon in the alloy. An increase of the creep resistance with increasing ratio Zr:C is in agreement with the behavior observed previously in alloys with substantially lower concentrations of zirconium.

  15. Fabrication and Characterization of Novel Fe-Ni Alloy Coated Carbon Fibers for High-Performance Shielding Materials

    NASA Astrophysics Data System (ADS)

    He, Fang; Li, Junjiao; Chen, Liang; Chen, Lixia; Huang, Yuan

    2015-03-01

    Novel Fe-Ni alloy coated carbon fibers (Fe-Ni-CFs) were prepared via two-step electrodeposition with an initial synthesis of Fe coatings on the activated carbon fibers and followed by the co-deposition of Fe and Ni. The effect of annealing treatment on structure and properties of Fe-Ni-CFs was studied through SEM, TEM, XRD and VSM. The results indicated that the Fe-Ni alloy coatings with the thickness of only 0.25 um are highly wrapped on the surface of carbon fibers. The un-annealed coatings showed high saturation magnetization values with 52 dB from 300-1200 MHz, which mainly due to Fe content (18.4 wt.%) of the coatings meets the requirements of high magnetic perm-alloy. The surface quality, crystallinity and conductivity of the Fe-Ni-CFs were obviously improved despite of the reduction of the saturation magnetization resulted from the bigger grains after annealing. Based on the above aspects, annealing at 400∘C was preferred for the Fe-Ni-CFs to obtain good comprehensive performance. Importantly, the Fe-Ni-CFs filled ABS resin composites showed better Electromagnetic Interference shielding effectiveness than the CFs reinforced ABS composites.

  16. Assessment of Post-eutectic Reactions in Multicomponent Al-Si Foundry Alloys Containing Cu, Mg, and Fe

    NASA Astrophysics Data System (ADS)

    Javidani, Mousa; Larouche, Daniel; Grant Chen, X.

    2015-07-01

    Post-eutectic reactions occurring in Al-Si hypoeutectic alloys containing different proportions of Cu, Mg, and Fe were thoroughly investigated in the current study. As-cast microstructures were initially studied by optical and electron microscopy to investigate the microconstituents of each alloy. Differential scanning calorimetry (DSC) was then used to examine the phase transformations occurring during the heating and cooling processes. Thermodynamic calculations were carried out to assess the phase formation under equilibrium and in nonequilibrium conditions. The Q-Al5Cu2Mg8Si6 phase was predicted to precipitate from the liquid phase, either at the same temperature or earlier than the θ-Al2Cu phase depending on the Cu content of the alloy. The AlCuFe-intermetallic, which was hardly observed in the as-cast microstructure, significantly increased after the solution heat treatment in the alloys containing high Cu and Fe contents following a solid-state transformation of the β-Al5FeSi phase. After the solution heat treatment, the AlCuFe-intermetallics were mostly identified with the stoichiometry of the Al7Cu2Fe phase. Thermodynamic calculations and microstructure analysis helped in determining the DSC peak corresponding to the melting temperature of the N-Al7Cu2Fe phase. The effect of Cu content on the formation temperature of π-Al8Mg3FeSi6 is also discussed.

  17. Nanoporous thin films from nanophase-separated hybrids of block copolymer/metal salt

    NASA Astrophysics Data System (ADS)

    Sageshima, Yoshio; Noro, Atsushi; Matsushita, Yushu

    2013-03-01

    Block copolymers self-assemble into periodic nanostructures, i.e. nanophase-separated structures, which can be scaffolds for nano-applications such as nanoporous membranes, nanolithographic masks, photonic crystals, etc. In this study, we report facile preparation to achieve nanoporous thin films from nanophase-separated hybrids comprising polystyrene- b-poly(4-vinylpyridine) (PS-P4VP, Mn = 54k, PDI =1.13, fs = 0.61) and water-soluble iron(III) chloride (FeCl3) , where FeCl3 are incorporated into a P4VP phase via metal-to-ligand coordination. To obtain a nanoporous film, firstly a hybrid thin film was prepared by microtoming. Then, the film was immersed into water to remove metal salts, this simple procedure can produce nanoporous thin film. Morphological observations were conducted by using transmission electron microscopy (TEM). Ordered cylindrical nanopores were observed in the thin film of the water-immersed hybrid, which originally presents cylindrical nanodomains. The nanoporous film was modified by loading another metal salt, samarium(III) nitrate, into nanopores via coordination between the metal salt and P4VP tethered to the pore walls. The structure of the sample after modification was evaluated by TEM and an energy dispersive X-ray spectroscopy.

  18. Thermoelectric Properties of Fe2VAl and Fe2V0.75M0.25Al (M = Mo, Nb, Ta) Alloys: First-Principles Calculations

    NASA Astrophysics Data System (ADS)

    Al-Yamani, H.; Hamad, B.

    2016-02-01

    Ab initio investigations of the structural, electronic, and thermoelectric properties of stoichiometric Fe2VAl full-Heusler alloy and Fe2V0.75M0.25Al (M = Mo, Nb, Ta) nonstoichiometric alloys have been performed using density functional theory on the basis of the full-potential linearized augmented plane wave method with the generalized gradient approximation. The thermoelectric properties are calculated using semiclassical Boltzmann transport theory within the constant-relaxation-time approximation. Fe2VAl, Fe2V0.75Nb0.25Al, and Fe2V0.75Ta0.25Al alloys are found to exhibit a semimetallic behavior, while Fe2V0.75Mo0.25Al acts as a metal. We found that Fe2VAl has a pseudogap of about -0.13 eV, whereas Fe2V0.75Nb0.25Al and Fe2V0.75Ta0.25Al are characterized by a zero energy gap around the Fermi level. Thermoelectric calculations showed that Fe2VAl has both p- and n-type thermoelectric properties, where the p-type thermopower values are found to be higher than those of n-type. The Seebeck coefficient S has maximum values from 20 μV K-1 to 125 μV K-1 and from 19 μV K-1 to 90 μV K-1 in the temperature range of 100 K to 800 K for p- and n-type, respectively. The maximum thermoelectric properties can be obtained at carrier concentration of the order of 1020 cm-3 for p- or n-type doping. Substitution of Nb and Ta atoms enhanced the thermoelectric properties to 150 μV K-1 at 800 K. The optimum concentrations for the three partially substituted alloys were found to be between 1020 cm-3 and 1021 cm-3.

  19. Understanding phase stability of Al-Co-Cr-Fe-Ni high entropy alloys

    DOE PAGES

    Zhang, Chuan; Zhang, Fan; Diao, Haoyan; ...

    2016-07-19

    The concept of high entropy alloy (HEA) opens a vast unexplored composition range for alloy design. As a well-studied system, Al-Co-Cr-Fe-Ni has attracted tremendous amount of attention to develop new-generation low-density structural materials for automobile and aerospace applications. In spite of intensive investigations in the past few years, the phase stability within this HEA system is still poorly understood and needs to be clarified, which poses obstacles to the discovery of promising Al-Co-Cr-Fe-Ni HEAs. In the present work, the CALPHAD approach is employed to understand the phase stability and explore the phase transformation within the Al-Co-Cr-Fe-Ni system. As a result,more » the phase-stability mapping coupled with density contours is then constructed within the composition - temperature space, which provides useful guidelines for the design of low-density Al-Co-Cr-Fe-Ni HEAs with desirable properties.« less

  20. Effects of Fe concentration on the ion-irradiation induced defect evolution and hardening in Ni-Fe solid solution alloys

    DOE PAGES

    Jin, Ke; Guo, Wei; Lu, Chenyang; ...

    2016-12-01

    Understanding alloying effects on the irradiation response of structural materials is pivotal in nuclear engineering. In order to systematically explore the effects of Fe concentration on the irradiation-induced defect evolution and hardening in face-centered cubic Ni-Fe binary solid solution alloys, single crystalline Ni-xFe (x = 0–60 at%) alloys have been grown and irradiated with 1.5 MeV Ni ions. The irradiations have been performed over a wide range of fluences from 3 × 1013 to 3 × 1016 cm-2 at room temperature. Ion channeling technique has shown reduced damage accumulation with increasing Fe concentration in the low fluence regime, which ismore » consistent to the results from molecular dynamic simulations. We did not observe any irradiation-induced compositional segregation in atom probe tomography within the detection limit, even in the samples irradiated with high fluence Ni ions. Transmission electron microscopy analyses have further demonstrated that the defect size significantly decreases with increasing Fe concentration, indicating a delay in defect evolution. Furthermore, irradiation induced hardening has been measured by nanoindentation tests. Ni and the Ni-Fe alloys have largely different initial hardness, but they all follow a similar trend for the increase of hardness as a function of irradiation fluence.« less

  1. Effects of Fe concentration on the ion-irradiation induced defect evolution and hardening in Ni-Fe solid solution alloys

    SciTech Connect

    Jin, Ke; Guo, Wei; Lu, Chenyang; Ullah, Mohammad W.; Zhang, Yanwen; Weber, William J.; Wang, Lumin; Poplawsky, Jonathan D.; Bei, Hongbin

    2016-12-01

    Understanding alloying effects on the irradiation response of structural materials is pivotal in nuclear engineering. In order to systematically explore the effects of Fe concentration on the irradiation-induced defect evolution and hardening in face-centered cubic Ni-Fe binary solid solution alloys, single crystalline Ni-xFe (x = 0–60 at%) alloys have been grown and irradiated with 1.5 MeV Ni ions. The irradiations have been performed over a wide range of fluences from 3 × 1013 to 3 × 1016 cm-2 at room temperature. Ion channeling technique has shown reduced damage accumulation with increasing Fe concentration in the low fluence regime, which is consistent to the results from molecular dynamic simulations. We did not observe any irradiation-induced compositional segregation in atom probe tomography within the detection limit, even in the samples irradiated with high fluence Ni ions. Transmission electron microscopy analyses have further demonstrated that the defect size significantly decreases with increasing Fe concentration, indicating a delay in defect evolution. Furthermore, irradiation induced hardening has been measured by nanoindentation tests. Ni and the Ni-Fe alloys have largely different initial hardness, but they all follow a similar trend for the increase of hardness as a function of irradiation fluence.

  2. The Analysis of the General Performance and Mechanical Behavior of Unirradiated FeCrAl Alloys Before and After Welding

    SciTech Connect

    Gussev, Maxim N.; Field, Kevin G.; Yamamoto, Yukinori

    2016-06-03

    The present report summarizes and discusses the preliminary results for the in-depth characterization of the modern, nuclear-grade FeCrAl alloys currently under development. The alloys were designed for enhanced radiation tolerance and weldability, and the research is currently being pursued by the Department of Energy (DOE) Nuclear Energy Enabling Technologies (NEET) program. Last year, seven candidate FeCrAl alloys with well-controlled chemistry and microstructures were designed and produced; welding was performed under well-controlled conditions. The structure and general performance of unirradiated alloys were assessed using standardized and advanced microstructural characterization techniques and mechanical testing. The primary objective is to identify the best candidate alloy, or at a minimum to identify the contributing factors that increase the weldability and radiation tolerance of FeCrAl alloys, therefore enabling future generations of FeCrAl alloys to deliver better performance parameters. This report is structured so as to describe these critical assessments of the weldability; radiation tolerance will be reported on in later reports from this program.

  3. Synthesis of Nd2Fe14C compound by high-energy ball-milling Nd-Fe alloy in heptane and annealing under vacuum

    NASA Astrophysics Data System (ADS)

    Geng, H. M.; Ji, Y.; Feng, X. Y.; Zhang, J. J.; Ran, Z.; Yan, Y.; Wang, W. Q.; Su, F.; Du, X. B.

    2016-06-01

    A simple synthesis route for the Nd2Fe14C compound with good permanent magnetic properties is presented. Being high-energy ball-milled in heptane (C7H16) for 8 h, the NdFe3.5 alloy consisting of Nd2Fe17 and Nd phases disproportionates into NdH2+δ and α-Fe. Subsequently, NdH2+δ decomposes when annealed from room temperature to 900 °C under vacuum, and H2 is released. Meanwhile Nd2Fe14C, NdC and little α-Fe phases are formed in the final product. H and C atoms come from the decomposition of heptane. Coercivity of 1.39 T and maximum magnetic energy product of 62.7 kJ m-3 have been achieved. Too short a ball-milling time results in the insufficient disproportionation of NdFe3.5 alloy and the residue of Nd2Fe17 phase in the final product. Too long a ball-milling time results in the appearance of NdC2 and more α-Fe phases besides Nd2Fe14C and NdC phases. Hexane (C6H14), octane (C8H18) and nonane (C9H20) have been proved to have a similar effect to heptane.

  4. Experimental Investigation and Computer Simulation of Diffusion in Fe-Mo and Fe-Mn-Mo Alloys with Different Optimization Methods

    NASA Astrophysics Data System (ADS)

    Zheng, Weisen; Ågren, John; Lu, Xiao-Gang; He, Yanlin; Li, Lin

    2017-01-01

    In order to simulate the diffusional phase transformations involving the fcc and bcc phases for microalloyed steels, the diffusion mobilities for fcc and bcc Fe-Mo and Fe-Mn-Mo alloys were experimentally investigated and critically assessed. The diffusion-couple technique was employed to extract the interdiffusion coefficients in Fe-Mo and Fe-Mn-Mo alloys with the Sauer-Freise and Whittle-Green methods. Based on the present experimental interdiffsivities, the mobility parameters for the fcc and bcc phases in the Fe-Mo and Fe-Mn-Mo systems were optimized using the traditional method. Simultaneously, a direct method was developed and utilized to directly fit mobilities to the diffusion profiles rather than the diffusivities in the present work. The satisfactory description of the diffusion behavior in the Fe-Mo and Fe-Mn-Mo systems has confirmed the reliability of the direct method. Particularly, the two sets of diffusion mobilities obtained with both methods could simulate the diffusion phenomenon between the fcc and bcc phases in the Fe-Mo and Fe-Mn-Mo systems successfully.

  5. Chromium Grain-boundary Segregation and Effect of Ion Beam Cleaning on Fe-Ni-Cr Alloys

    SciTech Connect

    Saraf, Laxmikant V.

    2011-04-01

    The grain boundaries play important role to control the mechanical strength of ternary alloys. From spacecrafts to naval vessels to nuclear reactors, stress corrosion cracking, brittleness, oxidation mostly originates at the grain boundaries and cause long term structural stability problems in most of the metallic structures [1]. Fe-Ni-Cr based ternary metal alloys have been widely studied for more than fifty years [2, 3]. Despite of vast amount of research, chromium diffusion in stainless steel or other Ni-Fe-Cr based ternary alloys is still an open scientific problem with challenges in structural stability and corrosion resistance [4]. Particularly, austenite Fe-Ni-Cr is looked upon favorably in space and jet engine industry for their improved resistance to stress corrosion cracking [5]. In solid oxide fuel cells (SOFC), Ni-alloys are frequently used as interconnects and seals [6]. In this communication, simultaneous energy dispersive spectroscopy (EDS) and electron backscatter diffraction (EBSD) mapping is utilized to study chemical and structural aspects of chromium segregation in Fe-Ni-Cr alloy. A focused Ga-ion beam is also utilized to study the effect of ion beam cleaning on EBSD image quality (IQ) and inverse pole figure (IPF) maps of Fe-Ni-Cr alloy.

  6. Preparation of Soft Magnetic Fe-Ni-Pb-B Alloy Nanoparticles by Room Temperature Solid-Solid Reaction

    PubMed Central

    Zhong, Qin

    2013-01-01

    The Fe-Ni-Pb-B alloy nanoparticles was prepared by a solid-solid chemical reaction of ferric trichloride, nickel chloride, lead acetate, and potassium borohydride powders at room temperature. The research results of the ICP and thermal analysis indicate that the resultants are composed of iron, nickel, lead, boron, and PVP, and the component of the alloy is connected with the mole ratio of potassium borohydride and the metal salts. The TEM images show that the resultants are ultrafine and spherical particles, and the particle size is about a diameter of 25 nm. The largest saturation magnetization value of the 21.18 emu g−1 is obtained in the Fe-Ni-Pb-B alloy. The mechanism of the preparation reaction for the Fe-Ni-Pb-B multicomponent alloys is discussed. PMID:24348196

  7. The role of rare earth elements in the structures of FeB-based glass forming liquid alloys

    NASA Astrophysics Data System (ADS)

    Pan, S. P.; Qin, J. Y.; Gu, T. K.

    2010-02-01

    The structures of liquid Fe72RE6B22 (RE=Sc, Er, Ho, Dy, Y, Sm, Gd, Nd, and Ce) alloys were investigated by ab initio molecular dynamics simulation. The results show that the chemical affinity of Fe-RE and RE-B may influence the glass forming ability more than the atomic size of RE atom in these alloys. As expected, the ⟨0,3,6,0⟩ polyhedron dominates around B atoms and is significantly enriched by adding RE elements to the liquid Fe78B22 alloy. The good glass formers do not correspond to the larger percentages but to more RE atoms in the shell of ⟨0,3,6,0⟩ polyhedron. These features suggest that the effect of the chemical composition of ⟨0,3,6,0⟩ polyhedron on the glass forming ability may be larger than that of its quantity in these alloys.

  8. Synthesization and characterization of FeS2 by mechanical alloying for Na/FeS2 cell.

    PubMed

    Liu, Xiaojing; Kang, Sang-Dae; Kim, Jong-Seon; Ahn, In-Shup; Ahn, Hyo-Jun

    2012-02-01

    In this study, the FeS2 fine compound powders were synthesized by mechanical alloying (MA) for 15 hrs and stearic acid was added as PCA (Process Control Agent) to prevent the excessive cold welding and agglomeration. For the purpose of ulteriorly reducing the particle size to improve the contact areas between the active materials and conducting agents, the wet ball milling process was applied by employing normal hexane (C6H14) as the milling solvent. The mean particle size of FeS2 powders about 1.14 microm were obtained after 24 hrs wet ball milling. The powders were characterized by FE-SEM, XRD, TEM and EDS. To compare the influence of particle size on the properties of charge/discharge, the same electrolyte was employed for both tests by dissolving 1M NaCF3SO3 (sodium trifluoromethanesulfonate) in a liquid of TEGDME (tetraethylene glycol dimethylether). The first discharge capacity of Na/FeS2 cell made by dry ball milled powders was 440 mAh/g with a plateau potential at approximately 1.25 V versus Na/Na+ and 260 mAh/g at the 25th cycle at room temperature. Meanwhile, the initial discharge capacity of Na/FeS2 cell made by wet ball milled powders was 614 mAh/g with the same discharge plateau potential and retained 385 mAh/g at the 25th cycle. And the discharge capacity for wet milled system decreased continuously by repeated charge/discharge cycling in the first 20 cycles and has little change after 60 cycles, which means the good cycling properties, remaining half of its initial discharge capacity of 320 mAh/g even after 100 cycles.

  9. Observation of clusters in Re60Fe30Al10 alloys and the associated magnetic properties

    NASA Astrophysics Data System (ADS)

    Z, Kong H.; J, Ding; L, Dong Z.; L, Wang; T, White; Y, Li

    2002-03-01

    Magnetic properties and microstructure of melt-spun ribbons of RE60Fe30Al10 alloys with RE{} = {}Nd, Sm, Dy, Gd and Y were studied in detail. High coercivity values in the range of MA m-1 were observed at low temperatures for amorphous ribbons. Presence of Fe-rich clusters and nanoscale rare-earth crystallites in the amorphous matrix in the ribbons were revealed by high-resolution transmission electron microscopy studies. The magnetic transition temperatures were estimated experimentally and compared with fitting results based on the cluster ferromagnetism model (Wang L et al 2001 Phys. Rev. B 64 214410). Possible mechanisms for the magnetic behaviour observed due to the presence of Fe-rich magnetic clusters are discussed.

  10. EXAFS determination of Hf localization in HDDR Nd Fe B Hf alloys

    NASA Astrophysics Data System (ADS)

    Torres, C. E. Rodríguez; Fernández van Raap, M. B.; Sánchez, F. H.; Pasquevich, A. F.

    2005-05-01

    The local structure around Hf in Nd 15.78Fe 76.3-xHf xB 7.8 ( x=0.1 and 0.2) submitted to conventional and solid hydrogenation-disproportionation-desorption-recombination (HDDR) sequence was studied by extended X-ray absorption fine structure (EXAFS) in order to understand the relation between the presence of Hf and magnetic anisotropy found only in solid-HDDR samples. EXAFS results show that Hf is not in the Nd 2Fe 14B structure but incorporated into a local atomic arrangement (HfB ClNa-type) which is the same for as-cast, solid and conventional HDDR samples. It is concluded that the magnetic anisotropy induced by Hf addition to NdFeB alloys must be related to microstructural features.

  11. Magnetic properties and martensitic transformation in quaternary Heusler alloy of NiMnFeGa

    NASA Astrophysics Data System (ADS)

    Liu, Z. H.; Zhang, M.; Wang, W. Q.; Wang, W. H.; Chen, J. L.; Wu, G. H.; Meng, F. B.; Liu, H. Y.; Liu, B. D.; Qu, J. P.

    2002-11-01

    Quaternary Heusler alloy Ni2)(Mn,FeGa has been studied systematically for the structure, martensitic transformation, and magnetic properties in two systems of Ni50.5Mn25-xFexGa24.5 and Ni50.4Mn28-xFexGa21.6. Substituting Fe for Mn up to about 70%, the pure L21 phase and the thermoelastic martensitic transformation still can be observed in these quaternary systems. Iron doping dropped the martensitic transformation temperature from 220 to 140 K, increased the Curie temperature from 351 to 429 K, and broadened the thermal hysteresis from about 7 to 18 K. Magnetic analysis revealed that Fe atoms contribute to the net magnetization of the material with a moment lower than that of Mn. The temperature dependence of magnetic-field-induced strains has been improved by this doping method.

  12. Metastable Demixing of Supercooled Cu-Co and Cu-Fe Alloys in an Oxide Flux

    NASA Technical Reports Server (NTRS)

    Li, D.; Robinson, M. B.; Rathz, T. J.; Williams, G.

    1998-01-01

    A systematic study on the liquid separation in supercooled Cu-Co and Cu-Fe alloys was performed using a melt fluxing which permits high supercooling to be achieved. Moreover, this method renders it possible to directly measure binodal temperatures and establish metastable liquid miscibility gap (LMG). All phase-separated samples at compositions ranging from 10 to 80 wt pct Co or to 83 wt pct Fe were found to exhibit droplet-shaped morphologies, in spite of various droplet distributions. Uniformly dispersed microstructures were obtained as the minority component was less than 20 vol.%; while beyond this percentage, serious coarsening was brought about. Calculations of the miscibility gap in the Cu-Co system and Stokes movement velocity of Co and Fe droplets in Cu matrix were made to analyze the experimental results.

  13. Vibrational Properties of α- and σ-Phase Fe-Cr Alloy

    NASA Astrophysics Data System (ADS)

    Dubiel, S. M.; Cieslak, J.; Sturhahn, W.; Sternik, M.; Piekarz, P.; Stankov, S.; Parlinski, K.

    2010-04-01

    Experimental and theoretical studies, of the Fe-partial phonon density of states (PDOS) for Fe52.5Cr47.5 alloy having α and σ phases were carried out. The former using the nuclear resonant inelastic x-ray scattering method, and the latter with the direct one. Characteristic features of PDOS, which distinguish one phase from the other, were revealed and successfully reproduced by the theory. Data pertinent to the dynamics such as the Lamb-Mössbauer factor, f, the kinetic energy per atom, Ek, and the mean force constant, D, were directly derived, while vibrational specific heat at constant volume, CV, and vibrational entropy, S were calculated using the Fe partial PDOS. Based on the values of f and CV, we determined Debye temperatures, ΘD. An excellent agreement for some quantities derived from experiment and first-principles theory, like CV and quite good ones for others like D and S were obtained.

  14. Influence of melt convection on the microstructure of levitated and undercooled Nd-Fe-B alloys

    NASA Astrophysics Data System (ADS)

    Filip, O.; Hermann, R.; Gerbeth, G.; Priede, J.; Shatrov, V.; Gueth, A.; Schultz, L.

    2004-05-01

    The influence of melt rotation on the microstructure formation of Nd-Fe-B alloys, mainly the volume fraction and grain size of the α-Fe phase, is investigated using the electromagnetic levitation technique. Molten droplets were subjected to a strong rotation during levitation and compared to fixed samples without rotation. Additionally, experiments have been carried out where sealed samples were subjected to a well-defined forced rotation. A distinct reduction of the α-Fe volume fraction in samples with strong rotation was observed by measuring the magnetic moment. The melt flow in a levitated droplet is studied numerically under the additional effect of a global sample rotation which may give a strong suppression of internal motions.

  15. Superferromagnetism in mechanically alloyed fcc Fe23Cu77 with bimodal cluster size distribution

    NASA Astrophysics Data System (ADS)

    Silva, N. J. O.; Amaral, J. S.; Amaral, V. S.; Costa, B. F. O.; LeCaër, G.

    2009-01-01

    Magnetic measurements, x-ray diffraction and Mössbauer spectroscopy were used to characterize a nanostructured fcc Fe23Cu77 at.% alloy prepared by high-energy ball-milling, addressing in particular the effect of clustering on the nature of the interacting magnetic entities. The interpretation of magnetization measurements leads to the conclusion that grains, whose mean size is ~16 nm, contain two populations of magnetic Fe-rich nanoclusters with a bimodal size distribution. These two sets of clusters contain about 14 and 400 Fe atoms and have magnetic moments of 30 µB and 860 µB, respectively. The inter-cluster ferromagnetic interactions that lead to superferromagnetism with a Curie temperature TC~220 K can be described by a mean field determined by the smaller clusters only, which account for 90% of the magnetization.

  16. Phase Separation kinetics in an Fe-Cr-Al alloy

    SciTech Connect

    Capdevila, C.; Miller, Michael K; Chao, J.

    2012-01-01

    The {alpha}-{alpha}{prime} phase separation kinetics in a commercial Fe-20 wt.% Cr-6 wt.% Al oxide dispersion-strengthened PM 2000{trademark} steel have been characterized with the complementary techniques atom probe tomography and thermoelectric power measurements during isothermal aging at 673, 708, and 748 K for times up to 3600 h. A progressive decrease in the Al content of the Cr-rich {alpha}{prime} phase was observed at 708 and 748 K with increasing time, but no partitioning was observed at 673 K. The variation in the volume fraction of the {alpha}{prime} phase well inside the coarsening regime, along with the Avrami exponent 1.2 and activation energy 264 kJ mol{sup -1}, obtained after fitting the experimental results to an Austin-Rickett type equation, indicates that phase separation in PM 2000{trademark} is a transient coarsening process with overlapping nucleation, growth, and coarsening stages.

  17. Mechanical Properties of High Entropy Alloy Al0.1CoCrFeNi for Peripheral Vascular Stent Application.

    PubMed

    Alagarsamy, Karthik; Fortier, Aleksandra; Komarasamy, Mageshwari; Kumar, Nilesh; Mohammad, Atif; Banerjee, Subhash; Han, Hai-Chao; Mishra, Rajiv S

    2016-12-01

    High entropy alloys (HEAs) are new class of metallic materials with five or more principal alloying elements. Due to this distinct concept of alloying, the HEAs exhibit unique properties compared to conventional alloys. The outstanding properties of HEAs include increased strength, superior wear resistance, high temperature stability, increased fatigue properties, good corrosion, and oxidation resistance. Such characteristics of HEAs have generated significant interest among the scientific community. However, their applications are yet to be explored. This paper discusses the mechanical behavior and microstructure of Al0.1CoCrFeNi HEA subjected to thermo-mechanical processing, and its potential application in peripheral vascular stent implants that are prone to high failure rates. Results show that Al0.1CoCrFeNi alloy possesses characteristics that compare well against currently used stent materials and it can potentially find use in peripheral vascular stent implants and extend their life-cycle.

  18. A NiFeCu alloy anode catalyst for direct-methane solid oxide fuel cells

    NASA Astrophysics Data System (ADS)

    Wang, Wei; Zhu, Huaiyu; Yang, Guangming; Park, Hee Jung; Jung, Doh Won; Kwak, Chan; Shao, Zongping

    2014-07-01

    In this study, a new anode catalyst based on a NiFeCu alloy is investigated for use in direct-methane solid oxide fuel cells (SOFCs). The influence of the conductive copper introduced into the anode catalyst layer on the performance of the SOFCs is systematically studied. The catalytic activity for partial oxidation of methane and coking resistance tests are proposed with various anode catalyst layer materials prepared using different methods, including glycine nitrate process (GNP), physical mixing (PM) and impregnation (IMP). The surface conductivity tests indicate that the conductivities of the NiFe-ZrO2/Cu (PM) and NiFe-ZrO2/Cu (IMP) catalysts are considerably greater than that of NiFe-ZrO2/Cu (GNP), which is consistent with the SEM results. Among the three preparation methods, the cell containing the NiFe-ZrO2/Cu (IMP) catalyst layer performs best on CH4-O2 fuel, especially under reduced temperatures, because the coking resistance should be considered in real fuel cell conditions. The cell containing the NiFe-ZrO2/Cu (IMP) catalyst layer also delivers an excellent operational stability using CH4-O2 fuel for 100 h without any signs of decay. In summary, this work provides new alternative anode catalytic materials to accelerate the commercialization of SOFC technology.

  19. Laser Processing of Fe-Based Bulk Amorphous Alloy Coatings on Titanium

    NASA Astrophysics Data System (ADS)

    Sahasrabudhe, Himanshu; Dittrick, Stanley A.; Bandyopadhyay, Amit

    2013-11-01

    Laser Engineered Net Shaping (LENS™), a solid freeform fabrication technique, was employed for the processing of Fe-based bulk amorphous alloy (Fe BAA) powder on titanium. One and two layers of the Fe BAA were deposited with the same processing parameters. SEM and XRD analyses of the Fe BAA coatings revealed the retention of the feedstock powder's amorphous nature. The mixing of the feedstock powder in the titanium substrate was very small. A crystalline-amorphous composite microstructure evolved from the laser processing in all types of coatings. The coatings were further laser remelted. The amorphous character was found to increase and the crystallites were found to grow during remelting. The Fe BAA coatings showed higher hardness and smaller wear volume compared to the Ti substrate. A further increase in these properties was observed after laser remelting treatment. During the wear testing in NaCl solution, Ti substrate showed intergranular corrosion, whereas the Fe BAA coatings showed signs of low and localized fretting corrosion in a saline environment. Our results demonstrate that using LENS™, amorphous coatings can be deposited on metallic substrates.

  20. One-step electrolytic preparation of Si-Fe alloys as anodes for lithium ion batteries

    NASA Astrophysics Data System (ADS)

    Wang, Hailong; Sun, Diankun; Song, Qiqi; Xie, Wenqi; Jiang, Xu; Zhang, Bo

    2016-06-01

    One-step electrolytic formation of uniform crystalline Si-Fe alloy particles was successfully demonstrated in direct electro-reduction of solid mixed oxides of SiO2 and Fe2O3 in molten CaCl2 at 900∘C. Upon constant voltage electrolysis of solid mixed oxides at 2.8V between solid oxide cathode and graphite anode for 5h, electrolytic Si-Fe with the same Si/Fe stoichimetry of the precursory oxides was generated. The firstly generated Fe could function as depolarizers to enhance reduction rate of SiO2, resulting in the enhanced reduction kinetics to the electrolysis of individual SiO2. When evaluated as anode for lithium ion batteries, the prepared SiFe electrode showed a reversible lithium storage capacity as high as 470mAh g-1 after 100 cycles at 200mA g-1, promising application in high-performance lithium ion batteries.